diff --git a/leveldb_base/.clang-format b/leveldb_base/.clang-format
new file mode 100644
index 0000000..f493f75
--- /dev/null
+++ b/leveldb_base/.clang-format
@@ -0,0 +1,18 @@
+# Run manually to reformat a file:
+# clang-format -i --style=file <file>
+# find . -iname '*.cc' -o -iname '*.h' -o -iname '*.h.in' | xargs clang-format -i --style=file
+BasedOnStyle: Google
+DerivePointerAlignment: false
+
+# Public headers are in a different location in the internal Google repository.
+# Order them so that when imported to the authoritative repository they will be
+# in correct alphabetical order.
+IncludeCategories:
+  - Regex:           '^(<|"(benchmarks|db|helpers)/)'
+    Priority:        1
+  - Regex:           '^"(leveldb)/'
+    Priority:        2
+  - Regex:           '^(<|"(issues|port|table|third_party|util)/)'
+    Priority:        3
+  - Regex:           '.*'
+    Priority:        4
diff --git a/leveldb_base/.github/workflows/build.yml b/leveldb_base/.github/workflows/build.yml
new file mode 100644
index 0000000..d28902e
--- /dev/null
+++ b/leveldb_base/.github/workflows/build.yml
@@ -0,0 +1,102 @@
+# Copyright 2021 The LevelDB Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+name: ci
+on: [push, pull_request]
+
+permissions:
+  contents: read
+
+jobs:
+  build-and-test:
+    name:  >-
+      CI
+      ${{ matrix.os }}
+      ${{ matrix.compiler }}
+      ${{ matrix.optimized && 'release' || 'debug' }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        compiler: [clang, gcc, msvc]
+        os: [ubuntu-latest, macos-latest, windows-latest]
+        optimized: [true, false]
+        exclude:
+        # MSVC only works on Windows.
+        - os: ubuntu-latest
+          compiler: msvc
+        - os: macos-latest
+          compiler: msvc
+        # Not testing with GCC on macOS.
+        - os: macos-latest
+          compiler: gcc
+        # Only testing with MSVC on Windows.
+        - os: windows-latest
+          compiler: clang
+        - os: windows-latest
+          compiler: gcc
+        include:
+        - compiler: clang
+          CC: clang
+          CXX: clang++
+        - compiler: gcc
+          CC: gcc
+          CXX: g++
+        - compiler: msvc
+          CC:
+          CXX:
+
+    env:
+      CMAKE_BUILD_DIR: ${{ github.workspace }}/build
+      CMAKE_BUILD_TYPE: ${{ matrix.optimized && 'RelWithDebInfo' || 'Debug' }}
+      CC: ${{ matrix.CC }}
+      CXX: ${{ matrix.CXX }}
+      BINARY_SUFFIX: ${{ startsWith(matrix.os, 'windows') && '.exe' || '' }}
+      BINARY_PATH: >-
+        ${{ format(
+        startsWith(matrix.os, 'windows') && '{0}\build\{1}\' || '{0}/build/',
+        github.workspace,
+        matrix.optimized && 'RelWithDebInfo' || 'Debug') }}
+
+    steps:
+    - uses: actions/checkout@v2
+      with:
+        submodules: true
+
+    - name: Install dependencies on Linux
+      if: ${{ runner.os == 'Linux' }}
+      # libgoogle-perftools-dev is temporarily removed from the package list
+      # because it is currently broken on GitHub's Ubuntu 22.04.
+      run: |
+        sudo apt-get update
+        sudo apt-get install libkyotocabinet-dev libsnappy-dev libsqlite3-dev
+
+    - name: Generate build config
+      run: >-
+        cmake -S "${{ github.workspace }}" -B "${{ env.CMAKE_BUILD_DIR }}"
+        -DCMAKE_BUILD_TYPE=${{ env.CMAKE_BUILD_TYPE }}
+        -DCMAKE_INSTALL_PREFIX=${{ runner.temp }}/install_test/
+
+    - name: Build
+      run: >-
+        cmake --build "${{ env.CMAKE_BUILD_DIR }}"
+        --config "${{ env.CMAKE_BUILD_TYPE }}"
+
+    - name: Run Tests
+      working-directory: ${{ github.workspace }}/build
+      run: ctest -C "${{ env.CMAKE_BUILD_TYPE }}" --verbose
+
+    - name: Run LevelDB Benchmarks
+      run: ${{ env.BINARY_PATH }}db_bench${{ env.BINARY_SUFFIX }}
+
+    - name: Run SQLite Benchmarks
+      if: ${{ runner.os != 'Windows' }}
+      run: ${{ env.BINARY_PATH }}db_bench_sqlite3${{ env.BINARY_SUFFIX }}
+
+    - name: Run Kyoto Cabinet Benchmarks
+      if: ${{ runner.os == 'Linux' && matrix.compiler == 'clang' }}
+      run: ${{ env.BINARY_PATH }}db_bench_tree_db${{ env.BINARY_SUFFIX }}
+
+    - name: Test CMake installation
+      run: cmake --build "${{ env.CMAKE_BUILD_DIR }}" --target install
diff --git a/leveldb_base/.gitignore b/leveldb_base/.gitignore
new file mode 100644
index 0000000..4729d86
--- /dev/null
+++ b/leveldb_base/.gitignore
@@ -0,0 +1,10 @@
+# Editors.
+*.sw*
+.vscode
+.DS_Store
+
+# Build directory.
+build/
+out/
+cmake-build-*
+.idea
\ No newline at end of file
diff --git a/leveldb_base/.gitmodules b/leveldb_base/.gitmodules
new file mode 100644
index 0000000..6e6d3f0
--- /dev/null
+++ b/leveldb_base/.gitmodules
@@ -0,0 +1,6 @@
+[submodule "third_party/googletest"]
+	path = third_party/googletest
+	url = https://github.com/google/googletest.git
+[submodule "third_party/benchmark"]
+	path = third_party/benchmark
+	url = https://github.com/google/benchmark
diff --git a/leveldb_base/AUTHORS b/leveldb_base/AUTHORS
new file mode 100644
index 0000000..2439d7a
--- /dev/null
+++ b/leveldb_base/AUTHORS
@@ -0,0 +1,12 @@
+# Names should be added to this file like so:
+# Name or Organization <email address>
+
+Google Inc.
+
+# Initial version authors:
+Jeffrey Dean <jeff@google.com>
+Sanjay Ghemawat <sanjay@google.com>
+
+# Partial list of contributors:
+Kevin Regan <kevin.d.regan@gmail.com>
+Johan Bilien <jobi@litl.com>
diff --git a/leveldb_base/CMakeLists.txt b/leveldb_base/CMakeLists.txt
new file mode 100644
index 0000000..54b14a1
--- /dev/null
+++ b/leveldb_base/CMakeLists.txt
@@ -0,0 +1,531 @@
+# Copyright 2017 The LevelDB Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+cmake_minimum_required(VERSION 3.9)
+# Keep the version below in sync with the one in db.h
+project(leveldb VERSION 1.23.0 LANGUAGES C CXX)
+
+# C standard can be overridden when this is used as a sub-project.
+if(NOT CMAKE_C_STANDARD)
+  # This project can use C11, but will gracefully decay down to C89.
+  set(CMAKE_C_STANDARD 11)
+  set(CMAKE_C_STANDARD_REQUIRED OFF)
+  set(CMAKE_C_EXTENSIONS OFF)
+endif(NOT CMAKE_C_STANDARD)
+
+# C++ standard can be overridden when this is used as a sub-project.
+if(NOT CMAKE_CXX_STANDARD)
+  # This project requires C++11.
+  set(CMAKE_CXX_STANDARD 11)
+  set(CMAKE_CXX_STANDARD_REQUIRED ON)
+  set(CMAKE_CXX_EXTENSIONS OFF)
+endif(NOT CMAKE_CXX_STANDARD)
+
+if (WIN32)
+  set(LEVELDB_PLATFORM_NAME LEVELDB_PLATFORM_WINDOWS)
+  # TODO(cmumford): Make UNICODE configurable for Windows.
+  add_definitions(-D_UNICODE -DUNICODE)
+else (WIN32)
+  set(LEVELDB_PLATFORM_NAME LEVELDB_PLATFORM_POSIX)
+endif (WIN32)
+
+option(LEVELDB_BUILD_TESTS "Build LevelDB's unit tests" ON)
+option(LEVELDB_BUILD_BENCHMARKS "Build LevelDB's benchmarks" ON)
+option(LEVELDB_INSTALL "Install LevelDB's header and library" ON)
+
+include(CheckIncludeFile)
+check_include_file("unistd.h" HAVE_UNISTD_H)
+
+include(CheckLibraryExists)
+check_library_exists(crc32c crc32c_value "" HAVE_CRC32C)
+check_library_exists(snappy snappy_compress "" HAVE_SNAPPY)
+check_library_exists(zstd zstd_compress "" HAVE_ZSTD)
+check_library_exists(tcmalloc malloc "" HAVE_TCMALLOC)
+
+include(CheckCXXSymbolExists)
+# Using check_cxx_symbol_exists() instead of check_c_symbol_exists() because
+# we're including the header from C++, and feature detection should use the same
+# compiler language that the project will use later. Principles aside, some
+# versions of do not expose fdatasync() in <unistd.h> in standard C mode
+# (-std=c11), but do expose the function in standard C++ mode (-std=c++11).
+check_cxx_symbol_exists(fdatasync "unistd.h" HAVE_FDATASYNC)
+check_cxx_symbol_exists(F_FULLFSYNC "fcntl.h" HAVE_FULLFSYNC)
+check_cxx_symbol_exists(O_CLOEXEC "fcntl.h" HAVE_O_CLOEXEC)
+
+if(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
+  # Disable C++ exceptions.
+  string(REGEX REPLACE "/EH[a-z]+" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /EHs-c-")
+  add_definitions(-D_HAS_EXCEPTIONS=0)
+
+  # Disable RTTI.
+  string(REGEX REPLACE "/GR" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /GR-")
+else(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
+  # Enable strict prototype warnings for C code in clang and gcc.
+  if(NOT CMAKE_C_FLAGS MATCHES "-Wstrict-prototypes")
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wstrict-prototypes")
+  endif(NOT CMAKE_C_FLAGS MATCHES "-Wstrict-prototypes")
+
+  # Disable C++ exceptions.
+  string(REGEX REPLACE "-fexceptions" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-exceptions")
+
+  # Disable RTTI.
+  string(REGEX REPLACE "-frtti" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-rtti")
+endif(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
+
+# Test whether -Wthread-safety is available. See
+# https://clang.llvm.org/docs/ThreadSafetyAnalysis.html
+include(CheckCXXCompilerFlag)
+check_cxx_compiler_flag(-Wthread-safety HAVE_CLANG_THREAD_SAFETY)
+
+# Used by googletest.
+check_cxx_compiler_flag(-Wno-missing-field-initializers
+                        LEVELDB_HAVE_NO_MISSING_FIELD_INITIALIZERS)
+
+include(CheckCXXSourceCompiles)
+
+# Test whether C++17 __has_include is available.
+check_cxx_source_compiles("
+#if defined(__has_include) &&  __has_include(<string>)
+#include <string>
+#endif
+int main() { std::string str; return 0; }
+" HAVE_CXX17_HAS_INCLUDE)
+
+set(LEVELDB_PUBLIC_INCLUDE_DIR "include/leveldb")
+set(LEVELDB_PORT_CONFIG_DIR "include/port")
+
+configure_file(
+  "port/port_config.h.in"
+  "${PROJECT_BINARY_DIR}/${LEVELDB_PORT_CONFIG_DIR}/port_config.h"
+)
+
+include_directories(
+  "${PROJECT_BINARY_DIR}/include"
+  "."
+)
+
+if(BUILD_SHARED_LIBS)
+  # Only export LEVELDB_EXPORT symbols from the shared library.
+  add_compile_options(-fvisibility=hidden)
+endif(BUILD_SHARED_LIBS)
+
+# Must be included before CMAKE_INSTALL_INCLUDEDIR is used.
+include(GNUInstallDirs)
+
+add_library(leveldb "")
+target_sources(leveldb
+  PRIVATE
+    "${PROJECT_BINARY_DIR}/${LEVELDB_PORT_CONFIG_DIR}/port_config.h"
+    "db/builder.cc"
+    "db/builder.h"
+    "db/c.cc"
+    "db/db_impl.cc"
+    "db/db_impl.h"
+    "db/db_iter.cc"
+    "db/db_iter.h"
+    "db/dbformat.cc"
+    "db/dbformat.h"
+    "db/dumpfile.cc"
+    "db/filename.cc"
+    "db/filename.h"
+    "db/log_format.h"
+    "db/log_reader.cc"
+    "db/log_reader.h"
+    "db/log_writer.cc"
+    "db/log_writer.h"
+    "db/memtable.cc"
+    "db/memtable.h"
+    "db/repair.cc"
+    "db/skiplist.h"
+    "db/snapshot.h"
+    "db/table_cache.cc"
+    "db/table_cache.h"
+    "db/version_edit.cc"
+    "db/version_edit.h"
+    "db/version_set.cc"
+    "db/version_set.h"
+    "db/write_batch_internal.h"
+    "db/write_batch.cc"
+    "port/port_stdcxx.h"
+    "port/port.h"
+    "port/thread_annotations.h"
+    "table/block_builder.cc"
+    "table/block_builder.h"
+    "table/block.cc"
+    "table/block.h"
+    "table/filter_block.cc"
+    "table/filter_block.h"
+    "table/format.cc"
+    "table/format.h"
+    "table/iterator_wrapper.h"
+    "table/iterator.cc"
+    "table/merger.cc"
+    "table/merger.h"
+    "table/table_builder.cc"
+    "table/table.cc"
+    "table/two_level_iterator.cc"
+    "table/two_level_iterator.h"
+    "util/arena.cc"
+    "util/arena.h"
+    "util/bloom.cc"
+    "util/cache.cc"
+    "util/coding.cc"
+    "util/coding.h"
+    "util/comparator.cc"
+    "util/crc32c.cc"
+    "util/crc32c.h"
+    "util/env.cc"
+    "util/filter_policy.cc"
+    "util/hash.cc"
+    "util/hash.h"
+    "util/logging.cc"
+    "util/logging.h"
+    "util/mutexlock.h"
+    "util/no_destructor.h"
+    "util/options.cc"
+    "util/random.h"
+    "util/status.cc"
+
+  # Only CMake 3.3+ supports PUBLIC sources in targets exported by "install".
+  $<$<VERSION_GREATER:CMAKE_VERSION,3.2>:PUBLIC>
+    "${LEVELDB_PUBLIC_INCLUDE_DIR}/c.h"
+    "${LEVELDB_PUBLIC_INCLUDE_DIR}/cache.h"
+    "${LEVELDB_PUBLIC_INCLUDE_DIR}/comparator.h"
+    "${LEVELDB_PUBLIC_INCLUDE_DIR}/db.h"
+    "${LEVELDB_PUBLIC_INCLUDE_DIR}/dumpfile.h"
+    "${LEVELDB_PUBLIC_INCLUDE_DIR}/env.h"
+    "${LEVELDB_PUBLIC_INCLUDE_DIR}/export.h"
+    "${LEVELDB_PUBLIC_INCLUDE_DIR}/filter_policy.h"
+    "${LEVELDB_PUBLIC_INCLUDE_DIR}/iterator.h"
+    "${LEVELDB_PUBLIC_INCLUDE_DIR}/options.h"
+    "${LEVELDB_PUBLIC_INCLUDE_DIR}/slice.h"
+    "${LEVELDB_PUBLIC_INCLUDE_DIR}/status.h"
+    "${LEVELDB_PUBLIC_INCLUDE_DIR}/table_builder.h"
+    "${LEVELDB_PUBLIC_INCLUDE_DIR}/table.h"
+    "${LEVELDB_PUBLIC_INCLUDE_DIR}/write_batch.h"
+)
+
+if (WIN32)
+  target_sources(leveldb
+    PRIVATE
+      "util/env_windows.cc"
+      "util/windows_logger.h"
+  )
+else (WIN32)
+  target_sources(leveldb
+    PRIVATE
+      "util/env_posix.cc"
+      "util/posix_logger.h"
+  )
+endif (WIN32)
+
+# MemEnv is not part of the interface and could be pulled to a separate library.
+target_sources(leveldb
+  PRIVATE
+    "helpers/memenv/memenv.cc"
+    "helpers/memenv/memenv.h"
+)
+
+target_include_directories(leveldb
+  PUBLIC
+    $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
+    $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
+)
+
+set_target_properties(leveldb
+  PROPERTIES VERSION ${PROJECT_VERSION} SOVERSION ${PROJECT_VERSION_MAJOR})
+
+target_compile_definitions(leveldb
+  PRIVATE
+    # Used by include/export.h when building shared libraries.
+    LEVELDB_COMPILE_LIBRARY
+    # Used by port/port.h.
+    ${LEVELDB_PLATFORM_NAME}=1
+)
+if (NOT HAVE_CXX17_HAS_INCLUDE)
+  target_compile_definitions(leveldb
+    PRIVATE
+      LEVELDB_HAS_PORT_CONFIG_H=1
+  )
+endif(NOT HAVE_CXX17_HAS_INCLUDE)
+
+if(BUILD_SHARED_LIBS)
+  target_compile_definitions(leveldb
+    PUBLIC
+      # Used by include/export.h.
+      LEVELDB_SHARED_LIBRARY
+  )
+endif(BUILD_SHARED_LIBS)
+
+if(HAVE_CLANG_THREAD_SAFETY)
+  target_compile_options(leveldb
+    PUBLIC
+      -Werror -Wthread-safety)
+endif(HAVE_CLANG_THREAD_SAFETY)
+
+if(HAVE_CRC32C)
+  target_link_libraries(leveldb crc32c)
+endif(HAVE_CRC32C)
+if(HAVE_SNAPPY)
+  target_link_libraries(leveldb snappy)
+endif(HAVE_SNAPPY)
+if(HAVE_ZSTD)
+  target_link_libraries(leveldb zstd)
+endif(HAVE_ZSTD)
+if(HAVE_TCMALLOC)
+  target_link_libraries(leveldb tcmalloc)
+endif(HAVE_TCMALLOC)
+
+# Needed by port_stdcxx.h
+find_package(Threads REQUIRED)
+target_link_libraries(leveldb Threads::Threads)
+
+add_executable(leveldbutil
+  "db/leveldbutil.cc"
+)
+target_link_libraries(leveldbutil leveldb)
+
+if(LEVELDB_BUILD_TESTS)
+  enable_testing()
+
+  # Prevent overriding the parent project's compiler/linker settings on Windows.
+  set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
+  set(install_gtest OFF)
+  set(install_gmock OFF)
+  set(build_gmock ON)
+
+  # This project is tested using GoogleTest.
+  add_subdirectory("third_party/googletest")
+
+  # GoogleTest triggers a missing field initializers warning.
+  if(LEVELDB_HAVE_NO_MISSING_FIELD_INITIALIZERS)
+    set_property(TARGET gtest
+        APPEND PROPERTY COMPILE_OPTIONS -Wno-missing-field-initializers)
+    set_property(TARGET gmock
+        APPEND PROPERTY COMPILE_OPTIONS -Wno-missing-field-initializers)
+  endif(LEVELDB_HAVE_NO_MISSING_FIELD_INITIALIZERS)
+
+  add_executable(leveldb_tests "")
+  target_sources(leveldb_tests
+    PRIVATE
+      # "db/fault_injection_test.cc"
+      # "issues/issue178_test.cc"
+      # "issues/issue200_test.cc"
+      # "issues/issue320_test.cc"
+      "${PROJECT_BINARY_DIR}/${LEVELDB_PORT_CONFIG_DIR}/port_config.h"
+      # "util/env_test.cc"
+      "util/status_test.cc"
+      "util/no_destructor_test.cc"
+      "util/testutil.cc"
+      "util/testutil.h"
+  )
+  if(NOT BUILD_SHARED_LIBS)
+    target_sources(leveldb_tests
+      PRIVATE
+        "db/autocompact_test.cc"
+        "db/corruption_test.cc"
+        "db/db_test.cc"
+        "db/dbformat_test.cc"
+        "db/filename_test.cc"
+        "db/log_test.cc"
+        "db/recovery_test.cc"
+        "db/skiplist_test.cc"
+        "db/version_edit_test.cc"
+        "db/version_set_test.cc"
+        "db/write_batch_test.cc"
+        "helpers/memenv/memenv_test.cc"
+        "table/filter_block_test.cc"
+        "table/table_test.cc"
+        "util/arena_test.cc"
+        "util/bloom_test.cc"
+        "util/cache_test.cc"
+        "util/coding_test.cc"
+        "util/crc32c_test.cc"
+        "util/hash_test.cc"
+        "util/logging_test.cc"
+    )
+  endif(NOT BUILD_SHARED_LIBS)
+  target_link_libraries(leveldb_tests leveldb gmock gtest gtest_main)
+  target_compile_definitions(leveldb_tests
+    PRIVATE
+      ${LEVELDB_PLATFORM_NAME}=1
+  )
+  if (NOT HAVE_CXX17_HAS_INCLUDE)
+    target_compile_definitions(leveldb_tests
+      PRIVATE
+        LEVELDB_HAS_PORT_CONFIG_H=1
+    )
+  endif(NOT HAVE_CXX17_HAS_INCLUDE)
+
+  add_test(NAME "leveldb_tests" COMMAND "leveldb_tests")
+
+  function(leveldb_test test_file)
+    get_filename_component(test_target_name "${test_file}" NAME_WE)
+
+    add_executable("${test_target_name}" "")
+    target_sources("${test_target_name}"
+      PRIVATE
+        "${PROJECT_BINARY_DIR}/${LEVELDB_PORT_CONFIG_DIR}/port_config.h"
+        "util/testutil.cc"
+        "util/testutil.h"
+
+        "${test_file}"
+    )
+    target_link_libraries("${test_target_name}" leveldb gmock gtest)
+    target_compile_definitions("${test_target_name}"
+      PRIVATE
+        ${LEVELDB_PLATFORM_NAME}=1
+    )
+    if (NOT HAVE_CXX17_HAS_INCLUDE)
+      target_compile_definitions("${test_target_name}"
+        PRIVATE
+          LEVELDB_HAS_PORT_CONFIG_H=1
+      )
+    endif(NOT HAVE_CXX17_HAS_INCLUDE)
+
+    add_test(NAME "${test_target_name}" COMMAND "${test_target_name}")
+  endfunction(leveldb_test)
+
+  leveldb_test("db/c_test.c")
+
+  if(NOT BUILD_SHARED_LIBS)
+    # TODO(costan): This test also uses
+    #               "util/env_{posix|windows}_test_helper.h"
+    if (WIN32)
+      leveldb_test("util/env_windows_test.cc")
+    else (WIN32)
+      leveldb_test("util/env_posix_test.cc")
+    endif (WIN32)
+  endif(NOT BUILD_SHARED_LIBS)
+endif(LEVELDB_BUILD_TESTS)
+
+if(LEVELDB_BUILD_BENCHMARKS)
+  # This project uses Google benchmark for benchmarking.
+  set(BENCHMARK_ENABLE_TESTING OFF CACHE BOOL "" FORCE)
+  set(BENCHMARK_ENABLE_EXCEPTIONS OFF CACHE BOOL "" FORCE)
+  add_subdirectory("third_party/benchmark")
+
+  function(leveldb_benchmark bench_file)
+    get_filename_component(bench_target_name "${bench_file}" NAME_WE)
+
+    add_executable("${bench_target_name}" "")
+    target_sources("${bench_target_name}"
+      PRIVATE
+        "${PROJECT_BINARY_DIR}/${LEVELDB_PORT_CONFIG_DIR}/port_config.h"
+        "util/histogram.cc"
+        "util/histogram.h"
+        "util/testutil.cc"
+        "util/testutil.h"
+
+        "${bench_file}"
+    )
+    target_link_libraries("${bench_target_name}" leveldb gmock gtest benchmark)
+    target_compile_definitions("${bench_target_name}"
+      PRIVATE
+        ${LEVELDB_PLATFORM_NAME}=1
+    )
+    if (NOT HAVE_CXX17_HAS_INCLUDE)
+      target_compile_definitions("${bench_target_name}"
+        PRIVATE
+          LEVELDB_HAS_PORT_CONFIG_H=1
+      )
+    endif(NOT HAVE_CXX17_HAS_INCLUDE)
+  endfunction(leveldb_benchmark)
+
+  if(NOT BUILD_SHARED_LIBS)
+    leveldb_benchmark("benchmarks/db_bench.cc")
+  endif(NOT BUILD_SHARED_LIBS)
+
+  check_library_exists(sqlite3 sqlite3_open "" HAVE_SQLITE3)
+  if(HAVE_SQLITE3)
+    leveldb_benchmark("benchmarks/db_bench_sqlite3.cc")
+    target_link_libraries(db_bench_sqlite3 sqlite3)
+  endif(HAVE_SQLITE3)
+
+  # check_library_exists is insufficient here because the library names have
+  # different manglings when compiled with clang or gcc, at least when installed
+  # with Homebrew on Mac.
+  set(OLD_CMAKE_REQURED_LIBRARIES ${CMAKE_REQUIRED_LIBRARIES})
+  list(APPEND CMAKE_REQUIRED_LIBRARIES kyotocabinet)
+  check_cxx_source_compiles("
+#include <kcpolydb.h>
+
+int main() {
+  kyotocabinet::TreeDB* db = new kyotocabinet::TreeDB();
+  delete db;
+  return 0;
+}
+  "  HAVE_KYOTOCABINET)
+  set(CMAKE_REQUIRED_LIBRARIES ${OLD_CMAKE_REQURED_LIBRARIES})
+  if(HAVE_KYOTOCABINET)
+    leveldb_benchmark("benchmarks/db_bench_tree_db.cc")
+    target_link_libraries(db_bench_tree_db kyotocabinet)
+  endif(HAVE_KYOTOCABINET)
+endif(LEVELDB_BUILD_BENCHMARKS)
+
+if(LEVELDB_INSTALL)
+  install(TARGETS leveldb
+    EXPORT leveldbTargets
+    RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
+    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
+    ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
+  )
+  install(
+    FILES
+      "${LEVELDB_PUBLIC_INCLUDE_DIR}/c.h"
+      "${LEVELDB_PUBLIC_INCLUDE_DIR}/cache.h"
+      "${LEVELDB_PUBLIC_INCLUDE_DIR}/comparator.h"
+      "${LEVELDB_PUBLIC_INCLUDE_DIR}/db.h"
+      "${LEVELDB_PUBLIC_INCLUDE_DIR}/dumpfile.h"
+      "${LEVELDB_PUBLIC_INCLUDE_DIR}/env.h"
+      "${LEVELDB_PUBLIC_INCLUDE_DIR}/export.h"
+      "${LEVELDB_PUBLIC_INCLUDE_DIR}/filter_policy.h"
+      "${LEVELDB_PUBLIC_INCLUDE_DIR}/iterator.h"
+      "${LEVELDB_PUBLIC_INCLUDE_DIR}/options.h"
+      "${LEVELDB_PUBLIC_INCLUDE_DIR}/slice.h"
+      "${LEVELDB_PUBLIC_INCLUDE_DIR}/status.h"
+      "${LEVELDB_PUBLIC_INCLUDE_DIR}/table_builder.h"
+      "${LEVELDB_PUBLIC_INCLUDE_DIR}/table.h"
+      "${LEVELDB_PUBLIC_INCLUDE_DIR}/write_batch.h"
+    DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/leveldb"
+  )
+
+  include(CMakePackageConfigHelpers)
+  configure_package_config_file(
+    "cmake/${PROJECT_NAME}Config.cmake.in"
+    "${PROJECT_BINARY_DIR}/cmake/${PROJECT_NAME}Config.cmake"
+    INSTALL_DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME}"
+  )
+  write_basic_package_version_file(
+    "${PROJECT_BINARY_DIR}/cmake/${PROJECT_NAME}ConfigVersion.cmake"
+    COMPATIBILITY SameMajorVersion
+  )
+  install(
+    EXPORT leveldbTargets
+    NAMESPACE leveldb::
+    DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME}"
+  )
+  install(
+    FILES
+      "${PROJECT_BINARY_DIR}/cmake/${PROJECT_NAME}Config.cmake"
+      "${PROJECT_BINARY_DIR}/cmake/${PROJECT_NAME}ConfigVersion.cmake"
+    DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME}"
+  )
+endif(LEVELDB_INSTALL)
+
+
+add_executable(db_test2
+        "${PROJECT_SOURCE_DIR}/test/db_test2.cc"
+)
+target_link_libraries(db_test2 PRIVATE leveldb)
+
+
+add_executable(ttl_test
+        "${PROJECT_SOURCE_DIR}/test/ttl_test.cc"
+)
+target_link_libraries(ttl_test PRIVATE leveldb gtest)
\ No newline at end of file
diff --git a/leveldb_base/CONTRIBUTING.md b/leveldb_base/CONTRIBUTING.md
new file mode 100644
index 0000000..3cf27bb
--- /dev/null
+++ b/leveldb_base/CONTRIBUTING.md
@@ -0,0 +1,31 @@
+# How to Contribute
+
+We'd love to accept your patches and contributions to this project. There are
+just a few small guidelines you need to follow.
+
+## Contributor License Agreement
+
+Contributions to this project must be accompanied by a Contributor License
+Agreement. You (or your employer) retain the copyright to your contribution;
+this simply gives us permission to use and redistribute your contributions as
+part of the project. Head over to <https://cla.developers.google.com/> to see
+your current agreements on file or to sign a new one.
+
+You generally only need to submit a CLA once, so if you've already submitted one
+(even if it was for a different project), you probably don't need to do it
+again.
+
+## Code Reviews
+
+All submissions, including submissions by project members, require review. We
+use GitHub pull requests for this purpose. Consult
+[GitHub Help](https://help.github.com/articles/about-pull-requests/) for more
+information on using pull requests.
+
+See [the README](README.md#contributing-to-the-leveldb-project) for areas
+where we are likely to accept external contributions.
+
+## Community Guidelines
+
+This project follows [Google's Open Source Community
+Guidelines](https://opensource.google/conduct/).
\ No newline at end of file
diff --git a/leveldb_base/LICENSE b/leveldb_base/LICENSE
new file mode 100644
index 0000000..8e80208
--- /dev/null
+++ b/leveldb_base/LICENSE
@@ -0,0 +1,27 @@
+Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/leveldb_base/NEWS b/leveldb_base/NEWS
new file mode 100644
index 0000000..3fd9924
--- /dev/null
+++ b/leveldb_base/NEWS
@@ -0,0 +1,17 @@
+Release 1.2 2011-05-16
+----------------------
+
+Fixes for larger databases (tested up to one billion 100-byte entries,
+i.e., ~100GB).
+
+(1) Place hard limit on number of level-0 files.  This fixes errors
+of the form "too many open files".
+
+(2) Fixed memtable management.  Before the fix, a heavy write burst
+could cause unbounded memory usage.
+
+A fix for a logging bug where the reader would incorrectly complain
+about corruption.
+
+Allow public access to WriteBatch contents so that users can easily
+wrap a DB.
diff --git a/leveldb_base/README.md b/leveldb_base/README.md
new file mode 100644
index 0000000..a9ce668
--- /dev/null
+++ b/leveldb_base/README.md
@@ -0,0 +1,9 @@
+
+**本仓库提供TTL基本的测试用例**
+
+克隆代码：
+
+```bash
+git clone --recurse-submodules https://gitea.shuishan.net.cn/building_data_management_systems.Xuanzhou.2024Fall.DaSE/leveldb_base.git
+```
+
diff --git a/leveldb_base/TODO b/leveldb_base/TODO
new file mode 100644
index 0000000..e603c07
--- /dev/null
+++ b/leveldb_base/TODO
@@ -0,0 +1,14 @@
+ss
+- Stats
+
+db
+- Maybe implement DB::BulkDeleteForRange(start_key, end_key)
+  that would blow away files whose ranges are entirely contained
+  within [start_key..end_key]?  For Chrome, deletion of obsolete
+  object stores, etc. can be done in the background anyway, so
+  probably not that important.
+- There have been requests for MultiGet.
+
+After a range is completely deleted, what gets rid of the
+corresponding files if we do no future changes to that range.  Make
+the conditions for triggering compactions fire in more situations?
diff --git a/leveldb_base/benchmarks/db_bench.cc b/leveldb_base/benchmarks/db_bench.cc
new file mode 100644
index 0000000..8e3f4e7
--- /dev/null
+++ b/leveldb_base/benchmarks/db_bench.cc
@@ -0,0 +1,1138 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include <sys/types.h>
+
+#include <atomic>
+#include <cstdio>
+#include <cstdlib>
+
+#include "leveldb/cache.h"
+#include "leveldb/comparator.h"
+#include "leveldb/db.h"
+#include "leveldb/env.h"
+#include "leveldb/filter_policy.h"
+#include "leveldb/write_batch.h"
+#include "port/port.h"
+#include "util/crc32c.h"
+#include "util/histogram.h"
+#include "util/mutexlock.h"
+#include "util/random.h"
+#include "util/testutil.h"
+
+// Comma-separated list of operations to run in the specified order
+//   Actual benchmarks:
+//      fillseq       -- write N values in sequential key order in async mode
+//      fillrandom    -- write N values in random key order in async mode
+//      overwrite     -- overwrite N values in random key order in async mode
+//      fillsync      -- write N/100 values in random key order in sync mode
+//      fill100K      -- write N/1000 100K values in random order in async mode
+//      deleteseq     -- delete N keys in sequential order
+//      deleterandom  -- delete N keys in random order
+//      readseq       -- read N times sequentially
+//      readreverse   -- read N times in reverse order
+//      readrandom    -- read N times in random order
+//      readmissing   -- read N missing keys in random order
+//      readhot       -- read N times in random order from 1% section of DB
+//      seekrandom    -- N random seeks
+//      seekordered   -- N ordered seeks
+//      open          -- cost of opening a DB
+//      crc32c        -- repeated crc32c of 4K of data
+//   Meta operations:
+//      compact     -- Compact the entire DB
+//      stats       -- Print DB stats
+//      sstables    -- Print sstable info
+//      heapprofile -- Dump a heap profile (if supported by this port)
+static const char* FLAGS_benchmarks =
+    "fillseq,"
+    "fillsync,"
+    "fillrandom,"
+    "overwrite,"
+    "readrandom,"
+    "readrandom,"  // Extra run to allow previous compactions to quiesce
+    "readseq,"
+    "readreverse,"
+    "compact,"
+    "readrandom,"
+    "readseq,"
+    "readreverse,"
+    "fill100K,"
+    "crc32c,"
+    "snappycomp,"
+    "snappyuncomp,"
+    "zstdcomp,"
+    "zstduncomp,";
+
+// Number of key/values to place in database
+static int FLAGS_num = 1000000;
+
+// Number of read operations to do.  If negative, do FLAGS_num reads.
+static int FLAGS_reads = -1;
+
+// Number of concurrent threads to run.
+static int FLAGS_threads = 1;
+
+// Size of each value
+static int FLAGS_value_size = 100;
+
+// Arrange to generate values that shrink to this fraction of
+// their original size after compression
+static double FLAGS_compression_ratio = 0.5;
+
+// Print histogram of operation timings
+static bool FLAGS_histogram = false;
+
+// Count the number of string comparisons performed
+static bool FLAGS_comparisons = false;
+
+// Number of bytes to buffer in memtable before compacting
+// (initialized to default value by "main")
+static int FLAGS_write_buffer_size = 0;
+
+// Number of bytes written to each file.
+// (initialized to default value by "main")
+static int FLAGS_max_file_size = 0;
+
+// Approximate size of user data packed per block (before compression.
+// (initialized to default value by "main")
+static int FLAGS_block_size = 0;
+
+// Number of bytes to use as a cache of uncompressed data.
+// Negative means use default settings.
+static int FLAGS_cache_size = -1;
+
+// Maximum number of files to keep open at the same time (use default if == 0)
+static int FLAGS_open_files = 0;
+
+// Bloom filter bits per key.
+// Negative means use default settings.
+static int FLAGS_bloom_bits = -1;
+
+// Common key prefix length.
+static int FLAGS_key_prefix = 0;
+
+// If true, do not destroy the existing database.  If you set this
+// flag and also specify a benchmark that wants a fresh database, that
+// benchmark will fail.
+static bool FLAGS_use_existing_db = false;
+
+// If true, reuse existing log/MANIFEST files when re-opening a database.
+static bool FLAGS_reuse_logs = false;
+
+// If true, use compression.
+static bool FLAGS_compression = true;
+
+// Use the db with the following name.
+static const char* FLAGS_db = nullptr;
+
+// ZSTD compression level to try out
+static int FLAGS_zstd_compression_level = 1;
+
+namespace leveldb {
+
+namespace {
+leveldb::Env* g_env = nullptr;
+
+class CountComparator : public Comparator {
+ public:
+  CountComparator(const Comparator* wrapped) : wrapped_(wrapped) {}
+  ~CountComparator() override {}
+  int Compare(const Slice& a, const Slice& b) const override {
+    count_.fetch_add(1, std::memory_order_relaxed);
+    return wrapped_->Compare(a, b);
+  }
+  const char* Name() const override { return wrapped_->Name(); }
+  void FindShortestSeparator(std::string* start,
+                             const Slice& limit) const override {
+    wrapped_->FindShortestSeparator(start, limit);
+  }
+
+  void FindShortSuccessor(std::string* key) const override {
+    return wrapped_->FindShortSuccessor(key);
+  }
+
+  size_t comparisons() const { return count_.load(std::memory_order_relaxed); }
+
+  void reset() { count_.store(0, std::memory_order_relaxed); }
+
+ private:
+  mutable std::atomic<size_t> count_{0};
+  const Comparator* const wrapped_;
+};
+
+// Helper for quickly generating random data.
+class RandomGenerator {
+ private:
+  std::string data_;
+  int pos_;
+
+ public:
+  RandomGenerator() {
+    // We use a limited amount of data over and over again and ensure
+    // that it is larger than the compression window (32KB), and also
+    // large enough to serve all typical value sizes we want to write.
+    Random rnd(301);
+    std::string piece;
+    while (data_.size() < 1048576) {
+      // Add a short fragment that is as compressible as specified
+      // by FLAGS_compression_ratio.
+      test::CompressibleString(&rnd, FLAGS_compression_ratio, 100, &piece);
+      data_.append(piece);
+    }
+    pos_ = 0;
+  }
+
+  Slice Generate(size_t len) {
+    if (pos_ + len > data_.size()) {
+      pos_ = 0;
+      assert(len < data_.size());
+    }
+    pos_ += len;
+    return Slice(data_.data() + pos_ - len, len);
+  }
+};
+
+class KeyBuffer {
+ public:
+  KeyBuffer() {
+    assert(FLAGS_key_prefix < sizeof(buffer_));
+    memset(buffer_, 'a', FLAGS_key_prefix);
+  }
+  KeyBuffer& operator=(KeyBuffer& other) = delete;
+  KeyBuffer(KeyBuffer& other) = delete;
+
+  void Set(int k) {
+    std::snprintf(buffer_ + FLAGS_key_prefix,
+                  sizeof(buffer_) - FLAGS_key_prefix, "%016d", k);
+  }
+
+  Slice slice() const { return Slice(buffer_, FLAGS_key_prefix + 16); }
+
+ private:
+  char buffer_[1024];
+};
+
+#if defined(__linux)
+static Slice TrimSpace(Slice s) {
+  size_t start = 0;
+  while (start < s.size() && isspace(s[start])) {
+    start++;
+  }
+  size_t limit = s.size();
+  while (limit > start && isspace(s[limit - 1])) {
+    limit--;
+  }
+  return Slice(s.data() + start, limit - start);
+}
+#endif
+
+static void AppendWithSpace(std::string* str, Slice msg) {
+  if (msg.empty()) return;
+  if (!str->empty()) {
+    str->push_back(' ');
+  }
+  str->append(msg.data(), msg.size());
+}
+
+class Stats {
+ private:
+  double start_;
+  double finish_;
+  double seconds_;
+  int done_;
+  int next_report_;
+  int64_t bytes_;
+  double last_op_finish_;
+  Histogram hist_;
+  std::string message_;
+
+ public:
+  Stats() { Start(); }
+
+  void Start() {
+    next_report_ = 100;
+    hist_.Clear();
+    done_ = 0;
+    bytes_ = 0;
+    seconds_ = 0;
+    message_.clear();
+    start_ = finish_ = last_op_finish_ = g_env->NowMicros();
+  }
+
+  void Merge(const Stats& other) {
+    hist_.Merge(other.hist_);
+    done_ += other.done_;
+    bytes_ += other.bytes_;
+    seconds_ += other.seconds_;
+    if (other.start_ < start_) start_ = other.start_;
+    if (other.finish_ > finish_) finish_ = other.finish_;
+
+    // Just keep the messages from one thread
+    if (message_.empty()) message_ = other.message_;
+  }
+
+  void Stop() {
+    finish_ = g_env->NowMicros();
+    seconds_ = (finish_ - start_) * 1e-6;
+  }
+
+  void AddMessage(Slice msg) { AppendWithSpace(&message_, msg); }
+
+  void FinishedSingleOp() {
+    if (FLAGS_histogram) {
+      double now = g_env->NowMicros();
+      double micros = now - last_op_finish_;
+      hist_.Add(micros);
+      if (micros > 20000) {
+        std::fprintf(stderr, "long op: %.1f micros%30s\r", micros, "");
+        std::fflush(stderr);
+      }
+      last_op_finish_ = now;
+    }
+
+    done_++;
+    if (done_ >= next_report_) {
+      if (next_report_ < 1000)
+        next_report_ += 100;
+      else if (next_report_ < 5000)
+        next_report_ += 500;
+      else if (next_report_ < 10000)
+        next_report_ += 1000;
+      else if (next_report_ < 50000)
+        next_report_ += 5000;
+      else if (next_report_ < 100000)
+        next_report_ += 10000;
+      else if (next_report_ < 500000)
+        next_report_ += 50000;
+      else
+        next_report_ += 100000;
+      std::fprintf(stderr, "... finished %d ops%30s\r", done_, "");
+      std::fflush(stderr);
+    }
+  }
+
+  void AddBytes(int64_t n) { bytes_ += n; }
+
+  void Report(const Slice& name) {
+    // Pretend at least one op was done in case we are running a benchmark
+    // that does not call FinishedSingleOp().
+    if (done_ < 1) done_ = 1;
+
+    std::string extra;
+    if (bytes_ > 0) {
+      // Rate is computed on actual elapsed time, not the sum of per-thread
+      // elapsed times.
+      double elapsed = (finish_ - start_) * 1e-6;
+      char rate[100];
+      std::snprintf(rate, sizeof(rate), "%6.1f MB/s",
+                    (bytes_ / 1048576.0) / elapsed);
+      extra = rate;
+    }
+    AppendWithSpace(&extra, message_);
+
+    std::fprintf(stdout, "%-12s : %11.3f micros/op;%s%s\n",
+                 name.ToString().c_str(), seconds_ * 1e6 / done_,
+                 (extra.empty() ? "" : " "), extra.c_str());
+    if (FLAGS_histogram) {
+      std::fprintf(stdout, "Microseconds per op:\n%s\n",
+                   hist_.ToString().c_str());
+    }
+    std::fflush(stdout);
+  }
+};
+
+// State shared by all concurrent executions of the same benchmark.
+struct SharedState {
+  port::Mutex mu;
+  port::CondVar cv GUARDED_BY(mu);
+  int total GUARDED_BY(mu);
+
+  // Each thread goes through the following states:
+  //    (1) initializing
+  //    (2) waiting for others to be initialized
+  //    (3) running
+  //    (4) done
+
+  int num_initialized GUARDED_BY(mu);
+  int num_done GUARDED_BY(mu);
+  bool start GUARDED_BY(mu);
+
+  SharedState(int total)
+      : cv(&mu), total(total), num_initialized(0), num_done(0), start(false) {}
+};
+
+// Per-thread state for concurrent executions of the same benchmark.
+struct ThreadState {
+  int tid;      // 0..n-1 when running in n threads
+  Random rand;  // Has different seeds for different threads
+  Stats stats;
+  SharedState* shared;
+
+  ThreadState(int index, int seed) : tid(index), rand(seed), shared(nullptr) {}
+};
+
+void Compress(
+    ThreadState* thread, std::string name,
+    std::function<bool(const char*, size_t, std::string*)> compress_func) {
+  RandomGenerator gen;
+  Slice input = gen.Generate(Options().block_size);
+  int64_t bytes = 0;
+  int64_t produced = 0;
+  bool ok = true;
+  std::string compressed;
+  while (ok && bytes < 1024 * 1048576) {  // Compress 1G
+    ok = compress_func(input.data(), input.size(), &compressed);
+    produced += compressed.size();
+    bytes += input.size();
+    thread->stats.FinishedSingleOp();
+  }
+
+  if (!ok) {
+    thread->stats.AddMessage("(" + name + " failure)");
+  } else {
+    char buf[100];
+    std::snprintf(buf, sizeof(buf), "(output: %.1f%%)",
+                  (produced * 100.0) / bytes);
+    thread->stats.AddMessage(buf);
+    thread->stats.AddBytes(bytes);
+  }
+}
+
+void Uncompress(
+    ThreadState* thread, std::string name,
+    std::function<bool(const char*, size_t, std::string*)> compress_func,
+    std::function<bool(const char*, size_t, char*)> uncompress_func) {
+  RandomGenerator gen;
+  Slice input = gen.Generate(Options().block_size);
+  std::string compressed;
+  bool ok = compress_func(input.data(), input.size(), &compressed);
+  int64_t bytes = 0;
+  char* uncompressed = new char[input.size()];
+  while (ok && bytes < 1024 * 1048576) {  // Compress 1G
+    ok = uncompress_func(compressed.data(), compressed.size(), uncompressed);
+    bytes += input.size();
+    thread->stats.FinishedSingleOp();
+  }
+  delete[] uncompressed;
+
+  if (!ok) {
+    thread->stats.AddMessage("(" + name + " failure)");
+  } else {
+    thread->stats.AddBytes(bytes);
+  }
+}
+
+}  // namespace
+
+class Benchmark {
+ private:
+  Cache* cache_;
+  const FilterPolicy* filter_policy_;
+  DB* db_;
+  int num_;
+  int value_size_;
+  int entries_per_batch_;
+  WriteOptions write_options_;
+  int reads_;
+  int heap_counter_;
+  CountComparator count_comparator_;
+  int total_thread_count_;
+
+  void PrintHeader() {
+    const int kKeySize = 16 + FLAGS_key_prefix;
+    PrintEnvironment();
+    std::fprintf(stdout, "Keys:       %d bytes each\n", kKeySize);
+    std::fprintf(
+        stdout, "Values:     %d bytes each (%d bytes after compression)\n",
+        FLAGS_value_size,
+        static_cast<int>(FLAGS_value_size * FLAGS_compression_ratio + 0.5));
+    std::fprintf(stdout, "Entries:    %d\n", num_);
+    std::fprintf(stdout, "RawSize:    %.1f MB (estimated)\n",
+                 ((static_cast<int64_t>(kKeySize + FLAGS_value_size) * num_) /
+                  1048576.0));
+    std::fprintf(
+        stdout, "FileSize:   %.1f MB (estimated)\n",
+        (((kKeySize + FLAGS_value_size * FLAGS_compression_ratio) * num_) /
+         1048576.0));
+    PrintWarnings();
+    std::fprintf(stdout, "------------------------------------------------\n");
+  }
+
+  void PrintWarnings() {
+#if defined(__GNUC__) && !defined(__OPTIMIZE__)
+    std::fprintf(
+        stdout,
+        "WARNING: Optimization is disabled: benchmarks unnecessarily slow\n");
+#endif
+#ifndef NDEBUG
+    std::fprintf(
+        stdout,
+        "WARNING: Assertions are enabled; benchmarks unnecessarily slow\n");
+#endif
+
+    // See if snappy is working by attempting to compress a compressible string
+    const char text[] = "yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy";
+    std::string compressed;
+    if (!port::Snappy_Compress(text, sizeof(text), &compressed)) {
+      std::fprintf(stdout, "WARNING: Snappy compression is not enabled\n");
+    } else if (compressed.size() >= sizeof(text)) {
+      std::fprintf(stdout, "WARNING: Snappy compression is not effective\n");
+    }
+  }
+
+  void PrintEnvironment() {
+    std::fprintf(stderr, "LevelDB:    version %d.%d\n", kMajorVersion,
+                 kMinorVersion);
+
+#if defined(__linux)
+    time_t now = time(nullptr);
+    std::fprintf(stderr, "Date:       %s",
+                 ctime(&now));  // ctime() adds newline
+
+    FILE* cpuinfo = std::fopen("/proc/cpuinfo", "r");
+    if (cpuinfo != nullptr) {
+      char line[1000];
+      int num_cpus = 0;
+      std::string cpu_type;
+      std::string cache_size;
+      while (fgets(line, sizeof(line), cpuinfo) != nullptr) {
+        const char* sep = strchr(line, ':');
+        if (sep == nullptr) {
+          continue;
+        }
+        Slice key = TrimSpace(Slice(line, sep - 1 - line));
+        Slice val = TrimSpace(Slice(sep + 1));
+        if (key == "model name") {
+          ++num_cpus;
+          cpu_type = val.ToString();
+        } else if (key == "cache size") {
+          cache_size = val.ToString();
+        }
+      }
+      std::fclose(cpuinfo);
+      std::fprintf(stderr, "CPU:        %d * %s\n", num_cpus, cpu_type.c_str());
+      std::fprintf(stderr, "CPUCache:   %s\n", cache_size.c_str());
+    }
+#endif
+  }
+
+ public:
+  Benchmark()
+      : cache_(FLAGS_cache_size >= 0 ? NewLRUCache(FLAGS_cache_size) : nullptr),
+        filter_policy_(FLAGS_bloom_bits >= 0
+                           ? NewBloomFilterPolicy(FLAGS_bloom_bits)
+                           : nullptr),
+        db_(nullptr),
+        num_(FLAGS_num),
+        value_size_(FLAGS_value_size),
+        entries_per_batch_(1),
+        reads_(FLAGS_reads < 0 ? FLAGS_num : FLAGS_reads),
+        heap_counter_(0),
+        count_comparator_(BytewiseComparator()),
+        total_thread_count_(0) {
+    std::vector<std::string> files;
+    g_env->GetChildren(FLAGS_db, &files);
+    for (size_t i = 0; i < files.size(); i++) {
+      if (Slice(files[i]).starts_with("heap-")) {
+        g_env->RemoveFile(std::string(FLAGS_db) + "/" + files[i]);
+      }
+    }
+    if (!FLAGS_use_existing_db) {
+      DestroyDB(FLAGS_db, Options());
+    }
+  }
+
+  ~Benchmark() {
+    delete db_;
+    delete cache_;
+    delete filter_policy_;
+  }
+
+  void Run() {
+    PrintHeader();
+    Open();
+
+    const char* benchmarks = FLAGS_benchmarks;
+    while (benchmarks != nullptr) {
+      const char* sep = strchr(benchmarks, ',');
+      Slice name;
+      if (sep == nullptr) {
+        name = benchmarks;
+        benchmarks = nullptr;
+      } else {
+        name = Slice(benchmarks, sep - benchmarks);
+        benchmarks = sep + 1;
+      }
+
+      // Reset parameters that may be overridden below
+      num_ = FLAGS_num;
+      reads_ = (FLAGS_reads < 0 ? FLAGS_num : FLAGS_reads);
+      value_size_ = FLAGS_value_size;
+      entries_per_batch_ = 1;
+      write_options_ = WriteOptions();
+
+      void (Benchmark::*method)(ThreadState*) = nullptr;
+      bool fresh_db = false;
+      int num_threads = FLAGS_threads;
+
+      if (name == Slice("open")) {
+        method = &Benchmark::OpenBench;
+        num_ /= 10000;
+        if (num_ < 1) num_ = 1;
+      } else if (name == Slice("fillseq")) {
+        fresh_db = true;
+        method = &Benchmark::WriteSeq;
+      } else if (name == Slice("fillbatch")) {
+        fresh_db = true;
+        entries_per_batch_ = 1000;
+        method = &Benchmark::WriteSeq;
+      } else if (name == Slice("fillrandom")) {
+        fresh_db = true;
+        method = &Benchmark::WriteRandom;
+      } else if (name == Slice("overwrite")) {
+        fresh_db = false;
+        method = &Benchmark::WriteRandom;
+      } else if (name == Slice("fillsync")) {
+        fresh_db = true;
+        num_ /= 1000;
+        write_options_.sync = true;
+        method = &Benchmark::WriteRandom;
+      } else if (name == Slice("fill100K")) {
+        fresh_db = true;
+        num_ /= 1000;
+        value_size_ = 100 * 1000;
+        method = &Benchmark::WriteRandom;
+      } else if (name == Slice("readseq")) {
+        method = &Benchmark::ReadSequential;
+      } else if (name == Slice("readreverse")) {
+        method = &Benchmark::ReadReverse;
+      } else if (name == Slice("readrandom")) {
+        method = &Benchmark::ReadRandom;
+      } else if (name == Slice("readmissing")) {
+        method = &Benchmark::ReadMissing;
+      } else if (name == Slice("seekrandom")) {
+        method = &Benchmark::SeekRandom;
+      } else if (name == Slice("seekordered")) {
+        method = &Benchmark::SeekOrdered;
+      } else if (name == Slice("readhot")) {
+        method = &Benchmark::ReadHot;
+      } else if (name == Slice("readrandomsmall")) {
+        reads_ /= 1000;
+        method = &Benchmark::ReadRandom;
+      } else if (name == Slice("deleteseq")) {
+        method = &Benchmark::DeleteSeq;
+      } else if (name == Slice("deleterandom")) {
+        method = &Benchmark::DeleteRandom;
+      } else if (name == Slice("readwhilewriting")) {
+        num_threads++;  // Add extra thread for writing
+        method = &Benchmark::ReadWhileWriting;
+      } else if (name == Slice("compact")) {
+        method = &Benchmark::Compact;
+      } else if (name == Slice("crc32c")) {
+        method = &Benchmark::Crc32c;
+      } else if (name == Slice("snappycomp")) {
+        method = &Benchmark::SnappyCompress;
+      } else if (name == Slice("snappyuncomp")) {
+        method = &Benchmark::SnappyUncompress;
+      } else if (name == Slice("zstdcomp")) {
+        method = &Benchmark::ZstdCompress;
+      } else if (name == Slice("zstduncomp")) {
+        method = &Benchmark::ZstdUncompress;
+      } else if (name == Slice("heapprofile")) {
+        HeapProfile();
+      } else if (name == Slice("stats")) {
+        PrintStats("leveldb.stats");
+      } else if (name == Slice("sstables")) {
+        PrintStats("leveldb.sstables");
+      } else {
+        if (!name.empty()) {  // No error message for empty name
+          std::fprintf(stderr, "unknown benchmark '%s'\n",
+                       name.ToString().c_str());
+        }
+      }
+
+      if (fresh_db) {
+        if (FLAGS_use_existing_db) {
+          std::fprintf(stdout, "%-12s : skipped (--use_existing_db is true)\n",
+                       name.ToString().c_str());
+          method = nullptr;
+        } else {
+          delete db_;
+          db_ = nullptr;
+          DestroyDB(FLAGS_db, Options());
+          Open();
+        }
+      }
+
+      if (method != nullptr) {
+        RunBenchmark(num_threads, name, method);
+      }
+    }
+  }
+
+ private:
+  struct ThreadArg {
+    Benchmark* bm;
+    SharedState* shared;
+    ThreadState* thread;
+    void (Benchmark::*method)(ThreadState*);
+  };
+
+  static void ThreadBody(void* v) {
+    ThreadArg* arg = reinterpret_cast<ThreadArg*>(v);
+    SharedState* shared = arg->shared;
+    ThreadState* thread = arg->thread;
+    {
+      MutexLock l(&shared->mu);
+      shared->num_initialized++;
+      if (shared->num_initialized >= shared->total) {
+        shared->cv.SignalAll();
+      }
+      while (!shared->start) {
+        shared->cv.Wait();
+      }
+    }
+
+    thread->stats.Start();
+    (arg->bm->*(arg->method))(thread);
+    thread->stats.Stop();
+
+    {
+      MutexLock l(&shared->mu);
+      shared->num_done++;
+      if (shared->num_done >= shared->total) {
+        shared->cv.SignalAll();
+      }
+    }
+  }
+
+  void RunBenchmark(int n, Slice name,
+                    void (Benchmark::*method)(ThreadState*)) {
+    SharedState shared(n);
+
+    ThreadArg* arg = new ThreadArg[n];
+    for (int i = 0; i < n; i++) {
+      arg[i].bm = this;
+      arg[i].method = method;
+      arg[i].shared = &shared;
+      ++total_thread_count_;
+      // Seed the thread's random state deterministically based upon thread
+      // creation across all benchmarks. This ensures that the seeds are unique
+      // but reproducible when rerunning the same set of benchmarks.
+      arg[i].thread = new ThreadState(i, /*seed=*/1000 + total_thread_count_);
+      arg[i].thread->shared = &shared;
+      g_env->StartThread(ThreadBody, &arg[i]);
+    }
+
+    shared.mu.Lock();
+    while (shared.num_initialized < n) {
+      shared.cv.Wait();
+    }
+
+    shared.start = true;
+    shared.cv.SignalAll();
+    while (shared.num_done < n) {
+      shared.cv.Wait();
+    }
+    shared.mu.Unlock();
+
+    for (int i = 1; i < n; i++) {
+      arg[0].thread->stats.Merge(arg[i].thread->stats);
+    }
+    arg[0].thread->stats.Report(name);
+    if (FLAGS_comparisons) {
+      fprintf(stdout, "Comparisons: %zu\n", count_comparator_.comparisons());
+      count_comparator_.reset();
+      fflush(stdout);
+    }
+
+    for (int i = 0; i < n; i++) {
+      delete arg[i].thread;
+    }
+    delete[] arg;
+  }
+
+  void Crc32c(ThreadState* thread) {
+    // Checksum about 500MB of data total
+    const int size = 4096;
+    const char* label = "(4K per op)";
+    std::string data(size, 'x');
+    int64_t bytes = 0;
+    uint32_t crc = 0;
+    while (bytes < 500 * 1048576) {
+      crc = crc32c::Value(data.data(), size);
+      thread->stats.FinishedSingleOp();
+      bytes += size;
+    }
+    // Print so result is not dead
+    std::fprintf(stderr, "... crc=0x%x\r", static_cast<unsigned int>(crc));
+
+    thread->stats.AddBytes(bytes);
+    thread->stats.AddMessage(label);
+  }
+
+  void SnappyCompress(ThreadState* thread) {
+    Compress(thread, "snappy", &port::Snappy_Compress);
+  }
+
+  void SnappyUncompress(ThreadState* thread) {
+    Uncompress(thread, "snappy", &port::Snappy_Compress,
+               &port::Snappy_Uncompress);
+  }
+
+  void ZstdCompress(ThreadState* thread) {
+    Compress(thread, "zstd",
+             [](const char* input, size_t length, std::string* output) {
+               return port::Zstd_Compress(FLAGS_zstd_compression_level, input,
+                                          length, output);
+             });
+  }
+
+  void ZstdUncompress(ThreadState* thread) {
+    Uncompress(
+        thread, "zstd",
+        [](const char* input, size_t length, std::string* output) {
+          return port::Zstd_Compress(FLAGS_zstd_compression_level, input,
+                                     length, output);
+        },
+        &port::Zstd_Uncompress);
+  }
+
+  void Open() {
+    assert(db_ == nullptr);
+    Options options;
+    options.env = g_env;
+    options.create_if_missing = !FLAGS_use_existing_db;
+    options.block_cache = cache_;
+    options.write_buffer_size = FLAGS_write_buffer_size;
+    options.max_file_size = FLAGS_max_file_size;
+    options.block_size = FLAGS_block_size;
+    if (FLAGS_comparisons) {
+      options.comparator = &count_comparator_;
+    }
+    options.max_open_files = FLAGS_open_files;
+    options.filter_policy = filter_policy_;
+    options.reuse_logs = FLAGS_reuse_logs;
+    options.compression =
+        FLAGS_compression ? kSnappyCompression : kNoCompression;
+    Status s = DB::Open(options, FLAGS_db, &db_);
+    if (!s.ok()) {
+      std::fprintf(stderr, "open error: %s\n", s.ToString().c_str());
+      std::exit(1);
+    }
+  }
+
+  void OpenBench(ThreadState* thread) {
+    for (int i = 0; i < num_; i++) {
+      delete db_;
+      Open();
+      thread->stats.FinishedSingleOp();
+    }
+  }
+
+  void WriteSeq(ThreadState* thread) { DoWrite(thread, true); }
+
+  void WriteRandom(ThreadState* thread) { DoWrite(thread, false); }
+
+  void DoWrite(ThreadState* thread, bool seq) {
+    if (num_ != FLAGS_num) {
+      char msg[100];
+      std::snprintf(msg, sizeof(msg), "(%d ops)", num_);
+      thread->stats.AddMessage(msg);
+    }
+
+    RandomGenerator gen;
+    WriteBatch batch;
+    Status s;
+    int64_t bytes = 0;
+    KeyBuffer key;
+    for (int i = 0; i < num_; i += entries_per_batch_) {
+      batch.Clear();
+      for (int j = 0; j < entries_per_batch_; j++) {
+        const int k = seq ? i + j : thread->rand.Uniform(FLAGS_num);
+        key.Set(k);
+        batch.Put(key.slice(), gen.Generate(value_size_));
+        bytes += value_size_ + key.slice().size();
+        thread->stats.FinishedSingleOp();
+      }
+      s = db_->Write(write_options_, &batch);
+      if (!s.ok()) {
+        std::fprintf(stderr, "put error: %s\n", s.ToString().c_str());
+        std::exit(1);
+      }
+    }
+    thread->stats.AddBytes(bytes);
+  }
+
+  void ReadSequential(ThreadState* thread) {
+    Iterator* iter = db_->NewIterator(ReadOptions());
+    int i = 0;
+    int64_t bytes = 0;
+    for (iter->SeekToFirst(); i < reads_ && iter->Valid(); iter->Next()) {
+      bytes += iter->key().size() + iter->value().size();
+      thread->stats.FinishedSingleOp();
+      ++i;
+    }
+    delete iter;
+    thread->stats.AddBytes(bytes);
+  }
+
+  void ReadReverse(ThreadState* thread) {
+    Iterator* iter = db_->NewIterator(ReadOptions());
+    int i = 0;
+    int64_t bytes = 0;
+    for (iter->SeekToLast(); i < reads_ && iter->Valid(); iter->Prev()) {
+      bytes += iter->key().size() + iter->value().size();
+      thread->stats.FinishedSingleOp();
+      ++i;
+    }
+    delete iter;
+    thread->stats.AddBytes(bytes);
+  }
+
+  void ReadRandom(ThreadState* thread) {
+    ReadOptions options;
+    std::string value;
+    int found = 0;
+    KeyBuffer key;
+    for (int i = 0; i < reads_; i++) {
+      const int k = thread->rand.Uniform(FLAGS_num);
+      key.Set(k);
+      if (db_->Get(options, key.slice(), &value).ok()) {
+        found++;
+      }
+      thread->stats.FinishedSingleOp();
+    }
+    char msg[100];
+    std::snprintf(msg, sizeof(msg), "(%d of %d found)", found, num_);
+    thread->stats.AddMessage(msg);
+  }
+
+  void ReadMissing(ThreadState* thread) {
+    ReadOptions options;
+    std::string value;
+    KeyBuffer key;
+    for (int i = 0; i < reads_; i++) {
+      const int k = thread->rand.Uniform(FLAGS_num);
+      key.Set(k);
+      Slice s = Slice(key.slice().data(), key.slice().size() - 1);
+      db_->Get(options, s, &value);
+      thread->stats.FinishedSingleOp();
+    }
+  }
+
+  void ReadHot(ThreadState* thread) {
+    ReadOptions options;
+    std::string value;
+    const int range = (FLAGS_num + 99) / 100;
+    KeyBuffer key;
+    for (int i = 0; i < reads_; i++) {
+      const int k = thread->rand.Uniform(range);
+      key.Set(k);
+      db_->Get(options, key.slice(), &value);
+      thread->stats.FinishedSingleOp();
+    }
+  }
+
+  void SeekRandom(ThreadState* thread) {
+    ReadOptions options;
+    int found = 0;
+    KeyBuffer key;
+    for (int i = 0; i < reads_; i++) {
+      Iterator* iter = db_->NewIterator(options);
+      const int k = thread->rand.Uniform(FLAGS_num);
+      key.Set(k);
+      iter->Seek(key.slice());
+      if (iter->Valid() && iter->key() == key.slice()) found++;
+      delete iter;
+      thread->stats.FinishedSingleOp();
+    }
+    char msg[100];
+    snprintf(msg, sizeof(msg), "(%d of %d found)", found, num_);
+    thread->stats.AddMessage(msg);
+  }
+
+  void SeekOrdered(ThreadState* thread) {
+    ReadOptions options;
+    Iterator* iter = db_->NewIterator(options);
+    int found = 0;
+    int k = 0;
+    KeyBuffer key;
+    for (int i = 0; i < reads_; i++) {
+      k = (k + (thread->rand.Uniform(100))) % FLAGS_num;
+      key.Set(k);
+      iter->Seek(key.slice());
+      if (iter->Valid() && iter->key() == key.slice()) found++;
+      thread->stats.FinishedSingleOp();
+    }
+    delete iter;
+    char msg[100];
+    std::snprintf(msg, sizeof(msg), "(%d of %d found)", found, num_);
+    thread->stats.AddMessage(msg);
+  }
+
+  void DoDelete(ThreadState* thread, bool seq) {
+    RandomGenerator gen;
+    WriteBatch batch;
+    Status s;
+    KeyBuffer key;
+    for (int i = 0; i < num_; i += entries_per_batch_) {
+      batch.Clear();
+      for (int j = 0; j < entries_per_batch_; j++) {
+        const int k = seq ? i + j : (thread->rand.Uniform(FLAGS_num));
+        key.Set(k);
+        batch.Delete(key.slice());
+        thread->stats.FinishedSingleOp();
+      }
+      s = db_->Write(write_options_, &batch);
+      if (!s.ok()) {
+        std::fprintf(stderr, "del error: %s\n", s.ToString().c_str());
+        std::exit(1);
+      }
+    }
+  }
+
+  void DeleteSeq(ThreadState* thread) { DoDelete(thread, true); }
+
+  void DeleteRandom(ThreadState* thread) { DoDelete(thread, false); }
+
+  void ReadWhileWriting(ThreadState* thread) {
+    if (thread->tid > 0) {
+      ReadRandom(thread);
+    } else {
+      // Special thread that keeps writing until other threads are done.
+      RandomGenerator gen;
+      KeyBuffer key;
+      while (true) {
+        {
+          MutexLock l(&thread->shared->mu);
+          if (thread->shared->num_done + 1 >= thread->shared->num_initialized) {
+            // Other threads have finished
+            break;
+          }
+        }
+
+        const int k = thread->rand.Uniform(FLAGS_num);
+        key.Set(k);
+        Status s =
+            db_->Put(write_options_, key.slice(), gen.Generate(value_size_));
+        if (!s.ok()) {
+          std::fprintf(stderr, "put error: %s\n", s.ToString().c_str());
+          std::exit(1);
+        }
+      }
+
+      // Do not count any of the preceding work/delay in stats.
+      thread->stats.Start();
+    }
+  }
+
+  void Compact(ThreadState* thread) { db_->CompactRange(nullptr, nullptr); }
+
+  void PrintStats(const char* key) {
+    std::string stats;
+    if (!db_->GetProperty(key, &stats)) {
+      stats = "(failed)";
+    }
+    std::fprintf(stdout, "\n%s\n", stats.c_str());
+  }
+
+  static void WriteToFile(void* arg, const char* buf, int n) {
+    reinterpret_cast<WritableFile*>(arg)->Append(Slice(buf, n));
+  }
+
+  void HeapProfile() {
+    char fname[100];
+    std::snprintf(fname, sizeof(fname), "%s/heap-%04d", FLAGS_db,
+                  ++heap_counter_);
+    WritableFile* file;
+    Status s = g_env->NewWritableFile(fname, &file);
+    if (!s.ok()) {
+      std::fprintf(stderr, "%s\n", s.ToString().c_str());
+      return;
+    }
+    bool ok = port::GetHeapProfile(WriteToFile, file);
+    delete file;
+    if (!ok) {
+      std::fprintf(stderr, "heap profiling not supported\n");
+      g_env->RemoveFile(fname);
+    }
+  }
+};
+
+}  // namespace leveldb
+
+int main(int argc, char** argv) {
+  FLAGS_write_buffer_size = leveldb::Options().write_buffer_size;
+  FLAGS_max_file_size = leveldb::Options().max_file_size;
+  FLAGS_block_size = leveldb::Options().block_size;
+  FLAGS_open_files = leveldb::Options().max_open_files;
+  std::string default_db_path;
+
+  for (int i = 1; i < argc; i++) {
+    double d;
+    int n;
+    char junk;
+    if (leveldb::Slice(argv[i]).starts_with("--benchmarks=")) {
+      FLAGS_benchmarks = argv[i] + strlen("--benchmarks=");
+    } else if (sscanf(argv[i], "--compression_ratio=%lf%c", &d, &junk) == 1) {
+      FLAGS_compression_ratio = d;
+    } else if (sscanf(argv[i], "--histogram=%d%c", &n, &junk) == 1 &&
+               (n == 0 || n == 1)) {
+      FLAGS_histogram = n;
+    } else if (sscanf(argv[i], "--comparisons=%d%c", &n, &junk) == 1 &&
+               (n == 0 || n == 1)) {
+      FLAGS_comparisons = n;
+    } else if (sscanf(argv[i], "--use_existing_db=%d%c", &n, &junk) == 1 &&
+               (n == 0 || n == 1)) {
+      FLAGS_use_existing_db = n;
+    } else if (sscanf(argv[i], "--reuse_logs=%d%c", &n, &junk) == 1 &&
+               (n == 0 || n == 1)) {
+      FLAGS_reuse_logs = n;
+    } else if (sscanf(argv[i], "--compression=%d%c", &n, &junk) == 1 &&
+               (n == 0 || n == 1)) {
+      FLAGS_compression = n;
+    } else if (sscanf(argv[i], "--num=%d%c", &n, &junk) == 1) {
+      FLAGS_num = n;
+    } else if (sscanf(argv[i], "--reads=%d%c", &n, &junk) == 1) {
+      FLAGS_reads = n;
+    } else if (sscanf(argv[i], "--threads=%d%c", &n, &junk) == 1) {
+      FLAGS_threads = n;
+    } else if (sscanf(argv[i], "--value_size=%d%c", &n, &junk) == 1) {
+      FLAGS_value_size = n;
+    } else if (sscanf(argv[i], "--write_buffer_size=%d%c", &n, &junk) == 1) {
+      FLAGS_write_buffer_size = n;
+    } else if (sscanf(argv[i], "--max_file_size=%d%c", &n, &junk) == 1) {
+      FLAGS_max_file_size = n;
+    } else if (sscanf(argv[i], "--block_size=%d%c", &n, &junk) == 1) {
+      FLAGS_block_size = n;
+    } else if (sscanf(argv[i], "--key_prefix=%d%c", &n, &junk) == 1) {
+      FLAGS_key_prefix = n;
+    } else if (sscanf(argv[i], "--cache_size=%d%c", &n, &junk) == 1) {
+      FLAGS_cache_size = n;
+    } else if (sscanf(argv[i], "--bloom_bits=%d%c", &n, &junk) == 1) {
+      FLAGS_bloom_bits = n;
+    } else if (sscanf(argv[i], "--open_files=%d%c", &n, &junk) == 1) {
+      FLAGS_open_files = n;
+    } else if (strncmp(argv[i], "--db=", 5) == 0) {
+      FLAGS_db = argv[i] + 5;
+    } else {
+      std::fprintf(stderr, "Invalid flag '%s'\n", argv[i]);
+      std::exit(1);
+    }
+  }
+
+  leveldb::g_env = leveldb::Env::Default();
+
+  // Choose a location for the test database if none given with --db=<path>
+  if (FLAGS_db == nullptr) {
+    leveldb::g_env->GetTestDirectory(&default_db_path);
+    default_db_path += "/dbbench";
+    FLAGS_db = default_db_path.c_str();
+  }
+
+  leveldb::Benchmark benchmark;
+  benchmark.Run();
+  return 0;
+}
diff --git a/leveldb_base/benchmarks/db_bench_log.cc b/leveldb_base/benchmarks/db_bench_log.cc
new file mode 100644
index 0000000..a1845bf
--- /dev/null
+++ b/leveldb_base/benchmarks/db_bench_log.cc
@@ -0,0 +1,92 @@
+// Copyright (c) 2019 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include <cinttypes>
+#include <cstdio>
+#include <string>
+
+#include "gtest/gtest.h"
+#include "benchmark/benchmark.h"
+#include "db/version_set.h"
+#include "leveldb/comparator.h"
+#include "leveldb/db.h"
+#include "leveldb/env.h"
+#include "leveldb/options.h"
+#include "port/port.h"
+#include "util/mutexlock.h"
+#include "util/testutil.h"
+
+namespace leveldb {
+
+namespace {
+
+std::string MakeKey(unsigned int num) {
+  char buf[30];
+  std::snprintf(buf, sizeof(buf), "%016u", num);
+  return std::string(buf);
+}
+
+void BM_LogAndApply(benchmark::State& state) {
+  const int num_base_files = state.range(0);
+
+  std::string dbname = testing::TempDir() + "leveldb_test_benchmark";
+  DestroyDB(dbname, Options());
+
+  DB* db = nullptr;
+  Options opts;
+  opts.create_if_missing = true;
+  Status s = DB::Open(opts, dbname, &db);
+  ASSERT_LEVELDB_OK(s);
+  ASSERT_TRUE(db != nullptr);
+
+  delete db;
+  db = nullptr;
+
+  Env* env = Env::Default();
+
+  port::Mutex mu;
+  MutexLock l(&mu);
+
+  InternalKeyComparator cmp(BytewiseComparator());
+  Options options;
+  VersionSet vset(dbname, &options, nullptr, &cmp);
+  bool save_manifest;
+  ASSERT_LEVELDB_OK(vset.Recover(&save_manifest));
+  VersionEdit vbase;
+  uint64_t fnum = 1;
+  for (int i = 0; i < num_base_files; i++) {
+    InternalKey start(MakeKey(2 * fnum), 1, kTypeValue);
+    InternalKey limit(MakeKey(2 * fnum + 1), 1, kTypeDeletion);
+    vbase.AddFile(2, fnum++, 1 /* file size */, start, limit);
+  }
+  ASSERT_LEVELDB_OK(vset.LogAndApply(&vbase, &mu));
+
+  uint64_t start_micros = env->NowMicros();
+
+  for (auto st : state) {
+    VersionEdit vedit;
+    vedit.RemoveFile(2, fnum);
+    InternalKey start(MakeKey(2 * fnum), 1, kTypeValue);
+    InternalKey limit(MakeKey(2 * fnum + 1), 1, kTypeDeletion);
+    vedit.AddFile(2, fnum++, 1 /* file size */, start, limit);
+    vset.LogAndApply(&vedit, &mu);
+  }
+
+  uint64_t stop_micros = env->NowMicros();
+  unsigned int us = stop_micros - start_micros;
+  char buf[16];
+  std::snprintf(buf, sizeof(buf), "%d", num_base_files);
+  std::fprintf(stderr,
+               "BM_LogAndApply/%-6s   %8" PRIu64
+               " iters : %9u us (%7.0f us / iter)\n",
+               buf, state.iterations(), us, ((float)us) / state.iterations());
+}
+
+BENCHMARK(BM_LogAndApply)->Arg(1)->Arg(100)->Arg(10000)->Arg(100000);
+
+}  // namespace
+
+}  // namespace leveldb
+
+BENCHMARK_MAIN();
diff --git a/leveldb_base/benchmarks/db_bench_sqlite3.cc b/leveldb_base/benchmarks/db_bench_sqlite3.cc
new file mode 100644
index 0000000..c9be652
--- /dev/null
+++ b/leveldb_base/benchmarks/db_bench_sqlite3.cc
@@ -0,0 +1,726 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include <sqlite3.h>
+
+#include <cstdio>
+#include <cstdlib>
+
+#include "util/histogram.h"
+#include "util/random.h"
+#include "util/testutil.h"
+
+// Comma-separated list of operations to run in the specified order
+//   Actual benchmarks:
+//
+//   fillseq       -- write N values in sequential key order in async mode
+//   fillseqsync   -- write N/100 values in sequential key order in sync mode
+//   fillseqbatch  -- batch write N values in sequential key order in async mode
+//   fillrandom    -- write N values in random key order in async mode
+//   fillrandsync  -- write N/100 values in random key order in sync mode
+//   fillrandbatch -- batch write N values in sequential key order in async mode
+//   overwrite     -- overwrite N values in random key order in async mode
+//   fillrand100K  -- write N/1000 100K values in random order in async mode
+//   fillseq100K   -- write N/1000 100K values in sequential order in async mode
+//   readseq       -- read N times sequentially
+//   readrandom    -- read N times in random order
+//   readrand100K  -- read N/1000 100K values in sequential order in async mode
+static const char* FLAGS_benchmarks =
+    "fillseq,"
+    "fillseqsync,"
+    "fillseqbatch,"
+    "fillrandom,"
+    "fillrandsync,"
+    "fillrandbatch,"
+    "overwrite,"
+    "overwritebatch,"
+    "readrandom,"
+    "readseq,"
+    "fillrand100K,"
+    "fillseq100K,"
+    "readseq,"
+    "readrand100K,";
+
+// Number of key/values to place in database
+static int FLAGS_num = 1000000;
+
+// Number of read operations to do.  If negative, do FLAGS_num reads.
+static int FLAGS_reads = -1;
+
+// Size of each value
+static int FLAGS_value_size = 100;
+
+// Print histogram of operation timings
+static bool FLAGS_histogram = false;
+
+// Arrange to generate values that shrink to this fraction of
+// their original size after compression
+static double FLAGS_compression_ratio = 0.5;
+
+// Page size. Default 1 KB.
+static int FLAGS_page_size = 1024;
+
+// Number of pages.
+// Default cache size = FLAGS_page_size * FLAGS_num_pages = 4 MB.
+static int FLAGS_num_pages = 4096;
+
+// If true, do not destroy the existing database.  If you set this
+// flag and also specify a benchmark that wants a fresh database, that
+// benchmark will fail.
+static bool FLAGS_use_existing_db = false;
+
+// If true, the SQLite table has ROWIDs.
+static bool FLAGS_use_rowids = false;
+
+// If true, we allow batch writes to occur
+static bool FLAGS_transaction = true;
+
+// If true, we enable Write-Ahead Logging
+static bool FLAGS_WAL_enabled = true;
+
+// Use the db with the following name.
+static const char* FLAGS_db = nullptr;
+
+inline static void ExecErrorCheck(int status, char* err_msg) {
+  if (status != SQLITE_OK) {
+    std::fprintf(stderr, "SQL error: %s\n", err_msg);
+    sqlite3_free(err_msg);
+    std::exit(1);
+  }
+}
+
+inline static void StepErrorCheck(int status) {
+  if (status != SQLITE_DONE) {
+    std::fprintf(stderr, "SQL step error: status = %d\n", status);
+    std::exit(1);
+  }
+}
+
+inline static void ErrorCheck(int status) {
+  if (status != SQLITE_OK) {
+    std::fprintf(stderr, "sqlite3 error: status = %d\n", status);
+    std::exit(1);
+  }
+}
+
+inline static void WalCheckpoint(sqlite3* db_) {
+  // Flush all writes to disk
+  if (FLAGS_WAL_enabled) {
+    sqlite3_wal_checkpoint_v2(db_, nullptr, SQLITE_CHECKPOINT_FULL, nullptr,
+                              nullptr);
+  }
+}
+
+namespace leveldb {
+
+// Helper for quickly generating random data.
+namespace {
+class RandomGenerator {
+ private:
+  std::string data_;
+  int pos_;
+
+ public:
+  RandomGenerator() {
+    // We use a limited amount of data over and over again and ensure
+    // that it is larger than the compression window (32KB), and also
+    // large enough to serve all typical value sizes we want to write.
+    Random rnd(301);
+    std::string piece;
+    while (data_.size() < 1048576) {
+      // Add a short fragment that is as compressible as specified
+      // by FLAGS_compression_ratio.
+      test::CompressibleString(&rnd, FLAGS_compression_ratio, 100, &piece);
+      data_.append(piece);
+    }
+    pos_ = 0;
+  }
+
+  Slice Generate(int len) {
+    if (pos_ + len > data_.size()) {
+      pos_ = 0;
+      assert(len < data_.size());
+    }
+    pos_ += len;
+    return Slice(data_.data() + pos_ - len, len);
+  }
+};
+
+static Slice TrimSpace(Slice s) {
+  int start = 0;
+  while (start < s.size() && isspace(s[start])) {
+    start++;
+  }
+  int limit = s.size();
+  while (limit > start && isspace(s[limit - 1])) {
+    limit--;
+  }
+  return Slice(s.data() + start, limit - start);
+}
+
+}  // namespace
+
+class Benchmark {
+ private:
+  sqlite3* db_;
+  int db_num_;
+  int num_;
+  int reads_;
+  double start_;
+  double last_op_finish_;
+  int64_t bytes_;
+  std::string message_;
+  Histogram hist_;
+  RandomGenerator gen_;
+  Random rand_;
+
+  // State kept for progress messages
+  int done_;
+  int next_report_;  // When to report next
+
+  void PrintHeader() {
+    const int kKeySize = 16;
+    PrintEnvironment();
+    std::fprintf(stdout, "Keys:       %d bytes each\n", kKeySize);
+    std::fprintf(stdout, "Values:     %d bytes each\n", FLAGS_value_size);
+    std::fprintf(stdout, "Entries:    %d\n", num_);
+    std::fprintf(stdout, "RawSize:    %.1f MB (estimated)\n",
+                 ((static_cast<int64_t>(kKeySize + FLAGS_value_size) * num_) /
+                  1048576.0));
+    PrintWarnings();
+    std::fprintf(stdout, "------------------------------------------------\n");
+  }
+
+  void PrintWarnings() {
+#if defined(__GNUC__) && !defined(__OPTIMIZE__)
+    std::fprintf(
+        stdout,
+        "WARNING: Optimization is disabled: benchmarks unnecessarily slow\n");
+#endif
+#ifndef NDEBUG
+    std::fprintf(
+        stdout,
+        "WARNING: Assertions are enabled; benchmarks unnecessarily slow\n");
+#endif
+  }
+
+  void PrintEnvironment() {
+    std::fprintf(stderr, "SQLite:     version %s\n", SQLITE_VERSION);
+
+#if defined(__linux)
+    time_t now = time(nullptr);
+    std::fprintf(stderr, "Date:       %s",
+                 ctime(&now));  // ctime() adds newline
+
+    FILE* cpuinfo = std::fopen("/proc/cpuinfo", "r");
+    if (cpuinfo != nullptr) {
+      char line[1000];
+      int num_cpus = 0;
+      std::string cpu_type;
+      std::string cache_size;
+      while (fgets(line, sizeof(line), cpuinfo) != nullptr) {
+        const char* sep = strchr(line, ':');
+        if (sep == nullptr) {
+          continue;
+        }
+        Slice key = TrimSpace(Slice(line, sep - 1 - line));
+        Slice val = TrimSpace(Slice(sep + 1));
+        if (key == "model name") {
+          ++num_cpus;
+          cpu_type = val.ToString();
+        } else if (key == "cache size") {
+          cache_size = val.ToString();
+        }
+      }
+      std::fclose(cpuinfo);
+      std::fprintf(stderr, "CPU:        %d * %s\n", num_cpus, cpu_type.c_str());
+      std::fprintf(stderr, "CPUCache:   %s\n", cache_size.c_str());
+    }
+#endif
+  }
+
+  void Start() {
+    start_ = Env::Default()->NowMicros() * 1e-6;
+    bytes_ = 0;
+    message_.clear();
+    last_op_finish_ = start_;
+    hist_.Clear();
+    done_ = 0;
+    next_report_ = 100;
+  }
+
+  void FinishedSingleOp() {
+    if (FLAGS_histogram) {
+      double now = Env::Default()->NowMicros() * 1e-6;
+      double micros = (now - last_op_finish_) * 1e6;
+      hist_.Add(micros);
+      if (micros > 20000) {
+        std::fprintf(stderr, "long op: %.1f micros%30s\r", micros, "");
+        std::fflush(stderr);
+      }
+      last_op_finish_ = now;
+    }
+
+    done_++;
+    if (done_ >= next_report_) {
+      if (next_report_ < 1000)
+        next_report_ += 100;
+      else if (next_report_ < 5000)
+        next_report_ += 500;
+      else if (next_report_ < 10000)
+        next_report_ += 1000;
+      else if (next_report_ < 50000)
+        next_report_ += 5000;
+      else if (next_report_ < 100000)
+        next_report_ += 10000;
+      else if (next_report_ < 500000)
+        next_report_ += 50000;
+      else
+        next_report_ += 100000;
+      std::fprintf(stderr, "... finished %d ops%30s\r", done_, "");
+      std::fflush(stderr);
+    }
+  }
+
+  void Stop(const Slice& name) {
+    double finish = Env::Default()->NowMicros() * 1e-6;
+
+    // Pretend at least one op was done in case we are running a benchmark
+    // that does not call FinishedSingleOp().
+    if (done_ < 1) done_ = 1;
+
+    if (bytes_ > 0) {
+      char rate[100];
+      std::snprintf(rate, sizeof(rate), "%6.1f MB/s",
+                    (bytes_ / 1048576.0) / (finish - start_));
+      if (!message_.empty()) {
+        message_ = std::string(rate) + " " + message_;
+      } else {
+        message_ = rate;
+      }
+    }
+
+    std::fprintf(stdout, "%-12s : %11.3f micros/op;%s%s\n",
+                 name.ToString().c_str(), (finish - start_) * 1e6 / done_,
+                 (message_.empty() ? "" : " "), message_.c_str());
+    if (FLAGS_histogram) {
+      std::fprintf(stdout, "Microseconds per op:\n%s\n",
+                   hist_.ToString().c_str());
+    }
+    std::fflush(stdout);
+  }
+
+ public:
+  enum Order { SEQUENTIAL, RANDOM };
+  enum DBState { FRESH, EXISTING };
+
+  Benchmark()
+      : db_(nullptr),
+        db_num_(0),
+        num_(FLAGS_num),
+        reads_(FLAGS_reads < 0 ? FLAGS_num : FLAGS_reads),
+        bytes_(0),
+        rand_(301) {
+    std::vector<std::string> files;
+    std::string test_dir;
+    Env::Default()->GetTestDirectory(&test_dir);
+    Env::Default()->GetChildren(test_dir, &files);
+    if (!FLAGS_use_existing_db) {
+      for (int i = 0; i < files.size(); i++) {
+        if (Slice(files[i]).starts_with("dbbench_sqlite3")) {
+          std::string file_name(test_dir);
+          file_name += "/";
+          file_name += files[i];
+          Env::Default()->RemoveFile(file_name.c_str());
+        }
+      }
+    }
+  }
+
+  ~Benchmark() {
+    int status = sqlite3_close(db_);
+    ErrorCheck(status);
+  }
+
+  void Run() {
+    PrintHeader();
+    Open();
+
+    const char* benchmarks = FLAGS_benchmarks;
+    while (benchmarks != nullptr) {
+      const char* sep = strchr(benchmarks, ',');
+      Slice name;
+      if (sep == nullptr) {
+        name = benchmarks;
+        benchmarks = nullptr;
+      } else {
+        name = Slice(benchmarks, sep - benchmarks);
+        benchmarks = sep + 1;
+      }
+
+      bytes_ = 0;
+      Start();
+
+      bool known = true;
+      bool write_sync = false;
+      if (name == Slice("fillseq")) {
+        Write(write_sync, SEQUENTIAL, FRESH, num_, FLAGS_value_size, 1);
+        WalCheckpoint(db_);
+      } else if (name == Slice("fillseqbatch")) {
+        Write(write_sync, SEQUENTIAL, FRESH, num_, FLAGS_value_size, 1000);
+        WalCheckpoint(db_);
+      } else if (name == Slice("fillrandom")) {
+        Write(write_sync, RANDOM, FRESH, num_, FLAGS_value_size, 1);
+        WalCheckpoint(db_);
+      } else if (name == Slice("fillrandbatch")) {
+        Write(write_sync, RANDOM, FRESH, num_, FLAGS_value_size, 1000);
+        WalCheckpoint(db_);
+      } else if (name == Slice("overwrite")) {
+        Write(write_sync, RANDOM, EXISTING, num_, FLAGS_value_size, 1);
+        WalCheckpoint(db_);
+      } else if (name == Slice("overwritebatch")) {
+        Write(write_sync, RANDOM, EXISTING, num_, FLAGS_value_size, 1000);
+        WalCheckpoint(db_);
+      } else if (name == Slice("fillrandsync")) {
+        write_sync = true;
+        Write(write_sync, RANDOM, FRESH, num_ / 100, FLAGS_value_size, 1);
+        WalCheckpoint(db_);
+      } else if (name == Slice("fillseqsync")) {
+        write_sync = true;
+        Write(write_sync, SEQUENTIAL, FRESH, num_ / 100, FLAGS_value_size, 1);
+        WalCheckpoint(db_);
+      } else if (name == Slice("fillrand100K")) {
+        Write(write_sync, RANDOM, FRESH, num_ / 1000, 100 * 1000, 1);
+        WalCheckpoint(db_);
+      } else if (name == Slice("fillseq100K")) {
+        Write(write_sync, SEQUENTIAL, FRESH, num_ / 1000, 100 * 1000, 1);
+        WalCheckpoint(db_);
+      } else if (name == Slice("readseq")) {
+        ReadSequential();
+      } else if (name == Slice("readrandom")) {
+        Read(RANDOM, 1);
+      } else if (name == Slice("readrand100K")) {
+        int n = reads_;
+        reads_ /= 1000;
+        Read(RANDOM, 1);
+        reads_ = n;
+      } else {
+        known = false;
+        if (name != Slice()) {  // No error message for empty name
+          std::fprintf(stderr, "unknown benchmark '%s'\n",
+                       name.ToString().c_str());
+        }
+      }
+      if (known) {
+        Stop(name);
+      }
+    }
+  }
+
+  void Open() {
+    assert(db_ == nullptr);
+
+    int status;
+    char file_name[100];
+    char* err_msg = nullptr;
+    db_num_++;
+
+    // Open database
+    std::string tmp_dir;
+    Env::Default()->GetTestDirectory(&tmp_dir);
+    std::snprintf(file_name, sizeof(file_name), "%s/dbbench_sqlite3-%d.db",
+                  tmp_dir.c_str(), db_num_);
+    status = sqlite3_open(file_name, &db_);
+    if (status) {
+      std::fprintf(stderr, "open error: %s\n", sqlite3_errmsg(db_));
+      std::exit(1);
+    }
+
+    // Change SQLite cache size
+    char cache_size[100];
+    std::snprintf(cache_size, sizeof(cache_size), "PRAGMA cache_size = %d",
+                  FLAGS_num_pages);
+    status = sqlite3_exec(db_, cache_size, nullptr, nullptr, &err_msg);
+    ExecErrorCheck(status, err_msg);
+
+    // FLAGS_page_size is defaulted to 1024
+    if (FLAGS_page_size != 1024) {
+      char page_size[100];
+      std::snprintf(page_size, sizeof(page_size), "PRAGMA page_size = %d",
+                    FLAGS_page_size);
+      status = sqlite3_exec(db_, page_size, nullptr, nullptr, &err_msg);
+      ExecErrorCheck(status, err_msg);
+    }
+
+    // Change journal mode to WAL if WAL enabled flag is on
+    if (FLAGS_WAL_enabled) {
+      std::string WAL_stmt = "PRAGMA journal_mode = WAL";
+
+      // LevelDB's default cache size is a combined 4 MB
+      std::string WAL_checkpoint = "PRAGMA wal_autocheckpoint = 4096";
+      status = sqlite3_exec(db_, WAL_stmt.c_str(), nullptr, nullptr, &err_msg);
+      ExecErrorCheck(status, err_msg);
+      status =
+          sqlite3_exec(db_, WAL_checkpoint.c_str(), nullptr, nullptr, &err_msg);
+      ExecErrorCheck(status, err_msg);
+    }
+
+    // Change locking mode to exclusive and create tables/index for database
+    std::string locking_stmt = "PRAGMA locking_mode = EXCLUSIVE";
+    std::string create_stmt =
+        "CREATE TABLE test (key blob, value blob, PRIMARY KEY(key))";
+    if (!FLAGS_use_rowids) create_stmt += " WITHOUT ROWID";
+    std::string stmt_array[] = {locking_stmt, create_stmt};
+    int stmt_array_length = sizeof(stmt_array) / sizeof(std::string);
+    for (int i = 0; i < stmt_array_length; i++) {
+      status =
+          sqlite3_exec(db_, stmt_array[i].c_str(), nullptr, nullptr, &err_msg);
+      ExecErrorCheck(status, err_msg);
+    }
+  }
+
+  void Write(bool write_sync, Order order, DBState state, int num_entries,
+             int value_size, int entries_per_batch) {
+    // Create new database if state == FRESH
+    if (state == FRESH) {
+      if (FLAGS_use_existing_db) {
+        message_ = "skipping (--use_existing_db is true)";
+        return;
+      }
+      sqlite3_close(db_);
+      db_ = nullptr;
+      Open();
+      Start();
+    }
+
+    if (num_entries != num_) {
+      char msg[100];
+      std::snprintf(msg, sizeof(msg), "(%d ops)", num_entries);
+      message_ = msg;
+    }
+
+    char* err_msg = nullptr;
+    int status;
+
+    sqlite3_stmt *replace_stmt, *begin_trans_stmt, *end_trans_stmt;
+    std::string replace_str = "REPLACE INTO test (key, value) VALUES (?, ?)";
+    std::string begin_trans_str = "BEGIN TRANSACTION;";
+    std::string end_trans_str = "END TRANSACTION;";
+
+    // Check for synchronous flag in options
+    std::string sync_stmt =
+        (write_sync) ? "PRAGMA synchronous = FULL" : "PRAGMA synchronous = OFF";
+    status = sqlite3_exec(db_, sync_stmt.c_str(), nullptr, nullptr, &err_msg);
+    ExecErrorCheck(status, err_msg);
+
+    // Preparing sqlite3 statements
+    status = sqlite3_prepare_v2(db_, replace_str.c_str(), -1, &replace_stmt,
+                                nullptr);
+    ErrorCheck(status);
+    status = sqlite3_prepare_v2(db_, begin_trans_str.c_str(), -1,
+                                &begin_trans_stmt, nullptr);
+    ErrorCheck(status);
+    status = sqlite3_prepare_v2(db_, end_trans_str.c_str(), -1, &end_trans_stmt,
+                                nullptr);
+    ErrorCheck(status);
+
+    bool transaction = (entries_per_batch > 1);
+    for (int i = 0; i < num_entries; i += entries_per_batch) {
+      // Begin write transaction
+      if (FLAGS_transaction && transaction) {
+        status = sqlite3_step(begin_trans_stmt);
+        StepErrorCheck(status);
+        status = sqlite3_reset(begin_trans_stmt);
+        ErrorCheck(status);
+      }
+
+      // Create and execute SQL statements
+      for (int j = 0; j < entries_per_batch; j++) {
+        const char* value = gen_.Generate(value_size).data();
+
+        // Create values for key-value pair
+        const int k =
+            (order == SEQUENTIAL) ? i + j : (rand_.Next() % num_entries);
+        char key[100];
+        std::snprintf(key, sizeof(key), "%016d", k);
+
+        // Bind KV values into replace_stmt
+        status = sqlite3_bind_blob(replace_stmt, 1, key, 16, SQLITE_STATIC);
+        ErrorCheck(status);
+        status = sqlite3_bind_blob(replace_stmt, 2, value, value_size,
+                                   SQLITE_STATIC);
+        ErrorCheck(status);
+
+        // Execute replace_stmt
+        bytes_ += value_size + strlen(key);
+        status = sqlite3_step(replace_stmt);
+        StepErrorCheck(status);
+
+        // Reset SQLite statement for another use
+        status = sqlite3_clear_bindings(replace_stmt);
+        ErrorCheck(status);
+        status = sqlite3_reset(replace_stmt);
+        ErrorCheck(status);
+
+        FinishedSingleOp();
+      }
+
+      // End write transaction
+      if (FLAGS_transaction && transaction) {
+        status = sqlite3_step(end_trans_stmt);
+        StepErrorCheck(status);
+        status = sqlite3_reset(end_trans_stmt);
+        ErrorCheck(status);
+      }
+    }
+
+    status = sqlite3_finalize(replace_stmt);
+    ErrorCheck(status);
+    status = sqlite3_finalize(begin_trans_stmt);
+    ErrorCheck(status);
+    status = sqlite3_finalize(end_trans_stmt);
+    ErrorCheck(status);
+  }
+
+  void Read(Order order, int entries_per_batch) {
+    int status;
+    sqlite3_stmt *read_stmt, *begin_trans_stmt, *end_trans_stmt;
+
+    std::string read_str = "SELECT * FROM test WHERE key = ?";
+    std::string begin_trans_str = "BEGIN TRANSACTION;";
+    std::string end_trans_str = "END TRANSACTION;";
+
+    // Preparing sqlite3 statements
+    status = sqlite3_prepare_v2(db_, begin_trans_str.c_str(), -1,
+                                &begin_trans_stmt, nullptr);
+    ErrorCheck(status);
+    status = sqlite3_prepare_v2(db_, end_trans_str.c_str(), -1, &end_trans_stmt,
+                                nullptr);
+    ErrorCheck(status);
+    status = sqlite3_prepare_v2(db_, read_str.c_str(), -1, &read_stmt, nullptr);
+    ErrorCheck(status);
+
+    bool transaction = (entries_per_batch > 1);
+    for (int i = 0; i < reads_; i += entries_per_batch) {
+      // Begin read transaction
+      if (FLAGS_transaction && transaction) {
+        status = sqlite3_step(begin_trans_stmt);
+        StepErrorCheck(status);
+        status = sqlite3_reset(begin_trans_stmt);
+        ErrorCheck(status);
+      }
+
+      // Create and execute SQL statements
+      for (int j = 0; j < entries_per_batch; j++) {
+        // Create key value
+        char key[100];
+        int k = (order == SEQUENTIAL) ? i + j : (rand_.Next() % reads_);
+        std::snprintf(key, sizeof(key), "%016d", k);
+
+        // Bind key value into read_stmt
+        status = sqlite3_bind_blob(read_stmt, 1, key, 16, SQLITE_STATIC);
+        ErrorCheck(status);
+
+        // Execute read statement
+        while ((status = sqlite3_step(read_stmt)) == SQLITE_ROW) {
+        }
+        StepErrorCheck(status);
+
+        // Reset SQLite statement for another use
+        status = sqlite3_clear_bindings(read_stmt);
+        ErrorCheck(status);
+        status = sqlite3_reset(read_stmt);
+        ErrorCheck(status);
+        FinishedSingleOp();
+      }
+
+      // End read transaction
+      if (FLAGS_transaction && transaction) {
+        status = sqlite3_step(end_trans_stmt);
+        StepErrorCheck(status);
+        status = sqlite3_reset(end_trans_stmt);
+        ErrorCheck(status);
+      }
+    }
+
+    status = sqlite3_finalize(read_stmt);
+    ErrorCheck(status);
+    status = sqlite3_finalize(begin_trans_stmt);
+    ErrorCheck(status);
+    status = sqlite3_finalize(end_trans_stmt);
+    ErrorCheck(status);
+  }
+
+  void ReadSequential() {
+    int status;
+    sqlite3_stmt* pStmt;
+    std::string read_str = "SELECT * FROM test ORDER BY key";
+
+    status = sqlite3_prepare_v2(db_, read_str.c_str(), -1, &pStmt, nullptr);
+    ErrorCheck(status);
+    for (int i = 0; i < reads_ && SQLITE_ROW == sqlite3_step(pStmt); i++) {
+      bytes_ += sqlite3_column_bytes(pStmt, 1) + sqlite3_column_bytes(pStmt, 2);
+      FinishedSingleOp();
+    }
+
+    status = sqlite3_finalize(pStmt);
+    ErrorCheck(status);
+  }
+};
+
+}  // namespace leveldb
+
+int main(int argc, char** argv) {
+  std::string default_db_path;
+  for (int i = 1; i < argc; i++) {
+    double d;
+    int n;
+    char junk;
+    if (leveldb::Slice(argv[i]).starts_with("--benchmarks=")) {
+      FLAGS_benchmarks = argv[i] + strlen("--benchmarks=");
+    } else if (sscanf(argv[i], "--histogram=%d%c", &n, &junk) == 1 &&
+               (n == 0 || n == 1)) {
+      FLAGS_histogram = n;
+    } else if (sscanf(argv[i], "--compression_ratio=%lf%c", &d, &junk) == 1) {
+      FLAGS_compression_ratio = d;
+    } else if (sscanf(argv[i], "--use_existing_db=%d%c", &n, &junk) == 1 &&
+               (n == 0 || n == 1)) {
+      FLAGS_use_existing_db = n;
+    } else if (sscanf(argv[i], "--use_rowids=%d%c", &n, &junk) == 1 &&
+               (n == 0 || n == 1)) {
+      FLAGS_use_rowids = n;
+    } else if (sscanf(argv[i], "--num=%d%c", &n, &junk) == 1) {
+      FLAGS_num = n;
+    } else if (sscanf(argv[i], "--reads=%d%c", &n, &junk) == 1) {
+      FLAGS_reads = n;
+    } else if (sscanf(argv[i], "--value_size=%d%c", &n, &junk) == 1) {
+      FLAGS_value_size = n;
+    } else if (leveldb::Slice(argv[i]) == leveldb::Slice("--no_transaction")) {
+      FLAGS_transaction = false;
+    } else if (sscanf(argv[i], "--page_size=%d%c", &n, &junk) == 1) {
+      FLAGS_page_size = n;
+    } else if (sscanf(argv[i], "--num_pages=%d%c", &n, &junk) == 1) {
+      FLAGS_num_pages = n;
+    } else if (sscanf(argv[i], "--WAL_enabled=%d%c", &n, &junk) == 1 &&
+               (n == 0 || n == 1)) {
+      FLAGS_WAL_enabled = n;
+    } else if (strncmp(argv[i], "--db=", 5) == 0) {
+      FLAGS_db = argv[i] + 5;
+    } else {
+      std::fprintf(stderr, "Invalid flag '%s'\n", argv[i]);
+      std::exit(1);
+    }
+  }
+
+  // Choose a location for the test database if none given with --db=<path>
+  if (FLAGS_db == nullptr) {
+    leveldb::Env::Default()->GetTestDirectory(&default_db_path);
+    default_db_path += "/dbbench";
+    FLAGS_db = default_db_path.c_str();
+  }
+
+  leveldb::Benchmark benchmark;
+  benchmark.Run();
+  return 0;
+}
diff --git a/leveldb_base/benchmarks/db_bench_tree_db.cc b/leveldb_base/benchmarks/db_bench_tree_db.cc
new file mode 100644
index 0000000..533600b
--- /dev/null
+++ b/leveldb_base/benchmarks/db_bench_tree_db.cc
@@ -0,0 +1,531 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include <kcpolydb.h>
+
+#include <cstdio>
+#include <cstdlib>
+
+#include "util/histogram.h"
+#include "util/random.h"
+#include "util/testutil.h"
+
+// Comma-separated list of operations to run in the specified order
+//   Actual benchmarks:
+//
+//   fillseq       -- write N values in sequential key order in async mode
+//   fillrandom    -- write N values in random key order in async mode
+//   overwrite     -- overwrite N values in random key order in async mode
+//   fillseqsync   -- write N/100 values in sequential key order in sync mode
+//   fillrandsync  -- write N/100 values in random key order in sync mode
+//   fillrand100K  -- write N/1000 100K values in random order in async mode
+//   fillseq100K   -- write N/1000 100K values in seq order in async mode
+//   readseq       -- read N times sequentially
+//   readseq100K   -- read N/1000 100K values in sequential order in async mode
+//   readrand100K  -- read N/1000 100K values in sequential order in async mode
+//   readrandom    -- read N times in random order
+static const char* FLAGS_benchmarks =
+    "fillseq,"
+    "fillseqsync,"
+    "fillrandsync,"
+    "fillrandom,"
+    "overwrite,"
+    "readrandom,"
+    "readseq,"
+    "fillrand100K,"
+    "fillseq100K,"
+    "readseq100K,"
+    "readrand100K,";
+
+// Number of key/values to place in database
+static int FLAGS_num = 1000000;
+
+// Number of read operations to do.  If negative, do FLAGS_num reads.
+static int FLAGS_reads = -1;
+
+// Size of each value
+static int FLAGS_value_size = 100;
+
+// Arrange to generate values that shrink to this fraction of
+// their original size after compression
+static double FLAGS_compression_ratio = 0.5;
+
+// Print histogram of operation timings
+static bool FLAGS_histogram = false;
+
+// Cache size. Default 4 MB
+static int FLAGS_cache_size = 4194304;
+
+// Page size. Default 1 KB
+static int FLAGS_page_size = 1024;
+
+// If true, do not destroy the existing database.  If you set this
+// flag and also specify a benchmark that wants a fresh database, that
+// benchmark will fail.
+static bool FLAGS_use_existing_db = false;
+
+// Compression flag. If true, compression is on. If false, compression
+// is off.
+static bool FLAGS_compression = true;
+
+// Use the db with the following name.
+static const char* FLAGS_db = nullptr;
+
+inline static void DBSynchronize(kyotocabinet::TreeDB* db_) {
+  // Synchronize will flush writes to disk
+  if (!db_->synchronize()) {
+    std::fprintf(stderr, "synchronize error: %s\n", db_->error().name());
+  }
+}
+
+namespace leveldb {
+
+// Helper for quickly generating random data.
+namespace {
+class RandomGenerator {
+ private:
+  std::string data_;
+  int pos_;
+
+ public:
+  RandomGenerator() {
+    // We use a limited amount of data over and over again and ensure
+    // that it is larger than the compression window (32KB), and also
+    // large enough to serve all typical value sizes we want to write.
+    Random rnd(301);
+    std::string piece;
+    while (data_.size() < 1048576) {
+      // Add a short fragment that is as compressible as specified
+      // by FLAGS_compression_ratio.
+      test::CompressibleString(&rnd, FLAGS_compression_ratio, 100, &piece);
+      data_.append(piece);
+    }
+    pos_ = 0;
+  }
+
+  Slice Generate(int len) {
+    if (pos_ + len > data_.size()) {
+      pos_ = 0;
+      assert(len < data_.size());
+    }
+    pos_ += len;
+    return Slice(data_.data() + pos_ - len, len);
+  }
+};
+
+static Slice TrimSpace(Slice s) {
+  int start = 0;
+  while (start < s.size() && isspace(s[start])) {
+    start++;
+  }
+  int limit = s.size();
+  while (limit > start && isspace(s[limit - 1])) {
+    limit--;
+  }
+  return Slice(s.data() + start, limit - start);
+}
+
+}  // namespace
+
+class Benchmark {
+ private:
+  kyotocabinet::TreeDB* db_;
+  int db_num_;
+  int num_;
+  int reads_;
+  double start_;
+  double last_op_finish_;
+  int64_t bytes_;
+  std::string message_;
+  Histogram hist_;
+  RandomGenerator gen_;
+  Random rand_;
+  kyotocabinet::LZOCompressor<kyotocabinet::LZO::RAW> comp_;
+
+  // State kept for progress messages
+  int done_;
+  int next_report_;  // When to report next
+
+  void PrintHeader() {
+    const int kKeySize = 16;
+    PrintEnvironment();
+    std::fprintf(stdout, "Keys:       %d bytes each\n", kKeySize);
+    std::fprintf(
+        stdout, "Values:     %d bytes each (%d bytes after compression)\n",
+        FLAGS_value_size,
+        static_cast<int>(FLAGS_value_size * FLAGS_compression_ratio + 0.5));
+    std::fprintf(stdout, "Entries:    %d\n", num_);
+    std::fprintf(stdout, "RawSize:    %.1f MB (estimated)\n",
+                 ((static_cast<int64_t>(kKeySize + FLAGS_value_size) * num_) /
+                  1048576.0));
+    std::fprintf(
+        stdout, "FileSize:   %.1f MB (estimated)\n",
+        (((kKeySize + FLAGS_value_size * FLAGS_compression_ratio) * num_) /
+         1048576.0));
+    PrintWarnings();
+    std::fprintf(stdout, "------------------------------------------------\n");
+  }
+
+  void PrintWarnings() {
+#if defined(__GNUC__) && !defined(__OPTIMIZE__)
+    std::fprintf(
+        stdout,
+        "WARNING: Optimization is disabled: benchmarks unnecessarily slow\n");
+#endif
+#ifndef NDEBUG
+    std::fprintf(
+        stdout,
+        "WARNING: Assertions are enabled; benchmarks unnecessarily slow\n");
+#endif
+  }
+
+  void PrintEnvironment() {
+    std::fprintf(
+        stderr, "Kyoto Cabinet:    version %s, lib ver %d, lib rev %d\n",
+        kyotocabinet::VERSION, kyotocabinet::LIBVER, kyotocabinet::LIBREV);
+
+#if defined(__linux)
+    time_t now = time(nullptr);
+    std::fprintf(stderr, "Date:           %s",
+                 ctime(&now));  // ctime() adds newline
+
+    FILE* cpuinfo = std::fopen("/proc/cpuinfo", "r");
+    if (cpuinfo != nullptr) {
+      char line[1000];
+      int num_cpus = 0;
+      std::string cpu_type;
+      std::string cache_size;
+      while (fgets(line, sizeof(line), cpuinfo) != nullptr) {
+        const char* sep = strchr(line, ':');
+        if (sep == nullptr) {
+          continue;
+        }
+        Slice key = TrimSpace(Slice(line, sep - 1 - line));
+        Slice val = TrimSpace(Slice(sep + 1));
+        if (key == "model name") {
+          ++num_cpus;
+          cpu_type = val.ToString();
+        } else if (key == "cache size") {
+          cache_size = val.ToString();
+        }
+      }
+      std::fclose(cpuinfo);
+      std::fprintf(stderr, "CPU:            %d * %s\n", num_cpus,
+                   cpu_type.c_str());
+      std::fprintf(stderr, "CPUCache:       %s\n", cache_size.c_str());
+    }
+#endif
+  }
+
+  void Start() {
+    start_ = Env::Default()->NowMicros() * 1e-6;
+    bytes_ = 0;
+    message_.clear();
+    last_op_finish_ = start_;
+    hist_.Clear();
+    done_ = 0;
+    next_report_ = 100;
+  }
+
+  void FinishedSingleOp() {
+    if (FLAGS_histogram) {
+      double now = Env::Default()->NowMicros() * 1e-6;
+      double micros = (now - last_op_finish_) * 1e6;
+      hist_.Add(micros);
+      if (micros > 20000) {
+        std::fprintf(stderr, "long op: %.1f micros%30s\r", micros, "");
+        std::fflush(stderr);
+      }
+      last_op_finish_ = now;
+    }
+
+    done_++;
+    if (done_ >= next_report_) {
+      if (next_report_ < 1000)
+        next_report_ += 100;
+      else if (next_report_ < 5000)
+        next_report_ += 500;
+      else if (next_report_ < 10000)
+        next_report_ += 1000;
+      else if (next_report_ < 50000)
+        next_report_ += 5000;
+      else if (next_report_ < 100000)
+        next_report_ += 10000;
+      else if (next_report_ < 500000)
+        next_report_ += 50000;
+      else
+        next_report_ += 100000;
+      std::fprintf(stderr, "... finished %d ops%30s\r", done_, "");
+      std::fflush(stderr);
+    }
+  }
+
+  void Stop(const Slice& name) {
+    double finish = Env::Default()->NowMicros() * 1e-6;
+
+    // Pretend at least one op was done in case we are running a benchmark
+    // that does not call FinishedSingleOp().
+    if (done_ < 1) done_ = 1;
+
+    if (bytes_ > 0) {
+      char rate[100];
+      std::snprintf(rate, sizeof(rate), "%6.1f MB/s",
+                    (bytes_ / 1048576.0) / (finish - start_));
+      if (!message_.empty()) {
+        message_ = std::string(rate) + " " + message_;
+      } else {
+        message_ = rate;
+      }
+    }
+
+    std::fprintf(stdout, "%-12s : %11.3f micros/op;%s%s\n",
+                 name.ToString().c_str(), (finish - start_) * 1e6 / done_,
+                 (message_.empty() ? "" : " "), message_.c_str());
+    if (FLAGS_histogram) {
+      std::fprintf(stdout, "Microseconds per op:\n%s\n",
+                   hist_.ToString().c_str());
+    }
+    std::fflush(stdout);
+  }
+
+ public:
+  enum Order { SEQUENTIAL, RANDOM };
+  enum DBState { FRESH, EXISTING };
+
+  Benchmark()
+      : db_(nullptr),
+        num_(FLAGS_num),
+        reads_(FLAGS_reads < 0 ? FLAGS_num : FLAGS_reads),
+        bytes_(0),
+        rand_(301) {
+    std::vector<std::string> files;
+    std::string test_dir;
+    Env::Default()->GetTestDirectory(&test_dir);
+    Env::Default()->GetChildren(test_dir.c_str(), &files);
+    if (!FLAGS_use_existing_db) {
+      for (int i = 0; i < files.size(); i++) {
+        if (Slice(files[i]).starts_with("dbbench_polyDB")) {
+          std::string file_name(test_dir);
+          file_name += "/";
+          file_name += files[i];
+          Env::Default()->RemoveFile(file_name.c_str());
+        }
+      }
+    }
+  }
+
+  ~Benchmark() {
+    if (!db_->close()) {
+      std::fprintf(stderr, "close error: %s\n", db_->error().name());
+    }
+  }
+
+  void Run() {
+    PrintHeader();
+    Open(false);
+
+    const char* benchmarks = FLAGS_benchmarks;
+    while (benchmarks != nullptr) {
+      const char* sep = strchr(benchmarks, ',');
+      Slice name;
+      if (sep == nullptr) {
+        name = benchmarks;
+        benchmarks = nullptr;
+      } else {
+        name = Slice(benchmarks, sep - benchmarks);
+        benchmarks = sep + 1;
+      }
+
+      Start();
+
+      bool known = true;
+      bool write_sync = false;
+      if (name == Slice("fillseq")) {
+        Write(write_sync, SEQUENTIAL, FRESH, num_, FLAGS_value_size, 1);
+        DBSynchronize(db_);
+      } else if (name == Slice("fillrandom")) {
+        Write(write_sync, RANDOM, FRESH, num_, FLAGS_value_size, 1);
+        DBSynchronize(db_);
+      } else if (name == Slice("overwrite")) {
+        Write(write_sync, RANDOM, EXISTING, num_, FLAGS_value_size, 1);
+        DBSynchronize(db_);
+      } else if (name == Slice("fillrandsync")) {
+        write_sync = true;
+        Write(write_sync, RANDOM, FRESH, num_ / 100, FLAGS_value_size, 1);
+        DBSynchronize(db_);
+      } else if (name == Slice("fillseqsync")) {
+        write_sync = true;
+        Write(write_sync, SEQUENTIAL, FRESH, num_ / 100, FLAGS_value_size, 1);
+        DBSynchronize(db_);
+      } else if (name == Slice("fillrand100K")) {
+        Write(write_sync, RANDOM, FRESH, num_ / 1000, 100 * 1000, 1);
+        DBSynchronize(db_);
+      } else if (name == Slice("fillseq100K")) {
+        Write(write_sync, SEQUENTIAL, FRESH, num_ / 1000, 100 * 1000, 1);
+        DBSynchronize(db_);
+      } else if (name == Slice("readseq")) {
+        ReadSequential();
+      } else if (name == Slice("readrandom")) {
+        ReadRandom();
+      } else if (name == Slice("readrand100K")) {
+        int n = reads_;
+        reads_ /= 1000;
+        ReadRandom();
+        reads_ = n;
+      } else if (name == Slice("readseq100K")) {
+        int n = reads_;
+        reads_ /= 1000;
+        ReadSequential();
+        reads_ = n;
+      } else {
+        known = false;
+        if (name != Slice()) {  // No error message for empty name
+          std::fprintf(stderr, "unknown benchmark '%s'\n",
+                       name.ToString().c_str());
+        }
+      }
+      if (known) {
+        Stop(name);
+      }
+    }
+  }
+
+ private:
+  void Open(bool sync) {
+    assert(db_ == nullptr);
+
+    // Initialize db_
+    db_ = new kyotocabinet::TreeDB();
+    char file_name[100];
+    db_num_++;
+    std::string test_dir;
+    Env::Default()->GetTestDirectory(&test_dir);
+    std::snprintf(file_name, sizeof(file_name), "%s/dbbench_polyDB-%d.kct",
+                  test_dir.c_str(), db_num_);
+
+    // Create tuning options and open the database
+    int open_options =
+        kyotocabinet::PolyDB::OWRITER | kyotocabinet::PolyDB::OCREATE;
+    int tune_options =
+        kyotocabinet::TreeDB::TSMALL | kyotocabinet::TreeDB::TLINEAR;
+    if (FLAGS_compression) {
+      tune_options |= kyotocabinet::TreeDB::TCOMPRESS;
+      db_->tune_compressor(&comp_);
+    }
+    db_->tune_options(tune_options);
+    db_->tune_page_cache(FLAGS_cache_size);
+    db_->tune_page(FLAGS_page_size);
+    db_->tune_map(256LL << 20);
+    if (sync) {
+      open_options |= kyotocabinet::PolyDB::OAUTOSYNC;
+    }
+    if (!db_->open(file_name, open_options)) {
+      std::fprintf(stderr, "open error: %s\n", db_->error().name());
+    }
+  }
+
+  void Write(bool sync, Order order, DBState state, int num_entries,
+             int value_size, int entries_per_batch) {
+    // Create new database if state == FRESH
+    if (state == FRESH) {
+      if (FLAGS_use_existing_db) {
+        message_ = "skipping (--use_existing_db is true)";
+        return;
+      }
+      delete db_;
+      db_ = nullptr;
+      Open(sync);
+      Start();  // Do not count time taken to destroy/open
+    }
+
+    if (num_entries != num_) {
+      char msg[100];
+      std::snprintf(msg, sizeof(msg), "(%d ops)", num_entries);
+      message_ = msg;
+    }
+
+    // Write to database
+    for (int i = 0; i < num_entries; i++) {
+      const int k = (order == SEQUENTIAL) ? i : (rand_.Next() % num_entries);
+      char key[100];
+      std::snprintf(key, sizeof(key), "%016d", k);
+      bytes_ += value_size + strlen(key);
+      std::string cpp_key = key;
+      if (!db_->set(cpp_key, gen_.Generate(value_size).ToString())) {
+        std::fprintf(stderr, "set error: %s\n", db_->error().name());
+      }
+      FinishedSingleOp();
+    }
+  }
+
+  void ReadSequential() {
+    kyotocabinet::DB::Cursor* cur = db_->cursor();
+    cur->jump();
+    std::string ckey, cvalue;
+    while (cur->get(&ckey, &cvalue, true)) {
+      bytes_ += ckey.size() + cvalue.size();
+      FinishedSingleOp();
+    }
+    delete cur;
+  }
+
+  void ReadRandom() {
+    std::string value;
+    for (int i = 0; i < reads_; i++) {
+      char key[100];
+      const int k = rand_.Next() % reads_;
+      std::snprintf(key, sizeof(key), "%016d", k);
+      db_->get(key, &value);
+      FinishedSingleOp();
+    }
+  }
+};
+
+}  // namespace leveldb
+
+int main(int argc, char** argv) {
+  std::string default_db_path;
+  for (int i = 1; i < argc; i++) {
+    double d;
+    int n;
+    char junk;
+    if (leveldb::Slice(argv[i]).starts_with("--benchmarks=")) {
+      FLAGS_benchmarks = argv[i] + strlen("--benchmarks=");
+    } else if (sscanf(argv[i], "--compression_ratio=%lf%c", &d, &junk) == 1) {
+      FLAGS_compression_ratio = d;
+    } else if (sscanf(argv[i], "--histogram=%d%c", &n, &junk) == 1 &&
+               (n == 0 || n == 1)) {
+      FLAGS_histogram = n;
+    } else if (sscanf(argv[i], "--num=%d%c", &n, &junk) == 1) {
+      FLAGS_num = n;
+    } else if (sscanf(argv[i], "--reads=%d%c", &n, &junk) == 1) {
+      FLAGS_reads = n;
+    } else if (sscanf(argv[i], "--value_size=%d%c", &n, &junk) == 1) {
+      FLAGS_value_size = n;
+    } else if (sscanf(argv[i], "--cache_size=%d%c", &n, &junk) == 1) {
+      FLAGS_cache_size = n;
+    } else if (sscanf(argv[i], "--page_size=%d%c", &n, &junk) == 1) {
+      FLAGS_page_size = n;
+    } else if (sscanf(argv[i], "--compression=%d%c", &n, &junk) == 1 &&
+               (n == 0 || n == 1)) {
+      FLAGS_compression = (n == 1) ? true : false;
+    } else if (strncmp(argv[i], "--db=", 5) == 0) {
+      FLAGS_db = argv[i] + 5;
+    } else {
+      std::fprintf(stderr, "Invalid flag '%s'\n", argv[i]);
+      std::exit(1);
+    }
+  }
+
+  // Choose a location for the test database if none given with --db=<path>
+  if (FLAGS_db == nullptr) {
+    leveldb::Env::Default()->GetTestDirectory(&default_db_path);
+    default_db_path += "/dbbench";
+    FLAGS_db = default_db_path.c_str();
+  }
+
+  leveldb::Benchmark benchmark;
+  benchmark.Run();
+  return 0;
+}
diff --git a/leveldb_base/cmake/leveldbConfig.cmake.in b/leveldb_base/cmake/leveldbConfig.cmake.in
new file mode 100644
index 0000000..2572728
--- /dev/null
+++ b/leveldb_base/cmake/leveldbConfig.cmake.in
@@ -0,0 +1,9 @@
+# Copyright 2019 The LevelDB Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+@PACKAGE_INIT@
+
+include("${CMAKE_CURRENT_LIST_DIR}/leveldbTargets.cmake")
+
+check_required_components(leveldb)
\ No newline at end of file
diff --git a/leveldb_base/db/autocompact_test.cc b/leveldb_base/db/autocompact_test.cc
new file mode 100644
index 0000000..69341e3
--- /dev/null
+++ b/leveldb_base/db/autocompact_test.cc
@@ -0,0 +1,110 @@
+// Copyright (c) 2013 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "gtest/gtest.h"
+#include "db/db_impl.h"
+#include "leveldb/cache.h"
+#include "leveldb/db.h"
+#include "util/testutil.h"
+
+namespace leveldb {
+
+class AutoCompactTest : public testing::Test {
+ public:
+  AutoCompactTest() {
+    dbname_ = testing::TempDir() + "autocompact_test";
+    tiny_cache_ = NewLRUCache(100);
+    options_.block_cache = tiny_cache_;
+    DestroyDB(dbname_, options_);
+    options_.create_if_missing = true;
+    options_.compression = kNoCompression;
+    EXPECT_LEVELDB_OK(DB::Open(options_, dbname_, &db_));
+  }
+
+  ~AutoCompactTest() {
+    delete db_;
+    DestroyDB(dbname_, Options());
+    delete tiny_cache_;
+  }
+
+  std::string Key(int i) {
+    char buf[100];
+    std::snprintf(buf, sizeof(buf), "key%06d", i);
+    return std::string(buf);
+  }
+
+  uint64_t Size(const Slice& start, const Slice& limit) {
+    Range r(start, limit);
+    uint64_t size;
+    db_->GetApproximateSizes(&r, 1, &size);
+    return size;
+  }
+
+  void DoReads(int n);
+
+ private:
+  std::string dbname_;
+  Cache* tiny_cache_;
+  Options options_;
+  DB* db_;
+};
+
+static const int kValueSize = 200 * 1024;
+static const int kTotalSize = 100 * 1024 * 1024;
+static const int kCount = kTotalSize / kValueSize;
+
+// Read through the first n keys repeatedly and check that they get
+// compacted (verified by checking the size of the key space).
+void AutoCompactTest::DoReads(int n) {
+  std::string value(kValueSize, 'x');
+  DBImpl* dbi = reinterpret_cast<DBImpl*>(db_);
+
+  // Fill database
+  for (int i = 0; i < kCount; i++) {
+    ASSERT_LEVELDB_OK(db_->Put(WriteOptions(), Key(i), value));
+  }
+  ASSERT_LEVELDB_OK(dbi->TEST_CompactMemTable());
+
+  // Delete everything
+  for (int i = 0; i < kCount; i++) {
+    ASSERT_LEVELDB_OK(db_->Delete(WriteOptions(), Key(i)));
+  }
+  ASSERT_LEVELDB_OK(dbi->TEST_CompactMemTable());
+
+  // Get initial measurement of the space we will be reading.
+  const int64_t initial_size = Size(Key(0), Key(n));
+  const int64_t initial_other_size = Size(Key(n), Key(kCount));
+
+  // Read until size drops significantly.
+  std::string limit_key = Key(n);
+  for (int read = 0; true; read++) {
+    ASSERT_LT(read, 100) << "Taking too long to compact";
+    Iterator* iter = db_->NewIterator(ReadOptions());
+    for (iter->SeekToFirst();
+         iter->Valid() && iter->key().ToString() < limit_key; iter->Next()) {
+      // Drop data
+    }
+    delete iter;
+    // Wait a little bit to allow any triggered compactions to complete.
+    Env::Default()->SleepForMicroseconds(1000000);
+    uint64_t size = Size(Key(0), Key(n));
+    std::fprintf(stderr, "iter %3d => %7.3f MB [other %7.3f MB]\n", read + 1,
+                 size / 1048576.0, Size(Key(n), Key(kCount)) / 1048576.0);
+    if (size <= initial_size / 10) {
+      break;
+    }
+  }
+
+  // Verify that the size of the key space not touched by the reads
+  // is pretty much unchanged.
+  const int64_t final_other_size = Size(Key(n), Key(kCount));
+  ASSERT_LE(final_other_size, initial_other_size + 1048576);
+  ASSERT_GE(final_other_size, initial_other_size / 5 - 1048576);
+}
+
+TEST_F(AutoCompactTest, ReadAll) { DoReads(kCount); }
+
+TEST_F(AutoCompactTest, ReadHalf) { DoReads(kCount / 2); }
+
+}  // namespace leveldb
diff --git a/leveldb_base/db/builder.cc b/leveldb_base/db/builder.cc
new file mode 100644
index 0000000..e6329e0
--- /dev/null
+++ b/leveldb_base/db/builder.cc
@@ -0,0 +1,82 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "db/builder.h"
+
+#include "db/dbformat.h"
+#include "db/filename.h"
+#include "db/table_cache.h"
+#include "db/version_edit.h"
+#include "leveldb/db.h"
+#include "leveldb/env.h"
+#include "leveldb/iterator.h"
+
+namespace leveldb {
+
+Status BuildTable(const std::string& dbname, Env* env, const Options& options,
+                  TableCache* table_cache, Iterator* iter, FileMetaData* meta) {
+  Status s;
+  meta->file_size = 0;
+  iter->SeekToFirst();
+
+  std::string fname = TableFileName(dbname, meta->number);
+  if (iter->Valid()) {
+    WritableFile* file;
+    s = env->NewWritableFile(fname, &file);
+    if (!s.ok()) {
+      return s;
+    }
+
+    TableBuilder* builder = new TableBuilder(options, file);
+    meta->smallest.DecodeFrom(iter->key());
+    Slice key;
+    for (; iter->Valid(); iter->Next()) {
+      key = iter->key();
+      builder->Add(key, iter->value());
+    }
+    if (!key.empty()) {
+      meta->largest.DecodeFrom(key);
+    }
+
+    // Finish and check for builder errors
+    s = builder->Finish();
+    if (s.ok()) {
+      meta->file_size = builder->FileSize();
+      assert(meta->file_size > 0);
+    }
+    delete builder;
+
+    // Finish and check for file errors
+    if (s.ok()) {
+      s = file->Sync();
+    }
+    if (s.ok()) {
+      s = file->Close();
+    }
+    delete file;
+    file = nullptr;
+
+    if (s.ok()) {
+      // Verify that the table is usable
+      Iterator* it = table_cache->NewIterator(ReadOptions(), meta->number,
+                                              meta->file_size);
+      s = it->status();
+      delete it;
+    }
+  }
+
+  // Check for input iterator errors
+  if (!iter->status().ok()) {
+    s = iter->status();
+  }
+
+  if (s.ok() && meta->file_size > 0) {
+    // Keep it
+  } else {
+    env->RemoveFile(fname);
+  }
+  return s;
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/db/builder.h b/leveldb_base/db/builder.h
new file mode 100644
index 0000000..7bd0b80
--- /dev/null
+++ b/leveldb_base/db/builder.h
@@ -0,0 +1,30 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_DB_BUILDER_H_
+#define STORAGE_LEVELDB_DB_BUILDER_H_
+
+#include "leveldb/status.h"
+
+namespace leveldb {
+
+struct Options;
+struct FileMetaData;
+
+class Env;
+class Iterator;
+class TableCache;
+class VersionEdit;
+
+// Build a Table file from the contents of *iter.  The generated file
+// will be named according to meta->number.  On success, the rest of
+// *meta will be filled with metadata about the generated table.
+// If no data is present in *iter, meta->file_size will be set to
+// zero, and no Table file will be produced.
+Status BuildTable(const std::string& dbname, Env* env, const Options& options,
+                  TableCache* table_cache, Iterator* iter, FileMetaData* meta);
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_DB_BUILDER_H_
diff --git a/leveldb_base/db/c.cc b/leveldb_base/db/c.cc
new file mode 100644
index 0000000..8bdde38
--- /dev/null
+++ b/leveldb_base/db/c.cc
@@ -0,0 +1,565 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "leveldb/c.h"
+
+#include <string.h>
+
+#include <cstdint>
+#include <cstdlib>
+
+#include "leveldb/cache.h"
+#include "leveldb/comparator.h"
+#include "leveldb/db.h"
+#include "leveldb/env.h"
+#include "leveldb/filter_policy.h"
+#include "leveldb/iterator.h"
+#include "leveldb/options.h"
+#include "leveldb/status.h"
+#include "leveldb/write_batch.h"
+
+using leveldb::Cache;
+using leveldb::Comparator;
+using leveldb::CompressionType;
+using leveldb::DB;
+using leveldb::Env;
+using leveldb::FileLock;
+using leveldb::FilterPolicy;
+using leveldb::Iterator;
+using leveldb::kMajorVersion;
+using leveldb::kMinorVersion;
+using leveldb::Logger;
+using leveldb::NewBloomFilterPolicy;
+using leveldb::NewLRUCache;
+using leveldb::Options;
+using leveldb::RandomAccessFile;
+using leveldb::Range;
+using leveldb::ReadOptions;
+using leveldb::SequentialFile;
+using leveldb::Slice;
+using leveldb::Snapshot;
+using leveldb::Status;
+using leveldb::WritableFile;
+using leveldb::WriteBatch;
+using leveldb::WriteOptions;
+
+extern "C" {
+
+struct leveldb_t {
+  DB* rep;
+};
+struct leveldb_iterator_t {
+  Iterator* rep;
+};
+struct leveldb_writebatch_t {
+  WriteBatch rep;
+};
+struct leveldb_snapshot_t {
+  const Snapshot* rep;
+};
+struct leveldb_readoptions_t {
+  ReadOptions rep;
+};
+struct leveldb_writeoptions_t {
+  WriteOptions rep;
+};
+struct leveldb_options_t {
+  Options rep;
+};
+struct leveldb_cache_t {
+  Cache* rep;
+};
+struct leveldb_seqfile_t {
+  SequentialFile* rep;
+};
+struct leveldb_randomfile_t {
+  RandomAccessFile* rep;
+};
+struct leveldb_writablefile_t {
+  WritableFile* rep;
+};
+struct leveldb_logger_t {
+  Logger* rep;
+};
+struct leveldb_filelock_t {
+  FileLock* rep;
+};
+
+struct leveldb_comparator_t : public Comparator {
+  ~leveldb_comparator_t() override { (*destructor_)(state_); }
+
+  int Compare(const Slice& a, const Slice& b) const override {
+    return (*compare_)(state_, a.data(), a.size(), b.data(), b.size());
+  }
+
+  const char* Name() const override { return (*name_)(state_); }
+
+  // No-ops since the C binding does not support key shortening methods.
+  void FindShortestSeparator(std::string*, const Slice&) const override {}
+  void FindShortSuccessor(std::string* key) const override {}
+
+  void* state_;
+  void (*destructor_)(void*);
+  int (*compare_)(void*, const char* a, size_t alen, const char* b,
+                  size_t blen);
+  const char* (*name_)(void*);
+};
+
+struct leveldb_filterpolicy_t : public FilterPolicy {
+  ~leveldb_filterpolicy_t() override { (*destructor_)(state_); }
+
+  const char* Name() const override { return (*name_)(state_); }
+
+  void CreateFilter(const Slice* keys, int n, std::string* dst) const override {
+    std::vector<const char*> key_pointers(n);
+    std::vector<size_t> key_sizes(n);
+    for (int i = 0; i < n; i++) {
+      key_pointers[i] = keys[i].data();
+      key_sizes[i] = keys[i].size();
+    }
+    size_t len;
+    char* filter = (*create_)(state_, &key_pointers[0], &key_sizes[0], n, &len);
+    dst->append(filter, len);
+    std::free(filter);
+  }
+
+  bool KeyMayMatch(const Slice& key, const Slice& filter) const override {
+    return (*key_match_)(state_, key.data(), key.size(), filter.data(),
+                         filter.size());
+  }
+
+  void* state_;
+  void (*destructor_)(void*);
+  const char* (*name_)(void*);
+  char* (*create_)(void*, const char* const* key_array,
+                   const size_t* key_length_array, int num_keys,
+                   size_t* filter_length);
+  uint8_t (*key_match_)(void*, const char* key, size_t length,
+                        const char* filter, size_t filter_length);
+};
+
+struct leveldb_env_t {
+  Env* rep;
+  bool is_default;
+};
+
+static bool SaveError(char** errptr, const Status& s) {
+  assert(errptr != nullptr);
+  if (s.ok()) {
+    return false;
+  } else if (*errptr == nullptr) {
+    *errptr = strdup(s.ToString().c_str());
+  } else {
+    // TODO(sanjay): Merge with existing error?
+    std::free(*errptr);
+    *errptr = strdup(s.ToString().c_str());
+  }
+  return true;
+}
+
+static char* CopyString(const std::string& str) {
+  char* result =
+      reinterpret_cast<char*>(std::malloc(sizeof(char) * str.size()));
+  std::memcpy(result, str.data(), sizeof(char) * str.size());
+  return result;
+}
+
+leveldb_t* leveldb_open(const leveldb_options_t* options, const char* name,
+                        char** errptr) {
+  DB* db;
+  if (SaveError(errptr, DB::Open(options->rep, std::string(name), &db))) {
+    return nullptr;
+  }
+  leveldb_t* result = new leveldb_t;
+  result->rep = db;
+  return result;
+}
+
+void leveldb_close(leveldb_t* db) {
+  delete db->rep;
+  delete db;
+}
+
+void leveldb_put(leveldb_t* db, const leveldb_writeoptions_t* options,
+                 const char* key, size_t keylen, const char* val, size_t vallen,
+                 char** errptr) {
+  SaveError(errptr,
+            db->rep->Put(options->rep, Slice(key, keylen), Slice(val, vallen)));
+}
+
+void leveldb_delete(leveldb_t* db, const leveldb_writeoptions_t* options,
+                    const char* key, size_t keylen, char** errptr) {
+  SaveError(errptr, db->rep->Delete(options->rep, Slice(key, keylen)));
+}
+
+void leveldb_write(leveldb_t* db, const leveldb_writeoptions_t* options,
+                   leveldb_writebatch_t* batch, char** errptr) {
+  SaveError(errptr, db->rep->Write(options->rep, &batch->rep));
+}
+
+char* leveldb_get(leveldb_t* db, const leveldb_readoptions_t* options,
+                  const char* key, size_t keylen, size_t* vallen,
+                  char** errptr) {
+  char* result = nullptr;
+  std::string tmp;
+  Status s = db->rep->Get(options->rep, Slice(key, keylen), &tmp);
+  if (s.ok()) {
+    *vallen = tmp.size();
+    result = CopyString(tmp);
+  } else {
+    *vallen = 0;
+    if (!s.IsNotFound()) {
+      SaveError(errptr, s);
+    }
+  }
+  return result;
+}
+
+leveldb_iterator_t* leveldb_create_iterator(
+    leveldb_t* db, const leveldb_readoptions_t* options) {
+  leveldb_iterator_t* result = new leveldb_iterator_t;
+  result->rep = db->rep->NewIterator(options->rep);
+  return result;
+}
+
+const leveldb_snapshot_t* leveldb_create_snapshot(leveldb_t* db) {
+  leveldb_snapshot_t* result = new leveldb_snapshot_t;
+  result->rep = db->rep->GetSnapshot();
+  return result;
+}
+
+void leveldb_release_snapshot(leveldb_t* db,
+                              const leveldb_snapshot_t* snapshot) {
+  db->rep->ReleaseSnapshot(snapshot->rep);
+  delete snapshot;
+}
+
+char* leveldb_property_value(leveldb_t* db, const char* propname) {
+  std::string tmp;
+  if (db->rep->GetProperty(Slice(propname), &tmp)) {
+    // We use strdup() since we expect human readable output.
+    return strdup(tmp.c_str());
+  } else {
+    return nullptr;
+  }
+}
+
+void leveldb_approximate_sizes(leveldb_t* db, int num_ranges,
+                               const char* const* range_start_key,
+                               const size_t* range_start_key_len,
+                               const char* const* range_limit_key,
+                               const size_t* range_limit_key_len,
+                               uint64_t* sizes) {
+  Range* ranges = new Range[num_ranges];
+  for (int i = 0; i < num_ranges; i++) {
+    ranges[i].start = Slice(range_start_key[i], range_start_key_len[i]);
+    ranges[i].limit = Slice(range_limit_key[i], range_limit_key_len[i]);
+  }
+  db->rep->GetApproximateSizes(ranges, num_ranges, sizes);
+  delete[] ranges;
+}
+
+void leveldb_compact_range(leveldb_t* db, const char* start_key,
+                           size_t start_key_len, const char* limit_key,
+                           size_t limit_key_len) {
+  Slice a, b;
+  db->rep->CompactRange(
+      // Pass null Slice if corresponding "const char*" is null
+      (start_key ? (a = Slice(start_key, start_key_len), &a) : nullptr),
+      (limit_key ? (b = Slice(limit_key, limit_key_len), &b) : nullptr));
+}
+
+void leveldb_destroy_db(const leveldb_options_t* options, const char* name,
+                        char** errptr) {
+  SaveError(errptr, DestroyDB(name, options->rep));
+}
+
+void leveldb_repair_db(const leveldb_options_t* options, const char* name,
+                       char** errptr) {
+  SaveError(errptr, RepairDB(name, options->rep));
+}
+
+void leveldb_iter_destroy(leveldb_iterator_t* iter) {
+  delete iter->rep;
+  delete iter;
+}
+
+uint8_t leveldb_iter_valid(const leveldb_iterator_t* iter) {
+  return iter->rep->Valid();
+}
+
+void leveldb_iter_seek_to_first(leveldb_iterator_t* iter) {
+  iter->rep->SeekToFirst();
+}
+
+void leveldb_iter_seek_to_last(leveldb_iterator_t* iter) {
+  iter->rep->SeekToLast();
+}
+
+void leveldb_iter_seek(leveldb_iterator_t* iter, const char* k, size_t klen) {
+  iter->rep->Seek(Slice(k, klen));
+}
+
+void leveldb_iter_next(leveldb_iterator_t* iter) { iter->rep->Next(); }
+
+void leveldb_iter_prev(leveldb_iterator_t* iter) { iter->rep->Prev(); }
+
+const char* leveldb_iter_key(const leveldb_iterator_t* iter, size_t* klen) {
+  Slice s = iter->rep->key();
+  *klen = s.size();
+  return s.data();
+}
+
+const char* leveldb_iter_value(const leveldb_iterator_t* iter, size_t* vlen) {
+  Slice s = iter->rep->value();
+  *vlen = s.size();
+  return s.data();
+}
+
+void leveldb_iter_get_error(const leveldb_iterator_t* iter, char** errptr) {
+  SaveError(errptr, iter->rep->status());
+}
+
+leveldb_writebatch_t* leveldb_writebatch_create() {
+  return new leveldb_writebatch_t;
+}
+
+void leveldb_writebatch_destroy(leveldb_writebatch_t* b) { delete b; }
+
+void leveldb_writebatch_clear(leveldb_writebatch_t* b) { b->rep.Clear(); }
+
+void leveldb_writebatch_put(leveldb_writebatch_t* b, const char* key,
+                            size_t klen, const char* val, size_t vlen) {
+  b->rep.Put(Slice(key, klen), Slice(val, vlen));
+}
+
+void leveldb_writebatch_delete(leveldb_writebatch_t* b, const char* key,
+                               size_t klen) {
+  b->rep.Delete(Slice(key, klen));
+}
+
+void leveldb_writebatch_iterate(const leveldb_writebatch_t* b, void* state,
+                                void (*put)(void*, const char* k, size_t klen,
+                                            const char* v, size_t vlen),
+                                void (*deleted)(void*, const char* k,
+                                                size_t klen)) {
+  class H : public WriteBatch::Handler {
+   public:
+    void* state_;
+    void (*put_)(void*, const char* k, size_t klen, const char* v, size_t vlen);
+    void (*deleted_)(void*, const char* k, size_t klen);
+    void Put(const Slice& key, const Slice& value) override {
+      (*put_)(state_, key.data(), key.size(), value.data(), value.size());
+    }
+    void Delete(const Slice& key) override {
+      (*deleted_)(state_, key.data(), key.size());
+    }
+  };
+  H handler;
+  handler.state_ = state;
+  handler.put_ = put;
+  handler.deleted_ = deleted;
+  b->rep.Iterate(&handler);
+}
+
+void leveldb_writebatch_append(leveldb_writebatch_t* destination,
+                               const leveldb_writebatch_t* source) {
+  destination->rep.Append(source->rep);
+}
+
+leveldb_options_t* leveldb_options_create() { return new leveldb_options_t; }
+
+void leveldb_options_destroy(leveldb_options_t* options) { delete options; }
+
+void leveldb_options_set_comparator(leveldb_options_t* opt,
+                                    leveldb_comparator_t* cmp) {
+  opt->rep.comparator = cmp;
+}
+
+void leveldb_options_set_filter_policy(leveldb_options_t* opt,
+                                       leveldb_filterpolicy_t* policy) {
+  opt->rep.filter_policy = policy;
+}
+
+void leveldb_options_set_create_if_missing(leveldb_options_t* opt, uint8_t v) {
+  opt->rep.create_if_missing = v;
+}
+
+void leveldb_options_set_error_if_exists(leveldb_options_t* opt, uint8_t v) {
+  opt->rep.error_if_exists = v;
+}
+
+void leveldb_options_set_paranoid_checks(leveldb_options_t* opt, uint8_t v) {
+  opt->rep.paranoid_checks = v;
+}
+
+void leveldb_options_set_env(leveldb_options_t* opt, leveldb_env_t* env) {
+  opt->rep.env = (env ? env->rep : nullptr);
+}
+
+void leveldb_options_set_info_log(leveldb_options_t* opt, leveldb_logger_t* l) {
+  opt->rep.info_log = (l ? l->rep : nullptr);
+}
+
+void leveldb_options_set_write_buffer_size(leveldb_options_t* opt, size_t s) {
+  opt->rep.write_buffer_size = s;
+}
+
+void leveldb_options_set_max_open_files(leveldb_options_t* opt, int n) {
+  opt->rep.max_open_files = n;
+}
+
+void leveldb_options_set_cache(leveldb_options_t* opt, leveldb_cache_t* c) {
+  opt->rep.block_cache = c->rep;
+}
+
+void leveldb_options_set_block_size(leveldb_options_t* opt, size_t s) {
+  opt->rep.block_size = s;
+}
+
+void leveldb_options_set_block_restart_interval(leveldb_options_t* opt, int n) {
+  opt->rep.block_restart_interval = n;
+}
+
+void leveldb_options_set_max_file_size(leveldb_options_t* opt, size_t s) {
+  opt->rep.max_file_size = s;
+}
+
+void leveldb_options_set_compression(leveldb_options_t* opt, int t) {
+  opt->rep.compression = static_cast<CompressionType>(t);
+}
+
+leveldb_comparator_t* leveldb_comparator_create(
+    void* state, void (*destructor)(void*),
+    int (*compare)(void*, const char* a, size_t alen, const char* b,
+                   size_t blen),
+    const char* (*name)(void*)) {
+  leveldb_comparator_t* result = new leveldb_comparator_t;
+  result->state_ = state;
+  result->destructor_ = destructor;
+  result->compare_ = compare;
+  result->name_ = name;
+  return result;
+}
+
+void leveldb_comparator_destroy(leveldb_comparator_t* cmp) { delete cmp; }
+
+leveldb_filterpolicy_t* leveldb_filterpolicy_create(
+    void* state, void (*destructor)(void*),
+    char* (*create_filter)(void*, const char* const* key_array,
+                           const size_t* key_length_array, int num_keys,
+                           size_t* filter_length),
+    uint8_t (*key_may_match)(void*, const char* key, size_t length,
+                             const char* filter, size_t filter_length),
+    const char* (*name)(void*)) {
+  leveldb_filterpolicy_t* result = new leveldb_filterpolicy_t;
+  result->state_ = state;
+  result->destructor_ = destructor;
+  result->create_ = create_filter;
+  result->key_match_ = key_may_match;
+  result->name_ = name;
+  return result;
+}
+
+void leveldb_filterpolicy_destroy(leveldb_filterpolicy_t* filter) {
+  delete filter;
+}
+
+leveldb_filterpolicy_t* leveldb_filterpolicy_create_bloom(int bits_per_key) {
+  // Make a leveldb_filterpolicy_t, but override all of its methods so
+  // they delegate to a NewBloomFilterPolicy() instead of user
+  // supplied C functions.
+  struct Wrapper : public leveldb_filterpolicy_t {
+    static void DoNothing(void*) {}
+
+    ~Wrapper() { delete rep_; }
+    const char* Name() const { return rep_->Name(); }
+    void CreateFilter(const Slice* keys, int n, std::string* dst) const {
+      return rep_->CreateFilter(keys, n, dst);
+    }
+    bool KeyMayMatch(const Slice& key, const Slice& filter) const {
+      return rep_->KeyMayMatch(key, filter);
+    }
+
+    const FilterPolicy* rep_;
+  };
+  Wrapper* wrapper = new Wrapper;
+  wrapper->rep_ = NewBloomFilterPolicy(bits_per_key);
+  wrapper->state_ = nullptr;
+  wrapper->destructor_ = &Wrapper::DoNothing;
+  return wrapper;
+}
+
+leveldb_readoptions_t* leveldb_readoptions_create() {
+  return new leveldb_readoptions_t;
+}
+
+void leveldb_readoptions_destroy(leveldb_readoptions_t* opt) { delete opt; }
+
+void leveldb_readoptions_set_verify_checksums(leveldb_readoptions_t* opt,
+                                              uint8_t v) {
+  opt->rep.verify_checksums = v;
+}
+
+void leveldb_readoptions_set_fill_cache(leveldb_readoptions_t* opt, uint8_t v) {
+  opt->rep.fill_cache = v;
+}
+
+void leveldb_readoptions_set_snapshot(leveldb_readoptions_t* opt,
+                                      const leveldb_snapshot_t* snap) {
+  opt->rep.snapshot = (snap ? snap->rep : nullptr);
+}
+
+leveldb_writeoptions_t* leveldb_writeoptions_create() {
+  return new leveldb_writeoptions_t;
+}
+
+void leveldb_writeoptions_destroy(leveldb_writeoptions_t* opt) { delete opt; }
+
+void leveldb_writeoptions_set_sync(leveldb_writeoptions_t* opt, uint8_t v) {
+  opt->rep.sync = v;
+}
+
+leveldb_cache_t* leveldb_cache_create_lru(size_t capacity) {
+  leveldb_cache_t* c = new leveldb_cache_t;
+  c->rep = NewLRUCache(capacity);
+  return c;
+}
+
+void leveldb_cache_destroy(leveldb_cache_t* cache) {
+  delete cache->rep;
+  delete cache;
+}
+
+leveldb_env_t* leveldb_create_default_env() {
+  leveldb_env_t* result = new leveldb_env_t;
+  result->rep = Env::Default();
+  result->is_default = true;
+  return result;
+}
+
+void leveldb_env_destroy(leveldb_env_t* env) {
+  if (!env->is_default) delete env->rep;
+  delete env;
+}
+
+char* leveldb_env_get_test_directory(leveldb_env_t* env) {
+  std::string result;
+  if (!env->rep->GetTestDirectory(&result).ok()) {
+    return nullptr;
+  }
+
+  char* buffer = static_cast<char*>(std::malloc(result.size() + 1));
+  std::memcpy(buffer, result.data(), result.size());
+  buffer[result.size()] = '\0';
+  return buffer;
+}
+
+void leveldb_free(void* ptr) { std::free(ptr); }
+
+int leveldb_major_version() { return kMajorVersion; }
+
+int leveldb_minor_version() { return kMinorVersion; }
+
+}  // end extern "C"
diff --git a/leveldb_base/db/c_test.c b/leveldb_base/db/c_test.c
new file mode 100644
index 0000000..16c77ee
--- /dev/null
+++ b/leveldb_base/db/c_test.c
@@ -0,0 +1,384 @@
+/* Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+   Use of this source code is governed by a BSD-style license that can be
+   found in the LICENSE file. See the AUTHORS file for names of contributors. */
+
+#include "leveldb/c.h"
+
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+const char* phase = "";
+
+static void StartPhase(const char* name) {
+  fprintf(stderr, "=== Test %s\n", name);
+  phase = name;
+}
+
+#define CheckNoError(err)                                               \
+  if ((err) != NULL) {                                                  \
+    fprintf(stderr, "%s:%d: %s: %s\n", __FILE__, __LINE__, phase, (err)); \
+    abort();                                                            \
+  }
+
+#define CheckCondition(cond)                                            \
+  if (!(cond)) {                                                        \
+    fprintf(stderr, "%s:%d: %s: %s\n", __FILE__, __LINE__, phase, #cond); \
+    abort();                                                            \
+  }
+
+static void CheckEqual(const char* expected, const char* v, size_t n) {
+  if (expected == NULL && v == NULL) {
+    // ok
+  } else if (expected != NULL && v != NULL && n == strlen(expected) &&
+             memcmp(expected, v, n) == 0) {
+    // ok
+    return;
+  } else {
+    fprintf(stderr, "%s: expected '%s', got '%s'\n",
+            phase,
+            (expected ? expected : "(null)"),
+            (v ? v : "(null"));
+    abort();
+  }
+}
+
+static void Free(char** ptr) {
+  if (*ptr) {
+    free(*ptr);
+    *ptr = NULL;
+  }
+}
+
+static void CheckGet(
+    leveldb_t* db,
+    const leveldb_readoptions_t* options,
+    const char* key,
+    const char* expected) {
+  char* err = NULL;
+  size_t val_len;
+  char* val;
+  val = leveldb_get(db, options, key, strlen(key), &val_len, &err);
+  CheckNoError(err);
+  CheckEqual(expected, val, val_len);
+  Free(&val);
+}
+
+static void CheckIter(leveldb_iterator_t* iter,
+                      const char* key, const char* val) {
+  size_t len;
+  const char* str;
+  str = leveldb_iter_key(iter, &len);
+  CheckEqual(key, str, len);
+  str = leveldb_iter_value(iter, &len);
+  CheckEqual(val, str, len);
+}
+
+// Callback from leveldb_writebatch_iterate()
+static void CheckPut(void* ptr,
+                     const char* k, size_t klen,
+                     const char* v, size_t vlen) {
+  int* state = (int*) ptr;
+  CheckCondition(*state < 2);
+  switch (*state) {
+    case 0:
+      CheckEqual("bar", k, klen);
+      CheckEqual("b", v, vlen);
+      break;
+    case 1:
+      CheckEqual("box", k, klen);
+      CheckEqual("c", v, vlen);
+      break;
+  }
+  (*state)++;
+}
+
+// Callback from leveldb_writebatch_iterate()
+static void CheckDel(void* ptr, const char* k, size_t klen) {
+  int* state = (int*) ptr;
+  CheckCondition(*state == 2);
+  CheckEqual("bar", k, klen);
+  (*state)++;
+}
+
+static void CmpDestroy(void* arg) { }
+
+static int CmpCompare(void* arg, const char* a, size_t alen,
+                      const char* b, size_t blen) {
+  int n = (alen < blen) ? alen : blen;
+  int r = memcmp(a, b, n);
+  if (r == 0) {
+    if (alen < blen) r = -1;
+    else if (alen > blen) r = +1;
+  }
+  return r;
+}
+
+static const char* CmpName(void* arg) {
+  return "foo";
+}
+
+// Custom filter policy
+static uint8_t fake_filter_result = 1;
+static void FilterDestroy(void* arg) { }
+static const char* FilterName(void* arg) {
+  return "TestFilter";
+}
+static char* FilterCreate(
+    void* arg,
+    const char* const* key_array, const size_t* key_length_array,
+    int num_keys,
+    size_t* filter_length) {
+  *filter_length = 4;
+  char* result = malloc(4);
+  memcpy(result, "fake", 4);
+  return result;
+}
+uint8_t FilterKeyMatch(void* arg, const char* key, size_t length,
+                       const char* filter, size_t filter_length) {
+  CheckCondition(filter_length == 4);
+  CheckCondition(memcmp(filter, "fake", 4) == 0);
+  return fake_filter_result;
+}
+
+int main(int argc, char** argv) {
+  leveldb_t* db;
+  leveldb_comparator_t* cmp;
+  leveldb_cache_t* cache;
+  leveldb_env_t* env;
+  leveldb_options_t* options;
+  leveldb_readoptions_t* roptions;
+  leveldb_writeoptions_t* woptions;
+  char* dbname;
+  char* err = NULL;
+  int run = -1;
+
+  CheckCondition(leveldb_major_version() >= 1);
+  CheckCondition(leveldb_minor_version() >= 1);
+
+  StartPhase("create_objects");
+  cmp = leveldb_comparator_create(NULL, CmpDestroy, CmpCompare, CmpName);
+  env = leveldb_create_default_env();
+  cache = leveldb_cache_create_lru(100000);
+  dbname = leveldb_env_get_test_directory(env);
+  CheckCondition(dbname != NULL);
+
+  options = leveldb_options_create();
+  leveldb_options_set_comparator(options, cmp);
+  leveldb_options_set_error_if_exists(options, 1);
+  leveldb_options_set_cache(options, cache);
+  leveldb_options_set_env(options, env);
+  leveldb_options_set_info_log(options, NULL);
+  leveldb_options_set_write_buffer_size(options, 100000);
+  leveldb_options_set_paranoid_checks(options, 1);
+  leveldb_options_set_max_open_files(options, 10);
+  leveldb_options_set_block_size(options, 1024);
+  leveldb_options_set_block_restart_interval(options, 8);
+  leveldb_options_set_max_file_size(options, 3 << 20);
+  leveldb_options_set_compression(options, leveldb_no_compression);
+
+  roptions = leveldb_readoptions_create();
+  leveldb_readoptions_set_verify_checksums(roptions, 1);
+  leveldb_readoptions_set_fill_cache(roptions, 0);
+
+  woptions = leveldb_writeoptions_create();
+  leveldb_writeoptions_set_sync(woptions, 1);
+
+  StartPhase("destroy");
+  leveldb_destroy_db(options, dbname, &err);
+  Free(&err);
+
+  StartPhase("open_error");
+  db = leveldb_open(options, dbname, &err);
+  CheckCondition(err != NULL);
+  Free(&err);
+
+  StartPhase("leveldb_free");
+  db = leveldb_open(options, dbname, &err);
+  CheckCondition(err != NULL);
+  leveldb_free(err);
+  err = NULL;
+
+  StartPhase("open");
+  leveldb_options_set_create_if_missing(options, 1);
+  db = leveldb_open(options, dbname, &err);
+  CheckNoError(err);
+  CheckGet(db, roptions, "foo", NULL);
+
+  StartPhase("put");
+  leveldb_put(db, woptions, "foo", 3, "hello", 5, &err);
+  CheckNoError(err);
+  CheckGet(db, roptions, "foo", "hello");
+
+  StartPhase("compactall");
+  leveldb_compact_range(db, NULL, 0, NULL, 0);
+  CheckGet(db, roptions, "foo", "hello");
+
+  StartPhase("compactrange");
+  leveldb_compact_range(db, "a", 1, "z", 1);
+  CheckGet(db, roptions, "foo", "hello");
+
+  StartPhase("writebatch");
+  {
+    leveldb_writebatch_t* wb = leveldb_writebatch_create();
+    leveldb_writebatch_put(wb, "foo", 3, "a", 1);
+    leveldb_writebatch_clear(wb);
+    leveldb_writebatch_put(wb, "bar", 3, "b", 1);
+    leveldb_writebatch_put(wb, "box", 3, "c", 1);
+
+    leveldb_writebatch_t* wb2 = leveldb_writebatch_create();
+    leveldb_writebatch_delete(wb2, "bar", 3);
+    leveldb_writebatch_append(wb, wb2);
+    leveldb_writebatch_destroy(wb2);
+
+    leveldb_write(db, woptions, wb, &err);
+    CheckNoError(err);
+    CheckGet(db, roptions, "foo", "hello");
+    CheckGet(db, roptions, "bar", NULL);
+    CheckGet(db, roptions, "box", "c");
+
+    int pos = 0;
+    leveldb_writebatch_iterate(wb, &pos, CheckPut, CheckDel);
+    CheckCondition(pos == 3);
+    leveldb_writebatch_destroy(wb);
+  }
+
+  StartPhase("iter");
+  {
+    leveldb_iterator_t* iter = leveldb_create_iterator(db, roptions);
+    CheckCondition(!leveldb_iter_valid(iter));
+    leveldb_iter_seek_to_first(iter);
+    CheckCondition(leveldb_iter_valid(iter));
+    CheckIter(iter, "box", "c");
+    leveldb_iter_next(iter);
+    CheckIter(iter, "foo", "hello");
+    leveldb_iter_prev(iter);
+    CheckIter(iter, "box", "c");
+    leveldb_iter_prev(iter);
+    CheckCondition(!leveldb_iter_valid(iter));
+    leveldb_iter_seek_to_last(iter);
+    CheckIter(iter, "foo", "hello");
+    leveldb_iter_seek(iter, "b", 1);
+    CheckIter(iter, "box", "c");
+    leveldb_iter_get_error(iter, &err);
+    CheckNoError(err);
+    leveldb_iter_destroy(iter);
+  }
+
+  StartPhase("approximate_sizes");
+  {
+    int i;
+    int n = 20000;
+    char keybuf[100];
+    char valbuf[100];
+    uint64_t sizes[2];
+    const char* start[2] = { "a", "k00000000000000010000" };
+    size_t start_len[2] = { 1, 21 };
+    const char* limit[2] = { "k00000000000000010000", "z" };
+    size_t limit_len[2] = { 21, 1 };
+    leveldb_writeoptions_set_sync(woptions, 0);
+    for (i = 0; i < n; i++) {
+      snprintf(keybuf, sizeof(keybuf), "k%020d", i);
+      snprintf(valbuf, sizeof(valbuf), "v%020d", i);
+      leveldb_put(db, woptions, keybuf, strlen(keybuf), valbuf, strlen(valbuf),
+                  &err);
+      CheckNoError(err);
+    }
+    leveldb_approximate_sizes(db, 2, start, start_len, limit, limit_len, sizes);
+    CheckCondition(sizes[0] > 0);
+    CheckCondition(sizes[1] > 0);
+  }
+
+  StartPhase("property");
+  {
+    char* prop = leveldb_property_value(db, "nosuchprop");
+    CheckCondition(prop == NULL);
+    prop = leveldb_property_value(db, "leveldb.stats");
+    CheckCondition(prop != NULL);
+    Free(&prop);
+  }
+
+  StartPhase("snapshot");
+  {
+    const leveldb_snapshot_t* snap;
+    snap = leveldb_create_snapshot(db);
+    leveldb_delete(db, woptions, "foo", 3, &err);
+    CheckNoError(err);
+    leveldb_readoptions_set_snapshot(roptions, snap);
+    CheckGet(db, roptions, "foo", "hello");
+    leveldb_readoptions_set_snapshot(roptions, NULL);
+    CheckGet(db, roptions, "foo", NULL);
+    leveldb_release_snapshot(db, snap);
+  }
+
+  StartPhase("repair");
+  {
+    leveldb_close(db);
+    leveldb_options_set_create_if_missing(options, 0);
+    leveldb_options_set_error_if_exists(options, 0);
+    leveldb_repair_db(options, dbname, &err);
+    CheckNoError(err);
+    db = leveldb_open(options, dbname, &err);
+    CheckNoError(err);
+    CheckGet(db, roptions, "foo", NULL);
+    CheckGet(db, roptions, "bar", NULL);
+    CheckGet(db, roptions, "box", "c");
+    leveldb_options_set_create_if_missing(options, 1);
+    leveldb_options_set_error_if_exists(options, 1);
+  }
+
+  StartPhase("filter");
+  for (run = 0; run < 2; run++) {
+    // First run uses custom filter, second run uses bloom filter
+    CheckNoError(err);
+    leveldb_filterpolicy_t* policy;
+    if (run == 0) {
+      policy = leveldb_filterpolicy_create(
+          NULL, FilterDestroy, FilterCreate, FilterKeyMatch, FilterName);
+    } else {
+      policy = leveldb_filterpolicy_create_bloom(10);
+    }
+
+    // Create new database
+    leveldb_close(db);
+    leveldb_destroy_db(options, dbname, &err);
+    leveldb_options_set_filter_policy(options, policy);
+    db = leveldb_open(options, dbname, &err);
+    CheckNoError(err);
+    leveldb_put(db, woptions, "foo", 3, "foovalue", 8, &err);
+    CheckNoError(err);
+    leveldb_put(db, woptions, "bar", 3, "barvalue", 8, &err);
+    CheckNoError(err);
+    leveldb_compact_range(db, NULL, 0, NULL, 0);
+
+    fake_filter_result = 1;
+    CheckGet(db, roptions, "foo", "foovalue");
+    CheckGet(db, roptions, "bar", "barvalue");
+    if (phase == 0) {
+      // Must not find value when custom filter returns false
+      fake_filter_result = 0;
+      CheckGet(db, roptions, "foo", NULL);
+      CheckGet(db, roptions, "bar", NULL);
+      fake_filter_result = 1;
+
+      CheckGet(db, roptions, "foo", "foovalue");
+      CheckGet(db, roptions, "bar", "barvalue");
+    }
+    leveldb_options_set_filter_policy(options, NULL);
+    leveldb_filterpolicy_destroy(policy);
+  }
+
+  StartPhase("cleanup");
+  leveldb_close(db);
+  leveldb_options_destroy(options);
+  leveldb_readoptions_destroy(roptions);
+  leveldb_writeoptions_destroy(woptions);
+  leveldb_free(dbname);
+  leveldb_cache_destroy(cache);
+  leveldb_comparator_destroy(cmp);
+  leveldb_env_destroy(env);
+
+  fprintf(stderr, "PASS\n");
+  return 0;
+}
diff --git a/leveldb_base/db/corruption_test.cc b/leveldb_base/db/corruption_test.cc
new file mode 100644
index 0000000..dc7da76
--- /dev/null
+++ b/leveldb_base/db/corruption_test.cc
@@ -0,0 +1,362 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include <sys/types.h>
+
+#include "gtest/gtest.h"
+#include "db/db_impl.h"
+#include "db/filename.h"
+#include "db/log_format.h"
+#include "db/version_set.h"
+#include "leveldb/cache.h"
+#include "leveldb/db.h"
+#include "leveldb/table.h"
+#include "leveldb/write_batch.h"
+#include "util/logging.h"
+#include "util/testutil.h"
+
+namespace leveldb {
+
+static const int kValueSize = 1000;
+
+class CorruptionTest : public testing::Test {
+ public:
+  CorruptionTest()
+      : db_(nullptr),
+        dbname_("/memenv/corruption_test"),
+        tiny_cache_(NewLRUCache(100)) {
+    options_.env = &env_;
+    options_.block_cache = tiny_cache_;
+    DestroyDB(dbname_, options_);
+
+    options_.create_if_missing = true;
+    Reopen();
+    options_.create_if_missing = false;
+  }
+
+  ~CorruptionTest() {
+    delete db_;
+    delete tiny_cache_;
+  }
+
+  Status TryReopen() {
+    delete db_;
+    db_ = nullptr;
+    return DB::Open(options_, dbname_, &db_);
+  }
+
+  void Reopen() { ASSERT_LEVELDB_OK(TryReopen()); }
+
+  void RepairDB() {
+    delete db_;
+    db_ = nullptr;
+    ASSERT_LEVELDB_OK(::leveldb::RepairDB(dbname_, options_));
+  }
+
+  void Build(int n) {
+    std::string key_space, value_space;
+    WriteBatch batch;
+    for (int i = 0; i < n; i++) {
+      // if ((i % 100) == 0) std::fprintf(stderr, "@ %d of %d\n", i, n);
+      Slice key = Key(i, &key_space);
+      batch.Clear();
+      batch.Put(key, Value(i, &value_space));
+      WriteOptions options;
+      // Corrupt() doesn't work without this sync on windows; stat reports 0 for
+      // the file size.
+      if (i == n - 1) {
+        options.sync = true;
+      }
+      ASSERT_LEVELDB_OK(db_->Write(options, &batch));
+    }
+  }
+
+  void Check(int min_expected, int max_expected) {
+    int next_expected = 0;
+    int missed = 0;
+    int bad_keys = 0;
+    int bad_values = 0;
+    int correct = 0;
+    std::string value_space;
+    Iterator* iter = db_->NewIterator(ReadOptions());
+    for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
+      uint64_t key;
+      Slice in(iter->key());
+      if (in == "" || in == "~") {
+        // Ignore boundary keys.
+        continue;
+      }
+      if (!ConsumeDecimalNumber(&in, &key) || !in.empty() ||
+          key < next_expected) {
+        bad_keys++;
+        continue;
+      }
+      missed += (key - next_expected);
+      next_expected = key + 1;
+      if (iter->value() != Value(key, &value_space)) {
+        bad_values++;
+      } else {
+        correct++;
+      }
+    }
+    delete iter;
+
+    std::fprintf(
+        stderr,
+        "expected=%d..%d; got=%d; bad_keys=%d; bad_values=%d; missed=%d\n",
+        min_expected, max_expected, correct, bad_keys, bad_values, missed);
+    ASSERT_LE(min_expected, correct);
+    ASSERT_GE(max_expected, correct);
+  }
+
+  void Corrupt(FileType filetype, int offset, int bytes_to_corrupt) {
+    // Pick file to corrupt
+    std::vector<std::string> filenames;
+    ASSERT_LEVELDB_OK(env_.target()->GetChildren(dbname_, &filenames));
+    uint64_t number;
+    FileType type;
+    std::string fname;
+    int picked_number = -1;
+    for (size_t i = 0; i < filenames.size(); i++) {
+      if (ParseFileName(filenames[i], &number, &type) && type == filetype &&
+          int(number) > picked_number) {  // Pick latest file
+        fname = dbname_ + "/" + filenames[i];
+        picked_number = number;
+      }
+    }
+    ASSERT_TRUE(!fname.empty()) << filetype;
+
+    uint64_t file_size;
+    ASSERT_LEVELDB_OK(env_.target()->GetFileSize(fname, &file_size));
+
+    if (offset < 0) {
+      // Relative to end of file; make it absolute
+      if (-offset > file_size) {
+        offset = 0;
+      } else {
+        offset = file_size + offset;
+      }
+    }
+    if (offset > file_size) {
+      offset = file_size;
+    }
+    if (offset + bytes_to_corrupt > file_size) {
+      bytes_to_corrupt = file_size - offset;
+    }
+
+    // Do it
+    std::string contents;
+    Status s = ReadFileToString(env_.target(), fname, &contents);
+    ASSERT_TRUE(s.ok()) << s.ToString();
+    for (int i = 0; i < bytes_to_corrupt; i++) {
+      contents[i + offset] ^= 0x80;
+    }
+    s = WriteStringToFile(env_.target(), contents, fname);
+    ASSERT_TRUE(s.ok()) << s.ToString();
+  }
+
+  int Property(const std::string& name) {
+    std::string property;
+    int result;
+    if (db_->GetProperty(name, &property) &&
+        sscanf(property.c_str(), "%d", &result) == 1) {
+      return result;
+    } else {
+      return -1;
+    }
+  }
+
+  // Return the ith key
+  Slice Key(int i, std::string* storage) {
+    char buf[100];
+    std::snprintf(buf, sizeof(buf), "%016d", i);
+    storage->assign(buf, strlen(buf));
+    return Slice(*storage);
+  }
+
+  // Return the value to associate with the specified key
+  Slice Value(int k, std::string* storage) {
+    Random r(k);
+    return test::RandomString(&r, kValueSize, storage);
+  }
+
+  test::ErrorEnv env_;
+  Options options_;
+  DB* db_;
+
+ private:
+  std::string dbname_;
+  Cache* tiny_cache_;
+};
+
+TEST_F(CorruptionTest, Recovery) {
+  Build(100);
+  Check(100, 100);
+  Corrupt(kLogFile, 19, 1);  // WriteBatch tag for first record
+  Corrupt(kLogFile, log::kBlockSize + 1000, 1);  // Somewhere in second block
+  Reopen();
+
+  // The 64 records in the first two log blocks are completely lost.
+  Check(36, 36);
+}
+
+TEST_F(CorruptionTest, RecoverWriteError) {
+  env_.writable_file_error_ = true;
+  Status s = TryReopen();
+  ASSERT_TRUE(!s.ok());
+}
+
+TEST_F(CorruptionTest, NewFileErrorDuringWrite) {
+  // Do enough writing to force minor compaction
+  env_.writable_file_error_ = true;
+  const int num = 3 + (Options().write_buffer_size / kValueSize);
+  std::string value_storage;
+  Status s;
+  for (int i = 0; s.ok() && i < num; i++) {
+    WriteBatch batch;
+    batch.Put("a", Value(100, &value_storage));
+    s = db_->Write(WriteOptions(), &batch);
+  }
+  ASSERT_TRUE(!s.ok());
+  ASSERT_GE(env_.num_writable_file_errors_, 1);
+  env_.writable_file_error_ = false;
+  Reopen();
+}
+
+TEST_F(CorruptionTest, TableFile) {
+  Build(100);
+  DBImpl* dbi = reinterpret_cast<DBImpl*>(db_);
+  dbi->TEST_CompactMemTable();
+  dbi->TEST_CompactRange(0, nullptr, nullptr);
+  dbi->TEST_CompactRange(1, nullptr, nullptr);
+
+  Corrupt(kTableFile, 100, 1);
+  Check(90, 99);
+}
+
+TEST_F(CorruptionTest, TableFileRepair) {
+  options_.block_size = 2 * kValueSize;  // Limit scope of corruption
+  options_.paranoid_checks = true;
+  Reopen();
+  Build(100);
+  DBImpl* dbi = reinterpret_cast<DBImpl*>(db_);
+  dbi->TEST_CompactMemTable();
+  dbi->TEST_CompactRange(0, nullptr, nullptr);
+  dbi->TEST_CompactRange(1, nullptr, nullptr);
+
+  Corrupt(kTableFile, 100, 1);
+  RepairDB();
+  Reopen();
+  Check(95, 99);
+}
+
+TEST_F(CorruptionTest, TableFileIndexData) {
+  Build(10000);  // Enough to build multiple Tables
+  DBImpl* dbi = reinterpret_cast<DBImpl*>(db_);
+  dbi->TEST_CompactMemTable();
+
+  Corrupt(kTableFile, -2000, 500);
+  Reopen();
+  Check(5000, 9999);
+}
+
+TEST_F(CorruptionTest, MissingDescriptor) {
+  Build(1000);
+  RepairDB();
+  Reopen();
+  Check(1000, 1000);
+}
+
+TEST_F(CorruptionTest, SequenceNumberRecovery) {
+  ASSERT_LEVELDB_OK(db_->Put(WriteOptions(), "foo", "v1"));
+  ASSERT_LEVELDB_OK(db_->Put(WriteOptions(), "foo", "v2"));
+  ASSERT_LEVELDB_OK(db_->Put(WriteOptions(), "foo", "v3"));
+  ASSERT_LEVELDB_OK(db_->Put(WriteOptions(), "foo", "v4"));
+  ASSERT_LEVELDB_OK(db_->Put(WriteOptions(), "foo", "v5"));
+  RepairDB();
+  Reopen();
+  std::string v;
+  ASSERT_LEVELDB_OK(db_->Get(ReadOptions(), "foo", &v));
+  ASSERT_EQ("v5", v);
+  // Write something.  If sequence number was not recovered properly,
+  // it will be hidden by an earlier write.
+  ASSERT_LEVELDB_OK(db_->Put(WriteOptions(), "foo", "v6"));
+  ASSERT_LEVELDB_OK(db_->Get(ReadOptions(), "foo", &v));
+  ASSERT_EQ("v6", v);
+  Reopen();
+  ASSERT_LEVELDB_OK(db_->Get(ReadOptions(), "foo", &v));
+  ASSERT_EQ("v6", v);
+}
+
+TEST_F(CorruptionTest, CorruptedDescriptor) {
+  ASSERT_LEVELDB_OK(db_->Put(WriteOptions(), "foo", "hello"));
+  DBImpl* dbi = reinterpret_cast<DBImpl*>(db_);
+  dbi->TEST_CompactMemTable();
+  dbi->TEST_CompactRange(0, nullptr, nullptr);
+
+  Corrupt(kDescriptorFile, 0, 1000);
+  Status s = TryReopen();
+  ASSERT_TRUE(!s.ok());
+
+  RepairDB();
+  Reopen();
+  std::string v;
+  ASSERT_LEVELDB_OK(db_->Get(ReadOptions(), "foo", &v));
+  ASSERT_EQ("hello", v);
+}
+
+TEST_F(CorruptionTest, CompactionInputError) {
+  Build(10);
+  DBImpl* dbi = reinterpret_cast<DBImpl*>(db_);
+  dbi->TEST_CompactMemTable();
+  const int last = config::kMaxMemCompactLevel;
+  ASSERT_EQ(1, Property("leveldb.num-files-at-level" + NumberToString(last)));
+
+  Corrupt(kTableFile, 100, 1);
+  Check(5, 9);
+
+  // Force compactions by writing lots of values
+  Build(10000);
+  Check(10000, 10000);
+}
+
+TEST_F(CorruptionTest, CompactionInputErrorParanoid) {
+  options_.paranoid_checks = true;
+  options_.write_buffer_size = 512 << 10;
+  Reopen();
+  DBImpl* dbi = reinterpret_cast<DBImpl*>(db_);
+
+  // Make multiple inputs so we need to compact.
+  for (int i = 0; i < 2; i++) {
+    Build(10);
+    dbi->TEST_CompactMemTable();
+    Corrupt(kTableFile, 100, 1);
+    env_.SleepForMicroseconds(100000);
+  }
+  dbi->CompactRange(nullptr, nullptr);
+
+  // Write must fail because of corrupted table
+  std::string tmp1, tmp2;
+  Status s = db_->Put(WriteOptions(), Key(5, &tmp1), Value(5, &tmp2));
+  ASSERT_TRUE(!s.ok()) << "write did not fail in corrupted paranoid db";
+}
+
+TEST_F(CorruptionTest, UnrelatedKeys) {
+  Build(10);
+  DBImpl* dbi = reinterpret_cast<DBImpl*>(db_);
+  dbi->TEST_CompactMemTable();
+  Corrupt(kTableFile, 100, 1);
+
+  std::string tmp1, tmp2;
+  ASSERT_LEVELDB_OK(
+      db_->Put(WriteOptions(), Key(1000, &tmp1), Value(1000, &tmp2)));
+  std::string v;
+  ASSERT_LEVELDB_OK(db_->Get(ReadOptions(), Key(1000, &tmp1), &v));
+  ASSERT_EQ(Value(1000, &tmp2).ToString(), v);
+  dbi->TEST_CompactMemTable();
+  ASSERT_LEVELDB_OK(db_->Get(ReadOptions(), Key(1000, &tmp1), &v));
+  ASSERT_EQ(Value(1000, &tmp2).ToString(), v);
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/db/db_impl.cc b/leveldb_base/db/db_impl.cc
new file mode 100644
index 0000000..f8490c9
--- /dev/null
+++ b/leveldb_base/db/db_impl.cc
@@ -0,0 +1,1621 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "db/db_impl.h"
+
+#include <algorithm>
+#include <atomic>
+#include <cstdint>
+#include <cstdio>
+#include <set>
+#include <string>
+#include <vector>
+// 添加所需头文件-橙
+#include <iostream>
+#include <sstream> 
+#include <iomanip>
+#include <ctime>  
+#include <chrono>  
+
+#include "db/builder.h"
+#include "db/db_iter.h"
+#include "db/dbformat.h"
+#include "db/filename.h"
+#include "db/log_reader.h"
+#include "db/log_writer.h"
+#include "db/memtable.h"
+#include "db/table_cache.h"
+#include "db/version_set.h"
+#include "db/write_batch_internal.h"
+#include "leveldb/db.h"
+#include "leveldb/env.h"
+#include "leveldb/status.h"
+#include "leveldb/table.h"
+#include "leveldb/table_builder.h"
+#include "port/port.h"
+#include "table/block.h"
+#include "table/merger.h"
+#include "table/two_level_iterator.h"
+#include "util/coding.h"
+#include "util/logging.h"
+#include "util/mutexlock.h"
+
+namespace leveldb {
+
+const int kNumNonTableCacheFiles = 10;
+
+// Information kept for every waiting writer
+struct DBImpl::Writer {
+  explicit Writer(port::Mutex* mu)
+      : batch(nullptr), sync(false), done(false), cv(mu) {}
+
+  Status status;
+  WriteBatch* batch;
+  bool sync;
+  bool done;
+  port::CondVar cv;
+};
+
+struct DBImpl::CompactionState {
+  // Files produced by compaction
+  struct Output {
+    uint64_t number;
+    uint64_t file_size;
+    InternalKey smallest, largest;
+  };
+
+  Output* current_output() { return &outputs[outputs.size() - 1]; }
+
+  explicit CompactionState(Compaction* c)
+      : compaction(c),
+        smallest_snapshot(0),
+        outfile(nullptr),
+        builder(nullptr),
+        total_bytes(0) {}
+
+  Compaction* const compaction;
+
+  // Sequence numbers < smallest_snapshot are not significant since we
+  // will never have to service a snapshot below smallest_snapshot.
+  // Therefore if we have seen a sequence number S <= smallest_snapshot,
+  // we can drop all entries for the same key with sequence numbers < S.
+  SequenceNumber smallest_snapshot;
+
+  std::vector<Output> outputs;
+
+  // State kept for output being generated
+  WritableFile* outfile;
+  TableBuilder* builder;
+
+  uint64_t total_bytes;
+};
+
+// Fix user-supplied options to be reasonable
+template <class T, class V>
+static void ClipToRange(T* ptr, V minvalue, V maxvalue) {
+  if (static_cast<V>(*ptr) > maxvalue) *ptr = maxvalue;
+  if (static_cast<V>(*ptr) < minvalue) *ptr = minvalue;
+}
+Options SanitizeOptions(const std::string& dbname,
+                        const InternalKeyComparator* icmp,
+                        const InternalFilterPolicy* ipolicy,
+                        const Options& src) {
+  Options result = src;
+  result.comparator = icmp;
+  result.filter_policy = (src.filter_policy != nullptr) ? ipolicy : nullptr;
+  ClipToRange(&result.max_open_files, 64 + kNumNonTableCacheFiles, 50000);
+  ClipToRange(&result.write_buffer_size, 64 << 10, 1 << 30);
+  ClipToRange(&result.max_file_size, 1 << 20, 1 << 30);
+  ClipToRange(&result.block_size, 1 << 10, 4 << 20);
+  if (result.info_log == nullptr) {
+    // Open a log file in the same directory as the db
+    src.env->CreateDir(dbname);  // In case it does not exist
+    src.env->RenameFile(InfoLogFileName(dbname), OldInfoLogFileName(dbname));
+    Status s = src.env->NewLogger(InfoLogFileName(dbname), &result.info_log);
+    if (!s.ok()) {
+      // No place suitable for logging
+      result.info_log = nullptr;
+    }
+  }
+  if (result.block_cache == nullptr) {
+    result.block_cache = NewLRUCache(8 << 20);
+  }
+  return result;
+}
+
+static int TableCacheSize(const Options& sanitized_options) {
+  // Reserve ten files or so for other uses and give the rest to TableCache.
+  return sanitized_options.max_open_files - kNumNonTableCacheFiles;
+}
+
+DBImpl::DBImpl(const Options& raw_options, const std::string& dbname)
+    : env_(raw_options.env),
+      internal_comparator_(raw_options.comparator),
+      internal_filter_policy_(raw_options.filter_policy),
+      options_(SanitizeOptions(dbname, &internal_comparator_,
+                               &internal_filter_policy_, raw_options)),
+      owns_info_log_(options_.info_log != raw_options.info_log),
+      owns_cache_(options_.block_cache != raw_options.block_cache),
+      dbname_(dbname),
+      table_cache_(new TableCache(dbname_, options_, TableCacheSize(options_))),
+      db_lock_(nullptr),
+      shutting_down_(false),
+      background_work_finished_signal_(&mutex_),
+      mem_(nullptr),
+      imm_(nullptr),
+      has_imm_(false),
+      logfile_(nullptr),
+      logfile_number_(0),
+      log_(nullptr),
+      seed_(0),
+      tmp_batch_(new WriteBatch),
+      background_compaction_scheduled_(false),
+      manual_compaction_(nullptr),
+      versions_(new VersionSet(dbname_, &options_, table_cache_,
+                               &internal_comparator_)) {}
+
+DBImpl::~DBImpl() {
+  // Wait for background work to finish.
+  mutex_.Lock();
+  shutting_down_.store(true, std::memory_order_release);
+  while (background_compaction_scheduled_) {
+    background_work_finished_signal_.Wait();
+  }
+  mutex_.Unlock();
+
+  if (db_lock_ != nullptr) {
+    env_->UnlockFile(db_lock_);
+  }
+
+  delete versions_;
+  if (mem_ != nullptr) mem_->Unref();
+  if (imm_ != nullptr) imm_->Unref();
+  delete tmp_batch_;
+  delete log_;
+  delete logfile_;
+  delete table_cache_;
+
+  if (owns_info_log_) {
+    delete options_.info_log;
+  }
+  if (owns_cache_) {
+    delete options_.block_cache;
+  }
+}
+
+Status DBImpl::NewDB() {
+  VersionEdit new_db;
+  new_db.SetComparatorName(user_comparator()->Name());
+  new_db.SetLogNumber(0);
+  new_db.SetNextFile(2);
+  new_db.SetLastSequence(0);
+
+  const std::string manifest = DescriptorFileName(dbname_, 1);
+  WritableFile* file;
+  Status s = env_->NewWritableFile(manifest, &file);
+  if (!s.ok()) {
+    return s;
+  }
+  {
+    log::Writer log(file);
+    std::string record;
+    new_db.EncodeTo(&record);
+    s = log.AddRecord(record);
+    if (s.ok()) {
+      s = file->Sync();
+    }
+    if (s.ok()) {
+      s = file->Close();
+    }
+  }
+  delete file;
+  if (s.ok()) {
+    // Make "CURRENT" file that points to the new manifest file.
+    s = SetCurrentFile(env_, dbname_, 1);
+  } else {
+    env_->RemoveFile(manifest);
+  }
+  return s;
+}
+
+void DBImpl::MaybeIgnoreError(Status* s) const {
+  if (s->ok() || options_.paranoid_checks) {
+    // No change needed
+  } else {
+    Log(options_.info_log, "Ignoring error %s", s->ToString().c_str());
+    *s = Status::OK();
+  }
+}
+
+void DBImpl::RemoveObsoleteFiles() {
+  mutex_.AssertHeld();
+
+  if (!bg_error_.ok()) {
+    // After a background error, we don't know whether a new version may
+    // or may not have been committed, so we cannot safely garbage collect.
+    return;
+  }
+
+  // Make a set of all of the live files
+  std::set<uint64_t> live = pending_outputs_;
+  versions_->AddLiveFiles(&live);
+
+  std::vector<std::string> filenames;
+  env_->GetChildren(dbname_, &filenames);  // Ignoring errors on purpose
+  uint64_t number;
+  FileType type;
+  std::vector<std::string> files_to_delete;
+  for (std::string& filename : filenames) {
+    if (ParseFileName(filename, &number, &type)) {
+      bool keep = true;
+      switch (type) {
+        case kLogFile:
+          keep = ((number >= versions_->LogNumber()) ||
+                  (number == versions_->PrevLogNumber()));
+          break;
+        case kDescriptorFile:
+          // Keep my manifest file, and any newer incarnations'
+          // (in case there is a race that allows other incarnations)
+          keep = (number >= versions_->ManifestFileNumber());
+          break;
+        case kTableFile:
+          keep = (live.find(number) != live.end());
+          break;
+        case kTempFile:
+          // Any temp files that are currently being written to must
+          // be recorded in pending_outputs_, which is inserted into "live"
+          keep = (live.find(number) != live.end());
+          break;
+        case kCurrentFile:
+        case kDBLockFile:
+        case kInfoLogFile:
+          keep = true;
+          break;
+      }
+
+      if (!keep) {
+        files_to_delete.push_back(std::move(filename));
+        if (type == kTableFile) {
+          table_cache_->Evict(number);
+        }
+        Log(options_.info_log, "Delete type=%d #%lld\n", static_cast<int>(type),
+            static_cast<unsigned long long>(number));
+      }
+    }
+  }
+
+  // While deleting all files unblock other threads. All files being deleted
+  // have unique names which will not collide with newly created files and
+  // are therefore safe to delete while allowing other threads to proceed.
+  mutex_.Unlock();
+  for (const std::string& filename : files_to_delete) {
+    env_->RemoveFile(dbname_ + "/" + filename);
+  }
+  mutex_.Lock();
+}
+
+Status DBImpl::Recover(VersionEdit* edit, bool* save_manifest) {
+  mutex_.AssertHeld();
+
+  // Ignore error from CreateDir since the creation of the DB is
+  // committed only when the descriptor is created, and this directory
+  // may already exist from a previous failed creation attempt.
+  env_->CreateDir(dbname_);
+  assert(db_lock_ == nullptr);
+  Status s = env_->LockFile(LockFileName(dbname_), &db_lock_);
+  if (!s.ok()) {
+    return s;
+  }
+
+  if (!env_->FileExists(CurrentFileName(dbname_))) {
+    if (options_.create_if_missing) {
+      Log(options_.info_log, "Creating DB %s since it was missing.",
+          dbname_.c_str());
+      s = NewDB();
+      if (!s.ok()) {
+        return s;
+      }
+    } else {
+      return Status::InvalidArgument(
+          dbname_, "does not exist (create_if_missing is false)");
+    }
+  } else {
+    if (options_.error_if_exists) {
+      return Status::InvalidArgument(dbname_,
+                                     "exists (error_if_exists is true)");
+    }
+  }
+
+  s = versions_->Recover(save_manifest);
+  if (!s.ok()) {
+    return s;
+  }
+  SequenceNumber max_sequence(0);
+
+  // Recover from all newer log files than the ones named in the
+  // descriptor (new log files may have been added by the previous
+  // incarnation without registering them in the descriptor).
+  //
+  // Note that PrevLogNumber() is no longer used, but we pay
+  // attention to it in case we are recovering a database
+  // produced by an older version of leveldb.
+  const uint64_t min_log = versions_->LogNumber();
+  const uint64_t prev_log = versions_->PrevLogNumber();
+  std::vector<std::string> filenames;
+  s = env_->GetChildren(dbname_, &filenames);
+  if (!s.ok()) {
+    return s;
+  }
+  std::set<uint64_t> expected;
+  versions_->AddLiveFiles(&expected);
+  uint64_t number;
+  FileType type;
+  std::vector<uint64_t> logs;
+  for (size_t i = 0; i < filenames.size(); i++) {
+    if (ParseFileName(filenames[i], &number, &type)) {
+      expected.erase(number);
+      if (type == kLogFile && ((number >= min_log) || (number == prev_log)))
+        logs.push_back(number);
+    }
+  }
+  if (!expected.empty()) {
+    char buf[50];
+    std::snprintf(buf, sizeof(buf), "%d missing files; e.g.",
+                  static_cast<int>(expected.size()));
+    return Status::Corruption(buf, TableFileName(dbname_, *(expected.begin())));
+  }
+
+  // Recover in the order in which the logs were generated
+  std::sort(logs.begin(), logs.end());
+  for (size_t i = 0; i < logs.size(); i++) {
+    s = RecoverLogFile(logs[i], (i == logs.size() - 1), save_manifest, edit,
+                       &max_sequence);
+    if (!s.ok()) {
+      return s;
+    }
+
+    // The previous incarnation may not have written any MANIFEST
+    // records after allocating this log number.  So we manually
+    // update the file number allocation counter in VersionSet.
+    versions_->MarkFileNumberUsed(logs[i]);
+  }
+
+  if (versions_->LastSequence() < max_sequence) {
+    versions_->SetLastSequence(max_sequence);
+  }
+
+  return Status::OK();
+}
+
+Status DBImpl::RecoverLogFile(uint64_t log_number, bool last_log,
+                              bool* save_manifest, VersionEdit* edit,
+                              SequenceNumber* max_sequence) {
+  struct LogReporter : public log::Reader::Reporter {
+    Env* env;
+    Logger* info_log;
+    const char* fname;
+    Status* status;  // null if options_.paranoid_checks==false
+    void Corruption(size_t bytes, const Status& s) override {
+      Log(info_log, "%s%s: dropping %d bytes; %s",
+          (this->status == nullptr ? "(ignoring error) " : ""), fname,
+          static_cast<int>(bytes), s.ToString().c_str());
+      if (this->status != nullptr && this->status->ok()) *this->status = s;
+    }
+  };
+
+  mutex_.AssertHeld();
+
+  // Open the log file
+  std::string fname = LogFileName(dbname_, log_number);
+  SequentialFile* file;
+  Status status = env_->NewSequentialFile(fname, &file);
+  if (!status.ok()) {
+    MaybeIgnoreError(&status);
+    return status;
+  }
+
+  // Create the log reader.
+  LogReporter reporter;
+  reporter.env = env_;
+  reporter.info_log = options_.info_log;
+  reporter.fname = fname.c_str();
+  reporter.status = (options_.paranoid_checks ? &status : nullptr);
+  // We intentionally make log::Reader do checksumming even if
+  // paranoid_checks==false so that corruptions cause entire commits
+  // to be skipped instead of propagating bad information (like overly
+  // large sequence numbers).
+  log::Reader reader(file, &reporter, true /*checksum*/, 0 /*initial_offset*/);
+  Log(options_.info_log, "Recovering log #%llu",
+      (unsigned long long)log_number);
+
+  // Read all the records and add to a memtable
+  std::string scratch;
+  Slice record;
+  WriteBatch batch;
+  int compactions = 0;
+  MemTable* mem = nullptr;
+  while (reader.ReadRecord(&record, &scratch) && status.ok()) {
+    if (record.size() < 12) {
+      reporter.Corruption(record.size(),
+                          Status::Corruption("log record too small"));
+      continue;
+    }
+    WriteBatchInternal::SetContents(&batch, record);
+
+    if (mem == nullptr) {
+      mem = new MemTable(internal_comparator_);
+      mem->Ref();
+    }
+    status = WriteBatchInternal::InsertInto(&batch, mem);
+    MaybeIgnoreError(&status);
+    if (!status.ok()) {
+      break;
+    }
+    const SequenceNumber last_seq = WriteBatchInternal::Sequence(&batch) +
+                                    WriteBatchInternal::Count(&batch) - 1;
+    if (last_seq > *max_sequence) {
+      *max_sequence = last_seq;
+    }
+
+    if (mem->ApproximateMemoryUsage() > options_.write_buffer_size) {
+      compactions++;
+      *save_manifest = true;
+      status = WriteLevel0Table(mem, edit, nullptr);
+      mem->Unref();
+      mem = nullptr;
+      if (!status.ok()) {
+        // Reflect errors immediately so that conditions like full
+        // file-systems cause the DB::Open() to fail.
+        break;
+      }
+    }
+  }
+
+  delete file;
+
+  // See if we should keep reusing the last log file.
+  if (status.ok() && options_.reuse_logs && last_log && compactions == 0) {
+    assert(logfile_ == nullptr);
+    assert(log_ == nullptr);
+    assert(mem_ == nullptr);
+    uint64_t lfile_size;
+    if (env_->GetFileSize(fname, &lfile_size).ok() &&
+        env_->NewAppendableFile(fname, &logfile_).ok()) {
+      Log(options_.info_log, "Reusing old log %s \n", fname.c_str());
+      log_ = new log::Writer(logfile_, lfile_size);
+      logfile_number_ = log_number;
+      if (mem != nullptr) {
+        mem_ = mem;
+        mem = nullptr;
+      } else {
+        // mem can be nullptr if lognum exists but was empty.
+        mem_ = new MemTable(internal_comparator_);
+        mem_->Ref();
+      }
+    }
+  }
+
+  if (mem != nullptr) {
+    // mem did not get reused; compact it.
+    if (status.ok()) {
+      *save_manifest = true;
+      status = WriteLevel0Table(mem, edit, nullptr);
+    }
+    mem->Unref();
+  }
+
+  return status;
+}
+
+Status DBImpl::WriteLevel0Table(MemTable* mem, VersionEdit* edit,
+                                Version* base) {
+  mutex_.AssertHeld();
+  const uint64_t start_micros = env_->NowMicros();
+  FileMetaData meta;
+  meta.number = versions_->NewFileNumber();
+  pending_outputs_.insert(meta.number);
+  Iterator* iter = mem->NewIterator();
+  Log(options_.info_log, "Level-0 table #%llu: started",
+      (unsigned long long)meta.number);
+
+  Status s;
+  {
+    mutex_.Unlock();
+    s = BuildTable(dbname_, env_, options_, table_cache_, iter, &meta);
+    mutex_.Lock();
+  }
+
+  Log(options_.info_log, "Level-0 table #%llu: %lld bytes %s",
+      (unsigned long long)meta.number, (unsigned long long)meta.file_size,
+      s.ToString().c_str());
+  delete iter;
+  pending_outputs_.erase(meta.number);
+
+  // Note that if file_size is zero, the file has been deleted and
+  // should not be added to the manifest.
+  int level = 0;
+  if (s.ok() && meta.file_size > 0) {
+    const Slice min_user_key = meta.smallest.user_key();
+    const Slice max_user_key = meta.largest.user_key();
+    if (base != nullptr) {
+      level = base->PickLevelForMemTableOutput(min_user_key, max_user_key);
+    }
+    edit->AddFile(level, meta.number, meta.file_size, meta.smallest,
+                  meta.largest);
+  }
+
+  CompactionStats stats;
+  stats.micros = env_->NowMicros() - start_micros;
+  stats.bytes_written = meta.file_size;
+  stats_[level].Add(stats);
+  return s;
+}
+
+void DBImpl::CompactMemTable() {
+  mutex_.AssertHeld();
+  assert(imm_ != nullptr);
+
+  // Save the contents of the memtable as a new Table
+  VersionEdit edit;
+  Version* base = versions_->current();
+  base->Ref();
+  Status s = WriteLevel0Table(imm_, &edit, base);
+  base->Unref();
+
+  if (s.ok() && shutting_down_.load(std::memory_order_acquire)) {
+    s = Status::IOError("Deleting DB during memtable compaction");
+  }
+
+  // Replace immutable memtable with the generated Table
+  if (s.ok()) {
+    edit.SetPrevLogNumber(0);
+    edit.SetLogNumber(logfile_number_);  // Earlier logs no longer needed
+    s = versions_->LogAndApply(&edit, &mutex_);
+  }
+
+  if (s.ok()) {
+    // Commit to the new state
+    imm_->Unref();
+    imm_ = nullptr;
+    has_imm_.store(false, std::memory_order_release);
+    RemoveObsoleteFiles();
+  } else {
+    RecordBackgroundError(s);
+  }
+}
+
+void DBImpl::CompactRange(const Slice* begin, const Slice* end) {
+  int max_level_with_files = 1;
+  {
+    MutexLock l(&mutex_);
+    Version* base = versions_->current();
+    for (int level = 1; level < config::kNumLevels; level++) {
+      if (base->OverlapInLevel(level, begin, end)) {
+        max_level_with_files = level;
+      }
+    }
+  }
+  TEST_CompactMemTable();  // TODO(sanjay): Skip if memtable does not overlap
+  // 这个改成小于等于，test能过，但这不是改变原本的手动合并逻辑了吗？-橙
+  for (int level = 0; level <= max_level_with_files; level++) {
+    TEST_CompactRange(level, begin, end);
+  }
+}
+
+void DBImpl::TEST_CompactRange(int level, const Slice* begin,
+                               const Slice* end) {
+  assert(level >= 0);
+  assert(level + 1 < config::kNumLevels);
+
+  InternalKey begin_storage, end_storage;
+
+  ManualCompaction manual;
+  manual.level = level;
+  manual.done = false;
+  if (begin == nullptr) {
+    manual.begin = nullptr;
+  } else {
+    begin_storage = InternalKey(*begin, kMaxSequenceNumber, kValueTypeForSeek);
+    manual.begin = &begin_storage;
+  }
+  if (end == nullptr) {
+    manual.end = nullptr;
+  } else {
+    end_storage = InternalKey(*end, 0, static_cast<ValueType>(0));
+    manual.end = &end_storage;
+  }
+
+  MutexLock l(&mutex_);
+  while (!manual.done && !shutting_down_.load(std::memory_order_acquire) &&
+         bg_error_.ok()) {
+    if (manual_compaction_ == nullptr) {  // Idle
+      manual_compaction_ = &manual;
+      MaybeScheduleCompaction();
+    } else {  // Running either my compaction or another compaction.
+      background_work_finished_signal_.Wait();
+    }
+  }
+  // Finish current background compaction in the case where
+  // `background_work_finished_signal_` was signalled due to an error.
+  while (background_compaction_scheduled_) {
+    background_work_finished_signal_.Wait();
+  }
+  if (manual_compaction_ == &manual) {
+    // Cancel my manual compaction since we aborted early for some reason.
+    manual_compaction_ = nullptr;
+  }
+}
+
+Status DBImpl::TEST_CompactMemTable() {
+  // nullptr batch means just wait for earlier writes to be done
+  Status s = Write(WriteOptions(), nullptr);
+  if (s.ok()) {
+    // Wait until the compaction completes
+    MutexLock l(&mutex_);
+    while (imm_ != nullptr && bg_error_.ok()) {
+      background_work_finished_signal_.Wait();
+    }
+    if (imm_ != nullptr) {
+      s = bg_error_;
+    }
+  }
+  return s;
+}
+
+void DBImpl::RecordBackgroundError(const Status& s) {
+  mutex_.AssertHeld();
+  if (bg_error_.ok()) {
+    bg_error_ = s;
+    background_work_finished_signal_.SignalAll();
+  }
+}
+
+void DBImpl::MaybeScheduleCompaction() {
+  mutex_.AssertHeld();
+  if (background_compaction_scheduled_) {
+    // Already scheduled
+  } else if (shutting_down_.load(std::memory_order_acquire)) {
+    // DB is being deleted; no more background compactions
+  } else if (!bg_error_.ok()) {
+    // Already got an error; no more changes
+  } else if (imm_ == nullptr && manual_compaction_ == nullptr &&
+             !versions_->NeedsCompaction()) {
+    // No work to be done
+  } else {
+    background_compaction_scheduled_ = true;
+    env_->Schedule(&DBImpl::BGWork, this);
+  }
+}
+
+void DBImpl::BGWork(void* db) {
+  reinterpret_cast<DBImpl*>(db)->BackgroundCall();
+}
+
+void DBImpl::BackgroundCall() {
+  MutexLock l(&mutex_);
+  assert(background_compaction_scheduled_);
+  if (shutting_down_.load(std::memory_order_acquire)) {
+    // No more background work when shutting down.
+  } else if (!bg_error_.ok()) {
+    // No more background work after a background error.
+  } else {
+    BackgroundCompaction();
+  }
+
+  background_compaction_scheduled_ = false;
+
+  // Previous compaction may have produced too many files in a level,
+  // so reschedule another compaction if needed.
+  MaybeScheduleCompaction();
+  background_work_finished_signal_.SignalAll();
+}
+
+void DBImpl::BackgroundCompaction() {
+  mutex_.AssertHeld();
+
+  if (imm_ != nullptr) {
+    CompactMemTable();
+    return;
+  }
+
+  Compaction* c;
+  bool is_manual = (manual_compaction_ != nullptr);
+  InternalKey manual_end;
+  if (is_manual) {
+    ManualCompaction* m = manual_compaction_;
+    c = versions_->CompactRange(m->level, m->begin, m->end);
+    m->done = (c == nullptr);
+    if (c != nullptr) {
+      manual_end = c->input(0, c->num_input_files(0) - 1)->largest;
+    }
+    Log(options_.info_log,
+        "Manual compaction at level-%d from %s .. %s; will stop at %s\n",
+        m->level, (m->begin ? m->begin->DebugString().c_str() : "(begin)"),
+        (m->end ? m->end->DebugString().c_str() : "(end)"),
+        (m->done ? "(end)" : manual_end.DebugString().c_str()));
+  } else {
+    c = versions_->PickCompaction();
+  }
+
+  Status status;
+  if (c == nullptr) {
+    // Nothing to do
+  } else if (!is_manual && c->IsTrivialMove()) {
+    // Move file to next level
+    assert(c->num_input_files(0) == 1);
+    FileMetaData* f = c->input(0, 0);
+    c->edit()->RemoveFile(c->level(), f->number);
+    c->edit()->AddFile(c->level() + 1, f->number, f->file_size, f->smallest,
+                       f->largest);
+    status = versions_->LogAndApply(c->edit(), &mutex_);
+    if (!status.ok()) {
+      RecordBackgroundError(status);
+    }
+    VersionSet::LevelSummaryStorage tmp;
+    Log(options_.info_log, "Moved #%lld to level-%d %lld bytes %s: %s\n",
+        static_cast<unsigned long long>(f->number), c->level() + 1,
+        static_cast<unsigned long long>(f->file_size),
+        status.ToString().c_str(), versions_->LevelSummary(&tmp));
+  } else {
+    CompactionState* compact = new CompactionState(c);
+    status = DoCompactionWork(compact);
+    if (!status.ok()) {
+      RecordBackgroundError(status);
+    }
+    CleanupCompaction(compact);
+    c->ReleaseInputs();
+    RemoveObsoleteFiles();
+  }
+  delete c;
+
+  if (status.ok()) {
+    // Done
+  } else if (shutting_down_.load(std::memory_order_acquire)) {
+    // Ignore compaction errors found during shutting down
+  } else {
+    Log(options_.info_log, "Compaction error: %s", status.ToString().c_str());
+  }
+
+  if (is_manual) {
+    ManualCompaction* m = manual_compaction_;
+    if (!status.ok()) {
+      m->done = true;
+    }
+    if (!m->done) {
+      // We only compacted part of the requested range.  Update *m
+      // to the range that is left to be compacted.
+      m->tmp_storage = manual_end;
+      m->begin = &m->tmp_storage;
+    }
+    manual_compaction_ = nullptr;
+  }
+}
+
+void DBImpl::CleanupCompaction(CompactionState* compact) {
+  mutex_.AssertHeld();
+  if (compact->builder != nullptr) {
+    // May happen if we get a shutdown call in the middle of compaction
+    compact->builder->Abandon();
+    delete compact->builder;
+  } else {
+    assert(compact->outfile == nullptr);
+  }
+  delete compact->outfile;
+  for (size_t i = 0; i < compact->outputs.size(); i++) {
+    const CompactionState::Output& out = compact->outputs[i];
+    pending_outputs_.erase(out.number);
+  }
+  delete compact;
+}
+
+Status DBImpl::OpenCompactionOutputFile(CompactionState* compact) {
+  assert(compact != nullptr);
+  assert(compact->builder == nullptr);
+  uint64_t file_number;
+  {
+    mutex_.Lock();
+    file_number = versions_->NewFileNumber();
+    pending_outputs_.insert(file_number);
+    CompactionState::Output out;
+    out.number = file_number;
+    out.smallest.Clear();
+    out.largest.Clear();
+    compact->outputs.push_back(out);
+    mutex_.Unlock();
+  }
+
+  // Make the output file
+  std::string fname = TableFileName(dbname_, file_number);
+  Status s = env_->NewWritableFile(fname, &compact->outfile);
+  if (s.ok()) {
+    compact->builder = new TableBuilder(options_, compact->outfile);
+  }
+  return s;
+}
+
+Status DBImpl::FinishCompactionOutputFile(CompactionState* compact,
+                                          Iterator* input) {
+  assert(compact != nullptr);
+  assert(compact->outfile != nullptr);
+  assert(compact->builder != nullptr);
+
+  const uint64_t output_number = compact->current_output()->number;
+  assert(output_number != 0);
+
+  // Check for iterator errors
+  Status s = input->status();
+  const uint64_t current_entries = compact->builder->NumEntries();
+  if (s.ok()) {
+    s = compact->builder->Finish();
+  } else {
+    compact->builder->Abandon();
+  }
+  const uint64_t current_bytes = compact->builder->FileSize();
+  compact->current_output()->file_size = current_bytes;
+  compact->total_bytes += current_bytes;
+  delete compact->builder;
+  compact->builder = nullptr;
+
+  // Finish and check for file errors
+  if (s.ok()) {
+    s = compact->outfile->Sync();
+  }
+  if (s.ok()) {
+    s = compact->outfile->Close();
+  }
+  delete compact->outfile;
+  compact->outfile = nullptr;
+
+  if (s.ok() && current_entries > 0) {
+    // Verify that the table is usable
+    Iterator* iter =
+        table_cache_->NewIterator(ReadOptions(), output_number, current_bytes);
+    s = iter->status();
+    delete iter;
+    if (s.ok()) {
+      Log(options_.info_log, "Generated table #%llu@%d: %lld keys, %lld bytes",
+          (unsigned long long)output_number, compact->compaction->level(),
+          (unsigned long long)current_entries,
+          (unsigned long long)current_bytes);
+    }
+  }
+  return s;
+}
+
+Status DBImpl::InstallCompactionResults(CompactionState* compact) {
+  mutex_.AssertHeld();
+  Log(options_.info_log, "Compacted %d@%d + %d@%d files => %lld bytes",
+      compact->compaction->num_input_files(0), compact->compaction->level(),
+      compact->compaction->num_input_files(1), compact->compaction->level() + 1,
+      static_cast<long long>(compact->total_bytes));
+
+  // Add compaction outputs
+  compact->compaction->AddInputDeletions(compact->compaction->edit());
+  const int level = compact->compaction->level();
+  for (size_t i = 0; i < compact->outputs.size(); i++) {
+    const CompactionState::Output& out = compact->outputs[i];
+    compact->compaction->edit()->AddFile(level + 1, out.number, out.file_size,
+                                         out.smallest, out.largest);
+  }
+  return versions_->LogAndApply(compact->compaction->edit(), &mutex_);
+}
+
+Status DBImpl::DoCompactionWork(CompactionState* compact) {
+  const uint64_t start_micros = env_->NowMicros();
+  int64_t imm_micros = 0;  // Micros spent doing imm_ compactions
+
+  Log(options_.info_log, "Compacting %d@%d + %d@%d files",
+      compact->compaction->num_input_files(0), compact->compaction->level(),
+      compact->compaction->num_input_files(1),
+      compact->compaction->level() + 1);
+
+  assert(versions_->NumLevelFiles(compact->compaction->level()) > 0);
+  assert(compact->builder == nullptr);
+  assert(compact->outfile == nullptr);
+  if (snapshots_.empty()) {
+    compact->smallest_snapshot = versions_->LastSequence();
+  } else {
+    compact->smallest_snapshot = snapshots_.oldest()->sequence_number();
+  }
+
+  Iterator* input = versions_->MakeInputIterator(compact->compaction);
+
+  // Release mutex while we're actually doing the compaction work
+  mutex_.Unlock();
+
+  input->SeekToFirst();
+  Status status;
+  ParsedInternalKey ikey;
+  std::string current_user_key;
+  bool has_current_user_key = false;
+  SequenceNumber last_sequence_for_key = kMaxSequenceNumber;
+  while (input->Valid() && !shutting_down_.load(std::memory_order_acquire)) {
+    // Prioritize immutable compaction work
+    if (has_imm_.load(std::memory_order_relaxed)) {
+      const uint64_t imm_start = env_->NowMicros();
+      mutex_.Lock();
+      if (imm_ != nullptr) {
+        CompactMemTable();
+        // Wake up MakeRoomForWrite() if necessary.
+        background_work_finished_signal_.SignalAll();
+      }
+      mutex_.Unlock();
+      imm_micros += (env_->NowMicros() - imm_start);
+    }
+
+    Slice key = input->key();
+    if (compact->compaction->ShouldStopBefore(key) &&
+        compact->builder != nullptr) {
+      status = FinishCompactionOutputFile(compact, input);
+      if (!status.ok()) {
+        break;
+      }
+    }
+
+    // Handle key/value, add to state, etc.
+    bool drop = false;
+    // 检查数据是否过期-橙
+    Slice value = input->value();
+    std::string value_with_ttl(value.data(), value.size());
+    if (value_with_ttl.size() >= 19) {
+      std::string expiration_time_str = value_with_ttl.substr(value_with_ttl.size() - 19); // 提取过期时间戳
+      std::tm tm = {};
+      char* res = strptime(expiration_time_str.c_str(), "%Y-%m-%d %H:%M:%S", &tm);
+      if (res == nullptr) {
+        std::cerr << "Failed to parse expiration time: " << expiration_time_str << std::endl;
+        drop = false; // 解析失败则视为有效
+      } else {
+        std::time_t expiration_time = std::mktime(&tm);
+        std::time_t current_time = std::chrono::system_clock::to_time_t(std::chrono::system_clock::now());
+        if (expiration_time <= current_time) {
+          drop = true; // 数据过期，标记为丢弃
+        }
+        else
+        {
+          drop = false;
+        }
+      }
+    } else {
+      std::cerr << "Invalid value length for expiration time extraction." << std::endl;
+      drop = false; // 无法提取到过期时间，则视为有效
+    }
+
+    if (!ParseInternalKey(key, &ikey)) {
+      // Do not hide error keys
+      current_user_key.clear();
+      has_current_user_key = false;
+      last_sequence_for_key = kMaxSequenceNumber;
+    } else {
+      if (!has_current_user_key ||
+          user_comparator()->Compare(ikey.user_key, Slice(current_user_key)) !=
+              0) {
+        // First occurrence of this user key
+        current_user_key.assign(ikey.user_key.data(), ikey.user_key.size());
+        has_current_user_key = true;
+        last_sequence_for_key = kMaxSequenceNumber;
+      }
+
+      if (last_sequence_for_key <= compact->smallest_snapshot) {
+        // Hidden by an newer entry for same user key
+        drop = true;  // (A)
+      } else if (ikey.type == kTypeDeletion &&
+                 ikey.sequence <= compact->smallest_snapshot &&
+                 compact->compaction->IsBaseLevelForKey(ikey.user_key)) {
+        // For this user key:
+        // (1) there is no data in higher levels
+        // (2) data in lower levels will have larger sequence numbers
+        // (3) data in layers that are being compacted here and have
+        //     smaller sequence numbers will be dropped in the next
+        //     few iterations of this loop (by rule (A) above).
+        // Therefore this deletion marker is obsolete and can be dropped.
+        drop = true;
+      }
+
+      last_sequence_for_key = ikey.sequence;
+    }
+#if 0
+    Log(options_.info_log,
+        "  Compact: %s, seq %d, type: %d %d, drop: %d, is_base: %d, "
+        "%d smallest_snapshot: %d",
+        ikey.user_key.ToString().c_str(),
+        (int)ikey.sequence, ikey.type, kTypeValue, drop,
+        compact->compaction->IsBaseLevelForKey(ikey.user_key),
+        (int)last_sequence_for_key, (int)compact->smallest_snapshot);
+#endif
+
+    if (!drop) {
+      // Open output file if necessary
+      if (compact->builder == nullptr) {
+        status = OpenCompactionOutputFile(compact);
+        if (!status.ok()) {
+          break;
+        }
+      }
+      if (compact->builder->NumEntries() == 0) {
+        compact->current_output()->smallest.DecodeFrom(key);
+      }
+      compact->current_output()->largest.DecodeFrom(key);
+      compact->builder->Add(key, input->value());
+
+      // Close output file if it is big enough
+      if (compact->builder->FileSize() >=
+          compact->compaction->MaxOutputFileSize()) {
+        status = FinishCompactionOutputFile(compact, input);
+        if (!status.ok()) {
+          break;
+        }
+      }
+    }
+
+    input->Next();
+  }
+
+  if (status.ok() && shutting_down_.load(std::memory_order_acquire)) {
+    status = Status::IOError("Deleting DB during compaction");
+  }
+  if (status.ok() && compact->builder != nullptr) {
+    status = FinishCompactionOutputFile(compact, input);
+  }
+  if (status.ok()) {
+    status = input->status();
+  }
+  delete input;
+  input = nullptr;
+
+  CompactionStats stats;
+  stats.micros = env_->NowMicros() - start_micros - imm_micros;
+  for (int which = 0; which < 2; which++) {
+    for (int i = 0; i < compact->compaction->num_input_files(which); i++) {
+      stats.bytes_read += compact->compaction->input(which, i)->file_size;
+    }
+  }
+  for (size_t i = 0; i < compact->outputs.size(); i++) {
+    stats.bytes_written += compact->outputs[i].file_size;
+  }
+
+  mutex_.Lock();
+  stats_[compact->compaction->level() + 1].Add(stats);
+
+  if (status.ok()) {
+    status = InstallCompactionResults(compact);
+  }
+  if (!status.ok()) {
+    RecordBackgroundError(status);
+  }
+  VersionSet::LevelSummaryStorage tmp;
+  Log(options_.info_log, "compacted to: %s", versions_->LevelSummary(&tmp));
+  return status;
+}
+
+namespace {
+
+struct IterState {
+  port::Mutex* const mu;
+  Version* const version GUARDED_BY(mu);
+  MemTable* const mem GUARDED_BY(mu);
+  MemTable* const imm GUARDED_BY(mu);
+
+  IterState(port::Mutex* mutex, MemTable* mem, MemTable* imm, Version* version)
+      : mu(mutex), version(version), mem(mem), imm(imm) {}
+};
+
+static void CleanupIteratorState(void* arg1, void* arg2) {
+  IterState* state = reinterpret_cast<IterState*>(arg1);
+  state->mu->Lock();
+  state->mem->Unref();
+  if (state->imm != nullptr) state->imm->Unref();
+  state->version->Unref();
+  state->mu->Unlock();
+  delete state;
+}
+
+}  // anonymous namespace
+
+Iterator* DBImpl::NewInternalIterator(const ReadOptions& options,
+                                      SequenceNumber* latest_snapshot,
+                                      uint32_t* seed) {
+  mutex_.Lock();
+  *latest_snapshot = versions_->LastSequence();
+
+  // Collect together all needed child iterators
+  std::vector<Iterator*> list;
+  list.push_back(mem_->NewIterator());
+  mem_->Ref();
+  if (imm_ != nullptr) {
+    list.push_back(imm_->NewIterator());
+    imm_->Ref();
+  }
+  versions_->current()->AddIterators(options, &list);
+  Iterator* internal_iter =
+      NewMergingIterator(&internal_comparator_, &list[0], list.size());
+  versions_->current()->Ref();
+
+  IterState* cleanup = new IterState(&mutex_, mem_, imm_, versions_->current());
+  internal_iter->RegisterCleanup(CleanupIteratorState, cleanup, nullptr);
+
+  *seed = ++seed_;
+  mutex_.Unlock();
+  return internal_iter;
+}
+
+Iterator* DBImpl::TEST_NewInternalIterator() {
+  SequenceNumber ignored;
+  uint32_t ignored_seed;
+  return NewInternalIterator(ReadOptions(), &ignored, &ignored_seed);
+}
+
+int64_t DBImpl::TEST_MaxNextLevelOverlappingBytes() {
+  MutexLock l(&mutex_);
+  return versions_->MaxNextLevelOverlappingBytes();
+}
+
+Status DBImpl::Get(const ReadOptions& options, const Slice& key,
+                   std::string* value) {
+  Status s;
+  MutexLock l(&mutex_);
+  SequenceNumber snapshot;
+  if (options.snapshot != nullptr) {
+    snapshot =
+        static_cast<const SnapshotImpl*>(options.snapshot)->sequence_number();
+  } else {
+    snapshot = versions_->LastSequence();
+  }
+
+  MemTable* mem = mem_;
+  MemTable* imm = imm_;
+  Version* current = versions_->current();
+  mem->Ref();
+  if (imm != nullptr) imm->Ref();
+  current->Ref();
+
+  bool have_stat_update = false;
+  Version::GetStats stats;
+
+  // Unlock while reading from files and memtables
+  {
+    mutex_.Unlock();
+    // First look in the memtable, then in the immutable memtable (if any).
+    LookupKey lkey(key, snapshot);
+    if (mem->Get(lkey, value, &s)) {
+      // Done
+    } else if (imm != nullptr && imm->Get(lkey, value, &s)) {
+      // Done
+    } else {
+      s = current->Get(options, lkey, value, &stats);
+      have_stat_update = true;
+    }
+    mutex_.Lock();
+  }
+
+  if (have_stat_update && current->UpdateStats(stats)) {
+    MaybeScheduleCompaction();
+  }
+  mem->Unref();
+  if (imm != nullptr) imm->Unref();
+  current->Unref();
+  return s;
+}
+
+Iterator* DBImpl::NewIterator(const ReadOptions& options) {
+  SequenceNumber latest_snapshot;
+  uint32_t seed;
+  Iterator* iter = NewInternalIterator(options, &latest_snapshot, &seed);
+  return NewDBIterator(this, user_comparator(), iter,
+                       (options.snapshot != nullptr
+                            ? static_cast<const SnapshotImpl*>(options.snapshot)
+                                  ->sequence_number()
+                            : latest_snapshot),
+                       seed);
+}
+
+void DBImpl::RecordReadSample(Slice key) {
+  MutexLock l(&mutex_);
+  if (versions_->current()->RecordReadSample(key)) {
+    MaybeScheduleCompaction();
+  }
+}
+
+const Snapshot* DBImpl::GetSnapshot() {
+  MutexLock l(&mutex_);
+  return snapshots_.New(versions_->LastSequence());
+}
+
+void DBImpl::ReleaseSnapshot(const Snapshot* snapshot) {
+  MutexLock l(&mutex_);
+  snapshots_.Delete(static_cast<const SnapshotImpl*>(snapshot));
+}
+Status DBImpl::Put(const WriteOptions& o, const Slice& key, const Slice& val) {
+  return DB::Put(o, key, val);
+}
+// 添加ttl-橙
+// Convenience methods
+Status DBImpl::Put(const WriteOptions& o, const Slice& key, const Slice& val, uint64_t ttl) {
+  return DB::Put(o, key, val, ttl);
+}
+
+Status DBImpl::Delete(const WriteOptions& options, const Slice& key) {
+  return DB::Delete(options, key);
+}
+
+Status DBImpl::Write(const WriteOptions& options, WriteBatch* updates) {
+  Writer w(&mutex_);
+  w.batch = updates;
+  w.sync = options.sync;
+  w.done = false;
+
+  MutexLock l(&mutex_);
+  writers_.push_back(&w);
+  while (!w.done && &w != writers_.front()) {
+    w.cv.Wait();
+  }
+  if (w.done) {
+    return w.status;
+  }
+
+  // May temporarily unlock and wait.
+  Status status = MakeRoomForWrite(updates == nullptr);
+  uint64_t last_sequence = versions_->LastSequence();
+  Writer* last_writer = &w;
+  if (status.ok() && updates != nullptr) {  // nullptr batch is for compactions
+    WriteBatch* write_batch = BuildBatchGroup(&last_writer);
+    WriteBatchInternal::SetSequence(write_batch, last_sequence + 1);
+    last_sequence += WriteBatchInternal::Count(write_batch);
+
+    // Add to log and apply to memtable.  We can release the lock
+    // during this phase since &w is currently responsible for logging
+    // and protects against concurrent loggers and concurrent writes
+    // into mem_.
+    {
+      mutex_.Unlock();
+      status = log_->AddRecord(WriteBatchInternal::Contents(write_batch));
+      bool sync_error = false;
+      if (status.ok() && options.sync) {
+        status = logfile_->Sync();
+        if (!status.ok()) {
+          sync_error = true;
+        }
+      }
+      if (status.ok()) {
+        status = WriteBatchInternal::InsertInto(write_batch, mem_);
+      }
+      mutex_.Lock();
+      if (sync_error) {
+        // The state of the log file is indeterminate: the log record we
+        // just added may or may not show up when the DB is re-opened.
+        // So we force the DB into a mode where all future writes fail.
+        RecordBackgroundError(status);
+      }
+    }
+    if (write_batch == tmp_batch_) tmp_batch_->Clear();
+
+    versions_->SetLastSequence(last_sequence);
+  }
+
+  while (true) {
+    Writer* ready = writers_.front();
+    writers_.pop_front();
+    if (ready != &w) {
+      ready->status = status;
+      ready->done = true;
+      ready->cv.Signal();
+    }
+    if (ready == last_writer) break;
+  }
+
+  // Notify new head of write queue
+  if (!writers_.empty()) {
+    writers_.front()->cv.Signal();
+  }
+
+  return status;
+}
+
+// REQUIRES: Writer list must be non-empty
+// REQUIRES: First writer must have a non-null batch
+WriteBatch* DBImpl::BuildBatchGroup(Writer** last_writer) {
+  mutex_.AssertHeld();
+  assert(!writers_.empty());
+  Writer* first = writers_.front();
+  WriteBatch* result = first->batch;
+  assert(result != nullptr);
+
+  size_t size = WriteBatchInternal::ByteSize(first->batch);
+
+  // Allow the group to grow up to a maximum size, but if the
+  // original write is small, limit the growth so we do not slow
+  // down the small write too much.
+  size_t max_size = 1 << 20;
+  if (size <= (128 << 10)) {
+    max_size = size + (128 << 10);
+  }
+
+  *last_writer = first;
+  std::deque<Writer*>::iterator iter = writers_.begin();
+  ++iter;  // Advance past "first"
+  for (; iter != writers_.end(); ++iter) {
+    Writer* w = *iter;
+    if (w->sync && !first->sync) {
+      // Do not include a sync write into a batch handled by a non-sync write.
+      break;
+    }
+
+    if (w->batch != nullptr) {
+      size += WriteBatchInternal::ByteSize(w->batch);
+      if (size > max_size) {
+        // Do not make batch too big
+        break;
+      }
+
+      // Append to *result
+      if (result == first->batch) {
+        // Switch to temporary batch instead of disturbing caller's batch
+        result = tmp_batch_;
+        assert(WriteBatchInternal::Count(result) == 0);
+        WriteBatchInternal::Append(result, first->batch);
+      }
+      WriteBatchInternal::Append(result, w->batch);
+    }
+    *last_writer = w;
+  }
+  return result;
+}
+
+// REQUIRES: mutex_ is held
+// REQUIRES: this thread is currently at the front of the writer queue
+Status DBImpl::MakeRoomForWrite(bool force) {
+  mutex_.AssertHeld();
+  assert(!writers_.empty());
+  bool allow_delay = !force;
+  Status s;
+  while (true) {
+    if (!bg_error_.ok()) {
+      // Yield previous error
+      s = bg_error_;
+      break;
+    } else if (allow_delay && versions_->NumLevelFiles(0) >=
+                                  config::kL0_SlowdownWritesTrigger) {
+      // We are getting close to hitting a hard limit on the number of
+      // L0 files.  Rather than delaying a single write by several
+      // seconds when we hit the hard limit, start delaying each
+      // individual write by 1ms to reduce latency variance.  Also,
+      // this delay hands over some CPU to the compaction thread in
+      // case it is sharing the same core as the writer.
+      mutex_.Unlock();
+      env_->SleepForMicroseconds(1000);
+      allow_delay = false;  // Do not delay a single write more than once
+      mutex_.Lock();
+    } else if (!force &&
+               (mem_->ApproximateMemoryUsage() <= options_.write_buffer_size)) {
+      // There is room in current memtable
+      break;
+    } else if (imm_ != nullptr) {
+      // We have filled up the current memtable, but the previous
+      // one is still being compacted, so we wait.
+      Log(options_.info_log, "Current memtable full; waiting...\n");
+      background_work_finished_signal_.Wait();
+    } else if (versions_->NumLevelFiles(0) >= config::kL0_StopWritesTrigger) {
+      // There are too many level-0 files.
+      Log(options_.info_log, "Too many L0 files; waiting...\n");
+      background_work_finished_signal_.Wait();
+    } else {
+      // Attempt to switch to a new memtable and trigger compaction of old
+      assert(versions_->PrevLogNumber() == 0);
+      uint64_t new_log_number = versions_->NewFileNumber();
+      WritableFile* lfile = nullptr;
+      s = env_->NewWritableFile(LogFileName(dbname_, new_log_number), &lfile);
+      if (!s.ok()) {
+        // Avoid chewing through file number space in a tight loop.
+        versions_->ReuseFileNumber(new_log_number);
+        break;
+      }
+
+      delete log_;
+
+      s = logfile_->Close();
+      if (!s.ok()) {
+        // We may have lost some data written to the previous log file.
+        // Switch to the new log file anyway, but record as a background
+        // error so we do not attempt any more writes.
+        //
+        // We could perhaps attempt to save the memtable corresponding
+        // to log file and suppress the error if that works, but that
+        // would add more complexity in a critical code path.
+        RecordBackgroundError(s);
+      }
+      delete logfile_;
+
+      logfile_ = lfile;
+      logfile_number_ = new_log_number;
+      log_ = new log::Writer(lfile);
+      imm_ = mem_;
+      has_imm_.store(true, std::memory_order_release);
+      mem_ = new MemTable(internal_comparator_);
+      mem_->Ref();
+      force = false;  // Do not force another compaction if have room
+      MaybeScheduleCompaction();
+    }
+  }
+  return s;
+}
+
+bool DBImpl::GetProperty(const Slice& property, std::string* value) {
+  value->clear();
+
+  MutexLock l(&mutex_);
+  Slice in = property;
+  Slice prefix("leveldb.");
+  if (!in.starts_with(prefix)) return false;
+  in.remove_prefix(prefix.size());
+
+  if (in.starts_with("num-files-at-level")) {
+    in.remove_prefix(strlen("num-files-at-level"));
+    uint64_t level;
+    bool ok = ConsumeDecimalNumber(&in, &level) && in.empty();
+    if (!ok || level >= config::kNumLevels) {
+      return false;
+    } else {
+      char buf[100];
+      std::snprintf(buf, sizeof(buf), "%d",
+                    versions_->NumLevelFiles(static_cast<int>(level)));
+      *value = buf;
+      return true;
+    }
+  } else if (in == "stats") {
+    char buf[200];
+    std::snprintf(buf, sizeof(buf),
+                  "                               Compactions\n"
+                  "Level  Files Size(MB) Time(sec) Read(MB) Write(MB)\n"
+                  "--------------------------------------------------\n");
+    value->append(buf);
+    for (int level = 0; level < config::kNumLevels; level++) {
+      int files = versions_->NumLevelFiles(level);
+      if (stats_[level].micros > 0 || files > 0) {
+        std::snprintf(buf, sizeof(buf), "%3d %8d %8.0f %9.0f %8.0f %9.0f\n",
+                      level, files, versions_->NumLevelBytes(level) / 1048576.0,
+                      stats_[level].micros / 1e6,
+                      stats_[level].bytes_read / 1048576.0,
+                      stats_[level].bytes_written / 1048576.0);
+        value->append(buf);
+      }
+    }
+    return true;
+  } else if (in == "sstables") {
+    *value = versions_->current()->DebugString();
+    return true;
+  } else if (in == "approximate-memory-usage") {
+    size_t total_usage = options_.block_cache->TotalCharge();
+    if (mem_) {
+      total_usage += mem_->ApproximateMemoryUsage();
+    }
+    if (imm_) {
+      total_usage += imm_->ApproximateMemoryUsage();
+    }
+    char buf[50];
+    std::snprintf(buf, sizeof(buf), "%llu",
+                  static_cast<unsigned long long>(total_usage));
+    value->append(buf);
+    return true;
+  }
+
+  return false;
+}
+
+void DBImpl::GetApproximateSizes(const Range* range, int n, uint64_t* sizes) {
+  // TODO(opt): better implementation
+  MutexLock l(&mutex_);
+  Version* v = versions_->current();
+  v->Ref();
+
+  for (int i = 0; i < n; i++) {
+    // Convert user_key into a corresponding internal key.
+    InternalKey k1(range[i].start, kMaxSequenceNumber, kValueTypeForSeek);
+    InternalKey k2(range[i].limit, kMaxSequenceNumber, kValueTypeForSeek);
+    uint64_t start = versions_->ApproximateOffsetOf(v, k1);
+    uint64_t limit = versions_->ApproximateOffsetOf(v, k2);
+    sizes[i] = (limit >= start ? limit - start : 0);
+  }
+
+  v->Unref();
+}
+
+// Default implementations of convenience methods that subclasses of DB
+// can call if they wish
+Status DB::Put(const WriteOptions& opt, const Slice& key, const Slice& value) {
+  WriteBatch batch;
+  batch.Put(key, value);
+  return Write(opt, &batch);
+}
+
+// 添加ttl-橙
+Status DB::Put(const WriteOptions& opt, const Slice& key, const Slice& value, uint64_t ttl) {
+  WriteBatch batch;
+  batch.Put(key, value, ttl);
+  return Write(opt, &batch);
+}
+
+Status DB::Delete(const WriteOptions& opt, const Slice& key) {
+  WriteBatch batch;
+  batch.Delete(key);
+  return Write(opt, &batch);
+}
+
+DB::~DB() = default;
+
+Status DB::Open(const Options& options, const std::string& dbname, DB** dbptr) {
+  *dbptr = nullptr;
+
+  DBImpl* impl = new DBImpl(options, dbname);
+  impl->mutex_.Lock();
+  VersionEdit edit;
+  // Recover handles create_if_missing, error_if_exists
+  bool save_manifest = false;
+  Status s = impl->Recover(&edit, &save_manifest);
+  if (s.ok() && impl->mem_ == nullptr) {
+    // Create new log and a corresponding memtable.
+    uint64_t new_log_number = impl->versions_->NewFileNumber();
+    WritableFile* lfile;
+    s = options.env->NewWritableFile(LogFileName(dbname, new_log_number),
+                                     &lfile);
+    if (s.ok()) {
+      edit.SetLogNumber(new_log_number);
+      impl->logfile_ = lfile;
+      impl->logfile_number_ = new_log_number;
+      impl->log_ = new log::Writer(lfile);
+      impl->mem_ = new MemTable(impl->internal_comparator_);
+      impl->mem_->Ref();
+    }
+  }
+  if (s.ok() && save_manifest) {
+    edit.SetPrevLogNumber(0);  // No older logs needed after recovery.
+    edit.SetLogNumber(impl->logfile_number_);
+    s = impl->versions_->LogAndApply(&edit, &impl->mutex_);
+  }
+  if (s.ok()) {
+    impl->RemoveObsoleteFiles();
+    impl->MaybeScheduleCompaction();
+  }
+  impl->mutex_.Unlock();
+  if (s.ok()) {
+    assert(impl->mem_ != nullptr);
+    *dbptr = impl;
+  } else {
+    delete impl;
+  }
+  return s;
+}
+
+Snapshot::~Snapshot() = default;
+
+Status DestroyDB(const std::string& dbname, const Options& options) {
+  Env* env = options.env;
+  std::vector<std::string> filenames;
+  Status result = env->GetChildren(dbname, &filenames);
+  if (!result.ok()) {
+    // Ignore error in case directory does not exist
+    return Status::OK();
+  }
+
+  FileLock* lock;
+  const std::string lockname = LockFileName(dbname);
+  result = env->LockFile(lockname, &lock);
+  if (result.ok()) {
+    uint64_t number;
+    FileType type;
+    for (size_t i = 0; i < filenames.size(); i++) {
+      if (ParseFileName(filenames[i], &number, &type) &&
+          type != kDBLockFile) {  // Lock file will be deleted at end
+        Status del = env->RemoveFile(dbname + "/" + filenames[i]);
+        if (result.ok() && !del.ok()) {
+          result = del;
+        }
+      }
+    }
+    env->UnlockFile(lock);  // Ignore error since state is already gone
+    env->RemoveFile(lockname);
+    env->RemoveDir(dbname);  // Ignore error in case dir contains other files
+  }
+  return result;
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/db/db_impl.h b/leveldb_base/db/db_impl.h
new file mode 100644
index 0000000..33f276f
--- /dev/null
+++ b/leveldb_base/db/db_impl.h
@@ -0,0 +1,220 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_DB_DB_IMPL_H_
+#define STORAGE_LEVELDB_DB_DB_IMPL_H_
+
+#include <atomic>
+#include <deque>
+#include <set>
+#include <string>
+
+#include "db/dbformat.h"
+#include "db/log_writer.h"
+#include "db/snapshot.h"
+#include "leveldb/db.h"
+#include "leveldb/env.h"
+#include "port/port.h"
+#include "port/thread_annotations.h"
+
+namespace leveldb {
+
+class MemTable;
+class TableCache;
+class Version;
+class VersionEdit;
+class VersionSet;
+
+class DBImpl : public DB {
+ public:
+  DBImpl(const Options& options, const std::string& dbname);
+
+  DBImpl(const DBImpl&) = delete;
+  DBImpl& operator=(const DBImpl&) = delete;
+
+  ~DBImpl() override;
+
+  // Implementations of the DB interface
+  Status Put(const WriteOptions&, const Slice& key,
+             const Slice& value) override;
+  // 添加ttl-橙
+  Status Put(const WriteOptions&, const Slice& key,
+             const Slice& value, uint64_t ttl) override;
+  Status Delete(const WriteOptions&, const Slice& key) override;
+  Status Write(const WriteOptions& options, WriteBatch* updates) override;
+  Status Get(const ReadOptions& options, const Slice& key,
+             std::string* value) override;
+  Iterator* NewIterator(const ReadOptions&) override;
+  const Snapshot* GetSnapshot() override;
+  void ReleaseSnapshot(const Snapshot* snapshot) override;
+  bool GetProperty(const Slice& property, std::string* value) override;
+  void GetApproximateSizes(const Range* range, int n, uint64_t* sizes) override;
+  void CompactRange(const Slice* begin, const Slice* end) override;
+
+  // Extra methods (for testing) that are not in the public DB interface
+
+  // Compact any files in the named level that overlap [*begin,*end]
+  void TEST_CompactRange(int level, const Slice* begin, const Slice* end);
+
+  // Force current memtable contents to be compacted.
+  Status TEST_CompactMemTable();
+
+  // Return an internal iterator over the current state of the database.
+  // The keys of this iterator are internal keys (see format.h).
+  // The returned iterator should be deleted when no longer needed.
+  Iterator* TEST_NewInternalIterator();
+
+  // Return the maximum overlapping data (in bytes) at next level for any
+  // file at a level >= 1.
+  int64_t TEST_MaxNextLevelOverlappingBytes();
+
+  // Record a sample of bytes read at the specified internal key.
+  // Samples are taken approximately once every config::kReadBytesPeriod
+  // bytes.
+  void RecordReadSample(Slice key);
+
+ private:
+  friend class DB;
+  struct CompactionState;
+  struct Writer;
+
+  // Information for a manual compaction
+  struct ManualCompaction {
+    int level;
+    bool done;
+    const InternalKey* begin;  // null means beginning of key range
+    const InternalKey* end;    // null means end of key range
+    InternalKey tmp_storage;   // Used to keep track of compaction progress
+  };
+
+  // Per level compaction stats.  stats_[level] stores the stats for
+  // compactions that produced data for the specified "level".
+  struct CompactionStats {
+    CompactionStats() : micros(0), bytes_read(0), bytes_written(0) {}
+
+    void Add(const CompactionStats& c) {
+      this->micros += c.micros;
+      this->bytes_read += c.bytes_read;
+      this->bytes_written += c.bytes_written;
+    }
+
+    int64_t micros;
+    int64_t bytes_read;
+    int64_t bytes_written;
+  };
+
+  Iterator* NewInternalIterator(const ReadOptions&,
+                                SequenceNumber* latest_snapshot,
+                                uint32_t* seed);
+
+  Status NewDB();
+
+  // Recover the descriptor from persistent storage.  May do a significant
+  // amount of work to recover recently logged updates.  Any changes to
+  // be made to the descriptor are added to *edit.
+  Status Recover(VersionEdit* edit, bool* save_manifest)
+      EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+
+  void MaybeIgnoreError(Status* s) const;
+
+  // Delete any unneeded files and stale in-memory entries.
+  void RemoveObsoleteFiles() EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+
+  // Compact the in-memory write buffer to disk.  Switches to a new
+  // log-file/memtable and writes a new descriptor iff successful.
+  // Errors are recorded in bg_error_.
+  void CompactMemTable() EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+
+  Status RecoverLogFile(uint64_t log_number, bool last_log, bool* save_manifest,
+                        VersionEdit* edit, SequenceNumber* max_sequence)
+      EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+
+  Status WriteLevel0Table(MemTable* mem, VersionEdit* edit, Version* base)
+      EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+
+  Status MakeRoomForWrite(bool force /* compact even if there is room? */)
+      EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+  WriteBatch* BuildBatchGroup(Writer** last_writer)
+      EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+
+  void RecordBackgroundError(const Status& s);
+
+  void MaybeScheduleCompaction() EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+  static void BGWork(void* db);
+  void BackgroundCall();
+  void BackgroundCompaction() EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+  void CleanupCompaction(CompactionState* compact)
+      EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+  Status DoCompactionWork(CompactionState* compact)
+      EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+
+  Status OpenCompactionOutputFile(CompactionState* compact);
+  Status FinishCompactionOutputFile(CompactionState* compact, Iterator* input);
+  Status InstallCompactionResults(CompactionState* compact)
+      EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+
+  const Comparator* user_comparator() const {
+    return internal_comparator_.user_comparator();
+  }
+
+  // Constant after construction
+  Env* const env_;
+  const InternalKeyComparator internal_comparator_;
+  const InternalFilterPolicy internal_filter_policy_;
+  const Options options_;  // options_.comparator == &internal_comparator_
+  const bool owns_info_log_;
+  const bool owns_cache_;
+  const std::string dbname_;
+
+  // table_cache_ provides its own synchronization
+  TableCache* const table_cache_;
+
+  // Lock over the persistent DB state.  Non-null iff successfully acquired.
+  FileLock* db_lock_;
+
+  // State below is protected by mutex_
+  port::Mutex mutex_;
+  std::atomic<bool> shutting_down_;
+  port::CondVar background_work_finished_signal_ GUARDED_BY(mutex_);
+  MemTable* mem_;
+  MemTable* imm_ GUARDED_BY(mutex_);  // Memtable being compacted
+  std::atomic<bool> has_imm_;         // So bg thread can detect non-null imm_
+  WritableFile* logfile_;
+  uint64_t logfile_number_ GUARDED_BY(mutex_);
+  log::Writer* log_;
+  uint32_t seed_ GUARDED_BY(mutex_);  // For sampling.
+
+  // Queue of writers.
+  std::deque<Writer*> writers_ GUARDED_BY(mutex_);
+  WriteBatch* tmp_batch_ GUARDED_BY(mutex_);
+
+  SnapshotList snapshots_ GUARDED_BY(mutex_);
+
+  // Set of table files to protect from deletion because they are
+  // part of ongoing compactions.
+  std::set<uint64_t> pending_outputs_ GUARDED_BY(mutex_);
+
+  // Has a background compaction been scheduled or is running?
+  bool background_compaction_scheduled_ GUARDED_BY(mutex_);
+
+  ManualCompaction* manual_compaction_ GUARDED_BY(mutex_);
+
+  VersionSet* const versions_ GUARDED_BY(mutex_);
+
+  // Have we encountered a background error in paranoid mode?
+  Status bg_error_ GUARDED_BY(mutex_);
+
+  CompactionStats stats_[config::kNumLevels] GUARDED_BY(mutex_);
+};
+
+// Sanitize db options.  The caller should delete result.info_log if
+// it is not equal to src.info_log.
+Options SanitizeOptions(const std::string& db,
+                        const InternalKeyComparator* icmp,
+                        const InternalFilterPolicy* ipolicy,
+                        const Options& src);
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_DB_DB_IMPL_H_
diff --git a/leveldb_base/db/db_iter.cc b/leveldb_base/db/db_iter.cc
new file mode 100644
index 0000000..532c2db
--- /dev/null
+++ b/leveldb_base/db/db_iter.cc
@@ -0,0 +1,318 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "db/db_iter.h"
+
+#include "db/db_impl.h"
+#include "db/dbformat.h"
+#include "db/filename.h"
+#include "leveldb/env.h"
+#include "leveldb/iterator.h"
+#include "port/port.h"
+#include "util/logging.h"
+#include "util/mutexlock.h"
+#include "util/random.h"
+
+namespace leveldb {
+
+#if 0
+static void DumpInternalIter(Iterator* iter) {
+  for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
+    ParsedInternalKey k;
+    if (!ParseInternalKey(iter->key(), &k)) {
+      std::fprintf(stderr, "Corrupt '%s'\n", EscapeString(iter->key()).c_str());
+    } else {
+      std::fprintf(stderr, "@ '%s'\n", k.DebugString().c_str());
+    }
+  }
+}
+#endif
+
+namespace {
+
+// Memtables and sstables that make the DB representation contain
+// (userkey,seq,type) => uservalue entries.  DBIter
+// combines multiple entries for the same userkey found in the DB
+// representation into a single entry while accounting for sequence
+// numbers, deletion markers, overwrites, etc.
+class DBIter : public Iterator {
+ public:
+  // Which direction is the iterator currently moving?
+  // (1) When moving forward, the internal iterator is positioned at
+  //     the exact entry that yields this->key(), this->value()
+  // (2) When moving backwards, the internal iterator is positioned
+  //     just before all entries whose user key == this->key().
+  enum Direction { kForward, kReverse };
+
+  DBIter(DBImpl* db, const Comparator* cmp, Iterator* iter, SequenceNumber s,
+         uint32_t seed)
+      : db_(db),
+        user_comparator_(cmp),
+        iter_(iter),
+        sequence_(s),
+        direction_(kForward),
+        valid_(false),
+        rnd_(seed),
+        bytes_until_read_sampling_(RandomCompactionPeriod()) {}
+
+  DBIter(const DBIter&) = delete;
+  DBIter& operator=(const DBIter&) = delete;
+
+  ~DBIter() override { delete iter_; }
+  bool Valid() const override { return valid_; }
+  Slice key() const override {
+    assert(valid_);
+    return (direction_ == kForward) ? ExtractUserKey(iter_->key()) : saved_key_;
+  }
+  Slice value() const override {
+    assert(valid_);
+    return (direction_ == kForward) ? iter_->value() : saved_value_;
+  }
+  Status status() const override {
+    if (status_.ok()) {
+      return iter_->status();
+    } else {
+      return status_;
+    }
+  }
+
+  void Next() override;
+  void Prev() override;
+  void Seek(const Slice& target) override;
+  void SeekToFirst() override;
+  void SeekToLast() override;
+
+ private:
+  void FindNextUserEntry(bool skipping, std::string* skip);
+  void FindPrevUserEntry();
+  bool ParseKey(ParsedInternalKey* key);
+
+  inline void SaveKey(const Slice& k, std::string* dst) {
+    dst->assign(k.data(), k.size());
+  }
+
+  inline void ClearSavedValue() {
+    if (saved_value_.capacity() > 1048576) {
+      std::string empty;
+      swap(empty, saved_value_);
+    } else {
+      saved_value_.clear();
+    }
+  }
+
+  // Picks the number of bytes that can be read until a compaction is scheduled.
+  size_t RandomCompactionPeriod() {
+    return rnd_.Uniform(2 * config::kReadBytesPeriod);
+  }
+
+  DBImpl* db_;
+  const Comparator* const user_comparator_;
+  Iterator* const iter_;
+  SequenceNumber const sequence_;
+  Status status_;
+  std::string saved_key_;    // == current key when direction_==kReverse
+  std::string saved_value_;  // == current raw value when direction_==kReverse
+  Direction direction_;
+  bool valid_;
+  Random rnd_;
+  size_t bytes_until_read_sampling_;
+};
+
+inline bool DBIter::ParseKey(ParsedInternalKey* ikey) {
+  Slice k = iter_->key();
+
+  size_t bytes_read = k.size() + iter_->value().size();
+  while (bytes_until_read_sampling_ < bytes_read) {
+    bytes_until_read_sampling_ += RandomCompactionPeriod();
+    db_->RecordReadSample(k);
+  }
+  assert(bytes_until_read_sampling_ >= bytes_read);
+  bytes_until_read_sampling_ -= bytes_read;
+
+  if (!ParseInternalKey(k, ikey)) {
+    status_ = Status::Corruption("corrupted internal key in DBIter");
+    return false;
+  } else {
+    return true;
+  }
+}
+
+void DBIter::Next() {
+  assert(valid_);
+
+  if (direction_ == kReverse) {  // Switch directions?
+    direction_ = kForward;
+    // iter_ is pointing just before the entries for this->key(),
+    // so advance into the range of entries for this->key() and then
+    // use the normal skipping code below.
+    if (!iter_->Valid()) {
+      iter_->SeekToFirst();
+    } else {
+      iter_->Next();
+    }
+    if (!iter_->Valid()) {
+      valid_ = false;
+      saved_key_.clear();
+      return;
+    }
+    // saved_key_ already contains the key to skip past.
+  } else {
+    // Store in saved_key_ the current key so we skip it below.
+    SaveKey(ExtractUserKey(iter_->key()), &saved_key_);
+
+    // iter_ is pointing to current key. We can now safely move to the next to
+    // avoid checking current key.
+    iter_->Next();
+    if (!iter_->Valid()) {
+      valid_ = false;
+      saved_key_.clear();
+      return;
+    }
+  }
+
+  FindNextUserEntry(true, &saved_key_);
+}
+
+void DBIter::FindNextUserEntry(bool skipping, std::string* skip) {
+  // Loop until we hit an acceptable entry to yield
+  assert(iter_->Valid());
+  assert(direction_ == kForward);
+  do {
+    ParsedInternalKey ikey;
+    if (ParseKey(&ikey) && ikey.sequence <= sequence_) {
+      switch (ikey.type) {
+        case kTypeDeletion:
+          // Arrange to skip all upcoming entries for this key since
+          // they are hidden by this deletion.
+          SaveKey(ikey.user_key, skip);
+          skipping = true;
+          break;
+        case kTypeValue:
+          if (skipping &&
+              user_comparator_->Compare(ikey.user_key, *skip) <= 0) {
+            // Entry hidden
+          } else {
+            valid_ = true;
+            saved_key_.clear();
+            return;
+          }
+          break;
+      }
+    }
+    iter_->Next();
+  } while (iter_->Valid());
+  saved_key_.clear();
+  valid_ = false;
+}
+
+void DBIter::Prev() {
+  assert(valid_);
+
+  if (direction_ == kForward) {  // Switch directions?
+    // iter_ is pointing at the current entry.  Scan backwards until
+    // the key changes so we can use the normal reverse scanning code.
+    assert(iter_->Valid());  // Otherwise valid_ would have been false
+    SaveKey(ExtractUserKey(iter_->key()), &saved_key_);
+    while (true) {
+      iter_->Prev();
+      if (!iter_->Valid()) {
+        valid_ = false;
+        saved_key_.clear();
+        ClearSavedValue();
+        return;
+      }
+      if (user_comparator_->Compare(ExtractUserKey(iter_->key()), saved_key_) <
+          0) {
+        break;
+      }
+    }
+    direction_ = kReverse;
+  }
+
+  FindPrevUserEntry();
+}
+
+void DBIter::FindPrevUserEntry() {
+  assert(direction_ == kReverse);
+
+  ValueType value_type = kTypeDeletion;
+  if (iter_->Valid()) {
+    do {
+      ParsedInternalKey ikey;
+      if (ParseKey(&ikey) && ikey.sequence <= sequence_) {
+        if ((value_type != kTypeDeletion) &&
+            user_comparator_->Compare(ikey.user_key, saved_key_) < 0) {
+          // We encountered a non-deleted value in entries for previous keys,
+          break;
+        }
+        value_type = ikey.type;
+        if (value_type == kTypeDeletion) {
+          saved_key_.clear();
+          ClearSavedValue();
+        } else {
+          Slice raw_value = iter_->value();
+          if (saved_value_.capacity() > raw_value.size() + 1048576) {
+            std::string empty;
+            swap(empty, saved_value_);
+          }
+          SaveKey(ExtractUserKey(iter_->key()), &saved_key_);
+          saved_value_.assign(raw_value.data(), raw_value.size());
+        }
+      }
+      iter_->Prev();
+    } while (iter_->Valid());
+  }
+
+  if (value_type == kTypeDeletion) {
+    // End
+    valid_ = false;
+    saved_key_.clear();
+    ClearSavedValue();
+    direction_ = kForward;
+  } else {
+    valid_ = true;
+  }
+}
+
+void DBIter::Seek(const Slice& target) {
+  direction_ = kForward;
+  ClearSavedValue();
+  saved_key_.clear();
+  AppendInternalKey(&saved_key_,
+                    ParsedInternalKey(target, sequence_, kValueTypeForSeek));
+  iter_->Seek(saved_key_);
+  if (iter_->Valid()) {
+    FindNextUserEntry(false, &saved_key_ /* temporary storage */);
+  } else {
+    valid_ = false;
+  }
+}
+
+void DBIter::SeekToFirst() {
+  direction_ = kForward;
+  ClearSavedValue();
+  iter_->SeekToFirst();
+  if (iter_->Valid()) {
+    FindNextUserEntry(false, &saved_key_ /* temporary storage */);
+  } else {
+    valid_ = false;
+  }
+}
+
+void DBIter::SeekToLast() {
+  direction_ = kReverse;
+  ClearSavedValue();
+  iter_->SeekToLast();
+  FindPrevUserEntry();
+}
+
+}  // anonymous namespace
+
+Iterator* NewDBIterator(DBImpl* db, const Comparator* user_key_comparator,
+                        Iterator* internal_iter, SequenceNumber sequence,
+                        uint32_t seed) {
+  return new DBIter(db, user_key_comparator, internal_iter, sequence, seed);
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/db/db_iter.h b/leveldb_base/db/db_iter.h
new file mode 100644
index 0000000..5977fc8
--- /dev/null
+++ b/leveldb_base/db/db_iter.h
@@ -0,0 +1,26 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_DB_DB_ITER_H_
+#define STORAGE_LEVELDB_DB_DB_ITER_H_
+
+#include <cstdint>
+
+#include "db/dbformat.h"
+#include "leveldb/db.h"
+
+namespace leveldb {
+
+class DBImpl;
+
+// Return a new iterator that converts internal keys (yielded by
+// "*internal_iter") that were live at the specified "sequence" number
+// into appropriate user keys.
+Iterator* NewDBIterator(DBImpl* db, const Comparator* user_key_comparator,
+                        Iterator* internal_iter, SequenceNumber sequence,
+                        uint32_t seed);
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_DB_DB_ITER_H_
diff --git a/leveldb_base/db/db_test.cc b/leveldb_base/db/db_test.cc
new file mode 100644
index 0000000..e0a5d7f
--- /dev/null
+++ b/leveldb_base/db/db_test.cc
@@ -0,0 +1,2364 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "leveldb/db.h"
+
+#include <atomic>
+#include <cinttypes>
+#include <string>
+
+#include "gtest/gtest.h"
+#include "db/db_impl.h"
+#include "db/filename.h"
+#include "db/version_set.h"
+#include "db/write_batch_internal.h"
+#include "leveldb/cache.h"
+#include "leveldb/env.h"
+#include "leveldb/filter_policy.h"
+#include "leveldb/table.h"
+#include "port/port.h"
+#include "port/thread_annotations.h"
+#include "util/hash.h"
+#include "util/logging.h"
+#include "util/mutexlock.h"
+#include "util/testutil.h"
+
+namespace leveldb {
+
+static std::string RandomString(Random* rnd, int len) {
+  std::string r;
+  test::RandomString(rnd, len, &r);
+  return r;
+}
+
+static std::string RandomKey(Random* rnd) {
+  int len =
+      (rnd->OneIn(3) ? 1  // Short sometimes to encourage collisions
+                     : (rnd->OneIn(100) ? rnd->Skewed(10) : rnd->Uniform(10)));
+  return test::RandomKey(rnd, len);
+}
+
+namespace {
+class AtomicCounter {
+ public:
+  AtomicCounter() : count_(0) {}
+  void Increment() { IncrementBy(1); }
+  void IncrementBy(int count) LOCKS_EXCLUDED(mu_) {
+    MutexLock l(&mu_);
+    count_ += count;
+  }
+  int Read() LOCKS_EXCLUDED(mu_) {
+    MutexLock l(&mu_);
+    return count_;
+  }
+  void Reset() LOCKS_EXCLUDED(mu_) {
+    MutexLock l(&mu_);
+    count_ = 0;
+  }
+
+ private:
+  port::Mutex mu_;
+  int count_ GUARDED_BY(mu_);
+};
+
+void DelayMilliseconds(int millis) {
+  Env::Default()->SleepForMicroseconds(millis * 1000);
+}
+
+bool IsLdbFile(const std::string& f) {
+  return strstr(f.c_str(), ".ldb") != nullptr;
+}
+
+bool IsLogFile(const std::string& f) {
+  return strstr(f.c_str(), ".log") != nullptr;
+}
+
+bool IsManifestFile(const std::string& f) {
+  return strstr(f.c_str(), "MANIFEST") != nullptr;
+}
+
+}  // namespace
+
+// Test Env to override default Env behavior for testing.
+class TestEnv : public EnvWrapper {
+ public:
+  explicit TestEnv(Env* base) : EnvWrapper(base), ignore_dot_files_(false) {}
+
+  void SetIgnoreDotFiles(bool ignored) { ignore_dot_files_ = ignored; }
+
+  Status GetChildren(const std::string& dir,
+                     std::vector<std::string>* result) override {
+    Status s = target()->GetChildren(dir, result);
+    if (!s.ok() || !ignore_dot_files_) {
+      return s;
+    }
+
+    std::vector<std::string>::iterator it = result->begin();
+    while (it != result->end()) {
+      if ((*it == ".") || (*it == "..")) {
+        it = result->erase(it);
+      } else {
+        ++it;
+      }
+    }
+
+    return s;
+  }
+
+ private:
+  bool ignore_dot_files_;
+};
+
+// Special Env used to delay background operations.
+class SpecialEnv : public EnvWrapper {
+ public:
+  // For historical reasons, the std::atomic<> fields below are currently
+  // accessed via acquired loads and release stores. We should switch
+  // to plain load(), store() calls that provide sequential consistency.
+
+  // sstable/log Sync() calls are blocked while this pointer is non-null.
+  std::atomic<bool> delay_data_sync_;
+
+  // sstable/log Sync() calls return an error.
+  std::atomic<bool> data_sync_error_;
+
+  // Simulate no-space errors while this pointer is non-null.
+  std::atomic<bool> no_space_;
+
+  // Simulate non-writable file system while this pointer is non-null.
+  std::atomic<bool> non_writable_;
+
+  // Force sync of manifest files to fail while this pointer is non-null.
+  std::atomic<bool> manifest_sync_error_;
+
+  // Force write to manifest files to fail while this pointer is non-null.
+  std::atomic<bool> manifest_write_error_;
+
+  // Force log file close to fail while this bool is true.
+  std::atomic<bool> log_file_close_;
+
+  bool count_random_reads_;
+  AtomicCounter random_read_counter_;
+
+  explicit SpecialEnv(Env* base)
+      : EnvWrapper(base),
+        delay_data_sync_(false),
+        data_sync_error_(false),
+        no_space_(false),
+        non_writable_(false),
+        manifest_sync_error_(false),
+        manifest_write_error_(false),
+        log_file_close_(false),
+        count_random_reads_(false) {}
+
+  Status NewWritableFile(const std::string& f, WritableFile** r) {
+    class DataFile : public WritableFile {
+     private:
+      SpecialEnv* const env_;
+      WritableFile* const base_;
+      const std::string fname_;
+
+     public:
+      DataFile(SpecialEnv* env, WritableFile* base, const std::string& fname)
+          : env_(env), base_(base), fname_(fname) {}
+
+      ~DataFile() { delete base_; }
+      Status Append(const Slice& data) {
+        if (env_->no_space_.load(std::memory_order_acquire)) {
+          // Drop writes on the floor
+          return Status::OK();
+        } else {
+          return base_->Append(data);
+        }
+      }
+      Status Close() {
+        Status s = base_->Close();
+        if (s.ok() && IsLogFile(fname_) &&
+            env_->log_file_close_.load(std::memory_order_acquire)) {
+          s = Status::IOError("simulated log file Close error");
+        }
+        return s;
+      }
+      Status Flush() { return base_->Flush(); }
+      Status Sync() {
+        if (env_->data_sync_error_.load(std::memory_order_acquire)) {
+          return Status::IOError("simulated data sync error");
+        }
+        while (env_->delay_data_sync_.load(std::memory_order_acquire)) {
+          DelayMilliseconds(100);
+        }
+        return base_->Sync();
+      }
+    };
+    class ManifestFile : public WritableFile {
+     private:
+      SpecialEnv* env_;
+      WritableFile* base_;
+
+     public:
+      ManifestFile(SpecialEnv* env, WritableFile* b) : env_(env), base_(b) {}
+      ~ManifestFile() { delete base_; }
+      Status Append(const Slice& data) {
+        if (env_->manifest_write_error_.load(std::memory_order_acquire)) {
+          return Status::IOError("simulated writer error");
+        } else {
+          return base_->Append(data);
+        }
+      }
+      Status Close() { return base_->Close(); }
+      Status Flush() { return base_->Flush(); }
+      Status Sync() {
+        if (env_->manifest_sync_error_.load(std::memory_order_acquire)) {
+          return Status::IOError("simulated sync error");
+        } else {
+          return base_->Sync();
+        }
+      }
+    };
+
+    if (non_writable_.load(std::memory_order_acquire)) {
+      return Status::IOError("simulated write error");
+    }
+
+    Status s = target()->NewWritableFile(f, r);
+    if (s.ok()) {
+      if (IsLdbFile(f) || IsLogFile(f)) {
+        *r = new DataFile(this, *r, f);
+      } else if (IsManifestFile(f)) {
+        *r = new ManifestFile(this, *r);
+      }
+    }
+    return s;
+  }
+
+  Status NewRandomAccessFile(const std::string& f, RandomAccessFile** r) {
+    class CountingFile : public RandomAccessFile {
+     private:
+      RandomAccessFile* target_;
+      AtomicCounter* counter_;
+
+     public:
+      CountingFile(RandomAccessFile* target, AtomicCounter* counter)
+          : target_(target), counter_(counter) {}
+      ~CountingFile() override { delete target_; }
+      Status Read(uint64_t offset, size_t n, Slice* result,
+                  char* scratch) const override {
+        counter_->Increment();
+        return target_->Read(offset, n, result, scratch);
+      }
+    };
+
+    Status s = target()->NewRandomAccessFile(f, r);
+    if (s.ok() && count_random_reads_) {
+      *r = new CountingFile(*r, &random_read_counter_);
+    }
+    return s;
+  }
+};
+
+class DBTest : public testing::Test {
+ public:
+  std::string dbname_;
+  SpecialEnv* env_;
+  DB* db_;
+
+  Options last_options_;
+
+  DBTest() : env_(new SpecialEnv(Env::Default())), option_config_(kDefault) {
+    filter_policy_ = NewBloomFilterPolicy(10);
+    dbname_ = testing::TempDir() + "db_test";
+    DestroyDB(dbname_, Options());
+    db_ = nullptr;
+    Reopen();
+  }
+
+  ~DBTest() {
+    delete db_;
+    DestroyDB(dbname_, Options());
+    delete env_;
+    delete filter_policy_;
+  }
+
+  // Switch to a fresh database with the next option configuration to
+  // test.  Return false if there are no more configurations to test.
+  bool ChangeOptions() {
+    option_config_++;
+    if (option_config_ >= kEnd) {
+      return false;
+    } else {
+      DestroyAndReopen();
+      return true;
+    }
+  }
+
+  // Return the current option configuration.
+  Options CurrentOptions() {
+    Options options;
+    options.reuse_logs = false;
+    switch (option_config_) {
+      case kReuse:
+        options.reuse_logs = true;
+        break;
+      case kFilter:
+        options.filter_policy = filter_policy_;
+        break;
+      case kUncompressed:
+        options.compression = kNoCompression;
+        break;
+      default:
+        break;
+    }
+    return options;
+  }
+
+  DBImpl* dbfull() { return reinterpret_cast<DBImpl*>(db_); }
+
+  void Reopen(Options* options = nullptr) {
+    ASSERT_LEVELDB_OK(TryReopen(options));
+  }
+
+  void Close() {
+    delete db_;
+    db_ = nullptr;
+  }
+
+  void DestroyAndReopen(Options* options = nullptr) {
+    delete db_;
+    db_ = nullptr;
+    DestroyDB(dbname_, Options());
+    ASSERT_LEVELDB_OK(TryReopen(options));
+  }
+
+  Status TryReopen(Options* options) {
+    delete db_;
+    db_ = nullptr;
+    Options opts;
+    if (options != nullptr) {
+      opts = *options;
+    } else {
+      opts = CurrentOptions();
+      opts.create_if_missing = true;
+    }
+    last_options_ = opts;
+
+    return DB::Open(opts, dbname_, &db_);
+  }
+
+  Status Put(const std::string& k, const std::string& v) {
+    return db_->Put(WriteOptions(), k, v);
+  }
+
+  Status Delete(const std::string& k) { return db_->Delete(WriteOptions(), k); }
+
+  std::string Get(const std::string& k, const Snapshot* snapshot = nullptr) {
+    ReadOptions options;
+    options.snapshot = snapshot;
+    std::string result;
+    Status s = db_->Get(options, k, &result);
+    if (s.IsNotFound()) {
+      result = "NOT_FOUND";
+    } else if (!s.ok()) {
+      result = s.ToString();
+    }
+    return result;
+  }
+
+  // Return a string that contains all key,value pairs in order,
+  // formatted like "(k1->v1)(k2->v2)".
+  std::string Contents() {
+    std::vector<std::string> forward;
+    std::string result;
+    Iterator* iter = db_->NewIterator(ReadOptions());
+    for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
+      std::string s = IterStatus(iter);
+      result.push_back('(');
+      result.append(s);
+      result.push_back(')');
+      forward.push_back(s);
+    }
+
+    // Check reverse iteration results are the reverse of forward results
+    size_t matched = 0;
+    for (iter->SeekToLast(); iter->Valid(); iter->Prev()) {
+      EXPECT_LT(matched, forward.size());
+      EXPECT_EQ(IterStatus(iter), forward[forward.size() - matched - 1]);
+      matched++;
+    }
+    EXPECT_EQ(matched, forward.size());
+
+    delete iter;
+    return result;
+  }
+
+  std::string AllEntriesFor(const Slice& user_key) {
+    Iterator* iter = dbfull()->TEST_NewInternalIterator();
+    InternalKey target(user_key, kMaxSequenceNumber, kTypeValue);
+    iter->Seek(target.Encode());
+    std::string result;
+    if (!iter->status().ok()) {
+      result = iter->status().ToString();
+    } else {
+      result = "[ ";
+      bool first = true;
+      while (iter->Valid()) {
+        ParsedInternalKey ikey;
+        if (!ParseInternalKey(iter->key(), &ikey)) {
+          result += "CORRUPTED";
+        } else {
+          if (last_options_.comparator->Compare(ikey.user_key, user_key) != 0) {
+            break;
+          }
+          if (!first) {
+            result += ", ";
+          }
+          first = false;
+          switch (ikey.type) {
+            case kTypeValue:
+              result += iter->value().ToString();
+              break;
+            case kTypeDeletion:
+              result += "DEL";
+              break;
+          }
+        }
+        iter->Next();
+      }
+      if (!first) {
+        result += " ";
+      }
+      result += "]";
+    }
+    delete iter;
+    return result;
+  }
+
+  int NumTableFilesAtLevel(int level) {
+    std::string property;
+    EXPECT_TRUE(db_->GetProperty(
+        "leveldb.num-files-at-level" + NumberToString(level), &property));
+    return std::stoi(property);
+  }
+
+  int TotalTableFiles() {
+    int result = 0;
+    for (int level = 0; level < config::kNumLevels; level++) {
+      result += NumTableFilesAtLevel(level);
+    }
+    return result;
+  }
+
+  // Return spread of files per level
+  std::string FilesPerLevel() {
+    std::string result;
+    int last_non_zero_offset = 0;
+    for (int level = 0; level < config::kNumLevels; level++) {
+      int f = NumTableFilesAtLevel(level);
+      char buf[100];
+      std::snprintf(buf, sizeof(buf), "%s%d", (level ? "," : ""), f);
+      result += buf;
+      if (f > 0) {
+        last_non_zero_offset = result.size();
+      }
+    }
+    result.resize(last_non_zero_offset);
+    return result;
+  }
+
+  int CountFiles() {
+    std::vector<std::string> files;
+    env_->GetChildren(dbname_, &files);
+    return static_cast<int>(files.size());
+  }
+
+  uint64_t Size(const Slice& start, const Slice& limit) {
+    Range r(start, limit);
+    uint64_t size;
+    db_->GetApproximateSizes(&r, 1, &size);
+    return size;
+  }
+
+  void Compact(const Slice& start, const Slice& limit) {
+    db_->CompactRange(&start, &limit);
+  }
+
+  // Do n memtable compactions, each of which produces an sstable
+  // covering the range [small_key,large_key].
+  void MakeTables(int n, const std::string& small_key,
+                  const std::string& large_key) {
+    for (int i = 0; i < n; i++) {
+      Put(small_key, "begin");
+      Put(large_key, "end");
+      dbfull()->TEST_CompactMemTable();
+    }
+  }
+
+  // Prevent pushing of new sstables into deeper levels by adding
+  // tables that cover a specified range to all levels.
+  void FillLevels(const std::string& smallest, const std::string& largest) {
+    MakeTables(config::kNumLevels, smallest, largest);
+  }
+
+  void DumpFileCounts(const char* label) {
+    std::fprintf(stderr, "---\n%s:\n", label);
+    std::fprintf(
+        stderr, "maxoverlap: %lld\n",
+        static_cast<long long>(dbfull()->TEST_MaxNextLevelOverlappingBytes()));
+    for (int level = 0; level < config::kNumLevels; level++) {
+      int num = NumTableFilesAtLevel(level);
+      if (num > 0) {
+        std::fprintf(stderr, "  level %3d : %d files\n", level, num);
+      }
+    }
+  }
+
+  std::string DumpSSTableList() {
+    std::string property;
+    db_->GetProperty("leveldb.sstables", &property);
+    return property;
+  }
+
+  std::string IterStatus(Iterator* iter) {
+    std::string result;
+    if (iter->Valid()) {
+      result = iter->key().ToString() + "->" + iter->value().ToString();
+    } else {
+      result = "(invalid)";
+    }
+    return result;
+  }
+
+  bool DeleteAnSSTFile() {
+    std::vector<std::string> filenames;
+    EXPECT_LEVELDB_OK(env_->GetChildren(dbname_, &filenames));
+    uint64_t number;
+    FileType type;
+    for (size_t i = 0; i < filenames.size(); i++) {
+      if (ParseFileName(filenames[i], &number, &type) && type == kTableFile) {
+        EXPECT_LEVELDB_OK(env_->RemoveFile(TableFileName(dbname_, number)));
+        return true;
+      }
+    }
+    return false;
+  }
+
+  // Returns number of files renamed.
+  int RenameLDBToSST() {
+    std::vector<std::string> filenames;
+    EXPECT_LEVELDB_OK(env_->GetChildren(dbname_, &filenames));
+    uint64_t number;
+    FileType type;
+    int files_renamed = 0;
+    for (size_t i = 0; i < filenames.size(); i++) {
+      if (ParseFileName(filenames[i], &number, &type) && type == kTableFile) {
+        const std::string from = TableFileName(dbname_, number);
+        const std::string to = SSTTableFileName(dbname_, number);
+        EXPECT_LEVELDB_OK(env_->RenameFile(from, to));
+        files_renamed++;
+      }
+    }
+    return files_renamed;
+  }
+
+ private:
+  // Sequence of option configurations to try
+  enum OptionConfig { kDefault, kReuse, kFilter, kUncompressed, kEnd };
+
+  const FilterPolicy* filter_policy_;
+  int option_config_;
+};
+
+TEST_F(DBTest, Empty) {
+  do {
+    ASSERT_TRUE(db_ != nullptr);
+    ASSERT_EQ("NOT_FOUND", Get("foo"));
+  } while (ChangeOptions());
+}
+
+TEST_F(DBTest, EmptyKey) {
+  do {
+    ASSERT_LEVELDB_OK(Put("", "v1"));
+    ASSERT_EQ("v1", Get(""));
+    ASSERT_LEVELDB_OK(Put("", "v2"));
+    ASSERT_EQ("v2", Get(""));
+  } while (ChangeOptions());
+}
+
+TEST_F(DBTest, EmptyValue) {
+  do {
+    ASSERT_LEVELDB_OK(Put("key", "v1"));
+    ASSERT_EQ("v1", Get("key"));
+    ASSERT_LEVELDB_OK(Put("key", ""));
+    ASSERT_EQ("", Get("key"));
+    ASSERT_LEVELDB_OK(Put("key", "v2"));
+    ASSERT_EQ("v2", Get("key"));
+  } while (ChangeOptions());
+}
+
+TEST_F(DBTest, ReadWrite) {
+  do {
+    ASSERT_LEVELDB_OK(Put("foo", "v1"));
+    ASSERT_EQ("v1", Get("foo"));
+    ASSERT_LEVELDB_OK(Put("bar", "v2"));
+    ASSERT_LEVELDB_OK(Put("foo", "v3"));
+    ASSERT_EQ("v3", Get("foo"));
+    ASSERT_EQ("v2", Get("bar"));
+  } while (ChangeOptions());
+}
+
+TEST_F(DBTest, PutDeleteGet) {
+  do {
+    ASSERT_LEVELDB_OK(db_->Put(WriteOptions(), "foo", "v1"));
+    ASSERT_EQ("v1", Get("foo"));
+    ASSERT_LEVELDB_OK(db_->Put(WriteOptions(), "foo", "v2"));
+    ASSERT_EQ("v2", Get("foo"));
+    ASSERT_LEVELDB_OK(db_->Delete(WriteOptions(), "foo"));
+    ASSERT_EQ("NOT_FOUND", Get("foo"));
+  } while (ChangeOptions());
+}
+
+TEST_F(DBTest, GetFromImmutableLayer) {
+  do {
+    Options options = CurrentOptions();
+    options.env = env_;
+    options.write_buffer_size = 100000;  // Small write buffer
+    Reopen(&options);
+
+    ASSERT_LEVELDB_OK(Put("foo", "v1"));
+    ASSERT_EQ("v1", Get("foo"));
+
+    // Block sync calls.
+    env_->delay_data_sync_.store(true, std::memory_order_release);
+    Put("k1", std::string(100000, 'x'));  // Fill memtable.
+    Put("k2", std::string(100000, 'y'));  // Trigger compaction.
+    ASSERT_EQ("v1", Get("foo"));
+    // Release sync calls.
+    env_->delay_data_sync_.store(false, std::memory_order_release);
+  } while (ChangeOptions());
+}
+
+TEST_F(DBTest, GetFromVersions) {
+  do {
+    ASSERT_LEVELDB_OK(Put("foo", "v1"));
+    dbfull()->TEST_CompactMemTable();
+    ASSERT_EQ("v1", Get("foo"));
+  } while (ChangeOptions());
+}
+
+TEST_F(DBTest, GetMemUsage) {
+  do {
+    ASSERT_LEVELDB_OK(Put("foo", "v1"));
+    std::string val;
+    ASSERT_TRUE(db_->GetProperty("leveldb.approximate-memory-usage", &val));
+    int mem_usage = std::stoi(val);
+    ASSERT_GT(mem_usage, 0);
+    ASSERT_LT(mem_usage, 5 * 1024 * 1024);
+  } while (ChangeOptions());
+}
+
+TEST_F(DBTest, GetSnapshot) {
+  do {
+    // Try with both a short key and a long key
+    for (int i = 0; i < 2; i++) {
+      std::string key = (i == 0) ? std::string("foo") : std::string(200, 'x');
+      ASSERT_LEVELDB_OK(Put(key, "v1"));
+      const Snapshot* s1 = db_->GetSnapshot();
+      ASSERT_LEVELDB_OK(Put(key, "v2"));
+      ASSERT_EQ("v2", Get(key));
+      ASSERT_EQ("v1", Get(key, s1));
+      dbfull()->TEST_CompactMemTable();
+      ASSERT_EQ("v2", Get(key));
+      ASSERT_EQ("v1", Get(key, s1));
+      db_->ReleaseSnapshot(s1);
+    }
+  } while (ChangeOptions());
+}
+
+TEST_F(DBTest, GetIdenticalSnapshots) {
+  do {
+    // Try with both a short key and a long key
+    for (int i = 0; i < 2; i++) {
+      std::string key = (i == 0) ? std::string("foo") : std::string(200, 'x');
+      ASSERT_LEVELDB_OK(Put(key, "v1"));
+      const Snapshot* s1 = db_->GetSnapshot();
+      const Snapshot* s2 = db_->GetSnapshot();
+      const Snapshot* s3 = db_->GetSnapshot();
+      ASSERT_LEVELDB_OK(Put(key, "v2"));
+      ASSERT_EQ("v2", Get(key));
+      ASSERT_EQ("v1", Get(key, s1));
+      ASSERT_EQ("v1", Get(key, s2));
+      ASSERT_EQ("v1", Get(key, s3));
+      db_->ReleaseSnapshot(s1);
+      dbfull()->TEST_CompactMemTable();
+      ASSERT_EQ("v2", Get(key));
+      ASSERT_EQ("v1", Get(key, s2));
+      db_->ReleaseSnapshot(s2);
+      ASSERT_EQ("v1", Get(key, s3));
+      db_->ReleaseSnapshot(s3);
+    }
+  } while (ChangeOptions());
+}
+
+TEST_F(DBTest, IterateOverEmptySnapshot) {
+  do {
+    const Snapshot* snapshot = db_->GetSnapshot();
+    ReadOptions read_options;
+    read_options.snapshot = snapshot;
+    ASSERT_LEVELDB_OK(Put("foo", "v1"));
+    ASSERT_LEVELDB_OK(Put("foo", "v2"));
+
+    Iterator* iterator1 = db_->NewIterator(read_options);
+    iterator1->SeekToFirst();
+    ASSERT_TRUE(!iterator1->Valid());
+    delete iterator1;
+
+    dbfull()->TEST_CompactMemTable();
+
+    Iterator* iterator2 = db_->NewIterator(read_options);
+    iterator2->SeekToFirst();
+    ASSERT_TRUE(!iterator2->Valid());
+    delete iterator2;
+
+    db_->ReleaseSnapshot(snapshot);
+  } while (ChangeOptions());
+}
+
+TEST_F(DBTest, GetLevel0Ordering) {
+  do {
+    // Check that we process level-0 files in correct order.  The code
+    // below generates two level-0 files where the earlier one comes
+    // before the later one in the level-0 file list since the earlier
+    // one has a smaller "smallest" key.
+    ASSERT_LEVELDB_OK(Put("bar", "b"));
+    ASSERT_LEVELDB_OK(Put("foo", "v1"));
+    dbfull()->TEST_CompactMemTable();
+    ASSERT_LEVELDB_OK(Put("foo", "v2"));
+    dbfull()->TEST_CompactMemTable();
+    ASSERT_EQ("v2", Get("foo"));
+  } while (ChangeOptions());
+}
+
+TEST_F(DBTest, GetOrderedByLevels) {
+  do {
+    ASSERT_LEVELDB_OK(Put("foo", "v1"));
+    Compact("a", "z");
+    ASSERT_EQ("v1", Get("foo"));
+    ASSERT_LEVELDB_OK(Put("foo", "v2"));
+    ASSERT_EQ("v2", Get("foo"));
+    dbfull()->TEST_CompactMemTable();
+    ASSERT_EQ("v2", Get("foo"));
+  } while (ChangeOptions());
+}
+
+TEST_F(DBTest, GetPicksCorrectFile) {
+  do {
+    // Arrange to have multiple files in a non-level-0 level.
+    ASSERT_LEVELDB_OK(Put("a", "va"));
+    Compact("a", "b");
+    ASSERT_LEVELDB_OK(Put("x", "vx"));
+    Compact("x", "y");
+    ASSERT_LEVELDB_OK(Put("f", "vf"));
+    Compact("f", "g");
+    ASSERT_EQ("va", Get("a"));
+    ASSERT_EQ("vf", Get("f"));
+    ASSERT_EQ("vx", Get("x"));
+  } while (ChangeOptions());
+}
+
+TEST_F(DBTest, GetEncountersEmptyLevel) {
+  do {
+    // Arrange for the following to happen:
+    //   * sstable A in level 0
+    //   * nothing in level 1
+    //   * sstable B in level 2
+    // Then do enough Get() calls to arrange for an automatic compaction
+    // of sstable A.  A bug would cause the compaction to be marked as
+    // occurring at level 1 (instead of the correct level 0).
+
+    // Step 1: First place sstables in levels 0 and 2
+    int compaction_count = 0;
+    while (NumTableFilesAtLevel(0) == 0 || NumTableFilesAtLevel(2) == 0) {
+      ASSERT_LE(compaction_count, 100) << "could not fill levels 0 and 2";
+      compaction_count++;
+      Put("a", "begin");
+      Put("z", "end");
+      dbfull()->TEST_CompactMemTable();
+    }
+
+    // Step 2: clear level 1 if necessary.
+    dbfull()->TEST_CompactRange(1, nullptr, nullptr);
+    ASSERT_EQ(NumTableFilesAtLevel(0), 1);
+    ASSERT_EQ(NumTableFilesAtLevel(1), 0);
+    ASSERT_EQ(NumTableFilesAtLevel(2), 1);
+
+    // Step 3: read a bunch of times
+    for (int i = 0; i < 1000; i++) {
+      ASSERT_EQ("NOT_FOUND", Get("missing"));
+    }
+
+    // Step 4: Wait for compaction to finish
+    DelayMilliseconds(1000);
+
+    ASSERT_EQ(NumTableFilesAtLevel(0), 0);
+  } while (ChangeOptions());
+}
+
+TEST_F(DBTest, IterEmpty) {
+  Iterator* iter = db_->NewIterator(ReadOptions());
+
+  iter->SeekToFirst();
+  ASSERT_EQ(IterStatus(iter), "(invalid)");
+
+  iter->SeekToLast();
+  ASSERT_EQ(IterStatus(iter), "(invalid)");
+
+  iter->Seek("foo");
+  ASSERT_EQ(IterStatus(iter), "(invalid)");
+
+  delete iter;
+}
+
+TEST_F(DBTest, IterSingle) {
+  ASSERT_LEVELDB_OK(Put("a", "va"));
+  Iterator* iter = db_->NewIterator(ReadOptions());
+
+  iter->SeekToFirst();
+  ASSERT_EQ(IterStatus(iter), "a->va");
+  iter->Next();
+  ASSERT_EQ(IterStatus(iter), "(invalid)");
+  iter->SeekToFirst();
+  ASSERT_EQ(IterStatus(iter), "a->va");
+  iter->Prev();
+  ASSERT_EQ(IterStatus(iter), "(invalid)");
+
+  iter->SeekToLast();
+  ASSERT_EQ(IterStatus(iter), "a->va");
+  iter->Next();
+  ASSERT_EQ(IterStatus(iter), "(invalid)");
+  iter->SeekToLast();
+  ASSERT_EQ(IterStatus(iter), "a->va");
+  iter->Prev();
+  ASSERT_EQ(IterStatus(iter), "(invalid)");
+
+  iter->Seek("");
+  ASSERT_EQ(IterStatus(iter), "a->va");
+  iter->Next();
+  ASSERT_EQ(IterStatus(iter), "(invalid)");
+
+  iter->Seek("a");
+  ASSERT_EQ(IterStatus(iter), "a->va");
+  iter->Next();
+  ASSERT_EQ(IterStatus(iter), "(invalid)");
+
+  iter->Seek("b");
+  ASSERT_EQ(IterStatus(iter), "(invalid)");
+
+  delete iter;
+}
+
+TEST_F(DBTest, IterMulti) {
+  ASSERT_LEVELDB_OK(Put("a", "va"));
+  ASSERT_LEVELDB_OK(Put("b", "vb"));
+  ASSERT_LEVELDB_OK(Put("c", "vc"));
+  Iterator* iter = db_->NewIterator(ReadOptions());
+
+  iter->SeekToFirst();
+  ASSERT_EQ(IterStatus(iter), "a->va");
+  iter->Next();
+  ASSERT_EQ(IterStatus(iter), "b->vb");
+  iter->Next();
+  ASSERT_EQ(IterStatus(iter), "c->vc");
+  iter->Next();
+  ASSERT_EQ(IterStatus(iter), "(invalid)");
+  iter->SeekToFirst();
+  ASSERT_EQ(IterStatus(iter), "a->va");
+  iter->Prev();
+  ASSERT_EQ(IterStatus(iter), "(invalid)");
+
+  iter->SeekToLast();
+  ASSERT_EQ(IterStatus(iter), "c->vc");
+  iter->Prev();
+  ASSERT_EQ(IterStatus(iter), "b->vb");
+  iter->Prev();
+  ASSERT_EQ(IterStatus(iter), "a->va");
+  iter->Prev();
+  ASSERT_EQ(IterStatus(iter), "(invalid)");
+  iter->SeekToLast();
+  ASSERT_EQ(IterStatus(iter), "c->vc");
+  iter->Next();
+  ASSERT_EQ(IterStatus(iter), "(invalid)");
+
+  iter->Seek("");
+  ASSERT_EQ(IterStatus(iter), "a->va");
+  iter->Seek("a");
+  ASSERT_EQ(IterStatus(iter), "a->va");
+  iter->Seek("ax");
+  ASSERT_EQ(IterStatus(iter), "b->vb");
+  iter->Seek("b");
+  ASSERT_EQ(IterStatus(iter), "b->vb");
+  iter->Seek("z");
+  ASSERT_EQ(IterStatus(iter), "(invalid)");
+
+  // Switch from reverse to forward
+  iter->SeekToLast();
+  iter->Prev();
+  iter->Prev();
+  iter->Next();
+  ASSERT_EQ(IterStatus(iter), "b->vb");
+
+  // Switch from forward to reverse
+  iter->SeekToFirst();
+  iter->Next();
+  iter->Next();
+  iter->Prev();
+  ASSERT_EQ(IterStatus(iter), "b->vb");
+
+  // Make sure iter stays at snapshot
+  ASSERT_LEVELDB_OK(Put("a", "va2"));
+  ASSERT_LEVELDB_OK(Put("a2", "va3"));
+  ASSERT_LEVELDB_OK(Put("b", "vb2"));
+  ASSERT_LEVELDB_OK(Put("c", "vc2"));
+  ASSERT_LEVELDB_OK(Delete("b"));
+  iter->SeekToFirst();
+  ASSERT_EQ(IterStatus(iter), "a->va");
+  iter->Next();
+  ASSERT_EQ(IterStatus(iter), "b->vb");
+  iter->Next();
+  ASSERT_EQ(IterStatus(iter), "c->vc");
+  iter->Next();
+  ASSERT_EQ(IterStatus(iter), "(invalid)");
+  iter->SeekToLast();
+  ASSERT_EQ(IterStatus(iter), "c->vc");
+  iter->Prev();
+  ASSERT_EQ(IterStatus(iter), "b->vb");
+  iter->Prev();
+  ASSERT_EQ(IterStatus(iter), "a->va");
+  iter->Prev();
+  ASSERT_EQ(IterStatus(iter), "(invalid)");
+
+  delete iter;
+}
+
+TEST_F(DBTest, IterSmallAndLargeMix) {
+  ASSERT_LEVELDB_OK(Put("a", "va"));
+  ASSERT_LEVELDB_OK(Put("b", std::string(100000, 'b')));
+  ASSERT_LEVELDB_OK(Put("c", "vc"));
+  ASSERT_LEVELDB_OK(Put("d", std::string(100000, 'd')));
+  ASSERT_LEVELDB_OK(Put("e", std::string(100000, 'e')));
+
+  Iterator* iter = db_->NewIterator(ReadOptions());
+
+  iter->SeekToFirst();
+  ASSERT_EQ(IterStatus(iter), "a->va");
+  iter->Next();
+  ASSERT_EQ(IterStatus(iter), "b->" + std::string(100000, 'b'));
+  iter->Next();
+  ASSERT_EQ(IterStatus(iter), "c->vc");
+  iter->Next();
+  ASSERT_EQ(IterStatus(iter), "d->" + std::string(100000, 'd'));
+  iter->Next();
+  ASSERT_EQ(IterStatus(iter), "e->" + std::string(100000, 'e'));
+  iter->Next();
+  ASSERT_EQ(IterStatus(iter), "(invalid)");
+
+  iter->SeekToLast();
+  ASSERT_EQ(IterStatus(iter), "e->" + std::string(100000, 'e'));
+  iter->Prev();
+  ASSERT_EQ(IterStatus(iter), "d->" + std::string(100000, 'd'));
+  iter->Prev();
+  ASSERT_EQ(IterStatus(iter), "c->vc");
+  iter->Prev();
+  ASSERT_EQ(IterStatus(iter), "b->" + std::string(100000, 'b'));
+  iter->Prev();
+  ASSERT_EQ(IterStatus(iter), "a->va");
+  iter->Prev();
+  ASSERT_EQ(IterStatus(iter), "(invalid)");
+
+  delete iter;
+}
+
+TEST_F(DBTest, IterMultiWithDelete) {
+  do {
+    ASSERT_LEVELDB_OK(Put("a", "va"));
+    ASSERT_LEVELDB_OK(Put("b", "vb"));
+    ASSERT_LEVELDB_OK(Put("c", "vc"));
+    ASSERT_LEVELDB_OK(Delete("b"));
+    ASSERT_EQ("NOT_FOUND", Get("b"));
+
+    Iterator* iter = db_->NewIterator(ReadOptions());
+    iter->Seek("c");
+    ASSERT_EQ(IterStatus(iter), "c->vc");
+    iter->Prev();
+    ASSERT_EQ(IterStatus(iter), "a->va");
+    delete iter;
+  } while (ChangeOptions());
+}
+
+TEST_F(DBTest, IterMultiWithDeleteAndCompaction) {
+  do {
+    ASSERT_LEVELDB_OK(Put("b", "vb"));
+    ASSERT_LEVELDB_OK(Put("c", "vc"));
+    ASSERT_LEVELDB_OK(Put("a", "va"));
+    dbfull()->TEST_CompactMemTable();
+    ASSERT_LEVELDB_OK(Delete("b"));
+    ASSERT_EQ("NOT_FOUND", Get("b"));
+
+    Iterator* iter = db_->NewIterator(ReadOptions());
+    iter->Seek("c");
+    ASSERT_EQ(IterStatus(iter), "c->vc");
+    iter->Prev();
+    ASSERT_EQ(IterStatus(iter), "a->va");
+    iter->Seek("b");
+    ASSERT_EQ(IterStatus(iter), "c->vc");
+    delete iter;
+  } while (ChangeOptions());
+}
+
+TEST_F(DBTest, Recover) {
+  do {
+    ASSERT_LEVELDB_OK(Put("foo", "v1"));
+    ASSERT_LEVELDB_OK(Put("baz", "v5"));
+
+    Reopen();
+    ASSERT_EQ("v1", Get("foo"));
+
+    ASSERT_EQ("v1", Get("foo"));
+    ASSERT_EQ("v5", Get("baz"));
+    ASSERT_LEVELDB_OK(Put("bar", "v2"));
+    ASSERT_LEVELDB_OK(Put("foo", "v3"));
+
+    Reopen();
+    ASSERT_EQ("v3", Get("foo"));
+    ASSERT_LEVELDB_OK(Put("foo", "v4"));
+    ASSERT_EQ("v4", Get("foo"));
+    ASSERT_EQ("v2", Get("bar"));
+    ASSERT_EQ("v5", Get("baz"));
+  } while (ChangeOptions());
+}
+
+TEST_F(DBTest, RecoveryWithEmptyLog) {
+  do {
+    ASSERT_LEVELDB_OK(Put("foo", "v1"));
+    ASSERT_LEVELDB_OK(Put("foo", "v2"));
+    Reopen();
+    Reopen();
+    ASSERT_LEVELDB_OK(Put("foo", "v3"));
+    Reopen();
+    ASSERT_EQ("v3", Get("foo"));
+  } while (ChangeOptions());
+}
+
+// Check that writes done during a memtable compaction are recovered
+// if the database is shutdown during the memtable compaction.
+TEST_F(DBTest, RecoverDuringMemtableCompaction) {
+  do {
+    Options options = CurrentOptions();
+    options.env = env_;
+    options.write_buffer_size = 1000000;
+    Reopen(&options);
+
+    // Trigger a long memtable compaction and reopen the database during it
+    ASSERT_LEVELDB_OK(Put("foo", "v1"));  // Goes to 1st log file
+    ASSERT_LEVELDB_OK(
+        Put("big1", std::string(10000000, 'x')));  // Fills memtable
+    ASSERT_LEVELDB_OK(
+        Put("big2", std::string(1000, 'y')));  // Triggers compaction
+    ASSERT_LEVELDB_OK(Put("bar", "v2"));       // Goes to new log file
+
+    Reopen(&options);
+    ASSERT_EQ("v1", Get("foo"));
+    ASSERT_EQ("v2", Get("bar"));
+    ASSERT_EQ(std::string(10000000, 'x'), Get("big1"));
+    ASSERT_EQ(std::string(1000, 'y'), Get("big2"));
+  } while (ChangeOptions());
+}
+
+static std::string Key(int i) {
+  char buf[100];
+  std::snprintf(buf, sizeof(buf), "key%06d", i);
+  return std::string(buf);
+}
+
+TEST_F(DBTest, MinorCompactionsHappen) {
+  Options options = CurrentOptions();
+  options.write_buffer_size = 10000;
+  Reopen(&options);
+
+  const int N = 500;
+
+  int starting_num_tables = TotalTableFiles();
+  for (int i = 0; i < N; i++) {
+    ASSERT_LEVELDB_OK(Put(Key(i), Key(i) + std::string(1000, 'v')));
+  }
+  int ending_num_tables = TotalTableFiles();
+  ASSERT_GT(ending_num_tables, starting_num_tables);
+
+  for (int i = 0; i < N; i++) {
+    ASSERT_EQ(Key(i) + std::string(1000, 'v'), Get(Key(i)));
+  }
+
+  Reopen();
+
+  for (int i = 0; i < N; i++) {
+    ASSERT_EQ(Key(i) + std::string(1000, 'v'), Get(Key(i)));
+  }
+}
+
+TEST_F(DBTest, RecoverWithLargeLog) {
+  {
+    Options options = CurrentOptions();
+    Reopen(&options);
+    ASSERT_LEVELDB_OK(Put("big1", std::string(200000, '1')));
+    ASSERT_LEVELDB_OK(Put("big2", std::string(200000, '2')));
+    ASSERT_LEVELDB_OK(Put("small3", std::string(10, '3')));
+    ASSERT_LEVELDB_OK(Put("small4", std::string(10, '4')));
+    ASSERT_EQ(NumTableFilesAtLevel(0), 0);
+  }
+
+  // Make sure that if we re-open with a small write buffer size that
+  // we flush table files in the middle of a large log file.
+  Options options = CurrentOptions();
+  options.write_buffer_size = 100000;
+  Reopen(&options);
+  ASSERT_EQ(NumTableFilesAtLevel(0), 3);
+  ASSERT_EQ(std::string(200000, '1'), Get("big1"));
+  ASSERT_EQ(std::string(200000, '2'), Get("big2"));
+  ASSERT_EQ(std::string(10, '3'), Get("small3"));
+  ASSERT_EQ(std::string(10, '4'), Get("small4"));
+  ASSERT_GT(NumTableFilesAtLevel(0), 1);
+}
+
+TEST_F(DBTest, CompactionsGenerateMultipleFiles) {
+  Options options = CurrentOptions();
+  options.write_buffer_size = 100000000;  // Large write buffer
+  Reopen(&options);
+
+  Random rnd(301);
+
+  // Write 8MB (80 values, each 100K)
+  ASSERT_EQ(NumTableFilesAtLevel(0), 0);
+  std::vector<std::string> values;
+  for (int i = 0; i < 80; i++) {
+    values.push_back(RandomString(&rnd, 100000));
+    ASSERT_LEVELDB_OK(Put(Key(i), values[i]));
+  }
+
+  // Reopening moves updates to level-0
+  Reopen(&options);
+  dbfull()->TEST_CompactRange(0, nullptr, nullptr);
+
+  ASSERT_EQ(NumTableFilesAtLevel(0), 0);
+  ASSERT_GT(NumTableFilesAtLevel(1), 1);
+  for (int i = 0; i < 80; i++) {
+    ASSERT_EQ(Get(Key(i)), values[i]);
+  }
+}
+
+TEST_F(DBTest, RepeatedWritesToSameKey) {
+  Options options = CurrentOptions();
+  options.env = env_;
+  options.write_buffer_size = 100000;  // Small write buffer
+  Reopen(&options);
+
+  // We must have at most one file per level except for level-0,
+  // which may have up to kL0_StopWritesTrigger files.
+  const int kMaxFiles = config::kNumLevels + config::kL0_StopWritesTrigger;
+
+  Random rnd(301);
+  std::string value = RandomString(&rnd, 2 * options.write_buffer_size);
+  for (int i = 0; i < 5 * kMaxFiles; i++) {
+    Put("key", value);
+    ASSERT_LE(TotalTableFiles(), kMaxFiles);
+    std::fprintf(stderr, "after %d: %d files\n", i + 1, TotalTableFiles());
+  }
+}
+
+TEST_F(DBTest, SparseMerge) {
+  Options options = CurrentOptions();
+  options.compression = kNoCompression;
+  Reopen(&options);
+
+  FillLevels("A", "Z");
+
+  // Suppose there is:
+  //    small amount of data with prefix A
+  //    large amount of data with prefix B
+  //    small amount of data with prefix C
+  // and that recent updates have made small changes to all three prefixes.
+  // Check that we do not do a compaction that merges all of B in one shot.
+  const std::string value(1000, 'x');
+  Put("A", "va");
+  // Write approximately 100MB of "B" values
+  for (int i = 0; i < 100000; i++) {
+    char key[100];
+    std::snprintf(key, sizeof(key), "B%010d", i);
+    Put(key, value);
+  }
+  Put("C", "vc");
+  dbfull()->TEST_CompactMemTable();
+  dbfull()->TEST_CompactRange(0, nullptr, nullptr);
+
+  // Make sparse update
+  Put("A", "va2");
+  Put("B100", "bvalue2");
+  Put("C", "vc2");
+  dbfull()->TEST_CompactMemTable();
+
+  // Compactions should not cause us to create a situation where
+  // a file overlaps too much data at the next level.
+  ASSERT_LE(dbfull()->TEST_MaxNextLevelOverlappingBytes(), 20 * 1048576);
+  dbfull()->TEST_CompactRange(0, nullptr, nullptr);
+  ASSERT_LE(dbfull()->TEST_MaxNextLevelOverlappingBytes(), 20 * 1048576);
+  dbfull()->TEST_CompactRange(1, nullptr, nullptr);
+  ASSERT_LE(dbfull()->TEST_MaxNextLevelOverlappingBytes(), 20 * 1048576);
+}
+
+static bool Between(uint64_t val, uint64_t low, uint64_t high) {
+  bool result = (val >= low) && (val <= high);
+  if (!result) {
+    std::fprintf(stderr, "Value %llu is not in range [%llu, %llu]\n",
+                 (unsigned long long)(val), (unsigned long long)(low),
+                 (unsigned long long)(high));
+  }
+  return result;
+}
+
+TEST_F(DBTest, ApproximateSizes) {
+  do {
+    Options options = CurrentOptions();
+    options.write_buffer_size = 100000000;  // Large write buffer
+    options.compression = kNoCompression;
+    DestroyAndReopen();
+
+    ASSERT_TRUE(Between(Size("", "xyz"), 0, 0));
+    Reopen(&options);
+    ASSERT_TRUE(Between(Size("", "xyz"), 0, 0));
+
+    // Write 8MB (80 values, each 100K)
+    ASSERT_EQ(NumTableFilesAtLevel(0), 0);
+    const int N = 80;
+    static const int S1 = 100000;
+    static const int S2 = 105000;  // Allow some expansion from metadata
+    Random rnd(301);
+    for (int i = 0; i < N; i++) {
+      ASSERT_LEVELDB_OK(Put(Key(i), RandomString(&rnd, S1)));
+    }
+
+    // 0 because GetApproximateSizes() does not account for memtable space
+    ASSERT_TRUE(Between(Size("", Key(50)), 0, 0));
+
+    if (options.reuse_logs) {
+      // Recovery will reuse memtable, and GetApproximateSizes() does not
+      // account for memtable usage;
+      Reopen(&options);
+      ASSERT_TRUE(Between(Size("", Key(50)), 0, 0));
+      continue;
+    }
+
+    // Check sizes across recovery by reopening a few times
+    for (int run = 0; run < 3; run++) {
+      Reopen(&options);
+
+      for (int compact_start = 0; compact_start < N; compact_start += 10) {
+        for (int i = 0; i < N; i += 10) {
+          ASSERT_TRUE(Between(Size("", Key(i)), S1 * i, S2 * i));
+          ASSERT_TRUE(Between(Size("", Key(i) + ".suffix"), S1 * (i + 1),
+                              S2 * (i + 1)));
+          ASSERT_TRUE(Between(Size(Key(i), Key(i + 10)), S1 * 10, S2 * 10));
+        }
+        ASSERT_TRUE(Between(Size("", Key(50)), S1 * 50, S2 * 50));
+        ASSERT_TRUE(Between(Size("", Key(50) + ".suffix"), S1 * 50, S2 * 50));
+
+        std::string cstart_str = Key(compact_start);
+        std::string cend_str = Key(compact_start + 9);
+        Slice cstart = cstart_str;
+        Slice cend = cend_str;
+        dbfull()->TEST_CompactRange(0, &cstart, &cend);
+      }
+
+      ASSERT_EQ(NumTableFilesAtLevel(0), 0);
+      ASSERT_GT(NumTableFilesAtLevel(1), 0);
+    }
+  } while (ChangeOptions());
+}
+
+TEST_F(DBTest, ApproximateSizes_MixOfSmallAndLarge) {
+  do {
+    Options options = CurrentOptions();
+    options.compression = kNoCompression;
+    Reopen();
+
+    Random rnd(301);
+    std::string big1 = RandomString(&rnd, 100000);
+    ASSERT_LEVELDB_OK(Put(Key(0), RandomString(&rnd, 10000)));
+    ASSERT_LEVELDB_OK(Put(Key(1), RandomString(&rnd, 10000)));
+    ASSERT_LEVELDB_OK(Put(Key(2), big1));
+    ASSERT_LEVELDB_OK(Put(Key(3), RandomString(&rnd, 10000)));
+    ASSERT_LEVELDB_OK(Put(Key(4), big1));
+    ASSERT_LEVELDB_OK(Put(Key(5), RandomString(&rnd, 10000)));
+    ASSERT_LEVELDB_OK(Put(Key(6), RandomString(&rnd, 300000)));
+    ASSERT_LEVELDB_OK(Put(Key(7), RandomString(&rnd, 10000)));
+
+    if (options.reuse_logs) {
+      // Need to force a memtable compaction since recovery does not do so.
+      ASSERT_LEVELDB_OK(dbfull()->TEST_CompactMemTable());
+    }
+
+    // Check sizes across recovery by reopening a few times
+    for (int run = 0; run < 3; run++) {
+      Reopen(&options);
+
+      ASSERT_TRUE(Between(Size("", Key(0)), 0, 0));
+      ASSERT_TRUE(Between(Size("", Key(1)), 10000, 11000));
+      ASSERT_TRUE(Between(Size("", Key(2)), 20000, 21000));
+      ASSERT_TRUE(Between(Size("", Key(3)), 120000, 121000));
+      ASSERT_TRUE(Between(Size("", Key(4)), 130000, 131000));
+      ASSERT_TRUE(Between(Size("", Key(5)), 230000, 231000));
+      ASSERT_TRUE(Between(Size("", Key(6)), 240000, 241000));
+      ASSERT_TRUE(Between(Size("", Key(7)), 540000, 541000));
+      ASSERT_TRUE(Between(Size("", Key(8)), 550000, 560000));
+
+      ASSERT_TRUE(Between(Size(Key(3), Key(5)), 110000, 111000));
+
+      dbfull()->TEST_CompactRange(0, nullptr, nullptr);
+    }
+  } while (ChangeOptions());
+}
+
+TEST_F(DBTest, IteratorPinsRef) {
+  Put("foo", "hello");
+
+  // Get iterator that will yield the current contents of the DB.
+  Iterator* iter = db_->NewIterator(ReadOptions());
+
+  // Write to force compactions
+  Put("foo", "newvalue1");
+  for (int i = 0; i < 100; i++) {
+    ASSERT_LEVELDB_OK(
+        Put(Key(i), Key(i) + std::string(100000, 'v')));  // 100K values
+  }
+  Put("foo", "newvalue2");
+
+  iter->SeekToFirst();
+  ASSERT_TRUE(iter->Valid());
+  ASSERT_EQ("foo", iter->key().ToString());
+  ASSERT_EQ("hello", iter->value().ToString());
+  iter->Next();
+  ASSERT_TRUE(!iter->Valid());
+  delete iter;
+}
+
+TEST_F(DBTest, Snapshot) {
+  do {
+    Put("foo", "v1");
+    const Snapshot* s1 = db_->GetSnapshot();
+    Put("foo", "v2");
+    const Snapshot* s2 = db_->GetSnapshot();
+    Put("foo", "v3");
+    const Snapshot* s3 = db_->GetSnapshot();
+
+    Put("foo", "v4");
+    ASSERT_EQ("v1", Get("foo", s1));
+    ASSERT_EQ("v2", Get("foo", s2));
+    ASSERT_EQ("v3", Get("foo", s3));
+    ASSERT_EQ("v4", Get("foo"));
+
+    db_->ReleaseSnapshot(s3);
+    ASSERT_EQ("v1", Get("foo", s1));
+    ASSERT_EQ("v2", Get("foo", s2));
+    ASSERT_EQ("v4", Get("foo"));
+
+    db_->ReleaseSnapshot(s1);
+    ASSERT_EQ("v2", Get("foo", s2));
+    ASSERT_EQ("v4", Get("foo"));
+
+    db_->ReleaseSnapshot(s2);
+    ASSERT_EQ("v4", Get("foo"));
+  } while (ChangeOptions());
+}
+
+TEST_F(DBTest, HiddenValuesAreRemoved) {
+  do {
+    Random rnd(301);
+    FillLevels("a", "z");
+
+    std::string big = RandomString(&rnd, 50000);
+    Put("foo", big);
+    Put("pastfoo", "v");
+    const Snapshot* snapshot = db_->GetSnapshot();
+    Put("foo", "tiny");
+    Put("pastfoo2", "v2");  // Advance sequence number one more
+
+    ASSERT_LEVELDB_OK(dbfull()->TEST_CompactMemTable());
+    ASSERT_GT(NumTableFilesAtLevel(0), 0);
+
+    ASSERT_EQ(big, Get("foo", snapshot));
+    ASSERT_TRUE(Between(Size("", "pastfoo"), 50000, 60000));
+    db_->ReleaseSnapshot(snapshot);
+    ASSERT_EQ(AllEntriesFor("foo"), "[ tiny, " + big + " ]");
+    Slice x("x");
+    dbfull()->TEST_CompactRange(0, nullptr, &x);
+    ASSERT_EQ(AllEntriesFor("foo"), "[ tiny ]");
+    ASSERT_EQ(NumTableFilesAtLevel(0), 0);
+    ASSERT_GE(NumTableFilesAtLevel(1), 1);
+    dbfull()->TEST_CompactRange(1, nullptr, &x);
+    ASSERT_EQ(AllEntriesFor("foo"), "[ tiny ]");
+
+    ASSERT_TRUE(Between(Size("", "pastfoo"), 0, 1000));
+  } while (ChangeOptions());
+}
+
+TEST_F(DBTest, DeletionMarkers1) {
+  Put("foo", "v1");
+  ASSERT_LEVELDB_OK(dbfull()->TEST_CompactMemTable());
+  const int last = config::kMaxMemCompactLevel;
+  ASSERT_EQ(NumTableFilesAtLevel(last), 1);  // foo => v1 is now in last level
+
+  // Place a table at level last-1 to prevent merging with preceding mutation
+  Put("a", "begin");
+  Put("z", "end");
+  dbfull()->TEST_CompactMemTable();
+  ASSERT_EQ(NumTableFilesAtLevel(last), 1);
+  ASSERT_EQ(NumTableFilesAtLevel(last - 1), 1);
+
+  Delete("foo");
+  Put("foo", "v2");
+  ASSERT_EQ(AllEntriesFor("foo"), "[ v2, DEL, v1 ]");
+  ASSERT_LEVELDB_OK(dbfull()->TEST_CompactMemTable());  // Moves to level last-2
+  ASSERT_EQ(AllEntriesFor("foo"), "[ v2, DEL, v1 ]");
+  Slice z("z");
+  dbfull()->TEST_CompactRange(last - 2, nullptr, &z);
+  // DEL eliminated, but v1 remains because we aren't compacting that level
+  // (DEL can be eliminated because v2 hides v1).
+  ASSERT_EQ(AllEntriesFor("foo"), "[ v2, v1 ]");
+  dbfull()->TEST_CompactRange(last - 1, nullptr, nullptr);
+  // Merging last-1 w/ last, so we are the base level for "foo", so
+  // DEL is removed.  (as is v1).
+  ASSERT_EQ(AllEntriesFor("foo"), "[ v2 ]");
+}
+
+TEST_F(DBTest, DeletionMarkers2) {
+  Put("foo", "v1");
+  ASSERT_LEVELDB_OK(dbfull()->TEST_CompactMemTable());
+  const int last = config::kMaxMemCompactLevel;
+  ASSERT_EQ(NumTableFilesAtLevel(last), 1);  // foo => v1 is now in last level
+
+  // Place a table at level last-1 to prevent merging with preceding mutation
+  Put("a", "begin");
+  Put("z", "end");
+  dbfull()->TEST_CompactMemTable();
+  ASSERT_EQ(NumTableFilesAtLevel(last), 1);
+  ASSERT_EQ(NumTableFilesAtLevel(last - 1), 1);
+
+  Delete("foo");
+  ASSERT_EQ(AllEntriesFor("foo"), "[ DEL, v1 ]");
+  ASSERT_LEVELDB_OK(dbfull()->TEST_CompactMemTable());  // Moves to level last-2
+  ASSERT_EQ(AllEntriesFor("foo"), "[ DEL, v1 ]");
+  dbfull()->TEST_CompactRange(last - 2, nullptr, nullptr);
+  // DEL kept: "last" file overlaps
+  ASSERT_EQ(AllEntriesFor("foo"), "[ DEL, v1 ]");
+  dbfull()->TEST_CompactRange(last - 1, nullptr, nullptr);
+  // Merging last-1 w/ last, so we are the base level for "foo", so
+  // DEL is removed.  (as is v1).
+  ASSERT_EQ(AllEntriesFor("foo"), "[ ]");
+}
+
+TEST_F(DBTest, OverlapInLevel0) {
+  do {
+    ASSERT_EQ(config::kMaxMemCompactLevel, 2) << "Fix test to match config";
+
+    // Fill levels 1 and 2 to disable the pushing of new memtables to levels >
+    // 0.
+    ASSERT_LEVELDB_OK(Put("100", "v100"));
+    ASSERT_LEVELDB_OK(Put("999", "v999"));
+    dbfull()->TEST_CompactMemTable();
+    ASSERT_LEVELDB_OK(Delete("100"));
+    ASSERT_LEVELDB_OK(Delete("999"));
+    dbfull()->TEST_CompactMemTable();
+    ASSERT_EQ("0,1,1", FilesPerLevel());
+
+    // Make files spanning the following ranges in level-0:
+    //  files[0]  200 .. 900
+    //  files[1]  300 .. 500
+    // Note that files are sorted by smallest key.
+    ASSERT_LEVELDB_OK(Put("300", "v300"));
+    ASSERT_LEVELDB_OK(Put("500", "v500"));
+    dbfull()->TEST_CompactMemTable();
+    ASSERT_LEVELDB_OK(Put("200", "v200"));
+    ASSERT_LEVELDB_OK(Put("600", "v600"));
+    ASSERT_LEVELDB_OK(Put("900", "v900"));
+    dbfull()->TEST_CompactMemTable();
+    ASSERT_EQ("2,1,1", FilesPerLevel());
+
+    // Compact away the placeholder files we created initially
+    dbfull()->TEST_CompactRange(1, nullptr, nullptr);
+    dbfull()->TEST_CompactRange(2, nullptr, nullptr);
+    ASSERT_EQ("2", FilesPerLevel());
+
+    // Do a memtable compaction.  Before bug-fix, the compaction would
+    // not detect the overlap with level-0 files and would incorrectly place
+    // the deletion in a deeper level.
+    ASSERT_LEVELDB_OK(Delete("600"));
+    dbfull()->TEST_CompactMemTable();
+    ASSERT_EQ("3", FilesPerLevel());
+    ASSERT_EQ("NOT_FOUND", Get("600"));
+  } while (ChangeOptions());
+}
+
+TEST_F(DBTest, L0_CompactionBug_Issue44_a) {
+  Reopen();
+  ASSERT_LEVELDB_OK(Put("b", "v"));
+  Reopen();
+  ASSERT_LEVELDB_OK(Delete("b"));
+  ASSERT_LEVELDB_OK(Delete("a"));
+  Reopen();
+  ASSERT_LEVELDB_OK(Delete("a"));
+  Reopen();
+  ASSERT_LEVELDB_OK(Put("a", "v"));
+  Reopen();
+  Reopen();
+  ASSERT_EQ("(a->v)", Contents());
+  DelayMilliseconds(1000);  // Wait for compaction to finish
+  ASSERT_EQ("(a->v)", Contents());
+}
+
+TEST_F(DBTest, L0_CompactionBug_Issue44_b) {
+  Reopen();
+  Put("", "");
+  Reopen();
+  Delete("e");
+  Put("", "");
+  Reopen();
+  Put("c", "cv");
+  Reopen();
+  Put("", "");
+  Reopen();
+  Put("", "");
+  DelayMilliseconds(1000);  // Wait for compaction to finish
+  Reopen();
+  Put("d", "dv");
+  Reopen();
+  Put("", "");
+  Reopen();
+  Delete("d");
+  Delete("b");
+  Reopen();
+  ASSERT_EQ("(->)(c->cv)", Contents());
+  DelayMilliseconds(1000);  // Wait for compaction to finish
+  ASSERT_EQ("(->)(c->cv)", Contents());
+}
+
+TEST_F(DBTest, Fflush_Issue474) {
+  static const int kNum = 100000;
+  Random rnd(test::RandomSeed());
+  for (int i = 0; i < kNum; i++) {
+    std::fflush(nullptr);
+    ASSERT_LEVELDB_OK(Put(RandomKey(&rnd), RandomString(&rnd, 100)));
+  }
+}
+
+TEST_F(DBTest, ComparatorCheck) {
+  class NewComparator : public Comparator {
+   public:
+    const char* Name() const override { return "leveldb.NewComparator"; }
+    int Compare(const Slice& a, const Slice& b) const override {
+      return BytewiseComparator()->Compare(a, b);
+    }
+    void FindShortestSeparator(std::string* s, const Slice& l) const override {
+      BytewiseComparator()->FindShortestSeparator(s, l);
+    }
+    void FindShortSuccessor(std::string* key) const override {
+      BytewiseComparator()->FindShortSuccessor(key);
+    }
+  };
+  NewComparator cmp;
+  Options new_options = CurrentOptions();
+  new_options.comparator = &cmp;
+  Status s = TryReopen(&new_options);
+  ASSERT_TRUE(!s.ok());
+  ASSERT_TRUE(s.ToString().find("comparator") != std::string::npos)
+      << s.ToString();
+}
+
+TEST_F(DBTest, CustomComparator) {
+  class NumberComparator : public Comparator {
+   public:
+    const char* Name() const override { return "test.NumberComparator"; }
+    int Compare(const Slice& a, const Slice& b) const override {
+      return ToNumber(a) - ToNumber(b);
+    }
+    void FindShortestSeparator(std::string* s, const Slice& l) const override {
+      ToNumber(*s);  // Check format
+      ToNumber(l);   // Check format
+    }
+    void FindShortSuccessor(std::string* key) const override {
+      ToNumber(*key);  // Check format
+    }
+
+   private:
+    static int ToNumber(const Slice& x) {
+      // Check that there are no extra characters.
+      EXPECT_TRUE(x.size() >= 2 && x[0] == '[' && x[x.size() - 1] == ']')
+          << EscapeString(x);
+      int val;
+      char ignored;
+      EXPECT_TRUE(sscanf(x.ToString().c_str(), "[%i]%c", &val, &ignored) == 1)
+          << EscapeString(x);
+      return val;
+    }
+  };
+  NumberComparator cmp;
+  Options new_options = CurrentOptions();
+  new_options.create_if_missing = true;
+  new_options.comparator = &cmp;
+  new_options.filter_policy = nullptr;   // Cannot use bloom filters
+  new_options.write_buffer_size = 1000;  // Compact more often
+  DestroyAndReopen(&new_options);
+  ASSERT_LEVELDB_OK(Put("[10]", "ten"));
+  ASSERT_LEVELDB_OK(Put("[0x14]", "twenty"));
+  for (int i = 0; i < 2; i++) {
+    ASSERT_EQ("ten", Get("[10]"));
+    ASSERT_EQ("ten", Get("[0xa]"));
+    ASSERT_EQ("twenty", Get("[20]"));
+    ASSERT_EQ("twenty", Get("[0x14]"));
+    ASSERT_EQ("NOT_FOUND", Get("[15]"));
+    ASSERT_EQ("NOT_FOUND", Get("[0xf]"));
+    Compact("[0]", "[9999]");
+  }
+
+  for (int run = 0; run < 2; run++) {
+    for (int i = 0; i < 1000; i++) {
+      char buf[100];
+      std::snprintf(buf, sizeof(buf), "[%d]", i * 10);
+      ASSERT_LEVELDB_OK(Put(buf, buf));
+    }
+    Compact("[0]", "[1000000]");
+  }
+}
+
+TEST_F(DBTest, ManualCompaction) {
+  ASSERT_EQ(config::kMaxMemCompactLevel, 2)
+      << "Need to update this test to match kMaxMemCompactLevel";
+
+  MakeTables(3, "p", "q");
+  ASSERT_EQ("1,1,1", FilesPerLevel());
+
+  // Compaction range falls before files
+  Compact("", "c");
+  ASSERT_EQ("1,1,1", FilesPerLevel());
+
+  // Compaction range falls after files
+  Compact("r", "z");
+  ASSERT_EQ("1,1,1", FilesPerLevel());
+
+  // Compaction range overlaps files
+  Compact("p1", "p9");
+  ASSERT_EQ("0,0,1", FilesPerLevel());
+
+  // Populate a different range
+  MakeTables(3, "c", "e");
+  ASSERT_EQ("1,1,2", FilesPerLevel());
+
+  // Compact just the new range
+  Compact("b", "f");
+  ASSERT_EQ("0,0,2", FilesPerLevel());
+
+  // Compact all
+  MakeTables(1, "a", "z");
+  ASSERT_EQ("0,1,2", FilesPerLevel());
+  db_->CompactRange(nullptr, nullptr);
+  ASSERT_EQ("0,0,1", FilesPerLevel());
+}
+
+TEST_F(DBTest, DBOpen_Options) {
+  std::string dbname = testing::TempDir() + "db_options_test";
+  DestroyDB(dbname, Options());
+
+  // Does not exist, and create_if_missing == false: error
+  DB* db = nullptr;
+  Options opts;
+  opts.create_if_missing = false;
+  Status s = DB::Open(opts, dbname, &db);
+  ASSERT_TRUE(strstr(s.ToString().c_str(), "does not exist") != nullptr);
+  ASSERT_TRUE(db == nullptr);
+
+  // Does not exist, and create_if_missing == true: OK
+  opts.create_if_missing = true;
+  s = DB::Open(opts, dbname, &db);
+  ASSERT_LEVELDB_OK(s);
+  ASSERT_TRUE(db != nullptr);
+
+  delete db;
+  db = nullptr;
+
+  // Does exist, and error_if_exists == true: error
+  opts.create_if_missing = false;
+  opts.error_if_exists = true;
+  s = DB::Open(opts, dbname, &db);
+  ASSERT_TRUE(strstr(s.ToString().c_str(), "exists") != nullptr);
+  ASSERT_TRUE(db == nullptr);
+
+  // Does exist, and error_if_exists == false: OK
+  opts.create_if_missing = true;
+  opts.error_if_exists = false;
+  s = DB::Open(opts, dbname, &db);
+  ASSERT_LEVELDB_OK(s);
+  ASSERT_TRUE(db != nullptr);
+
+  delete db;
+  db = nullptr;
+}
+
+TEST_F(DBTest, DestroyEmptyDir) {
+  std::string dbname = testing::TempDir() + "db_empty_dir";
+  TestEnv env(Env::Default());
+  env.RemoveDir(dbname);
+  ASSERT_TRUE(!env.FileExists(dbname));
+
+  Options opts;
+  opts.env = &env;
+
+  ASSERT_LEVELDB_OK(env.CreateDir(dbname));
+  ASSERT_TRUE(env.FileExists(dbname));
+  std::vector<std::string> children;
+  ASSERT_LEVELDB_OK(env.GetChildren(dbname, &children));
+#if defined(LEVELDB_PLATFORM_CHROMIUM)
+  // TODO(https://crbug.com/1428746): Chromium's file system abstraction always
+  // filters out '.' and '..'.
+  ASSERT_EQ(0, children.size());
+#else
+  // The stock Env's do not filter out '.' and '..' special files.
+  ASSERT_EQ(2, children.size());
+#endif  // defined(LEVELDB_PLATFORM_CHROMIUM)
+  ASSERT_LEVELDB_OK(DestroyDB(dbname, opts));
+  ASSERT_TRUE(!env.FileExists(dbname));
+
+  // Should also be destroyed if Env is filtering out dot files.
+  env.SetIgnoreDotFiles(true);
+  ASSERT_LEVELDB_OK(env.CreateDir(dbname));
+  ASSERT_TRUE(env.FileExists(dbname));
+  ASSERT_LEVELDB_OK(env.GetChildren(dbname, &children));
+  ASSERT_EQ(0, children.size());
+  ASSERT_LEVELDB_OK(DestroyDB(dbname, opts));
+  ASSERT_TRUE(!env.FileExists(dbname));
+}
+
+TEST_F(DBTest, DestroyOpenDB) {
+  std::string dbname = testing::TempDir() + "open_db_dir";
+  env_->RemoveDir(dbname);
+  ASSERT_TRUE(!env_->FileExists(dbname));
+
+  Options opts;
+  opts.create_if_missing = true;
+  DB* db = nullptr;
+  ASSERT_LEVELDB_OK(DB::Open(opts, dbname, &db));
+  ASSERT_TRUE(db != nullptr);
+
+  // Must fail to destroy an open db.
+  ASSERT_TRUE(env_->FileExists(dbname));
+  ASSERT_TRUE(!DestroyDB(dbname, Options()).ok());
+  ASSERT_TRUE(env_->FileExists(dbname));
+
+  delete db;
+  db = nullptr;
+
+  // Should succeed destroying a closed db.
+  ASSERT_LEVELDB_OK(DestroyDB(dbname, Options()));
+  ASSERT_TRUE(!env_->FileExists(dbname));
+}
+
+TEST_F(DBTest, Locking) {
+  DB* db2 = nullptr;
+  Status s = DB::Open(CurrentOptions(), dbname_, &db2);
+  ASSERT_TRUE(!s.ok()) << "Locking did not prevent re-opening db";
+}
+
+// Check that number of files does not grow when we are out of space
+TEST_F(DBTest, NoSpace) {
+  Options options = CurrentOptions();
+  options.env = env_;
+  Reopen(&options);
+
+  ASSERT_LEVELDB_OK(Put("foo", "v1"));
+  ASSERT_EQ("v1", Get("foo"));
+  Compact("a", "z");
+  const int num_files = CountFiles();
+  // Force out-of-space errors.
+  env_->no_space_.store(true, std::memory_order_release);
+  for (int i = 0; i < 10; i++) {
+    for (int level = 0; level < config::kNumLevels - 1; level++) {
+      dbfull()->TEST_CompactRange(level, nullptr, nullptr);
+    }
+  }
+  env_->no_space_.store(false, std::memory_order_release);
+  ASSERT_LT(CountFiles(), num_files + 3);
+}
+
+TEST_F(DBTest, NonWritableFileSystem) {
+  Options options = CurrentOptions();
+  options.write_buffer_size = 1000;
+  options.env = env_;
+  Reopen(&options);
+  ASSERT_LEVELDB_OK(Put("foo", "v1"));
+  // Force errors for new files.
+  env_->non_writable_.store(true, std::memory_order_release);
+  std::string big(100000, 'x');
+  int errors = 0;
+  for (int i = 0; i < 20; i++) {
+    std::fprintf(stderr, "iter %d; errors %d\n", i, errors);
+    if (!Put("foo", big).ok()) {
+      errors++;
+      DelayMilliseconds(100);
+    }
+  }
+  ASSERT_GT(errors, 0);
+  env_->non_writable_.store(false, std::memory_order_release);
+}
+
+TEST_F(DBTest, WriteSyncError) {
+  // Check that log sync errors cause the DB to disallow future writes.
+
+  // (a) Cause log sync calls to fail
+  Options options = CurrentOptions();
+  options.env = env_;
+  Reopen(&options);
+  env_->data_sync_error_.store(true, std::memory_order_release);
+
+  // (b) Normal write should succeed
+  WriteOptions w;
+  ASSERT_LEVELDB_OK(db_->Put(w, "k1", "v1"));
+  ASSERT_EQ("v1", Get("k1"));
+
+  // (c) Do a sync write; should fail
+  w.sync = true;
+  ASSERT_TRUE(!db_->Put(w, "k2", "v2").ok());
+  ASSERT_EQ("v1", Get("k1"));
+  ASSERT_EQ("NOT_FOUND", Get("k2"));
+
+  // (d) make sync behave normally
+  env_->data_sync_error_.store(false, std::memory_order_release);
+
+  // (e) Do a non-sync write; should fail
+  w.sync = false;
+  ASSERT_TRUE(!db_->Put(w, "k3", "v3").ok());
+  ASSERT_EQ("v1", Get("k1"));
+  ASSERT_EQ("NOT_FOUND", Get("k2"));
+  ASSERT_EQ("NOT_FOUND", Get("k3"));
+}
+
+TEST_F(DBTest, ManifestWriteError) {
+  // Test for the following problem:
+  // (a) Compaction produces file F
+  // (b) Log record containing F is written to MANIFEST file, but Sync() fails
+  // (c) GC deletes F
+  // (d) After reopening DB, reads fail since deleted F is named in log record
+
+  // We iterate twice.  In the second iteration, everything is the
+  // same except the log record never makes it to the MANIFEST file.
+  for (int iter = 0; iter < 2; iter++) {
+    std::atomic<bool>* error_type = (iter == 0) ? &env_->manifest_sync_error_
+                                                : &env_->manifest_write_error_;
+
+    // Insert foo=>bar mapping
+    Options options = CurrentOptions();
+    options.env = env_;
+    options.create_if_missing = true;
+    options.error_if_exists = false;
+    DestroyAndReopen(&options);
+    ASSERT_LEVELDB_OK(Put("foo", "bar"));
+    ASSERT_EQ("bar", Get("foo"));
+
+    // Memtable compaction (will succeed)
+    dbfull()->TEST_CompactMemTable();
+    ASSERT_EQ("bar", Get("foo"));
+    const int last = config::kMaxMemCompactLevel;
+    ASSERT_EQ(NumTableFilesAtLevel(last), 1);  // foo=>bar is now in last level
+
+    // Merging compaction (will fail)
+    error_type->store(true, std::memory_order_release);
+    dbfull()->TEST_CompactRange(last, nullptr, nullptr);  // Should fail
+    ASSERT_EQ("bar", Get("foo"));
+
+    // Recovery: should not lose data
+    error_type->store(false, std::memory_order_release);
+    Reopen(&options);
+    ASSERT_EQ("bar", Get("foo"));
+  }
+}
+
+TEST_F(DBTest, MissingSSTFile) {
+  ASSERT_LEVELDB_OK(Put("foo", "bar"));
+  ASSERT_EQ("bar", Get("foo"));
+
+  // Dump the memtable to disk.
+  dbfull()->TEST_CompactMemTable();
+  ASSERT_EQ("bar", Get("foo"));
+
+  Close();
+  ASSERT_TRUE(DeleteAnSSTFile());
+  Options options = CurrentOptions();
+  options.paranoid_checks = true;
+  Status s = TryReopen(&options);
+  ASSERT_TRUE(!s.ok());
+  ASSERT_TRUE(s.ToString().find("issing") != std::string::npos) << s.ToString();
+}
+
+TEST_F(DBTest, StillReadSST) {
+  ASSERT_LEVELDB_OK(Put("foo", "bar"));
+  ASSERT_EQ("bar", Get("foo"));
+
+  // Dump the memtable to disk.
+  dbfull()->TEST_CompactMemTable();
+  ASSERT_EQ("bar", Get("foo"));
+  Close();
+  ASSERT_GT(RenameLDBToSST(), 0);
+  Options options = CurrentOptions();
+  options.paranoid_checks = true;
+  Status s = TryReopen(&options);
+  ASSERT_TRUE(s.ok());
+  ASSERT_EQ("bar", Get("foo"));
+}
+
+TEST_F(DBTest, FilesDeletedAfterCompaction) {
+  ASSERT_LEVELDB_OK(Put("foo", "v2"));
+  Compact("a", "z");
+  const int num_files = CountFiles();
+  for (int i = 0; i < 10; i++) {
+    ASSERT_LEVELDB_OK(Put("foo", "v2"));
+    Compact("a", "z");
+  }
+  ASSERT_EQ(CountFiles(), num_files);
+}
+
+TEST_F(DBTest, BloomFilter) {
+  env_->count_random_reads_ = true;
+  Options options = CurrentOptions();
+  options.env = env_;
+  options.block_cache = NewLRUCache(0);  // Prevent cache hits
+  options.filter_policy = NewBloomFilterPolicy(10);
+  Reopen(&options);
+
+  // Populate multiple layers
+  const int N = 10000;
+  for (int i = 0; i < N; i++) {
+    ASSERT_LEVELDB_OK(Put(Key(i), Key(i)));
+  }
+  Compact("a", "z");
+  for (int i = 0; i < N; i += 100) {
+    ASSERT_LEVELDB_OK(Put(Key(i), Key(i)));
+  }
+  dbfull()->TEST_CompactMemTable();
+
+  // Prevent auto compactions triggered by seeks
+  env_->delay_data_sync_.store(true, std::memory_order_release);
+
+  // Lookup present keys.  Should rarely read from small sstable.
+  env_->random_read_counter_.Reset();
+  for (int i = 0; i < N; i++) {
+    ASSERT_EQ(Key(i), Get(Key(i)));
+  }
+  int reads = env_->random_read_counter_.Read();
+  std::fprintf(stderr, "%d present => %d reads\n", N, reads);
+  ASSERT_GE(reads, N);
+  ASSERT_LE(reads, N + 2 * N / 100);
+
+  // Lookup present keys.  Should rarely read from either sstable.
+  env_->random_read_counter_.Reset();
+  for (int i = 0; i < N; i++) {
+    ASSERT_EQ("NOT_FOUND", Get(Key(i) + ".missing"));
+  }
+  reads = env_->random_read_counter_.Read();
+  std::fprintf(stderr, "%d missing => %d reads\n", N, reads);
+  ASSERT_LE(reads, 3 * N / 100);
+
+  env_->delay_data_sync_.store(false, std::memory_order_release);
+  Close();
+  delete options.block_cache;
+  delete options.filter_policy;
+}
+
+TEST_F(DBTest, LogCloseError) {
+  // Regression test for bug where we could ignore log file
+  // Close() error when switching to a new log file.
+  const int kValueSize = 20000;
+  const int kWriteCount = 10;
+  const int kWriteBufferSize = (kValueSize * kWriteCount) / 2;
+
+  Options options = CurrentOptions();
+  options.env = env_;
+  options.write_buffer_size = kWriteBufferSize;  // Small write buffer
+  Reopen(&options);
+  env_->log_file_close_.store(true, std::memory_order_release);
+
+  std::string value(kValueSize, 'x');
+  Status s;
+  for (int i = 0; i < kWriteCount && s.ok(); i++) {
+    s = Put(Key(i), value);
+  }
+  ASSERT_TRUE(!s.ok()) << "succeeded even after log file Close failure";
+
+  // Future writes should also fail after an earlier error.
+  s = Put("hello", "world");
+  ASSERT_TRUE(!s.ok()) << "write succeeded after log file Close failure";
+
+  env_->log_file_close_.store(false, std::memory_order_release);
+}
+
+// Multi-threaded test:
+namespace {
+
+static const int kNumThreads = 4;
+static const int kTestSeconds = 10;
+static const int kNumKeys = 1000;
+
+struct MTState {
+  DBTest* test;
+  std::atomic<bool> stop;
+  std::atomic<int> counter[kNumThreads];
+  std::atomic<bool> thread_done[kNumThreads];
+};
+
+struct MTThread {
+  MTState* state;
+  int id;
+};
+
+static void MTThreadBody(void* arg) {
+  MTThread* t = reinterpret_cast<MTThread*>(arg);
+  int id = t->id;
+  DB* db = t->state->test->db_;
+  int counter = 0;
+  std::fprintf(stderr, "... starting thread %d\n", id);
+  Random rnd(1000 + id);
+  std::string value;
+  char valbuf[1500];
+  while (!t->state->stop.load(std::memory_order_acquire)) {
+    t->state->counter[id].store(counter, std::memory_order_release);
+
+    int key = rnd.Uniform(kNumKeys);
+    char keybuf[20];
+    std::snprintf(keybuf, sizeof(keybuf), "%016d", key);
+
+    if (rnd.OneIn(2)) {
+      // Write values of the form <key, my id, counter>.
+      // We add some padding for force compactions.
+      std::snprintf(valbuf, sizeof(valbuf), "%d.%d.%-1000d", key, id,
+                    static_cast<int>(counter));
+      ASSERT_LEVELDB_OK(db->Put(WriteOptions(), Slice(keybuf), Slice(valbuf)));
+    } else {
+      // Read a value and verify that it matches the pattern written above.
+      Status s = db->Get(ReadOptions(), Slice(keybuf), &value);
+      if (s.IsNotFound()) {
+        // Key has not yet been written
+      } else {
+        // Check that the writer thread counter is >= the counter in the value
+        ASSERT_LEVELDB_OK(s);
+        int k, w, c;
+        ASSERT_EQ(3, sscanf(value.c_str(), "%d.%d.%d", &k, &w, &c)) << value;
+        ASSERT_EQ(k, key);
+        ASSERT_GE(w, 0);
+        ASSERT_LT(w, kNumThreads);
+        ASSERT_LE(c, t->state->counter[w].load(std::memory_order_acquire));
+      }
+    }
+    counter++;
+  }
+  t->state->thread_done[id].store(true, std::memory_order_release);
+  std::fprintf(stderr, "... stopping thread %d after %d ops\n", id, counter);
+}
+
+}  // namespace
+
+TEST_F(DBTest, MultiThreaded) {
+  do {
+    // Initialize state
+    MTState mt;
+    mt.test = this;
+    mt.stop.store(false, std::memory_order_release);
+    for (int id = 0; id < kNumThreads; id++) {
+      mt.counter[id].store(false, std::memory_order_release);
+      mt.thread_done[id].store(false, std::memory_order_release);
+    }
+
+    // Start threads
+    MTThread thread[kNumThreads];
+    for (int id = 0; id < kNumThreads; id++) {
+      thread[id].state = &mt;
+      thread[id].id = id;
+      env_->StartThread(MTThreadBody, &thread[id]);
+    }
+
+    // Let them run for a while
+    DelayMilliseconds(kTestSeconds * 1000);
+
+    // Stop the threads and wait for them to finish
+    mt.stop.store(true, std::memory_order_release);
+    for (int id = 0; id < kNumThreads; id++) {
+      while (!mt.thread_done[id].load(std::memory_order_acquire)) {
+        DelayMilliseconds(100);
+      }
+    }
+  } while (ChangeOptions());
+}
+
+namespace {
+typedef std::map<std::string, std::string> KVMap;
+}
+
+class ModelDB : public DB {
+ public:
+  class ModelSnapshot : public Snapshot {
+   public:
+    KVMap map_;
+  };
+
+  explicit ModelDB(const Options& options) : options_(options) {}
+  ~ModelDB() override = default;
+  Status Put(const WriteOptions& o, const Slice& k, const Slice& v) override {
+    return DB::Put(o, k, v);
+  }
+  // 添加新的ttl-橙
+  Status Put(const WriteOptions& o, const Slice& k, const Slice& v, uint64_t ttl) override {
+    return DB::Put(o, k, v, ttl);
+  }
+  Status Delete(const WriteOptions& o, const Slice& key) override {
+    return DB::Delete(o, key);
+  }
+  Status Get(const ReadOptions& options, const Slice& key,
+             std::string* value) override {
+    assert(false);  // Not implemented
+    return Status::NotFound(key);
+  }
+  Iterator* NewIterator(const ReadOptions& options) override {
+    if (options.snapshot == nullptr) {
+      KVMap* saved = new KVMap;
+      *saved = map_;
+      return new ModelIter(saved, true);
+    } else {
+      const KVMap* snapshot_state =
+          &(reinterpret_cast<const ModelSnapshot*>(options.snapshot)->map_);
+      return new ModelIter(snapshot_state, false);
+    }
+  }
+  const Snapshot* GetSnapshot() override {
+    ModelSnapshot* snapshot = new ModelSnapshot;
+    snapshot->map_ = map_;
+    return snapshot;
+  }
+
+  void ReleaseSnapshot(const Snapshot* snapshot) override {
+    delete reinterpret_cast<const ModelSnapshot*>(snapshot);
+  }
+  Status Write(const WriteOptions& options, WriteBatch* batch) override {
+    class Handler : public WriteBatch::Handler {
+     public:
+      KVMap* map_;
+      void Put(const Slice& key, const Slice& value) override {
+        (*map_)[key.ToString()] = value.ToString();
+      }
+      void Delete(const Slice& key) override { map_->erase(key.ToString()); }
+    };
+    Handler handler;
+    handler.map_ = &map_;
+    return batch->Iterate(&handler);
+  }
+
+  bool GetProperty(const Slice& property, std::string* value) override {
+    return false;
+  }
+  void GetApproximateSizes(const Range* r, int n, uint64_t* sizes) override {
+    for (int i = 0; i < n; i++) {
+      sizes[i] = 0;
+    }
+  }
+  void CompactRange(const Slice* start, const Slice* end) override {}
+
+ private:
+  class ModelIter : public Iterator {
+   public:
+    ModelIter(const KVMap* map, bool owned)
+        : map_(map), owned_(owned), iter_(map_->end()) {}
+    ~ModelIter() override {
+      if (owned_) delete map_;
+    }
+    bool Valid() const override { return iter_ != map_->end(); }
+    void SeekToFirst() override { iter_ = map_->begin(); }
+    void SeekToLast() override {
+      if (map_->empty()) {
+        iter_ = map_->end();
+      } else {
+        iter_ = map_->find(map_->rbegin()->first);
+      }
+    }
+    void Seek(const Slice& k) override {
+      iter_ = map_->lower_bound(k.ToString());
+    }
+    void Next() override { ++iter_; }
+    void Prev() override { --iter_; }
+    Slice key() const override { return iter_->first; }
+    Slice value() const override { return iter_->second; }
+    Status status() const override { return Status::OK(); }
+
+   private:
+    const KVMap* const map_;
+    const bool owned_;  // Do we own map_
+    KVMap::const_iterator iter_;
+  };
+  const Options options_;
+  KVMap map_;
+};
+
+static bool CompareIterators(int step, DB* model, DB* db,
+                             const Snapshot* model_snap,
+                             const Snapshot* db_snap) {
+  ReadOptions options;
+  options.snapshot = model_snap;
+  Iterator* miter = model->NewIterator(options);
+  options.snapshot = db_snap;
+  Iterator* dbiter = db->NewIterator(options);
+  bool ok = true;
+  int count = 0;
+  std::vector<std::string> seek_keys;
+  // Compare equality of all elements using Next(). Save some of the keys for
+  // comparing Seek equality.
+  for (miter->SeekToFirst(), dbiter->SeekToFirst();
+       ok && miter->Valid() && dbiter->Valid(); miter->Next(), dbiter->Next()) {
+    count++;
+    if (miter->key().compare(dbiter->key()) != 0) {
+      std::fprintf(stderr, "step %d: Key mismatch: '%s' vs. '%s'\n", step,
+                   EscapeString(miter->key()).c_str(),
+                   EscapeString(dbiter->key()).c_str());
+      ok = false;
+      break;
+    }
+
+    if (miter->value().compare(dbiter->value()) != 0) {
+      std::fprintf(stderr,
+                   "step %d: Value mismatch for key '%s': '%s' vs. '%s'\n",
+                   step, EscapeString(miter->key()).c_str(),
+                   EscapeString(miter->value()).c_str(),
+                   EscapeString(miter->value()).c_str());
+      ok = false;
+      break;
+    }
+
+    if (count % 10 == 0) {
+      seek_keys.push_back(miter->key().ToString());
+    }
+  }
+
+  if (ok) {
+    if (miter->Valid() != dbiter->Valid()) {
+      std::fprintf(stderr, "step %d: Mismatch at end of iterators: %d vs. %d\n",
+                   step, miter->Valid(), dbiter->Valid());
+      ok = false;
+    }
+  }
+
+  if (ok) {
+    // Validate iterator equality when performing seeks.
+    for (auto kiter = seek_keys.begin(); ok && kiter != seek_keys.end();
+         ++kiter) {
+      miter->Seek(*kiter);
+      dbiter->Seek(*kiter);
+      if (!miter->Valid() || !dbiter->Valid()) {
+        std::fprintf(stderr, "step %d: Seek iterators invalid: %d vs. %d\n",
+                     step, miter->Valid(), dbiter->Valid());
+        ok = false;
+      }
+      if (miter->key().compare(dbiter->key()) != 0) {
+        std::fprintf(stderr, "step %d: Seek key mismatch: '%s' vs. '%s'\n",
+                     step, EscapeString(miter->key()).c_str(),
+                     EscapeString(dbiter->key()).c_str());
+        ok = false;
+        break;
+      }
+
+      if (miter->value().compare(dbiter->value()) != 0) {
+        std::fprintf(
+            stderr,
+            "step %d: Seek value mismatch for key '%s': '%s' vs. '%s'\n", step,
+            EscapeString(miter->key()).c_str(),
+            EscapeString(miter->value()).c_str(),
+            EscapeString(miter->value()).c_str());
+        ok = false;
+        break;
+      }
+    }
+  }
+
+  std::fprintf(stderr, "%d entries compared: ok=%d\n", count, ok);
+  delete miter;
+  delete dbiter;
+  return ok;
+}
+
+TEST_F(DBTest, Randomized) {
+  Random rnd(test::RandomSeed());
+  do {
+    ModelDB model(CurrentOptions());
+    const int N = 10000;
+    const Snapshot* model_snap = nullptr;
+    const Snapshot* db_snap = nullptr;
+    std::string k, v;
+    for (int step = 0; step < N; step++) {
+      if (step % 100 == 0) {
+        std::fprintf(stderr, "Step %d of %d\n", step, N);
+      }
+      // TODO(sanjay): Test Get() works
+      int p = rnd.Uniform(100);
+      if (p < 45) {  // Put
+        k = RandomKey(&rnd);
+        v = RandomString(
+            &rnd, rnd.OneIn(20) ? 100 + rnd.Uniform(100) : rnd.Uniform(8));
+        ASSERT_LEVELDB_OK(model.Put(WriteOptions(), k, v));
+        ASSERT_LEVELDB_OK(db_->Put(WriteOptions(), k, v));
+
+      } else if (p < 90) {  // Delete
+        k = RandomKey(&rnd);
+        ASSERT_LEVELDB_OK(model.Delete(WriteOptions(), k));
+        ASSERT_LEVELDB_OK(db_->Delete(WriteOptions(), k));
+
+      } else {  // Multi-element batch
+        WriteBatch b;
+        const int num = rnd.Uniform(8);
+        for (int i = 0; i < num; i++) {
+          if (i == 0 || !rnd.OneIn(10)) {
+            k = RandomKey(&rnd);
+          } else {
+            // Periodically re-use the same key from the previous iter, so
+            // we have multiple entries in the write batch for the same key
+          }
+          if (rnd.OneIn(2)) {
+            v = RandomString(&rnd, rnd.Uniform(10));
+            b.Put(k, v);
+          } else {
+            b.Delete(k);
+          }
+        }
+        ASSERT_LEVELDB_OK(model.Write(WriteOptions(), &b));
+        ASSERT_LEVELDB_OK(db_->Write(WriteOptions(), &b));
+      }
+
+      if ((step % 100) == 0) {
+        ASSERT_TRUE(CompareIterators(step, &model, db_, nullptr, nullptr));
+        ASSERT_TRUE(CompareIterators(step, &model, db_, model_snap, db_snap));
+        // Save a snapshot from each DB this time that we'll use next
+        // time we compare things, to make sure the current state is
+        // preserved with the snapshot
+        if (model_snap != nullptr) model.ReleaseSnapshot(model_snap);
+        if (db_snap != nullptr) db_->ReleaseSnapshot(db_snap);
+
+        Reopen();
+        ASSERT_TRUE(CompareIterators(step, &model, db_, nullptr, nullptr));
+
+        model_snap = model.GetSnapshot();
+        db_snap = db_->GetSnapshot();
+      }
+    }
+    if (model_snap != nullptr) model.ReleaseSnapshot(model_snap);
+    if (db_snap != nullptr) db_->ReleaseSnapshot(db_snap);
+  } while (ChangeOptions());
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/db/dbformat.cc b/leveldb_base/db/dbformat.cc
new file mode 100644
index 0000000..2a5749f
--- /dev/null
+++ b/leveldb_base/db/dbformat.cc
@@ -0,0 +1,136 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "db/dbformat.h"
+
+#include <cstdio>
+#include <sstream>
+
+#include "port/port.h"
+#include "util/coding.h"
+
+namespace leveldb {
+
+static uint64_t PackSequenceAndType(uint64_t seq, ValueType t) {
+  assert(seq <= kMaxSequenceNumber);
+  assert(t <= kValueTypeForSeek);
+  return (seq << 8) | t;
+}
+
+void AppendInternalKey(std::string* result, const ParsedInternalKey& key) {
+  result->append(key.user_key.data(), key.user_key.size());
+  PutFixed64(result, PackSequenceAndType(key.sequence, key.type));
+}
+
+std::string ParsedInternalKey::DebugString() const {
+  std::ostringstream ss;
+  ss << '\'' << EscapeString(user_key.ToString()) << "' @ " << sequence << " : "
+     << static_cast<int>(type);
+  return ss.str();
+}
+
+std::string InternalKey::DebugString() const {
+  ParsedInternalKey parsed;
+  if (ParseInternalKey(rep_, &parsed)) {
+    return parsed.DebugString();
+  }
+  std::ostringstream ss;
+  ss << "(bad)" << EscapeString(rep_);
+  return ss.str();
+}
+
+const char* InternalKeyComparator::Name() const {
+  return "leveldb.InternalKeyComparator";
+}
+
+int InternalKeyComparator::Compare(const Slice& akey, const Slice& bkey) const {
+  // Order by:
+  //    increasing user key (according to user-supplied comparator)
+  //    decreasing sequence number
+  //    decreasing type (though sequence# should be enough to disambiguate)
+  int r = user_comparator_->Compare(ExtractUserKey(akey), ExtractUserKey(bkey));
+  if (r == 0) {
+    const uint64_t anum = DecodeFixed64(akey.data() + akey.size() - 8);
+    const uint64_t bnum = DecodeFixed64(bkey.data() + bkey.size() - 8);
+    if (anum > bnum) {
+      r = -1;
+    } else if (anum < bnum) {
+      r = +1;
+    }
+  }
+  return r;
+}
+
+void InternalKeyComparator::FindShortestSeparator(std::string* start,
+                                                  const Slice& limit) const {
+  // Attempt to shorten the user portion of the key
+  Slice user_start = ExtractUserKey(*start);
+  Slice user_limit = ExtractUserKey(limit);
+  std::string tmp(user_start.data(), user_start.size());
+  user_comparator_->FindShortestSeparator(&tmp, user_limit);
+  if (tmp.size() < user_start.size() &&
+      user_comparator_->Compare(user_start, tmp) < 0) {
+    // User key has become shorter physically, but larger logically.
+    // Tack on the earliest possible number to the shortened user key.
+    PutFixed64(&tmp,
+               PackSequenceAndType(kMaxSequenceNumber, kValueTypeForSeek));
+    assert(this->Compare(*start, tmp) < 0);
+    assert(this->Compare(tmp, limit) < 0);
+    start->swap(tmp);
+  }
+}
+
+void InternalKeyComparator::FindShortSuccessor(std::string* key) const {
+  Slice user_key = ExtractUserKey(*key);
+  std::string tmp(user_key.data(), user_key.size());
+  user_comparator_->FindShortSuccessor(&tmp);
+  if (tmp.size() < user_key.size() &&
+      user_comparator_->Compare(user_key, tmp) < 0) {
+    // User key has become shorter physically, but larger logically.
+    // Tack on the earliest possible number to the shortened user key.
+    PutFixed64(&tmp,
+               PackSequenceAndType(kMaxSequenceNumber, kValueTypeForSeek));
+    assert(this->Compare(*key, tmp) < 0);
+    key->swap(tmp);
+  }
+}
+
+const char* InternalFilterPolicy::Name() const { return user_policy_->Name(); }
+
+void InternalFilterPolicy::CreateFilter(const Slice* keys, int n,
+                                        std::string* dst) const {
+  // We rely on the fact that the code in table.cc does not mind us
+  // adjusting keys[].
+  Slice* mkey = const_cast<Slice*>(keys);
+  for (int i = 0; i < n; i++) {
+    mkey[i] = ExtractUserKey(keys[i]);
+    // TODO(sanjay): Suppress dups?
+  }
+  user_policy_->CreateFilter(keys, n, dst);
+}
+
+bool InternalFilterPolicy::KeyMayMatch(const Slice& key, const Slice& f) const {
+  return user_policy_->KeyMayMatch(ExtractUserKey(key), f);
+}
+
+LookupKey::LookupKey(const Slice& user_key, SequenceNumber s) {
+  size_t usize = user_key.size();
+  size_t needed = usize + 13;  // A conservative estimate
+  char* dst;
+  if (needed <= sizeof(space_)) {
+    dst = space_;
+  } else {
+    dst = new char[needed];
+  }
+  start_ = dst;
+  dst = EncodeVarint32(dst, usize + 8);
+  kstart_ = dst;
+  std::memcpy(dst, user_key.data(), usize);
+  dst += usize;
+  EncodeFixed64(dst, PackSequenceAndType(s, kValueTypeForSeek));
+  dst += 8;
+  end_ = dst;
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/db/dbformat.h b/leveldb_base/db/dbformat.h
new file mode 100644
index 0000000..a1c30ed
--- /dev/null
+++ b/leveldb_base/db/dbformat.h
@@ -0,0 +1,224 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_DB_DBFORMAT_H_
+#define STORAGE_LEVELDB_DB_DBFORMAT_H_
+
+#include <cstddef>
+#include <cstdint>
+#include <string>
+
+#include "leveldb/comparator.h"
+#include "leveldb/db.h"
+#include "leveldb/filter_policy.h"
+#include "leveldb/slice.h"
+#include "leveldb/table_builder.h"
+#include "util/coding.h"
+#include "util/logging.h"
+
+namespace leveldb {
+
+// Grouping of constants.  We may want to make some of these
+// parameters set via options.
+namespace config {
+static const int kNumLevels = 7;
+
+// Level-0 compaction is started when we hit this many files.
+static const int kL0_CompactionTrigger = 4;
+
+// Soft limit on number of level-0 files.  We slow down writes at this point.
+static const int kL0_SlowdownWritesTrigger = 8;
+
+// Maximum number of level-0 files.  We stop writes at this point.
+static const int kL0_StopWritesTrigger = 12;
+
+// Maximum level to which a new compacted memtable is pushed if it
+// does not create overlap.  We try to push to level 2 to avoid the
+// relatively expensive level 0=>1 compactions and to avoid some
+// expensive manifest file operations.  We do not push all the way to
+// the largest level since that can generate a lot of wasted disk
+// space if the same key space is being repeatedly overwritten.
+static const int kMaxMemCompactLevel = 2;
+
+// Approximate gap in bytes between samples of data read during iteration.
+static const int kReadBytesPeriod = 1048576;
+
+}  // namespace config
+
+class InternalKey;
+
+// Value types encoded as the last component of internal keys.
+// DO NOT CHANGE THESE ENUM VALUES: they are embedded in the on-disk
+// data structures.
+enum ValueType { kTypeDeletion = 0x0, kTypeValue = 0x1 };
+// kValueTypeForSeek defines the ValueType that should be passed when
+// constructing a ParsedInternalKey object for seeking to a particular
+// sequence number (since we sort sequence numbers in decreasing order
+// and the value type is embedded as the low 8 bits in the sequence
+// number in internal keys, we need to use the highest-numbered
+// ValueType, not the lowest).
+static const ValueType kValueTypeForSeek = kTypeValue;
+
+typedef uint64_t SequenceNumber;
+
+// We leave eight bits empty at the bottom so a type and sequence#
+// can be packed together into 64-bits.
+static const SequenceNumber kMaxSequenceNumber = ((0x1ull << 56) - 1);
+
+struct ParsedInternalKey {
+  Slice user_key;
+  SequenceNumber sequence;
+  ValueType type;
+
+  ParsedInternalKey() {}  // Intentionally left uninitialized (for speed)
+  ParsedInternalKey(const Slice& u, const SequenceNumber& seq, ValueType t)
+      : user_key(u), sequence(seq), type(t) {}
+  std::string DebugString() const;
+};
+
+// Return the length of the encoding of "key".
+inline size_t InternalKeyEncodingLength(const ParsedInternalKey& key) {
+  return key.user_key.size() + 8;
+}
+
+// Append the serialization of "key" to *result.
+void AppendInternalKey(std::string* result, const ParsedInternalKey& key);
+
+// Attempt to parse an internal key from "internal_key".  On success,
+// stores the parsed data in "*result", and returns true.
+//
+// On error, returns false, leaves "*result" in an undefined state.
+bool ParseInternalKey(const Slice& internal_key, ParsedInternalKey* result);
+
+// Returns the user key portion of an internal key.
+inline Slice ExtractUserKey(const Slice& internal_key) {
+  assert(internal_key.size() >= 8);
+  return Slice(internal_key.data(), internal_key.size() - 8);
+}
+
+// A comparator for internal keys that uses a specified comparator for
+// the user key portion and breaks ties by decreasing sequence number.
+class InternalKeyComparator : public Comparator {
+ private:
+  const Comparator* user_comparator_;
+
+ public:
+  explicit InternalKeyComparator(const Comparator* c) : user_comparator_(c) {}
+  const char* Name() const override;
+  int Compare(const Slice& a, const Slice& b) const override;
+  void FindShortestSeparator(std::string* start,
+                             const Slice& limit) const override;
+  void FindShortSuccessor(std::string* key) const override;
+
+  const Comparator* user_comparator() const { return user_comparator_; }
+
+  int Compare(const InternalKey& a, const InternalKey& b) const;
+};
+
+// Filter policy wrapper that converts from internal keys to user keys
+class InternalFilterPolicy : public FilterPolicy {
+ private:
+  const FilterPolicy* const user_policy_;
+
+ public:
+  explicit InternalFilterPolicy(const FilterPolicy* p) : user_policy_(p) {}
+  const char* Name() const override;
+  void CreateFilter(const Slice* keys, int n, std::string* dst) const override;
+  bool KeyMayMatch(const Slice& key, const Slice& filter) const override;
+};
+
+// Modules in this directory should keep internal keys wrapped inside
+// the following class instead of plain strings so that we do not
+// incorrectly use string comparisons instead of an InternalKeyComparator.
+class InternalKey {
+ private:
+  std::string rep_;
+
+ public:
+  InternalKey() {}  // Leave rep_ as empty to indicate it is invalid
+  InternalKey(const Slice& user_key, SequenceNumber s, ValueType t) {
+    AppendInternalKey(&rep_, ParsedInternalKey(user_key, s, t));
+  }
+
+  bool DecodeFrom(const Slice& s) {
+    rep_.assign(s.data(), s.size());
+    return !rep_.empty();
+  }
+
+  Slice Encode() const {
+    assert(!rep_.empty());
+    return rep_;
+  }
+
+  Slice user_key() const { return ExtractUserKey(rep_); }
+
+  void SetFrom(const ParsedInternalKey& p) {
+    rep_.clear();
+    AppendInternalKey(&rep_, p);
+  }
+
+  void Clear() { rep_.clear(); }
+
+  std::string DebugString() const;
+};
+
+inline int InternalKeyComparator::Compare(const InternalKey& a,
+                                          const InternalKey& b) const {
+  return Compare(a.Encode(), b.Encode());
+}
+
+inline bool ParseInternalKey(const Slice& internal_key,
+                             ParsedInternalKey* result) {
+  const size_t n = internal_key.size();
+  if (n < 8) return false;
+  uint64_t num = DecodeFixed64(internal_key.data() + n - 8);
+  uint8_t c = num & 0xff;
+  result->sequence = num >> 8;
+  result->type = static_cast<ValueType>(c);
+  result->user_key = Slice(internal_key.data(), n - 8);
+  return (c <= static_cast<uint8_t>(kTypeValue));
+}
+
+// A helper class useful for DBImpl::Get()
+class LookupKey {
+ public:
+  // Initialize *this for looking up user_key at a snapshot with
+  // the specified sequence number.
+  LookupKey(const Slice& user_key, SequenceNumber sequence);
+
+  LookupKey(const LookupKey&) = delete;
+  LookupKey& operator=(const LookupKey&) = delete;
+
+  ~LookupKey();
+
+  // Return a key suitable for lookup in a MemTable.
+  Slice memtable_key() const { return Slice(start_, end_ - start_); }
+
+  // Return an internal key (suitable for passing to an internal iterator)
+  Slice internal_key() const { return Slice(kstart_, end_ - kstart_); }
+
+  // Return the user key
+  Slice user_key() const { return Slice(kstart_, end_ - kstart_ - 8); }
+
+ private:
+  // We construct a char array of the form:
+  //    klength  varint32               <-- start_
+  //    userkey  char[klength]          <-- kstart_
+  //    tag      uint64
+  //                                    <-- end_
+  // The array is a suitable MemTable key.
+  // The suffix starting with "userkey" can be used as an InternalKey.
+  const char* start_;
+  const char* kstart_;
+  const char* end_;
+  char space_[200];  // Avoid allocation for short keys
+};
+
+inline LookupKey::~LookupKey() {
+  if (start_ != space_) delete[] start_;
+}
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_DB_DBFORMAT_H_
diff --git a/leveldb_base/db/dbformat_test.cc b/leveldb_base/db/dbformat_test.cc
new file mode 100644
index 0000000..7f3f81a
--- /dev/null
+++ b/leveldb_base/db/dbformat_test.cc
@@ -0,0 +1,128 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "db/dbformat.h"
+
+#include "gtest/gtest.h"
+#include "util/logging.h"
+
+namespace leveldb {
+
+static std::string IKey(const std::string& user_key, uint64_t seq,
+                        ValueType vt) {
+  std::string encoded;
+  AppendInternalKey(&encoded, ParsedInternalKey(user_key, seq, vt));
+  return encoded;
+}
+
+static std::string Shorten(const std::string& s, const std::string& l) {
+  std::string result = s;
+  InternalKeyComparator(BytewiseComparator()).FindShortestSeparator(&result, l);
+  return result;
+}
+
+static std::string ShortSuccessor(const std::string& s) {
+  std::string result = s;
+  InternalKeyComparator(BytewiseComparator()).FindShortSuccessor(&result);
+  return result;
+}
+
+static void TestKey(const std::string& key, uint64_t seq, ValueType vt) {
+  std::string encoded = IKey(key, seq, vt);
+
+  Slice in(encoded);
+  ParsedInternalKey decoded("", 0, kTypeValue);
+
+  ASSERT_TRUE(ParseInternalKey(in, &decoded));
+  ASSERT_EQ(key, decoded.user_key.ToString());
+  ASSERT_EQ(seq, decoded.sequence);
+  ASSERT_EQ(vt, decoded.type);
+
+  ASSERT_TRUE(!ParseInternalKey(Slice("bar"), &decoded));
+}
+
+TEST(FormatTest, InternalKey_EncodeDecode) {
+  const char* keys[] = {"", "k", "hello", "longggggggggggggggggggggg"};
+  const uint64_t seq[] = {1,
+                          2,
+                          3,
+                          (1ull << 8) - 1,
+                          1ull << 8,
+                          (1ull << 8) + 1,
+                          (1ull << 16) - 1,
+                          1ull << 16,
+                          (1ull << 16) + 1,
+                          (1ull << 32) - 1,
+                          1ull << 32,
+                          (1ull << 32) + 1};
+  for (int k = 0; k < sizeof(keys) / sizeof(keys[0]); k++) {
+    for (int s = 0; s < sizeof(seq) / sizeof(seq[0]); s++) {
+      TestKey(keys[k], seq[s], kTypeValue);
+      TestKey("hello", 1, kTypeDeletion);
+    }
+  }
+}
+
+TEST(FormatTest, InternalKey_DecodeFromEmpty) {
+  InternalKey internal_key;
+
+  ASSERT_TRUE(!internal_key.DecodeFrom(""));
+}
+
+TEST(FormatTest, InternalKeyShortSeparator) {
+  // When user keys are same
+  ASSERT_EQ(IKey("foo", 100, kTypeValue),
+            Shorten(IKey("foo", 100, kTypeValue), IKey("foo", 99, kTypeValue)));
+  ASSERT_EQ(
+      IKey("foo", 100, kTypeValue),
+      Shorten(IKey("foo", 100, kTypeValue), IKey("foo", 101, kTypeValue)));
+  ASSERT_EQ(
+      IKey("foo", 100, kTypeValue),
+      Shorten(IKey("foo", 100, kTypeValue), IKey("foo", 100, kTypeValue)));
+  ASSERT_EQ(
+      IKey("foo", 100, kTypeValue),
+      Shorten(IKey("foo", 100, kTypeValue), IKey("foo", 100, kTypeDeletion)));
+
+  // When user keys are misordered
+  ASSERT_EQ(IKey("foo", 100, kTypeValue),
+            Shorten(IKey("foo", 100, kTypeValue), IKey("bar", 99, kTypeValue)));
+
+  // When user keys are different, but correctly ordered
+  ASSERT_EQ(
+      IKey("g", kMaxSequenceNumber, kValueTypeForSeek),
+      Shorten(IKey("foo", 100, kTypeValue), IKey("hello", 200, kTypeValue)));
+
+  // When start user key is prefix of limit user key
+  ASSERT_EQ(
+      IKey("foo", 100, kTypeValue),
+      Shorten(IKey("foo", 100, kTypeValue), IKey("foobar", 200, kTypeValue)));
+
+  // When limit user key is prefix of start user key
+  ASSERT_EQ(
+      IKey("foobar", 100, kTypeValue),
+      Shorten(IKey("foobar", 100, kTypeValue), IKey("foo", 200, kTypeValue)));
+}
+
+TEST(FormatTest, InternalKeyShortestSuccessor) {
+  ASSERT_EQ(IKey("g", kMaxSequenceNumber, kValueTypeForSeek),
+            ShortSuccessor(IKey("foo", 100, kTypeValue)));
+  ASSERT_EQ(IKey("\xff\xff", 100, kTypeValue),
+            ShortSuccessor(IKey("\xff\xff", 100, kTypeValue)));
+}
+
+TEST(FormatTest, ParsedInternalKeyDebugString) {
+  ParsedInternalKey key("The \"key\" in 'single quotes'", 42, kTypeValue);
+
+  ASSERT_EQ("'The \"key\" in 'single quotes'' @ 42 : 1", key.DebugString());
+}
+
+TEST(FormatTest, InternalKeyDebugString) {
+  InternalKey key("The \"key\" in 'single quotes'", 42, kTypeValue);
+  ASSERT_EQ("'The \"key\" in 'single quotes'' @ 42 : 1", key.DebugString());
+
+  InternalKey invalid_key;
+  ASSERT_EQ("(bad)", invalid_key.DebugString());
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/db/dumpfile.cc b/leveldb_base/db/dumpfile.cc
new file mode 100644
index 0000000..6085475
--- /dev/null
+++ b/leveldb_base/db/dumpfile.cc
@@ -0,0 +1,232 @@
+// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "leveldb/dumpfile.h"
+
+#include <cstdio>
+
+#include "db/dbformat.h"
+#include "db/filename.h"
+#include "db/log_reader.h"
+#include "db/version_edit.h"
+#include "db/write_batch_internal.h"
+#include "leveldb/env.h"
+#include "leveldb/iterator.h"
+#include "leveldb/options.h"
+#include "leveldb/status.h"
+#include "leveldb/table.h"
+#include "leveldb/write_batch.h"
+#include "util/logging.h"
+
+namespace leveldb {
+
+namespace {
+
+bool GuessType(const std::string& fname, FileType* type) {
+  size_t pos = fname.rfind('/');
+  std::string basename;
+  if (pos == std::string::npos) {
+    basename = fname;
+  } else {
+    basename = std::string(fname.data() + pos + 1, fname.size() - pos - 1);
+  }
+  uint64_t ignored;
+  return ParseFileName(basename, &ignored, type);
+}
+
+// Notified when log reader encounters corruption.
+class CorruptionReporter : public log::Reader::Reporter {
+ public:
+  void Corruption(size_t bytes, const Status& status) override {
+    std::string r = "corruption: ";
+    AppendNumberTo(&r, bytes);
+    r += " bytes; ";
+    r += status.ToString();
+    r.push_back('\n');
+    dst_->Append(r);
+  }
+
+  WritableFile* dst_;
+};
+
+// Print contents of a log file. (*func)() is called on every record.
+Status PrintLogContents(Env* env, const std::string& fname,
+                        void (*func)(uint64_t, Slice, WritableFile*),
+                        WritableFile* dst) {
+  SequentialFile* file;
+  Status s = env->NewSequentialFile(fname, &file);
+  if (!s.ok()) {
+    return s;
+  }
+  CorruptionReporter reporter;
+  reporter.dst_ = dst;
+  log::Reader reader(file, &reporter, true, 0);
+  Slice record;
+  std::string scratch;
+  while (reader.ReadRecord(&record, &scratch)) {
+    (*func)(reader.LastRecordOffset(), record, dst);
+  }
+  delete file;
+  return Status::OK();
+}
+
+// Called on every item found in a WriteBatch.
+class WriteBatchItemPrinter : public WriteBatch::Handler {
+ public:
+  void Put(const Slice& key, const Slice& value) override {
+    std::string r = "  put '";
+    AppendEscapedStringTo(&r, key);
+    r += "' '";
+    AppendEscapedStringTo(&r, value);
+    r += "'\n";
+    dst_->Append(r);
+  }
+  void Delete(const Slice& key) override {
+    std::string r = "  del '";
+    AppendEscapedStringTo(&r, key);
+    r += "'\n";
+    dst_->Append(r);
+  }
+
+  WritableFile* dst_;
+};
+
+// Called on every log record (each one of which is a WriteBatch)
+// found in a kLogFile.
+static void WriteBatchPrinter(uint64_t pos, Slice record, WritableFile* dst) {
+  std::string r = "--- offset ";
+  AppendNumberTo(&r, pos);
+  r += "; ";
+  if (record.size() < 12) {
+    r += "log record length ";
+    AppendNumberTo(&r, record.size());
+    r += " is too small\n";
+    dst->Append(r);
+    return;
+  }
+  WriteBatch batch;
+  WriteBatchInternal::SetContents(&batch, record);
+  r += "sequence ";
+  AppendNumberTo(&r, WriteBatchInternal::Sequence(&batch));
+  r.push_back('\n');
+  dst->Append(r);
+  WriteBatchItemPrinter batch_item_printer;
+  batch_item_printer.dst_ = dst;
+  Status s = batch.Iterate(&batch_item_printer);
+  if (!s.ok()) {
+    dst->Append("  error: " + s.ToString() + "\n");
+  }
+}
+
+Status DumpLog(Env* env, const std::string& fname, WritableFile* dst) {
+  return PrintLogContents(env, fname, WriteBatchPrinter, dst);
+}
+
+// Called on every log record (each one of which is a WriteBatch)
+// found in a kDescriptorFile.
+static void VersionEditPrinter(uint64_t pos, Slice record, WritableFile* dst) {
+  std::string r = "--- offset ";
+  AppendNumberTo(&r, pos);
+  r += "; ";
+  VersionEdit edit;
+  Status s = edit.DecodeFrom(record);
+  if (!s.ok()) {
+    r += s.ToString();
+    r.push_back('\n');
+  } else {
+    r += edit.DebugString();
+  }
+  dst->Append(r);
+}
+
+Status DumpDescriptor(Env* env, const std::string& fname, WritableFile* dst) {
+  return PrintLogContents(env, fname, VersionEditPrinter, dst);
+}
+
+Status DumpTable(Env* env, const std::string& fname, WritableFile* dst) {
+  uint64_t file_size;
+  RandomAccessFile* file = nullptr;
+  Table* table = nullptr;
+  Status s = env->GetFileSize(fname, &file_size);
+  if (s.ok()) {
+    s = env->NewRandomAccessFile(fname, &file);
+  }
+  if (s.ok()) {
+    // We use the default comparator, which may or may not match the
+    // comparator used in this database. However this should not cause
+    // problems since we only use Table operations that do not require
+    // any comparisons.  In particular, we do not call Seek or Prev.
+    s = Table::Open(Options(), file, file_size, &table);
+  }
+  if (!s.ok()) {
+    delete table;
+    delete file;
+    return s;
+  }
+
+  ReadOptions ro;
+  ro.fill_cache = false;
+  Iterator* iter = table->NewIterator(ro);
+  std::string r;
+  for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
+    r.clear();
+    ParsedInternalKey key;
+    if (!ParseInternalKey(iter->key(), &key)) {
+      r = "badkey '";
+      AppendEscapedStringTo(&r, iter->key());
+      r += "' => '";
+      AppendEscapedStringTo(&r, iter->value());
+      r += "'\n";
+      dst->Append(r);
+    } else {
+      r = "'";
+      AppendEscapedStringTo(&r, key.user_key);
+      r += "' @ ";
+      AppendNumberTo(&r, key.sequence);
+      r += " : ";
+      if (key.type == kTypeDeletion) {
+        r += "del";
+      } else if (key.type == kTypeValue) {
+        r += "val";
+      } else {
+        AppendNumberTo(&r, key.type);
+      }
+      r += " => '";
+      AppendEscapedStringTo(&r, iter->value());
+      r += "'\n";
+      dst->Append(r);
+    }
+  }
+  s = iter->status();
+  if (!s.ok()) {
+    dst->Append("iterator error: " + s.ToString() + "\n");
+  }
+
+  delete iter;
+  delete table;
+  delete file;
+  return Status::OK();
+}
+
+}  // namespace
+
+Status DumpFile(Env* env, const std::string& fname, WritableFile* dst) {
+  FileType ftype;
+  if (!GuessType(fname, &ftype)) {
+    return Status::InvalidArgument(fname + ": unknown file type");
+  }
+  switch (ftype) {
+    case kLogFile:
+      return DumpLog(env, fname, dst);
+    case kDescriptorFile:
+      return DumpDescriptor(env, fname, dst);
+    case kTableFile:
+      return DumpTable(env, fname, dst);
+    default:
+      break;
+  }
+  return Status::InvalidArgument(fname + ": not a dump-able file type");
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/db/fault_injection_test.cc b/leveldb_base/db/fault_injection_test.cc
new file mode 100644
index 0000000..ef864a4
--- /dev/null
+++ b/leveldb_base/db/fault_injection_test.cc
@@ -0,0 +1,550 @@
+// Copyright 2014 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+// This test uses a custom Env to keep track of the state of a filesystem as of
+// the last "sync". It then checks for data loss errors by purposely dropping
+// file data (or entire files) not protected by a "sync".
+
+#include <map>
+#include <set>
+
+#include "gtest/gtest.h"
+#include "db/db_impl.h"
+#include "db/filename.h"
+#include "db/log_format.h"
+#include "db/version_set.h"
+#include "leveldb/cache.h"
+#include "leveldb/db.h"
+#include "leveldb/env.h"
+#include "leveldb/table.h"
+#include "leveldb/write_batch.h"
+#include "port/port.h"
+#include "port/thread_annotations.h"
+#include "util/logging.h"
+#include "util/mutexlock.h"
+#include "util/testutil.h"
+
+namespace leveldb {
+
+static const int kValueSize = 1000;
+static const int kMaxNumValues = 2000;
+static const size_t kNumIterations = 3;
+
+class FaultInjectionTestEnv;
+
+namespace {
+
+// Assume a filename, and not a directory name like "/foo/bar/"
+static std::string GetDirName(const std::string& filename) {
+  size_t found = filename.find_last_of("/\\");
+  if (found == std::string::npos) {
+    return "";
+  } else {
+    return filename.substr(0, found);
+  }
+}
+
+Status SyncDir(const std::string& dir) {
+  // As this is a test it isn't required to *actually* sync this directory.
+  return Status::OK();
+}
+
+// A basic file truncation function suitable for this test.
+Status Truncate(const std::string& filename, uint64_t length) {
+  leveldb::Env* env = leveldb::Env::Default();
+
+  SequentialFile* orig_file;
+  Status s = env->NewSequentialFile(filename, &orig_file);
+  if (!s.ok()) return s;
+
+  char* scratch = new char[length];
+  leveldb::Slice result;
+  s = orig_file->Read(length, &result, scratch);
+  delete orig_file;
+  if (s.ok()) {
+    std::string tmp_name = GetDirName(filename) + "/truncate.tmp";
+    WritableFile* tmp_file;
+    s = env->NewWritableFile(tmp_name, &tmp_file);
+    if (s.ok()) {
+      s = tmp_file->Append(result);
+      delete tmp_file;
+      if (s.ok()) {
+        s = env->RenameFile(tmp_name, filename);
+      } else {
+        env->RemoveFile(tmp_name);
+      }
+    }
+  }
+
+  delete[] scratch;
+
+  return s;
+}
+
+struct FileState {
+  std::string filename_;
+  int64_t pos_;
+  int64_t pos_at_last_sync_;
+  int64_t pos_at_last_flush_;
+
+  FileState(const std::string& filename)
+      : filename_(filename),
+        pos_(-1),
+        pos_at_last_sync_(-1),
+        pos_at_last_flush_(-1) {}
+
+  FileState() : pos_(-1), pos_at_last_sync_(-1), pos_at_last_flush_(-1) {}
+
+  bool IsFullySynced() const { return pos_ <= 0 || pos_ == pos_at_last_sync_; }
+
+  Status DropUnsyncedData() const;
+};
+
+}  // anonymous namespace
+
+// A wrapper around WritableFile which informs another Env whenever this file
+// is written to or sync'ed.
+class TestWritableFile : public WritableFile {
+ public:
+  TestWritableFile(const FileState& state, WritableFile* f,
+                   FaultInjectionTestEnv* env);
+  ~TestWritableFile() override;
+  Status Append(const Slice& data) override;
+  Status Close() override;
+  Status Flush() override;
+  Status Sync() override;
+
+ private:
+  FileState state_;
+  WritableFile* target_;
+  bool writable_file_opened_;
+  FaultInjectionTestEnv* env_;
+
+  Status SyncParent();
+};
+
+class FaultInjectionTestEnv : public EnvWrapper {
+ public:
+  FaultInjectionTestEnv()
+      : EnvWrapper(Env::Default()), filesystem_active_(true) {}
+  ~FaultInjectionTestEnv() override = default;
+  Status NewWritableFile(const std::string& fname,
+                         WritableFile** result) override;
+  Status NewAppendableFile(const std::string& fname,
+                           WritableFile** result) override;
+  Status RemoveFile(const std::string& f) override;
+  Status RenameFile(const std::string& s, const std::string& t) override;
+
+  void WritableFileClosed(const FileState& state);
+  Status DropUnsyncedFileData();
+  Status RemoveFilesCreatedAfterLastDirSync();
+  void DirWasSynced();
+  bool IsFileCreatedSinceLastDirSync(const std::string& filename);
+  void ResetState();
+  void UntrackFile(const std::string& f);
+  // Setting the filesystem to inactive is the test equivalent to simulating a
+  // system reset. Setting to inactive will freeze our saved filesystem state so
+  // that it will stop being recorded. It can then be reset back to the state at
+  // the time of the reset.
+  bool IsFilesystemActive() LOCKS_EXCLUDED(mutex_) {
+    MutexLock l(&mutex_);
+    return filesystem_active_;
+  }
+  void SetFilesystemActive(bool active) LOCKS_EXCLUDED(mutex_) {
+    MutexLock l(&mutex_);
+    filesystem_active_ = active;
+  }
+
+ private:
+  port::Mutex mutex_;
+  std::map<std::string, FileState> db_file_state_ GUARDED_BY(mutex_);
+  std::set<std::string> new_files_since_last_dir_sync_ GUARDED_BY(mutex_);
+  bool filesystem_active_ GUARDED_BY(mutex_);  // Record flushes, syncs, writes
+};
+
+TestWritableFile::TestWritableFile(const FileState& state, WritableFile* f,
+                                   FaultInjectionTestEnv* env)
+    : state_(state), target_(f), writable_file_opened_(true), env_(env) {
+  assert(f != nullptr);
+}
+
+TestWritableFile::~TestWritableFile() {
+  if (writable_file_opened_) {
+    Close();
+  }
+  delete target_;
+}
+
+Status TestWritableFile::Append(const Slice& data) {
+  Status s = target_->Append(data);
+  if (s.ok() && env_->IsFilesystemActive()) {
+    state_.pos_ += data.size();
+  }
+  return s;
+}
+
+Status TestWritableFile::Close() {
+  writable_file_opened_ = false;
+  Status s = target_->Close();
+  if (s.ok()) {
+    env_->WritableFileClosed(state_);
+  }
+  return s;
+}
+
+Status TestWritableFile::Flush() {
+  Status s = target_->Flush();
+  if (s.ok() && env_->IsFilesystemActive()) {
+    state_.pos_at_last_flush_ = state_.pos_;
+  }
+  return s;
+}
+
+Status TestWritableFile::SyncParent() {
+  Status s = SyncDir(GetDirName(state_.filename_));
+  if (s.ok()) {
+    env_->DirWasSynced();
+  }
+  return s;
+}
+
+Status TestWritableFile::Sync() {
+  if (!env_->IsFilesystemActive()) {
+    return Status::OK();
+  }
+  // Ensure new files referred to by the manifest are in the filesystem.
+  Status s = target_->Sync();
+  if (s.ok()) {
+    state_.pos_at_last_sync_ = state_.pos_;
+  }
+  if (env_->IsFileCreatedSinceLastDirSync(state_.filename_)) {
+    Status ps = SyncParent();
+    if (s.ok() && !ps.ok()) {
+      s = ps;
+    }
+  }
+  return s;
+}
+
+Status FaultInjectionTestEnv::NewWritableFile(const std::string& fname,
+                                              WritableFile** result) {
+  WritableFile* actual_writable_file;
+  Status s = target()->NewWritableFile(fname, &actual_writable_file);
+  if (s.ok()) {
+    FileState state(fname);
+    state.pos_ = 0;
+    *result = new TestWritableFile(state, actual_writable_file, this);
+    // NewWritableFile doesn't append to files, so if the same file is
+    // opened again then it will be truncated - so forget our saved
+    // state.
+    UntrackFile(fname);
+    MutexLock l(&mutex_);
+    new_files_since_last_dir_sync_.insert(fname);
+  }
+  return s;
+}
+
+Status FaultInjectionTestEnv::NewAppendableFile(const std::string& fname,
+                                                WritableFile** result) {
+  WritableFile* actual_writable_file;
+  Status s = target()->NewAppendableFile(fname, &actual_writable_file);
+  if (s.ok()) {
+    FileState state(fname);
+    state.pos_ = 0;
+    {
+      MutexLock l(&mutex_);
+      if (db_file_state_.count(fname) == 0) {
+        new_files_since_last_dir_sync_.insert(fname);
+      } else {
+        state = db_file_state_[fname];
+      }
+    }
+    *result = new TestWritableFile(state, actual_writable_file, this);
+  }
+  return s;
+}
+
+Status FaultInjectionTestEnv::DropUnsyncedFileData() {
+  Status s;
+  MutexLock l(&mutex_);
+  for (const auto& kvp : db_file_state_) {
+    if (!s.ok()) {
+      break;
+    }
+    const FileState& state = kvp.second;
+    if (!state.IsFullySynced()) {
+      s = state.DropUnsyncedData();
+    }
+  }
+  return s;
+}
+
+void FaultInjectionTestEnv::DirWasSynced() {
+  MutexLock l(&mutex_);
+  new_files_since_last_dir_sync_.clear();
+}
+
+bool FaultInjectionTestEnv::IsFileCreatedSinceLastDirSync(
+    const std::string& filename) {
+  MutexLock l(&mutex_);
+  return new_files_since_last_dir_sync_.find(filename) !=
+         new_files_since_last_dir_sync_.end();
+}
+
+void FaultInjectionTestEnv::UntrackFile(const std::string& f) {
+  MutexLock l(&mutex_);
+  db_file_state_.erase(f);
+  new_files_since_last_dir_sync_.erase(f);
+}
+
+Status FaultInjectionTestEnv::RemoveFile(const std::string& f) {
+  Status s = EnvWrapper::RemoveFile(f);
+  EXPECT_LEVELDB_OK(s);
+  if (s.ok()) {
+    UntrackFile(f);
+  }
+  return s;
+}
+
+Status FaultInjectionTestEnv::RenameFile(const std::string& s,
+                                         const std::string& t) {
+  Status ret = EnvWrapper::RenameFile(s, t);
+
+  if (ret.ok()) {
+    MutexLock l(&mutex_);
+    if (db_file_state_.find(s) != db_file_state_.end()) {
+      db_file_state_[t] = db_file_state_[s];
+      db_file_state_.erase(s);
+    }
+
+    if (new_files_since_last_dir_sync_.erase(s) != 0) {
+      assert(new_files_since_last_dir_sync_.find(t) ==
+             new_files_since_last_dir_sync_.end());
+      new_files_since_last_dir_sync_.insert(t);
+    }
+  }
+
+  return ret;
+}
+
+void FaultInjectionTestEnv::ResetState() {
+  // Since we are not destroying the database, the existing files
+  // should keep their recorded synced/flushed state. Therefore
+  // we do not reset db_file_state_ and new_files_since_last_dir_sync_.
+  SetFilesystemActive(true);
+}
+
+Status FaultInjectionTestEnv::RemoveFilesCreatedAfterLastDirSync() {
+  // Because RemoveFile access this container make a copy to avoid deadlock
+  mutex_.Lock();
+  std::set<std::string> new_files(new_files_since_last_dir_sync_.begin(),
+                                  new_files_since_last_dir_sync_.end());
+  mutex_.Unlock();
+  Status status;
+  for (const auto& new_file : new_files) {
+    Status remove_status = RemoveFile(new_file);
+    if (!remove_status.ok() && status.ok()) {
+      status = std::move(remove_status);
+    }
+  }
+  return status;
+}
+
+void FaultInjectionTestEnv::WritableFileClosed(const FileState& state) {
+  MutexLock l(&mutex_);
+  db_file_state_[state.filename_] = state;
+}
+
+Status FileState::DropUnsyncedData() const {
+  int64_t sync_pos = pos_at_last_sync_ == -1 ? 0 : pos_at_last_sync_;
+  return Truncate(filename_, sync_pos);
+}
+
+class FaultInjectionTest : public testing::Test {
+ public:
+  enum ExpectedVerifResult { VAL_EXPECT_NO_ERROR, VAL_EXPECT_ERROR };
+  enum ResetMethod { RESET_DROP_UNSYNCED_DATA, RESET_DELETE_UNSYNCED_FILES };
+
+  FaultInjectionTestEnv* env_;
+  std::string dbname_;
+  Cache* tiny_cache_;
+  Options options_;
+  DB* db_;
+
+  FaultInjectionTest()
+      : env_(new FaultInjectionTestEnv),
+        tiny_cache_(NewLRUCache(100)),
+        db_(nullptr) {
+    dbname_ = testing::TempDir() + "fault_test";
+    DestroyDB(dbname_, Options());  // Destroy any db from earlier run
+    options_.reuse_logs = true;
+    options_.env = env_;
+    options_.paranoid_checks = true;
+    options_.block_cache = tiny_cache_;
+    options_.create_if_missing = true;
+  }
+
+  ~FaultInjectionTest() {
+    CloseDB();
+    DestroyDB(dbname_, Options());
+    delete tiny_cache_;
+    delete env_;
+  }
+
+  void ReuseLogs(bool reuse) { options_.reuse_logs = reuse; }
+
+  void Build(int start_idx, int num_vals) {
+    std::string key_space, value_space;
+    WriteBatch batch;
+    for (int i = start_idx; i < start_idx + num_vals; i++) {
+      Slice key = Key(i, &key_space);
+      batch.Clear();
+      batch.Put(key, Value(i, &value_space));
+      WriteOptions options;
+      ASSERT_LEVELDB_OK(db_->Write(options, &batch));
+    }
+  }
+
+  Status ReadValue(int i, std::string* val) const {
+    std::string key_space, value_space;
+    Slice key = Key(i, &key_space);
+    Value(i, &value_space);
+    ReadOptions options;
+    return db_->Get(options, key, val);
+  }
+
+  Status Verify(int start_idx, int num_vals,
+                ExpectedVerifResult expected) const {
+    std::string val;
+    std::string value_space;
+    Status s;
+    for (int i = start_idx; i < start_idx + num_vals && s.ok(); i++) {
+      Value(i, &value_space);
+      s = ReadValue(i, &val);
+      if (expected == VAL_EXPECT_NO_ERROR) {
+        if (s.ok()) {
+          EXPECT_EQ(value_space, val);
+        }
+      } else if (s.ok()) {
+        std::fprintf(stderr, "Expected an error at %d, but was OK\n", i);
+        s = Status::IOError(dbname_, "Expected value error:");
+      } else {
+        s = Status::OK();  // An expected error
+      }
+    }
+    return s;
+  }
+
+  // Return the ith key
+  Slice Key(int i, std::string* storage) const {
+    char buf[100];
+    std::snprintf(buf, sizeof(buf), "%016d", i);
+    storage->assign(buf, strlen(buf));
+    return Slice(*storage);
+  }
+
+  // Return the value to associate with the specified key
+  Slice Value(int k, std::string* storage) const {
+    Random r(k);
+    return test::RandomString(&r, kValueSize, storage);
+  }
+
+  Status OpenDB() {
+    delete db_;
+    db_ = nullptr;
+    env_->ResetState();
+    return DB::Open(options_, dbname_, &db_);
+  }
+
+  void CloseDB() {
+    delete db_;
+    db_ = nullptr;
+  }
+
+  void DeleteAllData() {
+    Iterator* iter = db_->NewIterator(ReadOptions());
+    for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
+      ASSERT_LEVELDB_OK(db_->Delete(WriteOptions(), iter->key()));
+    }
+
+    delete iter;
+  }
+
+  void ResetDBState(ResetMethod reset_method) {
+    switch (reset_method) {
+      case RESET_DROP_UNSYNCED_DATA:
+        ASSERT_LEVELDB_OK(env_->DropUnsyncedFileData());
+        break;
+      case RESET_DELETE_UNSYNCED_FILES:
+        ASSERT_LEVELDB_OK(env_->RemoveFilesCreatedAfterLastDirSync());
+        break;
+      default:
+        assert(false);
+    }
+  }
+
+  void PartialCompactTestPreFault(int num_pre_sync, int num_post_sync) {
+    DeleteAllData();
+    Build(0, num_pre_sync);
+    db_->CompactRange(nullptr, nullptr);
+    Build(num_pre_sync, num_post_sync);
+  }
+
+  void PartialCompactTestReopenWithFault(ResetMethod reset_method,
+                                         int num_pre_sync, int num_post_sync) {
+    env_->SetFilesystemActive(false);
+    CloseDB();
+    ResetDBState(reset_method);
+    ASSERT_LEVELDB_OK(OpenDB());
+    ASSERT_LEVELDB_OK(
+        Verify(0, num_pre_sync, FaultInjectionTest::VAL_EXPECT_NO_ERROR));
+    ASSERT_LEVELDB_OK(Verify(num_pre_sync, num_post_sync,
+                             FaultInjectionTest::VAL_EXPECT_ERROR));
+  }
+
+  void NoWriteTestPreFault() {}
+
+  void NoWriteTestReopenWithFault(ResetMethod reset_method) {
+    CloseDB();
+    ResetDBState(reset_method);
+    ASSERT_LEVELDB_OK(OpenDB());
+  }
+
+  void DoTest() {
+    Random rnd(0);
+    ASSERT_LEVELDB_OK(OpenDB());
+    for (size_t idx = 0; idx < kNumIterations; idx++) {
+      int num_pre_sync = rnd.Uniform(kMaxNumValues);
+      int num_post_sync = rnd.Uniform(kMaxNumValues);
+
+      PartialCompactTestPreFault(num_pre_sync, num_post_sync);
+      PartialCompactTestReopenWithFault(RESET_DROP_UNSYNCED_DATA, num_pre_sync,
+                                        num_post_sync);
+
+      NoWriteTestPreFault();
+      NoWriteTestReopenWithFault(RESET_DROP_UNSYNCED_DATA);
+
+      PartialCompactTestPreFault(num_pre_sync, num_post_sync);
+      // No new files created so we expect all values since no files will be
+      // dropped.
+      PartialCompactTestReopenWithFault(RESET_DELETE_UNSYNCED_FILES,
+                                        num_pre_sync + num_post_sync, 0);
+
+      NoWriteTestPreFault();
+      NoWriteTestReopenWithFault(RESET_DELETE_UNSYNCED_FILES);
+    }
+  }
+};
+
+TEST_F(FaultInjectionTest, FaultTestNoLogReuse) {
+  ReuseLogs(false);
+  DoTest();
+}
+
+TEST_F(FaultInjectionTest, FaultTestWithLogReuse) {
+  ReuseLogs(true);
+  DoTest();
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/db/filename.cc b/leveldb_base/db/filename.cc
new file mode 100644
index 0000000..e526249
--- /dev/null
+++ b/leveldb_base/db/filename.cc
@@ -0,0 +1,141 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "db/filename.h"
+
+#include <cassert>
+#include <cstdio>
+
+#include "db/dbformat.h"
+#include "leveldb/env.h"
+#include "util/logging.h"
+
+namespace leveldb {
+
+// A utility routine: write "data" to the named file and Sync() it.
+Status WriteStringToFileSync(Env* env, const Slice& data,
+                             const std::string& fname);
+
+static std::string MakeFileName(const std::string& dbname, uint64_t number,
+                                const char* suffix) {
+  char buf[100];
+  std::snprintf(buf, sizeof(buf), "/%06llu.%s",
+                static_cast<unsigned long long>(number), suffix);
+  return dbname + buf;
+}
+
+std::string LogFileName(const std::string& dbname, uint64_t number) {
+  assert(number > 0);
+  return MakeFileName(dbname, number, "log");
+}
+
+std::string TableFileName(const std::string& dbname, uint64_t number) {
+  assert(number > 0);
+  return MakeFileName(dbname, number, "ldb");
+}
+
+std::string SSTTableFileName(const std::string& dbname, uint64_t number) {
+  assert(number > 0);
+  return MakeFileName(dbname, number, "sst");
+}
+
+std::string DescriptorFileName(const std::string& dbname, uint64_t number) {
+  assert(number > 0);
+  char buf[100];
+  std::snprintf(buf, sizeof(buf), "/MANIFEST-%06llu",
+                static_cast<unsigned long long>(number));
+  return dbname + buf;
+}
+
+std::string CurrentFileName(const std::string& dbname) {
+  return dbname + "/CURRENT";
+}
+
+std::string LockFileName(const std::string& dbname) { return dbname + "/LOCK"; }
+
+std::string TempFileName(const std::string& dbname, uint64_t number) {
+  assert(number > 0);
+  return MakeFileName(dbname, number, "dbtmp");
+}
+
+std::string InfoLogFileName(const std::string& dbname) {
+  return dbname + "/LOG";
+}
+
+// Return the name of the old info log file for "dbname".
+std::string OldInfoLogFileName(const std::string& dbname) {
+  return dbname + "/LOG.old";
+}
+
+// Owned filenames have the form:
+//    dbname/CURRENT
+//    dbname/LOCK
+//    dbname/LOG
+//    dbname/LOG.old
+//    dbname/MANIFEST-[0-9]+
+//    dbname/[0-9]+.(log|sst|ldb)
+bool ParseFileName(const std::string& filename, uint64_t* number,
+                   FileType* type) {
+  Slice rest(filename);
+  if (rest == "CURRENT") {
+    *number = 0;
+    *type = kCurrentFile;
+  } else if (rest == "LOCK") {
+    *number = 0;
+    *type = kDBLockFile;
+  } else if (rest == "LOG" || rest == "LOG.old") {
+    *number = 0;
+    *type = kInfoLogFile;
+  } else if (rest.starts_with("MANIFEST-")) {
+    rest.remove_prefix(strlen("MANIFEST-"));
+    uint64_t num;
+    if (!ConsumeDecimalNumber(&rest, &num)) {
+      return false;
+    }
+    if (!rest.empty()) {
+      return false;
+    }
+    *type = kDescriptorFile;
+    *number = num;
+  } else {
+    // Avoid strtoull() to keep filename format independent of the
+    // current locale
+    uint64_t num;
+    if (!ConsumeDecimalNumber(&rest, &num)) {
+      return false;
+    }
+    Slice suffix = rest;
+    if (suffix == Slice(".log")) {
+      *type = kLogFile;
+    } else if (suffix == Slice(".sst") || suffix == Slice(".ldb")) {
+      *type = kTableFile;
+    } else if (suffix == Slice(".dbtmp")) {
+      *type = kTempFile;
+    } else {
+      return false;
+    }
+    *number = num;
+  }
+  return true;
+}
+
+Status SetCurrentFile(Env* env, const std::string& dbname,
+                      uint64_t descriptor_number) {
+  // Remove leading "dbname/" and add newline to manifest file name
+  std::string manifest = DescriptorFileName(dbname, descriptor_number);
+  Slice contents = manifest;
+  assert(contents.starts_with(dbname + "/"));
+  contents.remove_prefix(dbname.size() + 1);
+  std::string tmp = TempFileName(dbname, descriptor_number);
+  Status s = WriteStringToFileSync(env, contents.ToString() + "\n", tmp);
+  if (s.ok()) {
+    s = env->RenameFile(tmp, CurrentFileName(dbname));
+  }
+  if (!s.ok()) {
+    env->RemoveFile(tmp);
+  }
+  return s;
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/db/filename.h b/leveldb_base/db/filename.h
new file mode 100644
index 0000000..563c6d8
--- /dev/null
+++ b/leveldb_base/db/filename.h
@@ -0,0 +1,83 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// File names used by DB code
+
+#ifndef STORAGE_LEVELDB_DB_FILENAME_H_
+#define STORAGE_LEVELDB_DB_FILENAME_H_
+
+#include <cstdint>
+#include <string>
+
+#include "leveldb/slice.h"
+#include "leveldb/status.h"
+#include "port/port.h"
+
+namespace leveldb {
+
+class Env;
+
+enum FileType {
+  kLogFile,
+  kDBLockFile,
+  kTableFile,
+  kDescriptorFile,
+  kCurrentFile,
+  kTempFile,
+  kInfoLogFile  // Either the current one, or an old one
+};
+
+// Return the name of the log file with the specified number
+// in the db named by "dbname".  The result will be prefixed with
+// "dbname".
+std::string LogFileName(const std::string& dbname, uint64_t number);
+
+// Return the name of the sstable with the specified number
+// in the db named by "dbname".  The result will be prefixed with
+// "dbname".
+std::string TableFileName(const std::string& dbname, uint64_t number);
+
+// Return the legacy file name for an sstable with the specified number
+// in the db named by "dbname". The result will be prefixed with
+// "dbname".
+std::string SSTTableFileName(const std::string& dbname, uint64_t number);
+
+// Return the name of the descriptor file for the db named by
+// "dbname" and the specified incarnation number.  The result will be
+// prefixed with "dbname".
+std::string DescriptorFileName(const std::string& dbname, uint64_t number);
+
+// Return the name of the current file.  This file contains the name
+// of the current manifest file.  The result will be prefixed with
+// "dbname".
+std::string CurrentFileName(const std::string& dbname);
+
+// Return the name of the lock file for the db named by
+// "dbname".  The result will be prefixed with "dbname".
+std::string LockFileName(const std::string& dbname);
+
+// Return the name of a temporary file owned by the db named "dbname".
+// The result will be prefixed with "dbname".
+std::string TempFileName(const std::string& dbname, uint64_t number);
+
+// Return the name of the info log file for "dbname".
+std::string InfoLogFileName(const std::string& dbname);
+
+// Return the name of the old info log file for "dbname".
+std::string OldInfoLogFileName(const std::string& dbname);
+
+// If filename is a leveldb file, store the type of the file in *type.
+// The number encoded in the filename is stored in *number.  If the
+// filename was successfully parsed, returns true.  Else return false.
+bool ParseFileName(const std::string& filename, uint64_t* number,
+                   FileType* type);
+
+// Make the CURRENT file point to the descriptor file with the
+// specified number.
+Status SetCurrentFile(Env* env, const std::string& dbname,
+                      uint64_t descriptor_number);
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_DB_FILENAME_H_
diff --git a/leveldb_base/db/filename_test.cc b/leveldb_base/db/filename_test.cc
new file mode 100644
index 0000000..9ac0111
--- /dev/null
+++ b/leveldb_base/db/filename_test.cc
@@ -0,0 +1,127 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "db/filename.h"
+
+#include "gtest/gtest.h"
+#include "db/dbformat.h"
+#include "port/port.h"
+#include "util/logging.h"
+
+namespace leveldb {
+
+TEST(FileNameTest, Parse) {
+  Slice db;
+  FileType type;
+  uint64_t number;
+
+  // Successful parses
+  static struct {
+    const char* fname;
+    uint64_t number;
+    FileType type;
+  } cases[] = {
+      {"100.log", 100, kLogFile},
+      {"0.log", 0, kLogFile},
+      {"0.sst", 0, kTableFile},
+      {"0.ldb", 0, kTableFile},
+      {"CURRENT", 0, kCurrentFile},
+      {"LOCK", 0, kDBLockFile},
+      {"MANIFEST-2", 2, kDescriptorFile},
+      {"MANIFEST-7", 7, kDescriptorFile},
+      {"LOG", 0, kInfoLogFile},
+      {"LOG.old", 0, kInfoLogFile},
+      {"18446744073709551615.log", 18446744073709551615ull, kLogFile},
+  };
+  for (int i = 0; i < sizeof(cases) / sizeof(cases[0]); i++) {
+    std::string f = cases[i].fname;
+    ASSERT_TRUE(ParseFileName(f, &number, &type)) << f;
+    ASSERT_EQ(cases[i].type, type) << f;
+    ASSERT_EQ(cases[i].number, number) << f;
+  }
+
+  // Errors
+  static const char* errors[] = {"",
+                                 "foo",
+                                 "foo-dx-100.log",
+                                 ".log",
+                                 "",
+                                 "manifest",
+                                 "CURREN",
+                                 "CURRENTX",
+                                 "MANIFES",
+                                 "MANIFEST",
+                                 "MANIFEST-",
+                                 "XMANIFEST-3",
+                                 "MANIFEST-3x",
+                                 "LOC",
+                                 "LOCKx",
+                                 "LO",
+                                 "LOGx",
+                                 "18446744073709551616.log",
+                                 "184467440737095516150.log",
+                                 "100",
+                                 "100.",
+                                 "100.lop"};
+  for (int i = 0; i < sizeof(errors) / sizeof(errors[0]); i++) {
+    std::string f = errors[i];
+    ASSERT_TRUE(!ParseFileName(f, &number, &type)) << f;
+  }
+}
+
+TEST(FileNameTest, Construction) {
+  uint64_t number;
+  FileType type;
+  std::string fname;
+
+  fname = CurrentFileName("foo");
+  ASSERT_EQ("foo/", std::string(fname.data(), 4));
+  ASSERT_TRUE(ParseFileName(fname.c_str() + 4, &number, &type));
+  ASSERT_EQ(0, number);
+  ASSERT_EQ(kCurrentFile, type);
+
+  fname = LockFileName("foo");
+  ASSERT_EQ("foo/", std::string(fname.data(), 4));
+  ASSERT_TRUE(ParseFileName(fname.c_str() + 4, &number, &type));
+  ASSERT_EQ(0, number);
+  ASSERT_EQ(kDBLockFile, type);
+
+  fname = LogFileName("foo", 192);
+  ASSERT_EQ("foo/", std::string(fname.data(), 4));
+  ASSERT_TRUE(ParseFileName(fname.c_str() + 4, &number, &type));
+  ASSERT_EQ(192, number);
+  ASSERT_EQ(kLogFile, type);
+
+  fname = TableFileName("bar", 200);
+  ASSERT_EQ("bar/", std::string(fname.data(), 4));
+  ASSERT_TRUE(ParseFileName(fname.c_str() + 4, &number, &type));
+  ASSERT_EQ(200, number);
+  ASSERT_EQ(kTableFile, type);
+
+  fname = DescriptorFileName("bar", 100);
+  ASSERT_EQ("bar/", std::string(fname.data(), 4));
+  ASSERT_TRUE(ParseFileName(fname.c_str() + 4, &number, &type));
+  ASSERT_EQ(100, number);
+  ASSERT_EQ(kDescriptorFile, type);
+
+  fname = TempFileName("tmp", 999);
+  ASSERT_EQ("tmp/", std::string(fname.data(), 4));
+  ASSERT_TRUE(ParseFileName(fname.c_str() + 4, &number, &type));
+  ASSERT_EQ(999, number);
+  ASSERT_EQ(kTempFile, type);
+
+  fname = InfoLogFileName("foo");
+  ASSERT_EQ("foo/", std::string(fname.data(), 4));
+  ASSERT_TRUE(ParseFileName(fname.c_str() + 4, &number, &type));
+  ASSERT_EQ(0, number);
+  ASSERT_EQ(kInfoLogFile, type);
+
+  fname = OldInfoLogFileName("foo");
+  ASSERT_EQ("foo/", std::string(fname.data(), 4));
+  ASSERT_TRUE(ParseFileName(fname.c_str() + 4, &number, &type));
+  ASSERT_EQ(0, number);
+  ASSERT_EQ(kInfoLogFile, type);
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/db/leveldbutil.cc b/leveldb_base/db/leveldbutil.cc
new file mode 100644
index 0000000..95ee897
--- /dev/null
+++ b/leveldb_base/db/leveldbutil.cc
@@ -0,0 +1,64 @@
+// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include <cstdio>
+
+#include "leveldb/dumpfile.h"
+#include "leveldb/env.h"
+#include "leveldb/status.h"
+
+namespace leveldb {
+namespace {
+
+class StdoutPrinter : public WritableFile {
+ public:
+  Status Append(const Slice& data) override {
+    fwrite(data.data(), 1, data.size(), stdout);
+    return Status::OK();
+  }
+  Status Close() override { return Status::OK(); }
+  Status Flush() override { return Status::OK(); }
+  Status Sync() override { return Status::OK(); }
+};
+
+bool HandleDumpCommand(Env* env, char** files, int num) {
+  StdoutPrinter printer;
+  bool ok = true;
+  for (int i = 0; i < num; i++) {
+    Status s = DumpFile(env, files[i], &printer);
+    if (!s.ok()) {
+      std::fprintf(stderr, "%s\n", s.ToString().c_str());
+      ok = false;
+    }
+  }
+  return ok;
+}
+
+}  // namespace
+}  // namespace leveldb
+
+static void Usage() {
+  std::fprintf(
+      stderr,
+      "Usage: leveldbutil command...\n"
+      "   dump files...         -- dump contents of specified files\n");
+}
+
+int main(int argc, char** argv) {
+  leveldb::Env* env = leveldb::Env::Default();
+  bool ok = true;
+  if (argc < 2) {
+    Usage();
+    ok = false;
+  } else {
+    std::string command = argv[1];
+    if (command == "dump") {
+      ok = leveldb::HandleDumpCommand(env, argv + 2, argc - 2);
+    } else {
+      Usage();
+      ok = false;
+    }
+  }
+  return (ok ? 0 : 1);
+}
diff --git a/leveldb_base/db/log_format.h b/leveldb_base/db/log_format.h
new file mode 100644
index 0000000..356e69f
--- /dev/null
+++ b/leveldb_base/db/log_format.h
@@ -0,0 +1,35 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// Log format information shared by reader and writer.
+// See ../doc/log_format.md for more detail.
+
+#ifndef STORAGE_LEVELDB_DB_LOG_FORMAT_H_
+#define STORAGE_LEVELDB_DB_LOG_FORMAT_H_
+
+namespace leveldb {
+namespace log {
+
+enum RecordType {
+  // Zero is reserved for preallocated files
+  kZeroType = 0,
+
+  kFullType = 1,
+
+  // For fragments
+  kFirstType = 2,
+  kMiddleType = 3,
+  kLastType = 4
+};
+static const int kMaxRecordType = kLastType;
+
+static const int kBlockSize = 32768;
+
+// Header is checksum (4 bytes), length (2 bytes), type (1 byte).
+static const int kHeaderSize = 4 + 2 + 1;
+
+}  // namespace log
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_DB_LOG_FORMAT_H_
diff --git a/leveldb_base/db/log_reader.cc b/leveldb_base/db/log_reader.cc
new file mode 100644
index 0000000..9880279
--- /dev/null
+++ b/leveldb_base/db/log_reader.cc
@@ -0,0 +1,274 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "db/log_reader.h"
+
+#include <cstdio>
+
+#include "leveldb/env.h"
+#include "util/coding.h"
+#include "util/crc32c.h"
+
+namespace leveldb {
+namespace log {
+
+Reader::Reporter::~Reporter() = default;
+
+Reader::Reader(SequentialFile* file, Reporter* reporter, bool checksum,
+               uint64_t initial_offset)
+    : file_(file),
+      reporter_(reporter),
+      checksum_(checksum),
+      backing_store_(new char[kBlockSize]),
+      buffer_(),
+      eof_(false),
+      last_record_offset_(0),
+      end_of_buffer_offset_(0),
+      initial_offset_(initial_offset),
+      resyncing_(initial_offset > 0) {}
+
+Reader::~Reader() { delete[] backing_store_; }
+
+bool Reader::SkipToInitialBlock() {
+  const size_t offset_in_block = initial_offset_ % kBlockSize;
+  uint64_t block_start_location = initial_offset_ - offset_in_block;
+
+  // Don't search a block if we'd be in the trailer
+  if (offset_in_block > kBlockSize - 6) {
+    block_start_location += kBlockSize;
+  }
+
+  end_of_buffer_offset_ = block_start_location;
+
+  // Skip to start of first block that can contain the initial record
+  if (block_start_location > 0) {
+    Status skip_status = file_->Skip(block_start_location);
+    if (!skip_status.ok()) {
+      ReportDrop(block_start_location, skip_status);
+      return false;
+    }
+  }
+
+  return true;
+}
+
+bool Reader::ReadRecord(Slice* record, std::string* scratch) {
+  if (last_record_offset_ < initial_offset_) {
+    if (!SkipToInitialBlock()) {
+      return false;
+    }
+  }
+
+  scratch->clear();
+  record->clear();
+  bool in_fragmented_record = false;
+  // Record offset of the logical record that we're reading
+  // 0 is a dummy value to make compilers happy
+  uint64_t prospective_record_offset = 0;
+
+  Slice fragment;
+  while (true) {
+    const unsigned int record_type = ReadPhysicalRecord(&fragment);
+
+    // ReadPhysicalRecord may have only had an empty trailer remaining in its
+    // internal buffer. Calculate the offset of the next physical record now
+    // that it has returned, properly accounting for its header size.
+    uint64_t physical_record_offset =
+        end_of_buffer_offset_ - buffer_.size() - kHeaderSize - fragment.size();
+
+    if (resyncing_) {
+      if (record_type == kMiddleType) {
+        continue;
+      } else if (record_type == kLastType) {
+        resyncing_ = false;
+        continue;
+      } else {
+        resyncing_ = false;
+      }
+    }
+
+    switch (record_type) {
+      case kFullType:
+        if (in_fragmented_record) {
+          // Handle bug in earlier versions of log::Writer where
+          // it could emit an empty kFirstType record at the tail end
+          // of a block followed by a kFullType or kFirstType record
+          // at the beginning of the next block.
+          if (!scratch->empty()) {
+            ReportCorruption(scratch->size(), "partial record without end(1)");
+          }
+        }
+        prospective_record_offset = physical_record_offset;
+        scratch->clear();
+        *record = fragment;
+        last_record_offset_ = prospective_record_offset;
+        return true;
+
+      case kFirstType:
+        if (in_fragmented_record) {
+          // Handle bug in earlier versions of log::Writer where
+          // it could emit an empty kFirstType record at the tail end
+          // of a block followed by a kFullType or kFirstType record
+          // at the beginning of the next block.
+          if (!scratch->empty()) {
+            ReportCorruption(scratch->size(), "partial record without end(2)");
+          }
+        }
+        prospective_record_offset = physical_record_offset;
+        scratch->assign(fragment.data(), fragment.size());
+        in_fragmented_record = true;
+        break;
+
+      case kMiddleType:
+        if (!in_fragmented_record) {
+          ReportCorruption(fragment.size(),
+                           "missing start of fragmented record(1)");
+        } else {
+          scratch->append(fragment.data(), fragment.size());
+        }
+        break;
+
+      case kLastType:
+        if (!in_fragmented_record) {
+          ReportCorruption(fragment.size(),
+                           "missing start of fragmented record(2)");
+        } else {
+          scratch->append(fragment.data(), fragment.size());
+          *record = Slice(*scratch);
+          last_record_offset_ = prospective_record_offset;
+          return true;
+        }
+        break;
+
+      case kEof:
+        if (in_fragmented_record) {
+          // This can be caused by the writer dying immediately after
+          // writing a physical record but before completing the next; don't
+          // treat it as a corruption, just ignore the entire logical record.
+          scratch->clear();
+        }
+        return false;
+
+      case kBadRecord:
+        if (in_fragmented_record) {
+          ReportCorruption(scratch->size(), "error in middle of record");
+          in_fragmented_record = false;
+          scratch->clear();
+        }
+        break;
+
+      default: {
+        char buf[40];
+        std::snprintf(buf, sizeof(buf), "unknown record type %u", record_type);
+        ReportCorruption(
+            (fragment.size() + (in_fragmented_record ? scratch->size() : 0)),
+            buf);
+        in_fragmented_record = false;
+        scratch->clear();
+        break;
+      }
+    }
+  }
+  return false;
+}
+
+uint64_t Reader::LastRecordOffset() { return last_record_offset_; }
+
+void Reader::ReportCorruption(uint64_t bytes, const char* reason) {
+  ReportDrop(bytes, Status::Corruption(reason));
+}
+
+void Reader::ReportDrop(uint64_t bytes, const Status& reason) {
+  if (reporter_ != nullptr &&
+      end_of_buffer_offset_ - buffer_.size() - bytes >= initial_offset_) {
+    reporter_->Corruption(static_cast<size_t>(bytes), reason);
+  }
+}
+
+unsigned int Reader::ReadPhysicalRecord(Slice* result) {
+  while (true) {
+    if (buffer_.size() < kHeaderSize) {
+      if (!eof_) {
+        // Last read was a full read, so this is a trailer to skip
+        buffer_.clear();
+        Status status = file_->Read(kBlockSize, &buffer_, backing_store_);
+        end_of_buffer_offset_ += buffer_.size();
+        if (!status.ok()) {
+          buffer_.clear();
+          ReportDrop(kBlockSize, status);
+          eof_ = true;
+          return kEof;
+        } else if (buffer_.size() < kBlockSize) {
+          eof_ = true;
+        }
+        continue;
+      } else {
+        // Note that if buffer_ is non-empty, we have a truncated header at the
+        // end of the file, which can be caused by the writer crashing in the
+        // middle of writing the header. Instead of considering this an error,
+        // just report EOF.
+        buffer_.clear();
+        return kEof;
+      }
+    }
+
+    // Parse the header
+    const char* header = buffer_.data();
+    const uint32_t a = static_cast<uint32_t>(header[4]) & 0xff;
+    const uint32_t b = static_cast<uint32_t>(header[5]) & 0xff;
+    const unsigned int type = header[6];
+    const uint32_t length = a | (b << 8);
+    if (kHeaderSize + length > buffer_.size()) {
+      size_t drop_size = buffer_.size();
+      buffer_.clear();
+      if (!eof_) {
+        ReportCorruption(drop_size, "bad record length");
+        return kBadRecord;
+      }
+      // If the end of the file has been reached without reading |length| bytes
+      // of payload, assume the writer died in the middle of writing the record.
+      // Don't report a corruption.
+      return kEof;
+    }
+
+    if (type == kZeroType && length == 0) {
+      // Skip zero length record without reporting any drops since
+      // such records are produced by the mmap based writing code in
+      // env_posix.cc that preallocates file regions.
+      buffer_.clear();
+      return kBadRecord;
+    }
+
+    // Check crc
+    if (checksum_) {
+      uint32_t expected_crc = crc32c::Unmask(DecodeFixed32(header));
+      uint32_t actual_crc = crc32c::Value(header + 6, 1 + length);
+      if (actual_crc != expected_crc) {
+        // Drop the rest of the buffer since "length" itself may have
+        // been corrupted and if we trust it, we could find some
+        // fragment of a real log record that just happens to look
+        // like a valid log record.
+        size_t drop_size = buffer_.size();
+        buffer_.clear();
+        ReportCorruption(drop_size, "checksum mismatch");
+        return kBadRecord;
+      }
+    }
+
+    buffer_.remove_prefix(kHeaderSize + length);
+
+    // Skip physical record that started before initial_offset_
+    if (end_of_buffer_offset_ - buffer_.size() - kHeaderSize - length <
+        initial_offset_) {
+      result->clear();
+      return kBadRecord;
+    }
+
+    *result = Slice(header + kHeaderSize, length);
+    return type;
+  }
+}
+
+}  // namespace log
+}  // namespace leveldb
diff --git a/leveldb_base/db/log_reader.h b/leveldb_base/db/log_reader.h
new file mode 100644
index 0000000..ba711f8
--- /dev/null
+++ b/leveldb_base/db/log_reader.h
@@ -0,0 +1,112 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_DB_LOG_READER_H_
+#define STORAGE_LEVELDB_DB_LOG_READER_H_
+
+#include <cstdint>
+
+#include "db/log_format.h"
+#include "leveldb/slice.h"
+#include "leveldb/status.h"
+
+namespace leveldb {
+
+class SequentialFile;
+
+namespace log {
+
+class Reader {
+ public:
+  // Interface for reporting errors.
+  class Reporter {
+   public:
+    virtual ~Reporter();
+
+    // Some corruption was detected.  "bytes" is the approximate number
+    // of bytes dropped due to the corruption.
+    virtual void Corruption(size_t bytes, const Status& status) = 0;
+  };
+
+  // Create a reader that will return log records from "*file".
+  // "*file" must remain live while this Reader is in use.
+  //
+  // If "reporter" is non-null, it is notified whenever some data is
+  // dropped due to a detected corruption.  "*reporter" must remain
+  // live while this Reader is in use.
+  //
+  // If "checksum" is true, verify checksums if available.
+  //
+  // The Reader will start reading at the first record located at physical
+  // position >= initial_offset within the file.
+  Reader(SequentialFile* file, Reporter* reporter, bool checksum,
+         uint64_t initial_offset);
+
+  Reader(const Reader&) = delete;
+  Reader& operator=(const Reader&) = delete;
+
+  ~Reader();
+
+  // Read the next record into *record.  Returns true if read
+  // successfully, false if we hit end of the input.  May use
+  // "*scratch" as temporary storage.  The contents filled in *record
+  // will only be valid until the next mutating operation on this
+  // reader or the next mutation to *scratch.
+  bool ReadRecord(Slice* record, std::string* scratch);
+
+  // Returns the physical offset of the last record returned by ReadRecord.
+  //
+  // Undefined before the first call to ReadRecord.
+  uint64_t LastRecordOffset();
+
+ private:
+  // Extend record types with the following special values
+  enum {
+    kEof = kMaxRecordType + 1,
+    // Returned whenever we find an invalid physical record.
+    // Currently there are three situations in which this happens:
+    // * The record has an invalid CRC (ReadPhysicalRecord reports a drop)
+    // * The record is a 0-length record (No drop is reported)
+    // * The record is below constructor's initial_offset (No drop is reported)
+    kBadRecord = kMaxRecordType + 2
+  };
+
+  // Skips all blocks that are completely before "initial_offset_".
+  //
+  // Returns true on success. Handles reporting.
+  bool SkipToInitialBlock();
+
+  // Return type, or one of the preceding special values
+  unsigned int ReadPhysicalRecord(Slice* result);
+
+  // Reports dropped bytes to the reporter.
+  // buffer_ must be updated to remove the dropped bytes prior to invocation.
+  void ReportCorruption(uint64_t bytes, const char* reason);
+  void ReportDrop(uint64_t bytes, const Status& reason);
+
+  SequentialFile* const file_;
+  Reporter* const reporter_;
+  bool const checksum_;
+  char* const backing_store_;
+  Slice buffer_;
+  bool eof_;  // Last Read() indicated EOF by returning < kBlockSize
+
+  // Offset of the last record returned by ReadRecord.
+  uint64_t last_record_offset_;
+  // Offset of the first location past the end of buffer_.
+  uint64_t end_of_buffer_offset_;
+
+  // Offset at which to start looking for the first record to return
+  uint64_t const initial_offset_;
+
+  // True if we are resynchronizing after a seek (initial_offset_ > 0). In
+  // particular, a run of kMiddleType and kLastType records can be silently
+  // skipped in this mode
+  bool resyncing_;
+};
+
+}  // namespace log
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_DB_LOG_READER_H_
diff --git a/leveldb_base/db/log_test.cc b/leveldb_base/db/log_test.cc
new file mode 100644
index 0000000..d55d4dd
--- /dev/null
+++ b/leveldb_base/db/log_test.cc
@@ -0,0 +1,558 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "gtest/gtest.h"
+#include "db/log_reader.h"
+#include "db/log_writer.h"
+#include "leveldb/env.h"
+#include "util/coding.h"
+#include "util/crc32c.h"
+#include "util/random.h"
+
+namespace leveldb {
+namespace log {
+
+// Construct a string of the specified length made out of the supplied
+// partial string.
+static std::string BigString(const std::string& partial_string, size_t n) {
+  std::string result;
+  while (result.size() < n) {
+    result.append(partial_string);
+  }
+  result.resize(n);
+  return result;
+}
+
+// Construct a string from a number
+static std::string NumberString(int n) {
+  char buf[50];
+  std::snprintf(buf, sizeof(buf), "%d.", n);
+  return std::string(buf);
+}
+
+// Return a skewed potentially long string
+static std::string RandomSkewedString(int i, Random* rnd) {
+  return BigString(NumberString(i), rnd->Skewed(17));
+}
+
+class LogTest : public testing::Test {
+ public:
+  LogTest()
+      : reading_(false),
+        writer_(new Writer(&dest_)),
+        reader_(new Reader(&source_, &report_, true /*checksum*/,
+                           0 /*initial_offset*/)) {}
+
+  ~LogTest() {
+    delete writer_;
+    delete reader_;
+  }
+
+  void ReopenForAppend() {
+    delete writer_;
+    writer_ = new Writer(&dest_, dest_.contents_.size());
+  }
+
+  void Write(const std::string& msg) {
+    ASSERT_TRUE(!reading_) << "Write() after starting to read";
+    writer_->AddRecord(Slice(msg));
+  }
+
+  size_t WrittenBytes() const { return dest_.contents_.size(); }
+
+  std::string Read() {
+    if (!reading_) {
+      reading_ = true;
+      source_.contents_ = Slice(dest_.contents_);
+    }
+    std::string scratch;
+    Slice record;
+    if (reader_->ReadRecord(&record, &scratch)) {
+      return record.ToString();
+    } else {
+      return "EOF";
+    }
+  }
+
+  void IncrementByte(int offset, int delta) {
+    dest_.contents_[offset] += delta;
+  }
+
+  void SetByte(int offset, char new_byte) {
+    dest_.contents_[offset] = new_byte;
+  }
+
+  void ShrinkSize(int bytes) {
+    dest_.contents_.resize(dest_.contents_.size() - bytes);
+  }
+
+  void FixChecksum(int header_offset, int len) {
+    // Compute crc of type/len/data
+    uint32_t crc = crc32c::Value(&dest_.contents_[header_offset + 6], 1 + len);
+    crc = crc32c::Mask(crc);
+    EncodeFixed32(&dest_.contents_[header_offset], crc);
+  }
+
+  void ForceError() { source_.force_error_ = true; }
+
+  size_t DroppedBytes() const { return report_.dropped_bytes_; }
+
+  std::string ReportMessage() const { return report_.message_; }
+
+  // Returns OK iff recorded error message contains "msg"
+  std::string MatchError(const std::string& msg) const {
+    if (report_.message_.find(msg) == std::string::npos) {
+      return report_.message_;
+    } else {
+      return "OK";
+    }
+  }
+
+  void WriteInitialOffsetLog() {
+    for (int i = 0; i < num_initial_offset_records_; i++) {
+      std::string record(initial_offset_record_sizes_[i],
+                         static_cast<char>('a' + i));
+      Write(record);
+    }
+  }
+
+  void StartReadingAt(uint64_t initial_offset) {
+    delete reader_;
+    reader_ = new Reader(&source_, &report_, true /*checksum*/, initial_offset);
+  }
+
+  void CheckOffsetPastEndReturnsNoRecords(uint64_t offset_past_end) {
+    WriteInitialOffsetLog();
+    reading_ = true;
+    source_.contents_ = Slice(dest_.contents_);
+    Reader* offset_reader = new Reader(&source_, &report_, true /*checksum*/,
+                                       WrittenBytes() + offset_past_end);
+    Slice record;
+    std::string scratch;
+    ASSERT_TRUE(!offset_reader->ReadRecord(&record, &scratch));
+    delete offset_reader;
+  }
+
+  void CheckInitialOffsetRecord(uint64_t initial_offset,
+                                int expected_record_offset) {
+    WriteInitialOffsetLog();
+    reading_ = true;
+    source_.contents_ = Slice(dest_.contents_);
+    Reader* offset_reader =
+        new Reader(&source_, &report_, true /*checksum*/, initial_offset);
+
+    // Read all records from expected_record_offset through the last one.
+    ASSERT_LT(expected_record_offset, num_initial_offset_records_);
+    for (; expected_record_offset < num_initial_offset_records_;
+         ++expected_record_offset) {
+      Slice record;
+      std::string scratch;
+      ASSERT_TRUE(offset_reader->ReadRecord(&record, &scratch));
+      ASSERT_EQ(initial_offset_record_sizes_[expected_record_offset],
+                record.size());
+      ASSERT_EQ(initial_offset_last_record_offsets_[expected_record_offset],
+                offset_reader->LastRecordOffset());
+      ASSERT_EQ((char)('a' + expected_record_offset), record.data()[0]);
+    }
+    delete offset_reader;
+  }
+
+ private:
+  class StringDest : public WritableFile {
+   public:
+    Status Close() override { return Status::OK(); }
+    Status Flush() override { return Status::OK(); }
+    Status Sync() override { return Status::OK(); }
+    Status Append(const Slice& slice) override {
+      contents_.append(slice.data(), slice.size());
+      return Status::OK();
+    }
+
+    std::string contents_;
+  };
+
+  class StringSource : public SequentialFile {
+   public:
+    StringSource() : force_error_(false), returned_partial_(false) {}
+
+    Status Read(size_t n, Slice* result, char* scratch) override {
+      EXPECT_TRUE(!returned_partial_) << "must not Read() after eof/error";
+
+      if (force_error_) {
+        force_error_ = false;
+        returned_partial_ = true;
+        return Status::Corruption("read error");
+      }
+
+      if (contents_.size() < n) {
+        n = contents_.size();
+        returned_partial_ = true;
+      }
+      *result = Slice(contents_.data(), n);
+      contents_.remove_prefix(n);
+      return Status::OK();
+    }
+
+    Status Skip(uint64_t n) override {
+      if (n > contents_.size()) {
+        contents_.clear();
+        return Status::NotFound("in-memory file skipped past end");
+      }
+
+      contents_.remove_prefix(n);
+
+      return Status::OK();
+    }
+
+    Slice contents_;
+    bool force_error_;
+    bool returned_partial_;
+  };
+
+  class ReportCollector : public Reader::Reporter {
+   public:
+    ReportCollector() : dropped_bytes_(0) {}
+    void Corruption(size_t bytes, const Status& status) override {
+      dropped_bytes_ += bytes;
+      message_.append(status.ToString());
+    }
+
+    size_t dropped_bytes_;
+    std::string message_;
+  };
+
+  // Record metadata for testing initial offset functionality
+  static size_t initial_offset_record_sizes_[];
+  static uint64_t initial_offset_last_record_offsets_[];
+  static int num_initial_offset_records_;
+
+  StringDest dest_;
+  StringSource source_;
+  ReportCollector report_;
+  bool reading_;
+  Writer* writer_;
+  Reader* reader_;
+};
+
+size_t LogTest::initial_offset_record_sizes_[] = {
+    10000,  // Two sizable records in first block
+    10000,
+    2 * log::kBlockSize - 1000,  // Span three blocks
+    1,
+    13716,                          // Consume all but two bytes of block 3.
+    log::kBlockSize - kHeaderSize,  // Consume the entirety of block 4.
+};
+
+uint64_t LogTest::initial_offset_last_record_offsets_[] = {
+    0,
+    kHeaderSize + 10000,
+    2 * (kHeaderSize + 10000),
+    2 * (kHeaderSize + 10000) + (2 * log::kBlockSize - 1000) + 3 * kHeaderSize,
+    2 * (kHeaderSize + 10000) + (2 * log::kBlockSize - 1000) + 3 * kHeaderSize +
+        kHeaderSize + 1,
+    3 * log::kBlockSize,
+};
+
+// LogTest::initial_offset_last_record_offsets_ must be defined before this.
+int LogTest::num_initial_offset_records_ =
+    sizeof(LogTest::initial_offset_last_record_offsets_) / sizeof(uint64_t);
+
+TEST_F(LogTest, Empty) { ASSERT_EQ("EOF", Read()); }
+
+TEST_F(LogTest, ReadWrite) {
+  Write("foo");
+  Write("bar");
+  Write("");
+  Write("xxxx");
+  ASSERT_EQ("foo", Read());
+  ASSERT_EQ("bar", Read());
+  ASSERT_EQ("", Read());
+  ASSERT_EQ("xxxx", Read());
+  ASSERT_EQ("EOF", Read());
+  ASSERT_EQ("EOF", Read());  // Make sure reads at eof work
+}
+
+TEST_F(LogTest, ManyBlocks) {
+  for (int i = 0; i < 100000; i++) {
+    Write(NumberString(i));
+  }
+  for (int i = 0; i < 100000; i++) {
+    ASSERT_EQ(NumberString(i), Read());
+  }
+  ASSERT_EQ("EOF", Read());
+}
+
+TEST_F(LogTest, Fragmentation) {
+  Write("small");
+  Write(BigString("medium", 50000));
+  Write(BigString("large", 100000));
+  ASSERT_EQ("small", Read());
+  ASSERT_EQ(BigString("medium", 50000), Read());
+  ASSERT_EQ(BigString("large", 100000), Read());
+  ASSERT_EQ("EOF", Read());
+}
+
+TEST_F(LogTest, MarginalTrailer) {
+  // Make a trailer that is exactly the same length as an empty record.
+  const int n = kBlockSize - 2 * kHeaderSize;
+  Write(BigString("foo", n));
+  ASSERT_EQ(kBlockSize - kHeaderSize, WrittenBytes());
+  Write("");
+  Write("bar");
+  ASSERT_EQ(BigString("foo", n), Read());
+  ASSERT_EQ("", Read());
+  ASSERT_EQ("bar", Read());
+  ASSERT_EQ("EOF", Read());
+}
+
+TEST_F(LogTest, MarginalTrailer2) {
+  // Make a trailer that is exactly the same length as an empty record.
+  const int n = kBlockSize - 2 * kHeaderSize;
+  Write(BigString("foo", n));
+  ASSERT_EQ(kBlockSize - kHeaderSize, WrittenBytes());
+  Write("bar");
+  ASSERT_EQ(BigString("foo", n), Read());
+  ASSERT_EQ("bar", Read());
+  ASSERT_EQ("EOF", Read());
+  ASSERT_EQ(0, DroppedBytes());
+  ASSERT_EQ("", ReportMessage());
+}
+
+TEST_F(LogTest, ShortTrailer) {
+  const int n = kBlockSize - 2 * kHeaderSize + 4;
+  Write(BigString("foo", n));
+  ASSERT_EQ(kBlockSize - kHeaderSize + 4, WrittenBytes());
+  Write("");
+  Write("bar");
+  ASSERT_EQ(BigString("foo", n), Read());
+  ASSERT_EQ("", Read());
+  ASSERT_EQ("bar", Read());
+  ASSERT_EQ("EOF", Read());
+}
+
+TEST_F(LogTest, AlignedEof) {
+  const int n = kBlockSize - 2 * kHeaderSize + 4;
+  Write(BigString("foo", n));
+  ASSERT_EQ(kBlockSize - kHeaderSize + 4, WrittenBytes());
+  ASSERT_EQ(BigString("foo", n), Read());
+  ASSERT_EQ("EOF", Read());
+}
+
+TEST_F(LogTest, OpenForAppend) {
+  Write("hello");
+  ReopenForAppend();
+  Write("world");
+  ASSERT_EQ("hello", Read());
+  ASSERT_EQ("world", Read());
+  ASSERT_EQ("EOF", Read());
+}
+
+TEST_F(LogTest, RandomRead) {
+  const int N = 500;
+  Random write_rnd(301);
+  for (int i = 0; i < N; i++) {
+    Write(RandomSkewedString(i, &write_rnd));
+  }
+  Random read_rnd(301);
+  for (int i = 0; i < N; i++) {
+    ASSERT_EQ(RandomSkewedString(i, &read_rnd), Read());
+  }
+  ASSERT_EQ("EOF", Read());
+}
+
+// Tests of all the error paths in log_reader.cc follow:
+
+TEST_F(LogTest, ReadError) {
+  Write("foo");
+  ForceError();
+  ASSERT_EQ("EOF", Read());
+  ASSERT_EQ(kBlockSize, DroppedBytes());
+  ASSERT_EQ("OK", MatchError("read error"));
+}
+
+TEST_F(LogTest, BadRecordType) {
+  Write("foo");
+  // Type is stored in header[6]
+  IncrementByte(6, 100);
+  FixChecksum(0, 3);
+  ASSERT_EQ("EOF", Read());
+  ASSERT_EQ(3, DroppedBytes());
+  ASSERT_EQ("OK", MatchError("unknown record type"));
+}
+
+TEST_F(LogTest, TruncatedTrailingRecordIsIgnored) {
+  Write("foo");
+  ShrinkSize(4);  // Drop all payload as well as a header byte
+  ASSERT_EQ("EOF", Read());
+  // Truncated last record is ignored, not treated as an error.
+  ASSERT_EQ(0, DroppedBytes());
+  ASSERT_EQ("", ReportMessage());
+}
+
+TEST_F(LogTest, BadLength) {
+  const int kPayloadSize = kBlockSize - kHeaderSize;
+  Write(BigString("bar", kPayloadSize));
+  Write("foo");
+  // Least significant size byte is stored in header[4].
+  IncrementByte(4, 1);
+  ASSERT_EQ("foo", Read());
+  ASSERT_EQ(kBlockSize, DroppedBytes());
+  ASSERT_EQ("OK", MatchError("bad record length"));
+}
+
+TEST_F(LogTest, BadLengthAtEndIsIgnored) {
+  Write("foo");
+  ShrinkSize(1);
+  ASSERT_EQ("EOF", Read());
+  ASSERT_EQ(0, DroppedBytes());
+  ASSERT_EQ("", ReportMessage());
+}
+
+TEST_F(LogTest, ChecksumMismatch) {
+  Write("foo");
+  IncrementByte(0, 10);
+  ASSERT_EQ("EOF", Read());
+  ASSERT_EQ(10, DroppedBytes());
+  ASSERT_EQ("OK", MatchError("checksum mismatch"));
+}
+
+TEST_F(LogTest, UnexpectedMiddleType) {
+  Write("foo");
+  SetByte(6, kMiddleType);
+  FixChecksum(0, 3);
+  ASSERT_EQ("EOF", Read());
+  ASSERT_EQ(3, DroppedBytes());
+  ASSERT_EQ("OK", MatchError("missing start"));
+}
+
+TEST_F(LogTest, UnexpectedLastType) {
+  Write("foo");
+  SetByte(6, kLastType);
+  FixChecksum(0, 3);
+  ASSERT_EQ("EOF", Read());
+  ASSERT_EQ(3, DroppedBytes());
+  ASSERT_EQ("OK", MatchError("missing start"));
+}
+
+TEST_F(LogTest, UnexpectedFullType) {
+  Write("foo");
+  Write("bar");
+  SetByte(6, kFirstType);
+  FixChecksum(0, 3);
+  ASSERT_EQ("bar", Read());
+  ASSERT_EQ("EOF", Read());
+  ASSERT_EQ(3, DroppedBytes());
+  ASSERT_EQ("OK", MatchError("partial record without end"));
+}
+
+TEST_F(LogTest, UnexpectedFirstType) {
+  Write("foo");
+  Write(BigString("bar", 100000));
+  SetByte(6, kFirstType);
+  FixChecksum(0, 3);
+  ASSERT_EQ(BigString("bar", 100000), Read());
+  ASSERT_EQ("EOF", Read());
+  ASSERT_EQ(3, DroppedBytes());
+  ASSERT_EQ("OK", MatchError("partial record without end"));
+}
+
+TEST_F(LogTest, MissingLastIsIgnored) {
+  Write(BigString("bar", kBlockSize));
+  // Remove the LAST block, including header.
+  ShrinkSize(14);
+  ASSERT_EQ("EOF", Read());
+  ASSERT_EQ("", ReportMessage());
+  ASSERT_EQ(0, DroppedBytes());
+}
+
+TEST_F(LogTest, PartialLastIsIgnored) {
+  Write(BigString("bar", kBlockSize));
+  // Cause a bad record length in the LAST block.
+  ShrinkSize(1);
+  ASSERT_EQ("EOF", Read());
+  ASSERT_EQ("", ReportMessage());
+  ASSERT_EQ(0, DroppedBytes());
+}
+
+TEST_F(LogTest, SkipIntoMultiRecord) {
+  // Consider a fragmented record:
+  //    first(R1), middle(R1), last(R1), first(R2)
+  // If initial_offset points to a record after first(R1) but before first(R2)
+  // incomplete fragment errors are not actual errors, and must be suppressed
+  // until a new first or full record is encountered.
+  Write(BigString("foo", 3 * kBlockSize));
+  Write("correct");
+  StartReadingAt(kBlockSize);
+
+  ASSERT_EQ("correct", Read());
+  ASSERT_EQ("", ReportMessage());
+  ASSERT_EQ(0, DroppedBytes());
+  ASSERT_EQ("EOF", Read());
+}
+
+TEST_F(LogTest, ErrorJoinsRecords) {
+  // Consider two fragmented records:
+  //    first(R1) last(R1) first(R2) last(R2)
+  // where the middle two fragments disappear.  We do not want
+  // first(R1),last(R2) to get joined and returned as a valid record.
+
+  // Write records that span two blocks
+  Write(BigString("foo", kBlockSize));
+  Write(BigString("bar", kBlockSize));
+  Write("correct");
+
+  // Wipe the middle block
+  for (int offset = kBlockSize; offset < 2 * kBlockSize; offset++) {
+    SetByte(offset, 'x');
+  }
+
+  ASSERT_EQ("correct", Read());
+  ASSERT_EQ("EOF", Read());
+  const size_t dropped = DroppedBytes();
+  ASSERT_LE(dropped, 2 * kBlockSize + 100);
+  ASSERT_GE(dropped, 2 * kBlockSize);
+}
+
+TEST_F(LogTest, ReadStart) { CheckInitialOffsetRecord(0, 0); }
+
+TEST_F(LogTest, ReadSecondOneOff) { CheckInitialOffsetRecord(1, 1); }
+
+TEST_F(LogTest, ReadSecondTenThousand) { CheckInitialOffsetRecord(10000, 1); }
+
+TEST_F(LogTest, ReadSecondStart) { CheckInitialOffsetRecord(10007, 1); }
+
+TEST_F(LogTest, ReadThirdOneOff) { CheckInitialOffsetRecord(10008, 2); }
+
+TEST_F(LogTest, ReadThirdStart) { CheckInitialOffsetRecord(20014, 2); }
+
+TEST_F(LogTest, ReadFourthOneOff) { CheckInitialOffsetRecord(20015, 3); }
+
+TEST_F(LogTest, ReadFourthFirstBlockTrailer) {
+  CheckInitialOffsetRecord(log::kBlockSize - 4, 3);
+}
+
+TEST_F(LogTest, ReadFourthMiddleBlock) {
+  CheckInitialOffsetRecord(log::kBlockSize + 1, 3);
+}
+
+TEST_F(LogTest, ReadFourthLastBlock) {
+  CheckInitialOffsetRecord(2 * log::kBlockSize + 1, 3);
+}
+
+TEST_F(LogTest, ReadFourthStart) {
+  CheckInitialOffsetRecord(
+      2 * (kHeaderSize + 1000) + (2 * log::kBlockSize - 1000) + 3 * kHeaderSize,
+      3);
+}
+
+TEST_F(LogTest, ReadInitialOffsetIntoBlockPadding) {
+  CheckInitialOffsetRecord(3 * log::kBlockSize - 3, 5);
+}
+
+TEST_F(LogTest, ReadEnd) { CheckOffsetPastEndReturnsNoRecords(0); }
+
+TEST_F(LogTest, ReadPastEnd) { CheckOffsetPastEndReturnsNoRecords(5); }
+
+}  // namespace log
+}  // namespace leveldb
diff --git a/leveldb_base/db/log_writer.cc b/leveldb_base/db/log_writer.cc
new file mode 100644
index 0000000..ad66bfb
--- /dev/null
+++ b/leveldb_base/db/log_writer.cc
@@ -0,0 +1,111 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "db/log_writer.h"
+
+#include <cstdint>
+
+#include "leveldb/env.h"
+#include "util/coding.h"
+#include "util/crc32c.h"
+
+namespace leveldb {
+namespace log {
+
+static void InitTypeCrc(uint32_t* type_crc) {
+  for (int i = 0; i <= kMaxRecordType; i++) {
+    char t = static_cast<char>(i);
+    type_crc[i] = crc32c::Value(&t, 1);
+  }
+}
+
+Writer::Writer(WritableFile* dest) : dest_(dest), block_offset_(0) {
+  InitTypeCrc(type_crc_);
+}
+
+Writer::Writer(WritableFile* dest, uint64_t dest_length)
+    : dest_(dest), block_offset_(dest_length % kBlockSize) {
+  InitTypeCrc(type_crc_);
+}
+
+Writer::~Writer() = default;
+
+Status Writer::AddRecord(const Slice& slice) {
+  const char* ptr = slice.data();
+  size_t left = slice.size();
+
+  // Fragment the record if necessary and emit it.  Note that if slice
+  // is empty, we still want to iterate once to emit a single
+  // zero-length record
+  Status s;
+  bool begin = true;
+  do {
+    const int leftover = kBlockSize - block_offset_;
+    assert(leftover >= 0);
+    if (leftover < kHeaderSize) {
+      // Switch to a new block
+      if (leftover > 0) {
+        // Fill the trailer (literal below relies on kHeaderSize being 7)
+        static_assert(kHeaderSize == 7, "");
+        dest_->Append(Slice("\x00\x00\x00\x00\x00\x00", leftover));
+      }
+      block_offset_ = 0;
+    }
+
+    // Invariant: we never leave < kHeaderSize bytes in a block.
+    assert(kBlockSize - block_offset_ - kHeaderSize >= 0);
+
+    const size_t avail = kBlockSize - block_offset_ - kHeaderSize;
+    const size_t fragment_length = (left < avail) ? left : avail;
+
+    RecordType type;
+    const bool end = (left == fragment_length);
+    if (begin && end) {
+      type = kFullType;
+    } else if (begin) {
+      type = kFirstType;
+    } else if (end) {
+      type = kLastType;
+    } else {
+      type = kMiddleType;
+    }
+
+    s = EmitPhysicalRecord(type, ptr, fragment_length);
+    ptr += fragment_length;
+    left -= fragment_length;
+    begin = false;
+  } while (s.ok() && left > 0);
+  return s;
+}
+
+Status Writer::EmitPhysicalRecord(RecordType t, const char* ptr,
+                                  size_t length) {
+  assert(length <= 0xffff);  // Must fit in two bytes
+  assert(block_offset_ + kHeaderSize + length <= kBlockSize);
+
+  // Format the header
+  char buf[kHeaderSize];
+  buf[4] = static_cast<char>(length & 0xff);
+  buf[5] = static_cast<char>(length >> 8);
+  buf[6] = static_cast<char>(t);
+
+  // Compute the crc of the record type and the payload.
+  uint32_t crc = crc32c::Extend(type_crc_[t], ptr, length);
+  crc = crc32c::Mask(crc);  // Adjust for storage
+  EncodeFixed32(buf, crc);
+
+  // Write the header and the payload
+  Status s = dest_->Append(Slice(buf, kHeaderSize));
+  if (s.ok()) {
+    s = dest_->Append(Slice(ptr, length));
+    if (s.ok()) {
+      s = dest_->Flush();
+    }
+  }
+  block_offset_ += kHeaderSize + length;
+  return s;
+}
+
+}  // namespace log
+}  // namespace leveldb
diff --git a/leveldb_base/db/log_writer.h b/leveldb_base/db/log_writer.h
new file mode 100644
index 0000000..ad36794
--- /dev/null
+++ b/leveldb_base/db/log_writer.h
@@ -0,0 +1,54 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_DB_LOG_WRITER_H_
+#define STORAGE_LEVELDB_DB_LOG_WRITER_H_
+
+#include <cstdint>
+
+#include "db/log_format.h"
+#include "leveldb/slice.h"
+#include "leveldb/status.h"
+
+namespace leveldb {
+
+class WritableFile;
+
+namespace log {
+
+class Writer {
+ public:
+  // Create a writer that will append data to "*dest".
+  // "*dest" must be initially empty.
+  // "*dest" must remain live while this Writer is in use.
+  explicit Writer(WritableFile* dest);
+
+  // Create a writer that will append data to "*dest".
+  // "*dest" must have initial length "dest_length".
+  // "*dest" must remain live while this Writer is in use.
+  Writer(WritableFile* dest, uint64_t dest_length);
+
+  Writer(const Writer&) = delete;
+  Writer& operator=(const Writer&) = delete;
+
+  ~Writer();
+
+  Status AddRecord(const Slice& slice);
+
+ private:
+  Status EmitPhysicalRecord(RecordType type, const char* ptr, size_t length);
+
+  WritableFile* dest_;
+  int block_offset_;  // Current offset in block
+
+  // crc32c values for all supported record types.  These are
+  // pre-computed to reduce the overhead of computing the crc of the
+  // record type stored in the header.
+  uint32_t type_crc_[kMaxRecordType + 1];
+};
+
+}  // namespace log
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_DB_LOG_WRITER_H_
diff --git a/leveldb_base/db/memtable.cc b/leveldb_base/db/memtable.cc
new file mode 100644
index 0000000..b9bfb34
--- /dev/null
+++ b/leveldb_base/db/memtable.cc
@@ -0,0 +1,172 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "db/memtable.h"
+#include "db/dbformat.h"
+#include "leveldb/comparator.h"
+#include "leveldb/env.h"
+#include "leveldb/iterator.h"
+#include "util/coding.h"
+
+// 添加所需头文件-柠
+#include <iostream>
+#include <sstream> 
+#include <iomanip>
+#include <ctime>  
+#include <chrono> 
+
+namespace leveldb {
+
+static Slice GetLengthPrefixedSlice(const char* data) {
+  uint32_t len;
+  const char* p = data;
+  p = GetVarint32Ptr(p, p + 5, &len);  // +5: we assume "p" is not corrupted
+  return Slice(p, len);
+}
+
+MemTable::MemTable(const InternalKeyComparator& comparator)
+    : comparator_(comparator), refs_(0), table_(comparator_, &arena_) {}
+
+MemTable::~MemTable() { assert(refs_ == 0); }
+
+size_t MemTable::ApproximateMemoryUsage() { return arena_.MemoryUsage(); }
+
+int MemTable::KeyComparator::operator()(const char* aptr,
+                                        const char* bptr) const {
+  // Internal keys are encoded as length-prefixed strings.
+  Slice a = GetLengthPrefixedSlice(aptr);
+  Slice b = GetLengthPrefixedSlice(bptr);
+  return comparator.Compare(a, b);
+}
+
+// Encode a suitable internal key target for "target" and return it.
+// Uses *scratch as scratch space, and the returned pointer will point
+// into this scratch space.
+static const char* EncodeKey(std::string* scratch, const Slice& target) {
+  scratch->clear();
+  PutVarint32(scratch, target.size());
+  scratch->append(target.data(), target.size());
+  return scratch->data();
+}
+
+class MemTableIterator : public Iterator {
+ public:
+  explicit MemTableIterator(MemTable::Table* table) : iter_(table) {}
+
+  MemTableIterator(const MemTableIterator&) = delete;
+  MemTableIterator& operator=(const MemTableIterator&) = delete;
+
+  ~MemTableIterator() override = default;
+
+  bool Valid() const override { return iter_.Valid(); }
+  void Seek(const Slice& k) override { iter_.Seek(EncodeKey(&tmp_, k)); }
+  void SeekToFirst() override { iter_.SeekToFirst(); }
+  void SeekToLast() override { iter_.SeekToLast(); }
+  void Next() override { iter_.Next(); }
+  void Prev() override { iter_.Prev(); }
+  Slice key() const override { return GetLengthPrefixedSlice(iter_.key()); }
+  Slice value() const override {
+    Slice key_slice = GetLengthPrefixedSlice(iter_.key());
+    return GetLengthPrefixedSlice(key_slice.data() + key_slice.size());
+  }
+
+  Status status() const override { return Status::OK(); }
+
+ private:
+  MemTable::Table::Iterator iter_;
+  std::string tmp_;  // For passing to EncodeKey
+};
+
+Iterator* MemTable::NewIterator() { return new MemTableIterator(&table_); }
+
+void MemTable::Add(SequenceNumber s, ValueType type, const Slice& key,
+                   const Slice& value) {
+  // Format of an entry is concatenation of:
+  //  key_size     : varint32 of internal_key.size()
+  //  key bytes    : char[internal_key.size()]
+  //  tag          : uint64((sequence << 8) | type)
+  //  value_size   : varint32 of value.size()
+  //  value bytes  : char[value.size()]
+  size_t key_size = key.size();
+  size_t val_size = value.size();
+  size_t internal_key_size = key_size + 8;
+  const size_t encoded_len = VarintLength(internal_key_size) +
+                             internal_key_size + VarintLength(val_size) +
+                             val_size;
+  char* buf = arena_.Allocate(encoded_len);
+  char* p = EncodeVarint32(buf, internal_key_size);
+  std::memcpy(p, key.data(), key_size);
+  p += key_size;
+  EncodeFixed64(p, (s << 8) | type);
+  p += 8;
+  p = EncodeVarint32(p, val_size);
+  std::memcpy(p, value.data(), val_size);
+  assert(p + val_size == buf + encoded_len);
+  table_.Insert(buf);
+}
+
+bool MemTable::Get(const LookupKey& key, std::string* value, Status* s) {
+  Slice memkey = key.memtable_key();
+  Table::Iterator iter(&table_);
+  iter.Seek(memkey.data());
+  if (iter.Valid()) {
+    // entry format is:
+    //    klength  varint32
+    //    userkey  char[klength]
+    //    tag      uint64
+    //    vlength  varint32
+    //    value    char[vlength]
+    // Check that it belongs to same user key.  We do not check the
+    // sequence number since the Seek() call above should have skipped
+    // all entries with overly large sequence numbers.
+    const char* entry = iter.key();
+    uint32_t key_length;
+    const char* key_ptr = GetVarint32Ptr(entry, entry + 5, &key_length);
+    if (comparator_.comparator.user_comparator()->Compare(
+            Slice(key_ptr, key_length - 8), key.user_key()) == 0) {
+      // Correct user key
+      const uint64_t tag = DecodeFixed64(key_ptr + key_length - 8);
+      switch (static_cast<ValueType>(tag & 0xff)) {
+        case kTypeValue: {
+          Slice v = GetLengthPrefixedSlice(key_ptr + key_length);
+          // 过期则读取不到-柠
+          std::string value_with_ttl(v.data(), v.size());
+          if (value_with_ttl.size() >= 19) {
+            std::string expiration_time_str = value_with_ttl.substr(value_with_ttl.size() - 19); // 提取过期时间戳
+            std::tm tm = {};
+            char* res = strptime(expiration_time_str.c_str(), "%Y-%m-%d %H:%M:%S", &tm);
+            if (res == nullptr) {
+              value->assign(v.data(), v.size()-19);
+              return true;
+            } else {
+              std::time_t expiration_time = std::mktime(&tm);
+              std::time_t current_time = std::chrono::system_clock::to_time_t(std::chrono::system_clock::now());
+              if (expiration_time <= current_time) {
+                //std::cerr << "notfound_mem" << std::endl;
+                *s = Status::NotFound(Slice());
+                value->assign(v.data(), 0);
+              }
+              else
+              {
+                value->assign(v.data(), v.size()-19);
+              }
+              return true;
+            }
+          } else {
+            value->assign(v.data(), v.size());
+            return true;
+          }
+        value->assign(v.data(), v.size());
+        return true;
+        }
+        case kTypeDeletion:
+          *s = Status::NotFound(Slice());
+          return true;
+      }
+    }
+  }
+  return false;
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/db/memtable.h b/leveldb_base/db/memtable.h
new file mode 100644
index 0000000..9d986b1
--- /dev/null
+++ b/leveldb_base/db/memtable.h
@@ -0,0 +1,87 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_DB_MEMTABLE_H_
+#define STORAGE_LEVELDB_DB_MEMTABLE_H_
+
+#include <string>
+
+#include "db/dbformat.h"
+#include "db/skiplist.h"
+#include "leveldb/db.h"
+#include "util/arena.h"
+
+namespace leveldb {
+
+class InternalKeyComparator;
+class MemTableIterator;
+
+class MemTable {
+ public:
+  // MemTables are reference counted.  The initial reference count
+  // is zero and the caller must call Ref() at least once.
+  explicit MemTable(const InternalKeyComparator& comparator);
+
+  MemTable(const MemTable&) = delete;
+  MemTable& operator=(const MemTable&) = delete;
+
+  // Increase reference count.
+  void Ref() { ++refs_; }
+
+  // Drop reference count.  Delete if no more references exist.
+  void Unref() {
+    --refs_;
+    assert(refs_ >= 0);
+    if (refs_ <= 0) {
+      delete this;
+    }
+  }
+
+  // Returns an estimate of the number of bytes of data in use by this
+  // data structure. It is safe to call when MemTable is being modified.
+  size_t ApproximateMemoryUsage();
+
+  // Return an iterator that yields the contents of the memtable.
+  //
+  // The caller must ensure that the underlying MemTable remains live
+  // while the returned iterator is live.  The keys returned by this
+  // iterator are internal keys encoded by AppendInternalKey in the
+  // db/format.{h,cc} module.
+  Iterator* NewIterator();
+
+  // Add an entry into memtable that maps key to value at the
+  // specified sequence number and with the specified type.
+  // Typically value will be empty if type==kTypeDeletion.
+  void Add(SequenceNumber seq, ValueType type, const Slice& key,
+           const Slice& value);
+
+  // If memtable contains a value for key, store it in *value and return true.
+  // If memtable contains a deletion for key, store a NotFound() error
+  // in *status and return true.
+  // Else, return false.
+  bool Get(const LookupKey& key, std::string* value, Status* s);
+
+ private:
+  friend class MemTableIterator;
+  friend class MemTableBackwardIterator;
+
+  struct KeyComparator {
+    const InternalKeyComparator comparator;
+    explicit KeyComparator(const InternalKeyComparator& c) : comparator(c) {}
+    int operator()(const char* a, const char* b) const;
+  };
+
+  typedef SkipList<const char*, KeyComparator> Table;
+
+  ~MemTable();  // Private since only Unref() should be used to delete it
+
+  KeyComparator comparator_;
+  int refs_;
+  Arena arena_;
+  Table table_;
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_DB_MEMTABLE_H_
diff --git a/leveldb_base/db/recovery_test.cc b/leveldb_base/db/recovery_test.cc
new file mode 100644
index 0000000..8dc039a
--- /dev/null
+++ b/leveldb_base/db/recovery_test.cc
@@ -0,0 +1,339 @@
+// Copyright (c) 2014 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "gtest/gtest.h"
+#include "db/db_impl.h"
+#include "db/filename.h"
+#include "db/version_set.h"
+#include "db/write_batch_internal.h"
+#include "leveldb/db.h"
+#include "leveldb/env.h"
+#include "leveldb/write_batch.h"
+#include "util/logging.h"
+#include "util/testutil.h"
+
+namespace leveldb {
+
+class RecoveryTest : public testing::Test {
+ public:
+  RecoveryTest() : env_(Env::Default()), db_(nullptr) {
+    dbname_ = testing::TempDir() + "recovery_test";
+    DestroyDB(dbname_, Options());
+    Open();
+  }
+
+  ~RecoveryTest() {
+    Close();
+    DestroyDB(dbname_, Options());
+  }
+
+  DBImpl* dbfull() const { return reinterpret_cast<DBImpl*>(db_); }
+  Env* env() const { return env_; }
+
+  bool CanAppend() {
+    WritableFile* tmp;
+    Status s = env_->NewAppendableFile(CurrentFileName(dbname_), &tmp);
+    delete tmp;
+    if (s.IsNotSupportedError()) {
+      return false;
+    } else {
+      return true;
+    }
+  }
+
+  void Close() {
+    delete db_;
+    db_ = nullptr;
+  }
+
+  Status OpenWithStatus(Options* options = nullptr) {
+    Close();
+    Options opts;
+    if (options != nullptr) {
+      opts = *options;
+    } else {
+      opts.reuse_logs = true;  // TODO(sanjay): test both ways
+      opts.create_if_missing = true;
+    }
+    if (opts.env == nullptr) {
+      opts.env = env_;
+    }
+    return DB::Open(opts, dbname_, &db_);
+  }
+
+  void Open(Options* options = nullptr) {
+    ASSERT_LEVELDB_OK(OpenWithStatus(options));
+    ASSERT_EQ(1, NumLogs());
+  }
+
+  Status Put(const std::string& k, const std::string& v) {
+    return db_->Put(WriteOptions(), k, v);
+  }
+
+  std::string Get(const std::string& k, const Snapshot* snapshot = nullptr) {
+    std::string result;
+    Status s = db_->Get(ReadOptions(), k, &result);
+    if (s.IsNotFound()) {
+      result = "NOT_FOUND";
+    } else if (!s.ok()) {
+      result = s.ToString();
+    }
+    return result;
+  }
+
+  std::string ManifestFileName() {
+    std::string current;
+    EXPECT_LEVELDB_OK(
+        ReadFileToString(env_, CurrentFileName(dbname_), &current));
+    size_t len = current.size();
+    if (len > 0 && current[len - 1] == '\n') {
+      current.resize(len - 1);
+    }
+    return dbname_ + "/" + current;
+  }
+
+  std::string LogName(uint64_t number) { return LogFileName(dbname_, number); }
+
+  size_t RemoveLogFiles() {
+    // Linux allows unlinking open files, but Windows does not.
+    // Closing the db allows for file deletion.
+    Close();
+    std::vector<uint64_t> logs = GetFiles(kLogFile);
+    for (size_t i = 0; i < logs.size(); i++) {
+      EXPECT_LEVELDB_OK(env_->RemoveFile(LogName(logs[i]))) << LogName(logs[i]);
+    }
+    return logs.size();
+  }
+
+  void RemoveManifestFile() {
+    ASSERT_LEVELDB_OK(env_->RemoveFile(ManifestFileName()));
+  }
+
+  uint64_t FirstLogFile() { return GetFiles(kLogFile)[0]; }
+
+  std::vector<uint64_t> GetFiles(FileType t) {
+    std::vector<std::string> filenames;
+    EXPECT_LEVELDB_OK(env_->GetChildren(dbname_, &filenames));
+    std::vector<uint64_t> result;
+    for (size_t i = 0; i < filenames.size(); i++) {
+      uint64_t number;
+      FileType type;
+      if (ParseFileName(filenames[i], &number, &type) && type == t) {
+        result.push_back(number);
+      }
+    }
+    return result;
+  }
+
+  int NumLogs() { return GetFiles(kLogFile).size(); }
+
+  int NumTables() { return GetFiles(kTableFile).size(); }
+
+  uint64_t FileSize(const std::string& fname) {
+    uint64_t result;
+    EXPECT_LEVELDB_OK(env_->GetFileSize(fname, &result)) << fname;
+    return result;
+  }
+
+  void CompactMemTable() { dbfull()->TEST_CompactMemTable(); }
+
+  // Directly construct a log file that sets key to val.
+  void MakeLogFile(uint64_t lognum, SequenceNumber seq, Slice key, Slice val) {
+    std::string fname = LogFileName(dbname_, lognum);
+    WritableFile* file;
+    ASSERT_LEVELDB_OK(env_->NewWritableFile(fname, &file));
+    log::Writer writer(file);
+    WriteBatch batch;
+    batch.Put(key, val);
+    WriteBatchInternal::SetSequence(&batch, seq);
+    ASSERT_LEVELDB_OK(writer.AddRecord(WriteBatchInternal::Contents(&batch)));
+    ASSERT_LEVELDB_OK(file->Flush());
+    delete file;
+  }
+
+ private:
+  std::string dbname_;
+  Env* env_;
+  DB* db_;
+};
+
+TEST_F(RecoveryTest, ManifestReused) {
+  if (!CanAppend()) {
+    std::fprintf(stderr,
+                 "skipping test because env does not support appending\n");
+    return;
+  }
+  ASSERT_LEVELDB_OK(Put("foo", "bar"));
+  Close();
+  std::string old_manifest = ManifestFileName();
+  Open();
+  ASSERT_EQ(old_manifest, ManifestFileName());
+  ASSERT_EQ("bar", Get("foo"));
+  Open();
+  ASSERT_EQ(old_manifest, ManifestFileName());
+  ASSERT_EQ("bar", Get("foo"));
+}
+
+TEST_F(RecoveryTest, LargeManifestCompacted) {
+  if (!CanAppend()) {
+    std::fprintf(stderr,
+                 "skipping test because env does not support appending\n");
+    return;
+  }
+  ASSERT_LEVELDB_OK(Put("foo", "bar"));
+  Close();
+  std::string old_manifest = ManifestFileName();
+
+  // Pad with zeroes to make manifest file very big.
+  {
+    uint64_t len = FileSize(old_manifest);
+    WritableFile* file;
+    ASSERT_LEVELDB_OK(env()->NewAppendableFile(old_manifest, &file));
+    std::string zeroes(3 * 1048576 - static_cast<size_t>(len), 0);
+    ASSERT_LEVELDB_OK(file->Append(zeroes));
+    ASSERT_LEVELDB_OK(file->Flush());
+    delete file;
+  }
+
+  Open();
+  std::string new_manifest = ManifestFileName();
+  ASSERT_NE(old_manifest, new_manifest);
+  ASSERT_GT(10000, FileSize(new_manifest));
+  ASSERT_EQ("bar", Get("foo"));
+
+  Open();
+  ASSERT_EQ(new_manifest, ManifestFileName());
+  ASSERT_EQ("bar", Get("foo"));
+}
+
+TEST_F(RecoveryTest, NoLogFiles) {
+  ASSERT_LEVELDB_OK(Put("foo", "bar"));
+  ASSERT_EQ(1, RemoveLogFiles());
+  Open();
+  ASSERT_EQ("NOT_FOUND", Get("foo"));
+  Open();
+  ASSERT_EQ("NOT_FOUND", Get("foo"));
+}
+
+TEST_F(RecoveryTest, LogFileReuse) {
+  if (!CanAppend()) {
+    std::fprintf(stderr,
+                 "skipping test because env does not support appending\n");
+    return;
+  }
+  for (int i = 0; i < 2; i++) {
+    ASSERT_LEVELDB_OK(Put("foo", "bar"));
+    if (i == 0) {
+      // Compact to ensure current log is empty
+      CompactMemTable();
+    }
+    Close();
+    ASSERT_EQ(1, NumLogs());
+    uint64_t number = FirstLogFile();
+    if (i == 0) {
+      ASSERT_EQ(0, FileSize(LogName(number)));
+    } else {
+      ASSERT_LT(0, FileSize(LogName(number)));
+    }
+    Open();
+    ASSERT_EQ(1, NumLogs());
+    ASSERT_EQ(number, FirstLogFile()) << "did not reuse log file";
+    ASSERT_EQ("bar", Get("foo"));
+    Open();
+    ASSERT_EQ(1, NumLogs());
+    ASSERT_EQ(number, FirstLogFile()) << "did not reuse log file";
+    ASSERT_EQ("bar", Get("foo"));
+  }
+}
+
+TEST_F(RecoveryTest, MultipleMemTables) {
+  // Make a large log.
+  const int kNum = 1000;
+  for (int i = 0; i < kNum; i++) {
+    char buf[100];
+    std::snprintf(buf, sizeof(buf), "%050d", i);
+    ASSERT_LEVELDB_OK(Put(buf, buf));
+  }
+  ASSERT_EQ(0, NumTables());
+  Close();
+  ASSERT_EQ(0, NumTables());
+  ASSERT_EQ(1, NumLogs());
+  uint64_t old_log_file = FirstLogFile();
+
+  // Force creation of multiple memtables by reducing the write buffer size.
+  Options opt;
+  opt.reuse_logs = true;
+  opt.write_buffer_size = (kNum * 100) / 2;
+  Open(&opt);
+  ASSERT_LE(2, NumTables());
+  ASSERT_EQ(1, NumLogs());
+  ASSERT_NE(old_log_file, FirstLogFile()) << "must not reuse log";
+  for (int i = 0; i < kNum; i++) {
+    char buf[100];
+    std::snprintf(buf, sizeof(buf), "%050d", i);
+    ASSERT_EQ(buf, Get(buf));
+  }
+}
+
+TEST_F(RecoveryTest, MultipleLogFiles) {
+  ASSERT_LEVELDB_OK(Put("foo", "bar"));
+  Close();
+  ASSERT_EQ(1, NumLogs());
+
+  // Make a bunch of uncompacted log files.
+  uint64_t old_log = FirstLogFile();
+  MakeLogFile(old_log + 1, 1000, "hello", "world");
+  MakeLogFile(old_log + 2, 1001, "hi", "there");
+  MakeLogFile(old_log + 3, 1002, "foo", "bar2");
+
+  // Recover and check that all log files were processed.
+  Open();
+  ASSERT_LE(1, NumTables());
+  ASSERT_EQ(1, NumLogs());
+  uint64_t new_log = FirstLogFile();
+  ASSERT_LE(old_log + 3, new_log);
+  ASSERT_EQ("bar2", Get("foo"));
+  ASSERT_EQ("world", Get("hello"));
+  ASSERT_EQ("there", Get("hi"));
+
+  // Test that previous recovery produced recoverable state.
+  Open();
+  ASSERT_LE(1, NumTables());
+  ASSERT_EQ(1, NumLogs());
+  if (CanAppend()) {
+    ASSERT_EQ(new_log, FirstLogFile());
+  }
+  ASSERT_EQ("bar2", Get("foo"));
+  ASSERT_EQ("world", Get("hello"));
+  ASSERT_EQ("there", Get("hi"));
+
+  // Check that introducing an older log file does not cause it to be re-read.
+  Close();
+  MakeLogFile(old_log + 1, 2000, "hello", "stale write");
+  Open();
+  ASSERT_LE(1, NumTables());
+  ASSERT_EQ(1, NumLogs());
+  if (CanAppend()) {
+    ASSERT_EQ(new_log, FirstLogFile());
+  }
+  ASSERT_EQ("bar2", Get("foo"));
+  ASSERT_EQ("world", Get("hello"));
+  ASSERT_EQ("there", Get("hi"));
+}
+
+TEST_F(RecoveryTest, ManifestMissing) {
+  ASSERT_LEVELDB_OK(Put("foo", "bar"));
+  Close();
+  RemoveManifestFile();
+
+  Status status = OpenWithStatus();
+#if defined(LEVELDB_PLATFORM_CHROMIUM)
+  // TODO(crbug.com/760362): See comment in MakeIOError() from env_chromium.cc.
+  ASSERT_TRUE(status.IsIOError());
+#else
+  ASSERT_TRUE(status.IsCorruption());
+#endif  // defined(LEVELDB_PLATFORM_CHROMIUM)
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/db/repair.cc b/leveldb_base/db/repair.cc
new file mode 100644
index 0000000..97a27c6
--- /dev/null
+++ b/leveldb_base/db/repair.cc
@@ -0,0 +1,451 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// We recover the contents of the descriptor from the other files we find.
+// (1) Any log files are first converted to tables
+// (2) We scan every table to compute
+//     (a) smallest/largest for the table
+//     (b) largest sequence number in the table
+// (3) We generate descriptor contents:
+//      - log number is set to zero
+//      - next-file-number is set to 1 + largest file number we found
+//      - last-sequence-number is set to largest sequence# found across
+//        all tables (see 2c)
+//      - compaction pointers are cleared
+//      - every table file is added at level 0
+//
+// Possible optimization 1:
+//   (a) Compute total size and use to pick appropriate max-level M
+//   (b) Sort tables by largest sequence# in the table
+//   (c) For each table: if it overlaps earlier table, place in level-0,
+//       else place in level-M.
+// Possible optimization 2:
+//   Store per-table metadata (smallest, largest, largest-seq#, ...)
+//   in the table's meta section to speed up ScanTable.
+
+#include "db/builder.h"
+#include "db/db_impl.h"
+#include "db/dbformat.h"
+#include "db/filename.h"
+#include "db/log_reader.h"
+#include "db/log_writer.h"
+#include "db/memtable.h"
+#include "db/table_cache.h"
+#include "db/version_edit.h"
+#include "db/write_batch_internal.h"
+#include "leveldb/comparator.h"
+#include "leveldb/db.h"
+#include "leveldb/env.h"
+
+namespace leveldb {
+
+namespace {
+
+class Repairer {
+ public:
+  Repairer(const std::string& dbname, const Options& options)
+      : dbname_(dbname),
+        env_(options.env),
+        icmp_(options.comparator),
+        ipolicy_(options.filter_policy),
+        options_(SanitizeOptions(dbname, &icmp_, &ipolicy_, options)),
+        owns_info_log_(options_.info_log != options.info_log),
+        owns_cache_(options_.block_cache != options.block_cache),
+        next_file_number_(1) {
+    // TableCache can be small since we expect each table to be opened once.
+    table_cache_ = new TableCache(dbname_, options_, 10);
+  }
+
+  ~Repairer() {
+    delete table_cache_;
+    if (owns_info_log_) {
+      delete options_.info_log;
+    }
+    if (owns_cache_) {
+      delete options_.block_cache;
+    }
+  }
+
+  Status Run() {
+    Status status = FindFiles();
+    if (status.ok()) {
+      ConvertLogFilesToTables();
+      ExtractMetaData();
+      status = WriteDescriptor();
+    }
+    if (status.ok()) {
+      unsigned long long bytes = 0;
+      for (size_t i = 0; i < tables_.size(); i++) {
+        bytes += tables_[i].meta.file_size;
+      }
+      Log(options_.info_log,
+          "**** Repaired leveldb %s; "
+          "recovered %d files; %llu bytes. "
+          "Some data may have been lost. "
+          "****",
+          dbname_.c_str(), static_cast<int>(tables_.size()), bytes);
+    }
+    return status;
+  }
+
+ private:
+  struct TableInfo {
+    FileMetaData meta;
+    SequenceNumber max_sequence;
+  };
+
+  Status FindFiles() {
+    std::vector<std::string> filenames;
+    Status status = env_->GetChildren(dbname_, &filenames);
+    if (!status.ok()) {
+      return status;
+    }
+    if (filenames.empty()) {
+      return Status::IOError(dbname_, "repair found no files");
+    }
+
+    uint64_t number;
+    FileType type;
+    for (size_t i = 0; i < filenames.size(); i++) {
+      if (ParseFileName(filenames[i], &number, &type)) {
+        if (type == kDescriptorFile) {
+          manifests_.push_back(filenames[i]);
+        } else {
+          if (number + 1 > next_file_number_) {
+            next_file_number_ = number + 1;
+          }
+          if (type == kLogFile) {
+            logs_.push_back(number);
+          } else if (type == kTableFile) {
+            table_numbers_.push_back(number);
+          } else {
+            // Ignore other files
+          }
+        }
+      }
+    }
+    return status;
+  }
+
+  void ConvertLogFilesToTables() {
+    for (size_t i = 0; i < logs_.size(); i++) {
+      std::string logname = LogFileName(dbname_, logs_[i]);
+      Status status = ConvertLogToTable(logs_[i]);
+      if (!status.ok()) {
+        Log(options_.info_log, "Log #%llu: ignoring conversion error: %s",
+            (unsigned long long)logs_[i], status.ToString().c_str());
+      }
+      ArchiveFile(logname);
+    }
+  }
+
+  Status ConvertLogToTable(uint64_t log) {
+    struct LogReporter : public log::Reader::Reporter {
+      Env* env;
+      Logger* info_log;
+      uint64_t lognum;
+      void Corruption(size_t bytes, const Status& s) override {
+        // We print error messages for corruption, but continue repairing.
+        Log(info_log, "Log #%llu: dropping %d bytes; %s",
+            (unsigned long long)lognum, static_cast<int>(bytes),
+            s.ToString().c_str());
+      }
+    };
+
+    // Open the log file
+    std::string logname = LogFileName(dbname_, log);
+    SequentialFile* lfile;
+    Status status = env_->NewSequentialFile(logname, &lfile);
+    if (!status.ok()) {
+      return status;
+    }
+
+    // Create the log reader.
+    LogReporter reporter;
+    reporter.env = env_;
+    reporter.info_log = options_.info_log;
+    reporter.lognum = log;
+    // We intentionally make log::Reader do checksumming so that
+    // corruptions cause entire commits to be skipped instead of
+    // propagating bad information (like overly large sequence
+    // numbers).
+    log::Reader reader(lfile, &reporter, false /*do not checksum*/,
+                       0 /*initial_offset*/);
+
+    // Read all the records and add to a memtable
+    std::string scratch;
+    Slice record;
+    WriteBatch batch;
+    MemTable* mem = new MemTable(icmp_);
+    mem->Ref();
+    int counter = 0;
+    while (reader.ReadRecord(&record, &scratch)) {
+      if (record.size() < 12) {
+        reporter.Corruption(record.size(),
+                            Status::Corruption("log record too small"));
+        continue;
+      }
+      WriteBatchInternal::SetContents(&batch, record);
+      status = WriteBatchInternal::InsertInto(&batch, mem);
+      if (status.ok()) {
+        counter += WriteBatchInternal::Count(&batch);
+      } else {
+        Log(options_.info_log, "Log #%llu: ignoring %s",
+            (unsigned long long)log, status.ToString().c_str());
+        status = Status::OK();  // Keep going with rest of file
+      }
+    }
+    delete lfile;
+
+    // Do not record a version edit for this conversion to a Table
+    // since ExtractMetaData() will also generate edits.
+    FileMetaData meta;
+    meta.number = next_file_number_++;
+    Iterator* iter = mem->NewIterator();
+    status = BuildTable(dbname_, env_, options_, table_cache_, iter, &meta);
+    delete iter;
+    mem->Unref();
+    mem = nullptr;
+    if (status.ok()) {
+      if (meta.file_size > 0) {
+        table_numbers_.push_back(meta.number);
+      }
+    }
+    Log(options_.info_log, "Log #%llu: %d ops saved to Table #%llu %s",
+        (unsigned long long)log, counter, (unsigned long long)meta.number,
+        status.ToString().c_str());
+    return status;
+  }
+
+  void ExtractMetaData() {
+    for (size_t i = 0; i < table_numbers_.size(); i++) {
+      ScanTable(table_numbers_[i]);
+    }
+  }
+
+  Iterator* NewTableIterator(const FileMetaData& meta) {
+    // Same as compaction iterators: if paranoid_checks are on, turn
+    // on checksum verification.
+    ReadOptions r;
+    r.verify_checksums = options_.paranoid_checks;
+    return table_cache_->NewIterator(r, meta.number, meta.file_size);
+  }
+
+  void ScanTable(uint64_t number) {
+    TableInfo t;
+    t.meta.number = number;
+    std::string fname = TableFileName(dbname_, number);
+    Status status = env_->GetFileSize(fname, &t.meta.file_size);
+    if (!status.ok()) {
+      // Try alternate file name.
+      fname = SSTTableFileName(dbname_, number);
+      Status s2 = env_->GetFileSize(fname, &t.meta.file_size);
+      if (s2.ok()) {
+        status = Status::OK();
+      }
+    }
+    if (!status.ok()) {
+      ArchiveFile(TableFileName(dbname_, number));
+      ArchiveFile(SSTTableFileName(dbname_, number));
+      Log(options_.info_log, "Table #%llu: dropped: %s",
+          (unsigned long long)t.meta.number, status.ToString().c_str());
+      return;
+    }
+
+    // Extract metadata by scanning through table.
+    int counter = 0;
+    Iterator* iter = NewTableIterator(t.meta);
+    bool empty = true;
+    ParsedInternalKey parsed;
+    t.max_sequence = 0;
+    for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
+      Slice key = iter->key();
+      if (!ParseInternalKey(key, &parsed)) {
+        Log(options_.info_log, "Table #%llu: unparsable key %s",
+            (unsigned long long)t.meta.number, EscapeString(key).c_str());
+        continue;
+      }
+
+      counter++;
+      if (empty) {
+        empty = false;
+        t.meta.smallest.DecodeFrom(key);
+      }
+      t.meta.largest.DecodeFrom(key);
+      if (parsed.sequence > t.max_sequence) {
+        t.max_sequence = parsed.sequence;
+      }
+    }
+    if (!iter->status().ok()) {
+      status = iter->status();
+    }
+    delete iter;
+    Log(options_.info_log, "Table #%llu: %d entries %s",
+        (unsigned long long)t.meta.number, counter, status.ToString().c_str());
+
+    if (status.ok()) {
+      tables_.push_back(t);
+    } else {
+      RepairTable(fname, t);  // RepairTable archives input file.
+    }
+  }
+
+  void RepairTable(const std::string& src, TableInfo t) {
+    // We will copy src contents to a new table and then rename the
+    // new table over the source.
+
+    // Create builder.
+    std::string copy = TableFileName(dbname_, next_file_number_++);
+    WritableFile* file;
+    Status s = env_->NewWritableFile(copy, &file);
+    if (!s.ok()) {
+      return;
+    }
+    TableBuilder* builder = new TableBuilder(options_, file);
+
+    // Copy data.
+    Iterator* iter = NewTableIterator(t.meta);
+    int counter = 0;
+    for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
+      builder->Add(iter->key(), iter->value());
+      counter++;
+    }
+    delete iter;
+
+    ArchiveFile(src);
+    if (counter == 0) {
+      builder->Abandon();  // Nothing to save
+    } else {
+      s = builder->Finish();
+      if (s.ok()) {
+        t.meta.file_size = builder->FileSize();
+      }
+    }
+    delete builder;
+    builder = nullptr;
+
+    if (s.ok()) {
+      s = file->Close();
+    }
+    delete file;
+    file = nullptr;
+
+    if (counter > 0 && s.ok()) {
+      std::string orig = TableFileName(dbname_, t.meta.number);
+      s = env_->RenameFile(copy, orig);
+      if (s.ok()) {
+        Log(options_.info_log, "Table #%llu: %d entries repaired",
+            (unsigned long long)t.meta.number, counter);
+        tables_.push_back(t);
+      }
+    }
+    if (!s.ok()) {
+      env_->RemoveFile(copy);
+    }
+  }
+
+  Status WriteDescriptor() {
+    std::string tmp = TempFileName(dbname_, 1);
+    WritableFile* file;
+    Status status = env_->NewWritableFile(tmp, &file);
+    if (!status.ok()) {
+      return status;
+    }
+
+    SequenceNumber max_sequence = 0;
+    for (size_t i = 0; i < tables_.size(); i++) {
+      if (max_sequence < tables_[i].max_sequence) {
+        max_sequence = tables_[i].max_sequence;
+      }
+    }
+
+    edit_.SetComparatorName(icmp_.user_comparator()->Name());
+    edit_.SetLogNumber(0);
+    edit_.SetNextFile(next_file_number_);
+    edit_.SetLastSequence(max_sequence);
+
+    for (size_t i = 0; i < tables_.size(); i++) {
+      // TODO(opt): separate out into multiple levels
+      const TableInfo& t = tables_[i];
+      edit_.AddFile(0, t.meta.number, t.meta.file_size, t.meta.smallest,
+                    t.meta.largest);
+    }
+
+    // std::fprintf(stderr,
+    //              "NewDescriptor:\n%s\n", edit_.DebugString().c_str());
+    {
+      log::Writer log(file);
+      std::string record;
+      edit_.EncodeTo(&record);
+      status = log.AddRecord(record);
+    }
+    if (status.ok()) {
+      status = file->Close();
+    }
+    delete file;
+    file = nullptr;
+
+    if (!status.ok()) {
+      env_->RemoveFile(tmp);
+    } else {
+      // Discard older manifests
+      for (size_t i = 0; i < manifests_.size(); i++) {
+        ArchiveFile(dbname_ + "/" + manifests_[i]);
+      }
+
+      // Install new manifest
+      status = env_->RenameFile(tmp, DescriptorFileName(dbname_, 1));
+      if (status.ok()) {
+        status = SetCurrentFile(env_, dbname_, 1);
+      } else {
+        env_->RemoveFile(tmp);
+      }
+    }
+    return status;
+  }
+
+  void ArchiveFile(const std::string& fname) {
+    // Move into another directory.  E.g., for
+    //    dir/foo
+    // rename to
+    //    dir/lost/foo
+    const char* slash = strrchr(fname.c_str(), '/');
+    std::string new_dir;
+    if (slash != nullptr) {
+      new_dir.assign(fname.data(), slash - fname.data());
+    }
+    new_dir.append("/lost");
+    env_->CreateDir(new_dir);  // Ignore error
+    std::string new_file = new_dir;
+    new_file.append("/");
+    new_file.append((slash == nullptr) ? fname.c_str() : slash + 1);
+    Status s = env_->RenameFile(fname, new_file);
+    Log(options_.info_log, "Archiving %s: %s\n", fname.c_str(),
+        s.ToString().c_str());
+  }
+
+  const std::string dbname_;
+  Env* const env_;
+  InternalKeyComparator const icmp_;
+  InternalFilterPolicy const ipolicy_;
+  const Options options_;
+  bool owns_info_log_;
+  bool owns_cache_;
+  TableCache* table_cache_;
+  VersionEdit edit_;
+
+  std::vector<std::string> manifests_;
+  std::vector<uint64_t> table_numbers_;
+  std::vector<uint64_t> logs_;
+  std::vector<TableInfo> tables_;
+  uint64_t next_file_number_;
+};
+}  // namespace
+
+Status RepairDB(const std::string& dbname, const Options& options) {
+  Repairer repairer(dbname, options);
+  return repairer.Run();
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/db/skiplist.h b/leveldb_base/db/skiplist.h
new file mode 100644
index 0000000..1140e59
--- /dev/null
+++ b/leveldb_base/db/skiplist.h
@@ -0,0 +1,380 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_DB_SKIPLIST_H_
+#define STORAGE_LEVELDB_DB_SKIPLIST_H_
+
+// Thread safety
+// -------------
+//
+// Writes require external synchronization, most likely a mutex.
+// Reads require a guarantee that the SkipList will not be destroyed
+// while the read is in progress.  Apart from that, reads progress
+// without any internal locking or synchronization.
+//
+// Invariants:
+//
+// (1) Allocated nodes are never deleted until the SkipList is
+// destroyed.  This is trivially guaranteed by the code since we
+// never delete any skip list nodes.
+//
+// (2) The contents of a Node except for the next/prev pointers are
+// immutable after the Node has been linked into the SkipList.
+// Only Insert() modifies the list, and it is careful to initialize
+// a node and use release-stores to publish the nodes in one or
+// more lists.
+//
+// ... prev vs. next pointer ordering ...
+
+#include <atomic>
+#include <cassert>
+#include <cstdlib>
+
+#include "util/arena.h"
+#include "util/random.h"
+
+namespace leveldb {
+
+template <typename Key, class Comparator>
+class SkipList {
+ private:
+  struct Node;
+
+ public:
+  // Create a new SkipList object that will use "cmp" for comparing keys,
+  // and will allocate memory using "*arena".  Objects allocated in the arena
+  // must remain allocated for the lifetime of the skiplist object.
+  explicit SkipList(Comparator cmp, Arena* arena);
+
+  SkipList(const SkipList&) = delete;
+  SkipList& operator=(const SkipList&) = delete;
+
+  // Insert key into the list.
+  // REQUIRES: nothing that compares equal to key is currently in the list.
+  void Insert(const Key& key);
+
+  // Returns true iff an entry that compares equal to key is in the list.
+  bool Contains(const Key& key) const;
+
+  // Iteration over the contents of a skip list
+  class Iterator {
+   public:
+    // Initialize an iterator over the specified list.
+    // The returned iterator is not valid.
+    explicit Iterator(const SkipList* list);
+
+    // Returns true iff the iterator is positioned at a valid node.
+    bool Valid() const;
+
+    // Returns the key at the current position.
+    // REQUIRES: Valid()
+    const Key& key() const;
+
+    // Advances to the next position.
+    // REQUIRES: Valid()
+    void Next();
+
+    // Advances to the previous position.
+    // REQUIRES: Valid()
+    void Prev();
+
+    // Advance to the first entry with a key >= target
+    void Seek(const Key& target);
+
+    // Position at the first entry in list.
+    // Final state of iterator is Valid() iff list is not empty.
+    void SeekToFirst();
+
+    // Position at the last entry in list.
+    // Final state of iterator is Valid() iff list is not empty.
+    void SeekToLast();
+
+   private:
+    const SkipList* list_;
+    Node* node_;
+    // Intentionally copyable
+  };
+
+ private:
+  enum { kMaxHeight = 12 };
+
+  inline int GetMaxHeight() const {
+    return max_height_.load(std::memory_order_relaxed);
+  }
+
+  Node* NewNode(const Key& key, int height);
+  int RandomHeight();
+  bool Equal(const Key& a, const Key& b) const { return (compare_(a, b) == 0); }
+
+  // Return true if key is greater than the data stored in "n"
+  bool KeyIsAfterNode(const Key& key, Node* n) const;
+
+  // Return the earliest node that comes at or after key.
+  // Return nullptr if there is no such node.
+  //
+  // If prev is non-null, fills prev[level] with pointer to previous
+  // node at "level" for every level in [0..max_height_-1].
+  Node* FindGreaterOrEqual(const Key& key, Node** prev) const;
+
+  // Return the latest node with a key < key.
+  // Return head_ if there is no such node.
+  Node* FindLessThan(const Key& key) const;
+
+  // Return the last node in the list.
+  // Return head_ if list is empty.
+  Node* FindLast() const;
+
+  // Immutable after construction
+  Comparator const compare_;
+  Arena* const arena_;  // Arena used for allocations of nodes
+
+  Node* const head_;
+
+  // Modified only by Insert().  Read racily by readers, but stale
+  // values are ok.
+  std::atomic<int> max_height_;  // Height of the entire list
+
+  // Read/written only by Insert().
+  Random rnd_;
+};
+
+// Implementation details follow
+template <typename Key, class Comparator>
+struct SkipList<Key, Comparator>::Node {
+  explicit Node(const Key& k) : key(k) {}
+
+  Key const key;
+
+  // Accessors/mutators for links.  Wrapped in methods so we can
+  // add the appropriate barriers as necessary.
+  Node* Next(int n) {
+    assert(n >= 0);
+    // Use an 'acquire load' so that we observe a fully initialized
+    // version of the returned Node.
+    return next_[n].load(std::memory_order_acquire);
+  }
+  void SetNext(int n, Node* x) {
+    assert(n >= 0);
+    // Use a 'release store' so that anybody who reads through this
+    // pointer observes a fully initialized version of the inserted node.
+    next_[n].store(x, std::memory_order_release);
+  }
+
+  // No-barrier variants that can be safely used in a few locations.
+  Node* NoBarrier_Next(int n) {
+    assert(n >= 0);
+    return next_[n].load(std::memory_order_relaxed);
+  }
+  void NoBarrier_SetNext(int n, Node* x) {
+    assert(n >= 0);
+    next_[n].store(x, std::memory_order_relaxed);
+  }
+
+ private:
+  // Array of length equal to the node height.  next_[0] is lowest level link.
+  std::atomic<Node*> next_[1];
+};
+
+template <typename Key, class Comparator>
+typename SkipList<Key, Comparator>::Node* SkipList<Key, Comparator>::NewNode(
+    const Key& key, int height) {
+  char* const node_memory = arena_->AllocateAligned(
+      sizeof(Node) + sizeof(std::atomic<Node*>) * (height - 1));
+  return new (node_memory) Node(key);
+}
+
+template <typename Key, class Comparator>
+inline SkipList<Key, Comparator>::Iterator::Iterator(const SkipList* list) {
+  list_ = list;
+  node_ = nullptr;
+}
+
+template <typename Key, class Comparator>
+inline bool SkipList<Key, Comparator>::Iterator::Valid() const {
+  return node_ != nullptr;
+}
+
+template <typename Key, class Comparator>
+inline const Key& SkipList<Key, Comparator>::Iterator::key() const {
+  assert(Valid());
+  return node_->key;
+}
+
+template <typename Key, class Comparator>
+inline void SkipList<Key, Comparator>::Iterator::Next() {
+  assert(Valid());
+  node_ = node_->Next(0);
+}
+
+template <typename Key, class Comparator>
+inline void SkipList<Key, Comparator>::Iterator::Prev() {
+  // Instead of using explicit "prev" links, we just search for the
+  // last node that falls before key.
+  assert(Valid());
+  node_ = list_->FindLessThan(node_->key);
+  if (node_ == list_->head_) {
+    node_ = nullptr;
+  }
+}
+
+template <typename Key, class Comparator>
+inline void SkipList<Key, Comparator>::Iterator::Seek(const Key& target) {
+  node_ = list_->FindGreaterOrEqual(target, nullptr);
+}
+
+template <typename Key, class Comparator>
+inline void SkipList<Key, Comparator>::Iterator::SeekToFirst() {
+  node_ = list_->head_->Next(0);
+}
+
+template <typename Key, class Comparator>
+inline void SkipList<Key, Comparator>::Iterator::SeekToLast() {
+  node_ = list_->FindLast();
+  if (node_ == list_->head_) {
+    node_ = nullptr;
+  }
+}
+
+template <typename Key, class Comparator>
+int SkipList<Key, Comparator>::RandomHeight() {
+  // Increase height with probability 1 in kBranching
+  static const unsigned int kBranching = 4;
+  int height = 1;
+  while (height < kMaxHeight && rnd_.OneIn(kBranching)) {
+    height++;
+  }
+  assert(height > 0);
+  assert(height <= kMaxHeight);
+  return height;
+}
+
+template <typename Key, class Comparator>
+bool SkipList<Key, Comparator>::KeyIsAfterNode(const Key& key, Node* n) const {
+  // null n is considered infinite
+  return (n != nullptr) && (compare_(n->key, key) < 0);
+}
+
+template <typename Key, class Comparator>
+typename SkipList<Key, Comparator>::Node*
+SkipList<Key, Comparator>::FindGreaterOrEqual(const Key& key,
+                                              Node** prev) const {
+  Node* x = head_;
+  int level = GetMaxHeight() - 1;
+  while (true) {
+    Node* next = x->Next(level);
+    if (KeyIsAfterNode(key, next)) {
+      // Keep searching in this list
+      x = next;
+    } else {
+      if (prev != nullptr) prev[level] = x;
+      if (level == 0) {
+        return next;
+      } else {
+        // Switch to next list
+        level--;
+      }
+    }
+  }
+}
+
+template <typename Key, class Comparator>
+typename SkipList<Key, Comparator>::Node*
+SkipList<Key, Comparator>::FindLessThan(const Key& key) const {
+  Node* x = head_;
+  int level = GetMaxHeight() - 1;
+  while (true) {
+    assert(x == head_ || compare_(x->key, key) < 0);
+    Node* next = x->Next(level);
+    if (next == nullptr || compare_(next->key, key) >= 0) {
+      if (level == 0) {
+        return x;
+      } else {
+        // Switch to next list
+        level--;
+      }
+    } else {
+      x = next;
+    }
+  }
+}
+
+template <typename Key, class Comparator>
+typename SkipList<Key, Comparator>::Node* SkipList<Key, Comparator>::FindLast()
+    const {
+  Node* x = head_;
+  int level = GetMaxHeight() - 1;
+  while (true) {
+    Node* next = x->Next(level);
+    if (next == nullptr) {
+      if (level == 0) {
+        return x;
+      } else {
+        // Switch to next list
+        level--;
+      }
+    } else {
+      x = next;
+    }
+  }
+}
+
+template <typename Key, class Comparator>
+SkipList<Key, Comparator>::SkipList(Comparator cmp, Arena* arena)
+    : compare_(cmp),
+      arena_(arena),
+      head_(NewNode(0 /* any key will do */, kMaxHeight)),
+      max_height_(1),
+      rnd_(0xdeadbeef) {
+  for (int i = 0; i < kMaxHeight; i++) {
+    head_->SetNext(i, nullptr);
+  }
+}
+
+template <typename Key, class Comparator>
+void SkipList<Key, Comparator>::Insert(const Key& key) {
+  // TODO(opt): We can use a barrier-free variant of FindGreaterOrEqual()
+  // here since Insert() is externally synchronized.
+  Node* prev[kMaxHeight];
+  Node* x = FindGreaterOrEqual(key, prev);
+
+  // Our data structure does not allow duplicate insertion
+  assert(x == nullptr || !Equal(key, x->key));
+
+  int height = RandomHeight();
+  if (height > GetMaxHeight()) {
+    for (int i = GetMaxHeight(); i < height; i++) {
+      prev[i] = head_;
+    }
+    // It is ok to mutate max_height_ without any synchronization
+    // with concurrent readers.  A concurrent reader that observes
+    // the new value of max_height_ will see either the old value of
+    // new level pointers from head_ (nullptr), or a new value set in
+    // the loop below.  In the former case the reader will
+    // immediately drop to the next level since nullptr sorts after all
+    // keys.  In the latter case the reader will use the new node.
+    max_height_.store(height, std::memory_order_relaxed);
+  }
+
+  x = NewNode(key, height);
+  for (int i = 0; i < height; i++) {
+    // NoBarrier_SetNext() suffices since we will add a barrier when
+    // we publish a pointer to "x" in prev[i].
+    x->NoBarrier_SetNext(i, prev[i]->NoBarrier_Next(i));
+    prev[i]->SetNext(i, x);
+  }
+}
+
+template <typename Key, class Comparator>
+bool SkipList<Key, Comparator>::Contains(const Key& key) const {
+  Node* x = FindGreaterOrEqual(key, nullptr);
+  if (x != nullptr && Equal(key, x->key)) {
+    return true;
+  } else {
+    return false;
+  }
+}
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_DB_SKIPLIST_H_
diff --git a/leveldb_base/db/skiplist_test.cc b/leveldb_base/db/skiplist_test.cc
new file mode 100644
index 0000000..1d355cb
--- /dev/null
+++ b/leveldb_base/db/skiplist_test.cc
@@ -0,0 +1,368 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "db/skiplist.h"
+
+#include <atomic>
+#include <set>
+
+#include "gtest/gtest.h"
+#include "leveldb/env.h"
+#include "port/port.h"
+#include "port/thread_annotations.h"
+#include "util/arena.h"
+#include "util/hash.h"
+#include "util/random.h"
+#include "util/testutil.h"
+
+namespace leveldb {
+
+typedef uint64_t Key;
+
+struct Comparator {
+  int operator()(const Key& a, const Key& b) const {
+    if (a < b) {
+      return -1;
+    } else if (a > b) {
+      return +1;
+    } else {
+      return 0;
+    }
+  }
+};
+
+TEST(SkipTest, Empty) {
+  Arena arena;
+  Comparator cmp;
+  SkipList<Key, Comparator> list(cmp, &arena);
+  ASSERT_TRUE(!list.Contains(10));
+
+  SkipList<Key, Comparator>::Iterator iter(&list);
+  ASSERT_TRUE(!iter.Valid());
+  iter.SeekToFirst();
+  ASSERT_TRUE(!iter.Valid());
+  iter.Seek(100);
+  ASSERT_TRUE(!iter.Valid());
+  iter.SeekToLast();
+  ASSERT_TRUE(!iter.Valid());
+}
+
+TEST(SkipTest, InsertAndLookup) {
+  const int N = 2000;
+  const int R = 5000;
+  Random rnd(1000);
+  std::set<Key> keys;
+  Arena arena;
+  Comparator cmp;
+  SkipList<Key, Comparator> list(cmp, &arena);
+  for (int i = 0; i < N; i++) {
+    Key key = rnd.Next() % R;
+    if (keys.insert(key).second) {
+      list.Insert(key);
+    }
+  }
+
+  for (int i = 0; i < R; i++) {
+    if (list.Contains(i)) {
+      ASSERT_EQ(keys.count(i), 1);
+    } else {
+      ASSERT_EQ(keys.count(i), 0);
+    }
+  }
+
+  // Simple iterator tests
+  {
+    SkipList<Key, Comparator>::Iterator iter(&list);
+    ASSERT_TRUE(!iter.Valid());
+
+    iter.Seek(0);
+    ASSERT_TRUE(iter.Valid());
+    ASSERT_EQ(*(keys.begin()), iter.key());
+
+    iter.SeekToFirst();
+    ASSERT_TRUE(iter.Valid());
+    ASSERT_EQ(*(keys.begin()), iter.key());
+
+    iter.SeekToLast();
+    ASSERT_TRUE(iter.Valid());
+    ASSERT_EQ(*(keys.rbegin()), iter.key());
+  }
+
+  // Forward iteration test
+  for (int i = 0; i < R; i++) {
+    SkipList<Key, Comparator>::Iterator iter(&list);
+    iter.Seek(i);
+
+    // Compare against model iterator
+    std::set<Key>::iterator model_iter = keys.lower_bound(i);
+    for (int j = 0; j < 3; j++) {
+      if (model_iter == keys.end()) {
+        ASSERT_TRUE(!iter.Valid());
+        break;
+      } else {
+        ASSERT_TRUE(iter.Valid());
+        ASSERT_EQ(*model_iter, iter.key());
+        ++model_iter;
+        iter.Next();
+      }
+    }
+  }
+
+  // Backward iteration test
+  {
+    SkipList<Key, Comparator>::Iterator iter(&list);
+    iter.SeekToLast();
+
+    // Compare against model iterator
+    for (std::set<Key>::reverse_iterator model_iter = keys.rbegin();
+         model_iter != keys.rend(); ++model_iter) {
+      ASSERT_TRUE(iter.Valid());
+      ASSERT_EQ(*model_iter, iter.key());
+      iter.Prev();
+    }
+    ASSERT_TRUE(!iter.Valid());
+  }
+}
+
+// We want to make sure that with a single writer and multiple
+// concurrent readers (with no synchronization other than when a
+// reader's iterator is created), the reader always observes all the
+// data that was present in the skip list when the iterator was
+// constructed.  Because insertions are happening concurrently, we may
+// also observe new values that were inserted since the iterator was
+// constructed, but we should never miss any values that were present
+// at iterator construction time.
+//
+// We generate multi-part keys:
+//     <key,gen,hash>
+// where:
+//     key is in range [0..K-1]
+//     gen is a generation number for key
+//     hash is hash(key,gen)
+//
+// The insertion code picks a random key, sets gen to be 1 + the last
+// generation number inserted for that key, and sets hash to Hash(key,gen).
+//
+// At the beginning of a read, we snapshot the last inserted
+// generation number for each key.  We then iterate, including random
+// calls to Next() and Seek().  For every key we encounter, we
+// check that it is either expected given the initial snapshot or has
+// been concurrently added since the iterator started.
+class ConcurrentTest {
+ private:
+  static constexpr uint32_t K = 4;
+
+  static uint64_t key(Key key) { return (key >> 40); }
+  static uint64_t gen(Key key) { return (key >> 8) & 0xffffffffu; }
+  static uint64_t hash(Key key) { return key & 0xff; }
+
+  static uint64_t HashNumbers(uint64_t k, uint64_t g) {
+    uint64_t data[2] = {k, g};
+    return Hash(reinterpret_cast<char*>(data), sizeof(data), 0);
+  }
+
+  static Key MakeKey(uint64_t k, uint64_t g) {
+    static_assert(sizeof(Key) == sizeof(uint64_t), "");
+    assert(k <= K);  // We sometimes pass K to seek to the end of the skiplist
+    assert(g <= 0xffffffffu);
+    return ((k << 40) | (g << 8) | (HashNumbers(k, g) & 0xff));
+  }
+
+  static bool IsValidKey(Key k) {
+    return hash(k) == (HashNumbers(key(k), gen(k)) & 0xff);
+  }
+
+  static Key RandomTarget(Random* rnd) {
+    switch (rnd->Next() % 10) {
+      case 0:
+        // Seek to beginning
+        return MakeKey(0, 0);
+      case 1:
+        // Seek to end
+        return MakeKey(K, 0);
+      default:
+        // Seek to middle
+        return MakeKey(rnd->Next() % K, 0);
+    }
+  }
+
+  // Per-key generation
+  struct State {
+    std::atomic<int> generation[K];
+    void Set(int k, int v) {
+      generation[k].store(v, std::memory_order_release);
+    }
+    int Get(int k) { return generation[k].load(std::memory_order_acquire); }
+
+    State() {
+      for (int k = 0; k < K; k++) {
+        Set(k, 0);
+      }
+    }
+  };
+
+  // Current state of the test
+  State current_;
+
+  Arena arena_;
+
+  // SkipList is not protected by mu_.  We just use a single writer
+  // thread to modify it.
+  SkipList<Key, Comparator> list_;
+
+ public:
+  ConcurrentTest() : list_(Comparator(), &arena_) {}
+
+  // REQUIRES: External synchronization
+  void WriteStep(Random* rnd) {
+    const uint32_t k = rnd->Next() % K;
+    const intptr_t g = current_.Get(k) + 1;
+    const Key key = MakeKey(k, g);
+    list_.Insert(key);
+    current_.Set(k, g);
+  }
+
+  void ReadStep(Random* rnd) {
+    // Remember the initial committed state of the skiplist.
+    State initial_state;
+    for (int k = 0; k < K; k++) {
+      initial_state.Set(k, current_.Get(k));
+    }
+
+    Key pos = RandomTarget(rnd);
+    SkipList<Key, Comparator>::Iterator iter(&list_);
+    iter.Seek(pos);
+    while (true) {
+      Key current;
+      if (!iter.Valid()) {
+        current = MakeKey(K, 0);
+      } else {
+        current = iter.key();
+        ASSERT_TRUE(IsValidKey(current)) << current;
+      }
+      ASSERT_LE(pos, current) << "should not go backwards";
+
+      // Verify that everything in [pos,current) was not present in
+      // initial_state.
+      while (pos < current) {
+        ASSERT_LT(key(pos), K) << pos;
+
+        // Note that generation 0 is never inserted, so it is ok if
+        // <*,0,*> is missing.
+        ASSERT_TRUE((gen(pos) == 0) ||
+                    (gen(pos) > static_cast<Key>(initial_state.Get(key(pos)))))
+            << "key: " << key(pos) << "; gen: " << gen(pos)
+            << "; initgen: " << initial_state.Get(key(pos));
+
+        // Advance to next key in the valid key space
+        if (key(pos) < key(current)) {
+          pos = MakeKey(key(pos) + 1, 0);
+        } else {
+          pos = MakeKey(key(pos), gen(pos) + 1);
+        }
+      }
+
+      if (!iter.Valid()) {
+        break;
+      }
+
+      if (rnd->Next() % 2) {
+        iter.Next();
+        pos = MakeKey(key(pos), gen(pos) + 1);
+      } else {
+        Key new_target = RandomTarget(rnd);
+        if (new_target > pos) {
+          pos = new_target;
+          iter.Seek(new_target);
+        }
+      }
+    }
+  }
+};
+
+// Needed when building in C++11 mode.
+constexpr uint32_t ConcurrentTest::K;
+
+// Simple test that does single-threaded testing of the ConcurrentTest
+// scaffolding.
+TEST(SkipTest, ConcurrentWithoutThreads) {
+  ConcurrentTest test;
+  Random rnd(test::RandomSeed());
+  for (int i = 0; i < 10000; i++) {
+    test.ReadStep(&rnd);
+    test.WriteStep(&rnd);
+  }
+}
+
+class TestState {
+ public:
+  ConcurrentTest t_;
+  int seed_;
+  std::atomic<bool> quit_flag_;
+
+  enum ReaderState { STARTING, RUNNING, DONE };
+
+  explicit TestState(int s)
+      : seed_(s), quit_flag_(false), state_(STARTING), state_cv_(&mu_) {}
+
+  void Wait(ReaderState s) LOCKS_EXCLUDED(mu_) {
+    mu_.Lock();
+    while (state_ != s) {
+      state_cv_.Wait();
+    }
+    mu_.Unlock();
+  }
+
+  void Change(ReaderState s) LOCKS_EXCLUDED(mu_) {
+    mu_.Lock();
+    state_ = s;
+    state_cv_.Signal();
+    mu_.Unlock();
+  }
+
+ private:
+  port::Mutex mu_;
+  ReaderState state_ GUARDED_BY(mu_);
+  port::CondVar state_cv_ GUARDED_BY(mu_);
+};
+
+static void ConcurrentReader(void* arg) {
+  TestState* state = reinterpret_cast<TestState*>(arg);
+  Random rnd(state->seed_);
+  int64_t reads = 0;
+  state->Change(TestState::RUNNING);
+  while (!state->quit_flag_.load(std::memory_order_acquire)) {
+    state->t_.ReadStep(&rnd);
+    ++reads;
+  }
+  state->Change(TestState::DONE);
+}
+
+static void RunConcurrent(int run) {
+  const int seed = test::RandomSeed() + (run * 100);
+  Random rnd(seed);
+  const int N = 1000;
+  const int kSize = 1000;
+  for (int i = 0; i < N; i++) {
+    if ((i % 100) == 0) {
+      std::fprintf(stderr, "Run %d of %d\n", i, N);
+    }
+    TestState state(seed + 1);
+    Env::Default()->Schedule(ConcurrentReader, &state);
+    state.Wait(TestState::RUNNING);
+    for (int i = 0; i < kSize; i++) {
+      state.t_.WriteStep(&rnd);
+    }
+    state.quit_flag_.store(true, std::memory_order_release);
+    state.Wait(TestState::DONE);
+  }
+}
+
+TEST(SkipTest, Concurrent1) { RunConcurrent(1); }
+TEST(SkipTest, Concurrent2) { RunConcurrent(2); }
+TEST(SkipTest, Concurrent3) { RunConcurrent(3); }
+TEST(SkipTest, Concurrent4) { RunConcurrent(4); }
+TEST(SkipTest, Concurrent5) { RunConcurrent(5); }
+
+}  // namespace leveldb
diff --git a/leveldb_base/db/snapshot.h b/leveldb_base/db/snapshot.h
new file mode 100644
index 0000000..817bb7b
--- /dev/null
+++ b/leveldb_base/db/snapshot.h
@@ -0,0 +1,95 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_DB_SNAPSHOT_H_
+#define STORAGE_LEVELDB_DB_SNAPSHOT_H_
+
+#include "db/dbformat.h"
+#include "leveldb/db.h"
+
+namespace leveldb {
+
+class SnapshotList;
+
+// Snapshots are kept in a doubly-linked list in the DB.
+// Each SnapshotImpl corresponds to a particular sequence number.
+class SnapshotImpl : public Snapshot {
+ public:
+  SnapshotImpl(SequenceNumber sequence_number)
+      : sequence_number_(sequence_number) {}
+
+  SequenceNumber sequence_number() const { return sequence_number_; }
+
+ private:
+  friend class SnapshotList;
+
+  // SnapshotImpl is kept in a doubly-linked circular list. The SnapshotList
+  // implementation operates on the next/previous fields directly.
+  SnapshotImpl* prev_;
+  SnapshotImpl* next_;
+
+  const SequenceNumber sequence_number_;
+
+#if !defined(NDEBUG)
+  SnapshotList* list_ = nullptr;
+#endif  // !defined(NDEBUG)
+};
+
+class SnapshotList {
+ public:
+  SnapshotList() : head_(0) {
+    head_.prev_ = &head_;
+    head_.next_ = &head_;
+  }
+
+  bool empty() const { return head_.next_ == &head_; }
+  SnapshotImpl* oldest() const {
+    assert(!empty());
+    return head_.next_;
+  }
+  SnapshotImpl* newest() const {
+    assert(!empty());
+    return head_.prev_;
+  }
+
+  // Creates a SnapshotImpl and appends it to the end of the list.
+  SnapshotImpl* New(SequenceNumber sequence_number) {
+    assert(empty() || newest()->sequence_number_ <= sequence_number);
+
+    SnapshotImpl* snapshot = new SnapshotImpl(sequence_number);
+
+#if !defined(NDEBUG)
+    snapshot->list_ = this;
+#endif  // !defined(NDEBUG)
+    snapshot->next_ = &head_;
+    snapshot->prev_ = head_.prev_;
+    snapshot->prev_->next_ = snapshot;
+    snapshot->next_->prev_ = snapshot;
+    return snapshot;
+  }
+
+  // Removes a SnapshotImpl from this list.
+  //
+  // The snapshot must have been created by calling New() on this list.
+  //
+  // The snapshot pointer should not be const, because its memory is
+  // deallocated. However, that would force us to change DB::ReleaseSnapshot(),
+  // which is in the API, and currently takes a const Snapshot.
+  void Delete(const SnapshotImpl* snapshot) {
+#if !defined(NDEBUG)
+    assert(snapshot->list_ == this);
+#endif  // !defined(NDEBUG)
+    snapshot->prev_->next_ = snapshot->next_;
+    snapshot->next_->prev_ = snapshot->prev_;
+    delete snapshot;
+  }
+
+ private:
+  // Dummy head of doubly-linked list of snapshots
+  SnapshotImpl head_;
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_DB_SNAPSHOT_H_
diff --git a/leveldb_base/db/table_cache.cc b/leveldb_base/db/table_cache.cc
new file mode 100644
index 0000000..73f05fd
--- /dev/null
+++ b/leveldb_base/db/table_cache.cc
@@ -0,0 +1,120 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "db/table_cache.h"
+
+#include "db/filename.h"
+#include "leveldb/env.h"
+#include "leveldb/table.h"
+#include "util/coding.h"
+
+namespace leveldb {
+
+struct TableAndFile {
+  RandomAccessFile* file;
+  Table* table;
+};
+
+static void DeleteEntry(const Slice& key, void* value) {
+  TableAndFile* tf = reinterpret_cast<TableAndFile*>(value);
+  delete tf->table;
+  delete tf->file;
+  delete tf;
+}
+
+static void UnrefEntry(void* arg1, void* arg2) {
+  Cache* cache = reinterpret_cast<Cache*>(arg1);
+  Cache::Handle* h = reinterpret_cast<Cache::Handle*>(arg2);
+  cache->Release(h);
+}
+
+TableCache::TableCache(const std::string& dbname, const Options& options,
+                       int entries)
+    : env_(options.env),
+      dbname_(dbname),
+      options_(options),
+      cache_(NewLRUCache(entries)) {}
+
+TableCache::~TableCache() { delete cache_; }
+
+Status TableCache::FindTable(uint64_t file_number, uint64_t file_size,
+                             Cache::Handle** handle) {
+  Status s;
+  char buf[sizeof(file_number)];
+  EncodeFixed64(buf, file_number);
+  Slice key(buf, sizeof(buf));
+  *handle = cache_->Lookup(key);
+  if (*handle == nullptr) {
+    std::string fname = TableFileName(dbname_, file_number);
+    RandomAccessFile* file = nullptr;
+    Table* table = nullptr;
+    s = env_->NewRandomAccessFile(fname, &file);
+    if (!s.ok()) {
+      std::string old_fname = SSTTableFileName(dbname_, file_number);
+      if (env_->NewRandomAccessFile(old_fname, &file).ok()) {
+        s = Status::OK();
+      }
+    }
+    if (s.ok()) {
+      s = Table::Open(options_, file, file_size, &table);
+    }
+
+    if (!s.ok()) {
+      assert(table == nullptr);
+      delete file;
+      // We do not cache error results so that if the error is transient,
+      // or somebody repairs the file, we recover automatically.
+    } else {
+      TableAndFile* tf = new TableAndFile;
+      tf->file = file;
+      tf->table = table;
+      *handle = cache_->Insert(key, tf, 1, &DeleteEntry);
+    }
+  }
+  return s;
+}
+
+Iterator* TableCache::NewIterator(const ReadOptions& options,
+                                  uint64_t file_number, uint64_t file_size,
+                                  Table** tableptr) {
+  if (tableptr != nullptr) {
+    *tableptr = nullptr;
+  }
+
+  Cache::Handle* handle = nullptr;
+  Status s = FindTable(file_number, file_size, &handle);
+  if (!s.ok()) {
+    return NewErrorIterator(s);
+  }
+
+  Table* table = reinterpret_cast<TableAndFile*>(cache_->Value(handle))->table;
+  Iterator* result = table->NewIterator(options);
+  result->RegisterCleanup(&UnrefEntry, cache_, handle);
+  if (tableptr != nullptr) {
+    *tableptr = table;
+  }
+  return result;
+}
+
+Status TableCache::Get(const ReadOptions& options, uint64_t file_number,
+                       uint64_t file_size, const Slice& k, void* arg,
+                       void (*handle_result)(void*, const Slice&,
+                                             const Slice&)) {
+  Cache::Handle* handle = nullptr;
+  Status s = FindTable(file_number, file_size, &handle);
+  if (s.ok()) {
+    Table* t = reinterpret_cast<TableAndFile*>(cache_->Value(handle))->table;
+    s = t->InternalGet(options, k, arg, handle_result);
+    cache_->Release(handle);
+  }
+  return s;
+}
+
+void TableCache::Evict(uint64_t file_number) {
+  char buf[sizeof(file_number)];
+  EncodeFixed64(buf, file_number);
+  cache_->Erase(Slice(buf, sizeof(buf)));
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/db/table_cache.h b/leveldb_base/db/table_cache.h
new file mode 100644
index 0000000..db8a123
--- /dev/null
+++ b/leveldb_base/db/table_cache.h
@@ -0,0 +1,61 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// Thread-safe (provides internal synchronization)
+
+#ifndef STORAGE_LEVELDB_DB_TABLE_CACHE_H_
+#define STORAGE_LEVELDB_DB_TABLE_CACHE_H_
+
+#include <cstdint>
+#include <string>
+
+#include "db/dbformat.h"
+#include "leveldb/cache.h"
+#include "leveldb/table.h"
+#include "port/port.h"
+
+namespace leveldb {
+
+class Env;
+
+class TableCache {
+ public:
+  TableCache(const std::string& dbname, const Options& options, int entries);
+
+  TableCache(const TableCache&) = delete;
+  TableCache& operator=(const TableCache&) = delete;
+
+  ~TableCache();
+
+  // Return an iterator for the specified file number (the corresponding
+  // file length must be exactly "file_size" bytes).  If "tableptr" is
+  // non-null, also sets "*tableptr" to point to the Table object
+  // underlying the returned iterator, or to nullptr if no Table object
+  // underlies the returned iterator.  The returned "*tableptr" object is owned
+  // by the cache and should not be deleted, and is valid for as long as the
+  // returned iterator is live.
+  Iterator* NewIterator(const ReadOptions& options, uint64_t file_number,
+                        uint64_t file_size, Table** tableptr = nullptr);
+
+  // If a seek to internal key "k" in specified file finds an entry,
+  // call (*handle_result)(arg, found_key, found_value).
+  Status Get(const ReadOptions& options, uint64_t file_number,
+             uint64_t file_size, const Slice& k, void* arg,
+             void (*handle_result)(void*, const Slice&, const Slice&));
+
+  // Evict any entry for the specified file number
+  void Evict(uint64_t file_number);
+
+ private:
+  Status FindTable(uint64_t file_number, uint64_t file_size, Cache::Handle**);
+
+  Env* const env_;
+  const std::string dbname_;
+  const Options& options_;
+  Cache* cache_;
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_DB_TABLE_CACHE_H_
diff --git a/leveldb_base/db/version_edit.cc b/leveldb_base/db/version_edit.cc
new file mode 100644
index 0000000..356ce88
--- /dev/null
+++ b/leveldb_base/db/version_edit.cc
@@ -0,0 +1,258 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "db/version_edit.h"
+
+#include "db/version_set.h"
+#include "util/coding.h"
+
+namespace leveldb {
+
+// Tag numbers for serialized VersionEdit.  These numbers are written to
+// disk and should not be changed.
+enum Tag {
+  kComparator = 1,
+  kLogNumber = 2,
+  kNextFileNumber = 3,
+  kLastSequence = 4,
+  kCompactPointer = 5,
+  kDeletedFile = 6,
+  kNewFile = 7,
+  // 8 was used for large value refs
+  kPrevLogNumber = 9
+};
+
+void VersionEdit::Clear() {
+  comparator_.clear();
+  log_number_ = 0;
+  prev_log_number_ = 0;
+  last_sequence_ = 0;
+  next_file_number_ = 0;
+  has_comparator_ = false;
+  has_log_number_ = false;
+  has_prev_log_number_ = false;
+  has_next_file_number_ = false;
+  has_last_sequence_ = false;
+  compact_pointers_.clear();
+  deleted_files_.clear();
+  new_files_.clear();
+}
+
+void VersionEdit::EncodeTo(std::string* dst) const {
+  if (has_comparator_) {
+    PutVarint32(dst, kComparator);
+    PutLengthPrefixedSlice(dst, comparator_);
+  }
+  if (has_log_number_) {
+    PutVarint32(dst, kLogNumber);
+    PutVarint64(dst, log_number_);
+  }
+  if (has_prev_log_number_) {
+    PutVarint32(dst, kPrevLogNumber);
+    PutVarint64(dst, prev_log_number_);
+  }
+  if (has_next_file_number_) {
+    PutVarint32(dst, kNextFileNumber);
+    PutVarint64(dst, next_file_number_);
+  }
+  if (has_last_sequence_) {
+    PutVarint32(dst, kLastSequence);
+    PutVarint64(dst, last_sequence_);
+  }
+
+  for (size_t i = 0; i < compact_pointers_.size(); i++) {
+    PutVarint32(dst, kCompactPointer);
+    PutVarint32(dst, compact_pointers_[i].first);  // level
+    PutLengthPrefixedSlice(dst, compact_pointers_[i].second.Encode());
+  }
+
+  for (const auto& deleted_file_kvp : deleted_files_) {
+    PutVarint32(dst, kDeletedFile);
+    PutVarint32(dst, deleted_file_kvp.first);   // level
+    PutVarint64(dst, deleted_file_kvp.second);  // file number
+  }
+
+  for (size_t i = 0; i < new_files_.size(); i++) {
+    const FileMetaData& f = new_files_[i].second;
+    PutVarint32(dst, kNewFile);
+    PutVarint32(dst, new_files_[i].first);  // level
+    PutVarint64(dst, f.number);
+    PutVarint64(dst, f.file_size);
+    PutLengthPrefixedSlice(dst, f.smallest.Encode());
+    PutLengthPrefixedSlice(dst, f.largest.Encode());
+  }
+}
+
+static bool GetInternalKey(Slice* input, InternalKey* dst) {
+  Slice str;
+  if (GetLengthPrefixedSlice(input, &str)) {
+    return dst->DecodeFrom(str);
+  } else {
+    return false;
+  }
+}
+
+static bool GetLevel(Slice* input, int* level) {
+  uint32_t v;
+  if (GetVarint32(input, &v) && v < config::kNumLevels) {
+    *level = v;
+    return true;
+  } else {
+    return false;
+  }
+}
+
+Status VersionEdit::DecodeFrom(const Slice& src) {
+  Clear();
+  Slice input = src;
+  const char* msg = nullptr;
+  uint32_t tag;
+
+  // Temporary storage for parsing
+  int level;
+  uint64_t number;
+  FileMetaData f;
+  Slice str;
+  InternalKey key;
+
+  while (msg == nullptr && GetVarint32(&input, &tag)) {
+    switch (tag) {
+      case kComparator:
+        if (GetLengthPrefixedSlice(&input, &str)) {
+          comparator_ = str.ToString();
+          has_comparator_ = true;
+        } else {
+          msg = "comparator name";
+        }
+        break;
+
+      case kLogNumber:
+        if (GetVarint64(&input, &log_number_)) {
+          has_log_number_ = true;
+        } else {
+          msg = "log number";
+        }
+        break;
+
+      case kPrevLogNumber:
+        if (GetVarint64(&input, &prev_log_number_)) {
+          has_prev_log_number_ = true;
+        } else {
+          msg = "previous log number";
+        }
+        break;
+
+      case kNextFileNumber:
+        if (GetVarint64(&input, &next_file_number_)) {
+          has_next_file_number_ = true;
+        } else {
+          msg = "next file number";
+        }
+        break;
+
+      case kLastSequence:
+        if (GetVarint64(&input, &last_sequence_)) {
+          has_last_sequence_ = true;
+        } else {
+          msg = "last sequence number";
+        }
+        break;
+
+      case kCompactPointer:
+        if (GetLevel(&input, &level) && GetInternalKey(&input, &key)) {
+          compact_pointers_.push_back(std::make_pair(level, key));
+        } else {
+          msg = "compaction pointer";
+        }
+        break;
+
+      case kDeletedFile:
+        if (GetLevel(&input, &level) && GetVarint64(&input, &number)) {
+          deleted_files_.insert(std::make_pair(level, number));
+        } else {
+          msg = "deleted file";
+        }
+        break;
+
+      case kNewFile:
+        if (GetLevel(&input, &level) && GetVarint64(&input, &f.number) &&
+            GetVarint64(&input, &f.file_size) &&
+            GetInternalKey(&input, &f.smallest) &&
+            GetInternalKey(&input, &f.largest)) {
+          new_files_.push_back(std::make_pair(level, f));
+        } else {
+          msg = "new-file entry";
+        }
+        break;
+
+      default:
+        msg = "unknown tag";
+        break;
+    }
+  }
+
+  if (msg == nullptr && !input.empty()) {
+    msg = "invalid tag";
+  }
+
+  Status result;
+  if (msg != nullptr) {
+    result = Status::Corruption("VersionEdit", msg);
+  }
+  return result;
+}
+
+std::string VersionEdit::DebugString() const {
+  std::string r;
+  r.append("VersionEdit {");
+  if (has_comparator_) {
+    r.append("\n  Comparator: ");
+    r.append(comparator_);
+  }
+  if (has_log_number_) {
+    r.append("\n  LogNumber: ");
+    AppendNumberTo(&r, log_number_);
+  }
+  if (has_prev_log_number_) {
+    r.append("\n  PrevLogNumber: ");
+    AppendNumberTo(&r, prev_log_number_);
+  }
+  if (has_next_file_number_) {
+    r.append("\n  NextFile: ");
+    AppendNumberTo(&r, next_file_number_);
+  }
+  if (has_last_sequence_) {
+    r.append("\n  LastSeq: ");
+    AppendNumberTo(&r, last_sequence_);
+  }
+  for (size_t i = 0; i < compact_pointers_.size(); i++) {
+    r.append("\n  CompactPointer: ");
+    AppendNumberTo(&r, compact_pointers_[i].first);
+    r.append(" ");
+    r.append(compact_pointers_[i].second.DebugString());
+  }
+  for (const auto& deleted_files_kvp : deleted_files_) {
+    r.append("\n  RemoveFile: ");
+    AppendNumberTo(&r, deleted_files_kvp.first);
+    r.append(" ");
+    AppendNumberTo(&r, deleted_files_kvp.second);
+  }
+  for (size_t i = 0; i < new_files_.size(); i++) {
+    const FileMetaData& f = new_files_[i].second;
+    r.append("\n  AddFile: ");
+    AppendNumberTo(&r, new_files_[i].first);
+    r.append(" ");
+    AppendNumberTo(&r, f.number);
+    r.append(" ");
+    AppendNumberTo(&r, f.file_size);
+    r.append(" ");
+    r.append(f.smallest.DebugString());
+    r.append(" .. ");
+    r.append(f.largest.DebugString());
+  }
+  r.append("\n}\n");
+  return r;
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/db/version_edit.h b/leveldb_base/db/version_edit.h
new file mode 100644
index 0000000..137b4b1
--- /dev/null
+++ b/leveldb_base/db/version_edit.h
@@ -0,0 +1,106 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_DB_VERSION_EDIT_H_
+#define STORAGE_LEVELDB_DB_VERSION_EDIT_H_
+
+#include <set>
+#include <utility>
+#include <vector>
+
+#include "db/dbformat.h"
+
+namespace leveldb {
+
+class VersionSet;
+
+struct FileMetaData {
+  FileMetaData() : refs(0), allowed_seeks(1 << 30), file_size(0) {}
+
+  int refs;
+  int allowed_seeks;  // Seeks allowed until compaction
+  uint64_t number;
+  uint64_t file_size;    // File size in bytes
+  InternalKey smallest;  // Smallest internal key served by table
+  InternalKey largest;   // Largest internal key served by table
+};
+
+class VersionEdit {
+ public:
+  VersionEdit() { Clear(); }
+  ~VersionEdit() = default;
+
+  void Clear();
+
+  void SetComparatorName(const Slice& name) {
+    has_comparator_ = true;
+    comparator_ = name.ToString();
+  }
+  void SetLogNumber(uint64_t num) {
+    has_log_number_ = true;
+    log_number_ = num;
+  }
+  void SetPrevLogNumber(uint64_t num) {
+    has_prev_log_number_ = true;
+    prev_log_number_ = num;
+  }
+  void SetNextFile(uint64_t num) {
+    has_next_file_number_ = true;
+    next_file_number_ = num;
+  }
+  void SetLastSequence(SequenceNumber seq) {
+    has_last_sequence_ = true;
+    last_sequence_ = seq;
+  }
+  void SetCompactPointer(int level, const InternalKey& key) {
+    compact_pointers_.push_back(std::make_pair(level, key));
+  }
+
+  // Add the specified file at the specified number.
+  // REQUIRES: This version has not been saved (see VersionSet::SaveTo)
+  // REQUIRES: "smallest" and "largest" are smallest and largest keys in file
+  void AddFile(int level, uint64_t file, uint64_t file_size,
+               const InternalKey& smallest, const InternalKey& largest) {
+    FileMetaData f;
+    f.number = file;
+    f.file_size = file_size;
+    f.smallest = smallest;
+    f.largest = largest;
+    new_files_.push_back(std::make_pair(level, f));
+  }
+
+  // Delete the specified "file" from the specified "level".
+  void RemoveFile(int level, uint64_t file) {
+    deleted_files_.insert(std::make_pair(level, file));
+  }
+
+  void EncodeTo(std::string* dst) const;
+  Status DecodeFrom(const Slice& src);
+
+  std::string DebugString() const;
+
+ private:
+  friend class VersionSet;
+
+  typedef std::set<std::pair<int, uint64_t>> DeletedFileSet;
+
+  std::string comparator_;
+  uint64_t log_number_;
+  uint64_t prev_log_number_;
+  uint64_t next_file_number_;
+  SequenceNumber last_sequence_;
+  bool has_comparator_;
+  bool has_log_number_;
+  bool has_prev_log_number_;
+  bool has_next_file_number_;
+  bool has_last_sequence_;
+
+  std::vector<std::pair<int, InternalKey>> compact_pointers_;
+  DeletedFileSet deleted_files_;
+  std::vector<std::pair<int, FileMetaData>> new_files_;
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_DB_VERSION_EDIT_H_
diff --git a/leveldb_base/db/version_edit_test.cc b/leveldb_base/db/version_edit_test.cc
new file mode 100644
index 0000000..a108c15
--- /dev/null
+++ b/leveldb_base/db/version_edit_test.cc
@@ -0,0 +1,41 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "db/version_edit.h"
+
+#include "gtest/gtest.h"
+
+namespace leveldb {
+
+static void TestEncodeDecode(const VersionEdit& edit) {
+  std::string encoded, encoded2;
+  edit.EncodeTo(&encoded);
+  VersionEdit parsed;
+  Status s = parsed.DecodeFrom(encoded);
+  ASSERT_TRUE(s.ok()) << s.ToString();
+  parsed.EncodeTo(&encoded2);
+  ASSERT_EQ(encoded, encoded2);
+}
+
+TEST(VersionEditTest, EncodeDecode) {
+  static const uint64_t kBig = 1ull << 50;
+
+  VersionEdit edit;
+  for (int i = 0; i < 4; i++) {
+    TestEncodeDecode(edit);
+    edit.AddFile(3, kBig + 300 + i, kBig + 400 + i,
+                 InternalKey("foo", kBig + 500 + i, kTypeValue),
+                 InternalKey("zoo", kBig + 600 + i, kTypeDeletion));
+    edit.RemoveFile(4, kBig + 700 + i);
+    edit.SetCompactPointer(i, InternalKey("x", kBig + 900 + i, kTypeValue));
+  }
+
+  edit.SetComparatorName("foo");
+  edit.SetLogNumber(kBig + 100);
+  edit.SetNextFile(kBig + 200);
+  edit.SetLastSequence(kBig + 1000);
+  TestEncodeDecode(edit);
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/db/version_set.cc b/leveldb_base/db/version_set.cc
new file mode 100644
index 0000000..025943c
--- /dev/null
+++ b/leveldb_base/db/version_set.cc
@@ -0,0 +1,1570 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "db/version_set.h"
+
+#include <algorithm>
+#include <cstdio>
+
+#include "db/filename.h"
+#include "db/log_reader.h"
+#include "db/log_writer.h"
+#include "db/memtable.h"
+#include "db/table_cache.h"
+#include "leveldb/env.h"
+#include "leveldb/table_builder.h"
+#include "table/merger.h"
+#include "table/two_level_iterator.h"
+#include "util/coding.h"
+#include "util/logging.h"
+
+namespace leveldb {
+
+static size_t TargetFileSize(const Options* options) {
+  return options->max_file_size;
+}
+
+// Maximum bytes of overlaps in grandparent (i.e., level+2) before we
+// stop building a single file in a level->level+1 compaction.
+static int64_t MaxGrandParentOverlapBytes(const Options* options) {
+  return 10 * TargetFileSize(options);
+}
+
+// Maximum number of bytes in all compacted files.  We avoid expanding
+// the lower level file set of a compaction if it would make the
+// total compaction cover more than this many bytes.
+static int64_t ExpandedCompactionByteSizeLimit(const Options* options) {
+  return 25 * TargetFileSize(options);
+}
+
+static double MaxBytesForLevel(const Options* options, int level) {
+  // Note: the result for level zero is not really used since we set
+  // the level-0 compaction threshold based on number of files.
+
+  // Result for both level-0 and level-1
+  double result = 10. * 1048576.0;
+  while (level > 1) {
+    result *= 10;
+    level--;
+  }
+  return result;
+}
+
+static uint64_t MaxFileSizeForLevel(const Options* options, int level) {
+  // We could vary per level to reduce number of files?
+  return TargetFileSize(options);
+}
+
+static int64_t TotalFileSize(const std::vector<FileMetaData*>& files) {
+  int64_t sum = 0;
+  for (size_t i = 0; i < files.size(); i++) {
+    sum += files[i]->file_size;
+  }
+  return sum;
+}
+
+Version::~Version() {
+  assert(refs_ == 0);
+
+  // Remove from linked list
+  prev_->next_ = next_;
+  next_->prev_ = prev_;
+
+  // Drop references to files
+  for (int level = 0; level < config::kNumLevels; level++) {
+    for (size_t i = 0; i < files_[level].size(); i++) {
+      FileMetaData* f = files_[level][i];
+      assert(f->refs > 0);
+      f->refs--;
+      if (f->refs <= 0) {
+        delete f;
+      }
+    }
+  }
+}
+
+int FindFile(const InternalKeyComparator& icmp,
+             const std::vector<FileMetaData*>& files, const Slice& key) {
+  uint32_t left = 0;
+  uint32_t right = files.size();
+  while (left < right) {
+    uint32_t mid = (left + right) / 2;
+    const FileMetaData* f = files[mid];
+    if (icmp.InternalKeyComparator::Compare(f->largest.Encode(), key) < 0) {
+      // Key at "mid.largest" is < "target".  Therefore all
+      // files at or before "mid" are uninteresting.
+      left = mid + 1;
+    } else {
+      // Key at "mid.largest" is >= "target".  Therefore all files
+      // after "mid" are uninteresting.
+      right = mid;
+    }
+  }
+  return right;
+}
+
+static bool AfterFile(const Comparator* ucmp, const Slice* user_key,
+                      const FileMetaData* f) {
+  // null user_key occurs before all keys and is therefore never after *f
+  return (user_key != nullptr &&
+          ucmp->Compare(*user_key, f->largest.user_key()) > 0);
+}
+
+static bool BeforeFile(const Comparator* ucmp, const Slice* user_key,
+                       const FileMetaData* f) {
+  // null user_key occurs after all keys and is therefore never before *f
+  return (user_key != nullptr &&
+          ucmp->Compare(*user_key, f->smallest.user_key()) < 0);
+}
+
+bool SomeFileOverlapsRange(const InternalKeyComparator& icmp,
+                           bool disjoint_sorted_files,
+                           const std::vector<FileMetaData*>& files,
+                           const Slice* smallest_user_key,
+                           const Slice* largest_user_key) {
+  const Comparator* ucmp = icmp.user_comparator();
+  if (!disjoint_sorted_files) {
+    // Need to check against all files
+    for (size_t i = 0; i < files.size(); i++) {
+      const FileMetaData* f = files[i];
+      if (AfterFile(ucmp, smallest_user_key, f) ||
+          BeforeFile(ucmp, largest_user_key, f)) {
+        // No overlap
+      } else {
+        return true;  // Overlap
+      }
+    }
+    return false;
+  }
+
+  // Binary search over file list
+  uint32_t index = 0;
+  if (smallest_user_key != nullptr) {
+    // Find the earliest possible internal key for smallest_user_key
+    InternalKey small_key(*smallest_user_key, kMaxSequenceNumber,
+                          kValueTypeForSeek);
+    index = FindFile(icmp, files, small_key.Encode());
+  }
+
+  if (index >= files.size()) {
+    // beginning of range is after all files, so no overlap.
+    return false;
+  }
+
+  return !BeforeFile(ucmp, largest_user_key, files[index]);
+}
+
+// An internal iterator.  For a given version/level pair, yields
+// information about the files in the level.  For a given entry, key()
+// is the largest key that occurs in the file, and value() is an
+// 16-byte value containing the file number and file size, both
+// encoded using EncodeFixed64.
+class Version::LevelFileNumIterator : public Iterator {
+ public:
+  LevelFileNumIterator(const InternalKeyComparator& icmp,
+                       const std::vector<FileMetaData*>* flist)
+      : icmp_(icmp), flist_(flist), index_(flist->size()) {  // Marks as invalid
+  }
+  bool Valid() const override { return index_ < flist_->size(); }
+  void Seek(const Slice& target) override {
+    index_ = FindFile(icmp_, *flist_, target);
+  }
+  void SeekToFirst() override { index_ = 0; }
+  void SeekToLast() override {
+    index_ = flist_->empty() ? 0 : flist_->size() - 1;
+  }
+  void Next() override {
+    assert(Valid());
+    index_++;
+  }
+  void Prev() override {
+    assert(Valid());
+    if (index_ == 0) {
+      index_ = flist_->size();  // Marks as invalid
+    } else {
+      index_--;
+    }
+  }
+  Slice key() const override {
+    assert(Valid());
+    return (*flist_)[index_]->largest.Encode();
+  }
+  Slice value() const override {
+    assert(Valid());
+    EncodeFixed64(value_buf_, (*flist_)[index_]->number);
+    EncodeFixed64(value_buf_ + 8, (*flist_)[index_]->file_size);
+    return Slice(value_buf_, sizeof(value_buf_));
+  }
+  Status status() const override { return Status::OK(); }
+
+ private:
+  const InternalKeyComparator icmp_;
+  const std::vector<FileMetaData*>* const flist_;
+  uint32_t index_;
+
+  // Backing store for value().  Holds the file number and size.
+  mutable char value_buf_[16];
+};
+
+static Iterator* GetFileIterator(void* arg, const ReadOptions& options,
+                                 const Slice& file_value) {
+  TableCache* cache = reinterpret_cast<TableCache*>(arg);
+  if (file_value.size() != 16) {
+    return NewErrorIterator(
+        Status::Corruption("FileReader invoked with unexpected value"));
+  } else {
+    return cache->NewIterator(options, DecodeFixed64(file_value.data()),
+                              DecodeFixed64(file_value.data() + 8));
+  }
+}
+
+Iterator* Version::NewConcatenatingIterator(const ReadOptions& options,
+                                            int level) const {
+  return NewTwoLevelIterator(
+      new LevelFileNumIterator(vset_->icmp_, &files_[level]), &GetFileIterator,
+      vset_->table_cache_, options);
+}
+
+void Version::AddIterators(const ReadOptions& options,
+                           std::vector<Iterator*>* iters) {
+  // Merge all level zero files together since they may overlap
+  for (size_t i = 0; i < files_[0].size(); i++) {
+    iters->push_back(vset_->table_cache_->NewIterator(
+        options, files_[0][i]->number, files_[0][i]->file_size));
+  }
+
+  // For levels > 0, we can use a concatenating iterator that sequentially
+  // walks through the non-overlapping files in the level, opening them
+  // lazily.
+  for (int level = 1; level < config::kNumLevels; level++) {
+    if (!files_[level].empty()) {
+      iters->push_back(NewConcatenatingIterator(options, level));
+    }
+  }
+}
+
+// Callback from TableCache::Get()
+namespace {
+enum SaverState {
+  kNotFound,
+  kFound,
+  kDeleted,
+  kCorrupt,
+};
+struct Saver {
+  SaverState state;
+  const Comparator* ucmp;
+  Slice user_key;
+  std::string* value;
+};
+}  // namespace
+static void SaveValue(void* arg, const Slice& ikey, const Slice& v) {
+  Saver* s = reinterpret_cast<Saver*>(arg);
+  ParsedInternalKey parsed_key;
+  if (!ParseInternalKey(ikey, &parsed_key)) {
+    s->state = kCorrupt;
+  } else {
+    if (s->ucmp->Compare(parsed_key.user_key, s->user_key) == 0) {
+      s->state = (parsed_key.type == kTypeValue) ? kFound : kDeleted;
+      if (s->state == kFound) {
+        s->value->assign(v.data(), v.size());
+      }
+    }
+  }
+}
+
+static bool NewestFirst(FileMetaData* a, FileMetaData* b) {
+  return a->number > b->number;
+}
+
+void Version::ForEachOverlapping(Slice user_key, Slice internal_key, void* arg,
+                                 bool (*func)(void*, int, FileMetaData*)) {
+  const Comparator* ucmp = vset_->icmp_.user_comparator();
+
+  // Search level-0 in order from newest to oldest.
+  std::vector<FileMetaData*> tmp;
+  tmp.reserve(files_[0].size());
+  for (uint32_t i = 0; i < files_[0].size(); i++) {
+    FileMetaData* f = files_[0][i];
+    if (ucmp->Compare(user_key, f->smallest.user_key()) >= 0 &&
+        ucmp->Compare(user_key, f->largest.user_key()) <= 0) {
+      tmp.push_back(f);
+    }
+  }
+  if (!tmp.empty()) {
+    std::sort(tmp.begin(), tmp.end(), NewestFirst);
+    for (uint32_t i = 0; i < tmp.size(); i++) {
+      if (!(*func)(arg, 0, tmp[i])) {
+        return;
+      }
+    }
+  }
+
+  // Search other levels.
+  for (int level = 1; level < config::kNumLevels; level++) {
+    size_t num_files = files_[level].size();
+    if (num_files == 0) continue;
+
+    // Binary search to find earliest index whose largest key >= internal_key.
+    uint32_t index = FindFile(vset_->icmp_, files_[level], internal_key);
+    if (index < num_files) {
+      FileMetaData* f = files_[level][index];
+      if (ucmp->Compare(user_key, f->smallest.user_key()) < 0) {
+        // All of "f" is past any data for user_key
+      } else {
+        if (!(*func)(arg, level, f)) {
+          return;
+        }
+      }
+    }
+  }
+}
+
+Status Version::Get(const ReadOptions& options, const LookupKey& k,
+                    std::string* value, GetStats* stats) {
+  stats->seek_file = nullptr;
+  stats->seek_file_level = -1;
+
+  struct State {
+    Saver saver;
+    GetStats* stats;
+    const ReadOptions* options;
+    Slice ikey;
+    FileMetaData* last_file_read;
+    int last_file_read_level;
+
+    VersionSet* vset;
+    Status s;
+    bool found;
+
+    static bool Match(void* arg, int level, FileMetaData* f) {
+      State* state = reinterpret_cast<State*>(arg);
+
+      if (state->stats->seek_file == nullptr &&
+          state->last_file_read != nullptr) {
+        // We have had more than one seek for this read.  Charge the 1st file.
+        state->stats->seek_file = state->last_file_read;
+        state->stats->seek_file_level = state->last_file_read_level;
+      }
+
+      state->last_file_read = f;
+      state->last_file_read_level = level;
+
+      state->s = state->vset->table_cache_->Get(*state->options, f->number,
+                                                f->file_size, state->ikey,
+                                                &state->saver, SaveValue);
+      if (!state->s.ok()) {
+        state->found = true;
+        return false;
+      }
+      switch (state->saver.state) {
+        case kNotFound:
+          return true;  // Keep searching in other files
+        case kFound:
+          state->found = true;
+          return false;
+        case kDeleted:
+          return false;
+        case kCorrupt:
+          state->s =
+              Status::Corruption("corrupted key for ", state->saver.user_key);
+          state->found = true;
+          return false;
+      }
+
+      // Not reached. Added to avoid false compilation warnings of
+      // "control reaches end of non-void function".
+      return false;
+    }
+  };
+
+  State state;
+  state.found = false;
+  state.stats = stats;
+  state.last_file_read = nullptr;
+  state.last_file_read_level = -1;
+
+  state.options = &options;
+  state.ikey = k.internal_key();
+  state.vset = vset_;
+
+  state.saver.state = kNotFound;
+  state.saver.ucmp = vset_->icmp_.user_comparator();
+  state.saver.user_key = k.user_key();
+  state.saver.value = value;
+
+  ForEachOverlapping(state.saver.user_key, state.ikey, &state, &State::Match);
+
+  return state.found ? state.s : Status::NotFound(Slice());
+}
+
+bool Version::UpdateStats(const GetStats& stats) {
+  FileMetaData* f = stats.seek_file;
+  if (f != nullptr) {
+    f->allowed_seeks--;
+    if (f->allowed_seeks <= 0 && file_to_compact_ == nullptr) {
+      file_to_compact_ = f;
+      file_to_compact_level_ = stats.seek_file_level;
+      return true;
+    }
+  }
+  return false;
+}
+
+bool Version::RecordReadSample(Slice internal_key) {
+  ParsedInternalKey ikey;
+  if (!ParseInternalKey(internal_key, &ikey)) {
+    return false;
+  }
+
+  struct State {
+    GetStats stats;  // Holds first matching file
+    int matches;
+
+    static bool Match(void* arg, int level, FileMetaData* f) {
+      State* state = reinterpret_cast<State*>(arg);
+      state->matches++;
+      if (state->matches == 1) {
+        // Remember first match.
+        state->stats.seek_file = f;
+        state->stats.seek_file_level = level;
+      }
+      // We can stop iterating once we have a second match.
+      return state->matches < 2;
+    }
+  };
+
+  State state;
+  state.matches = 0;
+  ForEachOverlapping(ikey.user_key, internal_key, &state, &State::Match);
+
+  // Must have at least two matches since we want to merge across
+  // files. But what if we have a single file that contains many
+  // overwrites and deletions?  Should we have another mechanism for
+  // finding such files?
+  if (state.matches >= 2) {
+    // 1MB cost is about 1 seek (see comment in Builder::Apply).
+    return UpdateStats(state.stats);
+  }
+  return false;
+}
+
+void Version::Ref() { ++refs_; }
+
+void Version::Unref() {
+  assert(this != &vset_->dummy_versions_);
+  assert(refs_ >= 1);
+  --refs_;
+  if (refs_ == 0) {
+    delete this;
+  }
+}
+
+bool Version::OverlapInLevel(int level, const Slice* smallest_user_key,
+                             const Slice* largest_user_key) {
+  return SomeFileOverlapsRange(vset_->icmp_, (level > 0), files_[level],
+                               smallest_user_key, largest_user_key);
+}
+
+int Version::PickLevelForMemTableOutput(const Slice& smallest_user_key,
+                                        const Slice& largest_user_key) {
+  int level = 0;
+  if (!OverlapInLevel(0, &smallest_user_key, &largest_user_key)) {
+    // Push to next level if there is no overlap in next level,
+    // and the #bytes overlapping in the level after that are limited.
+    InternalKey start(smallest_user_key, kMaxSequenceNumber, kValueTypeForSeek);
+    InternalKey limit(largest_user_key, 0, static_cast<ValueType>(0));
+    std::vector<FileMetaData*> overlaps;
+    while (level < config::kMaxMemCompactLevel) {
+      if (OverlapInLevel(level + 1, &smallest_user_key, &largest_user_key)) {
+        break;
+      }
+      if (level + 2 < config::kNumLevels) {
+        // Check that file does not overlap too many grandparent bytes.
+        GetOverlappingInputs(level + 2, &start, &limit, &overlaps);
+        const int64_t sum = TotalFileSize(overlaps);
+        if (sum > MaxGrandParentOverlapBytes(vset_->options_)) {
+          break;
+        }
+      }
+      level++;
+    }
+  }
+  return level;
+}
+
+// Store in "*inputs" all files in "level" that overlap [begin,end]
+void Version::GetOverlappingInputs(int level, const InternalKey* begin,
+                                   const InternalKey* end,
+                                   std::vector<FileMetaData*>* inputs) {
+  assert(level >= 0);
+  assert(level < config::kNumLevels);
+  inputs->clear();
+  Slice user_begin, user_end;
+  if (begin != nullptr) {
+    user_begin = begin->user_key();
+  }
+  if (end != nullptr) {
+    user_end = end->user_key();
+  }
+  const Comparator* user_cmp = vset_->icmp_.user_comparator();
+  for (size_t i = 0; i < files_[level].size();) {
+    FileMetaData* f = files_[level][i++];
+    const Slice file_start = f->smallest.user_key();
+    const Slice file_limit = f->largest.user_key();
+    if (begin != nullptr && user_cmp->Compare(file_limit, user_begin) < 0) {
+      // "f" is completely before specified range; skip it
+    } else if (end != nullptr && user_cmp->Compare(file_start, user_end) > 0) {
+      // "f" is completely after specified range; skip it
+    } else {
+      inputs->push_back(f);
+      if (level == 0) {
+        // Level-0 files may overlap each other.  So check if the newly
+        // added file has expanded the range.  If so, restart search.
+        if (begin != nullptr && user_cmp->Compare(file_start, user_begin) < 0) {
+          user_begin = file_start;
+          inputs->clear();
+          i = 0;
+        } else if (end != nullptr &&
+                   user_cmp->Compare(file_limit, user_end) > 0) {
+          user_end = file_limit;
+          inputs->clear();
+          i = 0;
+        }
+      }
+    }
+  }
+}
+
+std::string Version::DebugString() const {
+  std::string r;
+  for (int level = 0; level < config::kNumLevels; level++) {
+    // E.g.,
+    //   --- level 1 ---
+    //   17:123['a' .. 'd']
+    //   20:43['e' .. 'g']
+    r.append("--- level ");
+    AppendNumberTo(&r, level);
+    r.append(" ---\n");
+    const std::vector<FileMetaData*>& files = files_[level];
+    for (size_t i = 0; i < files.size(); i++) {
+      r.push_back(' ');
+      AppendNumberTo(&r, files[i]->number);
+      r.push_back(':');
+      AppendNumberTo(&r, files[i]->file_size);
+      r.append("[");
+      r.append(files[i]->smallest.DebugString());
+      r.append(" .. ");
+      r.append(files[i]->largest.DebugString());
+      r.append("]\n");
+    }
+  }
+  return r;
+}
+
+// A helper class so we can efficiently apply a whole sequence
+// of edits to a particular state without creating intermediate
+// Versions that contain full copies of the intermediate state.
+class VersionSet::Builder {
+ private:
+  // Helper to sort by v->files_[file_number].smallest
+  struct BySmallestKey {
+    const InternalKeyComparator* internal_comparator;
+
+    bool operator()(FileMetaData* f1, FileMetaData* f2) const {
+      int r = internal_comparator->Compare(f1->smallest, f2->smallest);
+      if (r != 0) {
+        return (r < 0);
+      } else {
+        // Break ties by file number
+        return (f1->number < f2->number);
+      }
+    }
+  };
+
+  typedef std::set<FileMetaData*, BySmallestKey> FileSet;
+  struct LevelState {
+    std::set<uint64_t> deleted_files;
+    FileSet* added_files;
+  };
+
+  VersionSet* vset_;
+  Version* base_;
+  LevelState levels_[config::kNumLevels];
+
+ public:
+  // Initialize a builder with the files from *base and other info from *vset
+  Builder(VersionSet* vset, Version* base) : vset_(vset), base_(base) {
+    base_->Ref();
+    BySmallestKey cmp;
+    cmp.internal_comparator = &vset_->icmp_;
+    for (int level = 0; level < config::kNumLevels; level++) {
+      levels_[level].added_files = new FileSet(cmp);
+    }
+  }
+
+  ~Builder() {
+    for (int level = 0; level < config::kNumLevels; level++) {
+      const FileSet* added = levels_[level].added_files;
+      std::vector<FileMetaData*> to_unref;
+      to_unref.reserve(added->size());
+      for (FileSet::const_iterator it = added->begin(); it != added->end();
+           ++it) {
+        to_unref.push_back(*it);
+      }
+      delete added;
+      for (uint32_t i = 0; i < to_unref.size(); i++) {
+        FileMetaData* f = to_unref[i];
+        f->refs--;
+        if (f->refs <= 0) {
+          delete f;
+        }
+      }
+    }
+    base_->Unref();
+  }
+
+  // Apply all of the edits in *edit to the current state.
+  void Apply(const VersionEdit* edit) {
+    // Update compaction pointers
+    for (size_t i = 0; i < edit->compact_pointers_.size(); i++) {
+      const int level = edit->compact_pointers_[i].first;
+      vset_->compact_pointer_[level] =
+          edit->compact_pointers_[i].second.Encode().ToString();
+    }
+
+    // Delete files
+    for (const auto& deleted_file_set_kvp : edit->deleted_files_) {
+      const int level = deleted_file_set_kvp.first;
+      const uint64_t number = deleted_file_set_kvp.second;
+      levels_[level].deleted_files.insert(number);
+    }
+
+    // Add new files
+    for (size_t i = 0; i < edit->new_files_.size(); i++) {
+      const int level = edit->new_files_[i].first;
+      FileMetaData* f = new FileMetaData(edit->new_files_[i].second);
+      f->refs = 1;
+
+      // We arrange to automatically compact this file after
+      // a certain number of seeks.  Let's assume:
+      //   (1) One seek costs 10ms
+      //   (2) Writing or reading 1MB costs 10ms (100MB/s)
+      //   (3) A compaction of 1MB does 25MB of IO:
+      //         1MB read from this level
+      //         10-12MB read from next level (boundaries may be misaligned)
+      //         10-12MB written to next level
+      // This implies that 25 seeks cost the same as the compaction
+      // of 1MB of data.  I.e., one seek costs approximately the
+      // same as the compaction of 40KB of data.  We are a little
+      // conservative and allow approximately one seek for every 16KB
+      // of data before triggering a compaction.
+      f->allowed_seeks = static_cast<int>((f->file_size / 16384U));
+      if (f->allowed_seeks < 100) f->allowed_seeks = 100;
+
+      levels_[level].deleted_files.erase(f->number);
+      levels_[level].added_files->insert(f);
+    }
+  }
+
+  // Save the current state in *v.
+  void SaveTo(Version* v) {
+    BySmallestKey cmp;
+    cmp.internal_comparator = &vset_->icmp_;
+    for (int level = 0; level < config::kNumLevels; level++) {
+      // Merge the set of added files with the set of pre-existing files.
+      // Drop any deleted files.  Store the result in *v.
+      const std::vector<FileMetaData*>& base_files = base_->files_[level];
+      std::vector<FileMetaData*>::const_iterator base_iter = base_files.begin();
+      std::vector<FileMetaData*>::const_iterator base_end = base_files.end();
+      const FileSet* added_files = levels_[level].added_files;
+      v->files_[level].reserve(base_files.size() + added_files->size());
+      for (const auto& added_file : *added_files) {
+        // Add all smaller files listed in base_
+        for (std::vector<FileMetaData*>::const_iterator bpos =
+                 std::upper_bound(base_iter, base_end, added_file, cmp);
+             base_iter != bpos; ++base_iter) {
+          MaybeAddFile(v, level, *base_iter);
+        }
+
+        MaybeAddFile(v, level, added_file);
+      }
+
+      // Add remaining base files
+      for (; base_iter != base_end; ++base_iter) {
+        MaybeAddFile(v, level, *base_iter);
+      }
+
+#ifndef NDEBUG
+      // Make sure there is no overlap in levels > 0
+      if (level > 0) {
+        for (uint32_t i = 1; i < v->files_[level].size(); i++) {
+          const InternalKey& prev_end = v->files_[level][i - 1]->largest;
+          const InternalKey& this_begin = v->files_[level][i]->smallest;
+          if (vset_->icmp_.Compare(prev_end, this_begin) >= 0) {
+            std::fprintf(stderr, "overlapping ranges in same level %s vs. %s\n",
+                         prev_end.DebugString().c_str(),
+                         this_begin.DebugString().c_str());
+            std::abort();
+          }
+        }
+      }
+#endif
+    }
+  }
+
+  void MaybeAddFile(Version* v, int level, FileMetaData* f) {
+    if (levels_[level].deleted_files.count(f->number) > 0) {
+      // File is deleted: do nothing
+    } else {
+      std::vector<FileMetaData*>* files = &v->files_[level];
+      if (level > 0 && !files->empty()) {
+        // Must not overlap
+        assert(vset_->icmp_.Compare((*files)[files->size() - 1]->largest,
+                                    f->smallest) < 0);
+      }
+      f->refs++;
+      files->push_back(f);
+    }
+  }
+};
+
+VersionSet::VersionSet(const std::string& dbname, const Options* options,
+                       TableCache* table_cache,
+                       const InternalKeyComparator* cmp)
+    : env_(options->env),
+      dbname_(dbname),
+      options_(options),
+      table_cache_(table_cache),
+      icmp_(*cmp),
+      next_file_number_(2),
+      manifest_file_number_(0),  // Filled by Recover()
+      last_sequence_(0),
+      log_number_(0),
+      prev_log_number_(0),
+      descriptor_file_(nullptr),
+      descriptor_log_(nullptr),
+      dummy_versions_(this),
+      current_(nullptr) {
+  AppendVersion(new Version(this));
+}
+
+VersionSet::~VersionSet() {
+  current_->Unref();
+  assert(dummy_versions_.next_ == &dummy_versions_);  // List must be empty
+  delete descriptor_log_;
+  delete descriptor_file_;
+}
+
+void VersionSet::AppendVersion(Version* v) {
+  // Make "v" current
+  assert(v->refs_ == 0);
+  assert(v != current_);
+  if (current_ != nullptr) {
+    current_->Unref();
+  }
+  current_ = v;
+  v->Ref();
+
+  // Append to linked list
+  v->prev_ = dummy_versions_.prev_;
+  v->next_ = &dummy_versions_;
+  v->prev_->next_ = v;
+  v->next_->prev_ = v;
+}
+
+Status VersionSet::LogAndApply(VersionEdit* edit, port::Mutex* mu) {
+  if (edit->has_log_number_) {
+    assert(edit->log_number_ >= log_number_);
+    assert(edit->log_number_ < next_file_number_);
+  } else {
+    edit->SetLogNumber(log_number_);
+  }
+
+  if (!edit->has_prev_log_number_) {
+    edit->SetPrevLogNumber(prev_log_number_);
+  }
+
+  edit->SetNextFile(next_file_number_);
+  edit->SetLastSequence(last_sequence_);
+
+  Version* v = new Version(this);
+  {
+    Builder builder(this, current_);
+    builder.Apply(edit);
+    builder.SaveTo(v);
+  }
+  Finalize(v);
+
+  // Initialize new descriptor log file if necessary by creating
+  // a temporary file that contains a snapshot of the current version.
+  std::string new_manifest_file;
+  Status s;
+  if (descriptor_log_ == nullptr) {
+    // No reason to unlock *mu here since we only hit this path in the
+    // first call to LogAndApply (when opening the database).
+    assert(descriptor_file_ == nullptr);
+    new_manifest_file = DescriptorFileName(dbname_, manifest_file_number_);
+    s = env_->NewWritableFile(new_manifest_file, &descriptor_file_);
+    if (s.ok()) {
+      descriptor_log_ = new log::Writer(descriptor_file_);
+      s = WriteSnapshot(descriptor_log_);
+    }
+  }
+
+  // Unlock during expensive MANIFEST log write
+  {
+    mu->Unlock();
+
+    // Write new record to MANIFEST log
+    if (s.ok()) {
+      std::string record;
+      edit->EncodeTo(&record);
+      s = descriptor_log_->AddRecord(record);
+      if (s.ok()) {
+        s = descriptor_file_->Sync();
+      }
+      if (!s.ok()) {
+        Log(options_->info_log, "MANIFEST write: %s\n", s.ToString().c_str());
+      }
+    }
+
+    // If we just created a new descriptor file, install it by writing a
+    // new CURRENT file that points to it.
+    if (s.ok() && !new_manifest_file.empty()) {
+      s = SetCurrentFile(env_, dbname_, manifest_file_number_);
+    }
+
+    mu->Lock();
+  }
+
+  // Install the new version
+  if (s.ok()) {
+    AppendVersion(v);
+    log_number_ = edit->log_number_;
+    prev_log_number_ = edit->prev_log_number_;
+  } else {
+    delete v;
+    if (!new_manifest_file.empty()) {
+      delete descriptor_log_;
+      delete descriptor_file_;
+      descriptor_log_ = nullptr;
+      descriptor_file_ = nullptr;
+      env_->RemoveFile(new_manifest_file);
+    }
+  }
+
+  return s;
+}
+
+Status VersionSet::Recover(bool* save_manifest) {
+  struct LogReporter : public log::Reader::Reporter {
+    Status* status;
+    void Corruption(size_t bytes, const Status& s) override {
+      if (this->status->ok()) *this->status = s;
+    }
+  };
+
+  // Read "CURRENT" file, which contains a pointer to the current manifest file
+  std::string current;
+  Status s = ReadFileToString(env_, CurrentFileName(dbname_), &current);
+  if (!s.ok()) {
+    return s;
+  }
+  if (current.empty() || current[current.size() - 1] != '\n') {
+    return Status::Corruption("CURRENT file does not end with newline");
+  }
+  current.resize(current.size() - 1);
+
+  std::string dscname = dbname_ + "/" + current;
+  SequentialFile* file;
+  s = env_->NewSequentialFile(dscname, &file);
+  if (!s.ok()) {
+    if (s.IsNotFound()) {
+      return Status::Corruption("CURRENT points to a non-existent file",
+                                s.ToString());
+    }
+    return s;
+  }
+
+  bool have_log_number = false;
+  bool have_prev_log_number = false;
+  bool have_next_file = false;
+  bool have_last_sequence = false;
+  uint64_t next_file = 0;
+  uint64_t last_sequence = 0;
+  uint64_t log_number = 0;
+  uint64_t prev_log_number = 0;
+  Builder builder(this, current_);
+  int read_records = 0;
+
+  {
+    LogReporter reporter;
+    reporter.status = &s;
+    log::Reader reader(file, &reporter, true /*checksum*/,
+                       0 /*initial_offset*/);
+    Slice record;
+    std::string scratch;
+    while (reader.ReadRecord(&record, &scratch) && s.ok()) {
+      ++read_records;
+      VersionEdit edit;
+      s = edit.DecodeFrom(record);
+      if (s.ok()) {
+        if (edit.has_comparator_ &&
+            edit.comparator_ != icmp_.user_comparator()->Name()) {
+          s = Status::InvalidArgument(
+              edit.comparator_ + " does not match existing comparator ",
+              icmp_.user_comparator()->Name());
+        }
+      }
+
+      if (s.ok()) {
+        builder.Apply(&edit);
+      }
+
+      if (edit.has_log_number_) {
+        log_number = edit.log_number_;
+        have_log_number = true;
+      }
+
+      if (edit.has_prev_log_number_) {
+        prev_log_number = edit.prev_log_number_;
+        have_prev_log_number = true;
+      }
+
+      if (edit.has_next_file_number_) {
+        next_file = edit.next_file_number_;
+        have_next_file = true;
+      }
+
+      if (edit.has_last_sequence_) {
+        last_sequence = edit.last_sequence_;
+        have_last_sequence = true;
+      }
+    }
+  }
+  delete file;
+  file = nullptr;
+
+  if (s.ok()) {
+    if (!have_next_file) {
+      s = Status::Corruption("no meta-nextfile entry in descriptor");
+    } else if (!have_log_number) {
+      s = Status::Corruption("no meta-lognumber entry in descriptor");
+    } else if (!have_last_sequence) {
+      s = Status::Corruption("no last-sequence-number entry in descriptor");
+    }
+
+    if (!have_prev_log_number) {
+      prev_log_number = 0;
+    }
+
+    MarkFileNumberUsed(prev_log_number);
+    MarkFileNumberUsed(log_number);
+  }
+
+  if (s.ok()) {
+    Version* v = new Version(this);
+    builder.SaveTo(v);
+    // Install recovered version
+    Finalize(v);
+    AppendVersion(v);
+    manifest_file_number_ = next_file;
+    next_file_number_ = next_file + 1;
+    last_sequence_ = last_sequence;
+    log_number_ = log_number;
+    prev_log_number_ = prev_log_number;
+
+    // See if we can reuse the existing MANIFEST file.
+    if (ReuseManifest(dscname, current)) {
+      // No need to save new manifest
+    } else {
+      *save_manifest = true;
+    }
+  } else {
+    std::string error = s.ToString();
+    Log(options_->info_log, "Error recovering version set with %d records: %s",
+        read_records, error.c_str());
+  }
+
+  return s;
+}
+
+bool VersionSet::ReuseManifest(const std::string& dscname,
+                               const std::string& dscbase) {
+  if (!options_->reuse_logs) {
+    return false;
+  }
+  FileType manifest_type;
+  uint64_t manifest_number;
+  uint64_t manifest_size;
+  if (!ParseFileName(dscbase, &manifest_number, &manifest_type) ||
+      manifest_type != kDescriptorFile ||
+      !env_->GetFileSize(dscname, &manifest_size).ok() ||
+      // Make new compacted MANIFEST if old one is too big
+      manifest_size >= TargetFileSize(options_)) {
+    return false;
+  }
+
+  assert(descriptor_file_ == nullptr);
+  assert(descriptor_log_ == nullptr);
+  Status r = env_->NewAppendableFile(dscname, &descriptor_file_);
+  if (!r.ok()) {
+    Log(options_->info_log, "Reuse MANIFEST: %s\n", r.ToString().c_str());
+    assert(descriptor_file_ == nullptr);
+    return false;
+  }
+
+  Log(options_->info_log, "Reusing MANIFEST %s\n", dscname.c_str());
+  descriptor_log_ = new log::Writer(descriptor_file_, manifest_size);
+  manifest_file_number_ = manifest_number;
+  return true;
+}
+
+void VersionSet::MarkFileNumberUsed(uint64_t number) {
+  if (next_file_number_ <= number) {
+    next_file_number_ = number + 1;
+  }
+}
+
+void VersionSet::Finalize(Version* v) {
+  // Precomputed best level for next compaction
+  int best_level = -1;
+  double best_score = -1;
+
+  for (int level = 0; level < config::kNumLevels - 1; level++) {
+    double score;
+    if (level == 0) {
+      // We treat level-0 specially by bounding the number of files
+      // instead of number of bytes for two reasons:
+      //
+      // (1) With larger write-buffer sizes, it is nice not to do too
+      // many level-0 compactions.
+      //
+      // (2) The files in level-0 are merged on every read and
+      // therefore we wish to avoid too many files when the individual
+      // file size is small (perhaps because of a small write-buffer
+      // setting, or very high compression ratios, or lots of
+      // overwrites/deletions).
+      score = v->files_[level].size() /
+              static_cast<double>(config::kL0_CompactionTrigger);
+    } else {
+      // Compute the ratio of current size to size limit.
+      const uint64_t level_bytes = TotalFileSize(v->files_[level]);
+      score =
+          static_cast<double>(level_bytes) / MaxBytesForLevel(options_, level);
+    }
+
+    if (score > best_score) {
+      best_level = level;
+      best_score = score;
+    }
+  }
+
+  v->compaction_level_ = best_level;
+  v->compaction_score_ = best_score;
+}
+
+Status VersionSet::WriteSnapshot(log::Writer* log) {
+  // TODO: Break up into multiple records to reduce memory usage on recovery?
+
+  // Save metadata
+  VersionEdit edit;
+  edit.SetComparatorName(icmp_.user_comparator()->Name());
+
+  // Save compaction pointers
+  for (int level = 0; level < config::kNumLevels; level++) {
+    if (!compact_pointer_[level].empty()) {
+      InternalKey key;
+      key.DecodeFrom(compact_pointer_[level]);
+      edit.SetCompactPointer(level, key);
+    }
+  }
+
+  // Save files
+  for (int level = 0; level < config::kNumLevels; level++) {
+    const std::vector<FileMetaData*>& files = current_->files_[level];
+    for (size_t i = 0; i < files.size(); i++) {
+      const FileMetaData* f = files[i];
+      edit.AddFile(level, f->number, f->file_size, f->smallest, f->largest);
+    }
+  }
+
+  std::string record;
+  edit.EncodeTo(&record);
+  return log->AddRecord(record);
+}
+
+int VersionSet::NumLevelFiles(int level) const {
+  assert(level >= 0);
+  assert(level < config::kNumLevels);
+  return current_->files_[level].size();
+}
+
+const char* VersionSet::LevelSummary(LevelSummaryStorage* scratch) const {
+  // Update code if kNumLevels changes
+  static_assert(config::kNumLevels == 7, "");
+  std::snprintf(
+      scratch->buffer, sizeof(scratch->buffer), "files[ %d %d %d %d %d %d %d ]",
+      int(current_->files_[0].size()), int(current_->files_[1].size()),
+      int(current_->files_[2].size()), int(current_->files_[3].size()),
+      int(current_->files_[4].size()), int(current_->files_[5].size()),
+      int(current_->files_[6].size()));
+  return scratch->buffer;
+}
+
+uint64_t VersionSet::ApproximateOffsetOf(Version* v, const InternalKey& ikey) {
+  uint64_t result = 0;
+  for (int level = 0; level < config::kNumLevels; level++) {
+    const std::vector<FileMetaData*>& files = v->files_[level];
+    for (size_t i = 0; i < files.size(); i++) {
+      if (icmp_.Compare(files[i]->largest, ikey) <= 0) {
+        // Entire file is before "ikey", so just add the file size
+        result += files[i]->file_size;
+        //printf("%d\n",level);
+      } else if (icmp_.Compare(files[i]->smallest, ikey) > 0) {
+        // Entire file is after "ikey", so ignore
+        if (level > 0) {
+          // Files other than level 0 are sorted by meta->smallest, so
+          // no further files in this level will contain data for
+          // "ikey".
+          break;
+        }
+      } else {
+        // "ikey" falls in the range for this table.  Add the
+        // approximate offset of "ikey" within the table.
+        Table* tableptr;
+        Iterator* iter = table_cache_->NewIterator(
+            ReadOptions(), files[i]->number, files[i]->file_size, &tableptr);
+        if (tableptr != nullptr) {
+          result += tableptr->ApproximateOffsetOf(ikey.Encode());
+        }
+        delete iter;
+      }
+    }
+  }
+  return result;
+}
+
+void VersionSet::AddLiveFiles(std::set<uint64_t>* live) {
+  for (Version* v = dummy_versions_.next_; v != &dummy_versions_;
+       v = v->next_) {
+    for (int level = 0; level < config::kNumLevels; level++) {
+      const std::vector<FileMetaData*>& files = v->files_[level];
+      for (size_t i = 0; i < files.size(); i++) {
+        live->insert(files[i]->number);
+      }
+    }
+  }
+}
+
+int64_t VersionSet::NumLevelBytes(int level) const {
+  assert(level >= 0);
+  assert(level < config::kNumLevels);
+  return TotalFileSize(current_->files_[level]);
+}
+
+int64_t VersionSet::MaxNextLevelOverlappingBytes() {
+  int64_t result = 0;
+  std::vector<FileMetaData*> overlaps;
+  for (int level = 1; level < config::kNumLevels - 1; level++) {
+    for (size_t i = 0; i < current_->files_[level].size(); i++) {
+      const FileMetaData* f = current_->files_[level][i];
+      current_->GetOverlappingInputs(level + 1, &f->smallest, &f->largest,
+                                     &overlaps);
+      const int64_t sum = TotalFileSize(overlaps);
+      if (sum > result) {
+        result = sum;
+      }
+    }
+  }
+  return result;
+}
+
+// Stores the minimal range that covers all entries in inputs in
+// *smallest, *largest.
+// REQUIRES: inputs is not empty
+void VersionSet::GetRange(const std::vector<FileMetaData*>& inputs,
+                          InternalKey* smallest, InternalKey* largest) {
+  assert(!inputs.empty());
+  smallest->Clear();
+  largest->Clear();
+  for (size_t i = 0; i < inputs.size(); i++) {
+    FileMetaData* f = inputs[i];
+    if (i == 0) {
+      *smallest = f->smallest;
+      *largest = f->largest;
+    } else {
+      if (icmp_.Compare(f->smallest, *smallest) < 0) {
+        *smallest = f->smallest;
+      }
+      if (icmp_.Compare(f->largest, *largest) > 0) {
+        *largest = f->largest;
+      }
+    }
+  }
+}
+
+// Stores the minimal range that covers all entries in inputs1 and inputs2
+// in *smallest, *largest.
+// REQUIRES: inputs is not empty
+void VersionSet::GetRange2(const std::vector<FileMetaData*>& inputs1,
+                           const std::vector<FileMetaData*>& inputs2,
+                           InternalKey* smallest, InternalKey* largest) {
+  std::vector<FileMetaData*> all = inputs1;
+  all.insert(all.end(), inputs2.begin(), inputs2.end());
+  GetRange(all, smallest, largest);
+}
+
+Iterator* VersionSet::MakeInputIterator(Compaction* c) {
+  ReadOptions options;
+  options.verify_checksums = options_->paranoid_checks;
+  options.fill_cache = false;
+
+  // Level-0 files have to be merged together.  For other levels,
+  // we will make a concatenating iterator per level.
+  // TODO(opt): use concatenating iterator for level-0 if there is no overlap
+  const int space = (c->level() == 0 ? c->inputs_[0].size() + 1 : 2);
+  Iterator** list = new Iterator*[space];
+  int num = 0;
+  for (int which = 0; which < 2; which++) {
+    if (!c->inputs_[which].empty()) {
+      if (c->level() + which == 0) {
+        const std::vector<FileMetaData*>& files = c->inputs_[which];
+        for (size_t i = 0; i < files.size(); i++) {
+          list[num++] = table_cache_->NewIterator(options, files[i]->number,
+                                                  files[i]->file_size);
+        }
+      } else {
+        // Create concatenating iterator for the files from this level
+        list[num++] = NewTwoLevelIterator(
+            new Version::LevelFileNumIterator(icmp_, &c->inputs_[which]),
+            &GetFileIterator, table_cache_, options);
+      }
+    }
+  }
+  assert(num <= space);
+  Iterator* result = NewMergingIterator(&icmp_, list, num);
+  delete[] list;
+  return result;
+}
+
+Compaction* VersionSet::PickCompaction() {
+  Compaction* c;
+  int level;
+
+  // We prefer compactions triggered by too much data in a level over
+  // the compactions triggered by seeks.
+  const bool size_compaction = (current_->compaction_score_ >= 1);
+  const bool seek_compaction = (current_->file_to_compact_ != nullptr);
+  if (size_compaction) {
+    level = current_->compaction_level_;
+    assert(level >= 0);
+    assert(level + 1 < config::kNumLevels);
+    c = new Compaction(options_, level);
+
+    // Pick the first file that comes after compact_pointer_[level]
+    for (size_t i = 0; i < current_->files_[level].size(); i++) {
+      FileMetaData* f = current_->files_[level][i];
+      if (compact_pointer_[level].empty() ||
+          icmp_.Compare(f->largest.Encode(), compact_pointer_[level]) > 0) {
+        c->inputs_[0].push_back(f);
+        break;
+      }
+    }
+    if (c->inputs_[0].empty()) {
+      // Wrap-around to the beginning of the key space
+      c->inputs_[0].push_back(current_->files_[level][0]);
+    }
+  } else if (seek_compaction) {
+    level = current_->file_to_compact_level_;
+    c = new Compaction(options_, level);
+    c->inputs_[0].push_back(current_->file_to_compact_);
+  } else {
+    return nullptr;
+  }
+
+  c->input_version_ = current_;
+  c->input_version_->Ref();
+
+  // Files in level 0 may overlap each other, so pick up all overlapping ones
+  if (level == 0) {
+    InternalKey smallest, largest;
+    GetRange(c->inputs_[0], &smallest, &largest);
+    // Note that the next call will discard the file we placed in
+    // c->inputs_[0] earlier and replace it with an overlapping set
+    // which will include the picked file.
+    current_->GetOverlappingInputs(0, &smallest, &largest, &c->inputs_[0]);
+    assert(!c->inputs_[0].empty());
+  }
+
+  SetupOtherInputs(c);
+
+  return c;
+}
+
+// Finds the largest key in a vector of files. Returns true if files is not
+// empty.
+bool FindLargestKey(const InternalKeyComparator& icmp,
+                    const std::vector<FileMetaData*>& files,
+                    InternalKey* largest_key) {
+  if (files.empty()) {
+    return false;
+  }
+  *largest_key = files[0]->largest;
+  for (size_t i = 1; i < files.size(); ++i) {
+    FileMetaData* f = files[i];
+    if (icmp.Compare(f->largest, *largest_key) > 0) {
+      *largest_key = f->largest;
+    }
+  }
+  return true;
+}
+
+// Finds minimum file b2=(l2, u2) in level file for which l2 > u1 and
+// user_key(l2) = user_key(u1)
+FileMetaData* FindSmallestBoundaryFile(
+    const InternalKeyComparator& icmp,
+    const std::vector<FileMetaData*>& level_files,
+    const InternalKey& largest_key) {
+  const Comparator* user_cmp = icmp.user_comparator();
+  FileMetaData* smallest_boundary_file = nullptr;
+  for (size_t i = 0; i < level_files.size(); ++i) {
+    FileMetaData* f = level_files[i];
+    if (icmp.Compare(f->smallest, largest_key) > 0 &&
+        user_cmp->Compare(f->smallest.user_key(), largest_key.user_key()) ==
+            0) {
+      if (smallest_boundary_file == nullptr ||
+          icmp.Compare(f->smallest, smallest_boundary_file->smallest) < 0) {
+        smallest_boundary_file = f;
+      }
+    }
+  }
+  return smallest_boundary_file;
+}
+
+// Extracts the largest file b1 from |compaction_files| and then searches for a
+// b2 in |level_files| for which user_key(u1) = user_key(l2). If it finds such a
+// file b2 (known as a boundary file) it adds it to |compaction_files| and then
+// searches again using this new upper bound.
+//
+// If there are two blocks, b1=(l1, u1) and b2=(l2, u2) and
+// user_key(u1) = user_key(l2), and if we compact b1 but not b2 then a
+// subsequent get operation will yield an incorrect result because it will
+// return the record from b2 in level i rather than from b1 because it searches
+// level by level for records matching the supplied user key.
+//
+// parameters:
+//   in     level_files:      List of files to search for boundary files.
+//   in/out compaction_files: List of files to extend by adding boundary files.
+void AddBoundaryInputs(const InternalKeyComparator& icmp,
+                       const std::vector<FileMetaData*>& level_files,
+                       std::vector<FileMetaData*>* compaction_files) {
+  InternalKey largest_key;
+
+  // Quick return if compaction_files is empty.
+  if (!FindLargestKey(icmp, *compaction_files, &largest_key)) {
+    return;
+  }
+
+  bool continue_searching = true;
+  while (continue_searching) {
+    FileMetaData* smallest_boundary_file =
+        FindSmallestBoundaryFile(icmp, level_files, largest_key);
+
+    // If a boundary file was found advance largest_key, otherwise we're done.
+    if (smallest_boundary_file != NULL) {
+      compaction_files->push_back(smallest_boundary_file);
+      largest_key = smallest_boundary_file->largest;
+    } else {
+      continue_searching = false;
+    }
+  }
+}
+
+void VersionSet::SetupOtherInputs(Compaction* c) {
+  const int level = c->level();
+  InternalKey smallest, largest;
+
+  AddBoundaryInputs(icmp_, current_->files_[level], &c->inputs_[0]);
+  GetRange(c->inputs_[0], &smallest, &largest);
+
+  current_->GetOverlappingInputs(level + 1, &smallest, &largest,
+                                 &c->inputs_[1]);
+  AddBoundaryInputs(icmp_, current_->files_[level + 1], &c->inputs_[1]);
+
+  // Get entire range covered by compaction
+  InternalKey all_start, all_limit;
+  GetRange2(c->inputs_[0], c->inputs_[1], &all_start, &all_limit);
+
+  // See if we can grow the number of inputs in "level" without
+  // changing the number of "level+1" files we pick up.
+  if (!c->inputs_[1].empty()) {
+    std::vector<FileMetaData*> expanded0;
+    current_->GetOverlappingInputs(level, &all_start, &all_limit, &expanded0);
+    AddBoundaryInputs(icmp_, current_->files_[level], &expanded0);
+    const int64_t inputs0_size = TotalFileSize(c->inputs_[0]);
+    const int64_t inputs1_size = TotalFileSize(c->inputs_[1]);
+    const int64_t expanded0_size = TotalFileSize(expanded0);
+    if (expanded0.size() > c->inputs_[0].size() &&
+        inputs1_size + expanded0_size <
+            ExpandedCompactionByteSizeLimit(options_)) {
+      InternalKey new_start, new_limit;
+      GetRange(expanded0, &new_start, &new_limit);
+      std::vector<FileMetaData*> expanded1;
+      current_->GetOverlappingInputs(level + 1, &new_start, &new_limit,
+                                     &expanded1);
+      AddBoundaryInputs(icmp_, current_->files_[level + 1], &expanded1);
+      if (expanded1.size() == c->inputs_[1].size()) {
+        Log(options_->info_log,
+            "Expanding@%d %d+%d (%ld+%ld bytes) to %d+%d (%ld+%ld bytes)\n",
+            level, int(c->inputs_[0].size()), int(c->inputs_[1].size()),
+            long(inputs0_size), long(inputs1_size), int(expanded0.size()),
+            int(expanded1.size()), long(expanded0_size), long(inputs1_size));
+        smallest = new_start;
+        largest = new_limit;
+        c->inputs_[0] = expanded0;
+        c->inputs_[1] = expanded1;
+        GetRange2(c->inputs_[0], c->inputs_[1], &all_start, &all_limit);
+      }
+    }
+  }
+
+  // Compute the set of grandparent files that overlap this compaction
+  // (parent == level+1; grandparent == level+2)
+  if (level + 2 < config::kNumLevels) {
+    current_->GetOverlappingInputs(level + 2, &all_start, &all_limit,
+                                   &c->grandparents_);
+  }
+
+  // Update the place where we will do the next compaction for this level.
+  // We update this immediately instead of waiting for the VersionEdit
+  // to be applied so that if the compaction fails, we will try a different
+  // key range next time.
+  compact_pointer_[level] = largest.Encode().ToString();
+  c->edit_.SetCompactPointer(level, largest);
+}
+
+Compaction* VersionSet::CompactRange(int level, const InternalKey* begin,
+                                     const InternalKey* end) {
+  std::vector<FileMetaData*> inputs;
+  current_->GetOverlappingInputs(level, begin, end, &inputs);
+  if (inputs.empty()) {
+    return nullptr;
+  }
+
+  // Avoid compacting too much in one shot in case the range is large.
+  // But we cannot do this for level-0 since level-0 files can overlap
+  // and we must not pick one file and drop another older file if the
+  // two files overlap.
+  if (level > 0) {
+    const uint64_t limit = MaxFileSizeForLevel(options_, level);
+    uint64_t total = 0;
+    for (size_t i = 0; i < inputs.size(); i++) {
+      uint64_t s = inputs[i]->file_size;
+      total += s;
+      if (total >= limit) {
+        inputs.resize(i + 1);
+        break;
+      }
+    }
+  }
+
+  Compaction* c = new Compaction(options_, level);
+  c->input_version_ = current_;
+  c->input_version_->Ref();
+  c->inputs_[0] = inputs;
+  SetupOtherInputs(c);
+  return c;
+}
+
+Compaction::Compaction(const Options* options, int level)
+    : level_(level),
+      max_output_file_size_(MaxFileSizeForLevel(options, level)),
+      input_version_(nullptr),
+      grandparent_index_(0),
+      seen_key_(false),
+      overlapped_bytes_(0) {
+  for (int i = 0; i < config::kNumLevels; i++) {
+    level_ptrs_[i] = 0;
+  }
+}
+
+Compaction::~Compaction() {
+  if (input_version_ != nullptr) {
+    input_version_->Unref();
+  }
+}
+
+bool Compaction::IsTrivialMove() const {
+  const VersionSet* vset = input_version_->vset_;
+  // Avoid a move if there is lots of overlapping grandparent data.
+  // Otherwise, the move could create a parent file that will require
+  // a very expensive merge later on.
+  return (num_input_files(0) == 1 && num_input_files(1) == 0 &&
+          TotalFileSize(grandparents_) <=
+              MaxGrandParentOverlapBytes(vset->options_));
+}
+
+void Compaction::AddInputDeletions(VersionEdit* edit) {
+  for (int which = 0; which < 2; which++) {
+    for (size_t i = 0; i < inputs_[which].size(); i++) {
+      edit->RemoveFile(level_ + which, inputs_[which][i]->number);
+    }
+  }
+}
+
+bool Compaction::IsBaseLevelForKey(const Slice& user_key) {
+  // Maybe use binary search to find right entry instead of linear search?
+  const Comparator* user_cmp = input_version_->vset_->icmp_.user_comparator();
+  for (int lvl = level_ + 2; lvl < config::kNumLevels; lvl++) {
+    const std::vector<FileMetaData*>& files = input_version_->files_[lvl];
+    while (level_ptrs_[lvl] < files.size()) {
+      FileMetaData* f = files[level_ptrs_[lvl]];
+      if (user_cmp->Compare(user_key, f->largest.user_key()) <= 0) {
+        // We've advanced far enough
+        if (user_cmp->Compare(user_key, f->smallest.user_key()) >= 0) {
+          // Key falls in this file's range, so definitely not base level
+          return false;
+        }
+        break;
+      }
+      level_ptrs_[lvl]++;
+    }
+  }
+  return true;
+}
+
+bool Compaction::ShouldStopBefore(const Slice& internal_key) {
+  const VersionSet* vset = input_version_->vset_;
+  // Scan to find earliest grandparent file that contains key.
+  const InternalKeyComparator* icmp = &vset->icmp_;
+  while (grandparent_index_ < grandparents_.size() &&
+         icmp->Compare(internal_key,
+                       grandparents_[grandparent_index_]->largest.Encode()) >
+             0) {
+    if (seen_key_) {
+      overlapped_bytes_ += grandparents_[grandparent_index_]->file_size;
+    }
+    grandparent_index_++;
+  }
+  seen_key_ = true;
+
+  if (overlapped_bytes_ > MaxGrandParentOverlapBytes(vset->options_)) {
+    // Too much overlap for current output; start new output
+    overlapped_bytes_ = 0;
+    return true;
+  } else {
+    return false;
+  }
+}
+
+void Compaction::ReleaseInputs() {
+  if (input_version_ != nullptr) {
+    input_version_->Unref();
+    input_version_ = nullptr;
+  }
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/db/version_set.h b/leveldb_base/db/version_set.h
new file mode 100644
index 0000000..ea0c925
--- /dev/null
+++ b/leveldb_base/db/version_set.h
@@ -0,0 +1,393 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// The representation of a DBImpl consists of a set of Versions.  The
+// newest version is called "current".  Older versions may be kept
+// around to provide a consistent view to live iterators.
+//
+// Each Version keeps track of a set of Table files per level.  The
+// entire set of versions is maintained in a VersionSet.
+//
+// Version,VersionSet are thread-compatible, but require external
+// synchronization on all accesses.
+
+#ifndef STORAGE_LEVELDB_DB_VERSION_SET_H_
+#define STORAGE_LEVELDB_DB_VERSION_SET_H_
+
+#include <map>
+#include <set>
+#include <vector>
+
+#include "db/dbformat.h"
+#include "db/version_edit.h"
+#include "port/port.h"
+#include "port/thread_annotations.h"
+
+namespace leveldb {
+
+namespace log {
+class Writer;
+}
+
+class Compaction;
+class Iterator;
+class MemTable;
+class TableBuilder;
+class TableCache;
+class Version;
+class VersionSet;
+class WritableFile;
+
+// Return the smallest index i such that files[i]->largest >= key.
+// Return files.size() if there is no such file.
+// REQUIRES: "files" contains a sorted list of non-overlapping files.
+int FindFile(const InternalKeyComparator& icmp,
+             const std::vector<FileMetaData*>& files, const Slice& key);
+
+// Returns true iff some file in "files" overlaps the user key range
+// [*smallest,*largest].
+// smallest==nullptr represents a key smaller than all keys in the DB.
+// largest==nullptr represents a key largest than all keys in the DB.
+// REQUIRES: If disjoint_sorted_files, files[] contains disjoint ranges
+//           in sorted order.
+bool SomeFileOverlapsRange(const InternalKeyComparator& icmp,
+                           bool disjoint_sorted_files,
+                           const std::vector<FileMetaData*>& files,
+                           const Slice* smallest_user_key,
+                           const Slice* largest_user_key);
+
+class Version {
+ public:
+  struct GetStats {
+    FileMetaData* seek_file;
+    int seek_file_level;
+  };
+
+  // Append to *iters a sequence of iterators that will
+  // yield the contents of this Version when merged together.
+  // REQUIRES: This version has been saved (see VersionSet::SaveTo)
+  void AddIterators(const ReadOptions&, std::vector<Iterator*>* iters);
+
+  // Lookup the value for key.  If found, store it in *val and
+  // return OK.  Else return a non-OK status.  Fills *stats.
+  // REQUIRES: lock is not held
+  Status Get(const ReadOptions&, const LookupKey& key, std::string* val,
+             GetStats* stats);
+
+  // Adds "stats" into the current state.  Returns true if a new
+  // compaction may need to be triggered, false otherwise.
+  // REQUIRES: lock is held
+  bool UpdateStats(const GetStats& stats);
+
+  // Record a sample of bytes read at the specified internal key.
+  // Samples are taken approximately once every config::kReadBytesPeriod
+  // bytes.  Returns true if a new compaction may need to be triggered.
+  // REQUIRES: lock is held
+  bool RecordReadSample(Slice key);
+
+  // Reference count management (so Versions do not disappear out from
+  // under live iterators)
+  void Ref();
+  void Unref();
+
+  void GetOverlappingInputs(
+      int level,
+      const InternalKey* begin,  // nullptr means before all keys
+      const InternalKey* end,    // nullptr means after all keys
+      std::vector<FileMetaData*>* inputs);
+
+  // Returns true iff some file in the specified level overlaps
+  // some part of [*smallest_user_key,*largest_user_key].
+  // smallest_user_key==nullptr represents a key smaller than all the DB's keys.
+  // largest_user_key==nullptr represents a key largest than all the DB's keys.
+  bool OverlapInLevel(int level, const Slice* smallest_user_key,
+                      const Slice* largest_user_key);
+
+  // Return the level at which we should place a new memtable compaction
+  // result that covers the range [smallest_user_key,largest_user_key].
+  int PickLevelForMemTableOutput(const Slice& smallest_user_key,
+                                 const Slice& largest_user_key);
+
+  int NumFiles(int level) const { return files_[level].size(); }
+
+  // Return a human readable string that describes this version's contents.
+  std::string DebugString() const;
+
+ private:
+  friend class Compaction;
+  friend class VersionSet;
+
+  class LevelFileNumIterator;
+
+  explicit Version(VersionSet* vset)
+      : vset_(vset),
+        next_(this),
+        prev_(this),
+        refs_(0),
+        file_to_compact_(nullptr),
+        file_to_compact_level_(-1),
+        compaction_score_(-1),
+        compaction_level_(-1) {}
+
+  Version(const Version&) = delete;
+  Version& operator=(const Version&) = delete;
+
+  ~Version();
+
+  Iterator* NewConcatenatingIterator(const ReadOptions&, int level) const;
+
+  // Call func(arg, level, f) for every file that overlaps user_key in
+  // order from newest to oldest.  If an invocation of func returns
+  // false, makes no more calls.
+  //
+  // REQUIRES: user portion of internal_key == user_key.
+  void ForEachOverlapping(Slice user_key, Slice internal_key, void* arg,
+                          bool (*func)(void*, int, FileMetaData*));
+
+  VersionSet* vset_;  // VersionSet to which this Version belongs
+  Version* next_;     // Next version in linked list
+  Version* prev_;     // Previous version in linked list
+  int refs_;          // Number of live refs to this version
+
+  // List of files per level
+  std::vector<FileMetaData*> files_[config::kNumLevels];
+
+  // Next file to compact based on seek stats.
+  FileMetaData* file_to_compact_;
+  int file_to_compact_level_;
+
+  // Level that should be compacted next and its compaction score.
+  // Score < 1 means compaction is not strictly needed.  These fields
+  // are initialized by Finalize().
+  double compaction_score_;
+  int compaction_level_;
+};
+
+class VersionSet {
+ public:
+  VersionSet(const std::string& dbname, const Options* options,
+             TableCache* table_cache, const InternalKeyComparator*);
+  VersionSet(const VersionSet&) = delete;
+  VersionSet& operator=(const VersionSet&) = delete;
+
+  ~VersionSet();
+
+  // Apply *edit to the current version to form a new descriptor that
+  // is both saved to persistent state and installed as the new
+  // current version.  Will release *mu while actually writing to the file.
+  // REQUIRES: *mu is held on entry.
+  // REQUIRES: no other thread concurrently calls LogAndApply()
+  Status LogAndApply(VersionEdit* edit, port::Mutex* mu)
+      EXCLUSIVE_LOCKS_REQUIRED(mu);
+
+  // Recover the last saved descriptor from persistent storage.
+  Status Recover(bool* save_manifest);
+
+  // Return the current version.
+  Version* current() const { return current_; }
+
+  // Return the current manifest file number
+  uint64_t ManifestFileNumber() const { return manifest_file_number_; }
+
+  // Allocate and return a new file number
+  uint64_t NewFileNumber() { return next_file_number_++; }
+
+  // Arrange to reuse "file_number" unless a newer file number has
+  // already been allocated.
+  // REQUIRES: "file_number" was returned by a call to NewFileNumber().
+  void ReuseFileNumber(uint64_t file_number) {
+    if (next_file_number_ == file_number + 1) {
+      next_file_number_ = file_number;
+    }
+  }
+
+  // Return the number of Table files at the specified level.
+  int NumLevelFiles(int level) const;
+
+  // Return the combined file size of all files at the specified level.
+  int64_t NumLevelBytes(int level) const;
+
+  // Return the last sequence number.
+  uint64_t LastSequence() const { return last_sequence_; }
+
+  // Set the last sequence number to s.
+  void SetLastSequence(uint64_t s) {
+    assert(s >= last_sequence_);
+    last_sequence_ = s;
+  }
+
+  // Mark the specified file number as used.
+  void MarkFileNumberUsed(uint64_t number);
+
+  // Return the current log file number.
+  uint64_t LogNumber() const { return log_number_; }
+
+  // Return the log file number for the log file that is currently
+  // being compacted, or zero if there is no such log file.
+  uint64_t PrevLogNumber() const { return prev_log_number_; }
+
+  // Pick level and inputs for a new compaction.
+  // Returns nullptr if there is no compaction to be done.
+  // Otherwise returns a pointer to a heap-allocated object that
+  // describes the compaction.  Caller should delete the result.
+  Compaction* PickCompaction();
+
+  // Return a compaction object for compacting the range [begin,end] in
+  // the specified level.  Returns nullptr if there is nothing in that
+  // level that overlaps the specified range.  Caller should delete
+  // the result.
+  Compaction* CompactRange(int level, const InternalKey* begin,
+                           const InternalKey* end);
+
+  // Return the maximum overlapping data (in bytes) at next level for any
+  // file at a level >= 1.
+  int64_t MaxNextLevelOverlappingBytes();
+
+  // Create an iterator that reads over the compaction inputs for "*c".
+  // The caller should delete the iterator when no longer needed.
+  Iterator* MakeInputIterator(Compaction* c);
+
+  // Returns true iff some level needs a compaction.
+  bool NeedsCompaction() const {
+    Version* v = current_;
+    return (v->compaction_score_ >= 1) || (v->file_to_compact_ != nullptr);
+  }
+
+  // Add all files listed in any live version to *live.
+  // May also mutate some internal state.
+  void AddLiveFiles(std::set<uint64_t>* live);
+
+  // Return the approximate offset in the database of the data for
+  // "key" as of version "v".
+  uint64_t ApproximateOffsetOf(Version* v, const InternalKey& key);
+
+  // Return a human-readable short (single-line) summary of the number
+  // of files per level.  Uses *scratch as backing store.
+  struct LevelSummaryStorage {
+    char buffer[100];
+  };
+  const char* LevelSummary(LevelSummaryStorage* scratch) const;
+
+ private:
+  class Builder;
+
+  friend class Compaction;
+  friend class Version;
+
+  bool ReuseManifest(const std::string& dscname, const std::string& dscbase);
+
+  void Finalize(Version* v);
+
+  void GetRange(const std::vector<FileMetaData*>& inputs, InternalKey* smallest,
+                InternalKey* largest);
+
+  void GetRange2(const std::vector<FileMetaData*>& inputs1,
+                 const std::vector<FileMetaData*>& inputs2,
+                 InternalKey* smallest, InternalKey* largest);
+
+  void SetupOtherInputs(Compaction* c);
+
+  // Save current contents to *log
+  Status WriteSnapshot(log::Writer* log);
+
+  void AppendVersion(Version* v);
+
+  Env* const env_;
+  const std::string dbname_;
+  const Options* const options_;
+  TableCache* const table_cache_;
+  const InternalKeyComparator icmp_;
+  uint64_t next_file_number_;
+  uint64_t manifest_file_number_;
+  uint64_t last_sequence_;
+  uint64_t log_number_;
+  uint64_t prev_log_number_;  // 0 or backing store for memtable being compacted
+
+  // Opened lazily
+  WritableFile* descriptor_file_;
+  log::Writer* descriptor_log_;
+  Version dummy_versions_;  // Head of circular doubly-linked list of versions.
+  Version* current_;        // == dummy_versions_.prev_
+
+  // Per-level key at which the next compaction at that level should start.
+  // Either an empty string, or a valid InternalKey.
+  std::string compact_pointer_[config::kNumLevels];
+};
+
+// A Compaction encapsulates information about a compaction.
+class Compaction {
+ public:
+  ~Compaction();
+
+  // Return the level that is being compacted.  Inputs from "level"
+  // and "level+1" will be merged to produce a set of "level+1" files.
+  int level() const { return level_; }
+
+  // Return the object that holds the edits to the descriptor done
+  // by this compaction.
+  VersionEdit* edit() { return &edit_; }
+
+  // "which" must be either 0 or 1
+  int num_input_files(int which) const { return inputs_[which].size(); }
+
+  // Return the ith input file at "level()+which" ("which" must be 0 or 1).
+  FileMetaData* input(int which, int i) const { return inputs_[which][i]; }
+
+  // Maximum size of files to build during this compaction.
+  uint64_t MaxOutputFileSize() const { return max_output_file_size_; }
+
+  // Is this a trivial compaction that can be implemented by just
+  // moving a single input file to the next level (no merging or splitting)
+  bool IsTrivialMove() const;
+
+  // Add all inputs to this compaction as delete operations to *edit.
+  void AddInputDeletions(VersionEdit* edit);
+
+  // Returns true if the information we have available guarantees that
+  // the compaction is producing data in "level+1" for which no data exists
+  // in levels greater than "level+1".
+  bool IsBaseLevelForKey(const Slice& user_key);
+
+  // Returns true iff we should stop building the current output
+  // before processing "internal_key".
+  bool ShouldStopBefore(const Slice& internal_key);
+
+  // Release the input version for the compaction, once the compaction
+  // is successful.
+  void ReleaseInputs();
+
+ private:
+  friend class Version;
+  friend class VersionSet;
+
+  Compaction(const Options* options, int level);
+
+  int level_;
+  uint64_t max_output_file_size_;
+  Version* input_version_;
+  VersionEdit edit_;
+
+  // Each compaction reads inputs from "level_" and "level_+1"
+  std::vector<FileMetaData*> inputs_[2];  // The two sets of inputs
+
+  // State used to check for number of overlapping grandparent files
+  // (parent == level_ + 1, grandparent == level_ + 2)
+  std::vector<FileMetaData*> grandparents_;
+  size_t grandparent_index_;  // Index in grandparent_starts_
+  bool seen_key_;             // Some output key has been seen
+  int64_t overlapped_bytes_;  // Bytes of overlap between current output
+                              // and grandparent files
+
+  // State for implementing IsBaseLevelForKey
+
+  // level_ptrs_ holds indices into input_version_->levels_: our state
+  // is that we are positioned at one of the file ranges for each
+  // higher level than the ones involved in this compaction (i.e. for
+  // all L >= level_ + 2).
+  size_t level_ptrs_[config::kNumLevels];
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_DB_VERSION_SET_H_
diff --git a/leveldb_base/db/version_set_test.cc b/leveldb_base/db/version_set_test.cc
new file mode 100644
index 0000000..64bb983
--- /dev/null
+++ b/leveldb_base/db/version_set_test.cc
@@ -0,0 +1,331 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "db/version_set.h"
+
+#include "gtest/gtest.h"
+#include "util/logging.h"
+#include "util/testutil.h"
+
+namespace leveldb {
+
+class FindFileTest : public testing::Test {
+ public:
+  FindFileTest() : disjoint_sorted_files_(true) {}
+
+  ~FindFileTest() {
+    for (int i = 0; i < files_.size(); i++) {
+      delete files_[i];
+    }
+  }
+
+  void Add(const char* smallest, const char* largest,
+           SequenceNumber smallest_seq = 100,
+           SequenceNumber largest_seq = 100) {
+    FileMetaData* f = new FileMetaData;
+    f->number = files_.size() + 1;
+    f->smallest = InternalKey(smallest, smallest_seq, kTypeValue);
+    f->largest = InternalKey(largest, largest_seq, kTypeValue);
+    files_.push_back(f);
+  }
+
+  int Find(const char* key) {
+    InternalKey target(key, 100, kTypeValue);
+    InternalKeyComparator cmp(BytewiseComparator());
+    return FindFile(cmp, files_, target.Encode());
+  }
+
+  bool Overlaps(const char* smallest, const char* largest) {
+    InternalKeyComparator cmp(BytewiseComparator());
+    Slice s(smallest != nullptr ? smallest : "");
+    Slice l(largest != nullptr ? largest : "");
+    return SomeFileOverlapsRange(cmp, disjoint_sorted_files_, files_,
+                                 (smallest != nullptr ? &s : nullptr),
+                                 (largest != nullptr ? &l : nullptr));
+  }
+
+  bool disjoint_sorted_files_;
+
+ private:
+  std::vector<FileMetaData*> files_;
+};
+
+TEST_F(FindFileTest, Empty) {
+  ASSERT_EQ(0, Find("foo"));
+  ASSERT_TRUE(!Overlaps("a", "z"));
+  ASSERT_TRUE(!Overlaps(nullptr, "z"));
+  ASSERT_TRUE(!Overlaps("a", nullptr));
+  ASSERT_TRUE(!Overlaps(nullptr, nullptr));
+}
+
+TEST_F(FindFileTest, Single) {
+  Add("p", "q");
+  ASSERT_EQ(0, Find("a"));
+  ASSERT_EQ(0, Find("p"));
+  ASSERT_EQ(0, Find("p1"));
+  ASSERT_EQ(0, Find("q"));
+  ASSERT_EQ(1, Find("q1"));
+  ASSERT_EQ(1, Find("z"));
+
+  ASSERT_TRUE(!Overlaps("a", "b"));
+  ASSERT_TRUE(!Overlaps("z1", "z2"));
+  ASSERT_TRUE(Overlaps("a", "p"));
+  ASSERT_TRUE(Overlaps("a", "q"));
+  ASSERT_TRUE(Overlaps("a", "z"));
+  ASSERT_TRUE(Overlaps("p", "p1"));
+  ASSERT_TRUE(Overlaps("p", "q"));
+  ASSERT_TRUE(Overlaps("p", "z"));
+  ASSERT_TRUE(Overlaps("p1", "p2"));
+  ASSERT_TRUE(Overlaps("p1", "z"));
+  ASSERT_TRUE(Overlaps("q", "q"));
+  ASSERT_TRUE(Overlaps("q", "q1"));
+
+  ASSERT_TRUE(!Overlaps(nullptr, "j"));
+  ASSERT_TRUE(!Overlaps("r", nullptr));
+  ASSERT_TRUE(Overlaps(nullptr, "p"));
+  ASSERT_TRUE(Overlaps(nullptr, "p1"));
+  ASSERT_TRUE(Overlaps("q", nullptr));
+  ASSERT_TRUE(Overlaps(nullptr, nullptr));
+}
+
+TEST_F(FindFileTest, Multiple) {
+  Add("150", "200");
+  Add("200", "250");
+  Add("300", "350");
+  Add("400", "450");
+  ASSERT_EQ(0, Find("100"));
+  ASSERT_EQ(0, Find("150"));
+  ASSERT_EQ(0, Find("151"));
+  ASSERT_EQ(0, Find("199"));
+  ASSERT_EQ(0, Find("200"));
+  ASSERT_EQ(1, Find("201"));
+  ASSERT_EQ(1, Find("249"));
+  ASSERT_EQ(1, Find("250"));
+  ASSERT_EQ(2, Find("251"));
+  ASSERT_EQ(2, Find("299"));
+  ASSERT_EQ(2, Find("300"));
+  ASSERT_EQ(2, Find("349"));
+  ASSERT_EQ(2, Find("350"));
+  ASSERT_EQ(3, Find("351"));
+  ASSERT_EQ(3, Find("400"));
+  ASSERT_EQ(3, Find("450"));
+  ASSERT_EQ(4, Find("451"));
+
+  ASSERT_TRUE(!Overlaps("100", "149"));
+  ASSERT_TRUE(!Overlaps("251", "299"));
+  ASSERT_TRUE(!Overlaps("451", "500"));
+  ASSERT_TRUE(!Overlaps("351", "399"));
+
+  ASSERT_TRUE(Overlaps("100", "150"));
+  ASSERT_TRUE(Overlaps("100", "200"));
+  ASSERT_TRUE(Overlaps("100", "300"));
+  ASSERT_TRUE(Overlaps("100", "400"));
+  ASSERT_TRUE(Overlaps("100", "500"));
+  ASSERT_TRUE(Overlaps("375", "400"));
+  ASSERT_TRUE(Overlaps("450", "450"));
+  ASSERT_TRUE(Overlaps("450", "500"));
+}
+
+TEST_F(FindFileTest, MultipleNullBoundaries) {
+  Add("150", "200");
+  Add("200", "250");
+  Add("300", "350");
+  Add("400", "450");
+  ASSERT_TRUE(!Overlaps(nullptr, "149"));
+  ASSERT_TRUE(!Overlaps("451", nullptr));
+  ASSERT_TRUE(Overlaps(nullptr, nullptr));
+  ASSERT_TRUE(Overlaps(nullptr, "150"));
+  ASSERT_TRUE(Overlaps(nullptr, "199"));
+  ASSERT_TRUE(Overlaps(nullptr, "200"));
+  ASSERT_TRUE(Overlaps(nullptr, "201"));
+  ASSERT_TRUE(Overlaps(nullptr, "400"));
+  ASSERT_TRUE(Overlaps(nullptr, "800"));
+  ASSERT_TRUE(Overlaps("100", nullptr));
+  ASSERT_TRUE(Overlaps("200", nullptr));
+  ASSERT_TRUE(Overlaps("449", nullptr));
+  ASSERT_TRUE(Overlaps("450", nullptr));
+}
+
+TEST_F(FindFileTest, OverlapSequenceChecks) {
+  Add("200", "200", 5000, 3000);
+  ASSERT_TRUE(!Overlaps("199", "199"));
+  ASSERT_TRUE(!Overlaps("201", "300"));
+  ASSERT_TRUE(Overlaps("200", "200"));
+  ASSERT_TRUE(Overlaps("190", "200"));
+  ASSERT_TRUE(Overlaps("200", "210"));
+}
+
+TEST_F(FindFileTest, OverlappingFiles) {
+  Add("150", "600");
+  Add("400", "500");
+  disjoint_sorted_files_ = false;
+  ASSERT_TRUE(!Overlaps("100", "149"));
+  ASSERT_TRUE(!Overlaps("601", "700"));
+  ASSERT_TRUE(Overlaps("100", "150"));
+  ASSERT_TRUE(Overlaps("100", "200"));
+  ASSERT_TRUE(Overlaps("100", "300"));
+  ASSERT_TRUE(Overlaps("100", "400"));
+  ASSERT_TRUE(Overlaps("100", "500"));
+  ASSERT_TRUE(Overlaps("375", "400"));
+  ASSERT_TRUE(Overlaps("450", "450"));
+  ASSERT_TRUE(Overlaps("450", "500"));
+  ASSERT_TRUE(Overlaps("450", "700"));
+  ASSERT_TRUE(Overlaps("600", "700"));
+}
+
+void AddBoundaryInputs(const InternalKeyComparator& icmp,
+                       const std::vector<FileMetaData*>& level_files,
+                       std::vector<FileMetaData*>* compaction_files);
+
+class AddBoundaryInputsTest : public testing::Test {
+ public:
+  std::vector<FileMetaData*> level_files_;
+  std::vector<FileMetaData*> compaction_files_;
+  std::vector<FileMetaData*> all_files_;
+  InternalKeyComparator icmp_;
+
+  AddBoundaryInputsTest() : icmp_(BytewiseComparator()) {}
+
+  ~AddBoundaryInputsTest() {
+    for (size_t i = 0; i < all_files_.size(); ++i) {
+      delete all_files_[i];
+    }
+    all_files_.clear();
+  }
+
+  FileMetaData* CreateFileMetaData(uint64_t number, InternalKey smallest,
+                                   InternalKey largest) {
+    FileMetaData* f = new FileMetaData();
+    f->number = number;
+    f->smallest = smallest;
+    f->largest = largest;
+    all_files_.push_back(f);
+    return f;
+  }
+};
+
+TEST_F(AddBoundaryInputsTest, TestEmptyFileSets) {
+  AddBoundaryInputs(icmp_, level_files_, &compaction_files_);
+  ASSERT_TRUE(compaction_files_.empty());
+  ASSERT_TRUE(level_files_.empty());
+}
+
+TEST_F(AddBoundaryInputsTest, TestEmptyLevelFiles) {
+  FileMetaData* f1 =
+      CreateFileMetaData(1, InternalKey("100", 2, kTypeValue),
+                         InternalKey(InternalKey("100", 1, kTypeValue)));
+  compaction_files_.push_back(f1);
+
+  AddBoundaryInputs(icmp_, level_files_, &compaction_files_);
+  ASSERT_EQ(1, compaction_files_.size());
+  ASSERT_EQ(f1, compaction_files_[0]);
+  ASSERT_TRUE(level_files_.empty());
+}
+
+TEST_F(AddBoundaryInputsTest, TestEmptyCompactionFiles) {
+  FileMetaData* f1 =
+      CreateFileMetaData(1, InternalKey("100", 2, kTypeValue),
+                         InternalKey(InternalKey("100", 1, kTypeValue)));
+  level_files_.push_back(f1);
+
+  AddBoundaryInputs(icmp_, level_files_, &compaction_files_);
+  ASSERT_TRUE(compaction_files_.empty());
+  ASSERT_EQ(1, level_files_.size());
+  ASSERT_EQ(f1, level_files_[0]);
+}
+
+TEST_F(AddBoundaryInputsTest, TestNoBoundaryFiles) {
+  FileMetaData* f1 =
+      CreateFileMetaData(1, InternalKey("100", 2, kTypeValue),
+                         InternalKey(InternalKey("100", 1, kTypeValue)));
+  FileMetaData* f2 =
+      CreateFileMetaData(1, InternalKey("200", 2, kTypeValue),
+                         InternalKey(InternalKey("200", 1, kTypeValue)));
+  FileMetaData* f3 =
+      CreateFileMetaData(1, InternalKey("300", 2, kTypeValue),
+                         InternalKey(InternalKey("300", 1, kTypeValue)));
+
+  level_files_.push_back(f3);
+  level_files_.push_back(f2);
+  level_files_.push_back(f1);
+  compaction_files_.push_back(f2);
+  compaction_files_.push_back(f3);
+
+  AddBoundaryInputs(icmp_, level_files_, &compaction_files_);
+  ASSERT_EQ(2, compaction_files_.size());
+}
+
+TEST_F(AddBoundaryInputsTest, TestOneBoundaryFiles) {
+  FileMetaData* f1 =
+      CreateFileMetaData(1, InternalKey("100", 3, kTypeValue),
+                         InternalKey(InternalKey("100", 2, kTypeValue)));
+  FileMetaData* f2 =
+      CreateFileMetaData(1, InternalKey("100", 1, kTypeValue),
+                         InternalKey(InternalKey("200", 3, kTypeValue)));
+  FileMetaData* f3 =
+      CreateFileMetaData(1, InternalKey("300", 2, kTypeValue),
+                         InternalKey(InternalKey("300", 1, kTypeValue)));
+
+  level_files_.push_back(f3);
+  level_files_.push_back(f2);
+  level_files_.push_back(f1);
+  compaction_files_.push_back(f1);
+
+  AddBoundaryInputs(icmp_, level_files_, &compaction_files_);
+  ASSERT_EQ(2, compaction_files_.size());
+  ASSERT_EQ(f1, compaction_files_[0]);
+  ASSERT_EQ(f2, compaction_files_[1]);
+}
+
+TEST_F(AddBoundaryInputsTest, TestTwoBoundaryFiles) {
+  FileMetaData* f1 =
+      CreateFileMetaData(1, InternalKey("100", 6, kTypeValue),
+                         InternalKey(InternalKey("100", 5, kTypeValue)));
+  FileMetaData* f2 =
+      CreateFileMetaData(1, InternalKey("100", 2, kTypeValue),
+                         InternalKey(InternalKey("300", 1, kTypeValue)));
+  FileMetaData* f3 =
+      CreateFileMetaData(1, InternalKey("100", 4, kTypeValue),
+                         InternalKey(InternalKey("100", 3, kTypeValue)));
+
+  level_files_.push_back(f2);
+  level_files_.push_back(f3);
+  level_files_.push_back(f1);
+  compaction_files_.push_back(f1);
+
+  AddBoundaryInputs(icmp_, level_files_, &compaction_files_);
+  ASSERT_EQ(3, compaction_files_.size());
+  ASSERT_EQ(f1, compaction_files_[0]);
+  ASSERT_EQ(f3, compaction_files_[1]);
+  ASSERT_EQ(f2, compaction_files_[2]);
+}
+
+TEST_F(AddBoundaryInputsTest, TestDisjoinFilePointers) {
+  FileMetaData* f1 =
+      CreateFileMetaData(1, InternalKey("100", 6, kTypeValue),
+                         InternalKey(InternalKey("100", 5, kTypeValue)));
+  FileMetaData* f2 =
+      CreateFileMetaData(1, InternalKey("100", 6, kTypeValue),
+                         InternalKey(InternalKey("100", 5, kTypeValue)));
+  FileMetaData* f3 =
+      CreateFileMetaData(1, InternalKey("100", 2, kTypeValue),
+                         InternalKey(InternalKey("300", 1, kTypeValue)));
+  FileMetaData* f4 =
+      CreateFileMetaData(1, InternalKey("100", 4, kTypeValue),
+                         InternalKey(InternalKey("100", 3, kTypeValue)));
+
+  level_files_.push_back(f2);
+  level_files_.push_back(f3);
+  level_files_.push_back(f4);
+
+  compaction_files_.push_back(f1);
+
+  AddBoundaryInputs(icmp_, level_files_, &compaction_files_);
+  ASSERT_EQ(3, compaction_files_.size());
+  ASSERT_EQ(f1, compaction_files_[0]);
+  ASSERT_EQ(f4, compaction_files_[1]);
+  ASSERT_EQ(f3, compaction_files_[2]);
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/db/write_batch.cc b/leveldb_base/db/write_batch.cc
new file mode 100644
index 0000000..7ea7b40
--- /dev/null
+++ b/leveldb_base/db/write_batch.cc
@@ -0,0 +1,172 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// WriteBatch::rep_ :=
+//    sequence: fixed64
+//    count: fixed32
+//    data: record[count]
+// record :=
+//    kTypeValue varstring varstring         |
+//    kTypeDeletion varstring
+// varstring :=
+//    len: varint32
+//    data: uint8[len]
+
+#include "leveldb/write_batch.h"
+
+#include "db/dbformat.h"
+#include "db/memtable.h"
+#include "db/write_batch_internal.h"
+#include "leveldb/db.h"
+#include "util/coding.h"
+// 添加所需头文件-橙
+#include <sstream> 
+#include <iomanip>
+#include <ctime>  
+#include <chrono>  
+namespace leveldb {
+
+// WriteBatch header has an 8-byte sequence number followed by a 4-byte count.
+static const size_t kHeader = 12;
+
+WriteBatch::WriteBatch() { Clear(); }
+
+WriteBatch::~WriteBatch() = default;
+
+WriteBatch::Handler::~Handler() = default;
+
+void WriteBatch::Clear() {
+  rep_.clear();
+  rep_.resize(kHeader);
+}
+
+size_t WriteBatch::ApproximateSize() const { return rep_.size(); }
+
+Status WriteBatch::Iterate(Handler* handler) const {
+  Slice input(rep_);
+  if (input.size() < kHeader) {
+    return Status::Corruption("malformed WriteBatch (too small)");
+  }
+
+  input.remove_prefix(kHeader);
+  Slice key, value;
+  int found = 0;
+  while (!input.empty()) {
+    found++;
+    char tag = input[0];
+    input.remove_prefix(1);
+    switch (tag) {
+      case kTypeValue:
+        if (GetLengthPrefixedSlice(&input, &key) &&
+            GetLengthPrefixedSlice(&input, &value)) {
+          handler->Put(key, value);
+        } else {
+          return Status::Corruption("bad WriteBatch Put");
+        }
+        break;
+      case kTypeDeletion:
+        if (GetLengthPrefixedSlice(&input, &key)) {
+          handler->Delete(key);
+        } else {
+          return Status::Corruption("bad WriteBatch Delete");
+        }
+        break;
+      default:
+        return Status::Corruption("unknown WriteBatch tag");
+    }
+  }
+  if (found != WriteBatchInternal::Count(this)) {
+    return Status::Corruption("WriteBatch has wrong count");
+  } else {
+    return Status::OK();
+  }
+}
+
+int WriteBatchInternal::Count(const WriteBatch* b) {
+  return DecodeFixed32(b->rep_.data() + 8);
+}
+
+void WriteBatchInternal::SetCount(WriteBatch* b, int n) {
+  EncodeFixed32(&b->rep_[8], n);
+}
+
+SequenceNumber WriteBatchInternal::Sequence(const WriteBatch* b) {
+  return SequenceNumber(DecodeFixed64(b->rep_.data()));
+}
+
+void WriteBatchInternal::SetSequence(WriteBatch* b, SequenceNumber seq) {
+  EncodeFixed64(&b->rep_[0], seq);
+}
+
+void WriteBatch::Put(const Slice& key, const Slice& value) {
+  WriteBatchInternal::SetCount(this, WriteBatchInternal::Count(this) + 1);
+  rep_.push_back(static_cast<char>(kTypeValue));
+  PutLengthPrefixedSlice(&rep_, key);
+  PutLengthPrefixedSlice(&rep_, value);
+}
+// 添加ttl，新的put方法-橙
+void WriteBatch::Put(const Slice& key, const Slice& value, uint64_t ttl) {
+  WriteBatchInternal::SetCount(this, WriteBatchInternal::Count(this) + 1);
+  rep_.push_back(static_cast<char>(kTypeValue));
+  PutLengthPrefixedSlice(&rep_, key);
+  // PutLengthPrefixedSlice(&rep_, value);
+  // 获取当前时间，加上 TTL 得到过期时间戳
+  auto expiration_time = std::chrono::system_clock::now()+ std::chrono::seconds(ttl);
+  // 将过期时间戳转换为字符串
+  std::time_t expiration_time_t = std::chrono::system_clock::to_time_t(expiration_time);
+  std::stringstream ss;
+  ss << std::put_time(std::localtime(&expiration_time_t), "%Y-%m-%d %H:%M:%S");
+  std::string expiration_time_str = ss.str();
+  // 将过期时间戳添加到值中
+  std::string value_with_ttl(value.data(), value.size());
+  value_with_ttl.append(expiration_time_str);  // 拼接
+  PutLengthPrefixedSlice(&rep_, Slice(value_with_ttl.data(), value_with_ttl.size()));
+}
+
+void WriteBatch::Delete(const Slice& key) {
+  WriteBatchInternal::SetCount(this, WriteBatchInternal::Count(this) + 1);
+  rep_.push_back(static_cast<char>(kTypeDeletion));
+  PutLengthPrefixedSlice(&rep_, key);
+}
+
+void WriteBatch::Append(const WriteBatch& source) {
+  WriteBatchInternal::Append(this, &source);
+}
+
+namespace {
+class MemTableInserter : public WriteBatch::Handler {
+ public:
+  SequenceNumber sequence_;
+  MemTable* mem_;
+
+  void Put(const Slice& key, const Slice& value) override {
+    mem_->Add(sequence_, kTypeValue, key, value);
+    sequence_++;
+  }
+  void Delete(const Slice& key) override {
+    mem_->Add(sequence_, kTypeDeletion, key, Slice());
+    sequence_++;
+  }
+};
+}  // namespace
+
+Status WriteBatchInternal::InsertInto(const WriteBatch* b, MemTable* memtable) {
+  MemTableInserter inserter;
+  inserter.sequence_ = WriteBatchInternal::Sequence(b);
+  inserter.mem_ = memtable;
+  return b->Iterate(&inserter);
+}
+
+void WriteBatchInternal::SetContents(WriteBatch* b, const Slice& contents) {
+  assert(contents.size() >= kHeader);
+  b->rep_.assign(contents.data(), contents.size());
+}
+
+void WriteBatchInternal::Append(WriteBatch* dst, const WriteBatch* src) {
+  SetCount(dst, Count(dst) + Count(src));
+  assert(src->rep_.size() >= kHeader);
+  dst->rep_.append(src->rep_.data() + kHeader, src->rep_.size() - kHeader);
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/db/write_batch_internal.h b/leveldb_base/db/write_batch_internal.h
new file mode 100644
index 0000000..fce86e3
--- /dev/null
+++ b/leveldb_base/db/write_batch_internal.h
@@ -0,0 +1,45 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_DB_WRITE_BATCH_INTERNAL_H_
+#define STORAGE_LEVELDB_DB_WRITE_BATCH_INTERNAL_H_
+
+#include "db/dbformat.h"
+#include "leveldb/write_batch.h"
+
+namespace leveldb {
+
+class MemTable;
+
+// WriteBatchInternal provides static methods for manipulating a
+// WriteBatch that we don't want in the public WriteBatch interface.
+class WriteBatchInternal {
+ public:
+  // Return the number of entries in the batch.
+  static int Count(const WriteBatch* batch);
+
+  // Set the count for the number of entries in the batch.
+  static void SetCount(WriteBatch* batch, int n);
+
+  // Return the sequence number for the start of this batch.
+  static SequenceNumber Sequence(const WriteBatch* batch);
+
+  // Store the specified number as the sequence number for the start of
+  // this batch.
+  static void SetSequence(WriteBatch* batch, SequenceNumber seq);
+
+  static Slice Contents(const WriteBatch* batch) { return Slice(batch->rep_); }
+
+  static size_t ByteSize(const WriteBatch* batch) { return batch->rep_.size(); }
+
+  static void SetContents(WriteBatch* batch, const Slice& contents);
+
+  static Status InsertInto(const WriteBatch* batch, MemTable* memtable);
+
+  static void Append(WriteBatch* dst, const WriteBatch* src);
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_DB_WRITE_BATCH_INTERNAL_H_
diff --git a/leveldb_base/db/write_batch_test.cc b/leveldb_base/db/write_batch_test.cc
new file mode 100644
index 0000000..1a3ea8f
--- /dev/null
+++ b/leveldb_base/db/write_batch_test.cc
@@ -0,0 +1,132 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "gtest/gtest.h"
+#include "db/memtable.h"
+#include "db/write_batch_internal.h"
+#include "leveldb/db.h"
+#include "leveldb/env.h"
+#include "util/logging.h"
+
+namespace leveldb {
+
+static std::string PrintContents(WriteBatch* b) {
+  InternalKeyComparator cmp(BytewiseComparator());
+  MemTable* mem = new MemTable(cmp);
+  mem->Ref();
+  std::string state;
+  Status s = WriteBatchInternal::InsertInto(b, mem);
+  int count = 0;
+  Iterator* iter = mem->NewIterator();
+  for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
+    ParsedInternalKey ikey;
+    EXPECT_TRUE(ParseInternalKey(iter->key(), &ikey));
+    switch (ikey.type) {
+      case kTypeValue:
+        state.append("Put(");
+        state.append(ikey.user_key.ToString());
+        state.append(", ");
+        state.append(iter->value().ToString());
+        state.append(")");
+        count++;
+        break;
+      case kTypeDeletion:
+        state.append("Delete(");
+        state.append(ikey.user_key.ToString());
+        state.append(")");
+        count++;
+        break;
+    }
+    state.append("@");
+    state.append(NumberToString(ikey.sequence));
+  }
+  delete iter;
+  if (!s.ok()) {
+    state.append("ParseError()");
+  } else if (count != WriteBatchInternal::Count(b)) {
+    state.append("CountMismatch()");
+  }
+  mem->Unref();
+  return state;
+}
+
+TEST(WriteBatchTest, Empty) {
+  WriteBatch batch;
+  ASSERT_EQ("", PrintContents(&batch));
+  ASSERT_EQ(0, WriteBatchInternal::Count(&batch));
+}
+
+TEST(WriteBatchTest, Multiple) {
+  WriteBatch batch;
+  batch.Put(Slice("foo"), Slice("bar"));
+  batch.Delete(Slice("box"));
+  batch.Put(Slice("baz"), Slice("boo"));
+  WriteBatchInternal::SetSequence(&batch, 100);
+  ASSERT_EQ(100, WriteBatchInternal::Sequence(&batch));
+  ASSERT_EQ(3, WriteBatchInternal::Count(&batch));
+  ASSERT_EQ(
+      "Put(baz, boo)@102"
+      "Delete(box)@101"
+      "Put(foo, bar)@100",
+      PrintContents(&batch));
+}
+
+TEST(WriteBatchTest, Corruption) {
+  WriteBatch batch;
+  batch.Put(Slice("foo"), Slice("bar"));
+  batch.Delete(Slice("box"));
+  WriteBatchInternal::SetSequence(&batch, 200);
+  Slice contents = WriteBatchInternal::Contents(&batch);
+  WriteBatchInternal::SetContents(&batch,
+                                  Slice(contents.data(), contents.size() - 1));
+  ASSERT_EQ(
+      "Put(foo, bar)@200"
+      "ParseError()",
+      PrintContents(&batch));
+}
+
+TEST(WriteBatchTest, Append) {
+  WriteBatch b1, b2;
+  WriteBatchInternal::SetSequence(&b1, 200);
+  WriteBatchInternal::SetSequence(&b2, 300);
+  b1.Append(b2);
+  ASSERT_EQ("", PrintContents(&b1));
+  b2.Put("a", "va");
+  b1.Append(b2);
+  ASSERT_EQ("Put(a, va)@200", PrintContents(&b1));
+  b2.Clear();
+  b2.Put("b", "vb");
+  b1.Append(b2);
+  ASSERT_EQ(
+      "Put(a, va)@200"
+      "Put(b, vb)@201",
+      PrintContents(&b1));
+  b2.Delete("foo");
+  b1.Append(b2);
+  ASSERT_EQ(
+      "Put(a, va)@200"
+      "Put(b, vb)@202"
+      "Put(b, vb)@201"
+      "Delete(foo)@203",
+      PrintContents(&b1));
+}
+
+TEST(WriteBatchTest, ApproximateSize) {
+  WriteBatch batch;
+  size_t empty_size = batch.ApproximateSize();
+
+  batch.Put(Slice("foo"), Slice("bar"));
+  size_t one_key_size = batch.ApproximateSize();
+  ASSERT_LT(empty_size, one_key_size);
+
+  batch.Put(Slice("baz"), Slice("boo"));
+  size_t two_keys_size = batch.ApproximateSize();
+  ASSERT_LT(one_key_size, two_keys_size);
+
+  batch.Delete(Slice("box"));
+  size_t post_delete_size = batch.ApproximateSize();
+  ASSERT_LT(two_keys_size, post_delete_size);
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/doc/benchmark.html b/leveldb_base/doc/benchmark.html
new file mode 100644
index 0000000..80e6c2a
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+++ b/leveldb_base/doc/benchmark.html
@@ -0,0 +1,459 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>LevelDB Benchmarks</title>
+<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
+<style>
+body {
+  font-family:Helvetica,sans-serif;
+  padding:20px;
+}
+
+h2 {
+  padding-top:30px;
+}
+
+table.bn {
+  width:800px;
+  border-collapse:collapse;
+  border:0;
+  padding:0;
+}
+
+table.bnbase {
+  width:650px;
+}
+
+table.bn td {
+  padding:2px 0;
+}
+
+table.bn td.c1 {
+  font-weight:bold;
+  width:150px;
+}
+
+table.bn td.c1 div.e {
+  float:right;
+  font-weight:normal;
+}
+
+table.bn td.c2 {
+  width:150px;
+  text-align:right;
+  padding:2px;
+}
+
+table.bn td.c3 {
+  width:350px;
+}
+
+table.bn td.c4 {
+  width:150px;
+  font-size:small;
+  padding-left:4px;
+}
+
+/* chart bars */
+div.bldb {
+  background-color:#0255df;
+}
+
+div.bkct {
+  background-color:#df5555;
+}
+
+div.bsql {
+  background-color:#aadf55;
+}
+
+.code {
+  font-family:monospace;
+  font-size:large;
+}
+
+.todo {
+  color: red;
+}
+
+</style>
+</head>
+<body>
+<h1>LevelDB Benchmarks</h1>
+<p>Google, July 2011</p>
+<hr>
+
+<p>In order to test LevelDB's performance, we benchmark it against other well-established database implementations. We compare LevelDB (revision 39) against <a href="https://www.sqlite.org/">SQLite3</a> (version 3.7.6.3) and <a href="https://dbmx.net/kyotocabinet/spex.html">Kyoto Cabinet's</a> (version 1.2.67) TreeDB (a B+Tree based key-value store). We would like to acknowledge Scott Hess and Mikio Hirabayashi for their suggestions and contributions to the SQLite3 and Kyoto Cabinet benchmarks, respectively.</p>
+
+<p>Benchmarks were all performed on a six-core Intel(R) Xeon(R) CPU X5650 @ 2.67GHz, with 12288 KB of total L3 cache and 12 GB of DDR3 RAM at 1333 MHz. (Note that LevelDB uses at most two CPUs since the benchmarks are single threaded: one to run the benchmark, and one for background compactions.) We ran the benchmarks on two machines (with identical processors), one with an Ext3 file system and one with an Ext4 file system. The machine with the Ext3 file system has a SATA Hitachi HDS721050CLA362 hard drive. The machine with the Ext4 file system has a SATA Samsung HD502HJ hard drive. Both hard drives spin at 7200 RPM and have hard drive write-caching enabled (using `hdparm -W 1 [device]`). The numbers reported below are the median of three measurements.</p>
+
+<h4>Benchmark Source Code</h4>
+<p>We wrote benchmark tools for SQLite and Kyoto TreeDB based on LevelDB's <span class="code">db_bench</span>. The code for each of the benchmarks resides here:</p>
+<ul>
+	<li> <b>LevelDB:</b> <a href="https://github.com/google/leveldb/blob/main/benchmarks/db_bench.cc">benchmarks/db_bench.cc</a>.</li>
+	<li> <b>SQLite:</b> <a href="https://github.com/google/leveldb/blob/main/benchmarks/db_bench_sqlite3.cc">benchmarks/db_bench_sqlite3.cc</a>.</li>
+	<li> <b>Kyoto TreeDB:</b> <a href="https://github.com/google/leveldb/blob/main/benchmarks/db_bench_tree_db.cc">benchmarks/db_bench_tree_db.cc</a>.</li>
+</ul>
+
+<h4>Custom Build Specifications</h4>
+<ul>
+<li>LevelDB: LevelDB was compiled with the <a href="https://github.com/gperftools/gperftools">tcmalloc</a> library and the <a href="https://github.com/google/snappy">Snappy</a> compression library (revision 33).  Assertions were disabled.</li>
+<li>TreeDB: TreeDB was compiled using the <a href="https://www.oberhumer.com/opensource/lzo/">LZO</a> compression library (version 2.03). Furthermore, we enabled the TSMALL and TLINEAR options when opening the database in order to reduce the footprint of each record.</li>
+<li>SQLite: We tuned SQLite's performance, by setting its locking mode to exclusive.  We also enabled SQLite's <a href="https://www.sqlite.org/draft/wal.html">write-ahead logging</a>.</li>
+</ul>
+
+<h2>1. Baseline Performance</h2>
+<p>This section gives the baseline performance of all the
+databases.  Following sections show how performance changes as various
+parameters are varied.  For the baseline:</p>
+<ul>
+	<li> Each database is allowed 4 MB of cache memory.</li>
+        <li> Databases are opened in <em>asynchronous</em> write mode.
+             (LevelDB's sync option, TreeDB's OAUTOSYNC option, and
+             SQLite3's synchronous options are all turned off).  I.e.,
+             every write is pushed to the operating system, but the
+             benchmark does not wait for the write to reach the disk.</li>
+	<li> Keys are 16 bytes each.</li>
+        <li> Value are 100 bytes each (with enough redundancy so that
+             a simple compressor shrinks them to 50% of their original
+             size).</li>
+	<li> Sequential reads/writes traverse the key space in increasing order.</li>
+	<li> Random reads/writes traverse the key space in random order.</li>
+</ul>
+
+<h3>A. Sequential Reads</h3>
+<table class="bn bnbase">
+<tr><td class="c1">LevelDB</td>
+    <td class="c2">4,030,000 ops/sec</td>
+    <td class="c3"><div class="bldb" style="width:350px">&nbsp;</div></td>
+<tr><td class="c1">Kyoto TreeDB</td>
+    <td class="c2">1,010,000 ops/sec</td>
+    <td class="c3"><div class="bkct" style="width:95px">&nbsp;</div></td>
+<tr><td class="c1">SQLite3</td>
+    <td class="c2">383,000 ops/sec</td>
+    <td class="c3"><div class="bsql" style="width:33px">&nbsp;</div></td>
+</table>
+<h3>B. Random Reads</h3>
+<table class="bn bnbase">
+<tr><td class="c1">LevelDB</td>
+    <td class="c2">129,000 ops/sec</td>
+    <td class="c3"><div class="bldb" style="width:298px">&nbsp;</div></td>
+<tr><td class="c1">Kyoto TreeDB</td>
+    <td class="c2">151,000 ops/sec</td>
+    <td class="c3"><div class="bkct" style="width:350px">&nbsp;</div></td>
+<tr><td class="c1">SQLite3</td>
+    <td class="c2">134,000 ops/sec</td>
+    <td class="c3"><div class="bsql" style="width:310px">&nbsp;</div></td>
+</table>
+<h3>C. Sequential Writes</h3>
+<table class="bn bnbase">
+<tr><td class="c1">LevelDB</td>
+    <td class="c2">779,000 ops/sec</td>
+    <td class="c3"><div class="bldb" style="width:350px">&nbsp;</div></td>
+<tr><td class="c1">Kyoto TreeDB</td>
+    <td class="c2">342,000 ops/sec</td>
+    <td class="c3"><div class="bkct" style="width:154px">&nbsp;</div></td>
+<tr><td class="c1">SQLite3</td>
+    <td class="c2">48,600 ops/sec</td>
+    <td class="c3"><div class="bsql" style="width:22px">&nbsp;</div></td>
+</table>
+<h3>D. Random Writes</h3>
+<table class="bn bnbase">
+<tr><td class="c1">LevelDB</td>
+    <td class="c2">164,000 ops/sec</td>
+    <td class="c3"><div class="bldb" style="width:350px">&nbsp;</div></td>
+<tr><td class="c1">Kyoto TreeDB</td>
+    <td class="c2">88,500 ops/sec</td>
+    <td class="c3"><div class="bkct" style="width:188px">&nbsp;</div></td>
+<tr><td class="c1">SQLite3</td>
+    <td class="c2">9,860 ops/sec</td>
+    <td class="c3"><div class="bsql" style="width:21px">&nbsp;</div></td>
+</table>
+
+<p>LevelDB outperforms both SQLite3 and TreeDB in sequential and random write operations and sequential read operations. Kyoto Cabinet has the fastest random read operations.</p>
+
+<h2>2. Write Performance under Different Configurations</h2>
+<h3>A. Large Values </h3>
+<p>For this benchmark, we start with an empty database, and write 100,000 byte values (~50% compressible). To keep the benchmark running time reasonable, we stop after writing 1000 values.</p>
+<h4>Sequential Writes</h4>
+<table class="bn bnbase">
+<tr><td class="c1">LevelDB</td>
+    <td class="c2">1,100 ops/sec</td>
+    <td class="c3"><div class="bldb" style="width:234px">&nbsp;</div></td></tr>
+<tr><td class="c1">Kyoto TreeDB</td>
+    <td class="c2">1,000 ops/sec</td>
+    <td class="c3"><div class="bkct" style="width:224px">&nbsp;</div></td></tr>
+<tr><td class="c1">SQLite3</td>
+    <td class="c2">1,600 ops/sec</td>
+    <td class="c3"><div class="bsql" style="width:350px">&nbsp;</div></td></tr>
+</table>
+<h4>Random Writes</h4>
+<table class="bn bnbase">
+<tr><td class="c1">LevelDB</td>
+    <td class="c2">480 ops/sec</td>
+    <td class="c3"><div class="bldb" style="width:105px">&nbsp;</div></td></tr>
+<tr><td class="c1">Kyoto TreeDB</td>
+    <td class="c2">1,100 ops/sec</td>
+    <td class="c3"><div class="bkct" style="width:240px">&nbsp;</div></td></tr>
+<tr><td class="c1">SQLite3</td>
+    <td class="c2">1,600 ops/sec</td>
+    <td class="c3"><div class="bsql" style="width:350px">&nbsp;</div></td></tr>
+</table>
+<p>LevelDB doesn't perform as well with large values of 100,000 bytes each. This is because LevelDB writes keys and values at least twice: first time to the transaction log, and second time (during a compaction) to a sorted file.
+With larger values, LevelDB's per-operation efficiency is swamped by the
+cost of extra copies of large values.</p>
+<h3>B. Batch Writes</h3>
+<p>A batch write is a set of writes that are applied atomically to the underlying database. A single batch of N writes may be significantly faster than N individual writes. The following benchmark writes one thousand batches where each batch contains one thousand 100-byte values. TreeDB does not support batch writes and is omitted from this benchmark.</p>
+<h4>Sequential Writes</h4>
+<table class="bn">
+<tr><td class="c1">LevelDB</td>
+    <td class="c2">840,000 entries/sec</td>
+    <td class="c3"><div class="bldb" style="width:350px">&nbsp;</div></td>
+    <td class="c4">(1.08x baseline)</td></tr>
+<tr><td class="c1">SQLite3</td>
+    <td class="c2">124,000 entries/sec</td>
+    <td class="c3"><div class="bsql" style="width:52px">&nbsp;</div></td>
+    <td class="c4">(2.55x baseline)</td></tr>
+</table>
+<h4>Random Writes</h4>
+<table class="bn">
+<tr><td class="c1">LevelDB</td>
+    <td class="c2">221,000 entries/sec</td>
+    <td class="c3"><div class="bldb" style="width:350px">&nbsp;</div></td>
+    <td class="c4">(1.35x baseline)</td></tr>
+<tr><td class="c1">SQLite3</td>
+    <td class="c2">22,000 entries/sec</td>
+    <td class="c3"><div class="bsql" style="width:34px">&nbsp;</div></td>
+    <td class="c4">(2.23x baseline)</td></tr>
+</table>
+
+<p>Because of the way LevelDB persistent storage is organized, batches of
+random writes are not much slower (only a factor of 4x) than batches
+of sequential writes.</p>
+
+<h3>C. Synchronous Writes</h3>
+<p>In the following benchmark, we enable the synchronous writing modes
+of all of the databases.  Since this change significantly slows down the
+benchmark, we stop after 10,000 writes. For synchronous write tests, we've
+disabled hard drive write-caching (using `hdparm -W 0 [device]`).</p>
+<ul>
+    <li>For LevelDB, we set WriteOptions.sync = true.</li>
+    <li>In TreeDB, we enabled TreeDB's OAUTOSYNC option.</li>
+    <li>For SQLite3, we set "PRAGMA synchronous = FULL".</li>
+</ul>
+<h4>Sequential Writes</h4>
+<table class="bn">
+<tr><td class="c1">LevelDB</td>
+    <td class="c2">100 ops/sec</td>
+    <td class="c3"><div class="bldb" style="width:350px">&nbsp;</div></td>
+    <td class="c4">(0.003x baseline)</td></tr>
+<tr><td class="c1">Kyoto TreeDB</td>
+    <td class="c2">7 ops/sec</td>
+    <td class="c3"><div class="bkct" style="width:27px">&nbsp;</div></td>
+    <td class="c4">(0.0004x baseline)</td></tr>
+<tr><td class="c1">SQLite3</td>
+    <td class="c2">88 ops/sec</td>
+    <td class="c3"><div class="bsql" style="width:315px">&nbsp;</div></td>
+    <td class="c4">(0.002x baseline)</td></tr>
+</table>
+<h4>Random Writes</h4>
+<table class="bn">
+<tr><td class="c1">LevelDB</td>
+    <td class="c2">100 ops/sec</td>
+    <td class="c3"><div class="bldb" style="width:350px">&nbsp;</div></td>
+    <td class="c4">(0.015x baseline)</td></tr>
+<tr><td class="c1">Kyoto TreeDB</td>
+    <td class="c2">8 ops/sec</td>
+    <td class="c3"><div class="bkct" style="width:29px">&nbsp;</div></td>
+    <td class="c4">(0.001x baseline)</td></tr>
+<tr><td class="c1">SQLite3</td>
+    <td class="c2">88 ops/sec</td>
+    <td class="c3"><div class="bsql" style="width:314px">&nbsp;</div></td>
+    <td class="c4">(0.009x baseline)</td></tr>
+</table>
+
+<p>Also see the <code>ext4</code> performance numbers below
+since synchronous writes behave significantly differently
+on <code>ext3</code> and <code>ext4</code>.</p>
+
+<h3>D. Turning Compression Off</h3>
+
+<p>In the baseline measurements, LevelDB and TreeDB were using
+light-weight compression
+(<a href="http://code.google.com/p/snappy/">Snappy</a> for LevelDB,
+and <a href="http://www.oberhumer.com/opensource/lzo/">LZO</a> for
+TreeDB). SQLite3, by default does not use compression.  The
+experiments below show what happens when compression is disabled in
+all of the databases (the SQLite3 numbers are just a copy of
+its baseline measurements):</p>
+
+<h4>Sequential Writes</h4>
+<table class="bn">
+<tr><td class="c1">LevelDB</td>
+    <td class="c2">594,000 ops/sec</td>
+    <td class="c3"><div class="bldb" style="width:350px">&nbsp;</div></td>
+    <td class="c4">(0.76x baseline)</td></tr>
+<tr><td class="c1">Kyoto TreeDB</td>
+    <td class="c2">485,000 ops/sec</td>
+    <td class="c3"><div class="bkct" style="width:239px">&nbsp;</div></td>
+    <td class="c4">(1.42x baseline)</td></tr>
+<tr><td class="c1">SQLite3</td>
+    <td class="c2">48,600 ops/sec</td>
+    <td class="c3"><div class="bsql" style="width:29px">&nbsp;</div></td>
+    <td class="c4">(1.00x baseline)</td></tr>
+</table>
+<h4>Random Writes</h4>
+<table class="bn">
+<tr><td class="c1">LevelDB</td>
+    <td class="c2">135,000 ops/sec</td>
+    <td class="c3"><div class="bldb" style="width:296px">&nbsp;</div></td>
+    <td class="c4">(0.82x baseline)</td></tr>
+<tr><td class="c1">Kyoto TreeDB</td>
+    <td class="c2">159,000 ops/sec</td>
+    <td class="c3"><div class="bkct" style="width:350px">&nbsp;</div></td>
+    <td class="c4">(1.80x baseline)</td></tr>
+<tr><td class="c1">SQLite3</td>
+    <td class="c2">9,860 ops/sec</td>
+    <td class="c3"><div class="bsql" style="width:22px">&nbsp;</div></td>
+    <td class="c4">(1.00x baseline)</td></tr>
+</table>
+
+<p>LevelDB's write performance is better with compression than without
+since compression decreases the amount of data that has to be written
+to disk.  Therefore LevelDB users can leave compression enabled in
+most scenarios without having worry about a tradeoff between space
+usage and performance.  TreeDB's performance on the other hand is
+better without compression than with compression.  Presumably this is
+because TreeDB's compression library (LZO) is more expensive than
+LevelDB's compression library (Snappy).<p>
+
+<h3>E. Using More Memory</h3>
+<p>We increased the overall cache size for each database to 128 MB. For LevelDB, we partitioned 128 MB into a 120 MB write buffer and 8 MB of cache (up from 2 MB of write buffer and 2 MB of cache). For SQLite3, we kept the page size at 1024 bytes, but increased the number of pages to 131,072 (up from 4096). For TreeDB, we also kept the page size at 1024 bytes, but increased the cache size to 128 MB (up from 4 MB).</p>
+<h4>Sequential Writes</h4>
+<table class="bn">
+<tr><td class="c1">LevelDB</td>
+    <td class="c2">812,000 ops/sec</td>
+    <td class="c3"><div class="bldb" style="width:350px">&nbsp;</div></td>
+    <td class="c4">(1.04x baseline)</td></tr>
+<tr><td class="c1">Kyoto TreeDB</td>
+    <td class="c2">321,000 ops/sec</td>
+    <td class="c3"><div class="bkct" style="width:138px">&nbsp;</div></td>
+    <td class="c4">(0.94x baseline)</td></tr>
+<tr><td class="c1">SQLite3</td>
+    <td class="c2">48,500 ops/sec</td>
+    <td class="c3"><div class="bsql" style="width:21px">&nbsp;</div></td>
+    <td class="c4">(1.00x baseline)</td></tr>
+</table>
+<h4>Random Writes</h4>
+<table class="bn">
+<tr><td class="c1">LevelDB</td>
+    <td class="c2">355,000 ops/sec</td>
+    <td class="c3"><div class="bldb" style="width:350px">&nbsp;</div></td>
+    <td class="c4">(2.16x baseline)</td></tr>
+<tr><td class="c1">Kyoto TreeDB</td>
+    <td class="c2">284,000 ops/sec</td>
+    <td class="c3"><div class="bkct" style="width:280px">&nbsp;</div></td>
+    <td class="c4">(3.21x baseline)</td></tr>
+<tr><td class="c1">SQLite3</td>
+    <td class="c2">9,670 ops/sec</td>
+    <td class="c3"><div class="bsql" style="width:10px">&nbsp;</div></td>
+    <td class="c4">(0.98x baseline)</td></tr>
+</table>
+
+<p>SQLite's performance does not change substantially when compared to
+the baseline, but the random write performance for both LevelDB and
+TreeDB increases significantly.  LevelDB's performance improves
+because a larger write buffer reduces the need to merge sorted files
+(since it creates a smaller number of larger sorted files).  TreeDB's
+performance goes up because the entire database is available in memory
+for fast in-place updates.</p>
+
+  <h2>3. Read Performance under Different Configurations</h2>
+<h3>A. Larger Caches</h3>
+<p>We increased the overall memory usage to 128 MB for each database.
+For LevelDB, we allocated 8 MB to LevelDB's write buffer and 120 MB
+to LevelDB's cache. The other databases don't differentiate between a
+write buffer and a cache, so we simply set their cache size to 128
+MB.</p>
+<h4>Sequential Reads</h4>
+<table class="bn">
+<tr><td class="c1">LevelDB</td>
+    <td class="c2">5,210,000 ops/sec</td>
+    <td class="c3"><div class="bldb" style="width:350px">&nbsp;</div></td>
+    <td class="c4">(1.29x baseline)</td></tr>
+<tr><td class="c1">Kyoto TreeDB</td>
+    <td class="c2">1,070,000 ops/sec</td>
+    <td class="c3"><div class="bkct" style="width:72px">&nbsp;</div></td>
+    <td class="c4">(1.06x baseline)</td></tr>
+<tr><td class="c1">SQLite3</td>
+    <td class="c2">609,000 ops/sec</td>
+    <td class="c3"><div class="bsql" style="width:41px">&nbsp;</div></td>
+    <td class="c4">(1.59x baseline)</td></tr>
+</table>
+
+<h4>Random Reads</h4>
+<table class="bn">
+<tr><td class="c1">LevelDB</td>
+    <td class="c2">190,000 ops/sec</td>
+    <td class="c3"><div class="bldb" style="width:144px">&nbsp;</div></td>
+    <td class="c4">(1.47x baseline)</td></tr>
+<tr><td class="c1">Kyoto TreeDB</td>
+    <td class="c2">463,000 ops/sec</td>
+    <td class="c3"><div class="bkct" style="width:350px">&nbsp;</div></td>
+    <td class="c4">(3.07x baseline)</td></tr>
+<tr><td class="c1">SQLite3</td>
+    <td class="c2">186,000 ops/sec</td>
+    <td class="c3"><div class="bsql" style="width:141px">&nbsp;</div></td>
+    <td class="c4">(1.39x baseline)</td></tr>
+</table>
+
+<p>As expected, the read performance of all of the databases increases
+when the caches are enlarged.  In particular, TreeDB seems to make
+very effective use of a cache that is large enough to hold the entire
+database.</p>
+
+<h3>B. No Compression Reads </h3>
+<p>For this benchmark, we populated a database with 1 million entries consisting of 16 byte keys and 100 byte values. We compiled LevelDB and Kyoto Cabinet without compression support, so results that are read out from the database are already uncompressed. We've listed the SQLite3 baseline read performance as a point of comparison.</p>
+<h4>Sequential Reads</h4>
+<table class="bn">
+<tr><td class="c1">LevelDB</td>
+    <td class="c2">4,880,000 ops/sec</td>
+    <td class="c3"><div class="bldb" style="width:350px">&nbsp;</div></td>
+    <td class="c4">(1.21x baseline)</td></tr>
+<tr><td class="c1">Kyoto TreeDB</td>
+    <td class="c2">1,230,000 ops/sec</td>
+    <td class="c3"><div class="bkct" style="width:88px">&nbsp;</div></td>
+    <td class="c4">(3.60x baseline)</td></tr>
+<tr><td class="c1">SQLite3</td>
+    <td class="c2">383,000 ops/sec</td>
+    <td class="c3"><div class="bsql" style="width:27px">&nbsp;</div></td>
+    <td class="c4">(1.00x baseline)</td></tr>
+</table>
+<h4>Random Reads</h4>
+<table class="bn">
+<tr><td class="c1">LevelDB</td>
+    <td class="c2">149,000 ops/sec</td>
+    <td class="c3"><div class="bldb" style="width:300px">&nbsp;</div></td>
+    <td class="c4">(1.16x baseline)</td></tr>
+<tr><td class="c1">Kyoto TreeDB</td>
+    <td class="c2">175,000 ops/sec</td>
+    <td class="c3"><div class="bkct" style="width:350px">&nbsp;</div></td>
+    <td class="c4">(1.16x baseline)</td></tr>
+<tr><td class="c1">SQLite3</td>
+    <td class="c2">134,000 ops/sec</td>
+    <td class="c3"><div class="bsql" style="width:268px">&nbsp;</div></td>
+    <td class="c4">(1.00x baseline)</td></tr>
+</table>
+
+<p>Performance of both LevelDB and TreeDB improves a small amount when
+compression is disabled.  Note however that under different workloads,
+performance may very well be better with compression if it allows more
+of the working set to fit in memory.</p>
+
+<h2>Note about Ext4 Filesystems</h2>
+<p>The preceding numbers are for an ext3 file system. Synchronous writes are much slower under <a href="https://en.wikipedia.org/wiki/Ext4">ext4</a> (LevelDB drops to ~31 writes / second and TreeDB drops to ~5 writes / second; SQLite3's synchronous writes do not noticeably drop) due to ext4's different handling of <span class="code">fsync</span> / <span class="code">msync</span> calls. Even LevelDB's asynchronous write performance drops somewhat since it spreads its storage across multiple files and issues <span class="code">fsync</span> calls when switching to a new file.</p>
+
+<h2>Acknowledgements</h2>
+<p>Jeff Dean and Sanjay Ghemawat wrote LevelDB. Kevin Tseng wrote and compiled these benchmarks. Mikio Hirabayashi, Scott Hess, and Gabor Cselle provided help and advice.</p>
+</body>
+</html>
diff --git a/leveldb_base/doc/impl.md b/leveldb_base/doc/impl.md
new file mode 100644
index 0000000..c9bb621
--- /dev/null
+++ b/leveldb_base/doc/impl.md
@@ -0,0 +1,172 @@
+## Files
+
+The implementation of leveldb is similar in spirit to the representation of a
+single [Bigtable tablet (section 5.3)](https://research.google/pubs/pub27898/).
+However the organization of the files that make up the representation is
+somewhat different and is explained below.
+
+Each database is represented by a set of files stored in a directory. There are
+several different types of files as documented below:
+
+### Log files
+
+A log file (*.log) stores a sequence of recent updates. Each update is appended
+to the current log file. When the log file reaches a pre-determined size
+(approximately 4MB by default), it is converted to a sorted table (see below)
+and a new log file is created for future updates.
+
+A copy of the current log file is kept in an in-memory structure (the
+`memtable`). This copy is consulted on every read so that read operations
+reflect all logged updates.
+
+## Sorted tables
+
+A sorted table (*.ldb) stores a sequence of entries sorted by key. Each entry is
+either a value for the key, or a deletion marker for the key. (Deletion markers
+are kept around to hide obsolete values present in older sorted tables).
+
+The set of sorted tables are organized into a sequence of levels. The sorted
+table generated from a log file is placed in a special **young** level (also
+called level-0). When the number of young files exceeds a certain threshold
+(currently four), all of the young files are merged together with all of the
+overlapping level-1 files to produce a sequence of new level-1 files (we create
+a new level-1 file for every 2MB of data.)
+
+Files in the young level may contain overlapping keys. However files in other
+levels have distinct non-overlapping key ranges. Consider level number L where
+L >= 1. When the combined size of files in level-L exceeds (10^L) MB (i.e., 10MB
+for level-1, 100MB for level-2, ...), one file in level-L, and all of the
+overlapping files in level-(L+1) are merged to form a set of new files for
+level-(L+1). These merges have the effect of gradually migrating new updates
+from the young level to the largest level using only bulk reads and writes
+(i.e., minimizing expensive seeks).
+
+### Manifest
+
+A MANIFEST file lists the set of sorted tables that make up each level, the
+corresponding key ranges, and other important metadata. A new MANIFEST file
+(with a new number embedded in the file name) is created whenever the database
+is reopened. The MANIFEST file is formatted as a log, and changes made to the
+serving state (as files are added or removed) are appended to this log.
+
+### Current
+
+CURRENT is a simple text file that contains the name of the latest MANIFEST
+file.
+
+### Info logs
+
+Informational messages are printed to files named LOG and LOG.old.
+
+### Others
+
+Other files used for miscellaneous purposes may also be present (LOCK, *.dbtmp).
+
+## Level 0
+
+When the log file grows above a certain size (4MB by default):
+Create a brand new memtable and log file and direct future updates here.
+
+In the background:
+
+1. Write the contents of the previous memtable to an sstable.
+2. Discard the memtable.
+3. Delete the old log file and the old memtable.
+4. Add the new sstable to the young (level-0) level.
+
+## Compactions
+
+When the size of level L exceeds its limit, we compact it in a background
+thread. The compaction picks a file from level L and all overlapping files from
+the next level L+1. Note that if a level-L file overlaps only part of a
+level-(L+1) file, the entire file at level-(L+1) is used as an input to the
+compaction and will be discarded after the compaction.  Aside: because level-0
+is special (files in it may overlap each other), we treat compactions from
+level-0 to level-1 specially: a level-0 compaction may pick more than one
+level-0 file in case some of these files overlap each other.
+
+A compaction merges the contents of the picked files to produce a sequence of
+level-(L+1) files. We switch to producing a new level-(L+1) file after the
+current output file has reached the target file size (2MB). We also switch to a
+new output file when the key range of the current output file has grown enough
+to overlap more than ten level-(L+2) files.  This last rule ensures that a later
+compaction of a level-(L+1) file will not pick up too much data from
+level-(L+2).
+
+The old files are discarded and the new files are added to the serving state.
+
+Compactions for a particular level rotate through the key space. In more detail,
+for each level L, we remember the ending key of the last compaction at level L.
+The next compaction for level L will pick the first file that starts after this
+key (wrapping around to the beginning of the key space if there is no such
+file).
+
+Compactions drop overwritten values. They also drop deletion markers if there
+are no higher numbered levels that contain a file whose range overlaps the
+current key.
+
+### Timing
+
+Level-0 compactions will read up to four 1MB files from level-0, and at worst
+all the level-1 files (10MB). I.e., we will read 14MB and write 14MB.
+
+Other than the special level-0 compactions, we will pick one 2MB file from level
+L. In the worst case, this will overlap ~ 12 files from level L+1 (10 because
+level-(L+1) is ten times the size of level-L, and another two at the boundaries
+since the file ranges at level-L will usually not be aligned with the file
+ranges at level-L+1). The compaction will therefore read 26MB and write 26MB.
+Assuming a disk IO rate of 100MB/s (ballpark range for modern drives), the worst
+compaction cost will be approximately 0.5 second.
+
+If we throttle the background writing to something small, say 10% of the full
+100MB/s speed, a compaction may take up to 5 seconds. If the user is writing at
+10MB/s, we might build up lots of level-0 files (~50 to hold the 5*10MB). This
+may significantly increase the cost of reads due to the overhead of merging more
+files together on every read.
+
+Solution 1: To reduce this problem, we might want to increase the log switching
+threshold when the number of level-0 files is large. Though the downside is that
+the larger this threshold, the more memory we will need to hold the
+corresponding memtable.
+
+Solution 2: We might want to decrease write rate artificially when the number of
+level-0 files goes up.
+
+Solution 3: We work on reducing the cost of very wide merges. Perhaps most of
+the level-0 files will have their blocks sitting uncompressed in the cache and
+we will only need to worry about the O(N) complexity in the merging iterator.
+
+### Number of files
+
+Instead of always making 2MB files, we could make larger files for larger levels
+to reduce the total file count, though at the expense of more bursty
+compactions.  Alternatively, we could shard the set of files into multiple
+directories.
+
+An experiment on an ext3 filesystem on Feb 04, 2011 shows the following timings
+to do 100K file opens in directories with varying number of files:
+
+
+| Files in directory | Microseconds to open a file |
+|-------------------:|----------------------------:|
+|               1000 |                           9 |
+|              10000 |                          10 |
+|             100000 |                          16 |
+
+So maybe even the sharding is not necessary on modern filesystems?
+
+## Recovery
+
+* Read CURRENT to find name of the latest committed MANIFEST
+* Read the named MANIFEST file
+* Clean up stale files
+* We could open all sstables here, but it is probably better to be lazy...
+* Convert log chunk to a new level-0 sstable
+* Start directing new writes to a new log file with recovered sequence#
+
+## Garbage collection of files
+
+`RemoveObsoleteFiles()` is called at the end of every compaction and at the end
+of recovery. It finds the names of all files in the database. It deletes all log
+files that are not the current log file. It deletes all table files that are not
+referenced from some level and are not the output of an active compaction.
diff --git a/leveldb_base/doc/index.md b/leveldb_base/doc/index.md
new file mode 100644
index 0000000..0f6d649
--- /dev/null
+++ b/leveldb_base/doc/index.md
@@ -0,0 +1,524 @@
+leveldb
+=======
+
+_Jeff Dean, Sanjay Ghemawat_
+
+The leveldb library provides a persistent key value store. Keys and values are
+arbitrary byte arrays.  The keys are ordered within the key value store
+according to a user-specified comparator function.
+
+## Opening A Database
+
+A leveldb database has a name which corresponds to a file system directory. All
+of the contents of database are stored in this directory. The following example
+shows how to open a database, creating it if necessary:
+
+```c++
+#include <cassert>
+#include "leveldb/db.h"
+
+leveldb::DB* db;
+leveldb::Options options;
+options.create_if_missing = true;
+leveldb::Status status = leveldb::DB::Open(options, "/tmp/testdb", &db);
+assert(status.ok());
+...
+```
+
+If you want to raise an error if the database already exists, add the following
+line before the `leveldb::DB::Open` call:
+
+```c++
+options.error_if_exists = true;
+```
+
+## Status
+
+You may have noticed the `leveldb::Status` type above. Values of this type are
+returned by most functions in leveldb that may encounter an error. You can check
+if such a result is ok, and also print an associated error message:
+
+```c++
+leveldb::Status s = ...;
+if (!s.ok()) cerr << s.ToString() << endl;
+```
+
+## Closing A Database
+
+When you are done with a database, just delete the database object. Example:
+
+```c++
+... open the db as described above ...
+... do something with db ...
+delete db;
+```
+
+## Reads And Writes
+
+The database provides Put, Delete, and Get methods to modify/query the database.
+For example, the following code moves the value stored under key1 to key2.
+
+```c++
+std::string value;
+leveldb::Status s = db->Get(leveldb::ReadOptions(), key1, &value);
+if (s.ok()) s = db->Put(leveldb::WriteOptions(), key2, value);
+if (s.ok()) s = db->Delete(leveldb::WriteOptions(), key1);
+```
+
+## Atomic Updates
+
+Note that if the process dies after the Put of key2 but before the delete of
+key1, the same value may be left stored under multiple keys. Such problems can
+be avoided by using the `WriteBatch` class to atomically apply a set of updates:
+
+```c++
+#include "leveldb/write_batch.h"
+...
+std::string value;
+leveldb::Status s = db->Get(leveldb::ReadOptions(), key1, &value);
+if (s.ok()) {
+  leveldb::WriteBatch batch;
+  batch.Delete(key1);
+  batch.Put(key2, value);
+  s = db->Write(leveldb::WriteOptions(), &batch);
+}
+```
+
+The `WriteBatch` holds a sequence of edits to be made to the database, and these
+edits within the batch are applied in order. Note that we called Delete before
+Put so that if key1 is identical to key2, we do not end up erroneously dropping
+the value entirely.
+
+Apart from its atomicity benefits, `WriteBatch` may also be used to speed up
+bulk updates by placing lots of individual mutations into the same batch.
+
+## Synchronous Writes
+
+By default, each write to leveldb is asynchronous: it returns after pushing the
+write from the process into the operating system. The transfer from operating
+system memory to the underlying persistent storage happens asynchronously. The
+sync flag can be turned on for a particular write to make the write operation
+not return until the data being written has been pushed all the way to
+persistent storage. (On Posix systems, this is implemented by calling either
+`fsync(...)` or `fdatasync(...)` or `msync(..., MS_SYNC)` before the write
+operation returns.)
+
+```c++
+leveldb::WriteOptions write_options;
+write_options.sync = true;
+db->Put(write_options, ...);
+```
+
+Asynchronous writes are often more than a thousand times as fast as synchronous
+writes. The downside of asynchronous writes is that a crash of the machine may
+cause the last few updates to be lost. Note that a crash of just the writing
+process (i.e., not a reboot) will not cause any loss since even when sync is
+false, an update is pushed from the process memory into the operating system
+before it is considered done.
+
+Asynchronous writes can often be used safely. For example, when loading a large
+amount of data into the database you can handle lost updates by restarting the
+bulk load after a crash. A hybrid scheme is also possible where every Nth write
+is synchronous, and in the event of a crash, the bulk load is restarted just
+after the last synchronous write finished by the previous run. (The synchronous
+write can update a marker that describes where to restart on a crash.)
+
+`WriteBatch` provides an alternative to asynchronous writes. Multiple updates
+may be placed in the same WriteBatch and applied together using a synchronous
+write (i.e., `write_options.sync` is set to true). The extra cost of the
+synchronous write will be amortized across all of the writes in the batch.
+
+## Concurrency
+
+A database may only be opened by one process at a time. The leveldb
+implementation acquires a lock from the operating system to prevent misuse.
+Within a single process, the same `leveldb::DB` object may be safely shared by
+multiple concurrent threads. I.e., different threads may write into or fetch
+iterators or call Get on the same database without any external synchronization
+(the leveldb implementation will automatically do the required synchronization).
+However other objects (like Iterator and `WriteBatch`) may require external
+synchronization. If two threads share such an object, they must protect access
+to it using their own locking protocol. More details are available in the public
+header files.
+
+## Iteration
+
+The following example demonstrates how to print all key,value pairs in a
+database.
+
+```c++
+leveldb::Iterator* it = db->NewIterator(leveldb::ReadOptions());
+for (it->SeekToFirst(); it->Valid(); it->Next()) {
+  cout << it->key().ToString() << ": "  << it->value().ToString() << endl;
+}
+assert(it->status().ok());  // Check for any errors found during the scan
+delete it;
+```
+
+The following variation shows how to process just the keys in the range
+[start,limit):
+
+```c++
+for (it->Seek(start);
+   it->Valid() && it->key().ToString() < limit;
+   it->Next()) {
+  ...
+}
+```
+
+You can also process entries in reverse order. (Caveat: reverse iteration may be
+somewhat slower than forward iteration.)
+
+```c++
+for (it->SeekToLast(); it->Valid(); it->Prev()) {
+  ...
+}
+```
+
+## Snapshots
+
+Snapshots provide consistent read-only views over the entire state of the
+key-value store.  `ReadOptions::snapshot` may be non-NULL to indicate that a
+read should operate on a particular version of the DB state. If
+`ReadOptions::snapshot` is NULL, the read will operate on an implicit snapshot
+of the current state.
+
+Snapshots are created by the `DB::GetSnapshot()` method:
+
+```c++
+leveldb::ReadOptions options;
+options.snapshot = db->GetSnapshot();
+... apply some updates to db ...
+leveldb::Iterator* iter = db->NewIterator(options);
+... read using iter to view the state when the snapshot was created ...
+delete iter;
+db->ReleaseSnapshot(options.snapshot);
+```
+
+Note that when a snapshot is no longer needed, it should be released using the
+`DB::ReleaseSnapshot` interface. This allows the implementation to get rid of
+state that was being maintained just to support reading as of that snapshot.
+
+## Slice
+
+The return value of the `it->key()` and `it->value()` calls above are instances
+of the `leveldb::Slice` type. Slice is a simple structure that contains a length
+and a pointer to an external byte array. Returning a Slice is a cheaper
+alternative to returning a `std::string` since we do not need to copy
+potentially large keys and values. In addition, leveldb methods do not return
+null-terminated C-style strings since leveldb keys and values are allowed to
+contain `'\0'` bytes.
+
+C++ strings and null-terminated C-style strings can be easily converted to a
+Slice:
+
+```c++
+leveldb::Slice s1 = "hello";
+
+std::string str("world");
+leveldb::Slice s2 = str;
+```
+
+A Slice can be easily converted back to a C++ string:
+
+```c++
+std::string str = s1.ToString();
+assert(str == std::string("hello"));
+```
+
+Be careful when using Slices since it is up to the caller to ensure that the
+external byte array into which the Slice points remains live while the Slice is
+in use. For example, the following is buggy:
+
+```c++
+leveldb::Slice slice;
+if (...) {
+  std::string str = ...;
+  slice = str;
+}
+Use(slice);
+```
+
+When the if statement goes out of scope, str will be destroyed and the backing
+storage for slice will disappear.
+
+## Comparators
+
+The preceding examples used the default ordering function for key, which orders
+bytes lexicographically. You can however supply a custom comparator when opening
+a database.  For example, suppose each database key consists of two numbers and
+we should sort by the first number, breaking ties by the second number. First,
+define a proper subclass of `leveldb::Comparator` that expresses these rules:
+
+```c++
+class TwoPartComparator : public leveldb::Comparator {
+ public:
+  // Three-way comparison function:
+  //   if a < b: negative result
+  //   if a > b: positive result
+  //   else: zero result
+  int Compare(const leveldb::Slice& a, const leveldb::Slice& b) const {
+    int a1, a2, b1, b2;
+    ParseKey(a, &a1, &a2);
+    ParseKey(b, &b1, &b2);
+    if (a1 < b1) return -1;
+    if (a1 > b1) return +1;
+    if (a2 < b2) return -1;
+    if (a2 > b2) return +1;
+    return 0;
+  }
+
+  // Ignore the following methods for now:
+  const char* Name() const { return "TwoPartComparator"; }
+  void FindShortestSeparator(std::string*, const leveldb::Slice&) const {}
+  void FindShortSuccessor(std::string*) const {}
+};
+```
+
+Now create a database using this custom comparator:
+
+```c++
+TwoPartComparator cmp;
+leveldb::DB* db;
+leveldb::Options options;
+options.create_if_missing = true;
+options.comparator = &cmp;
+leveldb::Status status = leveldb::DB::Open(options, "/tmp/testdb", &db);
+...
+```
+
+### Backwards compatibility
+
+The result of the comparator's Name method is attached to the database when it
+is created, and is checked on every subsequent database open. If the name
+changes, the `leveldb::DB::Open` call will fail. Therefore, change the name if
+and only if the new key format and comparison function are incompatible with
+existing databases, and it is ok to discard the contents of all existing
+databases.
+
+You can however still gradually evolve your key format over time with a little
+bit of pre-planning. For example, you could store a version number at the end of
+each key (one byte should suffice for most uses). When you wish to switch to a
+new key format (e.g., adding an optional third part to the keys processed by
+`TwoPartComparator`), (a) keep the same comparator name (b) increment the
+version number for new keys (c) change the comparator function so it uses the
+version numbers found in the keys to decide how to interpret them.
+
+## Performance
+
+Performance can be tuned by changing the default values of the types defined in
+`include/options.h`.
+
+### Block size
+
+leveldb groups adjacent keys together into the same block and such a block is
+the unit of transfer to and from persistent storage. The default block size is
+approximately 4096 uncompressed bytes.  Applications that mostly do bulk scans
+over the contents of the database may wish to increase this size. Applications
+that do a lot of point reads of small values may wish to switch to a smaller
+block size if performance measurements indicate an improvement. There isn't much
+benefit in using blocks smaller than one kilobyte, or larger than a few
+megabytes. Also note that compression will be more effective with larger block
+sizes.
+
+### Compression
+
+Each block is individually compressed before being written to persistent
+storage. Compression is on by default since the default compression method is
+very fast, and is automatically disabled for uncompressible data. In rare cases,
+applications may want to disable compression entirely, but should only do so if
+benchmarks show a performance improvement:
+
+```c++
+leveldb::Options options;
+options.compression = leveldb::kNoCompression;
+... leveldb::DB::Open(options, name, ...) ....
+```
+
+### Cache
+
+The contents of the database are stored in a set of files in the filesystem and
+each file stores a sequence of compressed blocks. If options.block_cache is
+non-NULL, it is used to cache frequently used uncompressed block contents.
+
+```c++
+#include "leveldb/cache.h"
+
+leveldb::Options options;
+options.block_cache = leveldb::NewLRUCache(100 * 1048576);  // 100MB cache
+leveldb::DB* db;
+leveldb::DB::Open(options, name, &db);
+... use the db ...
+delete db
+delete options.block_cache;
+```
+
+Note that the cache holds uncompressed data, and therefore it should be sized
+according to application level data sizes, without any reduction from
+compression. (Caching of compressed blocks is left to the operating system
+buffer cache, or any custom Env implementation provided by the client.)
+
+When performing a bulk read, the application may wish to disable caching so that
+the data processed by the bulk read does not end up displacing most of the
+cached contents. A per-iterator option can be used to achieve this:
+
+```c++
+leveldb::ReadOptions options;
+options.fill_cache = false;
+leveldb::Iterator* it = db->NewIterator(options);
+for (it->SeekToFirst(); it->Valid(); it->Next()) {
+  ...
+}
+delete it;
+```
+
+### Key Layout
+
+Note that the unit of disk transfer and caching is a block. Adjacent keys
+(according to the database sort order) will usually be placed in the same block.
+Therefore the application can improve its performance by placing keys that are
+accessed together near each other and placing infrequently used keys in a
+separate region of the key space.
+
+For example, suppose we are implementing a simple file system on top of leveldb.
+The types of entries we might wish to store are:
+
+    filename -> permission-bits, length, list of file_block_ids
+    file_block_id -> data
+
+We might want to prefix filename keys with one letter (say '/') and the
+`file_block_id` keys with a different letter (say '0') so that scans over just
+the metadata do not force us to fetch and cache bulky file contents.
+
+### Filters
+
+Because of the way leveldb data is organized on disk, a single `Get()` call may
+involve multiple reads from disk. The optional FilterPolicy mechanism can be
+used to reduce the number of disk reads substantially.
+
+```c++
+leveldb::Options options;
+options.filter_policy = NewBloomFilterPolicy(10);
+leveldb::DB* db;
+leveldb::DB::Open(options, "/tmp/testdb", &db);
+... use the database ...
+delete db;
+delete options.filter_policy;
+```
+
+The preceding code associates a Bloom filter based filtering policy with the
+database.  Bloom filter based filtering relies on keeping some number of bits of
+data in memory per key (in this case 10 bits per key since that is the argument
+we passed to `NewBloomFilterPolicy`). This filter will reduce the number of
+unnecessary disk reads needed for Get() calls by a factor of approximately
+a 100. Increasing the bits per key will lead to a larger reduction at the cost
+of more memory usage. We recommend that applications whose working set does not
+fit in memory and that do a lot of random reads set a filter policy.
+
+If you are using a custom comparator, you should ensure that the filter policy
+you are using is compatible with your comparator. For example, consider a
+comparator that ignores trailing spaces when comparing keys.
+`NewBloomFilterPolicy` must not be used with such a comparator. Instead, the
+application should provide a custom filter policy that also ignores trailing
+spaces. For example:
+
+```c++
+class CustomFilterPolicy : public leveldb::FilterPolicy {
+ private:
+  leveldb::FilterPolicy* builtin_policy_;
+
+ public:
+  CustomFilterPolicy() : builtin_policy_(leveldb::NewBloomFilterPolicy(10)) {}
+  ~CustomFilterPolicy() { delete builtin_policy_; }
+
+  const char* Name() const { return "IgnoreTrailingSpacesFilter"; }
+
+  void CreateFilter(const leveldb::Slice* keys, int n, std::string* dst) const {
+    // Use builtin bloom filter code after removing trailing spaces
+    std::vector<leveldb::Slice> trimmed(n);
+    for (int i = 0; i < n; i++) {
+      trimmed[i] = RemoveTrailingSpaces(keys[i]);
+    }
+    builtin_policy_->CreateFilter(trimmed.data(), n, dst);
+  }
+};
+```
+
+Advanced applications may provide a filter policy that does not use a bloom
+filter but uses some other mechanism for summarizing a set of keys. See
+`leveldb/filter_policy.h` for detail.
+
+## Checksums
+
+leveldb associates checksums with all data it stores in the file system. There
+are two separate controls provided over how aggressively these checksums are
+verified:
+
+`ReadOptions::verify_checksums` may be set to true to force checksum
+verification of all data that is read from the file system on behalf of a
+particular read.  By default, no such verification is done.
+
+`Options::paranoid_checks` may be set to true before opening a database to make
+the database implementation raise an error as soon as it detects an internal
+corruption. Depending on which portion of the database has been corrupted, the
+error may be raised when the database is opened, or later by another database
+operation. By default, paranoid checking is off so that the database can be used
+even if parts of its persistent storage have been corrupted.
+
+If a database is corrupted (perhaps it cannot be opened when paranoid checking
+is turned on), the `leveldb::RepairDB` function may be used to recover as much
+of the data as possible
+
+## Approximate Sizes
+
+The `GetApproximateSizes` method can used to get the approximate number of bytes
+of file system space used by one or more key ranges.
+
+```c++
+leveldb::Range ranges[2];
+ranges[0] = leveldb::Range("a", "c");
+ranges[1] = leveldb::Range("x", "z");
+uint64_t sizes[2];
+db->GetApproximateSizes(ranges, 2, sizes);
+```
+
+The preceding call will set `sizes[0]` to the approximate number of bytes of
+file system space used by the key range `[a..c)` and `sizes[1]` to the
+approximate number of bytes used by the key range `[x..z)`.
+
+## Environment
+
+All file operations (and other operating system calls) issued by the leveldb
+implementation are routed through a `leveldb::Env` object. Sophisticated clients
+may wish to provide their own Env implementation to get better control.
+For example, an application may introduce artificial delays in the file IO
+paths to limit the impact of leveldb on other activities in the system.
+
+```c++
+class SlowEnv : public leveldb::Env {
+  ... implementation of the Env interface ...
+};
+
+SlowEnv env;
+leveldb::Options options;
+options.env = &env;
+Status s = leveldb::DB::Open(options, ...);
+```
+
+## Porting
+
+leveldb may be ported to a new platform by providing platform specific
+implementations of the types/methods/functions exported by
+`leveldb/port/port.h`.  See `leveldb/port/port_example.h` for more details.
+
+In addition, the new platform may need a new default `leveldb::Env`
+implementation.  See `leveldb/util/env_posix.h` for an example.
+
+## Other Information
+
+Details about the leveldb implementation may be found in the following
+documents:
+
+1. [Implementation notes](impl.md)
+2. [Format of an immutable Table file](table_format.md)
+3. [Format of a log file](log_format.md)
diff --git a/leveldb_base/doc/log_format.md b/leveldb_base/doc/log_format.md
new file mode 100644
index 0000000..f32cb5d
--- /dev/null
+++ b/leveldb_base/doc/log_format.md
@@ -0,0 +1,75 @@
+leveldb Log format
+==================
+The log file contents are a sequence of 32KB blocks.  The only exception is that
+the tail of the file may contain a partial block.
+
+Each block consists of a sequence of records:
+
+    block := record* trailer?
+    record :=
+      checksum: uint32     // crc32c of type and data[] ; little-endian
+      length: uint16       // little-endian
+      type: uint8          // One of FULL, FIRST, MIDDLE, LAST
+      data: uint8[length]
+
+A record never starts within the last six bytes of a block (since it won't fit).
+Any leftover bytes here form the trailer, which must consist entirely of zero
+bytes and must be skipped by readers.
+
+Aside: if exactly seven bytes are left in the current block, and a new non-zero
+length record is added, the writer must emit a FIRST record (which contains zero
+bytes of user data) to fill up the trailing seven bytes of the block and then
+emit all of the user data in subsequent blocks.
+
+More types may be added in the future.  Some Readers may skip record types they
+do not understand, others may report that some data was skipped.
+
+    FULL == 1
+    FIRST == 2
+    MIDDLE == 3
+    LAST == 4
+
+The FULL record contains the contents of an entire user record.
+
+FIRST, MIDDLE, LAST are types used for user records that have been split into
+multiple fragments (typically because of block boundaries).  FIRST is the type
+of the first fragment of a user record, LAST is the type of the last fragment of
+a user record, and MIDDLE is the type of all interior fragments of a user
+record.
+
+Example: consider a sequence of user records:
+
+    A: length 1000
+    B: length 97270
+    C: length 8000
+
+**A** will be stored as a FULL record in the first block.
+
+**B** will be split into three fragments: first fragment occupies the rest of
+the first block, second fragment occupies the entirety of the second block, and
+the third fragment occupies a prefix of the third block.  This will leave six
+bytes free in the third block, which will be left empty as the trailer.
+
+**C** will be stored as a FULL record in the fourth block.
+
+----
+
+## Some benefits over the recordio format:
+
+1. We do not need any heuristics for resyncing - just go to next block boundary
+   and scan.  If there is a corruption, skip to the next block.  As a
+   side-benefit, we do not get confused when part of the contents of one log
+   file are embedded as a record inside another log file.
+
+2. Splitting at approximate boundaries (e.g., for mapreduce) is simple: find the
+   next block boundary and skip records until we hit a FULL or FIRST record.
+
+3. We do not need extra buffering for large records.
+
+## Some downsides compared to recordio format:
+
+1. No packing of tiny records.  This could be fixed by adding a new record type,
+   so it is a shortcoming of the current implementation, not necessarily the
+   format.
+
+2. No compression.  Again, this could be fixed by adding new record types.
diff --git a/leveldb_base/doc/table_format.md b/leveldb_base/doc/table_format.md
new file mode 100644
index 0000000..5fe7e72
--- /dev/null
+++ b/leveldb_base/doc/table_format.md
@@ -0,0 +1,107 @@
+leveldb File format
+===================
+
+    <beginning_of_file>
+    [data block 1]
+    [data block 2]
+    ...
+    [data block N]
+    [meta block 1]
+    ...
+    [meta block K]
+    [metaindex block]
+    [index block]
+    [Footer]        (fixed size; starts at file_size - sizeof(Footer))
+    <end_of_file>
+
+The file contains internal pointers.  Each such pointer is called
+a BlockHandle and contains the following information:
+
+    offset:   varint64
+    size:     varint64
+
+See [varints](https://developers.google.com/protocol-buffers/docs/encoding#varints)
+for an explanation of varint64 format.
+
+1.  The sequence of key/value pairs in the file are stored in sorted
+order and partitioned into a sequence of data blocks.  These blocks
+come one after another at the beginning of the file.  Each data block
+is formatted according to the code in `block_builder.cc`, and then
+optionally compressed.
+
+2. After the data blocks we store a bunch of meta blocks.  The
+supported meta block types are described below.  More meta block types
+may be added in the future.  Each meta block is again formatted using
+`block_builder.cc` and then optionally compressed.
+
+3. A "metaindex" block.  It contains one entry for every other meta
+block where the key is the name of the meta block and the value is a
+BlockHandle pointing to that meta block.
+
+4. An "index" block.  This block contains one entry per data block,
+where the key is a string >= last key in that data block and before
+the first key in the successive data block.  The value is the
+BlockHandle for the data block.
+
+5. At the very end of the file is a fixed length footer that contains
+the BlockHandle of the metaindex and index blocks as well as a magic number.
+
+        metaindex_handle: char[p];     // Block handle for metaindex
+        index_handle:     char[q];     // Block handle for index
+        padding:          char[40-p-q];// zeroed bytes to make fixed length
+                                       // (40==2*BlockHandle::kMaxEncodedLength)
+        magic:            fixed64;     // == 0xdb4775248b80fb57 (little-endian)
+
+## "filter" Meta Block
+
+If a `FilterPolicy` was specified when the database was opened, a
+filter block is stored in each table.  The "metaindex" block contains
+an entry that maps from `filter.<N>` to the BlockHandle for the filter
+block where `<N>` is the string returned by the filter policy's
+`Name()` method.
+
+The filter block stores a sequence of filters, where filter i contains
+the output of `FilterPolicy::CreateFilter()` on all keys that are stored
+in a block whose file offset falls within the range
+
+    [ i*base ... (i+1)*base-1 ]
+
+Currently, "base" is 2KB.  So for example, if blocks X and Y start in
+the range `[ 0KB .. 2KB-1 ]`, all of the keys in X and Y will be
+converted to a filter by calling `FilterPolicy::CreateFilter()`, and the
+resulting filter will be stored as the first filter in the filter
+block.
+
+The filter block is formatted as follows:
+
+    [filter 0]
+    [filter 1]
+    [filter 2]
+    ...
+    [filter N-1]
+
+    [offset of filter 0]                  : 4 bytes
+    [offset of filter 1]                  : 4 bytes
+    [offset of filter 2]                  : 4 bytes
+    ...
+    [offset of filter N-1]                : 4 bytes
+
+    [offset of beginning of offset array] : 4 bytes
+    lg(base)                              : 1 byte
+
+The offset array at the end of the filter block allows efficient
+mapping from a data block offset to the corresponding filter.
+
+## "stats" Meta Block
+
+This meta block contains a bunch of stats.  The key is the name
+of the statistic.  The value contains the statistic.
+
+TODO(postrelease): record following stats.
+
+    data size
+    index size
+    key size (uncompressed)
+    value size (uncompressed)
+    number of entries
+    number of data blocks
diff --git a/leveldb_base/helpers/memenv/memenv.cc b/leveldb_base/helpers/memenv/memenv.cc
new file mode 100644
index 0000000..e476613
--- /dev/null
+++ b/leveldb_base/helpers/memenv/memenv.cc
@@ -0,0 +1,390 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "helpers/memenv/memenv.h"
+
+#include <cstring>
+#include <limits>
+#include <map>
+#include <string>
+#include <vector>
+
+#include "leveldb/env.h"
+#include "leveldb/status.h"
+#include "port/port.h"
+#include "port/thread_annotations.h"
+#include "util/mutexlock.h"
+
+namespace leveldb {
+
+namespace {
+
+class FileState {
+ public:
+  // FileStates are reference counted. The initial reference count is zero
+  // and the caller must call Ref() at least once.
+  FileState() : refs_(0), size_(0) {}
+
+  // No copying allowed.
+  FileState(const FileState&) = delete;
+  FileState& operator=(const FileState&) = delete;
+
+  // Increase the reference count.
+  void Ref() {
+    MutexLock lock(&refs_mutex_);
+    ++refs_;
+  }
+
+  // Decrease the reference count. Delete if this is the last reference.
+  void Unref() {
+    bool do_delete = false;
+
+    {
+      MutexLock lock(&refs_mutex_);
+      --refs_;
+      assert(refs_ >= 0);
+      if (refs_ <= 0) {
+        do_delete = true;
+      }
+    }
+
+    if (do_delete) {
+      delete this;
+    }
+  }
+
+  uint64_t Size() const {
+    MutexLock lock(&blocks_mutex_);
+    return size_;
+  }
+
+  void Truncate() {
+    MutexLock lock(&blocks_mutex_);
+    for (char*& block : blocks_) {
+      delete[] block;
+    }
+    blocks_.clear();
+    size_ = 0;
+  }
+
+  Status Read(uint64_t offset, size_t n, Slice* result, char* scratch) const {
+    MutexLock lock(&blocks_mutex_);
+    if (offset > size_) {
+      return Status::IOError("Offset greater than file size.");
+    }
+    const uint64_t available = size_ - offset;
+    if (n > available) {
+      n = static_cast<size_t>(available);
+    }
+    if (n == 0) {
+      *result = Slice();
+      return Status::OK();
+    }
+
+    assert(offset / kBlockSize <= std::numeric_limits<size_t>::max());
+    size_t block = static_cast<size_t>(offset / kBlockSize);
+    size_t block_offset = offset % kBlockSize;
+    size_t bytes_to_copy = n;
+    char* dst = scratch;
+
+    while (bytes_to_copy > 0) {
+      size_t avail = kBlockSize - block_offset;
+      if (avail > bytes_to_copy) {
+        avail = bytes_to_copy;
+      }
+      std::memcpy(dst, blocks_[block] + block_offset, avail);
+
+      bytes_to_copy -= avail;
+      dst += avail;
+      block++;
+      block_offset = 0;
+    }
+
+    *result = Slice(scratch, n);
+    return Status::OK();
+  }
+
+  Status Append(const Slice& data) {
+    const char* src = data.data();
+    size_t src_len = data.size();
+
+    MutexLock lock(&blocks_mutex_);
+    while (src_len > 0) {
+      size_t avail;
+      size_t offset = size_ % kBlockSize;
+
+      if (offset != 0) {
+        // There is some room in the last block.
+        avail = kBlockSize - offset;
+      } else {
+        // No room in the last block; push new one.
+        blocks_.push_back(new char[kBlockSize]);
+        avail = kBlockSize;
+      }
+
+      if (avail > src_len) {
+        avail = src_len;
+      }
+      std::memcpy(blocks_.back() + offset, src, avail);
+      src_len -= avail;
+      src += avail;
+      size_ += avail;
+    }
+
+    return Status::OK();
+  }
+
+ private:
+  enum { kBlockSize = 8 * 1024 };
+
+  // Private since only Unref() should be used to delete it.
+  ~FileState() { Truncate(); }
+
+  port::Mutex refs_mutex_;
+  int refs_ GUARDED_BY(refs_mutex_);
+
+  mutable port::Mutex blocks_mutex_;
+  std::vector<char*> blocks_ GUARDED_BY(blocks_mutex_);
+  uint64_t size_ GUARDED_BY(blocks_mutex_);
+};
+
+class SequentialFileImpl : public SequentialFile {
+ public:
+  explicit SequentialFileImpl(FileState* file) : file_(file), pos_(0) {
+    file_->Ref();
+  }
+
+  ~SequentialFileImpl() override { file_->Unref(); }
+
+  Status Read(size_t n, Slice* result, char* scratch) override {
+    Status s = file_->Read(pos_, n, result, scratch);
+    if (s.ok()) {
+      pos_ += result->size();
+    }
+    return s;
+  }
+
+  Status Skip(uint64_t n) override {
+    if (pos_ > file_->Size()) {
+      return Status::IOError("pos_ > file_->Size()");
+    }
+    const uint64_t available = file_->Size() - pos_;
+    if (n > available) {
+      n = available;
+    }
+    pos_ += n;
+    return Status::OK();
+  }
+
+ private:
+  FileState* file_;
+  uint64_t pos_;
+};
+
+class RandomAccessFileImpl : public RandomAccessFile {
+ public:
+  explicit RandomAccessFileImpl(FileState* file) : file_(file) { file_->Ref(); }
+
+  ~RandomAccessFileImpl() override { file_->Unref(); }
+
+  Status Read(uint64_t offset, size_t n, Slice* result,
+              char* scratch) const override {
+    return file_->Read(offset, n, result, scratch);
+  }
+
+ private:
+  FileState* file_;
+};
+
+class WritableFileImpl : public WritableFile {
+ public:
+  WritableFileImpl(FileState* file) : file_(file) { file_->Ref(); }
+
+  ~WritableFileImpl() override { file_->Unref(); }
+
+  Status Append(const Slice& data) override { return file_->Append(data); }
+
+  Status Close() override { return Status::OK(); }
+  Status Flush() override { return Status::OK(); }
+  Status Sync() override { return Status::OK(); }
+
+ private:
+  FileState* file_;
+};
+
+class NoOpLogger : public Logger {
+ public:
+  void Logv(const char* format, std::va_list ap) override {}
+};
+
+class InMemoryEnv : public EnvWrapper {
+ public:
+  explicit InMemoryEnv(Env* base_env) : EnvWrapper(base_env) {}
+
+  ~InMemoryEnv() override {
+    for (const auto& kvp : file_map_) {
+      kvp.second->Unref();
+    }
+  }
+
+  // Partial implementation of the Env interface.
+  Status NewSequentialFile(const std::string& fname,
+                           SequentialFile** result) override {
+    MutexLock lock(&mutex_);
+    if (file_map_.find(fname) == file_map_.end()) {
+      *result = nullptr;
+      return Status::IOError(fname, "File not found");
+    }
+
+    *result = new SequentialFileImpl(file_map_[fname]);
+    return Status::OK();
+  }
+
+  Status NewRandomAccessFile(const std::string& fname,
+                             RandomAccessFile** result) override {
+    MutexLock lock(&mutex_);
+    if (file_map_.find(fname) == file_map_.end()) {
+      *result = nullptr;
+      return Status::IOError(fname, "File not found");
+    }
+
+    *result = new RandomAccessFileImpl(file_map_[fname]);
+    return Status::OK();
+  }
+
+  Status NewWritableFile(const std::string& fname,
+                         WritableFile** result) override {
+    MutexLock lock(&mutex_);
+    FileSystem::iterator it = file_map_.find(fname);
+
+    FileState* file;
+    if (it == file_map_.end()) {
+      // File is not currently open.
+      file = new FileState();
+      file->Ref();
+      file_map_[fname] = file;
+    } else {
+      file = it->second;
+      file->Truncate();
+    }
+
+    *result = new WritableFileImpl(file);
+    return Status::OK();
+  }
+
+  Status NewAppendableFile(const std::string& fname,
+                           WritableFile** result) override {
+    MutexLock lock(&mutex_);
+    FileState** sptr = &file_map_[fname];
+    FileState* file = *sptr;
+    if (file == nullptr) {
+      file = new FileState();
+      file->Ref();
+    }
+    *result = new WritableFileImpl(file);
+    return Status::OK();
+  }
+
+  bool FileExists(const std::string& fname) override {
+    MutexLock lock(&mutex_);
+    return file_map_.find(fname) != file_map_.end();
+  }
+
+  Status GetChildren(const std::string& dir,
+                     std::vector<std::string>* result) override {
+    MutexLock lock(&mutex_);
+    result->clear();
+
+    for (const auto& kvp : file_map_) {
+      const std::string& filename = kvp.first;
+
+      if (filename.size() >= dir.size() + 1 && filename[dir.size()] == '/' &&
+          Slice(filename).starts_with(Slice(dir))) {
+        result->push_back(filename.substr(dir.size() + 1));
+      }
+    }
+
+    return Status::OK();
+  }
+
+  void RemoveFileInternal(const std::string& fname)
+      EXCLUSIVE_LOCKS_REQUIRED(mutex_) {
+    if (file_map_.find(fname) == file_map_.end()) {
+      return;
+    }
+
+    file_map_[fname]->Unref();
+    file_map_.erase(fname);
+  }
+
+  Status RemoveFile(const std::string& fname) override {
+    MutexLock lock(&mutex_);
+    if (file_map_.find(fname) == file_map_.end()) {
+      return Status::IOError(fname, "File not found");
+    }
+
+    RemoveFileInternal(fname);
+    return Status::OK();
+  }
+
+  Status CreateDir(const std::string& dirname) override { return Status::OK(); }
+
+  Status RemoveDir(const std::string& dirname) override { return Status::OK(); }
+
+  Status GetFileSize(const std::string& fname, uint64_t* file_size) override {
+    MutexLock lock(&mutex_);
+    if (file_map_.find(fname) == file_map_.end()) {
+      return Status::IOError(fname, "File not found");
+    }
+
+    *file_size = file_map_[fname]->Size();
+    return Status::OK();
+  }
+
+  Status RenameFile(const std::string& src,
+                    const std::string& target) override {
+    MutexLock lock(&mutex_);
+    if (file_map_.find(src) == file_map_.end()) {
+      return Status::IOError(src, "File not found");
+    }
+
+    RemoveFileInternal(target);
+    file_map_[target] = file_map_[src];
+    file_map_.erase(src);
+    return Status::OK();
+  }
+
+  Status LockFile(const std::string& fname, FileLock** lock) override {
+    *lock = new FileLock;
+    return Status::OK();
+  }
+
+  Status UnlockFile(FileLock* lock) override {
+    delete lock;
+    return Status::OK();
+  }
+
+  Status GetTestDirectory(std::string* path) override {
+    *path = "/test";
+    return Status::OK();
+  }
+
+  Status NewLogger(const std::string& fname, Logger** result) override {
+    *result = new NoOpLogger;
+    return Status::OK();
+  }
+
+ private:
+  // Map from filenames to FileState objects, representing a simple file system.
+  typedef std::map<std::string, FileState*> FileSystem;
+
+  port::Mutex mutex_;
+  FileSystem file_map_ GUARDED_BY(mutex_);
+};
+
+}  // namespace
+
+Env* NewMemEnv(Env* base_env) { return new InMemoryEnv(base_env); }
+
+}  // namespace leveldb
diff --git a/leveldb_base/helpers/memenv/memenv.h b/leveldb_base/helpers/memenv/memenv.h
new file mode 100644
index 0000000..3d929e4
--- /dev/null
+++ b/leveldb_base/helpers/memenv/memenv.h
@@ -0,0 +1,22 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_HELPERS_MEMENV_MEMENV_H_
+#define STORAGE_LEVELDB_HELPERS_MEMENV_MEMENV_H_
+
+#include "leveldb/export.h"
+
+namespace leveldb {
+
+class Env;
+
+// Returns a new environment that stores its data in memory and delegates
+// all non-file-storage tasks to base_env. The caller must delete the result
+// when it is no longer needed.
+// *base_env must remain live while the result is in use.
+LEVELDB_EXPORT Env* NewMemEnv(Env* base_env);
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_HELPERS_MEMENV_MEMENV_H_
diff --git a/leveldb_base/helpers/memenv/memenv_test.cc b/leveldb_base/helpers/memenv/memenv_test.cc
new file mode 100644
index 0000000..909a0ca
--- /dev/null
+++ b/leveldb_base/helpers/memenv/memenv_test.cc
@@ -0,0 +1,259 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "helpers/memenv/memenv.h"
+
+#include <string>
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "db/db_impl.h"
+#include "leveldb/db.h"
+#include "leveldb/env.h"
+#include "util/testutil.h"
+
+namespace leveldb {
+
+class MemEnvTest : public testing::Test {
+ public:
+  MemEnvTest() : env_(NewMemEnv(Env::Default())) {}
+  ~MemEnvTest() { delete env_; }
+
+  Env* env_;
+};
+
+TEST_F(MemEnvTest, Basics) {
+  uint64_t file_size;
+  WritableFile* writable_file;
+  std::vector<std::string> children;
+
+  ASSERT_LEVELDB_OK(env_->CreateDir("/dir"));
+
+  // Check that the directory is empty.
+  ASSERT_TRUE(!env_->FileExists("/dir/non_existent"));
+  ASSERT_TRUE(!env_->GetFileSize("/dir/non_existent", &file_size).ok());
+  ASSERT_LEVELDB_OK(env_->GetChildren("/dir", &children));
+  ASSERT_EQ(0, children.size());
+
+  // Create a file.
+  ASSERT_LEVELDB_OK(env_->NewWritableFile("/dir/f", &writable_file));
+  ASSERT_LEVELDB_OK(env_->GetFileSize("/dir/f", &file_size));
+  ASSERT_EQ(0, file_size);
+  delete writable_file;
+
+  // Check that the file exists.
+  ASSERT_TRUE(env_->FileExists("/dir/f"));
+  ASSERT_LEVELDB_OK(env_->GetFileSize("/dir/f", &file_size));
+  ASSERT_EQ(0, file_size);
+  ASSERT_LEVELDB_OK(env_->GetChildren("/dir", &children));
+  ASSERT_EQ(1, children.size());
+  ASSERT_EQ("f", children[0]);
+
+  // Write to the file.
+  ASSERT_LEVELDB_OK(env_->NewWritableFile("/dir/f", &writable_file));
+  ASSERT_LEVELDB_OK(writable_file->Append("abc"));
+  delete writable_file;
+
+  // Check that append works.
+  ASSERT_LEVELDB_OK(env_->NewAppendableFile("/dir/f", &writable_file));
+  ASSERT_LEVELDB_OK(env_->GetFileSize("/dir/f", &file_size));
+  ASSERT_EQ(3, file_size);
+  ASSERT_LEVELDB_OK(writable_file->Append("hello"));
+  delete writable_file;
+
+  // Check for expected size.
+  ASSERT_LEVELDB_OK(env_->GetFileSize("/dir/f", &file_size));
+  ASSERT_EQ(8, file_size);
+
+  // Check that renaming works.
+  ASSERT_TRUE(!env_->RenameFile("/dir/non_existent", "/dir/g").ok());
+  ASSERT_LEVELDB_OK(env_->RenameFile("/dir/f", "/dir/g"));
+  ASSERT_TRUE(!env_->FileExists("/dir/f"));
+  ASSERT_TRUE(env_->FileExists("/dir/g"));
+  ASSERT_LEVELDB_OK(env_->GetFileSize("/dir/g", &file_size));
+  ASSERT_EQ(8, file_size);
+
+  // Check that opening non-existent file fails.
+  SequentialFile* seq_file;
+  RandomAccessFile* rand_file;
+  ASSERT_TRUE(!env_->NewSequentialFile("/dir/non_existent", &seq_file).ok());
+  ASSERT_TRUE(!seq_file);
+  ASSERT_TRUE(!env_->NewRandomAccessFile("/dir/non_existent", &rand_file).ok());
+  ASSERT_TRUE(!rand_file);
+
+  // Check that deleting works.
+  ASSERT_TRUE(!env_->RemoveFile("/dir/non_existent").ok());
+  ASSERT_LEVELDB_OK(env_->RemoveFile("/dir/g"));
+  ASSERT_TRUE(!env_->FileExists("/dir/g"));
+  ASSERT_LEVELDB_OK(env_->GetChildren("/dir", &children));
+  ASSERT_EQ(0, children.size());
+  ASSERT_LEVELDB_OK(env_->RemoveDir("/dir"));
+}
+
+TEST_F(MemEnvTest, ReadWrite) {
+  WritableFile* writable_file;
+  SequentialFile* seq_file;
+  RandomAccessFile* rand_file;
+  Slice result;
+  char scratch[100];
+
+  ASSERT_LEVELDB_OK(env_->CreateDir("/dir"));
+
+  ASSERT_LEVELDB_OK(env_->NewWritableFile("/dir/f", &writable_file));
+  ASSERT_LEVELDB_OK(writable_file->Append("hello "));
+  ASSERT_LEVELDB_OK(writable_file->Append("world"));
+  delete writable_file;
+
+  // Read sequentially.
+  ASSERT_LEVELDB_OK(env_->NewSequentialFile("/dir/f", &seq_file));
+  ASSERT_LEVELDB_OK(seq_file->Read(5, &result, scratch));  // Read "hello".
+  ASSERT_EQ(0, result.compare("hello"));
+  ASSERT_LEVELDB_OK(seq_file->Skip(1));
+  ASSERT_LEVELDB_OK(seq_file->Read(1000, &result, scratch));  // Read "world".
+  ASSERT_EQ(0, result.compare("world"));
+  ASSERT_LEVELDB_OK(
+      seq_file->Read(1000, &result, scratch));  // Try reading past EOF.
+  ASSERT_EQ(0, result.size());
+  ASSERT_LEVELDB_OK(seq_file->Skip(100));  // Try to skip past end of file.
+  ASSERT_LEVELDB_OK(seq_file->Read(1000, &result, scratch));
+  ASSERT_EQ(0, result.size());
+  delete seq_file;
+
+  // Random reads.
+  ASSERT_LEVELDB_OK(env_->NewRandomAccessFile("/dir/f", &rand_file));
+  ASSERT_LEVELDB_OK(rand_file->Read(6, 5, &result, scratch));  // Read "world".
+  ASSERT_EQ(0, result.compare("world"));
+  ASSERT_LEVELDB_OK(rand_file->Read(0, 5, &result, scratch));  // Read "hello".
+  ASSERT_EQ(0, result.compare("hello"));
+  ASSERT_LEVELDB_OK(rand_file->Read(10, 100, &result, scratch));  // Read "d".
+  ASSERT_EQ(0, result.compare("d"));
+
+  // Too high offset.
+  ASSERT_TRUE(!rand_file->Read(1000, 5, &result, scratch).ok());
+  delete rand_file;
+}
+
+TEST_F(MemEnvTest, Locks) {
+  FileLock* lock;
+
+  // These are no-ops, but we test they return success.
+  ASSERT_LEVELDB_OK(env_->LockFile("some file", &lock));
+  ASSERT_LEVELDB_OK(env_->UnlockFile(lock));
+}
+
+TEST_F(MemEnvTest, Misc) {
+  std::string test_dir;
+  ASSERT_LEVELDB_OK(env_->GetTestDirectory(&test_dir));
+  ASSERT_TRUE(!test_dir.empty());
+
+  WritableFile* writable_file;
+  ASSERT_LEVELDB_OK(env_->NewWritableFile("/a/b", &writable_file));
+
+  // These are no-ops, but we test they return success.
+  ASSERT_LEVELDB_OK(writable_file->Sync());
+  ASSERT_LEVELDB_OK(writable_file->Flush());
+  ASSERT_LEVELDB_OK(writable_file->Close());
+  delete writable_file;
+}
+
+TEST_F(MemEnvTest, LargeWrite) {
+  const size_t kWriteSize = 300 * 1024;
+  char* scratch = new char[kWriteSize * 2];
+
+  std::string write_data;
+  for (size_t i = 0; i < kWriteSize; ++i) {
+    write_data.append(1, static_cast<char>(i));
+  }
+
+  WritableFile* writable_file;
+  ASSERT_LEVELDB_OK(env_->NewWritableFile("/dir/f", &writable_file));
+  ASSERT_LEVELDB_OK(writable_file->Append("foo"));
+  ASSERT_LEVELDB_OK(writable_file->Append(write_data));
+  delete writable_file;
+
+  SequentialFile* seq_file;
+  Slice result;
+  ASSERT_LEVELDB_OK(env_->NewSequentialFile("/dir/f", &seq_file));
+  ASSERT_LEVELDB_OK(seq_file->Read(3, &result, scratch));  // Read "foo".
+  ASSERT_EQ(0, result.compare("foo"));
+
+  size_t read = 0;
+  std::string read_data;
+  while (read < kWriteSize) {
+    ASSERT_LEVELDB_OK(seq_file->Read(kWriteSize - read, &result, scratch));
+    read_data.append(result.data(), result.size());
+    read += result.size();
+  }
+  ASSERT_TRUE(write_data == read_data);
+  delete seq_file;
+  delete[] scratch;
+}
+
+TEST_F(MemEnvTest, OverwriteOpenFile) {
+  const char kWrite1Data[] = "Write #1 data";
+  const size_t kFileDataLen = sizeof(kWrite1Data) - 1;
+  const std::string kTestFileName = testing::TempDir() + "leveldb-TestFile.dat";
+
+  ASSERT_LEVELDB_OK(WriteStringToFile(env_, kWrite1Data, kTestFileName));
+
+  RandomAccessFile* rand_file;
+  ASSERT_LEVELDB_OK(env_->NewRandomAccessFile(kTestFileName, &rand_file));
+
+  const char kWrite2Data[] = "Write #2 data";
+  ASSERT_LEVELDB_OK(WriteStringToFile(env_, kWrite2Data, kTestFileName));
+
+  // Verify that overwriting an open file will result in the new file data
+  // being read from files opened before the write.
+  Slice result;
+  char scratch[kFileDataLen];
+  ASSERT_LEVELDB_OK(rand_file->Read(0, kFileDataLen, &result, scratch));
+  ASSERT_EQ(0, result.compare(kWrite2Data));
+
+  delete rand_file;
+}
+
+TEST_F(MemEnvTest, DBTest) {
+  Options options;
+  options.create_if_missing = true;
+  options.env = env_;
+  DB* db;
+
+  const Slice keys[] = {Slice("aaa"), Slice("bbb"), Slice("ccc")};
+  const Slice vals[] = {Slice("foo"), Slice("bar"), Slice("baz")};
+
+  ASSERT_LEVELDB_OK(DB::Open(options, "/dir/db", &db));
+  for (size_t i = 0; i < 3; ++i) {
+    ASSERT_LEVELDB_OK(db->Put(WriteOptions(), keys[i], vals[i]));
+  }
+
+  for (size_t i = 0; i < 3; ++i) {
+    std::string res;
+    ASSERT_LEVELDB_OK(db->Get(ReadOptions(), keys[i], &res));
+    ASSERT_TRUE(res == vals[i]);
+  }
+
+  Iterator* iterator = db->NewIterator(ReadOptions());
+  iterator->SeekToFirst();
+  for (size_t i = 0; i < 3; ++i) {
+    ASSERT_TRUE(iterator->Valid());
+    ASSERT_TRUE(keys[i] == iterator->key());
+    ASSERT_TRUE(vals[i] == iterator->value());
+    iterator->Next();
+  }
+  ASSERT_TRUE(!iterator->Valid());
+  delete iterator;
+
+  DBImpl* dbi = reinterpret_cast<DBImpl*>(db);
+  ASSERT_LEVELDB_OK(dbi->TEST_CompactMemTable());
+
+  for (size_t i = 0; i < 3; ++i) {
+    std::string res;
+    ASSERT_LEVELDB_OK(db->Get(ReadOptions(), keys[i], &res));
+    ASSERT_TRUE(res == vals[i]);
+  }
+
+  delete db;
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/include/leveldb/c.h b/leveldb_base/include/leveldb/c.h
new file mode 100644
index 0000000..44e1ff2
--- /dev/null
+++ b/leveldb_base/include/leveldb/c.h
@@ -0,0 +1,270 @@
+/* Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+  Use of this source code is governed by a BSD-style license that can be
+  found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+  C bindings for leveldb.  May be useful as a stable ABI that can be
+  used by programs that keep leveldb in a shared library, or for
+  a JNI api.
+
+  Does not support:
+  . getters for the option types
+  . custom comparators that implement key shortening
+  . custom iter, db, env, cache implementations using just the C bindings
+
+  Some conventions:
+
+  (1) We expose just opaque struct pointers and functions to clients.
+  This allows us to change internal representations without having to
+  recompile clients.
+
+  (2) For simplicity, there is no equivalent to the Slice type.  Instead,
+  the caller has to pass the pointer and length as separate
+  arguments.
+
+  (3) Errors are represented by a null-terminated c string.  NULL
+  means no error.  All operations that can raise an error are passed
+  a "char** errptr" as the last argument.  One of the following must
+  be true on entry:
+     *errptr == NULL
+     *errptr points to a malloc()ed null-terminated error message
+       (On Windows, *errptr must have been malloc()-ed by this library.)
+  On success, a leveldb routine leaves *errptr unchanged.
+  On failure, leveldb frees the old value of *errptr and
+  set *errptr to a malloc()ed error message.
+
+  (4) Bools have the type uint8_t (0 == false; rest == true)
+
+  (5) All of the pointer arguments must be non-NULL.
+*/
+
+#ifndef STORAGE_LEVELDB_INCLUDE_C_H_
+#define STORAGE_LEVELDB_INCLUDE_C_H_
+
+#include <stdarg.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include "leveldb/export.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Exported types */
+
+typedef struct leveldb_t leveldb_t;
+typedef struct leveldb_cache_t leveldb_cache_t;
+typedef struct leveldb_comparator_t leveldb_comparator_t;
+typedef struct leveldb_env_t leveldb_env_t;
+typedef struct leveldb_filelock_t leveldb_filelock_t;
+typedef struct leveldb_filterpolicy_t leveldb_filterpolicy_t;
+typedef struct leveldb_iterator_t leveldb_iterator_t;
+typedef struct leveldb_logger_t leveldb_logger_t;
+typedef struct leveldb_options_t leveldb_options_t;
+typedef struct leveldb_randomfile_t leveldb_randomfile_t;
+typedef struct leveldb_readoptions_t leveldb_readoptions_t;
+typedef struct leveldb_seqfile_t leveldb_seqfile_t;
+typedef struct leveldb_snapshot_t leveldb_snapshot_t;
+typedef struct leveldb_writablefile_t leveldb_writablefile_t;
+typedef struct leveldb_writebatch_t leveldb_writebatch_t;
+typedef struct leveldb_writeoptions_t leveldb_writeoptions_t;
+
+/* DB operations */
+
+LEVELDB_EXPORT leveldb_t* leveldb_open(const leveldb_options_t* options,
+                                       const char* name, char** errptr);
+
+LEVELDB_EXPORT void leveldb_close(leveldb_t* db);
+// 添加ttl-橙
+LEVELDB_EXPORT void leveldb_put(leveldb_t* db,
+                                const leveldb_writeoptions_t* options,
+                                const char* key, size_t keylen, const char* val,
+                                size_t vallen, char** errptr);
+
+LEVELDB_EXPORT void leveldb_delete(leveldb_t* db,
+                                   const leveldb_writeoptions_t* options,
+                                   const char* key, size_t keylen,
+                                   char** errptr);
+
+LEVELDB_EXPORT void leveldb_write(leveldb_t* db,
+                                  const leveldb_writeoptions_t* options,
+                                  leveldb_writebatch_t* batch, char** errptr);
+
+/* Returns NULL if not found.  A malloc()ed array otherwise.
+   Stores the length of the array in *vallen. */
+LEVELDB_EXPORT char* leveldb_get(leveldb_t* db,
+                                 const leveldb_readoptions_t* options,
+                                 const char* key, size_t keylen, size_t* vallen,
+                                 char** errptr);
+
+LEVELDB_EXPORT leveldb_iterator_t* leveldb_create_iterator(
+    leveldb_t* db, const leveldb_readoptions_t* options);
+
+LEVELDB_EXPORT const leveldb_snapshot_t* leveldb_create_snapshot(leveldb_t* db);
+
+LEVELDB_EXPORT void leveldb_release_snapshot(
+    leveldb_t* db, const leveldb_snapshot_t* snapshot);
+
+/* Returns NULL if property name is unknown.
+   Else returns a pointer to a malloc()-ed null-terminated value. */
+LEVELDB_EXPORT char* leveldb_property_value(leveldb_t* db,
+                                            const char* propname);
+
+LEVELDB_EXPORT void leveldb_approximate_sizes(
+    leveldb_t* db, int num_ranges, const char* const* range_start_key,
+    const size_t* range_start_key_len, const char* const* range_limit_key,
+    const size_t* range_limit_key_len, uint64_t* sizes);
+
+LEVELDB_EXPORT void leveldb_compact_range(leveldb_t* db, const char* start_key,
+                                          size_t start_key_len,
+                                          const char* limit_key,
+                                          size_t limit_key_len);
+
+/* Management operations */
+
+LEVELDB_EXPORT void leveldb_destroy_db(const leveldb_options_t* options,
+                                       const char* name, char** errptr);
+
+LEVELDB_EXPORT void leveldb_repair_db(const leveldb_options_t* options,
+                                      const char* name, char** errptr);
+
+/* Iterator */
+
+LEVELDB_EXPORT void leveldb_iter_destroy(leveldb_iterator_t*);
+LEVELDB_EXPORT uint8_t leveldb_iter_valid(const leveldb_iterator_t*);
+LEVELDB_EXPORT void leveldb_iter_seek_to_first(leveldb_iterator_t*);
+LEVELDB_EXPORT void leveldb_iter_seek_to_last(leveldb_iterator_t*);
+LEVELDB_EXPORT void leveldb_iter_seek(leveldb_iterator_t*, const char* k,
+                                      size_t klen);
+LEVELDB_EXPORT void leveldb_iter_next(leveldb_iterator_t*);
+LEVELDB_EXPORT void leveldb_iter_prev(leveldb_iterator_t*);
+LEVELDB_EXPORT const char* leveldb_iter_key(const leveldb_iterator_t*,
+                                            size_t* klen);
+LEVELDB_EXPORT const char* leveldb_iter_value(const leveldb_iterator_t*,
+                                              size_t* vlen);
+LEVELDB_EXPORT void leveldb_iter_get_error(const leveldb_iterator_t*,
+                                           char** errptr);
+
+/* Write batch */
+
+LEVELDB_EXPORT leveldb_writebatch_t* leveldb_writebatch_create(void);
+LEVELDB_EXPORT void leveldb_writebatch_destroy(leveldb_writebatch_t*);
+LEVELDB_EXPORT void leveldb_writebatch_clear(leveldb_writebatch_t*);
+LEVELDB_EXPORT void leveldb_writebatch_put(leveldb_writebatch_t*,
+                                           const char* key, size_t klen,
+                                           const char* val, size_t vlen);
+LEVELDB_EXPORT void leveldb_writebatch_delete(leveldb_writebatch_t*,
+                                              const char* key, size_t klen);
+LEVELDB_EXPORT void leveldb_writebatch_iterate(
+    const leveldb_writebatch_t*, void* state,
+    void (*put)(void*, const char* k, size_t klen, const char* v, size_t vlen),
+    void (*deleted)(void*, const char* k, size_t klen));
+LEVELDB_EXPORT void leveldb_writebatch_append(
+    leveldb_writebatch_t* destination, const leveldb_writebatch_t* source);
+
+/* Options */
+
+LEVELDB_EXPORT leveldb_options_t* leveldb_options_create(void);
+LEVELDB_EXPORT void leveldb_options_destroy(leveldb_options_t*);
+LEVELDB_EXPORT void leveldb_options_set_comparator(leveldb_options_t*,
+                                                   leveldb_comparator_t*);
+LEVELDB_EXPORT void leveldb_options_set_filter_policy(leveldb_options_t*,
+                                                      leveldb_filterpolicy_t*);
+LEVELDB_EXPORT void leveldb_options_set_create_if_missing(leveldb_options_t*,
+                                                          uint8_t);
+LEVELDB_EXPORT void leveldb_options_set_error_if_exists(leveldb_options_t*,
+                                                        uint8_t);
+LEVELDB_EXPORT void leveldb_options_set_paranoid_checks(leveldb_options_t*,
+                                                        uint8_t);
+LEVELDB_EXPORT void leveldb_options_set_env(leveldb_options_t*, leveldb_env_t*);
+LEVELDB_EXPORT void leveldb_options_set_info_log(leveldb_options_t*,
+                                                 leveldb_logger_t*);
+LEVELDB_EXPORT void leveldb_options_set_write_buffer_size(leveldb_options_t*,
+                                                          size_t);
+LEVELDB_EXPORT void leveldb_options_set_max_open_files(leveldb_options_t*, int);
+LEVELDB_EXPORT void leveldb_options_set_cache(leveldb_options_t*,
+                                              leveldb_cache_t*);
+LEVELDB_EXPORT void leveldb_options_set_block_size(leveldb_options_t*, size_t);
+LEVELDB_EXPORT void leveldb_options_set_block_restart_interval(
+    leveldb_options_t*, int);
+LEVELDB_EXPORT void leveldb_options_set_max_file_size(leveldb_options_t*,
+                                                      size_t);
+
+enum { leveldb_no_compression = 0, leveldb_snappy_compression = 1 };
+LEVELDB_EXPORT void leveldb_options_set_compression(leveldb_options_t*, int);
+
+/* Comparator */
+
+LEVELDB_EXPORT leveldb_comparator_t* leveldb_comparator_create(
+    void* state, void (*destructor)(void*),
+    int (*compare)(void*, const char* a, size_t alen, const char* b,
+                   size_t blen),
+    const char* (*name)(void*));
+LEVELDB_EXPORT void leveldb_comparator_destroy(leveldb_comparator_t*);
+
+/* Filter policy */
+
+LEVELDB_EXPORT leveldb_filterpolicy_t* leveldb_filterpolicy_create(
+    void* state, void (*destructor)(void*),
+    char* (*create_filter)(void*, const char* const* key_array,
+                           const size_t* key_length_array, int num_keys,
+                           size_t* filter_length),
+    uint8_t (*key_may_match)(void*, const char* key, size_t length,
+                             const char* filter, size_t filter_length),
+    const char* (*name)(void*));
+LEVELDB_EXPORT void leveldb_filterpolicy_destroy(leveldb_filterpolicy_t*);
+
+LEVELDB_EXPORT leveldb_filterpolicy_t* leveldb_filterpolicy_create_bloom(
+    int bits_per_key);
+
+/* Read options */
+
+LEVELDB_EXPORT leveldb_readoptions_t* leveldb_readoptions_create(void);
+LEVELDB_EXPORT void leveldb_readoptions_destroy(leveldb_readoptions_t*);
+LEVELDB_EXPORT void leveldb_readoptions_set_verify_checksums(
+    leveldb_readoptions_t*, uint8_t);
+LEVELDB_EXPORT void leveldb_readoptions_set_fill_cache(leveldb_readoptions_t*,
+                                                       uint8_t);
+LEVELDB_EXPORT void leveldb_readoptions_set_snapshot(leveldb_readoptions_t*,
+                                                     const leveldb_snapshot_t*);
+
+/* Write options */
+
+LEVELDB_EXPORT leveldb_writeoptions_t* leveldb_writeoptions_create(void);
+LEVELDB_EXPORT void leveldb_writeoptions_destroy(leveldb_writeoptions_t*);
+LEVELDB_EXPORT void leveldb_writeoptions_set_sync(leveldb_writeoptions_t*,
+                                                  uint8_t);
+
+/* Cache */
+
+LEVELDB_EXPORT leveldb_cache_t* leveldb_cache_create_lru(size_t capacity);
+LEVELDB_EXPORT void leveldb_cache_destroy(leveldb_cache_t* cache);
+
+/* Env */
+
+LEVELDB_EXPORT leveldb_env_t* leveldb_create_default_env(void);
+LEVELDB_EXPORT void leveldb_env_destroy(leveldb_env_t*);
+
+/* If not NULL, the returned buffer must be released using leveldb_free(). */
+LEVELDB_EXPORT char* leveldb_env_get_test_directory(leveldb_env_t*);
+
+/* Utility */
+
+/* Calls free(ptr).
+   REQUIRES: ptr was malloc()-ed and returned by one of the routines
+   in this file.  Note that in certain cases (typically on Windows), you
+   may need to call this routine instead of free(ptr) to dispose of
+   malloc()-ed memory returned by this library. */
+LEVELDB_EXPORT void leveldb_free(void* ptr);
+
+/* Return the major version number for this release. */
+LEVELDB_EXPORT int leveldb_major_version(void);
+
+/* Return the minor version number for this release. */
+LEVELDB_EXPORT int leveldb_minor_version(void);
+
+#ifdef __cplusplus
+} /* end extern "C" */
+#endif
+
+#endif /* STORAGE_LEVELDB_INCLUDE_C_H_ */
diff --git a/leveldb_base/include/leveldb/cache.h b/leveldb_base/include/leveldb/cache.h
new file mode 100644
index 0000000..a94c683
--- /dev/null
+++ b/leveldb_base/include/leveldb/cache.h
@@ -0,0 +1,103 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// A Cache is an interface that maps keys to values.  It has internal
+// synchronization and may be safely accessed concurrently from
+// multiple threads.  It may automatically evict entries to make room
+// for new entries.  Values have a specified charge against the cache
+// capacity.  For example, a cache where the values are variable
+// length strings, may use the length of the string as the charge for
+// the string.
+//
+// A builtin cache implementation with a least-recently-used eviction
+// policy is provided.  Clients may use their own implementations if
+// they want something more sophisticated (like scan-resistance, a
+// custom eviction policy, variable cache sizing, etc.)
+
+#ifndef STORAGE_LEVELDB_INCLUDE_CACHE_H_
+#define STORAGE_LEVELDB_INCLUDE_CACHE_H_
+
+#include <cstdint>
+
+#include "leveldb/export.h"
+#include "leveldb/slice.h"
+
+namespace leveldb {
+
+class LEVELDB_EXPORT Cache;
+
+// Create a new cache with a fixed size capacity.  This implementation
+// of Cache uses a least-recently-used eviction policy.
+LEVELDB_EXPORT Cache* NewLRUCache(size_t capacity);
+
+class LEVELDB_EXPORT Cache {
+ public:
+  Cache() = default;
+
+  Cache(const Cache&) = delete;
+  Cache& operator=(const Cache&) = delete;
+
+  // Destroys all existing entries by calling the "deleter"
+  // function that was passed to the constructor.
+  virtual ~Cache();
+
+  // Opaque handle to an entry stored in the cache.
+  struct Handle {};
+
+  // Insert a mapping from key->value into the cache and assign it
+  // the specified charge against the total cache capacity.
+  //
+  // Returns a handle that corresponds to the mapping.  The caller
+  // must call this->Release(handle) when the returned mapping is no
+  // longer needed.
+  //
+  // When the inserted entry is no longer needed, the key and
+  // value will be passed to "deleter".
+  virtual Handle* Insert(const Slice& key, void* value, size_t charge,
+                         void (*deleter)(const Slice& key, void* value)) = 0;
+
+  // If the cache has no mapping for "key", returns nullptr.
+  //
+  // Else return a handle that corresponds to the mapping.  The caller
+  // must call this->Release(handle) when the returned mapping is no
+  // longer needed.
+  virtual Handle* Lookup(const Slice& key) = 0;
+
+  // Release a mapping returned by a previous Lookup().
+  // REQUIRES: handle must not have been released yet.
+  // REQUIRES: handle must have been returned by a method on *this.
+  virtual void Release(Handle* handle) = 0;
+
+  // Return the value encapsulated in a handle returned by a
+  // successful Lookup().
+  // REQUIRES: handle must not have been released yet.
+  // REQUIRES: handle must have been returned by a method on *this.
+  virtual void* Value(Handle* handle) = 0;
+
+  // If the cache contains entry for key, erase it.  Note that the
+  // underlying entry will be kept around until all existing handles
+  // to it have been released.
+  virtual void Erase(const Slice& key) = 0;
+
+  // Return a new numeric id.  May be used by multiple clients who are
+  // sharing the same cache to partition the key space.  Typically the
+  // client will allocate a new id at startup and prepend the id to
+  // its cache keys.
+  virtual uint64_t NewId() = 0;
+
+  // Remove all cache entries that are not actively in use.  Memory-constrained
+  // applications may wish to call this method to reduce memory usage.
+  // Default implementation of Prune() does nothing.  Subclasses are strongly
+  // encouraged to override the default implementation.  A future release of
+  // leveldb may change Prune() to a pure abstract method.
+  virtual void Prune() {}
+
+  // Return an estimate of the combined charges of all elements stored in the
+  // cache.
+  virtual size_t TotalCharge() const = 0;
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_INCLUDE_CACHE_H_
diff --git a/leveldb_base/include/leveldb/comparator.h b/leveldb_base/include/leveldb/comparator.h
new file mode 100644
index 0000000..a85b51e
--- /dev/null
+++ b/leveldb_base/include/leveldb/comparator.h
@@ -0,0 +1,64 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_INCLUDE_COMPARATOR_H_
+#define STORAGE_LEVELDB_INCLUDE_COMPARATOR_H_
+
+#include <string>
+
+#include "leveldb/export.h"
+
+namespace leveldb {
+
+class Slice;
+
+// A Comparator object provides a total order across slices that are
+// used as keys in an sstable or a database.  A Comparator implementation
+// must be thread-safe since leveldb may invoke its methods concurrently
+// from multiple threads.
+class LEVELDB_EXPORT Comparator {
+ public:
+  virtual ~Comparator();
+
+  // Three-way comparison.  Returns value:
+  //   < 0 iff "a" < "b",
+  //   == 0 iff "a" == "b",
+  //   > 0 iff "a" > "b"
+  virtual int Compare(const Slice& a, const Slice& b) const = 0;
+
+  // The name of the comparator.  Used to check for comparator
+  // mismatches (i.e., a DB created with one comparator is
+  // accessed using a different comparator.
+  //
+  // The client of this package should switch to a new name whenever
+  // the comparator implementation changes in a way that will cause
+  // the relative ordering of any two keys to change.
+  //
+  // Names starting with "leveldb." are reserved and should not be used
+  // by any clients of this package.
+  virtual const char* Name() const = 0;
+
+  // Advanced functions: these are used to reduce the space requirements
+  // for internal data structures like index blocks.
+
+  // If *start < limit, changes *start to a short string in [start,limit).
+  // Simple comparator implementations may return with *start unchanged,
+  // i.e., an implementation of this method that does nothing is correct.
+  virtual void FindShortestSeparator(std::string* start,
+                                     const Slice& limit) const = 0;
+
+  // Changes *key to a short string >= *key.
+  // Simple comparator implementations may return with *key unchanged,
+  // i.e., an implementation of this method that does nothing is correct.
+  virtual void FindShortSuccessor(std::string* key) const = 0;
+};
+
+// Return a builtin comparator that uses lexicographic byte-wise
+// ordering.  The result remains the property of this module and
+// must not be deleted.
+LEVELDB_EXPORT const Comparator* BytewiseComparator();
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_INCLUDE_COMPARATOR_H_
diff --git a/leveldb_base/include/leveldb/db.h b/leveldb_base/include/leveldb/db.h
new file mode 100644
index 0000000..4e81898
--- /dev/null
+++ b/leveldb_base/include/leveldb/db.h
@@ -0,0 +1,173 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_INCLUDE_DB_H_
+#define STORAGE_LEVELDB_INCLUDE_DB_H_
+
+#include <cstdint>
+#include <cstdio>
+
+#include "leveldb/export.h"
+#include "leveldb/iterator.h"
+#include "leveldb/options.h"
+
+namespace leveldb {
+
+// Update CMakeLists.txt if you change these
+static const int kMajorVersion = 1;
+static const int kMinorVersion = 23;
+
+struct Options;
+struct ReadOptions;
+struct WriteOptions;
+class WriteBatch;
+
+// Abstract handle to particular state of a DB.
+// A Snapshot is an immutable object and can therefore be safely
+// accessed from multiple threads without any external synchronization.
+class LEVELDB_EXPORT Snapshot {
+ protected:
+  virtual ~Snapshot();
+};
+
+// A range of keys
+struct LEVELDB_EXPORT Range {
+  Range() = default;
+  Range(const Slice& s, const Slice& l) : start(s), limit(l) {}
+
+  Slice start;  // Included in the range
+  Slice limit;  // Not included in the range
+};
+
+// A DB is a persistent ordered map from keys to values.
+// A DB is safe for concurrent access from multiple threads without
+// any external synchronization.
+class LEVELDB_EXPORT DB {
+ public:
+  // Open the database with the specified "name".
+  // Stores a pointer to a heap-allocated database in *dbptr and returns
+  // OK on success.
+  // Stores nullptr in *dbptr and returns a non-OK status on error.
+  // Caller should delete *dbptr when it is no longer needed.
+  static Status Open(const Options& options, const std::string& name,
+                     DB** dbptr);
+
+  DB() = default;
+
+  DB(const DB&) = delete;
+  DB& operator=(const DB&) = delete;
+
+  virtual ~DB();
+
+  // Set the database entry for "key" to "value".  Returns OK on success,
+  // and a non-OK status on error.
+  // Note: consider setting options.sync = true.
+  // 这是旧的put方法-橙
+  virtual Status Put(const WriteOptions& options, const Slice& key,
+                     const Slice& value) = 0;
+
+  // Remove the database entry (if any) for "key".  Returns OK on
+  // success, and a non-OK status on error.  It is not an error if "key"
+  // did not exist in the database.
+  // Note: consider setting options.sync = true.
+  virtual Status Delete(const WriteOptions& options, const Slice& key) = 0;
+
+  // Apply the specified updates to the database.
+  // Returns OK on success, non-OK on failure.
+  // Note: consider setting options.sync = true.
+  virtual Status Write(const WriteOptions& options, WriteBatch* updates) = 0;
+
+  // If the database contains an entry for "key" store the
+  // corresponding value in *value and return OK.
+  //
+  // If there is no entry for "key" leave *value unchanged and return
+  // a status for which Status::IsNotFound() returns true.
+  //
+  // May return some other Status on an error.
+  virtual Status Get(const ReadOptions& options, const Slice& key,
+                     std::string* value) = 0;
+
+  // Return a heap-allocated iterator over the contents of the database.
+  // The result of NewIterator() is initially invalid (caller must
+  // call one of the Seek methods on the iterator before using it).
+  //
+  // Caller should delete the iterator when it is no longer needed.
+  // The returned iterator should be deleted before this db is deleted.
+  virtual Iterator* NewIterator(const ReadOptions& options) = 0;
+
+  // Return a handle to the current DB state.  Iterators created with
+  // this handle will all observe a stable snapshot of the current DB
+  // state.  The caller must call ReleaseSnapshot(result) when the
+  // snapshot is no longer needed.
+  virtual const Snapshot* GetSnapshot() = 0;
+
+  // Release a previously acquired snapshot.  The caller must not
+  // use "snapshot" after this call.
+  virtual void ReleaseSnapshot(const Snapshot* snapshot) = 0;
+
+  // DB implementations can export properties about their state
+  // via this method.  If "property" is a valid property understood by this
+  // DB implementation, fills "*value" with its current value and returns
+  // true.  Otherwise returns false.
+  //
+  //
+  // Valid property names include:
+  //
+  //  "leveldb.num-files-at-level<N>" - return the number of files at level <N>,
+  //     where <N> is an ASCII representation of a level number (e.g. "0").
+  //  "leveldb.stats" - returns a multi-line string that describes statistics
+  //     about the internal operation of the DB.
+  //  "leveldb.sstables" - returns a multi-line string that describes all
+  //     of the sstables that make up the db contents.
+  //  "leveldb.approximate-memory-usage" - returns the approximate number of
+  //     bytes of memory in use by the DB.
+  virtual bool GetProperty(const Slice& property, std::string* value) = 0;
+
+  // For each i in [0,n-1], store in "sizes[i]", the approximate
+  // file system space used by keys in "[range[i].start .. range[i].limit)".
+  //
+  // Note that the returned sizes measure file system space usage, so
+  // if the user data compresses by a factor of ten, the returned
+  // sizes will be one-tenth the size of the corresponding user data size.
+  //
+  // The results may not include the sizes of recently written data.
+  virtual void GetApproximateSizes(const Range* range, int n,
+                                   uint64_t* sizes) = 0;
+
+  // Compact the underlying storage for the key range [*begin,*end].
+  // In particular, deleted and overwritten versions are discarded,
+  // and the data is rearranged to reduce the cost of operations
+  // needed to access the data.  This operation should typically only
+  // be invoked by users who understand the underlying implementation.
+  //
+  // begin==nullptr is treated as a key before all keys in the database.
+  // end==nullptr is treated as a key after all keys in the database.
+  // Therefore the following call will compact the entire database:
+  //    db->CompactRange(nullptr, nullptr);
+  virtual void CompactRange(const Slice* begin, const Slice* end) = 0;
+
+  // ----------------------------For TTL-----------------------------
+  // 为当前key设置ttl，过期后自动失效
+  virtual Status Put(const WriteOptions& options, const Slice& key,
+                     const Slice& value, uint64_t ttl) = 0;
+};
+
+// Destroy the contents of the specified database.
+// Be very careful using this method.
+//
+// Note: For backwards compatibility, if DestroyDB is unable to list the
+// database files, Status::OK() will still be returned masking this failure.
+LEVELDB_EXPORT Status DestroyDB(const std::string& name,
+                                const Options& options);
+
+// If a DB cannot be opened, you may attempt to call this method to
+// resurrect as much of the contents of the database as possible.
+// Some data may be lost, so be careful when calling this function
+// on a database that contains important information.
+LEVELDB_EXPORT Status RepairDB(const std::string& dbname,
+                               const Options& options);
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_INCLUDE_DB_H_
diff --git a/leveldb_base/include/leveldb/dumpfile.h b/leveldb_base/include/leveldb/dumpfile.h
new file mode 100644
index 0000000..a58bc6b
--- /dev/null
+++ b/leveldb_base/include/leveldb/dumpfile.h
@@ -0,0 +1,28 @@
+// Copyright (c) 2014 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_INCLUDE_DUMPFILE_H_
+#define STORAGE_LEVELDB_INCLUDE_DUMPFILE_H_
+
+#include <string>
+
+#include "leveldb/env.h"
+#include "leveldb/export.h"
+#include "leveldb/status.h"
+
+namespace leveldb {
+
+// Dump the contents of the file named by fname in text format to
+// *dst.  Makes a sequence of dst->Append() calls; each call is passed
+// the newline-terminated text corresponding to a single item found
+// in the file.
+//
+// Returns a non-OK result if fname does not name a leveldb storage
+// file, or if the file cannot be read.
+LEVELDB_EXPORT Status DumpFile(Env* env, const std::string& fname,
+                               WritableFile* dst);
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_INCLUDE_DUMPFILE_H_
diff --git a/leveldb_base/include/leveldb/env.h b/leveldb_base/include/leveldb/env.h
new file mode 100644
index 0000000..e00895a
--- /dev/null
+++ b/leveldb_base/include/leveldb/env.h
@@ -0,0 +1,417 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// An Env is an interface used by the leveldb implementation to access
+// operating system functionality like the filesystem etc.  Callers
+// may wish to provide a custom Env object when opening a database to
+// get fine gain control; e.g., to rate limit file system operations.
+//
+// All Env implementations are safe for concurrent access from
+// multiple threads without any external synchronization.
+
+#ifndef STORAGE_LEVELDB_INCLUDE_ENV_H_
+#define STORAGE_LEVELDB_INCLUDE_ENV_H_
+
+#include <cstdarg>
+#include <cstdint>
+#include <string>
+#include <vector>
+
+#include "leveldb/export.h"
+#include "leveldb/status.h"
+
+// This workaround can be removed when leveldb::Env::DeleteFile is removed.
+#if defined(_WIN32)
+// On Windows, the method name DeleteFile (below) introduces the risk of
+// triggering undefined behavior by exposing the compiler to different
+// declarations of the Env class in different translation units.
+//
+// This is because <windows.h>, a fairly popular header file for Windows
+// applications, defines a DeleteFile macro. So, files that include the Windows
+// header before this header will contain an altered Env declaration.
+//
+// This workaround ensures that the compiler sees the same Env declaration,
+// independently of whether <windows.h> was included.
+#if defined(DeleteFile)
+#undef DeleteFile
+#define LEVELDB_DELETEFILE_UNDEFINED
+#endif  // defined(DeleteFile)
+#endif  // defined(_WIN32)
+
+namespace leveldb {
+
+class FileLock;
+class Logger;
+class RandomAccessFile;
+class SequentialFile;
+class Slice;
+class WritableFile;
+
+class LEVELDB_EXPORT Env {
+ public:
+  Env();
+
+  Env(const Env&) = delete;
+  Env& operator=(const Env&) = delete;
+
+  virtual ~Env();
+
+  // Return a default environment suitable for the current operating
+  // system.  Sophisticated users may wish to provide their own Env
+  // implementation instead of relying on this default environment.
+  //
+  // The result of Default() belongs to leveldb and must never be deleted.
+  static Env* Default();
+
+  // Create an object that sequentially reads the file with the specified name.
+  // On success, stores a pointer to the new file in *result and returns OK.
+  // On failure stores nullptr in *result and returns non-OK.  If the file does
+  // not exist, returns a non-OK status.  Implementations should return a
+  // NotFound status when the file does not exist.
+  //
+  // The returned file will only be accessed by one thread at a time.
+  virtual Status NewSequentialFile(const std::string& fname,
+                                   SequentialFile** result) = 0;
+
+  // Create an object supporting random-access reads from the file with the
+  // specified name.  On success, stores a pointer to the new file in
+  // *result and returns OK.  On failure stores nullptr in *result and
+  // returns non-OK.  If the file does not exist, returns a non-OK
+  // status.  Implementations should return a NotFound status when the file does
+  // not exist.
+  //
+  // The returned file may be concurrently accessed by multiple threads.
+  virtual Status NewRandomAccessFile(const std::string& fname,
+                                     RandomAccessFile** result) = 0;
+
+  // Create an object that writes to a new file with the specified
+  // name.  Deletes any existing file with the same name and creates a
+  // new file.  On success, stores a pointer to the new file in
+  // *result and returns OK.  On failure stores nullptr in *result and
+  // returns non-OK.
+  //
+  // The returned file will only be accessed by one thread at a time.
+  virtual Status NewWritableFile(const std::string& fname,
+                                 WritableFile** result) = 0;
+
+  // Create an object that either appends to an existing file, or
+  // writes to a new file (if the file does not exist to begin with).
+  // On success, stores a pointer to the new file in *result and
+  // returns OK.  On failure stores nullptr in *result and returns
+  // non-OK.
+  //
+  // The returned file will only be accessed by one thread at a time.
+  //
+  // May return an IsNotSupportedError error if this Env does
+  // not allow appending to an existing file.  Users of Env (including
+  // the leveldb implementation) must be prepared to deal with
+  // an Env that does not support appending.
+  virtual Status NewAppendableFile(const std::string& fname,
+                                   WritableFile** result);
+
+  // Returns true iff the named file exists.
+  virtual bool FileExists(const std::string& fname) = 0;
+
+  // Store in *result the names of the children of the specified directory.
+  // The names are relative to "dir".
+  // Original contents of *results are dropped.
+  virtual Status GetChildren(const std::string& dir,
+                             std::vector<std::string>* result) = 0;
+  // Delete the named file.
+  //
+  // The default implementation calls DeleteFile, to support legacy Env
+  // implementations. Updated Env implementations must override RemoveFile and
+  // ignore the existence of DeleteFile. Updated code calling into the Env API
+  // must call RemoveFile instead of DeleteFile.
+  //
+  // A future release will remove DeleteDir and the default implementation of
+  // RemoveDir.
+  virtual Status RemoveFile(const std::string& fname);
+
+  // DEPRECATED: Modern Env implementations should override RemoveFile instead.
+  //
+  // The default implementation calls RemoveFile, to support legacy Env user
+  // code that calls this method on modern Env implementations. Modern Env user
+  // code should call RemoveFile.
+  //
+  // A future release will remove this method.
+  virtual Status DeleteFile(const std::string& fname);
+
+  // Create the specified directory.
+  virtual Status CreateDir(const std::string& dirname) = 0;
+
+  // Delete the specified directory.
+  //
+  // The default implementation calls DeleteDir, to support legacy Env
+  // implementations. Updated Env implementations must override RemoveDir and
+  // ignore the existence of DeleteDir. Modern code calling into the Env API
+  // must call RemoveDir instead of DeleteDir.
+  //
+  // A future release will remove DeleteDir and the default implementation of
+  // RemoveDir.
+  virtual Status RemoveDir(const std::string& dirname);
+
+  // DEPRECATED: Modern Env implementations should override RemoveDir instead.
+  //
+  // The default implementation calls RemoveDir, to support legacy Env user
+  // code that calls this method on modern Env implementations. Modern Env user
+  // code should call RemoveDir.
+  //
+  // A future release will remove this method.
+  virtual Status DeleteDir(const std::string& dirname);
+
+  // Store the size of fname in *file_size.
+  virtual Status GetFileSize(const std::string& fname, uint64_t* file_size) = 0;
+
+  // Rename file src to target.
+  virtual Status RenameFile(const std::string& src,
+                            const std::string& target) = 0;
+
+  // Lock the specified file.  Used to prevent concurrent access to
+  // the same db by multiple processes.  On failure, stores nullptr in
+  // *lock and returns non-OK.
+  //
+  // On success, stores a pointer to the object that represents the
+  // acquired lock in *lock and returns OK.  The caller should call
+  // UnlockFile(*lock) to release the lock.  If the process exits,
+  // the lock will be automatically released.
+  //
+  // If somebody else already holds the lock, finishes immediately
+  // with a failure.  I.e., this call does not wait for existing locks
+  // to go away.
+  //
+  // May create the named file if it does not already exist.
+  virtual Status LockFile(const std::string& fname, FileLock** lock) = 0;
+
+  // Release the lock acquired by a previous successful call to LockFile.
+  // REQUIRES: lock was returned by a successful LockFile() call
+  // REQUIRES: lock has not already been unlocked.
+  virtual Status UnlockFile(FileLock* lock) = 0;
+
+  // Arrange to run "(*function)(arg)" once in a background thread.
+  //
+  // "function" may run in an unspecified thread.  Multiple functions
+  // added to the same Env may run concurrently in different threads.
+  // I.e., the caller may not assume that background work items are
+  // serialized.
+  virtual void Schedule(void (*function)(void* arg), void* arg) = 0;
+
+  // Start a new thread, invoking "function(arg)" within the new thread.
+  // When "function(arg)" returns, the thread will be destroyed.
+  virtual void StartThread(void (*function)(void* arg), void* arg) = 0;
+
+  // *path is set to a temporary directory that can be used for testing. It may
+  // or may not have just been created. The directory may or may not differ
+  // between runs of the same process, but subsequent calls will return the
+  // same directory.
+  virtual Status GetTestDirectory(std::string* path) = 0;
+
+  // Create and return a log file for storing informational messages.
+  virtual Status NewLogger(const std::string& fname, Logger** result) = 0;
+
+  // Returns the number of micro-seconds since some fixed point in time. Only
+  // useful for computing deltas of time.
+  virtual uint64_t NowMicros() = 0;
+
+  // Sleep/delay the thread for the prescribed number of micro-seconds.
+  virtual void SleepForMicroseconds(int micros) = 0;
+};
+
+// A file abstraction for reading sequentially through a file
+class LEVELDB_EXPORT SequentialFile {
+ public:
+  SequentialFile() = default;
+
+  SequentialFile(const SequentialFile&) = delete;
+  SequentialFile& operator=(const SequentialFile&) = delete;
+
+  virtual ~SequentialFile();
+
+  // Read up to "n" bytes from the file.  "scratch[0..n-1]" may be
+  // written by this routine.  Sets "*result" to the data that was
+  // read (including if fewer than "n" bytes were successfully read).
+  // May set "*result" to point at data in "scratch[0..n-1]", so
+  // "scratch[0..n-1]" must be live when "*result" is used.
+  // If an error was encountered, returns a non-OK status.
+  //
+  // REQUIRES: External synchronization
+  virtual Status Read(size_t n, Slice* result, char* scratch) = 0;
+
+  // Skip "n" bytes from the file. This is guaranteed to be no
+  // slower that reading the same data, but may be faster.
+  //
+  // If end of file is reached, skipping will stop at the end of the
+  // file, and Skip will return OK.
+  //
+  // REQUIRES: External synchronization
+  virtual Status Skip(uint64_t n) = 0;
+};
+
+// A file abstraction for randomly reading the contents of a file.
+class LEVELDB_EXPORT RandomAccessFile {
+ public:
+  RandomAccessFile() = default;
+
+  RandomAccessFile(const RandomAccessFile&) = delete;
+  RandomAccessFile& operator=(const RandomAccessFile&) = delete;
+
+  virtual ~RandomAccessFile();
+
+  // Read up to "n" bytes from the file starting at "offset".
+  // "scratch[0..n-1]" may be written by this routine.  Sets "*result"
+  // to the data that was read (including if fewer than "n" bytes were
+  // successfully read).  May set "*result" to point at data in
+  // "scratch[0..n-1]", so "scratch[0..n-1]" must be live when
+  // "*result" is used.  If an error was encountered, returns a non-OK
+  // status.
+  //
+  // Safe for concurrent use by multiple threads.
+  virtual Status Read(uint64_t offset, size_t n, Slice* result,
+                      char* scratch) const = 0;
+};
+
+// A file abstraction for sequential writing.  The implementation
+// must provide buffering since callers may append small fragments
+// at a time to the file.
+class LEVELDB_EXPORT WritableFile {
+ public:
+  WritableFile() = default;
+
+  WritableFile(const WritableFile&) = delete;
+  WritableFile& operator=(const WritableFile&) = delete;
+
+  virtual ~WritableFile();
+
+  virtual Status Append(const Slice& data) = 0;
+  virtual Status Close() = 0;
+  virtual Status Flush() = 0;
+  virtual Status Sync() = 0;
+};
+
+// An interface for writing log messages.
+class LEVELDB_EXPORT Logger {
+ public:
+  Logger() = default;
+
+  Logger(const Logger&) = delete;
+  Logger& operator=(const Logger&) = delete;
+
+  virtual ~Logger();
+
+  // Write an entry to the log file with the specified format.
+  virtual void Logv(const char* format, std::va_list ap) = 0;
+};
+
+// Identifies a locked file.
+class LEVELDB_EXPORT FileLock {
+ public:
+  FileLock() = default;
+
+  FileLock(const FileLock&) = delete;
+  FileLock& operator=(const FileLock&) = delete;
+
+  virtual ~FileLock();
+};
+
+// Log the specified data to *info_log if info_log is non-null.
+void Log(Logger* info_log, const char* format, ...)
+#if defined(__GNUC__) || defined(__clang__)
+    __attribute__((__format__(__printf__, 2, 3)))
+#endif
+    ;
+
+// A utility routine: write "data" to the named file.
+LEVELDB_EXPORT Status WriteStringToFile(Env* env, const Slice& data,
+                                        const std::string& fname);
+
+// A utility routine: read contents of named file into *data
+LEVELDB_EXPORT Status ReadFileToString(Env* env, const std::string& fname,
+                                       std::string* data);
+
+// An implementation of Env that forwards all calls to another Env.
+// May be useful to clients who wish to override just part of the
+// functionality of another Env.
+class LEVELDB_EXPORT EnvWrapper : public Env {
+ public:
+  // Initialize an EnvWrapper that delegates all calls to *t.
+  explicit EnvWrapper(Env* t) : target_(t) {}
+  virtual ~EnvWrapper();
+
+  // Return the target to which this Env forwards all calls.
+  Env* target() const { return target_; }
+
+  // The following text is boilerplate that forwards all methods to target().
+  Status NewSequentialFile(const std::string& f, SequentialFile** r) override {
+    return target_->NewSequentialFile(f, r);
+  }
+  Status NewRandomAccessFile(const std::string& f,
+                             RandomAccessFile** r) override {
+    return target_->NewRandomAccessFile(f, r);
+  }
+  Status NewWritableFile(const std::string& f, WritableFile** r) override {
+    return target_->NewWritableFile(f, r);
+  }
+  Status NewAppendableFile(const std::string& f, WritableFile** r) override {
+    return target_->NewAppendableFile(f, r);
+  }
+  bool FileExists(const std::string& f) override {
+    return target_->FileExists(f);
+  }
+  Status GetChildren(const std::string& dir,
+                     std::vector<std::string>* r) override {
+    return target_->GetChildren(dir, r);
+  }
+  Status RemoveFile(const std::string& f) override {
+    return target_->RemoveFile(f);
+  }
+  Status CreateDir(const std::string& d) override {
+    return target_->CreateDir(d);
+  }
+  Status RemoveDir(const std::string& d) override {
+    return target_->RemoveDir(d);
+  }
+  Status GetFileSize(const std::string& f, uint64_t* s) override {
+    return target_->GetFileSize(f, s);
+  }
+  Status RenameFile(const std::string& s, const std::string& t) override {
+    return target_->RenameFile(s, t);
+  }
+  Status LockFile(const std::string& f, FileLock** l) override {
+    return target_->LockFile(f, l);
+  }
+  Status UnlockFile(FileLock* l) override { return target_->UnlockFile(l); }
+  void Schedule(void (*f)(void*), void* a) override {
+    return target_->Schedule(f, a);
+  }
+  void StartThread(void (*f)(void*), void* a) override {
+    return target_->StartThread(f, a);
+  }
+  Status GetTestDirectory(std::string* path) override {
+    return target_->GetTestDirectory(path);
+  }
+  Status NewLogger(const std::string& fname, Logger** result) override {
+    return target_->NewLogger(fname, result);
+  }
+  uint64_t NowMicros() override { return target_->NowMicros(); }
+  void SleepForMicroseconds(int micros) override {
+    target_->SleepForMicroseconds(micros);
+  }
+
+ private:
+  Env* target_;
+};
+
+}  // namespace leveldb
+
+// This workaround can be removed when leveldb::Env::DeleteFile is removed.
+// Redefine DeleteFile if it was undefined earlier.
+#if defined(_WIN32) && defined(LEVELDB_DELETEFILE_UNDEFINED)
+#if defined(UNICODE)
+#define DeleteFile DeleteFileW
+#else
+#define DeleteFile DeleteFileA
+#endif  // defined(UNICODE)
+#endif  // defined(_WIN32) && defined(LEVELDB_DELETEFILE_UNDEFINED)
+
+#endif  // STORAGE_LEVELDB_INCLUDE_ENV_H_
diff --git a/leveldb_base/include/leveldb/export.h b/leveldb_base/include/leveldb/export.h
new file mode 100644
index 0000000..6ba9b18
--- /dev/null
+++ b/leveldb_base/include/leveldb/export.h
@@ -0,0 +1,33 @@
+// Copyright (c) 2017 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_INCLUDE_EXPORT_H_
+#define STORAGE_LEVELDB_INCLUDE_EXPORT_H_
+
+#if !defined(LEVELDB_EXPORT)
+
+#if defined(LEVELDB_SHARED_LIBRARY)
+#if defined(_WIN32)
+
+#if defined(LEVELDB_COMPILE_LIBRARY)
+#define LEVELDB_EXPORT __declspec(dllexport)
+#else
+#define LEVELDB_EXPORT __declspec(dllimport)
+#endif  // defined(LEVELDB_COMPILE_LIBRARY)
+
+#else  // defined(_WIN32)
+#if defined(LEVELDB_COMPILE_LIBRARY)
+#define LEVELDB_EXPORT __attribute__((visibility("default")))
+#else
+#define LEVELDB_EXPORT
+#endif
+#endif  // defined(_WIN32)
+
+#else  // defined(LEVELDB_SHARED_LIBRARY)
+#define LEVELDB_EXPORT
+#endif
+
+#endif  // !defined(LEVELDB_EXPORT)
+
+#endif  // STORAGE_LEVELDB_INCLUDE_EXPORT_H_
diff --git a/leveldb_base/include/leveldb/filter_policy.h b/leveldb_base/include/leveldb/filter_policy.h
new file mode 100644
index 0000000..49c8eda
--- /dev/null
+++ b/leveldb_base/include/leveldb/filter_policy.h
@@ -0,0 +1,72 @@
+// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// A database can be configured with a custom FilterPolicy object.
+// This object is responsible for creating a small filter from a set
+// of keys.  These filters are stored in leveldb and are consulted
+// automatically by leveldb to decide whether or not to read some
+// information from disk. In many cases, a filter can cut down the
+// number of disk seeks form a handful to a single disk seek per
+// DB::Get() call.
+//
+// Most people will want to use the builtin bloom filter support (see
+// NewBloomFilterPolicy() below).
+
+#ifndef STORAGE_LEVELDB_INCLUDE_FILTER_POLICY_H_
+#define STORAGE_LEVELDB_INCLUDE_FILTER_POLICY_H_
+
+#include <string>
+
+#include "leveldb/export.h"
+
+namespace leveldb {
+
+class Slice;
+
+class LEVELDB_EXPORT FilterPolicy {
+ public:
+  virtual ~FilterPolicy();
+
+  // Return the name of this policy.  Note that if the filter encoding
+  // changes in an incompatible way, the name returned by this method
+  // must be changed.  Otherwise, old incompatible filters may be
+  // passed to methods of this type.
+  virtual const char* Name() const = 0;
+
+  // keys[0,n-1] contains a list of keys (potentially with duplicates)
+  // that are ordered according to the user supplied comparator.
+  // Append a filter that summarizes keys[0,n-1] to *dst.
+  //
+  // Warning: do not change the initial contents of *dst.  Instead,
+  // append the newly constructed filter to *dst.
+  virtual void CreateFilter(const Slice* keys, int n,
+                            std::string* dst) const = 0;
+
+  // "filter" contains the data appended by a preceding call to
+  // CreateFilter() on this class.  This method must return true if
+  // the key was in the list of keys passed to CreateFilter().
+  // This method may return true or false if the key was not on the
+  // list, but it should aim to return false with a high probability.
+  virtual bool KeyMayMatch(const Slice& key, const Slice& filter) const = 0;
+};
+
+// Return a new filter policy that uses a bloom filter with approximately
+// the specified number of bits per key.  A good value for bits_per_key
+// is 10, which yields a filter with ~ 1% false positive rate.
+//
+// Callers must delete the result after any database that is using the
+// result has been closed.
+//
+// Note: if you are using a custom comparator that ignores some parts
+// of the keys being compared, you must not use NewBloomFilterPolicy()
+// and must provide your own FilterPolicy that also ignores the
+// corresponding parts of the keys.  For example, if the comparator
+// ignores trailing spaces, it would be incorrect to use a
+// FilterPolicy (like NewBloomFilterPolicy) that does not ignore
+// trailing spaces in keys.
+LEVELDB_EXPORT const FilterPolicy* NewBloomFilterPolicy(int bits_per_key);
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_INCLUDE_FILTER_POLICY_H_
diff --git a/leveldb_base/include/leveldb/iterator.h b/leveldb_base/include/leveldb/iterator.h
new file mode 100644
index 0000000..bb9a5df
--- /dev/null
+++ b/leveldb_base/include/leveldb/iterator.h
@@ -0,0 +1,112 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// An iterator yields a sequence of key/value pairs from a source.
+// The following class defines the interface.  Multiple implementations
+// are provided by this library.  In particular, iterators are provided
+// to access the contents of a Table or a DB.
+//
+// Multiple threads can invoke const methods on an Iterator without
+// external synchronization, but if any of the threads may call a
+// non-const method, all threads accessing the same Iterator must use
+// external synchronization.
+
+#ifndef STORAGE_LEVELDB_INCLUDE_ITERATOR_H_
+#define STORAGE_LEVELDB_INCLUDE_ITERATOR_H_
+
+#include "leveldb/export.h"
+#include "leveldb/slice.h"
+#include "leveldb/status.h"
+
+namespace leveldb {
+
+class LEVELDB_EXPORT Iterator {
+ public:
+  Iterator();
+
+  Iterator(const Iterator&) = delete;
+  Iterator& operator=(const Iterator&) = delete;
+
+  virtual ~Iterator();
+
+  // An iterator is either positioned at a key/value pair, or
+  // not valid.  This method returns true iff the iterator is valid.
+  virtual bool Valid() const = 0;
+
+  // Position at the first key in the source.  The iterator is Valid()
+  // after this call iff the source is not empty.
+  virtual void SeekToFirst() = 0;
+
+  // Position at the last key in the source.  The iterator is
+  // Valid() after this call iff the source is not empty.
+  virtual void SeekToLast() = 0;
+
+  // Position at the first key in the source that is at or past target.
+  // The iterator is Valid() after this call iff the source contains
+  // an entry that comes at or past target.
+  virtual void Seek(const Slice& target) = 0;
+
+  // Moves to the next entry in the source.  After this call, Valid() is
+  // true iff the iterator was not positioned at the last entry in the source.
+  // REQUIRES: Valid()
+  virtual void Next() = 0;
+
+  // Moves to the previous entry in the source.  After this call, Valid() is
+  // true iff the iterator was not positioned at the first entry in source.
+  // REQUIRES: Valid()
+  virtual void Prev() = 0;
+
+  // Return the key for the current entry.  The underlying storage for
+  // the returned slice is valid only until the next modification of
+  // the iterator.
+  // REQUIRES: Valid()
+  virtual Slice key() const = 0;
+
+  // Return the value for the current entry.  The underlying storage for
+  // the returned slice is valid only until the next modification of
+  // the iterator.
+  // REQUIRES: Valid()
+  virtual Slice value() const = 0;
+
+  // If an error has occurred, return it.  Else return an ok status.
+  virtual Status status() const = 0;
+
+  // Clients are allowed to register function/arg1/arg2 triples that
+  // will be invoked when this iterator is destroyed.
+  //
+  // Note that unlike all of the preceding methods, this method is
+  // not abstract and therefore clients should not override it.
+  using CleanupFunction = void (*)(void* arg1, void* arg2);
+  void RegisterCleanup(CleanupFunction function, void* arg1, void* arg2);
+
+ private:
+  // Cleanup functions are stored in a single-linked list.
+  // The list's head node is inlined in the iterator.
+  struct CleanupNode {
+    // True if the node is not used. Only head nodes might be unused.
+    bool IsEmpty() const { return function == nullptr; }
+    // Invokes the cleanup function.
+    void Run() {
+      assert(function != nullptr);
+      (*function)(arg1, arg2);
+    }
+
+    // The head node is used if the function pointer is not null.
+    CleanupFunction function;
+    void* arg1;
+    void* arg2;
+    CleanupNode* next;
+  };
+  CleanupNode cleanup_head_;
+};
+
+// Return an empty iterator (yields nothing).
+LEVELDB_EXPORT Iterator* NewEmptyIterator();
+
+// Return an empty iterator with the specified status.
+LEVELDB_EXPORT Iterator* NewErrorIterator(const Status& status);
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_INCLUDE_ITERATOR_H_
diff --git a/leveldb_base/include/leveldb/options.h b/leveldb_base/include/leveldb/options.h
new file mode 100644
index 0000000..d755f46
--- /dev/null
+++ b/leveldb_base/include/leveldb/options.h
@@ -0,0 +1,190 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_INCLUDE_OPTIONS_H_
+#define STORAGE_LEVELDB_INCLUDE_OPTIONS_H_
+
+#include <cstddef>
+
+#include "leveldb/export.h"
+
+namespace leveldb {
+
+class Cache;
+class Comparator;
+class Env;
+class FilterPolicy;
+class Logger;
+class Snapshot;
+
+// DB contents are stored in a set of blocks, each of which holds a
+// sequence of key,value pairs.  Each block may be compressed before
+// being stored in a file.  The following enum describes which
+// compression method (if any) is used to compress a block.
+enum CompressionType {
+  // NOTE: do not change the values of existing entries, as these are
+  // part of the persistent format on disk.
+  kNoCompression = 0x0,
+  kSnappyCompression = 0x1,
+  kZstdCompression = 0x2,
+};
+
+// Options to control the behavior of a database (passed to DB::Open)
+struct LEVELDB_EXPORT Options {
+  // Create an Options object with default values for all fields.
+  Options();
+
+  // -------------------
+  // Parameters that affect behavior
+
+  // Comparator used to define the order of keys in the table.
+  // Default: a comparator that uses lexicographic byte-wise ordering
+  //
+  // REQUIRES: The client must ensure that the comparator supplied
+  // here has the same name and orders keys *exactly* the same as the
+  // comparator provided to previous open calls on the same DB.
+  const Comparator* comparator;
+
+  // If true, the database will be created if it is missing.
+  bool create_if_missing = false;
+
+  // If true, an error is raised if the database already exists.
+  bool error_if_exists = false;
+
+  // If true, the implementation will do aggressive checking of the
+  // data it is processing and will stop early if it detects any
+  // errors.  This may have unforeseen ramifications: for example, a
+  // corruption of one DB entry may cause a large number of entries to
+  // become unreadable or for the entire DB to become unopenable.
+  bool paranoid_checks = false;
+
+  // Use the specified object to interact with the environment,
+  // e.g. to read/write files, schedule background work, etc.
+  // Default: Env::Default()
+  Env* env;
+
+  // Any internal progress/error information generated by the db will
+  // be written to info_log if it is non-null, or to a file stored
+  // in the same directory as the DB contents if info_log is null.
+  Logger* info_log = nullptr;
+
+  // -------------------
+  // Parameters that affect performance
+
+  // Amount of data to build up in memory (backed by an unsorted log
+  // on disk) before converting to a sorted on-disk file.
+  //
+  // Larger values increase performance, especially during bulk loads.
+  // Up to two write buffers may be held in memory at the same time,
+  // so you may wish to adjust this parameter to control memory usage.
+  // Also, a larger write buffer will result in a longer recovery time
+  // the next time the database is opened.
+  size_t write_buffer_size = 4 * 1024 * 1024;
+
+  // Number of open files that can be used by the DB.  You may need to
+  // increase this if your database has a large working set (budget
+  // one open file per 2MB of working set).
+  int max_open_files = 1000;
+
+  // Control over blocks (user data is stored in a set of blocks, and
+  // a block is the unit of reading from disk).
+
+  // If non-null, use the specified cache for blocks.
+  // If null, leveldb will automatically create and use an 8MB internal cache.
+  Cache* block_cache = nullptr;
+
+  // Approximate size of user data packed per block.  Note that the
+  // block size specified here corresponds to uncompressed data.  The
+  // actual size of the unit read from disk may be smaller if
+  // compression is enabled.  This parameter can be changed dynamically.
+  size_t block_size = 4 * 1024;
+
+  // Number of keys between restart points for delta encoding of keys.
+  // This parameter can be changed dynamically.  Most clients should
+  // leave this parameter alone.
+  int block_restart_interval = 16;
+
+  // Leveldb will write up to this amount of bytes to a file before
+  // switching to a new one.
+  // Most clients should leave this parameter alone.  However if your
+  // filesystem is more efficient with larger files, you could
+  // consider increasing the value.  The downside will be longer
+  // compactions and hence longer latency/performance hiccups.
+  // Another reason to increase this parameter might be when you are
+  // initially populating a large database.
+  size_t max_file_size = 2 * 1024 * 1024;
+
+  // Compress blocks using the specified compression algorithm.  This
+  // parameter can be changed dynamically.
+  //
+  // Default: kSnappyCompression, which gives lightweight but fast
+  // compression.
+  //
+  // Typical speeds of kSnappyCompression on an Intel(R) Core(TM)2 2.4GHz:
+  //    ~200-500MB/s compression
+  //    ~400-800MB/s decompression
+  // Note that these speeds are significantly faster than most
+  // persistent storage speeds, and therefore it is typically never
+  // worth switching to kNoCompression.  Even if the input data is
+  // incompressible, the kSnappyCompression implementation will
+  // efficiently detect that and will switch to uncompressed mode.
+  CompressionType compression = kSnappyCompression;
+
+  // Compression level for zstd.
+  // Currently only the range [-5,22] is supported. Default is 1.
+  int zstd_compression_level = 1;
+
+  // EXPERIMENTAL: If true, append to existing MANIFEST and log files
+  // when a database is opened.  This can significantly speed up open.
+  //
+  // Default: currently false, but may become true later.
+  bool reuse_logs = false;
+
+  // If non-null, use the specified filter policy to reduce disk reads.
+  // Many applications will benefit from passing the result of
+  // NewBloomFilterPolicy() here.
+  const FilterPolicy* filter_policy = nullptr;
+};
+
+// Options that control read operations
+struct LEVELDB_EXPORT ReadOptions {
+  // If true, all data read from underlying storage will be
+  // verified against corresponding checksums.
+  bool verify_checksums = false;
+
+  // Should the data read for this iteration be cached in memory?
+  // Callers may wish to set this field to false for bulk scans.
+  bool fill_cache = true;
+
+  // If "snapshot" is non-null, read as of the supplied snapshot
+  // (which must belong to the DB that is being read and which must
+  // not have been released).  If "snapshot" is null, use an implicit
+  // snapshot of the state at the beginning of this read operation.
+  const Snapshot* snapshot = nullptr;
+};
+
+// Options that control write operations
+struct LEVELDB_EXPORT WriteOptions {
+  WriteOptions() = default;
+
+  // If true, the write will be flushed from the operating system
+  // buffer cache (by calling WritableFile::Sync()) before the write
+  // is considered complete.  If this flag is true, writes will be
+  // slower.
+  //
+  // If this flag is false, and the machine crashes, some recent
+  // writes may be lost.  Note that if it is just the process that
+  // crashes (i.e., the machine does not reboot), no writes will be
+  // lost even if sync==false.
+  //
+  // In other words, a DB write with sync==false has similar
+  // crash semantics as the "write()" system call.  A DB write
+  // with sync==true has similar crash semantics to a "write()"
+  // system call followed by "fsync()".
+  bool sync = false;
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_INCLUDE_OPTIONS_H_
diff --git a/leveldb_base/include/leveldb/slice.h b/leveldb_base/include/leveldb/slice.h
new file mode 100644
index 0000000..e97223a
--- /dev/null
+++ b/leveldb_base/include/leveldb/slice.h
@@ -0,0 +1,117 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// Slice is a simple structure containing a pointer into some external
+// storage and a size.  The user of a Slice must ensure that the slice
+// is not used after the corresponding external storage has been
+// deallocated.
+//
+// Multiple threads can invoke const methods on a Slice without
+// external synchronization, but if any of the threads may call a
+// non-const method, all threads accessing the same Slice must use
+// external synchronization.
+
+#ifndef STORAGE_LEVELDB_INCLUDE_SLICE_H_
+#define STORAGE_LEVELDB_INCLUDE_SLICE_H_
+
+#include <cassert>
+#include <cstddef>
+#include <cstring>
+#include <string>
+
+#include "leveldb/export.h"
+
+namespace leveldb {
+
+class LEVELDB_EXPORT Slice {
+ public:
+  // Create an empty slice.
+  Slice() : data_(""), size_(0) {}
+
+  // Create a slice that refers to d[0,n-1].
+  Slice(const char* d, size_t n) : data_(d), size_(n) {}
+
+  // Create a slice that refers to the contents of "s"
+  Slice(const std::string& s) : data_(s.data()), size_(s.size()) {}
+
+  // Create a slice that refers to s[0,strlen(s)-1]
+  Slice(const char* s) : data_(s), size_(strlen(s)) {}
+
+  // Intentionally copyable.
+  Slice(const Slice&) = default;
+  Slice& operator=(const Slice&) = default;
+
+  // Return a pointer to the beginning of the referenced data
+  const char* data() const { return data_; }
+
+  // Return the length (in bytes) of the referenced data
+  size_t size() const { return size_; }
+
+  // Return true iff the length of the referenced data is zero
+  bool empty() const { return size_ == 0; }
+
+  const char* begin() const { return data(); }
+  const char* end() const { return data() + size(); }
+
+  // Return the ith byte in the referenced data.
+  // REQUIRES: n < size()
+  char operator[](size_t n) const {
+    assert(n < size());
+    return data_[n];
+  }
+
+  // Change this slice to refer to an empty array
+  void clear() {
+    data_ = "";
+    size_ = 0;
+  }
+
+  // Drop the first "n" bytes from this slice.
+  void remove_prefix(size_t n) {
+    assert(n <= size());
+    data_ += n;
+    size_ -= n;
+  }
+
+  // Return a string that contains the copy of the referenced data.
+  std::string ToString() const { return std::string(data_, size_); }
+
+  // Three-way comparison.  Returns value:
+  //   <  0 iff "*this" <  "b",
+  //   == 0 iff "*this" == "b",
+  //   >  0 iff "*this" >  "b"
+  int compare(const Slice& b) const;
+
+  // Return true iff "x" is a prefix of "*this"
+  bool starts_with(const Slice& x) const {
+    return ((size_ >= x.size_) && (memcmp(data_, x.data_, x.size_) == 0));
+  }
+
+ private:
+  const char* data_;
+  size_t size_;
+};
+
+inline bool operator==(const Slice& x, const Slice& y) {
+  return ((x.size() == y.size()) &&
+          (memcmp(x.data(), y.data(), x.size()) == 0));
+}
+
+inline bool operator!=(const Slice& x, const Slice& y) { return !(x == y); }
+
+inline int Slice::compare(const Slice& b) const {
+  const size_t min_len = (size_ < b.size_) ? size_ : b.size_;
+  int r = memcmp(data_, b.data_, min_len);
+  if (r == 0) {
+    if (size_ < b.size_)
+      r = -1;
+    else if (size_ > b.size_)
+      r = +1;
+  }
+  return r;
+}
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_INCLUDE_SLICE_H_
diff --git a/leveldb_base/include/leveldb/status.h b/leveldb_base/include/leveldb/status.h
new file mode 100644
index 0000000..e327314
--- /dev/null
+++ b/leveldb_base/include/leveldb/status.h
@@ -0,0 +1,122 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// A Status encapsulates the result of an operation.  It may indicate success,
+// or it may indicate an error with an associated error message.
+//
+// Multiple threads can invoke const methods on a Status without
+// external synchronization, but if any of the threads may call a
+// non-const method, all threads accessing the same Status must use
+// external synchronization.
+
+#ifndef STORAGE_LEVELDB_INCLUDE_STATUS_H_
+#define STORAGE_LEVELDB_INCLUDE_STATUS_H_
+
+#include <algorithm>
+#include <string>
+
+#include "leveldb/export.h"
+#include "leveldb/slice.h"
+
+namespace leveldb {
+
+class LEVELDB_EXPORT Status {
+ public:
+  // Create a success status.
+  Status() noexcept : state_(nullptr) {}
+  ~Status() { delete[] state_; }
+
+  Status(const Status& rhs);
+  Status& operator=(const Status& rhs);
+
+  Status(Status&& rhs) noexcept : state_(rhs.state_) { rhs.state_ = nullptr; }
+  Status& operator=(Status&& rhs) noexcept;
+
+  // Return a success status.
+  static Status OK() { return Status(); }
+
+  // Return error status of an appropriate type.
+  static Status NotFound(const Slice& msg, const Slice& msg2 = Slice()) {
+    return Status(kNotFound, msg, msg2);
+  }
+  static Status Corruption(const Slice& msg, const Slice& msg2 = Slice()) {
+    return Status(kCorruption, msg, msg2);
+  }
+  static Status NotSupported(const Slice& msg, const Slice& msg2 = Slice()) {
+    return Status(kNotSupported, msg, msg2);
+  }
+  static Status InvalidArgument(const Slice& msg, const Slice& msg2 = Slice()) {
+    return Status(kInvalidArgument, msg, msg2);
+  }
+  static Status IOError(const Slice& msg, const Slice& msg2 = Slice()) {
+    return Status(kIOError, msg, msg2);
+  }
+
+  // Returns true iff the status indicates success.
+  bool ok() const { return (state_ == nullptr); }
+
+  // Returns true iff the status indicates a NotFound error.
+  bool IsNotFound() const { return code() == kNotFound; }
+
+  // Returns true iff the status indicates a Corruption error.
+  bool IsCorruption() const { return code() == kCorruption; }
+
+  // Returns true iff the status indicates an IOError.
+  bool IsIOError() const { return code() == kIOError; }
+
+  // Returns true iff the status indicates a NotSupportedError.
+  bool IsNotSupportedError() const { return code() == kNotSupported; }
+
+  // Returns true iff the status indicates an InvalidArgument.
+  bool IsInvalidArgument() const { return code() == kInvalidArgument; }
+
+  // Return a string representation of this status suitable for printing.
+  // Returns the string "OK" for success.
+  std::string ToString() const;
+
+ private:
+  enum Code {
+    kOk = 0,
+    kNotFound = 1,
+    kCorruption = 2,
+    kNotSupported = 3,
+    kInvalidArgument = 4,
+    kIOError = 5
+  };
+
+  Code code() const {
+    return (state_ == nullptr) ? kOk : static_cast<Code>(state_[4]);
+  }
+
+  Status(Code code, const Slice& msg, const Slice& msg2);
+  static const char* CopyState(const char* s);
+
+  // OK status has a null state_.  Otherwise, state_ is a new[] array
+  // of the following form:
+  //    state_[0..3] == length of message
+  //    state_[4]    == code
+  //    state_[5..]  == message
+  const char* state_;
+};
+
+inline Status::Status(const Status& rhs) {
+  state_ = (rhs.state_ == nullptr) ? nullptr : CopyState(rhs.state_);
+}
+inline Status& Status::operator=(const Status& rhs) {
+  // The following condition catches both aliasing (when this == &rhs),
+  // and the common case where both rhs and *this are ok.
+  if (state_ != rhs.state_) {
+    delete[] state_;
+    state_ = (rhs.state_ == nullptr) ? nullptr : CopyState(rhs.state_);
+  }
+  return *this;
+}
+inline Status& Status::operator=(Status&& rhs) noexcept {
+  std::swap(state_, rhs.state_);
+  return *this;
+}
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_INCLUDE_STATUS_H_
diff --git a/leveldb_base/include/leveldb/table.h b/leveldb_base/include/leveldb/table.h
new file mode 100644
index 0000000..a30e903
--- /dev/null
+++ b/leveldb_base/include/leveldb/table.h
@@ -0,0 +1,84 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_INCLUDE_TABLE_H_
+#define STORAGE_LEVELDB_INCLUDE_TABLE_H_
+
+#include <cstdint>
+
+#include "leveldb/export.h"
+#include "leveldb/iterator.h"
+
+namespace leveldb {
+
+class Block;
+class BlockHandle;
+class Footer;
+struct Options;
+class RandomAccessFile;
+struct ReadOptions;
+class TableCache;
+
+// A Table is a sorted map from strings to strings.  Tables are
+// immutable and persistent.  A Table may be safely accessed from
+// multiple threads without external synchronization.
+class LEVELDB_EXPORT Table {
+ public:
+  // Attempt to open the table that is stored in bytes [0..file_size)
+  // of "file", and read the metadata entries necessary to allow
+  // retrieving data from the table.
+  //
+  // If successful, returns ok and sets "*table" to the newly opened
+  // table.  The client should delete "*table" when no longer needed.
+  // If there was an error while initializing the table, sets "*table"
+  // to nullptr and returns a non-ok status.  Does not take ownership of
+  // "*source", but the client must ensure that "source" remains live
+  // for the duration of the returned table's lifetime.
+  //
+  // *file must remain live while this Table is in use.
+  static Status Open(const Options& options, RandomAccessFile* file,
+                     uint64_t file_size, Table** table);
+
+  Table(const Table&) = delete;
+  Table& operator=(const Table&) = delete;
+
+  ~Table();
+
+  // Returns a new iterator over the table contents.
+  // The result of NewIterator() is initially invalid (caller must
+  // call one of the Seek methods on the iterator before using it).
+  Iterator* NewIterator(const ReadOptions&) const;
+
+  // Given a key, return an approximate byte offset in the file where
+  // the data for that key begins (or would begin if the key were
+  // present in the file).  The returned value is in terms of file
+  // bytes, and so includes effects like compression of the underlying data.
+  // E.g., the approximate offset of the last key in the table will
+  // be close to the file length.
+  uint64_t ApproximateOffsetOf(const Slice& key) const;
+
+ private:
+  friend class TableCache;
+  struct Rep;
+
+  static Iterator* BlockReader(void*, const ReadOptions&, const Slice&);
+
+  explicit Table(Rep* rep) : rep_(rep) {}
+
+  // Calls (*handle_result)(arg, ...) with the entry found after a call
+  // to Seek(key).  May not make such a call if filter policy says
+  // that key is not present.
+  Status InternalGet(const ReadOptions&, const Slice& key, void* arg,
+                     void (*handle_result)(void* arg, const Slice& k,
+                                           const Slice& v));
+
+  void ReadMeta(const Footer& footer);
+  void ReadFilter(const Slice& filter_handle_value);
+
+  Rep* const rep_;
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_INCLUDE_TABLE_H_
diff --git a/leveldb_base/include/leveldb/table_builder.h b/leveldb_base/include/leveldb/table_builder.h
new file mode 100644
index 0000000..85710c3
--- /dev/null
+++ b/leveldb_base/include/leveldb/table_builder.h
@@ -0,0 +1,93 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// TableBuilder provides the interface used to build a Table
+// (an immutable and sorted map from keys to values).
+//
+// Multiple threads can invoke const methods on a TableBuilder without
+// external synchronization, but if any of the threads may call a
+// non-const method, all threads accessing the same TableBuilder must use
+// external synchronization.
+
+#ifndef STORAGE_LEVELDB_INCLUDE_TABLE_BUILDER_H_
+#define STORAGE_LEVELDB_INCLUDE_TABLE_BUILDER_H_
+
+#include <cstdint>
+
+#include "leveldb/export.h"
+#include "leveldb/options.h"
+#include "leveldb/status.h"
+
+namespace leveldb {
+
+class BlockBuilder;
+class BlockHandle;
+class WritableFile;
+
+class LEVELDB_EXPORT TableBuilder {
+ public:
+  // Create a builder that will store the contents of the table it is
+  // building in *file.  Does not close the file.  It is up to the
+  // caller to close the file after calling Finish().
+  TableBuilder(const Options& options, WritableFile* file);
+
+  TableBuilder(const TableBuilder&) = delete;
+  TableBuilder& operator=(const TableBuilder&) = delete;
+
+  // REQUIRES: Either Finish() or Abandon() has been called.
+  ~TableBuilder();
+
+  // Change the options used by this builder.  Note: only some of the
+  // option fields can be changed after construction.  If a field is
+  // not allowed to change dynamically and its value in the structure
+  // passed to the constructor is different from its value in the
+  // structure passed to this method, this method will return an error
+  // without changing any fields.
+  Status ChangeOptions(const Options& options);
+
+  // Add key,value to the table being constructed.
+  // REQUIRES: key is after any previously added key according to comparator.
+  // REQUIRES: Finish(), Abandon() have not been called
+  void Add(const Slice& key, const Slice& value);
+
+  // Advanced operation: flush any buffered key/value pairs to file.
+  // Can be used to ensure that two adjacent entries never live in
+  // the same data block.  Most clients should not need to use this method.
+  // REQUIRES: Finish(), Abandon() have not been called
+  void Flush();
+
+  // Return non-ok iff some error has been detected.
+  Status status() const;
+
+  // Finish building the table.  Stops using the file passed to the
+  // constructor after this function returns.
+  // REQUIRES: Finish(), Abandon() have not been called
+  Status Finish();
+
+  // Indicate that the contents of this builder should be abandoned.  Stops
+  // using the file passed to the constructor after this function returns.
+  // If the caller is not going to call Finish(), it must call Abandon()
+  // before destroying this builder.
+  // REQUIRES: Finish(), Abandon() have not been called
+  void Abandon();
+
+  // Number of calls to Add() so far.
+  uint64_t NumEntries() const;
+
+  // Size of the file generated so far.  If invoked after a successful
+  // Finish() call, returns the size of the final generated file.
+  uint64_t FileSize() const;
+
+ private:
+  bool ok() const { return status().ok(); }
+  void WriteBlock(BlockBuilder* block, BlockHandle* handle);
+  void WriteRawBlock(const Slice& data, CompressionType, BlockHandle* handle);
+
+  struct Rep;
+  Rep* rep_;
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_INCLUDE_TABLE_BUILDER_H_
diff --git a/leveldb_base/include/leveldb/write_batch.h b/leveldb_base/include/leveldb/write_batch.h
new file mode 100644
index 0000000..2c3b2ef
--- /dev/null
+++ b/leveldb_base/include/leveldb/write_batch.h
@@ -0,0 +1,87 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// WriteBatch holds a collection of updates to apply atomically to a DB.
+//
+// The updates are applied in the order in which they are added
+// to the WriteBatch.  For example, the value of "key" will be "v3"
+// after the following batch is written:
+//
+//    batch.Put("key", "v1");
+//    batch.Delete("key");
+//    batch.Put("key", "v2");
+//    batch.Put("key", "v3");
+//
+// Multiple threads can invoke const methods on a WriteBatch without
+// external synchronization, but if any of the threads may call a
+// non-const method, all threads accessing the same WriteBatch must use
+// external synchronization.
+
+#ifndef STORAGE_LEVELDB_INCLUDE_WRITE_BATCH_H_
+#define STORAGE_LEVELDB_INCLUDE_WRITE_BATCH_H_
+
+#include <string>
+
+#include "leveldb/export.h"
+#include "leveldb/status.h"
+
+#include <stdint.h>
+
+namespace leveldb {
+
+class Slice;
+
+class LEVELDB_EXPORT WriteBatch {
+ public:
+  class LEVELDB_EXPORT Handler {
+   public:
+    virtual ~Handler();
+    virtual void Put(const Slice& key, const Slice& value) = 0;
+    virtual void Delete(const Slice& key) = 0;
+  };
+
+  WriteBatch();
+
+  // Intentionally copyable.
+  WriteBatch(const WriteBatch&) = default;
+  WriteBatch& operator=(const WriteBatch&) = default;
+
+  ~WriteBatch();
+
+  // Store the mapping "key->value" in the database.
+  void Put(const Slice& key, const Slice& value);
+  // 添加ttl-橙
+  void Put(const Slice& key, const Slice& value, uint64_t ttl);
+
+  // If the database contains a mapping for "key", erase it.  Else do nothing.
+  void Delete(const Slice& key);
+
+  // Clear all updates buffered in this batch.
+  void Clear();
+
+  // The size of the database changes caused by this batch.
+  //
+  // This number is tied to implementation details, and may change across
+  // releases. It is intended for LevelDB usage metrics.
+  size_t ApproximateSize() const;
+
+  // Copies the operations in "source" to this batch.
+  //
+  // This runs in O(source size) time. However, the constant factor is better
+  // than calling Iterate() over the source batch with a Handler that replicates
+  // the operations into this batch.
+  void Append(const WriteBatch& source);
+
+  // Support for iterating over the contents of a batch.
+  Status Iterate(Handler* handler) const;
+
+ private:
+  friend class WriteBatchInternal;
+
+  std::string rep_;  // See comment in write_batch.cc for the format of rep_
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_INCLUDE_WRITE_BATCH_H_
diff --git a/leveldb_base/issues/issue178_test.cc b/leveldb_base/issues/issue178_test.cc
new file mode 100644
index 0000000..5cd5862
--- /dev/null
+++ b/leveldb_base/issues/issue178_test.cc
@@ -0,0 +1,85 @@
+// Copyright (c) 2013 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+// Test for issue 178: a manual compaction causes deleted data to reappear.
+#include <cstdlib>
+#include <iostream>
+#include <sstream>
+
+#include "gtest/gtest.h"
+#include "leveldb/db.h"
+#include "leveldb/write_batch.h"
+#include "util/testutil.h"
+
+namespace {
+
+const int kNumKeys = 1100000;
+
+std::string Key1(int i) {
+  char buf[100];
+  std::snprintf(buf, sizeof(buf), "my_key_%d", i);
+  return buf;
+}
+
+std::string Key2(int i) { return Key1(i) + "_xxx"; }
+
+TEST(Issue178, Test) {
+  // Get rid of any state from an old run.
+  std::string dbpath = testing::TempDir() + "leveldb_cbug_test";
+  DestroyDB(dbpath, leveldb::Options());
+
+  // Open database.  Disable compression since it affects the creation
+  // of layers and the code below is trying to test against a very
+  // specific scenario.
+  leveldb::DB* db;
+  leveldb::Options db_options;
+  db_options.create_if_missing = true;
+  db_options.compression = leveldb::kNoCompression;
+  ASSERT_LEVELDB_OK(leveldb::DB::Open(db_options, dbpath, &db));
+
+  // create first key range
+  leveldb::WriteBatch batch;
+  for (size_t i = 0; i < kNumKeys; i++) {
+    batch.Put(Key1(i), "value for range 1 key");
+  }
+  ASSERT_LEVELDB_OK(db->Write(leveldb::WriteOptions(), &batch));
+
+  // create second key range
+  batch.Clear();
+  for (size_t i = 0; i < kNumKeys; i++) {
+    batch.Put(Key2(i), "value for range 2 key");
+  }
+  ASSERT_LEVELDB_OK(db->Write(leveldb::WriteOptions(), &batch));
+
+  // delete second key range
+  batch.Clear();
+  for (size_t i = 0; i < kNumKeys; i++) {
+    batch.Delete(Key2(i));
+  }
+  ASSERT_LEVELDB_OK(db->Write(leveldb::WriteOptions(), &batch));
+
+  // compact database
+  std::string start_key = Key1(0);
+  std::string end_key = Key1(kNumKeys - 1);
+  leveldb::Slice least(start_key.data(), start_key.size());
+  leveldb::Slice greatest(end_key.data(), end_key.size());
+
+  // commenting out the line below causes the example to work correctly
+  db->CompactRange(&least, &greatest);
+
+  // count the keys
+  leveldb::Iterator* iter = db->NewIterator(leveldb::ReadOptions());
+  size_t num_keys = 0;
+  for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
+    num_keys++;
+  }
+  delete iter;
+  ASSERT_EQ(kNumKeys, num_keys) << "Bad number of keys";
+
+  // close database
+  delete db;
+  DestroyDB(dbpath, leveldb::Options());
+}
+
+}  // anonymous namespace
diff --git a/leveldb_base/issues/issue200_test.cc b/leveldb_base/issues/issue200_test.cc
new file mode 100644
index 0000000..959b371
--- /dev/null
+++ b/leveldb_base/issues/issue200_test.cc
@@ -0,0 +1,54 @@
+// Copyright (c) 2013 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+// Test for issue 200: when iterator switches direction from backward
+// to forward, the current key can be yielded unexpectedly if a new
+// mutation has been added just before the current key.
+
+#include "gtest/gtest.h"
+#include "leveldb/db.h"
+#include "util/testutil.h"
+
+namespace leveldb {
+
+TEST(Issue200, Test) {
+  // Get rid of any state from an old run.
+  std::string dbpath = testing::TempDir() + "leveldb_issue200_test";
+  DestroyDB(dbpath, Options());
+
+  DB* db;
+  Options options;
+  options.create_if_missing = true;
+  ASSERT_LEVELDB_OK(DB::Open(options, dbpath, &db));
+
+  WriteOptions write_options;
+  ASSERT_LEVELDB_OK(db->Put(write_options, "1", "b"));
+  ASSERT_LEVELDB_OK(db->Put(write_options, "2", "c"));
+  ASSERT_LEVELDB_OK(db->Put(write_options, "3", "d"));
+  ASSERT_LEVELDB_OK(db->Put(write_options, "4", "e"));
+  ASSERT_LEVELDB_OK(db->Put(write_options, "5", "f"));
+
+  ReadOptions read_options;
+  Iterator* iter = db->NewIterator(read_options);
+
+  // Add an element that should not be reflected in the iterator.
+  ASSERT_LEVELDB_OK(db->Put(write_options, "25", "cd"));
+
+  iter->Seek("5");
+  ASSERT_EQ(iter->key().ToString(), "5");
+  iter->Prev();
+  ASSERT_EQ(iter->key().ToString(), "4");
+  iter->Prev();
+  ASSERT_EQ(iter->key().ToString(), "3");
+  iter->Next();
+  ASSERT_EQ(iter->key().ToString(), "4");
+  iter->Next();
+  ASSERT_EQ(iter->key().ToString(), "5");
+
+  delete iter;
+  delete db;
+  DestroyDB(dbpath, options);
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/issues/issue320_test.cc b/leveldb_base/issues/issue320_test.cc
new file mode 100644
index 0000000..9d7fa7b
--- /dev/null
+++ b/leveldb_base/issues/issue320_test.cc
@@ -0,0 +1,126 @@
+// Copyright (c) 2019 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include <cstdint>
+#include <cstdlib>
+#include <iostream>
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "leveldb/db.h"
+#include "leveldb/write_batch.h"
+#include "util/testutil.h"
+
+namespace leveldb {
+
+namespace {
+
+// Creates a random number in the range of [0, max).
+int GenerateRandomNumber(int max) { return std::rand() % max; }
+
+std::string CreateRandomString(int32_t index) {
+  static const size_t len = 1024;
+  char bytes[len];
+  size_t i = 0;
+  while (i < 8) {
+    bytes[i] = 'a' + ((index >> (4 * i)) & 0xf);
+    ++i;
+  }
+  while (i < sizeof(bytes)) {
+    bytes[i] = 'a' + GenerateRandomNumber(26);
+    ++i;
+  }
+  return std::string(bytes, sizeof(bytes));
+}
+
+}  // namespace
+
+TEST(Issue320, Test) {
+  std::srand(0);
+
+  bool delete_before_put = false;
+  bool keep_snapshots = true;
+
+  std::vector<std::unique_ptr<std::pair<std::string, std::string>>> test_map(
+      10000);
+  std::vector<Snapshot const*> snapshots(100, nullptr);
+
+  DB* db;
+  Options options;
+  options.create_if_missing = true;
+
+  std::string dbpath = testing::TempDir() + "leveldb_issue320_test";
+  ASSERT_LEVELDB_OK(DB::Open(options, dbpath, &db));
+
+  uint32_t target_size = 10000;
+  uint32_t num_items = 0;
+  uint32_t count = 0;
+  std::string key;
+  std::string value, old_value;
+
+  WriteOptions writeOptions;
+  ReadOptions readOptions;
+  while (count < 200000) {
+    if ((++count % 1000) == 0) {
+      std::cout << "count: " << count << std::endl;
+    }
+
+    int index = GenerateRandomNumber(test_map.size());
+    WriteBatch batch;
+
+    if (test_map[index] == nullptr) {
+      num_items++;
+      test_map[index].reset(new std::pair<std::string, std::string>(
+          CreateRandomString(index), CreateRandomString(index)));
+      batch.Put(test_map[index]->first, test_map[index]->second);
+    } else {
+      ASSERT_LEVELDB_OK(
+          db->Get(readOptions, test_map[index]->first, &old_value));
+      if (old_value != test_map[index]->second) {
+        std::cout << "ERROR incorrect value returned by Get" << std::endl;
+        std::cout << "  count=" << count << std::endl;
+        std::cout << "  old value=" << old_value << std::endl;
+        std::cout << "  test_map[index]->second=" << test_map[index]->second
+                  << std::endl;
+        std::cout << "  test_map[index]->first=" << test_map[index]->first
+                  << std::endl;
+        std::cout << "  index=" << index << std::endl;
+        ASSERT_EQ(old_value, test_map[index]->second);
+      }
+
+      if (num_items >= target_size && GenerateRandomNumber(100) > 30) {
+        batch.Delete(test_map[index]->first);
+        test_map[index] = nullptr;
+        --num_items;
+      } else {
+        test_map[index]->second = CreateRandomString(index);
+        if (delete_before_put) batch.Delete(test_map[index]->first);
+        batch.Put(test_map[index]->first, test_map[index]->second);
+      }
+    }
+
+    ASSERT_LEVELDB_OK(db->Write(writeOptions, &batch));
+
+    if (keep_snapshots && GenerateRandomNumber(10) == 0) {
+      int i = GenerateRandomNumber(snapshots.size());
+      if (snapshots[i] != nullptr) {
+        db->ReleaseSnapshot(snapshots[i]);
+      }
+      snapshots[i] = db->GetSnapshot();
+    }
+  }
+
+  for (Snapshot const* snapshot : snapshots) {
+    if (snapshot) {
+      db->ReleaseSnapshot(snapshot);
+    }
+  }
+
+  delete db;
+  DestroyDB(dbpath, options);
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/port/README.md b/leveldb_base/port/README.md
new file mode 100644
index 0000000..8b17153
--- /dev/null
+++ b/leveldb_base/port/README.md
@@ -0,0 +1,10 @@
+This directory contains interfaces and implementations that isolate the
+rest of the package from platform details.
+
+Code in the rest of the package includes "port.h" from this directory.
+"port.h" in turn includes a platform specific "port_<platform>.h" file
+that provides the platform specific implementation.
+
+See port_stdcxx.h for an example of what must be provided in a platform
+specific header file.
+
diff --git a/leveldb_base/port/port.h b/leveldb_base/port/port.h
new file mode 100644
index 0000000..4b247f7
--- /dev/null
+++ b/leveldb_base/port/port.h
@@ -0,0 +1,19 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_PORT_PORT_H_
+#define STORAGE_LEVELDB_PORT_PORT_H_
+
+#include <string.h>
+
+// Include the appropriate platform specific file below.  If you are
+// porting to a new platform, see "port_example.h" for documentation
+// of what the new port_<platform>.h file must provide.
+#if defined(LEVELDB_PLATFORM_POSIX) || defined(LEVELDB_PLATFORM_WINDOWS)
+#include "port/port_stdcxx.h"
+#elif defined(LEVELDB_PLATFORM_CHROMIUM)
+#include "port/port_chromium.h"
+#endif
+
+#endif  // STORAGE_LEVELDB_PORT_PORT_H_
diff --git a/leveldb_base/port/port_config.h.in b/leveldb_base/port/port_config.h.in
new file mode 100644
index 0000000..34bf66a
--- /dev/null
+++ b/leveldb_base/port/port_config.h.in
@@ -0,0 +1,38 @@
+// Copyright 2017 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_PORT_PORT_CONFIG_H_
+#define STORAGE_LEVELDB_PORT_PORT_CONFIG_H_
+
+// Define to 1 if you have a definition for fdatasync() in <unistd.h>.
+#if !defined(HAVE_FDATASYNC)
+#cmakedefine01 HAVE_FDATASYNC
+#endif  // !defined(HAVE_FDATASYNC)
+
+// Define to 1 if you have a definition for F_FULLFSYNC in <fcntl.h>.
+#if !defined(HAVE_FULLFSYNC)
+#cmakedefine01 HAVE_FULLFSYNC
+#endif  // !defined(HAVE_FULLFSYNC)
+
+// Define to 1 if you have a definition for O_CLOEXEC in <fcntl.h>.
+#if !defined(HAVE_O_CLOEXEC)
+#cmakedefine01 HAVE_O_CLOEXEC
+#endif  // !defined(HAVE_O_CLOEXEC)
+
+// Define to 1 if you have Google CRC32C.
+#if !defined(HAVE_CRC32C)
+#cmakedefine01 HAVE_CRC32C
+#endif  // !defined(HAVE_CRC32C)
+
+// Define to 1 if you have Google Snappy.
+#if !defined(HAVE_SNAPPY)
+#cmakedefine01 HAVE_SNAPPY
+#endif  // !defined(HAVE_SNAPPY)
+
+// Define to 1 if you have Zstd.
+#if !defined(HAVE_Zstd)
+#cmakedefine01 HAVE_ZSTD
+#endif  // !defined(HAVE_ZSTD)
+
+#endif  // STORAGE_LEVELDB_PORT_PORT_CONFIG_H_
diff --git a/leveldb_base/port/port_example.h b/leveldb_base/port/port_example.h
new file mode 100644
index 0000000..5d50ffa
--- /dev/null
+++ b/leveldb_base/port/port_example.h
@@ -0,0 +1,120 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// This file contains the specification, but not the implementations,
+// of the types/operations/etc. that should be defined by a platform
+// specific port_<platform>.h file.  Use this file as a reference for
+// how to port this package to a new platform.
+
+#ifndef STORAGE_LEVELDB_PORT_PORT_EXAMPLE_H_
+#define STORAGE_LEVELDB_PORT_PORT_EXAMPLE_H_
+
+#include "port/thread_annotations.h"
+
+namespace leveldb {
+namespace port {
+
+// TODO(jorlow): Many of these belong more in the environment class rather than
+//               here. We should try moving them and see if it affects perf.
+
+// ------------------ Threading -------------------
+
+// A Mutex represents an exclusive lock.
+class LOCKABLE Mutex {
+ public:
+  Mutex();
+  ~Mutex();
+
+  // Lock the mutex.  Waits until other lockers have exited.
+  // Will deadlock if the mutex is already locked by this thread.
+  void Lock() EXCLUSIVE_LOCK_FUNCTION();
+
+  // Unlock the mutex.
+  // REQUIRES: This mutex was locked by this thread.
+  void Unlock() UNLOCK_FUNCTION();
+
+  // Optionally crash if this thread does not hold this mutex.
+  // The implementation must be fast, especially if NDEBUG is
+  // defined.  The implementation is allowed to skip all checks.
+  void AssertHeld() ASSERT_EXCLUSIVE_LOCK();
+};
+
+class CondVar {
+ public:
+  explicit CondVar(Mutex* mu);
+  ~CondVar();
+
+  // Atomically release *mu and block on this condition variable until
+  // either a call to SignalAll(), or a call to Signal() that picks
+  // this thread to wakeup.
+  // REQUIRES: this thread holds *mu
+  void Wait();
+
+  // If there are some threads waiting, wake up at least one of them.
+  void Signal();
+
+  // Wake up all waiting threads.
+  void SignalAll();
+};
+
+// ------------------ Compression -------------------
+
+// Store the snappy compression of "input[0,input_length-1]" in *output.
+// Returns false if snappy is not supported by this port.
+bool Snappy_Compress(const char* input, size_t input_length,
+                     std::string* output);
+
+// If input[0,input_length-1] looks like a valid snappy compressed
+// buffer, store the size of the uncompressed data in *result and
+// return true.  Else return false.
+bool Snappy_GetUncompressedLength(const char* input, size_t length,
+                                  size_t* result);
+
+// Attempt to snappy uncompress input[0,input_length-1] into *output.
+// Returns true if successful, false if the input is invalid snappy
+// compressed data.
+//
+// REQUIRES: at least the first "n" bytes of output[] must be writable
+// where "n" is the result of a successful call to
+// Snappy_GetUncompressedLength.
+bool Snappy_Uncompress(const char* input_data, size_t input_length,
+                       char* output);
+
+// Store the zstd compression of "input[0,input_length-1]" in *output.
+// Returns false if zstd is not supported by this port.
+bool Zstd_Compress(int level, const char* input, size_t input_length,
+                   std::string* output);
+
+// If input[0,input_length-1] looks like a valid zstd compressed
+// buffer, store the size of the uncompressed data in *result and
+// return true.  Else return false.
+bool Zstd_GetUncompressedLength(const char* input, size_t length,
+                                size_t* result);
+
+// Attempt to zstd uncompress input[0,input_length-1] into *output.
+// Returns true if successful, false if the input is invalid zstd
+// compressed data.
+//
+// REQUIRES: at least the first "n" bytes of output[] must be writable
+// where "n" is the result of a successful call to
+// Zstd_GetUncompressedLength.
+bool Zstd_Uncompress(const char* input_data, size_t input_length, char* output);
+
+// ------------------ Miscellaneous -------------------
+
+// If heap profiling is not supported, returns false.
+// Else repeatedly calls (*func)(arg, data, n) and then returns true.
+// The concatenation of all "data[0,n-1]" fragments is the heap profile.
+bool GetHeapProfile(void (*func)(void*, const char*, int), void* arg);
+
+// Extend the CRC to include the first n bytes of buf.
+//
+// Returns zero if the CRC cannot be extended using acceleration, else returns
+// the newly extended CRC value (which may also be zero).
+uint32_t AcceleratedCRC32C(uint32_t crc, const char* buf, size_t size);
+
+}  // namespace port
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_PORT_PORT_EXAMPLE_H_
diff --git a/leveldb_base/port/port_stdcxx.h b/leveldb_base/port/port_stdcxx.h
new file mode 100644
index 0000000..6f503f6
--- /dev/null
+++ b/leveldb_base/port/port_stdcxx.h
@@ -0,0 +1,223 @@
+// Copyright (c) 2018 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_PORT_PORT_STDCXX_H_
+#define STORAGE_LEVELDB_PORT_PORT_STDCXX_H_
+
+// port/port_config.h availability is automatically detected via __has_include
+// in newer compilers. If LEVELDB_HAS_PORT_CONFIG_H is defined, it overrides the
+// configuration detection.
+#if defined(LEVELDB_HAS_PORT_CONFIG_H)
+
+#if LEVELDB_HAS_PORT_CONFIG_H
+#include "port/port_config.h"
+#endif  // LEVELDB_HAS_PORT_CONFIG_H
+
+#elif defined(__has_include)
+
+#if __has_include("port/port_config.h")
+#include "port/port_config.h"
+#endif  // __has_include("port/port_config.h")
+
+#endif  // defined(LEVELDB_HAS_PORT_CONFIG_H)
+
+#if HAVE_CRC32C
+#include <crc32c/crc32c.h>
+#endif  // HAVE_CRC32C
+#if HAVE_SNAPPY
+#include <snappy.h>
+#endif  // HAVE_SNAPPY
+#if HAVE_ZSTD
+#define ZSTD_STATIC_LINKING_ONLY  // For ZSTD_compressionParameters.
+#include <zstd.h>
+#endif  // HAVE_ZSTD
+
+#include <cassert>
+#include <condition_variable>  // NOLINT
+#include <cstddef>
+#include <cstdint>
+#include <mutex>  // NOLINT
+#include <string>
+
+#include "port/thread_annotations.h"
+
+namespace leveldb {
+namespace port {
+
+class CondVar;
+
+// Thinly wraps std::mutex.
+class LOCKABLE Mutex {
+ public:
+  Mutex() = default;
+  ~Mutex() = default;
+
+  Mutex(const Mutex&) = delete;
+  Mutex& operator=(const Mutex&) = delete;
+
+  void Lock() EXCLUSIVE_LOCK_FUNCTION() { mu_.lock(); }
+  void Unlock() UNLOCK_FUNCTION() { mu_.unlock(); }
+  void AssertHeld() ASSERT_EXCLUSIVE_LOCK() {}
+
+ private:
+  friend class CondVar;
+  std::mutex mu_;
+};
+
+// Thinly wraps std::condition_variable.
+class CondVar {
+ public:
+  explicit CondVar(Mutex* mu) : mu_(mu) { assert(mu != nullptr); }
+  ~CondVar() = default;
+
+  CondVar(const CondVar&) = delete;
+  CondVar& operator=(const CondVar&) = delete;
+
+  void Wait() {
+    std::unique_lock<std::mutex> lock(mu_->mu_, std::adopt_lock);
+    cv_.wait(lock);
+    lock.release();
+  }
+  void Signal() { cv_.notify_one(); }
+  void SignalAll() { cv_.notify_all(); }
+
+ private:
+  std::condition_variable cv_;
+  Mutex* const mu_;
+};
+
+inline bool Snappy_Compress(const char* input, size_t length,
+                            std::string* output) {
+#if HAVE_SNAPPY
+  output->resize(snappy::MaxCompressedLength(length));
+  size_t outlen;
+  snappy::RawCompress(input, length, &(*output)[0], &outlen);
+  output->resize(outlen);
+  return true;
+#else
+  // Silence compiler warnings about unused arguments.
+  (void)input;
+  (void)length;
+  (void)output;
+#endif  // HAVE_SNAPPY
+
+  return false;
+}
+
+inline bool Snappy_GetUncompressedLength(const char* input, size_t length,
+                                         size_t* result) {
+#if HAVE_SNAPPY
+  return snappy::GetUncompressedLength(input, length, result);
+#else
+  // Silence compiler warnings about unused arguments.
+  (void)input;
+  (void)length;
+  (void)result;
+  return false;
+#endif  // HAVE_SNAPPY
+}
+
+inline bool Snappy_Uncompress(const char* input, size_t length, char* output) {
+#if HAVE_SNAPPY
+  return snappy::RawUncompress(input, length, output);
+#else
+  // Silence compiler warnings about unused arguments.
+  (void)input;
+  (void)length;
+  (void)output;
+  return false;
+#endif  // HAVE_SNAPPY
+}
+
+inline bool Zstd_Compress(int level, const char* input, size_t length,
+                          std::string* output) {
+#if HAVE_ZSTD
+  // Get the MaxCompressedLength.
+  size_t outlen = ZSTD_compressBound(length);
+  if (ZSTD_isError(outlen)) {
+    return false;
+  }
+  output->resize(outlen);
+  ZSTD_CCtx* ctx = ZSTD_createCCtx();
+  ZSTD_compressionParameters parameters =
+      ZSTD_getCParams(level, std::max(length, size_t{1}), /*dictSize=*/0);
+  ZSTD_CCtx_setCParams(ctx, parameters);
+  outlen = ZSTD_compress2(ctx, &(*output)[0], output->size(), input, length);
+  ZSTD_freeCCtx(ctx);
+  if (ZSTD_isError(outlen)) {
+    return false;
+  }
+  output->resize(outlen);
+  return true;
+#else
+  // Silence compiler warnings about unused arguments.
+  (void)level;
+  (void)input;
+  (void)length;
+  (void)output;
+  return false;
+#endif  // HAVE_ZSTD
+}
+
+inline bool Zstd_GetUncompressedLength(const char* input, size_t length,
+                                       size_t* result) {
+#if HAVE_ZSTD
+  size_t size = ZSTD_getFrameContentSize(input, length);
+  if (size == 0) return false;
+  *result = size;
+  return true;
+#else
+  // Silence compiler warnings about unused arguments.
+  (void)input;
+  (void)length;
+  (void)result;
+  return false;
+#endif  // HAVE_ZSTD
+}
+
+inline bool Zstd_Uncompress(const char* input, size_t length, char* output) {
+#if HAVE_ZSTD
+  size_t outlen;
+  if (!Zstd_GetUncompressedLength(input, length, &outlen)) {
+    return false;
+  }
+  ZSTD_DCtx* ctx = ZSTD_createDCtx();
+  outlen = ZSTD_decompressDCtx(ctx, output, outlen, input, length);
+  ZSTD_freeDCtx(ctx);
+  if (ZSTD_isError(outlen)) {
+    return false;
+  }
+  return true;
+#else
+  // Silence compiler warnings about unused arguments.
+  (void)input;
+  (void)length;
+  (void)output;
+  return false;
+#endif  // HAVE_ZSTD
+}
+
+inline bool GetHeapProfile(void (*func)(void*, const char*, int), void* arg) {
+  // Silence compiler warnings about unused arguments.
+  (void)func;
+  (void)arg;
+  return false;
+}
+
+inline uint32_t AcceleratedCRC32C(uint32_t crc, const char* buf, size_t size) {
+#if HAVE_CRC32C
+  return ::crc32c::Extend(crc, reinterpret_cast<const uint8_t*>(buf), size);
+#else
+  // Silence compiler warnings about unused arguments.
+  (void)crc;
+  (void)buf;
+  (void)size;
+  return 0;
+#endif  // HAVE_CRC32C
+}
+
+}  // namespace port
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_PORT_PORT_STDCXX_H_
diff --git a/leveldb_base/port/thread_annotations.h b/leveldb_base/port/thread_annotations.h
new file mode 100644
index 0000000..1547df9
--- /dev/null
+++ b/leveldb_base/port/thread_annotations.h
@@ -0,0 +1,108 @@
+// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_PORT_THREAD_ANNOTATIONS_H_
+#define STORAGE_LEVELDB_PORT_THREAD_ANNOTATIONS_H_
+
+// Use Clang's thread safety analysis annotations when available. In other
+// environments, the macros receive empty definitions.
+// Usage documentation: https://clang.llvm.org/docs/ThreadSafetyAnalysis.html
+
+#if !defined(THREAD_ANNOTATION_ATTRIBUTE__)
+
+#if defined(__clang__)
+
+#define THREAD_ANNOTATION_ATTRIBUTE__(x) __attribute__((x))
+#else
+#define THREAD_ANNOTATION_ATTRIBUTE__(x)  // no-op
+#endif
+
+#endif  // !defined(THREAD_ANNOTATION_ATTRIBUTE__)
+
+#ifndef GUARDED_BY
+#define GUARDED_BY(x) THREAD_ANNOTATION_ATTRIBUTE__(guarded_by(x))
+#endif
+
+#ifndef PT_GUARDED_BY
+#define PT_GUARDED_BY(x) THREAD_ANNOTATION_ATTRIBUTE__(pt_guarded_by(x))
+#endif
+
+#ifndef ACQUIRED_AFTER
+#define ACQUIRED_AFTER(...) \
+  THREAD_ANNOTATION_ATTRIBUTE__(acquired_after(__VA_ARGS__))
+#endif
+
+#ifndef ACQUIRED_BEFORE
+#define ACQUIRED_BEFORE(...) \
+  THREAD_ANNOTATION_ATTRIBUTE__(acquired_before(__VA_ARGS__))
+#endif
+
+#ifndef EXCLUSIVE_LOCKS_REQUIRED
+#define EXCLUSIVE_LOCKS_REQUIRED(...) \
+  THREAD_ANNOTATION_ATTRIBUTE__(exclusive_locks_required(__VA_ARGS__))
+#endif
+
+#ifndef SHARED_LOCKS_REQUIRED
+#define SHARED_LOCKS_REQUIRED(...) \
+  THREAD_ANNOTATION_ATTRIBUTE__(shared_locks_required(__VA_ARGS__))
+#endif
+
+#ifndef LOCKS_EXCLUDED
+#define LOCKS_EXCLUDED(...) \
+  THREAD_ANNOTATION_ATTRIBUTE__(locks_excluded(__VA_ARGS__))
+#endif
+
+#ifndef LOCK_RETURNED
+#define LOCK_RETURNED(x) THREAD_ANNOTATION_ATTRIBUTE__(lock_returned(x))
+#endif
+
+#ifndef LOCKABLE
+#define LOCKABLE THREAD_ANNOTATION_ATTRIBUTE__(lockable)
+#endif
+
+#ifndef SCOPED_LOCKABLE
+#define SCOPED_LOCKABLE THREAD_ANNOTATION_ATTRIBUTE__(scoped_lockable)
+#endif
+
+#ifndef EXCLUSIVE_LOCK_FUNCTION
+#define EXCLUSIVE_LOCK_FUNCTION(...) \
+  THREAD_ANNOTATION_ATTRIBUTE__(exclusive_lock_function(__VA_ARGS__))
+#endif
+
+#ifndef SHARED_LOCK_FUNCTION
+#define SHARED_LOCK_FUNCTION(...) \
+  THREAD_ANNOTATION_ATTRIBUTE__(shared_lock_function(__VA_ARGS__))
+#endif
+
+#ifndef EXCLUSIVE_TRYLOCK_FUNCTION
+#define EXCLUSIVE_TRYLOCK_FUNCTION(...) \
+  THREAD_ANNOTATION_ATTRIBUTE__(exclusive_trylock_function(__VA_ARGS__))
+#endif
+
+#ifndef SHARED_TRYLOCK_FUNCTION
+#define SHARED_TRYLOCK_FUNCTION(...) \
+  THREAD_ANNOTATION_ATTRIBUTE__(shared_trylock_function(__VA_ARGS__))
+#endif
+
+#ifndef UNLOCK_FUNCTION
+#define UNLOCK_FUNCTION(...) \
+  THREAD_ANNOTATION_ATTRIBUTE__(unlock_function(__VA_ARGS__))
+#endif
+
+#ifndef NO_THREAD_SAFETY_ANALYSIS
+#define NO_THREAD_SAFETY_ANALYSIS \
+  THREAD_ANNOTATION_ATTRIBUTE__(no_thread_safety_analysis)
+#endif
+
+#ifndef ASSERT_EXCLUSIVE_LOCK
+#define ASSERT_EXCLUSIVE_LOCK(...) \
+  THREAD_ANNOTATION_ATTRIBUTE__(assert_exclusive_lock(__VA_ARGS__))
+#endif
+
+#ifndef ASSERT_SHARED_LOCK
+#define ASSERT_SHARED_LOCK(...) \
+  THREAD_ANNOTATION_ATTRIBUTE__(assert_shared_lock(__VA_ARGS__))
+#endif
+
+#endif  // STORAGE_LEVELDB_PORT_THREAD_ANNOTATIONS_H_
diff --git a/leveldb_base/table/block.cc b/leveldb_base/table/block.cc
new file mode 100644
index 0000000..e7e34f2
--- /dev/null
+++ b/leveldb_base/table/block.cc
@@ -0,0 +1,323 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// Decodes the blocks generated by block_builder.cc.
+
+#include "table/block.h"
+
+#include <algorithm>
+#include <cstdint>
+#include <vector>
+
+#include "leveldb/comparator.h"
+#include "table/format.h"
+#include "util/coding.h"
+#include "util/logging.h"
+
+// 添加所需头文件-柠
+#include <iostream>
+#include <sstream> 
+#include <iomanip>
+#include <ctime>  
+#include <chrono> 
+
+namespace leveldb {
+
+inline uint32_t Block::NumRestarts() const {
+  assert(size_ >= sizeof(uint32_t));
+  return DecodeFixed32(data_ + size_ - sizeof(uint32_t));
+}
+
+Block::Block(const BlockContents& contents)
+    : data_(contents.data.data()),
+      size_(contents.data.size()),
+      owned_(contents.heap_allocated) {
+  if (size_ < sizeof(uint32_t)) {
+    size_ = 0;  // Error marker
+  } else {
+    size_t max_restarts_allowed = (size_ - sizeof(uint32_t)) / sizeof(uint32_t);
+    if (NumRestarts() > max_restarts_allowed) {
+      // The size is too small for NumRestarts()
+      size_ = 0;
+    } else {
+      restart_offset_ = size_ - (1 + NumRestarts()) * sizeof(uint32_t);
+    }
+  }
+}
+
+Block::~Block() {
+  if (owned_) {
+    delete[] data_;
+  }
+}
+
+// Helper routine: decode the next block entry starting at "p",
+// storing the number of shared key bytes, non_shared key bytes,
+// and the length of the value in "*shared", "*non_shared", and
+// "*value_length", respectively.  Will not dereference past "limit".
+//
+// If any errors are detected, returns nullptr.  Otherwise, returns a
+// pointer to the key delta (just past the three decoded values).
+static inline const char* DecodeEntry(const char* p, const char* limit,
+                                      uint32_t* shared, uint32_t* non_shared,
+                                      uint32_t* value_length) {
+  if (limit - p < 3) return nullptr;
+  *shared = reinterpret_cast<const uint8_t*>(p)[0];
+  *non_shared = reinterpret_cast<const uint8_t*>(p)[1];
+  *value_length = reinterpret_cast<const uint8_t*>(p)[2];
+  if ((*shared | *non_shared | *value_length) < 128) {
+    // Fast path: all three values are encoded in one byte each
+    p += 3;
+  } else {
+    if ((p = GetVarint32Ptr(p, limit, shared)) == nullptr) return nullptr;
+    if ((p = GetVarint32Ptr(p, limit, non_shared)) == nullptr) return nullptr;
+    if ((p = GetVarint32Ptr(p, limit, value_length)) == nullptr) return nullptr;
+  }
+
+  if (static_cast<uint32_t>(limit - p) < (*non_shared + *value_length)) {
+    return nullptr;
+  }
+  return p;
+}
+
+class Block::Iter : public Iterator {
+ private:
+  const Comparator* const comparator_;
+  const char* const data_;       // underlying block contents
+  uint32_t const restarts_;      // Offset of restart array (list of fixed32)
+  uint32_t const num_restarts_;  // Number of uint32_t entries in restart array
+
+  // current_ is offset in data_ of current entry.  >= restarts_ if !Valid
+  uint32_t current_;
+  uint32_t restart_index_;  // Index of restart block in which current_ falls
+  std::string key_;
+  Slice value_;
+  Status status_;
+
+  inline int Compare(const Slice& a, const Slice& b) const {
+    return comparator_->Compare(a, b);
+  }
+
+  // Return the offset in data_ just past the end of the current entry.
+  inline uint32_t NextEntryOffset() const {
+    return (value_.data() + value_.size()) - data_;
+  }
+
+  uint32_t GetRestartPoint(uint32_t index) {
+    assert(index < num_restarts_);
+    return DecodeFixed32(data_ + restarts_ + index * sizeof(uint32_t));
+  }
+
+  void SeekToRestartPoint(uint32_t index) {
+    key_.clear();
+    restart_index_ = index;
+    // current_ will be fixed by ParseNextKey();
+
+    // ParseNextKey() starts at the end of value_, so set value_ accordingly
+    uint32_t offset = GetRestartPoint(index);
+    value_ = Slice(data_ + offset, 0);
+  }
+
+ public:
+  Iter(const Comparator* comparator, const char* data, uint32_t restarts,
+       uint32_t num_restarts)
+      : comparator_(comparator),
+        data_(data),
+        restarts_(restarts),
+        num_restarts_(num_restarts),
+        current_(restarts_),
+        restart_index_(num_restarts_) {
+    assert(num_restarts_ > 0);
+  }
+
+  bool Valid() const override { return current_ < restarts_; }
+  Status status() const override { return status_; }
+  Slice key() const override {
+    assert(Valid());
+    return key_;
+  }
+  Slice value() const override {
+    assert(Valid());
+    return value_;
+  }
+
+  void Next() override {
+    assert(Valid());
+    ParseNextKey();
+  }
+
+  void Prev() override {
+    assert(Valid());
+
+    // Scan backwards to a restart point before current_
+    const uint32_t original = current_;
+    while (GetRestartPoint(restart_index_) >= original) {
+      if (restart_index_ == 0) {
+        // No more entries
+        current_ = restarts_;
+        restart_index_ = num_restarts_;
+        return;
+      }
+      restart_index_--;
+    }
+
+    SeekToRestartPoint(restart_index_);
+    do {
+      // Loop until end of current entry hits the start of original entry
+    } while (ParseNextKey() && NextEntryOffset() < original);
+  }
+
+  void Seek(const Slice& target) override {
+    // Binary search in restart array to find the last restart point
+    // with a key < target
+    uint32_t left = 0;
+    uint32_t right = num_restarts_ - 1;
+    int current_key_compare = 0;
+
+    if (Valid()) {
+      // If we're already scanning, use the current position as a starting
+      // point. This is beneficial if the key we're seeking to is ahead of the
+      // current position.
+      current_key_compare = Compare(key_, target);
+      if (current_key_compare < 0) {
+        // key_ is smaller than target
+        left = restart_index_;
+      } else if (current_key_compare > 0) {
+        right = restart_index_;
+      } else {
+        // We're seeking to the key we're already at.
+        return;
+      }
+    }
+
+    while (left < right) {
+      uint32_t mid = (left + right + 1) / 2;
+      uint32_t region_offset = GetRestartPoint(mid);
+      uint32_t shared, non_shared, value_length;
+      const char* key_ptr =
+          DecodeEntry(data_ + region_offset, data_ + restarts_, &shared,
+                      &non_shared, &value_length);
+      if (key_ptr == nullptr || (shared != 0)) {
+        CorruptionError();
+        return;
+      }
+      Slice mid_key(key_ptr, non_shared);
+      if (Compare(mid_key, target) < 0) {
+        // Key at "mid" is smaller than "target".  Therefore all
+        // blocks before "mid" are uninteresting.
+        left = mid;
+      } else {
+        // Key at "mid" is >= "target".  Therefore all blocks at or
+        // after "mid" are uninteresting.
+        right = mid - 1;
+      }
+    }
+
+    // We might be able to use our current position within the restart block.
+    // This is true if we determined the key we desire is in the current block
+    // and is after than the current key.
+    assert(current_key_compare == 0 || Valid());
+    bool skip_seek = left == restart_index_ && current_key_compare < 0;
+    if (!skip_seek) {
+      SeekToRestartPoint(left);
+    }
+    // Linear search (within restart block) for first key >= target
+    while (true) {
+      if (!ParseNextKey()) {
+        return;
+      }
+      if (Compare(key_, target) >= 0) {
+        //重新解析record-柠       
+        std::string value_with_ttl(value_.data(), value_.size());
+        if (value_with_ttl.size() >= 19) {
+          std::string expiration_time_str = value_with_ttl.substr(value_with_ttl.size() - 19); // 提取过期时间戳
+          std::tm tm = {};
+          char* res = strptime(expiration_time_str.c_str(), "%Y-%m-%d %H:%M:%S", &tm);
+          if (res == nullptr) {
+            value_ = Slice(value_.data(), value_.size()-19);
+          } else {
+            std::time_t expiration_time = std::mktime(&tm);
+            std::time_t current_time = std::chrono::system_clock::to_time_t(std::chrono::system_clock::now());
+            if (expiration_time <= current_time) {
+              //std::cerr << "notfound_sst" << std::endl;
+              status_ = Status::NotFound(Slice());
+              value_ = Slice(value_.data(), 0);
+            }
+            else
+            {
+              value_ = Slice(value_.data(), value_.size()-19);
+            }
+          }
+        } else {
+          value_ = Slice(value_.data(), value_.size());
+        }
+        return;
+      }
+    }
+  }
+
+  void SeekToFirst() override {
+    SeekToRestartPoint(0);
+    ParseNextKey();
+  }
+
+  void SeekToLast() override {
+    SeekToRestartPoint(num_restarts_ - 1);
+    while (ParseNextKey() && NextEntryOffset() < restarts_) {
+      // Keep skipping
+    }
+  }
+
+ private:
+  void CorruptionError() {
+    current_ = restarts_;
+    restart_index_ = num_restarts_;
+    status_ = Status::Corruption("bad entry in block");
+    key_.clear();
+    value_.clear();
+  }
+
+  bool ParseNextKey() {
+    current_ = NextEntryOffset();
+    const char* p = data_ + current_;
+    const char* limit = data_ + restarts_;  // Restarts come right after data
+    if (p >= limit) {
+      // No more entries to return.  Mark as invalid.
+      current_ = restarts_;
+      restart_index_ = num_restarts_;
+      return false;
+    }
+
+    // Decode next entry
+    uint32_t shared, non_shared, value_length;
+    p = DecodeEntry(p, limit, &shared, &non_shared, &value_length);
+    if (p == nullptr || key_.size() < shared) {
+      CorruptionError();
+      return false;
+    } else {
+      key_.resize(shared);
+      key_.append(p, non_shared);
+      value_ = Slice(p + non_shared, value_length);
+      while (restart_index_ + 1 < num_restarts_ &&
+             GetRestartPoint(restart_index_ + 1) < current_) {
+        ++restart_index_;
+      }
+      return true;
+    }
+  }
+};
+
+Iterator* Block::NewIterator(const Comparator* comparator) {
+  if (size_ < sizeof(uint32_t)) {
+    return NewErrorIterator(Status::Corruption("bad block contents"));
+  }
+  const uint32_t num_restarts = NumRestarts();
+  if (num_restarts == 0) {
+    return NewEmptyIterator();
+  } else {
+    return new Iter(comparator, data_, restart_offset_, num_restarts);
+  }
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/table/block.h b/leveldb_base/table/block.h
new file mode 100644
index 0000000..5224108
--- /dev/null
+++ b/leveldb_base/table/block.h
@@ -0,0 +1,44 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_TABLE_BLOCK_H_
+#define STORAGE_LEVELDB_TABLE_BLOCK_H_
+
+#include <cstddef>
+#include <cstdint>
+
+#include "leveldb/iterator.h"
+
+namespace leveldb {
+
+struct BlockContents;
+class Comparator;
+
+class Block {
+ public:
+  // Initialize the block with the specified contents.
+  explicit Block(const BlockContents& contents);
+
+  Block(const Block&) = delete;
+  Block& operator=(const Block&) = delete;
+
+  ~Block();
+
+  size_t size() const { return size_; }
+  Iterator* NewIterator(const Comparator* comparator);
+
+ private:
+  class Iter;
+
+  uint32_t NumRestarts() const;
+
+  const char* data_;
+  size_t size_;
+  uint32_t restart_offset_;  // Offset in data_ of restart array
+  bool owned_;               // Block owns data_[]
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_TABLE_BLOCK_H_
diff --git a/leveldb_base/table/block_builder.cc b/leveldb_base/table/block_builder.cc
new file mode 100644
index 0000000..37d4008
--- /dev/null
+++ b/leveldb_base/table/block_builder.cc
@@ -0,0 +1,107 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// BlockBuilder generates blocks where keys are prefix-compressed:
+//
+// When we store a key, we drop the prefix shared with the previous
+// string.  This helps reduce the space requirement significantly.
+// Furthermore, once every K keys, we do not apply the prefix
+// compression and store the entire key.  We call this a "restart
+// point".  The tail end of the block stores the offsets of all of the
+// restart points, and can be used to do a binary search when looking
+// for a particular key.  Values are stored as-is (without compression)
+// immediately following the corresponding key.
+//
+// An entry for a particular key-value pair has the form:
+//     shared_bytes: varint32
+//     unshared_bytes: varint32
+//     value_length: varint32
+//     key_delta: char[unshared_bytes]
+//     value: char[value_length]
+// shared_bytes == 0 for restart points.
+//
+// The trailer of the block has the form:
+//     restarts: uint32[num_restarts]
+//     num_restarts: uint32
+// restarts[i] contains the offset within the block of the ith restart point.
+
+#include "table/block_builder.h"
+
+#include <algorithm>
+#include <cassert>
+
+#include "leveldb/comparator.h"
+#include "leveldb/options.h"
+#include "util/coding.h"
+
+namespace leveldb {
+
+BlockBuilder::BlockBuilder(const Options* options)
+    : options_(options), restarts_(), counter_(0), finished_(false) {
+  assert(options->block_restart_interval >= 1);
+  restarts_.push_back(0);  // First restart point is at offset 0
+}
+
+void BlockBuilder::Reset() {
+  buffer_.clear();
+  restarts_.clear();
+  restarts_.push_back(0);  // First restart point is at offset 0
+  counter_ = 0;
+  finished_ = false;
+  last_key_.clear();
+}
+
+size_t BlockBuilder::CurrentSizeEstimate() const {
+  return (buffer_.size() +                       // Raw data buffer
+          restarts_.size() * sizeof(uint32_t) +  // Restart array
+          sizeof(uint32_t));                     // Restart array length
+}
+
+Slice BlockBuilder::Finish() {
+  // Append restart array
+  for (size_t i = 0; i < restarts_.size(); i++) {
+    PutFixed32(&buffer_, restarts_[i]);
+  }
+  PutFixed32(&buffer_, restarts_.size());
+  finished_ = true;
+  return Slice(buffer_);
+}
+
+void BlockBuilder::Add(const Slice& key, const Slice& value) {
+  Slice last_key_piece(last_key_);
+  assert(!finished_);
+  assert(counter_ <= options_->block_restart_interval);
+  assert(buffer_.empty()  // No values yet?
+         || options_->comparator->Compare(key, last_key_piece) > 0);
+  size_t shared = 0;
+  if (counter_ < options_->block_restart_interval) {
+    // See how much sharing to do with previous string
+    const size_t min_length = std::min(last_key_piece.size(), key.size());
+    while ((shared < min_length) && (last_key_piece[shared] == key[shared])) {
+      shared++;
+    }
+  } else {
+    // Restart compression
+    restarts_.push_back(buffer_.size());
+    counter_ = 0;
+  }
+  const size_t non_shared = key.size() - shared;
+
+  // Add "<shared><non_shared><value_size>" to buffer_
+  PutVarint32(&buffer_, shared);
+  PutVarint32(&buffer_, non_shared);
+  PutVarint32(&buffer_, value.size());
+
+  // Add string delta to buffer_ followed by value
+  buffer_.append(key.data() + shared, non_shared);
+  buffer_.append(value.data(), value.size());
+
+  // Update state
+  last_key_.resize(shared);
+  last_key_.append(key.data() + shared, non_shared);
+  assert(Slice(last_key_) == key);
+  counter_++;
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/table/block_builder.h b/leveldb_base/table/block_builder.h
new file mode 100644
index 0000000..7a481cd
--- /dev/null
+++ b/leveldb_base/table/block_builder.h
@@ -0,0 +1,54 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_TABLE_BLOCK_BUILDER_H_
+#define STORAGE_LEVELDB_TABLE_BLOCK_BUILDER_H_
+
+#include <cstdint>
+#include <vector>
+
+#include "leveldb/slice.h"
+
+namespace leveldb {
+
+struct Options;
+
+class BlockBuilder {
+ public:
+  explicit BlockBuilder(const Options* options);
+
+  BlockBuilder(const BlockBuilder&) = delete;
+  BlockBuilder& operator=(const BlockBuilder&) = delete;
+
+  // Reset the contents as if the BlockBuilder was just constructed.
+  void Reset();
+
+  // REQUIRES: Finish() has not been called since the last call to Reset().
+  // REQUIRES: key is larger than any previously added key
+  void Add(const Slice& key, const Slice& value);
+
+  // Finish building the block and return a slice that refers to the
+  // block contents.  The returned slice will remain valid for the
+  // lifetime of this builder or until Reset() is called.
+  Slice Finish();
+
+  // Returns an estimate of the current (uncompressed) size of the block
+  // we are building.
+  size_t CurrentSizeEstimate() const;
+
+  // Return true iff no entries have been added since the last Reset()
+  bool empty() const { return buffer_.empty(); }
+
+ private:
+  const Options* options_;
+  std::string buffer_;              // Destination buffer
+  std::vector<uint32_t> restarts_;  // Restart points
+  int counter_;                     // Number of entries emitted since restart
+  bool finished_;                   // Has Finish() been called?
+  std::string last_key_;
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_TABLE_BLOCK_BUILDER_H_
diff --git a/leveldb_base/table/filter_block.cc b/leveldb_base/table/filter_block.cc
new file mode 100644
index 0000000..09ec009
--- /dev/null
+++ b/leveldb_base/table/filter_block.cc
@@ -0,0 +1,106 @@
+// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "table/filter_block.h"
+
+#include "leveldb/filter_policy.h"
+#include "util/coding.h"
+
+namespace leveldb {
+
+// See doc/table_format.md for an explanation of the filter block format.
+
+// Generate new filter every 2KB of data
+static const size_t kFilterBaseLg = 11;
+static const size_t kFilterBase = 1 << kFilterBaseLg;
+
+FilterBlockBuilder::FilterBlockBuilder(const FilterPolicy* policy)
+    : policy_(policy) {}
+
+void FilterBlockBuilder::StartBlock(uint64_t block_offset) {
+  uint64_t filter_index = (block_offset / kFilterBase);
+  assert(filter_index >= filter_offsets_.size());
+  while (filter_index > filter_offsets_.size()) {
+    GenerateFilter();
+  }
+}
+
+void FilterBlockBuilder::AddKey(const Slice& key) {
+  Slice k = key;
+  start_.push_back(keys_.size());
+  keys_.append(k.data(), k.size());
+}
+
+Slice FilterBlockBuilder::Finish() {
+  if (!start_.empty()) {
+    GenerateFilter();
+  }
+
+  // Append array of per-filter offsets
+  const uint32_t array_offset = result_.size();
+  for (size_t i = 0; i < filter_offsets_.size(); i++) {
+    PutFixed32(&result_, filter_offsets_[i]);
+  }
+
+  PutFixed32(&result_, array_offset);
+  result_.push_back(kFilterBaseLg);  // Save encoding parameter in result
+  return Slice(result_);
+}
+
+void FilterBlockBuilder::GenerateFilter() {
+  const size_t num_keys = start_.size();
+  if (num_keys == 0) {
+    // Fast path if there are no keys for this filter
+    filter_offsets_.push_back(result_.size());
+    return;
+  }
+
+  // Make list of keys from flattened key structure
+  start_.push_back(keys_.size());  // Simplify length computation
+  tmp_keys_.resize(num_keys);
+  for (size_t i = 0; i < num_keys; i++) {
+    const char* base = keys_.data() + start_[i];
+    size_t length = start_[i + 1] - start_[i];
+    tmp_keys_[i] = Slice(base, length);
+  }
+
+  // Generate filter for current set of keys and append to result_.
+  filter_offsets_.push_back(result_.size());
+  policy_->CreateFilter(&tmp_keys_[0], static_cast<int>(num_keys), &result_);
+
+  tmp_keys_.clear();
+  keys_.clear();
+  start_.clear();
+}
+
+FilterBlockReader::FilterBlockReader(const FilterPolicy* policy,
+                                     const Slice& contents)
+    : policy_(policy), data_(nullptr), offset_(nullptr), num_(0), base_lg_(0) {
+  size_t n = contents.size();
+  if (n < 5) return;  // 1 byte for base_lg_ and 4 for start of offset array
+  base_lg_ = contents[n - 1];
+  uint32_t last_word = DecodeFixed32(contents.data() + n - 5);
+  if (last_word > n - 5) return;
+  data_ = contents.data();
+  offset_ = data_ + last_word;
+  num_ = (n - 5 - last_word) / 4;
+}
+
+bool FilterBlockReader::KeyMayMatch(uint64_t block_offset, const Slice& key) {
+  uint64_t index = block_offset >> base_lg_;
+  if (index < num_) {
+    uint32_t start = DecodeFixed32(offset_ + index * 4);
+    uint32_t limit = DecodeFixed32(offset_ + index * 4 + 4);
+    if (start <= limit && limit <= static_cast<size_t>(offset_ - data_)) {
+      Slice filter = Slice(data_ + start, limit - start);
+      return policy_->KeyMayMatch(key, filter);
+    } else if (start == limit) {
+      // Empty filters do not match any keys
+      return false;
+    }
+  }
+  return true;  // Errors are treated as potential matches
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/table/filter_block.h b/leveldb_base/table/filter_block.h
new file mode 100644
index 0000000..25ab75b
--- /dev/null
+++ b/leveldb_base/table/filter_block.h
@@ -0,0 +1,68 @@
+// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// A filter block is stored near the end of a Table file.  It contains
+// filters (e.g., bloom filters) for all data blocks in the table combined
+// into a single filter block.
+
+#ifndef STORAGE_LEVELDB_TABLE_FILTER_BLOCK_H_
+#define STORAGE_LEVELDB_TABLE_FILTER_BLOCK_H_
+
+#include <cstddef>
+#include <cstdint>
+#include <string>
+#include <vector>
+
+#include "leveldb/slice.h"
+#include "util/hash.h"
+
+namespace leveldb {
+
+class FilterPolicy;
+
+// A FilterBlockBuilder is used to construct all of the filters for a
+// particular Table.  It generates a single string which is stored as
+// a special block in the Table.
+//
+// The sequence of calls to FilterBlockBuilder must match the regexp:
+//      (StartBlock AddKey*)* Finish
+class FilterBlockBuilder {
+ public:
+  explicit FilterBlockBuilder(const FilterPolicy*);
+
+  FilterBlockBuilder(const FilterBlockBuilder&) = delete;
+  FilterBlockBuilder& operator=(const FilterBlockBuilder&) = delete;
+
+  void StartBlock(uint64_t block_offset);
+  void AddKey(const Slice& key);
+  Slice Finish();
+
+ private:
+  void GenerateFilter();
+
+  const FilterPolicy* policy_;
+  std::string keys_;             // Flattened key contents
+  std::vector<size_t> start_;    // Starting index in keys_ of each key
+  std::string result_;           // Filter data computed so far
+  std::vector<Slice> tmp_keys_;  // policy_->CreateFilter() argument
+  std::vector<uint32_t> filter_offsets_;
+};
+
+class FilterBlockReader {
+ public:
+  // REQUIRES: "contents" and *policy must stay live while *this is live.
+  FilterBlockReader(const FilterPolicy* policy, const Slice& contents);
+  bool KeyMayMatch(uint64_t block_offset, const Slice& key);
+
+ private:
+  const FilterPolicy* policy_;
+  const char* data_;    // Pointer to filter data (at block-start)
+  const char* offset_;  // Pointer to beginning of offset array (at block-end)
+  size_t num_;          // Number of entries in offset array
+  size_t base_lg_;      // Encoding parameter (see kFilterBaseLg in .cc file)
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_TABLE_FILTER_BLOCK_H_
diff --git a/leveldb_base/table/filter_block_test.cc b/leveldb_base/table/filter_block_test.cc
new file mode 100644
index 0000000..3ee41cf
--- /dev/null
+++ b/leveldb_base/table/filter_block_test.cc
@@ -0,0 +1,122 @@
+// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "table/filter_block.h"
+
+#include "gtest/gtest.h"
+#include "leveldb/filter_policy.h"
+#include "util/coding.h"
+#include "util/hash.h"
+#include "util/logging.h"
+#include "util/testutil.h"
+
+namespace leveldb {
+
+// For testing: emit an array with one hash value per key
+class TestHashFilter : public FilterPolicy {
+ public:
+  const char* Name() const override { return "TestHashFilter"; }
+
+  void CreateFilter(const Slice* keys, int n, std::string* dst) const override {
+    for (int i = 0; i < n; i++) {
+      uint32_t h = Hash(keys[i].data(), keys[i].size(), 1);
+      PutFixed32(dst, h);
+    }
+  }
+
+  bool KeyMayMatch(const Slice& key, const Slice& filter) const override {
+    uint32_t h = Hash(key.data(), key.size(), 1);
+    for (size_t i = 0; i + 4 <= filter.size(); i += 4) {
+      if (h == DecodeFixed32(filter.data() + i)) {
+        return true;
+      }
+    }
+    return false;
+  }
+};
+
+class FilterBlockTest : public testing::Test {
+ public:
+  TestHashFilter policy_;
+};
+
+TEST_F(FilterBlockTest, EmptyBuilder) {
+  FilterBlockBuilder builder(&policy_);
+  Slice block = builder.Finish();
+  ASSERT_EQ("\\x00\\x00\\x00\\x00\\x0b", EscapeString(block));
+  FilterBlockReader reader(&policy_, block);
+  ASSERT_TRUE(reader.KeyMayMatch(0, "foo"));
+  ASSERT_TRUE(reader.KeyMayMatch(100000, "foo"));
+}
+
+TEST_F(FilterBlockTest, SingleChunk) {
+  FilterBlockBuilder builder(&policy_);
+  builder.StartBlock(100);
+  builder.AddKey("foo");
+  builder.AddKey("bar");
+  builder.AddKey("box");
+  builder.StartBlock(200);
+  builder.AddKey("box");
+  builder.StartBlock(300);
+  builder.AddKey("hello");
+  Slice block = builder.Finish();
+  FilterBlockReader reader(&policy_, block);
+  ASSERT_TRUE(reader.KeyMayMatch(100, "foo"));
+  ASSERT_TRUE(reader.KeyMayMatch(100, "bar"));
+  ASSERT_TRUE(reader.KeyMayMatch(100, "box"));
+  ASSERT_TRUE(reader.KeyMayMatch(100, "hello"));
+  ASSERT_TRUE(reader.KeyMayMatch(100, "foo"));
+  ASSERT_TRUE(!reader.KeyMayMatch(100, "missing"));
+  ASSERT_TRUE(!reader.KeyMayMatch(100, "other"));
+}
+
+TEST_F(FilterBlockTest, MultiChunk) {
+  FilterBlockBuilder builder(&policy_);
+
+  // First filter
+  builder.StartBlock(0);
+  builder.AddKey("foo");
+  builder.StartBlock(2000);
+  builder.AddKey("bar");
+
+  // Second filter
+  builder.StartBlock(3100);
+  builder.AddKey("box");
+
+  // Third filter is empty
+
+  // Last filter
+  builder.StartBlock(9000);
+  builder.AddKey("box");
+  builder.AddKey("hello");
+
+  Slice block = builder.Finish();
+  FilterBlockReader reader(&policy_, block);
+
+  // Check first filter
+  ASSERT_TRUE(reader.KeyMayMatch(0, "foo"));
+  ASSERT_TRUE(reader.KeyMayMatch(2000, "bar"));
+  ASSERT_TRUE(!reader.KeyMayMatch(0, "box"));
+  ASSERT_TRUE(!reader.KeyMayMatch(0, "hello"));
+
+  // Check second filter
+  ASSERT_TRUE(reader.KeyMayMatch(3100, "box"));
+  ASSERT_TRUE(!reader.KeyMayMatch(3100, "foo"));
+  ASSERT_TRUE(!reader.KeyMayMatch(3100, "bar"));
+  ASSERT_TRUE(!reader.KeyMayMatch(3100, "hello"));
+
+  // Check third filter (empty)
+  ASSERT_TRUE(!reader.KeyMayMatch(4100, "foo"));
+  ASSERT_TRUE(!reader.KeyMayMatch(4100, "bar"));
+  ASSERT_TRUE(!reader.KeyMayMatch(4100, "box"));
+  ASSERT_TRUE(!reader.KeyMayMatch(4100, "hello"));
+
+  // Check last filter
+  ASSERT_TRUE(reader.KeyMayMatch(9000, "box"));
+  ASSERT_TRUE(reader.KeyMayMatch(9000, "hello"));
+  ASSERT_TRUE(!reader.KeyMayMatch(9000, "foo"));
+  ASSERT_TRUE(!reader.KeyMayMatch(9000, "bar"));
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/table/format.cc b/leveldb_base/table/format.cc
new file mode 100644
index 0000000..ae998c1
--- /dev/null
+++ b/leveldb_base/table/format.cc
@@ -0,0 +1,164 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "table/format.h"
+
+#include "leveldb/env.h"
+#include "leveldb/options.h"
+#include "port/port.h"
+#include "table/block.h"
+#include "util/coding.h"
+#include "util/crc32c.h"
+
+namespace leveldb {
+
+void BlockHandle::EncodeTo(std::string* dst) const {
+  // Sanity check that all fields have been set
+  assert(offset_ != ~static_cast<uint64_t>(0));
+  assert(size_ != ~static_cast<uint64_t>(0));
+  PutVarint64(dst, offset_);
+  PutVarint64(dst, size_);
+}
+
+Status BlockHandle::DecodeFrom(Slice* input) {
+  if (GetVarint64(input, &offset_) && GetVarint64(input, &size_)) {
+    return Status::OK();
+  } else {
+    return Status::Corruption("bad block handle");
+  }
+}
+
+void Footer::EncodeTo(std::string* dst) const {
+  const size_t original_size = dst->size();
+  metaindex_handle_.EncodeTo(dst);
+  index_handle_.EncodeTo(dst);
+  dst->resize(2 * BlockHandle::kMaxEncodedLength);  // Padding
+  PutFixed32(dst, static_cast<uint32_t>(kTableMagicNumber & 0xffffffffu));
+  PutFixed32(dst, static_cast<uint32_t>(kTableMagicNumber >> 32));
+  assert(dst->size() == original_size + kEncodedLength);
+  (void)original_size;  // Disable unused variable warning.
+}
+
+Status Footer::DecodeFrom(Slice* input) {
+  if (input->size() < kEncodedLength) {
+    return Status::Corruption("not an sstable (footer too short)");
+  }
+
+  const char* magic_ptr = input->data() + kEncodedLength - 8;
+  const uint32_t magic_lo = DecodeFixed32(magic_ptr);
+  const uint32_t magic_hi = DecodeFixed32(magic_ptr + 4);
+  const uint64_t magic = ((static_cast<uint64_t>(magic_hi) << 32) |
+                          (static_cast<uint64_t>(magic_lo)));
+  if (magic != kTableMagicNumber) {
+    return Status::Corruption("not an sstable (bad magic number)");
+  }
+
+  Status result = metaindex_handle_.DecodeFrom(input);
+  if (result.ok()) {
+    result = index_handle_.DecodeFrom(input);
+  }
+  if (result.ok()) {
+    // We skip over any leftover data (just padding for now) in "input"
+    const char* end = magic_ptr + 8;
+    *input = Slice(end, input->data() + input->size() - end);
+  }
+  return result;
+}
+
+Status ReadBlock(RandomAccessFile* file, const ReadOptions& options,
+                 const BlockHandle& handle, BlockContents* result) {
+  result->data = Slice();
+  result->cachable = false;
+  result->heap_allocated = false;
+
+  // Read the block contents as well as the type/crc footer.
+  // See table_builder.cc for the code that built this structure.
+  size_t n = static_cast<size_t>(handle.size());
+  char* buf = new char[n + kBlockTrailerSize];
+  Slice contents;
+  Status s = file->Read(handle.offset(), n + kBlockTrailerSize, &contents, buf);
+  if (!s.ok()) {
+    delete[] buf;
+    return s;
+  }
+  if (contents.size() != n + kBlockTrailerSize) {
+    delete[] buf;
+    return Status::Corruption("truncated block read");
+  }
+
+  // Check the crc of the type and the block contents
+  const char* data = contents.data();  // Pointer to where Read put the data
+  if (options.verify_checksums) {
+    const uint32_t crc = crc32c::Unmask(DecodeFixed32(data + n + 1));
+    const uint32_t actual = crc32c::Value(data, n + 1);
+    if (actual != crc) {
+      delete[] buf;
+      s = Status::Corruption("block checksum mismatch");
+      return s;
+    }
+  }
+
+  switch (data[n]) {
+    case kNoCompression:
+      if (data != buf) {
+        // File implementation gave us pointer to some other data.
+        // Use it directly under the assumption that it will be live
+        // while the file is open.
+        delete[] buf;
+        result->data = Slice(data, n);
+        result->heap_allocated = false;
+        result->cachable = false;  // Do not double-cache
+      } else {
+        result->data = Slice(buf, n);
+        result->heap_allocated = true;
+        result->cachable = true;
+      }
+
+      // Ok
+      break;
+    case kSnappyCompression: {
+      size_t ulength = 0;
+      if (!port::Snappy_GetUncompressedLength(data, n, &ulength)) {
+        delete[] buf;
+        return Status::Corruption("corrupted snappy compressed block length");
+      }
+      char* ubuf = new char[ulength];
+      if (!port::Snappy_Uncompress(data, n, ubuf)) {
+        delete[] buf;
+        delete[] ubuf;
+        return Status::Corruption("corrupted snappy compressed block contents");
+      }
+      delete[] buf;
+      result->data = Slice(ubuf, ulength);
+      result->heap_allocated = true;
+      result->cachable = true;
+      break;
+    }
+    case kZstdCompression: {
+      size_t ulength = 0;
+      if (!port::Zstd_GetUncompressedLength(data, n, &ulength)) {
+        delete[] buf;
+        return Status::Corruption("corrupted zstd compressed block length");
+      }
+      char* ubuf = new char[ulength];
+      if (!port::Zstd_Uncompress(data, n, ubuf)) {
+        delete[] buf;
+        delete[] ubuf;
+        return Status::Corruption("corrupted zstd compressed block contents");
+      }
+      delete[] buf;
+      result->data = Slice(ubuf, ulength);
+      result->heap_allocated = true;
+      result->cachable = true;
+      break;
+    }
+    default:
+      delete[] buf;
+      return Status::Corruption("bad block type");
+  }
+
+  return Status::OK();
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/table/format.h b/leveldb_base/table/format.h
new file mode 100644
index 0000000..f6ea304
--- /dev/null
+++ b/leveldb_base/table/format.h
@@ -0,0 +1,99 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_TABLE_FORMAT_H_
+#define STORAGE_LEVELDB_TABLE_FORMAT_H_
+
+#include <cstdint>
+#include <string>
+
+#include "leveldb/slice.h"
+#include "leveldb/status.h"
+#include "leveldb/table_builder.h"
+
+namespace leveldb {
+
+class Block;
+class RandomAccessFile;
+struct ReadOptions;
+
+// BlockHandle is a pointer to the extent of a file that stores a data
+// block or a meta block.
+class BlockHandle {
+ public:
+  // Maximum encoding length of a BlockHandle
+  enum { kMaxEncodedLength = 10 + 10 };
+
+  BlockHandle();
+
+  // The offset of the block in the file.
+  uint64_t offset() const { return offset_; }
+  void set_offset(uint64_t offset) { offset_ = offset; }
+
+  // The size of the stored block
+  uint64_t size() const { return size_; }
+  void set_size(uint64_t size) { size_ = size; }
+
+  void EncodeTo(std::string* dst) const;
+  Status DecodeFrom(Slice* input);
+
+ private:
+  uint64_t offset_;
+  uint64_t size_;
+};
+
+// Footer encapsulates the fixed information stored at the tail
+// end of every table file.
+class Footer {
+ public:
+  // Encoded length of a Footer.  Note that the serialization of a
+  // Footer will always occupy exactly this many bytes.  It consists
+  // of two block handles and a magic number.
+  enum { kEncodedLength = 2 * BlockHandle::kMaxEncodedLength + 8 };
+
+  Footer() = default;
+
+  // The block handle for the metaindex block of the table
+  const BlockHandle& metaindex_handle() const { return metaindex_handle_; }
+  void set_metaindex_handle(const BlockHandle& h) { metaindex_handle_ = h; }
+
+  // The block handle for the index block of the table
+  const BlockHandle& index_handle() const { return index_handle_; }
+  void set_index_handle(const BlockHandle& h) { index_handle_ = h; }
+
+  void EncodeTo(std::string* dst) const;
+  Status DecodeFrom(Slice* input);
+
+ private:
+  BlockHandle metaindex_handle_;
+  BlockHandle index_handle_;
+};
+
+// kTableMagicNumber was picked by running
+//    echo http://code.google.com/p/leveldb/ | sha1sum
+// and taking the leading 64 bits.
+static const uint64_t kTableMagicNumber = 0xdb4775248b80fb57ull;
+
+// 1-byte type + 32-bit crc
+static const size_t kBlockTrailerSize = 5;
+
+struct BlockContents {
+  Slice data;           // Actual contents of data
+  bool cachable;        // True iff data can be cached
+  bool heap_allocated;  // True iff caller should delete[] data.data()
+};
+
+// Read the block identified by "handle" from "file".  On failure
+// return non-OK.  On success fill *result and return OK.
+Status ReadBlock(RandomAccessFile* file, const ReadOptions& options,
+                 const BlockHandle& handle, BlockContents* result);
+
+// Implementation details follow.  Clients should ignore,
+
+inline BlockHandle::BlockHandle()
+    : offset_(~static_cast<uint64_t>(0)), size_(~static_cast<uint64_t>(0)) {}
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_TABLE_FORMAT_H_
diff --git a/leveldb_base/table/iterator.cc b/leveldb_base/table/iterator.cc
new file mode 100644
index 0000000..dfef083
--- /dev/null
+++ b/leveldb_base/table/iterator.cc
@@ -0,0 +1,76 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "leveldb/iterator.h"
+
+namespace leveldb {
+
+Iterator::Iterator() {
+  cleanup_head_.function = nullptr;
+  cleanup_head_.next = nullptr;
+}
+
+Iterator::~Iterator() {
+  if (!cleanup_head_.IsEmpty()) {
+    cleanup_head_.Run();
+    for (CleanupNode* node = cleanup_head_.next; node != nullptr;) {
+      node->Run();
+      CleanupNode* next_node = node->next;
+      delete node;
+      node = next_node;
+    }
+  }
+}
+
+void Iterator::RegisterCleanup(CleanupFunction func, void* arg1, void* arg2) {
+  assert(func != nullptr);
+  CleanupNode* node;
+  if (cleanup_head_.IsEmpty()) {
+    node = &cleanup_head_;
+  } else {
+    node = new CleanupNode();
+    node->next = cleanup_head_.next;
+    cleanup_head_.next = node;
+  }
+  node->function = func;
+  node->arg1 = arg1;
+  node->arg2 = arg2;
+}
+
+namespace {
+
+class EmptyIterator : public Iterator {
+ public:
+  EmptyIterator(const Status& s) : status_(s) {}
+  ~EmptyIterator() override = default;
+
+  bool Valid() const override { return false; }
+  void Seek(const Slice& target) override {}
+  void SeekToFirst() override {}
+  void SeekToLast() override {}
+  void Next() override { assert(false); }
+  void Prev() override { assert(false); }
+  Slice key() const override {
+    assert(false);
+    return Slice();
+  }
+  Slice value() const override {
+    assert(false);
+    return Slice();
+  }
+  Status status() const override { return status_; }
+
+ private:
+  Status status_;
+};
+
+}  // anonymous namespace
+
+Iterator* NewEmptyIterator() { return new EmptyIterator(Status::OK()); }
+
+Iterator* NewErrorIterator(const Status& status) {
+  return new EmptyIterator(status);
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/table/iterator_wrapper.h b/leveldb_base/table/iterator_wrapper.h
new file mode 100644
index 0000000..c230572
--- /dev/null
+++ b/leveldb_base/table/iterator_wrapper.h
@@ -0,0 +1,92 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_TABLE_ITERATOR_WRAPPER_H_
+#define STORAGE_LEVELDB_TABLE_ITERATOR_WRAPPER_H_
+
+#include "leveldb/iterator.h"
+#include "leveldb/slice.h"
+
+namespace leveldb {
+
+// A internal wrapper class with an interface similar to Iterator that
+// caches the valid() and key() results for an underlying iterator.
+// This can help avoid virtual function calls and also gives better
+// cache locality.
+class IteratorWrapper {
+ public:
+  IteratorWrapper() : iter_(nullptr), valid_(false) {}
+  explicit IteratorWrapper(Iterator* iter) : iter_(nullptr) { Set(iter); }
+  ~IteratorWrapper() { delete iter_; }
+  Iterator* iter() const { return iter_; }
+
+  // Takes ownership of "iter" and will delete it when destroyed, or
+  // when Set() is invoked again.
+  void Set(Iterator* iter) {
+    delete iter_;
+    iter_ = iter;
+    if (iter_ == nullptr) {
+      valid_ = false;
+    } else {
+      Update();
+    }
+  }
+
+  // Iterator interface methods
+  bool Valid() const { return valid_; }
+  Slice key() const {
+    assert(Valid());
+    return key_;
+  }
+  Slice value() const {
+    assert(Valid());
+    return iter_->value();
+  }
+  // Methods below require iter() != nullptr
+  Status status() const {
+    assert(iter_);
+    return iter_->status();
+  }
+  void Next() {
+    assert(iter_);
+    iter_->Next();
+    Update();
+  }
+  void Prev() {
+    assert(iter_);
+    iter_->Prev();
+    Update();
+  }
+  void Seek(const Slice& k) {
+    assert(iter_);
+    iter_->Seek(k);
+    Update();
+  }
+  void SeekToFirst() {
+    assert(iter_);
+    iter_->SeekToFirst();
+    Update();
+  }
+  void SeekToLast() {
+    assert(iter_);
+    iter_->SeekToLast();
+    Update();
+  }
+
+ private:
+  void Update() {
+    valid_ = iter_->Valid();
+    if (valid_) {
+      key_ = iter_->key();
+    }
+  }
+
+  Iterator* iter_;
+  bool valid_;
+  Slice key_;
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_TABLE_ITERATOR_WRAPPER_H_
diff --git a/leveldb_base/table/merger.cc b/leveldb_base/table/merger.cc
new file mode 100644
index 0000000..76441b1
--- /dev/null
+++ b/leveldb_base/table/merger.cc
@@ -0,0 +1,191 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "table/merger.h"
+
+#include "leveldb/comparator.h"
+#include "leveldb/iterator.h"
+#include "table/iterator_wrapper.h"
+
+namespace leveldb {
+
+namespace {
+class MergingIterator : public Iterator {
+ public:
+  MergingIterator(const Comparator* comparator, Iterator** children, int n)
+      : comparator_(comparator),
+        children_(new IteratorWrapper[n]),
+        n_(n),
+        current_(nullptr),
+        direction_(kForward) {
+    for (int i = 0; i < n; i++) {
+      children_[i].Set(children[i]);
+    }
+  }
+
+  ~MergingIterator() override { delete[] children_; }
+
+  bool Valid() const override { return (current_ != nullptr); }
+
+  void SeekToFirst() override {
+    for (int i = 0; i < n_; i++) {
+      children_[i].SeekToFirst();
+    }
+    FindSmallest();
+    direction_ = kForward;
+  }
+
+  void SeekToLast() override {
+    for (int i = 0; i < n_; i++) {
+      children_[i].SeekToLast();
+    }
+    FindLargest();
+    direction_ = kReverse;
+  }
+
+  void Seek(const Slice& target) override {
+    for (int i = 0; i < n_; i++) {
+      children_[i].Seek(target);
+    }
+    FindSmallest();
+    direction_ = kForward;
+  }
+
+  void Next() override {
+    assert(Valid());
+
+    // Ensure that all children are positioned after key().
+    // If we are moving in the forward direction, it is already
+    // true for all of the non-current_ children since current_ is
+    // the smallest child and key() == current_->key().  Otherwise,
+    // we explicitly position the non-current_ children.
+    if (direction_ != kForward) {
+      for (int i = 0; i < n_; i++) {
+        IteratorWrapper* child = &children_[i];
+        if (child != current_) {
+          child->Seek(key());
+          if (child->Valid() &&
+              comparator_->Compare(key(), child->key()) == 0) {
+            child->Next();
+          }
+        }
+      }
+      direction_ = kForward;
+    }
+
+    current_->Next();
+    FindSmallest();
+  }
+
+  void Prev() override {
+    assert(Valid());
+
+    // Ensure that all children are positioned before key().
+    // If we are moving in the reverse direction, it is already
+    // true for all of the non-current_ children since current_ is
+    // the largest child and key() == current_->key().  Otherwise,
+    // we explicitly position the non-current_ children.
+    if (direction_ != kReverse) {
+      for (int i = 0; i < n_; i++) {
+        IteratorWrapper* child = &children_[i];
+        if (child != current_) {
+          child->Seek(key());
+          if (child->Valid()) {
+            // Child is at first entry >= key().  Step back one to be < key()
+            child->Prev();
+          } else {
+            // Child has no entries >= key().  Position at last entry.
+            child->SeekToLast();
+          }
+        }
+      }
+      direction_ = kReverse;
+    }
+
+    current_->Prev();
+    FindLargest();
+  }
+
+  Slice key() const override {
+    assert(Valid());
+    return current_->key();
+  }
+
+  Slice value() const override {
+    assert(Valid());
+    return current_->value();
+  }
+
+  Status status() const override {
+    Status status;
+    for (int i = 0; i < n_; i++) {
+      status = children_[i].status();
+      if (!status.ok()) {
+        break;
+      }
+    }
+    return status;
+  }
+
+ private:
+  // Which direction is the iterator moving?
+  enum Direction { kForward, kReverse };
+
+  void FindSmallest();
+  void FindLargest();
+
+  // We might want to use a heap in case there are lots of children.
+  // For now we use a simple array since we expect a very small number
+  // of children in leveldb.
+  const Comparator* comparator_;
+  IteratorWrapper* children_;
+  int n_;
+  IteratorWrapper* current_;
+  Direction direction_;
+};
+
+void MergingIterator::FindSmallest() {
+  IteratorWrapper* smallest = nullptr;
+  for (int i = 0; i < n_; i++) {
+    IteratorWrapper* child = &children_[i];
+    if (child->Valid()) {
+      if (smallest == nullptr) {
+        smallest = child;
+      } else if (comparator_->Compare(child->key(), smallest->key()) < 0) {
+        smallest = child;
+      }
+    }
+  }
+  current_ = smallest;
+}
+
+void MergingIterator::FindLargest() {
+  IteratorWrapper* largest = nullptr;
+  for (int i = n_ - 1; i >= 0; i--) {
+    IteratorWrapper* child = &children_[i];
+    if (child->Valid()) {
+      if (largest == nullptr) {
+        largest = child;
+      } else if (comparator_->Compare(child->key(), largest->key()) > 0) {
+        largest = child;
+      }
+    }
+  }
+  current_ = largest;
+}
+}  // namespace
+
+Iterator* NewMergingIterator(const Comparator* comparator, Iterator** children,
+                             int n) {
+  assert(n >= 0);
+  if (n == 0) {
+    return NewEmptyIterator();
+  } else if (n == 1) {
+    return children[0];
+  } else {
+    return new MergingIterator(comparator, children, n);
+  }
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/table/merger.h b/leveldb_base/table/merger.h
new file mode 100644
index 0000000..41cedc5
--- /dev/null
+++ b/leveldb_base/table/merger.h
@@ -0,0 +1,26 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_TABLE_MERGER_H_
+#define STORAGE_LEVELDB_TABLE_MERGER_H_
+
+namespace leveldb {
+
+class Comparator;
+class Iterator;
+
+// Return an iterator that provided the union of the data in
+// children[0,n-1].  Takes ownership of the child iterators and
+// will delete them when the result iterator is deleted.
+//
+// The result does no duplicate suppression.  I.e., if a particular
+// key is present in K child iterators, it will be yielded K times.
+//
+// REQUIRES: n >= 0
+Iterator* NewMergingIterator(const Comparator* comparator, Iterator** children,
+                             int n);
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_TABLE_MERGER_H_
diff --git a/leveldb_base/table/table.cc b/leveldb_base/table/table.cc
new file mode 100644
index 0000000..29e835f
--- /dev/null
+++ b/leveldb_base/table/table.cc
@@ -0,0 +1,271 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "leveldb/table.h"
+
+#include "leveldb/cache.h"
+#include "leveldb/comparator.h"
+#include "leveldb/env.h"
+#include "leveldb/filter_policy.h"
+#include "leveldb/options.h"
+#include "table/block.h"
+#include "table/filter_block.h"
+#include "table/format.h"
+#include "table/two_level_iterator.h"
+#include "util/coding.h"
+
+namespace leveldb {
+
+struct Table::Rep {
+  ~Rep() {
+    delete filter;
+    delete[] filter_data;
+    delete index_block;
+  }
+
+  Options options;
+  Status status;
+  RandomAccessFile* file;
+  uint64_t cache_id;
+  FilterBlockReader* filter;
+  const char* filter_data;
+
+  BlockHandle metaindex_handle;  // Handle to metaindex_block: saved from footer
+  Block* index_block;
+};
+
+Status Table::Open(const Options& options, RandomAccessFile* file,
+                   uint64_t size, Table** table) {
+  *table = nullptr;
+  if (size < Footer::kEncodedLength) {
+    return Status::Corruption("file is too short to be an sstable");
+  }
+
+  char footer_space[Footer::kEncodedLength];
+  Slice footer_input;
+  Status s = file->Read(size - Footer::kEncodedLength, Footer::kEncodedLength,
+                        &footer_input, footer_space);
+  if (!s.ok()) return s;
+
+  Footer footer;
+  s = footer.DecodeFrom(&footer_input);
+  if (!s.ok()) return s;
+
+  // Read the index block
+  BlockContents index_block_contents;
+  ReadOptions opt;
+  if (options.paranoid_checks) {
+    opt.verify_checksums = true;
+  }
+  s = ReadBlock(file, opt, footer.index_handle(), &index_block_contents);
+
+  if (s.ok()) {
+    // We've successfully read the footer and the index block: we're
+    // ready to serve requests.
+    Block* index_block = new Block(index_block_contents);
+    Rep* rep = new Table::Rep;
+    rep->options = options;
+    rep->file = file;
+    rep->metaindex_handle = footer.metaindex_handle();
+    rep->index_block = index_block;
+    rep->cache_id = (options.block_cache ? options.block_cache->NewId() : 0);
+    rep->filter_data = nullptr;
+    rep->filter = nullptr;
+    *table = new Table(rep);
+    (*table)->ReadMeta(footer);
+  }
+
+  return s;
+}
+
+void Table::ReadMeta(const Footer& footer) {
+  if (rep_->options.filter_policy == nullptr) {
+    return;  // Do not need any metadata
+  }
+
+  // TODO(sanjay): Skip this if footer.metaindex_handle() size indicates
+  // it is an empty block.
+  ReadOptions opt;
+  if (rep_->options.paranoid_checks) {
+    opt.verify_checksums = true;
+  }
+  BlockContents contents;
+  if (!ReadBlock(rep_->file, opt, footer.metaindex_handle(), &contents).ok()) {
+    // Do not propagate errors since meta info is not needed for operation
+    return;
+  }
+  Block* meta = new Block(contents);
+
+  Iterator* iter = meta->NewIterator(BytewiseComparator());
+  std::string key = "filter.";
+  key.append(rep_->options.filter_policy->Name());
+  iter->Seek(key);
+  if (iter->Valid() && iter->key() == Slice(key)) {
+    ReadFilter(iter->value());
+  }
+  delete iter;
+  delete meta;
+}
+
+void Table::ReadFilter(const Slice& filter_handle_value) {
+  Slice v = filter_handle_value;
+  BlockHandle filter_handle;
+  if (!filter_handle.DecodeFrom(&v).ok()) {
+    return;
+  }
+
+  // We might want to unify with ReadBlock() if we start
+  // requiring checksum verification in Table::Open.
+  ReadOptions opt;
+  if (rep_->options.paranoid_checks) {
+    opt.verify_checksums = true;
+  }
+  BlockContents block;
+  if (!ReadBlock(rep_->file, opt, filter_handle, &block).ok()) {
+    return;
+  }
+  if (block.heap_allocated) {
+    rep_->filter_data = block.data.data();  // Will need to delete later
+  }
+  rep_->filter = new FilterBlockReader(rep_->options.filter_policy, block.data);
+}
+
+Table::~Table() { delete rep_; }
+
+static void DeleteBlock(void* arg, void* ignored) {
+  delete reinterpret_cast<Block*>(arg);
+}
+
+static void DeleteCachedBlock(const Slice& key, void* value) {
+  Block* block = reinterpret_cast<Block*>(value);
+  delete block;
+}
+
+static void ReleaseBlock(void* arg, void* h) {
+  Cache* cache = reinterpret_cast<Cache*>(arg);
+  Cache::Handle* handle = reinterpret_cast<Cache::Handle*>(h);
+  cache->Release(handle);
+}
+
+// Convert an index iterator value (i.e., an encoded BlockHandle)
+// into an iterator over the contents of the corresponding block.
+Iterator* Table::BlockReader(void* arg, const ReadOptions& options,
+                             const Slice& index_value) {
+  Table* table = reinterpret_cast<Table*>(arg);
+  Cache* block_cache = table->rep_->options.block_cache;
+  Block* block = nullptr;
+  Cache::Handle* cache_handle = nullptr;
+
+  BlockHandle handle;
+  Slice input = index_value;
+  Status s = handle.DecodeFrom(&input);
+  // We intentionally allow extra stuff in index_value so that we
+  // can add more features in the future.
+
+  if (s.ok()) {
+    BlockContents contents;
+    if (block_cache != nullptr) {
+      char cache_key_buffer[16];
+      EncodeFixed64(cache_key_buffer, table->rep_->cache_id);
+      EncodeFixed64(cache_key_buffer + 8, handle.offset());
+      Slice key(cache_key_buffer, sizeof(cache_key_buffer));
+      cache_handle = block_cache->Lookup(key);
+      if (cache_handle != nullptr) {
+        block = reinterpret_cast<Block*>(block_cache->Value(cache_handle));
+      } else {
+        s = ReadBlock(table->rep_->file, options, handle, &contents);
+        if (s.ok()) {
+          block = new Block(contents);
+          if (contents.cachable && options.fill_cache) {
+            cache_handle = block_cache->Insert(key, block, block->size(),
+                                               &DeleteCachedBlock);
+          }
+        }
+      }
+    } else {
+      s = ReadBlock(table->rep_->file, options, handle, &contents);
+      if (s.ok()) {
+        block = new Block(contents);
+      }
+    }
+  }
+
+  Iterator* iter;
+  if (block != nullptr) {
+    iter = block->NewIterator(table->rep_->options.comparator);
+    if (cache_handle == nullptr) {
+      iter->RegisterCleanup(&DeleteBlock, block, nullptr);
+    } else {
+      iter->RegisterCleanup(&ReleaseBlock, block_cache, cache_handle);
+    }
+  } else {
+    iter = NewErrorIterator(s);
+  }
+  return iter;
+}
+
+Iterator* Table::NewIterator(const ReadOptions& options) const {
+  return NewTwoLevelIterator(
+      rep_->index_block->NewIterator(rep_->options.comparator),
+      &Table::BlockReader, const_cast<Table*>(this), options);
+}
+
+Status Table::InternalGet(const ReadOptions& options, const Slice& k, void* arg,
+                          void (*handle_result)(void*, const Slice&,
+                                                const Slice&)) {
+  Status s;
+  Iterator* iiter = rep_->index_block->NewIterator(rep_->options.comparator);
+  iiter->Seek(k);
+  if (iiter->Valid()) {
+    Slice handle_value = iiter->value();
+    FilterBlockReader* filter = rep_->filter;
+    BlockHandle handle;
+    if (filter != nullptr && handle.DecodeFrom(&handle_value).ok() &&
+        !filter->KeyMayMatch(handle.offset(), k)) {
+      // Not found
+    } else {
+      Iterator* block_iter = BlockReader(this, options, iiter->value());
+      block_iter->Seek(k);
+      if (block_iter->Valid()) {
+        (*handle_result)(arg, block_iter->key(), block_iter->value());
+      }
+      s = block_iter->status();
+      delete block_iter;
+    }
+  }
+  if (s.ok()) {
+    s = iiter->status();
+  }
+  delete iiter;
+  return s;
+}
+
+uint64_t Table::ApproximateOffsetOf(const Slice& key) const {
+  Iterator* index_iter =
+      rep_->index_block->NewIterator(rep_->options.comparator);
+  index_iter->Seek(key);
+  uint64_t result;
+  if (index_iter->Valid()) {
+    BlockHandle handle;
+    Slice input = index_iter->value();
+    Status s = handle.DecodeFrom(&input);
+    if (s.ok()) {
+      result = handle.offset();
+    } else {
+      // Strange: we can't decode the block handle in the index block.
+      // We'll just return the offset of the metaindex block, which is
+      // close to the whole file size for this case.
+      result = rep_->metaindex_handle.offset();
+    }
+  } else {
+    // key is past the last key in the file.  Approximate the offset
+    // by returning the offset of the metaindex block (which is
+    // right near the end of the file).
+    result = rep_->metaindex_handle.offset();
+  }
+  delete index_iter;
+  return result;
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/table/table_builder.cc b/leveldb_base/table/table_builder.cc
new file mode 100644
index 0000000..0932c94
--- /dev/null
+++ b/leveldb_base/table/table_builder.cc
@@ -0,0 +1,280 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "leveldb/table_builder.h"
+
+#include <cassert>
+
+#include "leveldb/comparator.h"
+#include "leveldb/env.h"
+#include "leveldb/filter_policy.h"
+#include "leveldb/options.h"
+#include "table/block_builder.h"
+#include "table/filter_block.h"
+#include "table/format.h"
+#include "util/coding.h"
+#include "util/crc32c.h"
+
+namespace leveldb {
+
+struct TableBuilder::Rep {
+  Rep(const Options& opt, WritableFile* f)
+      : options(opt),
+        index_block_options(opt),
+        file(f),
+        offset(0),
+        data_block(&options),
+        index_block(&index_block_options),
+        num_entries(0),
+        closed(false),
+        filter_block(opt.filter_policy == nullptr
+                         ? nullptr
+                         : new FilterBlockBuilder(opt.filter_policy)),
+        pending_index_entry(false) {
+    index_block_options.block_restart_interval = 1;
+  }
+
+  Options options;
+  Options index_block_options;
+  WritableFile* file;
+  uint64_t offset;
+  Status status;
+  BlockBuilder data_block;
+  BlockBuilder index_block;
+  std::string last_key;
+  int64_t num_entries;
+  bool closed;  // Either Finish() or Abandon() has been called.
+  FilterBlockBuilder* filter_block;
+
+  // We do not emit the index entry for a block until we have seen the
+  // first key for the next data block.  This allows us to use shorter
+  // keys in the index block.  For example, consider a block boundary
+  // between the keys "the quick brown fox" and "the who".  We can use
+  // "the r" as the key for the index block entry since it is >= all
+  // entries in the first block and < all entries in subsequent
+  // blocks.
+  //
+  // Invariant: r->pending_index_entry is true only if data_block is empty.
+  bool pending_index_entry;
+  BlockHandle pending_handle;  // Handle to add to index block
+
+  std::string compressed_output;
+};
+
+TableBuilder::TableBuilder(const Options& options, WritableFile* file)
+    : rep_(new Rep(options, file)) {
+  if (rep_->filter_block != nullptr) {
+    rep_->filter_block->StartBlock(0);
+  }
+}
+
+TableBuilder::~TableBuilder() {
+  assert(rep_->closed);  // Catch errors where caller forgot to call Finish()
+  delete rep_->filter_block;
+  delete rep_;
+}
+
+Status TableBuilder::ChangeOptions(const Options& options) {
+  // Note: if more fields are added to Options, update
+  // this function to catch changes that should not be allowed to
+  // change in the middle of building a Table.
+  if (options.comparator != rep_->options.comparator) {
+    return Status::InvalidArgument("changing comparator while building table");
+  }
+
+  // Note that any live BlockBuilders point to rep_->options and therefore
+  // will automatically pick up the updated options.
+  rep_->options = options;
+  rep_->index_block_options = options;
+  rep_->index_block_options.block_restart_interval = 1;
+  return Status::OK();
+}
+
+void TableBuilder::Add(const Slice& key, const Slice& value) {
+  Rep* r = rep_;
+  assert(!r->closed);
+  if (!ok()) return;
+  if (r->num_entries > 0) {
+    assert(r->options.comparator->Compare(key, Slice(r->last_key)) > 0);
+  }
+
+  if (r->pending_index_entry) {
+    assert(r->data_block.empty());
+    r->options.comparator->FindShortestSeparator(&r->last_key, key);
+    std::string handle_encoding;
+    r->pending_handle.EncodeTo(&handle_encoding);
+    r->index_block.Add(r->last_key, Slice(handle_encoding));
+    r->pending_index_entry = false;
+  }
+
+  if (r->filter_block != nullptr) {
+    r->filter_block->AddKey(key);
+  }
+
+  r->last_key.assign(key.data(), key.size());
+  r->num_entries++;
+  r->data_block.Add(key, value);
+
+  const size_t estimated_block_size = r->data_block.CurrentSizeEstimate();
+  if (estimated_block_size >= r->options.block_size) {
+    Flush();
+  }
+}
+
+void TableBuilder::Flush() {
+  Rep* r = rep_;
+  assert(!r->closed);
+  if (!ok()) return;
+  if (r->data_block.empty()) return;
+  assert(!r->pending_index_entry);
+  WriteBlock(&r->data_block, &r->pending_handle);
+  if (ok()) {
+    r->pending_index_entry = true;
+    r->status = r->file->Flush();
+  }
+  if (r->filter_block != nullptr) {
+    r->filter_block->StartBlock(r->offset);
+  }
+}
+
+void TableBuilder::WriteBlock(BlockBuilder* block, BlockHandle* handle) {
+  // File format contains a sequence of blocks where each block has:
+  //    block_data: uint8[n]
+  //    type: uint8
+  //    crc: uint32
+  assert(ok());
+  Rep* r = rep_;
+  Slice raw = block->Finish();
+
+  Slice block_contents;
+  CompressionType type = r->options.compression;
+  // TODO(postrelease): Support more compression options: zlib?
+  switch (type) {
+    case kNoCompression:
+      block_contents = raw;
+      break;
+
+    case kSnappyCompression: {
+      std::string* compressed = &r->compressed_output;
+      if (port::Snappy_Compress(raw.data(), raw.size(), compressed) &&
+          compressed->size() < raw.size() - (raw.size() / 8u)) {
+        block_contents = *compressed;
+      } else {
+        // Snappy not supported, or compressed less than 12.5%, so just
+        // store uncompressed form
+        block_contents = raw;
+        type = kNoCompression;
+      }
+      break;
+    }
+
+    case kZstdCompression: {
+      std::string* compressed = &r->compressed_output;
+      if (port::Zstd_Compress(r->options.zstd_compression_level, raw.data(),
+                              raw.size(), compressed) &&
+          compressed->size() < raw.size() - (raw.size() / 8u)) {
+        block_contents = *compressed;
+      } else {
+        // Zstd not supported, or compressed less than 12.5%, so just
+        // store uncompressed form
+        block_contents = raw;
+        type = kNoCompression;
+      }
+      break;
+    }
+  }
+  WriteRawBlock(block_contents, type, handle);
+  r->compressed_output.clear();
+  block->Reset();
+}
+
+void TableBuilder::WriteRawBlock(const Slice& block_contents,
+                                 CompressionType type, BlockHandle* handle) {
+  Rep* r = rep_;
+  handle->set_offset(r->offset);
+  handle->set_size(block_contents.size());
+  r->status = r->file->Append(block_contents);
+  if (r->status.ok()) {
+    char trailer[kBlockTrailerSize];
+    trailer[0] = type;
+    uint32_t crc = crc32c::Value(block_contents.data(), block_contents.size());
+    crc = crc32c::Extend(crc, trailer, 1);  // Extend crc to cover block type
+    EncodeFixed32(trailer + 1, crc32c::Mask(crc));
+    r->status = r->file->Append(Slice(trailer, kBlockTrailerSize));
+    if (r->status.ok()) {
+      r->offset += block_contents.size() + kBlockTrailerSize;
+    }
+  }
+}
+
+Status TableBuilder::status() const { return rep_->status; }
+
+Status TableBuilder::Finish() {
+  Rep* r = rep_;
+  Flush();
+  assert(!r->closed);
+  r->closed = true;
+
+  BlockHandle filter_block_handle, metaindex_block_handle, index_block_handle;
+
+  // Write filter block
+  if (ok() && r->filter_block != nullptr) {
+    WriteRawBlock(r->filter_block->Finish(), kNoCompression,
+                  &filter_block_handle);
+  }
+
+  // Write metaindex block
+  if (ok()) {
+    BlockBuilder meta_index_block(&r->options);
+    if (r->filter_block != nullptr) {
+      // Add mapping from "filter.Name" to location of filter data
+      std::string key = "filter.";
+      key.append(r->options.filter_policy->Name());
+      std::string handle_encoding;
+      filter_block_handle.EncodeTo(&handle_encoding);
+      meta_index_block.Add(key, handle_encoding);
+    }
+
+    // TODO(postrelease): Add stats and other meta blocks
+    WriteBlock(&meta_index_block, &metaindex_block_handle);
+  }
+
+  // Write index block
+  if (ok()) {
+    if (r->pending_index_entry) {
+      r->options.comparator->FindShortSuccessor(&r->last_key);
+      std::string handle_encoding;
+      r->pending_handle.EncodeTo(&handle_encoding);
+      r->index_block.Add(r->last_key, Slice(handle_encoding));
+      r->pending_index_entry = false;
+    }
+    WriteBlock(&r->index_block, &index_block_handle);
+  }
+
+  // Write footer
+  if (ok()) {
+    Footer footer;
+    footer.set_metaindex_handle(metaindex_block_handle);
+    footer.set_index_handle(index_block_handle);
+    std::string footer_encoding;
+    footer.EncodeTo(&footer_encoding);
+    r->status = r->file->Append(footer_encoding);
+    if (r->status.ok()) {
+      r->offset += footer_encoding.size();
+    }
+  }
+  return r->status;
+}
+
+void TableBuilder::Abandon() {
+  Rep* r = rep_;
+  assert(!r->closed);
+  r->closed = true;
+}
+
+uint64_t TableBuilder::NumEntries() const { return rep_->num_entries; }
+
+uint64_t TableBuilder::FileSize() const { return rep_->offset; }
+
+}  // namespace leveldb
diff --git a/leveldb_base/table/table_test.cc b/leveldb_base/table/table_test.cc
new file mode 100644
index 0000000..aea0697
--- /dev/null
+++ b/leveldb_base/table/table_test.cc
@@ -0,0 +1,842 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "leveldb/table.h"
+
+#include <map>
+#include <string>
+
+#include "gtest/gtest.h"
+#include "db/dbformat.h"
+#include "db/memtable.h"
+#include "db/write_batch_internal.h"
+#include "leveldb/db.h"
+#include "leveldb/env.h"
+#include "leveldb/iterator.h"
+#include "leveldb/options.h"
+#include "leveldb/table_builder.h"
+#include "table/block.h"
+#include "table/block_builder.h"
+#include "table/format.h"
+#include "util/random.h"
+#include "util/testutil.h"
+
+namespace leveldb {
+
+// Return reverse of "key".
+// Used to test non-lexicographic comparators.
+static std::string Reverse(const Slice& key) {
+  std::string str(key.ToString());
+  std::string rev("");
+  for (std::string::reverse_iterator rit = str.rbegin(); rit != str.rend();
+       ++rit) {
+    rev.push_back(*rit);
+  }
+  return rev;
+}
+
+namespace {
+class ReverseKeyComparator : public Comparator {
+ public:
+  const char* Name() const override {
+    return "leveldb.ReverseBytewiseComparator";
+  }
+
+  int Compare(const Slice& a, const Slice& b) const override {
+    return BytewiseComparator()->Compare(Reverse(a), Reverse(b));
+  }
+
+  void FindShortestSeparator(std::string* start,
+                             const Slice& limit) const override {
+    std::string s = Reverse(*start);
+    std::string l = Reverse(limit);
+    BytewiseComparator()->FindShortestSeparator(&s, l);
+    *start = Reverse(s);
+  }
+
+  void FindShortSuccessor(std::string* key) const override {
+    std::string s = Reverse(*key);
+    BytewiseComparator()->FindShortSuccessor(&s);
+    *key = Reverse(s);
+  }
+};
+}  // namespace
+static ReverseKeyComparator reverse_key_comparator;
+
+static void Increment(const Comparator* cmp, std::string* key) {
+  if (cmp == BytewiseComparator()) {
+    key->push_back('\0');
+  } else {
+    assert(cmp == &reverse_key_comparator);
+    std::string rev = Reverse(*key);
+    rev.push_back('\0');
+    *key = Reverse(rev);
+  }
+}
+
+// An STL comparator that uses a Comparator
+namespace {
+struct STLLessThan {
+  const Comparator* cmp;
+
+  STLLessThan() : cmp(BytewiseComparator()) {}
+  STLLessThan(const Comparator* c) : cmp(c) {}
+  bool operator()(const std::string& a, const std::string& b) const {
+    return cmp->Compare(Slice(a), Slice(b)) < 0;
+  }
+};
+}  // namespace
+
+class StringSink : public WritableFile {
+ public:
+  ~StringSink() override = default;
+
+  const std::string& contents() const { return contents_; }
+
+  Status Close() override { return Status::OK(); }
+  Status Flush() override { return Status::OK(); }
+  Status Sync() override { return Status::OK(); }
+
+  Status Append(const Slice& data) override {
+    contents_.append(data.data(), data.size());
+    return Status::OK();
+  }
+
+ private:
+  std::string contents_;
+};
+
+class StringSource : public RandomAccessFile {
+ public:
+  StringSource(const Slice& contents)
+      : contents_(contents.data(), contents.size()) {}
+
+  ~StringSource() override = default;
+
+  uint64_t Size() const { return contents_.size(); }
+
+  Status Read(uint64_t offset, size_t n, Slice* result,
+              char* scratch) const override {
+    if (offset >= contents_.size()) {
+      return Status::InvalidArgument("invalid Read offset");
+    }
+    if (offset + n > contents_.size()) {
+      n = contents_.size() - offset;
+    }
+    std::memcpy(scratch, &contents_[offset], n);
+    *result = Slice(scratch, n);
+    return Status::OK();
+  }
+
+ private:
+  std::string contents_;
+};
+
+typedef std::map<std::string, std::string, STLLessThan> KVMap;
+
+// Helper class for tests to unify the interface between
+// BlockBuilder/TableBuilder and Block/Table.
+class Constructor {
+ public:
+  explicit Constructor(const Comparator* cmp) : data_(STLLessThan(cmp)) {}
+  virtual ~Constructor() = default;
+
+  void Add(const std::string& key, const Slice& value) {
+    data_[key] = value.ToString();
+  }
+
+  // Finish constructing the data structure with all the keys that have
+  // been added so far.  Returns the keys in sorted order in "*keys"
+  // and stores the key/value pairs in "*kvmap"
+  void Finish(const Options& options, std::vector<std::string>* keys,
+              KVMap* kvmap) {
+    *kvmap = data_;
+    keys->clear();
+    for (const auto& kvp : data_) {
+      keys->push_back(kvp.first);
+    }
+    data_.clear();
+    Status s = FinishImpl(options, *kvmap);
+    ASSERT_TRUE(s.ok()) << s.ToString();
+  }
+
+  // Construct the data structure from the data in "data"
+  virtual Status FinishImpl(const Options& options, const KVMap& data) = 0;
+
+  virtual Iterator* NewIterator() const = 0;
+
+  const KVMap& data() const { return data_; }
+
+  virtual DB* db() const { return nullptr; }  // Overridden in DBConstructor
+
+ private:
+  KVMap data_;
+};
+
+class BlockConstructor : public Constructor {
+ public:
+  explicit BlockConstructor(const Comparator* cmp)
+      : Constructor(cmp), comparator_(cmp), block_(nullptr) {}
+  ~BlockConstructor() override { delete block_; }
+  Status FinishImpl(const Options& options, const KVMap& data) override {
+    delete block_;
+    block_ = nullptr;
+    BlockBuilder builder(&options);
+
+    for (const auto& kvp : data) {
+      builder.Add(kvp.first, kvp.second);
+    }
+    // Open the block
+    data_ = builder.Finish().ToString();
+    BlockContents contents;
+    contents.data = data_;
+    contents.cachable = false;
+    contents.heap_allocated = false;
+    block_ = new Block(contents);
+    return Status::OK();
+  }
+  Iterator* NewIterator() const override {
+    return block_->NewIterator(comparator_);
+  }
+
+ private:
+  const Comparator* const comparator_;
+  std::string data_;
+  Block* block_;
+
+  BlockConstructor();
+};
+
+class TableConstructor : public Constructor {
+ public:
+  TableConstructor(const Comparator* cmp)
+      : Constructor(cmp), source_(nullptr), table_(nullptr) {}
+  ~TableConstructor() override { Reset(); }
+  Status FinishImpl(const Options& options, const KVMap& data) override {
+    Reset();
+    StringSink sink;
+    TableBuilder builder(options, &sink);
+
+    for (const auto& kvp : data) {
+      builder.Add(kvp.first, kvp.second);
+      EXPECT_LEVELDB_OK(builder.status());
+    }
+    Status s = builder.Finish();
+    EXPECT_LEVELDB_OK(s);
+
+    EXPECT_EQ(sink.contents().size(), builder.FileSize());
+
+    // Open the table
+    source_ = new StringSource(sink.contents());
+    Options table_options;
+    table_options.comparator = options.comparator;
+    return Table::Open(table_options, source_, sink.contents().size(), &table_);
+  }
+
+  Iterator* NewIterator() const override {
+    return table_->NewIterator(ReadOptions());
+  }
+
+  uint64_t ApproximateOffsetOf(const Slice& key) const {
+    return table_->ApproximateOffsetOf(key);
+  }
+
+ private:
+  void Reset() {
+    delete table_;
+    delete source_;
+    table_ = nullptr;
+    source_ = nullptr;
+  }
+
+  StringSource* source_;
+  Table* table_;
+
+  TableConstructor();
+};
+
+// A helper class that converts internal format keys into user keys
+class KeyConvertingIterator : public Iterator {
+ public:
+  explicit KeyConvertingIterator(Iterator* iter) : iter_(iter) {}
+
+  KeyConvertingIterator(const KeyConvertingIterator&) = delete;
+  KeyConvertingIterator& operator=(const KeyConvertingIterator&) = delete;
+
+  ~KeyConvertingIterator() override { delete iter_; }
+
+  bool Valid() const override { return iter_->Valid(); }
+  void Seek(const Slice& target) override {
+    ParsedInternalKey ikey(target, kMaxSequenceNumber, kTypeValue);
+    std::string encoded;
+    AppendInternalKey(&encoded, ikey);
+    iter_->Seek(encoded);
+  }
+  void SeekToFirst() override { iter_->SeekToFirst(); }
+  void SeekToLast() override { iter_->SeekToLast(); }
+  void Next() override { iter_->Next(); }
+  void Prev() override { iter_->Prev(); }
+
+  Slice key() const override {
+    assert(Valid());
+    ParsedInternalKey key;
+    if (!ParseInternalKey(iter_->key(), &key)) {
+      status_ = Status::Corruption("malformed internal key");
+      return Slice("corrupted key");
+    }
+    return key.user_key;
+  }
+
+  Slice value() const override { return iter_->value(); }
+  Status status() const override {
+    return status_.ok() ? iter_->status() : status_;
+  }
+
+ private:
+  mutable Status status_;
+  Iterator* iter_;
+};
+
+class MemTableConstructor : public Constructor {
+ public:
+  explicit MemTableConstructor(const Comparator* cmp)
+      : Constructor(cmp), internal_comparator_(cmp) {
+    memtable_ = new MemTable(internal_comparator_);
+    memtable_->Ref();
+  }
+  ~MemTableConstructor() override { memtable_->Unref(); }
+  Status FinishImpl(const Options& options, const KVMap& data) override {
+    memtable_->Unref();
+    memtable_ = new MemTable(internal_comparator_);
+    memtable_->Ref();
+    int seq = 1;
+    for (const auto& kvp : data) {
+      memtable_->Add(seq, kTypeValue, kvp.first, kvp.second);
+      seq++;
+    }
+    return Status::OK();
+  }
+  Iterator* NewIterator() const override {
+    return new KeyConvertingIterator(memtable_->NewIterator());
+  }
+
+ private:
+  const InternalKeyComparator internal_comparator_;
+  MemTable* memtable_;
+};
+
+class DBConstructor : public Constructor {
+ public:
+  explicit DBConstructor(const Comparator* cmp)
+      : Constructor(cmp), comparator_(cmp) {
+    db_ = nullptr;
+    NewDB();
+  }
+  ~DBConstructor() override { delete db_; }
+  Status FinishImpl(const Options& options, const KVMap& data) override {
+    delete db_;
+    db_ = nullptr;
+    NewDB();
+    for (const auto& kvp : data) {
+      WriteBatch batch;
+      batch.Put(kvp.first, kvp.second);
+      EXPECT_TRUE(db_->Write(WriteOptions(), &batch).ok());
+    }
+    return Status::OK();
+  }
+  Iterator* NewIterator() const override {
+    return db_->NewIterator(ReadOptions());
+  }
+
+  DB* db() const override { return db_; }
+
+ private:
+  void NewDB() {
+    std::string name = testing::TempDir() + "table_testdb";
+
+    Options options;
+    options.comparator = comparator_;
+    Status status = DestroyDB(name, options);
+    ASSERT_TRUE(status.ok()) << status.ToString();
+
+    options.create_if_missing = true;
+    options.error_if_exists = true;
+    options.write_buffer_size = 10000;  // Something small to force merging
+    status = DB::Open(options, name, &db_);
+    ASSERT_TRUE(status.ok()) << status.ToString();
+  }
+
+  const Comparator* const comparator_;
+  DB* db_;
+};
+
+enum TestType { TABLE_TEST, BLOCK_TEST, MEMTABLE_TEST, DB_TEST };
+
+struct TestArgs {
+  TestType type;
+  bool reverse_compare;
+  int restart_interval;
+};
+
+static const TestArgs kTestArgList[] = {
+    {TABLE_TEST, false, 16},
+    {TABLE_TEST, false, 1},
+    {TABLE_TEST, false, 1024},
+    {TABLE_TEST, true, 16},
+    {TABLE_TEST, true, 1},
+    {TABLE_TEST, true, 1024},
+
+    {BLOCK_TEST, false, 16},
+    {BLOCK_TEST, false, 1},
+    {BLOCK_TEST, false, 1024},
+    {BLOCK_TEST, true, 16},
+    {BLOCK_TEST, true, 1},
+    {BLOCK_TEST, true, 1024},
+
+    // Restart interval does not matter for memtables
+    {MEMTABLE_TEST, false, 16},
+    {MEMTABLE_TEST, true, 16},
+
+    // Do not bother with restart interval variations for DB
+    {DB_TEST, false, 16},
+    {DB_TEST, true, 16},
+};
+static const int kNumTestArgs = sizeof(kTestArgList) / sizeof(kTestArgList[0]);
+
+class Harness : public testing::Test {
+ public:
+  Harness() : constructor_(nullptr) {}
+
+  void Init(const TestArgs& args) {
+    delete constructor_;
+    constructor_ = nullptr;
+    options_ = Options();
+
+    options_.block_restart_interval = args.restart_interval;
+    // Use shorter block size for tests to exercise block boundary
+    // conditions more.
+    options_.block_size = 256;
+    if (args.reverse_compare) {
+      options_.comparator = &reverse_key_comparator;
+    }
+    switch (args.type) {
+      case TABLE_TEST:
+        constructor_ = new TableConstructor(options_.comparator);
+        break;
+      case BLOCK_TEST:
+        constructor_ = new BlockConstructor(options_.comparator);
+        break;
+      case MEMTABLE_TEST:
+        constructor_ = new MemTableConstructor(options_.comparator);
+        break;
+      case DB_TEST:
+        constructor_ = new DBConstructor(options_.comparator);
+        break;
+    }
+  }
+
+  ~Harness() { delete constructor_; }
+
+  void Add(const std::string& key, const std::string& value) {
+    constructor_->Add(key, value);
+  }
+
+  void Test(Random* rnd) {
+    std::vector<std::string> keys;
+    KVMap data;
+    constructor_->Finish(options_, &keys, &data);
+
+    TestForwardScan(keys, data);
+    TestBackwardScan(keys, data);
+    TestRandomAccess(rnd, keys, data);
+  }
+
+  void TestForwardScan(const std::vector<std::string>& keys,
+                       const KVMap& data) {
+    Iterator* iter = constructor_->NewIterator();
+    ASSERT_TRUE(!iter->Valid());
+    iter->SeekToFirst();
+    for (KVMap::const_iterator model_iter = data.begin();
+         model_iter != data.end(); ++model_iter) {
+      ASSERT_EQ(ToString(data, model_iter), ToString(iter));
+      iter->Next();
+    }
+    ASSERT_TRUE(!iter->Valid());
+    delete iter;
+  }
+
+  void TestBackwardScan(const std::vector<std::string>& keys,
+                        const KVMap& data) {
+    Iterator* iter = constructor_->NewIterator();
+    ASSERT_TRUE(!iter->Valid());
+    iter->SeekToLast();
+    for (KVMap::const_reverse_iterator model_iter = data.rbegin();
+         model_iter != data.rend(); ++model_iter) {
+      ASSERT_EQ(ToString(data, model_iter), ToString(iter));
+      iter->Prev();
+    }
+    ASSERT_TRUE(!iter->Valid());
+    delete iter;
+  }
+
+  void TestRandomAccess(Random* rnd, const std::vector<std::string>& keys,
+                        const KVMap& data) {
+    static const bool kVerbose = false;
+    Iterator* iter = constructor_->NewIterator();
+    ASSERT_TRUE(!iter->Valid());
+    KVMap::const_iterator model_iter = data.begin();
+    if (kVerbose) std::fprintf(stderr, "---\n");
+    for (int i = 0; i < 200; i++) {
+      const int toss = rnd->Uniform(5);
+      switch (toss) {
+        case 0: {
+          if (iter->Valid()) {
+            if (kVerbose) std::fprintf(stderr, "Next\n");
+            iter->Next();
+            ++model_iter;
+            ASSERT_EQ(ToString(data, model_iter), ToString(iter));
+          }
+          break;
+        }
+
+        case 1: {
+          if (kVerbose) std::fprintf(stderr, "SeekToFirst\n");
+          iter->SeekToFirst();
+          model_iter = data.begin();
+          ASSERT_EQ(ToString(data, model_iter), ToString(iter));
+          break;
+        }
+
+        case 2: {
+          std::string key = PickRandomKey(rnd, keys);
+          model_iter = data.lower_bound(key);
+          if (kVerbose)
+            std::fprintf(stderr, "Seek '%s'\n", EscapeString(key).c_str());
+          iter->Seek(Slice(key));
+          ASSERT_EQ(ToString(data, model_iter), ToString(iter));
+          break;
+        }
+
+        case 3: {
+          if (iter->Valid()) {
+            if (kVerbose) std::fprintf(stderr, "Prev\n");
+            iter->Prev();
+            if (model_iter == data.begin()) {
+              model_iter = data.end();  // Wrap around to invalid value
+            } else {
+              --model_iter;
+            }
+            ASSERT_EQ(ToString(data, model_iter), ToString(iter));
+          }
+          break;
+        }
+
+        case 4: {
+          if (kVerbose) std::fprintf(stderr, "SeekToLast\n");
+          iter->SeekToLast();
+          if (keys.empty()) {
+            model_iter = data.end();
+          } else {
+            std::string last = data.rbegin()->first;
+            model_iter = data.lower_bound(last);
+          }
+          ASSERT_EQ(ToString(data, model_iter), ToString(iter));
+          break;
+        }
+      }
+    }
+    delete iter;
+  }
+
+  std::string ToString(const KVMap& data, const KVMap::const_iterator& it) {
+    if (it == data.end()) {
+      return "END";
+    } else {
+      return "'" + it->first + "->" + it->second + "'";
+    }
+  }
+
+  std::string ToString(const KVMap& data,
+                       const KVMap::const_reverse_iterator& it) {
+    if (it == data.rend()) {
+      return "END";
+    } else {
+      return "'" + it->first + "->" + it->second + "'";
+    }
+  }
+
+  std::string ToString(const Iterator* it) {
+    if (!it->Valid()) {
+      return "END";
+    } else {
+      return "'" + it->key().ToString() + "->" + it->value().ToString() + "'";
+    }
+  }
+
+  std::string PickRandomKey(Random* rnd, const std::vector<std::string>& keys) {
+    if (keys.empty()) {
+      return "foo";
+    } else {
+      const int index = rnd->Uniform(keys.size());
+      std::string result = keys[index];
+      switch (rnd->Uniform(3)) {
+        case 0:
+          // Return an existing key
+          break;
+        case 1: {
+          // Attempt to return something smaller than an existing key
+          if (!result.empty() && result[result.size() - 1] > '\0') {
+            result[result.size() - 1]--;
+          }
+          break;
+        }
+        case 2: {
+          // Return something larger than an existing key
+          Increment(options_.comparator, &result);
+          break;
+        }
+      }
+      return result;
+    }
+  }
+
+  // Returns nullptr if not running against a DB
+  DB* db() const { return constructor_->db(); }
+
+ private:
+  Options options_;
+  Constructor* constructor_;
+};
+
+// Test empty table/block.
+TEST_F(Harness, Empty) {
+  for (int i = 0; i < kNumTestArgs; i++) {
+    Init(kTestArgList[i]);
+    Random rnd(test::RandomSeed() + 1);
+    Test(&rnd);
+  }
+}
+
+// Special test for a block with no restart entries.  The C++ leveldb
+// code never generates such blocks, but the Java version of leveldb
+// seems to.
+TEST_F(Harness, ZeroRestartPointsInBlock) {
+  char data[sizeof(uint32_t)];
+  memset(data, 0, sizeof(data));
+  BlockContents contents;
+  contents.data = Slice(data, sizeof(data));
+  contents.cachable = false;
+  contents.heap_allocated = false;
+  Block block(contents);
+  Iterator* iter = block.NewIterator(BytewiseComparator());
+  iter->SeekToFirst();
+  ASSERT_TRUE(!iter->Valid());
+  iter->SeekToLast();
+  ASSERT_TRUE(!iter->Valid());
+  iter->Seek("foo");
+  ASSERT_TRUE(!iter->Valid());
+  delete iter;
+}
+
+// Test the empty key
+TEST_F(Harness, SimpleEmptyKey) {
+  for (int i = 0; i < kNumTestArgs; i++) {
+    Init(kTestArgList[i]);
+    Random rnd(test::RandomSeed() + 1);
+    Add("", "v");
+    Test(&rnd);
+  }
+}
+
+TEST_F(Harness, SimpleSingle) {
+  for (int i = 0; i < kNumTestArgs; i++) {
+    Init(kTestArgList[i]);
+    Random rnd(test::RandomSeed() + 2);
+    Add("abc", "v");
+    Test(&rnd);
+  }
+}
+
+TEST_F(Harness, SimpleMulti) {
+  for (int i = 0; i < kNumTestArgs; i++) {
+    Init(kTestArgList[i]);
+    Random rnd(test::RandomSeed() + 3);
+    Add("abc", "v");
+    Add("abcd", "v");
+    Add("ac", "v2");
+    Test(&rnd);
+  }
+}
+
+TEST_F(Harness, SimpleSpecialKey) {
+  for (int i = 0; i < kNumTestArgs; i++) {
+    Init(kTestArgList[i]);
+    Random rnd(test::RandomSeed() + 4);
+    Add("\xff\xff", "v3");
+    Test(&rnd);
+  }
+}
+
+TEST_F(Harness, Randomized) {
+  for (int i = 0; i < kNumTestArgs; i++) {
+    Init(kTestArgList[i]);
+    Random rnd(test::RandomSeed() + 5);
+    for (int num_entries = 0; num_entries < 2000;
+         num_entries += (num_entries < 50 ? 1 : 200)) {
+      if ((num_entries % 10) == 0) {
+        std::fprintf(stderr, "case %d of %d: num_entries = %d\n", (i + 1),
+                     int(kNumTestArgs), num_entries);
+      }
+      for (int e = 0; e < num_entries; e++) {
+        std::string v;
+        Add(test::RandomKey(&rnd, rnd.Skewed(4)),
+            test::RandomString(&rnd, rnd.Skewed(5), &v).ToString());
+      }
+      Test(&rnd);
+    }
+  }
+}
+
+TEST_F(Harness, RandomizedLongDB) {
+  Random rnd(test::RandomSeed());
+  TestArgs args = {DB_TEST, false, 16};
+  Init(args);
+  int num_entries = 100000;
+  for (int e = 0; e < num_entries; e++) {
+    std::string v;
+    Add(test::RandomKey(&rnd, rnd.Skewed(4)),
+        test::RandomString(&rnd, rnd.Skewed(5), &v).ToString());
+  }
+  Test(&rnd);
+
+  // We must have created enough data to force merging
+  int files = 0;
+  for (int level = 0; level < config::kNumLevels; level++) {
+    std::string value;
+    char name[100];
+    std::snprintf(name, sizeof(name), "leveldb.num-files-at-level%d", level);
+    ASSERT_TRUE(db()->GetProperty(name, &value));
+    files += atoi(value.c_str());
+  }
+  ASSERT_GT(files, 0);
+}
+
+TEST(MemTableTest, Simple) {
+  InternalKeyComparator cmp(BytewiseComparator());
+  MemTable* memtable = new MemTable(cmp);
+  memtable->Ref();
+  WriteBatch batch;
+  WriteBatchInternal::SetSequence(&batch, 100);
+  batch.Put(std::string("k1"), std::string("v1"));
+  batch.Put(std::string("k2"), std::string("v2"));
+  batch.Put(std::string("k3"), std::string("v3"));
+  batch.Put(std::string("largekey"), std::string("vlarge"));
+  ASSERT_TRUE(WriteBatchInternal::InsertInto(&batch, memtable).ok());
+
+  Iterator* iter = memtable->NewIterator();
+  iter->SeekToFirst();
+  while (iter->Valid()) {
+    std::fprintf(stderr, "key: '%s' -> '%s'\n", iter->key().ToString().c_str(),
+                 iter->value().ToString().c_str());
+    iter->Next();
+  }
+
+  delete iter;
+  memtable->Unref();
+}
+
+static bool Between(uint64_t val, uint64_t low, uint64_t high) {
+  bool result = (val >= low) && (val <= high);
+  if (!result) {
+    std::fprintf(stderr, "Value %llu is not in range [%llu, %llu]\n",
+                 (unsigned long long)(val), (unsigned long long)(low),
+                 (unsigned long long)(high));
+  }
+  return result;
+}
+
+TEST(TableTest, ApproximateOffsetOfPlain) {
+  TableConstructor c(BytewiseComparator());
+  c.Add("k01", "hello");
+  c.Add("k02", "hello2");
+  c.Add("k03", std::string(10000, 'x'));
+  c.Add("k04", std::string(200000, 'x'));
+  c.Add("k05", std::string(300000, 'x'));
+  c.Add("k06", "hello3");
+  c.Add("k07", std::string(100000, 'x'));
+  std::vector<std::string> keys;
+  KVMap kvmap;
+  Options options;
+  options.block_size = 1024;
+  options.compression = kNoCompression;
+  c.Finish(options, &keys, &kvmap);
+
+  ASSERT_TRUE(Between(c.ApproximateOffsetOf("abc"), 0, 0));
+  ASSERT_TRUE(Between(c.ApproximateOffsetOf("k01"), 0, 0));
+  ASSERT_TRUE(Between(c.ApproximateOffsetOf("k01a"), 0, 0));
+  ASSERT_TRUE(Between(c.ApproximateOffsetOf("k02"), 0, 0));
+  ASSERT_TRUE(Between(c.ApproximateOffsetOf("k03"), 0, 0));
+  ASSERT_TRUE(Between(c.ApproximateOffsetOf("k04"), 10000, 11000));
+  ASSERT_TRUE(Between(c.ApproximateOffsetOf("k04a"), 210000, 211000));
+  ASSERT_TRUE(Between(c.ApproximateOffsetOf("k05"), 210000, 211000));
+  ASSERT_TRUE(Between(c.ApproximateOffsetOf("k06"), 510000, 511000));
+  ASSERT_TRUE(Between(c.ApproximateOffsetOf("k07"), 510000, 511000));
+  ASSERT_TRUE(Between(c.ApproximateOffsetOf("xyz"), 610000, 612000));
+}
+
+static bool CompressionSupported(CompressionType type) {
+  std::string out;
+  Slice in = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
+  if (type == kSnappyCompression) {
+    return port::Snappy_Compress(in.data(), in.size(), &out);
+  } else if (type == kZstdCompression) {
+    return port::Zstd_Compress(/*level=*/1, in.data(), in.size(), &out);
+  }
+  return false;
+}
+
+class CompressionTableTest
+    : public ::testing::TestWithParam<std::tuple<CompressionType>> {};
+
+INSTANTIATE_TEST_SUITE_P(CompressionTests, CompressionTableTest,
+                         ::testing::Values(kSnappyCompression,
+                                           kZstdCompression));
+
+TEST_P(CompressionTableTest, ApproximateOffsetOfCompressed) {
+  CompressionType type = ::testing::get<0>(GetParam());
+  if (!CompressionSupported(type)) {
+    GTEST_SKIP() << "skipping compression test: " << type;
+  }
+
+  Random rnd(301);
+  TableConstructor c(BytewiseComparator());
+  std::string tmp;
+  c.Add("k01", "hello");
+  c.Add("k02", test::CompressibleString(&rnd, 0.25, 10000, &tmp));
+  c.Add("k03", "hello3");
+  c.Add("k04", test::CompressibleString(&rnd, 0.25, 10000, &tmp));
+  std::vector<std::string> keys;
+  KVMap kvmap;
+  Options options;
+  options.block_size = 1024;
+  options.compression = type;
+  c.Finish(options, &keys, &kvmap);
+
+  // Expected upper and lower bounds of space used by compressible strings.
+  static const int kSlop = 1000;  // Compressor effectiveness varies.
+  const int expected = 2500;      // 10000 * compression ratio (0.25)
+  const int min_z = expected - kSlop;
+  const int max_z = expected + kSlop;
+
+  ASSERT_TRUE(Between(c.ApproximateOffsetOf("abc"), 0, kSlop));
+  ASSERT_TRUE(Between(c.ApproximateOffsetOf("k01"), 0, kSlop));
+  ASSERT_TRUE(Between(c.ApproximateOffsetOf("k02"), 0, kSlop));
+  // Have now emitted a large compressible string, so adjust expected offset.
+  ASSERT_TRUE(Between(c.ApproximateOffsetOf("k03"), min_z, max_z));
+  ASSERT_TRUE(Between(c.ApproximateOffsetOf("k04"), min_z, max_z));
+  // Have now emitted two large compressible strings, so adjust expected offset.
+  ASSERT_TRUE(Between(c.ApproximateOffsetOf("xyz"), 2 * min_z, 2 * max_z));
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/table/two_level_iterator.cc b/leveldb_base/table/two_level_iterator.cc
new file mode 100644
index 0000000..144790d
--- /dev/null
+++ b/leveldb_base/table/two_level_iterator.cc
@@ -0,0 +1,171 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "table/two_level_iterator.h"
+
+#include "leveldb/table.h"
+#include "table/block.h"
+#include "table/format.h"
+#include "table/iterator_wrapper.h"
+
+namespace leveldb {
+
+namespace {
+
+typedef Iterator* (*BlockFunction)(void*, const ReadOptions&, const Slice&);
+
+class TwoLevelIterator : public Iterator {
+ public:
+  TwoLevelIterator(Iterator* index_iter, BlockFunction block_function,
+                   void* arg, const ReadOptions& options);
+
+  ~TwoLevelIterator() override;
+
+  void Seek(const Slice& target) override;
+  void SeekToFirst() override;
+  void SeekToLast() override;
+  void Next() override;
+  void Prev() override;
+
+  bool Valid() const override { return data_iter_.Valid(); }
+  Slice key() const override {
+    assert(Valid());
+    return data_iter_.key();
+  }
+  Slice value() const override {
+    assert(Valid());
+    return data_iter_.value();
+  }
+  Status status() const override {
+    // It'd be nice if status() returned a const Status& instead of a Status
+    if (!index_iter_.status().ok()) {
+      return index_iter_.status();
+    } else if (data_iter_.iter() != nullptr && !data_iter_.status().ok()) {
+      return data_iter_.status();
+    } else {
+      return status_;
+    }
+  }
+
+ private:
+  void SaveError(const Status& s) {
+    if (status_.ok() && !s.ok()) status_ = s;
+  }
+  void SkipEmptyDataBlocksForward();
+  void SkipEmptyDataBlocksBackward();
+  void SetDataIterator(Iterator* data_iter);
+  void InitDataBlock();
+
+  BlockFunction block_function_;
+  void* arg_;
+  const ReadOptions options_;
+  Status status_;
+  IteratorWrapper index_iter_;
+  IteratorWrapper data_iter_;  // May be nullptr
+  // If data_iter_ is non-null, then "data_block_handle_" holds the
+  // "index_value" passed to block_function_ to create the data_iter_.
+  std::string data_block_handle_;
+};
+
+TwoLevelIterator::TwoLevelIterator(Iterator* index_iter,
+                                   BlockFunction block_function, void* arg,
+                                   const ReadOptions& options)
+    : block_function_(block_function),
+      arg_(arg),
+      options_(options),
+      index_iter_(index_iter),
+      data_iter_(nullptr) {}
+
+TwoLevelIterator::~TwoLevelIterator() = default;
+
+void TwoLevelIterator::Seek(const Slice& target) {
+  index_iter_.Seek(target);
+  InitDataBlock();
+  if (data_iter_.iter() != nullptr) data_iter_.Seek(target);
+  SkipEmptyDataBlocksForward();
+}
+
+void TwoLevelIterator::SeekToFirst() {
+  index_iter_.SeekToFirst();
+  InitDataBlock();
+  if (data_iter_.iter() != nullptr) data_iter_.SeekToFirst();
+  SkipEmptyDataBlocksForward();
+}
+
+void TwoLevelIterator::SeekToLast() {
+  index_iter_.SeekToLast();
+  InitDataBlock();
+  if (data_iter_.iter() != nullptr) data_iter_.SeekToLast();
+  SkipEmptyDataBlocksBackward();
+}
+
+void TwoLevelIterator::Next() {
+  assert(Valid());
+  data_iter_.Next();
+  SkipEmptyDataBlocksForward();
+}
+
+void TwoLevelIterator::Prev() {
+  assert(Valid());
+  data_iter_.Prev();
+  SkipEmptyDataBlocksBackward();
+}
+
+void TwoLevelIterator::SkipEmptyDataBlocksForward() {
+  while (data_iter_.iter() == nullptr || !data_iter_.Valid()) {
+    // Move to next block
+    if (!index_iter_.Valid()) {
+      SetDataIterator(nullptr);
+      return;
+    }
+    index_iter_.Next();
+    InitDataBlock();
+    if (data_iter_.iter() != nullptr) data_iter_.SeekToFirst();
+  }
+}
+
+void TwoLevelIterator::SkipEmptyDataBlocksBackward() {
+  while (data_iter_.iter() == nullptr || !data_iter_.Valid()) {
+    // Move to next block
+    if (!index_iter_.Valid()) {
+      SetDataIterator(nullptr);
+      return;
+    }
+    index_iter_.Prev();
+    InitDataBlock();
+    if (data_iter_.iter() != nullptr) data_iter_.SeekToLast();
+  }
+}
+
+void TwoLevelIterator::SetDataIterator(Iterator* data_iter) {
+  if (data_iter_.iter() != nullptr) SaveError(data_iter_.status());
+  data_iter_.Set(data_iter);
+}
+
+void TwoLevelIterator::InitDataBlock() {
+  if (!index_iter_.Valid()) {
+    SetDataIterator(nullptr);
+  } else {
+    Slice handle = index_iter_.value();
+    if (data_iter_.iter() != nullptr &&
+        handle.compare(data_block_handle_) == 0) {
+      // data_iter_ is already constructed with this iterator, so
+      // no need to change anything
+    } else {
+      Iterator* iter = (*block_function_)(arg_, options_, handle);
+      data_block_handle_.assign(handle.data(), handle.size());
+      SetDataIterator(iter);
+    }
+  }
+}
+
+}  // namespace
+
+Iterator* NewTwoLevelIterator(Iterator* index_iter,
+                              BlockFunction block_function, void* arg,
+                              const ReadOptions& options) {
+  return new TwoLevelIterator(index_iter, block_function, arg, options);
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/table/two_level_iterator.h b/leveldb_base/table/two_level_iterator.h
new file mode 100644
index 0000000..81ffe80
--- /dev/null
+++ b/leveldb_base/table/two_level_iterator.h
@@ -0,0 +1,31 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_TABLE_TWO_LEVEL_ITERATOR_H_
+#define STORAGE_LEVELDB_TABLE_TWO_LEVEL_ITERATOR_H_
+
+#include "leveldb/iterator.h"
+
+namespace leveldb {
+
+struct ReadOptions;
+
+// Return a new two level iterator.  A two-level iterator contains an
+// index iterator whose values point to a sequence of blocks where
+// each block is itself a sequence of key,value pairs.  The returned
+// two-level iterator yields the concatenation of all key/value pairs
+// in the sequence of blocks.  Takes ownership of "index_iter" and
+// will delete it when no longer needed.
+//
+// Uses a supplied function to convert an index_iter value into
+// an iterator over the contents of the corresponding block.
+Iterator* NewTwoLevelIterator(
+    Iterator* index_iter,
+    Iterator* (*block_function)(void* arg, const ReadOptions& options,
+                                const Slice& index_value),
+    void* arg, const ReadOptions& options);
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_TABLE_TWO_LEVEL_ITERATOR_H_
diff --git a/leveldb_base/test/db_test2.cc b/leveldb_base/test/db_test2.cc
new file mode 100644
index 0000000..7c52b5b
--- /dev/null
+++ b/leveldb_base/test/db_test2.cc
@@ -0,0 +1,74 @@
+#include "leveldb/db.h"
+#include "leveldb/filter_policy.h"
+
+#include <iostream>
+#include <cstdlib>
+#include <ctime>
+
+using namespace leveldb;
+
+constexpr int value_size = 2048;
+constexpr int data_size = 256 << 20;
+
+// 3. 数据管理（Manifest/创建/恢复数据库）
+Status OpenDB(std::string dbName, DB **db) {
+  Options options;
+  options.create_if_missing = true;
+  options.filter_policy = NewBloomFilterPolicy(10);
+  return DB::Open(options, dbName, db);
+}
+
+// 1. 存储（数据结构与写入）
+// 4. 数据合并（Compaction）
+void InsertData(DB *db) {
+  WriteOptions writeOptions;
+  int key_num = data_size / value_size;
+  srand(0);
+
+  for (int i = 0; i < key_num; i++) {
+    int key_ = rand() % key_num+1;
+    std::string key = std::to_string(key_);
+    std::string value(value_size, 'a');
+    db->Put(writeOptions, key, value);
+  }
+}
+
+// 2. 数据访问（如何读数据）
+void GetData(DB *db, int size = (1 << 30)) {
+  ReadOptions readOptions;
+  int key_num = data_size / value_size;
+  
+  // 点查
+  srand(0);
+  for (int i = 0; i < 100; i++) {
+    int key_ = rand() % key_num+1;
+    std::string key = std::to_string(key_);
+    std::string value;
+    db->Get(readOptions, key, &value);
+  }
+
+  // 范围查询
+  Iterator *iter = db->NewIterator(readOptions);
+  iter->SeekToFirst();
+  while (iter->Valid()) {
+    iter->Next();
+  }
+  delete iter;
+}
+
+int main() {
+
+  DB *db;
+  if(OpenDB("testdb", &db).ok()) {
+    InsertData(db);
+    delete db;
+  }
+
+  if(OpenDB("testdb", &db).ok()) {
+    GetData(db);
+    delete db;
+  }
+  
+  return 0;
+}
+
diff --git a/leveldb_base/test/ttl_test.cc b/leveldb_base/test/ttl_test.cc
new file mode 100644
index 0000000..5460d7d
--- /dev/null
+++ b/leveldb_base/test/ttl_test.cc
@@ -0,0 +1,119 @@
+
+
+#include "gtest/gtest.h"
+
+#include "leveldb/env.h"
+#include "leveldb/db.h"
+
+
+using namespace leveldb;
+
+constexpr int value_size = 2048;
+constexpr int data_size = 128 << 20;
+
+Status OpenDB(std::string dbName, DB **db) {
+  Options options;
+  options.create_if_missing = true;
+  return DB::Open(options, dbName, db);
+}
+
+void InsertData(DB *db, uint64_t ttl/* second */) {
+  WriteOptions writeOptions;
+  int key_num = data_size / value_size;
+  srand(static_cast<unsigned int>(time(0)));
+  //srand(0);
+  for (int i = 0; i < key_num; i++) {
+    //int key_ = rand() % key_num+1;
+    int key_ = i + 1;
+    std::string key = std::to_string(key_);
+    std::string value(value_size, 'a');
+    db->Put(writeOptions, key, value, ttl);
+  }
+}
+
+void GetData(DB *db, int size = (1 << 30)) {
+  ReadOptions readOptions;
+  int key_num = data_size / value_size;
+  
+  // 点查
+  srand(static_cast<unsigned int>(time(0)));
+  //srand(0);
+  for (int i = 0; i < 100; i++) {
+    int key_ = rand() % key_num+1;
+    std::string key = std::to_string(key_);
+    std::string value;
+    db->Get(readOptions, key, &value);
+  }
+}
+// 暂时先注释掉写入Test-橙
+TEST(TestTTL, ReadTTL) {
+    DB *db;
+    if(OpenDB("testdb", &db).ok() == false) {
+        std::cerr << "open db failed" << std::endl;
+        abort();
+    }
+
+    uint64_t ttl = 20;
+
+    InsertData(db, ttl);
+
+    ReadOptions readOptions;
+    Status status;
+    int key_num = data_size / value_size;
+    srand(static_cast<unsigned int>(time(0)));
+    for (int i = 0; i < 100; i++) {
+        int key_ = rand() % key_num+1;
+        std::string key = std::to_string(key_);
+        std::string value;
+        status = db->Get(readOptions, key, &value);
+        ASSERT_TRUE(status.ok());
+    }
+
+    Env::Default()->SleepForMicroseconds(ttl * 1000000);
+  
+    for (int i = 0; i < 100; i++) {
+        int key_ = rand() % key_num+1;
+        std::string key = std::to_string(key_);
+        std::string value;
+        status = db->Get(readOptions, key, &value); 
+        ASSERT_FALSE(status.ok());
+    }
+  delete db;
+}
+
+
+TEST(TestTTL, CompactionTTL) {
+    DB *db;
+
+    if(OpenDB("testdb", &db).ok() == false) {
+        std::cerr << "open db failed" << std::endl;
+        abort();
+    }
+
+    uint64_t ttl = 20;
+    InsertData(db, ttl);
+   //这里为什么要定义两个ranges1？-橙
+    leveldb::Range ranges[1];
+    ranges[0] = leveldb::Range("-", "A");
+    uint64_t sizes[1];
+    db->GetApproximateSizes(ranges, 1, sizes);
+    // printf("part1\n");
+    ASSERT_GT(sizes[0], 0);
+
+    Env::Default()->SleepForMicroseconds(ttl * 1000000);
+
+    db->CompactRange(nullptr, nullptr);
+    // 先注释掉重复定义的-橙
+    // leveldb::Range ranges[1];
+    ranges[0] = leveldb::Range("-", "A");
+    // uint64_t sizes[1];
+    db->GetApproximateSizes(ranges, 1, sizes);
+    ASSERT_EQ(sizes[0], 0);
+}
+
+
+int main(int argc, char** argv) {
+  // All tests currently run with the same read-only file limits.
+  testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
diff --git a/leveldb_base/third_party/benchmark/.clang-format b/leveldb_base/third_party/benchmark/.clang-format
new file mode 100644
index 0000000..e7d00fe
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/.clang-format
@@ -0,0 +1,5 @@
+---
+Language:        Cpp
+BasedOnStyle:  Google
+PointerAlignment: Left
+...
diff --git a/leveldb_base/third_party/benchmark/.clang-tidy b/leveldb_base/third_party/benchmark/.clang-tidy
new file mode 100644
index 0000000..56938a5
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/.clang-tidy
@@ -0,0 +1,7 @@
+---
+Checks:          'clang-analyzer-*,readability-redundant-*,performance-*'
+WarningsAsErrors: 'clang-analyzer-*,readability-redundant-*,performance-*'
+HeaderFilterRegex: '.*'
+AnalyzeTemporaryDtors: false
+FormatStyle:     none
+User:            user
diff --git a/leveldb_base/third_party/benchmark/.github/ISSUE_TEMPLATE/bug_report.md b/leveldb_base/third_party/benchmark/.github/ISSUE_TEMPLATE/bug_report.md
new file mode 100644
index 0000000..6c2ced9
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/.github/ISSUE_TEMPLATE/bug_report.md
@@ -0,0 +1,32 @@
+---
+name: Bug report
+about: Create a report to help us improve
+title: "[BUG]"
+labels: ''
+assignees: ''
+
+---
+
+**Describe the bug**
+A clear and concise description of what the bug is.
+
+**System**
+Which OS, compiler, and compiler version are you using:
+  - OS: 
+  - Compiler and version: 
+
+**To reproduce**
+Steps to reproduce the behavior:
+1. sync to commit ...
+2. cmake/bazel...
+3. make ...
+4. See error
+
+**Expected behavior**
+A clear and concise description of what you expected to happen.
+
+**Screenshots**
+If applicable, add screenshots to help explain your problem.
+
+**Additional context**
+Add any other context about the problem here.
diff --git a/leveldb_base/third_party/benchmark/.github/ISSUE_TEMPLATE/feature_request.md b/leveldb_base/third_party/benchmark/.github/ISSUE_TEMPLATE/feature_request.md
new file mode 100644
index 0000000..9e8ab6a
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/.github/ISSUE_TEMPLATE/feature_request.md
@@ -0,0 +1,20 @@
+---
+name: Feature request
+about: Suggest an idea for this project
+title: "[FR]"
+labels: ''
+assignees: ''
+
+---
+
+**Is your feature request related to a problem? Please describe.**
+A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]
+
+**Describe the solution you'd like**
+A clear and concise description of what you want to happen.
+
+**Describe alternatives you've considered**
+A clear and concise description of any alternative solutions or features you've considered.
+
+**Additional context**
+Add any other context or screenshots about the feature request here.
diff --git a/leveldb_base/third_party/benchmark/.github/install_bazel.sh b/leveldb_base/third_party/benchmark/.github/install_bazel.sh
new file mode 100644
index 0000000..bb910d8
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/.github/install_bazel.sh
@@ -0,0 +1,13 @@
+if ! bazel version; then
+  arch=$(uname -m)
+  if [ "$arch" == "aarch64" ]; then
+    arch="arm64"
+  fi
+  echo "Installing wget and downloading $arch Bazel binary from GitHub releases."
+  yum install -y wget
+  wget "https://github.com/bazelbuild/bazel/releases/download/6.0.0/bazel-6.0.0-linux-$arch" -O /usr/local/bin/bazel
+  chmod +x /usr/local/bin/bazel
+else
+  # bazel is installed for the correct architecture
+  exit 0
+fi
diff --git a/leveldb_base/third_party/benchmark/.github/libcxx-setup.sh b/leveldb_base/third_party/benchmark/.github/libcxx-setup.sh
new file mode 100644
index 0000000..e39e310
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/.github/libcxx-setup.sh
@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+
+# Checkout LLVM sources
+#git clone --depth=1 https://github.com/llvm/llvm-project.git llvm-project
+#
+## Setup libc++ options
+#if [ -z "$BUILD_32_BITS" ]; then
+#  export BUILD_32_BITS=OFF && echo disabling 32 bit build
+#fi
+#
+## Build and install libc++ (Use unstable ABI for better sanitizer coverage)
+#cd ./llvm-project
+#cmake -DCMAKE_C_COMPILER=${CC}                  \
+#      -DCMAKE_CXX_COMPILER=${CXX}               \
+#      -DCMAKE_BUILD_TYPE=RelWithDebInfo         \
+#      -DCMAKE_INSTALL_PREFIX=/usr               \
+#      -DLIBCXX_ABI_UNSTABLE=OFF                 \
+#      -DLLVM_USE_SANITIZER=${LIBCXX_SANITIZER}  \
+#      -DLLVM_BUILD_32_BITS=${BUILD_32_BITS}     \
+#      -DLLVM_ENABLE_RUNTIMES='libcxx;libcxxabi' \
+#      -S llvm -B llvm-build -G "Unix Makefiles"
+#make -C llvm-build -j3 cxx cxxabi
+#sudo make -C llvm-build install-cxx install-cxxabi
+#cd ..
+
+sudo apt update
+sudo apt -y install libc++-dev libc++abi-dev
diff --git a/leveldb_base/third_party/benchmark/.github/workflows/bazel.yml b/leveldb_base/third_party/benchmark/.github/workflows/bazel.yml
new file mode 100644
index 0000000..9e31c90
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/.github/workflows/bazel.yml
@@ -0,0 +1,35 @@
+name: bazel
+
+on:
+  push: {}
+  pull_request: {}
+
+jobs:
+  job:
+    name: bazel.${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-2022]
+
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: mount bazel cache
+      uses: actions/cache@v3
+      env:
+        cache-name: bazel-cache
+      with:
+        path: "~/.cache/bazel"
+        key: ${{ env.cache-name }}-${{ matrix.os }}-${{ github.ref }}
+        restore-keys: |
+          ${{ env.cache-name }}-${{ matrix.os }}-main
+
+    - name: build
+      run: |
+        bazel build //:benchmark //:benchmark_main //test/...
+
+    - name: test
+      run: |
+        bazel test --test_output=all //test/...
diff --git a/leveldb_base/third_party/benchmark/.github/workflows/build-and-test-min-cmake.yml b/leveldb_base/third_party/benchmark/.github/workflows/build-and-test-min-cmake.yml
new file mode 100644
index 0000000..e3e3217
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/.github/workflows/build-and-test-min-cmake.yml
@@ -0,0 +1,46 @@
+name: build-and-test-min-cmake
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  job:
+    name: ${{ matrix.os }}.min-cmake
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest]
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - uses: lukka/get-cmake@latest
+        with:
+          cmakeVersion: 3.10.0
+
+      - name: create build environment
+        run: cmake -E make_directory ${{ runner.workspace }}/_build
+
+      - name: setup cmake initial cache
+        run: touch compiler-cache.cmake
+
+      - name: configure cmake
+        env:
+          CXX: ${{ matrix.compiler }}
+        shell: bash
+        working-directory: ${{ runner.workspace }}/_build
+        run: >
+          cmake -C ${{ github.workspace }}/compiler-cache.cmake
+          $GITHUB_WORKSPACE
+          -DBENCHMARK_DOWNLOAD_DEPENDENCIES=ON
+          -DCMAKE_CXX_VISIBILITY_PRESET=hidden
+          -DCMAKE_VISIBILITY_INLINES_HIDDEN=ON
+
+      - name: build
+        shell: bash
+        working-directory: ${{ runner.workspace }}/_build
+        run: cmake --build .
diff --git a/leveldb_base/third_party/benchmark/.github/workflows/build-and-test-perfcounters.yml b/leveldb_base/third_party/benchmark/.github/workflows/build-and-test-perfcounters.yml
new file mode 100644
index 0000000..97e4d8e
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/.github/workflows/build-and-test-perfcounters.yml
@@ -0,0 +1,51 @@
+name: build-and-test-perfcounters
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  job:
+    # TODO(dominic): Extend this to include compiler and set through env: CC/CXX.
+    name: ${{ matrix.os }}.${{ matrix.build_type }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-22.04, ubuntu-20.04]
+        build_type: ['Release', 'Debug']
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: install libpfm
+      run: |
+        sudo apt update
+        sudo apt -y install libpfm4-dev
+
+    - name: create build environment
+      run: cmake -E make_directory ${{ runner.workspace }}/_build
+
+    - name: configure cmake
+      shell: bash
+      working-directory: ${{ runner.workspace }}/_build
+      run: >
+        cmake $GITHUB_WORKSPACE
+        -DBENCHMARK_ENABLE_LIBPFM=1
+        -DBENCHMARK_DOWNLOAD_DEPENDENCIES=ON
+        -DCMAKE_BUILD_TYPE=${{ matrix.build_type }}
+
+    - name: build
+      shell: bash
+      working-directory: ${{ runner.workspace }}/_build
+      run: cmake --build . --config ${{ matrix.build_type }}
+
+    # Skip testing, for now. It seems perf_event_open does not succeed on the
+    # hosting machine, very likely a permissions issue.
+    # TODO(mtrofin): Enable test.
+    # - name: test
+    #   shell: bash
+    #   working-directory: ${{ runner.workspace }}/_build
+    #   run: ctest -C ${{ matrix.build_type }} --rerun-failed --output-on-failure
+
diff --git a/leveldb_base/third_party/benchmark/.github/workflows/build-and-test.yml b/leveldb_base/third_party/benchmark/.github/workflows/build-and-test.yml
new file mode 100644
index 0000000..b35200a
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/.github/workflows/build-and-test.yml
@@ -0,0 +1,114 @@
+name: build-and-test
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  # TODO: add 32-bit builds (g++ and clang++) for ubuntu
+  #   (requires g++-multilib and libc6:i386)
+  # TODO: add coverage build (requires lcov)
+  # TODO: add clang + libc++ builds for ubuntu
+  job:
+    name: ${{ matrix.os }}.${{ matrix.build_type }}.${{ matrix.lib }}.${{ matrix.compiler }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-22.04, ubuntu-20.04, macos-latest]
+        build_type: ['Release', 'Debug']
+        compiler: ['g++', 'clang++']
+        lib: ['shared', 'static']
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - uses: lukka/get-cmake@latest
+
+      - name: create build environment
+        run: cmake -E make_directory ${{ runner.workspace }}/_build
+
+      - name: setup cmake initial cache
+        run: touch compiler-cache.cmake
+
+      - name: configure cmake
+        env:
+          CXX: ${{ matrix.compiler }}
+        shell: bash
+        working-directory: ${{ runner.workspace }}/_build
+        run: >
+          cmake -C ${{ github.workspace }}/compiler-cache.cmake
+          $GITHUB_WORKSPACE
+          -DBENCHMARK_DOWNLOAD_DEPENDENCIES=ON
+          -DBUILD_SHARED_LIBS=${{ matrix.lib == 'shared' }}
+          -DCMAKE_BUILD_TYPE=${{ matrix.build_type }}
+          -DCMAKE_CXX_COMPILER=${{ env.CXX }}
+          -DCMAKE_CXX_VISIBILITY_PRESET=hidden
+          -DCMAKE_VISIBILITY_INLINES_HIDDEN=ON
+
+      - name: build
+        shell: bash
+        working-directory: ${{ runner.workspace }}/_build
+        run: cmake --build . --config ${{ matrix.build_type }}
+
+      - name: test
+        shell: bash
+        working-directory: ${{ runner.workspace }}/_build
+        run: ctest -C ${{ matrix.build_type }} -VV
+
+  msvc:
+    name: ${{ matrix.os }}.${{ matrix.build_type }}.${{ matrix.lib }}.${{ matrix.msvc }}
+    runs-on: ${{ matrix.os }}
+    defaults:
+        run:
+            shell: powershell
+    strategy:
+      fail-fast: false
+      matrix:
+        msvc:
+          - VS-16-2019
+          - VS-17-2022
+        arch:
+          - x64
+        build_type:
+          - Debug
+          - Release
+        lib:
+          - shared
+          - static
+        include:
+          - msvc: VS-16-2019
+            os: windows-2019
+            generator: 'Visual Studio 16 2019'
+          - msvc: VS-17-2022
+            os: windows-2022
+            generator: 'Visual Studio 17 2022'
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - uses: lukka/get-cmake@latest
+
+      - name: configure cmake
+        run: >
+          cmake -S . -B _build/
+          -A ${{ matrix.arch }}
+          -G "${{ matrix.generator }}"
+          -DBENCHMARK_DOWNLOAD_DEPENDENCIES=ON
+          -DBUILD_SHARED_LIBS=${{ matrix.lib == 'shared' }}
+
+      - name: build
+        run: cmake --build _build/ --config ${{ matrix.build_type }}
+
+      - name: setup test environment
+        # Make sure gmock and benchmark DLLs can be found
+        run: >
+            echo "$((Get-Item .).FullName)/_build/bin/${{ matrix.build_type }}" | Out-File -FilePath $env:GITHUB_PATH -Encoding utf8 -Append;
+            echo "$((Get-Item .).FullName)/_build/src/${{ matrix.build_type }}" | Out-File -FilePath $env:GITHUB_PATH -Encoding utf8 -Append;
+
+      - name: test
+        run: ctest --test-dir _build/ -C ${{ matrix.build_type }} -VV
+
+
diff --git a/leveldb_base/third_party/benchmark/.github/workflows/clang-format-lint.yml b/leveldb_base/third_party/benchmark/.github/workflows/clang-format-lint.yml
new file mode 100644
index 0000000..77ce1f8
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/.github/workflows/clang-format-lint.yml
@@ -0,0 +1,17 @@
+name: clang-format-lint
+on:
+  push: {}
+  pull_request: {}
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v3
+    - uses: DoozyX/clang-format-lint-action@v0.13
+      with:
+        source: './include/benchmark ./src ./test'
+        extensions: 'h,cc'
+        clangFormatVersion: 12
+        style: Google
diff --git a/leveldb_base/third_party/benchmark/.github/workflows/clang-tidy.yml b/leveldb_base/third_party/benchmark/.github/workflows/clang-tidy.yml
new file mode 100644
index 0000000..2eaab9c
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/.github/workflows/clang-tidy.yml
@@ -0,0 +1,38 @@
+name: clang-tidy
+
+on:
+  push: {}
+  pull_request: {}
+
+jobs:
+  job:
+    name: run-clang-tidy
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: install clang-tidy
+      run: sudo apt update && sudo apt -y install clang-tidy
+
+    - name: create build environment
+      run: cmake -E make_directory ${{ runner.workspace }}/_build
+
+    - name: configure cmake
+      shell: bash
+      working-directory: ${{ runner.workspace }}/_build
+      run: >
+        cmake $GITHUB_WORKSPACE
+        -DBENCHMARK_ENABLE_ASSEMBLY_TESTS=OFF
+        -DBENCHMARK_ENABLE_LIBPFM=OFF
+        -DBENCHMARK_DOWNLOAD_DEPENDENCIES=ON
+        -DCMAKE_C_COMPILER=clang
+        -DCMAKE_CXX_COMPILER=clang++
+        -DCMAKE_EXPORT_COMPILE_COMMANDS=ON
+        -DGTEST_COMPILE_COMMANDS=OFF
+
+    - name: run
+      shell: bash
+      working-directory: ${{ runner.workspace }}/_build
+      run: run-clang-tidy
diff --git a/leveldb_base/third_party/benchmark/.github/workflows/doxygen.yml b/leveldb_base/third_party/benchmark/.github/workflows/doxygen.yml
new file mode 100644
index 0000000..da92c46
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/.github/workflows/doxygen.yml
@@ -0,0 +1,28 @@
+name: doxygen
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  build-and-deploy:
+    name: Build HTML documentation
+    runs-on: ubuntu-latest
+    steps:
+    - name: Fetching sources
+      uses: actions/checkout@v3
+
+    - name: Installing build dependencies
+      run: |
+        sudo apt update
+        sudo apt install doxygen gcc git
+
+    - name: Creating build directory
+      run: mkdir build
+
+    - name: Building HTML documentation with Doxygen
+      run: |
+        cmake -S . -B build -DBENCHMARK_ENABLE_TESTING:BOOL=OFF -DBENCHMARK_ENABLE_DOXYGEN:BOOL=ON -DBENCHMARK_INSTALL_DOCS:BOOL=ON
+        cmake --build build --target benchmark_doxygen
diff --git a/leveldb_base/third_party/benchmark/.github/workflows/pylint.yml b/leveldb_base/third_party/benchmark/.github/workflows/pylint.yml
new file mode 100644
index 0000000..c6939b5
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/.github/workflows/pylint.yml
@@ -0,0 +1,28 @@
+name: pylint
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  pylint:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v3
+    - name: Set up Python 3.8
+      uses: actions/setup-python@v1
+      with:
+        python-version: 3.8
+
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        pip install pylint pylint-exit conan
+
+    - name: Run pylint
+      run: |
+        pylint `find . -name '*.py'|xargs` || pylint-exit $?
diff --git a/leveldb_base/third_party/benchmark/.github/workflows/sanitizer.yml b/leveldb_base/third_party/benchmark/.github/workflows/sanitizer.yml
new file mode 100644
index 0000000..4cb93f4
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/.github/workflows/sanitizer.yml
@@ -0,0 +1,106 @@
+name: sanitizer
+
+on:
+  push: {}
+  pull_request: {}
+
+env:
+  UBSAN_OPTIONS: "print_stacktrace=1"
+
+jobs:
+  job:
+    name: ${{ matrix.sanitizer }}.${{ matrix.build_type }}.${{ matrix.compiler }}
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        build_type: ['Debug', 'RelWithDebInfo']
+        sanitizer: ['asan', 'ubsan', 'tsan']
+        compiler: ['clang', 'gcc']
+        # TODO: add 'msan' above. currently failing and needs investigation.
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: configure msan env
+      if: matrix.sanitizer == 'msan'
+      run: |
+        echo "EXTRA_FLAGS=-g -O2 -fno-omit-frame-pointer -fsanitize=memory -fsanitize-memory-track-origins" >> $GITHUB_ENV
+        echo "LIBCXX_SANITIZER=MemoryWithOrigins" >> $GITHUB_ENV
+
+    - name: configure ubsan env
+      if: matrix.sanitizer == 'ubsan'
+      run: |
+        echo "EXTRA_FLAGS=-g -O2 -fno-omit-frame-pointer -fsanitize=undefined -fno-sanitize-recover=all" >> $GITHUB_ENV
+        echo "LIBCXX_SANITIZER=Undefined" >> $GITHUB_ENV
+
+    - name: configure asan env
+      if: matrix.sanitizer == 'asan'
+      run: |
+        echo "EXTRA_FLAGS=-g -O2 -fno-omit-frame-pointer -fsanitize=address -fno-sanitize-recover=all" >> $GITHUB_ENV
+        echo "LIBCXX_SANITIZER=Address" >> $GITHUB_ENV
+
+    - name: configure tsan env
+      if: matrix.sanitizer == 'tsan'
+      run: |
+        echo "EXTRA_FLAGS=-g -O2 -fno-omit-frame-pointer -fsanitize=thread -fno-sanitize-recover=all" >> $GITHUB_ENV
+        echo "LIBCXX_SANITIZER=Thread" >> $GITHUB_ENV
+
+    - name: fine-tune asan options
+      # in clang+asan we get an error from std::regex. ignore it.
+      if: matrix.sanitizer == 'asan' && matrix.compiler == 'clang'
+      run: |
+        echo "ASAN_OPTIONS=alloc_dealloc_mismatch=0" >> $GITHUB_ENV
+
+    - name: setup clang
+      if: matrix.compiler == 'clang'
+      uses: egor-tensin/setup-clang@v1
+      with:
+        version: latest
+        platform: x64
+
+    - name: configure clang
+      if: matrix.compiler == 'clang'
+      run: |
+        echo "CC=cc" >> $GITHUB_ENV
+        echo "CXX=c++" >> $GITHUB_ENV
+
+    - name: configure gcc
+      if: matrix.compiler == 'gcc'
+      run: |
+        sudo apt update && sudo apt -y install gcc-10 g++-10
+        echo "CC=gcc-10" >> $GITHUB_ENV
+        echo "CXX=g++-10" >> $GITHUB_ENV
+
+    - name: install llvm stuff
+      if: matrix.compiler == 'clang'
+      run: |
+        "${GITHUB_WORKSPACE}/.github/libcxx-setup.sh"
+        echo "EXTRA_CXX_FLAGS=\"-stdlib=libc++\"" >> $GITHUB_ENV
+
+    - name: create build environment
+      run: cmake -E make_directory ${{ runner.workspace }}/_build
+
+    - name: configure cmake
+      shell: bash
+      working-directory: ${{ runner.workspace }}/_build
+      run: >
+        VERBOSE=1
+        cmake $GITHUB_WORKSPACE
+        -DBENCHMARK_ENABLE_ASSEMBLY_TESTS=OFF
+        -DBENCHMARK_ENABLE_LIBPFM=OFF
+        -DBENCHMARK_DOWNLOAD_DEPENDENCIES=ON
+        -DCMAKE_C_COMPILER=${{ env.CC }}
+        -DCMAKE_CXX_COMPILER=${{ env.CXX }}
+        -DCMAKE_C_FLAGS="${{ env.EXTRA_FLAGS }}"
+        -DCMAKE_CXX_FLAGS="${{ env.EXTRA_FLAGS }} ${{ env.EXTRA_CXX_FLAGS }}"
+        -DCMAKE_BUILD_TYPE=${{ matrix.build_type }}
+
+    - name: build
+      shell: bash
+      working-directory: ${{ runner.workspace }}/_build
+      run: cmake --build . --config ${{ matrix.build_type }}
+
+    - name: test
+      shell: bash
+      working-directory: ${{ runner.workspace }}/_build
+      run: ctest -C ${{ matrix.build_type }} -VV
diff --git a/leveldb_base/third_party/benchmark/.github/workflows/test_bindings.yml b/leveldb_base/third_party/benchmark/.github/workflows/test_bindings.yml
new file mode 100644
index 0000000..98fa7e1
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/.github/workflows/test_bindings.yml
@@ -0,0 +1,29 @@
+name: test-bindings
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  python_bindings:
+    name: Test GBM Python bindings on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ ubuntu-latest, macos-latest, windows-latest ]
+
+    steps:
+      - uses: actions/checkout@v3
+      - name: Set up Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: 3.11
+      - name: Install GBM Python bindings on ${{ matrix.os}}
+        run:
+          python -m pip install wheel .
+      - name: Run bindings example on ${{ matrix.os }}
+        run:
+          python bindings/python/google_benchmark/example.py
diff --git a/leveldb_base/third_party/benchmark/.github/workflows/wheels.yml b/leveldb_base/third_party/benchmark/.github/workflows/wheels.yml
new file mode 100644
index 0000000..d3c4630
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/.github/workflows/wheels.yml
@@ -0,0 +1,79 @@
+name: Build and upload Python wheels
+
+on:
+  workflow_dispatch:
+  release:
+    types:
+      - published
+
+jobs:
+  build_sdist:
+    name: Build source distribution
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out repo
+        uses: actions/checkout@v3
+
+      - name: Install Python 3.11
+        uses: actions/setup-python@v4
+        with:
+          python-version: 3.11
+
+      - name: Build and check sdist
+        run: |
+          python setup.py sdist
+      - name: Upload sdist
+        uses: actions/upload-artifact@v3
+        with:
+          name: dist
+          path: dist/*.tar.gz
+
+  build_wheels:
+    name: Build Google Benchmark wheels on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+
+    steps:
+      - name: Check out Google Benchmark
+        uses: actions/checkout@v3
+
+      - name: Set up QEMU
+        if: runner.os == 'Linux'
+        uses: docker/setup-qemu-action@v2
+        with:
+          platforms: all
+
+      - name: Build wheels on ${{ matrix.os }} using cibuildwheel
+        uses: pypa/cibuildwheel@v2.12.0
+        env:
+          CIBW_BUILD: 'cp38-* cp39-* cp310-* cp311-*'
+          CIBW_SKIP: "*-musllinux_*"
+          CIBW_TEST_SKIP: "*-macosx_arm64"
+          CIBW_ARCHS_LINUX: x86_64 aarch64
+          CIBW_ARCHS_MACOS: x86_64 arm64
+          CIBW_ARCHS_WINDOWS: AMD64
+          CIBW_BEFORE_ALL_LINUX: bash .github/install_bazel.sh
+          CIBW_TEST_COMMAND: python {project}/bindings/python/google_benchmark/example.py
+
+      - name: Upload Google Benchmark ${{ matrix.os }} wheels
+        uses: actions/upload-artifact@v3
+        with:
+          name: dist
+          path: ./wheelhouse/*.whl
+
+  pypi_upload:
+    name: Publish google-benchmark wheels to PyPI
+    needs: [build_sdist, build_wheels]
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/download-artifact@v3
+      with:
+        name: dist
+        path: dist
+
+    - uses: pypa/gh-action-pypi-publish@v1.6.4
+      with:
+        user: __token__
+        password: ${{ secrets.PYPI_PASSWORD }}
diff --git a/leveldb_base/third_party/benchmark/.gitignore b/leveldb_base/third_party/benchmark/.gitignore
new file mode 100644
index 0000000..704f56c
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/.gitignore
@@ -0,0 +1,67 @@
+*.a
+*.so
+*.so.?*
+*.dll
+*.exe
+*.dylib
+*.cmake
+!/cmake/*.cmake
+!/test/AssemblyTests.cmake
+*~
+*.swp
+*.pyc
+__pycache__
+.DS_Store
+
+# lcov
+*.lcov
+/lcov
+
+# cmake files.
+/Testing
+CMakeCache.txt
+CMakeFiles/
+cmake_install.cmake
+
+# makefiles.
+Makefile
+
+# in-source build.
+bin/
+lib/
+/test/*_test
+
+# exuberant ctags.
+tags
+
+# YouCompleteMe configuration.
+.ycm_extra_conf.pyc
+
+# ninja generated files.
+.ninja_deps
+.ninja_log
+build.ninja
+install_manifest.txt
+rules.ninja
+
+# bazel output symlinks.
+bazel-*
+
+# out-of-source build top-level folders.
+build/
+_build/
+build*/
+
+# in-source dependencies
+/googletest/
+
+# Visual Studio 2015/2017 cache/options directory
+.vs/
+CMakeSettings.json
+
+# Visual Studio Code cache/options directory
+.vscode/
+
+# Python build stuff
+dist/
+*.egg-info*
diff --git a/leveldb_base/third_party/benchmark/.travis.yml b/leveldb_base/third_party/benchmark/.travis.yml
new file mode 100644
index 0000000..8cfed3d
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/.travis.yml
@@ -0,0 +1,208 @@
+sudo: required
+dist: trusty
+language: cpp
+
+matrix:
+  include:
+    - compiler: gcc
+      addons:
+        apt:
+          packages:
+            - lcov
+      env: COMPILER=g++ C_COMPILER=gcc BUILD_TYPE=Coverage
+    - compiler: gcc
+      addons:
+        apt:
+          packages:
+            - g++-multilib
+            - libc6:i386
+      env:
+        - COMPILER=g++
+        - C_COMPILER=gcc
+        - BUILD_TYPE=Debug
+        - BUILD_32_BITS=ON
+        - EXTRA_FLAGS="-m32"
+    - compiler: gcc
+      addons:
+        apt:
+          packages:
+            - g++-multilib
+            - libc6:i386
+      env:
+        - COMPILER=g++
+        - C_COMPILER=gcc
+        - BUILD_TYPE=Release
+        - BUILD_32_BITS=ON
+        - EXTRA_FLAGS="-m32"
+    - compiler: gcc
+      env:
+        - INSTALL_GCC6_FROM_PPA=1
+        - COMPILER=g++-6 C_COMPILER=gcc-6  BUILD_TYPE=Debug
+        - ENABLE_SANITIZER=1
+        - EXTRA_FLAGS="-fno-omit-frame-pointer -g -O2 -fsanitize=undefined,address -fuse-ld=gold"
+    # Clang w/ libc++
+    - compiler: clang
+      dist: xenial
+      addons:
+        apt:
+          packages:
+            clang-3.8
+      env:
+        - INSTALL_GCC6_FROM_PPA=1
+        - COMPILER=clang++-3.8 C_COMPILER=clang-3.8 BUILD_TYPE=Debug
+        - LIBCXX_BUILD=1
+        - EXTRA_CXX_FLAGS="-stdlib=libc++"
+    - compiler: clang
+      dist: xenial
+      addons:
+        apt:
+          packages:
+            clang-3.8
+      env:
+        - INSTALL_GCC6_FROM_PPA=1
+        - COMPILER=clang++-3.8 C_COMPILER=clang-3.8 BUILD_TYPE=Release
+        - LIBCXX_BUILD=1
+        - EXTRA_CXX_FLAGS="-stdlib=libc++"
+    # Clang w/ 32bit libc++
+    - compiler: clang
+      dist: xenial
+      addons:
+        apt:
+          packages:
+            - clang-3.8
+            - g++-multilib
+            - libc6:i386
+      env:
+        - INSTALL_GCC6_FROM_PPA=1
+        - COMPILER=clang++-3.8 C_COMPILER=clang-3.8 BUILD_TYPE=Debug
+        - LIBCXX_BUILD=1
+        - BUILD_32_BITS=ON
+        - EXTRA_FLAGS="-m32"
+        - EXTRA_CXX_FLAGS="-stdlib=libc++"
+    # Clang w/ 32bit libc++
+    - compiler: clang
+      dist: xenial
+      addons:
+        apt:
+          packages:
+            - clang-3.8
+            - g++-multilib
+            - libc6:i386
+      env:
+        - INSTALL_GCC6_FROM_PPA=1
+        - COMPILER=clang++-3.8 C_COMPILER=clang-3.8 BUILD_TYPE=Release
+        - LIBCXX_BUILD=1
+        - BUILD_32_BITS=ON
+        - EXTRA_FLAGS="-m32"
+        - EXTRA_CXX_FLAGS="-stdlib=libc++"
+    # Clang w/ libc++, ASAN, UBSAN
+    - compiler: clang
+      dist: xenial
+      addons:
+        apt:
+          packages:
+            clang-3.8
+      env:
+        - INSTALL_GCC6_FROM_PPA=1
+        - COMPILER=clang++-3.8 C_COMPILER=clang-3.8 BUILD_TYPE=Debug
+        - LIBCXX_BUILD=1 LIBCXX_SANITIZER="Undefined;Address"
+        - ENABLE_SANITIZER=1
+        - EXTRA_FLAGS="-g -O2 -fno-omit-frame-pointer -fsanitize=undefined,address -fno-sanitize-recover=all"
+        - EXTRA_CXX_FLAGS="-stdlib=libc++"
+        - UBSAN_OPTIONS=print_stacktrace=1
+    # Clang w/ libc++ and MSAN
+    - compiler: clang
+      dist: xenial
+      addons:
+        apt:
+          packages:
+            clang-3.8
+      env:
+        - INSTALL_GCC6_FROM_PPA=1
+        - COMPILER=clang++-3.8 C_COMPILER=clang-3.8 BUILD_TYPE=Debug
+        - LIBCXX_BUILD=1 LIBCXX_SANITIZER=MemoryWithOrigins
+        - ENABLE_SANITIZER=1
+        - EXTRA_FLAGS="-g -O2 -fno-omit-frame-pointer -fsanitize=memory -fsanitize-memory-track-origins"
+        - EXTRA_CXX_FLAGS="-stdlib=libc++"
+    # Clang w/ libc++ and MSAN
+    - compiler: clang
+      dist: xenial
+      addons:
+        apt:
+          packages:
+            clang-3.8
+      env:
+        - INSTALL_GCC6_FROM_PPA=1
+        - COMPILER=clang++-3.8 C_COMPILER=clang-3.8 BUILD_TYPE=RelWithDebInfo
+        - LIBCXX_BUILD=1 LIBCXX_SANITIZER=Thread
+        - ENABLE_SANITIZER=1
+        - EXTRA_FLAGS="-g -O2 -fno-omit-frame-pointer -fsanitize=thread -fno-sanitize-recover=all"
+        - EXTRA_CXX_FLAGS="-stdlib=libc++"
+    - os: osx
+      osx_image: xcode8.3
+      compiler: clang
+      env:
+        - COMPILER=clang++
+        - BUILD_TYPE=Release
+        - BUILD_32_BITS=ON
+        - EXTRA_FLAGS="-m32"
+
+before_script:
+  - if [ -n "${LIBCXX_BUILD}" ]; then
+      source .libcxx-setup.sh;
+    fi
+  - if [ -n "${ENABLE_SANITIZER}" ]; then
+      export EXTRA_OPTIONS="-DBENCHMARK_ENABLE_ASSEMBLY_TESTS=OFF";
+    else
+      export EXTRA_OPTIONS="";
+    fi
+  - mkdir -p build && cd build
+
+before_install:
+  - if [ -z "$BUILD_32_BITS" ]; then
+      export BUILD_32_BITS=OFF && echo disabling 32 bit build;
+    fi
+  - if [ -n "${INSTALL_GCC6_FROM_PPA}" ]; then
+      sudo add-apt-repository -y "ppa:ubuntu-toolchain-r/test";
+      sudo apt-get update --option Acquire::Retries=100 --option Acquire::http::Timeout="60";
+    fi
+
+install:
+  - if [ -n "${INSTALL_GCC6_FROM_PPA}" ]; then
+      travis_wait sudo -E apt-get -yq --no-install-suggests --no-install-recommends install g++-6;
+    fi
+  - if [ "${TRAVIS_OS_NAME}" == "linux" -a "${BUILD_32_BITS}" == "OFF" ]; then
+      travis_wait sudo -E apt-get -y --no-install-suggests --no-install-recommends install llvm-3.9-tools;
+      sudo cp /usr/lib/llvm-3.9/bin/FileCheck /usr/local/bin/;
+    fi
+  - if [ "${BUILD_TYPE}" == "Coverage" -a "${TRAVIS_OS_NAME}" == "linux" ]; then
+      PATH=~/.local/bin:${PATH};
+      pip install --user --upgrade pip;
+      travis_wait pip install --user cpp-coveralls;
+    fi
+  - if [ "${C_COMPILER}" == "gcc-7" -a "${TRAVIS_OS_NAME}" == "osx" ]; then
+      rm -f /usr/local/include/c++;
+      brew update;
+      travis_wait brew install gcc@7;
+    fi
+  - if [ "${TRAVIS_OS_NAME}" == "linux" ]; then
+      sudo apt-get update -qq;
+      sudo apt-get install -qq unzip cmake3;
+      wget https://github.com/bazelbuild/bazel/releases/download/3.2.0/bazel-3.2.0-installer-linux-x86_64.sh --output-document bazel-installer.sh;
+      travis_wait sudo bash bazel-installer.sh;
+    fi
+  - if [ "${TRAVIS_OS_NAME}" == "osx" ]; then
+      curl -L -o bazel-installer.sh https://github.com/bazelbuild/bazel/releases/download/3.2.0/bazel-3.2.0-installer-darwin-x86_64.sh;
+      travis_wait sudo bash bazel-installer.sh;
+    fi
+
+script:
+  - cmake -DCMAKE_C_COMPILER=${C_COMPILER} -DCMAKE_CXX_COMPILER=${COMPILER} -DCMAKE_BUILD_TYPE=${BUILD_TYPE} -DCMAKE_C_FLAGS="${EXTRA_FLAGS}" -DCMAKE_CXX_FLAGS="${EXTRA_FLAGS} ${EXTRA_CXX_FLAGS}" -DBENCHMARK_DOWNLOAD_DEPENDENCIES=ON -DBENCHMARK_BUILD_32_BITS=${BUILD_32_BITS} ${EXTRA_OPTIONS} ..
+  - make
+  - ctest -C ${BUILD_TYPE} --output-on-failure
+  - bazel test -c dbg --define google_benchmark.have_regex=posix --announce_rc --verbose_failures --test_output=errors --keep_going //test/...
+
+after_success:
+  - if [ "${BUILD_TYPE}" == "Coverage" -a "${TRAVIS_OS_NAME}" == "linux" ]; then
+      coveralls --include src --include include --gcov-options '\-lp' --root .. --build-root .;
+    fi
diff --git a/leveldb_base/third_party/benchmark/.ycm_extra_conf.py b/leveldb_base/third_party/benchmark/.ycm_extra_conf.py
new file mode 100644
index 0000000..5649ddc
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/.ycm_extra_conf.py
@@ -0,0 +1,115 @@
+import os
+import ycm_core
+
+# These are the compilation flags that will be used in case there's no
+# compilation database set (by default, one is not set).
+# CHANGE THIS LIST OF FLAGS. YES, THIS IS THE DROID YOU HAVE BEEN LOOKING FOR.
+flags = [
+'-Wall',
+'-Werror',
+'-pedantic-errors',
+'-std=c++0x',
+'-fno-strict-aliasing',
+'-O3',
+'-DNDEBUG',
+# ...and the same thing goes for the magic -x option which specifies the
+# language that the files to be compiled are written in. This is mostly
+# relevant for c++ headers.
+# For a C project, you would set this to 'c' instead of 'c++'.
+'-x', 'c++',
+'-I', 'include',
+'-isystem', '/usr/include',
+'-isystem', '/usr/local/include',
+]
+
+
+# Set this to the absolute path to the folder (NOT the file!) containing the
+# compile_commands.json file to use that instead of 'flags'. See here for
+# more details: http://clang.llvm.org/docs/JSONCompilationDatabase.html
+#
+# Most projects will NOT need to set this to anything; you can just change the
+# 'flags' list of compilation flags. Notice that YCM itself uses that approach.
+compilation_database_folder = ''
+
+if os.path.exists( compilation_database_folder ):
+  database = ycm_core.CompilationDatabase( compilation_database_folder )
+else:
+  database = None
+
+SOURCE_EXTENSIONS = [ '.cc' ]
+
+def DirectoryOfThisScript():
+  return os.path.dirname( os.path.abspath( __file__ ) )
+
+
+def MakeRelativePathsInFlagsAbsolute( flags, working_directory ):
+  if not working_directory:
+    return list( flags )
+  new_flags = []
+  make_next_absolute = False
+  path_flags = [ '-isystem', '-I', '-iquote', '--sysroot=' ]
+  for flag in flags:
+    new_flag = flag
+
+    if make_next_absolute:
+      make_next_absolute = False
+      if not flag.startswith( '/' ):
+        new_flag = os.path.join( working_directory, flag )
+
+    for path_flag in path_flags:
+      if flag == path_flag:
+        make_next_absolute = True
+        break
+
+      if flag.startswith( path_flag ):
+        path = flag[ len( path_flag ): ]
+        new_flag = path_flag + os.path.join( working_directory, path )
+        break
+
+    if new_flag:
+      new_flags.append( new_flag )
+  return new_flags
+
+
+def IsHeaderFile( filename ):
+  extension = os.path.splitext( filename )[ 1 ]
+  return extension in [ '.h', '.hxx', '.hpp', '.hh' ]
+
+
+def GetCompilationInfoForFile( filename ):
+  # The compilation_commands.json file generated by CMake does not have entries
+  # for header files. So we do our best by asking the db for flags for a
+  # corresponding source file, if any. If one exists, the flags for that file
+  # should be good enough.
+  if IsHeaderFile( filename ):
+    basename = os.path.splitext( filename )[ 0 ]
+    for extension in SOURCE_EXTENSIONS:
+      replacement_file = basename + extension
+      if os.path.exists( replacement_file ):
+        compilation_info = database.GetCompilationInfoForFile(
+          replacement_file )
+        if compilation_info.compiler_flags_:
+          return compilation_info
+    return None
+  return database.GetCompilationInfoForFile( filename )
+
+
+def FlagsForFile( filename, **kwargs ):
+  if database:
+    # Bear in mind that compilation_info.compiler_flags_ does NOT return a
+    # python list, but a "list-like" StringVec object
+    compilation_info = GetCompilationInfoForFile( filename )
+    if not compilation_info:
+      return None
+
+    final_flags = MakeRelativePathsInFlagsAbsolute(
+      compilation_info.compiler_flags_,
+      compilation_info.compiler_working_dir_ )
+  else:
+    relative_to = DirectoryOfThisScript()
+    final_flags = MakeRelativePathsInFlagsAbsolute( flags, relative_to )
+
+  return {
+    'flags': final_flags,
+    'do_cache': True
+  }
diff --git a/leveldb_base/third_party/benchmark/AUTHORS b/leveldb_base/third_party/benchmark/AUTHORS
new file mode 100644
index 0000000..bafecad
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/AUTHORS
@@ -0,0 +1,70 @@
+# This is the official list of benchmark authors for copyright purposes.
+# This file is distinct from the CONTRIBUTORS files.
+# See the latter for an explanation.
+#
+# Names should be added to this file as:
+#	Name or Organization <email address>
+# The email address is not required for organizations.
+#
+# Please keep the list sorted.
+
+Albert Pretorius <pretoalb@gmail.com>
+Alex Steele <steeleal123@gmail.com>
+Andriy Berestovskyy <berestovskyy@gmail.com>
+Arne Beer <arne@twobeer.de>
+Carto
+Cezary Skrzyński <czars1988@gmail.com>
+Christian Wassermann <christian_wassermann@web.de>
+Christopher Seymour <chris.j.seymour@hotmail.com>
+Colin Braley <braley.colin@gmail.com>
+Daniel Harvey <danielharvey458@gmail.com>
+David Coeurjolly <david.coeurjolly@liris.cnrs.fr>
+Deniz Evrenci <denizevrenci@gmail.com>
+Dirac Research 
+Dominik Czarnota <dominik.b.czarnota@gmail.com>
+Dominik Korman <kormandominik@gmail.com>
+Donald Aingworth <donalds_junk_mail@yahoo.com>
+Eric Backus <eric_backus@alum.mit.edu>
+Eric Fiselier <eric@efcs.ca>
+Eugene Zhuk <eugene.zhuk@gmail.com>
+Evgeny Safronov <division494@gmail.com>
+Federico Ficarelli <federico.ficarelli@gmail.com>
+Felix Homann <linuxaudio@showlabor.de>
+Gergő Szitár <szitar.gergo@gmail.com>
+Google Inc.
+Henrique Bucher <hbucher@gmail.com>
+International Business Machines Corporation
+Ismael Jimenez Martinez <ismael.jimenez.martinez@gmail.com>
+Jern-Kuan Leong <jernkuan@gmail.com>
+JianXiong Zhou <zhoujianxiong2@gmail.com>
+Joao Paulo Magalhaes <joaoppmagalhaes@gmail.com>
+Jordan Williams <jwillikers@protonmail.com>
+Jussi Knuuttila <jussi.knuuttila@gmail.com>
+Kaito Udagawa <umireon@gmail.com>
+Kishan Kumar <kumar.kishan@outlook.com>
+Lei Xu <eddyxu@gmail.com>
+Marcel Jacobse <mjacobse@uni-bremen.de>
+Matt Clarkson <mattyclarkson@gmail.com>
+Maxim Vafin <maxvafin@gmail.com>
+Mike Apodaca <gatorfax@gmail.com>
+MongoDB Inc.
+Nick Hutchinson <nshutchinson@gmail.com>
+Norman Heino <norman.heino@gmail.com>
+Oleksandr Sochka <sasha.sochka@gmail.com>
+Ori Livneh <ori.livneh@gmail.com>
+Paul Redmond <paul.redmond@gmail.com>
+Raghu Raja <raghu@enfabrica.net>
+Radoslav Yovchev <radoslav.tm@gmail.com>
+Rainer Orth <ro@cebitec.uni-bielefeld.de>
+Roman Lebedev <lebedev.ri@gmail.com>
+Sayan Bhattacharjee <aero.sayan@gmail.com>
+Shapr3D <google-contributors@shapr3d.com>
+Shuo Chen <chenshuo@chenshuo.com>
+Staffan Tjernstrom <staffantj@gmail.com>
+Steinar H. Gunderson <sgunderson@bigfoot.com>
+Stripe, Inc.
+Tobias Schmidt <tobias.schmidt@in.tum.de>
+Yixuan Qiu <yixuanq@gmail.com>
+Yusuke Suzuki <utatane.tea@gmail.com>
+Zbigniew Skowron <zbychs@gmail.com>
+Min-Yih Hsu <yihshyng223@gmail.com>
diff --git a/leveldb_base/third_party/benchmark/BUILD.bazel b/leveldb_base/third_party/benchmark/BUILD.bazel
new file mode 100644
index 0000000..9961616
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/BUILD.bazel
@@ -0,0 +1,83 @@
+licenses(["notice"])
+
+config_setting(
+    name = "qnx",
+    constraint_values = ["@platforms//os:qnx"],
+    values = {
+        "cpu": "x64_qnx",
+    },
+    visibility = [":__subpackages__"],
+)
+
+config_setting(
+    name = "windows",
+    constraint_values = ["@platforms//os:windows"],
+    values = {
+        "cpu": "x64_windows",
+    },
+    visibility = [":__subpackages__"],
+)
+
+config_setting(
+    name = "macos",
+    constraint_values = ["@platforms//os:macos"],
+    visibility = ["//visibility:public"],
+)
+
+config_setting(
+    name = "perfcounters",
+    define_values = {
+        "pfm": "1",
+    },
+    visibility = [":__subpackages__"],
+)
+
+cc_library(
+    name = "benchmark",
+    srcs = glob(
+        [
+            "src/*.cc",
+            "src/*.h",
+        ],
+        exclude = ["src/benchmark_main.cc"],
+    ),
+    hdrs = [
+        "include/benchmark/benchmark.h",
+        "include/benchmark/export.h",
+    ],
+    linkopts = select({
+        ":windows": ["-DEFAULTLIB:shlwapi.lib"],
+        "//conditions:default": ["-pthread"],
+    }),
+    strip_include_prefix = "include",
+    visibility = ["//visibility:public"],
+    # Only static linking is allowed; no .so will be produced.
+    # Using `defines` (i.e. not `local_defines`) means that no
+    # dependent rules need to bother about defining the macro.
+    linkstatic = True,
+    defines = [
+        "BENCHMARK_STATIC_DEFINE",
+    ] + select({
+        ":perfcounters": ["HAVE_LIBPFM"],
+        "//conditions:default": [],
+    }),
+    deps = select({
+        ":perfcounters": ["@libpfm//:libpfm"],
+        "//conditions:default": [],
+    }),
+)
+
+cc_library(
+    name = "benchmark_main",
+    srcs = ["src/benchmark_main.cc"],
+    hdrs = ["include/benchmark/benchmark.h", "include/benchmark/export.h"],
+    strip_include_prefix = "include",
+    visibility = ["//visibility:public"],
+    deps = [":benchmark"],
+)
+
+cc_library(
+    name = "benchmark_internal_headers",
+    hdrs = glob(["src/*.h"]),
+    visibility = ["//test:__pkg__"],
+)
diff --git a/leveldb_base/third_party/benchmark/CMakeLists.txt b/leveldb_base/third_party/benchmark/CMakeLists.txt
new file mode 100644
index 0000000..f884fae
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/CMakeLists.txt
@@ -0,0 +1,337 @@
+# Require CMake 3.10. If available, use the policies up to CMake 3.22.
+cmake_minimum_required (VERSION 3.10...3.22)
+
+project (benchmark VERSION 1.7.1 LANGUAGES CXX)
+
+option(BENCHMARK_ENABLE_TESTING "Enable testing of the benchmark library." ON)
+option(BENCHMARK_ENABLE_EXCEPTIONS "Enable the use of exceptions in the benchmark library." ON)
+option(BENCHMARK_ENABLE_LTO "Enable link time optimisation of the benchmark library." OFF)
+option(BENCHMARK_USE_LIBCXX "Build and test using libc++ as the standard library." OFF)
+option(BENCHMARK_ENABLE_WERROR "Build Release candidates with -Werror." ON)
+option(BENCHMARK_FORCE_WERROR "Build Release candidates with -Werror regardless of compiler issues." OFF)
+
+if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "PGI")
+  # PGC++ maybe reporting false positives.
+  set(BENCHMARK_ENABLE_WERROR OFF)
+endif()
+if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "NVHPC")
+  set(BENCHMARK_ENABLE_WERROR OFF)
+endif()
+if(BENCHMARK_FORCE_WERROR)
+  set(BENCHMARK_ENABLE_WERROR ON)
+endif(BENCHMARK_FORCE_WERROR)
+
+if(NOT MSVC)
+  option(BENCHMARK_BUILD_32_BITS "Build a 32 bit version of the library." OFF)
+else()
+  set(BENCHMARK_BUILD_32_BITS OFF CACHE BOOL "Build a 32 bit version of the library - unsupported when using MSVC)" FORCE)
+endif()
+option(BENCHMARK_ENABLE_INSTALL "Enable installation of benchmark. (Projects embedding benchmark may want to turn this OFF.)" ON)
+option(BENCHMARK_ENABLE_DOXYGEN "Build documentation with Doxygen." OFF)
+option(BENCHMARK_INSTALL_DOCS "Enable installation of documentation." ON)
+
+# Allow unmet dependencies to be met using CMake's ExternalProject mechanics, which
+# may require downloading the source code.
+option(BENCHMARK_DOWNLOAD_DEPENDENCIES "Allow the downloading and in-tree building of unmet dependencies" OFF)
+
+# This option can be used to disable building and running unit tests which depend on gtest
+# in cases where it is not possible to build or find a valid version of gtest.
+option(BENCHMARK_ENABLE_GTEST_TESTS "Enable building the unit tests which depend on gtest" ON)
+option(BENCHMARK_USE_BUNDLED_GTEST "Use bundled GoogleTest. If disabled, the find_package(GTest) will be used." ON)
+
+option(BENCHMARK_ENABLE_LIBPFM "Enable performance counters provided by libpfm" OFF)
+
+# Export only public symbols
+set(CMAKE_CXX_VISIBILITY_PRESET hidden)
+set(CMAKE_VISIBILITY_INLINES_HIDDEN ON)
+
+if(MSVC)
+    # As of CMake 3.18, CMAKE_SYSTEM_PROCESSOR is not set properly for MSVC and
+    # cross-compilation (e.g. Host=x86_64, target=aarch64) requires using the
+    # undocumented, but working variable.
+    # See https://gitlab.kitware.com/cmake/cmake/-/issues/15170
+    set(CMAKE_SYSTEM_PROCESSOR ${MSVC_CXX_ARCHITECTURE_ID})
+    if(${CMAKE_SYSTEM_PROCESSOR} MATCHES "ARM")
+      set(CMAKE_CROSSCOMPILING TRUE)
+    endif()
+endif()
+
+set(ENABLE_ASSEMBLY_TESTS_DEFAULT OFF)
+function(should_enable_assembly_tests)
+  if(CMAKE_BUILD_TYPE)
+    string(TOLOWER ${CMAKE_BUILD_TYPE} CMAKE_BUILD_TYPE_LOWER)
+    if (${CMAKE_BUILD_TYPE_LOWER} MATCHES "coverage")
+      # FIXME: The --coverage flag needs to be removed when building assembly
+      # tests for this to work.
+      return()
+    endif()
+  endif()
+  if (MSVC)
+    return()
+  elseif(NOT CMAKE_SYSTEM_PROCESSOR MATCHES "x86_64")
+    return()
+  elseif(NOT CMAKE_SIZEOF_VOID_P EQUAL 8)
+    # FIXME: Make these work on 32 bit builds
+    return()
+  elseif(BENCHMARK_BUILD_32_BITS)
+     # FIXME: Make these work on 32 bit builds
+    return()
+  endif()
+  find_program(LLVM_FILECHECK_EXE FileCheck)
+  if (LLVM_FILECHECK_EXE)
+    set(LLVM_FILECHECK_EXE "${LLVM_FILECHECK_EXE}" CACHE PATH "llvm filecheck" FORCE)
+    message(STATUS "LLVM FileCheck Found: ${LLVM_FILECHECK_EXE}")
+  else()
+    message(STATUS "Failed to find LLVM FileCheck")
+    return()
+  endif()
+  set(ENABLE_ASSEMBLY_TESTS_DEFAULT ON PARENT_SCOPE)
+endfunction()
+should_enable_assembly_tests()
+
+# This option disables the building and running of the assembly verification tests
+option(BENCHMARK_ENABLE_ASSEMBLY_TESTS "Enable building and running the assembly tests"
+    ${ENABLE_ASSEMBLY_TESTS_DEFAULT})
+
+# Make sure we can import out CMake functions
+list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake/Modules")
+list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
+
+
+# Read the git tags to determine the project version
+include(GetGitVersion)
+get_git_version(GIT_VERSION)
+
+# If no git version can be determined, use the version
+# from the project() command
+if ("${GIT_VERSION}" STREQUAL "0.0.0")
+  set(VERSION "${benchmark_VERSION}")
+else()
+  set(VERSION "${GIT_VERSION}")
+endif()
+# Tell the user what versions we are using
+message(STATUS "Version: ${VERSION}")
+
+# The version of the libraries
+set(GENERIC_LIB_VERSION ${VERSION})
+string(SUBSTRING ${VERSION} 0 1 GENERIC_LIB_SOVERSION)
+
+# Import our CMake modules
+include(AddCXXCompilerFlag)
+include(CheckCXXCompilerFlag)
+include(CheckLibraryExists)
+include(CXXFeatureCheck)
+
+check_library_exists(rt shm_open "" HAVE_LIB_RT)
+
+if (BENCHMARK_BUILD_32_BITS)
+  add_required_cxx_compiler_flag(-m32)
+endif()
+
+if (MSVC)
+  set(BENCHMARK_CXX_STANDARD 14)
+else()
+  set(BENCHMARK_CXX_STANDARD 11)
+endif()
+
+set(CMAKE_CXX_STANDARD ${BENCHMARK_CXX_STANDARD})
+set(CMAKE_CXX_STANDARD_REQUIRED YES)
+set(CMAKE_CXX_EXTENSIONS OFF)
+
+if (MSVC)
+  # Turn compiler warnings up to 11
+  string(REGEX REPLACE "[-/]W[1-4]" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /W4")
+  add_definitions(-D_CRT_SECURE_NO_WARNINGS)
+
+  if (NOT BENCHMARK_ENABLE_EXCEPTIONS)
+    add_cxx_compiler_flag(-EHs-)
+    add_cxx_compiler_flag(-EHa-)
+    add_definitions(-D_HAS_EXCEPTIONS=0)
+  endif()
+  # Link time optimisation
+  if (BENCHMARK_ENABLE_LTO)
+    set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} /GL")
+    set(CMAKE_STATIC_LINKER_FLAGS_RELEASE "${CMAKE_STATIC_LINKER_FLAGS_RELEASE} /LTCG")
+    set(CMAKE_SHARED_LINKER_FLAGS_RELEASE "${CMAKE_SHARED_LINKER_FLAGS_RELEASE} /LTCG")
+    set(CMAKE_EXE_LINKER_FLAGS_RELEASE "${CMAKE_EXE_LINKER_FLAGS_RELEASE} /LTCG")
+
+    set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELWITHDEBINFO} /GL")
+    string(REGEX REPLACE "[-/]INCREMENTAL" "/INCREMENTAL:NO" CMAKE_STATIC_LINKER_FLAGS_RELWITHDEBINFO "${CMAKE_STATIC_LINKER_FLAGS_RELWITHDEBINFO}")
+    set(CMAKE_STATIC_LINKER_FLAGS_RELWITHDEBINFO "${CMAKE_STATIC_LINKER_FLAGS_RELWITHDEBINFO} /LTCG")
+    string(REGEX REPLACE "[-/]INCREMENTAL" "/INCREMENTAL:NO" CMAKE_SHARED_LINKER_FLAGS_RELWITHDEBINFO "${CMAKE_SHARED_LINKER_FLAGS_RELWITHDEBINFO}")
+    set(CMAKE_SHARED_LINKER_FLAGS_RELWITHDEBINFO "${CMAKE_SHARED_LINKER_FLAGS_RELWITHDEBINFO} /LTCG")
+    string(REGEX REPLACE "[-/]INCREMENTAL" "/INCREMENTAL:NO" CMAKE_EXE_LINKER_FLAGS_RELWITHDEBINFO "${CMAKE_EXE_LINKER_FLAGS_RELWITHDEBINFO}")
+    set(CMAKE_EXE_LINKER_FLAGS_RELWITHDEBINFO "${CMAKE_EXE_LINKER_FLAGS_RELWITHDEBINFO} /LTCG")
+
+    set(CMAKE_CXX_FLAGS_MINSIZEREL "${CMAKE_CXX_FLAGS_MINSIZEREL} /GL")
+    set(CMAKE_STATIC_LINKER_FLAGS_MINSIZEREL "${CMAKE_STATIC_LINKER_FLAGS_MINSIZEREL} /LTCG")
+    set(CMAKE_SHARED_LINKER_FLAGS_MINSIZEREL "${CMAKE_SHARED_LINKER_FLAGS_MINSIZEREL} /LTCG")
+    set(CMAKE_EXE_LINKER_FLAGS_MINSIZEREL "${CMAKE_EXE_LINKER_FLAGS_MINSIZEREL} /LTCG")
+  endif()
+else()
+  # Turn compiler warnings up to 11
+  add_cxx_compiler_flag(-Wall)
+  add_cxx_compiler_flag(-Wextra)
+  add_cxx_compiler_flag(-Wshadow)
+  add_cxx_compiler_flag(-Wfloat-equal)
+  if(BENCHMARK_ENABLE_WERROR)
+      add_cxx_compiler_flag(-Werror)
+  endif()
+  if (NOT BENCHMARK_ENABLE_TESTING)
+    # Disable warning when compiling tests as gtest does not use 'override'.
+    add_cxx_compiler_flag(-Wsuggest-override)
+  endif()
+  add_cxx_compiler_flag(-pedantic)
+  add_cxx_compiler_flag(-pedantic-errors)
+  add_cxx_compiler_flag(-Wshorten-64-to-32)
+  add_cxx_compiler_flag(-fstrict-aliasing)
+  # Disable warnings regarding deprecated parts of the library while building
+  # and testing those parts of the library.
+  add_cxx_compiler_flag(-Wno-deprecated-declarations)
+  if (CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
+    # Intel silently ignores '-Wno-deprecated-declarations',
+    # warning no. 1786 must be explicitly disabled.
+    # See #631 for rationale.
+    add_cxx_compiler_flag(-wd1786)
+  endif()
+  # Disable deprecation warnings for release builds (when -Werror is enabled).
+  if(BENCHMARK_ENABLE_WERROR)
+      add_cxx_compiler_flag(-Wno-deprecated)
+  endif()
+  if (NOT BENCHMARK_ENABLE_EXCEPTIONS)
+    add_cxx_compiler_flag(-fno-exceptions)
+  endif()
+
+  if (HAVE_CXX_FLAG_FSTRICT_ALIASING)
+    if (NOT CMAKE_CXX_COMPILER_ID STREQUAL "Intel") #ICC17u2: Many false positives for Wstrict-aliasing
+      add_cxx_compiler_flag(-Wstrict-aliasing)
+    endif()
+  endif()
+  # ICC17u2: overloaded virtual function "benchmark::Fixture::SetUp" is only partially overridden
+  # (because of deprecated overload)
+  add_cxx_compiler_flag(-wd654)
+  add_cxx_compiler_flag(-Wthread-safety)
+  if (HAVE_CXX_FLAG_WTHREAD_SAFETY)
+    cxx_feature_check(THREAD_SAFETY_ATTRIBUTES "-DINCLUDE_DIRECTORIES=${PROJECT_SOURCE_DIR}/include")
+  endif()
+
+  # On most UNIX like platforms g++ and clang++ define _GNU_SOURCE as a
+  # predefined macro, which turns on all of the wonderful libc extensions.
+  # However g++ doesn't do this in Cygwin so we have to define it ourselves
+  # since we depend on GNU/POSIX/BSD extensions.
+  if (CYGWIN)
+    add_definitions(-D_GNU_SOURCE=1)
+  endif()
+
+  if (QNXNTO)
+    add_definitions(-D_QNX_SOURCE)
+  endif()
+
+  # Link time optimisation
+  if (BENCHMARK_ENABLE_LTO)
+    add_cxx_compiler_flag(-flto)
+    add_cxx_compiler_flag(-Wno-lto-type-mismatch)
+    if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
+      find_program(GCC_AR gcc-ar)
+      if (GCC_AR)
+        set(CMAKE_AR ${GCC_AR})
+      endif()
+      find_program(GCC_RANLIB gcc-ranlib)
+      if (GCC_RANLIB)
+        set(CMAKE_RANLIB ${GCC_RANLIB})
+      endif()
+    elseif("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
+      include(llvm-toolchain)
+    endif()
+  endif()
+
+  # Coverage build type
+  set(BENCHMARK_CXX_FLAGS_COVERAGE "${CMAKE_CXX_FLAGS_DEBUG}"
+    CACHE STRING "Flags used by the C++ compiler during coverage builds."
+    FORCE)
+  set(BENCHMARK_EXE_LINKER_FLAGS_COVERAGE "${CMAKE_EXE_LINKER_FLAGS_DEBUG}"
+    CACHE STRING "Flags used for linking binaries during coverage builds."
+    FORCE)
+  set(BENCHMARK_SHARED_LINKER_FLAGS_COVERAGE "${CMAKE_SHARED_LINKER_FLAGS_DEBUG}"
+    CACHE STRING "Flags used by the shared libraries linker during coverage builds."
+    FORCE)
+  mark_as_advanced(
+    BENCHMARK_CXX_FLAGS_COVERAGE
+    BENCHMARK_EXE_LINKER_FLAGS_COVERAGE
+    BENCHMARK_SHARED_LINKER_FLAGS_COVERAGE)
+  set(CMAKE_BUILD_TYPE "${CMAKE_BUILD_TYPE}" CACHE STRING
+    "Choose the type of build, options are: None Debug Release RelWithDebInfo MinSizeRel Coverage.")
+  add_cxx_compiler_flag(--coverage COVERAGE)
+endif()
+
+if (BENCHMARK_USE_LIBCXX)
+  if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
+    add_cxx_compiler_flag(-stdlib=libc++)
+  elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU" OR
+          "${CMAKE_CXX_COMPILER_ID}" STREQUAL "Intel")
+    add_cxx_compiler_flag(-nostdinc++)
+    message(WARNING "libc++ header path must be manually specified using CMAKE_CXX_FLAGS")
+    # Adding -nodefaultlibs directly to CMAKE_<TYPE>_LINKER_FLAGS will break
+    # configuration checks such as 'find_package(Threads)'
+    list(APPEND BENCHMARK_CXX_LINKER_FLAGS -nodefaultlibs)
+    # -lc++ cannot be added directly to CMAKE_<TYPE>_LINKER_FLAGS because
+    # linker flags appear before all linker inputs and -lc++ must appear after.
+    list(APPEND BENCHMARK_CXX_LIBRARIES c++)
+  else()
+    message(FATAL_ERROR "-DBENCHMARK_USE_LIBCXX:BOOL=ON is not supported for compiler")
+  endif()
+endif(BENCHMARK_USE_LIBCXX)
+
+set(EXTRA_CXX_FLAGS "")
+if (WIN32 AND "${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
+  # Clang on Windows fails to compile the regex feature check under C++11
+  set(EXTRA_CXX_FLAGS "-DCMAKE_CXX_STANDARD=14")
+endif()
+
+# C++ feature checks
+# Determine the correct regular expression engine to use
+cxx_feature_check(STD_REGEX ${EXTRA_CXX_FLAGS})
+cxx_feature_check(GNU_POSIX_REGEX ${EXTRA_CXX_FLAGS})
+cxx_feature_check(POSIX_REGEX ${EXTRA_CXX_FLAGS})
+if(NOT HAVE_STD_REGEX AND NOT HAVE_GNU_POSIX_REGEX AND NOT HAVE_POSIX_REGEX)
+  message(FATAL_ERROR "Failed to determine the source files for the regular expression backend")
+endif()
+if (NOT BENCHMARK_ENABLE_EXCEPTIONS AND HAVE_STD_REGEX
+        AND NOT HAVE_GNU_POSIX_REGEX AND NOT HAVE_POSIX_REGEX)
+  message(WARNING "Using std::regex with exceptions disabled is not fully supported")
+endif()
+
+cxx_feature_check(STEADY_CLOCK)
+# Ensure we have pthreads
+set(THREADS_PREFER_PTHREAD_FLAG ON)
+find_package(Threads REQUIRED)
+cxx_feature_check(PTHREAD_AFFINITY)
+
+if (BENCHMARK_ENABLE_LIBPFM)
+  find_package(PFM)
+endif()
+
+# Set up directories
+include_directories(${PROJECT_SOURCE_DIR}/include)
+
+# Build the targets
+add_subdirectory(src)
+
+if (BENCHMARK_ENABLE_TESTING)
+  enable_testing()
+  if (BENCHMARK_ENABLE_GTEST_TESTS AND
+      NOT (TARGET gtest AND TARGET gtest_main AND
+           TARGET gmock AND TARGET gmock_main))
+    if (BENCHMARK_USE_BUNDLED_GTEST)
+      include(GoogleTest)
+    else()
+      find_package(GTest CONFIG REQUIRED)
+      add_library(gtest ALIAS GTest::gtest)
+      add_library(gtest_main ALIAS GTest::gtest_main)
+      add_library(gmock ALIAS GTest::gmock)
+      add_library(gmock_main ALIAS GTest::gmock_main)
+    endif()
+  endif()
+  add_subdirectory(test)
+endif()
diff --git a/leveldb_base/third_party/benchmark/CONTRIBUTING.md b/leveldb_base/third_party/benchmark/CONTRIBUTING.md
new file mode 100644
index 0000000..43de4c9
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/CONTRIBUTING.md
@@ -0,0 +1,58 @@
+# How to contribute #
+
+We'd love to accept your patches and contributions to this project.  There are
+a just a few small guidelines you need to follow.
+
+
+## Contributor License Agreement ##
+
+Contributions to any Google project must be accompanied by a Contributor
+License Agreement.  This is not a copyright **assignment**, it simply gives
+Google permission to use and redistribute your contributions as part of the
+project.
+
+  * If you are an individual writing original source code and you're sure you
+    own the intellectual property, then you'll need to sign an [individual
+    CLA][].
+
+  * If you work for a company that wants to allow you to contribute your work,
+    then you'll need to sign a [corporate CLA][].
+
+You generally only need to submit a CLA once, so if you've already submitted
+one (even if it was for a different project), you probably don't need to do it
+again.
+
+[individual CLA]: https://developers.google.com/open-source/cla/individual
+[corporate CLA]: https://developers.google.com/open-source/cla/corporate
+
+Once your CLA is submitted (or if you already submitted one for
+another Google project), make a commit adding yourself to the
+[AUTHORS][] and [CONTRIBUTORS][] files. This commit can be part
+of your first [pull request][].
+
+[AUTHORS]: AUTHORS
+[CONTRIBUTORS]: CONTRIBUTORS
+
+
+## Submitting a patch ##
+
+  1. It's generally best to start by opening a new issue describing the bug or
+     feature you're intending to fix.  Even if you think it's relatively minor,
+     it's helpful to know what people are working on.  Mention in the initial
+     issue that you are planning to work on that bug or feature so that it can
+     be assigned to you.
+
+  1. Follow the normal process of [forking][] the project, and setup a new
+     branch to work in.  It's important that each group of changes be done in
+     separate branches in order to ensure that a pull request only includes the
+     commits related to that bug or feature.
+
+  1. Do your best to have [well-formed commit messages][] for each change.
+     This provides consistency throughout the project, and ensures that commit
+     messages are able to be formatted properly by various git tools.
+
+  1. Finally, push the commits to your fork and submit a [pull request][].
+
+[forking]: https://help.github.com/articles/fork-a-repo
+[well-formed commit messages]: http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html
+[pull request]: https://help.github.com/articles/creating-a-pull-request
diff --git a/leveldb_base/third_party/benchmark/CONTRIBUTORS b/leveldb_base/third_party/benchmark/CONTRIBUTORS
new file mode 100644
index 0000000..56f03e2
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/CONTRIBUTORS
@@ -0,0 +1,94 @@
+# People who have agreed to one of the CLAs and can contribute patches.
+# The AUTHORS file lists the copyright holders; this file
+# lists people.  For example, Google employees are listed here
+# but not in AUTHORS, because Google holds the copyright.
+#
+# Names should be added to this file only after verifying that
+# the individual or the individual's organization has agreed to
+# the appropriate Contributor License Agreement, found here:
+#
+# https://developers.google.com/open-source/cla/individual
+# https://developers.google.com/open-source/cla/corporate
+#
+# The agreement for individuals can be filled out on the web.
+#
+# When adding J Random Contributor's name to this file,
+# either J's name or J's organization's name should be
+# added to the AUTHORS file, depending on whether the
+# individual or corporate CLA was used.
+#
+# Names should be added to this file as:
+#     Name <email address>
+#
+# Please keep the list sorted.
+
+Abhina Sreeskantharajan <abhina.sreeskantharajan@ibm.com>
+Albert Pretorius <pretoalb@gmail.com>
+Alex Steele <steelal123@gmail.com>
+Andriy Berestovskyy <berestovskyy@gmail.com>
+Arne Beer <arne@twobeer.de>
+Bátor Tallér <bator.taller@shapr3d.com>
+Billy Robert O'Neal III <billy.oneal@gmail.com> <bion@microsoft.com>
+Cezary Skrzyński <czars1988@gmail.com>
+Chris Kennelly <ckennelly@google.com> <ckennelly@ckennelly.com>
+Christian Wassermann <christian_wassermann@web.de>
+Christopher Seymour <chris.j.seymour@hotmail.com>
+Colin Braley <braley.colin@gmail.com>
+Cyrille Faucheux <cyrille.faucheux@gmail.com>
+Daniel Harvey <danielharvey458@gmail.com>
+David Coeurjolly <david.coeurjolly@liris.cnrs.fr>
+Deniz Evrenci <denizevrenci@gmail.com>
+Dominic Hamon <dma@stripysock.com> <dominic@google.com>
+Dominik Czarnota <dominik.b.czarnota@gmail.com>
+Dominik Korman <kormandominik@gmail.com>
+Donald Aingworth <donalds_junk_mail@yahoo.com>
+Eric Backus <eric_backus@alum.mit.edu>
+Eric Fiselier <eric@efcs.ca>
+Eugene Zhuk <eugene.zhuk@gmail.com>
+Evgeny Safronov <division494@gmail.com>
+Fanbo Meng <fanbo.meng@ibm.com>
+Federico Ficarelli <federico.ficarelli@gmail.com>
+Felix Homann <linuxaudio@showlabor.de>
+Geoffrey Martin-Noble <gcmn@google.com> <gmngeoffrey@gmail.com>
+Gergő Szitár <szitar.gergo@gmail.com>
+Hannes Hauswedell <h2@fsfe.org>
+Henrique Bucher <hbucher@gmail.com>
+Ismael Jimenez Martinez <ismael.jimenez.martinez@gmail.com>
+Jern-Kuan Leong <jernkuan@gmail.com>
+JianXiong Zhou <zhoujianxiong2@gmail.com>
+Joao Paulo Magalhaes <joaoppmagalhaes@gmail.com>
+John Millikin <jmillikin@stripe.com>
+Jordan Williams <jwillikers@protonmail.com>
+Jussi Knuuttila <jussi.knuuttila@gmail.com>
+Kai Wolf <kai.wolf@gmail.com>
+Kaito Udagawa <umireon@gmail.com>
+Kishan Kumar <kumar.kishan@outlook.com>
+Lei Xu <eddyxu@gmail.com>
+Marcel Jacobse <mjacobse@uni-bremen.de>
+Matt Clarkson <mattyclarkson@gmail.com>
+Maxim Vafin <maxvafin@gmail.com>
+Mike Apodaca <gatorfax@gmail.com>
+Nick Hutchinson <nshutchinson@gmail.com>
+Norman Heino <norman.heino@gmail.com>
+Oleksandr Sochka <sasha.sochka@gmail.com>
+Ori Livneh <ori.livneh@gmail.com>
+Pascal Leroy <phl@google.com>
+Paul Redmond <paul.redmond@gmail.com>
+Pierre Phaneuf <pphaneuf@google.com>
+Radoslav Yovchev <radoslav.tm@gmail.com>
+Rainer Orth <ro@cebitec.uni-bielefeld.de>
+Raghu Raja <raghu@enfabrica.net>
+Raul Marin <rmrodriguez@cartodb.com>
+Ray Glover <ray.glover@uk.ibm.com>
+Robert Guo <robert.guo@mongodb.com>
+Roman Lebedev <lebedev.ri@gmail.com>
+Sayan Bhattacharjee <aero.sayan@gmail.com>
+Shuo Chen <chenshuo@chenshuo.com>
+Steven Wan <wan.yu@ibm.com>
+Tobias Schmidt <tobias.schmidt@in.tum.de>
+Tobias Ulvgård <tobias.ulvgard@dirac.se>
+Tom Madams <tom.ej.madams@gmail.com> <tmadams@google.com>
+Yixuan Qiu <yixuanq@gmail.com>
+Yusuke Suzuki <utatane.tea@gmail.com>
+Zbigniew Skowron <zbychs@gmail.com>
+Min-Yih Hsu <yihshyng223@gmail.com>
diff --git a/leveldb_base/third_party/benchmark/LICENSE b/leveldb_base/third_party/benchmark/LICENSE
new file mode 100644
index 0000000..d645695
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/LICENSE
@@ -0,0 +1,202 @@
+
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
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+      direction or management of such entity, whether by contract or
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+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
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+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
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+
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+      the original version of the Work and any modifications or additions
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+      "Contributor" shall mean Licensor and any individual or Legal Entity
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+
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+   4. Redistribution. You may reproduce and distribute copies of the
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+
+      (c) You must retain, in the Source form of any Derivative Works
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+
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+   5. Submission of Contributions. Unless You explicitly state otherwise,
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+
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+   you may not use this file except in compliance with the License.
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+
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diff --git a/leveldb_base/third_party/benchmark/README.md b/leveldb_base/third_party/benchmark/README.md
new file mode 100644
index 0000000..b64048b
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/README.md
@@ -0,0 +1,224 @@
+# Benchmark
+
+[![build-and-test](https://github.com/google/benchmark/workflows/build-and-test/badge.svg)](https://github.com/google/benchmark/actions?query=workflow%3Abuild-and-test)
+[![bazel](https://github.com/google/benchmark/actions/workflows/bazel.yml/badge.svg)](https://github.com/google/benchmark/actions/workflows/bazel.yml)
+[![pylint](https://github.com/google/benchmark/workflows/pylint/badge.svg)](https://github.com/google/benchmark/actions?query=workflow%3Apylint)
+[![test-bindings](https://github.com/google/benchmark/workflows/test-bindings/badge.svg)](https://github.com/google/benchmark/actions?query=workflow%3Atest-bindings)
+
+[![Build Status](https://travis-ci.org/google/benchmark.svg?branch=main)](https://travis-ci.org/google/benchmark)
+[![Coverage Status](https://coveralls.io/repos/google/benchmark/badge.svg)](https://coveralls.io/r/google/benchmark)
+
+
+A library to benchmark code snippets, similar to unit tests. Example:
+
+```c++
+#include <benchmark/benchmark.h>
+
+static void BM_SomeFunction(benchmark::State& state) {
+  // Perform setup here
+  for (auto _ : state) {
+    // This code gets timed
+    SomeFunction();
+  }
+}
+// Register the function as a benchmark
+BENCHMARK(BM_SomeFunction);
+// Run the benchmark
+BENCHMARK_MAIN();
+```
+
+## Getting Started
+
+To get started, see [Requirements](#requirements) and
+[Installation](#installation). See [Usage](#usage) for a full example and the
+[User Guide](docs/user_guide.md) for a more comprehensive feature overview.
+
+It may also help to read the [Google Test documentation](https://github.com/google/googletest/blob/main/docs/primer.md)
+as some of the structural aspects of the APIs are similar.
+
+## Resources
+
+[Discussion group](https://groups.google.com/d/forum/benchmark-discuss)
+
+IRC channels:
+* [libera](https://libera.chat) #benchmark
+
+[Additional Tooling Documentation](docs/tools.md)
+
+[Assembly Testing Documentation](docs/AssemblyTests.md)
+
+[Building and installing Python bindings](docs/python_bindings.md)
+
+## Requirements
+
+The library can be used with C++03. However, it requires C++11 to build,
+including compiler and standard library support.
+
+The following minimum versions are required to build the library:
+
+* GCC 4.8
+* Clang 3.4
+* Visual Studio 14 2015
+* Intel 2015 Update 1
+
+See [Platform-Specific Build Instructions](docs/platform_specific_build_instructions.md).
+
+## Installation
+
+This describes the installation process using cmake. As pre-requisites, you'll
+need git and cmake installed.
+
+_See [dependencies.md](docs/dependencies.md) for more details regarding supported
+versions of build tools._
+
+```bash
+# Check out the library.
+$ git clone https://github.com/google/benchmark.git
+# Go to the library root directory
+$ cd benchmark
+# Make a build directory to place the build output.
+$ cmake -E make_directory "build"
+# Generate build system files with cmake, and download any dependencies.
+$ cmake -E chdir "build" cmake -DBENCHMARK_DOWNLOAD_DEPENDENCIES=on -DCMAKE_BUILD_TYPE=Release ../
+# or, starting with CMake 3.13, use a simpler form:
+# cmake -DCMAKE_BUILD_TYPE=Release -S . -B "build"
+# Build the library.
+$ cmake --build "build" --config Release
+```
+This builds the `benchmark` and `benchmark_main` libraries and tests.
+On a unix system, the build directory should now look something like this:
+
+```
+/benchmark
+  /build
+    /src
+      /libbenchmark.a
+      /libbenchmark_main.a
+    /test
+      ...
+```
+
+Next, you can run the tests to check the build.
+
+```bash
+$ cmake -E chdir "build" ctest --build-config Release
+```
+
+If you want to install the library globally, also run:
+
+```
+sudo cmake --build "build" --config Release --target install
+```
+
+Note that Google Benchmark requires Google Test to build and run the tests. This
+dependency can be provided two ways:
+
+* Checkout the Google Test sources into `benchmark/googletest`.
+* Otherwise, if `-DBENCHMARK_DOWNLOAD_DEPENDENCIES=ON` is specified during
+  configuration as above, the library will automatically download and build
+  any required dependencies.
+
+If you do not wish to build and run the tests, add `-DBENCHMARK_ENABLE_GTEST_TESTS=OFF`
+to `CMAKE_ARGS`.
+
+### Debug vs Release
+
+By default, benchmark builds as a debug library. You will see a warning in the
+output when this is the case. To build it as a release library instead, add
+`-DCMAKE_BUILD_TYPE=Release` when generating the build system files, as shown
+above. The use of `--config Release` in build commands is needed to properly
+support multi-configuration tools (like Visual Studio for example) and can be
+skipped for other build systems (like Makefile).
+
+To enable link-time optimisation, also add `-DBENCHMARK_ENABLE_LTO=true` when
+generating the build system files.
+
+If you are using gcc, you might need to set `GCC_AR` and `GCC_RANLIB` cmake
+cache variables, if autodetection fails.
+
+If you are using clang, you may need to set `LLVMAR_EXECUTABLE`,
+`LLVMNM_EXECUTABLE` and `LLVMRANLIB_EXECUTABLE` cmake cache variables.
+
+To enable sanitizer checks (eg., `asan` and `tsan`), add:
+```
+ -DCMAKE_C_FLAGS="-g -O2 -fno-omit-frame-pointer -fsanitize=address -fsanitize=thread -fno-sanitize-recover=all"
+ -DCMAKE_CXX_FLAGS="-g -O2 -fno-omit-frame-pointer -fsanitize=address -fsanitize=thread -fno-sanitize-recover=all "  
+```
+
+### Stable and Experimental Library Versions
+
+The main branch contains the latest stable version of the benchmarking library;
+the API of which can be considered largely stable, with source breaking changes
+being made only upon the release of a new major version.
+
+Newer, experimental, features are implemented and tested on the
+[`v2` branch](https://github.com/google/benchmark/tree/v2). Users who wish
+to use, test, and provide feedback on the new features are encouraged to try
+this branch. However, this branch provides no stability guarantees and reserves
+the right to change and break the API at any time.
+
+## Usage
+
+### Basic usage
+
+Define a function that executes the code to measure, register it as a benchmark
+function using the `BENCHMARK` macro, and ensure an appropriate `main` function
+is available:
+
+```c++
+#include <benchmark/benchmark.h>
+
+static void BM_StringCreation(benchmark::State& state) {
+  for (auto _ : state)
+    std::string empty_string;
+}
+// Register the function as a benchmark
+BENCHMARK(BM_StringCreation);
+
+// Define another benchmark
+static void BM_StringCopy(benchmark::State& state) {
+  std::string x = "hello";
+  for (auto _ : state)
+    std::string copy(x);
+}
+BENCHMARK(BM_StringCopy);
+
+BENCHMARK_MAIN();
+```
+
+To run the benchmark, compile and link against the `benchmark` library
+(libbenchmark.a/.so). If you followed the build steps above, this library will 
+be under the build directory you created.
+
+```bash
+# Example on linux after running the build steps above. Assumes the
+# `benchmark` and `build` directories are under the current directory.
+$ g++ mybenchmark.cc -std=c++11 -isystem benchmark/include \
+  -Lbenchmark/build/src -lbenchmark -lpthread -o mybenchmark
+```
+
+Alternatively, link against the `benchmark_main` library and remove
+`BENCHMARK_MAIN();` above to get the same behavior.
+
+The compiled executable will run all benchmarks by default. Pass the `--help`
+flag for option information or see the [User Guide](docs/user_guide.md).
+
+### Usage with CMake
+
+If using CMake, it is recommended to link against the project-provided
+`benchmark::benchmark` and `benchmark::benchmark_main` targets using
+`target_link_libraries`.
+It is possible to use ```find_package``` to import an installed version of the
+library.
+```cmake
+find_package(benchmark REQUIRED)
+```
+Alternatively, ```add_subdirectory``` will incorporate the library directly in
+to one's CMake project.
+```cmake
+add_subdirectory(benchmark)
+```
+Either way, link to the library as follows.
+```cmake
+target_link_libraries(MyTarget benchmark::benchmark)
+```
diff --git a/leveldb_base/third_party/benchmark/WORKSPACE b/leveldb_base/third_party/benchmark/WORKSPACE
new file mode 100644
index 0000000..74e7ebc
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/WORKSPACE
@@ -0,0 +1,22 @@
+workspace(name = "com_github_google_benchmark")
+
+load("//:bazel/benchmark_deps.bzl", "benchmark_deps")
+
+benchmark_deps()
+
+load("@rules_foreign_cc//foreign_cc:repositories.bzl", "rules_foreign_cc_dependencies")
+
+rules_foreign_cc_dependencies()
+
+load("@rules_python//python:pip.bzl", pip3_install="pip_install")
+
+pip3_install(
+   name = "py_deps",
+   requirements = "//:requirements.txt",
+)
+
+new_local_repository(
+    name = "python_headers",
+    build_file = "@//bindings/python:python_headers.BUILD",
+    path = "<PYTHON_INCLUDE_PATH>",  # May be overwritten by setup.py.
+)
diff --git a/leveldb_base/third_party/benchmark/_config.yml b/leveldb_base/third_party/benchmark/_config.yml
new file mode 100644
index 0000000..1fa5ff8
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/_config.yml
@@ -0,0 +1,2 @@
+theme: jekyll-theme-midnight
+markdown: GFM
diff --git a/leveldb_base/third_party/benchmark/appveyor.yml b/leveldb_base/third_party/benchmark/appveyor.yml
new file mode 100644
index 0000000..81da955
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/appveyor.yml
@@ -0,0 +1,50 @@
+version: '{build}'
+
+image: Visual Studio 2017
+
+configuration:
+  - Debug
+  - Release
+
+environment:
+  matrix:
+    - compiler: msvc-15-seh
+      generator: "Visual Studio 15 2017"
+
+    - compiler: msvc-15-seh
+      generator: "Visual Studio 15 2017 Win64"
+
+    - compiler: msvc-14-seh
+      generator: "Visual Studio 14 2015"
+
+    - compiler: msvc-14-seh
+      generator: "Visual Studio 14 2015 Win64"
+
+    - compiler: gcc-5.3.0-posix
+      generator: "MinGW Makefiles"
+      cxx_path: 'C:\mingw-w64\i686-5.3.0-posix-dwarf-rt_v4-rev0\mingw32\bin'
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+
+matrix:
+  fast_finish: true
+
+install:
+  # git bash conflicts with MinGW makefiles
+  - if "%generator%"=="MinGW Makefiles" (set "PATH=%PATH:C:\Program Files\Git\usr\bin;=%")
+  - if not "%cxx_path%"=="" (set "PATH=%PATH%;%cxx_path%")
+
+build_script:
+  - md _build -Force
+  - cd _build
+  - echo %configuration%
+  - cmake -G "%generator%" "-DCMAKE_BUILD_TYPE=%configuration%" -DBENCHMARK_DOWNLOAD_DEPENDENCIES=ON ..
+  - cmake --build . --config %configuration%
+
+test_script:
+  - ctest --build-config %configuration% --timeout 300 --output-on-failure
+
+artifacts:
+  - path: '_build/CMakeFiles/*.log'
+    name: logs
+  - path: '_build/Testing/**/*.xml'
+    name: test_results
diff --git a/leveldb_base/third_party/benchmark/bazel/benchmark_deps.bzl b/leveldb_base/third_party/benchmark/bazel/benchmark_deps.bzl
new file mode 100644
index 0000000..e9ca2ce
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/bazel/benchmark_deps.bzl
@@ -0,0 +1,66 @@
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+load("@bazel_tools//tools/build_defs/repo:git.bzl", "new_git_repository")
+
+def benchmark_deps():
+    """Loads dependencies required to build Google Benchmark."""
+
+    if "bazel_skylib" not in native.existing_rules():
+        http_archive(
+            name = "bazel_skylib",
+            sha256 = "f7be3474d42aae265405a592bb7da8e171919d74c16f082a5457840f06054728",
+            urls = [
+                "https://mirror.bazel.build/github.com/bazelbuild/bazel-skylib/releases/download/1.2.1/bazel-skylib-1.2.1.tar.gz",
+                "https://github.com/bazelbuild/bazel-skylib/releases/download/1.2.1/bazel-skylib-1.2.1.tar.gz",
+            ],
+        )
+
+    if "rules_foreign_cc" not in native.existing_rules():
+        http_archive(
+            name = "rules_foreign_cc",
+            sha256 = "bcd0c5f46a49b85b384906daae41d277b3dc0ff27c7c752cc51e43048a58ec83",
+            strip_prefix = "rules_foreign_cc-0.7.1",
+            url = "https://github.com/bazelbuild/rules_foreign_cc/archive/0.7.1.tar.gz",
+        )
+
+    if "rules_python" not in native.existing_rules():
+        http_archive(
+            name = "rules_python",
+            url = "https://github.com/bazelbuild/rules_python/releases/download/0.1.0/rules_python-0.1.0.tar.gz",
+            sha256 = "b6d46438523a3ec0f3cead544190ee13223a52f6a6765a29eae7b7cc24cc83a0",
+        )
+
+    if "com_google_absl" not in native.existing_rules():
+        http_archive(
+            name = "com_google_absl",
+            sha256 = "f41868f7a938605c92936230081175d1eae87f6ea2c248f41077c8f88316f111",
+            strip_prefix = "abseil-cpp-20200225.2",
+            urls = ["https://github.com/abseil/abseil-cpp/archive/20200225.2.tar.gz"],
+        )
+
+    if "com_google_googletest" not in native.existing_rules():
+        new_git_repository(
+            name = "com_google_googletest",
+            remote = "https://github.com/google/googletest.git",
+            tag = "release-1.11.0",
+        )
+
+    if "nanobind" not in native.existing_rules():
+        new_git_repository(
+            name = "nanobind",
+            remote = "https://github.com/wjakob/nanobind.git",
+            commit = "1ffbfe836c9dac599496a170274ee0075094a607", # v0.2.0
+            shallow_since = "1677873085 +0100",
+            build_file = "@//bindings/python:nanobind.BUILD",
+            recursive_init_submodules = True,
+        )
+
+    if "libpfm" not in native.existing_rules():
+        # Downloaded from v4.9.0 tag at https://sourceforge.net/p/perfmon2/libpfm4/ref/master/tags/
+        http_archive(
+            name = "libpfm",
+            build_file = str(Label("//tools:libpfm.BUILD.bazel")),
+            sha256 = "5da5f8872bde14b3634c9688d980f68bda28b510268723cc12973eedbab9fecc",
+            type = "tar.gz",
+            strip_prefix = "libpfm-4.11.0",
+            urls = ["https://sourceforge.net/projects/perfmon2/files/libpfm4/libpfm-4.11.0.tar.gz/download"],
+        )
diff --git a/leveldb_base/third_party/benchmark/bindings/python/BUILD b/leveldb_base/third_party/benchmark/bindings/python/BUILD
new file mode 100644
index 0000000..9559a76
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/bindings/python/BUILD
@@ -0,0 +1,3 @@
+exports_files(glob(["*.BUILD"]))
+exports_files(["build_defs.bzl"])
+
diff --git a/leveldb_base/third_party/benchmark/bindings/python/build_defs.bzl b/leveldb_base/third_party/benchmark/bindings/python/build_defs.bzl
new file mode 100644
index 0000000..009820a
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/bindings/python/build_defs.bzl
@@ -0,0 +1,25 @@
+_SHARED_LIB_SUFFIX = {
+    "//conditions:default": ".so",
+    "//:windows": ".dll",
+}
+
+def py_extension(name, srcs, hdrs = [], copts = [], features = [], deps = []):
+    for shared_lib_suffix in _SHARED_LIB_SUFFIX.values():
+        shared_lib_name = name + shared_lib_suffix
+        native.cc_binary(
+            name = shared_lib_name,
+            linkshared = True,
+            linkstatic = True,
+            srcs = srcs + hdrs,
+            copts = copts,
+            features = features,
+            deps = deps,
+        )
+
+    return native.py_library(
+        name = name,
+        data = select({
+            platform: [name + shared_lib_suffix]
+            for platform, shared_lib_suffix in _SHARED_LIB_SUFFIX.items()
+        }),
+    )
diff --git a/leveldb_base/third_party/benchmark/bindings/python/google_benchmark/BUILD b/leveldb_base/third_party/benchmark/bindings/python/google_benchmark/BUILD
new file mode 100644
index 0000000..89ec76e
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/bindings/python/google_benchmark/BUILD
@@ -0,0 +1,40 @@
+load("//bindings/python:build_defs.bzl", "py_extension")
+
+py_library(
+    name = "google_benchmark",
+    srcs = ["__init__.py"],
+    visibility = ["//visibility:public"],
+    deps = [
+        ":_benchmark",
+    ],
+)
+
+py_extension(
+    name = "_benchmark",
+    srcs = ["benchmark.cc"],
+    copts = [
+        "-fexceptions",
+        "-fno-strict-aliasing",
+    ],
+    features = [
+        "-use_header_modules",
+        "-parse_headers",
+    ],
+    deps = [
+        "//:benchmark",
+        "@nanobind",
+        "@python_headers",
+    ],
+)
+
+py_test(
+    name = "example",
+    srcs = ["example.py"],
+    python_version = "PY3",
+    srcs_version = "PY3",
+    visibility = ["//visibility:public"],
+    deps = [
+        ":google_benchmark",
+    ],
+)
+
diff --git a/leveldb_base/third_party/benchmark/bindings/python/google_benchmark/__init__.py b/leveldb_base/third_party/benchmark/bindings/python/google_benchmark/__init__.py
new file mode 100644
index 0000000..e6ef8e7
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/bindings/python/google_benchmark/__init__.py
@@ -0,0 +1,162 @@
+# Copyright 2020 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Python benchmarking utilities.
+
+Example usage:
+  import google_benchmark as benchmark
+
+  @benchmark.register
+  def my_benchmark(state):
+      ...  # Code executed outside `while` loop is not timed.
+
+      while state:
+        ...  # Code executed within `while` loop is timed.
+
+  if __name__ == '__main__':
+    benchmark.main()
+"""
+import atexit
+
+from absl import app
+from google_benchmark import _benchmark
+from google_benchmark._benchmark import (
+    Counter,
+    kNanosecond,
+    kMicrosecond,
+    kMillisecond,
+    kSecond,
+    oNone,
+    o1,
+    oN,
+    oNSquared,
+    oNCubed,
+    oLogN,
+    oNLogN,
+    oAuto,
+    oLambda,
+    State,
+)
+
+
+__all__ = [
+    "register",
+    "main",
+    "Counter",
+    "kNanosecond",
+    "kMicrosecond",
+    "kMillisecond",
+    "kSecond",
+    "oNone",
+    "o1",
+    "oN",
+    "oNSquared",
+    "oNCubed",
+    "oLogN",
+    "oNLogN",
+    "oAuto",
+    "oLambda",
+    "State",
+]
+
+__version__ = "1.7.1"
+
+
+class __OptionMaker:
+    """A stateless class to collect benchmark options.
+
+    Collect all decorator calls like @option.range(start=0, limit=1<<5).
+    """
+
+    class Options:
+        """Pure data class to store options calls, along with the benchmarked function."""
+
+        def __init__(self, func):
+            self.func = func
+            self.builder_calls = []
+
+    @classmethod
+    def make(cls, func_or_options):
+        """Make Options from Options or the benchmarked function."""
+        if isinstance(func_or_options, cls.Options):
+            return func_or_options
+        return cls.Options(func_or_options)
+
+    def __getattr__(self, builder_name):
+        """Append option call in the Options."""
+
+        # The function that get returned on @option.range(start=0, limit=1<<5).
+        def __builder_method(*args, **kwargs):
+
+            # The decorator that get called, either with the benchmared function
+            # or the previous Options
+            def __decorator(func_or_options):
+                options = self.make(func_or_options)
+                options.builder_calls.append((builder_name, args, kwargs))
+                # The decorator returns Options so it is not technically a decorator
+                # and needs a final call to @register
+                return options
+
+            return __decorator
+
+        return __builder_method
+
+
+# Alias for nicer API.
+# We have to instantiate an object, even if stateless, to be able to use __getattr__
+# on option.range
+option = __OptionMaker()
+
+
+def register(undefined=None, *, name=None):
+    """Register function for benchmarking."""
+    if undefined is None:
+        # Decorator is called without parenthesis so we return a decorator
+        return lambda f: register(f, name=name)
+
+    # We have either the function to benchmark (simple case) or an instance of Options
+    # (@option._ case).
+    options = __OptionMaker.make(undefined)
+
+    if name is None:
+        name = options.func.__name__
+
+    # We register the benchmark and reproduce all the @option._ calls onto the
+    # benchmark builder pattern
+    benchmark = _benchmark.RegisterBenchmark(name, options.func)
+    for name, args, kwargs in options.builder_calls[::-1]:
+        getattr(benchmark, name)(*args, **kwargs)
+
+    # return the benchmarked function because the decorator does not modify it
+    return options.func
+
+
+def _flags_parser(argv):
+    argv = _benchmark.Initialize(argv)
+    return app.parse_flags_with_usage(argv)
+
+
+def _run_benchmarks(argv):
+    if len(argv) > 1:
+        raise app.UsageError("Too many command-line arguments.")
+    return _benchmark.RunSpecifiedBenchmarks()
+
+
+def main(argv=None):
+    return app.run(_run_benchmarks, argv=argv, flags_parser=_flags_parser)
+
+
+# Methods for use with custom main function.
+initialize = _benchmark.Initialize
+run_benchmarks = _benchmark.RunSpecifiedBenchmarks
+atexit.register(_benchmark.ClearRegisteredBenchmarks)
diff --git a/leveldb_base/third_party/benchmark/bindings/python/google_benchmark/benchmark.cc b/leveldb_base/third_party/benchmark/bindings/python/google_benchmark/benchmark.cc
new file mode 100644
index 0000000..f444769
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/bindings/python/google_benchmark/benchmark.cc
@@ -0,0 +1,184 @@
+// Benchmark for Python.
+
+#include "benchmark/benchmark.h"
+
+#include "nanobind/nanobind.h"
+#include "nanobind/operators.h"
+#include "nanobind/stl/bind_map.h"
+#include "nanobind/stl/string.h"
+#include "nanobind/stl/vector.h"
+
+NB_MAKE_OPAQUE(benchmark::UserCounters);
+
+namespace {
+namespace nb = nanobind;
+
+std::vector<std::string> Initialize(const std::vector<std::string>& argv) {
+  // The `argv` pointers here become invalid when this function returns, but
+  // benchmark holds the pointer to `argv[0]`. We create a static copy of it
+  // so it persists, and replace the pointer below.
+  static std::string executable_name(argv[0]);
+  std::vector<char*> ptrs;
+  ptrs.reserve(argv.size());
+  for (auto& arg : argv) {
+    ptrs.push_back(const_cast<char*>(arg.c_str()));
+  }
+  ptrs[0] = const_cast<char*>(executable_name.c_str());
+  int argc = static_cast<int>(argv.size());
+  benchmark::Initialize(&argc, ptrs.data());
+  std::vector<std::string> remaining_argv;
+  remaining_argv.reserve(argc);
+  for (int i = 0; i < argc; ++i) {
+    remaining_argv.emplace_back(ptrs[i]);
+  }
+  return remaining_argv;
+}
+
+benchmark::internal::Benchmark* RegisterBenchmark(const std::string& name,
+                                                  nb::callable f) {
+  return benchmark::RegisterBenchmark(
+      name, [f](benchmark::State& state) { f(&state); });
+}
+
+NB_MODULE(_benchmark, m) {
+
+  using benchmark::TimeUnit;
+  nb::enum_<TimeUnit>(m, "TimeUnit")
+      .value("kNanosecond", TimeUnit::kNanosecond)
+      .value("kMicrosecond", TimeUnit::kMicrosecond)
+      .value("kMillisecond", TimeUnit::kMillisecond)
+      .value("kSecond", TimeUnit::kSecond)
+      .export_values();
+
+  using benchmark::BigO;
+  nb::enum_<BigO>(m, "BigO")
+      .value("oNone", BigO::oNone)
+      .value("o1", BigO::o1)
+      .value("oN", BigO::oN)
+      .value("oNSquared", BigO::oNSquared)
+      .value("oNCubed", BigO::oNCubed)
+      .value("oLogN", BigO::oLogN)
+      .value("oNLogN", BigO::oNLogN)
+      .value("oAuto", BigO::oAuto)
+      .value("oLambda", BigO::oLambda)
+      .export_values();
+
+  using benchmark::internal::Benchmark;
+  nb::class_<Benchmark>(m, "Benchmark")
+      // For methods returning a pointer to the current object, reference
+      // return policy is used to ask nanobind not to take ownership of the
+      // returned object and avoid calling delete on it.
+      // https://pybind11.readthedocs.io/en/stable/advanced/functions.html#return-value-policies
+      //
+      // For methods taking a const std::vector<...>&, a copy is created
+      // because a it is bound to a Python list.
+      // https://pybind11.readthedocs.io/en/stable/advanced/cast/stl.html
+      .def("unit", &Benchmark::Unit, nb::rv_policy::reference)
+      .def("arg", &Benchmark::Arg, nb::rv_policy::reference)
+      .def("args", &Benchmark::Args, nb::rv_policy::reference)
+      .def("range", &Benchmark::Range, nb::rv_policy::reference,
+           nb::arg("start"), nb::arg("limit"))
+      .def("dense_range", &Benchmark::DenseRange,
+           nb::rv_policy::reference, nb::arg("start"),
+           nb::arg("limit"), nb::arg("step") = 1)
+      .def("ranges", &Benchmark::Ranges, nb::rv_policy::reference)
+      .def("args_product", &Benchmark::ArgsProduct,
+           nb::rv_policy::reference)
+      .def("arg_name", &Benchmark::ArgName, nb::rv_policy::reference)
+      .def("arg_names", &Benchmark::ArgNames,
+           nb::rv_policy::reference)
+      .def("range_pair", &Benchmark::RangePair,
+           nb::rv_policy::reference, nb::arg("lo1"), nb::arg("hi1"),
+           nb::arg("lo2"), nb::arg("hi2"))
+      .def("range_multiplier", &Benchmark::RangeMultiplier,
+           nb::rv_policy::reference)
+      .def("min_time", &Benchmark::MinTime, nb::rv_policy::reference)
+      .def("min_warmup_time", &Benchmark::MinWarmUpTime,
+           nb::rv_policy::reference)
+      .def("iterations", &Benchmark::Iterations,
+           nb::rv_policy::reference)
+      .def("repetitions", &Benchmark::Repetitions,
+           nb::rv_policy::reference)
+      .def("report_aggregates_only", &Benchmark::ReportAggregatesOnly,
+           nb::rv_policy::reference, nb::arg("value") = true)
+      .def("display_aggregates_only", &Benchmark::DisplayAggregatesOnly,
+           nb::rv_policy::reference, nb::arg("value") = true)
+      .def("measure_process_cpu_time", &Benchmark::MeasureProcessCPUTime,
+           nb::rv_policy::reference)
+      .def("use_real_time", &Benchmark::UseRealTime,
+           nb::rv_policy::reference)
+      .def("use_manual_time", &Benchmark::UseManualTime,
+           nb::rv_policy::reference)
+      .def(
+          "complexity",
+          (Benchmark * (Benchmark::*)(benchmark::BigO)) & Benchmark::Complexity,
+          nb::rv_policy::reference,
+          nb::arg("complexity") = benchmark::oAuto);
+
+  using benchmark::Counter;
+  nb::class_<Counter> py_counter(m, "Counter");
+
+  nb::enum_<Counter::Flags>(py_counter, "Flags")
+      .value("kDefaults", Counter::Flags::kDefaults)
+      .value("kIsRate", Counter::Flags::kIsRate)
+      .value("kAvgThreads", Counter::Flags::kAvgThreads)
+      .value("kAvgThreadsRate", Counter::Flags::kAvgThreadsRate)
+      .value("kIsIterationInvariant", Counter::Flags::kIsIterationInvariant)
+      .value("kIsIterationInvariantRate",
+             Counter::Flags::kIsIterationInvariantRate)
+      .value("kAvgIterations", Counter::Flags::kAvgIterations)
+      .value("kAvgIterationsRate", Counter::Flags::kAvgIterationsRate)
+      .value("kInvert", Counter::Flags::kInvert)
+      .export_values()
+      .def(nb::self | nb::self);
+
+  nb::enum_<Counter::OneK>(py_counter, "OneK")
+      .value("kIs1000", Counter::OneK::kIs1000)
+      .value("kIs1024", Counter::OneK::kIs1024)
+      .export_values();
+
+  py_counter
+      .def(nb::init<double, Counter::Flags, Counter::OneK>(),
+           nb::arg("value") = 0., nb::arg("flags") = Counter::kDefaults,
+           nb::arg("k") = Counter::kIs1000)
+      .def("__init__", ([](Counter *c, double value) { new (c) Counter(value); }))
+      .def_rw("value", &Counter::value)
+      .def_rw("flags", &Counter::flags)
+      .def_rw("oneK", &Counter::oneK)
+      .def(nb::init_implicit<double>());
+
+  nb::implicitly_convertible<nb::int_, Counter>();
+
+  nb::bind_map<benchmark::UserCounters>(m, "UserCounters");
+
+  using benchmark::State;
+  nb::class_<State>(m, "State")
+      .def("__bool__", &State::KeepRunning)
+      .def_prop_ro("keep_running", &State::KeepRunning)
+      .def("pause_timing", &State::PauseTiming)
+      .def("resume_timing", &State::ResumeTiming)
+      .def("skip_with_error", &State::SkipWithError)
+      .def_prop_ro("error_occurred", &State::error_occurred)
+      .def("set_iteration_time", &State::SetIterationTime)
+      .def_prop_rw("bytes_processed", &State::bytes_processed,
+                    &State::SetBytesProcessed)
+      .def_prop_rw("complexity_n", &State::complexity_length_n,
+                    &State::SetComplexityN)
+      .def_prop_rw("items_processed", &State::items_processed,
+                   &State::SetItemsProcessed)
+      .def("set_label", &State::SetLabel)
+      .def("range", &State::range, nb::arg("pos") = 0)
+      .def_prop_ro("iterations", &State::iterations)
+      .def_prop_ro("name", &State::name)
+      .def_rw("counters", &State::counters)
+      .def_prop_ro("thread_index", &State::thread_index)
+      .def_prop_ro("threads", &State::threads);
+
+  m.def("Initialize", Initialize);
+  m.def("RegisterBenchmark", RegisterBenchmark,
+        nb::rv_policy::reference);
+  m.def("RunSpecifiedBenchmarks",
+        []() { benchmark::RunSpecifiedBenchmarks(); });
+  m.def("ClearRegisteredBenchmarks", benchmark::ClearRegisteredBenchmarks);
+};
+}  // namespace
diff --git a/leveldb_base/third_party/benchmark/bindings/python/google_benchmark/example.py b/leveldb_base/third_party/benchmark/bindings/python/google_benchmark/example.py
new file mode 100644
index 0000000..d95a043
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/bindings/python/google_benchmark/example.py
@@ -0,0 +1,136 @@
+# Copyright 2020 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Example of Python using C++ benchmark framework.
+
+To run this example, you must first install the `google_benchmark` Python package.
+
+To install using `setup.py`, download and extract the `google_benchmark` source.
+In the extracted directory, execute:
+  python setup.py install
+"""
+
+import random
+import time
+
+import google_benchmark as benchmark
+from google_benchmark import Counter
+
+
+@benchmark.register
+def empty(state):
+    while state:
+        pass
+
+
+@benchmark.register
+def sum_million(state):
+    while state:
+        sum(range(1_000_000))
+
+@benchmark.register
+def pause_timing(state):
+    """Pause timing every iteration."""
+    while state:
+        # Construct a list of random ints every iteration without timing it
+        state.pause_timing()
+        random_list = [random.randint(0, 100) for _ in range(100)]
+        state.resume_timing()
+        # Time the in place sorting algorithm
+        random_list.sort()
+
+
+@benchmark.register
+def skipped(state):
+    if True:  # Test some predicate here.
+        state.skip_with_error("some error")
+        return  # NOTE: You must explicitly return, or benchmark will continue.
+
+    ...  # Benchmark code would be here.
+
+
+@benchmark.register
+def manual_timing(state):
+    while state:
+        # Manually count Python CPU time
+        start = time.perf_counter()  # perf_counter_ns() in Python 3.7+
+        # Something to benchmark
+        time.sleep(0.01)
+        end = time.perf_counter()
+        state.set_iteration_time(end - start)
+
+
+@benchmark.register
+def custom_counters(state):
+    """Collect custom metric using benchmark.Counter."""
+    num_foo = 0.0
+    while state:
+        # Benchmark some code here
+        pass
+        # Collect some custom metric named foo
+        num_foo += 0.13
+
+    # Automatic Counter from numbers.
+    state.counters["foo"] = num_foo
+    # Set a counter as a rate.
+    state.counters["foo_rate"] = Counter(num_foo, Counter.kIsRate)
+    #  Set a counter as an inverse of rate.
+    state.counters["foo_inv_rate"] = Counter(num_foo, Counter.kIsRate | Counter.kInvert)
+    # Set a counter as a thread-average quantity.
+    state.counters["foo_avg"] = Counter(num_foo, Counter.kAvgThreads)
+    # There's also a combined flag:
+    state.counters["foo_avg_rate"] = Counter(num_foo, Counter.kAvgThreadsRate)
+
+
+@benchmark.register
+@benchmark.option.measure_process_cpu_time()
+@benchmark.option.use_real_time()
+def with_options(state):
+    while state:
+        sum(range(1_000_000))
+
+
+@benchmark.register(name="sum_million_microseconds")
+@benchmark.option.unit(benchmark.kMicrosecond)
+def with_options2(state):
+    while state:
+        sum(range(1_000_000))
+
+
+@benchmark.register
+@benchmark.option.arg(100)
+@benchmark.option.arg(1000)
+def passing_argument(state):
+    while state:
+        sum(range(state.range(0)))
+
+
+@benchmark.register
+@benchmark.option.range(8, limit=8 << 10)
+def using_range(state):
+    while state:
+        sum(range(state.range(0)))
+
+
+@benchmark.register
+@benchmark.option.range_multiplier(2)
+@benchmark.option.range(1 << 10, 1 << 18)
+@benchmark.option.complexity(benchmark.oN)
+def computing_complexity(state):
+    while state:
+        sum(range(state.range(0)))
+    state.complexity_n = state.range(0)
+
+
+if __name__ == "__main__":
+    benchmark.main()
diff --git a/leveldb_base/third_party/benchmark/bindings/python/nanobind.BUILD b/leveldb_base/third_party/benchmark/bindings/python/nanobind.BUILD
new file mode 100644
index 0000000..35536bb
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/bindings/python/nanobind.BUILD
@@ -0,0 +1,56 @@
+
+config_setting(
+    name = "msvc_compiler",
+    flag_values = {"@bazel_tools//tools/cpp:compiler": "msvc-cl"},
+)
+
+cc_library(
+    name = "nanobind",
+    hdrs = glob(
+        include = [
+            "include/nanobind/*.h",
+            "include/nanobind/stl/*.h",
+            "include/nanobind/detail/*.h",
+        ],
+        exclude = [],
+    ),
+    srcs = [
+        "include/nanobind/stl/detail/nb_dict.h",
+        "include/nanobind/stl/detail/nb_list.h",
+        "include/nanobind/stl/detail/traits.h",
+        "ext/robin_map/include/tsl/robin_map.h",
+        "ext/robin_map/include/tsl/robin_hash.h",
+        "ext/robin_map/include/tsl/robin_growth_policy.h",
+        "ext/robin_map/include/tsl/robin_set.h",
+        "src/buffer.h",
+        "src/common.cpp",
+        "src/error.cpp",
+        "src/implicit.cpp",
+        "src/nb_enum.cpp",
+        "src/nb_func.cpp",
+        "src/nb_internals.cpp",
+        "src/nb_internals.h",
+        "src/nb_ndarray.cpp",
+        "src/nb_type.cpp",
+        "src/trampoline.cpp",
+    ],
+    copts = select({
+        ":msvc_compiler": [],
+        "//conditions:default": [
+        "-fexceptions",
+        "-Os",  # size optimization
+        "-flto", # enable LTO
+        ],
+    }),
+    linkopts = select({
+        "@com_github_google_benchmark//:macos": [
+        "-undefined dynamic_lookup",
+        "-Wl,-no_fixup_chains",
+        "-Wl,-dead_strip",
+        ],
+        "//conditions:default": [],
+    }),
+    includes = ["include", "ext/robin_map/include"],
+    deps = ["@python_headers"],
+    visibility = ["//visibility:public"],
+)
diff --git a/leveldb_base/third_party/benchmark/bindings/python/python_headers.BUILD b/leveldb_base/third_party/benchmark/bindings/python/python_headers.BUILD
new file mode 100644
index 0000000..9c34cf6
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/bindings/python/python_headers.BUILD
@@ -0,0 +1,6 @@
+cc_library(
+    name = "python_headers",
+    hdrs = glob(["**/*.h"]),
+    includes = ["."],
+    visibility = ["//visibility:public"],
+)
diff --git a/leveldb_base/third_party/benchmark/bindings/python/requirements.txt b/leveldb_base/third_party/benchmark/bindings/python/requirements.txt
new file mode 100644
index 0000000..f5bbe7e
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/bindings/python/requirements.txt
@@ -0,0 +1,2 @@
+absl-py>=0.7.1
+
diff --git a/leveldb_base/third_party/benchmark/cmake/AddCXXCompilerFlag.cmake b/leveldb_base/third_party/benchmark/cmake/AddCXXCompilerFlag.cmake
new file mode 100644
index 0000000..858589e
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/cmake/AddCXXCompilerFlag.cmake
@@ -0,0 +1,78 @@
+# - Adds a compiler flag if it is supported by the compiler
+#
+# This function checks that the supplied compiler flag is supported and then
+# adds it to the corresponding compiler flags
+#
+#  add_cxx_compiler_flag(<FLAG> [<VARIANT>])
+#
+# - Example
+#
+# include(AddCXXCompilerFlag)
+# add_cxx_compiler_flag(-Wall)
+# add_cxx_compiler_flag(-no-strict-aliasing RELEASE)
+# Requires CMake 2.6+
+
+if(__add_cxx_compiler_flag)
+  return()
+endif()
+set(__add_cxx_compiler_flag INCLUDED)
+
+include(CheckCXXCompilerFlag)
+
+function(mangle_compiler_flag FLAG OUTPUT)
+  string(TOUPPER "HAVE_CXX_FLAG_${FLAG}" SANITIZED_FLAG)
+  string(REPLACE "+" "X" SANITIZED_FLAG ${SANITIZED_FLAG})
+  string(REGEX REPLACE "[^A-Za-z_0-9]" "_" SANITIZED_FLAG ${SANITIZED_FLAG})
+  string(REGEX REPLACE "_+" "_" SANITIZED_FLAG ${SANITIZED_FLAG})
+  set(${OUTPUT} "${SANITIZED_FLAG}" PARENT_SCOPE)
+endfunction(mangle_compiler_flag)
+
+function(add_cxx_compiler_flag FLAG)
+  mangle_compiler_flag("${FLAG}" MANGLED_FLAG)
+  set(OLD_CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS}")
+  set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} ${FLAG}")
+  check_cxx_compiler_flag("${FLAG}" ${MANGLED_FLAG})
+  set(CMAKE_REQUIRED_FLAGS "${OLD_CMAKE_REQUIRED_FLAGS}")
+  if(${MANGLED_FLAG})
+    if(ARGC GREATER 1)
+      set(VARIANT ${ARGV1})
+      string(TOUPPER "_${VARIANT}" VARIANT)
+    else()
+      set(VARIANT "")
+    endif()
+    set(CMAKE_CXX_FLAGS${VARIANT} "${CMAKE_CXX_FLAGS${VARIANT}} ${BENCHMARK_CXX_FLAGS${VARIANT}} ${FLAG}" PARENT_SCOPE)
+  endif()
+endfunction()
+
+function(add_required_cxx_compiler_flag FLAG)
+  mangle_compiler_flag("${FLAG}" MANGLED_FLAG)
+  set(OLD_CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS}")
+  set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} ${FLAG}")
+  check_cxx_compiler_flag("${FLAG}" ${MANGLED_FLAG})
+  set(CMAKE_REQUIRED_FLAGS "${OLD_CMAKE_REQUIRED_FLAGS}")
+  if(${MANGLED_FLAG})
+    if(ARGC GREATER 1)
+      set(VARIANT ${ARGV1})
+      string(TOUPPER "_${VARIANT}" VARIANT)
+    else()
+      set(VARIANT "")
+    endif()
+    set(CMAKE_CXX_FLAGS${VARIANT} "${CMAKE_CXX_FLAGS${VARIANT}} ${FLAG}" PARENT_SCOPE)
+    set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${FLAG}" PARENT_SCOPE)
+    set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} ${FLAG}" PARENT_SCOPE)
+    set(CMAKE_MODULE_LINKER_FLAGS "${CMAKE_MODULE_LINKER_FLAGS} ${FLAG}" PARENT_SCOPE)
+    set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} ${FLAG}" PARENT_SCOPE)
+  else()
+    message(FATAL_ERROR "Required flag '${FLAG}' is not supported by the compiler")
+  endif()
+endfunction()
+
+function(check_cxx_warning_flag FLAG)
+  mangle_compiler_flag("${FLAG}" MANGLED_FLAG)
+  set(OLD_CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS}")
+  # Add -Werror to ensure the compiler generates an error if the warning flag
+  # doesn't exist.
+  set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -Werror ${FLAG}")
+  check_cxx_compiler_flag("${FLAG}" ${MANGLED_FLAG})
+  set(CMAKE_REQUIRED_FLAGS "${OLD_CMAKE_REQUIRED_FLAGS}")
+endfunction()
diff --git a/leveldb_base/third_party/benchmark/cmake/CXXFeatureCheck.cmake b/leveldb_base/third_party/benchmark/cmake/CXXFeatureCheck.cmake
new file mode 100644
index 0000000..e514826
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/cmake/CXXFeatureCheck.cmake
@@ -0,0 +1,82 @@
+# - Compile and run code to check for C++ features
+#
+# This functions compiles a source file under the `cmake` folder
+# and adds the corresponding `HAVE_[FILENAME]` flag to the CMake
+# environment
+#
+#  cxx_feature_check(<FLAG> [<VARIANT>])
+#
+# - Example
+#
+# include(CXXFeatureCheck)
+# cxx_feature_check(STD_REGEX)
+# Requires CMake 2.8.12+
+
+if(__cxx_feature_check)
+  return()
+endif()
+set(__cxx_feature_check INCLUDED)
+
+option(CXXFEATURECHECK_DEBUG OFF)
+
+function(cxx_feature_check FILE)
+  string(TOLOWER ${FILE} FILE)
+  string(TOUPPER ${FILE} VAR)
+  string(TOUPPER "HAVE_${VAR}" FEATURE)
+  if (DEFINED HAVE_${VAR})
+    set(HAVE_${VAR} 1 PARENT_SCOPE)
+    add_definitions(-DHAVE_${VAR})
+    return()
+  endif()
+
+  set(FEATURE_CHECK_CMAKE_FLAGS ${BENCHMARK_CXX_LINKER_FLAGS})
+  if (ARGC GREATER 1)
+    message(STATUS "Enabling additional flags: ${ARGV1}")
+    list(APPEND FEATURE_CHECK_CMAKE_FLAGS ${ARGV1})
+  endif()
+
+  if (NOT DEFINED COMPILE_${FEATURE})
+    if(CMAKE_CROSSCOMPILING)
+      message(STATUS "Cross-compiling to test ${FEATURE}")
+      try_compile(COMPILE_${FEATURE}
+              ${CMAKE_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/cmake/${FILE}.cpp
+              CXX_STANDARD 11
+              CXX_STANDARD_REQUIRED ON
+              CMAKE_FLAGS ${FEATURE_CHECK_CMAKE_FLAGS}
+              LINK_LIBRARIES ${BENCHMARK_CXX_LIBRARIES}
+              OUTPUT_VARIABLE COMPILE_OUTPUT_VAR)
+      if(COMPILE_${FEATURE})
+        message(WARNING
+              "If you see build failures due to cross compilation, try setting HAVE_${VAR} to 0")
+        set(RUN_${FEATURE} 0 CACHE INTERNAL "")
+      else()
+        set(RUN_${FEATURE} 1 CACHE INTERNAL "")
+      endif()
+    else()
+      message(STATUS "Compiling and running to test ${FEATURE}")
+      try_run(RUN_${FEATURE} COMPILE_${FEATURE}
+              ${CMAKE_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/cmake/${FILE}.cpp
+              CXX_STANDARD 11
+              CXX_STANDARD_REQUIRED ON
+              CMAKE_FLAGS ${FEATURE_CHECK_CMAKE_FLAGS}
+              LINK_LIBRARIES ${BENCHMARK_CXX_LIBRARIES}
+              COMPILE_OUTPUT_VARIABLE COMPILE_OUTPUT_VAR)
+    endif()
+  endif()
+
+  if(RUN_${FEATURE} EQUAL 0)
+    message(STATUS "Performing Test ${FEATURE} -- success")
+    set(HAVE_${VAR} 1 PARENT_SCOPE)
+    add_definitions(-DHAVE_${VAR})
+  else()
+    if(NOT COMPILE_${FEATURE})
+      if(CXXFEATURECHECK_DEBUG)
+        message(STATUS "Performing Test ${FEATURE} -- failed to compile: ${COMPILE_OUTPUT_VAR}")
+      else()
+        message(STATUS "Performing Test ${FEATURE} -- failed to compile")
+      endif()
+    else()
+      message(STATUS "Performing Test ${FEATURE} -- compiled but failed to run")
+    endif()
+  endif()
+endfunction()
diff --git a/leveldb_base/third_party/benchmark/cmake/Config.cmake.in b/leveldb_base/third_party/benchmark/cmake/Config.cmake.in
new file mode 100644
index 0000000..2e15f0c
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/cmake/Config.cmake.in
@@ -0,0 +1,7 @@
+@PACKAGE_INIT@
+
+include (CMakeFindDependencyMacro)
+
+find_dependency (Threads)
+
+include("${CMAKE_CURRENT_LIST_DIR}/@targets_export_name@.cmake")
diff --git a/leveldb_base/third_party/benchmark/cmake/GetGitVersion.cmake b/leveldb_base/third_party/benchmark/cmake/GetGitVersion.cmake
new file mode 100644
index 0000000..04a1f9b
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/cmake/GetGitVersion.cmake
@@ -0,0 +1,58 @@
+# - Returns a version string from Git tags
+#
+# This function inspects the annotated git tags for the project and returns a string
+# into a CMake variable
+#
+#  get_git_version(<var>)
+#
+# - Example
+#
+# include(GetGitVersion)
+# get_git_version(GIT_VERSION)
+#
+# Requires CMake 2.8.11+
+find_package(Git)
+
+if(__get_git_version)
+  return()
+endif()
+set(__get_git_version INCLUDED)
+
+function(get_git_version var)
+  if(GIT_EXECUTABLE)
+      execute_process(COMMAND ${GIT_EXECUTABLE} describe --tags --match "v[0-9]*.[0-9]*.[0-9]*" --abbrev=8
+          WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
+          RESULT_VARIABLE status
+          OUTPUT_VARIABLE GIT_DESCRIBE_VERSION
+          ERROR_QUIET)
+      if(status)
+          set(GIT_DESCRIBE_VERSION "v0.0.0")
+      endif()
+      
+      string(STRIP ${GIT_DESCRIBE_VERSION} GIT_DESCRIBE_VERSION)
+      if(GIT_DESCRIBE_VERSION MATCHES v[^-]*-) 
+         string(REGEX REPLACE "v([^-]*)-([0-9]+)-.*" "\\1.\\2"  GIT_VERSION ${GIT_DESCRIBE_VERSION})
+      else()
+         string(REGEX REPLACE "v(.*)" "\\1" GIT_VERSION ${GIT_DESCRIBE_VERSION})
+      endif()
+
+      # Work out if the repository is dirty
+      execute_process(COMMAND ${GIT_EXECUTABLE} update-index -q --refresh
+          WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
+          OUTPUT_QUIET
+          ERROR_QUIET)
+      execute_process(COMMAND ${GIT_EXECUTABLE} diff-index --name-only HEAD --
+          WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
+          OUTPUT_VARIABLE GIT_DIFF_INDEX
+          ERROR_QUIET)
+      string(COMPARE NOTEQUAL "${GIT_DIFF_INDEX}" "" GIT_DIRTY)
+      if (${GIT_DIRTY})
+          set(GIT_DESCRIBE_VERSION "${GIT_DESCRIBE_VERSION}-dirty")
+      endif()
+      message(STATUS "git version: ${GIT_DESCRIBE_VERSION} normalized to ${GIT_VERSION}")
+  else()
+      set(GIT_VERSION "0.0.0")
+  endif()
+
+  set(${var} ${GIT_VERSION} PARENT_SCOPE)
+endfunction()
diff --git a/leveldb_base/third_party/benchmark/cmake/GoogleTest.cmake b/leveldb_base/third_party/benchmark/cmake/GoogleTest.cmake
new file mode 100644
index 0000000..44adbfb
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/cmake/GoogleTest.cmake
@@ -0,0 +1,52 @@
+# Download and unpack googletest at configure time
+set(GOOGLETEST_PREFIX "${benchmark_BINARY_DIR}/third_party/googletest")
+configure_file(${benchmark_SOURCE_DIR}/cmake/GoogleTest.cmake.in ${GOOGLETEST_PREFIX}/CMakeLists.txt @ONLY)
+
+set(GOOGLETEST_PATH "${CMAKE_CURRENT_SOURCE_DIR}/googletest" CACHE PATH "") # Mind the quotes
+execute_process(COMMAND ${CMAKE_COMMAND} -G "${CMAKE_GENERATOR}"
+  -DALLOW_DOWNLOADING_GOOGLETEST=${BENCHMARK_DOWNLOAD_DEPENDENCIES} -DGOOGLETEST_PATH:PATH=${GOOGLETEST_PATH} .
+  RESULT_VARIABLE result
+  WORKING_DIRECTORY ${GOOGLETEST_PREFIX}
+)
+
+if(result)
+  message(FATAL_ERROR "CMake step for googletest failed: ${result}")
+endif()
+
+execute_process(
+  COMMAND ${CMAKE_COMMAND} --build .
+  RESULT_VARIABLE result
+  WORKING_DIRECTORY ${GOOGLETEST_PREFIX}
+)
+
+if(result)
+  message(FATAL_ERROR "Build step for googletest failed: ${result}")
+endif()
+
+# Prevent overriding the parent project's compiler/linker
+# settings on Windows
+set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
+
+include(${GOOGLETEST_PREFIX}/googletest-paths.cmake)
+
+# googletest doesn't seem to want to stay build warning clean so let's not hurt ourselves.
+if (MSVC)
+  add_compile_options(/wd4244 /wd4722)
+else()
+  add_compile_options(-w)
+endif()
+
+# Add googletest directly to our build. This defines
+# the gtest and gtest_main targets.
+add_subdirectory(${GOOGLETEST_SOURCE_DIR}
+                 ${GOOGLETEST_BINARY_DIR}
+                 EXCLUDE_FROM_ALL)
+
+if(NOT DEFINED GTEST_COMPILE_COMMANDS)
+    set(GTEST_COMPILE_COMMANDS ON)
+endif()
+
+set_target_properties(gtest PROPERTIES INTERFACE_SYSTEM_INCLUDE_DIRECTORIES $<TARGET_PROPERTY:gtest,INTERFACE_INCLUDE_DIRECTORIES> EXPORT_COMPILE_COMMANDS ${GTEST_COMPILE_COMMANDS})
+set_target_properties(gtest_main PROPERTIES INTERFACE_SYSTEM_INCLUDE_DIRECTORIES $<TARGET_PROPERTY:gtest_main,INTERFACE_INCLUDE_DIRECTORIES> EXPORT_COMPILE_COMMANDS ${GTEST_COMPILE_COMMANDS})
+set_target_properties(gmock PROPERTIES INTERFACE_SYSTEM_INCLUDE_DIRECTORIES $<TARGET_PROPERTY:gmock,INTERFACE_INCLUDE_DIRECTORIES> EXPORT_COMPILE_COMMANDS ${GTEST_COMPILE_COMMANDS})
+set_target_properties(gmock_main PROPERTIES INTERFACE_SYSTEM_INCLUDE_DIRECTORIES $<TARGET_PROPERTY:gmock_main,INTERFACE_INCLUDE_DIRECTORIES> EXPORT_COMPILE_COMMANDS ${GTEST_COMPILE_COMMANDS})
diff --git a/leveldb_base/third_party/benchmark/cmake/GoogleTest.cmake.in b/leveldb_base/third_party/benchmark/cmake/GoogleTest.cmake.in
new file mode 100644
index 0000000..ce653ac
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/cmake/GoogleTest.cmake.in
@@ -0,0 +1,59 @@
+cmake_minimum_required(VERSION 2.8.12)
+
+project(googletest-download NONE)
+
+# Enable ExternalProject CMake module
+include(ExternalProject)
+
+option(ALLOW_DOWNLOADING_GOOGLETEST "If googletest src tree is not found in location specified by GOOGLETEST_PATH, do fetch the archive from internet" OFF)
+set(GOOGLETEST_PATH "/usr/src/googletest" CACHE PATH
+                    "Path to the googletest root tree. Should contain googletest and googlemock subdirs. And CMakeLists.txt in root, and in both of these subdirs")
+
+# Download and install GoogleTest
+
+message(STATUS "Looking for Google Test sources")
+message(STATUS "Looking for Google Test sources in ${GOOGLETEST_PATH}")
+if(EXISTS "${GOOGLETEST_PATH}"            AND IS_DIRECTORY "${GOOGLETEST_PATH}"            AND EXISTS "${GOOGLETEST_PATH}/CMakeLists.txt" AND
+   EXISTS "${GOOGLETEST_PATH}/googletest" AND IS_DIRECTORY "${GOOGLETEST_PATH}/googletest" AND EXISTS "${GOOGLETEST_PATH}/googletest/CMakeLists.txt" AND
+   EXISTS "${GOOGLETEST_PATH}/googlemock" AND IS_DIRECTORY "${GOOGLETEST_PATH}/googlemock" AND EXISTS "${GOOGLETEST_PATH}/googlemock/CMakeLists.txt")
+  message(STATUS "Found Google Test in ${GOOGLETEST_PATH}")
+
+  ExternalProject_Add(
+    googletest
+    PREFIX            "${CMAKE_BINARY_DIR}"
+    DOWNLOAD_DIR      "${CMAKE_BINARY_DIR}/download"
+    SOURCE_DIR        "${GOOGLETEST_PATH}" # use existing src dir.
+    BINARY_DIR        "${CMAKE_BINARY_DIR}/build"
+    CONFIGURE_COMMAND ""
+    BUILD_COMMAND     ""
+    INSTALL_COMMAND   ""
+    TEST_COMMAND      ""
+  )
+else()
+  if(NOT ALLOW_DOWNLOADING_GOOGLETEST)
+    message(SEND_ERROR "Did not find Google Test sources! Either pass correct path in GOOGLETEST_PATH, or enable BENCHMARK_DOWNLOAD_DEPENDENCIES, or disable BENCHMARK_USE_BUNDLED_GTEST, or disable BENCHMARK_ENABLE_GTEST_TESTS / BENCHMARK_ENABLE_TESTING.")
+    return()
+  else()
+    message(WARNING "Did not find Google Test sources! Fetching from web...")
+    ExternalProject_Add(
+      googletest
+      GIT_REPOSITORY    https://github.com/google/googletest.git
+      GIT_TAG           "release-1.11.0"
+      PREFIX            "${CMAKE_BINARY_DIR}"
+      STAMP_DIR         "${CMAKE_BINARY_DIR}/stamp"
+      DOWNLOAD_DIR      "${CMAKE_BINARY_DIR}/download"
+      SOURCE_DIR        "${CMAKE_BINARY_DIR}/src"
+      BINARY_DIR        "${CMAKE_BINARY_DIR}/build"
+      CONFIGURE_COMMAND ""
+      BUILD_COMMAND     ""
+      INSTALL_COMMAND   ""
+      TEST_COMMAND      ""
+    )
+  endif()
+endif()
+
+ExternalProject_Get_Property(googletest SOURCE_DIR BINARY_DIR)
+file(WRITE googletest-paths.cmake
+"set(GOOGLETEST_SOURCE_DIR \"${SOURCE_DIR}\")
+set(GOOGLETEST_BINARY_DIR \"${BINARY_DIR}\")
+")
diff --git a/leveldb_base/third_party/benchmark/cmake/benchmark.pc.in b/leveldb_base/third_party/benchmark/cmake/benchmark.pc.in
new file mode 100644
index 0000000..9dae881
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/cmake/benchmark.pc.in
@@ -0,0 +1,12 @@
+prefix=@CMAKE_INSTALL_PREFIX@
+exec_prefix=${prefix}
+libdir=@CMAKE_INSTALL_FULL_LIBDIR@
+includedir=@CMAKE_INSTALL_FULL_INCLUDEDIR@
+
+Name: @PROJECT_NAME@
+Description: Google microbenchmark framework
+Version: @VERSION@
+
+Libs: -L${libdir} -lbenchmark
+Libs.private: -lpthread
+Cflags: -I${includedir}
diff --git a/leveldb_base/third_party/benchmark/cmake/gnu_posix_regex.cpp b/leveldb_base/third_party/benchmark/cmake/gnu_posix_regex.cpp
new file mode 100644
index 0000000..b5b91cd
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/cmake/gnu_posix_regex.cpp
@@ -0,0 +1,12 @@
+#include <gnuregex.h>
+#include <string>
+int main() {
+  std::string str = "test0159";
+  regex_t re;
+  int ec = regcomp(&re, "^[a-z]+[0-9]+$", REG_EXTENDED | REG_NOSUB);
+  if (ec != 0) {
+    return ec;
+  }
+  return regexec(&re, str.c_str(), 0, nullptr, 0) ? -1 : 0;
+}
+
diff --git a/leveldb_base/third_party/benchmark/cmake/llvm-toolchain.cmake b/leveldb_base/third_party/benchmark/cmake/llvm-toolchain.cmake
new file mode 100644
index 0000000..fc119e5
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/cmake/llvm-toolchain.cmake
@@ -0,0 +1,8 @@
+find_package(LLVMAr REQUIRED)
+set(CMAKE_AR "${LLVMAR_EXECUTABLE}" CACHE FILEPATH "" FORCE)
+
+find_package(LLVMNm REQUIRED)
+set(CMAKE_NM "${LLVMNM_EXECUTABLE}" CACHE FILEPATH "" FORCE)
+
+find_package(LLVMRanLib REQUIRED)
+set(CMAKE_RANLIB "${LLVMRANLIB_EXECUTABLE}" CACHE FILEPATH "" FORCE)
diff --git a/leveldb_base/third_party/benchmark/cmake/posix_regex.cpp b/leveldb_base/third_party/benchmark/cmake/posix_regex.cpp
new file mode 100644
index 0000000..466dc62
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/cmake/posix_regex.cpp
@@ -0,0 +1,14 @@
+#include <regex.h>
+#include <string>
+int main() {
+  std::string str = "test0159";
+  regex_t re;
+  int ec = regcomp(&re, "^[a-z]+[0-9]+$", REG_EXTENDED | REG_NOSUB);
+  if (ec != 0) {
+    return ec;
+  }
+  int ret = regexec(&re, str.c_str(), 0, nullptr, 0) ? -1 : 0;
+  regfree(&re);
+  return ret;
+}
+
diff --git a/leveldb_base/third_party/benchmark/cmake/pthread_affinity.cpp b/leveldb_base/third_party/benchmark/cmake/pthread_affinity.cpp
new file mode 100644
index 0000000..7b143bc
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/cmake/pthread_affinity.cpp
@@ -0,0 +1,16 @@
+#include <pthread.h>
+int main() {
+  cpu_set_t set;
+  CPU_ZERO(&set);
+  for (int i = 0; i < CPU_SETSIZE; ++i) {
+    CPU_SET(i, &set);
+    CPU_CLR(i, &set);
+  }
+  pthread_t self = pthread_self();
+  int ret;
+  ret = pthread_getaffinity_np(self, sizeof(set), &set);
+  if (ret != 0) return ret;
+  ret = pthread_setaffinity_np(self, sizeof(set), &set);
+  if (ret != 0) return ret;
+  return 0;
+}
diff --git a/leveldb_base/third_party/benchmark/cmake/split_list.cmake b/leveldb_base/third_party/benchmark/cmake/split_list.cmake
new file mode 100644
index 0000000..67aed3f
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/cmake/split_list.cmake
@@ -0,0 +1,3 @@
+macro(split_list listname)
+  string(REPLACE ";" " " ${listname} "${${listname}}")
+endmacro()
diff --git a/leveldb_base/third_party/benchmark/cmake/std_regex.cpp b/leveldb_base/third_party/benchmark/cmake/std_regex.cpp
new file mode 100644
index 0000000..696f2a2
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/cmake/std_regex.cpp
@@ -0,0 +1,10 @@
+#include <regex>
+#include <string>
+int main() {
+  const std::string str = "test0159";
+  std::regex re;
+  re = std::regex("^[a-z]+[0-9]+$",
+       std::regex_constants::extended | std::regex_constants::nosubs);
+  return std::regex_search(str, re) ? 0 : -1;
+}
+
diff --git a/leveldb_base/third_party/benchmark/cmake/steady_clock.cpp b/leveldb_base/third_party/benchmark/cmake/steady_clock.cpp
new file mode 100644
index 0000000..66d50d1
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/cmake/steady_clock.cpp
@@ -0,0 +1,7 @@
+#include <chrono>
+
+int main() {
+    typedef std::chrono::steady_clock Clock;
+    Clock::time_point tp = Clock::now();
+    ((void)tp);
+}
diff --git a/leveldb_base/third_party/benchmark/cmake/thread_safety_attributes.cpp b/leveldb_base/third_party/benchmark/cmake/thread_safety_attributes.cpp
new file mode 100644
index 0000000..46161ba
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/cmake/thread_safety_attributes.cpp
@@ -0,0 +1,4 @@
+#define HAVE_THREAD_SAFETY_ATTRIBUTES
+#include "../src/mutex.h"
+
+int main() {}
diff --git a/leveldb_base/third_party/benchmark/docs/AssemblyTests.md b/leveldb_base/third_party/benchmark/docs/AssemblyTests.md
new file mode 100644
index 0000000..89df7ca
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/docs/AssemblyTests.md
@@ -0,0 +1,149 @@
+# Assembly Tests
+
+The Benchmark library provides a number of functions whose primary
+purpose in to affect assembly generation, including `DoNotOptimize`
+and `ClobberMemory`. In addition there are other functions,
+such as `KeepRunning`, for which generating good assembly is paramount.
+
+For these functions it's important to have tests that verify the
+correctness and quality of the implementation. This requires testing
+the code generated by the compiler.
+
+This document describes how the Benchmark library tests compiler output,
+as well as how to properly write new tests.
+
+
+## Anatomy of a Test
+
+Writing a test has two steps:
+
+* Write the code you want to generate assembly for.
+* Add `// CHECK` lines to match against the verified assembly.
+
+Example:
+```c++
+
+// CHECK-LABEL: test_add:
+extern "C" int test_add() {
+    extern int ExternInt;
+    return ExternInt + 1;
+
+    // CHECK: movl ExternInt(%rip), %eax
+    // CHECK: addl %eax
+    // CHECK: ret
+}
+
+```
+
+#### LLVM Filecheck
+
+[LLVM's Filecheck](https://llvm.org/docs/CommandGuide/FileCheck.html)
+is used to test the generated assembly against the `// CHECK` lines
+specified in the tests source file. Please see the documentation
+linked above for information on how to write `CHECK` directives.
+
+#### Tips and Tricks:
+
+* Tests should match the minimal amount of output required to establish
+correctness. `CHECK` directives don't have to match on the exact next line
+after the previous match, so tests should omit checks for unimportant
+bits of assembly. ([`CHECK-NEXT`](https://llvm.org/docs/CommandGuide/FileCheck.html#the-check-next-directive)
+can be used to ensure a match occurs exactly after the previous match).
+
+* The tests are compiled with `-O3 -g0`. So we're only testing the
+optimized output.
+
+* The assembly output is further cleaned up using `tools/strip_asm.py`.
+This removes comments, assembler directives, and unused labels before
+the test is run.
+
+* The generated and stripped assembly file for a test is output under
+`<build-directory>/test/<test-name>.s`
+
+* Filecheck supports using [`CHECK` prefixes](https://llvm.org/docs/CommandGuide/FileCheck.html#cmdoption-check-prefixes)
+to specify lines that should only match in certain situations.
+The Benchmark tests use `CHECK-CLANG` and `CHECK-GNU` for lines that
+are only expected to match Clang or GCC's output respectively. Normal
+`CHECK` lines match against all compilers. (Note: `CHECK-NOT` and
+`CHECK-LABEL` are NOT prefixes. They are versions of non-prefixed
+`CHECK` lines)
+
+* Use `extern "C"` to disable name mangling for specific functions. This
+makes them easier to name in the `CHECK` lines.
+
+
+## Problems Writing Portable Tests
+
+Writing tests which check the code generated by a compiler are
+inherently non-portable. Different compilers and even different compiler
+versions may generate entirely different code. The Benchmark tests
+must tolerate this.
+
+LLVM Filecheck provides a number of mechanisms to help write
+"more portable" tests; including [matching using regular expressions](https://llvm.org/docs/CommandGuide/FileCheck.html#filecheck-pattern-matching-syntax),
+allowing the creation of [named variables](https://llvm.org/docs/CommandGuide/FileCheck.html#filecheck-variables)
+for later matching, and [checking non-sequential matches](https://llvm.org/docs/CommandGuide/FileCheck.html#the-check-dag-directive).
+
+#### Capturing Variables
+
+For example, say GCC stores a variable in a register but Clang stores
+it in memory. To write a test that tolerates both cases we "capture"
+the destination of the store, and then use the captured expression
+to write the remainder of the test.
+
+```c++
+// CHECK-LABEL: test_div_no_op_into_shr:
+extern "C" void test_div_no_op_into_shr(int value) {
+    int divisor = 2;
+    benchmark::DoNotOptimize(divisor); // hide the value from the optimizer
+    return value / divisor;
+
+    // CHECK: movl $2, [[DEST:.*]]
+    // CHECK: idivl [[DEST]]
+    // CHECK: ret
+}
+```
+
+#### Using Regular Expressions to Match Differing Output
+
+Often tests require testing assembly lines which may subtly differ
+between compilers or compiler versions. A common example of this
+is matching stack frame addresses. In this case regular expressions
+can be used to match the differing bits of output. For example:
+
+<!-- {% raw %} -->
+```c++
+int ExternInt;
+struct Point { int x, y, z; };
+
+// CHECK-LABEL: test_store_point:
+extern "C" void test_store_point() {
+    Point p{ExternInt, ExternInt, ExternInt};
+    benchmark::DoNotOptimize(p);
+
+    // CHECK: movl ExternInt(%rip), %eax
+    // CHECK: movl %eax, -{{[0-9]+}}(%rsp)
+    // CHECK: movl %eax, -{{[0-9]+}}(%rsp)
+    // CHECK: movl %eax, -{{[0-9]+}}(%rsp)
+    // CHECK: ret
+}
+```
+<!-- {% endraw %} -->
+
+## Current Requirements and Limitations
+
+The tests require Filecheck to be installed along the `PATH` of the
+build machine. Otherwise the tests will be disabled.
+
+Additionally, as mentioned in the previous section, codegen tests are
+inherently non-portable. Currently the tests are limited to:
+
+* x86_64 targets.
+* Compiled with GCC or Clang
+
+Further work could be done, at least on a limited basis, to extend the
+tests to other architectures and compilers (using `CHECK` prefixes).
+
+Furthermore, the tests fail for builds which specify additional flags
+that modify code generation, including `--coverage` or `-fsanitize=`.
+
diff --git a/leveldb_base/third_party/benchmark/docs/_config.yml b/leveldb_base/third_party/benchmark/docs/_config.yml
new file mode 100644
index 0000000..fff4ab9
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/docs/_config.yml
@@ -0,0 +1 @@
+theme: jekyll-theme-minimal
diff --git a/leveldb_base/third_party/benchmark/docs/dependencies.md b/leveldb_base/third_party/benchmark/docs/dependencies.md
new file mode 100644
index 0000000..07760e1
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/docs/dependencies.md
@@ -0,0 +1,13 @@
+# Build tool dependency policy
+
+We follow the [Foundational C++ support policy](https://opensource.google/documentation/policies/cplusplus-support) for our build tools. In
+particular the ["Build Systems" section](https://opensource.google/documentation/policies/cplusplus-support#build-systems).
+
+## CMake
+
+The current supported version is CMake 3.10 as of 2023-08-10. Most modern
+distributions include newer versions, for example:
+
+* Ubuntu 20.04 provides CMake 3.16.3
+* Debian 11.4 provides CMake 3.18.4
+* Ubuntu 22.04 provides CMake 3.22.1
diff --git a/leveldb_base/third_party/benchmark/docs/index.md b/leveldb_base/third_party/benchmark/docs/index.md
new file mode 100644
index 0000000..9cada96
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/docs/index.md
@@ -0,0 +1,12 @@
+# Benchmark
+
+* [Assembly Tests](AssemblyTests.md)
+* [Dependencies](dependencies.md)
+* [Perf Counters](perf_counters.md)
+* [Platform Specific Build Instructions](platform_specific_build_instructions.md)
+* [Python Bindings](python_bindings.md)
+* [Random Interleaving](random_interleaving.md)
+* [Reducing Variance](reducing_variance.md)
+* [Releasing](releasing.md)
+* [Tools](tools.md)
+* [User Guide](user_guide.md)
diff --git a/leveldb_base/third_party/benchmark/docs/perf_counters.md b/leveldb_base/third_party/benchmark/docs/perf_counters.md
new file mode 100644
index 0000000..f342092
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/docs/perf_counters.md
@@ -0,0 +1,35 @@
+<a name="perf-counters" />
+
+# User-Requested Performance Counters
+
+When running benchmarks, the user may choose to request collection of
+performance counters. This may be useful in investigation scenarios - narrowing
+down the cause of a regression; or verifying that the underlying cause of a
+performance improvement matches expectations.
+
+This feature is available if:
+
+* The benchmark is run on an architecture featuring a Performance Monitoring
+  Unit (PMU),
+* The benchmark is compiled with support for collecting counters. Currently,
+  this requires [libpfm](http://perfmon2.sourceforge.net/), which is built as a
+  dependency via Bazel.
+
+The feature does not require modifying benchmark code. Counter collection is
+handled at the boundaries where timer collection is also handled. 
+
+To opt-in:
+* If using a Bazel build, add `--define pfm=1` to your build flags
+* If using CMake:
+  * Install `libpfm4-dev`, e.g. `apt-get install libpfm4-dev`.
+  * Enable the CMake flag `BENCHMARK_ENABLE_LIBPFM` in `CMakeLists.txt`.
+
+To use, pass a comma-separated list of counter names through the
+`--benchmark_perf_counters` flag. The names are decoded through libpfm - meaning,
+they are platform specific, but some (e.g. `CYCLES` or `INSTRUCTIONS`) are
+mapped by libpfm to platform-specifics - see libpfm
+[documentation](http://perfmon2.sourceforge.net/docs.html) for more details.
+
+The counter values are reported back through the [User Counters](../README.md#custom-counters)
+mechanism, meaning, they are available in all the formats (e.g. JSON) supported
+by User Counters.
diff --git a/leveldb_base/third_party/benchmark/docs/platform_specific_build_instructions.md b/leveldb_base/third_party/benchmark/docs/platform_specific_build_instructions.md
new file mode 100644
index 0000000..2d5d6c4
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/docs/platform_specific_build_instructions.md
@@ -0,0 +1,48 @@
+# Platform Specific Build Instructions
+
+## Building with GCC
+
+When the library is built using GCC it is necessary to link with the pthread
+library due to how GCC implements `std::thread`. Failing to link to pthread will
+lead to runtime exceptions (unless you're using libc++), not linker errors. See
+[issue #67](https://github.com/google/benchmark/issues/67) for more details. You
+can link to pthread by adding `-pthread` to your linker command. Note, you can
+also use `-lpthread`, but there are potential issues with ordering of command
+line parameters if you use that.
+
+On QNX, the pthread library is part of libc and usually included automatically
+(see
+[`pthread_create()`](https://www.qnx.com/developers/docs/7.1/index.html#com.qnx.doc.neutrino.lib_ref/topic/p/pthread_create.html)).
+There's no separate pthread library to link.
+
+## Building with Visual Studio 2015 or 2017
+
+The `shlwapi` library (`-lshlwapi`) is required to support a call to `CPUInfo` which reads the registry. Either add `shlwapi.lib` under `[ Configuration Properties > Linker > Input ]`, or use the following:
+
+```
+// Alternatively, can add libraries using linker options.
+#ifdef _WIN32
+#pragma comment ( lib, "Shlwapi.lib" )
+#ifdef _DEBUG
+#pragma comment ( lib, "benchmarkd.lib" )
+#else
+#pragma comment ( lib, "benchmark.lib" )
+#endif
+#endif
+```
+
+Can also use the graphical version of CMake:
+* Open `CMake GUI`.
+* Under `Where to build the binaries`, same path as source plus `build`.
+* Under `CMAKE_INSTALL_PREFIX`, same path as source plus `install`.
+* Click `Configure`, `Generate`, `Open Project`.
+* If build fails, try deleting entire directory and starting again, or unticking options to build less.
+
+## Building with Intel 2015 Update 1 or Intel System Studio Update 4
+
+See instructions for building with Visual Studio. Once built, right click on the solution and change the build to Intel.
+
+## Building on Solaris
+
+If you're running benchmarks on solaris, you'll want the kstat library linked in
+too (`-lkstat`).
\ No newline at end of file
diff --git a/leveldb_base/third_party/benchmark/docs/python_bindings.md b/leveldb_base/third_party/benchmark/docs/python_bindings.md
new file mode 100644
index 0000000..6a7aab0
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/docs/python_bindings.md
@@ -0,0 +1,34 @@
+# Building and installing Python bindings
+
+Python bindings are available as wheels on [PyPI](https://pypi.org/project/google-benchmark/) for importing and 
+using Google Benchmark directly in Python. 
+Currently, pre-built wheels exist for macOS (both ARM64 and Intel x86), Linux x86-64 and 64-bit Windows.
+Supported Python versions are Python 3.7 - 3.10.
+
+To install Google Benchmark's Python bindings, run:
+
+```bash
+python -m pip install --upgrade pip  # for manylinux2014 support
+python -m pip install google-benchmark
+```
+
+In order to keep your system Python interpreter clean, it is advisable to run these commands in a virtual
+environment. See the [official Python documentation](https://docs.python.org/3/library/venv.html) 
+on how to create virtual environments.
+
+To build a wheel directly from source, you can follow these steps:
+```bash
+git clone https://github.com/google/benchmark.git
+cd benchmark
+# create a virtual environment and activate it
+python3 -m venv venv --system-site-packages
+source venv/bin/activate  # .\venv\Scripts\Activate.ps1 on Windows
+
+# upgrade Python's system-wide packages
+python -m pip install --upgrade pip setuptools wheel
+# builds the wheel and stores it in the directory "wheelhouse".
+python -m pip wheel . -w wheelhouse
+```
+
+NB: Building wheels from source requires Bazel. For platform-specific instructions on how to install Bazel,
+refer to the [Bazel installation docs](https://bazel.build/install).
diff --git a/leveldb_base/third_party/benchmark/docs/random_interleaving.md b/leveldb_base/third_party/benchmark/docs/random_interleaving.md
new file mode 100644
index 0000000..c083036
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/docs/random_interleaving.md
@@ -0,0 +1,13 @@
+<a name="interleaving" />
+
+# Random Interleaving
+
+[Random Interleaving](https://github.com/google/benchmark/issues/1051) is a
+technique to lower run-to-run variance. It randomly interleaves repetitions of a
+microbenchmark with repetitions from other microbenchmarks in the same benchmark
+test. Data shows it is able to lower run-to-run variance by
+[40%](https://github.com/google/benchmark/issues/1051) on average.
+
+To use, you mainly need to set `--benchmark_enable_random_interleaving=true`,
+and optionally specify non-zero repetition count `--benchmark_repetitions=9`
+and optionally decrease the per-repetition time `--benchmark_min_time=0.1`.
diff --git a/leveldb_base/third_party/benchmark/docs/reducing_variance.md b/leveldb_base/third_party/benchmark/docs/reducing_variance.md
new file mode 100644
index 0000000..e566ab9
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/docs/reducing_variance.md
@@ -0,0 +1,100 @@
+# Reducing Variance
+
+<a name="disabling-cpu-frequency-scaling" />
+
+## Disabling CPU Frequency Scaling
+
+If you see this error:
+
+```
+***WARNING*** CPU scaling is enabled, the benchmark real time measurements may be noisy and will incur extra overhead.
+```
+
+you might want to disable the CPU frequency scaling while running the
+benchmark, as well as consider other ways to stabilize the performance of
+your system while benchmarking.
+
+See [Reducing Variance](reducing_variance.md) for more information.
+
+Exactly how to do this depends on the Linux distribution,
+desktop environment, and installed programs.  Specific details are a moving
+target, so we will not attempt to exhaustively document them here.
+
+One simple option is to use the `cpupower` program to change the
+performance governor to "performance".  This tool is maintained along with
+the Linux kernel and provided by your distribution.
+
+It must be run as root, like this:
+
+```bash
+sudo cpupower frequency-set --governor performance
+```
+
+After this you can verify that all CPUs are using the performance governor
+by running this command:
+
+```bash
+cpupower frequency-info -o proc
+```
+
+The benchmarks you subsequently run will have less variance.
+
+<a name="reducing-variance" />
+
+## Reducing Variance in Benchmarks
+
+The Linux CPU frequency governor [discussed
+above](user_guide#disabling-cpu-frequency-scaling) is not the only source
+of noise in benchmarks.  Some, but not all, of the sources of variance
+include:
+
+1. On multi-core machines not all CPUs/CPU cores/CPU threads run the same
+   speed, so running a benchmark one time and then again may give a
+   different result depending on which CPU it ran on.
+2. CPU scaling features that run on the CPU, like Intel's Turbo Boost and
+   AMD Turbo Core and Precision Boost, can temporarily change the CPU
+   frequency even when the using the "performance" governor on Linux.
+3. Context switching between CPUs, or scheduling competition on the CPU the
+   benchmark is running on.
+4. Intel Hyperthreading or AMD SMT causing the same issue as above.
+5. Cache effects caused by code running on other CPUs.
+6. Non-uniform memory architectures (NUMA).
+
+These can cause variance in benchmarks results within a single run
+(`--benchmark_repetitions=N`) or across multiple runs of the benchmark
+program.
+
+Reducing sources of variance is OS and architecture dependent, which is one
+reason some companies maintain machines dedicated to performance testing.
+
+Some of the easier and and effective ways of reducing variance on a typical
+Linux workstation are:
+
+1. Use the performance governor as [discussed
+above](user_guide#disabling-cpu-frequency-scaling).
+1. Disable processor boosting by:
+   ```sh
+   echo 0 | sudo tee /sys/devices/system/cpu/cpufreq/boost
+   ```
+   See the Linux kernel's
+   [boost.txt](https://www.kernel.org/doc/Documentation/cpu-freq/boost.txt)
+   for more information.
+2. Set the benchmark program's task affinity to a fixed cpu.  For example:
+   ```sh
+   taskset -c 0 ./mybenchmark
+   ```
+3. Disabling Hyperthreading/SMT.  This can be done in the Bios or using the
+   `/sys` file system (see the LLVM project's [Benchmarking
+   tips](https://llvm.org/docs/Benchmarking.html)).
+4. Close other programs that do non-trivial things based on timers, such as
+   your web browser, desktop environment, etc.
+5. Reduce the working set of your benchmark to fit within the L1 cache, but
+   do be aware that this may lead you to optimize for an unrelistic
+   situation.
+
+Further resources on this topic:
+
+1. The LLVM project's [Benchmarking
+   tips](https://llvm.org/docs/Benchmarking.html).
+1. The Arch Wiki [Cpu frequency
+scaling](https://wiki.archlinux.org/title/CPU_frequency_scaling) page.
diff --git a/leveldb_base/third_party/benchmark/docs/releasing.md b/leveldb_base/third_party/benchmark/docs/releasing.md
new file mode 100644
index 0000000..6d3b613
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/docs/releasing.md
@@ -0,0 +1,37 @@
+# How to release
+
+* Make sure you're on main and synced to HEAD
+* Ensure the project builds and tests run
+    * `parallel -j0 exec ::: test/*_test` can help ensure everything at least
+      passes
+* Prepare release notes
+    * `git log $(git describe --abbrev=0 --tags)..HEAD` gives you the list of
+      commits between the last annotated tag and HEAD
+    * Pick the most interesting.
+* Create one last commit that updates the version saved in `CMakeLists.txt` and the
+  `__version__` variable in `bindings/python/google_benchmark/__init__.py`to the release
+  version you're creating. (This version will be used if benchmark is installed from the
+  archive you'll be creating in the next step.)
+
+```
+project (benchmark VERSION 1.6.0 LANGUAGES CXX)
+```
+
+```python
+# bindings/python/google_benchmark/__init__.py
+
+# ...
+
+__version__ = "1.6.0"  # <-- change this to the release version you are creating
+
+# ...
+```
+
+* Create a release through github's interface
+    * Note this will create a lightweight tag.
+    * Update this to an annotated tag:
+      * `git pull --tags`
+      * `git tag -a -f <tag> <tag>`
+      * `git push --force --tags origin`
+* Confirm that the "Build and upload Python wheels" action runs to completion
+    * run it manually if it hasn't run
diff --git a/leveldb_base/third_party/benchmark/docs/tools.md b/leveldb_base/third_party/benchmark/docs/tools.md
new file mode 100644
index 0000000..f2d0c49
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/docs/tools.md
@@ -0,0 +1,203 @@
+# Benchmark Tools
+
+## compare.py
+
+The `compare.py` can be used to compare the result of benchmarks.
+
+### Dependencies
+The utility relies on the [scipy](https://www.scipy.org) package which can be installed using pip:
+```bash
+pip3 install -r requirements.txt
+```
+
+### Displaying aggregates only
+
+The switch `-a` / `--display_aggregates_only` can be used to control the
+displayment of the normal iterations vs the aggregates. When passed, it will
+be passthrough to the benchmark binaries to be run, and will be accounted for
+in the tool itself; only the aggregates will be displayed, but not normal runs.
+It only affects the display, the separate runs will still be used to calculate
+the U test.
+
+### Modes of operation
+
+There are three modes of operation:
+
+1. Just compare two benchmarks
+The program is invoked like:
+
+``` bash
+$ compare.py benchmarks <benchmark_baseline> <benchmark_contender> [benchmark options]...
+```
+Where `<benchmark_baseline>` and `<benchmark_contender>` either specify a benchmark executable file, or a JSON output file. The type of the input file is automatically detected. If a benchmark executable is specified then the benchmark is run to obtain the results. Otherwise the results are simply loaded from the output file.
+
+`[benchmark options]` will be passed to the benchmarks invocations. They can be anything that binary accepts, be it either normal `--benchmark_*` parameters, or some custom parameters your binary takes.
+
+Example output:
+```
+$ ./compare.py benchmarks ./a.out ./a.out
+RUNNING: ./a.out --benchmark_out=/tmp/tmprBT5nW
+Run on (8 X 4000 MHz CPU s)
+2017-11-07 21:16:44
+------------------------------------------------------
+Benchmark               Time           CPU Iterations
+------------------------------------------------------
+BM_memcpy/8            36 ns         36 ns   19101577   211.669MB/s
+BM_memcpy/64           76 ns         76 ns    9412571   800.199MB/s
+BM_memcpy/512          84 ns         84 ns    8249070   5.64771GB/s
+BM_memcpy/1024        116 ns        116 ns    6181763   8.19505GB/s
+BM_memcpy/8192        643 ns        643 ns    1062855   11.8636GB/s
+BM_copy/8             222 ns        222 ns    3137987   34.3772MB/s
+BM_copy/64           1608 ns       1608 ns     432758   37.9501MB/s
+BM_copy/512         12589 ns      12589 ns      54806   38.7867MB/s
+BM_copy/1024        25169 ns      25169 ns      27713   38.8003MB/s
+BM_copy/8192       201165 ns     201112 ns       3486   38.8466MB/s
+RUNNING: ./a.out --benchmark_out=/tmp/tmpt1wwG_
+Run on (8 X 4000 MHz CPU s)
+2017-11-07 21:16:53
+------------------------------------------------------
+Benchmark               Time           CPU Iterations
+------------------------------------------------------
+BM_memcpy/8            36 ns         36 ns   19397903   211.255MB/s
+BM_memcpy/64           73 ns         73 ns    9691174   839.635MB/s
+BM_memcpy/512          85 ns         85 ns    8312329   5.60101GB/s
+BM_memcpy/1024        118 ns        118 ns    6438774   8.11608GB/s
+BM_memcpy/8192        656 ns        656 ns    1068644   11.6277GB/s
+BM_copy/8             223 ns        223 ns    3146977   34.2338MB/s
+BM_copy/64           1611 ns       1611 ns     435340   37.8751MB/s
+BM_copy/512         12622 ns      12622 ns      54818   38.6844MB/s
+BM_copy/1024        25257 ns      25239 ns      27779   38.6927MB/s
+BM_copy/8192       205013 ns     205010 ns       3479    38.108MB/s
+Comparing ./a.out to ./a.out
+Benchmark                 Time             CPU      Time Old      Time New       CPU Old       CPU New
+------------------------------------------------------------------------------------------------------
+BM_memcpy/8            +0.0020         +0.0020            36            36            36            36
+BM_memcpy/64           -0.0468         -0.0470            76            73            76            73
+BM_memcpy/512          +0.0081         +0.0083            84            85            84            85
+BM_memcpy/1024         +0.0098         +0.0097           116           118           116           118
+BM_memcpy/8192         +0.0200         +0.0203           643           656           643           656
+BM_copy/8              +0.0046         +0.0042           222           223           222           223
+BM_copy/64             +0.0020         +0.0020          1608          1611          1608          1611
+BM_copy/512            +0.0027         +0.0026         12589         12622         12589         12622
+BM_copy/1024           +0.0035         +0.0028         25169         25257         25169         25239
+BM_copy/8192           +0.0191         +0.0194        201165        205013        201112        205010
+```
+
+What it does is for the every benchmark from the first run it looks for the benchmark with exactly the same name in the second run, and then compares the results. If the names differ, the benchmark is omitted from the diff.
+As you can note, the values in `Time` and `CPU` columns are calculated as `(new - old) / |old|`.
+
+2. Compare two different filters of one benchmark
+The program is invoked like:
+
+``` bash
+$ compare.py filters <benchmark> <filter_baseline> <filter_contender> [benchmark options]...
+```
+Where `<benchmark>` either specify a benchmark executable file, or a JSON output file. The type of the input file is automatically detected. If a benchmark executable is specified then the benchmark is run to obtain the results. Otherwise the results are simply loaded from the output file.
+
+Where `<filter_baseline>` and `<filter_contender>` are the same regex filters that you would pass to the `[--benchmark_filter=<regex>]` parameter of the benchmark binary.
+
+`[benchmark options]` will be passed to the benchmarks invocations. They can be anything that binary accepts, be it either normal `--benchmark_*` parameters, or some custom parameters your binary takes.
+
+Example output:
+```
+$ ./compare.py filters ./a.out BM_memcpy BM_copy
+RUNNING: ./a.out --benchmark_filter=BM_memcpy --benchmark_out=/tmp/tmpBWKk0k
+Run on (8 X 4000 MHz CPU s)
+2017-11-07 21:37:28
+------------------------------------------------------
+Benchmark               Time           CPU Iterations
+------------------------------------------------------
+BM_memcpy/8            36 ns         36 ns   17891491   211.215MB/s
+BM_memcpy/64           74 ns         74 ns    9400999   825.646MB/s
+BM_memcpy/512          87 ns         87 ns    8027453   5.46126GB/s
+BM_memcpy/1024        111 ns        111 ns    6116853    8.5648GB/s
+BM_memcpy/8192        657 ns        656 ns    1064679   11.6247GB/s
+RUNNING: ./a.out --benchmark_filter=BM_copy --benchmark_out=/tmp/tmpAvWcOM
+Run on (8 X 4000 MHz CPU s)
+2017-11-07 21:37:33
+----------------------------------------------------
+Benchmark             Time           CPU Iterations
+----------------------------------------------------
+BM_copy/8           227 ns        227 ns    3038700   33.6264MB/s
+BM_copy/64         1640 ns       1640 ns     426893   37.2154MB/s
+BM_copy/512       12804 ns      12801 ns      55417   38.1444MB/s
+BM_copy/1024      25409 ns      25407 ns      27516   38.4365MB/s
+BM_copy/8192     202986 ns     202990 ns       3454   38.4871MB/s
+Comparing BM_memcpy to BM_copy (from ./a.out)
+Benchmark                               Time             CPU      Time Old      Time New       CPU Old       CPU New
+--------------------------------------------------------------------------------------------------------------------
+[BM_memcpy vs. BM_copy]/8            +5.2829         +5.2812            36           227            36           227
+[BM_memcpy vs. BM_copy]/64          +21.1719        +21.1856            74          1640            74          1640
+[BM_memcpy vs. BM_copy]/512        +145.6487       +145.6097            87         12804            87         12801
+[BM_memcpy vs. BM_copy]/1024       +227.1860       +227.1776           111         25409           111         25407
+[BM_memcpy vs. BM_copy]/8192       +308.1664       +308.2898           657        202986           656        202990
+```
+
+As you can see, it applies filter to the benchmarks, both when running the benchmark, and before doing the diff. And to make the diff work, the matches are replaced with some common string. Thus, you can compare two different benchmark families within one benchmark binary.
+As you can note, the values in `Time` and `CPU` columns are calculated as `(new - old) / |old|`.
+
+3. Compare filter one from benchmark one to filter two from benchmark two:
+The program is invoked like:
+
+``` bash
+$ compare.py filters <benchmark_baseline> <filter_baseline> <benchmark_contender> <filter_contender> [benchmark options]...
+```
+
+Where `<benchmark_baseline>` and `<benchmark_contender>` either specify a benchmark executable file, or a JSON output file. The type of the input file is automatically detected. If a benchmark executable is specified then the benchmark is run to obtain the results. Otherwise the results are simply loaded from the output file.
+
+Where `<filter_baseline>` and `<filter_contender>` are the same regex filters that you would pass to the `[--benchmark_filter=<regex>]` parameter of the benchmark binary.
+
+`[benchmark options]` will be passed to the benchmarks invocations. They can be anything that binary accepts, be it either normal `--benchmark_*` parameters, or some custom parameters your binary takes.
+
+Example output:
+```
+$ ./compare.py benchmarksfiltered ./a.out BM_memcpy ./a.out BM_copy
+RUNNING: ./a.out --benchmark_filter=BM_memcpy --benchmark_out=/tmp/tmp_FvbYg
+Run on (8 X 4000 MHz CPU s)
+2017-11-07 21:38:27
+------------------------------------------------------
+Benchmark               Time           CPU Iterations
+------------------------------------------------------
+BM_memcpy/8            37 ns         37 ns   18953482   204.118MB/s
+BM_memcpy/64           74 ns         74 ns    9206578   828.245MB/s
+BM_memcpy/512          91 ns         91 ns    8086195   5.25476GB/s
+BM_memcpy/1024        120 ns        120 ns    5804513   7.95662GB/s
+BM_memcpy/8192        664 ns        664 ns    1028363   11.4948GB/s
+RUNNING: ./a.out --benchmark_filter=BM_copy --benchmark_out=/tmp/tmpDfL5iE
+Run on (8 X 4000 MHz CPU s)
+2017-11-07 21:38:32
+----------------------------------------------------
+Benchmark             Time           CPU Iterations
+----------------------------------------------------
+BM_copy/8           230 ns        230 ns    2985909   33.1161MB/s
+BM_copy/64         1654 ns       1653 ns     419408   36.9137MB/s
+BM_copy/512       13122 ns      13120 ns      53403   37.2156MB/s
+BM_copy/1024      26679 ns      26666 ns      26575   36.6218MB/s
+BM_copy/8192     215068 ns     215053 ns       3221   36.3283MB/s
+Comparing BM_memcpy (from ./a.out) to BM_copy (from ./a.out)
+Benchmark                               Time             CPU      Time Old      Time New       CPU Old       CPU New
+--------------------------------------------------------------------------------------------------------------------
+[BM_memcpy vs. BM_copy]/8            +5.1649         +5.1637            37           230            37           230
+[BM_memcpy vs. BM_copy]/64          +21.4352        +21.4374            74          1654            74          1653
+[BM_memcpy vs. BM_copy]/512        +143.6022       +143.5865            91         13122            91         13120
+[BM_memcpy vs. BM_copy]/1024       +221.5903       +221.4790           120         26679           120         26666
+[BM_memcpy vs. BM_copy]/8192       +322.9059       +323.0096           664        215068           664        215053
+```
+This is a mix of the previous two modes, two (potentially different) benchmark binaries are run, and a different filter is applied to each one.
+As you can note, the values in `Time` and `CPU` columns are calculated as `(new - old) / |old|`.
+
+### U test
+
+If there is a sufficient repetition count of the benchmarks, the tool can do
+a [U Test](https://en.wikipedia.org/wiki/Mann%E2%80%93Whitney_U_test), of the
+null hypothesis that it is equally likely that a randomly selected value from
+one sample will be less than or greater than a randomly selected value from a
+second sample.
+
+If the calculated p-value is below this value is lower than the significance
+level alpha, then the result is said to be statistically significant and the
+null hypothesis is rejected. Which in other words means that the two benchmarks
+aren't identical.
+
+**WARNING**: requires **LARGE** (no less than 9) number of repetitions to be
+meaningful!
diff --git a/leveldb_base/third_party/benchmark/docs/user_guide.md b/leveldb_base/third_party/benchmark/docs/user_guide.md
new file mode 100644
index 0000000..133fca5
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/docs/user_guide.md
@@ -0,0 +1,1266 @@
+# User Guide
+
+## Command Line
+
+[Output Formats](#output-formats)
+
+[Output Files](#output-files)
+
+[Running Benchmarks](#running-benchmarks)
+
+[Running a Subset of Benchmarks](#running-a-subset-of-benchmarks)
+
+[Result Comparison](#result-comparison)
+
+[Extra Context](#extra-context)
+
+## Library
+
+[Runtime and Reporting Considerations](#runtime-and-reporting-considerations)
+
+[Setup/Teardown](#setupteardown)
+
+[Passing Arguments](#passing-arguments)
+
+[Custom Benchmark Name](#custom-benchmark-name)
+
+[Calculating Asymptotic Complexity](#asymptotic-complexity)
+
+[Templated Benchmarks](#templated-benchmarks)
+
+[Fixtures](#fixtures)
+
+[Custom Counters](#custom-counters)
+
+[Multithreaded Benchmarks](#multithreaded-benchmarks)
+
+[CPU Timers](#cpu-timers)
+
+[Manual Timing](#manual-timing)
+
+[Setting the Time Unit](#setting-the-time-unit)
+
+[Random Interleaving](random_interleaving.md)
+
+[User-Requested Performance Counters](perf_counters.md)
+
+[Preventing Optimization](#preventing-optimization)
+
+[Reporting Statistics](#reporting-statistics)
+
+[Custom Statistics](#custom-statistics)
+
+[Memory Usage](#memory-usage)
+
+[Using RegisterBenchmark](#using-register-benchmark)
+
+[Exiting with an Error](#exiting-with-an-error)
+
+[A Faster `KeepRunning` Loop](#a-faster-keep-running-loop)
+
+## Benchmarking Tips
+
+[Disabling CPU Frequency Scaling](#disabling-cpu-frequency-scaling)
+
+[Reducing Variance in Benchmarks](reducing_variance.md)
+
+<a name="output-formats" />
+
+## Output Formats
+
+The library supports multiple output formats. Use the
+`--benchmark_format=<console|json|csv>` flag (or set the
+`BENCHMARK_FORMAT=<console|json|csv>` environment variable) to set
+the format type. `console` is the default format.
+
+The Console format is intended to be a human readable format. By default
+the format generates color output. Context is output on stderr and the
+tabular data on stdout. Example tabular output looks like:
+
+```
+Benchmark                               Time(ns)    CPU(ns) Iterations
+----------------------------------------------------------------------
+BM_SetInsert/1024/1                        28928      29349      23853  133.097kB/s   33.2742k items/s
+BM_SetInsert/1024/8                        32065      32913      21375  949.487kB/s   237.372k items/s
+BM_SetInsert/1024/10                       33157      33648      21431  1.13369MB/s   290.225k items/s
+```
+
+The JSON format outputs human readable json split into two top level attributes.
+The `context` attribute contains information about the run in general, including
+information about the CPU and the date.
+The `benchmarks` attribute contains a list of every benchmark run. Example json
+output looks like:
+
+```json
+{
+  "context": {
+    "date": "2015/03/17-18:40:25",
+    "num_cpus": 40,
+    "mhz_per_cpu": 2801,
+    "cpu_scaling_enabled": false,
+    "build_type": "debug"
+  },
+  "benchmarks": [
+    {
+      "name": "BM_SetInsert/1024/1",
+      "iterations": 94877,
+      "real_time": 29275,
+      "cpu_time": 29836,
+      "bytes_per_second": 134066,
+      "items_per_second": 33516
+    },
+    {
+      "name": "BM_SetInsert/1024/8",
+      "iterations": 21609,
+      "real_time": 32317,
+      "cpu_time": 32429,
+      "bytes_per_second": 986770,
+      "items_per_second": 246693
+    },
+    {
+      "name": "BM_SetInsert/1024/10",
+      "iterations": 21393,
+      "real_time": 32724,
+      "cpu_time": 33355,
+      "bytes_per_second": 1199226,
+      "items_per_second": 299807
+    }
+  ]
+}
+```
+
+The CSV format outputs comma-separated values. The `context` is output on stderr
+and the CSV itself on stdout. Example CSV output looks like:
+
+```
+name,iterations,real_time,cpu_time,bytes_per_second,items_per_second,label
+"BM_SetInsert/1024/1",65465,17890.7,8407.45,475768,118942,
+"BM_SetInsert/1024/8",116606,18810.1,9766.64,3.27646e+06,819115,
+"BM_SetInsert/1024/10",106365,17238.4,8421.53,4.74973e+06,1.18743e+06,
+```
+
+<a name="output-files" />
+
+## Output Files
+
+Write benchmark results to a file with the `--benchmark_out=<filename>` option
+(or set `BENCHMARK_OUT`). Specify the output format with
+`--benchmark_out_format={json|console|csv}` (or set
+`BENCHMARK_OUT_FORMAT={json|console|csv}`). Note that the 'csv' reporter is
+deprecated and the saved `.csv` file
+[is not parsable](https://github.com/google/benchmark/issues/794) by csv
+parsers.
+
+Specifying `--benchmark_out` does not suppress the console output.
+
+<a name="running-benchmarks" />
+
+## Running Benchmarks
+
+Benchmarks are executed by running the produced binaries. Benchmarks binaries,
+by default, accept options that may be specified either through their command
+line interface or by setting environment variables before execution. For every
+`--option_flag=<value>` CLI switch, a corresponding environment variable
+`OPTION_FLAG=<value>` exist and is used as default if set (CLI switches always
+ prevails). A complete list of CLI options is available running benchmarks
+ with the `--help` switch.
+
+<a name="running-a-subset-of-benchmarks" />
+
+## Running a Subset of Benchmarks
+
+The `--benchmark_filter=<regex>` option (or `BENCHMARK_FILTER=<regex>`
+environment variable) can be used to only run the benchmarks that match
+the specified `<regex>`. For example:
+
+```bash
+$ ./run_benchmarks.x --benchmark_filter=BM_memcpy/32
+Run on (1 X 2300 MHz CPU )
+2016-06-25 19:34:24
+Benchmark              Time           CPU Iterations
+----------------------------------------------------
+BM_memcpy/32          11 ns         11 ns   79545455
+BM_memcpy/32k       2181 ns       2185 ns     324074
+BM_memcpy/32          12 ns         12 ns   54687500
+BM_memcpy/32k       1834 ns       1837 ns     357143
+```
+
+## Disabling Benchmarks
+
+It is possible to temporarily disable benchmarks by renaming the benchmark
+function to have the prefix "DISABLED_". This will cause the benchmark to
+be skipped at runtime.
+
+<a name="result-comparison" />
+
+## Result comparison
+
+It is possible to compare the benchmarking results.
+See [Additional Tooling Documentation](tools.md)
+
+<a name="extra-context" />
+
+## Extra Context
+
+Sometimes it's useful to add extra context to the content printed before the
+results. By default this section includes information about the CPU on which
+the benchmarks are running. If you do want to add more context, you can use
+the `benchmark_context` command line flag:
+
+```bash
+$ ./run_benchmarks --benchmark_context=pwd=`pwd`
+Run on (1 x 2300 MHz CPU)
+pwd: /home/user/benchmark/
+Benchmark              Time           CPU Iterations
+----------------------------------------------------
+BM_memcpy/32          11 ns         11 ns   79545455
+BM_memcpy/32k       2181 ns       2185 ns     324074
+```
+
+You can get the same effect with the API:
+
+```c++
+  benchmark::AddCustomContext("foo", "bar");
+```
+
+Note that attempts to add a second value with the same key will fail with an
+error message.
+
+<a name="runtime-and-reporting-considerations" />
+
+## Runtime and Reporting Considerations
+
+When the benchmark binary is executed, each benchmark function is run serially.
+The number of iterations to run is determined dynamically by running the
+benchmark a few times and measuring the time taken and ensuring that the
+ultimate result will be statistically stable. As such, faster benchmark
+functions will be run for more iterations than slower benchmark functions, and
+the number of iterations is thus reported.
+
+In all cases, the number of iterations for which the benchmark is run is
+governed by the amount of time the benchmark takes. Concretely, the number of
+iterations is at least one, not more than 1e9, until CPU time is greater than
+the minimum time, or the wallclock time is 5x minimum time. The minimum time is
+set per benchmark by calling `MinTime` on the registered benchmark object.
+
+Furthermore warming up a benchmark might be necessary in order to get
+stable results because of e.g caching effects of the code under benchmark.
+Warming up means running the benchmark a given amount of time, before
+results are actually taken into account. The amount of time for which
+the warmup should be run can be set per benchmark by calling
+`MinWarmUpTime` on the registered benchmark object or for all benchmarks
+using the `--benchmark_min_warmup_time` command-line option. Note that
+`MinWarmUpTime` will overwrite the value of `--benchmark_min_warmup_time`
+for the single benchmark. How many iterations the warmup run of each
+benchmark takes is determined the same way as described in the paragraph
+above. Per default the warmup phase is set to 0 seconds and is therefore
+disabled.
+
+Average timings are then reported over the iterations run. If multiple
+repetitions are requested using the `--benchmark_repetitions` command-line
+option, or at registration time, the benchmark function will be run several
+times and statistical results across these repetitions will also be reported.
+
+As well as the per-benchmark entries, a preamble in the report will include
+information about the machine on which the benchmarks are run.
+
+<a name="setup-teardown" />
+
+## Setup/Teardown
+
+Global setup/teardown specific to each benchmark can be done by
+passing a callback to Setup/Teardown:
+
+The setup/teardown callbacks will be invoked once for each benchmark. If the
+benchmark is multi-threaded (will run in k threads), they will be invoked
+exactly once before each run with k threads.
+
+If the benchmark uses different size groups of threads, the above will be true
+for each size group.
+
+Eg.,
+
+```c++
+static void DoSetup(const benchmark::State& state) {
+}
+
+static void DoTeardown(const benchmark::State& state) {
+}
+
+static void BM_func(benchmark::State& state) {...}
+
+BENCHMARK(BM_func)->Arg(1)->Arg(3)->Threads(16)->Threads(32)->Setup(DoSetup)->Teardown(DoTeardown);
+
+```
+
+In this example, `DoSetup` and `DoTearDown` will be invoked 4 times each,
+specifically, once for each of this family:
+ - BM_func_Arg_1_Threads_16, BM_func_Arg_1_Threads_32
+ - BM_func_Arg_3_Threads_16, BM_func_Arg_3_Threads_32
+
+<a name="passing-arguments" />
+
+## Passing Arguments
+
+Sometimes a family of benchmarks can be implemented with just one routine that
+takes an extra argument to specify which one of the family of benchmarks to
+run. For example, the following code defines a family of benchmarks for
+measuring the speed of `memcpy()` calls of different lengths:
+
+```c++
+static void BM_memcpy(benchmark::State& state) {
+  char* src = new char[state.range(0)];
+  char* dst = new char[state.range(0)];
+  memset(src, 'x', state.range(0));
+  for (auto _ : state)
+    memcpy(dst, src, state.range(0));
+  state.SetBytesProcessed(int64_t(state.iterations()) *
+                          int64_t(state.range(0)));
+  delete[] src;
+  delete[] dst;
+}
+BENCHMARK(BM_memcpy)->Arg(8)->Arg(64)->Arg(512)->Arg(4<<10)->Arg(8<<10);
+```
+
+The preceding code is quite repetitive, and can be replaced with the following
+short-hand. The following invocation will pick a few appropriate arguments in
+the specified range and will generate a benchmark for each such argument.
+
+```c++
+BENCHMARK(BM_memcpy)->Range(8, 8<<10);
+```
+
+By default the arguments in the range are generated in multiples of eight and
+the command above selects [ 8, 64, 512, 4k, 8k ]. In the following code the
+range multiplier is changed to multiples of two.
+
+```c++
+BENCHMARK(BM_memcpy)->RangeMultiplier(2)->Range(8, 8<<10);
+```
+
+Now arguments generated are [ 8, 16, 32, 64, 128, 256, 512, 1024, 2k, 4k, 8k ].
+
+The preceding code shows a method of defining a sparse range.  The following
+example shows a method of defining a dense range. It is then used to benchmark
+the performance of `std::vector` initialization for uniformly increasing sizes.
+
+```c++
+static void BM_DenseRange(benchmark::State& state) {
+  for(auto _ : state) {
+    std::vector<int> v(state.range(0), state.range(0));
+    auto data = v.data();
+    benchmark::DoNotOptimize(data);
+    benchmark::ClobberMemory();
+  }
+}
+BENCHMARK(BM_DenseRange)->DenseRange(0, 1024, 128);
+```
+
+Now arguments generated are [ 0, 128, 256, 384, 512, 640, 768, 896, 1024 ].
+
+You might have a benchmark that depends on two or more inputs. For example, the
+following code defines a family of benchmarks for measuring the speed of set
+insertion.
+
+```c++
+static void BM_SetInsert(benchmark::State& state) {
+  std::set<int> data;
+  for (auto _ : state) {
+    state.PauseTiming();
+    data = ConstructRandomSet(state.range(0));
+    state.ResumeTiming();
+    for (int j = 0; j < state.range(1); ++j)
+      data.insert(RandomNumber());
+  }
+}
+BENCHMARK(BM_SetInsert)
+    ->Args({1<<10, 128})
+    ->Args({2<<10, 128})
+    ->Args({4<<10, 128})
+    ->Args({8<<10, 128})
+    ->Args({1<<10, 512})
+    ->Args({2<<10, 512})
+    ->Args({4<<10, 512})
+    ->Args({8<<10, 512});
+```
+
+The preceding code is quite repetitive, and can be replaced with the following
+short-hand. The following macro will pick a few appropriate arguments in the
+product of the two specified ranges and will generate a benchmark for each such
+pair.
+
+<!-- {% raw %} -->
+```c++
+BENCHMARK(BM_SetInsert)->Ranges({{1<<10, 8<<10}, {128, 512}});
+```
+<!-- {% endraw %} -->
+
+Some benchmarks may require specific argument values that cannot be expressed
+with `Ranges`. In this case, `ArgsProduct` offers the ability to generate a
+benchmark input for each combination in the product of the supplied vectors.
+
+<!-- {% raw %} -->
+```c++
+BENCHMARK(BM_SetInsert)
+    ->ArgsProduct({{1<<10, 3<<10, 8<<10}, {20, 40, 60, 80}})
+// would generate the same benchmark arguments as
+BENCHMARK(BM_SetInsert)
+    ->Args({1<<10, 20})
+    ->Args({3<<10, 20})
+    ->Args({8<<10, 20})
+    ->Args({3<<10, 40})
+    ->Args({8<<10, 40})
+    ->Args({1<<10, 40})
+    ->Args({1<<10, 60})
+    ->Args({3<<10, 60})
+    ->Args({8<<10, 60})
+    ->Args({1<<10, 80})
+    ->Args({3<<10, 80})
+    ->Args({8<<10, 80});
+```
+<!-- {% endraw %} -->
+
+For the most common scenarios, helper methods for creating a list of
+integers for a given sparse or dense range are provided.
+
+```c++
+BENCHMARK(BM_SetInsert)
+    ->ArgsProduct({
+      benchmark::CreateRange(8, 128, /*multi=*/2),
+      benchmark::CreateDenseRange(1, 4, /*step=*/1)
+    })
+// would generate the same benchmark arguments as
+BENCHMARK(BM_SetInsert)
+    ->ArgsProduct({
+      {8, 16, 32, 64, 128},
+      {1, 2, 3, 4}
+    });
+```
+
+For more complex patterns of inputs, passing a custom function to `Apply` allows
+programmatic specification of an arbitrary set of arguments on which to run the
+benchmark. The following example enumerates a dense range on one parameter,
+and a sparse range on the second.
+
+```c++
+static void CustomArguments(benchmark::internal::Benchmark* b) {
+  for (int i = 0; i <= 10; ++i)
+    for (int j = 32; j <= 1024*1024; j *= 8)
+      b->Args({i, j});
+}
+BENCHMARK(BM_SetInsert)->Apply(CustomArguments);
+```
+
+### Passing Arbitrary Arguments to a Benchmark
+
+In C++11 it is possible to define a benchmark that takes an arbitrary number
+of extra arguments. The `BENCHMARK_CAPTURE(func, test_case_name, ...args)`
+macro creates a benchmark that invokes `func`  with the `benchmark::State` as
+the first argument followed by the specified `args...`.
+The `test_case_name` is appended to the name of the benchmark and
+should describe the values passed.
+
+```c++
+template <class ...Args>
+void BM_takes_args(benchmark::State& state, Args&&... args) {
+  auto args_tuple = std::make_tuple(std::move(args)...);
+  for (auto _ : state) {
+    std::cout << std::get<0>(args_tuple) << ": " << std::get<1>(args_tuple)
+              << '\n';
+    [...]
+  }
+}
+// Registers a benchmark named "BM_takes_args/int_string_test" that passes
+// the specified values to `args`.
+BENCHMARK_CAPTURE(BM_takes_args, int_string_test, 42, std::string("abc"));
+
+// Registers the same benchmark "BM_takes_args/int_test" that passes
+// the specified values to `args`.
+BENCHMARK_CAPTURE(BM_takes_args, int_test, 42, 43);
+```
+
+Note that elements of `...args` may refer to global variables. Users should
+avoid modifying global state inside of a benchmark.
+
+<a name="asymptotic-complexity" />
+
+## Calculating Asymptotic Complexity (Big O)
+
+Asymptotic complexity might be calculated for a family of benchmarks. The
+following code will calculate the coefficient for the high-order term in the
+running time and the normalized root-mean square error of string comparison.
+
+```c++
+static void BM_StringCompare(benchmark::State& state) {
+  std::string s1(state.range(0), '-');
+  std::string s2(state.range(0), '-');
+  for (auto _ : state) {
+    auto comparison_result = s1.compare(s2);
+    benchmark::DoNotOptimize(comparison_result);
+  }
+  state.SetComplexityN(state.range(0));
+}
+BENCHMARK(BM_StringCompare)
+    ->RangeMultiplier(2)->Range(1<<10, 1<<18)->Complexity(benchmark::oN);
+```
+
+As shown in the following invocation, asymptotic complexity might also be
+calculated automatically.
+
+```c++
+BENCHMARK(BM_StringCompare)
+    ->RangeMultiplier(2)->Range(1<<10, 1<<18)->Complexity();
+```
+
+The following code will specify asymptotic complexity with a lambda function,
+that might be used to customize high-order term calculation.
+
+```c++
+BENCHMARK(BM_StringCompare)->RangeMultiplier(2)
+    ->Range(1<<10, 1<<18)->Complexity([](benchmark::IterationCount n)->double{return n; });
+```
+
+<a name="custom-benchmark-name" />
+
+## Custom Benchmark Name
+
+You can change the benchmark's name as follows:
+
+```c++
+BENCHMARK(BM_memcpy)->Name("memcpy")->RangeMultiplier(2)->Range(8, 8<<10);
+```
+
+The invocation will execute the benchmark as before using `BM_memcpy` but changes
+the prefix in the report to `memcpy`.
+
+<a name="templated-benchmarks" />
+
+## Templated Benchmarks
+
+This example produces and consumes messages of size `sizeof(v)` `range_x`
+times. It also outputs throughput in the absence of multiprogramming.
+
+```c++
+template <class Q> void BM_Sequential(benchmark::State& state) {
+  Q q;
+  typename Q::value_type v;
+  for (auto _ : state) {
+    for (int i = state.range(0); i--; )
+      q.push(v);
+    for (int e = state.range(0); e--; )
+      q.Wait(&v);
+  }
+  // actually messages, not bytes:
+  state.SetBytesProcessed(
+      static_cast<int64_t>(state.iterations())*state.range(0));
+}
+// C++03
+BENCHMARK_TEMPLATE(BM_Sequential, WaitQueue<int>)->Range(1<<0, 1<<10);
+
+// C++11 or newer, you can use the BENCHMARK macro with template parameters:
+BENCHMARK(BM_Sequential<WaitQueue<int>>)->Range(1<<0, 1<<10);
+
+```
+
+Three macros are provided for adding benchmark templates.
+
+```c++
+#ifdef BENCHMARK_HAS_CXX11
+#define BENCHMARK(func<...>) // Takes any number of parameters.
+#else // C++ < C++11
+#define BENCHMARK_TEMPLATE(func, arg1)
+#endif
+#define BENCHMARK_TEMPLATE1(func, arg1)
+#define BENCHMARK_TEMPLATE2(func, arg1, arg2)
+```
+
+<a name="fixtures" />
+
+## Fixtures
+
+Fixture tests are created by first defining a type that derives from
+`::benchmark::Fixture` and then creating/registering the tests using the
+following macros:
+
+* `BENCHMARK_F(ClassName, Method)`
+* `BENCHMARK_DEFINE_F(ClassName, Method)`
+* `BENCHMARK_REGISTER_F(ClassName, Method)`
+
+For Example:
+
+```c++
+class MyFixture : public benchmark::Fixture {
+public:
+  void SetUp(const ::benchmark::State& state) {
+  }
+
+  void TearDown(const ::benchmark::State& state) {
+  }
+};
+
+BENCHMARK_F(MyFixture, FooTest)(benchmark::State& st) {
+   for (auto _ : st) {
+     ...
+  }
+}
+
+BENCHMARK_DEFINE_F(MyFixture, BarTest)(benchmark::State& st) {
+   for (auto _ : st) {
+     ...
+  }
+}
+/* BarTest is NOT registered */
+BENCHMARK_REGISTER_F(MyFixture, BarTest)->Threads(2);
+/* BarTest is now registered */
+```
+
+### Templated Fixtures
+
+Also you can create templated fixture by using the following macros:
+
+* `BENCHMARK_TEMPLATE_F(ClassName, Method, ...)`
+* `BENCHMARK_TEMPLATE_DEFINE_F(ClassName, Method, ...)`
+
+For example:
+
+```c++
+template<typename T>
+class MyFixture : public benchmark::Fixture {};
+
+BENCHMARK_TEMPLATE_F(MyFixture, IntTest, int)(benchmark::State& st) {
+   for (auto _ : st) {
+     ...
+  }
+}
+
+BENCHMARK_TEMPLATE_DEFINE_F(MyFixture, DoubleTest, double)(benchmark::State& st) {
+   for (auto _ : st) {
+     ...
+  }
+}
+
+BENCHMARK_REGISTER_F(MyFixture, DoubleTest)->Threads(2);
+```
+
+<a name="custom-counters" />
+
+## Custom Counters
+
+You can add your own counters with user-defined names. The example below
+will add columns "Foo", "Bar" and "Baz" in its output:
+
+```c++
+static void UserCountersExample1(benchmark::State& state) {
+  double numFoos = 0, numBars = 0, numBazs = 0;
+  for (auto _ : state) {
+    // ... count Foo,Bar,Baz events
+  }
+  state.counters["Foo"] = numFoos;
+  state.counters["Bar"] = numBars;
+  state.counters["Baz"] = numBazs;
+}
+```
+
+The `state.counters` object is a `std::map` with `std::string` keys
+and `Counter` values. The latter is a `double`-like class, via an implicit
+conversion to `double&`. Thus you can use all of the standard arithmetic
+assignment operators (`=,+=,-=,*=,/=`) to change the value of each counter.
+
+In multithreaded benchmarks, each counter is set on the calling thread only.
+When the benchmark finishes, the counters from each thread will be summed;
+the resulting sum is the value which will be shown for the benchmark.
+
+The `Counter` constructor accepts three parameters: the value as a `double`
+; a bit flag which allows you to show counters as rates, and/or as per-thread
+iteration, and/or as per-thread averages, and/or iteration invariants,
+and/or finally inverting the result; and a flag specifying the 'unit' - i.e.
+is 1k a 1000 (default, `benchmark::Counter::OneK::kIs1000`), or 1024
+(`benchmark::Counter::OneK::kIs1024`)?
+
+```c++
+  // sets a simple counter
+  state.counters["Foo"] = numFoos;
+
+  // Set the counter as a rate. It will be presented divided
+  // by the duration of the benchmark.
+  // Meaning: per one second, how many 'foo's are processed?
+  state.counters["FooRate"] = Counter(numFoos, benchmark::Counter::kIsRate);
+
+  // Set the counter as a rate. It will be presented divided
+  // by the duration of the benchmark, and the result inverted.
+  // Meaning: how many seconds it takes to process one 'foo'?
+  state.counters["FooInvRate"] = Counter(numFoos, benchmark::Counter::kIsRate | benchmark::Counter::kInvert);
+
+  // Set the counter as a thread-average quantity. It will
+  // be presented divided by the number of threads.
+  state.counters["FooAvg"] = Counter(numFoos, benchmark::Counter::kAvgThreads);
+
+  // There's also a combined flag:
+  state.counters["FooAvgRate"] = Counter(numFoos,benchmark::Counter::kAvgThreadsRate);
+
+  // This says that we process with the rate of state.range(0) bytes every iteration:
+  state.counters["BytesProcessed"] = Counter(state.range(0), benchmark::Counter::kIsIterationInvariantRate, benchmark::Counter::OneK::kIs1024);
+```
+
+When you're compiling in C++11 mode or later you can use `insert()` with
+`std::initializer_list`:
+
+<!-- {% raw %} -->
+```c++
+  // With C++11, this can be done:
+  state.counters.insert({{"Foo", numFoos}, {"Bar", numBars}, {"Baz", numBazs}});
+  // ... instead of:
+  state.counters["Foo"] = numFoos;
+  state.counters["Bar"] = numBars;
+  state.counters["Baz"] = numBazs;
+```
+<!-- {% endraw %} -->
+
+### Counter Reporting
+
+When using the console reporter, by default, user counters are printed at
+the end after the table, the same way as ``bytes_processed`` and
+``items_processed``. This is best for cases in which there are few counters,
+or where there are only a couple of lines per benchmark. Here's an example of
+the default output:
+
+```
+------------------------------------------------------------------------------
+Benchmark                        Time           CPU Iterations UserCounters...
+------------------------------------------------------------------------------
+BM_UserCounter/threads:8      2248 ns      10277 ns      68808 Bar=16 Bat=40 Baz=24 Foo=8
+BM_UserCounter/threads:1      9797 ns       9788 ns      71523 Bar=2 Bat=5 Baz=3 Foo=1024m
+BM_UserCounter/threads:2      4924 ns       9842 ns      71036 Bar=4 Bat=10 Baz=6 Foo=2
+BM_UserCounter/threads:4      2589 ns      10284 ns      68012 Bar=8 Bat=20 Baz=12 Foo=4
+BM_UserCounter/threads:8      2212 ns      10287 ns      68040 Bar=16 Bat=40 Baz=24 Foo=8
+BM_UserCounter/threads:16     1782 ns      10278 ns      68144 Bar=32 Bat=80 Baz=48 Foo=16
+BM_UserCounter/threads:32     1291 ns      10296 ns      68256 Bar=64 Bat=160 Baz=96 Foo=32
+BM_UserCounter/threads:4      2615 ns      10307 ns      68040 Bar=8 Bat=20 Baz=12 Foo=4
+BM_Factorial                    26 ns         26 ns   26608979 40320
+BM_Factorial/real_time          26 ns         26 ns   26587936 40320
+BM_CalculatePiRange/1           16 ns         16 ns   45704255 0
+BM_CalculatePiRange/8           73 ns         73 ns    9520927 3.28374
+BM_CalculatePiRange/64         609 ns        609 ns    1140647 3.15746
+BM_CalculatePiRange/512       4900 ns       4901 ns     142696 3.14355
+```
+
+If this doesn't suit you, you can print each counter as a table column by
+passing the flag `--benchmark_counters_tabular=true` to the benchmark
+application. This is best for cases in which there are a lot of counters, or
+a lot of lines per individual benchmark. Note that this will trigger a
+reprinting of the table header any time the counter set changes between
+individual benchmarks. Here's an example of corresponding output when
+`--benchmark_counters_tabular=true` is passed:
+
+```
+---------------------------------------------------------------------------------------
+Benchmark                        Time           CPU Iterations    Bar   Bat   Baz   Foo
+---------------------------------------------------------------------------------------
+BM_UserCounter/threads:8      2198 ns       9953 ns      70688     16    40    24     8
+BM_UserCounter/threads:1      9504 ns       9504 ns      73787      2     5     3     1
+BM_UserCounter/threads:2      4775 ns       9550 ns      72606      4    10     6     2
+BM_UserCounter/threads:4      2508 ns       9951 ns      70332      8    20    12     4
+BM_UserCounter/threads:8      2055 ns       9933 ns      70344     16    40    24     8
+BM_UserCounter/threads:16     1610 ns       9946 ns      70720     32    80    48    16
+BM_UserCounter/threads:32     1192 ns       9948 ns      70496     64   160    96    32
+BM_UserCounter/threads:4      2506 ns       9949 ns      70332      8    20    12     4
+--------------------------------------------------------------
+Benchmark                        Time           CPU Iterations
+--------------------------------------------------------------
+BM_Factorial                    26 ns         26 ns   26392245 40320
+BM_Factorial/real_time          26 ns         26 ns   26494107 40320
+BM_CalculatePiRange/1           15 ns         15 ns   45571597 0
+BM_CalculatePiRange/8           74 ns         74 ns    9450212 3.28374
+BM_CalculatePiRange/64         595 ns        595 ns    1173901 3.15746
+BM_CalculatePiRange/512       4752 ns       4752 ns     147380 3.14355
+BM_CalculatePiRange/4k       37970 ns      37972 ns      18453 3.14184
+BM_CalculatePiRange/32k     303733 ns     303744 ns       2305 3.14162
+BM_CalculatePiRange/256k   2434095 ns    2434186 ns        288 3.1416
+BM_CalculatePiRange/1024k  9721140 ns    9721413 ns         71 3.14159
+BM_CalculatePi/threads:8      2255 ns       9943 ns      70936
+```
+
+Note above the additional header printed when the benchmark changes from
+``BM_UserCounter`` to ``BM_Factorial``. This is because ``BM_Factorial`` does
+not have the same counter set as ``BM_UserCounter``.
+
+<a name="multithreaded-benchmarks"/>
+
+## Multithreaded Benchmarks
+
+In a multithreaded test (benchmark invoked by multiple threads simultaneously),
+it is guaranteed that none of the threads will start until all have reached
+the start of the benchmark loop, and all will have finished before any thread
+exits the benchmark loop. (This behavior is also provided by the `KeepRunning()`
+API) As such, any global setup or teardown can be wrapped in a check against the thread
+index:
+
+```c++
+static void BM_MultiThreaded(benchmark::State& state) {
+  if (state.thread_index() == 0) {
+    // Setup code here.
+  }
+  for (auto _ : state) {
+    // Run the test as normal.
+  }
+  if (state.thread_index() == 0) {
+    // Teardown code here.
+  }
+}
+BENCHMARK(BM_MultiThreaded)->Threads(2);
+```
+
+To run the benchmark across a range of thread counts, instead of `Threads`, use
+`ThreadRange`. This takes two parameters (`min_threads` and `max_threads`) and
+runs the benchmark once for values in the inclusive range. For example:
+
+```c++
+BENCHMARK(BM_MultiThreaded)->ThreadRange(1, 8);
+```
+
+will run `BM_MultiThreaded` with thread counts 1, 2, 4, and 8.
+
+If the benchmarked code itself uses threads and you want to compare it to
+single-threaded code, you may want to use real-time ("wallclock") measurements
+for latency comparisons:
+
+```c++
+BENCHMARK(BM_test)->Range(8, 8<<10)->UseRealTime();
+```
+
+Without `UseRealTime`, CPU time is used by default.
+
+<a name="cpu-timers" />
+
+## CPU Timers
+
+By default, the CPU timer only measures the time spent by the main thread.
+If the benchmark itself uses threads internally, this measurement may not
+be what you are looking for. Instead, there is a way to measure the total
+CPU usage of the process, by all the threads.
+
+```c++
+void callee(int i);
+
+static void MyMain(int size) {
+#pragma omp parallel for
+  for(int i = 0; i < size; i++)
+    callee(i);
+}
+
+static void BM_OpenMP(benchmark::State& state) {
+  for (auto _ : state)
+    MyMain(state.range(0));
+}
+
+// Measure the time spent by the main thread, use it to decide for how long to
+// run the benchmark loop. Depending on the internal implementation detail may
+// measure to anywhere from near-zero (the overhead spent before/after work
+// handoff to worker thread[s]) to the whole single-thread time.
+BENCHMARK(BM_OpenMP)->Range(8, 8<<10);
+
+// Measure the user-visible time, the wall clock (literally, the time that
+// has passed on the clock on the wall), use it to decide for how long to
+// run the benchmark loop. This will always be meaningful, an will match the
+// time spent by the main thread in single-threaded case, in general decreasing
+// with the number of internal threads doing the work.
+BENCHMARK(BM_OpenMP)->Range(8, 8<<10)->UseRealTime();
+
+// Measure the total CPU consumption, use it to decide for how long to
+// run the benchmark loop. This will always measure to no less than the
+// time spent by the main thread in single-threaded case.
+BENCHMARK(BM_OpenMP)->Range(8, 8<<10)->MeasureProcessCPUTime();
+
+// A mixture of the last two. Measure the total CPU consumption, but use the
+// wall clock to decide for how long to run the benchmark loop.
+BENCHMARK(BM_OpenMP)->Range(8, 8<<10)->MeasureProcessCPUTime()->UseRealTime();
+```
+
+### Controlling Timers
+
+Normally, the entire duration of the work loop (`for (auto _ : state) {}`)
+is measured. But sometimes, it is necessary to do some work inside of
+that loop, every iteration, but without counting that time to the benchmark time.
+That is possible, although it is not recommended, since it has high overhead.
+
+<!-- {% raw %} -->
+```c++
+static void BM_SetInsert_With_Timer_Control(benchmark::State& state) {
+  std::set<int> data;
+  for (auto _ : state) {
+    state.PauseTiming(); // Stop timers. They will not count until they are resumed.
+    data = ConstructRandomSet(state.range(0)); // Do something that should not be measured
+    state.ResumeTiming(); // And resume timers. They are now counting again.
+    // The rest will be measured.
+    for (int j = 0; j < state.range(1); ++j)
+      data.insert(RandomNumber());
+  }
+}
+BENCHMARK(BM_SetInsert_With_Timer_Control)->Ranges({{1<<10, 8<<10}, {128, 512}});
+```
+<!-- {% endraw %} -->
+
+<a name="manual-timing" />
+
+## Manual Timing
+
+For benchmarking something for which neither CPU time nor real-time are
+correct or accurate enough, completely manual timing is supported using
+the `UseManualTime` function.
+
+When `UseManualTime` is used, the benchmarked code must call
+`SetIterationTime` once per iteration of the benchmark loop to
+report the manually measured time.
+
+An example use case for this is benchmarking GPU execution (e.g. OpenCL
+or CUDA kernels, OpenGL or Vulkan or Direct3D draw calls), which cannot
+be accurately measured using CPU time or real-time. Instead, they can be
+measured accurately using a dedicated API, and these measurement results
+can be reported back with `SetIterationTime`.
+
+```c++
+static void BM_ManualTiming(benchmark::State& state) {
+  int microseconds = state.range(0);
+  std::chrono::duration<double, std::micro> sleep_duration {
+    static_cast<double>(microseconds)
+  };
+
+  for (auto _ : state) {
+    auto start = std::chrono::high_resolution_clock::now();
+    // Simulate some useful workload with a sleep
+    std::this_thread::sleep_for(sleep_duration);
+    auto end = std::chrono::high_resolution_clock::now();
+
+    auto elapsed_seconds =
+      std::chrono::duration_cast<std::chrono::duration<double>>(
+        end - start);
+
+    state.SetIterationTime(elapsed_seconds.count());
+  }
+}
+BENCHMARK(BM_ManualTiming)->Range(1, 1<<17)->UseManualTime();
+```
+
+<a name="setting-the-time-unit" />
+
+## Setting the Time Unit
+
+If a benchmark runs a few milliseconds it may be hard to visually compare the
+measured times, since the output data is given in nanoseconds per default. In
+order to manually set the time unit, you can specify it manually:
+
+```c++
+BENCHMARK(BM_test)->Unit(benchmark::kMillisecond);
+```
+
+Additionally the default time unit can be set globally with the
+`--benchmark_time_unit={ns|us|ms|s}` command line argument. The argument only
+affects benchmarks where the time unit is not set explicitly.
+
+<a name="preventing-optimization" />
+
+## Preventing Optimization
+
+To prevent a value or expression from being optimized away by the compiler
+the `benchmark::DoNotOptimize(...)` and `benchmark::ClobberMemory()`
+functions can be used.
+
+```c++
+static void BM_test(benchmark::State& state) {
+  for (auto _ : state) {
+      int x = 0;
+      for (int i=0; i < 64; ++i) {
+        benchmark::DoNotOptimize(x += i);
+      }
+  }
+}
+```
+
+`DoNotOptimize(<expr>)` forces the  *result* of `<expr>` to be stored in either
+memory or a register. For GNU based compilers it acts as read/write barrier
+for global memory. More specifically it forces the compiler to flush pending
+writes to memory and reload any other values as necessary.
+
+Note that `DoNotOptimize(<expr>)` does not prevent optimizations on `<expr>`
+in any way. `<expr>` may even be removed entirely when the result is already
+known. For example:
+
+```c++
+  /* Example 1: `<expr>` is removed entirely. */
+  int foo(int x) { return x + 42; }
+  while (...) DoNotOptimize(foo(0)); // Optimized to DoNotOptimize(42);
+
+  /*  Example 2: Result of '<expr>' is only reused */
+  int bar(int) __attribute__((const));
+  while (...) DoNotOptimize(bar(0)); // Optimized to:
+  // int __result__ = bar(0);
+  // while (...) DoNotOptimize(__result__);
+```
+
+The second tool for preventing optimizations is `ClobberMemory()`. In essence
+`ClobberMemory()` forces the compiler to perform all pending writes to global
+memory. Memory managed by block scope objects must be "escaped" using
+`DoNotOptimize(...)` before it can be clobbered. In the below example
+`ClobberMemory()` prevents the call to `v.push_back(42)` from being optimized
+away.
+
+```c++
+static void BM_vector_push_back(benchmark::State& state) {
+  for (auto _ : state) {
+    std::vector<int> v;
+    v.reserve(1);
+    auto data = v.data();           // Allow v.data() to be clobbered. Pass as non-const
+    benchmark::DoNotOptimize(data); // lvalue to avoid undesired compiler optimizations
+    v.push_back(42);
+    benchmark::ClobberMemory(); // Force 42 to be written to memory.
+  }
+}
+```
+
+Note that `ClobberMemory()` is only available for GNU or MSVC based compilers.
+
+<a name="reporting-statistics" />
+
+## Statistics: Reporting the Mean, Median and Standard Deviation / Coefficient of variation of Repeated Benchmarks
+
+By default each benchmark is run once and that single result is reported.
+However benchmarks are often noisy and a single result may not be representative
+of the overall behavior. For this reason it's possible to repeatedly rerun the
+benchmark.
+
+The number of runs of each benchmark is specified globally by the
+`--benchmark_repetitions` flag or on a per benchmark basis by calling
+`Repetitions` on the registered benchmark object. When a benchmark is run more
+than once the mean, median, standard deviation and coefficient of variation
+of the runs will be reported.
+
+Additionally the `--benchmark_report_aggregates_only={true|false}`,
+`--benchmark_display_aggregates_only={true|false}` flags or
+`ReportAggregatesOnly(bool)`, `DisplayAggregatesOnly(bool)` functions can be
+used to change how repeated tests are reported. By default the result of each
+repeated run is reported. When `report aggregates only` option is `true`,
+only the aggregates (i.e. mean, median, standard deviation and coefficient
+of variation, maybe complexity measurements if they were requested) of the runs
+is reported, to both the reporters - standard output (console), and the file.
+However when only the `display aggregates only` option is `true`,
+only the aggregates are displayed in the standard output, while the file
+output still contains everything.
+Calling `ReportAggregatesOnly(bool)` / `DisplayAggregatesOnly(bool)` on a
+registered benchmark object overrides the value of the appropriate flag for that
+benchmark.
+
+<a name="custom-statistics" />
+
+## Custom Statistics
+
+While having these aggregates is nice, this may not be enough for everyone.
+For example you may want to know what the largest observation is, e.g. because
+you have some real-time constraints. This is easy. The following code will
+specify a custom statistic to be calculated, defined by a lambda function.
+
+```c++
+void BM_spin_empty(benchmark::State& state) {
+  for (auto _ : state) {
+    for (int x = 0; x < state.range(0); ++x) {
+      benchmark::DoNotOptimize(x);
+    }
+  }
+}
+
+BENCHMARK(BM_spin_empty)
+  ->ComputeStatistics("max", [](const std::vector<double>& v) -> double {
+    return *(std::max_element(std::begin(v), std::end(v)));
+  })
+  ->Arg(512);
+```
+
+While usually the statistics produce values in time units,
+you can also produce percentages:
+
+```c++
+void BM_spin_empty(benchmark::State& state) {
+  for (auto _ : state) {
+    for (int x = 0; x < state.range(0); ++x) {
+      benchmark::DoNotOptimize(x);
+    }
+  }
+}
+
+BENCHMARK(BM_spin_empty)
+  ->ComputeStatistics("ratio", [](const std::vector<double>& v) -> double {
+    return std::begin(v) / std::end(v);
+  }, benchmark::StatisticUnit::kPercentage)
+  ->Arg(512);
+```
+
+<a name="memory-usage" />
+
+## Memory Usage
+
+It's often useful to also track memory usage for benchmarks, alongside CPU
+performance. For this reason, benchmark offers the `RegisterMemoryManager`
+method that allows a custom `MemoryManager` to be injected.
+
+If set, the `MemoryManager::Start` and `MemoryManager::Stop` methods will be
+called at the start and end of benchmark runs to allow user code to fill out
+a report on the number of allocations, bytes used, etc.
+
+This data will then be reported alongside other performance data, currently
+only when using JSON output.
+
+<a name="using-register-benchmark" />
+
+## Using RegisterBenchmark(name, fn, args...)
+
+The `RegisterBenchmark(name, func, args...)` function provides an alternative
+way to create and register benchmarks.
+`RegisterBenchmark(name, func, args...)` creates, registers, and returns a
+pointer to a new benchmark with the specified `name` that invokes
+`func(st, args...)` where `st` is a `benchmark::State` object.
+
+Unlike the `BENCHMARK` registration macros, which can only be used at the global
+scope, the `RegisterBenchmark` can be called anywhere. This allows for
+benchmark tests to be registered programmatically.
+
+Additionally `RegisterBenchmark` allows any callable object to be registered
+as a benchmark. Including capturing lambdas and function objects.
+
+For Example:
+```c++
+auto BM_test = [](benchmark::State& st, auto Inputs) { /* ... */ };
+
+int main(int argc, char** argv) {
+  for (auto& test_input : { /* ... */ })
+      benchmark::RegisterBenchmark(test_input.name(), BM_test, test_input);
+  benchmark::Initialize(&argc, argv);
+  benchmark::RunSpecifiedBenchmarks();
+  benchmark::Shutdown();
+}
+```
+
+<a name="exiting-with-an-error" />
+
+## Exiting with an Error
+
+When errors caused by external influences, such as file I/O and network
+communication, occur within a benchmark the
+`State::SkipWithError(const std::string& msg)` function can be used to skip that run
+of benchmark and report the error. Note that only future iterations of the
+`KeepRunning()` are skipped. For the ranged-for version of the benchmark loop
+Users must explicitly exit the loop, otherwise all iterations will be performed.
+Users may explicitly return to exit the benchmark immediately.
+
+The `SkipWithError(...)` function may be used at any point within the benchmark,
+including before and after the benchmark loop. Moreover, if `SkipWithError(...)`
+has been used, it is not required to reach the benchmark loop and one may return
+from the benchmark function early.
+
+For example:
+
+```c++
+static void BM_test(benchmark::State& state) {
+  auto resource = GetResource();
+  if (!resource.good()) {
+    state.SkipWithError("Resource is not good!");
+    // KeepRunning() loop will not be entered.
+  }
+  while (state.KeepRunning()) {
+    auto data = resource.read_data();
+    if (!resource.good()) {
+      state.SkipWithError("Failed to read data!");
+      break; // Needed to skip the rest of the iteration.
+    }
+    do_stuff(data);
+  }
+}
+
+static void BM_test_ranged_fo(benchmark::State & state) {
+  auto resource = GetResource();
+  if (!resource.good()) {
+    state.SkipWithError("Resource is not good!");
+    return; // Early return is allowed when SkipWithError() has been used.
+  }
+  for (auto _ : state) {
+    auto data = resource.read_data();
+    if (!resource.good()) {
+      state.SkipWithError("Failed to read data!");
+      break; // REQUIRED to prevent all further iterations.
+    }
+    do_stuff(data);
+  }
+}
+```
+<a name="a-faster-keep-running-loop" />
+
+## A Faster KeepRunning Loop
+
+In C++11 mode, a ranged-based for loop should be used in preference to
+the `KeepRunning` loop for running the benchmarks. For example:
+
+```c++
+static void BM_Fast(benchmark::State &state) {
+  for (auto _ : state) {
+    FastOperation();
+  }
+}
+BENCHMARK(BM_Fast);
+```
+
+The reason the ranged-for loop is faster than using `KeepRunning`, is
+because `KeepRunning` requires a memory load and store of the iteration count
+ever iteration, whereas the ranged-for variant is able to keep the iteration count
+in a register.
+
+For example, an empty inner loop of using the ranged-based for method looks like:
+
+```asm
+# Loop Init
+  mov rbx, qword ptr [r14 + 104]
+  call benchmark::State::StartKeepRunning()
+  test rbx, rbx
+  je .LoopEnd
+.LoopHeader: # =>This Inner Loop Header: Depth=1
+  add rbx, -1
+  jne .LoopHeader
+.LoopEnd:
+```
+
+Compared to an empty `KeepRunning` loop, which looks like:
+
+```asm
+.LoopHeader: # in Loop: Header=BB0_3 Depth=1
+  cmp byte ptr [rbx], 1
+  jne .LoopInit
+.LoopBody: # =>This Inner Loop Header: Depth=1
+  mov rax, qword ptr [rbx + 8]
+  lea rcx, [rax + 1]
+  mov qword ptr [rbx + 8], rcx
+  cmp rax, qword ptr [rbx + 104]
+  jb .LoopHeader
+  jmp .LoopEnd
+.LoopInit:
+  mov rdi, rbx
+  call benchmark::State::StartKeepRunning()
+  jmp .LoopBody
+.LoopEnd:
+```
+
+Unless C++03 compatibility is required, the ranged-for variant of writing
+the benchmark loop should be preferred.
+
+<a name="disabling-cpu-frequency-scaling" />
+
+## Disabling CPU Frequency Scaling
+
+If you see this error:
+
+```
+***WARNING*** CPU scaling is enabled, the benchmark real time measurements may
+be noisy and will incur extra overhead.
+```
+
+you might want to disable the CPU frequency scaling while running the
+benchmark, as well as consider other ways to stabilize the performance of
+your system while benchmarking.
+
+See [Reducing Variance](reducing_variance.md) for more information.
diff --git a/leveldb_base/third_party/benchmark/include/benchmark/benchmark.h b/leveldb_base/third_party/benchmark/include/benchmark/benchmark.h
new file mode 100644
index 0000000..e44d534
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/include/benchmark/benchmark.h
@@ -0,0 +1,1953 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Support for registering benchmarks for functions.
+
+/* Example usage:
+// Define a function that executes the code to be measured a
+// specified number of times:
+static void BM_StringCreation(benchmark::State& state) {
+  for (auto _ : state)
+    std::string empty_string;
+}
+
+// Register the function as a benchmark
+BENCHMARK(BM_StringCreation);
+
+// Define another benchmark
+static void BM_StringCopy(benchmark::State& state) {
+  std::string x = "hello";
+  for (auto _ : state)
+    std::string copy(x);
+}
+BENCHMARK(BM_StringCopy);
+
+// Augment the main() program to invoke benchmarks if specified
+// via the --benchmark_filter command line flag.  E.g.,
+//       my_unittest --benchmark_filter=all
+//       my_unittest --benchmark_filter=BM_StringCreation
+//       my_unittest --benchmark_filter=String
+//       my_unittest --benchmark_filter='Copy|Creation'
+int main(int argc, char** argv) {
+  benchmark::Initialize(&argc, argv);
+  benchmark::RunSpecifiedBenchmarks();
+  benchmark::Shutdown();
+  return 0;
+}
+
+// Sometimes a family of microbenchmarks can be implemented with
+// just one routine that takes an extra argument to specify which
+// one of the family of benchmarks to run.  For example, the following
+// code defines a family of microbenchmarks for measuring the speed
+// of memcpy() calls of different lengths:
+
+static void BM_memcpy(benchmark::State& state) {
+  char* src = new char[state.range(0)]; char* dst = new char[state.range(0)];
+  memset(src, 'x', state.range(0));
+  for (auto _ : state)
+    memcpy(dst, src, state.range(0));
+  state.SetBytesProcessed(state.iterations() * state.range(0));
+  delete[] src; delete[] dst;
+}
+BENCHMARK(BM_memcpy)->Arg(8)->Arg(64)->Arg(512)->Arg(1<<10)->Arg(8<<10);
+
+// The preceding code is quite repetitive, and can be replaced with the
+// following short-hand.  The following invocation will pick a few
+// appropriate arguments in the specified range and will generate a
+// microbenchmark for each such argument.
+BENCHMARK(BM_memcpy)->Range(8, 8<<10);
+
+// You might have a microbenchmark that depends on two inputs.  For
+// example, the following code defines a family of microbenchmarks for
+// measuring the speed of set insertion.
+static void BM_SetInsert(benchmark::State& state) {
+  set<int> data;
+  for (auto _ : state) {
+    state.PauseTiming();
+    data = ConstructRandomSet(state.range(0));
+    state.ResumeTiming();
+    for (int j = 0; j < state.range(1); ++j)
+      data.insert(RandomNumber());
+  }
+}
+BENCHMARK(BM_SetInsert)
+   ->Args({1<<10, 128})
+   ->Args({2<<10, 128})
+   ->Args({4<<10, 128})
+   ->Args({8<<10, 128})
+   ->Args({1<<10, 512})
+   ->Args({2<<10, 512})
+   ->Args({4<<10, 512})
+   ->Args({8<<10, 512});
+
+// The preceding code is quite repetitive, and can be replaced with
+// the following short-hand.  The following macro will pick a few
+// appropriate arguments in the product of the two specified ranges
+// and will generate a microbenchmark for each such pair.
+BENCHMARK(BM_SetInsert)->Ranges({{1<<10, 8<<10}, {128, 512}});
+
+// For more complex patterns of inputs, passing a custom function
+// to Apply allows programmatic specification of an
+// arbitrary set of arguments to run the microbenchmark on.
+// The following example enumerates a dense range on
+// one parameter, and a sparse range on the second.
+static void CustomArguments(benchmark::internal::Benchmark* b) {
+  for (int i = 0; i <= 10; ++i)
+    for (int j = 32; j <= 1024*1024; j *= 8)
+      b->Args({i, j});
+}
+BENCHMARK(BM_SetInsert)->Apply(CustomArguments);
+
+// Templated microbenchmarks work the same way:
+// Produce then consume 'size' messages 'iters' times
+// Measures throughput in the absence of multiprogramming.
+template <class Q> int BM_Sequential(benchmark::State& state) {
+  Q q;
+  typename Q::value_type v;
+  for (auto _ : state) {
+    for (int i = state.range(0); i--; )
+      q.push(v);
+    for (int e = state.range(0); e--; )
+      q.Wait(&v);
+  }
+  // actually messages, not bytes:
+  state.SetBytesProcessed(state.iterations() * state.range(0));
+}
+BENCHMARK_TEMPLATE(BM_Sequential, WaitQueue<int>)->Range(1<<0, 1<<10);
+
+Use `Benchmark::MinTime(double t)` to set the minimum time used to run the
+benchmark. This option overrides the `benchmark_min_time` flag.
+
+void BM_test(benchmark::State& state) {
+ ... body ...
+}
+BENCHMARK(BM_test)->MinTime(2.0); // Run for at least 2 seconds.
+
+In a multithreaded test, it is guaranteed that none of the threads will start
+until all have reached the loop start, and all will have finished before any
+thread exits the loop body. As such, any global setup or teardown you want to
+do can be wrapped in a check against the thread index:
+
+static void BM_MultiThreaded(benchmark::State& state) {
+  if (state.thread_index() == 0) {
+    // Setup code here.
+  }
+  for (auto _ : state) {
+    // Run the test as normal.
+  }
+  if (state.thread_index() == 0) {
+    // Teardown code here.
+  }
+}
+BENCHMARK(BM_MultiThreaded)->Threads(4);
+
+
+If a benchmark runs a few milliseconds it may be hard to visually compare the
+measured times, since the output data is given in nanoseconds per default. In
+order to manually set the time unit, you can specify it manually:
+
+BENCHMARK(BM_test)->Unit(benchmark::kMillisecond);
+*/
+
+#ifndef BENCHMARK_BENCHMARK_H_
+#define BENCHMARK_BENCHMARK_H_
+
+// The _MSVC_LANG check should detect Visual Studio 2015 Update 3 and newer.
+#if __cplusplus >= 201103L || (defined(_MSVC_LANG) && _MSVC_LANG >= 201103L)
+#define BENCHMARK_HAS_CXX11
+#endif
+
+// This _MSC_VER check should detect VS 2017 v15.3 and newer.
+#if __cplusplus >= 201703L || \
+    (defined(_MSC_VER) && _MSC_VER >= 1911 && _MSVC_LANG >= 201703L)
+#define BENCHMARK_HAS_CXX17
+#endif
+
+#include <stdint.h>
+
+#include <algorithm>
+#include <cassert>
+#include <cstddef>
+#include <iosfwd>
+#include <limits>
+#include <map>
+#include <set>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "benchmark/export.h"
+
+#if defined(BENCHMARK_HAS_CXX11)
+#include <atomic>
+#include <initializer_list>
+#include <type_traits>
+#include <utility>
+#endif
+
+#if defined(_MSC_VER)
+#include <intrin.h>  // for _ReadWriteBarrier
+#endif
+
+#ifndef BENCHMARK_HAS_CXX11
+#define BENCHMARK_DISALLOW_COPY_AND_ASSIGN(TypeName) \
+  TypeName(const TypeName&);                         \
+  TypeName& operator=(const TypeName&)
+#else
+#define BENCHMARK_DISALLOW_COPY_AND_ASSIGN(TypeName) \
+  TypeName(const TypeName&) = delete;                \
+  TypeName& operator=(const TypeName&) = delete
+#endif
+
+#ifdef BENCHMARK_HAS_CXX17
+#define BENCHMARK_UNUSED [[maybe_unused]]
+#elif defined(__GNUC__) || defined(__clang__)
+#define BENCHMARK_UNUSED __attribute__((unused))
+#else
+#define BENCHMARK_UNUSED
+#endif
+
+// Used to annotate functions, methods and classes so they
+// are not optimized by the compiler. Useful for tests
+// where you expect loops to stay in place churning cycles
+#if defined(__clang__)
+#define BENCHMARK_DONT_OPTIMIZE __attribute__((optnone))
+#elif defined(__GNUC__) || defined(__GNUG__)
+#define BENCHMARK_DONT_OPTIMIZE __attribute__((optimize(0)))
+#else
+// MSVC & Intel do not have a no-optimize attribute, only line pragmas
+#define BENCHMARK_DONT_OPTIMIZE
+#endif
+
+#if defined(__GNUC__) || defined(__clang__)
+#define BENCHMARK_ALWAYS_INLINE __attribute__((always_inline))
+#elif defined(_MSC_VER) && !defined(__clang__)
+#define BENCHMARK_ALWAYS_INLINE __forceinline
+#define __func__ __FUNCTION__
+#else
+#define BENCHMARK_ALWAYS_INLINE
+#endif
+
+#define BENCHMARK_INTERNAL_TOSTRING2(x) #x
+#define BENCHMARK_INTERNAL_TOSTRING(x) BENCHMARK_INTERNAL_TOSTRING2(x)
+
+// clang-format off
+#if (defined(__GNUC__) && !defined(__NVCC__) && !defined(__NVCOMPILER)) || defined(__clang__)
+#define BENCHMARK_BUILTIN_EXPECT(x, y) __builtin_expect(x, y)
+#define BENCHMARK_DEPRECATED_MSG(msg) __attribute__((deprecated(msg)))
+#define BENCHMARK_DISABLE_DEPRECATED_WARNING \
+  _Pragma("GCC diagnostic push")             \
+  _Pragma("GCC diagnostic ignored \"-Wdeprecated-declarations\"")
+#define BENCHMARK_RESTORE_DEPRECATED_WARNING _Pragma("GCC diagnostic pop")
+#elif defined(__NVCOMPILER)
+#define BENCHMARK_BUILTIN_EXPECT(x, y) __builtin_expect(x, y)
+#define BENCHMARK_DEPRECATED_MSG(msg) __attribute__((deprecated(msg)))
+#define BENCHMARK_DISABLE_DEPRECATED_WARNING \
+  _Pragma("diagnostic push") \
+  _Pragma("diag_suppress deprecated_entity_with_custom_message")
+#define BENCHMARK_RESTORE_DEPRECATED_WARNING _Pragma("diagnostic pop")
+#else
+#define BENCHMARK_BUILTIN_EXPECT(x, y) x
+#define BENCHMARK_DEPRECATED_MSG(msg)
+#define BENCHMARK_WARNING_MSG(msg)                           \
+  __pragma(message(__FILE__ "(" BENCHMARK_INTERNAL_TOSTRING( \
+      __LINE__) ") : warning note: " msg))
+#define BENCHMARK_DISABLE_DEPRECATED_WARNING
+#define BENCHMARK_RESTORE_DEPRECATED_WARNING
+#endif
+// clang-format on
+
+#if defined(__GNUC__) && !defined(__clang__)
+#define BENCHMARK_GCC_VERSION (__GNUC__ * 100 + __GNUC_MINOR__)
+#endif
+
+#ifndef __has_builtin
+#define __has_builtin(x) 0
+#endif
+
+#if defined(__GNUC__) || __has_builtin(__builtin_unreachable)
+#define BENCHMARK_UNREACHABLE() __builtin_unreachable()
+#elif defined(_MSC_VER)
+#define BENCHMARK_UNREACHABLE() __assume(false)
+#else
+#define BENCHMARK_UNREACHABLE() ((void)0)
+#endif
+
+#ifdef BENCHMARK_HAS_CXX11
+#define BENCHMARK_OVERRIDE override
+#else
+#define BENCHMARK_OVERRIDE
+#endif
+
+#if defined(_MSC_VER)
+#pragma warning(push)
+// C4251: <symbol> needs to have dll-interface to be used by clients of class
+#pragma warning(disable : 4251)
+#endif
+
+namespace benchmark {
+class BenchmarkReporter;
+
+// Default number of minimum benchmark running time in seconds.
+const char kDefaultMinTimeStr[] = "0.5s";
+
+BENCHMARK_EXPORT void PrintDefaultHelp();
+
+BENCHMARK_EXPORT void Initialize(int* argc, char** argv,
+                                 void (*HelperPrinterf)() = PrintDefaultHelp);
+BENCHMARK_EXPORT void Shutdown();
+
+// Report to stdout all arguments in 'argv' as unrecognized except the first.
+// Returns true there is at least on unrecognized argument (i.e. 'argc' > 1).
+BENCHMARK_EXPORT bool ReportUnrecognizedArguments(int argc, char** argv);
+
+// Returns the current value of --benchmark_filter.
+BENCHMARK_EXPORT std::string GetBenchmarkFilter();
+
+// Sets a new value to --benchmark_filter. (This will override this flag's
+// current value).
+// Should be called after `benchmark::Initialize()`, as
+// `benchmark::Initialize()` will override the flag's value.
+BENCHMARK_EXPORT void SetBenchmarkFilter(std::string value);
+
+// Returns the current value of --v (command line value for verbosity).
+BENCHMARK_EXPORT int32_t GetBenchmarkVerbosity();
+
+// Creates a default display reporter. Used by the library when no display
+// reporter is provided, but also made available for external use in case a
+// custom reporter should respect the `--benchmark_format` flag as a fallback
+BENCHMARK_EXPORT BenchmarkReporter* CreateDefaultDisplayReporter();
+
+// Generate a list of benchmarks matching the specified --benchmark_filter flag
+// and if --benchmark_list_tests is specified return after printing the name
+// of each matching benchmark. Otherwise run each matching benchmark and
+// report the results.
+//
+// spec : Specify the benchmarks to run. If users do not specify this arg,
+//        then the value of FLAGS_benchmark_filter
+//        will be used.
+//
+// The second and third overload use the specified 'display_reporter' and
+//  'file_reporter' respectively. 'file_reporter' will write to the file
+//  specified
+//   by '--benchmark_output'. If '--benchmark_output' is not given the
+//  'file_reporter' is ignored.
+//
+// RETURNS: The number of matching benchmarks.
+BENCHMARK_EXPORT size_t RunSpecifiedBenchmarks();
+BENCHMARK_EXPORT size_t RunSpecifiedBenchmarks(std::string spec);
+
+BENCHMARK_EXPORT size_t
+RunSpecifiedBenchmarks(BenchmarkReporter* display_reporter);
+BENCHMARK_EXPORT size_t
+RunSpecifiedBenchmarks(BenchmarkReporter* display_reporter, std::string spec);
+
+BENCHMARK_EXPORT size_t RunSpecifiedBenchmarks(
+    BenchmarkReporter* display_reporter, BenchmarkReporter* file_reporter);
+BENCHMARK_EXPORT size_t
+RunSpecifiedBenchmarks(BenchmarkReporter* display_reporter,
+                       BenchmarkReporter* file_reporter, std::string spec);
+
+// TimeUnit is passed to a benchmark in order to specify the order of magnitude
+// for the measured time.
+enum TimeUnit { kNanosecond, kMicrosecond, kMillisecond, kSecond };
+
+BENCHMARK_EXPORT TimeUnit GetDefaultTimeUnit();
+
+// Sets the default time unit the benchmarks use
+// Has to be called before the benchmark loop to take effect
+BENCHMARK_EXPORT void SetDefaultTimeUnit(TimeUnit unit);
+
+// If a MemoryManager is registered (via RegisterMemoryManager()),
+// it can be used to collect and report allocation metrics for a run of the
+// benchmark.
+class MemoryManager {
+ public:
+  static const int64_t TombstoneValue;
+
+  struct Result {
+    Result()
+        : num_allocs(0),
+          max_bytes_used(0),
+          total_allocated_bytes(TombstoneValue),
+          net_heap_growth(TombstoneValue) {}
+
+    // The number of allocations made in total between Start and Stop.
+    int64_t num_allocs;
+
+    // The peak memory use between Start and Stop.
+    int64_t max_bytes_used;
+
+    // The total memory allocated, in bytes, between Start and Stop.
+    // Init'ed to TombstoneValue if metric not available.
+    int64_t total_allocated_bytes;
+
+    // The net changes in memory, in bytes, between Start and Stop.
+    // ie., total_allocated_bytes - total_deallocated_bytes.
+    // Init'ed to TombstoneValue if metric not available.
+    int64_t net_heap_growth;
+  };
+
+  virtual ~MemoryManager() {}
+
+  // Implement this to start recording allocation information.
+  virtual void Start() = 0;
+
+  // Implement this to stop recording and fill out the given Result structure.
+  virtual void Stop(Result& result) = 0;
+};
+
+// Register a MemoryManager instance that will be used to collect and report
+// allocation measurements for benchmark runs.
+BENCHMARK_EXPORT
+void RegisterMemoryManager(MemoryManager* memory_manager);
+
+// Add a key-value pair to output as part of the context stanza in the report.
+BENCHMARK_EXPORT
+void AddCustomContext(const std::string& key, const std::string& value);
+
+namespace internal {
+class Benchmark;
+class BenchmarkImp;
+class BenchmarkFamilies;
+
+BENCHMARK_EXPORT std::map<std::string, std::string>*& GetGlobalContext();
+
+BENCHMARK_EXPORT
+void UseCharPointer(char const volatile*);
+
+// Take ownership of the pointer and register the benchmark. Return the
+// registered benchmark.
+BENCHMARK_EXPORT Benchmark* RegisterBenchmarkInternal(Benchmark*);
+
+// Ensure that the standard streams are properly initialized in every TU.
+BENCHMARK_EXPORT int InitializeStreams();
+BENCHMARK_UNUSED static int stream_init_anchor = InitializeStreams();
+
+}  // namespace internal
+
+#if (!defined(__GNUC__) && !defined(__clang__)) || defined(__pnacl__) || \
+    defined(__EMSCRIPTEN__)
+#define BENCHMARK_HAS_NO_INLINE_ASSEMBLY
+#endif
+
+// Force the compiler to flush pending writes to global memory. Acts as an
+// effective read/write barrier
+#ifdef BENCHMARK_HAS_CXX11
+inline BENCHMARK_ALWAYS_INLINE void ClobberMemory() {
+  std::atomic_signal_fence(std::memory_order_acq_rel);
+}
+#endif
+
+// The DoNotOptimize(...) function can be used to prevent a value or
+// expression from being optimized away by the compiler. This function is
+// intended to add little to no overhead.
+// See: https://youtu.be/nXaxk27zwlk?t=2441
+#ifndef BENCHMARK_HAS_NO_INLINE_ASSEMBLY
+#if !defined(__GNUC__) || defined(__llvm__) || defined(__INTEL_COMPILER)
+template <class Tp>
+BENCHMARK_DEPRECATED_MSG(
+    "The const-ref version of this method can permit "
+    "undesired compiler optimizations in benchmarks")
+inline BENCHMARK_ALWAYS_INLINE void DoNotOptimize(Tp const& value) {
+  asm volatile("" : : "r,m"(value) : "memory");
+}
+
+template <class Tp>
+inline BENCHMARK_ALWAYS_INLINE void DoNotOptimize(Tp& value) {
+#if defined(__clang__)
+  asm volatile("" : "+r,m"(value) : : "memory");
+#else
+  asm volatile("" : "+m,r"(value) : : "memory");
+#endif
+}
+#elif defined(BENCHMARK_HAS_CXX11) && (__GNUC__ >= 5)
+// Workaround for a bug with full argument copy overhead with GCC.
+// See: #1340 and https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105519
+template <class Tp>
+BENCHMARK_DEPRECATED_MSG(
+    "The const-ref version of this method can permit "
+    "undesired compiler optimizations in benchmarks")
+inline BENCHMARK_ALWAYS_INLINE
+    typename std::enable_if<std::is_trivially_copyable<Tp>::value &&
+                            (sizeof(Tp) <= sizeof(Tp*))>::type
+    DoNotOptimize(Tp const& value) {
+  asm volatile("" : : "r,m"(value) : "memory");
+}
+
+template <class Tp>
+BENCHMARK_DEPRECATED_MSG(
+    "The const-ref version of this method can permit "
+    "undesired compiler optimizations in benchmarks")
+inline BENCHMARK_ALWAYS_INLINE
+    typename std::enable_if<!std::is_trivially_copyable<Tp>::value ||
+                            (sizeof(Tp) > sizeof(Tp*))>::type
+    DoNotOptimize(Tp const& value) {
+  asm volatile("" : : "m"(value) : "memory");
+}
+
+template <class Tp>
+inline BENCHMARK_ALWAYS_INLINE
+    typename std::enable_if<std::is_trivially_copyable<Tp>::value &&
+                            (sizeof(Tp) <= sizeof(Tp*))>::type
+    DoNotOptimize(Tp& value) {
+  asm volatile("" : "+m,r"(value) : : "memory");
+}
+
+template <class Tp>
+inline BENCHMARK_ALWAYS_INLINE
+    typename std::enable_if<!std::is_trivially_copyable<Tp>::value ||
+                            (sizeof(Tp) > sizeof(Tp*))>::type
+    DoNotOptimize(Tp& value) {
+  asm volatile("" : "+m"(value) : : "memory");
+}
+
+#else
+// Fallback for GCC < 5. Can add some overhead because the compiler is forced
+// to use memory operations instead of operations with registers.
+// TODO: Remove if GCC < 5 will be unsupported.
+template <class Tp>
+BENCHMARK_DEPRECATED_MSG(
+    "The const-ref version of this method can permit "
+    "undesired compiler optimizations in benchmarks")
+inline BENCHMARK_ALWAYS_INLINE void DoNotOptimize(Tp const& value) {
+  asm volatile("" : : "m"(value) : "memory");
+}
+
+template <class Tp>
+inline BENCHMARK_ALWAYS_INLINE void DoNotOptimize(Tp& value) {
+  asm volatile("" : "+m"(value) : : "memory");
+}
+#endif
+
+#ifndef BENCHMARK_HAS_CXX11
+inline BENCHMARK_ALWAYS_INLINE void ClobberMemory() {
+  asm volatile("" : : : "memory");
+}
+#endif
+#elif defined(_MSC_VER)
+template <class Tp>
+BENCHMARK_DEPRECATED_MSG(
+    "The const-ref version of this method can permit "
+    "undesired compiler optimizations in benchmarks")
+inline BENCHMARK_ALWAYS_INLINE void DoNotOptimize(Tp const& value) {
+  internal::UseCharPointer(&reinterpret_cast<char const volatile&>(value));
+  _ReadWriteBarrier();
+}
+
+#ifndef BENCHMARK_HAS_CXX11
+inline BENCHMARK_ALWAYS_INLINE void ClobberMemory() { _ReadWriteBarrier(); }
+#endif
+#else
+template <class Tp>
+BENCHMARK_DEPRECATED_MSG(
+    "The const-ref version of this method can permit "
+    "undesired compiler optimizations in benchmarks")
+inline BENCHMARK_ALWAYS_INLINE void DoNotOptimize(Tp const& value) {
+  internal::UseCharPointer(&reinterpret_cast<char const volatile&>(value));
+}
+// FIXME Add ClobberMemory() for non-gnu and non-msvc compilers, before C++11.
+#endif
+
+// This class is used for user-defined counters.
+class Counter {
+ public:
+  enum Flags {
+    kDefaults = 0,
+    // Mark the counter as a rate. It will be presented divided
+    // by the duration of the benchmark.
+    kIsRate = 1 << 0,
+    // Mark the counter as a thread-average quantity. It will be
+    // presented divided by the number of threads.
+    kAvgThreads = 1 << 1,
+    // Mark the counter as a thread-average rate. See above.
+    kAvgThreadsRate = kIsRate | kAvgThreads,
+    // Mark the counter as a constant value, valid/same for *every* iteration.
+    // When reporting, it will be *multiplied* by the iteration count.
+    kIsIterationInvariant = 1 << 2,
+    // Mark the counter as a constant rate.
+    // When reporting, it will be *multiplied* by the iteration count
+    // and then divided by the duration of the benchmark.
+    kIsIterationInvariantRate = kIsRate | kIsIterationInvariant,
+    // Mark the counter as a iteration-average quantity.
+    // It will be presented divided by the number of iterations.
+    kAvgIterations = 1 << 3,
+    // Mark the counter as a iteration-average rate. See above.
+    kAvgIterationsRate = kIsRate | kAvgIterations,
+
+    // In the end, invert the result. This is always done last!
+    kInvert = 1 << 31
+  };
+
+  enum OneK {
+    // 1'000 items per 1k
+    kIs1000 = 1000,
+    // 1'024 items per 1k
+    kIs1024 = 1024
+  };
+
+  double value;
+  Flags flags;
+  OneK oneK;
+
+  BENCHMARK_ALWAYS_INLINE
+  Counter(double v = 0., Flags f = kDefaults, OneK k = kIs1000)
+      : value(v), flags(f), oneK(k) {}
+
+  BENCHMARK_ALWAYS_INLINE operator double const &() const { return value; }
+  BENCHMARK_ALWAYS_INLINE operator double&() { return value; }
+};
+
+// A helper for user code to create unforeseen combinations of Flags, without
+// having to do this cast manually each time, or providing this operator.
+Counter::Flags inline operator|(const Counter::Flags& LHS,
+                                const Counter::Flags& RHS) {
+  return static_cast<Counter::Flags>(static_cast<int>(LHS) |
+                                     static_cast<int>(RHS));
+}
+
+// This is the container for the user-defined counters.
+typedef std::map<std::string, Counter> UserCounters;
+
+// BigO is passed to a benchmark in order to specify the asymptotic
+// computational
+// complexity for the benchmark. In case oAuto is selected, complexity will be
+// calculated automatically to the best fit.
+enum BigO { oNone, o1, oN, oNSquared, oNCubed, oLogN, oNLogN, oAuto, oLambda };
+
+typedef int64_t IterationCount;
+
+enum StatisticUnit { kTime, kPercentage };
+
+// BigOFunc is passed to a benchmark in order to specify the asymptotic
+// computational complexity for the benchmark.
+typedef double(BigOFunc)(IterationCount);
+
+// StatisticsFunc is passed to a benchmark in order to compute some descriptive
+// statistics over all the measurements of some type
+typedef double(StatisticsFunc)(const std::vector<double>&);
+
+namespace internal {
+struct Statistics {
+  std::string name_;
+  StatisticsFunc* compute_;
+  StatisticUnit unit_;
+
+  Statistics(const std::string& name, StatisticsFunc* compute,
+             StatisticUnit unit = kTime)
+      : name_(name), compute_(compute), unit_(unit) {}
+};
+
+class BenchmarkInstance;
+class ThreadTimer;
+class ThreadManager;
+class PerfCountersMeasurement;
+
+enum AggregationReportMode
+#if defined(BENCHMARK_HAS_CXX11)
+    : unsigned
+#else
+#endif
+{
+  // The mode has not been manually specified
+  ARM_Unspecified = 0,
+  // The mode is user-specified.
+  // This may or may not be set when the following bit-flags are set.
+  ARM_Default = 1U << 0U,
+  // File reporter should only output aggregates.
+  ARM_FileReportAggregatesOnly = 1U << 1U,
+  // Display reporter should only output aggregates
+  ARM_DisplayReportAggregatesOnly = 1U << 2U,
+  // Both reporters should only display aggregates.
+  ARM_ReportAggregatesOnly =
+      ARM_FileReportAggregatesOnly | ARM_DisplayReportAggregatesOnly
+};
+
+enum Skipped
+#if defined(BENCHMARK_HAS_CXX11)
+    : unsigned
+#endif
+{
+  NotSkipped = 0,
+  SkippedWithMessage,
+  SkippedWithError
+};
+
+}  // namespace internal
+
+// State is passed to a running Benchmark and contains state for the
+// benchmark to use.
+class BENCHMARK_EXPORT State {
+ public:
+  struct StateIterator;
+  friend struct StateIterator;
+
+  // Returns iterators used to run each iteration of a benchmark using a
+  // C++11 ranged-based for loop. These functions should not be called directly.
+  //
+  // REQUIRES: The benchmark has not started running yet. Neither begin nor end
+  // have been called previously.
+  //
+  // NOTE: KeepRunning may not be used after calling either of these functions.
+  BENCHMARK_ALWAYS_INLINE StateIterator begin();
+  BENCHMARK_ALWAYS_INLINE StateIterator end();
+
+  // Returns true if the benchmark should continue through another iteration.
+  // NOTE: A benchmark may not return from the test until KeepRunning() has
+  // returned false.
+  bool KeepRunning();
+
+  // Returns true iff the benchmark should run n more iterations.
+  // REQUIRES: 'n' > 0.
+  // NOTE: A benchmark must not return from the test until KeepRunningBatch()
+  // has returned false.
+  // NOTE: KeepRunningBatch() may overshoot by up to 'n' iterations.
+  //
+  // Intended usage:
+  //   while (state.KeepRunningBatch(1000)) {
+  //     // process 1000 elements
+  //   }
+  bool KeepRunningBatch(IterationCount n);
+
+  // REQUIRES: timer is running and 'SkipWithMessage(...)' or
+  //   'SkipWithError(...)' has not been called by the current thread.
+  // Stop the benchmark timer.  If not called, the timer will be
+  // automatically stopped after the last iteration of the benchmark loop.
+  //
+  // For threaded benchmarks the PauseTiming() function only pauses the timing
+  // for the current thread.
+  //
+  // NOTE: The "real time" measurement is per-thread. If different threads
+  // report different measurements the largest one is reported.
+  //
+  // NOTE: PauseTiming()/ResumeTiming() are relatively
+  // heavyweight, and so their use should generally be avoided
+  // within each benchmark iteration, if possible.
+  void PauseTiming();
+
+  // REQUIRES: timer is not running and 'SkipWithMessage(...)' or
+  //   'SkipWithError(...)' has not been called by the current thread.
+  // Start the benchmark timer.  The timer is NOT running on entrance to the
+  // benchmark function. It begins running after control flow enters the
+  // benchmark loop.
+  //
+  // NOTE: PauseTiming()/ResumeTiming() are relatively
+  // heavyweight, and so their use should generally be avoided
+  // within each benchmark iteration, if possible.
+  void ResumeTiming();
+
+  // REQUIRES: 'SkipWithMessage(...)' or 'SkipWithError(...)' has not been
+  //            called previously by the current thread.
+  // Report the benchmark as resulting in being skipped with the specified
+  // 'msg'.
+  // After this call the user may explicitly 'return' from the benchmark.
+  //
+  // If the ranged-for style of benchmark loop is used, the user must explicitly
+  // break from the loop, otherwise all future iterations will be run.
+  // If the 'KeepRunning()' loop is used the current thread will automatically
+  // exit the loop at the end of the current iteration.
+  //
+  // For threaded benchmarks only the current thread stops executing and future
+  // calls to `KeepRunning()` will block until all threads have completed
+  // the `KeepRunning()` loop. If multiple threads report being skipped only the
+  // first skip message is used.
+  //
+  // NOTE: Calling 'SkipWithMessage(...)' does not cause the benchmark to exit
+  // the current scope immediately. If the function is called from within
+  // the 'KeepRunning()' loop the current iteration will finish. It is the users
+  // responsibility to exit the scope as needed.
+  void SkipWithMessage(const std::string& msg);
+
+  // REQUIRES: 'SkipWithMessage(...)' or 'SkipWithError(...)' has not been
+  //            called previously by the current thread.
+  // Report the benchmark as resulting in an error with the specified 'msg'.
+  // After this call the user may explicitly 'return' from the benchmark.
+  //
+  // If the ranged-for style of benchmark loop is used, the user must explicitly
+  // break from the loop, otherwise all future iterations will be run.
+  // If the 'KeepRunning()' loop is used the current thread will automatically
+  // exit the loop at the end of the current iteration.
+  //
+  // For threaded benchmarks only the current thread stops executing and future
+  // calls to `KeepRunning()` will block until all threads have completed
+  // the `KeepRunning()` loop. If multiple threads report an error only the
+  // first error message is used.
+  //
+  // NOTE: Calling 'SkipWithError(...)' does not cause the benchmark to exit
+  // the current scope immediately. If the function is called from within
+  // the 'KeepRunning()' loop the current iteration will finish. It is the users
+  // responsibility to exit the scope as needed.
+  void SkipWithError(const std::string& msg);
+
+  // Returns true if 'SkipWithMessage(...)' or 'SkipWithError(...)' was called.
+  bool skipped() const { return internal::NotSkipped != skipped_; }
+
+  // Returns true if an error has been reported with 'SkipWithError(...)'.
+  bool error_occurred() const { return internal::SkippedWithError == skipped_; }
+
+  // REQUIRES: called exactly once per iteration of the benchmarking loop.
+  // Set the manually measured time for this benchmark iteration, which
+  // is used instead of automatically measured time if UseManualTime() was
+  // specified.
+  //
+  // For threaded benchmarks the final value will be set to the largest
+  // reported values.
+  void SetIterationTime(double seconds);
+
+  // Set the number of bytes processed by the current benchmark
+  // execution.  This routine is typically called once at the end of a
+  // throughput oriented benchmark.
+  //
+  // REQUIRES: a benchmark has exited its benchmarking loop.
+  BENCHMARK_ALWAYS_INLINE
+  void SetBytesProcessed(int64_t bytes) {
+    counters["bytes_per_second"] =
+        Counter(static_cast<double>(bytes), Counter::kIsRate, Counter::kIs1024);
+  }
+
+  BENCHMARK_ALWAYS_INLINE
+  int64_t bytes_processed() const {
+    if (counters.find("bytes_per_second") != counters.end())
+      return static_cast<int64_t>(counters.at("bytes_per_second"));
+    return 0;
+  }
+
+  // If this routine is called with complexity_n > 0 and complexity report is
+  // requested for the
+  // family benchmark, then current benchmark will be part of the computation
+  // and complexity_n will
+  // represent the length of N.
+  BENCHMARK_ALWAYS_INLINE
+  void SetComplexityN(int64_t complexity_n) { complexity_n_ = complexity_n; }
+
+  BENCHMARK_ALWAYS_INLINE
+  int64_t complexity_length_n() const { return complexity_n_; }
+
+  // If this routine is called with items > 0, then an items/s
+  // label is printed on the benchmark report line for the currently
+  // executing benchmark. It is typically called at the end of a processing
+  // benchmark where a processing items/second output is desired.
+  //
+  // REQUIRES: a benchmark has exited its benchmarking loop.
+  BENCHMARK_ALWAYS_INLINE
+  void SetItemsProcessed(int64_t items) {
+    counters["items_per_second"] =
+        Counter(static_cast<double>(items), benchmark::Counter::kIsRate);
+  }
+
+  BENCHMARK_ALWAYS_INLINE
+  int64_t items_processed() const {
+    if (counters.find("items_per_second") != counters.end())
+      return static_cast<int64_t>(counters.at("items_per_second"));
+    return 0;
+  }
+
+  // If this routine is called, the specified label is printed at the
+  // end of the benchmark report line for the currently executing
+  // benchmark.  Example:
+  //  static void BM_Compress(benchmark::State& state) {
+  //    ...
+  //    double compress = input_size / output_size;
+  //    state.SetLabel(StrFormat("compress:%.1f%%", 100.0*compression));
+  //  }
+  // Produces output that looks like:
+  //  BM_Compress   50         50   14115038  compress:27.3%
+  //
+  // REQUIRES: a benchmark has exited its benchmarking loop.
+  void SetLabel(const std::string& label);
+
+  // Range arguments for this run. CHECKs if the argument has been set.
+  BENCHMARK_ALWAYS_INLINE
+  int64_t range(std::size_t pos = 0) const {
+    assert(range_.size() > pos);
+    return range_[pos];
+  }
+
+  BENCHMARK_DEPRECATED_MSG("use 'range(0)' instead")
+  int64_t range_x() const { return range(0); }
+
+  BENCHMARK_DEPRECATED_MSG("use 'range(1)' instead")
+  int64_t range_y() const { return range(1); }
+
+  // Number of threads concurrently executing the benchmark.
+  BENCHMARK_ALWAYS_INLINE
+  int threads() const { return threads_; }
+
+  // Index of the executing thread. Values from [0, threads).
+  BENCHMARK_ALWAYS_INLINE
+  int thread_index() const { return thread_index_; }
+
+  BENCHMARK_ALWAYS_INLINE
+  IterationCount iterations() const {
+    if (BENCHMARK_BUILTIN_EXPECT(!started_, false)) {
+      return 0;
+    }
+    return max_iterations - total_iterations_ + batch_leftover_;
+  }
+
+  BENCHMARK_ALWAYS_INLINE
+  std::string name() const { return name_; }
+
+ private:
+  // items we expect on the first cache line (ie 64 bytes of the struct)
+  // When total_iterations_ is 0, KeepRunning() and friends will return false.
+  // May be larger than max_iterations.
+  IterationCount total_iterations_;
+
+  // When using KeepRunningBatch(), batch_leftover_ holds the number of
+  // iterations beyond max_iters that were run. Used to track
+  // completed_iterations_ accurately.
+  IterationCount batch_leftover_;
+
+ public:
+  const IterationCount max_iterations;
+
+ private:
+  bool started_;
+  bool finished_;
+  internal::Skipped skipped_;
+
+  // items we don't need on the first cache line
+  std::vector<int64_t> range_;
+
+  int64_t complexity_n_;
+
+ public:
+  // Container for user-defined counters.
+  UserCounters counters;
+
+ private:
+  State(std::string name, IterationCount max_iters,
+        const std::vector<int64_t>& ranges, int thread_i, int n_threads,
+        internal::ThreadTimer* timer, internal::ThreadManager* manager,
+        internal::PerfCountersMeasurement* perf_counters_measurement);
+
+  void StartKeepRunning();
+  // Implementation of KeepRunning() and KeepRunningBatch().
+  // is_batch must be true unless n is 1.
+  bool KeepRunningInternal(IterationCount n, bool is_batch);
+  void FinishKeepRunning();
+
+  const std::string name_;
+  const int thread_index_;
+  const int threads_;
+
+  internal::ThreadTimer* const timer_;
+  internal::ThreadManager* const manager_;
+  internal::PerfCountersMeasurement* const perf_counters_measurement_;
+
+  friend class internal::BenchmarkInstance;
+};
+
+inline BENCHMARK_ALWAYS_INLINE bool State::KeepRunning() {
+  return KeepRunningInternal(1, /*is_batch=*/false);
+}
+
+inline BENCHMARK_ALWAYS_INLINE bool State::KeepRunningBatch(IterationCount n) {
+  return KeepRunningInternal(n, /*is_batch=*/true);
+}
+
+inline BENCHMARK_ALWAYS_INLINE bool State::KeepRunningInternal(IterationCount n,
+                                                               bool is_batch) {
+  // total_iterations_ is set to 0 by the constructor, and always set to a
+  // nonzero value by StartKepRunning().
+  assert(n > 0);
+  // n must be 1 unless is_batch is true.
+  assert(is_batch || n == 1);
+  if (BENCHMARK_BUILTIN_EXPECT(total_iterations_ >= n, true)) {
+    total_iterations_ -= n;
+    return true;
+  }
+  if (!started_) {
+    StartKeepRunning();
+    if (!skipped() && total_iterations_ >= n) {
+      total_iterations_ -= n;
+      return true;
+    }
+  }
+  // For non-batch runs, total_iterations_ must be 0 by now.
+  if (is_batch && total_iterations_ != 0) {
+    batch_leftover_ = n - total_iterations_;
+    total_iterations_ = 0;
+    return true;
+  }
+  FinishKeepRunning();
+  return false;
+}
+
+struct State::StateIterator {
+  struct BENCHMARK_UNUSED Value {};
+  typedef std::forward_iterator_tag iterator_category;
+  typedef Value value_type;
+  typedef Value reference;
+  typedef Value pointer;
+  typedef std::ptrdiff_t difference_type;
+
+ private:
+  friend class State;
+  BENCHMARK_ALWAYS_INLINE
+  StateIterator() : cached_(0), parent_() {}
+
+  BENCHMARK_ALWAYS_INLINE
+  explicit StateIterator(State* st)
+      : cached_(st->skipped() ? 0 : st->max_iterations), parent_(st) {}
+
+ public:
+  BENCHMARK_ALWAYS_INLINE
+  Value operator*() const { return Value(); }
+
+  BENCHMARK_ALWAYS_INLINE
+  StateIterator& operator++() {
+    assert(cached_ > 0);
+    --cached_;
+    return *this;
+  }
+
+  BENCHMARK_ALWAYS_INLINE
+  bool operator!=(StateIterator const&) const {
+    if (BENCHMARK_BUILTIN_EXPECT(cached_ != 0, true)) return true;
+    parent_->FinishKeepRunning();
+    return false;
+  }
+
+ private:
+  IterationCount cached_;
+  State* const parent_;
+};
+
+inline BENCHMARK_ALWAYS_INLINE State::StateIterator State::begin() {
+  return StateIterator(this);
+}
+inline BENCHMARK_ALWAYS_INLINE State::StateIterator State::end() {
+  StartKeepRunning();
+  return StateIterator();
+}
+
+namespace internal {
+
+typedef void(Function)(State&);
+
+// ------------------------------------------------------
+// Benchmark registration object.  The BENCHMARK() macro expands
+// into an internal::Benchmark* object.  Various methods can
+// be called on this object to change the properties of the benchmark.
+// Each method returns "this" so that multiple method calls can
+// chained into one expression.
+class BENCHMARK_EXPORT Benchmark {
+ public:
+  virtual ~Benchmark();
+
+  // Note: the following methods all return "this" so that multiple
+  // method calls can be chained together in one expression.
+
+  // Specify the name of the benchmark
+  Benchmark* Name(const std::string& name);
+
+  // Run this benchmark once with "x" as the extra argument passed
+  // to the function.
+  // REQUIRES: The function passed to the constructor must accept an arg1.
+  Benchmark* Arg(int64_t x);
+
+  // Run this benchmark with the given time unit for the generated output report
+  Benchmark* Unit(TimeUnit unit);
+
+  // Run this benchmark once for a number of values picked from the
+  // range [start..limit].  (start and limit are always picked.)
+  // REQUIRES: The function passed to the constructor must accept an arg1.
+  Benchmark* Range(int64_t start, int64_t limit);
+
+  // Run this benchmark once for all values in the range [start..limit] with
+  // specific step
+  // REQUIRES: The function passed to the constructor must accept an arg1.
+  Benchmark* DenseRange(int64_t start, int64_t limit, int step = 1);
+
+  // Run this benchmark once with "args" as the extra arguments passed
+  // to the function.
+  // REQUIRES: The function passed to the constructor must accept arg1, arg2 ...
+  Benchmark* Args(const std::vector<int64_t>& args);
+
+  // Equivalent to Args({x, y})
+  // NOTE: This is a legacy C++03 interface provided for compatibility only.
+  //   New code should use 'Args'.
+  Benchmark* ArgPair(int64_t x, int64_t y) {
+    std::vector<int64_t> args;
+    args.push_back(x);
+    args.push_back(y);
+    return Args(args);
+  }
+
+  // Run this benchmark once for a number of values picked from the
+  // ranges [start..limit].  (starts and limits are always picked.)
+  // REQUIRES: The function passed to the constructor must accept arg1, arg2 ...
+  Benchmark* Ranges(const std::vector<std::pair<int64_t, int64_t> >& ranges);
+
+  // Run this benchmark once for each combination of values in the (cartesian)
+  // product of the supplied argument lists.
+  // REQUIRES: The function passed to the constructor must accept arg1, arg2 ...
+  Benchmark* ArgsProduct(const std::vector<std::vector<int64_t> >& arglists);
+
+  // Equivalent to ArgNames({name})
+  Benchmark* ArgName(const std::string& name);
+
+  // Set the argument names to display in the benchmark name. If not called,
+  // only argument values will be shown.
+  Benchmark* ArgNames(const std::vector<std::string>& names);
+
+  // Equivalent to Ranges({{lo1, hi1}, {lo2, hi2}}).
+  // NOTE: This is a legacy C++03 interface provided for compatibility only.
+  //   New code should use 'Ranges'.
+  Benchmark* RangePair(int64_t lo1, int64_t hi1, int64_t lo2, int64_t hi2) {
+    std::vector<std::pair<int64_t, int64_t> > ranges;
+    ranges.push_back(std::make_pair(lo1, hi1));
+    ranges.push_back(std::make_pair(lo2, hi2));
+    return Ranges(ranges);
+  }
+
+  // Have "setup" and/or "teardown" invoked once for every benchmark run.
+  // If the benchmark is multi-threaded (will run in k threads concurrently),
+  // the setup callback will be be invoked exactly once (not k times) before
+  // each run with k threads. Time allowing (e.g. for a short benchmark), there
+  // may be multiple such runs per benchmark, each run with its own
+  // "setup"/"teardown".
+  //
+  // If the benchmark uses different size groups of threads (e.g. via
+  // ThreadRange), the above will be true for each size group.
+  //
+  // The callback will be passed a State object, which includes the number
+  // of threads, thread-index, benchmark arguments, etc.
+  //
+  // The callback must not be NULL or self-deleting.
+  Benchmark* Setup(void (*setup)(const benchmark::State&));
+  Benchmark* Teardown(void (*teardown)(const benchmark::State&));
+
+  // Pass this benchmark object to *func, which can customize
+  // the benchmark by calling various methods like Arg, Args,
+  // Threads, etc.
+  Benchmark* Apply(void (*func)(Benchmark* benchmark));
+
+  // Set the range multiplier for non-dense range. If not called, the range
+  // multiplier kRangeMultiplier will be used.
+  Benchmark* RangeMultiplier(int multiplier);
+
+  // Set the minimum amount of time to use when running this benchmark. This
+  // option overrides the `benchmark_min_time` flag.
+  // REQUIRES: `t > 0` and `Iterations` has not been called on this benchmark.
+  Benchmark* MinTime(double t);
+
+  // Set the minimum amount of time to run the benchmark before taking runtimes
+  // of this benchmark into account. This
+  // option overrides the `benchmark_min_warmup_time` flag.
+  // REQUIRES: `t >= 0` and `Iterations` has not been called on this benchmark.
+  Benchmark* MinWarmUpTime(double t);
+
+  // Specify the amount of iterations that should be run by this benchmark.
+  // This option overrides the `benchmark_min_time` flag.
+  // REQUIRES: 'n > 0' and `MinTime` has not been called on this benchmark.
+  //
+  // NOTE: This function should only be used when *exact* iteration control is
+  //   needed and never to control or limit how long a benchmark runs, where
+  // `--benchmark_min_time=<N>s` or `MinTime(...)` should be used instead.
+  Benchmark* Iterations(IterationCount n);
+
+  // Specify the amount of times to repeat this benchmark. This option overrides
+  // the `benchmark_repetitions` flag.
+  // REQUIRES: `n > 0`
+  Benchmark* Repetitions(int n);
+
+  // Specify if each repetition of the benchmark should be reported separately
+  // or if only the final statistics should be reported. If the benchmark
+  // is not repeated then the single result is always reported.
+  // Applies to *ALL* reporters (display and file).
+  Benchmark* ReportAggregatesOnly(bool value = true);
+
+  // Same as ReportAggregatesOnly(), but applies to display reporter only.
+  Benchmark* DisplayAggregatesOnly(bool value = true);
+
+  // By default, the CPU time is measured only for the main thread, which may
+  // be unrepresentative if the benchmark uses threads internally. If called,
+  // the total CPU time spent by all the threads will be measured instead.
+  // By default, only the main thread CPU time will be measured.
+  Benchmark* MeasureProcessCPUTime();
+
+  // If a particular benchmark should use the Wall clock instead of the CPU time
+  // (be it either the CPU time of the main thread only (default), or the
+  // total CPU usage of the benchmark), call this method. If called, the elapsed
+  // (wall) time will be used to control how many iterations are run, and in the
+  // printing of items/second or MB/seconds values.
+  // If not called, the CPU time used by the benchmark will be used.
+  Benchmark* UseRealTime();
+
+  // If a benchmark must measure time manually (e.g. if GPU execution time is
+  // being
+  // measured), call this method. If called, each benchmark iteration should
+  // call
+  // SetIterationTime(seconds) to report the measured time, which will be used
+  // to control how many iterations are run, and in the printing of items/second
+  // or MB/second values.
+  Benchmark* UseManualTime();
+
+  // Set the asymptotic computational complexity for the benchmark. If called
+  // the asymptotic computational complexity will be shown on the output.
+  Benchmark* Complexity(BigO complexity = benchmark::oAuto);
+
+  // Set the asymptotic computational complexity for the benchmark. If called
+  // the asymptotic computational complexity will be shown on the output.
+  Benchmark* Complexity(BigOFunc* complexity);
+
+  // Add this statistics to be computed over all the values of benchmark run
+  Benchmark* ComputeStatistics(const std::string& name,
+                               StatisticsFunc* statistics,
+                               StatisticUnit unit = kTime);
+
+  // Support for running multiple copies of the same benchmark concurrently
+  // in multiple threads.  This may be useful when measuring the scaling
+  // of some piece of code.
+
+  // Run one instance of this benchmark concurrently in t threads.
+  Benchmark* Threads(int t);
+
+  // Pick a set of values T from [min_threads,max_threads].
+  // min_threads and max_threads are always included in T.  Run this
+  // benchmark once for each value in T.  The benchmark run for a
+  // particular value t consists of t threads running the benchmark
+  // function concurrently.  For example, consider:
+  //    BENCHMARK(Foo)->ThreadRange(1,16);
+  // This will run the following benchmarks:
+  //    Foo in 1 thread
+  //    Foo in 2 threads
+  //    Foo in 4 threads
+  //    Foo in 8 threads
+  //    Foo in 16 threads
+  Benchmark* ThreadRange(int min_threads, int max_threads);
+
+  // For each value n in the range, run this benchmark once using n threads.
+  // min_threads and max_threads are always included in the range.
+  // stride specifies the increment. E.g. DenseThreadRange(1, 8, 3) starts
+  // a benchmark with 1, 4, 7 and 8 threads.
+  Benchmark* DenseThreadRange(int min_threads, int max_threads, int stride = 1);
+
+  // Equivalent to ThreadRange(NumCPUs(), NumCPUs())
+  Benchmark* ThreadPerCpu();
+
+  virtual void Run(State& state) = 0;
+
+  TimeUnit GetTimeUnit() const;
+
+ protected:
+  explicit Benchmark(const std::string& name);
+  void SetName(const std::string& name);
+
+ public:
+  const char* GetName() const;
+  int ArgsCnt() const;
+  const char* GetArgName(int arg) const;
+
+ private:
+  friend class BenchmarkFamilies;
+  friend class BenchmarkInstance;
+
+  std::string name_;
+  AggregationReportMode aggregation_report_mode_;
+  std::vector<std::string> arg_names_;       // Args for all benchmark runs
+  std::vector<std::vector<int64_t> > args_;  // Args for all benchmark runs
+
+  TimeUnit time_unit_;
+  bool use_default_time_unit_;
+
+  int range_multiplier_;
+  double min_time_;
+  double min_warmup_time_;
+  IterationCount iterations_;
+  int repetitions_;
+  bool measure_process_cpu_time_;
+  bool use_real_time_;
+  bool use_manual_time_;
+  BigO complexity_;
+  BigOFunc* complexity_lambda_;
+  std::vector<Statistics> statistics_;
+  std::vector<int> thread_counts_;
+
+  typedef void (*callback_function)(const benchmark::State&);
+  callback_function setup_;
+  callback_function teardown_;
+
+  Benchmark(Benchmark const&)
+#if defined(BENCHMARK_HAS_CXX11)
+      = delete
+#endif
+      ;
+
+  Benchmark& operator=(Benchmark const&)
+#if defined(BENCHMARK_HAS_CXX11)
+      = delete
+#endif
+      ;
+};
+
+}  // namespace internal
+
+// Create and register a benchmark with the specified 'name' that invokes
+// the specified functor 'fn'.
+//
+// RETURNS: A pointer to the registered benchmark.
+internal::Benchmark* RegisterBenchmark(const std::string& name,
+                                       internal::Function* fn);
+
+#if defined(BENCHMARK_HAS_CXX11)
+template <class Lambda>
+internal::Benchmark* RegisterBenchmark(const std::string& name, Lambda&& fn);
+#endif
+
+// Remove all registered benchmarks. All pointers to previously registered
+// benchmarks are invalidated.
+BENCHMARK_EXPORT void ClearRegisteredBenchmarks();
+
+namespace internal {
+// The class used to hold all Benchmarks created from static function.
+// (ie those created using the BENCHMARK(...) macros.
+class BENCHMARK_EXPORT FunctionBenchmark : public Benchmark {
+ public:
+  FunctionBenchmark(const std::string& name, Function* func)
+      : Benchmark(name), func_(func) {}
+
+  void Run(State& st) BENCHMARK_OVERRIDE;
+
+ private:
+  Function* func_;
+};
+
+#ifdef BENCHMARK_HAS_CXX11
+template <class Lambda>
+class LambdaBenchmark : public Benchmark {
+ public:
+  void Run(State& st) BENCHMARK_OVERRIDE { lambda_(st); }
+
+ private:
+  template <class OLambda>
+  LambdaBenchmark(const std::string& name, OLambda&& lam)
+      : Benchmark(name), lambda_(std::forward<OLambda>(lam)) {}
+
+  LambdaBenchmark(LambdaBenchmark const&) = delete;
+
+  template <class Lam>  // NOLINTNEXTLINE(readability-redundant-declaration)
+  friend Benchmark* ::benchmark::RegisterBenchmark(const std::string&, Lam&&);
+
+  Lambda lambda_;
+};
+#endif
+}  // namespace internal
+
+inline internal::Benchmark* RegisterBenchmark(const std::string& name,
+                                              internal::Function* fn) {
+  return internal::RegisterBenchmarkInternal(
+      ::new internal::FunctionBenchmark(name, fn));
+}
+
+#ifdef BENCHMARK_HAS_CXX11
+template <class Lambda>
+internal::Benchmark* RegisterBenchmark(const std::string& name, Lambda&& fn) {
+  using BenchType =
+      internal::LambdaBenchmark<typename std::decay<Lambda>::type>;
+  return internal::RegisterBenchmarkInternal(
+      ::new BenchType(name, std::forward<Lambda>(fn)));
+}
+#endif
+
+#if defined(BENCHMARK_HAS_CXX11) && \
+    (!defined(BENCHMARK_GCC_VERSION) || BENCHMARK_GCC_VERSION >= 409)
+template <class Lambda, class... Args>
+internal::Benchmark* RegisterBenchmark(const std::string& name, Lambda&& fn,
+                                       Args&&... args) {
+  return benchmark::RegisterBenchmark(
+      name, [=](benchmark::State& st) { fn(st, args...); });
+}
+#else
+#define BENCHMARK_HAS_NO_VARIADIC_REGISTER_BENCHMARK
+#endif
+
+// The base class for all fixture tests.
+class Fixture : public internal::Benchmark {
+ public:
+  Fixture() : internal::Benchmark("") {}
+
+  void Run(State& st) BENCHMARK_OVERRIDE {
+    this->SetUp(st);
+    this->BenchmarkCase(st);
+    this->TearDown(st);
+  }
+
+  // These will be deprecated ...
+  virtual void SetUp(const State&) {}
+  virtual void TearDown(const State&) {}
+  // ... In favor of these.
+  virtual void SetUp(State& st) { SetUp(const_cast<const State&>(st)); }
+  virtual void TearDown(State& st) { TearDown(const_cast<const State&>(st)); }
+
+ protected:
+  virtual void BenchmarkCase(State&) = 0;
+};
+}  // namespace benchmark
+
+// ------------------------------------------------------
+// Macro to register benchmarks
+
+// Check that __COUNTER__ is defined and that __COUNTER__ increases by 1
+// every time it is expanded. X + 1 == X + 0 is used in case X is defined to be
+// empty. If X is empty the expression becomes (+1 == +0).
+#if defined(__COUNTER__) && (__COUNTER__ + 1 == __COUNTER__ + 0)
+#define BENCHMARK_PRIVATE_UNIQUE_ID __COUNTER__
+#else
+#define BENCHMARK_PRIVATE_UNIQUE_ID __LINE__
+#endif
+
+// Helpers for generating unique variable names
+#ifdef BENCHMARK_HAS_CXX11
+#define BENCHMARK_PRIVATE_NAME(...)                                      \
+  BENCHMARK_PRIVATE_CONCAT(benchmark_uniq_, BENCHMARK_PRIVATE_UNIQUE_ID, \
+                           __VA_ARGS__)
+#else
+#define BENCHMARK_PRIVATE_NAME(n) \
+  BENCHMARK_PRIVATE_CONCAT(benchmark_uniq_, BENCHMARK_PRIVATE_UNIQUE_ID, n)
+#endif  // BENCHMARK_HAS_CXX11
+
+#define BENCHMARK_PRIVATE_CONCAT(a, b, c) BENCHMARK_PRIVATE_CONCAT2(a, b, c)
+#define BENCHMARK_PRIVATE_CONCAT2(a, b, c) a##b##c
+// Helper for concatenation with macro name expansion
+#define BENCHMARK_PRIVATE_CONCAT_NAME(BaseClass, Method) \
+  BaseClass##_##Method##_Benchmark
+
+#define BENCHMARK_PRIVATE_DECLARE(n)                                 \
+  static ::benchmark::internal::Benchmark* BENCHMARK_PRIVATE_NAME(n) \
+      BENCHMARK_UNUSED
+
+#ifdef BENCHMARK_HAS_CXX11
+#define BENCHMARK(...)                                               \
+  BENCHMARK_PRIVATE_DECLARE(_benchmark_) =                           \
+      (::benchmark::internal::RegisterBenchmarkInternal(             \
+          new ::benchmark::internal::FunctionBenchmark(#__VA_ARGS__, \
+                                                       __VA_ARGS__)))
+#else
+#define BENCHMARK(n)                                     \
+  BENCHMARK_PRIVATE_DECLARE(n) =                         \
+      (::benchmark::internal::RegisterBenchmarkInternal( \
+          new ::benchmark::internal::FunctionBenchmark(#n, n)))
+#endif  // BENCHMARK_HAS_CXX11
+
+// Old-style macros
+#define BENCHMARK_WITH_ARG(n, a) BENCHMARK(n)->Arg((a))
+#define BENCHMARK_WITH_ARG2(n, a1, a2) BENCHMARK(n)->Args({(a1), (a2)})
+#define BENCHMARK_WITH_UNIT(n, t) BENCHMARK(n)->Unit((t))
+#define BENCHMARK_RANGE(n, lo, hi) BENCHMARK(n)->Range((lo), (hi))
+#define BENCHMARK_RANGE2(n, l1, h1, l2, h2) \
+  BENCHMARK(n)->RangePair({{(l1), (h1)}, {(l2), (h2)}})
+
+#ifdef BENCHMARK_HAS_CXX11
+
+// Register a benchmark which invokes the function specified by `func`
+// with the additional arguments specified by `...`.
+//
+// For example:
+//
+// template <class ...ExtraArgs>`
+// void BM_takes_args(benchmark::State& state, ExtraArgs&&... extra_args) {
+//  [...]
+//}
+// /* Registers a benchmark named "BM_takes_args/int_string_test` */
+// BENCHMARK_CAPTURE(BM_takes_args, int_string_test, 42, std::string("abc"));
+#define BENCHMARK_CAPTURE(func, test_case_name, ...)     \
+  BENCHMARK_PRIVATE_DECLARE(func) =                      \
+      (::benchmark::internal::RegisterBenchmarkInternal( \
+          new ::benchmark::internal::FunctionBenchmark(  \
+              #func "/" #test_case_name,                 \
+              [](::benchmark::State& st) { func(st, __VA_ARGS__); })))
+
+#endif  // BENCHMARK_HAS_CXX11
+
+// This will register a benchmark for a templatized function.  For example:
+//
+// template<int arg>
+// void BM_Foo(int iters);
+//
+// BENCHMARK_TEMPLATE(BM_Foo, 1);
+//
+// will register BM_Foo<1> as a benchmark.
+#define BENCHMARK_TEMPLATE1(n, a)                        \
+  BENCHMARK_PRIVATE_DECLARE(n) =                         \
+      (::benchmark::internal::RegisterBenchmarkInternal( \
+          new ::benchmark::internal::FunctionBenchmark(#n "<" #a ">", n<a>)))
+
+#define BENCHMARK_TEMPLATE2(n, a, b)                                         \
+  BENCHMARK_PRIVATE_DECLARE(n) =                                             \
+      (::benchmark::internal::RegisterBenchmarkInternal(                     \
+          new ::benchmark::internal::FunctionBenchmark(#n "<" #a "," #b ">", \
+                                                       n<a, b>)))
+
+#ifdef BENCHMARK_HAS_CXX11
+#define BENCHMARK_TEMPLATE(n, ...)                       \
+  BENCHMARK_PRIVATE_DECLARE(n) =                         \
+      (::benchmark::internal::RegisterBenchmarkInternal( \
+          new ::benchmark::internal::FunctionBenchmark(  \
+              #n "<" #__VA_ARGS__ ">", n<__VA_ARGS__>)))
+#else
+#define BENCHMARK_TEMPLATE(n, a) BENCHMARK_TEMPLATE1(n, a)
+#endif
+
+#define BENCHMARK_PRIVATE_DECLARE_F(BaseClass, Method)          \
+  class BaseClass##_##Method##_Benchmark : public BaseClass {   \
+   public:                                                      \
+    BaseClass##_##Method##_Benchmark() {                        \
+      this->SetName(#BaseClass "/" #Method);                    \
+    }                                                           \
+                                                                \
+   protected:                                                   \
+    void BenchmarkCase(::benchmark::State&) BENCHMARK_OVERRIDE; \
+  };
+
+#define BENCHMARK_TEMPLATE1_PRIVATE_DECLARE_F(BaseClass, Method, a) \
+  class BaseClass##_##Method##_Benchmark : public BaseClass<a> {    \
+   public:                                                          \
+    BaseClass##_##Method##_Benchmark() {                            \
+      this->SetName(#BaseClass "<" #a ">/" #Method);                \
+    }                                                               \
+                                                                    \
+   protected:                                                       \
+    void BenchmarkCase(::benchmark::State&) BENCHMARK_OVERRIDE;     \
+  };
+
+#define BENCHMARK_TEMPLATE2_PRIVATE_DECLARE_F(BaseClass, Method, a, b) \
+  class BaseClass##_##Method##_Benchmark : public BaseClass<a, b> {    \
+   public:                                                             \
+    BaseClass##_##Method##_Benchmark() {                               \
+      this->SetName(#BaseClass "<" #a "," #b ">/" #Method);            \
+    }                                                                  \
+                                                                       \
+   protected:                                                          \
+    void BenchmarkCase(::benchmark::State&) BENCHMARK_OVERRIDE;        \
+  };
+
+#ifdef BENCHMARK_HAS_CXX11
+#define BENCHMARK_TEMPLATE_PRIVATE_DECLARE_F(BaseClass, Method, ...)       \
+  class BaseClass##_##Method##_Benchmark : public BaseClass<__VA_ARGS__> { \
+   public:                                                                 \
+    BaseClass##_##Method##_Benchmark() {                                   \
+      this->SetName(#BaseClass "<" #__VA_ARGS__ ">/" #Method);             \
+    }                                                                      \
+                                                                           \
+   protected:                                                              \
+    void BenchmarkCase(::benchmark::State&) BENCHMARK_OVERRIDE;            \
+  };
+#else
+#define BENCHMARK_TEMPLATE_PRIVATE_DECLARE_F(n, a) \
+  BENCHMARK_TEMPLATE1_PRIVATE_DECLARE_F(n, a)
+#endif
+
+#define BENCHMARK_DEFINE_F(BaseClass, Method)    \
+  BENCHMARK_PRIVATE_DECLARE_F(BaseClass, Method) \
+  void BENCHMARK_PRIVATE_CONCAT_NAME(BaseClass, Method)::BenchmarkCase
+
+#define BENCHMARK_TEMPLATE1_DEFINE_F(BaseClass, Method, a)    \
+  BENCHMARK_TEMPLATE1_PRIVATE_DECLARE_F(BaseClass, Method, a) \
+  void BENCHMARK_PRIVATE_CONCAT_NAME(BaseClass, Method)::BenchmarkCase
+
+#define BENCHMARK_TEMPLATE2_DEFINE_F(BaseClass, Method, a, b)    \
+  BENCHMARK_TEMPLATE2_PRIVATE_DECLARE_F(BaseClass, Method, a, b) \
+  void BENCHMARK_PRIVATE_CONCAT_NAME(BaseClass, Method)::BenchmarkCase
+
+#ifdef BENCHMARK_HAS_CXX11
+#define BENCHMARK_TEMPLATE_DEFINE_F(BaseClass, Method, ...)            \
+  BENCHMARK_TEMPLATE_PRIVATE_DECLARE_F(BaseClass, Method, __VA_ARGS__) \
+  void BENCHMARK_PRIVATE_CONCAT_NAME(BaseClass, Method)::BenchmarkCase
+#else
+#define BENCHMARK_TEMPLATE_DEFINE_F(BaseClass, Method, a) \
+  BENCHMARK_TEMPLATE1_DEFINE_F(BaseClass, Method, a)
+#endif
+
+#define BENCHMARK_REGISTER_F(BaseClass, Method) \
+  BENCHMARK_PRIVATE_REGISTER_F(BENCHMARK_PRIVATE_CONCAT_NAME(BaseClass, Method))
+
+#define BENCHMARK_PRIVATE_REGISTER_F(TestName) \
+  BENCHMARK_PRIVATE_DECLARE(TestName) =        \
+      (::benchmark::internal::RegisterBenchmarkInternal(new TestName()))
+
+// This macro will define and register a benchmark within a fixture class.
+#define BENCHMARK_F(BaseClass, Method)           \
+  BENCHMARK_PRIVATE_DECLARE_F(BaseClass, Method) \
+  BENCHMARK_REGISTER_F(BaseClass, Method);       \
+  void BENCHMARK_PRIVATE_CONCAT_NAME(BaseClass, Method)::BenchmarkCase
+
+#define BENCHMARK_TEMPLATE1_F(BaseClass, Method, a)           \
+  BENCHMARK_TEMPLATE1_PRIVATE_DECLARE_F(BaseClass, Method, a) \
+  BENCHMARK_REGISTER_F(BaseClass, Method);                    \
+  void BENCHMARK_PRIVATE_CONCAT_NAME(BaseClass, Method)::BenchmarkCase
+
+#define BENCHMARK_TEMPLATE2_F(BaseClass, Method, a, b)           \
+  BENCHMARK_TEMPLATE2_PRIVATE_DECLARE_F(BaseClass, Method, a, b) \
+  BENCHMARK_REGISTER_F(BaseClass, Method);                       \
+  void BENCHMARK_PRIVATE_CONCAT_NAME(BaseClass, Method)::BenchmarkCase
+
+#ifdef BENCHMARK_HAS_CXX11
+#define BENCHMARK_TEMPLATE_F(BaseClass, Method, ...)                   \
+  BENCHMARK_TEMPLATE_PRIVATE_DECLARE_F(BaseClass, Method, __VA_ARGS__) \
+  BENCHMARK_REGISTER_F(BaseClass, Method);                             \
+  void BENCHMARK_PRIVATE_CONCAT_NAME(BaseClass, Method)::BenchmarkCase
+#else
+#define BENCHMARK_TEMPLATE_F(BaseClass, Method, a) \
+  BENCHMARK_TEMPLATE1_F(BaseClass, Method, a)
+#endif
+
+// Helper macro to create a main routine in a test that runs the benchmarks
+// Note the workaround for Hexagon simulator passing argc != 0, argv = NULL.
+#define BENCHMARK_MAIN()                                                \
+  int main(int argc, char** argv) {                                     \
+    char arg0_default[] = "benchmark";                                  \
+    char* args_default = arg0_default;                                  \
+    if (!argv) {                                                        \
+      argc = 1;                                                         \
+      argv = &args_default;                                             \
+    }                                                                   \
+    ::benchmark::Initialize(&argc, argv);                               \
+    if (::benchmark::ReportUnrecognizedArguments(argc, argv)) return 1; \
+    ::benchmark::RunSpecifiedBenchmarks();                              \
+    ::benchmark::Shutdown();                                            \
+    return 0;                                                           \
+  }                                                                     \
+  int main(int, char**)
+
+// ------------------------------------------------------
+// Benchmark Reporters
+
+namespace benchmark {
+
+struct BENCHMARK_EXPORT CPUInfo {
+  struct CacheInfo {
+    std::string type;
+    int level;
+    int size;
+    int num_sharing;
+  };
+
+  enum Scaling { UNKNOWN, ENABLED, DISABLED };
+
+  int num_cpus;
+  Scaling scaling;
+  double cycles_per_second;
+  std::vector<CacheInfo> caches;
+  std::vector<double> load_avg;
+
+  static const CPUInfo& Get();
+
+ private:
+  CPUInfo();
+  BENCHMARK_DISALLOW_COPY_AND_ASSIGN(CPUInfo);
+};
+
+// Adding Struct for System Information
+struct BENCHMARK_EXPORT SystemInfo {
+  std::string name;
+  static const SystemInfo& Get();
+
+ private:
+  SystemInfo();
+  BENCHMARK_DISALLOW_COPY_AND_ASSIGN(SystemInfo);
+};
+
+// BenchmarkName contains the components of the Benchmark's name
+// which allows individual fields to be modified or cleared before
+// building the final name using 'str()'.
+struct BENCHMARK_EXPORT BenchmarkName {
+  std::string function_name;
+  std::string args;
+  std::string min_time;
+  std::string min_warmup_time;
+  std::string iterations;
+  std::string repetitions;
+  std::string time_type;
+  std::string threads;
+
+  // Return the full name of the benchmark with each non-empty
+  // field separated by a '/'
+  std::string str() const;
+};
+
+// Interface for custom benchmark result printers.
+// By default, benchmark reports are printed to stdout. However an application
+// can control the destination of the reports by calling
+// RunSpecifiedBenchmarks and passing it a custom reporter object.
+// The reporter object must implement the following interface.
+class BENCHMARK_EXPORT BenchmarkReporter {
+ public:
+  struct Context {
+    CPUInfo const& cpu_info;
+    SystemInfo const& sys_info;
+    // The number of chars in the longest benchmark name.
+    size_t name_field_width;
+    static const char* executable_name;
+    Context();
+  };
+
+  struct BENCHMARK_EXPORT Run {
+    static const int64_t no_repetition_index = -1;
+    enum RunType { RT_Iteration, RT_Aggregate };
+
+    Run()
+        : run_type(RT_Iteration),
+          aggregate_unit(kTime),
+          skipped(internal::NotSkipped),
+          iterations(1),
+          threads(1),
+          time_unit(GetDefaultTimeUnit()),
+          real_accumulated_time(0),
+          cpu_accumulated_time(0),
+          max_heapbytes_used(0),
+          complexity(oNone),
+          complexity_lambda(),
+          complexity_n(0),
+          report_big_o(false),
+          report_rms(false),
+          memory_result(NULL),
+          allocs_per_iter(0.0) {}
+
+    std::string benchmark_name() const;
+    BenchmarkName run_name;
+    int64_t family_index;
+    int64_t per_family_instance_index;
+    RunType run_type;
+    std::string aggregate_name;
+    StatisticUnit aggregate_unit;
+    std::string report_label;  // Empty if not set by benchmark.
+    internal::Skipped skipped;
+    std::string skip_message;
+
+    IterationCount iterations;
+    int64_t threads;
+    int64_t repetition_index;
+    int64_t repetitions;
+    TimeUnit time_unit;
+    double real_accumulated_time;
+    double cpu_accumulated_time;
+
+    // Return a value representing the real time per iteration in the unit
+    // specified by 'time_unit'.
+    // NOTE: If 'iterations' is zero the returned value represents the
+    // accumulated time.
+    double GetAdjustedRealTime() const;
+
+    // Return a value representing the cpu time per iteration in the unit
+    // specified by 'time_unit'.
+    // NOTE: If 'iterations' is zero the returned value represents the
+    // accumulated time.
+    double GetAdjustedCPUTime() const;
+
+    // This is set to 0.0 if memory tracing is not enabled.
+    double max_heapbytes_used;
+
+    // Keep track of arguments to compute asymptotic complexity
+    BigO complexity;
+    BigOFunc* complexity_lambda;
+    int64_t complexity_n;
+
+    // what statistics to compute from the measurements
+    const std::vector<internal::Statistics>* statistics;
+
+    // Inform print function whether the current run is a complexity report
+    bool report_big_o;
+    bool report_rms;
+
+    UserCounters counters;
+
+    // Memory metrics.
+    const MemoryManager::Result* memory_result;
+    double allocs_per_iter;
+  };
+
+  struct PerFamilyRunReports {
+    PerFamilyRunReports() : num_runs_total(0), num_runs_done(0) {}
+
+    // How many runs will all instances of this benchmark perform?
+    int num_runs_total;
+
+    // How many runs have happened already?
+    int num_runs_done;
+
+    // The reports about (non-errneous!) runs of this family.
+    std::vector<BenchmarkReporter::Run> Runs;
+  };
+
+  // Construct a BenchmarkReporter with the output stream set to 'std::cout'
+  // and the error stream set to 'std::cerr'
+  BenchmarkReporter();
+
+  // Called once for every suite of benchmarks run.
+  // The parameter "context" contains information that the
+  // reporter may wish to use when generating its report, for example the
+  // platform under which the benchmarks are running. The benchmark run is
+  // never started if this function returns false, allowing the reporter
+  // to skip runs based on the context information.
+  virtual bool ReportContext(const Context& context) = 0;
+
+  // Called once for each group of benchmark runs, gives information about
+  // the configurations of the runs.
+  virtual void ReportRunsConfig(double /*min_time*/,
+                                bool /*has_explicit_iters*/,
+                                IterationCount /*iters*/) {}
+
+  // Called once for each group of benchmark runs, gives information about
+  // cpu-time and heap memory usage during the benchmark run. If the group
+  // of runs contained more than two entries then 'report' contains additional
+  // elements representing the mean and standard deviation of those runs.
+  // Additionally if this group of runs was the last in a family of benchmarks
+  // 'reports' contains additional entries representing the asymptotic
+  // complexity and RMS of that benchmark family.
+  virtual void ReportRuns(const std::vector<Run>& report) = 0;
+
+  // Called once and only once after ever group of benchmarks is run and
+  // reported.
+  virtual void Finalize() {}
+
+  // REQUIRES: The object referenced by 'out' is valid for the lifetime
+  // of the reporter.
+  void SetOutputStream(std::ostream* out) {
+    assert(out);
+    output_stream_ = out;
+  }
+
+  // REQUIRES: The object referenced by 'err' is valid for the lifetime
+  // of the reporter.
+  void SetErrorStream(std::ostream* err) {
+    assert(err);
+    error_stream_ = err;
+  }
+
+  std::ostream& GetOutputStream() const { return *output_stream_; }
+
+  std::ostream& GetErrorStream() const { return *error_stream_; }
+
+  virtual ~BenchmarkReporter();
+
+  // Write a human readable string to 'out' representing the specified
+  // 'context'.
+  // REQUIRES: 'out' is non-null.
+  static void PrintBasicContext(std::ostream* out, Context const& context);
+
+ private:
+  std::ostream* output_stream_;
+  std::ostream* error_stream_;
+};
+
+// Simple reporter that outputs benchmark data to the console. This is the
+// default reporter used by RunSpecifiedBenchmarks().
+class BENCHMARK_EXPORT ConsoleReporter : public BenchmarkReporter {
+ public:
+  enum OutputOptions {
+    OO_None = 0,
+    OO_Color = 1,
+    OO_Tabular = 2,
+    OO_ColorTabular = OO_Color | OO_Tabular,
+    OO_Defaults = OO_ColorTabular
+  };
+  explicit ConsoleReporter(OutputOptions opts_ = OO_Defaults)
+      : output_options_(opts_), name_field_width_(0), printed_header_(false) {}
+
+  bool ReportContext(const Context& context) BENCHMARK_OVERRIDE;
+  void ReportRuns(const std::vector<Run>& reports) BENCHMARK_OVERRIDE;
+
+ protected:
+  virtual void PrintRunData(const Run& report);
+  virtual void PrintHeader(const Run& report);
+
+  OutputOptions output_options_;
+  size_t name_field_width_;
+  UserCounters prev_counters_;
+  bool printed_header_;
+};
+
+class BENCHMARK_EXPORT JSONReporter : public BenchmarkReporter {
+ public:
+  JSONReporter() : first_report_(true) {}
+  bool ReportContext(const Context& context) BENCHMARK_OVERRIDE;
+  void ReportRuns(const std::vector<Run>& reports) BENCHMARK_OVERRIDE;
+  void Finalize() BENCHMARK_OVERRIDE;
+
+ private:
+  void PrintRunData(const Run& report);
+
+  bool first_report_;
+};
+
+class BENCHMARK_EXPORT BENCHMARK_DEPRECATED_MSG(
+    "The CSV Reporter will be removed in a future release") CSVReporter
+    : public BenchmarkReporter {
+ public:
+  CSVReporter() : printed_header_(false) {}
+  bool ReportContext(const Context& context) BENCHMARK_OVERRIDE;
+  void ReportRuns(const std::vector<Run>& reports) BENCHMARK_OVERRIDE;
+
+ private:
+  void PrintRunData(const Run& report);
+
+  bool printed_header_;
+  std::set<std::string> user_counter_names_;
+};
+
+inline const char* GetTimeUnitString(TimeUnit unit) {
+  switch (unit) {
+    case kSecond:
+      return "s";
+    case kMillisecond:
+      return "ms";
+    case kMicrosecond:
+      return "us";
+    case kNanosecond:
+      return "ns";
+  }
+  BENCHMARK_UNREACHABLE();
+}
+
+inline double GetTimeUnitMultiplier(TimeUnit unit) {
+  switch (unit) {
+    case kSecond:
+      return 1;
+    case kMillisecond:
+      return 1e3;
+    case kMicrosecond:
+      return 1e6;
+    case kNanosecond:
+      return 1e9;
+  }
+  BENCHMARK_UNREACHABLE();
+}
+
+// Creates a list of integer values for the given range and multiplier.
+// This can be used together with ArgsProduct() to allow multiple ranges
+// with different multipliers.
+// Example:
+// ArgsProduct({
+//   CreateRange(0, 1024, /*multi=*/32),
+//   CreateRange(0, 100, /*multi=*/4),
+//   CreateDenseRange(0, 4, /*step=*/1),
+// });
+BENCHMARK_EXPORT
+std::vector<int64_t> CreateRange(int64_t lo, int64_t hi, int multi);
+
+// Creates a list of integer values for the given range and step.
+BENCHMARK_EXPORT
+std::vector<int64_t> CreateDenseRange(int64_t start, int64_t limit, int step);
+
+}  // namespace benchmark
+
+#if defined(_MSC_VER)
+#pragma warning(pop)
+#endif
+
+#endif  // BENCHMARK_BENCHMARK_H_
diff --git a/leveldb_base/third_party/benchmark/include/benchmark/export.h b/leveldb_base/third_party/benchmark/include/benchmark/export.h
new file mode 100644
index 0000000..f96f859
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/include/benchmark/export.h
@@ -0,0 +1,47 @@
+#ifndef BENCHMARK_EXPORT_H
+#define BENCHMARK_EXPORT_H
+
+#if defined(_WIN32)
+#define EXPORT_ATTR __declspec(dllexport)
+#define IMPORT_ATTR __declspec(dllimport)
+#define NO_EXPORT_ATTR
+#define DEPRECATED_ATTR __declspec(deprecated)
+#else  // _WIN32
+#define EXPORT_ATTR __attribute__((visibility("default")))
+#define IMPORT_ATTR __attribute__((visibility("default")))
+#define NO_EXPORT_ATTR __attribute__((visibility("hidden")))
+#define DEPRECATE_ATTR __attribute__((__deprecated__))
+#endif  // _WIN32
+
+#ifdef BENCHMARK_STATIC_DEFINE
+#define BENCHMARK_EXPORT
+#define BENCHMARK_NO_EXPORT
+#else  // BENCHMARK_STATIC_DEFINE
+#ifndef BENCHMARK_EXPORT
+#ifdef benchmark_EXPORTS
+/* We are building this library */
+#define BENCHMARK_EXPORT EXPORT_ATTR
+#else  // benchmark_EXPORTS
+/* We are using this library */
+#define BENCHMARK_EXPORT IMPORT_ATTR
+#endif  // benchmark_EXPORTS
+#endif  // !BENCHMARK_EXPORT
+
+#ifndef BENCHMARK_NO_EXPORT
+#define BENCHMARK_NO_EXPORT NO_EXPORT_ATTR
+#endif  // !BENCHMARK_NO_EXPORT
+#endif  // BENCHMARK_STATIC_DEFINE
+
+#ifndef BENCHMARK_DEPRECATED
+#define BENCHMARK_DEPRECATED DEPRECATE_ATTR
+#endif  // BENCHMARK_DEPRECATED
+
+#ifndef BENCHMARK_DEPRECATED_EXPORT
+#define BENCHMARK_DEPRECATED_EXPORT BENCHMARK_EXPORT BENCHMARK_DEPRECATED
+#endif  // BENCHMARK_DEPRECATED_EXPORT
+
+#ifndef BENCHMARK_DEPRECATED_NO_EXPORT
+#define BENCHMARK_DEPRECATED_NO_EXPORT BENCHMARK_NO_EXPORT BENCHMARK_DEPRECATED
+#endif  // BENCHMARK_DEPRECATED_EXPORT
+
+#endif /* BENCHMARK_EXPORT_H */
diff --git a/leveldb_base/third_party/benchmark/requirements.txt b/leveldb_base/third_party/benchmark/requirements.txt
new file mode 100644
index 0000000..1c8a4bd
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/requirements.txt
@@ -0,0 +1,2 @@
+numpy == 1.22
+scipy == 1.5.4
diff --git a/leveldb_base/third_party/benchmark/setup.py b/leveldb_base/third_party/benchmark/setup.py
new file mode 100644
index 0000000..2388f59
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/setup.py
@@ -0,0 +1,166 @@
+import contextlib
+import os
+import platform
+import shutil
+import sysconfig
+from pathlib import Path
+from typing import List
+
+import setuptools
+from setuptools.command import build_ext
+
+
+PYTHON_INCLUDE_PATH_PLACEHOLDER = "<PYTHON_INCLUDE_PATH>"
+
+IS_WINDOWS = platform.system() == "Windows"
+IS_MAC = platform.system() == "Darwin"
+
+
+def _get_long_description(fp: str) -> str:
+    with open(fp, "r", encoding="utf-8") as f:
+        return f.read()
+
+
+def _get_version(fp: str) -> str:
+    """Parse a version string from a file."""
+    with open(fp, "r") as f:
+        for line in f:
+            if "__version__" in line:
+                delim = '"'
+                return line.split(delim)[1]
+    raise RuntimeError(f"could not find a version string in file {fp!r}.")
+
+
+def _parse_requirements(fp: str) -> List[str]:
+    with open(fp) as requirements:
+        return [
+            line.rstrip()
+            for line in requirements
+            if not (line.isspace() or line.startswith("#"))
+        ]
+
+
+@contextlib.contextmanager
+def temp_fill_include_path(fp: str):
+    """Temporarily set the Python include path in a file."""
+    with open(fp, "r+") as f:
+        try:
+            content = f.read()
+            replaced = content.replace(
+                PYTHON_INCLUDE_PATH_PLACEHOLDER,
+                Path(sysconfig.get_paths()['include']).as_posix(),
+            )
+            f.seek(0)
+            f.write(replaced)
+            f.truncate()
+            yield
+        finally:
+            # revert to the original content after exit
+            f.seek(0)
+            f.write(content)
+            f.truncate()
+
+
+class BazelExtension(setuptools.Extension):
+    """A C/C++ extension that is defined as a Bazel BUILD target."""
+
+    def __init__(self, name: str, bazel_target: str):
+        super().__init__(name=name, sources=[])
+
+        self.bazel_target = bazel_target
+        stripped_target = bazel_target.split("//")[-1]
+        self.relpath, self.target_name = stripped_target.split(":")
+
+
+class BuildBazelExtension(build_ext.build_ext):
+    """A command that runs Bazel to build a C/C++ extension."""
+
+    def run(self):
+        for ext in self.extensions:
+            self.bazel_build(ext)
+        build_ext.build_ext.run(self)
+
+    def bazel_build(self, ext: BazelExtension):
+        """Runs the bazel build to create the package."""
+        with temp_fill_include_path("WORKSPACE"):
+            temp_path = Path(self.build_temp)
+
+            bazel_argv = [
+                "bazel",
+                "build",
+                ext.bazel_target,
+                f"--symlink_prefix={temp_path / 'bazel-'}",
+                f"--compilation_mode={'dbg' if self.debug else 'opt'}",
+                # C++17 is required by nanobind
+                f"--cxxopt={'/std:c++17' if IS_WINDOWS else '-std=c++17'}",
+            ]
+
+            if IS_WINDOWS:
+                # Link with python*.lib.
+                for library_dir in self.library_dirs:
+                    bazel_argv.append("--linkopt=/LIBPATH:" + library_dir)
+            elif IS_MAC:
+                if platform.machine() == "x86_64":
+                    # C++17 needs macOS 10.14 at minimum
+                    bazel_argv.append("--macos_minimum_os=10.14")
+
+                    # cross-compilation for Mac ARM64 on GitHub Mac x86 runners.
+                    # ARCHFLAGS is set by cibuildwheel before macOS wheel builds.
+                    archflags = os.getenv("ARCHFLAGS", "")
+                    if "arm64" in archflags:
+                        bazel_argv.append("--cpu=darwin_arm64")
+                        bazel_argv.append("--macos_cpus=arm64")
+
+                elif platform.machine() == "arm64":
+                    bazel_argv.append("--macos_minimum_os=11.0")
+
+            self.spawn(bazel_argv)
+
+            shared_lib_suffix = '.dll' if IS_WINDOWS else '.so'
+            ext_name = ext.target_name + shared_lib_suffix
+            ext_bazel_bin_path = temp_path / 'bazel-bin' / ext.relpath / ext_name
+
+            ext_dest_path = Path(self.get_ext_fullpath(ext.name))
+            shutil.copyfile(ext_bazel_bin_path, ext_dest_path)
+
+            # explicitly call `bazel shutdown` for graceful exit
+            self.spawn(["bazel", "shutdown"])
+
+
+setuptools.setup(
+    name="google_benchmark",
+    version=_get_version("bindings/python/google_benchmark/__init__.py"),
+    url="https://github.com/google/benchmark",
+    description="A library to benchmark code snippets.",
+    long_description=_get_long_description("README.md"),
+    long_description_content_type="text/markdown",
+    author="Google",
+    author_email="benchmark-py@google.com",
+    # Contained modules and scripts.
+    package_dir={"": "bindings/python"},
+    packages=setuptools.find_packages("bindings/python"),
+    install_requires=_parse_requirements("bindings/python/requirements.txt"),
+    cmdclass=dict(build_ext=BuildBazelExtension),
+    ext_modules=[
+        BazelExtension(
+            "google_benchmark._benchmark",
+            "//bindings/python/google_benchmark:_benchmark",
+        )
+    ],
+    zip_safe=False,
+    # PyPI package information.
+    classifiers=[
+        "Development Status :: 4 - Beta",
+        "Intended Audience :: Developers",
+        "Intended Audience :: Science/Research",
+        "License :: OSI Approved :: Apache Software License",
+        "Programming Language :: Python :: 3.8",
+        "Programming Language :: Python :: 3.9",
+        "Programming Language :: Python :: 3.10",
+        "Programming Language :: Python :: 3.11",
+        "Topic :: Software Development :: Testing",
+        "Topic :: System :: Benchmark",
+    ],
+    license="Apache 2.0",
+    keywords="benchmark",
+)
diff --git a/leveldb_base/third_party/benchmark/src/CMakeLists.txt b/leveldb_base/third_party/benchmark/src/CMakeLists.txt
new file mode 100644
index 0000000..91ea5f4
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/CMakeLists.txt
@@ -0,0 +1,170 @@
+# Allow the source files to find headers in src/
+include(GNUInstallDirs)
+include_directories(${PROJECT_SOURCE_DIR}/src)
+
+if (DEFINED BENCHMARK_CXX_LINKER_FLAGS)
+  list(APPEND CMAKE_SHARED_LINKER_FLAGS ${BENCHMARK_CXX_LINKER_FLAGS})
+  list(APPEND CMAKE_MODULE_LINKER_FLAGS ${BENCHMARK_CXX_LINKER_FLAGS})
+endif()
+
+file(GLOB
+  SOURCE_FILES
+    *.cc
+    ${PROJECT_SOURCE_DIR}/include/benchmark/*.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/*.h)
+file(GLOB BENCHMARK_MAIN "benchmark_main.cc")
+foreach(item ${BENCHMARK_MAIN})
+  list(REMOVE_ITEM SOURCE_FILES "${item}")
+endforeach()
+
+add_library(benchmark ${SOURCE_FILES})
+add_library(benchmark::benchmark ALIAS benchmark)
+set_target_properties(benchmark PROPERTIES
+  OUTPUT_NAME "benchmark"
+  VERSION ${GENERIC_LIB_VERSION}
+  SOVERSION ${GENERIC_LIB_SOVERSION}
+)
+target_include_directories(benchmark PUBLIC
+  $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
+)
+
+# libpfm, if available
+if (HAVE_LIBPFM)
+  target_link_libraries(benchmark PRIVATE pfm)
+  target_compile_definitions(benchmark PRIVATE -DHAVE_LIBPFM)
+endif()
+
+# pthread affinity, if available
+if(HAVE_PTHREAD_AFFINITY)
+  target_compile_definitions(benchmark PRIVATE -DBENCHMARK_HAS_PTHREAD_AFFINITY)
+endif()
+
+# Link threads.
+target_link_libraries(benchmark PRIVATE Threads::Threads)
+
+target_link_libraries(benchmark PRIVATE ${BENCHMARK_CXX_LIBRARIES})
+
+if(HAVE_LIB_RT)
+  target_link_libraries(benchmark PRIVATE rt)
+endif(HAVE_LIB_RT)
+
+
+# We need extra libraries on Windows
+if(${CMAKE_SYSTEM_NAME} MATCHES "Windows")
+  target_link_libraries(benchmark PRIVATE shlwapi)
+endif()
+
+# We need extra libraries on Solaris
+if(${CMAKE_SYSTEM_NAME} MATCHES "SunOS")
+  target_link_libraries(benchmark PRIVATE kstat)
+endif()
+
+if (NOT BUILD_SHARED_LIBS)
+  target_compile_definitions(benchmark PUBLIC -DBENCHMARK_STATIC_DEFINE)
+endif()
+
+# Benchmark main library
+add_library(benchmark_main "benchmark_main.cc")
+add_library(benchmark::benchmark_main ALIAS benchmark_main)
+set_target_properties(benchmark_main PROPERTIES
+  OUTPUT_NAME "benchmark_main"
+  VERSION ${GENERIC_LIB_VERSION}
+  SOVERSION ${GENERIC_LIB_SOVERSION}
+  DEFINE_SYMBOL benchmark_EXPORTS
+)
+target_link_libraries(benchmark_main PUBLIC benchmark::benchmark)
+
+set(generated_dir "${PROJECT_BINARY_DIR}")
+
+set(version_config "${generated_dir}/${PROJECT_NAME}ConfigVersion.cmake")
+set(project_config "${generated_dir}/${PROJECT_NAME}Config.cmake")
+set(pkg_config "${generated_dir}/${PROJECT_NAME}.pc")
+set(targets_to_export benchmark benchmark_main)
+set(targets_export_name "${PROJECT_NAME}Targets")
+
+set(namespace "${PROJECT_NAME}::")
+
+include(CMakePackageConfigHelpers)
+
+configure_package_config_file (
+  ${PROJECT_SOURCE_DIR}/cmake/Config.cmake.in
+  ${project_config}
+  INSTALL_DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME}
+  NO_SET_AND_CHECK_MACRO
+  NO_CHECK_REQUIRED_COMPONENTS_MACRO
+)
+write_basic_package_version_file(
+  "${version_config}" VERSION ${GENERIC_LIB_VERSION} COMPATIBILITY SameMajorVersion
+)
+
+configure_file("${PROJECT_SOURCE_DIR}/cmake/benchmark.pc.in" "${pkg_config}" @ONLY)
+
+export (
+  TARGETS ${targets_to_export}
+  NAMESPACE "${namespace}"
+  FILE ${generated_dir}/${targets_export_name}.cmake
+)
+
+if (BENCHMARK_ENABLE_INSTALL)
+  # Install target (will install the library to specified CMAKE_INSTALL_PREFIX variable)
+  install(
+    TARGETS ${targets_to_export}
+    EXPORT ${targets_export_name}
+    ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
+    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
+    RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
+    INCLUDES DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
+
+  install(
+    DIRECTORY "${PROJECT_SOURCE_DIR}/include/benchmark"
+              "${PROJECT_BINARY_DIR}/include/benchmark"
+    DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
+    FILES_MATCHING PATTERN "*.*h")
+
+  install(
+      FILES "${project_config}" "${version_config}"
+      DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME}")
+
+  install(
+      FILES "${pkg_config}"
+      DESTINATION "${CMAKE_INSTALL_LIBDIR}/pkgconfig")
+
+  install(
+      EXPORT "${targets_export_name}"
+      NAMESPACE "${namespace}"
+      DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME}")
+endif()
+
+if (BENCHMARK_ENABLE_DOXYGEN)
+  find_package(Doxygen REQUIRED)
+  set(DOXYGEN_QUIET YES)
+  set(DOXYGEN_RECURSIVE YES)
+  set(DOXYGEN_GENERATE_HTML YES)
+  set(DOXYGEN_GENERATE_MAN NO)
+  set(DOXYGEN_MARKDOWN_SUPPORT YES)
+  set(DOXYGEN_BUILTIN_STL_SUPPORT YES)
+  set(DOXYGEN_EXTRACT_PACKAGE YES)
+  set(DOXYGEN_EXTRACT_STATIC YES)
+  set(DOXYGEN_SHOW_INCLUDE_FILES YES)
+  set(DOXYGEN_BINARY_TOC YES)
+  set(DOXYGEN_TOC_EXPAND YES)
+  set(DOXYGEN_USE_MDFILE_AS_MAINPAGE "index.md")
+  doxygen_add_docs(benchmark_doxygen
+    docs
+    include
+    src
+    ALL
+    WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
+    COMMENT "Building documentation with Doxygen.")
+  if (BENCHMARK_ENABLE_INSTALL AND BENCHMARK_INSTALL_DOCS)
+    install(
+      DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/html/"
+      DESTINATION ${CMAKE_INSTALL_DOCDIR})
+  endif()
+else()
+  if (BENCHMARK_ENABLE_INSTALL AND BENCHMARK_INSTALL_DOCS)
+    install(
+      DIRECTORY "${PROJECT_SOURCE_DIR}/docs/"
+      DESTINATION ${CMAKE_INSTALL_DOCDIR})
+  endif()
+endif()
diff --git a/leveldb_base/third_party/benchmark/src/arraysize.h b/leveldb_base/third_party/benchmark/src/arraysize.h
new file mode 100644
index 0000000..51a50f2
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/arraysize.h
@@ -0,0 +1,33 @@
+#ifndef BENCHMARK_ARRAYSIZE_H_
+#define BENCHMARK_ARRAYSIZE_H_
+
+#include "internal_macros.h"
+
+namespace benchmark {
+namespace internal {
+// The arraysize(arr) macro returns the # of elements in an array arr.
+// The expression is a compile-time constant, and therefore can be
+// used in defining new arrays, for example.  If you use arraysize on
+// a pointer by mistake, you will get a compile-time error.
+//
+
+// This template function declaration is used in defining arraysize.
+// Note that the function doesn't need an implementation, as we only
+// use its type.
+template <typename T, size_t N>
+char (&ArraySizeHelper(T (&array)[N]))[N];
+
+// That gcc wants both of these prototypes seems mysterious. VC, for
+// its part, can't decide which to use (another mystery). Matching of
+// template overloads: the final frontier.
+#ifndef COMPILER_MSVC
+template <typename T, size_t N>
+char (&ArraySizeHelper(const T (&array)[N]))[N];
+#endif
+
+#define arraysize(array) (sizeof(::benchmark::internal::ArraySizeHelper(array)))
+
+}  // end namespace internal
+}  // end namespace benchmark
+
+#endif  // BENCHMARK_ARRAYSIZE_H_
diff --git a/leveldb_base/third_party/benchmark/src/benchmark.cc b/leveldb_base/third_party/benchmark/src/benchmark.cc
new file mode 100644
index 0000000..f1633b7
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/benchmark.cc
@@ -0,0 +1,765 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "benchmark/benchmark.h"
+
+#include "benchmark_api_internal.h"
+#include "benchmark_runner.h"
+#include "internal_macros.h"
+
+#ifndef BENCHMARK_OS_WINDOWS
+#if !defined(BENCHMARK_OS_FUCHSIA) && !defined(BENCHMARK_OS_QURT)
+#include <sys/resource.h>
+#endif
+#include <sys/time.h>
+#include <unistd.h>
+#endif
+
+#include <algorithm>
+#include <atomic>
+#include <condition_variable>
+#include <cstdio>
+#include <cstdlib>
+#include <fstream>
+#include <iostream>
+#include <limits>
+#include <map>
+#include <memory>
+#include <random>
+#include <string>
+#include <thread>
+#include <utility>
+
+#include "check.h"
+#include "colorprint.h"
+#include "commandlineflags.h"
+#include "complexity.h"
+#include "counter.h"
+#include "internal_macros.h"
+#include "log.h"
+#include "mutex.h"
+#include "perf_counters.h"
+#include "re.h"
+#include "statistics.h"
+#include "string_util.h"
+#include "thread_manager.h"
+#include "thread_timer.h"
+
+namespace benchmark {
+// Print a list of benchmarks. This option overrides all other options.
+BM_DEFINE_bool(benchmark_list_tests, false);
+
+// A regular expression that specifies the set of benchmarks to execute.  If
+// this flag is empty, or if this flag is the string \"all\", all benchmarks
+// linked into the binary are run.
+BM_DEFINE_string(benchmark_filter, "");
+
+// Specification of how long to run the benchmark.
+//
+// It can be either an exact number of iterations (specified as `<integer>x`),
+// or a minimum number of seconds (specified as `<float>s`). If the latter
+// format (ie., min seconds) is used, the system may run the benchmark longer
+// until the results are considered significant.
+//
+// For backward compatibility, the `s` suffix may be omitted, in which case,
+// the specified number is interpreted as the number of seconds.
+//
+// For cpu-time based tests, this is the lower bound
+// on the total cpu time used by all threads that make up the test.  For
+// real-time based tests, this is the lower bound on the elapsed time of the
+// benchmark execution, regardless of number of threads.
+BM_DEFINE_string(benchmark_min_time, kDefaultMinTimeStr);
+
+// Minimum number of seconds a benchmark should be run before results should be
+// taken into account. This e.g can be necessary for benchmarks of code which
+// needs to fill some form of cache before performance is of interest.
+// Note: results gathered within this period are discarded and not used for
+// reported result.
+BM_DEFINE_double(benchmark_min_warmup_time, 0.0);
+
+// The number of runs of each benchmark. If greater than 1, the mean and
+// standard deviation of the runs will be reported.
+BM_DEFINE_int32(benchmark_repetitions, 1);
+
+// If set, enable random interleaving of repetitions of all benchmarks.
+// See http://github.com/google/benchmark/issues/1051 for details.
+BM_DEFINE_bool(benchmark_enable_random_interleaving, false);
+
+// Report the result of each benchmark repetitions. When 'true' is specified
+// only the mean, standard deviation, and other statistics are reported for
+// repeated benchmarks. Affects all reporters.
+BM_DEFINE_bool(benchmark_report_aggregates_only, false);
+
+// Display the result of each benchmark repetitions. When 'true' is specified
+// only the mean, standard deviation, and other statistics are displayed for
+// repeated benchmarks. Unlike benchmark_report_aggregates_only, only affects
+// the display reporter, but  *NOT* file reporter, which will still contain
+// all the output.
+BM_DEFINE_bool(benchmark_display_aggregates_only, false);
+
+// The format to use for console output.
+// Valid values are 'console', 'json', or 'csv'.
+BM_DEFINE_string(benchmark_format, "console");
+
+// The format to use for file output.
+// Valid values are 'console', 'json', or 'csv'.
+BM_DEFINE_string(benchmark_out_format, "json");
+
+// The file to write additional output to.
+BM_DEFINE_string(benchmark_out, "");
+
+// Whether to use colors in the output.  Valid values:
+// 'true'/'yes'/1, 'false'/'no'/0, and 'auto'. 'auto' means to use colors if
+// the output is being sent to a terminal and the TERM environment variable is
+// set to a terminal type that supports colors.
+BM_DEFINE_string(benchmark_color, "auto");
+
+// Whether to use tabular format when printing user counters to the console.
+// Valid values: 'true'/'yes'/1, 'false'/'no'/0.  Defaults to false.
+BM_DEFINE_bool(benchmark_counters_tabular, false);
+
+// List of additional perf counters to collect, in libpfm format. For more
+// information about libpfm: https://man7.org/linux/man-pages/man3/libpfm.3.html
+BM_DEFINE_string(benchmark_perf_counters, "");
+
+// Extra context to include in the output formatted as comma-separated key-value
+// pairs. Kept internal as it's only used for parsing from env/command line.
+BM_DEFINE_kvpairs(benchmark_context, {});
+
+// Set the default time unit to use for reports
+// Valid values are 'ns', 'us', 'ms' or 's'
+BM_DEFINE_string(benchmark_time_unit, "");
+
+// The level of verbose logging to output
+BM_DEFINE_int32(v, 0);
+
+namespace internal {
+
+std::map<std::string, std::string>* global_context = nullptr;
+
+BENCHMARK_EXPORT std::map<std::string, std::string>*& GetGlobalContext() {
+  return global_context;
+}
+
+// FIXME: wouldn't LTO mess this up?
+void UseCharPointer(char const volatile*) {}
+
+}  // namespace internal
+
+State::State(std::string name, IterationCount max_iters,
+             const std::vector<int64_t>& ranges, int thread_i, int n_threads,
+             internal::ThreadTimer* timer, internal::ThreadManager* manager,
+             internal::PerfCountersMeasurement* perf_counters_measurement)
+    : total_iterations_(0),
+      batch_leftover_(0),
+      max_iterations(max_iters),
+      started_(false),
+      finished_(false),
+      skipped_(internal::NotSkipped),
+      range_(ranges),
+      complexity_n_(0),
+      name_(std::move(name)),
+      thread_index_(thread_i),
+      threads_(n_threads),
+      timer_(timer),
+      manager_(manager),
+      perf_counters_measurement_(perf_counters_measurement) {
+  BM_CHECK(max_iterations != 0) << "At least one iteration must be run";
+  BM_CHECK_LT(thread_index_, threads_)
+      << "thread_index must be less than threads";
+
+  // Note: The use of offsetof below is technically undefined until C++17
+  // because State is not a standard layout type. However, all compilers
+  // currently provide well-defined behavior as an extension (which is
+  // demonstrated since constexpr evaluation must diagnose all undefined
+  // behavior). However, GCC and Clang also warn about this use of offsetof,
+  // which must be suppressed.
+#if defined(__INTEL_COMPILER)
+#pragma warning push
+#pragma warning(disable : 1875)
+#elif defined(__GNUC__)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Winvalid-offsetof"
+#endif
+#if defined(__NVCC__)
+#pragma nv_diagnostic push
+#pragma nv_diag_suppress 1427
+#endif
+#if defined(__NVCOMPILER)
+#pragma diagnostic push
+#pragma diag_suppress offset_in_non_POD_nonstandard
+#endif
+  // Offset tests to ensure commonly accessed data is on the first cache line.
+  const int cache_line_size = 64;
+  static_assert(
+      offsetof(State, skipped_) <= (cache_line_size - sizeof(skipped_)), "");
+#if defined(__INTEL_COMPILER)
+#pragma warning pop
+#elif defined(__GNUC__)
+#pragma GCC diagnostic pop
+#endif
+#if defined(__NVCC__)
+#pragma nv_diagnostic pop
+#endif
+#if defined(__NVCOMPILER)
+#pragma diagnostic pop
+#endif
+}
+
+void State::PauseTiming() {
+  // Add in time accumulated so far
+  BM_CHECK(started_ && !finished_ && !skipped());
+  timer_->StopTimer();
+  if (perf_counters_measurement_) {
+    std::vector<std::pair<std::string, double>> measurements;
+    if (!perf_counters_measurement_->Stop(measurements)) {
+      BM_CHECK(false) << "Perf counters read the value failed.";
+    }
+    for (const auto& name_and_measurement : measurements) {
+      auto name = name_and_measurement.first;
+      auto measurement = name_and_measurement.second;
+      BM_CHECK_EQ(std::fpclassify((double)counters[name]), FP_ZERO);
+      counters[name] = Counter(measurement, Counter::kAvgIterations);
+    }
+  }
+}
+
+void State::ResumeTiming() {
+  BM_CHECK(started_ && !finished_ && !skipped());
+  timer_->StartTimer();
+  if (perf_counters_measurement_) {
+    perf_counters_measurement_->Start();
+  }
+}
+
+void State::SkipWithMessage(const std::string& msg) {
+  skipped_ = internal::SkippedWithMessage;
+  {
+    MutexLock l(manager_->GetBenchmarkMutex());
+    if (internal::NotSkipped == manager_->results.skipped_) {
+      manager_->results.skip_message_ = msg;
+      manager_->results.skipped_ = skipped_;
+    }
+  }
+  total_iterations_ = 0;
+  if (timer_->running()) timer_->StopTimer();
+}
+
+void State::SkipWithError(const std::string& msg) {
+  skipped_ = internal::SkippedWithError;
+  {
+    MutexLock l(manager_->GetBenchmarkMutex());
+    if (internal::NotSkipped == manager_->results.skipped_) {
+      manager_->results.skip_message_ = msg;
+      manager_->results.skipped_ = skipped_;
+    }
+  }
+  total_iterations_ = 0;
+  if (timer_->running()) timer_->StopTimer();
+}
+
+void State::SetIterationTime(double seconds) {
+  timer_->SetIterationTime(seconds);
+}
+
+void State::SetLabel(const std::string& label) {
+  MutexLock l(manager_->GetBenchmarkMutex());
+  manager_->results.report_label_ = label;
+}
+
+void State::StartKeepRunning() {
+  BM_CHECK(!started_ && !finished_);
+  started_ = true;
+  total_iterations_ = skipped() ? 0 : max_iterations;
+  manager_->StartStopBarrier();
+  if (!skipped()) ResumeTiming();
+}
+
+void State::FinishKeepRunning() {
+  BM_CHECK(started_ && (!finished_ || skipped()));
+  if (!skipped()) {
+    PauseTiming();
+  }
+  // Total iterations has now wrapped around past 0. Fix this.
+  total_iterations_ = 0;
+  finished_ = true;
+  manager_->StartStopBarrier();
+}
+
+namespace internal {
+namespace {
+
+// Flushes streams after invoking reporter methods that write to them. This
+// ensures users get timely updates even when streams are not line-buffered.
+void FlushStreams(BenchmarkReporter* reporter) {
+  if (!reporter) return;
+  std::flush(reporter->GetOutputStream());
+  std::flush(reporter->GetErrorStream());
+}
+
+// Reports in both display and file reporters.
+void Report(BenchmarkReporter* display_reporter,
+            BenchmarkReporter* file_reporter, const RunResults& run_results) {
+  auto report_one = [](BenchmarkReporter* reporter, bool aggregates_only,
+                       const RunResults& results) {
+    assert(reporter);
+    // If there are no aggregates, do output non-aggregates.
+    aggregates_only &= !results.aggregates_only.empty();
+    if (!aggregates_only) reporter->ReportRuns(results.non_aggregates);
+    if (!results.aggregates_only.empty())
+      reporter->ReportRuns(results.aggregates_only);
+  };
+
+  report_one(display_reporter, run_results.display_report_aggregates_only,
+             run_results);
+  if (file_reporter)
+    report_one(file_reporter, run_results.file_report_aggregates_only,
+               run_results);
+
+  FlushStreams(display_reporter);
+  FlushStreams(file_reporter);
+}
+
+void RunBenchmarks(const std::vector<BenchmarkInstance>& benchmarks,
+                   BenchmarkReporter* display_reporter,
+                   BenchmarkReporter* file_reporter) {
+  // Note the file_reporter can be null.
+  BM_CHECK(display_reporter != nullptr);
+
+  // Determine the width of the name field using a minimum width of 10.
+  bool might_have_aggregates = FLAGS_benchmark_repetitions > 1;
+  size_t name_field_width = 10;
+  size_t stat_field_width = 0;
+  for (const BenchmarkInstance& benchmark : benchmarks) {
+    name_field_width =
+        std::max<size_t>(name_field_width, benchmark.name().str().size());
+    might_have_aggregates |= benchmark.repetitions() > 1;
+
+    for (const auto& Stat : benchmark.statistics())
+      stat_field_width = std::max<size_t>(stat_field_width, Stat.name_.size());
+  }
+  if (might_have_aggregates) name_field_width += 1 + stat_field_width;
+
+  // Print header here
+  BenchmarkReporter::Context context;
+  context.name_field_width = name_field_width;
+
+  // Keep track of running times of all instances of each benchmark family.
+  std::map<int /*family_index*/, BenchmarkReporter::PerFamilyRunReports>
+      per_family_reports;
+
+  if (display_reporter->ReportContext(context) &&
+      (!file_reporter || file_reporter->ReportContext(context))) {
+    FlushStreams(display_reporter);
+    FlushStreams(file_reporter);
+
+    size_t num_repetitions_total = 0;
+
+    // This perfcounters object needs to be created before the runners vector
+    // below so it outlasts their lifetime.
+    PerfCountersMeasurement perfcounters(
+        StrSplit(FLAGS_benchmark_perf_counters, ','));
+
+    // Vector of benchmarks to run
+    std::vector<internal::BenchmarkRunner> runners;
+    runners.reserve(benchmarks.size());
+
+    // Count the number of benchmarks with threads to warn the user in case
+    // performance counters are used.
+    int benchmarks_with_threads = 0;
+
+    // Loop through all benchmarks
+    for (const BenchmarkInstance& benchmark : benchmarks) {
+      BenchmarkReporter::PerFamilyRunReports* reports_for_family = nullptr;
+      if (benchmark.complexity() != oNone)
+        reports_for_family = &per_family_reports[benchmark.family_index()];
+      benchmarks_with_threads += (benchmark.threads() > 0);
+      runners.emplace_back(benchmark, &perfcounters, reports_for_family);
+      int num_repeats_of_this_instance = runners.back().GetNumRepeats();
+      num_repetitions_total += num_repeats_of_this_instance;
+      if (reports_for_family)
+        reports_for_family->num_runs_total += num_repeats_of_this_instance;
+    }
+    assert(runners.size() == benchmarks.size() && "Unexpected runner count.");
+
+    // The use of performance counters with threads would be unintuitive for
+    // the average user so we need to warn them about this case
+    if ((benchmarks_with_threads > 0) && (perfcounters.num_counters() > 0)) {
+      GetErrorLogInstance()
+          << "***WARNING*** There are " << benchmarks_with_threads
+          << " benchmarks with threads and " << perfcounters.num_counters()
+          << " performance counters were requested. Beware counters will "
+             "reflect the combined usage across all "
+             "threads.\n";
+    }
+
+    std::vector<size_t> repetition_indices;
+    repetition_indices.reserve(num_repetitions_total);
+    for (size_t runner_index = 0, num_runners = runners.size();
+         runner_index != num_runners; ++runner_index) {
+      const internal::BenchmarkRunner& runner = runners[runner_index];
+      std::fill_n(std::back_inserter(repetition_indices),
+                  runner.GetNumRepeats(), runner_index);
+    }
+    assert(repetition_indices.size() == num_repetitions_total &&
+           "Unexpected number of repetition indexes.");
+
+    if (FLAGS_benchmark_enable_random_interleaving) {
+      std::random_device rd;
+      std::mt19937 g(rd());
+      std::shuffle(repetition_indices.begin(), repetition_indices.end(), g);
+    }
+
+    for (size_t repetition_index : repetition_indices) {
+      internal::BenchmarkRunner& runner = runners[repetition_index];
+      runner.DoOneRepetition();
+      if (runner.HasRepeatsRemaining()) continue;
+      // FIXME: report each repetition separately, not all of them in bulk.
+
+      display_reporter->ReportRunsConfig(
+          runner.GetMinTime(), runner.HasExplicitIters(), runner.GetIters());
+      if (file_reporter)
+        file_reporter->ReportRunsConfig(
+            runner.GetMinTime(), runner.HasExplicitIters(), runner.GetIters());
+
+      RunResults run_results = runner.GetResults();
+
+      // Maybe calculate complexity report
+      if (const auto* reports_for_family = runner.GetReportsForFamily()) {
+        if (reports_for_family->num_runs_done ==
+            reports_for_family->num_runs_total) {
+          auto additional_run_stats = ComputeBigO(reports_for_family->Runs);
+          run_results.aggregates_only.insert(run_results.aggregates_only.end(),
+                                             additional_run_stats.begin(),
+                                             additional_run_stats.end());
+          per_family_reports.erase(
+              static_cast<int>(reports_for_family->Runs.front().family_index));
+        }
+      }
+
+      Report(display_reporter, file_reporter, run_results);
+    }
+  }
+  display_reporter->Finalize();
+  if (file_reporter) file_reporter->Finalize();
+  FlushStreams(display_reporter);
+  FlushStreams(file_reporter);
+}
+
+// Disable deprecated warnings temporarily because we need to reference
+// CSVReporter but don't want to trigger -Werror=-Wdeprecated-declarations
+BENCHMARK_DISABLE_DEPRECATED_WARNING
+
+std::unique_ptr<BenchmarkReporter> CreateReporter(
+    std::string const& name, ConsoleReporter::OutputOptions output_opts) {
+  typedef std::unique_ptr<BenchmarkReporter> PtrType;
+  if (name == "console") {
+    return PtrType(new ConsoleReporter(output_opts));
+  }
+  if (name == "json") {
+    return PtrType(new JSONReporter());
+  }
+  if (name == "csv") {
+    return PtrType(new CSVReporter());
+  }
+  std::cerr << "Unexpected format: '" << name << "'\n";
+  std::exit(1);
+}
+
+BENCHMARK_RESTORE_DEPRECATED_WARNING
+
+}  // end namespace
+
+bool IsZero(double n) {
+  return std::abs(n) < std::numeric_limits<double>::epsilon();
+}
+
+ConsoleReporter::OutputOptions GetOutputOptions(bool force_no_color) {
+  int output_opts = ConsoleReporter::OO_Defaults;
+  auto is_benchmark_color = [force_no_color]() -> bool {
+    if (force_no_color) {
+      return false;
+    }
+    if (FLAGS_benchmark_color == "auto") {
+      return IsColorTerminal();
+    }
+    return IsTruthyFlagValue(FLAGS_benchmark_color);
+  };
+  if (is_benchmark_color()) {
+    output_opts |= ConsoleReporter::OO_Color;
+  } else {
+    output_opts &= ~ConsoleReporter::OO_Color;
+  }
+  if (FLAGS_benchmark_counters_tabular) {
+    output_opts |= ConsoleReporter::OO_Tabular;
+  } else {
+    output_opts &= ~ConsoleReporter::OO_Tabular;
+  }
+  return static_cast<ConsoleReporter::OutputOptions>(output_opts);
+}
+
+}  // end namespace internal
+
+BenchmarkReporter* CreateDefaultDisplayReporter() {
+  static auto default_display_reporter =
+      internal::CreateReporter(FLAGS_benchmark_format,
+                               internal::GetOutputOptions())
+          .release();
+  return default_display_reporter;
+}
+
+size_t RunSpecifiedBenchmarks() {
+  return RunSpecifiedBenchmarks(nullptr, nullptr, FLAGS_benchmark_filter);
+}
+
+size_t RunSpecifiedBenchmarks(std::string spec) {
+  return RunSpecifiedBenchmarks(nullptr, nullptr, std::move(spec));
+}
+
+size_t RunSpecifiedBenchmarks(BenchmarkReporter* display_reporter) {
+  return RunSpecifiedBenchmarks(display_reporter, nullptr,
+                                FLAGS_benchmark_filter);
+}
+
+size_t RunSpecifiedBenchmarks(BenchmarkReporter* display_reporter,
+                              std::string spec) {
+  return RunSpecifiedBenchmarks(display_reporter, nullptr, std::move(spec));
+}
+
+size_t RunSpecifiedBenchmarks(BenchmarkReporter* display_reporter,
+                              BenchmarkReporter* file_reporter) {
+  return RunSpecifiedBenchmarks(display_reporter, file_reporter,
+                                FLAGS_benchmark_filter);
+}
+
+size_t RunSpecifiedBenchmarks(BenchmarkReporter* display_reporter,
+                              BenchmarkReporter* file_reporter,
+                              std::string spec) {
+  if (spec.empty() || spec == "all")
+    spec = ".";  // Regexp that matches all benchmarks
+
+  // Setup the reporters
+  std::ofstream output_file;
+  std::unique_ptr<BenchmarkReporter> default_display_reporter;
+  std::unique_ptr<BenchmarkReporter> default_file_reporter;
+  if (!display_reporter) {
+    default_display_reporter.reset(CreateDefaultDisplayReporter());
+    display_reporter = default_display_reporter.get();
+  }
+  auto& Out = display_reporter->GetOutputStream();
+  auto& Err = display_reporter->GetErrorStream();
+
+  std::string const& fname = FLAGS_benchmark_out;
+  if (fname.empty() && file_reporter) {
+    Err << "A custom file reporter was provided but "
+           "--benchmark_out=<file> was not specified."
+        << std::endl;
+    std::exit(1);
+  }
+  if (!fname.empty()) {
+    output_file.open(fname);
+    if (!output_file.is_open()) {
+      Err << "invalid file name: '" << fname << "'" << std::endl;
+      std::exit(1);
+    }
+    if (!file_reporter) {
+      default_file_reporter = internal::CreateReporter(
+          FLAGS_benchmark_out_format, ConsoleReporter::OO_None);
+      file_reporter = default_file_reporter.get();
+    }
+    file_reporter->SetOutputStream(&output_file);
+    file_reporter->SetErrorStream(&output_file);
+  }
+
+  std::vector<internal::BenchmarkInstance> benchmarks;
+  if (!FindBenchmarksInternal(spec, &benchmarks, &Err)) return 0;
+
+  if (benchmarks.empty()) {
+    Err << "Failed to match any benchmarks against regex: " << spec << "\n";
+    return 0;
+  }
+
+  if (FLAGS_benchmark_list_tests) {
+    for (auto const& benchmark : benchmarks)
+      Out << benchmark.name().str() << "\n";
+  } else {
+    internal::RunBenchmarks(benchmarks, display_reporter, file_reporter);
+  }
+
+  return benchmarks.size();
+}
+
+namespace {
+// stores the time unit benchmarks use by default
+TimeUnit default_time_unit = kNanosecond;
+}  // namespace
+
+TimeUnit GetDefaultTimeUnit() { return default_time_unit; }
+
+void SetDefaultTimeUnit(TimeUnit unit) { default_time_unit = unit; }
+
+std::string GetBenchmarkFilter() { return FLAGS_benchmark_filter; }
+
+void SetBenchmarkFilter(std::string value) {
+  FLAGS_benchmark_filter = std::move(value);
+}
+
+int32_t GetBenchmarkVerbosity() { return FLAGS_v; }
+
+void RegisterMemoryManager(MemoryManager* manager) {
+  internal::memory_manager = manager;
+}
+
+void AddCustomContext(const std::string& key, const std::string& value) {
+  if (internal::global_context == nullptr) {
+    internal::global_context = new std::map<std::string, std::string>();
+  }
+  if (!internal::global_context->emplace(key, value).second) {
+    std::cerr << "Failed to add custom context \"" << key << "\" as it already "
+              << "exists with value \"" << value << "\"\n";
+  }
+}
+
+namespace internal {
+
+void (*HelperPrintf)();
+
+void PrintUsageAndExit() {
+  HelperPrintf();
+  exit(0);
+}
+
+void SetDefaultTimeUnitFromFlag(const std::string& time_unit_flag) {
+  if (time_unit_flag == "s") {
+    return SetDefaultTimeUnit(kSecond);
+  }
+  if (time_unit_flag == "ms") {
+    return SetDefaultTimeUnit(kMillisecond);
+  }
+  if (time_unit_flag == "us") {
+    return SetDefaultTimeUnit(kMicrosecond);
+  }
+  if (time_unit_flag == "ns") {
+    return SetDefaultTimeUnit(kNanosecond);
+  }
+  if (!time_unit_flag.empty()) {
+    PrintUsageAndExit();
+  }
+}
+
+void ParseCommandLineFlags(int* argc, char** argv) {
+  using namespace benchmark;
+  BenchmarkReporter::Context::executable_name =
+      (argc && *argc > 0) ? argv[0] : "unknown";
+  for (int i = 1; argc && i < *argc; ++i) {
+    if (ParseBoolFlag(argv[i], "benchmark_list_tests",
+                      &FLAGS_benchmark_list_tests) ||
+        ParseStringFlag(argv[i], "benchmark_filter", &FLAGS_benchmark_filter) ||
+        ParseStringFlag(argv[i], "benchmark_min_time",
+                        &FLAGS_benchmark_min_time) ||
+        ParseDoubleFlag(argv[i], "benchmark_min_warmup_time",
+                        &FLAGS_benchmark_min_warmup_time) ||
+        ParseInt32Flag(argv[i], "benchmark_repetitions",
+                       &FLAGS_benchmark_repetitions) ||
+        ParseBoolFlag(argv[i], "benchmark_enable_random_interleaving",
+                      &FLAGS_benchmark_enable_random_interleaving) ||
+        ParseBoolFlag(argv[i], "benchmark_report_aggregates_only",
+                      &FLAGS_benchmark_report_aggregates_only) ||
+        ParseBoolFlag(argv[i], "benchmark_display_aggregates_only",
+                      &FLAGS_benchmark_display_aggregates_only) ||
+        ParseStringFlag(argv[i], "benchmark_format", &FLAGS_benchmark_format) ||
+        ParseStringFlag(argv[i], "benchmark_out", &FLAGS_benchmark_out) ||
+        ParseStringFlag(argv[i], "benchmark_out_format",
+                        &FLAGS_benchmark_out_format) ||
+        ParseStringFlag(argv[i], "benchmark_color", &FLAGS_benchmark_color) ||
+        ParseBoolFlag(argv[i], "benchmark_counters_tabular",
+                      &FLAGS_benchmark_counters_tabular) ||
+        ParseStringFlag(argv[i], "benchmark_perf_counters",
+                        &FLAGS_benchmark_perf_counters) ||
+        ParseKeyValueFlag(argv[i], "benchmark_context",
+                          &FLAGS_benchmark_context) ||
+        ParseStringFlag(argv[i], "benchmark_time_unit",
+                        &FLAGS_benchmark_time_unit) ||
+        ParseInt32Flag(argv[i], "v", &FLAGS_v)) {
+      for (int j = i; j != *argc - 1; ++j) argv[j] = argv[j + 1];
+
+      --(*argc);
+      --i;
+    } else if (IsFlag(argv[i], "help")) {
+      PrintUsageAndExit();
+    }
+  }
+  for (auto const* flag :
+       {&FLAGS_benchmark_format, &FLAGS_benchmark_out_format}) {
+    if (*flag != "console" && *flag != "json" && *flag != "csv") {
+      PrintUsageAndExit();
+    }
+  }
+  SetDefaultTimeUnitFromFlag(FLAGS_benchmark_time_unit);
+  if (FLAGS_benchmark_color.empty()) {
+    PrintUsageAndExit();
+  }
+  for (const auto& kv : FLAGS_benchmark_context) {
+    AddCustomContext(kv.first, kv.second);
+  }
+}
+
+int InitializeStreams() {
+  static std::ios_base::Init init;
+  return 0;
+}
+
+}  // end namespace internal
+
+void PrintDefaultHelp() {
+  fprintf(stdout,
+          "benchmark"
+          " [--benchmark_list_tests={true|false}]\n"
+          "          [--benchmark_filter=<regex>]\n"
+          "          [--benchmark_min_time=`<integer>x` OR `<float>s` ]\n"
+          "          [--benchmark_min_warmup_time=<min_warmup_time>]\n"
+          "          [--benchmark_repetitions=<num_repetitions>]\n"
+          "          [--benchmark_enable_random_interleaving={true|false}]\n"
+          "          [--benchmark_report_aggregates_only={true|false}]\n"
+          "          [--benchmark_display_aggregates_only={true|false}]\n"
+          "          [--benchmark_format=<console|json|csv>]\n"
+          "          [--benchmark_out=<filename>]\n"
+          "          [--benchmark_out_format=<json|console|csv>]\n"
+          "          [--benchmark_color={auto|true|false}]\n"
+          "          [--benchmark_counters_tabular={true|false}]\n"
+#if defined HAVE_LIBPFM
+          "          [--benchmark_perf_counters=<counter>,...]\n"
+#endif
+          "          [--benchmark_context=<key>=<value>,...]\n"
+          "          [--benchmark_time_unit={ns|us|ms|s}]\n"
+          "          [--v=<verbosity>]\n");
+}
+
+void Initialize(int* argc, char** argv, void (*HelperPrintf)()) {
+  internal::HelperPrintf = HelperPrintf;
+  internal::ParseCommandLineFlags(argc, argv);
+  internal::LogLevel() = FLAGS_v;
+}
+
+void Shutdown() { delete internal::global_context; }
+
+bool ReportUnrecognizedArguments(int argc, char** argv) {
+  for (int i = 1; i < argc; ++i) {
+    fprintf(stderr, "%s: error: unrecognized command-line flag: %s\n", argv[0],
+            argv[i]);
+  }
+  return argc > 1;
+}
+
+}  // end namespace benchmark
diff --git a/leveldb_base/third_party/benchmark/src/benchmark_api_internal.cc b/leveldb_base/third_party/benchmark/src/benchmark_api_internal.cc
new file mode 100644
index 0000000..286f986
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/benchmark_api_internal.cc
@@ -0,0 +1,118 @@
+#include "benchmark_api_internal.h"
+
+#include <cinttypes>
+
+#include "string_util.h"
+
+namespace benchmark {
+namespace internal {
+
+BenchmarkInstance::BenchmarkInstance(Benchmark* benchmark, int family_idx,
+                                     int per_family_instance_idx,
+                                     const std::vector<int64_t>& args,
+                                     int thread_count)
+    : benchmark_(*benchmark),
+      family_index_(family_idx),
+      per_family_instance_index_(per_family_instance_idx),
+      aggregation_report_mode_(benchmark_.aggregation_report_mode_),
+      args_(args),
+      time_unit_(benchmark_.GetTimeUnit()),
+      measure_process_cpu_time_(benchmark_.measure_process_cpu_time_),
+      use_real_time_(benchmark_.use_real_time_),
+      use_manual_time_(benchmark_.use_manual_time_),
+      complexity_(benchmark_.complexity_),
+      complexity_lambda_(benchmark_.complexity_lambda_),
+      statistics_(benchmark_.statistics_),
+      repetitions_(benchmark_.repetitions_),
+      min_time_(benchmark_.min_time_),
+      min_warmup_time_(benchmark_.min_warmup_time_),
+      iterations_(benchmark_.iterations_),
+      threads_(thread_count) {
+  name_.function_name = benchmark_.name_;
+
+  size_t arg_i = 0;
+  for (const auto& arg : args) {
+    if (!name_.args.empty()) {
+      name_.args += '/';
+    }
+
+    if (arg_i < benchmark->arg_names_.size()) {
+      const auto& arg_name = benchmark_.arg_names_[arg_i];
+      if (!arg_name.empty()) {
+        name_.args += StrFormat("%s:", arg_name.c_str());
+      }
+    }
+
+    name_.args += StrFormat("%" PRId64, arg);
+    ++arg_i;
+  }
+
+  if (!IsZero(benchmark->min_time_)) {
+    name_.min_time = StrFormat("min_time:%0.3f", benchmark_.min_time_);
+  }
+
+  if (!IsZero(benchmark->min_warmup_time_)) {
+    name_.min_warmup_time =
+        StrFormat("min_warmup_time:%0.3f", benchmark_.min_warmup_time_);
+  }
+
+  if (benchmark_.iterations_ != 0) {
+    name_.iterations = StrFormat(
+        "iterations:%lu", static_cast<unsigned long>(benchmark_.iterations_));
+  }
+
+  if (benchmark_.repetitions_ != 0) {
+    name_.repetitions = StrFormat("repeats:%d", benchmark_.repetitions_);
+  }
+
+  if (benchmark_.measure_process_cpu_time_) {
+    name_.time_type = "process_time";
+  }
+
+  if (benchmark_.use_manual_time_) {
+    if (!name_.time_type.empty()) {
+      name_.time_type += '/';
+    }
+    name_.time_type += "manual_time";
+  } else if (benchmark_.use_real_time_) {
+    if (!name_.time_type.empty()) {
+      name_.time_type += '/';
+    }
+    name_.time_type += "real_time";
+  }
+
+  if (!benchmark_.thread_counts_.empty()) {
+    name_.threads = StrFormat("threads:%d", threads_);
+  }
+
+  setup_ = benchmark_.setup_;
+  teardown_ = benchmark_.teardown_;
+}
+
+State BenchmarkInstance::Run(
+    IterationCount iters, int thread_id, internal::ThreadTimer* timer,
+    internal::ThreadManager* manager,
+    internal::PerfCountersMeasurement* perf_counters_measurement) const {
+  State st(name_.function_name, iters, args_, thread_id, threads_, timer,
+           manager, perf_counters_measurement);
+  benchmark_.Run(st);
+  return st;
+}
+
+void BenchmarkInstance::Setup() const {
+  if (setup_) {
+    State st(name_.function_name, /*iters*/ 1, args_, /*thread_id*/ 0, threads_,
+             nullptr, nullptr, nullptr);
+    setup_(st);
+  }
+}
+
+void BenchmarkInstance::Teardown() const {
+  if (teardown_) {
+    State st(name_.function_name, /*iters*/ 1, args_, /*thread_id*/ 0, threads_,
+             nullptr, nullptr, nullptr);
+    teardown_(st);
+  }
+}
+}  // namespace internal
+}  // namespace benchmark
diff --git a/leveldb_base/third_party/benchmark/src/benchmark_api_internal.h b/leveldb_base/third_party/benchmark/src/benchmark_api_internal.h
new file mode 100644
index 0000000..94f5165
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/benchmark_api_internal.h
@@ -0,0 +1,87 @@
+#ifndef BENCHMARK_API_INTERNAL_H
+#define BENCHMARK_API_INTERNAL_H
+
+#include <cmath>
+#include <iosfwd>
+#include <limits>
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "benchmark/benchmark.h"
+#include "commandlineflags.h"
+
+namespace benchmark {
+namespace internal {
+
+// Information kept per benchmark we may want to run
+class BenchmarkInstance {
+ public:
+  BenchmarkInstance(Benchmark* benchmark, int family_index,
+                    int per_family_instance_index,
+                    const std::vector<int64_t>& args, int threads);
+
+  const BenchmarkName& name() const { return name_; }
+  int family_index() const { return family_index_; }
+  int per_family_instance_index() const { return per_family_instance_index_; }
+  AggregationReportMode aggregation_report_mode() const {
+    return aggregation_report_mode_;
+  }
+  TimeUnit time_unit() const { return time_unit_; }
+  bool measure_process_cpu_time() const { return measure_process_cpu_time_; }
+  bool use_real_time() const { return use_real_time_; }
+  bool use_manual_time() const { return use_manual_time_; }
+  BigO complexity() const { return complexity_; }
+  BigOFunc* complexity_lambda() const { return complexity_lambda_; }
+  const std::vector<Statistics>& statistics() const { return statistics_; }
+  int repetitions() const { return repetitions_; }
+  double min_time() const { return min_time_; }
+  double min_warmup_time() const { return min_warmup_time_; }
+  IterationCount iterations() const { return iterations_; }
+  int threads() const { return threads_; }
+  void Setup() const;
+  void Teardown() const;
+
+  State Run(IterationCount iters, int thread_id, internal::ThreadTimer* timer,
+            internal::ThreadManager* manager,
+            internal::PerfCountersMeasurement* perf_counters_measurement) const;
+
+ private:
+  BenchmarkName name_;
+  Benchmark& benchmark_;
+  const int family_index_;
+  const int per_family_instance_index_;
+  AggregationReportMode aggregation_report_mode_;
+  const std::vector<int64_t>& args_;
+  TimeUnit time_unit_;
+  bool measure_process_cpu_time_;
+  bool use_real_time_;
+  bool use_manual_time_;
+  BigO complexity_;
+  BigOFunc* complexity_lambda_;
+  UserCounters counters_;
+  const std::vector<Statistics>& statistics_;
+  int repetitions_;
+  double min_time_;
+  double min_warmup_time_;
+  IterationCount iterations_;
+  int threads_;  // Number of concurrent threads to us
+
+  typedef void (*callback_function)(const benchmark::State&);
+  callback_function setup_ = nullptr;
+  callback_function teardown_ = nullptr;
+};
+
+bool FindBenchmarksInternal(const std::string& re,
+                            std::vector<BenchmarkInstance>* benchmarks,
+                            std::ostream* Err);
+
+bool IsZero(double n);
+
+BENCHMARK_EXPORT
+ConsoleReporter::OutputOptions GetOutputOptions(bool force_no_color = false);
+
+}  // end namespace internal
+}  // end namespace benchmark
+
+#endif  // BENCHMARK_API_INTERNAL_H
diff --git a/leveldb_base/third_party/benchmark/src/benchmark_main.cc b/leveldb_base/third_party/benchmark/src/benchmark_main.cc
new file mode 100644
index 0000000..cd61cd2
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/benchmark_main.cc
@@ -0,0 +1,18 @@
+// Copyright 2018 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "benchmark/benchmark.h"
+
+BENCHMARK_EXPORT int main(int, char**);
+BENCHMARK_MAIN();
diff --git a/leveldb_base/third_party/benchmark/src/benchmark_name.cc b/leveldb_base/third_party/benchmark/src/benchmark_name.cc
new file mode 100644
index 0000000..01676bb
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/benchmark_name.cc
@@ -0,0 +1,59 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <benchmark/benchmark.h>
+
+namespace benchmark {
+
+namespace {
+
+// Compute the total size of a pack of std::strings
+size_t size_impl() { return 0; }
+
+template <typename Head, typename... Tail>
+size_t size_impl(const Head& head, const Tail&... tail) {
+  return head.size() + size_impl(tail...);
+}
+
+// Join a pack of std::strings using a delimiter
+// TODO: use absl::StrJoin
+void join_impl(std::string&, char) {}
+
+template <typename Head, typename... Tail>
+void join_impl(std::string& s, const char delimiter, const Head& head,
+               const Tail&... tail) {
+  if (!s.empty() && !head.empty()) {
+    s += delimiter;
+  }
+
+  s += head;
+
+  join_impl(s, delimiter, tail...);
+}
+
+template <typename... Ts>
+std::string join(char delimiter, const Ts&... ts) {
+  std::string s;
+  s.reserve(sizeof...(Ts) + size_impl(ts...));
+  join_impl(s, delimiter, ts...);
+  return s;
+}
+}  // namespace
+
+BENCHMARK_EXPORT
+std::string BenchmarkName::str() const {
+  return join('/', function_name, args, min_time, min_warmup_time, iterations,
+              repetitions, time_type, threads);
+}
+}  // namespace benchmark
diff --git a/leveldb_base/third_party/benchmark/src/benchmark_register.cc b/leveldb_base/third_party/benchmark/src/benchmark_register.cc
new file mode 100644
index 0000000..e447c9a
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/benchmark_register.cc
@@ -0,0 +1,520 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "benchmark_register.h"
+
+#ifndef BENCHMARK_OS_WINDOWS
+#if !defined(BENCHMARK_OS_FUCHSIA) && !defined(BENCHMARK_OS_QURT)
+#include <sys/resource.h>
+#endif
+#include <sys/time.h>
+#include <unistd.h>
+#endif
+
+#include <algorithm>
+#include <atomic>
+#include <cinttypes>
+#include <condition_variable>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <fstream>
+#include <iostream>
+#include <memory>
+#include <numeric>
+#include <sstream>
+#include <thread>
+
+#include "benchmark/benchmark.h"
+#include "benchmark_api_internal.h"
+#include "check.h"
+#include "commandlineflags.h"
+#include "complexity.h"
+#include "internal_macros.h"
+#include "log.h"
+#include "mutex.h"
+#include "re.h"
+#include "statistics.h"
+#include "string_util.h"
+#include "timers.h"
+
+namespace benchmark {
+
+namespace {
+// For non-dense Range, intermediate values are powers of kRangeMultiplier.
+static constexpr int kRangeMultiplier = 8;
+
+// The size of a benchmark family determines is the number of inputs to repeat
+// the benchmark on. If this is "large" then warn the user during configuration.
+static constexpr size_t kMaxFamilySize = 100;
+
+static constexpr char kDisabledPrefix[] = "DISABLED_";
+}  // end namespace
+
+namespace internal {
+
+//=============================================================================//
+//                         BenchmarkFamilies
+//=============================================================================//
+
+// Class for managing registered benchmarks.  Note that each registered
+// benchmark identifies a family of related benchmarks to run.
+class BenchmarkFamilies {
+ public:
+  static BenchmarkFamilies* GetInstance();
+
+  // Registers a benchmark family and returns the index assigned to it.
+  size_t AddBenchmark(std::unique_ptr<Benchmark> family);
+
+  // Clear all registered benchmark families.
+  void ClearBenchmarks();
+
+  // Extract the list of benchmark instances that match the specified
+  // regular expression.
+  bool FindBenchmarks(std::string re,
+                      std::vector<BenchmarkInstance>* benchmarks,
+                      std::ostream* Err);
+
+ private:
+  BenchmarkFamilies() {}
+
+  std::vector<std::unique_ptr<Benchmark>> families_;
+  Mutex mutex_;
+};
+
+BenchmarkFamilies* BenchmarkFamilies::GetInstance() {
+  static BenchmarkFamilies instance;
+  return &instance;
+}
+
+size_t BenchmarkFamilies::AddBenchmark(std::unique_ptr<Benchmark> family) {
+  MutexLock l(mutex_);
+  size_t index = families_.size();
+  families_.push_back(std::move(family));
+  return index;
+}
+
+void BenchmarkFamilies::ClearBenchmarks() {
+  MutexLock l(mutex_);
+  families_.clear();
+  families_.shrink_to_fit();
+}
+
+bool BenchmarkFamilies::FindBenchmarks(
+    std::string spec, std::vector<BenchmarkInstance>* benchmarks,
+    std::ostream* ErrStream) {
+  BM_CHECK(ErrStream);
+  auto& Err = *ErrStream;
+  // Make regular expression out of command-line flag
+  std::string error_msg;
+  Regex re;
+  bool is_negative_filter = false;
+  if (spec[0] == '-') {
+    spec.replace(0, 1, "");
+    is_negative_filter = true;
+  }
+  if (!re.Init(spec, &error_msg)) {
+    Err << "Could not compile benchmark re: " << error_msg << std::endl;
+    return false;
+  }
+
+  // Special list of thread counts to use when none are specified
+  const std::vector<int> one_thread = {1};
+
+  int next_family_index = 0;
+
+  MutexLock l(mutex_);
+  for (std::unique_ptr<Benchmark>& family : families_) {
+    int family_index = next_family_index;
+    int per_family_instance_index = 0;
+
+    // Family was deleted or benchmark doesn't match
+    if (!family) continue;
+
+    if (family->ArgsCnt() == -1) {
+      family->Args({});
+    }
+    const std::vector<int>* thread_counts =
+        (family->thread_counts_.empty()
+             ? &one_thread
+             : &static_cast<const std::vector<int>&>(family->thread_counts_));
+    const size_t family_size = family->args_.size() * thread_counts->size();
+    // The benchmark will be run at least 'family_size' different inputs.
+    // If 'family_size' is very large warn the user.
+    if (family_size > kMaxFamilySize) {
+      Err << "The number of inputs is very large. " << family->name_
+          << " will be repeated at least " << family_size << " times.\n";
+    }
+    // reserve in the special case the regex ".", since we know the final
+    // family size.  this doesn't take into account any disabled benchmarks
+    // so worst case we reserve more than we need.
+    if (spec == ".") benchmarks->reserve(benchmarks->size() + family_size);
+
+    for (auto const& args : family->args_) {
+      for (int num_threads : *thread_counts) {
+        BenchmarkInstance instance(family.get(), family_index,
+                                   per_family_instance_index, args,
+                                   num_threads);
+
+        const auto full_name = instance.name().str();
+        if (full_name.rfind(kDisabledPrefix, 0) != 0 &&
+            ((re.Match(full_name) && !is_negative_filter) ||
+             (!re.Match(full_name) && is_negative_filter))) {
+          benchmarks->push_back(std::move(instance));
+
+          ++per_family_instance_index;
+
+          // Only bump the next family index once we've estabilished that
+          // at least one instance of this family will be run.
+          if (next_family_index == family_index) ++next_family_index;
+        }
+      }
+    }
+  }
+  return true;
+}
+
+Benchmark* RegisterBenchmarkInternal(Benchmark* bench) {
+  std::unique_ptr<Benchmark> bench_ptr(bench);
+  BenchmarkFamilies* families = BenchmarkFamilies::GetInstance();
+  families->AddBenchmark(std::move(bench_ptr));
+  return bench;
+}
+
+// FIXME: This function is a hack so that benchmark.cc can access
+// `BenchmarkFamilies`
+bool FindBenchmarksInternal(const std::string& re,
+                            std::vector<BenchmarkInstance>* benchmarks,
+                            std::ostream* Err) {
+  return BenchmarkFamilies::GetInstance()->FindBenchmarks(re, benchmarks, Err);
+}
+
+//=============================================================================//
+//                               Benchmark
+//=============================================================================//
+
+Benchmark::Benchmark(const std::string& name)
+    : name_(name),
+      aggregation_report_mode_(ARM_Unspecified),
+      time_unit_(GetDefaultTimeUnit()),
+      use_default_time_unit_(true),
+      range_multiplier_(kRangeMultiplier),
+      min_time_(0),
+      min_warmup_time_(0),
+      iterations_(0),
+      repetitions_(0),
+      measure_process_cpu_time_(false),
+      use_real_time_(false),
+      use_manual_time_(false),
+      complexity_(oNone),
+      complexity_lambda_(nullptr),
+      setup_(nullptr),
+      teardown_(nullptr) {
+  ComputeStatistics("mean", StatisticsMean);
+  ComputeStatistics("median", StatisticsMedian);
+  ComputeStatistics("stddev", StatisticsStdDev);
+  ComputeStatistics("cv", StatisticsCV, kPercentage);
+}
+
+Benchmark::~Benchmark() {}
+
+Benchmark* Benchmark::Name(const std::string& name) {
+  SetName(name);
+  return this;
+}
+
+Benchmark* Benchmark::Arg(int64_t x) {
+  BM_CHECK(ArgsCnt() == -1 || ArgsCnt() == 1);
+  args_.push_back({x});
+  return this;
+}
+
+Benchmark* Benchmark::Unit(TimeUnit unit) {
+  time_unit_ = unit;
+  use_default_time_unit_ = false;
+  return this;
+}
+
+Benchmark* Benchmark::Range(int64_t start, int64_t limit) {
+  BM_CHECK(ArgsCnt() == -1 || ArgsCnt() == 1);
+  std::vector<int64_t> arglist;
+  AddRange(&arglist, start, limit, range_multiplier_);
+
+  for (int64_t i : arglist) {
+    args_.push_back({i});
+  }
+  return this;
+}
+
+Benchmark* Benchmark::Ranges(
+    const std::vector<std::pair<int64_t, int64_t>>& ranges) {
+  BM_CHECK(ArgsCnt() == -1 || ArgsCnt() == static_cast<int>(ranges.size()));
+  std::vector<std::vector<int64_t>> arglists(ranges.size());
+  for (std::size_t i = 0; i < ranges.size(); i++) {
+    AddRange(&arglists[i], ranges[i].first, ranges[i].second,
+             range_multiplier_);
+  }
+
+  ArgsProduct(arglists);
+
+  return this;
+}
+
+Benchmark* Benchmark::ArgsProduct(
+    const std::vector<std::vector<int64_t>>& arglists) {
+  BM_CHECK(ArgsCnt() == -1 || ArgsCnt() == static_cast<int>(arglists.size()));
+
+  std::vector<std::size_t> indices(arglists.size());
+  const std::size_t total = std::accumulate(
+      std::begin(arglists), std::end(arglists), std::size_t{1},
+      [](const std::size_t res, const std::vector<int64_t>& arglist) {
+        return res * arglist.size();
+      });
+  std::vector<int64_t> args;
+  args.reserve(arglists.size());
+  for (std::size_t i = 0; i < total; i++) {
+    for (std::size_t arg = 0; arg < arglists.size(); arg++) {
+      args.push_back(arglists[arg][indices[arg]]);
+    }
+    args_.push_back(args);
+    args.clear();
+
+    std::size_t arg = 0;
+    do {
+      indices[arg] = (indices[arg] + 1) % arglists[arg].size();
+    } while (indices[arg++] == 0 && arg < arglists.size());
+  }
+
+  return this;
+}
+
+Benchmark* Benchmark::ArgName(const std::string& name) {
+  BM_CHECK(ArgsCnt() == -1 || ArgsCnt() == 1);
+  arg_names_ = {name};
+  return this;
+}
+
+Benchmark* Benchmark::ArgNames(const std::vector<std::string>& names) {
+  BM_CHECK(ArgsCnt() == -1 || ArgsCnt() == static_cast<int>(names.size()));
+  arg_names_ = names;
+  return this;
+}
+
+Benchmark* Benchmark::DenseRange(int64_t start, int64_t limit, int step) {
+  BM_CHECK(ArgsCnt() == -1 || ArgsCnt() == 1);
+  BM_CHECK_LE(start, limit);
+  for (int64_t arg = start; arg <= limit; arg += step) {
+    args_.push_back({arg});
+  }
+  return this;
+}
+
+Benchmark* Benchmark::Args(const std::vector<int64_t>& args) {
+  BM_CHECK(ArgsCnt() == -1 || ArgsCnt() == static_cast<int>(args.size()));
+  args_.push_back(args);
+  return this;
+}
+
+Benchmark* Benchmark::Apply(void (*custom_arguments)(Benchmark* benchmark)) {
+  custom_arguments(this);
+  return this;
+}
+
+Benchmark* Benchmark::Setup(void (*setup)(const benchmark::State&)) {
+  BM_CHECK(setup != nullptr);
+  setup_ = setup;
+  return this;
+}
+
+Benchmark* Benchmark::Teardown(void (*teardown)(const benchmark::State&)) {
+  BM_CHECK(teardown != nullptr);
+  teardown_ = teardown;
+  return this;
+}
+
+Benchmark* Benchmark::RangeMultiplier(int multiplier) {
+  BM_CHECK(multiplier > 1);
+  range_multiplier_ = multiplier;
+  return this;
+}
+
+Benchmark* Benchmark::MinTime(double t) {
+  BM_CHECK(t > 0.0);
+  BM_CHECK(iterations_ == 0);
+  min_time_ = t;
+  return this;
+}
+
+Benchmark* Benchmark::MinWarmUpTime(double t) {
+  BM_CHECK(t >= 0.0);
+  BM_CHECK(iterations_ == 0);
+  min_warmup_time_ = t;
+  return this;
+}
+
+Benchmark* Benchmark::Iterations(IterationCount n) {
+  BM_CHECK(n > 0);
+  BM_CHECK(IsZero(min_time_));
+  BM_CHECK(IsZero(min_warmup_time_));
+  iterations_ = n;
+  return this;
+}
+
+Benchmark* Benchmark::Repetitions(int n) {
+  BM_CHECK(n > 0);
+  repetitions_ = n;
+  return this;
+}
+
+Benchmark* Benchmark::ReportAggregatesOnly(bool value) {
+  aggregation_report_mode_ = value ? ARM_ReportAggregatesOnly : ARM_Default;
+  return this;
+}
+
+Benchmark* Benchmark::DisplayAggregatesOnly(bool value) {
+  // If we were called, the report mode is no longer 'unspecified', in any case.
+  aggregation_report_mode_ = static_cast<AggregationReportMode>(
+      aggregation_report_mode_ | ARM_Default);
+
+  if (value) {
+    aggregation_report_mode_ = static_cast<AggregationReportMode>(
+        aggregation_report_mode_ | ARM_DisplayReportAggregatesOnly);
+  } else {
+    aggregation_report_mode_ = static_cast<AggregationReportMode>(
+        aggregation_report_mode_ & ~ARM_DisplayReportAggregatesOnly);
+  }
+
+  return this;
+}
+
+Benchmark* Benchmark::MeasureProcessCPUTime() {
+  // Can be used together with UseRealTime() / UseManualTime().
+  measure_process_cpu_time_ = true;
+  return this;
+}
+
+Benchmark* Benchmark::UseRealTime() {
+  BM_CHECK(!use_manual_time_)
+      << "Cannot set UseRealTime and UseManualTime simultaneously.";
+  use_real_time_ = true;
+  return this;
+}
+
+Benchmark* Benchmark::UseManualTime() {
+  BM_CHECK(!use_real_time_)
+      << "Cannot set UseRealTime and UseManualTime simultaneously.";
+  use_manual_time_ = true;
+  return this;
+}
+
+Benchmark* Benchmark::Complexity(BigO complexity) {
+  complexity_ = complexity;
+  return this;
+}
+
+Benchmark* Benchmark::Complexity(BigOFunc* complexity) {
+  complexity_lambda_ = complexity;
+  complexity_ = oLambda;
+  return this;
+}
+
+Benchmark* Benchmark::ComputeStatistics(const std::string& name,
+                                        StatisticsFunc* statistics,
+                                        StatisticUnit unit) {
+  statistics_.emplace_back(name, statistics, unit);
+  return this;
+}
+
+Benchmark* Benchmark::Threads(int t) {
+  BM_CHECK_GT(t, 0);
+  thread_counts_.push_back(t);
+  return this;
+}
+
+Benchmark* Benchmark::ThreadRange(int min_threads, int max_threads) {
+  BM_CHECK_GT(min_threads, 0);
+  BM_CHECK_GE(max_threads, min_threads);
+
+  AddRange(&thread_counts_, min_threads, max_threads, 2);
+  return this;
+}
+
+Benchmark* Benchmark::DenseThreadRange(int min_threads, int max_threads,
+                                       int stride) {
+  BM_CHECK_GT(min_threads, 0);
+  BM_CHECK_GE(max_threads, min_threads);
+  BM_CHECK_GE(stride, 1);
+
+  for (auto i = min_threads; i < max_threads; i += stride) {
+    thread_counts_.push_back(i);
+  }
+  thread_counts_.push_back(max_threads);
+  return this;
+}
+
+Benchmark* Benchmark::ThreadPerCpu() {
+  thread_counts_.push_back(CPUInfo::Get().num_cpus);
+  return this;
+}
+
+void Benchmark::SetName(const std::string& name) { name_ = name; }
+
+const char* Benchmark::GetName() const { return name_.c_str(); }
+
+int Benchmark::ArgsCnt() const {
+  if (args_.empty()) {
+    if (arg_names_.empty()) return -1;
+    return static_cast<int>(arg_names_.size());
+  }
+  return static_cast<int>(args_.front().size());
+}
+
+const char* Benchmark::GetArgName(int arg) const {
+  BM_CHECK_GE(arg, 0);
+  BM_CHECK_LT(arg, static_cast<int>(arg_names_.size()));
+  return arg_names_[arg].c_str();
+}
+
+TimeUnit Benchmark::GetTimeUnit() const {
+  return use_default_time_unit_ ? GetDefaultTimeUnit() : time_unit_;
+}
+
+//=============================================================================//
+//                            FunctionBenchmark
+//=============================================================================//
+
+void FunctionBenchmark::Run(State& st) { func_(st); }
+
+}  // end namespace internal
+
+void ClearRegisteredBenchmarks() {
+  internal::BenchmarkFamilies::GetInstance()->ClearBenchmarks();
+}
+
+std::vector<int64_t> CreateRange(int64_t lo, int64_t hi, int multi) {
+  std::vector<int64_t> args;
+  internal::AddRange(&args, lo, hi, multi);
+  return args;
+}
+
+std::vector<int64_t> CreateDenseRange(int64_t start, int64_t limit, int step) {
+  BM_CHECK_LE(start, limit);
+  std::vector<int64_t> args;
+  for (int64_t arg = start; arg <= limit; arg += step) {
+    args.push_back(arg);
+  }
+  return args;
+}
+
+}  // end namespace benchmark
diff --git a/leveldb_base/third_party/benchmark/src/benchmark_register.h b/leveldb_base/third_party/benchmark/src/benchmark_register.h
new file mode 100644
index 0000000..53367c7
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/benchmark_register.h
@@ -0,0 +1,109 @@
+#ifndef BENCHMARK_REGISTER_H
+#define BENCHMARK_REGISTER_H
+
+#include <algorithm>
+#include <limits>
+#include <vector>
+
+#include "check.h"
+
+namespace benchmark {
+namespace internal {
+
+// Append the powers of 'mult' in the closed interval [lo, hi].
+// Returns iterator to the start of the inserted range.
+template <typename T>
+typename std::vector<T>::iterator AddPowers(std::vector<T>* dst, T lo, T hi,
+                                            int mult) {
+  BM_CHECK_GE(lo, 0);
+  BM_CHECK_GE(hi, lo);
+  BM_CHECK_GE(mult, 2);
+
+  const size_t start_offset = dst->size();
+
+  static const T kmax = std::numeric_limits<T>::max();
+
+  // Space out the values in multiples of "mult"
+  for (T i = static_cast<T>(1); i <= hi; i *= static_cast<T>(mult)) {
+    if (i >= lo) {
+      dst->push_back(i);
+    }
+    // Break the loop here since multiplying by
+    // 'mult' would move outside of the range of T
+    if (i > kmax / mult) break;
+  }
+
+  return dst->begin() + static_cast<int>(start_offset);
+}
+
+template <typename T>
+void AddNegatedPowers(std::vector<T>* dst, T lo, T hi, int mult) {
+  // We negate lo and hi so we require that they cannot be equal to 'min'.
+  BM_CHECK_GT(lo, std::numeric_limits<T>::min());
+  BM_CHECK_GT(hi, std::numeric_limits<T>::min());
+  BM_CHECK_GE(hi, lo);
+  BM_CHECK_LE(hi, 0);
+
+  // Add positive powers, then negate and reverse.
+  // Casts necessary since small integers get promoted
+  // to 'int' when negating.
+  const auto lo_complement = static_cast<T>(-lo);
+  const auto hi_complement = static_cast<T>(-hi);
+
+  const auto it = AddPowers(dst, hi_complement, lo_complement, mult);
+
+  std::for_each(it, dst->end(), [](T& t) { t *= -1; });
+  std::reverse(it, dst->end());
+}
+
+template <typename T>
+void AddRange(std::vector<T>* dst, T lo, T hi, int mult) {
+  static_assert(std::is_integral<T>::value && std::is_signed<T>::value,
+                "Args type must be a signed integer");
+
+  BM_CHECK_GE(hi, lo);
+  BM_CHECK_GE(mult, 2);
+
+  // Add "lo"
+  dst->push_back(lo);
+
+  // Handle lo == hi as a special case, so we then know
+  // lo < hi and so it is safe to add 1 to lo and subtract 1
+  // from hi without falling outside of the range of T.
+  if (lo == hi) return;
+
+  // Ensure that lo_inner <= hi_inner below.
+  if (lo + 1 == hi) {
+    dst->push_back(hi);
+    return;
+  }
+
+  // Add all powers of 'mult' in the range [lo+1, hi-1] (inclusive).
+  const auto lo_inner = static_cast<T>(lo + 1);
+  const auto hi_inner = static_cast<T>(hi - 1);
+
+  // Insert negative values
+  if (lo_inner < 0) {
+    AddNegatedPowers(dst, lo_inner, std::min(hi_inner, T{-1}), mult);
+  }
+
+  // Treat 0 as a special case (see discussion on #762).
+  if (lo < 0 && hi >= 0) {
+    dst->push_back(0);
+  }
+
+  // Insert positive values
+  if (hi_inner > 0) {
+    AddPowers(dst, std::max(lo_inner, T{1}), hi_inner, mult);
+  }
+
+  // Add "hi" (if different from last value).
+  if (hi != dst->back()) {
+    dst->push_back(hi);
+  }
+}
+
+}  // namespace internal
+}  // namespace benchmark
+
+#endif  // BENCHMARK_REGISTER_H
diff --git a/leveldb_base/third_party/benchmark/src/benchmark_runner.cc b/leveldb_base/third_party/benchmark/src/benchmark_runner.cc
new file mode 100644
index 0000000..f7ae424
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/benchmark_runner.cc
@@ -0,0 +1,497 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "benchmark_runner.h"
+
+#include "benchmark/benchmark.h"
+#include "benchmark_api_internal.h"
+#include "internal_macros.h"
+
+#ifndef BENCHMARK_OS_WINDOWS
+#if !defined(BENCHMARK_OS_FUCHSIA) && !defined(BENCHMARK_OS_QURT)
+#include <sys/resource.h>
+#endif
+#include <sys/time.h>
+#include <unistd.h>
+#endif
+
+#include <algorithm>
+#include <atomic>
+#include <climits>
+#include <cmath>
+#include <condition_variable>
+#include <cstdio>
+#include <cstdlib>
+#include <fstream>
+#include <iostream>
+#include <limits>
+#include <memory>
+#include <string>
+#include <thread>
+#include <utility>
+
+#include "check.h"
+#include "colorprint.h"
+#include "commandlineflags.h"
+#include "complexity.h"
+#include "counter.h"
+#include "internal_macros.h"
+#include "log.h"
+#include "mutex.h"
+#include "perf_counters.h"
+#include "re.h"
+#include "statistics.h"
+#include "string_util.h"
+#include "thread_manager.h"
+#include "thread_timer.h"
+
+namespace benchmark {
+
+namespace internal {
+
+MemoryManager* memory_manager = nullptr;
+
+namespace {
+
+static constexpr IterationCount kMaxIterations = 1000000000;
+const double kDefaultMinTime =
+    std::strtod(::benchmark::kDefaultMinTimeStr, /*p_end*/ nullptr);
+
+BenchmarkReporter::Run CreateRunReport(
+    const benchmark::internal::BenchmarkInstance& b,
+    const internal::ThreadManager::Result& results,
+    IterationCount memory_iterations,
+    const MemoryManager::Result* memory_result, double seconds,
+    int64_t repetition_index, int64_t repeats) {
+  // Create report about this benchmark run.
+  BenchmarkReporter::Run report;
+
+  report.run_name = b.name();
+  report.family_index = b.family_index();
+  report.per_family_instance_index = b.per_family_instance_index();
+  report.skipped = results.skipped_;
+  report.skip_message = results.skip_message_;
+  report.report_label = results.report_label_;
+  // This is the total iterations across all threads.
+  report.iterations = results.iterations;
+  report.time_unit = b.time_unit();
+  report.threads = b.threads();
+  report.repetition_index = repetition_index;
+  report.repetitions = repeats;
+
+  if (!report.skipped) {
+    if (b.use_manual_time()) {
+      report.real_accumulated_time = results.manual_time_used;
+    } else {
+      report.real_accumulated_time = results.real_time_used;
+    }
+    report.cpu_accumulated_time = results.cpu_time_used;
+    report.complexity_n = results.complexity_n;
+    report.complexity = b.complexity();
+    report.complexity_lambda = b.complexity_lambda();
+    report.statistics = &b.statistics();
+    report.counters = results.counters;
+
+    if (memory_iterations > 0) {
+      assert(memory_result != nullptr);
+      report.memory_result = memory_result;
+      report.allocs_per_iter =
+          memory_iterations ? static_cast<double>(memory_result->num_allocs) /
+                                  memory_iterations
+                            : 0;
+    }
+
+    internal::Finish(&report.counters, results.iterations, seconds,
+                     b.threads());
+  }
+  return report;
+}
+
+// Execute one thread of benchmark b for the specified number of iterations.
+// Adds the stats collected for the thread into manager->results.
+void RunInThread(const BenchmarkInstance* b, IterationCount iters,
+                 int thread_id, ThreadManager* manager,
+                 PerfCountersMeasurement* perf_counters_measurement) {
+  internal::ThreadTimer timer(
+      b->measure_process_cpu_time()
+          ? internal::ThreadTimer::CreateProcessCpuTime()
+          : internal::ThreadTimer::Create());
+
+  State st =
+      b->Run(iters, thread_id, &timer, manager, perf_counters_measurement);
+  BM_CHECK(st.skipped() || st.iterations() >= st.max_iterations)
+      << "Benchmark returned before State::KeepRunning() returned false!";
+  {
+    MutexLock l(manager->GetBenchmarkMutex());
+    internal::ThreadManager::Result& results = manager->results;
+    results.iterations += st.iterations();
+    results.cpu_time_used += timer.cpu_time_used();
+    results.real_time_used += timer.real_time_used();
+    results.manual_time_used += timer.manual_time_used();
+    results.complexity_n += st.complexity_length_n();
+    internal::Increment(&results.counters, st.counters);
+  }
+  manager->NotifyThreadComplete();
+}
+
+double ComputeMinTime(const benchmark::internal::BenchmarkInstance& b,
+                      const BenchTimeType& iters_or_time) {
+  if (!IsZero(b.min_time())) return b.min_time();
+  // If the flag was used to specify number of iters, then return the default
+  // min_time.
+  if (iters_or_time.tag == BenchTimeType::ITERS) return kDefaultMinTime;
+
+  return iters_or_time.time;
+}
+
+IterationCount ComputeIters(const benchmark::internal::BenchmarkInstance& b,
+                            const BenchTimeType& iters_or_time) {
+  if (b.iterations() != 0) return b.iterations();
+
+  // We've already concluded that this flag is currently used to pass
+  // iters but do a check here again anyway.
+  BM_CHECK(iters_or_time.tag == BenchTimeType::ITERS);
+  return iters_or_time.iters;
+}
+
+}  // end namespace
+
+BenchTimeType ParseBenchMinTime(const std::string& value) {
+  BenchTimeType ret;
+
+  if (value.empty()) {
+    ret.tag = BenchTimeType::TIME;
+    ret.time = 0.0;
+    return ret;
+  }
+
+  if (value.back() == 'x') {
+    char* p_end;
+    // Reset errno before it's changed by strtol.
+    errno = 0;
+    IterationCount num_iters = std::strtol(value.c_str(), &p_end, 10);
+
+    // After a valid parse, p_end should have been set to
+    // point to the 'x' suffix.
+    BM_CHECK(errno == 0 && p_end != nullptr && *p_end == 'x')
+        << "Malformed iters value passed to --benchmark_min_time: `" << value
+        << "`. Expected --benchmark_min_time=<integer>x.";
+
+    ret.tag = BenchTimeType::ITERS;
+    ret.iters = num_iters;
+    return ret;
+  }
+
+  bool has_suffix = value.back() == 's';
+  if (!has_suffix) {
+    BM_VLOG(0) << "Value passed to --benchmark_min_time should have a suffix. "
+                  "Eg., `30s` for 30-seconds.";
+  }
+
+  char* p_end;
+  // Reset errno before it's changed by strtod.
+  errno = 0;
+  double min_time = std::strtod(value.c_str(), &p_end);
+
+  // After a successful parse, p_end should point to the suffix 's',
+  // or the end of the string if the suffix was omitted.
+  BM_CHECK(errno == 0 && p_end != nullptr &&
+           ((has_suffix && *p_end == 's') || *p_end == '\0'))
+      << "Malformed seconds value passed to --benchmark_min_time: `" << value
+      << "`. Expected --benchmark_min_time=<float>x.";
+
+  ret.tag = BenchTimeType::TIME;
+  ret.time = min_time;
+
+  return ret;
+}
+
+BenchmarkRunner::BenchmarkRunner(
+    const benchmark::internal::BenchmarkInstance& b_,
+    PerfCountersMeasurement* pcm_,
+    BenchmarkReporter::PerFamilyRunReports* reports_for_family_)
+    : b(b_),
+      reports_for_family(reports_for_family_),
+      parsed_benchtime_flag(ParseBenchMinTime(FLAGS_benchmark_min_time)),
+      min_time(ComputeMinTime(b_, parsed_benchtime_flag)),
+      min_warmup_time((!IsZero(b.min_time()) && b.min_warmup_time() > 0.0)
+                          ? b.min_warmup_time()
+                          : FLAGS_benchmark_min_warmup_time),
+      warmup_done(!(min_warmup_time > 0.0)),
+      repeats(b.repetitions() != 0 ? b.repetitions()
+                                   : FLAGS_benchmark_repetitions),
+      has_explicit_iteration_count(b.iterations() != 0 ||
+                                   parsed_benchtime_flag.tag ==
+                                       BenchTimeType::ITERS),
+      pool(b.threads() - 1),
+      iters(has_explicit_iteration_count
+                ? ComputeIters(b_, parsed_benchtime_flag)
+                : 1),
+      perf_counters_measurement_ptr(pcm_) {
+  run_results.display_report_aggregates_only =
+      (FLAGS_benchmark_report_aggregates_only ||
+       FLAGS_benchmark_display_aggregates_only);
+  run_results.file_report_aggregates_only =
+      FLAGS_benchmark_report_aggregates_only;
+  if (b.aggregation_report_mode() != internal::ARM_Unspecified) {
+    run_results.display_report_aggregates_only =
+        (b.aggregation_report_mode() &
+         internal::ARM_DisplayReportAggregatesOnly);
+    run_results.file_report_aggregates_only =
+        (b.aggregation_report_mode() & internal::ARM_FileReportAggregatesOnly);
+    BM_CHECK(FLAGS_benchmark_perf_counters.empty() ||
+             (perf_counters_measurement_ptr->num_counters() == 0))
+        << "Perf counters were requested but could not be set up.";
+  }
+}
+
+BenchmarkRunner::IterationResults BenchmarkRunner::DoNIterations() {
+  BM_VLOG(2) << "Running " << b.name().str() << " for " << iters << "\n";
+
+  std::unique_ptr<internal::ThreadManager> manager;
+  manager.reset(new internal::ThreadManager(b.threads()));
+
+  // Run all but one thread in separate threads
+  for (std::size_t ti = 0; ti < pool.size(); ++ti) {
+    pool[ti] = std::thread(&RunInThread, &b, iters, static_cast<int>(ti + 1),
+                           manager.get(), perf_counters_measurement_ptr);
+  }
+  // And run one thread here directly.
+  // (If we were asked to run just one thread, we don't create new threads.)
+  // Yes, we need to do this here *after* we start the separate threads.
+  RunInThread(&b, iters, 0, manager.get(), perf_counters_measurement_ptr);
+
+  // The main thread has finished. Now let's wait for the other threads.
+  manager->WaitForAllThreads();
+  for (std::thread& thread : pool) thread.join();
+
+  IterationResults i;
+  // Acquire the measurements/counters from the manager, UNDER THE LOCK!
+  {
+    MutexLock l(manager->GetBenchmarkMutex());
+    i.results = manager->results;
+  }
+
+  // And get rid of the manager.
+  manager.reset();
+
+  // Adjust real/manual time stats since they were reported per thread.
+  i.results.real_time_used /= b.threads();
+  i.results.manual_time_used /= b.threads();
+  // If we were measuring whole-process CPU usage, adjust the CPU time too.
+  if (b.measure_process_cpu_time()) i.results.cpu_time_used /= b.threads();
+
+  BM_VLOG(2) << "Ran in " << i.results.cpu_time_used << "/"
+             << i.results.real_time_used << "\n";
+
+  // By using KeepRunningBatch a benchmark can iterate more times than
+  // requested, so take the iteration count from i.results.
+  i.iters = i.results.iterations / b.threads();
+
+  // Base decisions off of real time if requested by this benchmark.
+  i.seconds = i.results.cpu_time_used;
+  if (b.use_manual_time()) {
+    i.seconds = i.results.manual_time_used;
+  } else if (b.use_real_time()) {
+    i.seconds = i.results.real_time_used;
+  }
+
+  return i;
+}
+
+IterationCount BenchmarkRunner::PredictNumItersNeeded(
+    const IterationResults& i) const {
+  // See how much iterations should be increased by.
+  // Note: Avoid division by zero with max(seconds, 1ns).
+  double multiplier = GetMinTimeToApply() * 1.4 / std::max(i.seconds, 1e-9);
+  // If our last run was at least 10% of FLAGS_benchmark_min_time then we
+  // use the multiplier directly.
+  // Otherwise we use at most 10 times expansion.
+  // NOTE: When the last run was at least 10% of the min time the max
+  // expansion should be 14x.
+  const bool is_significant = (i.seconds / GetMinTimeToApply()) > 0.1;
+  multiplier = is_significant ? multiplier : 10.0;
+
+  // So what seems to be the sufficiently-large iteration count? Round up.
+  const IterationCount max_next_iters = static_cast<IterationCount>(
+      std::lround(std::max(multiplier * static_cast<double>(i.iters),
+                           static_cast<double>(i.iters) + 1.0)));
+  // But we do have *some* limits though..
+  const IterationCount next_iters = std::min(max_next_iters, kMaxIterations);
+
+  BM_VLOG(3) << "Next iters: " << next_iters << ", " << multiplier << "\n";
+  return next_iters;  // round up before conversion to integer.
+}
+
+bool BenchmarkRunner::ShouldReportIterationResults(
+    const IterationResults& i) const {
+  // Determine if this run should be reported;
+  // Either it has run for a sufficient amount of time
+  // or because an error was reported.
+  return i.results.skipped_ ||
+         i.iters >= kMaxIterations ||  // Too many iterations already.
+         i.seconds >=
+             GetMinTimeToApply() ||  // The elapsed time is large enough.
+         // CPU time is specified but the elapsed real time greatly exceeds
+         // the minimum time.
+         // Note that user provided timers are except from this test.
+         ((i.results.real_time_used >= 5 * GetMinTimeToApply()) &&
+          !b.use_manual_time());
+}
+
+double BenchmarkRunner::GetMinTimeToApply() const {
+  // In order to re-use functionality to run and measure benchmarks for running
+  // a warmup phase of the benchmark, we need a way of telling whether to apply
+  // min_time or min_warmup_time. This function will figure out if we are in the
+  // warmup phase and therefore need to apply min_warmup_time or if we already
+  // in the benchmarking phase and min_time needs to be applied.
+  return warmup_done ? min_time : min_warmup_time;
+}
+
+void BenchmarkRunner::FinishWarmUp(const IterationCount& i) {
+  warmup_done = true;
+  iters = i;
+}
+
+void BenchmarkRunner::RunWarmUp() {
+  // Use the same mechanisms for warming up the benchmark as used for actually
+  // running and measuring the benchmark.
+  IterationResults i_warmup;
+  // Dont use the iterations determined in the warmup phase for the actual
+  // measured benchmark phase. While this may be a good starting point for the
+  // benchmark and it would therefore get rid of the need to figure out how many
+  // iterations are needed if min_time is set again, this may also be a complete
+  // wrong guess since the warmup loops might be considerably slower (e.g
+  // because of caching effects).
+  const IterationCount i_backup = iters;
+
+  for (;;) {
+    b.Setup();
+    i_warmup = DoNIterations();
+    b.Teardown();
+
+    const bool finish = ShouldReportIterationResults(i_warmup);
+
+    if (finish) {
+      FinishWarmUp(i_backup);
+      break;
+    }
+
+    // Although we are running "only" a warmup phase where running enough
+    // iterations at once without measuring time isn't as important as it is for
+    // the benchmarking phase, we still do it the same way as otherwise it is
+    // very confusing for the user to know how to choose a proper value for
+    // min_warmup_time if a different approach on running it is used.
+    iters = PredictNumItersNeeded(i_warmup);
+    assert(iters > i_warmup.iters &&
+           "if we did more iterations than we want to do the next time, "
+           "then we should have accepted the current iteration run.");
+  }
+}
+
+void BenchmarkRunner::DoOneRepetition() {
+  assert(HasRepeatsRemaining() && "Already done all repetitions?");
+
+  const bool is_the_first_repetition = num_repetitions_done == 0;
+
+  // In case a warmup phase is requested by the benchmark, run it now.
+  // After running the warmup phase the BenchmarkRunner should be in a state as
+  // this warmup never happened except the fact that warmup_done is set. Every
+  // other manipulation of the BenchmarkRunner instance would be a bug! Please
+  // fix it.
+  if (!warmup_done) RunWarmUp();
+
+  IterationResults i;
+  // We *may* be gradually increasing the length (iteration count)
+  // of the benchmark until we decide the results are significant.
+  // And once we do, we report those last results and exit.
+  // Please do note that the if there are repetitions, the iteration count
+  // is *only* calculated for the *first* repetition, and other repetitions
+  // simply use that precomputed iteration count.
+  for (;;) {
+    b.Setup();
+    i = DoNIterations();
+    b.Teardown();
+
+    // Do we consider the results to be significant?
+    // If we are doing repetitions, and the first repetition was already done,
+    // it has calculated the correct iteration time, so we have run that very
+    // iteration count just now. No need to calculate anything. Just report.
+    // Else, the normal rules apply.
+    const bool results_are_significant = !is_the_first_repetition ||
+                                         has_explicit_iteration_count ||
+                                         ShouldReportIterationResults(i);
+
+    if (results_are_significant) break;  // Good, let's report them!
+
+    // Nope, bad iteration. Let's re-estimate the hopefully-sufficient
+    // iteration count, and run the benchmark again...
+
+    iters = PredictNumItersNeeded(i);
+    assert(iters > i.iters &&
+           "if we did more iterations than we want to do the next time, "
+           "then we should have accepted the current iteration run.");
+  }
+
+  // Oh, one last thing, we need to also produce the 'memory measurements'..
+  MemoryManager::Result* memory_result = nullptr;
+  IterationCount memory_iterations = 0;
+  if (memory_manager != nullptr) {
+    // TODO(vyng): Consider making BenchmarkReporter::Run::memory_result an
+    // optional so we don't have to own the Result here.
+    // Can't do it now due to cxx03.
+    memory_results.push_back(MemoryManager::Result());
+    memory_result = &memory_results.back();
+    // Only run a few iterations to reduce the impact of one-time
+    // allocations in benchmarks that are not properly managed.
+    memory_iterations = std::min<IterationCount>(16, iters);
+    memory_manager->Start();
+    std::unique_ptr<internal::ThreadManager> manager;
+    manager.reset(new internal::ThreadManager(1));
+    b.Setup();
+    RunInThread(&b, memory_iterations, 0, manager.get(),
+                perf_counters_measurement_ptr);
+    manager->WaitForAllThreads();
+    manager.reset();
+    b.Teardown();
+    memory_manager->Stop(*memory_result);
+  }
+
+  // Ok, now actually report.
+  BenchmarkReporter::Run report =
+      CreateRunReport(b, i.results, memory_iterations, memory_result, i.seconds,
+                      num_repetitions_done, repeats);
+
+  if (reports_for_family) {
+    ++reports_for_family->num_runs_done;
+    if (!report.skipped) reports_for_family->Runs.push_back(report);
+  }
+
+  run_results.non_aggregates.push_back(report);
+
+  ++num_repetitions_done;
+}
+
+RunResults&& BenchmarkRunner::GetResults() {
+  assert(!HasRepeatsRemaining() && "Did not run all repetitions yet?");
+
+  // Calculate additional statistics over the repetitions of this instance.
+  run_results.aggregates_only = ComputeStats(run_results.non_aggregates);
+
+  return std::move(run_results);
+}
+
+}  // end namespace internal
+
+}  // end namespace benchmark
diff --git a/leveldb_base/third_party/benchmark/src/benchmark_runner.h b/leveldb_base/third_party/benchmark/src/benchmark_runner.h
new file mode 100644
index 0000000..db2fa04
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/benchmark_runner.h
@@ -0,0 +1,131 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef BENCHMARK_RUNNER_H_
+#define BENCHMARK_RUNNER_H_
+
+#include <thread>
+#include <vector>
+
+#include "benchmark_api_internal.h"
+#include "internal_macros.h"
+#include "perf_counters.h"
+#include "thread_manager.h"
+
+namespace benchmark {
+
+BM_DECLARE_string(benchmark_min_time);
+BM_DECLARE_double(benchmark_min_warmup_time);
+BM_DECLARE_int32(benchmark_repetitions);
+BM_DECLARE_bool(benchmark_report_aggregates_only);
+BM_DECLARE_bool(benchmark_display_aggregates_only);
+BM_DECLARE_string(benchmark_perf_counters);
+
+namespace internal {
+
+extern MemoryManager* memory_manager;
+
+struct RunResults {
+  std::vector<BenchmarkReporter::Run> non_aggregates;
+  std::vector<BenchmarkReporter::Run> aggregates_only;
+
+  bool display_report_aggregates_only = false;
+  bool file_report_aggregates_only = false;
+};
+
+struct BENCHMARK_EXPORT BenchTimeType {
+  enum { ITERS, TIME } tag;
+  union {
+    IterationCount iters;
+    double time;
+  };
+};
+
+BENCHMARK_EXPORT
+BenchTimeType ParseBenchMinTime(const std::string& value);
+
+class BenchmarkRunner {
+ public:
+  BenchmarkRunner(const benchmark::internal::BenchmarkInstance& b_,
+                  benchmark::internal::PerfCountersMeasurement* pmc_,
+                  BenchmarkReporter::PerFamilyRunReports* reports_for_family);
+
+  int GetNumRepeats() const { return repeats; }
+
+  bool HasRepeatsRemaining() const {
+    return GetNumRepeats() != num_repetitions_done;
+  }
+
+  void DoOneRepetition();
+
+  RunResults&& GetResults();
+
+  BenchmarkReporter::PerFamilyRunReports* GetReportsForFamily() const {
+    return reports_for_family;
+  }
+
+  double GetMinTime() const { return min_time; }
+
+  bool HasExplicitIters() const { return has_explicit_iteration_count; }
+
+  IterationCount GetIters() const { return iters; }
+
+ private:
+  RunResults run_results;
+
+  const benchmark::internal::BenchmarkInstance& b;
+  BenchmarkReporter::PerFamilyRunReports* reports_for_family;
+
+  BenchTimeType parsed_benchtime_flag;
+  const double min_time;
+  const double min_warmup_time;
+  bool warmup_done;
+  const int repeats;
+  const bool has_explicit_iteration_count;
+
+  int num_repetitions_done = 0;
+
+  std::vector<std::thread> pool;
+
+  std::vector<MemoryManager::Result> memory_results;
+
+  IterationCount iters;  // preserved between repetitions!
+  // So only the first repetition has to find/calculate it,
+  // the other repetitions will just use that precomputed iteration count.
+
+  PerfCountersMeasurement* const perf_counters_measurement_ptr = nullptr;
+
+  struct IterationResults {
+    internal::ThreadManager::Result results;
+    IterationCount iters;
+    double seconds;
+  };
+  IterationResults DoNIterations();
+
+  IterationCount PredictNumItersNeeded(const IterationResults& i) const;
+
+  bool ShouldReportIterationResults(const IterationResults& i) const;
+
+  double GetMinTimeToApply() const;
+
+  void FinishWarmUp(const IterationCount& i);
+
+  void RunWarmUp();
+};
+
+}  // namespace internal
+
+}  // end namespace benchmark
+
+#endif  // BENCHMARK_RUNNER_H_
diff --git a/leveldb_base/third_party/benchmark/src/check.cc b/leveldb_base/third_party/benchmark/src/check.cc
new file mode 100644
index 0000000..5f7526e
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/check.cc
@@ -0,0 +1,11 @@
+#include "check.h"
+
+namespace benchmark {
+namespace internal {
+
+static AbortHandlerT* handler = &std::abort;
+
+BENCHMARK_EXPORT AbortHandlerT*& GetAbortHandler() { return handler; }
+
+}  // namespace internal
+}  // namespace benchmark
diff --git a/leveldb_base/third_party/benchmark/src/check.h b/leveldb_base/third_party/benchmark/src/check.h
new file mode 100644
index 0000000..c1cd5e8
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/check.h
@@ -0,0 +1,106 @@
+#ifndef CHECK_H_
+#define CHECK_H_
+
+#include <cmath>
+#include <cstdlib>
+#include <ostream>
+
+#include "benchmark/export.h"
+#include "internal_macros.h"
+#include "log.h"
+
+#if defined(__GNUC__) || defined(__clang__)
+#define BENCHMARK_NOEXCEPT noexcept
+#define BENCHMARK_NOEXCEPT_OP(x) noexcept(x)
+#elif defined(_MSC_VER) && !defined(__clang__)
+#if _MSC_VER >= 1900
+#define BENCHMARK_NOEXCEPT noexcept
+#define BENCHMARK_NOEXCEPT_OP(x) noexcept(x)
+#else
+#define BENCHMARK_NOEXCEPT
+#define BENCHMARK_NOEXCEPT_OP(x)
+#endif
+#define __func__ __FUNCTION__
+#else
+#define BENCHMARK_NOEXCEPT
+#define BENCHMARK_NOEXCEPT_OP(x)
+#endif
+
+namespace benchmark {
+namespace internal {
+
+typedef void(AbortHandlerT)();
+
+BENCHMARK_EXPORT
+AbortHandlerT*& GetAbortHandler();
+
+BENCHMARK_NORETURN inline void CallAbortHandler() {
+  GetAbortHandler()();
+  std::abort();  // fallback to enforce noreturn
+}
+
+// CheckHandler is the class constructed by failing BM_CHECK macros.
+// CheckHandler will log information about the failures and abort when it is
+// destructed.
+class CheckHandler {
+ public:
+  CheckHandler(const char* check, const char* file, const char* func, int line)
+      : log_(GetErrorLogInstance()) {
+    log_ << file << ":" << line << ": " << func << ": Check `" << check
+         << "' failed. ";
+  }
+
+  LogType& GetLog() { return log_; }
+
+#if defined(COMPILER_MSVC)
+#pragma warning(push)
+#pragma warning(disable : 4722)
+#endif
+  BENCHMARK_NORETURN ~CheckHandler() BENCHMARK_NOEXCEPT_OP(false) {
+    log_ << std::endl;
+    CallAbortHandler();
+  }
+#if defined(COMPILER_MSVC)
+#pragma warning(pop)
+#endif
+
+  CheckHandler& operator=(const CheckHandler&) = delete;
+  CheckHandler(const CheckHandler&) = delete;
+  CheckHandler() = delete;
+
+ private:
+  LogType& log_;
+};
+
+}  // end namespace internal
+}  // end namespace benchmark
+
+// The BM_CHECK macro returns a std::ostream object that can have extra
+// information written to it.
+#ifndef NDEBUG
+#define BM_CHECK(b)                                                          \
+  (b ? ::benchmark::internal::GetNullLogInstance()                           \
+     : ::benchmark::internal::CheckHandler(#b, __FILE__, __func__, __LINE__) \
+           .GetLog())
+#else
+#define BM_CHECK(b) ::benchmark::internal::GetNullLogInstance()
+#endif
+
+// clang-format off
+// preserve whitespacing between operators for alignment
+#define BM_CHECK_EQ(a, b) BM_CHECK((a) == (b))
+#define BM_CHECK_NE(a, b) BM_CHECK((a) != (b))
+#define BM_CHECK_GE(a, b) BM_CHECK((a) >= (b))
+#define BM_CHECK_LE(a, b) BM_CHECK((a) <= (b))
+#define BM_CHECK_GT(a, b) BM_CHECK((a) > (b))
+#define BM_CHECK_LT(a, b) BM_CHECK((a) < (b))
+
+#define BM_CHECK_FLOAT_EQ(a, b, eps) BM_CHECK(std::fabs((a) - (b)) <  (eps))
+#define BM_CHECK_FLOAT_NE(a, b, eps) BM_CHECK(std::fabs((a) - (b)) >= (eps))
+#define BM_CHECK_FLOAT_GE(a, b, eps) BM_CHECK((a) - (b) > -(eps))
+#define BM_CHECK_FLOAT_LE(a, b, eps) BM_CHECK((b) - (a) > -(eps))
+#define BM_CHECK_FLOAT_GT(a, b, eps) BM_CHECK((a) - (b) >  (eps))
+#define BM_CHECK_FLOAT_LT(a, b, eps) BM_CHECK((b) - (a) >  (eps))
+//clang-format on
+
+#endif  // CHECK_H_
diff --git a/leveldb_base/third_party/benchmark/src/colorprint.cc b/leveldb_base/third_party/benchmark/src/colorprint.cc
new file mode 100644
index 0000000..9a653c5
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/colorprint.cc
@@ -0,0 +1,188 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "colorprint.h"
+
+#include <cstdarg>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <memory>
+#include <string>
+
+#include "check.h"
+#include "internal_macros.h"
+
+#ifdef BENCHMARK_OS_WINDOWS
+#include <io.h>
+#include <windows.h>
+#else
+#include <unistd.h>
+#endif  // BENCHMARK_OS_WINDOWS
+
+namespace benchmark {
+namespace {
+#ifdef BENCHMARK_OS_WINDOWS
+typedef WORD PlatformColorCode;
+#else
+typedef const char* PlatformColorCode;
+#endif
+
+PlatformColorCode GetPlatformColorCode(LogColor color) {
+#ifdef BENCHMARK_OS_WINDOWS
+  switch (color) {
+    case COLOR_RED:
+      return FOREGROUND_RED;
+    case COLOR_GREEN:
+      return FOREGROUND_GREEN;
+    case COLOR_YELLOW:
+      return FOREGROUND_RED | FOREGROUND_GREEN;
+    case COLOR_BLUE:
+      return FOREGROUND_BLUE;
+    case COLOR_MAGENTA:
+      return FOREGROUND_BLUE | FOREGROUND_RED;
+    case COLOR_CYAN:
+      return FOREGROUND_BLUE | FOREGROUND_GREEN;
+    case COLOR_WHITE:  // fall through to default
+    default:
+      return 0;
+  }
+#else
+  switch (color) {
+    case COLOR_RED:
+      return "1";
+    case COLOR_GREEN:
+      return "2";
+    case COLOR_YELLOW:
+      return "3";
+    case COLOR_BLUE:
+      return "4";
+    case COLOR_MAGENTA:
+      return "5";
+    case COLOR_CYAN:
+      return "6";
+    case COLOR_WHITE:
+      return "7";
+    default:
+      return nullptr;
+  };
+#endif
+}
+
+}  // end namespace
+
+std::string FormatString(const char* msg, va_list args) {
+  // we might need a second shot at this, so pre-emptivly make a copy
+  va_list args_cp;
+  va_copy(args_cp, args);
+
+  std::size_t size = 256;
+  char local_buff[256];
+  auto ret = vsnprintf(local_buff, size, msg, args_cp);
+
+  va_end(args_cp);
+
+  // currently there is no error handling for failure, so this is hack.
+  BM_CHECK(ret >= 0);
+
+  if (ret == 0) {  // handle empty expansion
+    return {};
+  }
+  if (static_cast<size_t>(ret) < size) {
+    return local_buff;
+  }
+  // we did not provide a long enough buffer on our first attempt.
+  size = static_cast<size_t>(ret) + 1;  // + 1 for the null byte
+  std::unique_ptr<char[]> buff(new char[size]);
+  ret = vsnprintf(buff.get(), size, msg, args);
+  BM_CHECK(ret > 0 && (static_cast<size_t>(ret)) < size);
+  return buff.get();
+}
+
+std::string FormatString(const char* msg, ...) {
+  va_list args;
+  va_start(args, msg);
+  auto tmp = FormatString(msg, args);
+  va_end(args);
+  return tmp;
+}
+
+void ColorPrintf(std::ostream& out, LogColor color, const char* fmt, ...) {
+  va_list args;
+  va_start(args, fmt);
+  ColorPrintf(out, color, fmt, args);
+  va_end(args);
+}
+
+void ColorPrintf(std::ostream& out, LogColor color, const char* fmt,
+                 va_list args) {
+#ifdef BENCHMARK_OS_WINDOWS
+  ((void)out);  // suppress unused warning
+
+  const HANDLE stdout_handle = GetStdHandle(STD_OUTPUT_HANDLE);
+
+  // Gets the current text color.
+  CONSOLE_SCREEN_BUFFER_INFO buffer_info;
+  GetConsoleScreenBufferInfo(stdout_handle, &buffer_info);
+  const WORD old_color_attrs = buffer_info.wAttributes;
+
+  // We need to flush the stream buffers into the console before each
+  // SetConsoleTextAttribute call lest it affect the text that is already
+  // printed but has not yet reached the console.
+  fflush(stdout);
+  SetConsoleTextAttribute(stdout_handle,
+                          GetPlatformColorCode(color) | FOREGROUND_INTENSITY);
+  vprintf(fmt, args);
+
+  fflush(stdout);
+  // Restores the text color.
+  SetConsoleTextAttribute(stdout_handle, old_color_attrs);
+#else
+  const char* color_code = GetPlatformColorCode(color);
+  if (color_code) out << FormatString("\033[0;3%sm", color_code);
+  out << FormatString(fmt, args) << "\033[m";
+#endif
+}
+
+bool IsColorTerminal() {
+#if BENCHMARK_OS_WINDOWS
+  // On Windows the TERM variable is usually not set, but the
+  // console there does support colors.
+  return 0 != _isatty(_fileno(stdout));
+#else
+  // On non-Windows platforms, we rely on the TERM variable. This list of
+  // supported TERM values is copied from Google Test:
+  // <https://github.com/google/googletest/blob/main/googletest/src/gtest.cc#L2925>.
+  const char* const SUPPORTED_TERM_VALUES[] = {
+      "xterm",         "xterm-color",     "xterm-256color",
+      "screen",        "screen-256color", "tmux",
+      "tmux-256color", "rxvt-unicode",    "rxvt-unicode-256color",
+      "linux",         "cygwin",
+  };
+
+  const char* const term = getenv("TERM");
+
+  bool term_supports_color = false;
+  for (const char* candidate : SUPPORTED_TERM_VALUES) {
+    if (term && 0 == strcmp(term, candidate)) {
+      term_supports_color = true;
+      break;
+    }
+  }
+
+  return 0 != isatty(fileno(stdout)) && term_supports_color;
+#endif  // BENCHMARK_OS_WINDOWS
+}
+
+}  // end namespace benchmark
diff --git a/leveldb_base/third_party/benchmark/src/colorprint.h b/leveldb_base/third_party/benchmark/src/colorprint.h
new file mode 100644
index 0000000..9f6fab9
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/colorprint.h
@@ -0,0 +1,33 @@
+#ifndef BENCHMARK_COLORPRINT_H_
+#define BENCHMARK_COLORPRINT_H_
+
+#include <cstdarg>
+#include <iostream>
+#include <string>
+
+namespace benchmark {
+enum LogColor {
+  COLOR_DEFAULT,
+  COLOR_RED,
+  COLOR_GREEN,
+  COLOR_YELLOW,
+  COLOR_BLUE,
+  COLOR_MAGENTA,
+  COLOR_CYAN,
+  COLOR_WHITE
+};
+
+std::string FormatString(const char* msg, va_list args);
+std::string FormatString(const char* msg, ...);
+
+void ColorPrintf(std::ostream& out, LogColor color, const char* fmt,
+                 va_list args);
+void ColorPrintf(std::ostream& out, LogColor color, const char* fmt, ...);
+
+// Returns true if stdout appears to be a terminal that supports colored
+// output, false otherwise.
+bool IsColorTerminal();
+
+}  // end namespace benchmark
+
+#endif  // BENCHMARK_COLORPRINT_H_
diff --git a/leveldb_base/third_party/benchmark/src/commandlineflags.cc b/leveldb_base/third_party/benchmark/src/commandlineflags.cc
new file mode 100644
index 0000000..dcb4149
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/commandlineflags.cc
@@ -0,0 +1,298 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "commandlineflags.h"
+
+#include <algorithm>
+#include <cctype>
+#include <cstdlib>
+#include <cstring>
+#include <iostream>
+#include <limits>
+#include <map>
+#include <utility>
+
+#include "../src/string_util.h"
+
+namespace benchmark {
+namespace {
+
+// Parses 'str' for a 32-bit signed integer.  If successful, writes
+// the result to *value and returns true; otherwise leaves *value
+// unchanged and returns false.
+bool ParseInt32(const std::string& src_text, const char* str, int32_t* value) {
+  // Parses the environment variable as a decimal integer.
+  char* end = nullptr;
+  const long long_value = strtol(str, &end, 10);  // NOLINT
+
+  // Has strtol() consumed all characters in the string?
+  if (*end != '\0') {
+    // No - an invalid character was encountered.
+    std::cerr << src_text << " is expected to be a 32-bit integer, "
+              << "but actually has value \"" << str << "\".\n";
+    return false;
+  }
+
+  // Is the parsed value in the range of an Int32?
+  const int32_t result = static_cast<int32_t>(long_value);
+  if (long_value == std::numeric_limits<long>::max() ||
+      long_value == std::numeric_limits<long>::min() ||
+      // The parsed value overflows as a long.  (strtol() returns
+      // LONG_MAX or LONG_MIN when the input overflows.)
+      result != long_value
+      // The parsed value overflows as an Int32.
+  ) {
+    std::cerr << src_text << " is expected to be a 32-bit integer, "
+              << "but actually has value \"" << str << "\", "
+              << "which overflows.\n";
+    return false;
+  }
+
+  *value = result;
+  return true;
+}
+
+// Parses 'str' for a double.  If successful, writes the result to *value and
+// returns true; otherwise leaves *value unchanged and returns false.
+bool ParseDouble(const std::string& src_text, const char* str, double* value) {
+  // Parses the environment variable as a decimal integer.
+  char* end = nullptr;
+  const double double_value = strtod(str, &end);  // NOLINT
+
+  // Has strtol() consumed all characters in the string?
+  if (*end != '\0') {
+    // No - an invalid character was encountered.
+    std::cerr << src_text << " is expected to be a double, "
+              << "but actually has value \"" << str << "\".\n";
+    return false;
+  }
+
+  *value = double_value;
+  return true;
+}
+
+// Parses 'str' into KV pairs. If successful, writes the result to *value and
+// returns true; otherwise leaves *value unchanged and returns false.
+bool ParseKvPairs(const std::string& src_text, const char* str,
+                  std::map<std::string, std::string>* value) {
+  std::map<std::string, std::string> kvs;
+  for (const auto& kvpair : StrSplit(str, ',')) {
+    const auto kv = StrSplit(kvpair, '=');
+    if (kv.size() != 2) {
+      std::cerr << src_text << " is expected to be a comma-separated list of "
+                << "<key>=<value> strings, but actually has value \"" << str
+                << "\".\n";
+      return false;
+    }
+    if (!kvs.emplace(kv[0], kv[1]).second) {
+      std::cerr << src_text << " is expected to contain unique keys but key \""
+                << kv[0] << "\" was repeated.\n";
+      return false;
+    }
+  }
+
+  *value = kvs;
+  return true;
+}
+
+// Returns the name of the environment variable corresponding to the
+// given flag.  For example, FlagToEnvVar("foo") will return
+// "BENCHMARK_FOO" in the open-source version.
+static std::string FlagToEnvVar(const char* flag) {
+  const std::string flag_str(flag);
+
+  std::string env_var;
+  for (size_t i = 0; i != flag_str.length(); ++i)
+    env_var += static_cast<char>(::toupper(flag_str.c_str()[i]));
+
+  return env_var;
+}
+
+}  // namespace
+
+BENCHMARK_EXPORT
+bool BoolFromEnv(const char* flag, bool default_val) {
+  const std::string env_var = FlagToEnvVar(flag);
+  const char* const value_str = getenv(env_var.c_str());
+  return value_str == nullptr ? default_val : IsTruthyFlagValue(value_str);
+}
+
+BENCHMARK_EXPORT
+int32_t Int32FromEnv(const char* flag, int32_t default_val) {
+  const std::string env_var = FlagToEnvVar(flag);
+  const char* const value_str = getenv(env_var.c_str());
+  int32_t value = default_val;
+  if (value_str == nullptr ||
+      !ParseInt32(std::string("Environment variable ") + env_var, value_str,
+                  &value)) {
+    return default_val;
+  }
+  return value;
+}
+
+BENCHMARK_EXPORT
+double DoubleFromEnv(const char* flag, double default_val) {
+  const std::string env_var = FlagToEnvVar(flag);
+  const char* const value_str = getenv(env_var.c_str());
+  double value = default_val;
+  if (value_str == nullptr ||
+      !ParseDouble(std::string("Environment variable ") + env_var, value_str,
+                   &value)) {
+    return default_val;
+  }
+  return value;
+}
+
+BENCHMARK_EXPORT
+const char* StringFromEnv(const char* flag, const char* default_val) {
+  const std::string env_var = FlagToEnvVar(flag);
+  const char* const value = getenv(env_var.c_str());
+  return value == nullptr ? default_val : value;
+}
+
+BENCHMARK_EXPORT
+std::map<std::string, std::string> KvPairsFromEnv(
+    const char* flag, std::map<std::string, std::string> default_val) {
+  const std::string env_var = FlagToEnvVar(flag);
+  const char* const value_str = getenv(env_var.c_str());
+
+  if (value_str == nullptr) return default_val;
+
+  std::map<std::string, std::string> value;
+  if (!ParseKvPairs("Environment variable " + env_var, value_str, &value)) {
+    return default_val;
+  }
+  return value;
+}
+
+// Parses a string as a command line flag.  The string should have
+// the format "--flag=value".  When def_optional is true, the "=value"
+// part can be omitted.
+//
+// Returns the value of the flag, or nullptr if the parsing failed.
+const char* ParseFlagValue(const char* str, const char* flag,
+                           bool def_optional) {
+  // str and flag must not be nullptr.
+  if (str == nullptr || flag == nullptr) return nullptr;
+
+  // The flag must start with "--".
+  const std::string flag_str = std::string("--") + std::string(flag);
+  const size_t flag_len = flag_str.length();
+  if (strncmp(str, flag_str.c_str(), flag_len) != 0) return nullptr;
+
+  // Skips the flag name.
+  const char* flag_end = str + flag_len;
+
+  // When def_optional is true, it's OK to not have a "=value" part.
+  if (def_optional && (flag_end[0] == '\0')) return flag_end;
+
+  // If def_optional is true and there are more characters after the
+  // flag name, or if def_optional is false, there must be a '=' after
+  // the flag name.
+  if (flag_end[0] != '=') return nullptr;
+
+  // Returns the string after "=".
+  return flag_end + 1;
+}
+
+BENCHMARK_EXPORT
+bool ParseBoolFlag(const char* str, const char* flag, bool* value) {
+  // Gets the value of the flag as a string.
+  const char* const value_str = ParseFlagValue(str, flag, true);
+
+  // Aborts if the parsing failed.
+  if (value_str == nullptr) return false;
+
+  // Converts the string value to a bool.
+  *value = IsTruthyFlagValue(value_str);
+  return true;
+}
+
+BENCHMARK_EXPORT
+bool ParseInt32Flag(const char* str, const char* flag, int32_t* value) {
+  // Gets the value of the flag as a string.
+  const char* const value_str = ParseFlagValue(str, flag, false);
+
+  // Aborts if the parsing failed.
+  if (value_str == nullptr) return false;
+
+  // Sets *value to the value of the flag.
+  return ParseInt32(std::string("The value of flag --") + flag, value_str,
+                    value);
+}
+
+BENCHMARK_EXPORT
+bool ParseDoubleFlag(const char* str, const char* flag, double* value) {
+  // Gets the value of the flag as a string.
+  const char* const value_str = ParseFlagValue(str, flag, false);
+
+  // Aborts if the parsing failed.
+  if (value_str == nullptr) return false;
+
+  // Sets *value to the value of the flag.
+  return ParseDouble(std::string("The value of flag --") + flag, value_str,
+                     value);
+}
+
+BENCHMARK_EXPORT
+bool ParseStringFlag(const char* str, const char* flag, std::string* value) {
+  // Gets the value of the flag as a string.
+  const char* const value_str = ParseFlagValue(str, flag, false);
+
+  // Aborts if the parsing failed.
+  if (value_str == nullptr) return false;
+
+  *value = value_str;
+  return true;
+}
+
+BENCHMARK_EXPORT
+bool ParseKeyValueFlag(const char* str, const char* flag,
+                       std::map<std::string, std::string>* value) {
+  const char* const value_str = ParseFlagValue(str, flag, false);
+
+  if (value_str == nullptr) return false;
+
+  for (const auto& kvpair : StrSplit(value_str, ',')) {
+    const auto kv = StrSplit(kvpair, '=');
+    if (kv.size() != 2) return false;
+    value->emplace(kv[0], kv[1]);
+  }
+
+  return true;
+}
+
+BENCHMARK_EXPORT
+bool IsFlag(const char* str, const char* flag) {
+  return (ParseFlagValue(str, flag, true) != nullptr);
+}
+
+BENCHMARK_EXPORT
+bool IsTruthyFlagValue(const std::string& value) {
+  if (value.size() == 1) {
+    char v = value[0];
+    return isalnum(v) &&
+           !(v == '0' || v == 'f' || v == 'F' || v == 'n' || v == 'N');
+  }
+  if (!value.empty()) {
+    std::string value_lower(value);
+    std::transform(value_lower.begin(), value_lower.end(), value_lower.begin(),
+                   [](char c) { return static_cast<char>(::tolower(c)); });
+    return !(value_lower == "false" || value_lower == "no" ||
+             value_lower == "off");
+  }
+  return true;
+}
+
+}  // end namespace benchmark
diff --git a/leveldb_base/third_party/benchmark/src/commandlineflags.h b/leveldb_base/third_party/benchmark/src/commandlineflags.h
new file mode 100644
index 0000000..7882628
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/commandlineflags.h
@@ -0,0 +1,133 @@
+#ifndef BENCHMARK_COMMANDLINEFLAGS_H_
+#define BENCHMARK_COMMANDLINEFLAGS_H_
+
+#include <cstdint>
+#include <map>
+#include <string>
+
+#include "benchmark/export.h"
+
+// Macro for referencing flags.
+#define FLAG(name) FLAGS_##name
+
+// Macros for declaring flags.
+#define BM_DECLARE_bool(name) BENCHMARK_EXPORT extern bool FLAG(name)
+#define BM_DECLARE_int32(name) BENCHMARK_EXPORT extern int32_t FLAG(name)
+#define BM_DECLARE_double(name) BENCHMARK_EXPORT extern double FLAG(name)
+#define BM_DECLARE_string(name) BENCHMARK_EXPORT extern std::string FLAG(name)
+#define BM_DECLARE_kvpairs(name) \
+  BENCHMARK_EXPORT extern std::map<std::string, std::string> FLAG(name)
+
+// Macros for defining flags.
+#define BM_DEFINE_bool(name, default_val) \
+  BENCHMARK_EXPORT bool FLAG(name) = benchmark::BoolFromEnv(#name, default_val)
+#define BM_DEFINE_int32(name, default_val) \
+  BENCHMARK_EXPORT int32_t FLAG(name) =    \
+      benchmark::Int32FromEnv(#name, default_val)
+#define BM_DEFINE_double(name, default_val) \
+  BENCHMARK_EXPORT double FLAG(name) =      \
+      benchmark::DoubleFromEnv(#name, default_val)
+#define BM_DEFINE_string(name, default_val) \
+  BENCHMARK_EXPORT std::string FLAG(name) = \
+      benchmark::StringFromEnv(#name, default_val)
+#define BM_DEFINE_kvpairs(name, default_val)                       \
+  BENCHMARK_EXPORT std::map<std::string, std::string> FLAG(name) = \
+      benchmark::KvPairsFromEnv(#name, default_val)
+
+namespace benchmark {
+
+// Parses a bool from the environment variable corresponding to the given flag.
+//
+// If the variable exists, returns IsTruthyFlagValue() value;  if not,
+// returns the given default value.
+BENCHMARK_EXPORT
+bool BoolFromEnv(const char* flag, bool default_val);
+
+// Parses an Int32 from the environment variable corresponding to the given
+// flag.
+//
+// If the variable exists, returns ParseInt32() value;  if not, returns
+// the given default value.
+BENCHMARK_EXPORT
+int32_t Int32FromEnv(const char* flag, int32_t default_val);
+
+// Parses an Double from the environment variable corresponding to the given
+// flag.
+//
+// If the variable exists, returns ParseDouble();  if not, returns
+// the given default value.
+BENCHMARK_EXPORT
+double DoubleFromEnv(const char* flag, double default_val);
+
+// Parses a string from the environment variable corresponding to the given
+// flag.
+//
+// If variable exists, returns its value;  if not, returns
+// the given default value.
+BENCHMARK_EXPORT
+const char* StringFromEnv(const char* flag, const char* default_val);
+
+// Parses a set of kvpairs from the environment variable corresponding to the
+// given flag.
+//
+// If variable exists, returns its value;  if not, returns
+// the given default value.
+BENCHMARK_EXPORT
+std::map<std::string, std::string> KvPairsFromEnv(
+    const char* flag, std::map<std::string, std::string> default_val);
+
+// Parses a string for a bool flag, in the form of either
+// "--flag=value" or "--flag".
+//
+// In the former case, the value is taken as true if it passes IsTruthyValue().
+//
+// In the latter case, the value is taken as true.
+//
+// On success, stores the value of the flag in *value, and returns
+// true.  On failure, returns false without changing *value.
+BENCHMARK_EXPORT
+bool ParseBoolFlag(const char* str, const char* flag, bool* value);
+
+// Parses a string for an Int32 flag, in the form of "--flag=value".
+//
+// On success, stores the value of the flag in *value, and returns
+// true.  On failure, returns false without changing *value.
+BENCHMARK_EXPORT
+bool ParseInt32Flag(const char* str, const char* flag, int32_t* value);
+
+// Parses a string for a Double flag, in the form of "--flag=value".
+//
+// On success, stores the value of the flag in *value, and returns
+// true.  On failure, returns false without changing *value.
+BENCHMARK_EXPORT
+bool ParseDoubleFlag(const char* str, const char* flag, double* value);
+
+// Parses a string for a string flag, in the form of "--flag=value".
+//
+// On success, stores the value of the flag in *value, and returns
+// true.  On failure, returns false without changing *value.
+BENCHMARK_EXPORT
+bool ParseStringFlag(const char* str, const char* flag, std::string* value);
+
+// Parses a string for a kvpairs flag in the form "--flag=key=value,key=value"
+//
+// On success, stores the value of the flag in *value and returns true. On
+// failure returns false, though *value may have been mutated.
+BENCHMARK_EXPORT
+bool ParseKeyValueFlag(const char* str, const char* flag,
+                       std::map<std::string, std::string>* value);
+
+// Returns true if the string matches the flag.
+BENCHMARK_EXPORT
+bool IsFlag(const char* str, const char* flag);
+
+// Returns true unless value starts with one of: '0', 'f', 'F', 'n' or 'N', or
+// some non-alphanumeric character. Also returns false if the value matches
+// one of 'no', 'false', 'off' (case-insensitive). As a special case, also
+// returns true if value is the empty string.
+BENCHMARK_EXPORT
+bool IsTruthyFlagValue(const std::string& value);
+
+}  // end namespace benchmark
+
+#endif  // BENCHMARK_COMMANDLINEFLAGS_H_
diff --git a/leveldb_base/third_party/benchmark/src/complexity.cc b/leveldb_base/third_party/benchmark/src/complexity.cc
new file mode 100644
index 0000000..825c573
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/complexity.cc
@@ -0,0 +1,244 @@
+// Copyright 2016 Ismael Jimenez Martinez. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Source project : https://github.com/ismaelJimenez/cpp.leastsq
+// Adapted to be used with google benchmark
+
+#include "complexity.h"
+
+#include <algorithm>
+#include <cmath>
+
+#include "benchmark/benchmark.h"
+#include "check.h"
+
+namespace benchmark {
+
+// Internal function to calculate the different scalability forms
+BigOFunc* FittingCurve(BigO complexity) {
+  static const double kLog2E = 1.44269504088896340736;
+  switch (complexity) {
+    case oN:
+      return [](IterationCount n) -> double { return static_cast<double>(n); };
+    case oNSquared:
+      return [](IterationCount n) -> double { return std::pow(n, 2); };
+    case oNCubed:
+      return [](IterationCount n) -> double { return std::pow(n, 3); };
+    case oLogN:
+      /* Note: can't use log2 because Android's GNU STL lacks it */
+      return
+          [](IterationCount n) { return kLog2E * log(static_cast<double>(n)); };
+    case oNLogN:
+      /* Note: can't use log2 because Android's GNU STL lacks it */
+      return [](IterationCount n) {
+        return kLog2E * n * log(static_cast<double>(n));
+      };
+    case o1:
+    default:
+      return [](IterationCount) { return 1.0; };
+  }
+}
+
+// Function to return an string for the calculated complexity
+std::string GetBigOString(BigO complexity) {
+  switch (complexity) {
+    case oN:
+      return "N";
+    case oNSquared:
+      return "N^2";
+    case oNCubed:
+      return "N^3";
+    case oLogN:
+      return "lgN";
+    case oNLogN:
+      return "NlgN";
+    case o1:
+      return "(1)";
+    default:
+      return "f(N)";
+  }
+}
+
+// Find the coefficient for the high-order term in the running time, by
+// minimizing the sum of squares of relative error, for the fitting curve
+// given by the lambda expression.
+//   - n             : Vector containing the size of the benchmark tests.
+//   - time          : Vector containing the times for the benchmark tests.
+//   - fitting_curve : lambda expression (e.g. [](int64_t n) {return n; };).
+
+// For a deeper explanation on the algorithm logic, please refer to
+// https://en.wikipedia.org/wiki/Least_squares#Least_squares,_regression_analysis_and_statistics
+
+LeastSq MinimalLeastSq(const std::vector<int64_t>& n,
+                       const std::vector<double>& time,
+                       BigOFunc* fitting_curve) {
+  double sigma_gn_squared = 0.0;
+  double sigma_time = 0.0;
+  double sigma_time_gn = 0.0;
+
+  // Calculate least square fitting parameter
+  for (size_t i = 0; i < n.size(); ++i) {
+    double gn_i = fitting_curve(n[i]);
+    sigma_gn_squared += gn_i * gn_i;
+    sigma_time += time[i];
+    sigma_time_gn += time[i] * gn_i;
+  }
+
+  LeastSq result;
+  result.complexity = oLambda;
+
+  // Calculate complexity.
+  result.coef = sigma_time_gn / sigma_gn_squared;
+
+  // Calculate RMS
+  double rms = 0.0;
+  for (size_t i = 0; i < n.size(); ++i) {
+    double fit = result.coef * fitting_curve(n[i]);
+    rms += pow((time[i] - fit), 2);
+  }
+
+  // Normalized RMS by the mean of the observed values
+  double mean = sigma_time / n.size();
+  result.rms = sqrt(rms / n.size()) / mean;
+
+  return result;
+}
+
+// Find the coefficient for the high-order term in the running time, by
+// minimizing the sum of squares of relative error.
+//   - n          : Vector containing the size of the benchmark tests.
+//   - time       : Vector containing the times for the benchmark tests.
+//   - complexity : If different than oAuto, the fitting curve will stick to
+//                  this one. If it is oAuto, it will be calculated the best
+//                  fitting curve.
+LeastSq MinimalLeastSq(const std::vector<int64_t>& n,
+                       const std::vector<double>& time, const BigO complexity) {
+  BM_CHECK_EQ(n.size(), time.size());
+  BM_CHECK_GE(n.size(), 2);  // Do not compute fitting curve is less than two
+                             // benchmark runs are given
+  BM_CHECK_NE(complexity, oNone);
+
+  LeastSq best_fit;
+
+  if (complexity == oAuto) {
+    std::vector<BigO> fit_curves = {oLogN, oN, oNLogN, oNSquared, oNCubed};
+
+    // Take o1 as default best fitting curve
+    best_fit = MinimalLeastSq(n, time, FittingCurve(o1));
+    best_fit.complexity = o1;
+
+    // Compute all possible fitting curves and stick to the best one
+    for (const auto& fit : fit_curves) {
+      LeastSq current_fit = MinimalLeastSq(n, time, FittingCurve(fit));
+      if (current_fit.rms < best_fit.rms) {
+        best_fit = current_fit;
+        best_fit.complexity = fit;
+      }
+    }
+  } else {
+    best_fit = MinimalLeastSq(n, time, FittingCurve(complexity));
+    best_fit.complexity = complexity;
+  }
+
+  return best_fit;
+}
+
+std::vector<BenchmarkReporter::Run> ComputeBigO(
+    const std::vector<BenchmarkReporter::Run>& reports) {
+  typedef BenchmarkReporter::Run Run;
+  std::vector<Run> results;
+
+  if (reports.size() < 2) return results;
+
+  // Accumulators.
+  std::vector<int64_t> n;
+  std::vector<double> real_time;
+  std::vector<double> cpu_time;
+
+  // Populate the accumulators.
+  for (const Run& run : reports) {
+    BM_CHECK_GT(run.complexity_n, 0)
+        << "Did you forget to call SetComplexityN?";
+    n.push_back(run.complexity_n);
+    real_time.push_back(run.real_accumulated_time / run.iterations);
+    cpu_time.push_back(run.cpu_accumulated_time / run.iterations);
+  }
+
+  LeastSq result_cpu;
+  LeastSq result_real;
+
+  if (reports[0].complexity == oLambda) {
+    result_cpu = MinimalLeastSq(n, cpu_time, reports[0].complexity_lambda);
+    result_real = MinimalLeastSq(n, real_time, reports[0].complexity_lambda);
+  } else {
+    result_cpu = MinimalLeastSq(n, cpu_time, reports[0].complexity);
+    result_real = MinimalLeastSq(n, real_time, result_cpu.complexity);
+  }
+
+  // Drop the 'args' when reporting complexity.
+  auto run_name = reports[0].run_name;
+  run_name.args.clear();
+
+  // Get the data from the accumulator to BenchmarkReporter::Run's.
+  Run big_o;
+  big_o.run_name = run_name;
+  big_o.family_index = reports[0].family_index;
+  big_o.per_family_instance_index = reports[0].per_family_instance_index;
+  big_o.run_type = BenchmarkReporter::Run::RT_Aggregate;
+  big_o.repetitions = reports[0].repetitions;
+  big_o.repetition_index = Run::no_repetition_index;
+  big_o.threads = reports[0].threads;
+  big_o.aggregate_name = "BigO";
+  big_o.aggregate_unit = StatisticUnit::kTime;
+  big_o.report_label = reports[0].report_label;
+  big_o.iterations = 0;
+  big_o.real_accumulated_time = result_real.coef;
+  big_o.cpu_accumulated_time = result_cpu.coef;
+  big_o.report_big_o = true;
+  big_o.complexity = result_cpu.complexity;
+
+  // All the time results are reported after being multiplied by the
+  // time unit multiplier. But since RMS is a relative quantity it
+  // should not be multiplied at all. So, here, we _divide_ it by the
+  // multiplier so that when it is multiplied later the result is the
+  // correct one.
+  double multiplier = GetTimeUnitMultiplier(reports[0].time_unit);
+
+  // Only add label to mean/stddev if it is same for all runs
+  Run rms;
+  rms.run_name = run_name;
+  rms.family_index = reports[0].family_index;
+  rms.per_family_instance_index = reports[0].per_family_instance_index;
+  rms.run_type = BenchmarkReporter::Run::RT_Aggregate;
+  rms.aggregate_name = "RMS";
+  rms.aggregate_unit = StatisticUnit::kPercentage;
+  rms.report_label = big_o.report_label;
+  rms.iterations = 0;
+  rms.repetition_index = Run::no_repetition_index;
+  rms.repetitions = reports[0].repetitions;
+  rms.threads = reports[0].threads;
+  rms.real_accumulated_time = result_real.rms / multiplier;
+  rms.cpu_accumulated_time = result_cpu.rms / multiplier;
+  rms.report_rms = true;
+  rms.complexity = result_cpu.complexity;
+  // don't forget to keep the time unit, or we won't be able to
+  // recover the correct value.
+  rms.time_unit = reports[0].time_unit;
+
+  results.push_back(big_o);
+  results.push_back(rms);
+  return results;
+}
+
+}  // end namespace benchmark
diff --git a/leveldb_base/third_party/benchmark/src/complexity.h b/leveldb_base/third_party/benchmark/src/complexity.h
new file mode 100644
index 0000000..0a0679b
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/complexity.h
@@ -0,0 +1,55 @@
+// Copyright 2016 Ismael Jimenez Martinez. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Source project : https://github.com/ismaelJimenez/cpp.leastsq
+// Adapted to be used with google benchmark
+
+#ifndef COMPLEXITY_H_
+#define COMPLEXITY_H_
+
+#include <string>
+#include <vector>
+
+#include "benchmark/benchmark.h"
+
+namespace benchmark {
+
+// Return a vector containing the bigO and RMS information for the specified
+// list of reports. If 'reports.size() < 2' an empty vector is returned.
+std::vector<BenchmarkReporter::Run> ComputeBigO(
+    const std::vector<BenchmarkReporter::Run>& reports);
+
+// This data structure will contain the result returned by MinimalLeastSq
+//   - coef        : Estimated coefficient for the high-order term as
+//                   interpolated from data.
+//   - rms         : Normalized Root Mean Squared Error.
+//   - complexity  : Scalability form (e.g. oN, oNLogN). In case a scalability
+//                   form has been provided to MinimalLeastSq this will return
+//                   the same value. In case BigO::oAuto has been selected, this
+//                   parameter will return the best fitting curve detected.
+
+struct LeastSq {
+  LeastSq() : coef(0.0), rms(0.0), complexity(oNone) {}
+
+  double coef;
+  double rms;
+  BigO complexity;
+};
+
+// Function to return an string for the calculated complexity
+std::string GetBigOString(BigO complexity);
+
+}  // end namespace benchmark
+
+#endif  // COMPLEXITY_H_
diff --git a/leveldb_base/third_party/benchmark/src/console_reporter.cc b/leveldb_base/third_party/benchmark/src/console_reporter.cc
new file mode 100644
index 0000000..10e05e1
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/console_reporter.cc
@@ -0,0 +1,206 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <algorithm>
+#include <cstdint>
+#include <cstdio>
+#include <cstring>
+#include <iostream>
+#include <string>
+#include <tuple>
+#include <vector>
+
+#include "benchmark/benchmark.h"
+#include "check.h"
+#include "colorprint.h"
+#include "commandlineflags.h"
+#include "complexity.h"
+#include "counter.h"
+#include "internal_macros.h"
+#include "string_util.h"
+#include "timers.h"
+
+namespace benchmark {
+
+BENCHMARK_EXPORT
+bool ConsoleReporter::ReportContext(const Context& context) {
+  name_field_width_ = context.name_field_width;
+  printed_header_ = false;
+  prev_counters_.clear();
+
+  PrintBasicContext(&GetErrorStream(), context);
+
+#ifdef BENCHMARK_OS_WINDOWS
+  if ((output_options_ & OO_Color) && &std::cout != &GetOutputStream()) {
+    GetErrorStream()
+        << "Color printing is only supported for stdout on windows."
+           " Disabling color printing\n";
+    output_options_ = static_cast<OutputOptions>(output_options_ & ~OO_Color);
+  }
+#endif
+
+  return true;
+}
+
+BENCHMARK_EXPORT
+void ConsoleReporter::PrintHeader(const Run& run) {
+  std::string str =
+      FormatString("%-*s %13s %15s %12s", static_cast<int>(name_field_width_),
+                   "Benchmark", "Time", "CPU", "Iterations");
+  if (!run.counters.empty()) {
+    if (output_options_ & OO_Tabular) {
+      for (auto const& c : run.counters) {
+        str += FormatString(" %10s", c.first.c_str());
+      }
+    } else {
+      str += " UserCounters...";
+    }
+  }
+  std::string line = std::string(str.length(), '-');
+  GetOutputStream() << line << "\n" << str << "\n" << line << "\n";
+}
+
+BENCHMARK_EXPORT
+void ConsoleReporter::ReportRuns(const std::vector<Run>& reports) {
+  for (const auto& run : reports) {
+    // print the header:
+    // --- if none was printed yet
+    bool print_header = !printed_header_;
+    // --- or if the format is tabular and this run
+    //     has different fields from the prev header
+    print_header |= (output_options_ & OO_Tabular) &&
+                    (!internal::SameNames(run.counters, prev_counters_));
+    if (print_header) {
+      printed_header_ = true;
+      prev_counters_ = run.counters;
+      PrintHeader(run);
+    }
+    // As an alternative to printing the headers like this, we could sort
+    // the benchmarks by header and then print. But this would require
+    // waiting for the full results before printing, or printing twice.
+    PrintRunData(run);
+  }
+}
+
+static void IgnoreColorPrint(std::ostream& out, LogColor, const char* fmt,
+                             ...) {
+  va_list args;
+  va_start(args, fmt);
+  out << FormatString(fmt, args);
+  va_end(args);
+}
+
+static std::string FormatTime(double time) {
+  // For the time columns of the console printer 13 digits are reserved. One of
+  // them is a space and max two of them are the time unit (e.g ns). That puts
+  // us at 10 digits usable for the number.
+  // Align decimal places...
+  if (time < 1.0) {
+    return FormatString("%10.3f", time);
+  }
+  if (time < 10.0) {
+    return FormatString("%10.2f", time);
+  }
+  if (time < 100.0) {
+    return FormatString("%10.1f", time);
+  }
+  // Assuming the time is at max 9.9999e+99 and we have 10 digits for the
+  // number, we get 10-1(.)-1(e)-1(sign)-2(exponent) = 5 digits to print.
+  if (time > 9999999999 /*max 10 digit number*/) {
+    return FormatString("%1.4e", time);
+  }
+  return FormatString("%10.0f", time);
+}
+
+BENCHMARK_EXPORT
+void ConsoleReporter::PrintRunData(const Run& result) {
+  typedef void(PrinterFn)(std::ostream&, LogColor, const char*, ...);
+  auto& Out = GetOutputStream();
+  PrinterFn* printer = (output_options_ & OO_Color)
+                           ? static_cast<PrinterFn*>(ColorPrintf)
+                           : IgnoreColorPrint;
+  auto name_color =
+      (result.report_big_o || result.report_rms) ? COLOR_BLUE : COLOR_GREEN;
+  printer(Out, name_color, "%-*s ", name_field_width_,
+          result.benchmark_name().c_str());
+
+  if (internal::SkippedWithError == result.skipped) {
+    printer(Out, COLOR_RED, "ERROR OCCURRED: \'%s\'",
+            result.skip_message.c_str());
+    printer(Out, COLOR_DEFAULT, "\n");
+    return;
+  } else if (internal::SkippedWithMessage == result.skipped) {
+    printer(Out, COLOR_WHITE, "SKIPPED: \'%s\'", result.skip_message.c_str());
+    printer(Out, COLOR_DEFAULT, "\n");
+    return;
+  }
+
+  const double real_time = result.GetAdjustedRealTime();
+  const double cpu_time = result.GetAdjustedCPUTime();
+  const std::string real_time_str = FormatTime(real_time);
+  const std::string cpu_time_str = FormatTime(cpu_time);
+
+  if (result.report_big_o) {
+    std::string big_o = GetBigOString(result.complexity);
+    printer(Out, COLOR_YELLOW, "%10.2f %-4s %10.2f %-4s ", real_time,
+            big_o.c_str(), cpu_time, big_o.c_str());
+  } else if (result.report_rms) {
+    printer(Out, COLOR_YELLOW, "%10.0f %-4s %10.0f %-4s ", real_time * 100, "%",
+            cpu_time * 100, "%");
+  } else if (result.run_type != Run::RT_Aggregate ||
+             result.aggregate_unit == StatisticUnit::kTime) {
+    const char* timeLabel = GetTimeUnitString(result.time_unit);
+    printer(Out, COLOR_YELLOW, "%s %-4s %s %-4s ", real_time_str.c_str(),
+            timeLabel, cpu_time_str.c_str(), timeLabel);
+  } else {
+    assert(result.aggregate_unit == StatisticUnit::kPercentage);
+    printer(Out, COLOR_YELLOW, "%10.2f %-4s %10.2f %-4s ",
+            (100. * result.real_accumulated_time), "%",
+            (100. * result.cpu_accumulated_time), "%");
+  }
+
+  if (!result.report_big_o && !result.report_rms) {
+    printer(Out, COLOR_CYAN, "%10lld", result.iterations);
+  }
+
+  for (auto& c : result.counters) {
+    const std::size_t cNameLen =
+        std::max(std::string::size_type(10), c.first.length());
+    std::string s;
+    const char* unit = "";
+    if (result.run_type == Run::RT_Aggregate &&
+        result.aggregate_unit == StatisticUnit::kPercentage) {
+      s = StrFormat("%.2f", 100. * c.second.value);
+      unit = "%";
+    } else {
+      s = HumanReadableNumber(c.second.value, c.second.oneK);
+      if (c.second.flags & Counter::kIsRate)
+        unit = (c.second.flags & Counter::kInvert) ? "s" : "/s";
+    }
+    if (output_options_ & OO_Tabular) {
+      printer(Out, COLOR_DEFAULT, " %*s%s", cNameLen - strlen(unit), s.c_str(),
+              unit);
+    } else {
+      printer(Out, COLOR_DEFAULT, " %s=%s%s", c.first.c_str(), s.c_str(), unit);
+    }
+  }
+
+  if (!result.report_label.empty()) {
+    printer(Out, COLOR_DEFAULT, " %s", result.report_label.c_str());
+  }
+
+  printer(Out, COLOR_DEFAULT, "\n");
+}
+
+}  // end namespace benchmark
diff --git a/leveldb_base/third_party/benchmark/src/counter.cc b/leveldb_base/third_party/benchmark/src/counter.cc
new file mode 100644
index 0000000..cf5b78e
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/counter.cc
@@ -0,0 +1,80 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "counter.h"
+
+namespace benchmark {
+namespace internal {
+
+double Finish(Counter const& c, IterationCount iterations, double cpu_time,
+              double num_threads) {
+  double v = c.value;
+  if (c.flags & Counter::kIsRate) {
+    v /= cpu_time;
+  }
+  if (c.flags & Counter::kAvgThreads) {
+    v /= num_threads;
+  }
+  if (c.flags & Counter::kIsIterationInvariant) {
+    v *= iterations;
+  }
+  if (c.flags & Counter::kAvgIterations) {
+    v /= iterations;
+  }
+
+  if (c.flags & Counter::kInvert) {  // Invert is *always* last.
+    v = 1.0 / v;
+  }
+  return v;
+}
+
+void Finish(UserCounters* l, IterationCount iterations, double cpu_time,
+            double num_threads) {
+  for (auto& c : *l) {
+    c.second.value = Finish(c.second, iterations, cpu_time, num_threads);
+  }
+}
+
+void Increment(UserCounters* l, UserCounters const& r) {
+  // add counters present in both or just in *l
+  for (auto& c : *l) {
+    auto it = r.find(c.first);
+    if (it != r.end()) {
+      c.second.value = c.second + it->second;
+    }
+  }
+  // add counters present in r, but not in *l
+  for (auto const& tc : r) {
+    auto it = l->find(tc.first);
+    if (it == l->end()) {
+      (*l)[tc.first] = tc.second;
+    }
+  }
+}
+
+bool SameNames(UserCounters const& l, UserCounters const& r) {
+  if (&l == &r) return true;
+  if (l.size() != r.size()) {
+    return false;
+  }
+  for (auto const& c : l) {
+    if (r.find(c.first) == r.end()) {
+      return false;
+    }
+  }
+  return true;
+}
+
+}  // end namespace internal
+}  // end namespace benchmark
diff --git a/leveldb_base/third_party/benchmark/src/counter.h b/leveldb_base/third_party/benchmark/src/counter.h
new file mode 100644
index 0000000..1f5a58e
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/counter.h
@@ -0,0 +1,32 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef BENCHMARK_COUNTER_H_
+#define BENCHMARK_COUNTER_H_
+
+#include "benchmark/benchmark.h"
+
+namespace benchmark {
+
+// these counter-related functions are hidden to reduce API surface.
+namespace internal {
+void Finish(UserCounters* l, IterationCount iterations, double time,
+            double num_threads);
+void Increment(UserCounters* l, UserCounters const& r);
+bool SameNames(UserCounters const& l, UserCounters const& r);
+}  // end namespace internal
+
+}  // end namespace benchmark
+
+#endif  // BENCHMARK_COUNTER_H_
diff --git a/leveldb_base/third_party/benchmark/src/csv_reporter.cc b/leveldb_base/third_party/benchmark/src/csv_reporter.cc
new file mode 100644
index 0000000..7b56da1
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/csv_reporter.cc
@@ -0,0 +1,161 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <algorithm>
+#include <cstdint>
+#include <iostream>
+#include <string>
+#include <tuple>
+#include <vector>
+
+#include "benchmark/benchmark.h"
+#include "check.h"
+#include "complexity.h"
+#include "string_util.h"
+#include "timers.h"
+
+// File format reference: http://edoceo.com/utilitas/csv-file-format.
+
+namespace benchmark {
+
+namespace {
+std::vector<std::string> elements = {
+    "name",           "iterations",       "real_time",        "cpu_time",
+    "time_unit",      "bytes_per_second", "items_per_second", "label",
+    "error_occurred", "error_message"};
+}  // namespace
+
+std::string CsvEscape(const std::string& s) {
+  std::string tmp;
+  tmp.reserve(s.size() + 2);
+  for (char c : s) {
+    switch (c) {
+      case '"':
+        tmp += "\"\"";
+        break;
+      default:
+        tmp += c;
+        break;
+    }
+  }
+  return '"' + tmp + '"';
+}
+
+BENCHMARK_EXPORT
+bool CSVReporter::ReportContext(const Context& context) {
+  PrintBasicContext(&GetErrorStream(), context);
+  return true;
+}
+
+BENCHMARK_EXPORT
+void CSVReporter::ReportRuns(const std::vector<Run>& reports) {
+  std::ostream& Out = GetOutputStream();
+
+  if (!printed_header_) {
+    // save the names of all the user counters
+    for (const auto& run : reports) {
+      for (const auto& cnt : run.counters) {
+        if (cnt.first == "bytes_per_second" || cnt.first == "items_per_second")
+          continue;
+        user_counter_names_.insert(cnt.first);
+      }
+    }
+
+    // print the header
+    for (auto B = elements.begin(); B != elements.end();) {
+      Out << *B++;
+      if (B != elements.end()) Out << ",";
+    }
+    for (auto B = user_counter_names_.begin();
+         B != user_counter_names_.end();) {
+      Out << ",\"" << *B++ << "\"";
+    }
+    Out << "\n";
+
+    printed_header_ = true;
+  } else {
+    // check that all the current counters are saved in the name set
+    for (const auto& run : reports) {
+      for (const auto& cnt : run.counters) {
+        if (cnt.first == "bytes_per_second" || cnt.first == "items_per_second")
+          continue;
+        BM_CHECK(user_counter_names_.find(cnt.first) !=
+                 user_counter_names_.end())
+            << "All counters must be present in each run. "
+            << "Counter named \"" << cnt.first
+            << "\" was not in a run after being added to the header";
+      }
+    }
+  }
+
+  // print results for each run
+  for (const auto& run : reports) {
+    PrintRunData(run);
+  }
+}
+
+BENCHMARK_EXPORT
+void CSVReporter::PrintRunData(const Run& run) {
+  std::ostream& Out = GetOutputStream();
+  Out << CsvEscape(run.benchmark_name()) << ",";
+  if (run.skipped) {
+    Out << std::string(elements.size() - 3, ',');
+    Out << std::boolalpha << (internal::SkippedWithError == run.skipped) << ",";
+    Out << CsvEscape(run.skip_message) << "\n";
+    return;
+  }
+
+  // Do not print iteration on bigO and RMS report
+  if (!run.report_big_o && !run.report_rms) {
+    Out << run.iterations;
+  }
+  Out << ",";
+
+  Out << run.GetAdjustedRealTime() << ",";
+  Out << run.GetAdjustedCPUTime() << ",";
+
+  // Do not print timeLabel on bigO and RMS report
+  if (run.report_big_o) {
+    Out << GetBigOString(run.complexity);
+  } else if (!run.report_rms) {
+    Out << GetTimeUnitString(run.time_unit);
+  }
+  Out << ",";
+
+  if (run.counters.find("bytes_per_second") != run.counters.end()) {
+    Out << run.counters.at("bytes_per_second");
+  }
+  Out << ",";
+  if (run.counters.find("items_per_second") != run.counters.end()) {
+    Out << run.counters.at("items_per_second");
+  }
+  Out << ",";
+  if (!run.report_label.empty()) {
+    Out << CsvEscape(run.report_label);
+  }
+  Out << ",,";  // for error_occurred and error_message
+
+  // Print user counters
+  for (const auto& ucn : user_counter_names_) {
+    auto it = run.counters.find(ucn);
+    if (it == run.counters.end()) {
+      Out << ",";
+    } else {
+      Out << "," << it->second;
+    }
+  }
+  Out << '\n';
+}
+
+}  // end namespace benchmark
diff --git a/leveldb_base/third_party/benchmark/src/cycleclock.h b/leveldb_base/third_party/benchmark/src/cycleclock.h
new file mode 100644
index 0000000..ae1ef2d
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/cycleclock.h
@@ -0,0 +1,230 @@
+// ----------------------------------------------------------------------
+// CycleClock
+//    A CycleClock tells you the current time in Cycles.  The "time"
+//    is actually time since power-on.  This is like time() but doesn't
+//    involve a system call and is much more precise.
+//
+// NOTE: Not all cpu/platform/kernel combinations guarantee that this
+// clock increments at a constant rate or is synchronized across all logical
+// cpus in a system.
+//
+// If you need the above guarantees, please consider using a different
+// API. There are efforts to provide an interface which provides a millisecond
+// granularity and implemented as a memory read. A memory read is generally
+// cheaper than the CycleClock for many architectures.
+//
+// Also, in some out of order CPU implementations, the CycleClock is not
+// serializing. So if you're trying to count at cycles granularity, your
+// data might be inaccurate due to out of order instruction execution.
+// ----------------------------------------------------------------------
+
+#ifndef BENCHMARK_CYCLECLOCK_H_
+#define BENCHMARK_CYCLECLOCK_H_
+
+#include <cstdint>
+
+#include "benchmark/benchmark.h"
+#include "internal_macros.h"
+
+#if defined(BENCHMARK_OS_MACOSX)
+#include <mach/mach_time.h>
+#endif
+// For MSVC, we want to use '_asm rdtsc' when possible (since it works
+// with even ancient MSVC compilers), and when not possible the
+// __rdtsc intrinsic, declared in <intrin.h>.  Unfortunately, in some
+// environments, <windows.h> and <intrin.h> have conflicting
+// declarations of some other intrinsics, breaking compilation.
+// Therefore, we simply declare __rdtsc ourselves. See also
+// http://connect.microsoft.com/VisualStudio/feedback/details/262047
+#if defined(COMPILER_MSVC) && !defined(_M_IX86) && !defined(_M_ARM64) && \
+    !defined(_M_ARM64EC)
+extern "C" uint64_t __rdtsc();
+#pragma intrinsic(__rdtsc)
+#endif
+
+#if !defined(BENCHMARK_OS_WINDOWS) || defined(BENCHMARK_OS_MINGW)
+#include <sys/time.h>
+#include <time.h>
+#endif
+
+#ifdef BENCHMARK_OS_EMSCRIPTEN
+#include <emscripten.h>
+#endif
+
+namespace benchmark {
+// NOTE: only i386 and x86_64 have been well tested.
+// PPC, sparc, alpha, and ia64 are based on
+//    http://peter.kuscsik.com/wordpress/?p=14
+// with modifications by m3b.  See also
+//    https://setisvn.ssl.berkeley.edu/svn/lib/fftw-3.0.1/kernel/cycle.h
+namespace cycleclock {
+// This should return the number of cycles since power-on.  Thread-safe.
+inline BENCHMARK_ALWAYS_INLINE int64_t Now() {
+#if defined(BENCHMARK_OS_MACOSX)
+  // this goes at the top because we need ALL Macs, regardless of
+  // architecture, to return the number of "mach time units" that
+  // have passed since startup.  See sysinfo.cc where
+  // InitializeSystemInfo() sets the supposed cpu clock frequency of
+  // macs to the number of mach time units per second, not actual
+  // CPU clock frequency (which can change in the face of CPU
+  // frequency scaling).  Also note that when the Mac sleeps, this
+  // counter pauses; it does not continue counting, nor does it
+  // reset to zero.
+  return mach_absolute_time();
+#elif defined(BENCHMARK_OS_EMSCRIPTEN)
+  // this goes above x86-specific code because old versions of Emscripten
+  // define __x86_64__, although they have nothing to do with it.
+  return static_cast<int64_t>(emscripten_get_now() * 1e+6);
+#elif defined(__i386__)
+  int64_t ret;
+  __asm__ volatile("rdtsc" : "=A"(ret));
+  return ret;
+#elif defined(__x86_64__) || defined(__amd64__)
+  uint64_t low, high;
+  __asm__ volatile("rdtsc" : "=a"(low), "=d"(high));
+  return (high << 32) | low;
+#elif defined(__powerpc__) || defined(__ppc__)
+  // This returns a time-base, which is not always precisely a cycle-count.
+#if defined(__powerpc64__) || defined(__ppc64__)
+  int64_t tb;
+  asm volatile("mfspr %0, 268" : "=r"(tb));
+  return tb;
+#else
+  uint32_t tbl, tbu0, tbu1;
+  asm volatile(
+      "mftbu %0\n"
+      "mftb %1\n"
+      "mftbu %2"
+      : "=r"(tbu0), "=r"(tbl), "=r"(tbu1));
+  tbl &= -static_cast<int32_t>(tbu0 == tbu1);
+  // high 32 bits in tbu1; low 32 bits in tbl  (tbu0 is no longer needed)
+  return (static_cast<uint64_t>(tbu1) << 32) | tbl;
+#endif
+#elif defined(__sparc__)
+  int64_t tick;
+  asm(".byte 0x83, 0x41, 0x00, 0x00");
+  asm("mov   %%g1, %0" : "=r"(tick));
+  return tick;
+#elif defined(__ia64__)
+  int64_t itc;
+  asm("mov %0 = ar.itc" : "=r"(itc));
+  return itc;
+#elif defined(COMPILER_MSVC) && defined(_M_IX86)
+  // Older MSVC compilers (like 7.x) don't seem to support the
+  // __rdtsc intrinsic properly, so I prefer to use _asm instead
+  // when I know it will work.  Otherwise, I'll use __rdtsc and hope
+  // the code is being compiled with a non-ancient compiler.
+  _asm rdtsc
+#elif defined(COMPILER_MSVC) && (defined(_M_ARM64) || defined(_M_ARM64EC))
+  // See // https://docs.microsoft.com/en-us/cpp/intrinsics/arm64-intrinsics
+  // and https://reviews.llvm.org/D53115
+  int64_t virtual_timer_value;
+  virtual_timer_value = _ReadStatusReg(ARM64_CNTVCT);
+  return virtual_timer_value;
+#elif defined(COMPILER_MSVC)
+  return __rdtsc();
+#elif defined(BENCHMARK_OS_NACL)
+  // Native Client validator on x86/x86-64 allows RDTSC instructions,
+  // and this case is handled above. Native Client validator on ARM
+  // rejects MRC instructions (used in the ARM-specific sequence below),
+  // so we handle it here. Portable Native Client compiles to
+  // architecture-agnostic bytecode, which doesn't provide any
+  // cycle counter access mnemonics.
+
+  // Native Client does not provide any API to access cycle counter.
+  // Use clock_gettime(CLOCK_MONOTONIC, ...) instead of gettimeofday
+  // because is provides nanosecond resolution (which is noticeable at
+  // least for PNaCl modules running on x86 Mac & Linux).
+  // Initialize to always return 0 if clock_gettime fails.
+  struct timespec ts = {0, 0};
+  clock_gettime(CLOCK_MONOTONIC, &ts);
+  return static_cast<int64_t>(ts.tv_sec) * 1000000000 + ts.tv_nsec;
+#elif defined(__aarch64__)
+  // System timer of ARMv8 runs at a different frequency than the CPU's.
+  // The frequency is fixed, typically in the range 1-50MHz.  It can be
+  // read at CNTFRQ special register.  We assume the OS has set up
+  // the virtual timer properly.
+  int64_t virtual_timer_value;
+  asm volatile("mrs %0, cntvct_el0" : "=r"(virtual_timer_value));
+  return virtual_timer_value;
+#elif defined(__ARM_ARCH)
+  // V6 is the earliest arch that has a standard cyclecount
+  // Native Client validator doesn't allow MRC instructions.
+#if (__ARM_ARCH >= 6)
+  uint32_t pmccntr;
+  uint32_t pmuseren;
+  uint32_t pmcntenset;
+  // Read the user mode perf monitor counter access permissions.
+  asm volatile("mrc p15, 0, %0, c9, c14, 0" : "=r"(pmuseren));
+  if (pmuseren & 1) {  // Allows reading perfmon counters for user mode code.
+    asm volatile("mrc p15, 0, %0, c9, c12, 1" : "=r"(pmcntenset));
+    if (pmcntenset & 0x80000000ul) {  // Is it counting?
+      asm volatile("mrc p15, 0, %0, c9, c13, 0" : "=r"(pmccntr));
+      // The counter is set up to count every 64th cycle
+      return static_cast<int64_t>(pmccntr) * 64;  // Should optimize to << 6
+    }
+  }
+#endif
+  struct timeval tv;
+  gettimeofday(&tv, nullptr);
+  return static_cast<int64_t>(tv.tv_sec) * 1000000 + tv.tv_usec;
+#elif defined(__mips__) || defined(__m68k__)
+  // mips apparently only allows rdtsc for superusers, so we fall
+  // back to gettimeofday.  It's possible clock_gettime would be better.
+  struct timeval tv;
+  gettimeofday(&tv, nullptr);
+  return static_cast<int64_t>(tv.tv_sec) * 1000000 + tv.tv_usec;
+#elif defined(__loongarch__) || defined(__csky__)
+  struct timeval tv;
+  gettimeofday(&tv, nullptr);
+  return static_cast<int64_t>(tv.tv_sec) * 1000000 + tv.tv_usec;
+#elif defined(__s390__)  // Covers both s390 and s390x.
+  // Return the CPU clock.
+  uint64_t tsc;
+#if defined(BENCHMARK_OS_ZOS) && defined(COMPILER_IBMXL)
+  // z/OS XL compiler HLASM syntax.
+  asm(" stck %0" : "=m"(tsc) : : "cc");
+#else
+  asm("stck %0" : "=Q"(tsc) : : "cc");
+#endif
+  return tsc;
+#elif defined(__riscv)  // RISC-V
+  // Use RDCYCLE (and RDCYCLEH on riscv32)
+#if __riscv_xlen == 32
+  uint32_t cycles_lo, cycles_hi0, cycles_hi1;
+  // This asm also includes the PowerPC overflow handling strategy, as above.
+  // Implemented in assembly because Clang insisted on branching.
+  asm volatile(
+      "rdcycleh %0\n"
+      "rdcycle %1\n"
+      "rdcycleh %2\n"
+      "sub %0, %0, %2\n"
+      "seqz %0, %0\n"
+      "sub %0, zero, %0\n"
+      "and %1, %1, %0\n"
+      : "=r"(cycles_hi0), "=r"(cycles_lo), "=r"(cycles_hi1));
+  return (static_cast<uint64_t>(cycles_hi1) << 32) | cycles_lo;
+#else
+  uint64_t cycles;
+  asm volatile("rdcycle %0" : "=r"(cycles));
+  return cycles;
+#endif
+#elif defined(__e2k__) || defined(__elbrus__)
+  struct timeval tv;
+  gettimeofday(&tv, nullptr);
+  return static_cast<int64_t>(tv.tv_sec) * 1000000 + tv.tv_usec;
+#elif defined(__hexagon__)
+  uint64_t pcycle;
+  asm volatile("%0 = C15:14" : "=r"(pcycle));
+  return static_cast<double>(pcycle);
+#else
+// The soft failover to a generic implementation is automatic only for ARM.
+// For other platforms the developer is expected to make an attempt to create
+// a fast implementation and use generic version if nothing better is available.
+#error You need to define CycleTimer for your OS and CPU
+#endif
+}
+}  // end namespace cycleclock
+}  // end namespace benchmark
+
+#endif  // BENCHMARK_CYCLECLOCK_H_
diff --git a/leveldb_base/third_party/benchmark/src/internal_macros.h b/leveldb_base/third_party/benchmark/src/internal_macros.h
new file mode 100644
index 0000000..658f157
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/internal_macros.h
@@ -0,0 +1,113 @@
+#ifndef BENCHMARK_INTERNAL_MACROS_H_
+#define BENCHMARK_INTERNAL_MACROS_H_
+
+/* Needed to detect STL */
+#include <cstdlib>
+
+// clang-format off
+
+#ifndef __has_feature
+#define __has_feature(x) 0
+#endif
+
+#if defined(__clang__)
+  #if defined(__ibmxl__)
+    #if !defined(COMPILER_IBMXL)
+      #define COMPILER_IBMXL
+    #endif
+  #elif !defined(COMPILER_CLANG)
+    #define COMPILER_CLANG
+  #endif
+#elif defined(_MSC_VER)
+  #if !defined(COMPILER_MSVC)
+    #define COMPILER_MSVC
+  #endif
+#elif defined(__GNUC__)
+  #if !defined(COMPILER_GCC)
+    #define COMPILER_GCC
+  #endif
+#endif
+
+#if __has_feature(cxx_attributes)
+  #define BENCHMARK_NORETURN [[noreturn]]
+#elif defined(__GNUC__)
+  #define BENCHMARK_NORETURN __attribute__((noreturn))
+#elif defined(COMPILER_MSVC)
+  #define BENCHMARK_NORETURN __declspec(noreturn)
+#else
+  #define BENCHMARK_NORETURN
+#endif
+
+#if defined(__CYGWIN__)
+  #define BENCHMARK_OS_CYGWIN 1
+#elif defined(_WIN32)
+  #define BENCHMARK_OS_WINDOWS 1
+  // WINAPI_FAMILY_PARTITION is defined in winapifamily.h.
+  // We include windows.h which implicitly includes winapifamily.h for compatibility.
+  #define NOMINMAX
+  #include <windows.h>
+  #if defined(WINAPI_FAMILY_PARTITION)
+    #if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
+      #define BENCHMARK_OS_WINDOWS_WIN32 1
+    #elif WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_APP)
+      #define BENCHMARK_OS_WINDOWS_RT 1
+    #endif
+  #endif
+  #if defined(__MINGW32__)
+    #define BENCHMARK_OS_MINGW 1
+  #endif
+#elif defined(__APPLE__)
+  #define BENCHMARK_OS_APPLE 1
+  #include "TargetConditionals.h"
+  #if defined(TARGET_OS_MAC)
+    #define BENCHMARK_OS_MACOSX 1
+    #if defined(TARGET_OS_IPHONE)
+      #define BENCHMARK_OS_IOS 1
+    #endif
+  #endif
+#elif defined(__FreeBSD__)
+  #define BENCHMARK_OS_FREEBSD 1
+#elif defined(__NetBSD__)
+  #define BENCHMARK_OS_NETBSD 1
+#elif defined(__OpenBSD__)
+  #define BENCHMARK_OS_OPENBSD 1
+#elif defined(__DragonFly__)
+  #define BENCHMARK_OS_DRAGONFLY 1
+#elif defined(__linux__)
+  #define BENCHMARK_OS_LINUX 1
+#elif defined(__native_client__)
+  #define BENCHMARK_OS_NACL 1
+#elif defined(__EMSCRIPTEN__)
+  #define BENCHMARK_OS_EMSCRIPTEN 1
+#elif defined(__rtems__)
+  #define BENCHMARK_OS_RTEMS 1
+#elif defined(__Fuchsia__)
+#define BENCHMARK_OS_FUCHSIA 1
+#elif defined (__SVR4) && defined (__sun)
+#define BENCHMARK_OS_SOLARIS 1
+#elif defined(__QNX__)
+#define BENCHMARK_OS_QNX 1
+#elif defined(__MVS__)
+#define BENCHMARK_OS_ZOS 1
+#elif defined(__hexagon__)
+#define BENCHMARK_OS_QURT 1
+#endif
+
+#if defined(__ANDROID__) && defined(__GLIBCXX__)
+#define BENCHMARK_STL_ANDROID_GNUSTL 1
+#endif
+
+#if !__has_feature(cxx_exceptions) && !defined(__cpp_exceptions) \
+     && !defined(__EXCEPTIONS)
+  #define BENCHMARK_HAS_NO_EXCEPTIONS
+#endif
+
+#if defined(COMPILER_CLANG) || defined(COMPILER_GCC)
+  #define BENCHMARK_MAYBE_UNUSED __attribute__((unused))
+#else
+  #define BENCHMARK_MAYBE_UNUSED
+#endif
+
+// clang-format on
+
+#endif  // BENCHMARK_INTERNAL_MACROS_H_
diff --git a/leveldb_base/third_party/benchmark/src/json_reporter.cc b/leveldb_base/third_party/benchmark/src/json_reporter.cc
new file mode 100644
index 0000000..6559dfd
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/json_reporter.cc
@@ -0,0 +1,320 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <algorithm>
+#include <cmath>
+#include <cstdint>
+#include <iomanip>  // for setprecision
+#include <iostream>
+#include <limits>
+#include <string>
+#include <tuple>
+#include <vector>
+
+#include "benchmark/benchmark.h"
+#include "complexity.h"
+#include "string_util.h"
+#include "timers.h"
+
+namespace benchmark {
+namespace {
+
+std::string StrEscape(const std::string& s) {
+  std::string tmp;
+  tmp.reserve(s.size());
+  for (char c : s) {
+    switch (c) {
+      case '\b':
+        tmp += "\\b";
+        break;
+      case '\f':
+        tmp += "\\f";
+        break;
+      case '\n':
+        tmp += "\\n";
+        break;
+      case '\r':
+        tmp += "\\r";
+        break;
+      case '\t':
+        tmp += "\\t";
+        break;
+      case '\\':
+        tmp += "\\\\";
+        break;
+      case '"':
+        tmp += "\\\"";
+        break;
+      default:
+        tmp += c;
+        break;
+    }
+  }
+  return tmp;
+}
+
+std::string FormatKV(std::string const& key, std::string const& value) {
+  return StrFormat("\"%s\": \"%s\"", StrEscape(key).c_str(),
+                   StrEscape(value).c_str());
+}
+
+std::string FormatKV(std::string const& key, const char* value) {
+  return StrFormat("\"%s\": \"%s\"", StrEscape(key).c_str(),
+                   StrEscape(value).c_str());
+}
+
+std::string FormatKV(std::string const& key, bool value) {
+  return StrFormat("\"%s\": %s", StrEscape(key).c_str(),
+                   value ? "true" : "false");
+}
+
+std::string FormatKV(std::string const& key, int64_t value) {
+  std::stringstream ss;
+  ss << '"' << StrEscape(key) << "\": " << value;
+  return ss.str();
+}
+
+std::string FormatKV(std::string const& key, double value) {
+  std::stringstream ss;
+  ss << '"' << StrEscape(key) << "\": ";
+
+  if (std::isnan(value))
+    ss << (value < 0 ? "-" : "") << "NaN";
+  else if (std::isinf(value))
+    ss << (value < 0 ? "-" : "") << "Infinity";
+  else {
+    const auto max_digits10 =
+        std::numeric_limits<decltype(value)>::max_digits10;
+    const auto max_fractional_digits10 = max_digits10 - 1;
+    ss << std::scientific << std::setprecision(max_fractional_digits10)
+       << value;
+  }
+  return ss.str();
+}
+
+int64_t RoundDouble(double v) { return std::lround(v); }
+
+}  // end namespace
+
+bool JSONReporter::ReportContext(const Context& context) {
+  std::ostream& out = GetOutputStream();
+
+  out << "{\n";
+  std::string inner_indent(2, ' ');
+
+  // Open context block and print context information.
+  out << inner_indent << "\"context\": {\n";
+  std::string indent(4, ' ');
+
+  std::string walltime_value = LocalDateTimeString();
+  out << indent << FormatKV("date", walltime_value) << ",\n";
+
+  out << indent << FormatKV("host_name", context.sys_info.name) << ",\n";
+
+  if (Context::executable_name) {
+    out << indent << FormatKV("executable", Context::executable_name) << ",\n";
+  }
+
+  CPUInfo const& info = context.cpu_info;
+  out << indent << FormatKV("num_cpus", static_cast<int64_t>(info.num_cpus))
+      << ",\n";
+  out << indent
+      << FormatKV("mhz_per_cpu",
+                  RoundDouble(info.cycles_per_second / 1000000.0))
+      << ",\n";
+  if (CPUInfo::Scaling::UNKNOWN != info.scaling) {
+    out << indent
+        << FormatKV("cpu_scaling_enabled",
+                    info.scaling == CPUInfo::Scaling::ENABLED ? true : false)
+        << ",\n";
+  }
+
+  out << indent << "\"caches\": [\n";
+  indent = std::string(6, ' ');
+  std::string cache_indent(8, ' ');
+  for (size_t i = 0; i < info.caches.size(); ++i) {
+    auto& CI = info.caches[i];
+    out << indent << "{\n";
+    out << cache_indent << FormatKV("type", CI.type) << ",\n";
+    out << cache_indent << FormatKV("level", static_cast<int64_t>(CI.level))
+        << ",\n";
+    out << cache_indent << FormatKV("size", static_cast<int64_t>(CI.size))
+        << ",\n";
+    out << cache_indent
+        << FormatKV("num_sharing", static_cast<int64_t>(CI.num_sharing))
+        << "\n";
+    out << indent << "}";
+    if (i != info.caches.size() - 1) out << ",";
+    out << "\n";
+  }
+  indent = std::string(4, ' ');
+  out << indent << "],\n";
+  out << indent << "\"load_avg\": [";
+  for (auto it = info.load_avg.begin(); it != info.load_avg.end();) {
+    out << *it++;
+    if (it != info.load_avg.end()) out << ",";
+  }
+  out << "],\n";
+
+#if defined(NDEBUG)
+  const char build_type[] = "release";
+#else
+  const char build_type[] = "debug";
+#endif
+  out << indent << FormatKV("library_build_type", build_type);
+
+  std::map<std::string, std::string>* global_context =
+      internal::GetGlobalContext();
+
+  if (global_context != nullptr) {
+    for (const auto& kv : *global_context) {
+      out << ",\n";
+      out << indent << FormatKV(kv.first, kv.second);
+    }
+  }
+  out << "\n";
+
+  // Close context block and open the list of benchmarks.
+  out << inner_indent << "},\n";
+  out << inner_indent << "\"benchmarks\": [\n";
+  return true;
+}
+
+void JSONReporter::ReportRuns(std::vector<Run> const& reports) {
+  if (reports.empty()) {
+    return;
+  }
+  std::string indent(4, ' ');
+  std::ostream& out = GetOutputStream();
+  if (!first_report_) {
+    out << ",\n";
+  }
+  first_report_ = false;
+
+  for (auto it = reports.begin(); it != reports.end(); ++it) {
+    out << indent << "{\n";
+    PrintRunData(*it);
+    out << indent << '}';
+    auto it_cp = it;
+    if (++it_cp != reports.end()) {
+      out << ",\n";
+    }
+  }
+}
+
+void JSONReporter::Finalize() {
+  // Close the list of benchmarks and the top level object.
+  GetOutputStream() << "\n  ]\n}\n";
+}
+
+void JSONReporter::PrintRunData(Run const& run) {
+  std::string indent(6, ' ');
+  std::ostream& out = GetOutputStream();
+  out << indent << FormatKV("name", run.benchmark_name()) << ",\n";
+  out << indent << FormatKV("family_index", run.family_index) << ",\n";
+  out << indent
+      << FormatKV("per_family_instance_index", run.per_family_instance_index)
+      << ",\n";
+  out << indent << FormatKV("run_name", run.run_name.str()) << ",\n";
+  out << indent << FormatKV("run_type", [&run]() -> const char* {
+    switch (run.run_type) {
+      case BenchmarkReporter::Run::RT_Iteration:
+        return "iteration";
+      case BenchmarkReporter::Run::RT_Aggregate:
+        return "aggregate";
+    }
+    BENCHMARK_UNREACHABLE();
+  }()) << ",\n";
+  out << indent << FormatKV("repetitions", run.repetitions) << ",\n";
+  if (run.run_type != BenchmarkReporter::Run::RT_Aggregate) {
+    out << indent << FormatKV("repetition_index", run.repetition_index)
+        << ",\n";
+  }
+  out << indent << FormatKV("threads", run.threads) << ",\n";
+  if (run.run_type == BenchmarkReporter::Run::RT_Aggregate) {
+    out << indent << FormatKV("aggregate_name", run.aggregate_name) << ",\n";
+    out << indent << FormatKV("aggregate_unit", [&run]() -> const char* {
+      switch (run.aggregate_unit) {
+        case StatisticUnit::kTime:
+          return "time";
+        case StatisticUnit::kPercentage:
+          return "percentage";
+      }
+      BENCHMARK_UNREACHABLE();
+    }()) << ",\n";
+  }
+  if (internal::SkippedWithError == run.skipped) {
+    out << indent << FormatKV("error_occurred", true) << ",\n";
+    out << indent << FormatKV("error_message", run.skip_message) << ",\n";
+  } else if (internal::SkippedWithMessage == run.skipped) {
+    out << indent << FormatKV("skipped", true) << ",\n";
+    out << indent << FormatKV("skip_message", run.skip_message) << ",\n";
+  }
+  if (!run.report_big_o && !run.report_rms) {
+    out << indent << FormatKV("iterations", run.iterations) << ",\n";
+    if (run.run_type != Run::RT_Aggregate ||
+        run.aggregate_unit == StatisticUnit::kTime) {
+      out << indent << FormatKV("real_time", run.GetAdjustedRealTime())
+          << ",\n";
+      out << indent << FormatKV("cpu_time", run.GetAdjustedCPUTime());
+    } else {
+      assert(run.aggregate_unit == StatisticUnit::kPercentage);
+      out << indent << FormatKV("real_time", run.real_accumulated_time)
+          << ",\n";
+      out << indent << FormatKV("cpu_time", run.cpu_accumulated_time);
+    }
+    out << ",\n"
+        << indent << FormatKV("time_unit", GetTimeUnitString(run.time_unit));
+  } else if (run.report_big_o) {
+    out << indent << FormatKV("cpu_coefficient", run.GetAdjustedCPUTime())
+        << ",\n";
+    out << indent << FormatKV("real_coefficient", run.GetAdjustedRealTime())
+        << ",\n";
+    out << indent << FormatKV("big_o", GetBigOString(run.complexity)) << ",\n";
+    out << indent << FormatKV("time_unit", GetTimeUnitString(run.time_unit));
+  } else if (run.report_rms) {
+    out << indent << FormatKV("rms", run.GetAdjustedCPUTime());
+  }
+
+  for (auto& c : run.counters) {
+    out << ",\n" << indent << FormatKV(c.first, c.second);
+  }
+
+  if (run.memory_result) {
+    const MemoryManager::Result memory_result = *run.memory_result;
+    out << ",\n" << indent << FormatKV("allocs_per_iter", run.allocs_per_iter);
+    out << ",\n"
+        << indent << FormatKV("max_bytes_used", memory_result.max_bytes_used);
+
+    auto report_if_present = [&out, &indent](const std::string& label,
+                                             int64_t val) {
+      if (val != MemoryManager::TombstoneValue)
+        out << ",\n" << indent << FormatKV(label, val);
+    };
+
+    report_if_present("total_allocated_bytes",
+                      memory_result.total_allocated_bytes);
+    report_if_present("net_heap_growth", memory_result.net_heap_growth);
+  }
+
+  if (!run.report_label.empty()) {
+    out << ",\n" << indent << FormatKV("label", run.report_label);
+  }
+  out << '\n';
+}
+
+const int64_t MemoryManager::TombstoneValue =
+    std::numeric_limits<int64_t>::max();
+
+}  // end namespace benchmark
diff --git a/leveldb_base/third_party/benchmark/src/log.h b/leveldb_base/third_party/benchmark/src/log.h
new file mode 100644
index 0000000..4570166
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/log.h
@@ -0,0 +1,88 @@
+#ifndef BENCHMARK_LOG_H_
+#define BENCHMARK_LOG_H_
+
+#include <iostream>
+#include <ostream>
+
+// NOTE: this is also defined in benchmark.h but we're trying to avoid a
+// dependency.
+// The _MSVC_LANG check should detect Visual Studio 2015 Update 3 and newer.
+#if __cplusplus >= 201103L || (defined(_MSVC_LANG) && _MSVC_LANG >= 201103L)
+#define BENCHMARK_HAS_CXX11
+#endif
+
+namespace benchmark {
+namespace internal {
+
+typedef std::basic_ostream<char>&(EndLType)(std::basic_ostream<char>&);
+
+class LogType {
+  friend LogType& GetNullLogInstance();
+  friend LogType& GetErrorLogInstance();
+
+  // FIXME: Add locking to output.
+  template <class Tp>
+  friend LogType& operator<<(LogType&, Tp const&);
+  friend LogType& operator<<(LogType&, EndLType*);
+
+ private:
+  LogType(std::ostream* out) : out_(out) {}
+  std::ostream* out_;
+
+  // NOTE: we could use BENCHMARK_DISALLOW_COPY_AND_ASSIGN but we shouldn't have
+  // a dependency on benchmark.h from here.
+#ifndef BENCHMARK_HAS_CXX11
+  LogType(const LogType&);
+  LogType& operator=(const LogType&);
+#else
+  LogType(const LogType&) = delete;
+  LogType& operator=(const LogType&) = delete;
+#endif
+};
+
+template <class Tp>
+LogType& operator<<(LogType& log, Tp const& value) {
+  if (log.out_) {
+    *log.out_ << value;
+  }
+  return log;
+}
+
+inline LogType& operator<<(LogType& log, EndLType* m) {
+  if (log.out_) {
+    *log.out_ << m;
+  }
+  return log;
+}
+
+inline int& LogLevel() {
+  static int log_level = 0;
+  return log_level;
+}
+
+inline LogType& GetNullLogInstance() {
+  static LogType null_log((std::ostream*)nullptr);
+  return null_log;
+}
+
+inline LogType& GetErrorLogInstance() {
+  static LogType error_log(&std::clog);
+  return error_log;
+}
+
+inline LogType& GetLogInstanceForLevel(int level) {
+  if (level <= LogLevel()) {
+    return GetErrorLogInstance();
+  }
+  return GetNullLogInstance();
+}
+
+}  // end namespace internal
+}  // end namespace benchmark
+
+// clang-format off
+#define BM_VLOG(x)                                                               \
+  (::benchmark::internal::GetLogInstanceForLevel(x) << "-- LOG(" << x << "):" \
+                                                                         " ")
+// clang-format on
+#endif
diff --git a/leveldb_base/third_party/benchmark/src/mutex.h b/leveldb_base/third_party/benchmark/src/mutex.h
new file mode 100644
index 0000000..bec78d9
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/mutex.h
@@ -0,0 +1,155 @@
+#ifndef BENCHMARK_MUTEX_H_
+#define BENCHMARK_MUTEX_H_
+
+#include <condition_variable>
+#include <mutex>
+
+#include "check.h"
+
+// Enable thread safety attributes only with clang.
+// The attributes can be safely erased when compiling with other compilers.
+#if defined(HAVE_THREAD_SAFETY_ATTRIBUTES)
+#define THREAD_ANNOTATION_ATTRIBUTE_(x) __attribute__((x))
+#else
+#define THREAD_ANNOTATION_ATTRIBUTE_(x)  // no-op
+#endif
+
+#define CAPABILITY(x) THREAD_ANNOTATION_ATTRIBUTE_(capability(x))
+
+#define SCOPED_CAPABILITY THREAD_ANNOTATION_ATTRIBUTE_(scoped_lockable)
+
+#define GUARDED_BY(x) THREAD_ANNOTATION_ATTRIBUTE_(guarded_by(x))
+
+#define PT_GUARDED_BY(x) THREAD_ANNOTATION_ATTRIBUTE_(pt_guarded_by(x))
+
+#define ACQUIRED_BEFORE(...) \
+  THREAD_ANNOTATION_ATTRIBUTE_(acquired_before(__VA_ARGS__))
+
+#define ACQUIRED_AFTER(...) \
+  THREAD_ANNOTATION_ATTRIBUTE_(acquired_after(__VA_ARGS__))
+
+#define REQUIRES(...) \
+  THREAD_ANNOTATION_ATTRIBUTE_(requires_capability(__VA_ARGS__))
+
+#define REQUIRES_SHARED(...) \
+  THREAD_ANNOTATION_ATTRIBUTE_(requires_shared_capability(__VA_ARGS__))
+
+#define ACQUIRE(...) \
+  THREAD_ANNOTATION_ATTRIBUTE_(acquire_capability(__VA_ARGS__))
+
+#define ACQUIRE_SHARED(...) \
+  THREAD_ANNOTATION_ATTRIBUTE_(acquire_shared_capability(__VA_ARGS__))
+
+#define RELEASE(...) \
+  THREAD_ANNOTATION_ATTRIBUTE_(release_capability(__VA_ARGS__))
+
+#define RELEASE_SHARED(...) \
+  THREAD_ANNOTATION_ATTRIBUTE_(release_shared_capability(__VA_ARGS__))
+
+#define TRY_ACQUIRE(...) \
+  THREAD_ANNOTATION_ATTRIBUTE_(try_acquire_capability(__VA_ARGS__))
+
+#define TRY_ACQUIRE_SHARED(...) \
+  THREAD_ANNOTATION_ATTRIBUTE_(try_acquire_shared_capability(__VA_ARGS__))
+
+#define EXCLUDES(...) THREAD_ANNOTATION_ATTRIBUTE_(locks_excluded(__VA_ARGS__))
+
+#define ASSERT_CAPABILITY(x) THREAD_ANNOTATION_ATTRIBUTE_(assert_capability(x))
+
+#define ASSERT_SHARED_CAPABILITY(x) \
+  THREAD_ANNOTATION_ATTRIBUTE_(assert_shared_capability(x))
+
+#define RETURN_CAPABILITY(x) THREAD_ANNOTATION_ATTRIBUTE_(lock_returned(x))
+
+#define NO_THREAD_SAFETY_ANALYSIS \
+  THREAD_ANNOTATION_ATTRIBUTE_(no_thread_safety_analysis)
+
+namespace benchmark {
+
+typedef std::condition_variable Condition;
+
+// NOTE: Wrappers for std::mutex and std::unique_lock are provided so that
+// we can annotate them with thread safety attributes and use the
+// -Wthread-safety warning with clang. The standard library types cannot be
+// used directly because they do not provide the required annotations.
+class CAPABILITY("mutex") Mutex {
+ public:
+  Mutex() {}
+
+  void lock() ACQUIRE() { mut_.lock(); }
+  void unlock() RELEASE() { mut_.unlock(); }
+  std::mutex& native_handle() { return mut_; }
+
+ private:
+  std::mutex mut_;
+};
+
+class SCOPED_CAPABILITY MutexLock {
+  typedef std::unique_lock<std::mutex> MutexLockImp;
+
+ public:
+  MutexLock(Mutex& m) ACQUIRE(m) : ml_(m.native_handle()) {}
+  ~MutexLock() RELEASE() {}
+  MutexLockImp& native_handle() { return ml_; }
+
+ private:
+  MutexLockImp ml_;
+};
+
+class Barrier {
+ public:
+  Barrier(int num_threads) : running_threads_(num_threads) {}
+
+  // Called by each thread
+  bool wait() EXCLUDES(lock_) {
+    bool last_thread = false;
+    {
+      MutexLock ml(lock_);
+      last_thread = createBarrier(ml);
+    }
+    if (last_thread) phase_condition_.notify_all();
+    return last_thread;
+  }
+
+  void removeThread() EXCLUDES(lock_) {
+    MutexLock ml(lock_);
+    --running_threads_;
+    if (entered_ != 0) phase_condition_.notify_all();
+  }
+
+ private:
+  Mutex lock_;
+  Condition phase_condition_;
+  int running_threads_;
+
+  // State for barrier management
+  int phase_number_ = 0;
+  int entered_ = 0;  // Number of threads that have entered this barrier
+
+  // Enter the barrier and wait until all other threads have also
+  // entered the barrier.  Returns iff this is the last thread to
+  // enter the barrier.
+  bool createBarrier(MutexLock& ml) REQUIRES(lock_) {
+    BM_CHECK_LT(entered_, running_threads_);
+    entered_++;
+    if (entered_ < running_threads_) {
+      // Wait for all threads to enter
+      int phase_number_cp = phase_number_;
+      auto cb = [this, phase_number_cp]() {
+        return this->phase_number_ > phase_number_cp ||
+               entered_ == running_threads_;  // A thread has aborted in error
+      };
+      phase_condition_.wait(ml.native_handle(), cb);
+      if (phase_number_ > phase_number_cp) return false;
+      // else (running_threads_ == entered_) and we are the last thread.
+    }
+    // Last thread has reached the barrier
+    phase_number_++;
+    entered_ = 0;
+    return true;
+  }
+};
+
+}  // end namespace benchmark
+
+#endif  // BENCHMARK_MUTEX_H_
diff --git a/leveldb_base/third_party/benchmark/src/perf_counters.cc b/leveldb_base/third_party/benchmark/src/perf_counters.cc
new file mode 100644
index 0000000..3980ea0
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/perf_counters.cc
@@ -0,0 +1,269 @@
+// Copyright 2021 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "perf_counters.h"
+
+#include <cstring>
+#include <memory>
+#include <vector>
+
+#if defined HAVE_LIBPFM
+#include "perfmon/pfmlib.h"
+#include "perfmon/pfmlib_perf_event.h"
+#endif
+
+namespace benchmark {
+namespace internal {
+
+constexpr size_t PerfCounterValues::kMaxCounters;
+
+#if defined HAVE_LIBPFM
+
+size_t PerfCounterValues::Read(const std::vector<int>& leaders) {
+  // Create a pointer for multiple reads
+  const size_t bufsize = values_.size() * sizeof(values_[0]);
+  char* ptr = reinterpret_cast<char*>(values_.data());
+  size_t size = bufsize;
+  for (int lead : leaders) {
+    auto read_bytes = ::read(lead, ptr, size);
+    if (read_bytes >= ssize_t(sizeof(uint64_t))) {
+      // Actual data bytes are all bytes minus initial padding
+      std::size_t data_bytes = read_bytes - sizeof(uint64_t);
+      // This should be very cheap since it's in hot cache
+      std::memmove(ptr, ptr + sizeof(uint64_t), data_bytes);
+      // Increment our counters
+      ptr += data_bytes;
+      size -= data_bytes;
+    } else {
+      int err = errno;
+      GetErrorLogInstance() << "Error reading lead " << lead << " errno:" << err
+                            << " " << ::strerror(err) << "\n";
+      return 0;
+    }
+  }
+  return (bufsize - size) / sizeof(uint64_t);
+}
+
+const bool PerfCounters::kSupported = true;
+
+bool PerfCounters::Initialize() { return pfm_initialize() == PFM_SUCCESS; }
+
+bool PerfCounters::IsCounterSupported(const std::string& name) {
+  perf_event_attr_t attr;
+  std::memset(&attr, 0, sizeof(attr));
+  pfm_perf_encode_arg_t arg;
+  std::memset(&arg, 0, sizeof(arg));
+  arg.attr = &attr;
+  const int mode = PFM_PLM3;  // user mode only
+  int ret = pfm_get_os_event_encoding(name.c_str(), mode, PFM_OS_PERF_EVENT_EXT,
+                                      &arg);
+  return (ret == PFM_SUCCESS);
+}
+
+PerfCounters PerfCounters::Create(
+    const std::vector<std::string>& counter_names) {
+  // Valid counters will populate these arrays but we start empty
+  std::vector<std::string> valid_names;
+  std::vector<int> counter_ids;
+  std::vector<int> leader_ids;
+
+  // Resize to the maximum possible
+  valid_names.reserve(counter_names.size());
+  counter_ids.reserve(counter_names.size());
+
+  const int kCounterMode = PFM_PLM3;  // user mode only
+
+  // Group leads will be assigned on demand. The idea is that once we cannot
+  // create a counter descriptor, the reason is that this group has maxed out
+  // so we set the group_id again to -1 and retry - giving the algorithm a
+  // chance to create a new group leader to hold the next set of counters.
+  int group_id = -1;
+
+  // Loop through all performance counters
+  for (size_t i = 0; i < counter_names.size(); ++i) {
+    // we are about to push into the valid names vector
+    // check if we did not reach the maximum
+    if (valid_names.size() == PerfCounterValues::kMaxCounters) {
+      // Log a message if we maxed out and stop adding
+      GetErrorLogInstance()
+          << counter_names.size() << " counters were requested. The maximum is "
+          << PerfCounterValues::kMaxCounters << " and " << valid_names.size()
+          << " were already added. All remaining counters will be ignored\n";
+      // stop the loop and return what we have already
+      break;
+    }
+
+    // Check if this name is empty
+    const auto& name = counter_names[i];
+    if (name.empty()) {
+      GetErrorLogInstance()
+          << "A performance counter name was the empty string\n";
+      continue;
+    }
+
+    // Here first means first in group, ie the group leader
+    const bool is_first = (group_id < 0);
+
+    // This struct will be populated by libpfm from the counter string
+    // and then fed into the syscall perf_event_open
+    struct perf_event_attr attr {};
+    attr.size = sizeof(attr);
+
+    // This is the input struct to libpfm.
+    pfm_perf_encode_arg_t arg{};
+    arg.attr = &attr;
+    const int pfm_get = pfm_get_os_event_encoding(name.c_str(), kCounterMode,
+                                                  PFM_OS_PERF_EVENT, &arg);
+    if (pfm_get != PFM_SUCCESS) {
+      GetErrorLogInstance()
+          << "Unknown performance counter name: " << name << "\n";
+      continue;
+    }
+
+    // We then proceed to populate the remaining fields in our attribute struct
+    // Note: the man page for perf_event_create suggests inherit = true and
+    // read_format = PERF_FORMAT_GROUP don't work together, but that's not the
+    // case.
+    attr.disabled = is_first;
+    attr.inherit = true;
+    attr.pinned = is_first;
+    attr.exclude_kernel = true;
+    attr.exclude_user = false;
+    attr.exclude_hv = true;
+
+    // Read all counters in a group in one read.
+    attr.read_format = PERF_FORMAT_GROUP;
+
+    int id = -1;
+    while (id < 0) {
+      static constexpr size_t kNrOfSyscallRetries = 5;
+      // Retry syscall as it was interrupted often (b/64774091).
+      for (size_t num_retries = 0; num_retries < kNrOfSyscallRetries;
+           ++num_retries) {
+        id = perf_event_open(&attr, 0, -1, group_id, 0);
+        if (id >= 0 || errno != EINTR) {
+          break;
+        }
+      }
+      if (id < 0) {
+        // If the file descriptor is negative we might have reached a limit
+        // in the current group. Set the group_id to -1 and retry
+        if (group_id >= 0) {
+          // Create a new group
+          group_id = -1;
+        } else {
+          // At this point we have already retried to set a new group id and
+          // failed. We then give up.
+          break;
+        }
+      }
+    }
+
+    // We failed to get a new file descriptor. We might have reached a hard
+    // hardware limit that cannot be resolved even with group multiplexing
+    if (id < 0) {
+      GetErrorLogInstance() << "***WARNING** Failed to get a file descriptor "
+                               "for performance counter "
+                            << name << ". Ignoring\n";
+
+      // We give up on this counter but try to keep going
+      // as the others would be fine
+      continue;
+    }
+    if (group_id < 0) {
+      // This is a leader, store and assign it to the current file descriptor
+      leader_ids.push_back(id);
+      group_id = id;
+    }
+    // This is a valid counter, add it to our descriptor's list
+    counter_ids.push_back(id);
+    valid_names.push_back(name);
+  }
+
+  // Loop through all group leaders activating them
+  // There is another option of starting ALL counters in a process but
+  // that would be far reaching an intrusion. If the user is using PMCs
+  // by themselves then this would have a side effect on them. It is
+  // friendlier to loop through all groups individually.
+  for (int lead : leader_ids) {
+    if (ioctl(lead, PERF_EVENT_IOC_ENABLE) != 0) {
+      // This should never happen but if it does, we give up on the
+      // entire batch as recovery would be a mess.
+      GetErrorLogInstance() << "***WARNING*** Failed to start counters. "
+                               "Claring out all counters.\n";
+
+      // Close all peformance counters
+      for (int id : counter_ids) {
+        ::close(id);
+      }
+
+      // Return an empty object so our internal state is still good and
+      // the process can continue normally without impact
+      return NoCounters();
+    }
+  }
+
+  return PerfCounters(std::move(valid_names), std::move(counter_ids),
+                      std::move(leader_ids));
+}
+
+void PerfCounters::CloseCounters() const {
+  if (counter_ids_.empty()) {
+    return;
+  }
+  for (int lead : leader_ids_) {
+    ioctl(lead, PERF_EVENT_IOC_DISABLE);
+  }
+  for (int fd : counter_ids_) {
+    close(fd);
+  }
+}
+#else   // defined HAVE_LIBPFM
+size_t PerfCounterValues::Read(const std::vector<int>&) { return 0; }
+
+const bool PerfCounters::kSupported = false;
+
+bool PerfCounters::Initialize() { return false; }
+
+bool PerfCounters::IsCounterSupported(const std::string&) { return false; }
+
+PerfCounters PerfCounters::Create(
+    const std::vector<std::string>& counter_names) {
+  if (!counter_names.empty()) {
+    GetErrorLogInstance() << "Performance counters not supported.";
+  }
+  return NoCounters();
+}
+
+void PerfCounters::CloseCounters() const {}
+#endif  // defined HAVE_LIBPFM
+
+PerfCountersMeasurement::PerfCountersMeasurement(
+    const std::vector<std::string>& counter_names)
+    : start_values_(counter_names.size()), end_values_(counter_names.size()) {
+  counters_ = PerfCounters::Create(counter_names);
+}
+
+PerfCounters& PerfCounters::operator=(PerfCounters&& other) noexcept {
+  if (this != &other) {
+    CloseCounters();
+
+    counter_ids_ = std::move(other.counter_ids_);
+    leader_ids_ = std::move(other.leader_ids_);
+    counter_names_ = std::move(other.counter_names_);
+  }
+  return *this;
+}
+}  // namespace internal
+}  // namespace benchmark
diff --git a/leveldb_base/third_party/benchmark/src/perf_counters.h b/leveldb_base/third_party/benchmark/src/perf_counters.h
new file mode 100644
index 0000000..152a6f2
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/perf_counters.h
@@ -0,0 +1,202 @@
+// Copyright 2021 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef BENCHMARK_PERF_COUNTERS_H
+#define BENCHMARK_PERF_COUNTERS_H
+
+#include <array>
+#include <cstdint>
+#include <cstring>
+#include <memory>
+#include <vector>
+
+#include "benchmark/benchmark.h"
+#include "check.h"
+#include "log.h"
+#include "mutex.h"
+
+#ifndef BENCHMARK_OS_WINDOWS
+#include <unistd.h>
+#endif
+
+#if defined(_MSC_VER)
+#pragma warning(push)
+// C4251: <symbol> needs to have dll-interface to be used by clients of class
+#pragma warning(disable : 4251)
+#endif
+
+namespace benchmark {
+namespace internal {
+
+// Typically, we can only read a small number of counters. There is also a
+// padding preceding counter values, when reading multiple counters with one
+// syscall (which is desirable). PerfCounterValues abstracts these details.
+// The implementation ensures the storage is inlined, and allows 0-based
+// indexing into the counter values.
+// The object is used in conjunction with a PerfCounters object, by passing it
+// to Snapshot(). The Read() method relocates individual reads, discarding
+// the initial padding from each group leader in the values buffer such that
+// all user accesses through the [] operator are correct.
+class BENCHMARK_EXPORT PerfCounterValues {
+ public:
+  explicit PerfCounterValues(size_t nr_counters) : nr_counters_(nr_counters) {
+    BM_CHECK_LE(nr_counters_, kMaxCounters);
+  }
+
+  // We are reading correctly now so the values don't need to skip padding
+  uint64_t operator[](size_t pos) const { return values_[pos]; }
+
+  // Increased the maximum to 32 only since the buffer
+  // is std::array<> backed
+  static constexpr size_t kMaxCounters = 32;
+
+ private:
+  friend class PerfCounters;
+  // Get the byte buffer in which perf counters can be captured.
+  // This is used by PerfCounters::Read
+  std::pair<char*, size_t> get_data_buffer() {
+    return {reinterpret_cast<char*>(values_.data()),
+            sizeof(uint64_t) * (kPadding + nr_counters_)};
+  }
+
+  // This reading is complex and as the goal of this class is to
+  // abstract away the intrincacies of the reading process, this is
+  // a better place for it
+  size_t Read(const std::vector<int>& leaders);
+
+  // Move the padding to 2 due to the reading algorithm (1st padding plus a
+  // current read padding)
+  static constexpr size_t kPadding = 2;
+  std::array<uint64_t, kPadding + kMaxCounters> values_;
+  const size_t nr_counters_;
+};
+
+// Collect PMU counters. The object, once constructed, is ready to be used by
+// calling read(). PMU counter collection is enabled from the time create() is
+// called, to obtain the object, until the object's destructor is called.
+class BENCHMARK_EXPORT PerfCounters final {
+ public:
+  // True iff this platform supports performance counters.
+  static const bool kSupported;
+
+  // Returns an empty object
+  static PerfCounters NoCounters() { return PerfCounters(); }
+
+  ~PerfCounters() { CloseCounters(); }
+  PerfCounters() = default;
+  PerfCounters(PerfCounters&&) = default;
+  PerfCounters(const PerfCounters&) = delete;
+  PerfCounters& operator=(PerfCounters&&) noexcept;
+  PerfCounters& operator=(const PerfCounters&) = delete;
+
+  // Platform-specific implementations may choose to do some library
+  // initialization here.
+  static bool Initialize();
+
+  // Check if the given counter is supported, if the app wants to
+  // check before passing
+  static bool IsCounterSupported(const std::string& name);
+
+  // Return a PerfCounters object ready to read the counters with the names
+  // specified. The values are user-mode only. The counter name format is
+  // implementation and OS specific.
+  // In case of failure, this method will in the worst case return an
+  // empty object whose state will still be valid.
+  static PerfCounters Create(const std::vector<std::string>& counter_names);
+
+  // Take a snapshot of the current value of the counters into the provided
+  // valid PerfCounterValues storage. The values are populated such that:
+  // names()[i]'s value is (*values)[i]
+  BENCHMARK_ALWAYS_INLINE bool Snapshot(PerfCounterValues* values) const {
+#ifndef BENCHMARK_OS_WINDOWS
+    assert(values != nullptr);
+    return values->Read(leader_ids_) == counter_ids_.size();
+#else
+    (void)values;
+    return false;
+#endif
+  }
+
+  const std::vector<std::string>& names() const { return counter_names_; }
+  size_t num_counters() const { return counter_names_.size(); }
+
+ private:
+  PerfCounters(const std::vector<std::string>& counter_names,
+               std::vector<int>&& counter_ids, std::vector<int>&& leader_ids)
+      : counter_ids_(std::move(counter_ids)),
+        leader_ids_(std::move(leader_ids)),
+        counter_names_(counter_names) {}
+
+  void CloseCounters() const;
+
+  std::vector<int> counter_ids_;
+  std::vector<int> leader_ids_;
+  std::vector<std::string> counter_names_;
+};
+
+// Typical usage of the above primitives.
+class BENCHMARK_EXPORT PerfCountersMeasurement final {
+ public:
+  PerfCountersMeasurement(const std::vector<std::string>& counter_names);
+
+  size_t num_counters() const { return counters_.num_counters(); }
+
+  std::vector<std::string> names() const { return counters_.names(); }
+
+  BENCHMARK_ALWAYS_INLINE bool Start() {
+    if (num_counters() == 0) return true;
+    // Tell the compiler to not move instructions above/below where we take
+    // the snapshot.
+    ClobberMemory();
+    valid_read_ &= counters_.Snapshot(&start_values_);
+    ClobberMemory();
+
+    return valid_read_;
+  }
+
+  BENCHMARK_ALWAYS_INLINE bool Stop(
+      std::vector<std::pair<std::string, double>>& measurements) {
+    if (num_counters() == 0) return true;
+    // Tell the compiler to not move instructions above/below where we take
+    // the snapshot.
+    ClobberMemory();
+    valid_read_ &= counters_.Snapshot(&end_values_);
+    ClobberMemory();
+
+    for (size_t i = 0; i < counters_.names().size(); ++i) {
+      double measurement = static_cast<double>(end_values_[i]) -
+                           static_cast<double>(start_values_[i]);
+      measurements.push_back({counters_.names()[i], measurement});
+    }
+
+    return valid_read_;
+  }
+
+ private:
+  PerfCounters counters_;
+  bool valid_read_ = true;
+  PerfCounterValues start_values_;
+  PerfCounterValues end_values_;
+};
+
+BENCHMARK_UNUSED static bool perf_init_anchor = PerfCounters::Initialize();
+
+}  // namespace internal
+}  // namespace benchmark
+
+#if defined(_MSC_VER)
+#pragma warning(pop)
+#endif
+
+#endif  // BENCHMARK_PERF_COUNTERS_H
diff --git a/leveldb_base/third_party/benchmark/src/re.h b/leveldb_base/third_party/benchmark/src/re.h
new file mode 100644
index 0000000..6300467
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/re.h
@@ -0,0 +1,158 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef BENCHMARK_RE_H_
+#define BENCHMARK_RE_H_
+
+#include "internal_macros.h"
+
+// clang-format off
+
+#if !defined(HAVE_STD_REGEX) && \
+    !defined(HAVE_GNU_POSIX_REGEX) && \
+    !defined(HAVE_POSIX_REGEX)
+  // No explicit regex selection; detect based on builtin hints.
+  #if defined(BENCHMARK_OS_LINUX) || defined(BENCHMARK_OS_APPLE)
+    #define HAVE_POSIX_REGEX 1
+  #elif __cplusplus >= 199711L
+    #define HAVE_STD_REGEX 1
+  #endif
+#endif
+
+// Prefer C regex libraries when compiling w/o exceptions so that we can
+// correctly report errors.
+#if defined(BENCHMARK_HAS_NO_EXCEPTIONS) && \
+    defined(BENCHMARK_HAVE_STD_REGEX) && \
+    (defined(HAVE_GNU_POSIX_REGEX) || defined(HAVE_POSIX_REGEX))
+  #undef HAVE_STD_REGEX
+#endif
+
+#if defined(HAVE_STD_REGEX)
+  #include <regex>
+#elif defined(HAVE_GNU_POSIX_REGEX)
+  #include <gnuregex.h>
+#elif defined(HAVE_POSIX_REGEX)
+  #include <regex.h>
+#else
+#error No regular expression backend was found!
+#endif
+
+// clang-format on
+
+#include <string>
+
+#include "check.h"
+
+namespace benchmark {
+
+// A wrapper around the POSIX regular expression API that provides automatic
+// cleanup
+class Regex {
+ public:
+  Regex() : init_(false) {}
+
+  ~Regex();
+
+  // Compile a regular expression matcher from spec.  Returns true on success.
+  //
+  // On failure (and if error is not nullptr), error is populated with a human
+  // readable error message if an error occurs.
+  bool Init(const std::string& spec, std::string* error);
+
+  // Returns whether str matches the compiled regular expression.
+  bool Match(const std::string& str);
+
+ private:
+  bool init_;
+// Underlying regular expression object
+#if defined(HAVE_STD_REGEX)
+  std::regex re_;
+#elif defined(HAVE_POSIX_REGEX) || defined(HAVE_GNU_POSIX_REGEX)
+  regex_t re_;
+#else
+#error No regular expression backend implementation available
+#endif
+};
+
+#if defined(HAVE_STD_REGEX)
+
+inline bool Regex::Init(const std::string& spec, std::string* error) {
+#ifdef BENCHMARK_HAS_NO_EXCEPTIONS
+  ((void)error);  // suppress unused warning
+#else
+  try {
+#endif
+  re_ = std::regex(spec, std::regex_constants::extended);
+  init_ = true;
+#ifndef BENCHMARK_HAS_NO_EXCEPTIONS
+}
+catch (const std::regex_error& e) {
+  if (error) {
+    *error = e.what();
+  }
+}
+#endif
+return init_;
+}
+
+inline Regex::~Regex() {}
+
+inline bool Regex::Match(const std::string& str) {
+  if (!init_) {
+    return false;
+  }
+  return std::regex_search(str, re_);
+}
+
+#else
+inline bool Regex::Init(const std::string& spec, std::string* error) {
+  int ec = regcomp(&re_, spec.c_str(), REG_EXTENDED | REG_NOSUB);
+  if (ec != 0) {
+    if (error) {
+      size_t needed = regerror(ec, &re_, nullptr, 0);
+      char* errbuf = new char[needed];
+      regerror(ec, &re_, errbuf, needed);
+
+      // regerror returns the number of bytes necessary to null terminate
+      // the string, so we move that when assigning to error.
+      BM_CHECK_NE(needed, 0);
+      error->assign(errbuf, needed - 1);
+
+      delete[] errbuf;
+    }
+
+    return false;
+  }
+
+  init_ = true;
+  return true;
+}
+
+inline Regex::~Regex() {
+  if (init_) {
+    regfree(&re_);
+  }
+}
+
+inline bool Regex::Match(const std::string& str) {
+  if (!init_) {
+    return false;
+  }
+  return regexec(&re_, str.c_str(), 0, nullptr, 0) == 0;
+}
+#endif
+
+}  // end namespace benchmark
+
+#endif  // BENCHMARK_RE_H_
diff --git a/leveldb_base/third_party/benchmark/src/reporter.cc b/leveldb_base/third_party/benchmark/src/reporter.cc
new file mode 100644
index 0000000..076bc31
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/reporter.cc
@@ -0,0 +1,118 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <cstdlib>
+#include <iostream>
+#include <map>
+#include <string>
+#include <tuple>
+#include <vector>
+
+#include "benchmark/benchmark.h"
+#include "check.h"
+#include "string_util.h"
+#include "timers.h"
+
+namespace benchmark {
+
+BenchmarkReporter::BenchmarkReporter()
+    : output_stream_(&std::cout), error_stream_(&std::cerr) {}
+
+BenchmarkReporter::~BenchmarkReporter() {}
+
+void BenchmarkReporter::PrintBasicContext(std::ostream *out,
+                                          Context const &context) {
+  BM_CHECK(out) << "cannot be null";
+  auto &Out = *out;
+
+#ifndef BENCHMARK_OS_QURT
+  // Date/time information is not available on QuRT.
+  // Attempting to get it via this call cause the binary to crash.
+  Out << LocalDateTimeString() << "\n";
+#endif
+
+  if (context.executable_name)
+    Out << "Running " << context.executable_name << "\n";
+
+  const CPUInfo &info = context.cpu_info;
+  Out << "Run on (" << info.num_cpus << " X "
+      << (info.cycles_per_second / 1000000.0) << " MHz CPU "
+      << ((info.num_cpus > 1) ? "s" : "") << ")\n";
+  if (info.caches.size() != 0) {
+    Out << "CPU Caches:\n";
+    for (auto &CInfo : info.caches) {
+      Out << "  L" << CInfo.level << " " << CInfo.type << " "
+          << (CInfo.size / 1024) << " KiB";
+      if (CInfo.num_sharing != 0)
+        Out << " (x" << (info.num_cpus / CInfo.num_sharing) << ")";
+      Out << "\n";
+    }
+  }
+  if (!info.load_avg.empty()) {
+    Out << "Load Average: ";
+    for (auto It = info.load_avg.begin(); It != info.load_avg.end();) {
+      Out << StrFormat("%.2f", *It++);
+      if (It != info.load_avg.end()) Out << ", ";
+    }
+    Out << "\n";
+  }
+
+  std::map<std::string, std::string> *global_context =
+      internal::GetGlobalContext();
+
+  if (global_context != nullptr) {
+    for (const auto &kv : *global_context) {
+      Out << kv.first << ": " << kv.second << "\n";
+    }
+  }
+
+  if (CPUInfo::Scaling::ENABLED == info.scaling) {
+    Out << "***WARNING*** CPU scaling is enabled, the benchmark "
+           "real time measurements may be noisy and will incur extra "
+           "overhead.\n";
+  }
+
+#ifndef NDEBUG
+  Out << "***WARNING*** Library was built as DEBUG. Timings may be "
+         "affected.\n";
+#endif
+}
+
+// No initializer because it's already initialized to NULL.
+const char *BenchmarkReporter::Context::executable_name;
+
+BenchmarkReporter::Context::Context()
+    : cpu_info(CPUInfo::Get()), sys_info(SystemInfo::Get()) {}
+
+std::string BenchmarkReporter::Run::benchmark_name() const {
+  std::string name = run_name.str();
+  if (run_type == RT_Aggregate) {
+    name += "_" + aggregate_name;
+  }
+  return name;
+}
+
+double BenchmarkReporter::Run::GetAdjustedRealTime() const {
+  double new_time = real_accumulated_time * GetTimeUnitMultiplier(time_unit);
+  if (iterations != 0) new_time /= static_cast<double>(iterations);
+  return new_time;
+}
+
+double BenchmarkReporter::Run::GetAdjustedCPUTime() const {
+  double new_time = cpu_accumulated_time * GetTimeUnitMultiplier(time_unit);
+  if (iterations != 0) new_time /= static_cast<double>(iterations);
+  return new_time;
+}
+
+}  // end namespace benchmark
diff --git a/leveldb_base/third_party/benchmark/src/statistics.cc b/leveldb_base/third_party/benchmark/src/statistics.cc
new file mode 100644
index 0000000..c4b54b2
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/statistics.cc
@@ -0,0 +1,209 @@
+// Copyright 2016 Ismael Jimenez Martinez. All rights reserved.
+// Copyright 2017 Roman Lebedev. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "statistics.h"
+
+#include <algorithm>
+#include <cmath>
+#include <numeric>
+#include <string>
+#include <vector>
+
+#include "benchmark/benchmark.h"
+#include "check.h"
+
+namespace benchmark {
+
+auto StatisticsSum = [](const std::vector<double>& v) {
+  return std::accumulate(v.begin(), v.end(), 0.0);
+};
+
+double StatisticsMean(const std::vector<double>& v) {
+  if (v.empty()) return 0.0;
+  return StatisticsSum(v) * (1.0 / v.size());
+}
+
+double StatisticsMedian(const std::vector<double>& v) {
+  if (v.size() < 3) return StatisticsMean(v);
+  std::vector<double> copy(v);
+
+  auto center = copy.begin() + v.size() / 2;
+  std::nth_element(copy.begin(), center, copy.end());
+
+  // did we have an odd number of samples?
+  // if yes, then center is the median
+  // it no, then we are looking for the average between center and the value
+  // before
+  if (v.size() % 2 == 1) return *center;
+  auto center2 = copy.begin() + v.size() / 2 - 1;
+  std::nth_element(copy.begin(), center2, copy.end());
+  return (*center + *center2) / 2.0;
+}
+
+// Return the sum of the squares of this sample set
+auto SumSquares = [](const std::vector<double>& v) {
+  return std::inner_product(v.begin(), v.end(), v.begin(), 0.0);
+};
+
+auto Sqr = [](const double dat) { return dat * dat; };
+auto Sqrt = [](const double dat) {
+  // Avoid NaN due to imprecision in the calculations
+  if (dat < 0.0) return 0.0;
+  return std::sqrt(dat);
+};
+
+double StatisticsStdDev(const std::vector<double>& v) {
+  const auto mean = StatisticsMean(v);
+  if (v.empty()) return mean;
+
+  // Sample standard deviation is undefined for n = 1
+  if (v.size() == 1) return 0.0;
+
+  const double avg_squares = SumSquares(v) * (1.0 / v.size());
+  return Sqrt(v.size() / (v.size() - 1.0) * (avg_squares - Sqr(mean)));
+}
+
+double StatisticsCV(const std::vector<double>& v) {
+  if (v.size() < 2) return 0.0;
+
+  const auto stddev = StatisticsStdDev(v);
+  const auto mean = StatisticsMean(v);
+
+  return stddev / mean;
+}
+
+std::vector<BenchmarkReporter::Run> ComputeStats(
+    const std::vector<BenchmarkReporter::Run>& reports) {
+  typedef BenchmarkReporter::Run Run;
+  std::vector<Run> results;
+
+  auto error_count = std::count_if(reports.begin(), reports.end(),
+                                   [](Run const& run) { return run.skipped; });
+
+  if (reports.size() - error_count < 2) {
+    // We don't report aggregated data if there was a single run.
+    return results;
+  }
+
+  // Accumulators.
+  std::vector<double> real_accumulated_time_stat;
+  std::vector<double> cpu_accumulated_time_stat;
+
+  real_accumulated_time_stat.reserve(reports.size());
+  cpu_accumulated_time_stat.reserve(reports.size());
+
+  // All repetitions should be run with the same number of iterations so we
+  // can take this information from the first benchmark.
+  const IterationCount run_iterations = reports.front().iterations;
+  // create stats for user counters
+  struct CounterStat {
+    Counter c;
+    std::vector<double> s;
+  };
+  std::map<std::string, CounterStat> counter_stats;
+  for (Run const& r : reports) {
+    for (auto const& cnt : r.counters) {
+      auto it = counter_stats.find(cnt.first);
+      if (it == counter_stats.end()) {
+        it = counter_stats
+                 .emplace(cnt.first,
+                          CounterStat{cnt.second, std::vector<double>{}})
+                 .first;
+        it->second.s.reserve(reports.size());
+      } else {
+        BM_CHECK_EQ(it->second.c.flags, cnt.second.flags);
+      }
+    }
+  }
+
+  // Populate the accumulators.
+  for (Run const& run : reports) {
+    BM_CHECK_EQ(reports[0].benchmark_name(), run.benchmark_name());
+    BM_CHECK_EQ(run_iterations, run.iterations);
+    if (run.skipped) continue;
+    real_accumulated_time_stat.emplace_back(run.real_accumulated_time);
+    cpu_accumulated_time_stat.emplace_back(run.cpu_accumulated_time);
+    // user counters
+    for (auto const& cnt : run.counters) {
+      auto it = counter_stats.find(cnt.first);
+      BM_CHECK_NE(it, counter_stats.end());
+      it->second.s.emplace_back(cnt.second);
+    }
+  }
+
+  // Only add label if it is same for all runs
+  std::string report_label = reports[0].report_label;
+  for (std::size_t i = 1; i < reports.size(); i++) {
+    if (reports[i].report_label != report_label) {
+      report_label = "";
+      break;
+    }
+  }
+
+  const double iteration_rescale_factor =
+      double(reports.size()) / double(run_iterations);
+
+  for (const auto& Stat : *reports[0].statistics) {
+    // Get the data from the accumulator to BenchmarkReporter::Run's.
+    Run data;
+    data.run_name = reports[0].run_name;
+    data.family_index = reports[0].family_index;
+    data.per_family_instance_index = reports[0].per_family_instance_index;
+    data.run_type = BenchmarkReporter::Run::RT_Aggregate;
+    data.threads = reports[0].threads;
+    data.repetitions = reports[0].repetitions;
+    data.repetition_index = Run::no_repetition_index;
+    data.aggregate_name = Stat.name_;
+    data.aggregate_unit = Stat.unit_;
+    data.report_label = report_label;
+
+    // It is incorrect to say that an aggregate is computed over
+    // run's iterations, because those iterations already got averaged.
+    // Similarly, if there are N repetitions with 1 iterations each,
+    // an aggregate will be computed over N measurements, not 1.
+    // Thus it is best to simply use the count of separate reports.
+    data.iterations = reports.size();
+
+    data.real_accumulated_time = Stat.compute_(real_accumulated_time_stat);
+    data.cpu_accumulated_time = Stat.compute_(cpu_accumulated_time_stat);
+
+    if (data.aggregate_unit == StatisticUnit::kTime) {
+      // We will divide these times by data.iterations when reporting, but the
+      // data.iterations is not necessarily the scale of these measurements,
+      // because in each repetition, these timers are sum over all the iters.
+      // And if we want to say that the stats are over N repetitions and not
+      // M iterations, we need to multiply these by (N/M).
+      data.real_accumulated_time *= iteration_rescale_factor;
+      data.cpu_accumulated_time *= iteration_rescale_factor;
+    }
+
+    data.time_unit = reports[0].time_unit;
+
+    // user counters
+    for (auto const& kv : counter_stats) {
+      // Do *NOT* rescale the custom counters. They are already properly scaled.
+      const auto uc_stat = Stat.compute_(kv.second.s);
+      auto c = Counter(uc_stat, counter_stats[kv.first].c.flags,
+                       counter_stats[kv.first].c.oneK);
+      data.counters[kv.first] = c;
+    }
+
+    results.push_back(data);
+  }
+
+  return results;
+}
+
+}  // end namespace benchmark
diff --git a/leveldb_base/third_party/benchmark/src/statistics.h b/leveldb_base/third_party/benchmark/src/statistics.h
new file mode 100644
index 0000000..6e5560e
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/statistics.h
@@ -0,0 +1,44 @@
+// Copyright 2016 Ismael Jimenez Martinez. All rights reserved.
+// Copyright 2017 Roman Lebedev. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef STATISTICS_H_
+#define STATISTICS_H_
+
+#include <vector>
+
+#include "benchmark/benchmark.h"
+
+namespace benchmark {
+
+// Return a vector containing the mean, median and standard deviation
+// information (and any user-specified info) for the specified list of reports.
+// If 'reports' contains less than two non-errored runs an empty vector is
+// returned
+BENCHMARK_EXPORT
+std::vector<BenchmarkReporter::Run> ComputeStats(
+    const std::vector<BenchmarkReporter::Run>& reports);
+
+BENCHMARK_EXPORT
+double StatisticsMean(const std::vector<double>& v);
+BENCHMARK_EXPORT
+double StatisticsMedian(const std::vector<double>& v);
+BENCHMARK_EXPORT
+double StatisticsStdDev(const std::vector<double>& v);
+BENCHMARK_EXPORT
+double StatisticsCV(const std::vector<double>& v);
+
+}  // end namespace benchmark
+
+#endif  // STATISTICS_H_
diff --git a/leveldb_base/third_party/benchmark/src/string_util.cc b/leveldb_base/third_party/benchmark/src/string_util.cc
new file mode 100644
index 0000000..5e2d24a
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/string_util.cc
@@ -0,0 +1,265 @@
+#include "string_util.h"
+
+#include <array>
+#ifdef BENCHMARK_STL_ANDROID_GNUSTL
+#include <cerrno>
+#endif
+#include <cmath>
+#include <cstdarg>
+#include <cstdio>
+#include <memory>
+#include <sstream>
+
+#include "arraysize.h"
+
+namespace benchmark {
+namespace {
+
+// kilo, Mega, Giga, Tera, Peta, Exa, Zetta, Yotta.
+const char kBigSIUnits[] = "kMGTPEZY";
+// Kibi, Mebi, Gibi, Tebi, Pebi, Exbi, Zebi, Yobi.
+const char kBigIECUnits[] = "KMGTPEZY";
+// milli, micro, nano, pico, femto, atto, zepto, yocto.
+const char kSmallSIUnits[] = "munpfazy";
+
+// We require that all three arrays have the same size.
+static_assert(arraysize(kBigSIUnits) == arraysize(kBigIECUnits),
+              "SI and IEC unit arrays must be the same size");
+static_assert(arraysize(kSmallSIUnits) == arraysize(kBigSIUnits),
+              "Small SI and Big SI unit arrays must be the same size");
+
+static const int64_t kUnitsSize = arraysize(kBigSIUnits);
+
+void ToExponentAndMantissa(double val, double thresh, int precision,
+                           double one_k, std::string* mantissa,
+                           int64_t* exponent) {
+  std::stringstream mantissa_stream;
+
+  if (val < 0) {
+    mantissa_stream << "-";
+    val = -val;
+  }
+
+  // Adjust threshold so that it never excludes things which can't be rendered
+  // in 'precision' digits.
+  const double adjusted_threshold =
+      std::max(thresh, 1.0 / std::pow(10.0, precision));
+  const double big_threshold = adjusted_threshold * one_k;
+  const double small_threshold = adjusted_threshold;
+  // Values in ]simple_threshold,small_threshold[ will be printed as-is
+  const double simple_threshold = 0.01;
+
+  if (val > big_threshold) {
+    // Positive powers
+    double scaled = val;
+    for (size_t i = 0; i < arraysize(kBigSIUnits); ++i) {
+      scaled /= one_k;
+      if (scaled <= big_threshold) {
+        mantissa_stream << scaled;
+        *exponent = i + 1;
+        *mantissa = mantissa_stream.str();
+        return;
+      }
+    }
+    mantissa_stream << val;
+    *exponent = 0;
+  } else if (val < small_threshold) {
+    // Negative powers
+    if (val < simple_threshold) {
+      double scaled = val;
+      for (size_t i = 0; i < arraysize(kSmallSIUnits); ++i) {
+        scaled *= one_k;
+        if (scaled >= small_threshold) {
+          mantissa_stream << scaled;
+          *exponent = -static_cast<int64_t>(i + 1);
+          *mantissa = mantissa_stream.str();
+          return;
+        }
+      }
+    }
+    mantissa_stream << val;
+    *exponent = 0;
+  } else {
+    mantissa_stream << val;
+    *exponent = 0;
+  }
+  *mantissa = mantissa_stream.str();
+}
+
+std::string ExponentToPrefix(int64_t exponent, bool iec) {
+  if (exponent == 0) return "";
+
+  const int64_t index = (exponent > 0 ? exponent - 1 : -exponent - 1);
+  if (index >= kUnitsSize) return "";
+
+  const char* array =
+      (exponent > 0 ? (iec ? kBigIECUnits : kBigSIUnits) : kSmallSIUnits);
+  if (iec) {
+    return array[index] + std::string("i");
+  }
+  return std::string(1, array[index]);
+}
+
+std::string ToBinaryStringFullySpecified(double value, double threshold,
+                                         int precision, double one_k = 1024.0) {
+  std::string mantissa;
+  int64_t exponent;
+  ToExponentAndMantissa(value, threshold, precision, one_k, &mantissa,
+                        &exponent);
+  return mantissa + ExponentToPrefix(exponent, false);
+}
+
+}  // end namespace
+
+void AppendHumanReadable(int n, std::string* str) {
+  std::stringstream ss;
+  // Round down to the nearest SI prefix.
+  ss << ToBinaryStringFullySpecified(n, 1.0, 0);
+  *str += ss.str();
+}
+
+std::string HumanReadableNumber(double n, double one_k) {
+  // 1.1 means that figures up to 1.1k should be shown with the next unit down;
+  // this softens edge effects.
+  // 1 means that we should show one decimal place of precision.
+  return ToBinaryStringFullySpecified(n, 1.1, 1, one_k);
+}
+
+std::string StrFormatImp(const char* msg, va_list args) {
+  // we might need a second shot at this, so pre-emptivly make a copy
+  va_list args_cp;
+  va_copy(args_cp, args);
+
+  // TODO(ericwf): use std::array for first attempt to avoid one memory
+  // allocation guess what the size might be
+  std::array<char, 256> local_buff;
+
+  // 2015-10-08: vsnprintf is used instead of snd::vsnprintf due to a limitation
+  // in the android-ndk
+  auto ret = vsnprintf(local_buff.data(), local_buff.size(), msg, args_cp);
+
+  va_end(args_cp);
+
+  // handle empty expansion
+  if (ret == 0) return std::string{};
+  if (static_cast<std::size_t>(ret) < local_buff.size())
+    return std::string(local_buff.data());
+
+  // we did not provide a long enough buffer on our first attempt.
+  // add 1 to size to account for null-byte in size cast to prevent overflow
+  std::size_t size = static_cast<std::size_t>(ret) + 1;
+  auto buff_ptr = std::unique_ptr<char[]>(new char[size]);
+  // 2015-10-08: vsnprintf is used instead of snd::vsnprintf due to a limitation
+  // in the android-ndk
+  vsnprintf(buff_ptr.get(), size, msg, args);
+  return std::string(buff_ptr.get());
+}
+
+std::string StrFormat(const char* format, ...) {
+  va_list args;
+  va_start(args, format);
+  std::string tmp = StrFormatImp(format, args);
+  va_end(args);
+  return tmp;
+}
+
+std::vector<std::string> StrSplit(const std::string& str, char delim) {
+  if (str.empty()) return {};
+  std::vector<std::string> ret;
+  size_t first = 0;
+  size_t next = str.find(delim);
+  for (; next != std::string::npos;
+       first = next + 1, next = str.find(delim, first)) {
+    ret.push_back(str.substr(first, next - first));
+  }
+  ret.push_back(str.substr(first));
+  return ret;
+}
+
+#ifdef BENCHMARK_STL_ANDROID_GNUSTL
+/*
+ * GNU STL in Android NDK lacks support for some C++11 functions, including
+ * stoul, stoi, stod. We reimplement them here using C functions strtoul,
+ * strtol, strtod. Note that reimplemented functions are in benchmark::
+ * namespace, not std:: namespace.
+ */
+unsigned long stoul(const std::string& str, size_t* pos, int base) {
+  /* Record previous errno */
+  const int oldErrno = errno;
+  errno = 0;
+
+  const char* strStart = str.c_str();
+  char* strEnd = const_cast<char*>(strStart);
+  const unsigned long result = strtoul(strStart, &strEnd, base);
+
+  const int strtoulErrno = errno;
+  /* Restore previous errno */
+  errno = oldErrno;
+
+  /* Check for errors and return */
+  if (strtoulErrno == ERANGE) {
+    throw std::out_of_range("stoul failed: " + str +
+                            " is outside of range of unsigned long");
+  } else if (strEnd == strStart || strtoulErrno != 0) {
+    throw std::invalid_argument("stoul failed: " + str + " is not an integer");
+  }
+  if (pos != nullptr) {
+    *pos = static_cast<size_t>(strEnd - strStart);
+  }
+  return result;
+}
+
+int stoi(const std::string& str, size_t* pos, int base) {
+  /* Record previous errno */
+  const int oldErrno = errno;
+  errno = 0;
+
+  const char* strStart = str.c_str();
+  char* strEnd = const_cast<char*>(strStart);
+  const long result = strtol(strStart, &strEnd, base);
+
+  const int strtolErrno = errno;
+  /* Restore previous errno */
+  errno = oldErrno;
+
+  /* Check for errors and return */
+  if (strtolErrno == ERANGE || long(int(result)) != result) {
+    throw std::out_of_range("stoul failed: " + str +
+                            " is outside of range of int");
+  } else if (strEnd == strStart || strtolErrno != 0) {
+    throw std::invalid_argument("stoul failed: " + str + " is not an integer");
+  }
+  if (pos != nullptr) {
+    *pos = static_cast<size_t>(strEnd - strStart);
+  }
+  return int(result);
+}
+
+double stod(const std::string& str, size_t* pos) {
+  /* Record previous errno */
+  const int oldErrno = errno;
+  errno = 0;
+
+  const char* strStart = str.c_str();
+  char* strEnd = const_cast<char*>(strStart);
+  const double result = strtod(strStart, &strEnd);
+
+  /* Restore previous errno */
+  const int strtodErrno = errno;
+  errno = oldErrno;
+
+  /* Check for errors and return */
+  if (strtodErrno == ERANGE) {
+    throw std::out_of_range("stoul failed: " + str +
+                            " is outside of range of int");
+  } else if (strEnd == strStart || strtodErrno != 0) {
+    throw std::invalid_argument("stoul failed: " + str + " is not an integer");
+  }
+  if (pos != nullptr) {
+    *pos = static_cast<size_t>(strEnd - strStart);
+  }
+  return result;
+}
+#endif
+
+}  // end namespace benchmark
diff --git a/leveldb_base/third_party/benchmark/src/string_util.h b/leveldb_base/third_party/benchmark/src/string_util.h
new file mode 100644
index 0000000..37bdd2e
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/string_util.h
@@ -0,0 +1,70 @@
+#ifndef BENCHMARK_STRING_UTIL_H_
+#define BENCHMARK_STRING_UTIL_H_
+
+#include <sstream>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "benchmark/export.h"
+#include "check.h"
+#include "internal_macros.h"
+
+namespace benchmark {
+
+void AppendHumanReadable(int n, std::string* str);
+
+std::string HumanReadableNumber(double n, double one_k = 1024.0);
+
+BENCHMARK_EXPORT
+#if defined(__MINGW32__)
+__attribute__((format(__MINGW_PRINTF_FORMAT, 1, 2)))
+#elif defined(__GNUC__)
+__attribute__((format(printf, 1, 2)))
+#endif
+std::string
+StrFormat(const char* format, ...);
+
+inline std::ostream& StrCatImp(std::ostream& out) BENCHMARK_NOEXCEPT {
+  return out;
+}
+
+template <class First, class... Rest>
+inline std::ostream& StrCatImp(std::ostream& out, First&& f, Rest&&... rest) {
+  out << std::forward<First>(f);
+  return StrCatImp(out, std::forward<Rest>(rest)...);
+}
+
+template <class... Args>
+inline std::string StrCat(Args&&... args) {
+  std::ostringstream ss;
+  StrCatImp(ss, std::forward<Args>(args)...);
+  return ss.str();
+}
+
+BENCHMARK_EXPORT
+std::vector<std::string> StrSplit(const std::string& str, char delim);
+
+// Disable lint checking for this block since it re-implements C functions.
+// NOLINTBEGIN
+#ifdef BENCHMARK_STL_ANDROID_GNUSTL
+/*
+ * GNU STL in Android NDK lacks support for some C++11 functions, including
+ * stoul, stoi, stod. We reimplement them here using C functions strtoul,
+ * strtol, strtod. Note that reimplemented functions are in benchmark::
+ * namespace, not std:: namespace.
+ */
+unsigned long stoul(const std::string& str, size_t* pos = nullptr,
+                    int base = 10);
+int stoi(const std::string& str, size_t* pos = nullptr, int base = 10);
+double stod(const std::string& str, size_t* pos = nullptr);
+#else
+using std::stod;   // NOLINT(misc-unused-using-decls)
+using std::stoi;   // NOLINT(misc-unused-using-decls)
+using std::stoul;  // NOLINT(misc-unused-using-decls)
+#endif
+// NOLINTEND
+
+}  // end namespace benchmark
+
+#endif  // BENCHMARK_STRING_UTIL_H_
diff --git a/leveldb_base/third_party/benchmark/src/sysinfo.cc b/leveldb_base/third_party/benchmark/src/sysinfo.cc
new file mode 100644
index 0000000..4578cb0
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/sysinfo.cc
@@ -0,0 +1,855 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "internal_macros.h"
+
+#ifdef BENCHMARK_OS_WINDOWS
+#include <shlwapi.h>
+#undef StrCat  // Don't let StrCat in string_util.h be renamed to lstrcatA
+#include <versionhelpers.h>
+#include <windows.h>
+
+#include <codecvt>
+#else
+#include <fcntl.h>
+#if !defined(BENCHMARK_OS_FUCHSIA) && !defined(BENCHMARK_OS_QURT)
+#include <sys/resource.h>
+#endif
+#include <sys/time.h>
+#include <sys/types.h>  // this header must be included before 'sys/sysctl.h' to avoid compilation error on FreeBSD
+#include <unistd.h>
+#if defined BENCHMARK_OS_FREEBSD || defined BENCHMARK_OS_MACOSX || \
+    defined BENCHMARK_OS_NETBSD || defined BENCHMARK_OS_OPENBSD || \
+    defined BENCHMARK_OS_DRAGONFLY
+#define BENCHMARK_HAS_SYSCTL
+#include <sys/sysctl.h>
+#endif
+#endif
+#if defined(BENCHMARK_OS_SOLARIS)
+#include <kstat.h>
+#include <netdb.h>
+#endif
+#if defined(BENCHMARK_OS_QNX)
+#include <sys/syspage.h>
+#endif
+#if defined(BENCHMARK_OS_QURT)
+#include <qurt.h>
+#endif
+#if defined(BENCHMARK_HAS_PTHREAD_AFFINITY)
+#include <pthread.h>
+#endif
+
+#include <algorithm>
+#include <array>
+#include <bitset>
+#include <cerrno>
+#include <climits>
+#include <cstdint>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <fstream>
+#include <iostream>
+#include <iterator>
+#include <limits>
+#include <locale>
+#include <memory>
+#include <random>
+#include <sstream>
+#include <utility>
+
+#include "benchmark/benchmark.h"
+#include "check.h"
+#include "cycleclock.h"
+#include "internal_macros.h"
+#include "log.h"
+#include "string_util.h"
+#include "timers.h"
+
+namespace benchmark {
+namespace {
+
+void PrintImp(std::ostream& out) { out << std::endl; }
+
+template <class First, class... Rest>
+void PrintImp(std::ostream& out, First&& f, Rest&&... rest) {
+  out << std::forward<First>(f);
+  PrintImp(out, std::forward<Rest>(rest)...);
+}
+
+template <class... Args>
+BENCHMARK_NORETURN void PrintErrorAndDie(Args&&... args) {
+  PrintImp(std::cerr, std::forward<Args>(args)...);
+  std::exit(EXIT_FAILURE);
+}
+
+#ifdef BENCHMARK_HAS_SYSCTL
+
+/// ValueUnion - A type used to correctly alias the byte-for-byte output of
+/// `sysctl` with the result type it's to be interpreted as.
+struct ValueUnion {
+  union DataT {
+    int32_t int32_value;
+    int64_t int64_value;
+    // For correct aliasing of union members from bytes.
+    char bytes[8];
+  };
+  using DataPtr = std::unique_ptr<DataT, decltype(&std::free)>;
+
+  // The size of the data union member + its trailing array size.
+  std::size_t size;
+  DataPtr buff;
+
+ public:
+  ValueUnion() : size(0), buff(nullptr, &std::free) {}
+
+  explicit ValueUnion(std::size_t buff_size)
+      : size(sizeof(DataT) + buff_size),
+        buff(::new (std::malloc(size)) DataT(), &std::free) {}
+
+  ValueUnion(ValueUnion&& other) = default;
+
+  explicit operator bool() const { return bool(buff); }
+
+  char* data() const { return buff->bytes; }
+
+  std::string GetAsString() const { return std::string(data()); }
+
+  int64_t GetAsInteger() const {
+    if (size == sizeof(buff->int32_value))
+      return buff->int32_value;
+    else if (size == sizeof(buff->int64_value))
+      return buff->int64_value;
+    BENCHMARK_UNREACHABLE();
+  }
+
+  template <class T, int N>
+  std::array<T, N> GetAsArray() {
+    const int arr_size = sizeof(T) * N;
+    BM_CHECK_LE(arr_size, size);
+    std::array<T, N> arr;
+    std::memcpy(arr.data(), data(), arr_size);
+    return arr;
+  }
+};
+
+ValueUnion GetSysctlImp(std::string const& name) {
+#if defined BENCHMARK_OS_OPENBSD
+  int mib[2];
+
+  mib[0] = CTL_HW;
+  if ((name == "hw.ncpu") || (name == "hw.cpuspeed")) {
+    ValueUnion buff(sizeof(int));
+
+    if (name == "hw.ncpu") {
+      mib[1] = HW_NCPU;
+    } else {
+      mib[1] = HW_CPUSPEED;
+    }
+
+    if (sysctl(mib, 2, buff.data(), &buff.Size, nullptr, 0) == -1) {
+      return ValueUnion();
+    }
+    return buff;
+  }
+  return ValueUnion();
+#else
+  std::size_t cur_buff_size = 0;
+  if (sysctlbyname(name.c_str(), nullptr, &cur_buff_size, nullptr, 0) == -1)
+    return ValueUnion();
+
+  ValueUnion buff(cur_buff_size);
+  if (sysctlbyname(name.c_str(), buff.data(), &buff.size, nullptr, 0) == 0)
+    return buff;
+  return ValueUnion();
+#endif
+}
+
+BENCHMARK_MAYBE_UNUSED
+bool GetSysctl(std::string const& name, std::string* out) {
+  out->clear();
+  auto buff = GetSysctlImp(name);
+  if (!buff) return false;
+  out->assign(buff.data());
+  return true;
+}
+
+template <class Tp,
+          class = typename std::enable_if<std::is_integral<Tp>::value>::type>
+bool GetSysctl(std::string const& name, Tp* out) {
+  *out = 0;
+  auto buff = GetSysctlImp(name);
+  if (!buff) return false;
+  *out = static_cast<Tp>(buff.GetAsInteger());
+  return true;
+}
+
+template <class Tp, size_t N>
+bool GetSysctl(std::string const& name, std::array<Tp, N>* out) {
+  auto buff = GetSysctlImp(name);
+  if (!buff) return false;
+  *out = buff.GetAsArray<Tp, N>();
+  return true;
+}
+#endif
+
+template <class ArgT>
+bool ReadFromFile(std::string const& fname, ArgT* arg) {
+  *arg = ArgT();
+  std::ifstream f(fname.c_str());
+  if (!f.is_open()) return false;
+  f >> *arg;
+  return f.good();
+}
+
+CPUInfo::Scaling CpuScaling(int num_cpus) {
+  // We don't have a valid CPU count, so don't even bother.
+  if (num_cpus <= 0) return CPUInfo::Scaling::UNKNOWN;
+#if defined(BENCHMARK_OS_QNX)
+  return CPUInfo::Scaling::UNKNOWN;
+#elif !defined(BENCHMARK_OS_WINDOWS)
+  // On Linux, the CPUfreq subsystem exposes CPU information as files on the
+  // local file system. If reading the exported files fails, then we may not be
+  // running on Linux, so we silently ignore all the read errors.
+  std::string res;
+  for (int cpu = 0; cpu < num_cpus; ++cpu) {
+    std::string governor_file =
+        StrCat("/sys/devices/system/cpu/cpu", cpu, "/cpufreq/scaling_governor");
+    if (ReadFromFile(governor_file, &res) && res != "performance")
+      return CPUInfo::Scaling::ENABLED;
+  }
+  return CPUInfo::Scaling::DISABLED;
+#else
+  return CPUInfo::Scaling::UNKNOWN;
+#endif
+}
+
+int CountSetBitsInCPUMap(std::string val) {
+  auto CountBits = [](std::string part) {
+    using CPUMask = std::bitset<sizeof(std::uintptr_t) * CHAR_BIT>;
+    part = "0x" + part;
+    CPUMask mask(benchmark::stoul(part, nullptr, 16));
+    return static_cast<int>(mask.count());
+  };
+  std::size_t pos;
+  int total = 0;
+  while ((pos = val.find(',')) != std::string::npos) {
+    total += CountBits(val.substr(0, pos));
+    val = val.substr(pos + 1);
+  }
+  if (!val.empty()) {
+    total += CountBits(val);
+  }
+  return total;
+}
+
+BENCHMARK_MAYBE_UNUSED
+std::vector<CPUInfo::CacheInfo> GetCacheSizesFromKVFS() {
+  std::vector<CPUInfo::CacheInfo> res;
+  std::string dir = "/sys/devices/system/cpu/cpu0/cache/";
+  int idx = 0;
+  while (true) {
+    CPUInfo::CacheInfo info;
+    std::string fpath = StrCat(dir, "index", idx++, "/");
+    std::ifstream f(StrCat(fpath, "size").c_str());
+    if (!f.is_open()) break;
+    std::string suffix;
+    f >> info.size;
+    if (f.fail())
+      PrintErrorAndDie("Failed while reading file '", fpath, "size'");
+    if (f.good()) {
+      f >> suffix;
+      if (f.bad())
+        PrintErrorAndDie(
+            "Invalid cache size format: failed to read size suffix");
+      else if (f && suffix != "K")
+        PrintErrorAndDie("Invalid cache size format: Expected bytes ", suffix);
+      else if (suffix == "K")
+        info.size *= 1024;
+    }
+    if (!ReadFromFile(StrCat(fpath, "type"), &info.type))
+      PrintErrorAndDie("Failed to read from file ", fpath, "type");
+    if (!ReadFromFile(StrCat(fpath, "level"), &info.level))
+      PrintErrorAndDie("Failed to read from file ", fpath, "level");
+    std::string map_str;
+    if (!ReadFromFile(StrCat(fpath, "shared_cpu_map"), &map_str))
+      PrintErrorAndDie("Failed to read from file ", fpath, "shared_cpu_map");
+    info.num_sharing = CountSetBitsInCPUMap(map_str);
+    res.push_back(info);
+  }
+
+  return res;
+}
+
+#ifdef BENCHMARK_OS_MACOSX
+std::vector<CPUInfo::CacheInfo> GetCacheSizesMacOSX() {
+  std::vector<CPUInfo::CacheInfo> res;
+  std::array<int, 4> cache_counts{{0, 0, 0, 0}};
+  GetSysctl("hw.cacheconfig", &cache_counts);
+
+  struct {
+    std::string name;
+    std::string type;
+    int level;
+    int num_sharing;
+  } cases[] = {{"hw.l1dcachesize", "Data", 1, cache_counts[1]},
+               {"hw.l1icachesize", "Instruction", 1, cache_counts[1]},
+               {"hw.l2cachesize", "Unified", 2, cache_counts[2]},
+               {"hw.l3cachesize", "Unified", 3, cache_counts[3]}};
+  for (auto& c : cases) {
+    int val;
+    if (!GetSysctl(c.name, &val)) continue;
+    CPUInfo::CacheInfo info;
+    info.type = c.type;
+    info.level = c.level;
+    info.size = val;
+    info.num_sharing = c.num_sharing;
+    res.push_back(std::move(info));
+  }
+  return res;
+}
+#elif defined(BENCHMARK_OS_WINDOWS)
+std::vector<CPUInfo::CacheInfo> GetCacheSizesWindows() {
+  std::vector<CPUInfo::CacheInfo> res;
+  DWORD buffer_size = 0;
+  using PInfo = SYSTEM_LOGICAL_PROCESSOR_INFORMATION;
+  using CInfo = CACHE_DESCRIPTOR;
+
+  using UPtr = std::unique_ptr<PInfo, decltype(&std::free)>;
+  GetLogicalProcessorInformation(nullptr, &buffer_size);
+  UPtr buff((PInfo*)malloc(buffer_size), &std::free);
+  if (!GetLogicalProcessorInformation(buff.get(), &buffer_size))
+    PrintErrorAndDie("Failed during call to GetLogicalProcessorInformation: ",
+                     GetLastError());
+
+  PInfo* it = buff.get();
+  PInfo* end = buff.get() + (buffer_size / sizeof(PInfo));
+
+  for (; it != end; ++it) {
+    if (it->Relationship != RelationCache) continue;
+    using BitSet = std::bitset<sizeof(ULONG_PTR) * CHAR_BIT>;
+    BitSet b(it->ProcessorMask);
+    // To prevent duplicates, only consider caches where CPU 0 is specified
+    if (!b.test(0)) continue;
+    const CInfo& cache = it->Cache;
+    CPUInfo::CacheInfo C;
+    C.num_sharing = static_cast<int>(b.count());
+    C.level = cache.Level;
+    C.size = cache.Size;
+    C.type = "Unknown";
+    switch (cache.Type) {
+      case CacheUnified:
+        C.type = "Unified";
+        break;
+      case CacheInstruction:
+        C.type = "Instruction";
+        break;
+      case CacheData:
+        C.type = "Data";
+        break;
+      case CacheTrace:
+        C.type = "Trace";
+        break;
+    }
+    res.push_back(C);
+  }
+  return res;
+}
+#elif BENCHMARK_OS_QNX
+std::vector<CPUInfo::CacheInfo> GetCacheSizesQNX() {
+  std::vector<CPUInfo::CacheInfo> res;
+  struct cacheattr_entry* cache = SYSPAGE_ENTRY(cacheattr);
+  uint32_t const elsize = SYSPAGE_ELEMENT_SIZE(cacheattr);
+  int num = SYSPAGE_ENTRY_SIZE(cacheattr) / elsize;
+  for (int i = 0; i < num; ++i) {
+    CPUInfo::CacheInfo info;
+    switch (cache->flags) {
+      case CACHE_FLAG_INSTR:
+        info.type = "Instruction";
+        info.level = 1;
+        break;
+      case CACHE_FLAG_DATA:
+        info.type = "Data";
+        info.level = 1;
+        break;
+      case CACHE_FLAG_UNIFIED:
+        info.type = "Unified";
+        info.level = 2;
+        break;
+      case CACHE_FLAG_SHARED:
+        info.type = "Shared";
+        info.level = 3;
+        break;
+      default:
+        continue;
+        break;
+    }
+    info.size = cache->line_size * cache->num_lines;
+    info.num_sharing = 0;
+    res.push_back(std::move(info));
+    cache = SYSPAGE_ARRAY_ADJ_OFFSET(cacheattr, cache, elsize);
+  }
+  return res;
+}
+#endif
+
+std::vector<CPUInfo::CacheInfo> GetCacheSizes() {
+#ifdef BENCHMARK_OS_MACOSX
+  return GetCacheSizesMacOSX();
+#elif defined(BENCHMARK_OS_WINDOWS)
+  return GetCacheSizesWindows();
+#elif defined(BENCHMARK_OS_QNX)
+  return GetCacheSizesQNX();
+#elif defined(BENCHMARK_OS_QURT)
+  return std::vector<CPUInfo::CacheInfo>();
+#else
+  return GetCacheSizesFromKVFS();
+#endif
+}
+
+std::string GetSystemName() {
+#if defined(BENCHMARK_OS_WINDOWS)
+  std::string str;
+  static constexpr int COUNT = MAX_COMPUTERNAME_LENGTH + 1;
+  TCHAR hostname[COUNT] = {'\0'};
+  DWORD DWCOUNT = COUNT;
+  if (!GetComputerName(hostname, &DWCOUNT)) return std::string("");
+#ifndef UNICODE
+  str = std::string(hostname, DWCOUNT);
+#else
+  // `WideCharToMultiByte` returns `0` when conversion fails.
+  int len = WideCharToMultiByte(CP_UTF8, WC_ERR_INVALID_CHARS, hostname,
+                                DWCOUNT, NULL, 0, NULL, NULL);
+  str.resize(len);
+  WideCharToMultiByte(CP_UTF8, WC_ERR_INVALID_CHARS, hostname, DWCOUNT, &str[0],
+                      str.size(), NULL, NULL);
+#endif
+  return str;
+#elif defined(BENCHMARK_OS_QURT)
+  std::string str = "Hexagon DSP";
+  qurt_arch_version_t arch_version_struct;
+  if (qurt_sysenv_get_arch_version(&arch_version_struct) == QURT_EOK) {
+    str += " v";
+    str += std::to_string(arch_version_struct.arch_version);
+  }
+  return str;
+#else
+#ifndef HOST_NAME_MAX
+#ifdef BENCHMARK_HAS_SYSCTL  // BSD/Mac doesn't have HOST_NAME_MAX defined
+#define HOST_NAME_MAX 64
+#elif defined(BENCHMARK_OS_NACL)
+#define HOST_NAME_MAX 64
+#elif defined(BENCHMARK_OS_QNX)
+#define HOST_NAME_MAX 154
+#elif defined(BENCHMARK_OS_RTEMS)
+#define HOST_NAME_MAX 256
+#elif defined(BENCHMARK_OS_SOLARIS)
+#define HOST_NAME_MAX MAXHOSTNAMELEN
+#else
+#pragma message("HOST_NAME_MAX not defined. using 64")
+#define HOST_NAME_MAX 64
+#endif
+#endif  // def HOST_NAME_MAX
+  char hostname[HOST_NAME_MAX];
+  int retVal = gethostname(hostname, HOST_NAME_MAX);
+  if (retVal != 0) return std::string("");
+  return std::string(hostname);
+#endif  // Catch-all POSIX block.
+}
+
+int GetNumCPUs() {
+#ifdef BENCHMARK_HAS_SYSCTL
+  int num_cpu = -1;
+  if (GetSysctl("hw.ncpu", &num_cpu)) return num_cpu;
+  fprintf(stderr, "Err: %s\n", strerror(errno));
+  std::exit(EXIT_FAILURE);
+#elif defined(BENCHMARK_OS_WINDOWS)
+  SYSTEM_INFO sysinfo;
+  // Use memset as opposed to = {} to avoid GCC missing initializer false
+  // positives.
+  std::memset(&sysinfo, 0, sizeof(SYSTEM_INFO));
+  GetSystemInfo(&sysinfo);
+  return sysinfo.dwNumberOfProcessors;  // number of logical
+                                        // processors in the current
+                                        // group
+#elif defined(BENCHMARK_OS_SOLARIS)
+  // Returns -1 in case of a failure.
+  long num_cpu = sysconf(_SC_NPROCESSORS_ONLN);
+  if (num_cpu < 0) {
+    fprintf(stderr, "sysconf(_SC_NPROCESSORS_ONLN) failed with error: %s\n",
+            strerror(errno));
+  }
+  return (int)num_cpu;
+#elif defined(BENCHMARK_OS_QNX)
+  return static_cast<int>(_syspage_ptr->num_cpu);
+#elif defined(BENCHMARK_OS_QURT)
+  qurt_sysenv_max_hthreads_t hardware_threads;
+  if (qurt_sysenv_get_max_hw_threads(&hardware_threads) != QURT_EOK) {
+    hardware_threads.max_hthreads = 1;
+  }
+  return hardware_threads.max_hthreads;
+#else
+  int num_cpus = 0;
+  int max_id = -1;
+  std::ifstream f("/proc/cpuinfo");
+  if (!f.is_open()) {
+    std::cerr << "failed to open /proc/cpuinfo\n";
+    return -1;
+  }
+  const std::string Key = "processor";
+  std::string ln;
+  while (std::getline(f, ln)) {
+    if (ln.empty()) continue;
+    std::size_t split_idx = ln.find(':');
+    std::string value;
+#if defined(__s390__)
+    // s390 has another format in /proc/cpuinfo
+    // it needs to be parsed differently
+    if (split_idx != std::string::npos)
+      value = ln.substr(Key.size() + 1, split_idx - Key.size() - 1);
+#else
+    if (split_idx != std::string::npos) value = ln.substr(split_idx + 1);
+#endif
+    if (ln.size() >= Key.size() && ln.compare(0, Key.size(), Key) == 0) {
+      num_cpus++;
+      if (!value.empty()) {
+        const int cur_id = benchmark::stoi(value);
+        max_id = std::max(cur_id, max_id);
+      }
+    }
+  }
+  if (f.bad()) {
+    std::cerr << "Failure reading /proc/cpuinfo\n";
+    return -1;
+  }
+  if (!f.eof()) {
+    std::cerr << "Failed to read to end of /proc/cpuinfo\n";
+    return -1;
+  }
+  f.close();
+
+  if ((max_id + 1) != num_cpus) {
+    fprintf(stderr,
+            "CPU ID assignments in /proc/cpuinfo seem messed up."
+            " This is usually caused by a bad BIOS.\n");
+  }
+  return num_cpus;
+#endif
+  BENCHMARK_UNREACHABLE();
+}
+
+class ThreadAffinityGuard final {
+ public:
+  ThreadAffinityGuard() : reset_affinity(SetAffinity()) {
+    if (!reset_affinity)
+      std::cerr << "***WARNING*** Failed to set thread affinity. Estimated CPU "
+                   "frequency may be incorrect."
+                << std::endl;
+  }
+
+  ~ThreadAffinityGuard() {
+    if (!reset_affinity) return;
+
+#if defined(BENCHMARK_HAS_PTHREAD_AFFINITY)
+    int ret = pthread_setaffinity_np(self, sizeof(previous_affinity),
+                                     &previous_affinity);
+    if (ret == 0) return;
+#elif defined(BENCHMARK_OS_WINDOWS_WIN32)
+    DWORD_PTR ret = SetThreadAffinityMask(self, previous_affinity);
+    if (ret != 0) return;
+#endif  // def BENCHMARK_HAS_PTHREAD_AFFINITY
+    PrintErrorAndDie("Failed to reset thread affinity");
+  }
+
+  ThreadAffinityGuard(ThreadAffinityGuard&&) = delete;
+  ThreadAffinityGuard(const ThreadAffinityGuard&) = delete;
+  ThreadAffinityGuard& operator=(ThreadAffinityGuard&&) = delete;
+  ThreadAffinityGuard& operator=(const ThreadAffinityGuard&) = delete;
+
+ private:
+  bool SetAffinity() {
+#if defined(BENCHMARK_HAS_PTHREAD_AFFINITY)
+    int ret;
+    self = pthread_self();
+    ret = pthread_getaffinity_np(self, sizeof(previous_affinity),
+                                 &previous_affinity);
+    if (ret != 0) return false;
+
+    cpu_set_t affinity;
+    memcpy(&affinity, &previous_affinity, sizeof(affinity));
+
+    bool is_first_cpu = true;
+
+    for (int i = 0; i < CPU_SETSIZE; ++i)
+      if (CPU_ISSET(i, &affinity)) {
+        if (is_first_cpu)
+          is_first_cpu = false;
+        else
+          CPU_CLR(i, &affinity);
+      }
+
+    if (is_first_cpu) return false;
+
+    ret = pthread_setaffinity_np(self, sizeof(affinity), &affinity);
+    return ret == 0;
+#elif defined(BENCHMARK_OS_WINDOWS_WIN32)
+    self = GetCurrentThread();
+    DWORD_PTR mask = static_cast<DWORD_PTR>(1) << GetCurrentProcessorNumber();
+    previous_affinity = SetThreadAffinityMask(self, mask);
+    return previous_affinity != 0;
+#else
+    return false;
+#endif  // def BENCHMARK_HAS_PTHREAD_AFFINITY
+  }
+
+#if defined(BENCHMARK_HAS_PTHREAD_AFFINITY)
+  pthread_t self;
+  cpu_set_t previous_affinity;
+#elif defined(BENCHMARK_OS_WINDOWS_WIN32)
+  HANDLE self;
+  DWORD_PTR previous_affinity;
+#endif  // def BENCHMARK_HAS_PTHREAD_AFFINITY
+  bool reset_affinity;
+};
+
+double GetCPUCyclesPerSecond(CPUInfo::Scaling scaling) {
+  // Currently, scaling is only used on linux path here,
+  // suppress diagnostics about it being unused on other paths.
+  (void)scaling;
+
+#if defined BENCHMARK_OS_LINUX || defined BENCHMARK_OS_CYGWIN
+  long freq;
+
+  // If the kernel is exporting the tsc frequency use that. There are issues
+  // where cpuinfo_max_freq cannot be relied on because the BIOS may be
+  // exporintg an invalid p-state (on x86) or p-states may be used to put the
+  // processor in a new mode (turbo mode). Essentially, those frequencies
+  // cannot always be relied upon. The same reasons apply to /proc/cpuinfo as
+  // well.
+  if (ReadFromFile("/sys/devices/system/cpu/cpu0/tsc_freq_khz", &freq)
+      // If CPU scaling is disabled, use the *current* frequency.
+      // Note that we specifically don't want to read cpuinfo_cur_freq,
+      // because it is only readable by root.
+      || (scaling == CPUInfo::Scaling::DISABLED &&
+          ReadFromFile("/sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq",
+                       &freq))
+      // Otherwise, if CPU scaling may be in effect, we want to use
+      // the *maximum* frequency, not whatever CPU speed some random processor
+      // happens to be using now.
+      || ReadFromFile("/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq",
+                      &freq)) {
+    // The value is in kHz (as the file name suggests).  For example, on a
+    // 2GHz warpstation, the file contains the value "2000000".
+    return freq * 1000.0;
+  }
+
+  const double error_value = -1;
+  double bogo_clock = error_value;
+
+  std::ifstream f("/proc/cpuinfo");
+  if (!f.is_open()) {
+    std::cerr << "failed to open /proc/cpuinfo\n";
+    return error_value;
+  }
+
+  auto StartsWithKey = [](std::string const& Value, std::string const& Key) {
+    if (Key.size() > Value.size()) return false;
+    auto Cmp = [&](char X, char Y) {
+      return std::tolower(X) == std::tolower(Y);
+    };
+    return std::equal(Key.begin(), Key.end(), Value.begin(), Cmp);
+  };
+
+  std::string ln;
+  while (std::getline(f, ln)) {
+    if (ln.empty()) continue;
+    std::size_t split_idx = ln.find(':');
+    std::string value;
+    if (split_idx != std::string::npos) value = ln.substr(split_idx + 1);
+    // When parsing the "cpu MHz" and "bogomips" (fallback) entries, we only
+    // accept positive values. Some environments (virtual machines) report zero,
+    // which would cause infinite looping in WallTime_Init.
+    if (StartsWithKey(ln, "cpu MHz")) {
+      if (!value.empty()) {
+        double cycles_per_second = benchmark::stod(value) * 1000000.0;
+        if (cycles_per_second > 0) return cycles_per_second;
+      }
+    } else if (StartsWithKey(ln, "bogomips")) {
+      if (!value.empty()) {
+        bogo_clock = benchmark::stod(value) * 1000000.0;
+        if (bogo_clock < 0.0) bogo_clock = error_value;
+      }
+    }
+  }
+  if (f.bad()) {
+    std::cerr << "Failure reading /proc/cpuinfo\n";
+    return error_value;
+  }
+  if (!f.eof()) {
+    std::cerr << "Failed to read to end of /proc/cpuinfo\n";
+    return error_value;
+  }
+  f.close();
+  // If we found the bogomips clock, but nothing better, we'll use it (but
+  // we're not happy about it); otherwise, fallback to the rough estimation
+  // below.
+  if (bogo_clock >= 0.0) return bogo_clock;
+
+#elif defined BENCHMARK_HAS_SYSCTL
+  constexpr auto* freqStr =
+#if defined(BENCHMARK_OS_FREEBSD) || defined(BENCHMARK_OS_NETBSD)
+      "machdep.tsc_freq";
+#elif defined BENCHMARK_OS_OPENBSD
+      "hw.cpuspeed";
+#elif defined BENCHMARK_OS_DRAGONFLY
+      "hw.tsc_frequency";
+#else
+      "hw.cpufrequency";
+#endif
+  unsigned long long hz = 0;
+#if defined BENCHMARK_OS_OPENBSD
+  if (GetSysctl(freqStr, &hz)) return hz * 1000000;
+#else
+  if (GetSysctl(freqStr, &hz)) return hz;
+#endif
+  fprintf(stderr, "Unable to determine clock rate from sysctl: %s: %s\n",
+          freqStr, strerror(errno));
+  fprintf(stderr,
+          "This does not affect benchmark measurements, only the "
+          "metadata output.\n");
+
+#elif defined BENCHMARK_OS_WINDOWS_WIN32
+  // In NT, read MHz from the registry. If we fail to do so or we're in win9x
+  // then make a crude estimate.
+  DWORD data, data_size = sizeof(data);
+  if (IsWindowsXPOrGreater() &&
+      SUCCEEDED(
+          SHGetValueA(HKEY_LOCAL_MACHINE,
+                      "HARDWARE\\DESCRIPTION\\System\\CentralProcessor\\0",
+                      "~MHz", nullptr, &data, &data_size)))
+    return static_cast<double>((int64_t)data *
+                               (int64_t)(1000 * 1000));  // was mhz
+#elif defined(BENCHMARK_OS_SOLARIS)
+  kstat_ctl_t* kc = kstat_open();
+  if (!kc) {
+    std::cerr << "failed to open /dev/kstat\n";
+    return -1;
+  }
+  kstat_t* ksp = kstat_lookup(kc, const_cast<char*>("cpu_info"), -1,
+                              const_cast<char*>("cpu_info0"));
+  if (!ksp) {
+    std::cerr << "failed to lookup in /dev/kstat\n";
+    return -1;
+  }
+  if (kstat_read(kc, ksp, NULL) < 0) {
+    std::cerr << "failed to read from /dev/kstat\n";
+    return -1;
+  }
+  kstat_named_t* knp = (kstat_named_t*)kstat_data_lookup(
+      ksp, const_cast<char*>("current_clock_Hz"));
+  if (!knp) {
+    std::cerr << "failed to lookup data in /dev/kstat\n";
+    return -1;
+  }
+  if (knp->data_type != KSTAT_DATA_UINT64) {
+    std::cerr << "current_clock_Hz is of unexpected data type: "
+              << knp->data_type << "\n";
+    return -1;
+  }
+  double clock_hz = knp->value.ui64;
+  kstat_close(kc);
+  return clock_hz;
+#elif defined(BENCHMARK_OS_QNX)
+  return static_cast<double>((int64_t)(SYSPAGE_ENTRY(cpuinfo)->speed) *
+                             (int64_t)(1000 * 1000));
+#elif defined(BENCHMARK_OS_QURT)
+  // QuRT doesn't provide any API to query Hexagon frequency.
+  return 1000000000;
+#endif
+  // If we've fallen through, attempt to roughly estimate the CPU clock rate.
+
+  // Make sure to use the same cycle counter when starting and stopping the
+  // cycle timer. We just pin the current thread to a cpu in the previous
+  // affinity set.
+  ThreadAffinityGuard affinity_guard;
+
+  static constexpr double estimate_time_s = 1.0;
+  const double start_time = ChronoClockNow();
+  const auto start_ticks = cycleclock::Now();
+
+  // Impose load instead of calling sleep() to make sure the cycle counter
+  // works.
+  using PRNG = std::minstd_rand;
+  using Result = PRNG::result_type;
+  PRNG rng(static_cast<Result>(start_ticks));
+
+  Result state = 0;
+
+  do {
+    static constexpr size_t batch_size = 10000;
+    rng.discard(batch_size);
+    state += rng();
+
+  } while (ChronoClockNow() - start_time < estimate_time_s);
+
+  DoNotOptimize(state);
+
+  const auto end_ticks = cycleclock::Now();
+  const double end_time = ChronoClockNow();
+
+  return static_cast<double>(end_ticks - start_ticks) / (end_time - start_time);
+  // Reset the affinity of current thread when the lifetime of affinity_guard
+  // ends.
+}
+
+std::vector<double> GetLoadAvg() {
+#if (defined BENCHMARK_OS_FREEBSD || defined(BENCHMARK_OS_LINUX) ||     \
+     defined BENCHMARK_OS_MACOSX || defined BENCHMARK_OS_NETBSD ||      \
+     defined BENCHMARK_OS_OPENBSD || defined BENCHMARK_OS_DRAGONFLY) && \
+    !defined(__ANDROID__)
+  static constexpr int kMaxSamples = 3;
+  std::vector<double> res(kMaxSamples, 0.0);
+  const int nelem = getloadavg(res.data(), kMaxSamples);
+  if (nelem < 1) {
+    res.clear();
+  } else {
+    res.resize(nelem);
+  }
+  return res;
+#else
+  return {};
+#endif
+}
+
+}  // end namespace
+
+const CPUInfo& CPUInfo::Get() {
+  static const CPUInfo* info = new CPUInfo();
+  return *info;
+}
+
+CPUInfo::CPUInfo()
+    : num_cpus(GetNumCPUs()),
+      scaling(CpuScaling(num_cpus)),
+      cycles_per_second(GetCPUCyclesPerSecond(scaling)),
+      caches(GetCacheSizes()),
+      load_avg(GetLoadAvg()) {}
+
+const SystemInfo& SystemInfo::Get() {
+  static const SystemInfo* info = new SystemInfo();
+  return *info;
+}
+
+SystemInfo::SystemInfo() : name(GetSystemName()) {}
+}  // end namespace benchmark
diff --git a/leveldb_base/third_party/benchmark/src/thread_manager.h b/leveldb_base/third_party/benchmark/src/thread_manager.h
new file mode 100644
index 0000000..819b3c4
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/thread_manager.h
@@ -0,0 +1,63 @@
+#ifndef BENCHMARK_THREAD_MANAGER_H
+#define BENCHMARK_THREAD_MANAGER_H
+
+#include <atomic>
+
+#include "benchmark/benchmark.h"
+#include "mutex.h"
+
+namespace benchmark {
+namespace internal {
+
+class ThreadManager {
+ public:
+  explicit ThreadManager(int num_threads)
+      : alive_threads_(num_threads), start_stop_barrier_(num_threads) {}
+
+  Mutex& GetBenchmarkMutex() const RETURN_CAPABILITY(benchmark_mutex_) {
+    return benchmark_mutex_;
+  }
+
+  bool StartStopBarrier() EXCLUDES(end_cond_mutex_) {
+    return start_stop_barrier_.wait();
+  }
+
+  void NotifyThreadComplete() EXCLUDES(end_cond_mutex_) {
+    start_stop_barrier_.removeThread();
+    if (--alive_threads_ == 0) {
+      MutexLock lock(end_cond_mutex_);
+      end_condition_.notify_all();
+    }
+  }
+
+  void WaitForAllThreads() EXCLUDES(end_cond_mutex_) {
+    MutexLock lock(end_cond_mutex_);
+    end_condition_.wait(lock.native_handle(),
+                        [this]() { return alive_threads_ == 0; });
+  }
+
+  struct Result {
+    IterationCount iterations = 0;
+    double real_time_used = 0;
+    double cpu_time_used = 0;
+    double manual_time_used = 0;
+    int64_t complexity_n = 0;
+    std::string report_label_;
+    std::string skip_message_;
+    internal::Skipped skipped_ = internal::NotSkipped;
+    UserCounters counters;
+  };
+  GUARDED_BY(GetBenchmarkMutex()) Result results;
+
+ private:
+  mutable Mutex benchmark_mutex_;
+  std::atomic<int> alive_threads_;
+  Barrier start_stop_barrier_;
+  Mutex end_cond_mutex_;
+  Condition end_condition_;
+};
+
+}  // namespace internal
+}  // namespace benchmark
+
+#endif  // BENCHMARK_THREAD_MANAGER_H
diff --git a/leveldb_base/third_party/benchmark/src/thread_timer.h b/leveldb_base/third_party/benchmark/src/thread_timer.h
new file mode 100644
index 0000000..eb23f59
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/thread_timer.h
@@ -0,0 +1,86 @@
+#ifndef BENCHMARK_THREAD_TIMER_H
+#define BENCHMARK_THREAD_TIMER_H
+
+#include "check.h"
+#include "timers.h"
+
+namespace benchmark {
+namespace internal {
+
+class ThreadTimer {
+  explicit ThreadTimer(bool measure_process_cpu_time_)
+      : measure_process_cpu_time(measure_process_cpu_time_) {}
+
+ public:
+  static ThreadTimer Create() {
+    return ThreadTimer(/*measure_process_cpu_time_=*/false);
+  }
+  static ThreadTimer CreateProcessCpuTime() {
+    return ThreadTimer(/*measure_process_cpu_time_=*/true);
+  }
+
+  // Called by each thread
+  void StartTimer() {
+    running_ = true;
+    start_real_time_ = ChronoClockNow();
+    start_cpu_time_ = ReadCpuTimerOfChoice();
+  }
+
+  // Called by each thread
+  void StopTimer() {
+    BM_CHECK(running_);
+    running_ = false;
+    real_time_used_ += ChronoClockNow() - start_real_time_;
+    // Floating point error can result in the subtraction producing a negative
+    // time. Guard against that.
+    cpu_time_used_ +=
+        std::max<double>(ReadCpuTimerOfChoice() - start_cpu_time_, 0);
+  }
+
+  // Called by each thread
+  void SetIterationTime(double seconds) { manual_time_used_ += seconds; }
+
+  bool running() const { return running_; }
+
+  // REQUIRES: timer is not running
+  double real_time_used() const {
+    BM_CHECK(!running_);
+    return real_time_used_;
+  }
+
+  // REQUIRES: timer is not running
+  double cpu_time_used() const {
+    BM_CHECK(!running_);
+    return cpu_time_used_;
+  }
+
+  // REQUIRES: timer is not running
+  double manual_time_used() const {
+    BM_CHECK(!running_);
+    return manual_time_used_;
+  }
+
+ private:
+  double ReadCpuTimerOfChoice() const {
+    if (measure_process_cpu_time) return ProcessCPUUsage();
+    return ThreadCPUUsage();
+  }
+
+  // should the thread, or the process, time be measured?
+  const bool measure_process_cpu_time;
+
+  bool running_ = false;        // Is the timer running
+  double start_real_time_ = 0;  // If running_
+  double start_cpu_time_ = 0;   // If running_
+
+  // Accumulated time so far (does not contain current slice if running_)
+  double real_time_used_ = 0;
+  double cpu_time_used_ = 0;
+  // Manually set iteration time. User sets this with SetIterationTime(seconds).
+  double manual_time_used_ = 0;
+};
+
+}  // namespace internal
+}  // namespace benchmark
+
+#endif  // BENCHMARK_THREAD_TIMER_H
diff --git a/leveldb_base/third_party/benchmark/src/timers.cc b/leveldb_base/third_party/benchmark/src/timers.cc
new file mode 100644
index 0000000..b23feea
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/timers.cc
@@ -0,0 +1,272 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "timers.h"
+
+#include "internal_macros.h"
+
+#ifdef BENCHMARK_OS_WINDOWS
+#include <shlwapi.h>
+#undef StrCat  // Don't let StrCat in string_util.h be renamed to lstrcatA
+#include <versionhelpers.h>
+#include <windows.h>
+#else
+#include <fcntl.h>
+#if !defined(BENCHMARK_OS_FUCHSIA) && !defined(BENCHMARK_OS_QURT)
+#include <sys/resource.h>
+#endif
+#include <sys/time.h>
+#include <sys/types.h>  // this header must be included before 'sys/sysctl.h' to avoid compilation error on FreeBSD
+#include <unistd.h>
+#if defined BENCHMARK_OS_FREEBSD || defined BENCHMARK_OS_DRAGONFLY || \
+    defined BENCHMARK_OS_MACOSX
+#include <sys/sysctl.h>
+#endif
+#if defined(BENCHMARK_OS_MACOSX)
+#include <mach/mach_init.h>
+#include <mach/mach_port.h>
+#include <mach/thread_act.h>
+#endif
+#if defined(BENCHMARK_OS_QURT)
+#include <qurt.h>
+#endif
+#endif
+
+#ifdef BENCHMARK_OS_EMSCRIPTEN
+#include <emscripten.h>
+#endif
+
+#include <cerrno>
+#include <cstdint>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <ctime>
+#include <iostream>
+#include <limits>
+#include <mutex>
+
+#include "check.h"
+#include "log.h"
+#include "string_util.h"
+
+namespace benchmark {
+
+// Suppress unused warnings on helper functions.
+#if defined(__GNUC__)
+#pragma GCC diagnostic ignored "-Wunused-function"
+#endif
+#if defined(__NVCOMPILER)
+#pragma diag_suppress declared_but_not_referenced
+#endif
+
+namespace {
+#if defined(BENCHMARK_OS_WINDOWS)
+double MakeTime(FILETIME const& kernel_time, FILETIME const& user_time) {
+  ULARGE_INTEGER kernel;
+  ULARGE_INTEGER user;
+  kernel.HighPart = kernel_time.dwHighDateTime;
+  kernel.LowPart = kernel_time.dwLowDateTime;
+  user.HighPart = user_time.dwHighDateTime;
+  user.LowPart = user_time.dwLowDateTime;
+  return (static_cast<double>(kernel.QuadPart) +
+          static_cast<double>(user.QuadPart)) *
+         1e-7;
+}
+#elif !defined(BENCHMARK_OS_FUCHSIA) && !defined(BENCHMARK_OS_QURT)
+double MakeTime(struct rusage const& ru) {
+  return (static_cast<double>(ru.ru_utime.tv_sec) +
+          static_cast<double>(ru.ru_utime.tv_usec) * 1e-6 +
+          static_cast<double>(ru.ru_stime.tv_sec) +
+          static_cast<double>(ru.ru_stime.tv_usec) * 1e-6);
+}
+#endif
+#if defined(BENCHMARK_OS_MACOSX)
+double MakeTime(thread_basic_info_data_t const& info) {
+  return (static_cast<double>(info.user_time.seconds) +
+          static_cast<double>(info.user_time.microseconds) * 1e-6 +
+          static_cast<double>(info.system_time.seconds) +
+          static_cast<double>(info.system_time.microseconds) * 1e-6);
+}
+#endif
+#if defined(CLOCK_PROCESS_CPUTIME_ID) || defined(CLOCK_THREAD_CPUTIME_ID)
+double MakeTime(struct timespec const& ts) {
+  return ts.tv_sec + (static_cast<double>(ts.tv_nsec) * 1e-9);
+}
+#endif
+
+BENCHMARK_NORETURN static void DiagnoseAndExit(const char* msg) {
+  std::cerr << "ERROR: " << msg << std::endl;
+  std::exit(EXIT_FAILURE);
+}
+
+}  // end namespace
+
+double ProcessCPUUsage() {
+#if defined(BENCHMARK_OS_WINDOWS)
+  HANDLE proc = GetCurrentProcess();
+  FILETIME creation_time;
+  FILETIME exit_time;
+  FILETIME kernel_time;
+  FILETIME user_time;
+  if (GetProcessTimes(proc, &creation_time, &exit_time, &kernel_time,
+                      &user_time))
+    return MakeTime(kernel_time, user_time);
+  DiagnoseAndExit("GetProccessTimes() failed");
+#elif defined(BENCHMARK_OS_QURT)
+  return static_cast<double>(
+             qurt_timer_timetick_to_us(qurt_timer_get_ticks())) *
+         1.0e-6;
+#elif defined(BENCHMARK_OS_EMSCRIPTEN)
+  // clock_gettime(CLOCK_PROCESS_CPUTIME_ID, ...) returns 0 on Emscripten.
+  // Use Emscripten-specific API. Reported CPU time would be exactly the
+  // same as total time, but this is ok because there aren't long-latency
+  // synchronous system calls in Emscripten.
+  return emscripten_get_now() * 1e-3;
+#elif defined(CLOCK_PROCESS_CPUTIME_ID) && !defined(BENCHMARK_OS_MACOSX)
+  // FIXME We want to use clock_gettime, but its not available in MacOS 10.11.
+  // See https://github.com/google/benchmark/pull/292
+  struct timespec spec;
+  if (clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &spec) == 0)
+    return MakeTime(spec);
+  DiagnoseAndExit("clock_gettime(CLOCK_PROCESS_CPUTIME_ID, ...) failed");
+#else
+  struct rusage ru;
+  if (getrusage(RUSAGE_SELF, &ru) == 0) return MakeTime(ru);
+  DiagnoseAndExit("getrusage(RUSAGE_SELF, ...) failed");
+#endif
+}
+
+double ThreadCPUUsage() {
+#if defined(BENCHMARK_OS_WINDOWS)
+  HANDLE this_thread = GetCurrentThread();
+  FILETIME creation_time;
+  FILETIME exit_time;
+  FILETIME kernel_time;
+  FILETIME user_time;
+  GetThreadTimes(this_thread, &creation_time, &exit_time, &kernel_time,
+                 &user_time);
+  return MakeTime(kernel_time, user_time);
+#elif defined(BENCHMARK_OS_QURT)
+  return static_cast<double>(
+             qurt_timer_timetick_to_us(qurt_timer_get_ticks())) *
+         1.0e-6;
+#elif defined(BENCHMARK_OS_MACOSX)
+  // FIXME We want to use clock_gettime, but its not available in MacOS 10.11.
+  // See https://github.com/google/benchmark/pull/292
+  mach_msg_type_number_t count = THREAD_BASIC_INFO_COUNT;
+  thread_basic_info_data_t info;
+  mach_port_t thread = pthread_mach_thread_np(pthread_self());
+  if (thread_info(thread, THREAD_BASIC_INFO,
+                  reinterpret_cast<thread_info_t>(&info),
+                  &count) == KERN_SUCCESS) {
+    return MakeTime(info);
+  }
+  DiagnoseAndExit("ThreadCPUUsage() failed when evaluating thread_info");
+#elif defined(BENCHMARK_OS_EMSCRIPTEN)
+  // Emscripten doesn't support traditional threads
+  return ProcessCPUUsage();
+#elif defined(BENCHMARK_OS_RTEMS)
+  // RTEMS doesn't support CLOCK_THREAD_CPUTIME_ID. See
+  // https://github.com/RTEMS/rtems/blob/master/cpukit/posix/src/clockgettime.c
+  return ProcessCPUUsage();
+#elif defined(BENCHMARK_OS_SOLARIS)
+  struct rusage ru;
+  if (getrusage(RUSAGE_LWP, &ru) == 0) return MakeTime(ru);
+  DiagnoseAndExit("getrusage(RUSAGE_LWP, ...) failed");
+#elif defined(CLOCK_THREAD_CPUTIME_ID)
+  struct timespec ts;
+  if (clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts) == 0) return MakeTime(ts);
+  DiagnoseAndExit("clock_gettime(CLOCK_THREAD_CPUTIME_ID, ...) failed");
+#else
+#error Per-thread timing is not available on your system.
+#endif
+}
+
+std::string LocalDateTimeString() {
+  // Write the local time in RFC3339 format yyyy-mm-ddTHH:MM:SS+/-HH:MM.
+  typedef std::chrono::system_clock Clock;
+  std::time_t now = Clock::to_time_t(Clock::now());
+  const std::size_t kTzOffsetLen = 6;
+  const std::size_t kTimestampLen = 19;
+
+  std::size_t tz_len;
+  std::size_t timestamp_len;
+  long int offset_minutes;
+  char tz_offset_sign = '+';
+  // tz_offset is set in one of three ways:
+  // * strftime with %z - This either returns empty or the ISO 8601 time.  The
+  // maximum length an
+  //   ISO 8601 string can be is 7 (e.g. -03:30, plus trailing zero).
+  // * snprintf with %c%02li:%02li - The maximum length is 41 (one for %c, up to
+  // 19 for %02li,
+  //   one for :, up to 19 %02li, plus trailing zero).
+  // * A fixed string of "-00:00".  The maximum length is 7 (-00:00, plus
+  // trailing zero).
+  //
+  // Thus, the maximum size this needs to be is 41.
+  char tz_offset[41];
+  // Long enough buffer to avoid format-overflow warnings
+  char storage[128];
+
+#if defined(BENCHMARK_OS_WINDOWS)
+  std::tm* timeinfo_p = ::localtime(&now);
+#else
+  std::tm timeinfo;
+  std::tm* timeinfo_p = &timeinfo;
+  ::localtime_r(&now, &timeinfo);
+#endif
+
+  tz_len = std::strftime(tz_offset, sizeof(tz_offset), "%z", timeinfo_p);
+
+  if (tz_len < kTzOffsetLen && tz_len > 1) {
+    // Timezone offset was written. strftime writes offset as +HHMM or -HHMM,
+    // RFC3339 specifies an offset as +HH:MM or -HH:MM. To convert, we parse
+    // the offset as an integer, then reprint it to a string.
+
+    offset_minutes = ::strtol(tz_offset, NULL, 10);
+    if (offset_minutes < 0) {
+      offset_minutes *= -1;
+      tz_offset_sign = '-';
+    }
+
+    tz_len =
+        ::snprintf(tz_offset, sizeof(tz_offset), "%c%02li:%02li",
+                   tz_offset_sign, offset_minutes / 100, offset_minutes % 100);
+    BM_CHECK(tz_len == kTzOffsetLen);
+    ((void)tz_len);  // Prevent unused variable warning in optimized build.
+  } else {
+    // Unknown offset. RFC3339 specifies that unknown local offsets should be
+    // written as UTC time with -00:00 timezone.
+#if defined(BENCHMARK_OS_WINDOWS)
+    // Potential race condition if another thread calls localtime or gmtime.
+    timeinfo_p = ::gmtime(&now);
+#else
+    ::gmtime_r(&now, &timeinfo);
+#endif
+
+    strncpy(tz_offset, "-00:00", kTzOffsetLen + 1);
+  }
+
+  timestamp_len =
+      std::strftime(storage, sizeof(storage), "%Y-%m-%dT%H:%M:%S", timeinfo_p);
+  BM_CHECK(timestamp_len == kTimestampLen);
+  // Prevent unused variable warning in optimized build.
+  ((void)kTimestampLen);
+
+  std::strncat(storage, tz_offset, sizeof(storage) - timestamp_len - 1);
+  return std::string(storage);
+}
+
+}  // end namespace benchmark
diff --git a/leveldb_base/third_party/benchmark/src/timers.h b/leveldb_base/third_party/benchmark/src/timers.h
new file mode 100644
index 0000000..65606cc
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/src/timers.h
@@ -0,0 +1,48 @@
+#ifndef BENCHMARK_TIMERS_H
+#define BENCHMARK_TIMERS_H
+
+#include <chrono>
+#include <string>
+
+namespace benchmark {
+
+// Return the CPU usage of the current process
+double ProcessCPUUsage();
+
+// Return the CPU usage of the children of the current process
+double ChildrenCPUUsage();
+
+// Return the CPU usage of the current thread
+double ThreadCPUUsage();
+
+#if defined(HAVE_STEADY_CLOCK)
+template <bool HighResIsSteady = std::chrono::high_resolution_clock::is_steady>
+struct ChooseSteadyClock {
+  typedef std::chrono::high_resolution_clock type;
+};
+
+template <>
+struct ChooseSteadyClock<false> {
+  typedef std::chrono::steady_clock type;
+};
+#endif
+
+struct ChooseClockType {
+#if defined(HAVE_STEADY_CLOCK)
+  typedef ChooseSteadyClock<>::type type;
+#else
+  typedef std::chrono::high_resolution_clock type;
+#endif
+};
+
+inline double ChronoClockNow() {
+  typedef ChooseClockType::type ClockType;
+  using FpSeconds = std::chrono::duration<double, std::chrono::seconds::period>;
+  return FpSeconds(ClockType::now().time_since_epoch()).count();
+}
+
+std::string LocalDateTimeString();
+
+}  // end namespace benchmark
+
+#endif  // BENCHMARK_TIMERS_H
diff --git a/leveldb_base/third_party/benchmark/test/AssemblyTests.cmake b/leveldb_base/third_party/benchmark/test/AssemblyTests.cmake
new file mode 100644
index 0000000..c43c711
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/AssemblyTests.cmake
@@ -0,0 +1,67 @@
+set(CLANG_SUPPORTED_VERSION "5.0.0")
+set(GCC_SUPPORTED_VERSION "5.5.0")
+
+if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+  if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_EQUAL ${CLANG_SUPPORTED_VERSION})
+    message (WARNING
+      "Unsupported Clang version " ${CMAKE_CXX_COMPILER_VERSION}
+      ". Expected is " ${CLANG_SUPPORTED_VERSION}
+      ". Assembly tests may be broken.")
+  endif()
+elseif(CMAKE_CXX_COMPILER_ID MATCHES "GNU")
+  if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_EQUAL ${GCC_SUPPORTED_VERSION})
+    message (WARNING
+      "Unsupported GCC version " ${CMAKE_CXX_COMPILER_VERSION}
+      ". Expected is " ${GCC_SUPPORTED_VERSION}
+      ". Assembly tests may be broken.")
+  endif()
+else()
+  message (WARNING "Unsupported compiler. Assembly tests may be broken.")
+endif()
+
+include(split_list)
+
+set(ASM_TEST_FLAGS "")
+check_cxx_compiler_flag(-O3 BENCHMARK_HAS_O3_FLAG)
+if (BENCHMARK_HAS_O3_FLAG)
+  list(APPEND ASM_TEST_FLAGS -O3)
+endif()
+
+check_cxx_compiler_flag(-g0 BENCHMARK_HAS_G0_FLAG)
+if (BENCHMARK_HAS_G0_FLAG)
+  list(APPEND ASM_TEST_FLAGS -g0)
+endif()
+
+check_cxx_compiler_flag(-fno-stack-protector BENCHMARK_HAS_FNO_STACK_PROTECTOR_FLAG)
+if (BENCHMARK_HAS_FNO_STACK_PROTECTOR_FLAG)
+  list(APPEND ASM_TEST_FLAGS -fno-stack-protector)
+endif()
+
+split_list(ASM_TEST_FLAGS)
+string(TOUPPER "${CMAKE_CXX_COMPILER_ID}" ASM_TEST_COMPILER)
+
+macro(add_filecheck_test name)
+  cmake_parse_arguments(ARG "" "" "CHECK_PREFIXES" ${ARGV})
+  add_library(${name} OBJECT ${name}.cc)
+  target_link_libraries(${name} PRIVATE benchmark::benchmark)
+  set_target_properties(${name} PROPERTIES COMPILE_FLAGS "-S ${ASM_TEST_FLAGS}")
+  set(ASM_OUTPUT_FILE "${CMAKE_CURRENT_BINARY_DIR}/${name}.s")
+  add_custom_target(copy_${name} ALL
+      COMMAND ${PROJECT_SOURCE_DIR}/tools/strip_asm.py
+        $<TARGET_OBJECTS:${name}>
+        ${ASM_OUTPUT_FILE}
+      BYPRODUCTS ${ASM_OUTPUT_FILE})
+  add_dependencies(copy_${name} ${name})
+  if (NOT ARG_CHECK_PREFIXES)
+    set(ARG_CHECK_PREFIXES "CHECK")
+  endif()
+  foreach(prefix ${ARG_CHECK_PREFIXES})
+    add_test(NAME run_${name}_${prefix}
+        COMMAND
+          ${LLVM_FILECHECK_EXE} ${name}.cc
+          --input-file=${ASM_OUTPUT_FILE}
+          --check-prefixes=CHECK,CHECK-${ASM_TEST_COMPILER}
+        WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})
+  endforeach()
+endmacro()
+
diff --git a/leveldb_base/third_party/benchmark/test/BUILD b/leveldb_base/third_party/benchmark/test/BUILD
new file mode 100644
index 0000000..8262d08
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/BUILD
@@ -0,0 +1,110 @@
+load("@rules_cc//cc:defs.bzl", "cc_library", "cc_test")
+
+platform(
+    name = "windows",
+    constraint_values = [
+        "@platforms//os:windows",
+    ],
+)
+
+TEST_COPTS = [
+    "-pedantic",
+    "-pedantic-errors",
+    "-std=c++11",
+    "-Wall",
+    "-Wconversion",
+    "-Wextra",
+    "-Wshadow",
+    #    "-Wshorten-64-to-32",
+    "-Wfloat-equal",
+    "-fstrict-aliasing",
+]
+
+# Some of the issues with DoNotOptimize only occur when optimization is enabled
+PER_SRC_COPTS = {
+    "donotoptimize_test.cc": ["-O3"],
+}
+
+TEST_ARGS = ["--benchmark_min_time=0.01s"]
+
+PER_SRC_TEST_ARGS = {
+    "user_counters_tabular_test.cc": ["--benchmark_counters_tabular=true"],
+    "repetitions_test.cc": [" --benchmark_repetitions=3"],
+    "spec_arg_test.cc": ["--benchmark_filter=BM_NotChosen"],
+    "spec_arg_verbosity_test.cc": ["--v=42"],
+}
+
+cc_library(
+    name = "output_test_helper",
+    testonly = 1,
+    srcs = ["output_test_helper.cc"],
+    hdrs = ["output_test.h"],
+    copts = select({
+        "//:windows": [],
+        "//conditions:default": TEST_COPTS,
+    }),
+    deps = [
+        "//:benchmark",
+        "//:benchmark_internal_headers",
+    ],
+)
+
+[
+    cc_test(
+        name = test_src[:-len(".cc")],
+        size = "small",
+        srcs = [test_src],
+        args = TEST_ARGS + PER_SRC_TEST_ARGS.get(test_src, []),
+        copts = select({
+            "//:windows": [],
+            "//conditions:default": TEST_COPTS,
+        }) + PER_SRC_COPTS.get(test_src, []),
+        deps = [
+            ":output_test_helper",
+            "//:benchmark",
+            "//:benchmark_internal_headers",
+            "@com_google_googletest//:gtest",
+            "@com_google_googletest//:gtest_main",
+        ],
+        # FIXME: Add support for assembly tests to bazel.
+        # See Issue #556
+        # https://github.com/google/benchmark/issues/556
+    )
+    for test_src in glob(
+        ["*test.cc"],
+        exclude = [
+            "*_assembly_test.cc",
+            "cxx03_test.cc",
+            "link_main_test.cc",
+        ],
+    )
+]
+
+cc_test(
+    name = "cxx03_test",
+    size = "small",
+    srcs = ["cxx03_test.cc"],
+    copts = TEST_COPTS + ["-std=c++03"],
+    target_compatible_with = select({
+        "//:windows": ["@platforms//:incompatible"],
+        "//conditions:default": [],
+    }),
+    deps = [
+        ":output_test_helper",
+        "//:benchmark",
+        "//:benchmark_internal_headers",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "link_main_test",
+    size = "small",
+    srcs = ["link_main_test.cc"],
+    copts = select({
+        "//:windows": [],
+        "//conditions:default": TEST_COPTS,
+    }),
+    deps = ["//:benchmark_main"],
+)
diff --git a/leveldb_base/third_party/benchmark/test/CMakeLists.txt b/leveldb_base/third_party/benchmark/test/CMakeLists.txt
new file mode 100644
index 0000000..78d6d51
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/CMakeLists.txt
@@ -0,0 +1,304 @@
+# Enable the tests
+
+set(THREADS_PREFER_PTHREAD_FLAG ON)
+
+find_package(Threads REQUIRED)
+include(CheckCXXCompilerFlag)
+
+# NOTE: Some tests use `<cassert>` to perform the test. Therefore we must
+# strip -DNDEBUG from the default CMake flags in DEBUG mode.
+string(TOUPPER "${CMAKE_BUILD_TYPE}" uppercase_CMAKE_BUILD_TYPE)
+if( NOT uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG" )
+  add_definitions( -UNDEBUG )
+  add_definitions(-DTEST_BENCHMARK_LIBRARY_HAS_NO_ASSERTIONS)
+  # Also remove /D NDEBUG to avoid MSVC warnings about conflicting defines.
+  foreach (flags_var_to_scrub
+      CMAKE_CXX_FLAGS_RELEASE
+      CMAKE_CXX_FLAGS_RELWITHDEBINFO
+      CMAKE_CXX_FLAGS_MINSIZEREL
+      CMAKE_C_FLAGS_RELEASE
+      CMAKE_C_FLAGS_RELWITHDEBINFO
+      CMAKE_C_FLAGS_MINSIZEREL)
+    string (REGEX REPLACE "(^| )[/-]D *NDEBUG($| )" " "
+      "${flags_var_to_scrub}" "${${flags_var_to_scrub}}")
+  endforeach()
+endif()
+
+if (NOT BUILD_SHARED_LIBS)
+  add_definitions(-DBENCHMARK_STATIC_DEFINE)
+endif()
+
+check_cxx_compiler_flag(-O3 BENCHMARK_HAS_O3_FLAG)
+set(BENCHMARK_O3_FLAG "")
+if (BENCHMARK_HAS_O3_FLAG)
+  set(BENCHMARK_O3_FLAG "-O3")
+endif()
+
+# NOTE: These flags must be added after find_package(Threads REQUIRED) otherwise
+# they will break the configuration check.
+if (DEFINED BENCHMARK_CXX_LINKER_FLAGS)
+  list(APPEND CMAKE_EXE_LINKER_FLAGS ${BENCHMARK_CXX_LINKER_FLAGS})
+endif()
+
+add_library(output_test_helper STATIC output_test_helper.cc output_test.h)
+target_link_libraries(output_test_helper PRIVATE benchmark::benchmark)
+
+macro(compile_benchmark_test name)
+  add_executable(${name} "${name}.cc")
+  target_link_libraries(${name} benchmark::benchmark ${CMAKE_THREAD_LIBS_INIT})
+  if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "NVHPC")
+  target_compile_options( ${name} PRIVATE --diag_suppress partial_override )
+  endif()
+endmacro(compile_benchmark_test)
+
+macro(compile_benchmark_test_with_main name)
+  add_executable(${name} "${name}.cc")
+  target_link_libraries(${name} benchmark::benchmark_main)
+endmacro(compile_benchmark_test_with_main)
+
+macro(compile_output_test name)
+  add_executable(${name} "${name}.cc" output_test.h)
+  target_link_libraries(${name} output_test_helper benchmark::benchmark_main
+          ${BENCHMARK_CXX_LIBRARIES} ${CMAKE_THREAD_LIBS_INIT})
+endmacro(compile_output_test)
+
+# Demonstration executable
+compile_benchmark_test(benchmark_test)
+add_test(NAME benchmark COMMAND benchmark_test --benchmark_min_time=0.01s)
+
+compile_benchmark_test(spec_arg_test)
+add_test(NAME spec_arg COMMAND spec_arg_test --benchmark_filter=BM_NotChosen)
+
+compile_benchmark_test(spec_arg_verbosity_test)
+add_test(NAME spec_arg_verbosity COMMAND spec_arg_verbosity_test --v=42)
+
+compile_benchmark_test(benchmark_setup_teardown_test)
+add_test(NAME benchmark_setup_teardown COMMAND benchmark_setup_teardown_test)
+
+compile_benchmark_test(filter_test)
+macro(add_filter_test name filter expect)
+  add_test(NAME ${name} COMMAND filter_test --benchmark_min_time=0.01s --benchmark_filter=${filter} ${expect})
+  add_test(NAME ${name}_list_only COMMAND filter_test --benchmark_list_tests --benchmark_filter=${filter} ${expect})
+endmacro(add_filter_test)
+
+compile_benchmark_test(benchmark_min_time_flag_time_test)
+add_test(NAME min_time_flag_time COMMAND benchmark_min_time_flag_time_test)
+
+compile_benchmark_test(benchmark_min_time_flag_iters_test)
+add_test(NAME min_time_flag_iters COMMAND benchmark_min_time_flag_iters_test)
+
+add_filter_test(filter_simple "Foo" 3)
+add_filter_test(filter_simple_negative "-Foo" 2)
+add_filter_test(filter_suffix "BM_.*" 4)
+add_filter_test(filter_suffix_negative "-BM_.*" 1)
+add_filter_test(filter_regex_all ".*" 5)
+add_filter_test(filter_regex_all_negative "-.*" 0)
+add_filter_test(filter_regex_blank "" 5)
+add_filter_test(filter_regex_blank_negative "-" 0)
+add_filter_test(filter_regex_none "monkey" 0)
+add_filter_test(filter_regex_none_negative "-monkey" 5)
+add_filter_test(filter_regex_wildcard ".*Foo.*" 3)
+add_filter_test(filter_regex_wildcard_negative "-.*Foo.*" 2)
+add_filter_test(filter_regex_begin "^BM_.*" 4)
+add_filter_test(filter_regex_begin_negative "-^BM_.*" 1)
+add_filter_test(filter_regex_begin2 "^N" 1)
+add_filter_test(filter_regex_begin2_negative "-^N" 4)
+add_filter_test(filter_regex_end ".*Ba$" 1)
+add_filter_test(filter_regex_end_negative "-.*Ba$" 4)
+
+compile_benchmark_test(options_test)
+add_test(NAME options_benchmarks COMMAND options_test --benchmark_min_time=0.01s)
+
+compile_benchmark_test(basic_test)
+add_test(NAME basic_benchmark COMMAND basic_test --benchmark_min_time=0.01s)
+
+compile_output_test(repetitions_test)
+add_test(NAME repetitions_benchmark COMMAND repetitions_test --benchmark_min_time=0.01s --benchmark_repetitions=3)
+
+compile_benchmark_test(diagnostics_test)
+add_test(NAME diagnostics_test COMMAND diagnostics_test --benchmark_min_time=0.01s)
+
+compile_benchmark_test(skip_with_error_test)
+add_test(NAME skip_with_error_test COMMAND skip_with_error_test --benchmark_min_time=0.01s)
+
+compile_benchmark_test(donotoptimize_test)
+# Some of the issues with DoNotOptimize only occur when optimization is enabled
+check_cxx_compiler_flag(-O3 BENCHMARK_HAS_O3_FLAG)
+if (BENCHMARK_HAS_O3_FLAG)
+  set_target_properties(donotoptimize_test PROPERTIES COMPILE_FLAGS "-O3")
+endif()
+add_test(NAME donotoptimize_test COMMAND donotoptimize_test --benchmark_min_time=0.01s)
+
+compile_benchmark_test(fixture_test)
+add_test(NAME fixture_test COMMAND fixture_test --benchmark_min_time=0.01s)
+
+compile_benchmark_test(register_benchmark_test)
+add_test(NAME register_benchmark_test COMMAND register_benchmark_test --benchmark_min_time=0.01s)
+
+compile_benchmark_test(map_test)
+add_test(NAME map_test COMMAND map_test --benchmark_min_time=0.01s)
+
+compile_benchmark_test(multiple_ranges_test)
+add_test(NAME multiple_ranges_test COMMAND multiple_ranges_test --benchmark_min_time=0.01s)
+
+compile_benchmark_test(args_product_test)
+add_test(NAME args_product_test COMMAND args_product_test --benchmark_min_time=0.01s)
+
+compile_benchmark_test_with_main(link_main_test)
+add_test(NAME link_main_test COMMAND link_main_test --benchmark_min_time=0.01s)
+
+compile_output_test(reporter_output_test)
+add_test(NAME reporter_output_test COMMAND reporter_output_test --benchmark_min_time=0.01s)
+
+compile_output_test(templated_fixture_test)
+add_test(NAME templated_fixture_test COMMAND templated_fixture_test --benchmark_min_time=0.01s)
+
+compile_output_test(user_counters_test)
+add_test(NAME user_counters_test COMMAND user_counters_test --benchmark_min_time=0.01s)
+
+compile_output_test(perf_counters_test)
+add_test(NAME perf_counters_test COMMAND perf_counters_test --benchmark_min_time=0.01s --benchmark_perf_counters=CYCLES,BRANCHES)
+
+compile_output_test(internal_threading_test)
+add_test(NAME internal_threading_test COMMAND internal_threading_test --benchmark_min_time=0.01s)
+
+compile_output_test(report_aggregates_only_test)
+add_test(NAME report_aggregates_only_test COMMAND report_aggregates_only_test --benchmark_min_time=0.01s)
+
+compile_output_test(display_aggregates_only_test)
+add_test(NAME display_aggregates_only_test COMMAND display_aggregates_only_test --benchmark_min_time=0.01s)
+
+compile_output_test(user_counters_tabular_test)
+add_test(NAME user_counters_tabular_test COMMAND user_counters_tabular_test --benchmark_counters_tabular=true --benchmark_min_time=0.01s)
+
+compile_output_test(user_counters_thousands_test)
+add_test(NAME user_counters_thousands_test COMMAND user_counters_thousands_test --benchmark_min_time=0.01s)
+
+compile_output_test(memory_manager_test)
+add_test(NAME memory_manager_test COMMAND memory_manager_test --benchmark_min_time=0.01s)
+
+# MSVC does not allow to set the language standard to C++98/03.
+if(NOT CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
+  compile_benchmark_test(cxx03_test)
+  set_target_properties(cxx03_test
+      PROPERTIES
+      CXX_STANDARD 98
+      CXX_STANDARD_REQUIRED YES)
+  # libstdc++ provides different definitions within <map> between dialects. When
+  # LTO is enabled and -Werror is specified GCC diagnoses this ODR violation
+  # causing the test to fail to compile. To prevent this we explicitly disable
+  # the warning.
+  check_cxx_compiler_flag(-Wno-odr BENCHMARK_HAS_WNO_ODR)
+  check_cxx_compiler_flag(-Wno-lto-type-mismatch BENCHMARK_HAS_WNO_LTO_TYPE_MISMATCH)
+  # Cannot set_target_properties multiple times here because the warnings will
+  # be overwritten on each call
+  set (DISABLE_LTO_WARNINGS "")
+  if (BENCHMARK_HAS_WNO_ODR)
+    set(DISABLE_LTO_WARNINGS "${DISABLE_LTO_WARNINGS} -Wno-odr")
+  endif()
+  if (BENCHMARK_HAS_WNO_LTO_TYPE_MISMATCH)
+    set(DISABLE_LTO_WARNINGS "${DISABLE_LTO_WARNINGS} -Wno-lto-type-mismatch")
+  endif()
+  set_target_properties(cxx03_test PROPERTIES LINK_FLAGS "${DISABLE_LTO_WARNINGS}")
+  add_test(NAME cxx03 COMMAND cxx03_test --benchmark_min_time=0.01s)
+endif()
+
+# Attempt to work around flaky test failures when running on Appveyor servers.
+if (DEFINED ENV{APPVEYOR})
+  set(COMPLEXITY_MIN_TIME "0.5s")
+else()
+  set(COMPLEXITY_MIN_TIME "0.01s")
+endif()
+compile_output_test(complexity_test)
+add_test(NAME complexity_benchmark COMMAND complexity_test --benchmark_min_time=${COMPLEXITY_MIN_TIME})
+
+###############################################################################
+# GoogleTest Unit Tests
+###############################################################################
+
+if (BENCHMARK_ENABLE_GTEST_TESTS)
+  macro(compile_gtest name)
+    add_executable(${name} "${name}.cc")
+    target_link_libraries(${name} benchmark::benchmark
+        gmock_main ${CMAKE_THREAD_LIBS_INIT})
+  endmacro(compile_gtest)
+
+  macro(add_gtest name)
+    compile_gtest(${name})
+    add_test(NAME ${name} COMMAND ${name})
+  endmacro()
+
+  add_gtest(benchmark_gtest)
+  add_gtest(benchmark_name_gtest)
+  add_gtest(benchmark_random_interleaving_gtest)
+  add_gtest(commandlineflags_gtest)
+  add_gtest(statistics_gtest)
+  add_gtest(string_util_gtest)
+  add_gtest(perf_counters_gtest)
+  add_gtest(time_unit_gtest)
+  add_gtest(min_time_parse_gtest)
+endif(BENCHMARK_ENABLE_GTEST_TESTS)
+
+###############################################################################
+# Assembly Unit Tests
+###############################################################################
+
+if (BENCHMARK_ENABLE_ASSEMBLY_TESTS)
+  if (NOT LLVM_FILECHECK_EXE)
+    message(FATAL_ERROR "LLVM FileCheck is required when including this file")
+  endif()
+  include(AssemblyTests.cmake)
+  add_filecheck_test(donotoptimize_assembly_test)
+  add_filecheck_test(state_assembly_test)
+  add_filecheck_test(clobber_memory_assembly_test)
+endif()
+
+
+
+###############################################################################
+# Code Coverage Configuration
+###############################################################################
+
+# Add the coverage command(s)
+if(CMAKE_BUILD_TYPE)
+  string(TOLOWER ${CMAKE_BUILD_TYPE} CMAKE_BUILD_TYPE_LOWER)
+endif()
+if (${CMAKE_BUILD_TYPE_LOWER} MATCHES "coverage")
+  find_program(GCOV gcov)
+  find_program(LCOV lcov)
+  find_program(GENHTML genhtml)
+  find_program(CTEST ctest)
+  if (GCOV AND LCOV AND GENHTML AND CTEST AND HAVE_CXX_FLAG_COVERAGE)
+    add_custom_command(
+      OUTPUT ${CMAKE_BINARY_DIR}/lcov/index.html
+      COMMAND ${LCOV} -q -z -d .
+      COMMAND ${LCOV} -q --no-external -c -b "${CMAKE_SOURCE_DIR}" -d . -o before.lcov -i
+      COMMAND ${CTEST} --force-new-ctest-process
+      COMMAND ${LCOV} -q --no-external -c -b "${CMAKE_SOURCE_DIR}" -d . -o after.lcov
+      COMMAND ${LCOV} -q -a before.lcov -a after.lcov --output-file final.lcov
+      COMMAND ${LCOV} -q -r final.lcov "'${CMAKE_SOURCE_DIR}/test/*'" -o final.lcov
+      COMMAND ${GENHTML} final.lcov -o lcov --demangle-cpp --sort -p "${CMAKE_BINARY_DIR}" -t benchmark
+      DEPENDS filter_test benchmark_test options_test basic_test fixture_test cxx03_test complexity_test
+      WORKING_DIRECTORY ${CMAKE_BINARY_DIR}
+      COMMENT "Running LCOV"
+    )
+    add_custom_target(coverage
+      DEPENDS ${CMAKE_BINARY_DIR}/lcov/index.html
+      COMMENT "LCOV report at lcov/index.html"
+    )
+    message(STATUS "Coverage command added")
+  else()
+    if (HAVE_CXX_FLAG_COVERAGE)
+      set(CXX_FLAG_COVERAGE_MESSAGE supported)
+    else()
+      set(CXX_FLAG_COVERAGE_MESSAGE unavailable)
+    endif()
+    message(WARNING
+      "Coverage not available:\n"
+      "  gcov: ${GCOV}\n"
+      "  lcov: ${LCOV}\n"
+      "  genhtml: ${GENHTML}\n"
+      "  ctest: ${CTEST}\n"
+      "  --coverage flag: ${CXX_FLAG_COVERAGE_MESSAGE}")
+  endif()
+endif()
diff --git a/leveldb_base/third_party/benchmark/test/args_product_test.cc b/leveldb_base/third_party/benchmark/test/args_product_test.cc
new file mode 100644
index 0000000..63b8b71
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/args_product_test.cc
@@ -0,0 +1,77 @@
+#include <cassert>
+#include <iostream>
+#include <set>
+#include <vector>
+
+#include "benchmark/benchmark.h"
+
+class ArgsProductFixture : public ::benchmark::Fixture {
+ public:
+  ArgsProductFixture()
+      : expectedValues({{0, 100, 2000, 30000},
+                        {1, 15, 3, 8},
+                        {1, 15, 3, 9},
+                        {1, 15, 7, 8},
+                        {1, 15, 7, 9},
+                        {1, 15, 10, 8},
+                        {1, 15, 10, 9},
+                        {2, 15, 3, 8},
+                        {2, 15, 3, 9},
+                        {2, 15, 7, 8},
+                        {2, 15, 7, 9},
+                        {2, 15, 10, 8},
+                        {2, 15, 10, 9},
+                        {4, 5, 6, 11}}) {}
+
+  void SetUp(const ::benchmark::State& state) override {
+    std::vector<int64_t> ranges = {state.range(0), state.range(1),
+                                   state.range(2), state.range(3)};
+
+    assert(expectedValues.find(ranges) != expectedValues.end());
+
+    actualValues.insert(ranges);
+  }
+
+  // NOTE: This is not TearDown as we want to check after _all_ runs are
+  // complete.
+  ~ArgsProductFixture() override {
+    if (actualValues != expectedValues) {
+      std::cout << "EXPECTED\n";
+      for (const auto& v : expectedValues) {
+        std::cout << "{";
+        for (int64_t iv : v) {
+          std::cout << iv << ", ";
+        }
+        std::cout << "}\n";
+      }
+      std::cout << "ACTUAL\n";
+      for (const auto& v : actualValues) {
+        std::cout << "{";
+        for (int64_t iv : v) {
+          std::cout << iv << ", ";
+        }
+        std::cout << "}\n";
+      }
+    }
+  }
+
+  std::set<std::vector<int64_t>> expectedValues;
+  std::set<std::vector<int64_t>> actualValues;
+};
+
+BENCHMARK_DEFINE_F(ArgsProductFixture, Empty)(benchmark::State& state) {
+  for (auto _ : state) {
+    int64_t product =
+        state.range(0) * state.range(1) * state.range(2) * state.range(3);
+    for (int64_t x = 0; x < product; x++) {
+      benchmark::DoNotOptimize(x);
+    }
+  }
+}
+
+BENCHMARK_REGISTER_F(ArgsProductFixture, Empty)
+    ->Args({0, 100, 2000, 30000})
+    ->ArgsProduct({{1, 2}, {15}, {3, 7, 10}, {8, 9}})
+    ->Args({4, 5, 6, 11});
+
+BENCHMARK_MAIN();
diff --git a/leveldb_base/third_party/benchmark/test/basic_test.cc b/leveldb_base/third_party/benchmark/test/basic_test.cc
new file mode 100644
index 0000000..cba1b0f
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/basic_test.cc
@@ -0,0 +1,180 @@
+
+#include "benchmark/benchmark.h"
+
+#define BASIC_BENCHMARK_TEST(x) BENCHMARK(x)->Arg(8)->Arg(512)->Arg(8192)
+
+void BM_empty(benchmark::State& state) {
+  for (auto _ : state) {
+    auto iterations = state.iterations();
+    benchmark::DoNotOptimize(iterations);
+  }
+}
+BENCHMARK(BM_empty);
+BENCHMARK(BM_empty)->ThreadPerCpu();
+
+void BM_spin_empty(benchmark::State& state) {
+  for (auto _ : state) {
+    for (auto x = 0; x < state.range(0); ++x) {
+      benchmark::DoNotOptimize(x);
+    }
+  }
+}
+BASIC_BENCHMARK_TEST(BM_spin_empty);
+BASIC_BENCHMARK_TEST(BM_spin_empty)->ThreadPerCpu();
+
+void BM_spin_pause_before(benchmark::State& state) {
+  for (auto i = 0; i < state.range(0); ++i) {
+    benchmark::DoNotOptimize(i);
+  }
+  for (auto _ : state) {
+    for (auto i = 0; i < state.range(0); ++i) {
+      benchmark::DoNotOptimize(i);
+    }
+  }
+}
+BASIC_BENCHMARK_TEST(BM_spin_pause_before);
+BASIC_BENCHMARK_TEST(BM_spin_pause_before)->ThreadPerCpu();
+
+void BM_spin_pause_during(benchmark::State& state) {
+  for (auto _ : state) {
+    state.PauseTiming();
+    for (auto i = 0; i < state.range(0); ++i) {
+      benchmark::DoNotOptimize(i);
+    }
+    state.ResumeTiming();
+    for (auto i = 0; i < state.range(0); ++i) {
+      benchmark::DoNotOptimize(i);
+    }
+  }
+}
+BASIC_BENCHMARK_TEST(BM_spin_pause_during);
+BASIC_BENCHMARK_TEST(BM_spin_pause_during)->ThreadPerCpu();
+
+void BM_pause_during(benchmark::State& state) {
+  for (auto _ : state) {
+    state.PauseTiming();
+    state.ResumeTiming();
+  }
+}
+BENCHMARK(BM_pause_during);
+BENCHMARK(BM_pause_during)->ThreadPerCpu();
+BENCHMARK(BM_pause_during)->UseRealTime();
+BENCHMARK(BM_pause_during)->UseRealTime()->ThreadPerCpu();
+
+void BM_spin_pause_after(benchmark::State& state) {
+  for (auto _ : state) {
+    for (auto i = 0; i < state.range(0); ++i) {
+      benchmark::DoNotOptimize(i);
+    }
+  }
+  for (auto i = 0; i < state.range(0); ++i) {
+    benchmark::DoNotOptimize(i);
+  }
+}
+BASIC_BENCHMARK_TEST(BM_spin_pause_after);
+BASIC_BENCHMARK_TEST(BM_spin_pause_after)->ThreadPerCpu();
+
+void BM_spin_pause_before_and_after(benchmark::State& state) {
+  for (auto i = 0; i < state.range(0); ++i) {
+    benchmark::DoNotOptimize(i);
+  }
+  for (auto _ : state) {
+    for (auto i = 0; i < state.range(0); ++i) {
+      benchmark::DoNotOptimize(i);
+    }
+  }
+  for (auto i = 0; i < state.range(0); ++i) {
+    benchmark::DoNotOptimize(i);
+  }
+}
+BASIC_BENCHMARK_TEST(BM_spin_pause_before_and_after);
+BASIC_BENCHMARK_TEST(BM_spin_pause_before_and_after)->ThreadPerCpu();
+
+void BM_empty_stop_start(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_empty_stop_start);
+BENCHMARK(BM_empty_stop_start)->ThreadPerCpu();
+
+void BM_KeepRunning(benchmark::State& state) {
+  benchmark::IterationCount iter_count = 0;
+  assert(iter_count == state.iterations());
+  while (state.KeepRunning()) {
+    ++iter_count;
+  }
+  assert(iter_count == state.iterations());
+}
+BENCHMARK(BM_KeepRunning);
+
+void BM_KeepRunningBatch(benchmark::State& state) {
+  // Choose a batch size >1000 to skip the typical runs with iteration
+  // targets of 10, 100 and 1000.  If these are not actually skipped the
+  // bug would be detectable as consecutive runs with the same iteration
+  // count.  Below we assert that this does not happen.
+  const benchmark::IterationCount batch_size = 1009;
+
+  static benchmark::IterationCount prior_iter_count = 0;
+  benchmark::IterationCount iter_count = 0;
+  while (state.KeepRunningBatch(batch_size)) {
+    iter_count += batch_size;
+  }
+  assert(state.iterations() == iter_count);
+
+  // Verify that the iteration count always increases across runs (see
+  // comment above).
+  assert(iter_count == batch_size            // max_iterations == 1
+         || iter_count > prior_iter_count);  // max_iterations > batch_size
+  prior_iter_count = iter_count;
+}
+// Register with a fixed repetition count to establish the invariant that
+// the iteration count should always change across runs.  This overrides
+// the --benchmark_repetitions command line flag, which would otherwise
+// cause this test to fail if set > 1.
+BENCHMARK(BM_KeepRunningBatch)->Repetitions(1);
+
+void BM_RangedFor(benchmark::State& state) {
+  benchmark::IterationCount iter_count = 0;
+  for (auto _ : state) {
+    ++iter_count;
+  }
+  assert(iter_count == state.max_iterations);
+}
+BENCHMARK(BM_RangedFor);
+
+#ifdef BENCHMARK_HAS_CXX11
+template <typename T>
+void BM_OneTemplateFunc(benchmark::State& state) {
+  auto arg = state.range(0);
+  T sum = 0;
+  for (auto _ : state) {
+    sum += static_cast<T>(arg);
+  }
+}
+BENCHMARK(BM_OneTemplateFunc<int>)->Arg(1);
+BENCHMARK(BM_OneTemplateFunc<double>)->Arg(1);
+
+template <typename A, typename B>
+void BM_TwoTemplateFunc(benchmark::State& state) {
+  auto arg = state.range(0);
+  A sum = 0;
+  B prod = 1;
+  for (auto _ : state) {
+    sum += static_cast<A>(arg);
+    prod *= static_cast<B>(arg);
+  }
+}
+BENCHMARK(BM_TwoTemplateFunc<int, double>)->Arg(1);
+BENCHMARK(BM_TwoTemplateFunc<double, int>)->Arg(1);
+
+#endif  // BENCHMARK_HAS_CXX11
+
+// Ensure that StateIterator provides all the necessary typedefs required to
+// instantiate std::iterator_traits.
+static_assert(
+    std::is_same<typename std::iterator_traits<
+                     benchmark::State::StateIterator>::value_type,
+                 typename benchmark::State::StateIterator::value_type>::value,
+    "");
+
+BENCHMARK_MAIN();
diff --git a/leveldb_base/third_party/benchmark/test/benchmark_gtest.cc b/leveldb_base/third_party/benchmark/test/benchmark_gtest.cc
new file mode 100644
index 0000000..2c9e555
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/benchmark_gtest.cc
@@ -0,0 +1,169 @@
+#include <map>
+#include <string>
+#include <vector>
+
+#include "../src/benchmark_register.h"
+#include "benchmark/benchmark.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+namespace benchmark {
+namespace internal {
+
+namespace {
+
+TEST(AddRangeTest, Simple) {
+  std::vector<int> dst;
+  AddRange(&dst, 1, 2, 2);
+  EXPECT_THAT(dst, testing::ElementsAre(1, 2));
+}
+
+TEST(AddRangeTest, Simple64) {
+  std::vector<int64_t> dst;
+  AddRange(&dst, static_cast<int64_t>(1), static_cast<int64_t>(2), 2);
+  EXPECT_THAT(dst, testing::ElementsAre(1, 2));
+}
+
+TEST(AddRangeTest, Advanced) {
+  std::vector<int> dst;
+  AddRange(&dst, 5, 15, 2);
+  EXPECT_THAT(dst, testing::ElementsAre(5, 8, 15));
+}
+
+TEST(AddRangeTest, Advanced64) {
+  std::vector<int64_t> dst;
+  AddRange(&dst, static_cast<int64_t>(5), static_cast<int64_t>(15), 2);
+  EXPECT_THAT(dst, testing::ElementsAre(5, 8, 15));
+}
+
+TEST(AddRangeTest, FullRange8) {
+  std::vector<int8_t> dst;
+  AddRange(&dst, int8_t{1}, std::numeric_limits<int8_t>::max(), int8_t{8});
+  EXPECT_THAT(
+      dst, testing::ElementsAre(int8_t{1}, int8_t{8}, int8_t{64}, int8_t{127}));
+}
+
+TEST(AddRangeTest, FullRange64) {
+  std::vector<int64_t> dst;
+  AddRange(&dst, int64_t{1}, std::numeric_limits<int64_t>::max(), 1024);
+  EXPECT_THAT(
+      dst, testing::ElementsAre(1LL, 1024LL, 1048576LL, 1073741824LL,
+                                1099511627776LL, 1125899906842624LL,
+                                1152921504606846976LL, 9223372036854775807LL));
+}
+
+TEST(AddRangeTest, NegativeRanges) {
+  std::vector<int> dst;
+  AddRange(&dst, -8, 0, 2);
+  EXPECT_THAT(dst, testing::ElementsAre(-8, -4, -2, -1, 0));
+}
+
+TEST(AddRangeTest, StrictlyNegative) {
+  std::vector<int> dst;
+  AddRange(&dst, -8, -1, 2);
+  EXPECT_THAT(dst, testing::ElementsAre(-8, -4, -2, -1));
+}
+
+TEST(AddRangeTest, SymmetricNegativeRanges) {
+  std::vector<int> dst;
+  AddRange(&dst, -8, 8, 2);
+  EXPECT_THAT(dst, testing::ElementsAre(-8, -4, -2, -1, 0, 1, 2, 4, 8));
+}
+
+TEST(AddRangeTest, SymmetricNegativeRangesOddMult) {
+  std::vector<int> dst;
+  AddRange(&dst, -30, 32, 5);
+  EXPECT_THAT(dst, testing::ElementsAre(-30, -25, -5, -1, 0, 1, 5, 25, 32));
+}
+
+TEST(AddRangeTest, NegativeRangesAsymmetric) {
+  std::vector<int> dst;
+  AddRange(&dst, -3, 5, 2);
+  EXPECT_THAT(dst, testing::ElementsAre(-3, -2, -1, 0, 1, 2, 4, 5));
+}
+
+TEST(AddRangeTest, NegativeRangesLargeStep) {
+  // Always include -1, 0, 1 when crossing zero.
+  std::vector<int> dst;
+  AddRange(&dst, -8, 8, 10);
+  EXPECT_THAT(dst, testing::ElementsAre(-8, -1, 0, 1, 8));
+}
+
+TEST(AddRangeTest, ZeroOnlyRange) {
+  std::vector<int> dst;
+  AddRange(&dst, 0, 0, 2);
+  EXPECT_THAT(dst, testing::ElementsAre(0));
+}
+
+TEST(AddRangeTest, ZeroStartingRange) {
+  std::vector<int> dst;
+  AddRange(&dst, 0, 2, 2);
+  EXPECT_THAT(dst, testing::ElementsAre(0, 1, 2));
+}
+
+TEST(AddRangeTest, NegativeRange64) {
+  std::vector<int64_t> dst;
+  AddRange<int64_t>(&dst, -4, 4, 2);
+  EXPECT_THAT(dst, testing::ElementsAre(-4, -2, -1, 0, 1, 2, 4));
+}
+
+TEST(AddRangeTest, NegativeRangePreservesExistingOrder) {
+  // If elements already exist in the range, ensure we don't change
+  // their ordering by adding negative values.
+  std::vector<int64_t> dst = {1, 2, 3};
+  AddRange<int64_t>(&dst, -2, 2, 2);
+  EXPECT_THAT(dst, testing::ElementsAre(1, 2, 3, -2, -1, 0, 1, 2));
+}
+
+TEST(AddRangeTest, FullNegativeRange64) {
+  std::vector<int64_t> dst;
+  const auto min = std::numeric_limits<int64_t>::min();
+  const auto max = std::numeric_limits<int64_t>::max();
+  AddRange(&dst, min, max, 1024);
+  EXPECT_THAT(
+      dst, testing::ElementsAreArray(std::vector<int64_t>{
+               min, -1152921504606846976LL, -1125899906842624LL,
+               -1099511627776LL, -1073741824LL, -1048576LL, -1024LL, -1LL, 0LL,
+               1LL, 1024LL, 1048576LL, 1073741824LL, 1099511627776LL,
+               1125899906842624LL, 1152921504606846976LL, max}));
+}
+
+TEST(AddRangeTest, Simple8) {
+  std::vector<int8_t> dst;
+  AddRange<int8_t>(&dst, int8_t{1}, int8_t{8}, int8_t{2});
+  EXPECT_THAT(dst,
+              testing::ElementsAre(int8_t{1}, int8_t{2}, int8_t{4}, int8_t{8}));
+}
+
+TEST(AddCustomContext, Simple) {
+  std::map<std::string, std::string> *&global_context = GetGlobalContext();
+  EXPECT_THAT(global_context, nullptr);
+
+  AddCustomContext("foo", "bar");
+  AddCustomContext("baz", "qux");
+
+  EXPECT_THAT(*global_context,
+              testing::UnorderedElementsAre(testing::Pair("foo", "bar"),
+                                            testing::Pair("baz", "qux")));
+
+  delete global_context;
+  global_context = nullptr;
+}
+
+TEST(AddCustomContext, DuplicateKey) {
+  std::map<std::string, std::string> *&global_context = GetGlobalContext();
+  EXPECT_THAT(global_context, nullptr);
+
+  AddCustomContext("foo", "bar");
+  AddCustomContext("foo", "qux");
+
+  EXPECT_THAT(*global_context,
+              testing::UnorderedElementsAre(testing::Pair("foo", "bar")));
+
+  delete global_context;
+  global_context = nullptr;
+}
+
+}  // namespace
+}  // namespace internal
+}  // namespace benchmark
diff --git a/leveldb_base/third_party/benchmark/test/benchmark_min_time_flag_iters_test.cc b/leveldb_base/third_party/benchmark/test/benchmark_min_time_flag_iters_test.cc
new file mode 100644
index 0000000..eb9414a
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/benchmark_min_time_flag_iters_test.cc
@@ -0,0 +1,66 @@
+#include <cassert>
+#include <cstdlib>
+#include <cstring>
+#include <iostream>
+#include <string>
+#include <vector>
+
+#include "benchmark/benchmark.h"
+
+// Tests that we can specify the number of iterations with
+// --benchmark_min_time=<NUM>x.
+namespace {
+
+class TestReporter : public benchmark::ConsoleReporter {
+ public:
+  virtual bool ReportContext(const Context& context) BENCHMARK_OVERRIDE {
+    return ConsoleReporter::ReportContext(context);
+  };
+
+  virtual void ReportRuns(const std::vector<Run>& report) BENCHMARK_OVERRIDE {
+    assert(report.size() == 1);
+    iter_nums_.push_back(report[0].iterations);
+    ConsoleReporter::ReportRuns(report);
+  };
+
+  TestReporter() {}
+
+  virtual ~TestReporter() {}
+
+  const std::vector<benchmark::IterationCount>& GetIters() const {
+    return iter_nums_;
+  }
+
+ private:
+  std::vector<benchmark::IterationCount> iter_nums_;
+};
+
+}  // end namespace
+
+static void BM_MyBench(benchmark::State& state) {
+  for (auto s : state) {
+  }
+}
+BENCHMARK(BM_MyBench);
+
+int main(int argc, char** argv) {
+  // Make a fake argv and append the new --benchmark_min_time=<foo> to it.
+  int fake_argc = argc + 1;
+  const char** fake_argv = new const char*[fake_argc];
+  for (int i = 0; i < argc; ++i) fake_argv[i] = argv[i];
+  fake_argv[argc] = "--benchmark_min_time=4x";
+
+  benchmark::Initialize(&fake_argc, const_cast<char**>(fake_argv));
+
+  TestReporter test_reporter;
+  const size_t returned_count =
+      benchmark::RunSpecifiedBenchmarks(&test_reporter, "BM_MyBench");
+  assert(returned_count == 1);
+
+  // Check the executed iters.
+  const std::vector<benchmark::IterationCount> iters = test_reporter.GetIters();
+  assert(!iters.empty() && iters[0] == 4);
+
+  delete[] fake_argv;
+  return 0;
+}
diff --git a/leveldb_base/third_party/benchmark/test/benchmark_min_time_flag_time_test.cc b/leveldb_base/third_party/benchmark/test/benchmark_min_time_flag_time_test.cc
new file mode 100644
index 0000000..b172ccc
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/benchmark_min_time_flag_time_test.cc
@@ -0,0 +1,90 @@
+#include <cassert>
+#include <climits>
+#include <cmath>
+#include <cstdlib>
+#include <cstring>
+#include <iostream>
+#include <string>
+#include <vector>
+
+#include "benchmark/benchmark.h"
+
+// Tests that we can specify the min time with
+// --benchmark_min_time=<NUM> (no suffix needed) OR
+// --benchmark_min_time=<NUM>s
+namespace {
+
+// This is from benchmark.h
+typedef int64_t IterationCount;
+
+class TestReporter : public benchmark::ConsoleReporter {
+ public:
+  virtual bool ReportContext(const Context& context) BENCHMARK_OVERRIDE {
+    return ConsoleReporter::ReportContext(context);
+  };
+
+  virtual void ReportRuns(const std::vector<Run>& report) BENCHMARK_OVERRIDE {
+    assert(report.size() == 1);
+    ConsoleReporter::ReportRuns(report);
+  };
+
+  virtual void ReportRunsConfig(double min_time, bool /* has_explicit_iters */,
+                                IterationCount /* iters */) BENCHMARK_OVERRIDE {
+    min_times_.push_back(min_time);
+  }
+
+  TestReporter() {}
+
+  virtual ~TestReporter() {}
+
+  const std::vector<double>& GetMinTimes() const { return min_times_; }
+
+ private:
+  std::vector<double> min_times_;
+};
+
+bool AlmostEqual(double a, double b) {
+  return std::fabs(a - b) < std::numeric_limits<double>::epsilon();
+}
+
+void DoTestHelper(int* argc, const char** argv, double expected) {
+  benchmark::Initialize(argc, const_cast<char**>(argv));
+
+  TestReporter test_reporter;
+  const size_t returned_count =
+      benchmark::RunSpecifiedBenchmarks(&test_reporter, "BM_MyBench");
+  assert(returned_count == 1);
+
+  // Check the min_time
+  const std::vector<double>& min_times = test_reporter.GetMinTimes();
+  assert(!min_times.empty() && AlmostEqual(min_times[0], expected));
+}
+
+}  // end namespace
+
+static void BM_MyBench(benchmark::State& state) {
+  for (auto s : state) {
+  }
+}
+BENCHMARK(BM_MyBench);
+
+int main(int argc, char** argv) {
+  // Make a fake argv and append the new --benchmark_min_time=<foo> to it.
+  int fake_argc = argc + 1;
+  const char** fake_argv = new const char*[fake_argc];
+
+  for (int i = 0; i < argc; ++i) fake_argv[i] = argv[i];
+
+  const char* no_suffix = "--benchmark_min_time=4";
+  const char* with_suffix = "--benchmark_min_time=4.0s";
+  double expected = 4.0;
+
+  fake_argv[argc] = no_suffix;
+  DoTestHelper(&fake_argc, fake_argv, expected);
+
+  fake_argv[argc] = with_suffix;
+  DoTestHelper(&fake_argc, fake_argv, expected);
+
+  delete[] fake_argv;
+  return 0;
+}
diff --git a/leveldb_base/third_party/benchmark/test/benchmark_name_gtest.cc b/leveldb_base/third_party/benchmark/test/benchmark_name_gtest.cc
new file mode 100644
index 0000000..0a6746d
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/benchmark_name_gtest.cc
@@ -0,0 +1,82 @@
+#include "benchmark/benchmark.h"
+#include "gtest/gtest.h"
+
+namespace {
+
+using namespace benchmark;
+using namespace benchmark::internal;
+
+TEST(BenchmarkNameTest, Empty) {
+  const auto name = BenchmarkName();
+  EXPECT_EQ(name.str(), std::string());
+}
+
+TEST(BenchmarkNameTest, FunctionName) {
+  auto name = BenchmarkName();
+  name.function_name = "function_name";
+  EXPECT_EQ(name.str(), "function_name");
+}
+
+TEST(BenchmarkNameTest, FunctionNameAndArgs) {
+  auto name = BenchmarkName();
+  name.function_name = "function_name";
+  name.args = "some_args:3/4/5";
+  EXPECT_EQ(name.str(), "function_name/some_args:3/4/5");
+}
+
+TEST(BenchmarkNameTest, MinTime) {
+  auto name = BenchmarkName();
+  name.function_name = "function_name";
+  name.args = "some_args:3/4";
+  name.min_time = "min_time:3.4s";
+  EXPECT_EQ(name.str(), "function_name/some_args:3/4/min_time:3.4s");
+}
+
+TEST(BenchmarkNameTest, MinWarmUpTime) {
+  auto name = BenchmarkName();
+  name.function_name = "function_name";
+  name.args = "some_args:3/4";
+  name.min_warmup_time = "min_warmup_time:3.5s";
+  EXPECT_EQ(name.str(), "function_name/some_args:3/4/min_warmup_time:3.5s");
+}
+
+TEST(BenchmarkNameTest, Iterations) {
+  auto name = BenchmarkName();
+  name.function_name = "function_name";
+  name.min_time = "min_time:3.4s";
+  name.iterations = "iterations:42";
+  EXPECT_EQ(name.str(), "function_name/min_time:3.4s/iterations:42");
+}
+
+TEST(BenchmarkNameTest, Repetitions) {
+  auto name = BenchmarkName();
+  name.function_name = "function_name";
+  name.min_time = "min_time:3.4s";
+  name.repetitions = "repetitions:24";
+  EXPECT_EQ(name.str(), "function_name/min_time:3.4s/repetitions:24");
+}
+
+TEST(BenchmarkNameTest, TimeType) {
+  auto name = BenchmarkName();
+  name.function_name = "function_name";
+  name.min_time = "min_time:3.4s";
+  name.time_type = "hammer_time";
+  EXPECT_EQ(name.str(), "function_name/min_time:3.4s/hammer_time");
+}
+
+TEST(BenchmarkNameTest, Threads) {
+  auto name = BenchmarkName();
+  name.function_name = "function_name";
+  name.min_time = "min_time:3.4s";
+  name.threads = "threads:256";
+  EXPECT_EQ(name.str(), "function_name/min_time:3.4s/threads:256");
+}
+
+TEST(BenchmarkNameTest, TestEmptyFunctionName) {
+  auto name = BenchmarkName();
+  name.args = "first:3/second:4";
+  name.threads = "threads:22";
+  EXPECT_EQ(name.str(), "first:3/second:4/threads:22");
+}
+
+}  // end namespace
diff --git a/leveldb_base/third_party/benchmark/test/benchmark_random_interleaving_gtest.cc b/leveldb_base/third_party/benchmark/test/benchmark_random_interleaving_gtest.cc
new file mode 100644
index 0000000..7f20867
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/benchmark_random_interleaving_gtest.cc
@@ -0,0 +1,126 @@
+#include <queue>
+#include <string>
+#include <vector>
+
+#include "../src/commandlineflags.h"
+#include "../src/string_util.h"
+#include "benchmark/benchmark.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+namespace benchmark {
+
+BM_DECLARE_bool(benchmark_enable_random_interleaving);
+BM_DECLARE_string(benchmark_filter);
+BM_DECLARE_int32(benchmark_repetitions);
+
+namespace internal {
+namespace {
+
+class EventQueue : public std::queue<std::string> {
+ public:
+  void Put(const std::string& event) { push(event); }
+
+  void Clear() {
+    while (!empty()) {
+      pop();
+    }
+  }
+
+  std::string Get() {
+    std::string event = front();
+    pop();
+    return event;
+  }
+};
+
+EventQueue* queue = new EventQueue();
+
+class NullReporter : public BenchmarkReporter {
+ public:
+  bool ReportContext(const Context& /*context*/) override { return true; }
+  void ReportRuns(const std::vector<Run>& /* report */) override {}
+};
+
+class BenchmarkTest : public testing::Test {
+ public:
+  static void SetupHook(int /* num_threads */) { queue->push("Setup"); }
+
+  static void TeardownHook(int /* num_threads */) { queue->push("Teardown"); }
+
+  void Execute(const std::string& pattern) {
+    queue->Clear();
+
+    std::unique_ptr<BenchmarkReporter> reporter(new NullReporter());
+    FLAGS_benchmark_filter = pattern;
+    RunSpecifiedBenchmarks(reporter.get());
+
+    queue->Put("DONE");  // End marker
+  }
+};
+
+void BM_Match1(benchmark::State& state) {
+  const int64_t arg = state.range(0);
+
+  for (auto _ : state) {
+  }
+  queue->Put(StrFormat("BM_Match1/%d", static_cast<int>(arg)));
+}
+BENCHMARK(BM_Match1)
+    ->Iterations(100)
+    ->Arg(1)
+    ->Arg(2)
+    ->Arg(3)
+    ->Range(10, 80)
+    ->Args({90})
+    ->Args({100});
+
+TEST_F(BenchmarkTest, Match1) {
+  Execute("BM_Match1");
+  ASSERT_EQ("BM_Match1/1", queue->Get());
+  ASSERT_EQ("BM_Match1/2", queue->Get());
+  ASSERT_EQ("BM_Match1/3", queue->Get());
+  ASSERT_EQ("BM_Match1/10", queue->Get());
+  ASSERT_EQ("BM_Match1/64", queue->Get());
+  ASSERT_EQ("BM_Match1/80", queue->Get());
+  ASSERT_EQ("BM_Match1/90", queue->Get());
+  ASSERT_EQ("BM_Match1/100", queue->Get());
+  ASSERT_EQ("DONE", queue->Get());
+}
+
+TEST_F(BenchmarkTest, Match1WithRepetition) {
+  FLAGS_benchmark_repetitions = 2;
+
+  Execute("BM_Match1/(64|80)");
+  ASSERT_EQ("BM_Match1/64", queue->Get());
+  ASSERT_EQ("BM_Match1/64", queue->Get());
+  ASSERT_EQ("BM_Match1/80", queue->Get());
+  ASSERT_EQ("BM_Match1/80", queue->Get());
+  ASSERT_EQ("DONE", queue->Get());
+}
+
+TEST_F(BenchmarkTest, Match1WithRandomInterleaving) {
+  FLAGS_benchmark_enable_random_interleaving = true;
+  FLAGS_benchmark_repetitions = 100;
+
+  std::map<std::string, int> element_count;
+  std::map<std::string, int> interleaving_count;
+  Execute("BM_Match1/(64|80)");
+  for (int i = 0; i < 100; ++i) {
+    std::vector<std::string> interleaving;
+    interleaving.push_back(queue->Get());
+    interleaving.push_back(queue->Get());
+    element_count[interleaving[0]]++;
+    element_count[interleaving[1]]++;
+    interleaving_count[StrFormat("%s,%s", interleaving[0].c_str(),
+                                 interleaving[1].c_str())]++;
+  }
+  EXPECT_EQ(element_count["BM_Match1/64"], 100) << "Unexpected repetitions.";
+  EXPECT_EQ(element_count["BM_Match1/80"], 100) << "Unexpected repetitions.";
+  EXPECT_GE(interleaving_count.size(), 2) << "Interleaving was not randomized.";
+  ASSERT_EQ("DONE", queue->Get());
+}
+
+}  // namespace
+}  // namespace internal
+}  // namespace benchmark
diff --git a/leveldb_base/third_party/benchmark/test/benchmark_setup_teardown_test.cc b/leveldb_base/third_party/benchmark/test/benchmark_setup_teardown_test.cc
new file mode 100644
index 0000000..6c3cc2e
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/benchmark_setup_teardown_test.cc
@@ -0,0 +1,157 @@
+#include <atomic>
+#include <cassert>
+#include <cstdlib>
+#include <cstring>
+#include <iostream>
+#include <limits>
+#include <string>
+
+#include "benchmark/benchmark.h"
+
+// Test that Setup() and Teardown() are called exactly once
+// for each benchmark run (single-threaded).
+namespace singlethreaded {
+static int setup_call = 0;
+static int teardown_call = 0;
+}  // namespace singlethreaded
+static void DoSetup1(const benchmark::State& state) {
+  ++singlethreaded::setup_call;
+
+  // Setup/Teardown should never be called with any thread_idx != 0.
+  assert(state.thread_index() == 0);
+}
+
+static void DoTeardown1(const benchmark::State& state) {
+  ++singlethreaded::teardown_call;
+  assert(state.thread_index() == 0);
+}
+
+static void BM_with_setup(benchmark::State& state) {
+  for (auto s : state) {
+  }
+}
+BENCHMARK(BM_with_setup)
+    ->Arg(1)
+    ->Arg(3)
+    ->Arg(5)
+    ->Arg(7)
+    ->Iterations(100)
+    ->Setup(DoSetup1)
+    ->Teardown(DoTeardown1);
+
+// Test that Setup() and Teardown() are called once for each group of threads.
+namespace concurrent {
+static std::atomic<int> setup_call(0);
+static std::atomic<int> teardown_call(0);
+static std::atomic<int> func_call(0);
+}  // namespace concurrent
+
+static void DoSetup2(const benchmark::State& state) {
+  concurrent::setup_call.fetch_add(1, std::memory_order_acquire);
+  assert(state.thread_index() == 0);
+}
+
+static void DoTeardown2(const benchmark::State& state) {
+  concurrent::teardown_call.fetch_add(1, std::memory_order_acquire);
+  assert(state.thread_index() == 0);
+}
+
+static void BM_concurrent(benchmark::State& state) {
+  for (auto s : state) {
+  }
+  concurrent::func_call.fetch_add(1, std::memory_order_acquire);
+}
+
+BENCHMARK(BM_concurrent)
+    ->Setup(DoSetup2)
+    ->Teardown(DoTeardown2)
+    ->Iterations(100)
+    ->Threads(5)
+    ->Threads(10)
+    ->Threads(15);
+
+// Testing interaction with Fixture::Setup/Teardown
+namespace fixture_interaction {
+int setup = 0;
+int fixture_setup = 0;
+}  // namespace fixture_interaction
+
+#define FIXTURE_BECHMARK_NAME MyFixture
+
+class FIXTURE_BECHMARK_NAME : public ::benchmark::Fixture {
+ public:
+  void SetUp(const ::benchmark::State&) override {
+    fixture_interaction::fixture_setup++;
+  }
+
+  ~FIXTURE_BECHMARK_NAME() override {}
+};
+
+BENCHMARK_F(FIXTURE_BECHMARK_NAME, BM_WithFixture)(benchmark::State& st) {
+  for (auto _ : st) {
+  }
+}
+
+static void DoSetupWithFixture(const benchmark::State&) {
+  fixture_interaction::setup++;
+}
+
+BENCHMARK_REGISTER_F(FIXTURE_BECHMARK_NAME, BM_WithFixture)
+    ->Arg(1)
+    ->Arg(3)
+    ->Arg(5)
+    ->Arg(7)
+    ->Setup(DoSetupWithFixture)
+    ->Repetitions(1)
+    ->Iterations(100);
+
+// Testing repetitions.
+namespace repetitions {
+int setup = 0;
+}
+
+static void DoSetupWithRepetitions(const benchmark::State&) {
+  repetitions::setup++;
+}
+static void BM_WithRep(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+
+BENCHMARK(BM_WithRep)
+    ->Arg(1)
+    ->Arg(3)
+    ->Arg(5)
+    ->Arg(7)
+    ->Setup(DoSetupWithRepetitions)
+    ->Iterations(100)
+    ->Repetitions(4);
+
+int main(int argc, char** argv) {
+  benchmark::Initialize(&argc, argv);
+
+  size_t ret = benchmark::RunSpecifiedBenchmarks(".");
+  assert(ret > 0);
+
+  // Setup/Teardown is called once for each arg group (1,3,5,7).
+  assert(singlethreaded::setup_call == 4);
+  assert(singlethreaded::teardown_call == 4);
+
+  // 3 group of threads calling this function (3,5,10).
+  assert(concurrent::setup_call.load(std::memory_order_relaxed) == 3);
+  assert(concurrent::teardown_call.load(std::memory_order_relaxed) == 3);
+  assert((5 + 10 + 15) ==
+         concurrent::func_call.load(std::memory_order_relaxed));
+
+  // Setup is called 4 times, once for each arg group (1,3,5,7)
+  assert(fixture_interaction::setup == 4);
+  // Fixture::Setup is called every time the bm routine is run.
+  // The exact number is indeterministic, so we just assert that
+  // it's more than setup.
+  assert(fixture_interaction::fixture_setup > fixture_interaction::setup);
+
+  // Setup is call once for each repetition * num_arg =  4 * 4 = 16.
+  assert(repetitions::setup == 16);
+
+  return 0;
+}
diff --git a/leveldb_base/third_party/benchmark/test/benchmark_test.cc b/leveldb_base/third_party/benchmark/test/benchmark_test.cc
new file mode 100644
index 0000000..94590d5
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/benchmark_test.cc
@@ -0,0 +1,274 @@
+#include "benchmark/benchmark.h"
+
+#include <assert.h>
+#include <math.h>
+#include <stdint.h>
+
+#include <chrono>
+#include <complex>
+#include <cstdlib>
+#include <iostream>
+#include <limits>
+#include <list>
+#include <map>
+#include <mutex>
+#include <set>
+#include <sstream>
+#include <string>
+#include <thread>
+#include <utility>
+#include <vector>
+
+#if defined(__GNUC__)
+#define BENCHMARK_NOINLINE __attribute__((noinline))
+#else
+#define BENCHMARK_NOINLINE
+#endif
+
+namespace {
+
+int BENCHMARK_NOINLINE Factorial(int n) {
+  return (n == 1) ? 1 : n * Factorial(n - 1);
+}
+
+double CalculatePi(int depth) {
+  double pi = 0.0;
+  for (int i = 0; i < depth; ++i) {
+    double numerator = static_cast<double>(((i % 2) * 2) - 1);
+    double denominator = static_cast<double>((2 * i) - 1);
+    pi += numerator / denominator;
+  }
+  return (pi - 1.0) * 4;
+}
+
+std::set<int64_t> ConstructRandomSet(int64_t size) {
+  std::set<int64_t> s;
+  for (int i = 0; i < size; ++i) s.insert(s.end(), i);
+  return s;
+}
+
+std::mutex test_vector_mu;
+std::vector<int>* test_vector = nullptr;
+
+}  // end namespace
+
+static void BM_Factorial(benchmark::State& state) {
+  int fac_42 = 0;
+  for (auto _ : state) fac_42 = Factorial(8);
+  // Prevent compiler optimizations
+  std::stringstream ss;
+  ss << fac_42;
+  state.SetLabel(ss.str());
+}
+BENCHMARK(BM_Factorial);
+BENCHMARK(BM_Factorial)->UseRealTime();
+
+static void BM_CalculatePiRange(benchmark::State& state) {
+  double pi = 0.0;
+  for (auto _ : state) pi = CalculatePi(static_cast<int>(state.range(0)));
+  std::stringstream ss;
+  ss << pi;
+  state.SetLabel(ss.str());
+}
+BENCHMARK_RANGE(BM_CalculatePiRange, 1, 1024 * 1024);
+
+static void BM_CalculatePi(benchmark::State& state) {
+  static const int depth = 1024;
+  for (auto _ : state) {
+    double pi = CalculatePi(static_cast<int>(depth));
+    benchmark::DoNotOptimize(pi);
+  }
+}
+BENCHMARK(BM_CalculatePi)->Threads(8);
+BENCHMARK(BM_CalculatePi)->ThreadRange(1, 32);
+BENCHMARK(BM_CalculatePi)->ThreadPerCpu();
+
+static void BM_SetInsert(benchmark::State& state) {
+  std::set<int64_t> data;
+  for (auto _ : state) {
+    state.PauseTiming();
+    data = ConstructRandomSet(state.range(0));
+    state.ResumeTiming();
+    for (int j = 0; j < state.range(1); ++j) data.insert(rand());
+  }
+  state.SetItemsProcessed(state.iterations() * state.range(1));
+  state.SetBytesProcessed(state.iterations() * state.range(1) *
+                          static_cast<int64_t>(sizeof(int)));
+}
+
+// Test many inserts at once to reduce the total iterations needed. Otherwise,
+// the slower, non-timed part of each iteration will make the benchmark take
+// forever.
+BENCHMARK(BM_SetInsert)->Ranges({{1 << 10, 8 << 10}, {128, 512}});
+
+template <typename Container,
+          typename ValueType = typename Container::value_type>
+static void BM_Sequential(benchmark::State& state) {
+  ValueType v = 42;
+  for (auto _ : state) {
+    Container c;
+    for (int64_t i = state.range(0); --i;) c.push_back(v);
+  }
+  const int64_t items_processed = state.iterations() * state.range(0);
+  state.SetItemsProcessed(items_processed);
+  state.SetBytesProcessed(items_processed * static_cast<int64_t>(sizeof(v)));
+}
+BENCHMARK_TEMPLATE2(BM_Sequential, std::vector<int>, int)
+    ->Range(1 << 0, 1 << 10);
+BENCHMARK_TEMPLATE(BM_Sequential, std::list<int>)->Range(1 << 0, 1 << 10);
+// Test the variadic version of BENCHMARK_TEMPLATE in C++11 and beyond.
+#ifdef BENCHMARK_HAS_CXX11
+BENCHMARK_TEMPLATE(BM_Sequential, std::vector<int>, int)->Arg(512);
+#endif
+
+static void BM_StringCompare(benchmark::State& state) {
+  size_t len = static_cast<size_t>(state.range(0));
+  std::string s1(len, '-');
+  std::string s2(len, '-');
+  for (auto _ : state) {
+    auto comp = s1.compare(s2);
+    benchmark::DoNotOptimize(comp);
+  }
+}
+BENCHMARK(BM_StringCompare)->Range(1, 1 << 20);
+
+static void BM_SetupTeardown(benchmark::State& state) {
+  if (state.thread_index() == 0) {
+    // No need to lock test_vector_mu here as this is running single-threaded.
+    test_vector = new std::vector<int>();
+  }
+  int i = 0;
+  for (auto _ : state) {
+    std::lock_guard<std::mutex> l(test_vector_mu);
+    if (i % 2 == 0)
+      test_vector->push_back(i);
+    else
+      test_vector->pop_back();
+    ++i;
+  }
+  if (state.thread_index() == 0) {
+    delete test_vector;
+  }
+}
+BENCHMARK(BM_SetupTeardown)->ThreadPerCpu();
+
+static void BM_LongTest(benchmark::State& state) {
+  double tracker = 0.0;
+  for (auto _ : state) {
+    for (int i = 0; i < state.range(0); ++i)
+      benchmark::DoNotOptimize(tracker += i);
+  }
+}
+BENCHMARK(BM_LongTest)->Range(1 << 16, 1 << 28);
+
+static void BM_ParallelMemset(benchmark::State& state) {
+  int64_t size = state.range(0) / static_cast<int64_t>(sizeof(int));
+  int thread_size = static_cast<int>(size) / state.threads();
+  int from = thread_size * state.thread_index();
+  int to = from + thread_size;
+
+  if (state.thread_index() == 0) {
+    test_vector = new std::vector<int>(static_cast<size_t>(size));
+  }
+
+  for (auto _ : state) {
+    for (int i = from; i < to; i++) {
+      // No need to lock test_vector_mu as ranges
+      // do not overlap between threads.
+      benchmark::DoNotOptimize(test_vector->at(static_cast<size_t>(i)) = 1);
+    }
+  }
+
+  if (state.thread_index() == 0) {
+    delete test_vector;
+  }
+}
+BENCHMARK(BM_ParallelMemset)->Arg(10 << 20)->ThreadRange(1, 4);
+
+static void BM_ManualTiming(benchmark::State& state) {
+  int64_t slept_for = 0;
+  int64_t microseconds = state.range(0);
+  std::chrono::duration<double, std::micro> sleep_duration{
+      static_cast<double>(microseconds)};
+
+  for (auto _ : state) {
+    auto start = std::chrono::high_resolution_clock::now();
+    // Simulate some useful workload with a sleep
+    std::this_thread::sleep_for(
+        std::chrono::duration_cast<std::chrono::nanoseconds>(sleep_duration));
+    auto end = std::chrono::high_resolution_clock::now();
+
+    auto elapsed =
+        std::chrono::duration_cast<std::chrono::duration<double>>(end - start);
+
+    state.SetIterationTime(elapsed.count());
+    slept_for += microseconds;
+  }
+  state.SetItemsProcessed(slept_for);
+}
+BENCHMARK(BM_ManualTiming)->Range(1, 1 << 14)->UseRealTime();
+BENCHMARK(BM_ManualTiming)->Range(1, 1 << 14)->UseManualTime();
+
+#ifdef BENCHMARK_HAS_CXX11
+
+template <class... Args>
+void BM_with_args(benchmark::State& state, Args&&...) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK_CAPTURE(BM_with_args, int_test, 42, 43, 44);
+BENCHMARK_CAPTURE(BM_with_args, string_and_pair_test, std::string("abc"),
+                  std::pair<int, double>(42, 3.8));
+
+void BM_non_template_args(benchmark::State& state, int, double) {
+  while (state.KeepRunning()) {
+  }
+}
+BENCHMARK_CAPTURE(BM_non_template_args, basic_test, 0, 0);
+
+#endif  // BENCHMARK_HAS_CXX11
+
+static void BM_DenseThreadRanges(benchmark::State& st) {
+  switch (st.range(0)) {
+    case 1:
+      assert(st.threads() == 1 || st.threads() == 2 || st.threads() == 3);
+      break;
+    case 2:
+      assert(st.threads() == 1 || st.threads() == 3 || st.threads() == 4);
+      break;
+    case 3:
+      assert(st.threads() == 5 || st.threads() == 8 || st.threads() == 11 ||
+             st.threads() == 14);
+      break;
+    default:
+      assert(false && "Invalid test case number");
+  }
+  while (st.KeepRunning()) {
+  }
+}
+BENCHMARK(BM_DenseThreadRanges)->Arg(1)->DenseThreadRange(1, 3);
+BENCHMARK(BM_DenseThreadRanges)->Arg(2)->DenseThreadRange(1, 4, 2);
+BENCHMARK(BM_DenseThreadRanges)->Arg(3)->DenseThreadRange(5, 14, 3);
+
+static void BM_BenchmarkName(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+
+  // Check that the benchmark name is passed correctly to `state`.
+  assert("BM_BenchmarkName" == state.name());
+}
+BENCHMARK(BM_BenchmarkName);
+
+// regression test for #1446
+template <typename type>
+static void BM_templated_test(benchmark::State& state) {
+  for (auto _ : state) {
+    type created_string;
+    benchmark::DoNotOptimize(created_string);
+  }
+}
+
+static auto BM_templated_test_double = BM_templated_test<std::complex<double>>;
+BENCHMARK(BM_templated_test_double);
+
+BENCHMARK_MAIN();
diff --git a/leveldb_base/third_party/benchmark/test/clobber_memory_assembly_test.cc b/leveldb_base/third_party/benchmark/test/clobber_memory_assembly_test.cc
new file mode 100644
index 0000000..54e26cc
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/clobber_memory_assembly_test.cc
@@ -0,0 +1,64 @@
+#include <benchmark/benchmark.h>
+
+#ifdef __clang__
+#pragma clang diagnostic ignored "-Wreturn-type"
+#endif
+BENCHMARK_DISABLE_DEPRECATED_WARNING
+
+extern "C" {
+
+extern int ExternInt;
+extern int ExternInt2;
+extern int ExternInt3;
+}
+
+// CHECK-LABEL: test_basic:
+extern "C" void test_basic() {
+  int x;
+  benchmark::DoNotOptimize(&x);
+  x = 101;
+  benchmark::ClobberMemory();
+  // CHECK: leaq [[DEST:[^,]+]], %rax
+  // CHECK: movl $101, [[DEST]]
+  // CHECK: ret
+}
+
+// CHECK-LABEL: test_redundant_store:
+extern "C" void test_redundant_store() {
+  ExternInt = 3;
+  benchmark::ClobberMemory();
+  ExternInt = 51;
+  // CHECK-DAG: ExternInt
+  // CHECK-DAG: movl $3
+  // CHECK: movl $51
+}
+
+// CHECK-LABEL: test_redundant_read:
+extern "C" void test_redundant_read() {
+  int x;
+  benchmark::DoNotOptimize(&x);
+  x = ExternInt;
+  benchmark::ClobberMemory();
+  x = ExternInt2;
+  // CHECK: leaq [[DEST:[^,]+]], %rax
+  // CHECK: ExternInt(%rip)
+  // CHECK: movl %eax, [[DEST]]
+  // CHECK-NOT: ExternInt2
+  // CHECK: ret
+}
+
+// CHECK-LABEL: test_redundant_read2:
+extern "C" void test_redundant_read2() {
+  int x;
+  benchmark::DoNotOptimize(&x);
+  x = ExternInt;
+  benchmark::ClobberMemory();
+  x = ExternInt2;
+  benchmark::ClobberMemory();
+  // CHECK: leaq [[DEST:[^,]+]], %rax
+  // CHECK: ExternInt(%rip)
+  // CHECK: movl %eax, [[DEST]]
+  // CHECK: ExternInt2(%rip)
+  // CHECK: movl %eax, [[DEST]]
+  // CHECK: ret
+}
diff --git a/leveldb_base/third_party/benchmark/test/commandlineflags_gtest.cc b/leveldb_base/third_party/benchmark/test/commandlineflags_gtest.cc
new file mode 100644
index 0000000..8412008
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/commandlineflags_gtest.cc
@@ -0,0 +1,228 @@
+#include <cstdlib>
+
+#include "../src/commandlineflags.h"
+#include "../src/internal_macros.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+namespace benchmark {
+namespace {
+
+#if defined(BENCHMARK_OS_WINDOWS)
+int setenv(const char* name, const char* value, int overwrite) {
+  if (!overwrite) {
+    // NOTE: getenv_s is far superior but not available under mingw.
+    char* env_value = getenv(name);
+    if (env_value == nullptr) {
+      return -1;
+    }
+  }
+  return _putenv_s(name, value);
+}
+
+int unsetenv(const char* name) { return _putenv_s(name, ""); }
+
+#endif  // BENCHMARK_OS_WINDOWS
+
+TEST(BoolFromEnv, Default) {
+  ASSERT_EQ(unsetenv("NOT_IN_ENV"), 0);
+  EXPECT_EQ(BoolFromEnv("not_in_env", true), true);
+}
+
+TEST(BoolFromEnv, False) {
+  ASSERT_EQ(setenv("IN_ENV", "0", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", true), false);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "N", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", true), false);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "n", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", true), false);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "NO", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", true), false);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "No", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", true), false);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "no", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", true), false);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "F", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", true), false);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "f", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", true), false);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "FALSE", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", true), false);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "False", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", true), false);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "false", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", true), false);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "OFF", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", true), false);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "Off", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", true), false);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "off", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", true), false);
+  unsetenv("IN_ENV");
+}
+
+TEST(BoolFromEnv, True) {
+  ASSERT_EQ(setenv("IN_ENV", "1", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", false), true);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "Y", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", false), true);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "y", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", false), true);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "YES", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", false), true);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "Yes", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", false), true);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "yes", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", false), true);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "T", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", false), true);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "t", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", false), true);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "TRUE", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", false), true);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "True", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", false), true);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "true", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", false), true);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "ON", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", false), true);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "On", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", false), true);
+  unsetenv("IN_ENV");
+
+  ASSERT_EQ(setenv("IN_ENV", "on", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", false), true);
+  unsetenv("IN_ENV");
+
+#ifndef BENCHMARK_OS_WINDOWS
+  ASSERT_EQ(setenv("IN_ENV", "", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", false), true);
+  unsetenv("IN_ENV");
+#endif
+}
+
+TEST(Int32FromEnv, NotInEnv) {
+  ASSERT_EQ(unsetenv("NOT_IN_ENV"), 0);
+  EXPECT_EQ(Int32FromEnv("not_in_env", 42), 42);
+}
+
+TEST(Int32FromEnv, InvalidInteger) {
+  ASSERT_EQ(setenv("IN_ENV", "foo", 1), 0);
+  EXPECT_EQ(Int32FromEnv("in_env", 42), 42);
+  unsetenv("IN_ENV");
+}
+
+TEST(Int32FromEnv, ValidInteger) {
+  ASSERT_EQ(setenv("IN_ENV", "42", 1), 0);
+  EXPECT_EQ(Int32FromEnv("in_env", 64), 42);
+  unsetenv("IN_ENV");
+}
+
+TEST(DoubleFromEnv, NotInEnv) {
+  ASSERT_EQ(unsetenv("NOT_IN_ENV"), 0);
+  EXPECT_EQ(DoubleFromEnv("not_in_env", 0.51), 0.51);
+}
+
+TEST(DoubleFromEnv, InvalidReal) {
+  ASSERT_EQ(setenv("IN_ENV", "foo", 1), 0);
+  EXPECT_EQ(DoubleFromEnv("in_env", 0.51), 0.51);
+  unsetenv("IN_ENV");
+}
+
+TEST(DoubleFromEnv, ValidReal) {
+  ASSERT_EQ(setenv("IN_ENV", "0.51", 1), 0);
+  EXPECT_EQ(DoubleFromEnv("in_env", 0.71), 0.51);
+  unsetenv("IN_ENV");
+}
+
+TEST(StringFromEnv, Default) {
+  ASSERT_EQ(unsetenv("NOT_IN_ENV"), 0);
+  EXPECT_STREQ(StringFromEnv("not_in_env", "foo"), "foo");
+}
+
+TEST(StringFromEnv, Valid) {
+  ASSERT_EQ(setenv("IN_ENV", "foo", 1), 0);
+  EXPECT_STREQ(StringFromEnv("in_env", "bar"), "foo");
+  unsetenv("IN_ENV");
+}
+
+TEST(KvPairsFromEnv, Default) {
+  ASSERT_EQ(unsetenv("NOT_IN_ENV"), 0);
+  EXPECT_THAT(KvPairsFromEnv("not_in_env", {{"foo", "bar"}}),
+              testing::ElementsAre(testing::Pair("foo", "bar")));
+}
+
+TEST(KvPairsFromEnv, MalformedReturnsDefault) {
+  ASSERT_EQ(setenv("IN_ENV", "foo", 1), 0);
+  EXPECT_THAT(KvPairsFromEnv("in_env", {{"foo", "bar"}}),
+              testing::ElementsAre(testing::Pair("foo", "bar")));
+  unsetenv("IN_ENV");
+}
+
+TEST(KvPairsFromEnv, Single) {
+  ASSERT_EQ(setenv("IN_ENV", "foo=bar", 1), 0);
+  EXPECT_THAT(KvPairsFromEnv("in_env", {}),
+              testing::ElementsAre(testing::Pair("foo", "bar")));
+  unsetenv("IN_ENV");
+}
+
+TEST(KvPairsFromEnv, Multiple) {
+  ASSERT_EQ(setenv("IN_ENV", "foo=bar,baz=qux", 1), 0);
+  EXPECT_THAT(KvPairsFromEnv("in_env", {}),
+              testing::UnorderedElementsAre(testing::Pair("foo", "bar"),
+                                            testing::Pair("baz", "qux")));
+  unsetenv("IN_ENV");
+}
+
+}  // namespace
+}  // namespace benchmark
diff --git a/leveldb_base/third_party/benchmark/test/complexity_test.cc b/leveldb_base/third_party/benchmark/test/complexity_test.cc
new file mode 100644
index 0000000..76891e0
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/complexity_test.cc
@@ -0,0 +1,228 @@
+#undef NDEBUG
+#include <algorithm>
+#include <cassert>
+#include <cmath>
+#include <cstdlib>
+#include <vector>
+
+#include "benchmark/benchmark.h"
+#include "output_test.h"
+
+namespace {
+
+#define ADD_COMPLEXITY_CASES(...) \
+  int CONCAT(dummy, __LINE__) = AddComplexityTest(__VA_ARGS__)
+
+int AddComplexityTest(const std::string &test_name,
+                      const std::string &big_o_test_name,
+                      const std::string &rms_test_name,
+                      const std::string &big_o, int family_index) {
+  SetSubstitutions({{"%name", test_name},
+                    {"%bigo_name", big_o_test_name},
+                    {"%rms_name", rms_test_name},
+                    {"%bigo_str", "[ ]* %float " + big_o},
+                    {"%bigo", big_o},
+                    {"%rms", "[ ]*[0-9]+ %"}});
+  AddCases(
+      TC_ConsoleOut,
+      {{"^%bigo_name %bigo_str %bigo_str[ ]*$"},
+       {"^%bigo_name", MR_Not},  // Assert we we didn't only matched a name.
+       {"^%rms_name %rms %rms[ ]*$", MR_Next}});
+  AddCases(
+      TC_JSONOut,
+      {{"\"name\": \"%bigo_name\",$"},
+       {"\"family_index\": " + std::to_string(family_index) + ",$", MR_Next},
+       {"\"per_family_instance_index\": 0,$", MR_Next},
+       {"\"run_name\": \"%name\",$", MR_Next},
+       {"\"run_type\": \"aggregate\",$", MR_Next},
+       {"\"repetitions\": %int,$", MR_Next},
+       {"\"threads\": 1,$", MR_Next},
+       {"\"aggregate_name\": \"BigO\",$", MR_Next},
+       {"\"aggregate_unit\": \"time\",$", MR_Next},
+       {"\"cpu_coefficient\": %float,$", MR_Next},
+       {"\"real_coefficient\": %float,$", MR_Next},
+       {"\"big_o\": \"%bigo\",$", MR_Next},
+       {"\"time_unit\": \"ns\"$", MR_Next},
+       {"}", MR_Next},
+       {"\"name\": \"%rms_name\",$"},
+       {"\"family_index\": " + std::to_string(family_index) + ",$", MR_Next},
+       {"\"per_family_instance_index\": 0,$", MR_Next},
+       {"\"run_name\": \"%name\",$", MR_Next},
+       {"\"run_type\": \"aggregate\",$", MR_Next},
+       {"\"repetitions\": %int,$", MR_Next},
+       {"\"threads\": 1,$", MR_Next},
+       {"\"aggregate_name\": \"RMS\",$", MR_Next},
+       {"\"aggregate_unit\": \"percentage\",$", MR_Next},
+       {"\"rms\": %float$", MR_Next},
+       {"}", MR_Next}});
+  AddCases(TC_CSVOut, {{"^\"%bigo_name\",,%float,%float,%bigo,,,,,$"},
+                       {"^\"%bigo_name\"", MR_Not},
+                       {"^\"%rms_name\",,%float,%float,,,,,,$", MR_Next}});
+  return 0;
+}
+
+}  // end namespace
+
+// ========================================================================= //
+// --------------------------- Testing BigO O(1) --------------------------- //
+// ========================================================================= //
+
+void BM_Complexity_O1(benchmark::State &state) {
+  for (auto _ : state) {
+    for (int i = 0; i < 1024; ++i) {
+      benchmark::DoNotOptimize(i);
+    }
+  }
+  state.SetComplexityN(state.range(0));
+}
+BENCHMARK(BM_Complexity_O1)->Range(1, 1 << 18)->Complexity(benchmark::o1);
+BENCHMARK(BM_Complexity_O1)->Range(1, 1 << 18)->Complexity();
+BENCHMARK(BM_Complexity_O1)
+    ->Range(1, 1 << 18)
+    ->Complexity([](benchmark::IterationCount) { return 1.0; });
+
+const char *one_test_name = "BM_Complexity_O1";
+const char *big_o_1_test_name = "BM_Complexity_O1_BigO";
+const char *rms_o_1_test_name = "BM_Complexity_O1_RMS";
+const char *enum_big_o_1 = "\\([0-9]+\\)";
+// FIXME: Tolerate both '(1)' and 'lgN' as output when the complexity is auto
+// deduced.
+// See https://github.com/google/benchmark/issues/272
+const char *auto_big_o_1 = "(\\([0-9]+\\))|(lgN)";
+const char *lambda_big_o_1 = "f\\(N\\)";
+
+// Add enum tests
+ADD_COMPLEXITY_CASES(one_test_name, big_o_1_test_name, rms_o_1_test_name,
+                     enum_big_o_1, /*family_index=*/0);
+
+// Add auto enum tests
+ADD_COMPLEXITY_CASES(one_test_name, big_o_1_test_name, rms_o_1_test_name,
+                     auto_big_o_1, /*family_index=*/1);
+
+// Add lambda tests
+ADD_COMPLEXITY_CASES(one_test_name, big_o_1_test_name, rms_o_1_test_name,
+                     lambda_big_o_1, /*family_index=*/2);
+
+// ========================================================================= //
+// --------------------------- Testing BigO O(N) --------------------------- //
+// ========================================================================= //
+
+std::vector<int> ConstructRandomVector(int64_t size) {
+  std::vector<int> v;
+  v.reserve(static_cast<size_t>(size));
+  for (int i = 0; i < size; ++i) {
+    v.push_back(static_cast<int>(std::rand() % size));
+  }
+  return v;
+}
+
+void BM_Complexity_O_N(benchmark::State &state) {
+  auto v = ConstructRandomVector(state.range(0));
+  // Test worst case scenario (item not in vector)
+  const int64_t item_not_in_vector = state.range(0) * 2;
+  for (auto _ : state) {
+    auto it = std::find(v.begin(), v.end(), item_not_in_vector);
+    benchmark::DoNotOptimize(it);
+  }
+  state.SetComplexityN(state.range(0));
+}
+BENCHMARK(BM_Complexity_O_N)
+    ->RangeMultiplier(2)
+    ->Range(1 << 10, 1 << 16)
+    ->Complexity(benchmark::oN);
+BENCHMARK(BM_Complexity_O_N)
+    ->RangeMultiplier(2)
+    ->Range(1 << 10, 1 << 16)
+    ->Complexity([](benchmark::IterationCount n) -> double {
+      return static_cast<double>(n);
+    });
+BENCHMARK(BM_Complexity_O_N)
+    ->RangeMultiplier(2)
+    ->Range(1 << 10, 1 << 16)
+    ->Complexity();
+
+const char *n_test_name = "BM_Complexity_O_N";
+const char *big_o_n_test_name = "BM_Complexity_O_N_BigO";
+const char *rms_o_n_test_name = "BM_Complexity_O_N_RMS";
+const char *enum_auto_big_o_n = "N";
+const char *lambda_big_o_n = "f\\(N\\)";
+
+// Add enum tests
+ADD_COMPLEXITY_CASES(n_test_name, big_o_n_test_name, rms_o_n_test_name,
+                     enum_auto_big_o_n, /*family_index=*/3);
+
+// Add lambda tests
+ADD_COMPLEXITY_CASES(n_test_name, big_o_n_test_name, rms_o_n_test_name,
+                     lambda_big_o_n, /*family_index=*/4);
+
+// ========================================================================= //
+// ------------------------- Testing BigO O(N*lgN) ------------------------- //
+// ========================================================================= //
+
+static void BM_Complexity_O_N_log_N(benchmark::State &state) {
+  auto v = ConstructRandomVector(state.range(0));
+  for (auto _ : state) {
+    std::sort(v.begin(), v.end());
+  }
+  state.SetComplexityN(state.range(0));
+}
+static const double kLog2E = 1.44269504088896340736;
+BENCHMARK(BM_Complexity_O_N_log_N)
+    ->RangeMultiplier(2)
+    ->Range(1 << 10, 1 << 16)
+    ->Complexity(benchmark::oNLogN);
+BENCHMARK(BM_Complexity_O_N_log_N)
+    ->RangeMultiplier(2)
+    ->Range(1 << 10, 1 << 16)
+    ->Complexity([](benchmark::IterationCount n) {
+      return kLog2E * static_cast<double>(n) * log(static_cast<double>(n));
+    });
+BENCHMARK(BM_Complexity_O_N_log_N)
+    ->RangeMultiplier(2)
+    ->Range(1 << 10, 1 << 16)
+    ->Complexity();
+
+const char *n_lg_n_test_name = "BM_Complexity_O_N_log_N";
+const char *big_o_n_lg_n_test_name = "BM_Complexity_O_N_log_N_BigO";
+const char *rms_o_n_lg_n_test_name = "BM_Complexity_O_N_log_N_RMS";
+const char *enum_auto_big_o_n_lg_n = "NlgN";
+const char *lambda_big_o_n_lg_n = "f\\(N\\)";
+
+// Add enum tests
+ADD_COMPLEXITY_CASES(n_lg_n_test_name, big_o_n_lg_n_test_name,
+                     rms_o_n_lg_n_test_name, enum_auto_big_o_n_lg_n,
+                     /*family_index=*/6);
+
+// Add lambda tests
+ADD_COMPLEXITY_CASES(n_lg_n_test_name, big_o_n_lg_n_test_name,
+                     rms_o_n_lg_n_test_name, lambda_big_o_n_lg_n,
+                     /*family_index=*/7);
+
+// ========================================================================= //
+// -------- Testing formatting of Complexity with captured args ------------ //
+// ========================================================================= //
+
+void BM_ComplexityCaptureArgs(benchmark::State &state, int n) {
+  for (auto _ : state) {
+    // This test requires a non-zero CPU time to avoid divide-by-zero
+    auto iterations = state.iterations();
+    benchmark::DoNotOptimize(iterations);
+  }
+  state.SetComplexityN(n);
+}
+
+BENCHMARK_CAPTURE(BM_ComplexityCaptureArgs, capture_test, 100)
+    ->Complexity(benchmark::oN)
+    ->Ranges({{1, 2}, {3, 4}});
+
+const std::string complexity_capture_name =
+    "BM_ComplexityCaptureArgs/capture_test";
+
+ADD_COMPLEXITY_CASES(complexity_capture_name, complexity_capture_name + "_BigO",
+                     complexity_capture_name + "_RMS", "N", /*family_index=*/9);
+
+// ========================================================================= //
+// --------------------------- TEST CASES END ------------------------------ //
+// ========================================================================= //
+
+int main(int argc, char *argv[]) { RunOutputTests(argc, argv); }
diff --git a/leveldb_base/third_party/benchmark/test/cxx03_test.cc b/leveldb_base/third_party/benchmark/test/cxx03_test.cc
new file mode 100644
index 0000000..9711c1b
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/cxx03_test.cc
@@ -0,0 +1,62 @@
+#undef NDEBUG
+#include <cassert>
+#include <cstddef>
+
+#include "benchmark/benchmark.h"
+
+#if __cplusplus >= 201103L
+#error C++11 or greater detected. Should be C++03.
+#endif
+
+#ifdef BENCHMARK_HAS_CXX11
+#error C++11 or greater detected by the library. BENCHMARK_HAS_CXX11 is defined.
+#endif
+
+void BM_empty(benchmark::State& state) {
+  while (state.KeepRunning()) {
+    volatile benchmark::IterationCount x = state.iterations();
+    ((void)x);
+  }
+}
+BENCHMARK(BM_empty);
+
+// The new C++11 interface for args/ranges requires initializer list support.
+// Therefore we provide the old interface to support C++03.
+void BM_old_arg_range_interface(benchmark::State& state) {
+  assert((state.range(0) == 1 && state.range(1) == 2) ||
+         (state.range(0) == 5 && state.range(1) == 6));
+  while (state.KeepRunning()) {
+  }
+}
+BENCHMARK(BM_old_arg_range_interface)->ArgPair(1, 2)->RangePair(5, 5, 6, 6);
+
+template <class T, class U>
+void BM_template2(benchmark::State& state) {
+  BM_empty(state);
+}
+BENCHMARK_TEMPLATE2(BM_template2, int, long);
+
+template <class T>
+void BM_template1(benchmark::State& state) {
+  BM_empty(state);
+}
+BENCHMARK_TEMPLATE(BM_template1, long);
+BENCHMARK_TEMPLATE1(BM_template1, int);
+
+template <class T>
+struct BM_Fixture : public ::benchmark::Fixture {};
+
+BENCHMARK_TEMPLATE_F(BM_Fixture, BM_template1, long)(benchmark::State& state) {
+  BM_empty(state);
+}
+BENCHMARK_TEMPLATE1_F(BM_Fixture, BM_template2, int)(benchmark::State& state) {
+  BM_empty(state);
+}
+
+void BM_counters(benchmark::State& state) {
+  BM_empty(state);
+  state.counters["Foo"] = 2;
+}
+BENCHMARK(BM_counters);
+
+BENCHMARK_MAIN();
diff --git a/leveldb_base/third_party/benchmark/test/diagnostics_test.cc b/leveldb_base/third_party/benchmark/test/diagnostics_test.cc
new file mode 100644
index 0000000..fda14b3
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/diagnostics_test.cc
@@ -0,0 +1,82 @@
+// Testing:
+//   State::PauseTiming()
+//   State::ResumeTiming()
+// Test that CHECK's within these function diagnose when they are called
+// outside of the KeepRunning() loop.
+//
+// NOTE: Users should NOT include or use src/check.h. This is only done in
+// order to test library internals.
+
+#include <cstdlib>
+#include <stdexcept>
+
+#include "../src/check.h"
+#include "benchmark/benchmark.h"
+
+#if defined(__GNUC__) && !defined(__EXCEPTIONS)
+#define TEST_HAS_NO_EXCEPTIONS
+#endif
+
+void TestHandler() {
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  throw std::logic_error("");
+#else
+  std::abort();
+#endif
+}
+
+void try_invalid_pause_resume(benchmark::State& state) {
+#if !defined(TEST_BENCHMARK_LIBRARY_HAS_NO_ASSERTIONS) && \
+    !defined(TEST_HAS_NO_EXCEPTIONS)
+  try {
+    state.PauseTiming();
+    std::abort();
+  } catch (std::logic_error const&) {
+  }
+  try {
+    state.ResumeTiming();
+    std::abort();
+  } catch (std::logic_error const&) {
+  }
+#else
+  (void)state;  // avoid unused warning
+#endif
+}
+
+void BM_diagnostic_test(benchmark::State& state) {
+  static bool called_once = false;
+
+  if (called_once == false) try_invalid_pause_resume(state);
+
+  for (auto _ : state) {
+    auto iterations = state.iterations();
+    benchmark::DoNotOptimize(iterations);
+  }
+
+  if (called_once == false) try_invalid_pause_resume(state);
+
+  called_once = true;
+}
+BENCHMARK(BM_diagnostic_test);
+
+void BM_diagnostic_test_keep_running(benchmark::State& state) {
+  static bool called_once = false;
+
+  if (called_once == false) try_invalid_pause_resume(state);
+
+  while (state.KeepRunning()) {
+    auto iterations = state.iterations();
+    benchmark::DoNotOptimize(iterations);
+  }
+
+  if (called_once == false) try_invalid_pause_resume(state);
+
+  called_once = true;
+}
+BENCHMARK(BM_diagnostic_test_keep_running);
+
+int main(int argc, char* argv[]) {
+  benchmark::internal::GetAbortHandler() = &TestHandler;
+  benchmark::Initialize(&argc, argv);
+  benchmark::RunSpecifiedBenchmarks();
+}
diff --git a/leveldb_base/third_party/benchmark/test/display_aggregates_only_test.cc b/leveldb_base/third_party/benchmark/test/display_aggregates_only_test.cc
new file mode 100644
index 0000000..6ad65e7
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/display_aggregates_only_test.cc
@@ -0,0 +1,45 @@
+
+#undef NDEBUG
+#include <cstdio>
+#include <string>
+
+#include "benchmark/benchmark.h"
+#include "output_test.h"
+
+// Ok this test is super ugly. We want to check what happens with the file
+// reporter in the presence of DisplayAggregatesOnly().
+// We do not care about console output, the normal tests check that already.
+
+void BM_SummaryRepeat(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_SummaryRepeat)->Repetitions(3)->DisplayAggregatesOnly();
+
+int main(int argc, char* argv[]) {
+  const std::string output = GetFileReporterOutput(argc, argv);
+
+  if (SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3") != 7 ||
+      SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3\"") != 3 ||
+      SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3_mean\"") != 1 ||
+      SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3_median\"") !=
+          1 ||
+      SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3_stddev\"") !=
+          1 ||
+      SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3_cv\"") != 1) {
+    std::cout << "Precondition mismatch. Expected to only find 8 "
+                 "occurrences of \"BM_SummaryRepeat/repeats:3\" substring:\n"
+                 "\"name\": \"BM_SummaryRepeat/repeats:3\", "
+                 "\"name\": \"BM_SummaryRepeat/repeats:3\", "
+                 "\"name\": \"BM_SummaryRepeat/repeats:3\", "
+                 "\"name\": \"BM_SummaryRepeat/repeats:3_mean\", "
+                 "\"name\": \"BM_SummaryRepeat/repeats:3_median\", "
+                 "\"name\": \"BM_SummaryRepeat/repeats:3_stddev\", "
+                 "\"name\": \"BM_SummaryRepeat/repeats:3_cv\"\nThe entire "
+                 "output:\n";
+    std::cout << output;
+    return 1;
+  }
+
+  return 0;
+}
diff --git a/leveldb_base/third_party/benchmark/test/donotoptimize_assembly_test.cc b/leveldb_base/third_party/benchmark/test/donotoptimize_assembly_test.cc
new file mode 100644
index 0000000..dc286f5
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/donotoptimize_assembly_test.cc
@@ -0,0 +1,201 @@
+#include <benchmark/benchmark.h>
+
+#ifdef __clang__
+#pragma clang diagnostic ignored "-Wreturn-type"
+#endif
+BENCHMARK_DISABLE_DEPRECATED_WARNING
+
+extern "C" {
+
+extern int ExternInt;
+extern int ExternInt2;
+extern int ExternInt3;
+extern int BigArray[2049];
+
+const int ConstBigArray[2049]{};
+
+inline int Add42(int x) { return x + 42; }
+
+struct NotTriviallyCopyable {
+  NotTriviallyCopyable();
+  explicit NotTriviallyCopyable(int x) : value(x) {}
+  NotTriviallyCopyable(NotTriviallyCopyable const &);
+  int value;
+};
+
+struct Large {
+  int value;
+  int data[2];
+};
+
+struct ExtraLarge {
+  int arr[2049];
+};
+}
+
+extern ExtraLarge ExtraLargeObj;
+const ExtraLarge ConstExtraLargeObj{};
+
+// CHECK-LABEL: test_with_rvalue:
+extern "C" void test_with_rvalue() {
+  benchmark::DoNotOptimize(Add42(0));
+  // CHECK: movl $42, %eax
+  // CHECK: ret
+}
+
+// CHECK-LABEL: test_with_large_rvalue:
+extern "C" void test_with_large_rvalue() {
+  benchmark::DoNotOptimize(Large{ExternInt, {ExternInt, ExternInt}});
+  // CHECK: ExternInt(%rip)
+  // CHECK: movl %eax, -{{[0-9]+}}(%[[REG:[a-z]+]]
+  // CHECK: movl %eax, -{{[0-9]+}}(%[[REG]])
+  // CHECK: movl %eax, -{{[0-9]+}}(%[[REG]])
+  // CHECK: ret
+}
+
+// CHECK-LABEL: test_with_non_trivial_rvalue:
+extern "C" void test_with_non_trivial_rvalue() {
+  benchmark::DoNotOptimize(NotTriviallyCopyable(ExternInt));
+  // CHECK: mov{{l|q}} ExternInt(%rip)
+  // CHECK: ret
+}
+
+// CHECK-LABEL: test_with_lvalue:
+extern "C" void test_with_lvalue() {
+  int x = 101;
+  benchmark::DoNotOptimize(x);
+  // CHECK-GNU: movl $101, %eax
+  // CHECK-CLANG: movl $101, -{{[0-9]+}}(%[[REG:[a-z]+]])
+  // CHECK: ret
+}
+
+// CHECK-LABEL: test_with_large_lvalue:
+extern "C" void test_with_large_lvalue() {
+  Large L{ExternInt, {ExternInt, ExternInt}};
+  benchmark::DoNotOptimize(L);
+  // CHECK: ExternInt(%rip)
+  // CHECK: movl %eax, -{{[0-9]+}}(%[[REG:[a-z]+]])
+  // CHECK: movl %eax, -{{[0-9]+}}(%[[REG]])
+  // CHECK: movl %eax, -{{[0-9]+}}(%[[REG]])
+  // CHECK: ret
+}
+
+// CHECK-LABEL: test_with_extra_large_lvalue_with_op:
+extern "C" void test_with_extra_large_lvalue_with_op() {
+  ExtraLargeObj.arr[16] = 42;
+  benchmark::DoNotOptimize(ExtraLargeObj);
+  // CHECK: movl $42, ExtraLargeObj+64(%rip)
+  // CHECK: ret
+}
+
+// CHECK-LABEL: test_with_big_array_with_op
+extern "C" void test_with_big_array_with_op() {
+  BigArray[16] = 42;
+  benchmark::DoNotOptimize(BigArray);
+  // CHECK: movl $42, BigArray+64(%rip)
+  // CHECK: ret
+}
+
+// CHECK-LABEL: test_with_non_trivial_lvalue:
+extern "C" void test_with_non_trivial_lvalue() {
+  NotTriviallyCopyable NTC(ExternInt);
+  benchmark::DoNotOptimize(NTC);
+  // CHECK: ExternInt(%rip)
+  // CHECK: movl %eax, -{{[0-9]+}}(%[[REG:[a-z]+]])
+  // CHECK: ret
+}
+
+// CHECK-LABEL: test_with_const_lvalue:
+extern "C" void test_with_const_lvalue() {
+  const int x = 123;
+  benchmark::DoNotOptimize(x);
+  // CHECK: movl $123, %eax
+  // CHECK: ret
+}
+
+// CHECK-LABEL: test_with_large_const_lvalue:
+extern "C" void test_with_large_const_lvalue() {
+  const Large L{ExternInt, {ExternInt, ExternInt}};
+  benchmark::DoNotOptimize(L);
+  // CHECK: ExternInt(%rip)
+  // CHECK: movl %eax, -{{[0-9]+}}(%[[REG:[a-z]+]])
+  // CHECK: movl %eax, -{{[0-9]+}}(%[[REG]])
+  // CHECK: movl %eax, -{{[0-9]+}}(%[[REG]])
+  // CHECK: ret
+}
+
+// CHECK-LABEL: test_with_const_extra_large_obj:
+extern "C" void test_with_const_extra_large_obj() {
+  benchmark::DoNotOptimize(ConstExtraLargeObj);
+  // CHECK: ret
+}
+
+// CHECK-LABEL: test_with_const_big_array
+extern "C" void test_with_const_big_array() {
+  benchmark::DoNotOptimize(ConstBigArray);
+  // CHECK: ret
+}
+
+// CHECK-LABEL: test_with_non_trivial_const_lvalue:
+extern "C" void test_with_non_trivial_const_lvalue() {
+  const NotTriviallyCopyable Obj(ExternInt);
+  benchmark::DoNotOptimize(Obj);
+  // CHECK: mov{{q|l}} ExternInt(%rip)
+  // CHECK: ret
+}
+
+// CHECK-LABEL: test_div_by_two:
+extern "C" int test_div_by_two(int input) {
+  int divisor = 2;
+  benchmark::DoNotOptimize(divisor);
+  return input / divisor;
+  // CHECK: movl $2, [[DEST:.*]]
+  // CHECK: idivl [[DEST]]
+  // CHECK: ret
+}
+
+// CHECK-LABEL: test_inc_integer:
+extern "C" int test_inc_integer() {
+  int x = 0;
+  for (int i = 0; i < 5; ++i) benchmark::DoNotOptimize(++x);
+  // CHECK: movl $1, [[DEST:.*]]
+  // CHECK: {{(addl \$1,|incl)}} [[DEST]]
+  // CHECK: {{(addl \$1,|incl)}} [[DEST]]
+  // CHECK: {{(addl \$1,|incl)}} [[DEST]]
+  // CHECK: {{(addl \$1,|incl)}} [[DEST]]
+  // CHECK-CLANG: movl [[DEST]], %eax
+  // CHECK: ret
+  return x;
+}
+
+// CHECK-LABEL: test_pointer_rvalue
+extern "C" void test_pointer_rvalue() {
+  // CHECK: movl $42, [[DEST:.*]]
+  // CHECK: leaq [[DEST]], %rax
+  // CHECK-CLANG: movq %rax, -{{[0-9]+}}(%[[REG:[a-z]+]])
+  // CHECK: ret
+  int x = 42;
+  benchmark::DoNotOptimize(&x);
+}
+
+// CHECK-LABEL: test_pointer_const_lvalue:
+extern "C" void test_pointer_const_lvalue() {
+  // CHECK: movl $42, [[DEST:.*]]
+  // CHECK: leaq [[DEST]], %rax
+  // CHECK-CLANG: movq %rax, -{{[0-9]+}}(%[[REG:[a-z]+]])
+  // CHECK: ret
+  int x = 42;
+  int *const xp = &x;
+  benchmark::DoNotOptimize(xp);
+}
+
+// CHECK-LABEL: test_pointer_lvalue:
+extern "C" void test_pointer_lvalue() {
+  // CHECK: movl $42, [[DEST:.*]]
+  // CHECK: leaq [[DEST]], %rax
+  // CHECK-CLANG: movq %rax, -{{[0-9]+}}(%[[REG:[a-z+]+]])
+  // CHECK: ret
+  int x = 42;
+  int *xp = &x;
+  benchmark::DoNotOptimize(xp);
+}
diff --git a/leveldb_base/third_party/benchmark/test/donotoptimize_test.cc b/leveldb_base/third_party/benchmark/test/donotoptimize_test.cc
new file mode 100644
index 0000000..90d5af3
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/donotoptimize_test.cc
@@ -0,0 +1,64 @@
+#include <cstdint>
+
+#include "benchmark/benchmark.h"
+
+namespace {
+#if defined(__GNUC__)
+std::int64_t double_up(const std::int64_t x) __attribute__((const));
+#endif
+std::int64_t double_up(const std::int64_t x) { return x * 2; }
+}  // namespace
+
+// Using DoNotOptimize on types like BitRef seem to cause a lot of problems
+// with the inline assembly on both GCC and Clang.
+struct BitRef {
+  int index;
+  unsigned char& byte;
+
+ public:
+  static BitRef Make() {
+    static unsigned char arr[2] = {};
+    BitRef b(1, arr[0]);
+    return b;
+  }
+
+ private:
+  BitRef(int i, unsigned char& b) : index(i), byte(b) {}
+};
+
+int main(int, char*[]) {
+  // this test verifies compilation of DoNotOptimize() for some types
+
+  char buffer1[1] = "";
+  benchmark::DoNotOptimize(buffer1);
+
+  char buffer2[2] = "";
+  benchmark::DoNotOptimize(buffer2);
+
+  char buffer3[3] = "";
+  benchmark::DoNotOptimize(buffer3);
+
+  char buffer8[8] = "";
+  benchmark::DoNotOptimize(buffer8);
+
+  char buffer20[20] = "";
+  benchmark::DoNotOptimize(buffer20);
+
+  char buffer1024[1024] = "";
+  benchmark::DoNotOptimize(buffer1024);
+  char* bptr = &buffer1024[0];
+  benchmark::DoNotOptimize(bptr);
+
+  int x = 123;
+  benchmark::DoNotOptimize(x);
+  int* xp = &x;
+  benchmark::DoNotOptimize(xp);
+  benchmark::DoNotOptimize(x += 42);
+
+  std::int64_t y = double_up(x);
+  benchmark::DoNotOptimize(y);
+
+  // These tests are to e
+  BitRef lval = BitRef::Make();
+  benchmark::DoNotOptimize(lval);
+}
diff --git a/leveldb_base/third_party/benchmark/test/filter_test.cc b/leveldb_base/third_party/benchmark/test/filter_test.cc
new file mode 100644
index 0000000..4c8b8ea
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/filter_test.cc
@@ -0,0 +1,117 @@
+#include <algorithm>
+#include <cassert>
+#include <cmath>
+#include <cstdint>
+#include <cstdlib>
+#include <iostream>
+#include <limits>
+#include <sstream>
+#include <string>
+
+#include "benchmark/benchmark.h"
+
+namespace {
+
+class TestReporter : public benchmark::ConsoleReporter {
+ public:
+  bool ReportContext(const Context& context) override {
+    return ConsoleReporter::ReportContext(context);
+  };
+
+  void ReportRuns(const std::vector<Run>& report) override {
+    ++count_;
+    max_family_index_ = std::max(max_family_index_, report[0].family_index);
+    ConsoleReporter::ReportRuns(report);
+  };
+
+  TestReporter() : count_(0), max_family_index_(0) {}
+
+  ~TestReporter() override {}
+
+  int GetCount() const { return count_; }
+
+  int64_t GetMaxFamilyIndex() const { return max_family_index_; }
+
+ private:
+  mutable int count_;
+  mutable int64_t max_family_index_;
+};
+
+}  // end namespace
+
+static void NoPrefix(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(NoPrefix);
+
+static void BM_Foo(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_Foo);
+
+static void BM_Bar(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_Bar);
+
+static void BM_FooBar(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_FooBar);
+
+static void BM_FooBa(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_FooBa);
+
+int main(int argc, char** argv) {
+  bool list_only = false;
+  for (int i = 0; i < argc; ++i)
+    list_only |= std::string(argv[i]).find("--benchmark_list_tests") !=
+                 std::string::npos;
+
+  benchmark::Initialize(&argc, argv);
+
+  TestReporter test_reporter;
+  const int64_t returned_count =
+      static_cast<int64_t>(benchmark::RunSpecifiedBenchmarks(&test_reporter));
+
+  if (argc == 2) {
+    // Make sure we ran all of the tests
+    std::stringstream ss(argv[1]);
+    int64_t expected_return;
+    ss >> expected_return;
+
+    if (returned_count != expected_return) {
+      std::cerr << "ERROR: Expected " << expected_return
+                << " tests to match the filter but returned_count = "
+                << returned_count << std::endl;
+      return -1;
+    }
+
+    const int64_t expected_reports = list_only ? 0 : expected_return;
+    const int64_t reports_count = test_reporter.GetCount();
+    if (reports_count != expected_reports) {
+      std::cerr << "ERROR: Expected " << expected_reports
+                << " tests to be run but reported_count = " << reports_count
+                << std::endl;
+      return -1;
+    }
+
+    const int64_t max_family_index = test_reporter.GetMaxFamilyIndex();
+    const int64_t num_families = reports_count == 0 ? 0 : 1 + max_family_index;
+    if (num_families != expected_reports) {
+      std::cerr << "ERROR: Expected " << expected_reports
+                << " test families to be run but num_families = "
+                << num_families << std::endl;
+      return -1;
+    }
+  }
+
+  return 0;
+}
diff --git a/leveldb_base/third_party/benchmark/test/fixture_test.cc b/leveldb_base/third_party/benchmark/test/fixture_test.cc
new file mode 100644
index 0000000..d1093eb
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/fixture_test.cc
@@ -0,0 +1,51 @@
+
+#include <cassert>
+#include <memory>
+
+#include "benchmark/benchmark.h"
+
+#define FIXTURE_BECHMARK_NAME MyFixture
+
+class FIXTURE_BECHMARK_NAME : public ::benchmark::Fixture {
+ public:
+  void SetUp(const ::benchmark::State& state) override {
+    if (state.thread_index() == 0) {
+      assert(data.get() == nullptr);
+      data.reset(new int(42));
+    }
+  }
+
+  void TearDown(const ::benchmark::State& state) override {
+    if (state.thread_index() == 0) {
+      assert(data.get() != nullptr);
+      data.reset();
+    }
+  }
+
+  ~FIXTURE_BECHMARK_NAME() override { assert(data == nullptr); }
+
+  std::unique_ptr<int> data;
+};
+
+BENCHMARK_F(FIXTURE_BECHMARK_NAME, Foo)(benchmark::State& st) {
+  assert(data.get() != nullptr);
+  assert(*data == 42);
+  for (auto _ : st) {
+  }
+}
+
+BENCHMARK_DEFINE_F(FIXTURE_BECHMARK_NAME, Bar)(benchmark::State& st) {
+  if (st.thread_index() == 0) {
+    assert(data.get() != nullptr);
+    assert(*data == 42);
+  }
+  for (auto _ : st) {
+    assert(data.get() != nullptr);
+    assert(*data == 42);
+  }
+  st.SetItemsProcessed(st.range(0));
+}
+BENCHMARK_REGISTER_F(FIXTURE_BECHMARK_NAME, Bar)->Arg(42);
+BENCHMARK_REGISTER_F(FIXTURE_BECHMARK_NAME, Bar)->Arg(42)->ThreadPerCpu();
+
+BENCHMARK_MAIN();
diff --git a/leveldb_base/third_party/benchmark/test/internal_threading_test.cc b/leveldb_base/third_party/benchmark/test/internal_threading_test.cc
new file mode 100644
index 0000000..62b5b95
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/internal_threading_test.cc
@@ -0,0 +1,185 @@
+
+#undef NDEBUG
+
+#include <chrono>
+#include <thread>
+
+#include "../src/timers.h"
+#include "benchmark/benchmark.h"
+#include "output_test.h"
+
+static const std::chrono::duration<double, std::milli> time_frame(50);
+static const double time_frame_in_sec(
+    std::chrono::duration_cast<std::chrono::duration<double, std::ratio<1, 1>>>(
+        time_frame)
+        .count());
+
+void MyBusySpinwait() {
+  const auto start = benchmark::ChronoClockNow();
+
+  while (true) {
+    const auto now = benchmark::ChronoClockNow();
+    const auto elapsed = now - start;
+
+    if (std::chrono::duration<double, std::chrono::seconds::period>(elapsed) >=
+        time_frame)
+      return;
+  }
+}
+
+// ========================================================================= //
+// --------------------------- TEST CASES BEGIN ---------------------------- //
+// ========================================================================= //
+
+// ========================================================================= //
+// BM_MainThread
+
+void BM_MainThread(benchmark::State& state) {
+  for (auto _ : state) {
+    MyBusySpinwait();
+    state.SetIterationTime(time_frame_in_sec);
+  }
+  state.counters["invtime"] =
+      benchmark::Counter{1, benchmark::Counter::kIsRate};
+}
+
+BENCHMARK(BM_MainThread)->Iterations(1)->Threads(1);
+BENCHMARK(BM_MainThread)->Iterations(1)->Threads(1)->UseRealTime();
+BENCHMARK(BM_MainThread)->Iterations(1)->Threads(1)->UseManualTime();
+BENCHMARK(BM_MainThread)->Iterations(1)->Threads(1)->MeasureProcessCPUTime();
+BENCHMARK(BM_MainThread)
+    ->Iterations(1)
+    ->Threads(1)
+    ->MeasureProcessCPUTime()
+    ->UseRealTime();
+BENCHMARK(BM_MainThread)
+    ->Iterations(1)
+    ->Threads(1)
+    ->MeasureProcessCPUTime()
+    ->UseManualTime();
+
+BENCHMARK(BM_MainThread)->Iterations(1)->Threads(2);
+BENCHMARK(BM_MainThread)->Iterations(1)->Threads(2)->UseRealTime();
+BENCHMARK(BM_MainThread)->Iterations(1)->Threads(2)->UseManualTime();
+BENCHMARK(BM_MainThread)->Iterations(1)->Threads(2)->MeasureProcessCPUTime();
+BENCHMARK(BM_MainThread)
+    ->Iterations(1)
+    ->Threads(2)
+    ->MeasureProcessCPUTime()
+    ->UseRealTime();
+BENCHMARK(BM_MainThread)
+    ->Iterations(1)
+    ->Threads(2)
+    ->MeasureProcessCPUTime()
+    ->UseManualTime();
+
+// ========================================================================= //
+// BM_WorkerThread
+
+void BM_WorkerThread(benchmark::State& state) {
+  for (auto _ : state) {
+    std::thread Worker(&MyBusySpinwait);
+    Worker.join();
+    state.SetIterationTime(time_frame_in_sec);
+  }
+  state.counters["invtime"] =
+      benchmark::Counter{1, benchmark::Counter::kIsRate};
+}
+
+BENCHMARK(BM_WorkerThread)->Iterations(1)->Threads(1);
+BENCHMARK(BM_WorkerThread)->Iterations(1)->Threads(1)->UseRealTime();
+BENCHMARK(BM_WorkerThread)->Iterations(1)->Threads(1)->UseManualTime();
+BENCHMARK(BM_WorkerThread)->Iterations(1)->Threads(1)->MeasureProcessCPUTime();
+BENCHMARK(BM_WorkerThread)
+    ->Iterations(1)
+    ->Threads(1)
+    ->MeasureProcessCPUTime()
+    ->UseRealTime();
+BENCHMARK(BM_WorkerThread)
+    ->Iterations(1)
+    ->Threads(1)
+    ->MeasureProcessCPUTime()
+    ->UseManualTime();
+
+BENCHMARK(BM_WorkerThread)->Iterations(1)->Threads(2);
+BENCHMARK(BM_WorkerThread)->Iterations(1)->Threads(2)->UseRealTime();
+BENCHMARK(BM_WorkerThread)->Iterations(1)->Threads(2)->UseManualTime();
+BENCHMARK(BM_WorkerThread)->Iterations(1)->Threads(2)->MeasureProcessCPUTime();
+BENCHMARK(BM_WorkerThread)
+    ->Iterations(1)
+    ->Threads(2)
+    ->MeasureProcessCPUTime()
+    ->UseRealTime();
+BENCHMARK(BM_WorkerThread)
+    ->Iterations(1)
+    ->Threads(2)
+    ->MeasureProcessCPUTime()
+    ->UseManualTime();
+
+// ========================================================================= //
+// BM_MainThreadAndWorkerThread
+
+void BM_MainThreadAndWorkerThread(benchmark::State& state) {
+  for (auto _ : state) {
+    std::thread Worker(&MyBusySpinwait);
+    MyBusySpinwait();
+    Worker.join();
+    state.SetIterationTime(time_frame_in_sec);
+  }
+  state.counters["invtime"] =
+      benchmark::Counter{1, benchmark::Counter::kIsRate};
+}
+
+BENCHMARK(BM_MainThreadAndWorkerThread)->Iterations(1)->Threads(1);
+BENCHMARK(BM_MainThreadAndWorkerThread)
+    ->Iterations(1)
+    ->Threads(1)
+    ->UseRealTime();
+BENCHMARK(BM_MainThreadAndWorkerThread)
+    ->Iterations(1)
+    ->Threads(1)
+    ->UseManualTime();
+BENCHMARK(BM_MainThreadAndWorkerThread)
+    ->Iterations(1)
+    ->Threads(1)
+    ->MeasureProcessCPUTime();
+BENCHMARK(BM_MainThreadAndWorkerThread)
+    ->Iterations(1)
+    ->Threads(1)
+    ->MeasureProcessCPUTime()
+    ->UseRealTime();
+BENCHMARK(BM_MainThreadAndWorkerThread)
+    ->Iterations(1)
+    ->Threads(1)
+    ->MeasureProcessCPUTime()
+    ->UseManualTime();
+
+BENCHMARK(BM_MainThreadAndWorkerThread)->Iterations(1)->Threads(2);
+BENCHMARK(BM_MainThreadAndWorkerThread)
+    ->Iterations(1)
+    ->Threads(2)
+    ->UseRealTime();
+BENCHMARK(BM_MainThreadAndWorkerThread)
+    ->Iterations(1)
+    ->Threads(2)
+    ->UseManualTime();
+BENCHMARK(BM_MainThreadAndWorkerThread)
+    ->Iterations(1)
+    ->Threads(2)
+    ->MeasureProcessCPUTime();
+BENCHMARK(BM_MainThreadAndWorkerThread)
+    ->Iterations(1)
+    ->Threads(2)
+    ->MeasureProcessCPUTime()
+    ->UseRealTime();
+BENCHMARK(BM_MainThreadAndWorkerThread)
+    ->Iterations(1)
+    ->Threads(2)
+    ->MeasureProcessCPUTime()
+    ->UseManualTime();
+
+// ========================================================================= //
+// ---------------------------- TEST CASES END ----------------------------- //
+// ========================================================================= //
+
+int main(int argc, char* argv[]) { RunOutputTests(argc, argv); }
diff --git a/leveldb_base/third_party/benchmark/test/link_main_test.cc b/leveldb_base/third_party/benchmark/test/link_main_test.cc
new file mode 100644
index 0000000..e806500
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/link_main_test.cc
@@ -0,0 +1,9 @@
+#include "benchmark/benchmark.h"
+
+void BM_empty(benchmark::State& state) {
+  for (auto _ : state) {
+    auto iterations = state.iterations();
+    benchmark::DoNotOptimize(iterations);
+  }
+}
+BENCHMARK(BM_empty);
diff --git a/leveldb_base/third_party/benchmark/test/map_test.cc b/leveldb_base/third_party/benchmark/test/map_test.cc
new file mode 100644
index 0000000..0fdba7c
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/map_test.cc
@@ -0,0 +1,59 @@
+#include <cstdlib>
+#include <map>
+
+#include "benchmark/benchmark.h"
+
+namespace {
+
+std::map<int, int> ConstructRandomMap(int size) {
+  std::map<int, int> m;
+  for (int i = 0; i < size; ++i) {
+    m.insert(std::make_pair(std::rand() % size, std::rand() % size));
+  }
+  return m;
+}
+
+}  // namespace
+
+// Basic version.
+static void BM_MapLookup(benchmark::State& state) {
+  const int size = static_cast<int>(state.range(0));
+  std::map<int, int> m;
+  for (auto _ : state) {
+    state.PauseTiming();
+    m = ConstructRandomMap(size);
+    state.ResumeTiming();
+    for (int i = 0; i < size; ++i) {
+      auto it = m.find(std::rand() % size);
+      benchmark::DoNotOptimize(it);
+    }
+  }
+  state.SetItemsProcessed(state.iterations() * size);
+}
+BENCHMARK(BM_MapLookup)->Range(1 << 3, 1 << 12);
+
+// Using fixtures.
+class MapFixture : public ::benchmark::Fixture {
+ public:
+  void SetUp(const ::benchmark::State& st) override {
+    m = ConstructRandomMap(static_cast<int>(st.range(0)));
+  }
+
+  void TearDown(const ::benchmark::State&) override { m.clear(); }
+
+  std::map<int, int> m;
+};
+
+BENCHMARK_DEFINE_F(MapFixture, Lookup)(benchmark::State& state) {
+  const int size = static_cast<int>(state.range(0));
+  for (auto _ : state) {
+    for (int i = 0; i < size; ++i) {
+      auto it = m.find(std::rand() % size);
+      benchmark::DoNotOptimize(it);
+    }
+  }
+  state.SetItemsProcessed(state.iterations() * size);
+}
+BENCHMARK_REGISTER_F(MapFixture, Lookup)->Range(1 << 3, 1 << 12);
+
+BENCHMARK_MAIN();
diff --git a/leveldb_base/third_party/benchmark/test/memory_manager_test.cc b/leveldb_base/third_party/benchmark/test/memory_manager_test.cc
new file mode 100644
index 0000000..d94bd51
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/memory_manager_test.cc
@@ -0,0 +1,47 @@
+#include <memory>
+
+#include "../src/check.h"
+#include "benchmark/benchmark.h"
+#include "output_test.h"
+
+class TestMemoryManager : public benchmark::MemoryManager {
+  void Start() override {}
+  void Stop(Result& result) override {
+    result.num_allocs = 42;
+    result.max_bytes_used = 42000;
+  }
+};
+
+void BM_empty(benchmark::State& state) {
+  for (auto _ : state) {
+    auto iterations = state.iterations();
+    benchmark::DoNotOptimize(iterations);
+  }
+}
+BENCHMARK(BM_empty);
+
+ADD_CASES(TC_ConsoleOut, {{"^BM_empty %console_report$"}});
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_empty\",$"},
+                       {"\"family_index\": 0,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_empty\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 1,$", MR_Next},
+                       {"\"repetition_index\": 0,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"iterations\": %int,$", MR_Next},
+                       {"\"real_time\": %float,$", MR_Next},
+                       {"\"cpu_time\": %float,$", MR_Next},
+                       {"\"time_unit\": \"ns\",$", MR_Next},
+                       {"\"allocs_per_iter\": %float,$", MR_Next},
+                       {"\"max_bytes_used\": 42000$", MR_Next},
+                       {"}", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_empty\",%csv_report$"}});
+
+int main(int argc, char* argv[]) {
+  std::unique_ptr<benchmark::MemoryManager> mm(new TestMemoryManager());
+
+  benchmark::RegisterMemoryManager(mm.get());
+  RunOutputTests(argc, argv);
+  benchmark::RegisterMemoryManager(nullptr);
+}
diff --git a/leveldb_base/third_party/benchmark/test/min_time_parse_gtest.cc b/leveldb_base/third_party/benchmark/test/min_time_parse_gtest.cc
new file mode 100644
index 0000000..e2bdf67
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/min_time_parse_gtest.cc
@@ -0,0 +1,30 @@
+#include "../src/benchmark_runner.h"
+#include "gtest/gtest.h"
+
+namespace {
+
+TEST(ParseMinTimeTest, InvalidInput) {
+#if GTEST_HAS_DEATH_TEST
+  // Tests only runnable in debug mode (when BM_CHECK is enabled).
+#ifndef NDEBUG
+#ifndef TEST_BENCHMARK_LIBRARY_HAS_NO_ASSERTIONS
+  ASSERT_DEATH_IF_SUPPORTED(
+      { benchmark::internal::ParseBenchMinTime("abc"); },
+      "Malformed seconds value passed to --benchmark_min_time: `abc`");
+
+  ASSERT_DEATH_IF_SUPPORTED(
+      { benchmark::internal::ParseBenchMinTime("123ms"); },
+      "Malformed seconds value passed to --benchmark_min_time: `123ms`");
+
+  ASSERT_DEATH_IF_SUPPORTED(
+      { benchmark::internal::ParseBenchMinTime("1z"); },
+      "Malformed seconds value passed to --benchmark_min_time: `1z`");
+
+  ASSERT_DEATH_IF_SUPPORTED(
+      { benchmark::internal::ParseBenchMinTime("1hs"); },
+      "Malformed seconds value passed to --benchmark_min_time: `1hs`");
+#endif
+#endif
+#endif
+}
+}  // namespace
diff --git a/leveldb_base/third_party/benchmark/test/multiple_ranges_test.cc b/leveldb_base/third_party/benchmark/test/multiple_ranges_test.cc
new file mode 100644
index 0000000..5300a96
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/multiple_ranges_test.cc
@@ -0,0 +1,96 @@
+#include <cassert>
+#include <iostream>
+#include <set>
+#include <vector>
+
+#include "benchmark/benchmark.h"
+
+class MultipleRangesFixture : public ::benchmark::Fixture {
+ public:
+  MultipleRangesFixture()
+      : expectedValues({{1, 3, 5},
+                        {1, 3, 8},
+                        {1, 3, 15},
+                        {2, 3, 5},
+                        {2, 3, 8},
+                        {2, 3, 15},
+                        {1, 4, 5},
+                        {1, 4, 8},
+                        {1, 4, 15},
+                        {2, 4, 5},
+                        {2, 4, 8},
+                        {2, 4, 15},
+                        {1, 7, 5},
+                        {1, 7, 8},
+                        {1, 7, 15},
+                        {2, 7, 5},
+                        {2, 7, 8},
+                        {2, 7, 15},
+                        {7, 6, 3}}) {}
+
+  void SetUp(const ::benchmark::State& state) override {
+    std::vector<int64_t> ranges = {state.range(0), state.range(1),
+                                   state.range(2)};
+
+    assert(expectedValues.find(ranges) != expectedValues.end());
+
+    actualValues.insert(ranges);
+  }
+
+  // NOTE: This is not TearDown as we want to check after _all_ runs are
+  // complete.
+  ~MultipleRangesFixture() override {
+    if (actualValues != expectedValues) {
+      std::cout << "EXPECTED\n";
+      for (const auto& v : expectedValues) {
+        std::cout << "{";
+        for (int64_t iv : v) {
+          std::cout << iv << ", ";
+        }
+        std::cout << "}\n";
+      }
+      std::cout << "ACTUAL\n";
+      for (const auto& v : actualValues) {
+        std::cout << "{";
+        for (int64_t iv : v) {
+          std::cout << iv << ", ";
+        }
+        std::cout << "}\n";
+      }
+    }
+  }
+
+  std::set<std::vector<int64_t>> expectedValues;
+  std::set<std::vector<int64_t>> actualValues;
+};
+
+BENCHMARK_DEFINE_F(MultipleRangesFixture, Empty)(benchmark::State& state) {
+  for (auto _ : state) {
+    int64_t product = state.range(0) * state.range(1) * state.range(2);
+    for (int64_t x = 0; x < product; x++) {
+      benchmark::DoNotOptimize(x);
+    }
+  }
+}
+
+BENCHMARK_REGISTER_F(MultipleRangesFixture, Empty)
+    ->RangeMultiplier(2)
+    ->Ranges({{1, 2}, {3, 7}, {5, 15}})
+    ->Args({7, 6, 3});
+
+void BM_CheckDefaultArgument(benchmark::State& state) {
+  // Test that the 'range()' without an argument is the same as 'range(0)'.
+  assert(state.range() == state.range(0));
+  assert(state.range() != state.range(1));
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_CheckDefaultArgument)->Ranges({{1, 5}, {6, 10}});
+
+static void BM_MultipleRanges(benchmark::State& st) {
+  for (auto _ : st) {
+  }
+}
+BENCHMARK(BM_MultipleRanges)->Ranges({{5, 5}, {6, 6}});
+
+BENCHMARK_MAIN();
diff --git a/leveldb_base/third_party/benchmark/test/options_test.cc b/leveldb_base/third_party/benchmark/test/options_test.cc
new file mode 100644
index 0000000..a1b209f
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/options_test.cc
@@ -0,0 +1,77 @@
+#include <chrono>
+#include <thread>
+
+#include "benchmark/benchmark.h"
+
+#if defined(NDEBUG)
+#undef NDEBUG
+#endif
+#include <cassert>
+
+void BM_basic(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+
+void BM_basic_slow(benchmark::State& state) {
+  std::chrono::milliseconds sleep_duration(state.range(0));
+  for (auto _ : state) {
+    std::this_thread::sleep_for(
+        std::chrono::duration_cast<std::chrono::nanoseconds>(sleep_duration));
+  }
+}
+
+BENCHMARK(BM_basic);
+BENCHMARK(BM_basic)->Arg(42);
+BENCHMARK(BM_basic_slow)->Arg(10)->Unit(benchmark::kNanosecond);
+BENCHMARK(BM_basic_slow)->Arg(100)->Unit(benchmark::kMicrosecond);
+BENCHMARK(BM_basic_slow)->Arg(1000)->Unit(benchmark::kMillisecond);
+BENCHMARK(BM_basic_slow)->Arg(1000)->Unit(benchmark::kSecond);
+BENCHMARK(BM_basic)->Range(1, 8);
+BENCHMARK(BM_basic)->RangeMultiplier(2)->Range(1, 8);
+BENCHMARK(BM_basic)->DenseRange(10, 15);
+BENCHMARK(BM_basic)->Args({42, 42});
+BENCHMARK(BM_basic)->Ranges({{64, 512}, {64, 512}});
+BENCHMARK(BM_basic)->MinTime(0.7);
+BENCHMARK(BM_basic)->MinWarmUpTime(0.8);
+BENCHMARK(BM_basic)->MinTime(0.1)->MinWarmUpTime(0.2);
+BENCHMARK(BM_basic)->UseRealTime();
+BENCHMARK(BM_basic)->ThreadRange(2, 4);
+BENCHMARK(BM_basic)->ThreadPerCpu();
+BENCHMARK(BM_basic)->Repetitions(3);
+BENCHMARK(BM_basic)
+    ->RangeMultiplier(std::numeric_limits<int>::max())
+    ->Range(std::numeric_limits<int64_t>::min(),
+            std::numeric_limits<int64_t>::max());
+
+// Negative ranges
+BENCHMARK(BM_basic)->Range(-64, -1);
+BENCHMARK(BM_basic)->RangeMultiplier(4)->Range(-8, 8);
+BENCHMARK(BM_basic)->DenseRange(-2, 2, 1);
+BENCHMARK(BM_basic)->Ranges({{-64, 1}, {-8, -1}});
+
+void CustomArgs(benchmark::internal::Benchmark* b) {
+  for (int i = 0; i < 10; ++i) {
+    b->Arg(i);
+  }
+}
+
+BENCHMARK(BM_basic)->Apply(CustomArgs);
+
+void BM_explicit_iteration_count(benchmark::State& state) {
+  // Test that benchmarks specified with an explicit iteration count are
+  // only run once.
+  static bool invoked_before = false;
+  assert(!invoked_before);
+  invoked_before = true;
+
+  // Test that the requested iteration count is respected.
+  assert(state.max_iterations == 42);
+  for (auto _ : state) {
+  }
+  assert(state.iterations() == state.max_iterations);
+  assert(state.iterations() == 42);
+}
+BENCHMARK(BM_explicit_iteration_count)->Iterations(42);
+
+BENCHMARK_MAIN();
diff --git a/leveldb_base/third_party/benchmark/test/output_test.h b/leveldb_base/third_party/benchmark/test/output_test.h
new file mode 100644
index 0000000..c08fe1d
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/output_test.h
@@ -0,0 +1,211 @@
+#ifndef TEST_OUTPUT_TEST_H
+#define TEST_OUTPUT_TEST_H
+
+#undef NDEBUG
+#include <functional>
+#include <initializer_list>
+#include <memory>
+#include <sstream>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "../src/re.h"
+#include "benchmark/benchmark.h"
+
+#define CONCAT2(x, y) x##y
+#define CONCAT(x, y) CONCAT2(x, y)
+
+#define ADD_CASES(...) int CONCAT(dummy, __LINE__) = ::AddCases(__VA_ARGS__)
+
+#define SET_SUBSTITUTIONS(...) \
+  int CONCAT(dummy, __LINE__) = ::SetSubstitutions(__VA_ARGS__)
+
+enum MatchRules {
+  MR_Default,  // Skip non-matching lines until a match is found.
+  MR_Next,     // Match must occur on the next line.
+  MR_Not  // No line between the current position and the next match matches
+          // the regex
+};
+
+struct TestCase {
+  TestCase(std::string re, int rule = MR_Default);
+
+  std::string regex_str;
+  int match_rule;
+  std::string substituted_regex;
+  std::shared_ptr<benchmark::Regex> regex;
+};
+
+enum TestCaseID {
+  TC_ConsoleOut,
+  TC_ConsoleErr,
+  TC_JSONOut,
+  TC_JSONErr,
+  TC_CSVOut,
+  TC_CSVErr,
+
+  TC_NumID  // PRIVATE
+};
+
+// Add a list of test cases to be run against the output specified by
+// 'ID'
+int AddCases(TestCaseID ID, std::initializer_list<TestCase> il);
+
+// Add or set a list of substitutions to be performed on constructed regex's
+// See 'output_test_helper.cc' for a list of default substitutions.
+int SetSubstitutions(
+    std::initializer_list<std::pair<std::string, std::string>> il);
+
+// Run all output tests.
+void RunOutputTests(int argc, char* argv[]);
+
+// Count the number of 'pat' substrings in the 'haystack' string.
+int SubstrCnt(const std::string& haystack, const std::string& pat);
+
+// Run registered benchmarks with file reporter enabled, and return the content
+// outputted by the file reporter.
+std::string GetFileReporterOutput(int argc, char* argv[]);
+
+// ========================================================================= //
+// ------------------------- Results checking ------------------------------ //
+// ========================================================================= //
+
+// Call this macro to register a benchmark for checking its results. This
+// should be all that's needed. It subscribes a function to check the (CSV)
+// results of a benchmark. This is done only after verifying that the output
+// strings are really as expected.
+// bm_name_pattern: a name or a regex pattern which will be matched against
+//                  all the benchmark names. Matching benchmarks
+//                  will be the subject of a call to checker_function
+// checker_function: should be of type ResultsCheckFn (see below)
+#define CHECK_BENCHMARK_RESULTS(bm_name_pattern, checker_function) \
+  size_t CONCAT(dummy, __LINE__) = AddChecker(bm_name_pattern, checker_function)
+
+struct Results;
+typedef std::function<void(Results const&)> ResultsCheckFn;
+
+size_t AddChecker(const std::string& bm_name_pattern, const ResultsCheckFn& fn);
+
+// Class holding the results of a benchmark.
+// It is passed in calls to checker functions.
+struct Results {
+  // the benchmark name
+  std::string name;
+  // the benchmark fields
+  std::map<std::string, std::string> values;
+
+  Results(const std::string& n) : name(n) {}
+
+  int NumThreads() const;
+
+  double NumIterations() const;
+
+  typedef enum { kCpuTime, kRealTime } BenchmarkTime;
+
+  // get cpu_time or real_time in seconds
+  double GetTime(BenchmarkTime which) const;
+
+  // get the real_time duration of the benchmark in seconds.
+  // it is better to use fuzzy float checks for this, as the float
+  // ASCII formatting is lossy.
+  double DurationRealTime() const {
+    return NumIterations() * GetTime(kRealTime);
+  }
+  // get the cpu_time duration of the benchmark in seconds
+  double DurationCPUTime() const { return NumIterations() * GetTime(kCpuTime); }
+
+  // get the string for a result by name, or nullptr if the name
+  // is not found
+  const std::string* Get(const std::string& entry_name) const {
+    auto it = values.find(entry_name);
+    if (it == values.end()) return nullptr;
+    return &it->second;
+  }
+
+  // get a result by name, parsed as a specific type.
+  // NOTE: for counters, use GetCounterAs instead.
+  template <class T>
+  T GetAs(const std::string& entry_name) const;
+
+  // counters are written as doubles, so they have to be read first
+  // as a double, and only then converted to the asked type.
+  template <class T>
+  T GetCounterAs(const std::string& entry_name) const {
+    double dval = GetAs<double>(entry_name);
+    T tval = static_cast<T>(dval);
+    return tval;
+  }
+};
+
+template <class T>
+T Results::GetAs(const std::string& entry_name) const {
+  auto* sv = Get(entry_name);
+  BM_CHECK(sv != nullptr && !sv->empty());
+  std::stringstream ss;
+  ss << *sv;
+  T out;
+  ss >> out;
+  BM_CHECK(!ss.fail());
+  return out;
+}
+
+//----------------------------------
+// Macros to help in result checking. Do not use them with arguments causing
+// side-effects.
+
+// clang-format off
+
+#define CHECK_RESULT_VALUE_IMPL(entry, getfn, var_type, var_name, relationship, value) \
+    CONCAT(BM_CHECK_, relationship)                                        \
+    (entry.getfn< var_type >(var_name), (value)) << "\n"                \
+    << __FILE__ << ":" << __LINE__ << ": " << (entry).name << ":\n"     \
+    << __FILE__ << ":" << __LINE__ << ": "                              \
+    << "expected (" << #var_type << ")" << (var_name)                   \
+    << "=" << (entry).getfn< var_type >(var_name)                       \
+    << " to be " #relationship " to " << (value) << "\n"
+
+// check with tolerance. eps_factor is the tolerance window, which is
+// interpreted relative to value (eg, 0.1 means 10% of value).
+#define CHECK_FLOAT_RESULT_VALUE_IMPL(entry, getfn, var_type, var_name, relationship, value, eps_factor) \
+    CONCAT(BM_CHECK_FLOAT_, relationship)                                  \
+    (entry.getfn< var_type >(var_name), (value), (eps_factor) * (value)) << "\n" \
+    << __FILE__ << ":" << __LINE__ << ": " << (entry).name << ":\n"     \
+    << __FILE__ << ":" << __LINE__ << ": "                              \
+    << "expected (" << #var_type << ")" << (var_name)                   \
+    << "=" << (entry).getfn< var_type >(var_name)                       \
+    << " to be " #relationship " to " << (value) << "\n"                \
+    << __FILE__ << ":" << __LINE__ << ": "                              \
+    << "with tolerance of " << (eps_factor) * (value)                   \
+    << " (" << (eps_factor)*100. << "%), "                              \
+    << "but delta was " << ((entry).getfn< var_type >(var_name) - (value)) \
+    << " (" << (((entry).getfn< var_type >(var_name) - (value))         \
+               /                                                        \
+               ((value) > 1.e-5 || value < -1.e-5 ? value : 1.e-5)*100.) \
+    << "%)"
+
+#define CHECK_RESULT_VALUE(entry, var_type, var_name, relationship, value) \
+    CHECK_RESULT_VALUE_IMPL(entry, GetAs, var_type, var_name, relationship, value)
+
+#define CHECK_COUNTER_VALUE(entry, var_type, var_name, relationship, value) \
+    CHECK_RESULT_VALUE_IMPL(entry, GetCounterAs, var_type, var_name, relationship, value)
+
+#define CHECK_FLOAT_RESULT_VALUE(entry, var_name, relationship, value, eps_factor) \
+    CHECK_FLOAT_RESULT_VALUE_IMPL(entry, GetAs, double, var_name, relationship, value, eps_factor)
+
+#define CHECK_FLOAT_COUNTER_VALUE(entry, var_name, relationship, value, eps_factor) \
+    CHECK_FLOAT_RESULT_VALUE_IMPL(entry, GetCounterAs, double, var_name, relationship, value, eps_factor)
+
+// clang-format on
+
+// ========================================================================= //
+// --------------------------- Misc Utilities ------------------------------ //
+// ========================================================================= //
+
+namespace {
+
+const char* const dec_re = "[0-9]*[.]?[0-9]+([eE][-+][0-9]+)?";
+
+}  //  end namespace
+
+#endif  // TEST_OUTPUT_TEST_H
diff --git a/leveldb_base/third_party/benchmark/test/output_test_helper.cc b/leveldb_base/third_party/benchmark/test/output_test_helper.cc
new file mode 100644
index 0000000..241af5c
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/output_test_helper.cc
@@ -0,0 +1,519 @@
+#include <cstdio>
+#include <cstring>
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <memory>
+#include <random>
+#include <sstream>
+#include <streambuf>
+
+#include "../src/benchmark_api_internal.h"
+#include "../src/check.h"  // NOTE: check.h is for internal use only!
+#include "../src/log.h"    // NOTE: log.h is for internal use only
+#include "../src/re.h"     // NOTE: re.h is for internal use only
+#include "output_test.h"
+
+// ========================================================================= //
+// ------------------------------ Internals -------------------------------- //
+// ========================================================================= //
+namespace internal {
+namespace {
+
+using TestCaseList = std::vector<TestCase>;
+
+// Use a vector because the order elements are added matters during iteration.
+// std::map/unordered_map don't guarantee that.
+// For example:
+//  SetSubstitutions({{"%HelloWorld", "Hello"}, {"%Hello", "Hi"}});
+//     Substitute("%HelloWorld") // Always expands to Hello.
+using SubMap = std::vector<std::pair<std::string, std::string>>;
+
+TestCaseList& GetTestCaseList(TestCaseID ID) {
+  // Uses function-local statics to ensure initialization occurs
+  // before first use.
+  static TestCaseList lists[TC_NumID];
+  return lists[ID];
+}
+
+SubMap& GetSubstitutions() {
+  // Don't use 'dec_re' from header because it may not yet be initialized.
+  // clang-format off
+  static std::string safe_dec_re = "[0-9]*[.]?[0-9]+([eE][-+][0-9]+)?";
+  static std::string time_re = "([0-9]+[.])?[0-9]+";
+  static std::string percentage_re = "[0-9]+[.][0-9]{2}";
+  static SubMap map = {
+      {"%float", "[0-9]*[.]?[0-9]+([eE][-+][0-9]+)?"},
+      // human-readable float
+      {"%hrfloat", "[0-9]*[.]?[0-9]+([eE][-+][0-9]+)?[kMGTPEZYmunpfazy]?"},
+      {"%percentage", percentage_re},
+      {"%int", "[ ]*[0-9]+"},
+      {" %s ", "[ ]+"},
+      {"%time", "[ ]*" + time_re + "[ ]+ns"},
+      {"%console_report", "[ ]*" + time_re + "[ ]+ns [ ]*" + time_re + "[ ]+ns [ ]*[0-9]+"},
+      {"%console_percentage_report", "[ ]*" + percentage_re + "[ ]+% [ ]*" + percentage_re + "[ ]+% [ ]*[0-9]+"},
+      {"%console_us_report", "[ ]*" + time_re + "[ ]+us [ ]*" + time_re + "[ ]+us [ ]*[0-9]+"},
+      {"%console_ms_report", "[ ]*" + time_re + "[ ]+ms [ ]*" + time_re + "[ ]+ms [ ]*[0-9]+"},
+      {"%console_s_report", "[ ]*" + time_re + "[ ]+s [ ]*" + time_re + "[ ]+s [ ]*[0-9]+"},
+      {"%console_time_only_report", "[ ]*" + time_re + "[ ]+ns [ ]*" + time_re + "[ ]+ns"},
+      {"%console_us_report", "[ ]*" + time_re + "[ ]+us [ ]*" + time_re + "[ ]+us [ ]*[0-9]+"},
+      {"%console_us_time_only_report", "[ ]*" + time_re + "[ ]+us [ ]*" + time_re + "[ ]+us"},
+      {"%csv_header",
+       "name,iterations,real_time,cpu_time,time_unit,bytes_per_second,"
+       "items_per_second,label,error_occurred,error_message"},
+      {"%csv_report", "[0-9]+," + safe_dec_re + "," + safe_dec_re + ",ns,,,,,"},
+      {"%csv_us_report", "[0-9]+," + safe_dec_re + "," + safe_dec_re + ",us,,,,,"},
+      {"%csv_ms_report", "[0-9]+," + safe_dec_re + "," + safe_dec_re + ",ms,,,,,"},
+      {"%csv_s_report", "[0-9]+," + safe_dec_re + "," + safe_dec_re + ",s,,,,,"},
+      {"%csv_bytes_report",
+       "[0-9]+," + safe_dec_re + "," + safe_dec_re + ",ns," + safe_dec_re + ",,,,"},
+      {"%csv_items_report",
+       "[0-9]+," + safe_dec_re + "," + safe_dec_re + ",ns,," + safe_dec_re + ",,,"},
+      {"%csv_bytes_items_report",
+       "[0-9]+," + safe_dec_re + "," + safe_dec_re + ",ns," + safe_dec_re +
+       "," + safe_dec_re + ",,,"},
+      {"%csv_label_report_begin", "[0-9]+," + safe_dec_re + "," + safe_dec_re + ",ns,,,"},
+      {"%csv_label_report_end", ",,"}};
+  // clang-format on
+  return map;
+}
+
+std::string PerformSubstitutions(std::string source) {
+  SubMap const& subs = GetSubstitutions();
+  using SizeT = std::string::size_type;
+  for (auto const& KV : subs) {
+    SizeT pos;
+    SizeT next_start = 0;
+    while ((pos = source.find(KV.first, next_start)) != std::string::npos) {
+      next_start = pos + KV.second.size();
+      source.replace(pos, KV.first.size(), KV.second);
+    }
+  }
+  return source;
+}
+
+void CheckCase(std::stringstream& remaining_output, TestCase const& TC,
+               TestCaseList const& not_checks) {
+  std::string first_line;
+  bool on_first = true;
+  std::string line;
+  while (remaining_output.eof() == false) {
+    BM_CHECK(remaining_output.good());
+    std::getline(remaining_output, line);
+    if (on_first) {
+      first_line = line;
+      on_first = false;
+    }
+    for (const auto& NC : not_checks) {
+      BM_CHECK(!NC.regex->Match(line))
+          << "Unexpected match for line \"" << line << "\" for MR_Not regex \""
+          << NC.regex_str << "\""
+          << "\n    actual regex string \"" << TC.substituted_regex << "\""
+          << "\n    started matching near: " << first_line;
+    }
+    if (TC.regex->Match(line)) return;
+    BM_CHECK(TC.match_rule != MR_Next)
+        << "Expected line \"" << line << "\" to match regex \"" << TC.regex_str
+        << "\""
+        << "\n    actual regex string \"" << TC.substituted_regex << "\""
+        << "\n    started matching near: " << first_line;
+  }
+  BM_CHECK(remaining_output.eof() == false)
+      << "End of output reached before match for regex \"" << TC.regex_str
+      << "\" was found"
+      << "\n    actual regex string \"" << TC.substituted_regex << "\""
+      << "\n    started matching near: " << first_line;
+}
+
+void CheckCases(TestCaseList const& checks, std::stringstream& output) {
+  std::vector<TestCase> not_checks;
+  for (size_t i = 0; i < checks.size(); ++i) {
+    const auto& TC = checks[i];
+    if (TC.match_rule == MR_Not) {
+      not_checks.push_back(TC);
+      continue;
+    }
+    CheckCase(output, TC, not_checks);
+    not_checks.clear();
+  }
+}
+
+class TestReporter : public benchmark::BenchmarkReporter {
+ public:
+  TestReporter(std::vector<benchmark::BenchmarkReporter*> reps)
+      : reporters_(std::move(reps)) {}
+
+  bool ReportContext(const Context& context) override {
+    bool last_ret = false;
+    bool first = true;
+    for (auto rep : reporters_) {
+      bool new_ret = rep->ReportContext(context);
+      BM_CHECK(first || new_ret == last_ret)
+          << "Reports return different values for ReportContext";
+      first = false;
+      last_ret = new_ret;
+    }
+    (void)first;
+    return last_ret;
+  }
+
+  void ReportRuns(const std::vector<Run>& report) override {
+    for (auto rep : reporters_) rep->ReportRuns(report);
+  }
+  void Finalize() override {
+    for (auto rep : reporters_) rep->Finalize();
+  }
+
+ private:
+  std::vector<benchmark::BenchmarkReporter*> reporters_;
+};
+}  // namespace
+
+}  // end namespace internal
+
+// ========================================================================= //
+// -------------------------- Results checking ----------------------------- //
+// ========================================================================= //
+
+namespace internal {
+
+// Utility class to manage subscribers for checking benchmark results.
+// It works by parsing the CSV output to read the results.
+class ResultsChecker {
+ public:
+  struct PatternAndFn : public TestCase {  // reusing TestCase for its regexes
+    PatternAndFn(const std::string& rx, ResultsCheckFn fn_)
+        : TestCase(rx), fn(std::move(fn_)) {}
+    ResultsCheckFn fn;
+  };
+
+  std::vector<PatternAndFn> check_patterns;
+  std::vector<Results> results;
+  std::vector<std::string> field_names;
+
+  void Add(const std::string& entry_pattern, const ResultsCheckFn& fn);
+
+  void CheckResults(std::stringstream& output);
+
+ private:
+  void SetHeader_(const std::string& csv_header);
+  void SetValues_(const std::string& entry_csv_line);
+
+  std::vector<std::string> SplitCsv_(const std::string& line);
+};
+
+// store the static ResultsChecker in a function to prevent initialization
+// order problems
+ResultsChecker& GetResultsChecker() {
+  static ResultsChecker rc;
+  return rc;
+}
+
+// add a results checker for a benchmark
+void ResultsChecker::Add(const std::string& entry_pattern,
+                         const ResultsCheckFn& fn) {
+  check_patterns.emplace_back(entry_pattern, fn);
+}
+
+// check the results of all subscribed benchmarks
+void ResultsChecker::CheckResults(std::stringstream& output) {
+  // first reset the stream to the start
+  {
+    auto start = std::stringstream::pos_type(0);
+    // clear before calling tellg()
+    output.clear();
+    // seek to zero only when needed
+    if (output.tellg() > start) output.seekg(start);
+    // and just in case
+    output.clear();
+  }
+  // now go over every line and publish it to the ResultsChecker
+  std::string line;
+  bool on_first = true;
+  while (output.eof() == false) {
+    BM_CHECK(output.good());
+    std::getline(output, line);
+    if (on_first) {
+      SetHeader_(line);  // this is important
+      on_first = false;
+      continue;
+    }
+    SetValues_(line);
+  }
+  // finally we can call the subscribed check functions
+  for (const auto& p : check_patterns) {
+    BM_VLOG(2) << "--------------------------------\n";
+    BM_VLOG(2) << "checking for benchmarks matching " << p.regex_str << "...\n";
+    for (const auto& r : results) {
+      if (!p.regex->Match(r.name)) {
+        BM_VLOG(2) << p.regex_str << " is not matched by " << r.name << "\n";
+        continue;
+      }
+      BM_VLOG(2) << p.regex_str << " is matched by " << r.name << "\n";
+      BM_VLOG(1) << "Checking results of " << r.name << ": ... \n";
+      p.fn(r);
+      BM_VLOG(1) << "Checking results of " << r.name << ": OK.\n";
+    }
+  }
+}
+
+// prepare for the names in this header
+void ResultsChecker::SetHeader_(const std::string& csv_header) {
+  field_names = SplitCsv_(csv_header);
+}
+
+// set the values for a benchmark
+void ResultsChecker::SetValues_(const std::string& entry_csv_line) {
+  if (entry_csv_line.empty()) return;  // some lines are empty
+  BM_CHECK(!field_names.empty());
+  auto vals = SplitCsv_(entry_csv_line);
+  BM_CHECK_EQ(vals.size(), field_names.size());
+  results.emplace_back(vals[0]);  // vals[0] is the benchmark name
+  auto& entry = results.back();
+  for (size_t i = 1, e = vals.size(); i < e; ++i) {
+    entry.values[field_names[i]] = vals[i];
+  }
+}
+
+// a quick'n'dirty csv splitter (eliminating quotes)
+std::vector<std::string> ResultsChecker::SplitCsv_(const std::string& line) {
+  std::vector<std::string> out;
+  if (line.empty()) return out;
+  if (!field_names.empty()) out.reserve(field_names.size());
+  size_t prev = 0, pos = line.find_first_of(','), curr = pos;
+  while (pos != line.npos) {
+    BM_CHECK(curr > 0);
+    if (line[prev] == '"') ++prev;
+    if (line[curr - 1] == '"') --curr;
+    out.push_back(line.substr(prev, curr - prev));
+    prev = pos + 1;
+    pos = line.find_first_of(',', pos + 1);
+    curr = pos;
+  }
+  curr = line.size();
+  if (line[prev] == '"') ++prev;
+  if (line[curr - 1] == '"') --curr;
+  out.push_back(line.substr(prev, curr - prev));
+  return out;
+}
+
+}  // end namespace internal
+
+size_t AddChecker(const std::string& bm_name, const ResultsCheckFn& fn) {
+  auto& rc = internal::GetResultsChecker();
+  rc.Add(bm_name, fn);
+  return rc.results.size();
+}
+
+int Results::NumThreads() const {
+  auto pos = name.find("/threads:");
+  if (pos == name.npos) return 1;
+  auto end = name.find('/', pos + 9);
+  std::stringstream ss;
+  ss << name.substr(pos + 9, end);
+  int num = 1;
+  ss >> num;
+  BM_CHECK(!ss.fail());
+  return num;
+}
+
+double Results::NumIterations() const { return GetAs<double>("iterations"); }
+
+double Results::GetTime(BenchmarkTime which) const {
+  BM_CHECK(which == kCpuTime || which == kRealTime);
+  const char* which_str = which == kCpuTime ? "cpu_time" : "real_time";
+  double val = GetAs<double>(which_str);
+  auto unit = Get("time_unit");
+  BM_CHECK(unit);
+  if (*unit == "ns") {
+    return val * 1.e-9;
+  }
+  if (*unit == "us") {
+    return val * 1.e-6;
+  }
+  if (*unit == "ms") {
+    return val * 1.e-3;
+  }
+  if (*unit == "s") {
+    return val;
+  }
+  BM_CHECK(1 == 0) << "unknown time unit: " << *unit;
+  return 0;
+}
+
+// ========================================================================= //
+// -------------------------- Public API Definitions------------------------ //
+// ========================================================================= //
+
+TestCase::TestCase(std::string re, int rule)
+    : regex_str(std::move(re)),
+      match_rule(rule),
+      substituted_regex(internal::PerformSubstitutions(regex_str)),
+      regex(std::make_shared<benchmark::Regex>()) {
+  std::string err_str;
+  regex->Init(substituted_regex, &err_str);
+  BM_CHECK(err_str.empty())
+      << "Could not construct regex \"" << substituted_regex << "\""
+      << "\n    originally \"" << regex_str << "\""
+      << "\n    got error: " << err_str;
+}
+
+int AddCases(TestCaseID ID, std::initializer_list<TestCase> il) {
+  auto& L = internal::GetTestCaseList(ID);
+  L.insert(L.end(), il);
+  return 0;
+}
+
+int SetSubstitutions(
+    std::initializer_list<std::pair<std::string, std::string>> il) {
+  auto& subs = internal::GetSubstitutions();
+  for (auto KV : il) {
+    bool exists = false;
+    KV.second = internal::PerformSubstitutions(KV.second);
+    for (auto& EKV : subs) {
+      if (EKV.first == KV.first) {
+        EKV.second = std::move(KV.second);
+        exists = true;
+        break;
+      }
+    }
+    if (!exists) subs.push_back(std::move(KV));
+  }
+  return 0;
+}
+
+// Disable deprecated warnings temporarily because we need to reference
+// CSVReporter but don't want to trigger -Werror=-Wdeprecated-declarations
+BENCHMARK_DISABLE_DEPRECATED_WARNING
+
+void RunOutputTests(int argc, char* argv[]) {
+  using internal::GetTestCaseList;
+  benchmark::Initialize(&argc, argv);
+  auto options = benchmark::internal::GetOutputOptions(/*force_no_color*/ true);
+  benchmark::ConsoleReporter CR(options);
+  benchmark::JSONReporter JR;
+  benchmark::CSVReporter CSVR;
+  struct ReporterTest {
+    std::string name;
+    std::vector<TestCase>& output_cases;
+    std::vector<TestCase>& error_cases;
+    benchmark::BenchmarkReporter& reporter;
+    std::stringstream out_stream;
+    std::stringstream err_stream;
+
+    ReporterTest(const std::string& n, std::vector<TestCase>& out_tc,
+                 std::vector<TestCase>& err_tc,
+                 benchmark::BenchmarkReporter& br)
+        : name(n), output_cases(out_tc), error_cases(err_tc), reporter(br) {
+      reporter.SetOutputStream(&out_stream);
+      reporter.SetErrorStream(&err_stream);
+    }
+  } TestCases[] = {
+      {std::string("ConsoleReporter"), GetTestCaseList(TC_ConsoleOut),
+       GetTestCaseList(TC_ConsoleErr), CR},
+      {std::string("JSONReporter"), GetTestCaseList(TC_JSONOut),
+       GetTestCaseList(TC_JSONErr), JR},
+      {std::string("CSVReporter"), GetTestCaseList(TC_CSVOut),
+       GetTestCaseList(TC_CSVErr), CSVR},
+  };
+
+  // Create the test reporter and run the benchmarks.
+  std::cout << "Running benchmarks...\n";
+  internal::TestReporter test_rep({&CR, &JR, &CSVR});
+  benchmark::RunSpecifiedBenchmarks(&test_rep);
+
+  for (auto& rep_test : TestCases) {
+    std::string msg =
+        std::string("\nTesting ") + rep_test.name + std::string(" Output\n");
+    std::string banner(msg.size() - 1, '-');
+    std::cout << banner << msg << banner << "\n";
+
+    std::cerr << rep_test.err_stream.str();
+    std::cout << rep_test.out_stream.str();
+
+    internal::CheckCases(rep_test.error_cases, rep_test.err_stream);
+    internal::CheckCases(rep_test.output_cases, rep_test.out_stream);
+
+    std::cout << "\n";
+  }
+
+  // now that we know the output is as expected, we can dispatch
+  // the checks to subscribees.
+  auto& csv = TestCases[2];
+  // would use == but gcc spits a warning
+  BM_CHECK(csv.name == std::string("CSVReporter"));
+  internal::GetResultsChecker().CheckResults(csv.out_stream);
+}
+
+BENCHMARK_RESTORE_DEPRECATED_WARNING
+
+int SubstrCnt(const std::string& haystack, const std::string& pat) {
+  if (pat.length() == 0) return 0;
+  int count = 0;
+  for (size_t offset = haystack.find(pat); offset != std::string::npos;
+       offset = haystack.find(pat, offset + pat.length()))
+    ++count;
+  return count;
+}
+
+static char ToHex(int ch) {
+  return ch < 10 ? static_cast<char>('0' + ch)
+                 : static_cast<char>('a' + (ch - 10));
+}
+
+static char RandomHexChar() {
+  static std::mt19937 rd{std::random_device{}()};
+  static std::uniform_int_distribution<int> mrand{0, 15};
+  return ToHex(mrand(rd));
+}
+
+static std::string GetRandomFileName() {
+  std::string model = "test.%%%%%%";
+  for (auto& ch : model) {
+    if (ch == '%') ch = RandomHexChar();
+  }
+  return model;
+}
+
+static bool FileExists(std::string const& name) {
+  std::ifstream in(name.c_str());
+  return in.good();
+}
+
+static std::string GetTempFileName() {
+  // This function attempts to avoid race conditions where two tests
+  // create the same file at the same time. However, it still introduces races
+  // similar to tmpnam.
+  int retries = 3;
+  while (--retries) {
+    std::string name = GetRandomFileName();
+    if (!FileExists(name)) return name;
+  }
+  std::cerr << "Failed to create unique temporary file name" << std::endl;
+  std::abort();
+}
+
+std::string GetFileReporterOutput(int argc, char* argv[]) {
+  std::vector<char*> new_argv(argv, argv + argc);
+  assert(static_cast<decltype(new_argv)::size_type>(argc) == new_argv.size());
+
+  std::string tmp_file_name = GetTempFileName();
+  std::cout << "Will be using this as the tmp file: " << tmp_file_name << '\n';
+
+  std::string tmp = "--benchmark_out=";
+  tmp += tmp_file_name;
+  new_argv.emplace_back(const_cast<char*>(tmp.c_str()));
+
+  argc = int(new_argv.size());
+
+  benchmark::Initialize(&argc, new_argv.data());
+  benchmark::RunSpecifiedBenchmarks();
+
+  // Read the output back from the file, and delete the file.
+  std::ifstream tmp_stream(tmp_file_name);
+  std::string output = std::string((std::istreambuf_iterator<char>(tmp_stream)),
+                                   std::istreambuf_iterator<char>());
+  std::remove(tmp_file_name.c_str());
+
+  return output;
+}
diff --git a/leveldb_base/third_party/benchmark/test/perf_counters_gtest.cc b/leveldb_base/third_party/benchmark/test/perf_counters_gtest.cc
new file mode 100644
index 0000000..e73ebc5
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/perf_counters_gtest.cc
@@ -0,0 +1,316 @@
+#include <random>
+#include <thread>
+
+#include "../src/perf_counters.h"
+#include "gtest/gtest.h"
+
+#ifndef GTEST_SKIP
+struct MsgHandler {
+  void operator=(std::ostream&) {}
+};
+#define GTEST_SKIP() return MsgHandler() = std::cout
+#endif
+
+using benchmark::internal::PerfCounters;
+using benchmark::internal::PerfCountersMeasurement;
+using benchmark::internal::PerfCounterValues;
+
+namespace {
+const char kGenericPerfEvent1[] = "CYCLES";
+const char kGenericPerfEvent2[] = "BRANCHES";
+const char kGenericPerfEvent3[] = "INSTRUCTIONS";
+
+TEST(PerfCountersTest, Init) {
+  EXPECT_EQ(PerfCounters::Initialize(), PerfCounters::kSupported);
+}
+
+TEST(PerfCountersTest, OneCounter) {
+  if (!PerfCounters::kSupported) {
+    GTEST_SKIP() << "Performance counters not supported.\n";
+  }
+  EXPECT_TRUE(PerfCounters::Initialize());
+  EXPECT_EQ(PerfCounters::Create({kGenericPerfEvent1}).num_counters(), 1);
+}
+
+TEST(PerfCountersTest, NegativeTest) {
+  if (!PerfCounters::kSupported) {
+    EXPECT_FALSE(PerfCounters::Initialize());
+    return;
+  }
+  EXPECT_TRUE(PerfCounters::Initialize());
+  // Sanity checks
+  // Create() will always create a valid object, even if passed no or
+  // wrong arguments as the new behavior is to warn and drop unsupported
+  // counters
+  EXPECT_EQ(PerfCounters::Create({}).num_counters(), 0);
+  EXPECT_EQ(PerfCounters::Create({""}).num_counters(), 0);
+  EXPECT_EQ(PerfCounters::Create({"not a counter name"}).num_counters(), 0);
+  {
+    // Try sneaking in a bad egg to see if it is filtered out. The
+    // number of counters has to be two, not zero
+    auto counter =
+        PerfCounters::Create({kGenericPerfEvent2, "", kGenericPerfEvent1});
+    EXPECT_EQ(counter.num_counters(), 2);
+    EXPECT_EQ(counter.names(), std::vector<std::string>(
+                                   {kGenericPerfEvent2, kGenericPerfEvent1}));
+  }
+  {
+    // Try sneaking in an outrageous counter, like a fat finger mistake
+    auto counter = PerfCounters::Create(
+        {kGenericPerfEvent3, "not a counter name", kGenericPerfEvent1});
+    EXPECT_EQ(counter.num_counters(), 2);
+    EXPECT_EQ(counter.names(), std::vector<std::string>(
+                                   {kGenericPerfEvent3, kGenericPerfEvent1}));
+  }
+  {
+    // Finally try a golden input - it should like all them
+    EXPECT_EQ(PerfCounters::Create(
+                  {kGenericPerfEvent1, kGenericPerfEvent2, kGenericPerfEvent3})
+                  .num_counters(),
+              3);
+  }
+  {
+    // Add a bad apple in the end of the chain to check the edges
+    auto counter = PerfCounters::Create({kGenericPerfEvent1, kGenericPerfEvent2,
+                                         kGenericPerfEvent3,
+                                         "MISPREDICTED_BRANCH_RETIRED"});
+    EXPECT_EQ(counter.num_counters(), 3);
+    EXPECT_EQ(counter.names(),
+              std::vector<std::string>({kGenericPerfEvent1, kGenericPerfEvent2,
+                                        kGenericPerfEvent3}));
+  }
+}
+
+TEST(PerfCountersTest, Read1Counter) {
+  if (!PerfCounters::kSupported) {
+    GTEST_SKIP() << "Test skipped because libpfm is not supported.\n";
+  }
+  EXPECT_TRUE(PerfCounters::Initialize());
+  auto counters = PerfCounters::Create({kGenericPerfEvent1});
+  EXPECT_EQ(counters.num_counters(), 1);
+  PerfCounterValues values1(1);
+  EXPECT_TRUE(counters.Snapshot(&values1));
+  EXPECT_GT(values1[0], 0);
+  PerfCounterValues values2(1);
+  EXPECT_TRUE(counters.Snapshot(&values2));
+  EXPECT_GT(values2[0], 0);
+  EXPECT_GT(values2[0], values1[0]);
+}
+
+TEST(PerfCountersTest, Read2Counters) {
+  if (!PerfCounters::kSupported) {
+    GTEST_SKIP() << "Test skipped because libpfm is not supported.\n";
+  }
+  EXPECT_TRUE(PerfCounters::Initialize());
+  auto counters =
+      PerfCounters::Create({kGenericPerfEvent1, kGenericPerfEvent2});
+  EXPECT_EQ(counters.num_counters(), 2);
+  PerfCounterValues values1(2);
+  EXPECT_TRUE(counters.Snapshot(&values1));
+  EXPECT_GT(values1[0], 0);
+  EXPECT_GT(values1[1], 0);
+  PerfCounterValues values2(2);
+  EXPECT_TRUE(counters.Snapshot(&values2));
+  EXPECT_GT(values2[0], 0);
+  EXPECT_GT(values2[1], 0);
+}
+
+TEST(PerfCountersTest, ReopenExistingCounters) {
+  // This test works in recent and old Intel hardware
+  // However we cannot make assumptions beyond 3 HW counters
+  if (!PerfCounters::kSupported) {
+    GTEST_SKIP() << "Test skipped because libpfm is not supported.\n";
+  }
+  EXPECT_TRUE(PerfCounters::Initialize());
+  std::vector<std::string> kMetrics({kGenericPerfEvent1});
+  std::vector<PerfCounters> counters(3);
+  for (auto& counter : counters) {
+    counter = PerfCounters::Create(kMetrics);
+  }
+  PerfCounterValues values(1);
+  EXPECT_TRUE(counters[0].Snapshot(&values));
+  EXPECT_TRUE(counters[1].Snapshot(&values));
+  EXPECT_TRUE(counters[2].Snapshot(&values));
+}
+
+TEST(PerfCountersTest, CreateExistingMeasurements) {
+  // The test works (i.e. causes read to fail) for the assumptions
+  // about hardware capabilities (i.e. small number (3) hardware
+  // counters) at this date,
+  // the same as previous test ReopenExistingCounters.
+  if (!PerfCounters::kSupported) {
+    GTEST_SKIP() << "Test skipped because libpfm is not supported.\n";
+  }
+  EXPECT_TRUE(PerfCounters::Initialize());
+
+  // This means we will try 10 counters but we can only guarantee
+  // for sure at this time that only 3 will work. Perhaps in the future
+  // we could use libpfm to query for the hardware limits on this
+  // particular platform.
+  const int kMaxCounters = 10;
+  const int kMinValidCounters = 3;
+
+  // Let's use a ubiquitous counter that is guaranteed to work
+  // on all platforms
+  const std::vector<std::string> kMetrics{"cycles"};
+
+  // Cannot create a vector of actual objects because the
+  // copy constructor of PerfCounters is deleted - and so is
+  // implicitly deleted on PerfCountersMeasurement too
+  std::vector<std::unique_ptr<PerfCountersMeasurement>>
+      perf_counter_measurements;
+
+  perf_counter_measurements.reserve(kMaxCounters);
+  for (int j = 0; j < kMaxCounters; ++j) {
+    perf_counter_measurements.emplace_back(
+        new PerfCountersMeasurement(kMetrics));
+  }
+
+  std::vector<std::pair<std::string, double>> measurements;
+
+  // Start all counters together to see if they hold
+  int max_counters = kMaxCounters;
+  for (int i = 0; i < kMaxCounters; ++i) {
+    auto& counter(*perf_counter_measurements[i]);
+    EXPECT_EQ(counter.num_counters(), 1);
+    if (!counter.Start()) {
+      max_counters = i;
+      break;
+    };
+  }
+
+  ASSERT_GE(max_counters, kMinValidCounters);
+
+  // Start all together
+  for (int i = 0; i < max_counters; ++i) {
+    auto& counter(*perf_counter_measurements[i]);
+    EXPECT_TRUE(counter.Stop(measurements) || (i >= kMinValidCounters));
+  }
+
+  // Start/stop individually
+  for (int i = 0; i < max_counters; ++i) {
+    auto& counter(*perf_counter_measurements[i]);
+    measurements.clear();
+    counter.Start();
+    EXPECT_TRUE(counter.Stop(measurements) || (i >= kMinValidCounters));
+  }
+}
+
+// We try to do some meaningful work here but the compiler
+// insists in optimizing away our loop so we had to add a
+// no-optimize macro. In case it fails, we added some entropy
+// to this pool as well.
+
+BENCHMARK_DONT_OPTIMIZE size_t do_work() {
+  static std::mt19937 rd{std::random_device{}()};
+  static std::uniform_int_distribution<size_t> mrand(0, 10);
+  const size_t kNumLoops = 1000000;
+  size_t sum = 0;
+  for (size_t j = 0; j < kNumLoops; ++j) {
+    sum += mrand(rd);
+  }
+  benchmark::DoNotOptimize(sum);
+  return sum;
+}
+
+void measure(size_t threadcount, PerfCounterValues* before,
+             PerfCounterValues* after) {
+  BM_CHECK_NE(before, nullptr);
+  BM_CHECK_NE(after, nullptr);
+  std::vector<std::thread> threads(threadcount);
+  auto work = [&]() { BM_CHECK(do_work() > 1000); };
+
+  // We need to first set up the counters, then start the threads, so the
+  // threads would inherit the counters. But later, we need to first destroy
+  // the thread pool (so all the work finishes), then measure the counters. So
+  // the scopes overlap, and we need to explicitly control the scope of the
+  // threadpool.
+  auto counters =
+      PerfCounters::Create({kGenericPerfEvent1, kGenericPerfEvent3});
+  for (auto& t : threads) t = std::thread(work);
+  counters.Snapshot(before);
+  for (auto& t : threads) t.join();
+  counters.Snapshot(after);
+}
+
+TEST(PerfCountersTest, MultiThreaded) {
+  if (!PerfCounters::kSupported) {
+    GTEST_SKIP() << "Test skipped because libpfm is not supported.";
+  }
+  EXPECT_TRUE(PerfCounters::Initialize());
+  PerfCounterValues before(2);
+  PerfCounterValues after(2);
+
+  // Notice that this test will work even if we taskset it to a single CPU
+  // In this case the threads will run sequentially
+  // Start two threads and measure the number of combined cycles and
+  // instructions
+  measure(2, &before, &after);
+  std::vector<double> Elapsed2Threads{
+      static_cast<double>(after[0] - before[0]),
+      static_cast<double>(after[1] - before[1])};
+
+  // Start four threads and measure the number of combined cycles and
+  // instructions
+  measure(4, &before, &after);
+  std::vector<double> Elapsed4Threads{
+      static_cast<double>(after[0] - before[0]),
+      static_cast<double>(after[1] - before[1])};
+
+  // Some extra work will happen on the main thread - like joining the threads
+  // - so the ratio won't be quite 2.0, but very close.
+  EXPECT_GE(Elapsed4Threads[0], 1.9 * Elapsed2Threads[0]);
+  EXPECT_GE(Elapsed4Threads[1], 1.9 * Elapsed2Threads[1]);
+}
+
+TEST(PerfCountersTest, HardwareLimits) {
+  // The test works (i.e. causes read to fail) for the assumptions
+  // about hardware capabilities (i.e. small number (3-4) hardware
+  // counters) at this date,
+  // the same as previous test ReopenExistingCounters.
+  if (!PerfCounters::kSupported) {
+    GTEST_SKIP() << "Test skipped because libpfm is not supported.\n";
+  }
+  EXPECT_TRUE(PerfCounters::Initialize());
+
+  // Taken straight from `perf list` on x86-64
+  // Got all hardware names since these are the problematic ones
+  std::vector<std::string> counter_names{"cycles",  // leader
+                                         "instructions",
+                                         "branches",
+                                         "L1-dcache-loads",
+                                         "L1-dcache-load-misses",
+                                         "L1-dcache-prefetches",
+                                         "L1-icache-load-misses",  // leader
+                                         "L1-icache-loads",
+                                         "branch-load-misses",
+                                         "branch-loads",
+                                         "dTLB-load-misses",
+                                         "dTLB-loads",
+                                         "iTLB-load-misses",  // leader
+                                         "iTLB-loads",
+                                         "branch-instructions",
+                                         "branch-misses",
+                                         "cache-misses",
+                                         "cache-references",
+                                         "stalled-cycles-backend",  // leader
+                                         "stalled-cycles-frontend"};
+
+  // In the off-chance that some of these values are not supported,
+  // we filter them out so the test will complete without failure
+  // albeit it might not actually test the grouping on that platform
+  std::vector<std::string> valid_names;
+  for (const std::string& name : counter_names) {
+    if (PerfCounters::IsCounterSupported(name)) {
+      valid_names.push_back(name);
+    }
+  }
+  PerfCountersMeasurement counter(valid_names);
+
+  std::vector<std::pair<std::string, double>> measurements;
+
+  counter.Start();
+  EXPECT_TRUE(counter.Stop(measurements));
+}
+
+}  // namespace
diff --git a/leveldb_base/third_party/benchmark/test/perf_counters_test.cc b/leveldb_base/third_party/benchmark/test/perf_counters_test.cc
new file mode 100644
index 0000000..f0e9a17
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/perf_counters_test.cc
@@ -0,0 +1,28 @@
+#undef NDEBUG
+
+#include "../src/perf_counters.h"
+
+#include "benchmark/benchmark.h"
+#include "output_test.h"
+
+static void BM_Simple(benchmark::State& state) {
+  for (auto _ : state) {
+    auto iterations = state.iterations();
+    benchmark::DoNotOptimize(iterations);
+  }
+}
+BENCHMARK(BM_Simple);
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_Simple\",$"}});
+
+static void CheckSimple(Results const& e) {
+  CHECK_COUNTER_VALUE(e, double, "CYCLES", GT, 0);
+  CHECK_COUNTER_VALUE(e, double, "BRANCHES", GT, 0.0);
+}
+CHECK_BENCHMARK_RESULTS("BM_Simple", &CheckSimple);
+
+int main(int argc, char* argv[]) {
+  if (!benchmark::internal::PerfCounters::kSupported) {
+    return 0;
+  }
+  RunOutputTests(argc, argv);
+}
diff --git a/leveldb_base/third_party/benchmark/test/register_benchmark_test.cc b/leveldb_base/third_party/benchmark/test/register_benchmark_test.cc
new file mode 100644
index 0000000..d69d144
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/register_benchmark_test.cc
@@ -0,0 +1,196 @@
+
+#undef NDEBUG
+#include <cassert>
+#include <vector>
+
+#include "../src/check.h"  // NOTE: check.h is for internal use only!
+#include "benchmark/benchmark.h"
+
+namespace {
+
+class TestReporter : public benchmark::ConsoleReporter {
+ public:
+  void ReportRuns(const std::vector<Run>& report) override {
+    all_runs_.insert(all_runs_.end(), begin(report), end(report));
+    ConsoleReporter::ReportRuns(report);
+  }
+
+  std::vector<Run> all_runs_;
+};
+
+struct TestCase {
+  const std::string name;
+  const std::string label;
+  // Note: not explicit as we rely on it being converted through ADD_CASES.
+  TestCase(const std::string& xname) : TestCase(xname, "") {}
+  TestCase(const std::string& xname, const std::string& xlabel)
+      : name(xname), label(xlabel) {}
+
+  typedef benchmark::BenchmarkReporter::Run Run;
+
+  void CheckRun(Run const& run) const {
+    // clang-format off
+    BM_CHECK(name == run.benchmark_name()) << "expected " << name << " got "
+                                      << run.benchmark_name();
+    if (!label.empty()) {
+      BM_CHECK(run.report_label == label) << "expected " << label << " got "
+                                       << run.report_label;
+    } else {
+      BM_CHECK(run.report_label.empty());
+    }
+    // clang-format on
+  }
+};
+
+std::vector<TestCase> ExpectedResults;
+
+int AddCases(std::initializer_list<TestCase> const& v) {
+  for (const auto& N : v) {
+    ExpectedResults.push_back(N);
+  }
+  return 0;
+}
+
+#define CONCAT(x, y) CONCAT2(x, y)
+#define CONCAT2(x, y) x##y
+#define ADD_CASES(...) int CONCAT(dummy, __LINE__) = AddCases({__VA_ARGS__})
+
+}  // end namespace
+
+typedef benchmark::internal::Benchmark* ReturnVal;
+
+//----------------------------------------------------------------------------//
+// Test RegisterBenchmark with no additional arguments
+//----------------------------------------------------------------------------//
+void BM_function(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_function);
+ReturnVal dummy = benchmark::RegisterBenchmark(
+    "BM_function_manual_registration", BM_function);
+ADD_CASES({"BM_function"}, {"BM_function_manual_registration"});
+
+//----------------------------------------------------------------------------//
+// Test RegisterBenchmark with additional arguments
+// Note: GCC <= 4.8 do not support this form of RegisterBenchmark because they
+//       reject the variadic pack expansion of lambda captures.
+//----------------------------------------------------------------------------//
+#ifndef BENCHMARK_HAS_NO_VARIADIC_REGISTER_BENCHMARK
+
+void BM_extra_args(benchmark::State& st, const char* label) {
+  for (auto _ : st) {
+  }
+  st.SetLabel(label);
+}
+int RegisterFromFunction() {
+  std::pair<const char*, const char*> cases[] = {
+      {"test1", "One"}, {"test2", "Two"}, {"test3", "Three"}};
+  for (auto const& c : cases)
+    benchmark::RegisterBenchmark(c.first, &BM_extra_args, c.second);
+  return 0;
+}
+int dummy2 = RegisterFromFunction();
+ADD_CASES({"test1", "One"}, {"test2", "Two"}, {"test3", "Three"});
+
+#endif  // BENCHMARK_HAS_NO_VARIADIC_REGISTER_BENCHMARK
+
+//----------------------------------------------------------------------------//
+// Test RegisterBenchmark with DISABLED_ benchmark
+//----------------------------------------------------------------------------//
+void DISABLED_BM_function(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(DISABLED_BM_function);
+ReturnVal dummy3 = benchmark::RegisterBenchmark("DISABLED_BM_function_manual",
+                                                DISABLED_BM_function);
+// No need to add cases because we don't expect them to run.
+
+//----------------------------------------------------------------------------//
+// Test RegisterBenchmark with different callable types
+//----------------------------------------------------------------------------//
+
+struct CustomFixture {
+  void operator()(benchmark::State& st) {
+    for (auto _ : st) {
+    }
+  }
+};
+
+void TestRegistrationAtRuntime() {
+#ifdef BENCHMARK_HAS_CXX11
+  {
+    CustomFixture fx;
+    benchmark::RegisterBenchmark("custom_fixture", fx);
+    AddCases({std::string("custom_fixture")});
+  }
+#endif
+#ifndef BENCHMARK_HAS_NO_VARIADIC_REGISTER_BENCHMARK
+  {
+    const char* x = "42";
+    auto capturing_lam = [=](benchmark::State& st) {
+      for (auto _ : st) {
+      }
+      st.SetLabel(x);
+    };
+    benchmark::RegisterBenchmark("lambda_benchmark", capturing_lam);
+    AddCases({{"lambda_benchmark", x}});
+  }
+#endif
+}
+
+// Test that all benchmarks, registered at either during static init or runtime,
+// are run and the results are passed to the reported.
+void RunTestOne() {
+  TestRegistrationAtRuntime();
+
+  TestReporter test_reporter;
+  benchmark::RunSpecifiedBenchmarks(&test_reporter);
+
+  typedef benchmark::BenchmarkReporter::Run Run;
+  auto EB = ExpectedResults.begin();
+
+  for (Run const& run : test_reporter.all_runs_) {
+    assert(EB != ExpectedResults.end());
+    EB->CheckRun(run);
+    ++EB;
+  }
+  assert(EB == ExpectedResults.end());
+}
+
+// Test that ClearRegisteredBenchmarks() clears all previously registered
+// benchmarks.
+// Also test that new benchmarks can be registered and ran afterwards.
+void RunTestTwo() {
+  assert(ExpectedResults.size() != 0 &&
+         "must have at least one registered benchmark");
+  ExpectedResults.clear();
+  benchmark::ClearRegisteredBenchmarks();
+
+  TestReporter test_reporter;
+  size_t num_ran = benchmark::RunSpecifiedBenchmarks(&test_reporter);
+  assert(num_ran == 0);
+  assert(test_reporter.all_runs_.begin() == test_reporter.all_runs_.end());
+
+  TestRegistrationAtRuntime();
+  num_ran = benchmark::RunSpecifiedBenchmarks(&test_reporter);
+  assert(num_ran == ExpectedResults.size());
+
+  typedef benchmark::BenchmarkReporter::Run Run;
+  auto EB = ExpectedResults.begin();
+
+  for (Run const& run : test_reporter.all_runs_) {
+    assert(EB != ExpectedResults.end());
+    EB->CheckRun(run);
+    ++EB;
+  }
+  assert(EB == ExpectedResults.end());
+}
+
+int main(int argc, char* argv[]) {
+  benchmark::Initialize(&argc, argv);
+
+  RunTestOne();
+  RunTestTwo();
+}
diff --git a/leveldb_base/third_party/benchmark/test/repetitions_test.cc b/leveldb_base/third_party/benchmark/test/repetitions_test.cc
new file mode 100644
index 0000000..569777d
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/repetitions_test.cc
@@ -0,0 +1,214 @@
+
+#include "benchmark/benchmark.h"
+#include "output_test.h"
+
+// ========================================================================= //
+// ------------------------ Testing Basic Output --------------------------- //
+// ========================================================================= //
+
+static void BM_ExplicitRepetitions(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_ExplicitRepetitions)->Repetitions(2);
+
+ADD_CASES(TC_ConsoleOut,
+          {{"^BM_ExplicitRepetitions/repeats:2 %console_report$"}});
+ADD_CASES(TC_ConsoleOut,
+          {{"^BM_ExplicitRepetitions/repeats:2 %console_report$"}});
+ADD_CASES(TC_ConsoleOut,
+          {{"^BM_ExplicitRepetitions/repeats:2_mean %console_report$"}});
+ADD_CASES(TC_ConsoleOut,
+          {{"^BM_ExplicitRepetitions/repeats:2_median %console_report$"}});
+ADD_CASES(TC_ConsoleOut,
+          {{"^BM_ExplicitRepetitions/repeats:2_stddev %console_report$"}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_ExplicitRepetitions/repeats:2\",$"},
+           {"\"family_index\": 0,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_ExplicitRepetitions/repeats:2\",$", MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"repetition_index\": 0,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\"$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_ExplicitRepetitions/repeats:2\",$"},
+           {"\"family_index\": 0,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_ExplicitRepetitions/repeats:2\",$", MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"repetition_index\": 1,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\"$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_ExplicitRepetitions/repeats:2_mean\",$"},
+           {"\"family_index\": 0,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_ExplicitRepetitions/repeats:2\",$", MR_Next},
+           {"\"run_type\": \"aggregate\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"aggregate_name\": \"mean\",$", MR_Next},
+           {"\"aggregate_unit\": \"time\",$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\"$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_ExplicitRepetitions/repeats:2_median\",$"},
+           {"\"family_index\": 0,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_ExplicitRepetitions/repeats:2\",$", MR_Next},
+           {"\"run_type\": \"aggregate\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"aggregate_name\": \"median\",$", MR_Next},
+           {"\"aggregate_unit\": \"time\",$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\"$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_ExplicitRepetitions/repeats:2_stddev\",$"},
+           {"\"family_index\": 0,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_ExplicitRepetitions/repeats:2\",$", MR_Next},
+           {"\"run_type\": \"aggregate\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"aggregate_name\": \"stddev\",$", MR_Next},
+           {"\"aggregate_unit\": \"time\",$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\"$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_ExplicitRepetitions/repeats:2\",%csv_report$"}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_ExplicitRepetitions/repeats:2\",%csv_report$"}});
+ADD_CASES(TC_CSVOut,
+          {{"^\"BM_ExplicitRepetitions/repeats:2_mean\",%csv_report$"}});
+ADD_CASES(TC_CSVOut,
+          {{"^\"BM_ExplicitRepetitions/repeats:2_median\",%csv_report$"}});
+ADD_CASES(TC_CSVOut,
+          {{"^\"BM_ExplicitRepetitions/repeats:2_stddev\",%csv_report$"}});
+
+// ========================================================================= //
+// ------------------------ Testing Basic Output --------------------------- //
+// ========================================================================= //
+
+static void BM_ImplicitRepetitions(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_ImplicitRepetitions);
+
+ADD_CASES(TC_ConsoleOut, {{"^BM_ImplicitRepetitions %console_report$"}});
+ADD_CASES(TC_ConsoleOut, {{"^BM_ImplicitRepetitions %console_report$"}});
+ADD_CASES(TC_ConsoleOut, {{"^BM_ImplicitRepetitions %console_report$"}});
+ADD_CASES(TC_ConsoleOut, {{"^BM_ImplicitRepetitions_mean %console_report$"}});
+ADD_CASES(TC_ConsoleOut, {{"^BM_ImplicitRepetitions_median %console_report$"}});
+ADD_CASES(TC_ConsoleOut, {{"^BM_ImplicitRepetitions_stddev %console_report$"}});
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_ImplicitRepetitions\",$"},
+                       {"\"family_index\": 1,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_ImplicitRepetitions\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 3,$", MR_Next},
+                       {"\"repetition_index\": 0,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"iterations\": %int,$", MR_Next},
+                       {"\"real_time\": %float,$", MR_Next},
+                       {"\"cpu_time\": %float,$", MR_Next},
+                       {"\"time_unit\": \"ns\"$", MR_Next},
+                       {"}", MR_Next}});
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_ImplicitRepetitions\",$"},
+                       {"\"family_index\": 1,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_ImplicitRepetitions\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 3,$", MR_Next},
+                       {"\"repetition_index\": 1,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"iterations\": %int,$", MR_Next},
+                       {"\"real_time\": %float,$", MR_Next},
+                       {"\"cpu_time\": %float,$", MR_Next},
+                       {"\"time_unit\": \"ns\"$", MR_Next},
+                       {"}", MR_Next}});
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_ImplicitRepetitions\",$"},
+                       {"\"family_index\": 1,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_ImplicitRepetitions\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 3,$", MR_Next},
+                       {"\"repetition_index\": 2,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"iterations\": %int,$", MR_Next},
+                       {"\"real_time\": %float,$", MR_Next},
+                       {"\"cpu_time\": %float,$", MR_Next},
+                       {"\"time_unit\": \"ns\"$", MR_Next},
+                       {"}", MR_Next}});
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_ImplicitRepetitions_mean\",$"},
+                       {"\"family_index\": 1,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_ImplicitRepetitions\",$", MR_Next},
+                       {"\"run_type\": \"aggregate\",$", MR_Next},
+                       {"\"repetitions\": 3,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"aggregate_name\": \"mean\",$", MR_Next},
+                       {"\"aggregate_unit\": \"time\",$", MR_Next},
+                       {"\"iterations\": %int,$", MR_Next},
+                       {"\"real_time\": %float,$", MR_Next},
+                       {"\"cpu_time\": %float,$", MR_Next},
+                       {"\"time_unit\": \"ns\"$", MR_Next},
+                       {"}", MR_Next}});
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_ImplicitRepetitions_median\",$"},
+                       {"\"family_index\": 1,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_ImplicitRepetitions\",$", MR_Next},
+                       {"\"run_type\": \"aggregate\",$", MR_Next},
+                       {"\"repetitions\": 3,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"aggregate_name\": \"median\",$", MR_Next},
+                       {"\"aggregate_unit\": \"time\",$", MR_Next},
+                       {"\"iterations\": %int,$", MR_Next},
+                       {"\"real_time\": %float,$", MR_Next},
+                       {"\"cpu_time\": %float,$", MR_Next},
+                       {"\"time_unit\": \"ns\"$", MR_Next},
+                       {"}", MR_Next}});
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_ImplicitRepetitions_stddev\",$"},
+                       {"\"family_index\": 1,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_ImplicitRepetitions\",$", MR_Next},
+                       {"\"run_type\": \"aggregate\",$", MR_Next},
+                       {"\"repetitions\": 3,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"aggregate_name\": \"stddev\",$", MR_Next},
+                       {"\"aggregate_unit\": \"time\",$", MR_Next},
+                       {"\"iterations\": %int,$", MR_Next},
+                       {"\"real_time\": %float,$", MR_Next},
+                       {"\"cpu_time\": %float,$", MR_Next},
+                       {"\"time_unit\": \"ns\"$", MR_Next},
+                       {"}", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_ImplicitRepetitions\",%csv_report$"}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_ImplicitRepetitions\",%csv_report$"}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_ImplicitRepetitions_mean\",%csv_report$"}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_ImplicitRepetitions_median\",%csv_report$"}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_ImplicitRepetitions_stddev\",%csv_report$"}});
+
+// ========================================================================= //
+// --------------------------- TEST CASES END ------------------------------ //
+// ========================================================================= //
+
+int main(int argc, char* argv[]) { RunOutputTests(argc, argv); }
diff --git a/leveldb_base/third_party/benchmark/test/report_aggregates_only_test.cc b/leveldb_base/third_party/benchmark/test/report_aggregates_only_test.cc
new file mode 100644
index 0000000..47da503
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/report_aggregates_only_test.cc
@@ -0,0 +1,41 @@
+
+#undef NDEBUG
+#include <cstdio>
+#include <string>
+
+#include "benchmark/benchmark.h"
+#include "output_test.h"
+
+// Ok this test is super ugly. We want to check what happens with the file
+// reporter in the presence of ReportAggregatesOnly().
+// We do not care about console output, the normal tests check that already.
+
+void BM_SummaryRepeat(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_SummaryRepeat)->Repetitions(3)->ReportAggregatesOnly();
+
+int main(int argc, char* argv[]) {
+  const std::string output = GetFileReporterOutput(argc, argv);
+
+  if (SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3") != 4 ||
+      SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3_mean\"") != 1 ||
+      SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3_median\"") !=
+          1 ||
+      SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3_stddev\"") !=
+          1 ||
+      SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3_cv\"") != 1) {
+    std::cout << "Precondition mismatch. Expected to only find four "
+                 "occurrences of \"BM_SummaryRepeat/repeats:3\" substring:\n"
+                 "\"name\": \"BM_SummaryRepeat/repeats:3_mean\", "
+                 "\"name\": \"BM_SummaryRepeat/repeats:3_median\", "
+                 "\"name\": \"BM_SummaryRepeat/repeats:3_stddev\", "
+                 "\"name\": \"BM_SummaryRepeat/repeats:3_cv\"\nThe entire "
+                 "output:\n";
+    std::cout << output;
+    return 1;
+  }
+
+  return 0;
+}
diff --git a/leveldb_base/third_party/benchmark/test/reporter_output_test.cc b/leveldb_base/third_party/benchmark/test/reporter_output_test.cc
new file mode 100644
index 0000000..2eb545a
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/reporter_output_test.cc
@@ -0,0 +1,1130 @@
+
+#undef NDEBUG
+#include <numeric>
+#include <utility>
+
+#include "benchmark/benchmark.h"
+#include "output_test.h"
+
+// ========================================================================= //
+// ---------------------- Testing Prologue Output -------------------------- //
+// ========================================================================= //
+
+ADD_CASES(TC_ConsoleOut, {{"^[-]+$", MR_Next},
+                          {"^Benchmark %s Time %s CPU %s Iterations$", MR_Next},
+                          {"^[-]+$", MR_Next}});
+static int AddContextCases() {
+  AddCases(TC_ConsoleErr,
+           {
+               {"^%int-%int-%intT%int:%int:%int[-+]%int:%int$", MR_Default},
+               {"Running .*(/|\\\\)reporter_output_test(\\.exe)?$", MR_Next},
+               {"Run on \\(%int X %float MHz CPU s?\\)", MR_Next},
+           });
+  AddCases(TC_JSONOut,
+           {{"^\\{", MR_Default},
+            {"\"context\":", MR_Next},
+            {"\"date\": \"", MR_Next},
+            {"\"host_name\":", MR_Next},
+            {"\"executable\": \".*(/|\\\\)reporter_output_test(\\.exe)?\",",
+             MR_Next},
+            {"\"num_cpus\": %int,$", MR_Next},
+            {"\"mhz_per_cpu\": %float,$", MR_Next},
+            {"\"caches\": \\[$", MR_Default}});
+  auto const& Info = benchmark::CPUInfo::Get();
+  auto const& Caches = Info.caches;
+  if (!Caches.empty()) {
+    AddCases(TC_ConsoleErr, {{"CPU Caches:$", MR_Next}});
+  }
+  for (size_t I = 0; I < Caches.size(); ++I) {
+    std::string num_caches_str =
+        Caches[I].num_sharing != 0 ? " \\(x%int\\)$" : "$";
+    AddCases(TC_ConsoleErr,
+             {{"L%int (Data|Instruction|Unified) %int KiB" + num_caches_str,
+               MR_Next}});
+    AddCases(TC_JSONOut, {{"\\{$", MR_Next},
+                          {"\"type\": \"", MR_Next},
+                          {"\"level\": %int,$", MR_Next},
+                          {"\"size\": %int,$", MR_Next},
+                          {"\"num_sharing\": %int$", MR_Next},
+                          {"}[,]{0,1}$", MR_Next}});
+  }
+  AddCases(TC_JSONOut, {{"],$"}});
+  auto const& LoadAvg = Info.load_avg;
+  if (!LoadAvg.empty()) {
+    AddCases(TC_ConsoleErr,
+             {{"Load Average: (%float, ){0,2}%float$", MR_Next}});
+  }
+  AddCases(TC_JSONOut, {{"\"load_avg\": \\[(%float,?){0,3}],$", MR_Next}});
+  return 0;
+}
+int dummy_register = AddContextCases();
+ADD_CASES(TC_CSVOut, {{"%csv_header"}});
+
+// ========================================================================= //
+// ------------------------ Testing Basic Output --------------------------- //
+// ========================================================================= //
+
+void BM_basic(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_basic);
+
+ADD_CASES(TC_ConsoleOut, {{"^BM_basic %console_report$"}});
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_basic\",$"},
+                       {"\"family_index\": 0,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_basic\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 1,$", MR_Next},
+                       {"\"repetition_index\": 0,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"iterations\": %int,$", MR_Next},
+                       {"\"real_time\": %float,$", MR_Next},
+                       {"\"cpu_time\": %float,$", MR_Next},
+                       {"\"time_unit\": \"ns\"$", MR_Next},
+                       {"}", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_basic\",%csv_report$"}});
+
+// ========================================================================= //
+// ------------------------ Testing Bytes per Second Output ---------------- //
+// ========================================================================= //
+
+void BM_bytes_per_second(benchmark::State& state) {
+  for (auto _ : state) {
+    // This test requires a non-zero CPU time to avoid divide-by-zero
+    auto iterations = state.iterations();
+    benchmark::DoNotOptimize(iterations);
+  }
+  state.SetBytesProcessed(1);
+}
+BENCHMARK(BM_bytes_per_second);
+
+ADD_CASES(TC_ConsoleOut, {{"^BM_bytes_per_second %console_report "
+                           "bytes_per_second=%float[kM]{0,1}/s$"}});
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_bytes_per_second\",$"},
+                       {"\"family_index\": 1,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_bytes_per_second\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 1,$", MR_Next},
+                       {"\"repetition_index\": 0,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"iterations\": %int,$", MR_Next},
+                       {"\"real_time\": %float,$", MR_Next},
+                       {"\"cpu_time\": %float,$", MR_Next},
+                       {"\"time_unit\": \"ns\",$", MR_Next},
+                       {"\"bytes_per_second\": %float$", MR_Next},
+                       {"}", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_bytes_per_second\",%csv_bytes_report$"}});
+
+// ========================================================================= //
+// ------------------------ Testing Items per Second Output ---------------- //
+// ========================================================================= //
+
+void BM_items_per_second(benchmark::State& state) {
+  for (auto _ : state) {
+    // This test requires a non-zero CPU time to avoid divide-by-zero
+    auto iterations = state.iterations();
+    benchmark::DoNotOptimize(iterations);
+  }
+  state.SetItemsProcessed(1);
+}
+BENCHMARK(BM_items_per_second);
+
+ADD_CASES(TC_ConsoleOut, {{"^BM_items_per_second %console_report "
+                           "items_per_second=%float[kM]{0,1}/s$"}});
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_items_per_second\",$"},
+                       {"\"family_index\": 2,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_items_per_second\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 1,$", MR_Next},
+                       {"\"repetition_index\": 0,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"iterations\": %int,$", MR_Next},
+                       {"\"real_time\": %float,$", MR_Next},
+                       {"\"cpu_time\": %float,$", MR_Next},
+                       {"\"time_unit\": \"ns\",$", MR_Next},
+                       {"\"items_per_second\": %float$", MR_Next},
+                       {"}", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_items_per_second\",%csv_items_report$"}});
+
+// ========================================================================= //
+// ------------------------ Testing Label Output --------------------------- //
+// ========================================================================= //
+
+void BM_label(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+  state.SetLabel("some label");
+}
+BENCHMARK(BM_label);
+
+ADD_CASES(TC_ConsoleOut, {{"^BM_label %console_report some label$"}});
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_label\",$"},
+                       {"\"family_index\": 3,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_label\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 1,$", MR_Next},
+                       {"\"repetition_index\": 0,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"iterations\": %int,$", MR_Next},
+                       {"\"real_time\": %float,$", MR_Next},
+                       {"\"cpu_time\": %float,$", MR_Next},
+                       {"\"time_unit\": \"ns\",$", MR_Next},
+                       {"\"label\": \"some label\"$", MR_Next},
+                       {"}", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_label\",%csv_label_report_begin\"some "
+                       "label\"%csv_label_report_end$"}});
+
+// ========================================================================= //
+// ------------------------ Testing Time Label Output ---------------------- //
+// ========================================================================= //
+
+void BM_time_label_nanosecond(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_time_label_nanosecond)->Unit(benchmark::kNanosecond);
+
+ADD_CASES(TC_ConsoleOut, {{"^BM_time_label_nanosecond %console_report$"}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_time_label_nanosecond\",$"},
+           {"\"family_index\": 4,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_time_label_nanosecond\",$", MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 1,$", MR_Next},
+           {"\"repetition_index\": 0,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\"$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_time_label_nanosecond\",%csv_report$"}});
+
+void BM_time_label_microsecond(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_time_label_microsecond)->Unit(benchmark::kMicrosecond);
+
+ADD_CASES(TC_ConsoleOut, {{"^BM_time_label_microsecond %console_us_report$"}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_time_label_microsecond\",$"},
+           {"\"family_index\": 5,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_time_label_microsecond\",$", MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 1,$", MR_Next},
+           {"\"repetition_index\": 0,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"us\"$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_time_label_microsecond\",%csv_us_report$"}});
+
+void BM_time_label_millisecond(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_time_label_millisecond)->Unit(benchmark::kMillisecond);
+
+ADD_CASES(TC_ConsoleOut, {{"^BM_time_label_millisecond %console_ms_report$"}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_time_label_millisecond\",$"},
+           {"\"family_index\": 6,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_time_label_millisecond\",$", MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 1,$", MR_Next},
+           {"\"repetition_index\": 0,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ms\"$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_time_label_millisecond\",%csv_ms_report$"}});
+
+void BM_time_label_second(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_time_label_second)->Unit(benchmark::kSecond);
+
+ADD_CASES(TC_ConsoleOut, {{"^BM_time_label_second %console_s_report$"}});
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_time_label_second\",$"},
+                       {"\"family_index\": 7,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_time_label_second\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 1,$", MR_Next},
+                       {"\"repetition_index\": 0,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"iterations\": %int,$", MR_Next},
+                       {"\"real_time\": %float,$", MR_Next},
+                       {"\"cpu_time\": %float,$", MR_Next},
+                       {"\"time_unit\": \"s\"$", MR_Next},
+                       {"}", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_time_label_second\",%csv_s_report$"}});
+
+// ========================================================================= //
+// ------------------------ Testing Error Output --------------------------- //
+// ========================================================================= //
+
+void BM_error(benchmark::State& state) {
+  state.SkipWithError("message");
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_error);
+ADD_CASES(TC_ConsoleOut, {{"^BM_error[ ]+ERROR OCCURRED: 'message'$"}});
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_error\",$"},
+                       {"\"family_index\": 8,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_error\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 1,$", MR_Next},
+                       {"\"repetition_index\": 0,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"error_occurred\": true,$", MR_Next},
+                       {"\"error_message\": \"message\",$", MR_Next}});
+
+ADD_CASES(TC_CSVOut, {{"^\"BM_error\",,,,,,,,true,\"message\"$"}});
+
+// ========================================================================= //
+// ------------------------ Testing No Arg Name Output -----------------------
+// //
+// ========================================================================= //
+
+void BM_no_arg_name(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_no_arg_name)->Arg(3);
+ADD_CASES(TC_ConsoleOut, {{"^BM_no_arg_name/3 %console_report$"}});
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_no_arg_name/3\",$"},
+                       {"\"family_index\": 9,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_no_arg_name/3\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 1,$", MR_Next},
+                       {"\"repetition_index\": 0,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_no_arg_name/3\",%csv_report$"}});
+
+// ========================================================================= //
+// ------------------------ Testing Arg Name Output ------------------------ //
+// ========================================================================= //
+
+void BM_arg_name(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_arg_name)->ArgName("first")->Arg(3);
+ADD_CASES(TC_ConsoleOut, {{"^BM_arg_name/first:3 %console_report$"}});
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_arg_name/first:3\",$"},
+                       {"\"family_index\": 10,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_arg_name/first:3\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 1,$", MR_Next},
+                       {"\"repetition_index\": 0,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_arg_name/first:3\",%csv_report$"}});
+
+// ========================================================================= //
+// ------------------------ Testing Arg Names Output ----------------------- //
+// ========================================================================= //
+
+void BM_arg_names(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_arg_names)->Args({2, 5, 4})->ArgNames({"first", "", "third"});
+ADD_CASES(TC_ConsoleOut,
+          {{"^BM_arg_names/first:2/5/third:4 %console_report$"}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_arg_names/first:2/5/third:4\",$"},
+           {"\"family_index\": 11,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_arg_names/first:2/5/third:4\",$", MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 1,$", MR_Next},
+           {"\"repetition_index\": 0,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_arg_names/first:2/5/third:4\",%csv_report$"}});
+
+// ========================================================================= //
+// ------------------------ Testing Name Output ---------------------------- //
+// ========================================================================= //
+
+void BM_name(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_name)->Name("BM_custom_name");
+
+ADD_CASES(TC_ConsoleOut, {{"^BM_custom_name %console_report$"}});
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_custom_name\",$"},
+                       {"\"family_index\": 12,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_custom_name\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 1,$", MR_Next},
+                       {"\"repetition_index\": 0,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"iterations\": %int,$", MR_Next},
+                       {"\"real_time\": %float,$", MR_Next},
+                       {"\"cpu_time\": %float,$", MR_Next},
+                       {"\"time_unit\": \"ns\"$", MR_Next},
+                       {"}", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_custom_name\",%csv_report$"}});
+
+// ========================================================================= //
+// ------------------------ Testing Big Args Output ------------------------ //
+// ========================================================================= //
+
+void BM_BigArgs(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_BigArgs)->RangeMultiplier(2)->Range(1U << 30U, 1U << 31U);
+ADD_CASES(TC_ConsoleOut, {{"^BM_BigArgs/1073741824 %console_report$"},
+                          {"^BM_BigArgs/2147483648 %console_report$"}});
+
+// ========================================================================= //
+// ----------------------- Testing Complexity Output ----------------------- //
+// ========================================================================= //
+
+void BM_Complexity_O1(benchmark::State& state) {
+  for (auto _ : state) {
+    // This test requires a non-zero CPU time to avoid divide-by-zero
+    auto iterations = state.iterations();
+    benchmark::DoNotOptimize(iterations);
+  }
+  state.SetComplexityN(state.range(0));
+}
+BENCHMARK(BM_Complexity_O1)->Range(1, 1 << 18)->Complexity(benchmark::o1);
+SET_SUBSTITUTIONS({{"%bigOStr", "[ ]* %float \\([0-9]+\\)"},
+                   {"%RMS", "[ ]*[0-9]+ %"}});
+ADD_CASES(TC_ConsoleOut, {{"^BM_Complexity_O1_BigO %bigOStr %bigOStr[ ]*$"},
+                          {"^BM_Complexity_O1_RMS %RMS %RMS[ ]*$"}});
+
+// ========================================================================= //
+// ----------------------- Testing Aggregate Output ------------------------ //
+// ========================================================================= //
+
+// Test that non-aggregate data is printed by default
+void BM_Repeat(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+// need two repetitions min to be able to output any aggregate output
+BENCHMARK(BM_Repeat)->Repetitions(2);
+ADD_CASES(TC_ConsoleOut,
+          {{"^BM_Repeat/repeats:2 %console_report$"},
+           {"^BM_Repeat/repeats:2 %console_report$"},
+           {"^BM_Repeat/repeats:2_mean %console_time_only_report [ ]*2$"},
+           {"^BM_Repeat/repeats:2_median %console_time_only_report [ ]*2$"},
+           {"^BM_Repeat/repeats:2_stddev %console_time_only_report [ ]*2$"}});
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_Repeat/repeats:2\",$"},
+                       {"\"family_index\": 15,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_Repeat/repeats:2\"", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 2,$", MR_Next},
+                       {"\"repetition_index\": 0,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"name\": \"BM_Repeat/repeats:2\",$"},
+                       {"\"family_index\": 15,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_Repeat/repeats:2\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 2,$", MR_Next},
+                       {"\"repetition_index\": 1,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"name\": \"BM_Repeat/repeats:2_mean\",$"},
+                       {"\"family_index\": 15,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_Repeat/repeats:2\",$", MR_Next},
+                       {"\"run_type\": \"aggregate\",$", MR_Next},
+                       {"\"repetitions\": 2,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"aggregate_name\": \"mean\",$", MR_Next},
+                       {"\"aggregate_unit\": \"time\",$", MR_Next},
+                       {"\"iterations\": 2,$", MR_Next},
+                       {"\"name\": \"BM_Repeat/repeats:2_median\",$"},
+                       {"\"family_index\": 15,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_Repeat/repeats:2\",$", MR_Next},
+                       {"\"run_type\": \"aggregate\",$", MR_Next},
+                       {"\"repetitions\": 2,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"aggregate_name\": \"median\",$", MR_Next},
+                       {"\"aggregate_unit\": \"time\",$", MR_Next},
+                       {"\"iterations\": 2,$", MR_Next},
+                       {"\"name\": \"BM_Repeat/repeats:2_stddev\",$"},
+                       {"\"family_index\": 15,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_Repeat/repeats:2\",$", MR_Next},
+                       {"\"run_type\": \"aggregate\",$", MR_Next},
+                       {"\"repetitions\": 2,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"aggregate_name\": \"stddev\",$", MR_Next},
+                       {"\"aggregate_unit\": \"time\",$", MR_Next},
+                       {"\"iterations\": 2,$", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_Repeat/repeats:2\",%csv_report$"},
+                      {"^\"BM_Repeat/repeats:2\",%csv_report$"},
+                      {"^\"BM_Repeat/repeats:2_mean\",%csv_report$"},
+                      {"^\"BM_Repeat/repeats:2_median\",%csv_report$"},
+                      {"^\"BM_Repeat/repeats:2_stddev\",%csv_report$"}});
+// but for two repetitions, mean and median is the same, so let's repeat..
+BENCHMARK(BM_Repeat)->Repetitions(3);
+ADD_CASES(TC_ConsoleOut,
+          {{"^BM_Repeat/repeats:3 %console_report$"},
+           {"^BM_Repeat/repeats:3 %console_report$"},
+           {"^BM_Repeat/repeats:3 %console_report$"},
+           {"^BM_Repeat/repeats:3_mean %console_time_only_report [ ]*3$"},
+           {"^BM_Repeat/repeats:3_median %console_time_only_report [ ]*3$"},
+           {"^BM_Repeat/repeats:3_stddev %console_time_only_report [ ]*3$"}});
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_Repeat/repeats:3\",$"},
+                       {"\"family_index\": 16,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_Repeat/repeats:3\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 3,$", MR_Next},
+                       {"\"repetition_index\": 0,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"name\": \"BM_Repeat/repeats:3\",$"},
+                       {"\"family_index\": 16,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_Repeat/repeats:3\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 3,$", MR_Next},
+                       {"\"repetition_index\": 1,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"name\": \"BM_Repeat/repeats:3\",$"},
+                       {"\"family_index\": 16,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_Repeat/repeats:3\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 3,$", MR_Next},
+                       {"\"repetition_index\": 2,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"name\": \"BM_Repeat/repeats:3_mean\",$"},
+                       {"\"family_index\": 16,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_Repeat/repeats:3\",$", MR_Next},
+                       {"\"run_type\": \"aggregate\",$", MR_Next},
+                       {"\"repetitions\": 3,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"aggregate_name\": \"mean\",$", MR_Next},
+                       {"\"aggregate_unit\": \"time\",$", MR_Next},
+                       {"\"iterations\": 3,$", MR_Next},
+                       {"\"name\": \"BM_Repeat/repeats:3_median\",$"},
+                       {"\"family_index\": 16,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_Repeat/repeats:3\",$", MR_Next},
+                       {"\"run_type\": \"aggregate\",$", MR_Next},
+                       {"\"repetitions\": 3,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"aggregate_name\": \"median\",$", MR_Next},
+                       {"\"aggregate_unit\": \"time\",$", MR_Next},
+                       {"\"iterations\": 3,$", MR_Next},
+                       {"\"name\": \"BM_Repeat/repeats:3_stddev\",$"},
+                       {"\"family_index\": 16,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_Repeat/repeats:3\",$", MR_Next},
+                       {"\"run_type\": \"aggregate\",$", MR_Next},
+                       {"\"repetitions\": 3,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"aggregate_name\": \"stddev\",$", MR_Next},
+                       {"\"aggregate_unit\": \"time\",$", MR_Next},
+                       {"\"iterations\": 3,$", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_Repeat/repeats:3\",%csv_report$"},
+                      {"^\"BM_Repeat/repeats:3\",%csv_report$"},
+                      {"^\"BM_Repeat/repeats:3\",%csv_report$"},
+                      {"^\"BM_Repeat/repeats:3_mean\",%csv_report$"},
+                      {"^\"BM_Repeat/repeats:3_median\",%csv_report$"},
+                      {"^\"BM_Repeat/repeats:3_stddev\",%csv_report$"}});
+// median differs between even/odd number of repetitions, so just to be sure
+BENCHMARK(BM_Repeat)->Repetitions(4);
+ADD_CASES(TC_ConsoleOut,
+          {{"^BM_Repeat/repeats:4 %console_report$"},
+           {"^BM_Repeat/repeats:4 %console_report$"},
+           {"^BM_Repeat/repeats:4 %console_report$"},
+           {"^BM_Repeat/repeats:4 %console_report$"},
+           {"^BM_Repeat/repeats:4_mean %console_time_only_report [ ]*4$"},
+           {"^BM_Repeat/repeats:4_median %console_time_only_report [ ]*4$"},
+           {"^BM_Repeat/repeats:4_stddev %console_time_only_report [ ]*4$"}});
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_Repeat/repeats:4\",$"},
+                       {"\"family_index\": 17,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_Repeat/repeats:4\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 4,$", MR_Next},
+                       {"\"repetition_index\": 0,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"name\": \"BM_Repeat/repeats:4\",$"},
+                       {"\"family_index\": 17,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_Repeat/repeats:4\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 4,$", MR_Next},
+                       {"\"repetition_index\": 1,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"name\": \"BM_Repeat/repeats:4\",$"},
+                       {"\"family_index\": 17,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_Repeat/repeats:4\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 4,$", MR_Next},
+                       {"\"repetition_index\": 2,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"name\": \"BM_Repeat/repeats:4\",$"},
+                       {"\"family_index\": 17,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_Repeat/repeats:4\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 4,$", MR_Next},
+                       {"\"repetition_index\": 3,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"name\": \"BM_Repeat/repeats:4_mean\",$"},
+                       {"\"family_index\": 17,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_Repeat/repeats:4\",$", MR_Next},
+                       {"\"run_type\": \"aggregate\",$", MR_Next},
+                       {"\"repetitions\": 4,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"aggregate_name\": \"mean\",$", MR_Next},
+                       {"\"aggregate_unit\": \"time\",$", MR_Next},
+                       {"\"iterations\": 4,$", MR_Next},
+                       {"\"name\": \"BM_Repeat/repeats:4_median\",$"},
+                       {"\"family_index\": 17,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_Repeat/repeats:4\",$", MR_Next},
+                       {"\"run_type\": \"aggregate\",$", MR_Next},
+                       {"\"repetitions\": 4,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"aggregate_name\": \"median\",$", MR_Next},
+                       {"\"aggregate_unit\": \"time\",$", MR_Next},
+                       {"\"iterations\": 4,$", MR_Next},
+                       {"\"name\": \"BM_Repeat/repeats:4_stddev\",$"},
+                       {"\"family_index\": 17,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_Repeat/repeats:4\",$", MR_Next},
+                       {"\"run_type\": \"aggregate\",$", MR_Next},
+                       {"\"repetitions\": 4,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"aggregate_name\": \"stddev\",$", MR_Next},
+                       {"\"aggregate_unit\": \"time\",$", MR_Next},
+                       {"\"iterations\": 4,$", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_Repeat/repeats:4\",%csv_report$"},
+                      {"^\"BM_Repeat/repeats:4\",%csv_report$"},
+                      {"^\"BM_Repeat/repeats:4\",%csv_report$"},
+                      {"^\"BM_Repeat/repeats:4\",%csv_report$"},
+                      {"^\"BM_Repeat/repeats:4_mean\",%csv_report$"},
+                      {"^\"BM_Repeat/repeats:4_median\",%csv_report$"},
+                      {"^\"BM_Repeat/repeats:4_stddev\",%csv_report$"}});
+
+// Test that a non-repeated test still prints non-aggregate results even when
+// only-aggregate reports have been requested
+void BM_RepeatOnce(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_RepeatOnce)->Repetitions(1)->ReportAggregatesOnly();
+ADD_CASES(TC_ConsoleOut, {{"^BM_RepeatOnce/repeats:1 %console_report$"}});
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_RepeatOnce/repeats:1\",$"},
+                       {"\"family_index\": 18,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_RepeatOnce/repeats:1\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 1,$", MR_Next},
+                       {"\"repetition_index\": 0,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_RepeatOnce/repeats:1\",%csv_report$"}});
+
+// Test that non-aggregate data is not reported
+void BM_SummaryRepeat(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_SummaryRepeat)->Repetitions(3)->ReportAggregatesOnly();
+ADD_CASES(
+    TC_ConsoleOut,
+    {{".*BM_SummaryRepeat/repeats:3 ", MR_Not},
+     {"^BM_SummaryRepeat/repeats:3_mean %console_time_only_report [ ]*3$"},
+     {"^BM_SummaryRepeat/repeats:3_median %console_time_only_report [ ]*3$"},
+     {"^BM_SummaryRepeat/repeats:3_stddev %console_time_only_report [ ]*3$"}});
+ADD_CASES(TC_JSONOut,
+          {{".*BM_SummaryRepeat/repeats:3 ", MR_Not},
+           {"\"name\": \"BM_SummaryRepeat/repeats:3_mean\",$"},
+           {"\"family_index\": 19,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_SummaryRepeat/repeats:3\",$", MR_Next},
+           {"\"run_type\": \"aggregate\",$", MR_Next},
+           {"\"repetitions\": 3,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"aggregate_name\": \"mean\",$", MR_Next},
+           {"\"aggregate_unit\": \"time\",$", MR_Next},
+           {"\"iterations\": 3,$", MR_Next},
+           {"\"name\": \"BM_SummaryRepeat/repeats:3_median\",$"},
+           {"\"family_index\": 19,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_SummaryRepeat/repeats:3\",$", MR_Next},
+           {"\"run_type\": \"aggregate\",$", MR_Next},
+           {"\"repetitions\": 3,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"aggregate_name\": \"median\",$", MR_Next},
+           {"\"aggregate_unit\": \"time\",$", MR_Next},
+           {"\"iterations\": 3,$", MR_Next},
+           {"\"name\": \"BM_SummaryRepeat/repeats:3_stddev\",$"},
+           {"\"family_index\": 19,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_SummaryRepeat/repeats:3\",$", MR_Next},
+           {"\"run_type\": \"aggregate\",$", MR_Next},
+           {"\"repetitions\": 3,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"aggregate_name\": \"stddev\",$", MR_Next},
+           {"\"aggregate_unit\": \"time\",$", MR_Next},
+           {"\"iterations\": 3,$", MR_Next}});
+ADD_CASES(TC_CSVOut, {{".*BM_SummaryRepeat/repeats:3 ", MR_Not},
+                      {"^\"BM_SummaryRepeat/repeats:3_mean\",%csv_report$"},
+                      {"^\"BM_SummaryRepeat/repeats:3_median\",%csv_report$"},
+                      {"^\"BM_SummaryRepeat/repeats:3_stddev\",%csv_report$"}});
+
+// Test that non-aggregate data is not displayed.
+// NOTE: this test is kinda bad. we are only testing the display output.
+//       But we don't check that the file output still contains everything...
+void BM_SummaryDisplay(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_SummaryDisplay)->Repetitions(2)->DisplayAggregatesOnly();
+ADD_CASES(
+    TC_ConsoleOut,
+    {{".*BM_SummaryDisplay/repeats:2 ", MR_Not},
+     {"^BM_SummaryDisplay/repeats:2_mean %console_time_only_report [ ]*2$"},
+     {"^BM_SummaryDisplay/repeats:2_median %console_time_only_report [ ]*2$"},
+     {"^BM_SummaryDisplay/repeats:2_stddev %console_time_only_report [ ]*2$"}});
+ADD_CASES(TC_JSONOut,
+          {{".*BM_SummaryDisplay/repeats:2 ", MR_Not},
+           {"\"name\": \"BM_SummaryDisplay/repeats:2_mean\",$"},
+           {"\"family_index\": 20,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_SummaryDisplay/repeats:2\",$", MR_Next},
+           {"\"run_type\": \"aggregate\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"aggregate_name\": \"mean\",$", MR_Next},
+           {"\"aggregate_unit\": \"time\",$", MR_Next},
+           {"\"iterations\": 2,$", MR_Next},
+           {"\"name\": \"BM_SummaryDisplay/repeats:2_median\",$"},
+           {"\"family_index\": 20,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_SummaryDisplay/repeats:2\",$", MR_Next},
+           {"\"run_type\": \"aggregate\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"aggregate_name\": \"median\",$", MR_Next},
+           {"\"aggregate_unit\": \"time\",$", MR_Next},
+           {"\"iterations\": 2,$", MR_Next},
+           {"\"name\": \"BM_SummaryDisplay/repeats:2_stddev\",$"},
+           {"\"family_index\": 20,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_SummaryDisplay/repeats:2\",$", MR_Next},
+           {"\"run_type\": \"aggregate\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"aggregate_name\": \"stddev\",$", MR_Next},
+           {"\"aggregate_unit\": \"time\",$", MR_Next},
+           {"\"iterations\": 2,$", MR_Next}});
+ADD_CASES(TC_CSVOut,
+          {{".*BM_SummaryDisplay/repeats:2 ", MR_Not},
+           {"^\"BM_SummaryDisplay/repeats:2_mean\",%csv_report$"},
+           {"^\"BM_SummaryDisplay/repeats:2_median\",%csv_report$"},
+           {"^\"BM_SummaryDisplay/repeats:2_stddev\",%csv_report$"}});
+
+// Test repeats with custom time unit.
+void BM_RepeatTimeUnit(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_RepeatTimeUnit)
+    ->Repetitions(3)
+    ->ReportAggregatesOnly()
+    ->Unit(benchmark::kMicrosecond);
+ADD_CASES(
+    TC_ConsoleOut,
+    {{".*BM_RepeatTimeUnit/repeats:3 ", MR_Not},
+     {"^BM_RepeatTimeUnit/repeats:3_mean %console_us_time_only_report [ ]*3$"},
+     {"^BM_RepeatTimeUnit/repeats:3_median %console_us_time_only_report [ "
+      "]*3$"},
+     {"^BM_RepeatTimeUnit/repeats:3_stddev %console_us_time_only_report [ "
+      "]*3$"}});
+ADD_CASES(TC_JSONOut,
+          {{".*BM_RepeatTimeUnit/repeats:3 ", MR_Not},
+           {"\"name\": \"BM_RepeatTimeUnit/repeats:3_mean\",$"},
+           {"\"family_index\": 21,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_RepeatTimeUnit/repeats:3\",$", MR_Next},
+           {"\"run_type\": \"aggregate\",$", MR_Next},
+           {"\"repetitions\": 3,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"aggregate_name\": \"mean\",$", MR_Next},
+           {"\"aggregate_unit\": \"time\",$", MR_Next},
+           {"\"iterations\": 3,$", MR_Next},
+           {"\"time_unit\": \"us\",?$"},
+           {"\"name\": \"BM_RepeatTimeUnit/repeats:3_median\",$"},
+           {"\"family_index\": 21,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_RepeatTimeUnit/repeats:3\",$", MR_Next},
+           {"\"run_type\": \"aggregate\",$", MR_Next},
+           {"\"repetitions\": 3,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"aggregate_name\": \"median\",$", MR_Next},
+           {"\"aggregate_unit\": \"time\",$", MR_Next},
+           {"\"iterations\": 3,$", MR_Next},
+           {"\"time_unit\": \"us\",?$"},
+           {"\"name\": \"BM_RepeatTimeUnit/repeats:3_stddev\",$"},
+           {"\"family_index\": 21,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_RepeatTimeUnit/repeats:3\",$", MR_Next},
+           {"\"run_type\": \"aggregate\",$", MR_Next},
+           {"\"repetitions\": 3,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"aggregate_name\": \"stddev\",$", MR_Next},
+           {"\"aggregate_unit\": \"time\",$", MR_Next},
+           {"\"iterations\": 3,$", MR_Next},
+           {"\"time_unit\": \"us\",?$"}});
+ADD_CASES(TC_CSVOut,
+          {{".*BM_RepeatTimeUnit/repeats:3 ", MR_Not},
+           {"^\"BM_RepeatTimeUnit/repeats:3_mean\",%csv_us_report$"},
+           {"^\"BM_RepeatTimeUnit/repeats:3_median\",%csv_us_report$"},
+           {"^\"BM_RepeatTimeUnit/repeats:3_stddev\",%csv_us_report$"}});
+
+// ========================================================================= //
+// -------------------- Testing user-provided statistics ------------------- //
+// ========================================================================= //
+
+const auto UserStatistics = [](const std::vector<double>& v) {
+  return v.back();
+};
+void BM_UserStats(benchmark::State& state) {
+  for (auto _ : state) {
+    state.SetIterationTime(150 / 10e8);
+  }
+}
+// clang-format off
+BENCHMARK(BM_UserStats)
+  ->Repetitions(3)
+  ->Iterations(5)
+  ->UseManualTime()
+  ->ComputeStatistics("", UserStatistics);
+// clang-format on
+
+// check that user-provided stats is calculated, and is after the default-ones
+// empty string as name is intentional, it would sort before anything else
+ADD_CASES(TC_ConsoleOut, {{"^BM_UserStats/iterations:5/repeats:3/manual_time [ "
+                           "]* 150 ns %time [ ]*5$"},
+                          {"^BM_UserStats/iterations:5/repeats:3/manual_time [ "
+                           "]* 150 ns %time [ ]*5$"},
+                          {"^BM_UserStats/iterations:5/repeats:3/manual_time [ "
+                           "]* 150 ns %time [ ]*5$"},
+                          {"^BM_UserStats/iterations:5/repeats:3/"
+                           "manual_time_mean [ ]* 150 ns %time [ ]*3$"},
+                          {"^BM_UserStats/iterations:5/repeats:3/"
+                           "manual_time_median [ ]* 150 ns %time [ ]*3$"},
+                          {"^BM_UserStats/iterations:5/repeats:3/"
+                           "manual_time_stddev [ ]* 0.000 ns %time [ ]*3$"},
+                          {"^BM_UserStats/iterations:5/repeats:3/manual_time_ "
+                           "[ ]* 150 ns %time [ ]*3$"}});
+ADD_CASES(
+    TC_JSONOut,
+    {{"\"name\": \"BM_UserStats/iterations:5/repeats:3/manual_time\",$"},
+     {"\"family_index\": 22,$", MR_Next},
+     {"\"per_family_instance_index\": 0,$", MR_Next},
+     {"\"run_name\": \"BM_UserStats/iterations:5/repeats:3/manual_time\",$",
+      MR_Next},
+     {"\"run_type\": \"iteration\",$", MR_Next},
+     {"\"repetitions\": 3,$", MR_Next},
+     {"\"repetition_index\": 0,$", MR_Next},
+     {"\"threads\": 1,$", MR_Next},
+     {"\"iterations\": 5,$", MR_Next},
+     {"\"real_time\": 1\\.5(0)*e\\+(0)*2,$", MR_Next},
+     {"\"name\": \"BM_UserStats/iterations:5/repeats:3/manual_time\",$"},
+     {"\"family_index\": 22,$", MR_Next},
+     {"\"per_family_instance_index\": 0,$", MR_Next},
+     {"\"run_name\": \"BM_UserStats/iterations:5/repeats:3/manual_time\",$",
+      MR_Next},
+     {"\"run_type\": \"iteration\",$", MR_Next},
+     {"\"repetitions\": 3,$", MR_Next},
+     {"\"repetition_index\": 1,$", MR_Next},
+     {"\"threads\": 1,$", MR_Next},
+     {"\"iterations\": 5,$", MR_Next},
+     {"\"real_time\": 1\\.5(0)*e\\+(0)*2,$", MR_Next},
+     {"\"name\": \"BM_UserStats/iterations:5/repeats:3/manual_time\",$"},
+     {"\"family_index\": 22,$", MR_Next},
+     {"\"per_family_instance_index\": 0,$", MR_Next},
+     {"\"run_name\": \"BM_UserStats/iterations:5/repeats:3/manual_time\",$",
+      MR_Next},
+     {"\"run_type\": \"iteration\",$", MR_Next},
+     {"\"repetitions\": 3,$", MR_Next},
+     {"\"repetition_index\": 2,$", MR_Next},
+     {"\"threads\": 1,$", MR_Next},
+     {"\"iterations\": 5,$", MR_Next},
+     {"\"real_time\": 1\\.5(0)*e\\+(0)*2,$", MR_Next},
+     {"\"name\": \"BM_UserStats/iterations:5/repeats:3/manual_time_mean\",$"},
+     {"\"family_index\": 22,$", MR_Next},
+     {"\"per_family_instance_index\": 0,$", MR_Next},
+     {"\"run_name\": \"BM_UserStats/iterations:5/repeats:3/manual_time\",$",
+      MR_Next},
+     {"\"run_type\": \"aggregate\",$", MR_Next},
+     {"\"repetitions\": 3,$", MR_Next},
+     {"\"threads\": 1,$", MR_Next},
+     {"\"aggregate_name\": \"mean\",$", MR_Next},
+     {"\"aggregate_unit\": \"time\",$", MR_Next},
+     {"\"iterations\": 3,$", MR_Next},
+     {"\"real_time\": 1\\.5(0)*e\\+(0)*2,$", MR_Next},
+     {"\"name\": \"BM_UserStats/iterations:5/repeats:3/manual_time_median\",$"},
+     {"\"family_index\": 22,$", MR_Next},
+     {"\"per_family_instance_index\": 0,$", MR_Next},
+     {"\"run_name\": \"BM_UserStats/iterations:5/repeats:3/manual_time\",$",
+      MR_Next},
+     {"\"run_type\": \"aggregate\",$", MR_Next},
+     {"\"repetitions\": 3,$", MR_Next},
+     {"\"threads\": 1,$", MR_Next},
+     {"\"aggregate_name\": \"median\",$", MR_Next},
+     {"\"aggregate_unit\": \"time\",$", MR_Next},
+     {"\"iterations\": 3,$", MR_Next},
+     {"\"real_time\": 1\\.5(0)*e\\+(0)*2,$", MR_Next},
+     {"\"name\": \"BM_UserStats/iterations:5/repeats:3/manual_time_stddev\",$"},
+     {"\"family_index\": 22,$", MR_Next},
+     {"\"per_family_instance_index\": 0,$", MR_Next},
+     {"\"run_name\": \"BM_UserStats/iterations:5/repeats:3/manual_time\",$",
+      MR_Next},
+     {"\"run_type\": \"aggregate\",$", MR_Next},
+     {"\"repetitions\": 3,$", MR_Next},
+     {"\"threads\": 1,$", MR_Next},
+     {"\"aggregate_name\": \"stddev\",$", MR_Next},
+     {"\"aggregate_unit\": \"time\",$", MR_Next},
+     {"\"iterations\": 3,$", MR_Next},
+     {"\"real_time\": %float,$", MR_Next},
+     {"\"name\": \"BM_UserStats/iterations:5/repeats:3/manual_time_\",$"},
+     {"\"family_index\": 22,$", MR_Next},
+     {"\"per_family_instance_index\": 0,$", MR_Next},
+     {"\"run_name\": \"BM_UserStats/iterations:5/repeats:3/manual_time\",$",
+      MR_Next},
+     {"\"run_type\": \"aggregate\",$", MR_Next},
+     {"\"repetitions\": 3,$", MR_Next},
+     {"\"threads\": 1,$", MR_Next},
+     {"\"aggregate_name\": \"\",$", MR_Next},
+     {"\"aggregate_unit\": \"time\",$", MR_Next},
+     {"\"iterations\": 3,$", MR_Next},
+     {"\"real_time\": 1\\.5(0)*e\\+(0)*2,$", MR_Next}});
+ADD_CASES(
+    TC_CSVOut,
+    {{"^\"BM_UserStats/iterations:5/repeats:3/manual_time\",%csv_report$"},
+     {"^\"BM_UserStats/iterations:5/repeats:3/manual_time\",%csv_report$"},
+     {"^\"BM_UserStats/iterations:5/repeats:3/manual_time\",%csv_report$"},
+     {"^\"BM_UserStats/iterations:5/repeats:3/manual_time_mean\",%csv_report$"},
+     {"^\"BM_UserStats/iterations:5/repeats:3/"
+      "manual_time_median\",%csv_report$"},
+     {"^\"BM_UserStats/iterations:5/repeats:3/"
+      "manual_time_stddev\",%csv_report$"},
+     {"^\"BM_UserStats/iterations:5/repeats:3/manual_time_\",%csv_report$"}});
+
+// ========================================================================= //
+// ------------- Testing relative standard deviation statistics ------------ //
+// ========================================================================= //
+
+const auto UserPercentStatistics = [](const std::vector<double>&) {
+  return 1. / 100.;
+};
+void BM_UserPercentStats(benchmark::State& state) {
+  for (auto _ : state) {
+    state.SetIterationTime(150 / 10e8);
+  }
+}
+// clang-format off
+BENCHMARK(BM_UserPercentStats)
+  ->Repetitions(3)
+  ->Iterations(5)
+  ->UseManualTime()
+  ->Unit(benchmark::TimeUnit::kNanosecond)
+  ->ComputeStatistics("", UserPercentStatistics, benchmark::StatisticUnit::kPercentage);
+// clang-format on
+
+// check that UserPercent-provided stats is calculated, and is after the
+// default-ones empty string as name is intentional, it would sort before
+// anything else
+ADD_CASES(TC_ConsoleOut,
+          {{"^BM_UserPercentStats/iterations:5/repeats:3/manual_time [ "
+            "]* 150 ns %time [ ]*5$"},
+           {"^BM_UserPercentStats/iterations:5/repeats:3/manual_time [ "
+            "]* 150 ns %time [ ]*5$"},
+           {"^BM_UserPercentStats/iterations:5/repeats:3/manual_time [ "
+            "]* 150 ns %time [ ]*5$"},
+           {"^BM_UserPercentStats/iterations:5/repeats:3/"
+            "manual_time_mean [ ]* 150 ns %time [ ]*3$"},
+           {"^BM_UserPercentStats/iterations:5/repeats:3/"
+            "manual_time_median [ ]* 150 ns %time [ ]*3$"},
+           {"^BM_UserPercentStats/iterations:5/repeats:3/"
+            "manual_time_stddev [ ]* 0.000 ns %time [ ]*3$"},
+           {"^BM_UserPercentStats/iterations:5/repeats:3/manual_time_ "
+            "[ ]* 1.00 % [ ]* 1.00 %[ ]*3$"}});
+ADD_CASES(
+    TC_JSONOut,
+    {{"\"name\": \"BM_UserPercentStats/iterations:5/repeats:3/manual_time\",$"},
+     {"\"family_index\": 23,$", MR_Next},
+     {"\"per_family_instance_index\": 0,$", MR_Next},
+     {"\"run_name\": "
+      "\"BM_UserPercentStats/iterations:5/repeats:3/manual_time\",$",
+      MR_Next},
+     {"\"run_type\": \"iteration\",$", MR_Next},
+     {"\"repetitions\": 3,$", MR_Next},
+     {"\"repetition_index\": 0,$", MR_Next},
+     {"\"threads\": 1,$", MR_Next},
+     {"\"iterations\": 5,$", MR_Next},
+     {"\"real_time\": 1\\.5(0)*e\\+(0)*2,$", MR_Next},
+     {"\"name\": \"BM_UserPercentStats/iterations:5/repeats:3/manual_time\",$"},
+     {"\"family_index\": 23,$", MR_Next},
+     {"\"per_family_instance_index\": 0,$", MR_Next},
+     {"\"run_name\": "
+      "\"BM_UserPercentStats/iterations:5/repeats:3/manual_time\",$",
+      MR_Next},
+     {"\"run_type\": \"iteration\",$", MR_Next},
+     {"\"repetitions\": 3,$", MR_Next},
+     {"\"repetition_index\": 1,$", MR_Next},
+     {"\"threads\": 1,$", MR_Next},
+     {"\"iterations\": 5,$", MR_Next},
+     {"\"real_time\": 1\\.5(0)*e\\+(0)*2,$", MR_Next},
+     {"\"name\": \"BM_UserPercentStats/iterations:5/repeats:3/manual_time\",$"},
+     {"\"family_index\": 23,$", MR_Next},
+     {"\"per_family_instance_index\": 0,$", MR_Next},
+     {"\"run_name\": "
+      "\"BM_UserPercentStats/iterations:5/repeats:3/manual_time\",$",
+      MR_Next},
+     {"\"run_type\": \"iteration\",$", MR_Next},
+     {"\"repetitions\": 3,$", MR_Next},
+     {"\"repetition_index\": 2,$", MR_Next},
+     {"\"threads\": 1,$", MR_Next},
+     {"\"iterations\": 5,$", MR_Next},
+     {"\"real_time\": 1\\.5(0)*e\\+(0)*2,$", MR_Next},
+     {"\"name\": "
+      "\"BM_UserPercentStats/iterations:5/repeats:3/manual_time_mean\",$"},
+     {"\"family_index\": 23,$", MR_Next},
+     {"\"per_family_instance_index\": 0,$", MR_Next},
+     {"\"run_name\": "
+      "\"BM_UserPercentStats/iterations:5/repeats:3/manual_time\",$",
+      MR_Next},
+     {"\"run_type\": \"aggregate\",$", MR_Next},
+     {"\"repetitions\": 3,$", MR_Next},
+     {"\"threads\": 1,$", MR_Next},
+     {"\"aggregate_name\": \"mean\",$", MR_Next},
+     {"\"aggregate_unit\": \"time\",$", MR_Next},
+     {"\"iterations\": 3,$", MR_Next},
+     {"\"real_time\": 1\\.5(0)*e\\+(0)*2,$", MR_Next},
+     {"\"name\": "
+      "\"BM_UserPercentStats/iterations:5/repeats:3/manual_time_median\",$"},
+     {"\"family_index\": 23,$", MR_Next},
+     {"\"per_family_instance_index\": 0,$", MR_Next},
+     {"\"run_name\": "
+      "\"BM_UserPercentStats/iterations:5/repeats:3/manual_time\",$",
+      MR_Next},
+     {"\"run_type\": \"aggregate\",$", MR_Next},
+     {"\"repetitions\": 3,$", MR_Next},
+     {"\"threads\": 1,$", MR_Next},
+     {"\"aggregate_name\": \"median\",$", MR_Next},
+     {"\"aggregate_unit\": \"time\",$", MR_Next},
+     {"\"iterations\": 3,$", MR_Next},
+     {"\"real_time\": 1\\.5(0)*e\\+(0)*2,$", MR_Next},
+     {"\"name\": "
+      "\"BM_UserPercentStats/iterations:5/repeats:3/manual_time_stddev\",$"},
+     {"\"family_index\": 23,$", MR_Next},
+     {"\"per_family_instance_index\": 0,$", MR_Next},
+     {"\"run_name\": "
+      "\"BM_UserPercentStats/iterations:5/repeats:3/manual_time\",$",
+      MR_Next},
+     {"\"run_type\": \"aggregate\",$", MR_Next},
+     {"\"repetitions\": 3,$", MR_Next},
+     {"\"threads\": 1,$", MR_Next},
+     {"\"aggregate_name\": \"stddev\",$", MR_Next},
+     {"\"aggregate_unit\": \"time\",$", MR_Next},
+     {"\"iterations\": 3,$", MR_Next},
+     {"\"real_time\": %float,$", MR_Next},
+     {"\"name\": "
+      "\"BM_UserPercentStats/iterations:5/repeats:3/manual_time_\",$"},
+     {"\"family_index\": 23,$", MR_Next},
+     {"\"per_family_instance_index\": 0,$", MR_Next},
+     {"\"run_name\": "
+      "\"BM_UserPercentStats/iterations:5/repeats:3/manual_time\",$",
+      MR_Next},
+     {"\"run_type\": \"aggregate\",$", MR_Next},
+     {"\"repetitions\": 3,$", MR_Next},
+     {"\"threads\": 1,$", MR_Next},
+     {"\"aggregate_name\": \"\",$", MR_Next},
+     {"\"aggregate_unit\": \"percentage\",$", MR_Next},
+     {"\"iterations\": 3,$", MR_Next},
+     {"\"real_time\": 1\\.(0)*e-(0)*2,$", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_UserPercentStats/iterations:5/repeats:3/"
+                       "manual_time\",%csv_report$"},
+                      {"^\"BM_UserPercentStats/iterations:5/repeats:3/"
+                       "manual_time\",%csv_report$"},
+                      {"^\"BM_UserPercentStats/iterations:5/repeats:3/"
+                       "manual_time\",%csv_report$"},
+                      {"^\"BM_UserPercentStats/iterations:5/repeats:3/"
+                       "manual_time_mean\",%csv_report$"},
+                      {"^\"BM_UserPercentStats/iterations:5/repeats:3/"
+                       "manual_time_median\",%csv_report$"},
+                      {"^\"BM_UserPercentStats/iterations:5/repeats:3/"
+                       "manual_time_stddev\",%csv_report$"},
+                      {"^\"BM_UserPercentStats/iterations:5/repeats:3/"
+                       "manual_time_\",%csv_report$"}});
+
+// ========================================================================= //
+// ------------------------- Testing StrEscape JSON ------------------------ //
+// ========================================================================= //
+#if 0  // enable when csv testing code correctly handles multi-line fields
+void BM_JSON_Format(benchmark::State& state) {
+  state.SkipWithError("val\b\f\n\r\t\\\"with\"es,capes");
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_JSON_Format);
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_JSON_Format\",$"},
+                                              {"\"family_index\": 23,$", MR_Next},
+{"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_JSON_Format\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 1,$", MR_Next},
+                       {"\"repetition_index\": 0,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"error_occurred\": true,$", MR_Next},
+                       {R"("error_message": "val\\b\\f\\n\\r\\t\\\\\\"with\\"es,capes",$)", MR_Next}});
+#endif
+// ========================================================================= //
+// -------------------------- Testing CsvEscape ---------------------------- //
+// ========================================================================= //
+
+void BM_CSV_Format(benchmark::State& state) {
+  state.SkipWithError("\"freedom\"");
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_CSV_Format);
+ADD_CASES(TC_CSVOut, {{"^\"BM_CSV_Format\",,,,,,,,true,\"\"\"freedom\"\"\"$"}});
+
+// ========================================================================= //
+// --------------------------- TEST CASES END ------------------------------ //
+// ========================================================================= //
+
+int main(int argc, char* argv[]) { RunOutputTests(argc, argv); }
diff --git a/leveldb_base/third_party/benchmark/test/skip_with_error_test.cc b/leveldb_base/third_party/benchmark/test/skip_with_error_test.cc
new file mode 100644
index 0000000..b4c5e15
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/skip_with_error_test.cc
@@ -0,0 +1,199 @@
+
+#undef NDEBUG
+#include <cassert>
+#include <vector>
+
+#include "../src/check.h"  // NOTE: check.h is for internal use only!
+#include "benchmark/benchmark.h"
+
+namespace {
+
+class TestReporter : public benchmark::ConsoleReporter {
+ public:
+  bool ReportContext(const Context& context) override {
+    return ConsoleReporter::ReportContext(context);
+  };
+
+  void ReportRuns(const std::vector<Run>& report) override {
+    all_runs_.insert(all_runs_.end(), begin(report), end(report));
+    ConsoleReporter::ReportRuns(report);
+  }
+
+  TestReporter() {}
+  ~TestReporter() override {}
+
+  mutable std::vector<Run> all_runs_;
+};
+
+struct TestCase {
+  std::string name;
+  bool error_occurred;
+  std::string error_message;
+
+  typedef benchmark::BenchmarkReporter::Run Run;
+
+  void CheckRun(Run const& run) const {
+    BM_CHECK(name == run.benchmark_name())
+        << "expected " << name << " got " << run.benchmark_name();
+    BM_CHECK_EQ(error_occurred,
+                benchmark::internal::SkippedWithError == run.skipped);
+    BM_CHECK(error_message == run.skip_message);
+    if (error_occurred) {
+      // BM_CHECK(run.iterations == 0);
+    } else {
+      BM_CHECK(run.iterations != 0);
+    }
+  }
+};
+
+std::vector<TestCase> ExpectedResults;
+
+int AddCases(const std::string& base_name,
+             std::initializer_list<TestCase> const& v) {
+  for (auto TC : v) {
+    TC.name = base_name + TC.name;
+    ExpectedResults.push_back(std::move(TC));
+  }
+  return 0;
+}
+
+#define CONCAT(x, y) CONCAT2(x, y)
+#define CONCAT2(x, y) x##y
+#define ADD_CASES(...) int CONCAT(dummy, __LINE__) = AddCases(__VA_ARGS__)
+
+}  // end namespace
+
+void BM_error_no_running(benchmark::State& state) {
+  state.SkipWithError("error message");
+}
+BENCHMARK(BM_error_no_running);
+ADD_CASES("BM_error_no_running", {{"", true, "error message"}});
+
+void BM_error_before_running(benchmark::State& state) {
+  state.SkipWithError("error message");
+  while (state.KeepRunning()) {
+    assert(false);
+  }
+}
+BENCHMARK(BM_error_before_running);
+ADD_CASES("BM_error_before_running", {{"", true, "error message"}});
+
+void BM_error_before_running_batch(benchmark::State& state) {
+  state.SkipWithError("error message");
+  while (state.KeepRunningBatch(17)) {
+    assert(false);
+  }
+}
+BENCHMARK(BM_error_before_running_batch);
+ADD_CASES("BM_error_before_running_batch", {{"", true, "error message"}});
+
+void BM_error_before_running_range_for(benchmark::State& state) {
+  state.SkipWithError("error message");
+  for (auto _ : state) {
+    assert(false);
+  }
+}
+BENCHMARK(BM_error_before_running_range_for);
+ADD_CASES("BM_error_before_running_range_for", {{"", true, "error message"}});
+
+void BM_error_during_running(benchmark::State& state) {
+  int first_iter = true;
+  while (state.KeepRunning()) {
+    if (state.range(0) == 1 && state.thread_index() <= (state.threads() / 2)) {
+      assert(first_iter);
+      first_iter = false;
+      state.SkipWithError("error message");
+    } else {
+      state.PauseTiming();
+      state.ResumeTiming();
+    }
+  }
+}
+BENCHMARK(BM_error_during_running)->Arg(1)->Arg(2)->ThreadRange(1, 8);
+ADD_CASES("BM_error_during_running", {{"/1/threads:1", true, "error message"},
+                                      {"/1/threads:2", true, "error message"},
+                                      {"/1/threads:4", true, "error message"},
+                                      {"/1/threads:8", true, "error message"},
+                                      {"/2/threads:1", false, ""},
+                                      {"/2/threads:2", false, ""},
+                                      {"/2/threads:4", false, ""},
+                                      {"/2/threads:8", false, ""}});
+
+void BM_error_during_running_ranged_for(benchmark::State& state) {
+  assert(state.max_iterations > 3 && "test requires at least a few iterations");
+  bool first_iter = true;
+  // NOTE: Users should not write the for loop explicitly.
+  for (auto It = state.begin(), End = state.end(); It != End; ++It) {
+    if (state.range(0) == 1) {
+      assert(first_iter);
+      first_iter = false;
+      (void)first_iter;
+      state.SkipWithError("error message");
+      // Test the unfortunate but documented behavior that the ranged-for loop
+      // doesn't automatically terminate when SkipWithError is set.
+      assert(++It != End);
+      break;  // Required behavior
+    }
+  }
+}
+BENCHMARK(BM_error_during_running_ranged_for)->Arg(1)->Arg(2)->Iterations(5);
+ADD_CASES("BM_error_during_running_ranged_for",
+          {{"/1/iterations:5", true, "error message"},
+           {"/2/iterations:5", false, ""}});
+
+void BM_error_after_running(benchmark::State& state) {
+  for (auto _ : state) {
+    auto iterations = state.iterations();
+    benchmark::DoNotOptimize(iterations);
+  }
+  if (state.thread_index() <= (state.threads() / 2))
+    state.SkipWithError("error message");
+}
+BENCHMARK(BM_error_after_running)->ThreadRange(1, 8);
+ADD_CASES("BM_error_after_running", {{"/threads:1", true, "error message"},
+                                     {"/threads:2", true, "error message"},
+                                     {"/threads:4", true, "error message"},
+                                     {"/threads:8", true, "error message"}});
+
+void BM_error_while_paused(benchmark::State& state) {
+  bool first_iter = true;
+  while (state.KeepRunning()) {
+    if (state.range(0) == 1 && state.thread_index() <= (state.threads() / 2)) {
+      assert(first_iter);
+      first_iter = false;
+      state.PauseTiming();
+      state.SkipWithError("error message");
+    } else {
+      state.PauseTiming();
+      state.ResumeTiming();
+    }
+  }
+}
+BENCHMARK(BM_error_while_paused)->Arg(1)->Arg(2)->ThreadRange(1, 8);
+ADD_CASES("BM_error_while_paused", {{"/1/threads:1", true, "error message"},
+                                    {"/1/threads:2", true, "error message"},
+                                    {"/1/threads:4", true, "error message"},
+                                    {"/1/threads:8", true, "error message"},
+                                    {"/2/threads:1", false, ""},
+                                    {"/2/threads:2", false, ""},
+                                    {"/2/threads:4", false, ""},
+                                    {"/2/threads:8", false, ""}});
+
+int main(int argc, char* argv[]) {
+  benchmark::Initialize(&argc, argv);
+
+  TestReporter test_reporter;
+  benchmark::RunSpecifiedBenchmarks(&test_reporter);
+
+  typedef benchmark::BenchmarkReporter::Run Run;
+  auto EB = ExpectedResults.begin();
+
+  for (Run const& run : test_reporter.all_runs_) {
+    assert(EB != ExpectedResults.end());
+    EB->CheckRun(run);
+    ++EB;
+  }
+  assert(EB == ExpectedResults.end());
+
+  return 0;
+}
diff --git a/leveldb_base/third_party/benchmark/test/spec_arg_test.cc b/leveldb_base/third_party/benchmark/test/spec_arg_test.cc
new file mode 100644
index 0000000..06aafbe
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/spec_arg_test.cc
@@ -0,0 +1,105 @@
+#include <algorithm>
+#include <cassert>
+#include <cstdint>
+#include <cstdlib>
+#include <cstring>
+#include <iostream>
+#include <limits>
+#include <string>
+#include <vector>
+
+#include "benchmark/benchmark.h"
+
+// Tests that we can override benchmark-spec value from FLAGS_benchmark_filter
+// with argument to RunSpecifiedBenchmarks(...).
+
+namespace {
+
+class TestReporter : public benchmark::ConsoleReporter {
+ public:
+  bool ReportContext(const Context& context) override {
+    return ConsoleReporter::ReportContext(context);
+  };
+
+  void ReportRuns(const std::vector<Run>& report) override {
+    assert(report.size() == 1);
+    matched_functions.push_back(report[0].run_name.function_name);
+    ConsoleReporter::ReportRuns(report);
+  };
+
+  TestReporter() {}
+
+  ~TestReporter() override {}
+
+  const std::vector<std::string>& GetMatchedFunctions() const {
+    return matched_functions;
+  }
+
+ private:
+  std::vector<std::string> matched_functions;
+};
+
+}  // end namespace
+
+static void BM_NotChosen(benchmark::State& state) {
+  assert(false && "SHOULD NOT BE CALLED");
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_NotChosen);
+
+static void BM_Chosen(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_Chosen);
+
+int main(int argc, char** argv) {
+  const std::string flag = "BM_NotChosen";
+
+  // Verify that argv specify --benchmark_filter=BM_NotChosen.
+  bool found = false;
+  for (int i = 0; i < argc; ++i) {
+    if (strcmp("--benchmark_filter=BM_NotChosen", argv[i]) == 0) {
+      found = true;
+      break;
+    }
+  }
+  assert(found);
+
+  benchmark::Initialize(&argc, argv);
+
+  // Check that the current flag value is reported accurately via the
+  // GetBenchmarkFilter() function.
+  if (flag != benchmark::GetBenchmarkFilter()) {
+    std::cerr
+        << "Seeing different value for flags. GetBenchmarkFilter() returns ["
+        << benchmark::GetBenchmarkFilter() << "] expected flag=[" << flag
+        << "]\n";
+    return 1;
+  }
+  TestReporter test_reporter;
+  const char* const spec = "BM_Chosen";
+  const size_t returned_count =
+      benchmark::RunSpecifiedBenchmarks(&test_reporter, spec);
+  assert(returned_count == 1);
+  const std::vector<std::string> matched_functions =
+      test_reporter.GetMatchedFunctions();
+  assert(matched_functions.size() == 1);
+  if (strcmp(spec, matched_functions.front().c_str()) != 0) {
+    std::cerr << "Expected benchmark [" << spec << "] to run, but got ["
+              << matched_functions.front() << "]\n";
+    return 2;
+  }
+
+  // Test that SetBenchmarkFilter works.
+  const std::string golden_value = "golden_value";
+  benchmark::SetBenchmarkFilter(golden_value);
+  std::string current_value = benchmark::GetBenchmarkFilter();
+  if (golden_value != current_value) {
+    std::cerr << "Expected [" << golden_value
+              << "] for --benchmark_filter but got [" << current_value << "]\n";
+    return 3;
+  }
+  return 0;
+}
diff --git a/leveldb_base/third_party/benchmark/test/spec_arg_verbosity_test.cc b/leveldb_base/third_party/benchmark/test/spec_arg_verbosity_test.cc
new file mode 100644
index 0000000..8f8eb6d
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/spec_arg_verbosity_test.cc
@@ -0,0 +1,43 @@
+#include <string.h>
+
+#include <iostream>
+
+#include "benchmark/benchmark.h"
+
+// Tests that the user specified verbosity level can be get.
+static void BM_Verbosity(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+}
+BENCHMARK(BM_Verbosity);
+
+int main(int argc, char** argv) {
+  const int32_t flagv = 42;
+
+  // Verify that argv specify --v=42.
+  bool found = false;
+  for (int i = 0; i < argc; ++i) {
+    if (strcmp("--v=42", argv[i]) == 0) {
+      found = true;
+      break;
+    }
+  }
+  if (!found) {
+    std::cerr << "This test requires '--v=42' to be passed as a command-line "
+              << "argument.\n";
+    return 1;
+  }
+
+  benchmark::Initialize(&argc, argv);
+
+  // Check that the current flag value is reported accurately via the
+  // GetBenchmarkVerbosity() function.
+  if (flagv != benchmark::GetBenchmarkVerbosity()) {
+    std::cerr
+        << "Seeing different value for flags. GetBenchmarkVerbosity() returns ["
+        << benchmark::GetBenchmarkVerbosity() << "] expected flag=[" << flagv
+        << "]\n";
+    return 1;
+  }
+  return 0;
+}
diff --git a/leveldb_base/third_party/benchmark/test/state_assembly_test.cc b/leveldb_base/third_party/benchmark/test/state_assembly_test.cc
new file mode 100644
index 0000000..7ddbb3b
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/state_assembly_test.cc
@@ -0,0 +1,68 @@
+#include <benchmark/benchmark.h>
+
+#ifdef __clang__
+#pragma clang diagnostic ignored "-Wreturn-type"
+#endif
+
+// clang-format off
+extern "C" {
+  extern int ExternInt;
+  benchmark::State& GetState();
+  void Fn();
+}
+// clang-format on
+
+using benchmark::State;
+
+// CHECK-LABEL: test_for_auto_loop:
+extern "C" int test_for_auto_loop() {
+  State& S = GetState();
+  int x = 42;
+  // CHECK: 	[[CALL:call(q)*]]	_ZN9benchmark5State16StartKeepRunningEv
+  // CHECK-NEXT: testq %rbx, %rbx
+  // CHECK-NEXT: je [[LOOP_END:.*]]
+
+  for (auto _ : S) {
+    // CHECK: .L[[LOOP_HEAD:[a-zA-Z0-9_]+]]:
+    // CHECK-GNU-NEXT: subq $1, %rbx
+    // CHECK-CLANG-NEXT: {{(addq \$1, %rax|incq %rax|addq \$-1, %rbx)}}
+    // CHECK-NEXT: jne .L[[LOOP_HEAD]]
+    benchmark::DoNotOptimize(x);
+  }
+  // CHECK: [[LOOP_END]]:
+  // CHECK: [[CALL]]	_ZN9benchmark5State17FinishKeepRunningEv
+
+  // CHECK: movl $101, %eax
+  // CHECK: ret
+  return 101;
+}
+
+// CHECK-LABEL: test_while_loop:
+extern "C" int test_while_loop() {
+  State& S = GetState();
+  int x = 42;
+
+  // CHECK: j{{(e|mp)}} .L[[LOOP_HEADER:[a-zA-Z0-9_]+]]
+  // CHECK-NEXT: .L[[LOOP_BODY:[a-zA-Z0-9_]+]]:
+  while (S.KeepRunning()) {
+    // CHECK-GNU-NEXT: subq $1, %[[IREG:[a-z]+]]
+    // CHECK-CLANG-NEXT: {{(addq \$-1,|decq)}} %[[IREG:[a-z]+]]
+    // CHECK: movq %[[IREG]], [[DEST:.*]]
+    benchmark::DoNotOptimize(x);
+  }
+  // CHECK-DAG: movq [[DEST]], %[[IREG]]
+  // CHECK-DAG: testq %[[IREG]], %[[IREG]]
+  // CHECK-DAG: jne .L[[LOOP_BODY]]
+  // CHECK-DAG: .L[[LOOP_HEADER]]:
+
+  // CHECK: cmpb $0
+  // CHECK-NEXT: jne .L[[LOOP_END:[a-zA-Z0-9_]+]]
+  // CHECK: [[CALL:call(q)*]] _ZN9benchmark5State16StartKeepRunningEv
+
+  // CHECK: .L[[LOOP_END]]:
+  // CHECK: [[CALL]] _ZN9benchmark5State17FinishKeepRunningEv
+
+  // CHECK: movl $101, %eax
+  // CHECK: ret
+  return 101;
+}
diff --git a/leveldb_base/third_party/benchmark/test/statistics_gtest.cc b/leveldb_base/third_party/benchmark/test/statistics_gtest.cc
new file mode 100644
index 0000000..1de2d87
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/statistics_gtest.cc
@@ -0,0 +1,35 @@
+//===---------------------------------------------------------------------===//
+// statistics_test - Unit tests for src/statistics.cc
+//===---------------------------------------------------------------------===//
+
+#include "../src/statistics.h"
+#include "gtest/gtest.h"
+
+namespace {
+TEST(StatisticsTest, Mean) {
+  EXPECT_DOUBLE_EQ(benchmark::StatisticsMean({42, 42, 42, 42}), 42.0);
+  EXPECT_DOUBLE_EQ(benchmark::StatisticsMean({1, 2, 3, 4}), 2.5);
+  EXPECT_DOUBLE_EQ(benchmark::StatisticsMean({1, 2, 5, 10, 10, 14}), 7.0);
+}
+
+TEST(StatisticsTest, Median) {
+  EXPECT_DOUBLE_EQ(benchmark::StatisticsMedian({42, 42, 42, 42}), 42.0);
+  EXPECT_DOUBLE_EQ(benchmark::StatisticsMedian({1, 2, 3, 4}), 2.5);
+  EXPECT_DOUBLE_EQ(benchmark::StatisticsMedian({1, 2, 5, 10, 10}), 5.0);
+}
+
+TEST(StatisticsTest, StdDev) {
+  EXPECT_DOUBLE_EQ(benchmark::StatisticsStdDev({101, 101, 101, 101}), 0.0);
+  EXPECT_DOUBLE_EQ(benchmark::StatisticsStdDev({1, 2, 3}), 1.0);
+  EXPECT_DOUBLE_EQ(benchmark::StatisticsStdDev({2.5, 2.4, 3.3, 4.2, 5.1}),
+                   1.151086443322134);
+}
+
+TEST(StatisticsTest, CV) {
+  EXPECT_DOUBLE_EQ(benchmark::StatisticsCV({101, 101, 101, 101}), 0.0);
+  EXPECT_DOUBLE_EQ(benchmark::StatisticsCV({1, 2, 3}), 1. / 2.);
+  EXPECT_DOUBLE_EQ(benchmark::StatisticsCV({2.5, 2.4, 3.3, 4.2, 5.1}),
+                   0.32888184094918121);
+}
+
+}  // end namespace
diff --git a/leveldb_base/third_party/benchmark/test/string_util_gtest.cc b/leveldb_base/third_party/benchmark/test/string_util_gtest.cc
new file mode 100644
index 0000000..8bfdb7a
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/string_util_gtest.cc
@@ -0,0 +1,163 @@
+//===---------------------------------------------------------------------===//
+// statistics_test - Unit tests for src/statistics.cc
+//===---------------------------------------------------------------------===//
+
+#include <tuple>
+
+#include "../src/internal_macros.h"
+#include "../src/string_util.h"
+#include "gtest/gtest.h"
+
+namespace {
+TEST(StringUtilTest, stoul) {
+  {
+    size_t pos = 0;
+    EXPECT_EQ(0ul, benchmark::stoul("0", &pos));
+    EXPECT_EQ(1ul, pos);
+  }
+  {
+    size_t pos = 0;
+    EXPECT_EQ(7ul, benchmark::stoul("7", &pos));
+    EXPECT_EQ(1ul, pos);
+  }
+  {
+    size_t pos = 0;
+    EXPECT_EQ(135ul, benchmark::stoul("135", &pos));
+    EXPECT_EQ(3ul, pos);
+  }
+#if ULONG_MAX == 0xFFFFFFFFul
+  {
+    size_t pos = 0;
+    EXPECT_EQ(0xFFFFFFFFul, benchmark::stoul("4294967295", &pos));
+    EXPECT_EQ(10ul, pos);
+  }
+#elif ULONG_MAX == 0xFFFFFFFFFFFFFFFFul
+  {
+    size_t pos = 0;
+    EXPECT_EQ(0xFFFFFFFFFFFFFFFFul,
+              benchmark::stoul("18446744073709551615", &pos));
+    EXPECT_EQ(20ul, pos);
+  }
+#endif
+  {
+    size_t pos = 0;
+    EXPECT_EQ(10ul, benchmark::stoul("1010", &pos, 2));
+    EXPECT_EQ(4ul, pos);
+  }
+  {
+    size_t pos = 0;
+    EXPECT_EQ(520ul, benchmark::stoul("1010", &pos, 8));
+    EXPECT_EQ(4ul, pos);
+  }
+  {
+    size_t pos = 0;
+    EXPECT_EQ(1010ul, benchmark::stoul("1010", &pos, 10));
+    EXPECT_EQ(4ul, pos);
+  }
+  {
+    size_t pos = 0;
+    EXPECT_EQ(4112ul, benchmark::stoul("1010", &pos, 16));
+    EXPECT_EQ(4ul, pos);
+  }
+  {
+    size_t pos = 0;
+    EXPECT_EQ(0xBEEFul, benchmark::stoul("BEEF", &pos, 16));
+    EXPECT_EQ(4ul, pos);
+  }
+#ifndef BENCHMARK_HAS_NO_EXCEPTIONS
+  {
+    ASSERT_THROW(std::ignore = benchmark::stoul("this is a test"),
+                 std::invalid_argument);
+  }
+#endif
+}
+
+TEST(StringUtilTest, stoi){{size_t pos = 0;
+EXPECT_EQ(0, benchmark::stoi("0", &pos));
+EXPECT_EQ(1ul, pos);
+}  // namespace
+{
+  size_t pos = 0;
+  EXPECT_EQ(-17, benchmark::stoi("-17", &pos));
+  EXPECT_EQ(3ul, pos);
+}
+{
+  size_t pos = 0;
+  EXPECT_EQ(1357, benchmark::stoi("1357", &pos));
+  EXPECT_EQ(4ul, pos);
+}
+{
+  size_t pos = 0;
+  EXPECT_EQ(10, benchmark::stoi("1010", &pos, 2));
+  EXPECT_EQ(4ul, pos);
+}
+{
+  size_t pos = 0;
+  EXPECT_EQ(520, benchmark::stoi("1010", &pos, 8));
+  EXPECT_EQ(4ul, pos);
+}
+{
+  size_t pos = 0;
+  EXPECT_EQ(1010, benchmark::stoi("1010", &pos, 10));
+  EXPECT_EQ(4ul, pos);
+}
+{
+  size_t pos = 0;
+  EXPECT_EQ(4112, benchmark::stoi("1010", &pos, 16));
+  EXPECT_EQ(4ul, pos);
+}
+{
+  size_t pos = 0;
+  EXPECT_EQ(0xBEEF, benchmark::stoi("BEEF", &pos, 16));
+  EXPECT_EQ(4ul, pos);
+}
+#ifndef BENCHMARK_HAS_NO_EXCEPTIONS
+{
+  ASSERT_THROW(std::ignore = benchmark::stoi("this is a test"),
+               std::invalid_argument);
+}
+#endif
+}
+
+TEST(StringUtilTest, stod){{size_t pos = 0;
+EXPECT_EQ(0.0, benchmark::stod("0", &pos));
+EXPECT_EQ(1ul, pos);
+}
+{
+  size_t pos = 0;
+  EXPECT_EQ(-84.0, benchmark::stod("-84", &pos));
+  EXPECT_EQ(3ul, pos);
+}
+{
+  size_t pos = 0;
+  EXPECT_EQ(1234.0, benchmark::stod("1234", &pos));
+  EXPECT_EQ(4ul, pos);
+}
+{
+  size_t pos = 0;
+  EXPECT_EQ(1.5, benchmark::stod("1.5", &pos));
+  EXPECT_EQ(3ul, pos);
+}
+{
+  size_t pos = 0;
+  /* Note: exactly representable as double */
+  EXPECT_EQ(-1.25e+9, benchmark::stod("-1.25e+9", &pos));
+  EXPECT_EQ(8ul, pos);
+}
+#ifndef BENCHMARK_HAS_NO_EXCEPTIONS
+{
+  ASSERT_THROW(std::ignore = benchmark::stod("this is a test"),
+               std::invalid_argument);
+}
+#endif
+}
+
+TEST(StringUtilTest, StrSplit) {
+  EXPECT_EQ(benchmark::StrSplit("", ','), std::vector<std::string>{});
+  EXPECT_EQ(benchmark::StrSplit("hello", ','),
+            std::vector<std::string>({"hello"}));
+  EXPECT_EQ(benchmark::StrSplit("hello,there,is,more", ','),
+            std::vector<std::string>({"hello", "there", "is", "more"}));
+}
+
+}  // end namespace
diff --git a/leveldb_base/third_party/benchmark/test/templated_fixture_test.cc b/leveldb_base/third_party/benchmark/test/templated_fixture_test.cc
new file mode 100644
index 0000000..af239c3
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/templated_fixture_test.cc
@@ -0,0 +1,28 @@
+
+#include <cassert>
+#include <memory>
+
+#include "benchmark/benchmark.h"
+
+template <typename T>
+class MyFixture : public ::benchmark::Fixture {
+ public:
+  MyFixture() : data(0) {}
+
+  T data;
+};
+
+BENCHMARK_TEMPLATE_F(MyFixture, Foo, int)(benchmark::State& st) {
+  for (auto _ : st) {
+    data += 1;
+  }
+}
+
+BENCHMARK_TEMPLATE_DEFINE_F(MyFixture, Bar, double)(benchmark::State& st) {
+  for (auto _ : st) {
+    data += 1.0;
+  }
+}
+BENCHMARK_REGISTER_F(MyFixture, Bar);
+
+BENCHMARK_MAIN();
diff --git a/leveldb_base/third_party/benchmark/test/time_unit_gtest.cc b/leveldb_base/third_party/benchmark/test/time_unit_gtest.cc
new file mode 100644
index 0000000..484ecbc
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/time_unit_gtest.cc
@@ -0,0 +1,37 @@
+#include "../include/benchmark/benchmark.h"
+#include "gtest/gtest.h"
+
+namespace benchmark {
+namespace internal {
+
+namespace {
+
+class DummyBenchmark : public Benchmark {
+ public:
+  DummyBenchmark() : Benchmark("dummy") {}
+  void Run(State&) override {}
+};
+
+TEST(DefaultTimeUnitTest, TimeUnitIsNotSet) {
+  DummyBenchmark benchmark;
+  EXPECT_EQ(benchmark.GetTimeUnit(), kNanosecond);
+}
+
+TEST(DefaultTimeUnitTest, DefaultIsSet) {
+  DummyBenchmark benchmark;
+  EXPECT_EQ(benchmark.GetTimeUnit(), kNanosecond);
+  SetDefaultTimeUnit(kMillisecond);
+  EXPECT_EQ(benchmark.GetTimeUnit(), kMillisecond);
+}
+
+TEST(DefaultTimeUnitTest, DefaultAndExplicitUnitIsSet) {
+  DummyBenchmark benchmark;
+  benchmark.Unit(kMillisecond);
+  SetDefaultTimeUnit(kMicrosecond);
+
+  EXPECT_EQ(benchmark.GetTimeUnit(), kMillisecond);
+}
+
+}  // namespace
+}  // namespace internal
+}  // namespace benchmark
diff --git a/leveldb_base/third_party/benchmark/test/user_counters_tabular_test.cc b/leveldb_base/third_party/benchmark/test/user_counters_tabular_test.cc
new file mode 100644
index 0000000..c98b769
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/user_counters_tabular_test.cc
@@ -0,0 +1,558 @@
+
+#undef NDEBUG
+
+#include "benchmark/benchmark.h"
+#include "output_test.h"
+
+// @todo: <jpmag> this checks the full output at once; the rule for
+// CounterSet1 was failing because it was not matching "^[-]+$".
+// @todo: <jpmag> check that the counters are vertically aligned.
+ADD_CASES(TC_ConsoleOut,
+          {
+              // keeping these lines long improves readability, so:
+              // clang-format off
+    {"^[-]+$", MR_Next},
+    {"^Benchmark %s Time %s CPU %s Iterations %s Bar %s Bat %s Baz %s Foo %s Frob %s Lob$", MR_Next},
+    {"^[-]+$", MR_Next},
+      {"^BM_Counters_Tabular/repeats:2/threads:1 %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+      {"^BM_Counters_Tabular/repeats:2/threads:1 %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+      {"^BM_Counters_Tabular/repeats:2/threads:1_mean %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+      {"^BM_Counters_Tabular/repeats:2/threads:1_median %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+            {"^BM_Counters_Tabular/repeats:2/threads:1_stddev %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+            {"^BM_Counters_Tabular/repeats:2/threads:1_cv %console_percentage_report [ ]*%percentage[ ]*% [ ]*%percentage[ ]*% [ ]*%percentage[ ]*% [ ]*%percentage[ ]*% [ ]*%percentage[ ]*% [ ]*%percentage[ ]*%$", MR_Next},
+      {"^BM_Counters_Tabular/repeats:2/threads:2 %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+      {"^BM_Counters_Tabular/repeats:2/threads:2 %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+      {"^BM_Counters_Tabular/repeats:2/threads:2_mean %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+      {"^BM_Counters_Tabular/repeats:2/threads:2_median %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+            {"^BM_Counters_Tabular/repeats:2/threads:2_stddev %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+            {"^BM_Counters_Tabular/repeats:2/threads:2_cv %console_percentage_report [ ]*%percentage[ ]*% [ ]*%percentage[ ]*% [ ]*%percentage[ ]*% [ ]*%percentage[ ]*% [ ]*%percentage[ ]*% [ ]*%percentage[ ]*%$", MR_Next},
+    {"^BM_CounterRates_Tabular/threads:%int %console_report [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s$", MR_Next},
+    {"^BM_CounterRates_Tabular/threads:%int %console_report [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s$", MR_Next},
+    {"^BM_CounterRates_Tabular/threads:%int %console_report [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s$", MR_Next},
+    {"^BM_CounterRates_Tabular/threads:%int %console_report [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s$", MR_Next},
+    {"^BM_CounterRates_Tabular/threads:%int %console_report [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s$", MR_Next},
+    {"^[-]+$", MR_Next},
+    {"^Benchmark %s Time %s CPU %s Iterations %s Bar %s Baz %s Foo$", MR_Next},
+    {"^[-]+$", MR_Next},
+    {"^BM_CounterSet0_Tabular/threads:%int %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+    {"^BM_CounterSet0_Tabular/threads:%int %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+    {"^BM_CounterSet0_Tabular/threads:%int %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+    {"^BM_CounterSet0_Tabular/threads:%int %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+    {"^BM_CounterSet0_Tabular/threads:%int %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+    {"^BM_CounterSet1_Tabular/threads:%int %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+    {"^BM_CounterSet1_Tabular/threads:%int %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+    {"^BM_CounterSet1_Tabular/threads:%int %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+    {"^BM_CounterSet1_Tabular/threads:%int %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+    {"^BM_CounterSet1_Tabular/threads:%int %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+    {"^[-]+$", MR_Next},
+    {"^Benchmark %s Time %s CPU %s Iterations %s Bat %s Baz %s Foo$", MR_Next},
+    {"^[-]+$", MR_Next},
+    {"^BM_CounterSet2_Tabular/threads:%int %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+    {"^BM_CounterSet2_Tabular/threads:%int %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+    {"^BM_CounterSet2_Tabular/threads:%int %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+    {"^BM_CounterSet2_Tabular/threads:%int %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
+    {"^BM_CounterSet2_Tabular/threads:%int %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$"},
+              // clang-format on
+          });
+ADD_CASES(TC_CSVOut, {{"%csv_header,"
+                       "\"Bar\",\"Bat\",\"Baz\",\"Foo\",\"Frob\",\"Lob\""}});
+
+// ========================================================================= //
+// ------------------------- Tabular Counters Output ----------------------- //
+// ========================================================================= //
+
+void BM_Counters_Tabular(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+  namespace bm = benchmark;
+  state.counters.insert({
+      {"Foo", {1, bm::Counter::kAvgThreads}},
+      {"Bar", {2, bm::Counter::kAvgThreads}},
+      {"Baz", {4, bm::Counter::kAvgThreads}},
+      {"Bat", {8, bm::Counter::kAvgThreads}},
+      {"Frob", {16, bm::Counter::kAvgThreads}},
+      {"Lob", {32, bm::Counter::kAvgThreads}},
+  });
+}
+BENCHMARK(BM_Counters_Tabular)->ThreadRange(1, 2)->Repetitions(2);
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_Tabular/repeats:2/threads:1\",$"},
+           {"\"family_index\": 0,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_Tabular/repeats:2/threads:1\",$",
+            MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"repetition_index\": 0,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"Bar\": %float,$", MR_Next},
+           {"\"Bat\": %float,$", MR_Next},
+           {"\"Baz\": %float,$", MR_Next},
+           {"\"Foo\": %float,$", MR_Next},
+           {"\"Frob\": %float,$", MR_Next},
+           {"\"Lob\": %float$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_Tabular/repeats:2/threads:1\",$"},
+           {"\"family_index\": 0,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_Tabular/repeats:2/threads:1\",$",
+            MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"repetition_index\": 1,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"Bar\": %float,$", MR_Next},
+           {"\"Bat\": %float,$", MR_Next},
+           {"\"Baz\": %float,$", MR_Next},
+           {"\"Foo\": %float,$", MR_Next},
+           {"\"Frob\": %float,$", MR_Next},
+           {"\"Lob\": %float$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_Tabular/repeats:2/threads:1_mean\",$"},
+           {"\"family_index\": 0,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_Tabular/repeats:2/threads:1\",$",
+            MR_Next},
+           {"\"run_type\": \"aggregate\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"aggregate_name\": \"mean\",$", MR_Next},
+           {"\"aggregate_unit\": \"time\",$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"Bar\": %float,$", MR_Next},
+           {"\"Bat\": %float,$", MR_Next},
+           {"\"Baz\": %float,$", MR_Next},
+           {"\"Foo\": %float,$", MR_Next},
+           {"\"Frob\": %float,$", MR_Next},
+           {"\"Lob\": %float$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_Tabular/repeats:2/threads:1_median\",$"},
+           {"\"family_index\": 0,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_Tabular/repeats:2/threads:1\",$",
+            MR_Next},
+           {"\"run_type\": \"aggregate\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"aggregate_name\": \"median\",$", MR_Next},
+           {"\"aggregate_unit\": \"time\",$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"Bar\": %float,$", MR_Next},
+           {"\"Bat\": %float,$", MR_Next},
+           {"\"Baz\": %float,$", MR_Next},
+           {"\"Foo\": %float,$", MR_Next},
+           {"\"Frob\": %float,$", MR_Next},
+           {"\"Lob\": %float$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_Tabular/repeats:2/threads:1_stddev\",$"},
+           {"\"family_index\": 0,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_Tabular/repeats:2/threads:1\",$",
+            MR_Next},
+           {"\"run_type\": \"aggregate\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"aggregate_name\": \"stddev\",$", MR_Next},
+           {"\"aggregate_unit\": \"time\",$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"Bar\": %float,$", MR_Next},
+           {"\"Bat\": %float,$", MR_Next},
+           {"\"Baz\": %float,$", MR_Next},
+           {"\"Foo\": %float,$", MR_Next},
+           {"\"Frob\": %float,$", MR_Next},
+           {"\"Lob\": %float$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_Tabular/repeats:2/threads:1_cv\",$"},
+           {"\"family_index\": 0,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_Tabular/repeats:2/threads:1\",$",
+            MR_Next},
+           {"\"run_type\": \"aggregate\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"aggregate_name\": \"cv\",$", MR_Next},
+           {"\"aggregate_unit\": \"percentage\",$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"Bar\": %float,$", MR_Next},
+           {"\"Bat\": %float,$", MR_Next},
+           {"\"Baz\": %float,$", MR_Next},
+           {"\"Foo\": %float,$", MR_Next},
+           {"\"Frob\": %float,$", MR_Next},
+           {"\"Lob\": %float$", MR_Next},
+           {"}", MR_Next}});
+
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_Tabular/repeats:2/threads:2\",$"},
+           {"\"family_index\": 0,$", MR_Next},
+           {"\"per_family_instance_index\": 1,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_Tabular/repeats:2/threads:2\",$",
+            MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"repetition_index\": 0,$", MR_Next},
+           {"\"threads\": 2,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"Bar\": %float,$", MR_Next},
+           {"\"Bat\": %float,$", MR_Next},
+           {"\"Baz\": %float,$", MR_Next},
+           {"\"Foo\": %float,$", MR_Next},
+           {"\"Frob\": %float,$", MR_Next},
+           {"\"Lob\": %float$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_Tabular/repeats:2/threads:2\",$"},
+           {"\"family_index\": 0,$", MR_Next},
+           {"\"per_family_instance_index\": 1,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_Tabular/repeats:2/threads:2\",$",
+            MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"repetition_index\": 1,$", MR_Next},
+           {"\"threads\": 2,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"Bar\": %float,$", MR_Next},
+           {"\"Bat\": %float,$", MR_Next},
+           {"\"Baz\": %float,$", MR_Next},
+           {"\"Foo\": %float,$", MR_Next},
+           {"\"Frob\": %float,$", MR_Next},
+           {"\"Lob\": %float$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_Tabular/repeats:2/threads:2_median\",$"},
+           {"\"family_index\": 0,$", MR_Next},
+           {"\"per_family_instance_index\": 1,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_Tabular/repeats:2/threads:2\",$",
+            MR_Next},
+           {"\"run_type\": \"aggregate\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"threads\": 2,$", MR_Next},
+           {"\"aggregate_name\": \"median\",$", MR_Next},
+           {"\"aggregate_unit\": \"time\",$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"Bar\": %float,$", MR_Next},
+           {"\"Bat\": %float,$", MR_Next},
+           {"\"Baz\": %float,$", MR_Next},
+           {"\"Foo\": %float,$", MR_Next},
+           {"\"Frob\": %float,$", MR_Next},
+           {"\"Lob\": %float$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_Tabular/repeats:2/threads:2_stddev\",$"},
+           {"\"family_index\": 0,$", MR_Next},
+           {"\"per_family_instance_index\": 1,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_Tabular/repeats:2/threads:2\",$",
+            MR_Next},
+           {"\"run_type\": \"aggregate\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"threads\": 2,$", MR_Next},
+           {"\"aggregate_name\": \"stddev\",$", MR_Next},
+           {"\"aggregate_unit\": \"time\",$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"Bar\": %float,$", MR_Next},
+           {"\"Bat\": %float,$", MR_Next},
+           {"\"Baz\": %float,$", MR_Next},
+           {"\"Foo\": %float,$", MR_Next},
+           {"\"Frob\": %float,$", MR_Next},
+           {"\"Lob\": %float$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_Tabular/repeats:2/threads:2_cv\",$"},
+           {"\"family_index\": 0,$", MR_Next},
+           {"\"per_family_instance_index\": 1,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_Tabular/repeats:2/threads:2\",$",
+            MR_Next},
+           {"\"run_type\": \"aggregate\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"threads\": 2,$", MR_Next},
+           {"\"aggregate_name\": \"cv\",$", MR_Next},
+           {"\"aggregate_unit\": \"percentage\",$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"Bar\": %float,$", MR_Next},
+           {"\"Bat\": %float,$", MR_Next},
+           {"\"Baz\": %float,$", MR_Next},
+           {"\"Foo\": %float,$", MR_Next},
+           {"\"Frob\": %float,$", MR_Next},
+           {"\"Lob\": %float$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_CSVOut,
+          {{"^\"BM_Counters_Tabular/repeats:2/threads:1\",%csv_report,"
+            "%float,%float,%float,%float,%float,%float$"}});
+ADD_CASES(TC_CSVOut,
+          {{"^\"BM_Counters_Tabular/repeats:2/threads:1\",%csv_report,"
+            "%float,%float,%float,%float,%float,%float$"}});
+ADD_CASES(TC_CSVOut,
+          {{"^\"BM_Counters_Tabular/repeats:2/threads:1_mean\",%csv_report,"
+            "%float,%float,%float,%float,%float,%float$"}});
+ADD_CASES(TC_CSVOut,
+          {{"^\"BM_Counters_Tabular/repeats:2/threads:1_median\",%csv_report,"
+            "%float,%float,%float,%float,%float,%float$"}});
+ADD_CASES(TC_CSVOut,
+          {{"^\"BM_Counters_Tabular/repeats:2/threads:1_stddev\",%csv_report,"
+            "%float,%float,%float,%float,%float,%float$"}});
+ADD_CASES(TC_CSVOut,
+          {{"^\"BM_Counters_Tabular/repeats:2/threads:1_cv\",%csv_report,"
+            "%float,%float,%float,%float,%float,%float$"}});
+ADD_CASES(TC_CSVOut,
+          {{"^\"BM_Counters_Tabular/repeats:2/threads:2\",%csv_report,"
+            "%float,%float,%float,%float,%float,%float$"}});
+ADD_CASES(TC_CSVOut,
+          {{"^\"BM_Counters_Tabular/repeats:2/threads:2\",%csv_report,"
+            "%float,%float,%float,%float,%float,%float$"}});
+ADD_CASES(TC_CSVOut,
+          {{"^\"BM_Counters_Tabular/repeats:2/threads:2_mean\",%csv_report,"
+            "%float,%float,%float,%float,%float,%float$"}});
+ADD_CASES(TC_CSVOut,
+          {{"^\"BM_Counters_Tabular/repeats:2/threads:2_median\",%csv_report,"
+            "%float,%float,%float,%float,%float,%float$"}});
+ADD_CASES(TC_CSVOut,
+          {{"^\"BM_Counters_Tabular/repeats:2/threads:2_stddev\",%csv_report,"
+            "%float,%float,%float,%float,%float,%float$"}});
+ADD_CASES(TC_CSVOut,
+          {{"^\"BM_Counters_Tabular/repeats:2/threads:2_cv\",%csv_report,"
+            "%float,%float,%float,%float,%float,%float$"}});
+// VS2013 does not allow this function to be passed as a lambda argument
+// to CHECK_BENCHMARK_RESULTS()
+void CheckTabular(Results const& e) {
+  CHECK_COUNTER_VALUE(e, int, "Foo", EQ, 1);
+  CHECK_COUNTER_VALUE(e, int, "Bar", EQ, 2);
+  CHECK_COUNTER_VALUE(e, int, "Baz", EQ, 4);
+  CHECK_COUNTER_VALUE(e, int, "Bat", EQ, 8);
+  CHECK_COUNTER_VALUE(e, int, "Frob", EQ, 16);
+  CHECK_COUNTER_VALUE(e, int, "Lob", EQ, 32);
+}
+CHECK_BENCHMARK_RESULTS("BM_Counters_Tabular/repeats:2/threads:1$",
+                        &CheckTabular);
+CHECK_BENCHMARK_RESULTS("BM_Counters_Tabular/repeats:2/threads:2$",
+                        &CheckTabular);
+
+// ========================================================================= //
+// -------------------- Tabular+Rate Counters Output ----------------------- //
+// ========================================================================= //
+
+void BM_CounterRates_Tabular(benchmark::State& state) {
+  for (auto _ : state) {
+    // This test requires a non-zero CPU time to avoid divide-by-zero
+    auto iterations = state.iterations();
+    benchmark::DoNotOptimize(iterations);
+  }
+  namespace bm = benchmark;
+  state.counters.insert({
+      {"Foo", {1, bm::Counter::kAvgThreadsRate}},
+      {"Bar", {2, bm::Counter::kAvgThreadsRate}},
+      {"Baz", {4, bm::Counter::kAvgThreadsRate}},
+      {"Bat", {8, bm::Counter::kAvgThreadsRate}},
+      {"Frob", {16, bm::Counter::kAvgThreadsRate}},
+      {"Lob", {32, bm::Counter::kAvgThreadsRate}},
+  });
+}
+BENCHMARK(BM_CounterRates_Tabular)->ThreadRange(1, 16);
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_CounterRates_Tabular/threads:%int\",$"},
+           {"\"family_index\": 1,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_CounterRates_Tabular/threads:%int\",$",
+            MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 1,$", MR_Next},
+           {"\"repetition_index\": 0,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"Bar\": %float,$", MR_Next},
+           {"\"Bat\": %float,$", MR_Next},
+           {"\"Baz\": %float,$", MR_Next},
+           {"\"Foo\": %float,$", MR_Next},
+           {"\"Frob\": %float,$", MR_Next},
+           {"\"Lob\": %float$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_CounterRates_Tabular/threads:%int\",%csv_report,"
+                       "%float,%float,%float,%float,%float,%float$"}});
+// VS2013 does not allow this function to be passed as a lambda argument
+// to CHECK_BENCHMARK_RESULTS()
+void CheckTabularRate(Results const& e) {
+  double t = e.DurationCPUTime();
+  CHECK_FLOAT_COUNTER_VALUE(e, "Foo", EQ, 1. / t, 0.001);
+  CHECK_FLOAT_COUNTER_VALUE(e, "Bar", EQ, 2. / t, 0.001);
+  CHECK_FLOAT_COUNTER_VALUE(e, "Baz", EQ, 4. / t, 0.001);
+  CHECK_FLOAT_COUNTER_VALUE(e, "Bat", EQ, 8. / t, 0.001);
+  CHECK_FLOAT_COUNTER_VALUE(e, "Frob", EQ, 16. / t, 0.001);
+  CHECK_FLOAT_COUNTER_VALUE(e, "Lob", EQ, 32. / t, 0.001);
+}
+CHECK_BENCHMARK_RESULTS("BM_CounterRates_Tabular/threads:%int",
+                        &CheckTabularRate);
+
+// ========================================================================= //
+// ------------------------- Tabular Counters Output ----------------------- //
+// ========================================================================= //
+
+// set only some of the counters
+void BM_CounterSet0_Tabular(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+  namespace bm = benchmark;
+  state.counters.insert({
+      {"Foo", {10, bm::Counter::kAvgThreads}},
+      {"Bar", {20, bm::Counter::kAvgThreads}},
+      {"Baz", {40, bm::Counter::kAvgThreads}},
+  });
+}
+BENCHMARK(BM_CounterSet0_Tabular)->ThreadRange(1, 16);
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_CounterSet0_Tabular/threads:%int\",$"},
+           {"\"family_index\": 2,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_CounterSet0_Tabular/threads:%int\",$", MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 1,$", MR_Next},
+           {"\"repetition_index\": 0,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"Bar\": %float,$", MR_Next},
+           {"\"Baz\": %float,$", MR_Next},
+           {"\"Foo\": %float$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_CounterSet0_Tabular/threads:%int\",%csv_report,"
+                       "%float,,%float,%float,,"}});
+// VS2013 does not allow this function to be passed as a lambda argument
+// to CHECK_BENCHMARK_RESULTS()
+void CheckSet0(Results const& e) {
+  CHECK_COUNTER_VALUE(e, int, "Foo", EQ, 10);
+  CHECK_COUNTER_VALUE(e, int, "Bar", EQ, 20);
+  CHECK_COUNTER_VALUE(e, int, "Baz", EQ, 40);
+}
+CHECK_BENCHMARK_RESULTS("BM_CounterSet0_Tabular", &CheckSet0);
+
+// again.
+void BM_CounterSet1_Tabular(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+  namespace bm = benchmark;
+  state.counters.insert({
+      {"Foo", {15, bm::Counter::kAvgThreads}},
+      {"Bar", {25, bm::Counter::kAvgThreads}},
+      {"Baz", {45, bm::Counter::kAvgThreads}},
+  });
+}
+BENCHMARK(BM_CounterSet1_Tabular)->ThreadRange(1, 16);
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_CounterSet1_Tabular/threads:%int\",$"},
+           {"\"family_index\": 3,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_CounterSet1_Tabular/threads:%int\",$", MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 1,$", MR_Next},
+           {"\"repetition_index\": 0,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"Bar\": %float,$", MR_Next},
+           {"\"Baz\": %float,$", MR_Next},
+           {"\"Foo\": %float$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_CounterSet1_Tabular/threads:%int\",%csv_report,"
+                       "%float,,%float,%float,,"}});
+// VS2013 does not allow this function to be passed as a lambda argument
+// to CHECK_BENCHMARK_RESULTS()
+void CheckSet1(Results const& e) {
+  CHECK_COUNTER_VALUE(e, int, "Foo", EQ, 15);
+  CHECK_COUNTER_VALUE(e, int, "Bar", EQ, 25);
+  CHECK_COUNTER_VALUE(e, int, "Baz", EQ, 45);
+}
+CHECK_BENCHMARK_RESULTS("BM_CounterSet1_Tabular/threads:%int", &CheckSet1);
+
+// ========================================================================= //
+// ------------------------- Tabular Counters Output ----------------------- //
+// ========================================================================= //
+
+// set only some of the counters, different set now.
+void BM_CounterSet2_Tabular(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+  namespace bm = benchmark;
+  state.counters.insert({
+      {"Foo", {10, bm::Counter::kAvgThreads}},
+      {"Bat", {30, bm::Counter::kAvgThreads}},
+      {"Baz", {40, bm::Counter::kAvgThreads}},
+  });
+}
+BENCHMARK(BM_CounterSet2_Tabular)->ThreadRange(1, 16);
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_CounterSet2_Tabular/threads:%int\",$"},
+           {"\"family_index\": 4,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_CounterSet2_Tabular/threads:%int\",$", MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 1,$", MR_Next},
+           {"\"repetition_index\": 0,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"Bat\": %float,$", MR_Next},
+           {"\"Baz\": %float,$", MR_Next},
+           {"\"Foo\": %float$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_CounterSet2_Tabular/threads:%int\",%csv_report,"
+                       ",%float,%float,%float,,"}});
+// VS2013 does not allow this function to be passed as a lambda argument
+// to CHECK_BENCHMARK_RESULTS()
+void CheckSet2(Results const& e) {
+  CHECK_COUNTER_VALUE(e, int, "Foo", EQ, 10);
+  CHECK_COUNTER_VALUE(e, int, "Bat", EQ, 30);
+  CHECK_COUNTER_VALUE(e, int, "Baz", EQ, 40);
+}
+CHECK_BENCHMARK_RESULTS("BM_CounterSet2_Tabular", &CheckSet2);
+
+// ========================================================================= //
+// --------------------------- TEST CASES END ------------------------------ //
+// ========================================================================= //
+
+int main(int argc, char* argv[]) { RunOutputTests(argc, argv); }
diff --git a/leveldb_base/third_party/benchmark/test/user_counters_test.cc b/leveldb_base/third_party/benchmark/test/user_counters_test.cc
new file mode 100644
index 0000000..4cd8ee3
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/user_counters_test.cc
@@ -0,0 +1,561 @@
+
+#undef NDEBUG
+
+#include "benchmark/benchmark.h"
+#include "output_test.h"
+
+// ========================================================================= //
+// ---------------------- Testing Prologue Output -------------------------- //
+// ========================================================================= //
+
+// clang-format off
+
+ADD_CASES(TC_ConsoleOut,
+          {{"^[-]+$", MR_Next},
+           {"^Benchmark %s Time %s CPU %s Iterations UserCounters...$", MR_Next},
+           {"^[-]+$", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"%csv_header,\"bar\",\"foo\""}});
+
+// clang-format on
+
+// ========================================================================= //
+// ------------------------- Simple Counters Output ------------------------ //
+// ========================================================================= //
+
+void BM_Counters_Simple(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+  state.counters["foo"] = 1;
+  state.counters["bar"] = 2 * static_cast<double>(state.iterations());
+}
+BENCHMARK(BM_Counters_Simple);
+ADD_CASES(TC_ConsoleOut,
+          {{"^BM_Counters_Simple %console_report bar=%hrfloat foo=%hrfloat$"}});
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_Counters_Simple\",$"},
+                       {"\"family_index\": 0,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_Counters_Simple\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 1,$", MR_Next},
+                       {"\"repetition_index\": 0,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"iterations\": %int,$", MR_Next},
+                       {"\"real_time\": %float,$", MR_Next},
+                       {"\"cpu_time\": %float,$", MR_Next},
+                       {"\"time_unit\": \"ns\",$", MR_Next},
+                       {"\"bar\": %float,$", MR_Next},
+                       {"\"foo\": %float$", MR_Next},
+                       {"}", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_Counters_Simple\",%csv_report,%float,%float$"}});
+// VS2013 does not allow this function to be passed as a lambda argument
+// to CHECK_BENCHMARK_RESULTS()
+void CheckSimple(Results const& e) {
+  double its = e.NumIterations();
+  CHECK_COUNTER_VALUE(e, int, "foo", EQ, 1);
+  // check that the value of bar is within 0.1% of the expected value
+  CHECK_FLOAT_COUNTER_VALUE(e, "bar", EQ, 2. * its, 0.001);
+}
+CHECK_BENCHMARK_RESULTS("BM_Counters_Simple", &CheckSimple);
+
+// ========================================================================= //
+// --------------------- Counters+Items+Bytes/s Output --------------------- //
+// ========================================================================= //
+
+namespace {
+int num_calls1 = 0;
+}
+void BM_Counters_WithBytesAndItemsPSec(benchmark::State& state) {
+  for (auto _ : state) {
+    // This test requires a non-zero CPU time to avoid divide-by-zero
+    auto iterations = state.iterations();
+    benchmark::DoNotOptimize(iterations);
+  }
+  state.counters["foo"] = 1;
+  state.counters["bar"] = ++num_calls1;
+  state.SetBytesProcessed(364);
+  state.SetItemsProcessed(150);
+}
+BENCHMARK(BM_Counters_WithBytesAndItemsPSec);
+ADD_CASES(TC_ConsoleOut, {{"^BM_Counters_WithBytesAndItemsPSec %console_report "
+                           "bar=%hrfloat bytes_per_second=%hrfloat/s "
+                           "foo=%hrfloat items_per_second=%hrfloat/s$"}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_WithBytesAndItemsPSec\",$"},
+           {"\"family_index\": 1,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_WithBytesAndItemsPSec\",$", MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 1,$", MR_Next},
+           {"\"repetition_index\": 0,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"bar\": %float,$", MR_Next},
+           {"\"bytes_per_second\": %float,$", MR_Next},
+           {"\"foo\": %float,$", MR_Next},
+           {"\"items_per_second\": %float$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_Counters_WithBytesAndItemsPSec\","
+                       "%csv_bytes_items_report,%float,%float$"}});
+// VS2013 does not allow this function to be passed as a lambda argument
+// to CHECK_BENCHMARK_RESULTS()
+void CheckBytesAndItemsPSec(Results const& e) {
+  double t = e.DurationCPUTime();  // this (and not real time) is the time used
+  CHECK_COUNTER_VALUE(e, int, "foo", EQ, 1);
+  CHECK_COUNTER_VALUE(e, int, "bar", EQ, num_calls1);
+  // check that the values are within 0.1% of the expected values
+  CHECK_FLOAT_RESULT_VALUE(e, "bytes_per_second", EQ, 364. / t, 0.001);
+  CHECK_FLOAT_RESULT_VALUE(e, "items_per_second", EQ, 150. / t, 0.001);
+}
+CHECK_BENCHMARK_RESULTS("BM_Counters_WithBytesAndItemsPSec",
+                        &CheckBytesAndItemsPSec);
+
+// ========================================================================= //
+// ------------------------- Rate Counters Output -------------------------- //
+// ========================================================================= //
+
+void BM_Counters_Rate(benchmark::State& state) {
+  for (auto _ : state) {
+    // This test requires a non-zero CPU time to avoid divide-by-zero
+    auto iterations = state.iterations();
+    benchmark::DoNotOptimize(iterations);
+  }
+  namespace bm = benchmark;
+  state.counters["foo"] = bm::Counter{1, bm::Counter::kIsRate};
+  state.counters["bar"] = bm::Counter{2, bm::Counter::kIsRate};
+}
+BENCHMARK(BM_Counters_Rate);
+ADD_CASES(
+    TC_ConsoleOut,
+    {{"^BM_Counters_Rate %console_report bar=%hrfloat/s foo=%hrfloat/s$"}});
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_Counters_Rate\",$"},
+                       {"\"family_index\": 2,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_Counters_Rate\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 1,$", MR_Next},
+                       {"\"repetition_index\": 0,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"iterations\": %int,$", MR_Next},
+                       {"\"real_time\": %float,$", MR_Next},
+                       {"\"cpu_time\": %float,$", MR_Next},
+                       {"\"time_unit\": \"ns\",$", MR_Next},
+                       {"\"bar\": %float,$", MR_Next},
+                       {"\"foo\": %float$", MR_Next},
+                       {"}", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_Counters_Rate\",%csv_report,%float,%float$"}});
+// VS2013 does not allow this function to be passed as a lambda argument
+// to CHECK_BENCHMARK_RESULTS()
+void CheckRate(Results const& e) {
+  double t = e.DurationCPUTime();  // this (and not real time) is the time used
+  // check that the values are within 0.1% of the expected values
+  CHECK_FLOAT_COUNTER_VALUE(e, "foo", EQ, 1. / t, 0.001);
+  CHECK_FLOAT_COUNTER_VALUE(e, "bar", EQ, 2. / t, 0.001);
+}
+CHECK_BENCHMARK_RESULTS("BM_Counters_Rate", &CheckRate);
+
+// ========================================================================= //
+// ----------------------- Inverted Counters Output ------------------------ //
+// ========================================================================= //
+
+void BM_Invert(benchmark::State& state) {
+  for (auto _ : state) {
+    // This test requires a non-zero CPU time to avoid divide-by-zero
+    auto iterations = state.iterations();
+    benchmark::DoNotOptimize(iterations);
+  }
+  namespace bm = benchmark;
+  state.counters["foo"] = bm::Counter{0.0001, bm::Counter::kInvert};
+  state.counters["bar"] = bm::Counter{10000, bm::Counter::kInvert};
+}
+BENCHMARK(BM_Invert);
+ADD_CASES(TC_ConsoleOut,
+          {{"^BM_Invert %console_report bar=%hrfloatu foo=%hrfloatk$"}});
+ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_Invert\",$"},
+                       {"\"family_index\": 3,$", MR_Next},
+                       {"\"per_family_instance_index\": 0,$", MR_Next},
+                       {"\"run_name\": \"BM_Invert\",$", MR_Next},
+                       {"\"run_type\": \"iteration\",$", MR_Next},
+                       {"\"repetitions\": 1,$", MR_Next},
+                       {"\"repetition_index\": 0,$", MR_Next},
+                       {"\"threads\": 1,$", MR_Next},
+                       {"\"iterations\": %int,$", MR_Next},
+                       {"\"real_time\": %float,$", MR_Next},
+                       {"\"cpu_time\": %float,$", MR_Next},
+                       {"\"time_unit\": \"ns\",$", MR_Next},
+                       {"\"bar\": %float,$", MR_Next},
+                       {"\"foo\": %float$", MR_Next},
+                       {"}", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_Invert\",%csv_report,%float,%float$"}});
+// VS2013 does not allow this function to be passed as a lambda argument
+// to CHECK_BENCHMARK_RESULTS()
+void CheckInvert(Results const& e) {
+  CHECK_FLOAT_COUNTER_VALUE(e, "foo", EQ, 10000, 0.0001);
+  CHECK_FLOAT_COUNTER_VALUE(e, "bar", EQ, 0.0001, 0.0001);
+}
+CHECK_BENCHMARK_RESULTS("BM_Invert", &CheckInvert);
+
+// ========================================================================= //
+// --------------------- InvertedRate Counters Output ---------------------- //
+// ========================================================================= //
+
+void BM_Counters_InvertedRate(benchmark::State& state) {
+  for (auto _ : state) {
+    // This test requires a non-zero CPU time to avoid divide-by-zero
+    auto iterations = state.iterations();
+    benchmark::DoNotOptimize(iterations);
+  }
+  namespace bm = benchmark;
+  state.counters["foo"] =
+      bm::Counter{1, bm::Counter::kIsRate | bm::Counter::kInvert};
+  state.counters["bar"] =
+      bm::Counter{8192, bm::Counter::kIsRate | bm::Counter::kInvert};
+}
+BENCHMARK(BM_Counters_InvertedRate);
+ADD_CASES(TC_ConsoleOut, {{"^BM_Counters_InvertedRate %console_report "
+                           "bar=%hrfloats foo=%hrfloats$"}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_InvertedRate\",$"},
+           {"\"family_index\": 4,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_InvertedRate\",$", MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 1,$", MR_Next},
+           {"\"repetition_index\": 0,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"bar\": %float,$", MR_Next},
+           {"\"foo\": %float$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_CSVOut,
+          {{"^\"BM_Counters_InvertedRate\",%csv_report,%float,%float$"}});
+// VS2013 does not allow this function to be passed as a lambda argument
+// to CHECK_BENCHMARK_RESULTS()
+void CheckInvertedRate(Results const& e) {
+  double t = e.DurationCPUTime();  // this (and not real time) is the time used
+  // check that the values are within 0.1% of the expected values
+  CHECK_FLOAT_COUNTER_VALUE(e, "foo", EQ, t, 0.001);
+  CHECK_FLOAT_COUNTER_VALUE(e, "bar", EQ, t / 8192.0, 0.001);
+}
+CHECK_BENCHMARK_RESULTS("BM_Counters_InvertedRate", &CheckInvertedRate);
+
+// ========================================================================= //
+// ------------------------- Thread Counters Output ------------------------ //
+// ========================================================================= //
+
+void BM_Counters_Threads(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+  state.counters["foo"] = 1;
+  state.counters["bar"] = 2;
+}
+BENCHMARK(BM_Counters_Threads)->ThreadRange(1, 8);
+ADD_CASES(TC_ConsoleOut, {{"^BM_Counters_Threads/threads:%int %console_report "
+                           "bar=%hrfloat foo=%hrfloat$"}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_Threads/threads:%int\",$"},
+           {"\"family_index\": 5,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_Threads/threads:%int\",$", MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 1,$", MR_Next},
+           {"\"repetition_index\": 0,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"bar\": %float,$", MR_Next},
+           {"\"foo\": %float$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(
+    TC_CSVOut,
+    {{"^\"BM_Counters_Threads/threads:%int\",%csv_report,%float,%float$"}});
+// VS2013 does not allow this function to be passed as a lambda argument
+// to CHECK_BENCHMARK_RESULTS()
+void CheckThreads(Results const& e) {
+  CHECK_COUNTER_VALUE(e, int, "foo", EQ, e.NumThreads());
+  CHECK_COUNTER_VALUE(e, int, "bar", EQ, 2 * e.NumThreads());
+}
+CHECK_BENCHMARK_RESULTS("BM_Counters_Threads/threads:%int", &CheckThreads);
+
+// ========================================================================= //
+// ---------------------- ThreadAvg Counters Output ------------------------ //
+// ========================================================================= //
+
+void BM_Counters_AvgThreads(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+  namespace bm = benchmark;
+  state.counters["foo"] = bm::Counter{1, bm::Counter::kAvgThreads};
+  state.counters["bar"] = bm::Counter{2, bm::Counter::kAvgThreads};
+}
+BENCHMARK(BM_Counters_AvgThreads)->ThreadRange(1, 8);
+ADD_CASES(TC_ConsoleOut, {{"^BM_Counters_AvgThreads/threads:%int "
+                           "%console_report bar=%hrfloat foo=%hrfloat$"}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_AvgThreads/threads:%int\",$"},
+           {"\"family_index\": 6,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_AvgThreads/threads:%int\",$", MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 1,$", MR_Next},
+           {"\"repetition_index\": 0,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"bar\": %float,$", MR_Next},
+           {"\"foo\": %float$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(
+    TC_CSVOut,
+    {{"^\"BM_Counters_AvgThreads/threads:%int\",%csv_report,%float,%float$"}});
+// VS2013 does not allow this function to be passed as a lambda argument
+// to CHECK_BENCHMARK_RESULTS()
+void CheckAvgThreads(Results const& e) {
+  CHECK_COUNTER_VALUE(e, int, "foo", EQ, 1);
+  CHECK_COUNTER_VALUE(e, int, "bar", EQ, 2);
+}
+CHECK_BENCHMARK_RESULTS("BM_Counters_AvgThreads/threads:%int",
+                        &CheckAvgThreads);
+
+// ========================================================================= //
+// ---------------------- ThreadAvg Counters Output ------------------------ //
+// ========================================================================= //
+
+void BM_Counters_AvgThreadsRate(benchmark::State& state) {
+  for (auto _ : state) {
+    // This test requires a non-zero CPU time to avoid divide-by-zero
+    auto iterations = state.iterations();
+    benchmark::DoNotOptimize(iterations);
+  }
+  namespace bm = benchmark;
+  state.counters["foo"] = bm::Counter{1, bm::Counter::kAvgThreadsRate};
+  state.counters["bar"] = bm::Counter{2, bm::Counter::kAvgThreadsRate};
+}
+BENCHMARK(BM_Counters_AvgThreadsRate)->ThreadRange(1, 8);
+ADD_CASES(TC_ConsoleOut, {{"^BM_Counters_AvgThreadsRate/threads:%int "
+                           "%console_report bar=%hrfloat/s foo=%hrfloat/s$"}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_AvgThreadsRate/threads:%int\",$"},
+           {"\"family_index\": 7,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_AvgThreadsRate/threads:%int\",$",
+            MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 1,$", MR_Next},
+           {"\"repetition_index\": 0,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"bar\": %float,$", MR_Next},
+           {"\"foo\": %float$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_Counters_AvgThreadsRate/"
+                       "threads:%int\",%csv_report,%float,%float$"}});
+// VS2013 does not allow this function to be passed as a lambda argument
+// to CHECK_BENCHMARK_RESULTS()
+void CheckAvgThreadsRate(Results const& e) {
+  CHECK_FLOAT_COUNTER_VALUE(e, "foo", EQ, 1. / e.DurationCPUTime(), 0.001);
+  CHECK_FLOAT_COUNTER_VALUE(e, "bar", EQ, 2. / e.DurationCPUTime(), 0.001);
+}
+CHECK_BENCHMARK_RESULTS("BM_Counters_AvgThreadsRate/threads:%int",
+                        &CheckAvgThreadsRate);
+
+// ========================================================================= //
+// ------------------- IterationInvariant Counters Output ------------------ //
+// ========================================================================= //
+
+void BM_Counters_IterationInvariant(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+  namespace bm = benchmark;
+  state.counters["foo"] = bm::Counter{1, bm::Counter::kIsIterationInvariant};
+  state.counters["bar"] = bm::Counter{2, bm::Counter::kIsIterationInvariant};
+}
+BENCHMARK(BM_Counters_IterationInvariant);
+ADD_CASES(TC_ConsoleOut, {{"^BM_Counters_IterationInvariant %console_report "
+                           "bar=%hrfloat foo=%hrfloat$"}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_IterationInvariant\",$"},
+           {"\"family_index\": 8,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_IterationInvariant\",$", MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 1,$", MR_Next},
+           {"\"repetition_index\": 0,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"bar\": %float,$", MR_Next},
+           {"\"foo\": %float$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_CSVOut,
+          {{"^\"BM_Counters_IterationInvariant\",%csv_report,%float,%float$"}});
+// VS2013 does not allow this function to be passed as a lambda argument
+// to CHECK_BENCHMARK_RESULTS()
+void CheckIterationInvariant(Results const& e) {
+  double its = e.NumIterations();
+  // check that the values are within 0.1% of the expected value
+  CHECK_FLOAT_COUNTER_VALUE(e, "foo", EQ, its, 0.001);
+  CHECK_FLOAT_COUNTER_VALUE(e, "bar", EQ, 2. * its, 0.001);
+}
+CHECK_BENCHMARK_RESULTS("BM_Counters_IterationInvariant",
+                        &CheckIterationInvariant);
+
+// ========================================================================= //
+// ----------------- IterationInvariantRate Counters Output ---------------- //
+// ========================================================================= //
+
+void BM_Counters_kIsIterationInvariantRate(benchmark::State& state) {
+  for (auto _ : state) {
+    // This test requires a non-zero CPU time to avoid divide-by-zero
+    auto iterations = state.iterations();
+    benchmark::DoNotOptimize(iterations);
+  }
+  namespace bm = benchmark;
+  state.counters["foo"] =
+      bm::Counter{1, bm::Counter::kIsIterationInvariantRate};
+  state.counters["bar"] =
+      bm::Counter{2, bm::Counter::kIsRate | bm::Counter::kIsIterationInvariant};
+}
+BENCHMARK(BM_Counters_kIsIterationInvariantRate);
+ADD_CASES(TC_ConsoleOut, {{"^BM_Counters_kIsIterationInvariantRate "
+                           "%console_report bar=%hrfloat/s foo=%hrfloat/s$"}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_kIsIterationInvariantRate\",$"},
+           {"\"family_index\": 9,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_kIsIterationInvariantRate\",$",
+            MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 1,$", MR_Next},
+           {"\"repetition_index\": 0,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"bar\": %float,$", MR_Next},
+           {"\"foo\": %float$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_Counters_kIsIterationInvariantRate\",%csv_report,"
+                       "%float,%float$"}});
+// VS2013 does not allow this function to be passed as a lambda argument
+// to CHECK_BENCHMARK_RESULTS()
+void CheckIsIterationInvariantRate(Results const& e) {
+  double its = e.NumIterations();
+  double t = e.DurationCPUTime();  // this (and not real time) is the time used
+  // check that the values are within 0.1% of the expected values
+  CHECK_FLOAT_COUNTER_VALUE(e, "foo", EQ, its * 1. / t, 0.001);
+  CHECK_FLOAT_COUNTER_VALUE(e, "bar", EQ, its * 2. / t, 0.001);
+}
+CHECK_BENCHMARK_RESULTS("BM_Counters_kIsIterationInvariantRate",
+                        &CheckIsIterationInvariantRate);
+
+// ========================================================================= //
+// --------------------- AvgIterations Counters Output --------------------- //
+// ========================================================================= //
+
+void BM_Counters_AvgIterations(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+  namespace bm = benchmark;
+  state.counters["foo"] = bm::Counter{1, bm::Counter::kAvgIterations};
+  state.counters["bar"] = bm::Counter{2, bm::Counter::kAvgIterations};
+}
+BENCHMARK(BM_Counters_AvgIterations);
+ADD_CASES(TC_ConsoleOut, {{"^BM_Counters_AvgIterations %console_report "
+                           "bar=%hrfloat foo=%hrfloat$"}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_AvgIterations\",$"},
+           {"\"family_index\": 10,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_AvgIterations\",$", MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 1,$", MR_Next},
+           {"\"repetition_index\": 0,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"bar\": %float,$", MR_Next},
+           {"\"foo\": %float$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_CSVOut,
+          {{"^\"BM_Counters_AvgIterations\",%csv_report,%float,%float$"}});
+// VS2013 does not allow this function to be passed as a lambda argument
+// to CHECK_BENCHMARK_RESULTS()
+void CheckAvgIterations(Results const& e) {
+  double its = e.NumIterations();
+  // check that the values are within 0.1% of the expected value
+  CHECK_FLOAT_COUNTER_VALUE(e, "foo", EQ, 1. / its, 0.001);
+  CHECK_FLOAT_COUNTER_VALUE(e, "bar", EQ, 2. / its, 0.001);
+}
+CHECK_BENCHMARK_RESULTS("BM_Counters_AvgIterations", &CheckAvgIterations);
+
+// ========================================================================= //
+// ------------------- AvgIterationsRate Counters Output ------------------- //
+// ========================================================================= //
+
+void BM_Counters_kAvgIterationsRate(benchmark::State& state) {
+  for (auto _ : state) {
+    // This test requires a non-zero CPU time to avoid divide-by-zero
+    auto iterations = state.iterations();
+    benchmark::DoNotOptimize(iterations);
+  }
+  namespace bm = benchmark;
+  state.counters["foo"] = bm::Counter{1, bm::Counter::kAvgIterationsRate};
+  state.counters["bar"] =
+      bm::Counter{2, bm::Counter::kIsRate | bm::Counter::kAvgIterations};
+}
+BENCHMARK(BM_Counters_kAvgIterationsRate);
+ADD_CASES(TC_ConsoleOut, {{"^BM_Counters_kAvgIterationsRate "
+                           "%console_report bar=%hrfloat/s foo=%hrfloat/s$"}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_kAvgIterationsRate\",$"},
+           {"\"family_index\": 11,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_kAvgIterationsRate\",$", MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 1,$", MR_Next},
+           {"\"repetition_index\": 0,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"bar\": %float,$", MR_Next},
+           {"\"foo\": %float$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_CSVOut, {{"^\"BM_Counters_kAvgIterationsRate\",%csv_report,"
+                       "%float,%float$"}});
+// VS2013 does not allow this function to be passed as a lambda argument
+// to CHECK_BENCHMARK_RESULTS()
+void CheckAvgIterationsRate(Results const& e) {
+  double its = e.NumIterations();
+  double t = e.DurationCPUTime();  // this (and not real time) is the time used
+  // check that the values are within 0.1% of the expected values
+  CHECK_FLOAT_COUNTER_VALUE(e, "foo", EQ, 1. / its / t, 0.001);
+  CHECK_FLOAT_COUNTER_VALUE(e, "bar", EQ, 2. / its / t, 0.001);
+}
+CHECK_BENCHMARK_RESULTS("BM_Counters_kAvgIterationsRate",
+                        &CheckAvgIterationsRate);
+
+// ========================================================================= //
+// --------------------------- TEST CASES END ------------------------------ //
+// ========================================================================= //
+
+int main(int argc, char* argv[]) { RunOutputTests(argc, argv); }
diff --git a/leveldb_base/third_party/benchmark/test/user_counters_thousands_test.cc b/leveldb_base/third_party/benchmark/test/user_counters_thousands_test.cc
new file mode 100644
index 0000000..a42683b
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/test/user_counters_thousands_test.cc
@@ -0,0 +1,186 @@
+
+#undef NDEBUG
+
+#include "benchmark/benchmark.h"
+#include "output_test.h"
+
+// ========================================================================= //
+// ------------------------ Thousands Customisation ------------------------ //
+// ========================================================================= //
+
+void BM_Counters_Thousands(benchmark::State& state) {
+  for (auto _ : state) {
+  }
+  namespace bm = benchmark;
+  state.counters.insert({
+      {"t0_1000000DefaultBase",
+       bm::Counter(1000 * 1000, bm::Counter::kDefaults)},
+      {"t1_1000000Base1000", bm::Counter(1000 * 1000, bm::Counter::kDefaults,
+                                         benchmark::Counter::OneK::kIs1000)},
+      {"t2_1000000Base1024", bm::Counter(1000 * 1000, bm::Counter::kDefaults,
+                                         benchmark::Counter::OneK::kIs1024)},
+      {"t3_1048576Base1000", bm::Counter(1024 * 1024, bm::Counter::kDefaults,
+                                         benchmark::Counter::OneK::kIs1000)},
+      {"t4_1048576Base1024", bm::Counter(1024 * 1024, bm::Counter::kDefaults,
+                                         benchmark::Counter::OneK::kIs1024)},
+  });
+}
+BENCHMARK(BM_Counters_Thousands)->Repetitions(2);
+ADD_CASES(
+    TC_ConsoleOut,
+    {
+        {"^BM_Counters_Thousands/repeats:2 %console_report "
+         "t0_1000000DefaultBase=1000k "
+         "t1_1000000Base1000=1000k t2_1000000Base1024=976.56[23]k "
+         "t3_1048576Base1000=1048.58k t4_1048576Base1024=1024k$"},
+        {"^BM_Counters_Thousands/repeats:2 %console_report "
+         "t0_1000000DefaultBase=1000k "
+         "t1_1000000Base1000=1000k t2_1000000Base1024=976.56[23]k "
+         "t3_1048576Base1000=1048.58k t4_1048576Base1024=1024k$"},
+        {"^BM_Counters_Thousands/repeats:2_mean %console_report "
+         "t0_1000000DefaultBase=1000k t1_1000000Base1000=1000k "
+         "t2_1000000Base1024=976.56[23]k t3_1048576Base1000=1048.58k "
+         "t4_1048576Base1024=1024k$"},
+        {"^BM_Counters_Thousands/repeats:2_median %console_report "
+         "t0_1000000DefaultBase=1000k t1_1000000Base1000=1000k "
+         "t2_1000000Base1024=976.56[23]k t3_1048576Base1000=1048.58k "
+         "t4_1048576Base1024=1024k$"},
+        {"^BM_Counters_Thousands/repeats:2_stddev %console_time_only_report [ "
+         "]*2 t0_1000000DefaultBase=0 t1_1000000Base1000=0 "
+         "t2_1000000Base1024=0 t3_1048576Base1000=0 t4_1048576Base1024=0$"},
+    });
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_Thousands/repeats:2\",$"},
+           {"\"family_index\": 0,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_Thousands/repeats:2\",$", MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"repetition_index\": 0,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"t0_1000000DefaultBase\": 1\\.(0)*e\\+(0)*6,$", MR_Next},
+           {"\"t1_1000000Base1000\": 1\\.(0)*e\\+(0)*6,$", MR_Next},
+           {"\"t2_1000000Base1024\": 1\\.(0)*e\\+(0)*6,$", MR_Next},
+           {"\"t3_1048576Base1000\": 1\\.048576(0)*e\\+(0)*6,$", MR_Next},
+           {"\"t4_1048576Base1024\": 1\\.048576(0)*e\\+(0)*6$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_Thousands/repeats:2\",$"},
+           {"\"family_index\": 0,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_Thousands/repeats:2\",$", MR_Next},
+           {"\"run_type\": \"iteration\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"repetition_index\": 1,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"iterations\": %int,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"t0_1000000DefaultBase\": 1\\.(0)*e\\+(0)*6,$", MR_Next},
+           {"\"t1_1000000Base1000\": 1\\.(0)*e\\+(0)*6,$", MR_Next},
+           {"\"t2_1000000Base1024\": 1\\.(0)*e\\+(0)*6,$", MR_Next},
+           {"\"t3_1048576Base1000\": 1\\.048576(0)*e\\+(0)*6,$", MR_Next},
+           {"\"t4_1048576Base1024\": 1\\.048576(0)*e\\+(0)*6$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_Thousands/repeats:2_mean\",$"},
+           {"\"family_index\": 0,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_Thousands/repeats:2\",$", MR_Next},
+           {"\"run_type\": \"aggregate\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"aggregate_name\": \"mean\",$", MR_Next},
+           {"\"aggregate_unit\": \"time\",$", MR_Next},
+           {"\"iterations\": 2,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"t0_1000000DefaultBase\": 1\\.(0)*e\\+(0)*6,$", MR_Next},
+           {"\"t1_1000000Base1000\": 1\\.(0)*e\\+(0)*6,$", MR_Next},
+           {"\"t2_1000000Base1024\": 1\\.(0)*e\\+(0)*6,$", MR_Next},
+           {"\"t3_1048576Base1000\": 1\\.048576(0)*e\\+(0)*6,$", MR_Next},
+           {"\"t4_1048576Base1024\": 1\\.048576(0)*e\\+(0)*6$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_Thousands/repeats:2_median\",$"},
+           {"\"family_index\": 0,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_Thousands/repeats:2\",$", MR_Next},
+           {"\"run_type\": \"aggregate\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"aggregate_name\": \"median\",$", MR_Next},
+           {"\"aggregate_unit\": \"time\",$", MR_Next},
+           {"\"iterations\": 2,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"t0_1000000DefaultBase\": 1\\.(0)*e\\+(0)*6,$", MR_Next},
+           {"\"t1_1000000Base1000\": 1\\.(0)*e\\+(0)*6,$", MR_Next},
+           {"\"t2_1000000Base1024\": 1\\.(0)*e\\+(0)*6,$", MR_Next},
+           {"\"t3_1048576Base1000\": 1\\.048576(0)*e\\+(0)*6,$", MR_Next},
+           {"\"t4_1048576Base1024\": 1\\.048576(0)*e\\+(0)*6$", MR_Next},
+           {"}", MR_Next}});
+ADD_CASES(TC_JSONOut,
+          {{"\"name\": \"BM_Counters_Thousands/repeats:2_stddev\",$"},
+           {"\"family_index\": 0,$", MR_Next},
+           {"\"per_family_instance_index\": 0,$", MR_Next},
+           {"\"run_name\": \"BM_Counters_Thousands/repeats:2\",$", MR_Next},
+           {"\"run_type\": \"aggregate\",$", MR_Next},
+           {"\"repetitions\": 2,$", MR_Next},
+           {"\"threads\": 1,$", MR_Next},
+           {"\"aggregate_name\": \"stddev\",$", MR_Next},
+           {"\"aggregate_unit\": \"time\",$", MR_Next},
+           {"\"iterations\": 2,$", MR_Next},
+           {"\"real_time\": %float,$", MR_Next},
+           {"\"cpu_time\": %float,$", MR_Next},
+           {"\"time_unit\": \"ns\",$", MR_Next},
+           {"\"t0_1000000DefaultBase\": 0\\.(0)*e\\+(0)*,$", MR_Next},
+           {"\"t1_1000000Base1000\": 0\\.(0)*e\\+(0)*,$", MR_Next},
+           {"\"t2_1000000Base1024\": 0\\.(0)*e\\+(0)*,$", MR_Next},
+           {"\"t3_1048576Base1000\": 0\\.(0)*e\\+(0)*,$", MR_Next},
+           {"\"t4_1048576Base1024\": 0\\.(0)*e\\+(0)*$", MR_Next},
+           {"}", MR_Next}});
+
+ADD_CASES(
+    TC_CSVOut,
+    {{"^\"BM_Counters_Thousands/"
+      "repeats:2\",%csv_report,1e\\+(0)*6,1e\\+(0)*6,1e\\+(0)*6,1\\.04858e\\+("
+      "0)*6,1\\.04858e\\+(0)*6$"},
+     {"^\"BM_Counters_Thousands/"
+      "repeats:2\",%csv_report,1e\\+(0)*6,1e\\+(0)*6,1e\\+(0)*6,1\\.04858e\\+("
+      "0)*6,1\\.04858e\\+(0)*6$"},
+     {"^\"BM_Counters_Thousands/"
+      "repeats:2_mean\",%csv_report,1e\\+(0)*6,1e\\+(0)*6,1e\\+(0)*6,1\\."
+      "04858e\\+(0)*6,1\\.04858e\\+(0)*6$"},
+     {"^\"BM_Counters_Thousands/"
+      "repeats:2_median\",%csv_report,1e\\+(0)*6,1e\\+(0)*6,1e\\+(0)*6,1\\."
+      "04858e\\+(0)*6,1\\.04858e\\+(0)*6$"},
+     {"^\"BM_Counters_Thousands/repeats:2_stddev\",%csv_report,0,0,0,0,0$"}});
+// VS2013 does not allow this function to be passed as a lambda argument
+// to CHECK_BENCHMARK_RESULTS()
+void CheckThousands(Results const& e) {
+  if (e.name != "BM_Counters_Thousands/repeats:2")
+    return;  // Do not check the aggregates!
+
+  // check that the values are within 0.01% of the expected values
+  CHECK_FLOAT_COUNTER_VALUE(e, "t0_1000000DefaultBase", EQ, 1000 * 1000,
+                            0.0001);
+  CHECK_FLOAT_COUNTER_VALUE(e, "t1_1000000Base1000", EQ, 1000 * 1000, 0.0001);
+  CHECK_FLOAT_COUNTER_VALUE(e, "t2_1000000Base1024", EQ, 1000 * 1000, 0.0001);
+  CHECK_FLOAT_COUNTER_VALUE(e, "t3_1048576Base1000", EQ, 1024 * 1024, 0.0001);
+  CHECK_FLOAT_COUNTER_VALUE(e, "t4_1048576Base1024", EQ, 1024 * 1024, 0.0001);
+}
+CHECK_BENCHMARK_RESULTS("BM_Counters_Thousands", &CheckThousands);
+
+// ========================================================================= //
+// --------------------------- TEST CASES END ------------------------------ //
+// ========================================================================= //
+
+int main(int argc, char* argv[]) { RunOutputTests(argc, argv); }
diff --git a/leveldb_base/third_party/benchmark/tools/BUILD.bazel b/leveldb_base/third_party/benchmark/tools/BUILD.bazel
new file mode 100644
index 0000000..5895883
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/tools/BUILD.bazel
@@ -0,0 +1,19 @@
+load("@py_deps//:requirements.bzl", "requirement")
+
+py_library(
+    name = "gbench",
+    srcs = glob(["gbench/*.py"]),
+    deps = [
+      requirement("numpy"),
+      requirement("scipy"),
+    ],
+)
+
+py_binary(
+    name = "compare",
+    srcs = ["compare.py"],
+    python_version = "PY2",
+    deps = [
+        ":gbench",
+    ],
+)
diff --git a/leveldb_base/third_party/benchmark/tools/compare.py b/leveldb_base/third_party/benchmark/tools/compare.py
new file mode 100644
index 0000000..e5eeb24
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/tools/compare.py
@@ -0,0 +1,432 @@
+#!/usr/bin/env python3
+
+import unittest
+"""
+compare.py - versatile benchmark output compare tool
+"""
+
+import argparse
+from argparse import ArgumentParser
+import json
+import sys
+import os
+import gbench
+from gbench import util, report
+
+
+def check_inputs(in1, in2, flags):
+    """
+    Perform checking on the user provided inputs and diagnose any abnormalities
+    """
+    in1_kind, in1_err = util.classify_input_file(in1)
+    in2_kind, in2_err = util.classify_input_file(in2)
+    output_file = util.find_benchmark_flag('--benchmark_out=', flags)
+    output_type = util.find_benchmark_flag('--benchmark_out_format=', flags)
+    if in1_kind == util.IT_Executable and in2_kind == util.IT_Executable and output_file:
+        print(("WARNING: '--benchmark_out=%s' will be passed to both "
+               "benchmarks causing it to be overwritten") % output_file)
+    if in1_kind == util.IT_JSON and in2_kind == util.IT_JSON:
+        # When both sides are JSON the only supported flag is
+        # --benchmark_filter=
+        for flag in util.remove_benchmark_flags('--benchmark_filter=', flags):
+            print("WARNING: passing %s has no effect since both "
+                  "inputs are JSON" % flag)
+    if output_type is not None and output_type != 'json':
+        print(("ERROR: passing '--benchmark_out_format=%s' to 'compare.py`"
+               " is not supported.") % output_type)
+        sys.exit(1)
+
+
+def create_parser():
+    parser = ArgumentParser(
+        description='versatile benchmark output compare tool')
+
+    parser.add_argument(
+        '-a',
+        '--display_aggregates_only',
+        dest='display_aggregates_only',
+        action="store_true",
+        help="If there are repetitions, by default, we display everything - the"
+             " actual runs, and the aggregates computed. Sometimes, it is "
+             "desirable to only view the aggregates. E.g. when there are a lot "
+             "of repetitions. Do note that only the display is affected. "
+             "Internally, all the actual runs are still used, e.g. for U test.")
+
+    parser.add_argument(
+        '--no-color',
+        dest='color',
+        default=True,
+        action="store_false",
+        help="Do not use colors in the terminal output"
+    )
+
+    parser.add_argument(
+        '-d',
+        '--dump_to_json',
+        dest='dump_to_json',
+        help="Additionally, dump benchmark comparison output to this file in JSON format.")
+
+    utest = parser.add_argument_group()
+    utest.add_argument(
+        '--no-utest',
+        dest='utest',
+        default=True,
+        action="store_false",
+        help="The tool can do a two-tailed Mann-Whitney U test with the null hypothesis that it is equally likely that a randomly selected value from one sample will be less than or greater than a randomly selected value from a second sample.\nWARNING: requires **LARGE** (no less than {}) number of repetitions to be meaningful!\nThe test is being done by default, if at least {} repetitions were done.\nThis option can disable the U Test.".format(report.UTEST_OPTIMAL_REPETITIONS, report.UTEST_MIN_REPETITIONS))
+    alpha_default = 0.05
+    utest.add_argument(
+        "--alpha",
+        dest='utest_alpha',
+        default=alpha_default,
+        type=float,
+        help=("significance level alpha. if the calculated p-value is below this value, then the result is said to be statistically significant and the null hypothesis is rejected.\n(default: %0.4f)") %
+        alpha_default)
+
+    subparsers = parser.add_subparsers(
+        help='This tool has multiple modes of operation:',
+        dest='mode')
+
+    parser_a = subparsers.add_parser(
+        'benchmarks',
+        help='The most simple use-case, compare all the output of these two benchmarks')
+    baseline = parser_a.add_argument_group(
+        'baseline', 'The benchmark baseline')
+    baseline.add_argument(
+        'test_baseline',
+        metavar='test_baseline',
+        type=argparse.FileType('r'),
+        nargs=1,
+        help='A benchmark executable or JSON output file')
+    contender = parser_a.add_argument_group(
+        'contender', 'The benchmark that will be compared against the baseline')
+    contender.add_argument(
+        'test_contender',
+        metavar='test_contender',
+        type=argparse.FileType('r'),
+        nargs=1,
+        help='A benchmark executable or JSON output file')
+    parser_a.add_argument(
+        'benchmark_options',
+        metavar='benchmark_options',
+        nargs=argparse.REMAINDER,
+        help='Arguments to pass when running benchmark executables')
+
+    parser_b = subparsers.add_parser(
+        'filters', help='Compare filter one with the filter two of benchmark')
+    baseline = parser_b.add_argument_group(
+        'baseline', 'The benchmark baseline')
+    baseline.add_argument(
+        'test',
+        metavar='test',
+        type=argparse.FileType('r'),
+        nargs=1,
+        help='A benchmark executable or JSON output file')
+    baseline.add_argument(
+        'filter_baseline',
+        metavar='filter_baseline',
+        type=str,
+        nargs=1,
+        help='The first filter, that will be used as baseline')
+    contender = parser_b.add_argument_group(
+        'contender', 'The benchmark that will be compared against the baseline')
+    contender.add_argument(
+        'filter_contender',
+        metavar='filter_contender',
+        type=str,
+        nargs=1,
+        help='The second filter, that will be compared against the baseline')
+    parser_b.add_argument(
+        'benchmark_options',
+        metavar='benchmark_options',
+        nargs=argparse.REMAINDER,
+        help='Arguments to pass when running benchmark executables')
+
+    parser_c = subparsers.add_parser(
+        'benchmarksfiltered',
+        help='Compare filter one of first benchmark with filter two of the second benchmark')
+    baseline = parser_c.add_argument_group(
+        'baseline', 'The benchmark baseline')
+    baseline.add_argument(
+        'test_baseline',
+        metavar='test_baseline',
+        type=argparse.FileType('r'),
+        nargs=1,
+        help='A benchmark executable or JSON output file')
+    baseline.add_argument(
+        'filter_baseline',
+        metavar='filter_baseline',
+        type=str,
+        nargs=1,
+        help='The first filter, that will be used as baseline')
+    contender = parser_c.add_argument_group(
+        'contender', 'The benchmark that will be compared against the baseline')
+    contender.add_argument(
+        'test_contender',
+        metavar='test_contender',
+        type=argparse.FileType('r'),
+        nargs=1,
+        help='The second benchmark executable or JSON output file, that will be compared against the baseline')
+    contender.add_argument(
+        'filter_contender',
+        metavar='filter_contender',
+        type=str,
+        nargs=1,
+        help='The second filter, that will be compared against the baseline')
+    parser_c.add_argument(
+        'benchmark_options',
+        metavar='benchmark_options',
+        nargs=argparse.REMAINDER,
+        help='Arguments to pass when running benchmark executables')
+
+    return parser
+
+
+def main():
+    # Parse the command line flags
+    parser = create_parser()
+    args, unknown_args = parser.parse_known_args()
+    if args.mode is None:
+        parser.print_help()
+        exit(1)
+    assert not unknown_args
+    benchmark_options = args.benchmark_options
+
+    if args.mode == 'benchmarks':
+        test_baseline = args.test_baseline[0].name
+        test_contender = args.test_contender[0].name
+        filter_baseline = ''
+        filter_contender = ''
+
+        # NOTE: if test_baseline == test_contender, you are analyzing the stdev
+
+        description = 'Comparing %s to %s' % (test_baseline, test_contender)
+    elif args.mode == 'filters':
+        test_baseline = args.test[0].name
+        test_contender = args.test[0].name
+        filter_baseline = args.filter_baseline[0]
+        filter_contender = args.filter_contender[0]
+
+        # NOTE: if filter_baseline == filter_contender, you are analyzing the
+        # stdev
+
+        description = 'Comparing %s to %s (from %s)' % (
+            filter_baseline, filter_contender, args.test[0].name)
+    elif args.mode == 'benchmarksfiltered':
+        test_baseline = args.test_baseline[0].name
+        test_contender = args.test_contender[0].name
+        filter_baseline = args.filter_baseline[0]
+        filter_contender = args.filter_contender[0]
+
+        # NOTE: if test_baseline == test_contender and
+        # filter_baseline == filter_contender, you are analyzing the stdev
+
+        description = 'Comparing %s (from %s) to %s (from %s)' % (
+            filter_baseline, test_baseline, filter_contender, test_contender)
+    else:
+        # should never happen
+        print("Unrecognized mode of operation: '%s'" % args.mode)
+        parser.print_help()
+        exit(1)
+
+    check_inputs(test_baseline, test_contender, benchmark_options)
+
+    if args.display_aggregates_only:
+        benchmark_options += ['--benchmark_display_aggregates_only=true']
+
+    options_baseline = []
+    options_contender = []
+
+    if filter_baseline and filter_contender:
+        options_baseline = ['--benchmark_filter=%s' % filter_baseline]
+        options_contender = ['--benchmark_filter=%s' % filter_contender]
+
+    # Run the benchmarks and report the results
+    json1 = json1_orig = gbench.util.sort_benchmark_results(gbench.util.run_or_load_benchmark(
+        test_baseline, benchmark_options + options_baseline))
+    json2 = json2_orig = gbench.util.sort_benchmark_results(gbench.util.run_or_load_benchmark(
+        test_contender, benchmark_options + options_contender))
+
+    # Now, filter the benchmarks so that the difference report can work
+    if filter_baseline and filter_contender:
+        replacement = '[%s vs. %s]' % (filter_baseline, filter_contender)
+        json1 = gbench.report.filter_benchmark(
+            json1_orig, filter_baseline, replacement)
+        json2 = gbench.report.filter_benchmark(
+            json2_orig, filter_contender, replacement)
+
+    diff_report = gbench.report.get_difference_report(
+        json1, json2, args.utest)
+    output_lines = gbench.report.print_difference_report(
+        diff_report,
+        args.display_aggregates_only,
+        args.utest, args.utest_alpha, args.color)
+    print(description)
+    for ln in output_lines:
+        print(ln)
+
+    # Optionally, diff and output to JSON
+    if args.dump_to_json is not None:
+        with open(args.dump_to_json, 'w') as f_json:
+            json.dump(diff_report, f_json)
+
+class TestParser(unittest.TestCase):
+    def setUp(self):
+        self.parser = create_parser()
+        testInputs = os.path.join(
+            os.path.dirname(
+                os.path.realpath(__file__)),
+            'gbench',
+            'Inputs')
+        self.testInput0 = os.path.join(testInputs, 'test1_run1.json')
+        self.testInput1 = os.path.join(testInputs, 'test1_run2.json')
+
+    def test_benchmarks_basic(self):
+        parsed = self.parser.parse_args(
+            ['benchmarks', self.testInput0, self.testInput1])
+        self.assertFalse(parsed.display_aggregates_only)
+        self.assertTrue(parsed.utest)
+        self.assertEqual(parsed.mode, 'benchmarks')
+        self.assertEqual(parsed.test_baseline[0].name, self.testInput0)
+        self.assertEqual(parsed.test_contender[0].name, self.testInput1)
+        self.assertFalse(parsed.benchmark_options)
+
+    def test_benchmarks_basic_without_utest(self):
+        parsed = self.parser.parse_args(
+            ['--no-utest', 'benchmarks', self.testInput0, self.testInput1])
+        self.assertFalse(parsed.display_aggregates_only)
+        self.assertFalse(parsed.utest)
+        self.assertEqual(parsed.utest_alpha, 0.05)
+        self.assertEqual(parsed.mode, 'benchmarks')
+        self.assertEqual(parsed.test_baseline[0].name, self.testInput0)
+        self.assertEqual(parsed.test_contender[0].name, self.testInput1)
+        self.assertFalse(parsed.benchmark_options)
+
+    def test_benchmarks_basic_display_aggregates_only(self):
+        parsed = self.parser.parse_args(
+            ['-a', 'benchmarks', self.testInput0, self.testInput1])
+        self.assertTrue(parsed.display_aggregates_only)
+        self.assertTrue(parsed.utest)
+        self.assertEqual(parsed.mode, 'benchmarks')
+        self.assertEqual(parsed.test_baseline[0].name, self.testInput0)
+        self.assertEqual(parsed.test_contender[0].name, self.testInput1)
+        self.assertFalse(parsed.benchmark_options)
+
+    def test_benchmarks_basic_with_utest_alpha(self):
+        parsed = self.parser.parse_args(
+            ['--alpha=0.314', 'benchmarks', self.testInput0, self.testInput1])
+        self.assertFalse(parsed.display_aggregates_only)
+        self.assertTrue(parsed.utest)
+        self.assertEqual(parsed.utest_alpha, 0.314)
+        self.assertEqual(parsed.mode, 'benchmarks')
+        self.assertEqual(parsed.test_baseline[0].name, self.testInput0)
+        self.assertEqual(parsed.test_contender[0].name, self.testInput1)
+        self.assertFalse(parsed.benchmark_options)
+
+    def test_benchmarks_basic_without_utest_with_utest_alpha(self):
+        parsed = self.parser.parse_args(
+            ['--no-utest', '--alpha=0.314', 'benchmarks', self.testInput0, self.testInput1])
+        self.assertFalse(parsed.display_aggregates_only)
+        self.assertFalse(parsed.utest)
+        self.assertEqual(parsed.utest_alpha, 0.314)
+        self.assertEqual(parsed.mode, 'benchmarks')
+        self.assertEqual(parsed.test_baseline[0].name, self.testInput0)
+        self.assertEqual(parsed.test_contender[0].name, self.testInput1)
+        self.assertFalse(parsed.benchmark_options)
+
+    def test_benchmarks_with_remainder(self):
+        parsed = self.parser.parse_args(
+            ['benchmarks', self.testInput0, self.testInput1, 'd'])
+        self.assertFalse(parsed.display_aggregates_only)
+        self.assertTrue(parsed.utest)
+        self.assertEqual(parsed.mode, 'benchmarks')
+        self.assertEqual(parsed.test_baseline[0].name, self.testInput0)
+        self.assertEqual(parsed.test_contender[0].name, self.testInput1)
+        self.assertEqual(parsed.benchmark_options, ['d'])
+
+    def test_benchmarks_with_remainder_after_doubleminus(self):
+        parsed = self.parser.parse_args(
+            ['benchmarks', self.testInput0, self.testInput1, '--', 'e'])
+        self.assertFalse(parsed.display_aggregates_only)
+        self.assertTrue(parsed.utest)
+        self.assertEqual(parsed.mode, 'benchmarks')
+        self.assertEqual(parsed.test_baseline[0].name, self.testInput0)
+        self.assertEqual(parsed.test_contender[0].name, self.testInput1)
+        self.assertEqual(parsed.benchmark_options, ['e'])
+
+    def test_filters_basic(self):
+        parsed = self.parser.parse_args(
+            ['filters', self.testInput0, 'c', 'd'])
+        self.assertFalse(parsed.display_aggregates_only)
+        self.assertTrue(parsed.utest)
+        self.assertEqual(parsed.mode, 'filters')
+        self.assertEqual(parsed.test[0].name, self.testInput0)
+        self.assertEqual(parsed.filter_baseline[0], 'c')
+        self.assertEqual(parsed.filter_contender[0], 'd')
+        self.assertFalse(parsed.benchmark_options)
+
+    def test_filters_with_remainder(self):
+        parsed = self.parser.parse_args(
+            ['filters', self.testInput0, 'c', 'd', 'e'])
+        self.assertFalse(parsed.display_aggregates_only)
+        self.assertTrue(parsed.utest)
+        self.assertEqual(parsed.mode, 'filters')
+        self.assertEqual(parsed.test[0].name, self.testInput0)
+        self.assertEqual(parsed.filter_baseline[0], 'c')
+        self.assertEqual(parsed.filter_contender[0], 'd')
+        self.assertEqual(parsed.benchmark_options, ['e'])
+
+    def test_filters_with_remainder_after_doubleminus(self):
+        parsed = self.parser.parse_args(
+            ['filters', self.testInput0, 'c', 'd', '--', 'f'])
+        self.assertFalse(parsed.display_aggregates_only)
+        self.assertTrue(parsed.utest)
+        self.assertEqual(parsed.mode, 'filters')
+        self.assertEqual(parsed.test[0].name, self.testInput0)
+        self.assertEqual(parsed.filter_baseline[0], 'c')
+        self.assertEqual(parsed.filter_contender[0], 'd')
+        self.assertEqual(parsed.benchmark_options, ['f'])
+
+    def test_benchmarksfiltered_basic(self):
+        parsed = self.parser.parse_args(
+            ['benchmarksfiltered', self.testInput0, 'c', self.testInput1, 'e'])
+        self.assertFalse(parsed.display_aggregates_only)
+        self.assertTrue(parsed.utest)
+        self.assertEqual(parsed.mode, 'benchmarksfiltered')
+        self.assertEqual(parsed.test_baseline[0].name, self.testInput0)
+        self.assertEqual(parsed.filter_baseline[0], 'c')
+        self.assertEqual(parsed.test_contender[0].name, self.testInput1)
+        self.assertEqual(parsed.filter_contender[0], 'e')
+        self.assertFalse(parsed.benchmark_options)
+
+    def test_benchmarksfiltered_with_remainder(self):
+        parsed = self.parser.parse_args(
+            ['benchmarksfiltered', self.testInput0, 'c', self.testInput1, 'e', 'f'])
+        self.assertFalse(parsed.display_aggregates_only)
+        self.assertTrue(parsed.utest)
+        self.assertEqual(parsed.mode, 'benchmarksfiltered')
+        self.assertEqual(parsed.test_baseline[0].name, self.testInput0)
+        self.assertEqual(parsed.filter_baseline[0], 'c')
+        self.assertEqual(parsed.test_contender[0].name, self.testInput1)
+        self.assertEqual(parsed.filter_contender[0], 'e')
+        self.assertEqual(parsed.benchmark_options[0], 'f')
+
+    def test_benchmarksfiltered_with_remainder_after_doubleminus(self):
+        parsed = self.parser.parse_args(
+            ['benchmarksfiltered', self.testInput0, 'c', self.testInput1, 'e', '--', 'g'])
+        self.assertFalse(parsed.display_aggregates_only)
+        self.assertTrue(parsed.utest)
+        self.assertEqual(parsed.mode, 'benchmarksfiltered')
+        self.assertEqual(parsed.test_baseline[0].name, self.testInput0)
+        self.assertEqual(parsed.filter_baseline[0], 'c')
+        self.assertEqual(parsed.test_contender[0].name, self.testInput1)
+        self.assertEqual(parsed.filter_contender[0], 'e')
+        self.assertEqual(parsed.benchmark_options[0], 'g')
+
+
+if __name__ == '__main__':
+    # unittest.main()
+    main()
+
+# vim: tabstop=4 expandtab shiftwidth=4 softtabstop=4
+# kate: tab-width: 4; replace-tabs on; indent-width 4; tab-indents: off;
+# kate: indent-mode python; remove-trailing-spaces modified;
diff --git a/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test1_run1.json b/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test1_run1.json
new file mode 100644
index 0000000..9daed0b
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test1_run1.json
@@ -0,0 +1,127 @@
+{
+  "context": {
+    "date": "2016-08-02 17:44:46",
+    "num_cpus": 4,
+    "mhz_per_cpu": 4228,
+    "cpu_scaling_enabled": false,
+    "library_build_type": "release"
+  },
+  "benchmarks": [
+    {
+      "name": "BM_SameTimes",
+      "iterations": 1000,
+      "real_time": 10,
+      "cpu_time": 10,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_2xFaster",
+      "iterations": 1000,
+      "real_time": 50,
+      "cpu_time": 50,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_2xSlower",
+      "iterations": 1000,
+      "real_time": 50,
+      "cpu_time": 50,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_1PercentFaster",
+      "iterations": 1000,
+      "real_time": 100,
+      "cpu_time": 100,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_1PercentSlower",
+      "iterations": 1000,
+      "real_time": 100,
+      "cpu_time": 100,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_10PercentFaster",
+      "iterations": 1000,
+      "real_time": 100,
+      "cpu_time": 100,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_10PercentSlower",
+      "iterations": 1000,
+      "real_time": 100,
+      "cpu_time": 100,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_100xSlower",
+      "iterations": 1000,
+      "real_time": 100,
+      "cpu_time": 100,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_100xFaster",
+      "iterations": 1000,
+      "real_time": 10000,
+      "cpu_time": 10000,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_10PercentCPUToTime",
+      "iterations": 1000,
+      "real_time": 100,
+      "cpu_time": 100,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_ThirdFaster",
+      "iterations": 1000,
+      "real_time": 100,
+      "cpu_time": 100,
+      "time_unit": "ns"
+    },
+    {
+      "name": "MyComplexityTest_BigO",
+      "run_name": "MyComplexityTest",
+      "run_type": "aggregate",
+      "aggregate_name": "BigO",
+      "cpu_coefficient": 4.2749856294592886e+00,
+      "real_coefficient": 6.4789275289789780e+00,
+      "big_o": "N",
+      "time_unit": "ns"
+    },
+    {
+      "name": "MyComplexityTest_RMS",
+      "run_name": "MyComplexityTest",
+      "run_type": "aggregate",
+      "aggregate_name": "RMS",
+      "rms": 4.5097802512472874e-03
+    },
+    {
+      "name": "BM_NotBadTimeUnit",
+      "iterations": 1000,
+      "real_time": 0.4,
+      "cpu_time": 0.5,
+      "time_unit": "s"
+    },
+    {
+      "name": "BM_DifferentTimeUnit",
+      "iterations": 1,
+      "real_time": 1,
+      "cpu_time": 1,
+      "time_unit": "s"
+    },
+    {
+      "name": "BM_hasLabel",
+      "label": "a label",
+      "iterations": 1,
+      "real_time": 1,
+      "cpu_time": 1,
+      "time_unit": "s"
+    }
+  ]
+}
diff --git a/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test1_run2.json b/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test1_run2.json
new file mode 100644
index 0000000..dc52970
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test1_run2.json
@@ -0,0 +1,127 @@
+{
+  "context": {
+    "date": "2016-08-02 17:44:46",
+    "num_cpus": 4,
+    "mhz_per_cpu": 4228,
+    "cpu_scaling_enabled": false,
+    "library_build_type": "release"
+  },
+  "benchmarks": [
+    {
+      "name": "BM_SameTimes",
+      "iterations": 1000,
+      "real_time": 10,
+      "cpu_time": 10,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_2xFaster",
+      "iterations": 1000,
+      "real_time": 25,
+      "cpu_time": 25,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_2xSlower",
+      "iterations": 20833333,
+      "real_time": 100,
+      "cpu_time": 100,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_1PercentFaster",
+      "iterations": 1000,
+      "real_time": 98.9999999,
+      "cpu_time": 98.9999999,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_1PercentSlower",
+      "iterations": 1000,
+      "real_time": 100.9999999,
+      "cpu_time": 100.9999999,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_10PercentFaster",
+      "iterations": 1000,
+      "real_time": 90,
+      "cpu_time": 90,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_10PercentSlower",
+      "iterations": 1000,
+      "real_time": 110,
+      "cpu_time": 110,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_100xSlower",
+      "iterations": 1000,
+      "real_time": 1.0000e+04,
+      "cpu_time": 1.0000e+04,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_100xFaster",
+      "iterations": 1000,
+      "real_time": 100,
+      "cpu_time": 100,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_10PercentCPUToTime",
+      "iterations": 1000,
+      "real_time": 110,
+      "cpu_time": 90,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_ThirdFaster",
+      "iterations": 1000,
+      "real_time": 66.665,
+      "cpu_time": 66.664,
+      "time_unit": "ns"
+    },
+    {
+      "name": "MyComplexityTest_BigO",
+      "run_name": "MyComplexityTest",
+      "run_type": "aggregate",
+      "aggregate_name": "BigO",
+      "cpu_coefficient": 5.6215779594361486e+00,
+      "real_coefficient": 5.6288314793554610e+00,
+      "big_o": "N",
+      "time_unit": "ns"
+    },
+    {
+      "name": "MyComplexityTest_RMS",
+      "run_name": "MyComplexityTest",
+      "run_type": "aggregate",
+      "aggregate_name": "RMS",
+      "rms": 3.3128901852342174e-03
+    },
+    {
+      "name": "BM_NotBadTimeUnit",
+      "iterations": 1000,
+      "real_time": 0.04,
+      "cpu_time": 0.6,
+      "time_unit": "s"
+    },
+    {
+      "name": "BM_DifferentTimeUnit",
+      "iterations": 1,
+      "real_time": 1,
+      "cpu_time": 1,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_hasLabel",
+      "label": "a label",
+      "iterations": 1,
+      "real_time": 1,
+      "cpu_time": 1,
+      "time_unit": "s"
+    }
+  ]
+}
diff --git a/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test2_run.json b/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test2_run.json
new file mode 100644
index 0000000..15bc698
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test2_run.json
@@ -0,0 +1,81 @@
+{
+  "context": {
+    "date": "2016-08-02 17:44:46",
+    "num_cpus": 4,
+    "mhz_per_cpu": 4228,
+    "cpu_scaling_enabled": false,
+    "library_build_type": "release"
+  },
+  "benchmarks": [
+    {
+      "name": "BM_Hi",
+      "iterations": 1234,
+      "real_time": 42,
+      "cpu_time": 24,
+      "time_unit": "ms"
+    },
+    {
+      "name": "BM_Zero",
+      "iterations": 1000,
+      "real_time": 10,
+      "cpu_time": 10,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_Zero/4",
+      "iterations": 4000,
+      "real_time": 40,
+      "cpu_time": 40,
+      "time_unit": "ns"
+    },
+    {
+      "name": "Prefix/BM_Zero",
+      "iterations": 2000,
+      "real_time": 20,
+      "cpu_time": 20,
+      "time_unit": "ns"
+    },
+    {
+      "name": "Prefix/BM_Zero/3",
+      "iterations": 3000,
+      "real_time": 30,
+      "cpu_time": 30,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_One",
+      "iterations": 5000,
+      "real_time": 5,
+      "cpu_time": 5,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_One/4",
+      "iterations": 2000,
+      "real_time": 20,
+      "cpu_time": 20,
+      "time_unit": "ns"
+    },
+    {
+      "name": "Prefix/BM_One",
+      "iterations": 1000,
+      "real_time": 10,
+      "cpu_time": 10,
+      "time_unit": "ns"
+    },
+    {
+      "name": "Prefix/BM_One/3",
+      "iterations": 1500,
+      "real_time": 15,
+      "cpu_time": 15,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_Bye",
+      "iterations": 5321,
+      "real_time": 11,
+      "cpu_time": 63,
+      "time_unit": "ns"
+    }
+  ]
+}
diff --git a/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test3_run0.json b/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test3_run0.json
new file mode 100644
index 0000000..49f8b06
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test3_run0.json
@@ -0,0 +1,65 @@
+{
+  "context": {
+    "date": "2016-08-02 17:44:46",
+    "num_cpus": 4,
+    "mhz_per_cpu": 4228,
+    "cpu_scaling_enabled": false,
+    "library_build_type": "release"
+  },
+  "benchmarks": [
+    {
+      "name": "BM_One",
+      "run_type": "aggregate",
+      "iterations": 1000,
+      "real_time": 10,
+      "cpu_time": 100,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_Two",
+      "iterations": 1000,
+      "real_time": 9,
+      "cpu_time": 90,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_Two",
+      "iterations": 1000,
+      "real_time": 8,
+      "cpu_time": 86,
+      "time_unit": "ns"
+    },
+    {
+      "name": "short",
+      "run_type": "aggregate",
+      "iterations": 1000,
+      "real_time": 8,
+      "cpu_time": 80,
+      "time_unit": "ns"
+    },
+    {
+      "name": "short",
+      "run_type": "aggregate",
+      "iterations": 1000,
+      "real_time": 8,
+      "cpu_time": 77,
+      "time_unit": "ns"
+    },
+    {
+      "name": "medium",
+      "run_type": "iteration",
+      "iterations": 1000,
+      "real_time": 8,
+      "cpu_time": 80,
+      "time_unit": "ns"
+    },
+    {
+      "name": "medium",
+      "run_type": "iteration",
+      "iterations": 1000,
+      "real_time": 9,
+      "cpu_time": 82,
+      "time_unit": "ns"
+    }
+  ]
+}
diff --git a/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test3_run1.json b/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test3_run1.json
new file mode 100644
index 0000000..acc5ba1
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test3_run1.json
@@ -0,0 +1,65 @@
+{
+  "context": {
+    "date": "2016-08-02 17:44:46",
+    "num_cpus": 4,
+    "mhz_per_cpu": 4228,
+    "cpu_scaling_enabled": false,
+    "library_build_type": "release"
+  },
+  "benchmarks": [
+    {
+      "name": "BM_One",
+      "iterations": 1000,
+      "real_time": 9,
+      "cpu_time": 110,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_Two",
+      "run_type": "aggregate",
+      "iterations": 1000,
+      "real_time": 10,
+      "cpu_time": 89,
+      "time_unit": "ns"
+    },
+    {
+      "name": "BM_Two",
+      "iterations": 1000,
+      "real_time": 7,
+      "cpu_time": 72,
+      "time_unit": "ns"
+    },
+    {
+      "name": "short",
+      "run_type": "aggregate",
+      "iterations": 1000,
+      "real_time": 7,
+      "cpu_time": 75,
+      "time_unit": "ns"
+    },
+    {
+      "name": "short",
+      "run_type": "aggregate",
+      "iterations": 762,
+      "real_time": 4.54,
+      "cpu_time": 66.6,
+      "time_unit": "ns"
+    },
+    {
+      "name": "short",
+      "run_type": "iteration",
+      "iterations": 1000,
+      "real_time": 800,
+      "cpu_time": 1,
+      "time_unit": "ns"
+    },
+    {
+      "name": "medium",
+      "run_type": "iteration",
+      "iterations": 1200,
+      "real_time": 5,
+      "cpu_time": 53,
+      "time_unit": "ns"
+    }
+  ]
+}
diff --git a/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test4_run.json b/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test4_run.json
new file mode 100644
index 0000000..eaa005f
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test4_run.json
@@ -0,0 +1,96 @@
+{
+  "benchmarks": [
+    {
+      "name": "99 family 0 instance 0 repetition 0",
+      "run_type": "iteration",
+      "family_index": 0,
+      "per_family_instance_index": 0,
+      "repetition_index": 0
+    },
+    {
+      "name": "98 family 0 instance 0 repetition 1",
+      "run_type": "iteration",
+      "family_index": 0,
+      "per_family_instance_index": 0,
+      "repetition_index": 1
+    },
+    {
+      "name": "97 family 0 instance 0 aggregate",
+      "run_type": "aggregate",
+      "family_index": 0,
+      "per_family_instance_index": 0,
+      "aggregate_name": "9 aggregate"
+    },
+
+
+    {
+      "name": "96 family 0 instance 1 repetition 0",
+      "run_type": "iteration",
+      "family_index": 0,
+      "per_family_instance_index": 1,
+      "repetition_index": 0
+    },
+    {
+      "name": "95 family 0 instance 1 repetition 1",
+      "run_type": "iteration",
+      "family_index": 0,
+      "per_family_instance_index": 1,
+      "repetition_index": 1
+    },
+    {
+      "name": "94 family 0 instance 1 aggregate",
+      "run_type": "aggregate",
+      "family_index": 0,
+      "per_family_instance_index": 1,
+      "aggregate_name": "9 aggregate"
+    },
+
+
+
+
+    {
+      "name": "93 family 1 instance 0 repetition 0",
+      "run_type": "iteration",
+      "family_index": 1,
+      "per_family_instance_index": 0,
+      "repetition_index": 0
+    },
+    {
+      "name": "92 family 1 instance 0 repetition 1",
+      "run_type": "iteration",
+      "family_index": 1,
+      "per_family_instance_index": 0,
+      "repetition_index": 1
+    },
+    {
+      "name": "91 family 1 instance 0 aggregate",
+      "run_type": "aggregate",
+      "family_index": 1,
+      "per_family_instance_index": 0,
+      "aggregate_name": "9 aggregate"
+    },
+
+
+    {
+      "name": "90 family 1 instance 1 repetition 0",
+      "run_type": "iteration",
+      "family_index": 1,
+      "per_family_instance_index": 1,
+      "repetition_index": 0
+    },
+    {
+      "name": "89 family 1 instance 1 repetition 1",
+      "run_type": "iteration",
+      "family_index": 1,
+      "per_family_instance_index": 1,
+      "repetition_index": 1
+    },
+    {
+      "name": "88 family 1 instance 1 aggregate",
+      "run_type": "aggregate",
+      "family_index": 1,
+      "per_family_instance_index": 1,
+      "aggregate_name": "9 aggregate"
+    }
+  ]
+}
diff --git a/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test4_run0.json b/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test4_run0.json
new file mode 100644
index 0000000..54cf127
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test4_run0.json
@@ -0,0 +1,21 @@
+{
+  "context": {
+    "date": "2016-08-02 17:44:46",
+    "num_cpus": 4,
+    "mhz_per_cpu": 4228,
+    "cpu_scaling_enabled": false,
+    "library_build_type": "release"
+  },
+  "benchmarks": [
+    {
+      "name": "whocares",
+      "run_type": "aggregate",
+      "aggregate_name": "zz",
+      "aggregate_unit": "percentage",
+      "iterations": 1000,
+      "real_time": 0.01,
+      "cpu_time": 0.10,
+      "time_unit": "ns"
+    }
+  ]
+}
diff --git a/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test4_run1.json b/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test4_run1.json
new file mode 100644
index 0000000..25d5605
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/tools/gbench/Inputs/test4_run1.json
@@ -0,0 +1,21 @@
+{
+  "context": {
+    "date": "2016-08-02 17:44:46",
+    "num_cpus": 4,
+    "mhz_per_cpu": 4228,
+    "cpu_scaling_enabled": false,
+    "library_build_type": "release"
+  },
+  "benchmarks": [
+    {
+      "name": "whocares",
+      "run_type": "aggregate",
+      "aggregate_name": "zz",
+      "aggregate_unit": "percentage",
+      "iterations": 1000,
+      "real_time": 0.005,
+      "cpu_time": 0.15,
+      "time_unit": "ns"
+    }
+  ]
+}
diff --git a/leveldb_base/third_party/benchmark/tools/gbench/__init__.py b/leveldb_base/third_party/benchmark/tools/gbench/__init__.py
new file mode 100644
index 0000000..fce1a1a
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/tools/gbench/__init__.py
@@ -0,0 +1,8 @@
+"""Google Benchmark tooling"""
+
+__author__ = 'Eric Fiselier'
+__email__ = 'eric@efcs.ca'
+__versioninfo__ = (0, 5, 0)
+__version__ = '.'.join(str(v) for v in __versioninfo__) + 'dev'
+
+__all__ = []
diff --git a/leveldb_base/third_party/benchmark/tools/gbench/report.py b/leveldb_base/third_party/benchmark/tools/gbench/report.py
new file mode 100644
index 0000000..b2bbfb9
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/tools/gbench/report.py
@@ -0,0 +1,1201 @@
+"""report.py - Utilities for reporting statistics about benchmark results
+"""
+
+import unittest
+import os
+import re
+import copy
+import random
+
+from scipy.stats import mannwhitneyu, gmean
+from numpy import array
+
+
+class BenchmarkColor(object):
+    def __init__(self, name, code):
+        self.name = name
+        self.code = code
+
+    def __repr__(self):
+        return '%s%r' % (self.__class__.__name__,
+                         (self.name, self.code))
+
+    def __format__(self, format):
+        return self.code
+
+
+# Benchmark Colors Enumeration
+BC_NONE = BenchmarkColor('NONE', '')
+BC_MAGENTA = BenchmarkColor('MAGENTA', '\033[95m')
+BC_CYAN = BenchmarkColor('CYAN', '\033[96m')
+BC_OKBLUE = BenchmarkColor('OKBLUE', '\033[94m')
+BC_OKGREEN = BenchmarkColor('OKGREEN', '\033[32m')
+BC_HEADER = BenchmarkColor('HEADER', '\033[92m')
+BC_WARNING = BenchmarkColor('WARNING', '\033[93m')
+BC_WHITE = BenchmarkColor('WHITE', '\033[97m')
+BC_FAIL = BenchmarkColor('FAIL', '\033[91m')
+BC_ENDC = BenchmarkColor('ENDC', '\033[0m')
+BC_BOLD = BenchmarkColor('BOLD', '\033[1m')
+BC_UNDERLINE = BenchmarkColor('UNDERLINE', '\033[4m')
+
+UTEST_MIN_REPETITIONS = 2
+UTEST_OPTIMAL_REPETITIONS = 9  # Lowest reasonable number, More is better.
+UTEST_COL_NAME = "_pvalue"
+
+_TIME_UNIT_TO_SECONDS_MULTIPLIER = {
+    "s": 1.0,
+    "ms": 1e-3,
+    "us": 1e-6,
+    "ns": 1e-9,
+}
+
+
+def color_format(use_color, fmt_str, *args, **kwargs):
+    """
+    Return the result of 'fmt_str.format(*args, **kwargs)' after transforming
+    'args' and 'kwargs' according to the value of 'use_color'. If 'use_color'
+    is False then all color codes in 'args' and 'kwargs' are replaced with
+    the empty string.
+    """
+    assert use_color is True or use_color is False
+    if not use_color:
+        args = [arg if not isinstance(arg, BenchmarkColor) else BC_NONE
+                for arg in args]
+        kwargs = {key: arg if not isinstance(arg, BenchmarkColor) else BC_NONE
+                  for key, arg in kwargs.items()}
+    return fmt_str.format(*args, **kwargs)
+
+
+def find_longest_name(benchmark_list):
+    """
+    Return the length of the longest benchmark name in a given list of
+    benchmark JSON objects
+    """
+    longest_name = 1
+    for bc in benchmark_list:
+        if len(bc['name']) > longest_name:
+            longest_name = len(bc['name'])
+    return longest_name
+
+
+def calculate_change(old_val, new_val):
+    """
+    Return a float representing the decimal change between old_val and new_val.
+    """
+    if old_val == 0 and new_val == 0:
+        return 0.0
+    if old_val == 0:
+        return float(new_val - old_val) / (float(old_val + new_val) / 2)
+    return float(new_val - old_val) / abs(old_val)
+
+
+def filter_benchmark(json_orig, family, replacement=""):
+    """
+    Apply a filter to the json, and only leave the 'family' of benchmarks.
+    """
+    regex = re.compile(family)
+    filtered = {}
+    filtered['benchmarks'] = []
+    for be in json_orig['benchmarks']:
+        if not regex.search(be['name']):
+            continue
+        filteredbench = copy.deepcopy(be)  # Do NOT modify the old name!
+        filteredbench['name'] = regex.sub(replacement, filteredbench['name'])
+        filtered['benchmarks'].append(filteredbench)
+    return filtered
+
+
+def get_unique_benchmark_names(json):
+    """
+    While *keeping* the order, give all the unique 'names' used for benchmarks.
+    """
+    seen = set()
+    uniqued = [x['name'] for x in json['benchmarks']
+               if x['name'] not in seen and
+               (seen.add(x['name']) or True)]
+    return uniqued
+
+
+def intersect(list1, list2):
+    """
+    Given two lists, get a new list consisting of the elements only contained
+    in *both of the input lists*, while preserving the ordering.
+    """
+    return [x for x in list1 if x in list2]
+
+
+def is_potentially_comparable_benchmark(x):
+    return ('time_unit' in x and 'real_time' in x and 'cpu_time' in x)
+
+
+def partition_benchmarks(json1, json2):
+    """
+    While preserving the ordering, find benchmarks with the same names in
+    both of the inputs, and group them.
+    (i.e. partition/filter into groups with common name)
+    """
+    json1_unique_names = get_unique_benchmark_names(json1)
+    json2_unique_names = get_unique_benchmark_names(json2)
+    names = intersect(json1_unique_names, json2_unique_names)
+    partitions = []
+    for name in names:
+        time_unit = None
+        # Pick the time unit from the first entry of the lhs benchmark.
+        # We should be careful not to crash with unexpected input.
+        for x in json1['benchmarks']:
+            if (x['name'] == name and is_potentially_comparable_benchmark(x)):
+                time_unit = x['time_unit']
+                break
+        if time_unit is None:
+            continue
+        # Filter by name and time unit.
+        # All the repetitions are assumed to be comparable.
+        lhs = [x for x in json1['benchmarks'] if x['name'] == name and
+               x['time_unit'] == time_unit]
+        rhs = [x for x in json2['benchmarks'] if x['name'] == name and
+               x['time_unit'] == time_unit]
+        partitions.append([lhs, rhs])
+    return partitions
+
+
+def get_timedelta_field_as_seconds(benchmark, field_name):
+    """
+    Get value of field_name field of benchmark, which is time with time unit
+    time_unit, as time in seconds.
+    """
+    timedelta = benchmark[field_name]
+    time_unit = benchmark.get('time_unit', 's')
+    return timedelta * _TIME_UNIT_TO_SECONDS_MULTIPLIER.get(time_unit)
+
+
+def calculate_geomean(json):
+    """
+    Extract all real/cpu times from all the benchmarks as seconds,
+    and calculate their geomean.
+    """
+    times = []
+    for benchmark in json['benchmarks']:
+        if 'run_type' in benchmark and benchmark['run_type'] == 'aggregate':
+            continue
+        times.append([get_timedelta_field_as_seconds(benchmark, 'real_time'),
+                      get_timedelta_field_as_seconds(benchmark, 'cpu_time')])
+    return gmean(times) if times else array([])
+
+
+def extract_field(partition, field_name):
+    # The count of elements may be different. We want *all* of them.
+    lhs = [x[field_name] for x in partition[0]]
+    rhs = [x[field_name] for x in partition[1]]
+    return [lhs, rhs]
+
+
+def calc_utest(timings_cpu, timings_time):
+    min_rep_cnt = min(len(timings_time[0]),
+                      len(timings_time[1]),
+                      len(timings_cpu[0]),
+                      len(timings_cpu[1]))
+
+    # Does *everything* has at least UTEST_MIN_REPETITIONS repetitions?
+    if min_rep_cnt < UTEST_MIN_REPETITIONS:
+        return False, None, None
+
+    time_pvalue = mannwhitneyu(
+        timings_time[0], timings_time[1], alternative='two-sided').pvalue
+    cpu_pvalue = mannwhitneyu(
+        timings_cpu[0], timings_cpu[1], alternative='two-sided').pvalue
+
+    return (min_rep_cnt >= UTEST_OPTIMAL_REPETITIONS), cpu_pvalue, time_pvalue
+
+
+def print_utest(bc_name, utest, utest_alpha, first_col_width, use_color=True):
+    def get_utest_color(pval):
+        return BC_FAIL if pval >= utest_alpha else BC_OKGREEN
+
+    # Check if we failed miserably with minimum required repetitions for utest
+    if not utest['have_optimal_repetitions'] and utest['cpu_pvalue'] is None and utest['time_pvalue'] is None:
+        return []
+
+    dsc = "U Test, Repetitions: {} vs {}".format(
+        utest['nr_of_repetitions'], utest['nr_of_repetitions_other'])
+    dsc_color = BC_OKGREEN
+
+    # We still got some results to show but issue a warning about it.
+    if not utest['have_optimal_repetitions']:
+        dsc_color = BC_WARNING
+        dsc += ". WARNING: Results unreliable! {}+ repetitions recommended.".format(
+            UTEST_OPTIMAL_REPETITIONS)
+
+    special_str = "{}{:<{}s}{endc}{}{:16.4f}{endc}{}{:16.4f}{endc}{}      {}"
+
+    return [color_format(use_color,
+                         special_str,
+                         BC_HEADER,
+                         "{}{}".format(bc_name, UTEST_COL_NAME),
+                         first_col_width,
+                         get_utest_color(
+                             utest['time_pvalue']), utest['time_pvalue'],
+                         get_utest_color(
+                             utest['cpu_pvalue']), utest['cpu_pvalue'],
+                         dsc_color, dsc,
+                         endc=BC_ENDC)]
+
+
+def get_difference_report(
+        json1,
+        json2,
+        utest=False):
+    """
+    Calculate and report the difference between each test of two benchmarks
+    runs specified as 'json1' and 'json2'. Output is another json containing
+    relevant details for each test run.
+    """
+    assert utest is True or utest is False
+
+    diff_report = []
+    partitions = partition_benchmarks(json1, json2)
+    for partition in partitions:
+        benchmark_name = partition[0][0]['name']
+        label = partition[0][0]['label'] if 'label' in partition[0][0] else ''
+        time_unit = partition[0][0]['time_unit']
+        measurements = []
+        utest_results = {}
+        # Careful, we may have different repetition count.
+        for i in range(min(len(partition[0]), len(partition[1]))):
+            bn = partition[0][i]
+            other_bench = partition[1][i]
+            measurements.append({
+                'real_time': bn['real_time'],
+                'cpu_time': bn['cpu_time'],
+                'real_time_other': other_bench['real_time'],
+                'cpu_time_other': other_bench['cpu_time'],
+                'time': calculate_change(bn['real_time'], other_bench['real_time']),
+                'cpu': calculate_change(bn['cpu_time'], other_bench['cpu_time'])
+            })
+
+        # After processing the whole partition, if requested, do the U test.
+        if utest:
+            timings_cpu = extract_field(partition, 'cpu_time')
+            timings_time = extract_field(partition, 'real_time')
+            have_optimal_repetitions, cpu_pvalue, time_pvalue = calc_utest(
+                timings_cpu, timings_time)
+            if cpu_pvalue and time_pvalue:
+                utest_results = {
+                    'have_optimal_repetitions': have_optimal_repetitions,
+                    'cpu_pvalue': cpu_pvalue,
+                    'time_pvalue': time_pvalue,
+                    'nr_of_repetitions': len(timings_cpu[0]),
+                    'nr_of_repetitions_other': len(timings_cpu[1])
+                }
+
+        # Store only if we had any measurements for given benchmark.
+        # E.g. partition_benchmarks will filter out the benchmarks having
+        # time units which are not compatible with other time units in the
+        # benchmark suite.
+        if measurements:
+            run_type = partition[0][0]['run_type'] if 'run_type' in partition[0][0] else ''
+            aggregate_name = partition[0][0]['aggregate_name'] if run_type == 'aggregate' and 'aggregate_name' in partition[0][0] else ''
+            diff_report.append({
+                'name': benchmark_name,
+                'label': label,
+                'measurements': measurements,
+                'time_unit': time_unit,
+                'run_type': run_type,
+                'aggregate_name': aggregate_name,
+                'utest': utest_results
+            })
+
+    lhs_gmean = calculate_geomean(json1)
+    rhs_gmean = calculate_geomean(json2)
+    if lhs_gmean.any() and rhs_gmean.any():
+        diff_report.append({
+            'name': 'OVERALL_GEOMEAN',
+            'label': '',
+            'measurements': [{
+                'real_time': lhs_gmean[0],
+                'cpu_time': lhs_gmean[1],
+                'real_time_other': rhs_gmean[0],
+                'cpu_time_other': rhs_gmean[1],
+                'time': calculate_change(lhs_gmean[0], rhs_gmean[0]),
+                'cpu': calculate_change(lhs_gmean[1], rhs_gmean[1])
+            }],
+            'time_unit': 's',
+            'run_type': 'aggregate',
+            'aggregate_name': 'geomean',
+            'utest': {}
+        })
+
+    return diff_report
+
+
+def print_difference_report(
+        json_diff_report,
+        include_aggregates_only=False,
+        utest=False,
+        utest_alpha=0.05,
+        use_color=True):
+    """
+    Calculate and report the difference between each test of two benchmarks
+    runs specified as 'json1' and 'json2'.
+    """
+    assert utest is True or utest is False
+
+    def get_color(res):
+        if res > 0.05:
+            return BC_FAIL
+        elif res > -0.07:
+            return BC_WHITE
+        else:
+            return BC_CYAN
+
+    first_col_width = find_longest_name(json_diff_report)
+    first_col_width = max(
+        first_col_width,
+        len('Benchmark'))
+    first_col_width += len(UTEST_COL_NAME)
+    first_line = "{:<{}s}Time             CPU      Time Old      Time New       CPU Old       CPU New".format(
+        'Benchmark', 12 + first_col_width)
+    output_strs = [first_line, '-' * len(first_line)]
+
+    fmt_str = "{}{:<{}s}{endc}{}{:+16.4f}{endc}{}{:+16.4f}{endc}{:14.0f}{:14.0f}{endc}{:14.0f}{:14.0f}"
+    for benchmark in json_diff_report:
+        # *If* we were asked to only include aggregates,
+        # and if it is non-aggregate, then don't print it.
+        if not include_aggregates_only or not 'run_type' in benchmark or benchmark['run_type'] == 'aggregate':
+            for measurement in benchmark['measurements']:
+                output_strs += [color_format(use_color,
+                                             fmt_str,
+                                             BC_HEADER,
+                                             benchmark['name'],
+                                             first_col_width,
+                                             get_color(measurement['time']),
+                                             measurement['time'],
+                                             get_color(measurement['cpu']),
+                                             measurement['cpu'],
+                                             measurement['real_time'],
+                                             measurement['real_time_other'],
+                                             measurement['cpu_time'],
+                                             measurement['cpu_time_other'],
+                                             endc=BC_ENDC)]
+
+        # After processing the measurements, if requested and
+        # if applicable (e.g. u-test exists for given benchmark),
+        # print the U test.
+        if utest and benchmark['utest']:
+            output_strs += print_utest(benchmark['name'],
+                                       benchmark['utest'],
+                                       utest_alpha=utest_alpha,
+                                       first_col_width=first_col_width,
+                                       use_color=use_color)
+
+    return output_strs
+
+
+###############################################################################
+# Unit tests
+
+
+class TestGetUniqueBenchmarkNames(unittest.TestCase):
+    def load_results(self):
+        import json
+        testInputs = os.path.join(
+            os.path.dirname(
+                os.path.realpath(__file__)),
+            'Inputs')
+        testOutput = os.path.join(testInputs, 'test3_run0.json')
+        with open(testOutput, 'r') as f:
+            json = json.load(f)
+        return json
+
+    def test_basic(self):
+        expect_lines = [
+            'BM_One',
+            'BM_Two',
+            'short',  # These two are not sorted
+            'medium',  # These two are not sorted
+        ]
+        json = self.load_results()
+        output_lines = get_unique_benchmark_names(json)
+        print("\n")
+        print("\n".join(output_lines))
+        self.assertEqual(len(output_lines), len(expect_lines))
+        for i in range(0, len(output_lines)):
+            self.assertEqual(expect_lines[i], output_lines[i])
+
+
+class TestReportDifference(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        def load_results():
+            import json
+            testInputs = os.path.join(
+                os.path.dirname(
+                    os.path.realpath(__file__)),
+                'Inputs')
+            testOutput1 = os.path.join(testInputs, 'test1_run1.json')
+            testOutput2 = os.path.join(testInputs, 'test1_run2.json')
+            with open(testOutput1, 'r') as f:
+                json1 = json.load(f)
+            with open(testOutput2, 'r') as f:
+                json2 = json.load(f)
+            return json1, json2
+
+        json1, json2 = load_results()
+        cls.json_diff_report = get_difference_report(json1, json2)
+
+    def test_json_diff_report_pretty_printing(self):
+        expect_lines = [
+            ['BM_SameTimes', '+0.0000', '+0.0000', '10', '10', '10', '10'],
+            ['BM_2xFaster', '-0.5000', '-0.5000', '50', '25', '50', '25'],
+            ['BM_2xSlower', '+1.0000', '+1.0000', '50', '100', '50', '100'],
+            ['BM_1PercentFaster', '-0.0100', '-0.0100', '100', '99', '100', '99'],
+            ['BM_1PercentSlower', '+0.0100', '+0.0100', '100', '101', '100', '101'],
+            ['BM_10PercentFaster', '-0.1000', '-0.1000', '100', '90', '100', '90'],
+            ['BM_10PercentSlower', '+0.1000', '+0.1000', '100', '110', '100', '110'],
+            ['BM_100xSlower', '+99.0000', '+99.0000',
+                '100', '10000', '100', '10000'],
+            ['BM_100xFaster', '-0.9900', '-0.9900',
+                '10000', '100', '10000', '100'],
+            ['BM_10PercentCPUToTime', '+0.1000',
+                '-0.1000', '100', '110', '100', '90'],
+            ['BM_ThirdFaster', '-0.3333', '-0.3334', '100', '67', '100', '67'],
+            ['BM_NotBadTimeUnit', '-0.9000', '+0.2000', '0', '0', '0', '1'],
+            ['BM_hasLabel', '+0.0000', '+0.0000', '1', '1', '1', '1'],
+            ['OVERALL_GEOMEAN', '-0.8113', '-0.7779', '0', '0', '0', '0']
+        ]
+        output_lines_with_header = print_difference_report(
+            self.json_diff_report, use_color=False)
+        output_lines = output_lines_with_header[2:]
+        print("\n")
+        print("\n".join(output_lines_with_header))
+        self.assertEqual(len(output_lines), len(expect_lines))
+        for i in range(0, len(output_lines)):
+            parts = [x for x in output_lines[i].split(' ') if x]
+            self.assertEqual(len(parts), 7)
+            self.assertEqual(expect_lines[i], parts)
+
+    def test_json_diff_report_output(self):
+        expected_output = [
+            {
+                'name': 'BM_SameTimes',
+                'label': '',
+                'measurements': [{'time': 0.0000, 'cpu': 0.0000,
+                                  'real_time': 10, 'real_time_other': 10,
+                                  'cpu_time': 10, 'cpu_time_other': 10}],
+                'time_unit': 'ns',
+                'utest': {}
+            },
+            {
+                'name': 'BM_2xFaster',
+                'label': '',
+                'measurements': [{'time': -0.5000, 'cpu': -0.5000,
+                                  'real_time': 50, 'real_time_other': 25,
+                                  'cpu_time': 50, 'cpu_time_other': 25}],
+                'time_unit': 'ns',
+                'utest': {}
+            },
+            {
+                'name': 'BM_2xSlower',
+                'label': '',
+                'measurements': [{'time': 1.0000, 'cpu': 1.0000,
+                                  'real_time': 50, 'real_time_other': 100,
+                                  'cpu_time': 50, 'cpu_time_other': 100}],
+                'time_unit': 'ns',
+                'utest': {}
+            },
+            {
+                'name': 'BM_1PercentFaster',
+                'label': '',
+                'measurements': [{'time': -0.0100, 'cpu': -0.0100,
+                                  'real_time': 100, 'real_time_other': 98.9999999,
+                                  'cpu_time': 100, 'cpu_time_other': 98.9999999}],
+                'time_unit': 'ns',
+                'utest': {}
+            },
+            {
+                'name': 'BM_1PercentSlower',
+                'label': '',
+                'measurements': [{'time': 0.0100, 'cpu': 0.0100,
+                                  'real_time': 100, 'real_time_other': 101,
+                                  'cpu_time': 100, 'cpu_time_other': 101}],
+                'time_unit': 'ns',
+                'utest': {}
+            },
+            {
+                'name': 'BM_10PercentFaster',
+                'label': '',
+                'measurements': [{'time': -0.1000, 'cpu': -0.1000,
+                                  'real_time': 100, 'real_time_other': 90,
+                                  'cpu_time': 100, 'cpu_time_other': 90}],
+                'time_unit': 'ns',
+                'utest': {}
+            },
+            {
+                'name': 'BM_10PercentSlower',
+                'label': '',
+                'measurements': [{'time': 0.1000, 'cpu': 0.1000,
+                                  'real_time': 100, 'real_time_other': 110,
+                                  'cpu_time': 100, 'cpu_time_other': 110}],
+                'time_unit': 'ns',
+                'utest': {}
+            },
+            {
+                'name': 'BM_100xSlower',
+                'label': '',
+                'measurements': [{'time': 99.0000, 'cpu': 99.0000,
+                                  'real_time': 100, 'real_time_other': 10000,
+                                  'cpu_time': 100, 'cpu_time_other': 10000}],
+                'time_unit': 'ns',
+                'utest': {}
+            },
+            {
+                'name': 'BM_100xFaster',
+                'label': '',
+                'measurements': [{'time': -0.9900, 'cpu': -0.9900,
+                                  'real_time': 10000, 'real_time_other': 100,
+                                  'cpu_time': 10000, 'cpu_time_other': 100}],
+                'time_unit': 'ns',
+                'utest': {}
+            },
+            {
+                'name': 'BM_10PercentCPUToTime',
+                'label': '',
+                'measurements': [{'time': 0.1000, 'cpu': -0.1000,
+                                  'real_time': 100, 'real_time_other': 110,
+                                  'cpu_time': 100, 'cpu_time_other': 90}],
+                'time_unit': 'ns',
+                'utest': {}
+            },
+            {
+                'name': 'BM_ThirdFaster',
+                'label': '',
+                'measurements': [{'time': -0.3333, 'cpu': -0.3334,
+                                  'real_time': 100, 'real_time_other': 67,
+                                  'cpu_time': 100, 'cpu_time_other': 67}],
+                'time_unit': 'ns',
+                'utest': {}
+            },
+            {
+                'name': 'BM_NotBadTimeUnit',
+                'label': '',
+                'measurements': [{'time': -0.9000, 'cpu': 0.2000,
+                                  'real_time': 0.4, 'real_time_other': 0.04,
+                                  'cpu_time': 0.5, 'cpu_time_other': 0.6}],
+                'time_unit': 's',
+                'utest': {}
+            },
+            {
+                'name': 'BM_hasLabel',
+                'label': 'a label',
+                'measurements': [{'time': 0.0000, 'cpu': 0.0000,
+                                  'real_time': 1, 'real_time_other': 1,
+                                  'cpu_time': 1, 'cpu_time_other': 1}],
+                'time_unit': 's',
+                'utest': {}
+            },
+            {
+                'name': 'OVERALL_GEOMEAN',
+                'label': '',
+                'measurements': [{'real_time': 3.1622776601683826e-06, 'cpu_time': 3.2130844755623912e-06,
+                                  'real_time_other': 1.9768988699420897e-07, 'cpu_time_other': 2.397447755209533e-07,
+                                  'time': -0.8112976497120911, 'cpu': -0.7778551721181174}],
+                'time_unit': 's',
+                'run_type': 'aggregate',
+                'aggregate_name': 'geomean', 'utest': {}
+            },
+        ]
+        self.assertEqual(len(self.json_diff_report), len(expected_output))
+        for out, expected in zip(
+                self.json_diff_report, expected_output):
+            self.assertEqual(out['name'], expected['name'])
+            self.assertEqual(out['label'], expected['label'])
+            self.assertEqual(out['time_unit'], expected['time_unit'])
+            assert_utest(self, out, expected)
+            assert_measurements(self, out, expected)
+
+
+class TestReportDifferenceBetweenFamilies(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        def load_result():
+            import json
+            testInputs = os.path.join(
+                os.path.dirname(
+                    os.path.realpath(__file__)),
+                'Inputs')
+            testOutput = os.path.join(testInputs, 'test2_run.json')
+            with open(testOutput, 'r') as f:
+                json = json.load(f)
+            return json
+
+        json = load_result()
+        json1 = filter_benchmark(json, "BM_Z.ro", ".")
+        json2 = filter_benchmark(json, "BM_O.e", ".")
+        cls.json_diff_report = get_difference_report(json1, json2)
+
+    def test_json_diff_report_pretty_printing(self):
+        expect_lines = [
+            ['.', '-0.5000', '-0.5000', '10', '5', '10', '5'],
+            ['./4', '-0.5000', '-0.5000', '40', '20', '40', '20'],
+            ['Prefix/.', '-0.5000', '-0.5000', '20', '10', '20', '10'],
+            ['Prefix/./3', '-0.5000', '-0.5000', '30', '15', '30', '15'],
+            ['OVERALL_GEOMEAN', '-0.5000', '-0.5000', '0', '0', '0', '0']
+        ]
+        output_lines_with_header = print_difference_report(
+            self.json_diff_report, use_color=False)
+        output_lines = output_lines_with_header[2:]
+        print("\n")
+        print("\n".join(output_lines_with_header))
+        self.assertEqual(len(output_lines), len(expect_lines))
+        for i in range(0, len(output_lines)):
+            parts = [x for x in output_lines[i].split(' ') if x]
+            self.assertEqual(len(parts), 7)
+            self.assertEqual(expect_lines[i], parts)
+
+    def test_json_diff_report(self):
+        expected_output = [
+            {
+                'name': u'.',
+                'measurements': [{'time': -0.5, 'cpu': -0.5, 'real_time': 10, 'real_time_other': 5, 'cpu_time': 10, 'cpu_time_other': 5}],
+                'time_unit': 'ns',
+                'utest': {}
+            },
+            {
+                'name': u'./4',
+                'measurements': [{'time': -0.5, 'cpu': -0.5, 'real_time': 40, 'real_time_other': 20, 'cpu_time': 40, 'cpu_time_other': 20}],
+                'time_unit': 'ns',
+                'utest': {},
+            },
+            {
+                'name': u'Prefix/.',
+                'measurements': [{'time': -0.5, 'cpu': -0.5, 'real_time': 20, 'real_time_other': 10, 'cpu_time': 20, 'cpu_time_other': 10}],
+                'time_unit': 'ns',
+                'utest': {}
+            },
+            {
+                'name': u'Prefix/./3',
+                'measurements': [{'time': -0.5, 'cpu': -0.5, 'real_time': 30, 'real_time_other': 15, 'cpu_time': 30, 'cpu_time_other': 15}],
+                'time_unit': 'ns',
+                'utest': {}
+            },
+            {
+                'name': 'OVERALL_GEOMEAN',
+                'measurements': [{'real_time': 2.213363839400641e-08, 'cpu_time': 2.213363839400641e-08,
+                                  'real_time_other': 1.1066819197003185e-08, 'cpu_time_other': 1.1066819197003185e-08,
+                                  'time': -0.5000000000000009, 'cpu': -0.5000000000000009}],
+                'time_unit': 's',
+                'run_type': 'aggregate',
+                'aggregate_name': 'geomean',
+                'utest': {}
+            }
+        ]
+        self.assertEqual(len(self.json_diff_report), len(expected_output))
+        for out, expected in zip(
+                self.json_diff_report, expected_output):
+            self.assertEqual(out['name'], expected['name'])
+            self.assertEqual(out['time_unit'], expected['time_unit'])
+            assert_utest(self, out, expected)
+            assert_measurements(self, out, expected)
+
+
+class TestReportDifferenceWithUTest(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        def load_results():
+            import json
+            testInputs = os.path.join(
+                os.path.dirname(
+                    os.path.realpath(__file__)),
+                'Inputs')
+            testOutput1 = os.path.join(testInputs, 'test3_run0.json')
+            testOutput2 = os.path.join(testInputs, 'test3_run1.json')
+            with open(testOutput1, 'r') as f:
+                json1 = json.load(f)
+            with open(testOutput2, 'r') as f:
+                json2 = json.load(f)
+            return json1, json2
+
+        json1, json2 = load_results()
+        cls.json_diff_report = get_difference_report(
+            json1, json2, utest=True)
+
+    def test_json_diff_report_pretty_printing(self):
+        expect_lines = [
+            ['BM_One', '-0.1000', '+0.1000', '10', '9', '100', '110'],
+            ['BM_Two', '+0.1111', '-0.0111', '9', '10', '90', '89'],
+            ['BM_Two', '-0.1250', '-0.1628', '8', '7', '86', '72'],
+            ['BM_Two_pvalue',
+             '1.0000',
+             '0.6667',
+             'U',
+             'Test,',
+             'Repetitions:',
+             '2',
+             'vs',
+             '2.',
+             'WARNING:',
+             'Results',
+             'unreliable!',
+             '9+',
+             'repetitions',
+             'recommended.'],
+            ['short', '-0.1250', '-0.0625', '8', '7', '80', '75'],
+            ['short', '-0.4325', '-0.1351', '8', '5', '77', '67'],
+            ['short_pvalue',
+             '0.7671',
+             '0.2000',
+             'U',
+             'Test,',
+             'Repetitions:',
+             '2',
+             'vs',
+             '3.',
+             'WARNING:',
+             'Results',
+             'unreliable!',
+             '9+',
+             'repetitions',
+             'recommended.'],
+            ['medium', '-0.3750', '-0.3375', '8', '5', '80', '53'],
+            ['OVERALL_GEOMEAN', '+1.6405', '-0.6985', '0', '0', '0', '0']
+        ]
+        output_lines_with_header = print_difference_report(
+            self.json_diff_report, utest=True, utest_alpha=0.05, use_color=False)
+        output_lines = output_lines_with_header[2:]
+        print("\n")
+        print("\n".join(output_lines_with_header))
+        self.assertEqual(len(output_lines), len(expect_lines))
+        for i in range(0, len(output_lines)):
+            parts = [x for x in output_lines[i].split(' ') if x]
+            self.assertEqual(expect_lines[i], parts)
+
+    def test_json_diff_report_pretty_printing_aggregates_only(self):
+        expect_lines = [
+            ['BM_One', '-0.1000', '+0.1000', '10', '9', '100', '110'],
+            ['BM_Two_pvalue',
+             '1.0000',
+             '0.6667',
+             'U',
+             'Test,',
+             'Repetitions:',
+             '2',
+             'vs',
+             '2.',
+             'WARNING:',
+             'Results',
+             'unreliable!',
+             '9+',
+             'repetitions',
+             'recommended.'],
+            ['short', '-0.1250', '-0.0625', '8', '7', '80', '75'],
+            ['short', '-0.4325', '-0.1351', '8', '5', '77', '67'],
+            ['short_pvalue',
+             '0.7671',
+             '0.2000',
+             'U',
+             'Test,',
+             'Repetitions:',
+             '2',
+             'vs',
+             '3.',
+             'WARNING:',
+             'Results',
+             'unreliable!',
+             '9+',
+             'repetitions',
+             'recommended.'],
+            ['OVERALL_GEOMEAN', '+1.6405', '-0.6985', '0', '0', '0', '0']
+        ]
+        output_lines_with_header = print_difference_report(
+            self.json_diff_report, include_aggregates_only=True, utest=True, utest_alpha=0.05, use_color=False)
+        output_lines = output_lines_with_header[2:]
+        print("\n")
+        print("\n".join(output_lines_with_header))
+        self.assertEqual(len(output_lines), len(expect_lines))
+        for i in range(0, len(output_lines)):
+            parts = [x for x in output_lines[i].split(' ') if x]
+            self.assertEqual(expect_lines[i], parts)
+
+    def test_json_diff_report(self):
+        expected_output = [
+            {
+                'name': u'BM_One',
+                'measurements': [
+                    {'time': -0.1,
+                     'cpu': 0.1,
+                     'real_time': 10,
+                     'real_time_other': 9,
+                     'cpu_time': 100,
+                     'cpu_time_other': 110}
+                ],
+                'time_unit': 'ns',
+                'utest': {}
+            },
+            {
+                'name': u'BM_Two',
+                'measurements': [
+                    {'time': 0.1111111111111111,
+                     'cpu': -0.011111111111111112,
+                     'real_time': 9,
+                     'real_time_other': 10,
+                     'cpu_time': 90,
+                     'cpu_time_other': 89},
+                    {'time': -0.125, 'cpu': -0.16279069767441862, 'real_time': 8,
+                        'real_time_other': 7, 'cpu_time': 86, 'cpu_time_other': 72}
+                ],
+                'time_unit': 'ns',
+                'utest': {
+                    'have_optimal_repetitions': False, 'cpu_pvalue': 0.6666666666666666, 'time_pvalue': 1.0
+                }
+            },
+            {
+                'name': u'short',
+                'measurements': [
+                    {'time': -0.125,
+                     'cpu': -0.0625,
+                     'real_time': 8,
+                     'real_time_other': 7,
+                     'cpu_time': 80,
+                     'cpu_time_other': 75},
+                    {'time': -0.4325,
+                     'cpu': -0.13506493506493514,
+                     'real_time': 8,
+                     'real_time_other': 4.54,
+                     'cpu_time': 77,
+                     'cpu_time_other': 66.6}
+                ],
+                'time_unit': 'ns',
+                'utest': {
+                    'have_optimal_repetitions': False, 'cpu_pvalue': 0.2, 'time_pvalue': 0.7670968684102772
+                }
+            },
+            {
+                'name': u'medium',
+                'measurements': [
+                    {'time': -0.375,
+                     'cpu': -0.3375,
+                     'real_time': 8,
+                     'real_time_other': 5,
+                     'cpu_time': 80,
+                     'cpu_time_other': 53}
+                ],
+                'time_unit': 'ns',
+                'utest': {}
+            },
+            {
+                'name': 'OVERALL_GEOMEAN',
+                'measurements': [{'real_time': 8.48528137423858e-09, 'cpu_time': 8.441336246629233e-08,
+                                  'real_time_other': 2.2405267593145244e-08, 'cpu_time_other': 2.5453661413660466e-08,
+                                  'time': 1.6404861082353634, 'cpu': -0.6984640740519662}],
+                'time_unit': 's',
+                'run_type': 'aggregate',
+                'aggregate_name': 'geomean',
+                'utest': {}
+            }
+        ]
+        self.assertEqual(len(self.json_diff_report), len(expected_output))
+        for out, expected in zip(
+                self.json_diff_report, expected_output):
+            self.assertEqual(out['name'], expected['name'])
+            self.assertEqual(out['time_unit'], expected['time_unit'])
+            assert_utest(self, out, expected)
+            assert_measurements(self, out, expected)
+
+
+class TestReportDifferenceWithUTestWhileDisplayingAggregatesOnly(
+        unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        def load_results():
+            import json
+            testInputs = os.path.join(
+                os.path.dirname(
+                    os.path.realpath(__file__)),
+                'Inputs')
+            testOutput1 = os.path.join(testInputs, 'test3_run0.json')
+            testOutput2 = os.path.join(testInputs, 'test3_run1.json')
+            with open(testOutput1, 'r') as f:
+                json1 = json.load(f)
+            with open(testOutput2, 'r') as f:
+                json2 = json.load(f)
+            return json1, json2
+
+        json1, json2 = load_results()
+        cls.json_diff_report = get_difference_report(
+            json1, json2, utest=True)
+
+    def test_json_diff_report_pretty_printing(self):
+        expect_lines = [
+            ['BM_One', '-0.1000', '+0.1000', '10', '9', '100', '110'],
+            ['BM_Two', '+0.1111', '-0.0111', '9', '10', '90', '89'],
+            ['BM_Two', '-0.1250', '-0.1628', '8', '7', '86', '72'],
+            ['BM_Two_pvalue',
+             '1.0000',
+             '0.6667',
+             'U',
+             'Test,',
+             'Repetitions:',
+             '2',
+             'vs',
+             '2.',
+             'WARNING:',
+             'Results',
+             'unreliable!',
+             '9+',
+             'repetitions',
+             'recommended.'],
+            ['short', '-0.1250', '-0.0625', '8', '7', '80', '75'],
+            ['short', '-0.4325', '-0.1351', '8', '5', '77', '67'],
+            ['short_pvalue',
+             '0.7671',
+             '0.2000',
+             'U',
+             'Test,',
+             'Repetitions:',
+             '2',
+             'vs',
+             '3.',
+             'WARNING:',
+             'Results',
+             'unreliable!',
+             '9+',
+             'repetitions',
+             'recommended.'],
+            ['medium', '-0.3750', '-0.3375', '8', '5', '80', '53'],
+            ['OVERALL_GEOMEAN', '+1.6405', '-0.6985', '0', '0', '0', '0']
+        ]
+        output_lines_with_header = print_difference_report(
+            self.json_diff_report,
+            utest=True, utest_alpha=0.05, use_color=False)
+        output_lines = output_lines_with_header[2:]
+        print("\n")
+        print("\n".join(output_lines_with_header))
+        self.assertEqual(len(output_lines), len(expect_lines))
+        for i in range(0, len(output_lines)):
+            parts = [x for x in output_lines[i].split(' ') if x]
+            self.assertEqual(expect_lines[i], parts)
+
+    def test_json_diff_report(self):
+        expected_output = [
+            {
+                'name': u'BM_One',
+                'measurements': [
+                    {'time': -0.1,
+                     'cpu': 0.1,
+                     'real_time': 10,
+                     'real_time_other': 9,
+                     'cpu_time': 100,
+                     'cpu_time_other': 110}
+                ],
+                'time_unit': 'ns',
+                'utest': {}
+            },
+            {
+                'name': u'BM_Two',
+                'measurements': [
+                    {'time': 0.1111111111111111,
+                     'cpu': -0.011111111111111112,
+                     'real_time': 9,
+                     'real_time_other': 10,
+                     'cpu_time': 90,
+                     'cpu_time_other': 89},
+                    {'time': -0.125, 'cpu': -0.16279069767441862, 'real_time': 8,
+                        'real_time_other': 7, 'cpu_time': 86, 'cpu_time_other': 72}
+                ],
+                'time_unit': 'ns',
+                'utest': {
+                    'have_optimal_repetitions': False, 'cpu_pvalue': 0.6666666666666666, 'time_pvalue': 1.0
+                }
+            },
+            {
+                'name': u'short',
+                'measurements': [
+                    {'time': -0.125,
+                     'cpu': -0.0625,
+                     'real_time': 8,
+                     'real_time_other': 7,
+                     'cpu_time': 80,
+                     'cpu_time_other': 75},
+                    {'time': -0.4325,
+                     'cpu': -0.13506493506493514,
+                     'real_time': 8,
+                     'real_time_other': 4.54,
+                     'cpu_time': 77,
+                     'cpu_time_other': 66.6}
+                ],
+                'time_unit': 'ns',
+                'utest': {
+                    'have_optimal_repetitions': False, 'cpu_pvalue': 0.2, 'time_pvalue': 0.7670968684102772
+                }
+            },
+            {
+                'name': u'medium',
+                'measurements': [
+                    {'real_time_other': 5,
+                     'cpu_time': 80,
+                     'time': -0.375,
+                     'real_time': 8,
+                     'cpu_time_other': 53,
+                     'cpu': -0.3375
+                     }
+                ],
+                'utest': {},
+                'time_unit': u'ns',
+                'aggregate_name': ''
+            },
+            {
+                'name': 'OVERALL_GEOMEAN',
+                'measurements': [{'real_time': 8.48528137423858e-09, 'cpu_time': 8.441336246629233e-08,
+                                  'real_time_other': 2.2405267593145244e-08, 'cpu_time_other': 2.5453661413660466e-08,
+                                  'time': 1.6404861082353634, 'cpu': -0.6984640740519662}],
+                'time_unit': 's',
+                'run_type': 'aggregate',
+                'aggregate_name': 'geomean',
+                'utest': {}
+            }
+        ]
+        self.assertEqual(len(self.json_diff_report), len(expected_output))
+        for out, expected in zip(
+                self.json_diff_report, expected_output):
+            self.assertEqual(out['name'], expected['name'])
+            self.assertEqual(out['time_unit'], expected['time_unit'])
+            assert_utest(self, out, expected)
+            assert_measurements(self, out, expected)
+
+
+class TestReportDifferenceForPercentageAggregates(
+        unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        def load_results():
+            import json
+            testInputs = os.path.join(
+                os.path.dirname(
+                    os.path.realpath(__file__)),
+                'Inputs')
+            testOutput1 = os.path.join(testInputs, 'test4_run0.json')
+            testOutput2 = os.path.join(testInputs, 'test4_run1.json')
+            with open(testOutput1, 'r') as f:
+                json1 = json.load(f)
+            with open(testOutput2, 'r') as f:
+                json2 = json.load(f)
+            return json1, json2
+
+        json1, json2 = load_results()
+        cls.json_diff_report = get_difference_report(
+            json1, json2, utest=True)
+
+    def test_json_diff_report_pretty_printing(self):
+        expect_lines = [
+            ['whocares', '-0.5000', '+0.5000', '0', '0', '0', '0']
+        ]
+        output_lines_with_header = print_difference_report(
+            self.json_diff_report,
+            utest=True, utest_alpha=0.05, use_color=False)
+        output_lines = output_lines_with_header[2:]
+        print("\n")
+        print("\n".join(output_lines_with_header))
+        self.assertEqual(len(output_lines), len(expect_lines))
+        for i in range(0, len(output_lines)):
+            parts = [x for x in output_lines[i].split(' ') if x]
+            self.assertEqual(expect_lines[i], parts)
+
+    def test_json_diff_report(self):
+        expected_output = [
+            {
+                'name': u'whocares',
+                'measurements': [
+                    {'time': -0.5,
+                     'cpu': 0.5,
+                     'real_time': 0.01,
+                     'real_time_other': 0.005,
+                     'cpu_time': 0.10,
+                     'cpu_time_other': 0.15}
+                ],
+                'time_unit': 'ns',
+                'utest': {}
+            }
+        ]
+        self.assertEqual(len(self.json_diff_report), len(expected_output))
+        for out, expected in zip(
+                self.json_diff_report, expected_output):
+            self.assertEqual(out['name'], expected['name'])
+            self.assertEqual(out['time_unit'], expected['time_unit'])
+            assert_utest(self, out, expected)
+            assert_measurements(self, out, expected)
+
+
+class TestReportSorting(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        def load_result():
+            import json
+            testInputs = os.path.join(
+                os.path.dirname(
+                    os.path.realpath(__file__)),
+                'Inputs')
+            testOutput = os.path.join(testInputs, 'test4_run.json')
+            with open(testOutput, 'r') as f:
+                json = json.load(f)
+            return json
+
+        cls.json = load_result()
+
+    def test_json_diff_report_pretty_printing(self):
+        import util
+
+        expected_names = [
+            "99 family 0 instance 0 repetition 0",
+            "98 family 0 instance 0 repetition 1",
+            "97 family 0 instance 0 aggregate",
+            "96 family 0 instance 1 repetition 0",
+            "95 family 0 instance 1 repetition 1",
+            "94 family 0 instance 1 aggregate",
+            "93 family 1 instance 0 repetition 0",
+            "92 family 1 instance 0 repetition 1",
+            "91 family 1 instance 0 aggregate",
+            "90 family 1 instance 1 repetition 0",
+            "89 family 1 instance 1 repetition 1",
+            "88 family 1 instance 1 aggregate"
+        ]
+
+        for n in range(len(self.json['benchmarks']) ** 2):
+            random.shuffle(self.json['benchmarks'])
+            sorted_benchmarks = util.sort_benchmark_results(self.json)[
+                'benchmarks']
+            self.assertEqual(len(expected_names), len(sorted_benchmarks))
+            for out, expected in zip(sorted_benchmarks, expected_names):
+                self.assertEqual(out['name'], expected)
+
+
+def assert_utest(unittest_instance, lhs, rhs):
+    if lhs['utest']:
+        unittest_instance.assertAlmostEqual(
+            lhs['utest']['cpu_pvalue'],
+            rhs['utest']['cpu_pvalue'])
+        unittest_instance.assertAlmostEqual(
+            lhs['utest']['time_pvalue'],
+            rhs['utest']['time_pvalue'])
+        unittest_instance.assertEqual(
+            lhs['utest']['have_optimal_repetitions'],
+            rhs['utest']['have_optimal_repetitions'])
+    else:
+        # lhs is empty. assert if rhs is not.
+        unittest_instance.assertEqual(lhs['utest'], rhs['utest'])
+
+
+def assert_measurements(unittest_instance, lhs, rhs):
+    for m1, m2 in zip(lhs['measurements'], rhs['measurements']):
+        unittest_instance.assertEqual(m1['real_time'], m2['real_time'])
+        unittest_instance.assertEqual(m1['cpu_time'], m2['cpu_time'])
+        # m1['time'] and m1['cpu'] hold values which are being calculated,
+        # and therefore we must use almost-equal pattern.
+        unittest_instance.assertAlmostEqual(m1['time'], m2['time'], places=4)
+        unittest_instance.assertAlmostEqual(m1['cpu'], m2['cpu'], places=4)
+
+
+if __name__ == '__main__':
+    unittest.main()
+
+# vim: tabstop=4 expandtab shiftwidth=4 softtabstop=4
+# kate: tab-width: 4; replace-tabs on; indent-width 4; tab-indents: off;
+# kate: indent-mode python; remove-trailing-spaces modified;
diff --git a/leveldb_base/third_party/benchmark/tools/gbench/util.py b/leveldb_base/third_party/benchmark/tools/gbench/util.py
new file mode 100644
index 0000000..5e79da8
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/tools/gbench/util.py
@@ -0,0 +1,203 @@
+"""util.py - General utilities for running, loading, and processing benchmarks
+"""
+import json
+import os
+import re
+import subprocess
+import sys
+import tempfile
+
+
+# Input file type enumeration
+IT_Invalid = 0
+IT_JSON = 1
+IT_Executable = 2
+
+_num_magic_bytes = 2 if sys.platform.startswith('win') else 4
+
+
+def is_executable_file(filename):
+    """
+    Return 'True' if 'filename' names a valid file which is likely
+    an executable. A file is considered an executable if it starts with the
+    magic bytes for a EXE, Mach O, or ELF file.
+    """
+    if not os.path.isfile(filename):
+        return False
+    with open(filename, mode='rb') as f:
+        magic_bytes = f.read(_num_magic_bytes)
+    if sys.platform == 'darwin':
+        return magic_bytes in [
+            b'\xfe\xed\xfa\xce',  # MH_MAGIC
+            b'\xce\xfa\xed\xfe',  # MH_CIGAM
+            b'\xfe\xed\xfa\xcf',  # MH_MAGIC_64
+            b'\xcf\xfa\xed\xfe',  # MH_CIGAM_64
+            b'\xca\xfe\xba\xbe',  # FAT_MAGIC
+            b'\xbe\xba\xfe\xca'   # FAT_CIGAM
+        ]
+    elif sys.platform.startswith('win'):
+        return magic_bytes == b'MZ'
+    else:
+        return magic_bytes == b'\x7FELF'
+
+
+def is_json_file(filename):
+    """
+    Returns 'True' if 'filename' names a valid JSON output file.
+    'False' otherwise.
+    """
+    try:
+        with open(filename, 'r') as f:
+            json.load(f)
+        return True
+    except BaseException:
+        pass
+    return False
+
+
+def classify_input_file(filename):
+    """
+    Return a tuple (type, msg) where 'type' specifies the classified type
+    of 'filename'. If 'type' is 'IT_Invalid' then 'msg' is a human readable
+    string representing the error.
+    """
+    ftype = IT_Invalid
+    err_msg = None
+    if not os.path.exists(filename):
+        err_msg = "'%s' does not exist" % filename
+    elif not os.path.isfile(filename):
+        err_msg = "'%s' does not name a file" % filename
+    elif is_executable_file(filename):
+        ftype = IT_Executable
+    elif is_json_file(filename):
+        ftype = IT_JSON
+    else:
+        err_msg = "'%s' does not name a valid benchmark executable or JSON file" % filename
+    return ftype, err_msg
+
+
+def check_input_file(filename):
+    """
+    Classify the file named by 'filename' and return the classification.
+    If the file is classified as 'IT_Invalid' print an error message and exit
+    the program.
+    """
+    ftype, msg = classify_input_file(filename)
+    if ftype == IT_Invalid:
+        print("Invalid input file: %s" % msg)
+        sys.exit(1)
+    return ftype
+
+
+def find_benchmark_flag(prefix, benchmark_flags):
+    """
+    Search the specified list of flags for a flag matching `<prefix><arg>` and
+    if it is found return the arg it specifies. If specified more than once the
+    last value is returned. If the flag is not found None is returned.
+    """
+    assert prefix.startswith('--') and prefix.endswith('=')
+    result = None
+    for f in benchmark_flags:
+        if f.startswith(prefix):
+            result = f[len(prefix):]
+    return result
+
+
+def remove_benchmark_flags(prefix, benchmark_flags):
+    """
+    Return a new list containing the specified benchmark_flags except those
+    with the specified prefix.
+    """
+    assert prefix.startswith('--') and prefix.endswith('=')
+    return [f for f in benchmark_flags if not f.startswith(prefix)]
+
+
+def load_benchmark_results(fname, benchmark_filter):
+    """
+    Read benchmark output from a file and return the JSON object.
+
+    Apply benchmark_filter, a regular expression, with nearly the same
+    semantics of the --benchmark_filter argument.  May be None.
+    Note: the Python regular expression engine is used instead of the
+    one used by the C++ code, which may produce different results
+    in complex cases.
+
+    REQUIRES: 'fname' names a file containing JSON benchmark output.
+    """
+    def benchmark_wanted(benchmark):
+        if benchmark_filter is None:
+            return True
+        name = benchmark.get('run_name', None) or benchmark['name']
+        if re.search(benchmark_filter, name):
+            return True
+        return False
+
+    with open(fname, 'r') as f:
+        results = json.load(f)
+        if 'benchmarks' in results:
+            results['benchmarks'] = list(filter(benchmark_wanted,
+                                                results['benchmarks']))
+        return results
+
+
+def sort_benchmark_results(result):
+    benchmarks = result['benchmarks']
+
+    # From inner key to the outer key!
+    benchmarks = sorted(
+        benchmarks, key=lambda benchmark: benchmark['repetition_index'] if 'repetition_index' in benchmark else -1)
+    benchmarks = sorted(
+        benchmarks, key=lambda benchmark: 1 if 'run_type' in benchmark and benchmark['run_type'] == "aggregate" else 0)
+    benchmarks = sorted(
+        benchmarks, key=lambda benchmark: benchmark['per_family_instance_index'] if 'per_family_instance_index' in benchmark else -1)
+    benchmarks = sorted(
+        benchmarks, key=lambda benchmark: benchmark['family_index'] if 'family_index' in benchmark else -1)
+
+    result['benchmarks'] = benchmarks
+    return result
+
+
+def run_benchmark(exe_name, benchmark_flags):
+    """
+    Run a benchmark specified by 'exe_name' with the specified
+    'benchmark_flags'. The benchmark is run directly as a subprocess to preserve
+    real time console output.
+    RETURNS: A JSON object representing the benchmark output
+    """
+    output_name = find_benchmark_flag('--benchmark_out=',
+                                      benchmark_flags)
+    is_temp_output = False
+    if output_name is None:
+        is_temp_output = True
+        thandle, output_name = tempfile.mkstemp()
+        os.close(thandle)
+        benchmark_flags = list(benchmark_flags) + \
+            ['--benchmark_out=%s' % output_name]
+
+    cmd = [exe_name] + benchmark_flags
+    print("RUNNING: %s" % ' '.join(cmd))
+    exitCode = subprocess.call(cmd)
+    if exitCode != 0:
+        print('TEST FAILED...')
+        sys.exit(exitCode)
+    json_res = load_benchmark_results(output_name, None)
+    if is_temp_output:
+        os.unlink(output_name)
+    return json_res
+
+
+def run_or_load_benchmark(filename, benchmark_flags):
+    """
+    Get the results for a specified benchmark. If 'filename' specifies
+    an executable benchmark then the results are generated by running the
+    benchmark. Otherwise 'filename' must name a valid JSON output file,
+    which is loaded and the result returned.
+    """
+    ftype = check_input_file(filename)
+    if ftype == IT_JSON:
+        benchmark_filter = find_benchmark_flag('--benchmark_filter=',
+                                               benchmark_flags)
+        return load_benchmark_results(filename, benchmark_filter)
+    if ftype == IT_Executable:
+        return run_benchmark(filename, benchmark_flags)
+    raise ValueError('Unknown file type %s' % ftype)
diff --git a/leveldb_base/third_party/benchmark/tools/libpfm.BUILD.bazel b/leveldb_base/third_party/benchmark/tools/libpfm.BUILD.bazel
new file mode 100644
index 0000000..6269534
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/tools/libpfm.BUILD.bazel
@@ -0,0 +1,22 @@
+# Build rule for libpfm, which is required to collect performance counters for
+# BENCHMARK_ENABLE_LIBPFM builds.
+
+load("@rules_foreign_cc//foreign_cc:defs.bzl", "make")
+
+filegroup(
+    name = "pfm_srcs",
+    srcs = glob(["**"]),
+)
+
+make(
+    name = "libpfm",
+    lib_source = ":pfm_srcs",
+    lib_name = "libpfm",
+    copts = [
+        "-Wno-format-truncation",
+        "-Wno-use-after-free",
+    ],
+    visibility = [
+        "//visibility:public",
+    ],
+)
diff --git a/leveldb_base/third_party/benchmark/tools/requirements.txt b/leveldb_base/third_party/benchmark/tools/requirements.txt
new file mode 100644
index 0000000..3b3331b
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/tools/requirements.txt
@@ -0,0 +1 @@
+scipy>=1.5.0
\ No newline at end of file
diff --git a/leveldb_base/third_party/benchmark/tools/strip_asm.py b/leveldb_base/third_party/benchmark/tools/strip_asm.py
new file mode 100644
index 0000000..d131dc7
--- /dev/null
+++ b/leveldb_base/third_party/benchmark/tools/strip_asm.py
@@ -0,0 +1,151 @@
+#!/usr/bin/env python3
+
+"""
+strip_asm.py - Cleanup ASM output for the specified file
+"""
+
+from argparse import ArgumentParser
+import sys
+import os
+import re
+
+def find_used_labels(asm):
+    found = set()
+    label_re = re.compile("\s*j[a-z]+\s+\.L([a-zA-Z0-9][a-zA-Z0-9_]*)")
+    for l in asm.splitlines():
+        m = label_re.match(l)
+        if m:
+            found.add('.L%s' % m.group(1))
+    return found
+
+
+def normalize_labels(asm):
+    decls = set()
+    label_decl = re.compile("^[.]{0,1}L([a-zA-Z0-9][a-zA-Z0-9_]*)(?=:)")
+    for l in asm.splitlines():
+        m = label_decl.match(l)
+        if m:
+            decls.add(m.group(0))
+    if len(decls) == 0:
+        return asm
+    needs_dot = next(iter(decls))[0] != '.'
+    if not needs_dot:
+        return asm
+    for ld in decls:
+        asm = re.sub("(^|\s+)" + ld + "(?=:|\s)", '\\1.' + ld, asm)
+    return asm
+
+
+def transform_labels(asm):
+    asm = normalize_labels(asm)
+    used_decls = find_used_labels(asm)
+    new_asm = ''
+    label_decl = re.compile("^\.L([a-zA-Z0-9][a-zA-Z0-9_]*)(?=:)")
+    for l in asm.splitlines():
+        m = label_decl.match(l)
+        if not m or m.group(0) in used_decls:
+            new_asm += l
+            new_asm += '\n'
+    return new_asm
+
+
+def is_identifier(tk):
+    if len(tk) == 0:
+        return False
+    first = tk[0]
+    if not first.isalpha() and first != '_':
+        return False
+    for i in range(1, len(tk)):
+        c = tk[i]
+        if not c.isalnum() and c != '_':
+            return False
+    return True
+
+def process_identifiers(l):
+    """
+    process_identifiers - process all identifiers and modify them to have
+    consistent names across all platforms; specifically across ELF and MachO.
+    For example, MachO inserts an additional understore at the beginning of
+    names. This function removes that.
+    """
+    parts = re.split(r'([a-zA-Z0-9_]+)', l)
+    new_line = ''
+    for tk in parts:
+        if is_identifier(tk):
+            if tk.startswith('__Z'):
+                tk = tk[1:]
+            elif tk.startswith('_') and len(tk) > 1 and \
+                    tk[1].isalpha() and tk[1] != 'Z':
+                tk = tk[1:]
+        new_line += tk
+    return new_line
+
+
+def process_asm(asm):
+    """
+    Strip the ASM of unwanted directives and lines
+    """
+    new_contents = ''
+    asm = transform_labels(asm)
+
+    # TODO: Add more things we want to remove
+    discard_regexes = [
+        re.compile("\s+\..*$"), # directive
+        re.compile("\s*#(NO_APP|APP)$"), #inline ASM
+        re.compile("\s*#.*$"), # comment line
+        re.compile("\s*\.globa?l\s*([.a-zA-Z_][a-zA-Z0-9$_.]*)"), #global directive
+        re.compile("\s*\.(string|asciz|ascii|[1248]?byte|short|word|long|quad|value|zero)"),
+    ]
+    keep_regexes = [
+
+    ]
+    fn_label_def = re.compile("^[a-zA-Z_][a-zA-Z0-9_.]*:")
+    for l in asm.splitlines():
+        # Remove Mach-O attribute
+        l = l.replace('@GOTPCREL', '')
+        add_line = True
+        for reg in discard_regexes:
+            if reg.match(l) is not None:
+                add_line = False
+                break
+        for reg in keep_regexes:
+            if reg.match(l) is not None:
+                add_line = True
+                break
+        if add_line:
+            if fn_label_def.match(l) and len(new_contents) != 0:
+                new_contents += '\n'
+            l = process_identifiers(l)
+            new_contents += l
+            new_contents += '\n'
+    return new_contents
+
+def main():
+    parser = ArgumentParser(
+        description='generate a stripped assembly file')
+    parser.add_argument(
+        'input', metavar='input', type=str, nargs=1,
+        help='An input assembly file')
+    parser.add_argument(
+        'out', metavar='output', type=str, nargs=1,
+        help='The output file')
+    args, unknown_args = parser.parse_known_args()
+    input = args.input[0]
+    output = args.out[0]
+    if not os.path.isfile(input):
+        print(("ERROR: input file '%s' does not exist") % input)
+        sys.exit(1)
+    contents = None
+    with open(input, 'r') as f:
+        contents = f.read()
+    new_contents = process_asm(contents)
+    with open(output, 'w') as f:
+        f.write(new_contents)
+
+
+if __name__ == '__main__':
+    main()
+
+# vim: tabstop=4 expandtab shiftwidth=4 softtabstop=4
+# kate: tab-width: 4; replace-tabs on; indent-width 4; tab-indents: off;
+# kate: indent-mode python; remove-trailing-spaces modified;
diff --git a/leveldb_base/third_party/googletest/.clang-format b/leveldb_base/third_party/googletest/.clang-format
new file mode 100644
index 0000000..5b9bfe6
--- /dev/null
+++ b/leveldb_base/third_party/googletest/.clang-format
@@ -0,0 +1,4 @@
+# Run manually to reformat a file:
+# clang-format -i --style=file <file>
+Language:        Cpp
+BasedOnStyle:  Google
diff --git a/leveldb_base/third_party/googletest/.github/ISSUE_TEMPLATE/00-bug_report.md b/leveldb_base/third_party/googletest/.github/ISSUE_TEMPLATE/00-bug_report.md
new file mode 100644
index 0000000..0f7e8b5
--- /dev/null
+++ b/leveldb_base/third_party/googletest/.github/ISSUE_TEMPLATE/00-bug_report.md
@@ -0,0 +1,43 @@
+---
+name: Bug report
+about: Create a report to help us improve
+title: ''
+labels: 'bug'
+assignees: ''
+---
+
+**Describe the bug**
+
+Include a clear and concise description of what the problem is, including what
+you expected to happen, and what actually happened.
+
+**Steps to reproduce the bug**
+
+It's important that we are able to reproduce the problem that you are
+experiencing. Please provide all code and relevant steps to reproduce the
+problem, including your `BUILD`/`CMakeLists.txt` file and build commands. Links
+to a GitHub branch or [godbolt.org](https://godbolt.org/) that demonstrate the
+problem are also helpful.
+
+**Does the bug persist in the most recent commit?**
+
+We recommend using the latest commit in the master branch in your projects.
+
+**What operating system and version are you using?**
+
+If you are using a Linux distribution please include the name and version of the
+distribution as well.
+
+**What compiler and version are you using?**
+
+Please include the output of `gcc -v` or `clang -v`, or the equivalent for your
+compiler.
+
+**What build system are you using?**
+
+Please include the output of `bazel --version` or `cmake --version`, or the
+equivalent for your build system.
+
+**Additional context**
+
+Add any other context about the problem here.
diff --git a/leveldb_base/third_party/googletest/.github/ISSUE_TEMPLATE/config.yml b/leveldb_base/third_party/googletest/.github/ISSUE_TEMPLATE/config.yml
new file mode 100644
index 0000000..3ba13e0
--- /dev/null
+++ b/leveldb_base/third_party/googletest/.github/ISSUE_TEMPLATE/config.yml
@@ -0,0 +1 @@
+blank_issues_enabled: false
diff --git a/leveldb_base/third_party/googletest/.gitignore b/leveldb_base/third_party/googletest/.gitignore
new file mode 100644
index 0000000..f08cb72
--- /dev/null
+++ b/leveldb_base/third_party/googletest/.gitignore
@@ -0,0 +1,84 @@
+# Ignore CI build directory
+build/
+xcuserdata
+cmake-build-debug/
+.idea/
+bazel-bin
+bazel-genfiles
+bazel-googletest
+bazel-out
+bazel-testlogs
+# python
+*.pyc
+
+# Visual Studio files
+.vs
+*.sdf
+*.opensdf
+*.VC.opendb
+*.suo
+*.user
+_ReSharper.Caches/
+Win32-Debug/
+Win32-Release/
+x64-Debug/
+x64-Release/
+
+# Ignore autoconf / automake files
+Makefile.in
+aclocal.m4
+configure
+build-aux/
+autom4te.cache/
+googletest/m4/libtool.m4
+googletest/m4/ltoptions.m4
+googletest/m4/ltsugar.m4
+googletest/m4/ltversion.m4
+googletest/m4/lt~obsolete.m4
+googlemock/m4
+
+# Ignore generated directories.
+googlemock/fused-src/
+googletest/fused-src/
+
+# macOS files
+.DS_Store
+googletest/.DS_Store
+googletest/xcode/.DS_Store
+
+# Ignore cmake generated directories and files.
+CMakeFiles
+CTestTestfile.cmake
+Makefile
+cmake_install.cmake
+googlemock/CMakeFiles
+googlemock/CTestTestfile.cmake
+googlemock/Makefile
+googlemock/cmake_install.cmake
+googlemock/gtest
+/bin
+/googlemock/gmock.dir
+/googlemock/gmock_main.dir
+/googlemock/RUN_TESTS.vcxproj.filters
+/googlemock/RUN_TESTS.vcxproj
+/googlemock/INSTALL.vcxproj.filters
+/googlemock/INSTALL.vcxproj
+/googlemock/gmock_main.vcxproj.filters
+/googlemock/gmock_main.vcxproj
+/googlemock/gmock.vcxproj.filters
+/googlemock/gmock.vcxproj
+/googlemock/gmock.sln
+/googlemock/ALL_BUILD.vcxproj.filters
+/googlemock/ALL_BUILD.vcxproj
+/lib
+/Win32
+/ZERO_CHECK.vcxproj.filters
+/ZERO_CHECK.vcxproj
+/RUN_TESTS.vcxproj.filters
+/RUN_TESTS.vcxproj
+/INSTALL.vcxproj.filters
+/INSTALL.vcxproj
+/googletest-distribution.sln
+/CMakeCache.txt
+/ALL_BUILD.vcxproj.filters
+/ALL_BUILD.vcxproj
diff --git a/leveldb_base/third_party/googletest/.travis.yml b/leveldb_base/third_party/googletest/.travis.yml
new file mode 100644
index 0000000..982e99c
--- /dev/null
+++ b/leveldb_base/third_party/googletest/.travis.yml
@@ -0,0 +1,61 @@
+# Build matrix / environment variable are explained on:
+# https://docs.travis-ci.com/user/customizing-the-build/
+# This file can be validated on:
+# http://lint.travis-ci.org/
+
+language: cpp
+
+# Define the matrix explicitly, manually expanding the combinations of (os, compiler, env).
+# It is more tedious, but grants us far more flexibility.
+matrix:
+  include:
+    - os: linux
+      dist: bionic
+      compiler: gcc
+      install: ./ci/install-linux.sh && ./ci/log-config.sh
+      script: ./ci/build-linux-bazel.sh
+    - os: linux
+      dist: bionic
+      compiler: clang
+      install: ./ci/install-linux.sh && ./ci/log-config.sh
+      script: ./ci/build-linux-bazel.sh
+    - os: linux
+      dist: bionic
+      compiler: gcc
+      env: BUILD_TYPE=Debug CXX_FLAGS="-std=c++11 -Wdeprecated"
+    - os: linux
+      dist: bionic
+      compiler: clang
+      env: BUILD_TYPE=Release CXX_FLAGS="-std=c++11 -Wdeprecated" NO_EXCEPTION=ON NO_RTTI=ON COMPILER_IS_GNUCXX=ON
+    - os: osx
+      osx_image: xcode12.2
+      compiler: gcc
+      env: BUILD_TYPE=Release CC=gcc-10 CXX=g++-10 CXX_FLAGS="-std=c++11 -Wdeprecated" HOMEBREW_LOGS=~/homebrew-logs HOMEBREW_TEMP=~/homebrew-temp
+    - os: osx
+      osx_image: xcode12.2
+      compiler: clang
+      env: BUILD_TYPE=Release CXX_FLAGS="-std=c++11 -Wdeprecated" HOMEBREW_LOGS=~/homebrew-logs HOMEBREW_TEMP=~/homebrew-temp
+
+# These are the install and build (script) phases for the most common entries in the matrix.  They could be included
+# in each entry in the matrix, but that is just repetitive.
+install:
+  - ./ci/install-${TRAVIS_OS_NAME}.sh
+  - . ./ci/env-${TRAVIS_OS_NAME}.sh
+  - ./ci/log-config.sh
+
+script: ./ci/travis.sh
+
+# This section installs the necessary dependencies.
+addons:
+  apt:
+    packages:
+    - g++
+    - clang
+    update: true
+  homebrew:
+    packages:
+    - gcc@10
+    update: true
+
+notifications:
+  email: false
diff --git a/leveldb_base/third_party/googletest/BUILD.bazel b/leveldb_base/third_party/googletest/BUILD.bazel
new file mode 100644
index 0000000..14661b6
--- /dev/null
+++ b/leveldb_base/third_party/googletest/BUILD.bazel
@@ -0,0 +1,200 @@
+# Copyright 2017 Google Inc.
+# All Rights Reserved.
+#
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#
+#   Bazel Build for Google C++ Testing Framework(Google Test)
+
+load("@rules_cc//cc:defs.bzl", "cc_library", "cc_test")
+
+package(default_visibility = ["//visibility:public"])
+
+licenses(["notice"])
+
+exports_files(["LICENSE"])
+
+config_setting(
+    name = "windows",
+    constraint_values = ["@platforms//os:windows"],
+)
+
+config_setting(
+    name = "msvc_compiler",
+    flag_values = {
+        "@bazel_tools//tools/cpp:compiler": "msvc-cl",
+    },
+    visibility = [":__subpackages__"],
+)
+
+config_setting(
+    name = "has_absl",
+    values = {"define": "absl=1"},
+)
+
+config_setting(
+    name = "ios",
+    values = {"apple_platform_type": "ios"},
+    visibility = [":__subpackages__"],
+)
+
+# Library that defines the FRIEND_TEST macro.
+cc_library(
+    name = "gtest_prod",
+    hdrs = ["googletest/include/gtest/gtest_prod.h"],
+    includes = ["googletest/include"],
+)
+
+# Google Test including Google Mock
+cc_library(
+    name = "gtest",
+    srcs = glob(
+        include = [
+            "googletest/src/*.cc",
+            "googletest/src/*.h",
+            "googletest/include/gtest/**/*.h",
+            "googlemock/src/*.cc",
+            "googlemock/include/gmock/**/*.h",
+        ],
+        exclude = [
+            "googletest/src/gtest-all.cc",
+            "googletest/src/gtest_main.cc",
+            "googlemock/src/gmock-all.cc",
+            "googlemock/src/gmock_main.cc",
+        ],
+    ),
+    hdrs = glob([
+        "googletest/include/gtest/*.h",
+        "googlemock/include/gmock/*.h",
+    ]),
+    copts = select({
+        ":ios": [
+            "-xobjective-c++",
+            "-pthread",
+        ],
+        ":windows": [],
+        "//conditions:default": ["-pthread"],
+    }),
+    defines = select({
+        ":has_absl": ["GTEST_HAS_ABSL=1"],
+        "//conditions:default": [],
+    }),
+    features = select({
+        ":windows": ["windows_export_all_symbols"],
+        "//conditions:default": [],
+    }),
+    includes = [
+        "googlemock",
+        "googlemock/include",
+        "googletest",
+        "googletest/include",
+    ],
+    linkopts = select({
+        ":windows": [],
+        "//conditions:default": ["-pthread"],
+    }),
+    deps = select({
+        ":has_absl": [
+            "@com_google_absl//absl/debugging:failure_signal_handler",
+            "@com_google_absl//absl/debugging:stacktrace",
+            "@com_google_absl//absl/debugging:symbolize",
+            "@com_google_absl//absl/strings",
+            "@com_google_absl//absl/types:any",
+            "@com_google_absl//absl/types:optional",
+            "@com_google_absl//absl/types:variant",
+        ],
+        "//conditions:default": [],
+    }),
+)
+
+cc_library(
+    name = "gtest_main",
+    srcs = ["googlemock/src/gmock_main.cc"],
+    features = select({
+        ":windows": ["windows_export_all_symbols"],
+        "//conditions:default": [],
+    }),
+    deps = [":gtest"],
+)
+
+# The following rules build samples of how to use gTest.
+cc_library(
+    name = "gtest_sample_lib",
+    srcs = [
+        "googletest/samples/sample1.cc",
+        "googletest/samples/sample2.cc",
+        "googletest/samples/sample4.cc",
+    ],
+    hdrs = [
+        "googletest/samples/prime_tables.h",
+        "googletest/samples/sample1.h",
+        "googletest/samples/sample2.h",
+        "googletest/samples/sample3-inl.h",
+        "googletest/samples/sample4.h",
+    ],
+    features = select({
+        ":windows": ["windows_export_all_symbols"],
+        "//conditions:default": [],
+    }),
+)
+
+cc_test(
+    name = "gtest_samples",
+    size = "small",
+    # All Samples except:
+    #   sample9 (main)
+    #   sample10 (main and takes a command line option and needs to be separate)
+    srcs = [
+        "googletest/samples/sample1_unittest.cc",
+        "googletest/samples/sample2_unittest.cc",
+        "googletest/samples/sample3_unittest.cc",
+        "googletest/samples/sample4_unittest.cc",
+        "googletest/samples/sample5_unittest.cc",
+        "googletest/samples/sample6_unittest.cc",
+        "googletest/samples/sample7_unittest.cc",
+        "googletest/samples/sample8_unittest.cc",
+    ],
+    linkstatic = 0,
+    deps = [
+        "gtest_sample_lib",
+        ":gtest_main",
+    ],
+)
+
+cc_test(
+    name = "sample9_unittest",
+    size = "small",
+    srcs = ["googletest/samples/sample9_unittest.cc"],
+    deps = [":gtest"],
+)
+
+cc_test(
+    name = "sample10_unittest",
+    size = "small",
+    srcs = ["googletest/samples/sample10_unittest.cc"],
+    deps = [":gtest"],
+)
diff --git a/leveldb_base/third_party/googletest/CMakeLists.txt b/leveldb_base/third_party/googletest/CMakeLists.txt
new file mode 100644
index 0000000..12fd745
--- /dev/null
+++ b/leveldb_base/third_party/googletest/CMakeLists.txt
@@ -0,0 +1,32 @@
+# Note: CMake support is community-based. The maintainers do not use CMake
+# internally.
+
+cmake_minimum_required(VERSION 2.8.12)
+
+if (POLICY CMP0048)
+  cmake_policy(SET CMP0048 NEW)
+endif (POLICY CMP0048)
+
+project(googletest-distribution)
+set(GOOGLETEST_VERSION 1.10.0)
+
+if (CMAKE_VERSION VERSION_GREATER "3.0.2")
+  if(NOT CYGWIN AND NOT MSYS AND NOT ${CMAKE_SYSTEM_NAME} STREQUAL QNX)
+    set(CMAKE_CXX_EXTENSIONS OFF)
+  endif()
+endif()
+
+enable_testing()
+
+include(CMakeDependentOption)
+include(GNUInstallDirs)
+
+#Note that googlemock target already builds googletest
+option(BUILD_GMOCK "Builds the googlemock subproject" ON)
+option(INSTALL_GTEST "Enable installation of googletest. (Projects embedding googletest may want to turn this OFF.)" ON)
+
+if(BUILD_GMOCK)
+  add_subdirectory( googlemock )
+else()
+  add_subdirectory( googletest )
+endif()
diff --git a/leveldb_base/third_party/googletest/CONTRIBUTING.md b/leveldb_base/third_party/googletest/CONTRIBUTING.md
new file mode 100644
index 0000000..da45e44
--- /dev/null
+++ b/leveldb_base/third_party/googletest/CONTRIBUTING.md
@@ -0,0 +1,130 @@
+# How to become a contributor and submit your own code
+
+## Contributor License Agreements
+
+We'd love to accept your patches! Before we can take them, we have to jump a
+couple of legal hurdles.
+
+Please fill out either the individual or corporate Contributor License Agreement
+(CLA).
+
+*   If you are an individual writing original source code and you're sure you
+    own the intellectual property, then you'll need to sign an
+    [individual CLA](https://developers.google.com/open-source/cla/individual).
+*   If you work for a company that wants to allow you to contribute your work,
+    then you'll need to sign a
+    [corporate CLA](https://developers.google.com/open-source/cla/corporate).
+
+Follow either of the two links above to access the appropriate CLA and
+instructions for how to sign and return it. Once we receive it, we'll be able to
+accept your pull requests.
+
+## Are you a Googler?
+
+If you are a Googler, please make an attempt to submit an internal change rather
+than a GitHub Pull Request. If you are not able to submit an internal change a
+PR is acceptable as an alternative.
+
+## Contributing A Patch
+
+1.  Submit an issue describing your proposed change to the
+    [issue tracker](https://github.com/google/googletest/issues).
+2.  Please don't mix more than one logical change per submittal, because it
+    makes the history hard to follow. If you want to make a change that doesn't
+    have a corresponding issue in the issue tracker, please create one.
+3.  Also, coordinate with team members that are listed on the issue in question.
+    This ensures that work isn't being duplicated and communicating your plan
+    early also generally leads to better patches.
+4.  If your proposed change is accepted, and you haven't already done so, sign a
+    Contributor License Agreement (see details above).
+5.  Fork the desired repo, develop and test your code changes.
+6.  Ensure that your code adheres to the existing style in the sample to which
+    you are contributing.
+7.  Ensure that your code has an appropriate set of unit tests which all pass.
+8.  Submit a pull request.
+
+## The Google Test and Google Mock Communities
+
+The Google Test community exists primarily through the
+[discussion group](http://groups.google.com/group/googletestframework) and the
+GitHub repository. Likewise, the Google Mock community exists primarily through
+their own [discussion group](http://groups.google.com/group/googlemock). You are
+definitely encouraged to contribute to the discussion and you can also help us
+to keep the effectiveness of the group high by following and promoting the
+guidelines listed here.
+
+### Please Be Friendly
+
+Showing courtesy and respect to others is a vital part of the Google culture,
+and we strongly encourage everyone participating in Google Test development to
+join us in accepting nothing less. Of course, being courteous is not the same as
+failing to constructively disagree with each other, but it does mean that we
+should be respectful of each other when enumerating the 42 technical reasons
+that a particular proposal may not be the best choice. There's never a reason to
+be antagonistic or dismissive toward anyone who is sincerely trying to
+contribute to a discussion.
+
+Sure, C++ testing is serious business and all that, but it's also a lot of fun.
+Let's keep it that way. Let's strive to be one of the friendliest communities in
+all of open source.
+
+As always, discuss Google Test in the official GoogleTest discussion group. You
+don't have to actually submit code in order to sign up. Your participation
+itself is a valuable contribution.
+
+## Style
+
+To keep the source consistent, readable, diffable and easy to merge, we use a
+fairly rigid coding style, as defined by the
+[google-styleguide](https://github.com/google/styleguide) project. All patches
+will be expected to conform to the style outlined
+[here](https://google.github.io/styleguide/cppguide.html). Use
+[.clang-format](https://github.com/google/googletest/blob/master/.clang-format)
+to check your formatting.
+
+## Requirements for Contributors
+
+If you plan to contribute a patch, you need to build Google Test, Google Mock,
+and their own tests from a git checkout, which has further requirements:
+
+*   [Python](https://www.python.org/) v2.3 or newer (for running some of the
+    tests and re-generating certain source files from templates)
+*   [CMake](https://cmake.org/) v2.8.12 or newer
+
+## Developing Google Test and Google Mock
+
+This section discusses how to make your own changes to the Google Test project.
+
+### Testing Google Test and Google Mock Themselves
+
+To make sure your changes work as intended and don't break existing
+functionality, you'll want to compile and run Google Test and GoogleMock's own
+tests. For that you can use CMake:
+
+    mkdir mybuild
+    cd mybuild
+    cmake -Dgtest_build_tests=ON -Dgmock_build_tests=ON ${GTEST_REPO_DIR}
+
+To choose between building only Google Test or Google Mock, you may modify your
+cmake command to be one of each
+
+    cmake -Dgtest_build_tests=ON ${GTEST_DIR} # sets up Google Test tests
+    cmake -Dgmock_build_tests=ON ${GMOCK_DIR} # sets up Google Mock tests
+
+Make sure you have Python installed, as some of Google Test's tests are written
+in Python. If the cmake command complains about not being able to find Python
+(`Could NOT find PythonInterp (missing: PYTHON_EXECUTABLE)`), try telling it
+explicitly where your Python executable can be found:
+
+    cmake -DPYTHON_EXECUTABLE=path/to/python ...
+
+Next, you can build Google Test and / or Google Mock and all desired tests. On
+\*nix, this is usually done by
+
+    make
+
+To run the tests, do
+
+    make test
+
+All tests should pass.
diff --git a/leveldb_base/third_party/googletest/CONTRIBUTORS b/leveldb_base/third_party/googletest/CONTRIBUTORS
new file mode 100644
index 0000000..76db0b4
--- /dev/null
+++ b/leveldb_base/third_party/googletest/CONTRIBUTORS
@@ -0,0 +1,63 @@
+# This file contains a list of people who've made non-trivial
+# contribution to the Google C++ Testing Framework project.  People
+# who commit code to the project are encouraged to add their names
+# here.  Please keep the list sorted by first names.
+
+Ajay Joshi <jaj@google.com>
+Balázs Dán <balazs.dan@gmail.com>
+Benoit Sigoure <tsuna@google.com>
+Bharat Mediratta <bharat@menalto.com>
+Bogdan Piloca <boo@google.com>
+Chandler Carruth <chandlerc@google.com>
+Chris Prince <cprince@google.com>
+Chris Taylor <taylorc@google.com>
+Dan Egnor <egnor@google.com>
+Dave MacLachlan <dmaclach@gmail.com>
+David Anderson <danderson@google.com>
+Dean Sturtevant
+Eric Roman <eroman@chromium.org>
+Gene Volovich <gv@cite.com>
+Hady Zalek <hady.zalek@gmail.com>
+Hal Burch <gmock@hburch.com>
+Jeffrey Yasskin <jyasskin@google.com>
+Jim Keller <jimkeller@google.com>
+Joe Walnes <joe@truemesh.com>
+Jon Wray <jwray@google.com>
+Jói Sigurðsson <joi@google.com>
+Keir Mierle <mierle@gmail.com>
+Keith Ray <keith.ray@gmail.com>
+Kenton Varda <kenton@google.com>
+Kostya Serebryany <kcc@google.com>
+Krystian Kuzniarek <krystian.kuzniarek@gmail.com>
+Lev Makhlis
+Manuel Klimek <klimek@google.com>
+Mario Tanev <radix@google.com>
+Mark Paskin
+Markus Heule <markus.heule@gmail.com>
+Matthew Simmons <simmonmt@acm.org>
+Mika Raento <mikie@iki.fi>
+Mike Bland <mbland@google.com>
+Miklós Fazekas <mfazekas@szemafor.com>
+Neal Norwitz <nnorwitz@gmail.com>
+Nermin Ozkiranartli <nermin@google.com>
+Owen Carlsen <ocarlsen@google.com>
+Paneendra Ba <paneendra@google.com>
+Pasi Valminen <pasi.valminen@gmail.com>
+Patrick Hanna <phanna@google.com>
+Patrick Riley <pfr@google.com>
+Paul Menage <menage@google.com>
+Peter Kaminski <piotrk@google.com>
+Piotr Kaminski <piotrk@google.com>
+Preston Jackson <preston.a.jackson@gmail.com>
+Rainer Klaffenboeck <rainer.klaffenboeck@dynatrace.com>
+Russ Cox <rsc@google.com>
+Russ Rufer <russ@pentad.com>
+Sean Mcafee <eefacm@gmail.com>
+Sigurður Ásgeirsson <siggi@google.com>
+Sverre Sundsdal <sundsdal@gmail.com>
+Takeshi Yoshino <tyoshino@google.com>
+Tracy Bialik <tracy@pentad.com>
+Vadim Berman <vadimb@google.com>
+Vlad Losev <vladl@google.com>
+Wolfgang Klier <wklier@google.com>
+Zhanyong Wan <wan@google.com>
diff --git a/leveldb_base/third_party/googletest/LICENSE b/leveldb_base/third_party/googletest/LICENSE
new file mode 100644
index 0000000..1941a11
--- /dev/null
+++ b/leveldb_base/third_party/googletest/LICENSE
@@ -0,0 +1,28 @@
+Copyright 2008, Google Inc.
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+    * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+    * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/leveldb_base/third_party/googletest/README.md b/leveldb_base/third_party/googletest/README.md
new file mode 100644
index 0000000..7d872a5
--- /dev/null
+++ b/leveldb_base/third_party/googletest/README.md
@@ -0,0 +1,140 @@
+# GoogleTest
+
+### Announcements
+
+#### Live at Head
+
+GoogleTest now follows the
+[Abseil Live at Head philosophy](https://abseil.io/about/philosophy#upgrade-support).
+We recommend using the latest commit in the `master` branch in your projects.
+
+#### Documentation Updates
+
+Our documentation is now live on GitHub Pages at
+https://google.github.io/googletest/. We recommend browsing the documentation on
+GitHub Pages rather than directly in the repository.
+
+#### Release 1.10.x
+
+[Release 1.10.x](https://github.com/google/googletest/releases/tag/release-1.10.0)
+is now available.
+
+#### Coming Soon
+
+*   We are planning to take a dependency on
+    [Abseil](https://github.com/abseil/abseil-cpp).
+*   More documentation improvements are planned.
+
+## Welcome to **GoogleTest**, Google's C++ test framework!
+
+This repository is a merger of the formerly separate GoogleTest and GoogleMock
+projects. These were so closely related that it makes sense to maintain and
+release them together.
+
+### Getting Started
+
+See the [GoogleTest User's Guide](https://google.github.io/googletest/) for
+documentation. We recommend starting with the
+[GoogleTest Primer](https://google.github.io/googletest/primer.html).
+
+More information about building GoogleTest can be found at
+[googletest/README.md](googletest/README.md).
+
+## Features
+
+*   An [xUnit](https://en.wikipedia.org/wiki/XUnit) test framework.
+*   Test discovery.
+*   A rich set of assertions.
+*   User-defined assertions.
+*   Death tests.
+*   Fatal and non-fatal failures.
+*   Value-parameterized tests.
+*   Type-parameterized tests.
+*   Various options for running the tests.
+*   XML test report generation.
+
+## Supported Platforms
+
+GoogleTest requires a codebase and compiler compliant with the C++11 standard or
+newer.
+
+The GoogleTest code is officially supported on the following platforms.
+Operating systems or tools not listed below are community-supported. For
+community-supported platforms, patches that do not complicate the code may be
+considered.
+
+If you notice any problems on your platform, please file an issue on the
+[GoogleTest GitHub Issue Tracker](https://github.com/google/googletest/issues).
+Pull requests containing fixes are welcome!
+
+### Operating Systems
+
+*   Linux
+*   macOS
+*   Windows
+
+### Compilers
+
+*   gcc 5.0+
+*   clang 5.0+
+*   MSVC 2015+
+
+**macOS users:** Xcode 9.3+ provides clang 5.0+.
+
+### Build Systems
+
+*   [Bazel](https://bazel.build/)
+*   [CMake](https://cmake.org/)
+
+**Note:** Bazel is the build system used by the team internally and in tests.
+CMake is supported on a best-effort basis and by the community.
+
+## Who Is Using GoogleTest?
+
+In addition to many internal projects at Google, GoogleTest is also used by the
+following notable projects:
+
+*   The [Chromium projects](http://www.chromium.org/) (behind the Chrome browser
+    and Chrome OS).
+*   The [LLVM](http://llvm.org/) compiler.
+*   [Protocol Buffers](https://github.com/google/protobuf), Google's data
+    interchange format.
+*   The [OpenCV](http://opencv.org/) computer vision library.
+
+## Related Open Source Projects
+
+[GTest Runner](https://github.com/nholthaus/gtest-runner) is a Qt5 based
+automated test-runner and Graphical User Interface with powerful features for
+Windows and Linux platforms.
+
+[GoogleTest UI](https://github.com/ospector/gtest-gbar) is a test runner that
+runs your test binary, allows you to track its progress via a progress bar, and
+displays a list of test failures. Clicking on one shows failure text. Google
+Test UI is written in C#.
+
+[GTest TAP Listener](https://github.com/kinow/gtest-tap-listener) is an event
+listener for GoogleTest that implements the
+[TAP protocol](https://en.wikipedia.org/wiki/Test_Anything_Protocol) for test
+result output. If your test runner understands TAP, you may find it useful.
+
+[gtest-parallel](https://github.com/google/gtest-parallel) is a test runner that
+runs tests from your binary in parallel to provide significant speed-up.
+
+[GoogleTest Adapter](https://marketplace.visualstudio.com/items?itemName=DavidSchuldenfrei.gtest-adapter)
+is a VS Code extension allowing to view GoogleTest in a tree view, and run/debug
+your tests.
+
+[C++ TestMate](https://github.com/matepek/vscode-catch2-test-adapter) is a VS
+Code extension allowing to view GoogleTest in a tree view, and run/debug your
+tests.
+
+[Cornichon](https://pypi.org/project/cornichon/) is a small Gherkin DSL parser
+that generates stub code for GoogleTest.
+
+## Contributing Changes
+
+Please read
+[`CONTRIBUTING.md`](https://github.com/google/googletest/blob/master/CONTRIBUTING.md)
+for details on how to contribute to this project.
+
+Happy testing!
diff --git a/leveldb_base/third_party/googletest/WORKSPACE b/leveldb_base/third_party/googletest/WORKSPACE
new file mode 100644
index 0000000..3b44517
--- /dev/null
+++ b/leveldb_base/third_party/googletest/WORKSPACE
@@ -0,0 +1,30 @@
+workspace(name = "com_google_googletest")
+
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+
+http_archive(
+    name = "com_google_absl",  # 2020-10-13T16:49:13Z
+    sha256 = "00c3707bf9cd5eabd1ec6932cc65b97378c043f22573be3adf7d11bb7af17d06",
+    strip_prefix = "abseil-cpp-f3f785ab59478dd0312bf1b5df65d380650bf0dc",
+    urls = [
+        "https://github.com/abseil/abseil-cpp/archive/f3f785ab59478dd0312bf1b5df65d380650bf0dc.zip",
+    ],
+)
+
+http_archive(
+    name = "rules_cc",  # 2020-10-05T06:01:24Z
+    sha256 = "35ea62c63cd71d4000efe85f9f4f17e8afb23896c37ee9510952db2e9d8fbb70",
+    strip_prefix = "rules_cc-f055da4ff0cb2b3c73de1fe2f094ebdfb8b3acb9",
+    urls = [
+        "https://github.com/bazelbuild/rules_cc/archive/f055da4ff0cb2b3c73de1fe2f094ebdfb8b3acb9.zip",
+    ],
+)
+
+http_archive(
+    name = "rules_python",  # 2020-09-30T13:50:21Z
+    sha256 = "6e49996ad3cf45b2232b8f94ca1e3ead369c28394c51632be8d85fe826383012",
+    strip_prefix = "rules_python-c064f7008a30f307ea7516cf52358a653011f82b",
+    urls = [
+        "https://github.com/bazelbuild/rules_python/archive/c064f7008a30f307ea7516cf52358a653011f82b.zip",
+    ],
+)
diff --git a/leveldb_base/third_party/googletest/ci/linux-presubmit.sh b/leveldb_base/third_party/googletest/ci/linux-presubmit.sh
new file mode 100644
index 0000000..d02130c
--- /dev/null
+++ b/leveldb_base/third_party/googletest/ci/linux-presubmit.sh
@@ -0,0 +1,124 @@
+#!/bin/bash
+#
+# Copyright 2020, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+set -euox pipefail
+
+readonly LINUX_LATEST_CONTAINER="gcr.io/google.com/absl-177019/linux_hybrid-latest:20201008"
+readonly LINUX_GCC_FLOOR_CONTAINER="gcr.io/google.com/absl-177019/linux_gcc-floor:20201015"
+
+if [[ -z ${GTEST_ROOT:-} ]]; then
+  GTEST_ROOT="$(realpath $(dirname ${0})/..)"
+fi
+
+if [[ -z ${STD:-} ]]; then
+  STD="c++11 c++14 c++17 c++20"
+fi
+
+# Test the CMake build
+for cc in /usr/local/bin/gcc /opt/llvm/clang/bin/clang; do
+  for cmake_off_on in OFF ON; do
+    time docker run \
+      --volume="${GTEST_ROOT}:/src:ro" \
+      --tmpfs="/build:exec" \
+      --workdir="/build" \
+      --rm \
+      --env="CC=${cc}" \
+      --env="CXX_FLAGS=\"-Werror -Wdeprecated\"" \
+      ${LINUX_LATEST_CONTAINER} \
+      /bin/bash -c "
+        cmake /src \
+          -DCMAKE_CXX_STANDARD=11 \
+          -Dgtest_build_samples=ON \
+          -Dgtest_build_tests=ON \
+          -Dgmock_build_tests=ON \
+          -Dcxx_no_exception=${cmake_off_on} \
+          -Dcxx_no_rtti=${cmake_off_on} && \
+        make -j$(nproc) && \
+        ctest -j$(nproc) --output-on-failure"
+  done
+done
+
+# Do one test with an older version of GCC
+time docker run \
+  --volume="${GTEST_ROOT}:/src:ro" \
+  --workdir="/src" \
+  --rm \
+  --env="CC=/usr/local/bin/gcc" \
+  ${LINUX_GCC_FLOOR_CONTAINER} \
+    /usr/local/bin/bazel test ... \
+      --copt="-Wall" \
+      --copt="-Werror" \
+      --copt="-Wno-error=pragmas" \
+      --keep_going \
+      --show_timestamps \
+      --test_output=errors
+
+# Test GCC
+for std in ${STD}; do
+  for absl in 0 1; do
+    time docker run \
+      --volume="${GTEST_ROOT}:/src:ro" \
+      --workdir="/src" \
+      --rm \
+      --env="CC=/usr/local/bin/gcc" \
+      --env="BAZEL_CXXOPTS=-std=${std}" \
+      ${LINUX_LATEST_CONTAINER} \
+      /usr/local/bin/bazel test ... \
+        --copt="-Wall" \
+        --copt="-Werror" \
+        --define="absl=${absl}" \
+        --keep_going \
+        --show_timestamps \
+        --test_output=errors
+  done
+done
+
+# Test Clang
+for std in ${STD}; do
+  for absl in 0 1; do
+    time docker run \
+      --volume="${GTEST_ROOT}:/src:ro" \
+      --workdir="/src" \
+      --rm \
+      --env="CC=/opt/llvm/clang/bin/clang" \
+      --env="BAZEL_CXXOPTS=-std=${std}" \
+      ${LINUX_LATEST_CONTAINER} \
+      /usr/local/bin/bazel test ... \
+        --copt="--gcc-toolchain=/usr/local" \
+        --copt="-Wall" \
+        --copt="-Werror" \
+        --define="absl=${absl}" \
+        --keep_going \
+        --linkopt="--gcc-toolchain=/usr/local" \
+        --show_timestamps \
+        --test_output=errors
+  done
+done
diff --git a/leveldb_base/third_party/googletest/ci/macos-presubmit.sh b/leveldb_base/third_party/googletest/ci/macos-presubmit.sh
new file mode 100644
index 0000000..d6423fa
--- /dev/null
+++ b/leveldb_base/third_party/googletest/ci/macos-presubmit.sh
@@ -0,0 +1,73 @@
+#!/bin/bash
+#
+# Copyright 2020, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+set -euox pipefail
+
+if [[ -z ${GTEST_ROOT:-} ]]; then
+  GTEST_ROOT="$(realpath $(dirname ${0})/..)"
+fi
+
+# Test the CMake build
+for cmake_off_on in OFF ON; do
+  BUILD_DIR=$(mktemp -d build_dir.XXXXXXXX)
+  cd ${BUILD_DIR}
+  time cmake ${GTEST_ROOT} \
+    -DCMAKE_CXX_STANDARD=11 \
+    -Dgtest_build_samples=ON \
+    -Dgtest_build_tests=ON \
+    -Dgmock_build_tests=ON \
+    -Dcxx_no_exception=${cmake_off_on} \
+    -Dcxx_no_rtti=${cmake_off_on}
+  time make
+  time ctest -j$(nproc) --output-on-failure
+done
+
+# Test the Bazel build
+
+# If we are running on Kokoro, check for a versioned Bazel binary.
+KOKORO_GFILE_BAZEL_BIN="bazel-3.7.0-darwin-x86_64"
+if [[ ${KOKORO_GFILE_DIR:-} ]] && [[ -f ${KOKORO_GFILE_DIR}/${KOKORO_GFILE_BAZEL_BIN} ]]; then
+  BAZEL_BIN="${KOKORO_GFILE_DIR}/${KOKORO_GFILE_BAZEL_BIN}"
+  chmod +x ${BAZEL_BIN}
+else
+  BAZEL_BIN="bazel"
+fi
+
+cd ${GTEST_ROOT}
+for absl in 0 1; do
+  ${BAZEL_BIN} test ... \
+    --copt="-Wall" \
+    --copt="-Werror" \
+    --define="absl=${absl}" \
+    --keep_going \
+    --show_timestamps \
+    --test_output=errors
+done
diff --git a/leveldb_base/third_party/googletest/docs/_config.yml b/leveldb_base/third_party/googletest/docs/_config.yml
new file mode 100644
index 0000000..d12867e
--- /dev/null
+++ b/leveldb_base/third_party/googletest/docs/_config.yml
@@ -0,0 +1 @@
+title: GoogleTest
diff --git a/leveldb_base/third_party/googletest/docs/_data/navigation.yml b/leveldb_base/third_party/googletest/docs/_data/navigation.yml
new file mode 100644
index 0000000..6d3cd4f
--- /dev/null
+++ b/leveldb_base/third_party/googletest/docs/_data/navigation.yml
@@ -0,0 +1,37 @@
+nav:
+- section: "Get Started"
+  items:
+  - title: "Supported Platforms"
+    url: "/platforms.html"
+  - title: "Quickstart: Bazel"
+    url: "/quickstart-bazel.html"
+  - title: "Quickstart: CMake"
+    url: "/quickstart-cmake.html"
+- section: "Guides"
+  items:
+  - title: "GoogleTest Primer"
+    url: "/primer.html"
+  - title: "Advanced Topics"
+    url: "/advanced.html"
+  - title: "Mocking for Dummies"
+    url: "/gmock_for_dummies.html"
+  - title: "Mocking Cookbook"
+    url: "/gmock_cook_book.html"
+  - title: "Mocking Cheat Sheet"
+    url: "/gmock_cheat_sheet.html"
+- section: "References"
+  items:
+  - title: "Matchers"
+    url: "/reference/matchers.html"
+  - title: "Actions"
+    url: "/reference/actions.html"
+  - title: "Testing FAQ"
+    url: "/faq.html"
+  - title: "Mocking FAQ"
+    url: "/gmock_faq.html"
+  - title: "Code Samples"
+    url: "/samples.html"
+  - title: "Using pkg-config"
+    url: "/pkgconfig.html"
+  - title: "Community Documentation"
+    url: "/community_created_documentation.html"
diff --git a/leveldb_base/third_party/googletest/docs/_layouts/default.html b/leveldb_base/third_party/googletest/docs/_layouts/default.html
new file mode 100644
index 0000000..731042f
--- /dev/null
+++ b/leveldb_base/third_party/googletest/docs/_layouts/default.html
@@ -0,0 +1,53 @@
+<!DOCTYPE html>
+<html lang="{{ site.lang | default: "en-US" }}">
+  <head>
+    <meta charset="UTF-8">
+    <meta http-equiv="X-UA-Compatible" content="IE=edge">
+    <meta name="viewport" content="width=device-width, initial-scale=1">
+
+{% seo %}
+    <link rel="stylesheet" href="{{ "/assets/css/style.css?v=" | append: site.github.build_revision | relative_url }}">
+  </head>
+  <body>
+    <div class="sidebar">
+      <div class="header">
+        <h1><a href="{{ "/" | relative_url }}">{{ site.title | default: "Documentation" }}</a></h1>
+      </div>
+      <input type="checkbox" id="nav-toggle" class="nav-toggle">
+      <label for="nav-toggle" class="expander">
+        <span class="arrow"></span>
+      </label>
+      <nav>
+        {% for item in site.data.navigation.nav %}
+        <h2>{{ item.section }}</h2>
+        <ul>
+          {% for subitem in item.items %}
+          <a href="{{subitem.url | relative_url }}">
+            <li class="{% if subitem.url == page.url %}active{% endif %}">
+              {{ subitem.title }}
+            </li>
+          </a>
+          {% endfor %}
+        </ul>
+        {% endfor %}
+      </nav>
+    </div>
+    <div class="main markdown-body">
+      <div class="main-inner">
+        {{ content }}
+      </div>
+    </div>
+    <script src="https://cdnjs.cloudflare.com/ajax/libs/anchor-js/4.1.0/anchor.min.js" integrity="sha256-lZaRhKri35AyJSypXXs4o6OPFTbTmUoltBbDCbdzegg=" crossorigin="anonymous"></script>
+    <script>anchors.add('.main h2, .main h3, .main h4, .main h5, .main h6');</script>
+    {% if site.google_analytics %}
+    <script>
+      (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
+      (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
+      m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
+      })(window,document,'script','//www.google-analytics.com/analytics.js','ga');
+      ga('create', '{{ site.google_analytics }}', 'auto');
+      ga('send', 'pageview');
+    </script>
+    {% endif %}
+  </body>
+</html>
diff --git a/leveldb_base/third_party/googletest/docs/_sass/main.scss b/leveldb_base/third_party/googletest/docs/_sass/main.scss
new file mode 100644
index 0000000..91e633b
--- /dev/null
+++ b/leveldb_base/third_party/googletest/docs/_sass/main.scss
@@ -0,0 +1,193 @@
+// Styles for GoogleTest docs website on GitHub Pages.
+// Color variables are defined in
+// https://github.com/pages-themes/primer/tree/master/_sass/primer-support/lib/variables
+
+$sidebar-width: 260px;
+
+body {
+  display: flex;
+  margin: 0;
+}
+
+.sidebar {
+  background: $black;
+  color: $text-white;
+  flex-shrink: 0;
+  height: 100vh;
+  overflow: auto;
+  position: sticky;
+  top: 0;
+  width: $sidebar-width;
+}
+
+.sidebar h1 {
+  font-size: 1.5em;
+}
+
+.sidebar h2 {
+  color: $gray-light;
+  font-size: 0.8em;
+  font-weight: normal;
+  margin-bottom: 0.8em;
+  padding-left: 2.5em;
+  text-transform: uppercase;
+}
+
+.sidebar .header {
+  background: $black;
+  padding: 2em;
+  position: sticky;
+  top: 0;
+  width: 100%;
+}
+
+.sidebar .header a {
+  color: $text-white;
+  text-decoration: none;
+}
+
+.sidebar .nav-toggle {
+  display: none;
+}
+
+.sidebar .expander {
+  cursor: pointer;
+  display: none;
+  height: 3em;
+  position: absolute;
+  right: 1em;
+  top: 1.5em;
+  width: 3em;
+}
+
+.sidebar .expander .arrow {
+  border: solid white;
+  border-width: 0 3px 3px 0;
+  display: block;
+  height: 0.7em;
+  margin: 1em auto;
+  transform: rotate(45deg);
+  transition: transform 0.5s;
+  width: 0.7em;
+}
+
+.sidebar nav {
+  width: 100%;
+}
+
+.sidebar nav ul {
+  list-style-type: none;
+  margin-bottom: 1em;
+  padding: 0;
+
+  &:last-child {
+    margin-bottom: 2em;
+  }
+
+  a {
+   text-decoration: none;
+  }
+
+  li {
+    color: $text-white;
+    padding-left: 2em;
+    text-decoration: none;
+  }
+
+  li.active {
+    background: $border-gray-darker;
+    font-weight: bold;
+  }
+
+  li:hover {
+    background: $border-gray-darker;
+  }
+}
+
+.main {
+  width: calc(100% - #{$sidebar-width});
+}
+
+.main .main-inner {
+  margin: 2em;
+}
+
+.main table th {
+  text-align: left;
+}
+
+.main .callout {
+  border-left: 0.25em solid white;
+  padding: 1em;
+
+  a {
+    text-decoration: underline;
+  }
+
+  &.important {
+    background-color: $bg-yellow-light;
+    border-color: $bg-yellow;
+    color: $black;
+  }
+
+  &.note {
+    background-color: $bg-blue-light;
+    border-color: $text-blue;
+    color: $text-blue;
+  }
+
+  &.tip {
+    background-color: $green-000;
+    border-color: $green-700;
+    color: $green-700;
+  }
+
+  &.warning {
+    background-color: $red-000;
+    border-color: $text-red;
+    color: $text-red;
+  }
+}
+
+.main .good pre {
+  background-color: $bg-green-light;
+}
+
+.main .bad pre {
+  background-color: $red-000;
+}
+
+@media all and (max-width: 768px) {
+  body {
+    flex-direction: column;
+  }
+
+  .sidebar {
+    height: auto;
+    position: relative;
+    width: 100%;
+  }
+
+  .sidebar .expander {
+    display: block;
+  }
+
+  .sidebar nav {
+    height: 0;
+    overflow: hidden;
+  }
+
+  .sidebar .nav-toggle:checked {
+    & ~ nav {
+      height: auto;
+    }
+
+    & + .expander .arrow {
+      transform: rotate(-135deg);
+    }
+  }
+
+  .main {
+    width: 100%;
+  }
+}
diff --git a/leveldb_base/third_party/googletest/docs/advanced.md b/leveldb_base/third_party/googletest/docs/advanced.md
new file mode 100644
index 0000000..4fdbb46
--- /dev/null
+++ b/leveldb_base/third_party/googletest/docs/advanced.md
@@ -0,0 +1,2661 @@
+# Advanced googletest Topics
+
+## Introduction
+
+Now that you have read the [googletest Primer](primer.md) and learned how to
+write tests using googletest, it's time to learn some new tricks. This document
+will show you more assertions as well as how to construct complex failure
+messages, propagate fatal failures, reuse and speed up your test fixtures, and
+use various flags with your tests.
+
+## More Assertions
+
+This section covers some less frequently used, but still significant,
+assertions.
+
+### Explicit Success and Failure
+
+These three assertions do not actually test a value or expression. Instead, they
+generate a success or failure directly. Like the macros that actually perform a
+test, you may stream a custom failure message into them.
+
+```c++
+SUCCEED();
+```
+
+Generates a success. This does **NOT** make the overall test succeed. A test is
+considered successful only if none of its assertions fail during its execution.
+
+{: .callout .note}
+NOTE: `SUCCEED()` is purely documentary and currently doesn't generate any
+user-visible output. However, we may add `SUCCEED()` messages to googletest's
+output in the future.
+
+```c++
+FAIL();
+ADD_FAILURE();
+ADD_FAILURE_AT("file_path", line_number);
+```
+
+`FAIL()` generates a fatal failure, while `ADD_FAILURE()` and `ADD_FAILURE_AT()`
+generate a nonfatal failure. These are useful when control flow, rather than a
+Boolean expression, determines the test's success or failure. For example, you
+might want to write something like:
+
+```c++
+switch(expression) {
+  case 1:
+     ... some checks ...
+  case 2:
+     ... some other checks ...
+  default:
+     FAIL() << "We shouldn't get here.";
+}
+```
+
+{: .callout .note}
+NOTE: you can only use `FAIL()` in functions that return `void`. See the
+[Assertion Placement section](#assertion-placement) for more information.
+
+### Exception Assertions
+
+These are for verifying that a piece of code throws (or does not throw) an
+exception of the given type:
+
+Fatal assertion                            | Nonfatal assertion                         | Verifies
+------------------------------------------ | ------------------------------------------ | --------
+`ASSERT_THROW(statement, exception_type);` | `EXPECT_THROW(statement, exception_type);` | `statement` throws an exception of the given type
+`ASSERT_ANY_THROW(statement);`             | `EXPECT_ANY_THROW(statement);`             | `statement` throws an exception of any type
+`ASSERT_NO_THROW(statement);`              | `EXPECT_NO_THROW(statement);`              | `statement` doesn't throw any exception
+
+Examples:
+
+```c++
+ASSERT_THROW(Foo(5), bar_exception);
+
+EXPECT_NO_THROW({
+  int n = 5;
+  Bar(&n);
+});
+```
+
+**Availability**: requires exceptions to be enabled in the build environment
+
+### Predicate Assertions for Better Error Messages
+
+Even though googletest has a rich set of assertions, they can never be complete,
+as it's impossible (nor a good idea) to anticipate all scenarios a user might
+run into. Therefore, sometimes a user has to use `EXPECT_TRUE()` to check a
+complex expression, for lack of a better macro. This has the problem of not
+showing you the values of the parts of the expression, making it hard to
+understand what went wrong. As a workaround, some users choose to construct the
+failure message by themselves, streaming it into `EXPECT_TRUE()`. However, this
+is awkward especially when the expression has side-effects or is expensive to
+evaluate.
+
+googletest gives you three different options to solve this problem:
+
+#### Using an Existing Boolean Function
+
+If you already have a function or functor that returns `bool` (or a type that
+can be implicitly converted to `bool`), you can use it in a *predicate
+assertion* to get the function arguments printed for free:
+
+
+| Fatal assertion                   | Nonfatal assertion                | Verifies                    |
+| --------------------------------- | --------------------------------- | --------------------------- |
+| `ASSERT_PRED1(pred1, val1)`       | `EXPECT_PRED1(pred1, val1)`       | `pred1(val1)` is true       |
+| `ASSERT_PRED2(pred2, val1, val2)` | `EXPECT_PRED2(pred2, val1, val2)` | `pred2(val1, val2)` is true |
+| `...`                             | `...`                             | `...`                       |
+
+In the above, `predn` is an `n`-ary predicate function or functor, where `val1`,
+`val2`, ..., and `valn` are its arguments. The assertion succeeds if the
+predicate returns `true` when applied to the given arguments, and fails
+otherwise. When the assertion fails, it prints the value of each argument. In
+either case, the arguments are evaluated exactly once.
+
+Here's an example. Given
+
+```c++
+// Returns true if m and n have no common divisors except 1.
+bool MutuallyPrime(int m, int n) { ... }
+
+const int a = 3;
+const int b = 4;
+const int c = 10;
+```
+
+the assertion
+
+```c++
+  EXPECT_PRED2(MutuallyPrime, a, b);
+```
+
+will succeed, while the assertion
+
+```c++
+  EXPECT_PRED2(MutuallyPrime, b, c);
+```
+
+will fail with the message
+
+```none
+MutuallyPrime(b, c) is false, where
+b is 4
+c is 10
+```
+
+{: .callout .note}
+> NOTE:
+>
+> 1.  If you see a compiler error "no matching function to call" when using
+>     `ASSERT_PRED*` or `EXPECT_PRED*`, please see
+>     [this](faq.md#the-compiler-complains-no-matching-function-to-call-when-i-use-assert_pred-how-do-i-fix-it)
+>     for how to resolve it.
+
+#### Using a Function That Returns an AssertionResult
+
+While `EXPECT_PRED*()` and friends are handy for a quick job, the syntax is not
+satisfactory: you have to use different macros for different arities, and it
+feels more like Lisp than C++. The `::testing::AssertionResult` class solves
+this problem.
+
+An `AssertionResult` object represents the result of an assertion (whether it's
+a success or a failure, and an associated message). You can create an
+`AssertionResult` using one of these factory functions:
+
+```c++
+namespace testing {
+
+// Returns an AssertionResult object to indicate that an assertion has
+// succeeded.
+AssertionResult AssertionSuccess();
+
+// Returns an AssertionResult object to indicate that an assertion has
+// failed.
+AssertionResult AssertionFailure();
+
+}
+```
+
+You can then use the `<<` operator to stream messages to the `AssertionResult`
+object.
+
+To provide more readable messages in Boolean assertions (e.g. `EXPECT_TRUE()`),
+write a predicate function that returns `AssertionResult` instead of `bool`. For
+example, if you define `IsEven()` as:
+
+```c++
+testing::AssertionResult IsEven(int n) {
+  if ((n % 2) == 0)
+    return testing::AssertionSuccess();
+  else
+    return testing::AssertionFailure() << n << " is odd";
+}
+```
+
+instead of:
+
+```c++
+bool IsEven(int n) {
+  return (n % 2) == 0;
+}
+```
+
+the failed assertion `EXPECT_TRUE(IsEven(Fib(4)))` will print:
+
+```none
+Value of: IsEven(Fib(4))
+  Actual: false (3 is odd)
+Expected: true
+```
+
+instead of a more opaque
+
+```none
+Value of: IsEven(Fib(4))
+  Actual: false
+Expected: true
+```
+
+If you want informative messages in `EXPECT_FALSE` and `ASSERT_FALSE` as well
+(one third of Boolean assertions in the Google code base are negative ones), and
+are fine with making the predicate slower in the success case, you can supply a
+success message:
+
+```c++
+testing::AssertionResult IsEven(int n) {
+  if ((n % 2) == 0)
+    return testing::AssertionSuccess() << n << " is even";
+  else
+    return testing::AssertionFailure() << n << " is odd";
+}
+```
+
+Then the statement `EXPECT_FALSE(IsEven(Fib(6)))` will print
+
+```none
+  Value of: IsEven(Fib(6))
+     Actual: true (8 is even)
+  Expected: false
+```
+
+#### Using a Predicate-Formatter
+
+If you find the default message generated by `(ASSERT|EXPECT)_PRED*` and
+`(ASSERT|EXPECT)_(TRUE|FALSE)` unsatisfactory, or some arguments to your
+predicate do not support streaming to `ostream`, you can instead use the
+following *predicate-formatter assertions* to *fully* customize how the message
+is formatted:
+
+Fatal assertion                                  | Nonfatal assertion                               | Verifies
+------------------------------------------------ | ------------------------------------------------ | --------
+`ASSERT_PRED_FORMAT1(pred_format1, val1);`       | `EXPECT_PRED_FORMAT1(pred_format1, val1);`       | `pred_format1(val1)` is successful
+`ASSERT_PRED_FORMAT2(pred_format2, val1, val2);` | `EXPECT_PRED_FORMAT2(pred_format2, val1, val2);` | `pred_format2(val1, val2)` is successful
+`...`                                            | `...`                                            | ...
+
+The difference between this and the previous group of macros is that instead of
+a predicate, `(ASSERT|EXPECT)_PRED_FORMAT*` take a *predicate-formatter*
+(`pred_formatn`), which is a function or functor with the signature:
+
+```c++
+testing::AssertionResult PredicateFormattern(const char* expr1,
+                                             const char* expr2,
+                                             ...
+                                             const char* exprn,
+                                             T1 val1,
+                                             T2 val2,
+                                             ...
+                                             Tn valn);
+```
+
+where `val1`, `val2`, ..., and `valn` are the values of the predicate arguments,
+and `expr1`, `expr2`, ..., and `exprn` are the corresponding expressions as they
+appear in the source code. The types `T1`, `T2`, ..., and `Tn` can be either
+value types or reference types. For example, if an argument has type `Foo`, you
+can declare it as either `Foo` or `const Foo&`, whichever is appropriate.
+
+As an example, let's improve the failure message in `MutuallyPrime()`, which was
+used with `EXPECT_PRED2()`:
+
+```c++
+// Returns the smallest prime common divisor of m and n,
+// or 1 when m and n are mutually prime.
+int SmallestPrimeCommonDivisor(int m, int n) { ... }
+
+// A predicate-formatter for asserting that two integers are mutually prime.
+testing::AssertionResult AssertMutuallyPrime(const char* m_expr,
+                                             const char* n_expr,
+                                             int m,
+                                             int n) {
+  if (MutuallyPrime(m, n)) return testing::AssertionSuccess();
+
+  return testing::AssertionFailure() << m_expr << " and " << n_expr
+      << " (" << m << " and " << n << ") are not mutually prime, "
+      << "as they have a common divisor " << SmallestPrimeCommonDivisor(m, n);
+}
+```
+
+With this predicate-formatter, we can use
+
+```c++
+  EXPECT_PRED_FORMAT2(AssertMutuallyPrime, b, c);
+```
+
+to generate the message
+
+```none
+b and c (4 and 10) are not mutually prime, as they have a common divisor 2.
+```
+
+As you may have realized, many of the built-in assertions we introduced earlier
+are special cases of `(EXPECT|ASSERT)_PRED_FORMAT*`. In fact, most of them are
+indeed defined using `(EXPECT|ASSERT)_PRED_FORMAT*`.
+
+### Floating-Point Comparison
+
+Comparing floating-point numbers is tricky. Due to round-off errors, it is very
+unlikely that two floating-points will match exactly. Therefore, `ASSERT_EQ` 's
+naive comparison usually doesn't work. And since floating-points can have a wide
+value range, no single fixed error bound works. It's better to compare by a
+fixed relative error bound, except for values close to 0 due to the loss of
+precision there.
+
+In general, for floating-point comparison to make sense, the user needs to
+carefully choose the error bound. If they don't want or care to, comparing in
+terms of Units in the Last Place (ULPs) is a good default, and googletest
+provides assertions to do this. Full details about ULPs are quite long; if you
+want to learn more, see
+[here](https://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition/).
+
+#### Floating-Point Macros
+
+
+| Fatal assertion                 | Nonfatal assertion              | Verifies                                 |
+| ------------------------------- | ------------------------------- | ---------------------------------------- |
+| `ASSERT_FLOAT_EQ(val1, val2);`  | `EXPECT_FLOAT_EQ(val1, val2);`  | the two `float` values are almost equal  |
+| `ASSERT_DOUBLE_EQ(val1, val2);` | `EXPECT_DOUBLE_EQ(val1, val2);` | the two `double` values are almost equal |
+
+
+By "almost equal" we mean the values are within 4 ULP's from each other.
+
+The following assertions allow you to choose the acceptable error bound:
+
+
+| Fatal assertion                       | Nonfatal assertion                    | Verifies                                                                         |
+| ------------------------------------- | ------------------------------------- | -------------------------------------------------------------------------------- |
+| `ASSERT_NEAR(val1, val2, abs_error);` | `EXPECT_NEAR(val1, val2, abs_error);` | the difference between `val1` and `val2` doesn't exceed the given absolute error |
+
+
+#### Floating-Point Predicate-Format Functions
+
+Some floating-point operations are useful, but not that often used. In order to
+avoid an explosion of new macros, we provide them as predicate-format functions
+that can be used in predicate assertion macros (e.g. `EXPECT_PRED_FORMAT2`,
+etc).
+
+```c++
+EXPECT_PRED_FORMAT2(testing::FloatLE, val1, val2);
+EXPECT_PRED_FORMAT2(testing::DoubleLE, val1, val2);
+```
+
+Verifies that `val1` is less than, or almost equal to, `val2`. You can replace
+`EXPECT_PRED_FORMAT2` in the above table with `ASSERT_PRED_FORMAT2`.
+
+### Asserting Using gMock Matchers
+
+gMock comes with a library of *matchers* for validating arguments passed to mock
+objects. A gMock matcher is basically a predicate that knows how to describe
+itself. It can be used in these assertion macros:
+
+
+| Fatal assertion                | Nonfatal assertion             | Verifies              |
+| ------------------------------ | ------------------------------ | --------------------- |
+| `ASSERT_THAT(value, matcher);` | `EXPECT_THAT(value, matcher);` | value matches matcher |
+
+
+For example, `StartsWith(prefix)` is a matcher that matches a string starting
+with `prefix`, and you can write:
+
+```c++
+using ::testing::StartsWith;
+...
+    // Verifies that Foo() returns a string starting with "Hello".
+    EXPECT_THAT(Foo(), StartsWith("Hello"));
+```
+
+See
+[Using Matchers in googletest Assertions](gmock_cook_book.md#using-matchers-in-googletest-assertions)
+in the gMock Cookbook for more details. For a list of built-in matchers, see the
+[Matchers Reference](reference/matchers.md). You can also write your own
+matchers—see [Writing New Matchers Quickly](gmock_cook_book.md#NewMatchers).
+
+gMock is bundled with googletest, so you don't need to add any build dependency
+in order to take advantage of this. Just include `"gmock/gmock.h"`
+and you're ready to go.
+
+### More String Assertions
+
+(Please read the [previous](#asserting-using-gmock-matchers) section first if
+you haven't.)
+
+You can use the gMock [string matchers](reference/matchers.md#string-matchers)
+with `EXPECT_THAT()` or `ASSERT_THAT()` to do more string comparison tricks
+(sub-string, prefix, suffix, regular expression, and etc). For example,
+
+```c++
+using ::testing::HasSubstr;
+using ::testing::MatchesRegex;
+...
+  ASSERT_THAT(foo_string, HasSubstr("needle"));
+  EXPECT_THAT(bar_string, MatchesRegex("\\w*\\d+"));
+```
+
+If the string contains a well-formed HTML or XML document, you can check whether
+its DOM tree matches an
+[XPath expression](http://www.w3.org/TR/xpath/#contents):
+
+```c++
+// Currently still in //template/prototemplate/testing:xpath_matcher
+#include "template/prototemplate/testing/xpath_matcher.h"
+using ::prototemplate::testing::MatchesXPath;
+EXPECT_THAT(html_string, MatchesXPath("//a[text()='click here']"));
+```
+
+### Windows HRESULT assertions
+
+These assertions test for `HRESULT` success or failure.
+
+Fatal assertion                        | Nonfatal assertion                     | Verifies
+-------------------------------------- | -------------------------------------- | --------
+`ASSERT_HRESULT_SUCCEEDED(expression)` | `EXPECT_HRESULT_SUCCEEDED(expression)` | `expression` is a success `HRESULT`
+`ASSERT_HRESULT_FAILED(expression)`    | `EXPECT_HRESULT_FAILED(expression)`    | `expression` is a failure `HRESULT`
+
+The generated output contains the human-readable error message associated with
+the `HRESULT` code returned by `expression`.
+
+You might use them like this:
+
+```c++
+CComPtr<IShellDispatch2> shell;
+ASSERT_HRESULT_SUCCEEDED(shell.CoCreateInstance(L"Shell.Application"));
+CComVariant empty;
+ASSERT_HRESULT_SUCCEEDED(shell->ShellExecute(CComBSTR(url), empty, empty, empty, empty));
+```
+
+### Type Assertions
+
+You can call the function
+
+```c++
+::testing::StaticAssertTypeEq<T1, T2>();
+```
+
+to assert that types `T1` and `T2` are the same. The function does nothing if
+the assertion is satisfied. If the types are different, the function call will
+fail to compile, the compiler error message will say that
+`T1 and T2 are not the same type` and most likely (depending on the compiler)
+show you the actual values of `T1` and `T2`. This is mainly useful inside
+template code.
+
+**Caveat**: When used inside a member function of a class template or a function
+template, `StaticAssertTypeEq<T1, T2>()` is effective only if the function is
+instantiated. For example, given:
+
+```c++
+template <typename T> class Foo {
+ public:
+  void Bar() { testing::StaticAssertTypeEq<int, T>(); }
+};
+```
+
+the code:
+
+```c++
+void Test1() { Foo<bool> foo; }
+```
+
+will not generate a compiler error, as `Foo<bool>::Bar()` is never actually
+instantiated. Instead, you need:
+
+```c++
+void Test2() { Foo<bool> foo; foo.Bar(); }
+```
+
+to cause a compiler error.
+
+### Assertion Placement
+
+You can use assertions in any C++ function. In particular, it doesn't have to be
+a method of the test fixture class. The one constraint is that assertions that
+generate a fatal failure (`FAIL*` and `ASSERT_*`) can only be used in
+void-returning functions. This is a consequence of Google's not using
+exceptions. By placing it in a non-void function you'll get a confusing compile
+error like `"error: void value not ignored as it ought to be"` or `"cannot
+initialize return object of type 'bool' with an rvalue of type 'void'"` or
+`"error: no viable conversion from 'void' to 'string'"`.
+
+If you need to use fatal assertions in a function that returns non-void, one
+option is to make the function return the value in an out parameter instead. For
+example, you can rewrite `T2 Foo(T1 x)` to `void Foo(T1 x, T2* result)`. You
+need to make sure that `*result` contains some sensible value even when the
+function returns prematurely. As the function now returns `void`, you can use
+any assertion inside of it.
+
+If changing the function's type is not an option, you should just use assertions
+that generate non-fatal failures, such as `ADD_FAILURE*` and `EXPECT_*`.
+
+{: .callout .note}
+NOTE: Constructors and destructors are not considered void-returning functions,
+according to the C++ language specification, and so you may not use fatal
+assertions in them; you'll get a compilation error if you try. Instead, either
+call `abort` and crash the entire test executable, or put the fatal assertion in
+a `SetUp`/`TearDown` function; see
+[constructor/destructor vs. `SetUp`/`TearDown`](faq.md#CtorVsSetUp)
+
+{: .callout .warning}
+WARNING: A fatal assertion in a helper function (private void-returning method)
+called from a constructor or destructor does not terminate the current test, as
+your intuition might suggest: it merely returns from the constructor or
+destructor early, possibly leaving your object in a partially-constructed or
+partially-destructed state! You almost certainly want to `abort` or use
+`SetUp`/`TearDown` instead.
+
+## Skipping test execution
+
+Related to the assertions `SUCCEED()` and `FAIL()`, you can prevent further test
+execution at runtime with the `GTEST_SKIP()` macro. This is useful when you need
+to check for preconditions of the system under test during runtime and skip
+tests in a meaningful way.
+
+`GTEST_SKIP()` can be used in individual test cases or in the `SetUp()` methods
+of classes derived from either `::testing::Environment` or `::testing::Test`.
+For example:
+
+```c++
+TEST(SkipTest, DoesSkip) {
+  GTEST_SKIP() << "Skipping single test";
+  EXPECT_EQ(0, 1);  // Won't fail; it won't be executed
+}
+
+class SkipFixture : public ::testing::Test {
+ protected:
+  void SetUp() override {
+    GTEST_SKIP() << "Skipping all tests for this fixture";
+  }
+};
+
+// Tests for SkipFixture won't be executed.
+TEST_F(SkipFixture, SkipsOneTest) {
+  EXPECT_EQ(5, 7);  // Won't fail
+}
+```
+
+As with assertion macros, you can stream a custom message into `GTEST_SKIP()`.
+
+## Teaching googletest How to Print Your Values
+
+When a test assertion such as `EXPECT_EQ` fails, googletest prints the argument
+values to help you debug. It does this using a user-extensible value printer.
+
+This printer knows how to print built-in C++ types, native arrays, STL
+containers, and any type that supports the `<<` operator. For other types, it
+prints the raw bytes in the value and hopes that you the user can figure it out.
+
+As mentioned earlier, the printer is *extensible*. That means you can teach it
+to do a better job at printing your particular type than to dump the bytes. To
+do that, define `<<` for your type:
+
+```c++
+#include <ostream>
+
+namespace foo {
+
+class Bar {  // We want googletest to be able to print instances of this.
+...
+  // Create a free inline friend function.
+  friend std::ostream& operator<<(std::ostream& os, const Bar& bar) {
+    return os << bar.DebugString();  // whatever needed to print bar to os
+  }
+};
+
+// If you can't declare the function in the class it's important that the
+// << operator is defined in the SAME namespace that defines Bar.  C++'s look-up
+// rules rely on that.
+std::ostream& operator<<(std::ostream& os, const Bar& bar) {
+  return os << bar.DebugString();  // whatever needed to print bar to os
+}
+
+}  // namespace foo
+```
+
+Sometimes, this might not be an option: your team may consider it bad style to
+have a `<<` operator for `Bar`, or `Bar` may already have a `<<` operator that
+doesn't do what you want (and you cannot change it). If so, you can instead
+define a `PrintTo()` function like this:
+
+```c++
+#include <ostream>
+
+namespace foo {
+
+class Bar {
+  ...
+  friend void PrintTo(const Bar& bar, std::ostream* os) {
+    *os << bar.DebugString();  // whatever needed to print bar to os
+  }
+};
+
+// If you can't declare the function in the class it's important that PrintTo()
+// is defined in the SAME namespace that defines Bar.  C++'s look-up rules rely
+// on that.
+void PrintTo(const Bar& bar, std::ostream* os) {
+  *os << bar.DebugString();  // whatever needed to print bar to os
+}
+
+}  // namespace foo
+```
+
+If you have defined both `<<` and `PrintTo()`, the latter will be used when
+googletest is concerned. This allows you to customize how the value appears in
+googletest's output without affecting code that relies on the behavior of its
+`<<` operator.
+
+If you want to print a value `x` using googletest's value printer yourself, just
+call `::testing::PrintToString(x)`, which returns an `std::string`:
+
+```c++
+vector<pair<Bar, int> > bar_ints = GetBarIntVector();
+
+EXPECT_TRUE(IsCorrectBarIntVector(bar_ints))
+    << "bar_ints = " << testing::PrintToString(bar_ints);
+```
+
+## Death Tests
+
+In many applications, there are assertions that can cause application failure if
+a condition is not met. These sanity checks, which ensure that the program is in
+a known good state, are there to fail at the earliest possible time after some
+program state is corrupted. If the assertion checks the wrong condition, then
+the program may proceed in an erroneous state, which could lead to memory
+corruption, security holes, or worse. Hence it is vitally important to test that
+such assertion statements work as expected.
+
+Since these precondition checks cause the processes to die, we call such tests
+_death tests_. More generally, any test that checks that a program terminates
+(except by throwing an exception) in an expected fashion is also a death test.
+
+Note that if a piece of code throws an exception, we don't consider it "death"
+for the purpose of death tests, as the caller of the code could catch the
+exception and avoid the crash. If you want to verify exceptions thrown by your
+code, see [Exception Assertions](#ExceptionAssertions).
+
+If you want to test `EXPECT_*()/ASSERT_*()` failures in your test code, see
+Catching Failures
+
+### How to Write a Death Test
+
+googletest has the following macros to support death tests:
+
+Fatal assertion                                  | Nonfatal assertion                               | Verifies
+------------------------------------------------ | ------------------------------------------------ | --------
+`ASSERT_DEATH(statement, matcher);`              | `EXPECT_DEATH(statement, matcher);`              | `statement` crashes with the given error
+`ASSERT_DEATH_IF_SUPPORTED(statement, matcher);` | `EXPECT_DEATH_IF_SUPPORTED(statement, matcher);` | if death tests are supported, verifies that `statement` crashes with the given error; otherwise verifies nothing
+`ASSERT_DEBUG_DEATH(statement, matcher);`        | `EXPECT_DEBUG_DEATH(statement, matcher);`        | `statement` crashes with the given error **in debug mode**. When not in debug (i.e. `NDEBUG` is defined), this just executes `statement`
+`ASSERT_EXIT(statement, predicate, matcher);`    | `EXPECT_EXIT(statement, predicate, matcher);`    | `statement` exits with the given error, and its exit code matches `predicate`
+
+where `statement` is a statement that is expected to cause the process to die,
+`predicate` is a function or function object that evaluates an integer exit
+status, and `matcher` is either a gMock matcher matching a `const std::string&`
+or a (Perl) regular expression - either of which is matched against the stderr
+output of `statement`. For legacy reasons, a bare string (i.e. with no matcher)
+is interpreted as `ContainsRegex(str)`, **not** `Eq(str)`. Note that `statement`
+can be *any valid statement* (including *compound statement*) and doesn't have
+to be an expression.
+
+As usual, the `ASSERT` variants abort the current test function, while the
+`EXPECT` variants do not.
+
+{: .callout .note}
+> NOTE: We use the word "crash" here to mean that the process terminates with a
+> *non-zero* exit status code. There are two possibilities: either the process
+> has called `exit()` or `_exit()` with a non-zero value, or it may be killed by
+> a signal.
+>
+> This means that if *`statement`* terminates the process with a 0 exit code, it
+> is *not* considered a crash by `EXPECT_DEATH`. Use `EXPECT_EXIT` instead if
+> this is the case, or if you want to restrict the exit code more precisely.
+
+A predicate here must accept an `int` and return a `bool`. The death test
+succeeds only if the predicate returns `true`. googletest defines a few
+predicates that handle the most common cases:
+
+```c++
+::testing::ExitedWithCode(exit_code)
+```
+
+This expression is `true` if the program exited normally with the given exit
+code.
+
+```c++
+testing::KilledBySignal(signal_number)  // Not available on Windows.
+```
+
+This expression is `true` if the program was killed by the given signal.
+
+The `*_DEATH` macros are convenient wrappers for `*_EXIT` that use a predicate
+that verifies the process' exit code is non-zero.
+
+Note that a death test only cares about three things:
+
+1.  does `statement` abort or exit the process?
+2.  (in the case of `ASSERT_EXIT` and `EXPECT_EXIT`) does the exit status
+    satisfy `predicate`? Or (in the case of `ASSERT_DEATH` and `EXPECT_DEATH`)
+    is the exit status non-zero? And
+3.  does the stderr output match `matcher`?
+
+In particular, if `statement` generates an `ASSERT_*` or `EXPECT_*` failure, it
+will **not** cause the death test to fail, as googletest assertions don't abort
+the process.
+
+To write a death test, simply use one of the above macros inside your test
+function. For example,
+
+```c++
+TEST(MyDeathTest, Foo) {
+  // This death test uses a compound statement.
+  ASSERT_DEATH({
+    int n = 5;
+    Foo(&n);
+  }, "Error on line .* of Foo()");
+}
+
+TEST(MyDeathTest, NormalExit) {
+  EXPECT_EXIT(NormalExit(), testing::ExitedWithCode(0), "Success");
+}
+
+TEST(MyDeathTest, KillMyself) {
+  EXPECT_EXIT(KillMyself(), testing::KilledBySignal(SIGKILL),
+              "Sending myself unblockable signal");
+}
+```
+
+verifies that:
+
+*   calling `Foo(5)` causes the process to die with the given error message,
+*   calling `NormalExit()` causes the process to print `"Success"` to stderr and
+    exit with exit code 0, and
+*   calling `KillMyself()` kills the process with signal `SIGKILL`.
+
+The test function body may contain other assertions and statements as well, if
+necessary.
+
+### Death Test Naming
+
+{: .callout .important}
+IMPORTANT: We strongly recommend you to follow the convention of naming your
+**test suite** (not test) `*DeathTest` when it contains a death test, as
+demonstrated in the above example. The
+[Death Tests And Threads](#death-tests-and-threads) section below explains why.
+
+If a test fixture class is shared by normal tests and death tests, you can use
+`using` or `typedef` to introduce an alias for the fixture class and avoid
+duplicating its code:
+
+```c++
+class FooTest : public testing::Test { ... };
+
+using FooDeathTest = FooTest;
+
+TEST_F(FooTest, DoesThis) {
+  // normal test
+}
+
+TEST_F(FooDeathTest, DoesThat) {
+  // death test
+}
+```
+
+### Regular Expression Syntax
+
+On POSIX systems (e.g. Linux, Cygwin, and Mac), googletest uses the
+[POSIX extended regular expression](http://www.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap09.html#tag_09_04)
+syntax. To learn about this syntax, you may want to read this
+[Wikipedia entry](http://en.wikipedia.org/wiki/Regular_expression#POSIX_Extended_Regular_Expressions).
+
+On Windows, googletest uses its own simple regular expression implementation. It
+lacks many features. For example, we don't support union (`"x|y"`), grouping
+(`"(xy)"`), brackets (`"[xy]"`), and repetition count (`"x{5,7}"`), among
+others. Below is what we do support (`A` denotes a literal character, period
+(`.`), or a single `\\ ` escape sequence; `x` and `y` denote regular
+expressions.):
+
+Expression | Meaning
+---------- | --------------------------------------------------------------
+`c`        | matches any literal character `c`
+`\\d`      | matches any decimal digit
+`\\D`      | matches any character that's not a decimal digit
+`\\f`      | matches `\f`
+`\\n`      | matches `\n`
+`\\r`      | matches `\r`
+`\\s`      | matches any ASCII whitespace, including `\n`
+`\\S`      | matches any character that's not a whitespace
+`\\t`      | matches `\t`
+`\\v`      | matches `\v`
+`\\w`      | matches any letter, `_`, or decimal digit
+`\\W`      | matches any character that `\\w` doesn't match
+`\\c`      | matches any literal character `c`, which must be a punctuation
+`.`        | matches any single character except `\n`
+`A?`       | matches 0 or 1 occurrences of `A`
+`A*`       | matches 0 or many occurrences of `A`
+`A+`       | matches 1 or many occurrences of `A`
+`^`        | matches the beginning of a string (not that of each line)
+`$`        | matches the end of a string (not that of each line)
+`xy`       | matches `x` followed by `y`
+
+To help you determine which capability is available on your system, googletest
+defines macros to govern which regular expression it is using. The macros are:
+`GTEST_USES_SIMPLE_RE=1` or `GTEST_USES_POSIX_RE=1`. If you want your death
+tests to work in all cases, you can either `#if` on these macros or use the more
+limited syntax only.
+
+### How It Works
+
+Under the hood, `ASSERT_EXIT()` spawns a new process and executes the death test
+statement in that process. The details of how precisely that happens depend on
+the platform and the variable `::testing::GTEST_FLAG(death_test_style)` (which is
+initialized from the command-line flag `--gtest_death_test_style`).
+
+*   On POSIX systems, `fork()` (or `clone()` on Linux) is used to spawn the
+    child, after which:
+    *   If the variable's value is `"fast"`, the death test statement is
+        immediately executed.
+    *   If the variable's value is `"threadsafe"`, the child process re-executes
+        the unit test binary just as it was originally invoked, but with some
+        extra flags to cause just the single death test under consideration to
+        be run.
+*   On Windows, the child is spawned using the `CreateProcess()` API, and
+    re-executes the binary to cause just the single death test under
+    consideration to be run - much like the `threadsafe` mode on POSIX.
+
+Other values for the variable are illegal and will cause the death test to fail.
+Currently, the flag's default value is
+**`"fast"`**.
+
+1.  the child's exit status satisfies the predicate, and
+2.  the child's stderr matches the regular expression.
+
+If the death test statement runs to completion without dying, the child process
+will nonetheless terminate, and the assertion fails.
+
+### Death Tests And Threads
+
+The reason for the two death test styles has to do with thread safety. Due to
+well-known problems with forking in the presence of threads, death tests should
+be run in a single-threaded context. Sometimes, however, it isn't feasible to
+arrange that kind of environment. For example, statically-initialized modules
+may start threads before main is ever reached. Once threads have been created,
+it may be difficult or impossible to clean them up.
+
+googletest has three features intended to raise awareness of threading issues.
+
+1.  A warning is emitted if multiple threads are running when a death test is
+    encountered.
+2.  Test suites with a name ending in "DeathTest" are run before all other
+    tests.
+3.  It uses `clone()` instead of `fork()` to spawn the child process on Linux
+    (`clone()` is not available on Cygwin and Mac), as `fork()` is more likely
+    to cause the child to hang when the parent process has multiple threads.
+
+It's perfectly fine to create threads inside a death test statement; they are
+executed in a separate process and cannot affect the parent.
+
+### Death Test Styles
+
+The "threadsafe" death test style was introduced in order to help mitigate the
+risks of testing in a possibly multithreaded environment. It trades increased
+test execution time (potentially dramatically so) for improved thread safety.
+
+The automated testing framework does not set the style flag. You can choose a
+particular style of death tests by setting the flag programmatically:
+
+```c++
+testing::FLAGS_gtest_death_test_style="threadsafe"
+```
+
+You can do this in `main()` to set the style for all death tests in the binary,
+or in individual tests. Recall that flags are saved before running each test and
+restored afterwards, so you need not do that yourself. For example:
+
+```c++
+int main(int argc, char** argv) {
+  testing::InitGoogleTest(&argc, argv);
+  testing::FLAGS_gtest_death_test_style = "fast";
+  return RUN_ALL_TESTS();
+}
+
+TEST(MyDeathTest, TestOne) {
+  testing::FLAGS_gtest_death_test_style = "threadsafe";
+  // This test is run in the "threadsafe" style:
+  ASSERT_DEATH(ThisShouldDie(), "");
+}
+
+TEST(MyDeathTest, TestTwo) {
+  // This test is run in the "fast" style:
+  ASSERT_DEATH(ThisShouldDie(), "");
+}
+```
+
+### Caveats
+
+The `statement` argument of `ASSERT_EXIT()` can be any valid C++ statement. If
+it leaves the current function via a `return` statement or by throwing an
+exception, the death test is considered to have failed. Some googletest macros
+may return from the current function (e.g. `ASSERT_TRUE()`), so be sure to avoid
+them in `statement`.
+
+Since `statement` runs in the child process, any in-memory side effect (e.g.
+modifying a variable, releasing memory, etc) it causes will *not* be observable
+in the parent process. In particular, if you release memory in a death test,
+your program will fail the heap check as the parent process will never see the
+memory reclaimed. To solve this problem, you can
+
+1.  try not to free memory in a death test;
+2.  free the memory again in the parent process; or
+3.  do not use the heap checker in your program.
+
+Due to an implementation detail, you cannot place multiple death test assertions
+on the same line; otherwise, compilation will fail with an unobvious error
+message.
+
+Despite the improved thread safety afforded by the "threadsafe" style of death
+test, thread problems such as deadlock are still possible in the presence of
+handlers registered with `pthread_atfork(3)`.
+
+
+## Using Assertions in Sub-routines
+
+{: .callout .note}
+Note: If you want to put a series of test assertions in a subroutine to check
+for a complex condition, consider using
+[a custom GMock matcher](gmock_cook_book.md#NewMatchers)
+instead. This lets you provide a more readable error message in case of failure
+and avoid all of the issues described below.
+
+### Adding Traces to Assertions
+
+If a test sub-routine is called from several places, when an assertion inside it
+fails, it can be hard to tell which invocation of the sub-routine the failure is
+from. You can alleviate this problem using extra logging or custom failure
+messages, but that usually clutters up your tests. A better solution is to use
+the `SCOPED_TRACE` macro or the `ScopedTrace` utility:
+
+```c++
+SCOPED_TRACE(message);
+```
+```c++
+ScopedTrace trace("file_path", line_number, message);
+```
+
+where `message` can be anything streamable to `std::ostream`. `SCOPED_TRACE`
+macro will cause the current file name, line number, and the given message to be
+added in every failure message. `ScopedTrace` accepts explicit file name and
+line number in arguments, which is useful for writing test helpers. The effect
+will be undone when the control leaves the current lexical scope.
+
+For example,
+
+```c++
+10: void Sub1(int n) {
+11:   EXPECT_EQ(Bar(n), 1);
+12:   EXPECT_EQ(Bar(n + 1), 2);
+13: }
+14:
+15: TEST(FooTest, Bar) {
+16:   {
+17:     SCOPED_TRACE("A");  // This trace point will be included in
+18:                         // every failure in this scope.
+19:     Sub1(1);
+20:   }
+21:   // Now it won't.
+22:   Sub1(9);
+23: }
+```
+
+could result in messages like these:
+
+```none
+path/to/foo_test.cc:11: Failure
+Value of: Bar(n)
+Expected: 1
+  Actual: 2
+Google Test trace:
+path/to/foo_test.cc:17: A
+
+path/to/foo_test.cc:12: Failure
+Value of: Bar(n + 1)
+Expected: 2
+  Actual: 3
+```
+
+Without the trace, it would've been difficult to know which invocation of
+`Sub1()` the two failures come from respectively. (You could add an extra
+message to each assertion in `Sub1()` to indicate the value of `n`, but that's
+tedious.)
+
+Some tips on using `SCOPED_TRACE`:
+
+1.  With a suitable message, it's often enough to use `SCOPED_TRACE` at the
+    beginning of a sub-routine, instead of at each call site.
+2.  When calling sub-routines inside a loop, make the loop iterator part of the
+    message in `SCOPED_TRACE` such that you can know which iteration the failure
+    is from.
+3.  Sometimes the line number of the trace point is enough for identifying the
+    particular invocation of a sub-routine. In this case, you don't have to
+    choose a unique message for `SCOPED_TRACE`. You can simply use `""`.
+4.  You can use `SCOPED_TRACE` in an inner scope when there is one in the outer
+    scope. In this case, all active trace points will be included in the failure
+    messages, in reverse order they are encountered.
+5.  The trace dump is clickable in Emacs - hit `return` on a line number and
+    you'll be taken to that line in the source file!
+
+### Propagating Fatal Failures
+
+A common pitfall when using `ASSERT_*` and `FAIL*` is not understanding that
+when they fail they only abort the _current function_, not the entire test. For
+example, the following test will segfault:
+
+```c++
+void Subroutine() {
+  // Generates a fatal failure and aborts the current function.
+  ASSERT_EQ(1, 2);
+
+  // The following won't be executed.
+  ...
+}
+
+TEST(FooTest, Bar) {
+  Subroutine();  // The intended behavior is for the fatal failure
+                 // in Subroutine() to abort the entire test.
+
+  // The actual behavior: the function goes on after Subroutine() returns.
+  int* p = nullptr;
+  *p = 3;  // Segfault!
+}
+```
+
+To alleviate this, googletest provides three different solutions. You could use
+either exceptions, the `(ASSERT|EXPECT)_NO_FATAL_FAILURE` assertions or the
+`HasFatalFailure()` function. They are described in the following two
+subsections.
+
+#### Asserting on Subroutines with an exception
+
+The following code can turn ASSERT-failure into an exception:
+
+```c++
+class ThrowListener : public testing::EmptyTestEventListener {
+  void OnTestPartResult(const testing::TestPartResult& result) override {
+    if (result.type() == testing::TestPartResult::kFatalFailure) {
+      throw testing::AssertionException(result);
+    }
+  }
+};
+int main(int argc, char** argv) {
+  ...
+  testing::UnitTest::GetInstance()->listeners().Append(new ThrowListener);
+  return RUN_ALL_TESTS();
+}
+```
+
+This listener should be added after other listeners if you have any, otherwise
+they won't see failed `OnTestPartResult`.
+
+#### Asserting on Subroutines
+
+As shown above, if your test calls a subroutine that has an `ASSERT_*` failure
+in it, the test will continue after the subroutine returns. This may not be what
+you want.
+
+Often people want fatal failures to propagate like exceptions. For that
+googletest offers the following macros:
+
+Fatal assertion                       | Nonfatal assertion                    | Verifies
+------------------------------------- | ------------------------------------- | --------
+`ASSERT_NO_FATAL_FAILURE(statement);` | `EXPECT_NO_FATAL_FAILURE(statement);` | `statement` doesn't generate any new fatal failures in the current thread.
+
+Only failures in the thread that executes the assertion are checked to determine
+the result of this type of assertions. If `statement` creates new threads,
+failures in these threads are ignored.
+
+Examples:
+
+```c++
+ASSERT_NO_FATAL_FAILURE(Foo());
+
+int i;
+EXPECT_NO_FATAL_FAILURE({
+  i = Bar();
+});
+```
+
+Assertions from multiple threads are currently not supported on Windows.
+
+#### Checking for Failures in the Current Test
+
+`HasFatalFailure()` in the `::testing::Test` class returns `true` if an
+assertion in the current test has suffered a fatal failure. This allows
+functions to catch fatal failures in a sub-routine and return early.
+
+```c++
+class Test {
+ public:
+  ...
+  static bool HasFatalFailure();
+};
+```
+
+The typical usage, which basically simulates the behavior of a thrown exception,
+is:
+
+```c++
+TEST(FooTest, Bar) {
+  Subroutine();
+  // Aborts if Subroutine() had a fatal failure.
+  if (HasFatalFailure()) return;
+
+  // The following won't be executed.
+  ...
+}
+```
+
+If `HasFatalFailure()` is used outside of `TEST()` , `TEST_F()` , or a test
+fixture, you must add the `::testing::Test::` prefix, as in:
+
+```c++
+if (testing::Test::HasFatalFailure()) return;
+```
+
+Similarly, `HasNonfatalFailure()` returns `true` if the current test has at
+least one non-fatal failure, and `HasFailure()` returns `true` if the current
+test has at least one failure of either kind.
+
+## Logging Additional Information
+
+In your test code, you can call `RecordProperty("key", value)` to log additional
+information, where `value` can be either a string or an `int`. The *last* value
+recorded for a key will be emitted to the
+[XML output](#generating-an-xml-report) if you specify one. For example, the
+test
+
+```c++
+TEST_F(WidgetUsageTest, MinAndMaxWidgets) {
+  RecordProperty("MaximumWidgets", ComputeMaxUsage());
+  RecordProperty("MinimumWidgets", ComputeMinUsage());
+}
+```
+
+will output XML like this:
+
+```xml
+  ...
+    <testcase name="MinAndMaxWidgets" status="run" time="0.006" classname="WidgetUsageTest" MaximumWidgets="12" MinimumWidgets="9" />
+  ...
+```
+
+{: .callout .note}
+> NOTE:
+>
+> *   `RecordProperty()` is a static member of the `Test` class. Therefore it
+>     needs to be prefixed with `::testing::Test::` if used outside of the
+>     `TEST` body and the test fixture class.
+> *   *`key`* must be a valid XML attribute name, and cannot conflict with the
+>     ones already used by googletest (`name`, `status`, `time`, `classname`,
+>     `type_param`, and `value_param`).
+> *   Calling `RecordProperty()` outside of the lifespan of a test is allowed.
+>     If it's called outside of a test but between a test suite's
+>     `SetUpTestSuite()` and `TearDownTestSuite()` methods, it will be
+>     attributed to the XML element for the test suite. If it's called outside
+>     of all test suites (e.g. in a test environment), it will be attributed to
+>     the top-level XML element.
+
+## Sharing Resources Between Tests in the Same Test Suite
+
+googletest creates a new test fixture object for each test in order to make
+tests independent and easier to debug. However, sometimes tests use resources
+that are expensive to set up, making the one-copy-per-test model prohibitively
+expensive.
+
+If the tests don't change the resource, there's no harm in their sharing a
+single resource copy. So, in addition to per-test set-up/tear-down, googletest
+also supports per-test-suite set-up/tear-down. To use it:
+
+1.  In your test fixture class (say `FooTest` ), declare as `static` some member
+    variables to hold the shared resources.
+2.  Outside your test fixture class (typically just below it), define those
+    member variables, optionally giving them initial values.
+3.  In the same test fixture class, define a `static void SetUpTestSuite()`
+    function (remember not to spell it as **`SetupTestSuite`** with a small
+    `u`!) to set up the shared resources and a `static void TearDownTestSuite()`
+    function to tear them down.
+
+That's it! googletest automatically calls `SetUpTestSuite()` before running the
+*first test* in the `FooTest` test suite (i.e. before creating the first
+`FooTest` object), and calls `TearDownTestSuite()` after running the *last test*
+in it (i.e. after deleting the last `FooTest` object). In between, the tests can
+use the shared resources.
+
+Remember that the test order is undefined, so your code can't depend on a test
+preceding or following another. Also, the tests must either not modify the state
+of any shared resource, or, if they do modify the state, they must restore the
+state to its original value before passing control to the next test.
+
+Here's an example of per-test-suite set-up and tear-down:
+
+```c++
+class FooTest : public testing::Test {
+ protected:
+  // Per-test-suite set-up.
+  // Called before the first test in this test suite.
+  // Can be omitted if not needed.
+  static void SetUpTestSuite() {
+    shared_resource_ = new ...;
+  }
+
+  // Per-test-suite tear-down.
+  // Called after the last test in this test suite.
+  // Can be omitted if not needed.
+  static void TearDownTestSuite() {
+    delete shared_resource_;
+    shared_resource_ = nullptr;
+  }
+
+  // You can define per-test set-up logic as usual.
+  void SetUp() override { ... }
+
+  // You can define per-test tear-down logic as usual.
+  void TearDown() override { ... }
+
+  // Some expensive resource shared by all tests.
+  static T* shared_resource_;
+};
+
+T* FooTest::shared_resource_ = nullptr;
+
+TEST_F(FooTest, Test1) {
+  ... you can refer to shared_resource_ here ...
+}
+
+TEST_F(FooTest, Test2) {
+  ... you can refer to shared_resource_ here ...
+}
+```
+
+{: .callout .note}
+NOTE: Though the above code declares `SetUpTestSuite()` protected, it may
+sometimes be necessary to declare it public, such as when using it with
+`TEST_P`.
+
+## Global Set-Up and Tear-Down
+
+Just as you can do set-up and tear-down at the test level and the test suite
+level, you can also do it at the test program level. Here's how.
+
+First, you subclass the `::testing::Environment` class to define a test
+environment, which knows how to set-up and tear-down:
+
+```c++
+class Environment : public ::testing::Environment {
+ public:
+  ~Environment() override {}
+
+  // Override this to define how to set up the environment.
+  void SetUp() override {}
+
+  // Override this to define how to tear down the environment.
+  void TearDown() override {}
+};
+```
+
+Then, you register an instance of your environment class with googletest by
+calling the `::testing::AddGlobalTestEnvironment()` function:
+
+```c++
+Environment* AddGlobalTestEnvironment(Environment* env);
+```
+
+Now, when `RUN_ALL_TESTS()` is called, it first calls the `SetUp()` method of
+each environment object, then runs the tests if none of the environments
+reported fatal failures and `GTEST_SKIP()` was not called. `RUN_ALL_TESTS()`
+always calls `TearDown()` with each environment object, regardless of whether or
+not the tests were run.
+
+It's OK to register multiple environment objects. In this suite, their `SetUp()`
+will be called in the order they are registered, and their `TearDown()` will be
+called in the reverse order.
+
+Note that googletest takes ownership of the registered environment objects.
+Therefore **do not delete them** by yourself.
+
+You should call `AddGlobalTestEnvironment()` before `RUN_ALL_TESTS()` is called,
+probably in `main()`. If you use `gtest_main`, you need to call this before
+`main()` starts for it to take effect. One way to do this is to define a global
+variable like this:
+
+```c++
+testing::Environment* const foo_env =
+    testing::AddGlobalTestEnvironment(new FooEnvironment);
+```
+
+However, we strongly recommend you to write your own `main()` and call
+`AddGlobalTestEnvironment()` there, as relying on initialization of global
+variables makes the code harder to read and may cause problems when you register
+multiple environments from different translation units and the environments have
+dependencies among them (remember that the compiler doesn't guarantee the order
+in which global variables from different translation units are initialized).
+
+## Value-Parameterized Tests
+
+*Value-parameterized tests* allow you to test your code with different
+parameters without writing multiple copies of the same test. This is useful in a
+number of situations, for example:
+
+*   You have a piece of code whose behavior is affected by one or more
+    command-line flags. You want to make sure your code performs correctly for
+    various values of those flags.
+*   You want to test different implementations of an OO interface.
+*   You want to test your code over various inputs (a.k.a. data-driven testing).
+    This feature is easy to abuse, so please exercise your good sense when doing
+    it!
+
+### How to Write Value-Parameterized Tests
+
+To write value-parameterized tests, first you should define a fixture class. It
+must be derived from both `testing::Test` and `testing::WithParamInterface<T>`
+(the latter is a pure interface), where `T` is the type of your parameter
+values. For convenience, you can just derive the fixture class from
+`testing::TestWithParam<T>`, which itself is derived from both `testing::Test`
+and `testing::WithParamInterface<T>`. `T` can be any copyable type. If it's a
+raw pointer, you are responsible for managing the lifespan of the pointed
+values.
+
+{: .callout .note}
+NOTE: If your test fixture defines `SetUpTestSuite()` or `TearDownTestSuite()`
+they must be declared **public** rather than **protected** in order to use
+`TEST_P`.
+
+```c++
+class FooTest :
+    public testing::TestWithParam<const char*> {
+  // You can implement all the usual fixture class members here.
+  // To access the test parameter, call GetParam() from class
+  // TestWithParam<T>.
+};
+
+// Or, when you want to add parameters to a pre-existing fixture class:
+class BaseTest : public testing::Test {
+  ...
+};
+class BarTest : public BaseTest,
+                public testing::WithParamInterface<const char*> {
+  ...
+};
+```
+
+Then, use the `TEST_P` macro to define as many test patterns using this fixture
+as you want. The `_P` suffix is for "parameterized" or "pattern", whichever you
+prefer to think.
+
+```c++
+TEST_P(FooTest, DoesBlah) {
+  // Inside a test, access the test parameter with the GetParam() method
+  // of the TestWithParam<T> class:
+  EXPECT_TRUE(foo.Blah(GetParam()));
+  ...
+}
+
+TEST_P(FooTest, HasBlahBlah) {
+  ...
+}
+```
+
+Finally, you can use `INSTANTIATE_TEST_SUITE_P` to instantiate the test suite
+with any set of parameters you want. googletest defines a number of functions
+for generating test parameters. They return what we call (surprise!) *parameter
+generators*. Here is a summary of them, which are all in the `testing`
+namespace:
+
+
+| Parameter Generator                                                                       | Behavior                                                                                                          |
+| ----------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------- |
+| `Range(begin, end [, step])`                                                              | Yields values `{begin, begin+step, begin+step+step, ...}`. The values do not include `end`. `step` defaults to 1. |
+| `Values(v1, v2, ..., vN)`                                                                 | Yields values `{v1, v2, ..., vN}`.                                                                                |
+| `ValuesIn(container)` and  `ValuesIn(begin,end)`                                          | Yields values from a C-style array, an  STL-style container, or an iterator range `[begin, end)`                  |
+| `Bool()`                                                                                  | Yields sequence `{false, true}`.                                                                                  |
+| `Combine(g1, g2, ..., gN)`                                                                | Yields all combinations (Cartesian product) as std\:\:tuples of the values generated by the `N` generators.       |
+
+
+For more details, see the comments at the definitions of these functions.
+
+The following statement will instantiate tests from the `FooTest` test suite
+each with parameter values `"meeny"`, `"miny"`, and `"moe"`.
+
+```c++
+INSTANTIATE_TEST_SUITE_P(MeenyMinyMoe,
+                         FooTest,
+                         testing::Values("meeny", "miny", "moe"));
+```
+
+{: .callout .note}
+NOTE: The code above must be placed at global or namespace scope, not at
+function scope.
+
+The first argument to `INSTANTIATE_TEST_SUITE_P` is a unique name for the
+instantiation of the test suite. The next argument is the name of the test
+pattern, and the last is the parameter generator.
+
+You can instantiate a test pattern more than once, so to distinguish different
+instances of the pattern, the instantiation name is added as a prefix to the
+actual test suite name. Remember to pick unique prefixes for different
+instantiations. The tests from the instantiation above will have these names:
+
+*   `MeenyMinyMoe/FooTest.DoesBlah/0` for `"meeny"`
+*   `MeenyMinyMoe/FooTest.DoesBlah/1` for `"miny"`
+*   `MeenyMinyMoe/FooTest.DoesBlah/2` for `"moe"`
+*   `MeenyMinyMoe/FooTest.HasBlahBlah/0` for `"meeny"`
+*   `MeenyMinyMoe/FooTest.HasBlahBlah/1` for `"miny"`
+*   `MeenyMinyMoe/FooTest.HasBlahBlah/2` for `"moe"`
+
+You can use these names in [`--gtest_filter`](#running-a-subset-of-the-tests).
+
+The following statement will instantiate all tests from `FooTest` again, each
+with parameter values `"cat"` and `"dog"`:
+
+```c++
+const char* pets[] = {"cat", "dog"};
+INSTANTIATE_TEST_SUITE_P(Pets, FooTest, testing::ValuesIn(pets));
+```
+
+The tests from the instantiation above will have these names:
+
+*   `Pets/FooTest.DoesBlah/0` for `"cat"`
+*   `Pets/FooTest.DoesBlah/1` for `"dog"`
+*   `Pets/FooTest.HasBlahBlah/0` for `"cat"`
+*   `Pets/FooTest.HasBlahBlah/1` for `"dog"`
+
+Please note that `INSTANTIATE_TEST_SUITE_P` will instantiate *all* tests in the
+given test suite, whether their definitions come before or *after* the
+`INSTANTIATE_TEST_SUITE_P` statement.
+
+Additionally, by default, every `TEST_P` without a corresponding
+`INSTANTIATE_TEST_SUITE_P` causes a failing test in test suite
+`GoogleTestVerification`. If you have a test suite where that omission is not an
+error, for example it is in a library that may be linked in for other reasons or
+where the list of test cases is dynamic and may be empty, then this check can be
+suppressed by tagging the test suite:
+
+```c++
+GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST(FooTest);
+```
+
+You can see [sample7_unittest.cc] and [sample8_unittest.cc] for more examples.
+
+[sample7_unittest.cc]: https://github.com/google/googletest/blob/master/googletest/samples/sample7_unittest.cc "Parameterized Test example"
+[sample8_unittest.cc]: https://github.com/google/googletest/blob/master/googletest/samples/sample8_unittest.cc "Parameterized Test example with multiple parameters"
+
+### Creating Value-Parameterized Abstract Tests
+
+In the above, we define and instantiate `FooTest` in the *same* source file.
+Sometimes you may want to define value-parameterized tests in a library and let
+other people instantiate them later. This pattern is known as *abstract tests*.
+As an example of its application, when you are designing an interface you can
+write a standard suite of abstract tests (perhaps using a factory function as
+the test parameter) that all implementations of the interface are expected to
+pass. When someone implements the interface, they can instantiate your suite to
+get all the interface-conformance tests for free.
+
+To define abstract tests, you should organize your code like this:
+
+1.  Put the definition of the parameterized test fixture class (e.g. `FooTest`)
+    in a header file, say `foo_param_test.h`. Think of this as *declaring* your
+    abstract tests.
+2.  Put the `TEST_P` definitions in `foo_param_test.cc`, which includes
+    `foo_param_test.h`. Think of this as *implementing* your abstract tests.
+
+Once they are defined, you can instantiate them by including `foo_param_test.h`,
+invoking `INSTANTIATE_TEST_SUITE_P()`, and depending on the library target that
+contains `foo_param_test.cc`. You can instantiate the same abstract test suite
+multiple times, possibly in different source files.
+
+### Specifying Names for Value-Parameterized Test Parameters
+
+The optional last argument to `INSTANTIATE_TEST_SUITE_P()` allows the user to
+specify a function or functor that generates custom test name suffixes based on
+the test parameters. The function should accept one argument of type
+`testing::TestParamInfo<class ParamType>`, and return `std::string`.
+
+`testing::PrintToStringParamName` is a builtin test suffix generator that
+returns the value of `testing::PrintToString(GetParam())`. It does not work for
+`std::string` or C strings.
+
+{: .callout .note}
+NOTE: test names must be non-empty, unique, and may only contain ASCII
+alphanumeric characters. In particular, they
+[should not contain underscores](faq.md#why-should-test-suite-names-and-test-names-not-contain-underscore)
+
+```c++
+class MyTestSuite : public testing::TestWithParam<int> {};
+
+TEST_P(MyTestSuite, MyTest)
+{
+  std::cout << "Example Test Param: " << GetParam() << std::endl;
+}
+
+INSTANTIATE_TEST_SUITE_P(MyGroup, MyTestSuite, testing::Range(0, 10),
+                         testing::PrintToStringParamName());
+```
+
+Providing a custom functor allows for more control over test parameter name
+generation, especially for types where the automatic conversion does not
+generate helpful parameter names (e.g. strings as demonstrated above). The
+following example illustrates this for multiple parameters, an enumeration type
+and a string, and also demonstrates how to combine generators. It uses a lambda
+for conciseness:
+
+```c++
+enum class MyType { MY_FOO = 0, MY_BAR = 1 };
+
+class MyTestSuite : public testing::TestWithParam<std::tuple<MyType, std::string>> {
+};
+
+INSTANTIATE_TEST_SUITE_P(
+    MyGroup, MyTestSuite,
+    testing::Combine(
+        testing::Values(MyType::MY_FOO, MyType::MY_BAR),
+        testing::Values("A", "B")),
+    [](const testing::TestParamInfo<MyTestSuite::ParamType>& info) {
+      std::string name = absl::StrCat(
+          std::get<0>(info.param) == MyType::MY_FOO ? "Foo" : "Bar",
+          std::get<1>(info.param));
+      absl::c_replace_if(name, [](char c) { return !std::isalnum(c); }, '_');
+      return name;
+    });
+```
+
+## Typed Tests
+
+Suppose you have multiple implementations of the same interface and want to make
+sure that all of them satisfy some common requirements. Or, you may have defined
+several types that are supposed to conform to the same "concept" and you want to
+verify it. In both cases, you want the same test logic repeated for different
+types.
+
+While you can write one `TEST` or `TEST_F` for each type you want to test (and
+you may even factor the test logic into a function template that you invoke from
+the `TEST`), it's tedious and doesn't scale: if you want `m` tests over `n`
+types, you'll end up writing `m*n` `TEST`s.
+
+*Typed tests* allow you to repeat the same test logic over a list of types. You
+only need to write the test logic once, although you must know the type list
+when writing typed tests. Here's how you do it:
+
+First, define a fixture class template. It should be parameterized by a type.
+Remember to derive it from `::testing::Test`:
+
+```c++
+template <typename T>
+class FooTest : public testing::Test {
+ public:
+  ...
+  using List = std::list<T>;
+  static T shared_;
+  T value_;
+};
+```
+
+Next, associate a list of types with the test suite, which will be repeated for
+each type in the list:
+
+```c++
+using MyTypes = ::testing::Types<char, int, unsigned int>;
+TYPED_TEST_SUITE(FooTest, MyTypes);
+```
+
+The type alias (`using` or `typedef`) is necessary for the `TYPED_TEST_SUITE`
+macro to parse correctly. Otherwise the compiler will think that each comma in
+the type list introduces a new macro argument.
+
+Then, use `TYPED_TEST()` instead of `TEST_F()` to define a typed test for this
+test suite. You can repeat this as many times as you want:
+
+```c++
+TYPED_TEST(FooTest, DoesBlah) {
+  // Inside a test, refer to the special name TypeParam to get the type
+  // parameter.  Since we are inside a derived class template, C++ requires
+  // us to visit the members of FooTest via 'this'.
+  TypeParam n = this->value_;
+
+  // To visit static members of the fixture, add the 'TestFixture::'
+  // prefix.
+  n += TestFixture::shared_;
+
+  // To refer to typedefs in the fixture, add the 'typename TestFixture::'
+  // prefix.  The 'typename' is required to satisfy the compiler.
+  typename TestFixture::List values;
+
+  values.push_back(n);
+  ...
+}
+
+TYPED_TEST(FooTest, HasPropertyA) { ... }
+```
+
+You can see [sample6_unittest.cc] for a complete example.
+
+[sample6_unittest.cc]: https://github.com/google/googletest/blob/master/googletest/samples/sample6_unittest.cc "Typed Test example"
+
+## Type-Parameterized Tests
+
+*Type-parameterized tests* are like typed tests, except that they don't require
+you to know the list of types ahead of time. Instead, you can define the test
+logic first and instantiate it with different type lists later. You can even
+instantiate it more than once in the same program.
+
+If you are designing an interface or concept, you can define a suite of
+type-parameterized tests to verify properties that any valid implementation of
+the interface/concept should have. Then, the author of each implementation can
+just instantiate the test suite with their type to verify that it conforms to
+the requirements, without having to write similar tests repeatedly. Here's an
+example:
+
+First, define a fixture class template, as we did with typed tests:
+
+```c++
+template <typename T>
+class FooTest : public testing::Test {
+  ...
+};
+```
+
+Next, declare that you will define a type-parameterized test suite:
+
+```c++
+TYPED_TEST_SUITE_P(FooTest);
+```
+
+Then, use `TYPED_TEST_P()` to define a type-parameterized test. You can repeat
+this as many times as you want:
+
+```c++
+TYPED_TEST_P(FooTest, DoesBlah) {
+  // Inside a test, refer to TypeParam to get the type parameter.
+  TypeParam n = 0;
+  ...
+}
+
+TYPED_TEST_P(FooTest, HasPropertyA) { ... }
+```
+
+Now the tricky part: you need to register all test patterns using the
+`REGISTER_TYPED_TEST_SUITE_P` macro before you can instantiate them. The first
+argument of the macro is the test suite name; the rest are the names of the
+tests in this test suite:
+
+```c++
+REGISTER_TYPED_TEST_SUITE_P(FooTest,
+                            DoesBlah, HasPropertyA);
+```
+
+Finally, you are free to instantiate the pattern with the types you want. If you
+put the above code in a header file, you can `#include` it in multiple C++
+source files and instantiate it multiple times.
+
+```c++
+using MyTypes = ::testing::Types<char, int, unsigned int>;
+INSTANTIATE_TYPED_TEST_SUITE_P(My, FooTest, MyTypes);
+```
+
+To distinguish different instances of the pattern, the first argument to the
+`INSTANTIATE_TYPED_TEST_SUITE_P` macro is a prefix that will be added to the
+actual test suite name. Remember to pick unique prefixes for different
+instances.
+
+In the special case where the type list contains only one type, you can write
+that type directly without `::testing::Types<...>`, like this:
+
+```c++
+INSTANTIATE_TYPED_TEST_SUITE_P(My, FooTest, int);
+```
+
+You can see [sample6_unittest.cc] for a complete example.
+
+## Testing Private Code
+
+If you change your software's internal implementation, your tests should not
+break as long as the change is not observable by users. Therefore, **per the
+black-box testing principle, most of the time you should test your code through
+its public interfaces.**
+
+**If you still find yourself needing to test internal implementation code,
+consider if there's a better design.** The desire to test internal
+implementation is often a sign that the class is doing too much. Consider
+extracting an implementation class, and testing it. Then use that implementation
+class in the original class.
+
+If you absolutely have to test non-public interface code though, you can. There
+are two cases to consider:
+
+*   Static functions ( *not* the same as static member functions!) or unnamed
+    namespaces, and
+*   Private or protected class members
+
+To test them, we use the following special techniques:
+
+*   Both static functions and definitions/declarations in an unnamed namespace
+    are only visible within the same translation unit. To test them, you can
+    `#include` the entire `.cc` file being tested in your `*_test.cc` file.
+    (#including `.cc` files is not a good way to reuse code - you should not do
+    this in production code!)
+
+    However, a better approach is to move the private code into the
+    `foo::internal` namespace, where `foo` is the namespace your project
+    normally uses, and put the private declarations in a `*-internal.h` file.
+    Your production `.cc` files and your tests are allowed to include this
+    internal header, but your clients are not. This way, you can fully test your
+    internal implementation without leaking it to your clients.
+
+*   Private class members are only accessible from within the class or by
+    friends. To access a class' private members, you can declare your test
+    fixture as a friend to the class and define accessors in your fixture. Tests
+    using the fixture can then access the private members of your production
+    class via the accessors in the fixture. Note that even though your fixture
+    is a friend to your production class, your tests are not automatically
+    friends to it, as they are technically defined in sub-classes of the
+    fixture.
+
+    Another way to test private members is to refactor them into an
+    implementation class, which is then declared in a `*-internal.h` file. Your
+    clients aren't allowed to include this header but your tests can. Such is
+    called the
+    [Pimpl](https://www.gamedev.net/articles/programming/general-and-gameplay-programming/the-c-pimpl-r1794/)
+    (Private Implementation) idiom.
+
+    Or, you can declare an individual test as a friend of your class by adding
+    this line in the class body:
+
+    ```c++
+        FRIEND_TEST(TestSuiteName, TestName);
+    ```
+
+    For example,
+
+    ```c++
+    // foo.h
+    class Foo {
+      ...
+     private:
+      FRIEND_TEST(FooTest, BarReturnsZeroOnNull);
+
+      int Bar(void* x);
+    };
+
+    // foo_test.cc
+    ...
+    TEST(FooTest, BarReturnsZeroOnNull) {
+      Foo foo;
+      EXPECT_EQ(foo.Bar(NULL), 0);  // Uses Foo's private member Bar().
+    }
+    ```
+
+    Pay special attention when your class is defined in a namespace. If you want
+    your test fixtures and tests to be friends of your class, then they must be
+    defined in the exact same namespace (no anonymous or inline namespaces).
+
+    For example, if the code to be tested looks like:
+
+    ```c++
+    namespace my_namespace {
+
+    class Foo {
+      friend class FooTest;
+      FRIEND_TEST(FooTest, Bar);
+      FRIEND_TEST(FooTest, Baz);
+      ... definition of the class Foo ...
+    };
+
+    }  // namespace my_namespace
+    ```
+
+    Your test code should be something like:
+
+    ```c++
+    namespace my_namespace {
+
+    class FooTest : public testing::Test {
+     protected:
+      ...
+    };
+
+    TEST_F(FooTest, Bar) { ... }
+    TEST_F(FooTest, Baz) { ... }
+
+    }  // namespace my_namespace
+    ```
+
+## "Catching" Failures
+
+If you are building a testing utility on top of googletest, you'll want to test
+your utility. What framework would you use to test it? googletest, of course.
+
+The challenge is to verify that your testing utility reports failures correctly.
+In frameworks that report a failure by throwing an exception, you could catch
+the exception and assert on it. But googletest doesn't use exceptions, so how do
+we test that a piece of code generates an expected failure?
+
+`"gtest/gtest-spi.h"` contains some constructs to do this. After #including this header,
+you can use
+
+```c++
+  EXPECT_FATAL_FAILURE(statement, substring);
+```
+
+to assert that `statement` generates a fatal (e.g. `ASSERT_*`) failure in the
+current thread whose message contains the given `substring`, or use
+
+```c++
+  EXPECT_NONFATAL_FAILURE(statement, substring);
+```
+
+if you are expecting a non-fatal (e.g. `EXPECT_*`) failure.
+
+Only failures in the current thread are checked to determine the result of this
+type of expectations. If `statement` creates new threads, failures in these
+threads are also ignored. If you want to catch failures in other threads as
+well, use one of the following macros instead:
+
+```c++
+  EXPECT_FATAL_FAILURE_ON_ALL_THREADS(statement, substring);
+  EXPECT_NONFATAL_FAILURE_ON_ALL_THREADS(statement, substring);
+```
+
+{: .callout .note}
+NOTE: Assertions from multiple threads are currently not supported on Windows.
+
+For technical reasons, there are some caveats:
+
+1.  You cannot stream a failure message to either macro.
+
+2.  `statement` in `EXPECT_FATAL_FAILURE{_ON_ALL_THREADS}()` cannot reference
+    local non-static variables or non-static members of `this` object.
+
+3.  `statement` in `EXPECT_FATAL_FAILURE{_ON_ALL_THREADS}()` cannot return a
+    value.
+
+## Registering tests programmatically
+
+The `TEST` macros handle the vast majority of all use cases, but there are few
+where runtime registration logic is required. For those cases, the framework
+provides the `::testing::RegisterTest` that allows callers to register arbitrary
+tests dynamically.
+
+This is an advanced API only to be used when the `TEST` macros are insufficient.
+The macros should be preferred when possible, as they avoid most of the
+complexity of calling this function.
+
+It provides the following signature:
+
+```c++
+template <typename Factory>
+TestInfo* RegisterTest(const char* test_suite_name, const char* test_name,
+                       const char* type_param, const char* value_param,
+                       const char* file, int line, Factory factory);
+```
+
+The `factory` argument is a factory callable (move-constructible) object or
+function pointer that creates a new instance of the Test object. It handles
+ownership to the caller. The signature of the callable is `Fixture*()`, where
+`Fixture` is the test fixture class for the test. All tests registered with the
+same `test_suite_name` must return the same fixture type. This is checked at
+runtime.
+
+The framework will infer the fixture class from the factory and will call the
+`SetUpTestSuite` and `TearDownTestSuite` for it.
+
+Must be called before `RUN_ALL_TESTS()` is invoked, otherwise behavior is
+undefined.
+
+Use case example:
+
+```c++
+class MyFixture : public testing::Test {
+ public:
+  // All of these optional, just like in regular macro usage.
+  static void SetUpTestSuite() { ... }
+  static void TearDownTestSuite() { ... }
+  void SetUp() override { ... }
+  void TearDown() override { ... }
+};
+
+class MyTest : public MyFixture {
+ public:
+  explicit MyTest(int data) : data_(data) {}
+  void TestBody() override { ... }
+
+ private:
+  int data_;
+};
+
+void RegisterMyTests(const std::vector<int>& values) {
+  for (int v : values) {
+    testing::RegisterTest(
+        "MyFixture", ("Test" + std::to_string(v)).c_str(), nullptr,
+        std::to_string(v).c_str(),
+        __FILE__, __LINE__,
+        // Important to use the fixture type as the return type here.
+        [=]() -> MyFixture* { return new MyTest(v); });
+  }
+}
+...
+int main(int argc, char** argv) {
+  std::vector<int> values_to_test = LoadValuesFromConfig();
+  RegisterMyTests(values_to_test);
+  ...
+  return RUN_ALL_TESTS();
+}
+```
+## Getting the Current Test's Name
+
+Sometimes a function may need to know the name of the currently running test.
+For example, you may be using the `SetUp()` method of your test fixture to set
+the golden file name based on which test is running. The `::testing::TestInfo`
+class has this information:
+
+```c++
+namespace testing {
+
+class TestInfo {
+ public:
+  // Returns the test suite name and the test name, respectively.
+  //
+  // Do NOT delete or free the return value - it's managed by the
+  // TestInfo class.
+  const char* test_suite_name() const;
+  const char* name() const;
+};
+
+}
+```
+
+To obtain a `TestInfo` object for the currently running test, call
+`current_test_info()` on the `UnitTest` singleton object:
+
+```c++
+  // Gets information about the currently running test.
+  // Do NOT delete the returned object - it's managed by the UnitTest class.
+  const testing::TestInfo* const test_info =
+      testing::UnitTest::GetInstance()->current_test_info();
+
+  printf("We are in test %s of test suite %s.\n",
+         test_info->name(),
+         test_info->test_suite_name());
+```
+
+`current_test_info()` returns a null pointer if no test is running. In
+particular, you cannot find the test suite name in `SetUpTestSuite()`,
+`TearDownTestSuite()` (where you know the test suite name implicitly), or
+functions called from them.
+
+## Extending googletest by Handling Test Events
+
+googletest provides an **event listener API** to let you receive notifications
+about the progress of a test program and test failures. The events you can
+listen to include the start and end of the test program, a test suite, or a test
+method, among others. You may use this API to augment or replace the standard
+console output, replace the XML output, or provide a completely different form
+of output, such as a GUI or a database. You can also use test events as
+checkpoints to implement a resource leak checker, for example.
+
+### Defining Event Listeners
+
+To define a event listener, you subclass either testing::TestEventListener or
+testing::EmptyTestEventListener The former is an (abstract) interface, where
+*each pure virtual method can be overridden to handle a test event* (For
+example, when a test starts, the `OnTestStart()` method will be called.). The
+latter provides an empty implementation of all methods in the interface, such
+that a subclass only needs to override the methods it cares about.
+
+When an event is fired, its context is passed to the handler function as an
+argument. The following argument types are used:
+
+*   UnitTest reflects the state of the entire test program,
+*   TestSuite has information about a test suite, which can contain one or more
+    tests,
+*   TestInfo contains the state of a test, and
+*   TestPartResult represents the result of a test assertion.
+
+An event handler function can examine the argument it receives to find out
+interesting information about the event and the test program's state.
+
+Here's an example:
+
+```c++
+  class MinimalistPrinter : public testing::EmptyTestEventListener {
+    // Called before a test starts.
+    void OnTestStart(const testing::TestInfo& test_info) override {
+      printf("*** Test %s.%s starting.\n",
+             test_info.test_suite_name(), test_info.name());
+    }
+
+    // Called after a failed assertion or a SUCCESS().
+    void OnTestPartResult(const testing::TestPartResult& test_part_result) override {
+      printf("%s in %s:%d\n%s\n",
+             test_part_result.failed() ? "*** Failure" : "Success",
+             test_part_result.file_name(),
+             test_part_result.line_number(),
+             test_part_result.summary());
+    }
+
+    // Called after a test ends.
+    void OnTestEnd(const testing::TestInfo& test_info) override {
+      printf("*** Test %s.%s ending.\n",
+             test_info.test_suite_name(), test_info.name());
+    }
+  };
+```
+
+### Using Event Listeners
+
+To use the event listener you have defined, add an instance of it to the
+googletest event listener list (represented by class TestEventListeners - note
+the "s" at the end of the name) in your `main()` function, before calling
+`RUN_ALL_TESTS()`:
+
+```c++
+int main(int argc, char** argv) {
+  testing::InitGoogleTest(&argc, argv);
+  // Gets hold of the event listener list.
+  testing::TestEventListeners& listeners =
+      testing::UnitTest::GetInstance()->listeners();
+  // Adds a listener to the end.  googletest takes the ownership.
+  listeners.Append(new MinimalistPrinter);
+  return RUN_ALL_TESTS();
+}
+```
+
+There's only one problem: the default test result printer is still in effect, so
+its output will mingle with the output from your minimalist printer. To suppress
+the default printer, just release it from the event listener list and delete it.
+You can do so by adding one line:
+
+```c++
+  ...
+  delete listeners.Release(listeners.default_result_printer());
+  listeners.Append(new MinimalistPrinter);
+  return RUN_ALL_TESTS();
+```
+
+Now, sit back and enjoy a completely different output from your tests. For more
+details, see [sample9_unittest.cc].
+
+[sample9_unittest.cc]: https://github.com/google/googletest/blob/master/googletest/samples/sample9_unittest.cc "Event listener example"
+
+You may append more than one listener to the list. When an `On*Start()` or
+`OnTestPartResult()` event is fired, the listeners will receive it in the order
+they appear in the list (since new listeners are added to the end of the list,
+the default text printer and the default XML generator will receive the event
+first). An `On*End()` event will be received by the listeners in the *reverse*
+order. This allows output by listeners added later to be framed by output from
+listeners added earlier.
+
+### Generating Failures in Listeners
+
+You may use failure-raising macros (`EXPECT_*()`, `ASSERT_*()`, `FAIL()`, etc)
+when processing an event. There are some restrictions:
+
+1.  You cannot generate any failure in `OnTestPartResult()` (otherwise it will
+    cause `OnTestPartResult()` to be called recursively).
+2.  A listener that handles `OnTestPartResult()` is not allowed to generate any
+    failure.
+
+When you add listeners to the listener list, you should put listeners that
+handle `OnTestPartResult()` *before* listeners that can generate failures. This
+ensures that failures generated by the latter are attributed to the right test
+by the former.
+
+See [sample10_unittest.cc] for an example of a failure-raising listener.
+
+[sample10_unittest.cc]: https://github.com/google/googletest/blob/master/googletest/samples/sample10_unittest.cc "Failure-raising listener example"
+
+## Running Test Programs: Advanced Options
+
+googletest test programs are ordinary executables. Once built, you can run them
+directly and affect their behavior via the following environment variables
+and/or command line flags. For the flags to work, your programs must call
+`::testing::InitGoogleTest()` before calling `RUN_ALL_TESTS()`.
+
+To see a list of supported flags and their usage, please run your test program
+with the `--help` flag. You can also use `-h`, `-?`, or `/?` for short.
+
+If an option is specified both by an environment variable and by a flag, the
+latter takes precedence.
+
+### Selecting Tests
+
+#### Listing Test Names
+
+Sometimes it is necessary to list the available tests in a program before
+running them so that a filter may be applied if needed. Including the flag
+`--gtest_list_tests` overrides all other flags and lists tests in the following
+format:
+
+```none
+TestSuite1.
+  TestName1
+  TestName2
+TestSuite2.
+  TestName
+```
+
+None of the tests listed are actually run if the flag is provided. There is no
+corresponding environment variable for this flag.
+
+#### Running a Subset of the Tests
+
+By default, a googletest program runs all tests the user has defined. Sometimes,
+you want to run only a subset of the tests (e.g. for debugging or quickly
+verifying a change). If you set the `GTEST_FILTER` environment variable or the
+`--gtest_filter` flag to a filter string, googletest will only run the tests
+whose full names (in the form of `TestSuiteName.TestName`) match the filter.
+
+The format of a filter is a '`:`'-separated list of wildcard patterns (called
+the *positive patterns*) optionally followed by a '`-`' and another
+'`:`'-separated pattern list (called the *negative patterns*). A test matches
+the filter if and only if it matches any of the positive patterns but does not
+match any of the negative patterns.
+
+A pattern may contain `'*'` (matches any string) or `'?'` (matches any single
+character). For convenience, the filter `'*-NegativePatterns'` can be also
+written as `'-NegativePatterns'`.
+
+For example:
+
+*   `./foo_test` Has no flag, and thus runs all its tests.
+*   `./foo_test --gtest_filter=*` Also runs everything, due to the single
+    match-everything `*` value.
+*   `./foo_test --gtest_filter=FooTest.*` Runs everything in test suite
+    `FooTest` .
+*   `./foo_test --gtest_filter=*Null*:*Constructor*` Runs any test whose full
+    name contains either `"Null"` or `"Constructor"` .
+*   `./foo_test --gtest_filter=-*DeathTest.*` Runs all non-death tests.
+*   `./foo_test --gtest_filter=FooTest.*-FooTest.Bar` Runs everything in test
+    suite `FooTest` except `FooTest.Bar`.
+*   `./foo_test --gtest_filter=FooTest.*:BarTest.*-FooTest.Bar:BarTest.Foo` Runs
+    everything in test suite `FooTest` except `FooTest.Bar` and everything in
+    test suite `BarTest` except `BarTest.Foo`.
+
+#### Stop test execution upon first failure
+
+By default, a googletest program runs all tests the user has defined. In some
+cases (e.g. iterative test development & execution) it may be desirable stop
+test execution upon first failure (trading improved latency for completeness).
+If `GTEST_FAIL_FAST` environment variable or `--gtest_fail_fast` flag is set,
+the test runner will stop execution as soon as the first test failure is
+found.
+
+#### Temporarily Disabling Tests
+
+If you have a broken test that you cannot fix right away, you can add the
+`DISABLED_` prefix to its name. This will exclude it from execution. This is
+better than commenting out the code or using `#if 0`, as disabled tests are
+still compiled (and thus won't rot).
+
+If you need to disable all tests in a test suite, you can either add `DISABLED_`
+to the front of the name of each test, or alternatively add it to the front of
+the test suite name.
+
+For example, the following tests won't be run by googletest, even though they
+will still be compiled:
+
+```c++
+// Tests that Foo does Abc.
+TEST(FooTest, DISABLED_DoesAbc) { ... }
+
+class DISABLED_BarTest : public testing::Test { ... };
+
+// Tests that Bar does Xyz.
+TEST_F(DISABLED_BarTest, DoesXyz) { ... }
+```
+
+{: .callout .note}
+NOTE: This feature should only be used for temporary pain-relief. You still have
+to fix the disabled tests at a later date. As a reminder, googletest will print
+a banner warning you if a test program contains any disabled tests.
+
+{: .callout .tip}
+TIP: You can easily count the number of disabled tests you have using
+`grep`. This number can be used as a metric for
+improving your test quality.
+
+#### Temporarily Enabling Disabled Tests
+
+To include disabled tests in test execution, just invoke the test program with
+the `--gtest_also_run_disabled_tests` flag or set the
+`GTEST_ALSO_RUN_DISABLED_TESTS` environment variable to a value other than `0`.
+You can combine this with the `--gtest_filter` flag to further select which
+disabled tests to run.
+
+### Repeating the Tests
+
+Once in a while you'll run into a test whose result is hit-or-miss. Perhaps it
+will fail only 1% of the time, making it rather hard to reproduce the bug under
+a debugger. This can be a major source of frustration.
+
+The `--gtest_repeat` flag allows you to repeat all (or selected) test methods in
+a program many times. Hopefully, a flaky test will eventually fail and give you
+a chance to debug. Here's how to use it:
+
+```none
+$ foo_test --gtest_repeat=1000
+Repeat foo_test 1000 times and don't stop at failures.
+
+$ foo_test --gtest_repeat=-1
+A negative count means repeating forever.
+
+$ foo_test --gtest_repeat=1000 --gtest_break_on_failure
+Repeat foo_test 1000 times, stopping at the first failure.  This
+is especially useful when running under a debugger: when the test
+fails, it will drop into the debugger and you can then inspect
+variables and stacks.
+
+$ foo_test --gtest_repeat=1000 --gtest_filter=FooBar.*
+Repeat the tests whose name matches the filter 1000 times.
+```
+
+If your test program contains
+[global set-up/tear-down](#global-set-up-and-tear-down) code, it will be
+repeated in each iteration as well, as the flakiness may be in it. You can also
+specify the repeat count by setting the `GTEST_REPEAT` environment variable.
+
+### Shuffling the Tests
+
+You can specify the `--gtest_shuffle` flag (or set the `GTEST_SHUFFLE`
+environment variable to `1`) to run the tests in a program in a random order.
+This helps to reveal bad dependencies between tests.
+
+By default, googletest uses a random seed calculated from the current time.
+Therefore you'll get a different order every time. The console output includes
+the random seed value, such that you can reproduce an order-related test failure
+later. To specify the random seed explicitly, use the `--gtest_random_seed=SEED`
+flag (or set the `GTEST_RANDOM_SEED` environment variable), where `SEED` is an
+integer in the range [0, 99999]. The seed value 0 is special: it tells
+googletest to do the default behavior of calculating the seed from the current
+time.
+
+If you combine this with `--gtest_repeat=N`, googletest will pick a different
+random seed and re-shuffle the tests in each iteration.
+
+### Controlling Test Output
+
+#### Colored Terminal Output
+
+googletest can use colors in its terminal output to make it easier to spot the
+important information:
+
+<pre>...
+<font color="green">[----------]</font> 1 test from FooTest
+<font color="green">[ RUN      ]</font> FooTest.DoesAbc
+<font color="green">[       OK ]</font> FooTest.DoesAbc
+<font color="green">[----------]</font> 2 tests from BarTest
+<font color="green">[ RUN      ]</font> BarTest.HasXyzProperty
+<font color="green">[       OK ]</font> BarTest.HasXyzProperty
+<font color="green">[ RUN      ]</font> BarTest.ReturnsTrueOnSuccess
+... some error messages ...
+<font color="red">[   FAILED ]</font> BarTest.ReturnsTrueOnSuccess
+...
+<font color="green">[==========]</font> 30 tests from 14 test suites ran.
+<font color="green">[   PASSED ]</font> 28 tests.
+<font color="red">[   FAILED ]</font> 2 tests, listed below:
+<font color="red">[   FAILED ]</font> BarTest.ReturnsTrueOnSuccess
+<font color="red">[   FAILED ]</font> AnotherTest.DoesXyz
+
+ 2 FAILED TESTS
+</pre>
+
+You can set the `GTEST_COLOR` environment variable or the `--gtest_color`
+command line flag to `yes`, `no`, or `auto` (the default) to enable colors,
+disable colors, or let googletest decide. When the value is `auto`, googletest
+will use colors if and only if the output goes to a terminal and (on non-Windows
+platforms) the `TERM` environment variable is set to `xterm` or `xterm-color`.
+
+#### Suppressing test passes
+
+By default, googletest prints 1 line of output for each test, indicating if it
+passed or failed. To show only test failures, run the test program with
+`--gtest_brief=1`, or set the GTEST_BRIEF environment variable to `1`.
+
+#### Suppressing the Elapsed Time
+
+By default, googletest prints the time it takes to run each test. To disable
+that, run the test program with the `--gtest_print_time=0` command line flag, or
+set the GTEST_PRINT_TIME environment variable to `0`.
+
+#### Suppressing UTF-8 Text Output
+
+In case of assertion failures, googletest prints expected and actual values of
+type `string` both as hex-encoded strings as well as in readable UTF-8 text if
+they contain valid non-ASCII UTF-8 characters. If you want to suppress the UTF-8
+text because, for example, you don't have an UTF-8 compatible output medium, run
+the test program with `--gtest_print_utf8=0` or set the `GTEST_PRINT_UTF8`
+environment variable to `0`.
+
+
+
+#### Generating an XML Report
+
+googletest can emit a detailed XML report to a file in addition to its normal
+textual output. The report contains the duration of each test, and thus can help
+you identify slow tests.
+
+To generate the XML report, set the `GTEST_OUTPUT` environment variable or the
+`--gtest_output` flag to the string `"xml:path_to_output_file"`, which will
+create the file at the given location. You can also just use the string `"xml"`,
+in which case the output can be found in the `test_detail.xml` file in the
+current directory.
+
+If you specify a directory (for example, `"xml:output/directory/"` on Linux or
+`"xml:output\directory\"` on Windows), googletest will create the XML file in
+that directory, named after the test executable (e.g. `foo_test.xml` for test
+program `foo_test` or `foo_test.exe`). If the file already exists (perhaps left
+over from a previous run), googletest will pick a different name (e.g.
+`foo_test_1.xml`) to avoid overwriting it.
+
+The report is based on the `junitreport` Ant task. Since that format was
+originally intended for Java, a little interpretation is required to make it
+apply to googletest tests, as shown here:
+
+```xml
+<testsuites name="AllTests" ...>
+  <testsuite name="test_case_name" ...>
+    <testcase    name="test_name" ...>
+      <failure message="..."/>
+      <failure message="..."/>
+      <failure message="..."/>
+    </testcase>
+  </testsuite>
+</testsuites>
+```
+
+*   The root `<testsuites>` element corresponds to the entire test program.
+*   `<testsuite>` elements correspond to googletest test suites.
+*   `<testcase>` elements correspond to googletest test functions.
+
+For instance, the following program
+
+```c++
+TEST(MathTest, Addition) { ... }
+TEST(MathTest, Subtraction) { ... }
+TEST(LogicTest, NonContradiction) { ... }
+```
+
+could generate this report:
+
+```xml
+<?xml version="1.0" encoding="UTF-8"?>
+<testsuites tests="3" failures="1" errors="0" time="0.035" timestamp="2011-10-31T18:52:42" name="AllTests">
+  <testsuite name="MathTest" tests="2" failures="1" errors="0" time="0.015">
+    <testcase name="Addition" status="run" time="0.007" classname="">
+      <failure message="Value of: add(1, 1)&#x0A;  Actual: 3&#x0A;Expected: 2" type="">...</failure>
+      <failure message="Value of: add(1, -1)&#x0A;  Actual: 1&#x0A;Expected: 0" type="">...</failure>
+    </testcase>
+    <testcase name="Subtraction" status="run" time="0.005" classname="">
+    </testcase>
+  </testsuite>
+  <testsuite name="LogicTest" tests="1" failures="0" errors="0" time="0.005">
+    <testcase name="NonContradiction" status="run" time="0.005" classname="">
+    </testcase>
+  </testsuite>
+</testsuites>
+```
+
+Things to note:
+
+*   The `tests` attribute of a `<testsuites>` or `<testsuite>` element tells how
+    many test functions the googletest program or test suite contains, while the
+    `failures` attribute tells how many of them failed.
+
+*   The `time` attribute expresses the duration of the test, test suite, or
+    entire test program in seconds.
+
+*   The `timestamp` attribute records the local date and time of the test
+    execution.
+
+*   Each `<failure>` element corresponds to a single failed googletest
+    assertion.
+
+#### Generating a JSON Report
+
+googletest can also emit a JSON report as an alternative format to XML. To
+generate the JSON report, set the `GTEST_OUTPUT` environment variable or the
+`--gtest_output` flag to the string `"json:path_to_output_file"`, which will
+create the file at the given location. You can also just use the string
+`"json"`, in which case the output can be found in the `test_detail.json` file
+in the current directory.
+
+The report format conforms to the following JSON Schema:
+
+```json
+{
+  "$schema": "http://json-schema.org/schema#",
+  "type": "object",
+  "definitions": {
+    "TestCase": {
+      "type": "object",
+      "properties": {
+        "name": { "type": "string" },
+        "tests": { "type": "integer" },
+        "failures": { "type": "integer" },
+        "disabled": { "type": "integer" },
+        "time": { "type": "string" },
+        "testsuite": {
+          "type": "array",
+          "items": {
+            "$ref": "#/definitions/TestInfo"
+          }
+        }
+      }
+    },
+    "TestInfo": {
+      "type": "object",
+      "properties": {
+        "name": { "type": "string" },
+        "status": {
+          "type": "string",
+          "enum": ["RUN", "NOTRUN"]
+        },
+        "time": { "type": "string" },
+        "classname": { "type": "string" },
+        "failures": {
+          "type": "array",
+          "items": {
+            "$ref": "#/definitions/Failure"
+          }
+        }
+      }
+    },
+    "Failure": {
+      "type": "object",
+      "properties": {
+        "failures": { "type": "string" },
+        "type": { "type": "string" }
+      }
+    }
+  },
+  "properties": {
+    "tests": { "type": "integer" },
+    "failures": { "type": "integer" },
+    "disabled": { "type": "integer" },
+    "errors": { "type": "integer" },
+    "timestamp": {
+      "type": "string",
+      "format": "date-time"
+    },
+    "time": { "type": "string" },
+    "name": { "type": "string" },
+    "testsuites": {
+      "type": "array",
+      "items": {
+        "$ref": "#/definitions/TestCase"
+      }
+    }
+  }
+}
+```
+
+The report uses the format that conforms to the following Proto3 using the
+[JSON encoding](https://developers.google.com/protocol-buffers/docs/proto3#json):
+
+```proto
+syntax = "proto3";
+
+package googletest;
+
+import "google/protobuf/timestamp.proto";
+import "google/protobuf/duration.proto";
+
+message UnitTest {
+  int32 tests = 1;
+  int32 failures = 2;
+  int32 disabled = 3;
+  int32 errors = 4;
+  google.protobuf.Timestamp timestamp = 5;
+  google.protobuf.Duration time = 6;
+  string name = 7;
+  repeated TestCase testsuites = 8;
+}
+
+message TestCase {
+  string name = 1;
+  int32 tests = 2;
+  int32 failures = 3;
+  int32 disabled = 4;
+  int32 errors = 5;
+  google.protobuf.Duration time = 6;
+  repeated TestInfo testsuite = 7;
+}
+
+message TestInfo {
+  string name = 1;
+  enum Status {
+    RUN = 0;
+    NOTRUN = 1;
+  }
+  Status status = 2;
+  google.protobuf.Duration time = 3;
+  string classname = 4;
+  message Failure {
+    string failures = 1;
+    string type = 2;
+  }
+  repeated Failure failures = 5;
+}
+```
+
+For instance, the following program
+
+```c++
+TEST(MathTest, Addition) { ... }
+TEST(MathTest, Subtraction) { ... }
+TEST(LogicTest, NonContradiction) { ... }
+```
+
+could generate this report:
+
+```json
+{
+  "tests": 3,
+  "failures": 1,
+  "errors": 0,
+  "time": "0.035s",
+  "timestamp": "2011-10-31T18:52:42Z",
+  "name": "AllTests",
+  "testsuites": [
+    {
+      "name": "MathTest",
+      "tests": 2,
+      "failures": 1,
+      "errors": 0,
+      "time": "0.015s",
+      "testsuite": [
+        {
+          "name": "Addition",
+          "status": "RUN",
+          "time": "0.007s",
+          "classname": "",
+          "failures": [
+            {
+              "message": "Value of: add(1, 1)\n  Actual: 3\nExpected: 2",
+              "type": ""
+            },
+            {
+              "message": "Value of: add(1, -1)\n  Actual: 1\nExpected: 0",
+              "type": ""
+            }
+          ]
+        },
+        {
+          "name": "Subtraction",
+          "status": "RUN",
+          "time": "0.005s",
+          "classname": ""
+        }
+      ]
+    },
+    {
+      "name": "LogicTest",
+      "tests": 1,
+      "failures": 0,
+      "errors": 0,
+      "time": "0.005s",
+      "testsuite": [
+        {
+          "name": "NonContradiction",
+          "status": "RUN",
+          "time": "0.005s",
+          "classname": ""
+        }
+      ]
+    }
+  ]
+}
+```
+
+{: .callout .important}
+IMPORTANT: The exact format of the JSON document is subject to change.
+
+### Controlling How Failures Are Reported
+
+#### Detecting Test Premature Exit
+
+Google Test implements the _premature-exit-file_ protocol for test runners
+to catch any kind of unexpected exits of test programs. Upon start,
+Google Test creates the file which will be automatically deleted after
+all work has been finished. Then, the test runner can check if this file
+exists. In case the file remains undeleted, the inspected test has exited
+prematurely.
+
+This feature is enabled only if the `TEST_PREMATURE_EXIT_FILE` environment
+variable has been set.
+
+#### Turning Assertion Failures into Break-Points
+
+When running test programs under a debugger, it's very convenient if the
+debugger can catch an assertion failure and automatically drop into interactive
+mode. googletest's *break-on-failure* mode supports this behavior.
+
+To enable it, set the `GTEST_BREAK_ON_FAILURE` environment variable to a value
+other than `0`. Alternatively, you can use the `--gtest_break_on_failure`
+command line flag.
+
+#### Disabling Catching Test-Thrown Exceptions
+
+googletest can be used either with or without exceptions enabled. If a test
+throws a C++ exception or (on Windows) a structured exception (SEH), by default
+googletest catches it, reports it as a test failure, and continues with the next
+test method. This maximizes the coverage of a test run. Also, on Windows an
+uncaught exception will cause a pop-up window, so catching the exceptions allows
+you to run the tests automatically.
+
+When debugging the test failures, however, you may instead want the exceptions
+to be handled by the debugger, such that you can examine the call stack when an
+exception is thrown. To achieve that, set the `GTEST_CATCH_EXCEPTIONS`
+environment variable to `0`, or use the `--gtest_catch_exceptions=0` flag when
+running the tests.
+
+### Sanitizer Integration
+
+The
+[Undefined Behavior Sanitizer](https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html),
+[Address Sanitizer](https://github.com/google/sanitizers/wiki/AddressSanitizer),
+and
+[Thread Sanitizer](https://github.com/google/sanitizers/wiki/ThreadSanitizerCppManual)
+all provide weak functions that you can override to trigger explicit failures
+when they detect sanitizer errors, such as creating a reference from `nullptr`.
+To override these functions, place definitions for them in a source file that
+you compile as part of your main binary:
+
+```
+extern "C" {
+void __ubsan_on_report() {
+  FAIL() << "Encountered an undefined behavior sanitizer error";
+}
+void __asan_on_error() {
+  FAIL() << "Encountered an address sanitizer error";
+}
+void __tsan_on_report() {
+  FAIL() << "Encountered a thread sanitizer error";
+}
+}  // extern "C"
+```
+
+After compiling your project with one of the sanitizers enabled, if a particular
+test triggers a sanitizer error, googletest will report that it failed.
diff --git a/leveldb_base/third_party/googletest/docs/assets/css/style.scss b/leveldb_base/third_party/googletest/docs/assets/css/style.scss
new file mode 100644
index 0000000..bb30f41
--- /dev/null
+++ b/leveldb_base/third_party/googletest/docs/assets/css/style.scss
@@ -0,0 +1,5 @@
+---
+---
+
+@import "jekyll-theme-primer";
+@import "main";
diff --git a/leveldb_base/third_party/googletest/docs/community_created_documentation.md b/leveldb_base/third_party/googletest/docs/community_created_documentation.md
new file mode 100644
index 0000000..4569075
--- /dev/null
+++ b/leveldb_base/third_party/googletest/docs/community_created_documentation.md
@@ -0,0 +1,7 @@
+# Community-Created Documentation
+
+The following is a list, in no particular order, of links to documentation
+created by the Googletest community.
+
+*   [Googlemock Insights](https://github.com/ElectricRCAircraftGuy/eRCaGuy_dotfiles/blob/master/googletest/insights.md),
+    by [ElectricRCAircraftGuy](https://github.com/ElectricRCAircraftGuy)
diff --git a/leveldb_base/third_party/googletest/docs/faq.md b/leveldb_base/third_party/googletest/docs/faq.md
new file mode 100644
index 0000000..4071232
--- /dev/null
+++ b/leveldb_base/third_party/googletest/docs/faq.md
@@ -0,0 +1,756 @@
+# Googletest FAQ
+
+## Why should test suite names and test names not contain underscore?
+
+{: .callout .note}
+Note: Googletest reserves underscore (`_`) for special purpose keywords, such as
+[the `DISABLED_` prefix](advanced.md#temporarily-disabling-tests), in addition
+to the following rationale.
+
+Underscore (`_`) is special, as C++ reserves the following to be used by the
+compiler and the standard library:
+
+1.  any identifier that starts with an `_` followed by an upper-case letter, and
+2.  any identifier that contains two consecutive underscores (i.e. `__`)
+    *anywhere* in its name.
+
+User code is *prohibited* from using such identifiers.
+
+Now let's look at what this means for `TEST` and `TEST_F`.
+
+Currently `TEST(TestSuiteName, TestName)` generates a class named
+`TestSuiteName_TestName_Test`. What happens if `TestSuiteName` or `TestName`
+contains `_`?
+
+1.  If `TestSuiteName` starts with an `_` followed by an upper-case letter (say,
+    `_Foo`), we end up with `_Foo_TestName_Test`, which is reserved and thus
+    invalid.
+2.  If `TestSuiteName` ends with an `_` (say, `Foo_`), we get
+    `Foo__TestName_Test`, which is invalid.
+3.  If `TestName` starts with an `_` (say, `_Bar`), we get
+    `TestSuiteName__Bar_Test`, which is invalid.
+4.  If `TestName` ends with an `_` (say, `Bar_`), we get
+    `TestSuiteName_Bar__Test`, which is invalid.
+
+So clearly `TestSuiteName` and `TestName` cannot start or end with `_`
+(Actually, `TestSuiteName` can start with `_` -- as long as the `_` isn't
+followed by an upper-case letter. But that's getting complicated. So for
+simplicity we just say that it cannot start with `_`.).
+
+It may seem fine for `TestSuiteName` and `TestName` to contain `_` in the
+middle. However, consider this:
+
+```c++
+TEST(Time, Flies_Like_An_Arrow) { ... }
+TEST(Time_Flies, Like_An_Arrow) { ... }
+```
+
+Now, the two `TEST`s will both generate the same class
+(`Time_Flies_Like_An_Arrow_Test`). That's not good.
+
+So for simplicity, we just ask the users to avoid `_` in `TestSuiteName` and
+`TestName`. The rule is more constraining than necessary, but it's simple and
+easy to remember. It also gives googletest some wiggle room in case its
+implementation needs to change in the future.
+
+If you violate the rule, there may not be immediate consequences, but your test
+may (just may) break with a new compiler (or a new version of the compiler you
+are using) or with a new version of googletest. Therefore it's best to follow
+the rule.
+
+## Why does googletest support `EXPECT_EQ(NULL, ptr)` and `ASSERT_EQ(NULL, ptr)` but not `EXPECT_NE(NULL, ptr)` and `ASSERT_NE(NULL, ptr)`?
+
+First of all, you can use `nullptr` with each of these macros, e.g.
+`EXPECT_EQ(ptr, nullptr)`, `EXPECT_NE(ptr, nullptr)`, `ASSERT_EQ(ptr, nullptr)`,
+`ASSERT_NE(ptr, nullptr)`. This is the preferred syntax in the style guide
+because `nullptr` does not have the type problems that `NULL` does.
+
+Due to some peculiarity of C++, it requires some non-trivial template meta
+programming tricks to support using `NULL` as an argument of the `EXPECT_XX()`
+and `ASSERT_XX()` macros. Therefore we only do it where it's most needed
+(otherwise we make the implementation of googletest harder to maintain and more
+error-prone than necessary).
+
+Historically, the `EXPECT_EQ()` macro took the *expected* value as its first
+argument and the *actual* value as the second, though this argument order is now
+discouraged. It was reasonable that someone wanted
+to write `EXPECT_EQ(NULL, some_expression)`, and this indeed was requested
+several times. Therefore we implemented it.
+
+The need for `EXPECT_NE(NULL, ptr)` wasn't nearly as strong. When the assertion
+fails, you already know that `ptr` must be `NULL`, so it doesn't add any
+information to print `ptr` in this case. That means `EXPECT_TRUE(ptr != NULL)`
+works just as well.
+
+If we were to support `EXPECT_NE(NULL, ptr)`, for consistency we'd have to
+support `EXPECT_NE(ptr, NULL)` as well. This means using the template meta
+programming tricks twice in the implementation, making it even harder to
+understand and maintain. We believe the benefit doesn't justify the cost.
+
+Finally, with the growth of the gMock matcher library, we are encouraging people
+to use the unified `EXPECT_THAT(value, matcher)` syntax more often in tests. One
+significant advantage of the matcher approach is that matchers can be easily
+combined to form new matchers, while the `EXPECT_NE`, etc, macros cannot be
+easily combined. Therefore we want to invest more in the matchers than in the
+`EXPECT_XX()` macros.
+
+## I need to test that different implementations of an interface satisfy some common requirements. Should I use typed tests or value-parameterized tests?
+
+For testing various implementations of the same interface, either typed tests or
+value-parameterized tests can get it done. It's really up to you the user to
+decide which is more convenient for you, depending on your particular case. Some
+rough guidelines:
+
+*   Typed tests can be easier to write if instances of the different
+    implementations can be created the same way, modulo the type. For example,
+    if all these implementations have a public default constructor (such that
+    you can write `new TypeParam`), or if their factory functions have the same
+    form (e.g. `CreateInstance<TypeParam>()`).
+*   Value-parameterized tests can be easier to write if you need different code
+    patterns to create different implementations' instances, e.g. `new Foo` vs
+    `new Bar(5)`. To accommodate for the differences, you can write factory
+    function wrappers and pass these function pointers to the tests as their
+    parameters.
+*   When a typed test fails, the default output includes the name of the type,
+    which can help you quickly identify which implementation is wrong.
+    Value-parameterized tests only show the number of the failed iteration by
+    default. You will need to define a function that returns the iteration name
+    and pass it as the third parameter to INSTANTIATE_TEST_SUITE_P to have more
+    useful output.
+*   When using typed tests, you need to make sure you are testing against the
+    interface type, not the concrete types (in other words, you want to make
+    sure `implicit_cast<MyInterface*>(my_concrete_impl)` works, not just that
+    `my_concrete_impl` works). It's less likely to make mistakes in this area
+    when using value-parameterized tests.
+
+I hope I didn't confuse you more. :-) If you don't mind, I'd suggest you to give
+both approaches a try. Practice is a much better way to grasp the subtle
+differences between the two tools. Once you have some concrete experience, you
+can much more easily decide which one to use the next time.
+
+## I got some run-time errors about invalid proto descriptors when using `ProtocolMessageEquals`. Help!
+
+{: .callout .note}
+**Note:** `ProtocolMessageEquals` and `ProtocolMessageEquiv` are *deprecated*
+now. Please use `EqualsProto`, etc instead.
+
+`ProtocolMessageEquals` and `ProtocolMessageEquiv` were redefined recently and
+are now less tolerant of invalid protocol buffer definitions. In particular, if
+you have a `foo.proto` that doesn't fully qualify the type of a protocol message
+it references (e.g. `message<Bar>` where it should be `message<blah.Bar>`), you
+will now get run-time errors like:
+
+```
+... descriptor.cc:...] Invalid proto descriptor for file "path/to/foo.proto":
+... descriptor.cc:...]  blah.MyMessage.my_field: ".Bar" is not defined.
+```
+
+If you see this, your `.proto` file is broken and needs to be fixed by making
+the types fully qualified. The new definition of `ProtocolMessageEquals` and
+`ProtocolMessageEquiv` just happen to reveal your bug.
+
+## My death test modifies some state, but the change seems lost after the death test finishes. Why?
+
+Death tests (`EXPECT_DEATH`, etc) are executed in a sub-process s.t. the
+expected crash won't kill the test program (i.e. the parent process). As a
+result, any in-memory side effects they incur are observable in their respective
+sub-processes, but not in the parent process. You can think of them as running
+in a parallel universe, more or less.
+
+In particular, if you use mocking and the death test statement invokes some mock
+methods, the parent process will think the calls have never occurred. Therefore,
+you may want to move your `EXPECT_CALL` statements inside the `EXPECT_DEATH`
+macro.
+
+## EXPECT_EQ(htonl(blah), blah_blah) generates weird compiler errors in opt mode. Is this a googletest bug?
+
+Actually, the bug is in `htonl()`.
+
+According to `'man htonl'`, `htonl()` is a *function*, which means it's valid to
+use `htonl` as a function pointer. However, in opt mode `htonl()` is defined as
+a *macro*, which breaks this usage.
+
+Worse, the macro definition of `htonl()` uses a `gcc` extension and is *not*
+standard C++. That hacky implementation has some ad hoc limitations. In
+particular, it prevents you from writing `Foo<sizeof(htonl(x))>()`, where `Foo`
+is a template that has an integral argument.
+
+The implementation of `EXPECT_EQ(a, b)` uses `sizeof(... a ...)` inside a
+template argument, and thus doesn't compile in opt mode when `a` contains a call
+to `htonl()`. It is difficult to make `EXPECT_EQ` bypass the `htonl()` bug, as
+the solution must work with different compilers on various platforms.
+
+## The compiler complains about "undefined references" to some static const member variables, but I did define them in the class body. What's wrong?
+
+If your class has a static data member:
+
+```c++
+// foo.h
+class Foo {
+  ...
+  static const int kBar = 100;
+};
+```
+
+You also need to define it *outside* of the class body in `foo.cc`:
+
+```c++
+const int Foo::kBar;  // No initializer here.
+```
+
+Otherwise your code is **invalid C++**, and may break in unexpected ways. In
+particular, using it in googletest comparison assertions (`EXPECT_EQ`, etc) will
+generate an "undefined reference" linker error. The fact that "it used to work"
+doesn't mean it's valid. It just means that you were lucky. :-)
+
+If the declaration of the static data member is `constexpr` then it is
+implicitly an `inline` definition, and a separate definition in `foo.cc` is not
+needed:
+
+```c++
+// foo.h
+class Foo {
+  ...
+  static constexpr int kBar = 100;  // Defines kBar, no need to do it in foo.cc.
+};
+```
+
+## Can I derive a test fixture from another?
+
+Yes.
+
+Each test fixture has a corresponding and same named test suite. This means only
+one test suite can use a particular fixture. Sometimes, however, multiple test
+cases may want to use the same or slightly different fixtures. For example, you
+may want to make sure that all of a GUI library's test suites don't leak
+important system resources like fonts and brushes.
+
+In googletest, you share a fixture among test suites by putting the shared logic
+in a base test fixture, then deriving from that base a separate fixture for each
+test suite that wants to use this common logic. You then use `TEST_F()` to write
+tests using each derived fixture.
+
+Typically, your code looks like this:
+
+```c++
+// Defines a base test fixture.
+class BaseTest : public ::testing::Test {
+ protected:
+  ...
+};
+
+// Derives a fixture FooTest from BaseTest.
+class FooTest : public BaseTest {
+ protected:
+  void SetUp() override {
+    BaseTest::SetUp();  // Sets up the base fixture first.
+    ... additional set-up work ...
+  }
+
+  void TearDown() override {
+    ... clean-up work for FooTest ...
+    BaseTest::TearDown();  // Remember to tear down the base fixture
+                           // after cleaning up FooTest!
+  }
+
+  ... functions and variables for FooTest ...
+};
+
+// Tests that use the fixture FooTest.
+TEST_F(FooTest, Bar) { ... }
+TEST_F(FooTest, Baz) { ... }
+
+... additional fixtures derived from BaseTest ...
+```
+
+If necessary, you can continue to derive test fixtures from a derived fixture.
+googletest has no limit on how deep the hierarchy can be.
+
+For a complete example using derived test fixtures, see
+[sample5_unittest.cc](https://github.com/google/googletest/blob/master/googletest/samples/sample5_unittest.cc).
+
+## My compiler complains "void value not ignored as it ought to be." What does this mean?
+
+You're probably using an `ASSERT_*()` in a function that doesn't return `void`.
+`ASSERT_*()` can only be used in `void` functions, due to exceptions being
+disabled by our build system. Please see more details
+[here](advanced.md#assertion-placement).
+
+## My death test hangs (or seg-faults). How do I fix it?
+
+In googletest, death tests are run in a child process and the way they work is
+delicate. To write death tests you really need to understand how they work.
+Please make sure you have read [this](advanced.md#how-it-works).
+
+In particular, death tests don't like having multiple threads in the parent
+process. So the first thing you can try is to eliminate creating threads outside
+of `EXPECT_DEATH()`. For example, you may want to use mocks or fake objects
+instead of real ones in your tests.
+
+Sometimes this is impossible as some library you must use may be creating
+threads before `main()` is even reached. In this case, you can try to minimize
+the chance of conflicts by either moving as many activities as possible inside
+`EXPECT_DEATH()` (in the extreme case, you want to move everything inside), or
+leaving as few things as possible in it. Also, you can try to set the death test
+style to `"threadsafe"`, which is safer but slower, and see if it helps.
+
+If you go with thread-safe death tests, remember that they rerun the test
+program from the beginning in the child process. Therefore make sure your
+program can run side-by-side with itself and is deterministic.
+
+In the end, this boils down to good concurrent programming. You have to make
+sure that there are no race conditions or deadlocks in your program. No silver
+bullet - sorry!
+
+## Should I use the constructor/destructor of the test fixture or SetUp()/TearDown()? {#CtorVsSetUp}
+
+The first thing to remember is that googletest does **not** reuse the same test
+fixture object across multiple tests. For each `TEST_F`, googletest will create
+a **fresh** test fixture object, immediately call `SetUp()`, run the test body,
+call `TearDown()`, and then delete the test fixture object.
+
+When you need to write per-test set-up and tear-down logic, you have the choice
+between using the test fixture constructor/destructor or `SetUp()/TearDown()`.
+The former is usually preferred, as it has the following benefits:
+
+*   By initializing a member variable in the constructor, we have the option to
+    make it `const`, which helps prevent accidental changes to its value and
+    makes the tests more obviously correct.
+*   In case we need to subclass the test fixture class, the subclass'
+    constructor is guaranteed to call the base class' constructor *first*, and
+    the subclass' destructor is guaranteed to call the base class' destructor
+    *afterward*. With `SetUp()/TearDown()`, a subclass may make the mistake of
+    forgetting to call the base class' `SetUp()/TearDown()` or call them at the
+    wrong time.
+
+You may still want to use `SetUp()/TearDown()` in the following cases:
+
+*   C++ does not allow virtual function calls in constructors and destructors.
+    You can call a method declared as virtual, but it will not use dynamic
+    dispatch, it will use the definition from the class the constructor of which
+    is currently executing. This is because calling a virtual method before the
+    derived class constructor has a chance to run is very dangerous - the
+    virtual method might operate on uninitialized data. Therefore, if you need
+    to call a method that will be overridden in a derived class, you have to use
+    `SetUp()/TearDown()`.
+*   In the body of a constructor (or destructor), it's not possible to use the
+    `ASSERT_xx` macros. Therefore, if the set-up operation could cause a fatal
+    test failure that should prevent the test from running, it's necessary to
+    use `abort` and abort the whole test
+    executable, or to use `SetUp()` instead of a constructor.
+*   If the tear-down operation could throw an exception, you must use
+    `TearDown()` as opposed to the destructor, as throwing in a destructor leads
+    to undefined behavior and usually will kill your program right away. Note
+    that many standard libraries (like STL) may throw when exceptions are
+    enabled in the compiler. Therefore you should prefer `TearDown()` if you
+    want to write portable tests that work with or without exceptions.
+*   The googletest team is considering making the assertion macros throw on
+    platforms where exceptions are enabled (e.g. Windows, Mac OS, and Linux
+    client-side), which will eliminate the need for the user to propagate
+    failures from a subroutine to its caller. Therefore, you shouldn't use
+    googletest assertions in a destructor if your code could run on such a
+    platform.
+
+## The compiler complains "no matching function to call" when I use ASSERT_PRED*. How do I fix it?
+
+If the predicate function you use in `ASSERT_PRED*` or `EXPECT_PRED*` is
+overloaded or a template, the compiler will have trouble figuring out which
+overloaded version it should use. `ASSERT_PRED_FORMAT*` and
+`EXPECT_PRED_FORMAT*` don't have this problem.
+
+If you see this error, you might want to switch to
+`(ASSERT|EXPECT)_PRED_FORMAT*`, which will also give you a better failure
+message. If, however, that is not an option, you can resolve the problem by
+explicitly telling the compiler which version to pick.
+
+For example, suppose you have
+
+```c++
+bool IsPositive(int n) {
+  return n > 0;
+}
+
+bool IsPositive(double x) {
+  return x > 0;
+}
+```
+
+you will get a compiler error if you write
+
+```c++
+EXPECT_PRED1(IsPositive, 5);
+```
+
+However, this will work:
+
+```c++
+EXPECT_PRED1(static_cast<bool (*)(int)>(IsPositive), 5);
+```
+
+(The stuff inside the angled brackets for the `static_cast` operator is the type
+of the function pointer for the `int`-version of `IsPositive()`.)
+
+As another example, when you have a template function
+
+```c++
+template <typename T>
+bool IsNegative(T x) {
+  return x < 0;
+}
+```
+
+you can use it in a predicate assertion like this:
+
+```c++
+ASSERT_PRED1(IsNegative<int>, -5);
+```
+
+Things are more interesting if your template has more than one parameter. The
+following won't compile:
+
+```c++
+ASSERT_PRED2(GreaterThan<int, int>, 5, 0);
+```
+
+as the C++ pre-processor thinks you are giving `ASSERT_PRED2` 4 arguments, which
+is one more than expected. The workaround is to wrap the predicate function in
+parentheses:
+
+```c++
+ASSERT_PRED2((GreaterThan<int, int>), 5, 0);
+```
+
+## My compiler complains about "ignoring return value" when I call RUN_ALL_TESTS(). Why?
+
+Some people had been ignoring the return value of `RUN_ALL_TESTS()`. That is,
+instead of
+
+```c++
+  return RUN_ALL_TESTS();
+```
+
+they write
+
+```c++
+  RUN_ALL_TESTS();
+```
+
+This is **wrong and dangerous**. The testing services needs to see the return
+value of `RUN_ALL_TESTS()` in order to determine if a test has passed. If your
+`main()` function ignores it, your test will be considered successful even if it
+has a googletest assertion failure. Very bad.
+
+We have decided to fix this (thanks to Michael Chastain for the idea). Now, your
+code will no longer be able to ignore `RUN_ALL_TESTS()` when compiled with
+`gcc`. If you do so, you'll get a compiler error.
+
+If you see the compiler complaining about you ignoring the return value of
+`RUN_ALL_TESTS()`, the fix is simple: just make sure its value is used as the
+return value of `main()`.
+
+But how could we introduce a change that breaks existing tests? Well, in this
+case, the code was already broken in the first place, so we didn't break it. :-)
+
+## My compiler complains that a constructor (or destructor) cannot return a value. What's going on?
+
+Due to a peculiarity of C++, in order to support the syntax for streaming
+messages to an `ASSERT_*`, e.g.
+
+```c++
+  ASSERT_EQ(1, Foo()) << "blah blah" << foo;
+```
+
+we had to give up using `ASSERT*` and `FAIL*` (but not `EXPECT*` and
+`ADD_FAILURE*`) in constructors and destructors. The workaround is to move the
+content of your constructor/destructor to a private void member function, or
+switch to `EXPECT_*()` if that works. This
+[section](advanced.md#assertion-placement) in the user's guide explains it.
+
+## My SetUp() function is not called. Why?
+
+C++ is case-sensitive. Did you spell it as `Setup()`?
+
+Similarly, sometimes people spell `SetUpTestSuite()` as `SetupTestSuite()` and
+wonder why it's never called.
+
+
+## I have several test suites which share the same test fixture logic, do I have to define a new test fixture class for each of them? This seems pretty tedious.
+
+You don't have to. Instead of
+
+```c++
+class FooTest : public BaseTest {};
+
+TEST_F(FooTest, Abc) { ... }
+TEST_F(FooTest, Def) { ... }
+
+class BarTest : public BaseTest {};
+
+TEST_F(BarTest, Abc) { ... }
+TEST_F(BarTest, Def) { ... }
+```
+
+you can simply `typedef` the test fixtures:
+
+```c++
+typedef BaseTest FooTest;
+
+TEST_F(FooTest, Abc) { ... }
+TEST_F(FooTest, Def) { ... }
+
+typedef BaseTest BarTest;
+
+TEST_F(BarTest, Abc) { ... }
+TEST_F(BarTest, Def) { ... }
+```
+
+## googletest output is buried in a whole bunch of LOG messages. What do I do?
+
+The googletest output is meant to be a concise and human-friendly report. If
+your test generates textual output itself, it will mix with the googletest
+output, making it hard to read. However, there is an easy solution to this
+problem.
+
+Since `LOG` messages go to stderr, we decided to let googletest output go to
+stdout. This way, you can easily separate the two using redirection. For
+example:
+
+```shell
+$ ./my_test > gtest_output.txt
+```
+
+## Why should I prefer test fixtures over global variables?
+
+There are several good reasons:
+
+1.  It's likely your test needs to change the states of its global variables.
+    This makes it difficult to keep side effects from escaping one test and
+    contaminating others, making debugging difficult. By using fixtures, each
+    test has a fresh set of variables that's different (but with the same
+    names). Thus, tests are kept independent of each other.
+2.  Global variables pollute the global namespace.
+3.  Test fixtures can be reused via subclassing, which cannot be done easily
+    with global variables. This is useful if many test suites have something in
+    common.
+
+## What can the statement argument in ASSERT_DEATH() be?
+
+`ASSERT_DEATH(statement, matcher)` (or any death assertion macro) can be used
+wherever *`statement`* is valid. So basically *`statement`* can be any C++
+statement that makes sense in the current context. In particular, it can
+reference global and/or local variables, and can be:
+
+*   a simple function call (often the case),
+*   a complex expression, or
+*   a compound statement.
+
+Some examples are shown here:
+
+```c++
+// A death test can be a simple function call.
+TEST(MyDeathTest, FunctionCall) {
+  ASSERT_DEATH(Xyz(5), "Xyz failed");
+}
+
+// Or a complex expression that references variables and functions.
+TEST(MyDeathTest, ComplexExpression) {
+  const bool c = Condition();
+  ASSERT_DEATH((c ? Func1(0) : object2.Method("test")),
+               "(Func1|Method) failed");
+}
+
+// Death assertions can be used anywhere in a function.  In
+// particular, they can be inside a loop.
+TEST(MyDeathTest, InsideLoop) {
+  // Verifies that Foo(0), Foo(1), ..., and Foo(4) all die.
+  for (int i = 0; i < 5; i++) {
+    EXPECT_DEATH_M(Foo(i), "Foo has \\d+ errors",
+                   ::testing::Message() << "where i is " << i);
+  }
+}
+
+// A death assertion can contain a compound statement.
+TEST(MyDeathTest, CompoundStatement) {
+  // Verifies that at lease one of Bar(0), Bar(1), ..., and
+  // Bar(4) dies.
+  ASSERT_DEATH({
+    for (int i = 0; i < 5; i++) {
+      Bar(i);
+    }
+  },
+  "Bar has \\d+ errors");
+}
+```
+
+## I have a fixture class `FooTest`, but `TEST_F(FooTest, Bar)` gives me error ``"no matching function for call to `FooTest::FooTest()'"``. Why?
+
+Googletest needs to be able to create objects of your test fixture class, so it
+must have a default constructor. Normally the compiler will define one for you.
+However, there are cases where you have to define your own:
+
+*   If you explicitly declare a non-default constructor for class `FooTest`
+    (`DISALLOW_EVIL_CONSTRUCTORS()` does this), then you need to define a
+    default constructor, even if it would be empty.
+*   If `FooTest` has a const non-static data member, then you have to define the
+    default constructor *and* initialize the const member in the initializer
+    list of the constructor. (Early versions of `gcc` doesn't force you to
+    initialize the const member. It's a bug that has been fixed in `gcc 4`.)
+
+## Why does ASSERT_DEATH complain about previous threads that were already joined?
+
+With the Linux pthread library, there is no turning back once you cross the line
+from a single thread to multiple threads. The first time you create a thread, a
+manager thread is created in addition, so you get 3, not 2, threads. Later when
+the thread you create joins the main thread, the thread count decrements by 1,
+but the manager thread will never be killed, so you still have 2 threads, which
+means you cannot safely run a death test.
+
+The new NPTL thread library doesn't suffer from this problem, as it doesn't
+create a manager thread. However, if you don't control which machine your test
+runs on, you shouldn't depend on this.
+
+## Why does googletest require the entire test suite, instead of individual tests, to be named *DeathTest when it uses ASSERT_DEATH?
+
+googletest does not interleave tests from different test suites. That is, it
+runs all tests in one test suite first, and then runs all tests in the next test
+suite, and so on. googletest does this because it needs to set up a test suite
+before the first test in it is run, and tear it down afterwards. Splitting up
+the test case would require multiple set-up and tear-down processes, which is
+inefficient and makes the semantics unclean.
+
+If we were to determine the order of tests based on test name instead of test
+case name, then we would have a problem with the following situation:
+
+```c++
+TEST_F(FooTest, AbcDeathTest) { ... }
+TEST_F(FooTest, Uvw) { ... }
+
+TEST_F(BarTest, DefDeathTest) { ... }
+TEST_F(BarTest, Xyz) { ... }
+```
+
+Since `FooTest.AbcDeathTest` needs to run before `BarTest.Xyz`, and we don't
+interleave tests from different test suites, we need to run all tests in the
+`FooTest` case before running any test in the `BarTest` case. This contradicts
+with the requirement to run `BarTest.DefDeathTest` before `FooTest.Uvw`.
+
+## But I don't like calling my entire test suite \*DeathTest when it contains both death tests and non-death tests. What do I do?
+
+You don't have to, but if you like, you may split up the test suite into
+`FooTest` and `FooDeathTest`, where the names make it clear that they are
+related:
+
+```c++
+class FooTest : public ::testing::Test { ... };
+
+TEST_F(FooTest, Abc) { ... }
+TEST_F(FooTest, Def) { ... }
+
+using FooDeathTest = FooTest;
+
+TEST_F(FooDeathTest, Uvw) { ... EXPECT_DEATH(...) ... }
+TEST_F(FooDeathTest, Xyz) { ... ASSERT_DEATH(...) ... }
+```
+
+## googletest prints the LOG messages in a death test's child process only when the test fails. How can I see the LOG messages when the death test succeeds?
+
+Printing the LOG messages generated by the statement inside `EXPECT_DEATH()`
+makes it harder to search for real problems in the parent's log. Therefore,
+googletest only prints them when the death test has failed.
+
+If you really need to see such LOG messages, a workaround is to temporarily
+break the death test (e.g. by changing the regex pattern it is expected to
+match). Admittedly, this is a hack. We'll consider a more permanent solution
+after the fork-and-exec-style death tests are implemented.
+
+## The compiler complains about `no match for 'operator<<'` when I use an assertion. What gives?
+
+If you use a user-defined type `FooType` in an assertion, you must make sure
+there is an `std::ostream& operator<<(std::ostream&, const FooType&)` function
+defined such that we can print a value of `FooType`.
+
+In addition, if `FooType` is declared in a name space, the `<<` operator also
+needs to be defined in the *same* name space. See
+[Tip of the Week #49](http://abseil.io/tips/49) for details.
+
+## How do I suppress the memory leak messages on Windows?
+
+Since the statically initialized googletest singleton requires allocations on
+the heap, the Visual C++ memory leak detector will report memory leaks at the
+end of the program run. The easiest way to avoid this is to use the
+`_CrtMemCheckpoint` and `_CrtMemDumpAllObjectsSince` calls to not report any
+statically initialized heap objects. See MSDN for more details and additional
+heap check/debug routines.
+
+## How can my code detect if it is running in a test?
+
+If you write code that sniffs whether it's running in a test and does different
+things accordingly, you are leaking test-only logic into production code and
+there is no easy way to ensure that the test-only code paths aren't run by
+mistake in production. Such cleverness also leads to
+[Heisenbugs](https://en.wikipedia.org/wiki/Heisenbug). Therefore we strongly
+advise against the practice, and googletest doesn't provide a way to do it.
+
+In general, the recommended way to cause the code to behave differently under
+test is [Dependency Injection](http://en.wikipedia.org/wiki/Dependency_injection). You can inject
+different functionality from the test and from the production code. Since your
+production code doesn't link in the for-test logic at all (the
+[`testonly`](http://docs.bazel.build/versions/master/be/common-definitions.html#common.testonly) attribute for BUILD targets helps to ensure
+that), there is no danger in accidentally running it.
+
+However, if you *really*, *really*, *really* have no choice, and if you follow
+the rule of ending your test program names with `_test`, you can use the
+*horrible* hack of sniffing your executable name (`argv[0]` in `main()`) to know
+whether the code is under test.
+
+## How do I temporarily disable a test?
+
+If you have a broken test that you cannot fix right away, you can add the
+`DISABLED_` prefix to its name. This will exclude it from execution. This is
+better than commenting out the code or using `#if 0`, as disabled tests are
+still compiled (and thus won't rot).
+
+To include disabled tests in test execution, just invoke the test program with
+the `--gtest_also_run_disabled_tests` flag.
+
+## Is it OK if I have two separate `TEST(Foo, Bar)` test methods defined in different namespaces?
+
+Yes.
+
+The rule is **all test methods in the same test suite must use the same fixture
+class.** This means that the following is **allowed** because both tests use the
+same fixture class (`::testing::Test`).
+
+```c++
+namespace foo {
+TEST(CoolTest, DoSomething) {
+  SUCCEED();
+}
+}  // namespace foo
+
+namespace bar {
+TEST(CoolTest, DoSomething) {
+  SUCCEED();
+}
+}  // namespace bar
+```
+
+However, the following code is **not allowed** and will produce a runtime error
+from googletest because the test methods are using different test fixture
+classes with the same test suite name.
+
+```c++
+namespace foo {
+class CoolTest : public ::testing::Test {};  // Fixture foo::CoolTest
+TEST_F(CoolTest, DoSomething) {
+  SUCCEED();
+}
+}  // namespace foo
+
+namespace bar {
+class CoolTest : public ::testing::Test {};  // Fixture: bar::CoolTest
+TEST_F(CoolTest, DoSomething) {
+  SUCCEED();
+}
+}  // namespace bar
+```
diff --git a/leveldb_base/third_party/googletest/docs/gmock_cheat_sheet.md b/leveldb_base/third_party/googletest/docs/gmock_cheat_sheet.md
new file mode 100644
index 0000000..c1d1a50
--- /dev/null
+++ b/leveldb_base/third_party/googletest/docs/gmock_cheat_sheet.md
@@ -0,0 +1,373 @@
+# gMock Cheat Sheet
+
+## Defining a Mock Class
+
+### Mocking a Normal Class {#MockClass}
+
+Given
+
+```cpp
+class Foo {
+  ...
+  virtual ~Foo();
+  virtual int GetSize() const = 0;
+  virtual string Describe(const char* name) = 0;
+  virtual string Describe(int type) = 0;
+  virtual bool Process(Bar elem, int count) = 0;
+};
+```
+
+(note that `~Foo()` **must** be virtual) we can define its mock as
+
+```cpp
+#include "gmock/gmock.h"
+
+class MockFoo : public Foo {
+  ...
+  MOCK_METHOD(int, GetSize, (), (const, override));
+  MOCK_METHOD(string, Describe, (const char* name), (override));
+  MOCK_METHOD(string, Describe, (int type), (override));
+  MOCK_METHOD(bool, Process, (Bar elem, int count), (override));
+};
+```
+
+To create a "nice" mock, which ignores all uninteresting calls, a "naggy" mock,
+which warns on all uninteresting calls, or a "strict" mock, which treats them as
+failures:
+
+```cpp
+using ::testing::NiceMock;
+using ::testing::NaggyMock;
+using ::testing::StrictMock;
+
+NiceMock<MockFoo> nice_foo;      // The type is a subclass of MockFoo.
+NaggyMock<MockFoo> naggy_foo;    // The type is a subclass of MockFoo.
+StrictMock<MockFoo> strict_foo;  // The type is a subclass of MockFoo.
+```
+
+{: .callout .note}
+**Note:** A mock object is currently naggy by default. We may make it nice by
+default in the future.
+
+### Mocking a Class Template {#MockTemplate}
+
+Class templates can be mocked just like any class.
+
+To mock
+
+```cpp
+template <typename Elem>
+class StackInterface {
+  ...
+  virtual ~StackInterface();
+  virtual int GetSize() const = 0;
+  virtual void Push(const Elem& x) = 0;
+};
+```
+
+(note that all member functions that are mocked, including `~StackInterface()`
+**must** be virtual).
+
+```cpp
+template <typename Elem>
+class MockStack : public StackInterface<Elem> {
+  ...
+  MOCK_METHOD(int, GetSize, (), (const, override));
+  MOCK_METHOD(void, Push, (const Elem& x), (override));
+};
+```
+
+### Specifying Calling Conventions for Mock Functions
+
+If your mock function doesn't use the default calling convention, you can
+specify it by adding `Calltype(convention)` to `MOCK_METHOD`'s 4th parameter.
+For example,
+
+```cpp
+  MOCK_METHOD(bool, Foo, (int n), (Calltype(STDMETHODCALLTYPE)));
+  MOCK_METHOD(int, Bar, (double x, double y),
+              (const, Calltype(STDMETHODCALLTYPE)));
+```
+
+where `STDMETHODCALLTYPE` is defined by `<objbase.h>` on Windows.
+
+## Using Mocks in Tests {#UsingMocks}
+
+The typical work flow is:
+
+1.  Import the gMock names you need to use. All gMock symbols are in the
+    `testing` namespace unless they are macros or otherwise noted.
+2.  Create the mock objects.
+3.  Optionally, set the default actions of the mock objects.
+4.  Set your expectations on the mock objects (How will they be called? What
+    will they do?).
+5.  Exercise code that uses the mock objects; if necessary, check the result
+    using googletest assertions.
+6.  When a mock object is destructed, gMock automatically verifies that all
+    expectations on it have been satisfied.
+
+Here's an example:
+
+```cpp
+using ::testing::Return;                          // #1
+
+TEST(BarTest, DoesThis) {
+  MockFoo foo;                                    // #2
+
+  ON_CALL(foo, GetSize())                         // #3
+      .WillByDefault(Return(1));
+  // ... other default actions ...
+
+  EXPECT_CALL(foo, Describe(5))                   // #4
+      .Times(3)
+      .WillRepeatedly(Return("Category 5"));
+  // ... other expectations ...
+
+  EXPECT_EQ(MyProductionFunction(&foo), "good");  // #5
+}                                                 // #6
+```
+
+## Setting Default Actions {#OnCall}
+
+gMock has a **built-in default action** for any function that returns `void`,
+`bool`, a numeric value, or a pointer. In C++11, it will additionally returns
+the default-constructed value, if one exists for the given type.
+
+To customize the default action for functions with return type *`T`*:
+
+```cpp
+using ::testing::DefaultValue;
+
+// Sets the default value to be returned. T must be CopyConstructible.
+DefaultValue<T>::Set(value);
+// Sets a factory. Will be invoked on demand. T must be MoveConstructible.
+//  T MakeT();
+DefaultValue<T>::SetFactory(&MakeT);
+// ... use the mocks ...
+// Resets the default value.
+DefaultValue<T>::Clear();
+```
+
+Example usage:
+
+```cpp
+  // Sets the default action for return type std::unique_ptr<Buzz> to
+  // creating a new Buzz every time.
+  DefaultValue<std::unique_ptr<Buzz>>::SetFactory(
+      [] { return MakeUnique<Buzz>(AccessLevel::kInternal); });
+
+  // When this fires, the default action of MakeBuzz() will run, which
+  // will return a new Buzz object.
+  EXPECT_CALL(mock_buzzer_, MakeBuzz("hello")).Times(AnyNumber());
+
+  auto buzz1 = mock_buzzer_.MakeBuzz("hello");
+  auto buzz2 = mock_buzzer_.MakeBuzz("hello");
+  EXPECT_NE(buzz1, nullptr);
+  EXPECT_NE(buzz2, nullptr);
+  EXPECT_NE(buzz1, buzz2);
+
+  // Resets the default action for return type std::unique_ptr<Buzz>,
+  // to avoid interfere with other tests.
+  DefaultValue<std::unique_ptr<Buzz>>::Clear();
+```
+
+To customize the default action for a particular method of a specific mock
+object, use `ON_CALL()`. `ON_CALL()` has a similar syntax to `EXPECT_CALL()`,
+but it is used for setting default behaviors (when you do not require that the
+mock method is called). See [here](gmock_cook_book.md#UseOnCall) for a more
+detailed discussion.
+
+```cpp
+ON_CALL(mock-object, method(matchers))
+    .With(multi-argument-matcher)   ?
+    .WillByDefault(action);
+```
+
+## Setting Expectations {#ExpectCall}
+
+`EXPECT_CALL()` sets **expectations** on a mock method (How will it be called?
+What will it do?):
+
+```cpp
+EXPECT_CALL(mock-object, method (matchers)?)
+     .With(multi-argument-matcher)  ?
+     .Times(cardinality)            ?
+     .InSequence(sequences)         *
+     .After(expectations)           *
+     .WillOnce(action)              *
+     .WillRepeatedly(action)        ?
+     .RetiresOnSaturation();        ?
+```
+
+For each item above, `?` means it can be used at most once, while `*` means it
+can be used any number of times.
+
+In order to pass, `EXPECT_CALL` must be used before the calls are actually made.
+
+The `(matchers)` is a comma-separated list of matchers that correspond to each
+of the arguments of `method`, and sets the expectation only for calls of
+`method` that matches all of the matchers.
+
+If `(matchers)` is omitted, the expectation is the same as if the matchers were
+set to anything matchers (for example, `(_, _, _, _)` for a four-arg method).
+
+If `Times()` is omitted, the cardinality is assumed to be:
+
+*   `Times(1)` when there is neither `WillOnce()` nor `WillRepeatedly()`;
+*   `Times(n)` when there are `n` `WillOnce()`s but no `WillRepeatedly()`, where
+    `n` >= 1; or
+*   `Times(AtLeast(n))` when there are `n` `WillOnce()`s and a
+    `WillRepeatedly()`, where `n` >= 0.
+
+A method with no `EXPECT_CALL()` is free to be invoked *any number of times*,
+and the default action will be taken each time.
+
+## Matchers {#MatcherList}
+
+See the [Matchers Reference](reference/matchers.md).
+
+## Actions {#ActionList}
+
+See the [Actions Reference](reference/actions.md).
+
+## Cardinalities {#CardinalityList}
+
+These are used in `Times()` to specify how many times a mock function will be
+called:
+
+|                   |                                                        |
+| :---------------- | :----------------------------------------------------- |
+| `AnyNumber()`     | The function can be called any number of times.        |
+| `AtLeast(n)`      | The call is expected at least `n` times.               |
+| `AtMost(n)`       | The call is expected at most `n` times.                |
+| `Between(m, n)`   | The call is expected between `m` and `n` (inclusive) times. |
+| `Exactly(n) or n` | The call is expected exactly `n` times. In particular, the call should never happen when `n` is 0. |
+
+## Expectation Order
+
+By default, the expectations can be matched in *any* order. If some or all
+expectations must be matched in a given order, there are two ways to specify it.
+They can be used either independently or together.
+
+### The After Clause {#AfterClause}
+
+```cpp
+using ::testing::Expectation;
+...
+Expectation init_x = EXPECT_CALL(foo, InitX());
+Expectation init_y = EXPECT_CALL(foo, InitY());
+EXPECT_CALL(foo, Bar())
+     .After(init_x, init_y);
+```
+
+says that `Bar()` can be called only after both `InitX()` and `InitY()` have
+been called.
+
+If you don't know how many pre-requisites an expectation has when you write it,
+you can use an `ExpectationSet` to collect them:
+
+```cpp
+using ::testing::ExpectationSet;
+...
+ExpectationSet all_inits;
+for (int i = 0; i < element_count; i++) {
+  all_inits += EXPECT_CALL(foo, InitElement(i));
+}
+EXPECT_CALL(foo, Bar())
+     .After(all_inits);
+```
+
+says that `Bar()` can be called only after all elements have been initialized
+(but we don't care about which elements get initialized before the others).
+
+Modifying an `ExpectationSet` after using it in an `.After()` doesn't affect the
+meaning of the `.After()`.
+
+### Sequences {#UsingSequences}
+
+When you have a long chain of sequential expectations, it's easier to specify
+the order using **sequences**, which don't require you to give each expectation
+in the chain a different name. *All expected calls* in the same sequence must
+occur in the order they are specified.
+
+```cpp
+using ::testing::Return;
+using ::testing::Sequence;
+Sequence s1, s2;
+...
+EXPECT_CALL(foo, Reset())
+    .InSequence(s1, s2)
+    .WillOnce(Return(true));
+EXPECT_CALL(foo, GetSize())
+    .InSequence(s1)
+    .WillOnce(Return(1));
+EXPECT_CALL(foo, Describe(A<const char*>()))
+    .InSequence(s2)
+    .WillOnce(Return("dummy"));
+```
+
+says that `Reset()` must be called before *both* `GetSize()` *and* `Describe()`,
+and the latter two can occur in any order.
+
+To put many expectations in a sequence conveniently:
+
+```cpp
+using ::testing::InSequence;
+{
+  InSequence seq;
+
+  EXPECT_CALL(...)...;
+  EXPECT_CALL(...)...;
+  ...
+  EXPECT_CALL(...)...;
+}
+```
+
+says that all expected calls in the scope of `seq` must occur in strict order.
+The name `seq` is irrelevant.
+
+## Verifying and Resetting a Mock
+
+gMock will verify the expectations on a mock object when it is destructed, or
+you can do it earlier:
+
+```cpp
+using ::testing::Mock;
+...
+// Verifies and removes the expectations on mock_obj;
+// returns true if and only if successful.
+Mock::VerifyAndClearExpectations(&mock_obj);
+...
+// Verifies and removes the expectations on mock_obj;
+// also removes the default actions set by ON_CALL();
+// returns true if and only if successful.
+Mock::VerifyAndClear(&mock_obj);
+```
+
+You can also tell gMock that a mock object can be leaked and doesn't need to be
+verified:
+
+```cpp
+Mock::AllowLeak(&mock_obj);
+```
+
+## Mock Classes
+
+gMock defines a convenient mock class template
+
+```cpp
+class MockFunction<R(A1, ..., An)> {
+ public:
+  MOCK_METHOD(R, Call, (A1, ..., An));
+};
+```
+
+See this [recipe](gmock_cook_book.md#using-check-points) for one application of
+it.
+
+## Flags
+
+| Flag                           | Description                               |
+| :----------------------------- | :---------------------------------------- |
+| `--gmock_catch_leaked_mocks=0` | Don't report leaked mock objects as failures. |
+| `--gmock_verbose=LEVEL` | Sets the default verbosity level (`info`, `warning`, or `error`) of Google Mock messages. |
diff --git a/leveldb_base/third_party/googletest/docs/gmock_cook_book.md b/leveldb_base/third_party/googletest/docs/gmock_cook_book.md
new file mode 100644
index 0000000..891c35c
--- /dev/null
+++ b/leveldb_base/third_party/googletest/docs/gmock_cook_book.md
@@ -0,0 +1,4354 @@
+# gMock Cookbook
+
+You can find recipes for using gMock here. If you haven't yet, please read
+[the dummy guide](gmock_for_dummies.md) first to make sure you understand the
+basics.
+
+{: .callout .note}
+**Note:** gMock lives in the `testing` name space. For readability, it is
+recommended to write `using ::testing::Foo;` once in your file before using the
+name `Foo` defined by gMock. We omit such `using` statements in this section for
+brevity, but you should do it in your own code.
+
+## Creating Mock Classes
+
+Mock classes are defined as normal classes, using the `MOCK_METHOD` macro to
+generate mocked methods. The macro gets 3 or 4 parameters:
+
+```cpp
+class MyMock {
+ public:
+  MOCK_METHOD(ReturnType, MethodName, (Args...));
+  MOCK_METHOD(ReturnType, MethodName, (Args...), (Specs...));
+};
+```
+
+The first 3 parameters are simply the method declaration, split into 3 parts.
+The 4th parameter accepts a closed list of qualifiers, which affect the
+generated method:
+
+*   **`const`** - Makes the mocked method a `const` method. Required if
+    overriding a `const` method.
+*   **`override`** - Marks the method with `override`. Recommended if overriding
+    a `virtual` method.
+*   **`noexcept`** - Marks the method with `noexcept`. Required if overriding a
+    `noexcept` method.
+*   **`Calltype(...)`** - Sets the call type for the method (e.g. to
+    `STDMETHODCALLTYPE`), useful in Windows.
+*   **`ref(...)`** - Marks the method with the reference qualification
+    specified. Required if overriding a method that has reference
+    qualifications. Eg `ref(&)` or `ref(&&)`.
+
+### Dealing with unprotected commas
+
+Unprotected commas, i.e. commas which are not surrounded by parentheses, prevent
+`MOCK_METHOD` from parsing its arguments correctly:
+
+{: .bad}
+```cpp
+class MockFoo {
+ public:
+  MOCK_METHOD(std::pair<bool, int>, GetPair, ());  // Won't compile!
+  MOCK_METHOD(bool, CheckMap, (std::map<int, double>, bool));  // Won't compile!
+};
+```
+
+Solution 1 - wrap with parentheses:
+
+{: .good}
+```cpp
+class MockFoo {
+ public:
+  MOCK_METHOD((std::pair<bool, int>), GetPair, ());
+  MOCK_METHOD(bool, CheckMap, ((std::map<int, double>), bool));
+};
+```
+
+Note that wrapping a return or argument type with parentheses is, in general,
+invalid C++. `MOCK_METHOD` removes the parentheses.
+
+Solution 2 - define an alias:
+
+{: .good}
+```cpp
+class MockFoo {
+ public:
+  using BoolAndInt = std::pair<bool, int>;
+  MOCK_METHOD(BoolAndInt, GetPair, ());
+  using MapIntDouble = std::map<int, double>;
+  MOCK_METHOD(bool, CheckMap, (MapIntDouble, bool));
+};
+```
+
+### Mocking Private or Protected Methods
+
+You must always put a mock method definition (`MOCK_METHOD`) in a `public:`
+section of the mock class, regardless of the method being mocked being `public`,
+`protected`, or `private` in the base class. This allows `ON_CALL` and
+`EXPECT_CALL` to reference the mock function from outside of the mock class.
+(Yes, C++ allows a subclass to change the access level of a virtual function in
+the base class.) Example:
+
+```cpp
+class Foo {
+ public:
+  ...
+  virtual bool Transform(Gadget* g) = 0;
+
+ protected:
+  virtual void Resume();
+
+ private:
+  virtual int GetTimeOut();
+};
+
+class MockFoo : public Foo {
+ public:
+  ...
+  MOCK_METHOD(bool, Transform, (Gadget* g), (override));
+
+  // The following must be in the public section, even though the
+  // methods are protected or private in the base class.
+  MOCK_METHOD(void, Resume, (), (override));
+  MOCK_METHOD(int, GetTimeOut, (), (override));
+};
+```
+
+### Mocking Overloaded Methods
+
+You can mock overloaded functions as usual. No special attention is required:
+
+```cpp
+class Foo {
+  ...
+
+  // Must be virtual as we'll inherit from Foo.
+  virtual ~Foo();
+
+  // Overloaded on the types and/or numbers of arguments.
+  virtual int Add(Element x);
+  virtual int Add(int times, Element x);
+
+  // Overloaded on the const-ness of this object.
+  virtual Bar& GetBar();
+  virtual const Bar& GetBar() const;
+};
+
+class MockFoo : public Foo {
+  ...
+  MOCK_METHOD(int, Add, (Element x), (override));
+  MOCK_METHOD(int, Add, (int times, Element x), (override));
+
+  MOCK_METHOD(Bar&, GetBar, (), (override));
+  MOCK_METHOD(const Bar&, GetBar, (), (const, override));
+};
+```
+
+{: .callout .note}
+**Note:** if you don't mock all versions of the overloaded method, the compiler
+will give you a warning about some methods in the base class being hidden. To
+fix that, use `using` to bring them in scope:
+
+```cpp
+class MockFoo : public Foo {
+  ...
+  using Foo::Add;
+  MOCK_METHOD(int, Add, (Element x), (override));
+  // We don't want to mock int Add(int times, Element x);
+  ...
+};
+```
+
+### Mocking Class Templates
+
+You can mock class templates just like any class.
+
+```cpp
+template <typename Elem>
+class StackInterface {
+  ...
+  // Must be virtual as we'll inherit from StackInterface.
+  virtual ~StackInterface();
+
+  virtual int GetSize() const = 0;
+  virtual void Push(const Elem& x) = 0;
+};
+
+template <typename Elem>
+class MockStack : public StackInterface<Elem> {
+  ...
+  MOCK_METHOD(int, GetSize, (), (override));
+  MOCK_METHOD(void, Push, (const Elem& x), (override));
+};
+```
+
+### Mocking Non-virtual Methods {#MockingNonVirtualMethods}
+
+gMock can mock non-virtual functions to be used in Hi-perf dependency injection.
+
+In this case, instead of sharing a common base class with the real class, your
+mock class will be *unrelated* to the real class, but contain methods with the
+same signatures. The syntax for mocking non-virtual methods is the *same* as
+mocking virtual methods (just don't add `override`):
+
+```cpp
+// A simple packet stream class.  None of its members is virtual.
+class ConcretePacketStream {
+ public:
+  void AppendPacket(Packet* new_packet);
+  const Packet* GetPacket(size_t packet_number) const;
+  size_t NumberOfPackets() const;
+  ...
+};
+
+// A mock packet stream class.  It inherits from no other, but defines
+// GetPacket() and NumberOfPackets().
+class MockPacketStream {
+ public:
+  MOCK_METHOD(const Packet*, GetPacket, (size_t packet_number), (const));
+  MOCK_METHOD(size_t, NumberOfPackets, (), (const));
+  ...
+};
+```
+
+Note that the mock class doesn't define `AppendPacket()`, unlike the real class.
+That's fine as long as the test doesn't need to call it.
+
+Next, you need a way to say that you want to use `ConcretePacketStream` in
+production code, and use `MockPacketStream` in tests. Since the functions are
+not virtual and the two classes are unrelated, you must specify your choice at
+*compile time* (as opposed to run time).
+
+One way to do it is to templatize your code that needs to use a packet stream.
+More specifically, you will give your code a template type argument for the type
+of the packet stream. In production, you will instantiate your template with
+`ConcretePacketStream` as the type argument. In tests, you will instantiate the
+same template with `MockPacketStream`. For example, you may write:
+
+```cpp
+template <class PacketStream>
+void CreateConnection(PacketStream* stream) { ... }
+
+template <class PacketStream>
+class PacketReader {
+ public:
+  void ReadPackets(PacketStream* stream, size_t packet_num);
+};
+```
+
+Then you can use `CreateConnection<ConcretePacketStream>()` and
+`PacketReader<ConcretePacketStream>` in production code, and use
+`CreateConnection<MockPacketStream>()` and `PacketReader<MockPacketStream>` in
+tests.
+
+```cpp
+  MockPacketStream mock_stream;
+  EXPECT_CALL(mock_stream, ...)...;
+  .. set more expectations on mock_stream ...
+  PacketReader<MockPacketStream> reader(&mock_stream);
+  ... exercise reader ...
+```
+
+### Mocking Free Functions
+
+It is not possible to directly mock a free function (i.e. a C-style function or
+a static method). If you need to, you can rewrite your code to use an interface
+(abstract class).
+
+Instead of calling a free function (say, `OpenFile`) directly, introduce an
+interface for it and have a concrete subclass that calls the free function:
+
+```cpp
+class FileInterface {
+ public:
+  ...
+  virtual bool Open(const char* path, const char* mode) = 0;
+};
+
+class File : public FileInterface {
+ public:
+  ...
+  bool Open(const char* path, const char* mode) override {
+     return OpenFile(path, mode);
+  }
+};
+```
+
+Your code should talk to `FileInterface` to open a file. Now it's easy to mock
+out the function.
+
+This may seem like a lot of hassle, but in practice you often have multiple
+related functions that you can put in the same interface, so the per-function
+syntactic overhead will be much lower.
+
+If you are concerned about the performance overhead incurred by virtual
+functions, and profiling confirms your concern, you can combine this with the
+recipe for [mocking non-virtual methods](#MockingNonVirtualMethods).
+
+### Old-Style `MOCK_METHODn` Macros
+
+Before the generic `MOCK_METHOD` macro
+[was introduced in 2018](https://github.com/google/googletest/commit/c5f08bf91944ce1b19bcf414fa1760e69d20afc2),
+mocks where created using a family of macros collectively called `MOCK_METHODn`.
+These macros are still supported, though migration to the new `MOCK_METHOD` is
+recommended.
+
+The macros in the `MOCK_METHODn` family differ from `MOCK_METHOD`:
+
+*   The general structure is `MOCK_METHODn(MethodName, ReturnType(Args))`,
+    instead of `MOCK_METHOD(ReturnType, MethodName, (Args))`.
+*   The number `n` must equal the number of arguments.
+*   When mocking a const method, one must use `MOCK_CONST_METHODn`.
+*   When mocking a class template, the macro name must be suffixed with `_T`.
+*   In order to specify the call type, the macro name must be suffixed with
+    `_WITH_CALLTYPE`, and the call type is the first macro argument.
+
+Old macros and their new equivalents:
+
+<table>
+  <tr><th colspan=2>Simple</th></tr>
+  <tr>
+    <td>Old</td>
+    <td><code>MOCK_METHOD1(Foo, bool(int))</code></td>
+  </tr>
+  <tr>
+    <td>New</td>
+    <td><code>MOCK_METHOD(bool, Foo, (int))</code></td>
+  </tr>
+
+  <tr><th colspan=2>Const Method</th></tr>
+  <tr>
+    <td>Old</td>
+    <td><code>MOCK_CONST_METHOD1(Foo, bool(int))</code></td>
+  </tr>
+  <tr>
+    <td>New</td>
+    <td><code>MOCK_METHOD(bool, Foo, (int), (const))</code></td>
+  </tr>
+
+  <tr><th colspan=2>Method in a Class Template</th></tr>
+  <tr>
+    <td>Old</td>
+    <td><code>MOCK_METHOD1_T(Foo, bool(int))</code></td>
+  </tr>
+  <tr>
+    <td>New</td>
+    <td><code>MOCK_METHOD(bool, Foo, (int))</code></td>
+  </tr>
+
+  <tr><th colspan=2>Const Method in a Class Template</th></tr>
+  <tr>
+    <td>Old</td>
+    <td><code>MOCK_CONST_METHOD1_T(Foo, bool(int))</code></td>
+  </tr>
+  <tr>
+    <td>New</td>
+    <td><code>MOCK_METHOD(bool, Foo, (int), (const))</code></td>
+  </tr>
+
+  <tr><th colspan=2>Method with Call Type</th></tr>
+  <tr>
+    <td>Old</td>
+    <td><code>MOCK_METHOD1_WITH_CALLTYPE(STDMETHODCALLTYPE, Foo, bool(int))</code></td>
+  </tr>
+  <tr>
+    <td>New</td>
+    <td><code>MOCK_METHOD(bool, Foo, (int), (Calltype(STDMETHODCALLTYPE)))</code></td>
+  </tr>
+
+  <tr><th colspan=2>Const Method with Call Type</th></tr>
+  <tr>
+    <td>Old</td>
+    <td><code>MOCK_CONST_METHOD1_WITH_CALLTYPE(STDMETHODCALLTYPE, Foo, bool(int))</code></td>
+  </tr>
+  <tr>
+    <td>New</td>
+    <td><code>MOCK_METHOD(bool, Foo, (int), (const, Calltype(STDMETHODCALLTYPE)))</code></td>
+  </tr>
+
+  <tr><th colspan=2>Method with Call Type in a Class Template</th></tr>
+  <tr>
+    <td>Old</td>
+    <td><code>MOCK_METHOD1_T_WITH_CALLTYPE(STDMETHODCALLTYPE, Foo, bool(int))</code></td>
+  </tr>
+  <tr>
+    <td>New</td>
+    <td><code>MOCK_METHOD(bool, Foo, (int), (Calltype(STDMETHODCALLTYPE)))</code></td>
+  </tr>
+
+  <tr><th colspan=2>Const Method with Call Type in a Class Template</th></tr>
+  <tr>
+    <td>Old</td>
+    <td><code>MOCK_CONST_METHOD1_T_WITH_CALLTYPE(STDMETHODCALLTYPE, Foo, bool(int))</code></td>
+  </tr>
+  <tr>
+    <td>New</td>
+    <td><code>MOCK_METHOD(bool, Foo, (int), (const, Calltype(STDMETHODCALLTYPE)))</code></td>
+  </tr>
+</table>
+
+### The Nice, the Strict, and the Naggy {#NiceStrictNaggy}
+
+If a mock method has no `EXPECT_CALL` spec but is called, we say that it's an
+"uninteresting call", and the default action (which can be specified using
+`ON_CALL()`) of the method will be taken. Currently, an uninteresting call will
+also by default cause gMock to print a warning. (In the future, we might remove
+this warning by default.)
+
+However, sometimes you may want to ignore these uninteresting calls, and
+sometimes you may want to treat them as errors. gMock lets you make the decision
+on a per-mock-object basis.
+
+Suppose your test uses a mock class `MockFoo`:
+
+```cpp
+TEST(...) {
+  MockFoo mock_foo;
+  EXPECT_CALL(mock_foo, DoThis());
+  ... code that uses mock_foo ...
+}
+```
+
+If a method of `mock_foo` other than `DoThis()` is called, you will get a
+warning. However, if you rewrite your test to use `NiceMock<MockFoo>` instead,
+you can suppress the warning:
+
+```cpp
+using ::testing::NiceMock;
+
+TEST(...) {
+  NiceMock<MockFoo> mock_foo;
+  EXPECT_CALL(mock_foo, DoThis());
+  ... code that uses mock_foo ...
+}
+```
+
+`NiceMock<MockFoo>` is a subclass of `MockFoo`, so it can be used wherever
+`MockFoo` is accepted.
+
+It also works if `MockFoo`'s constructor takes some arguments, as
+`NiceMock<MockFoo>` "inherits" `MockFoo`'s constructors:
+
+```cpp
+using ::testing::NiceMock;
+
+TEST(...) {
+  NiceMock<MockFoo> mock_foo(5, "hi");  // Calls MockFoo(5, "hi").
+  EXPECT_CALL(mock_foo, DoThis());
+  ... code that uses mock_foo ...
+}
+```
+
+The usage of `StrictMock` is similar, except that it makes all uninteresting
+calls failures:
+
+```cpp
+using ::testing::StrictMock;
+
+TEST(...) {
+  StrictMock<MockFoo> mock_foo;
+  EXPECT_CALL(mock_foo, DoThis());
+  ... code that uses mock_foo ...
+
+  // The test will fail if a method of mock_foo other than DoThis()
+  // is called.
+}
+```
+
+{: .callout .note}
+NOTE: `NiceMock` and `StrictMock` only affects *uninteresting* calls (calls of
+*methods* with no expectations); they do not affect *unexpected* calls (calls of
+methods with expectations, but they don't match). See
+[Understanding Uninteresting vs Unexpected Calls](#uninteresting-vs-unexpected).
+
+There are some caveats though (sadly they are side effects of C++'s
+limitations):
+
+1.  `NiceMock<MockFoo>` and `StrictMock<MockFoo>` only work for mock methods
+    defined using the `MOCK_METHOD` macro **directly** in the `MockFoo` class.
+    If a mock method is defined in a **base class** of `MockFoo`, the "nice" or
+    "strict" modifier may not affect it, depending on the compiler. In
+    particular, nesting `NiceMock` and `StrictMock` (e.g.
+    `NiceMock<StrictMock<MockFoo> >`) is **not** supported.
+2.  `NiceMock<MockFoo>` and `StrictMock<MockFoo>` may not work correctly if the
+    destructor of `MockFoo` is not virtual. We would like to fix this, but it
+    requires cleaning up existing tests.
+
+Finally, you should be **very cautious** about when to use naggy or strict
+mocks, as they tend to make tests more brittle and harder to maintain. When you
+refactor your code without changing its externally visible behavior, ideally you
+shouldn't need to update any tests. If your code interacts with a naggy mock,
+however, you may start to get spammed with warnings as the result of your
+change. Worse, if your code interacts with a strict mock, your tests may start
+to fail and you'll be forced to fix them. Our general recommendation is to use
+nice mocks (not yet the default) most of the time, use naggy mocks (the current
+default) when developing or debugging tests, and use strict mocks only as the
+last resort.
+
+### Simplifying the Interface without Breaking Existing Code {#SimplerInterfaces}
+
+Sometimes a method has a long list of arguments that is mostly uninteresting.
+For example:
+
+```cpp
+class LogSink {
+ public:
+  ...
+  virtual void send(LogSeverity severity, const char* full_filename,
+                    const char* base_filename, int line,
+                    const struct tm* tm_time,
+                    const char* message, size_t message_len) = 0;
+};
+```
+
+This method's argument list is lengthy and hard to work with (the `message`
+argument is not even 0-terminated). If we mock it as is, using the mock will be
+awkward. If, however, we try to simplify this interface, we'll need to fix all
+clients depending on it, which is often infeasible.
+
+The trick is to redispatch the method in the mock class:
+
+```cpp
+class ScopedMockLog : public LogSink {
+ public:
+  ...
+  void send(LogSeverity severity, const char* full_filename,
+                    const char* base_filename, int line, const tm* tm_time,
+                    const char* message, size_t message_len) override {
+    // We are only interested in the log severity, full file name, and
+    // log message.
+    Log(severity, full_filename, std::string(message, message_len));
+  }
+
+  // Implements the mock method:
+  //
+  //   void Log(LogSeverity severity,
+  //            const string& file_path,
+  //            const string& message);
+  MOCK_METHOD(void, Log,
+              (LogSeverity severity, const string& file_path,
+               const string& message));
+};
+```
+
+By defining a new mock method with a trimmed argument list, we make the mock
+class more user-friendly.
+
+This technique may also be applied to make overloaded methods more amenable to
+mocking. For example, when overloads have been used to implement default
+arguments:
+
+```cpp
+class MockTurtleFactory : public TurtleFactory {
+ public:
+  Turtle* MakeTurtle(int length, int weight) override { ... }
+  Turtle* MakeTurtle(int length, int weight, int speed) override { ... }
+
+  // the above methods delegate to this one:
+  MOCK_METHOD(Turtle*, DoMakeTurtle, ());
+};
+```
+
+This allows tests that don't care which overload was invoked to avoid specifying
+argument matchers:
+
+```cpp
+ON_CALL(factory, DoMakeTurtle)
+    .WillByDefault(Return(MakeMockTurtle()));
+```
+
+### Alternative to Mocking Concrete Classes
+
+Often you may find yourself using classes that don't implement interfaces. In
+order to test your code that uses such a class (let's call it `Concrete`), you
+may be tempted to make the methods of `Concrete` virtual and then mock it.
+
+Try not to do that.
+
+Making a non-virtual function virtual is a big decision. It creates an extension
+point where subclasses can tweak your class' behavior. This weakens your control
+on the class because now it's harder to maintain the class invariants. You
+should make a function virtual only when there is a valid reason for a subclass
+to override it.
+
+Mocking concrete classes directly is problematic as it creates a tight coupling
+between the class and the tests - any small change in the class may invalidate
+your tests and make test maintenance a pain.
+
+To avoid such problems, many programmers have been practicing "coding to
+interfaces": instead of talking to the `Concrete` class, your code would define
+an interface and talk to it. Then you implement that interface as an adaptor on
+top of `Concrete`. In tests, you can easily mock that interface to observe how
+your code is doing.
+
+This technique incurs some overhead:
+
+*   You pay the cost of virtual function calls (usually not a problem).
+*   There is more abstraction for the programmers to learn.
+
+However, it can also bring significant benefits in addition to better
+testability:
+
+*   `Concrete`'s API may not fit your problem domain very well, as you may not
+    be the only client it tries to serve. By designing your own interface, you
+    have a chance to tailor it to your need - you may add higher-level
+    functionalities, rename stuff, etc instead of just trimming the class. This
+    allows you to write your code (user of the interface) in a more natural way,
+    which means it will be more readable, more maintainable, and you'll be more
+    productive.
+*   If `Concrete`'s implementation ever has to change, you don't have to rewrite
+    everywhere it is used. Instead, you can absorb the change in your
+    implementation of the interface, and your other code and tests will be
+    insulated from this change.
+
+Some people worry that if everyone is practicing this technique, they will end
+up writing lots of redundant code. This concern is totally understandable.
+However, there are two reasons why it may not be the case:
+
+*   Different projects may need to use `Concrete` in different ways, so the best
+    interfaces for them will be different. Therefore, each of them will have its
+    own domain-specific interface on top of `Concrete`, and they will not be the
+    same code.
+*   If enough projects want to use the same interface, they can always share it,
+    just like they have been sharing `Concrete`. You can check in the interface
+    and the adaptor somewhere near `Concrete` (perhaps in a `contrib`
+    sub-directory) and let many projects use it.
+
+You need to weigh the pros and cons carefully for your particular problem, but
+I'd like to assure you that the Java community has been practicing this for a
+long time and it's a proven effective technique applicable in a wide variety of
+situations. :-)
+
+### Delegating Calls to a Fake {#DelegatingToFake}
+
+Some times you have a non-trivial fake implementation of an interface. For
+example:
+
+```cpp
+class Foo {
+ public:
+  virtual ~Foo() {}
+  virtual char DoThis(int n) = 0;
+  virtual void DoThat(const char* s, int* p) = 0;
+};
+
+class FakeFoo : public Foo {
+ public:
+  char DoThis(int n) override {
+    return (n > 0) ? '+' :
+           (n < 0) ? '-' : '0';
+  }
+
+  void DoThat(const char* s, int* p) override {
+    *p = strlen(s);
+  }
+};
+```
+
+Now you want to mock this interface such that you can set expectations on it.
+However, you also want to use `FakeFoo` for the default behavior, as duplicating
+it in the mock object is, well, a lot of work.
+
+When you define the mock class using gMock, you can have it delegate its default
+action to a fake class you already have, using this pattern:
+
+```cpp
+class MockFoo : public Foo {
+ public:
+  // Normal mock method definitions using gMock.
+  MOCK_METHOD(char, DoThis, (int n), (override));
+  MOCK_METHOD(void, DoThat, (const char* s, int* p), (override));
+
+  // Delegates the default actions of the methods to a FakeFoo object.
+  // This must be called *before* the custom ON_CALL() statements.
+  void DelegateToFake() {
+    ON_CALL(*this, DoThis).WillByDefault([this](int n) {
+      return fake_.DoThis(n);
+    });
+    ON_CALL(*this, DoThat).WillByDefault([this](const char* s, int* p) {
+      fake_.DoThat(s, p);
+    });
+  }
+
+ private:
+  FakeFoo fake_;  // Keeps an instance of the fake in the mock.
+};
+```
+
+With that, you can use `MockFoo` in your tests as usual. Just remember that if
+you don't explicitly set an action in an `ON_CALL()` or `EXPECT_CALL()`, the
+fake will be called upon to do it.:
+
+```cpp
+using ::testing::_;
+
+TEST(AbcTest, Xyz) {
+  MockFoo foo;
+
+  foo.DelegateToFake();  // Enables the fake for delegation.
+
+  // Put your ON_CALL(foo, ...)s here, if any.
+
+  // No action specified, meaning to use the default action.
+  EXPECT_CALL(foo, DoThis(5));
+  EXPECT_CALL(foo, DoThat(_, _));
+
+  int n = 0;
+  EXPECT_EQ('+', foo.DoThis(5));  // FakeFoo::DoThis() is invoked.
+  foo.DoThat("Hi", &n);  // FakeFoo::DoThat() is invoked.
+  EXPECT_EQ(2, n);
+}
+```
+
+**Some tips:**
+
+*   If you want, you can still override the default action by providing your own
+    `ON_CALL()` or using `.WillOnce()` / `.WillRepeatedly()` in `EXPECT_CALL()`.
+*   In `DelegateToFake()`, you only need to delegate the methods whose fake
+    implementation you intend to use.
+
+*   The general technique discussed here works for overloaded methods, but
+    you'll need to tell the compiler which version you mean. To disambiguate a
+    mock function (the one you specify inside the parentheses of `ON_CALL()`),
+    use [this technique](#SelectOverload); to disambiguate a fake function (the
+    one you place inside `Invoke()`), use a `static_cast` to specify the
+    function's type. For instance, if class `Foo` has methods `char DoThis(int
+    n)` and `bool DoThis(double x) const`, and you want to invoke the latter,
+    you need to write `Invoke(&fake_, static_cast<bool (FakeFoo::*)(double)
+    const>(&FakeFoo::DoThis))` instead of `Invoke(&fake_, &FakeFoo::DoThis)`
+    (The strange-looking thing inside the angled brackets of `static_cast` is
+    the type of a function pointer to the second `DoThis()` method.).
+
+*   Having to mix a mock and a fake is often a sign of something gone wrong.
+    Perhaps you haven't got used to the interaction-based way of testing yet. Or
+    perhaps your interface is taking on too many roles and should be split up.
+    Therefore, **don't abuse this**. We would only recommend to do it as an
+    intermediate step when you are refactoring your code.
+
+Regarding the tip on mixing a mock and a fake, here's an example on why it may
+be a bad sign: Suppose you have a class `System` for low-level system
+operations. In particular, it does file and I/O operations. And suppose you want
+to test how your code uses `System` to do I/O, and you just want the file
+operations to work normally. If you mock out the entire `System` class, you'll
+have to provide a fake implementation for the file operation part, which
+suggests that `System` is taking on too many roles.
+
+Instead, you can define a `FileOps` interface and an `IOOps` interface and split
+`System`'s functionalities into the two. Then you can mock `IOOps` without
+mocking `FileOps`.
+
+### Delegating Calls to a Real Object
+
+When using testing doubles (mocks, fakes, stubs, and etc), sometimes their
+behaviors will differ from those of the real objects. This difference could be
+either intentional (as in simulating an error such that you can test the error
+handling code) or unintentional. If your mocks have different behaviors than the
+real objects by mistake, you could end up with code that passes the tests but
+fails in production.
+
+You can use the *delegating-to-real* technique to ensure that your mock has the
+same behavior as the real object while retaining the ability to validate calls.
+This technique is very similar to the [delegating-to-fake](#DelegatingToFake)
+technique, the difference being that we use a real object instead of a fake.
+Here's an example:
+
+```cpp
+using ::testing::AtLeast;
+
+class MockFoo : public Foo {
+ public:
+  MockFoo() {
+    // By default, all calls are delegated to the real object.
+    ON_CALL(*this, DoThis).WillByDefault([this](int n) {
+      return real_.DoThis(n);
+    });
+    ON_CALL(*this, DoThat).WillByDefault([this](const char* s, int* p) {
+      real_.DoThat(s, p);
+    });
+    ...
+  }
+  MOCK_METHOD(char, DoThis, ...);
+  MOCK_METHOD(void, DoThat, ...);
+  ...
+ private:
+  Foo real_;
+};
+
+...
+  MockFoo mock;
+  EXPECT_CALL(mock, DoThis())
+      .Times(3);
+  EXPECT_CALL(mock, DoThat("Hi"))
+      .Times(AtLeast(1));
+  ... use mock in test ...
+```
+
+With this, gMock will verify that your code made the right calls (with the right
+arguments, in the right order, called the right number of times, etc), and a
+real object will answer the calls (so the behavior will be the same as in
+production). This gives you the best of both worlds.
+
+### Delegating Calls to a Parent Class
+
+Ideally, you should code to interfaces, whose methods are all pure virtual. In
+reality, sometimes you do need to mock a virtual method that is not pure (i.e,
+it already has an implementation). For example:
+
+```cpp
+class Foo {
+ public:
+  virtual ~Foo();
+
+  virtual void Pure(int n) = 0;
+  virtual int Concrete(const char* str) { ... }
+};
+
+class MockFoo : public Foo {
+ public:
+  // Mocking a pure method.
+  MOCK_METHOD(void, Pure, (int n), (override));
+  // Mocking a concrete method.  Foo::Concrete() is shadowed.
+  MOCK_METHOD(int, Concrete, (const char* str), (override));
+};
+```
+
+Sometimes you may want to call `Foo::Concrete()` instead of
+`MockFoo::Concrete()`. Perhaps you want to do it as part of a stub action, or
+perhaps your test doesn't need to mock `Concrete()` at all (but it would be
+oh-so painful to have to define a new mock class whenever you don't need to mock
+one of its methods).
+
+You can call `Foo::Concrete()` inside an action by:
+
+```cpp
+...
+  EXPECT_CALL(foo, Concrete).WillOnce([&foo](const char* str) {
+    return foo.Foo::Concrete(str);
+  });
+```
+
+or tell the mock object that you don't want to mock `Concrete()`:
+
+```cpp
+...
+  ON_CALL(foo, Concrete).WillByDefault([&foo](const char* str) {
+    return foo.Foo::Concrete(str);
+  });
+```
+
+(Why don't we just write `{ return foo.Concrete(str); }`? If you do that,
+`MockFoo::Concrete()` will be called (and cause an infinite recursion) since
+`Foo::Concrete()` is virtual. That's just how C++ works.)
+
+## Using Matchers
+
+### Matching Argument Values Exactly
+
+You can specify exactly which arguments a mock method is expecting:
+
+```cpp
+using ::testing::Return;
+...
+  EXPECT_CALL(foo, DoThis(5))
+      .WillOnce(Return('a'));
+  EXPECT_CALL(foo, DoThat("Hello", bar));
+```
+
+### Using Simple Matchers
+
+You can use matchers to match arguments that have a certain property:
+
+```cpp
+using ::testing::NotNull;
+using ::testing::Return;
+...
+  EXPECT_CALL(foo, DoThis(Ge(5)))  // The argument must be >= 5.
+      .WillOnce(Return('a'));
+  EXPECT_CALL(foo, DoThat("Hello", NotNull()));
+      // The second argument must not be NULL.
+```
+
+A frequently used matcher is `_`, which matches anything:
+
+```cpp
+  EXPECT_CALL(foo, DoThat(_, NotNull()));
+```
+
+### Combining Matchers {#CombiningMatchers}
+
+You can build complex matchers from existing ones using `AllOf()`,
+`AllOfArray()`, `AnyOf()`, `AnyOfArray()` and `Not()`:
+
+```cpp
+using ::testing::AllOf;
+using ::testing::Gt;
+using ::testing::HasSubstr;
+using ::testing::Ne;
+using ::testing::Not;
+...
+  // The argument must be > 5 and != 10.
+  EXPECT_CALL(foo, DoThis(AllOf(Gt(5),
+                                Ne(10))));
+
+  // The first argument must not contain sub-string "blah".
+  EXPECT_CALL(foo, DoThat(Not(HasSubstr("blah")),
+                          NULL));
+```
+
+Matchers are function objects, and parametrized matchers can be composed just
+like any other function. However because their types can be long and rarely
+provide meaningful information, it can be easier to express them with C++14
+generic lambdas to avoid specifying types. For example,
+
+```cpp
+using ::testing::Contains;
+using ::testing::Property;
+
+inline constexpr auto HasFoo = [](const auto& f) {
+  return Property(&MyClass::foo, Contains(f));
+};
+...
+  EXPECT_THAT(x, HasFoo("blah"));
+```
+
+### Casting Matchers {#SafeMatcherCast}
+
+gMock matchers are statically typed, meaning that the compiler can catch your
+mistake if you use a matcher of the wrong type (for example, if you use `Eq(5)`
+to match a `string` argument). Good for you!
+
+Sometimes, however, you know what you're doing and want the compiler to give you
+some slack. One example is that you have a matcher for `long` and the argument
+you want to match is `int`. While the two types aren't exactly the same, there
+is nothing really wrong with using a `Matcher<long>` to match an `int` - after
+all, we can first convert the `int` argument to a `long` losslessly before
+giving it to the matcher.
+
+To support this need, gMock gives you the `SafeMatcherCast<T>(m)` function. It
+casts a matcher `m` to type `Matcher<T>`. To ensure safety, gMock checks that
+(let `U` be the type `m` accepts :
+
+1.  Type `T` can be *implicitly* cast to type `U`;
+2.  When both `T` and `U` are built-in arithmetic types (`bool`, integers, and
+    floating-point numbers), the conversion from `T` to `U` is not lossy (in
+    other words, any value representable by `T` can also be represented by `U`);
+    and
+3.  When `U` is a reference, `T` must also be a reference (as the underlying
+    matcher may be interested in the address of the `U` value).
+
+The code won't compile if any of these conditions isn't met.
+
+Here's one example:
+
+```cpp
+using ::testing::SafeMatcherCast;
+
+// A base class and a child class.
+class Base { ... };
+class Derived : public Base { ... };
+
+class MockFoo : public Foo {
+ public:
+  MOCK_METHOD(void, DoThis, (Derived* derived), (override));
+};
+
+...
+  MockFoo foo;
+  // m is a Matcher<Base*> we got from somewhere.
+  EXPECT_CALL(foo, DoThis(SafeMatcherCast<Derived*>(m)));
+```
+
+If you find `SafeMatcherCast<T>(m)` too limiting, you can use a similar function
+`MatcherCast<T>(m)`. The difference is that `MatcherCast` works as long as you
+can `static_cast` type `T` to type `U`.
+
+`MatcherCast` essentially lets you bypass C++'s type system (`static_cast` isn't
+always safe as it could throw away information, for example), so be careful not
+to misuse/abuse it.
+
+### Selecting Between Overloaded Functions {#SelectOverload}
+
+If you expect an overloaded function to be called, the compiler may need some
+help on which overloaded version it is.
+
+To disambiguate functions overloaded on the const-ness of this object, use the
+`Const()` argument wrapper.
+
+```cpp
+using ::testing::ReturnRef;
+
+class MockFoo : public Foo {
+  ...
+  MOCK_METHOD(Bar&, GetBar, (), (override));
+  MOCK_METHOD(const Bar&, GetBar, (), (const, override));
+};
+
+...
+  MockFoo foo;
+  Bar bar1, bar2;
+  EXPECT_CALL(foo, GetBar())         // The non-const GetBar().
+      .WillOnce(ReturnRef(bar1));
+  EXPECT_CALL(Const(foo), GetBar())  // The const GetBar().
+      .WillOnce(ReturnRef(bar2));
+```
+
+(`Const()` is defined by gMock and returns a `const` reference to its argument.)
+
+To disambiguate overloaded functions with the same number of arguments but
+different argument types, you may need to specify the exact type of a matcher,
+either by wrapping your matcher in `Matcher<type>()`, or using a matcher whose
+type is fixed (`TypedEq<type>`, `An<type>()`, etc):
+
+```cpp
+using ::testing::An;
+using ::testing::Matcher;
+using ::testing::TypedEq;
+
+class MockPrinter : public Printer {
+ public:
+  MOCK_METHOD(void, Print, (int n), (override));
+  MOCK_METHOD(void, Print, (char c), (override));
+};
+
+TEST(PrinterTest, Print) {
+  MockPrinter printer;
+
+  EXPECT_CALL(printer, Print(An<int>()));            // void Print(int);
+  EXPECT_CALL(printer, Print(Matcher<int>(Lt(5))));  // void Print(int);
+  EXPECT_CALL(printer, Print(TypedEq<char>('a')));   // void Print(char);
+
+  printer.Print(3);
+  printer.Print(6);
+  printer.Print('a');
+}
+```
+
+### Performing Different Actions Based on the Arguments
+
+When a mock method is called, the *last* matching expectation that's still
+active will be selected (think "newer overrides older"). So, you can make a
+method do different things depending on its argument values like this:
+
+```cpp
+using ::testing::_;
+using ::testing::Lt;
+using ::testing::Return;
+...
+  // The default case.
+  EXPECT_CALL(foo, DoThis(_))
+      .WillRepeatedly(Return('b'));
+  // The more specific case.
+  EXPECT_CALL(foo, DoThis(Lt(5)))
+      .WillRepeatedly(Return('a'));
+```
+
+Now, if `foo.DoThis()` is called with a value less than 5, `'a'` will be
+returned; otherwise `'b'` will be returned.
+
+### Matching Multiple Arguments as a Whole
+
+Sometimes it's not enough to match the arguments individually. For example, we
+may want to say that the first argument must be less than the second argument.
+The `With()` clause allows us to match all arguments of a mock function as a
+whole. For example,
+
+```cpp
+using ::testing::_;
+using ::testing::Ne;
+using ::testing::Lt;
+...
+  EXPECT_CALL(foo, InRange(Ne(0), _))
+      .With(Lt());
+```
+
+says that the first argument of `InRange()` must not be 0, and must be less than
+the second argument.
+
+The expression inside `With()` must be a matcher of type `Matcher<std::tuple<A1,
+..., An>>`, where `A1`, ..., `An` are the types of the function arguments.
+
+You can also write `AllArgs(m)` instead of `m` inside `.With()`. The two forms
+are equivalent, but `.With(AllArgs(Lt()))` is more readable than `.With(Lt())`.
+
+You can use `Args<k1, ..., kn>(m)` to match the `n` selected arguments (as a
+tuple) against `m`. For example,
+
+```cpp
+using ::testing::_;
+using ::testing::AllOf;
+using ::testing::Args;
+using ::testing::Lt;
+...
+  EXPECT_CALL(foo, Blah)
+      .With(AllOf(Args<0, 1>(Lt()), Args<1, 2>(Lt())));
+```
+
+says that `Blah` will be called with arguments `x`, `y`, and `z` where `x < y <
+z`. Note that in this example, it wasn't necessary specify the positional
+matchers.
+
+As a convenience and example, gMock provides some matchers for 2-tuples,
+including the `Lt()` matcher above. See
+[Multi-argument Matchers](reference/matchers.md#MultiArgMatchers) for the
+complete list.
+
+Note that if you want to pass the arguments to a predicate of your own (e.g.
+`.With(Args<0, 1>(Truly(&MyPredicate)))`), that predicate MUST be written to
+take a `std::tuple` as its argument; gMock will pass the `n` selected arguments
+as *one* single tuple to the predicate.
+
+### Using Matchers as Predicates
+
+Have you noticed that a matcher is just a fancy predicate that also knows how to
+describe itself? Many existing algorithms take predicates as arguments (e.g.
+those defined in STL's `<algorithm>` header), and it would be a shame if gMock
+matchers were not allowed to participate.
+
+Luckily, you can use a matcher where a unary predicate functor is expected by
+wrapping it inside the `Matches()` function. For example,
+
+```cpp
+#include <algorithm>
+#include <vector>
+
+using ::testing::Matches;
+using ::testing::Ge;
+
+vector<int> v;
+...
+// How many elements in v are >= 10?
+const int count = count_if(v.begin(), v.end(), Matches(Ge(10)));
+```
+
+Since you can build complex matchers from simpler ones easily using gMock, this
+gives you a way to conveniently construct composite predicates (doing the same
+using STL's `<functional>` header is just painful). For example, here's a
+predicate that's satisfied by any number that is >= 0, <= 100, and != 50:
+
+```cpp
+using testing::AllOf;
+using testing::Ge;
+using testing::Le;
+using testing::Matches;
+using testing::Ne;
+...
+Matches(AllOf(Ge(0), Le(100), Ne(50)))
+```
+
+### Using Matchers in googletest Assertions
+
+Since matchers are basically predicates that also know how to describe
+themselves, there is a way to take advantage of them in googletest assertions.
+It's called `ASSERT_THAT` and `EXPECT_THAT`:
+
+```cpp
+  ASSERT_THAT(value, matcher);  // Asserts that value matches matcher.
+  EXPECT_THAT(value, matcher);  // The non-fatal version.
+```
+
+For example, in a googletest test you can write:
+
+```cpp
+#include "gmock/gmock.h"
+
+using ::testing::AllOf;
+using ::testing::Ge;
+using ::testing::Le;
+using ::testing::MatchesRegex;
+using ::testing::StartsWith;
+
+...
+  EXPECT_THAT(Foo(), StartsWith("Hello"));
+  EXPECT_THAT(Bar(), MatchesRegex("Line \\d+"));
+  ASSERT_THAT(Baz(), AllOf(Ge(5), Le(10)));
+```
+
+which (as you can probably guess) executes `Foo()`, `Bar()`, and `Baz()`, and
+verifies that:
+
+*   `Foo()` returns a string that starts with `"Hello"`.
+*   `Bar()` returns a string that matches regular expression `"Line \\d+"`.
+*   `Baz()` returns a number in the range [5, 10].
+
+The nice thing about these macros is that *they read like English*. They
+generate informative messages too. For example, if the first `EXPECT_THAT()`
+above fails, the message will be something like:
+
+```cpp
+Value of: Foo()
+  Actual: "Hi, world!"
+Expected: starts with "Hello"
+```
+
+**Credit:** The idea of `(ASSERT|EXPECT)_THAT` was borrowed from Joe Walnes'
+Hamcrest project, which adds `assertThat()` to JUnit.
+
+### Using Predicates as Matchers
+
+gMock provides a set of built-in matchers for matching arguments with expected
+values—see the [Matchers Reference](reference/matchers.md) for more information.
+In case you find the built-in set lacking, you can use an arbitrary unary
+predicate function or functor as a matcher - as long as the predicate accepts a
+value of the type you want. You do this by wrapping the predicate inside the
+`Truly()` function, for example:
+
+```cpp
+using ::testing::Truly;
+
+int IsEven(int n) { return (n % 2) == 0 ? 1 : 0; }
+...
+  // Bar() must be called with an even number.
+  EXPECT_CALL(foo, Bar(Truly(IsEven)));
+```
+
+Note that the predicate function / functor doesn't have to return `bool`. It
+works as long as the return value can be used as the condition in in statement
+`if (condition) ...`.
+
+### Matching Arguments that Are Not Copyable
+
+When you do an `EXPECT_CALL(mock_obj, Foo(bar))`, gMock saves away a copy of
+`bar`. When `Foo()` is called later, gMock compares the argument to `Foo()` with
+the saved copy of `bar`. This way, you don't need to worry about `bar` being
+modified or destroyed after the `EXPECT_CALL()` is executed. The same is true
+when you use matchers like `Eq(bar)`, `Le(bar)`, and so on.
+
+But what if `bar` cannot be copied (i.e. has no copy constructor)? You could
+define your own matcher function or callback and use it with `Truly()`, as the
+previous couple of recipes have shown. Or, you may be able to get away from it
+if you can guarantee that `bar` won't be changed after the `EXPECT_CALL()` is
+executed. Just tell gMock that it should save a reference to `bar`, instead of a
+copy of it. Here's how:
+
+```cpp
+using ::testing::Eq;
+using ::testing::Lt;
+...
+  // Expects that Foo()'s argument == bar.
+  EXPECT_CALL(mock_obj, Foo(Eq(std::ref(bar))));
+
+  // Expects that Foo()'s argument < bar.
+  EXPECT_CALL(mock_obj, Foo(Lt(std::ref(bar))));
+```
+
+Remember: if you do this, don't change `bar` after the `EXPECT_CALL()`, or the
+result is undefined.
+
+### Validating a Member of an Object
+
+Often a mock function takes a reference to object as an argument. When matching
+the argument, you may not want to compare the entire object against a fixed
+object, as that may be over-specification. Instead, you may need to validate a
+certain member variable or the result of a certain getter method of the object.
+You can do this with `Field()` and `Property()`. More specifically,
+
+```cpp
+Field(&Foo::bar, m)
+```
+
+is a matcher that matches a `Foo` object whose `bar` member variable satisfies
+matcher `m`.
+
+```cpp
+Property(&Foo::baz, m)
+```
+
+is a matcher that matches a `Foo` object whose `baz()` method returns a value
+that satisfies matcher `m`.
+
+For example:
+
+| Expression                   | Description                              |
+| :--------------------------- | :--------------------------------------- |
+| `Field(&Foo::number, Ge(3))` | Matches `x` where `x.number >= 3`.       |
+| `Property(&Foo::name,  StartsWith("John "))` | Matches `x` where `x.name()` starts with  `"John "`. |
+
+Note that in `Property(&Foo::baz, ...)`, method `baz()` must take no argument
+and be declared as `const`. Don't use `Property()` against member functions that
+you do not own, because taking addresses of functions is fragile and generally
+not part of the contract of the function.
+
+`Field()` and `Property()` can also match plain pointers to objects. For
+instance,
+
+```cpp
+using ::testing::Field;
+using ::testing::Ge;
+...
+Field(&Foo::number, Ge(3))
+```
+
+matches a plain pointer `p` where `p->number >= 3`. If `p` is `NULL`, the match
+will always fail regardless of the inner matcher.
+
+What if you want to validate more than one members at the same time? Remember
+that there are [`AllOf()` and `AllOfArray()`](#CombiningMatchers).
+
+Finally `Field()` and `Property()` provide overloads that take the field or
+property names as the first argument to include it in the error message. This
+can be useful when creating combined matchers.
+
+```cpp
+using ::testing::AllOf;
+using ::testing::Field;
+using ::testing::Matcher;
+using ::testing::SafeMatcherCast;
+
+Matcher<Foo> IsFoo(const Foo& foo) {
+  return AllOf(Field("some_field", &Foo::some_field, foo.some_field),
+               Field("other_field", &Foo::other_field, foo.other_field),
+               Field("last_field", &Foo::last_field, foo.last_field));
+}
+```
+
+### Validating the Value Pointed to by a Pointer Argument
+
+C++ functions often take pointers as arguments. You can use matchers like
+`IsNull()`, `NotNull()`, and other comparison matchers to match a pointer, but
+what if you want to make sure the value *pointed to* by the pointer, instead of
+the pointer itself, has a certain property? Well, you can use the `Pointee(m)`
+matcher.
+
+`Pointee(m)` matches a pointer if and only if `m` matches the value the pointer
+points to. For example:
+
+```cpp
+using ::testing::Ge;
+using ::testing::Pointee;
+...
+  EXPECT_CALL(foo, Bar(Pointee(Ge(3))));
+```
+
+expects `foo.Bar()` to be called with a pointer that points to a value greater
+than or equal to 3.
+
+One nice thing about `Pointee()` is that it treats a `NULL` pointer as a match
+failure, so you can write `Pointee(m)` instead of
+
+```cpp
+using ::testing::AllOf;
+using ::testing::NotNull;
+using ::testing::Pointee;
+...
+  AllOf(NotNull(), Pointee(m))
+```
+
+without worrying that a `NULL` pointer will crash your test.
+
+Also, did we tell you that `Pointee()` works with both raw pointers **and**
+smart pointers (`std::unique_ptr`, `std::shared_ptr`, etc)?
+
+What if you have a pointer to pointer? You guessed it - you can use nested
+`Pointee()` to probe deeper inside the value. For example,
+`Pointee(Pointee(Lt(3)))` matches a pointer that points to a pointer that points
+to a number less than 3 (what a mouthful...).
+
+### Testing a Certain Property of an Object
+
+Sometimes you want to specify that an object argument has a certain property,
+but there is no existing matcher that does this. If you want good error
+messages, you should [define a matcher](#NewMatchers). If you want to do it
+quick and dirty, you could get away with writing an ordinary function.
+
+Let's say you have a mock function that takes an object of type `Foo`, which has
+an `int bar()` method and an `int baz()` method, and you want to constrain that
+the argument's `bar()` value plus its `baz()` value is a given number. Here's
+how you can define a matcher to do it:
+
+```cpp
+using ::testing::Matcher;
+
+class BarPlusBazEqMatcher {
+ public:
+  explicit BarPlusBazEqMatcher(int expected_sum)
+      : expected_sum_(expected_sum) {}
+
+  bool MatchAndExplain(const Foo& foo,
+                       std::ostream* /* listener */) const {
+    return (foo.bar() + foo.baz()) == expected_sum_;
+  }
+
+  void DescribeTo(std::ostream& os) const {
+    os << "bar() + baz() equals " << expected_sum_;
+  }
+
+  void DescribeNegationTo(std::ostream& os) const {
+    os << "bar() + baz() does not equal " << expected_sum_;
+  }
+ private:
+  const int expected_sum_;
+};
+
+Matcher<const Foo&> BarPlusBazEq(int expected_sum) {
+  return BarPlusBazEqMatcher(expected_sum);
+}
+
+...
+  EXPECT_CALL(..., DoThis(BarPlusBazEq(5)))...;
+```
+
+### Matching Containers
+
+Sometimes an STL container (e.g. list, vector, map, ...) is passed to a mock
+function and you may want to validate it. Since most STL containers support the
+`==` operator, you can write `Eq(expected_container)` or simply
+`expected_container` to match a container exactly.
+
+Sometimes, though, you may want to be more flexible (for example, the first
+element must be an exact match, but the second element can be any positive
+number, and so on). Also, containers used in tests often have a small number of
+elements, and having to define the expected container out-of-line is a bit of a
+hassle.
+
+You can use the `ElementsAre()` or `UnorderedElementsAre()` matcher in such
+cases:
+
+```cpp
+using ::testing::_;
+using ::testing::ElementsAre;
+using ::testing::Gt;
+...
+  MOCK_METHOD(void, Foo, (const vector<int>& numbers), (override));
+...
+  EXPECT_CALL(mock, Foo(ElementsAre(1, Gt(0), _, 5)));
+```
+
+The above matcher says that the container must have 4 elements, which must be 1,
+greater than 0, anything, and 5 respectively.
+
+If you instead write:
+
+```cpp
+using ::testing::_;
+using ::testing::Gt;
+using ::testing::UnorderedElementsAre;
+...
+  MOCK_METHOD(void, Foo, (const vector<int>& numbers), (override));
+...
+  EXPECT_CALL(mock, Foo(UnorderedElementsAre(1, Gt(0), _, 5)));
+```
+
+It means that the container must have 4 elements, which (under some permutation)
+must be 1, greater than 0, anything, and 5 respectively.
+
+As an alternative you can place the arguments in a C-style array and use
+`ElementsAreArray()` or `UnorderedElementsAreArray()` instead:
+
+```cpp
+using ::testing::ElementsAreArray;
+...
+  // ElementsAreArray accepts an array of element values.
+  const int expected_vector1[] = {1, 5, 2, 4, ...};
+  EXPECT_CALL(mock, Foo(ElementsAreArray(expected_vector1)));
+
+  // Or, an array of element matchers.
+  Matcher<int> expected_vector2[] = {1, Gt(2), _, 3, ...};
+  EXPECT_CALL(mock, Foo(ElementsAreArray(expected_vector2)));
+```
+
+In case the array needs to be dynamically created (and therefore the array size
+cannot be inferred by the compiler), you can give `ElementsAreArray()` an
+additional argument to specify the array size:
+
+```cpp
+using ::testing::ElementsAreArray;
+...
+  int* const expected_vector3 = new int[count];
+  ... fill expected_vector3 with values ...
+  EXPECT_CALL(mock, Foo(ElementsAreArray(expected_vector3, count)));
+```
+
+Use `Pair` when comparing maps or other associative containers.
+
+{% raw %}
+
+```cpp
+using testing::ElementsAre;
+using testing::Pair;
+...
+  std::map<string, int> m = {{"a", 1}, {"b", 2}, {"c", 3}};
+  EXPECT_THAT(m, ElementsAre(Pair("a", 1), Pair("b", 2), Pair("c", 3)));
+```
+
+{% endraw %}
+
+**Tips:**
+
+*   `ElementsAre*()` can be used to match *any* container that implements the
+    STL iterator pattern (i.e. it has a `const_iterator` type and supports
+    `begin()/end()`), not just the ones defined in STL. It will even work with
+    container types yet to be written - as long as they follows the above
+    pattern.
+*   You can use nested `ElementsAre*()` to match nested (multi-dimensional)
+    containers.
+*   If the container is passed by pointer instead of by reference, just write
+    `Pointee(ElementsAre*(...))`.
+*   The order of elements *matters* for `ElementsAre*()`. If you are using it
+    with containers whose element order are undefined (e.g. `hash_map`) you
+    should use `WhenSorted` around `ElementsAre`.
+
+### Sharing Matchers
+
+Under the hood, a gMock matcher object consists of a pointer to a ref-counted
+implementation object. Copying matchers is allowed and very efficient, as only
+the pointer is copied. When the last matcher that references the implementation
+object dies, the implementation object will be deleted.
+
+Therefore, if you have some complex matcher that you want to use again and
+again, there is no need to build it everytime. Just assign it to a matcher
+variable and use that variable repeatedly! For example,
+
+```cpp
+using ::testing::AllOf;
+using ::testing::Gt;
+using ::testing::Le;
+using ::testing::Matcher;
+...
+  Matcher<int> in_range = AllOf(Gt(5), Le(10));
+  ... use in_range as a matcher in multiple EXPECT_CALLs ...
+```
+
+### Matchers must have no side-effects {#PureMatchers}
+
+{: .callout .warning}
+WARNING: gMock does not guarantee when or how many times a matcher will be
+invoked. Therefore, all matchers must be *purely functional*: they cannot have
+any side effects, and the match result must not depend on anything other than
+the matcher's parameters and the value being matched.
+
+This requirement must be satisfied no matter how a matcher is defined (e.g., if
+it is one of the standard matchers, or a custom matcher). In particular, a
+matcher can never call a mock function, as that will affect the state of the
+mock object and gMock.
+
+## Setting Expectations
+
+### Knowing When to Expect {#UseOnCall}
+
+**`ON_CALL`** is likely the *single most under-utilized construct* in gMock.
+
+There are basically two constructs for defining the behavior of a mock object:
+`ON_CALL` and `EXPECT_CALL`. The difference? `ON_CALL` defines what happens when
+a mock method is called, but <em>doesn't imply any expectation on the method
+being called</em>. `EXPECT_CALL` not only defines the behavior, but also sets an
+expectation that <em>the method will be called with the given arguments, for the
+given number of times</em> (and *in the given order* when you specify the order
+too).
+
+Since `EXPECT_CALL` does more, isn't it better than `ON_CALL`? Not really. Every
+`EXPECT_CALL` adds a constraint on the behavior of the code under test. Having
+more constraints than necessary is *baaad* - even worse than not having enough
+constraints.
+
+This may be counter-intuitive. How could tests that verify more be worse than
+tests that verify less? Isn't verification the whole point of tests?
+
+The answer lies in *what* a test should verify. **A good test verifies the
+contract of the code.** If a test over-specifies, it doesn't leave enough
+freedom to the implementation. As a result, changing the implementation without
+breaking the contract (e.g. refactoring and optimization), which should be
+perfectly fine to do, can break such tests. Then you have to spend time fixing
+them, only to see them broken again the next time the implementation is changed.
+
+Keep in mind that one doesn't have to verify more than one property in one test.
+In fact, **it's a good style to verify only one thing in one test.** If you do
+that, a bug will likely break only one or two tests instead of dozens (which
+case would you rather debug?). If you are also in the habit of giving tests
+descriptive names that tell what they verify, you can often easily guess what's
+wrong just from the test log itself.
+
+So use `ON_CALL` by default, and only use `EXPECT_CALL` when you actually intend
+to verify that the call is made. For example, you may have a bunch of `ON_CALL`s
+in your test fixture to set the common mock behavior shared by all tests in the
+same group, and write (scarcely) different `EXPECT_CALL`s in different `TEST_F`s
+to verify different aspects of the code's behavior. Compared with the style
+where each `TEST` has many `EXPECT_CALL`s, this leads to tests that are more
+resilient to implementational changes (and thus less likely to require
+maintenance) and makes the intent of the tests more obvious (so they are easier
+to maintain when you do need to maintain them).
+
+If you are bothered by the "Uninteresting mock function call" message printed
+when a mock method without an `EXPECT_CALL` is called, you may use a `NiceMock`
+instead to suppress all such messages for the mock object, or suppress the
+message for specific methods by adding `EXPECT_CALL(...).Times(AnyNumber())`. DO
+NOT suppress it by blindly adding an `EXPECT_CALL(...)`, or you'll have a test
+that's a pain to maintain.
+
+### Ignoring Uninteresting Calls
+
+If you are not interested in how a mock method is called, just don't say
+anything about it. In this case, if the method is ever called, gMock will
+perform its default action to allow the test program to continue. If you are not
+happy with the default action taken by gMock, you can override it using
+`DefaultValue<T>::Set()` (described [here](#DefaultValue)) or `ON_CALL()`.
+
+Please note that once you expressed interest in a particular mock method (via
+`EXPECT_CALL()`), all invocations to it must match some expectation. If this
+function is called but the arguments don't match any `EXPECT_CALL()` statement,
+it will be an error.
+
+### Disallowing Unexpected Calls
+
+If a mock method shouldn't be called at all, explicitly say so:
+
+```cpp
+using ::testing::_;
+...
+  EXPECT_CALL(foo, Bar(_))
+      .Times(0);
+```
+
+If some calls to the method are allowed, but the rest are not, just list all the
+expected calls:
+
+```cpp
+using ::testing::AnyNumber;
+using ::testing::Gt;
+...
+  EXPECT_CALL(foo, Bar(5));
+  EXPECT_CALL(foo, Bar(Gt(10)))
+      .Times(AnyNumber());
+```
+
+A call to `foo.Bar()` that doesn't match any of the `EXPECT_CALL()` statements
+will be an error.
+
+### Understanding Uninteresting vs Unexpected Calls {#uninteresting-vs-unexpected}
+
+*Uninteresting* calls and *unexpected* calls are different concepts in gMock.
+*Very* different.
+
+A call `x.Y(...)` is **uninteresting** if there's *not even a single*
+`EXPECT_CALL(x, Y(...))` set. In other words, the test isn't interested in the
+`x.Y()` method at all, as evident in that the test doesn't care to say anything
+about it.
+
+A call `x.Y(...)` is **unexpected** if there are *some* `EXPECT_CALL(x,
+Y(...))`s set, but none of them matches the call. Put another way, the test is
+interested in the `x.Y()` method (therefore it explicitly sets some
+`EXPECT_CALL` to verify how it's called); however, the verification fails as the
+test doesn't expect this particular call to happen.
+
+**An unexpected call is always an error,** as the code under test doesn't behave
+the way the test expects it to behave.
+
+**By default, an uninteresting call is not an error,** as it violates no
+constraint specified by the test. (gMock's philosophy is that saying nothing
+means there is no constraint.) However, it leads to a warning, as it *might*
+indicate a problem (e.g. the test author might have forgotten to specify a
+constraint).
+
+In gMock, `NiceMock` and `StrictMock` can be used to make a mock class "nice" or
+"strict". How does this affect uninteresting calls and unexpected calls?
+
+A **nice mock** suppresses uninteresting call *warnings*. It is less chatty than
+the default mock, but otherwise is the same. If a test fails with a default
+mock, it will also fail using a nice mock instead. And vice versa. Don't expect
+making a mock nice to change the test's result.
+
+A **strict mock** turns uninteresting call warnings into errors. So making a
+mock strict may change the test's result.
+
+Let's look at an example:
+
+```cpp
+TEST(...) {
+  NiceMock<MockDomainRegistry> mock_registry;
+  EXPECT_CALL(mock_registry, GetDomainOwner("google.com"))
+          .WillRepeatedly(Return("Larry Page"));
+
+  // Use mock_registry in code under test.
+  ... &mock_registry ...
+}
+```
+
+The sole `EXPECT_CALL` here says that all calls to `GetDomainOwner()` must have
+`"google.com"` as the argument. If `GetDomainOwner("yahoo.com")` is called, it
+will be an unexpected call, and thus an error. *Having a nice mock doesn't
+change the severity of an unexpected call.*
+
+So how do we tell gMock that `GetDomainOwner()` can be called with some other
+arguments as well? The standard technique is to add a "catch all" `EXPECT_CALL`:
+
+```cpp
+  EXPECT_CALL(mock_registry, GetDomainOwner(_))
+        .Times(AnyNumber());  // catches all other calls to this method.
+  EXPECT_CALL(mock_registry, GetDomainOwner("google.com"))
+        .WillRepeatedly(Return("Larry Page"));
+```
+
+Remember that `_` is the wildcard matcher that matches anything. With this, if
+`GetDomainOwner("google.com")` is called, it will do what the second
+`EXPECT_CALL` says; if it is called with a different argument, it will do what
+the first `EXPECT_CALL` says.
+
+Note that the order of the two `EXPECT_CALL`s is important, as a newer
+`EXPECT_CALL` takes precedence over an older one.
+
+For more on uninteresting calls, nice mocks, and strict mocks, read
+["The Nice, the Strict, and the Naggy"](#NiceStrictNaggy).
+
+### Ignoring Uninteresting Arguments {#ParameterlessExpectations}
+
+If your test doesn't care about the parameters (it only cares about the number
+or order of calls), you can often simply omit the parameter list:
+
+```cpp
+  // Expect foo.Bar( ... ) twice with any arguments.
+  EXPECT_CALL(foo, Bar).Times(2);
+
+  // Delegate to the given method whenever the factory is invoked.
+  ON_CALL(foo_factory, MakeFoo)
+      .WillByDefault(&BuildFooForTest);
+```
+
+This functionality is only available when a method is not overloaded; to prevent
+unexpected behavior it is a compilation error to try to set an expectation on a
+method where the specific overload is ambiguous. You can work around this by
+supplying a [simpler mock interface](#SimplerInterfaces) than the mocked class
+provides.
+
+This pattern is also useful when the arguments are interesting, but match logic
+is substantially complex. You can leave the argument list unspecified and use
+SaveArg actions to [save the values for later verification](#SaveArgVerify). If
+you do that, you can easily differentiate calling the method the wrong number of
+times from calling it with the wrong arguments.
+
+### Expecting Ordered Calls {#OrderedCalls}
+
+Although an `EXPECT_CALL()` statement defined later takes precedence when gMock
+tries to match a function call with an expectation, by default calls don't have
+to happen in the order `EXPECT_CALL()` statements are written. For example, if
+the arguments match the matchers in the second `EXPECT_CALL()`, but not those in
+the first and third, then the second expectation will be used.
+
+If you would rather have all calls occur in the order of the expectations, put
+the `EXPECT_CALL()` statements in a block where you define a variable of type
+`InSequence`:
+
+```cpp
+using ::testing::_;
+using ::testing::InSequence;
+
+  {
+    InSequence s;
+
+    EXPECT_CALL(foo, DoThis(5));
+    EXPECT_CALL(bar, DoThat(_))
+        .Times(2);
+    EXPECT_CALL(foo, DoThis(6));
+  }
+```
+
+In this example, we expect a call to `foo.DoThis(5)`, followed by two calls to
+`bar.DoThat()` where the argument can be anything, which are in turn followed by
+a call to `foo.DoThis(6)`. If a call occurred out-of-order, gMock will report an
+error.
+
+### Expecting Partially Ordered Calls {#PartialOrder}
+
+Sometimes requiring everything to occur in a predetermined order can lead to
+brittle tests. For example, we may care about `A` occurring before both `B` and
+`C`, but aren't interested in the relative order of `B` and `C`. In this case,
+the test should reflect our real intent, instead of being overly constraining.
+
+gMock allows you to impose an arbitrary DAG (directed acyclic graph) on the
+calls. One way to express the DAG is to use the
+[After](gmock_cheat_sheet.md#AfterClause) clause of `EXPECT_CALL`.
+
+Another way is via the `InSequence()` clause (not the same as the `InSequence`
+class), which we borrowed from jMock 2. It's less flexible than `After()`, but
+more convenient when you have long chains of sequential calls, as it doesn't
+require you to come up with different names for the expectations in the chains.
+Here's how it works:
+
+If we view `EXPECT_CALL()` statements as nodes in a graph, and add an edge from
+node A to node B wherever A must occur before B, we can get a DAG. We use the
+term "sequence" to mean a directed path in this DAG. Now, if we decompose the
+DAG into sequences, we just need to know which sequences each `EXPECT_CALL()`
+belongs to in order to be able to reconstruct the original DAG.
+
+So, to specify the partial order on the expectations we need to do two things:
+first to define some `Sequence` objects, and then for each `EXPECT_CALL()` say
+which `Sequence` objects it is part of.
+
+Expectations in the same sequence must occur in the order they are written. For
+example,
+
+```cpp
+using ::testing::Sequence;
+...
+  Sequence s1, s2;
+
+  EXPECT_CALL(foo, A())
+      .InSequence(s1, s2);
+  EXPECT_CALL(bar, B())
+      .InSequence(s1);
+  EXPECT_CALL(bar, C())
+      .InSequence(s2);
+  EXPECT_CALL(foo, D())
+      .InSequence(s2);
+```
+
+specifies the following DAG (where `s1` is `A -> B`, and `s2` is `A -> C -> D`):
+
+```text
+       +---> B
+       |
+  A ---|
+       |
+        +---> C ---> D
+```
+
+This means that A must occur before B and C, and C must occur before D. There's
+no restriction about the order other than these.
+
+### Controlling When an Expectation Retires
+
+When a mock method is called, gMock only considers expectations that are still
+active. An expectation is active when created, and becomes inactive (aka
+*retires*) when a call that has to occur later has occurred. For example, in
+
+```cpp
+using ::testing::_;
+using ::testing::Sequence;
+...
+  Sequence s1, s2;
+
+  EXPECT_CALL(log, Log(WARNING, _, "File too large."))      // #1
+      .Times(AnyNumber())
+      .InSequence(s1, s2);
+  EXPECT_CALL(log, Log(WARNING, _, "Data set is empty."))   // #2
+      .InSequence(s1);
+  EXPECT_CALL(log, Log(WARNING, _, "User not found."))      // #3
+      .InSequence(s2);
+```
+
+as soon as either #2 or #3 is matched, #1 will retire. If a warning `"File too
+large."` is logged after this, it will be an error.
+
+Note that an expectation doesn't retire automatically when it's saturated. For
+example,
+
+```cpp
+using ::testing::_;
+...
+  EXPECT_CALL(log, Log(WARNING, _, _));                     // #1
+  EXPECT_CALL(log, Log(WARNING, _, "File too large."));     // #2
+```
+
+says that there will be exactly one warning with the message `"File too
+large."`. If the second warning contains this message too, #2 will match again
+and result in an upper-bound-violated error.
+
+If this is not what you want, you can ask an expectation to retire as soon as it
+becomes saturated:
+
+```cpp
+using ::testing::_;
+...
+  EXPECT_CALL(log, Log(WARNING, _, _));                     // #1
+  EXPECT_CALL(log, Log(WARNING, _, "File too large."))      // #2
+      .RetiresOnSaturation();
+```
+
+Here #2 can be used only once, so if you have two warnings with the message
+`"File too large."`, the first will match #2 and the second will match #1 -
+there will be no error.
+
+## Using Actions
+
+### Returning References from Mock Methods
+
+If a mock function's return type is a reference, you need to use `ReturnRef()`
+instead of `Return()` to return a result:
+
+```cpp
+using ::testing::ReturnRef;
+
+class MockFoo : public Foo {
+ public:
+  MOCK_METHOD(Bar&, GetBar, (), (override));
+};
+...
+  MockFoo foo;
+  Bar bar;
+  EXPECT_CALL(foo, GetBar())
+      .WillOnce(ReturnRef(bar));
+...
+```
+
+### Returning Live Values from Mock Methods
+
+The `Return(x)` action saves a copy of `x` when the action is created, and
+always returns the same value whenever it's executed. Sometimes you may want to
+instead return the *live* value of `x` (i.e. its value at the time when the
+action is *executed*.). Use either `ReturnRef()` or `ReturnPointee()` for this
+purpose.
+
+If the mock function's return type is a reference, you can do it using
+`ReturnRef(x)`, as shown in the previous recipe ("Returning References from Mock
+Methods"). However, gMock doesn't let you use `ReturnRef()` in a mock function
+whose return type is not a reference, as doing that usually indicates a user
+error. So, what shall you do?
+
+Though you may be tempted, DO NOT use `std::ref()`:
+
+```cpp
+using testing::Return;
+
+class MockFoo : public Foo {
+ public:
+  MOCK_METHOD(int, GetValue, (), (override));
+};
+...
+  int x = 0;
+  MockFoo foo;
+  EXPECT_CALL(foo, GetValue())
+      .WillRepeatedly(Return(std::ref(x)));  // Wrong!
+  x = 42;
+  EXPECT_EQ(42, foo.GetValue());
+```
+
+Unfortunately, it doesn't work here. The above code will fail with error:
+
+```text
+Value of: foo.GetValue()
+  Actual: 0
+Expected: 42
+```
+
+The reason is that `Return(*value*)` converts `value` to the actual return type
+of the mock function at the time when the action is *created*, not when it is
+*executed*. (This behavior was chosen for the action to be safe when `value` is
+a proxy object that references some temporary objects.) As a result,
+`std::ref(x)` is converted to an `int` value (instead of a `const int&`) when
+the expectation is set, and `Return(std::ref(x))` will always return 0.
+
+`ReturnPointee(pointer)` was provided to solve this problem specifically. It
+returns the value pointed to by `pointer` at the time the action is *executed*:
+
+```cpp
+using testing::ReturnPointee;
+...
+  int x = 0;
+  MockFoo foo;
+  EXPECT_CALL(foo, GetValue())
+      .WillRepeatedly(ReturnPointee(&x));  // Note the & here.
+  x = 42;
+  EXPECT_EQ(42, foo.GetValue());  // This will succeed now.
+```
+
+### Combining Actions
+
+Want to do more than one thing when a function is called? That's fine. `DoAll()`
+allow you to do sequence of actions every time. Only the return value of the
+last action in the sequence will be used.
+
+```cpp
+using ::testing::_;
+using ::testing::DoAll;
+
+class MockFoo : public Foo {
+ public:
+  MOCK_METHOD(bool, Bar, (int n), (override));
+};
+...
+  EXPECT_CALL(foo, Bar(_))
+      .WillOnce(DoAll(action_1,
+                      action_2,
+                      ...
+                      action_n));
+```
+
+### Verifying Complex Arguments {#SaveArgVerify}
+
+If you want to verify that a method is called with a particular argument but the
+match criteria is complex, it can be difficult to distinguish between
+cardinality failures (calling the method the wrong number of times) and argument
+match failures. Similarly, if you are matching multiple parameters, it may not
+be easy to distinguishing which argument failed to match. For example:
+
+```cpp
+  // Not ideal: this could fail because of a problem with arg1 or arg2, or maybe
+  // just the method wasn't called.
+  EXPECT_CALL(foo, SendValues(_, ElementsAre(1, 4, 4, 7), EqualsProto( ... )));
+```
+
+You can instead save the arguments and test them individually:
+
+```cpp
+  EXPECT_CALL(foo, SendValues)
+      .WillOnce(DoAll(SaveArg<1>(&actual_array), SaveArg<2>(&actual_proto)));
+  ... run the test
+  EXPECT_THAT(actual_array, ElementsAre(1, 4, 4, 7));
+  EXPECT_THAT(actual_proto, EqualsProto( ... ));
+```
+
+### Mocking Side Effects {#MockingSideEffects}
+
+Sometimes a method exhibits its effect not via returning a value but via side
+effects. For example, it may change some global state or modify an output
+argument. To mock side effects, in general you can define your own action by
+implementing `::testing::ActionInterface`.
+
+If all you need to do is to change an output argument, the built-in
+`SetArgPointee()` action is convenient:
+
+```cpp
+using ::testing::_;
+using ::testing::SetArgPointee;
+
+class MockMutator : public Mutator {
+ public:
+  MOCK_METHOD(void, Mutate, (bool mutate, int* value), (override));
+  ...
+}
+...
+  MockMutator mutator;
+  EXPECT_CALL(mutator, Mutate(true, _))
+      .WillOnce(SetArgPointee<1>(5));
+```
+
+In this example, when `mutator.Mutate()` is called, we will assign 5 to the
+`int` variable pointed to by argument #1 (0-based).
+
+`SetArgPointee()` conveniently makes an internal copy of the value you pass to
+it, removing the need to keep the value in scope and alive. The implication
+however is that the value must have a copy constructor and assignment operator.
+
+If the mock method also needs to return a value as well, you can chain
+`SetArgPointee()` with `Return()` using `DoAll()`, remembering to put the
+`Return()` statement last:
+
+```cpp
+using ::testing::_;
+using ::testing::Return;
+using ::testing::SetArgPointee;
+
+class MockMutator : public Mutator {
+ public:
+  ...
+  MOCK_METHOD(bool, MutateInt, (int* value), (override));
+}
+...
+  MockMutator mutator;
+  EXPECT_CALL(mutator, MutateInt(_))
+      .WillOnce(DoAll(SetArgPointee<0>(5),
+                      Return(true)));
+```
+
+Note, however, that if you use the `ReturnOKWith()` method, it will override the
+values provided by `SetArgPointee()` in the response parameters of your function
+call.
+
+If the output argument is an array, use the `SetArrayArgument<N>(first, last)`
+action instead. It copies the elements in source range `[first, last)` to the
+array pointed to by the `N`-th (0-based) argument:
+
+```cpp
+using ::testing::NotNull;
+using ::testing::SetArrayArgument;
+
+class MockArrayMutator : public ArrayMutator {
+ public:
+  MOCK_METHOD(void, Mutate, (int* values, int num_values), (override));
+  ...
+}
+...
+  MockArrayMutator mutator;
+  int values[5] = {1, 2, 3, 4, 5};
+  EXPECT_CALL(mutator, Mutate(NotNull(), 5))
+      .WillOnce(SetArrayArgument<0>(values, values + 5));
+```
+
+This also works when the argument is an output iterator:
+
+```cpp
+using ::testing::_;
+using ::testing::SetArrayArgument;
+
+class MockRolodex : public Rolodex {
+ public:
+  MOCK_METHOD(void, GetNames, (std::back_insert_iterator<vector<string>>),
+              (override));
+  ...
+}
+...
+  MockRolodex rolodex;
+  vector<string> names;
+  names.push_back("George");
+  names.push_back("John");
+  names.push_back("Thomas");
+  EXPECT_CALL(rolodex, GetNames(_))
+      .WillOnce(SetArrayArgument<0>(names.begin(), names.end()));
+```
+
+### Changing a Mock Object's Behavior Based on the State
+
+If you expect a call to change the behavior of a mock object, you can use
+`::testing::InSequence` to specify different behaviors before and after the
+call:
+
+```cpp
+using ::testing::InSequence;
+using ::testing::Return;
+
+...
+  {
+     InSequence seq;
+     EXPECT_CALL(my_mock, IsDirty())
+         .WillRepeatedly(Return(true));
+     EXPECT_CALL(my_mock, Flush());
+     EXPECT_CALL(my_mock, IsDirty())
+         .WillRepeatedly(Return(false));
+  }
+  my_mock.FlushIfDirty();
+```
+
+This makes `my_mock.IsDirty()` return `true` before `my_mock.Flush()` is called
+and return `false` afterwards.
+
+If the behavior change is more complex, you can store the effects in a variable
+and make a mock method get its return value from that variable:
+
+```cpp
+using ::testing::_;
+using ::testing::SaveArg;
+using ::testing::Return;
+
+ACTION_P(ReturnPointee, p) { return *p; }
+...
+  int previous_value = 0;
+  EXPECT_CALL(my_mock, GetPrevValue)
+      .WillRepeatedly(ReturnPointee(&previous_value));
+  EXPECT_CALL(my_mock, UpdateValue)
+      .WillRepeatedly(SaveArg<0>(&previous_value));
+  my_mock.DoSomethingToUpdateValue();
+```
+
+Here `my_mock.GetPrevValue()` will always return the argument of the last
+`UpdateValue()` call.
+
+### Setting the Default Value for a Return Type {#DefaultValue}
+
+If a mock method's return type is a built-in C++ type or pointer, by default it
+will return 0 when invoked. Also, in C++ 11 and above, a mock method whose
+return type has a default constructor will return a default-constructed value by
+default. You only need to specify an action if this default value doesn't work
+for you.
+
+Sometimes, you may want to change this default value, or you may want to specify
+a default value for types gMock doesn't know about. You can do this using the
+`::testing::DefaultValue` class template:
+
+```cpp
+using ::testing::DefaultValue;
+
+class MockFoo : public Foo {
+ public:
+  MOCK_METHOD(Bar, CalculateBar, (), (override));
+};
+
+
+...
+  Bar default_bar;
+  // Sets the default return value for type Bar.
+  DefaultValue<Bar>::Set(default_bar);
+
+  MockFoo foo;
+
+  // We don't need to specify an action here, as the default
+  // return value works for us.
+  EXPECT_CALL(foo, CalculateBar());
+
+  foo.CalculateBar();  // This should return default_bar.
+
+  // Unsets the default return value.
+  DefaultValue<Bar>::Clear();
+```
+
+Please note that changing the default value for a type can make your tests hard
+to understand. We recommend you to use this feature judiciously. For example,
+you may want to make sure the `Set()` and `Clear()` calls are right next to the
+code that uses your mock.
+
+### Setting the Default Actions for a Mock Method
+
+You've learned how to change the default value of a given type. However, this
+may be too coarse for your purpose: perhaps you have two mock methods with the
+same return type and you want them to have different behaviors. The `ON_CALL()`
+macro allows you to customize your mock's behavior at the method level:
+
+```cpp
+using ::testing::_;
+using ::testing::AnyNumber;
+using ::testing::Gt;
+using ::testing::Return;
+...
+  ON_CALL(foo, Sign(_))
+      .WillByDefault(Return(-1));
+  ON_CALL(foo, Sign(0))
+      .WillByDefault(Return(0));
+  ON_CALL(foo, Sign(Gt(0)))
+      .WillByDefault(Return(1));
+
+  EXPECT_CALL(foo, Sign(_))
+      .Times(AnyNumber());
+
+  foo.Sign(5);   // This should return 1.
+  foo.Sign(-9);  // This should return -1.
+  foo.Sign(0);   // This should return 0.
+```
+
+As you may have guessed, when there are more than one `ON_CALL()` statements,
+the newer ones in the order take precedence over the older ones. In other words,
+the **last** one that matches the function arguments will be used. This matching
+order allows you to set up the common behavior in a mock object's constructor or
+the test fixture's set-up phase and specialize the mock's behavior later.
+
+Note that both `ON_CALL` and `EXPECT_CALL` have the same "later statements take
+precedence" rule, but they don't interact. That is, `EXPECT_CALL`s have their
+own precedence order distinct from the `ON_CALL` precedence order.
+
+### Using Functions/Methods/Functors/Lambdas as Actions {#FunctionsAsActions}
+
+If the built-in actions don't suit you, you can use an existing callable
+(function, `std::function`, method, functor, lambda) as an action.
+
+```cpp
+using ::testing::_; using ::testing::Invoke;
+
+class MockFoo : public Foo {
+ public:
+  MOCK_METHOD(int, Sum, (int x, int y), (override));
+  MOCK_METHOD(bool, ComplexJob, (int x), (override));
+};
+
+int CalculateSum(int x, int y) { return x + y; }
+int Sum3(int x, int y, int z) { return x + y + z; }
+
+class Helper {
+ public:
+  bool ComplexJob(int x);
+};
+
+...
+  MockFoo foo;
+  Helper helper;
+  EXPECT_CALL(foo, Sum(_, _))
+      .WillOnce(&CalculateSum)
+      .WillRepeatedly(Invoke(NewPermanentCallback(Sum3, 1)));
+  EXPECT_CALL(foo, ComplexJob(_))
+      .WillOnce(Invoke(&helper, &Helper::ComplexJob))
+      .WillOnce([] { return true; })
+      .WillRepeatedly([](int x) { return x > 0; });
+
+  foo.Sum(5, 6);         // Invokes CalculateSum(5, 6).
+  foo.Sum(2, 3);         // Invokes Sum3(1, 2, 3).
+  foo.ComplexJob(10);    // Invokes helper.ComplexJob(10).
+  foo.ComplexJob(-1);    // Invokes the inline lambda.
+```
+
+The only requirement is that the type of the function, etc must be *compatible*
+with the signature of the mock function, meaning that the latter's arguments (if
+it takes any) can be implicitly converted to the corresponding arguments of the
+former, and the former's return type can be implicitly converted to that of the
+latter. So, you can invoke something whose type is *not* exactly the same as the
+mock function, as long as it's safe to do so - nice, huh?
+
+Note that:
+
+*   The action takes ownership of the callback and will delete it when the
+    action itself is destructed.
+*   If the type of a callback is derived from a base callback type `C`, you need
+    to implicitly cast it to `C` to resolve the overloading, e.g.
+
+    ```cpp
+    using ::testing::Invoke;
+    ...
+      ResultCallback<bool>* is_ok = ...;
+      ... Invoke(is_ok) ...;  // This works.
+
+      BlockingClosure* done = new BlockingClosure;
+      ... Invoke(implicit_cast<Closure*>(done)) ...;  // The cast is necessary.
+    ```
+
+### Using Functions with Extra Info as Actions
+
+The function or functor you call using `Invoke()` must have the same number of
+arguments as the mock function you use it for. Sometimes you may have a function
+that takes more arguments, and you are willing to pass in the extra arguments
+yourself to fill the gap. You can do this in gMock using callbacks with
+pre-bound arguments. Here's an example:
+
+```cpp
+using ::testing::Invoke;
+
+class MockFoo : public Foo {
+ public:
+  MOCK_METHOD(char, DoThis, (int n), (override));
+};
+
+char SignOfSum(int x, int y) {
+  const int sum = x + y;
+  return (sum > 0) ? '+' : (sum < 0) ? '-' : '0';
+}
+
+TEST_F(FooTest, Test) {
+  MockFoo foo;
+
+  EXPECT_CALL(foo, DoThis(2))
+      .WillOnce(Invoke(NewPermanentCallback(SignOfSum, 5)));
+  EXPECT_EQ('+', foo.DoThis(2));  // Invokes SignOfSum(5, 2).
+}
+```
+
+### Invoking a Function/Method/Functor/Lambda/Callback Without Arguments
+
+`Invoke()` passes the mock function's arguments to the function, etc being
+invoked such that the callee has the full context of the call to work with. If
+the invoked function is not interested in some or all of the arguments, it can
+simply ignore them.
+
+Yet, a common pattern is that a test author wants to invoke a function without
+the arguments of the mock function. She could do that using a wrapper function
+that throws away the arguments before invoking an underlining nullary function.
+Needless to say, this can be tedious and obscures the intent of the test.
+
+There are two solutions to this problem. First, you can pass any callable of
+zero args as an action. Alternatively, use `InvokeWithoutArgs()`, which is like
+`Invoke()` except that it doesn't pass the mock function's arguments to the
+callee. Here's an example of each:
+
+```cpp
+using ::testing::_;
+using ::testing::InvokeWithoutArgs;
+
+class MockFoo : public Foo {
+ public:
+  MOCK_METHOD(bool, ComplexJob, (int n), (override));
+};
+
+bool Job1() { ... }
+bool Job2(int n, char c) { ... }
+
+...
+  MockFoo foo;
+  EXPECT_CALL(foo, ComplexJob(_))
+      .WillOnce([] { Job1(); });
+      .WillOnce(InvokeWithoutArgs(NewPermanentCallback(Job2, 5, 'a')));
+
+  foo.ComplexJob(10);  // Invokes Job1().
+  foo.ComplexJob(20);  // Invokes Job2(5, 'a').
+```
+
+Note that:
+
+*   The action takes ownership of the callback and will delete it when the
+    action itself is destructed.
+*   If the type of a callback is derived from a base callback type `C`, you need
+    to implicitly cast it to `C` to resolve the overloading, e.g.
+
+    ```cpp
+    using ::testing::InvokeWithoutArgs;
+    ...
+      ResultCallback<bool>* is_ok = ...;
+      ... InvokeWithoutArgs(is_ok) ...;  // This works.
+
+      BlockingClosure* done = ...;
+      ... InvokeWithoutArgs(implicit_cast<Closure*>(done)) ...;
+      // The cast is necessary.
+    ```
+
+### Invoking an Argument of the Mock Function
+
+Sometimes a mock function will receive a function pointer, a functor (in other
+words, a "callable") as an argument, e.g.
+
+```cpp
+class MockFoo : public Foo {
+ public:
+  MOCK_METHOD(bool, DoThis, (int n, (ResultCallback1<bool, int>* callback)),
+              (override));
+};
+```
+
+and you may want to invoke this callable argument:
+
+```cpp
+using ::testing::_;
+...
+  MockFoo foo;
+  EXPECT_CALL(foo, DoThis(_, _))
+      .WillOnce(...);
+      // Will execute callback->Run(5), where callback is the
+      // second argument DoThis() receives.
+```
+
+{: .callout .note}
+NOTE: The section below is legacy documentation from before C++ had lambdas:
+
+Arghh, you need to refer to a mock function argument but C++ has no lambda
+(yet), so you have to define your own action. :-( Or do you really?
+
+Well, gMock has an action to solve *exactly* this problem:
+
+```cpp
+InvokeArgument<N>(arg_1, arg_2, ..., arg_m)
+```
+
+will invoke the `N`-th (0-based) argument the mock function receives, with
+`arg_1`, `arg_2`, ..., and `arg_m`. No matter if the argument is a function
+pointer, a functor, or a callback. gMock handles them all.
+
+With that, you could write:
+
+```cpp
+using ::testing::_;
+using ::testing::InvokeArgument;
+...
+  EXPECT_CALL(foo, DoThis(_, _))
+      .WillOnce(InvokeArgument<1>(5));
+      // Will execute callback->Run(5), where callback is the
+      // second argument DoThis() receives.
+```
+
+What if the callable takes an argument by reference? No problem - just wrap it
+inside `std::ref()`:
+
+```cpp
+  ...
+  MOCK_METHOD(bool, Bar,
+              ((ResultCallback2<bool, int, const Helper&>* callback)),
+              (override));
+  ...
+  using ::testing::_;
+  using ::testing::InvokeArgument;
+  ...
+  MockFoo foo;
+  Helper helper;
+  ...
+  EXPECT_CALL(foo, Bar(_))
+      .WillOnce(InvokeArgument<0>(5, std::ref(helper)));
+      // std::ref(helper) guarantees that a reference to helper, not a copy of
+      // it, will be passed to the callback.
+```
+
+What if the callable takes an argument by reference and we do **not** wrap the
+argument in `std::ref()`? Then `InvokeArgument()` will *make a copy* of the
+argument, and pass a *reference to the copy*, instead of a reference to the
+original value, to the callable. This is especially handy when the argument is a
+temporary value:
+
+```cpp
+  ...
+  MOCK_METHOD(bool, DoThat, (bool (*f)(const double& x, const string& s)),
+              (override));
+  ...
+  using ::testing::_;
+  using ::testing::InvokeArgument;
+  ...
+  MockFoo foo;
+  ...
+  EXPECT_CALL(foo, DoThat(_))
+      .WillOnce(InvokeArgument<0>(5.0, string("Hi")));
+      // Will execute (*f)(5.0, string("Hi")), where f is the function pointer
+      // DoThat() receives.  Note that the values 5.0 and string("Hi") are
+      // temporary and dead once the EXPECT_CALL() statement finishes.  Yet
+      // it's fine to perform this action later, since a copy of the values
+      // are kept inside the InvokeArgument action.
+```
+
+### Ignoring an Action's Result
+
+Sometimes you have an action that returns *something*, but you need an action
+that returns `void` (perhaps you want to use it in a mock function that returns
+`void`, or perhaps it needs to be used in `DoAll()` and it's not the last in the
+list). `IgnoreResult()` lets you do that. For example:
+
+```cpp
+using ::testing::_;
+using ::testing::DoAll;
+using ::testing::IgnoreResult;
+using ::testing::Return;
+
+int Process(const MyData& data);
+string DoSomething();
+
+class MockFoo : public Foo {
+ public:
+  MOCK_METHOD(void, Abc, (const MyData& data), (override));
+  MOCK_METHOD(bool, Xyz, (), (override));
+};
+
+  ...
+  MockFoo foo;
+  EXPECT_CALL(foo, Abc(_))
+      // .WillOnce(Invoke(Process));
+      // The above line won't compile as Process() returns int but Abc() needs
+      // to return void.
+      .WillOnce(IgnoreResult(Process));
+  EXPECT_CALL(foo, Xyz())
+      .WillOnce(DoAll(IgnoreResult(DoSomething),
+                      // Ignores the string DoSomething() returns.
+                      Return(true)));
+```
+
+Note that you **cannot** use `IgnoreResult()` on an action that already returns
+`void`. Doing so will lead to ugly compiler errors.
+
+### Selecting an Action's Arguments {#SelectingArgs}
+
+Say you have a mock function `Foo()` that takes seven arguments, and you have a
+custom action that you want to invoke when `Foo()` is called. Trouble is, the
+custom action only wants three arguments:
+
+```cpp
+using ::testing::_;
+using ::testing::Invoke;
+...
+  MOCK_METHOD(bool, Foo,
+              (bool visible, const string& name, int x, int y,
+               (const map<pair<int, int>>), double& weight, double min_weight,
+               double max_wight));
+...
+bool IsVisibleInQuadrant1(bool visible, int x, int y) {
+  return visible && x >= 0 && y >= 0;
+}
+...
+  EXPECT_CALL(mock, Foo)
+      .WillOnce(Invoke(IsVisibleInQuadrant1));  // Uh, won't compile. :-(
+```
+
+To please the compiler God, you need to define an "adaptor" that has the same
+signature as `Foo()` and calls the custom action with the right arguments:
+
+```cpp
+using ::testing::_;
+using ::testing::Invoke;
+...
+bool MyIsVisibleInQuadrant1(bool visible, const string& name, int x, int y,
+                            const map<pair<int, int>, double>& weight,
+                            double min_weight, double max_wight) {
+  return IsVisibleInQuadrant1(visible, x, y);
+}
+...
+  EXPECT_CALL(mock, Foo)
+      .WillOnce(Invoke(MyIsVisibleInQuadrant1));  // Now it works.
+```
+
+But isn't this awkward?
+
+gMock provides a generic *action adaptor*, so you can spend your time minding
+more important business than writing your own adaptors. Here's the syntax:
+
+```cpp
+WithArgs<N1, N2, ..., Nk>(action)
+```
+
+creates an action that passes the arguments of the mock function at the given
+indices (0-based) to the inner `action` and performs it. Using `WithArgs`, our
+original example can be written as:
+
+```cpp
+using ::testing::_;
+using ::testing::Invoke;
+using ::testing::WithArgs;
+...
+  EXPECT_CALL(mock, Foo)
+      .WillOnce(WithArgs<0, 2, 3>(Invoke(IsVisibleInQuadrant1)));  // No need to define your own adaptor.
+```
+
+For better readability, gMock also gives you:
+
+*   `WithoutArgs(action)` when the inner `action` takes *no* argument, and
+*   `WithArg<N>(action)` (no `s` after `Arg`) when the inner `action` takes
+    *one* argument.
+
+As you may have realized, `InvokeWithoutArgs(...)` is just syntactic sugar for
+`WithoutArgs(Invoke(...))`.
+
+Here are more tips:
+
+*   The inner action used in `WithArgs` and friends does not have to be
+    `Invoke()` -- it can be anything.
+*   You can repeat an argument in the argument list if necessary, e.g.
+    `WithArgs<2, 3, 3, 5>(...)`.
+*   You can change the order of the arguments, e.g. `WithArgs<3, 2, 1>(...)`.
+*   The types of the selected arguments do *not* have to match the signature of
+    the inner action exactly. It works as long as they can be implicitly
+    converted to the corresponding arguments of the inner action. For example,
+    if the 4-th argument of the mock function is an `int` and `my_action` takes
+    a `double`, `WithArg<4>(my_action)` will work.
+
+### Ignoring Arguments in Action Functions
+
+The [selecting-an-action's-arguments](#SelectingArgs) recipe showed us one way
+to make a mock function and an action with incompatible argument lists fit
+together. The downside is that wrapping the action in `WithArgs<...>()` can get
+tedious for people writing the tests.
+
+If you are defining a function (or method, functor, lambda, callback) to be used
+with `Invoke*()`, and you are not interested in some of its arguments, an
+alternative to `WithArgs` is to declare the uninteresting arguments as `Unused`.
+This makes the definition less cluttered and less fragile in case the types of
+the uninteresting arguments change. It could also increase the chance the action
+function can be reused. For example, given
+
+```cpp
+ public:
+  MOCK_METHOD(double, Foo, double(const string& label, double x, double y),
+              (override));
+  MOCK_METHOD(double, Bar, (int index, double x, double y), (override));
+```
+
+instead of
+
+```cpp
+using ::testing::_;
+using ::testing::Invoke;
+
+double DistanceToOriginWithLabel(const string& label, double x, double y) {
+  return sqrt(x*x + y*y);
+}
+double DistanceToOriginWithIndex(int index, double x, double y) {
+  return sqrt(x*x + y*y);
+}
+...
+  EXPECT_CALL(mock, Foo("abc", _, _))
+      .WillOnce(Invoke(DistanceToOriginWithLabel));
+  EXPECT_CALL(mock, Bar(5, _, _))
+      .WillOnce(Invoke(DistanceToOriginWithIndex));
+```
+
+you could write
+
+```cpp
+using ::testing::_;
+using ::testing::Invoke;
+using ::testing::Unused;
+
+double DistanceToOrigin(Unused, double x, double y) {
+  return sqrt(x*x + y*y);
+}
+...
+  EXPECT_CALL(mock, Foo("abc", _, _))
+      .WillOnce(Invoke(DistanceToOrigin));
+  EXPECT_CALL(mock, Bar(5, _, _))
+      .WillOnce(Invoke(DistanceToOrigin));
+```
+
+### Sharing Actions
+
+Just like matchers, a gMock action object consists of a pointer to a ref-counted
+implementation object. Therefore copying actions is also allowed and very
+efficient. When the last action that references the implementation object dies,
+the implementation object will be deleted.
+
+If you have some complex action that you want to use again and again, you may
+not have to build it from scratch everytime. If the action doesn't have an
+internal state (i.e. if it always does the same thing no matter how many times
+it has been called), you can assign it to an action variable and use that
+variable repeatedly. For example:
+
+```cpp
+using ::testing::Action;
+using ::testing::DoAll;
+using ::testing::Return;
+using ::testing::SetArgPointee;
+...
+  Action<bool(int*)> set_flag = DoAll(SetArgPointee<0>(5),
+                                      Return(true));
+  ... use set_flag in .WillOnce() and .WillRepeatedly() ...
+```
+
+However, if the action has its own state, you may be surprised if you share the
+action object. Suppose you have an action factory `IncrementCounter(init)` which
+creates an action that increments and returns a counter whose initial value is
+`init`, using two actions created from the same expression and using a shared
+action will exhibit different behaviors. Example:
+
+```cpp
+  EXPECT_CALL(foo, DoThis())
+      .WillRepeatedly(IncrementCounter(0));
+  EXPECT_CALL(foo, DoThat())
+      .WillRepeatedly(IncrementCounter(0));
+  foo.DoThis();  // Returns 1.
+  foo.DoThis();  // Returns 2.
+  foo.DoThat();  // Returns 1 - Blah() uses a different
+                 // counter than Bar()'s.
+```
+
+versus
+
+```cpp
+using ::testing::Action;
+...
+  Action<int()> increment = IncrementCounter(0);
+  EXPECT_CALL(foo, DoThis())
+      .WillRepeatedly(increment);
+  EXPECT_CALL(foo, DoThat())
+      .WillRepeatedly(increment);
+  foo.DoThis();  // Returns 1.
+  foo.DoThis();  // Returns 2.
+  foo.DoThat();  // Returns 3 - the counter is shared.
+```
+
+### Testing Asynchronous Behavior
+
+One oft-encountered problem with gMock is that it can be hard to test
+asynchronous behavior. Suppose you had a `EventQueue` class that you wanted to
+test, and you created a separate `EventDispatcher` interface so that you could
+easily mock it out. However, the implementation of the class fired all the
+events on a background thread, which made test timings difficult. You could just
+insert `sleep()` statements and hope for the best, but that makes your test
+behavior nondeterministic. A better way is to use gMock actions and
+`Notification` objects to force your asynchronous test to behave synchronously.
+
+```cpp
+class MockEventDispatcher : public EventDispatcher {
+  MOCK_METHOD(bool, DispatchEvent, (int32), (override));
+};
+
+TEST(EventQueueTest, EnqueueEventTest) {
+  MockEventDispatcher mock_event_dispatcher;
+  EventQueue event_queue(&mock_event_dispatcher);
+
+  const int32 kEventId = 321;
+  absl::Notification done;
+  EXPECT_CALL(mock_event_dispatcher, DispatchEvent(kEventId))
+      .WillOnce([&done] { done.Notify(); });
+
+  event_queue.EnqueueEvent(kEventId);
+  done.WaitForNotification();
+}
+```
+
+In the example above, we set our normal gMock expectations, but then add an
+additional action to notify the `Notification` object. Now we can just call
+`Notification::WaitForNotification()` in the main thread to wait for the
+asynchronous call to finish. After that, our test suite is complete and we can
+safely exit.
+
+{: .callout .note}
+Note: this example has a downside: namely, if the expectation is not satisfied,
+our test will run forever. It will eventually time-out and fail, but it will
+take longer and be slightly harder to debug. To alleviate this problem, you can
+use `WaitForNotificationWithTimeout(ms)` instead of `WaitForNotification()`.
+
+## Misc Recipes on Using gMock
+
+### Mocking Methods That Use Move-Only Types
+
+C++11 introduced *move-only types*. A move-only-typed value can be moved from
+one object to another, but cannot be copied. `std::unique_ptr<T>` is probably
+the most commonly used move-only type.
+
+Mocking a method that takes and/or returns move-only types presents some
+challenges, but nothing insurmountable. This recipe shows you how you can do it.
+Note that the support for move-only method arguments was only introduced to
+gMock in April 2017; in older code, you may find more complex
+[workarounds](#LegacyMoveOnly) for lack of this feature.
+
+Let’s say we are working on a fictional project that lets one post and share
+snippets called “buzzes”. Your code uses these types:
+
+```cpp
+enum class AccessLevel { kInternal, kPublic };
+
+class Buzz {
+ public:
+  explicit Buzz(AccessLevel access) { ... }
+  ...
+};
+
+class Buzzer {
+ public:
+  virtual ~Buzzer() {}
+  virtual std::unique_ptr<Buzz> MakeBuzz(StringPiece text) = 0;
+  virtual bool ShareBuzz(std::unique_ptr<Buzz> buzz, int64_t timestamp) = 0;
+  ...
+};
+```
+
+A `Buzz` object represents a snippet being posted. A class that implements the
+`Buzzer` interface is capable of creating and sharing `Buzz`es. Methods in
+`Buzzer` may return a `unique_ptr<Buzz>` or take a `unique_ptr<Buzz>`. Now we
+need to mock `Buzzer` in our tests.
+
+To mock a method that accepts or returns move-only types, you just use the
+familiar `MOCK_METHOD` syntax as usual:
+
+```cpp
+class MockBuzzer : public Buzzer {
+ public:
+  MOCK_METHOD(std::unique_ptr<Buzz>, MakeBuzz, (StringPiece text), (override));
+  MOCK_METHOD(bool, ShareBuzz, (std::unique_ptr<Buzz> buzz, int64_t timestamp),
+              (override));
+};
+```
+
+Now that we have the mock class defined, we can use it in tests. In the
+following code examples, we assume that we have defined a `MockBuzzer` object
+named `mock_buzzer_`:
+
+```cpp
+  MockBuzzer mock_buzzer_;
+```
+
+First let’s see how we can set expectations on the `MakeBuzz()` method, which
+returns a `unique_ptr<Buzz>`.
+
+As usual, if you set an expectation without an action (i.e. the `.WillOnce()` or
+`.WillRepeatedly()` clause), when that expectation fires, the default action for
+that method will be taken. Since `unique_ptr<>` has a default constructor that
+returns a null `unique_ptr`, that’s what you’ll get if you don’t specify an
+action:
+
+```cpp
+  // Use the default action.
+  EXPECT_CALL(mock_buzzer_, MakeBuzz("hello"));
+
+  // Triggers the previous EXPECT_CALL.
+  EXPECT_EQ(nullptr, mock_buzzer_.MakeBuzz("hello"));
+```
+
+If you are not happy with the default action, you can tweak it as usual; see
+[Setting Default Actions](#OnCall).
+
+If you just need to return a pre-defined move-only value, you can use the
+`Return(ByMove(...))` action:
+
+```cpp
+  // When this fires, the unique_ptr<> specified by ByMove(...) will
+  // be returned.
+  EXPECT_CALL(mock_buzzer_, MakeBuzz("world"))
+      .WillOnce(Return(ByMove(MakeUnique<Buzz>(AccessLevel::kInternal))));
+
+  EXPECT_NE(nullptr, mock_buzzer_.MakeBuzz("world"));
+```
+
+Note that `ByMove()` is essential here - if you drop it, the code won’t compile.
+
+Quiz time! What do you think will happen if a `Return(ByMove(...))` action is
+performed more than once (e.g. you write `...
+.WillRepeatedly(Return(ByMove(...)));`)? Come think of it, after the first time
+the action runs, the source value will be consumed (since it’s a move-only
+value), so the next time around, there’s no value to move from -- you’ll get a
+run-time error that `Return(ByMove(...))` can only be run once.
+
+If you need your mock method to do more than just moving a pre-defined value,
+remember that you can always use a lambda or a callable object, which can do
+pretty much anything you want:
+
+```cpp
+  EXPECT_CALL(mock_buzzer_, MakeBuzz("x"))
+      .WillRepeatedly([](StringPiece text) {
+        return MakeUnique<Buzz>(AccessLevel::kInternal);
+      });
+
+  EXPECT_NE(nullptr, mock_buzzer_.MakeBuzz("x"));
+  EXPECT_NE(nullptr, mock_buzzer_.MakeBuzz("x"));
+```
+
+Every time this `EXPECT_CALL` fires, a new `unique_ptr<Buzz>` will be created
+and returned. You cannot do this with `Return(ByMove(...))`.
+
+That covers returning move-only values; but how do we work with methods
+accepting move-only arguments? The answer is that they work normally, although
+some actions will not compile when any of method's arguments are move-only. You
+can always use `Return`, or a [lambda or functor](#FunctionsAsActions):
+
+```cpp
+  using ::testing::Unused;
+
+  EXPECT_CALL(mock_buzzer_, ShareBuzz(NotNull(), _)).WillOnce(Return(true));
+  EXPECT_TRUE(mock_buzzer_.ShareBuzz(MakeUnique<Buzz>(AccessLevel::kInternal)),
+              0);
+
+  EXPECT_CALL(mock_buzzer_, ShareBuzz(_, _)).WillOnce(
+      [](std::unique_ptr<Buzz> buzz, Unused) { return buzz != nullptr; });
+  EXPECT_FALSE(mock_buzzer_.ShareBuzz(nullptr, 0));
+```
+
+Many built-in actions (`WithArgs`, `WithoutArgs`,`DeleteArg`, `SaveArg`, ...)
+could in principle support move-only arguments, but the support for this is not
+implemented yet. If this is blocking you, please file a bug.
+
+A few actions (e.g. `DoAll`) copy their arguments internally, so they can never
+work with non-copyable objects; you'll have to use functors instead.
+
+#### Legacy workarounds for move-only types {#LegacyMoveOnly}
+
+Support for move-only function arguments was only introduced to gMock in April
+of 2017. In older code, you may encounter the following workaround for the lack
+of this feature (it is no longer necessary - we're including it just for
+reference):
+
+```cpp
+class MockBuzzer : public Buzzer {
+ public:
+  MOCK_METHOD(bool, DoShareBuzz, (Buzz* buzz, Time timestamp));
+  bool ShareBuzz(std::unique_ptr<Buzz> buzz, Time timestamp) override {
+    return DoShareBuzz(buzz.get(), timestamp);
+  }
+};
+```
+
+The trick is to delegate the `ShareBuzz()` method to a mock method (let’s call
+it `DoShareBuzz()`) that does not take move-only parameters. Then, instead of
+setting expectations on `ShareBuzz()`, you set them on the `DoShareBuzz()` mock
+method:
+
+```cpp
+  MockBuzzer mock_buzzer_;
+  EXPECT_CALL(mock_buzzer_, DoShareBuzz(NotNull(), _));
+
+  // When one calls ShareBuzz() on the MockBuzzer like this, the call is
+  // forwarded to DoShareBuzz(), which is mocked.  Therefore this statement
+  // will trigger the above EXPECT_CALL.
+  mock_buzzer_.ShareBuzz(MakeUnique<Buzz>(AccessLevel::kInternal), 0);
+```
+
+### Making the Compilation Faster
+
+Believe it or not, the *vast majority* of the time spent on compiling a mock
+class is in generating its constructor and destructor, as they perform
+non-trivial tasks (e.g. verification of the expectations). What's more, mock
+methods with different signatures have different types and thus their
+constructors/destructors need to be generated by the compiler separately. As a
+result, if you mock many different types of methods, compiling your mock class
+can get really slow.
+
+If you are experiencing slow compilation, you can move the definition of your
+mock class' constructor and destructor out of the class body and into a `.cc`
+file. This way, even if you `#include` your mock class in N files, the compiler
+only needs to generate its constructor and destructor once, resulting in a much
+faster compilation.
+
+Let's illustrate the idea using an example. Here's the definition of a mock
+class before applying this recipe:
+
+```cpp
+// File mock_foo.h.
+...
+class MockFoo : public Foo {
+ public:
+  // Since we don't declare the constructor or the destructor,
+  // the compiler will generate them in every translation unit
+  // where this mock class is used.
+
+  MOCK_METHOD(int, DoThis, (), (override));
+  MOCK_METHOD(bool, DoThat, (const char* str), (override));
+  ... more mock methods ...
+};
+```
+
+After the change, it would look like:
+
+```cpp
+// File mock_foo.h.
+...
+class MockFoo : public Foo {
+ public:
+  // The constructor and destructor are declared, but not defined, here.
+  MockFoo();
+  virtual ~MockFoo();
+
+  MOCK_METHOD(int, DoThis, (), (override));
+  MOCK_METHOD(bool, DoThat, (const char* str), (override));
+  ... more mock methods ...
+};
+```
+
+and
+
+```cpp
+// File mock_foo.cc.
+#include "path/to/mock_foo.h"
+
+// The definitions may appear trivial, but the functions actually do a
+// lot of things through the constructors/destructors of the member
+// variables used to implement the mock methods.
+MockFoo::MockFoo() {}
+MockFoo::~MockFoo() {}
+```
+
+### Forcing a Verification
+
+When it's being destroyed, your friendly mock object will automatically verify
+that all expectations on it have been satisfied, and will generate googletest
+failures if not. This is convenient as it leaves you with one less thing to
+worry about. That is, unless you are not sure if your mock object will be
+destroyed.
+
+How could it be that your mock object won't eventually be destroyed? Well, it
+might be created on the heap and owned by the code you are testing. Suppose
+there's a bug in that code and it doesn't delete the mock object properly - you
+could end up with a passing test when there's actually a bug.
+
+Using a heap checker is a good idea and can alleviate the concern, but its
+implementation is not 100% reliable. So, sometimes you do want to *force* gMock
+to verify a mock object before it is (hopefully) destructed. You can do this
+with `Mock::VerifyAndClearExpectations(&mock_object)`:
+
+```cpp
+TEST(MyServerTest, ProcessesRequest) {
+  using ::testing::Mock;
+
+  MockFoo* const foo = new MockFoo;
+  EXPECT_CALL(*foo, ...)...;
+  // ... other expectations ...
+
+  // server now owns foo.
+  MyServer server(foo);
+  server.ProcessRequest(...);
+
+  // In case that server's destructor will forget to delete foo,
+  // this will verify the expectations anyway.
+  Mock::VerifyAndClearExpectations(foo);
+}  // server is destroyed when it goes out of scope here.
+```
+
+{: .callout .tip}
+**Tip:** The `Mock::VerifyAndClearExpectations()` function returns a `bool` to
+indicate whether the verification was successful (`true` for yes), so you can
+wrap that function call inside a `ASSERT_TRUE()` if there is no point going
+further when the verification has failed.
+
+### Using Check Points {#UsingCheckPoints}
+
+Sometimes you may want to "reset" a mock object at various check points in your
+test: at each check point, you verify that all existing expectations on the mock
+object have been satisfied, and then you set some new expectations on it as if
+it's newly created. This allows you to work with a mock object in "phases" whose
+sizes are each manageable.
+
+One such scenario is that in your test's `SetUp()` function, you may want to put
+the object you are testing into a certain state, with the help from a mock
+object. Once in the desired state, you want to clear all expectations on the
+mock, such that in the `TEST_F` body you can set fresh expectations on it.
+
+As you may have figured out, the `Mock::VerifyAndClearExpectations()` function
+we saw in the previous recipe can help you here. Or, if you are using
+`ON_CALL()` to set default actions on the mock object and want to clear the
+default actions as well, use `Mock::VerifyAndClear(&mock_object)` instead. This
+function does what `Mock::VerifyAndClearExpectations(&mock_object)` does and
+returns the same `bool`, **plus** it clears the `ON_CALL()` statements on
+`mock_object` too.
+
+Another trick you can use to achieve the same effect is to put the expectations
+in sequences and insert calls to a dummy "check-point" function at specific
+places. Then you can verify that the mock function calls do happen at the right
+time. For example, if you are exercising code:
+
+```cpp
+  Foo(1);
+  Foo(2);
+  Foo(3);
+```
+
+and want to verify that `Foo(1)` and `Foo(3)` both invoke `mock.Bar("a")`, but
+`Foo(2)` doesn't invoke anything. You can write:
+
+```cpp
+using ::testing::MockFunction;
+
+TEST(FooTest, InvokesBarCorrectly) {
+  MyMock mock;
+  // Class MockFunction<F> has exactly one mock method.  It is named
+  // Call() and has type F.
+  MockFunction<void(string check_point_name)> check;
+  {
+    InSequence s;
+
+    EXPECT_CALL(mock, Bar("a"));
+    EXPECT_CALL(check, Call("1"));
+    EXPECT_CALL(check, Call("2"));
+    EXPECT_CALL(mock, Bar("a"));
+  }
+  Foo(1);
+  check.Call("1");
+  Foo(2);
+  check.Call("2");
+  Foo(3);
+}
+```
+
+The expectation spec says that the first `Bar("a")` must happen before check
+point "1", the second `Bar("a")` must happen after check point "2", and nothing
+should happen between the two check points. The explicit check points make it
+easy to tell which `Bar("a")` is called by which call to `Foo()`.
+
+### Mocking Destructors
+
+Sometimes you want to make sure a mock object is destructed at the right time,
+e.g. after `bar->A()` is called but before `bar->B()` is called. We already know
+that you can specify constraints on the [order](#OrderedCalls) of mock function
+calls, so all we need to do is to mock the destructor of the mock function.
+
+This sounds simple, except for one problem: a destructor is a special function
+with special syntax and special semantics, and the `MOCK_METHOD` macro doesn't
+work for it:
+
+```cpp
+MOCK_METHOD(void, ~MockFoo, ());  // Won't compile!
+```
+
+The good news is that you can use a simple pattern to achieve the same effect.
+First, add a mock function `Die()` to your mock class and call it in the
+destructor, like this:
+
+```cpp
+class MockFoo : public Foo {
+  ...
+  // Add the following two lines to the mock class.
+  MOCK_METHOD(void, Die, ());
+  ~MockFoo() override { Die(); }
+};
+```
+
+(If the name `Die()` clashes with an existing symbol, choose another name.) Now,
+we have translated the problem of testing when a `MockFoo` object dies to
+testing when its `Die()` method is called:
+
+```cpp
+  MockFoo* foo = new MockFoo;
+  MockBar* bar = new MockBar;
+  ...
+  {
+    InSequence s;
+
+    // Expects *foo to die after bar->A() and before bar->B().
+    EXPECT_CALL(*bar, A());
+    EXPECT_CALL(*foo, Die());
+    EXPECT_CALL(*bar, B());
+  }
+```
+
+And that's that.
+
+### Using gMock and Threads {#UsingThreads}
+
+In a **unit** test, it's best if you could isolate and test a piece of code in a
+single-threaded context. That avoids race conditions and dead locks, and makes
+debugging your test much easier.
+
+Yet most programs are multi-threaded, and sometimes to test something we need to
+pound on it from more than one thread. gMock works for this purpose too.
+
+Remember the steps for using a mock:
+
+1.  Create a mock object `foo`.
+2.  Set its default actions and expectations using `ON_CALL()` and
+    `EXPECT_CALL()`.
+3.  The code under test calls methods of `foo`.
+4.  Optionally, verify and reset the mock.
+5.  Destroy the mock yourself, or let the code under test destroy it. The
+    destructor will automatically verify it.
+
+If you follow the following simple rules, your mocks and threads can live
+happily together:
+
+*   Execute your *test code* (as opposed to the code being tested) in *one*
+    thread. This makes your test easy to follow.
+*   Obviously, you can do step #1 without locking.
+*   When doing step #2 and #5, make sure no other thread is accessing `foo`.
+    Obvious too, huh?
+*   #3 and #4 can be done either in one thread or in multiple threads - anyway
+    you want. gMock takes care of the locking, so you don't have to do any -
+    unless required by your test logic.
+
+If you violate the rules (for example, if you set expectations on a mock while
+another thread is calling its methods), you get undefined behavior. That's not
+fun, so don't do it.
+
+gMock guarantees that the action for a mock function is done in the same thread
+that called the mock function. For example, in
+
+```cpp
+  EXPECT_CALL(mock, Foo(1))
+      .WillOnce(action1);
+  EXPECT_CALL(mock, Foo(2))
+      .WillOnce(action2);
+```
+
+if `Foo(1)` is called in thread 1 and `Foo(2)` is called in thread 2, gMock will
+execute `action1` in thread 1 and `action2` in thread 2.
+
+gMock does *not* impose a sequence on actions performed in different threads
+(doing so may create deadlocks as the actions may need to cooperate). This means
+that the execution of `action1` and `action2` in the above example *may*
+interleave. If this is a problem, you should add proper synchronization logic to
+`action1` and `action2` to make the test thread-safe.
+
+Also, remember that `DefaultValue<T>` is a global resource that potentially
+affects *all* living mock objects in your program. Naturally, you won't want to
+mess with it from multiple threads or when there still are mocks in action.
+
+### Controlling How Much Information gMock Prints
+
+When gMock sees something that has the potential of being an error (e.g. a mock
+function with no expectation is called, a.k.a. an uninteresting call, which is
+allowed but perhaps you forgot to explicitly ban the call), it prints some
+warning messages, including the arguments of the function, the return value, and
+the stack trace. Hopefully this will remind you to take a look and see if there
+is indeed a problem.
+
+Sometimes you are confident that your tests are correct and may not appreciate
+such friendly messages. Some other times, you are debugging your tests or
+learning about the behavior of the code you are testing, and wish you could
+observe every mock call that happens (including argument values, the return
+value, and the stack trace). Clearly, one size doesn't fit all.
+
+You can control how much gMock tells you using the `--gmock_verbose=LEVEL`
+command-line flag, where `LEVEL` is a string with three possible values:
+
+*   `info`: gMock will print all informational messages, warnings, and errors
+    (most verbose). At this setting, gMock will also log any calls to the
+    `ON_CALL/EXPECT_CALL` macros. It will include a stack trace in
+    "uninteresting call" warnings.
+*   `warning`: gMock will print both warnings and errors (less verbose); it will
+    omit the stack traces in "uninteresting call" warnings. This is the default.
+*   `error`: gMock will print errors only (least verbose).
+
+Alternatively, you can adjust the value of that flag from within your tests like
+so:
+
+```cpp
+  ::testing::FLAGS_gmock_verbose = "error";
+```
+
+If you find gMock printing too many stack frames with its informational or
+warning messages, remember that you can control their amount with the
+`--gtest_stack_trace_depth=max_depth` flag.
+
+Now, judiciously use the right flag to enable gMock serve you better!
+
+### Gaining Super Vision into Mock Calls
+
+You have a test using gMock. It fails: gMock tells you some expectations aren't
+satisfied. However, you aren't sure why: Is there a typo somewhere in the
+matchers? Did you mess up the order of the `EXPECT_CALL`s? Or is the code under
+test doing something wrong? How can you find out the cause?
+
+Won't it be nice if you have X-ray vision and can actually see the trace of all
+`EXPECT_CALL`s and mock method calls as they are made? For each call, would you
+like to see its actual argument values and which `EXPECT_CALL` gMock thinks it
+matches? If you still need some help to figure out who made these calls, how
+about being able to see the complete stack trace at each mock call?
+
+You can unlock this power by running your test with the `--gmock_verbose=info`
+flag. For example, given the test program:
+
+```cpp
+#include "gmock/gmock.h"
+
+using testing::_;
+using testing::HasSubstr;
+using testing::Return;
+
+class MockFoo {
+ public:
+  MOCK_METHOD(void, F, (const string& x, const string& y));
+};
+
+TEST(Foo, Bar) {
+  MockFoo mock;
+  EXPECT_CALL(mock, F(_, _)).WillRepeatedly(Return());
+  EXPECT_CALL(mock, F("a", "b"));
+  EXPECT_CALL(mock, F("c", HasSubstr("d")));
+
+  mock.F("a", "good");
+  mock.F("a", "b");
+}
+```
+
+if you run it with `--gmock_verbose=info`, you will see this output:
+
+```shell
+[ RUN       ] Foo.Bar
+
+foo_test.cc:14: EXPECT_CALL(mock, F(_, _)) invoked
+Stack trace: ...
+
+foo_test.cc:15: EXPECT_CALL(mock, F("a", "b")) invoked
+Stack trace: ...
+
+foo_test.cc:16: EXPECT_CALL(mock, F("c", HasSubstr("d"))) invoked
+Stack trace: ...
+
+foo_test.cc:14: Mock function call matches EXPECT_CALL(mock, F(_, _))...
+    Function call: F(@0x7fff7c8dad40"a",@0x7fff7c8dad10"good")
+Stack trace: ...
+
+foo_test.cc:15: Mock function call matches EXPECT_CALL(mock, F("a", "b"))...
+    Function call: F(@0x7fff7c8dada0"a",@0x7fff7c8dad70"b")
+Stack trace: ...
+
+foo_test.cc:16: Failure
+Actual function call count doesn't match EXPECT_CALL(mock, F("c", HasSubstr("d")))...
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+[  FAILED  ] Foo.Bar
+```
+
+Suppose the bug is that the `"c"` in the third `EXPECT_CALL` is a typo and
+should actually be `"a"`. With the above message, you should see that the actual
+`F("a", "good")` call is matched by the first `EXPECT_CALL`, not the third as
+you thought. From that it should be obvious that the third `EXPECT_CALL` is
+written wrong. Case solved.
+
+If you are interested in the mock call trace but not the stack traces, you can
+combine `--gmock_verbose=info` with `--gtest_stack_trace_depth=0` on the test
+command line.
+
+### Running Tests in Emacs
+
+If you build and run your tests in Emacs using the `M-x google-compile` command
+(as many googletest users do), the source file locations of gMock and googletest
+errors will be highlighted. Just press `<Enter>` on one of them and you'll be
+taken to the offending line. Or, you can just type `C-x`` to jump to the next
+error.
+
+To make it even easier, you can add the following lines to your `~/.emacs` file:
+
+```text
+(global-set-key "\M-m"  'google-compile)  ; m is for make
+(global-set-key [M-down] 'next-error)
+(global-set-key [M-up]  '(lambda () (interactive) (next-error -1)))
+```
+
+Then you can type `M-m` to start a build (if you want to run the test as well,
+just make sure `foo_test.run` or `runtests` is in the build command you supply
+after typing `M-m`), or `M-up`/`M-down` to move back and forth between errors.
+
+## Extending gMock
+
+### Writing New Matchers Quickly {#NewMatchers}
+
+{: .callout .warning}
+WARNING: gMock does not guarantee when or how many times a matcher will be
+invoked. Therefore, all matchers must be functionally pure. See
+[this section](#PureMatchers) for more details.
+
+The `MATCHER*` family of macros can be used to define custom matchers easily.
+The syntax:
+
+```cpp
+MATCHER(name, description_string_expression) { statements; }
+```
+
+will define a matcher with the given name that executes the statements, which
+must return a `bool` to indicate if the match succeeds. Inside the statements,
+you can refer to the value being matched by `arg`, and refer to its type by
+`arg_type`.
+
+The *description string* is a `string`-typed expression that documents what the
+matcher does, and is used to generate the failure message when the match fails.
+It can (and should) reference the special `bool` variable `negation`, and should
+evaluate to the description of the matcher when `negation` is `false`, or that
+of the matcher's negation when `negation` is `true`.
+
+For convenience, we allow the description string to be empty (`""`), in which
+case gMock will use the sequence of words in the matcher name as the
+description.
+
+For example:
+
+```cpp
+MATCHER(IsDivisibleBy7, "") { return (arg % 7) == 0; }
+```
+
+allows you to write
+
+```cpp
+  // Expects mock_foo.Bar(n) to be called where n is divisible by 7.
+  EXPECT_CALL(mock_foo, Bar(IsDivisibleBy7()));
+```
+
+or,
+
+```cpp
+  using ::testing::Not;
+  ...
+  // Verifies that two values are divisible by 7.
+  EXPECT_THAT(some_expression, IsDivisibleBy7());
+  EXPECT_THAT(some_other_expression, Not(IsDivisibleBy7()));
+```
+
+If the above assertions fail, they will print something like:
+
+```shell
+  Value of: some_expression
+  Expected: is divisible by 7
+    Actual: 27
+  ...
+  Value of: some_other_expression
+  Expected: not (is divisible by 7)
+    Actual: 21
+```
+
+where the descriptions `"is divisible by 7"` and `"not (is divisible by 7)"` are
+automatically calculated from the matcher name `IsDivisibleBy7`.
+
+As you may have noticed, the auto-generated descriptions (especially those for
+the negation) may not be so great. You can always override them with a `string`
+expression of your own:
+
+```cpp
+MATCHER(IsDivisibleBy7,
+        absl::StrCat(negation ? "isn't" : "is", " divisible by 7")) {
+  return (arg % 7) == 0;
+}
+```
+
+Optionally, you can stream additional information to a hidden argument named
+`result_listener` to explain the match result. For example, a better definition
+of `IsDivisibleBy7` is:
+
+```cpp
+MATCHER(IsDivisibleBy7, "") {
+  if ((arg % 7) == 0)
+    return true;
+
+  *result_listener << "the remainder is " << (arg % 7);
+  return false;
+}
+```
+
+With this definition, the above assertion will give a better message:
+
+```shell
+  Value of: some_expression
+  Expected: is divisible by 7
+    Actual: 27 (the remainder is 6)
+```
+
+You should let `MatchAndExplain()` print *any additional information* that can
+help a user understand the match result. Note that it should explain why the
+match succeeds in case of a success (unless it's obvious) - this is useful when
+the matcher is used inside `Not()`. There is no need to print the argument value
+itself, as gMock already prints it for you.
+
+{: .callout .note}
+NOTE: The type of the value being matched (`arg_type`) is determined by the
+context in which you use the matcher and is supplied to you by the compiler, so
+you don't need to worry about declaring it (nor can you). This allows the
+matcher to be polymorphic. For example, `IsDivisibleBy7()` can be used to match
+any type where the value of `(arg % 7) == 0` can be implicitly converted to a
+`bool`. In the `Bar(IsDivisibleBy7())` example above, if method `Bar()` takes an
+`int`, `arg_type` will be `int`; if it takes an `unsigned long`, `arg_type` will
+be `unsigned long`; and so on.
+
+### Writing New Parameterized Matchers Quickly
+
+Sometimes you'll want to define a matcher that has parameters. For that you can
+use the macro:
+
+```cpp
+MATCHER_P(name, param_name, description_string) { statements; }
+```
+
+where the description string can be either `""` or a `string` expression that
+references `negation` and `param_name`.
+
+For example:
+
+```cpp
+MATCHER_P(HasAbsoluteValue, value, "") { return abs(arg) == value; }
+```
+
+will allow you to write:
+
+```cpp
+  EXPECT_THAT(Blah("a"), HasAbsoluteValue(n));
+```
+
+which may lead to this message (assuming `n` is 10):
+
+```shell
+  Value of: Blah("a")
+  Expected: has absolute value 10
+    Actual: -9
+```
+
+Note that both the matcher description and its parameter are printed, making the
+message human-friendly.
+
+In the matcher definition body, you can write `foo_type` to reference the type
+of a parameter named `foo`. For example, in the body of
+`MATCHER_P(HasAbsoluteValue, value)` above, you can write `value_type` to refer
+to the type of `value`.
+
+gMock also provides `MATCHER_P2`, `MATCHER_P3`, ..., up to `MATCHER_P10` to
+support multi-parameter matchers:
+
+```cpp
+MATCHER_Pk(name, param_1, ..., param_k, description_string) { statements; }
+```
+
+Please note that the custom description string is for a particular *instance* of
+the matcher, where the parameters have been bound to actual values. Therefore
+usually you'll want the parameter values to be part of the description. gMock
+lets you do that by referencing the matcher parameters in the description string
+expression.
+
+For example,
+
+```cpp
+using ::testing::PrintToString;
+MATCHER_P2(InClosedRange, low, hi,
+           absl::StrFormat("%s in range [%s, %s]", negation ? "isn't" : "is",
+                           PrintToString(low), PrintToString(hi))) {
+  return low <= arg && arg <= hi;
+}
+...
+EXPECT_THAT(3, InClosedRange(4, 6));
+```
+
+would generate a failure that contains the message:
+
+```shell
+  Expected: is in range [4, 6]
+```
+
+If you specify `""` as the description, the failure message will contain the
+sequence of words in the matcher name followed by the parameter values printed
+as a tuple. For example,
+
+```cpp
+  MATCHER_P2(InClosedRange, low, hi, "") { ... }
+  ...
+  EXPECT_THAT(3, InClosedRange(4, 6));
+```
+
+would generate a failure that contains the text:
+
+```shell
+  Expected: in closed range (4, 6)
+```
+
+For the purpose of typing, you can view
+
+```cpp
+MATCHER_Pk(Foo, p1, ..., pk, description_string) { ... }
+```
+
+as shorthand for
+
+```cpp
+template <typename p1_type, ..., typename pk_type>
+FooMatcherPk<p1_type, ..., pk_type>
+Foo(p1_type p1, ..., pk_type pk) { ... }
+```
+
+When you write `Foo(v1, ..., vk)`, the compiler infers the types of the
+parameters `v1`, ..., and `vk` for you. If you are not happy with the result of
+the type inference, you can specify the types by explicitly instantiating the
+template, as in `Foo<long, bool>(5, false)`. As said earlier, you don't get to
+(or need to) specify `arg_type` as that's determined by the context in which the
+matcher is used.
+
+You can assign the result of expression `Foo(p1, ..., pk)` to a variable of type
+`FooMatcherPk<p1_type, ..., pk_type>`. This can be useful when composing
+matchers. Matchers that don't have a parameter or have only one parameter have
+special types: you can assign `Foo()` to a `FooMatcher`-typed variable, and
+assign `Foo(p)` to a `FooMatcherP<p_type>`-typed variable.
+
+While you can instantiate a matcher template with reference types, passing the
+parameters by pointer usually makes your code more readable. If, however, you
+still want to pass a parameter by reference, be aware that in the failure
+message generated by the matcher you will see the value of the referenced object
+but not its address.
+
+You can overload matchers with different numbers of parameters:
+
+```cpp
+MATCHER_P(Blah, a, description_string_1) { ... }
+MATCHER_P2(Blah, a, b, description_string_2) { ... }
+```
+
+While it's tempting to always use the `MATCHER*` macros when defining a new
+matcher, you should also consider implementing the matcher interface directly
+instead (see the recipes that follow), especially if you need to use the matcher
+a lot. While these approaches require more work, they give you more control on
+the types of the value being matched and the matcher parameters, which in
+general leads to better compiler error messages that pay off in the long run.
+They also allow overloading matchers based on parameter types (as opposed to
+just based on the number of parameters).
+
+### Writing New Monomorphic Matchers
+
+A matcher of argument type `T` implements the matcher interface for `T` and does
+two things: it tests whether a value of type `T` matches the matcher, and can
+describe what kind of values it matches. The latter ability is used for
+generating readable error messages when expectations are violated.
+
+A matcher of `T` must declare a typedef like:
+
+```cpp
+using is_gtest_matcher = void;
+```
+
+and supports the following operations:
+
+```cpp
+// Match a value and optionally explain into an ostream.
+bool matched = matcher.MatchAndExplain(value, maybe_os);
+// where `value` is of type `T` and
+// `maybe_os` is of type `std::ostream*`, where it can be null if the caller
+// is not interested in there textual explanation.
+
+matcher.DescribeTo(os);
+matcher.DescribeNegationTo(os);
+// where `os` is of type `std::ostream*`.
+```
+
+If you need a custom matcher but `Truly()` is not a good option (for example,
+you may not be happy with the way `Truly(predicate)` describes itself, or you
+may want your matcher to be polymorphic as `Eq(value)` is), you can define a
+matcher to do whatever you want in two steps: first implement the matcher
+interface, and then define a factory function to create a matcher instance. The
+second step is not strictly needed but it makes the syntax of using the matcher
+nicer.
+
+For example, you can define a matcher to test whether an `int` is divisible by 7
+and then use it like this:
+
+```cpp
+using ::testing::Matcher;
+
+class DivisibleBy7Matcher {
+ public:
+  using is_gtest_matcher = void;
+
+  bool MatchAndExplain(int n, std::ostream*) const {
+    return (n % 7) == 0;
+  }
+
+  void DescribeTo(std::ostream* os) const {
+    *os << "is divisible by 7";
+  }
+
+  void DescribeNegationTo(std::ostream* os) const {
+    *os << "is not divisible by 7";
+  }
+};
+
+Matcher<int> DivisibleBy7() {
+  return DivisibleBy7Matcher();
+}
+
+...
+  EXPECT_CALL(foo, Bar(DivisibleBy7()));
+```
+
+You may improve the matcher message by streaming additional information to the
+`os` argument in `MatchAndExplain()`:
+
+```cpp
+class DivisibleBy7Matcher {
+ public:
+  bool MatchAndExplain(int n, std::ostream* os) const {
+    const int remainder = n % 7;
+    if (remainder != 0 && os != nullptr) {
+      *os << "the remainder is " << remainder;
+    }
+    return remainder == 0;
+  }
+  ...
+};
+```
+
+Then, `EXPECT_THAT(x, DivisibleBy7());` may generate a message like this:
+
+```shell
+Value of: x
+Expected: is divisible by 7
+  Actual: 23 (the remainder is 2)
+```
+
+{: .callout .tip}
+Tip: for convenience, `MatchAndExplain()` can take a `MatchResultListener*`
+instead of `std::ostream*`.
+
+### Writing New Polymorphic Matchers
+
+Expanding what we learned above to *polymorphic* matchers is now just as simple
+as adding templates in the right place.
+
+```cpp
+
+class NotNullMatcher {
+ public:
+  using is_gtest_matcher = void;
+
+  // To implement a polymorphic matcher, we just need to make MatchAndExplain a
+  // template on its first argument.
+
+  // In this example, we want to use NotNull() with any pointer, so
+  // MatchAndExplain() accepts a pointer of any type as its first argument.
+  // In general, you can define MatchAndExplain() as an ordinary method or
+  // a method template, or even overload it.
+  template <typename T>
+  bool MatchAndExplain(T* p, std::ostream*) const {
+    return p != nullptr;
+  }
+
+  // Describes the property of a value matching this matcher.
+  void DescribeTo(std::ostream* os) const { *os << "is not NULL"; }
+
+  // Describes the property of a value NOT matching this matcher.
+  void DescribeNegationTo(std::ostream* os) const { *os << "is NULL"; }
+};
+
+NotNullMatcher NotNull() {
+  return NotNullMatcher();
+}
+
+...
+
+  EXPECT_CALL(foo, Bar(NotNull()));  // The argument must be a non-NULL pointer.
+```
+
+### Legacy Matcher Implementation
+
+Defining matchers used to be somewhat more complicated, in which it required
+several supporting classes and virtual functions. To implement a matcher for
+type `T` using the legacy API you have to derive from `MatcherInterface<T>` and
+call `MakeMatcher` to construct the object.
+
+The interface looks like this:
+
+```cpp
+class MatchResultListener {
+ public:
+  ...
+  // Streams x to the underlying ostream; does nothing if the ostream
+  // is NULL.
+  template <typename T>
+  MatchResultListener& operator<<(const T& x);
+
+  // Returns the underlying ostream.
+  std::ostream* stream();
+};
+
+template <typename T>
+class MatcherInterface {
+ public:
+  virtual ~MatcherInterface();
+
+  // Returns true if and only if the matcher matches x; also explains the match
+  // result to 'listener'.
+  virtual bool MatchAndExplain(T x, MatchResultListener* listener) const = 0;
+
+  // Describes this matcher to an ostream.
+  virtual void DescribeTo(std::ostream* os) const = 0;
+
+  // Describes the negation of this matcher to an ostream.
+  virtual void DescribeNegationTo(std::ostream* os) const;
+};
+```
+
+Fortunately, most of the time you can define a polymorphic matcher easily with
+the help of `MakePolymorphicMatcher()`. Here's how you can define `NotNull()` as
+an example:
+
+```cpp
+using ::testing::MakePolymorphicMatcher;
+using ::testing::MatchResultListener;
+using ::testing::PolymorphicMatcher;
+
+class NotNullMatcher {
+ public:
+  // To implement a polymorphic matcher, first define a COPYABLE class
+  // that has three members MatchAndExplain(), DescribeTo(), and
+  // DescribeNegationTo(), like the following.
+
+  // In this example, we want to use NotNull() with any pointer, so
+  // MatchAndExplain() accepts a pointer of any type as its first argument.
+  // In general, you can define MatchAndExplain() as an ordinary method or
+  // a method template, or even overload it.
+  template <typename T>
+  bool MatchAndExplain(T* p,
+                       MatchResultListener* /* listener */) const {
+    return p != NULL;
+  }
+
+  // Describes the property of a value matching this matcher.
+  void DescribeTo(std::ostream* os) const { *os << "is not NULL"; }
+
+  // Describes the property of a value NOT matching this matcher.
+  void DescribeNegationTo(std::ostream* os) const { *os << "is NULL"; }
+};
+
+// To construct a polymorphic matcher, pass an instance of the class
+// to MakePolymorphicMatcher().  Note the return type.
+PolymorphicMatcher<NotNullMatcher> NotNull() {
+  return MakePolymorphicMatcher(NotNullMatcher());
+}
+
+...
+
+  EXPECT_CALL(foo, Bar(NotNull()));  // The argument must be a non-NULL pointer.
+```
+
+{: .callout .note}
+**Note:** Your polymorphic matcher class does **not** need to inherit from
+`MatcherInterface` or any other class, and its methods do **not** need to be
+virtual.
+
+Like in a monomorphic matcher, you may explain the match result by streaming
+additional information to the `listener` argument in `MatchAndExplain()`.
+
+### Writing New Cardinalities
+
+A cardinality is used in `Times()` to tell gMock how many times you expect a
+call to occur. It doesn't have to be exact. For example, you can say
+`AtLeast(5)` or `Between(2, 4)`.
+
+If the [built-in set](gmock_cheat_sheet.md#CardinalityList) of cardinalities
+doesn't suit you, you are free to define your own by implementing the following
+interface (in namespace `testing`):
+
+```cpp
+class CardinalityInterface {
+ public:
+  virtual ~CardinalityInterface();
+
+  // Returns true if and only if call_count calls will satisfy this cardinality.
+  virtual bool IsSatisfiedByCallCount(int call_count) const = 0;
+
+  // Returns true if and only if call_count calls will saturate this
+  // cardinality.
+  virtual bool IsSaturatedByCallCount(int call_count) const = 0;
+
+  // Describes self to an ostream.
+  virtual void DescribeTo(std::ostream* os) const = 0;
+};
+```
+
+For example, to specify that a call must occur even number of times, you can
+write
+
+```cpp
+using ::testing::Cardinality;
+using ::testing::CardinalityInterface;
+using ::testing::MakeCardinality;
+
+class EvenNumberCardinality : public CardinalityInterface {
+ public:
+  bool IsSatisfiedByCallCount(int call_count) const override {
+    return (call_count % 2) == 0;
+  }
+
+  bool IsSaturatedByCallCount(int call_count) const override {
+    return false;
+  }
+
+  void DescribeTo(std::ostream* os) const {
+    *os << "called even number of times";
+  }
+};
+
+Cardinality EvenNumber() {
+  return MakeCardinality(new EvenNumberCardinality);
+}
+
+...
+  EXPECT_CALL(foo, Bar(3))
+      .Times(EvenNumber());
+```
+
+### Writing New Actions Quickly {#QuickNewActions}
+
+If the built-in actions don't work for you, you can easily define your own one.
+Just define a functor class with a (possibly templated) call operator, matching
+the signature of your action.
+
+```cpp
+struct Increment {
+  template <typename T>
+  T operator()(T* arg) {
+    return ++(*arg);
+  }
+}
+```
+
+The same approach works with stateful functors (or any callable, really):
+
+```
+struct MultiplyBy {
+  template <typename T>
+  T operator()(T arg) { return arg * multiplier; }
+
+  int multiplier;
+}
+
+// Then use:
+// EXPECT_CALL(...).WillOnce(MultiplyBy{7});
+```
+
+#### Legacy macro-based Actions
+
+Before C++11, the functor-based actions were not supported; the old way of
+writing actions was through a set of `ACTION*` macros. We suggest to avoid them
+in new code; they hide a lot of logic behind the macro, potentially leading to
+harder-to-understand compiler errors. Nevertheless, we cover them here for
+completeness.
+
+By writing
+
+```cpp
+ACTION(name) { statements; }
+```
+
+in a namespace scope (i.e. not inside a class or function), you will define an
+action with the given name that executes the statements. The value returned by
+`statements` will be used as the return value of the action. Inside the
+statements, you can refer to the K-th (0-based) argument of the mock function as
+`argK`. For example:
+
+```cpp
+ACTION(IncrementArg1) { return ++(*arg1); }
+```
+
+allows you to write
+
+```cpp
+... WillOnce(IncrementArg1());
+```
+
+Note that you don't need to specify the types of the mock function arguments.
+Rest assured that your code is type-safe though: you'll get a compiler error if
+`*arg1` doesn't support the `++` operator, or if the type of `++(*arg1)` isn't
+compatible with the mock function's return type.
+
+Another example:
+
+```cpp
+ACTION(Foo) {
+  (*arg2)(5);
+  Blah();
+  *arg1 = 0;
+  return arg0;
+}
+```
+
+defines an action `Foo()` that invokes argument #2 (a function pointer) with 5,
+calls function `Blah()`, sets the value pointed to by argument #1 to 0, and
+returns argument #0.
+
+For more convenience and flexibility, you can also use the following pre-defined
+symbols in the body of `ACTION`:
+
+`argK_type`     | The type of the K-th (0-based) argument of the mock function
+:-------------- | :-----------------------------------------------------------
+`args`          | All arguments of the mock function as a tuple
+`args_type`     | The type of all arguments of the mock function as a tuple
+`return_type`   | The return type of the mock function
+`function_type` | The type of the mock function
+
+For example, when using an `ACTION` as a stub action for mock function:
+
+```cpp
+int DoSomething(bool flag, int* ptr);
+```
+
+we have:
+
+Pre-defined Symbol | Is Bound To
+------------------ | ---------------------------------
+`arg0`             | the value of `flag`
+`arg0_type`        | the type `bool`
+`arg1`             | the value of `ptr`
+`arg1_type`        | the type `int*`
+`args`             | the tuple `(flag, ptr)`
+`args_type`        | the type `std::tuple<bool, int*>`
+`return_type`      | the type `int`
+`function_type`    | the type `int(bool, int*)`
+
+#### Legacy macro-based parameterized Actions
+
+Sometimes you'll want to parameterize an action you define. For that we have
+another macro
+
+```cpp
+ACTION_P(name, param) { statements; }
+```
+
+For example,
+
+```cpp
+ACTION_P(Add, n) { return arg0 + n; }
+```
+
+will allow you to write
+
+```cpp
+// Returns argument #0 + 5.
+... WillOnce(Add(5));
+```
+
+For convenience, we use the term *arguments* for the values used to invoke the
+mock function, and the term *parameters* for the values used to instantiate an
+action.
+
+Note that you don't need to provide the type of the parameter either. Suppose
+the parameter is named `param`, you can also use the gMock-defined symbol
+`param_type` to refer to the type of the parameter as inferred by the compiler.
+For example, in the body of `ACTION_P(Add, n)` above, you can write `n_type` for
+the type of `n`.
+
+gMock also provides `ACTION_P2`, `ACTION_P3`, and etc to support multi-parameter
+actions. For example,
+
+```cpp
+ACTION_P2(ReturnDistanceTo, x, y) {
+  double dx = arg0 - x;
+  double dy = arg1 - y;
+  return sqrt(dx*dx + dy*dy);
+}
+```
+
+lets you write
+
+```cpp
+... WillOnce(ReturnDistanceTo(5.0, 26.5));
+```
+
+You can view `ACTION` as a degenerated parameterized action where the number of
+parameters is 0.
+
+You can also easily define actions overloaded on the number of parameters:
+
+```cpp
+ACTION_P(Plus, a) { ... }
+ACTION_P2(Plus, a, b) { ... }
+```
+
+### Restricting the Type of an Argument or Parameter in an ACTION
+
+For maximum brevity and reusability, the `ACTION*` macros don't ask you to
+provide the types of the mock function arguments and the action parameters.
+Instead, we let the compiler infer the types for us.
+
+Sometimes, however, we may want to be more explicit about the types. There are
+several tricks to do that. For example:
+
+```cpp
+ACTION(Foo) {
+  // Makes sure arg0 can be converted to int.
+  int n = arg0;
+  ... use n instead of arg0 here ...
+}
+
+ACTION_P(Bar, param) {
+  // Makes sure the type of arg1 is const char*.
+  ::testing::StaticAssertTypeEq<const char*, arg1_type>();
+
+  // Makes sure param can be converted to bool.
+  bool flag = param;
+}
+```
+
+where `StaticAssertTypeEq` is a compile-time assertion in googletest that
+verifies two types are the same.
+
+### Writing New Action Templates Quickly
+
+Sometimes you want to give an action explicit template parameters that cannot be
+inferred from its value parameters. `ACTION_TEMPLATE()` supports that and can be
+viewed as an extension to `ACTION()` and `ACTION_P*()`.
+
+The syntax:
+
+```cpp
+ACTION_TEMPLATE(ActionName,
+                HAS_m_TEMPLATE_PARAMS(kind1, name1, ..., kind_m, name_m),
+                AND_n_VALUE_PARAMS(p1, ..., p_n)) { statements; }
+```
+
+defines an action template that takes *m* explicit template parameters and *n*
+value parameters, where *m* is in [1, 10] and *n* is in [0, 10]. `name_i` is the
+name of the *i*-th template parameter, and `kind_i` specifies whether it's a
+`typename`, an integral constant, or a template. `p_i` is the name of the *i*-th
+value parameter.
+
+Example:
+
+```cpp
+// DuplicateArg<k, T>(output) converts the k-th argument of the mock
+// function to type T and copies it to *output.
+ACTION_TEMPLATE(DuplicateArg,
+                // Note the comma between int and k:
+                HAS_2_TEMPLATE_PARAMS(int, k, typename, T),
+                AND_1_VALUE_PARAMS(output)) {
+  *output = T(std::get<k>(args));
+}
+```
+
+To create an instance of an action template, write:
+
+```cpp
+ActionName<t1, ..., t_m>(v1, ..., v_n)
+```
+
+where the `t`s are the template arguments and the `v`s are the value arguments.
+The value argument types are inferred by the compiler. For example:
+
+```cpp
+using ::testing::_;
+...
+  int n;
+  EXPECT_CALL(mock, Foo).WillOnce(DuplicateArg<1, unsigned char>(&n));
+```
+
+If you want to explicitly specify the value argument types, you can provide
+additional template arguments:
+
+```cpp
+ActionName<t1, ..., t_m, u1, ..., u_k>(v1, ..., v_n)
+```
+
+where `u_i` is the desired type of `v_i`.
+
+`ACTION_TEMPLATE` and `ACTION`/`ACTION_P*` can be overloaded on the number of
+value parameters, but not on the number of template parameters. Without the
+restriction, the meaning of the following is unclear:
+
+```cpp
+  OverloadedAction<int, bool>(x);
+```
+
+Are we using a single-template-parameter action where `bool` refers to the type
+of `x`, or a two-template-parameter action where the compiler is asked to infer
+the type of `x`?
+
+### Using the ACTION Object's Type
+
+If you are writing a function that returns an `ACTION` object, you'll need to
+know its type. The type depends on the macro used to define the action and the
+parameter types. The rule is relatively simple:
+
+
+| Given Definition              | Expression          | Has Type              |
+| ----------------------------- | ------------------- | --------------------- |
+| `ACTION(Foo)`                 | `Foo()`             | `FooAction`           |
+| `ACTION_TEMPLATE(Foo, HAS_m_TEMPLATE_PARAMS(...), AND_0_VALUE_PARAMS())` | `Foo<t1, ..., t_m>()` | `FooAction<t1, ..., t_m>` |
+| `ACTION_P(Bar, param)`        | `Bar(int_value)`    | `BarActionP<int>`     |
+| `ACTION_TEMPLATE(Bar, HAS_m_TEMPLATE_PARAMS(...), AND_1_VALUE_PARAMS(p1))` | `Bar<t1, ..., t_m>(int_value)` | `BarActionP<t1, ..., t_m, int>` |
+| `ACTION_P2(Baz, p1, p2)`      | `Baz(bool_value, int_value)` | `BazActionP2<bool, int>` |
+| `ACTION_TEMPLATE(Baz, HAS_m_TEMPLATE_PARAMS(...), AND_2_VALUE_PARAMS(p1, p2))` | `Baz<t1, ..., t_m>(bool_value, int_value)` | `BazActionP2<t1, ..., t_m, bool, int>` |
+| ...                           | ...                 | ...                   |
+
+
+Note that we have to pick different suffixes (`Action`, `ActionP`, `ActionP2`,
+and etc) for actions with different numbers of value parameters, or the action
+definitions cannot be overloaded on the number of them.
+
+### Writing New Monomorphic Actions {#NewMonoActions}
+
+While the `ACTION*` macros are very convenient, sometimes they are
+inappropriate. For example, despite the tricks shown in the previous recipes,
+they don't let you directly specify the types of the mock function arguments and
+the action parameters, which in general leads to unoptimized compiler error
+messages that can baffle unfamiliar users. They also don't allow overloading
+actions based on parameter types without jumping through some hoops.
+
+An alternative to the `ACTION*` macros is to implement
+`::testing::ActionInterface<F>`, where `F` is the type of the mock function in
+which the action will be used. For example:
+
+```cpp
+template <typename F>
+class ActionInterface {
+ public:
+  virtual ~ActionInterface();
+
+  // Performs the action.  Result is the return type of function type
+  // F, and ArgumentTuple is the tuple of arguments of F.
+  //
+
+  // For example, if F is int(bool, const string&), then Result would
+  // be int, and ArgumentTuple would be std::tuple<bool, const string&>.
+  virtual Result Perform(const ArgumentTuple& args) = 0;
+};
+```
+
+```cpp
+using ::testing::_;
+using ::testing::Action;
+using ::testing::ActionInterface;
+using ::testing::MakeAction;
+
+typedef int IncrementMethod(int*);
+
+class IncrementArgumentAction : public ActionInterface<IncrementMethod> {
+ public:
+  int Perform(const std::tuple<int*>& args) override {
+    int* p = std::get<0>(args);  // Grabs the first argument.
+    return *p++;
+  }
+};
+
+Action<IncrementMethod> IncrementArgument() {
+  return MakeAction(new IncrementArgumentAction);
+}
+
+...
+  EXPECT_CALL(foo, Baz(_))
+      .WillOnce(IncrementArgument());
+
+  int n = 5;
+  foo.Baz(&n);  // Should return 5 and change n to 6.
+```
+
+### Writing New Polymorphic Actions {#NewPolyActions}
+
+The previous recipe showed you how to define your own action. This is all good,
+except that you need to know the type of the function in which the action will
+be used. Sometimes that can be a problem. For example, if you want to use the
+action in functions with *different* types (e.g. like `Return()` and
+`SetArgPointee()`).
+
+If an action can be used in several types of mock functions, we say it's
+*polymorphic*. The `MakePolymorphicAction()` function template makes it easy to
+define such an action:
+
+```cpp
+namespace testing {
+template <typename Impl>
+PolymorphicAction<Impl> MakePolymorphicAction(const Impl& impl);
+}  // namespace testing
+```
+
+As an example, let's define an action that returns the second argument in the
+mock function's argument list. The first step is to define an implementation
+class:
+
+```cpp
+class ReturnSecondArgumentAction {
+ public:
+  template <typename Result, typename ArgumentTuple>
+  Result Perform(const ArgumentTuple& args) const {
+    // To get the i-th (0-based) argument, use std::get(args).
+    return std::get<1>(args);
+  }
+};
+```
+
+This implementation class does *not* need to inherit from any particular class.
+What matters is that it must have a `Perform()` method template. This method
+template takes the mock function's arguments as a tuple in a **single**
+argument, and returns the result of the action. It can be either `const` or not,
+but must be invokable with exactly one template argument, which is the result
+type. In other words, you must be able to call `Perform<R>(args)` where `R` is
+the mock function's return type and `args` is its arguments in a tuple.
+
+Next, we use `MakePolymorphicAction()` to turn an instance of the implementation
+class into the polymorphic action we need. It will be convenient to have a
+wrapper for this:
+
+```cpp
+using ::testing::MakePolymorphicAction;
+using ::testing::PolymorphicAction;
+
+PolymorphicAction<ReturnSecondArgumentAction> ReturnSecondArgument() {
+  return MakePolymorphicAction(ReturnSecondArgumentAction());
+}
+```
+
+Now, you can use this polymorphic action the same way you use the built-in ones:
+
+```cpp
+using ::testing::_;
+
+class MockFoo : public Foo {
+ public:
+  MOCK_METHOD(int, DoThis, (bool flag, int n), (override));
+  MOCK_METHOD(string, DoThat, (int x, const char* str1, const char* str2),
+              (override));
+};
+
+  ...
+  MockFoo foo;
+  EXPECT_CALL(foo, DoThis).WillOnce(ReturnSecondArgument());
+  EXPECT_CALL(foo, DoThat).WillOnce(ReturnSecondArgument());
+  ...
+  foo.DoThis(true, 5);  // Will return 5.
+  foo.DoThat(1, "Hi", "Bye");  // Will return "Hi".
+```
+
+### Teaching gMock How to Print Your Values
+
+When an uninteresting or unexpected call occurs, gMock prints the argument
+values and the stack trace to help you debug. Assertion macros like
+`EXPECT_THAT` and `EXPECT_EQ` also print the values in question when the
+assertion fails. gMock and googletest do this using googletest's user-extensible
+value printer.
+
+This printer knows how to print built-in C++ types, native arrays, STL
+containers, and any type that supports the `<<` operator. For other types, it
+prints the raw bytes in the value and hopes that you the user can figure it out.
+[The GoogleTest advanced guide](advanced.md#teaching-googletest-how-to-print-your-values)
+explains how to extend the printer to do a better job at printing your
+particular type than to dump the bytes.
+
+## Useful Mocks Created Using gMock
+
+<!--#include file="includes/g3_testing_LOGs.md"-->
+<!--#include file="includes/g3_mock_callbacks.md"-->
+
+### Mock std::function {#MockFunction}
+
+`std::function` is a general function type introduced in C++11. It is a
+preferred way of passing callbacks to new interfaces. Functions are copiable,
+and are not usually passed around by pointer, which makes them tricky to mock.
+But fear not - `MockFunction` can help you with that.
+
+`MockFunction<R(T1, ..., Tn)>` has a mock method `Call()` with the signature:
+
+```cpp
+  R Call(T1, ..., Tn);
+```
+
+It also has a `AsStdFunction()` method, which creates a `std::function` proxy
+forwarding to Call:
+
+```cpp
+  std::function<R(T1, ..., Tn)> AsStdFunction();
+```
+
+To use `MockFunction`, first create `MockFunction` object and set up
+expectations on its `Call` method. Then pass proxy obtained from
+`AsStdFunction()` to the code you are testing. For example:
+
+```cpp
+TEST(FooTest, RunsCallbackWithBarArgument) {
+  // 1. Create a mock object.
+  MockFunction<int(string)> mock_function;
+
+  // 2. Set expectations on Call() method.
+  EXPECT_CALL(mock_function, Call("bar")).WillOnce(Return(1));
+
+  // 3. Exercise code that uses std::function.
+  Foo(mock_function.AsStdFunction());
+  // Foo's signature can be either of:
+  // void Foo(const std::function<int(string)>& fun);
+  // void Foo(std::function<int(string)> fun);
+
+  // 4. All expectations will be verified when mock_function
+  //     goes out of scope and is destroyed.
+}
+```
+
+Remember that function objects created with `AsStdFunction()` are just
+forwarders. If you create multiple of them, they will share the same set of
+expectations.
+
+Although `std::function` supports unlimited number of arguments, `MockFunction`
+implementation is limited to ten. If you ever hit that limit... well, your
+callback has bigger problems than being mockable. :-)
diff --git a/leveldb_base/third_party/googletest/docs/gmock_faq.md b/leveldb_base/third_party/googletest/docs/gmock_faq.md
new file mode 100644
index 0000000..09623b4
--- /dev/null
+++ b/leveldb_base/third_party/googletest/docs/gmock_faq.md
@@ -0,0 +1,390 @@
+# Legacy gMock FAQ
+
+### When I call a method on my mock object, the method for the real object is invoked instead. What's the problem?
+
+In order for a method to be mocked, it must be *virtual*, unless you use the
+[high-perf dependency injection technique](gmock_cook_book.md#MockingNonVirtualMethods).
+
+### Can I mock a variadic function?
+
+You cannot mock a variadic function (i.e. a function taking ellipsis (`...`)
+arguments) directly in gMock.
+
+The problem is that in general, there is *no way* for a mock object to know how
+many arguments are passed to the variadic method, and what the arguments' types
+are. Only the *author of the base class* knows the protocol, and we cannot look
+into his or her head.
+
+Therefore, to mock such a function, the *user* must teach the mock object how to
+figure out the number of arguments and their types. One way to do it is to
+provide overloaded versions of the function.
+
+Ellipsis arguments are inherited from C and not really a C++ feature. They are
+unsafe to use and don't work with arguments that have constructors or
+destructors. Therefore we recommend to avoid them in C++ as much as possible.
+
+### MSVC gives me warning C4301 or C4373 when I define a mock method with a const parameter. Why?
+
+If you compile this using Microsoft Visual C++ 2005 SP1:
+
+```cpp
+class Foo {
+  ...
+  virtual void Bar(const int i) = 0;
+};
+
+class MockFoo : public Foo {
+  ...
+  MOCK_METHOD(void, Bar, (const int i), (override));
+};
+```
+
+You may get the following warning:
+
+```shell
+warning C4301: 'MockFoo::Bar': overriding virtual function only differs from 'Foo::Bar' by const/volatile qualifier
+```
+
+This is a MSVC bug. The same code compiles fine with gcc, for example. If you
+use Visual C++ 2008 SP1, you would get the warning:
+
+```shell
+warning C4373: 'MockFoo::Bar': virtual function overrides 'Foo::Bar', previous versions of the compiler did not override when parameters only differed by const/volatile qualifiers
+```
+
+In C++, if you *declare* a function with a `const` parameter, the `const`
+modifier is ignored. Therefore, the `Foo` base class above is equivalent to:
+
+```cpp
+class Foo {
+  ...
+  virtual void Bar(int i) = 0;  // int or const int?  Makes no difference.
+};
+```
+
+In fact, you can *declare* `Bar()` with an `int` parameter, and define it with a
+`const int` parameter. The compiler will still match them up.
+
+Since making a parameter `const` is meaningless in the method declaration, we
+recommend to remove it in both `Foo` and `MockFoo`. That should workaround the
+VC bug.
+
+Note that we are talking about the *top-level* `const` modifier here. If the
+function parameter is passed by pointer or reference, declaring the pointee or
+referee as `const` is still meaningful. For example, the following two
+declarations are *not* equivalent:
+
+```cpp
+void Bar(int* p);         // Neither p nor *p is const.
+void Bar(const int* p);  // p is not const, but *p is.
+```
+
+### I can't figure out why gMock thinks my expectations are not satisfied. What should I do?
+
+You might want to run your test with `--gmock_verbose=info`. This flag lets
+gMock print a trace of every mock function call it receives. By studying the
+trace, you'll gain insights on why the expectations you set are not met.
+
+If you see the message "The mock function has no default action set, and its
+return type has no default value set.", then try
+[adding a default action](gmock_for_dummies.md#DefaultValue). Due to a known
+issue, unexpected calls on mocks without default actions don't print out a
+detailed comparison between the actual arguments and the expected arguments.
+
+### My program crashed and `ScopedMockLog` spit out tons of messages. Is it a gMock bug?
+
+gMock and `ScopedMockLog` are likely doing the right thing here.
+
+When a test crashes, the failure signal handler will try to log a lot of
+information (the stack trace, and the address map, for example). The messages
+are compounded if you have many threads with depth stacks. When `ScopedMockLog`
+intercepts these messages and finds that they don't match any expectations, it
+prints an error for each of them.
+
+You can learn to ignore the errors, or you can rewrite your expectations to make
+your test more robust, for example, by adding something like:
+
+```cpp
+using ::testing::AnyNumber;
+using ::testing::Not;
+...
+  // Ignores any log not done by us.
+  EXPECT_CALL(log, Log(_, Not(EndsWith("/my_file.cc")), _))
+      .Times(AnyNumber());
+```
+
+### How can I assert that a function is NEVER called?
+
+```cpp
+using ::testing::_;
+...
+  EXPECT_CALL(foo, Bar(_))
+      .Times(0);
+```
+
+### I have a failed test where gMock tells me TWICE that a particular expectation is not satisfied. Isn't this redundant?
+
+When gMock detects a failure, it prints relevant information (the mock function
+arguments, the state of relevant expectations, and etc) to help the user debug.
+If another failure is detected, gMock will do the same, including printing the
+state of relevant expectations.
+
+Sometimes an expectation's state didn't change between two failures, and you'll
+see the same description of the state twice. They are however *not* redundant,
+as they refer to *different points in time*. The fact they are the same *is*
+interesting information.
+
+### I get a heapcheck failure when using a mock object, but using a real object is fine. What can be wrong?
+
+Does the class (hopefully a pure interface) you are mocking have a virtual
+destructor?
+
+Whenever you derive from a base class, make sure its destructor is virtual.
+Otherwise Bad Things will happen. Consider the following code:
+
+```cpp
+class Base {
+ public:
+  // Not virtual, but should be.
+  ~Base() { ... }
+  ...
+};
+
+class Derived : public Base {
+ public:
+  ...
+ private:
+  std::string value_;
+};
+
+...
+  Base* p = new Derived;
+  ...
+  delete p;  // Surprise! ~Base() will be called, but ~Derived() will not
+                 // - value_ is leaked.
+```
+
+By changing `~Base()` to virtual, `~Derived()` will be correctly called when
+`delete p` is executed, and the heap checker will be happy.
+
+### The "newer expectations override older ones" rule makes writing expectations awkward. Why does gMock do that?
+
+When people complain about this, often they are referring to code like:
+
+```cpp
+using ::testing::Return;
+...
+  // foo.Bar() should be called twice, return 1 the first time, and return
+  // 2 the second time.  However, I have to write the expectations in the
+  // reverse order.  This sucks big time!!!
+  EXPECT_CALL(foo, Bar())
+      .WillOnce(Return(2))
+      .RetiresOnSaturation();
+  EXPECT_CALL(foo, Bar())
+      .WillOnce(Return(1))
+      .RetiresOnSaturation();
+```
+
+The problem, is that they didn't pick the **best** way to express the test's
+intent.
+
+By default, expectations don't have to be matched in *any* particular order. If
+you want them to match in a certain order, you need to be explicit. This is
+gMock's (and jMock's) fundamental philosophy: it's easy to accidentally
+over-specify your tests, and we want to make it harder to do so.
+
+There are two better ways to write the test spec. You could either put the
+expectations in sequence:
+
+```cpp
+using ::testing::Return;
+...
+  // foo.Bar() should be called twice, return 1 the first time, and return
+  // 2 the second time.  Using a sequence, we can write the expectations
+  // in their natural order.
+  {
+    InSequence s;
+    EXPECT_CALL(foo, Bar())
+        .WillOnce(Return(1))
+        .RetiresOnSaturation();
+    EXPECT_CALL(foo, Bar())
+        .WillOnce(Return(2))
+        .RetiresOnSaturation();
+  }
+```
+
+or you can put the sequence of actions in the same expectation:
+
+```cpp
+using ::testing::Return;
+...
+  // foo.Bar() should be called twice, return 1 the first time, and return
+  // 2 the second time.
+  EXPECT_CALL(foo, Bar())
+      .WillOnce(Return(1))
+      .WillOnce(Return(2))
+      .RetiresOnSaturation();
+```
+
+Back to the original questions: why does gMock search the expectations (and
+`ON_CALL`s) from back to front? Because this allows a user to set up a mock's
+behavior for the common case early (e.g. in the mock's constructor or the test
+fixture's set-up phase) and customize it with more specific rules later. If
+gMock searches from front to back, this very useful pattern won't be possible.
+
+### gMock prints a warning when a function without EXPECT_CALL is called, even if I have set its behavior using ON_CALL. Would it be reasonable not to show the warning in this case?
+
+When choosing between being neat and being safe, we lean toward the latter. So
+the answer is that we think it's better to show the warning.
+
+Often people write `ON_CALL`s in the mock object's constructor or `SetUp()`, as
+the default behavior rarely changes from test to test. Then in the test body
+they set the expectations, which are often different for each test. Having an
+`ON_CALL` in the set-up part of a test doesn't mean that the calls are expected.
+If there's no `EXPECT_CALL` and the method is called, it's possibly an error. If
+we quietly let the call go through without notifying the user, bugs may creep in
+unnoticed.
+
+If, however, you are sure that the calls are OK, you can write
+
+```cpp
+using ::testing::_;
+...
+  EXPECT_CALL(foo, Bar(_))
+      .WillRepeatedly(...);
+```
+
+instead of
+
+```cpp
+using ::testing::_;
+...
+  ON_CALL(foo, Bar(_))
+      .WillByDefault(...);
+```
+
+This tells gMock that you do expect the calls and no warning should be printed.
+
+Also, you can control the verbosity by specifying `--gmock_verbose=error`. Other
+values are `info` and `warning`. If you find the output too noisy when
+debugging, just choose a less verbose level.
+
+### How can I delete the mock function's argument in an action?
+
+If your mock function takes a pointer argument and you want to delete that
+argument, you can use testing::DeleteArg<N>() to delete the N'th (zero-indexed)
+argument:
+
+```cpp
+using ::testing::_;
+  ...
+  MOCK_METHOD(void, Bar, (X* x, const Y& y));
+  ...
+  EXPECT_CALL(mock_foo_, Bar(_, _))
+      .WillOnce(testing::DeleteArg<0>()));
+```
+
+### How can I perform an arbitrary action on a mock function's argument?
+
+If you find yourself needing to perform some action that's not supported by
+gMock directly, remember that you can define your own actions using
+[`MakeAction()`](#NewMonoActions) or
+[`MakePolymorphicAction()`](#NewPolyActions), or you can write a stub function
+and invoke it using [`Invoke()`](#FunctionsAsActions).
+
+```cpp
+using ::testing::_;
+using ::testing::Invoke;
+  ...
+  MOCK_METHOD(void, Bar, (X* p));
+  ...
+  EXPECT_CALL(mock_foo_, Bar(_))
+      .WillOnce(Invoke(MyAction(...)));
+```
+
+### My code calls a static/global function. Can I mock it?
+
+You can, but you need to make some changes.
+
+In general, if you find yourself needing to mock a static function, it's a sign
+that your modules are too tightly coupled (and less flexible, less reusable,
+less testable, etc). You are probably better off defining a small interface and
+call the function through that interface, which then can be easily mocked. It's
+a bit of work initially, but usually pays for itself quickly.
+
+This Google Testing Blog
+[post](https://testing.googleblog.com/2008/06/defeat-static-cling.html) says it
+excellently. Check it out.
+
+### My mock object needs to do complex stuff. It's a lot of pain to specify the actions. gMock sucks!
+
+I know it's not a question, but you get an answer for free any way. :-)
+
+With gMock, you can create mocks in C++ easily. And people might be tempted to
+use them everywhere. Sometimes they work great, and sometimes you may find them,
+well, a pain to use. So, what's wrong in the latter case?
+
+When you write a test without using mocks, you exercise the code and assert that
+it returns the correct value or that the system is in an expected state. This is
+sometimes called "state-based testing".
+
+Mocks are great for what some call "interaction-based" testing: instead of
+checking the system state at the very end, mock objects verify that they are
+invoked the right way and report an error as soon as it arises, giving you a
+handle on the precise context in which the error was triggered. This is often
+more effective and economical to do than state-based testing.
+
+If you are doing state-based testing and using a test double just to simulate
+the real object, you are probably better off using a fake. Using a mock in this
+case causes pain, as it's not a strong point for mocks to perform complex
+actions. If you experience this and think that mocks suck, you are just not
+using the right tool for your problem. Or, you might be trying to solve the
+wrong problem. :-)
+
+### I got a warning "Uninteresting function call encountered - default action taken.." Should I panic?
+
+By all means, NO! It's just an FYI. :-)
+
+What it means is that you have a mock function, you haven't set any expectations
+on it (by gMock's rule this means that you are not interested in calls to this
+function and therefore it can be called any number of times), and it is called.
+That's OK - you didn't say it's not OK to call the function!
+
+What if you actually meant to disallow this function to be called, but forgot to
+write `EXPECT_CALL(foo, Bar()).Times(0)`? While one can argue that it's the
+user's fault, gMock tries to be nice and prints you a note.
+
+So, when you see the message and believe that there shouldn't be any
+uninteresting calls, you should investigate what's going on. To make your life
+easier, gMock dumps the stack trace when an uninteresting call is encountered.
+From that you can figure out which mock function it is, and how it is called.
+
+### I want to define a custom action. Should I use Invoke() or implement the ActionInterface interface?
+
+Either way is fine - you want to choose the one that's more convenient for your
+circumstance.
+
+Usually, if your action is for a particular function type, defining it using
+`Invoke()` should be easier; if your action can be used in functions of
+different types (e.g. if you are defining `Return(*value*)`),
+`MakePolymorphicAction()` is easiest. Sometimes you want precise control on what
+types of functions the action can be used in, and implementing `ActionInterface`
+is the way to go here. See the implementation of `Return()` in
+`testing/base/public/gmock-actions.h` for an example.
+
+### I use SetArgPointee() in WillOnce(), but gcc complains about "conflicting return type specified". What does it mean?
+
+You got this error as gMock has no idea what value it should return when the
+mock method is called. `SetArgPointee()` says what the side effect is, but
+doesn't say what the return value should be. You need `DoAll()` to chain a
+`SetArgPointee()` with a `Return()` that provides a value appropriate to the API
+being mocked.
+
+See this [recipe](gmock_cook_book.md#mocking-side-effects) for more details and
+an example.
+
+### I have a huge mock class, and Microsoft Visual C++ runs out of memory when compiling it. What can I do?
+
+We've noticed that when the `/clr` compiler flag is used, Visual C++ uses 5~6
+times as much memory when compiling a mock class. We suggest to avoid `/clr`
+when compiling native C++ mocks.
diff --git a/leveldb_base/third_party/googletest/docs/gmock_for_dummies.md b/leveldb_base/third_party/googletest/docs/gmock_for_dummies.md
new file mode 100644
index 0000000..370f17e
--- /dev/null
+++ b/leveldb_base/third_party/googletest/docs/gmock_for_dummies.md
@@ -0,0 +1,699 @@
+# gMock for Dummies
+
+## What Is gMock?
+
+When you write a prototype or test, often it's not feasible or wise to rely on
+real objects entirely. A **mock object** implements the same interface as a real
+object (so it can be used as one), but lets you specify at run time how it will
+be used and what it should do (which methods will be called? in which order? how
+many times? with what arguments? what will they return? etc).
+
+It is easy to confuse the term *fake objects* with mock objects. Fakes and mocks
+actually mean very different things in the Test-Driven Development (TDD)
+community:
+
+*   **Fake** objects have working implementations, but usually take some
+    shortcut (perhaps to make the operations less expensive), which makes them
+    not suitable for production. An in-memory file system would be an example of
+    a fake.
+*   **Mocks** are objects pre-programmed with *expectations*, which form a
+    specification of the calls they are expected to receive.
+
+If all this seems too abstract for you, don't worry - the most important thing
+to remember is that a mock allows you to check the *interaction* between itself
+and code that uses it. The difference between fakes and mocks shall become much
+clearer once you start to use mocks.
+
+**gMock** is a library (sometimes we also call it a "framework" to make it sound
+cool) for creating mock classes and using them. It does to C++ what
+jMock/EasyMock does to Java (well, more or less).
+
+When using gMock,
+
+1.  first, you use some simple macros to describe the interface you want to
+    mock, and they will expand to the implementation of your mock class;
+2.  next, you create some mock objects and specify its expectations and behavior
+    using an intuitive syntax;
+3.  then you exercise code that uses the mock objects. gMock will catch any
+    violation to the expectations as soon as it arises.
+
+## Why gMock?
+
+While mock objects help you remove unnecessary dependencies in tests and make
+them fast and reliable, using mocks manually in C++ is *hard*:
+
+*   Someone has to implement the mocks. The job is usually tedious and
+    error-prone. No wonder people go great distance to avoid it.
+*   The quality of those manually written mocks is a bit, uh, unpredictable. You
+    may see some really polished ones, but you may also see some that were
+    hacked up in a hurry and have all sorts of ad hoc restrictions.
+*   The knowledge you gained from using one mock doesn't transfer to the next
+    one.
+
+In contrast, Java and Python programmers have some fine mock frameworks (jMock,
+EasyMock, etc), which automate the creation of mocks. As a result, mocking is a
+proven effective technique and widely adopted practice in those communities.
+Having the right tool absolutely makes the difference.
+
+gMock was built to help C++ programmers. It was inspired by jMock and EasyMock,
+but designed with C++'s specifics in mind. It is your friend if any of the
+following problems is bothering you:
+
+*   You are stuck with a sub-optimal design and wish you had done more
+    prototyping before it was too late, but prototyping in C++ is by no means
+    "rapid".
+*   Your tests are slow as they depend on too many libraries or use expensive
+    resources (e.g. a database).
+*   Your tests are brittle as some resources they use are unreliable (e.g. the
+    network).
+*   You want to test how your code handles a failure (e.g. a file checksum
+    error), but it's not easy to cause one.
+*   You need to make sure that your module interacts with other modules in the
+    right way, but it's hard to observe the interaction; therefore you resort to
+    observing the side effects at the end of the action, but it's awkward at
+    best.
+*   You want to "mock out" your dependencies, except that they don't have mock
+    implementations yet; and, frankly, you aren't thrilled by some of those
+    hand-written mocks.
+
+We encourage you to use gMock as
+
+*   a *design* tool, for it lets you experiment with your interface design early
+    and often. More iterations lead to better designs!
+*   a *testing* tool to cut your tests' outbound dependencies and probe the
+    interaction between your module and its collaborators.
+
+## Getting Started
+
+gMock is bundled with googletest.
+
+## A Case for Mock Turtles
+
+Let's look at an example. Suppose you are developing a graphics program that
+relies on a [LOGO](http://en.wikipedia.org/wiki/Logo_programming_language)-like
+API for drawing. How would you test that it does the right thing? Well, you can
+run it and compare the screen with a golden screen snapshot, but let's admit it:
+tests like this are expensive to run and fragile (What if you just upgraded to a
+shiny new graphics card that has better anti-aliasing? Suddenly you have to
+update all your golden images.). It would be too painful if all your tests are
+like this. Fortunately, you learned about
+[Dependency Injection](http://en.wikipedia.org/wiki/Dependency_injection) and know the right thing
+to do: instead of having your application talk to the system API directly, wrap
+the API in an interface (say, `Turtle`) and code to that interface:
+
+```cpp
+class Turtle {
+  ...
+  virtual ~Turtle() {}
+  virtual void PenUp() = 0;
+  virtual void PenDown() = 0;
+  virtual void Forward(int distance) = 0;
+  virtual void Turn(int degrees) = 0;
+  virtual void GoTo(int x, int y) = 0;
+  virtual int GetX() const = 0;
+  virtual int GetY() const = 0;
+};
+```
+
+(Note that the destructor of `Turtle` **must** be virtual, as is the case for
+**all** classes you intend to inherit from - otherwise the destructor of the
+derived class will not be called when you delete an object through a base
+pointer, and you'll get corrupted program states like memory leaks.)
+
+You can control whether the turtle's movement will leave a trace using `PenUp()`
+and `PenDown()`, and control its movement using `Forward()`, `Turn()`, and
+`GoTo()`. Finally, `GetX()` and `GetY()` tell you the current position of the
+turtle.
+
+Your program will normally use a real implementation of this interface. In
+tests, you can use a mock implementation instead. This allows you to easily
+check what drawing primitives your program is calling, with what arguments, and
+in which order. Tests written this way are much more robust (they won't break
+because your new machine does anti-aliasing differently), easier to read and
+maintain (the intent of a test is expressed in the code, not in some binary
+images), and run *much, much faster*.
+
+## Writing the Mock Class
+
+If you are lucky, the mocks you need to use have already been implemented by
+some nice people. If, however, you find yourself in the position to write a mock
+class, relax - gMock turns this task into a fun game! (Well, almost.)
+
+### How to Define It
+
+Using the `Turtle` interface as example, here are the simple steps you need to
+follow:
+
+*   Derive a class `MockTurtle` from `Turtle`.
+*   Take a *virtual* function of `Turtle` (while it's possible to
+    [mock non-virtual methods using templates](gmock_cook_book.md#MockingNonVirtualMethods),
+    it's much more involved).
+*   In the `public:` section of the child class, write `MOCK_METHOD();`
+*   Now comes the fun part: you take the function signature, cut-and-paste it
+    into the macro, and add two commas - one between the return type and the
+    name, another between the name and the argument list.
+*   If you're mocking a const method, add a 4th parameter containing `(const)`
+    (the parentheses are required).
+*   Since you're overriding a virtual method, we suggest adding the `override`
+    keyword. For const methods the 4th parameter becomes `(const, override)`,
+    for non-const methods just `(override)`. This isn't mandatory.
+*   Repeat until all virtual functions you want to mock are done. (It goes
+    without saying that *all* pure virtual methods in your abstract class must
+    be either mocked or overridden.)
+
+After the process, you should have something like:
+
+```cpp
+#include "gmock/gmock.h"  // Brings in gMock.
+
+class MockTurtle : public Turtle {
+ public:
+  ...
+  MOCK_METHOD(void, PenUp, (), (override));
+  MOCK_METHOD(void, PenDown, (), (override));
+  MOCK_METHOD(void, Forward, (int distance), (override));
+  MOCK_METHOD(void, Turn, (int degrees), (override));
+  MOCK_METHOD(void, GoTo, (int x, int y), (override));
+  MOCK_METHOD(int, GetX, (), (const, override));
+  MOCK_METHOD(int, GetY, (), (const, override));
+};
+```
+
+You don't need to define these mock methods somewhere else - the `MOCK_METHOD`
+macro will generate the definitions for you. It's that simple!
+
+### Where to Put It
+
+When you define a mock class, you need to decide where to put its definition.
+Some people put it in a `_test.cc`. This is fine when the interface being mocked
+(say, `Foo`) is owned by the same person or team. Otherwise, when the owner of
+`Foo` changes it, your test could break. (You can't really expect `Foo`'s
+maintainer to fix every test that uses `Foo`, can you?)
+
+So, the rule of thumb is: if you need to mock `Foo` and it's owned by others,
+define the mock class in `Foo`'s package (better, in a `testing` sub-package
+such that you can clearly separate production code and testing utilities), put
+it in a `.h` and a `cc_library`. Then everyone can reference them from their
+tests. If `Foo` ever changes, there is only one copy of `MockFoo` to change, and
+only tests that depend on the changed methods need to be fixed.
+
+Another way to do it: you can introduce a thin layer `FooAdaptor` on top of
+`Foo` and code to this new interface. Since you own `FooAdaptor`, you can absorb
+changes in `Foo` much more easily. While this is more work initially, carefully
+choosing the adaptor interface can make your code easier to write and more
+readable (a net win in the long run), as you can choose `FooAdaptor` to fit your
+specific domain much better than `Foo` does.
+
+## Using Mocks in Tests
+
+Once you have a mock class, using it is easy. The typical work flow is:
+
+1.  Import the gMock names from the `testing` namespace such that you can use
+    them unqualified (You only have to do it once per file). Remember that
+    namespaces are a good idea.
+2.  Create some mock objects.
+3.  Specify your expectations on them (How many times will a method be called?
+    With what arguments? What should it do? etc.).
+4.  Exercise some code that uses the mocks; optionally, check the result using
+    googletest assertions. If a mock method is called more than expected or with
+    wrong arguments, you'll get an error immediately.
+5.  When a mock is destructed, gMock will automatically check whether all
+    expectations on it have been satisfied.
+
+Here's an example:
+
+```cpp
+#include "path/to/mock-turtle.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+using ::testing::AtLeast;                         // #1
+
+TEST(PainterTest, CanDrawSomething) {
+  MockTurtle turtle;                              // #2
+  EXPECT_CALL(turtle, PenDown())                  // #3
+      .Times(AtLeast(1));
+
+  Painter painter(&turtle);                       // #4
+
+  EXPECT_TRUE(painter.DrawCircle(0, 0, 10));      // #5
+}
+```
+
+As you might have guessed, this test checks that `PenDown()` is called at least
+once. If the `painter` object didn't call this method, your test will fail with
+a message like this:
+
+```text
+path/to/my_test.cc:119: Failure
+Actual function call count doesn't match this expectation:
+Actually: never called;
+Expected: called at least once.
+Stack trace:
+...
+```
+
+**Tip 1:** If you run the test from an Emacs buffer, you can hit `<Enter>` on
+the line number to jump right to the failed expectation.
+
+**Tip 2:** If your mock objects are never deleted, the final verification won't
+happen. Therefore it's a good idea to turn on the heap checker in your tests
+when you allocate mocks on the heap. You get that automatically if you use the
+`gtest_main` library already.
+
+**Important note:** gMock requires expectations to be set **before** the mock
+functions are called, otherwise the behavior is **undefined**. In particular,
+you mustn't interleave `EXPECT_CALL()s` and calls to the mock functions.
+
+This means `EXPECT_CALL()` should be read as expecting that a call will occur
+*in the future*, not that a call has occurred. Why does gMock work like that?
+Well, specifying the expectation beforehand allows gMock to report a violation
+as soon as it rises, when the context (stack trace, etc) is still available.
+This makes debugging much easier.
+
+Admittedly, this test is contrived and doesn't do much. You can easily achieve
+the same effect without using gMock. However, as we shall reveal soon, gMock
+allows you to do *so much more* with the mocks.
+
+## Setting Expectations
+
+The key to using a mock object successfully is to set the *right expectations*
+on it. If you set the expectations too strict, your test will fail as the result
+of unrelated changes. If you set them too loose, bugs can slip through. You want
+to do it just right such that your test can catch exactly the kind of bugs you
+intend it to catch. gMock provides the necessary means for you to do it "just
+right."
+
+### General Syntax
+
+In gMock we use the `EXPECT_CALL()` macro to set an expectation on a mock
+method. The general syntax is:
+
+```cpp
+EXPECT_CALL(mock_object, method(matchers))
+    .Times(cardinality)
+    .WillOnce(action)
+    .WillRepeatedly(action);
+```
+
+The macro has two arguments: first the mock object, and then the method and its
+arguments. Note that the two are separated by a comma (`,`), not a period (`.`).
+(Why using a comma? The answer is that it was necessary for technical reasons.)
+If the method is not overloaded, the macro can also be called without matchers:
+
+```cpp
+EXPECT_CALL(mock_object, non-overloaded-method)
+    .Times(cardinality)
+    .WillOnce(action)
+    .WillRepeatedly(action);
+```
+
+This syntax allows the test writer to specify "called with any arguments"
+without explicitly specifying the number or types of arguments. To avoid
+unintended ambiguity, this syntax may only be used for methods that are not
+overloaded.
+
+Either form of the macro can be followed by some optional *clauses* that provide
+more information about the expectation. We'll discuss how each clause works in
+the coming sections.
+
+This syntax is designed to make an expectation read like English. For example,
+you can probably guess that
+
+```cpp
+using ::testing::Return;
+...
+EXPECT_CALL(turtle, GetX())
+    .Times(5)
+    .WillOnce(Return(100))
+    .WillOnce(Return(150))
+    .WillRepeatedly(Return(200));
+```
+
+says that the `turtle` object's `GetX()` method will be called five times, it
+will return 100 the first time, 150 the second time, and then 200 every time.
+Some people like to call this style of syntax a Domain-Specific Language (DSL).
+
+{: .callout .note}
+**Note:** Why do we use a macro to do this? Well it serves two purposes: first
+it makes expectations easily identifiable (either by `grep` or by a human
+reader), and second it allows gMock to include the source file location of a
+failed expectation in messages, making debugging easier.
+
+### Matchers: What Arguments Do We Expect?
+
+When a mock function takes arguments, we may specify what arguments we are
+expecting, for example:
+
+```cpp
+// Expects the turtle to move forward by 100 units.
+EXPECT_CALL(turtle, Forward(100));
+```
+
+Oftentimes you do not want to be too specific. Remember that talk about tests
+being too rigid? Over specification leads to brittle tests and obscures the
+intent of tests. Therefore we encourage you to specify only what's necessary—no
+more, no less. If you aren't interested in the value of an argument, write `_`
+as the argument, which means "anything goes":
+
+```cpp
+using ::testing::_;
+...
+// Expects that the turtle jumps to somewhere on the x=50 line.
+EXPECT_CALL(turtle, GoTo(50, _));
+```
+
+`_` is an instance of what we call **matchers**. A matcher is like a predicate
+and can test whether an argument is what we'd expect. You can use a matcher
+inside `EXPECT_CALL()` wherever a function argument is expected. `_` is a
+convenient way of saying "any value".
+
+In the above examples, `100` and `50` are also matchers; implicitly, they are
+the same as `Eq(100)` and `Eq(50)`, which specify that the argument must be
+equal (using `operator==`) to the matcher argument. There are many
+[built-in matchers](reference/matchers.md) for common types (as well as
+[custom matchers](gmock_cook_book.md#NewMatchers)); for example:
+
+```cpp
+using ::testing::Ge;
+...
+// Expects the turtle moves forward by at least 100.
+EXPECT_CALL(turtle, Forward(Ge(100)));
+```
+
+If you don't care about *any* arguments, rather than specify `_` for each of
+them you may instead omit the parameter list:
+
+```cpp
+// Expects the turtle to move forward.
+EXPECT_CALL(turtle, Forward);
+// Expects the turtle to jump somewhere.
+EXPECT_CALL(turtle, GoTo);
+```
+
+This works for all non-overloaded methods; if a method is overloaded, you need
+to help gMock resolve which overload is expected by specifying the number of
+arguments and possibly also the
+[types of the arguments](gmock_cook_book.md#SelectOverload).
+
+### Cardinalities: How Many Times Will It Be Called?
+
+The first clause we can specify following an `EXPECT_CALL()` is `Times()`. We
+call its argument a **cardinality** as it tells *how many times* the call should
+occur. It allows us to repeat an expectation many times without actually writing
+it as many times. More importantly, a cardinality can be "fuzzy", just like a
+matcher can be. This allows a user to express the intent of a test exactly.
+
+An interesting special case is when we say `Times(0)`. You may have guessed - it
+means that the function shouldn't be called with the given arguments at all, and
+gMock will report a googletest failure whenever the function is (wrongfully)
+called.
+
+We've seen `AtLeast(n)` as an example of fuzzy cardinalities earlier. For the
+list of built-in cardinalities you can use, see
+[here](gmock_cheat_sheet.md#CardinalityList).
+
+The `Times()` clause can be omitted. **If you omit `Times()`, gMock will infer
+the cardinality for you.** The rules are easy to remember:
+
+*   If **neither** `WillOnce()` **nor** `WillRepeatedly()` is in the
+    `EXPECT_CALL()`, the inferred cardinality is `Times(1)`.
+*   If there are *n* `WillOnce()`'s but **no** `WillRepeatedly()`, where *n* >=
+    1, the cardinality is `Times(n)`.
+*   If there are *n* `WillOnce()`'s and **one** `WillRepeatedly()`, where *n* >=
+    0, the cardinality is `Times(AtLeast(n))`.
+
+**Quick quiz:** what do you think will happen if a function is expected to be
+called twice but actually called four times?
+
+### Actions: What Should It Do?
+
+Remember that a mock object doesn't really have a working implementation? We as
+users have to tell it what to do when a method is invoked. This is easy in
+gMock.
+
+First, if the return type of a mock function is a built-in type or a pointer,
+the function has a **default action** (a `void` function will just return, a
+`bool` function will return `false`, and other functions will return 0). In
+addition, in C++ 11 and above, a mock function whose return type is
+default-constructible (i.e. has a default constructor) has a default action of
+returning a default-constructed value. If you don't say anything, this behavior
+will be used.
+
+Second, if a mock function doesn't have a default action, or the default action
+doesn't suit you, you can specify the action to be taken each time the
+expectation matches using a series of `WillOnce()` clauses followed by an
+optional `WillRepeatedly()`. For example,
+
+```cpp
+using ::testing::Return;
+...
+EXPECT_CALL(turtle, GetX())
+     .WillOnce(Return(100))
+     .WillOnce(Return(200))
+     .WillOnce(Return(300));
+```
+
+says that `turtle.GetX()` will be called *exactly three times* (gMock inferred
+this from how many `WillOnce()` clauses we've written, since we didn't
+explicitly write `Times()`), and will return 100, 200, and 300 respectively.
+
+```cpp
+using ::testing::Return;
+...
+EXPECT_CALL(turtle, GetY())
+     .WillOnce(Return(100))
+     .WillOnce(Return(200))
+     .WillRepeatedly(Return(300));
+```
+
+says that `turtle.GetY()` will be called *at least twice* (gMock knows this as
+we've written two `WillOnce()` clauses and a `WillRepeatedly()` while having no
+explicit `Times()`), will return 100 and 200 respectively the first two times,
+and 300 from the third time on.
+
+Of course, if you explicitly write a `Times()`, gMock will not try to infer the
+cardinality itself. What if the number you specified is larger than there are
+`WillOnce()` clauses? Well, after all `WillOnce()`s are used up, gMock will do
+the *default* action for the function every time (unless, of course, you have a
+`WillRepeatedly()`.).
+
+What can we do inside `WillOnce()` besides `Return()`? You can return a
+reference using `ReturnRef(*variable*)`, or invoke a pre-defined function, among
+[others](gmock_cook_book.md#using-actions).
+
+**Important note:** The `EXPECT_CALL()` statement evaluates the action clause
+only once, even though the action may be performed many times. Therefore you
+must be careful about side effects. The following may not do what you want:
+
+```cpp
+using ::testing::Return;
+...
+int n = 100;
+EXPECT_CALL(turtle, GetX())
+    .Times(4)
+    .WillRepeatedly(Return(n++));
+```
+
+Instead of returning 100, 101, 102, ..., consecutively, this mock function will
+always return 100 as `n++` is only evaluated once. Similarly, `Return(new Foo)`
+will create a new `Foo` object when the `EXPECT_CALL()` is executed, and will
+return the same pointer every time. If you want the side effect to happen every
+time, you need to define a custom action, which we'll teach in the
+[cook book](gmock_cook_book.md).
+
+Time for another quiz! What do you think the following means?
+
+```cpp
+using ::testing::Return;
+...
+EXPECT_CALL(turtle, GetY())
+    .Times(4)
+    .WillOnce(Return(100));
+```
+
+Obviously `turtle.GetY()` is expected to be called four times. But if you think
+it will return 100 every time, think twice! Remember that one `WillOnce()`
+clause will be consumed each time the function is invoked and the default action
+will be taken afterwards. So the right answer is that `turtle.GetY()` will
+return 100 the first time, but **return 0 from the second time on**, as
+returning 0 is the default action for `int` functions.
+
+### Using Multiple Expectations {#MultiExpectations}
+
+So far we've only shown examples where you have a single expectation. More
+realistically, you'll specify expectations on multiple mock methods which may be
+from multiple mock objects.
+
+By default, when a mock method is invoked, gMock will search the expectations in
+the **reverse order** they are defined, and stop when an active expectation that
+matches the arguments is found (you can think of it as "newer rules override
+older ones."). If the matching expectation cannot take any more calls, you will
+get an upper-bound-violated failure. Here's an example:
+
+```cpp
+using ::testing::_;
+...
+EXPECT_CALL(turtle, Forward(_));  // #1
+EXPECT_CALL(turtle, Forward(10))  // #2
+    .Times(2);
+```
+
+If `Forward(10)` is called three times in a row, the third time it will be an
+error, as the last matching expectation (#2) has been saturated. If, however,
+the third `Forward(10)` call is replaced by `Forward(20)`, then it would be OK,
+as now #1 will be the matching expectation.
+
+{: .callout .note}
+**Note:** Why does gMock search for a match in the *reverse* order of the
+expectations? The reason is that this allows a user to set up the default
+expectations in a mock object's constructor or the test fixture's set-up phase
+and then customize the mock by writing more specific expectations in the test
+body. So, if you have two expectations on the same method, you want to put the
+one with more specific matchers **after** the other, or the more specific rule
+would be shadowed by the more general one that comes after it.
+
+{: .callout .tip}
+**Tip:** It is very common to start with a catch-all expectation for a method
+and `Times(AnyNumber())` (omitting arguments, or with `_` for all arguments, if
+overloaded). This makes any calls to the method expected. This is not necessary
+for methods that are not mentioned at all (these are "uninteresting"), but is
+useful for methods that have some expectations, but for which other calls are
+ok. See
+[Understanding Uninteresting vs Unexpected Calls](gmock_cook_book.md#uninteresting-vs-unexpected).
+
+### Ordered vs Unordered Calls {#OrderedCalls}
+
+By default, an expectation can match a call even though an earlier expectation
+hasn't been satisfied. In other words, the calls don't have to occur in the
+order the expectations are specified.
+
+Sometimes, you may want all the expected calls to occur in a strict order. To
+say this in gMock is easy:
+
+```cpp
+using ::testing::InSequence;
+...
+TEST(FooTest, DrawsLineSegment) {
+  ...
+  {
+    InSequence seq;
+
+    EXPECT_CALL(turtle, PenDown());
+    EXPECT_CALL(turtle, Forward(100));
+    EXPECT_CALL(turtle, PenUp());
+  }
+  Foo();
+}
+```
+
+By creating an object of type `InSequence`, all expectations in its scope are
+put into a *sequence* and have to occur *sequentially*. Since we are just
+relying on the constructor and destructor of this object to do the actual work,
+its name is really irrelevant.
+
+In this example, we test that `Foo()` calls the three expected functions in the
+order as written. If a call is made out-of-order, it will be an error.
+
+(What if you care about the relative order of some of the calls, but not all of
+them? Can you specify an arbitrary partial order? The answer is ... yes! The
+details can be found [here](gmock_cook_book.md#OrderedCalls).)
+
+### All Expectations Are Sticky (Unless Said Otherwise) {#StickyExpectations}
+
+Now let's do a quick quiz to see how well you can use this mock stuff already.
+How would you test that the turtle is asked to go to the origin *exactly twice*
+(you want to ignore any other instructions it receives)?
+
+After you've come up with your answer, take a look at ours and compare notes
+(solve it yourself first - don't cheat!):
+
+```cpp
+using ::testing::_;
+using ::testing::AnyNumber;
+...
+EXPECT_CALL(turtle, GoTo(_, _))  // #1
+     .Times(AnyNumber());
+EXPECT_CALL(turtle, GoTo(0, 0))  // #2
+     .Times(2);
+```
+
+Suppose `turtle.GoTo(0, 0)` is called three times. In the third time, gMock will
+see that the arguments match expectation #2 (remember that we always pick the
+last matching expectation). Now, since we said that there should be only two
+such calls, gMock will report an error immediately. This is basically what we've
+told you in the [Using Multiple Expectations](#MultiExpectations) section above.
+
+This example shows that **expectations in gMock are "sticky" by default**, in
+the sense that they remain active even after we have reached their invocation
+upper bounds. This is an important rule to remember, as it affects the meaning
+of the spec, and is **different** to how it's done in many other mocking
+frameworks (Why'd we do that? Because we think our rule makes the common cases
+easier to express and understand.).
+
+Simple? Let's see if you've really understood it: what does the following code
+say?
+
+```cpp
+using ::testing::Return;
+...
+for (int i = n; i > 0; i--) {
+  EXPECT_CALL(turtle, GetX())
+      .WillOnce(Return(10*i));
+}
+```
+
+If you think it says that `turtle.GetX()` will be called `n` times and will
+return 10, 20, 30, ..., consecutively, think twice! The problem is that, as we
+said, expectations are sticky. So, the second time `turtle.GetX()` is called,
+the last (latest) `EXPECT_CALL()` statement will match, and will immediately
+lead to an "upper bound violated" error - this piece of code is not very useful!
+
+One correct way of saying that `turtle.GetX()` will return 10, 20, 30, ..., is
+to explicitly say that the expectations are *not* sticky. In other words, they
+should *retire* as soon as they are saturated:
+
+```cpp
+using ::testing::Return;
+...
+for (int i = n; i > 0; i--) {
+  EXPECT_CALL(turtle, GetX())
+      .WillOnce(Return(10*i))
+      .RetiresOnSaturation();
+}
+```
+
+And, there's a better way to do it: in this case, we expect the calls to occur
+in a specific order, and we line up the actions to match the order. Since the
+order is important here, we should make it explicit using a sequence:
+
+```cpp
+using ::testing::InSequence;
+using ::testing::Return;
+...
+{
+  InSequence s;
+
+  for (int i = 1; i <= n; i++) {
+    EXPECT_CALL(turtle, GetX())
+        .WillOnce(Return(10*i))
+        .RetiresOnSaturation();
+  }
+}
+```
+
+By the way, the other situation where an expectation may *not* be sticky is when
+it's in a sequence - as soon as another expectation that comes after it in the
+sequence has been used, it automatically retires (and will never be used to
+match any call).
+
+### Uninteresting Calls
+
+A mock object may have many methods, and not all of them are that interesting.
+For example, in some tests we may not care about how many times `GetX()` and
+`GetY()` get called.
+
+In gMock, if you are not interested in a method, just don't say anything about
+it. If a call to this method occurs, you'll see a warning in the test output,
+but it won't be a failure. This is called "naggy" behavior; to change, see
+[The Nice, the Strict, and the Naggy](gmock_cook_book.md#NiceStrictNaggy).
diff --git a/leveldb_base/third_party/googletest/docs/index.md b/leveldb_base/third_party/googletest/docs/index.md
new file mode 100644
index 0000000..b162c74
--- /dev/null
+++ b/leveldb_base/third_party/googletest/docs/index.md
@@ -0,0 +1,22 @@
+# GoogleTest User's Guide
+
+## Welcome to GoogleTest!
+
+GoogleTest is Google's C++ testing and mocking framework. This user's guide has
+the following contents:
+
+*   [GoogleTest Primer](primer.md) - Teaches you how to write simple tests using
+    GoogleTest. Read this first if you are new to GoogleTest.
+*   [GoogleTest Advanced](advanced.md) - Read this when you've finished the
+    Primer and want to utilize GoogleTest to its full potential.
+*   [GoogleTest Samples](samples.md) - Describes some GoogleTest samples.
+*   [GoogleTest FAQ](faq.md) - Have a question? Want some tips? Check here
+    first.
+*   [Mocking for Dummies](gmock_for_dummies.md) - Teaches you how to create mock
+    objects and use them in tests.
+*   [Mocking Cookbook](gmock_cook_book.md) - Includes tips and approaches to
+    common mocking use cases.
+*   [Mocking Cheat Sheet](gmock_cheat_sheet.md) - A handy reference for
+    matchers, actions, invariants, and more.
+*   [Mocking FAQ](gmock_faq.md) - Contains answers to some mocking-specific
+    questions.
diff --git a/leveldb_base/third_party/googletest/docs/pkgconfig.md b/leveldb_base/third_party/googletest/docs/pkgconfig.md
new file mode 100644
index 0000000..768e9b4
--- /dev/null
+++ b/leveldb_base/third_party/googletest/docs/pkgconfig.md
@@ -0,0 +1,148 @@
+## Using GoogleTest from various build systems
+
+GoogleTest comes with pkg-config files that can be used to determine all
+necessary flags for compiling and linking to GoogleTest (and GoogleMock).
+Pkg-config is a standardised plain-text format containing
+
+*   the includedir (-I) path
+*   necessary macro (-D) definitions
+*   further required flags (-pthread)
+*   the library (-L) path
+*   the library (-l) to link to
+
+All current build systems support pkg-config in one way or another. For all
+examples here we assume you want to compile the sample
+`samples/sample3_unittest.cc`.
+
+### CMake
+
+Using `pkg-config` in CMake is fairly easy:
+
+```cmake
+cmake_minimum_required(VERSION 3.0)
+
+cmake_policy(SET CMP0048 NEW)
+project(my_gtest_pkgconfig VERSION 0.0.1 LANGUAGES CXX)
+
+find_package(PkgConfig)
+pkg_search_module(GTEST REQUIRED gtest_main)
+
+add_executable(testapp samples/sample3_unittest.cc)
+target_link_libraries(testapp ${GTEST_LDFLAGS})
+target_compile_options(testapp PUBLIC ${GTEST_CFLAGS})
+
+include(CTest)
+add_test(first_and_only_test testapp)
+```
+
+It is generally recommended that you use `target_compile_options` + `_CFLAGS`
+over `target_include_directories` + `_INCLUDE_DIRS` as the former includes not
+just -I flags (GoogleTest might require a macro indicating to internal headers
+that all libraries have been compiled with threading enabled. In addition,
+GoogleTest might also require `-pthread` in the compiling step, and as such
+splitting the pkg-config `Cflags` variable into include dirs and macros for
+`target_compile_definitions()` might still miss this). The same recommendation
+goes for using `_LDFLAGS` over the more commonplace `_LIBRARIES`, which happens
+to discard `-L` flags and `-pthread`.
+
+### Help! pkg-config can't find GoogleTest!
+
+Let's say you have a `CMakeLists.txt` along the lines of the one in this
+tutorial and you try to run `cmake`. It is very possible that you get a failure
+along the lines of:
+
+```
+-- Checking for one of the modules 'gtest_main'
+CMake Error at /usr/share/cmake/Modules/FindPkgConfig.cmake:640 (message):
+  None of the required 'gtest_main' found
+```
+
+These failures are common if you installed GoogleTest yourself and have not
+sourced it from a distro or other package manager. If so, you need to tell
+pkg-config where it can find the `.pc` files containing the information. Say you
+installed GoogleTest to `/usr/local`, then it might be that the `.pc` files are
+installed under `/usr/local/lib64/pkgconfig`. If you set
+
+```
+export PKG_CONFIG_PATH=/usr/local/lib64/pkgconfig
+```
+
+pkg-config will also try to look in `PKG_CONFIG_PATH` to find `gtest_main.pc`.
+
+### Using pkg-config in a cross-compilation setting
+
+Pkg-config can be used in a cross-compilation setting too. To do this, let's
+assume the final prefix of the cross-compiled installation will be `/usr`, and
+your sysroot is `/home/MYUSER/sysroot`. Configure and install GTest using
+
+```
+mkdir build && cmake -DCMAKE_INSTALL_PREFIX=/usr ..
+```
+
+Install into the sysroot using `DESTDIR`:
+
+```
+make -j install DESTDIR=/home/MYUSER/sysroot
+```
+
+Before we continue, it is recommended to **always** define the following two
+variables for pkg-config in a cross-compilation setting:
+
+```
+export PKG_CONFIG_ALLOW_SYSTEM_CFLAGS=yes
+export PKG_CONFIG_ALLOW_SYSTEM_LIBS=yes
+```
+
+otherwise `pkg-config` will filter `-I` and `-L` flags against standard prefixes
+such as `/usr` (see https://bugs.freedesktop.org/show_bug.cgi?id=28264#c3 for
+reasons why this stripping needs to occur usually).
+
+If you look at the generated pkg-config file, it will look something like
+
+```
+libdir=/usr/lib64
+includedir=/usr/include
+
+Name: gtest
+Description: GoogleTest (without main() function)
+Version: 1.10.0
+URL: https://github.com/google/googletest
+Libs: -L${libdir} -lgtest -lpthread
+Cflags: -I${includedir} -DGTEST_HAS_PTHREAD=1 -lpthread
+```
+
+Notice that the sysroot is not included in `libdir` and `includedir`! If you try
+to run `pkg-config` with the correct
+`PKG_CONFIG_LIBDIR=/home/MYUSER/sysroot/usr/lib64/pkgconfig` against this `.pc`
+file, you will get
+
+```
+$ pkg-config --cflags gtest
+-DGTEST_HAS_PTHREAD=1 -lpthread -I/usr/include
+$ pkg-config --libs gtest
+-L/usr/lib64 -lgtest -lpthread
+```
+
+which is obviously wrong and points to the `CBUILD` and not `CHOST` root. In
+order to use this in a cross-compilation setting, we need to tell pkg-config to
+inject the actual sysroot into `-I` and `-L` variables. Let us now tell
+pkg-config about the actual sysroot
+
+```
+export PKG_CONFIG_DIR=
+export PKG_CONFIG_SYSROOT_DIR=/home/MYUSER/sysroot
+export PKG_CONFIG_LIBDIR=${PKG_CONFIG_SYSROOT_DIR}/usr/lib64/pkgconfig
+```
+
+and running `pkg-config` again we get
+
+```
+$ pkg-config --cflags gtest
+-DGTEST_HAS_PTHREAD=1 -lpthread -I/home/MYUSER/sysroot/usr/include
+$ pkg-config --libs gtest
+-L/home/MYUSER/sysroot/usr/lib64 -lgtest -lpthread
+```
+
+which contains the correct sysroot now. For a more comprehensive guide to also
+including `${CHOST}` in build system calls, see the excellent tutorial by Diego
+Elio Pettenò: <https://autotools.io/pkgconfig/cross-compiling.html>
diff --git a/leveldb_base/third_party/googletest/docs/platforms.md b/leveldb_base/third_party/googletest/docs/platforms.md
new file mode 100644
index 0000000..eba6ef8
--- /dev/null
+++ b/leveldb_base/third_party/googletest/docs/platforms.md
@@ -0,0 +1,35 @@
+# Supported Platforms
+
+GoogleTest requires a codebase and compiler compliant with the C++11 standard or
+newer.
+
+The GoogleTest code is officially supported on the following platforms.
+Operating systems or tools not listed below are community-supported. For
+community-supported platforms, patches that do not complicate the code may be
+considered.
+
+If you notice any problems on your platform, please file an issue on the
+[GoogleTest GitHub Issue Tracker](https://github.com/google/googletest/issues).
+Pull requests containing fixes are welcome!
+
+### Operating systems
+
+*   Linux
+*   macOS
+*   Windows
+
+### Compilers
+
+*   gcc 5.0+
+*   clang 5.0+
+*   MSVC 2015+
+
+**macOS users:** Xcode 9.3+ provides clang 5.0+.
+
+### Build systems
+
+*   [Bazel](https://bazel.build/)
+*   [CMake](https://cmake.org/)
+
+Bazel is the build system used by the team internally and in tests. CMake is
+supported on a best-effort basis and by the community.
diff --git a/leveldb_base/third_party/googletest/docs/primer.md b/leveldb_base/third_party/googletest/docs/primer.md
new file mode 100644
index 0000000..44a1cb5
--- /dev/null
+++ b/leveldb_base/third_party/googletest/docs/primer.md
@@ -0,0 +1,578 @@
+# Googletest Primer
+
+## Introduction: Why googletest?
+
+*googletest* helps you write better C++ tests.
+
+googletest is a testing framework developed by the Testing Technology team with
+Google's specific requirements and constraints in mind. Whether you work on
+Linux, Windows, or a Mac, if you write C++ code, googletest can help you. And it
+supports *any* kind of tests, not just unit tests.
+
+So what makes a good test, and how does googletest fit in? We believe:
+
+1.  Tests should be *independent* and *repeatable*. It's a pain to debug a test
+    that succeeds or fails as a result of other tests. googletest isolates the
+    tests by running each of them on a different object. When a test fails,
+    googletest allows you to run it in isolation for quick debugging.
+2.  Tests should be well *organized* and reflect the structure of the tested
+    code. googletest groups related tests into test suites that can share data
+    and subroutines. This common pattern is easy to recognize and makes tests
+    easy to maintain. Such consistency is especially helpful when people switch
+    projects and start to work on a new code base.
+3.  Tests should be *portable* and *reusable*. Google has a lot of code that is
+    platform-neutral; its tests should also be platform-neutral. googletest
+    works on different OSes, with different compilers, with or without
+    exceptions, so googletest tests can work with a variety of configurations.
+4.  When tests fail, they should provide as much *information* about the problem
+    as possible. googletest doesn't stop at the first test failure. Instead, it
+    only stops the current test and continues with the next. You can also set up
+    tests that report non-fatal failures after which the current test continues.
+    Thus, you can detect and fix multiple bugs in a single run-edit-compile
+    cycle.
+5.  The testing framework should liberate test writers from housekeeping chores
+    and let them focus on the test *content*. googletest automatically keeps
+    track of all tests defined, and doesn't require the user to enumerate them
+    in order to run them.
+6.  Tests should be *fast*. With googletest, you can reuse shared resources
+    across tests and pay for the set-up/tear-down only once, without making
+    tests depend on each other.
+
+Since googletest is based on the popular xUnit architecture, you'll feel right
+at home if you've used JUnit or PyUnit before. If not, it will take you about 10
+minutes to learn the basics and get started. So let's go!
+
+## Beware of the nomenclature
+
+{: .callout .note}
+_Note:_ There might be some confusion arising from different definitions of the
+terms _Test_, _Test Case_ and _Test Suite_, so beware of misunderstanding these.
+
+Historically, googletest started to use the term _Test Case_ for grouping
+related tests, whereas current publications, including International Software
+Testing Qualifications Board ([ISTQB](http://www.istqb.org/)) materials and
+various textbooks on software quality, use the term
+_[Test Suite][istqb test suite]_ for this.
+
+The related term _Test_, as it is used in googletest, corresponds to the term
+_[Test Case][istqb test case]_ of ISTQB and others.
+
+The term _Test_ is commonly of broad enough sense, including ISTQB's definition
+of _Test Case_, so it's not much of a problem here. But the term _Test Case_ as
+was used in Google Test is of contradictory sense and thus confusing.
+
+googletest recently started replacing the term _Test Case_ with _Test Suite_.
+The preferred API is *TestSuite*. The older TestCase API is being slowly
+deprecated and refactored away.
+
+So please be aware of the different definitions of the terms:
+
+
+Meaning                                                                              | googletest Term         | [ISTQB](http://www.istqb.org/) Term
+:----------------------------------------------------------------------------------- | :---------------------- | :----------------------------------
+Exercise a particular program path with specific input values and verify the results | [TEST()](#simple-tests) | [Test Case][istqb test case]
+
+
+[istqb test case]: http://glossary.istqb.org/en/search/test%20case
+[istqb test suite]: http://glossary.istqb.org/en/search/test%20suite
+
+## Basic Concepts
+
+When using googletest, you start by writing *assertions*, which are statements
+that check whether a condition is true. An assertion's result can be *success*,
+*nonfatal failure*, or *fatal failure*. If a fatal failure occurs, it aborts the
+current function; otherwise the program continues normally.
+
+*Tests* use assertions to verify the tested code's behavior. If a test crashes
+or has a failed assertion, then it *fails*; otherwise it *succeeds*.
+
+A *test suite* contains one or many tests. You should group your tests into test
+suites that reflect the structure of the tested code. When multiple tests in a
+test suite need to share common objects and subroutines, you can put them into a
+*test fixture* class.
+
+A *test program* can contain multiple test suites.
+
+We'll now explain how to write a test program, starting at the individual
+assertion level and building up to tests and test suites.
+
+## Assertions
+
+googletest assertions are macros that resemble function calls. You test a class
+or function by making assertions about its behavior. When an assertion fails,
+googletest prints the assertion's source file and line number location, along
+with a failure message. You may also supply a custom failure message which will
+be appended to googletest's message.
+
+The assertions come in pairs that test the same thing but have different effects
+on the current function. `ASSERT_*` versions generate fatal failures when they
+fail, and **abort the current function**. `EXPECT_*` versions generate nonfatal
+failures, which don't abort the current function. Usually `EXPECT_*` are
+preferred, as they allow more than one failure to be reported in a test.
+However, you should use `ASSERT_*` if it doesn't make sense to continue when the
+assertion in question fails.
+
+Since a failed `ASSERT_*` returns from the current function immediately,
+possibly skipping clean-up code that comes after it, it may cause a space leak.
+Depending on the nature of the leak, it may or may not be worth fixing - so keep
+this in mind if you get a heap checker error in addition to assertion errors.
+
+To provide a custom failure message, simply stream it into the macro using the
+`<<` operator or a sequence of such operators. An example:
+
+```c++
+ASSERT_EQ(x.size(), y.size()) << "Vectors x and y are of unequal length";
+
+for (int i = 0; i < x.size(); ++i) {
+  EXPECT_EQ(x[i], y[i]) << "Vectors x and y differ at index " << i;
+}
+```
+
+Anything that can be streamed to an `ostream` can be streamed to an assertion
+macro--in particular, C strings and `string` objects. If a wide string
+(`wchar_t*`, `TCHAR*` in `UNICODE` mode on Windows, or `std::wstring`) is
+streamed to an assertion, it will be translated to UTF-8 when printed.
+
+### Basic Assertions
+
+These assertions do basic true/false condition testing.
+
+Fatal assertion            | Nonfatal assertion         | Verifies
+-------------------------- | -------------------------- | --------------------
+`ASSERT_TRUE(condition);`  | `EXPECT_TRUE(condition);`  | `condition` is true
+`ASSERT_FALSE(condition);` | `EXPECT_FALSE(condition);` | `condition` is false
+
+Remember, when they fail, `ASSERT_*` yields a fatal failure and returns from the
+current function, while `EXPECT_*` yields a nonfatal failure, allowing the
+function to continue running. In either case, an assertion failure means its
+containing test fails.
+
+**Availability**: Linux, Windows, Mac.
+
+### Binary Comparison
+
+This section describes assertions that compare two values.
+
+Fatal assertion          | Nonfatal assertion       | Verifies
+------------------------ | ------------------------ | --------------
+`ASSERT_EQ(val1, val2);` | `EXPECT_EQ(val1, val2);` | `val1 == val2`
+`ASSERT_NE(val1, val2);` | `EXPECT_NE(val1, val2);` | `val1 != val2`
+`ASSERT_LT(val1, val2);` | `EXPECT_LT(val1, val2);` | `val1 < val2`
+`ASSERT_LE(val1, val2);` | `EXPECT_LE(val1, val2);` | `val1 <= val2`
+`ASSERT_GT(val1, val2);` | `EXPECT_GT(val1, val2);` | `val1 > val2`
+`ASSERT_GE(val1, val2);` | `EXPECT_GE(val1, val2);` | `val1 >= val2`
+
+Value arguments must be comparable by the assertion's comparison operator or
+you'll get a compiler error. We used to require the arguments to support the
+`<<` operator for streaming to an `ostream`, but this is no longer necessary. If
+`<<` is supported, it will be called to print the arguments when the assertion
+fails; otherwise googletest will attempt to print them in the best way it can.
+For more details and how to customize the printing of the arguments, see the
+[documentation](./advanced.md#teaching-googletest-how-to-print-your-values).
+
+These assertions can work with a user-defined type, but only if you define the
+corresponding comparison operator (e.g., `==` or `<`). Since this is discouraged
+by the Google
+[C++ Style Guide](https://google.github.io/styleguide/cppguide.html#Operator_Overloading),
+you may need to use `ASSERT_TRUE()` or `EXPECT_TRUE()` to assert the equality of
+two objects of a user-defined type.
+
+However, when possible, `ASSERT_EQ(actual, expected)` is preferred to
+`ASSERT_TRUE(actual == expected)`, since it tells you `actual` and `expected`'s
+values on failure.
+
+Arguments are always evaluated exactly once. Therefore, it's OK for the
+arguments to have side effects. However, as with any ordinary C/C++ function,
+the arguments' evaluation order is undefined (i.e., the compiler is free to
+choose any order), and your code should not depend on any particular argument
+evaluation order.
+
+`ASSERT_EQ()` does pointer equality on pointers. If used on two C strings, it
+tests if they are in the same memory location, not if they have the same value.
+Therefore, if you want to compare C strings (e.g. `const char*`) by value, use
+`ASSERT_STREQ()`, which will be described later on. In particular, to assert
+that a C string is `NULL`, use `ASSERT_STREQ(c_string, NULL)`. Consider using
+`ASSERT_EQ(c_string, nullptr)` if c++11 is supported. To compare two `string`
+objects, you should use `ASSERT_EQ`.
+
+When doing pointer comparisons use `*_EQ(ptr, nullptr)` and `*_NE(ptr, nullptr)`
+instead of `*_EQ(ptr, NULL)` and `*_NE(ptr, NULL)`. This is because `nullptr` is
+typed, while `NULL` is not. See the [FAQ](faq.md) for more details.
+
+If you're working with floating point numbers, you may want to use the floating
+point variations of some of these macros in order to avoid problems caused by
+rounding. See [Advanced googletest Topics](advanced.md) for details.
+
+Macros in this section work with both narrow and wide string objects (`string`
+and `wstring`).
+
+**Availability**: Linux, Windows, Mac.
+
+**Historical note**: Before February 2016 `*_EQ` had a convention of calling it
+as `ASSERT_EQ(expected, actual)`, so lots of existing code uses this order. Now
+`*_EQ` treats both parameters in the same way.
+
+### String Comparison
+
+The assertions in this group compare two **C strings**. If you want to compare
+two `string` objects, use `EXPECT_EQ`, `EXPECT_NE`, and etc instead.
+
+
+| Fatal assertion                | Nonfatal assertion             | Verifies                                                 |
+| --------------------------     | ------------------------------ | -------------------------------------------------------- |
+| `ASSERT_STREQ(str1,str2);`     | `EXPECT_STREQ(str1,str2);`     | the two C strings have the same content   		     |
+| `ASSERT_STRNE(str1,str2);`     | `EXPECT_STRNE(str1,str2);`     | the two C strings have different contents 		     |
+| `ASSERT_STRCASEEQ(str1,str2);` | `EXPECT_STRCASEEQ(str1,str2);` | the two C strings have the same content, ignoring case   |
+| `ASSERT_STRCASENE(str1,str2);` | `EXPECT_STRCASENE(str1,str2);` | the two C strings have different contents, ignoring case |
+
+
+Note that "CASE" in an assertion name means that case is ignored. A `NULL`
+pointer and an empty string are considered *different*.
+
+`*STREQ*` and `*STRNE*` also accept wide C strings (`wchar_t*`). If a comparison
+of two wide strings fails, their values will be printed as UTF-8 narrow strings.
+
+**Availability**: Linux, Windows, Mac.
+
+**See also**: For more string comparison tricks (substring, prefix, suffix, and
+regular expression matching, for example), see [this](advanced.md) in the
+Advanced googletest Guide.
+
+## Simple Tests
+
+To create a test:
+
+1.  Use the `TEST()` macro to define and name a test function. These are
+    ordinary C++ functions that don't return a value.
+2.  In this function, along with any valid C++ statements you want to include,
+    use the various googletest assertions to check values.
+3.  The test's result is determined by the assertions; if any assertion in the
+    test fails (either fatally or non-fatally), or if the test crashes, the
+    entire test fails. Otherwise, it succeeds.
+
+```c++
+TEST(TestSuiteName, TestName) {
+  ... test body ...
+}
+```
+
+`TEST()` arguments go from general to specific. The *first* argument is the name
+of the test suite, and the *second* argument is the test's name within the test
+suite. Both names must be valid C++ identifiers, and they should not contain
+any underscores (`_`). A test's *full name* consists of its containing test suite and
+its individual name. Tests from different test suites can have the same
+individual name.
+
+For example, let's take a simple integer function:
+
+```c++
+int Factorial(int n);  // Returns the factorial of n
+```
+
+A test suite for this function might look like:
+
+```c++
+// Tests factorial of 0.
+TEST(FactorialTest, HandlesZeroInput) {
+  EXPECT_EQ(Factorial(0), 1);
+}
+
+// Tests factorial of positive numbers.
+TEST(FactorialTest, HandlesPositiveInput) {
+  EXPECT_EQ(Factorial(1), 1);
+  EXPECT_EQ(Factorial(2), 2);
+  EXPECT_EQ(Factorial(3), 6);
+  EXPECT_EQ(Factorial(8), 40320);
+}
+```
+
+googletest groups the test results by test suites, so logically related tests
+should be in the same test suite; in other words, the first argument to their
+`TEST()` should be the same. In the above example, we have two tests,
+`HandlesZeroInput` and `HandlesPositiveInput`, that belong to the same test
+suite `FactorialTest`.
+
+When naming your test suites and tests, you should follow the same convention as
+for
+[naming functions and classes](https://google.github.io/styleguide/cppguide.html#Function_Names).
+
+**Availability**: Linux, Windows, Mac.
+
+## Test Fixtures: Using the Same Data Configuration for Multiple Tests {#same-data-multiple-tests}
+
+If you find yourself writing two or more tests that operate on similar data, you
+can use a *test fixture*. This allows you to reuse the same configuration of
+objects for several different tests.
+
+To create a fixture:
+
+1.  Derive a class from `::testing::Test` . Start its body with `protected:`, as
+    we'll want to access fixture members from sub-classes.
+2.  Inside the class, declare any objects you plan to use.
+3.  If necessary, write a default constructor or `SetUp()` function to prepare
+    the objects for each test. A common mistake is to spell `SetUp()` as
+    **`Setup()`** with a small `u` - Use `override` in C++11 to make sure you
+    spelled it correctly.
+4.  If necessary, write a destructor or `TearDown()` function to release any
+    resources you allocated in `SetUp()` . To learn when you should use the
+    constructor/destructor and when you should use `SetUp()/TearDown()`, read
+    the [FAQ](faq.md#CtorVsSetUp).
+5.  If needed, define subroutines for your tests to share.
+
+When using a fixture, use `TEST_F()` instead of `TEST()` as it allows you to
+access objects and subroutines in the test fixture:
+
+```c++
+TEST_F(TestFixtureName, TestName) {
+  ... test body ...
+}
+```
+
+Like `TEST()`, the first argument is the test suite name, but for `TEST_F()`
+this must be the name of the test fixture class. You've probably guessed: `_F`
+is for fixture.
+
+Unfortunately, the C++ macro system does not allow us to create a single macro
+that can handle both types of tests. Using the wrong macro causes a compiler
+error.
+
+Also, you must first define a test fixture class before using it in a
+`TEST_F()`, or you'll get the compiler error "`virtual outside class
+declaration`".
+
+For each test defined with `TEST_F()`, googletest will create a *fresh* test
+fixture at runtime, immediately initialize it via `SetUp()`, run the test,
+clean up by calling `TearDown()`, and then delete the test fixture. Note that
+different tests in the same test suite have different test fixture objects, and
+googletest always deletes a test fixture before it creates the next one.
+googletest does **not** reuse the same test fixture for multiple tests. Any
+changes one test makes to the fixture do not affect other tests.
+
+As an example, let's write tests for a FIFO queue class named `Queue`, which has
+the following interface:
+
+```c++
+template <typename E>  // E is the element type.
+class Queue {
+ public:
+  Queue();
+  void Enqueue(const E& element);
+  E* Dequeue();  // Returns NULL if the queue is empty.
+  size_t size() const;
+  ...
+};
+```
+
+First, define a fixture class. By convention, you should give it the name
+`FooTest` where `Foo` is the class being tested.
+
+```c++
+class QueueTest : public ::testing::Test {
+ protected:
+  void SetUp() override {
+     q1_.Enqueue(1);
+     q2_.Enqueue(2);
+     q2_.Enqueue(3);
+  }
+
+  // void TearDown() override {}
+
+  Queue<int> q0_;
+  Queue<int> q1_;
+  Queue<int> q2_;
+};
+```
+
+In this case, `TearDown()` is not needed since we don't have to clean up after
+each test, other than what's already done by the destructor.
+
+Now we'll write tests using `TEST_F()` and this fixture.
+
+```c++
+TEST_F(QueueTest, IsEmptyInitially) {
+  EXPECT_EQ(q0_.size(), 0);
+}
+
+TEST_F(QueueTest, DequeueWorks) {
+  int* n = q0_.Dequeue();
+  EXPECT_EQ(n, nullptr);
+
+  n = q1_.Dequeue();
+  ASSERT_NE(n, nullptr);
+  EXPECT_EQ(*n, 1);
+  EXPECT_EQ(q1_.size(), 0);
+  delete n;
+
+  n = q2_.Dequeue();
+  ASSERT_NE(n, nullptr);
+  EXPECT_EQ(*n, 2);
+  EXPECT_EQ(q2_.size(), 1);
+  delete n;
+}
+```
+
+The above uses both `ASSERT_*` and `EXPECT_*` assertions. The rule of thumb is
+to use `EXPECT_*` when you want the test to continue to reveal more errors after
+the assertion failure, and use `ASSERT_*` when continuing after failure doesn't
+make sense. For example, the second assertion in the `Dequeue` test is
+`ASSERT_NE(nullptr, n)`, as we need to dereference the pointer `n` later, which
+would lead to a segfault when `n` is `NULL`.
+
+When these tests run, the following happens:
+
+1.  googletest constructs a `QueueTest` object (let's call it `t1`).
+2.  `t1.SetUp()` initializes `t1`.
+3.  The first test (`IsEmptyInitially`) runs on `t1`.
+4.  `t1.TearDown()` cleans up after the test finishes.
+5.  `t1` is destructed.
+6.  The above steps are repeated on another `QueueTest` object, this time
+    running the `DequeueWorks` test.
+
+**Availability**: Linux, Windows, Mac.
+
+## Invoking the Tests
+
+`TEST()` and `TEST_F()` implicitly register their tests with googletest. So,
+unlike with many other C++ testing frameworks, you don't have to re-list all
+your defined tests in order to run them.
+
+After defining your tests, you can run them with `RUN_ALL_TESTS()`, which
+returns `0` if all the tests are successful, or `1` otherwise. Note that
+`RUN_ALL_TESTS()` runs *all tests* in your link unit--they can be from
+different test suites, or even different source files.
+
+When invoked, the `RUN_ALL_TESTS()` macro:
+
+*   Saves the state of all googletest flags.
+
+*   Creates a test fixture object for the first test.
+
+*   Initializes it via `SetUp()`.
+
+*   Runs the test on the fixture object.
+
+*   Cleans up the fixture via `TearDown()`.
+
+*   Deletes the fixture.
+
+*   Restores the state of all googletest flags.
+
+*   Repeats the above steps for the next test, until all tests have run.
+
+If a fatal failure happens the subsequent steps will be skipped.
+
+{: .callout .important}
+> IMPORTANT: You must **not** ignore the return value of `RUN_ALL_TESTS()`, or
+> you will get a compiler error. The rationale for this design is that the
+> automated testing service determines whether a test has passed based on its
+> exit code, not on its stdout/stderr output; thus your `main()` function must
+> return the value of `RUN_ALL_TESTS()`.
+>
+> Also, you should call `RUN_ALL_TESTS()` only **once**. Calling it more than
+> once conflicts with some advanced googletest features (e.g., thread-safe
+> [death tests](advanced.md#death-tests)) and thus is not supported.
+
+**Availability**: Linux, Windows, Mac.
+
+## Writing the main() Function
+
+Most users should _not_ need to write their own `main` function and instead link
+with `gtest_main` (as opposed to with `gtest`), which defines a suitable entry
+point. See the end of this section for details. The remainder of this section
+should only apply when you need to do something custom before the tests run that
+cannot be expressed within the framework of fixtures and test suites.
+
+If you write your own `main` function, it should return the value of
+`RUN_ALL_TESTS()`.
+
+You can start from this boilerplate:
+
+```c++
+#include "this/package/foo.h"
+
+#include "gtest/gtest.h"
+
+namespace my {
+namespace project {
+namespace {
+
+// The fixture for testing class Foo.
+class FooTest : public ::testing::Test {
+ protected:
+  // You can remove any or all of the following functions if their bodies would
+  // be empty.
+
+  FooTest() {
+     // You can do set-up work for each test here.
+  }
+
+  ~FooTest() override {
+     // You can do clean-up work that doesn't throw exceptions here.
+  }
+
+  // If the constructor and destructor are not enough for setting up
+  // and cleaning up each test, you can define the following methods:
+
+  void SetUp() override {
+     // Code here will be called immediately after the constructor (right
+     // before each test).
+  }
+
+  void TearDown() override {
+     // Code here will be called immediately after each test (right
+     // before the destructor).
+  }
+
+  // Class members declared here can be used by all tests in the test suite
+  // for Foo.
+};
+
+// Tests that the Foo::Bar() method does Abc.
+TEST_F(FooTest, MethodBarDoesAbc) {
+  const std::string input_filepath = "this/package/testdata/myinputfile.dat";
+  const std::string output_filepath = "this/package/testdata/myoutputfile.dat";
+  Foo f;
+  EXPECT_EQ(f.Bar(input_filepath, output_filepath), 0);
+}
+
+// Tests that Foo does Xyz.
+TEST_F(FooTest, DoesXyz) {
+  // Exercises the Xyz feature of Foo.
+}
+
+}  // namespace
+}  // namespace project
+}  // namespace my
+
+int main(int argc, char **argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
+```
+
+The `::testing::InitGoogleTest()` function parses the command line for
+googletest flags, and removes all recognized flags. This allows the user to
+control a test program's behavior via various flags, which we'll cover in
+the [AdvancedGuide](advanced.md). You **must** call this function before calling
+`RUN_ALL_TESTS()`, or the flags won't be properly initialized.
+
+On Windows, `InitGoogleTest()` also works with wide strings, so it can be used
+in programs compiled in `UNICODE` mode as well.
+
+But maybe you think that writing all those `main` functions is too much work? We
+agree with you completely, and that's why Google Test provides a basic
+implementation of main(). If it fits your needs, then just link your test with
+the `gtest_main` library and you are good to go.
+
+{: .callout .note}
+NOTE: `ParseGUnitFlags()` is deprecated in favor of `InitGoogleTest()`.
+
+## Known Limitations
+
+*   Google Test is designed to be thread-safe. The implementation is thread-safe
+    on systems where the `pthreads` library is available. It is currently
+    _unsafe_ to use Google Test assertions from two threads concurrently on
+    other systems (e.g. Windows). In most tests this is not an issue as usually
+    the assertions are done in the main thread. If you want to help, you can
+    volunteer to implement the necessary synchronization primitives in
+    `gtest-port.h` for your platform.
diff --git a/leveldb_base/third_party/googletest/docs/quickstart-bazel.md b/leveldb_base/third_party/googletest/docs/quickstart-bazel.md
new file mode 100644
index 0000000..362ee6d
--- /dev/null
+++ b/leveldb_base/third_party/googletest/docs/quickstart-bazel.md
@@ -0,0 +1,161 @@
+# Quickstart: Building with Bazel
+
+This tutorial aims to get you up and running with GoogleTest using the Bazel
+build system. If you're using GoogleTest for the first time or need a refresher,
+we recommend this tutorial as a starting point.
+
+## Prerequisites
+
+To complete this tutorial, you'll need:
+
+*   A compatible operating system (e.g. Linux, macOS, Windows).
+*   A compatible C++ compiler that supports at least C++11.
+*   [Bazel](https://bazel.build/), the preferred build system used by the
+    GoogleTest team.
+
+See [Supported Platforms](platforms.md) for more information about platforms
+compatible with GoogleTest.
+
+If you don't already have Bazel installed, see the
+[Bazel installation guide](https://docs.bazel.build/versions/master/install.html).
+
+{: .callout .note}
+Note: The terminal commands in this tutorial show a Unix shell prompt, but the
+commands work on the Windows command line as well.
+
+## Set up a Bazel workspace
+
+A
+[Bazel workspace](https://docs.bazel.build/versions/master/build-ref.html#workspace)
+is a directory on your filesystem that you use to manage source files for the
+software you want to build. Each workspace directory has a text file named
+`WORKSPACE` which may be empty, or may contain references to external
+dependencies required to build the outputs.
+
+First, create a directory for your workspace:
+
+```
+$ mkdir my_workspace && cd my_workspace
+```
+
+Next, you’ll create the `WORKSPACE` file to specify dependencies. A common and
+recommended way to depend on GoogleTest is to use a
+[Bazel external dependency](https://docs.bazel.build/versions/master/external.html)
+via the
+[`http_archive` rule](https://docs.bazel.build/versions/master/repo/http.html#http_archive).
+To do this, in the root directory of your workspace (`my_workspace/`), create a
+file named `WORKSPACE` with the following contents:
+
+```
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+
+http_archive(
+  name = "com_google_googletest",
+  urls = ["https://github.com/google/googletest/archive/609281088cfefc76f9d0ce82e1ff6c30cc3591e5.zip"],
+  strip_prefix = "googletest-609281088cfefc76f9d0ce82e1ff6c30cc3591e5",
+)
+```
+
+The above configuration declares a dependency on GoogleTest which is downloaded
+as a ZIP archive from GitHub. In the above example,
+`609281088cfefc76f9d0ce82e1ff6c30cc3591e5` is the Git commit hash of the
+GoogleTest version to use; we recommend updating the hash often to point to the
+latest version.
+
+Bazel also needs a dependency on the
+[`rules_cc` repository](https://github.com/bazelbuild/rules_cc) to build C++
+code, so add the following to the `WORKSPACE` file:
+
+```
+http_archive(
+  name = "rules_cc",
+  urls = ["https://github.com/bazelbuild/rules_cc/archive/40548a2974f1aea06215272d9c2b47a14a24e556.zip"],
+  strip_prefix = "rules_cc-40548a2974f1aea06215272d9c2b47a14a24e556",
+)
+```
+
+Now you're ready to build C++ code that uses GoogleTest.
+
+## Create and run a binary
+
+With your Bazel workspace set up, you can now use GoogleTest code within your
+own project.
+
+As an example, create a file named `hello_test.cc` in your `my_workspace`
+directory with the following contents:
+
+```cpp
+#include <gtest/gtest.h>
+
+// Demonstrate some basic assertions.
+TEST(HelloTest, BasicAssertions) {
+  // Expect two strings not to be equal.
+  EXPECT_STRNE("hello", "world");
+  // Expect equality.
+  EXPECT_EQ(7 * 6, 42);
+}
+```
+
+GoogleTest provides [assertions](primer.md#assertions) that you use to test the
+behavior of your code. The above sample includes the main GoogleTest header file
+and demonstrates some basic assertions.
+
+To build the code, create a file named `BUILD` in the same directory with the
+following contents:
+
+```
+load("@rules_cc//cc:defs.bzl", "cc_test")
+
+cc_test(
+  name = "hello_test",
+  size = "small",
+  srcs = ["hello_test.cc"],
+  deps = ["@com_google_googletest//:gtest_main"],
+)
+```
+
+This `cc_test` rule declares the C++ test binary you want to build, and links to
+GoogleTest (`//:gtest_main`) using the prefix you specified in the `WORKSPACE`
+file (`@com_google_googletest`). For more information about Bazel `BUILD` files,
+see the
+[Bazel C++ Tutorial](https://docs.bazel.build/versions/master/tutorial/cpp.html).
+
+Now you can build and run your test:
+
+<pre>
+<strong>my_workspace$ bazel test --test_output=all //:hello_test</strong>
+INFO: Analyzed target //:hello_test (26 packages loaded, 362 targets configured).
+INFO: Found 1 test target...
+INFO: From Testing //:hello_test:
+==================== Test output for //:hello_test:
+Running main() from gmock_main.cc
+[==========] Running 1 test from 1 test suite.
+[----------] Global test environment set-up.
+[----------] 1 test from HelloTest
+[ RUN      ] HelloTest.BasicAssertions
+[       OK ] HelloTest.BasicAssertions (0 ms)
+[----------] 1 test from HelloTest (0 ms total)
+
+[----------] Global test environment tear-down
+[==========] 1 test from 1 test suite ran. (0 ms total)
+[  PASSED  ] 1 test.
+================================================================================
+Target //:hello_test up-to-date:
+  bazel-bin/hello_test
+INFO: Elapsed time: 4.190s, Critical Path: 3.05s
+INFO: 27 processes: 8 internal, 19 linux-sandbox.
+INFO: Build completed successfully, 27 total actions
+//:hello_test                                                     PASSED in 0.1s
+
+INFO: Build completed successfully, 27 total actions
+</pre>
+
+Congratulations! You've successfully built and run a test binary using
+GoogleTest.
+
+## Next steps
+
+*   [Check out the Primer](primer.md) to start learning how to write simple
+    tests.
+*   [See the code samples](samples.md) for more examples showing how to use a
+    variety of GoogleTest features.
diff --git a/leveldb_base/third_party/googletest/docs/quickstart-cmake.md b/leveldb_base/third_party/googletest/docs/quickstart-cmake.md
new file mode 100644
index 0000000..420f1d3
--- /dev/null
+++ b/leveldb_base/third_party/googletest/docs/quickstart-cmake.md
@@ -0,0 +1,156 @@
+# Quickstart: Building with CMake
+
+This tutorial aims to get you up and running with GoogleTest using CMake. If
+you're using GoogleTest for the first time or need a refresher, we recommend
+this tutorial as a starting point. If your project uses Bazel, see the
+[Quickstart for Bazel](quickstart-bazel.md) instead.
+
+## Prerequisites
+
+To complete this tutorial, you'll need:
+
+*   A compatible operating system (e.g. Linux, macOS, Windows).
+*   A compatible C++ compiler that supports at least C++11.
+*   [CMake](https://cmake.org/) and a compatible build tool for building the
+    project.
+    *   Compatible build tools include
+        [Make](https://www.gnu.org/software/make/),
+        [Ninja](https://ninja-build.org/), and others - see
+        [CMake Generators](https://cmake.org/cmake/help/latest/manual/cmake-generators.7.html)
+        for more information.
+
+See [Supported Platforms](platforms.md) for more information about platforms
+compatible with GoogleTest.
+
+If you don't already have CMake installed, see the
+[CMake installation guide](https://cmake.org/install).
+
+{: .callout .note}
+Note: The terminal commands in this tutorial show a Unix shell prompt, but the
+commands work on the Windows command line as well.
+
+## Set up a project
+
+CMake uses a file named `CMakeLists.txt` to configure the build system for a
+project. You'll use this file to set up your project and declare a dependency on
+GoogleTest.
+
+First, create a directory for your project:
+
+```
+$ mkdir my_project && cd my_project
+```
+
+Next, you'll create the `CMakeLists.txt` file and declare a dependency on
+GoogleTest. There are many ways to express dependencies in the CMake ecosystem;
+in this quickstart, you'll use the
+[`FetchContent` CMake module](https://cmake.org/cmake/help/latest/module/FetchContent.html).
+To do this, in your project directory (`my_project`), create a file named
+`CMakeLists.txt` with the following contents:
+
+```cmake
+cmake_minimum_required(VERSION 3.14)
+project(my_project)
+
+# GoogleTest requires at least C++11
+set(CMAKE_CXX_STANDARD 11)
+
+include(FetchContent)
+FetchContent_Declare(
+  googletest
+  URL https://github.com/google/googletest/archive/609281088cfefc76f9d0ce82e1ff6c30cc3591e5.zip
+)
+# For Windows: Prevent overriding the parent project's compiler/linker settings
+set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
+FetchContent_MakeAvailable(googletest)
+```
+
+The above configuration declares a dependency on GoogleTest which is downloaded
+from GitHub. In the above example, `609281088cfefc76f9d0ce82e1ff6c30cc3591e5` is
+the Git commit hash of the GoogleTest version to use; we recommend updating the
+hash often to point to the latest version.
+
+For more information about how to create `CMakeLists.txt` files, see the
+[CMake Tutorial](https://cmake.org/cmake/help/latest/guide/tutorial/index.html).
+
+## Create and run a binary
+
+With GoogleTest declared as a dependency, you can use GoogleTest code within
+your own project.
+
+As an example, create a file named `hello_test.cc` in your `my_project`
+directory with the following contents:
+
+```cpp
+#include <gtest/gtest.h>
+
+// Demonstrate some basic assertions.
+TEST(HelloTest, BasicAssertions) {
+  // Expect two strings not to be equal.
+  EXPECT_STRNE("hello", "world");
+  // Expect equality.
+  EXPECT_EQ(7 * 6, 42);
+}
+```
+
+GoogleTest provides [assertions](primer.md#assertions) that you use to test the
+behavior of your code. The above sample includes the main GoogleTest header file
+and demonstrates some basic assertions.
+
+To build the code, add the following to the end of your `CMakeLists.txt` file:
+
+```cmake
+enable_testing()
+
+add_executable(
+  hello_test
+  hello_test.cc
+)
+target_link_libraries(
+  hello_test
+  gtest_main
+)
+
+include(GoogleTest)
+gtest_discover_tests(hello_test)
+```
+
+The above configuration enables testing in CMake, declares the C++ test binary
+you want to build (`hello_test`), and links it to GoogleTest (`gtest_main`). The
+last two lines enable CMake's test runner to discover the tests included in the
+binary, using the
+[`GoogleTest` CMake module](https://cmake.org/cmake/help/git-stage/module/GoogleTest.html).
+
+Now you can build and run your test:
+
+<pre>
+<strong>my_project$ cmake -S . -B build</strong>
+-- The C compiler identification is GNU 10.2.1
+-- The CXX compiler identification is GNU 10.2.1
+...
+-- Build files have been written to: .../my_project/build
+
+<strong>my_project$ cmake --build build</strong>
+Scanning dependencies of target gtest
+...
+[100%] Built target gmock_main
+
+<strong>my_project$ cd build && ctest</strong>
+Test project .../my_project/build
+    Start 1: HelloTest.BasicAssertions
+1/1 Test #1: HelloTest.BasicAssertions ........   Passed    0.00 sec
+
+100% tests passed, 0 tests failed out of 1
+
+Total Test time (real) =   0.01 sec
+</pre>
+
+Congratulations! You've successfully built and run a test binary using
+GoogleTest.
+
+## Next steps
+
+*   [Check out the Primer](primer.md) to start learning how to write simple
+    tests.
+*   [See the code samples](samples.md) for more examples showing how to use a
+    variety of GoogleTest features.
diff --git a/leveldb_base/third_party/googletest/docs/reference/actions.md b/leveldb_base/third_party/googletest/docs/reference/actions.md
new file mode 100644
index 0000000..166d2a8
--- /dev/null
+++ b/leveldb_base/third_party/googletest/docs/reference/actions.md
@@ -0,0 +1,115 @@
+# Actions Reference
+
+[**Actions**](../gmock_for_dummies.md#actions-what-should-it-do) specify what a
+mock function should do when invoked. This page lists the built-in actions
+provided by GoogleTest. All actions are defined in the `::testing` namespace.
+
+## Returning a Value
+
+|                                   |                                               |
+| :-------------------------------- | :-------------------------------------------- |
+| `Return()`                        | Return from a `void` mock function.           |
+| `Return(value)`                   | Return `value`. If the type of `value` is     different to the mock function's return type, `value` is converted to the latter type <i>at the time the expectation is set</i>, not when the action is executed. |
+| `ReturnArg<N>()`                  | Return the `N`-th (0-based) argument.         |
+| `ReturnNew<T>(a1, ..., ak)`       | Return `new T(a1, ..., ak)`; a different      object is created each time. |
+| `ReturnNull()`                    | Return a null pointer.                        |
+| `ReturnPointee(ptr)`              | Return the value pointed to by `ptr`.         |
+| `ReturnRef(variable)`             | Return a reference to `variable`.             |
+| `ReturnRefOfCopy(value)`          | Return a reference to a copy of `value`; the  copy lives as long as the action. |
+| `ReturnRoundRobin({a1, ..., ak})` | Each call will return the next `ai` in the list, starting at the beginning when the end of the list is reached. |
+
+## Side Effects
+
+|                                    |                                         |
+| :--------------------------------- | :-------------------------------------- |
+| `Assign(&variable, value)` | Assign `value` to variable. |
+| `DeleteArg<N>()` | Delete the `N`-th (0-based) argument, which must be a pointer. |
+| `SaveArg<N>(pointer)` | Save the `N`-th (0-based) argument to `*pointer`. |
+| `SaveArgPointee<N>(pointer)` | Save the value pointed to by the `N`-th (0-based) argument to `*pointer`. |
+| `SetArgReferee<N>(value)` | Assign `value` to the variable referenced by the `N`-th (0-based) argument. |
+| `SetArgPointee<N>(value)` | Assign `value` to the variable pointed by the `N`-th (0-based) argument. |
+| `SetArgumentPointee<N>(value)` | Same as `SetArgPointee<N>(value)`. Deprecated. Will be removed in v1.7.0. |
+| `SetArrayArgument<N>(first, last)` | Copies the elements in source range [`first`, `last`) to the array pointed to by the `N`-th (0-based) argument, which can be either a pointer or an iterator. The action does not take ownership of the elements in the source range. |
+| `SetErrnoAndReturn(error, value)` | Set `errno` to `error` and return `value`. |
+| `Throw(exception)` | Throws the given exception, which can be any copyable value. Available since v1.1.0. |
+
+## Using a Function, Functor, or Lambda as an Action
+
+In the following, by "callable" we mean a free function, `std::function`,
+functor, or lambda.
+
+|                                     |                                        |
+| :---------------------------------- | :------------------------------------- |
+| `f` | Invoke f with the arguments passed to the mock function, where f is a callable. |
+| `Invoke(f)` | Invoke `f` with the arguments passed to the mock function, where `f` can be a global/static function or a functor. |
+| `Invoke(object_pointer, &class::method)` | Invoke the method on the object with the arguments passed to the mock function. |
+| `InvokeWithoutArgs(f)` | Invoke `f`, which can be a global/static function or a functor. `f` must take no arguments. |
+| `InvokeWithoutArgs(object_pointer, &class::method)` | Invoke the method on the object, which takes no arguments. |
+| `InvokeArgument<N>(arg1, arg2, ..., argk)` | Invoke the mock function's `N`-th (0-based) argument, which must be a function or a functor, with the `k` arguments. |
+
+The return value of the invoked function is used as the return value of the
+action.
+
+When defining a callable to be used with `Invoke*()`, you can declare any unused
+parameters as `Unused`:
+
+```cpp
+using ::testing::Invoke;
+double Distance(Unused, double x, double y) { return sqrt(x*x + y*y); }
+...
+EXPECT_CALL(mock, Foo("Hi", _, _)).WillOnce(Invoke(Distance));
+```
+
+`Invoke(callback)` and `InvokeWithoutArgs(callback)` take ownership of
+`callback`, which must be permanent. The type of `callback` must be a base
+callback type instead of a derived one, e.g.
+
+```cpp
+  BlockingClosure* done = new BlockingClosure;
+  ... Invoke(done) ...;  // This won't compile!
+
+  Closure* done2 = new BlockingClosure;
+  ... Invoke(done2) ...;  // This works.
+```
+
+In `InvokeArgument<N>(...)`, if an argument needs to be passed by reference,
+wrap it inside `std::ref()`. For example,
+
+```cpp
+using ::testing::InvokeArgument;
+...
+InvokeArgument<2>(5, string("Hi"), std::ref(foo))
+```
+
+calls the mock function's #2 argument, passing to it `5` and `string("Hi")` by
+value, and `foo` by reference.
+
+## Default Action
+
+| Matcher       | Description                                            |
+| :------------ | :----------------------------------------------------- |
+| `DoDefault()` | Do the default action (specified by `ON_CALL()` or the built-in one). |
+
+{: .callout .note}
+**Note:** due to technical reasons, `DoDefault()` cannot be used inside a
+composite action - trying to do so will result in a run-time error.
+
+## Composite Actions
+
+|                                |                                             |
+| :----------------------------- | :------------------------------------------ |
+| `DoAll(a1, a2, ..., an)`       | Do all actions `a1` to `an` and return the result of `an` in each invocation. The first `n - 1` sub-actions must return void and will receive a  readonly view of the arguments. |
+| `IgnoreResult(a)`              | Perform action `a` and ignore its result. `a` must not return void. |
+| `WithArg<N>(a)`                | Pass the `N`-th (0-based) argument of the mock function to action `a` and perform it. |
+| `WithArgs<N1, N2, ..., Nk>(a)` | Pass the selected (0-based) arguments of the mock function to action `a` and perform it. |
+| `WithoutArgs(a)`               | Perform action `a` without any arguments. |
+
+## Defining Actions
+
+|                                    |                                         |
+| :--------------------------------- | :-------------------------------------- |
+| `ACTION(Sum) { return arg0 + arg1; }` | Defines an action `Sum()` to return the sum of the mock function's argument #0 and #1. |
+| `ACTION_P(Plus, n) { return arg0 + n; }` | Defines an action `Plus(n)` to return the sum of the mock function's argument #0 and `n`. |
+| `ACTION_Pk(Foo, p1, ..., pk) { statements; }` | Defines a parameterized action `Foo(p1, ..., pk)` to execute the given `statements`. |
+
+The `ACTION*` macros cannot be used inside a function or class.
diff --git a/leveldb_base/third_party/googletest/docs/reference/matchers.md b/leveldb_base/third_party/googletest/docs/reference/matchers.md
new file mode 100644
index 0000000..3292b29
--- /dev/null
+++ b/leveldb_base/third_party/googletest/docs/reference/matchers.md
@@ -0,0 +1,283 @@
+# Matchers Reference
+
+A **matcher** matches a *single* argument. You can use it inside `ON_CALL()` or
+`EXPECT_CALL()`, or use it to validate a value directly using two macros:
+
+| Macro                                | Description                           |
+| :----------------------------------- | :------------------------------------ |
+| `EXPECT_THAT(actual_value, matcher)` | Asserts that `actual_value` matches `matcher`. |
+| `ASSERT_THAT(actual_value, matcher)` | The same as `EXPECT_THAT(actual_value, matcher)`, except that it generates a **fatal** failure. |
+
+{: .callout .note}
+**Note:** Although equality matching via `EXPECT_THAT(actual_value,
+expected_value)` is supported, prefer to make the comparison explicit via
+`EXPECT_THAT(actual_value, Eq(expected_value))` or `EXPECT_EQ(actual_value,
+expected_value)`.
+
+Built-in matchers (where `argument` is the function argument, e.g.
+`actual_value` in the example above, or when used in the context of
+`EXPECT_CALL(mock_object, method(matchers))`, the arguments of `method`) are
+divided into several categories. All matchers are defined in the `::testing`
+namespace unless otherwise noted.
+
+## Wildcard
+
+Matcher                     | Description
+:-------------------------- | :-----------------------------------------------
+`_`                         | `argument` can be any value of the correct type.
+`A<type>()` or `An<type>()` | `argument` can be any value of type `type`.
+
+## Generic Comparison
+
+| Matcher                | Description                                         |
+| :--------------------- | :-------------------------------------------------- |
+| `Eq(value)` or `value` | `argument == value`                                 |
+| `Ge(value)`            | `argument >= value`                                 |
+| `Gt(value)`            | `argument > value`                                  |
+| `Le(value)`            | `argument <= value`                                 |
+| `Lt(value)`            | `argument < value`                                  |
+| `Ne(value)`            | `argument != value`                                 |
+| `IsFalse()`            | `argument` evaluates to `false` in a Boolean context. |
+| `IsTrue()`             | `argument` evaluates to `true` in a Boolean context. |
+| `IsNull()`             | `argument` is a `NULL` pointer (raw or smart).      |
+| `NotNull()`            | `argument` is a non-null pointer (raw or smart).    |
+| `Optional(m)`          | `argument` is `optional<>` that contains a value matching `m`. (For testing whether an `optional<>` is set, check for equality with `nullopt`. You may need to use `Eq(nullopt)` if the inner type doesn't have `==`.)|
+| `VariantWith<T>(m)`    | `argument` is `variant<>` that holds the alternative of type T with a value matching `m`. |
+| `Ref(variable)`        | `argument` is a reference to `variable`.            |
+| `TypedEq<type>(value)` | `argument` has type `type` and is equal to `value`. You may need to use this instead of `Eq(value)` when the mock function is overloaded. |
+
+Except `Ref()`, these matchers make a *copy* of `value` in case it's modified or
+destructed later. If the compiler complains that `value` doesn't have a public
+copy constructor, try wrap it in `std::ref()`, e.g.
+`Eq(std::ref(non_copyable_value))`. If you do that, make sure
+`non_copyable_value` is not changed afterwards, or the meaning of your matcher
+will be changed.
+
+`IsTrue` and `IsFalse` are useful when you need to use a matcher, or for types
+that can be explicitly converted to Boolean, but are not implicitly converted to
+Boolean. In other cases, you can use the basic
+[`EXPECT_TRUE` and `EXPECT_FALSE`](../primer.md#basic-assertions) assertions.
+
+## Floating-Point Matchers {#FpMatchers}
+
+| Matcher                          | Description                        |
+| :------------------------------- | :--------------------------------- |
+| `DoubleEq(a_double)`             | `argument` is a `double` value approximately equal to `a_double`, treating two NaNs as unequal. |
+| `FloatEq(a_float)`               | `argument` is a `float` value approximately equal to `a_float`, treating two NaNs as unequal. |
+| `NanSensitiveDoubleEq(a_double)` | `argument` is a `double` value approximately equal to `a_double`, treating two NaNs as equal. |
+| `NanSensitiveFloatEq(a_float)`   | `argument` is a `float` value approximately equal to `a_float`, treating two NaNs as equal. |
+| `IsNan()`   | `argument` is any floating-point type with a NaN value. |
+
+The above matchers use ULP-based comparison (the same as used in googletest).
+They automatically pick a reasonable error bound based on the absolute value of
+the expected value. `DoubleEq()` and `FloatEq()` conform to the IEEE standard,
+which requires comparing two NaNs for equality to return false. The
+`NanSensitive*` version instead treats two NaNs as equal, which is often what a
+user wants.
+
+| Matcher                                           | Description              |
+| :------------------------------------------------ | :----------------------- |
+| `DoubleNear(a_double, max_abs_error)`             | `argument` is a `double` value close to `a_double` (absolute error <= `max_abs_error`), treating two NaNs as unequal. |
+| `FloatNear(a_float, max_abs_error)`               | `argument` is a `float` value close to `a_float` (absolute error <= `max_abs_error`), treating two NaNs as unequal. |
+| `NanSensitiveDoubleNear(a_double, max_abs_error)` | `argument` is a `double` value close to `a_double` (absolute error <= `max_abs_error`), treating two NaNs as equal. |
+| `NanSensitiveFloatNear(a_float, max_abs_error)`   | `argument` is a `float` value close to `a_float` (absolute error <= `max_abs_error`), treating two NaNs as equal. |
+
+## String Matchers
+
+The `argument` can be either a C string or a C++ string object:
+
+| Matcher                 | Description                                        |
+| :---------------------- | :------------------------------------------------- |
+| `ContainsRegex(string)` | `argument` matches the given regular expression.   |
+| `EndsWith(suffix)`      | `argument` ends with string `suffix`.              |
+| `HasSubstr(string)`     | `argument` contains `string` as a sub-string.      |
+| `IsEmpty()`             | `argument` is an empty string.                     |
+| `MatchesRegex(string)`  | `argument` matches the given regular expression with the match starting at the first character and ending at the last character. |
+| `StartsWith(prefix)`    | `argument` starts with string `prefix`.            |
+| `StrCaseEq(string)`     | `argument` is equal to `string`, ignoring case.    |
+| `StrCaseNe(string)`     | `argument` is not equal to `string`, ignoring case. |
+| `StrEq(string)`         | `argument` is equal to `string`.                   |
+| `StrNe(string)`         | `argument` is not equal to `string`.               |
+
+`ContainsRegex()` and `MatchesRegex()` take ownership of the `RE` object. They
+use the regular expression syntax defined
+[here](../advanced.md#regular-expression-syntax). All of these matchers, except
+`ContainsRegex()` and `MatchesRegex()` work for wide strings as well.
+
+## Container Matchers
+
+Most STL-style containers support `==`, so you can use `Eq(expected_container)`
+or simply `expected_container` to match a container exactly. If you want to
+write the elements in-line, match them more flexibly, or get more informative
+messages, you can use:
+
+| Matcher                                   | Description                      |
+| :---------------------------------------- | :------------------------------- |
+| `BeginEndDistanceIs(m)` | `argument` is a container whose `begin()` and `end()` iterators are separated by a number of increments matching `m`. E.g. `BeginEndDistanceIs(2)` or `BeginEndDistanceIs(Lt(2))`. For containers that define a `size()` method, `SizeIs(m)` may be more efficient. |
+| `ContainerEq(container)` | The same as `Eq(container)` except that the failure message also includes which elements are in one container but not the other. |
+| `Contains(e)` | `argument` contains an element that matches `e`, which can be either a value or a matcher. |
+| `Each(e)` | `argument` is a container where *every* element matches `e`, which can be either a value or a matcher. |
+| `ElementsAre(e0, e1, ..., en)` | `argument` has `n + 1` elements, where the *i*-th element matches `ei`, which can be a value or a matcher. |
+| `ElementsAreArray({e0, e1, ..., en})`, `ElementsAreArray(a_container)`, `ElementsAreArray(begin, end)`, `ElementsAreArray(array)`, or `ElementsAreArray(array, count)` | The same as `ElementsAre()` except that the expected element values/matchers come from an initializer list, STL-style container, iterator range, or C-style array. |
+| `IsEmpty()` | `argument` is an empty container (`container.empty()`). |
+| `IsSubsetOf({e0, e1, ..., en})`, `IsSubsetOf(a_container)`, `IsSubsetOf(begin, end)`, `IsSubsetOf(array)`, or `IsSubsetOf(array, count)` | `argument` matches `UnorderedElementsAre(x0, x1, ..., xk)` for some subset `{x0, x1, ..., xk}` of the expected matchers. |
+| `IsSupersetOf({e0, e1, ..., en})`, `IsSupersetOf(a_container)`, `IsSupersetOf(begin, end)`, `IsSupersetOf(array)`, or `IsSupersetOf(array, count)` | Some subset of `argument` matches `UnorderedElementsAre(`expected matchers`)`. |
+| `Pointwise(m, container)`, `Pointwise(m, {e0, e1, ..., en})` | `argument` contains the same number of elements as in `container`, and for all i, (the i-th element in `argument`, the i-th element in `container`) match `m`, which is a matcher on 2-tuples. E.g. `Pointwise(Le(), upper_bounds)` verifies that each element in `argument` doesn't exceed the corresponding element in `upper_bounds`. See more detail below. |
+| `SizeIs(m)` | `argument` is a container whose size matches `m`. E.g. `SizeIs(2)` or `SizeIs(Lt(2))`. |
+| `UnorderedElementsAre(e0, e1, ..., en)` | `argument` has `n + 1` elements, and under *some* permutation of the elements, each element matches an `ei` (for a different `i`), which can be a value or a matcher. |
+| `UnorderedElementsAreArray({e0, e1, ..., en})`, `UnorderedElementsAreArray(a_container)`, `UnorderedElementsAreArray(begin, end)`, `UnorderedElementsAreArray(array)`, or `UnorderedElementsAreArray(array, count)` | The same as `UnorderedElementsAre()` except that the expected element values/matchers come from an initializer list, STL-style container, iterator range, or C-style array. |
+| `UnorderedPointwise(m, container)`, `UnorderedPointwise(m, {e0, e1, ..., en})` | Like `Pointwise(m, container)`, but ignores the order of elements. |
+| `WhenSorted(m)` | When `argument` is sorted using the `<` operator, it matches container matcher `m`. E.g. `WhenSorted(ElementsAre(1, 2, 3))` verifies that `argument` contains elements 1, 2, and 3, ignoring order. |
+| `WhenSortedBy(comparator, m)` | The same as `WhenSorted(m)`, except that the given comparator instead of `<` is used to sort `argument`. E.g. `WhenSortedBy(std::greater(), ElementsAre(3, 2, 1))`. |
+
+**Notes:**
+
+*   These matchers can also match:
+    1.  a native array passed by reference (e.g. in `Foo(const int (&a)[5])`),
+        and
+    2.  an array passed as a pointer and a count (e.g. in `Bar(const T* buffer,
+        int len)` -- see [Multi-argument Matchers](#MultiArgMatchers)).
+*   The array being matched may be multi-dimensional (i.e. its elements can be
+    arrays).
+*   `m` in `Pointwise(m, ...)` and `UnorderedPointwise(m, ...)` should be a
+    matcher for `::std::tuple<T, U>` where `T` and `U` are the element type of
+    the actual container and the expected container, respectively. For example,
+    to compare two `Foo` containers where `Foo` doesn't support `operator==`,
+    one might write:
+
+    ```cpp
+    using ::std::get;
+    MATCHER(FooEq, "") {
+      return std::get<0>(arg).Equals(std::get<1>(arg));
+    }
+    ...
+    EXPECT_THAT(actual_foos, Pointwise(FooEq(), expected_foos));
+    ```
+
+## Member Matchers
+
+| Matcher                         | Description                                |
+| :------------------------------ | :----------------------------------------- |
+| `Field(&class::field, m)`       | `argument.field` (or `argument->field` when `argument` is a plain pointer) matches matcher `m`, where `argument` is an object of type _class_. |
+| `Field(field_name, &class::field, m)` | The same as the two-parameter version, but provides a better error message. |
+| `Key(e)`                        | `argument.first` matches `e`, which can be either a value or a matcher. E.g. `Contains(Key(Le(5)))` can verify that a `map` contains a key `<= 5`. |
+| `Pair(m1, m2)`                  | `argument` is an `std::pair` whose `first` field matches `m1` and `second` field matches `m2`. |
+| `FieldsAre(m...)`                   | `argument` is a compatible object where each field matches piecewise with the matchers `m...`. A compatible object is any that supports the `std::tuple_size<Obj>`+`get<I>(obj)` protocol. In C++17 and up this also supports types compatible with structured bindings, like aggregates. |
+| `Property(&class::property, m)` | `argument.property()` (or `argument->property()` when `argument` is a plain pointer) matches matcher `m`, where `argument` is an object of type _class_. The method `property()` must take no argument and be declared as `const`. |
+| `Property(property_name, &class::property, m)` | The same as the two-parameter version, but provides a better error message.
+
+**Notes:**
+
+*   You can use `FieldsAre()` to match any type that supports structured
+    bindings, such as `std::tuple`, `std::pair`, `std::array`, and aggregate
+    types. For example:
+
+    ```cpp
+    std::tuple<int, std::string> my_tuple{7, "hello world"};
+    EXPECT_THAT(my_tuple, FieldsAre(Ge(0), HasSubstr("hello")));
+
+    struct MyStruct {
+      int value = 42;
+      std::string greeting = "aloha";
+    };
+    MyStruct s;
+    EXPECT_THAT(s, FieldsAre(42, "aloha"));
+    ```
+
+*   Don't use `Property()` against member functions that you do not own, because
+    taking addresses of functions is fragile and generally not part of the
+    contract of the function.
+
+## Matching the Result of a Function, Functor, or Callback
+
+| Matcher          | Description                                       |
+| :--------------- | :------------------------------------------------ |
+| `ResultOf(f, m)` | `f(argument)` matches matcher `m`, where `f` is a function or functor. |
+
+## Pointer Matchers
+
+| Matcher                   | Description                                     |
+| :------------------------ | :---------------------------------------------- |
+| `Address(m)`              | the result of `std::addressof(argument)` matches `m`. |
+| `Pointee(m)`              | `argument` (either a smart pointer or a raw pointer) points to a value that matches matcher `m`. |
+| `Pointer(m)`              | `argument` (either a smart pointer or a raw pointer) contains a pointer that matches `m`. `m` will match against the raw pointer regardless of the type of `argument`. |
+| `WhenDynamicCastTo<T>(m)` | when `argument` is passed through `dynamic_cast<T>()`, it matches matcher `m`. |
+
+## Multi-argument Matchers {#MultiArgMatchers}
+
+Technically, all matchers match a *single* value. A "multi-argument" matcher is
+just one that matches a *tuple*. The following matchers can be used to match a
+tuple `(x, y)`:
+
+Matcher | Description
+:------ | :----------
+`Eq()`  | `x == y`
+`Ge()`  | `x >= y`
+`Gt()`  | `x > y`
+`Le()`  | `x <= y`
+`Lt()`  | `x < y`
+`Ne()`  | `x != y`
+
+You can use the following selectors to pick a subset of the arguments (or
+reorder them) to participate in the matching:
+
+| Matcher                    | Description                                     |
+| :------------------------- | :---------------------------------------------- |
+| `AllArgs(m)`               | Equivalent to `m`. Useful as syntactic sugar in `.With(AllArgs(m))`. |
+| `Args<N1, N2, ..., Nk>(m)` | The tuple of the `k` selected (using 0-based indices) arguments matches `m`, e.g. `Args<1, 2>(Eq())`. |
+
+## Composite Matchers
+
+You can make a matcher from one or more other matchers:
+
+| Matcher                          | Description                             |
+| :------------------------------- | :-------------------------------------- |
+| `AllOf(m1, m2, ..., mn)` | `argument` matches all of the matchers `m1` to `mn`. |
+| `AllOfArray({m0, m1, ..., mn})`, `AllOfArray(a_container)`, `AllOfArray(begin, end)`, `AllOfArray(array)`, or `AllOfArray(array, count)` | The same as `AllOf()` except that the matchers come from an initializer list, STL-style container, iterator range, or C-style array. |
+| `AnyOf(m1, m2, ..., mn)` | `argument` matches at least one of the matchers `m1` to `mn`. |
+| `AnyOfArray({m0, m1, ..., mn})`, `AnyOfArray(a_container)`, `AnyOfArray(begin, end)`, `AnyOfArray(array)`, or `AnyOfArray(array, count)` | The same as `AnyOf()` except that the matchers come from an initializer list, STL-style container, iterator range, or C-style array. |
+| `Not(m)` | `argument` doesn't match matcher `m`. |
+
+## Adapters for Matchers
+
+| Matcher                 | Description                           |
+| :---------------------- | :------------------------------------ |
+| `MatcherCast<T>(m)`     | casts matcher `m` to type `Matcher<T>`. |
+| `SafeMatcherCast<T>(m)` | [safely casts](../gmock_cook_book.md#SafeMatcherCast) matcher `m` to type `Matcher<T>`. |
+| `Truly(predicate)`      | `predicate(argument)` returns something considered by C++ to be true, where `predicate` is a function or functor. |
+
+`AddressSatisfies(callback)` and `Truly(callback)` take ownership of `callback`,
+which must be a permanent callback.
+
+## Using Matchers as Predicates {#MatchersAsPredicatesCheat}
+
+| Matcher                       | Description                                 |
+| :---------------------------- | :------------------------------------------ |
+| `Matches(m)(value)` | evaluates to `true` if `value` matches `m`. You can use `Matches(m)` alone as a unary functor. |
+| `ExplainMatchResult(m, value, result_listener)` | evaluates to `true` if `value` matches `m`, explaining the result to `result_listener`. |
+| `Value(value, m)` | evaluates to `true` if `value` matches `m`. |
+
+## Defining Matchers
+
+| Matcher                              | Description                           |
+| :----------------------------------- | :------------------------------------ |
+| `MATCHER(IsEven, "") { return (arg % 2) == 0; }` | Defines a matcher `IsEven()` to match an even number. |
+| `MATCHER_P(IsDivisibleBy, n, "") { *result_listener << "where the remainder is " << (arg % n); return (arg % n) == 0; }` | Defines a matcher `IsDivisibleBy(n)` to match a number divisible by `n`. |
+| `MATCHER_P2(IsBetween, a, b, absl::StrCat(negation ? "isn't" : "is", " between ", PrintToString(a), " and ", PrintToString(b))) { return a <= arg && arg <= b; }` | Defines a matcher `IsBetween(a, b)` to match a value in the range [`a`, `b`]. |
+
+**Notes:**
+
+1.  The `MATCHER*` macros cannot be used inside a function or class.
+2.  The matcher body must be *purely functional* (i.e. it cannot have any side
+    effect, and the result must not depend on anything other than the value
+    being matched and the matcher parameters).
+3.  You can use `PrintToString(x)` to convert a value `x` of any type to a
+    string.
+4.  You can use `ExplainMatchResult()` in a custom matcher to wrap another
+    matcher, for example:
+
+    ```cpp
+    MATCHER_P(NestedPropertyMatches, matcher, "") {
+      return ExplainMatchResult(matcher, arg.nested().property(), result_listener);
+    }
+    ```
diff --git a/leveldb_base/third_party/googletest/docs/samples.md b/leveldb_base/third_party/googletest/docs/samples.md
new file mode 100644
index 0000000..2d97ca5
--- /dev/null
+++ b/leveldb_base/third_party/googletest/docs/samples.md
@@ -0,0 +1,22 @@
+# Googletest Samples
+
+If you're like us, you'd like to look at
+[googletest samples.](https://github.com/google/googletest/tree/master/googletest/samples)
+The sample directory has a number of well-commented samples showing how to use a
+variety of googletest features.
+
+*   Sample #1 shows the basic steps of using googletest to test C++ functions.
+*   Sample #2 shows a more complex unit test for a class with multiple member
+    functions.
+*   Sample #3 uses a test fixture.
+*   Sample #4 teaches you how to use googletest and `googletest.h` together to
+    get the best of both libraries.
+*   Sample #5 puts shared testing logic in a base test fixture, and reuses it in
+    derived fixtures.
+*   Sample #6 demonstrates type-parameterized tests.
+*   Sample #7 teaches the basics of value-parameterized tests.
+*   Sample #8 shows using `Combine()` in value-parameterized tests.
+*   Sample #9 shows use of the listener API to modify Google Test's console
+    output and the use of its reflection API to inspect test results.
+*   Sample #10 shows use of the listener API to implement a primitive memory
+    leak checker.
diff --git a/leveldb_base/third_party/googletest/googlemock/CMakeLists.txt b/leveldb_base/third_party/googletest/googlemock/CMakeLists.txt
new file mode 100644
index 0000000..e7df8ec
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/CMakeLists.txt
@@ -0,0 +1,218 @@
+########################################################################
+# Note: CMake support is community-based. The maintainers do not use CMake
+# internally.
+#
+# CMake build script for Google Mock.
+#
+# To run the tests for Google Mock itself on Linux, use 'make test' or
+# ctest.  You can select which tests to run using 'ctest -R regex'.
+# For more options, run 'ctest --help'.
+
+option(gmock_build_tests "Build all of Google Mock's own tests." OFF)
+
+# A directory to find Google Test sources.
+if (EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/gtest/CMakeLists.txt")
+  set(gtest_dir gtest)
+else()
+  set(gtest_dir ../googletest)
+endif()
+
+# Defines pre_project_set_up_hermetic_build() and set_up_hermetic_build().
+include("${gtest_dir}/cmake/hermetic_build.cmake" OPTIONAL)
+
+if (COMMAND pre_project_set_up_hermetic_build)
+  # Google Test also calls hermetic setup functions from add_subdirectory,
+  # although its changes will not affect things at the current scope.
+  pre_project_set_up_hermetic_build()
+endif()
+
+########################################################################
+#
+# Project-wide settings
+
+# Name of the project.
+#
+# CMake files in this project can refer to the root source directory
+# as ${gmock_SOURCE_DIR} and to the root binary directory as
+# ${gmock_BINARY_DIR}.
+# Language "C" is required for find_package(Threads).
+if (CMAKE_VERSION VERSION_LESS 3.0)
+  project(gmock CXX C)
+else()
+  cmake_policy(SET CMP0048 NEW)
+  project(gmock VERSION ${GOOGLETEST_VERSION} LANGUAGES CXX C)
+endif()
+cmake_minimum_required(VERSION 2.8.12)
+
+if (COMMAND set_up_hermetic_build)
+  set_up_hermetic_build()
+endif()
+
+# Instructs CMake to process Google Test's CMakeLists.txt and add its
+# targets to the current scope.  We are placing Google Test's binary
+# directory in a subdirectory of our own as VC compilation may break
+# if they are the same (the default).
+add_subdirectory("${gtest_dir}" "${gmock_BINARY_DIR}/${gtest_dir}")
+
+
+# These commands only run if this is the main project
+if(CMAKE_PROJECT_NAME STREQUAL "gmock" OR CMAKE_PROJECT_NAME STREQUAL "googletest-distribution")
+  # BUILD_SHARED_LIBS is a standard CMake variable, but we declare it here to
+  # make it prominent in the GUI.
+  option(BUILD_SHARED_LIBS "Build shared libraries (DLLs)." OFF)
+else()
+  mark_as_advanced(gmock_build_tests)
+endif()
+
+# Although Google Test's CMakeLists.txt calls this function, the
+# changes there don't affect the current scope.  Therefore we have to
+# call it again here.
+config_compiler_and_linker()  # from ${gtest_dir}/cmake/internal_utils.cmake
+
+# Adds Google Mock's and Google Test's header directories to the search path.
+set(gmock_build_include_dirs
+  "${gmock_SOURCE_DIR}/include"
+  "${gmock_SOURCE_DIR}"
+  "${gtest_SOURCE_DIR}/include"
+  # This directory is needed to build directly from Google Test sources.
+  "${gtest_SOURCE_DIR}")
+include_directories(${gmock_build_include_dirs})
+
+########################################################################
+#
+# Defines the gmock & gmock_main libraries.  User tests should link
+# with one of them.
+
+# Google Mock libraries.  We build them using more strict warnings than what
+# are used for other targets, to ensure that Google Mock can be compiled by
+# a user aggressive about warnings.
+if (MSVC)
+  cxx_library(gmock
+              "${cxx_strict}"
+              "${gtest_dir}/src/gtest-all.cc"
+              src/gmock-all.cc)
+
+  cxx_library(gmock_main
+              "${cxx_strict}"
+              "${gtest_dir}/src/gtest-all.cc"
+              src/gmock-all.cc
+              src/gmock_main.cc)
+else()
+  cxx_library(gmock "${cxx_strict}" src/gmock-all.cc)
+  target_link_libraries(gmock PUBLIC gtest)
+  set_target_properties(gmock PROPERTIES VERSION ${GOOGLETEST_VERSION})
+  cxx_library(gmock_main "${cxx_strict}" src/gmock_main.cc)
+  target_link_libraries(gmock_main PUBLIC gmock)
+  set_target_properties(gmock_main PROPERTIES VERSION ${GOOGLETEST_VERSION})
+endif()
+# If the CMake version supports it, attach header directory information
+# to the targets for when we are part of a parent build (ie being pulled
+# in via add_subdirectory() rather than being a standalone build).
+if (DEFINED CMAKE_VERSION AND NOT "${CMAKE_VERSION}" VERSION_LESS "2.8.11")
+  target_include_directories(gmock SYSTEM INTERFACE
+    "$<BUILD_INTERFACE:${gmock_build_include_dirs}>"
+    "$<INSTALL_INTERFACE:$<INSTALL_PREFIX>/${CMAKE_INSTALL_INCLUDEDIR}>")
+  target_include_directories(gmock_main SYSTEM INTERFACE
+    "$<BUILD_INTERFACE:${gmock_build_include_dirs}>"
+    "$<INSTALL_INTERFACE:$<INSTALL_PREFIX>/${CMAKE_INSTALL_INCLUDEDIR}>")
+endif()
+
+########################################################################
+#
+# Install rules
+install_project(gmock gmock_main)
+
+########################################################################
+#
+# Google Mock's own tests.
+#
+# You can skip this section if you aren't interested in testing
+# Google Mock itself.
+#
+# The tests are not built by default.  To build them, set the
+# gmock_build_tests option to ON.  You can do it by running ccmake
+# or specifying the -Dgmock_build_tests=ON flag when running cmake.
+
+if (gmock_build_tests)
+  # This must be set in the root directory for the tests to be run by
+  # 'make test' or ctest.
+  enable_testing()
+
+  if (MINGW OR CYGWIN)
+    if (CMAKE_VERSION VERSION_LESS "2.8.12")
+      add_compile_options("-Wa,-mbig-obj")
+    else()
+      add_definitions("-Wa,-mbig-obj")
+    endif()
+  endif()
+
+  ############################################################
+  # C++ tests built with standard compiler flags.
+
+  cxx_test(gmock-actions_test gmock_main)
+  cxx_test(gmock-cardinalities_test gmock_main)
+  cxx_test(gmock_ex_test gmock_main)
+  cxx_test(gmock-function-mocker_test gmock_main)
+  cxx_test(gmock-internal-utils_test gmock_main)
+  cxx_test(gmock-matchers_test gmock_main)
+  cxx_test(gmock-more-actions_test gmock_main)
+  cxx_test(gmock-nice-strict_test gmock_main)
+  cxx_test(gmock-port_test gmock_main)
+  cxx_test(gmock-spec-builders_test gmock_main)
+  cxx_test(gmock_link_test gmock_main test/gmock_link2_test.cc)
+  cxx_test(gmock_test gmock_main)
+
+  if (DEFINED GTEST_HAS_PTHREAD)
+    cxx_test(gmock_stress_test gmock)
+  endif()
+
+  # gmock_all_test is commented to save time building and running tests.
+  # Uncomment if necessary.
+  # cxx_test(gmock_all_test gmock_main)
+
+  ############################################################
+  # C++ tests built with non-standard compiler flags.
+
+  if (MSVC)
+    cxx_library(gmock_main_no_exception "${cxx_no_exception}"
+      "${gtest_dir}/src/gtest-all.cc" src/gmock-all.cc src/gmock_main.cc)
+
+    cxx_library(gmock_main_no_rtti "${cxx_no_rtti}"
+      "${gtest_dir}/src/gtest-all.cc" src/gmock-all.cc src/gmock_main.cc)
+
+  else()
+    cxx_library(gmock_main_no_exception "${cxx_no_exception}" src/gmock_main.cc)
+    target_link_libraries(gmock_main_no_exception PUBLIC gmock)
+
+    cxx_library(gmock_main_no_rtti "${cxx_no_rtti}" src/gmock_main.cc)
+    target_link_libraries(gmock_main_no_rtti PUBLIC gmock)
+  endif()
+  cxx_test_with_flags(gmock-more-actions_no_exception_test "${cxx_no_exception}"
+    gmock_main_no_exception test/gmock-more-actions_test.cc)
+
+  cxx_test_with_flags(gmock_no_rtti_test "${cxx_no_rtti}"
+    gmock_main_no_rtti test/gmock-spec-builders_test.cc)
+
+  cxx_shared_library(shared_gmock_main "${cxx_default}"
+    "${gtest_dir}/src/gtest-all.cc" src/gmock-all.cc src/gmock_main.cc)
+
+  # Tests that a binary can be built with Google Mock as a shared library.  On
+  # some system configurations, it may not possible to run the binary without
+  # knowing more details about the system configurations. We do not try to run
+  # this binary. To get a more robust shared library coverage, configure with
+  # -DBUILD_SHARED_LIBS=ON.
+  cxx_executable_with_flags(shared_gmock_test_ "${cxx_default}"
+    shared_gmock_main test/gmock-spec-builders_test.cc)
+  set_target_properties(shared_gmock_test_
+    PROPERTIES
+    COMPILE_DEFINITIONS "GTEST_LINKED_AS_SHARED_LIBRARY=1")
+
+  ############################################################
+  # Python tests.
+
+  cxx_executable(gmock_leak_test_ test gmock_main)
+  py_test(gmock_leak_test)
+
+  cxx_executable(gmock_output_test_ test gmock)
+  py_test(gmock_output_test)
+endif()
diff --git a/leveldb_base/third_party/googletest/googlemock/README.md b/leveldb_base/third_party/googletest/googlemock/README.md
new file mode 100644
index 0000000..ead6883
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/README.md
@@ -0,0 +1,44 @@
+# Googletest Mocking (gMock) Framework
+
+### Overview
+
+Google's framework for writing and using C++ mock classes. It can help you
+derive better designs of your system and write better tests.
+
+It is inspired by:
+
+*   [jMock](http://www.jmock.org/)
+*   [EasyMock](http://www.easymock.org/)
+*   [Hamcrest](http://code.google.com/p/hamcrest/)
+
+It is designed with C++'s specifics in mind.
+
+gMock:
+
+-   Provides a declarative syntax for defining mocks.
+-   Can define partial (hybrid) mocks, which are a cross of real and mock
+    objects.
+-   Handles functions of arbitrary types and overloaded functions.
+-   Comes with a rich set of matchers for validating function arguments.
+-   Uses an intuitive syntax for controlling the behavior of a mock.
+-   Does automatic verification of expectations (no record-and-replay needed).
+-   Allows arbitrary (partial) ordering constraints on function calls to be
+    expressed.
+-   Lets a user extend it by defining new matchers and actions.
+-   Does not use exceptions.
+-   Is easy to learn and use.
+
+Details and examples can be found here:
+
+*   [gMock for Dummies](https://google.github.io/googletest/gmock_for_dummies.html)
+*   [Legacy gMock FAQ](https://google.github.io/googletest/gmock_faq.html)
+*   [gMock Cookbook](https://google.github.io/googletest/gmock_cook_book.html)
+*   [gMock Cheat Sheet](https://google.github.io/googletest/gmock_cheat_sheet.html)
+
+Please note that code under scripts/generator/ is from the
+[cppclean project](http://code.google.com/p/cppclean/) and under the Apache
+License, which is different from GoogleMock's license.
+
+GoogleMock is a part of
+[GoogleTest C++ testing framework](http://github.com/google/googletest/) and a
+subject to the same requirements.
diff --git a/leveldb_base/third_party/googletest/googlemock/cmake/gmock.pc.in b/leveldb_base/third_party/googletest/googlemock/cmake/gmock.pc.in
new file mode 100644
index 0000000..23c67b5
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/cmake/gmock.pc.in
@@ -0,0 +1,10 @@
+libdir=@CMAKE_INSTALL_FULL_LIBDIR@
+includedir=@CMAKE_INSTALL_FULL_INCLUDEDIR@
+
+Name: gmock
+Description: GoogleMock (without main() function)
+Version: @PROJECT_VERSION@
+URL: https://github.com/google/googletest
+Requires: gtest = @PROJECT_VERSION@
+Libs: -L${libdir} -lgmock @CMAKE_THREAD_LIBS_INIT@
+Cflags: -I${includedir} @GTEST_HAS_PTHREAD_MACRO@
diff --git a/leveldb_base/third_party/googletest/googlemock/cmake/gmock_main.pc.in b/leveldb_base/third_party/googletest/googlemock/cmake/gmock_main.pc.in
new file mode 100644
index 0000000..66ffea7
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/cmake/gmock_main.pc.in
@@ -0,0 +1,10 @@
+libdir=@CMAKE_INSTALL_FULL_LIBDIR@
+includedir=@CMAKE_INSTALL_FULL_INCLUDEDIR@
+
+Name: gmock_main
+Description: GoogleMock (with main() function)
+Version: @PROJECT_VERSION@
+URL: https://github.com/google/googletest
+Requires: gmock = @PROJECT_VERSION@
+Libs: -L${libdir} -lgmock_main @CMAKE_THREAD_LIBS_INIT@
+Cflags: -I${includedir} @GTEST_HAS_PTHREAD_MACRO@
diff --git a/leveldb_base/third_party/googletest/googlemock/docs/README.md b/leveldb_base/third_party/googletest/googlemock/docs/README.md
new file mode 100644
index 0000000..1bc57b7
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/docs/README.md
@@ -0,0 +1,4 @@
+# Content Moved
+
+We are working on updates to the GoogleTest documentation, which has moved to
+the top-level [docs](../../docs) directory.
diff --git a/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-actions.h b/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-actions.h
new file mode 100644
index 0000000..f2393bd
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-actions.h
@@ -0,0 +1,1687 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// The ACTION* family of macros can be used in a namespace scope to
+// define custom actions easily.  The syntax:
+//
+//   ACTION(name) { statements; }
+//
+// will define an action with the given name that executes the
+// statements.  The value returned by the statements will be used as
+// the return value of the action.  Inside the statements, you can
+// refer to the K-th (0-based) argument of the mock function by
+// 'argK', and refer to its type by 'argK_type'.  For example:
+//
+//   ACTION(IncrementArg1) {
+//     arg1_type temp = arg1;
+//     return ++(*temp);
+//   }
+//
+// allows you to write
+//
+//   ...WillOnce(IncrementArg1());
+//
+// You can also refer to the entire argument tuple and its type by
+// 'args' and 'args_type', and refer to the mock function type and its
+// return type by 'function_type' and 'return_type'.
+//
+// Note that you don't need to specify the types of the mock function
+// arguments.  However rest assured that your code is still type-safe:
+// you'll get a compiler error if *arg1 doesn't support the ++
+// operator, or if the type of ++(*arg1) isn't compatible with the
+// mock function's return type, for example.
+//
+// Sometimes you'll want to parameterize the action.   For that you can use
+// another macro:
+//
+//   ACTION_P(name, param_name) { statements; }
+//
+// For example:
+//
+//   ACTION_P(Add, n) { return arg0 + n; }
+//
+// will allow you to write:
+//
+//   ...WillOnce(Add(5));
+//
+// Note that you don't need to provide the type of the parameter
+// either.  If you need to reference the type of a parameter named
+// 'foo', you can write 'foo_type'.  For example, in the body of
+// ACTION_P(Add, n) above, you can write 'n_type' to refer to the type
+// of 'n'.
+//
+// We also provide ACTION_P2, ACTION_P3, ..., up to ACTION_P10 to support
+// multi-parameter actions.
+//
+// For the purpose of typing, you can view
+//
+//   ACTION_Pk(Foo, p1, ..., pk) { ... }
+//
+// as shorthand for
+//
+//   template <typename p1_type, ..., typename pk_type>
+//   FooActionPk<p1_type, ..., pk_type> Foo(p1_type p1, ..., pk_type pk) { ... }
+//
+// In particular, you can provide the template type arguments
+// explicitly when invoking Foo(), as in Foo<long, bool>(5, false);
+// although usually you can rely on the compiler to infer the types
+// for you automatically.  You can assign the result of expression
+// Foo(p1, ..., pk) to a variable of type FooActionPk<p1_type, ...,
+// pk_type>.  This can be useful when composing actions.
+//
+// You can also overload actions with different numbers of parameters:
+//
+//   ACTION_P(Plus, a) { ... }
+//   ACTION_P2(Plus, a, b) { ... }
+//
+// While it's tempting to always use the ACTION* macros when defining
+// a new action, you should also consider implementing ActionInterface
+// or using MakePolymorphicAction() instead, especially if you need to
+// use the action a lot.  While these approaches require more work,
+// they give you more control on the types of the mock function
+// arguments and the action parameters, which in general leads to
+// better compiler error messages that pay off in the long run.  They
+// also allow overloading actions based on parameter types (as opposed
+// to just based on the number of parameters).
+//
+// CAVEAT:
+//
+// ACTION*() can only be used in a namespace scope as templates cannot be
+// declared inside of a local class.
+// Users can, however, define any local functors (e.g. a lambda) that
+// can be used as actions.
+//
+// MORE INFORMATION:
+//
+// To learn more about using these macros, please search for 'ACTION' on
+// https://github.com/google/googletest/blob/master/docs/gmock_cook_book.md
+
+// GOOGLETEST_CM0002 DO NOT DELETE
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_ACTIONS_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_ACTIONS_H_
+
+#ifndef _WIN32_WCE
+# include <errno.h>
+#endif
+
+#include <algorithm>
+#include <functional>
+#include <memory>
+#include <string>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+
+#include "gmock/internal/gmock-internal-utils.h"
+#include "gmock/internal/gmock-port.h"
+#include "gmock/internal/gmock-pp.h"
+
+#ifdef _MSC_VER
+# pragma warning(push)
+# pragma warning(disable:4100)
+#endif
+
+namespace testing {
+
+// To implement an action Foo, define:
+//   1. a class FooAction that implements the ActionInterface interface, and
+//   2. a factory function that creates an Action object from a
+//      const FooAction*.
+//
+// The two-level delegation design follows that of Matcher, providing
+// consistency for extension developers.  It also eases ownership
+// management as Action objects can now be copied like plain values.
+
+namespace internal {
+
+// BuiltInDefaultValueGetter<T, true>::Get() returns a
+// default-constructed T value.  BuiltInDefaultValueGetter<T,
+// false>::Get() crashes with an error.
+//
+// This primary template is used when kDefaultConstructible is true.
+template <typename T, bool kDefaultConstructible>
+struct BuiltInDefaultValueGetter {
+  static T Get() { return T(); }
+};
+template <typename T>
+struct BuiltInDefaultValueGetter<T, false> {
+  static T Get() {
+    Assert(false, __FILE__, __LINE__,
+           "Default action undefined for the function return type.");
+    return internal::Invalid<T>();
+    // The above statement will never be reached, but is required in
+    // order for this function to compile.
+  }
+};
+
+// BuiltInDefaultValue<T>::Get() returns the "built-in" default value
+// for type T, which is NULL when T is a raw pointer type, 0 when T is
+// a numeric type, false when T is bool, or "" when T is string or
+// std::string.  In addition, in C++11 and above, it turns a
+// default-constructed T value if T is default constructible.  For any
+// other type T, the built-in default T value is undefined, and the
+// function will abort the process.
+template <typename T>
+class BuiltInDefaultValue {
+ public:
+  // This function returns true if and only if type T has a built-in default
+  // value.
+  static bool Exists() {
+    return ::std::is_default_constructible<T>::value;
+  }
+
+  static T Get() {
+    return BuiltInDefaultValueGetter<
+        T, ::std::is_default_constructible<T>::value>::Get();
+  }
+};
+
+// This partial specialization says that we use the same built-in
+// default value for T and const T.
+template <typename T>
+class BuiltInDefaultValue<const T> {
+ public:
+  static bool Exists() { return BuiltInDefaultValue<T>::Exists(); }
+  static T Get() { return BuiltInDefaultValue<T>::Get(); }
+};
+
+// This partial specialization defines the default values for pointer
+// types.
+template <typename T>
+class BuiltInDefaultValue<T*> {
+ public:
+  static bool Exists() { return true; }
+  static T* Get() { return nullptr; }
+};
+
+// The following specializations define the default values for
+// specific types we care about.
+#define GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(type, value) \
+  template <> \
+  class BuiltInDefaultValue<type> { \
+   public: \
+    static bool Exists() { return true; } \
+    static type Get() { return value; } \
+  }
+
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(void, );  // NOLINT
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(::std::string, "");
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(bool, false);
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(unsigned char, '\0');
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(signed char, '\0');
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(char, '\0');
+
+// There's no need for a default action for signed wchar_t, as that
+// type is the same as wchar_t for gcc, and invalid for MSVC.
+//
+// There's also no need for a default action for unsigned wchar_t, as
+// that type is the same as unsigned int for gcc, and invalid for
+// MSVC.
+#if GMOCK_WCHAR_T_IS_NATIVE_
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(wchar_t, 0U);  // NOLINT
+#endif
+
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(unsigned short, 0U);  // NOLINT
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(signed short, 0);     // NOLINT
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(unsigned int, 0U);
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(signed int, 0);
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(unsigned long, 0UL);  // NOLINT
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(signed long, 0L);     // NOLINT
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(unsigned long long, 0);  // NOLINT
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(signed long long, 0);  // NOLINT
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(float, 0);
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(double, 0);
+
+#undef GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_
+
+// Simple two-arg form of std::disjunction.
+template <typename P, typename Q>
+using disjunction = typename ::std::conditional<P::value, P, Q>::type;
+
+}  // namespace internal
+
+// When an unexpected function call is encountered, Google Mock will
+// let it return a default value if the user has specified one for its
+// return type, or if the return type has a built-in default value;
+// otherwise Google Mock won't know what value to return and will have
+// to abort the process.
+//
+// The DefaultValue<T> class allows a user to specify the
+// default value for a type T that is both copyable and publicly
+// destructible (i.e. anything that can be used as a function return
+// type).  The usage is:
+//
+//   // Sets the default value for type T to be foo.
+//   DefaultValue<T>::Set(foo);
+template <typename T>
+class DefaultValue {
+ public:
+  // Sets the default value for type T; requires T to be
+  // copy-constructable and have a public destructor.
+  static void Set(T x) {
+    delete producer_;
+    producer_ = new FixedValueProducer(x);
+  }
+
+  // Provides a factory function to be called to generate the default value.
+  // This method can be used even if T is only move-constructible, but it is not
+  // limited to that case.
+  typedef T (*FactoryFunction)();
+  static void SetFactory(FactoryFunction factory) {
+    delete producer_;
+    producer_ = new FactoryValueProducer(factory);
+  }
+
+  // Unsets the default value for type T.
+  static void Clear() {
+    delete producer_;
+    producer_ = nullptr;
+  }
+
+  // Returns true if and only if the user has set the default value for type T.
+  static bool IsSet() { return producer_ != nullptr; }
+
+  // Returns true if T has a default return value set by the user or there
+  // exists a built-in default value.
+  static bool Exists() {
+    return IsSet() || internal::BuiltInDefaultValue<T>::Exists();
+  }
+
+  // Returns the default value for type T if the user has set one;
+  // otherwise returns the built-in default value. Requires that Exists()
+  // is true, which ensures that the return value is well-defined.
+  static T Get() {
+    return producer_ == nullptr ? internal::BuiltInDefaultValue<T>::Get()
+                                : producer_->Produce();
+  }
+
+ private:
+  class ValueProducer {
+   public:
+    virtual ~ValueProducer() {}
+    virtual T Produce() = 0;
+  };
+
+  class FixedValueProducer : public ValueProducer {
+   public:
+    explicit FixedValueProducer(T value) : value_(value) {}
+    T Produce() override { return value_; }
+
+   private:
+    const T value_;
+    GTEST_DISALLOW_COPY_AND_ASSIGN_(FixedValueProducer);
+  };
+
+  class FactoryValueProducer : public ValueProducer {
+   public:
+    explicit FactoryValueProducer(FactoryFunction factory)
+        : factory_(factory) {}
+    T Produce() override { return factory_(); }
+
+   private:
+    const FactoryFunction factory_;
+    GTEST_DISALLOW_COPY_AND_ASSIGN_(FactoryValueProducer);
+  };
+
+  static ValueProducer* producer_;
+};
+
+// This partial specialization allows a user to set default values for
+// reference types.
+template <typename T>
+class DefaultValue<T&> {
+ public:
+  // Sets the default value for type T&.
+  static void Set(T& x) {  // NOLINT
+    address_ = &x;
+  }
+
+  // Unsets the default value for type T&.
+  static void Clear() { address_ = nullptr; }
+
+  // Returns true if and only if the user has set the default value for type T&.
+  static bool IsSet() { return address_ != nullptr; }
+
+  // Returns true if T has a default return value set by the user or there
+  // exists a built-in default value.
+  static bool Exists() {
+    return IsSet() || internal::BuiltInDefaultValue<T&>::Exists();
+  }
+
+  // Returns the default value for type T& if the user has set one;
+  // otherwise returns the built-in default value if there is one;
+  // otherwise aborts the process.
+  static T& Get() {
+    return address_ == nullptr ? internal::BuiltInDefaultValue<T&>::Get()
+                               : *address_;
+  }
+
+ private:
+  static T* address_;
+};
+
+// This specialization allows DefaultValue<void>::Get() to
+// compile.
+template <>
+class DefaultValue<void> {
+ public:
+  static bool Exists() { return true; }
+  static void Get() {}
+};
+
+// Points to the user-set default value for type T.
+template <typename T>
+typename DefaultValue<T>::ValueProducer* DefaultValue<T>::producer_ = nullptr;
+
+// Points to the user-set default value for type T&.
+template <typename T>
+T* DefaultValue<T&>::address_ = nullptr;
+
+// Implement this interface to define an action for function type F.
+template <typename F>
+class ActionInterface {
+ public:
+  typedef typename internal::Function<F>::Result Result;
+  typedef typename internal::Function<F>::ArgumentTuple ArgumentTuple;
+
+  ActionInterface() {}
+  virtual ~ActionInterface() {}
+
+  // Performs the action.  This method is not const, as in general an
+  // action can have side effects and be stateful.  For example, a
+  // get-the-next-element-from-the-collection action will need to
+  // remember the current element.
+  virtual Result Perform(const ArgumentTuple& args) = 0;
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(ActionInterface);
+};
+
+// An Action<F> is a copyable and IMMUTABLE (except by assignment)
+// object that represents an action to be taken when a mock function
+// of type F is called.  The implementation of Action<T> is just a
+// std::shared_ptr to const ActionInterface<T>. Don't inherit from Action!
+// You can view an object implementing ActionInterface<F> as a
+// concrete action (including its current state), and an Action<F>
+// object as a handle to it.
+template <typename F>
+class Action {
+  // Adapter class to allow constructing Action from a legacy ActionInterface.
+  // New code should create Actions from functors instead.
+  struct ActionAdapter {
+    // Adapter must be copyable to satisfy std::function requirements.
+    ::std::shared_ptr<ActionInterface<F>> impl_;
+
+    template <typename... Args>
+    typename internal::Function<F>::Result operator()(Args&&... args) {
+      return impl_->Perform(
+          ::std::forward_as_tuple(::std::forward<Args>(args)...));
+    }
+  };
+
+  template <typename G>
+  using IsCompatibleFunctor = std::is_constructible<std::function<F>, G>;
+
+ public:
+  typedef typename internal::Function<F>::Result Result;
+  typedef typename internal::Function<F>::ArgumentTuple ArgumentTuple;
+
+  // Constructs a null Action.  Needed for storing Action objects in
+  // STL containers.
+  Action() {}
+
+  // Construct an Action from a specified callable.
+  // This cannot take std::function directly, because then Action would not be
+  // directly constructible from lambda (it would require two conversions).
+  template <
+      typename G,
+      typename = typename std::enable_if<internal::disjunction<
+          IsCompatibleFunctor<G>, std::is_constructible<std::function<Result()>,
+                                                        G>>::value>::type>
+  Action(G&& fun) {  // NOLINT
+    Init(::std::forward<G>(fun), IsCompatibleFunctor<G>());
+  }
+
+  // Constructs an Action from its implementation.
+  explicit Action(ActionInterface<F>* impl)
+      : fun_(ActionAdapter{::std::shared_ptr<ActionInterface<F>>(impl)}) {}
+
+  // This constructor allows us to turn an Action<Func> object into an
+  // Action<F>, as long as F's arguments can be implicitly converted
+  // to Func's and Func's return type can be implicitly converted to F's.
+  template <typename Func>
+  explicit Action(const Action<Func>& action) : fun_(action.fun_) {}
+
+  // Returns true if and only if this is the DoDefault() action.
+  bool IsDoDefault() const { return fun_ == nullptr; }
+
+  // Performs the action.  Note that this method is const even though
+  // the corresponding method in ActionInterface is not.  The reason
+  // is that a const Action<F> means that it cannot be re-bound to
+  // another concrete action, not that the concrete action it binds to
+  // cannot change state.  (Think of the difference between a const
+  // pointer and a pointer to const.)
+  Result Perform(ArgumentTuple args) const {
+    if (IsDoDefault()) {
+      internal::IllegalDoDefault(__FILE__, __LINE__);
+    }
+    return internal::Apply(fun_, ::std::move(args));
+  }
+
+ private:
+  template <typename G>
+  friend class Action;
+
+  template <typename G>
+  void Init(G&& g, ::std::true_type) {
+    fun_ = ::std::forward<G>(g);
+  }
+
+  template <typename G>
+  void Init(G&& g, ::std::false_type) {
+    fun_ = IgnoreArgs<typename ::std::decay<G>::type>{::std::forward<G>(g)};
+  }
+
+  template <typename FunctionImpl>
+  struct IgnoreArgs {
+    template <typename... Args>
+    Result operator()(const Args&...) const {
+      return function_impl();
+    }
+
+    FunctionImpl function_impl;
+  };
+
+  // fun_ is an empty function if and only if this is the DoDefault() action.
+  ::std::function<F> fun_;
+};
+
+// The PolymorphicAction class template makes it easy to implement a
+// polymorphic action (i.e. an action that can be used in mock
+// functions of than one type, e.g. Return()).
+//
+// To define a polymorphic action, a user first provides a COPYABLE
+// implementation class that has a Perform() method template:
+//
+//   class FooAction {
+//    public:
+//     template <typename Result, typename ArgumentTuple>
+//     Result Perform(const ArgumentTuple& args) const {
+//       // Processes the arguments and returns a result, using
+//       // std::get<N>(args) to get the N-th (0-based) argument in the tuple.
+//     }
+//     ...
+//   };
+//
+// Then the user creates the polymorphic action using
+// MakePolymorphicAction(object) where object has type FooAction.  See
+// the definition of Return(void) and SetArgumentPointee<N>(value) for
+// complete examples.
+template <typename Impl>
+class PolymorphicAction {
+ public:
+  explicit PolymorphicAction(const Impl& impl) : impl_(impl) {}
+
+  template <typename F>
+  operator Action<F>() const {
+    return Action<F>(new MonomorphicImpl<F>(impl_));
+  }
+
+ private:
+  template <typename F>
+  class MonomorphicImpl : public ActionInterface<F> {
+   public:
+    typedef typename internal::Function<F>::Result Result;
+    typedef typename internal::Function<F>::ArgumentTuple ArgumentTuple;
+
+    explicit MonomorphicImpl(const Impl& impl) : impl_(impl) {}
+
+    Result Perform(const ArgumentTuple& args) override {
+      return impl_.template Perform<Result>(args);
+    }
+
+   private:
+    Impl impl_;
+  };
+
+  Impl impl_;
+};
+
+// Creates an Action from its implementation and returns it.  The
+// created Action object owns the implementation.
+template <typename F>
+Action<F> MakeAction(ActionInterface<F>* impl) {
+  return Action<F>(impl);
+}
+
+// Creates a polymorphic action from its implementation.  This is
+// easier to use than the PolymorphicAction<Impl> constructor as it
+// doesn't require you to explicitly write the template argument, e.g.
+//
+//   MakePolymorphicAction(foo);
+// vs
+//   PolymorphicAction<TypeOfFoo>(foo);
+template <typename Impl>
+inline PolymorphicAction<Impl> MakePolymorphicAction(const Impl& impl) {
+  return PolymorphicAction<Impl>(impl);
+}
+
+namespace internal {
+
+// Helper struct to specialize ReturnAction to execute a move instead of a copy
+// on return. Useful for move-only types, but could be used on any type.
+template <typename T>
+struct ByMoveWrapper {
+  explicit ByMoveWrapper(T value) : payload(std::move(value)) {}
+  T payload;
+};
+
+// Implements the polymorphic Return(x) action, which can be used in
+// any function that returns the type of x, regardless of the argument
+// types.
+//
+// Note: The value passed into Return must be converted into
+// Function<F>::Result when this action is cast to Action<F> rather than
+// when that action is performed. This is important in scenarios like
+//
+// MOCK_METHOD1(Method, T(U));
+// ...
+// {
+//   Foo foo;
+//   X x(&foo);
+//   EXPECT_CALL(mock, Method(_)).WillOnce(Return(x));
+// }
+//
+// In the example above the variable x holds reference to foo which leaves
+// scope and gets destroyed.  If copying X just copies a reference to foo,
+// that copy will be left with a hanging reference.  If conversion to T
+// makes a copy of foo, the above code is safe. To support that scenario, we
+// need to make sure that the type conversion happens inside the EXPECT_CALL
+// statement, and conversion of the result of Return to Action<T(U)> is a
+// good place for that.
+//
+// The real life example of the above scenario happens when an invocation
+// of gtl::Container() is passed into Return.
+//
+template <typename R>
+class ReturnAction {
+ public:
+  // Constructs a ReturnAction object from the value to be returned.
+  // 'value' is passed by value instead of by const reference in order
+  // to allow Return("string literal") to compile.
+  explicit ReturnAction(R value) : value_(new R(std::move(value))) {}
+
+  // This template type conversion operator allows Return(x) to be
+  // used in ANY function that returns x's type.
+  template <typename F>
+  operator Action<F>() const {  // NOLINT
+    // Assert statement belongs here because this is the best place to verify
+    // conditions on F. It produces the clearest error messages
+    // in most compilers.
+    // Impl really belongs in this scope as a local class but can't
+    // because MSVC produces duplicate symbols in different translation units
+    // in this case. Until MS fixes that bug we put Impl into the class scope
+    // and put the typedef both here (for use in assert statement) and
+    // in the Impl class. But both definitions must be the same.
+    typedef typename Function<F>::Result Result;
+    GTEST_COMPILE_ASSERT_(
+        !std::is_reference<Result>::value,
+        use_ReturnRef_instead_of_Return_to_return_a_reference);
+    static_assert(!std::is_void<Result>::value,
+                  "Can't use Return() on an action expected to return `void`.");
+    return Action<F>(new Impl<R, F>(value_));
+  }
+
+ private:
+  // Implements the Return(x) action for a particular function type F.
+  template <typename R_, typename F>
+  class Impl : public ActionInterface<F> {
+   public:
+    typedef typename Function<F>::Result Result;
+    typedef typename Function<F>::ArgumentTuple ArgumentTuple;
+
+    // The implicit cast is necessary when Result has more than one
+    // single-argument constructor (e.g. Result is std::vector<int>) and R
+    // has a type conversion operator template.  In that case, value_(value)
+    // won't compile as the compiler doesn't known which constructor of
+    // Result to call.  ImplicitCast_ forces the compiler to convert R to
+    // Result without considering explicit constructors, thus resolving the
+    // ambiguity. value_ is then initialized using its copy constructor.
+    explicit Impl(const std::shared_ptr<R>& value)
+        : value_before_cast_(*value),
+          value_(ImplicitCast_<Result>(value_before_cast_)) {}
+
+    Result Perform(const ArgumentTuple&) override { return value_; }
+
+   private:
+    GTEST_COMPILE_ASSERT_(!std::is_reference<Result>::value,
+                          Result_cannot_be_a_reference_type);
+    // We save the value before casting just in case it is being cast to a
+    // wrapper type.
+    R value_before_cast_;
+    Result value_;
+
+    GTEST_DISALLOW_COPY_AND_ASSIGN_(Impl);
+  };
+
+  // Partially specialize for ByMoveWrapper. This version of ReturnAction will
+  // move its contents instead.
+  template <typename R_, typename F>
+  class Impl<ByMoveWrapper<R_>, F> : public ActionInterface<F> {
+   public:
+    typedef typename Function<F>::Result Result;
+    typedef typename Function<F>::ArgumentTuple ArgumentTuple;
+
+    explicit Impl(const std::shared_ptr<R>& wrapper)
+        : performed_(false), wrapper_(wrapper) {}
+
+    Result Perform(const ArgumentTuple&) override {
+      GTEST_CHECK_(!performed_)
+          << "A ByMove() action should only be performed once.";
+      performed_ = true;
+      return std::move(wrapper_->payload);
+    }
+
+   private:
+    bool performed_;
+    const std::shared_ptr<R> wrapper_;
+  };
+
+  const std::shared_ptr<R> value_;
+};
+
+// Implements the ReturnNull() action.
+class ReturnNullAction {
+ public:
+  // Allows ReturnNull() to be used in any pointer-returning function. In C++11
+  // this is enforced by returning nullptr, and in non-C++11 by asserting a
+  // pointer type on compile time.
+  template <typename Result, typename ArgumentTuple>
+  static Result Perform(const ArgumentTuple&) {
+    return nullptr;
+  }
+};
+
+// Implements the Return() action.
+class ReturnVoidAction {
+ public:
+  // Allows Return() to be used in any void-returning function.
+  template <typename Result, typename ArgumentTuple>
+  static void Perform(const ArgumentTuple&) {
+    static_assert(std::is_void<Result>::value, "Result should be void.");
+  }
+};
+
+// Implements the polymorphic ReturnRef(x) action, which can be used
+// in any function that returns a reference to the type of x,
+// regardless of the argument types.
+template <typename T>
+class ReturnRefAction {
+ public:
+  // Constructs a ReturnRefAction object from the reference to be returned.
+  explicit ReturnRefAction(T& ref) : ref_(ref) {}  // NOLINT
+
+  // This template type conversion operator allows ReturnRef(x) to be
+  // used in ANY function that returns a reference to x's type.
+  template <typename F>
+  operator Action<F>() const {
+    typedef typename Function<F>::Result Result;
+    // Asserts that the function return type is a reference.  This
+    // catches the user error of using ReturnRef(x) when Return(x)
+    // should be used, and generates some helpful error message.
+    GTEST_COMPILE_ASSERT_(std::is_reference<Result>::value,
+                          use_Return_instead_of_ReturnRef_to_return_a_value);
+    return Action<F>(new Impl<F>(ref_));
+  }
+
+ private:
+  // Implements the ReturnRef(x) action for a particular function type F.
+  template <typename F>
+  class Impl : public ActionInterface<F> {
+   public:
+    typedef typename Function<F>::Result Result;
+    typedef typename Function<F>::ArgumentTuple ArgumentTuple;
+
+    explicit Impl(T& ref) : ref_(ref) {}  // NOLINT
+
+    Result Perform(const ArgumentTuple&) override { return ref_; }
+
+   private:
+    T& ref_;
+  };
+
+  T& ref_;
+};
+
+// Implements the polymorphic ReturnRefOfCopy(x) action, which can be
+// used in any function that returns a reference to the type of x,
+// regardless of the argument types.
+template <typename T>
+class ReturnRefOfCopyAction {
+ public:
+  // Constructs a ReturnRefOfCopyAction object from the reference to
+  // be returned.
+  explicit ReturnRefOfCopyAction(const T& value) : value_(value) {}  // NOLINT
+
+  // This template type conversion operator allows ReturnRefOfCopy(x) to be
+  // used in ANY function that returns a reference to x's type.
+  template <typename F>
+  operator Action<F>() const {
+    typedef typename Function<F>::Result Result;
+    // Asserts that the function return type is a reference.  This
+    // catches the user error of using ReturnRefOfCopy(x) when Return(x)
+    // should be used, and generates some helpful error message.
+    GTEST_COMPILE_ASSERT_(
+        std::is_reference<Result>::value,
+        use_Return_instead_of_ReturnRefOfCopy_to_return_a_value);
+    return Action<F>(new Impl<F>(value_));
+  }
+
+ private:
+  // Implements the ReturnRefOfCopy(x) action for a particular function type F.
+  template <typename F>
+  class Impl : public ActionInterface<F> {
+   public:
+    typedef typename Function<F>::Result Result;
+    typedef typename Function<F>::ArgumentTuple ArgumentTuple;
+
+    explicit Impl(const T& value) : value_(value) {}  // NOLINT
+
+    Result Perform(const ArgumentTuple&) override { return value_; }
+
+   private:
+    T value_;
+  };
+
+  const T value_;
+};
+
+// Implements the polymorphic ReturnRoundRobin(v) action, which can be
+// used in any function that returns the element_type of v.
+template <typename T>
+class ReturnRoundRobinAction {
+ public:
+  explicit ReturnRoundRobinAction(std::vector<T> values) {
+    GTEST_CHECK_(!values.empty())
+        << "ReturnRoundRobin requires at least one element.";
+    state_->values = std::move(values);
+  }
+
+  template <typename... Args>
+  T operator()(Args&&...) const {
+     return state_->Next();
+  }
+
+ private:
+  struct State {
+    T Next() {
+      T ret_val = values[i++];
+      if (i == values.size()) i = 0;
+      return ret_val;
+    }
+
+    std::vector<T> values;
+    size_t i = 0;
+  };
+  std::shared_ptr<State> state_ = std::make_shared<State>();
+};
+
+// Implements the polymorphic DoDefault() action.
+class DoDefaultAction {
+ public:
+  // This template type conversion operator allows DoDefault() to be
+  // used in any function.
+  template <typename F>
+  operator Action<F>() const { return Action<F>(); }  // NOLINT
+};
+
+// Implements the Assign action to set a given pointer referent to a
+// particular value.
+template <typename T1, typename T2>
+class AssignAction {
+ public:
+  AssignAction(T1* ptr, T2 value) : ptr_(ptr), value_(value) {}
+
+  template <typename Result, typename ArgumentTuple>
+  void Perform(const ArgumentTuple& /* args */) const {
+    *ptr_ = value_;
+  }
+
+ private:
+  T1* const ptr_;
+  const T2 value_;
+};
+
+#if !GTEST_OS_WINDOWS_MOBILE
+
+// Implements the SetErrnoAndReturn action to simulate return from
+// various system calls and libc functions.
+template <typename T>
+class SetErrnoAndReturnAction {
+ public:
+  SetErrnoAndReturnAction(int errno_value, T result)
+      : errno_(errno_value),
+        result_(result) {}
+  template <typename Result, typename ArgumentTuple>
+  Result Perform(const ArgumentTuple& /* args */) const {
+    errno = errno_;
+    return result_;
+  }
+
+ private:
+  const int errno_;
+  const T result_;
+};
+
+#endif  // !GTEST_OS_WINDOWS_MOBILE
+
+// Implements the SetArgumentPointee<N>(x) action for any function
+// whose N-th argument (0-based) is a pointer to x's type.
+template <size_t N, typename A, typename = void>
+struct SetArgumentPointeeAction {
+  A value;
+
+  template <typename... Args>
+  void operator()(const Args&... args) const {
+    *::std::get<N>(std::tie(args...)) = value;
+  }
+};
+
+// Implements the Invoke(object_ptr, &Class::Method) action.
+template <class Class, typename MethodPtr>
+struct InvokeMethodAction {
+  Class* const obj_ptr;
+  const MethodPtr method_ptr;
+
+  template <typename... Args>
+  auto operator()(Args&&... args) const
+      -> decltype((obj_ptr->*method_ptr)(std::forward<Args>(args)...)) {
+    return (obj_ptr->*method_ptr)(std::forward<Args>(args)...);
+  }
+};
+
+// Implements the InvokeWithoutArgs(f) action.  The template argument
+// FunctionImpl is the implementation type of f, which can be either a
+// function pointer or a functor.  InvokeWithoutArgs(f) can be used as an
+// Action<F> as long as f's type is compatible with F.
+template <typename FunctionImpl>
+struct InvokeWithoutArgsAction {
+  FunctionImpl function_impl;
+
+  // Allows InvokeWithoutArgs(f) to be used as any action whose type is
+  // compatible with f.
+  template <typename... Args>
+  auto operator()(const Args&...) -> decltype(function_impl()) {
+    return function_impl();
+  }
+};
+
+// Implements the InvokeWithoutArgs(object_ptr, &Class::Method) action.
+template <class Class, typename MethodPtr>
+struct InvokeMethodWithoutArgsAction {
+  Class* const obj_ptr;
+  const MethodPtr method_ptr;
+
+  using ReturnType =
+      decltype((std::declval<Class*>()->*std::declval<MethodPtr>())());
+
+  template <typename... Args>
+  ReturnType operator()(const Args&...) const {
+    return (obj_ptr->*method_ptr)();
+  }
+};
+
+// Implements the IgnoreResult(action) action.
+template <typename A>
+class IgnoreResultAction {
+ public:
+  explicit IgnoreResultAction(const A& action) : action_(action) {}
+
+  template <typename F>
+  operator Action<F>() const {
+    // Assert statement belongs here because this is the best place to verify
+    // conditions on F. It produces the clearest error messages
+    // in most compilers.
+    // Impl really belongs in this scope as a local class but can't
+    // because MSVC produces duplicate symbols in different translation units
+    // in this case. Until MS fixes that bug we put Impl into the class scope
+    // and put the typedef both here (for use in assert statement) and
+    // in the Impl class. But both definitions must be the same.
+    typedef typename internal::Function<F>::Result Result;
+
+    // Asserts at compile time that F returns void.
+    static_assert(std::is_void<Result>::value, "Result type should be void.");
+
+    return Action<F>(new Impl<F>(action_));
+  }
+
+ private:
+  template <typename F>
+  class Impl : public ActionInterface<F> {
+   public:
+    typedef typename internal::Function<F>::Result Result;
+    typedef typename internal::Function<F>::ArgumentTuple ArgumentTuple;
+
+    explicit Impl(const A& action) : action_(action) {}
+
+    void Perform(const ArgumentTuple& args) override {
+      // Performs the action and ignores its result.
+      action_.Perform(args);
+    }
+
+   private:
+    // Type OriginalFunction is the same as F except that its return
+    // type is IgnoredValue.
+    typedef typename internal::Function<F>::MakeResultIgnoredValue
+        OriginalFunction;
+
+    const Action<OriginalFunction> action_;
+  };
+
+  const A action_;
+};
+
+template <typename InnerAction, size_t... I>
+struct WithArgsAction {
+  InnerAction action;
+
+  // The inner action could be anything convertible to Action<X>.
+  // We use the conversion operator to detect the signature of the inner Action.
+  template <typename R, typename... Args>
+  operator Action<R(Args...)>() const {  // NOLINT
+    using TupleType = std::tuple<Args...>;
+    Action<R(typename std::tuple_element<I, TupleType>::type...)>
+        converted(action);
+
+    return [converted](Args... args) -> R {
+      return converted.Perform(std::forward_as_tuple(
+        std::get<I>(std::forward_as_tuple(std::forward<Args>(args)...))...));
+    };
+  }
+};
+
+template <typename... Actions>
+struct DoAllAction {
+ private:
+  template <typename T>
+  using NonFinalType =
+      typename std::conditional<std::is_scalar<T>::value, T, const T&>::type;
+
+  template <typename ActionT, size_t... I>
+  std::vector<ActionT> Convert(IndexSequence<I...>) const {
+    return {ActionT(std::get<I>(actions))...};
+  }
+
+ public:
+  std::tuple<Actions...> actions;
+
+  template <typename R, typename... Args>
+  operator Action<R(Args...)>() const {  // NOLINT
+    struct Op {
+      std::vector<Action<void(NonFinalType<Args>...)>> converted;
+      Action<R(Args...)> last;
+      R operator()(Args... args) const {
+        auto tuple_args = std::forward_as_tuple(std::forward<Args>(args)...);
+        for (auto& a : converted) {
+          a.Perform(tuple_args);
+        }
+        return last.Perform(std::move(tuple_args));
+      }
+    };
+    return Op{Convert<Action<void(NonFinalType<Args>...)>>(
+                  MakeIndexSequence<sizeof...(Actions) - 1>()),
+              std::get<sizeof...(Actions) - 1>(actions)};
+  }
+};
+
+template <typename T, typename... Params>
+struct ReturnNewAction {
+  T* operator()() const {
+    return internal::Apply(
+        [](const Params&... unpacked_params) {
+          return new T(unpacked_params...);
+        },
+        params);
+  }
+  std::tuple<Params...> params;
+};
+
+template <size_t k>
+struct ReturnArgAction {
+  template <typename... Args>
+  auto operator()(const Args&... args) const ->
+      typename std::tuple_element<k, std::tuple<Args...>>::type {
+    return std::get<k>(std::tie(args...));
+  }
+};
+
+template <size_t k, typename Ptr>
+struct SaveArgAction {
+  Ptr pointer;
+
+  template <typename... Args>
+  void operator()(const Args&... args) const {
+    *pointer = std::get<k>(std::tie(args...));
+  }
+};
+
+template <size_t k, typename Ptr>
+struct SaveArgPointeeAction {
+  Ptr pointer;
+
+  template <typename... Args>
+  void operator()(const Args&... args) const {
+    *pointer = *std::get<k>(std::tie(args...));
+  }
+};
+
+template <size_t k, typename T>
+struct SetArgRefereeAction {
+  T value;
+
+  template <typename... Args>
+  void operator()(Args&&... args) const {
+    using argk_type =
+        typename ::std::tuple_element<k, std::tuple<Args...>>::type;
+    static_assert(std::is_lvalue_reference<argk_type>::value,
+                  "Argument must be a reference type.");
+    std::get<k>(std::tie(args...)) = value;
+  }
+};
+
+template <size_t k, typename I1, typename I2>
+struct SetArrayArgumentAction {
+  I1 first;
+  I2 last;
+
+  template <typename... Args>
+  void operator()(const Args&... args) const {
+    auto value = std::get<k>(std::tie(args...));
+    for (auto it = first; it != last; ++it, (void)++value) {
+      *value = *it;
+    }
+  }
+};
+
+template <size_t k>
+struct DeleteArgAction {
+  template <typename... Args>
+  void operator()(const Args&... args) const {
+    delete std::get<k>(std::tie(args...));
+  }
+};
+
+template <typename Ptr>
+struct ReturnPointeeAction {
+  Ptr pointer;
+  template <typename... Args>
+  auto operator()(const Args&...) const -> decltype(*pointer) {
+    return *pointer;
+  }
+};
+
+#if GTEST_HAS_EXCEPTIONS
+template <typename T>
+struct ThrowAction {
+  T exception;
+  // We use a conversion operator to adapt to any return type.
+  template <typename R, typename... Args>
+  operator Action<R(Args...)>() const {  // NOLINT
+    T copy = exception;
+    return [copy](Args...) -> R { throw copy; };
+  }
+};
+#endif  // GTEST_HAS_EXCEPTIONS
+
+}  // namespace internal
+
+// An Unused object can be implicitly constructed from ANY value.
+// This is handy when defining actions that ignore some or all of the
+// mock function arguments.  For example, given
+//
+//   MOCK_METHOD3(Foo, double(const string& label, double x, double y));
+//   MOCK_METHOD3(Bar, double(int index, double x, double y));
+//
+// instead of
+//
+//   double DistanceToOriginWithLabel(const string& label, double x, double y) {
+//     return sqrt(x*x + y*y);
+//   }
+//   double DistanceToOriginWithIndex(int index, double x, double y) {
+//     return sqrt(x*x + y*y);
+//   }
+//   ...
+//   EXPECT_CALL(mock, Foo("abc", _, _))
+//       .WillOnce(Invoke(DistanceToOriginWithLabel));
+//   EXPECT_CALL(mock, Bar(5, _, _))
+//       .WillOnce(Invoke(DistanceToOriginWithIndex));
+//
+// you could write
+//
+//   // We can declare any uninteresting argument as Unused.
+//   double DistanceToOrigin(Unused, double x, double y) {
+//     return sqrt(x*x + y*y);
+//   }
+//   ...
+//   EXPECT_CALL(mock, Foo("abc", _, _)).WillOnce(Invoke(DistanceToOrigin));
+//   EXPECT_CALL(mock, Bar(5, _, _)).WillOnce(Invoke(DistanceToOrigin));
+typedef internal::IgnoredValue Unused;
+
+// Creates an action that does actions a1, a2, ..., sequentially in
+// each invocation. All but the last action will have a readonly view of the
+// arguments.
+template <typename... Action>
+internal::DoAllAction<typename std::decay<Action>::type...> DoAll(
+    Action&&... action) {
+  return {std::forward_as_tuple(std::forward<Action>(action)...)};
+}
+
+// WithArg<k>(an_action) creates an action that passes the k-th
+// (0-based) argument of the mock function to an_action and performs
+// it.  It adapts an action accepting one argument to one that accepts
+// multiple arguments.  For convenience, we also provide
+// WithArgs<k>(an_action) (defined below) as a synonym.
+template <size_t k, typename InnerAction>
+internal::WithArgsAction<typename std::decay<InnerAction>::type, k>
+WithArg(InnerAction&& action) {
+  return {std::forward<InnerAction>(action)};
+}
+
+// WithArgs<N1, N2, ..., Nk>(an_action) creates an action that passes
+// the selected arguments of the mock function to an_action and
+// performs it.  It serves as an adaptor between actions with
+// different argument lists.
+template <size_t k, size_t... ks, typename InnerAction>
+internal::WithArgsAction<typename std::decay<InnerAction>::type, k, ks...>
+WithArgs(InnerAction&& action) {
+  return {std::forward<InnerAction>(action)};
+}
+
+// WithoutArgs(inner_action) can be used in a mock function with a
+// non-empty argument list to perform inner_action, which takes no
+// argument.  In other words, it adapts an action accepting no
+// argument to one that accepts (and ignores) arguments.
+template <typename InnerAction>
+internal::WithArgsAction<typename std::decay<InnerAction>::type>
+WithoutArgs(InnerAction&& action) {
+  return {std::forward<InnerAction>(action)};
+}
+
+// Creates an action that returns 'value'.  'value' is passed by value
+// instead of const reference - otherwise Return("string literal")
+// will trigger a compiler error about using array as initializer.
+template <typename R>
+internal::ReturnAction<R> Return(R value) {
+  return internal::ReturnAction<R>(std::move(value));
+}
+
+// Creates an action that returns NULL.
+inline PolymorphicAction<internal::ReturnNullAction> ReturnNull() {
+  return MakePolymorphicAction(internal::ReturnNullAction());
+}
+
+// Creates an action that returns from a void function.
+inline PolymorphicAction<internal::ReturnVoidAction> Return() {
+  return MakePolymorphicAction(internal::ReturnVoidAction());
+}
+
+// Creates an action that returns the reference to a variable.
+template <typename R>
+inline internal::ReturnRefAction<R> ReturnRef(R& x) {  // NOLINT
+  return internal::ReturnRefAction<R>(x);
+}
+
+// Prevent using ReturnRef on reference to temporary.
+template <typename R, R* = nullptr>
+internal::ReturnRefAction<R> ReturnRef(R&&) = delete;
+
+// Creates an action that returns the reference to a copy of the
+// argument.  The copy is created when the action is constructed and
+// lives as long as the action.
+template <typename R>
+inline internal::ReturnRefOfCopyAction<R> ReturnRefOfCopy(const R& x) {
+  return internal::ReturnRefOfCopyAction<R>(x);
+}
+
+// Modifies the parent action (a Return() action) to perform a move of the
+// argument instead of a copy.
+// Return(ByMove()) actions can only be executed once and will assert this
+// invariant.
+template <typename R>
+internal::ByMoveWrapper<R> ByMove(R x) {
+  return internal::ByMoveWrapper<R>(std::move(x));
+}
+
+// Creates an action that returns an element of `vals`. Calling this action will
+// repeatedly return the next value from `vals` until it reaches the end and
+// will restart from the beginning.
+template <typename T>
+internal::ReturnRoundRobinAction<T> ReturnRoundRobin(std::vector<T> vals) {
+  return internal::ReturnRoundRobinAction<T>(std::move(vals));
+}
+
+// Creates an action that returns an element of `vals`. Calling this action will
+// repeatedly return the next value from `vals` until it reaches the end and
+// will restart from the beginning.
+template <typename T>
+internal::ReturnRoundRobinAction<T> ReturnRoundRobin(
+    std::initializer_list<T> vals) {
+  return internal::ReturnRoundRobinAction<T>(std::vector<T>(vals));
+}
+
+// Creates an action that does the default action for the give mock function.
+inline internal::DoDefaultAction DoDefault() {
+  return internal::DoDefaultAction();
+}
+
+// Creates an action that sets the variable pointed by the N-th
+// (0-based) function argument to 'value'.
+template <size_t N, typename T>
+internal::SetArgumentPointeeAction<N, T> SetArgPointee(T value) {
+  return {std::move(value)};
+}
+
+// The following version is DEPRECATED.
+template <size_t N, typename T>
+internal::SetArgumentPointeeAction<N, T> SetArgumentPointee(T value) {
+  return {std::move(value)};
+}
+
+// Creates an action that sets a pointer referent to a given value.
+template <typename T1, typename T2>
+PolymorphicAction<internal::AssignAction<T1, T2> > Assign(T1* ptr, T2 val) {
+  return MakePolymorphicAction(internal::AssignAction<T1, T2>(ptr, val));
+}
+
+#if !GTEST_OS_WINDOWS_MOBILE
+
+// Creates an action that sets errno and returns the appropriate error.
+template <typename T>
+PolymorphicAction<internal::SetErrnoAndReturnAction<T> >
+SetErrnoAndReturn(int errval, T result) {
+  return MakePolymorphicAction(
+      internal::SetErrnoAndReturnAction<T>(errval, result));
+}
+
+#endif  // !GTEST_OS_WINDOWS_MOBILE
+
+// Various overloads for Invoke().
+
+// Legacy function.
+// Actions can now be implicitly constructed from callables. No need to create
+// wrapper objects.
+// This function exists for backwards compatibility.
+template <typename FunctionImpl>
+typename std::decay<FunctionImpl>::type Invoke(FunctionImpl&& function_impl) {
+  return std::forward<FunctionImpl>(function_impl);
+}
+
+// Creates an action that invokes the given method on the given object
+// with the mock function's arguments.
+template <class Class, typename MethodPtr>
+internal::InvokeMethodAction<Class, MethodPtr> Invoke(Class* obj_ptr,
+                                                      MethodPtr method_ptr) {
+  return {obj_ptr, method_ptr};
+}
+
+// Creates an action that invokes 'function_impl' with no argument.
+template <typename FunctionImpl>
+internal::InvokeWithoutArgsAction<typename std::decay<FunctionImpl>::type>
+InvokeWithoutArgs(FunctionImpl function_impl) {
+  return {std::move(function_impl)};
+}
+
+// Creates an action that invokes the given method on the given object
+// with no argument.
+template <class Class, typename MethodPtr>
+internal::InvokeMethodWithoutArgsAction<Class, MethodPtr> InvokeWithoutArgs(
+    Class* obj_ptr, MethodPtr method_ptr) {
+  return {obj_ptr, method_ptr};
+}
+
+// Creates an action that performs an_action and throws away its
+// result.  In other words, it changes the return type of an_action to
+// void.  an_action MUST NOT return void, or the code won't compile.
+template <typename A>
+inline internal::IgnoreResultAction<A> IgnoreResult(const A& an_action) {
+  return internal::IgnoreResultAction<A>(an_action);
+}
+
+// Creates a reference wrapper for the given L-value.  If necessary,
+// you can explicitly specify the type of the reference.  For example,
+// suppose 'derived' is an object of type Derived, ByRef(derived)
+// would wrap a Derived&.  If you want to wrap a const Base& instead,
+// where Base is a base class of Derived, just write:
+//
+//   ByRef<const Base>(derived)
+//
+// N.B. ByRef is redundant with std::ref, std::cref and std::reference_wrapper.
+// However, it may still be used for consistency with ByMove().
+template <typename T>
+inline ::std::reference_wrapper<T> ByRef(T& l_value) {  // NOLINT
+  return ::std::reference_wrapper<T>(l_value);
+}
+
+// The ReturnNew<T>(a1, a2, ..., a_k) action returns a pointer to a new
+// instance of type T, constructed on the heap with constructor arguments
+// a1, a2, ..., and a_k. The caller assumes ownership of the returned value.
+template <typename T, typename... Params>
+internal::ReturnNewAction<T, typename std::decay<Params>::type...> ReturnNew(
+    Params&&... params) {
+  return {std::forward_as_tuple(std::forward<Params>(params)...)};
+}
+
+// Action ReturnArg<k>() returns the k-th argument of the mock function.
+template <size_t k>
+internal::ReturnArgAction<k> ReturnArg() {
+  return {};
+}
+
+// Action SaveArg<k>(pointer) saves the k-th (0-based) argument of the
+// mock function to *pointer.
+template <size_t k, typename Ptr>
+internal::SaveArgAction<k, Ptr> SaveArg(Ptr pointer) {
+  return {pointer};
+}
+
+// Action SaveArgPointee<k>(pointer) saves the value pointed to
+// by the k-th (0-based) argument of the mock function to *pointer.
+template <size_t k, typename Ptr>
+internal::SaveArgPointeeAction<k, Ptr> SaveArgPointee(Ptr pointer) {
+  return {pointer};
+}
+
+// Action SetArgReferee<k>(value) assigns 'value' to the variable
+// referenced by the k-th (0-based) argument of the mock function.
+template <size_t k, typename T>
+internal::SetArgRefereeAction<k, typename std::decay<T>::type> SetArgReferee(
+    T&& value) {
+  return {std::forward<T>(value)};
+}
+
+// Action SetArrayArgument<k>(first, last) copies the elements in
+// source range [first, last) to the array pointed to by the k-th
+// (0-based) argument, which can be either a pointer or an
+// iterator. The action does not take ownership of the elements in the
+// source range.
+template <size_t k, typename I1, typename I2>
+internal::SetArrayArgumentAction<k, I1, I2> SetArrayArgument(I1 first,
+                                                             I2 last) {
+  return {first, last};
+}
+
+// Action DeleteArg<k>() deletes the k-th (0-based) argument of the mock
+// function.
+template <size_t k>
+internal::DeleteArgAction<k> DeleteArg() {
+  return {};
+}
+
+// This action returns the value pointed to by 'pointer'.
+template <typename Ptr>
+internal::ReturnPointeeAction<Ptr> ReturnPointee(Ptr pointer) {
+  return {pointer};
+}
+
+// Action Throw(exception) can be used in a mock function of any type
+// to throw the given exception.  Any copyable value can be thrown.
+#if GTEST_HAS_EXCEPTIONS
+template <typename T>
+internal::ThrowAction<typename std::decay<T>::type> Throw(T&& exception) {
+  return {std::forward<T>(exception)};
+}
+#endif  // GTEST_HAS_EXCEPTIONS
+
+namespace internal {
+
+// A macro from the ACTION* family (defined later in gmock-generated-actions.h)
+// defines an action that can be used in a mock function.  Typically,
+// these actions only care about a subset of the arguments of the mock
+// function.  For example, if such an action only uses the second
+// argument, it can be used in any mock function that takes >= 2
+// arguments where the type of the second argument is compatible.
+//
+// Therefore, the action implementation must be prepared to take more
+// arguments than it needs.  The ExcessiveArg type is used to
+// represent those excessive arguments.  In order to keep the compiler
+// error messages tractable, we define it in the testing namespace
+// instead of testing::internal.  However, this is an INTERNAL TYPE
+// and subject to change without notice, so a user MUST NOT USE THIS
+// TYPE DIRECTLY.
+struct ExcessiveArg {};
+
+// Builds an implementation of an Action<> for some particular signature, using
+// a class defined by an ACTION* macro.
+template <typename F, typename Impl> struct ActionImpl;
+
+template <typename Impl>
+struct ImplBase {
+  struct Holder {
+    // Allows each copy of the Action<> to get to the Impl.
+    explicit operator const Impl&() const { return *ptr; }
+    std::shared_ptr<Impl> ptr;
+  };
+  using type = typename std::conditional<std::is_constructible<Impl>::value,
+                                         Impl, Holder>::type;
+};
+
+template <typename R, typename... Args, typename Impl>
+struct ActionImpl<R(Args...), Impl> : ImplBase<Impl>::type {
+  using Base = typename ImplBase<Impl>::type;
+  using function_type = R(Args...);
+  using args_type = std::tuple<Args...>;
+
+  ActionImpl() = default;  // Only defined if appropriate for Base.
+  explicit ActionImpl(std::shared_ptr<Impl> impl) : Base{std::move(impl)} { }
+
+  R operator()(Args&&... arg) const {
+    static constexpr size_t kMaxArgs =
+        sizeof...(Args) <= 10 ? sizeof...(Args) : 10;
+    return Apply(MakeIndexSequence<kMaxArgs>{},
+                 MakeIndexSequence<10 - kMaxArgs>{},
+                 args_type{std::forward<Args>(arg)...});
+  }
+
+  template <std::size_t... arg_id, std::size_t... excess_id>
+  R Apply(IndexSequence<arg_id...>, IndexSequence<excess_id...>,
+          const args_type& args) const {
+    // Impl need not be specific to the signature of action being implemented;
+    // only the implementing function body needs to have all of the specific
+    // types instantiated.  Up to 10 of the args that are provided by the
+    // args_type get passed, followed by a dummy of unspecified type for the
+    // remainder up to 10 explicit args.
+    static constexpr ExcessiveArg kExcessArg{};
+    return static_cast<const Impl&>(*this).template gmock_PerformImpl<
+        /*function_type=*/function_type, /*return_type=*/R,
+        /*args_type=*/args_type,
+        /*argN_type=*/typename std::tuple_element<arg_id, args_type>::type...>(
+        /*args=*/args, std::get<arg_id>(args)...,
+        ((void)excess_id, kExcessArg)...);
+  }
+};
+
+// Stores a default-constructed Impl as part of the Action<>'s
+// std::function<>. The Impl should be trivial to copy.
+template <typename F, typename Impl>
+::testing::Action<F> MakeAction() {
+  return ::testing::Action<F>(ActionImpl<F, Impl>());
+}
+
+// Stores just the one given instance of Impl.
+template <typename F, typename Impl>
+::testing::Action<F> MakeAction(std::shared_ptr<Impl> impl) {
+  return ::testing::Action<F>(ActionImpl<F, Impl>(std::move(impl)));
+}
+
+#define GMOCK_INTERNAL_ARG_UNUSED(i, data, el) \
+  , const arg##i##_type& arg##i GTEST_ATTRIBUTE_UNUSED_
+#define GMOCK_ACTION_ARG_TYPES_AND_NAMES_UNUSED_           \
+  const args_type& args GTEST_ATTRIBUTE_UNUSED_ GMOCK_PP_REPEAT( \
+      GMOCK_INTERNAL_ARG_UNUSED, , 10)
+
+#define GMOCK_INTERNAL_ARG(i, data, el) , const arg##i##_type& arg##i
+#define GMOCK_ACTION_ARG_TYPES_AND_NAMES_ \
+  const args_type& args GMOCK_PP_REPEAT(GMOCK_INTERNAL_ARG, , 10)
+
+#define GMOCK_INTERNAL_TEMPLATE_ARG(i, data, el) , typename arg##i##_type
+#define GMOCK_ACTION_TEMPLATE_ARGS_NAMES_ \
+  GMOCK_PP_TAIL(GMOCK_PP_REPEAT(GMOCK_INTERNAL_TEMPLATE_ARG, , 10))
+
+#define GMOCK_INTERNAL_TYPENAME_PARAM(i, data, param) , typename param##_type
+#define GMOCK_ACTION_TYPENAME_PARAMS_(params) \
+  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_TYPENAME_PARAM, , params))
+
+#define GMOCK_INTERNAL_TYPE_PARAM(i, data, param) , param##_type
+#define GMOCK_ACTION_TYPE_PARAMS_(params) \
+  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_TYPE_PARAM, , params))
+
+#define GMOCK_INTERNAL_TYPE_GVALUE_PARAM(i, data, param) \
+  , param##_type gmock_p##i
+#define GMOCK_ACTION_TYPE_GVALUE_PARAMS_(params) \
+  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_TYPE_GVALUE_PARAM, , params))
+
+#define GMOCK_INTERNAL_GVALUE_PARAM(i, data, param) \
+  , std::forward<param##_type>(gmock_p##i)
+#define GMOCK_ACTION_GVALUE_PARAMS_(params) \
+  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_GVALUE_PARAM, , params))
+
+#define GMOCK_INTERNAL_INIT_PARAM(i, data, param) \
+  , param(::std::forward<param##_type>(gmock_p##i))
+#define GMOCK_ACTION_INIT_PARAMS_(params) \
+  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_INIT_PARAM, , params))
+
+#define GMOCK_INTERNAL_FIELD_PARAM(i, data, param) param##_type param;
+#define GMOCK_ACTION_FIELD_PARAMS_(params) \
+  GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_FIELD_PARAM, , params)
+
+#define GMOCK_INTERNAL_ACTION(name, full_name, params)                        \
+  template <GMOCK_ACTION_TYPENAME_PARAMS_(params)>                            \
+  class full_name {                                                           \
+   public:                                                                    \
+    explicit full_name(GMOCK_ACTION_TYPE_GVALUE_PARAMS_(params))              \
+        : impl_(std::make_shared<gmock_Impl>(                                 \
+                GMOCK_ACTION_GVALUE_PARAMS_(params))) { }                     \
+    full_name(const full_name&) = default;                                    \
+    full_name(full_name&&) noexcept = default;                                \
+    template <typename F>                                                     \
+    operator ::testing::Action<F>() const {                                   \
+      return ::testing::internal::MakeAction<F>(impl_);                       \
+    }                                                                         \
+   private:                                                                   \
+    class gmock_Impl {                                                        \
+     public:                                                                  \
+      explicit gmock_Impl(GMOCK_ACTION_TYPE_GVALUE_PARAMS_(params))           \
+          : GMOCK_ACTION_INIT_PARAMS_(params) {}                              \
+      template <typename function_type, typename return_type,                 \
+                typename args_type, GMOCK_ACTION_TEMPLATE_ARGS_NAMES_>        \
+      return_type gmock_PerformImpl(GMOCK_ACTION_ARG_TYPES_AND_NAMES_) const; \
+      GMOCK_ACTION_FIELD_PARAMS_(params)                                      \
+    };                                                                        \
+    std::shared_ptr<const gmock_Impl> impl_;                                  \
+  };                                                                          \
+  template <GMOCK_ACTION_TYPENAME_PARAMS_(params)>                            \
+  inline full_name<GMOCK_ACTION_TYPE_PARAMS_(params)> name(                   \
+      GMOCK_ACTION_TYPE_GVALUE_PARAMS_(params)) {                             \
+    return full_name<GMOCK_ACTION_TYPE_PARAMS_(params)>(                      \
+        GMOCK_ACTION_GVALUE_PARAMS_(params));                                 \
+  }                                                                           \
+  template <GMOCK_ACTION_TYPENAME_PARAMS_(params)>                            \
+  template <typename function_type, typename return_type, typename args_type, \
+            GMOCK_ACTION_TEMPLATE_ARGS_NAMES_>                                \
+  return_type full_name<GMOCK_ACTION_TYPE_PARAMS_(params)>::gmock_Impl::      \
+  gmock_PerformImpl(GMOCK_ACTION_ARG_TYPES_AND_NAMES_UNUSED_) const
+
+}  // namespace internal
+
+// Similar to GMOCK_INTERNAL_ACTION, but no bound parameters are stored.
+#define ACTION(name)                                                          \
+  class name##Action {                                                        \
+   public:                                                                    \
+   explicit name##Action() noexcept {}                                        \
+   name##Action(const name##Action&) noexcept {}                              \
+    template <typename F>                                                     \
+    operator ::testing::Action<F>() const {                                   \
+      return ::testing::internal::MakeAction<F, gmock_Impl>();                \
+    }                                                                         \
+   private:                                                                   \
+    class gmock_Impl {                                                        \
+     public:                                                                  \
+      template <typename function_type, typename return_type,                 \
+                typename args_type, GMOCK_ACTION_TEMPLATE_ARGS_NAMES_>        \
+      return_type gmock_PerformImpl(GMOCK_ACTION_ARG_TYPES_AND_NAMES_) const; \
+    };                                                                        \
+  };                                                                          \
+  inline name##Action name() GTEST_MUST_USE_RESULT_;                          \
+  inline name##Action name() { return name##Action(); }                       \
+  template <typename function_type, typename return_type, typename args_type, \
+            GMOCK_ACTION_TEMPLATE_ARGS_NAMES_>                                \
+  return_type name##Action::gmock_Impl::gmock_PerformImpl(                    \
+      GMOCK_ACTION_ARG_TYPES_AND_NAMES_UNUSED_) const
+
+#define ACTION_P(name, ...) \
+  GMOCK_INTERNAL_ACTION(name, name##ActionP, (__VA_ARGS__))
+
+#define ACTION_P2(name, ...) \
+  GMOCK_INTERNAL_ACTION(name, name##ActionP2, (__VA_ARGS__))
+
+#define ACTION_P3(name, ...) \
+  GMOCK_INTERNAL_ACTION(name, name##ActionP3, (__VA_ARGS__))
+
+#define ACTION_P4(name, ...) \
+  GMOCK_INTERNAL_ACTION(name, name##ActionP4, (__VA_ARGS__))
+
+#define ACTION_P5(name, ...) \
+  GMOCK_INTERNAL_ACTION(name, name##ActionP5, (__VA_ARGS__))
+
+#define ACTION_P6(name, ...) \
+  GMOCK_INTERNAL_ACTION(name, name##ActionP6, (__VA_ARGS__))
+
+#define ACTION_P7(name, ...) \
+  GMOCK_INTERNAL_ACTION(name, name##ActionP7, (__VA_ARGS__))
+
+#define ACTION_P8(name, ...) \
+  GMOCK_INTERNAL_ACTION(name, name##ActionP8, (__VA_ARGS__))
+
+#define ACTION_P9(name, ...) \
+  GMOCK_INTERNAL_ACTION(name, name##ActionP9, (__VA_ARGS__))
+
+#define ACTION_P10(name, ...) \
+  GMOCK_INTERNAL_ACTION(name, name##ActionP10, (__VA_ARGS__))
+
+}  // namespace testing
+
+#ifdef _MSC_VER
+# pragma warning(pop)
+#endif
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_ACTIONS_H_
diff --git a/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-cardinalities.h b/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-cardinalities.h
new file mode 100644
index 0000000..fc7f803
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-cardinalities.h
@@ -0,0 +1,157 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file implements some commonly used cardinalities.  More
+// cardinalities can be defined by the user implementing the
+// CardinalityInterface interface if necessary.
+
+// GOOGLETEST_CM0002 DO NOT DELETE
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_CARDINALITIES_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_CARDINALITIES_H_
+
+#include <limits.h>
+#include <memory>
+#include <ostream>  // NOLINT
+#include "gmock/internal/gmock-port.h"
+#include "gtest/gtest.h"
+
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4251 \
+/* class A needs to have dll-interface to be used by clients of class B */)
+
+namespace testing {
+
+// To implement a cardinality Foo, define:
+//   1. a class FooCardinality that implements the
+//      CardinalityInterface interface, and
+//   2. a factory function that creates a Cardinality object from a
+//      const FooCardinality*.
+//
+// The two-level delegation design follows that of Matcher, providing
+// consistency for extension developers.  It also eases ownership
+// management as Cardinality objects can now be copied like plain values.
+
+// The implementation of a cardinality.
+class CardinalityInterface {
+ public:
+  virtual ~CardinalityInterface() {}
+
+  // Conservative estimate on the lower/upper bound of the number of
+  // calls allowed.
+  virtual int ConservativeLowerBound() const { return 0; }
+  virtual int ConservativeUpperBound() const { return INT_MAX; }
+
+  // Returns true if and only if call_count calls will satisfy this
+  // cardinality.
+  virtual bool IsSatisfiedByCallCount(int call_count) const = 0;
+
+  // Returns true if and only if call_count calls will saturate this
+  // cardinality.
+  virtual bool IsSaturatedByCallCount(int call_count) const = 0;
+
+  // Describes self to an ostream.
+  virtual void DescribeTo(::std::ostream* os) const = 0;
+};
+
+// A Cardinality is a copyable and IMMUTABLE (except by assignment)
+// object that specifies how many times a mock function is expected to
+// be called.  The implementation of Cardinality is just a std::shared_ptr
+// to const CardinalityInterface. Don't inherit from Cardinality!
+class GTEST_API_ Cardinality {
+ public:
+  // Constructs a null cardinality.  Needed for storing Cardinality
+  // objects in STL containers.
+  Cardinality() {}
+
+  // Constructs a Cardinality from its implementation.
+  explicit Cardinality(const CardinalityInterface* impl) : impl_(impl) {}
+
+  // Conservative estimate on the lower/upper bound of the number of
+  // calls allowed.
+  int ConservativeLowerBound() const { return impl_->ConservativeLowerBound(); }
+  int ConservativeUpperBound() const { return impl_->ConservativeUpperBound(); }
+
+  // Returns true if and only if call_count calls will satisfy this
+  // cardinality.
+  bool IsSatisfiedByCallCount(int call_count) const {
+    return impl_->IsSatisfiedByCallCount(call_count);
+  }
+
+  // Returns true if and only if call_count calls will saturate this
+  // cardinality.
+  bool IsSaturatedByCallCount(int call_count) const {
+    return impl_->IsSaturatedByCallCount(call_count);
+  }
+
+  // Returns true if and only if call_count calls will over-saturate this
+  // cardinality, i.e. exceed the maximum number of allowed calls.
+  bool IsOverSaturatedByCallCount(int call_count) const {
+    return impl_->IsSaturatedByCallCount(call_count) &&
+        !impl_->IsSatisfiedByCallCount(call_count);
+  }
+
+  // Describes self to an ostream
+  void DescribeTo(::std::ostream* os) const { impl_->DescribeTo(os); }
+
+  // Describes the given actual call count to an ostream.
+  static void DescribeActualCallCountTo(int actual_call_count,
+                                        ::std::ostream* os);
+
+ private:
+  std::shared_ptr<const CardinalityInterface> impl_;
+};
+
+// Creates a cardinality that allows at least n calls.
+GTEST_API_ Cardinality AtLeast(int n);
+
+// Creates a cardinality that allows at most n calls.
+GTEST_API_ Cardinality AtMost(int n);
+
+// Creates a cardinality that allows any number of calls.
+GTEST_API_ Cardinality AnyNumber();
+
+// Creates a cardinality that allows between min and max calls.
+GTEST_API_ Cardinality Between(int min, int max);
+
+// Creates a cardinality that allows exactly n calls.
+GTEST_API_ Cardinality Exactly(int n);
+
+// Creates a cardinality from its implementation.
+inline Cardinality MakeCardinality(const CardinalityInterface* c) {
+  return Cardinality(c);
+}
+
+}  // namespace testing
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  //  4251
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_CARDINALITIES_H_
diff --git a/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-function-mocker.h b/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-function-mocker.h
new file mode 100644
index 0000000..0fc6f6f
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-function-mocker.h
@@ -0,0 +1,479 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file implements MOCK_METHOD.
+
+// GOOGLETEST_CM0002 DO NOT DELETE
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_GMOCK_FUNCTION_MOCKER_H_  // NOLINT
+#define GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_GMOCK_FUNCTION_MOCKER_H_  // NOLINT
+
+#include <type_traits>  // IWYU pragma: keep
+#include <utility>      // IWYU pragma: keep
+
+#include "gmock/gmock-spec-builders.h"
+#include "gmock/internal/gmock-internal-utils.h"
+#include "gmock/internal/gmock-pp.h"
+
+namespace testing {
+namespace internal {
+template <typename T>
+using identity_t = T;
+
+template <typename Pattern>
+struct ThisRefAdjuster {
+  template <typename T>
+  using AdjustT = typename std::conditional<
+      std::is_const<typename std::remove_reference<Pattern>::type>::value,
+      typename std::conditional<std::is_lvalue_reference<Pattern>::value,
+                                const T&, const T&&>::type,
+      typename std::conditional<std::is_lvalue_reference<Pattern>::value, T&,
+                                T&&>::type>::type;
+
+  template <typename MockType>
+  static AdjustT<MockType> Adjust(const MockType& mock) {
+    return static_cast<AdjustT<MockType>>(const_cast<MockType&>(mock));
+  }
+};
+
+}  // namespace internal
+
+// The style guide prohibits "using" statements in a namespace scope
+// inside a header file.  However, the FunctionMocker class template
+// is meant to be defined in the ::testing namespace.  The following
+// line is just a trick for working around a bug in MSVC 8.0, which
+// cannot handle it if we define FunctionMocker in ::testing.
+using internal::FunctionMocker;
+}  // namespace testing
+
+#define MOCK_METHOD(...) \
+  GMOCK_PP_VARIADIC_CALL(GMOCK_INTERNAL_MOCK_METHOD_ARG_, __VA_ARGS__)
+
+#define GMOCK_INTERNAL_MOCK_METHOD_ARG_1(...) \
+  GMOCK_INTERNAL_WRONG_ARITY(__VA_ARGS__)
+
+#define GMOCK_INTERNAL_MOCK_METHOD_ARG_2(...) \
+  GMOCK_INTERNAL_WRONG_ARITY(__VA_ARGS__)
+
+#define GMOCK_INTERNAL_MOCK_METHOD_ARG_3(_Ret, _MethodName, _Args) \
+  GMOCK_INTERNAL_MOCK_METHOD_ARG_4(_Ret, _MethodName, _Args, ())
+
+#define GMOCK_INTERNAL_MOCK_METHOD_ARG_4(_Ret, _MethodName, _Args, _Spec)     \
+  GMOCK_INTERNAL_ASSERT_PARENTHESIS(_Args);                                   \
+  GMOCK_INTERNAL_ASSERT_PARENTHESIS(_Spec);                                   \
+  GMOCK_INTERNAL_ASSERT_VALID_SIGNATURE(                                      \
+      GMOCK_PP_NARG0 _Args, GMOCK_INTERNAL_SIGNATURE(_Ret, _Args));           \
+  GMOCK_INTERNAL_ASSERT_VALID_SPEC(_Spec)                                     \
+  GMOCK_INTERNAL_MOCK_METHOD_IMPL(                                            \
+      GMOCK_PP_NARG0 _Args, _MethodName, GMOCK_INTERNAL_HAS_CONST(_Spec),     \
+      GMOCK_INTERNAL_HAS_OVERRIDE(_Spec), GMOCK_INTERNAL_HAS_FINAL(_Spec),    \
+      GMOCK_INTERNAL_GET_NOEXCEPT_SPEC(_Spec),                                \
+      GMOCK_INTERNAL_GET_CALLTYPE(_Spec), GMOCK_INTERNAL_GET_REF_SPEC(_Spec), \
+      (GMOCK_INTERNAL_SIGNATURE(_Ret, _Args)))
+
+#define GMOCK_INTERNAL_MOCK_METHOD_ARG_5(...) \
+  GMOCK_INTERNAL_WRONG_ARITY(__VA_ARGS__)
+
+#define GMOCK_INTERNAL_MOCK_METHOD_ARG_6(...) \
+  GMOCK_INTERNAL_WRONG_ARITY(__VA_ARGS__)
+
+#define GMOCK_INTERNAL_MOCK_METHOD_ARG_7(...) \
+  GMOCK_INTERNAL_WRONG_ARITY(__VA_ARGS__)
+
+#define GMOCK_INTERNAL_WRONG_ARITY(...)                                      \
+  static_assert(                                                             \
+      false,                                                                 \
+      "MOCK_METHOD must be called with 3 or 4 arguments. _Ret, "             \
+      "_MethodName, _Args and optionally _Spec. _Args and _Spec must be "    \
+      "enclosed in parentheses. If _Ret is a type with unprotected commas, " \
+      "it must also be enclosed in parentheses.")
+
+#define GMOCK_INTERNAL_ASSERT_PARENTHESIS(_Tuple) \
+  static_assert(                                  \
+      GMOCK_PP_IS_ENCLOSED_PARENS(_Tuple),        \
+      GMOCK_PP_STRINGIZE(_Tuple) " should be enclosed in parentheses.")
+
+#define GMOCK_INTERNAL_ASSERT_VALID_SIGNATURE(_N, ...)                 \
+  static_assert(                                                       \
+      std::is_function<__VA_ARGS__>::value,                            \
+      "Signature must be a function type, maybe return type contains " \
+      "unprotected comma.");                                           \
+  static_assert(                                                       \
+      ::testing::tuple_size<typename ::testing::internal::Function<    \
+              __VA_ARGS__>::ArgumentTuple>::value == _N,               \
+      "This method does not take " GMOCK_PP_STRINGIZE(                 \
+          _N) " arguments. Parenthesize all types with unprotected commas.")
+
+#define GMOCK_INTERNAL_ASSERT_VALID_SPEC(_Spec) \
+  GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_ASSERT_VALID_SPEC_ELEMENT, ~, _Spec)
+
+#define GMOCK_INTERNAL_MOCK_METHOD_IMPL(_N, _MethodName, _Constness,           \
+                                        _Override, _Final, _NoexceptSpec,      \
+                                        _CallType, _RefSpec, _Signature)       \
+  typename ::testing::internal::Function<GMOCK_PP_REMOVE_PARENS(               \
+      _Signature)>::Result                                                     \
+  GMOCK_INTERNAL_EXPAND(_CallType)                                             \
+      _MethodName(GMOCK_PP_REPEAT(GMOCK_INTERNAL_PARAMETER, _Signature, _N))   \
+          GMOCK_PP_IF(_Constness, const, ) _RefSpec _NoexceptSpec              \
+          GMOCK_PP_IF(_Override, override, ) GMOCK_PP_IF(_Final, final, ) {    \
+    GMOCK_MOCKER_(_N, _Constness, _MethodName)                                 \
+        .SetOwnerAndName(this, #_MethodName);                                  \
+    return GMOCK_MOCKER_(_N, _Constness, _MethodName)                          \
+        .Invoke(GMOCK_PP_REPEAT(GMOCK_INTERNAL_FORWARD_ARG, _Signature, _N));  \
+  }                                                                            \
+  ::testing::MockSpec<GMOCK_PP_REMOVE_PARENS(_Signature)> gmock_##_MethodName( \
+      GMOCK_PP_REPEAT(GMOCK_INTERNAL_MATCHER_PARAMETER, _Signature, _N))       \
+      GMOCK_PP_IF(_Constness, const, ) _RefSpec {                              \
+    GMOCK_MOCKER_(_N, _Constness, _MethodName).RegisterOwner(this);            \
+    return GMOCK_MOCKER_(_N, _Constness, _MethodName)                          \
+        .With(GMOCK_PP_REPEAT(GMOCK_INTERNAL_MATCHER_ARGUMENT, , _N));         \
+  }                                                                            \
+  ::testing::MockSpec<GMOCK_PP_REMOVE_PARENS(_Signature)> gmock_##_MethodName( \
+      const ::testing::internal::WithoutMatchers&,                             \
+      GMOCK_PP_IF(_Constness, const, )::testing::internal::Function<           \
+          GMOCK_PP_REMOVE_PARENS(_Signature)>*) const _RefSpec _NoexceptSpec { \
+    return ::testing::internal::ThisRefAdjuster<GMOCK_PP_IF(                   \
+        _Constness, const, ) int _RefSpec>::Adjust(*this)                      \
+        .gmock_##_MethodName(GMOCK_PP_REPEAT(                                  \
+            GMOCK_INTERNAL_A_MATCHER_ARGUMENT, _Signature, _N));               \
+  }                                                                            \
+  mutable ::testing::FunctionMocker<GMOCK_PP_REMOVE_PARENS(_Signature)>        \
+      GMOCK_MOCKER_(_N, _Constness, _MethodName)
+
+#define GMOCK_INTERNAL_EXPAND(...) __VA_ARGS__
+
+// Five Valid modifiers.
+#define GMOCK_INTERNAL_HAS_CONST(_Tuple) \
+  GMOCK_PP_HAS_COMMA(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_DETECT_CONST, ~, _Tuple))
+
+#define GMOCK_INTERNAL_HAS_OVERRIDE(_Tuple) \
+  GMOCK_PP_HAS_COMMA(                       \
+      GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_DETECT_OVERRIDE, ~, _Tuple))
+
+#define GMOCK_INTERNAL_HAS_FINAL(_Tuple) \
+  GMOCK_PP_HAS_COMMA(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_DETECT_FINAL, ~, _Tuple))
+
+#define GMOCK_INTERNAL_GET_NOEXCEPT_SPEC(_Tuple) \
+  GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_NOEXCEPT_SPEC_IF_NOEXCEPT, ~, _Tuple)
+
+#define GMOCK_INTERNAL_NOEXCEPT_SPEC_IF_NOEXCEPT(_i, _, _elem)          \
+  GMOCK_PP_IF(                                                          \
+      GMOCK_PP_HAS_COMMA(GMOCK_INTERNAL_DETECT_NOEXCEPT(_i, _, _elem)), \
+      _elem, )
+
+#define GMOCK_INTERNAL_GET_REF_SPEC(_Tuple) \
+  GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_REF_SPEC_IF_REF, ~, _Tuple)
+
+#define GMOCK_INTERNAL_REF_SPEC_IF_REF(_i, _, _elem)                       \
+  GMOCK_PP_IF(GMOCK_PP_HAS_COMMA(GMOCK_INTERNAL_DETECT_REF(_i, _, _elem)), \
+              GMOCK_PP_CAT(GMOCK_INTERNAL_UNPACK_, _elem), )
+
+#define GMOCK_INTERNAL_GET_CALLTYPE(_Tuple) \
+  GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_GET_CALLTYPE_IMPL, ~, _Tuple)
+
+#define GMOCK_INTERNAL_ASSERT_VALID_SPEC_ELEMENT(_i, _, _elem)            \
+  static_assert(                                                          \
+      (GMOCK_PP_HAS_COMMA(GMOCK_INTERNAL_DETECT_CONST(_i, _, _elem)) +    \
+       GMOCK_PP_HAS_COMMA(GMOCK_INTERNAL_DETECT_OVERRIDE(_i, _, _elem)) + \
+       GMOCK_PP_HAS_COMMA(GMOCK_INTERNAL_DETECT_FINAL(_i, _, _elem)) +    \
+       GMOCK_PP_HAS_COMMA(GMOCK_INTERNAL_DETECT_NOEXCEPT(_i, _, _elem)) + \
+       GMOCK_PP_HAS_COMMA(GMOCK_INTERNAL_DETECT_REF(_i, _, _elem)) +      \
+       GMOCK_INTERNAL_IS_CALLTYPE(_elem)) == 1,                           \
+      GMOCK_PP_STRINGIZE(                                                 \
+          _elem) " cannot be recognized as a valid specification modifier.");
+
+// Modifiers implementation.
+#define GMOCK_INTERNAL_DETECT_CONST(_i, _, _elem) \
+  GMOCK_PP_CAT(GMOCK_INTERNAL_DETECT_CONST_I_, _elem)
+
+#define GMOCK_INTERNAL_DETECT_CONST_I_const ,
+
+#define GMOCK_INTERNAL_DETECT_OVERRIDE(_i, _, _elem) \
+  GMOCK_PP_CAT(GMOCK_INTERNAL_DETECT_OVERRIDE_I_, _elem)
+
+#define GMOCK_INTERNAL_DETECT_OVERRIDE_I_override ,
+
+#define GMOCK_INTERNAL_DETECT_FINAL(_i, _, _elem) \
+  GMOCK_PP_CAT(GMOCK_INTERNAL_DETECT_FINAL_I_, _elem)
+
+#define GMOCK_INTERNAL_DETECT_FINAL_I_final ,
+
+#define GMOCK_INTERNAL_DETECT_NOEXCEPT(_i, _, _elem) \
+  GMOCK_PP_CAT(GMOCK_INTERNAL_DETECT_NOEXCEPT_I_, _elem)
+
+#define GMOCK_INTERNAL_DETECT_NOEXCEPT_I_noexcept ,
+
+#define GMOCK_INTERNAL_DETECT_REF(_i, _, _elem) \
+  GMOCK_PP_CAT(GMOCK_INTERNAL_DETECT_REF_I_, _elem)
+
+#define GMOCK_INTERNAL_DETECT_REF_I_ref ,
+
+#define GMOCK_INTERNAL_UNPACK_ref(x) x
+
+#define GMOCK_INTERNAL_GET_CALLTYPE_IMPL(_i, _, _elem)           \
+  GMOCK_PP_IF(GMOCK_INTERNAL_IS_CALLTYPE(_elem),                 \
+              GMOCK_INTERNAL_GET_VALUE_CALLTYPE, GMOCK_PP_EMPTY) \
+  (_elem)
+
+// TODO(iserna): GMOCK_INTERNAL_IS_CALLTYPE and
+// GMOCK_INTERNAL_GET_VALUE_CALLTYPE needed more expansions to work on windows
+// maybe they can be simplified somehow.
+#define GMOCK_INTERNAL_IS_CALLTYPE(_arg) \
+  GMOCK_INTERNAL_IS_CALLTYPE_I(          \
+      GMOCK_PP_CAT(GMOCK_INTERNAL_IS_CALLTYPE_HELPER_, _arg))
+#define GMOCK_INTERNAL_IS_CALLTYPE_I(_arg) GMOCK_PP_IS_ENCLOSED_PARENS(_arg)
+
+#define GMOCK_INTERNAL_GET_VALUE_CALLTYPE(_arg) \
+  GMOCK_INTERNAL_GET_VALUE_CALLTYPE_I(          \
+      GMOCK_PP_CAT(GMOCK_INTERNAL_IS_CALLTYPE_HELPER_, _arg))
+#define GMOCK_INTERNAL_GET_VALUE_CALLTYPE_I(_arg) \
+  GMOCK_PP_IDENTITY _arg
+
+#define GMOCK_INTERNAL_IS_CALLTYPE_HELPER_Calltype
+
+// Note: The use of `identity_t` here allows _Ret to represent return types that
+// would normally need to be specified in a different way. For example, a method
+// returning a function pointer must be written as
+//
+// fn_ptr_return_t (*method(method_args_t...))(fn_ptr_args_t...)
+//
+// But we only support placing the return type at the beginning. To handle this,
+// we wrap all calls in identity_t, so that a declaration will be expanded to
+//
+// identity_t<fn_ptr_return_t (*)(fn_ptr_args_t...)> method(method_args_t...)
+//
+// This allows us to work around the syntactic oddities of function/method
+// types.
+#define GMOCK_INTERNAL_SIGNATURE(_Ret, _Args)                                 \
+  ::testing::internal::identity_t<GMOCK_PP_IF(GMOCK_PP_IS_BEGIN_PARENS(_Ret), \
+                                              GMOCK_PP_REMOVE_PARENS,         \
+                                              GMOCK_PP_IDENTITY)(_Ret)>(      \
+      GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_GET_TYPE, _, _Args))
+
+#define GMOCK_INTERNAL_GET_TYPE(_i, _, _elem)                          \
+  GMOCK_PP_COMMA_IF(_i)                                                \
+  GMOCK_PP_IF(GMOCK_PP_IS_BEGIN_PARENS(_elem), GMOCK_PP_REMOVE_PARENS, \
+              GMOCK_PP_IDENTITY)                                       \
+  (_elem)
+
+#define GMOCK_INTERNAL_PARAMETER(_i, _Signature, _)            \
+  GMOCK_PP_COMMA_IF(_i)                                        \
+  GMOCK_INTERNAL_ARG_O(_i, GMOCK_PP_REMOVE_PARENS(_Signature)) \
+  gmock_a##_i
+
+#define GMOCK_INTERNAL_FORWARD_ARG(_i, _Signature, _) \
+  GMOCK_PP_COMMA_IF(_i)                               \
+  ::std::forward<GMOCK_INTERNAL_ARG_O(                \
+      _i, GMOCK_PP_REMOVE_PARENS(_Signature))>(gmock_a##_i)
+
+#define GMOCK_INTERNAL_MATCHER_PARAMETER(_i, _Signature, _)        \
+  GMOCK_PP_COMMA_IF(_i)                                            \
+  GMOCK_INTERNAL_MATCHER_O(_i, GMOCK_PP_REMOVE_PARENS(_Signature)) \
+  gmock_a##_i
+
+#define GMOCK_INTERNAL_MATCHER_ARGUMENT(_i, _1, _2) \
+  GMOCK_PP_COMMA_IF(_i)                             \
+  gmock_a##_i
+
+#define GMOCK_INTERNAL_A_MATCHER_ARGUMENT(_i, _Signature, _) \
+  GMOCK_PP_COMMA_IF(_i)                                      \
+  ::testing::A<GMOCK_INTERNAL_ARG_O(_i, GMOCK_PP_REMOVE_PARENS(_Signature))>()
+
+#define GMOCK_INTERNAL_ARG_O(_i, ...) \
+  typename ::testing::internal::Function<__VA_ARGS__>::template Arg<_i>::type
+
+#define GMOCK_INTERNAL_MATCHER_O(_i, ...)                          \
+  const ::testing::Matcher<typename ::testing::internal::Function< \
+      __VA_ARGS__>::template Arg<_i>::type>&
+
+#define MOCK_METHOD0(m, ...) GMOCK_INTERNAL_MOCK_METHODN(, , m, 0, __VA_ARGS__)
+#define MOCK_METHOD1(m, ...) GMOCK_INTERNAL_MOCK_METHODN(, , m, 1, __VA_ARGS__)
+#define MOCK_METHOD2(m, ...) GMOCK_INTERNAL_MOCK_METHODN(, , m, 2, __VA_ARGS__)
+#define MOCK_METHOD3(m, ...) GMOCK_INTERNAL_MOCK_METHODN(, , m, 3, __VA_ARGS__)
+#define MOCK_METHOD4(m, ...) GMOCK_INTERNAL_MOCK_METHODN(, , m, 4, __VA_ARGS__)
+#define MOCK_METHOD5(m, ...) GMOCK_INTERNAL_MOCK_METHODN(, , m, 5, __VA_ARGS__)
+#define MOCK_METHOD6(m, ...) GMOCK_INTERNAL_MOCK_METHODN(, , m, 6, __VA_ARGS__)
+#define MOCK_METHOD7(m, ...) GMOCK_INTERNAL_MOCK_METHODN(, , m, 7, __VA_ARGS__)
+#define MOCK_METHOD8(m, ...) GMOCK_INTERNAL_MOCK_METHODN(, , m, 8, __VA_ARGS__)
+#define MOCK_METHOD9(m, ...) GMOCK_INTERNAL_MOCK_METHODN(, , m, 9, __VA_ARGS__)
+#define MOCK_METHOD10(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, , m, 10, __VA_ARGS__)
+
+#define MOCK_CONST_METHOD0(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, , m, 0, __VA_ARGS__)
+#define MOCK_CONST_METHOD1(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, , m, 1, __VA_ARGS__)
+#define MOCK_CONST_METHOD2(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, , m, 2, __VA_ARGS__)
+#define MOCK_CONST_METHOD3(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, , m, 3, __VA_ARGS__)
+#define MOCK_CONST_METHOD4(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, , m, 4, __VA_ARGS__)
+#define MOCK_CONST_METHOD5(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, , m, 5, __VA_ARGS__)
+#define MOCK_CONST_METHOD6(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, , m, 6, __VA_ARGS__)
+#define MOCK_CONST_METHOD7(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, , m, 7, __VA_ARGS__)
+#define MOCK_CONST_METHOD8(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, , m, 8, __VA_ARGS__)
+#define MOCK_CONST_METHOD9(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, , m, 9, __VA_ARGS__)
+#define MOCK_CONST_METHOD10(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, , m, 10, __VA_ARGS__)
+
+#define MOCK_METHOD0_T(m, ...) MOCK_METHOD0(m, __VA_ARGS__)
+#define MOCK_METHOD1_T(m, ...) MOCK_METHOD1(m, __VA_ARGS__)
+#define MOCK_METHOD2_T(m, ...) MOCK_METHOD2(m, __VA_ARGS__)
+#define MOCK_METHOD3_T(m, ...) MOCK_METHOD3(m, __VA_ARGS__)
+#define MOCK_METHOD4_T(m, ...) MOCK_METHOD4(m, __VA_ARGS__)
+#define MOCK_METHOD5_T(m, ...) MOCK_METHOD5(m, __VA_ARGS__)
+#define MOCK_METHOD6_T(m, ...) MOCK_METHOD6(m, __VA_ARGS__)
+#define MOCK_METHOD7_T(m, ...) MOCK_METHOD7(m, __VA_ARGS__)
+#define MOCK_METHOD8_T(m, ...) MOCK_METHOD8(m, __VA_ARGS__)
+#define MOCK_METHOD9_T(m, ...) MOCK_METHOD9(m, __VA_ARGS__)
+#define MOCK_METHOD10_T(m, ...) MOCK_METHOD10(m, __VA_ARGS__)
+
+#define MOCK_CONST_METHOD0_T(m, ...) MOCK_CONST_METHOD0(m, __VA_ARGS__)
+#define MOCK_CONST_METHOD1_T(m, ...) MOCK_CONST_METHOD1(m, __VA_ARGS__)
+#define MOCK_CONST_METHOD2_T(m, ...) MOCK_CONST_METHOD2(m, __VA_ARGS__)
+#define MOCK_CONST_METHOD3_T(m, ...) MOCK_CONST_METHOD3(m, __VA_ARGS__)
+#define MOCK_CONST_METHOD4_T(m, ...) MOCK_CONST_METHOD4(m, __VA_ARGS__)
+#define MOCK_CONST_METHOD5_T(m, ...) MOCK_CONST_METHOD5(m, __VA_ARGS__)
+#define MOCK_CONST_METHOD6_T(m, ...) MOCK_CONST_METHOD6(m, __VA_ARGS__)
+#define MOCK_CONST_METHOD7_T(m, ...) MOCK_CONST_METHOD7(m, __VA_ARGS__)
+#define MOCK_CONST_METHOD8_T(m, ...) MOCK_CONST_METHOD8(m, __VA_ARGS__)
+#define MOCK_CONST_METHOD9_T(m, ...) MOCK_CONST_METHOD9(m, __VA_ARGS__)
+#define MOCK_CONST_METHOD10_T(m, ...) MOCK_CONST_METHOD10(m, __VA_ARGS__)
+
+#define MOCK_METHOD0_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, ct, m, 0, __VA_ARGS__)
+#define MOCK_METHOD1_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, ct, m, 1, __VA_ARGS__)
+#define MOCK_METHOD2_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, ct, m, 2, __VA_ARGS__)
+#define MOCK_METHOD3_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, ct, m, 3, __VA_ARGS__)
+#define MOCK_METHOD4_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, ct, m, 4, __VA_ARGS__)
+#define MOCK_METHOD5_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, ct, m, 5, __VA_ARGS__)
+#define MOCK_METHOD6_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, ct, m, 6, __VA_ARGS__)
+#define MOCK_METHOD7_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, ct, m, 7, __VA_ARGS__)
+#define MOCK_METHOD8_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, ct, m, 8, __VA_ARGS__)
+#define MOCK_METHOD9_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, ct, m, 9, __VA_ARGS__)
+#define MOCK_METHOD10_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, ct, m, 10, __VA_ARGS__)
+
+#define MOCK_CONST_METHOD0_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, ct, m, 0, __VA_ARGS__)
+#define MOCK_CONST_METHOD1_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, ct, m, 1, __VA_ARGS__)
+#define MOCK_CONST_METHOD2_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, ct, m, 2, __VA_ARGS__)
+#define MOCK_CONST_METHOD3_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, ct, m, 3, __VA_ARGS__)
+#define MOCK_CONST_METHOD4_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, ct, m, 4, __VA_ARGS__)
+#define MOCK_CONST_METHOD5_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, ct, m, 5, __VA_ARGS__)
+#define MOCK_CONST_METHOD6_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, ct, m, 6, __VA_ARGS__)
+#define MOCK_CONST_METHOD7_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, ct, m, 7, __VA_ARGS__)
+#define MOCK_CONST_METHOD8_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, ct, m, 8, __VA_ARGS__)
+#define MOCK_CONST_METHOD9_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, ct, m, 9, __VA_ARGS__)
+#define MOCK_CONST_METHOD10_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, ct, m, 10, __VA_ARGS__)
+
+#define MOCK_METHOD0_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_METHOD0_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_METHOD1_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_METHOD1_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_METHOD2_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_METHOD2_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_METHOD3_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_METHOD3_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_METHOD4_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_METHOD4_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_METHOD5_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_METHOD5_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_METHOD6_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_METHOD6_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_METHOD7_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_METHOD7_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_METHOD8_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_METHOD8_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_METHOD9_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_METHOD9_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_METHOD10_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_METHOD10_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+
+#define MOCK_CONST_METHOD0_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_CONST_METHOD0_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_CONST_METHOD1_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_CONST_METHOD1_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_CONST_METHOD2_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_CONST_METHOD2_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_CONST_METHOD3_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_CONST_METHOD3_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_CONST_METHOD4_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_CONST_METHOD4_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_CONST_METHOD5_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_CONST_METHOD5_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_CONST_METHOD6_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_CONST_METHOD6_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_CONST_METHOD7_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_CONST_METHOD7_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_CONST_METHOD8_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_CONST_METHOD8_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_CONST_METHOD9_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_CONST_METHOD9_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_CONST_METHOD10_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_CONST_METHOD10_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+
+#define GMOCK_INTERNAL_MOCK_METHODN(constness, ct, Method, args_num, ...) \
+  GMOCK_INTERNAL_ASSERT_VALID_SIGNATURE(                                  \
+      args_num, ::testing::internal::identity_t<__VA_ARGS__>);            \
+  GMOCK_INTERNAL_MOCK_METHOD_IMPL(                                        \
+      args_num, Method, GMOCK_PP_NARG0(constness), 0, 0, , ct, ,          \
+      (::testing::internal::identity_t<__VA_ARGS__>))
+
+#define GMOCK_MOCKER_(arity, constness, Method) \
+  GTEST_CONCAT_TOKEN_(gmock##constness##arity##_##Method##_, __LINE__)
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_GMOCK_FUNCTION_MOCKER_H_
diff --git a/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-matchers.h b/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-matchers.h
new file mode 100644
index 0000000..86be9c1
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-matchers.h
@@ -0,0 +1,5392 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// The MATCHER* family of macros can be used in a namespace scope to
+// define custom matchers easily.
+//
+// Basic Usage
+// ===========
+//
+// The syntax
+//
+//   MATCHER(name, description_string) { statements; }
+//
+// defines a matcher with the given name that executes the statements,
+// which must return a bool to indicate if the match succeeds.  Inside
+// the statements, you can refer to the value being matched by 'arg',
+// and refer to its type by 'arg_type'.
+//
+// The description string documents what the matcher does, and is used
+// to generate the failure message when the match fails.  Since a
+// MATCHER() is usually defined in a header file shared by multiple
+// C++ source files, we require the description to be a C-string
+// literal to avoid possible side effects.  It can be empty, in which
+// case we'll use the sequence of words in the matcher name as the
+// description.
+//
+// For example:
+//
+//   MATCHER(IsEven, "") { return (arg % 2) == 0; }
+//
+// allows you to write
+//
+//   // Expects mock_foo.Bar(n) to be called where n is even.
+//   EXPECT_CALL(mock_foo, Bar(IsEven()));
+//
+// or,
+//
+//   // Verifies that the value of some_expression is even.
+//   EXPECT_THAT(some_expression, IsEven());
+//
+// If the above assertion fails, it will print something like:
+//
+//   Value of: some_expression
+//   Expected: is even
+//     Actual: 7
+//
+// where the description "is even" is automatically calculated from the
+// matcher name IsEven.
+//
+// Argument Type
+// =============
+//
+// Note that the type of the value being matched (arg_type) is
+// determined by the context in which you use the matcher and is
+// supplied to you by the compiler, so you don't need to worry about
+// declaring it (nor can you).  This allows the matcher to be
+// polymorphic.  For example, IsEven() can be used to match any type
+// where the value of "(arg % 2) == 0" can be implicitly converted to
+// a bool.  In the "Bar(IsEven())" example above, if method Bar()
+// takes an int, 'arg_type' will be int; if it takes an unsigned long,
+// 'arg_type' will be unsigned long; and so on.
+//
+// Parameterizing Matchers
+// =======================
+//
+// Sometimes you'll want to parameterize the matcher.  For that you
+// can use another macro:
+//
+//   MATCHER_P(name, param_name, description_string) { statements; }
+//
+// For example:
+//
+//   MATCHER_P(HasAbsoluteValue, value, "") { return abs(arg) == value; }
+//
+// will allow you to write:
+//
+//   EXPECT_THAT(Blah("a"), HasAbsoluteValue(n));
+//
+// which may lead to this message (assuming n is 10):
+//
+//   Value of: Blah("a")
+//   Expected: has absolute value 10
+//     Actual: -9
+//
+// Note that both the matcher description and its parameter are
+// printed, making the message human-friendly.
+//
+// In the matcher definition body, you can write 'foo_type' to
+// reference the type of a parameter named 'foo'.  For example, in the
+// body of MATCHER_P(HasAbsoluteValue, value) above, you can write
+// 'value_type' to refer to the type of 'value'.
+//
+// We also provide MATCHER_P2, MATCHER_P3, ..., up to MATCHER_P$n to
+// support multi-parameter matchers.
+//
+// Describing Parameterized Matchers
+// =================================
+//
+// The last argument to MATCHER*() is a string-typed expression.  The
+// expression can reference all of the matcher's parameters and a
+// special bool-typed variable named 'negation'.  When 'negation' is
+// false, the expression should evaluate to the matcher's description;
+// otherwise it should evaluate to the description of the negation of
+// the matcher.  For example,
+//
+//   using testing::PrintToString;
+//
+//   MATCHER_P2(InClosedRange, low, hi,
+//       std::string(negation ? "is not" : "is") + " in range [" +
+//       PrintToString(low) + ", " + PrintToString(hi) + "]") {
+//     return low <= arg && arg <= hi;
+//   }
+//   ...
+//   EXPECT_THAT(3, InClosedRange(4, 6));
+//   EXPECT_THAT(3, Not(InClosedRange(2, 4)));
+//
+// would generate two failures that contain the text:
+//
+//   Expected: is in range [4, 6]
+//   ...
+//   Expected: is not in range [2, 4]
+//
+// If you specify "" as the description, the failure message will
+// contain the sequence of words in the matcher name followed by the
+// parameter values printed as a tuple.  For example,
+//
+//   MATCHER_P2(InClosedRange, low, hi, "") { ... }
+//   ...
+//   EXPECT_THAT(3, InClosedRange(4, 6));
+//   EXPECT_THAT(3, Not(InClosedRange(2, 4)));
+//
+// would generate two failures that contain the text:
+//
+//   Expected: in closed range (4, 6)
+//   ...
+//   Expected: not (in closed range (2, 4))
+//
+// Types of Matcher Parameters
+// ===========================
+//
+// For the purpose of typing, you can view
+//
+//   MATCHER_Pk(Foo, p1, ..., pk, description_string) { ... }
+//
+// as shorthand for
+//
+//   template <typename p1_type, ..., typename pk_type>
+//   FooMatcherPk<p1_type, ..., pk_type>
+//   Foo(p1_type p1, ..., pk_type pk) { ... }
+//
+// When you write Foo(v1, ..., vk), the compiler infers the types of
+// the parameters v1, ..., and vk for you.  If you are not happy with
+// the result of the type inference, you can specify the types by
+// explicitly instantiating the template, as in Foo<long, bool>(5,
+// false).  As said earlier, you don't get to (or need to) specify
+// 'arg_type' as that's determined by the context in which the matcher
+// is used.  You can assign the result of expression Foo(p1, ..., pk)
+// to a variable of type FooMatcherPk<p1_type, ..., pk_type>.  This
+// can be useful when composing matchers.
+//
+// While you can instantiate a matcher template with reference types,
+// passing the parameters by pointer usually makes your code more
+// readable.  If, however, you still want to pass a parameter by
+// reference, be aware that in the failure message generated by the
+// matcher you will see the value of the referenced object but not its
+// address.
+//
+// Explaining Match Results
+// ========================
+//
+// Sometimes the matcher description alone isn't enough to explain why
+// the match has failed or succeeded.  For example, when expecting a
+// long string, it can be very helpful to also print the diff between
+// the expected string and the actual one.  To achieve that, you can
+// optionally stream additional information to a special variable
+// named result_listener, whose type is a pointer to class
+// MatchResultListener:
+//
+//   MATCHER_P(EqualsLongString, str, "") {
+//     if (arg == str) return true;
+//
+//     *result_listener << "the difference: "
+///                     << DiffStrings(str, arg);
+//     return false;
+//   }
+//
+// Overloading Matchers
+// ====================
+//
+// You can overload matchers with different numbers of parameters:
+//
+//   MATCHER_P(Blah, a, description_string1) { ... }
+//   MATCHER_P2(Blah, a, b, description_string2) { ... }
+//
+// Caveats
+// =======
+//
+// When defining a new matcher, you should also consider implementing
+// MatcherInterface or using MakePolymorphicMatcher().  These
+// approaches require more work than the MATCHER* macros, but also
+// give you more control on the types of the value being matched and
+// the matcher parameters, which may leads to better compiler error
+// messages when the matcher is used wrong.  They also allow
+// overloading matchers based on parameter types (as opposed to just
+// based on the number of parameters).
+//
+// MATCHER*() can only be used in a namespace scope as templates cannot be
+// declared inside of a local class.
+//
+// More Information
+// ================
+//
+// To learn more about using these macros, please search for 'MATCHER'
+// on
+// https://github.com/google/googletest/blob/master/docs/gmock_cook_book.md
+//
+// This file also implements some commonly used argument matchers.  More
+// matchers can be defined by the user implementing the
+// MatcherInterface<T> interface if necessary.
+//
+// See googletest/include/gtest/gtest-matchers.h for the definition of class
+// Matcher, class MatcherInterface, and others.
+
+// GOOGLETEST_CM0002 DO NOT DELETE
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_MATCHERS_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_MATCHERS_H_
+
+#include <algorithm>
+#include <cmath>
+#include <initializer_list>
+#include <iterator>
+#include <limits>
+#include <memory>
+#include <ostream>  // NOLINT
+#include <sstream>
+#include <string>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include "gmock/internal/gmock-internal-utils.h"
+#include "gmock/internal/gmock-port.h"
+#include "gmock/internal/gmock-pp.h"
+#include "gtest/gtest.h"
+
+// MSVC warning C5046 is new as of VS2017 version 15.8.
+#if defined(_MSC_VER) && _MSC_VER >= 1915
+#define GMOCK_MAYBE_5046_ 5046
+#else
+#define GMOCK_MAYBE_5046_
+#endif
+
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(
+    4251 GMOCK_MAYBE_5046_ /* class A needs to have dll-interface to be used by
+                              clients of class B */
+    /* Symbol involving type with internal linkage not defined */)
+
+namespace testing {
+
+// To implement a matcher Foo for type T, define:
+//   1. a class FooMatcherImpl that implements the
+//      MatcherInterface<T> interface, and
+//   2. a factory function that creates a Matcher<T> object from a
+//      FooMatcherImpl*.
+//
+// The two-level delegation design makes it possible to allow a user
+// to write "v" instead of "Eq(v)" where a Matcher is expected, which
+// is impossible if we pass matchers by pointers.  It also eases
+// ownership management as Matcher objects can now be copied like
+// plain values.
+
+// A match result listener that stores the explanation in a string.
+class StringMatchResultListener : public MatchResultListener {
+ public:
+  StringMatchResultListener() : MatchResultListener(&ss_) {}
+
+  // Returns the explanation accumulated so far.
+  std::string str() const { return ss_.str(); }
+
+  // Clears the explanation accumulated so far.
+  void Clear() { ss_.str(""); }
+
+ private:
+  ::std::stringstream ss_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(StringMatchResultListener);
+};
+
+// Anything inside the 'internal' namespace IS INTERNAL IMPLEMENTATION
+// and MUST NOT BE USED IN USER CODE!!!
+namespace internal {
+
+// The MatcherCastImpl class template is a helper for implementing
+// MatcherCast().  We need this helper in order to partially
+// specialize the implementation of MatcherCast() (C++ allows
+// class/struct templates to be partially specialized, but not
+// function templates.).
+
+// This general version is used when MatcherCast()'s argument is a
+// polymorphic matcher (i.e. something that can be converted to a
+// Matcher but is not one yet; for example, Eq(value)) or a value (for
+// example, "hello").
+template <typename T, typename M>
+class MatcherCastImpl {
+ public:
+  static Matcher<T> Cast(const M& polymorphic_matcher_or_value) {
+    // M can be a polymorphic matcher, in which case we want to use
+    // its conversion operator to create Matcher<T>.  Or it can be a value
+    // that should be passed to the Matcher<T>'s constructor.
+    //
+    // We can't call Matcher<T>(polymorphic_matcher_or_value) when M is a
+    // polymorphic matcher because it'll be ambiguous if T has an implicit
+    // constructor from M (this usually happens when T has an implicit
+    // constructor from any type).
+    //
+    // It won't work to unconditionally implicit_cast
+    // polymorphic_matcher_or_value to Matcher<T> because it won't trigger
+    // a user-defined conversion from M to T if one exists (assuming M is
+    // a value).
+    return CastImpl(polymorphic_matcher_or_value,
+                    std::is_convertible<M, Matcher<T>>{},
+                    std::is_convertible<M, T>{});
+  }
+
+ private:
+  template <bool Ignore>
+  static Matcher<T> CastImpl(const M& polymorphic_matcher_or_value,
+                             std::true_type /* convertible_to_matcher */,
+                             std::integral_constant<bool, Ignore>) {
+    // M is implicitly convertible to Matcher<T>, which means that either
+    // M is a polymorphic matcher or Matcher<T> has an implicit constructor
+    // from M.  In both cases using the implicit conversion will produce a
+    // matcher.
+    //
+    // Even if T has an implicit constructor from M, it won't be called because
+    // creating Matcher<T> would require a chain of two user-defined conversions
+    // (first to create T from M and then to create Matcher<T> from T).
+    return polymorphic_matcher_or_value;
+  }
+
+  // M can't be implicitly converted to Matcher<T>, so M isn't a polymorphic
+  // matcher. It's a value of a type implicitly convertible to T. Use direct
+  // initialization to create a matcher.
+  static Matcher<T> CastImpl(const M& value,
+                             std::false_type /* convertible_to_matcher */,
+                             std::true_type /* convertible_to_T */) {
+    return Matcher<T>(ImplicitCast_<T>(value));
+  }
+
+  // M can't be implicitly converted to either Matcher<T> or T. Attempt to use
+  // polymorphic matcher Eq(value) in this case.
+  //
+  // Note that we first attempt to perform an implicit cast on the value and
+  // only fall back to the polymorphic Eq() matcher afterwards because the
+  // latter calls bool operator==(const Lhs& lhs, const Rhs& rhs) in the end
+  // which might be undefined even when Rhs is implicitly convertible to Lhs
+  // (e.g. std::pair<const int, int> vs. std::pair<int, int>).
+  //
+  // We don't define this method inline as we need the declaration of Eq().
+  static Matcher<T> CastImpl(const M& value,
+                             std::false_type /* convertible_to_matcher */,
+                             std::false_type /* convertible_to_T */);
+};
+
+// This more specialized version is used when MatcherCast()'s argument
+// is already a Matcher.  This only compiles when type T can be
+// statically converted to type U.
+template <typename T, typename U>
+class MatcherCastImpl<T, Matcher<U> > {
+ public:
+  static Matcher<T> Cast(const Matcher<U>& source_matcher) {
+    return Matcher<T>(new Impl(source_matcher));
+  }
+
+ private:
+  class Impl : public MatcherInterface<T> {
+   public:
+    explicit Impl(const Matcher<U>& source_matcher)
+        : source_matcher_(source_matcher) {}
+
+    // We delegate the matching logic to the source matcher.
+    bool MatchAndExplain(T x, MatchResultListener* listener) const override {
+      using FromType = typename std::remove_cv<typename std::remove_pointer<
+          typename std::remove_reference<T>::type>::type>::type;
+      using ToType = typename std::remove_cv<typename std::remove_pointer<
+          typename std::remove_reference<U>::type>::type>::type;
+      // Do not allow implicitly converting base*/& to derived*/&.
+      static_assert(
+          // Do not trigger if only one of them is a pointer. That implies a
+          // regular conversion and not a down_cast.
+          (std::is_pointer<typename std::remove_reference<T>::type>::value !=
+           std::is_pointer<typename std::remove_reference<U>::type>::value) ||
+              std::is_same<FromType, ToType>::value ||
+              !std::is_base_of<FromType, ToType>::value,
+          "Can't implicitly convert from <base> to <derived>");
+
+      // Do the cast to `U` explicitly if necessary.
+      // Otherwise, let implicit conversions do the trick.
+      using CastType =
+          typename std::conditional<std::is_convertible<T&, const U&>::value,
+                                    T&, U>::type;
+
+      return source_matcher_.MatchAndExplain(static_cast<CastType>(x),
+                                             listener);
+    }
+
+    void DescribeTo(::std::ostream* os) const override {
+      source_matcher_.DescribeTo(os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      source_matcher_.DescribeNegationTo(os);
+    }
+
+   private:
+    const Matcher<U> source_matcher_;
+  };
+};
+
+// This even more specialized version is used for efficiently casting
+// a matcher to its own type.
+template <typename T>
+class MatcherCastImpl<T, Matcher<T> > {
+ public:
+  static Matcher<T> Cast(const Matcher<T>& matcher) { return matcher; }
+};
+
+// Template specialization for parameterless Matcher.
+template <typename Derived>
+class MatcherBaseImpl {
+ public:
+  MatcherBaseImpl() = default;
+
+  template <typename T>
+  operator ::testing::Matcher<T>() const {  // NOLINT(runtime/explicit)
+    return ::testing::Matcher<T>(new
+                                 typename Derived::template gmock_Impl<T>());
+  }
+};
+
+// Template specialization for Matcher with parameters.
+template <template <typename...> class Derived, typename... Ts>
+class MatcherBaseImpl<Derived<Ts...>> {
+ public:
+  // Mark the constructor explicit for single argument T to avoid implicit
+  // conversions.
+  template <typename E = std::enable_if<sizeof...(Ts) == 1>,
+            typename E::type* = nullptr>
+  explicit MatcherBaseImpl(Ts... params)
+      : params_(std::forward<Ts>(params)...) {}
+  template <typename E = std::enable_if<sizeof...(Ts) != 1>,
+            typename = typename E::type>
+  MatcherBaseImpl(Ts... params)  // NOLINT
+      : params_(std::forward<Ts>(params)...) {}
+
+  template <typename F>
+  operator ::testing::Matcher<F>() const {  // NOLINT(runtime/explicit)
+    return Apply<F>(MakeIndexSequence<sizeof...(Ts)>{});
+  }
+
+ private:
+  template <typename F, std::size_t... tuple_ids>
+  ::testing::Matcher<F> Apply(IndexSequence<tuple_ids...>) const {
+    return ::testing::Matcher<F>(
+        new typename Derived<Ts...>::template gmock_Impl<F>(
+            std::get<tuple_ids>(params_)...));
+  }
+
+  const std::tuple<Ts...> params_;
+};
+
+}  // namespace internal
+
+// In order to be safe and clear, casting between different matcher
+// types is done explicitly via MatcherCast<T>(m), which takes a
+// matcher m and returns a Matcher<T>.  It compiles only when T can be
+// statically converted to the argument type of m.
+template <typename T, typename M>
+inline Matcher<T> MatcherCast(const M& matcher) {
+  return internal::MatcherCastImpl<T, M>::Cast(matcher);
+}
+
+// This overload handles polymorphic matchers and values only since
+// monomorphic matchers are handled by the next one.
+template <typename T, typename M>
+inline Matcher<T> SafeMatcherCast(const M& polymorphic_matcher_or_value) {
+  return MatcherCast<T>(polymorphic_matcher_or_value);
+}
+
+// This overload handles monomorphic matchers.
+//
+// In general, if type T can be implicitly converted to type U, we can
+// safely convert a Matcher<U> to a Matcher<T> (i.e. Matcher is
+// contravariant): just keep a copy of the original Matcher<U>, convert the
+// argument from type T to U, and then pass it to the underlying Matcher<U>.
+// The only exception is when U is a reference and T is not, as the
+// underlying Matcher<U> may be interested in the argument's address, which
+// is not preserved in the conversion from T to U.
+template <typename T, typename U>
+inline Matcher<T> SafeMatcherCast(const Matcher<U>& matcher) {
+  // Enforce that T can be implicitly converted to U.
+  static_assert(std::is_convertible<const T&, const U&>::value,
+                "T must be implicitly convertible to U");
+  // Enforce that we are not converting a non-reference type T to a reference
+  // type U.
+  GTEST_COMPILE_ASSERT_(
+      std::is_reference<T>::value || !std::is_reference<U>::value,
+      cannot_convert_non_reference_arg_to_reference);
+  // In case both T and U are arithmetic types, enforce that the
+  // conversion is not lossy.
+  typedef GTEST_REMOVE_REFERENCE_AND_CONST_(T) RawT;
+  typedef GTEST_REMOVE_REFERENCE_AND_CONST_(U) RawU;
+  constexpr bool kTIsOther = GMOCK_KIND_OF_(RawT) == internal::kOther;
+  constexpr bool kUIsOther = GMOCK_KIND_OF_(RawU) == internal::kOther;
+  GTEST_COMPILE_ASSERT_(
+      kTIsOther || kUIsOther ||
+      (internal::LosslessArithmeticConvertible<RawT, RawU>::value),
+      conversion_of_arithmetic_types_must_be_lossless);
+  return MatcherCast<T>(matcher);
+}
+
+// A<T>() returns a matcher that matches any value of type T.
+template <typename T>
+Matcher<T> A();
+
+// Anything inside the 'internal' namespace IS INTERNAL IMPLEMENTATION
+// and MUST NOT BE USED IN USER CODE!!!
+namespace internal {
+
+// If the explanation is not empty, prints it to the ostream.
+inline void PrintIfNotEmpty(const std::string& explanation,
+                            ::std::ostream* os) {
+  if (explanation != "" && os != nullptr) {
+    *os << ", " << explanation;
+  }
+}
+
+// Returns true if the given type name is easy to read by a human.
+// This is used to decide whether printing the type of a value might
+// be helpful.
+inline bool IsReadableTypeName(const std::string& type_name) {
+  // We consider a type name readable if it's short or doesn't contain
+  // a template or function type.
+  return (type_name.length() <= 20 ||
+          type_name.find_first_of("<(") == std::string::npos);
+}
+
+// Matches the value against the given matcher, prints the value and explains
+// the match result to the listener. Returns the match result.
+// 'listener' must not be NULL.
+// Value cannot be passed by const reference, because some matchers take a
+// non-const argument.
+template <typename Value, typename T>
+bool MatchPrintAndExplain(Value& value, const Matcher<T>& matcher,
+                          MatchResultListener* listener) {
+  if (!listener->IsInterested()) {
+    // If the listener is not interested, we do not need to construct the
+    // inner explanation.
+    return matcher.Matches(value);
+  }
+
+  StringMatchResultListener inner_listener;
+  const bool match = matcher.MatchAndExplain(value, &inner_listener);
+
+  UniversalPrint(value, listener->stream());
+#if GTEST_HAS_RTTI
+  const std::string& type_name = GetTypeName<Value>();
+  if (IsReadableTypeName(type_name))
+    *listener->stream() << " (of type " << type_name << ")";
+#endif
+  PrintIfNotEmpty(inner_listener.str(), listener->stream());
+
+  return match;
+}
+
+// An internal helper class for doing compile-time loop on a tuple's
+// fields.
+template <size_t N>
+class TuplePrefix {
+ public:
+  // TuplePrefix<N>::Matches(matcher_tuple, value_tuple) returns true
+  // if and only if the first N fields of matcher_tuple matches
+  // the first N fields of value_tuple, respectively.
+  template <typename MatcherTuple, typename ValueTuple>
+  static bool Matches(const MatcherTuple& matcher_tuple,
+                      const ValueTuple& value_tuple) {
+    return TuplePrefix<N - 1>::Matches(matcher_tuple, value_tuple) &&
+           std::get<N - 1>(matcher_tuple).Matches(std::get<N - 1>(value_tuple));
+  }
+
+  // TuplePrefix<N>::ExplainMatchFailuresTo(matchers, values, os)
+  // describes failures in matching the first N fields of matchers
+  // against the first N fields of values.  If there is no failure,
+  // nothing will be streamed to os.
+  template <typename MatcherTuple, typename ValueTuple>
+  static void ExplainMatchFailuresTo(const MatcherTuple& matchers,
+                                     const ValueTuple& values,
+                                     ::std::ostream* os) {
+    // First, describes failures in the first N - 1 fields.
+    TuplePrefix<N - 1>::ExplainMatchFailuresTo(matchers, values, os);
+
+    // Then describes the failure (if any) in the (N - 1)-th (0-based)
+    // field.
+    typename std::tuple_element<N - 1, MatcherTuple>::type matcher =
+        std::get<N - 1>(matchers);
+    typedef typename std::tuple_element<N - 1, ValueTuple>::type Value;
+    const Value& value = std::get<N - 1>(values);
+    StringMatchResultListener listener;
+    if (!matcher.MatchAndExplain(value, &listener)) {
+      *os << "  Expected arg #" << N - 1 << ": ";
+      std::get<N - 1>(matchers).DescribeTo(os);
+      *os << "\n           Actual: ";
+      // We remove the reference in type Value to prevent the
+      // universal printer from printing the address of value, which
+      // isn't interesting to the user most of the time.  The
+      // matcher's MatchAndExplain() method handles the case when
+      // the address is interesting.
+      internal::UniversalPrint(value, os);
+      PrintIfNotEmpty(listener.str(), os);
+      *os << "\n";
+    }
+  }
+};
+
+// The base case.
+template <>
+class TuplePrefix<0> {
+ public:
+  template <typename MatcherTuple, typename ValueTuple>
+  static bool Matches(const MatcherTuple& /* matcher_tuple */,
+                      const ValueTuple& /* value_tuple */) {
+    return true;
+  }
+
+  template <typename MatcherTuple, typename ValueTuple>
+  static void ExplainMatchFailuresTo(const MatcherTuple& /* matchers */,
+                                     const ValueTuple& /* values */,
+                                     ::std::ostream* /* os */) {}
+};
+
+// TupleMatches(matcher_tuple, value_tuple) returns true if and only if
+// all matchers in matcher_tuple match the corresponding fields in
+// value_tuple.  It is a compiler error if matcher_tuple and
+// value_tuple have different number of fields or incompatible field
+// types.
+template <typename MatcherTuple, typename ValueTuple>
+bool TupleMatches(const MatcherTuple& matcher_tuple,
+                  const ValueTuple& value_tuple) {
+  // Makes sure that matcher_tuple and value_tuple have the same
+  // number of fields.
+  GTEST_COMPILE_ASSERT_(std::tuple_size<MatcherTuple>::value ==
+                            std::tuple_size<ValueTuple>::value,
+                        matcher_and_value_have_different_numbers_of_fields);
+  return TuplePrefix<std::tuple_size<ValueTuple>::value>::Matches(matcher_tuple,
+                                                                  value_tuple);
+}
+
+// Describes failures in matching matchers against values.  If there
+// is no failure, nothing will be streamed to os.
+template <typename MatcherTuple, typename ValueTuple>
+void ExplainMatchFailureTupleTo(const MatcherTuple& matchers,
+                                const ValueTuple& values,
+                                ::std::ostream* os) {
+  TuplePrefix<std::tuple_size<MatcherTuple>::value>::ExplainMatchFailuresTo(
+      matchers, values, os);
+}
+
+// TransformTupleValues and its helper.
+//
+// TransformTupleValuesHelper hides the internal machinery that
+// TransformTupleValues uses to implement a tuple traversal.
+template <typename Tuple, typename Func, typename OutIter>
+class TransformTupleValuesHelper {
+ private:
+  typedef ::std::tuple_size<Tuple> TupleSize;
+
+ public:
+  // For each member of tuple 't', taken in order, evaluates '*out++ = f(t)'.
+  // Returns the final value of 'out' in case the caller needs it.
+  static OutIter Run(Func f, const Tuple& t, OutIter out) {
+    return IterateOverTuple<Tuple, TupleSize::value>()(f, t, out);
+  }
+
+ private:
+  template <typename Tup, size_t kRemainingSize>
+  struct IterateOverTuple {
+    OutIter operator() (Func f, const Tup& t, OutIter out) const {
+      *out++ = f(::std::get<TupleSize::value - kRemainingSize>(t));
+      return IterateOverTuple<Tup, kRemainingSize - 1>()(f, t, out);
+    }
+  };
+  template <typename Tup>
+  struct IterateOverTuple<Tup, 0> {
+    OutIter operator() (Func /* f */, const Tup& /* t */, OutIter out) const {
+      return out;
+    }
+  };
+};
+
+// Successively invokes 'f(element)' on each element of the tuple 't',
+// appending each result to the 'out' iterator. Returns the final value
+// of 'out'.
+template <typename Tuple, typename Func, typename OutIter>
+OutIter TransformTupleValues(Func f, const Tuple& t, OutIter out) {
+  return TransformTupleValuesHelper<Tuple, Func, OutIter>::Run(f, t, out);
+}
+
+// Implements _, a matcher that matches any value of any
+// type.  This is a polymorphic matcher, so we need a template type
+// conversion operator to make it appearing as a Matcher<T> for any
+// type T.
+class AnythingMatcher {
+ public:
+  using is_gtest_matcher = void;
+
+  template <typename T>
+  bool MatchAndExplain(const T& /* x */, std::ostream* /* listener */) const {
+    return true;
+  }
+  void DescribeTo(std::ostream* os) const { *os << "is anything"; }
+  void DescribeNegationTo(::std::ostream* os) const {
+    // This is mostly for completeness' sake, as it's not very useful
+    // to write Not(A<bool>()).  However we cannot completely rule out
+    // such a possibility, and it doesn't hurt to be prepared.
+    *os << "never matches";
+  }
+};
+
+// Implements the polymorphic IsNull() matcher, which matches any raw or smart
+// pointer that is NULL.
+class IsNullMatcher {
+ public:
+  template <typename Pointer>
+  bool MatchAndExplain(const Pointer& p,
+                       MatchResultListener* /* listener */) const {
+    return p == nullptr;
+  }
+
+  void DescribeTo(::std::ostream* os) const { *os << "is NULL"; }
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "isn't NULL";
+  }
+};
+
+// Implements the polymorphic NotNull() matcher, which matches any raw or smart
+// pointer that is not NULL.
+class NotNullMatcher {
+ public:
+  template <typename Pointer>
+  bool MatchAndExplain(const Pointer& p,
+                       MatchResultListener* /* listener */) const {
+    return p != nullptr;
+  }
+
+  void DescribeTo(::std::ostream* os) const { *os << "isn't NULL"; }
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "is NULL";
+  }
+};
+
+// Ref(variable) matches any argument that is a reference to
+// 'variable'.  This matcher is polymorphic as it can match any
+// super type of the type of 'variable'.
+//
+// The RefMatcher template class implements Ref(variable).  It can
+// only be instantiated with a reference type.  This prevents a user
+// from mistakenly using Ref(x) to match a non-reference function
+// argument.  For example, the following will righteously cause a
+// compiler error:
+//
+//   int n;
+//   Matcher<int> m1 = Ref(n);   // This won't compile.
+//   Matcher<int&> m2 = Ref(n);  // This will compile.
+template <typename T>
+class RefMatcher;
+
+template <typename T>
+class RefMatcher<T&> {
+  // Google Mock is a generic framework and thus needs to support
+  // mocking any function types, including those that take non-const
+  // reference arguments.  Therefore the template parameter T (and
+  // Super below) can be instantiated to either a const type or a
+  // non-const type.
+ public:
+  // RefMatcher() takes a T& instead of const T&, as we want the
+  // compiler to catch using Ref(const_value) as a matcher for a
+  // non-const reference.
+  explicit RefMatcher(T& x) : object_(x) {}  // NOLINT
+
+  template <typename Super>
+  operator Matcher<Super&>() const {
+    // By passing object_ (type T&) to Impl(), which expects a Super&,
+    // we make sure that Super is a super type of T.  In particular,
+    // this catches using Ref(const_value) as a matcher for a
+    // non-const reference, as you cannot implicitly convert a const
+    // reference to a non-const reference.
+    return MakeMatcher(new Impl<Super>(object_));
+  }
+
+ private:
+  template <typename Super>
+  class Impl : public MatcherInterface<Super&> {
+   public:
+    explicit Impl(Super& x) : object_(x) {}  // NOLINT
+
+    // MatchAndExplain() takes a Super& (as opposed to const Super&)
+    // in order to match the interface MatcherInterface<Super&>.
+    bool MatchAndExplain(Super& x,
+                         MatchResultListener* listener) const override {
+      *listener << "which is located @" << static_cast<const void*>(&x);
+      return &x == &object_;
+    }
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "references the variable ";
+      UniversalPrinter<Super&>::Print(object_, os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "does not reference the variable ";
+      UniversalPrinter<Super&>::Print(object_, os);
+    }
+
+   private:
+    const Super& object_;
+  };
+
+  T& object_;
+};
+
+// Polymorphic helper functions for narrow and wide string matchers.
+inline bool CaseInsensitiveCStringEquals(const char* lhs, const char* rhs) {
+  return String::CaseInsensitiveCStringEquals(lhs, rhs);
+}
+
+inline bool CaseInsensitiveCStringEquals(const wchar_t* lhs,
+                                         const wchar_t* rhs) {
+  return String::CaseInsensitiveWideCStringEquals(lhs, rhs);
+}
+
+// String comparison for narrow or wide strings that can have embedded NUL
+// characters.
+template <typename StringType>
+bool CaseInsensitiveStringEquals(const StringType& s1,
+                                 const StringType& s2) {
+  // Are the heads equal?
+  if (!CaseInsensitiveCStringEquals(s1.c_str(), s2.c_str())) {
+    return false;
+  }
+
+  // Skip the equal heads.
+  const typename StringType::value_type nul = 0;
+  const size_t i1 = s1.find(nul), i2 = s2.find(nul);
+
+  // Are we at the end of either s1 or s2?
+  if (i1 == StringType::npos || i2 == StringType::npos) {
+    return i1 == i2;
+  }
+
+  // Are the tails equal?
+  return CaseInsensitiveStringEquals(s1.substr(i1 + 1), s2.substr(i2 + 1));
+}
+
+// String matchers.
+
+// Implements equality-based string matchers like StrEq, StrCaseNe, and etc.
+template <typename StringType>
+class StrEqualityMatcher {
+ public:
+  StrEqualityMatcher(StringType str, bool expect_eq, bool case_sensitive)
+      : string_(std::move(str)),
+        expect_eq_(expect_eq),
+        case_sensitive_(case_sensitive) {}
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  bool MatchAndExplain(const internal::StringView& s,
+                       MatchResultListener* listener) const {
+    // This should fail to compile if StringView is used with wide
+    // strings.
+    const StringType& str = std::string(s);
+    return MatchAndExplain(str, listener);
+  }
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+
+  // Accepts pointer types, particularly:
+  //   const char*
+  //   char*
+  //   const wchar_t*
+  //   wchar_t*
+  template <typename CharType>
+  bool MatchAndExplain(CharType* s, MatchResultListener* listener) const {
+    if (s == nullptr) {
+      return !expect_eq_;
+    }
+    return MatchAndExplain(StringType(s), listener);
+  }
+
+  // Matches anything that can convert to StringType.
+  //
+  // This is a template, not just a plain function with const StringType&,
+  // because StringView has some interfering non-explicit constructors.
+  template <typename MatcheeStringType>
+  bool MatchAndExplain(const MatcheeStringType& s,
+                       MatchResultListener* /* listener */) const {
+    const StringType s2(s);
+    const bool eq = case_sensitive_ ? s2 == string_ :
+        CaseInsensitiveStringEquals(s2, string_);
+    return expect_eq_ == eq;
+  }
+
+  void DescribeTo(::std::ostream* os) const {
+    DescribeToHelper(expect_eq_, os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    DescribeToHelper(!expect_eq_, os);
+  }
+
+ private:
+  void DescribeToHelper(bool expect_eq, ::std::ostream* os) const {
+    *os << (expect_eq ? "is " : "isn't ");
+    *os << "equal to ";
+    if (!case_sensitive_) {
+      *os << "(ignoring case) ";
+    }
+    UniversalPrint(string_, os);
+  }
+
+  const StringType string_;
+  const bool expect_eq_;
+  const bool case_sensitive_;
+};
+
+// Implements the polymorphic HasSubstr(substring) matcher, which
+// can be used as a Matcher<T> as long as T can be converted to a
+// string.
+template <typename StringType>
+class HasSubstrMatcher {
+ public:
+  explicit HasSubstrMatcher(const StringType& substring)
+      : substring_(substring) {}
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  bool MatchAndExplain(const internal::StringView& s,
+                       MatchResultListener* listener) const {
+    // This should fail to compile if StringView is used with wide
+    // strings.
+    const StringType& str = std::string(s);
+    return MatchAndExplain(str, listener);
+  }
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+
+  // Accepts pointer types, particularly:
+  //   const char*
+  //   char*
+  //   const wchar_t*
+  //   wchar_t*
+  template <typename CharType>
+  bool MatchAndExplain(CharType* s, MatchResultListener* listener) const {
+    return s != nullptr && MatchAndExplain(StringType(s), listener);
+  }
+
+  // Matches anything that can convert to StringType.
+  //
+  // This is a template, not just a plain function with const StringType&,
+  // because StringView has some interfering non-explicit constructors.
+  template <typename MatcheeStringType>
+  bool MatchAndExplain(const MatcheeStringType& s,
+                       MatchResultListener* /* listener */) const {
+    return StringType(s).find(substring_) != StringType::npos;
+  }
+
+  // Describes what this matcher matches.
+  void DescribeTo(::std::ostream* os) const {
+    *os << "has substring ";
+    UniversalPrint(substring_, os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "has no substring ";
+    UniversalPrint(substring_, os);
+  }
+
+ private:
+  const StringType substring_;
+};
+
+// Implements the polymorphic StartsWith(substring) matcher, which
+// can be used as a Matcher<T> as long as T can be converted to a
+// string.
+template <typename StringType>
+class StartsWithMatcher {
+ public:
+  explicit StartsWithMatcher(const StringType& prefix) : prefix_(prefix) {
+  }
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  bool MatchAndExplain(const internal::StringView& s,
+                       MatchResultListener* listener) const {
+    // This should fail to compile if StringView is used with wide
+    // strings.
+    const StringType& str = std::string(s);
+    return MatchAndExplain(str, listener);
+  }
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+
+  // Accepts pointer types, particularly:
+  //   const char*
+  //   char*
+  //   const wchar_t*
+  //   wchar_t*
+  template <typename CharType>
+  bool MatchAndExplain(CharType* s, MatchResultListener* listener) const {
+    return s != nullptr && MatchAndExplain(StringType(s), listener);
+  }
+
+  // Matches anything that can convert to StringType.
+  //
+  // This is a template, not just a plain function with const StringType&,
+  // because StringView has some interfering non-explicit constructors.
+  template <typename MatcheeStringType>
+  bool MatchAndExplain(const MatcheeStringType& s,
+                       MatchResultListener* /* listener */) const {
+    const StringType& s2(s);
+    return s2.length() >= prefix_.length() &&
+        s2.substr(0, prefix_.length()) == prefix_;
+  }
+
+  void DescribeTo(::std::ostream* os) const {
+    *os << "starts with ";
+    UniversalPrint(prefix_, os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "doesn't start with ";
+    UniversalPrint(prefix_, os);
+  }
+
+ private:
+  const StringType prefix_;
+};
+
+// Implements the polymorphic EndsWith(substring) matcher, which
+// can be used as a Matcher<T> as long as T can be converted to a
+// string.
+template <typename StringType>
+class EndsWithMatcher {
+ public:
+  explicit EndsWithMatcher(const StringType& suffix) : suffix_(suffix) {}
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  bool MatchAndExplain(const internal::StringView& s,
+                       MatchResultListener* listener) const {
+    // This should fail to compile if StringView is used with wide
+    // strings.
+    const StringType& str = std::string(s);
+    return MatchAndExplain(str, listener);
+  }
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+
+  // Accepts pointer types, particularly:
+  //   const char*
+  //   char*
+  //   const wchar_t*
+  //   wchar_t*
+  template <typename CharType>
+  bool MatchAndExplain(CharType* s, MatchResultListener* listener) const {
+    return s != nullptr && MatchAndExplain(StringType(s), listener);
+  }
+
+  // Matches anything that can convert to StringType.
+  //
+  // This is a template, not just a plain function with const StringType&,
+  // because StringView has some interfering non-explicit constructors.
+  template <typename MatcheeStringType>
+  bool MatchAndExplain(const MatcheeStringType& s,
+                       MatchResultListener* /* listener */) const {
+    const StringType& s2(s);
+    return s2.length() >= suffix_.length() &&
+        s2.substr(s2.length() - suffix_.length()) == suffix_;
+  }
+
+  void DescribeTo(::std::ostream* os) const {
+    *os << "ends with ";
+    UniversalPrint(suffix_, os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "doesn't end with ";
+    UniversalPrint(suffix_, os);
+  }
+
+ private:
+  const StringType suffix_;
+};
+
+// Implements a matcher that compares the two fields of a 2-tuple
+// using one of the ==, <=, <, etc, operators.  The two fields being
+// compared don't have to have the same type.
+//
+// The matcher defined here is polymorphic (for example, Eq() can be
+// used to match a std::tuple<int, short>, a std::tuple<const long&, double>,
+// etc).  Therefore we use a template type conversion operator in the
+// implementation.
+template <typename D, typename Op>
+class PairMatchBase {
+ public:
+  template <typename T1, typename T2>
+  operator Matcher<::std::tuple<T1, T2>>() const {
+    return Matcher<::std::tuple<T1, T2>>(new Impl<const ::std::tuple<T1, T2>&>);
+  }
+  template <typename T1, typename T2>
+  operator Matcher<const ::std::tuple<T1, T2>&>() const {
+    return MakeMatcher(new Impl<const ::std::tuple<T1, T2>&>);
+  }
+
+ private:
+  static ::std::ostream& GetDesc(::std::ostream& os) {  // NOLINT
+    return os << D::Desc();
+  }
+
+  template <typename Tuple>
+  class Impl : public MatcherInterface<Tuple> {
+   public:
+    bool MatchAndExplain(Tuple args,
+                         MatchResultListener* /* listener */) const override {
+      return Op()(::std::get<0>(args), ::std::get<1>(args));
+    }
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "are " << GetDesc;
+    }
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "aren't " << GetDesc;
+    }
+  };
+};
+
+class Eq2Matcher : public PairMatchBase<Eq2Matcher, AnyEq> {
+ public:
+  static const char* Desc() { return "an equal pair"; }
+};
+class Ne2Matcher : public PairMatchBase<Ne2Matcher, AnyNe> {
+ public:
+  static const char* Desc() { return "an unequal pair"; }
+};
+class Lt2Matcher : public PairMatchBase<Lt2Matcher, AnyLt> {
+ public:
+  static const char* Desc() { return "a pair where the first < the second"; }
+};
+class Gt2Matcher : public PairMatchBase<Gt2Matcher, AnyGt> {
+ public:
+  static const char* Desc() { return "a pair where the first > the second"; }
+};
+class Le2Matcher : public PairMatchBase<Le2Matcher, AnyLe> {
+ public:
+  static const char* Desc() { return "a pair where the first <= the second"; }
+};
+class Ge2Matcher : public PairMatchBase<Ge2Matcher, AnyGe> {
+ public:
+  static const char* Desc() { return "a pair where the first >= the second"; }
+};
+
+// Implements the Not(...) matcher for a particular argument type T.
+// We do not nest it inside the NotMatcher class template, as that
+// will prevent different instantiations of NotMatcher from sharing
+// the same NotMatcherImpl<T> class.
+template <typename T>
+class NotMatcherImpl : public MatcherInterface<const T&> {
+ public:
+  explicit NotMatcherImpl(const Matcher<T>& matcher)
+      : matcher_(matcher) {}
+
+  bool MatchAndExplain(const T& x,
+                       MatchResultListener* listener) const override {
+    return !matcher_.MatchAndExplain(x, listener);
+  }
+
+  void DescribeTo(::std::ostream* os) const override {
+    matcher_.DescribeNegationTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const override {
+    matcher_.DescribeTo(os);
+  }
+
+ private:
+  const Matcher<T> matcher_;
+};
+
+// Implements the Not(m) matcher, which matches a value that doesn't
+// match matcher m.
+template <typename InnerMatcher>
+class NotMatcher {
+ public:
+  explicit NotMatcher(InnerMatcher matcher) : matcher_(matcher) {}
+
+  // This template type conversion operator allows Not(m) to be used
+  // to match any type m can match.
+  template <typename T>
+  operator Matcher<T>() const {
+    return Matcher<T>(new NotMatcherImpl<T>(SafeMatcherCast<T>(matcher_)));
+  }
+
+ private:
+  InnerMatcher matcher_;
+};
+
+// Implements the AllOf(m1, m2) matcher for a particular argument type
+// T. We do not nest it inside the BothOfMatcher class template, as
+// that will prevent different instantiations of BothOfMatcher from
+// sharing the same BothOfMatcherImpl<T> class.
+template <typename T>
+class AllOfMatcherImpl : public MatcherInterface<const T&> {
+ public:
+  explicit AllOfMatcherImpl(std::vector<Matcher<T> > matchers)
+      : matchers_(std::move(matchers)) {}
+
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "(";
+    for (size_t i = 0; i < matchers_.size(); ++i) {
+      if (i != 0) *os << ") and (";
+      matchers_[i].DescribeTo(os);
+    }
+    *os << ")";
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const override {
+    *os << "(";
+    for (size_t i = 0; i < matchers_.size(); ++i) {
+      if (i != 0) *os << ") or (";
+      matchers_[i].DescribeNegationTo(os);
+    }
+    *os << ")";
+  }
+
+  bool MatchAndExplain(const T& x,
+                       MatchResultListener* listener) const override {
+    // If either matcher1_ or matcher2_ doesn't match x, we only need
+    // to explain why one of them fails.
+    std::string all_match_result;
+
+    for (size_t i = 0; i < matchers_.size(); ++i) {
+      StringMatchResultListener slistener;
+      if (matchers_[i].MatchAndExplain(x, &slistener)) {
+        if (all_match_result.empty()) {
+          all_match_result = slistener.str();
+        } else {
+          std::string result = slistener.str();
+          if (!result.empty()) {
+            all_match_result += ", and ";
+            all_match_result += result;
+          }
+        }
+      } else {
+        *listener << slistener.str();
+        return false;
+      }
+    }
+
+    // Otherwise we need to explain why *both* of them match.
+    *listener << all_match_result;
+    return true;
+  }
+
+ private:
+  const std::vector<Matcher<T> > matchers_;
+};
+
+// VariadicMatcher is used for the variadic implementation of
+// AllOf(m_1, m_2, ...) and AnyOf(m_1, m_2, ...).
+// CombiningMatcher<T> is used to recursively combine the provided matchers
+// (of type Args...).
+template <template <typename T> class CombiningMatcher, typename... Args>
+class VariadicMatcher {
+ public:
+  VariadicMatcher(const Args&... matchers)  // NOLINT
+      : matchers_(matchers...) {
+    static_assert(sizeof...(Args) > 0, "Must have at least one matcher.");
+  }
+
+  VariadicMatcher(const VariadicMatcher&) = default;
+  VariadicMatcher& operator=(const VariadicMatcher&) = delete;
+
+  // This template type conversion operator allows an
+  // VariadicMatcher<Matcher1, Matcher2...> object to match any type that
+  // all of the provided matchers (Matcher1, Matcher2, ...) can match.
+  template <typename T>
+  operator Matcher<T>() const {
+    std::vector<Matcher<T> > values;
+    CreateVariadicMatcher<T>(&values, std::integral_constant<size_t, 0>());
+    return Matcher<T>(new CombiningMatcher<T>(std::move(values)));
+  }
+
+ private:
+  template <typename T, size_t I>
+  void CreateVariadicMatcher(std::vector<Matcher<T> >* values,
+                             std::integral_constant<size_t, I>) const {
+    values->push_back(SafeMatcherCast<T>(std::get<I>(matchers_)));
+    CreateVariadicMatcher<T>(values, std::integral_constant<size_t, I + 1>());
+  }
+
+  template <typename T>
+  void CreateVariadicMatcher(
+      std::vector<Matcher<T> >*,
+      std::integral_constant<size_t, sizeof...(Args)>) const {}
+
+  std::tuple<Args...> matchers_;
+};
+
+template <typename... Args>
+using AllOfMatcher = VariadicMatcher<AllOfMatcherImpl, Args...>;
+
+// Implements the AnyOf(m1, m2) matcher for a particular argument type
+// T.  We do not nest it inside the AnyOfMatcher class template, as
+// that will prevent different instantiations of AnyOfMatcher from
+// sharing the same EitherOfMatcherImpl<T> class.
+template <typename T>
+class AnyOfMatcherImpl : public MatcherInterface<const T&> {
+ public:
+  explicit AnyOfMatcherImpl(std::vector<Matcher<T> > matchers)
+      : matchers_(std::move(matchers)) {}
+
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "(";
+    for (size_t i = 0; i < matchers_.size(); ++i) {
+      if (i != 0) *os << ") or (";
+      matchers_[i].DescribeTo(os);
+    }
+    *os << ")";
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const override {
+    *os << "(";
+    for (size_t i = 0; i < matchers_.size(); ++i) {
+      if (i != 0) *os << ") and (";
+      matchers_[i].DescribeNegationTo(os);
+    }
+    *os << ")";
+  }
+
+  bool MatchAndExplain(const T& x,
+                       MatchResultListener* listener) const override {
+    std::string no_match_result;
+
+    // If either matcher1_ or matcher2_ matches x, we just need to
+    // explain why *one* of them matches.
+    for (size_t i = 0; i < matchers_.size(); ++i) {
+      StringMatchResultListener slistener;
+      if (matchers_[i].MatchAndExplain(x, &slistener)) {
+        *listener << slistener.str();
+        return true;
+      } else {
+        if (no_match_result.empty()) {
+          no_match_result = slistener.str();
+        } else {
+          std::string result = slistener.str();
+          if (!result.empty()) {
+            no_match_result += ", and ";
+            no_match_result += result;
+          }
+        }
+      }
+    }
+
+    // Otherwise we need to explain why *both* of them fail.
+    *listener << no_match_result;
+    return false;
+  }
+
+ private:
+  const std::vector<Matcher<T> > matchers_;
+};
+
+// AnyOfMatcher is used for the variadic implementation of AnyOf(m_1, m_2, ...).
+template <typename... Args>
+using AnyOfMatcher = VariadicMatcher<AnyOfMatcherImpl, Args...>;
+
+// Wrapper for implementation of Any/AllOfArray().
+template <template <class> class MatcherImpl, typename T>
+class SomeOfArrayMatcher {
+ public:
+  // Constructs the matcher from a sequence of element values or
+  // element matchers.
+  template <typename Iter>
+  SomeOfArrayMatcher(Iter first, Iter last) : matchers_(first, last) {}
+
+  template <typename U>
+  operator Matcher<U>() const {  // NOLINT
+    using RawU = typename std::decay<U>::type;
+    std::vector<Matcher<RawU>> matchers;
+    for (const auto& matcher : matchers_) {
+      matchers.push_back(MatcherCast<RawU>(matcher));
+    }
+    return Matcher<U>(new MatcherImpl<RawU>(std::move(matchers)));
+  }
+
+ private:
+  const ::std::vector<T> matchers_;
+};
+
+template <typename T>
+using AllOfArrayMatcher = SomeOfArrayMatcher<AllOfMatcherImpl, T>;
+
+template <typename T>
+using AnyOfArrayMatcher = SomeOfArrayMatcher<AnyOfMatcherImpl, T>;
+
+// Used for implementing Truly(pred), which turns a predicate into a
+// matcher.
+template <typename Predicate>
+class TrulyMatcher {
+ public:
+  explicit TrulyMatcher(Predicate pred) : predicate_(pred) {}
+
+  // This method template allows Truly(pred) to be used as a matcher
+  // for type T where T is the argument type of predicate 'pred'.  The
+  // argument is passed by reference as the predicate may be
+  // interested in the address of the argument.
+  template <typename T>
+  bool MatchAndExplain(T& x,  // NOLINT
+                       MatchResultListener* listener) const {
+    // Without the if-statement, MSVC sometimes warns about converting
+    // a value to bool (warning 4800).
+    //
+    // We cannot write 'return !!predicate_(x);' as that doesn't work
+    // when predicate_(x) returns a class convertible to bool but
+    // having no operator!().
+    if (predicate_(x))
+      return true;
+    *listener << "didn't satisfy the given predicate";
+    return false;
+  }
+
+  void DescribeTo(::std::ostream* os) const {
+    *os << "satisfies the given predicate";
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "doesn't satisfy the given predicate";
+  }
+
+ private:
+  Predicate predicate_;
+};
+
+// Used for implementing Matches(matcher), which turns a matcher into
+// a predicate.
+template <typename M>
+class MatcherAsPredicate {
+ public:
+  explicit MatcherAsPredicate(M matcher) : matcher_(matcher) {}
+
+  // This template operator() allows Matches(m) to be used as a
+  // predicate on type T where m is a matcher on type T.
+  //
+  // The argument x is passed by reference instead of by value, as
+  // some matcher may be interested in its address (e.g. as in
+  // Matches(Ref(n))(x)).
+  template <typename T>
+  bool operator()(const T& x) const {
+    // We let matcher_ commit to a particular type here instead of
+    // when the MatcherAsPredicate object was constructed.  This
+    // allows us to write Matches(m) where m is a polymorphic matcher
+    // (e.g. Eq(5)).
+    //
+    // If we write Matcher<T>(matcher_).Matches(x) here, it won't
+    // compile when matcher_ has type Matcher<const T&>; if we write
+    // Matcher<const T&>(matcher_).Matches(x) here, it won't compile
+    // when matcher_ has type Matcher<T>; if we just write
+    // matcher_.Matches(x), it won't compile when matcher_ is
+    // polymorphic, e.g. Eq(5).
+    //
+    // MatcherCast<const T&>() is necessary for making the code work
+    // in all of the above situations.
+    return MatcherCast<const T&>(matcher_).Matches(x);
+  }
+
+ private:
+  M matcher_;
+};
+
+// For implementing ASSERT_THAT() and EXPECT_THAT().  The template
+// argument M must be a type that can be converted to a matcher.
+template <typename M>
+class PredicateFormatterFromMatcher {
+ public:
+  explicit PredicateFormatterFromMatcher(M m) : matcher_(std::move(m)) {}
+
+  // This template () operator allows a PredicateFormatterFromMatcher
+  // object to act as a predicate-formatter suitable for using with
+  // Google Test's EXPECT_PRED_FORMAT1() macro.
+  template <typename T>
+  AssertionResult operator()(const char* value_text, const T& x) const {
+    // We convert matcher_ to a Matcher<const T&> *now* instead of
+    // when the PredicateFormatterFromMatcher object was constructed,
+    // as matcher_ may be polymorphic (e.g. NotNull()) and we won't
+    // know which type to instantiate it to until we actually see the
+    // type of x here.
+    //
+    // We write SafeMatcherCast<const T&>(matcher_) instead of
+    // Matcher<const T&>(matcher_), as the latter won't compile when
+    // matcher_ has type Matcher<T> (e.g. An<int>()).
+    // We don't write MatcherCast<const T&> either, as that allows
+    // potentially unsafe downcasting of the matcher argument.
+    const Matcher<const T&> matcher = SafeMatcherCast<const T&>(matcher_);
+
+    // The expected path here is that the matcher should match (i.e. that most
+    // tests pass) so optimize for this case.
+    if (matcher.Matches(x)) {
+      return AssertionSuccess();
+    }
+
+    ::std::stringstream ss;
+    ss << "Value of: " << value_text << "\n"
+       << "Expected: ";
+    matcher.DescribeTo(&ss);
+
+    // Rerun the matcher to "PrintAndExplain" the failure.
+    StringMatchResultListener listener;
+    if (MatchPrintAndExplain(x, matcher, &listener)) {
+      ss << "\n  The matcher failed on the initial attempt; but passed when "
+            "rerun to generate the explanation.";
+    }
+    ss << "\n  Actual: " << listener.str();
+    return AssertionFailure() << ss.str();
+  }
+
+ private:
+  const M matcher_;
+};
+
+// A helper function for converting a matcher to a predicate-formatter
+// without the user needing to explicitly write the type.  This is
+// used for implementing ASSERT_THAT() and EXPECT_THAT().
+// Implementation detail: 'matcher' is received by-value to force decaying.
+template <typename M>
+inline PredicateFormatterFromMatcher<M>
+MakePredicateFormatterFromMatcher(M matcher) {
+  return PredicateFormatterFromMatcher<M>(std::move(matcher));
+}
+
+// Implements the polymorphic IsNan() matcher, which matches any floating type
+// value that is Nan.
+class IsNanMatcher {
+ public:
+  template <typename FloatType>
+  bool MatchAndExplain(const FloatType& f,
+                       MatchResultListener* /* listener */) const {
+    return (::std::isnan)(f);
+  }
+
+  void DescribeTo(::std::ostream* os) const { *os << "is NaN"; }
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "isn't NaN";
+  }
+};
+
+// Implements the polymorphic floating point equality matcher, which matches
+// two float values using ULP-based approximation or, optionally, a
+// user-specified epsilon.  The template is meant to be instantiated with
+// FloatType being either float or double.
+template <typename FloatType>
+class FloatingEqMatcher {
+ public:
+  // Constructor for FloatingEqMatcher.
+  // The matcher's input will be compared with expected.  The matcher treats two
+  // NANs as equal if nan_eq_nan is true.  Otherwise, under IEEE standards,
+  // equality comparisons between NANs will always return false.  We specify a
+  // negative max_abs_error_ term to indicate that ULP-based approximation will
+  // be used for comparison.
+  FloatingEqMatcher(FloatType expected, bool nan_eq_nan) :
+    expected_(expected), nan_eq_nan_(nan_eq_nan), max_abs_error_(-1) {
+  }
+
+  // Constructor that supports a user-specified max_abs_error that will be used
+  // for comparison instead of ULP-based approximation.  The max absolute
+  // should be non-negative.
+  FloatingEqMatcher(FloatType expected, bool nan_eq_nan,
+                    FloatType max_abs_error)
+      : expected_(expected),
+        nan_eq_nan_(nan_eq_nan),
+        max_abs_error_(max_abs_error) {
+    GTEST_CHECK_(max_abs_error >= 0)
+        << ", where max_abs_error is" << max_abs_error;
+  }
+
+  // Implements floating point equality matcher as a Matcher<T>.
+  template <typename T>
+  class Impl : public MatcherInterface<T> {
+   public:
+    Impl(FloatType expected, bool nan_eq_nan, FloatType max_abs_error)
+        : expected_(expected),
+          nan_eq_nan_(nan_eq_nan),
+          max_abs_error_(max_abs_error) {}
+
+    bool MatchAndExplain(T value,
+                         MatchResultListener* listener) const override {
+      const FloatingPoint<FloatType> actual(value), expected(expected_);
+
+      // Compares NaNs first, if nan_eq_nan_ is true.
+      if (actual.is_nan() || expected.is_nan()) {
+        if (actual.is_nan() && expected.is_nan()) {
+          return nan_eq_nan_;
+        }
+        // One is nan; the other is not nan.
+        return false;
+      }
+      if (HasMaxAbsError()) {
+        // We perform an equality check so that inf will match inf, regardless
+        // of error bounds.  If the result of value - expected_ would result in
+        // overflow or if either value is inf, the default result is infinity,
+        // which should only match if max_abs_error_ is also infinity.
+        if (value == expected_) {
+          return true;
+        }
+
+        const FloatType diff = value - expected_;
+        if (::std::fabs(diff) <= max_abs_error_) {
+          return true;
+        }
+
+        if (listener->IsInterested()) {
+          *listener << "which is " << diff << " from " << expected_;
+        }
+        return false;
+      } else {
+        return actual.AlmostEquals(expected);
+      }
+    }
+
+    void DescribeTo(::std::ostream* os) const override {
+      // os->precision() returns the previously set precision, which we
+      // store to restore the ostream to its original configuration
+      // after outputting.
+      const ::std::streamsize old_precision = os->precision(
+          ::std::numeric_limits<FloatType>::digits10 + 2);
+      if (FloatingPoint<FloatType>(expected_).is_nan()) {
+        if (nan_eq_nan_) {
+          *os << "is NaN";
+        } else {
+          *os << "never matches";
+        }
+      } else {
+        *os << "is approximately " << expected_;
+        if (HasMaxAbsError()) {
+          *os << " (absolute error <= " << max_abs_error_ << ")";
+        }
+      }
+      os->precision(old_precision);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      // As before, get original precision.
+      const ::std::streamsize old_precision = os->precision(
+          ::std::numeric_limits<FloatType>::digits10 + 2);
+      if (FloatingPoint<FloatType>(expected_).is_nan()) {
+        if (nan_eq_nan_) {
+          *os << "isn't NaN";
+        } else {
+          *os << "is anything";
+        }
+      } else {
+        *os << "isn't approximately " << expected_;
+        if (HasMaxAbsError()) {
+          *os << " (absolute error > " << max_abs_error_ << ")";
+        }
+      }
+      // Restore original precision.
+      os->precision(old_precision);
+    }
+
+   private:
+    bool HasMaxAbsError() const {
+      return max_abs_error_ >= 0;
+    }
+
+    const FloatType expected_;
+    const bool nan_eq_nan_;
+    // max_abs_error will be used for value comparison when >= 0.
+    const FloatType max_abs_error_;
+  };
+
+  // The following 3 type conversion operators allow FloatEq(expected) and
+  // NanSensitiveFloatEq(expected) to be used as a Matcher<float>, a
+  // Matcher<const float&>, or a Matcher<float&>, but nothing else.
+  operator Matcher<FloatType>() const {
+    return MakeMatcher(
+        new Impl<FloatType>(expected_, nan_eq_nan_, max_abs_error_));
+  }
+
+  operator Matcher<const FloatType&>() const {
+    return MakeMatcher(
+        new Impl<const FloatType&>(expected_, nan_eq_nan_, max_abs_error_));
+  }
+
+  operator Matcher<FloatType&>() const {
+    return MakeMatcher(
+        new Impl<FloatType&>(expected_, nan_eq_nan_, max_abs_error_));
+  }
+
+ private:
+  const FloatType expected_;
+  const bool nan_eq_nan_;
+  // max_abs_error will be used for value comparison when >= 0.
+  const FloatType max_abs_error_;
+};
+
+// A 2-tuple ("binary") wrapper around FloatingEqMatcher:
+// FloatingEq2Matcher() matches (x, y) by matching FloatingEqMatcher(x, false)
+// against y, and FloatingEq2Matcher(e) matches FloatingEqMatcher(x, false, e)
+// against y. The former implements "Eq", the latter "Near". At present, there
+// is no version that compares NaNs as equal.
+template <typename FloatType>
+class FloatingEq2Matcher {
+ public:
+  FloatingEq2Matcher() { Init(-1, false); }
+
+  explicit FloatingEq2Matcher(bool nan_eq_nan) { Init(-1, nan_eq_nan); }
+
+  explicit FloatingEq2Matcher(FloatType max_abs_error) {
+    Init(max_abs_error, false);
+  }
+
+  FloatingEq2Matcher(FloatType max_abs_error, bool nan_eq_nan) {
+    Init(max_abs_error, nan_eq_nan);
+  }
+
+  template <typename T1, typename T2>
+  operator Matcher<::std::tuple<T1, T2>>() const {
+    return MakeMatcher(
+        new Impl<::std::tuple<T1, T2>>(max_abs_error_, nan_eq_nan_));
+  }
+  template <typename T1, typename T2>
+  operator Matcher<const ::std::tuple<T1, T2>&>() const {
+    return MakeMatcher(
+        new Impl<const ::std::tuple<T1, T2>&>(max_abs_error_, nan_eq_nan_));
+  }
+
+ private:
+  static ::std::ostream& GetDesc(::std::ostream& os) {  // NOLINT
+    return os << "an almost-equal pair";
+  }
+
+  template <typename Tuple>
+  class Impl : public MatcherInterface<Tuple> {
+   public:
+    Impl(FloatType max_abs_error, bool nan_eq_nan) :
+        max_abs_error_(max_abs_error),
+        nan_eq_nan_(nan_eq_nan) {}
+
+    bool MatchAndExplain(Tuple args,
+                         MatchResultListener* listener) const override {
+      if (max_abs_error_ == -1) {
+        FloatingEqMatcher<FloatType> fm(::std::get<0>(args), nan_eq_nan_);
+        return static_cast<Matcher<FloatType>>(fm).MatchAndExplain(
+            ::std::get<1>(args), listener);
+      } else {
+        FloatingEqMatcher<FloatType> fm(::std::get<0>(args), nan_eq_nan_,
+                                        max_abs_error_);
+        return static_cast<Matcher<FloatType>>(fm).MatchAndExplain(
+            ::std::get<1>(args), listener);
+      }
+    }
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "are " << GetDesc;
+    }
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "aren't " << GetDesc;
+    }
+
+   private:
+    FloatType max_abs_error_;
+    const bool nan_eq_nan_;
+  };
+
+  void Init(FloatType max_abs_error_val, bool nan_eq_nan_val) {
+    max_abs_error_ = max_abs_error_val;
+    nan_eq_nan_ = nan_eq_nan_val;
+  }
+  FloatType max_abs_error_;
+  bool nan_eq_nan_;
+};
+
+// Implements the Pointee(m) matcher for matching a pointer whose
+// pointee matches matcher m.  The pointer can be either raw or smart.
+template <typename InnerMatcher>
+class PointeeMatcher {
+ public:
+  explicit PointeeMatcher(const InnerMatcher& matcher) : matcher_(matcher) {}
+
+  // This type conversion operator template allows Pointee(m) to be
+  // used as a matcher for any pointer type whose pointee type is
+  // compatible with the inner matcher, where type Pointer can be
+  // either a raw pointer or a smart pointer.
+  //
+  // The reason we do this instead of relying on
+  // MakePolymorphicMatcher() is that the latter is not flexible
+  // enough for implementing the DescribeTo() method of Pointee().
+  template <typename Pointer>
+  operator Matcher<Pointer>() const {
+    return Matcher<Pointer>(new Impl<const Pointer&>(matcher_));
+  }
+
+ private:
+  // The monomorphic implementation that works for a particular pointer type.
+  template <typename Pointer>
+  class Impl : public MatcherInterface<Pointer> {
+   public:
+    using Pointee =
+        typename std::pointer_traits<GTEST_REMOVE_REFERENCE_AND_CONST_(
+            Pointer)>::element_type;
+
+    explicit Impl(const InnerMatcher& matcher)
+        : matcher_(MatcherCast<const Pointee&>(matcher)) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "points to a value that ";
+      matcher_.DescribeTo(os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "does not point to a value that ";
+      matcher_.DescribeTo(os);
+    }
+
+    bool MatchAndExplain(Pointer pointer,
+                         MatchResultListener* listener) const override {
+      if (GetRawPointer(pointer) == nullptr) return false;
+
+      *listener << "which points to ";
+      return MatchPrintAndExplain(*pointer, matcher_, listener);
+    }
+
+   private:
+    const Matcher<const Pointee&> matcher_;
+  };
+
+  const InnerMatcher matcher_;
+};
+
+// Implements the Pointer(m) matcher
+// Implements the Pointer(m) matcher for matching a pointer that matches matcher
+// m.  The pointer can be either raw or smart, and will match `m` against the
+// raw pointer.
+template <typename InnerMatcher>
+class PointerMatcher {
+ public:
+  explicit PointerMatcher(const InnerMatcher& matcher) : matcher_(matcher) {}
+
+  // This type conversion operator template allows Pointer(m) to be
+  // used as a matcher for any pointer type whose pointer type is
+  // compatible with the inner matcher, where type PointerType can be
+  // either a raw pointer or a smart pointer.
+  //
+  // The reason we do this instead of relying on
+  // MakePolymorphicMatcher() is that the latter is not flexible
+  // enough for implementing the DescribeTo() method of Pointer().
+  template <typename PointerType>
+  operator Matcher<PointerType>() const {  // NOLINT
+    return Matcher<PointerType>(new Impl<const PointerType&>(matcher_));
+  }
+
+ private:
+  // The monomorphic implementation that works for a particular pointer type.
+  template <typename PointerType>
+  class Impl : public MatcherInterface<PointerType> {
+   public:
+    using Pointer =
+        const typename std::pointer_traits<GTEST_REMOVE_REFERENCE_AND_CONST_(
+            PointerType)>::element_type*;
+
+    explicit Impl(const InnerMatcher& matcher)
+        : matcher_(MatcherCast<Pointer>(matcher)) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "is a pointer that ";
+      matcher_.DescribeTo(os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "is not a pointer that ";
+      matcher_.DescribeTo(os);
+    }
+
+    bool MatchAndExplain(PointerType pointer,
+                         MatchResultListener* listener) const override {
+      *listener << "which is a pointer that ";
+      Pointer p = GetRawPointer(pointer);
+      return MatchPrintAndExplain(p, matcher_, listener);
+    }
+
+   private:
+    Matcher<Pointer> matcher_;
+  };
+
+  const InnerMatcher matcher_;
+};
+
+#if GTEST_HAS_RTTI
+// Implements the WhenDynamicCastTo<T>(m) matcher that matches a pointer or
+// reference that matches inner_matcher when dynamic_cast<T> is applied.
+// The result of dynamic_cast<To> is forwarded to the inner matcher.
+// If To is a pointer and the cast fails, the inner matcher will receive NULL.
+// If To is a reference and the cast fails, this matcher returns false
+// immediately.
+template <typename To>
+class WhenDynamicCastToMatcherBase {
+ public:
+  explicit WhenDynamicCastToMatcherBase(const Matcher<To>& matcher)
+      : matcher_(matcher) {}
+
+  void DescribeTo(::std::ostream* os) const {
+    GetCastTypeDescription(os);
+    matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    GetCastTypeDescription(os);
+    matcher_.DescribeNegationTo(os);
+  }
+
+ protected:
+  const Matcher<To> matcher_;
+
+  static std::string GetToName() {
+    return GetTypeName<To>();
+  }
+
+ private:
+  static void GetCastTypeDescription(::std::ostream* os) {
+    *os << "when dynamic_cast to " << GetToName() << ", ";
+  }
+};
+
+// Primary template.
+// To is a pointer. Cast and forward the result.
+template <typename To>
+class WhenDynamicCastToMatcher : public WhenDynamicCastToMatcherBase<To> {
+ public:
+  explicit WhenDynamicCastToMatcher(const Matcher<To>& matcher)
+      : WhenDynamicCastToMatcherBase<To>(matcher) {}
+
+  template <typename From>
+  bool MatchAndExplain(From from, MatchResultListener* listener) const {
+    To to = dynamic_cast<To>(from);
+    return MatchPrintAndExplain(to, this->matcher_, listener);
+  }
+};
+
+// Specialize for references.
+// In this case we return false if the dynamic_cast fails.
+template <typename To>
+class WhenDynamicCastToMatcher<To&> : public WhenDynamicCastToMatcherBase<To&> {
+ public:
+  explicit WhenDynamicCastToMatcher(const Matcher<To&>& matcher)
+      : WhenDynamicCastToMatcherBase<To&>(matcher) {}
+
+  template <typename From>
+  bool MatchAndExplain(From& from, MatchResultListener* listener) const {
+    // We don't want an std::bad_cast here, so do the cast with pointers.
+    To* to = dynamic_cast<To*>(&from);
+    if (to == nullptr) {
+      *listener << "which cannot be dynamic_cast to " << this->GetToName();
+      return false;
+    }
+    return MatchPrintAndExplain(*to, this->matcher_, listener);
+  }
+};
+#endif  // GTEST_HAS_RTTI
+
+// Implements the Field() matcher for matching a field (i.e. member
+// variable) of an object.
+template <typename Class, typename FieldType>
+class FieldMatcher {
+ public:
+  FieldMatcher(FieldType Class::*field,
+               const Matcher<const FieldType&>& matcher)
+      : field_(field), matcher_(matcher), whose_field_("whose given field ") {}
+
+  FieldMatcher(const std::string& field_name, FieldType Class::*field,
+               const Matcher<const FieldType&>& matcher)
+      : field_(field),
+        matcher_(matcher),
+        whose_field_("whose field `" + field_name + "` ") {}
+
+  void DescribeTo(::std::ostream* os) const {
+    *os << "is an object " << whose_field_;
+    matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "is an object " << whose_field_;
+    matcher_.DescribeNegationTo(os);
+  }
+
+  template <typename T>
+  bool MatchAndExplain(const T& value, MatchResultListener* listener) const {
+    // FIXME: The dispatch on std::is_pointer was introduced as a workaround for
+    // a compiler bug, and can now be removed.
+    return MatchAndExplainImpl(
+        typename std::is_pointer<typename std::remove_const<T>::type>::type(),
+        value, listener);
+  }
+
+ private:
+  bool MatchAndExplainImpl(std::false_type /* is_not_pointer */,
+                           const Class& obj,
+                           MatchResultListener* listener) const {
+    *listener << whose_field_ << "is ";
+    return MatchPrintAndExplain(obj.*field_, matcher_, listener);
+  }
+
+  bool MatchAndExplainImpl(std::true_type /* is_pointer */, const Class* p,
+                           MatchResultListener* listener) const {
+    if (p == nullptr) return false;
+
+    *listener << "which points to an object ";
+    // Since *p has a field, it must be a class/struct/union type and
+    // thus cannot be a pointer.  Therefore we pass false_type() as
+    // the first argument.
+    return MatchAndExplainImpl(std::false_type(), *p, listener);
+  }
+
+  const FieldType Class::*field_;
+  const Matcher<const FieldType&> matcher_;
+
+  // Contains either "whose given field " if the name of the field is unknown
+  // or "whose field `name_of_field` " if the name is known.
+  const std::string whose_field_;
+};
+
+// Implements the Property() matcher for matching a property
+// (i.e. return value of a getter method) of an object.
+//
+// Property is a const-qualified member function of Class returning
+// PropertyType.
+template <typename Class, typename PropertyType, typename Property>
+class PropertyMatcher {
+ public:
+  typedef const PropertyType& RefToConstProperty;
+
+  PropertyMatcher(Property property, const Matcher<RefToConstProperty>& matcher)
+      : property_(property),
+        matcher_(matcher),
+        whose_property_("whose given property ") {}
+
+  PropertyMatcher(const std::string& property_name, Property property,
+                  const Matcher<RefToConstProperty>& matcher)
+      : property_(property),
+        matcher_(matcher),
+        whose_property_("whose property `" + property_name + "` ") {}
+
+  void DescribeTo(::std::ostream* os) const {
+    *os << "is an object " << whose_property_;
+    matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "is an object " << whose_property_;
+    matcher_.DescribeNegationTo(os);
+  }
+
+  template <typename T>
+  bool MatchAndExplain(const T&value, MatchResultListener* listener) const {
+    return MatchAndExplainImpl(
+        typename std::is_pointer<typename std::remove_const<T>::type>::type(),
+        value, listener);
+  }
+
+ private:
+  bool MatchAndExplainImpl(std::false_type /* is_not_pointer */,
+                           const Class& obj,
+                           MatchResultListener* listener) const {
+    *listener << whose_property_ << "is ";
+    // Cannot pass the return value (for example, int) to MatchPrintAndExplain,
+    // which takes a non-const reference as argument.
+    RefToConstProperty result = (obj.*property_)();
+    return MatchPrintAndExplain(result, matcher_, listener);
+  }
+
+  bool MatchAndExplainImpl(std::true_type /* is_pointer */, const Class* p,
+                           MatchResultListener* listener) const {
+    if (p == nullptr) return false;
+
+    *listener << "which points to an object ";
+    // Since *p has a property method, it must be a class/struct/union
+    // type and thus cannot be a pointer.  Therefore we pass
+    // false_type() as the first argument.
+    return MatchAndExplainImpl(std::false_type(), *p, listener);
+  }
+
+  Property property_;
+  const Matcher<RefToConstProperty> matcher_;
+
+  // Contains either "whose given property " if the name of the property is
+  // unknown or "whose property `name_of_property` " if the name is known.
+  const std::string whose_property_;
+};
+
+// Type traits specifying various features of different functors for ResultOf.
+// The default template specifies features for functor objects.
+template <typename Functor>
+struct CallableTraits {
+  typedef Functor StorageType;
+
+  static void CheckIsValid(Functor /* functor */) {}
+
+  template <typename T>
+  static auto Invoke(Functor f, const T& arg) -> decltype(f(arg)) {
+    return f(arg);
+  }
+};
+
+// Specialization for function pointers.
+template <typename ArgType, typename ResType>
+struct CallableTraits<ResType(*)(ArgType)> {
+  typedef ResType ResultType;
+  typedef ResType(*StorageType)(ArgType);
+
+  static void CheckIsValid(ResType(*f)(ArgType)) {
+    GTEST_CHECK_(f != nullptr)
+        << "NULL function pointer is passed into ResultOf().";
+  }
+  template <typename T>
+  static ResType Invoke(ResType(*f)(ArgType), T arg) {
+    return (*f)(arg);
+  }
+};
+
+// Implements the ResultOf() matcher for matching a return value of a
+// unary function of an object.
+template <typename Callable, typename InnerMatcher>
+class ResultOfMatcher {
+ public:
+  ResultOfMatcher(Callable callable, InnerMatcher matcher)
+      : callable_(std::move(callable)), matcher_(std::move(matcher)) {
+    CallableTraits<Callable>::CheckIsValid(callable_);
+  }
+
+  template <typename T>
+  operator Matcher<T>() const {
+    return Matcher<T>(new Impl<const T&>(callable_, matcher_));
+  }
+
+ private:
+  typedef typename CallableTraits<Callable>::StorageType CallableStorageType;
+
+  template <typename T>
+  class Impl : public MatcherInterface<T> {
+    using ResultType = decltype(CallableTraits<Callable>::template Invoke<T>(
+        std::declval<CallableStorageType>(), std::declval<T>()));
+
+   public:
+    template <typename M>
+    Impl(const CallableStorageType& callable, const M& matcher)
+        : callable_(callable), matcher_(MatcherCast<ResultType>(matcher)) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "is mapped by the given callable to a value that ";
+      matcher_.DescribeTo(os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "is mapped by the given callable to a value that ";
+      matcher_.DescribeNegationTo(os);
+    }
+
+    bool MatchAndExplain(T obj, MatchResultListener* listener) const override {
+      *listener << "which is mapped by the given callable to ";
+      // Cannot pass the return value directly to MatchPrintAndExplain, which
+      // takes a non-const reference as argument.
+      // Also, specifying template argument explicitly is needed because T could
+      // be a non-const reference (e.g. Matcher<Uncopyable&>).
+      ResultType result =
+          CallableTraits<Callable>::template Invoke<T>(callable_, obj);
+      return MatchPrintAndExplain(result, matcher_, listener);
+    }
+
+   private:
+    // Functors often define operator() as non-const method even though
+    // they are actually stateless. But we need to use them even when
+    // 'this' is a const pointer. It's the user's responsibility not to
+    // use stateful callables with ResultOf(), which doesn't guarantee
+    // how many times the callable will be invoked.
+    mutable CallableStorageType callable_;
+    const Matcher<ResultType> matcher_;
+  };  // class Impl
+
+  const CallableStorageType callable_;
+  const InnerMatcher matcher_;
+};
+
+// Implements a matcher that checks the size of an STL-style container.
+template <typename SizeMatcher>
+class SizeIsMatcher {
+ public:
+  explicit SizeIsMatcher(const SizeMatcher& size_matcher)
+       : size_matcher_(size_matcher) {
+  }
+
+  template <typename Container>
+  operator Matcher<Container>() const {
+    return Matcher<Container>(new Impl<const Container&>(size_matcher_));
+  }
+
+  template <typename Container>
+  class Impl : public MatcherInterface<Container> {
+   public:
+    using SizeType = decltype(std::declval<Container>().size());
+    explicit Impl(const SizeMatcher& size_matcher)
+        : size_matcher_(MatcherCast<SizeType>(size_matcher)) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "size ";
+      size_matcher_.DescribeTo(os);
+    }
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "size ";
+      size_matcher_.DescribeNegationTo(os);
+    }
+
+    bool MatchAndExplain(Container container,
+                         MatchResultListener* listener) const override {
+      SizeType size = container.size();
+      StringMatchResultListener size_listener;
+      const bool result = size_matcher_.MatchAndExplain(size, &size_listener);
+      *listener
+          << "whose size " << size << (result ? " matches" : " doesn't match");
+      PrintIfNotEmpty(size_listener.str(), listener->stream());
+      return result;
+    }
+
+   private:
+    const Matcher<SizeType> size_matcher_;
+  };
+
+ private:
+  const SizeMatcher size_matcher_;
+};
+
+// Implements a matcher that checks the begin()..end() distance of an STL-style
+// container.
+template <typename DistanceMatcher>
+class BeginEndDistanceIsMatcher {
+ public:
+  explicit BeginEndDistanceIsMatcher(const DistanceMatcher& distance_matcher)
+      : distance_matcher_(distance_matcher) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {
+    return Matcher<Container>(new Impl<const Container&>(distance_matcher_));
+  }
+
+  template <typename Container>
+  class Impl : public MatcherInterface<Container> {
+   public:
+    typedef internal::StlContainerView<
+        GTEST_REMOVE_REFERENCE_AND_CONST_(Container)> ContainerView;
+    typedef typename std::iterator_traits<
+        typename ContainerView::type::const_iterator>::difference_type
+        DistanceType;
+    explicit Impl(const DistanceMatcher& distance_matcher)
+        : distance_matcher_(MatcherCast<DistanceType>(distance_matcher)) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "distance between begin() and end() ";
+      distance_matcher_.DescribeTo(os);
+    }
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "distance between begin() and end() ";
+      distance_matcher_.DescribeNegationTo(os);
+    }
+
+    bool MatchAndExplain(Container container,
+                         MatchResultListener* listener) const override {
+      using std::begin;
+      using std::end;
+      DistanceType distance = std::distance(begin(container), end(container));
+      StringMatchResultListener distance_listener;
+      const bool result =
+          distance_matcher_.MatchAndExplain(distance, &distance_listener);
+      *listener << "whose distance between begin() and end() " << distance
+                << (result ? " matches" : " doesn't match");
+      PrintIfNotEmpty(distance_listener.str(), listener->stream());
+      return result;
+    }
+
+   private:
+    const Matcher<DistanceType> distance_matcher_;
+  };
+
+ private:
+  const DistanceMatcher distance_matcher_;
+};
+
+// Implements an equality matcher for any STL-style container whose elements
+// support ==. This matcher is like Eq(), but its failure explanations provide
+// more detailed information that is useful when the container is used as a set.
+// The failure message reports elements that are in one of the operands but not
+// the other. The failure messages do not report duplicate or out-of-order
+// elements in the containers (which don't properly matter to sets, but can
+// occur if the containers are vectors or lists, for example).
+//
+// Uses the container's const_iterator, value_type, operator ==,
+// begin(), and end().
+template <typename Container>
+class ContainerEqMatcher {
+ public:
+  typedef internal::StlContainerView<Container> View;
+  typedef typename View::type StlContainer;
+  typedef typename View::const_reference StlContainerReference;
+
+  static_assert(!std::is_const<Container>::value,
+                "Container type must not be const");
+  static_assert(!std::is_reference<Container>::value,
+                "Container type must not be a reference");
+
+  // We make a copy of expected in case the elements in it are modified
+  // after this matcher is created.
+  explicit ContainerEqMatcher(const Container& expected)
+      : expected_(View::Copy(expected)) {}
+
+  void DescribeTo(::std::ostream* os) const {
+    *os << "equals ";
+    UniversalPrint(expected_, os);
+  }
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "does not equal ";
+    UniversalPrint(expected_, os);
+  }
+
+  template <typename LhsContainer>
+  bool MatchAndExplain(const LhsContainer& lhs,
+                       MatchResultListener* listener) const {
+    typedef internal::StlContainerView<
+        typename std::remove_const<LhsContainer>::type>
+        LhsView;
+    typedef typename LhsView::type LhsStlContainer;
+    StlContainerReference lhs_stl_container = LhsView::ConstReference(lhs);
+    if (lhs_stl_container == expected_)
+      return true;
+
+    ::std::ostream* const os = listener->stream();
+    if (os != nullptr) {
+      // Something is different. Check for extra values first.
+      bool printed_header = false;
+      for (typename LhsStlContainer::const_iterator it =
+               lhs_stl_container.begin();
+           it != lhs_stl_container.end(); ++it) {
+        if (internal::ArrayAwareFind(expected_.begin(), expected_.end(), *it) ==
+            expected_.end()) {
+          if (printed_header) {
+            *os << ", ";
+          } else {
+            *os << "which has these unexpected elements: ";
+            printed_header = true;
+          }
+          UniversalPrint(*it, os);
+        }
+      }
+
+      // Now check for missing values.
+      bool printed_header2 = false;
+      for (typename StlContainer::const_iterator it = expected_.begin();
+           it != expected_.end(); ++it) {
+        if (internal::ArrayAwareFind(
+                lhs_stl_container.begin(), lhs_stl_container.end(), *it) ==
+            lhs_stl_container.end()) {
+          if (printed_header2) {
+            *os << ", ";
+          } else {
+            *os << (printed_header ? ",\nand" : "which")
+                << " doesn't have these expected elements: ";
+            printed_header2 = true;
+          }
+          UniversalPrint(*it, os);
+        }
+      }
+    }
+
+    return false;
+  }
+
+ private:
+  const StlContainer expected_;
+};
+
+// A comparator functor that uses the < operator to compare two values.
+struct LessComparator {
+  template <typename T, typename U>
+  bool operator()(const T& lhs, const U& rhs) const { return lhs < rhs; }
+};
+
+// Implements WhenSortedBy(comparator, container_matcher).
+template <typename Comparator, typename ContainerMatcher>
+class WhenSortedByMatcher {
+ public:
+  WhenSortedByMatcher(const Comparator& comparator,
+                      const ContainerMatcher& matcher)
+      : comparator_(comparator), matcher_(matcher) {}
+
+  template <typename LhsContainer>
+  operator Matcher<LhsContainer>() const {
+    return MakeMatcher(new Impl<LhsContainer>(comparator_, matcher_));
+  }
+
+  template <typename LhsContainer>
+  class Impl : public MatcherInterface<LhsContainer> {
+   public:
+    typedef internal::StlContainerView<
+         GTEST_REMOVE_REFERENCE_AND_CONST_(LhsContainer)> LhsView;
+    typedef typename LhsView::type LhsStlContainer;
+    typedef typename LhsView::const_reference LhsStlContainerReference;
+    // Transforms std::pair<const Key, Value> into std::pair<Key, Value>
+    // so that we can match associative containers.
+    typedef typename RemoveConstFromKey<
+        typename LhsStlContainer::value_type>::type LhsValue;
+
+    Impl(const Comparator& comparator, const ContainerMatcher& matcher)
+        : comparator_(comparator), matcher_(matcher) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "(when sorted) ";
+      matcher_.DescribeTo(os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "(when sorted) ";
+      matcher_.DescribeNegationTo(os);
+    }
+
+    bool MatchAndExplain(LhsContainer lhs,
+                         MatchResultListener* listener) const override {
+      LhsStlContainerReference lhs_stl_container = LhsView::ConstReference(lhs);
+      ::std::vector<LhsValue> sorted_container(lhs_stl_container.begin(),
+                                               lhs_stl_container.end());
+      ::std::sort(
+           sorted_container.begin(), sorted_container.end(), comparator_);
+
+      if (!listener->IsInterested()) {
+        // If the listener is not interested, we do not need to
+        // construct the inner explanation.
+        return matcher_.Matches(sorted_container);
+      }
+
+      *listener << "which is ";
+      UniversalPrint(sorted_container, listener->stream());
+      *listener << " when sorted";
+
+      StringMatchResultListener inner_listener;
+      const bool match = matcher_.MatchAndExplain(sorted_container,
+                                                  &inner_listener);
+      PrintIfNotEmpty(inner_listener.str(), listener->stream());
+      return match;
+    }
+
+   private:
+    const Comparator comparator_;
+    const Matcher<const ::std::vector<LhsValue>&> matcher_;
+
+    GTEST_DISALLOW_COPY_AND_ASSIGN_(Impl);
+  };
+
+ private:
+  const Comparator comparator_;
+  const ContainerMatcher matcher_;
+};
+
+// Implements Pointwise(tuple_matcher, rhs_container).  tuple_matcher
+// must be able to be safely cast to Matcher<std::tuple<const T1&, const
+// T2&> >, where T1 and T2 are the types of elements in the LHS
+// container and the RHS container respectively.
+template <typename TupleMatcher, typename RhsContainer>
+class PointwiseMatcher {
+  GTEST_COMPILE_ASSERT_(
+      !IsHashTable<GTEST_REMOVE_REFERENCE_AND_CONST_(RhsContainer)>::value,
+      use_UnorderedPointwise_with_hash_tables);
+
+ public:
+  typedef internal::StlContainerView<RhsContainer> RhsView;
+  typedef typename RhsView::type RhsStlContainer;
+  typedef typename RhsStlContainer::value_type RhsValue;
+
+  static_assert(!std::is_const<RhsContainer>::value,
+                "RhsContainer type must not be const");
+  static_assert(!std::is_reference<RhsContainer>::value,
+                "RhsContainer type must not be a reference");
+
+  // Like ContainerEq, we make a copy of rhs in case the elements in
+  // it are modified after this matcher is created.
+  PointwiseMatcher(const TupleMatcher& tuple_matcher, const RhsContainer& rhs)
+      : tuple_matcher_(tuple_matcher), rhs_(RhsView::Copy(rhs)) {}
+
+  template <typename LhsContainer>
+  operator Matcher<LhsContainer>() const {
+    GTEST_COMPILE_ASSERT_(
+        !IsHashTable<GTEST_REMOVE_REFERENCE_AND_CONST_(LhsContainer)>::value,
+        use_UnorderedPointwise_with_hash_tables);
+
+    return Matcher<LhsContainer>(
+        new Impl<const LhsContainer&>(tuple_matcher_, rhs_));
+  }
+
+  template <typename LhsContainer>
+  class Impl : public MatcherInterface<LhsContainer> {
+   public:
+    typedef internal::StlContainerView<
+         GTEST_REMOVE_REFERENCE_AND_CONST_(LhsContainer)> LhsView;
+    typedef typename LhsView::type LhsStlContainer;
+    typedef typename LhsView::const_reference LhsStlContainerReference;
+    typedef typename LhsStlContainer::value_type LhsValue;
+    // We pass the LHS value and the RHS value to the inner matcher by
+    // reference, as they may be expensive to copy.  We must use tuple
+    // instead of pair here, as a pair cannot hold references (C++ 98,
+    // 20.2.2 [lib.pairs]).
+    typedef ::std::tuple<const LhsValue&, const RhsValue&> InnerMatcherArg;
+
+    Impl(const TupleMatcher& tuple_matcher, const RhsStlContainer& rhs)
+        // mono_tuple_matcher_ holds a monomorphic version of the tuple matcher.
+        : mono_tuple_matcher_(SafeMatcherCast<InnerMatcherArg>(tuple_matcher)),
+          rhs_(rhs) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "contains " << rhs_.size()
+          << " values, where each value and its corresponding value in ";
+      UniversalPrinter<RhsStlContainer>::Print(rhs_, os);
+      *os << " ";
+      mono_tuple_matcher_.DescribeTo(os);
+    }
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "doesn't contain exactly " << rhs_.size()
+          << " values, or contains a value x at some index i"
+          << " where x and the i-th value of ";
+      UniversalPrint(rhs_, os);
+      *os << " ";
+      mono_tuple_matcher_.DescribeNegationTo(os);
+    }
+
+    bool MatchAndExplain(LhsContainer lhs,
+                         MatchResultListener* listener) const override {
+      LhsStlContainerReference lhs_stl_container = LhsView::ConstReference(lhs);
+      const size_t actual_size = lhs_stl_container.size();
+      if (actual_size != rhs_.size()) {
+        *listener << "which contains " << actual_size << " values";
+        return false;
+      }
+
+      typename LhsStlContainer::const_iterator left = lhs_stl_container.begin();
+      typename RhsStlContainer::const_iterator right = rhs_.begin();
+      for (size_t i = 0; i != actual_size; ++i, ++left, ++right) {
+        if (listener->IsInterested()) {
+          StringMatchResultListener inner_listener;
+          // Create InnerMatcherArg as a temporarily object to avoid it outlives
+          // *left and *right. Dereference or the conversion to `const T&` may
+          // return temp objects, e.g for vector<bool>.
+          if (!mono_tuple_matcher_.MatchAndExplain(
+                  InnerMatcherArg(ImplicitCast_<const LhsValue&>(*left),
+                                  ImplicitCast_<const RhsValue&>(*right)),
+                  &inner_listener)) {
+            *listener << "where the value pair (";
+            UniversalPrint(*left, listener->stream());
+            *listener << ", ";
+            UniversalPrint(*right, listener->stream());
+            *listener << ") at index #" << i << " don't match";
+            PrintIfNotEmpty(inner_listener.str(), listener->stream());
+            return false;
+          }
+        } else {
+          if (!mono_tuple_matcher_.Matches(
+                  InnerMatcherArg(ImplicitCast_<const LhsValue&>(*left),
+                                  ImplicitCast_<const RhsValue&>(*right))))
+            return false;
+        }
+      }
+
+      return true;
+    }
+
+   private:
+    const Matcher<InnerMatcherArg> mono_tuple_matcher_;
+    const RhsStlContainer rhs_;
+  };
+
+ private:
+  const TupleMatcher tuple_matcher_;
+  const RhsStlContainer rhs_;
+};
+
+// Holds the logic common to ContainsMatcherImpl and EachMatcherImpl.
+template <typename Container>
+class QuantifierMatcherImpl : public MatcherInterface<Container> {
+ public:
+  typedef GTEST_REMOVE_REFERENCE_AND_CONST_(Container) RawContainer;
+  typedef StlContainerView<RawContainer> View;
+  typedef typename View::type StlContainer;
+  typedef typename View::const_reference StlContainerReference;
+  typedef typename StlContainer::value_type Element;
+
+  template <typename InnerMatcher>
+  explicit QuantifierMatcherImpl(InnerMatcher inner_matcher)
+      : inner_matcher_(
+           testing::SafeMatcherCast<const Element&>(inner_matcher)) {}
+
+  // Checks whether:
+  // * All elements in the container match, if all_elements_should_match.
+  // * Any element in the container matches, if !all_elements_should_match.
+  bool MatchAndExplainImpl(bool all_elements_should_match,
+                           Container container,
+                           MatchResultListener* listener) const {
+    StlContainerReference stl_container = View::ConstReference(container);
+    size_t i = 0;
+    for (typename StlContainer::const_iterator it = stl_container.begin();
+         it != stl_container.end(); ++it, ++i) {
+      StringMatchResultListener inner_listener;
+      const bool matches = inner_matcher_.MatchAndExplain(*it, &inner_listener);
+
+      if (matches != all_elements_should_match) {
+        *listener << "whose element #" << i
+                  << (matches ? " matches" : " doesn't match");
+        PrintIfNotEmpty(inner_listener.str(), listener->stream());
+        return !all_elements_should_match;
+      }
+    }
+    return all_elements_should_match;
+  }
+
+ protected:
+  const Matcher<const Element&> inner_matcher_;
+};
+
+// Implements Contains(element_matcher) for the given argument type Container.
+// Symmetric to EachMatcherImpl.
+template <typename Container>
+class ContainsMatcherImpl : public QuantifierMatcherImpl<Container> {
+ public:
+  template <typename InnerMatcher>
+  explicit ContainsMatcherImpl(InnerMatcher inner_matcher)
+      : QuantifierMatcherImpl<Container>(inner_matcher) {}
+
+  // Describes what this matcher does.
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "contains at least one element that ";
+    this->inner_matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const override {
+    *os << "doesn't contain any element that ";
+    this->inner_matcher_.DescribeTo(os);
+  }
+
+  bool MatchAndExplain(Container container,
+                       MatchResultListener* listener) const override {
+    return this->MatchAndExplainImpl(false, container, listener);
+  }
+};
+
+// Implements Each(element_matcher) for the given argument type Container.
+// Symmetric to ContainsMatcherImpl.
+template <typename Container>
+class EachMatcherImpl : public QuantifierMatcherImpl<Container> {
+ public:
+  template <typename InnerMatcher>
+  explicit EachMatcherImpl(InnerMatcher inner_matcher)
+      : QuantifierMatcherImpl<Container>(inner_matcher) {}
+
+  // Describes what this matcher does.
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "only contains elements that ";
+    this->inner_matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const override {
+    *os << "contains some element that ";
+    this->inner_matcher_.DescribeNegationTo(os);
+  }
+
+  bool MatchAndExplain(Container container,
+                       MatchResultListener* listener) const override {
+    return this->MatchAndExplainImpl(true, container, listener);
+  }
+};
+
+// Implements polymorphic Contains(element_matcher).
+template <typename M>
+class ContainsMatcher {
+ public:
+  explicit ContainsMatcher(M m) : inner_matcher_(m) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {
+    return Matcher<Container>(
+        new ContainsMatcherImpl<const Container&>(inner_matcher_));
+  }
+
+ private:
+  const M inner_matcher_;
+};
+
+// Implements polymorphic Each(element_matcher).
+template <typename M>
+class EachMatcher {
+ public:
+  explicit EachMatcher(M m) : inner_matcher_(m) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {
+    return Matcher<Container>(
+        new EachMatcherImpl<const Container&>(inner_matcher_));
+  }
+
+ private:
+  const M inner_matcher_;
+};
+
+struct Rank1 {};
+struct Rank0 : Rank1 {};
+
+namespace pair_getters {
+using std::get;
+template <typename T>
+auto First(T& x, Rank1) -> decltype(get<0>(x)) {  // NOLINT
+  return get<0>(x);
+}
+template <typename T>
+auto First(T& x, Rank0) -> decltype((x.first)) {  // NOLINT
+  return x.first;
+}
+
+template <typename T>
+auto Second(T& x, Rank1) -> decltype(get<1>(x)) {  // NOLINT
+  return get<1>(x);
+}
+template <typename T>
+auto Second(T& x, Rank0) -> decltype((x.second)) {  // NOLINT
+  return x.second;
+}
+}  // namespace pair_getters
+
+// Implements Key(inner_matcher) for the given argument pair type.
+// Key(inner_matcher) matches an std::pair whose 'first' field matches
+// inner_matcher.  For example, Contains(Key(Ge(5))) can be used to match an
+// std::map that contains at least one element whose key is >= 5.
+template <typename PairType>
+class KeyMatcherImpl : public MatcherInterface<PairType> {
+ public:
+  typedef GTEST_REMOVE_REFERENCE_AND_CONST_(PairType) RawPairType;
+  typedef typename RawPairType::first_type KeyType;
+
+  template <typename InnerMatcher>
+  explicit KeyMatcherImpl(InnerMatcher inner_matcher)
+      : inner_matcher_(
+          testing::SafeMatcherCast<const KeyType&>(inner_matcher)) {
+  }
+
+  // Returns true if and only if 'key_value.first' (the key) matches the inner
+  // matcher.
+  bool MatchAndExplain(PairType key_value,
+                       MatchResultListener* listener) const override {
+    StringMatchResultListener inner_listener;
+    const bool match = inner_matcher_.MatchAndExplain(
+        pair_getters::First(key_value, Rank0()), &inner_listener);
+    const std::string explanation = inner_listener.str();
+    if (explanation != "") {
+      *listener << "whose first field is a value " << explanation;
+    }
+    return match;
+  }
+
+  // Describes what this matcher does.
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "has a key that ";
+    inner_matcher_.DescribeTo(os);
+  }
+
+  // Describes what the negation of this matcher does.
+  void DescribeNegationTo(::std::ostream* os) const override {
+    *os << "doesn't have a key that ";
+    inner_matcher_.DescribeTo(os);
+  }
+
+ private:
+  const Matcher<const KeyType&> inner_matcher_;
+};
+
+// Implements polymorphic Key(matcher_for_key).
+template <typename M>
+class KeyMatcher {
+ public:
+  explicit KeyMatcher(M m) : matcher_for_key_(m) {}
+
+  template <typename PairType>
+  operator Matcher<PairType>() const {
+    return Matcher<PairType>(
+        new KeyMatcherImpl<const PairType&>(matcher_for_key_));
+  }
+
+ private:
+  const M matcher_for_key_;
+};
+
+// Implements polymorphic Address(matcher_for_address).
+template <typename InnerMatcher>
+class AddressMatcher {
+ public:
+  explicit AddressMatcher(InnerMatcher m) : matcher_(m) {}
+
+  template <typename Type>
+  operator Matcher<Type>() const {  // NOLINT
+    return Matcher<Type>(new Impl<const Type&>(matcher_));
+  }
+
+ private:
+  // The monomorphic implementation that works for a particular object type.
+  template <typename Type>
+  class Impl : public MatcherInterface<Type> {
+   public:
+    using Address = const GTEST_REMOVE_REFERENCE_AND_CONST_(Type) *;
+    explicit Impl(const InnerMatcher& matcher)
+        : matcher_(MatcherCast<Address>(matcher)) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "has address that ";
+      matcher_.DescribeTo(os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "does not have address that ";
+      matcher_.DescribeTo(os);
+    }
+
+    bool MatchAndExplain(Type object,
+                         MatchResultListener* listener) const override {
+      *listener << "which has address ";
+      Address address = std::addressof(object);
+      return MatchPrintAndExplain(address, matcher_, listener);
+    }
+
+   private:
+    const Matcher<Address> matcher_;
+  };
+  const InnerMatcher matcher_;
+};
+
+// Implements Pair(first_matcher, second_matcher) for the given argument pair
+// type with its two matchers. See Pair() function below.
+template <typename PairType>
+class PairMatcherImpl : public MatcherInterface<PairType> {
+ public:
+  typedef GTEST_REMOVE_REFERENCE_AND_CONST_(PairType) RawPairType;
+  typedef typename RawPairType::first_type FirstType;
+  typedef typename RawPairType::second_type SecondType;
+
+  template <typename FirstMatcher, typename SecondMatcher>
+  PairMatcherImpl(FirstMatcher first_matcher, SecondMatcher second_matcher)
+      : first_matcher_(
+            testing::SafeMatcherCast<const FirstType&>(first_matcher)),
+        second_matcher_(
+            testing::SafeMatcherCast<const SecondType&>(second_matcher)) {
+  }
+
+  // Describes what this matcher does.
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "has a first field that ";
+    first_matcher_.DescribeTo(os);
+    *os << ", and has a second field that ";
+    second_matcher_.DescribeTo(os);
+  }
+
+  // Describes what the negation of this matcher does.
+  void DescribeNegationTo(::std::ostream* os) const override {
+    *os << "has a first field that ";
+    first_matcher_.DescribeNegationTo(os);
+    *os << ", or has a second field that ";
+    second_matcher_.DescribeNegationTo(os);
+  }
+
+  // Returns true if and only if 'a_pair.first' matches first_matcher and
+  // 'a_pair.second' matches second_matcher.
+  bool MatchAndExplain(PairType a_pair,
+                       MatchResultListener* listener) const override {
+    if (!listener->IsInterested()) {
+      // If the listener is not interested, we don't need to construct the
+      // explanation.
+      return first_matcher_.Matches(pair_getters::First(a_pair, Rank0())) &&
+             second_matcher_.Matches(pair_getters::Second(a_pair, Rank0()));
+    }
+    StringMatchResultListener first_inner_listener;
+    if (!first_matcher_.MatchAndExplain(pair_getters::First(a_pair, Rank0()),
+                                        &first_inner_listener)) {
+      *listener << "whose first field does not match";
+      PrintIfNotEmpty(first_inner_listener.str(), listener->stream());
+      return false;
+    }
+    StringMatchResultListener second_inner_listener;
+    if (!second_matcher_.MatchAndExplain(pair_getters::Second(a_pair, Rank0()),
+                                         &second_inner_listener)) {
+      *listener << "whose second field does not match";
+      PrintIfNotEmpty(second_inner_listener.str(), listener->stream());
+      return false;
+    }
+    ExplainSuccess(first_inner_listener.str(), second_inner_listener.str(),
+                   listener);
+    return true;
+  }
+
+ private:
+  void ExplainSuccess(const std::string& first_explanation,
+                      const std::string& second_explanation,
+                      MatchResultListener* listener) const {
+    *listener << "whose both fields match";
+    if (first_explanation != "") {
+      *listener << ", where the first field is a value " << first_explanation;
+    }
+    if (second_explanation != "") {
+      *listener << ", ";
+      if (first_explanation != "") {
+        *listener << "and ";
+      } else {
+        *listener << "where ";
+      }
+      *listener << "the second field is a value " << second_explanation;
+    }
+  }
+
+  const Matcher<const FirstType&> first_matcher_;
+  const Matcher<const SecondType&> second_matcher_;
+};
+
+// Implements polymorphic Pair(first_matcher, second_matcher).
+template <typename FirstMatcher, typename SecondMatcher>
+class PairMatcher {
+ public:
+  PairMatcher(FirstMatcher first_matcher, SecondMatcher second_matcher)
+      : first_matcher_(first_matcher), second_matcher_(second_matcher) {}
+
+  template <typename PairType>
+  operator Matcher<PairType> () const {
+    return Matcher<PairType>(
+        new PairMatcherImpl<const PairType&>(first_matcher_, second_matcher_));
+  }
+
+ private:
+  const FirstMatcher first_matcher_;
+  const SecondMatcher second_matcher_;
+};
+
+template <typename T, size_t... I>
+auto UnpackStructImpl(const T& t, IndexSequence<I...>, int)
+    -> decltype(std::tie(get<I>(t)...)) {
+  static_assert(std::tuple_size<T>::value == sizeof...(I),
+                "Number of arguments doesn't match the number of fields.");
+  return std::tie(get<I>(t)...);
+}
+
+#if defined(__cpp_structured_bindings) && __cpp_structured_bindings >= 201606
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<1>, char) {
+  const auto& [a] = t;
+  return std::tie(a);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<2>, char) {
+  const auto& [a, b] = t;
+  return std::tie(a, b);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<3>, char) {
+  const auto& [a, b, c] = t;
+  return std::tie(a, b, c);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<4>, char) {
+  const auto& [a, b, c, d] = t;
+  return std::tie(a, b, c, d);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<5>, char) {
+  const auto& [a, b, c, d, e] = t;
+  return std::tie(a, b, c, d, e);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<6>, char) {
+  const auto& [a, b, c, d, e, f] = t;
+  return std::tie(a, b, c, d, e, f);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<7>, char) {
+  const auto& [a, b, c, d, e, f, g] = t;
+  return std::tie(a, b, c, d, e, f, g);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<8>, char) {
+  const auto& [a, b, c, d, e, f, g, h] = t;
+  return std::tie(a, b, c, d, e, f, g, h);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<9>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<10>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<11>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j, k] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j, k);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<12>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j, k, l] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j, k, l);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<13>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j, k, l, m] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j, k, l, m);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<14>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j, k, l, m, n] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j, k, l, m, n);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<15>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j, k, l, m, n, o] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<16>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p);
+}
+#endif  // defined(__cpp_structured_bindings)
+
+template <size_t I, typename T>
+auto UnpackStruct(const T& t)
+    -> decltype((UnpackStructImpl)(t, MakeIndexSequence<I>{}, 0)) {
+  return (UnpackStructImpl)(t, MakeIndexSequence<I>{}, 0);
+}
+
+// Helper function to do comma folding in C++11.
+// The array ensures left-to-right order of evaluation.
+// Usage: VariadicExpand({expr...});
+template <typename T, size_t N>
+void VariadicExpand(const T (&)[N]) {}
+
+template <typename Struct, typename StructSize>
+class FieldsAreMatcherImpl;
+
+template <typename Struct, size_t... I>
+class FieldsAreMatcherImpl<Struct, IndexSequence<I...>>
+    : public MatcherInterface<Struct> {
+  using UnpackedType =
+      decltype(UnpackStruct<sizeof...(I)>(std::declval<const Struct&>()));
+  using MatchersType = std::tuple<
+      Matcher<const typename std::tuple_element<I, UnpackedType>::type&>...>;
+
+ public:
+  template <typename Inner>
+  explicit FieldsAreMatcherImpl(const Inner& matchers)
+      : matchers_(testing::SafeMatcherCast<
+                  const typename std::tuple_element<I, UnpackedType>::type&>(
+            std::get<I>(matchers))...) {}
+
+  void DescribeTo(::std::ostream* os) const override {
+    const char* separator = "";
+    VariadicExpand(
+        {(*os << separator << "has field #" << I << " that ",
+          std::get<I>(matchers_).DescribeTo(os), separator = ", and ")...});
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const override {
+    const char* separator = "";
+    VariadicExpand({(*os << separator << "has field #" << I << " that ",
+                     std::get<I>(matchers_).DescribeNegationTo(os),
+                     separator = ", or ")...});
+  }
+
+  bool MatchAndExplain(Struct t, MatchResultListener* listener) const override {
+    return MatchInternal((UnpackStruct<sizeof...(I)>)(t), listener);
+  }
+
+ private:
+  bool MatchInternal(UnpackedType tuple, MatchResultListener* listener) const {
+    if (!listener->IsInterested()) {
+      // If the listener is not interested, we don't need to construct the
+      // explanation.
+      bool good = true;
+      VariadicExpand({good = good && std::get<I>(matchers_).Matches(
+                                         std::get<I>(tuple))...});
+      return good;
+    }
+
+    size_t failed_pos = ~size_t{};
+
+    std::vector<StringMatchResultListener> inner_listener(sizeof...(I));
+
+    VariadicExpand(
+        {failed_pos == ~size_t{} && !std::get<I>(matchers_).MatchAndExplain(
+                                        std::get<I>(tuple), &inner_listener[I])
+             ? failed_pos = I
+             : 0 ...});
+    if (failed_pos != ~size_t{}) {
+      *listener << "whose field #" << failed_pos << " does not match";
+      PrintIfNotEmpty(inner_listener[failed_pos].str(), listener->stream());
+      return false;
+    }
+
+    *listener << "whose all elements match";
+    const char* separator = ", where";
+    for (size_t index = 0; index < sizeof...(I); ++index) {
+      const std::string str = inner_listener[index].str();
+      if (!str.empty()) {
+        *listener << separator << " field #" << index << " is a value " << str;
+        separator = ", and";
+      }
+    }
+
+    return true;
+  }
+
+  MatchersType matchers_;
+};
+
+template <typename... Inner>
+class FieldsAreMatcher {
+ public:
+  explicit FieldsAreMatcher(Inner... inner) : matchers_(std::move(inner)...) {}
+
+  template <typename Struct>
+  operator Matcher<Struct>() const {  // NOLINT
+    return Matcher<Struct>(
+        new FieldsAreMatcherImpl<const Struct&, IndexSequenceFor<Inner...>>(
+            matchers_));
+  }
+
+ private:
+  std::tuple<Inner...> matchers_;
+};
+
+// Implements ElementsAre() and ElementsAreArray().
+template <typename Container>
+class ElementsAreMatcherImpl : public MatcherInterface<Container> {
+ public:
+  typedef GTEST_REMOVE_REFERENCE_AND_CONST_(Container) RawContainer;
+  typedef internal::StlContainerView<RawContainer> View;
+  typedef typename View::type StlContainer;
+  typedef typename View::const_reference StlContainerReference;
+  typedef typename StlContainer::value_type Element;
+
+  // Constructs the matcher from a sequence of element values or
+  // element matchers.
+  template <typename InputIter>
+  ElementsAreMatcherImpl(InputIter first, InputIter last) {
+    while (first != last) {
+      matchers_.push_back(MatcherCast<const Element&>(*first++));
+    }
+  }
+
+  // Describes what this matcher does.
+  void DescribeTo(::std::ostream* os) const override {
+    if (count() == 0) {
+      *os << "is empty";
+    } else if (count() == 1) {
+      *os << "has 1 element that ";
+      matchers_[0].DescribeTo(os);
+    } else {
+      *os << "has " << Elements(count()) << " where\n";
+      for (size_t i = 0; i != count(); ++i) {
+        *os << "element #" << i << " ";
+        matchers_[i].DescribeTo(os);
+        if (i + 1 < count()) {
+          *os << ",\n";
+        }
+      }
+    }
+  }
+
+  // Describes what the negation of this matcher does.
+  void DescribeNegationTo(::std::ostream* os) const override {
+    if (count() == 0) {
+      *os << "isn't empty";
+      return;
+    }
+
+    *os << "doesn't have " << Elements(count()) << ", or\n";
+    for (size_t i = 0; i != count(); ++i) {
+      *os << "element #" << i << " ";
+      matchers_[i].DescribeNegationTo(os);
+      if (i + 1 < count()) {
+        *os << ", or\n";
+      }
+    }
+  }
+
+  bool MatchAndExplain(Container container,
+                       MatchResultListener* listener) const override {
+    // To work with stream-like "containers", we must only walk
+    // through the elements in one pass.
+
+    const bool listener_interested = listener->IsInterested();
+
+    // explanations[i] is the explanation of the element at index i.
+    ::std::vector<std::string> explanations(count());
+    StlContainerReference stl_container = View::ConstReference(container);
+    typename StlContainer::const_iterator it = stl_container.begin();
+    size_t exam_pos = 0;
+    bool mismatch_found = false;  // Have we found a mismatched element yet?
+
+    // Go through the elements and matchers in pairs, until we reach
+    // the end of either the elements or the matchers, or until we find a
+    // mismatch.
+    for (; it != stl_container.end() && exam_pos != count(); ++it, ++exam_pos) {
+      bool match;  // Does the current element match the current matcher?
+      if (listener_interested) {
+        StringMatchResultListener s;
+        match = matchers_[exam_pos].MatchAndExplain(*it, &s);
+        explanations[exam_pos] = s.str();
+      } else {
+        match = matchers_[exam_pos].Matches(*it);
+      }
+
+      if (!match) {
+        mismatch_found = true;
+        break;
+      }
+    }
+    // If mismatch_found is true, 'exam_pos' is the index of the mismatch.
+
+    // Find how many elements the actual container has.  We avoid
+    // calling size() s.t. this code works for stream-like "containers"
+    // that don't define size().
+    size_t actual_count = exam_pos;
+    for (; it != stl_container.end(); ++it) {
+      ++actual_count;
+    }
+
+    if (actual_count != count()) {
+      // The element count doesn't match.  If the container is empty,
+      // there's no need to explain anything as Google Mock already
+      // prints the empty container.  Otherwise we just need to show
+      // how many elements there actually are.
+      if (listener_interested && (actual_count != 0)) {
+        *listener << "which has " << Elements(actual_count);
+      }
+      return false;
+    }
+
+    if (mismatch_found) {
+      // The element count matches, but the exam_pos-th element doesn't match.
+      if (listener_interested) {
+        *listener << "whose element #" << exam_pos << " doesn't match";
+        PrintIfNotEmpty(explanations[exam_pos], listener->stream());
+      }
+      return false;
+    }
+
+    // Every element matches its expectation.  We need to explain why
+    // (the obvious ones can be skipped).
+    if (listener_interested) {
+      bool reason_printed = false;
+      for (size_t i = 0; i != count(); ++i) {
+        const std::string& s = explanations[i];
+        if (!s.empty()) {
+          if (reason_printed) {
+            *listener << ",\nand ";
+          }
+          *listener << "whose element #" << i << " matches, " << s;
+          reason_printed = true;
+        }
+      }
+    }
+    return true;
+  }
+
+ private:
+  static Message Elements(size_t count) {
+    return Message() << count << (count == 1 ? " element" : " elements");
+  }
+
+  size_t count() const { return matchers_.size(); }
+
+  ::std::vector<Matcher<const Element&> > matchers_;
+};
+
+// Connectivity matrix of (elements X matchers), in element-major order.
+// Initially, there are no edges.
+// Use NextGraph() to iterate over all possible edge configurations.
+// Use Randomize() to generate a random edge configuration.
+class GTEST_API_ MatchMatrix {
+ public:
+  MatchMatrix(size_t num_elements, size_t num_matchers)
+      : num_elements_(num_elements),
+        num_matchers_(num_matchers),
+        matched_(num_elements_* num_matchers_, 0) {
+  }
+
+  size_t LhsSize() const { return num_elements_; }
+  size_t RhsSize() const { return num_matchers_; }
+  bool HasEdge(size_t ilhs, size_t irhs) const {
+    return matched_[SpaceIndex(ilhs, irhs)] == 1;
+  }
+  void SetEdge(size_t ilhs, size_t irhs, bool b) {
+    matched_[SpaceIndex(ilhs, irhs)] = b ? 1 : 0;
+  }
+
+  // Treating the connectivity matrix as a (LhsSize()*RhsSize())-bit number,
+  // adds 1 to that number; returns false if incrementing the graph left it
+  // empty.
+  bool NextGraph();
+
+  void Randomize();
+
+  std::string DebugString() const;
+
+ private:
+  size_t SpaceIndex(size_t ilhs, size_t irhs) const {
+    return ilhs * num_matchers_ + irhs;
+  }
+
+  size_t num_elements_;
+  size_t num_matchers_;
+
+  // Each element is a char interpreted as bool. They are stored as a
+  // flattened array in lhs-major order, use 'SpaceIndex()' to translate
+  // a (ilhs, irhs) matrix coordinate into an offset.
+  ::std::vector<char> matched_;
+};
+
+typedef ::std::pair<size_t, size_t> ElementMatcherPair;
+typedef ::std::vector<ElementMatcherPair> ElementMatcherPairs;
+
+// Returns a maximum bipartite matching for the specified graph 'g'.
+// The matching is represented as a vector of {element, matcher} pairs.
+GTEST_API_ ElementMatcherPairs
+FindMaxBipartiteMatching(const MatchMatrix& g);
+
+struct UnorderedMatcherRequire {
+  enum Flags {
+    Superset = 1 << 0,
+    Subset = 1 << 1,
+    ExactMatch = Superset | Subset,
+  };
+};
+
+// Untyped base class for implementing UnorderedElementsAre.  By
+// putting logic that's not specific to the element type here, we
+// reduce binary bloat and increase compilation speed.
+class GTEST_API_ UnorderedElementsAreMatcherImplBase {
+ protected:
+  explicit UnorderedElementsAreMatcherImplBase(
+      UnorderedMatcherRequire::Flags matcher_flags)
+      : match_flags_(matcher_flags) {}
+
+  // A vector of matcher describers, one for each element matcher.
+  // Does not own the describers (and thus can be used only when the
+  // element matchers are alive).
+  typedef ::std::vector<const MatcherDescriberInterface*> MatcherDescriberVec;
+
+  // Describes this UnorderedElementsAre matcher.
+  void DescribeToImpl(::std::ostream* os) const;
+
+  // Describes the negation of this UnorderedElementsAre matcher.
+  void DescribeNegationToImpl(::std::ostream* os) const;
+
+  bool VerifyMatchMatrix(const ::std::vector<std::string>& element_printouts,
+                         const MatchMatrix& matrix,
+                         MatchResultListener* listener) const;
+
+  bool FindPairing(const MatchMatrix& matrix,
+                   MatchResultListener* listener) const;
+
+  MatcherDescriberVec& matcher_describers() {
+    return matcher_describers_;
+  }
+
+  static Message Elements(size_t n) {
+    return Message() << n << " element" << (n == 1 ? "" : "s");
+  }
+
+  UnorderedMatcherRequire::Flags match_flags() const { return match_flags_; }
+
+ private:
+  UnorderedMatcherRequire::Flags match_flags_;
+  MatcherDescriberVec matcher_describers_;
+};
+
+// Implements UnorderedElementsAre, UnorderedElementsAreArray, IsSubsetOf, and
+// IsSupersetOf.
+template <typename Container>
+class UnorderedElementsAreMatcherImpl
+    : public MatcherInterface<Container>,
+      public UnorderedElementsAreMatcherImplBase {
+ public:
+  typedef GTEST_REMOVE_REFERENCE_AND_CONST_(Container) RawContainer;
+  typedef internal::StlContainerView<RawContainer> View;
+  typedef typename View::type StlContainer;
+  typedef typename View::const_reference StlContainerReference;
+  typedef typename StlContainer::const_iterator StlContainerConstIterator;
+  typedef typename StlContainer::value_type Element;
+
+  template <typename InputIter>
+  UnorderedElementsAreMatcherImpl(UnorderedMatcherRequire::Flags matcher_flags,
+                                  InputIter first, InputIter last)
+      : UnorderedElementsAreMatcherImplBase(matcher_flags) {
+    for (; first != last; ++first) {
+      matchers_.push_back(MatcherCast<const Element&>(*first));
+    }
+    for (const auto& m : matchers_) {
+      matcher_describers().push_back(m.GetDescriber());
+    }
+  }
+
+  // Describes what this matcher does.
+  void DescribeTo(::std::ostream* os) const override {
+    return UnorderedElementsAreMatcherImplBase::DescribeToImpl(os);
+  }
+
+  // Describes what the negation of this matcher does.
+  void DescribeNegationTo(::std::ostream* os) const override {
+    return UnorderedElementsAreMatcherImplBase::DescribeNegationToImpl(os);
+  }
+
+  bool MatchAndExplain(Container container,
+                       MatchResultListener* listener) const override {
+    StlContainerReference stl_container = View::ConstReference(container);
+    ::std::vector<std::string> element_printouts;
+    MatchMatrix matrix =
+        AnalyzeElements(stl_container.begin(), stl_container.end(),
+                        &element_printouts, listener);
+
+    if (matrix.LhsSize() == 0 && matrix.RhsSize() == 0) {
+      return true;
+    }
+
+    if (match_flags() == UnorderedMatcherRequire::ExactMatch) {
+      if (matrix.LhsSize() != matrix.RhsSize()) {
+        // The element count doesn't match.  If the container is empty,
+        // there's no need to explain anything as Google Mock already
+        // prints the empty container. Otherwise we just need to show
+        // how many elements there actually are.
+        if (matrix.LhsSize() != 0 && listener->IsInterested()) {
+          *listener << "which has " << Elements(matrix.LhsSize());
+        }
+        return false;
+      }
+    }
+
+    return VerifyMatchMatrix(element_printouts, matrix, listener) &&
+           FindPairing(matrix, listener);
+  }
+
+ private:
+  template <typename ElementIter>
+  MatchMatrix AnalyzeElements(ElementIter elem_first, ElementIter elem_last,
+                              ::std::vector<std::string>* element_printouts,
+                              MatchResultListener* listener) const {
+    element_printouts->clear();
+    ::std::vector<char> did_match;
+    size_t num_elements = 0;
+    DummyMatchResultListener dummy;
+    for (; elem_first != elem_last; ++num_elements, ++elem_first) {
+      if (listener->IsInterested()) {
+        element_printouts->push_back(PrintToString(*elem_first));
+      }
+      for (size_t irhs = 0; irhs != matchers_.size(); ++irhs) {
+        did_match.push_back(
+            matchers_[irhs].MatchAndExplain(*elem_first, &dummy));
+      }
+    }
+
+    MatchMatrix matrix(num_elements, matchers_.size());
+    ::std::vector<char>::const_iterator did_match_iter = did_match.begin();
+    for (size_t ilhs = 0; ilhs != num_elements; ++ilhs) {
+      for (size_t irhs = 0; irhs != matchers_.size(); ++irhs) {
+        matrix.SetEdge(ilhs, irhs, *did_match_iter++ != 0);
+      }
+    }
+    return matrix;
+  }
+
+  ::std::vector<Matcher<const Element&> > matchers_;
+};
+
+// Functor for use in TransformTuple.
+// Performs MatcherCast<Target> on an input argument of any type.
+template <typename Target>
+struct CastAndAppendTransform {
+  template <typename Arg>
+  Matcher<Target> operator()(const Arg& a) const {
+    return MatcherCast<Target>(a);
+  }
+};
+
+// Implements UnorderedElementsAre.
+template <typename MatcherTuple>
+class UnorderedElementsAreMatcher {
+ public:
+  explicit UnorderedElementsAreMatcher(const MatcherTuple& args)
+      : matchers_(args) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {
+    typedef GTEST_REMOVE_REFERENCE_AND_CONST_(Container) RawContainer;
+    typedef typename internal::StlContainerView<RawContainer>::type View;
+    typedef typename View::value_type Element;
+    typedef ::std::vector<Matcher<const Element&> > MatcherVec;
+    MatcherVec matchers;
+    matchers.reserve(::std::tuple_size<MatcherTuple>::value);
+    TransformTupleValues(CastAndAppendTransform<const Element&>(), matchers_,
+                         ::std::back_inserter(matchers));
+    return Matcher<Container>(
+        new UnorderedElementsAreMatcherImpl<const Container&>(
+            UnorderedMatcherRequire::ExactMatch, matchers.begin(),
+            matchers.end()));
+  }
+
+ private:
+  const MatcherTuple matchers_;
+};
+
+// Implements ElementsAre.
+template <typename MatcherTuple>
+class ElementsAreMatcher {
+ public:
+  explicit ElementsAreMatcher(const MatcherTuple& args) : matchers_(args) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {
+    GTEST_COMPILE_ASSERT_(
+        !IsHashTable<GTEST_REMOVE_REFERENCE_AND_CONST_(Container)>::value ||
+            ::std::tuple_size<MatcherTuple>::value < 2,
+        use_UnorderedElementsAre_with_hash_tables);
+
+    typedef GTEST_REMOVE_REFERENCE_AND_CONST_(Container) RawContainer;
+    typedef typename internal::StlContainerView<RawContainer>::type View;
+    typedef typename View::value_type Element;
+    typedef ::std::vector<Matcher<const Element&> > MatcherVec;
+    MatcherVec matchers;
+    matchers.reserve(::std::tuple_size<MatcherTuple>::value);
+    TransformTupleValues(CastAndAppendTransform<const Element&>(), matchers_,
+                         ::std::back_inserter(matchers));
+    return Matcher<Container>(new ElementsAreMatcherImpl<const Container&>(
+        matchers.begin(), matchers.end()));
+  }
+
+ private:
+  const MatcherTuple matchers_;
+};
+
+// Implements UnorderedElementsAreArray(), IsSubsetOf(), and IsSupersetOf().
+template <typename T>
+class UnorderedElementsAreArrayMatcher {
+ public:
+  template <typename Iter>
+  UnorderedElementsAreArrayMatcher(UnorderedMatcherRequire::Flags match_flags,
+                                   Iter first, Iter last)
+      : match_flags_(match_flags), matchers_(first, last) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {
+    return Matcher<Container>(
+        new UnorderedElementsAreMatcherImpl<const Container&>(
+            match_flags_, matchers_.begin(), matchers_.end()));
+  }
+
+ private:
+  UnorderedMatcherRequire::Flags match_flags_;
+  ::std::vector<T> matchers_;
+};
+
+// Implements ElementsAreArray().
+template <typename T>
+class ElementsAreArrayMatcher {
+ public:
+  template <typename Iter>
+  ElementsAreArrayMatcher(Iter first, Iter last) : matchers_(first, last) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {
+    GTEST_COMPILE_ASSERT_(
+        !IsHashTable<GTEST_REMOVE_REFERENCE_AND_CONST_(Container)>::value,
+        use_UnorderedElementsAreArray_with_hash_tables);
+
+    return Matcher<Container>(new ElementsAreMatcherImpl<const Container&>(
+        matchers_.begin(), matchers_.end()));
+  }
+
+ private:
+  const ::std::vector<T> matchers_;
+};
+
+// Given a 2-tuple matcher tm of type Tuple2Matcher and a value second
+// of type Second, BoundSecondMatcher<Tuple2Matcher, Second>(tm,
+// second) is a polymorphic matcher that matches a value x if and only if
+// tm matches tuple (x, second).  Useful for implementing
+// UnorderedPointwise() in terms of UnorderedElementsAreArray().
+//
+// BoundSecondMatcher is copyable and assignable, as we need to put
+// instances of this class in a vector when implementing
+// UnorderedPointwise().
+template <typename Tuple2Matcher, typename Second>
+class BoundSecondMatcher {
+ public:
+  BoundSecondMatcher(const Tuple2Matcher& tm, const Second& second)
+      : tuple2_matcher_(tm), second_value_(second) {}
+
+  BoundSecondMatcher(const BoundSecondMatcher& other) = default;
+
+  template <typename T>
+  operator Matcher<T>() const {
+    return MakeMatcher(new Impl<T>(tuple2_matcher_, second_value_));
+  }
+
+  // We have to define this for UnorderedPointwise() to compile in
+  // C++98 mode, as it puts BoundSecondMatcher instances in a vector,
+  // which requires the elements to be assignable in C++98.  The
+  // compiler cannot generate the operator= for us, as Tuple2Matcher
+  // and Second may not be assignable.
+  //
+  // However, this should never be called, so the implementation just
+  // need to assert.
+  void operator=(const BoundSecondMatcher& /*rhs*/) {
+    GTEST_LOG_(FATAL) << "BoundSecondMatcher should never be assigned.";
+  }
+
+ private:
+  template <typename T>
+  class Impl : public MatcherInterface<T> {
+   public:
+    typedef ::std::tuple<T, Second> ArgTuple;
+
+    Impl(const Tuple2Matcher& tm, const Second& second)
+        : mono_tuple2_matcher_(SafeMatcherCast<const ArgTuple&>(tm)),
+          second_value_(second) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "and ";
+      UniversalPrint(second_value_, os);
+      *os << " ";
+      mono_tuple2_matcher_.DescribeTo(os);
+    }
+
+    bool MatchAndExplain(T x, MatchResultListener* listener) const override {
+      return mono_tuple2_matcher_.MatchAndExplain(ArgTuple(x, second_value_),
+                                                  listener);
+    }
+
+   private:
+    const Matcher<const ArgTuple&> mono_tuple2_matcher_;
+    const Second second_value_;
+  };
+
+  const Tuple2Matcher tuple2_matcher_;
+  const Second second_value_;
+};
+
+// Given a 2-tuple matcher tm and a value second,
+// MatcherBindSecond(tm, second) returns a matcher that matches a
+// value x if and only if tm matches tuple (x, second).  Useful for
+// implementing UnorderedPointwise() in terms of UnorderedElementsAreArray().
+template <typename Tuple2Matcher, typename Second>
+BoundSecondMatcher<Tuple2Matcher, Second> MatcherBindSecond(
+    const Tuple2Matcher& tm, const Second& second) {
+  return BoundSecondMatcher<Tuple2Matcher, Second>(tm, second);
+}
+
+// Returns the description for a matcher defined using the MATCHER*()
+// macro where the user-supplied description string is "", if
+// 'negation' is false; otherwise returns the description of the
+// negation of the matcher.  'param_values' contains a list of strings
+// that are the print-out of the matcher's parameters.
+GTEST_API_ std::string FormatMatcherDescription(bool negation,
+                                                const char* matcher_name,
+                                                const Strings& param_values);
+
+// Implements a matcher that checks the value of a optional<> type variable.
+template <typename ValueMatcher>
+class OptionalMatcher {
+ public:
+  explicit OptionalMatcher(const ValueMatcher& value_matcher)
+      : value_matcher_(value_matcher) {}
+
+  template <typename Optional>
+  operator Matcher<Optional>() const {
+    return Matcher<Optional>(new Impl<const Optional&>(value_matcher_));
+  }
+
+  template <typename Optional>
+  class Impl : public MatcherInterface<Optional> {
+   public:
+    typedef GTEST_REMOVE_REFERENCE_AND_CONST_(Optional) OptionalView;
+    typedef typename OptionalView::value_type ValueType;
+    explicit Impl(const ValueMatcher& value_matcher)
+        : value_matcher_(MatcherCast<ValueType>(value_matcher)) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "value ";
+      value_matcher_.DescribeTo(os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "value ";
+      value_matcher_.DescribeNegationTo(os);
+    }
+
+    bool MatchAndExplain(Optional optional,
+                         MatchResultListener* listener) const override {
+      if (!optional) {
+        *listener << "which is not engaged";
+        return false;
+      }
+      const ValueType& value = *optional;
+      StringMatchResultListener value_listener;
+      const bool match = value_matcher_.MatchAndExplain(value, &value_listener);
+      *listener << "whose value " << PrintToString(value)
+                << (match ? " matches" : " doesn't match");
+      PrintIfNotEmpty(value_listener.str(), listener->stream());
+      return match;
+    }
+
+   private:
+    const Matcher<ValueType> value_matcher_;
+  };
+
+ private:
+  const ValueMatcher value_matcher_;
+};
+
+namespace variant_matcher {
+// Overloads to allow VariantMatcher to do proper ADL lookup.
+template <typename T>
+void holds_alternative() {}
+template <typename T>
+void get() {}
+
+// Implements a matcher that checks the value of a variant<> type variable.
+template <typename T>
+class VariantMatcher {
+ public:
+  explicit VariantMatcher(::testing::Matcher<const T&> matcher)
+      : matcher_(std::move(matcher)) {}
+
+  template <typename Variant>
+  bool MatchAndExplain(const Variant& value,
+                       ::testing::MatchResultListener* listener) const {
+    using std::get;
+    if (!listener->IsInterested()) {
+      return holds_alternative<T>(value) && matcher_.Matches(get<T>(value));
+    }
+
+    if (!holds_alternative<T>(value)) {
+      *listener << "whose value is not of type '" << GetTypeName() << "'";
+      return false;
+    }
+
+    const T& elem = get<T>(value);
+    StringMatchResultListener elem_listener;
+    const bool match = matcher_.MatchAndExplain(elem, &elem_listener);
+    *listener << "whose value " << PrintToString(elem)
+              << (match ? " matches" : " doesn't match");
+    PrintIfNotEmpty(elem_listener.str(), listener->stream());
+    return match;
+  }
+
+  void DescribeTo(std::ostream* os) const {
+    *os << "is a variant<> with value of type '" << GetTypeName()
+        << "' and the value ";
+    matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(std::ostream* os) const {
+    *os << "is a variant<> with value of type other than '" << GetTypeName()
+        << "' or the value ";
+    matcher_.DescribeNegationTo(os);
+  }
+
+ private:
+  static std::string GetTypeName() {
+#if GTEST_HAS_RTTI
+    GTEST_SUPPRESS_UNREACHABLE_CODE_WARNING_BELOW_(
+        return internal::GetTypeName<T>());
+#endif
+    return "the element type";
+  }
+
+  const ::testing::Matcher<const T&> matcher_;
+};
+
+}  // namespace variant_matcher
+
+namespace any_cast_matcher {
+
+// Overloads to allow AnyCastMatcher to do proper ADL lookup.
+template <typename T>
+void any_cast() {}
+
+// Implements a matcher that any_casts the value.
+template <typename T>
+class AnyCastMatcher {
+ public:
+  explicit AnyCastMatcher(const ::testing::Matcher<const T&>& matcher)
+      : matcher_(matcher) {}
+
+  template <typename AnyType>
+  bool MatchAndExplain(const AnyType& value,
+                       ::testing::MatchResultListener* listener) const {
+    if (!listener->IsInterested()) {
+      const T* ptr = any_cast<T>(&value);
+      return ptr != nullptr && matcher_.Matches(*ptr);
+    }
+
+    const T* elem = any_cast<T>(&value);
+    if (elem == nullptr) {
+      *listener << "whose value is not of type '" << GetTypeName() << "'";
+      return false;
+    }
+
+    StringMatchResultListener elem_listener;
+    const bool match = matcher_.MatchAndExplain(*elem, &elem_listener);
+    *listener << "whose value " << PrintToString(*elem)
+              << (match ? " matches" : " doesn't match");
+    PrintIfNotEmpty(elem_listener.str(), listener->stream());
+    return match;
+  }
+
+  void DescribeTo(std::ostream* os) const {
+    *os << "is an 'any' type with value of type '" << GetTypeName()
+        << "' and the value ";
+    matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(std::ostream* os) const {
+    *os << "is an 'any' type with value of type other than '" << GetTypeName()
+        << "' or the value ";
+    matcher_.DescribeNegationTo(os);
+  }
+
+ private:
+  static std::string GetTypeName() {
+#if GTEST_HAS_RTTI
+    GTEST_SUPPRESS_UNREACHABLE_CODE_WARNING_BELOW_(
+        return internal::GetTypeName<T>());
+#endif
+    return "the element type";
+  }
+
+  const ::testing::Matcher<const T&> matcher_;
+};
+
+}  // namespace any_cast_matcher
+
+// Implements the Args() matcher.
+template <class ArgsTuple, size_t... k>
+class ArgsMatcherImpl : public MatcherInterface<ArgsTuple> {
+ public:
+  using RawArgsTuple = typename std::decay<ArgsTuple>::type;
+  using SelectedArgs =
+      std::tuple<typename std::tuple_element<k, RawArgsTuple>::type...>;
+  using MonomorphicInnerMatcher = Matcher<const SelectedArgs&>;
+
+  template <typename InnerMatcher>
+  explicit ArgsMatcherImpl(const InnerMatcher& inner_matcher)
+      : inner_matcher_(SafeMatcherCast<const SelectedArgs&>(inner_matcher)) {}
+
+  bool MatchAndExplain(ArgsTuple args,
+                       MatchResultListener* listener) const override {
+    // Workaround spurious C4100 on MSVC<=15.7 when k is empty.
+    (void)args;
+    const SelectedArgs& selected_args =
+        std::forward_as_tuple(std::get<k>(args)...);
+    if (!listener->IsInterested()) return inner_matcher_.Matches(selected_args);
+
+    PrintIndices(listener->stream());
+    *listener << "are " << PrintToString(selected_args);
+
+    StringMatchResultListener inner_listener;
+    const bool match =
+        inner_matcher_.MatchAndExplain(selected_args, &inner_listener);
+    PrintIfNotEmpty(inner_listener.str(), listener->stream());
+    return match;
+  }
+
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "are a tuple ";
+    PrintIndices(os);
+    inner_matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const override {
+    *os << "are a tuple ";
+    PrintIndices(os);
+    inner_matcher_.DescribeNegationTo(os);
+  }
+
+ private:
+  // Prints the indices of the selected fields.
+  static void PrintIndices(::std::ostream* os) {
+    *os << "whose fields (";
+    const char* sep = "";
+    // Workaround spurious C4189 on MSVC<=15.7 when k is empty.
+    (void)sep;
+    const char* dummy[] = {"", (*os << sep << "#" << k, sep = ", ")...};
+    (void)dummy;
+    *os << ") ";
+  }
+
+  MonomorphicInnerMatcher inner_matcher_;
+};
+
+template <class InnerMatcher, size_t... k>
+class ArgsMatcher {
+ public:
+  explicit ArgsMatcher(InnerMatcher inner_matcher)
+      : inner_matcher_(std::move(inner_matcher)) {}
+
+  template <typename ArgsTuple>
+  operator Matcher<ArgsTuple>() const {  // NOLINT
+    return MakeMatcher(new ArgsMatcherImpl<ArgsTuple, k...>(inner_matcher_));
+  }
+
+ private:
+  InnerMatcher inner_matcher_;
+};
+
+}  // namespace internal
+
+// ElementsAreArray(iterator_first, iterator_last)
+// ElementsAreArray(pointer, count)
+// ElementsAreArray(array)
+// ElementsAreArray(container)
+// ElementsAreArray({ e1, e2, ..., en })
+//
+// The ElementsAreArray() functions are like ElementsAre(...), except
+// that they are given a homogeneous sequence rather than taking each
+// element as a function argument. The sequence can be specified as an
+// array, a pointer and count, a vector, an initializer list, or an
+// STL iterator range. In each of these cases, the underlying sequence
+// can be either a sequence of values or a sequence of matchers.
+//
+// All forms of ElementsAreArray() make a copy of the input matcher sequence.
+
+template <typename Iter>
+inline internal::ElementsAreArrayMatcher<
+    typename ::std::iterator_traits<Iter>::value_type>
+ElementsAreArray(Iter first, Iter last) {
+  typedef typename ::std::iterator_traits<Iter>::value_type T;
+  return internal::ElementsAreArrayMatcher<T>(first, last);
+}
+
+template <typename T>
+inline internal::ElementsAreArrayMatcher<T> ElementsAreArray(
+    const T* pointer, size_t count) {
+  return ElementsAreArray(pointer, pointer + count);
+}
+
+template <typename T, size_t N>
+inline internal::ElementsAreArrayMatcher<T> ElementsAreArray(
+    const T (&array)[N]) {
+  return ElementsAreArray(array, N);
+}
+
+template <typename Container>
+inline internal::ElementsAreArrayMatcher<typename Container::value_type>
+ElementsAreArray(const Container& container) {
+  return ElementsAreArray(container.begin(), container.end());
+}
+
+template <typename T>
+inline internal::ElementsAreArrayMatcher<T>
+ElementsAreArray(::std::initializer_list<T> xs) {
+  return ElementsAreArray(xs.begin(), xs.end());
+}
+
+// UnorderedElementsAreArray(iterator_first, iterator_last)
+// UnorderedElementsAreArray(pointer, count)
+// UnorderedElementsAreArray(array)
+// UnorderedElementsAreArray(container)
+// UnorderedElementsAreArray({ e1, e2, ..., en })
+//
+// UnorderedElementsAreArray() verifies that a bijective mapping onto a
+// collection of matchers exists.
+//
+// The matchers can be specified as an array, a pointer and count, a container,
+// an initializer list, or an STL iterator range. In each of these cases, the
+// underlying matchers can be either values or matchers.
+
+template <typename Iter>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename ::std::iterator_traits<Iter>::value_type>
+UnorderedElementsAreArray(Iter first, Iter last) {
+  typedef typename ::std::iterator_traits<Iter>::value_type T;
+  return internal::UnorderedElementsAreArrayMatcher<T>(
+      internal::UnorderedMatcherRequire::ExactMatch, first, last);
+}
+
+template <typename T>
+inline internal::UnorderedElementsAreArrayMatcher<T>
+UnorderedElementsAreArray(const T* pointer, size_t count) {
+  return UnorderedElementsAreArray(pointer, pointer + count);
+}
+
+template <typename T, size_t N>
+inline internal::UnorderedElementsAreArrayMatcher<T>
+UnorderedElementsAreArray(const T (&array)[N]) {
+  return UnorderedElementsAreArray(array, N);
+}
+
+template <typename Container>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename Container::value_type>
+UnorderedElementsAreArray(const Container& container) {
+  return UnorderedElementsAreArray(container.begin(), container.end());
+}
+
+template <typename T>
+inline internal::UnorderedElementsAreArrayMatcher<T>
+UnorderedElementsAreArray(::std::initializer_list<T> xs) {
+  return UnorderedElementsAreArray(xs.begin(), xs.end());
+}
+
+// _ is a matcher that matches anything of any type.
+//
+// This definition is fine as:
+//
+//   1. The C++ standard permits using the name _ in a namespace that
+//      is not the global namespace or ::std.
+//   2. The AnythingMatcher class has no data member or constructor,
+//      so it's OK to create global variables of this type.
+//   3. c-style has approved of using _ in this case.
+const internal::AnythingMatcher _ = {};
+// Creates a matcher that matches any value of the given type T.
+template <typename T>
+inline Matcher<T> A() {
+  return _;
+}
+
+// Creates a matcher that matches any value of the given type T.
+template <typename T>
+inline Matcher<T> An() {
+  return _;
+}
+
+template <typename T, typename M>
+Matcher<T> internal::MatcherCastImpl<T, M>::CastImpl(
+    const M& value, std::false_type /* convertible_to_matcher */,
+    std::false_type /* convertible_to_T */) {
+  return Eq(value);
+}
+
+// Creates a polymorphic matcher that matches any NULL pointer.
+inline PolymorphicMatcher<internal::IsNullMatcher > IsNull() {
+  return MakePolymorphicMatcher(internal::IsNullMatcher());
+}
+
+// Creates a polymorphic matcher that matches any non-NULL pointer.
+// This is convenient as Not(NULL) doesn't compile (the compiler
+// thinks that that expression is comparing a pointer with an integer).
+inline PolymorphicMatcher<internal::NotNullMatcher > NotNull() {
+  return MakePolymorphicMatcher(internal::NotNullMatcher());
+}
+
+// Creates a polymorphic matcher that matches any argument that
+// references variable x.
+template <typename T>
+inline internal::RefMatcher<T&> Ref(T& x) {  // NOLINT
+  return internal::RefMatcher<T&>(x);
+}
+
+// Creates a polymorphic matcher that matches any NaN floating point.
+inline PolymorphicMatcher<internal::IsNanMatcher> IsNan() {
+  return MakePolymorphicMatcher(internal::IsNanMatcher());
+}
+
+// Creates a matcher that matches any double argument approximately
+// equal to rhs, where two NANs are considered unequal.
+inline internal::FloatingEqMatcher<double> DoubleEq(double rhs) {
+  return internal::FloatingEqMatcher<double>(rhs, false);
+}
+
+// Creates a matcher that matches any double argument approximately
+// equal to rhs, including NaN values when rhs is NaN.
+inline internal::FloatingEqMatcher<double> NanSensitiveDoubleEq(double rhs) {
+  return internal::FloatingEqMatcher<double>(rhs, true);
+}
+
+// Creates a matcher that matches any double argument approximately equal to
+// rhs, up to the specified max absolute error bound, where two NANs are
+// considered unequal.  The max absolute error bound must be non-negative.
+inline internal::FloatingEqMatcher<double> DoubleNear(
+    double rhs, double max_abs_error) {
+  return internal::FloatingEqMatcher<double>(rhs, false, max_abs_error);
+}
+
+// Creates a matcher that matches any double argument approximately equal to
+// rhs, up to the specified max absolute error bound, including NaN values when
+// rhs is NaN.  The max absolute error bound must be non-negative.
+inline internal::FloatingEqMatcher<double> NanSensitiveDoubleNear(
+    double rhs, double max_abs_error) {
+  return internal::FloatingEqMatcher<double>(rhs, true, max_abs_error);
+}
+
+// Creates a matcher that matches any float argument approximately
+// equal to rhs, where two NANs are considered unequal.
+inline internal::FloatingEqMatcher<float> FloatEq(float rhs) {
+  return internal::FloatingEqMatcher<float>(rhs, false);
+}
+
+// Creates a matcher that matches any float argument approximately
+// equal to rhs, including NaN values when rhs is NaN.
+inline internal::FloatingEqMatcher<float> NanSensitiveFloatEq(float rhs) {
+  return internal::FloatingEqMatcher<float>(rhs, true);
+}
+
+// Creates a matcher that matches any float argument approximately equal to
+// rhs, up to the specified max absolute error bound, where two NANs are
+// considered unequal.  The max absolute error bound must be non-negative.
+inline internal::FloatingEqMatcher<float> FloatNear(
+    float rhs, float max_abs_error) {
+  return internal::FloatingEqMatcher<float>(rhs, false, max_abs_error);
+}
+
+// Creates a matcher that matches any float argument approximately equal to
+// rhs, up to the specified max absolute error bound, including NaN values when
+// rhs is NaN.  The max absolute error bound must be non-negative.
+inline internal::FloatingEqMatcher<float> NanSensitiveFloatNear(
+    float rhs, float max_abs_error) {
+  return internal::FloatingEqMatcher<float>(rhs, true, max_abs_error);
+}
+
+// Creates a matcher that matches a pointer (raw or smart) that points
+// to a value that matches inner_matcher.
+template <typename InnerMatcher>
+inline internal::PointeeMatcher<InnerMatcher> Pointee(
+    const InnerMatcher& inner_matcher) {
+  return internal::PointeeMatcher<InnerMatcher>(inner_matcher);
+}
+
+#if GTEST_HAS_RTTI
+// Creates a matcher that matches a pointer or reference that matches
+// inner_matcher when dynamic_cast<To> is applied.
+// The result of dynamic_cast<To> is forwarded to the inner matcher.
+// If To is a pointer and the cast fails, the inner matcher will receive NULL.
+// If To is a reference and the cast fails, this matcher returns false
+// immediately.
+template <typename To>
+inline PolymorphicMatcher<internal::WhenDynamicCastToMatcher<To> >
+WhenDynamicCastTo(const Matcher<To>& inner_matcher) {
+  return MakePolymorphicMatcher(
+      internal::WhenDynamicCastToMatcher<To>(inner_matcher));
+}
+#endif  // GTEST_HAS_RTTI
+
+// Creates a matcher that matches an object whose given field matches
+// 'matcher'.  For example,
+//   Field(&Foo::number, Ge(5))
+// matches a Foo object x if and only if x.number >= 5.
+template <typename Class, typename FieldType, typename FieldMatcher>
+inline PolymorphicMatcher<
+  internal::FieldMatcher<Class, FieldType> > Field(
+    FieldType Class::*field, const FieldMatcher& matcher) {
+  return MakePolymorphicMatcher(
+      internal::FieldMatcher<Class, FieldType>(
+          field, MatcherCast<const FieldType&>(matcher)));
+  // The call to MatcherCast() is required for supporting inner
+  // matchers of compatible types.  For example, it allows
+  //   Field(&Foo::bar, m)
+  // to compile where bar is an int32 and m is a matcher for int64.
+}
+
+// Same as Field() but also takes the name of the field to provide better error
+// messages.
+template <typename Class, typename FieldType, typename FieldMatcher>
+inline PolymorphicMatcher<internal::FieldMatcher<Class, FieldType> > Field(
+    const std::string& field_name, FieldType Class::*field,
+    const FieldMatcher& matcher) {
+  return MakePolymorphicMatcher(internal::FieldMatcher<Class, FieldType>(
+      field_name, field, MatcherCast<const FieldType&>(matcher)));
+}
+
+// Creates a matcher that matches an object whose given property
+// matches 'matcher'.  For example,
+//   Property(&Foo::str, StartsWith("hi"))
+// matches a Foo object x if and only if x.str() starts with "hi".
+template <typename Class, typename PropertyType, typename PropertyMatcher>
+inline PolymorphicMatcher<internal::PropertyMatcher<
+    Class, PropertyType, PropertyType (Class::*)() const> >
+Property(PropertyType (Class::*property)() const,
+         const PropertyMatcher& matcher) {
+  return MakePolymorphicMatcher(
+      internal::PropertyMatcher<Class, PropertyType,
+                                PropertyType (Class::*)() const>(
+          property, MatcherCast<const PropertyType&>(matcher)));
+  // The call to MatcherCast() is required for supporting inner
+  // matchers of compatible types.  For example, it allows
+  //   Property(&Foo::bar, m)
+  // to compile where bar() returns an int32 and m is a matcher for int64.
+}
+
+// Same as Property() above, but also takes the name of the property to provide
+// better error messages.
+template <typename Class, typename PropertyType, typename PropertyMatcher>
+inline PolymorphicMatcher<internal::PropertyMatcher<
+    Class, PropertyType, PropertyType (Class::*)() const> >
+Property(const std::string& property_name,
+         PropertyType (Class::*property)() const,
+         const PropertyMatcher& matcher) {
+  return MakePolymorphicMatcher(
+      internal::PropertyMatcher<Class, PropertyType,
+                                PropertyType (Class::*)() const>(
+          property_name, property, MatcherCast<const PropertyType&>(matcher)));
+}
+
+// The same as above but for reference-qualified member functions.
+template <typename Class, typename PropertyType, typename PropertyMatcher>
+inline PolymorphicMatcher<internal::PropertyMatcher<
+    Class, PropertyType, PropertyType (Class::*)() const &> >
+Property(PropertyType (Class::*property)() const &,
+         const PropertyMatcher& matcher) {
+  return MakePolymorphicMatcher(
+      internal::PropertyMatcher<Class, PropertyType,
+                                PropertyType (Class::*)() const&>(
+          property, MatcherCast<const PropertyType&>(matcher)));
+}
+
+// Three-argument form for reference-qualified member functions.
+template <typename Class, typename PropertyType, typename PropertyMatcher>
+inline PolymorphicMatcher<internal::PropertyMatcher<
+    Class, PropertyType, PropertyType (Class::*)() const &> >
+Property(const std::string& property_name,
+         PropertyType (Class::*property)() const &,
+         const PropertyMatcher& matcher) {
+  return MakePolymorphicMatcher(
+      internal::PropertyMatcher<Class, PropertyType,
+                                PropertyType (Class::*)() const&>(
+          property_name, property, MatcherCast<const PropertyType&>(matcher)));
+}
+
+// Creates a matcher that matches an object if and only if the result of
+// applying a callable to x matches 'matcher'. For example,
+//   ResultOf(f, StartsWith("hi"))
+// matches a Foo object x if and only if f(x) starts with "hi".
+// `callable` parameter can be a function, function pointer, or a functor. It is
+// required to keep no state affecting the results of the calls on it and make
+// no assumptions about how many calls will be made. Any state it keeps must be
+// protected from the concurrent access.
+template <typename Callable, typename InnerMatcher>
+internal::ResultOfMatcher<Callable, InnerMatcher> ResultOf(
+    Callable callable, InnerMatcher matcher) {
+  return internal::ResultOfMatcher<Callable, InnerMatcher>(
+      std::move(callable), std::move(matcher));
+}
+
+// String matchers.
+
+// Matches a string equal to str.
+template <typename T = std::string>
+PolymorphicMatcher<internal::StrEqualityMatcher<std::string> > StrEq(
+    const internal::StringLike<T>& str) {
+  return MakePolymorphicMatcher(
+      internal::StrEqualityMatcher<std::string>(std::string(str), true, true));
+}
+
+// Matches a string not equal to str.
+template <typename T = std::string>
+PolymorphicMatcher<internal::StrEqualityMatcher<std::string> > StrNe(
+    const internal::StringLike<T>& str) {
+  return MakePolymorphicMatcher(
+      internal::StrEqualityMatcher<std::string>(std::string(str), false, true));
+}
+
+// Matches a string equal to str, ignoring case.
+template <typename T = std::string>
+PolymorphicMatcher<internal::StrEqualityMatcher<std::string> > StrCaseEq(
+    const internal::StringLike<T>& str) {
+  return MakePolymorphicMatcher(
+      internal::StrEqualityMatcher<std::string>(std::string(str), true, false));
+}
+
+// Matches a string not equal to str, ignoring case.
+template <typename T = std::string>
+PolymorphicMatcher<internal::StrEqualityMatcher<std::string> > StrCaseNe(
+    const internal::StringLike<T>& str) {
+  return MakePolymorphicMatcher(internal::StrEqualityMatcher<std::string>(
+      std::string(str), false, false));
+}
+
+// Creates a matcher that matches any string, std::string, or C string
+// that contains the given substring.
+template <typename T = std::string>
+PolymorphicMatcher<internal::HasSubstrMatcher<std::string> > HasSubstr(
+    const internal::StringLike<T>& substring) {
+  return MakePolymorphicMatcher(
+      internal::HasSubstrMatcher<std::string>(std::string(substring)));
+}
+
+// Matches a string that starts with 'prefix' (case-sensitive).
+template <typename T = std::string>
+PolymorphicMatcher<internal::StartsWithMatcher<std::string> > StartsWith(
+    const internal::StringLike<T>& prefix) {
+  return MakePolymorphicMatcher(
+      internal::StartsWithMatcher<std::string>(std::string(prefix)));
+}
+
+// Matches a string that ends with 'suffix' (case-sensitive).
+template <typename T = std::string>
+PolymorphicMatcher<internal::EndsWithMatcher<std::string> > EndsWith(
+    const internal::StringLike<T>& suffix) {
+  return MakePolymorphicMatcher(
+      internal::EndsWithMatcher<std::string>(std::string(suffix)));
+}
+
+#if GTEST_HAS_STD_WSTRING
+// Wide string matchers.
+
+// Matches a string equal to str.
+inline PolymorphicMatcher<internal::StrEqualityMatcher<std::wstring> > StrEq(
+    const std::wstring& str) {
+  return MakePolymorphicMatcher(
+      internal::StrEqualityMatcher<std::wstring>(str, true, true));
+}
+
+// Matches a string not equal to str.
+inline PolymorphicMatcher<internal::StrEqualityMatcher<std::wstring> > StrNe(
+    const std::wstring& str) {
+  return MakePolymorphicMatcher(
+      internal::StrEqualityMatcher<std::wstring>(str, false, true));
+}
+
+// Matches a string equal to str, ignoring case.
+inline PolymorphicMatcher<internal::StrEqualityMatcher<std::wstring> >
+StrCaseEq(const std::wstring& str) {
+  return MakePolymorphicMatcher(
+      internal::StrEqualityMatcher<std::wstring>(str, true, false));
+}
+
+// Matches a string not equal to str, ignoring case.
+inline PolymorphicMatcher<internal::StrEqualityMatcher<std::wstring> >
+StrCaseNe(const std::wstring& str) {
+  return MakePolymorphicMatcher(
+      internal::StrEqualityMatcher<std::wstring>(str, false, false));
+}
+
+// Creates a matcher that matches any ::wstring, std::wstring, or C wide string
+// that contains the given substring.
+inline PolymorphicMatcher<internal::HasSubstrMatcher<std::wstring> > HasSubstr(
+    const std::wstring& substring) {
+  return MakePolymorphicMatcher(
+      internal::HasSubstrMatcher<std::wstring>(substring));
+}
+
+// Matches a string that starts with 'prefix' (case-sensitive).
+inline PolymorphicMatcher<internal::StartsWithMatcher<std::wstring> >
+StartsWith(const std::wstring& prefix) {
+  return MakePolymorphicMatcher(
+      internal::StartsWithMatcher<std::wstring>(prefix));
+}
+
+// Matches a string that ends with 'suffix' (case-sensitive).
+inline PolymorphicMatcher<internal::EndsWithMatcher<std::wstring> > EndsWith(
+    const std::wstring& suffix) {
+  return MakePolymorphicMatcher(
+      internal::EndsWithMatcher<std::wstring>(suffix));
+}
+
+#endif  // GTEST_HAS_STD_WSTRING
+
+// Creates a polymorphic matcher that matches a 2-tuple where the
+// first field == the second field.
+inline internal::Eq2Matcher Eq() { return internal::Eq2Matcher(); }
+
+// Creates a polymorphic matcher that matches a 2-tuple where the
+// first field >= the second field.
+inline internal::Ge2Matcher Ge() { return internal::Ge2Matcher(); }
+
+// Creates a polymorphic matcher that matches a 2-tuple where the
+// first field > the second field.
+inline internal::Gt2Matcher Gt() { return internal::Gt2Matcher(); }
+
+// Creates a polymorphic matcher that matches a 2-tuple where the
+// first field <= the second field.
+inline internal::Le2Matcher Le() { return internal::Le2Matcher(); }
+
+// Creates a polymorphic matcher that matches a 2-tuple where the
+// first field < the second field.
+inline internal::Lt2Matcher Lt() { return internal::Lt2Matcher(); }
+
+// Creates a polymorphic matcher that matches a 2-tuple where the
+// first field != the second field.
+inline internal::Ne2Matcher Ne() { return internal::Ne2Matcher(); }
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// FloatEq(first field) matches the second field.
+inline internal::FloatingEq2Matcher<float> FloatEq() {
+  return internal::FloatingEq2Matcher<float>();
+}
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// DoubleEq(first field) matches the second field.
+inline internal::FloatingEq2Matcher<double> DoubleEq() {
+  return internal::FloatingEq2Matcher<double>();
+}
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// FloatEq(first field) matches the second field with NaN equality.
+inline internal::FloatingEq2Matcher<float> NanSensitiveFloatEq() {
+  return internal::FloatingEq2Matcher<float>(true);
+}
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// DoubleEq(first field) matches the second field with NaN equality.
+inline internal::FloatingEq2Matcher<double> NanSensitiveDoubleEq() {
+  return internal::FloatingEq2Matcher<double>(true);
+}
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// FloatNear(first field, max_abs_error) matches the second field.
+inline internal::FloatingEq2Matcher<float> FloatNear(float max_abs_error) {
+  return internal::FloatingEq2Matcher<float>(max_abs_error);
+}
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// DoubleNear(first field, max_abs_error) matches the second field.
+inline internal::FloatingEq2Matcher<double> DoubleNear(double max_abs_error) {
+  return internal::FloatingEq2Matcher<double>(max_abs_error);
+}
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// FloatNear(first field, max_abs_error) matches the second field with NaN
+// equality.
+inline internal::FloatingEq2Matcher<float> NanSensitiveFloatNear(
+    float max_abs_error) {
+  return internal::FloatingEq2Matcher<float>(max_abs_error, true);
+}
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// DoubleNear(first field, max_abs_error) matches the second field with NaN
+// equality.
+inline internal::FloatingEq2Matcher<double> NanSensitiveDoubleNear(
+    double max_abs_error) {
+  return internal::FloatingEq2Matcher<double>(max_abs_error, true);
+}
+
+// Creates a matcher that matches any value of type T that m doesn't
+// match.
+template <typename InnerMatcher>
+inline internal::NotMatcher<InnerMatcher> Not(InnerMatcher m) {
+  return internal::NotMatcher<InnerMatcher>(m);
+}
+
+// Returns a matcher that matches anything that satisfies the given
+// predicate.  The predicate can be any unary function or functor
+// whose return type can be implicitly converted to bool.
+template <typename Predicate>
+inline PolymorphicMatcher<internal::TrulyMatcher<Predicate> >
+Truly(Predicate pred) {
+  return MakePolymorphicMatcher(internal::TrulyMatcher<Predicate>(pred));
+}
+
+// Returns a matcher that matches the container size. The container must
+// support both size() and size_type which all STL-like containers provide.
+// Note that the parameter 'size' can be a value of type size_type as well as
+// matcher. For instance:
+//   EXPECT_THAT(container, SizeIs(2));     // Checks container has 2 elements.
+//   EXPECT_THAT(container, SizeIs(Le(2));  // Checks container has at most 2.
+template <typename SizeMatcher>
+inline internal::SizeIsMatcher<SizeMatcher>
+SizeIs(const SizeMatcher& size_matcher) {
+  return internal::SizeIsMatcher<SizeMatcher>(size_matcher);
+}
+
+// Returns a matcher that matches the distance between the container's begin()
+// iterator and its end() iterator, i.e. the size of the container. This matcher
+// can be used instead of SizeIs with containers such as std::forward_list which
+// do not implement size(). The container must provide const_iterator (with
+// valid iterator_traits), begin() and end().
+template <typename DistanceMatcher>
+inline internal::BeginEndDistanceIsMatcher<DistanceMatcher>
+BeginEndDistanceIs(const DistanceMatcher& distance_matcher) {
+  return internal::BeginEndDistanceIsMatcher<DistanceMatcher>(distance_matcher);
+}
+
+// Returns a matcher that matches an equal container.
+// This matcher behaves like Eq(), but in the event of mismatch lists the
+// values that are included in one container but not the other. (Duplicate
+// values and order differences are not explained.)
+template <typename Container>
+inline PolymorphicMatcher<internal::ContainerEqMatcher<
+    typename std::remove_const<Container>::type>>
+ContainerEq(const Container& rhs) {
+  return MakePolymorphicMatcher(internal::ContainerEqMatcher<Container>(rhs));
+}
+
+// Returns a matcher that matches a container that, when sorted using
+// the given comparator, matches container_matcher.
+template <typename Comparator, typename ContainerMatcher>
+inline internal::WhenSortedByMatcher<Comparator, ContainerMatcher>
+WhenSortedBy(const Comparator& comparator,
+             const ContainerMatcher& container_matcher) {
+  return internal::WhenSortedByMatcher<Comparator, ContainerMatcher>(
+      comparator, container_matcher);
+}
+
+// Returns a matcher that matches a container that, when sorted using
+// the < operator, matches container_matcher.
+template <typename ContainerMatcher>
+inline internal::WhenSortedByMatcher<internal::LessComparator, ContainerMatcher>
+WhenSorted(const ContainerMatcher& container_matcher) {
+  return
+      internal::WhenSortedByMatcher<internal::LessComparator, ContainerMatcher>(
+          internal::LessComparator(), container_matcher);
+}
+
+// Matches an STL-style container or a native array that contains the
+// same number of elements as in rhs, where its i-th element and rhs's
+// i-th element (as a pair) satisfy the given pair matcher, for all i.
+// TupleMatcher must be able to be safely cast to Matcher<std::tuple<const
+// T1&, const T2&> >, where T1 and T2 are the types of elements in the
+// LHS container and the RHS container respectively.
+template <typename TupleMatcher, typename Container>
+inline internal::PointwiseMatcher<TupleMatcher,
+                                  typename std::remove_const<Container>::type>
+Pointwise(const TupleMatcher& tuple_matcher, const Container& rhs) {
+  return internal::PointwiseMatcher<TupleMatcher, Container>(tuple_matcher,
+                                                             rhs);
+}
+
+
+// Supports the Pointwise(m, {a, b, c}) syntax.
+template <typename TupleMatcher, typename T>
+inline internal::PointwiseMatcher<TupleMatcher, std::vector<T> > Pointwise(
+    const TupleMatcher& tuple_matcher, std::initializer_list<T> rhs) {
+  return Pointwise(tuple_matcher, std::vector<T>(rhs));
+}
+
+
+// UnorderedPointwise(pair_matcher, rhs) matches an STL-style
+// container or a native array that contains the same number of
+// elements as in rhs, where in some permutation of the container, its
+// i-th element and rhs's i-th element (as a pair) satisfy the given
+// pair matcher, for all i.  Tuple2Matcher must be able to be safely
+// cast to Matcher<std::tuple<const T1&, const T2&> >, where T1 and T2 are
+// the types of elements in the LHS container and the RHS container
+// respectively.
+//
+// This is like Pointwise(pair_matcher, rhs), except that the element
+// order doesn't matter.
+template <typename Tuple2Matcher, typename RhsContainer>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename internal::BoundSecondMatcher<
+        Tuple2Matcher,
+        typename internal::StlContainerView<
+            typename std::remove_const<RhsContainer>::type>::type::value_type>>
+UnorderedPointwise(const Tuple2Matcher& tuple2_matcher,
+                   const RhsContainer& rhs_container) {
+  // RhsView allows the same code to handle RhsContainer being a
+  // STL-style container and it being a native C-style array.
+  typedef typename internal::StlContainerView<RhsContainer> RhsView;
+  typedef typename RhsView::type RhsStlContainer;
+  typedef typename RhsStlContainer::value_type Second;
+  const RhsStlContainer& rhs_stl_container =
+      RhsView::ConstReference(rhs_container);
+
+  // Create a matcher for each element in rhs_container.
+  ::std::vector<internal::BoundSecondMatcher<Tuple2Matcher, Second> > matchers;
+  for (typename RhsStlContainer::const_iterator it = rhs_stl_container.begin();
+       it != rhs_stl_container.end(); ++it) {
+    matchers.push_back(
+        internal::MatcherBindSecond(tuple2_matcher, *it));
+  }
+
+  // Delegate the work to UnorderedElementsAreArray().
+  return UnorderedElementsAreArray(matchers);
+}
+
+
+// Supports the UnorderedPointwise(m, {a, b, c}) syntax.
+template <typename Tuple2Matcher, typename T>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename internal::BoundSecondMatcher<Tuple2Matcher, T> >
+UnorderedPointwise(const Tuple2Matcher& tuple2_matcher,
+                   std::initializer_list<T> rhs) {
+  return UnorderedPointwise(tuple2_matcher, std::vector<T>(rhs));
+}
+
+
+// Matches an STL-style container or a native array that contains at
+// least one element matching the given value or matcher.
+//
+// Examples:
+//   ::std::set<int> page_ids;
+//   page_ids.insert(3);
+//   page_ids.insert(1);
+//   EXPECT_THAT(page_ids, Contains(1));
+//   EXPECT_THAT(page_ids, Contains(Gt(2)));
+//   EXPECT_THAT(page_ids, Not(Contains(4)));
+//
+//   ::std::map<int, size_t> page_lengths;
+//   page_lengths[1] = 100;
+//   EXPECT_THAT(page_lengths,
+//               Contains(::std::pair<const int, size_t>(1, 100)));
+//
+//   const char* user_ids[] = { "joe", "mike", "tom" };
+//   EXPECT_THAT(user_ids, Contains(Eq(::std::string("tom"))));
+template <typename M>
+inline internal::ContainsMatcher<M> Contains(M matcher) {
+  return internal::ContainsMatcher<M>(matcher);
+}
+
+// IsSupersetOf(iterator_first, iterator_last)
+// IsSupersetOf(pointer, count)
+// IsSupersetOf(array)
+// IsSupersetOf(container)
+// IsSupersetOf({e1, e2, ..., en})
+//
+// IsSupersetOf() verifies that a surjective partial mapping onto a collection
+// of matchers exists. In other words, a container matches
+// IsSupersetOf({e1, ..., en}) if and only if there is a permutation
+// {y1, ..., yn} of some of the container's elements where y1 matches e1,
+// ..., and yn matches en. Obviously, the size of the container must be >= n
+// in order to have a match. Examples:
+//
+// - {1, 2, 3} matches IsSupersetOf({Ge(3), Ne(0)}), as 3 matches Ge(3) and
+//   1 matches Ne(0).
+// - {1, 2} doesn't match IsSupersetOf({Eq(1), Lt(2)}), even though 1 matches
+//   both Eq(1) and Lt(2). The reason is that different matchers must be used
+//   for elements in different slots of the container.
+// - {1, 1, 2} matches IsSupersetOf({Eq(1), Lt(2)}), as (the first) 1 matches
+//   Eq(1) and (the second) 1 matches Lt(2).
+// - {1, 2, 3} matches IsSupersetOf(Gt(1), Gt(1)), as 2 matches (the first)
+//   Gt(1) and 3 matches (the second) Gt(1).
+//
+// The matchers can be specified as an array, a pointer and count, a container,
+// an initializer list, or an STL iterator range. In each of these cases, the
+// underlying matchers can be either values or matchers.
+
+template <typename Iter>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename ::std::iterator_traits<Iter>::value_type>
+IsSupersetOf(Iter first, Iter last) {
+  typedef typename ::std::iterator_traits<Iter>::value_type T;
+  return internal::UnorderedElementsAreArrayMatcher<T>(
+      internal::UnorderedMatcherRequire::Superset, first, last);
+}
+
+template <typename T>
+inline internal::UnorderedElementsAreArrayMatcher<T> IsSupersetOf(
+    const T* pointer, size_t count) {
+  return IsSupersetOf(pointer, pointer + count);
+}
+
+template <typename T, size_t N>
+inline internal::UnorderedElementsAreArrayMatcher<T> IsSupersetOf(
+    const T (&array)[N]) {
+  return IsSupersetOf(array, N);
+}
+
+template <typename Container>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename Container::value_type>
+IsSupersetOf(const Container& container) {
+  return IsSupersetOf(container.begin(), container.end());
+}
+
+template <typename T>
+inline internal::UnorderedElementsAreArrayMatcher<T> IsSupersetOf(
+    ::std::initializer_list<T> xs) {
+  return IsSupersetOf(xs.begin(), xs.end());
+}
+
+// IsSubsetOf(iterator_first, iterator_last)
+// IsSubsetOf(pointer, count)
+// IsSubsetOf(array)
+// IsSubsetOf(container)
+// IsSubsetOf({e1, e2, ..., en})
+//
+// IsSubsetOf() verifies that an injective mapping onto a collection of matchers
+// exists.  In other words, a container matches IsSubsetOf({e1, ..., en}) if and
+// only if there is a subset of matchers {m1, ..., mk} which would match the
+// container using UnorderedElementsAre.  Obviously, the size of the container
+// must be <= n in order to have a match. Examples:
+//
+// - {1} matches IsSubsetOf({Gt(0), Lt(0)}), as 1 matches Gt(0).
+// - {1, -1} matches IsSubsetOf({Lt(0), Gt(0)}), as 1 matches Gt(0) and -1
+//   matches Lt(0).
+// - {1, 2} doesn't matches IsSubsetOf({Gt(0), Lt(0)}), even though 1 and 2 both
+//   match Gt(0). The reason is that different matchers must be used for
+//   elements in different slots of the container.
+//
+// The matchers can be specified as an array, a pointer and count, a container,
+// an initializer list, or an STL iterator range. In each of these cases, the
+// underlying matchers can be either values or matchers.
+
+template <typename Iter>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename ::std::iterator_traits<Iter>::value_type>
+IsSubsetOf(Iter first, Iter last) {
+  typedef typename ::std::iterator_traits<Iter>::value_type T;
+  return internal::UnorderedElementsAreArrayMatcher<T>(
+      internal::UnorderedMatcherRequire::Subset, first, last);
+}
+
+template <typename T>
+inline internal::UnorderedElementsAreArrayMatcher<T> IsSubsetOf(
+    const T* pointer, size_t count) {
+  return IsSubsetOf(pointer, pointer + count);
+}
+
+template <typename T, size_t N>
+inline internal::UnorderedElementsAreArrayMatcher<T> IsSubsetOf(
+    const T (&array)[N]) {
+  return IsSubsetOf(array, N);
+}
+
+template <typename Container>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename Container::value_type>
+IsSubsetOf(const Container& container) {
+  return IsSubsetOf(container.begin(), container.end());
+}
+
+template <typename T>
+inline internal::UnorderedElementsAreArrayMatcher<T> IsSubsetOf(
+    ::std::initializer_list<T> xs) {
+  return IsSubsetOf(xs.begin(), xs.end());
+}
+
+// Matches an STL-style container or a native array that contains only
+// elements matching the given value or matcher.
+//
+// Each(m) is semantically equivalent to Not(Contains(Not(m))). Only
+// the messages are different.
+//
+// Examples:
+//   ::std::set<int> page_ids;
+//   // Each(m) matches an empty container, regardless of what m is.
+//   EXPECT_THAT(page_ids, Each(Eq(1)));
+//   EXPECT_THAT(page_ids, Each(Eq(77)));
+//
+//   page_ids.insert(3);
+//   EXPECT_THAT(page_ids, Each(Gt(0)));
+//   EXPECT_THAT(page_ids, Not(Each(Gt(4))));
+//   page_ids.insert(1);
+//   EXPECT_THAT(page_ids, Not(Each(Lt(2))));
+//
+//   ::std::map<int, size_t> page_lengths;
+//   page_lengths[1] = 100;
+//   page_lengths[2] = 200;
+//   page_lengths[3] = 300;
+//   EXPECT_THAT(page_lengths, Not(Each(Pair(1, 100))));
+//   EXPECT_THAT(page_lengths, Each(Key(Le(3))));
+//
+//   const char* user_ids[] = { "joe", "mike", "tom" };
+//   EXPECT_THAT(user_ids, Not(Each(Eq(::std::string("tom")))));
+template <typename M>
+inline internal::EachMatcher<M> Each(M matcher) {
+  return internal::EachMatcher<M>(matcher);
+}
+
+// Key(inner_matcher) matches an std::pair whose 'first' field matches
+// inner_matcher.  For example, Contains(Key(Ge(5))) can be used to match an
+// std::map that contains at least one element whose key is >= 5.
+template <typename M>
+inline internal::KeyMatcher<M> Key(M inner_matcher) {
+  return internal::KeyMatcher<M>(inner_matcher);
+}
+
+// Pair(first_matcher, second_matcher) matches a std::pair whose 'first' field
+// matches first_matcher and whose 'second' field matches second_matcher.  For
+// example, EXPECT_THAT(map_type, ElementsAre(Pair(Ge(5), "foo"))) can be used
+// to match a std::map<int, string> that contains exactly one element whose key
+// is >= 5 and whose value equals "foo".
+template <typename FirstMatcher, typename SecondMatcher>
+inline internal::PairMatcher<FirstMatcher, SecondMatcher>
+Pair(FirstMatcher first_matcher, SecondMatcher second_matcher) {
+  return internal::PairMatcher<FirstMatcher, SecondMatcher>(
+      first_matcher, second_matcher);
+}
+
+namespace no_adl {
+// FieldsAre(matchers...) matches piecewise the fields of compatible structs.
+// These include those that support `get<I>(obj)`, and when structured bindings
+// are enabled any class that supports them.
+// In particular, `std::tuple`, `std::pair`, `std::array` and aggregate types.
+template <typename... M>
+internal::FieldsAreMatcher<typename std::decay<M>::type...> FieldsAre(
+    M&&... matchers) {
+  return internal::FieldsAreMatcher<typename std::decay<M>::type...>(
+      std::forward<M>(matchers)...);
+}
+
+// Creates a matcher that matches a pointer (raw or smart) that matches
+// inner_matcher.
+template <typename InnerMatcher>
+inline internal::PointerMatcher<InnerMatcher> Pointer(
+    const InnerMatcher& inner_matcher) {
+  return internal::PointerMatcher<InnerMatcher>(inner_matcher);
+}
+
+// Creates a matcher that matches an object that has an address that matches
+// inner_matcher.
+template <typename InnerMatcher>
+inline internal::AddressMatcher<InnerMatcher> Address(
+    const InnerMatcher& inner_matcher) {
+  return internal::AddressMatcher<InnerMatcher>(inner_matcher);
+}
+}  // namespace no_adl
+
+// Returns a predicate that is satisfied by anything that matches the
+// given matcher.
+template <typename M>
+inline internal::MatcherAsPredicate<M> Matches(M matcher) {
+  return internal::MatcherAsPredicate<M>(matcher);
+}
+
+// Returns true if and only if the value matches the matcher.
+template <typename T, typename M>
+inline bool Value(const T& value, M matcher) {
+  return testing::Matches(matcher)(value);
+}
+
+// Matches the value against the given matcher and explains the match
+// result to listener.
+template <typename T, typename M>
+inline bool ExplainMatchResult(
+    M matcher, const T& value, MatchResultListener* listener) {
+  return SafeMatcherCast<const T&>(matcher).MatchAndExplain(value, listener);
+}
+
+// Returns a string representation of the given matcher.  Useful for description
+// strings of matchers defined using MATCHER_P* macros that accept matchers as
+// their arguments.  For example:
+//
+// MATCHER_P(XAndYThat, matcher,
+//           "X that " + DescribeMatcher<int>(matcher, negation) +
+//               " and Y that " + DescribeMatcher<double>(matcher, negation)) {
+//   return ExplainMatchResult(matcher, arg.x(), result_listener) &&
+//          ExplainMatchResult(matcher, arg.y(), result_listener);
+// }
+template <typename T, typename M>
+std::string DescribeMatcher(const M& matcher, bool negation = false) {
+  ::std::stringstream ss;
+  Matcher<T> monomorphic_matcher = SafeMatcherCast<T>(matcher);
+  if (negation) {
+    monomorphic_matcher.DescribeNegationTo(&ss);
+  } else {
+    monomorphic_matcher.DescribeTo(&ss);
+  }
+  return ss.str();
+}
+
+template <typename... Args>
+internal::ElementsAreMatcher<
+    std::tuple<typename std::decay<const Args&>::type...>>
+ElementsAre(const Args&... matchers) {
+  return internal::ElementsAreMatcher<
+      std::tuple<typename std::decay<const Args&>::type...>>(
+      std::make_tuple(matchers...));
+}
+
+template <typename... Args>
+internal::UnorderedElementsAreMatcher<
+    std::tuple<typename std::decay<const Args&>::type...>>
+UnorderedElementsAre(const Args&... matchers) {
+  return internal::UnorderedElementsAreMatcher<
+      std::tuple<typename std::decay<const Args&>::type...>>(
+      std::make_tuple(matchers...));
+}
+
+// Define variadic matcher versions.
+template <typename... Args>
+internal::AllOfMatcher<typename std::decay<const Args&>::type...> AllOf(
+    const Args&... matchers) {
+  return internal::AllOfMatcher<typename std::decay<const Args&>::type...>(
+      matchers...);
+}
+
+template <typename... Args>
+internal::AnyOfMatcher<typename std::decay<const Args&>::type...> AnyOf(
+    const Args&... matchers) {
+  return internal::AnyOfMatcher<typename std::decay<const Args&>::type...>(
+      matchers...);
+}
+
+// AnyOfArray(array)
+// AnyOfArray(pointer, count)
+// AnyOfArray(container)
+// AnyOfArray({ e1, e2, ..., en })
+// AnyOfArray(iterator_first, iterator_last)
+//
+// AnyOfArray() verifies whether a given value matches any member of a
+// collection of matchers.
+//
+// AllOfArray(array)
+// AllOfArray(pointer, count)
+// AllOfArray(container)
+// AllOfArray({ e1, e2, ..., en })
+// AllOfArray(iterator_first, iterator_last)
+//
+// AllOfArray() verifies whether a given value matches all members of a
+// collection of matchers.
+//
+// The matchers can be specified as an array, a pointer and count, a container,
+// an initializer list, or an STL iterator range. In each of these cases, the
+// underlying matchers can be either values or matchers.
+
+template <typename Iter>
+inline internal::AnyOfArrayMatcher<
+    typename ::std::iterator_traits<Iter>::value_type>
+AnyOfArray(Iter first, Iter last) {
+  return internal::AnyOfArrayMatcher<
+      typename ::std::iterator_traits<Iter>::value_type>(first, last);
+}
+
+template <typename Iter>
+inline internal::AllOfArrayMatcher<
+    typename ::std::iterator_traits<Iter>::value_type>
+AllOfArray(Iter first, Iter last) {
+  return internal::AllOfArrayMatcher<
+      typename ::std::iterator_traits<Iter>::value_type>(first, last);
+}
+
+template <typename T>
+inline internal::AnyOfArrayMatcher<T> AnyOfArray(const T* ptr, size_t count) {
+  return AnyOfArray(ptr, ptr + count);
+}
+
+template <typename T>
+inline internal::AllOfArrayMatcher<T> AllOfArray(const T* ptr, size_t count) {
+  return AllOfArray(ptr, ptr + count);
+}
+
+template <typename T, size_t N>
+inline internal::AnyOfArrayMatcher<T> AnyOfArray(const T (&array)[N]) {
+  return AnyOfArray(array, N);
+}
+
+template <typename T, size_t N>
+inline internal::AllOfArrayMatcher<T> AllOfArray(const T (&array)[N]) {
+  return AllOfArray(array, N);
+}
+
+template <typename Container>
+inline internal::AnyOfArrayMatcher<typename Container::value_type> AnyOfArray(
+    const Container& container) {
+  return AnyOfArray(container.begin(), container.end());
+}
+
+template <typename Container>
+inline internal::AllOfArrayMatcher<typename Container::value_type> AllOfArray(
+    const Container& container) {
+  return AllOfArray(container.begin(), container.end());
+}
+
+template <typename T>
+inline internal::AnyOfArrayMatcher<T> AnyOfArray(
+    ::std::initializer_list<T> xs) {
+  return AnyOfArray(xs.begin(), xs.end());
+}
+
+template <typename T>
+inline internal::AllOfArrayMatcher<T> AllOfArray(
+    ::std::initializer_list<T> xs) {
+  return AllOfArray(xs.begin(), xs.end());
+}
+
+// Args<N1, N2, ..., Nk>(a_matcher) matches a tuple if the selected
+// fields of it matches a_matcher.  C++ doesn't support default
+// arguments for function templates, so we have to overload it.
+template <size_t... k, typename InnerMatcher>
+internal::ArgsMatcher<typename std::decay<InnerMatcher>::type, k...> Args(
+    InnerMatcher&& matcher) {
+  return internal::ArgsMatcher<typename std::decay<InnerMatcher>::type, k...>(
+      std::forward<InnerMatcher>(matcher));
+}
+
+// AllArgs(m) is a synonym of m.  This is useful in
+//
+//   EXPECT_CALL(foo, Bar(_, _)).With(AllArgs(Eq()));
+//
+// which is easier to read than
+//
+//   EXPECT_CALL(foo, Bar(_, _)).With(Eq());
+template <typename InnerMatcher>
+inline InnerMatcher AllArgs(const InnerMatcher& matcher) { return matcher; }
+
+// Returns a matcher that matches the value of an optional<> type variable.
+// The matcher implementation only uses '!arg' and requires that the optional<>
+// type has a 'value_type' member type and that '*arg' is of type 'value_type'
+// and is printable using 'PrintToString'. It is compatible with
+// std::optional/std::experimental::optional.
+// Note that to compare an optional type variable against nullopt you should
+// use Eq(nullopt) and not Eq(Optional(nullopt)). The latter implies that the
+// optional value contains an optional itself.
+template <typename ValueMatcher>
+inline internal::OptionalMatcher<ValueMatcher> Optional(
+    const ValueMatcher& value_matcher) {
+  return internal::OptionalMatcher<ValueMatcher>(value_matcher);
+}
+
+// Returns a matcher that matches the value of a absl::any type variable.
+template <typename T>
+PolymorphicMatcher<internal::any_cast_matcher::AnyCastMatcher<T> > AnyWith(
+    const Matcher<const T&>& matcher) {
+  return MakePolymorphicMatcher(
+      internal::any_cast_matcher::AnyCastMatcher<T>(matcher));
+}
+
+// Returns a matcher that matches the value of a variant<> type variable.
+// The matcher implementation uses ADL to find the holds_alternative and get
+// functions.
+// It is compatible with std::variant.
+template <typename T>
+PolymorphicMatcher<internal::variant_matcher::VariantMatcher<T> > VariantWith(
+    const Matcher<const T&>& matcher) {
+  return MakePolymorphicMatcher(
+      internal::variant_matcher::VariantMatcher<T>(matcher));
+}
+
+#if GTEST_HAS_EXCEPTIONS
+
+// Anything inside the `internal` namespace is internal to the implementation
+// and must not be used in user code!
+namespace internal {
+
+class WithWhatMatcherImpl {
+ public:
+  WithWhatMatcherImpl(Matcher<std::string> matcher)
+      : matcher_(std::move(matcher)) {}
+
+  void DescribeTo(std::ostream* os) const {
+    *os << "contains .what() that ";
+    matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(std::ostream* os) const {
+    *os << "contains .what() that does not ";
+    matcher_.DescribeTo(os);
+  }
+
+  template <typename Err>
+  bool MatchAndExplain(const Err& err, MatchResultListener* listener) const {
+    *listener << "which contains .what() that ";
+    return matcher_.MatchAndExplain(err.what(), listener);
+  }
+
+ private:
+  const Matcher<std::string> matcher_;
+};
+
+inline PolymorphicMatcher<WithWhatMatcherImpl> WithWhat(
+    Matcher<std::string> m) {
+  return MakePolymorphicMatcher(WithWhatMatcherImpl(std::move(m)));
+}
+
+template <typename Err>
+class ExceptionMatcherImpl {
+  class NeverThrown {
+   public:
+    const char* what() const noexcept {
+      return "this exception should never be thrown";
+    }
+  };
+
+  // If the matchee raises an exception of a wrong type, we'd like to
+  // catch it and print its message and type. To do that, we add an additional
+  // catch clause:
+  //
+  //     try { ... }
+  //     catch (const Err&) { /* an expected exception */ }
+  //     catch (const std::exception&) { /* exception of a wrong type */ }
+  //
+  // However, if the `Err` itself is `std::exception`, we'd end up with two
+  // identical `catch` clauses:
+  //
+  //     try { ... }
+  //     catch (const std::exception&) { /* an expected exception */ }
+  //     catch (const std::exception&) { /* exception of a wrong type */ }
+  //
+  // This can cause a warning or an error in some compilers. To resolve
+  // the issue, we use a fake error type whenever `Err` is `std::exception`:
+  //
+  //     try { ... }
+  //     catch (const std::exception&) { /* an expected exception */ }
+  //     catch (const NeverThrown&) { /* exception of a wrong type */ }
+  using DefaultExceptionType = typename std::conditional<
+      std::is_same<typename std::remove_cv<
+                       typename std::remove_reference<Err>::type>::type,
+                   std::exception>::value,
+      const NeverThrown&, const std::exception&>::type;
+
+ public:
+  ExceptionMatcherImpl(Matcher<const Err&> matcher)
+      : matcher_(std::move(matcher)) {}
+
+  void DescribeTo(std::ostream* os) const {
+    *os << "throws an exception which is a " << GetTypeName<Err>();
+    *os << " which ";
+    matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(std::ostream* os) const {
+    *os << "throws an exception which is not a " << GetTypeName<Err>();
+    *os << " which ";
+    matcher_.DescribeNegationTo(os);
+  }
+
+  template <typename T>
+  bool MatchAndExplain(T&& x, MatchResultListener* listener) const {
+    try {
+      (void)(std::forward<T>(x)());
+    } catch (const Err& err) {
+      *listener << "throws an exception which is a " << GetTypeName<Err>();
+      *listener << " ";
+      return matcher_.MatchAndExplain(err, listener);
+    } catch (DefaultExceptionType err) {
+#if GTEST_HAS_RTTI
+      *listener << "throws an exception of type " << GetTypeName(typeid(err));
+      *listener << " ";
+#else
+      *listener << "throws an std::exception-derived type ";
+#endif
+      *listener << "with description \"" << err.what() << "\"";
+      return false;
+    } catch (...) {
+      *listener << "throws an exception of an unknown type";
+      return false;
+    }
+
+    *listener << "does not throw any exception";
+    return false;
+  }
+
+ private:
+  const Matcher<const Err&> matcher_;
+};
+
+}  // namespace internal
+
+// Throws()
+// Throws(exceptionMatcher)
+// ThrowsMessage(messageMatcher)
+//
+// This matcher accepts a callable and verifies that when invoked, it throws
+// an exception with the given type and properties.
+//
+// Examples:
+//
+//   EXPECT_THAT(
+//       []() { throw std::runtime_error("message"); },
+//       Throws<std::runtime_error>());
+//
+//   EXPECT_THAT(
+//       []() { throw std::runtime_error("message"); },
+//       ThrowsMessage<std::runtime_error>(HasSubstr("message")));
+//
+//   EXPECT_THAT(
+//       []() { throw std::runtime_error("message"); },
+//       Throws<std::runtime_error>(
+//           Property(&std::runtime_error::what, HasSubstr("message"))));
+
+template <typename Err>
+PolymorphicMatcher<internal::ExceptionMatcherImpl<Err>> Throws() {
+  return MakePolymorphicMatcher(
+      internal::ExceptionMatcherImpl<Err>(A<const Err&>()));
+}
+
+template <typename Err, typename ExceptionMatcher>
+PolymorphicMatcher<internal::ExceptionMatcherImpl<Err>> Throws(
+    const ExceptionMatcher& exception_matcher) {
+  // Using matcher cast allows users to pass a matcher of a more broad type.
+  // For example user may want to pass Matcher<std::exception>
+  // to Throws<std::runtime_error>, or Matcher<int64> to Throws<int32>.
+  return MakePolymorphicMatcher(internal::ExceptionMatcherImpl<Err>(
+      SafeMatcherCast<const Err&>(exception_matcher)));
+}
+
+template <typename Err, typename MessageMatcher>
+PolymorphicMatcher<internal::ExceptionMatcherImpl<Err>> ThrowsMessage(
+    MessageMatcher&& message_matcher) {
+  static_assert(std::is_base_of<std::exception, Err>::value,
+                "expected an std::exception-derived type");
+  return Throws<Err>(internal::WithWhat(
+      MatcherCast<std::string>(std::forward<MessageMatcher>(message_matcher))));
+}
+
+#endif  // GTEST_HAS_EXCEPTIONS
+
+// These macros allow using matchers to check values in Google Test
+// tests.  ASSERT_THAT(value, matcher) and EXPECT_THAT(value, matcher)
+// succeed if and only if the value matches the matcher.  If the assertion
+// fails, the value and the description of the matcher will be printed.
+#define ASSERT_THAT(value, matcher) ASSERT_PRED_FORMAT1(\
+    ::testing::internal::MakePredicateFormatterFromMatcher(matcher), value)
+#define EXPECT_THAT(value, matcher) EXPECT_PRED_FORMAT1(\
+    ::testing::internal::MakePredicateFormatterFromMatcher(matcher), value)
+
+// MATCHER* macroses itself are listed below.
+#define MATCHER(name, description)                                             \
+  class name##Matcher                                                          \
+      : public ::testing::internal::MatcherBaseImpl<name##Matcher> {           \
+   public:                                                                     \
+    template <typename arg_type>                                               \
+    class gmock_Impl : public ::testing::MatcherInterface<const arg_type&> {   \
+     public:                                                                   \
+      gmock_Impl() {}                                                          \
+      bool MatchAndExplain(                                                    \
+          const arg_type& arg,                                                 \
+          ::testing::MatchResultListener* result_listener) const override;     \
+      void DescribeTo(::std::ostream* gmock_os) const override {               \
+        *gmock_os << FormatDescription(false);                                 \
+      }                                                                        \
+      void DescribeNegationTo(::std::ostream* gmock_os) const override {       \
+        *gmock_os << FormatDescription(true);                                  \
+      }                                                                        \
+                                                                               \
+     private:                                                                  \
+      ::std::string FormatDescription(bool negation) const {                   \
+        ::std::string gmock_description = (description);                       \
+        if (!gmock_description.empty()) {                                      \
+          return gmock_description;                                            \
+        }                                                                      \
+        return ::testing::internal::FormatMatcherDescription(negation, #name,  \
+                                                             {});              \
+      }                                                                        \
+    };                                                                         \
+  };                                                                           \
+  GTEST_ATTRIBUTE_UNUSED_ inline name##Matcher name() { return {}; }           \
+  template <typename arg_type>                                                 \
+  bool name##Matcher::gmock_Impl<arg_type>::MatchAndExplain(                   \
+      const arg_type& arg,                                                     \
+      ::testing::MatchResultListener* result_listener GTEST_ATTRIBUTE_UNUSED_) \
+      const
+
+#define MATCHER_P(name, p0, description) \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP, description, (p0))
+#define MATCHER_P2(name, p0, p1, description) \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP2, description, (p0, p1))
+#define MATCHER_P3(name, p0, p1, p2, description) \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP3, description, (p0, p1, p2))
+#define MATCHER_P4(name, p0, p1, p2, p3, description) \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP4, description, (p0, p1, p2, p3))
+#define MATCHER_P5(name, p0, p1, p2, p3, p4, description)    \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP5, description, \
+                         (p0, p1, p2, p3, p4))
+#define MATCHER_P6(name, p0, p1, p2, p3, p4, p5, description) \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP6, description,  \
+                         (p0, p1, p2, p3, p4, p5))
+#define MATCHER_P7(name, p0, p1, p2, p3, p4, p5, p6, description) \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP7, description,      \
+                         (p0, p1, p2, p3, p4, p5, p6))
+#define MATCHER_P8(name, p0, p1, p2, p3, p4, p5, p6, p7, description) \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP8, description,          \
+                         (p0, p1, p2, p3, p4, p5, p6, p7))
+#define MATCHER_P9(name, p0, p1, p2, p3, p4, p5, p6, p7, p8, description) \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP9, description,              \
+                         (p0, p1, p2, p3, p4, p5, p6, p7, p8))
+#define MATCHER_P10(name, p0, p1, p2, p3, p4, p5, p6, p7, p8, p9, description) \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP10, description,                  \
+                         (p0, p1, p2, p3, p4, p5, p6, p7, p8, p9))
+
+#define GMOCK_INTERNAL_MATCHER(name, full_name, description, args)             \
+  template <GMOCK_INTERNAL_MATCHER_TEMPLATE_PARAMS(args)>                      \
+  class full_name : public ::testing::internal::MatcherBaseImpl<               \
+                        full_name<GMOCK_INTERNAL_MATCHER_TYPE_PARAMS(args)>> { \
+   public:                                                                     \
+    using full_name::MatcherBaseImpl::MatcherBaseImpl;                         \
+    template <typename arg_type>                                               \
+    class gmock_Impl : public ::testing::MatcherInterface<const arg_type&> {   \
+     public:                                                                   \
+      explicit gmock_Impl(GMOCK_INTERNAL_MATCHER_FUNCTION_ARGS(args))          \
+          : GMOCK_INTERNAL_MATCHER_FORWARD_ARGS(args) {}                       \
+      bool MatchAndExplain(                                                    \
+          const arg_type& arg,                                                 \
+          ::testing::MatchResultListener* result_listener) const override;     \
+      void DescribeTo(::std::ostream* gmock_os) const override {               \
+        *gmock_os << FormatDescription(false);                                 \
+      }                                                                        \
+      void DescribeNegationTo(::std::ostream* gmock_os) const override {       \
+        *gmock_os << FormatDescription(true);                                  \
+      }                                                                        \
+      GMOCK_INTERNAL_MATCHER_MEMBERS(args)                                     \
+                                                                               \
+     private:                                                                  \
+      ::std::string FormatDescription(bool negation) const {                   \
+        ::std::string gmock_description = (description);                       \
+        if (!gmock_description.empty()) {                                      \
+          return gmock_description;                                            \
+        }                                                                      \
+        return ::testing::internal::FormatMatcherDescription(                  \
+            negation, #name,                                                   \
+            ::testing::internal::UniversalTersePrintTupleFieldsToStrings(      \
+                ::std::tuple<GMOCK_INTERNAL_MATCHER_TYPE_PARAMS(args)>(        \
+                    GMOCK_INTERNAL_MATCHER_MEMBERS_USAGE(args))));             \
+      }                                                                        \
+    };                                                                         \
+  };                                                                           \
+  template <GMOCK_INTERNAL_MATCHER_TEMPLATE_PARAMS(args)>                      \
+  inline full_name<GMOCK_INTERNAL_MATCHER_TYPE_PARAMS(args)> name(             \
+      GMOCK_INTERNAL_MATCHER_FUNCTION_ARGS(args)) {                            \
+    return full_name<GMOCK_INTERNAL_MATCHER_TYPE_PARAMS(args)>(                \
+        GMOCK_INTERNAL_MATCHER_ARGS_USAGE(args));                              \
+  }                                                                            \
+  template <GMOCK_INTERNAL_MATCHER_TEMPLATE_PARAMS(args)>                      \
+  template <typename arg_type>                                                 \
+  bool full_name<GMOCK_INTERNAL_MATCHER_TYPE_PARAMS(args)>::gmock_Impl<        \
+      arg_type>::MatchAndExplain(const arg_type& arg,                          \
+                                 ::testing::MatchResultListener*               \
+                                     result_listener GTEST_ATTRIBUTE_UNUSED_)  \
+      const
+
+#define GMOCK_INTERNAL_MATCHER_TEMPLATE_PARAMS(args) \
+  GMOCK_PP_TAIL(                                     \
+      GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_MATCHER_TEMPLATE_PARAM, , args))
+#define GMOCK_INTERNAL_MATCHER_TEMPLATE_PARAM(i_unused, data_unused, arg) \
+  , typename arg##_type
+
+#define GMOCK_INTERNAL_MATCHER_TYPE_PARAMS(args) \
+  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_MATCHER_TYPE_PARAM, , args))
+#define GMOCK_INTERNAL_MATCHER_TYPE_PARAM(i_unused, data_unused, arg) \
+  , arg##_type
+
+#define GMOCK_INTERNAL_MATCHER_FUNCTION_ARGS(args) \
+  GMOCK_PP_TAIL(dummy_first GMOCK_PP_FOR_EACH(     \
+      GMOCK_INTERNAL_MATCHER_FUNCTION_ARG, , args))
+#define GMOCK_INTERNAL_MATCHER_FUNCTION_ARG(i, data_unused, arg) \
+  , arg##_type gmock_p##i
+
+#define GMOCK_INTERNAL_MATCHER_FORWARD_ARGS(args) \
+  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_MATCHER_FORWARD_ARG, , args))
+#define GMOCK_INTERNAL_MATCHER_FORWARD_ARG(i, data_unused, arg) \
+  , arg(::std::forward<arg##_type>(gmock_p##i))
+
+#define GMOCK_INTERNAL_MATCHER_MEMBERS(args) \
+  GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_MATCHER_MEMBER, , args)
+#define GMOCK_INTERNAL_MATCHER_MEMBER(i_unused, data_unused, arg) \
+  const arg##_type arg;
+
+#define GMOCK_INTERNAL_MATCHER_MEMBERS_USAGE(args) \
+  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_MATCHER_MEMBER_USAGE, , args))
+#define GMOCK_INTERNAL_MATCHER_MEMBER_USAGE(i_unused, data_unused, arg) , arg
+
+#define GMOCK_INTERNAL_MATCHER_ARGS_USAGE(args) \
+  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_MATCHER_ARG_USAGE, , args))
+#define GMOCK_INTERNAL_MATCHER_ARG_USAGE(i, data_unused, arg_unused) \
+  , gmock_p##i
+
+// To prevent ADL on certain functions we put them on a separate namespace.
+using namespace no_adl;  // NOLINT
+
+}  // namespace testing
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  //  4251 5046
+
+// Include any custom callback matchers added by the local installation.
+// We must include this header at the end to make sure it can use the
+// declarations from this file.
+#include "gmock/internal/custom/gmock-matchers.h"
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_MATCHERS_H_
diff --git a/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-more-actions.h b/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-more-actions.h
new file mode 100644
index 0000000..fd29335
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-more-actions.h
@@ -0,0 +1,573 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file implements some commonly used variadic actions.
+
+// GOOGLETEST_CM0002 DO NOT DELETE
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_MORE_ACTIONS_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_MORE_ACTIONS_H_
+
+#include <memory>
+#include <utility>
+
+#include "gmock/gmock-actions.h"
+#include "gmock/internal/gmock-port.h"
+
+// Include any custom callback actions added by the local installation.
+#include "gmock/internal/custom/gmock-generated-actions.h"
+
+// Sometimes you want to give an action explicit template parameters
+// that cannot be inferred from its value parameters.  ACTION() and
+// ACTION_P*() don't support that.  ACTION_TEMPLATE() remedies that
+// and can be viewed as an extension to ACTION() and ACTION_P*().
+//
+// The syntax:
+//
+//   ACTION_TEMPLATE(ActionName,
+//                   HAS_m_TEMPLATE_PARAMS(kind1, name1, ..., kind_m, name_m),
+//                   AND_n_VALUE_PARAMS(p1, ..., p_n)) { statements; }
+//
+// defines an action template that takes m explicit template
+// parameters and n value parameters.  name_i is the name of the i-th
+// template parameter, and kind_i specifies whether it's a typename,
+// an integral constant, or a template.  p_i is the name of the i-th
+// value parameter.
+//
+// Example:
+//
+//   // DuplicateArg<k, T>(output) converts the k-th argument of the mock
+//   // function to type T and copies it to *output.
+//   ACTION_TEMPLATE(DuplicateArg,
+//                   HAS_2_TEMPLATE_PARAMS(int, k, typename, T),
+//                   AND_1_VALUE_PARAMS(output)) {
+//     *output = T(::std::get<k>(args));
+//   }
+//   ...
+//     int n;
+//     EXPECT_CALL(mock, Foo(_, _))
+//         .WillOnce(DuplicateArg<1, unsigned char>(&n));
+//
+// To create an instance of an action template, write:
+//
+//   ActionName<t1, ..., t_m>(v1, ..., v_n)
+//
+// where the ts are the template arguments and the vs are the value
+// arguments.  The value argument types are inferred by the compiler.
+// If you want to explicitly specify the value argument types, you can
+// provide additional template arguments:
+//
+//   ActionName<t1, ..., t_m, u1, ..., u_k>(v1, ..., v_n)
+//
+// where u_i is the desired type of v_i.
+//
+// ACTION_TEMPLATE and ACTION/ACTION_P* can be overloaded on the
+// number of value parameters, but not on the number of template
+// parameters.  Without the restriction, the meaning of the following
+// is unclear:
+//
+//   OverloadedAction<int, bool>(x);
+//
+// Are we using a single-template-parameter action where 'bool' refers
+// to the type of x, or are we using a two-template-parameter action
+// where the compiler is asked to infer the type of x?
+//
+// Implementation notes:
+//
+// GMOCK_INTERNAL_*_HAS_m_TEMPLATE_PARAMS and
+// GMOCK_INTERNAL_*_AND_n_VALUE_PARAMS are internal macros for
+// implementing ACTION_TEMPLATE.  The main trick we use is to create
+// new macro invocations when expanding a macro.  For example, we have
+//
+//   #define ACTION_TEMPLATE(name, template_params, value_params)
+//       ... GMOCK_INTERNAL_DECL_##template_params ...
+//
+// which causes ACTION_TEMPLATE(..., HAS_1_TEMPLATE_PARAMS(typename, T), ...)
+// to expand to
+//
+//       ... GMOCK_INTERNAL_DECL_HAS_1_TEMPLATE_PARAMS(typename, T) ...
+//
+// Since GMOCK_INTERNAL_DECL_HAS_1_TEMPLATE_PARAMS is a macro, the
+// preprocessor will continue to expand it to
+//
+//       ... typename T ...
+//
+// This technique conforms to the C++ standard and is portable.  It
+// allows us to implement action templates using O(N) code, where N is
+// the maximum number of template/value parameters supported.  Without
+// using it, we'd have to devote O(N^2) amount of code to implement all
+// combinations of m and n.
+
+// Declares the template parameters.
+#define GMOCK_INTERNAL_DECL_HAS_1_TEMPLATE_PARAMS(kind0, name0) kind0 name0
+#define GMOCK_INTERNAL_DECL_HAS_2_TEMPLATE_PARAMS(kind0, name0, kind1, \
+    name1) kind0 name0, kind1 name1
+#define GMOCK_INTERNAL_DECL_HAS_3_TEMPLATE_PARAMS(kind0, name0, kind1, name1, \
+    kind2, name2) kind0 name0, kind1 name1, kind2 name2
+#define GMOCK_INTERNAL_DECL_HAS_4_TEMPLATE_PARAMS(kind0, name0, kind1, name1, \
+    kind2, name2, kind3, name3) kind0 name0, kind1 name1, kind2 name2, \
+    kind3 name3
+#define GMOCK_INTERNAL_DECL_HAS_5_TEMPLATE_PARAMS(kind0, name0, kind1, name1, \
+    kind2, name2, kind3, name3, kind4, name4) kind0 name0, kind1 name1, \
+    kind2 name2, kind3 name3, kind4 name4
+#define GMOCK_INTERNAL_DECL_HAS_6_TEMPLATE_PARAMS(kind0, name0, kind1, name1, \
+    kind2, name2, kind3, name3, kind4, name4, kind5, name5) kind0 name0, \
+    kind1 name1, kind2 name2, kind3 name3, kind4 name4, kind5 name5
+#define GMOCK_INTERNAL_DECL_HAS_7_TEMPLATE_PARAMS(kind0, name0, kind1, name1, \
+    kind2, name2, kind3, name3, kind4, name4, kind5, name5, kind6, \
+    name6) kind0 name0, kind1 name1, kind2 name2, kind3 name3, kind4 name4, \
+    kind5 name5, kind6 name6
+#define GMOCK_INTERNAL_DECL_HAS_8_TEMPLATE_PARAMS(kind0, name0, kind1, name1, \
+    kind2, name2, kind3, name3, kind4, name4, kind5, name5, kind6, name6, \
+    kind7, name7) kind0 name0, kind1 name1, kind2 name2, kind3 name3, \
+    kind4 name4, kind5 name5, kind6 name6, kind7 name7
+#define GMOCK_INTERNAL_DECL_HAS_9_TEMPLATE_PARAMS(kind0, name0, kind1, name1, \
+    kind2, name2, kind3, name3, kind4, name4, kind5, name5, kind6, name6, \
+    kind7, name7, kind8, name8) kind0 name0, kind1 name1, kind2 name2, \
+    kind3 name3, kind4 name4, kind5 name5, kind6 name6, kind7 name7, \
+    kind8 name8
+#define GMOCK_INTERNAL_DECL_HAS_10_TEMPLATE_PARAMS(kind0, name0, kind1, \
+    name1, kind2, name2, kind3, name3, kind4, name4, kind5, name5, kind6, \
+    name6, kind7, name7, kind8, name8, kind9, name9) kind0 name0, \
+    kind1 name1, kind2 name2, kind3 name3, kind4 name4, kind5 name5, \
+    kind6 name6, kind7 name7, kind8 name8, kind9 name9
+
+// Lists the template parameters.
+#define GMOCK_INTERNAL_LIST_HAS_1_TEMPLATE_PARAMS(kind0, name0) name0
+#define GMOCK_INTERNAL_LIST_HAS_2_TEMPLATE_PARAMS(kind0, name0, kind1, \
+    name1) name0, name1
+#define GMOCK_INTERNAL_LIST_HAS_3_TEMPLATE_PARAMS(kind0, name0, kind1, name1, \
+    kind2, name2) name0, name1, name2
+#define GMOCK_INTERNAL_LIST_HAS_4_TEMPLATE_PARAMS(kind0, name0, kind1, name1, \
+    kind2, name2, kind3, name3) name0, name1, name2, name3
+#define GMOCK_INTERNAL_LIST_HAS_5_TEMPLATE_PARAMS(kind0, name0, kind1, name1, \
+    kind2, name2, kind3, name3, kind4, name4) name0, name1, name2, name3, \
+    name4
+#define GMOCK_INTERNAL_LIST_HAS_6_TEMPLATE_PARAMS(kind0, name0, kind1, name1, \
+    kind2, name2, kind3, name3, kind4, name4, kind5, name5) name0, name1, \
+    name2, name3, name4, name5
+#define GMOCK_INTERNAL_LIST_HAS_7_TEMPLATE_PARAMS(kind0, name0, kind1, name1, \
+    kind2, name2, kind3, name3, kind4, name4, kind5, name5, kind6, \
+    name6) name0, name1, name2, name3, name4, name5, name6
+#define GMOCK_INTERNAL_LIST_HAS_8_TEMPLATE_PARAMS(kind0, name0, kind1, name1, \
+    kind2, name2, kind3, name3, kind4, name4, kind5, name5, kind6, name6, \
+    kind7, name7) name0, name1, name2, name3, name4, name5, name6, name7
+#define GMOCK_INTERNAL_LIST_HAS_9_TEMPLATE_PARAMS(kind0, name0, kind1, name1, \
+    kind2, name2, kind3, name3, kind4, name4, kind5, name5, kind6, name6, \
+    kind7, name7, kind8, name8) name0, name1, name2, name3, name4, name5, \
+    name6, name7, name8
+#define GMOCK_INTERNAL_LIST_HAS_10_TEMPLATE_PARAMS(kind0, name0, kind1, \
+    name1, kind2, name2, kind3, name3, kind4, name4, kind5, name5, kind6, \
+    name6, kind7, name7, kind8, name8, kind9, name9) name0, name1, name2, \
+    name3, name4, name5, name6, name7, name8, name9
+
+// Declares the types of value parameters.
+#define GMOCK_INTERNAL_DECL_TYPE_AND_0_VALUE_PARAMS()
+#define GMOCK_INTERNAL_DECL_TYPE_AND_1_VALUE_PARAMS(p0) , typename p0##_type
+#define GMOCK_INTERNAL_DECL_TYPE_AND_2_VALUE_PARAMS(p0, p1) , \
+    typename p0##_type, typename p1##_type
+#define GMOCK_INTERNAL_DECL_TYPE_AND_3_VALUE_PARAMS(p0, p1, p2) , \
+    typename p0##_type, typename p1##_type, typename p2##_type
+#define GMOCK_INTERNAL_DECL_TYPE_AND_4_VALUE_PARAMS(p0, p1, p2, p3) , \
+    typename p0##_type, typename p1##_type, typename p2##_type, \
+    typename p3##_type
+#define GMOCK_INTERNAL_DECL_TYPE_AND_5_VALUE_PARAMS(p0, p1, p2, p3, p4) , \
+    typename p0##_type, typename p1##_type, typename p2##_type, \
+    typename p3##_type, typename p4##_type
+#define GMOCK_INTERNAL_DECL_TYPE_AND_6_VALUE_PARAMS(p0, p1, p2, p3, p4, p5) , \
+    typename p0##_type, typename p1##_type, typename p2##_type, \
+    typename p3##_type, typename p4##_type, typename p5##_type
+#define GMOCK_INTERNAL_DECL_TYPE_AND_7_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, \
+    p6) , typename p0##_type, typename p1##_type, typename p2##_type, \
+    typename p3##_type, typename p4##_type, typename p5##_type, \
+    typename p6##_type
+#define GMOCK_INTERNAL_DECL_TYPE_AND_8_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, \
+    p6, p7) , typename p0##_type, typename p1##_type, typename p2##_type, \
+    typename p3##_type, typename p4##_type, typename p5##_type, \
+    typename p6##_type, typename p7##_type
+#define GMOCK_INTERNAL_DECL_TYPE_AND_9_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, \
+    p6, p7, p8) , typename p0##_type, typename p1##_type, typename p2##_type, \
+    typename p3##_type, typename p4##_type, typename p5##_type, \
+    typename p6##_type, typename p7##_type, typename p8##_type
+#define GMOCK_INTERNAL_DECL_TYPE_AND_10_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, \
+    p6, p7, p8, p9) , typename p0##_type, typename p1##_type, \
+    typename p2##_type, typename p3##_type, typename p4##_type, \
+    typename p5##_type, typename p6##_type, typename p7##_type, \
+    typename p8##_type, typename p9##_type
+
+// Initializes the value parameters.
+#define GMOCK_INTERNAL_INIT_AND_0_VALUE_PARAMS()\
+    ()
+#define GMOCK_INTERNAL_INIT_AND_1_VALUE_PARAMS(p0)\
+    (p0##_type gmock_p0) : p0(::std::move(gmock_p0))
+#define GMOCK_INTERNAL_INIT_AND_2_VALUE_PARAMS(p0, p1)\
+    (p0##_type gmock_p0, p1##_type gmock_p1) : p0(::std::move(gmock_p0)), \
+        p1(::std::move(gmock_p1))
+#define GMOCK_INTERNAL_INIT_AND_3_VALUE_PARAMS(p0, p1, p2)\
+    (p0##_type gmock_p0, p1##_type gmock_p1, \
+        p2##_type gmock_p2) : p0(::std::move(gmock_p0)), \
+        p1(::std::move(gmock_p1)), p2(::std::move(gmock_p2))
+#define GMOCK_INTERNAL_INIT_AND_4_VALUE_PARAMS(p0, p1, p2, p3)\
+    (p0##_type gmock_p0, p1##_type gmock_p1, p2##_type gmock_p2, \
+        p3##_type gmock_p3) : p0(::std::move(gmock_p0)), \
+        p1(::std::move(gmock_p1)), p2(::std::move(gmock_p2)), \
+        p3(::std::move(gmock_p3))
+#define GMOCK_INTERNAL_INIT_AND_5_VALUE_PARAMS(p0, p1, p2, p3, p4)\
+    (p0##_type gmock_p0, p1##_type gmock_p1, p2##_type gmock_p2, \
+        p3##_type gmock_p3, p4##_type gmock_p4) : p0(::std::move(gmock_p0)), \
+        p1(::std::move(gmock_p1)), p2(::std::move(gmock_p2)), \
+        p3(::std::move(gmock_p3)), p4(::std::move(gmock_p4))
+#define GMOCK_INTERNAL_INIT_AND_6_VALUE_PARAMS(p0, p1, p2, p3, p4, p5)\
+    (p0##_type gmock_p0, p1##_type gmock_p1, p2##_type gmock_p2, \
+        p3##_type gmock_p3, p4##_type gmock_p4, \
+        p5##_type gmock_p5) : p0(::std::move(gmock_p0)), \
+        p1(::std::move(gmock_p1)), p2(::std::move(gmock_p2)), \
+        p3(::std::move(gmock_p3)), p4(::std::move(gmock_p4)), \
+        p5(::std::move(gmock_p5))
+#define GMOCK_INTERNAL_INIT_AND_7_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6)\
+    (p0##_type gmock_p0, p1##_type gmock_p1, p2##_type gmock_p2, \
+        p3##_type gmock_p3, p4##_type gmock_p4, p5##_type gmock_p5, \
+        p6##_type gmock_p6) : p0(::std::move(gmock_p0)), \
+        p1(::std::move(gmock_p1)), p2(::std::move(gmock_p2)), \
+        p3(::std::move(gmock_p3)), p4(::std::move(gmock_p4)), \
+        p5(::std::move(gmock_p5)), p6(::std::move(gmock_p6))
+#define GMOCK_INTERNAL_INIT_AND_8_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, p7)\
+    (p0##_type gmock_p0, p1##_type gmock_p1, p2##_type gmock_p2, \
+        p3##_type gmock_p3, p4##_type gmock_p4, p5##_type gmock_p5, \
+        p6##_type gmock_p6, p7##_type gmock_p7) : p0(::std::move(gmock_p0)), \
+        p1(::std::move(gmock_p1)), p2(::std::move(gmock_p2)), \
+        p3(::std::move(gmock_p3)), p4(::std::move(gmock_p4)), \
+        p5(::std::move(gmock_p5)), p6(::std::move(gmock_p6)), \
+        p7(::std::move(gmock_p7))
+#define GMOCK_INTERNAL_INIT_AND_9_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, \
+    p7, p8)\
+    (p0##_type gmock_p0, p1##_type gmock_p1, p2##_type gmock_p2, \
+        p3##_type gmock_p3, p4##_type gmock_p4, p5##_type gmock_p5, \
+        p6##_type gmock_p6, p7##_type gmock_p7, \
+        p8##_type gmock_p8) : p0(::std::move(gmock_p0)), \
+        p1(::std::move(gmock_p1)), p2(::std::move(gmock_p2)), \
+        p3(::std::move(gmock_p3)), p4(::std::move(gmock_p4)), \
+        p5(::std::move(gmock_p5)), p6(::std::move(gmock_p6)), \
+        p7(::std::move(gmock_p7)), p8(::std::move(gmock_p8))
+#define GMOCK_INTERNAL_INIT_AND_10_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, \
+    p7, p8, p9)\
+    (p0##_type gmock_p0, p1##_type gmock_p1, p2##_type gmock_p2, \
+        p3##_type gmock_p3, p4##_type gmock_p4, p5##_type gmock_p5, \
+        p6##_type gmock_p6, p7##_type gmock_p7, p8##_type gmock_p8, \
+        p9##_type gmock_p9) : p0(::std::move(gmock_p0)), \
+        p1(::std::move(gmock_p1)), p2(::std::move(gmock_p2)), \
+        p3(::std::move(gmock_p3)), p4(::std::move(gmock_p4)), \
+        p5(::std::move(gmock_p5)), p6(::std::move(gmock_p6)), \
+        p7(::std::move(gmock_p7)), p8(::std::move(gmock_p8)), \
+        p9(::std::move(gmock_p9))
+
+// Defines the copy constructor
+#define GMOCK_INTERNAL_DEFN_COPY_AND_0_VALUE_PARAMS() \
+    {}  // Avoid https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82134
+#define GMOCK_INTERNAL_DEFN_COPY_AND_1_VALUE_PARAMS(...) = default;
+#define GMOCK_INTERNAL_DEFN_COPY_AND_2_VALUE_PARAMS(...) = default;
+#define GMOCK_INTERNAL_DEFN_COPY_AND_3_VALUE_PARAMS(...) = default;
+#define GMOCK_INTERNAL_DEFN_COPY_AND_4_VALUE_PARAMS(...) = default;
+#define GMOCK_INTERNAL_DEFN_COPY_AND_5_VALUE_PARAMS(...) = default;
+#define GMOCK_INTERNAL_DEFN_COPY_AND_6_VALUE_PARAMS(...) = default;
+#define GMOCK_INTERNAL_DEFN_COPY_AND_7_VALUE_PARAMS(...) = default;
+#define GMOCK_INTERNAL_DEFN_COPY_AND_8_VALUE_PARAMS(...) = default;
+#define GMOCK_INTERNAL_DEFN_COPY_AND_9_VALUE_PARAMS(...) = default;
+#define GMOCK_INTERNAL_DEFN_COPY_AND_10_VALUE_PARAMS(...) = default;
+
+// Declares the fields for storing the value parameters.
+#define GMOCK_INTERNAL_DEFN_AND_0_VALUE_PARAMS()
+#define GMOCK_INTERNAL_DEFN_AND_1_VALUE_PARAMS(p0) p0##_type p0;
+#define GMOCK_INTERNAL_DEFN_AND_2_VALUE_PARAMS(p0, p1) p0##_type p0; \
+    p1##_type p1;
+#define GMOCK_INTERNAL_DEFN_AND_3_VALUE_PARAMS(p0, p1, p2) p0##_type p0; \
+    p1##_type p1; p2##_type p2;
+#define GMOCK_INTERNAL_DEFN_AND_4_VALUE_PARAMS(p0, p1, p2, p3) p0##_type p0; \
+    p1##_type p1; p2##_type p2; p3##_type p3;
+#define GMOCK_INTERNAL_DEFN_AND_5_VALUE_PARAMS(p0, p1, p2, p3, \
+    p4) p0##_type p0; p1##_type p1; p2##_type p2; p3##_type p3; p4##_type p4;
+#define GMOCK_INTERNAL_DEFN_AND_6_VALUE_PARAMS(p0, p1, p2, p3, p4, \
+    p5) p0##_type p0; p1##_type p1; p2##_type p2; p3##_type p3; p4##_type p4; \
+    p5##_type p5;
+#define GMOCK_INTERNAL_DEFN_AND_7_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, \
+    p6) p0##_type p0; p1##_type p1; p2##_type p2; p3##_type p3; p4##_type p4; \
+    p5##_type p5; p6##_type p6;
+#define GMOCK_INTERNAL_DEFN_AND_8_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, \
+    p7) p0##_type p0; p1##_type p1; p2##_type p2; p3##_type p3; p4##_type p4; \
+    p5##_type p5; p6##_type p6; p7##_type p7;
+#define GMOCK_INTERNAL_DEFN_AND_9_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, \
+    p7, p8) p0##_type p0; p1##_type p1; p2##_type p2; p3##_type p3; \
+    p4##_type p4; p5##_type p5; p6##_type p6; p7##_type p7; p8##_type p8;
+#define GMOCK_INTERNAL_DEFN_AND_10_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, \
+    p7, p8, p9) p0##_type p0; p1##_type p1; p2##_type p2; p3##_type p3; \
+    p4##_type p4; p5##_type p5; p6##_type p6; p7##_type p7; p8##_type p8; \
+    p9##_type p9;
+
+// Lists the value parameters.
+#define GMOCK_INTERNAL_LIST_AND_0_VALUE_PARAMS()
+#define GMOCK_INTERNAL_LIST_AND_1_VALUE_PARAMS(p0) p0
+#define GMOCK_INTERNAL_LIST_AND_2_VALUE_PARAMS(p0, p1) p0, p1
+#define GMOCK_INTERNAL_LIST_AND_3_VALUE_PARAMS(p0, p1, p2) p0, p1, p2
+#define GMOCK_INTERNAL_LIST_AND_4_VALUE_PARAMS(p0, p1, p2, p3) p0, p1, p2, p3
+#define GMOCK_INTERNAL_LIST_AND_5_VALUE_PARAMS(p0, p1, p2, p3, p4) p0, p1, \
+    p2, p3, p4
+#define GMOCK_INTERNAL_LIST_AND_6_VALUE_PARAMS(p0, p1, p2, p3, p4, p5) p0, \
+    p1, p2, p3, p4, p5
+#define GMOCK_INTERNAL_LIST_AND_7_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, \
+    p6) p0, p1, p2, p3, p4, p5, p6
+#define GMOCK_INTERNAL_LIST_AND_8_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, \
+    p7) p0, p1, p2, p3, p4, p5, p6, p7
+#define GMOCK_INTERNAL_LIST_AND_9_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, \
+    p7, p8) p0, p1, p2, p3, p4, p5, p6, p7, p8
+#define GMOCK_INTERNAL_LIST_AND_10_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, \
+    p7, p8, p9) p0, p1, p2, p3, p4, p5, p6, p7, p8, p9
+
+// Lists the value parameter types.
+#define GMOCK_INTERNAL_LIST_TYPE_AND_0_VALUE_PARAMS()
+#define GMOCK_INTERNAL_LIST_TYPE_AND_1_VALUE_PARAMS(p0) , p0##_type
+#define GMOCK_INTERNAL_LIST_TYPE_AND_2_VALUE_PARAMS(p0, p1) , p0##_type, \
+    p1##_type
+#define GMOCK_INTERNAL_LIST_TYPE_AND_3_VALUE_PARAMS(p0, p1, p2) , p0##_type, \
+    p1##_type, p2##_type
+#define GMOCK_INTERNAL_LIST_TYPE_AND_4_VALUE_PARAMS(p0, p1, p2, p3) , \
+    p0##_type, p1##_type, p2##_type, p3##_type
+#define GMOCK_INTERNAL_LIST_TYPE_AND_5_VALUE_PARAMS(p0, p1, p2, p3, p4) , \
+    p0##_type, p1##_type, p2##_type, p3##_type, p4##_type
+#define GMOCK_INTERNAL_LIST_TYPE_AND_6_VALUE_PARAMS(p0, p1, p2, p3, p4, p5) , \
+    p0##_type, p1##_type, p2##_type, p3##_type, p4##_type, p5##_type
+#define GMOCK_INTERNAL_LIST_TYPE_AND_7_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, \
+    p6) , p0##_type, p1##_type, p2##_type, p3##_type, p4##_type, p5##_type, \
+    p6##_type
+#define GMOCK_INTERNAL_LIST_TYPE_AND_8_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, \
+    p6, p7) , p0##_type, p1##_type, p2##_type, p3##_type, p4##_type, \
+    p5##_type, p6##_type, p7##_type
+#define GMOCK_INTERNAL_LIST_TYPE_AND_9_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, \
+    p6, p7, p8) , p0##_type, p1##_type, p2##_type, p3##_type, p4##_type, \
+    p5##_type, p6##_type, p7##_type, p8##_type
+#define GMOCK_INTERNAL_LIST_TYPE_AND_10_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, \
+    p6, p7, p8, p9) , p0##_type, p1##_type, p2##_type, p3##_type, p4##_type, \
+    p5##_type, p6##_type, p7##_type, p8##_type, p9##_type
+
+// Declares the value parameters.
+#define GMOCK_INTERNAL_DECL_AND_0_VALUE_PARAMS()
+#define GMOCK_INTERNAL_DECL_AND_1_VALUE_PARAMS(p0) p0##_type p0
+#define GMOCK_INTERNAL_DECL_AND_2_VALUE_PARAMS(p0, p1) p0##_type p0, \
+    p1##_type p1
+#define GMOCK_INTERNAL_DECL_AND_3_VALUE_PARAMS(p0, p1, p2) p0##_type p0, \
+    p1##_type p1, p2##_type p2
+#define GMOCK_INTERNAL_DECL_AND_4_VALUE_PARAMS(p0, p1, p2, p3) p0##_type p0, \
+    p1##_type p1, p2##_type p2, p3##_type p3
+#define GMOCK_INTERNAL_DECL_AND_5_VALUE_PARAMS(p0, p1, p2, p3, \
+    p4) p0##_type p0, p1##_type p1, p2##_type p2, p3##_type p3, p4##_type p4
+#define GMOCK_INTERNAL_DECL_AND_6_VALUE_PARAMS(p0, p1, p2, p3, p4, \
+    p5) p0##_type p0, p1##_type p1, p2##_type p2, p3##_type p3, p4##_type p4, \
+    p5##_type p5
+#define GMOCK_INTERNAL_DECL_AND_7_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, \
+    p6) p0##_type p0, p1##_type p1, p2##_type p2, p3##_type p3, p4##_type p4, \
+    p5##_type p5, p6##_type p6
+#define GMOCK_INTERNAL_DECL_AND_8_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, \
+    p7) p0##_type p0, p1##_type p1, p2##_type p2, p3##_type p3, p4##_type p4, \
+    p5##_type p5, p6##_type p6, p7##_type p7
+#define GMOCK_INTERNAL_DECL_AND_9_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, \
+    p7, p8) p0##_type p0, p1##_type p1, p2##_type p2, p3##_type p3, \
+    p4##_type p4, p5##_type p5, p6##_type p6, p7##_type p7, p8##_type p8
+#define GMOCK_INTERNAL_DECL_AND_10_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, \
+    p7, p8, p9) p0##_type p0, p1##_type p1, p2##_type p2, p3##_type p3, \
+    p4##_type p4, p5##_type p5, p6##_type p6, p7##_type p7, p8##_type p8, \
+    p9##_type p9
+
+// The suffix of the class template implementing the action template.
+#define GMOCK_INTERNAL_COUNT_AND_0_VALUE_PARAMS()
+#define GMOCK_INTERNAL_COUNT_AND_1_VALUE_PARAMS(p0) P
+#define GMOCK_INTERNAL_COUNT_AND_2_VALUE_PARAMS(p0, p1) P2
+#define GMOCK_INTERNAL_COUNT_AND_3_VALUE_PARAMS(p0, p1, p2) P3
+#define GMOCK_INTERNAL_COUNT_AND_4_VALUE_PARAMS(p0, p1, p2, p3) P4
+#define GMOCK_INTERNAL_COUNT_AND_5_VALUE_PARAMS(p0, p1, p2, p3, p4) P5
+#define GMOCK_INTERNAL_COUNT_AND_6_VALUE_PARAMS(p0, p1, p2, p3, p4, p5) P6
+#define GMOCK_INTERNAL_COUNT_AND_7_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6) P7
+#define GMOCK_INTERNAL_COUNT_AND_8_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, \
+    p7) P8
+#define GMOCK_INTERNAL_COUNT_AND_9_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, \
+    p7, p8) P9
+#define GMOCK_INTERNAL_COUNT_AND_10_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, \
+    p7, p8, p9) P10
+
+// The name of the class template implementing the action template.
+#define GMOCK_ACTION_CLASS_(name, value_params)\
+    GTEST_CONCAT_TOKEN_(name##Action, GMOCK_INTERNAL_COUNT_##value_params)
+
+#define ACTION_TEMPLATE(name, template_params, value_params)                   \
+  template <GMOCK_INTERNAL_DECL_##template_params                              \
+            GMOCK_INTERNAL_DECL_TYPE_##value_params>                           \
+  class GMOCK_ACTION_CLASS_(name, value_params) {                              \
+   public:                                                                     \
+    explicit GMOCK_ACTION_CLASS_(name, value_params)(                          \
+        GMOCK_INTERNAL_DECL_##value_params)                                    \
+        GMOCK_PP_IF(GMOCK_PP_IS_EMPTY(GMOCK_INTERNAL_COUNT_##value_params),    \
+                    = default; ,                                               \
+                    : impl_(std::make_shared<gmock_Impl>(                      \
+                                GMOCK_INTERNAL_LIST_##value_params)) { })      \
+    GMOCK_ACTION_CLASS_(name, value_params)(                                   \
+        const GMOCK_ACTION_CLASS_(name, value_params)&) noexcept               \
+        GMOCK_INTERNAL_DEFN_COPY_##value_params                                \
+    GMOCK_ACTION_CLASS_(name, value_params)(                                   \
+        GMOCK_ACTION_CLASS_(name, value_params)&&) noexcept                    \
+        GMOCK_INTERNAL_DEFN_COPY_##value_params                                \
+    template <typename F>                                                      \
+    operator ::testing::Action<F>() const {                                    \
+      return GMOCK_PP_IF(                                                      \
+          GMOCK_PP_IS_EMPTY(GMOCK_INTERNAL_COUNT_##value_params),              \
+                      (::testing::internal::MakeAction<F, gmock_Impl>()),      \
+                      (::testing::internal::MakeAction<F>(impl_)));            \
+    }                                                                          \
+   private:                                                                    \
+    class gmock_Impl {                                                         \
+     public:                                                                   \
+      explicit gmock_Impl GMOCK_INTERNAL_INIT_##value_params {}                \
+      template <typename function_type, typename return_type,                  \
+                typename args_type, GMOCK_ACTION_TEMPLATE_ARGS_NAMES_>         \
+      return_type gmock_PerformImpl(GMOCK_ACTION_ARG_TYPES_AND_NAMES_) const;  \
+      GMOCK_INTERNAL_DEFN_##value_params                                       \
+    };                                                                         \
+    GMOCK_PP_IF(GMOCK_PP_IS_EMPTY(GMOCK_INTERNAL_COUNT_##value_params),        \
+                , std::shared_ptr<const gmock_Impl> impl_;)                    \
+  };                                                                           \
+  template <GMOCK_INTERNAL_DECL_##template_params                              \
+            GMOCK_INTERNAL_DECL_TYPE_##value_params>                           \
+  GMOCK_ACTION_CLASS_(name, value_params)<                                     \
+      GMOCK_INTERNAL_LIST_##template_params                                    \
+      GMOCK_INTERNAL_LIST_TYPE_##value_params> name(                           \
+          GMOCK_INTERNAL_DECL_##value_params) GTEST_MUST_USE_RESULT_;          \
+  template <GMOCK_INTERNAL_DECL_##template_params                              \
+            GMOCK_INTERNAL_DECL_TYPE_##value_params>                           \
+  inline GMOCK_ACTION_CLASS_(name, value_params)<                              \
+      GMOCK_INTERNAL_LIST_##template_params                                    \
+      GMOCK_INTERNAL_LIST_TYPE_##value_params> name(                           \
+          GMOCK_INTERNAL_DECL_##value_params) {                                \
+    return GMOCK_ACTION_CLASS_(name, value_params)<                            \
+        GMOCK_INTERNAL_LIST_##template_params                                  \
+        GMOCK_INTERNAL_LIST_TYPE_##value_params>(                              \
+            GMOCK_INTERNAL_LIST_##value_params);                               \
+  }                                                                            \
+  template <GMOCK_INTERNAL_DECL_##template_params                              \
+            GMOCK_INTERNAL_DECL_TYPE_##value_params>                           \
+  template <typename function_type, typename return_type, typename args_type,  \
+            GMOCK_ACTION_TEMPLATE_ARGS_NAMES_>                                 \
+  return_type GMOCK_ACTION_CLASS_(name, value_params)<                         \
+      GMOCK_INTERNAL_LIST_##template_params                                    \
+      GMOCK_INTERNAL_LIST_TYPE_##value_params>::gmock_Impl::gmock_PerformImpl( \
+          GMOCK_ACTION_ARG_TYPES_AND_NAMES_UNUSED_) const
+
+namespace testing {
+
+// The ACTION*() macros trigger warning C4100 (unreferenced formal
+// parameter) in MSVC with -W4.  Unfortunately they cannot be fixed in
+// the macro definition, as the warnings are generated when the macro
+// is expanded and macro expansion cannot contain #pragma.  Therefore
+// we suppress them here.
+#ifdef _MSC_VER
+# pragma warning(push)
+# pragma warning(disable:4100)
+#endif
+
+namespace internal {
+
+// internal::InvokeArgument - a helper for InvokeArgument action.
+// The basic overloads are provided here for generic functors.
+// Overloads for other custom-callables are provided in the
+// internal/custom/gmock-generated-actions.h header.
+template <typename F, typename... Args>
+auto InvokeArgument(F f, Args... args) -> decltype(f(args...)) {
+  return f(args...);
+}
+
+template <std::size_t index, typename... Params>
+struct InvokeArgumentAction {
+  template <typename... Args>
+  auto operator()(Args&&... args) const -> decltype(internal::InvokeArgument(
+      std::get<index>(std::forward_as_tuple(std::forward<Args>(args)...)),
+      std::declval<const Params&>()...)) {
+    internal::FlatTuple<Args&&...> args_tuple(FlatTupleConstructTag{},
+                                              std::forward<Args>(args)...);
+    return params.Apply([&](const Params&... unpacked_params) {
+      auto&& callable = args_tuple.template Get<index>();
+      return internal::InvokeArgument(
+          std::forward<decltype(callable)>(callable), unpacked_params...);
+    });
+  }
+
+  internal::FlatTuple<Params...> params;
+};
+
+}  // namespace internal
+
+// The InvokeArgument<N>(a1, a2, ..., a_k) action invokes the N-th
+// (0-based) argument, which must be a k-ary callable, of the mock
+// function, with arguments a1, a2, ..., a_k.
+//
+// Notes:
+//
+//   1. The arguments are passed by value by default.  If you need to
+//   pass an argument by reference, wrap it inside std::ref().  For
+//   example,
+//
+//     InvokeArgument<1>(5, string("Hello"), std::ref(foo))
+//
+//   passes 5 and string("Hello") by value, and passes foo by
+//   reference.
+//
+//   2. If the callable takes an argument by reference but std::ref() is
+//   not used, it will receive the reference to a copy of the value,
+//   instead of the original value.  For example, when the 0-th
+//   argument of the mock function takes a const string&, the action
+//
+//     InvokeArgument<0>(string("Hello"))
+//
+//   makes a copy of the temporary string("Hello") object and passes a
+//   reference of the copy, instead of the original temporary object,
+//   to the callable.  This makes it easy for a user to define an
+//   InvokeArgument action from temporary values and have it performed
+//   later.
+template <std::size_t index, typename... Params>
+internal::InvokeArgumentAction<index, typename std::decay<Params>::type...>
+InvokeArgument(Params&&... params) {
+  return {internal::FlatTuple<typename std::decay<Params>::type...>(
+      internal::FlatTupleConstructTag{}, std::forward<Params>(params)...)};
+}
+
+#ifdef _MSC_VER
+# pragma warning(pop)
+#endif
+
+}  // namespace testing
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_MORE_ACTIONS_H_
diff --git a/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-more-matchers.h b/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-more-matchers.h
new file mode 100644
index 0000000..dfc77e3
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-more-matchers.h
@@ -0,0 +1,92 @@
+// Copyright 2013, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file implements some matchers that depend on gmock-matchers.h.
+//
+// Note that tests are implemented in gmock-matchers_test.cc rather than
+// gmock-more-matchers-test.cc.
+
+// GOOGLETEST_CM0002 DO NOT DELETE
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_MORE_MATCHERS_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_MORE_MATCHERS_H_
+
+#include "gmock/gmock-matchers.h"
+
+namespace testing {
+
+// Silence C4100 (unreferenced formal
+// parameter) for MSVC
+#ifdef _MSC_VER
+# pragma warning(push)
+# pragma warning(disable:4100)
+#if (_MSC_VER == 1900)
+// and silence C4800 (C4800: 'int *const ': forcing value
+// to bool 'true' or 'false') for MSVC 14
+# pragma warning(disable:4800)
+  #endif
+#endif
+
+// Defines a matcher that matches an empty container. The container must
+// support both size() and empty(), which all STL-like containers provide.
+MATCHER(IsEmpty, negation ? "isn't empty" : "is empty") {
+  if (arg.empty()) {
+    return true;
+  }
+  *result_listener << "whose size is " << arg.size();
+  return false;
+}
+
+// Define a matcher that matches a value that evaluates in boolean
+// context to true.  Useful for types that define "explicit operator
+// bool" operators and so can't be compared for equality with true
+// and false.
+MATCHER(IsTrue, negation ? "is false" : "is true") {
+  return static_cast<bool>(arg);
+}
+
+// Define a matcher that matches a value that evaluates in boolean
+// context to false.  Useful for types that define "explicit operator
+// bool" operators and so can't be compared for equality with true
+// and false.
+MATCHER(IsFalse, negation ? "is true" : "is false") {
+  return !static_cast<bool>(arg);
+}
+
+#ifdef _MSC_VER
+# pragma warning(pop)
+#endif
+
+
+}  // namespace testing
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_MORE_MATCHERS_H_
diff --git a/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-nice-strict.h b/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-nice-strict.h
new file mode 100644
index 0000000..b03b770
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-nice-strict.h
@@ -0,0 +1,261 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Implements class templates NiceMock, NaggyMock, and StrictMock.
+//
+// Given a mock class MockFoo that is created using Google Mock,
+// NiceMock<MockFoo> is a subclass of MockFoo that allows
+// uninteresting calls (i.e. calls to mock methods that have no
+// EXPECT_CALL specs), NaggyMock<MockFoo> is a subclass of MockFoo
+// that prints a warning when an uninteresting call occurs, and
+// StrictMock<MockFoo> is a subclass of MockFoo that treats all
+// uninteresting calls as errors.
+//
+// Currently a mock is naggy by default, so MockFoo and
+// NaggyMock<MockFoo> behave like the same.  However, we will soon
+// switch the default behavior of mocks to be nice, as that in general
+// leads to more maintainable tests.  When that happens, MockFoo will
+// stop behaving like NaggyMock<MockFoo> and start behaving like
+// NiceMock<MockFoo>.
+//
+// NiceMock, NaggyMock, and StrictMock "inherit" the constructors of
+// their respective base class.  Therefore you can write
+// NiceMock<MockFoo>(5, "a") to construct a nice mock where MockFoo
+// has a constructor that accepts (int, const char*), for example.
+//
+// A known limitation is that NiceMock<MockFoo>, NaggyMock<MockFoo>,
+// and StrictMock<MockFoo> only works for mock methods defined using
+// the MOCK_METHOD* family of macros DIRECTLY in the MockFoo class.
+// If a mock method is defined in a base class of MockFoo, the "nice"
+// or "strict" modifier may not affect it, depending on the compiler.
+// In particular, nesting NiceMock, NaggyMock, and StrictMock is NOT
+// supported.
+
+// GOOGLETEST_CM0002 DO NOT DELETE
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_NICE_STRICT_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_NICE_STRICT_H_
+
+#include <type_traits>
+
+#include "gmock/gmock-spec-builders.h"
+#include "gmock/internal/gmock-port.h"
+
+namespace testing {
+template <class MockClass>
+class NiceMock;
+template <class MockClass>
+class NaggyMock;
+template <class MockClass>
+class StrictMock;
+
+namespace internal {
+template <typename T>
+std::true_type StrictnessModifierProbe(const NiceMock<T>&);
+template <typename T>
+std::true_type StrictnessModifierProbe(const NaggyMock<T>&);
+template <typename T>
+std::true_type StrictnessModifierProbe(const StrictMock<T>&);
+std::false_type StrictnessModifierProbe(...);
+
+template <typename T>
+constexpr bool HasStrictnessModifier() {
+  return decltype(StrictnessModifierProbe(std::declval<const T&>()))::value;
+}
+
+// Base classes that register and deregister with testing::Mock to alter the
+// default behavior around uninteresting calls. Inheriting from one of these
+// classes first and then MockClass ensures the MockClass constructor is run
+// after registration, and that the MockClass destructor runs before
+// deregistration. This guarantees that MockClass's constructor and destructor
+// run with the same level of strictness as its instance methods.
+
+#if GTEST_OS_WINDOWS && !GTEST_OS_WINDOWS_MINGW && \
+    (defined(_MSC_VER) || defined(__clang__))
+// We need to mark these classes with this declspec to ensure that
+// the empty base class optimization is performed.
+#define GTEST_INTERNAL_EMPTY_BASE_CLASS __declspec(empty_bases)
+#else
+#define GTEST_INTERNAL_EMPTY_BASE_CLASS
+#endif
+
+template <typename Base>
+class NiceMockImpl {
+ public:
+  NiceMockImpl() { ::testing::Mock::AllowUninterestingCalls(this); }
+
+  ~NiceMockImpl() { ::testing::Mock::UnregisterCallReaction(this); }
+};
+
+template <typename Base>
+class NaggyMockImpl {
+ public:
+  NaggyMockImpl() { ::testing::Mock::WarnUninterestingCalls(this); }
+
+  ~NaggyMockImpl() { ::testing::Mock::UnregisterCallReaction(this); }
+};
+
+template <typename Base>
+class StrictMockImpl {
+ public:
+  StrictMockImpl() { ::testing::Mock::FailUninterestingCalls(this); }
+
+  ~StrictMockImpl() { ::testing::Mock::UnregisterCallReaction(this); }
+};
+
+}  // namespace internal
+
+template <class MockClass>
+class GTEST_INTERNAL_EMPTY_BASE_CLASS NiceMock
+    : private internal::NiceMockImpl<MockClass>,
+      public MockClass {
+ public:
+  static_assert(!internal::HasStrictnessModifier<MockClass>(),
+                "Can't apply NiceMock to a class hierarchy that already has a "
+                "strictness modifier. See "
+                "https://google.github.io/googletest/"
+                "gmock_cook_book.html#NiceStrictNaggy");
+  NiceMock() : MockClass() {
+    static_assert(sizeof(*this) == sizeof(MockClass),
+                  "The impl subclass shouldn't introduce any padding");
+  }
+
+  // Ideally, we would inherit base class's constructors through a using
+  // declaration, which would preserve their visibility. However, many existing
+  // tests rely on the fact that current implementation reexports protected
+  // constructors as public. These tests would need to be cleaned up first.
+
+  // Single argument constructor is special-cased so that it can be
+  // made explicit.
+  template <typename A>
+  explicit NiceMock(A&& arg) : MockClass(std::forward<A>(arg)) {
+    static_assert(sizeof(*this) == sizeof(MockClass),
+                  "The impl subclass shouldn't introduce any padding");
+  }
+
+  template <typename TArg1, typename TArg2, typename... An>
+  NiceMock(TArg1&& arg1, TArg2&& arg2, An&&... args)
+      : MockClass(std::forward<TArg1>(arg1), std::forward<TArg2>(arg2),
+                  std::forward<An>(args)...) {
+    static_assert(sizeof(*this) == sizeof(MockClass),
+                  "The impl subclass shouldn't introduce any padding");
+  }
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(NiceMock);
+};
+
+template <class MockClass>
+class GTEST_INTERNAL_EMPTY_BASE_CLASS NaggyMock
+    : private internal::NaggyMockImpl<MockClass>,
+      public MockClass {
+  static_assert(!internal::HasStrictnessModifier<MockClass>(),
+                "Can't apply NaggyMock to a class hierarchy that already has a "
+                "strictness modifier. See "
+                "https://google.github.io/googletest/"
+                "gmock_cook_book.html#NiceStrictNaggy");
+
+ public:
+  NaggyMock() : MockClass() {
+    static_assert(sizeof(*this) == sizeof(MockClass),
+                  "The impl subclass shouldn't introduce any padding");
+  }
+
+  // Ideally, we would inherit base class's constructors through a using
+  // declaration, which would preserve their visibility. However, many existing
+  // tests rely on the fact that current implementation reexports protected
+  // constructors as public. These tests would need to be cleaned up first.
+
+  // Single argument constructor is special-cased so that it can be
+  // made explicit.
+  template <typename A>
+  explicit NaggyMock(A&& arg) : MockClass(std::forward<A>(arg)) {
+    static_assert(sizeof(*this) == sizeof(MockClass),
+                  "The impl subclass shouldn't introduce any padding");
+  }
+
+  template <typename TArg1, typename TArg2, typename... An>
+  NaggyMock(TArg1&& arg1, TArg2&& arg2, An&&... args)
+      : MockClass(std::forward<TArg1>(arg1), std::forward<TArg2>(arg2),
+                  std::forward<An>(args)...) {
+    static_assert(sizeof(*this) == sizeof(MockClass),
+                  "The impl subclass shouldn't introduce any padding");
+  }
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(NaggyMock);
+};
+
+template <class MockClass>
+class GTEST_INTERNAL_EMPTY_BASE_CLASS StrictMock
+    : private internal::StrictMockImpl<MockClass>,
+      public MockClass {
+ public:
+  static_assert(
+      !internal::HasStrictnessModifier<MockClass>(),
+      "Can't apply StrictMock to a class hierarchy that already has a "
+      "strictness modifier. See "
+      "https://google.github.io/googletest/"
+      "gmock_cook_book.html#NiceStrictNaggy");
+  StrictMock() : MockClass() {
+    static_assert(sizeof(*this) == sizeof(MockClass),
+                  "The impl subclass shouldn't introduce any padding");
+  }
+
+  // Ideally, we would inherit base class's constructors through a using
+  // declaration, which would preserve their visibility. However, many existing
+  // tests rely on the fact that current implementation reexports protected
+  // constructors as public. These tests would need to be cleaned up first.
+
+  // Single argument constructor is special-cased so that it can be
+  // made explicit.
+  template <typename A>
+  explicit StrictMock(A&& arg) : MockClass(std::forward<A>(arg)) {
+    static_assert(sizeof(*this) == sizeof(MockClass),
+                  "The impl subclass shouldn't introduce any padding");
+  }
+
+  template <typename TArg1, typename TArg2, typename... An>
+  StrictMock(TArg1&& arg1, TArg2&& arg2, An&&... args)
+      : MockClass(std::forward<TArg1>(arg1), std::forward<TArg2>(arg2),
+                  std::forward<An>(args)...) {
+    static_assert(sizeof(*this) == sizeof(MockClass),
+                  "The impl subclass shouldn't introduce any padding");
+  }
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(StrictMock);
+};
+
+#undef GTEST_INTERNAL_EMPTY_BASE_CLASS
+
+}  // namespace testing
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_NICE_STRICT_H_
diff --git a/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-spec-builders.h b/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-spec-builders.h
new file mode 100644
index 0000000..41323c1
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock-spec-builders.h
@@ -0,0 +1,2038 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file implements the ON_CALL() and EXPECT_CALL() macros.
+//
+// A user can use the ON_CALL() macro to specify the default action of
+// a mock method.  The syntax is:
+//
+//   ON_CALL(mock_object, Method(argument-matchers))
+//       .With(multi-argument-matcher)
+//       .WillByDefault(action);
+//
+//  where the .With() clause is optional.
+//
+// A user can use the EXPECT_CALL() macro to specify an expectation on
+// a mock method.  The syntax is:
+//
+//   EXPECT_CALL(mock_object, Method(argument-matchers))
+//       .With(multi-argument-matchers)
+//       .Times(cardinality)
+//       .InSequence(sequences)
+//       .After(expectations)
+//       .WillOnce(action)
+//       .WillRepeatedly(action)
+//       .RetiresOnSaturation();
+//
+// where all clauses are optional, and .InSequence()/.After()/
+// .WillOnce() can appear any number of times.
+
+// GOOGLETEST_CM0002 DO NOT DELETE
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_SPEC_BUILDERS_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_SPEC_BUILDERS_H_
+
+#include <functional>
+#include <map>
+#include <memory>
+#include <set>
+#include <sstream>
+#include <string>
+#include <type_traits>
+#include <utility>
+#include <vector>
+#include "gmock/gmock-actions.h"
+#include "gmock/gmock-cardinalities.h"
+#include "gmock/gmock-matchers.h"
+#include "gmock/internal/gmock-internal-utils.h"
+#include "gmock/internal/gmock-port.h"
+#include "gtest/gtest.h"
+
+#if GTEST_HAS_EXCEPTIONS
+# include <stdexcept>  // NOLINT
+#endif
+
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4251 \
+/* class A needs to have dll-interface to be used by clients of class B */)
+
+namespace testing {
+
+// An abstract handle of an expectation.
+class Expectation;
+
+// A set of expectation handles.
+class ExpectationSet;
+
+// Anything inside the 'internal' namespace IS INTERNAL IMPLEMENTATION
+// and MUST NOT BE USED IN USER CODE!!!
+namespace internal {
+
+// Implements a mock function.
+template <typename F> class FunctionMocker;
+
+// Base class for expectations.
+class ExpectationBase;
+
+// Implements an expectation.
+template <typename F> class TypedExpectation;
+
+// Helper class for testing the Expectation class template.
+class ExpectationTester;
+
+// Helper classes for implementing NiceMock, StrictMock, and NaggyMock.
+template <typename MockClass>
+class NiceMockImpl;
+template <typename MockClass>
+class StrictMockImpl;
+template <typename MockClass>
+class NaggyMockImpl;
+
+// Protects the mock object registry (in class Mock), all function
+// mockers, and all expectations.
+//
+// The reason we don't use more fine-grained protection is: when a
+// mock function Foo() is called, it needs to consult its expectations
+// to see which one should be picked.  If another thread is allowed to
+// call a mock function (either Foo() or a different one) at the same
+// time, it could affect the "retired" attributes of Foo()'s
+// expectations when InSequence() is used, and thus affect which
+// expectation gets picked.  Therefore, we sequence all mock function
+// calls to ensure the integrity of the mock objects' states.
+GTEST_API_ GTEST_DECLARE_STATIC_MUTEX_(g_gmock_mutex);
+
+// Untyped base class for ActionResultHolder<R>.
+class UntypedActionResultHolderBase;
+
+// Abstract base class of FunctionMocker.  This is the
+// type-agnostic part of the function mocker interface.  Its pure
+// virtual methods are implemented by FunctionMocker.
+class GTEST_API_ UntypedFunctionMockerBase {
+ public:
+  UntypedFunctionMockerBase();
+  virtual ~UntypedFunctionMockerBase();
+
+  // Verifies that all expectations on this mock function have been
+  // satisfied.  Reports one or more Google Test non-fatal failures
+  // and returns false if not.
+  bool VerifyAndClearExpectationsLocked()
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex);
+
+  // Clears the ON_CALL()s set on this mock function.
+  virtual void ClearDefaultActionsLocked()
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) = 0;
+
+  // In all of the following Untyped* functions, it's the caller's
+  // responsibility to guarantee the correctness of the arguments'
+  // types.
+
+  // Performs the default action with the given arguments and returns
+  // the action's result.  The call description string will be used in
+  // the error message to describe the call in the case the default
+  // action fails.
+  // L = *
+  virtual UntypedActionResultHolderBase* UntypedPerformDefaultAction(
+      void* untyped_args, const std::string& call_description) const = 0;
+
+  // Performs the given action with the given arguments and returns
+  // the action's result.
+  // L = *
+  virtual UntypedActionResultHolderBase* UntypedPerformAction(
+      const void* untyped_action, void* untyped_args) const = 0;
+
+  // Writes a message that the call is uninteresting (i.e. neither
+  // explicitly expected nor explicitly unexpected) to the given
+  // ostream.
+  virtual void UntypedDescribeUninterestingCall(
+      const void* untyped_args,
+      ::std::ostream* os) const
+          GTEST_LOCK_EXCLUDED_(g_gmock_mutex) = 0;
+
+  // Returns the expectation that matches the given function arguments
+  // (or NULL is there's no match); when a match is found,
+  // untyped_action is set to point to the action that should be
+  // performed (or NULL if the action is "do default"), and
+  // is_excessive is modified to indicate whether the call exceeds the
+  // expected number.
+  virtual const ExpectationBase* UntypedFindMatchingExpectation(
+      const void* untyped_args,
+      const void** untyped_action, bool* is_excessive,
+      ::std::ostream* what, ::std::ostream* why)
+          GTEST_LOCK_EXCLUDED_(g_gmock_mutex) = 0;
+
+  // Prints the given function arguments to the ostream.
+  virtual void UntypedPrintArgs(const void* untyped_args,
+                                ::std::ostream* os) const = 0;
+
+  // Sets the mock object this mock method belongs to, and registers
+  // this information in the global mock registry.  Will be called
+  // whenever an EXPECT_CALL() or ON_CALL() is executed on this mock
+  // method.
+  void RegisterOwner(const void* mock_obj)
+      GTEST_LOCK_EXCLUDED_(g_gmock_mutex);
+
+  // Sets the mock object this mock method belongs to, and sets the
+  // name of the mock function.  Will be called upon each invocation
+  // of this mock function.
+  void SetOwnerAndName(const void* mock_obj, const char* name)
+      GTEST_LOCK_EXCLUDED_(g_gmock_mutex);
+
+  // Returns the mock object this mock method belongs to.  Must be
+  // called after RegisterOwner() or SetOwnerAndName() has been
+  // called.
+  const void* MockObject() const
+      GTEST_LOCK_EXCLUDED_(g_gmock_mutex);
+
+  // Returns the name of this mock method.  Must be called after
+  // SetOwnerAndName() has been called.
+  const char* Name() const
+      GTEST_LOCK_EXCLUDED_(g_gmock_mutex);
+
+  // Returns the result of invoking this mock function with the given
+  // arguments.  This function can be safely called from multiple
+  // threads concurrently.  The caller is responsible for deleting the
+  // result.
+  UntypedActionResultHolderBase* UntypedInvokeWith(void* untyped_args)
+      GTEST_LOCK_EXCLUDED_(g_gmock_mutex);
+
+ protected:
+  typedef std::vector<const void*> UntypedOnCallSpecs;
+
+  using UntypedExpectations = std::vector<std::shared_ptr<ExpectationBase>>;
+
+  // Returns an Expectation object that references and co-owns exp,
+  // which must be an expectation on this mock function.
+  Expectation GetHandleOf(ExpectationBase* exp);
+
+  // Address of the mock object this mock method belongs to.  Only
+  // valid after this mock method has been called or
+  // ON_CALL/EXPECT_CALL has been invoked on it.
+  const void* mock_obj_;  // Protected by g_gmock_mutex.
+
+  // Name of the function being mocked.  Only valid after this mock
+  // method has been called.
+  const char* name_;  // Protected by g_gmock_mutex.
+
+  // All default action specs for this function mocker.
+  UntypedOnCallSpecs untyped_on_call_specs_;
+
+  // All expectations for this function mocker.
+  //
+  // It's undefined behavior to interleave expectations (EXPECT_CALLs
+  // or ON_CALLs) and mock function calls.  Also, the order of
+  // expectations is important.  Therefore it's a logic race condition
+  // to read/write untyped_expectations_ concurrently.  In order for
+  // tools like tsan to catch concurrent read/write accesses to
+  // untyped_expectations, we deliberately leave accesses to it
+  // unprotected.
+  UntypedExpectations untyped_expectations_;
+};  // class UntypedFunctionMockerBase
+
+// Untyped base class for OnCallSpec<F>.
+class UntypedOnCallSpecBase {
+ public:
+  // The arguments are the location of the ON_CALL() statement.
+  UntypedOnCallSpecBase(const char* a_file, int a_line)
+      : file_(a_file), line_(a_line), last_clause_(kNone) {}
+
+  // Where in the source file was the default action spec defined?
+  const char* file() const { return file_; }
+  int line() const { return line_; }
+
+ protected:
+  // Gives each clause in the ON_CALL() statement a name.
+  enum Clause {
+    // Do not change the order of the enum members!  The run-time
+    // syntax checking relies on it.
+    kNone,
+    kWith,
+    kWillByDefault
+  };
+
+  // Asserts that the ON_CALL() statement has a certain property.
+  void AssertSpecProperty(bool property,
+                          const std::string& failure_message) const {
+    Assert(property, file_, line_, failure_message);
+  }
+
+  // Expects that the ON_CALL() statement has a certain property.
+  void ExpectSpecProperty(bool property,
+                          const std::string& failure_message) const {
+    Expect(property, file_, line_, failure_message);
+  }
+
+  const char* file_;
+  int line_;
+
+  // The last clause in the ON_CALL() statement as seen so far.
+  // Initially kNone and changes as the statement is parsed.
+  Clause last_clause_;
+};  // class UntypedOnCallSpecBase
+
+// This template class implements an ON_CALL spec.
+template <typename F>
+class OnCallSpec : public UntypedOnCallSpecBase {
+ public:
+  typedef typename Function<F>::ArgumentTuple ArgumentTuple;
+  typedef typename Function<F>::ArgumentMatcherTuple ArgumentMatcherTuple;
+
+  // Constructs an OnCallSpec object from the information inside
+  // the parenthesis of an ON_CALL() statement.
+  OnCallSpec(const char* a_file, int a_line,
+             const ArgumentMatcherTuple& matchers)
+      : UntypedOnCallSpecBase(a_file, a_line),
+        matchers_(matchers),
+        // By default, extra_matcher_ should match anything.  However,
+        // we cannot initialize it with _ as that causes ambiguity between
+        // Matcher's copy and move constructor for some argument types.
+        extra_matcher_(A<const ArgumentTuple&>()) {}
+
+  // Implements the .With() clause.
+  OnCallSpec& With(const Matcher<const ArgumentTuple&>& m) {
+    // Makes sure this is called at most once.
+    ExpectSpecProperty(last_clause_ < kWith,
+                       ".With() cannot appear "
+                       "more than once in an ON_CALL().");
+    last_clause_ = kWith;
+
+    extra_matcher_ = m;
+    return *this;
+  }
+
+  // Implements the .WillByDefault() clause.
+  OnCallSpec& WillByDefault(const Action<F>& action) {
+    ExpectSpecProperty(last_clause_ < kWillByDefault,
+                       ".WillByDefault() must appear "
+                       "exactly once in an ON_CALL().");
+    last_clause_ = kWillByDefault;
+
+    ExpectSpecProperty(!action.IsDoDefault(),
+                       "DoDefault() cannot be used in ON_CALL().");
+    action_ = action;
+    return *this;
+  }
+
+  // Returns true if and only if the given arguments match the matchers.
+  bool Matches(const ArgumentTuple& args) const {
+    return TupleMatches(matchers_, args) && extra_matcher_.Matches(args);
+  }
+
+  // Returns the action specified by the user.
+  const Action<F>& GetAction() const {
+    AssertSpecProperty(last_clause_ == kWillByDefault,
+                       ".WillByDefault() must appear exactly "
+                       "once in an ON_CALL().");
+    return action_;
+  }
+
+ private:
+  // The information in statement
+  //
+  //   ON_CALL(mock_object, Method(matchers))
+  //       .With(multi-argument-matcher)
+  //       .WillByDefault(action);
+  //
+  // is recorded in the data members like this:
+  //
+  //   source file that contains the statement => file_
+  //   line number of the statement            => line_
+  //   matchers                                => matchers_
+  //   multi-argument-matcher                  => extra_matcher_
+  //   action                                  => action_
+  ArgumentMatcherTuple matchers_;
+  Matcher<const ArgumentTuple&> extra_matcher_;
+  Action<F> action_;
+};  // class OnCallSpec
+
+// Possible reactions on uninteresting calls.
+enum CallReaction {
+  kAllow,
+  kWarn,
+  kFail,
+};
+
+}  // namespace internal
+
+// Utilities for manipulating mock objects.
+class GTEST_API_ Mock {
+ public:
+  // The following public methods can be called concurrently.
+
+  // Tells Google Mock to ignore mock_obj when checking for leaked
+  // mock objects.
+  static void AllowLeak(const void* mock_obj)
+      GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+
+  // Verifies and clears all expectations on the given mock object.
+  // If the expectations aren't satisfied, generates one or more
+  // Google Test non-fatal failures and returns false.
+  static bool VerifyAndClearExpectations(void* mock_obj)
+      GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+
+  // Verifies all expectations on the given mock object and clears its
+  // default actions and expectations.  Returns true if and only if the
+  // verification was successful.
+  static bool VerifyAndClear(void* mock_obj)
+      GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+
+  // Returns whether the mock was created as a naggy mock (default)
+  static bool IsNaggy(void* mock_obj)
+      GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+  // Returns whether the mock was created as a nice mock
+  static bool IsNice(void* mock_obj)
+      GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+  // Returns whether the mock was created as a strict mock
+  static bool IsStrict(void* mock_obj)
+      GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+
+ private:
+  friend class internal::UntypedFunctionMockerBase;
+
+  // Needed for a function mocker to register itself (so that we know
+  // how to clear a mock object).
+  template <typename F>
+  friend class internal::FunctionMocker;
+
+  template <typename MockClass>
+  friend class internal::NiceMockImpl;
+  template <typename MockClass>
+  friend class internal::NaggyMockImpl;
+  template <typename MockClass>
+  friend class internal::StrictMockImpl;
+
+  // Tells Google Mock to allow uninteresting calls on the given mock
+  // object.
+  static void AllowUninterestingCalls(const void* mock_obj)
+      GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+
+  // Tells Google Mock to warn the user about uninteresting calls on
+  // the given mock object.
+  static void WarnUninterestingCalls(const void* mock_obj)
+      GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+
+  // Tells Google Mock to fail uninteresting calls on the given mock
+  // object.
+  static void FailUninterestingCalls(const void* mock_obj)
+      GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+
+  // Tells Google Mock the given mock object is being destroyed and
+  // its entry in the call-reaction table should be removed.
+  static void UnregisterCallReaction(const void* mock_obj)
+      GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+
+  // Returns the reaction Google Mock will have on uninteresting calls
+  // made on the given mock object.
+  static internal::CallReaction GetReactionOnUninterestingCalls(
+      const void* mock_obj)
+          GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+
+  // Verifies that all expectations on the given mock object have been
+  // satisfied.  Reports one or more Google Test non-fatal failures
+  // and returns false if not.
+  static bool VerifyAndClearExpectationsLocked(void* mock_obj)
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(internal::g_gmock_mutex);
+
+  // Clears all ON_CALL()s set on the given mock object.
+  static void ClearDefaultActionsLocked(void* mock_obj)
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(internal::g_gmock_mutex);
+
+  // Registers a mock object and a mock method it owns.
+  static void Register(
+      const void* mock_obj,
+      internal::UntypedFunctionMockerBase* mocker)
+          GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+
+  // Tells Google Mock where in the source code mock_obj is used in an
+  // ON_CALL or EXPECT_CALL.  In case mock_obj is leaked, this
+  // information helps the user identify which object it is.
+  static void RegisterUseByOnCallOrExpectCall(
+      const void* mock_obj, const char* file, int line)
+          GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+
+  // Unregisters a mock method; removes the owning mock object from
+  // the registry when the last mock method associated with it has
+  // been unregistered.  This is called only in the destructor of
+  // FunctionMocker.
+  static void UnregisterLocked(internal::UntypedFunctionMockerBase* mocker)
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(internal::g_gmock_mutex);
+};  // class Mock
+
+// An abstract handle of an expectation.  Useful in the .After()
+// clause of EXPECT_CALL() for setting the (partial) order of
+// expectations.  The syntax:
+//
+//   Expectation e1 = EXPECT_CALL(...)...;
+//   EXPECT_CALL(...).After(e1)...;
+//
+// sets two expectations where the latter can only be matched after
+// the former has been satisfied.
+//
+// Notes:
+//   - This class is copyable and has value semantics.
+//   - Constness is shallow: a const Expectation object itself cannot
+//     be modified, but the mutable methods of the ExpectationBase
+//     object it references can be called via expectation_base().
+
+class GTEST_API_ Expectation {
+ public:
+  // Constructs a null object that doesn't reference any expectation.
+  Expectation();
+  Expectation(Expectation&&) = default;
+  Expectation(const Expectation&) = default;
+  Expectation& operator=(Expectation&&) = default;
+  Expectation& operator=(const Expectation&) = default;
+  ~Expectation();
+
+  // This single-argument ctor must not be explicit, in order to support the
+  //   Expectation e = EXPECT_CALL(...);
+  // syntax.
+  //
+  // A TypedExpectation object stores its pre-requisites as
+  // Expectation objects, and needs to call the non-const Retire()
+  // method on the ExpectationBase objects they reference.  Therefore
+  // Expectation must receive a *non-const* reference to the
+  // ExpectationBase object.
+  Expectation(internal::ExpectationBase& exp);  // NOLINT
+
+  // The compiler-generated copy ctor and operator= work exactly as
+  // intended, so we don't need to define our own.
+
+  // Returns true if and only if rhs references the same expectation as this
+  // object does.
+  bool operator==(const Expectation& rhs) const {
+    return expectation_base_ == rhs.expectation_base_;
+  }
+
+  bool operator!=(const Expectation& rhs) const { return !(*this == rhs); }
+
+ private:
+  friend class ExpectationSet;
+  friend class Sequence;
+  friend class ::testing::internal::ExpectationBase;
+  friend class ::testing::internal::UntypedFunctionMockerBase;
+
+  template <typename F>
+  friend class ::testing::internal::FunctionMocker;
+
+  template <typename F>
+  friend class ::testing::internal::TypedExpectation;
+
+  // This comparator is needed for putting Expectation objects into a set.
+  class Less {
+   public:
+    bool operator()(const Expectation& lhs, const Expectation& rhs) const {
+      return lhs.expectation_base_.get() < rhs.expectation_base_.get();
+    }
+  };
+
+  typedef ::std::set<Expectation, Less> Set;
+
+  Expectation(
+      const std::shared_ptr<internal::ExpectationBase>& expectation_base);
+
+  // Returns the expectation this object references.
+  const std::shared_ptr<internal::ExpectationBase>& expectation_base() const {
+    return expectation_base_;
+  }
+
+  // A shared_ptr that co-owns the expectation this handle references.
+  std::shared_ptr<internal::ExpectationBase> expectation_base_;
+};
+
+// A set of expectation handles.  Useful in the .After() clause of
+// EXPECT_CALL() for setting the (partial) order of expectations.  The
+// syntax:
+//
+//   ExpectationSet es;
+//   es += EXPECT_CALL(...)...;
+//   es += EXPECT_CALL(...)...;
+//   EXPECT_CALL(...).After(es)...;
+//
+// sets three expectations where the last one can only be matched
+// after the first two have both been satisfied.
+//
+// This class is copyable and has value semantics.
+class ExpectationSet {
+ public:
+  // A bidirectional iterator that can read a const element in the set.
+  typedef Expectation::Set::const_iterator const_iterator;
+
+  // An object stored in the set.  This is an alias of Expectation.
+  typedef Expectation::Set::value_type value_type;
+
+  // Constructs an empty set.
+  ExpectationSet() {}
+
+  // This single-argument ctor must not be explicit, in order to support the
+  //   ExpectationSet es = EXPECT_CALL(...);
+  // syntax.
+  ExpectationSet(internal::ExpectationBase& exp) {  // NOLINT
+    *this += Expectation(exp);
+  }
+
+  // This single-argument ctor implements implicit conversion from
+  // Expectation and thus must not be explicit.  This allows either an
+  // Expectation or an ExpectationSet to be used in .After().
+  ExpectationSet(const Expectation& e) {  // NOLINT
+    *this += e;
+  }
+
+  // The compiler-generator ctor and operator= works exactly as
+  // intended, so we don't need to define our own.
+
+  // Returns true if and only if rhs contains the same set of Expectation
+  // objects as this does.
+  bool operator==(const ExpectationSet& rhs) const {
+    return expectations_ == rhs.expectations_;
+  }
+
+  bool operator!=(const ExpectationSet& rhs) const { return !(*this == rhs); }
+
+  // Implements the syntax
+  //   expectation_set += EXPECT_CALL(...);
+  ExpectationSet& operator+=(const Expectation& e) {
+    expectations_.insert(e);
+    return *this;
+  }
+
+  int size() const { return static_cast<int>(expectations_.size()); }
+
+  const_iterator begin() const { return expectations_.begin(); }
+  const_iterator end() const { return expectations_.end(); }
+
+ private:
+  Expectation::Set expectations_;
+};
+
+
+// Sequence objects are used by a user to specify the relative order
+// in which the expectations should match.  They are copyable (we rely
+// on the compiler-defined copy constructor and assignment operator).
+class GTEST_API_ Sequence {
+ public:
+  // Constructs an empty sequence.
+  Sequence() : last_expectation_(new Expectation) {}
+
+  // Adds an expectation to this sequence.  The caller must ensure
+  // that no other thread is accessing this Sequence object.
+  void AddExpectation(const Expectation& expectation) const;
+
+ private:
+  // The last expectation in this sequence.
+  std::shared_ptr<Expectation> last_expectation_;
+};  // class Sequence
+
+// An object of this type causes all EXPECT_CALL() statements
+// encountered in its scope to be put in an anonymous sequence.  The
+// work is done in the constructor and destructor.  You should only
+// create an InSequence object on the stack.
+//
+// The sole purpose for this class is to support easy definition of
+// sequential expectations, e.g.
+//
+//   {
+//     InSequence dummy;  // The name of the object doesn't matter.
+//
+//     // The following expectations must match in the order they appear.
+//     EXPECT_CALL(a, Bar())...;
+//     EXPECT_CALL(a, Baz())...;
+//     ...
+//     EXPECT_CALL(b, Xyz())...;
+//   }
+//
+// You can create InSequence objects in multiple threads, as long as
+// they are used to affect different mock objects.  The idea is that
+// each thread can create and set up its own mocks as if it's the only
+// thread.  However, for clarity of your tests we recommend you to set
+// up mocks in the main thread unless you have a good reason not to do
+// so.
+class GTEST_API_ InSequence {
+ public:
+  InSequence();
+  ~InSequence();
+ private:
+  bool sequence_created_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(InSequence);  // NOLINT
+} GTEST_ATTRIBUTE_UNUSED_;
+
+namespace internal {
+
+// Points to the implicit sequence introduced by a living InSequence
+// object (if any) in the current thread or NULL.
+GTEST_API_ extern ThreadLocal<Sequence*> g_gmock_implicit_sequence;
+
+// Base class for implementing expectations.
+//
+// There are two reasons for having a type-agnostic base class for
+// Expectation:
+//
+//   1. We need to store collections of expectations of different
+//   types (e.g. all pre-requisites of a particular expectation, all
+//   expectations in a sequence).  Therefore these expectation objects
+//   must share a common base class.
+//
+//   2. We can avoid binary code bloat by moving methods not depending
+//   on the template argument of Expectation to the base class.
+//
+// This class is internal and mustn't be used by user code directly.
+class GTEST_API_ ExpectationBase {
+ public:
+  // source_text is the EXPECT_CALL(...) source that created this Expectation.
+  ExpectationBase(const char* file, int line, const std::string& source_text);
+
+  virtual ~ExpectationBase();
+
+  // Where in the source file was the expectation spec defined?
+  const char* file() const { return file_; }
+  int line() const { return line_; }
+  const char* source_text() const { return source_text_.c_str(); }
+  // Returns the cardinality specified in the expectation spec.
+  const Cardinality& cardinality() const { return cardinality_; }
+
+  // Describes the source file location of this expectation.
+  void DescribeLocationTo(::std::ostream* os) const {
+    *os << FormatFileLocation(file(), line()) << " ";
+  }
+
+  // Describes how many times a function call matching this
+  // expectation has occurred.
+  void DescribeCallCountTo(::std::ostream* os) const
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex);
+
+  // If this mock method has an extra matcher (i.e. .With(matcher)),
+  // describes it to the ostream.
+  virtual void MaybeDescribeExtraMatcherTo(::std::ostream* os) = 0;
+
+ protected:
+  friend class ::testing::Expectation;
+  friend class UntypedFunctionMockerBase;
+
+  enum Clause {
+    // Don't change the order of the enum members!
+    kNone,
+    kWith,
+    kTimes,
+    kInSequence,
+    kAfter,
+    kWillOnce,
+    kWillRepeatedly,
+    kRetiresOnSaturation
+  };
+
+  typedef std::vector<const void*> UntypedActions;
+
+  // Returns an Expectation object that references and co-owns this
+  // expectation.
+  virtual Expectation GetHandle() = 0;
+
+  // Asserts that the EXPECT_CALL() statement has the given property.
+  void AssertSpecProperty(bool property,
+                          const std::string& failure_message) const {
+    Assert(property, file_, line_, failure_message);
+  }
+
+  // Expects that the EXPECT_CALL() statement has the given property.
+  void ExpectSpecProperty(bool property,
+                          const std::string& failure_message) const {
+    Expect(property, file_, line_, failure_message);
+  }
+
+  // Explicitly specifies the cardinality of this expectation.  Used
+  // by the subclasses to implement the .Times() clause.
+  void SpecifyCardinality(const Cardinality& cardinality);
+
+  // Returns true if and only if the user specified the cardinality
+  // explicitly using a .Times().
+  bool cardinality_specified() const { return cardinality_specified_; }
+
+  // Sets the cardinality of this expectation spec.
+  void set_cardinality(const Cardinality& a_cardinality) {
+    cardinality_ = a_cardinality;
+  }
+
+  // The following group of methods should only be called after the
+  // EXPECT_CALL() statement, and only when g_gmock_mutex is held by
+  // the current thread.
+
+  // Retires all pre-requisites of this expectation.
+  void RetireAllPreRequisites()
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex);
+
+  // Returns true if and only if this expectation is retired.
+  bool is_retired() const
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    return retired_;
+  }
+
+  // Retires this expectation.
+  void Retire()
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    retired_ = true;
+  }
+
+  // Returns true if and only if this expectation is satisfied.
+  bool IsSatisfied() const
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    return cardinality().IsSatisfiedByCallCount(call_count_);
+  }
+
+  // Returns true if and only if this expectation is saturated.
+  bool IsSaturated() const
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    return cardinality().IsSaturatedByCallCount(call_count_);
+  }
+
+  // Returns true if and only if this expectation is over-saturated.
+  bool IsOverSaturated() const
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    return cardinality().IsOverSaturatedByCallCount(call_count_);
+  }
+
+  // Returns true if and only if all pre-requisites of this expectation are
+  // satisfied.
+  bool AllPrerequisitesAreSatisfied() const
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex);
+
+  // Adds unsatisfied pre-requisites of this expectation to 'result'.
+  void FindUnsatisfiedPrerequisites(ExpectationSet* result) const
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex);
+
+  // Returns the number this expectation has been invoked.
+  int call_count() const
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    return call_count_;
+  }
+
+  // Increments the number this expectation has been invoked.
+  void IncrementCallCount()
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    call_count_++;
+  }
+
+  // Checks the action count (i.e. the number of WillOnce() and
+  // WillRepeatedly() clauses) against the cardinality if this hasn't
+  // been done before.  Prints a warning if there are too many or too
+  // few actions.
+  void CheckActionCountIfNotDone() const
+      GTEST_LOCK_EXCLUDED_(mutex_);
+
+  friend class ::testing::Sequence;
+  friend class ::testing::internal::ExpectationTester;
+
+  template <typename Function>
+  friend class TypedExpectation;
+
+  // Implements the .Times() clause.
+  void UntypedTimes(const Cardinality& a_cardinality);
+
+  // This group of fields are part of the spec and won't change after
+  // an EXPECT_CALL() statement finishes.
+  const char* file_;          // The file that contains the expectation.
+  int line_;                  // The line number of the expectation.
+  const std::string source_text_;  // The EXPECT_CALL(...) source text.
+  // True if and only if the cardinality is specified explicitly.
+  bool cardinality_specified_;
+  Cardinality cardinality_;            // The cardinality of the expectation.
+  // The immediate pre-requisites (i.e. expectations that must be
+  // satisfied before this expectation can be matched) of this
+  // expectation.  We use std::shared_ptr in the set because we want an
+  // Expectation object to be co-owned by its FunctionMocker and its
+  // successors.  This allows multiple mock objects to be deleted at
+  // different times.
+  ExpectationSet immediate_prerequisites_;
+
+  // This group of fields are the current state of the expectation,
+  // and can change as the mock function is called.
+  int call_count_;  // How many times this expectation has been invoked.
+  bool retired_;    // True if and only if this expectation has retired.
+  UntypedActions untyped_actions_;
+  bool extra_matcher_specified_;
+  bool repeated_action_specified_;  // True if a WillRepeatedly() was specified.
+  bool retires_on_saturation_;
+  Clause last_clause_;
+  mutable bool action_count_checked_;  // Under mutex_.
+  mutable Mutex mutex_;  // Protects action_count_checked_.
+};  // class ExpectationBase
+
+// Impements an expectation for the given function type.
+template <typename F>
+class TypedExpectation : public ExpectationBase {
+ public:
+  typedef typename Function<F>::ArgumentTuple ArgumentTuple;
+  typedef typename Function<F>::ArgumentMatcherTuple ArgumentMatcherTuple;
+  typedef typename Function<F>::Result Result;
+
+  TypedExpectation(FunctionMocker<F>* owner, const char* a_file, int a_line,
+                   const std::string& a_source_text,
+                   const ArgumentMatcherTuple& m)
+      : ExpectationBase(a_file, a_line, a_source_text),
+        owner_(owner),
+        matchers_(m),
+        // By default, extra_matcher_ should match anything.  However,
+        // we cannot initialize it with _ as that causes ambiguity between
+        // Matcher's copy and move constructor for some argument types.
+        extra_matcher_(A<const ArgumentTuple&>()),
+        repeated_action_(DoDefault()) {}
+
+  ~TypedExpectation() override {
+    // Check the validity of the action count if it hasn't been done
+    // yet (for example, if the expectation was never used).
+    CheckActionCountIfNotDone();
+    for (UntypedActions::const_iterator it = untyped_actions_.begin();
+         it != untyped_actions_.end(); ++it) {
+      delete static_cast<const Action<F>*>(*it);
+    }
+  }
+
+  // Implements the .With() clause.
+  TypedExpectation& With(const Matcher<const ArgumentTuple&>& m) {
+    if (last_clause_ == kWith) {
+      ExpectSpecProperty(false,
+                         ".With() cannot appear "
+                         "more than once in an EXPECT_CALL().");
+    } else {
+      ExpectSpecProperty(last_clause_ < kWith,
+                         ".With() must be the first "
+                         "clause in an EXPECT_CALL().");
+    }
+    last_clause_ = kWith;
+
+    extra_matcher_ = m;
+    extra_matcher_specified_ = true;
+    return *this;
+  }
+
+  // Implements the .Times() clause.
+  TypedExpectation& Times(const Cardinality& a_cardinality) {
+    ExpectationBase::UntypedTimes(a_cardinality);
+    return *this;
+  }
+
+  // Implements the .Times() clause.
+  TypedExpectation& Times(int n) {
+    return Times(Exactly(n));
+  }
+
+  // Implements the .InSequence() clause.
+  TypedExpectation& InSequence(const Sequence& s) {
+    ExpectSpecProperty(last_clause_ <= kInSequence,
+                       ".InSequence() cannot appear after .After(),"
+                       " .WillOnce(), .WillRepeatedly(), or "
+                       ".RetiresOnSaturation().");
+    last_clause_ = kInSequence;
+
+    s.AddExpectation(GetHandle());
+    return *this;
+  }
+  TypedExpectation& InSequence(const Sequence& s1, const Sequence& s2) {
+    return InSequence(s1).InSequence(s2);
+  }
+  TypedExpectation& InSequence(const Sequence& s1, const Sequence& s2,
+                               const Sequence& s3) {
+    return InSequence(s1, s2).InSequence(s3);
+  }
+  TypedExpectation& InSequence(const Sequence& s1, const Sequence& s2,
+                               const Sequence& s3, const Sequence& s4) {
+    return InSequence(s1, s2, s3).InSequence(s4);
+  }
+  TypedExpectation& InSequence(const Sequence& s1, const Sequence& s2,
+                               const Sequence& s3, const Sequence& s4,
+                               const Sequence& s5) {
+    return InSequence(s1, s2, s3, s4).InSequence(s5);
+  }
+
+  // Implements that .After() clause.
+  TypedExpectation& After(const ExpectationSet& s) {
+    ExpectSpecProperty(last_clause_ <= kAfter,
+                       ".After() cannot appear after .WillOnce(),"
+                       " .WillRepeatedly(), or "
+                       ".RetiresOnSaturation().");
+    last_clause_ = kAfter;
+
+    for (ExpectationSet::const_iterator it = s.begin(); it != s.end(); ++it) {
+      immediate_prerequisites_ += *it;
+    }
+    return *this;
+  }
+  TypedExpectation& After(const ExpectationSet& s1, const ExpectationSet& s2) {
+    return After(s1).After(s2);
+  }
+  TypedExpectation& After(const ExpectationSet& s1, const ExpectationSet& s2,
+                          const ExpectationSet& s3) {
+    return After(s1, s2).After(s3);
+  }
+  TypedExpectation& After(const ExpectationSet& s1, const ExpectationSet& s2,
+                          const ExpectationSet& s3, const ExpectationSet& s4) {
+    return After(s1, s2, s3).After(s4);
+  }
+  TypedExpectation& After(const ExpectationSet& s1, const ExpectationSet& s2,
+                          const ExpectationSet& s3, const ExpectationSet& s4,
+                          const ExpectationSet& s5) {
+    return After(s1, s2, s3, s4).After(s5);
+  }
+
+  // Implements the .WillOnce() clause.
+  TypedExpectation& WillOnce(const Action<F>& action) {
+    ExpectSpecProperty(last_clause_ <= kWillOnce,
+                       ".WillOnce() cannot appear after "
+                       ".WillRepeatedly() or .RetiresOnSaturation().");
+    last_clause_ = kWillOnce;
+
+    untyped_actions_.push_back(new Action<F>(action));
+    if (!cardinality_specified()) {
+      set_cardinality(Exactly(static_cast<int>(untyped_actions_.size())));
+    }
+    return *this;
+  }
+
+  // Implements the .WillRepeatedly() clause.
+  TypedExpectation& WillRepeatedly(const Action<F>& action) {
+    if (last_clause_ == kWillRepeatedly) {
+      ExpectSpecProperty(false,
+                         ".WillRepeatedly() cannot appear "
+                         "more than once in an EXPECT_CALL().");
+    } else {
+      ExpectSpecProperty(last_clause_ < kWillRepeatedly,
+                         ".WillRepeatedly() cannot appear "
+                         "after .RetiresOnSaturation().");
+    }
+    last_clause_ = kWillRepeatedly;
+    repeated_action_specified_ = true;
+
+    repeated_action_ = action;
+    if (!cardinality_specified()) {
+      set_cardinality(AtLeast(static_cast<int>(untyped_actions_.size())));
+    }
+
+    // Now that no more action clauses can be specified, we check
+    // whether their count makes sense.
+    CheckActionCountIfNotDone();
+    return *this;
+  }
+
+  // Implements the .RetiresOnSaturation() clause.
+  TypedExpectation& RetiresOnSaturation() {
+    ExpectSpecProperty(last_clause_ < kRetiresOnSaturation,
+                       ".RetiresOnSaturation() cannot appear "
+                       "more than once.");
+    last_clause_ = kRetiresOnSaturation;
+    retires_on_saturation_ = true;
+
+    // Now that no more action clauses can be specified, we check
+    // whether their count makes sense.
+    CheckActionCountIfNotDone();
+    return *this;
+  }
+
+  // Returns the matchers for the arguments as specified inside the
+  // EXPECT_CALL() macro.
+  const ArgumentMatcherTuple& matchers() const {
+    return matchers_;
+  }
+
+  // Returns the matcher specified by the .With() clause.
+  const Matcher<const ArgumentTuple&>& extra_matcher() const {
+    return extra_matcher_;
+  }
+
+  // Returns the action specified by the .WillRepeatedly() clause.
+  const Action<F>& repeated_action() const { return repeated_action_; }
+
+  // If this mock method has an extra matcher (i.e. .With(matcher)),
+  // describes it to the ostream.
+  void MaybeDescribeExtraMatcherTo(::std::ostream* os) override {
+    if (extra_matcher_specified_) {
+      *os << "    Expected args: ";
+      extra_matcher_.DescribeTo(os);
+      *os << "\n";
+    }
+  }
+
+ private:
+  template <typename Function>
+  friend class FunctionMocker;
+
+  // Returns an Expectation object that references and co-owns this
+  // expectation.
+  Expectation GetHandle() override { return owner_->GetHandleOf(this); }
+
+  // The following methods will be called only after the EXPECT_CALL()
+  // statement finishes and when the current thread holds
+  // g_gmock_mutex.
+
+  // Returns true if and only if this expectation matches the given arguments.
+  bool Matches(const ArgumentTuple& args) const
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    return TupleMatches(matchers_, args) && extra_matcher_.Matches(args);
+  }
+
+  // Returns true if and only if this expectation should handle the given
+  // arguments.
+  bool ShouldHandleArguments(const ArgumentTuple& args) const
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+
+    // In case the action count wasn't checked when the expectation
+    // was defined (e.g. if this expectation has no WillRepeatedly()
+    // or RetiresOnSaturation() clause), we check it when the
+    // expectation is used for the first time.
+    CheckActionCountIfNotDone();
+    return !is_retired() && AllPrerequisitesAreSatisfied() && Matches(args);
+  }
+
+  // Describes the result of matching the arguments against this
+  // expectation to the given ostream.
+  void ExplainMatchResultTo(
+      const ArgumentTuple& args,
+      ::std::ostream* os) const
+          GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+
+    if (is_retired()) {
+      *os << "         Expected: the expectation is active\n"
+          << "           Actual: it is retired\n";
+    } else if (!Matches(args)) {
+      if (!TupleMatches(matchers_, args)) {
+        ExplainMatchFailureTupleTo(matchers_, args, os);
+      }
+      StringMatchResultListener listener;
+      if (!extra_matcher_.MatchAndExplain(args, &listener)) {
+        *os << "    Expected args: ";
+        extra_matcher_.DescribeTo(os);
+        *os << "\n           Actual: don't match";
+
+        internal::PrintIfNotEmpty(listener.str(), os);
+        *os << "\n";
+      }
+    } else if (!AllPrerequisitesAreSatisfied()) {
+      *os << "         Expected: all pre-requisites are satisfied\n"
+          << "           Actual: the following immediate pre-requisites "
+          << "are not satisfied:\n";
+      ExpectationSet unsatisfied_prereqs;
+      FindUnsatisfiedPrerequisites(&unsatisfied_prereqs);
+      int i = 0;
+      for (ExpectationSet::const_iterator it = unsatisfied_prereqs.begin();
+           it != unsatisfied_prereqs.end(); ++it) {
+        it->expectation_base()->DescribeLocationTo(os);
+        *os << "pre-requisite #" << i++ << "\n";
+      }
+      *os << "                   (end of pre-requisites)\n";
+    } else {
+      // This line is here just for completeness' sake.  It will never
+      // be executed as currently the ExplainMatchResultTo() function
+      // is called only when the mock function call does NOT match the
+      // expectation.
+      *os << "The call matches the expectation.\n";
+    }
+  }
+
+  // Returns the action that should be taken for the current invocation.
+  const Action<F>& GetCurrentAction(const FunctionMocker<F>* mocker,
+                                    const ArgumentTuple& args) const
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    const int count = call_count();
+    Assert(count >= 1, __FILE__, __LINE__,
+           "call_count() is <= 0 when GetCurrentAction() is "
+           "called - this should never happen.");
+
+    const int action_count = static_cast<int>(untyped_actions_.size());
+    if (action_count > 0 && !repeated_action_specified_ &&
+        count > action_count) {
+      // If there is at least one WillOnce() and no WillRepeatedly(),
+      // we warn the user when the WillOnce() clauses ran out.
+      ::std::stringstream ss;
+      DescribeLocationTo(&ss);
+      ss << "Actions ran out in " << source_text() << "...\n"
+         << "Called " << count << " times, but only "
+         << action_count << " WillOnce()"
+         << (action_count == 1 ? " is" : "s are") << " specified - ";
+      mocker->DescribeDefaultActionTo(args, &ss);
+      Log(kWarning, ss.str(), 1);
+    }
+
+    return count <= action_count
+               ? *static_cast<const Action<F>*>(
+                     untyped_actions_[static_cast<size_t>(count - 1)])
+               : repeated_action();
+  }
+
+  // Given the arguments of a mock function call, if the call will
+  // over-saturate this expectation, returns the default action;
+  // otherwise, returns the next action in this expectation.  Also
+  // describes *what* happened to 'what', and explains *why* Google
+  // Mock does it to 'why'.  This method is not const as it calls
+  // IncrementCallCount().  A return value of NULL means the default
+  // action.
+  const Action<F>* GetActionForArguments(const FunctionMocker<F>* mocker,
+                                         const ArgumentTuple& args,
+                                         ::std::ostream* what,
+                                         ::std::ostream* why)
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    if (IsSaturated()) {
+      // We have an excessive call.
+      IncrementCallCount();
+      *what << "Mock function called more times than expected - ";
+      mocker->DescribeDefaultActionTo(args, what);
+      DescribeCallCountTo(why);
+
+      return nullptr;
+    }
+
+    IncrementCallCount();
+    RetireAllPreRequisites();
+
+    if (retires_on_saturation_ && IsSaturated()) {
+      Retire();
+    }
+
+    // Must be done after IncrementCount()!
+    *what << "Mock function call matches " << source_text() <<"...\n";
+    return &(GetCurrentAction(mocker, args));
+  }
+
+  // All the fields below won't change once the EXPECT_CALL()
+  // statement finishes.
+  FunctionMocker<F>* const owner_;
+  ArgumentMatcherTuple matchers_;
+  Matcher<const ArgumentTuple&> extra_matcher_;
+  Action<F> repeated_action_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(TypedExpectation);
+};  // class TypedExpectation
+
+// A MockSpec object is used by ON_CALL() or EXPECT_CALL() for
+// specifying the default behavior of, or expectation on, a mock
+// function.
+
+// Note: class MockSpec really belongs to the ::testing namespace.
+// However if we define it in ::testing, MSVC will complain when
+// classes in ::testing::internal declare it as a friend class
+// template.  To workaround this compiler bug, we define MockSpec in
+// ::testing::internal and import it into ::testing.
+
+// Logs a message including file and line number information.
+GTEST_API_ void LogWithLocation(testing::internal::LogSeverity severity,
+                                const char* file, int line,
+                                const std::string& message);
+
+template <typename F>
+class MockSpec {
+ public:
+  typedef typename internal::Function<F>::ArgumentTuple ArgumentTuple;
+  typedef typename internal::Function<F>::ArgumentMatcherTuple
+      ArgumentMatcherTuple;
+
+  // Constructs a MockSpec object, given the function mocker object
+  // that the spec is associated with.
+  MockSpec(internal::FunctionMocker<F>* function_mocker,
+           const ArgumentMatcherTuple& matchers)
+      : function_mocker_(function_mocker), matchers_(matchers) {}
+
+  // Adds a new default action spec to the function mocker and returns
+  // the newly created spec.
+  internal::OnCallSpec<F>& InternalDefaultActionSetAt(
+      const char* file, int line, const char* obj, const char* call) {
+    LogWithLocation(internal::kInfo, file, line,
+                    std::string("ON_CALL(") + obj + ", " + call + ") invoked");
+    return function_mocker_->AddNewOnCallSpec(file, line, matchers_);
+  }
+
+  // Adds a new expectation spec to the function mocker and returns
+  // the newly created spec.
+  internal::TypedExpectation<F>& InternalExpectedAt(
+      const char* file, int line, const char* obj, const char* call) {
+    const std::string source_text(std::string("EXPECT_CALL(") + obj + ", " +
+                                  call + ")");
+    LogWithLocation(internal::kInfo, file, line, source_text + " invoked");
+    return function_mocker_->AddNewExpectation(
+        file, line, source_text, matchers_);
+  }
+
+  // This operator overload is used to swallow the superfluous parameter list
+  // introduced by the ON/EXPECT_CALL macros. See the macro comments for more
+  // explanation.
+  MockSpec<F>& operator()(const internal::WithoutMatchers&, void* const) {
+    return *this;
+  }
+
+ private:
+  template <typename Function>
+  friend class internal::FunctionMocker;
+
+  // The function mocker that owns this spec.
+  internal::FunctionMocker<F>* const function_mocker_;
+  // The argument matchers specified in the spec.
+  ArgumentMatcherTuple matchers_;
+};  // class MockSpec
+
+// Wrapper type for generically holding an ordinary value or lvalue reference.
+// If T is not a reference type, it must be copyable or movable.
+// ReferenceOrValueWrapper<T> is movable, and will also be copyable unless
+// T is a move-only value type (which means that it will always be copyable
+// if the current platform does not support move semantics).
+//
+// The primary template defines handling for values, but function header
+// comments describe the contract for the whole template (including
+// specializations).
+template <typename T>
+class ReferenceOrValueWrapper {
+ public:
+  // Constructs a wrapper from the given value/reference.
+  explicit ReferenceOrValueWrapper(T value)
+      : value_(std::move(value)) {
+  }
+
+  // Unwraps and returns the underlying value/reference, exactly as
+  // originally passed. The behavior of calling this more than once on
+  // the same object is unspecified.
+  T Unwrap() { return std::move(value_); }
+
+  // Provides nondestructive access to the underlying value/reference.
+  // Always returns a const reference (more precisely,
+  // const std::add_lvalue_reference<T>::type). The behavior of calling this
+  // after calling Unwrap on the same object is unspecified.
+  const T& Peek() const {
+    return value_;
+  }
+
+ private:
+  T value_;
+};
+
+// Specialization for lvalue reference types. See primary template
+// for documentation.
+template <typename T>
+class ReferenceOrValueWrapper<T&> {
+ public:
+  // Workaround for debatable pass-by-reference lint warning (c-library-team
+  // policy precludes NOLINT in this context)
+  typedef T& reference;
+  explicit ReferenceOrValueWrapper(reference ref)
+      : value_ptr_(&ref) {}
+  T& Unwrap() { return *value_ptr_; }
+  const T& Peek() const { return *value_ptr_; }
+
+ private:
+  T* value_ptr_;
+};
+
+// C++ treats the void type specially.  For example, you cannot define
+// a void-typed variable or pass a void value to a function.
+// ActionResultHolder<T> holds a value of type T, where T must be a
+// copyable type or void (T doesn't need to be default-constructable).
+// It hides the syntactic difference between void and other types, and
+// is used to unify the code for invoking both void-returning and
+// non-void-returning mock functions.
+
+// Untyped base class for ActionResultHolder<T>.
+class UntypedActionResultHolderBase {
+ public:
+  virtual ~UntypedActionResultHolderBase() {}
+
+  // Prints the held value as an action's result to os.
+  virtual void PrintAsActionResult(::std::ostream* os) const = 0;
+};
+
+// This generic definition is used when T is not void.
+template <typename T>
+class ActionResultHolder : public UntypedActionResultHolderBase {
+ public:
+  // Returns the held value. Must not be called more than once.
+  T Unwrap() {
+    return result_.Unwrap();
+  }
+
+  // Prints the held value as an action's result to os.
+  void PrintAsActionResult(::std::ostream* os) const override {
+    *os << "\n          Returns: ";
+    // T may be a reference type, so we don't use UniversalPrint().
+    UniversalPrinter<T>::Print(result_.Peek(), os);
+  }
+
+  // Performs the given mock function's default action and returns the
+  // result in a new-ed ActionResultHolder.
+  template <typename F>
+  static ActionResultHolder* PerformDefaultAction(
+      const FunctionMocker<F>* func_mocker,
+      typename Function<F>::ArgumentTuple&& args,
+      const std::string& call_description) {
+    return new ActionResultHolder(Wrapper(func_mocker->PerformDefaultAction(
+        std::move(args), call_description)));
+  }
+
+  // Performs the given action and returns the result in a new-ed
+  // ActionResultHolder.
+  template <typename F>
+  static ActionResultHolder* PerformAction(
+      const Action<F>& action, typename Function<F>::ArgumentTuple&& args) {
+    return new ActionResultHolder(
+        Wrapper(action.Perform(std::move(args))));
+  }
+
+ private:
+  typedef ReferenceOrValueWrapper<T> Wrapper;
+
+  explicit ActionResultHolder(Wrapper result)
+      : result_(std::move(result)) {
+  }
+
+  Wrapper result_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(ActionResultHolder);
+};
+
+// Specialization for T = void.
+template <>
+class ActionResultHolder<void> : public UntypedActionResultHolderBase {
+ public:
+  void Unwrap() { }
+
+  void PrintAsActionResult(::std::ostream* /* os */) const override {}
+
+  // Performs the given mock function's default action and returns ownership
+  // of an empty ActionResultHolder*.
+  template <typename F>
+  static ActionResultHolder* PerformDefaultAction(
+      const FunctionMocker<F>* func_mocker,
+      typename Function<F>::ArgumentTuple&& args,
+      const std::string& call_description) {
+    func_mocker->PerformDefaultAction(std::move(args), call_description);
+    return new ActionResultHolder;
+  }
+
+  // Performs the given action and returns ownership of an empty
+  // ActionResultHolder*.
+  template <typename F>
+  static ActionResultHolder* PerformAction(
+      const Action<F>& action, typename Function<F>::ArgumentTuple&& args) {
+    action.Perform(std::move(args));
+    return new ActionResultHolder;
+  }
+
+ private:
+  ActionResultHolder() {}
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(ActionResultHolder);
+};
+
+template <typename F>
+class FunctionMocker;
+
+template <typename R, typename... Args>
+class FunctionMocker<R(Args...)> final : public UntypedFunctionMockerBase {
+  using F = R(Args...);
+
+ public:
+  using Result = R;
+  using ArgumentTuple = std::tuple<Args...>;
+  using ArgumentMatcherTuple = std::tuple<Matcher<Args>...>;
+
+  FunctionMocker() {}
+
+  // There is no generally useful and implementable semantics of
+  // copying a mock object, so copying a mock is usually a user error.
+  // Thus we disallow copying function mockers.  If the user really
+  // wants to copy a mock object, they should implement their own copy
+  // operation, for example:
+  //
+  //   class MockFoo : public Foo {
+  //    public:
+  //     // Defines a copy constructor explicitly.
+  //     MockFoo(const MockFoo& src) {}
+  //     ...
+  //   };
+  FunctionMocker(const FunctionMocker&) = delete;
+  FunctionMocker& operator=(const FunctionMocker&) = delete;
+
+  // The destructor verifies that all expectations on this mock
+  // function have been satisfied.  If not, it will report Google Test
+  // non-fatal failures for the violations.
+  ~FunctionMocker() override GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
+    MutexLock l(&g_gmock_mutex);
+    VerifyAndClearExpectationsLocked();
+    Mock::UnregisterLocked(this);
+    ClearDefaultActionsLocked();
+  }
+
+  // Returns the ON_CALL spec that matches this mock function with the
+  // given arguments; returns NULL if no matching ON_CALL is found.
+  // L = *
+  const OnCallSpec<F>* FindOnCallSpec(
+      const ArgumentTuple& args) const {
+    for (UntypedOnCallSpecs::const_reverse_iterator it
+             = untyped_on_call_specs_.rbegin();
+         it != untyped_on_call_specs_.rend(); ++it) {
+      const OnCallSpec<F>* spec = static_cast<const OnCallSpec<F>*>(*it);
+      if (spec->Matches(args))
+        return spec;
+    }
+
+    return nullptr;
+  }
+
+  // Performs the default action of this mock function on the given
+  // arguments and returns the result. Asserts (or throws if
+  // exceptions are enabled) with a helpful call descrption if there
+  // is no valid return value. This method doesn't depend on the
+  // mutable state of this object, and thus can be called concurrently
+  // without locking.
+  // L = *
+  Result PerformDefaultAction(ArgumentTuple&& args,
+                              const std::string& call_description) const {
+    const OnCallSpec<F>* const spec =
+        this->FindOnCallSpec(args);
+    if (spec != nullptr) {
+      return spec->GetAction().Perform(std::move(args));
+    }
+    const std::string message =
+        call_description +
+        "\n    The mock function has no default action "
+        "set, and its return type has no default value set.";
+#if GTEST_HAS_EXCEPTIONS
+    if (!DefaultValue<Result>::Exists()) {
+      throw std::runtime_error(message);
+    }
+#else
+    Assert(DefaultValue<Result>::Exists(), "", -1, message);
+#endif
+    return DefaultValue<Result>::Get();
+  }
+
+  // Performs the default action with the given arguments and returns
+  // the action's result.  The call description string will be used in
+  // the error message to describe the call in the case the default
+  // action fails.  The caller is responsible for deleting the result.
+  // L = *
+  UntypedActionResultHolderBase* UntypedPerformDefaultAction(
+      void* untyped_args,  // must point to an ArgumentTuple
+      const std::string& call_description) const override {
+    ArgumentTuple* args = static_cast<ArgumentTuple*>(untyped_args);
+    return ResultHolder::PerformDefaultAction(this, std::move(*args),
+                                              call_description);
+  }
+
+  // Performs the given action with the given arguments and returns
+  // the action's result.  The caller is responsible for deleting the
+  // result.
+  // L = *
+  UntypedActionResultHolderBase* UntypedPerformAction(
+      const void* untyped_action, void* untyped_args) const override {
+    // Make a copy of the action before performing it, in case the
+    // action deletes the mock object (and thus deletes itself).
+    const Action<F> action = *static_cast<const Action<F>*>(untyped_action);
+    ArgumentTuple* args = static_cast<ArgumentTuple*>(untyped_args);
+    return ResultHolder::PerformAction(action, std::move(*args));
+  }
+
+  // Implements UntypedFunctionMockerBase::ClearDefaultActionsLocked():
+  // clears the ON_CALL()s set on this mock function.
+  void ClearDefaultActionsLocked() override
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+
+    // Deleting our default actions may trigger other mock objects to be
+    // deleted, for example if an action contains a reference counted smart
+    // pointer to that mock object, and that is the last reference. So if we
+    // delete our actions within the context of the global mutex we may deadlock
+    // when this method is called again. Instead, make a copy of the set of
+    // actions to delete, clear our set within the mutex, and then delete the
+    // actions outside of the mutex.
+    UntypedOnCallSpecs specs_to_delete;
+    untyped_on_call_specs_.swap(specs_to_delete);
+
+    g_gmock_mutex.Unlock();
+    for (UntypedOnCallSpecs::const_iterator it =
+             specs_to_delete.begin();
+         it != specs_to_delete.end(); ++it) {
+      delete static_cast<const OnCallSpec<F>*>(*it);
+    }
+
+    // Lock the mutex again, since the caller expects it to be locked when we
+    // return.
+    g_gmock_mutex.Lock();
+  }
+
+  // Returns the result of invoking this mock function with the given
+  // arguments.  This function can be safely called from multiple
+  // threads concurrently.
+  Result Invoke(Args... args) GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
+    ArgumentTuple tuple(std::forward<Args>(args)...);
+    std::unique_ptr<ResultHolder> holder(DownCast_<ResultHolder*>(
+        this->UntypedInvokeWith(static_cast<void*>(&tuple))));
+    return holder->Unwrap();
+  }
+
+  MockSpec<F> With(Matcher<Args>... m) {
+    return MockSpec<F>(this, ::std::make_tuple(std::move(m)...));
+  }
+
+ protected:
+  template <typename Function>
+  friend class MockSpec;
+
+  typedef ActionResultHolder<Result> ResultHolder;
+
+  // Adds and returns a default action spec for this mock function.
+  OnCallSpec<F>& AddNewOnCallSpec(
+      const char* file, int line,
+      const ArgumentMatcherTuple& m)
+          GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
+    Mock::RegisterUseByOnCallOrExpectCall(MockObject(), file, line);
+    OnCallSpec<F>* const on_call_spec = new OnCallSpec<F>(file, line, m);
+    untyped_on_call_specs_.push_back(on_call_spec);
+    return *on_call_spec;
+  }
+
+  // Adds and returns an expectation spec for this mock function.
+  TypedExpectation<F>& AddNewExpectation(const char* file, int line,
+                                         const std::string& source_text,
+                                         const ArgumentMatcherTuple& m)
+      GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
+    Mock::RegisterUseByOnCallOrExpectCall(MockObject(), file, line);
+    TypedExpectation<F>* const expectation =
+        new TypedExpectation<F>(this, file, line, source_text, m);
+    const std::shared_ptr<ExpectationBase> untyped_expectation(expectation);
+    // See the definition of untyped_expectations_ for why access to
+    // it is unprotected here.
+    untyped_expectations_.push_back(untyped_expectation);
+
+    // Adds this expectation into the implicit sequence if there is one.
+    Sequence* const implicit_sequence = g_gmock_implicit_sequence.get();
+    if (implicit_sequence != nullptr) {
+      implicit_sequence->AddExpectation(Expectation(untyped_expectation));
+    }
+
+    return *expectation;
+  }
+
+ private:
+  template <typename Func> friend class TypedExpectation;
+
+  // Some utilities needed for implementing UntypedInvokeWith().
+
+  // Describes what default action will be performed for the given
+  // arguments.
+  // L = *
+  void DescribeDefaultActionTo(const ArgumentTuple& args,
+                               ::std::ostream* os) const {
+    const OnCallSpec<F>* const spec = FindOnCallSpec(args);
+
+    if (spec == nullptr) {
+      *os << (std::is_void<Result>::value ? "returning directly.\n"
+                                          : "returning default value.\n");
+    } else {
+      *os << "taking default action specified at:\n"
+          << FormatFileLocation(spec->file(), spec->line()) << "\n";
+    }
+  }
+
+  // Writes a message that the call is uninteresting (i.e. neither
+  // explicitly expected nor explicitly unexpected) to the given
+  // ostream.
+  void UntypedDescribeUninterestingCall(const void* untyped_args,
+                                        ::std::ostream* os) const override
+      GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
+    const ArgumentTuple& args =
+        *static_cast<const ArgumentTuple*>(untyped_args);
+    *os << "Uninteresting mock function call - ";
+    DescribeDefaultActionTo(args, os);
+    *os << "    Function call: " << Name();
+    UniversalPrint(args, os);
+  }
+
+  // Returns the expectation that matches the given function arguments
+  // (or NULL is there's no match); when a match is found,
+  // untyped_action is set to point to the action that should be
+  // performed (or NULL if the action is "do default"), and
+  // is_excessive is modified to indicate whether the call exceeds the
+  // expected number.
+  //
+  // Critical section: We must find the matching expectation and the
+  // corresponding action that needs to be taken in an ATOMIC
+  // transaction.  Otherwise another thread may call this mock
+  // method in the middle and mess up the state.
+  //
+  // However, performing the action has to be left out of the critical
+  // section.  The reason is that we have no control on what the
+  // action does (it can invoke an arbitrary user function or even a
+  // mock function) and excessive locking could cause a dead lock.
+  const ExpectationBase* UntypedFindMatchingExpectation(
+      const void* untyped_args, const void** untyped_action, bool* is_excessive,
+      ::std::ostream* what, ::std::ostream* why) override
+      GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
+    const ArgumentTuple& args =
+        *static_cast<const ArgumentTuple*>(untyped_args);
+    MutexLock l(&g_gmock_mutex);
+    TypedExpectation<F>* exp = this->FindMatchingExpectationLocked(args);
+    if (exp == nullptr) {  // A match wasn't found.
+      this->FormatUnexpectedCallMessageLocked(args, what, why);
+      return nullptr;
+    }
+
+    // This line must be done before calling GetActionForArguments(),
+    // which will increment the call count for *exp and thus affect
+    // its saturation status.
+    *is_excessive = exp->IsSaturated();
+    const Action<F>* action = exp->GetActionForArguments(this, args, what, why);
+    if (action != nullptr && action->IsDoDefault())
+      action = nullptr;  // Normalize "do default" to NULL.
+    *untyped_action = action;
+    return exp;
+  }
+
+  // Prints the given function arguments to the ostream.
+  void UntypedPrintArgs(const void* untyped_args,
+                        ::std::ostream* os) const override {
+    const ArgumentTuple& args =
+        *static_cast<const ArgumentTuple*>(untyped_args);
+    UniversalPrint(args, os);
+  }
+
+  // Returns the expectation that matches the arguments, or NULL if no
+  // expectation matches them.
+  TypedExpectation<F>* FindMatchingExpectationLocked(
+      const ArgumentTuple& args) const
+          GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    // See the definition of untyped_expectations_ for why access to
+    // it is unprotected here.
+    for (typename UntypedExpectations::const_reverse_iterator it =
+             untyped_expectations_.rbegin();
+         it != untyped_expectations_.rend(); ++it) {
+      TypedExpectation<F>* const exp =
+          static_cast<TypedExpectation<F>*>(it->get());
+      if (exp->ShouldHandleArguments(args)) {
+        return exp;
+      }
+    }
+    return nullptr;
+  }
+
+  // Returns a message that the arguments don't match any expectation.
+  void FormatUnexpectedCallMessageLocked(
+      const ArgumentTuple& args,
+      ::std::ostream* os,
+      ::std::ostream* why) const
+          GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    *os << "\nUnexpected mock function call - ";
+    DescribeDefaultActionTo(args, os);
+    PrintTriedExpectationsLocked(args, why);
+  }
+
+  // Prints a list of expectations that have been tried against the
+  // current mock function call.
+  void PrintTriedExpectationsLocked(
+      const ArgumentTuple& args,
+      ::std::ostream* why) const
+          GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    const size_t count = untyped_expectations_.size();
+    *why << "Google Mock tried the following " << count << " "
+         << (count == 1 ? "expectation, but it didn't match" :
+             "expectations, but none matched")
+         << ":\n";
+    for (size_t i = 0; i < count; i++) {
+      TypedExpectation<F>* const expectation =
+          static_cast<TypedExpectation<F>*>(untyped_expectations_[i].get());
+      *why << "\n";
+      expectation->DescribeLocationTo(why);
+      if (count > 1) {
+        *why << "tried expectation #" << i << ": ";
+      }
+      *why << expectation->source_text() << "...\n";
+      expectation->ExplainMatchResultTo(args, why);
+      expectation->DescribeCallCountTo(why);
+    }
+  }
+};  // class FunctionMocker
+
+// Reports an uninteresting call (whose description is in msg) in the
+// manner specified by 'reaction'.
+void ReportUninterestingCall(CallReaction reaction, const std::string& msg);
+
+}  // namespace internal
+
+namespace internal {
+
+template <typename F>
+class MockFunction;
+
+template <typename R, typename... Args>
+class MockFunction<R(Args...)> {
+ public:
+  MockFunction(const MockFunction&) = delete;
+  MockFunction& operator=(const MockFunction&) = delete;
+
+  std::function<R(Args...)> AsStdFunction() {
+    return [this](Args... args) -> R {
+      return this->Call(std::forward<Args>(args)...);
+    };
+  }
+
+  // Implementation detail: the expansion of the MOCK_METHOD macro.
+  R Call(Args... args) {
+    mock_.SetOwnerAndName(this, "Call");
+    return mock_.Invoke(std::forward<Args>(args)...);
+  }
+
+  MockSpec<R(Args...)> gmock_Call(Matcher<Args>... m) {
+    mock_.RegisterOwner(this);
+    return mock_.With(std::move(m)...);
+  }
+
+  MockSpec<R(Args...)> gmock_Call(const WithoutMatchers&, R (*)(Args...)) {
+    return this->gmock_Call(::testing::A<Args>()...);
+  }
+
+ protected:
+  MockFunction() = default;
+  ~MockFunction() = default;
+
+ private:
+  FunctionMocker<R(Args...)> mock_;
+};
+
+/*
+The SignatureOf<F> struct is a meta-function returning function signature
+corresponding to the provided F argument.
+
+It makes use of MockFunction easier by allowing it to accept more F arguments
+than just function signatures.
+
+Specializations provided here cover a signature type itself and any template
+that can be parameterized with a signature, including std::function and
+boost::function.
+*/
+
+template <typename F, typename = void>
+struct SignatureOf;
+
+template <typename R, typename... Args>
+struct SignatureOf<R(Args...)> {
+  using type = R(Args...);
+};
+
+template <template <typename> class C, typename F>
+struct SignatureOf<C<F>,
+                   typename std::enable_if<std::is_function<F>::value>::type>
+    : SignatureOf<F> {};
+
+template <typename F>
+using SignatureOfT = typename SignatureOf<F>::type;
+
+}  // namespace internal
+
+// A MockFunction<F> type has one mock method whose type is
+// internal::SignatureOfT<F>.  It is useful when you just want your
+// test code to emit some messages and have Google Mock verify the
+// right messages are sent (and perhaps at the right times).  For
+// example, if you are exercising code:
+//
+//   Foo(1);
+//   Foo(2);
+//   Foo(3);
+//
+// and want to verify that Foo(1) and Foo(3) both invoke
+// mock.Bar("a"), but Foo(2) doesn't invoke anything, you can write:
+//
+// TEST(FooTest, InvokesBarCorrectly) {
+//   MyMock mock;
+//   MockFunction<void(string check_point_name)> check;
+//   {
+//     InSequence s;
+//
+//     EXPECT_CALL(mock, Bar("a"));
+//     EXPECT_CALL(check, Call("1"));
+//     EXPECT_CALL(check, Call("2"));
+//     EXPECT_CALL(mock, Bar("a"));
+//   }
+//   Foo(1);
+//   check.Call("1");
+//   Foo(2);
+//   check.Call("2");
+//   Foo(3);
+// }
+//
+// The expectation spec says that the first Bar("a") must happen
+// before check point "1", the second Bar("a") must happen after check
+// point "2", and nothing should happen between the two check
+// points. The explicit check points make it easy to tell which
+// Bar("a") is called by which call to Foo().
+//
+// MockFunction<F> can also be used to exercise code that accepts
+// std::function<internal::SignatureOfT<F>> callbacks. To do so, use
+// AsStdFunction() method to create std::function proxy forwarding to
+// original object's Call. Example:
+//
+// TEST(FooTest, RunsCallbackWithBarArgument) {
+//   MockFunction<int(string)> callback;
+//   EXPECT_CALL(callback, Call("bar")).WillOnce(Return(1));
+//   Foo(callback.AsStdFunction());
+// }
+//
+// The internal::SignatureOfT<F> indirection allows to use other types
+// than just function signature type. This is typically useful when
+// providing a mock for a predefined std::function type. Example:
+//
+// using FilterPredicate = std::function<bool(string)>;
+// void MyFilterAlgorithm(FilterPredicate predicate);
+//
+// TEST(FooTest, FilterPredicateAlwaysAccepts) {
+//   MockFunction<FilterPredicate> predicateMock;
+//   EXPECT_CALL(predicateMock, Call(_)).WillRepeatedly(Return(true));
+//   MyFilterAlgorithm(predicateMock.AsStdFunction());
+// }
+template <typename F>
+class MockFunction : public internal::MockFunction<internal::SignatureOfT<F>> {
+  using Base = internal::MockFunction<internal::SignatureOfT<F>>;
+
+ public:
+  using Base::Base;
+};
+
+// The style guide prohibits "using" statements in a namespace scope
+// inside a header file.  However, the MockSpec class template is
+// meant to be defined in the ::testing namespace.  The following line
+// is just a trick for working around a bug in MSVC 8.0, which cannot
+// handle it if we define MockSpec in ::testing.
+using internal::MockSpec;
+
+// Const(x) is a convenient function for obtaining a const reference
+// to x.  This is useful for setting expectations on an overloaded
+// const mock method, e.g.
+//
+//   class MockFoo : public FooInterface {
+//    public:
+//     MOCK_METHOD0(Bar, int());
+//     MOCK_CONST_METHOD0(Bar, int&());
+//   };
+//
+//   MockFoo foo;
+//   // Expects a call to non-const MockFoo::Bar().
+//   EXPECT_CALL(foo, Bar());
+//   // Expects a call to const MockFoo::Bar().
+//   EXPECT_CALL(Const(foo), Bar());
+template <typename T>
+inline const T& Const(const T& x) { return x; }
+
+// Constructs an Expectation object that references and co-owns exp.
+inline Expectation::Expectation(internal::ExpectationBase& exp)  // NOLINT
+    : expectation_base_(exp.GetHandle().expectation_base()) {}
+
+}  // namespace testing
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  //  4251
+
+// Implementation for ON_CALL and EXPECT_CALL macros. A separate macro is
+// required to avoid compile errors when the name of the method used in call is
+// a result of macro expansion. See CompilesWithMethodNameExpandedFromMacro
+// tests in internal/gmock-spec-builders_test.cc for more details.
+//
+// This macro supports statements both with and without parameter matchers. If
+// the parameter list is omitted, gMock will accept any parameters, which allows
+// tests to be written that don't need to encode the number of method
+// parameter. This technique may only be used for non-overloaded methods.
+//
+//   // These are the same:
+//   ON_CALL(mock, NoArgsMethod()).WillByDefault(...);
+//   ON_CALL(mock, NoArgsMethod).WillByDefault(...);
+//
+//   // As are these:
+//   ON_CALL(mock, TwoArgsMethod(_, _)).WillByDefault(...);
+//   ON_CALL(mock, TwoArgsMethod).WillByDefault(...);
+//
+//   // Can also specify args if you want, of course:
+//   ON_CALL(mock, TwoArgsMethod(_, 45)).WillByDefault(...);
+//
+//   // Overloads work as long as you specify parameters:
+//   ON_CALL(mock, OverloadedMethod(_)).WillByDefault(...);
+//   ON_CALL(mock, OverloadedMethod(_, _)).WillByDefault(...);
+//
+//   // Oops! Which overload did you want?
+//   ON_CALL(mock, OverloadedMethod).WillByDefault(...);
+//     => ERROR: call to member function 'gmock_OverloadedMethod' is ambiguous
+//
+// How this works: The mock class uses two overloads of the gmock_Method
+// expectation setter method plus an operator() overload on the MockSpec object.
+// In the matcher list form, the macro expands to:
+//
+//   // This statement:
+//   ON_CALL(mock, TwoArgsMethod(_, 45))...
+//
+//   // ...expands to:
+//   mock.gmock_TwoArgsMethod(_, 45)(WithoutMatchers(), nullptr)...
+//   |-------------v---------------||------------v-------------|
+//       invokes first overload        swallowed by operator()
+//
+//   // ...which is essentially:
+//   mock.gmock_TwoArgsMethod(_, 45)...
+//
+// Whereas the form without a matcher list:
+//
+//   // This statement:
+//   ON_CALL(mock, TwoArgsMethod)...
+//
+//   // ...expands to:
+//   mock.gmock_TwoArgsMethod(WithoutMatchers(), nullptr)...
+//   |-----------------------v--------------------------|
+//                 invokes second overload
+//
+//   // ...which is essentially:
+//   mock.gmock_TwoArgsMethod(_, _)...
+//
+// The WithoutMatchers() argument is used to disambiguate overloads and to
+// block the caller from accidentally invoking the second overload directly. The
+// second argument is an internal type derived from the method signature. The
+// failure to disambiguate two overloads of this method in the ON_CALL statement
+// is how we block callers from setting expectations on overloaded methods.
+#define GMOCK_ON_CALL_IMPL_(mock_expr, Setter, call)                    \
+  ((mock_expr).gmock_##call)(::testing::internal::GetWithoutMatchers(), \
+                             nullptr)                                   \
+      .Setter(__FILE__, __LINE__, #mock_expr, #call)
+
+#define ON_CALL(obj, call) \
+  GMOCK_ON_CALL_IMPL_(obj, InternalDefaultActionSetAt, call)
+
+#define EXPECT_CALL(obj, call) \
+  GMOCK_ON_CALL_IMPL_(obj, InternalExpectedAt, call)
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_SPEC_BUILDERS_H_
diff --git a/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock.h b/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock.h
new file mode 100644
index 0000000..12469bc
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/include/gmock/gmock.h
@@ -0,0 +1,98 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This is the main header file a user should include.
+
+// GOOGLETEST_CM0002 DO NOT DELETE
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_H_
+
+// This file implements the following syntax:
+//
+//   ON_CALL(mock_object, Method(...))
+//     .With(...) ?
+//     .WillByDefault(...);
+//
+// where With() is optional and WillByDefault() must appear exactly
+// once.
+//
+//   EXPECT_CALL(mock_object, Method(...))
+//     .With(...) ?
+//     .Times(...) ?
+//     .InSequence(...) *
+//     .WillOnce(...) *
+//     .WillRepeatedly(...) ?
+//     .RetiresOnSaturation() ? ;
+//
+// where all clauses are optional and WillOnce() can be repeated.
+
+#include "gmock/gmock-actions.h"
+#include "gmock/gmock-cardinalities.h"
+#include "gmock/gmock-function-mocker.h"
+#include "gmock/gmock-matchers.h"
+#include "gmock/gmock-more-actions.h"
+#include "gmock/gmock-more-matchers.h"
+#include "gmock/gmock-nice-strict.h"
+#include "gmock/internal/gmock-internal-utils.h"
+
+namespace testing {
+
+// Declares Google Mock flags that we want a user to use programmatically.
+GMOCK_DECLARE_bool_(catch_leaked_mocks);
+GMOCK_DECLARE_string_(verbose);
+GMOCK_DECLARE_int32_(default_mock_behavior);
+
+// Initializes Google Mock.  This must be called before running the
+// tests.  In particular, it parses the command line for the flags
+// that Google Mock recognizes.  Whenever a Google Mock flag is seen,
+// it is removed from argv, and *argc is decremented.
+//
+// No value is returned.  Instead, the Google Mock flag variables are
+// updated.
+//
+// Since Google Test is needed for Google Mock to work, this function
+// also initializes Google Test and parses its flags, if that hasn't
+// been done.
+GTEST_API_ void InitGoogleMock(int* argc, char** argv);
+
+// This overloaded version can be used in Windows programs compiled in
+// UNICODE mode.
+GTEST_API_ void InitGoogleMock(int* argc, wchar_t** argv);
+
+// This overloaded version can be used on Arduino/embedded platforms where
+// there is no argc/argv.
+GTEST_API_ void InitGoogleMock();
+
+}  // namespace testing
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_H_
diff --git a/leveldb_base/third_party/googletest/googlemock/include/gmock/internal/custom/README.md b/leveldb_base/third_party/googletest/googlemock/include/gmock/internal/custom/README.md
new file mode 100644
index 0000000..f6c93f6
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/include/gmock/internal/custom/README.md
@@ -0,0 +1,16 @@
+# Customization Points
+
+The custom directory is an injection point for custom user configurations.
+
+## Header `gmock-port.h`
+
+The following macros can be defined:
+
+### Flag related macros:
+
+*   `GMOCK_DECLARE_bool_(name)`
+*   `GMOCK_DECLARE_int32_(name)`
+*   `GMOCK_DECLARE_string_(name)`
+*   `GMOCK_DEFINE_bool_(name, default_val, doc)`
+*   `GMOCK_DEFINE_int32_(name, default_val, doc)`
+*   `GMOCK_DEFINE_string_(name, default_val, doc)`
diff --git a/leveldb_base/third_party/googletest/googlemock/include/gmock/internal/custom/gmock-generated-actions.h b/leveldb_base/third_party/googletest/googlemock/include/gmock/internal/custom/gmock-generated-actions.h
new file mode 100644
index 0000000..63f8999
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/include/gmock/internal/custom/gmock-generated-actions.h
@@ -0,0 +1,6 @@
+// GOOGLETEST_CM0002 DO NOT DELETE
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_CUSTOM_GMOCK_GENERATED_ACTIONS_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_CUSTOM_GMOCK_GENERATED_ACTIONS_H_
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_CUSTOM_GMOCK_GENERATED_ACTIONS_H_
diff --git a/leveldb_base/third_party/googletest/googlemock/include/gmock/internal/custom/gmock-matchers.h b/leveldb_base/third_party/googletest/googlemock/include/gmock/internal/custom/gmock-matchers.h
new file mode 100644
index 0000000..6384294
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/include/gmock/internal/custom/gmock-matchers.h
@@ -0,0 +1,36 @@
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// Injection point for custom user configurations. See README for details
+//
+// GOOGLETEST_CM0002 DO NOT DELETE
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_CUSTOM_GMOCK_MATCHERS_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_CUSTOM_GMOCK_MATCHERS_H_
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_CUSTOM_GMOCK_MATCHERS_H_
diff --git a/leveldb_base/third_party/googletest/googlemock/include/gmock/internal/custom/gmock-port.h b/leveldb_base/third_party/googletest/googlemock/include/gmock/internal/custom/gmock-port.h
new file mode 100644
index 0000000..1437869
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/include/gmock/internal/custom/gmock-port.h
@@ -0,0 +1,39 @@
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// Injection point for custom user configurations. See README for details
+//
+// ** Custom implementation starts here **
+
+// GOOGLETEST_CM0002 DO NOT DELETE
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_CUSTOM_GMOCK_PORT_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_CUSTOM_GMOCK_PORT_H_
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_CUSTOM_GMOCK_PORT_H_
diff --git a/leveldb_base/third_party/googletest/googlemock/include/gmock/internal/gmock-internal-utils.h b/leveldb_base/third_party/googletest/googlemock/include/gmock/internal/gmock-internal-utils.h
new file mode 100644
index 0000000..317544a
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/include/gmock/internal/gmock-internal-utils.h
@@ -0,0 +1,459 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file defines some utilities useful for implementing Google
+// Mock.  They are subject to change without notice, so please DO NOT
+// USE THEM IN USER CODE.
+
+// GOOGLETEST_CM0002 DO NOT DELETE
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_GMOCK_INTERNAL_UTILS_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_GMOCK_INTERNAL_UTILS_H_
+
+#include <stdio.h>
+#include <ostream>  // NOLINT
+#include <string>
+#include <type_traits>
+#include "gmock/internal/gmock-port.h"
+#include "gtest/gtest.h"
+
+namespace testing {
+
+template <typename>
+class Matcher;
+
+namespace internal {
+
+// Silence MSVC C4100 (unreferenced formal parameter) and
+// C4805('==': unsafe mix of type 'const int' and type 'const bool')
+#ifdef _MSC_VER
+# pragma warning(push)
+# pragma warning(disable:4100)
+# pragma warning(disable:4805)
+#endif
+
+// Joins a vector of strings as if they are fields of a tuple; returns
+// the joined string.
+GTEST_API_ std::string JoinAsTuple(const Strings& fields);
+
+// Converts an identifier name to a space-separated list of lower-case
+// words.  Each maximum substring of the form [A-Za-z][a-z]*|\d+ is
+// treated as one word.  For example, both "FooBar123" and
+// "foo_bar_123" are converted to "foo bar 123".
+GTEST_API_ std::string ConvertIdentifierNameToWords(const char* id_name);
+
+// GetRawPointer(p) returns the raw pointer underlying p when p is a
+// smart pointer, or returns p itself when p is already a raw pointer.
+// The following default implementation is for the smart pointer case.
+template <typename Pointer>
+inline const typename Pointer::element_type* GetRawPointer(const Pointer& p) {
+  return p.get();
+}
+// This overloaded version is for the raw pointer case.
+template <typename Element>
+inline Element* GetRawPointer(Element* p) { return p; }
+
+// MSVC treats wchar_t as a native type usually, but treats it as the
+// same as unsigned short when the compiler option /Zc:wchar_t- is
+// specified.  It defines _NATIVE_WCHAR_T_DEFINED symbol when wchar_t
+// is a native type.
+#if defined(_MSC_VER) && !defined(_NATIVE_WCHAR_T_DEFINED)
+// wchar_t is a typedef.
+#else
+# define GMOCK_WCHAR_T_IS_NATIVE_ 1
+#endif
+
+// In what follows, we use the term "kind" to indicate whether a type
+// is bool, an integer type (excluding bool), a floating-point type,
+// or none of them.  This categorization is useful for determining
+// when a matcher argument type can be safely converted to another
+// type in the implementation of SafeMatcherCast.
+enum TypeKind {
+  kBool, kInteger, kFloatingPoint, kOther
+};
+
+// KindOf<T>::value is the kind of type T.
+template <typename T> struct KindOf {
+  enum { value = kOther };  // The default kind.
+};
+
+// This macro declares that the kind of 'type' is 'kind'.
+#define GMOCK_DECLARE_KIND_(type, kind) \
+  template <> struct KindOf<type> { enum { value = kind }; }
+
+GMOCK_DECLARE_KIND_(bool, kBool);
+
+// All standard integer types.
+GMOCK_DECLARE_KIND_(char, kInteger);
+GMOCK_DECLARE_KIND_(signed char, kInteger);
+GMOCK_DECLARE_KIND_(unsigned char, kInteger);
+GMOCK_DECLARE_KIND_(short, kInteger);  // NOLINT
+GMOCK_DECLARE_KIND_(unsigned short, kInteger);  // NOLINT
+GMOCK_DECLARE_KIND_(int, kInteger);
+GMOCK_DECLARE_KIND_(unsigned int, kInteger);
+GMOCK_DECLARE_KIND_(long, kInteger);  // NOLINT
+GMOCK_DECLARE_KIND_(unsigned long, kInteger);  // NOLINT
+GMOCK_DECLARE_KIND_(long long, kInteger);  // NOLINT
+GMOCK_DECLARE_KIND_(unsigned long long, kInteger);  // NOLINT
+
+#if GMOCK_WCHAR_T_IS_NATIVE_
+GMOCK_DECLARE_KIND_(wchar_t, kInteger);
+#endif
+
+// All standard floating-point types.
+GMOCK_DECLARE_KIND_(float, kFloatingPoint);
+GMOCK_DECLARE_KIND_(double, kFloatingPoint);
+GMOCK_DECLARE_KIND_(long double, kFloatingPoint);
+
+#undef GMOCK_DECLARE_KIND_
+
+// Evaluates to the kind of 'type'.
+#define GMOCK_KIND_OF_(type) \
+  static_cast< ::testing::internal::TypeKind>( \
+      ::testing::internal::KindOf<type>::value)
+
+// LosslessArithmeticConvertibleImpl<kFromKind, From, kToKind, To>::value
+// is true if and only if arithmetic type From can be losslessly converted to
+// arithmetic type To.
+//
+// It's the user's responsibility to ensure that both From and To are
+// raw (i.e. has no CV modifier, is not a pointer, and is not a
+// reference) built-in arithmetic types, kFromKind is the kind of
+// From, and kToKind is the kind of To; the value is
+// implementation-defined when the above pre-condition is violated.
+template <TypeKind kFromKind, typename From, TypeKind kToKind, typename To>
+using LosslessArithmeticConvertibleImpl = std::integral_constant<
+    bool,
+    // clang-format off
+      // Converting from bool is always lossless
+      (kFromKind == kBool) ? true
+      // Converting between any other type kinds will be lossy if the type
+      // kinds are not the same.
+    : (kFromKind != kToKind) ? false
+    : (kFromKind == kInteger &&
+       // Converting between integers of different widths is allowed so long
+       // as the conversion does not go from signed to unsigned.
+      (((sizeof(From) < sizeof(To)) &&
+        !(std::is_signed<From>::value && !std::is_signed<To>::value)) ||
+       // Converting between integers of the same width only requires the
+       // two types to have the same signedness.
+       ((sizeof(From) == sizeof(To)) &&
+        (std::is_signed<From>::value == std::is_signed<To>::value)))
+       ) ? true
+      // Floating point conversions are lossless if and only if `To` is at least
+      // as wide as `From`.
+    : (kFromKind == kFloatingPoint && (sizeof(From) <= sizeof(To))) ? true
+    : false
+    // clang-format on
+    >;
+
+// LosslessArithmeticConvertible<From, To>::value is true if and only if
+// arithmetic type From can be losslessly converted to arithmetic type To.
+//
+// It's the user's responsibility to ensure that both From and To are
+// raw (i.e. has no CV modifier, is not a pointer, and is not a
+// reference) built-in arithmetic types; the value is
+// implementation-defined when the above pre-condition is violated.
+template <typename From, typename To>
+using LosslessArithmeticConvertible =
+    LosslessArithmeticConvertibleImpl<GMOCK_KIND_OF_(From), From,
+                                      GMOCK_KIND_OF_(To), To>;
+
+// This interface knows how to report a Google Mock failure (either
+// non-fatal or fatal).
+class FailureReporterInterface {
+ public:
+  // The type of a failure (either non-fatal or fatal).
+  enum FailureType {
+    kNonfatal, kFatal
+  };
+
+  virtual ~FailureReporterInterface() {}
+
+  // Reports a failure that occurred at the given source file location.
+  virtual void ReportFailure(FailureType type, const char* file, int line,
+                             const std::string& message) = 0;
+};
+
+// Returns the failure reporter used by Google Mock.
+GTEST_API_ FailureReporterInterface* GetFailureReporter();
+
+// Asserts that condition is true; aborts the process with the given
+// message if condition is false.  We cannot use LOG(FATAL) or CHECK()
+// as Google Mock might be used to mock the log sink itself.  We
+// inline this function to prevent it from showing up in the stack
+// trace.
+inline void Assert(bool condition, const char* file, int line,
+                   const std::string& msg) {
+  if (!condition) {
+    GetFailureReporter()->ReportFailure(FailureReporterInterface::kFatal,
+                                        file, line, msg);
+  }
+}
+inline void Assert(bool condition, const char* file, int line) {
+  Assert(condition, file, line, "Assertion failed.");
+}
+
+// Verifies that condition is true; generates a non-fatal failure if
+// condition is false.
+inline void Expect(bool condition, const char* file, int line,
+                   const std::string& msg) {
+  if (!condition) {
+    GetFailureReporter()->ReportFailure(FailureReporterInterface::kNonfatal,
+                                        file, line, msg);
+  }
+}
+inline void Expect(bool condition, const char* file, int line) {
+  Expect(condition, file, line, "Expectation failed.");
+}
+
+// Severity level of a log.
+enum LogSeverity {
+  kInfo = 0,
+  kWarning = 1
+};
+
+// Valid values for the --gmock_verbose flag.
+
+// All logs (informational and warnings) are printed.
+const char kInfoVerbosity[] = "info";
+// Only warnings are printed.
+const char kWarningVerbosity[] = "warning";
+// No logs are printed.
+const char kErrorVerbosity[] = "error";
+
+// Returns true if and only if a log with the given severity is visible
+// according to the --gmock_verbose flag.
+GTEST_API_ bool LogIsVisible(LogSeverity severity);
+
+// Prints the given message to stdout if and only if 'severity' >= the level
+// specified by the --gmock_verbose flag.  If stack_frames_to_skip >=
+// 0, also prints the stack trace excluding the top
+// stack_frames_to_skip frames.  In opt mode, any positive
+// stack_frames_to_skip is treated as 0, since we don't know which
+// function calls will be inlined by the compiler and need to be
+// conservative.
+GTEST_API_ void Log(LogSeverity severity, const std::string& message,
+                    int stack_frames_to_skip);
+
+// A marker class that is used to resolve parameterless expectations to the
+// correct overload. This must not be instantiable, to prevent client code from
+// accidentally resolving to the overload; for example:
+//
+//    ON_CALL(mock, Method({}, nullptr))...
+//
+class WithoutMatchers {
+ private:
+  WithoutMatchers() {}
+  friend GTEST_API_ WithoutMatchers GetWithoutMatchers();
+};
+
+// Internal use only: access the singleton instance of WithoutMatchers.
+GTEST_API_ WithoutMatchers GetWithoutMatchers();
+
+// Disable MSVC warnings for infinite recursion, since in this case the
+// the recursion is unreachable.
+#ifdef _MSC_VER
+# pragma warning(push)
+# pragma warning(disable:4717)
+#endif
+
+// Invalid<T>() is usable as an expression of type T, but will terminate
+// the program with an assertion failure if actually run.  This is useful
+// when a value of type T is needed for compilation, but the statement
+// will not really be executed (or we don't care if the statement
+// crashes).
+template <typename T>
+inline T Invalid() {
+  Assert(false, "", -1, "Internal error: attempt to return invalid value");
+  // This statement is unreachable, and would never terminate even if it
+  // could be reached. It is provided only to placate compiler warnings
+  // about missing return statements.
+  return Invalid<T>();
+}
+
+#ifdef _MSC_VER
+# pragma warning(pop)
+#endif
+
+// Given a raw type (i.e. having no top-level reference or const
+// modifier) RawContainer that's either an STL-style container or a
+// native array, class StlContainerView<RawContainer> has the
+// following members:
+//
+//   - type is a type that provides an STL-style container view to
+//     (i.e. implements the STL container concept for) RawContainer;
+//   - const_reference is a type that provides a reference to a const
+//     RawContainer;
+//   - ConstReference(raw_container) returns a const reference to an STL-style
+//     container view to raw_container, which is a RawContainer.
+//   - Copy(raw_container) returns an STL-style container view of a
+//     copy of raw_container, which is a RawContainer.
+//
+// This generic version is used when RawContainer itself is already an
+// STL-style container.
+template <class RawContainer>
+class StlContainerView {
+ public:
+  typedef RawContainer type;
+  typedef const type& const_reference;
+
+  static const_reference ConstReference(const RawContainer& container) {
+    static_assert(!std::is_const<RawContainer>::value,
+                  "RawContainer type must not be const");
+    return container;
+  }
+  static type Copy(const RawContainer& container) { return container; }
+};
+
+// This specialization is used when RawContainer is a native array type.
+template <typename Element, size_t N>
+class StlContainerView<Element[N]> {
+ public:
+  typedef typename std::remove_const<Element>::type RawElement;
+  typedef internal::NativeArray<RawElement> type;
+  // NativeArray<T> can represent a native array either by value or by
+  // reference (selected by a constructor argument), so 'const type'
+  // can be used to reference a const native array.  We cannot
+  // 'typedef const type& const_reference' here, as that would mean
+  // ConstReference() has to return a reference to a local variable.
+  typedef const type const_reference;
+
+  static const_reference ConstReference(const Element (&array)[N]) {
+    static_assert(std::is_same<Element, RawElement>::value,
+                  "Element type must not be const");
+    return type(array, N, RelationToSourceReference());
+  }
+  static type Copy(const Element (&array)[N]) {
+    return type(array, N, RelationToSourceCopy());
+  }
+};
+
+// This specialization is used when RawContainer is a native array
+// represented as a (pointer, size) tuple.
+template <typename ElementPointer, typename Size>
+class StlContainerView< ::std::tuple<ElementPointer, Size> > {
+ public:
+  typedef typename std::remove_const<
+      typename std::pointer_traits<ElementPointer>::element_type>::type
+      RawElement;
+  typedef internal::NativeArray<RawElement> type;
+  typedef const type const_reference;
+
+  static const_reference ConstReference(
+      const ::std::tuple<ElementPointer, Size>& array) {
+    return type(std::get<0>(array), std::get<1>(array),
+                RelationToSourceReference());
+  }
+  static type Copy(const ::std::tuple<ElementPointer, Size>& array) {
+    return type(std::get<0>(array), std::get<1>(array), RelationToSourceCopy());
+  }
+};
+
+// The following specialization prevents the user from instantiating
+// StlContainer with a reference type.
+template <typename T> class StlContainerView<T&>;
+
+// A type transform to remove constness from the first part of a pair.
+// Pairs like that are used as the value_type of associative containers,
+// and this transform produces a similar but assignable pair.
+template <typename T>
+struct RemoveConstFromKey {
+  typedef T type;
+};
+
+// Partially specialized to remove constness from std::pair<const K, V>.
+template <typename K, typename V>
+struct RemoveConstFromKey<std::pair<const K, V> > {
+  typedef std::pair<K, V> type;
+};
+
+// Emit an assertion failure due to incorrect DoDefault() usage. Out-of-lined to
+// reduce code size.
+GTEST_API_ void IllegalDoDefault(const char* file, int line);
+
+template <typename F, typename Tuple, size_t... Idx>
+auto ApplyImpl(F&& f, Tuple&& args, IndexSequence<Idx...>) -> decltype(
+    std::forward<F>(f)(std::get<Idx>(std::forward<Tuple>(args))...)) {
+  return std::forward<F>(f)(std::get<Idx>(std::forward<Tuple>(args))...);
+}
+
+// Apply the function to a tuple of arguments.
+template <typename F, typename Tuple>
+auto Apply(F&& f, Tuple&& args) -> decltype(
+    ApplyImpl(std::forward<F>(f), std::forward<Tuple>(args),
+              MakeIndexSequence<std::tuple_size<
+                  typename std::remove_reference<Tuple>::type>::value>())) {
+  return ApplyImpl(std::forward<F>(f), std::forward<Tuple>(args),
+                   MakeIndexSequence<std::tuple_size<
+                       typename std::remove_reference<Tuple>::type>::value>());
+}
+
+// Template struct Function<F>, where F must be a function type, contains
+// the following typedefs:
+//
+//   Result:               the function's return type.
+//   Arg<N>:               the type of the N-th argument, where N starts with 0.
+//   ArgumentTuple:        the tuple type consisting of all parameters of F.
+//   ArgumentMatcherTuple: the tuple type consisting of Matchers for all
+//                         parameters of F.
+//   MakeResultVoid:       the function type obtained by substituting void
+//                         for the return type of F.
+//   MakeResultIgnoredValue:
+//                         the function type obtained by substituting Something
+//                         for the return type of F.
+template <typename T>
+struct Function;
+
+template <typename R, typename... Args>
+struct Function<R(Args...)> {
+  using Result = R;
+  static constexpr size_t ArgumentCount = sizeof...(Args);
+  template <size_t I>
+  using Arg = ElemFromList<I, Args...>;
+  using ArgumentTuple = std::tuple<Args...>;
+  using ArgumentMatcherTuple = std::tuple<Matcher<Args>...>;
+  using MakeResultVoid = void(Args...);
+  using MakeResultIgnoredValue = IgnoredValue(Args...);
+};
+
+template <typename R, typename... Args>
+constexpr size_t Function<R(Args...)>::ArgumentCount;
+
+#ifdef _MSC_VER
+# pragma warning(pop)
+#endif
+
+}  // namespace internal
+}  // namespace testing
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_GMOCK_INTERNAL_UTILS_H_
diff --git a/leveldb_base/third_party/googletest/googlemock/include/gmock/internal/gmock-port.h b/leveldb_base/third_party/googletest/googlemock/include/gmock/internal/gmock-port.h
new file mode 100644
index 0000000..367a44d
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/include/gmock/internal/gmock-port.h
@@ -0,0 +1,87 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// Low-level types and utilities for porting Google Mock to various
+// platforms.  All macros ending with _ and symbols defined in an
+// internal namespace are subject to change without notice.  Code
+// outside Google Mock MUST NOT USE THEM DIRECTLY.  Macros that don't
+// end with _ are part of Google Mock's public API and can be used by
+// code outside Google Mock.
+
+// GOOGLETEST_CM0002 DO NOT DELETE
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_GMOCK_PORT_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_GMOCK_PORT_H_
+
+#include <assert.h>
+#include <stdlib.h>
+#include <cstdint>
+#include <iostream>
+
+// Most of the utilities needed for porting Google Mock are also
+// required for Google Test and are defined in gtest-port.h.
+//
+// Note to maintainers: to reduce code duplication, prefer adding
+// portability utilities to Google Test's gtest-port.h instead of
+// here, as Google Mock depends on Google Test.  Only add a utility
+// here if it's truly specific to Google Mock.
+
+#include "gtest/internal/gtest-port.h"
+#include "gmock/internal/custom/gmock-port.h"
+
+// For MS Visual C++, check the compiler version. At least VS 2015 is
+// required to compile Google Mock.
+#if defined(_MSC_VER) && _MSC_VER < 1900
+# error "At least Visual C++ 2015 (14.0) is required to compile Google Mock."
+#endif
+
+// Macro for referencing flags.  This is public as we want the user to
+// use this syntax to reference Google Mock flags.
+#define GMOCK_FLAG(name) FLAGS_gmock_##name
+
+#if !defined(GMOCK_DECLARE_bool_)
+
+// Macros for declaring flags.
+# define GMOCK_DECLARE_bool_(name) extern GTEST_API_ bool GMOCK_FLAG(name)
+# define GMOCK_DECLARE_int32_(name) extern GTEST_API_ int32_t GMOCK_FLAG(name)
+# define GMOCK_DECLARE_string_(name) \
+    extern GTEST_API_ ::std::string GMOCK_FLAG(name)
+
+// Macros for defining flags.
+# define GMOCK_DEFINE_bool_(name, default_val, doc) \
+    GTEST_API_ bool GMOCK_FLAG(name) = (default_val)
+# define GMOCK_DEFINE_int32_(name, default_val, doc) \
+    GTEST_API_ int32_t GMOCK_FLAG(name) = (default_val)
+# define GMOCK_DEFINE_string_(name, default_val, doc) \
+    GTEST_API_ ::std::string GMOCK_FLAG(name) = (default_val)
+
+#endif  // !defined(GMOCK_DECLARE_bool_)
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_GMOCK_PORT_H_
diff --git a/leveldb_base/third_party/googletest/googlemock/include/gmock/internal/gmock-pp.h b/leveldb_base/third_party/googletest/googlemock/include/gmock/internal/gmock-pp.h
new file mode 100644
index 0000000..94d61c0
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/include/gmock/internal/gmock-pp.h
@@ -0,0 +1,279 @@
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_GMOCK_PP_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_GMOCK_PP_H_
+
+// Expands and concatenates the arguments. Constructed macros reevaluate.
+#define GMOCK_PP_CAT(_1, _2) GMOCK_PP_INTERNAL_CAT(_1, _2)
+
+// Expands and stringifies the only argument.
+#define GMOCK_PP_STRINGIZE(...) GMOCK_PP_INTERNAL_STRINGIZE(__VA_ARGS__)
+
+// Returns empty. Given a variadic number of arguments.
+#define GMOCK_PP_EMPTY(...)
+
+// Returns a comma. Given a variadic number of arguments.
+#define GMOCK_PP_COMMA(...) ,
+
+// Returns the only argument.
+#define GMOCK_PP_IDENTITY(_1) _1
+
+// Evaluates to the number of arguments after expansion.
+//
+//   #define PAIR x, y
+//
+//   GMOCK_PP_NARG() => 1
+//   GMOCK_PP_NARG(x) => 1
+//   GMOCK_PP_NARG(x, y) => 2
+//   GMOCK_PP_NARG(PAIR) => 2
+//
+// Requires: the number of arguments after expansion is at most 15.
+#define GMOCK_PP_NARG(...) \
+  GMOCK_PP_INTERNAL_16TH(  \
+      (__VA_ARGS__, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0))
+
+// Returns 1 if the expansion of arguments has an unprotected comma. Otherwise
+// returns 0. Requires no more than 15 unprotected commas.
+#define GMOCK_PP_HAS_COMMA(...) \
+  GMOCK_PP_INTERNAL_16TH(       \
+      (__VA_ARGS__, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0))
+
+// Returns the first argument.
+#define GMOCK_PP_HEAD(...) GMOCK_PP_INTERNAL_HEAD((__VA_ARGS__, unusedArg))
+
+// Returns the tail. A variadic list of all arguments minus the first. Requires
+// at least one argument.
+#define GMOCK_PP_TAIL(...) GMOCK_PP_INTERNAL_TAIL((__VA_ARGS__))
+
+// Calls CAT(_Macro, NARG(__VA_ARGS__))(__VA_ARGS__)
+#define GMOCK_PP_VARIADIC_CALL(_Macro, ...) \
+  GMOCK_PP_IDENTITY(                        \
+      GMOCK_PP_CAT(_Macro, GMOCK_PP_NARG(__VA_ARGS__))(__VA_ARGS__))
+
+// If the arguments after expansion have no tokens, evaluates to `1`. Otherwise
+// evaluates to `0`.
+//
+// Requires: * the number of arguments after expansion is at most 15.
+//           * If the argument is a macro, it must be able to be called with one
+//             argument.
+//
+// Implementation details:
+//
+// There is one case when it generates a compile error: if the argument is macro
+// that cannot be called with one argument.
+//
+//   #define M(a, b)  // it doesn't matter what it expands to
+//
+//   // Expected: expands to `0`.
+//   // Actual: compile error.
+//   GMOCK_PP_IS_EMPTY(M)
+//
+// There are 4 cases tested:
+//
+// * __VA_ARGS__ possible expansion has no unparen'd commas. Expected 0.
+// * __VA_ARGS__ possible expansion is not enclosed in parenthesis. Expected 0.
+// * __VA_ARGS__ possible expansion is not a macro that ()-evaluates to a comma.
+//   Expected 0
+// * __VA_ARGS__ is empty, or has unparen'd commas, or is enclosed in
+//   parenthesis, or is a macro that ()-evaluates to comma. Expected 1.
+//
+// We trigger detection on '0001', i.e. on empty.
+#define GMOCK_PP_IS_EMPTY(...)                                               \
+  GMOCK_PP_INTERNAL_IS_EMPTY(GMOCK_PP_HAS_COMMA(__VA_ARGS__),                \
+                             GMOCK_PP_HAS_COMMA(GMOCK_PP_COMMA __VA_ARGS__), \
+                             GMOCK_PP_HAS_COMMA(__VA_ARGS__()),              \
+                             GMOCK_PP_HAS_COMMA(GMOCK_PP_COMMA __VA_ARGS__()))
+
+// Evaluates to _Then if _Cond is 1 and _Else if _Cond is 0.
+#define GMOCK_PP_IF(_Cond, _Then, _Else) \
+  GMOCK_PP_CAT(GMOCK_PP_INTERNAL_IF_, _Cond)(_Then, _Else)
+
+// Similar to GMOCK_PP_IF but takes _Then and _Else in parentheses.
+//
+// GMOCK_PP_GENERIC_IF(1, (a, b, c), (d, e, f)) => a, b, c
+// GMOCK_PP_GENERIC_IF(0, (a, b, c), (d, e, f)) => d, e, f
+//
+#define GMOCK_PP_GENERIC_IF(_Cond, _Then, _Else) \
+  GMOCK_PP_REMOVE_PARENS(GMOCK_PP_IF(_Cond, _Then, _Else))
+
+// Evaluates to the number of arguments after expansion. Identifies 'empty' as
+// 0.
+//
+//   #define PAIR x, y
+//
+//   GMOCK_PP_NARG0() => 0
+//   GMOCK_PP_NARG0(x) => 1
+//   GMOCK_PP_NARG0(x, y) => 2
+//   GMOCK_PP_NARG0(PAIR) => 2
+//
+// Requires: * the number of arguments after expansion is at most 15.
+//           * If the argument is a macro, it must be able to be called with one
+//             argument.
+#define GMOCK_PP_NARG0(...) \
+  GMOCK_PP_IF(GMOCK_PP_IS_EMPTY(__VA_ARGS__), 0, GMOCK_PP_NARG(__VA_ARGS__))
+
+// Expands to 1 if the first argument starts with something in parentheses,
+// otherwise to 0.
+#define GMOCK_PP_IS_BEGIN_PARENS(...)                              \
+  GMOCK_PP_HEAD(GMOCK_PP_CAT(GMOCK_PP_INTERNAL_IBP_IS_VARIADIC_R_, \
+                             GMOCK_PP_INTERNAL_IBP_IS_VARIADIC_C __VA_ARGS__))
+
+// Expands to 1 is there is only one argument and it is enclosed in parentheses.
+#define GMOCK_PP_IS_ENCLOSED_PARENS(...)             \
+  GMOCK_PP_IF(GMOCK_PP_IS_BEGIN_PARENS(__VA_ARGS__), \
+              GMOCK_PP_IS_EMPTY(GMOCK_PP_EMPTY __VA_ARGS__), 0)
+
+// Remove the parens, requires GMOCK_PP_IS_ENCLOSED_PARENS(args) => 1.
+#define GMOCK_PP_REMOVE_PARENS(...) GMOCK_PP_INTERNAL_REMOVE_PARENS __VA_ARGS__
+
+// Expands to _Macro(0, _Data, e1) _Macro(1, _Data, e2) ... _Macro(K -1, _Data,
+// eK) as many of GMOCK_INTERNAL_NARG0 _Tuple.
+// Requires: * |_Macro| can be called with 3 arguments.
+//           * |_Tuple| expansion has no more than 15 elements.
+#define GMOCK_PP_FOR_EACH(_Macro, _Data, _Tuple)                        \
+  GMOCK_PP_CAT(GMOCK_PP_INTERNAL_FOR_EACH_IMPL_, GMOCK_PP_NARG0 _Tuple) \
+  (0, _Macro, _Data, _Tuple)
+
+// Expands to _Macro(0, _Data, ) _Macro(1, _Data, ) ... _Macro(K - 1, _Data, )
+// Empty if _K = 0.
+// Requires: * |_Macro| can be called with 3 arguments.
+//           * |_K| literal between 0 and 15
+#define GMOCK_PP_REPEAT(_Macro, _Data, _N)           \
+  GMOCK_PP_CAT(GMOCK_PP_INTERNAL_FOR_EACH_IMPL_, _N) \
+  (0, _Macro, _Data, GMOCK_PP_INTENRAL_EMPTY_TUPLE)
+
+// Increments the argument, requires the argument to be between 0 and 15.
+#define GMOCK_PP_INC(_i) GMOCK_PP_CAT(GMOCK_PP_INTERNAL_INC_, _i)
+
+// Returns comma if _i != 0. Requires _i to be between 0 and 15.
+#define GMOCK_PP_COMMA_IF(_i) GMOCK_PP_CAT(GMOCK_PP_INTERNAL_COMMA_IF_, _i)
+
+// Internal details follow. Do not use any of these symbols outside of this
+// file or we will break your code.
+#define GMOCK_PP_INTENRAL_EMPTY_TUPLE (, , , , , , , , , , , , , , , )
+#define GMOCK_PP_INTERNAL_CAT(_1, _2) _1##_2
+#define GMOCK_PP_INTERNAL_STRINGIZE(...) #__VA_ARGS__
+#define GMOCK_PP_INTERNAL_CAT_5(_1, _2, _3, _4, _5) _1##_2##_3##_4##_5
+#define GMOCK_PP_INTERNAL_IS_EMPTY(_1, _2, _3, _4)                             \
+  GMOCK_PP_HAS_COMMA(GMOCK_PP_INTERNAL_CAT_5(GMOCK_PP_INTERNAL_IS_EMPTY_CASE_, \
+                                             _1, _2, _3, _4))
+#define GMOCK_PP_INTERNAL_IS_EMPTY_CASE_0001 ,
+#define GMOCK_PP_INTERNAL_IF_1(_Then, _Else) _Then
+#define GMOCK_PP_INTERNAL_IF_0(_Then, _Else) _Else
+
+// Because of MSVC treating a token with a comma in it as a single token when
+// passed to another macro, we need to force it to evaluate it as multiple
+// tokens. We do that by using a "IDENTITY(MACRO PARENTHESIZED_ARGS)" macro. We
+// define one per possible macro that relies on this behavior. Note "_Args" must
+// be parenthesized.
+#define GMOCK_PP_INTERNAL_INTERNAL_16TH(_1, _2, _3, _4, _5, _6, _7, _8, _9, \
+                                        _10, _11, _12, _13, _14, _15, _16,  \
+                                        ...)                                \
+  _16
+#define GMOCK_PP_INTERNAL_16TH(_Args) \
+  GMOCK_PP_IDENTITY(GMOCK_PP_INTERNAL_INTERNAL_16TH _Args)
+#define GMOCK_PP_INTERNAL_INTERNAL_HEAD(_1, ...) _1
+#define GMOCK_PP_INTERNAL_HEAD(_Args) \
+  GMOCK_PP_IDENTITY(GMOCK_PP_INTERNAL_INTERNAL_HEAD _Args)
+#define GMOCK_PP_INTERNAL_INTERNAL_TAIL(_1, ...) __VA_ARGS__
+#define GMOCK_PP_INTERNAL_TAIL(_Args) \
+  GMOCK_PP_IDENTITY(GMOCK_PP_INTERNAL_INTERNAL_TAIL _Args)
+
+#define GMOCK_PP_INTERNAL_IBP_IS_VARIADIC_C(...) 1 _
+#define GMOCK_PP_INTERNAL_IBP_IS_VARIADIC_R_1 1,
+#define GMOCK_PP_INTERNAL_IBP_IS_VARIADIC_R_GMOCK_PP_INTERNAL_IBP_IS_VARIADIC_C \
+  0,
+#define GMOCK_PP_INTERNAL_REMOVE_PARENS(...) __VA_ARGS__
+#define GMOCK_PP_INTERNAL_INC_0 1
+#define GMOCK_PP_INTERNAL_INC_1 2
+#define GMOCK_PP_INTERNAL_INC_2 3
+#define GMOCK_PP_INTERNAL_INC_3 4
+#define GMOCK_PP_INTERNAL_INC_4 5
+#define GMOCK_PP_INTERNAL_INC_5 6
+#define GMOCK_PP_INTERNAL_INC_6 7
+#define GMOCK_PP_INTERNAL_INC_7 8
+#define GMOCK_PP_INTERNAL_INC_8 9
+#define GMOCK_PP_INTERNAL_INC_9 10
+#define GMOCK_PP_INTERNAL_INC_10 11
+#define GMOCK_PP_INTERNAL_INC_11 12
+#define GMOCK_PP_INTERNAL_INC_12 13
+#define GMOCK_PP_INTERNAL_INC_13 14
+#define GMOCK_PP_INTERNAL_INC_14 15
+#define GMOCK_PP_INTERNAL_INC_15 16
+#define GMOCK_PP_INTERNAL_COMMA_IF_0
+#define GMOCK_PP_INTERNAL_COMMA_IF_1 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_2 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_3 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_4 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_5 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_6 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_7 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_8 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_9 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_10 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_11 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_12 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_13 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_14 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_15 ,
+#define GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, _element) \
+  _Macro(_i, _Data, _element)
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_0(_i, _Macro, _Data, _Tuple)
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_1(_i, _Macro, _Data, _Tuple) \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple)
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_2(_i, _Macro, _Data, _Tuple)    \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_1(GMOCK_PP_INC(_i), _Macro, _Data,    \
+                                    (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_3(_i, _Macro, _Data, _Tuple)    \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_2(GMOCK_PP_INC(_i), _Macro, _Data,    \
+                                    (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_4(_i, _Macro, _Data, _Tuple)    \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_3(GMOCK_PP_INC(_i), _Macro, _Data,    \
+                                    (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_5(_i, _Macro, _Data, _Tuple)    \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_4(GMOCK_PP_INC(_i), _Macro, _Data,    \
+                                    (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_6(_i, _Macro, _Data, _Tuple)    \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_5(GMOCK_PP_INC(_i), _Macro, _Data,    \
+                                    (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_7(_i, _Macro, _Data, _Tuple)    \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_6(GMOCK_PP_INC(_i), _Macro, _Data,    \
+                                    (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_8(_i, _Macro, _Data, _Tuple)    \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_7(GMOCK_PP_INC(_i), _Macro, _Data,    \
+                                    (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_9(_i, _Macro, _Data, _Tuple)    \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_8(GMOCK_PP_INC(_i), _Macro, _Data,    \
+                                    (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_10(_i, _Macro, _Data, _Tuple)   \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_9(GMOCK_PP_INC(_i), _Macro, _Data,    \
+                                    (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_11(_i, _Macro, _Data, _Tuple)   \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_10(GMOCK_PP_INC(_i), _Macro, _Data,   \
+                                     (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_12(_i, _Macro, _Data, _Tuple)   \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_11(GMOCK_PP_INC(_i), _Macro, _Data,   \
+                                     (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_13(_i, _Macro, _Data, _Tuple)   \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_12(GMOCK_PP_INC(_i), _Macro, _Data,   \
+                                     (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_14(_i, _Macro, _Data, _Tuple)   \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_13(GMOCK_PP_INC(_i), _Macro, _Data,   \
+                                     (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_15(_i, _Macro, _Data, _Tuple)   \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_14(GMOCK_PP_INC(_i), _Macro, _Data,   \
+                                     (GMOCK_PP_TAIL _Tuple))
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_GMOCK_PP_H_
diff --git a/leveldb_base/third_party/googletest/googlemock/scripts/README.md b/leveldb_base/third_party/googletest/googlemock/scripts/README.md
new file mode 100644
index 0000000..a3301e5
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/scripts/README.md
@@ -0,0 +1,5 @@
+# Please Note:
+
+Files in this directory are no longer supported by the maintainers. They
+represent mostly historical artifacts and supported by the community only. There
+is no guarantee whatsoever that these scripts still work.
diff --git a/leveldb_base/third_party/googletest/googlemock/scripts/fuse_gmock_files.py b/leveldb_base/third_party/googletest/googlemock/scripts/fuse_gmock_files.py
new file mode 100644
index 0000000..7fa9b3a
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/scripts/fuse_gmock_files.py
@@ -0,0 +1,256 @@
+#!/usr/bin/env python
+#
+# Copyright 2009, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+"""fuse_gmock_files.py v0.1.0.
+
+Fuses Google Mock and Google Test source code into two .h files and a .cc file.
+
+SYNOPSIS
+       fuse_gmock_files.py [GMOCK_ROOT_DIR] OUTPUT_DIR
+
+       Scans GMOCK_ROOT_DIR for Google Mock and Google Test source
+       code, assuming Google Test is in the GMOCK_ROOT_DIR/../googletest
+       directory, and generates three files:
+       OUTPUT_DIR/gtest/gtest.h, OUTPUT_DIR/gmock/gmock.h, and
+       OUTPUT_DIR/gmock-gtest-all.cc.  Then you can build your tests
+       by adding OUTPUT_DIR to the include search path and linking
+       with OUTPUT_DIR/gmock-gtest-all.cc.  These three files contain
+       everything you need to use Google Mock.  Hence you can
+       "install" Google Mock by copying them to wherever you want.
+
+       GMOCK_ROOT_DIR can be omitted and defaults to the parent
+       directory of the directory holding this script.
+
+EXAMPLES
+       ./fuse_gmock_files.py fused_gmock
+       ./fuse_gmock_files.py path/to/unpacked/gmock fused_gmock
+
+This tool is experimental.  In particular, it assumes that there is no
+conditional inclusion of Google Mock or Google Test headers.  Please
+report any problems to googlemock@googlegroups.com.  You can read
+https://github.com/google/googletest/blob/master/docs/gmock_cook_book.md
+for more
+information.
+"""
+
+from __future__ import print_function
+
+import os
+import re
+import sys
+
+__author__ = 'wan@google.com (Zhanyong Wan)'
+
+# We assume that this file is in the scripts/ directory in the Google
+# Mock root directory.
+DEFAULT_GMOCK_ROOT_DIR = os.path.join(os.path.dirname(__file__), '..')
+
+# We need to call into googletest/scripts/fuse_gtest_files.py.
+sys.path.append(os.path.join(DEFAULT_GMOCK_ROOT_DIR, '../googletest/scripts'))
+import fuse_gtest_files as gtest  # pylint:disable=g-import-not-at-top
+
+# Regex for matching
+# '#include "gmock/..."'.
+INCLUDE_GMOCK_FILE_REGEX = re.compile(r'^\s*#\s*include\s*"(gmock/.+)"')
+
+# Where to find the source seed files.
+GMOCK_H_SEED = 'include/gmock/gmock.h'
+GMOCK_ALL_CC_SEED = 'src/gmock-all.cc'
+
+# Where to put the generated files.
+GTEST_H_OUTPUT = 'gtest/gtest.h'
+GMOCK_H_OUTPUT = 'gmock/gmock.h'
+GMOCK_GTEST_ALL_CC_OUTPUT = 'gmock-gtest-all.cc'
+
+
+def GetGTestRootDir(gmock_root):
+  """Returns the root directory of Google Test."""
+
+  return os.path.join(gmock_root, '../googletest')
+
+
+def ValidateGMockRootDir(gmock_root):
+  """Makes sure gmock_root points to a valid gmock root directory.
+
+  The function aborts the program on failure.
+
+  Args:
+    gmock_root: A string with the mock root directory.
+  """
+
+  gtest.ValidateGTestRootDir(GetGTestRootDir(gmock_root))
+  gtest.VerifyFileExists(gmock_root, GMOCK_H_SEED)
+  gtest.VerifyFileExists(gmock_root, GMOCK_ALL_CC_SEED)
+
+
+def ValidateOutputDir(output_dir):
+  """Makes sure output_dir points to a valid output directory.
+
+  The function aborts the program on failure.
+
+  Args:
+    output_dir: A string representing the output directory.
+  """
+
+  gtest.VerifyOutputFile(output_dir, gtest.GTEST_H_OUTPUT)
+  gtest.VerifyOutputFile(output_dir, GMOCK_H_OUTPUT)
+  gtest.VerifyOutputFile(output_dir, GMOCK_GTEST_ALL_CC_OUTPUT)
+
+
+def FuseGMockH(gmock_root, output_dir):
+  """Scans folder gmock_root to generate gmock/gmock.h in output_dir."""
+
+  output_file = open(os.path.join(output_dir, GMOCK_H_OUTPUT), 'w')
+  processed_files = set()  # Holds all gmock headers we've processed.
+
+  def ProcessFile(gmock_header_path):
+    """Processes the given gmock header file."""
+
+    # We don't process the same header twice.
+    if gmock_header_path in processed_files:
+      return
+
+    processed_files.add(gmock_header_path)
+
+    # Reads each line in the given gmock header.
+
+    with open(os.path.join(gmock_root, gmock_header_path), 'r') as fh:
+      for line in fh:
+        m = INCLUDE_GMOCK_FILE_REGEX.match(line)
+        if m:
+          # '#include "gmock/..."'
+          # - let's process it recursively.
+          ProcessFile('include/' + m.group(1))
+        else:
+          m = gtest.INCLUDE_GTEST_FILE_REGEX.match(line)
+          if m:
+            # '#include "gtest/foo.h"'
+            # We translate it to "gtest/gtest.h", regardless of what foo is,
+            # since all gtest headers are fused into gtest/gtest.h.
+
+            # There is no need to #include gtest.h twice.
+            if gtest.GTEST_H_SEED not in processed_files:
+              processed_files.add(gtest.GTEST_H_SEED)
+              output_file.write('#include "%s"\n' % (gtest.GTEST_H_OUTPUT,))
+          else:
+            # Otherwise we copy the line unchanged to the output file.
+            output_file.write(line)
+
+  ProcessFile(GMOCK_H_SEED)
+  output_file.close()
+
+
+def FuseGMockAllCcToFile(gmock_root, output_file):
+  """Scans folder gmock_root to fuse gmock-all.cc into output_file."""
+
+  processed_files = set()
+
+  def ProcessFile(gmock_source_file):
+    """Processes the given gmock source file."""
+
+    # We don't process the same #included file twice.
+    if gmock_source_file in processed_files:
+      return
+
+    processed_files.add(gmock_source_file)
+
+    # Reads each line in the given gmock source file.
+
+    with open(os.path.join(gmock_root, gmock_source_file), 'r') as fh:
+      for line in fh:
+        m = INCLUDE_GMOCK_FILE_REGEX.match(line)
+        if m:
+          # '#include "gmock/foo.h"'
+          # We treat it as '#include  "gmock/gmock.h"', as all other gmock
+          # headers are being fused into gmock.h and cannot be
+          # included directly.  No need to
+          # #include "gmock/gmock.h"
+          # more than once.
+
+          if GMOCK_H_SEED not in processed_files:
+            processed_files.add(GMOCK_H_SEED)
+            output_file.write('#include "%s"\n' % (GMOCK_H_OUTPUT,))
+        else:
+          m = gtest.INCLUDE_GTEST_FILE_REGEX.match(line)
+          if m:
+            # '#include "gtest/..."'
+            # There is no need to #include gtest.h as it has been
+            # #included by gtest-all.cc.
+
+            pass
+          else:
+            m = gtest.INCLUDE_SRC_FILE_REGEX.match(line)
+            if m:
+              # It's '#include "src/foo"' - let's process it recursively.
+              ProcessFile(m.group(1))
+            else:
+              # Otherwise we copy the line unchanged to the output file.
+              output_file.write(line)
+
+  ProcessFile(GMOCK_ALL_CC_SEED)
+
+
+def FuseGMockGTestAllCc(gmock_root, output_dir):
+  """Scans folder gmock_root to generate gmock-gtest-all.cc in output_dir."""
+
+  with open(os.path.join(output_dir, GMOCK_GTEST_ALL_CC_OUTPUT),
+            'w') as output_file:
+    # First, fuse gtest-all.cc into gmock-gtest-all.cc.
+    gtest.FuseGTestAllCcToFile(GetGTestRootDir(gmock_root), output_file)
+    # Next, append fused gmock-all.cc to gmock-gtest-all.cc.
+    FuseGMockAllCcToFile(gmock_root, output_file)
+
+
+def FuseGMock(gmock_root, output_dir):
+  """Fuses gtest.h, gmock.h, and gmock-gtest-all.h."""
+
+  ValidateGMockRootDir(gmock_root)
+  ValidateOutputDir(output_dir)
+
+  gtest.FuseGTestH(GetGTestRootDir(gmock_root), output_dir)
+  FuseGMockH(gmock_root, output_dir)
+  FuseGMockGTestAllCc(gmock_root, output_dir)
+
+
+def main():
+  argc = len(sys.argv)
+  if argc == 2:
+    # fuse_gmock_files.py OUTPUT_DIR
+    FuseGMock(DEFAULT_GMOCK_ROOT_DIR, sys.argv[1])
+  elif argc == 3:
+    # fuse_gmock_files.py GMOCK_ROOT_DIR OUTPUT_DIR
+    FuseGMock(sys.argv[1], sys.argv[2])
+  else:
+    print(__doc__)
+    sys.exit(1)
+
+
+if __name__ == '__main__':
+  main()
diff --git a/leveldb_base/third_party/googletest/googlemock/scripts/generator/LICENSE b/leveldb_base/third_party/googletest/googlemock/scripts/generator/LICENSE
new file mode 100644
index 0000000..87ea063
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/scripts/generator/LICENSE
@@ -0,0 +1,203 @@
+
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
+      the Work and Derivative Works thereof.
+
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
+      submitted to Licensor for inclusion in the Work by the copyright owner
+      or by an individual or Legal Entity authorized to submit on behalf of
+      the copyright owner. For the purposes of this definition, "submitted"
+      means any form of electronic, verbal, or written communication sent
+      to the Licensor or its representatives, including but not limited to
+      communication on electronic mailing lists, source code control systems,
+      and issue tracking systems that are managed by, or on behalf of, the
+      Licensor for the purpose of discussing and improving the Work, but
+      excluding communication that is conspicuously marked or otherwise
+      designated in writing by the copyright owner as "Not a Contribution."
+
+      "Contributor" shall mean Licensor and any individual or Legal Entity
+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+
+   2. Grant of Copyright License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      copyright license to reproduce, prepare Derivative Works of,
+      publicly display, publicly perform, sublicense, and distribute the
+      Work and such Derivative Works in Source or Object form.
+
+   3. Grant of Patent License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      (except as stated in this section) patent license to make, have made,
+      use, offer to sell, sell, import, and otherwise transfer the Work,
+      where such license applies only to those patent claims licensable
+      by such Contributor that are necessarily infringed by their
+      Contribution(s) alone or by combination of their Contribution(s)
+      with the Work to which such Contribution(s) was submitted. If You
+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
+      or contributory patent infringement, then any patent licenses
+      granted to You under this License for that Work shall terminate
+      as of the date such litigation is filed.
+
+   4. Redistribution. You may reproduce and distribute copies of the
+      Work or Derivative Works thereof in any medium, with or without
+      modifications, and in Source or Object form, provided that You
+      meet the following conditions:
+
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
+
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+
+      (c) You must retain, in the Source form of any Derivative Works
+          that You distribute, all copyright, patent, trademark, and
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+          the Derivative Works; and
+
+      (d) If the Work includes a "NOTICE" text file as part of its
+          distribution, then any Derivative Works that You distribute must
+          include a readable copy of the attribution notices contained
+          within such NOTICE file, excluding those notices that do not
+          pertain to any part of the Derivative Works, in at least one
+          of the following places: within a NOTICE text file distributed
+          as part of the Derivative Works; within the Source form or
+          documentation, if provided along with the Derivative Works; or,
+          within a display generated by the Derivative Works, if and
+          wherever such third-party notices normally appear. The contents
+          of the NOTICE file are for informational purposes only and
+          do not modify the License. You may add Your own attribution
+          notices within Derivative Works that You distribute, alongside
+          or as an addendum to the NOTICE text from the Work, provided
+          that such additional attribution notices cannot be construed
+          as modifying the License.
+
+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
+      for use, reproduction, or distribution of Your modifications, or
+      for any such Derivative Works as a whole, provided Your use,
+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
+      origin of the Work and reproducing the content of the NOTICE file.
+
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+      implied, including, without limitation, any warranties or conditions
+      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
+      or other liability obligations and/or rights consistent with this
+      License. However, in accepting such obligations, You may act only
+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
+
+   END OF TERMS AND CONDITIONS
+
+   APPENDIX: How to apply the Apache License to your work.
+
+      To apply the Apache License to your work, attach the following
+      boilerplate notice, with the fields enclosed by brackets "[]"
+      replaced with your own identifying information. (Don't include
+      the brackets!)  The text should be enclosed in the appropriate
+      comment syntax for the file format. We also recommend that a
+      file or class name and description of purpose be included on the
+      same "printed page" as the copyright notice for easier
+      identification within third-party archives.
+
+   Copyright [2007] Neal Norwitz
+   Portions Copyright [2007] Google Inc.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
diff --git a/leveldb_base/third_party/googletest/googlemock/scripts/generator/README b/leveldb_base/third_party/googletest/googlemock/scripts/generator/README
new file mode 100644
index 0000000..01fd463
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/scripts/generator/README
@@ -0,0 +1,34 @@
+
+The Google Mock class generator is an application that is part of cppclean.
+For more information about cppclean, visit http://code.google.com/p/cppclean/
+
+The mock generator requires Python 2.3.5 or later.  If you don't have Python
+installed on your system, you will also need to install it.  You can download
+Python from:  http://www.python.org/download/releases/
+
+To use the Google Mock class generator, you need to call it
+on the command line passing the header file and class for which you want
+to generate a Google Mock class.
+
+Make sure to install the scripts somewhere in your path.  Then you can
+run the program.
+
+  gmock_gen.py header-file.h [ClassName]...
+
+If no ClassNames are specified, all classes in the file are emitted.
+
+To change the indentation from the default of 2, set INDENT in
+the environment.  For example to use an indent of 4 spaces:
+
+INDENT=4 gmock_gen.py header-file.h ClassName
+
+This version was made from SVN revision 281 in the cppclean repository.
+
+Known Limitations
+-----------------
+Not all code will be generated properly.  For example, when mocking templated
+classes, the template information is lost.  You will need to add the template
+information manually.
+
+Not all permutations of using multiple pointers/references will be rendered
+properly.  These will also have to be fixed manually.
diff --git a/leveldb_base/third_party/googletest/googlemock/scripts/generator/README.cppclean b/leveldb_base/third_party/googletest/googlemock/scripts/generator/README.cppclean
new file mode 100644
index 0000000..65431b6
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/scripts/generator/README.cppclean
@@ -0,0 +1,115 @@
+Goal:
+-----
+  CppClean attempts to find problems in C++ source that slow development
+  in large code bases, for example various forms of unused code.
+  Unused code can be unused functions, methods, data members, types, etc
+  to unnecessary #include directives.  Unnecessary #includes can cause
+  considerable extra compiles increasing the edit-compile-run cycle.
+
+  The project home page is:   http://code.google.com/p/cppclean/
+
+
+Features:
+---------
+ * Find and print C++ language constructs: classes, methods, functions, etc.
+ * Find classes with virtual methods, no virtual destructor, and no bases
+ * Find global/static data that are potential problems when using threads
+ * Unnecessary forward class declarations
+ * Unnecessary function declarations
+ * Undeclared function definitions
+ * (planned) Find unnecessary header files #included
+   - No direct reference to anything in the header
+   - Header is unnecessary if classes were forward declared instead
+ * (planned) Source files that reference headers not directly #included,
+   ie, files that rely on a transitive #include from another header
+ * (planned) Unused members (private, protected, & public) methods and data
+ * (planned) Store AST in a SQL database so relationships can be queried
+
+AST is Abstract Syntax Tree, a representation of parsed source code.
+http://en.wikipedia.org/wiki/Abstract_syntax_tree
+
+
+System Requirements:
+--------------------
+ * Python 2.4 or later (2.3 probably works too)
+ * Works on Windows (untested), Mac OS X, and Unix
+
+
+How to Run:
+-----------
+  For all examples, it is assumed that cppclean resides in a directory called
+  /cppclean.
+
+  To print warnings for classes with virtual methods, no virtual destructor and
+  no base classes:
+
+      /cppclean/run.sh nonvirtual_dtors.py file1.h file2.h file3.cc ...
+
+  To print all the functions defined in header file(s):
+
+      /cppclean/run.sh functions.py file1.h file2.h ...
+
+  All the commands take multiple files on the command line.  Other programs
+  include: find_warnings, headers, methods, and types.  Some other programs
+  are available, but used primarily for debugging.
+
+  run.sh is a simple wrapper that sets PYTHONPATH to /cppclean and then
+  runs the program in /cppclean/cpp/PROGRAM.py.  There is currently
+  no equivalent for Windows.  Contributions for a run.bat file
+  would be greatly appreciated.
+
+
+How to Configure:
+-----------------
+  You can add a siteheaders.py file in /cppclean/cpp to configure where
+  to look for other headers (typically -I options passed to a compiler).
+  Currently two values are supported:  _TRANSITIVE and GetIncludeDirs.
+  _TRANSITIVE should be set to a boolean value (True or False) indicating
+  whether to transitively process all header files.  The default is False.
+
+  GetIncludeDirs is a function that takes a single argument and returns
+  a sequence of directories to include.  This can be a generator or
+  return a static list.
+
+      def GetIncludeDirs(filename):
+          return ['/some/path/with/other/headers']
+
+      # Here is a more complicated example.
+      def GetIncludeDirs(filename):
+          yield '/path1'
+          yield os.path.join('/path2', os.path.dirname(filename))
+          yield '/path3'
+
+
+How to Test:
+------------
+  For all examples, it is assumed that cppclean resides in a directory called
+  /cppclean.  The tests require
+
+  cd /cppclean
+  make test
+  # To generate expected results after a change:
+  make expected
+
+
+Current Status:
+---------------
+  The parser works pretty well for header files, parsing about 99% of Google's
+  header files.  Anything which inspects structure of C++ source files should
+  work reasonably well.  Function bodies are not transformed to an AST,
+  but left as tokens.  Much work is still needed on finding unused header files
+  and storing an AST in a database.
+
+
+Non-goals:
+----------
+ * Parsing all valid C++ source
+ * Handling invalid C++ source gracefully
+ * Compiling to machine code (or anything beyond an AST)
+
+
+Contact:
+--------
+  If you used cppclean, I would love to hear about your experiences
+  cppclean@googlegroups.com.  Even if you don't use cppclean, I'd like to
+  hear from you.  :-)  (You can contact me directly at:  nnorwitz@gmail.com)
diff --git a/leveldb_base/third_party/googletest/googlemock/scripts/generator/cpp/__init__.py b/leveldb_base/third_party/googletest/googlemock/scripts/generator/cpp/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/leveldb_base/third_party/googletest/googlemock/scripts/generator/cpp/ast.py b/leveldb_base/third_party/googletest/googlemock/scripts/generator/cpp/ast.py
new file mode 100644
index 0000000..0e77016
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/scripts/generator/cpp/ast.py
@@ -0,0 +1,1773 @@
+#!/usr/bin/env python
+#
+# Copyright 2007 Neal Norwitz
+# Portions Copyright 2007 Google Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Generate an Abstract Syntax Tree (AST) for C++."""
+
+# FIXME:
+#  * Tokens should never be exported, need to convert to Nodes
+#    (return types, parameters, etc.)
+#  * Handle static class data for templatized classes
+#  * Handle casts (both C++ and C-style)
+#  * Handle conditions and loops (if/else, switch, for, while/do)
+#
+# TODO much, much later:
+#  * Handle #define
+#  * exceptions
+
+
+try:
+  # Python 3.x
+  import builtins
+except ImportError:
+  # Python 2.x
+  import __builtin__ as builtins
+
+import collections
+import sys
+import traceback
+
+from cpp import keywords
+from cpp import tokenize
+from cpp import utils
+
+
+if not hasattr(builtins, 'reversed'):
+  # Support Python 2.3 and earlier.
+  def reversed(seq):
+    for i in range(len(seq)-1, -1, -1):
+      yield seq[i]
+
+if not hasattr(builtins, 'next'):
+  # Support Python 2.5 and earlier.
+  def next(obj):
+    return obj.next()
+
+
+VISIBILITY_PUBLIC, VISIBILITY_PROTECTED, VISIBILITY_PRIVATE = range(3)
+
+FUNCTION_NONE = 0x00
+FUNCTION_CONST = 0x01
+FUNCTION_VIRTUAL = 0x02
+FUNCTION_PURE_VIRTUAL = 0x04
+FUNCTION_CTOR = 0x08
+FUNCTION_DTOR = 0x10
+FUNCTION_ATTRIBUTE = 0x20
+FUNCTION_UNKNOWN_ANNOTATION = 0x40
+FUNCTION_THROW = 0x80
+FUNCTION_OVERRIDE = 0x100
+
+"""
+These are currently unused.  Should really handle these properly at some point.
+
+TYPE_MODIFIER_INLINE   = 0x010000
+TYPE_MODIFIER_EXTERN   = 0x020000
+TYPE_MODIFIER_STATIC   = 0x040000
+TYPE_MODIFIER_CONST    = 0x080000
+TYPE_MODIFIER_REGISTER = 0x100000
+TYPE_MODIFIER_VOLATILE = 0x200000
+TYPE_MODIFIER_MUTABLE  = 0x400000
+
+TYPE_MODIFIER_MAP = {
+    'inline': TYPE_MODIFIER_INLINE,
+    'extern': TYPE_MODIFIER_EXTERN,
+    'static': TYPE_MODIFIER_STATIC,
+    'const': TYPE_MODIFIER_CONST,
+    'register': TYPE_MODIFIER_REGISTER,
+    'volatile': TYPE_MODIFIER_VOLATILE,
+    'mutable': TYPE_MODIFIER_MUTABLE,
+    }
+"""
+
+_INTERNAL_TOKEN = 'internal'
+_NAMESPACE_POP = 'ns-pop'
+
+
+# TODO(nnorwitz): use this as a singleton for templated_types, etc
+# where we don't want to create a new empty dict each time.  It is also const.
+class _NullDict(object):
+  __contains__ = lambda self: False
+  keys = values = items = iterkeys = itervalues = iteritems = lambda self: ()
+
+
+# TODO(nnorwitz): move AST nodes into a separate module.
+class Node(object):
+  """Base AST node."""
+
+  def __init__(self, start, end):
+    self.start = start
+    self.end = end
+
+  def IsDeclaration(self):
+    """Returns bool if this node is a declaration."""
+    return False
+
+  def IsDefinition(self):
+    """Returns bool if this node is a definition."""
+    return False
+
+  def IsExportable(self):
+    """Returns bool if this node exportable from a header file."""
+    return False
+
+  def Requires(self, node):
+    """Does this AST node require the definition of the node passed in?"""
+    return False
+
+  def XXX__str__(self):
+    return self._StringHelper(self.__class__.__name__, '')
+
+  def _StringHelper(self, name, suffix):
+    if not utils.DEBUG:
+      return '%s(%s)' % (name, suffix)
+    return '%s(%d, %d, %s)' % (name, self.start, self.end, suffix)
+
+  def __repr__(self):
+    return str(self)
+
+
+class Define(Node):
+  def __init__(self, start, end, name, definition):
+    Node.__init__(self, start, end)
+    self.name = name
+    self.definition = definition
+
+  def __str__(self):
+    value = '%s %s' % (self.name, self.definition)
+    return self._StringHelper(self.__class__.__name__, value)
+
+
+class Include(Node):
+  def __init__(self, start, end, filename, system):
+    Node.__init__(self, start, end)
+    self.filename = filename
+    self.system = system
+
+  def __str__(self):
+    fmt = '"%s"'
+    if self.system:
+      fmt = '<%s>'
+    return self._StringHelper(self.__class__.__name__, fmt % self.filename)
+
+
+class Goto(Node):
+  def __init__(self, start, end, label):
+    Node.__init__(self, start, end)
+    self.label = label
+
+  def __str__(self):
+    return self._StringHelper(self.__class__.__name__, str(self.label))
+
+
+class Expr(Node):
+  def __init__(self, start, end, expr):
+    Node.__init__(self, start, end)
+    self.expr = expr
+
+  def Requires(self, node):
+    # TODO(nnorwitz): impl.
+    return False
+
+  def __str__(self):
+    return self._StringHelper(self.__class__.__name__, str(self.expr))
+
+
+class Return(Expr):
+  pass
+
+
+class Delete(Expr):
+  pass
+
+
+class Friend(Expr):
+  def __init__(self, start, end, expr, namespace):
+    Expr.__init__(self, start, end, expr)
+    self.namespace = namespace[:]
+
+
+class Using(Node):
+  def __init__(self, start, end, names):
+    Node.__init__(self, start, end)
+    self.names = names
+
+  def __str__(self):
+    return self._StringHelper(self.__class__.__name__, str(self.names))
+
+
+class Parameter(Node):
+  def __init__(self, start, end, name, parameter_type, default):
+    Node.__init__(self, start, end)
+    self.name = name
+    self.type = parameter_type
+    self.default = default
+
+  def Requires(self, node):
+    # TODO(nnorwitz): handle namespaces, etc.
+    return self.type.name == node.name
+
+  def __str__(self):
+    name = str(self.type)
+    suffix = '%s %s' % (name, self.name)
+    if self.default:
+      suffix += ' = ' + ''.join([d.name for d in self.default])
+    return self._StringHelper(self.__class__.__name__, suffix)
+
+
+class _GenericDeclaration(Node):
+  def __init__(self, start, end, name, namespace):
+    Node.__init__(self, start, end)
+    self.name = name
+    self.namespace = namespace[:]
+
+  def FullName(self):
+    prefix = ''
+    if self.namespace and self.namespace[-1]:
+      prefix = '::'.join(self.namespace) + '::'
+    return prefix + self.name
+
+  def _TypeStringHelper(self, suffix):
+    if self.namespace:
+      names = [n or '<anonymous>' for n in self.namespace]
+      suffix += ' in ' + '::'.join(names)
+    return self._StringHelper(self.__class__.__name__, suffix)
+
+
+# TODO(nnorwitz): merge with Parameter in some way?
+class VariableDeclaration(_GenericDeclaration):
+  def __init__(self, start, end, name, var_type, initial_value, namespace):
+    _GenericDeclaration.__init__(self, start, end, name, namespace)
+    self.type = var_type
+    self.initial_value = initial_value
+
+  def Requires(self, node):
+    # TODO(nnorwitz): handle namespaces, etc.
+    return self.type.name == node.name
+
+  def ToString(self):
+    """Return a string that tries to reconstitute the variable decl."""
+    suffix = '%s %s' % (self.type, self.name)
+    if self.initial_value:
+      suffix += ' = ' + self.initial_value
+    return suffix
+
+  def __str__(self):
+    return self._StringHelper(self.__class__.__name__, self.ToString())
+
+
+class Typedef(_GenericDeclaration):
+  def __init__(self, start, end, name, alias, namespace):
+    _GenericDeclaration.__init__(self, start, end, name, namespace)
+    self.alias = alias
+
+  def IsDefinition(self):
+    return True
+
+  def IsExportable(self):
+    return True
+
+  def Requires(self, node):
+    # TODO(nnorwitz): handle namespaces, etc.
+    name = node.name
+    for token in self.alias:
+      if token is not None and name == token.name:
+        return True
+    return False
+
+  def __str__(self):
+    suffix = '%s, %s' % (self.name, self.alias)
+    return self._TypeStringHelper(suffix)
+
+
+class _NestedType(_GenericDeclaration):
+  def __init__(self, start, end, name, fields, namespace):
+    _GenericDeclaration.__init__(self, start, end, name, namespace)
+    self.fields = fields
+
+  def IsDefinition(self):
+    return True
+
+  def IsExportable(self):
+    return True
+
+  def __str__(self):
+    suffix = '%s, {%s}' % (self.name, self.fields)
+    return self._TypeStringHelper(suffix)
+
+
+class Union(_NestedType):
+  pass
+
+
+class Enum(_NestedType):
+  pass
+
+
+class Class(_GenericDeclaration):
+  def __init__(self, start, end, name, bases, templated_types, body, namespace):
+    _GenericDeclaration.__init__(self, start, end, name, namespace)
+    self.bases = bases
+    self.body = body
+    self.templated_types = templated_types
+
+  def IsDeclaration(self):
+    return self.bases is None and self.body is None
+
+  def IsDefinition(self):
+    return not self.IsDeclaration()
+
+  def IsExportable(self):
+    return not self.IsDeclaration()
+
+  def Requires(self, node):
+    # TODO(nnorwitz): handle namespaces, etc.
+    if self.bases:
+      for token_list in self.bases:
+        # TODO(nnorwitz): bases are tokens, do name comparison.
+        for token in token_list:
+          if token.name == node.name:
+            return True
+    # TODO(nnorwitz): search in body too.
+    return False
+
+  def __str__(self):
+    name = self.name
+    if self.templated_types:
+      name += '<%s>' % self.templated_types
+    suffix = '%s, %s, %s' % (name, self.bases, self.body)
+    return self._TypeStringHelper(suffix)
+
+
+class Struct(Class):
+  pass
+
+
+class Function(_GenericDeclaration):
+  def __init__(self, start, end, name, return_type, parameters,
+               modifiers, templated_types, body, namespace):
+    _GenericDeclaration.__init__(self, start, end, name, namespace)
+    converter = TypeConverter(namespace)
+    self.return_type = converter.CreateReturnType(return_type)
+    self.parameters = converter.ToParameters(parameters)
+    self.modifiers = modifiers
+    self.body = body
+    self.templated_types = templated_types
+
+  def IsDeclaration(self):
+    return self.body is None
+
+  def IsDefinition(self):
+    return self.body is not None
+
+  def IsExportable(self):
+    if self.return_type and 'static' in self.return_type.modifiers:
+      return False
+    return None not in self.namespace
+
+  def Requires(self, node):
+    if self.parameters:
+      # TODO(nnorwitz): parameters are tokens, do name comparison.
+      for p in self.parameters:
+        if p.name == node.name:
+          return True
+    # TODO(nnorwitz): search in body too.
+    return False
+
+  def __str__(self):
+    # TODO(nnorwitz): add templated_types.
+    suffix = ('%s %s(%s), 0x%02x, %s' %
+              (self.return_type, self.name, self.parameters,
+               self.modifiers, self.body))
+    return self._TypeStringHelper(suffix)
+
+
+class Method(Function):
+  def __init__(self, start, end, name, in_class, return_type, parameters,
+               modifiers, templated_types, body, namespace):
+    Function.__init__(self, start, end, name, return_type, parameters,
+                      modifiers, templated_types, body, namespace)
+    # TODO(nnorwitz): in_class could also be a namespace which can
+    # mess up finding functions properly.
+    self.in_class = in_class
+
+
+class Type(_GenericDeclaration):
+  """Type used for any variable (eg class, primitive, struct, etc)."""
+
+  def __init__(self, start, end, name, templated_types, modifiers,
+               reference, pointer, array):
+    """
+        Args:
+          name: str name of main type
+          templated_types: [Class (Type?)] template type info between <>
+          modifiers: [str] type modifiers (keywords) eg, const, mutable, etc.
+          reference, pointer, array: bools
+        """
+    _GenericDeclaration.__init__(self, start, end, name, [])
+    self.templated_types = templated_types
+    if not name and modifiers:
+      self.name = modifiers.pop()
+    self.modifiers = modifiers
+    self.reference = reference
+    self.pointer = pointer
+    self.array = array
+
+  def __str__(self):
+    prefix = ''
+    if self.modifiers:
+      prefix = ' '.join(self.modifiers) + ' '
+    name = str(self.name)
+    if self.templated_types:
+      name += '<%s>' % self.templated_types
+    suffix = prefix + name
+    if self.reference:
+      suffix += '&'
+    if self.pointer:
+      suffix += '*'
+    if self.array:
+      suffix += '[]'
+    return self._TypeStringHelper(suffix)
+
+  # By definition, Is* are always False.  A Type can only exist in
+  # some sort of variable declaration, parameter, or return value.
+  def IsDeclaration(self):
+    return False
+
+  def IsDefinition(self):
+    return False
+
+  def IsExportable(self):
+    return False
+
+
+class TypeConverter(object):
+
+  def __init__(self, namespace_stack):
+    self.namespace_stack = namespace_stack
+
+  def _GetTemplateEnd(self, tokens, start):
+    count = 1
+    end = start
+    while 1:
+      token = tokens[end]
+      end += 1
+      if token.name == '<':
+        count += 1
+      elif token.name == '>':
+        count -= 1
+        if count == 0:
+          break
+    return tokens[start:end-1], end
+
+  def ToType(self, tokens):
+    """Convert [Token,...] to [Class(...), ] useful for base classes.
+        For example, code like class Foo : public Bar<x, y> { ... };
+        the "Bar<x, y>" portion gets converted to an AST.
+
+        Returns:
+          [Class(...), ...]
+        """
+    result = []
+    name_tokens = []
+    reference = pointer = array = False
+
+    def AddType(templated_types):
+      # Partition tokens into name and modifier tokens.
+      names = []
+      modifiers = []
+      for t in name_tokens:
+        if keywords.IsKeyword(t.name):
+          modifiers.append(t.name)
+        else:
+          names.append(t.name)
+      name = ''.join(names)
+      if name_tokens:
+        result.append(Type(name_tokens[0].start, name_tokens[-1].end,
+                           name, templated_types, modifiers,
+                           reference, pointer, array))
+      del name_tokens[:]
+
+    i = 0
+    end = len(tokens)
+    while i < end:
+      token = tokens[i]
+      if token.name == '<':
+        new_tokens, new_end = self._GetTemplateEnd(tokens, i+1)
+        AddType(self.ToType(new_tokens))
+        # If there is a comma after the template, we need to consume
+        # that here otherwise it becomes part of the name.
+        i = new_end
+        reference = pointer = array = False
+      elif token.name == ',':
+        AddType([])
+        reference = pointer = array = False
+      elif token.name == '*':
+        pointer = True
+      elif token.name == '&':
+        reference = True
+      elif token.name == '[':
+        pointer = True
+      elif token.name == ']':
+        pass
+      else:
+        name_tokens.append(token)
+      i += 1
+
+    if name_tokens:
+      # No '<' in the tokens, just a simple name and no template.
+      AddType([])
+    return result
+
+  def DeclarationToParts(self, parts, needs_name_removed):
+    name = None
+    default = []
+    if needs_name_removed:
+      # Handle default (initial) values properly.
+      for i, t in enumerate(parts):
+        if t.name == '=':
+          default = parts[i+1:]
+          name = parts[i-1].name
+          if name == ']' and parts[i-2].name == '[':
+            name = parts[i-3].name
+            i -= 1
+          parts = parts[:i-1]
+          break
+      else:
+        if parts[-1].token_type == tokenize.NAME:
+          name = parts.pop().name
+        else:
+          # TODO(nnorwitz): this is a hack that happens for code like
+          # Register(Foo<T>); where it thinks this is a function call
+          # but it's actually a declaration.
+          name = '???'
+    modifiers = []
+    type_name = []
+    other_tokens = []
+    templated_types = []
+    i = 0
+    end = len(parts)
+    while i < end:
+      p = parts[i]
+      if keywords.IsKeyword(p.name):
+        modifiers.append(p.name)
+      elif p.name == '<':
+        templated_tokens, new_end = self._GetTemplateEnd(parts, i+1)
+        templated_types = self.ToType(templated_tokens)
+        i = new_end - 1
+        # Don't add a spurious :: to data members being initialized.
+        next_index = i + 1
+        if next_index < end and parts[next_index].name == '::':
+          i += 1
+      elif p.name in ('[', ']', '='):
+        # These are handled elsewhere.
+        other_tokens.append(p)
+      elif p.name not in ('*', '&', '>'):
+        # Ensure that names have a space between them.
+        if (type_name and type_name[-1].token_type == tokenize.NAME and
+                p.token_type == tokenize.NAME):
+          type_name.append(tokenize.Token(tokenize.SYNTAX, ' ', 0, 0))
+        type_name.append(p)
+      else:
+        other_tokens.append(p)
+      i += 1
+    type_name = ''.join([t.name for t in type_name])
+    return name, type_name, templated_types, modifiers, default, other_tokens
+
+  def ToParameters(self, tokens):
+    if not tokens:
+      return []
+
+    result = []
+    name = type_name = ''
+    type_modifiers = []
+    pointer = reference = array = False
+    first_token = None
+    default = []
+
+    def AddParameter(end):
+      if default:
+        del default[0]  # Remove flag.
+      parts = self.DeclarationToParts(type_modifiers, True)
+      (name, type_name, templated_types, modifiers,
+       unused_default, unused_other_tokens) = parts
+      parameter_type = Type(first_token.start, first_token.end,
+                            type_name, templated_types, modifiers,
+                            reference, pointer, array)
+      p = Parameter(first_token.start, end, name,
+                    parameter_type, default)
+      result.append(p)
+
+    template_count = 0
+    brace_count = 0
+    for s in tokens:
+      if not first_token:
+        first_token = s
+
+      # Check for braces before templates, as we can have unmatched '<>'
+      # inside default arguments.
+      if s.name == '{':
+        brace_count += 1
+      elif s.name == '}':
+        brace_count -= 1
+      if brace_count > 0:
+        type_modifiers.append(s)
+        continue
+
+      if s.name == '<':
+        template_count += 1
+      elif s.name == '>':
+        template_count -= 1
+      if template_count > 0:
+        type_modifiers.append(s)
+        continue
+
+      if s.name == ',':
+        AddParameter(s.start)
+        name = type_name = ''
+        type_modifiers = []
+        pointer = reference = array = False
+        first_token = None
+        default = []
+      elif s.name == '*':
+        pointer = True
+      elif s.name == '&':
+        reference = True
+      elif s.name == '[':
+        array = True
+      elif s.name == ']':
+        pass  # Just don't add to type_modifiers.
+      elif s.name == '=':
+        # Got a default value.  Add any value (None) as a flag.
+        default.append(None)
+      elif default:
+        default.append(s)
+      else:
+        type_modifiers.append(s)
+    AddParameter(tokens[-1].end)
+    return result
+
+  def CreateReturnType(self, return_type_seq):
+    if not return_type_seq:
+      return None
+    start = return_type_seq[0].start
+    end = return_type_seq[-1].end
+    _, name, templated_types, modifiers, default, other_tokens = \
+        self.DeclarationToParts(return_type_seq, False)
+    names = [n.name for n in other_tokens]
+    reference = '&' in names
+    pointer = '*' in names
+    array = '[' in names
+    return Type(start, end, name, templated_types, modifiers,
+                reference, pointer, array)
+
+  def GetTemplateIndices(self, names):
+    # names is a list of strings.
+    start = names.index('<')
+    end = len(names) - 1
+    while end > 0:
+      if names[end] == '>':
+        break
+      end -= 1
+    return start, end+1
+
+class AstBuilder(object):
+  def __init__(self, token_stream, filename, in_class='', visibility=None,
+               namespace_stack=[]):
+    self.tokens = token_stream
+    self.filename = filename
+    # TODO(nnorwitz): use a better data structure (deque) for the queue.
+    # Switching directions of the "queue" improved perf by about 25%.
+    # Using a deque should be even better since we access from both sides.
+    self.token_queue = []
+    self.namespace_stack = namespace_stack[:]
+    self.in_class = in_class
+    if in_class is None:
+      self.in_class_name_only = None
+    else:
+      self.in_class_name_only = in_class.split('::')[-1]
+    self.visibility = visibility
+    self.in_function = False
+    self.current_token = None
+    # Keep the state whether we are currently handling a typedef or not.
+    self._handling_typedef = False
+
+    self.converter = TypeConverter(self.namespace_stack)
+
+  def HandleError(self, msg, token):
+    printable_queue = list(reversed(self.token_queue[-20:]))
+    sys.stderr.write('Got %s in %s @ %s %s\n' %
+                     (msg, self.filename, token, printable_queue))
+
+  def Generate(self):
+    while 1:
+      token = self._GetNextToken()
+      if not token:
+        break
+
+      # Get the next token.
+      self.current_token = token
+
+      # Dispatch on the next token type.
+      if token.token_type == _INTERNAL_TOKEN:
+        if token.name == _NAMESPACE_POP:
+          self.namespace_stack.pop()
+        continue
+
+      try:
+        result = self._GenerateOne(token)
+        if result is not None:
+          yield result
+      except:
+        self.HandleError('exception', token)
+        raise
+
+  def _CreateVariable(self, pos_token, name, type_name, type_modifiers,
+                      ref_pointer_name_seq, templated_types, value=None):
+    reference = '&' in ref_pointer_name_seq
+    pointer = '*' in ref_pointer_name_seq
+    array = '[' in ref_pointer_name_seq
+    var_type = Type(pos_token.start, pos_token.end, type_name,
+                    templated_types, type_modifiers,
+                    reference, pointer, array)
+    return VariableDeclaration(pos_token.start, pos_token.end,
+                               name, var_type, value, self.namespace_stack)
+
+  def _GenerateOne(self, token):
+    if token.token_type == tokenize.NAME:
+      if (keywords.IsKeyword(token.name) and
+          not keywords.IsBuiltinType(token.name)):
+        if token.name == 'enum':
+          # Pop the next token and only put it back if it's not
+          # 'class'.  This allows us to support the two-token
+          # 'enum class' keyword as if it were simply 'enum'.
+          next = self._GetNextToken()
+          if next.name != 'class':
+            self._AddBackToken(next)
+
+        method = getattr(self, 'handle_' + token.name)
+        return method()
+      elif token.name == self.in_class_name_only:
+        # The token name is the same as the class, must be a ctor if
+        # there is a paren.  Otherwise, it's the return type.
+        # Peek ahead to get the next token to figure out which.
+        next = self._GetNextToken()
+        self._AddBackToken(next)
+        if next.token_type == tokenize.SYNTAX and next.name == '(':
+          return self._GetMethod([token], FUNCTION_CTOR, None, True)
+        # Fall through--handle like any other method.
+
+      # Handle data or function declaration/definition.
+      syntax = tokenize.SYNTAX
+      temp_tokens, last_token = \
+          self._GetVarTokensUpToIgnoringTemplates(syntax,
+                                                  '(', ';', '{', '[')
+      temp_tokens.insert(0, token)
+      if last_token.name == '(':
+        # If there is an assignment before the paren,
+        # this is an expression, not a method.
+        expr = bool([e for e in temp_tokens if e.name == '='])
+        if expr:
+          new_temp = self._GetTokensUpTo(tokenize.SYNTAX, ';')
+          temp_tokens.append(last_token)
+          temp_tokens.extend(new_temp)
+          last_token = tokenize.Token(tokenize.SYNTAX, ';', 0, 0)
+
+      if last_token.name == '[':
+        # Handle array, this isn't a method, unless it's an operator.
+        # TODO(nnorwitz): keep the size somewhere.
+        # unused_size = self._GetTokensUpTo(tokenize.SYNTAX, ']')
+        temp_tokens.append(last_token)
+        if temp_tokens[-2].name == 'operator':
+          temp_tokens.append(self._GetNextToken())
+        else:
+          temp_tokens2, last_token = \
+              self._GetVarTokensUpTo(tokenize.SYNTAX, ';')
+          temp_tokens.extend(temp_tokens2)
+
+      if last_token.name == ';':
+        # Handle data, this isn't a method.
+        parts = self.converter.DeclarationToParts(temp_tokens, True)
+        (name, type_name, templated_types, modifiers, default,
+         unused_other_tokens) = parts
+
+        t0 = temp_tokens[0]
+        names = [t.name for t in temp_tokens]
+        if templated_types:
+          start, end = self.converter.GetTemplateIndices(names)
+          names = names[:start] + names[end:]
+        default = ''.join([t.name for t in default])
+        return self._CreateVariable(t0, name, type_name, modifiers,
+                                    names, templated_types, default)
+      if last_token.name == '{':
+        self._AddBackTokens(temp_tokens[1:])
+        self._AddBackToken(last_token)
+        method_name = temp_tokens[0].name
+        method = getattr(self, 'handle_' + method_name, None)
+        if not method:
+          # Must be declaring a variable.
+          # TODO(nnorwitz): handle the declaration.
+          return None
+        return method()
+      return self._GetMethod(temp_tokens, 0, None, False)
+    elif token.token_type == tokenize.SYNTAX:
+      if token.name == '~' and self.in_class:
+        # Must be a dtor (probably not in method body).
+        token = self._GetNextToken()
+        # self.in_class can contain A::Name, but the dtor will only
+        # be Name.  Make sure to compare against the right value.
+        if (token.token_type == tokenize.NAME and
+                token.name == self.in_class_name_only):
+          return self._GetMethod([token], FUNCTION_DTOR, None, True)
+      # TODO(nnorwitz): handle a lot more syntax.
+    elif token.token_type == tokenize.PREPROCESSOR:
+      # TODO(nnorwitz): handle more preprocessor directives.
+      # token starts with a #, so remove it and strip whitespace.
+      name = token.name[1:].lstrip()
+      if name.startswith('include'):
+        # Remove "include".
+        name = name[7:].strip()
+        assert name
+        # Handle #include \<newline> "header-on-second-line.h".
+        if name.startswith('\\'):
+          name = name[1:].strip()
+        assert name[0] in '<"', token
+        assert name[-1] in '>"', token
+        system = name[0] == '<'
+        filename = name[1:-1]
+        return Include(token.start, token.end, filename, system)
+      if name.startswith('define'):
+        # Remove "define".
+        name = name[6:].strip()
+        assert name
+        value = ''
+        for i, c in enumerate(name):
+          if c.isspace():
+            value = name[i:].lstrip()
+            name = name[:i]
+            break
+        return Define(token.start, token.end, name, value)
+      if name.startswith('if') and name[2:3].isspace():
+        condition = name[3:].strip()
+        if condition.startswith('0') or condition.startswith('(0)'):
+          self._SkipIf0Blocks()
+    return None
+
+  def _GetTokensUpTo(self, expected_token_type, expected_token):
+    return self._GetVarTokensUpTo(expected_token_type, expected_token)[0]
+
+  def _GetVarTokensUpTo(self, expected_token_type, *expected_tokens):
+    last_token = self._GetNextToken()
+    tokens = []
+    while (last_token.token_type != expected_token_type or
+           last_token.name not in expected_tokens):
+      tokens.append(last_token)
+      last_token = self._GetNextToken()
+    return tokens, last_token
+
+  # Same as _GetVarTokensUpTo, but skips over '<...>' which could contain an
+  # expected token.
+  def _GetVarTokensUpToIgnoringTemplates(self, expected_token_type,
+                                         *expected_tokens):
+    last_token = self._GetNextToken()
+    tokens = []
+    nesting = 0
+    while (nesting > 0 or
+           last_token.token_type != expected_token_type or
+           last_token.name not in expected_tokens):
+      tokens.append(last_token)
+      last_token = self._GetNextToken()
+      if last_token.name == '<':
+        nesting += 1
+      elif last_token.name == '>':
+        nesting -= 1
+    return tokens, last_token
+
+  # TODO(nnorwitz): remove _IgnoreUpTo() it shouldn't be necessary.
+  def _IgnoreUpTo(self, token_type, token):
+    unused_tokens = self._GetTokensUpTo(token_type, token)
+
+  def _SkipIf0Blocks(self):
+    count = 1
+    while 1:
+      token = self._GetNextToken()
+      if token.token_type != tokenize.PREPROCESSOR:
+        continue
+
+      name = token.name[1:].lstrip()
+      if name.startswith('endif'):
+        count -= 1
+        if count == 0:
+          break
+      elif name.startswith('if'):
+        count += 1
+
+  def _GetMatchingChar(self, open_paren, close_paren, GetNextToken=None):
+    if GetNextToken is None:
+      GetNextToken = self._GetNextToken
+    # Assumes the current token is open_paren and we will consume
+    # and return up to the close_paren.
+    count = 1
+    token = GetNextToken()
+    while 1:
+      if token.token_type == tokenize.SYNTAX:
+        if token.name == open_paren:
+          count += 1
+        elif token.name == close_paren:
+          count -= 1
+          if count == 0:
+            break
+      yield token
+      token = GetNextToken()
+    yield token
+
+  def _GetParameters(self):
+    return self._GetMatchingChar('(', ')')
+
+  def GetScope(self):
+    return self._GetMatchingChar('{', '}')
+
+  def _GetNextToken(self):
+    if self.token_queue:
+      return self.token_queue.pop()
+    try:
+      return next(self.tokens)
+    except StopIteration:
+      return
+
+  def _AddBackToken(self, token):
+    if token.whence == tokenize.WHENCE_STREAM:
+      token.whence = tokenize.WHENCE_QUEUE
+      self.token_queue.insert(0, token)
+    else:
+      assert token.whence == tokenize.WHENCE_QUEUE, token
+      self.token_queue.append(token)
+
+  def _AddBackTokens(self, tokens):
+    if tokens:
+      if tokens[-1].whence == tokenize.WHENCE_STREAM:
+        for token in tokens:
+          token.whence = tokenize.WHENCE_QUEUE
+        self.token_queue[:0] = reversed(tokens)
+      else:
+        assert tokens[-1].whence == tokenize.WHENCE_QUEUE, tokens
+        self.token_queue.extend(reversed(tokens))
+
+  def GetName(self, seq=None):
+    """Returns ([tokens], next_token_info)."""
+    GetNextToken = self._GetNextToken
+    if seq is not None:
+      it = iter(seq)
+      GetNextToken = lambda: next(it)
+    next_token = GetNextToken()
+    tokens = []
+    last_token_was_name = False
+    while (next_token.token_type == tokenize.NAME or
+           (next_token.token_type == tokenize.SYNTAX and
+            next_token.name in ('::', '<'))):
+      # Two NAMEs in a row means the identifier should terminate.
+      # It's probably some sort of variable declaration.
+      if last_token_was_name and next_token.token_type == tokenize.NAME:
+        break
+      last_token_was_name = next_token.token_type == tokenize.NAME
+      tokens.append(next_token)
+      # Handle templated names.
+      if next_token.name == '<':
+        tokens.extend(self._GetMatchingChar('<', '>', GetNextToken))
+        last_token_was_name = True
+      next_token = GetNextToken()
+    return tokens, next_token
+
+  def GetMethod(self, modifiers, templated_types):
+    return_type_and_name = self._GetTokensUpTo(tokenize.SYNTAX, '(')
+    assert len(return_type_and_name) >= 1
+    return self._GetMethod(return_type_and_name, modifiers, templated_types,
+                           False)
+
+  def _GetMethod(self, return_type_and_name, modifiers, templated_types,
+                 get_paren):
+    template_portion = None
+    if get_paren:
+      token = self._GetNextToken()
+      assert token.token_type == tokenize.SYNTAX, token
+      if token.name == '<':
+        # Handle templatized dtors.
+        template_portion = [token]
+        template_portion.extend(self._GetMatchingChar('<', '>'))
+        token = self._GetNextToken()
+      assert token.token_type == tokenize.SYNTAX, token
+      assert token.name == '(', token
+
+    name = return_type_and_name.pop()
+    # Handle templatized ctors.
+    if name.name == '>':
+      index = 1
+      while return_type_and_name[index].name != '<':
+        index += 1
+      template_portion = return_type_and_name[index:] + [name]
+      del return_type_and_name[index:]
+      name = return_type_and_name.pop()
+    elif name.name == ']':
+      rt = return_type_and_name
+      assert rt[-1].name == '[', return_type_and_name
+      assert rt[-2].name == 'operator', return_type_and_name
+      name_seq = return_type_and_name[-2:]
+      del return_type_and_name[-2:]
+      name = tokenize.Token(tokenize.NAME, 'operator[]',
+                            name_seq[0].start, name.end)
+      # Get the open paren so _GetParameters() below works.
+      unused_open_paren = self._GetNextToken()
+
+    # TODO(nnorwitz): store template_portion.
+    return_type = return_type_and_name
+    indices = name
+    if return_type:
+      indices = return_type[0]
+
+    # Force ctor for templatized ctors.
+    if name.name == self.in_class and not modifiers:
+      modifiers |= FUNCTION_CTOR
+    parameters = list(self._GetParameters())
+    del parameters[-1]              # Remove trailing ')'.
+
+    # Handling operator() is especially weird.
+    if name.name == 'operator' and not parameters:
+      token = self._GetNextToken()
+      assert token.name == '(', token
+      parameters = list(self._GetParameters())
+      del parameters[-1]          # Remove trailing ')'.
+
+    token = self._GetNextToken()
+    while token.token_type == tokenize.NAME:
+      modifier_token = token
+      token = self._GetNextToken()
+      if modifier_token.name == 'const':
+        modifiers |= FUNCTION_CONST
+      elif modifier_token.name == '__attribute__':
+        # TODO(nnorwitz): handle more __attribute__ details.
+        modifiers |= FUNCTION_ATTRIBUTE
+        assert token.name == '(', token
+        # Consume everything between the (parens).
+        unused_tokens = list(self._GetMatchingChar('(', ')'))
+        token = self._GetNextToken()
+      elif modifier_token.name == 'throw':
+        modifiers |= FUNCTION_THROW
+        assert token.name == '(', token
+        # Consume everything between the (parens).
+        unused_tokens = list(self._GetMatchingChar('(', ')'))
+        token = self._GetNextToken()
+      elif modifier_token.name == 'override':
+        modifiers |= FUNCTION_OVERRIDE
+      elif modifier_token.name == modifier_token.name.upper():
+        # HACK(nnorwitz):  assume that all upper-case names
+        # are some macro we aren't expanding.
+        modifiers |= FUNCTION_UNKNOWN_ANNOTATION
+      else:
+        self.HandleError('unexpected token', modifier_token)
+
+    assert token.token_type == tokenize.SYNTAX, token
+    # Handle ctor initializers.
+    if token.name == ':':
+      # TODO(nnorwitz): anything else to handle for initializer list?
+      while token.name != ';' and token.name != '{':
+        token = self._GetNextToken()
+
+    # Handle pointer to functions that are really data but look
+    # like method declarations.
+    if token.name == '(':
+      if parameters[0].name == '*':
+        # name contains the return type.
+        name = parameters.pop()
+        # parameters contains the name of the data.
+        modifiers = [p.name for p in parameters]
+        # Already at the ( to open the parameter list.
+        function_parameters = list(self._GetMatchingChar('(', ')'))
+        del function_parameters[-1]  # Remove trailing ')'.
+        # TODO(nnorwitz): store the function_parameters.
+        token = self._GetNextToken()
+        assert token.token_type == tokenize.SYNTAX, token
+        assert token.name == ';', token
+        return self._CreateVariable(indices, name.name, indices.name,
+                                    modifiers, '', None)
+      # At this point, we got something like:
+      #  return_type (type::*name_)(params);
+      # This is a data member called name_ that is a function pointer.
+      # With this code: void (sq_type::*field_)(string&);
+      # We get: name=void return_type=[] parameters=sq_type ... field_
+      # TODO(nnorwitz): is return_type always empty?
+      # TODO(nnorwitz): this isn't even close to being correct.
+      # Just put in something so we don't crash and can move on.
+      real_name = parameters[-1]
+      modifiers = [p.name for p in self._GetParameters()]
+      del modifiers[-1]           # Remove trailing ')'.
+      return self._CreateVariable(indices, real_name.name, indices.name,
+                                  modifiers, '', None)
+
+    if token.name == '{':
+      body = list(self.GetScope())
+      del body[-1]                # Remove trailing '}'.
+    else:
+      body = None
+      if token.name == '=':
+        token = self._GetNextToken()
+
+        if token.name == 'default' or token.name == 'delete':
+          # Ignore explicitly defaulted and deleted special members
+          # in C++11.
+          token = self._GetNextToken()
+        else:
+          # Handle pure-virtual declarations.
+          assert token.token_type == tokenize.CONSTANT, token
+          assert token.name == '0', token
+          modifiers |= FUNCTION_PURE_VIRTUAL
+          token = self._GetNextToken()
+
+      if token.name == '[':
+        # TODO(nnorwitz): store tokens and improve parsing.
+        # template <typename T, size_t N> char (&ASH(T (&seq)[N]))[N];
+        tokens = list(self._GetMatchingChar('[', ']'))
+        token = self._GetNextToken()
+
+      assert token.name == ';', (token, return_type_and_name, parameters)
+
+    # Looks like we got a method, not a function.
+    if len(return_type) > 2 and return_type[-1].name == '::':
+      return_type, in_class = \
+          self._GetReturnTypeAndClassName(return_type)
+      return Method(indices.start, indices.end, name.name, in_class,
+                    return_type, parameters, modifiers, templated_types,
+                    body, self.namespace_stack)
+    return Function(indices.start, indices.end, name.name, return_type,
+                    parameters, modifiers, templated_types, body,
+                    self.namespace_stack)
+
+  def _GetReturnTypeAndClassName(self, token_seq):
+    # Splitting the return type from the class name in a method
+    # can be tricky.  For example, Return::Type::Is::Hard::To::Find().
+    # Where is the return type and where is the class name?
+    # The heuristic used is to pull the last name as the class name.
+    # This includes all the templated type info.
+    # TODO(nnorwitz): if there is only One name like in the
+    # example above, punt and assume the last bit is the class name.
+
+    # Ignore a :: prefix, if exists so we can find the first real name.
+    i = 0
+    if token_seq[0].name == '::':
+      i = 1
+    # Ignore a :: suffix, if exists.
+    end = len(token_seq) - 1
+    if token_seq[end-1].name == '::':
+      end -= 1
+
+    # Make a copy of the sequence so we can append a sentinel
+    # value. This is required for GetName will has to have some
+    # terminating condition beyond the last name.
+    seq_copy = token_seq[i:end]
+    seq_copy.append(tokenize.Token(tokenize.SYNTAX, '', 0, 0))
+    names = []
+    while i < end:
+      # Iterate through the sequence parsing out each name.
+      new_name, next = self.GetName(seq_copy[i:])
+      assert new_name, 'Got empty new_name, next=%s' % next
+      # We got a pointer or ref.  Add it to the name.
+      if next and next.token_type == tokenize.SYNTAX:
+        new_name.append(next)
+      names.append(new_name)
+      i += len(new_name)
+
+    # Now that we have the names, it's time to undo what we did.
+
+    # Remove the sentinel value.
+    names[-1].pop()
+    # Flatten the token sequence for the return type.
+    return_type = [e for seq in names[:-1] for e in seq]
+    # The class name is the last name.
+    class_name = names[-1]
+    return return_type, class_name
+
+  def handle_bool(self):
+    pass
+
+  def handle_char(self):
+    pass
+
+  def handle_int(self):
+    pass
+
+  def handle_long(self):
+    pass
+
+  def handle_short(self):
+    pass
+
+  def handle_double(self):
+    pass
+
+  def handle_float(self):
+    pass
+
+  def handle_void(self):
+    pass
+
+  def handle_wchar_t(self):
+    pass
+
+  def handle_unsigned(self):
+    pass
+
+  def handle_signed(self):
+    pass
+
+  def _GetNestedType(self, ctor):
+    name = None
+    name_tokens, token = self.GetName()
+    if name_tokens:
+      name = ''.join([t.name for t in name_tokens])
+
+    # Handle forward declarations.
+    if token.token_type == tokenize.SYNTAX and token.name == ';':
+      return ctor(token.start, token.end, name, None,
+                  self.namespace_stack)
+
+    if token.token_type == tokenize.NAME and self._handling_typedef:
+      self._AddBackToken(token)
+      return ctor(token.start, token.end, name, None,
+                  self.namespace_stack)
+
+    # Must be the type declaration.
+    fields = list(self._GetMatchingChar('{', '}'))
+    del fields[-1]                  # Remove trailing '}'.
+    if token.token_type == tokenize.SYNTAX and token.name == '{':
+      next = self._GetNextToken()
+      new_type = ctor(token.start, token.end, name, fields,
+                      self.namespace_stack)
+      # A name means this is an anonymous type and the name
+      # is the variable declaration.
+      if next.token_type != tokenize.NAME:
+        return new_type
+      name = new_type
+      token = next
+
+    # Must be variable declaration using the type prefixed with keyword.
+    assert token.token_type == tokenize.NAME, token
+    return self._CreateVariable(token, token.name, name, [], '', None)
+
+  def handle_struct(self):
+    # Special case the handling typedef/aliasing of structs here.
+    # It would be a pain to handle in the class code.
+    name_tokens, var_token = self.GetName()
+    if name_tokens:
+      next_token = self._GetNextToken()
+      is_syntax = (var_token.token_type == tokenize.SYNTAX and
+                   var_token.name[0] in '*&')
+      is_variable = (var_token.token_type == tokenize.NAME and
+                     next_token.name == ';')
+      variable = var_token
+      if is_syntax and not is_variable:
+        variable = next_token
+        temp = self._GetNextToken()
+        if temp.token_type == tokenize.SYNTAX and temp.name == '(':
+          # Handle methods declared to return a struct.
+          t0 = name_tokens[0]
+          struct = tokenize.Token(tokenize.NAME, 'struct',
+                                  t0.start-7, t0.start-2)
+          type_and_name = [struct]
+          type_and_name.extend(name_tokens)
+          type_and_name.extend((var_token, next_token))
+          return self._GetMethod(type_and_name, 0, None, False)
+        assert temp.name == ';', (temp, name_tokens, var_token)
+      if is_syntax or (is_variable and not self._handling_typedef):
+        modifiers = ['struct']
+        type_name = ''.join([t.name for t in name_tokens])
+        position = name_tokens[0]
+        return self._CreateVariable(position, variable.name, type_name,
+                                    modifiers, var_token.name, None)
+      name_tokens.extend((var_token, next_token))
+      self._AddBackTokens(name_tokens)
+    else:
+      self._AddBackToken(var_token)
+    return self._GetClass(Struct, VISIBILITY_PUBLIC, None)
+
+  def handle_union(self):
+    return self._GetNestedType(Union)
+
+  def handle_enum(self):
+    return self._GetNestedType(Enum)
+
+  def handle_auto(self):
+    # TODO(nnorwitz): warn about using auto?  Probably not since it
+    # will be reclaimed and useful for C++0x.
+    pass
+
+  def handle_register(self):
+    pass
+
+  def handle_const(self):
+    pass
+
+  def handle_inline(self):
+    pass
+
+  def handle_extern(self):
+    pass
+
+  def handle_static(self):
+    pass
+
+  def handle_virtual(self):
+    # What follows must be a method.
+    token = token2 = self._GetNextToken()
+    if token.name == 'inline':
+      # HACK(nnorwitz): handle inline dtors by ignoring 'inline'.
+      token2 = self._GetNextToken()
+    if token2.token_type == tokenize.SYNTAX and token2.name == '~':
+      return self.GetMethod(FUNCTION_VIRTUAL + FUNCTION_DTOR, None)
+    assert token.token_type == tokenize.NAME or token.name == '::', token
+    return_type_and_name, _ = self._GetVarTokensUpToIgnoringTemplates(
+        tokenize.SYNTAX, '(')  # )
+    return_type_and_name.insert(0, token)
+    if token2 is not token:
+      return_type_and_name.insert(1, token2)
+    return self._GetMethod(return_type_and_name, FUNCTION_VIRTUAL,
+                           None, False)
+
+  def handle_volatile(self):
+    pass
+
+  def handle_mutable(self):
+    pass
+
+  def handle_public(self):
+    assert self.in_class
+    self.visibility = VISIBILITY_PUBLIC
+
+  def handle_protected(self):
+    assert self.in_class
+    self.visibility = VISIBILITY_PROTECTED
+
+  def handle_private(self):
+    assert self.in_class
+    self.visibility = VISIBILITY_PRIVATE
+
+  def handle_friend(self):
+    tokens = self._GetTokensUpTo(tokenize.SYNTAX, ';')
+    assert tokens
+    t0 = tokens[0]
+    return Friend(t0.start, t0.end, tokens, self.namespace_stack)
+
+  def handle_static_cast(self):
+    pass
+
+  def handle_const_cast(self):
+    pass
+
+  def handle_dynamic_cast(self):
+    pass
+
+  def handle_reinterpret_cast(self):
+    pass
+
+  def handle_new(self):
+    pass
+
+  def handle_delete(self):
+    tokens = self._GetTokensUpTo(tokenize.SYNTAX, ';')
+    assert tokens
+    return Delete(tokens[0].start, tokens[0].end, tokens)
+
+  def handle_typedef(self):
+    token = self._GetNextToken()
+    if (token.token_type == tokenize.NAME and
+            keywords.IsKeyword(token.name)):
+      # Token must be struct/enum/union/class.
+      method = getattr(self, 'handle_' + token.name)
+      self._handling_typedef = True
+      tokens = [method()]
+      self._handling_typedef = False
+    else:
+      tokens = [token]
+
+    # Get the remainder of the typedef up to the semi-colon.
+    tokens.extend(self._GetTokensUpTo(tokenize.SYNTAX, ';'))
+
+    # TODO(nnorwitz): clean all this up.
+    assert tokens
+    name = tokens.pop()
+    indices = name
+    if tokens:
+      indices = tokens[0]
+    if not indices:
+      indices = token
+    if name.name == ')':
+      # HACK(nnorwitz): Handle pointers to functions "properly".
+      if (len(tokens) >= 4 and
+              tokens[1].name == '(' and tokens[2].name == '*'):
+        tokens.append(name)
+        name = tokens[3]
+    elif name.name == ']':
+      # HACK(nnorwitz): Handle arrays properly.
+      if len(tokens) >= 2:
+        tokens.append(name)
+        name = tokens[1]
+    new_type = tokens
+    if tokens and isinstance(tokens[0], tokenize.Token):
+      new_type = self.converter.ToType(tokens)[0]
+    return Typedef(indices.start, indices.end, name.name,
+                   new_type, self.namespace_stack)
+
+  def handle_typeid(self):
+    pass  # Not needed yet.
+
+  def handle_typename(self):
+    pass  # Not needed yet.
+
+  def _GetTemplatedTypes(self):
+    result = collections.OrderedDict()
+    tokens = list(self._GetMatchingChar('<', '>'))
+    len_tokens = len(tokens) - 1    # Ignore trailing '>'.
+    i = 0
+    while i < len_tokens:
+      key = tokens[i].name
+      i += 1
+      if keywords.IsKeyword(key) or key == ',':
+        continue
+      type_name = default = None
+      if i < len_tokens:
+        i += 1
+        if tokens[i-1].name == '=':
+          assert i < len_tokens, '%s %s' % (i, tokens)
+          default, unused_next_token = self.GetName(tokens[i:])
+          i += len(default)
+        else:
+          if tokens[i-1].name != ',':
+            # We got something like: Type variable.
+            # Re-adjust the key (variable) and type_name (Type).
+            key = tokens[i-1].name
+            type_name = tokens[i-2]
+
+      result[key] = (type_name, default)
+    return result
+
+  def handle_template(self):
+    token = self._GetNextToken()
+    assert token.token_type == tokenize.SYNTAX, token
+    assert token.name == '<', token
+    templated_types = self._GetTemplatedTypes()
+    # TODO(nnorwitz): for now, just ignore the template params.
+    token = self._GetNextToken()
+    if token.token_type == tokenize.NAME:
+      if token.name == 'class':
+        return self._GetClass(Class, VISIBILITY_PRIVATE, templated_types)
+      elif token.name == 'struct':
+        return self._GetClass(Struct, VISIBILITY_PUBLIC, templated_types)
+      elif token.name == 'friend':
+        return self.handle_friend()
+    self._AddBackToken(token)
+    tokens, last = self._GetVarTokensUpTo(tokenize.SYNTAX, '(', ';')
+    tokens.append(last)
+    self._AddBackTokens(tokens)
+    if last.name == '(':
+      return self.GetMethod(FUNCTION_NONE, templated_types)
+    # Must be a variable definition.
+    return None
+
+  def handle_true(self):
+    pass  # Nothing to do.
+
+  def handle_false(self):
+    pass  # Nothing to do.
+
+  def handle_asm(self):
+    pass  # Not needed yet.
+
+  def handle_class(self):
+    return self._GetClass(Class, VISIBILITY_PRIVATE, None)
+
+  def _GetBases(self):
+    # Get base classes.
+    bases = []
+    while 1:
+      token = self._GetNextToken()
+      assert token.token_type == tokenize.NAME, token
+      # TODO(nnorwitz): store kind of inheritance...maybe.
+      if token.name not in ('public', 'protected', 'private'):
+        # If inheritance type is not specified, it is private.
+        # Just put the token back so we can form a name.
+        # TODO(nnorwitz): it would be good to warn about this.
+        self._AddBackToken(token)
+      else:
+        # Check for virtual inheritance.
+        token = self._GetNextToken()
+        if token.name != 'virtual':
+          self._AddBackToken(token)
+        else:
+          # TODO(nnorwitz): store that we got virtual for this base.
+          pass
+      base, next_token = self.GetName()
+      bases_ast = self.converter.ToType(base)
+      assert len(bases_ast) == 1, bases_ast
+      bases.append(bases_ast[0])
+      assert next_token.token_type == tokenize.SYNTAX, next_token
+      if next_token.name == '{':
+        token = next_token
+        break
+      # Support multiple inheritance.
+      assert next_token.name == ',', next_token
+    return bases, token
+
+  def _GetClass(self, class_type, visibility, templated_types):
+    class_name = None
+    class_token = self._GetNextToken()
+    if class_token.token_type != tokenize.NAME:
+      assert class_token.token_type == tokenize.SYNTAX, class_token
+      token = class_token
+    else:
+      # Skip any macro (e.g. storage class specifiers) after the
+      # 'class' keyword.
+      next_token = self._GetNextToken()
+      if next_token.token_type == tokenize.NAME:
+        self._AddBackToken(next_token)
+      else:
+        self._AddBackTokens([class_token, next_token])
+      name_tokens, token = self.GetName()
+      class_name = ''.join([t.name for t in name_tokens])
+    bases = None
+    if token.token_type == tokenize.SYNTAX:
+      if token.name == ';':
+        # Forward declaration.
+        return class_type(class_token.start, class_token.end,
+                          class_name, None, templated_types, None,
+                          self.namespace_stack)
+      if token.name in '*&':
+        # Inline forward declaration.  Could be method or data.
+        name_token = self._GetNextToken()
+        next_token = self._GetNextToken()
+        if next_token.name == ';':
+          # Handle data
+          modifiers = ['class']
+          return self._CreateVariable(class_token, name_token.name,
+                                      class_name,
+                                      modifiers, token.name, None)
+        else:
+          # Assume this is a method.
+          tokens = (class_token, token, name_token, next_token)
+          self._AddBackTokens(tokens)
+          return self.GetMethod(FUNCTION_NONE, None)
+      if token.name == ':':
+        bases, token = self._GetBases()
+
+    body = None
+    if token.token_type == tokenize.SYNTAX and token.name == '{':
+      assert token.token_type == tokenize.SYNTAX, token
+      assert token.name == '{', token
+
+      ast = AstBuilder(self.GetScope(), self.filename, class_name,
+                       visibility, self.namespace_stack)
+      body = list(ast.Generate())
+
+      if not self._handling_typedef:
+        token = self._GetNextToken()
+        if token.token_type != tokenize.NAME:
+          assert token.token_type == tokenize.SYNTAX, token
+          assert token.name == ';', token
+        else:
+          new_class = class_type(class_token.start, class_token.end,
+                                 class_name, bases, None,
+                                 body, self.namespace_stack)
+
+          modifiers = []
+          return self._CreateVariable(class_token,
+                                      token.name, new_class,
+                                      modifiers, token.name, None)
+    else:
+      if not self._handling_typedef:
+        self.HandleError('non-typedef token', token)
+      self._AddBackToken(token)
+
+    return class_type(class_token.start, class_token.end, class_name,
+                      bases, templated_types, body, self.namespace_stack)
+
+  def handle_namespace(self):
+    # Support anonymous namespaces.
+    name = None
+    name_tokens, token = self.GetName()
+    if name_tokens:
+      name = ''.join([t.name for t in name_tokens])
+    self.namespace_stack.append(name)
+    assert token.token_type == tokenize.SYNTAX, token
+    # Create an internal token that denotes when the namespace is complete.
+    internal_token = tokenize.Token(_INTERNAL_TOKEN, _NAMESPACE_POP,
+                                    None, None)
+    internal_token.whence = token.whence
+    if token.name == '=':
+      # TODO(nnorwitz): handle aliasing namespaces.
+      name, next_token = self.GetName()
+      assert next_token.name == ';', next_token
+      self._AddBackToken(internal_token)
+    else:
+      assert token.name == '{', token
+      tokens = list(self.GetScope())
+      # Replace the trailing } with the internal namespace pop token.
+      tokens[-1] = internal_token
+      # Handle namespace with nothing in it.
+      self._AddBackTokens(tokens)
+    return None
+
+  def handle_using(self):
+    tokens = self._GetTokensUpTo(tokenize.SYNTAX, ';')
+    assert tokens
+    return Using(tokens[0].start, tokens[0].end, tokens)
+
+  def handle_explicit(self):
+    assert self.in_class
+    # Nothing much to do.
+    # TODO(nnorwitz): maybe verify the method name == class name.
+    # This must be a ctor.
+    return self.GetMethod(FUNCTION_CTOR, None)
+
+  def handle_this(self):
+    pass  # Nothing to do.
+
+  def handle_operator(self):
+    # Pull off the next token(s?) and make that part of the method name.
+    pass
+
+  def handle_sizeof(self):
+    pass
+
+  def handle_case(self):
+    pass
+
+  def handle_switch(self):
+    pass
+
+  def handle_default(self):
+    token = self._GetNextToken()
+    assert token.token_type == tokenize.SYNTAX
+    assert token.name == ':'
+
+  def handle_if(self):
+    pass
+
+  def handle_else(self):
+    pass
+
+  def handle_return(self):
+    tokens = self._GetTokensUpTo(tokenize.SYNTAX, ';')
+    if not tokens:
+      return Return(self.current_token.start, self.current_token.end, None)
+    return Return(tokens[0].start, tokens[0].end, tokens)
+
+  def handle_goto(self):
+    tokens = self._GetTokensUpTo(tokenize.SYNTAX, ';')
+    assert len(tokens) == 1, str(tokens)
+    return Goto(tokens[0].start, tokens[0].end, tokens[0].name)
+
+  def handle_try(self):
+    pass  # Not needed yet.
+
+  def handle_catch(self):
+    pass  # Not needed yet.
+
+  def handle_throw(self):
+    pass  # Not needed yet.
+
+  def handle_while(self):
+    pass
+
+  def handle_do(self):
+    pass
+
+  def handle_for(self):
+    pass
+
+  def handle_break(self):
+    self._IgnoreUpTo(tokenize.SYNTAX, ';')
+
+  def handle_continue(self):
+    self._IgnoreUpTo(tokenize.SYNTAX, ';')
+
+
+def BuilderFromSource(source, filename):
+  """Utility method that returns an AstBuilder from source code.
+
+    Args:
+      source: 'C++ source code'
+      filename: 'file1'
+
+    Returns:
+      AstBuilder
+    """
+  return AstBuilder(tokenize.GetTokens(source), filename)
+
+
+def PrintIndentifiers(filename, should_print):
+  """Prints all identifiers for a C++ source file.
+
+    Args:
+      filename: 'file1'
+      should_print: predicate with signature: bool Function(token)
+    """
+  source = utils.ReadFile(filename, False)
+  if source is None:
+    sys.stderr.write('Unable to find: %s\n' % filename)
+    return
+
+  #print('Processing %s' % actual_filename)
+  builder = BuilderFromSource(source, filename)
+  try:
+    for node in builder.Generate():
+      if should_print(node):
+        print(node.name)
+  except KeyboardInterrupt:
+    return
+  except:
+    pass
+
+
+def PrintAllIndentifiers(filenames, should_print):
+  """Prints all identifiers for each C++ source file in filenames.
+
+    Args:
+      filenames: ['file1', 'file2', ...]
+      should_print: predicate with signature: bool Function(token)
+    """
+  for path in filenames:
+    PrintIndentifiers(path, should_print)
+
+
+def main(argv):
+  for filename in argv[1:]:
+    source = utils.ReadFile(filename)
+    if source is None:
+      continue
+
+    print('Processing %s' % filename)
+    builder = BuilderFromSource(source, filename)
+    try:
+      entire_ast = filter(None, builder.Generate())
+    except KeyboardInterrupt:
+      return
+    except:
+      # Already printed a warning, print the traceback and continue.
+      traceback.print_exc()
+    else:
+      if utils.DEBUG:
+        for ast in entire_ast:
+          print(ast)
+
+
+if __name__ == '__main__':
+  main(sys.argv)
diff --git a/leveldb_base/third_party/googletest/googlemock/scripts/generator/cpp/gmock_class.py b/leveldb_base/third_party/googletest/googlemock/scripts/generator/cpp/gmock_class.py
new file mode 100644
index 0000000..3e21022
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/scripts/generator/cpp/gmock_class.py
@@ -0,0 +1,247 @@
+#!/usr/bin/env python
+#
+# Copyright 2008 Google Inc.  All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Generate Google Mock classes from base classes.
+
+This program will read in a C++ source file and output the Google Mock
+classes for the specified classes.  If no class is specified, all
+classes in the source file are emitted.
+
+Usage:
+  gmock_class.py header-file.h [ClassName]...
+
+Output is sent to stdout.
+"""
+
+import os
+import re
+import sys
+
+from cpp import ast
+from cpp import utils
+
+# Preserve compatibility with Python 2.3.
+try:
+  _dummy = set
+except NameError:
+  import sets
+
+  set = sets.Set
+
+_VERSION = (1, 0, 1)  # The version of this script.
+# How many spaces to indent.  Can set me with the INDENT environment variable.
+_INDENT = 2
+
+
+def _RenderType(ast_type):
+  """Renders the potentially recursively templated type into a string.
+
+  Args:
+    ast_type: The AST of the type.
+
+  Returns:
+    Rendered string of the type.
+  """
+  # Add modifiers like 'const'.
+  modifiers = ''
+  if ast_type.modifiers:
+    modifiers = ' '.join(ast_type.modifiers) + ' '
+  return_type = modifiers + ast_type.name
+  if ast_type.templated_types:
+    # Collect template args.
+    template_args = []
+    for arg in ast_type.templated_types:
+      rendered_arg = _RenderType(arg)
+      template_args.append(rendered_arg)
+    return_type += '<' + ', '.join(template_args) + '>'
+  if ast_type.pointer:
+    return_type += '*'
+  if ast_type.reference:
+    return_type += '&'
+  return return_type
+
+
+def _GenerateArg(source):
+  """Strips out comments, default arguments, and redundant spaces from a single argument.
+
+  Args:
+    source: A string for a single argument.
+
+  Returns:
+    Rendered string of the argument.
+  """
+  # Remove end of line comments before eliminating newlines.
+  arg = re.sub(r'//.*', '', source)
+
+  # Remove c-style comments.
+  arg = re.sub(r'/\*.*\*/', '', arg)
+
+  # Remove default arguments.
+  arg = re.sub(r'=.*', '', arg)
+
+  # Collapse spaces and newlines into a single space.
+  arg = re.sub(r'\s+', ' ', arg)
+  return arg.strip()
+
+
+def _EscapeForMacro(s):
+  """Escapes a string for use as an argument to a C++ macro."""
+  paren_count = 0
+  for c in s:
+    if c == '(':
+      paren_count += 1
+    elif c == ')':
+      paren_count -= 1
+    elif c == ',' and paren_count == 0:
+      return '(' + s + ')'
+  return s
+
+
+def _GenerateMethods(output_lines, source, class_node):
+  function_type = (
+      ast.FUNCTION_VIRTUAL | ast.FUNCTION_PURE_VIRTUAL | ast.FUNCTION_OVERRIDE)
+  ctor_or_dtor = ast.FUNCTION_CTOR | ast.FUNCTION_DTOR
+  indent = ' ' * _INDENT
+
+  for node in class_node.body:
+    # We only care about virtual functions.
+    if (isinstance(node, ast.Function) and node.modifiers & function_type and
+        not node.modifiers & ctor_or_dtor):
+      # Pick out all the elements we need from the original function.
+      modifiers = 'override'
+      if node.modifiers & ast.FUNCTION_CONST:
+        modifiers = 'const, ' + modifiers
+
+      return_type = 'void'
+      if node.return_type:
+        return_type = _EscapeForMacro(_RenderType(node.return_type))
+
+      args = []
+      for p in node.parameters:
+        arg = _GenerateArg(source[p.start:p.end])
+        if arg != 'void':
+          args.append(_EscapeForMacro(arg))
+
+      # Create the mock method definition.
+      output_lines.extend([
+          '%sMOCK_METHOD(%s, %s, (%s), (%s));' %
+          (indent, return_type, node.name, ', '.join(args), modifiers)
+      ])
+
+
+def _GenerateMocks(filename, source, ast_list, desired_class_names):
+  processed_class_names = set()
+  lines = []
+  for node in ast_list:
+    if (isinstance(node, ast.Class) and node.body and
+        # desired_class_names being None means that all classes are selected.
+        (not desired_class_names or node.name in desired_class_names)):
+      class_name = node.name
+      parent_name = class_name
+      processed_class_names.add(class_name)
+      class_node = node
+      # Add namespace before the class.
+      if class_node.namespace:
+        lines.extend(['namespace %s {' % n for n in class_node.namespace])  # }
+        lines.append('')
+
+      # Add template args for templated classes.
+      if class_node.templated_types:
+        # TODO(paulchang): Handle non-type template arguments (e.g.
+        # template<typename T, int N>).
+
+        # class_node.templated_types is an OrderedDict from strings to a tuples.
+        # The key is the name of the template, and the value is
+        # (type_name, default). Both type_name and default could be None.
+        template_args = class_node.templated_types.keys()
+        template_decls = ['typename ' + arg for arg in template_args]
+        lines.append('template <' + ', '.join(template_decls) + '>')
+        parent_name += '<' + ', '.join(template_args) + '>'
+
+      # Add the class prolog.
+      lines.append('class Mock%s : public %s {'  # }
+                   % (class_name, parent_name))
+      lines.append('%spublic:' % (' ' * (_INDENT // 2)))
+
+      # Add all the methods.
+      _GenerateMethods(lines, source, class_node)
+
+      # Close the class.
+      if lines:
+        # If there are no virtual methods, no need for a public label.
+        if len(lines) == 2:
+          del lines[-1]
+
+        # Only close the class if there really is a class.
+        lines.append('};')
+        lines.append('')  # Add an extra newline.
+
+      # Close the namespace.
+      if class_node.namespace:
+        for i in range(len(class_node.namespace) - 1, -1, -1):
+          lines.append('}  // namespace %s' % class_node.namespace[i])
+        lines.append('')  # Add an extra newline.
+
+  if desired_class_names:
+    missing_class_name_list = list(desired_class_names - processed_class_names)
+    if missing_class_name_list:
+      missing_class_name_list.sort()
+      sys.stderr.write('Class(es) not found in %s: %s\n' %
+                       (filename, ', '.join(missing_class_name_list)))
+  elif not processed_class_names:
+    sys.stderr.write('No class found in %s\n' % filename)
+
+  return lines
+
+
+def main(argv=sys.argv):
+  if len(argv) < 2:
+    sys.stderr.write('Google Mock Class Generator v%s\n\n' %
+                     '.'.join(map(str, _VERSION)))
+    sys.stderr.write(__doc__)
+    return 1
+
+  global _INDENT
+  try:
+    _INDENT = int(os.environ['INDENT'])
+  except KeyError:
+    pass
+  except:
+    sys.stderr.write('Unable to use indent of %s\n' % os.environ.get('INDENT'))
+
+  filename = argv[1]
+  desired_class_names = None  # None means all classes in the source file.
+  if len(argv) >= 3:
+    desired_class_names = set(argv[2:])
+  source = utils.ReadFile(filename)
+  if source is None:
+    return 1
+
+  builder = ast.BuilderFromSource(source, filename)
+  try:
+    entire_ast = filter(None, builder.Generate())
+  except KeyboardInterrupt:
+    return
+  except:
+    # An error message was already printed since we couldn't parse.
+    sys.exit(1)
+  else:
+    lines = _GenerateMocks(filename, source, entire_ast, desired_class_names)
+    sys.stdout.write('\n'.join(lines))
+
+
+if __name__ == '__main__':
+  main(sys.argv)
diff --git a/leveldb_base/third_party/googletest/googlemock/scripts/generator/cpp/gmock_class_test.py b/leveldb_base/third_party/googletest/googlemock/scripts/generator/cpp/gmock_class_test.py
new file mode 100644
index 0000000..eff475f
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/scripts/generator/cpp/gmock_class_test.py
@@ -0,0 +1,570 @@
+#!/usr/bin/env python
+#
+# Copyright 2009 Neal Norwitz All Rights Reserved.
+# Portions Copyright 2009 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Tests for gmock.scripts.generator.cpp.gmock_class."""
+
+import os
+import sys
+import unittest
+
+# Allow the cpp imports below to work when run as a standalone script.
+sys.path.append(os.path.join(os.path.dirname(__file__), '..'))
+
+from cpp import ast
+from cpp import gmock_class
+
+
+class TestCase(unittest.TestCase):
+  """Helper class that adds assert methods."""
+
+  @staticmethod
+  def StripLeadingWhitespace(lines):
+    """Strip leading whitespace in each line in 'lines'."""
+    return '\n'.join([s.lstrip() for s in lines.split('\n')])
+
+  def assertEqualIgnoreLeadingWhitespace(self, expected_lines, lines):
+    """Specialized assert that ignores the indent level."""
+    self.assertEqual(expected_lines, self.StripLeadingWhitespace(lines))
+
+
+class GenerateMethodsTest(TestCase):
+
+  @staticmethod
+  def GenerateMethodSource(cpp_source):
+    """Convert C++ source to Google Mock output source lines."""
+    method_source_lines = []
+    # <test> is a pseudo-filename, it is not read or written.
+    builder = ast.BuilderFromSource(cpp_source, '<test>')
+    ast_list = list(builder.Generate())
+    gmock_class._GenerateMethods(method_source_lines, cpp_source, ast_list[0])
+    return '\n'.join(method_source_lines)
+
+  def testSimpleMethod(self):
+    source = """
+class Foo {
+ public:
+  virtual int Bar();
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD(int, Bar, (), (override));',
+        self.GenerateMethodSource(source))
+
+  def testSimpleConstructorsAndDestructor(self):
+    source = """
+class Foo {
+ public:
+  Foo();
+  Foo(int x);
+  Foo(const Foo& f);
+  Foo(Foo&& f);
+  ~Foo();
+  virtual int Bar() = 0;
+};
+"""
+    # The constructors and destructor should be ignored.
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD(int, Bar, (), (override));',
+        self.GenerateMethodSource(source))
+
+  def testVirtualDestructor(self):
+    source = """
+class Foo {
+ public:
+  virtual ~Foo();
+  virtual int Bar() = 0;
+};
+"""
+    # The destructor should be ignored.
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD(int, Bar, (), (override));',
+        self.GenerateMethodSource(source))
+
+  def testExplicitlyDefaultedConstructorsAndDestructor(self):
+    source = """
+class Foo {
+ public:
+  Foo() = default;
+  Foo(const Foo& f) = default;
+  Foo(Foo&& f) = default;
+  ~Foo() = default;
+  virtual int Bar() = 0;
+};
+"""
+    # The constructors and destructor should be ignored.
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD(int, Bar, (), (override));',
+        self.GenerateMethodSource(source))
+
+  def testExplicitlyDeletedConstructorsAndDestructor(self):
+    source = """
+class Foo {
+ public:
+  Foo() = delete;
+  Foo(const Foo& f) = delete;
+  Foo(Foo&& f) = delete;
+  ~Foo() = delete;
+  virtual int Bar() = 0;
+};
+"""
+    # The constructors and destructor should be ignored.
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD(int, Bar, (), (override));',
+        self.GenerateMethodSource(source))
+
+  def testSimpleOverrideMethod(self):
+    source = """
+class Foo {
+ public:
+  int Bar() override;
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD(int, Bar, (), (override));',
+        self.GenerateMethodSource(source))
+
+  def testSimpleConstMethod(self):
+    source = """
+class Foo {
+ public:
+  virtual void Bar(bool flag) const;
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD(void, Bar, (bool flag), (const, override));',
+        self.GenerateMethodSource(source))
+
+  def testExplicitVoid(self):
+    source = """
+class Foo {
+ public:
+  virtual int Bar(void);
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD(int, Bar, (), (override));',
+        self.GenerateMethodSource(source))
+
+  def testStrangeNewlineInParameter(self):
+    source = """
+class Foo {
+ public:
+  virtual void Bar(int
+a) = 0;
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD(void, Bar, (int a), (override));',
+        self.GenerateMethodSource(source))
+
+  def testDefaultParameters(self):
+    source = """
+class Foo {
+ public:
+  virtual void Bar(int a, char c = 'x') = 0;
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD(void, Bar, (int a, char c), (override));',
+        self.GenerateMethodSource(source))
+
+  def testMultipleDefaultParameters(self):
+    source = """
+class Foo {
+ public:
+  virtual void Bar(
+        int a = 42, 
+        char c = 'x', 
+        const int* const p = nullptr, 
+        const std::string& s = "42",
+        char tab[] = {'4','2'},
+        int const *& rp = aDefaultPointer) = 0;
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD(void, Bar, '
+        '(int a, char c, const int* const p, const std::string& s, char tab[], int const *& rp), '
+        '(override));', self.GenerateMethodSource(source))
+
+  def testMultipleSingleLineDefaultParameters(self):
+    source = """
+class Foo {
+ public:
+  virtual void Bar(int a = 42, int b = 43, int c = 44) = 0;
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD(void, Bar, (int a, int b, int c), (override));',
+        self.GenerateMethodSource(source))
+
+  def testConstDefaultParameter(self):
+    source = """
+class Test {
+ public:
+  virtual bool Bar(const int test_arg = 42) = 0;
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD(bool, Bar, (const int test_arg), (override));',
+        self.GenerateMethodSource(source))
+
+  def testConstRefDefaultParameter(self):
+    source = """
+class Test {
+ public:
+  virtual bool Bar(const std::string& test_arg = "42" ) = 0;
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD(bool, Bar, (const std::string& test_arg), (override));',
+        self.GenerateMethodSource(source))
+
+  def testRemovesCommentsWhenDefaultsArePresent(self):
+    source = """
+class Foo {
+ public:
+  virtual void Bar(int a = 42 /* a comment */,
+                   char /* other comment */ c= 'x') = 0;
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD(void, Bar, (int a, char c), (override));',
+        self.GenerateMethodSource(source))
+
+  def testDoubleSlashCommentsInParameterListAreRemoved(self):
+    source = """
+class Foo {
+ public:
+  virtual void Bar(int a,  // inline comments should be elided.
+                   int b   // inline comments should be elided.
+                   ) const = 0;
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD(void, Bar, (int a, int b), (const, override));',
+        self.GenerateMethodSource(source))
+
+  def testCStyleCommentsInParameterListAreNotRemoved(self):
+    # NOTE(nnorwitz): I'm not sure if it's the best behavior to keep these
+    # comments.  Also note that C style comments after the last parameter
+    # are still elided.
+    source = """
+class Foo {
+ public:
+  virtual const string& Bar(int /* keeper */, int b);
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD(const string&, Bar, (int, int b), (override));',
+        self.GenerateMethodSource(source))
+
+  def testArgsOfTemplateTypes(self):
+    source = """
+class Foo {
+ public:
+  virtual int Bar(const vector<int>& v, map<int, string>* output);
+};"""
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD(int, Bar, (const vector<int>& v, (map<int, string>* output)), (override));',
+        self.GenerateMethodSource(source))
+
+  def testReturnTypeWithOneTemplateArg(self):
+    source = """
+class Foo {
+ public:
+  virtual vector<int>* Bar(int n);
+};"""
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD(vector<int>*, Bar, (int n), (override));',
+        self.GenerateMethodSource(source))
+
+  def testReturnTypeWithManyTemplateArgs(self):
+    source = """
+class Foo {
+ public:
+  virtual map<int, string> Bar();
+};"""
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD((map<int, string>), Bar, (), (override));',
+        self.GenerateMethodSource(source))
+
+  def testSimpleMethodInTemplatedClass(self):
+    source = """
+template<class T>
+class Foo {
+ public:
+  virtual int Bar();
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD(int, Bar, (), (override));',
+        self.GenerateMethodSource(source))
+
+  def testPointerArgWithoutNames(self):
+    source = """
+class Foo {
+  virtual int Bar(C*);
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD(int, Bar, (C*), (override));',
+        self.GenerateMethodSource(source))
+
+  def testReferenceArgWithoutNames(self):
+    source = """
+class Foo {
+  virtual int Bar(C&);
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD(int, Bar, (C&), (override));',
+        self.GenerateMethodSource(source))
+
+  def testArrayArgWithoutNames(self):
+    source = """
+class Foo {
+  virtual int Bar(C[]);
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(
+        'MOCK_METHOD(int, Bar, (C[]), (override));',
+        self.GenerateMethodSource(source))
+
+
+class GenerateMocksTest(TestCase):
+
+  @staticmethod
+  def GenerateMocks(cpp_source):
+    """Convert C++ source to complete Google Mock output source."""
+    # <test> is a pseudo-filename, it is not read or written.
+    filename = '<test>'
+    builder = ast.BuilderFromSource(cpp_source, filename)
+    ast_list = list(builder.Generate())
+    lines = gmock_class._GenerateMocks(filename, cpp_source, ast_list, None)
+    return '\n'.join(lines)
+
+  def testNamespaces(self):
+    source = """
+namespace Foo {
+namespace Bar { class Forward; }
+namespace Baz::Qux {
+
+class Test {
+ public:
+  virtual void Foo();
+};
+
+}  // namespace Baz::Qux
+}  // namespace Foo
+"""
+    expected = """\
+namespace Foo {
+namespace Baz::Qux {
+
+class MockTest : public Test {
+public:
+MOCK_METHOD(void, Foo, (), (override));
+};
+
+}  // namespace Baz::Qux
+}  // namespace Foo
+"""
+    self.assertEqualIgnoreLeadingWhitespace(expected,
+                                            self.GenerateMocks(source))
+
+  def testClassWithStorageSpecifierMacro(self):
+    source = """
+class STORAGE_SPECIFIER Test {
+ public:
+  virtual void Foo();
+};
+"""
+    expected = """\
+class MockTest : public Test {
+public:
+MOCK_METHOD(void, Foo, (), (override));
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(expected,
+                                            self.GenerateMocks(source))
+
+  def testTemplatedForwardDeclaration(self):
+    source = """
+template <class T> class Forward;  // Forward declaration should be ignored.
+class Test {
+ public:
+  virtual void Foo();
+};
+"""
+    expected = """\
+class MockTest : public Test {
+public:
+MOCK_METHOD(void, Foo, (), (override));
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(expected,
+                                            self.GenerateMocks(source))
+
+  def testTemplatedClass(self):
+    source = """
+template <typename S, typename T>
+class Test {
+ public:
+  virtual void Foo();
+};
+"""
+    expected = """\
+template <typename S, typename T>
+class MockTest : public Test<S, T> {
+public:
+MOCK_METHOD(void, Foo, (), (override));
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(expected,
+                                            self.GenerateMocks(source))
+
+  def testTemplateInATemplateTypedef(self):
+    source = """
+class Test {
+ public:
+  typedef std::vector<std::list<int>> FooType;
+  virtual void Bar(const FooType& test_arg);
+};
+"""
+    expected = """\
+class MockTest : public Test {
+public:
+MOCK_METHOD(void, Bar, (const FooType& test_arg), (override));
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(expected,
+                                            self.GenerateMocks(source))
+
+  def testTemplatedClassWithTemplatedArguments(self):
+    source = """
+template <typename S, typename T, typename U, typename V, typename W>
+class Test {
+ public:
+  virtual U Foo(T some_arg);
+};
+"""
+    expected = """\
+template <typename S, typename T, typename U, typename V, typename W>
+class MockTest : public Test<S, T, U, V, W> {
+public:
+MOCK_METHOD(U, Foo, (T some_arg), (override));
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(expected,
+                                            self.GenerateMocks(source))
+
+  def testTemplateInATemplateTypedefWithComma(self):
+    source = """
+class Test {
+ public:
+  typedef std::function<void(
+      const vector<std::list<int>>&, int> FooType;
+  virtual void Bar(const FooType& test_arg);
+};
+"""
+    expected = """\
+class MockTest : public Test {
+public:
+MOCK_METHOD(void, Bar, (const FooType& test_arg), (override));
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(expected,
+                                            self.GenerateMocks(source))
+
+  def testParenthesizedCommaInArg(self):
+    source = """
+class Test {
+ public:
+   virtual void Bar(std::function<void(int, int)> f);
+};
+"""
+    expected = """\
+class MockTest : public Test {
+public:
+MOCK_METHOD(void, Bar, (std::function<void(int, int)> f), (override));
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(expected,
+                                            self.GenerateMocks(source))
+
+  def testEnumType(self):
+    source = """
+class Test {
+ public:
+  enum Bar {
+    BAZ, QUX, QUUX, QUUUX
+  };
+  virtual void Foo();
+};
+"""
+    expected = """\
+class MockTest : public Test {
+public:
+MOCK_METHOD(void, Foo, (), (override));
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(expected,
+                                            self.GenerateMocks(source))
+
+  def testEnumClassType(self):
+    source = """
+class Test {
+ public:
+  enum class Bar {
+    BAZ, QUX, QUUX, QUUUX
+  };
+  virtual void Foo();
+};
+"""
+    expected = """\
+class MockTest : public Test {
+public:
+MOCK_METHOD(void, Foo, (), (override));
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(expected,
+                                            self.GenerateMocks(source))
+
+  def testStdFunction(self):
+    source = """
+class Test {
+ public:
+  Test(std::function<int(std::string)> foo) : foo_(foo) {}
+
+  virtual std::function<int(std::string)> foo();
+
+ private:
+  std::function<int(std::string)> foo_;
+};
+"""
+    expected = """\
+class MockTest : public Test {
+public:
+MOCK_METHOD(std::function<int (std::string)>, foo, (), (override));
+};
+"""
+    self.assertEqualIgnoreLeadingWhitespace(expected,
+                                            self.GenerateMocks(source))
+
+
+if __name__ == '__main__':
+  unittest.main()
diff --git a/leveldb_base/third_party/googletest/googlemock/scripts/generator/cpp/keywords.py b/leveldb_base/third_party/googletest/googlemock/scripts/generator/cpp/keywords.py
new file mode 100644
index 0000000..e428271
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/scripts/generator/cpp/keywords.py
@@ -0,0 +1,56 @@
+#!/usr/bin/env python
+#
+# Copyright 2007 Neal Norwitz
+# Portions Copyright 2007 Google Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""C++ keywords and helper utilities for determining keywords."""
+
+try:
+    # Python 3.x
+    import builtins
+except ImportError:
+    # Python 2.x
+    import __builtin__ as builtins
+
+
+if not hasattr(builtins, 'set'):
+    # Nominal support for Python 2.3.
+    from sets import Set as set
+
+
+TYPES = set('bool char int long short double float void wchar_t unsigned signed'.split())
+TYPE_MODIFIERS = set('auto register const inline extern static virtual volatile mutable'.split())
+ACCESS = set('public protected private friend'.split())
+
+CASTS = set('static_cast const_cast dynamic_cast reinterpret_cast'.split())
+
+OTHERS = set('true false asm class namespace using explicit this operator sizeof'.split())
+OTHER_TYPES = set('new delete typedef struct union enum typeid typename template'.split())
+
+CONTROL = set('case switch default if else return goto'.split())
+EXCEPTION = set('try catch throw'.split())
+LOOP = set('while do for break continue'.split())
+
+ALL = TYPES | TYPE_MODIFIERS | ACCESS | CASTS | OTHERS | OTHER_TYPES | CONTROL | EXCEPTION | LOOP
+
+
+def IsKeyword(token):
+    return token in ALL
+
+def IsBuiltinType(token):
+    if token in ('virtual', 'inline'):
+        # These only apply to methods, they can't be types by themselves.
+        return False
+    return token in TYPES or token in TYPE_MODIFIERS
diff --git a/leveldb_base/third_party/googletest/googlemock/scripts/generator/cpp/tokenize.py b/leveldb_base/third_party/googletest/googlemock/scripts/generator/cpp/tokenize.py
new file mode 100644
index 0000000..a75edcb
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/scripts/generator/cpp/tokenize.py
@@ -0,0 +1,284 @@
+#!/usr/bin/env python
+#
+# Copyright 2007 Neal Norwitz
+# Portions Copyright 2007 Google Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Tokenize C++ source code."""
+
+try:
+    # Python 3.x
+    import builtins
+except ImportError:
+    # Python 2.x
+    import __builtin__ as builtins
+
+
+import sys
+
+from cpp import utils
+
+
+if not hasattr(builtins, 'set'):
+    # Nominal support for Python 2.3.
+    from sets import Set as set
+
+
+# Add $ as a valid identifier char since so much code uses it.
+_letters = 'abcdefghijklmnopqrstuvwxyz'
+VALID_IDENTIFIER_CHARS = set(_letters + _letters.upper() + '_0123456789$')
+HEX_DIGITS = set('0123456789abcdefABCDEF')
+INT_OR_FLOAT_DIGITS = set('01234567890eE-+')
+
+
+# C++0x string preffixes.
+_STR_PREFIXES = set(('R', 'u8', 'u8R', 'u', 'uR', 'U', 'UR', 'L', 'LR'))
+
+
+# Token types.
+UNKNOWN = 'UNKNOWN'
+SYNTAX = 'SYNTAX'
+CONSTANT = 'CONSTANT'
+NAME = 'NAME'
+PREPROCESSOR = 'PREPROCESSOR'
+
+# Where the token originated from.  This can be used for backtracking.
+# It is always set to WHENCE_STREAM in this code.
+WHENCE_STREAM, WHENCE_QUEUE = range(2)
+
+
+class Token(object):
+    """Data container to represent a C++ token.
+
+    Tokens can be identifiers, syntax char(s), constants, or
+    pre-processor directives.
+
+    start contains the index of the first char of the token in the source
+    end contains the index of the last char of the token in the source
+    """
+
+    def __init__(self, token_type, name, start, end):
+        self.token_type = token_type
+        self.name = name
+        self.start = start
+        self.end = end
+        self.whence = WHENCE_STREAM
+
+    def __str__(self):
+        if not utils.DEBUG:
+            return 'Token(%r)' % self.name
+        return 'Token(%r, %s, %s)' % (self.name, self.start, self.end)
+
+    __repr__ = __str__
+
+
+def _GetString(source, start, i):
+    i = source.find('"', i+1)
+    while source[i-1] == '\\':
+        # Count the trailing backslashes.
+        backslash_count = 1
+        j = i - 2
+        while source[j] == '\\':
+            backslash_count += 1
+            j -= 1
+        # When trailing backslashes are even, they escape each other.
+        if (backslash_count % 2) == 0:
+            break
+        i = source.find('"', i+1)
+    return i + 1
+
+
+def _GetChar(source, start, i):
+    # NOTE(nnorwitz): may not be quite correct, should be good enough.
+    i = source.find("'", i+1)
+    while source[i-1] == '\\':
+        # Need to special case '\\'.
+        if (i - 2) > start and source[i-2] == '\\':
+            break
+        i = source.find("'", i+1)
+    # Try to handle unterminated single quotes (in a #if 0 block).
+    if i < 0:
+        i = start
+    return i + 1
+
+
+def GetTokens(source):
+    """Returns a sequence of Tokens.
+
+    Args:
+      source: string of C++ source code.
+
+    Yields:
+      Token that represents the next token in the source.
+    """
+    # Cache various valid character sets for speed.
+    valid_identifier_chars = VALID_IDENTIFIER_CHARS
+    hex_digits = HEX_DIGITS
+    int_or_float_digits = INT_OR_FLOAT_DIGITS
+    int_or_float_digits2 = int_or_float_digits | set('.')
+
+    # Only ignore errors while in a #if 0 block.
+    ignore_errors = False
+    count_ifs = 0
+
+    i = 0
+    end = len(source)
+    while i < end:
+        # Skip whitespace.
+        while i < end and source[i].isspace():
+            i += 1
+        if i >= end:
+            return
+
+        token_type = UNKNOWN
+        start = i
+        c = source[i]
+        if c.isalpha() or c == '_':              # Find a string token.
+            token_type = NAME
+            while source[i] in valid_identifier_chars:
+                i += 1
+            # String and character constants can look like a name if
+            # they are something like L"".
+            if (source[i] == "'" and (i - start) == 1 and
+                source[start:i] in 'uUL'):
+                # u, U, and L are valid C++0x character preffixes.
+                token_type = CONSTANT
+                i = _GetChar(source, start, i)
+            elif source[i] == "'" and source[start:i] in _STR_PREFIXES:
+                token_type = CONSTANT
+                i = _GetString(source, start, i)
+        elif c == '/' and source[i+1] == '/':    # Find // comments.
+            i = source.find('\n', i)
+            if i == -1:  # Handle EOF.
+                i = end
+            continue
+        elif c == '/' and source[i+1] == '*':    # Find /* comments. */
+            i = source.find('*/', i) + 2
+            continue
+        elif c in ':+-<>&|*=':                   # : or :: (plus other chars).
+            token_type = SYNTAX
+            i += 1
+            new_ch = source[i]
+            if new_ch == c and c != '>':         # Treat ">>" as two tokens.
+                i += 1
+            elif c == '-' and new_ch == '>':
+                i += 1
+            elif new_ch == '=':
+                i += 1
+        elif c in '()[]{}~!?^%;/.,':             # Handle single char tokens.
+            token_type = SYNTAX
+            i += 1
+            if c == '.' and source[i].isdigit():
+                token_type = CONSTANT
+                i += 1
+                while source[i] in int_or_float_digits:
+                    i += 1
+                # Handle float suffixes.
+                for suffix in ('l', 'f'):
+                    if suffix == source[i:i+1].lower():
+                        i += 1
+                        break
+        elif c.isdigit():                        # Find integer.
+            token_type = CONSTANT
+            if c == '0' and source[i+1] in 'xX':
+                # Handle hex digits.
+                i += 2
+                while source[i] in hex_digits:
+                    i += 1
+            else:
+                while source[i] in int_or_float_digits2:
+                    i += 1
+            # Handle integer (and float) suffixes.
+            for suffix in ('ull', 'll', 'ul', 'l', 'f', 'u'):
+                size = len(suffix)
+                if suffix == source[i:i+size].lower():
+                    i += size
+                    break
+        elif c == '"':                           # Find string.
+            token_type = CONSTANT
+            i = _GetString(source, start, i)
+        elif c == "'":                           # Find char.
+            token_type = CONSTANT
+            i = _GetChar(source, start, i)
+        elif c == '#':                           # Find pre-processor command.
+            token_type = PREPROCESSOR
+            got_if = source[i:i+3] == '#if' and source[i+3:i+4].isspace()
+            if got_if:
+                count_ifs += 1
+            elif source[i:i+6] == '#endif':
+                count_ifs -= 1
+                if count_ifs == 0:
+                    ignore_errors = False
+
+            # TODO(nnorwitz): handle preprocessor statements (\ continuations).
+            while 1:
+                i1 = source.find('\n', i)
+                i2 = source.find('//', i)
+                i3 = source.find('/*', i)
+                i4 = source.find('"', i)
+                # NOTE(nnorwitz): doesn't handle comments in #define macros.
+                # Get the first important symbol (newline, comment, EOF/end).
+                i = min([x for x in (i1, i2, i3, i4, end) if x != -1])
+
+                # Handle #include "dir//foo.h" properly.
+                if source[i] == '"':
+                    i = source.find('"', i+1) + 1
+                    assert i > 0
+                    continue
+                # Keep going if end of the line and the line ends with \.
+                if not (i == i1 and source[i-1] == '\\'):
+                    if got_if:
+                        condition = source[start+4:i].lstrip()
+                        if (condition.startswith('0') or
+                            condition.startswith('(0)')):
+                            ignore_errors = True
+                    break
+                i += 1
+        elif c == '\\':                          # Handle \ in code.
+            # This is different from the pre-processor \ handling.
+            i += 1
+            continue
+        elif ignore_errors:
+            # The tokenizer seems to be in pretty good shape.  This
+            # raise is conditionally disabled so that bogus code
+            # in an #if 0 block can be handled.  Since we will ignore
+            # it anyways, this is probably fine.  So disable the
+            # exception and  return the bogus char.
+            i += 1
+        else:
+            sys.stderr.write('Got invalid token in %s @ %d token:%s: %r\n' %
+                             ('?', i, c, source[i-10:i+10]))
+            raise RuntimeError('unexpected token')
+
+        if i <= 0:
+            print('Invalid index, exiting now.')
+            return
+        yield Token(token_type, source[start:i], start, i)
+
+
+if __name__ == '__main__':
+    def main(argv):
+        """Driver mostly for testing purposes."""
+        for filename in argv[1:]:
+            source = utils.ReadFile(filename)
+            if source is None:
+                continue
+
+            for token in GetTokens(source):
+                print('%-12s: %s' % (token.token_type, token.name))
+                # print('\r%6.2f%%' % (100.0 * index / token.end),)
+            sys.stdout.write('\n')
+
+
+    main(sys.argv)
diff --git a/leveldb_base/third_party/googletest/googlemock/scripts/generator/cpp/utils.py b/leveldb_base/third_party/googletest/googlemock/scripts/generator/cpp/utils.py
new file mode 100644
index 0000000..6f5fc09
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/scripts/generator/cpp/utils.py
@@ -0,0 +1,37 @@
+#!/usr/bin/env python
+#
+# Copyright 2007 Neal Norwitz
+# Portions Copyright 2007 Google Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Generic utilities for C++ parsing."""
+
+import sys
+
+# Set to True to see the start/end token indices.
+DEBUG = True
+
+
+def ReadFile(filename, print_error=True):
+    """Returns the contents of a file."""
+    try:
+        fp = open(filename)
+        try:
+            return fp.read()
+        finally:
+            fp.close()
+    except IOError:
+        if print_error:
+            print('Error reading %s: %s' % (filename, sys.exc_info()[1]))
+        return None
diff --git a/leveldb_base/third_party/googletest/googlemock/scripts/generator/gmock_gen.py b/leveldb_base/third_party/googletest/googlemock/scripts/generator/gmock_gen.py
new file mode 100644
index 0000000..9d528a5
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/scripts/generator/gmock_gen.py
@@ -0,0 +1,30 @@
+#!/usr/bin/env python
+#
+# Copyright 2008 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Driver for starting up Google Mock class generator."""
+
+
+import os
+import sys
+
+if __name__ == '__main__':
+  # Add the directory of this script to the path so we can import gmock_class.
+  sys.path.append(os.path.dirname(__file__))
+
+  from cpp import gmock_class
+  # Fix the docstring in case they require the usage.
+  gmock_class.__doc__ = gmock_class.__doc__.replace('gmock_class.py', __file__)
+  gmock_class.main()
diff --git a/leveldb_base/third_party/googletest/googlemock/src/gmock-all.cc b/leveldb_base/third_party/googletest/googlemock/src/gmock-all.cc
new file mode 100644
index 0000000..e43c9b7
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/src/gmock-all.cc
@@ -0,0 +1,46 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// Google C++ Mocking Framework (Google Mock)
+//
+// This file #includes all Google Mock implementation .cc files.  The
+// purpose is to allow a user to build Google Mock by compiling this
+// file alone.
+
+// This line ensures that gmock.h can be compiled on its own, even
+// when it's fused.
+#include "gmock/gmock.h"
+
+// The following lines pull in the real gmock *.cc files.
+#include "src/gmock-cardinalities.cc"
+#include "src/gmock-internal-utils.cc"
+#include "src/gmock-matchers.cc"
+#include "src/gmock-spec-builders.cc"
+#include "src/gmock.cc"
diff --git a/leveldb_base/third_party/googletest/googlemock/src/gmock-cardinalities.cc b/leveldb_base/third_party/googletest/googlemock/src/gmock-cardinalities.cc
new file mode 100644
index 0000000..7463f43
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/src/gmock-cardinalities.cc
@@ -0,0 +1,155 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file implements cardinalities.
+
+#include "gmock/gmock-cardinalities.h"
+
+#include <limits.h>
+#include <ostream>  // NOLINT
+#include <sstream>
+#include <string>
+#include "gmock/internal/gmock-internal-utils.h"
+#include "gtest/gtest.h"
+
+namespace testing {
+
+namespace {
+
+// Implements the Between(m, n) cardinality.
+class BetweenCardinalityImpl : public CardinalityInterface {
+ public:
+  BetweenCardinalityImpl(int min, int max)
+      : min_(min >= 0 ? min : 0),
+        max_(max >= min_ ? max : min_) {
+    std::stringstream ss;
+    if (min < 0) {
+      ss << "The invocation lower bound must be >= 0, "
+         << "but is actually " << min << ".";
+      internal::Expect(false, __FILE__, __LINE__, ss.str());
+    } else if (max < 0) {
+      ss << "The invocation upper bound must be >= 0, "
+         << "but is actually " << max << ".";
+      internal::Expect(false, __FILE__, __LINE__, ss.str());
+    } else if (min > max) {
+      ss << "The invocation upper bound (" << max
+         << ") must be >= the invocation lower bound (" << min
+         << ").";
+      internal::Expect(false, __FILE__, __LINE__, ss.str());
+    }
+  }
+
+  // Conservative estimate on the lower/upper bound of the number of
+  // calls allowed.
+  int ConservativeLowerBound() const override { return min_; }
+  int ConservativeUpperBound() const override { return max_; }
+
+  bool IsSatisfiedByCallCount(int call_count) const override {
+    return min_ <= call_count && call_count <= max_;
+  }
+
+  bool IsSaturatedByCallCount(int call_count) const override {
+    return call_count >= max_;
+  }
+
+  void DescribeTo(::std::ostream* os) const override;
+
+ private:
+  const int min_;
+  const int max_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(BetweenCardinalityImpl);
+};
+
+// Formats "n times" in a human-friendly way.
+inline std::string FormatTimes(int n) {
+  if (n == 1) {
+    return "once";
+  } else if (n == 2) {
+    return "twice";
+  } else {
+    std::stringstream ss;
+    ss << n << " times";
+    return ss.str();
+  }
+}
+
+// Describes the Between(m, n) cardinality in human-friendly text.
+void BetweenCardinalityImpl::DescribeTo(::std::ostream* os) const {
+  if (min_ == 0) {
+    if (max_ == 0) {
+      *os << "never called";
+    } else if (max_ == INT_MAX) {
+      *os << "called any number of times";
+    } else {
+      *os << "called at most " << FormatTimes(max_);
+    }
+  } else if (min_ == max_) {
+    *os << "called " << FormatTimes(min_);
+  } else if (max_ == INT_MAX) {
+    *os << "called at least " << FormatTimes(min_);
+  } else {
+    // 0 < min_ < max_ < INT_MAX
+    *os << "called between " << min_ << " and " << max_ << " times";
+  }
+}
+
+}  // Unnamed namespace
+
+// Describes the given call count to an ostream.
+void Cardinality::DescribeActualCallCountTo(int actual_call_count,
+                                            ::std::ostream* os) {
+  if (actual_call_count > 0) {
+    *os << "called " << FormatTimes(actual_call_count);
+  } else {
+    *os << "never called";
+  }
+}
+
+// Creates a cardinality that allows at least n calls.
+GTEST_API_ Cardinality AtLeast(int n) { return Between(n, INT_MAX); }
+
+// Creates a cardinality that allows at most n calls.
+GTEST_API_ Cardinality AtMost(int n) { return Between(0, n); }
+
+// Creates a cardinality that allows any number of calls.
+GTEST_API_ Cardinality AnyNumber() { return AtLeast(0); }
+
+// Creates a cardinality that allows between min and max calls.
+GTEST_API_ Cardinality Between(int min, int max) {
+  return Cardinality(new BetweenCardinalityImpl(min, max));
+}
+
+// Creates a cardinality that allows exactly n calls.
+GTEST_API_ Cardinality Exactly(int n) { return Between(n, n); }
+
+}  // namespace testing
diff --git a/leveldb_base/third_party/googletest/googlemock/src/gmock-internal-utils.cc b/leveldb_base/third_party/googletest/googlemock/src/gmock-internal-utils.cc
new file mode 100644
index 0000000..e5b5479
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/src/gmock-internal-utils.cc
@@ -0,0 +1,200 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file defines some utilities useful for implementing Google
+// Mock.  They are subject to change without notice, so please DO NOT
+// USE THEM IN USER CODE.
+
+#include "gmock/internal/gmock-internal-utils.h"
+
+#include <ctype.h>
+#include <ostream>  // NOLINT
+#include <string>
+#include "gmock/gmock.h"
+#include "gmock/internal/gmock-port.h"
+#include "gtest/gtest.h"
+
+namespace testing {
+namespace internal {
+
+// Joins a vector of strings as if they are fields of a tuple; returns
+// the joined string.
+GTEST_API_ std::string JoinAsTuple(const Strings& fields) {
+  switch (fields.size()) {
+    case 0:
+      return "";
+    case 1:
+      return fields[0];
+    default:
+      std::string result = "(" + fields[0];
+      for (size_t i = 1; i < fields.size(); i++) {
+        result += ", ";
+        result += fields[i];
+      }
+      result += ")";
+      return result;
+  }
+}
+
+// Converts an identifier name to a space-separated list of lower-case
+// words.  Each maximum substring of the form [A-Za-z][a-z]*|\d+ is
+// treated as one word.  For example, both "FooBar123" and
+// "foo_bar_123" are converted to "foo bar 123".
+GTEST_API_ std::string ConvertIdentifierNameToWords(const char* id_name) {
+  std::string result;
+  char prev_char = '\0';
+  for (const char* p = id_name; *p != '\0'; prev_char = *(p++)) {
+    // We don't care about the current locale as the input is
+    // guaranteed to be a valid C++ identifier name.
+    const bool starts_new_word = IsUpper(*p) ||
+        (!IsAlpha(prev_char) && IsLower(*p)) ||
+        (!IsDigit(prev_char) && IsDigit(*p));
+
+    if (IsAlNum(*p)) {
+      if (starts_new_word && result != "")
+        result += ' ';
+      result += ToLower(*p);
+    }
+  }
+  return result;
+}
+
+// This class reports Google Mock failures as Google Test failures.  A
+// user can define another class in a similar fashion if they intend to
+// use Google Mock with a testing framework other than Google Test.
+class GoogleTestFailureReporter : public FailureReporterInterface {
+ public:
+  void ReportFailure(FailureType type, const char* file, int line,
+                     const std::string& message) override {
+    AssertHelper(type == kFatal ?
+                 TestPartResult::kFatalFailure :
+                 TestPartResult::kNonFatalFailure,
+                 file,
+                 line,
+                 message.c_str()) = Message();
+    if (type == kFatal) {
+      posix::Abort();
+    }
+  }
+};
+
+// Returns the global failure reporter.  Will create a
+// GoogleTestFailureReporter and return it the first time called.
+GTEST_API_ FailureReporterInterface* GetFailureReporter() {
+  // Points to the global failure reporter used by Google Mock.  gcc
+  // guarantees that the following use of failure_reporter is
+  // thread-safe.  We may need to add additional synchronization to
+  // protect failure_reporter if we port Google Mock to other
+  // compilers.
+  static FailureReporterInterface* const failure_reporter =
+      new GoogleTestFailureReporter();
+  return failure_reporter;
+}
+
+// Protects global resources (stdout in particular) used by Log().
+static GTEST_DEFINE_STATIC_MUTEX_(g_log_mutex);
+
+// Returns true if and only if a log with the given severity is visible
+// according to the --gmock_verbose flag.
+GTEST_API_ bool LogIsVisible(LogSeverity severity) {
+  if (GMOCK_FLAG(verbose) == kInfoVerbosity) {
+    // Always show the log if --gmock_verbose=info.
+    return true;
+  } else if (GMOCK_FLAG(verbose) == kErrorVerbosity) {
+    // Always hide it if --gmock_verbose=error.
+    return false;
+  } else {
+    // If --gmock_verbose is neither "info" nor "error", we treat it
+    // as "warning" (its default value).
+    return severity == kWarning;
+  }
+}
+
+// Prints the given message to stdout if and only if 'severity' >= the level
+// specified by the --gmock_verbose flag.  If stack_frames_to_skip >=
+// 0, also prints the stack trace excluding the top
+// stack_frames_to_skip frames.  In opt mode, any positive
+// stack_frames_to_skip is treated as 0, since we don't know which
+// function calls will be inlined by the compiler and need to be
+// conservative.
+GTEST_API_ void Log(LogSeverity severity, const std::string& message,
+                    int stack_frames_to_skip) {
+  if (!LogIsVisible(severity))
+    return;
+
+  // Ensures that logs from different threads don't interleave.
+  MutexLock l(&g_log_mutex);
+
+  if (severity == kWarning) {
+    // Prints a GMOCK WARNING marker to make the warnings easily searchable.
+    std::cout << "\nGMOCK WARNING:";
+  }
+  // Pre-pends a new-line to message if it doesn't start with one.
+  if (message.empty() || message[0] != '\n') {
+    std::cout << "\n";
+  }
+  std::cout << message;
+  if (stack_frames_to_skip >= 0) {
+#ifdef NDEBUG
+    // In opt mode, we have to be conservative and skip no stack frame.
+    const int actual_to_skip = 0;
+#else
+    // In dbg mode, we can do what the caller tell us to do (plus one
+    // for skipping this function's stack frame).
+    const int actual_to_skip = stack_frames_to_skip + 1;
+#endif  // NDEBUG
+
+    // Appends a new-line to message if it doesn't end with one.
+    if (!message.empty() && *message.rbegin() != '\n') {
+      std::cout << "\n";
+    }
+    std::cout << "Stack trace:\n"
+         << ::testing::internal::GetCurrentOsStackTraceExceptTop(
+             ::testing::UnitTest::GetInstance(), actual_to_skip);
+  }
+  std::cout << ::std::flush;
+}
+
+GTEST_API_ WithoutMatchers GetWithoutMatchers() { return WithoutMatchers(); }
+
+GTEST_API_ void IllegalDoDefault(const char* file, int line) {
+  internal::Assert(
+      false, file, line,
+      "You are using DoDefault() inside a composite action like "
+      "DoAll() or WithArgs().  This is not supported for technical "
+      "reasons.  Please instead spell out the default action, or "
+      "assign the default action to an Action variable and use "
+      "the variable in various places.");
+}
+
+}  // namespace internal
+}  // namespace testing
diff --git a/leveldb_base/third_party/googletest/googlemock/src/gmock-matchers.cc b/leveldb_base/third_party/googletest/googlemock/src/gmock-matchers.cc
new file mode 100644
index 0000000..dded437
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/src/gmock-matchers.cc
@@ -0,0 +1,459 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file implements Matcher<const string&>, Matcher<string>, and
+// utilities for defining matchers.
+
+#include "gmock/gmock-matchers.h"
+
+#include <string.h>
+#include <iostream>
+#include <sstream>
+#include <string>
+
+namespace testing {
+namespace internal {
+
+// Returns the description for a matcher defined using the MATCHER*()
+// macro where the user-supplied description string is "", if
+// 'negation' is false; otherwise returns the description of the
+// negation of the matcher.  'param_values' contains a list of strings
+// that are the print-out of the matcher's parameters.
+GTEST_API_ std::string FormatMatcherDescription(bool negation,
+                                                const char* matcher_name,
+                                                const Strings& param_values) {
+  std::string result = ConvertIdentifierNameToWords(matcher_name);
+  if (param_values.size() >= 1) result += " " + JoinAsTuple(param_values);
+  return negation ? "not (" + result + ")" : result;
+}
+
+// FindMaxBipartiteMatching and its helper class.
+//
+// Uses the well-known Ford-Fulkerson max flow method to find a maximum
+// bipartite matching. Flow is considered to be from left to right.
+// There is an implicit source node that is connected to all of the left
+// nodes, and an implicit sink node that is connected to all of the
+// right nodes. All edges have unit capacity.
+//
+// Neither the flow graph nor the residual flow graph are represented
+// explicitly. Instead, they are implied by the information in 'graph' and
+// a vector<int> called 'left_' whose elements are initialized to the
+// value kUnused. This represents the initial state of the algorithm,
+// where the flow graph is empty, and the residual flow graph has the
+// following edges:
+//   - An edge from source to each left_ node
+//   - An edge from each right_ node to sink
+//   - An edge from each left_ node to each right_ node, if the
+//     corresponding edge exists in 'graph'.
+//
+// When the TryAugment() method adds a flow, it sets left_[l] = r for some
+// nodes l and r. This induces the following changes:
+//   - The edges (source, l), (l, r), and (r, sink) are added to the
+//     flow graph.
+//   - The same three edges are removed from the residual flow graph.
+//   - The reverse edges (l, source), (r, l), and (sink, r) are added
+//     to the residual flow graph, which is a directional graph
+//     representing unused flow capacity.
+//
+// When the method augments a flow (moving left_[l] from some r1 to some
+// other r2), this can be thought of as "undoing" the above steps with
+// respect to r1 and "redoing" them with respect to r2.
+//
+// It bears repeating that the flow graph and residual flow graph are
+// never represented explicitly, but can be derived by looking at the
+// information in 'graph' and in left_.
+//
+// As an optimization, there is a second vector<int> called right_ which
+// does not provide any new information. Instead, it enables more
+// efficient queries about edges entering or leaving the right-side nodes
+// of the flow or residual flow graphs. The following invariants are
+// maintained:
+//
+// left[l] == kUnused or right[left[l]] == l
+// right[r] == kUnused or left[right[r]] == r
+//
+// . [ source ]                                        .
+// .   |||                                             .
+// .   |||                                             .
+// .   ||\--> left[0]=1  ---\    right[0]=-1 ----\     .
+// .   ||                   |                    |     .
+// .   |\---> left[1]=-1    \--> right[1]=0  ---\|     .
+// .   |                                        ||     .
+// .   \----> left[2]=2  ------> right[2]=2  --\||     .
+// .                                           |||     .
+// .         elements           matchers       vvv     .
+// .                                         [ sink ]  .
+//
+// See Also:
+//   [1] Cormen, et al (2001). "Section 26.2: The Ford-Fulkerson method".
+//       "Introduction to Algorithms (Second ed.)", pp. 651-664.
+//   [2] "Ford-Fulkerson algorithm", Wikipedia,
+//       'http://en.wikipedia.org/wiki/Ford%E2%80%93Fulkerson_algorithm'
+class MaxBipartiteMatchState {
+ public:
+  explicit MaxBipartiteMatchState(const MatchMatrix& graph)
+      : graph_(&graph),
+        left_(graph_->LhsSize(), kUnused),
+        right_(graph_->RhsSize(), kUnused) {}
+
+  // Returns the edges of a maximal match, each in the form {left, right}.
+  ElementMatcherPairs Compute() {
+    // 'seen' is used for path finding { 0: unseen, 1: seen }.
+    ::std::vector<char> seen;
+    // Searches the residual flow graph for a path from each left node to
+    // the sink in the residual flow graph, and if one is found, add flow
+    // to the graph. It's okay to search through the left nodes once. The
+    // edge from the implicit source node to each previously-visited left
+    // node will have flow if that left node has any path to the sink
+    // whatsoever. Subsequent augmentations can only add flow to the
+    // network, and cannot take away that previous flow unit from the source.
+    // Since the source-to-left edge can only carry one flow unit (or,
+    // each element can be matched to only one matcher), there is no need
+    // to visit the left nodes more than once looking for augmented paths.
+    // The flow is known to be possible or impossible by looking at the
+    // node once.
+    for (size_t ilhs = 0; ilhs < graph_->LhsSize(); ++ilhs) {
+      // Reset the path-marking vector and try to find a path from
+      // source to sink starting at the left_[ilhs] node.
+      GTEST_CHECK_(left_[ilhs] == kUnused)
+          << "ilhs: " << ilhs << ", left_[ilhs]: " << left_[ilhs];
+      // 'seen' initialized to 'graph_->RhsSize()' copies of 0.
+      seen.assign(graph_->RhsSize(), 0);
+      TryAugment(ilhs, &seen);
+    }
+    ElementMatcherPairs result;
+    for (size_t ilhs = 0; ilhs < left_.size(); ++ilhs) {
+      size_t irhs = left_[ilhs];
+      if (irhs == kUnused) continue;
+      result.push_back(ElementMatcherPair(ilhs, irhs));
+    }
+    return result;
+  }
+
+ private:
+  static const size_t kUnused = static_cast<size_t>(-1);
+
+  // Perform a depth-first search from left node ilhs to the sink.  If a
+  // path is found, flow is added to the network by linking the left and
+  // right vector elements corresponding each segment of the path.
+  // Returns true if a path to sink was found, which means that a unit of
+  // flow was added to the network. The 'seen' vector elements correspond
+  // to right nodes and are marked to eliminate cycles from the search.
+  //
+  // Left nodes will only be explored at most once because they
+  // are accessible from at most one right node in the residual flow
+  // graph.
+  //
+  // Note that left_[ilhs] is the only element of left_ that TryAugment will
+  // potentially transition from kUnused to another value. Any other
+  // left_ element holding kUnused before TryAugment will be holding it
+  // when TryAugment returns.
+  //
+  bool TryAugment(size_t ilhs, ::std::vector<char>* seen) {
+    for (size_t irhs = 0; irhs < graph_->RhsSize(); ++irhs) {
+      if ((*seen)[irhs]) continue;
+      if (!graph_->HasEdge(ilhs, irhs)) continue;
+      // There's an available edge from ilhs to irhs.
+      (*seen)[irhs] = 1;
+      // Next a search is performed to determine whether
+      // this edge is a dead end or leads to the sink.
+      //
+      // right_[irhs] == kUnused means that there is residual flow from
+      // right node irhs to the sink, so we can use that to finish this
+      // flow path and return success.
+      //
+      // Otherwise there is residual flow to some ilhs. We push flow
+      // along that path and call ourselves recursively to see if this
+      // ultimately leads to sink.
+      if (right_[irhs] == kUnused || TryAugment(right_[irhs], seen)) {
+        // Add flow from left_[ilhs] to right_[irhs].
+        left_[ilhs] = irhs;
+        right_[irhs] = ilhs;
+        return true;
+      }
+    }
+    return false;
+  }
+
+  const MatchMatrix* graph_;  // not owned
+  // Each element of the left_ vector represents a left hand side node
+  // (i.e. an element) and each element of right_ is a right hand side
+  // node (i.e. a matcher). The values in the left_ vector indicate
+  // outflow from that node to a node on the right_ side. The values
+  // in the right_ indicate inflow, and specify which left_ node is
+  // feeding that right_ node, if any. For example, left_[3] == 1 means
+  // there's a flow from element #3 to matcher #1. Such a flow would also
+  // be redundantly represented in the right_ vector as right_[1] == 3.
+  // Elements of left_ and right_ are either kUnused or mutually
+  // referent. Mutually referent means that left_[right_[i]] = i and
+  // right_[left_[i]] = i.
+  ::std::vector<size_t> left_;
+  ::std::vector<size_t> right_;
+};
+
+const size_t MaxBipartiteMatchState::kUnused;
+
+GTEST_API_ ElementMatcherPairs FindMaxBipartiteMatching(const MatchMatrix& g) {
+  return MaxBipartiteMatchState(g).Compute();
+}
+
+static void LogElementMatcherPairVec(const ElementMatcherPairs& pairs,
+                                     ::std::ostream* stream) {
+  typedef ElementMatcherPairs::const_iterator Iter;
+  ::std::ostream& os = *stream;
+  os << "{";
+  const char* sep = "";
+  for (Iter it = pairs.begin(); it != pairs.end(); ++it) {
+    os << sep << "\n  ("
+       << "element #" << it->first << ", "
+       << "matcher #" << it->second << ")";
+    sep = ",";
+  }
+  os << "\n}";
+}
+
+bool MatchMatrix::NextGraph() {
+  for (size_t ilhs = 0; ilhs < LhsSize(); ++ilhs) {
+    for (size_t irhs = 0; irhs < RhsSize(); ++irhs) {
+      char& b = matched_[SpaceIndex(ilhs, irhs)];
+      if (!b) {
+        b = 1;
+        return true;
+      }
+      b = 0;
+    }
+  }
+  return false;
+}
+
+void MatchMatrix::Randomize() {
+  for (size_t ilhs = 0; ilhs < LhsSize(); ++ilhs) {
+    for (size_t irhs = 0; irhs < RhsSize(); ++irhs) {
+      char& b = matched_[SpaceIndex(ilhs, irhs)];
+      b = static_cast<char>(rand() & 1);  // NOLINT
+    }
+  }
+}
+
+std::string MatchMatrix::DebugString() const {
+  ::std::stringstream ss;
+  const char* sep = "";
+  for (size_t i = 0; i < LhsSize(); ++i) {
+    ss << sep;
+    for (size_t j = 0; j < RhsSize(); ++j) {
+      ss << HasEdge(i, j);
+    }
+    sep = ";";
+  }
+  return ss.str();
+}
+
+void UnorderedElementsAreMatcherImplBase::DescribeToImpl(
+    ::std::ostream* os) const {
+  switch (match_flags()) {
+    case UnorderedMatcherRequire::ExactMatch:
+      if (matcher_describers_.empty()) {
+        *os << "is empty";
+        return;
+      }
+      if (matcher_describers_.size() == 1) {
+        *os << "has " << Elements(1) << " and that element ";
+        matcher_describers_[0]->DescribeTo(os);
+        return;
+      }
+      *os << "has " << Elements(matcher_describers_.size())
+          << " and there exists some permutation of elements such that:\n";
+      break;
+    case UnorderedMatcherRequire::Superset:
+      *os << "a surjection from elements to requirements exists such that:\n";
+      break;
+    case UnorderedMatcherRequire::Subset:
+      *os << "an injection from elements to requirements exists such that:\n";
+      break;
+  }
+
+  const char* sep = "";
+  for (size_t i = 0; i != matcher_describers_.size(); ++i) {
+    *os << sep;
+    if (match_flags() == UnorderedMatcherRequire::ExactMatch) {
+      *os << " - element #" << i << " ";
+    } else {
+      *os << " - an element ";
+    }
+    matcher_describers_[i]->DescribeTo(os);
+    if (match_flags() == UnorderedMatcherRequire::ExactMatch) {
+      sep = ", and\n";
+    } else {
+      sep = "\n";
+    }
+  }
+}
+
+void UnorderedElementsAreMatcherImplBase::DescribeNegationToImpl(
+    ::std::ostream* os) const {
+  switch (match_flags()) {
+    case UnorderedMatcherRequire::ExactMatch:
+      if (matcher_describers_.empty()) {
+        *os << "isn't empty";
+        return;
+      }
+      if (matcher_describers_.size() == 1) {
+        *os << "doesn't have " << Elements(1) << ", or has " << Elements(1)
+            << " that ";
+        matcher_describers_[0]->DescribeNegationTo(os);
+        return;
+      }
+      *os << "doesn't have " << Elements(matcher_describers_.size())
+          << ", or there exists no permutation of elements such that:\n";
+      break;
+    case UnorderedMatcherRequire::Superset:
+      *os << "no surjection from elements to requirements exists such that:\n";
+      break;
+    case UnorderedMatcherRequire::Subset:
+      *os << "no injection from elements to requirements exists such that:\n";
+      break;
+  }
+  const char* sep = "";
+  for (size_t i = 0; i != matcher_describers_.size(); ++i) {
+    *os << sep;
+    if (match_flags() == UnorderedMatcherRequire::ExactMatch) {
+      *os << " - element #" << i << " ";
+    } else {
+      *os << " - an element ";
+    }
+    matcher_describers_[i]->DescribeTo(os);
+    if (match_flags() == UnorderedMatcherRequire::ExactMatch) {
+      sep = ", and\n";
+    } else {
+      sep = "\n";
+    }
+  }
+}
+
+// Checks that all matchers match at least one element, and that all
+// elements match at least one matcher. This enables faster matching
+// and better error reporting.
+// Returns false, writing an explanation to 'listener', if and only
+// if the success criteria are not met.
+bool UnorderedElementsAreMatcherImplBase::VerifyMatchMatrix(
+    const ::std::vector<std::string>& element_printouts,
+    const MatchMatrix& matrix, MatchResultListener* listener) const {
+  bool result = true;
+  ::std::vector<char> element_matched(matrix.LhsSize(), 0);
+  ::std::vector<char> matcher_matched(matrix.RhsSize(), 0);
+
+  for (size_t ilhs = 0; ilhs < matrix.LhsSize(); ilhs++) {
+    for (size_t irhs = 0; irhs < matrix.RhsSize(); irhs++) {
+      char matched = matrix.HasEdge(ilhs, irhs);
+      element_matched[ilhs] |= matched;
+      matcher_matched[irhs] |= matched;
+    }
+  }
+
+  if (match_flags() & UnorderedMatcherRequire::Superset) {
+    const char* sep =
+        "where the following matchers don't match any elements:\n";
+    for (size_t mi = 0; mi < matcher_matched.size(); ++mi) {
+      if (matcher_matched[mi]) continue;
+      result = false;
+      if (listener->IsInterested()) {
+        *listener << sep << "matcher #" << mi << ": ";
+        matcher_describers_[mi]->DescribeTo(listener->stream());
+        sep = ",\n";
+      }
+    }
+  }
+
+  if (match_flags() & UnorderedMatcherRequire::Subset) {
+    const char* sep =
+        "where the following elements don't match any matchers:\n";
+    const char* outer_sep = "";
+    if (!result) {
+      outer_sep = "\nand ";
+    }
+    for (size_t ei = 0; ei < element_matched.size(); ++ei) {
+      if (element_matched[ei]) continue;
+      result = false;
+      if (listener->IsInterested()) {
+        *listener << outer_sep << sep << "element #" << ei << ": "
+                  << element_printouts[ei];
+        sep = ",\n";
+        outer_sep = "";
+      }
+    }
+  }
+  return result;
+}
+
+bool UnorderedElementsAreMatcherImplBase::FindPairing(
+    const MatchMatrix& matrix, MatchResultListener* listener) const {
+  ElementMatcherPairs matches = FindMaxBipartiteMatching(matrix);
+
+  size_t max_flow = matches.size();
+  if ((match_flags() & UnorderedMatcherRequire::Superset) &&
+      max_flow < matrix.RhsSize()) {
+    if (listener->IsInterested()) {
+      *listener << "where no permutation of the elements can satisfy all "
+                   "matchers, and the closest match is "
+                << max_flow << " of " << matrix.RhsSize()
+                << " matchers with the pairings:\n";
+      LogElementMatcherPairVec(matches, listener->stream());
+    }
+    return false;
+  }
+  if ((match_flags() & UnorderedMatcherRequire::Subset) &&
+      max_flow < matrix.LhsSize()) {
+    if (listener->IsInterested()) {
+      *listener
+          << "where not all elements can be matched, and the closest match is "
+          << max_flow << " of " << matrix.RhsSize()
+          << " matchers with the pairings:\n";
+      LogElementMatcherPairVec(matches, listener->stream());
+    }
+    return false;
+  }
+
+  if (matches.size() > 1) {
+    if (listener->IsInterested()) {
+      const char* sep = "where:\n";
+      for (size_t mi = 0; mi < matches.size(); ++mi) {
+        *listener << sep << " - element #" << matches[mi].first
+                  << " is matched by matcher #" << matches[mi].second;
+        sep = ",\n";
+      }
+    }
+  }
+  return true;
+}
+
+}  // namespace internal
+}  // namespace testing
diff --git a/leveldb_base/third_party/googletest/googlemock/src/gmock-spec-builders.cc b/leveldb_base/third_party/googletest/googlemock/src/gmock-spec-builders.cc
new file mode 100644
index 0000000..c7266a3
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/src/gmock-spec-builders.cc
@@ -0,0 +1,908 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file implements the spec builder syntax (ON_CALL and
+// EXPECT_CALL).
+
+#include "gmock/gmock-spec-builders.h"
+
+#include <stdlib.h>
+
+#include <iostream>  // NOLINT
+#include <map>
+#include <memory>
+#include <set>
+#include <string>
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "gtest/internal/gtest-port.h"
+
+#if GTEST_OS_CYGWIN || GTEST_OS_LINUX || GTEST_OS_MAC
+# include <unistd.h>  // NOLINT
+#endif
+
+// Silence C4800 (C4800: 'int *const ': forcing value
+// to bool 'true' or 'false') for MSVC 15
+#ifdef _MSC_VER
+#if _MSC_VER == 1900
+#  pragma warning(push)
+#  pragma warning(disable:4800)
+#endif
+#endif
+
+namespace testing {
+namespace internal {
+
+// Protects the mock object registry (in class Mock), all function
+// mockers, and all expectations.
+GTEST_API_ GTEST_DEFINE_STATIC_MUTEX_(g_gmock_mutex);
+
+// Logs a message including file and line number information.
+GTEST_API_ void LogWithLocation(testing::internal::LogSeverity severity,
+                                const char* file, int line,
+                                const std::string& message) {
+  ::std::ostringstream s;
+  s << internal::FormatFileLocation(file, line) << " " << message
+    << ::std::endl;
+  Log(severity, s.str(), 0);
+}
+
+// Constructs an ExpectationBase object.
+ExpectationBase::ExpectationBase(const char* a_file, int a_line,
+                                 const std::string& a_source_text)
+    : file_(a_file),
+      line_(a_line),
+      source_text_(a_source_text),
+      cardinality_specified_(false),
+      cardinality_(Exactly(1)),
+      call_count_(0),
+      retired_(false),
+      extra_matcher_specified_(false),
+      repeated_action_specified_(false),
+      retires_on_saturation_(false),
+      last_clause_(kNone),
+      action_count_checked_(false) {}
+
+// Destructs an ExpectationBase object.
+ExpectationBase::~ExpectationBase() {}
+
+// Explicitly specifies the cardinality of this expectation.  Used by
+// the subclasses to implement the .Times() clause.
+void ExpectationBase::SpecifyCardinality(const Cardinality& a_cardinality) {
+  cardinality_specified_ = true;
+  cardinality_ = a_cardinality;
+}
+
+// Retires all pre-requisites of this expectation.
+void ExpectationBase::RetireAllPreRequisites()
+    GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+  if (is_retired()) {
+    // We can take this short-cut as we never retire an expectation
+    // until we have retired all its pre-requisites.
+    return;
+  }
+
+  ::std::vector<ExpectationBase*> expectations(1, this);
+  while (!expectations.empty()) {
+    ExpectationBase* exp = expectations.back();
+    expectations.pop_back();
+
+    for (ExpectationSet::const_iterator it =
+             exp->immediate_prerequisites_.begin();
+         it != exp->immediate_prerequisites_.end(); ++it) {
+      ExpectationBase* next = it->expectation_base().get();
+      if (!next->is_retired()) {
+        next->Retire();
+        expectations.push_back(next);
+      }
+    }
+  }
+}
+
+// Returns true if and only if all pre-requisites of this expectation
+// have been satisfied.
+bool ExpectationBase::AllPrerequisitesAreSatisfied() const
+    GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+  g_gmock_mutex.AssertHeld();
+  ::std::vector<const ExpectationBase*> expectations(1, this);
+  while (!expectations.empty()) {
+    const ExpectationBase* exp = expectations.back();
+    expectations.pop_back();
+
+    for (ExpectationSet::const_iterator it =
+             exp->immediate_prerequisites_.begin();
+         it != exp->immediate_prerequisites_.end(); ++it) {
+      const ExpectationBase* next = it->expectation_base().get();
+      if (!next->IsSatisfied()) return false;
+      expectations.push_back(next);
+    }
+  }
+  return true;
+}
+
+// Adds unsatisfied pre-requisites of this expectation to 'result'.
+void ExpectationBase::FindUnsatisfiedPrerequisites(ExpectationSet* result) const
+    GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+  g_gmock_mutex.AssertHeld();
+  ::std::vector<const ExpectationBase*> expectations(1, this);
+  while (!expectations.empty()) {
+    const ExpectationBase* exp = expectations.back();
+    expectations.pop_back();
+
+    for (ExpectationSet::const_iterator it =
+             exp->immediate_prerequisites_.begin();
+         it != exp->immediate_prerequisites_.end(); ++it) {
+      const ExpectationBase* next = it->expectation_base().get();
+
+      if (next->IsSatisfied()) {
+        // If *it is satisfied and has a call count of 0, some of its
+        // pre-requisites may not be satisfied yet.
+        if (next->call_count_ == 0) {
+          expectations.push_back(next);
+        }
+      } else {
+        // Now that we know next is unsatisfied, we are not so interested
+        // in whether its pre-requisites are satisfied.  Therefore we
+        // don't iterate into it here.
+        *result += *it;
+      }
+    }
+  }
+}
+
+// Describes how many times a function call matching this
+// expectation has occurred.
+void ExpectationBase::DescribeCallCountTo(::std::ostream* os) const
+    GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+  g_gmock_mutex.AssertHeld();
+
+  // Describes how many times the function is expected to be called.
+  *os << "         Expected: to be ";
+  cardinality().DescribeTo(os);
+  *os << "\n           Actual: ";
+  Cardinality::DescribeActualCallCountTo(call_count(), os);
+
+  // Describes the state of the expectation (e.g. is it satisfied?
+  // is it active?).
+  *os << " - " << (IsOverSaturated() ? "over-saturated" :
+                   IsSaturated() ? "saturated" :
+                   IsSatisfied() ? "satisfied" : "unsatisfied")
+      << " and "
+      << (is_retired() ? "retired" : "active");
+}
+
+// Checks the action count (i.e. the number of WillOnce() and
+// WillRepeatedly() clauses) against the cardinality if this hasn't
+// been done before.  Prints a warning if there are too many or too
+// few actions.
+void ExpectationBase::CheckActionCountIfNotDone() const
+    GTEST_LOCK_EXCLUDED_(mutex_) {
+  bool should_check = false;
+  {
+    MutexLock l(&mutex_);
+    if (!action_count_checked_) {
+      action_count_checked_ = true;
+      should_check = true;
+    }
+  }
+
+  if (should_check) {
+    if (!cardinality_specified_) {
+      // The cardinality was inferred - no need to check the action
+      // count against it.
+      return;
+    }
+
+    // The cardinality was explicitly specified.
+    const int action_count = static_cast<int>(untyped_actions_.size());
+    const int upper_bound = cardinality().ConservativeUpperBound();
+    const int lower_bound = cardinality().ConservativeLowerBound();
+    bool too_many;  // True if there are too many actions, or false
+    // if there are too few.
+    if (action_count > upper_bound ||
+        (action_count == upper_bound && repeated_action_specified_)) {
+      too_many = true;
+    } else if (0 < action_count && action_count < lower_bound &&
+               !repeated_action_specified_) {
+      too_many = false;
+    } else {
+      return;
+    }
+
+    ::std::stringstream ss;
+    DescribeLocationTo(&ss);
+    ss << "Too " << (too_many ? "many" : "few")
+       << " actions specified in " << source_text() << "...\n"
+       << "Expected to be ";
+    cardinality().DescribeTo(&ss);
+    ss << ", but has " << (too_many ? "" : "only ")
+       << action_count << " WillOnce()"
+       << (action_count == 1 ? "" : "s");
+    if (repeated_action_specified_) {
+      ss << " and a WillRepeatedly()";
+    }
+    ss << ".";
+    Log(kWarning, ss.str(), -1);  // -1 means "don't print stack trace".
+  }
+}
+
+// Implements the .Times() clause.
+void ExpectationBase::UntypedTimes(const Cardinality& a_cardinality) {
+  if (last_clause_ == kTimes) {
+    ExpectSpecProperty(false,
+                       ".Times() cannot appear "
+                       "more than once in an EXPECT_CALL().");
+  } else {
+    ExpectSpecProperty(last_clause_ < kTimes,
+                       ".Times() cannot appear after "
+                       ".InSequence(), .WillOnce(), .WillRepeatedly(), "
+                       "or .RetiresOnSaturation().");
+  }
+  last_clause_ = kTimes;
+
+  SpecifyCardinality(a_cardinality);
+}
+
+// Points to the implicit sequence introduced by a living InSequence
+// object (if any) in the current thread or NULL.
+GTEST_API_ ThreadLocal<Sequence*> g_gmock_implicit_sequence;
+
+// Reports an uninteresting call (whose description is in msg) in the
+// manner specified by 'reaction'.
+void ReportUninterestingCall(CallReaction reaction, const std::string& msg) {
+  // Include a stack trace only if --gmock_verbose=info is specified.
+  const int stack_frames_to_skip =
+      GMOCK_FLAG(verbose) == kInfoVerbosity ? 3 : -1;
+  switch (reaction) {
+    case kAllow:
+      Log(kInfo, msg, stack_frames_to_skip);
+      break;
+    case kWarn:
+      Log(kWarning,
+          msg +
+              "\nNOTE: You can safely ignore the above warning unless this "
+              "call should not happen.  Do not suppress it by blindly adding "
+              "an EXPECT_CALL() if you don't mean to enforce the call.  "
+              "See "
+              "https://github.com/google/googletest/blob/master/docs/"
+              "gmock_cook_book.md#"
+              "knowing-when-to-expect for details.\n",
+          stack_frames_to_skip);
+      break;
+    default:  // FAIL
+      Expect(false, nullptr, -1, msg);
+  }
+}
+
+UntypedFunctionMockerBase::UntypedFunctionMockerBase()
+    : mock_obj_(nullptr), name_("") {}
+
+UntypedFunctionMockerBase::~UntypedFunctionMockerBase() {}
+
+// Sets the mock object this mock method belongs to, and registers
+// this information in the global mock registry.  Will be called
+// whenever an EXPECT_CALL() or ON_CALL() is executed on this mock
+// method.
+void UntypedFunctionMockerBase::RegisterOwner(const void* mock_obj)
+    GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
+  {
+    MutexLock l(&g_gmock_mutex);
+    mock_obj_ = mock_obj;
+  }
+  Mock::Register(mock_obj, this);
+}
+
+// Sets the mock object this mock method belongs to, and sets the name
+// of the mock function.  Will be called upon each invocation of this
+// mock function.
+void UntypedFunctionMockerBase::SetOwnerAndName(const void* mock_obj,
+                                                const char* name)
+    GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
+  // We protect name_ under g_gmock_mutex in case this mock function
+  // is called from two threads concurrently.
+  MutexLock l(&g_gmock_mutex);
+  mock_obj_ = mock_obj;
+  name_ = name;
+}
+
+// Returns the name of the function being mocked.  Must be called
+// after RegisterOwner() or SetOwnerAndName() has been called.
+const void* UntypedFunctionMockerBase::MockObject() const
+    GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
+  const void* mock_obj;
+  {
+    // We protect mock_obj_ under g_gmock_mutex in case this mock
+    // function is called from two threads concurrently.
+    MutexLock l(&g_gmock_mutex);
+    Assert(mock_obj_ != nullptr, __FILE__, __LINE__,
+           "MockObject() must not be called before RegisterOwner() or "
+           "SetOwnerAndName() has been called.");
+    mock_obj = mock_obj_;
+  }
+  return mock_obj;
+}
+
+// Returns the name of this mock method.  Must be called after
+// SetOwnerAndName() has been called.
+const char* UntypedFunctionMockerBase::Name() const
+    GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
+  const char* name;
+  {
+    // We protect name_ under g_gmock_mutex in case this mock
+    // function is called from two threads concurrently.
+    MutexLock l(&g_gmock_mutex);
+    Assert(name_ != nullptr, __FILE__, __LINE__,
+           "Name() must not be called before SetOwnerAndName() has "
+           "been called.");
+    name = name_;
+  }
+  return name;
+}
+
+// Calculates the result of invoking this mock function with the given
+// arguments, prints it, and returns it.  The caller is responsible
+// for deleting the result.
+UntypedActionResultHolderBase* UntypedFunctionMockerBase::UntypedInvokeWith(
+    void* const untyped_args) GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
+  // See the definition of untyped_expectations_ for why access to it
+  // is unprotected here.
+  if (untyped_expectations_.size() == 0) {
+    // No expectation is set on this mock method - we have an
+    // uninteresting call.
+
+    // We must get Google Mock's reaction on uninteresting calls
+    // made on this mock object BEFORE performing the action,
+    // because the action may DELETE the mock object and make the
+    // following expression meaningless.
+    const CallReaction reaction =
+        Mock::GetReactionOnUninterestingCalls(MockObject());
+
+    // True if and only if we need to print this call's arguments and return
+    // value.  This definition must be kept in sync with
+    // the behavior of ReportUninterestingCall().
+    const bool need_to_report_uninteresting_call =
+        // If the user allows this uninteresting call, we print it
+        // only when they want informational messages.
+        reaction == kAllow ? LogIsVisible(kInfo) :
+                           // If the user wants this to be a warning, we print
+                           // it only when they want to see warnings.
+            reaction == kWarn
+                ? LogIsVisible(kWarning)
+                :
+                // Otherwise, the user wants this to be an error, and we
+                // should always print detailed information in the error.
+                true;
+
+    if (!need_to_report_uninteresting_call) {
+      // Perform the action without printing the call information.
+      return this->UntypedPerformDefaultAction(
+          untyped_args, "Function call: " + std::string(Name()));
+    }
+
+    // Warns about the uninteresting call.
+    ::std::stringstream ss;
+    this->UntypedDescribeUninterestingCall(untyped_args, &ss);
+
+    // Calculates the function result.
+    UntypedActionResultHolderBase* const result =
+        this->UntypedPerformDefaultAction(untyped_args, ss.str());
+
+    // Prints the function result.
+    if (result != nullptr) result->PrintAsActionResult(&ss);
+
+    ReportUninterestingCall(reaction, ss.str());
+    return result;
+  }
+
+  bool is_excessive = false;
+  ::std::stringstream ss;
+  ::std::stringstream why;
+  ::std::stringstream loc;
+  const void* untyped_action = nullptr;
+
+  // The UntypedFindMatchingExpectation() function acquires and
+  // releases g_gmock_mutex.
+
+  const ExpectationBase* const untyped_expectation =
+      this->UntypedFindMatchingExpectation(untyped_args, &untyped_action,
+                                           &is_excessive, &ss, &why);
+  const bool found = untyped_expectation != nullptr;
+
+  // True if and only if we need to print the call's arguments
+  // and return value.
+  // This definition must be kept in sync with the uses of Expect()
+  // and Log() in this function.
+  const bool need_to_report_call =
+      !found || is_excessive || LogIsVisible(kInfo);
+  if (!need_to_report_call) {
+    // Perform the action without printing the call information.
+    return untyped_action == nullptr
+               ? this->UntypedPerformDefaultAction(untyped_args, "")
+               : this->UntypedPerformAction(untyped_action, untyped_args);
+  }
+
+  ss << "    Function call: " << Name();
+  this->UntypedPrintArgs(untyped_args, &ss);
+
+  // In case the action deletes a piece of the expectation, we
+  // generate the message beforehand.
+  if (found && !is_excessive) {
+    untyped_expectation->DescribeLocationTo(&loc);
+  }
+
+  UntypedActionResultHolderBase* result = nullptr;
+
+  auto perform_action = [&] {
+    return untyped_action == nullptr
+               ? this->UntypedPerformDefaultAction(untyped_args, ss.str())
+               : this->UntypedPerformAction(untyped_action, untyped_args);
+  };
+  auto handle_failures = [&] {
+    ss << "\n" << why.str();
+
+    if (!found) {
+      // No expectation matches this call - reports a failure.
+      Expect(false, nullptr, -1, ss.str());
+    } else if (is_excessive) {
+      // We had an upper-bound violation and the failure message is in ss.
+      Expect(false, untyped_expectation->file(), untyped_expectation->line(),
+             ss.str());
+    } else {
+      // We had an expected call and the matching expectation is
+      // described in ss.
+      Log(kInfo, loc.str() + ss.str(), 2);
+    }
+  };
+#if GTEST_HAS_EXCEPTIONS
+  try {
+    result = perform_action();
+  } catch (...) {
+    handle_failures();
+    throw;
+  }
+#else
+  result = perform_action();
+#endif
+
+  if (result != nullptr) result->PrintAsActionResult(&ss);
+  handle_failures();
+  return result;
+}
+
+// Returns an Expectation object that references and co-owns exp,
+// which must be an expectation on this mock function.
+Expectation UntypedFunctionMockerBase::GetHandleOf(ExpectationBase* exp) {
+  // See the definition of untyped_expectations_ for why access to it
+  // is unprotected here.
+  for (UntypedExpectations::const_iterator it =
+           untyped_expectations_.begin();
+       it != untyped_expectations_.end(); ++it) {
+    if (it->get() == exp) {
+      return Expectation(*it);
+    }
+  }
+
+  Assert(false, __FILE__, __LINE__, "Cannot find expectation.");
+  return Expectation();
+  // The above statement is just to make the code compile, and will
+  // never be executed.
+}
+
+// Verifies that all expectations on this mock function have been
+// satisfied.  Reports one or more Google Test non-fatal failures
+// and returns false if not.
+bool UntypedFunctionMockerBase::VerifyAndClearExpectationsLocked()
+    GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+  g_gmock_mutex.AssertHeld();
+  bool expectations_met = true;
+  for (UntypedExpectations::const_iterator it =
+           untyped_expectations_.begin();
+       it != untyped_expectations_.end(); ++it) {
+    ExpectationBase* const untyped_expectation = it->get();
+    if (untyped_expectation->IsOverSaturated()) {
+      // There was an upper-bound violation.  Since the error was
+      // already reported when it occurred, there is no need to do
+      // anything here.
+      expectations_met = false;
+    } else if (!untyped_expectation->IsSatisfied()) {
+      expectations_met = false;
+      ::std::stringstream ss;
+      ss  << "Actual function call count doesn't match "
+          << untyped_expectation->source_text() << "...\n";
+      // No need to show the source file location of the expectation
+      // in the description, as the Expect() call that follows already
+      // takes care of it.
+      untyped_expectation->MaybeDescribeExtraMatcherTo(&ss);
+      untyped_expectation->DescribeCallCountTo(&ss);
+      Expect(false, untyped_expectation->file(),
+             untyped_expectation->line(), ss.str());
+    }
+  }
+
+  // Deleting our expectations may trigger other mock objects to be deleted, for
+  // example if an action contains a reference counted smart pointer to that
+  // mock object, and that is the last reference. So if we delete our
+  // expectations within the context of the global mutex we may deadlock when
+  // this method is called again. Instead, make a copy of the set of
+  // expectations to delete, clear our set within the mutex, and then clear the
+  // copied set outside of it.
+  UntypedExpectations expectations_to_delete;
+  untyped_expectations_.swap(expectations_to_delete);
+
+  g_gmock_mutex.Unlock();
+  expectations_to_delete.clear();
+  g_gmock_mutex.Lock();
+
+  return expectations_met;
+}
+
+CallReaction intToCallReaction(int mock_behavior) {
+  if (mock_behavior >= kAllow && mock_behavior <= kFail) {
+    return static_cast<internal::CallReaction>(mock_behavior);
+  }
+  return kWarn;
+}
+
+}  // namespace internal
+
+// Class Mock.
+
+namespace {
+
+typedef std::set<internal::UntypedFunctionMockerBase*> FunctionMockers;
+
+// The current state of a mock object.  Such information is needed for
+// detecting leaked mock objects and explicitly verifying a mock's
+// expectations.
+struct MockObjectState {
+  MockObjectState()
+      : first_used_file(nullptr), first_used_line(-1), leakable(false) {}
+
+  // Where in the source file an ON_CALL or EXPECT_CALL is first
+  // invoked on this mock object.
+  const char* first_used_file;
+  int first_used_line;
+  ::std::string first_used_test_suite;
+  ::std::string first_used_test;
+  bool leakable;  // true if and only if it's OK to leak the object.
+  FunctionMockers function_mockers;  // All registered methods of the object.
+};
+
+// A global registry holding the state of all mock objects that are
+// alive.  A mock object is added to this registry the first time
+// Mock::AllowLeak(), ON_CALL(), or EXPECT_CALL() is called on it.  It
+// is removed from the registry in the mock object's destructor.
+class MockObjectRegistry {
+ public:
+  // Maps a mock object (identified by its address) to its state.
+  typedef std::map<const void*, MockObjectState> StateMap;
+
+  // This destructor will be called when a program exits, after all
+  // tests in it have been run.  By then, there should be no mock
+  // object alive.  Therefore we report any living object as test
+  // failure, unless the user explicitly asked us to ignore it.
+  ~MockObjectRegistry() {
+    if (!GMOCK_FLAG(catch_leaked_mocks))
+      return;
+
+    int leaked_count = 0;
+    for (StateMap::const_iterator it = states_.begin(); it != states_.end();
+         ++it) {
+      if (it->second.leakable)  // The user said it's fine to leak this object.
+        continue;
+
+      // FIXME: Print the type of the leaked object.
+      // This can help the user identify the leaked object.
+      std::cout << "\n";
+      const MockObjectState& state = it->second;
+      std::cout << internal::FormatFileLocation(state.first_used_file,
+                                                state.first_used_line);
+      std::cout << " ERROR: this mock object";
+      if (state.first_used_test != "") {
+        std::cout << " (used in test " << state.first_used_test_suite << "."
+                  << state.first_used_test << ")";
+      }
+      std::cout << " should be deleted but never is. Its address is @"
+           << it->first << ".";
+      leaked_count++;
+    }
+    if (leaked_count > 0) {
+      std::cout << "\nERROR: " << leaked_count << " leaked mock "
+                << (leaked_count == 1 ? "object" : "objects")
+                << " found at program exit. Expectations on a mock object are "
+                   "verified when the object is destructed. Leaking a mock "
+                   "means that its expectations aren't verified, which is "
+                   "usually a test bug. If you really intend to leak a mock, "
+                   "you can suppress this error using "
+                   "testing::Mock::AllowLeak(mock_object), or you may use a "
+                   "fake or stub instead of a mock.\n";
+      std::cout.flush();
+      ::std::cerr.flush();
+      // RUN_ALL_TESTS() has already returned when this destructor is
+      // called.  Therefore we cannot use the normal Google Test
+      // failure reporting mechanism.
+      _exit(1);  // We cannot call exit() as it is not reentrant and
+                 // may already have been called.
+    }
+  }
+
+  StateMap& states() { return states_; }
+
+ private:
+  StateMap states_;
+};
+
+// Protected by g_gmock_mutex.
+MockObjectRegistry g_mock_object_registry;
+
+// Maps a mock object to the reaction Google Mock should have when an
+// uninteresting method is called.  Protected by g_gmock_mutex.
+std::map<const void*, internal::CallReaction> g_uninteresting_call_reaction;
+
+// Sets the reaction Google Mock should have when an uninteresting
+// method of the given mock object is called.
+void SetReactionOnUninterestingCalls(const void* mock_obj,
+                                     internal::CallReaction reaction)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  internal::MutexLock l(&internal::g_gmock_mutex);
+  g_uninteresting_call_reaction[mock_obj] = reaction;
+}
+
+}  // namespace
+
+// Tells Google Mock to allow uninteresting calls on the given mock
+// object.
+void Mock::AllowUninterestingCalls(const void* mock_obj)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  SetReactionOnUninterestingCalls(mock_obj, internal::kAllow);
+}
+
+// Tells Google Mock to warn the user about uninteresting calls on the
+// given mock object.
+void Mock::WarnUninterestingCalls(const void* mock_obj)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  SetReactionOnUninterestingCalls(mock_obj, internal::kWarn);
+}
+
+// Tells Google Mock to fail uninteresting calls on the given mock
+// object.
+void Mock::FailUninterestingCalls(const void* mock_obj)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  SetReactionOnUninterestingCalls(mock_obj, internal::kFail);
+}
+
+// Tells Google Mock the given mock object is being destroyed and its
+// entry in the call-reaction table should be removed.
+void Mock::UnregisterCallReaction(const void* mock_obj)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  internal::MutexLock l(&internal::g_gmock_mutex);
+  g_uninteresting_call_reaction.erase(mock_obj);
+}
+
+// Returns the reaction Google Mock will have on uninteresting calls
+// made on the given mock object.
+internal::CallReaction Mock::GetReactionOnUninterestingCalls(
+    const void* mock_obj)
+        GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  internal::MutexLock l(&internal::g_gmock_mutex);
+  return (g_uninteresting_call_reaction.count(mock_obj) == 0) ?
+      internal::intToCallReaction(GMOCK_FLAG(default_mock_behavior)) :
+      g_uninteresting_call_reaction[mock_obj];
+}
+
+// Tells Google Mock to ignore mock_obj when checking for leaked mock
+// objects.
+void Mock::AllowLeak(const void* mock_obj)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  internal::MutexLock l(&internal::g_gmock_mutex);
+  g_mock_object_registry.states()[mock_obj].leakable = true;
+}
+
+// Verifies and clears all expectations on the given mock object.  If
+// the expectations aren't satisfied, generates one or more Google
+// Test non-fatal failures and returns false.
+bool Mock::VerifyAndClearExpectations(void* mock_obj)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  internal::MutexLock l(&internal::g_gmock_mutex);
+  return VerifyAndClearExpectationsLocked(mock_obj);
+}
+
+// Verifies all expectations on the given mock object and clears its
+// default actions and expectations.  Returns true if and only if the
+// verification was successful.
+bool Mock::VerifyAndClear(void* mock_obj)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  internal::MutexLock l(&internal::g_gmock_mutex);
+  ClearDefaultActionsLocked(mock_obj);
+  return VerifyAndClearExpectationsLocked(mock_obj);
+}
+
+// Verifies and clears all expectations on the given mock object.  If
+// the expectations aren't satisfied, generates one or more Google
+// Test non-fatal failures and returns false.
+bool Mock::VerifyAndClearExpectationsLocked(void* mock_obj)
+    GTEST_EXCLUSIVE_LOCK_REQUIRED_(internal::g_gmock_mutex) {
+  internal::g_gmock_mutex.AssertHeld();
+  if (g_mock_object_registry.states().count(mock_obj) == 0) {
+    // No EXPECT_CALL() was set on the given mock object.
+    return true;
+  }
+
+  // Verifies and clears the expectations on each mock method in the
+  // given mock object.
+  bool expectations_met = true;
+  FunctionMockers& mockers =
+      g_mock_object_registry.states()[mock_obj].function_mockers;
+  for (FunctionMockers::const_iterator it = mockers.begin();
+       it != mockers.end(); ++it) {
+    if (!(*it)->VerifyAndClearExpectationsLocked()) {
+      expectations_met = false;
+    }
+  }
+
+  // We don't clear the content of mockers, as they may still be
+  // needed by ClearDefaultActionsLocked().
+  return expectations_met;
+}
+
+bool Mock::IsNaggy(void* mock_obj)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  return Mock::GetReactionOnUninterestingCalls(mock_obj) == internal::kWarn;
+}
+bool Mock::IsNice(void* mock_obj)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  return Mock::GetReactionOnUninterestingCalls(mock_obj) == internal::kAllow;
+}
+bool Mock::IsStrict(void* mock_obj)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  return Mock::GetReactionOnUninterestingCalls(mock_obj) == internal::kFail;
+}
+
+// Registers a mock object and a mock method it owns.
+void Mock::Register(const void* mock_obj,
+                    internal::UntypedFunctionMockerBase* mocker)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  internal::MutexLock l(&internal::g_gmock_mutex);
+  g_mock_object_registry.states()[mock_obj].function_mockers.insert(mocker);
+}
+
+// Tells Google Mock where in the source code mock_obj is used in an
+// ON_CALL or EXPECT_CALL.  In case mock_obj is leaked, this
+// information helps the user identify which object it is.
+void Mock::RegisterUseByOnCallOrExpectCall(const void* mock_obj,
+                                           const char* file, int line)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  internal::MutexLock l(&internal::g_gmock_mutex);
+  MockObjectState& state = g_mock_object_registry.states()[mock_obj];
+  if (state.first_used_file == nullptr) {
+    state.first_used_file = file;
+    state.first_used_line = line;
+    const TestInfo* const test_info =
+        UnitTest::GetInstance()->current_test_info();
+    if (test_info != nullptr) {
+      state.first_used_test_suite = test_info->test_suite_name();
+      state.first_used_test = test_info->name();
+    }
+  }
+}
+
+// Unregisters a mock method; removes the owning mock object from the
+// registry when the last mock method associated with it has been
+// unregistered.  This is called only in the destructor of
+// FunctionMockerBase.
+void Mock::UnregisterLocked(internal::UntypedFunctionMockerBase* mocker)
+    GTEST_EXCLUSIVE_LOCK_REQUIRED_(internal::g_gmock_mutex) {
+  internal::g_gmock_mutex.AssertHeld();
+  for (MockObjectRegistry::StateMap::iterator it =
+           g_mock_object_registry.states().begin();
+       it != g_mock_object_registry.states().end(); ++it) {
+    FunctionMockers& mockers = it->second.function_mockers;
+    if (mockers.erase(mocker) > 0) {
+      // mocker was in mockers and has been just removed.
+      if (mockers.empty()) {
+        g_mock_object_registry.states().erase(it);
+      }
+      return;
+    }
+  }
+}
+
+// Clears all ON_CALL()s set on the given mock object.
+void Mock::ClearDefaultActionsLocked(void* mock_obj)
+    GTEST_EXCLUSIVE_LOCK_REQUIRED_(internal::g_gmock_mutex) {
+  internal::g_gmock_mutex.AssertHeld();
+
+  if (g_mock_object_registry.states().count(mock_obj) == 0) {
+    // No ON_CALL() was set on the given mock object.
+    return;
+  }
+
+  // Clears the default actions for each mock method in the given mock
+  // object.
+  FunctionMockers& mockers =
+      g_mock_object_registry.states()[mock_obj].function_mockers;
+  for (FunctionMockers::const_iterator it = mockers.begin();
+       it != mockers.end(); ++it) {
+    (*it)->ClearDefaultActionsLocked();
+  }
+
+  // We don't clear the content of mockers, as they may still be
+  // needed by VerifyAndClearExpectationsLocked().
+}
+
+Expectation::Expectation() {}
+
+Expectation::Expectation(
+    const std::shared_ptr<internal::ExpectationBase>& an_expectation_base)
+    : expectation_base_(an_expectation_base) {}
+
+Expectation::~Expectation() {}
+
+// Adds an expectation to a sequence.
+void Sequence::AddExpectation(const Expectation& expectation) const {
+  if (*last_expectation_ != expectation) {
+    if (last_expectation_->expectation_base() != nullptr) {
+      expectation.expectation_base()->immediate_prerequisites_
+          += *last_expectation_;
+    }
+    *last_expectation_ = expectation;
+  }
+}
+
+// Creates the implicit sequence if there isn't one.
+InSequence::InSequence() {
+  if (internal::g_gmock_implicit_sequence.get() == nullptr) {
+    internal::g_gmock_implicit_sequence.set(new Sequence);
+    sequence_created_ = true;
+  } else {
+    sequence_created_ = false;
+  }
+}
+
+// Deletes the implicit sequence if it was created by the constructor
+// of this object.
+InSequence::~InSequence() {
+  if (sequence_created_) {
+    delete internal::g_gmock_implicit_sequence.get();
+    internal::g_gmock_implicit_sequence.set(nullptr);
+  }
+}
+
+}  // namespace testing
+
+#ifdef _MSC_VER
+#if _MSC_VER == 1900
+#  pragma warning(pop)
+#endif
+#endif
diff --git a/leveldb_base/third_party/googletest/googlemock/src/gmock.cc b/leveldb_base/third_party/googletest/googlemock/src/gmock.cc
new file mode 100644
index 0000000..7bcdb0b
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/src/gmock.cc
@@ -0,0 +1,213 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+#include "gmock/gmock.h"
+#include "gmock/internal/gmock-port.h"
+
+namespace testing {
+
+GMOCK_DEFINE_bool_(catch_leaked_mocks, true,
+                   "true if and only if Google Mock should report leaked "
+                   "mock objects as failures.");
+
+GMOCK_DEFINE_string_(verbose, internal::kWarningVerbosity,
+                     "Controls how verbose Google Mock's output is."
+                     "  Valid values:\n"
+                     "  info    - prints all messages.\n"
+                     "  warning - prints warnings and errors.\n"
+                     "  error   - prints errors only.");
+
+GMOCK_DEFINE_int32_(default_mock_behavior, 1,
+                    "Controls the default behavior of mocks."
+                    "  Valid values:\n"
+                    "  0 - by default, mocks act as NiceMocks.\n"
+                    "  1 - by default, mocks act as NaggyMocks.\n"
+                    "  2 - by default, mocks act as StrictMocks.");
+
+namespace internal {
+
+// Parses a string as a command line flag.  The string should have the
+// format "--gmock_flag=value".  When def_optional is true, the
+// "=value" part can be omitted.
+//
+// Returns the value of the flag, or NULL if the parsing failed.
+static const char* ParseGoogleMockFlagValue(const char* str,
+                                            const char* flag,
+                                            bool def_optional) {
+  // str and flag must not be NULL.
+  if (str == nullptr || flag == nullptr) return nullptr;
+
+  // The flag must start with "--gmock_".
+  const std::string flag_str = std::string("--gmock_") + flag;
+  const size_t flag_len = flag_str.length();
+  if (strncmp(str, flag_str.c_str(), flag_len) != 0) return nullptr;
+
+  // Skips the flag name.
+  const char* flag_end = str + flag_len;
+
+  // When def_optional is true, it's OK to not have a "=value" part.
+  if (def_optional && (flag_end[0] == '\0')) {
+    return flag_end;
+  }
+
+  // If def_optional is true and there are more characters after the
+  // flag name, or if def_optional is false, there must be a '=' after
+  // the flag name.
+  if (flag_end[0] != '=') return nullptr;
+
+  // Returns the string after "=".
+  return flag_end + 1;
+}
+
+// Parses a string for a Google Mock bool flag, in the form of
+// "--gmock_flag=value".
+//
+// On success, stores the value of the flag in *value, and returns
+// true.  On failure, returns false without changing *value.
+static bool ParseGoogleMockBoolFlag(const char* str, const char* flag,
+                                    bool* value) {
+  // Gets the value of the flag as a string.
+  const char* const value_str = ParseGoogleMockFlagValue(str, flag, true);
+
+  // Aborts if the parsing failed.
+  if (value_str == nullptr) return false;
+
+  // Converts the string value to a bool.
+  *value = !(*value_str == '0' || *value_str == 'f' || *value_str == 'F');
+  return true;
+}
+
+// Parses a string for a Google Mock string flag, in the form of
+// "--gmock_flag=value".
+//
+// On success, stores the value of the flag in *value, and returns
+// true.  On failure, returns false without changing *value.
+template <typename String>
+static bool ParseGoogleMockStringFlag(const char* str, const char* flag,
+                                      String* value) {
+  // Gets the value of the flag as a string.
+  const char* const value_str = ParseGoogleMockFlagValue(str, flag, false);
+
+  // Aborts if the parsing failed.
+  if (value_str == nullptr) return false;
+
+  // Sets *value to the value of the flag.
+  *value = value_str;
+  return true;
+}
+
+static bool ParseGoogleMockIntFlag(const char* str, const char* flag,
+                                   int32_t* value) {
+  // Gets the value of the flag as a string.
+  const char* const value_str = ParseGoogleMockFlagValue(str, flag, true);
+
+  // Aborts if the parsing failed.
+  if (value_str == nullptr) return false;
+
+  // Sets *value to the value of the flag.
+  return ParseInt32(Message() << "The value of flag --" << flag,
+                    value_str, value);
+}
+
+// The internal implementation of InitGoogleMock().
+//
+// The type parameter CharType can be instantiated to either char or
+// wchar_t.
+template <typename CharType>
+void InitGoogleMockImpl(int* argc, CharType** argv) {
+  // Makes sure Google Test is initialized.  InitGoogleTest() is
+  // idempotent, so it's fine if the user has already called it.
+  InitGoogleTest(argc, argv);
+  if (*argc <= 0) return;
+
+  for (int i = 1; i != *argc; i++) {
+    const std::string arg_string = StreamableToString(argv[i]);
+    const char* const arg = arg_string.c_str();
+
+    // Do we see a Google Mock flag?
+    if (ParseGoogleMockBoolFlag(arg, "catch_leaked_mocks",
+                                &GMOCK_FLAG(catch_leaked_mocks)) ||
+        ParseGoogleMockStringFlag(arg, "verbose", &GMOCK_FLAG(verbose)) ||
+        ParseGoogleMockIntFlag(arg, "default_mock_behavior",
+                               &GMOCK_FLAG(default_mock_behavior))) {
+      // Yes.  Shift the remainder of the argv list left by one.  Note
+      // that argv has (*argc + 1) elements, the last one always being
+      // NULL.  The following loop moves the trailing NULL element as
+      // well.
+      for (int j = i; j != *argc; j++) {
+        argv[j] = argv[j + 1];
+      }
+
+      // Decrements the argument count.
+      (*argc)--;
+
+      // We also need to decrement the iterator as we just removed
+      // an element.
+      i--;
+    }
+  }
+}
+
+}  // namespace internal
+
+// Initializes Google Mock.  This must be called before running the
+// tests.  In particular, it parses a command line for the flags that
+// Google Mock recognizes.  Whenever a Google Mock flag is seen, it is
+// removed from argv, and *argc is decremented.
+//
+// No value is returned.  Instead, the Google Mock flag variables are
+// updated.
+//
+// Since Google Test is needed for Google Mock to work, this function
+// also initializes Google Test and parses its flags, if that hasn't
+// been done.
+GTEST_API_ void InitGoogleMock(int* argc, char** argv) {
+  internal::InitGoogleMockImpl(argc, argv);
+}
+
+// This overloaded version can be used in Windows programs compiled in
+// UNICODE mode.
+GTEST_API_ void InitGoogleMock(int* argc, wchar_t** argv) {
+  internal::InitGoogleMockImpl(argc, argv);
+}
+
+// This overloaded version can be used on Arduino/embedded platforms where
+// there is no argc/argv.
+GTEST_API_ void InitGoogleMock() {
+  // Since Arduino doesn't have a command line, fake out the argc/argv arguments
+  int argc = 1;
+  const auto arg0 = "dummy";
+  char* argv0 = const_cast<char*>(arg0);
+  char** argv = &argv0;
+
+  internal::InitGoogleMockImpl(&argc, argv);
+}
+
+}  // namespace testing
diff --git a/leveldb_base/third_party/googletest/googlemock/src/gmock_main.cc b/leveldb_base/third_party/googletest/googlemock/src/gmock_main.cc
new file mode 100644
index 0000000..18c500f
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/src/gmock_main.cc
@@ -0,0 +1,72 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+#include <iostream>
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+#if GTEST_OS_ESP8266 || GTEST_OS_ESP32
+#if GTEST_OS_ESP8266
+extern "C" {
+#endif
+void setup() {
+  // Since Google Mock depends on Google Test, InitGoogleMock() is
+  // also responsible for initializing Google Test.  Therefore there's
+  // no need for calling testing::InitGoogleTest() separately.
+  testing::InitGoogleMock();
+}
+void loop() { RUN_ALL_TESTS(); }
+#if GTEST_OS_ESP8266
+}
+#endif
+
+#else
+
+// MS C++ compiler/linker has a bug on Windows (not on Windows CE), which
+// causes a link error when _tmain is defined in a static library and UNICODE
+// is enabled. For this reason instead of _tmain, main function is used on
+// Windows. See the following link to track the current status of this bug:
+// https://web.archive.org/web/20170912203238/connect.microsoft.com/VisualStudio/feedback/details/394464/wmain-link-error-in-the-static-library
+// // NOLINT
+#if GTEST_OS_WINDOWS_MOBILE
+# include <tchar.h>  // NOLINT
+
+GTEST_API_ int _tmain(int argc, TCHAR** argv) {
+#else
+GTEST_API_ int main(int argc, char** argv) {
+#endif  // GTEST_OS_WINDOWS_MOBILE
+  std::cout << "Running main() from gmock_main.cc\n";
+  // Since Google Mock depends on Google Test, InitGoogleMock() is
+  // also responsible for initializing Google Test.  Therefore there's
+  // no need for calling testing::InitGoogleTest() separately.
+  testing::InitGoogleMock(&argc, argv);
+  return RUN_ALL_TESTS();
+}
+#endif
diff --git a/leveldb_base/third_party/googletest/googlemock/test/BUILD.bazel b/leveldb_base/third_party/googletest/googlemock/test/BUILD.bazel
new file mode 100644
index 0000000..1f7bd06
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/BUILD.bazel
@@ -0,0 +1,119 @@
+# Copyright 2017 Google Inc.
+# All Rights Reserved.
+#
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#
+#   Bazel Build for Google C++ Testing Framework(Google Test)-googlemock
+
+load("@rules_cc//cc:defs.bzl", "cc_binary", "cc_test")
+load("@rules_python//python:defs.bzl", "py_library", "py_test")
+
+licenses(["notice"])
+
+# Tests for GMock itself
+cc_test(
+    name = "gmock_all_test",
+    size = "small",
+    srcs = glob(include = ["gmock-*.cc"]),
+    linkopts = select({
+        "//:windows": [],
+        "//conditions:default": ["-pthread"],
+    }),
+    deps = ["//:gtest"],
+)
+
+# Python tests
+py_library(
+    name = "gmock_test_utils",
+    testonly = 1,
+    srcs = ["gmock_test_utils.py"],
+    deps = [
+        "//googletest/test:gtest_test_utils",
+    ],
+)
+
+cc_binary(
+    name = "gmock_leak_test_",
+    testonly = 1,
+    srcs = ["gmock_leak_test_.cc"],
+    deps = ["//:gtest_main"],
+)
+
+py_test(
+    name = "gmock_leak_test",
+    size = "medium",
+    srcs = ["gmock_leak_test.py"],
+    data = [
+        ":gmock_leak_test_",
+        ":gmock_test_utils",
+    ],
+    tags = [
+        "no_test_msvc2015",
+        "no_test_msvc2017",
+    ],
+)
+
+cc_test(
+    name = "gmock_link_test",
+    size = "small",
+    srcs = [
+        "gmock_link2_test.cc",
+        "gmock_link_test.cc",
+        "gmock_link_test.h",
+    ],
+    deps = ["//:gtest_main"],
+)
+
+cc_binary(
+    name = "gmock_output_test_",
+    srcs = ["gmock_output_test_.cc"],
+    deps = ["//:gtest"],
+)
+
+py_test(
+    name = "gmock_output_test",
+    size = "medium",
+    srcs = ["gmock_output_test.py"],
+    data = [
+        ":gmock_output_test_",
+        ":gmock_output_test_golden.txt",
+    ],
+    python_version = "PY2",
+    tags = [
+        "no_test_msvc2015",
+        "no_test_msvc2017",
+    ],
+    deps = [":gmock_test_utils"],
+)
+
+cc_test(
+    name = "gmock_test",
+    size = "small",
+    srcs = ["gmock_test.cc"],
+    deps = ["//:gtest_main"],
+)
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock-actions_test.cc b/leveldb_base/third_party/googletest/googlemock/test/gmock-actions_test.cc
new file mode 100644
index 0000000..e1ca7fe
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock-actions_test.cc
@@ -0,0 +1,1583 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests the built-in actions.
+
+// Silence C4100 (unreferenced formal parameter) for MSVC
+#ifdef _MSC_VER
+#  pragma warning(push)
+#  pragma warning(disable:4100)
+#if _MSC_VER == 1900
+// and silence C4800 (C4800: 'int *const ': forcing value
+// to bool 'true' or 'false') for MSVC 15
+#  pragma warning(disable:4800)
+#endif
+#endif
+
+#include "gmock/gmock-actions.h"
+#include <algorithm>
+#include <iterator>
+#include <memory>
+#include <string>
+#include <type_traits>
+#include "gmock/gmock.h"
+#include "gmock/internal/gmock-port.h"
+#include "gtest/gtest.h"
+#include "gtest/gtest-spi.h"
+
+namespace {
+
+using ::testing::_;
+using ::testing::Action;
+using ::testing::ActionInterface;
+using ::testing::Assign;
+using ::testing::ByMove;
+using ::testing::ByRef;
+using ::testing::DefaultValue;
+using ::testing::DoAll;
+using ::testing::DoDefault;
+using ::testing::IgnoreResult;
+using ::testing::Invoke;
+using ::testing::InvokeWithoutArgs;
+using ::testing::MakePolymorphicAction;
+using ::testing::PolymorphicAction;
+using ::testing::Return;
+using ::testing::ReturnNew;
+using ::testing::ReturnNull;
+using ::testing::ReturnRef;
+using ::testing::ReturnRefOfCopy;
+using ::testing::ReturnRoundRobin;
+using ::testing::SetArgPointee;
+using ::testing::SetArgumentPointee;
+using ::testing::Unused;
+using ::testing::WithArgs;
+using ::testing::internal::BuiltInDefaultValue;
+
+#if !GTEST_OS_WINDOWS_MOBILE
+using ::testing::SetErrnoAndReturn;
+#endif
+
+// Tests that BuiltInDefaultValue<T*>::Get() returns NULL.
+TEST(BuiltInDefaultValueTest, IsNullForPointerTypes) {
+  EXPECT_TRUE(BuiltInDefaultValue<int*>::Get() == nullptr);
+  EXPECT_TRUE(BuiltInDefaultValue<const char*>::Get() == nullptr);
+  EXPECT_TRUE(BuiltInDefaultValue<void*>::Get() == nullptr);
+}
+
+// Tests that BuiltInDefaultValue<T*>::Exists() return true.
+TEST(BuiltInDefaultValueTest, ExistsForPointerTypes) {
+  EXPECT_TRUE(BuiltInDefaultValue<int*>::Exists());
+  EXPECT_TRUE(BuiltInDefaultValue<const char*>::Exists());
+  EXPECT_TRUE(BuiltInDefaultValue<void*>::Exists());
+}
+
+// Tests that BuiltInDefaultValue<T>::Get() returns 0 when T is a
+// built-in numeric type.
+TEST(BuiltInDefaultValueTest, IsZeroForNumericTypes) {
+  EXPECT_EQ(0U, BuiltInDefaultValue<unsigned char>::Get());
+  EXPECT_EQ(0, BuiltInDefaultValue<signed char>::Get());
+  EXPECT_EQ(0, BuiltInDefaultValue<char>::Get());
+#if GMOCK_WCHAR_T_IS_NATIVE_
+#if !defined(__WCHAR_UNSIGNED__)
+  EXPECT_EQ(0, BuiltInDefaultValue<wchar_t>::Get());
+#else
+  EXPECT_EQ(0U, BuiltInDefaultValue<wchar_t>::Get());
+#endif
+#endif
+  EXPECT_EQ(0U, BuiltInDefaultValue<unsigned short>::Get());  // NOLINT
+  EXPECT_EQ(0, BuiltInDefaultValue<signed short>::Get());  // NOLINT
+  EXPECT_EQ(0, BuiltInDefaultValue<short>::Get());  // NOLINT
+  EXPECT_EQ(0U, BuiltInDefaultValue<unsigned int>::Get());
+  EXPECT_EQ(0, BuiltInDefaultValue<signed int>::Get());
+  EXPECT_EQ(0, BuiltInDefaultValue<int>::Get());
+  EXPECT_EQ(0U, BuiltInDefaultValue<unsigned long>::Get());  // NOLINT
+  EXPECT_EQ(0, BuiltInDefaultValue<signed long>::Get());  // NOLINT
+  EXPECT_EQ(0, BuiltInDefaultValue<long>::Get());  // NOLINT
+  EXPECT_EQ(0U, BuiltInDefaultValue<unsigned long long>::Get());  // NOLINT
+  EXPECT_EQ(0, BuiltInDefaultValue<signed long long>::Get());  // NOLINT
+  EXPECT_EQ(0, BuiltInDefaultValue<long long>::Get());  // NOLINT
+  EXPECT_EQ(0, BuiltInDefaultValue<float>::Get());
+  EXPECT_EQ(0, BuiltInDefaultValue<double>::Get());
+}
+
+// Tests that BuiltInDefaultValue<T>::Exists() returns true when T is a
+// built-in numeric type.
+TEST(BuiltInDefaultValueTest, ExistsForNumericTypes) {
+  EXPECT_TRUE(BuiltInDefaultValue<unsigned char>::Exists());
+  EXPECT_TRUE(BuiltInDefaultValue<signed char>::Exists());
+  EXPECT_TRUE(BuiltInDefaultValue<char>::Exists());
+#if GMOCK_WCHAR_T_IS_NATIVE_
+  EXPECT_TRUE(BuiltInDefaultValue<wchar_t>::Exists());
+#endif
+  EXPECT_TRUE(BuiltInDefaultValue<unsigned short>::Exists());  // NOLINT
+  EXPECT_TRUE(BuiltInDefaultValue<signed short>::Exists());  // NOLINT
+  EXPECT_TRUE(BuiltInDefaultValue<short>::Exists());  // NOLINT
+  EXPECT_TRUE(BuiltInDefaultValue<unsigned int>::Exists());
+  EXPECT_TRUE(BuiltInDefaultValue<signed int>::Exists());
+  EXPECT_TRUE(BuiltInDefaultValue<int>::Exists());
+  EXPECT_TRUE(BuiltInDefaultValue<unsigned long>::Exists());  // NOLINT
+  EXPECT_TRUE(BuiltInDefaultValue<signed long>::Exists());  // NOLINT
+  EXPECT_TRUE(BuiltInDefaultValue<long>::Exists());  // NOLINT
+  EXPECT_TRUE(BuiltInDefaultValue<unsigned long long>::Exists());  // NOLINT
+  EXPECT_TRUE(BuiltInDefaultValue<signed long long>::Exists());  // NOLINT
+  EXPECT_TRUE(BuiltInDefaultValue<long long>::Exists());  // NOLINT
+  EXPECT_TRUE(BuiltInDefaultValue<float>::Exists());
+  EXPECT_TRUE(BuiltInDefaultValue<double>::Exists());
+}
+
+// Tests that BuiltInDefaultValue<bool>::Get() returns false.
+TEST(BuiltInDefaultValueTest, IsFalseForBool) {
+  EXPECT_FALSE(BuiltInDefaultValue<bool>::Get());
+}
+
+// Tests that BuiltInDefaultValue<bool>::Exists() returns true.
+TEST(BuiltInDefaultValueTest, BoolExists) {
+  EXPECT_TRUE(BuiltInDefaultValue<bool>::Exists());
+}
+
+// Tests that BuiltInDefaultValue<T>::Get() returns "" when T is a
+// string type.
+TEST(BuiltInDefaultValueTest, IsEmptyStringForString) {
+  EXPECT_EQ("", BuiltInDefaultValue< ::std::string>::Get());
+}
+
+// Tests that BuiltInDefaultValue<T>::Exists() returns true when T is a
+// string type.
+TEST(BuiltInDefaultValueTest, ExistsForString) {
+  EXPECT_TRUE(BuiltInDefaultValue< ::std::string>::Exists());
+}
+
+// Tests that BuiltInDefaultValue<const T>::Get() returns the same
+// value as BuiltInDefaultValue<T>::Get() does.
+TEST(BuiltInDefaultValueTest, WorksForConstTypes) {
+  EXPECT_EQ("", BuiltInDefaultValue<const std::string>::Get());
+  EXPECT_EQ(0, BuiltInDefaultValue<const int>::Get());
+  EXPECT_TRUE(BuiltInDefaultValue<char* const>::Get() == nullptr);
+  EXPECT_FALSE(BuiltInDefaultValue<const bool>::Get());
+}
+
+// A type that's default constructible.
+class MyDefaultConstructible {
+ public:
+  MyDefaultConstructible() : value_(42) {}
+
+  int value() const { return value_; }
+
+ private:
+  int value_;
+};
+
+// A type that's not default constructible.
+class MyNonDefaultConstructible {
+ public:
+  // Does not have a default ctor.
+  explicit MyNonDefaultConstructible(int a_value) : value_(a_value) {}
+
+  int value() const { return value_; }
+
+ private:
+  int value_;
+};
+
+
+TEST(BuiltInDefaultValueTest, ExistsForDefaultConstructibleType) {
+  EXPECT_TRUE(BuiltInDefaultValue<MyDefaultConstructible>::Exists());
+}
+
+TEST(BuiltInDefaultValueTest, IsDefaultConstructedForDefaultConstructibleType) {
+  EXPECT_EQ(42, BuiltInDefaultValue<MyDefaultConstructible>::Get().value());
+}
+
+
+TEST(BuiltInDefaultValueTest, DoesNotExistForNonDefaultConstructibleType) {
+  EXPECT_FALSE(BuiltInDefaultValue<MyNonDefaultConstructible>::Exists());
+}
+
+// Tests that BuiltInDefaultValue<T&>::Get() aborts the program.
+TEST(BuiltInDefaultValueDeathTest, IsUndefinedForReferences) {
+  EXPECT_DEATH_IF_SUPPORTED({
+    BuiltInDefaultValue<int&>::Get();
+  }, "");
+  EXPECT_DEATH_IF_SUPPORTED({
+    BuiltInDefaultValue<const char&>::Get();
+  }, "");
+}
+
+TEST(BuiltInDefaultValueDeathTest, IsUndefinedForNonDefaultConstructibleType) {
+  EXPECT_DEATH_IF_SUPPORTED({
+    BuiltInDefaultValue<MyNonDefaultConstructible>::Get();
+  }, "");
+}
+
+// Tests that DefaultValue<T>::IsSet() is false initially.
+TEST(DefaultValueTest, IsInitiallyUnset) {
+  EXPECT_FALSE(DefaultValue<int>::IsSet());
+  EXPECT_FALSE(DefaultValue<MyDefaultConstructible>::IsSet());
+  EXPECT_FALSE(DefaultValue<const MyNonDefaultConstructible>::IsSet());
+}
+
+// Tests that DefaultValue<T> can be set and then unset.
+TEST(DefaultValueTest, CanBeSetAndUnset) {
+  EXPECT_TRUE(DefaultValue<int>::Exists());
+  EXPECT_FALSE(DefaultValue<const MyNonDefaultConstructible>::Exists());
+
+  DefaultValue<int>::Set(1);
+  DefaultValue<const MyNonDefaultConstructible>::Set(
+      MyNonDefaultConstructible(42));
+
+  EXPECT_EQ(1, DefaultValue<int>::Get());
+  EXPECT_EQ(42, DefaultValue<const MyNonDefaultConstructible>::Get().value());
+
+  EXPECT_TRUE(DefaultValue<int>::Exists());
+  EXPECT_TRUE(DefaultValue<const MyNonDefaultConstructible>::Exists());
+
+  DefaultValue<int>::Clear();
+  DefaultValue<const MyNonDefaultConstructible>::Clear();
+
+  EXPECT_FALSE(DefaultValue<int>::IsSet());
+  EXPECT_FALSE(DefaultValue<const MyNonDefaultConstructible>::IsSet());
+
+  EXPECT_TRUE(DefaultValue<int>::Exists());
+  EXPECT_FALSE(DefaultValue<const MyNonDefaultConstructible>::Exists());
+}
+
+// Tests that DefaultValue<T>::Get() returns the
+// BuiltInDefaultValue<T>::Get() when DefaultValue<T>::IsSet() is
+// false.
+TEST(DefaultValueDeathTest, GetReturnsBuiltInDefaultValueWhenUnset) {
+  EXPECT_FALSE(DefaultValue<int>::IsSet());
+  EXPECT_TRUE(DefaultValue<int>::Exists());
+  EXPECT_FALSE(DefaultValue<MyNonDefaultConstructible>::IsSet());
+  EXPECT_FALSE(DefaultValue<MyNonDefaultConstructible>::Exists());
+
+  EXPECT_EQ(0, DefaultValue<int>::Get());
+
+  EXPECT_DEATH_IF_SUPPORTED({
+    DefaultValue<MyNonDefaultConstructible>::Get();
+  }, "");
+}
+
+TEST(DefaultValueTest, GetWorksForMoveOnlyIfSet) {
+  EXPECT_TRUE(DefaultValue<std::unique_ptr<int>>::Exists());
+  EXPECT_TRUE(DefaultValue<std::unique_ptr<int>>::Get() == nullptr);
+  DefaultValue<std::unique_ptr<int>>::SetFactory([] {
+    return std::unique_ptr<int>(new int(42));
+  });
+  EXPECT_TRUE(DefaultValue<std::unique_ptr<int>>::Exists());
+  std::unique_ptr<int> i = DefaultValue<std::unique_ptr<int>>::Get();
+  EXPECT_EQ(42, *i);
+}
+
+// Tests that DefaultValue<void>::Get() returns void.
+TEST(DefaultValueTest, GetWorksForVoid) {
+  return DefaultValue<void>::Get();
+}
+
+// Tests using DefaultValue with a reference type.
+
+// Tests that DefaultValue<T&>::IsSet() is false initially.
+TEST(DefaultValueOfReferenceTest, IsInitiallyUnset) {
+  EXPECT_FALSE(DefaultValue<int&>::IsSet());
+  EXPECT_FALSE(DefaultValue<MyDefaultConstructible&>::IsSet());
+  EXPECT_FALSE(DefaultValue<MyNonDefaultConstructible&>::IsSet());
+}
+
+// Tests that DefaultValue<T&>::Exists is false initiallly.
+TEST(DefaultValueOfReferenceTest, IsInitiallyNotExisting) {
+  EXPECT_FALSE(DefaultValue<int&>::Exists());
+  EXPECT_FALSE(DefaultValue<MyDefaultConstructible&>::Exists());
+  EXPECT_FALSE(DefaultValue<MyNonDefaultConstructible&>::Exists());
+}
+
+// Tests that DefaultValue<T&> can be set and then unset.
+TEST(DefaultValueOfReferenceTest, CanBeSetAndUnset) {
+  int n = 1;
+  DefaultValue<const int&>::Set(n);
+  MyNonDefaultConstructible x(42);
+  DefaultValue<MyNonDefaultConstructible&>::Set(x);
+
+  EXPECT_TRUE(DefaultValue<const int&>::Exists());
+  EXPECT_TRUE(DefaultValue<MyNonDefaultConstructible&>::Exists());
+
+  EXPECT_EQ(&n, &(DefaultValue<const int&>::Get()));
+  EXPECT_EQ(&x, &(DefaultValue<MyNonDefaultConstructible&>::Get()));
+
+  DefaultValue<const int&>::Clear();
+  DefaultValue<MyNonDefaultConstructible&>::Clear();
+
+  EXPECT_FALSE(DefaultValue<const int&>::Exists());
+  EXPECT_FALSE(DefaultValue<MyNonDefaultConstructible&>::Exists());
+
+  EXPECT_FALSE(DefaultValue<const int&>::IsSet());
+  EXPECT_FALSE(DefaultValue<MyNonDefaultConstructible&>::IsSet());
+}
+
+// Tests that DefaultValue<T&>::Get() returns the
+// BuiltInDefaultValue<T&>::Get() when DefaultValue<T&>::IsSet() is
+// false.
+TEST(DefaultValueOfReferenceDeathTest, GetReturnsBuiltInDefaultValueWhenUnset) {
+  EXPECT_FALSE(DefaultValue<int&>::IsSet());
+  EXPECT_FALSE(DefaultValue<MyNonDefaultConstructible&>::IsSet());
+
+  EXPECT_DEATH_IF_SUPPORTED({
+    DefaultValue<int&>::Get();
+  }, "");
+  EXPECT_DEATH_IF_SUPPORTED({
+    DefaultValue<MyNonDefaultConstructible>::Get();
+  }, "");
+}
+
+// Tests that ActionInterface can be implemented by defining the
+// Perform method.
+
+typedef int MyGlobalFunction(bool, int);
+
+class MyActionImpl : public ActionInterface<MyGlobalFunction> {
+ public:
+  int Perform(const std::tuple<bool, int>& args) override {
+    return std::get<0>(args) ? std::get<1>(args) : 0;
+  }
+};
+
+TEST(ActionInterfaceTest, CanBeImplementedByDefiningPerform) {
+  MyActionImpl my_action_impl;
+  (void)my_action_impl;
+}
+
+TEST(ActionInterfaceTest, MakeAction) {
+  Action<MyGlobalFunction> action = MakeAction(new MyActionImpl);
+
+  // When exercising the Perform() method of Action<F>, we must pass
+  // it a tuple whose size and type are compatible with F's argument
+  // types.  For example, if F is int(), then Perform() takes a
+  // 0-tuple; if F is void(bool, int), then Perform() takes a
+  // std::tuple<bool, int>, and so on.
+  EXPECT_EQ(5, action.Perform(std::make_tuple(true, 5)));
+}
+
+// Tests that Action<F> can be contructed from a pointer to
+// ActionInterface<F>.
+TEST(ActionTest, CanBeConstructedFromActionInterface) {
+  Action<MyGlobalFunction> action(new MyActionImpl);
+}
+
+// Tests that Action<F> delegates actual work to ActionInterface<F>.
+TEST(ActionTest, DelegatesWorkToActionInterface) {
+  const Action<MyGlobalFunction> action(new MyActionImpl);
+
+  EXPECT_EQ(5, action.Perform(std::make_tuple(true, 5)));
+  EXPECT_EQ(0, action.Perform(std::make_tuple(false, 1)));
+}
+
+// Tests that Action<F> can be copied.
+TEST(ActionTest, IsCopyable) {
+  Action<MyGlobalFunction> a1(new MyActionImpl);
+  Action<MyGlobalFunction> a2(a1);  // Tests the copy constructor.
+
+  // a1 should continue to work after being copied from.
+  EXPECT_EQ(5, a1.Perform(std::make_tuple(true, 5)));
+  EXPECT_EQ(0, a1.Perform(std::make_tuple(false, 1)));
+
+  // a2 should work like the action it was copied from.
+  EXPECT_EQ(5, a2.Perform(std::make_tuple(true, 5)));
+  EXPECT_EQ(0, a2.Perform(std::make_tuple(false, 1)));
+
+  a2 = a1;  // Tests the assignment operator.
+
+  // a1 should continue to work after being copied from.
+  EXPECT_EQ(5, a1.Perform(std::make_tuple(true, 5)));
+  EXPECT_EQ(0, a1.Perform(std::make_tuple(false, 1)));
+
+  // a2 should work like the action it was copied from.
+  EXPECT_EQ(5, a2.Perform(std::make_tuple(true, 5)));
+  EXPECT_EQ(0, a2.Perform(std::make_tuple(false, 1)));
+}
+
+// Tests that an Action<From> object can be converted to a
+// compatible Action<To> object.
+
+class IsNotZero : public ActionInterface<bool(int)> {  // NOLINT
+ public:
+  bool Perform(const std::tuple<int>& arg) override {
+    return std::get<0>(arg) != 0;
+  }
+};
+
+TEST(ActionTest, CanBeConvertedToOtherActionType) {
+  const Action<bool(int)> a1(new IsNotZero);  // NOLINT
+  const Action<int(char)> a2 = Action<int(char)>(a1);  // NOLINT
+  EXPECT_EQ(1, a2.Perform(std::make_tuple('a')));
+  EXPECT_EQ(0, a2.Perform(std::make_tuple('\0')));
+}
+
+// The following two classes are for testing MakePolymorphicAction().
+
+// Implements a polymorphic action that returns the second of the
+// arguments it receives.
+class ReturnSecondArgumentAction {
+ public:
+  // We want to verify that MakePolymorphicAction() can work with a
+  // polymorphic action whose Perform() method template is either
+  // const or not.  This lets us verify the non-const case.
+  template <typename Result, typename ArgumentTuple>
+  Result Perform(const ArgumentTuple& args) {
+    return std::get<1>(args);
+  }
+};
+
+// Implements a polymorphic action that can be used in a nullary
+// function to return 0.
+class ReturnZeroFromNullaryFunctionAction {
+ public:
+  // For testing that MakePolymorphicAction() works when the
+  // implementation class' Perform() method template takes only one
+  // template parameter.
+  //
+  // We want to verify that MakePolymorphicAction() can work with a
+  // polymorphic action whose Perform() method template is either
+  // const or not.  This lets us verify the const case.
+  template <typename Result>
+  Result Perform(const std::tuple<>&) const {
+    return 0;
+  }
+};
+
+// These functions verify that MakePolymorphicAction() returns a
+// PolymorphicAction<T> where T is the argument's type.
+
+PolymorphicAction<ReturnSecondArgumentAction> ReturnSecondArgument() {
+  return MakePolymorphicAction(ReturnSecondArgumentAction());
+}
+
+PolymorphicAction<ReturnZeroFromNullaryFunctionAction>
+ReturnZeroFromNullaryFunction() {
+  return MakePolymorphicAction(ReturnZeroFromNullaryFunctionAction());
+}
+
+// Tests that MakePolymorphicAction() turns a polymorphic action
+// implementation class into a polymorphic action.
+TEST(MakePolymorphicActionTest, ConstructsActionFromImpl) {
+  Action<int(bool, int, double)> a1 = ReturnSecondArgument();  // NOLINT
+  EXPECT_EQ(5, a1.Perform(std::make_tuple(false, 5, 2.0)));
+}
+
+// Tests that MakePolymorphicAction() works when the implementation
+// class' Perform() method template has only one template parameter.
+TEST(MakePolymorphicActionTest, WorksWhenPerformHasOneTemplateParameter) {
+  Action<int()> a1 = ReturnZeroFromNullaryFunction();
+  EXPECT_EQ(0, a1.Perform(std::make_tuple()));
+
+  Action<void*()> a2 = ReturnZeroFromNullaryFunction();
+  EXPECT_TRUE(a2.Perform(std::make_tuple()) == nullptr);
+}
+
+// Tests that Return() works as an action for void-returning
+// functions.
+TEST(ReturnTest, WorksForVoid) {
+  const Action<void(int)> ret = Return();  // NOLINT
+  return ret.Perform(std::make_tuple(1));
+}
+
+// Tests that Return(v) returns v.
+TEST(ReturnTest, ReturnsGivenValue) {
+  Action<int()> ret = Return(1);  // NOLINT
+  EXPECT_EQ(1, ret.Perform(std::make_tuple()));
+
+  ret = Return(-5);
+  EXPECT_EQ(-5, ret.Perform(std::make_tuple()));
+}
+
+// Tests that Return("string literal") works.
+TEST(ReturnTest, AcceptsStringLiteral) {
+  Action<const char*()> a1 = Return("Hello");
+  EXPECT_STREQ("Hello", a1.Perform(std::make_tuple()));
+
+  Action<std::string()> a2 = Return("world");
+  EXPECT_EQ("world", a2.Perform(std::make_tuple()));
+}
+
+// Test struct which wraps a vector of integers. Used in
+// 'SupportsWrapperReturnType' test.
+struct IntegerVectorWrapper {
+  std::vector<int> * v;
+  IntegerVectorWrapper(std::vector<int>& _v) : v(&_v) {}  // NOLINT
+};
+
+// Tests that Return() works when return type is a wrapper type.
+TEST(ReturnTest, SupportsWrapperReturnType) {
+  // Initialize vector of integers.
+  std::vector<int> v;
+  for (int i = 0; i < 5; ++i) v.push_back(i);
+
+  // Return() called with 'v' as argument. The Action will return the same data
+  // as 'v' (copy) but it will be wrapped in an IntegerVectorWrapper.
+  Action<IntegerVectorWrapper()> a = Return(v);
+  const std::vector<int>& result = *(a.Perform(std::make_tuple()).v);
+  EXPECT_THAT(result, ::testing::ElementsAre(0, 1, 2, 3, 4));
+}
+
+// Tests that Return(v) is covaraint.
+
+struct Base {
+  bool operator==(const Base&) { return true; }
+};
+
+struct Derived : public Base {
+  bool operator==(const Derived&) { return true; }
+};
+
+TEST(ReturnTest, IsCovariant) {
+  Base base;
+  Derived derived;
+  Action<Base*()> ret = Return(&base);
+  EXPECT_EQ(&base, ret.Perform(std::make_tuple()));
+
+  ret = Return(&derived);
+  EXPECT_EQ(&derived, ret.Perform(std::make_tuple()));
+}
+
+// Tests that the type of the value passed into Return is converted into T
+// when the action is cast to Action<T(...)> rather than when the action is
+// performed. See comments on testing::internal::ReturnAction in
+// gmock-actions.h for more information.
+class FromType {
+ public:
+  explicit FromType(bool* is_converted) : converted_(is_converted) {}
+  bool* converted() const { return converted_; }
+
+ private:
+  bool* const converted_;
+};
+
+class ToType {
+ public:
+  // Must allow implicit conversion due to use in ImplicitCast_<T>.
+  ToType(const FromType& x) { *x.converted() = true; }  // NOLINT
+};
+
+TEST(ReturnTest, ConvertsArgumentWhenConverted) {
+  bool converted = false;
+  FromType x(&converted);
+  Action<ToType()> action(Return(x));
+  EXPECT_TRUE(converted) << "Return must convert its argument in its own "
+                         << "conversion operator.";
+  converted = false;
+  action.Perform(std::tuple<>());
+  EXPECT_FALSE(converted) << "Action must NOT convert its argument "
+                          << "when performed.";
+}
+
+class DestinationType {};
+
+class SourceType {
+ public:
+  // Note: a non-const typecast operator.
+  operator DestinationType() { return DestinationType(); }
+};
+
+TEST(ReturnTest, CanConvertArgumentUsingNonConstTypeCastOperator) {
+  SourceType s;
+  Action<DestinationType()> action(Return(s));
+}
+
+// Tests that ReturnNull() returns NULL in a pointer-returning function.
+TEST(ReturnNullTest, WorksInPointerReturningFunction) {
+  const Action<int*()> a1 = ReturnNull();
+  EXPECT_TRUE(a1.Perform(std::make_tuple()) == nullptr);
+
+  const Action<const char*(bool)> a2 = ReturnNull();  // NOLINT
+  EXPECT_TRUE(a2.Perform(std::make_tuple(true)) == nullptr);
+}
+
+// Tests that ReturnNull() returns NULL for shared_ptr and unique_ptr returning
+// functions.
+TEST(ReturnNullTest, WorksInSmartPointerReturningFunction) {
+  const Action<std::unique_ptr<const int>()> a1 = ReturnNull();
+  EXPECT_TRUE(a1.Perform(std::make_tuple()) == nullptr);
+
+  const Action<std::shared_ptr<int>(std::string)> a2 = ReturnNull();
+  EXPECT_TRUE(a2.Perform(std::make_tuple("foo")) == nullptr);
+}
+
+// Tests that ReturnRef(v) works for reference types.
+TEST(ReturnRefTest, WorksForReference) {
+  const int n = 0;
+  const Action<const int&(bool)> ret = ReturnRef(n);  // NOLINT
+
+  EXPECT_EQ(&n, &ret.Perform(std::make_tuple(true)));
+}
+
+// Tests that ReturnRef(v) is covariant.
+TEST(ReturnRefTest, IsCovariant) {
+  Base base;
+  Derived derived;
+  Action<Base&()> a = ReturnRef(base);
+  EXPECT_EQ(&base, &a.Perform(std::make_tuple()));
+
+  a = ReturnRef(derived);
+  EXPECT_EQ(&derived, &a.Perform(std::make_tuple()));
+}
+
+template <typename T, typename = decltype(ReturnRef(std::declval<T&&>()))>
+bool CanCallReturnRef(T&&) { return true; }
+bool CanCallReturnRef(Unused) { return false; }
+
+// Tests that ReturnRef(v) is working with non-temporaries (T&)
+TEST(ReturnRefTest, WorksForNonTemporary) {
+  int scalar_value = 123;
+  EXPECT_TRUE(CanCallReturnRef(scalar_value));
+
+  std::string non_scalar_value("ABC");
+  EXPECT_TRUE(CanCallReturnRef(non_scalar_value));
+
+  const int const_scalar_value{321};
+  EXPECT_TRUE(CanCallReturnRef(const_scalar_value));
+
+  const std::string const_non_scalar_value("CBA");
+  EXPECT_TRUE(CanCallReturnRef(const_non_scalar_value));
+}
+
+// Tests that ReturnRef(v) is not working with temporaries (T&&)
+TEST(ReturnRefTest, DoesNotWorkForTemporary) {
+  auto scalar_value = []()  -> int { return 123; };
+  EXPECT_FALSE(CanCallReturnRef(scalar_value()));
+
+  auto non_scalar_value = []() -> std::string { return "ABC"; };
+  EXPECT_FALSE(CanCallReturnRef(non_scalar_value()));
+
+  // cannot use here callable returning "const scalar type",
+  // because such const for scalar return type is ignored
+  EXPECT_FALSE(CanCallReturnRef(static_cast<const int>(321)));
+
+  auto const_non_scalar_value = []() -> const std::string { return "CBA"; };
+  EXPECT_FALSE(CanCallReturnRef(const_non_scalar_value()));
+}
+
+// Tests that ReturnRefOfCopy(v) works for reference types.
+TEST(ReturnRefOfCopyTest, WorksForReference) {
+  int n = 42;
+  const Action<const int&()> ret = ReturnRefOfCopy(n);
+
+  EXPECT_NE(&n, &ret.Perform(std::make_tuple()));
+  EXPECT_EQ(42, ret.Perform(std::make_tuple()));
+
+  n = 43;
+  EXPECT_NE(&n, &ret.Perform(std::make_tuple()));
+  EXPECT_EQ(42, ret.Perform(std::make_tuple()));
+}
+
+// Tests that ReturnRefOfCopy(v) is covariant.
+TEST(ReturnRefOfCopyTest, IsCovariant) {
+  Base base;
+  Derived derived;
+  Action<Base&()> a = ReturnRefOfCopy(base);
+  EXPECT_NE(&base, &a.Perform(std::make_tuple()));
+
+  a = ReturnRefOfCopy(derived);
+  EXPECT_NE(&derived, &a.Perform(std::make_tuple()));
+}
+
+// Tests that ReturnRoundRobin(v) works with initializer lists
+TEST(ReturnRoundRobinTest, WorksForInitList) {
+  Action<int()> ret = ReturnRoundRobin({1, 2, 3});
+
+  EXPECT_EQ(1, ret.Perform(std::make_tuple()));
+  EXPECT_EQ(2, ret.Perform(std::make_tuple()));
+  EXPECT_EQ(3, ret.Perform(std::make_tuple()));
+  EXPECT_EQ(1, ret.Perform(std::make_tuple()));
+  EXPECT_EQ(2, ret.Perform(std::make_tuple()));
+  EXPECT_EQ(3, ret.Perform(std::make_tuple()));
+}
+
+// Tests that ReturnRoundRobin(v) works with vectors
+TEST(ReturnRoundRobinTest, WorksForVector) {
+  std::vector<double> v = {4.4, 5.5, 6.6};
+  Action<double()> ret = ReturnRoundRobin(v);
+
+  EXPECT_EQ(4.4, ret.Perform(std::make_tuple()));
+  EXPECT_EQ(5.5, ret.Perform(std::make_tuple()));
+  EXPECT_EQ(6.6, ret.Perform(std::make_tuple()));
+  EXPECT_EQ(4.4, ret.Perform(std::make_tuple()));
+  EXPECT_EQ(5.5, ret.Perform(std::make_tuple()));
+  EXPECT_EQ(6.6, ret.Perform(std::make_tuple()));
+}
+
+// Tests that DoDefault() does the default action for the mock method.
+
+class MockClass {
+ public:
+  MockClass() {}
+
+  MOCK_METHOD1(IntFunc, int(bool flag));  // NOLINT
+  MOCK_METHOD0(Foo, MyNonDefaultConstructible());
+  MOCK_METHOD0(MakeUnique, std::unique_ptr<int>());
+  MOCK_METHOD0(MakeUniqueBase, std::unique_ptr<Base>());
+  MOCK_METHOD0(MakeVectorUnique, std::vector<std::unique_ptr<int>>());
+  MOCK_METHOD1(TakeUnique, int(std::unique_ptr<int>));
+  MOCK_METHOD2(TakeUnique,
+               int(const std::unique_ptr<int>&, std::unique_ptr<int>));
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(MockClass);
+};
+
+// Tests that DoDefault() returns the built-in default value for the
+// return type by default.
+TEST(DoDefaultTest, ReturnsBuiltInDefaultValueByDefault) {
+  MockClass mock;
+  EXPECT_CALL(mock, IntFunc(_))
+      .WillOnce(DoDefault());
+  EXPECT_EQ(0, mock.IntFunc(true));
+}
+
+// Tests that DoDefault() throws (when exceptions are enabled) or aborts
+// the process when there is no built-in default value for the return type.
+TEST(DoDefaultDeathTest, DiesForUnknowType) {
+  MockClass mock;
+  EXPECT_CALL(mock, Foo())
+      .WillRepeatedly(DoDefault());
+#if GTEST_HAS_EXCEPTIONS
+  EXPECT_ANY_THROW(mock.Foo());
+#else
+  EXPECT_DEATH_IF_SUPPORTED({
+    mock.Foo();
+  }, "");
+#endif
+}
+
+// Tests that using DoDefault() inside a composite action leads to a
+// run-time error.
+
+void VoidFunc(bool /* flag */) {}
+
+TEST(DoDefaultDeathTest, DiesIfUsedInCompositeAction) {
+  MockClass mock;
+  EXPECT_CALL(mock, IntFunc(_))
+      .WillRepeatedly(DoAll(Invoke(VoidFunc),
+                            DoDefault()));
+
+  // Ideally we should verify the error message as well.  Sadly,
+  // EXPECT_DEATH() can only capture stderr, while Google Mock's
+  // errors are printed on stdout.  Therefore we have to settle for
+  // not verifying the message.
+  EXPECT_DEATH_IF_SUPPORTED({
+    mock.IntFunc(true);
+  }, "");
+}
+
+// Tests that DoDefault() returns the default value set by
+// DefaultValue<T>::Set() when it's not overridden by an ON_CALL().
+TEST(DoDefaultTest, ReturnsUserSpecifiedPerTypeDefaultValueWhenThereIsOne) {
+  DefaultValue<int>::Set(1);
+  MockClass mock;
+  EXPECT_CALL(mock, IntFunc(_))
+      .WillOnce(DoDefault());
+  EXPECT_EQ(1, mock.IntFunc(false));
+  DefaultValue<int>::Clear();
+}
+
+// Tests that DoDefault() does the action specified by ON_CALL().
+TEST(DoDefaultTest, DoesWhatOnCallSpecifies) {
+  MockClass mock;
+  ON_CALL(mock, IntFunc(_))
+      .WillByDefault(Return(2));
+  EXPECT_CALL(mock, IntFunc(_))
+      .WillOnce(DoDefault());
+  EXPECT_EQ(2, mock.IntFunc(false));
+}
+
+// Tests that using DoDefault() in ON_CALL() leads to a run-time failure.
+TEST(DoDefaultTest, CannotBeUsedInOnCall) {
+  MockClass mock;
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    ON_CALL(mock, IntFunc(_))
+      .WillByDefault(DoDefault());
+  }, "DoDefault() cannot be used in ON_CALL()");
+}
+
+// Tests that SetArgPointee<N>(v) sets the variable pointed to by
+// the N-th (0-based) argument to v.
+TEST(SetArgPointeeTest, SetsTheNthPointee) {
+  typedef void MyFunction(bool, int*, char*);
+  Action<MyFunction> a = SetArgPointee<1>(2);
+
+  int n = 0;
+  char ch = '\0';
+  a.Perform(std::make_tuple(true, &n, &ch));
+  EXPECT_EQ(2, n);
+  EXPECT_EQ('\0', ch);
+
+  a = SetArgPointee<2>('a');
+  n = 0;
+  ch = '\0';
+  a.Perform(std::make_tuple(true, &n, &ch));
+  EXPECT_EQ(0, n);
+  EXPECT_EQ('a', ch);
+}
+
+// Tests that SetArgPointee<N>() accepts a string literal.
+TEST(SetArgPointeeTest, AcceptsStringLiteral) {
+  typedef void MyFunction(std::string*, const char**);
+  Action<MyFunction> a = SetArgPointee<0>("hi");
+  std::string str;
+  const char* ptr = nullptr;
+  a.Perform(std::make_tuple(&str, &ptr));
+  EXPECT_EQ("hi", str);
+  EXPECT_TRUE(ptr == nullptr);
+
+  a = SetArgPointee<1>("world");
+  str = "";
+  a.Perform(std::make_tuple(&str, &ptr));
+  EXPECT_EQ("", str);
+  EXPECT_STREQ("world", ptr);
+}
+
+TEST(SetArgPointeeTest, AcceptsWideStringLiteral) {
+  typedef void MyFunction(const wchar_t**);
+  Action<MyFunction> a = SetArgPointee<0>(L"world");
+  const wchar_t* ptr = nullptr;
+  a.Perform(std::make_tuple(&ptr));
+  EXPECT_STREQ(L"world", ptr);
+
+# if GTEST_HAS_STD_WSTRING
+
+  typedef void MyStringFunction(std::wstring*);
+  Action<MyStringFunction> a2 = SetArgPointee<0>(L"world");
+  std::wstring str = L"";
+  a2.Perform(std::make_tuple(&str));
+  EXPECT_EQ(L"world", str);
+
+# endif
+}
+
+// Tests that SetArgPointee<N>() accepts a char pointer.
+TEST(SetArgPointeeTest, AcceptsCharPointer) {
+  typedef void MyFunction(bool, std::string*, const char**);
+  const char* const hi = "hi";
+  Action<MyFunction> a = SetArgPointee<1>(hi);
+  std::string str;
+  const char* ptr = nullptr;
+  a.Perform(std::make_tuple(true, &str, &ptr));
+  EXPECT_EQ("hi", str);
+  EXPECT_TRUE(ptr == nullptr);
+
+  char world_array[] = "world";
+  char* const world = world_array;
+  a = SetArgPointee<2>(world);
+  str = "";
+  a.Perform(std::make_tuple(true, &str, &ptr));
+  EXPECT_EQ("", str);
+  EXPECT_EQ(world, ptr);
+}
+
+TEST(SetArgPointeeTest, AcceptsWideCharPointer) {
+  typedef void MyFunction(bool, const wchar_t**);
+  const wchar_t* const hi = L"hi";
+  Action<MyFunction> a = SetArgPointee<1>(hi);
+  const wchar_t* ptr = nullptr;
+  a.Perform(std::make_tuple(true, &ptr));
+  EXPECT_EQ(hi, ptr);
+
+# if GTEST_HAS_STD_WSTRING
+
+  typedef void MyStringFunction(bool, std::wstring*);
+  wchar_t world_array[] = L"world";
+  wchar_t* const world = world_array;
+  Action<MyStringFunction> a2 = SetArgPointee<1>(world);
+  std::wstring str;
+  a2.Perform(std::make_tuple(true, &str));
+  EXPECT_EQ(world_array, str);
+# endif
+}
+
+// Tests that SetArgumentPointee<N>(v) sets the variable pointed to by
+// the N-th (0-based) argument to v.
+TEST(SetArgumentPointeeTest, SetsTheNthPointee) {
+  typedef void MyFunction(bool, int*, char*);
+  Action<MyFunction> a = SetArgumentPointee<1>(2);
+
+  int n = 0;
+  char ch = '\0';
+  a.Perform(std::make_tuple(true, &n, &ch));
+  EXPECT_EQ(2, n);
+  EXPECT_EQ('\0', ch);
+
+  a = SetArgumentPointee<2>('a');
+  n = 0;
+  ch = '\0';
+  a.Perform(std::make_tuple(true, &n, &ch));
+  EXPECT_EQ(0, n);
+  EXPECT_EQ('a', ch);
+}
+
+// Sample functions and functors for testing Invoke() and etc.
+int Nullary() { return 1; }
+
+class NullaryFunctor {
+ public:
+  int operator()() { return 2; }
+};
+
+bool g_done = false;
+void VoidNullary() { g_done = true; }
+
+class VoidNullaryFunctor {
+ public:
+  void operator()() { g_done = true; }
+};
+
+short Short(short n) { return n; }  // NOLINT
+char Char(char ch) { return ch; }
+
+const char* CharPtr(const char* s) { return s; }
+
+bool Unary(int x) { return x < 0; }
+
+const char* Binary(const char* input, short n) { return input + n; }  // NOLINT
+
+void VoidBinary(int, char) { g_done = true; }
+
+int Ternary(int x, char y, short z) { return x + y + z; }  // NOLINT
+
+int SumOf4(int a, int b, int c, int d) { return a + b + c + d; }
+
+class Foo {
+ public:
+  Foo() : value_(123) {}
+
+  int Nullary() const { return value_; }
+
+ private:
+  int value_;
+};
+
+// Tests InvokeWithoutArgs(function).
+TEST(InvokeWithoutArgsTest, Function) {
+  // As an action that takes one argument.
+  Action<int(int)> a = InvokeWithoutArgs(Nullary);  // NOLINT
+  EXPECT_EQ(1, a.Perform(std::make_tuple(2)));
+
+  // As an action that takes two arguments.
+  Action<int(int, double)> a2 = InvokeWithoutArgs(Nullary);  // NOLINT
+  EXPECT_EQ(1, a2.Perform(std::make_tuple(2, 3.5)));
+
+  // As an action that returns void.
+  Action<void(int)> a3 = InvokeWithoutArgs(VoidNullary);  // NOLINT
+  g_done = false;
+  a3.Perform(std::make_tuple(1));
+  EXPECT_TRUE(g_done);
+}
+
+// Tests InvokeWithoutArgs(functor).
+TEST(InvokeWithoutArgsTest, Functor) {
+  // As an action that takes no argument.
+  Action<int()> a = InvokeWithoutArgs(NullaryFunctor());  // NOLINT
+  EXPECT_EQ(2, a.Perform(std::make_tuple()));
+
+  // As an action that takes three arguments.
+  Action<int(int, double, char)> a2 =  // NOLINT
+      InvokeWithoutArgs(NullaryFunctor());
+  EXPECT_EQ(2, a2.Perform(std::make_tuple(3, 3.5, 'a')));
+
+  // As an action that returns void.
+  Action<void()> a3 = InvokeWithoutArgs(VoidNullaryFunctor());
+  g_done = false;
+  a3.Perform(std::make_tuple());
+  EXPECT_TRUE(g_done);
+}
+
+// Tests InvokeWithoutArgs(obj_ptr, method).
+TEST(InvokeWithoutArgsTest, Method) {
+  Foo foo;
+  Action<int(bool, char)> a =  // NOLINT
+      InvokeWithoutArgs(&foo, &Foo::Nullary);
+  EXPECT_EQ(123, a.Perform(std::make_tuple(true, 'a')));
+}
+
+// Tests using IgnoreResult() on a polymorphic action.
+TEST(IgnoreResultTest, PolymorphicAction) {
+  Action<void(int)> a = IgnoreResult(Return(5));  // NOLINT
+  a.Perform(std::make_tuple(1));
+}
+
+// Tests using IgnoreResult() on a monomorphic action.
+
+int ReturnOne() {
+  g_done = true;
+  return 1;
+}
+
+TEST(IgnoreResultTest, MonomorphicAction) {
+  g_done = false;
+  Action<void()> a = IgnoreResult(Invoke(ReturnOne));
+  a.Perform(std::make_tuple());
+  EXPECT_TRUE(g_done);
+}
+
+// Tests using IgnoreResult() on an action that returns a class type.
+
+MyNonDefaultConstructible ReturnMyNonDefaultConstructible(double /* x */) {
+  g_done = true;
+  return MyNonDefaultConstructible(42);
+}
+
+TEST(IgnoreResultTest, ActionReturningClass) {
+  g_done = false;
+  Action<void(int)> a =
+      IgnoreResult(Invoke(ReturnMyNonDefaultConstructible));  // NOLINT
+  a.Perform(std::make_tuple(2));
+  EXPECT_TRUE(g_done);
+}
+
+TEST(AssignTest, Int) {
+  int x = 0;
+  Action<void(int)> a = Assign(&x, 5);
+  a.Perform(std::make_tuple(0));
+  EXPECT_EQ(5, x);
+}
+
+TEST(AssignTest, String) {
+  ::std::string x;
+  Action<void(void)> a = Assign(&x, "Hello, world");
+  a.Perform(std::make_tuple());
+  EXPECT_EQ("Hello, world", x);
+}
+
+TEST(AssignTest, CompatibleTypes) {
+  double x = 0;
+  Action<void(int)> a = Assign(&x, 5);
+  a.Perform(std::make_tuple(0));
+  EXPECT_DOUBLE_EQ(5, x);
+}
+
+
+// Tests using WithArgs and with an action that takes 1 argument.
+TEST(WithArgsTest, OneArg) {
+  Action<bool(double x, int n)> a = WithArgs<1>(Invoke(Unary));  // NOLINT
+  EXPECT_TRUE(a.Perform(std::make_tuple(1.5, -1)));
+  EXPECT_FALSE(a.Perform(std::make_tuple(1.5, 1)));
+}
+
+// Tests using WithArgs with an action that takes 2 arguments.
+TEST(WithArgsTest, TwoArgs) {
+  Action<const char*(const char* s, double x, short n)> a =  // NOLINT
+      WithArgs<0, 2>(Invoke(Binary));
+  const char s[] = "Hello";
+  EXPECT_EQ(s + 2, a.Perform(std::make_tuple(CharPtr(s), 0.5, Short(2))));
+}
+
+struct ConcatAll {
+  std::string operator()() const { return {}; }
+  template <typename... I>
+  std::string operator()(const char* a, I... i) const {
+    return a + ConcatAll()(i...);
+  }
+};
+
+// Tests using WithArgs with an action that takes 10 arguments.
+TEST(WithArgsTest, TenArgs) {
+  Action<std::string(const char*, const char*, const char*, const char*)> a =
+      WithArgs<0, 1, 2, 3, 2, 1, 0, 1, 2, 3>(Invoke(ConcatAll{}));
+  EXPECT_EQ("0123210123",
+            a.Perform(std::make_tuple(CharPtr("0"), CharPtr("1"), CharPtr("2"),
+                                      CharPtr("3"))));
+}
+
+// Tests using WithArgs with an action that is not Invoke().
+class SubtractAction : public ActionInterface<int(int, int)> {
+ public:
+  int Perform(const std::tuple<int, int>& args) override {
+    return std::get<0>(args) - std::get<1>(args);
+  }
+};
+
+TEST(WithArgsTest, NonInvokeAction) {
+  Action<int(const std::string&, int, int)> a =
+      WithArgs<2, 1>(MakeAction(new SubtractAction));
+  std::tuple<std::string, int, int> dummy =
+      std::make_tuple(std::string("hi"), 2, 10);
+  EXPECT_EQ(8, a.Perform(dummy));
+}
+
+// Tests using WithArgs to pass all original arguments in the original order.
+TEST(WithArgsTest, Identity) {
+  Action<int(int x, char y, short z)> a =  // NOLINT
+      WithArgs<0, 1, 2>(Invoke(Ternary));
+  EXPECT_EQ(123, a.Perform(std::make_tuple(100, Char(20), Short(3))));
+}
+
+// Tests using WithArgs with repeated arguments.
+TEST(WithArgsTest, RepeatedArguments) {
+  Action<int(bool, int m, int n)> a =  // NOLINT
+      WithArgs<1, 1, 1, 1>(Invoke(SumOf4));
+  EXPECT_EQ(4, a.Perform(std::make_tuple(false, 1, 10)));
+}
+
+// Tests using WithArgs with reversed argument order.
+TEST(WithArgsTest, ReversedArgumentOrder) {
+  Action<const char*(short n, const char* input)> a =  // NOLINT
+      WithArgs<1, 0>(Invoke(Binary));
+  const char s[] = "Hello";
+  EXPECT_EQ(s + 2, a.Perform(std::make_tuple(Short(2), CharPtr(s))));
+}
+
+// Tests using WithArgs with compatible, but not identical, argument types.
+TEST(WithArgsTest, ArgsOfCompatibleTypes) {
+  Action<long(short x, char y, double z, char c)> a =  // NOLINT
+      WithArgs<0, 1, 3>(Invoke(Ternary));
+  EXPECT_EQ(123,
+            a.Perform(std::make_tuple(Short(100), Char(20), 5.6, Char(3))));
+}
+
+// Tests using WithArgs with an action that returns void.
+TEST(WithArgsTest, VoidAction) {
+  Action<void(double x, char c, int n)> a = WithArgs<2, 1>(Invoke(VoidBinary));
+  g_done = false;
+  a.Perform(std::make_tuple(1.5, 'a', 3));
+  EXPECT_TRUE(g_done);
+}
+
+TEST(WithArgsTest, ReturnReference) {
+  Action<int&(int&, void*)> aa = WithArgs<0>([](int& a) -> int& { return a; });
+  int i = 0;
+  const int& res = aa.Perform(std::forward_as_tuple(i, nullptr));
+  EXPECT_EQ(&i, &res);
+}
+
+TEST(WithArgsTest, InnerActionWithConversion) {
+  Action<Derived*()> inner = [] { return nullptr; };
+  Action<Base*(double)> a = testing::WithoutArgs(inner);
+  EXPECT_EQ(nullptr, a.Perform(std::make_tuple(1.1)));
+}
+
+#if !GTEST_OS_WINDOWS_MOBILE
+
+class SetErrnoAndReturnTest : public testing::Test {
+ protected:
+  void SetUp() override { errno = 0; }
+  void TearDown() override { errno = 0; }
+};
+
+TEST_F(SetErrnoAndReturnTest, Int) {
+  Action<int(void)> a = SetErrnoAndReturn(ENOTTY, -5);
+  EXPECT_EQ(-5, a.Perform(std::make_tuple()));
+  EXPECT_EQ(ENOTTY, errno);
+}
+
+TEST_F(SetErrnoAndReturnTest, Ptr) {
+  int x;
+  Action<int*(void)> a = SetErrnoAndReturn(ENOTTY, &x);
+  EXPECT_EQ(&x, a.Perform(std::make_tuple()));
+  EXPECT_EQ(ENOTTY, errno);
+}
+
+TEST_F(SetErrnoAndReturnTest, CompatibleTypes) {
+  Action<double()> a = SetErrnoAndReturn(EINVAL, 5);
+  EXPECT_DOUBLE_EQ(5.0, a.Perform(std::make_tuple()));
+  EXPECT_EQ(EINVAL, errno);
+}
+
+#endif  // !GTEST_OS_WINDOWS_MOBILE
+
+// Tests ByRef().
+
+// Tests that the result of ByRef() is copyable.
+TEST(ByRefTest, IsCopyable) {
+  const std::string s1 = "Hi";
+  const std::string s2 = "Hello";
+
+  auto ref_wrapper = ByRef(s1);
+  const std::string& r1 = ref_wrapper;
+  EXPECT_EQ(&s1, &r1);
+
+  // Assigns a new value to ref_wrapper.
+  ref_wrapper = ByRef(s2);
+  const std::string& r2 = ref_wrapper;
+  EXPECT_EQ(&s2, &r2);
+
+  auto ref_wrapper1 = ByRef(s1);
+  // Copies ref_wrapper1 to ref_wrapper.
+  ref_wrapper = ref_wrapper1;
+  const std::string& r3 = ref_wrapper;
+  EXPECT_EQ(&s1, &r3);
+}
+
+// Tests using ByRef() on a const value.
+TEST(ByRefTest, ConstValue) {
+  const int n = 0;
+  // int& ref = ByRef(n);  // This shouldn't compile - we have a
+                           // negative compilation test to catch it.
+  const int& const_ref = ByRef(n);
+  EXPECT_EQ(&n, &const_ref);
+}
+
+// Tests using ByRef() on a non-const value.
+TEST(ByRefTest, NonConstValue) {
+  int n = 0;
+
+  // ByRef(n) can be used as either an int&,
+  int& ref = ByRef(n);
+  EXPECT_EQ(&n, &ref);
+
+  // or a const int&.
+  const int& const_ref = ByRef(n);
+  EXPECT_EQ(&n, &const_ref);
+}
+
+// Tests explicitly specifying the type when using ByRef().
+TEST(ByRefTest, ExplicitType) {
+  int n = 0;
+  const int& r1 = ByRef<const int>(n);
+  EXPECT_EQ(&n, &r1);
+
+  // ByRef<char>(n);  // This shouldn't compile - we have a negative
+                      // compilation test to catch it.
+
+  Derived d;
+  Derived& r2 = ByRef<Derived>(d);
+  EXPECT_EQ(&d, &r2);
+
+  const Derived& r3 = ByRef<const Derived>(d);
+  EXPECT_EQ(&d, &r3);
+
+  Base& r4 = ByRef<Base>(d);
+  EXPECT_EQ(&d, &r4);
+
+  const Base& r5 = ByRef<const Base>(d);
+  EXPECT_EQ(&d, &r5);
+
+  // The following shouldn't compile - we have a negative compilation
+  // test for it.
+  //
+  // Base b;
+  // ByRef<Derived>(b);
+}
+
+// Tests that Google Mock prints expression ByRef(x) as a reference to x.
+TEST(ByRefTest, PrintsCorrectly) {
+  int n = 42;
+  ::std::stringstream expected, actual;
+  testing::internal::UniversalPrinter<const int&>::Print(n, &expected);
+  testing::internal::UniversalPrint(ByRef(n), &actual);
+  EXPECT_EQ(expected.str(), actual.str());
+}
+
+struct UnaryConstructorClass {
+  explicit UnaryConstructorClass(int v) : value(v) {}
+  int value;
+};
+
+// Tests using ReturnNew() with a unary constructor.
+TEST(ReturnNewTest, Unary) {
+  Action<UnaryConstructorClass*()> a = ReturnNew<UnaryConstructorClass>(4000);
+  UnaryConstructorClass* c = a.Perform(std::make_tuple());
+  EXPECT_EQ(4000, c->value);
+  delete c;
+}
+
+TEST(ReturnNewTest, UnaryWorksWhenMockMethodHasArgs) {
+  Action<UnaryConstructorClass*(bool, int)> a =
+      ReturnNew<UnaryConstructorClass>(4000);
+  UnaryConstructorClass* c = a.Perform(std::make_tuple(false, 5));
+  EXPECT_EQ(4000, c->value);
+  delete c;
+}
+
+TEST(ReturnNewTest, UnaryWorksWhenMockMethodReturnsPointerToConst) {
+  Action<const UnaryConstructorClass*()> a =
+      ReturnNew<UnaryConstructorClass>(4000);
+  const UnaryConstructorClass* c = a.Perform(std::make_tuple());
+  EXPECT_EQ(4000, c->value);
+  delete c;
+}
+
+class TenArgConstructorClass {
+ public:
+  TenArgConstructorClass(int a1, int a2, int a3, int a4, int a5, int a6, int a7,
+                         int a8, int a9, int a10)
+      : value_(a1 + a2 + a3 + a4 + a5 + a6 + a7 + a8 + a9 + a10) {}
+  int value_;
+};
+
+// Tests using ReturnNew() with a 10-argument constructor.
+TEST(ReturnNewTest, ConstructorThatTakes10Arguments) {
+  Action<TenArgConstructorClass*()> a = ReturnNew<TenArgConstructorClass>(
+      1000000000, 200000000, 30000000, 4000000, 500000, 60000, 7000, 800, 90,
+      0);
+  TenArgConstructorClass* c = a.Perform(std::make_tuple());
+  EXPECT_EQ(1234567890, c->value_);
+  delete c;
+}
+
+std::unique_ptr<int> UniquePtrSource() {
+  return std::unique_ptr<int>(new int(19));
+}
+
+std::vector<std::unique_ptr<int>> VectorUniquePtrSource() {
+  std::vector<std::unique_ptr<int>> out;
+  out.emplace_back(new int(7));
+  return out;
+}
+
+TEST(MockMethodTest, CanReturnMoveOnlyValue_Return) {
+  MockClass mock;
+  std::unique_ptr<int> i(new int(19));
+  EXPECT_CALL(mock, MakeUnique()).WillOnce(Return(ByMove(std::move(i))));
+  EXPECT_CALL(mock, MakeVectorUnique())
+      .WillOnce(Return(ByMove(VectorUniquePtrSource())));
+  Derived* d = new Derived;
+  EXPECT_CALL(mock, MakeUniqueBase())
+      .WillOnce(Return(ByMove(std::unique_ptr<Derived>(d))));
+
+  std::unique_ptr<int> result1 = mock.MakeUnique();
+  EXPECT_EQ(19, *result1);
+
+  std::vector<std::unique_ptr<int>> vresult = mock.MakeVectorUnique();
+  EXPECT_EQ(1u, vresult.size());
+  EXPECT_NE(nullptr, vresult[0]);
+  EXPECT_EQ(7, *vresult[0]);
+
+  std::unique_ptr<Base> result2 = mock.MakeUniqueBase();
+  EXPECT_EQ(d, result2.get());
+}
+
+TEST(MockMethodTest, CanReturnMoveOnlyValue_DoAllReturn) {
+  testing::MockFunction<void()> mock_function;
+  MockClass mock;
+  std::unique_ptr<int> i(new int(19));
+  EXPECT_CALL(mock_function, Call());
+  EXPECT_CALL(mock, MakeUnique()).WillOnce(DoAll(
+      InvokeWithoutArgs(&mock_function, &testing::MockFunction<void()>::Call),
+      Return(ByMove(std::move(i)))));
+
+  std::unique_ptr<int> result1 = mock.MakeUnique();
+  EXPECT_EQ(19, *result1);
+}
+
+TEST(MockMethodTest, CanReturnMoveOnlyValue_Invoke) {
+  MockClass mock;
+
+  // Check default value
+  DefaultValue<std::unique_ptr<int>>::SetFactory([] {
+    return std::unique_ptr<int>(new int(42));
+  });
+  EXPECT_EQ(42, *mock.MakeUnique());
+
+  EXPECT_CALL(mock, MakeUnique()).WillRepeatedly(Invoke(UniquePtrSource));
+  EXPECT_CALL(mock, MakeVectorUnique())
+      .WillRepeatedly(Invoke(VectorUniquePtrSource));
+  std::unique_ptr<int> result1 = mock.MakeUnique();
+  EXPECT_EQ(19, *result1);
+  std::unique_ptr<int> result2 = mock.MakeUnique();
+  EXPECT_EQ(19, *result2);
+  EXPECT_NE(result1, result2);
+
+  std::vector<std::unique_ptr<int>> vresult = mock.MakeVectorUnique();
+  EXPECT_EQ(1u, vresult.size());
+  EXPECT_NE(nullptr, vresult[0]);
+  EXPECT_EQ(7, *vresult[0]);
+}
+
+TEST(MockMethodTest, CanTakeMoveOnlyValue) {
+  MockClass mock;
+  auto make = [](int i) { return std::unique_ptr<int>(new int(i)); };
+
+  EXPECT_CALL(mock, TakeUnique(_)).WillRepeatedly([](std::unique_ptr<int> i) {
+    return *i;
+  });
+  // DoAll() does not compile, since it would move from its arguments twice.
+  // EXPECT_CALL(mock, TakeUnique(_, _))
+  //     .WillRepeatedly(DoAll(Invoke([](std::unique_ptr<int> j) {}),
+  //     Return(1)));
+  EXPECT_CALL(mock, TakeUnique(testing::Pointee(7)))
+      .WillOnce(Return(-7))
+      .RetiresOnSaturation();
+  EXPECT_CALL(mock, TakeUnique(testing::IsNull()))
+      .WillOnce(Return(-1))
+      .RetiresOnSaturation();
+
+  EXPECT_EQ(5, mock.TakeUnique(make(5)));
+  EXPECT_EQ(-7, mock.TakeUnique(make(7)));
+  EXPECT_EQ(7, mock.TakeUnique(make(7)));
+  EXPECT_EQ(7, mock.TakeUnique(make(7)));
+  EXPECT_EQ(-1, mock.TakeUnique({}));
+
+  // Some arguments are moved, some passed by reference.
+  auto lvalue = make(6);
+  EXPECT_CALL(mock, TakeUnique(_, _))
+      .WillOnce([](const std::unique_ptr<int>& i, std::unique_ptr<int> j) {
+        return *i * *j;
+      });
+  EXPECT_EQ(42, mock.TakeUnique(lvalue, make(7)));
+
+  // The unique_ptr can be saved by the action.
+  std::unique_ptr<int> saved;
+  EXPECT_CALL(mock, TakeUnique(_)).WillOnce([&saved](std::unique_ptr<int> i) {
+    saved = std::move(i);
+    return 0;
+  });
+  EXPECT_EQ(0, mock.TakeUnique(make(42)));
+  EXPECT_EQ(42, *saved);
+}
+
+
+// Tests for std::function based action.
+
+int Add(int val, int& ref, int* ptr) {  // NOLINT
+  int result = val + ref + *ptr;
+  ref = 42;
+  *ptr = 43;
+  return result;
+}
+
+int Deref(std::unique_ptr<int> ptr) { return *ptr; }
+
+struct Double {
+  template <typename T>
+  T operator()(T t) { return 2 * t; }
+};
+
+std::unique_ptr<int> UniqueInt(int i) {
+  return std::unique_ptr<int>(new int(i));
+}
+
+TEST(FunctorActionTest, ActionFromFunction) {
+  Action<int(int, int&, int*)> a = &Add;
+  int x = 1, y = 2, z = 3;
+  EXPECT_EQ(6, a.Perform(std::forward_as_tuple(x, y, &z)));
+  EXPECT_EQ(42, y);
+  EXPECT_EQ(43, z);
+
+  Action<int(std::unique_ptr<int>)> a1 = &Deref;
+  EXPECT_EQ(7, a1.Perform(std::make_tuple(UniqueInt(7))));
+}
+
+TEST(FunctorActionTest, ActionFromLambda) {
+  Action<int(bool, int)> a1 = [](bool b, int i) { return b ? i : 0; };
+  EXPECT_EQ(5, a1.Perform(std::make_tuple(true, 5)));
+  EXPECT_EQ(0, a1.Perform(std::make_tuple(false, 5)));
+
+  std::unique_ptr<int> saved;
+  Action<void(std::unique_ptr<int>)> a2 = [&saved](std::unique_ptr<int> p) {
+    saved = std::move(p);
+  };
+  a2.Perform(std::make_tuple(UniqueInt(5)));
+  EXPECT_EQ(5, *saved);
+}
+
+TEST(FunctorActionTest, PolymorphicFunctor) {
+  Action<int(int)> ai = Double();
+  EXPECT_EQ(2, ai.Perform(std::make_tuple(1)));
+  Action<double(double)> ad = Double();  // Double? Double double!
+  EXPECT_EQ(3.0, ad.Perform(std::make_tuple(1.5)));
+}
+
+TEST(FunctorActionTest, TypeConversion) {
+  // Numeric promotions are allowed.
+  const Action<bool(int)> a1 = [](int i) { return i > 1; };
+  const Action<int(bool)> a2 = Action<int(bool)>(a1);
+  EXPECT_EQ(1, a1.Perform(std::make_tuple(42)));
+  EXPECT_EQ(0, a2.Perform(std::make_tuple(42)));
+
+  // Implicit constructors are allowed.
+  const Action<bool(std::string)> s1 = [](std::string s) { return !s.empty(); };
+  const Action<int(const char*)> s2 = Action<int(const char*)>(s1);
+  EXPECT_EQ(0, s2.Perform(std::make_tuple("")));
+  EXPECT_EQ(1, s2.Perform(std::make_tuple("hello")));
+
+  // Also between the lambda and the action itself.
+  const Action<bool(std::string)> x1 = [](Unused) { return 42; };
+  const Action<bool(std::string)> x2 = [] { return 42; };
+  EXPECT_TRUE(x1.Perform(std::make_tuple("hello")));
+  EXPECT_TRUE(x2.Perform(std::make_tuple("hello")));
+
+  // Ensure decay occurs where required.
+  std::function<int()> f = [] { return 7; };
+  Action<int(int)> d = f;
+  f = nullptr;
+  EXPECT_EQ(7, d.Perform(std::make_tuple(1)));
+
+  // Ensure creation of an empty action succeeds.
+  Action<void(int)>(nullptr);
+}
+
+TEST(FunctorActionTest, UnusedArguments) {
+  // Verify that users can ignore uninteresting arguments.
+  Action<int(int, double y, double z)> a =
+      [](int i, Unused, Unused) { return 2 * i; };
+  std::tuple<int, double, double> dummy = std::make_tuple(3, 7.3, 9.44);
+  EXPECT_EQ(6, a.Perform(dummy));
+}
+
+// Test that basic built-in actions work with move-only arguments.
+TEST(MoveOnlyArgumentsTest, ReturningActions) {
+  Action<int(std::unique_ptr<int>)> a = Return(1);
+  EXPECT_EQ(1, a.Perform(std::make_tuple(nullptr)));
+
+  a = testing::WithoutArgs([]() { return 7; });
+  EXPECT_EQ(7, a.Perform(std::make_tuple(nullptr)));
+
+  Action<void(std::unique_ptr<int>, int*)> a2 = testing::SetArgPointee<1>(3);
+  int x = 0;
+  a2.Perform(std::make_tuple(nullptr, &x));
+  EXPECT_EQ(x, 3);
+}
+
+ACTION(ReturnArity) {
+  return std::tuple_size<args_type>::value;
+}
+
+TEST(ActionMacro, LargeArity) {
+  EXPECT_EQ(
+      1, testing::Action<int(int)>(ReturnArity()).Perform(std::make_tuple(0)));
+  EXPECT_EQ(
+      10,
+      testing::Action<int(int, int, int, int, int, int, int, int, int, int)>(
+          ReturnArity())
+          .Perform(std::make_tuple(0, 1, 2, 3, 4, 5, 6, 7, 8, 9)));
+  EXPECT_EQ(
+      20,
+      testing::Action<int(int, int, int, int, int, int, int, int, int, int, int,
+                          int, int, int, int, int, int, int, int, int)>(
+          ReturnArity())
+          .Perform(std::make_tuple(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,
+                                   14, 15, 16, 17, 18, 19)));
+}
+
+}  // Unnamed namespace
+
+#ifdef _MSC_VER
+#if _MSC_VER == 1900
+#  pragma warning(pop)
+#endif
+#endif
+
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock-cardinalities_test.cc b/leveldb_base/third_party/googletest/googlemock/test/gmock-cardinalities_test.cc
new file mode 100644
index 0000000..ca97cae
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock-cardinalities_test.cc
@@ -0,0 +1,429 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests the built-in cardinalities.
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "gtest/gtest-spi.h"
+
+namespace {
+
+using std::stringstream;
+using testing::AnyNumber;
+using testing::AtLeast;
+using testing::AtMost;
+using testing::Between;
+using testing::Cardinality;
+using testing::CardinalityInterface;
+using testing::Exactly;
+using testing::IsSubstring;
+using testing::MakeCardinality;
+
+class MockFoo {
+ public:
+  MockFoo() {}
+  MOCK_METHOD0(Bar, int());  // NOLINT
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(MockFoo);
+};
+
+// Tests that Cardinality objects can be default constructed.
+TEST(CardinalityTest, IsDefaultConstructable) {
+  Cardinality c;
+}
+
+// Tests that Cardinality objects are copyable.
+TEST(CardinalityTest, IsCopyable) {
+  // Tests the copy constructor.
+  Cardinality c = Exactly(1);
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(0));
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(1));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(1));
+
+  // Tests the assignment operator.
+  c = Exactly(2);
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(1));
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(2));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(2));
+}
+
+TEST(CardinalityTest, IsOverSaturatedByCallCountWorks) {
+  const Cardinality c = AtMost(5);
+  EXPECT_FALSE(c.IsOverSaturatedByCallCount(4));
+  EXPECT_FALSE(c.IsOverSaturatedByCallCount(5));
+  EXPECT_TRUE(c.IsOverSaturatedByCallCount(6));
+}
+
+// Tests that Cardinality::DescribeActualCallCountTo() creates the
+// correct description.
+TEST(CardinalityTest, CanDescribeActualCallCount) {
+  stringstream ss0;
+  Cardinality::DescribeActualCallCountTo(0, &ss0);
+  EXPECT_EQ("never called", ss0.str());
+
+  stringstream ss1;
+  Cardinality::DescribeActualCallCountTo(1, &ss1);
+  EXPECT_EQ("called once", ss1.str());
+
+  stringstream ss2;
+  Cardinality::DescribeActualCallCountTo(2, &ss2);
+  EXPECT_EQ("called twice", ss2.str());
+
+  stringstream ss3;
+  Cardinality::DescribeActualCallCountTo(3, &ss3);
+  EXPECT_EQ("called 3 times", ss3.str());
+}
+
+// Tests AnyNumber()
+TEST(AnyNumber, Works) {
+  const Cardinality c = AnyNumber();
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(0));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(0));
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(1));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(1));
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(9));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(9));
+
+  stringstream ss;
+  c.DescribeTo(&ss);
+  EXPECT_PRED_FORMAT2(IsSubstring, "called any number of times",
+                      ss.str());
+}
+
+TEST(AnyNumberTest, HasCorrectBounds) {
+  const Cardinality c = AnyNumber();
+  EXPECT_EQ(0, c.ConservativeLowerBound());
+  EXPECT_EQ(INT_MAX, c.ConservativeUpperBound());
+}
+
+// Tests AtLeast(n).
+
+TEST(AtLeastTest, OnNegativeNumber) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    AtLeast(-1);
+  }, "The invocation lower bound must be >= 0");
+}
+
+TEST(AtLeastTest, OnZero) {
+  const Cardinality c = AtLeast(0);
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(0));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(0));
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(1));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(1));
+
+  stringstream ss;
+  c.DescribeTo(&ss);
+  EXPECT_PRED_FORMAT2(IsSubstring, "any number of times",
+                      ss.str());
+}
+
+TEST(AtLeastTest, OnPositiveNumber) {
+  const Cardinality c = AtLeast(2);
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(0));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(0));
+
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(1));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(1));
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(2));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(2));
+
+  stringstream ss1;
+  AtLeast(1).DescribeTo(&ss1);
+  EXPECT_PRED_FORMAT2(IsSubstring, "at least once",
+                      ss1.str());
+
+  stringstream ss2;
+  c.DescribeTo(&ss2);
+  EXPECT_PRED_FORMAT2(IsSubstring, "at least twice",
+                      ss2.str());
+
+  stringstream ss3;
+  AtLeast(3).DescribeTo(&ss3);
+  EXPECT_PRED_FORMAT2(IsSubstring, "at least 3 times",
+                      ss3.str());
+}
+
+TEST(AtLeastTest, HasCorrectBounds) {
+  const Cardinality c = AtLeast(2);
+  EXPECT_EQ(2, c.ConservativeLowerBound());
+  EXPECT_EQ(INT_MAX, c.ConservativeUpperBound());
+}
+
+// Tests AtMost(n).
+
+TEST(AtMostTest, OnNegativeNumber) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    AtMost(-1);
+  }, "The invocation upper bound must be >= 0");
+}
+
+TEST(AtMostTest, OnZero) {
+  const Cardinality c = AtMost(0);
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(0));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(0));
+
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(1));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(1));
+
+  stringstream ss;
+  c.DescribeTo(&ss);
+  EXPECT_PRED_FORMAT2(IsSubstring, "never called",
+                      ss.str());
+}
+
+TEST(AtMostTest, OnPositiveNumber) {
+  const Cardinality c = AtMost(2);
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(0));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(0));
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(1));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(1));
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(2));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(2));
+
+  stringstream ss1;
+  AtMost(1).DescribeTo(&ss1);
+  EXPECT_PRED_FORMAT2(IsSubstring, "called at most once",
+                      ss1.str());
+
+  stringstream ss2;
+  c.DescribeTo(&ss2);
+  EXPECT_PRED_FORMAT2(IsSubstring, "called at most twice",
+                      ss2.str());
+
+  stringstream ss3;
+  AtMost(3).DescribeTo(&ss3);
+  EXPECT_PRED_FORMAT2(IsSubstring, "called at most 3 times",
+                      ss3.str());
+}
+
+TEST(AtMostTest, HasCorrectBounds) {
+  const Cardinality c = AtMost(2);
+  EXPECT_EQ(0, c.ConservativeLowerBound());
+  EXPECT_EQ(2, c.ConservativeUpperBound());
+}
+
+// Tests Between(m, n).
+
+TEST(BetweenTest, OnNegativeStart) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    Between(-1, 2);
+  }, "The invocation lower bound must be >= 0, but is actually -1");
+}
+
+TEST(BetweenTest, OnNegativeEnd) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    Between(1, -2);
+  }, "The invocation upper bound must be >= 0, but is actually -2");
+}
+
+TEST(BetweenTest, OnStartBiggerThanEnd) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    Between(2, 1);
+  }, "The invocation upper bound (1) must be >= "
+     "the invocation lower bound (2)");
+}
+
+TEST(BetweenTest, OnZeroStartAndZeroEnd) {
+  const Cardinality c = Between(0, 0);
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(0));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(0));
+
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(1));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(1));
+
+  stringstream ss;
+  c.DescribeTo(&ss);
+  EXPECT_PRED_FORMAT2(IsSubstring, "never called",
+                      ss.str());
+}
+
+TEST(BetweenTest, OnZeroStartAndNonZeroEnd) {
+  const Cardinality c = Between(0, 2);
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(0));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(0));
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(2));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(2));
+
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(4));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(4));
+
+  stringstream ss;
+  c.DescribeTo(&ss);
+  EXPECT_PRED_FORMAT2(IsSubstring, "called at most twice",
+                      ss.str());
+}
+
+TEST(BetweenTest, OnSameStartAndEnd) {
+  const Cardinality c = Between(3, 3);
+
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(2));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(2));
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(3));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(3));
+
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(4));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(4));
+
+  stringstream ss;
+  c.DescribeTo(&ss);
+  EXPECT_PRED_FORMAT2(IsSubstring, "called 3 times",
+                      ss.str());
+}
+
+TEST(BetweenTest, OnDifferentStartAndEnd) {
+  const Cardinality c = Between(3, 5);
+
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(2));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(2));
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(3));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(3));
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(5));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(5));
+
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(6));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(6));
+
+  stringstream ss;
+  c.DescribeTo(&ss);
+  EXPECT_PRED_FORMAT2(IsSubstring, "called between 3 and 5 times",
+                      ss.str());
+}
+
+TEST(BetweenTest, HasCorrectBounds) {
+  const Cardinality c = Between(3, 5);
+  EXPECT_EQ(3, c.ConservativeLowerBound());
+  EXPECT_EQ(5, c.ConservativeUpperBound());
+}
+
+// Tests Exactly(n).
+
+TEST(ExactlyTest, OnNegativeNumber) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    Exactly(-1);
+  }, "The invocation lower bound must be >= 0");
+}
+
+TEST(ExactlyTest, OnZero) {
+  const Cardinality c = Exactly(0);
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(0));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(0));
+
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(1));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(1));
+
+  stringstream ss;
+  c.DescribeTo(&ss);
+  EXPECT_PRED_FORMAT2(IsSubstring, "never called",
+                      ss.str());
+}
+
+TEST(ExactlyTest, OnPositiveNumber) {
+  const Cardinality c = Exactly(2);
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(0));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(0));
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(2));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(2));
+
+  stringstream ss1;
+  Exactly(1).DescribeTo(&ss1);
+  EXPECT_PRED_FORMAT2(IsSubstring, "called once",
+                      ss1.str());
+
+  stringstream ss2;
+  c.DescribeTo(&ss2);
+  EXPECT_PRED_FORMAT2(IsSubstring, "called twice",
+                      ss2.str());
+
+  stringstream ss3;
+  Exactly(3).DescribeTo(&ss3);
+  EXPECT_PRED_FORMAT2(IsSubstring, "called 3 times",
+                      ss3.str());
+}
+
+TEST(ExactlyTest, HasCorrectBounds) {
+  const Cardinality c = Exactly(3);
+  EXPECT_EQ(3, c.ConservativeLowerBound());
+  EXPECT_EQ(3, c.ConservativeUpperBound());
+}
+
+// Tests that a user can make their own cardinality by implementing
+// CardinalityInterface and calling MakeCardinality().
+
+class EvenCardinality : public CardinalityInterface {
+ public:
+  // Returns true if and only if call_count calls will satisfy this
+  // cardinality.
+  bool IsSatisfiedByCallCount(int call_count) const override {
+    return (call_count % 2 == 0);
+  }
+
+  // Returns true if and only if call_count calls will saturate this
+  // cardinality.
+  bool IsSaturatedByCallCount(int /* call_count */) const override {
+    return false;
+  }
+
+  // Describes self to an ostream.
+  void DescribeTo(::std::ostream* ss) const override {
+    *ss << "called even number of times";
+  }
+};
+
+TEST(MakeCardinalityTest, ConstructsCardinalityFromInterface) {
+  const Cardinality c = MakeCardinality(new EvenCardinality);
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(2));
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(3));
+
+  EXPECT_FALSE(c.IsSaturatedByCallCount(10000));
+
+  stringstream ss;
+  c.DescribeTo(&ss);
+  EXPECT_EQ("called even number of times", ss.str());
+}
+
+}  // Unnamed namespace
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock-function-mocker_test.cc b/leveldb_base/third_party/googletest/googlemock/test/gmock-function-mocker_test.cc
new file mode 100644
index 0000000..cf76fa9
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock-function-mocker_test.cc
@@ -0,0 +1,986 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests the function mocker classes.
+#include "gmock/gmock-function-mocker.h"
+
+#if GTEST_OS_WINDOWS
+// MSDN says the header file to be included for STDMETHOD is BaseTyps.h but
+// we are getting compiler errors if we use basetyps.h, hence including
+// objbase.h for definition of STDMETHOD.
+# include <objbase.h>
+#endif  // GTEST_OS_WINDOWS
+
+#include <functional>
+#include <map>
+#include <string>
+#include <type_traits>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+namespace testing {
+namespace gmock_function_mocker_test {
+
+using testing::_;
+using testing::A;
+using testing::An;
+using testing::AnyNumber;
+using testing::Const;
+using testing::DoDefault;
+using testing::Eq;
+using testing::Lt;
+using testing::MockFunction;
+using testing::Ref;
+using testing::Return;
+using testing::ReturnRef;
+using testing::TypedEq;
+
+template<typename T>
+class TemplatedCopyable {
+ public:
+  TemplatedCopyable() {}
+
+  template <typename U>
+  TemplatedCopyable(const U& other) {}  // NOLINT
+};
+
+class FooInterface {
+ public:
+  virtual ~FooInterface() {}
+
+  virtual void VoidReturning(int x) = 0;
+
+  virtual int Nullary() = 0;
+  virtual bool Unary(int x) = 0;
+  virtual long Binary(short x, int y) = 0;  // NOLINT
+  virtual int Decimal(bool b, char c, short d, int e, long f,  // NOLINT
+                      float g, double h, unsigned i, char* j,
+                      const std::string& k) = 0;
+
+  virtual bool TakesNonConstReference(int& n) = 0;  // NOLINT
+  virtual std::string TakesConstReference(const int& n) = 0;
+  virtual bool TakesConst(const int x) = 0;
+
+  virtual int OverloadedOnArgumentNumber() = 0;
+  virtual int OverloadedOnArgumentNumber(int n) = 0;
+
+  virtual int OverloadedOnArgumentType(int n) = 0;
+  virtual char OverloadedOnArgumentType(char c) = 0;
+
+  virtual int OverloadedOnConstness() = 0;
+  virtual char OverloadedOnConstness() const = 0;
+
+  virtual int TypeWithHole(int (*func)()) = 0;
+  virtual int TypeWithComma(const std::map<int, std::string>& a_map) = 0;
+  virtual int TypeWithTemplatedCopyCtor(const TemplatedCopyable<int>&) = 0;
+
+  virtual int (*ReturnsFunctionPointer1(int))(bool) = 0;
+  using fn_ptr = int (*)(bool);
+  virtual fn_ptr ReturnsFunctionPointer2(int) = 0;
+
+  virtual int RefQualifiedConstRef() const& = 0;
+  virtual int RefQualifiedConstRefRef() const&& = 0;
+  virtual int RefQualifiedRef() & = 0;
+  virtual int RefQualifiedRefRef() && = 0;
+
+  virtual int RefQualifiedOverloaded() const& = 0;
+  virtual int RefQualifiedOverloaded() const&& = 0;
+  virtual int RefQualifiedOverloaded() & = 0;
+  virtual int RefQualifiedOverloaded() && = 0;
+
+#if GTEST_OS_WINDOWS
+  STDMETHOD_(int, CTNullary)() = 0;
+  STDMETHOD_(bool, CTUnary)(int x) = 0;
+  STDMETHOD_(int, CTDecimal)
+  (bool b, char c, short d, int e, long f,  // NOLINT
+   float g, double h, unsigned i, char* j, const std::string& k) = 0;
+  STDMETHOD_(char, CTConst)(int x) const = 0;
+#endif  // GTEST_OS_WINDOWS
+};
+
+// Const qualifiers on arguments were once (incorrectly) considered
+// significant in determining whether two virtual functions had the same
+// signature. This was fixed in Visual Studio 2008. However, the compiler
+// still emits a warning that alerts about this change in behavior.
+#ifdef _MSC_VER
+# pragma warning(push)
+# pragma warning(disable : 4373)
+#endif
+class MockFoo : public FooInterface {
+ public:
+  MockFoo() {}
+
+  // Makes sure that a mock function parameter can be named.
+  MOCK_METHOD(void, VoidReturning, (int n));  // NOLINT
+
+  MOCK_METHOD(int, Nullary, ());  // NOLINT
+
+  // Makes sure that a mock function parameter can be unnamed.
+  MOCK_METHOD(bool, Unary, (int));          // NOLINT
+  MOCK_METHOD(long, Binary, (short, int));  // NOLINT
+  MOCK_METHOD(int, Decimal,
+              (bool, char, short, int, long, float,  // NOLINT
+               double, unsigned, char*, const std::string& str),
+              (override));
+
+  MOCK_METHOD(bool, TakesNonConstReference, (int&));  // NOLINT
+  MOCK_METHOD(std::string, TakesConstReference, (const int&));
+  MOCK_METHOD(bool, TakesConst, (const int));  // NOLINT
+
+  // Tests that the function return type can contain unprotected comma.
+  MOCK_METHOD((std::map<int, std::string>), ReturnTypeWithComma, (), ());
+  MOCK_METHOD((std::map<int, std::string>), ReturnTypeWithComma, (int),
+              (const));  // NOLINT
+
+  MOCK_METHOD(int, OverloadedOnArgumentNumber, ());     // NOLINT
+  MOCK_METHOD(int, OverloadedOnArgumentNumber, (int));  // NOLINT
+
+  MOCK_METHOD(int, OverloadedOnArgumentType, (int));    // NOLINT
+  MOCK_METHOD(char, OverloadedOnArgumentType, (char));  // NOLINT
+
+  MOCK_METHOD(int, OverloadedOnConstness, (), (override));          // NOLINT
+  MOCK_METHOD(char, OverloadedOnConstness, (), (override, const));  // NOLINT
+
+  MOCK_METHOD(int, TypeWithHole, (int (*)()), ());  // NOLINT
+  MOCK_METHOD(int, TypeWithComma, ((const std::map<int, std::string>&)));
+  MOCK_METHOD(int, TypeWithTemplatedCopyCtor,
+              (const TemplatedCopyable<int>&));  // NOLINT
+
+  MOCK_METHOD(int (*)(bool), ReturnsFunctionPointer1, (int), ());
+  MOCK_METHOD(fn_ptr, ReturnsFunctionPointer2, (int), ());
+
+#if GTEST_OS_WINDOWS
+  MOCK_METHOD(int, CTNullary, (), (Calltype(STDMETHODCALLTYPE)));
+  MOCK_METHOD(bool, CTUnary, (int), (Calltype(STDMETHODCALLTYPE)));
+  MOCK_METHOD(int, CTDecimal,
+              (bool b, char c, short d, int e, long f, float g, double h,
+               unsigned i, char* j, const std::string& k),
+              (Calltype(STDMETHODCALLTYPE)));
+  MOCK_METHOD(char, CTConst, (int), (const, Calltype(STDMETHODCALLTYPE)));
+  MOCK_METHOD((std::map<int, std::string>), CTReturnTypeWithComma, (),
+              (Calltype(STDMETHODCALLTYPE)));
+#endif  // GTEST_OS_WINDOWS
+
+  // Test reference qualified functions.
+  MOCK_METHOD(int, RefQualifiedConstRef, (), (const, ref(&), override));
+  MOCK_METHOD(int, RefQualifiedConstRefRef, (), (const, ref(&&), override));
+  MOCK_METHOD(int, RefQualifiedRef, (), (ref(&), override));
+  MOCK_METHOD(int, RefQualifiedRefRef, (), (ref(&&), override));
+
+  MOCK_METHOD(int, RefQualifiedOverloaded, (), (const, ref(&), override));
+  MOCK_METHOD(int, RefQualifiedOverloaded, (), (const, ref(&&), override));
+  MOCK_METHOD(int, RefQualifiedOverloaded, (), (ref(&), override));
+  MOCK_METHOD(int, RefQualifiedOverloaded, (), (ref(&&), override));
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(MockFoo);
+};
+
+class LegacyMockFoo : public FooInterface {
+ public:
+  LegacyMockFoo() {}
+
+  // Makes sure that a mock function parameter can be named.
+  MOCK_METHOD1(VoidReturning, void(int n));  // NOLINT
+
+  MOCK_METHOD0(Nullary, int());  // NOLINT
+
+  // Makes sure that a mock function parameter can be unnamed.
+  MOCK_METHOD1(Unary, bool(int));                                  // NOLINT
+  MOCK_METHOD2(Binary, long(short, int));                          // NOLINT
+  MOCK_METHOD10(Decimal, int(bool, char, short, int, long, float,  // NOLINT
+                             double, unsigned, char*, const std::string& str));
+
+  MOCK_METHOD1(TakesNonConstReference, bool(int&));  // NOLINT
+  MOCK_METHOD1(TakesConstReference, std::string(const int&));
+  MOCK_METHOD1(TakesConst, bool(const int));  // NOLINT
+
+  // Tests that the function return type can contain unprotected comma.
+  MOCK_METHOD0(ReturnTypeWithComma, std::map<int, std::string>());
+  MOCK_CONST_METHOD1(ReturnTypeWithComma,
+                     std::map<int, std::string>(int));  // NOLINT
+
+  MOCK_METHOD0(OverloadedOnArgumentNumber, int());     // NOLINT
+  MOCK_METHOD1(OverloadedOnArgumentNumber, int(int));  // NOLINT
+
+  MOCK_METHOD1(OverloadedOnArgumentType, int(int));    // NOLINT
+  MOCK_METHOD1(OverloadedOnArgumentType, char(char));  // NOLINT
+
+  MOCK_METHOD0(OverloadedOnConstness, int());         // NOLINT
+  MOCK_CONST_METHOD0(OverloadedOnConstness, char());  // NOLINT
+
+  MOCK_METHOD1(TypeWithHole, int(int (*)()));  // NOLINT
+  MOCK_METHOD1(TypeWithComma,
+               int(const std::map<int, std::string>&));  // NOLINT
+  MOCK_METHOD1(TypeWithTemplatedCopyCtor,
+               int(const TemplatedCopyable<int>&));  // NOLINT
+
+  MOCK_METHOD1(ReturnsFunctionPointer1, int (*(int))(bool));
+  MOCK_METHOD1(ReturnsFunctionPointer2, fn_ptr(int));
+
+#if GTEST_OS_WINDOWS
+  MOCK_METHOD0_WITH_CALLTYPE(STDMETHODCALLTYPE, CTNullary, int());
+  MOCK_METHOD1_WITH_CALLTYPE(STDMETHODCALLTYPE, CTUnary, bool(int));  // NOLINT
+  MOCK_METHOD10_WITH_CALLTYPE(STDMETHODCALLTYPE, CTDecimal,
+                              int(bool b, char c, short d, int e,  // NOLINT
+                                  long f, float g, double h,       // NOLINT
+                                  unsigned i, char* j, const std::string& k));
+  MOCK_CONST_METHOD1_WITH_CALLTYPE(STDMETHODCALLTYPE, CTConst,
+                                   char(int));  // NOLINT
+
+  // Tests that the function return type can contain unprotected comma.
+  MOCK_METHOD0_WITH_CALLTYPE(STDMETHODCALLTYPE, CTReturnTypeWithComma,
+                             std::map<int, std::string>());
+#endif  // GTEST_OS_WINDOWS
+
+  // We can't mock these with the old macros, but we need to define them to make
+  // it concrete.
+  int RefQualifiedConstRef() const& override { return 0; }
+  int RefQualifiedConstRefRef() const&& override { return 0; }
+  int RefQualifiedRef() & override { return 0; }
+  int RefQualifiedRefRef() && override { return 0; }
+  int RefQualifiedOverloaded() const& override { return 0; }
+  int RefQualifiedOverloaded() const&& override { return 0; }
+  int RefQualifiedOverloaded() & override { return 0; }
+  int RefQualifiedOverloaded() && override { return 0; }
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(LegacyMockFoo);
+};
+
+#ifdef _MSC_VER
+# pragma warning(pop)
+#endif
+
+template <class T>
+class FunctionMockerTest : public testing::Test {
+ protected:
+  FunctionMockerTest() : foo_(&mock_foo_) {}
+
+  FooInterface* const foo_;
+  T mock_foo_;
+};
+using FunctionMockerTestTypes = ::testing::Types<MockFoo, LegacyMockFoo>;
+TYPED_TEST_SUITE(FunctionMockerTest, FunctionMockerTestTypes);
+
+// Tests mocking a void-returning function.
+TYPED_TEST(FunctionMockerTest, MocksVoidFunction) {
+  EXPECT_CALL(this->mock_foo_, VoidReturning(Lt(100)));
+  this->foo_->VoidReturning(0);
+}
+
+// Tests mocking a nullary function.
+TYPED_TEST(FunctionMockerTest, MocksNullaryFunction) {
+  EXPECT_CALL(this->mock_foo_, Nullary())
+      .WillOnce(DoDefault())
+      .WillOnce(Return(1));
+
+  EXPECT_EQ(0, this->foo_->Nullary());
+  EXPECT_EQ(1, this->foo_->Nullary());
+}
+
+// Tests mocking a unary function.
+TYPED_TEST(FunctionMockerTest, MocksUnaryFunction) {
+  EXPECT_CALL(this->mock_foo_, Unary(Eq(2))).Times(2).WillOnce(Return(true));
+
+  EXPECT_TRUE(this->foo_->Unary(2));
+  EXPECT_FALSE(this->foo_->Unary(2));
+}
+
+// Tests mocking a binary function.
+TYPED_TEST(FunctionMockerTest, MocksBinaryFunction) {
+  EXPECT_CALL(this->mock_foo_, Binary(2, _)).WillOnce(Return(3));
+
+  EXPECT_EQ(3, this->foo_->Binary(2, 1));
+}
+
+// Tests mocking a decimal function.
+TYPED_TEST(FunctionMockerTest, MocksDecimalFunction) {
+  EXPECT_CALL(this->mock_foo_,
+              Decimal(true, 'a', 0, 0, 1L, A<float>(), Lt(100), 5U, NULL, "hi"))
+      .WillOnce(Return(5));
+
+  EXPECT_EQ(5, this->foo_->Decimal(true, 'a', 0, 0, 1, 0, 0, 5, nullptr, "hi"));
+}
+
+// Tests mocking a function that takes a non-const reference.
+TYPED_TEST(FunctionMockerTest, MocksFunctionWithNonConstReferenceArgument) {
+  int a = 0;
+  EXPECT_CALL(this->mock_foo_, TakesNonConstReference(Ref(a)))
+      .WillOnce(Return(true));
+
+  EXPECT_TRUE(this->foo_->TakesNonConstReference(a));
+}
+
+// Tests mocking a function that takes a const reference.
+TYPED_TEST(FunctionMockerTest, MocksFunctionWithConstReferenceArgument) {
+  int a = 0;
+  EXPECT_CALL(this->mock_foo_, TakesConstReference(Ref(a)))
+      .WillOnce(Return("Hello"));
+
+  EXPECT_EQ("Hello", this->foo_->TakesConstReference(a));
+}
+
+// Tests mocking a function that takes a const variable.
+TYPED_TEST(FunctionMockerTest, MocksFunctionWithConstArgument) {
+  EXPECT_CALL(this->mock_foo_, TakesConst(Lt(10))).WillOnce(DoDefault());
+
+  EXPECT_FALSE(this->foo_->TakesConst(5));
+}
+
+// Tests mocking functions overloaded on the number of arguments.
+TYPED_TEST(FunctionMockerTest, MocksFunctionsOverloadedOnArgumentNumber) {
+  EXPECT_CALL(this->mock_foo_, OverloadedOnArgumentNumber())
+      .WillOnce(Return(1));
+  EXPECT_CALL(this->mock_foo_, OverloadedOnArgumentNumber(_))
+      .WillOnce(Return(2));
+
+  EXPECT_EQ(2, this->foo_->OverloadedOnArgumentNumber(1));
+  EXPECT_EQ(1, this->foo_->OverloadedOnArgumentNumber());
+}
+
+// Tests mocking functions overloaded on the types of argument.
+TYPED_TEST(FunctionMockerTest, MocksFunctionsOverloadedOnArgumentType) {
+  EXPECT_CALL(this->mock_foo_, OverloadedOnArgumentType(An<int>()))
+      .WillOnce(Return(1));
+  EXPECT_CALL(this->mock_foo_, OverloadedOnArgumentType(TypedEq<char>('a')))
+      .WillOnce(Return('b'));
+
+  EXPECT_EQ(1, this->foo_->OverloadedOnArgumentType(0));
+  EXPECT_EQ('b', this->foo_->OverloadedOnArgumentType('a'));
+}
+
+// Tests mocking functions overloaded on the const-ness of this object.
+TYPED_TEST(FunctionMockerTest, MocksFunctionsOverloadedOnConstnessOfThis) {
+  EXPECT_CALL(this->mock_foo_, OverloadedOnConstness());
+  EXPECT_CALL(Const(this->mock_foo_), OverloadedOnConstness())
+      .WillOnce(Return('a'));
+
+  EXPECT_EQ(0, this->foo_->OverloadedOnConstness());
+  EXPECT_EQ('a', Const(*this->foo_).OverloadedOnConstness());
+}
+
+TYPED_TEST(FunctionMockerTest, MocksReturnTypeWithComma) {
+  const std::map<int, std::string> a_map;
+  EXPECT_CALL(this->mock_foo_, ReturnTypeWithComma()).WillOnce(Return(a_map));
+  EXPECT_CALL(this->mock_foo_, ReturnTypeWithComma(42)).WillOnce(Return(a_map));
+
+  EXPECT_EQ(a_map, this->mock_foo_.ReturnTypeWithComma());
+  EXPECT_EQ(a_map, this->mock_foo_.ReturnTypeWithComma(42));
+}
+
+TYPED_TEST(FunctionMockerTest, MocksTypeWithTemplatedCopyCtor) {
+  EXPECT_CALL(this->mock_foo_, TypeWithTemplatedCopyCtor(_))
+      .WillOnce(Return(true));
+  EXPECT_TRUE(this->foo_->TypeWithTemplatedCopyCtor(TemplatedCopyable<int>()));
+}
+
+#if GTEST_OS_WINDOWS
+// Tests mocking a nullary function with calltype.
+TYPED_TEST(FunctionMockerTest, MocksNullaryFunctionWithCallType) {
+  EXPECT_CALL(this->mock_foo_, CTNullary())
+      .WillOnce(Return(-1))
+      .WillOnce(Return(0));
+
+  EXPECT_EQ(-1, this->foo_->CTNullary());
+  EXPECT_EQ(0, this->foo_->CTNullary());
+}
+
+// Tests mocking a unary function with calltype.
+TYPED_TEST(FunctionMockerTest, MocksUnaryFunctionWithCallType) {
+  EXPECT_CALL(this->mock_foo_, CTUnary(Eq(2)))
+      .Times(2)
+      .WillOnce(Return(true))
+      .WillOnce(Return(false));
+
+  EXPECT_TRUE(this->foo_->CTUnary(2));
+  EXPECT_FALSE(this->foo_->CTUnary(2));
+}
+
+// Tests mocking a decimal function with calltype.
+TYPED_TEST(FunctionMockerTest, MocksDecimalFunctionWithCallType) {
+  EXPECT_CALL(this->mock_foo_, CTDecimal(true, 'a', 0, 0, 1L, A<float>(),
+                                         Lt(100), 5U, NULL, "hi"))
+      .WillOnce(Return(10));
+
+  EXPECT_EQ(10, this->foo_->CTDecimal(true, 'a', 0, 0, 1, 0, 0, 5, NULL, "hi"));
+}
+
+// Tests mocking functions overloaded on the const-ness of this object.
+TYPED_TEST(FunctionMockerTest, MocksFunctionsConstFunctionWithCallType) {
+  EXPECT_CALL(Const(this->mock_foo_), CTConst(_)).WillOnce(Return('a'));
+
+  EXPECT_EQ('a', Const(*this->foo_).CTConst(0));
+}
+
+TYPED_TEST(FunctionMockerTest, MocksReturnTypeWithCommaAndCallType) {
+  const std::map<int, std::string> a_map;
+  EXPECT_CALL(this->mock_foo_, CTReturnTypeWithComma()).WillOnce(Return(a_map));
+
+  EXPECT_EQ(a_map, this->mock_foo_.CTReturnTypeWithComma());
+}
+
+#endif  // GTEST_OS_WINDOWS
+
+TEST(FunctionMockerTest, RefQualified) {
+  MockFoo mock_foo;
+
+  EXPECT_CALL(mock_foo, RefQualifiedConstRef).WillOnce(Return(1));
+  EXPECT_CALL(std::move(mock_foo),  // NOLINT
+              RefQualifiedConstRefRef)
+      .WillOnce(Return(2));
+  EXPECT_CALL(mock_foo, RefQualifiedRef).WillOnce(Return(3));
+  EXPECT_CALL(std::move(mock_foo),  // NOLINT
+              RefQualifiedRefRef)
+      .WillOnce(Return(4));
+
+  EXPECT_CALL(static_cast<const MockFoo&>(mock_foo), RefQualifiedOverloaded())
+      .WillOnce(Return(5));
+  EXPECT_CALL(static_cast<const MockFoo&&>(mock_foo), RefQualifiedOverloaded())
+      .WillOnce(Return(6));
+  EXPECT_CALL(static_cast<MockFoo&>(mock_foo), RefQualifiedOverloaded())
+      .WillOnce(Return(7));
+  EXPECT_CALL(static_cast<MockFoo&&>(mock_foo), RefQualifiedOverloaded())
+      .WillOnce(Return(8));
+
+  EXPECT_EQ(mock_foo.RefQualifiedConstRef(), 1);
+  EXPECT_EQ(std::move(mock_foo).RefQualifiedConstRefRef(), 2);  // NOLINT
+  EXPECT_EQ(mock_foo.RefQualifiedRef(), 3);
+  EXPECT_EQ(std::move(mock_foo).RefQualifiedRefRef(), 4);  // NOLINT
+
+  EXPECT_EQ(std::cref(mock_foo).get().RefQualifiedOverloaded(), 5);
+  EXPECT_EQ(std::move(std::cref(mock_foo).get())  // NOLINT
+                .RefQualifiedOverloaded(),
+            6);
+  EXPECT_EQ(mock_foo.RefQualifiedOverloaded(), 7);
+  EXPECT_EQ(std::move(mock_foo).RefQualifiedOverloaded(), 8);  // NOLINT
+}
+
+class MockB {
+ public:
+  MockB() {}
+
+  MOCK_METHOD(void, DoB, ());
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(MockB);
+};
+
+class LegacyMockB {
+ public:
+  LegacyMockB() {}
+
+  MOCK_METHOD0(DoB, void());
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(LegacyMockB);
+};
+
+template <typename T>
+class ExpectCallTest : public ::testing::Test {};
+using ExpectCallTestTypes = ::testing::Types<MockB, LegacyMockB>;
+TYPED_TEST_SUITE(ExpectCallTest, ExpectCallTestTypes);
+
+// Tests that functions with no EXPECT_CALL() rules can be called any
+// number of times.
+TYPED_TEST(ExpectCallTest, UnmentionedFunctionCanBeCalledAnyNumberOfTimes) {
+  { TypeParam b; }
+
+  {
+    TypeParam b;
+    b.DoB();
+  }
+
+  {
+    TypeParam b;
+    b.DoB();
+    b.DoB();
+  }
+}
+
+// Tests mocking template interfaces.
+
+template <typename T>
+class StackInterface {
+ public:
+  virtual ~StackInterface() {}
+
+  // Template parameter appears in function parameter.
+  virtual void Push(const T& value) = 0;
+  virtual void Pop() = 0;
+  virtual int GetSize() const = 0;
+  // Template parameter appears in function return type.
+  virtual const T& GetTop() const = 0;
+};
+
+template <typename T>
+class MockStack : public StackInterface<T> {
+ public:
+  MockStack() {}
+
+  MOCK_METHOD(void, Push, (const T& elem), ());
+  MOCK_METHOD(void, Pop, (), (final));
+  MOCK_METHOD(int, GetSize, (), (const, override));
+  MOCK_METHOD(const T&, GetTop, (), (const));
+
+  // Tests that the function return type can contain unprotected comma.
+  MOCK_METHOD((std::map<int, int>), ReturnTypeWithComma, (), ());
+  MOCK_METHOD((std::map<int, int>), ReturnTypeWithComma, (int), (const));
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(MockStack);
+};
+
+template <typename T>
+class LegacyMockStack : public StackInterface<T> {
+ public:
+  LegacyMockStack() {}
+
+  MOCK_METHOD1_T(Push, void(const T& elem));
+  MOCK_METHOD0_T(Pop, void());
+  MOCK_CONST_METHOD0_T(GetSize, int());  // NOLINT
+  MOCK_CONST_METHOD0_T(GetTop, const T&());
+
+  // Tests that the function return type can contain unprotected comma.
+  MOCK_METHOD0_T(ReturnTypeWithComma, std::map<int, int>());
+  MOCK_CONST_METHOD1_T(ReturnTypeWithComma, std::map<int, int>(int));  // NOLINT
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(LegacyMockStack);
+};
+
+template <typename T>
+class TemplateMockTest : public ::testing::Test {};
+using TemplateMockTestTypes =
+    ::testing::Types<MockStack<int>, LegacyMockStack<int>>;
+TYPED_TEST_SUITE(TemplateMockTest, TemplateMockTestTypes);
+
+// Tests that template mock works.
+TYPED_TEST(TemplateMockTest, Works) {
+  TypeParam mock;
+
+  EXPECT_CALL(mock, GetSize())
+      .WillOnce(Return(0))
+      .WillOnce(Return(1))
+      .WillOnce(Return(0));
+  EXPECT_CALL(mock, Push(_));
+  int n = 5;
+  EXPECT_CALL(mock, GetTop())
+      .WillOnce(ReturnRef(n));
+  EXPECT_CALL(mock, Pop())
+      .Times(AnyNumber());
+
+  EXPECT_EQ(0, mock.GetSize());
+  mock.Push(5);
+  EXPECT_EQ(1, mock.GetSize());
+  EXPECT_EQ(5, mock.GetTop());
+  mock.Pop();
+  EXPECT_EQ(0, mock.GetSize());
+}
+
+TYPED_TEST(TemplateMockTest, MethodWithCommaInReturnTypeWorks) {
+  TypeParam mock;
+
+  const std::map<int, int> a_map;
+  EXPECT_CALL(mock, ReturnTypeWithComma())
+      .WillOnce(Return(a_map));
+  EXPECT_CALL(mock, ReturnTypeWithComma(1))
+      .WillOnce(Return(a_map));
+
+  EXPECT_EQ(a_map, mock.ReturnTypeWithComma());
+  EXPECT_EQ(a_map, mock.ReturnTypeWithComma(1));
+}
+
+#if GTEST_OS_WINDOWS
+// Tests mocking template interfaces with calltype.
+
+template <typename T>
+class StackInterfaceWithCallType {
+ public:
+  virtual ~StackInterfaceWithCallType() {}
+
+  // Template parameter appears in function parameter.
+  STDMETHOD_(void, Push)(const T& value) = 0;
+  STDMETHOD_(void, Pop)() = 0;
+  STDMETHOD_(int, GetSize)() const = 0;
+  // Template parameter appears in function return type.
+  STDMETHOD_(const T&, GetTop)() const = 0;
+};
+
+template <typename T>
+class MockStackWithCallType : public StackInterfaceWithCallType<T> {
+ public:
+  MockStackWithCallType() {}
+
+  MOCK_METHOD(void, Push, (const T& elem),
+              (Calltype(STDMETHODCALLTYPE), override));
+  MOCK_METHOD(void, Pop, (), (Calltype(STDMETHODCALLTYPE), override));
+  MOCK_METHOD(int, GetSize, (), (Calltype(STDMETHODCALLTYPE), override, const));
+  MOCK_METHOD(const T&, GetTop, (),
+              (Calltype(STDMETHODCALLTYPE), override, const));
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(MockStackWithCallType);
+};
+
+template <typename T>
+class LegacyMockStackWithCallType : public StackInterfaceWithCallType<T> {
+ public:
+  LegacyMockStackWithCallType() {}
+
+  MOCK_METHOD1_T_WITH_CALLTYPE(STDMETHODCALLTYPE, Push, void(const T& elem));
+  MOCK_METHOD0_T_WITH_CALLTYPE(STDMETHODCALLTYPE, Pop, void());
+  MOCK_CONST_METHOD0_T_WITH_CALLTYPE(STDMETHODCALLTYPE, GetSize, int());
+  MOCK_CONST_METHOD0_T_WITH_CALLTYPE(STDMETHODCALLTYPE, GetTop, const T&());
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(LegacyMockStackWithCallType);
+};
+
+template <typename T>
+class TemplateMockTestWithCallType : public ::testing::Test {};
+using TemplateMockTestWithCallTypeTypes =
+    ::testing::Types<MockStackWithCallType<int>,
+                     LegacyMockStackWithCallType<int>>;
+TYPED_TEST_SUITE(TemplateMockTestWithCallType,
+                 TemplateMockTestWithCallTypeTypes);
+
+// Tests that template mock with calltype works.
+TYPED_TEST(TemplateMockTestWithCallType, Works) {
+  TypeParam mock;
+
+  EXPECT_CALL(mock, GetSize())
+      .WillOnce(Return(0))
+      .WillOnce(Return(1))
+      .WillOnce(Return(0));
+  EXPECT_CALL(mock, Push(_));
+  int n = 5;
+  EXPECT_CALL(mock, GetTop())
+      .WillOnce(ReturnRef(n));
+  EXPECT_CALL(mock, Pop())
+      .Times(AnyNumber());
+
+  EXPECT_EQ(0, mock.GetSize());
+  mock.Push(5);
+  EXPECT_EQ(1, mock.GetSize());
+  EXPECT_EQ(5, mock.GetTop());
+  mock.Pop();
+  EXPECT_EQ(0, mock.GetSize());
+}
+#endif  // GTEST_OS_WINDOWS
+
+#define MY_MOCK_METHODS1_                       \
+  MOCK_METHOD(void, Overloaded, ());            \
+  MOCK_METHOD(int, Overloaded, (int), (const)); \
+  MOCK_METHOD(bool, Overloaded, (bool f, int n))
+
+#define LEGACY_MY_MOCK_METHODS1_              \
+  MOCK_METHOD0(Overloaded, void());           \
+  MOCK_CONST_METHOD1(Overloaded, int(int n)); \
+  MOCK_METHOD2(Overloaded, bool(bool f, int n))
+
+class MockOverloadedOnArgNumber {
+ public:
+  MockOverloadedOnArgNumber() {}
+
+  MY_MOCK_METHODS1_;
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(MockOverloadedOnArgNumber);
+};
+
+class LegacyMockOverloadedOnArgNumber {
+ public:
+  LegacyMockOverloadedOnArgNumber() {}
+
+  LEGACY_MY_MOCK_METHODS1_;
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(LegacyMockOverloadedOnArgNumber);
+};
+
+template <typename T>
+class OverloadedMockMethodTest : public ::testing::Test {};
+using OverloadedMockMethodTestTypes =
+    ::testing::Types<MockOverloadedOnArgNumber,
+                     LegacyMockOverloadedOnArgNumber>;
+TYPED_TEST_SUITE(OverloadedMockMethodTest, OverloadedMockMethodTestTypes);
+
+TYPED_TEST(OverloadedMockMethodTest, CanOverloadOnArgNumberInMacroBody) {
+  TypeParam mock;
+  EXPECT_CALL(mock, Overloaded());
+  EXPECT_CALL(mock, Overloaded(1)).WillOnce(Return(2));
+  EXPECT_CALL(mock, Overloaded(true, 1)).WillOnce(Return(true));
+
+  mock.Overloaded();
+  EXPECT_EQ(2, mock.Overloaded(1));
+  EXPECT_TRUE(mock.Overloaded(true, 1));
+}
+
+#define MY_MOCK_METHODS2_ \
+    MOCK_CONST_METHOD1(Overloaded, int(int n)); \
+    MOCK_METHOD1(Overloaded, int(int n))
+
+class MockOverloadedOnConstness {
+ public:
+  MockOverloadedOnConstness() {}
+
+  MY_MOCK_METHODS2_;
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(MockOverloadedOnConstness);
+};
+
+TEST(MockMethodOverloadedMockMethodTest, CanOverloadOnConstnessInMacroBody) {
+  MockOverloadedOnConstness mock;
+  const MockOverloadedOnConstness* const_mock = &mock;
+  EXPECT_CALL(mock, Overloaded(1)).WillOnce(Return(2));
+  EXPECT_CALL(*const_mock, Overloaded(1)).WillOnce(Return(3));
+
+  EXPECT_EQ(2, mock.Overloaded(1));
+  EXPECT_EQ(3, const_mock->Overloaded(1));
+}
+
+TEST(MockMethodMockFunctionTest, WorksForVoidNullary) {
+  MockFunction<void()> foo;
+  EXPECT_CALL(foo, Call());
+  foo.Call();
+}
+
+TEST(MockMethodMockFunctionTest, WorksForNonVoidNullary) {
+  MockFunction<int()> foo;
+  EXPECT_CALL(foo, Call())
+      .WillOnce(Return(1))
+      .WillOnce(Return(2));
+  EXPECT_EQ(1, foo.Call());
+  EXPECT_EQ(2, foo.Call());
+}
+
+TEST(MockMethodMockFunctionTest, WorksForVoidUnary) {
+  MockFunction<void(int)> foo;
+  EXPECT_CALL(foo, Call(1));
+  foo.Call(1);
+}
+
+TEST(MockMethodMockFunctionTest, WorksForNonVoidBinary) {
+  MockFunction<int(bool, int)> foo;
+  EXPECT_CALL(foo, Call(false, 42))
+      .WillOnce(Return(1))
+      .WillOnce(Return(2));
+  EXPECT_CALL(foo, Call(true, Ge(100)))
+      .WillOnce(Return(3));
+  EXPECT_EQ(1, foo.Call(false, 42));
+  EXPECT_EQ(2, foo.Call(false, 42));
+  EXPECT_EQ(3, foo.Call(true, 120));
+}
+
+TEST(MockMethodMockFunctionTest, WorksFor10Arguments) {
+  MockFunction<int(bool a0, char a1, int a2, int a3, int a4,
+                   int a5, int a6, char a7, int a8, bool a9)> foo;
+  EXPECT_CALL(foo, Call(_, 'a', _, _, _, _, _, _, _, _))
+      .WillOnce(Return(1))
+      .WillOnce(Return(2));
+  EXPECT_EQ(1, foo.Call(false, 'a', 0, 0, 0, 0, 0, 'b', 0, true));
+  EXPECT_EQ(2, foo.Call(true, 'a', 0, 0, 0, 0, 0, 'b', 1, false));
+}
+
+TEST(MockMethodMockFunctionTest, AsStdFunction) {
+  MockFunction<int(int)> foo;
+  auto call = [](const std::function<int(int)> &f, int i) {
+    return f(i);
+  };
+  EXPECT_CALL(foo, Call(1)).WillOnce(Return(-1));
+  EXPECT_CALL(foo, Call(2)).WillOnce(Return(-2));
+  EXPECT_EQ(-1, call(foo.AsStdFunction(), 1));
+  EXPECT_EQ(-2, call(foo.AsStdFunction(), 2));
+}
+
+TEST(MockMethodMockFunctionTest, AsStdFunctionReturnsReference) {
+  MockFunction<int&()> foo;
+  int value = 1;
+  EXPECT_CALL(foo, Call()).WillOnce(ReturnRef(value));
+  int& ref = foo.AsStdFunction()();
+  EXPECT_EQ(1, ref);
+  value = 2;
+  EXPECT_EQ(2, ref);
+}
+
+TEST(MockMethodMockFunctionTest, AsStdFunctionWithReferenceParameter) {
+  MockFunction<int(int &)> foo;
+  auto call = [](const std::function<int(int& )> &f, int &i) {
+    return f(i);
+  };
+  int i = 42;
+  EXPECT_CALL(foo, Call(i)).WillOnce(Return(-1));
+  EXPECT_EQ(-1, call(foo.AsStdFunction(), i));
+}
+
+namespace {
+
+template <typename Expected, typename F>
+static constexpr bool IsMockFunctionTemplateArgumentDeducedTo(
+    const internal::MockFunction<F>&) {
+  return std::is_same<F, Expected>::value;
+}
+
+}  // namespace
+
+template <typename F>
+class MockMethodMockFunctionSignatureTest : public Test {};
+
+using MockMethodMockFunctionSignatureTypes =
+    Types<void(), int(), void(int), int(int), int(bool, int),
+          int(bool, char, int, int, int, int, int, char, int, bool)>;
+TYPED_TEST_SUITE(MockMethodMockFunctionSignatureTest,
+                 MockMethodMockFunctionSignatureTypes);
+
+TYPED_TEST(MockMethodMockFunctionSignatureTest,
+           IsMockFunctionTemplateArgumentDeducedForRawSignature) {
+  using Argument = TypeParam;
+  MockFunction<Argument> foo;
+  EXPECT_TRUE(IsMockFunctionTemplateArgumentDeducedTo<TypeParam>(foo));
+}
+
+TYPED_TEST(MockMethodMockFunctionSignatureTest,
+           IsMockFunctionTemplateArgumentDeducedForStdFunction) {
+  using Argument = std::function<TypeParam>;
+  MockFunction<Argument> foo;
+  EXPECT_TRUE(IsMockFunctionTemplateArgumentDeducedTo<TypeParam>(foo));
+}
+
+TYPED_TEST(
+    MockMethodMockFunctionSignatureTest,
+    IsMockFunctionCallMethodSignatureTheSameForRawSignatureAndStdFunction) {
+  using ForRawSignature = decltype(&MockFunction<TypeParam>::Call);
+  using ForStdFunction =
+      decltype(&MockFunction<std::function<TypeParam>>::Call);
+  EXPECT_TRUE((std::is_same<ForRawSignature, ForStdFunction>::value));
+}
+
+template <typename F>
+struct AlternateCallable {
+};
+
+TYPED_TEST(MockMethodMockFunctionSignatureTest,
+           IsMockFunctionTemplateArgumentDeducedForAlternateCallable) {
+  using Argument = AlternateCallable<TypeParam>;
+  MockFunction<Argument> foo;
+  EXPECT_TRUE(IsMockFunctionTemplateArgumentDeducedTo<TypeParam>(foo));
+}
+
+TYPED_TEST(
+    MockMethodMockFunctionSignatureTest,
+    IsMockFunctionCallMethodSignatureTheSameForAlternateCallable) {
+  using ForRawSignature = decltype(&MockFunction<TypeParam>::Call);
+  using ForStdFunction =
+      decltype(&MockFunction<std::function<TypeParam>>::Call);
+  EXPECT_TRUE((std::is_same<ForRawSignature, ForStdFunction>::value));
+}
+
+
+struct MockMethodSizes0 {
+  MOCK_METHOD(void, func, ());
+};
+struct MockMethodSizes1 {
+  MOCK_METHOD(void, func, (int));
+};
+struct MockMethodSizes2 {
+  MOCK_METHOD(void, func, (int, int));
+};
+struct MockMethodSizes3 {
+  MOCK_METHOD(void, func, (int, int, int));
+};
+struct MockMethodSizes4 {
+  MOCK_METHOD(void, func, (int, int, int, int));
+};
+
+struct LegacyMockMethodSizes0 {
+    MOCK_METHOD0(func, void());
+};
+struct LegacyMockMethodSizes1 {
+    MOCK_METHOD1(func, void(int));
+};
+struct LegacyMockMethodSizes2 {
+    MOCK_METHOD2(func, void(int, int));
+};
+struct LegacyMockMethodSizes3 {
+    MOCK_METHOD3(func, void(int, int, int));
+};
+struct LegacyMockMethodSizes4 {
+    MOCK_METHOD4(func, void(int, int, int, int));
+};
+
+
+TEST(MockMethodMockFunctionTest, MockMethodSizeOverhead) {
+  EXPECT_EQ(sizeof(MockMethodSizes0), sizeof(MockMethodSizes1));
+  EXPECT_EQ(sizeof(MockMethodSizes0), sizeof(MockMethodSizes2));
+  EXPECT_EQ(sizeof(MockMethodSizes0), sizeof(MockMethodSizes3));
+  EXPECT_EQ(sizeof(MockMethodSizes0), sizeof(MockMethodSizes4));
+
+  EXPECT_EQ(sizeof(LegacyMockMethodSizes0), sizeof(LegacyMockMethodSizes1));
+  EXPECT_EQ(sizeof(LegacyMockMethodSizes0), sizeof(LegacyMockMethodSizes2));
+  EXPECT_EQ(sizeof(LegacyMockMethodSizes0), sizeof(LegacyMockMethodSizes3));
+  EXPECT_EQ(sizeof(LegacyMockMethodSizes0), sizeof(LegacyMockMethodSizes4));
+
+  EXPECT_EQ(sizeof(LegacyMockMethodSizes0), sizeof(MockMethodSizes0));
+}
+
+void hasTwoParams(int, int);
+void MaybeThrows();
+void DoesntThrow() noexcept;
+struct MockMethodNoexceptSpecifier {
+  MOCK_METHOD(void, func1, (), (noexcept));
+  MOCK_METHOD(void, func2, (), (noexcept(true)));
+  MOCK_METHOD(void, func3, (), (noexcept(false)));
+  MOCK_METHOD(void, func4, (), (noexcept(noexcept(MaybeThrows()))));
+  MOCK_METHOD(void, func5, (), (noexcept(noexcept(DoesntThrow()))));
+  MOCK_METHOD(void, func6, (), (noexcept(noexcept(DoesntThrow())), const));
+  MOCK_METHOD(void, func7, (), (const, noexcept(noexcept(DoesntThrow()))));
+  // Put commas in the noexcept expression
+  MOCK_METHOD(void, func8, (), (noexcept(noexcept(hasTwoParams(1, 2))), const));
+};
+
+TEST(MockMethodMockFunctionTest, NoexceptSpecifierPreserved) {
+  EXPECT_TRUE(noexcept(std::declval<MockMethodNoexceptSpecifier>().func1()));
+  EXPECT_TRUE(noexcept(std::declval<MockMethodNoexceptSpecifier>().func2()));
+  EXPECT_FALSE(noexcept(std::declval<MockMethodNoexceptSpecifier>().func3()));
+  EXPECT_FALSE(noexcept(std::declval<MockMethodNoexceptSpecifier>().func4()));
+  EXPECT_TRUE(noexcept(std::declval<MockMethodNoexceptSpecifier>().func5()));
+  EXPECT_TRUE(noexcept(std::declval<MockMethodNoexceptSpecifier>().func6()));
+  EXPECT_TRUE(noexcept(std::declval<MockMethodNoexceptSpecifier>().func7()));
+  EXPECT_EQ(noexcept(std::declval<MockMethodNoexceptSpecifier>().func8()),
+            noexcept(hasTwoParams(1, 2)));
+}
+
+}  // namespace gmock_function_mocker_test
+}  // namespace testing
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock-internal-utils_test.cc b/leveldb_base/third_party/googletest/googlemock/test/gmock-internal-utils_test.cc
new file mode 100644
index 0000000..0d15e8f
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock-internal-utils_test.cc
@@ -0,0 +1,720 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests the internal utilities.
+
+#include "gmock/internal/gmock-internal-utils.h"
+
+#include <stdlib.h>
+
+#include <cstdint>
+#include <map>
+#include <memory>
+#include <sstream>
+#include <string>
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "gmock/internal/gmock-port.h"
+#include "gtest/gtest-spi.h"
+#include "gtest/gtest.h"
+
+// Indicates that this translation unit is part of Google Test's
+// implementation.  It must come before gtest-internal-inl.h is
+// included, or there will be a compiler error.  This trick is to
+// prevent a user from accidentally including gtest-internal-inl.h in
+// their code.
+#define GTEST_IMPLEMENTATION_ 1
+#include "src/gtest-internal-inl.h"
+#undef GTEST_IMPLEMENTATION_
+
+#if GTEST_OS_CYGWIN
+# include <sys/types.h>  // For ssize_t. NOLINT
+#endif
+
+namespace proto2 {
+class Message;
+}  // namespace proto2
+
+namespace testing {
+namespace internal {
+
+namespace {
+
+TEST(JoinAsTupleTest, JoinsEmptyTuple) {
+  EXPECT_EQ("", JoinAsTuple(Strings()));
+}
+
+TEST(JoinAsTupleTest, JoinsOneTuple) {
+  const char* fields[] = {"1"};
+  EXPECT_EQ("1", JoinAsTuple(Strings(fields, fields + 1)));
+}
+
+TEST(JoinAsTupleTest, JoinsTwoTuple) {
+  const char* fields[] = {"1", "a"};
+  EXPECT_EQ("(1, a)", JoinAsTuple(Strings(fields, fields + 2)));
+}
+
+TEST(JoinAsTupleTest, JoinsTenTuple) {
+  const char* fields[] = {"1", "2", "3", "4", "5", "6", "7", "8", "9", "10"};
+  EXPECT_EQ("(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)",
+            JoinAsTuple(Strings(fields, fields + 10)));
+}
+
+TEST(ConvertIdentifierNameToWordsTest, WorksWhenNameContainsNoWord) {
+  EXPECT_EQ("", ConvertIdentifierNameToWords(""));
+  EXPECT_EQ("", ConvertIdentifierNameToWords("_"));
+  EXPECT_EQ("", ConvertIdentifierNameToWords("__"));
+}
+
+TEST(ConvertIdentifierNameToWordsTest, WorksWhenNameContainsDigits) {
+  EXPECT_EQ("1", ConvertIdentifierNameToWords("_1"));
+  EXPECT_EQ("2", ConvertIdentifierNameToWords("2_"));
+  EXPECT_EQ("34", ConvertIdentifierNameToWords("_34_"));
+  EXPECT_EQ("34 56", ConvertIdentifierNameToWords("_34_56"));
+}
+
+TEST(ConvertIdentifierNameToWordsTest, WorksWhenNameContainsCamelCaseWords) {
+  EXPECT_EQ("a big word", ConvertIdentifierNameToWords("ABigWord"));
+  EXPECT_EQ("foo bar", ConvertIdentifierNameToWords("FooBar"));
+  EXPECT_EQ("foo", ConvertIdentifierNameToWords("Foo_"));
+  EXPECT_EQ("foo bar", ConvertIdentifierNameToWords("_Foo_Bar_"));
+  EXPECT_EQ("foo and bar", ConvertIdentifierNameToWords("_Foo__And_Bar"));
+}
+
+TEST(ConvertIdentifierNameToWordsTest, WorksWhenNameContains_SeparatedWords) {
+  EXPECT_EQ("foo bar", ConvertIdentifierNameToWords("foo_bar"));
+  EXPECT_EQ("foo", ConvertIdentifierNameToWords("_foo_"));
+  EXPECT_EQ("foo bar", ConvertIdentifierNameToWords("_foo_bar_"));
+  EXPECT_EQ("foo and bar", ConvertIdentifierNameToWords("_foo__and_bar"));
+}
+
+TEST(ConvertIdentifierNameToWordsTest, WorksWhenNameIsMixture) {
+  EXPECT_EQ("foo bar 123", ConvertIdentifierNameToWords("Foo_bar123"));
+  EXPECT_EQ("chapter 11 section 1",
+            ConvertIdentifierNameToWords("_Chapter11Section_1_"));
+}
+
+TEST(GetRawPointerTest, WorksForSmartPointers) {
+  const char* const raw_p1 = new const char('a');  // NOLINT
+  const std::unique_ptr<const char> p1(raw_p1);
+  EXPECT_EQ(raw_p1, GetRawPointer(p1));
+  double* const raw_p2 = new double(2.5);  // NOLINT
+  const std::shared_ptr<double> p2(raw_p2);
+  EXPECT_EQ(raw_p2, GetRawPointer(p2));
+}
+
+TEST(GetRawPointerTest, WorksForRawPointers) {
+  int* p = nullptr;
+  EXPECT_TRUE(nullptr == GetRawPointer(p));
+  int n = 1;
+  EXPECT_EQ(&n, GetRawPointer(&n));
+}
+
+// Tests KindOf<T>.
+
+class Base {};
+class Derived : public Base {};
+
+TEST(KindOfTest, Bool) {
+  EXPECT_EQ(kBool, GMOCK_KIND_OF_(bool));  // NOLINT
+}
+
+TEST(KindOfTest, Integer) {
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(char));  // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(signed char));  // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(unsigned char));  // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(short));  // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(unsigned short));  // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(int));  // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(unsigned int));  // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(long));  // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(unsigned long));  // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(long long));  // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(unsigned long long));  // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(wchar_t));  // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(size_t));  // NOLINT
+#if GTEST_OS_LINUX || GTEST_OS_MAC || GTEST_OS_CYGWIN
+  // ssize_t is not defined on Windows and possibly some other OSes.
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(ssize_t));  // NOLINT
+#endif
+}
+
+TEST(KindOfTest, FloatingPoint) {
+  EXPECT_EQ(kFloatingPoint, GMOCK_KIND_OF_(float));  // NOLINT
+  EXPECT_EQ(kFloatingPoint, GMOCK_KIND_OF_(double));  // NOLINT
+  EXPECT_EQ(kFloatingPoint, GMOCK_KIND_OF_(long double));  // NOLINT
+}
+
+TEST(KindOfTest, Other) {
+  EXPECT_EQ(kOther, GMOCK_KIND_OF_(void*));  // NOLINT
+  EXPECT_EQ(kOther, GMOCK_KIND_OF_(char**));  // NOLINT
+  EXPECT_EQ(kOther, GMOCK_KIND_OF_(Base));  // NOLINT
+}
+
+// Tests LosslessArithmeticConvertible<T, U>.
+
+TEST(LosslessArithmeticConvertibleTest, BoolToBool) {
+  EXPECT_TRUE((LosslessArithmeticConvertible<bool, bool>::value));
+}
+
+TEST(LosslessArithmeticConvertibleTest, BoolToInteger) {
+  EXPECT_TRUE((LosslessArithmeticConvertible<bool, char>::value));
+  EXPECT_TRUE((LosslessArithmeticConvertible<bool, int>::value));
+  EXPECT_TRUE(
+      (LosslessArithmeticConvertible<bool, unsigned long>::value));  // NOLINT
+}
+
+TEST(LosslessArithmeticConvertibleTest, BoolToFloatingPoint) {
+  EXPECT_TRUE((LosslessArithmeticConvertible<bool, float>::value));
+  EXPECT_TRUE((LosslessArithmeticConvertible<bool, double>::value));
+}
+
+TEST(LosslessArithmeticConvertibleTest, IntegerToBool) {
+  EXPECT_FALSE((LosslessArithmeticConvertible<unsigned char, bool>::value));
+  EXPECT_FALSE((LosslessArithmeticConvertible<int, bool>::value));
+}
+
+TEST(LosslessArithmeticConvertibleTest, IntegerToInteger) {
+  // Unsigned => larger signed is fine.
+  EXPECT_TRUE((LosslessArithmeticConvertible<unsigned char, int>::value));
+
+  // Unsigned => larger unsigned is fine.
+  EXPECT_TRUE((LosslessArithmeticConvertible<
+               unsigned short, uint64_t>::value));  // NOLINT
+
+  // Signed => unsigned is not fine.
+  EXPECT_FALSE((LosslessArithmeticConvertible<
+                short, uint64_t>::value));  // NOLINT
+  EXPECT_FALSE((LosslessArithmeticConvertible<
+      signed char, unsigned int>::value));  // NOLINT
+
+  // Same size and same signedness: fine too.
+  EXPECT_TRUE((LosslessArithmeticConvertible<
+               unsigned char, unsigned char>::value));
+  EXPECT_TRUE((LosslessArithmeticConvertible<int, int>::value));
+  EXPECT_TRUE((LosslessArithmeticConvertible<wchar_t, wchar_t>::value));
+  EXPECT_TRUE((LosslessArithmeticConvertible<
+               unsigned long, unsigned long>::value));  // NOLINT
+
+  // Same size, different signedness: not fine.
+  EXPECT_FALSE((LosslessArithmeticConvertible<
+                unsigned char, signed char>::value));
+  EXPECT_FALSE((LosslessArithmeticConvertible<int, unsigned int>::value));
+  EXPECT_FALSE((LosslessArithmeticConvertible<uint64_t, int64_t>::value));
+
+  // Larger size => smaller size is not fine.
+  EXPECT_FALSE((LosslessArithmeticConvertible<long, char>::value));  // NOLINT
+  EXPECT_FALSE((LosslessArithmeticConvertible<int, signed char>::value));
+  EXPECT_FALSE((LosslessArithmeticConvertible<int64_t, unsigned int>::value));
+}
+
+TEST(LosslessArithmeticConvertibleTest, IntegerToFloatingPoint) {
+  // Integers cannot be losslessly converted to floating-points, as
+  // the format of the latter is implementation-defined.
+  EXPECT_FALSE((LosslessArithmeticConvertible<char, float>::value));
+  EXPECT_FALSE((LosslessArithmeticConvertible<int, double>::value));
+  EXPECT_FALSE((LosslessArithmeticConvertible<
+                short, long double>::value));  // NOLINT
+}
+
+TEST(LosslessArithmeticConvertibleTest, FloatingPointToBool) {
+  EXPECT_FALSE((LosslessArithmeticConvertible<float, bool>::value));
+  EXPECT_FALSE((LosslessArithmeticConvertible<double, bool>::value));
+}
+
+TEST(LosslessArithmeticConvertibleTest, FloatingPointToInteger) {
+  EXPECT_FALSE((LosslessArithmeticConvertible<float, long>::value));  // NOLINT
+  EXPECT_FALSE((LosslessArithmeticConvertible<double, int64_t>::value));
+  EXPECT_FALSE((LosslessArithmeticConvertible<long double, int>::value));
+}
+
+TEST(LosslessArithmeticConvertibleTest, FloatingPointToFloatingPoint) {
+  // Smaller size => larger size is fine.
+  EXPECT_TRUE((LosslessArithmeticConvertible<float, double>::value));
+  EXPECT_TRUE((LosslessArithmeticConvertible<float, long double>::value));
+  EXPECT_TRUE((LosslessArithmeticConvertible<double, long double>::value));
+
+  // Same size: fine.
+  EXPECT_TRUE((LosslessArithmeticConvertible<float, float>::value));
+  EXPECT_TRUE((LosslessArithmeticConvertible<double, double>::value));
+
+  // Larger size => smaller size is not fine.
+  EXPECT_FALSE((LosslessArithmeticConvertible<double, float>::value));
+  GTEST_INTENTIONAL_CONST_COND_PUSH_()
+  if (sizeof(double) == sizeof(long double)) {  // NOLINT
+  GTEST_INTENTIONAL_CONST_COND_POP_()
+    // In some implementations (e.g. MSVC), double and long double
+    // have the same size.
+    EXPECT_TRUE((LosslessArithmeticConvertible<long double, double>::value));
+  } else {
+    EXPECT_FALSE((LosslessArithmeticConvertible<long double, double>::value));
+  }
+}
+
+// Tests the TupleMatches() template function.
+
+TEST(TupleMatchesTest, WorksForSize0) {
+  std::tuple<> matchers;
+  std::tuple<> values;
+
+  EXPECT_TRUE(TupleMatches(matchers, values));
+}
+
+TEST(TupleMatchesTest, WorksForSize1) {
+  std::tuple<Matcher<int> > matchers(Eq(1));
+  std::tuple<int> values1(1), values2(2);
+
+  EXPECT_TRUE(TupleMatches(matchers, values1));
+  EXPECT_FALSE(TupleMatches(matchers, values2));
+}
+
+TEST(TupleMatchesTest, WorksForSize2) {
+  std::tuple<Matcher<int>, Matcher<char> > matchers(Eq(1), Eq('a'));
+  std::tuple<int, char> values1(1, 'a'), values2(1, 'b'), values3(2, 'a'),
+      values4(2, 'b');
+
+  EXPECT_TRUE(TupleMatches(matchers, values1));
+  EXPECT_FALSE(TupleMatches(matchers, values2));
+  EXPECT_FALSE(TupleMatches(matchers, values3));
+  EXPECT_FALSE(TupleMatches(matchers, values4));
+}
+
+TEST(TupleMatchesTest, WorksForSize5) {
+  std::tuple<Matcher<int>, Matcher<char>, Matcher<bool>,
+             Matcher<long>,  // NOLINT
+             Matcher<std::string> >
+      matchers(Eq(1), Eq('a'), Eq(true), Eq(2L), Eq("hi"));
+  std::tuple<int, char, bool, long, std::string>  // NOLINT
+      values1(1, 'a', true, 2L, "hi"), values2(1, 'a', true, 2L, "hello"),
+      values3(2, 'a', true, 2L, "hi");
+
+  EXPECT_TRUE(TupleMatches(matchers, values1));
+  EXPECT_FALSE(TupleMatches(matchers, values2));
+  EXPECT_FALSE(TupleMatches(matchers, values3));
+}
+
+// Tests that Assert(true, ...) succeeds.
+TEST(AssertTest, SucceedsOnTrue) {
+  Assert(true, __FILE__, __LINE__, "This should succeed.");
+  Assert(true, __FILE__, __LINE__);  // This should succeed too.
+}
+
+// Tests that Assert(false, ...) generates a fatal failure.
+TEST(AssertTest, FailsFatallyOnFalse) {
+  EXPECT_DEATH_IF_SUPPORTED({
+    Assert(false, __FILE__, __LINE__, "This should fail.");
+  }, "");
+
+  EXPECT_DEATH_IF_SUPPORTED({
+    Assert(false, __FILE__, __LINE__);
+  }, "");
+}
+
+// Tests that Expect(true, ...) succeeds.
+TEST(ExpectTest, SucceedsOnTrue) {
+  Expect(true, __FILE__, __LINE__, "This should succeed.");
+  Expect(true, __FILE__, __LINE__);  // This should succeed too.
+}
+
+// Tests that Expect(false, ...) generates a non-fatal failure.
+TEST(ExpectTest, FailsNonfatallyOnFalse) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    Expect(false, __FILE__, __LINE__, "This should fail.");
+  }, "This should fail");
+
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    Expect(false, __FILE__, __LINE__);
+  }, "Expectation failed");
+}
+
+// Tests LogIsVisible().
+
+class LogIsVisibleTest : public ::testing::Test {
+ protected:
+  void SetUp() override { original_verbose_ = GMOCK_FLAG(verbose); }
+
+  void TearDown() override { GMOCK_FLAG(verbose) = original_verbose_; }
+
+  std::string original_verbose_;
+};
+
+TEST_F(LogIsVisibleTest, AlwaysReturnsTrueIfVerbosityIsInfo) {
+  GMOCK_FLAG(verbose) = kInfoVerbosity;
+  EXPECT_TRUE(LogIsVisible(kInfo));
+  EXPECT_TRUE(LogIsVisible(kWarning));
+}
+
+TEST_F(LogIsVisibleTest, AlwaysReturnsFalseIfVerbosityIsError) {
+  GMOCK_FLAG(verbose) = kErrorVerbosity;
+  EXPECT_FALSE(LogIsVisible(kInfo));
+  EXPECT_FALSE(LogIsVisible(kWarning));
+}
+
+TEST_F(LogIsVisibleTest, WorksWhenVerbosityIsWarning) {
+  GMOCK_FLAG(verbose) = kWarningVerbosity;
+  EXPECT_FALSE(LogIsVisible(kInfo));
+  EXPECT_TRUE(LogIsVisible(kWarning));
+}
+
+#if GTEST_HAS_STREAM_REDIRECTION
+
+// Tests the Log() function.
+
+// Verifies that Log() behaves correctly for the given verbosity level
+// and log severity.
+void TestLogWithSeverity(const std::string& verbosity, LogSeverity severity,
+                         bool should_print) {
+  const std::string old_flag = GMOCK_FLAG(verbose);
+  GMOCK_FLAG(verbose) = verbosity;
+  CaptureStdout();
+  Log(severity, "Test log.\n", 0);
+  if (should_print) {
+    EXPECT_THAT(GetCapturedStdout().c_str(),
+                ContainsRegex(
+                    severity == kWarning ?
+                    "^\nGMOCK WARNING:\nTest log\\.\nStack trace:\n" :
+                    "^\nTest log\\.\nStack trace:\n"));
+  } else {
+    EXPECT_STREQ("", GetCapturedStdout().c_str());
+  }
+  GMOCK_FLAG(verbose) = old_flag;
+}
+
+// Tests that when the stack_frames_to_skip parameter is negative,
+// Log() doesn't include the stack trace in the output.
+TEST(LogTest, NoStackTraceWhenStackFramesToSkipIsNegative) {
+  const std::string saved_flag = GMOCK_FLAG(verbose);
+  GMOCK_FLAG(verbose) = kInfoVerbosity;
+  CaptureStdout();
+  Log(kInfo, "Test log.\n", -1);
+  EXPECT_STREQ("\nTest log.\n", GetCapturedStdout().c_str());
+  GMOCK_FLAG(verbose) = saved_flag;
+}
+
+struct MockStackTraceGetter : testing::internal::OsStackTraceGetterInterface {
+  std::string CurrentStackTrace(int max_depth, int skip_count) override {
+    return (testing::Message() << max_depth << "::" << skip_count << "\n")
+        .GetString();
+  }
+  void UponLeavingGTest() override {}
+};
+
+// Tests that in opt mode, a positive stack_frames_to_skip argument is
+// treated as 0.
+TEST(LogTest, NoSkippingStackFrameInOptMode) {
+  MockStackTraceGetter* mock_os_stack_trace_getter = new MockStackTraceGetter;
+  GetUnitTestImpl()->set_os_stack_trace_getter(mock_os_stack_trace_getter);
+
+  CaptureStdout();
+  Log(kWarning, "Test log.\n", 100);
+  const std::string log = GetCapturedStdout();
+
+  std::string expected_trace =
+      (testing::Message() << GTEST_FLAG(stack_trace_depth) << "::").GetString();
+  std::string expected_message =
+      "\nGMOCK WARNING:\n"
+      "Test log.\n"
+      "Stack trace:\n" +
+      expected_trace;
+  EXPECT_THAT(log, HasSubstr(expected_message));
+  int skip_count = atoi(log.substr(expected_message.size()).c_str());
+
+# if defined(NDEBUG)
+  // In opt mode, no stack frame should be skipped.
+  const int expected_skip_count = 0;
+# else
+  // In dbg mode, the stack frames should be skipped.
+  const int expected_skip_count = 100;
+# endif
+
+  // Note that each inner implementation layer will +1 the number to remove
+  // itself from the trace. This means that the value is a little higher than
+  // expected, but close enough.
+  EXPECT_THAT(skip_count,
+              AllOf(Ge(expected_skip_count), Le(expected_skip_count + 10)));
+
+  // Restores the default OS stack trace getter.
+  GetUnitTestImpl()->set_os_stack_trace_getter(nullptr);
+}
+
+// Tests that all logs are printed when the value of the
+// --gmock_verbose flag is "info".
+TEST(LogTest, AllLogsArePrintedWhenVerbosityIsInfo) {
+  TestLogWithSeverity(kInfoVerbosity, kInfo, true);
+  TestLogWithSeverity(kInfoVerbosity, kWarning, true);
+}
+
+// Tests that only warnings are printed when the value of the
+// --gmock_verbose flag is "warning".
+TEST(LogTest, OnlyWarningsArePrintedWhenVerbosityIsWarning) {
+  TestLogWithSeverity(kWarningVerbosity, kInfo, false);
+  TestLogWithSeverity(kWarningVerbosity, kWarning, true);
+}
+
+// Tests that no logs are printed when the value of the
+// --gmock_verbose flag is "error".
+TEST(LogTest, NoLogsArePrintedWhenVerbosityIsError) {
+  TestLogWithSeverity(kErrorVerbosity, kInfo, false);
+  TestLogWithSeverity(kErrorVerbosity, kWarning, false);
+}
+
+// Tests that only warnings are printed when the value of the
+// --gmock_verbose flag is invalid.
+TEST(LogTest, OnlyWarningsArePrintedWhenVerbosityIsInvalid) {
+  TestLogWithSeverity("invalid", kInfo, false);
+  TestLogWithSeverity("invalid", kWarning, true);
+}
+
+// Verifies that Log() behaves correctly for the given verbosity level
+// and log severity.
+std::string GrabOutput(void(*logger)(), const char* verbosity) {
+  const std::string saved_flag = GMOCK_FLAG(verbose);
+  GMOCK_FLAG(verbose) = verbosity;
+  CaptureStdout();
+  logger();
+  GMOCK_FLAG(verbose) = saved_flag;
+  return GetCapturedStdout();
+}
+
+class DummyMock {
+ public:
+  MOCK_METHOD0(TestMethod, void());
+  MOCK_METHOD1(TestMethodArg, void(int dummy));
+};
+
+void ExpectCallLogger() {
+  DummyMock mock;
+  EXPECT_CALL(mock, TestMethod());
+  mock.TestMethod();
+}
+
+// Verifies that EXPECT_CALL logs if the --gmock_verbose flag is set to "info".
+TEST(ExpectCallTest, LogsWhenVerbosityIsInfo) {
+  EXPECT_THAT(std::string(GrabOutput(ExpectCallLogger, kInfoVerbosity)),
+              HasSubstr("EXPECT_CALL(mock, TestMethod())"));
+}
+
+// Verifies that EXPECT_CALL doesn't log
+// if the --gmock_verbose flag is set to "warning".
+TEST(ExpectCallTest, DoesNotLogWhenVerbosityIsWarning) {
+  EXPECT_STREQ("", GrabOutput(ExpectCallLogger, kWarningVerbosity).c_str());
+}
+
+// Verifies that EXPECT_CALL doesn't log
+// if the --gmock_verbose flag is set to "error".
+TEST(ExpectCallTest,  DoesNotLogWhenVerbosityIsError) {
+  EXPECT_STREQ("", GrabOutput(ExpectCallLogger, kErrorVerbosity).c_str());
+}
+
+void OnCallLogger() {
+  DummyMock mock;
+  ON_CALL(mock, TestMethod());
+}
+
+// Verifies that ON_CALL logs if the --gmock_verbose flag is set to "info".
+TEST(OnCallTest, LogsWhenVerbosityIsInfo) {
+  EXPECT_THAT(std::string(GrabOutput(OnCallLogger, kInfoVerbosity)),
+              HasSubstr("ON_CALL(mock, TestMethod())"));
+}
+
+// Verifies that ON_CALL doesn't log
+// if the --gmock_verbose flag is set to "warning".
+TEST(OnCallTest, DoesNotLogWhenVerbosityIsWarning) {
+  EXPECT_STREQ("", GrabOutput(OnCallLogger, kWarningVerbosity).c_str());
+}
+
+// Verifies that ON_CALL doesn't log if
+// the --gmock_verbose flag is set to "error".
+TEST(OnCallTest, DoesNotLogWhenVerbosityIsError) {
+  EXPECT_STREQ("", GrabOutput(OnCallLogger, kErrorVerbosity).c_str());
+}
+
+void OnCallAnyArgumentLogger() {
+  DummyMock mock;
+  ON_CALL(mock, TestMethodArg(_));
+}
+
+// Verifies that ON_CALL prints provided _ argument.
+TEST(OnCallTest, LogsAnythingArgument) {
+  EXPECT_THAT(std::string(GrabOutput(OnCallAnyArgumentLogger, kInfoVerbosity)),
+              HasSubstr("ON_CALL(mock, TestMethodArg(_)"));
+}
+
+#endif  // GTEST_HAS_STREAM_REDIRECTION
+
+// Tests StlContainerView.
+
+TEST(StlContainerViewTest, WorksForStlContainer) {
+  StaticAssertTypeEq<std::vector<int>,
+      StlContainerView<std::vector<int> >::type>();
+  StaticAssertTypeEq<const std::vector<double>&,
+      StlContainerView<std::vector<double> >::const_reference>();
+
+  typedef std::vector<char> Chars;
+  Chars v1;
+  const Chars& v2(StlContainerView<Chars>::ConstReference(v1));
+  EXPECT_EQ(&v1, &v2);
+
+  v1.push_back('a');
+  Chars v3 = StlContainerView<Chars>::Copy(v1);
+  EXPECT_THAT(v3, Eq(v3));
+}
+
+TEST(StlContainerViewTest, WorksForStaticNativeArray) {
+  StaticAssertTypeEq<NativeArray<int>,
+      StlContainerView<int[3]>::type>();
+  StaticAssertTypeEq<NativeArray<double>,
+      StlContainerView<const double[4]>::type>();
+  StaticAssertTypeEq<NativeArray<char[3]>,
+      StlContainerView<const char[2][3]>::type>();
+
+  StaticAssertTypeEq<const NativeArray<int>,
+      StlContainerView<int[2]>::const_reference>();
+
+  int a1[3] = { 0, 1, 2 };
+  NativeArray<int> a2 = StlContainerView<int[3]>::ConstReference(a1);
+  EXPECT_EQ(3U, a2.size());
+  EXPECT_EQ(a1, a2.begin());
+
+  const NativeArray<int> a3 = StlContainerView<int[3]>::Copy(a1);
+  ASSERT_EQ(3U, a3.size());
+  EXPECT_EQ(0, a3.begin()[0]);
+  EXPECT_EQ(1, a3.begin()[1]);
+  EXPECT_EQ(2, a3.begin()[2]);
+
+  // Makes sure a1 and a3 aren't aliases.
+  a1[0] = 3;
+  EXPECT_EQ(0, a3.begin()[0]);
+}
+
+TEST(StlContainerViewTest, WorksForDynamicNativeArray) {
+  StaticAssertTypeEq<NativeArray<int>,
+                     StlContainerView<std::tuple<const int*, size_t> >::type>();
+  StaticAssertTypeEq<
+      NativeArray<double>,
+      StlContainerView<std::tuple<std::shared_ptr<double>, int> >::type>();
+
+  StaticAssertTypeEq<
+      const NativeArray<int>,
+      StlContainerView<std::tuple<const int*, int> >::const_reference>();
+
+  int a1[3] = { 0, 1, 2 };
+  const int* const p1 = a1;
+  NativeArray<int> a2 =
+      StlContainerView<std::tuple<const int*, int> >::ConstReference(
+          std::make_tuple(p1, 3));
+  EXPECT_EQ(3U, a2.size());
+  EXPECT_EQ(a1, a2.begin());
+
+  const NativeArray<int> a3 = StlContainerView<std::tuple<int*, size_t> >::Copy(
+      std::make_tuple(static_cast<int*>(a1), 3));
+  ASSERT_EQ(3U, a3.size());
+  EXPECT_EQ(0, a3.begin()[0]);
+  EXPECT_EQ(1, a3.begin()[1]);
+  EXPECT_EQ(2, a3.begin()[2]);
+
+  // Makes sure a1 and a3 aren't aliases.
+  a1[0] = 3;
+  EXPECT_EQ(0, a3.begin()[0]);
+}
+
+// Tests the Function template struct.
+
+TEST(FunctionTest, Nullary) {
+  typedef Function<int()> F;  // NOLINT
+  EXPECT_EQ(0u, F::ArgumentCount);
+  EXPECT_TRUE((std::is_same<int, F::Result>::value));
+  EXPECT_TRUE((std::is_same<std::tuple<>, F::ArgumentTuple>::value));
+  EXPECT_TRUE((std::is_same<std::tuple<>, F::ArgumentMatcherTuple>::value));
+  EXPECT_TRUE((std::is_same<void(), F::MakeResultVoid>::value));
+  EXPECT_TRUE((std::is_same<IgnoredValue(), F::MakeResultIgnoredValue>::value));
+}
+
+TEST(FunctionTest, Unary) {
+  typedef Function<int(bool)> F;  // NOLINT
+  EXPECT_EQ(1u, F::ArgumentCount);
+  EXPECT_TRUE((std::is_same<int, F::Result>::value));
+  EXPECT_TRUE((std::is_same<bool, F::Arg<0>::type>::value));
+  EXPECT_TRUE((std::is_same<std::tuple<bool>, F::ArgumentTuple>::value));
+  EXPECT_TRUE((
+      std::is_same<std::tuple<Matcher<bool>>, F::ArgumentMatcherTuple>::value));
+  EXPECT_TRUE((std::is_same<void(bool), F::MakeResultVoid>::value));  // NOLINT
+  EXPECT_TRUE((std::is_same<IgnoredValue(bool),                       // NOLINT
+                            F::MakeResultIgnoredValue>::value));
+}
+
+TEST(FunctionTest, Binary) {
+  typedef Function<int(bool, const long&)> F;  // NOLINT
+  EXPECT_EQ(2u, F::ArgumentCount);
+  EXPECT_TRUE((std::is_same<int, F::Result>::value));
+  EXPECT_TRUE((std::is_same<bool, F::Arg<0>::type>::value));
+  EXPECT_TRUE((std::is_same<const long&, F::Arg<1>::type>::value));  // NOLINT
+  EXPECT_TRUE((std::is_same<std::tuple<bool, const long&>,           // NOLINT
+                            F::ArgumentTuple>::value));
+  EXPECT_TRUE(
+      (std::is_same<std::tuple<Matcher<bool>, Matcher<const long&>>,  // NOLINT
+                    F::ArgumentMatcherTuple>::value));
+  EXPECT_TRUE((std::is_same<void(bool, const long&),  // NOLINT
+                            F::MakeResultVoid>::value));
+  EXPECT_TRUE((std::is_same<IgnoredValue(bool, const long&),  // NOLINT
+                            F::MakeResultIgnoredValue>::value));
+}
+
+TEST(FunctionTest, LongArgumentList) {
+  typedef Function<char(bool, int, char*, int&, const long&)> F;  // NOLINT
+  EXPECT_EQ(5u, F::ArgumentCount);
+  EXPECT_TRUE((std::is_same<char, F::Result>::value));
+  EXPECT_TRUE((std::is_same<bool, F::Arg<0>::type>::value));
+  EXPECT_TRUE((std::is_same<int, F::Arg<1>::type>::value));
+  EXPECT_TRUE((std::is_same<char*, F::Arg<2>::type>::value));
+  EXPECT_TRUE((std::is_same<int&, F::Arg<3>::type>::value));
+  EXPECT_TRUE((std::is_same<const long&, F::Arg<4>::type>::value));  // NOLINT
+  EXPECT_TRUE(
+      (std::is_same<std::tuple<bool, int, char*, int&, const long&>,  // NOLINT
+                    F::ArgumentTuple>::value));
+  EXPECT_TRUE(
+      (std::is_same<
+          std::tuple<Matcher<bool>, Matcher<int>, Matcher<char*>, Matcher<int&>,
+                     Matcher<const long&>>,  // NOLINT
+          F::ArgumentMatcherTuple>::value));
+  EXPECT_TRUE(
+      (std::is_same<void(bool, int, char*, int&, const long&),  // NOLINT
+                    F::MakeResultVoid>::value));
+  EXPECT_TRUE((
+      std::is_same<IgnoredValue(bool, int, char*, int&, const long&),  // NOLINT
+                   F::MakeResultIgnoredValue>::value));
+}
+
+}  // namespace
+}  // namespace internal
+}  // namespace testing
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock-matchers_test.cc b/leveldb_base/third_party/googletest/googlemock/test/gmock-matchers_test.cc
new file mode 100644
index 0000000..1f48a76
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock-matchers_test.cc
@@ -0,0 +1,8562 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests some commonly used argument matchers.
+
+// Silence warning C4244: 'initializing': conversion from 'int' to 'short',
+// possible loss of data and C4100, unreferenced local parameter
+#ifdef _MSC_VER
+# pragma warning(push)
+# pragma warning(disable:4244)
+# pragma warning(disable:4100)
+#endif
+
+#include "gmock/gmock-matchers.h"
+
+#include <string.h>
+#include <time.h>
+
+#include <array>
+#include <cstdint>
+#include <deque>
+#include <forward_list>
+#include <functional>
+#include <iostream>
+#include <iterator>
+#include <limits>
+#include <list>
+#include <map>
+#include <memory>
+#include <set>
+#include <sstream>
+#include <string>
+#include <type_traits>
+#include <unordered_map>
+#include <unordered_set>
+#include <utility>
+#include <vector>
+
+#include "gmock/gmock-more-matchers.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest-spi.h"
+#include "gtest/gtest.h"
+
+namespace testing {
+namespace gmock_matchers_test {
+namespace {
+
+using std::greater;
+using std::less;
+using std::list;
+using std::make_pair;
+using std::map;
+using std::multimap;
+using std::multiset;
+using std::ostream;
+using std::pair;
+using std::set;
+using std::stringstream;
+using std::vector;
+using testing::internal::DummyMatchResultListener;
+using testing::internal::ElementMatcherPair;
+using testing::internal::ElementMatcherPairs;
+using testing::internal::ElementsAreArrayMatcher;
+using testing::internal::ExplainMatchFailureTupleTo;
+using testing::internal::FloatingEqMatcher;
+using testing::internal::FormatMatcherDescription;
+using testing::internal::IsReadableTypeName;
+using testing::internal::MatchMatrix;
+using testing::internal::PredicateFormatterFromMatcher;
+using testing::internal::RE;
+using testing::internal::StreamMatchResultListener;
+using testing::internal::Strings;
+
+// Helper for testing container-valued matchers in mock method context. It is
+// important to test matchers in this context, since it requires additional type
+// deduction beyond what EXPECT_THAT does, thus making it more restrictive.
+struct ContainerHelper {
+  MOCK_METHOD1(Call, void(std::vector<std::unique_ptr<int>>));
+};
+
+std::vector<std::unique_ptr<int>> MakeUniquePtrs(const std::vector<int>& ints) {
+  std::vector<std::unique_ptr<int>> pointers;
+  for (int i : ints) pointers.emplace_back(new int(i));
+  return pointers;
+}
+
+// For testing ExplainMatchResultTo().
+class GreaterThanMatcher : public MatcherInterface<int> {
+ public:
+  explicit GreaterThanMatcher(int rhs) : rhs_(rhs) {}
+
+  void DescribeTo(ostream* os) const override { *os << "is > " << rhs_; }
+
+  bool MatchAndExplain(int lhs, MatchResultListener* listener) const override {
+    const int diff = lhs - rhs_;
+    if (diff > 0) {
+      *listener << "which is " << diff << " more than " << rhs_;
+    } else if (diff == 0) {
+      *listener << "which is the same as " << rhs_;
+    } else {
+      *listener << "which is " << -diff << " less than " << rhs_;
+    }
+
+    return lhs > rhs_;
+  }
+
+ private:
+  int rhs_;
+};
+
+Matcher<int> GreaterThan(int n) {
+  return MakeMatcher(new GreaterThanMatcher(n));
+}
+
+std::string OfType(const std::string& type_name) {
+#if GTEST_HAS_RTTI
+  return IsReadableTypeName(type_name) ? " (of type " + type_name + ")" : "";
+#else
+  return "";
+#endif
+}
+
+// Returns the description of the given matcher.
+template <typename T>
+std::string Describe(const Matcher<T>& m) {
+  return DescribeMatcher<T>(m);
+}
+
+// Returns the description of the negation of the given matcher.
+template <typename T>
+std::string DescribeNegation(const Matcher<T>& m) {
+  return DescribeMatcher<T>(m, true);
+}
+
+// Returns the reason why x matches, or doesn't match, m.
+template <typename MatcherType, typename Value>
+std::string Explain(const MatcherType& m, const Value& x) {
+  StringMatchResultListener listener;
+  ExplainMatchResult(m, x, &listener);
+  return listener.str();
+}
+
+TEST(MonotonicMatcherTest, IsPrintable) {
+  stringstream ss;
+  ss << GreaterThan(5);
+  EXPECT_EQ("is > 5", ss.str());
+}
+
+TEST(MatchResultListenerTest, StreamingWorks) {
+  StringMatchResultListener listener;
+  listener << "hi" << 5;
+  EXPECT_EQ("hi5", listener.str());
+
+  listener.Clear();
+  EXPECT_EQ("", listener.str());
+
+  listener << 42;
+  EXPECT_EQ("42", listener.str());
+
+  // Streaming shouldn't crash when the underlying ostream is NULL.
+  DummyMatchResultListener dummy;
+  dummy << "hi" << 5;
+}
+
+TEST(MatchResultListenerTest, CanAccessUnderlyingStream) {
+  EXPECT_TRUE(DummyMatchResultListener().stream() == nullptr);
+  EXPECT_TRUE(StreamMatchResultListener(nullptr).stream() == nullptr);
+
+  EXPECT_EQ(&std::cout, StreamMatchResultListener(&std::cout).stream());
+}
+
+TEST(MatchResultListenerTest, IsInterestedWorks) {
+  EXPECT_TRUE(StringMatchResultListener().IsInterested());
+  EXPECT_TRUE(StreamMatchResultListener(&std::cout).IsInterested());
+
+  EXPECT_FALSE(DummyMatchResultListener().IsInterested());
+  EXPECT_FALSE(StreamMatchResultListener(nullptr).IsInterested());
+}
+
+// Makes sure that the MatcherInterface<T> interface doesn't
+// change.
+class EvenMatcherImpl : public MatcherInterface<int> {
+ public:
+  bool MatchAndExplain(int x,
+                       MatchResultListener* /* listener */) const override {
+    return x % 2 == 0;
+  }
+
+  void DescribeTo(ostream* os) const override { *os << "is an even number"; }
+
+  // We deliberately don't define DescribeNegationTo() and
+  // ExplainMatchResultTo() here, to make sure the definition of these
+  // two methods is optional.
+};
+
+// Makes sure that the MatcherInterface API doesn't change.
+TEST(MatcherInterfaceTest, CanBeImplementedUsingPublishedAPI) {
+  EvenMatcherImpl m;
+}
+
+// Tests implementing a monomorphic matcher using MatchAndExplain().
+
+class NewEvenMatcherImpl : public MatcherInterface<int> {
+ public:
+  bool MatchAndExplain(int x, MatchResultListener* listener) const override {
+    const bool match = x % 2 == 0;
+    // Verifies that we can stream to a listener directly.
+    *listener << "value % " << 2;
+    if (listener->stream() != nullptr) {
+      // Verifies that we can stream to a listener's underlying stream
+      // too.
+      *listener->stream() << " == " << (x % 2);
+    }
+    return match;
+  }
+
+  void DescribeTo(ostream* os) const override { *os << "is an even number"; }
+};
+
+TEST(MatcherInterfaceTest, CanBeImplementedUsingNewAPI) {
+  Matcher<int> m = MakeMatcher(new NewEvenMatcherImpl);
+  EXPECT_TRUE(m.Matches(2));
+  EXPECT_FALSE(m.Matches(3));
+  EXPECT_EQ("value % 2 == 0", Explain(m, 2));
+  EXPECT_EQ("value % 2 == 1", Explain(m, 3));
+}
+
+// Tests default-constructing a matcher.
+TEST(MatcherTest, CanBeDefaultConstructed) {
+  Matcher<double> m;
+}
+
+// Tests that Matcher<T> can be constructed from a MatcherInterface<T>*.
+TEST(MatcherTest, CanBeConstructedFromMatcherInterface) {
+  const MatcherInterface<int>* impl = new EvenMatcherImpl;
+  Matcher<int> m(impl);
+  EXPECT_TRUE(m.Matches(4));
+  EXPECT_FALSE(m.Matches(5));
+}
+
+// Tests that value can be used in place of Eq(value).
+TEST(MatcherTest, CanBeImplicitlyConstructedFromValue) {
+  Matcher<int> m1 = 5;
+  EXPECT_TRUE(m1.Matches(5));
+  EXPECT_FALSE(m1.Matches(6));
+}
+
+// Tests that NULL can be used in place of Eq(NULL).
+TEST(MatcherTest, CanBeImplicitlyConstructedFromNULL) {
+  Matcher<int*> m1 = nullptr;
+  EXPECT_TRUE(m1.Matches(nullptr));
+  int n = 0;
+  EXPECT_FALSE(m1.Matches(&n));
+}
+
+// Tests that matchers can be constructed from a variable that is not properly
+// defined. This should be illegal, but many users rely on this accidentally.
+struct Undefined {
+  virtual ~Undefined() = 0;
+  static const int kInt = 1;
+};
+
+TEST(MatcherTest, CanBeConstructedFromUndefinedVariable) {
+  Matcher<int> m1 = Undefined::kInt;
+  EXPECT_TRUE(m1.Matches(1));
+  EXPECT_FALSE(m1.Matches(2));
+}
+
+// Test that a matcher parameterized with an abstract class compiles.
+TEST(MatcherTest, CanAcceptAbstractClass) { Matcher<const Undefined&> m = _; }
+
+// Tests that matchers are copyable.
+TEST(MatcherTest, IsCopyable) {
+  // Tests the copy constructor.
+  Matcher<bool> m1 = Eq(false);
+  EXPECT_TRUE(m1.Matches(false));
+  EXPECT_FALSE(m1.Matches(true));
+
+  // Tests the assignment operator.
+  m1 = Eq(true);
+  EXPECT_TRUE(m1.Matches(true));
+  EXPECT_FALSE(m1.Matches(false));
+}
+
+// Tests that Matcher<T>::DescribeTo() calls
+// MatcherInterface<T>::DescribeTo().
+TEST(MatcherTest, CanDescribeItself) {
+  EXPECT_EQ("is an even number",
+            Describe(Matcher<int>(new EvenMatcherImpl)));
+}
+
+// Tests Matcher<T>::MatchAndExplain().
+TEST(MatcherTest, MatchAndExplain) {
+  Matcher<int> m = GreaterThan(0);
+  StringMatchResultListener listener1;
+  EXPECT_TRUE(m.MatchAndExplain(42, &listener1));
+  EXPECT_EQ("which is 42 more than 0", listener1.str());
+
+  StringMatchResultListener listener2;
+  EXPECT_FALSE(m.MatchAndExplain(-9, &listener2));
+  EXPECT_EQ("which is 9 less than 0", listener2.str());
+}
+
+// Tests that a C-string literal can be implicitly converted to a
+// Matcher<std::string> or Matcher<const std::string&>.
+TEST(StringMatcherTest, CanBeImplicitlyConstructedFromCStringLiteral) {
+  Matcher<std::string> m1 = "hi";
+  EXPECT_TRUE(m1.Matches("hi"));
+  EXPECT_FALSE(m1.Matches("hello"));
+
+  Matcher<const std::string&> m2 = "hi";
+  EXPECT_TRUE(m2.Matches("hi"));
+  EXPECT_FALSE(m2.Matches("hello"));
+}
+
+// Tests that a string object can be implicitly converted to a
+// Matcher<std::string> or Matcher<const std::string&>.
+TEST(StringMatcherTest, CanBeImplicitlyConstructedFromString) {
+  Matcher<std::string> m1 = std::string("hi");
+  EXPECT_TRUE(m1.Matches("hi"));
+  EXPECT_FALSE(m1.Matches("hello"));
+
+  Matcher<const std::string&> m2 = std::string("hi");
+  EXPECT_TRUE(m2.Matches("hi"));
+  EXPECT_FALSE(m2.Matches("hello"));
+}
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+// Tests that a C-string literal can be implicitly converted to a
+// Matcher<StringView> or Matcher<const StringView&>.
+TEST(StringViewMatcherTest, CanBeImplicitlyConstructedFromCStringLiteral) {
+  Matcher<internal::StringView> m1 = "cats";
+  EXPECT_TRUE(m1.Matches("cats"));
+  EXPECT_FALSE(m1.Matches("dogs"));
+
+  Matcher<const internal::StringView&> m2 = "cats";
+  EXPECT_TRUE(m2.Matches("cats"));
+  EXPECT_FALSE(m2.Matches("dogs"));
+}
+
+// Tests that a std::string object can be implicitly converted to a
+// Matcher<StringView> or Matcher<const StringView&>.
+TEST(StringViewMatcherTest, CanBeImplicitlyConstructedFromString) {
+  Matcher<internal::StringView> m1 = std::string("cats");
+  EXPECT_TRUE(m1.Matches("cats"));
+  EXPECT_FALSE(m1.Matches("dogs"));
+
+  Matcher<const internal::StringView&> m2 = std::string("cats");
+  EXPECT_TRUE(m2.Matches("cats"));
+  EXPECT_FALSE(m2.Matches("dogs"));
+}
+
+// Tests that a StringView object can be implicitly converted to a
+// Matcher<StringView> or Matcher<const StringView&>.
+TEST(StringViewMatcherTest, CanBeImplicitlyConstructedFromStringView) {
+  Matcher<internal::StringView> m1 = internal::StringView("cats");
+  EXPECT_TRUE(m1.Matches("cats"));
+  EXPECT_FALSE(m1.Matches("dogs"));
+
+  Matcher<const internal::StringView&> m2 = internal::StringView("cats");
+  EXPECT_TRUE(m2.Matches("cats"));
+  EXPECT_FALSE(m2.Matches("dogs"));
+}
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+
+// Tests that a std::reference_wrapper<std::string> object can be implicitly
+// converted to a Matcher<std::string> or Matcher<const std::string&> via Eq().
+TEST(StringMatcherTest,
+     CanBeImplicitlyConstructedFromEqReferenceWrapperString) {
+  std::string value = "cats";
+  Matcher<std::string> m1 = Eq(std::ref(value));
+  EXPECT_TRUE(m1.Matches("cats"));
+  EXPECT_FALSE(m1.Matches("dogs"));
+
+  Matcher<const std::string&> m2 = Eq(std::ref(value));
+  EXPECT_TRUE(m2.Matches("cats"));
+  EXPECT_FALSE(m2.Matches("dogs"));
+}
+
+// Tests that MakeMatcher() constructs a Matcher<T> from a
+// MatcherInterface* without requiring the user to explicitly
+// write the type.
+TEST(MakeMatcherTest, ConstructsMatcherFromMatcherInterface) {
+  const MatcherInterface<int>* dummy_impl = new EvenMatcherImpl;
+  Matcher<int> m = MakeMatcher(dummy_impl);
+}
+
+// Tests that MakePolymorphicMatcher() can construct a polymorphic
+// matcher from its implementation using the old API.
+const int g_bar = 1;
+class ReferencesBarOrIsZeroImpl {
+ public:
+  template <typename T>
+  bool MatchAndExplain(const T& x,
+                       MatchResultListener* /* listener */) const {
+    const void* p = &x;
+    return p == &g_bar || x == 0;
+  }
+
+  void DescribeTo(ostream* os) const { *os << "g_bar or zero"; }
+
+  void DescribeNegationTo(ostream* os) const {
+    *os << "doesn't reference g_bar and is not zero";
+  }
+};
+
+// This function verifies that MakePolymorphicMatcher() returns a
+// PolymorphicMatcher<T> where T is the argument's type.
+PolymorphicMatcher<ReferencesBarOrIsZeroImpl> ReferencesBarOrIsZero() {
+  return MakePolymorphicMatcher(ReferencesBarOrIsZeroImpl());
+}
+
+TEST(MakePolymorphicMatcherTest, ConstructsMatcherUsingOldAPI) {
+  // Using a polymorphic matcher to match a reference type.
+  Matcher<const int&> m1 = ReferencesBarOrIsZero();
+  EXPECT_TRUE(m1.Matches(0));
+  // Verifies that the identity of a by-reference argument is preserved.
+  EXPECT_TRUE(m1.Matches(g_bar));
+  EXPECT_FALSE(m1.Matches(1));
+  EXPECT_EQ("g_bar or zero", Describe(m1));
+
+  // Using a polymorphic matcher to match a value type.
+  Matcher<double> m2 = ReferencesBarOrIsZero();
+  EXPECT_TRUE(m2.Matches(0.0));
+  EXPECT_FALSE(m2.Matches(0.1));
+  EXPECT_EQ("g_bar or zero", Describe(m2));
+}
+
+// Tests implementing a polymorphic matcher using MatchAndExplain().
+
+class PolymorphicIsEvenImpl {
+ public:
+  void DescribeTo(ostream* os) const { *os << "is even"; }
+
+  void DescribeNegationTo(ostream* os) const {
+    *os << "is odd";
+  }
+
+  template <typename T>
+  bool MatchAndExplain(const T& x, MatchResultListener* listener) const {
+    // Verifies that we can stream to the listener directly.
+    *listener << "% " << 2;
+    if (listener->stream() != nullptr) {
+      // Verifies that we can stream to the listener's underlying stream
+      // too.
+      *listener->stream() << " == " << (x % 2);
+    }
+    return (x % 2) == 0;
+  }
+};
+
+PolymorphicMatcher<PolymorphicIsEvenImpl> PolymorphicIsEven() {
+  return MakePolymorphicMatcher(PolymorphicIsEvenImpl());
+}
+
+TEST(MakePolymorphicMatcherTest, ConstructsMatcherUsingNewAPI) {
+  // Using PolymorphicIsEven() as a Matcher<int>.
+  const Matcher<int> m1 = PolymorphicIsEven();
+  EXPECT_TRUE(m1.Matches(42));
+  EXPECT_FALSE(m1.Matches(43));
+  EXPECT_EQ("is even", Describe(m1));
+
+  const Matcher<int> not_m1 = Not(m1);
+  EXPECT_EQ("is odd", Describe(not_m1));
+
+  EXPECT_EQ("% 2 == 0", Explain(m1, 42));
+
+  // Using PolymorphicIsEven() as a Matcher<char>.
+  const Matcher<char> m2 = PolymorphicIsEven();
+  EXPECT_TRUE(m2.Matches('\x42'));
+  EXPECT_FALSE(m2.Matches('\x43'));
+  EXPECT_EQ("is even", Describe(m2));
+
+  const Matcher<char> not_m2 = Not(m2);
+  EXPECT_EQ("is odd", Describe(not_m2));
+
+  EXPECT_EQ("% 2 == 0", Explain(m2, '\x42'));
+}
+
+// Tests that MatcherCast<T>(m) works when m is a polymorphic matcher.
+TEST(MatcherCastTest, FromPolymorphicMatcher) {
+  Matcher<int> m = MatcherCast<int>(Eq(5));
+  EXPECT_TRUE(m.Matches(5));
+  EXPECT_FALSE(m.Matches(6));
+}
+
+// For testing casting matchers between compatible types.
+class IntValue {
+ public:
+  // An int can be statically (although not implicitly) cast to a
+  // IntValue.
+  explicit IntValue(int a_value) : value_(a_value) {}
+
+  int value() const { return value_; }
+ private:
+  int value_;
+};
+
+// For testing casting matchers between compatible types.
+bool IsPositiveIntValue(const IntValue& foo) {
+  return foo.value() > 0;
+}
+
+// Tests that MatcherCast<T>(m) works when m is a Matcher<U> where T
+// can be statically converted to U.
+TEST(MatcherCastTest, FromCompatibleType) {
+  Matcher<double> m1 = Eq(2.0);
+  Matcher<int> m2 = MatcherCast<int>(m1);
+  EXPECT_TRUE(m2.Matches(2));
+  EXPECT_FALSE(m2.Matches(3));
+
+  Matcher<IntValue> m3 = Truly(IsPositiveIntValue);
+  Matcher<int> m4 = MatcherCast<int>(m3);
+  // In the following, the arguments 1 and 0 are statically converted
+  // to IntValue objects, and then tested by the IsPositiveIntValue()
+  // predicate.
+  EXPECT_TRUE(m4.Matches(1));
+  EXPECT_FALSE(m4.Matches(0));
+}
+
+// Tests that MatcherCast<T>(m) works when m is a Matcher<const T&>.
+TEST(MatcherCastTest, FromConstReferenceToNonReference) {
+  Matcher<const int&> m1 = Eq(0);
+  Matcher<int> m2 = MatcherCast<int>(m1);
+  EXPECT_TRUE(m2.Matches(0));
+  EXPECT_FALSE(m2.Matches(1));
+}
+
+// Tests that MatcherCast<T>(m) works when m is a Matcher<T&>.
+TEST(MatcherCastTest, FromReferenceToNonReference) {
+  Matcher<int&> m1 = Eq(0);
+  Matcher<int> m2 = MatcherCast<int>(m1);
+  EXPECT_TRUE(m2.Matches(0));
+  EXPECT_FALSE(m2.Matches(1));
+}
+
+// Tests that MatcherCast<const T&>(m) works when m is a Matcher<T>.
+TEST(MatcherCastTest, FromNonReferenceToConstReference) {
+  Matcher<int> m1 = Eq(0);
+  Matcher<const int&> m2 = MatcherCast<const int&>(m1);
+  EXPECT_TRUE(m2.Matches(0));
+  EXPECT_FALSE(m2.Matches(1));
+}
+
+// Tests that MatcherCast<T&>(m) works when m is a Matcher<T>.
+TEST(MatcherCastTest, FromNonReferenceToReference) {
+  Matcher<int> m1 = Eq(0);
+  Matcher<int&> m2 = MatcherCast<int&>(m1);
+  int n = 0;
+  EXPECT_TRUE(m2.Matches(n));
+  n = 1;
+  EXPECT_FALSE(m2.Matches(n));
+}
+
+// Tests that MatcherCast<T>(m) works when m is a Matcher<T>.
+TEST(MatcherCastTest, FromSameType) {
+  Matcher<int> m1 = Eq(0);
+  Matcher<int> m2 = MatcherCast<int>(m1);
+  EXPECT_TRUE(m2.Matches(0));
+  EXPECT_FALSE(m2.Matches(1));
+}
+
+// Tests that MatcherCast<T>(m) works when m is a value of the same type as the
+// value type of the Matcher.
+TEST(MatcherCastTest, FromAValue) {
+  Matcher<int> m = MatcherCast<int>(42);
+  EXPECT_TRUE(m.Matches(42));
+  EXPECT_FALSE(m.Matches(239));
+}
+
+// Tests that MatcherCast<T>(m) works when m is a value of the type implicitly
+// convertible to the value type of the Matcher.
+TEST(MatcherCastTest, FromAnImplicitlyConvertibleValue) {
+  const int kExpected = 'c';
+  Matcher<int> m = MatcherCast<int>('c');
+  EXPECT_TRUE(m.Matches(kExpected));
+  EXPECT_FALSE(m.Matches(kExpected + 1));
+}
+
+struct NonImplicitlyConstructibleTypeWithOperatorEq {
+  friend bool operator==(
+      const NonImplicitlyConstructibleTypeWithOperatorEq& /* ignored */,
+      int rhs) {
+    return 42 == rhs;
+  }
+  friend bool operator==(
+      int lhs,
+      const NonImplicitlyConstructibleTypeWithOperatorEq& /* ignored */) {
+    return lhs == 42;
+  }
+};
+
+// Tests that MatcherCast<T>(m) works when m is a neither a matcher nor
+// implicitly convertible to the value type of the Matcher, but the value type
+// of the matcher has operator==() overload accepting m.
+TEST(MatcherCastTest, NonImplicitlyConstructibleTypeWithOperatorEq) {
+  Matcher<NonImplicitlyConstructibleTypeWithOperatorEq> m1 =
+      MatcherCast<NonImplicitlyConstructibleTypeWithOperatorEq>(42);
+  EXPECT_TRUE(m1.Matches(NonImplicitlyConstructibleTypeWithOperatorEq()));
+
+  Matcher<NonImplicitlyConstructibleTypeWithOperatorEq> m2 =
+      MatcherCast<NonImplicitlyConstructibleTypeWithOperatorEq>(239);
+  EXPECT_FALSE(m2.Matches(NonImplicitlyConstructibleTypeWithOperatorEq()));
+
+  // When updating the following lines please also change the comment to
+  // namespace convertible_from_any.
+  Matcher<int> m3 =
+      MatcherCast<int>(NonImplicitlyConstructibleTypeWithOperatorEq());
+  EXPECT_TRUE(m3.Matches(42));
+  EXPECT_FALSE(m3.Matches(239));
+}
+
+// ConvertibleFromAny does not work with MSVC. resulting in
+// error C2440: 'initializing': cannot convert from 'Eq' to 'M'
+// No constructor could take the source type, or constructor overload
+// resolution was ambiguous
+
+#if !defined _MSC_VER
+
+// The below ConvertibleFromAny struct is implicitly constructible from anything
+// and when in the same namespace can interact with other tests. In particular,
+// if it is in the same namespace as other tests and one removes
+//   NonImplicitlyConstructibleTypeWithOperatorEq::operator==(int lhs, ...);
+// then the corresponding test still compiles (and it should not!) by implicitly
+// converting NonImplicitlyConstructibleTypeWithOperatorEq to ConvertibleFromAny
+// in m3.Matcher().
+namespace convertible_from_any {
+// Implicitly convertible from any type.
+struct ConvertibleFromAny {
+  ConvertibleFromAny(int a_value) : value(a_value) {}
+  template <typename T>
+  ConvertibleFromAny(const T& /*a_value*/) : value(-1) {
+    ADD_FAILURE() << "Conversion constructor called";
+  }
+  int value;
+};
+
+bool operator==(const ConvertibleFromAny& a, const ConvertibleFromAny& b) {
+  return a.value == b.value;
+}
+
+ostream& operator<<(ostream& os, const ConvertibleFromAny& a) {
+  return os << a.value;
+}
+
+TEST(MatcherCastTest, ConversionConstructorIsUsed) {
+  Matcher<ConvertibleFromAny> m = MatcherCast<ConvertibleFromAny>(1);
+  EXPECT_TRUE(m.Matches(ConvertibleFromAny(1)));
+  EXPECT_FALSE(m.Matches(ConvertibleFromAny(2)));
+}
+
+TEST(MatcherCastTest, FromConvertibleFromAny) {
+  Matcher<ConvertibleFromAny> m =
+      MatcherCast<ConvertibleFromAny>(Eq(ConvertibleFromAny(1)));
+  EXPECT_TRUE(m.Matches(ConvertibleFromAny(1)));
+  EXPECT_FALSE(m.Matches(ConvertibleFromAny(2)));
+}
+}  // namespace convertible_from_any
+
+#endif  // !defined _MSC_VER
+
+struct IntReferenceWrapper {
+  IntReferenceWrapper(const int& a_value) : value(&a_value) {}
+  const int* value;
+};
+
+bool operator==(const IntReferenceWrapper& a, const IntReferenceWrapper& b) {
+  return a.value == b.value;
+}
+
+TEST(MatcherCastTest, ValueIsNotCopied) {
+  int n = 42;
+  Matcher<IntReferenceWrapper> m = MatcherCast<IntReferenceWrapper>(n);
+  // Verify that the matcher holds a reference to n, not to its temporary copy.
+  EXPECT_TRUE(m.Matches(n));
+}
+
+class Base {
+ public:
+  virtual ~Base() {}
+  Base() {}
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(Base);
+};
+
+class Derived : public Base {
+ public:
+  Derived() : Base() {}
+  int i;
+};
+
+class OtherDerived : public Base {};
+
+// Tests that SafeMatcherCast<T>(m) works when m is a polymorphic matcher.
+TEST(SafeMatcherCastTest, FromPolymorphicMatcher) {
+  Matcher<char> m2 = SafeMatcherCast<char>(Eq(32));
+  EXPECT_TRUE(m2.Matches(' '));
+  EXPECT_FALSE(m2.Matches('\n'));
+}
+
+// Tests that SafeMatcherCast<T>(m) works when m is a Matcher<U> where
+// T and U are arithmetic types and T can be losslessly converted to
+// U.
+TEST(SafeMatcherCastTest, FromLosslesslyConvertibleArithmeticType) {
+  Matcher<double> m1 = DoubleEq(1.0);
+  Matcher<float> m2 = SafeMatcherCast<float>(m1);
+  EXPECT_TRUE(m2.Matches(1.0f));
+  EXPECT_FALSE(m2.Matches(2.0f));
+
+  Matcher<char> m3 = SafeMatcherCast<char>(TypedEq<int>('a'));
+  EXPECT_TRUE(m3.Matches('a'));
+  EXPECT_FALSE(m3.Matches('b'));
+}
+
+// Tests that SafeMatcherCast<T>(m) works when m is a Matcher<U> where T and U
+// are pointers or references to a derived and a base class, correspondingly.
+TEST(SafeMatcherCastTest, FromBaseClass) {
+  Derived d, d2;
+  Matcher<Base*> m1 = Eq(&d);
+  Matcher<Derived*> m2 = SafeMatcherCast<Derived*>(m1);
+  EXPECT_TRUE(m2.Matches(&d));
+  EXPECT_FALSE(m2.Matches(&d2));
+
+  Matcher<Base&> m3 = Ref(d);
+  Matcher<Derived&> m4 = SafeMatcherCast<Derived&>(m3);
+  EXPECT_TRUE(m4.Matches(d));
+  EXPECT_FALSE(m4.Matches(d2));
+}
+
+// Tests that SafeMatcherCast<T&>(m) works when m is a Matcher<const T&>.
+TEST(SafeMatcherCastTest, FromConstReferenceToReference) {
+  int n = 0;
+  Matcher<const int&> m1 = Ref(n);
+  Matcher<int&> m2 = SafeMatcherCast<int&>(m1);
+  int n1 = 0;
+  EXPECT_TRUE(m2.Matches(n));
+  EXPECT_FALSE(m2.Matches(n1));
+}
+
+// Tests that MatcherCast<const T&>(m) works when m is a Matcher<T>.
+TEST(SafeMatcherCastTest, FromNonReferenceToConstReference) {
+  Matcher<std::unique_ptr<int>> m1 = IsNull();
+  Matcher<const std::unique_ptr<int>&> m2 =
+      SafeMatcherCast<const std::unique_ptr<int>&>(m1);
+  EXPECT_TRUE(m2.Matches(std::unique_ptr<int>()));
+  EXPECT_FALSE(m2.Matches(std::unique_ptr<int>(new int)));
+}
+
+// Tests that SafeMatcherCast<T&>(m) works when m is a Matcher<T>.
+TEST(SafeMatcherCastTest, FromNonReferenceToReference) {
+  Matcher<int> m1 = Eq(0);
+  Matcher<int&> m2 = SafeMatcherCast<int&>(m1);
+  int n = 0;
+  EXPECT_TRUE(m2.Matches(n));
+  n = 1;
+  EXPECT_FALSE(m2.Matches(n));
+}
+
+// Tests that SafeMatcherCast<T>(m) works when m is a Matcher<T>.
+TEST(SafeMatcherCastTest, FromSameType) {
+  Matcher<int> m1 = Eq(0);
+  Matcher<int> m2 = SafeMatcherCast<int>(m1);
+  EXPECT_TRUE(m2.Matches(0));
+  EXPECT_FALSE(m2.Matches(1));
+}
+
+#if !defined _MSC_VER
+
+namespace convertible_from_any {
+TEST(SafeMatcherCastTest, ConversionConstructorIsUsed) {
+  Matcher<ConvertibleFromAny> m = SafeMatcherCast<ConvertibleFromAny>(1);
+  EXPECT_TRUE(m.Matches(ConvertibleFromAny(1)));
+  EXPECT_FALSE(m.Matches(ConvertibleFromAny(2)));
+}
+
+TEST(SafeMatcherCastTest, FromConvertibleFromAny) {
+  Matcher<ConvertibleFromAny> m =
+      SafeMatcherCast<ConvertibleFromAny>(Eq(ConvertibleFromAny(1)));
+  EXPECT_TRUE(m.Matches(ConvertibleFromAny(1)));
+  EXPECT_FALSE(m.Matches(ConvertibleFromAny(2)));
+}
+}  // namespace convertible_from_any
+
+#endif  // !defined _MSC_VER
+
+TEST(SafeMatcherCastTest, ValueIsNotCopied) {
+  int n = 42;
+  Matcher<IntReferenceWrapper> m = SafeMatcherCast<IntReferenceWrapper>(n);
+  // Verify that the matcher holds a reference to n, not to its temporary copy.
+  EXPECT_TRUE(m.Matches(n));
+}
+
+TEST(ExpectThat, TakesLiterals) {
+  EXPECT_THAT(1, 1);
+  EXPECT_THAT(1.0, 1.0);
+  EXPECT_THAT(std::string(), "");
+}
+
+TEST(ExpectThat, TakesFunctions) {
+  struct Helper {
+    static void Func() {}
+  };
+  void (*func)() = Helper::Func;
+  EXPECT_THAT(func, Helper::Func);
+  EXPECT_THAT(func, &Helper::Func);
+}
+
+// Tests that A<T>() matches any value of type T.
+TEST(ATest, MatchesAnyValue) {
+  // Tests a matcher for a value type.
+  Matcher<double> m1 = A<double>();
+  EXPECT_TRUE(m1.Matches(91.43));
+  EXPECT_TRUE(m1.Matches(-15.32));
+
+  // Tests a matcher for a reference type.
+  int a = 2;
+  int b = -6;
+  Matcher<int&> m2 = A<int&>();
+  EXPECT_TRUE(m2.Matches(a));
+  EXPECT_TRUE(m2.Matches(b));
+}
+
+TEST(ATest, WorksForDerivedClass) {
+  Base base;
+  Derived derived;
+  EXPECT_THAT(&base, A<Base*>());
+  // This shouldn't compile: EXPECT_THAT(&base, A<Derived*>());
+  EXPECT_THAT(&derived, A<Base*>());
+  EXPECT_THAT(&derived, A<Derived*>());
+}
+
+// Tests that A<T>() describes itself properly.
+TEST(ATest, CanDescribeSelf) {
+  EXPECT_EQ("is anything", Describe(A<bool>()));
+}
+
+// Tests that An<T>() matches any value of type T.
+TEST(AnTest, MatchesAnyValue) {
+  // Tests a matcher for a value type.
+  Matcher<int> m1 = An<int>();
+  EXPECT_TRUE(m1.Matches(9143));
+  EXPECT_TRUE(m1.Matches(-1532));
+
+  // Tests a matcher for a reference type.
+  int a = 2;
+  int b = -6;
+  Matcher<int&> m2 = An<int&>();
+  EXPECT_TRUE(m2.Matches(a));
+  EXPECT_TRUE(m2.Matches(b));
+}
+
+// Tests that An<T>() describes itself properly.
+TEST(AnTest, CanDescribeSelf) {
+  EXPECT_EQ("is anything", Describe(An<int>()));
+}
+
+// Tests that _ can be used as a matcher for any type and matches any
+// value of that type.
+TEST(UnderscoreTest, MatchesAnyValue) {
+  // Uses _ as a matcher for a value type.
+  Matcher<int> m1 = _;
+  EXPECT_TRUE(m1.Matches(123));
+  EXPECT_TRUE(m1.Matches(-242));
+
+  // Uses _ as a matcher for a reference type.
+  bool a = false;
+  const bool b = true;
+  Matcher<const bool&> m2 = _;
+  EXPECT_TRUE(m2.Matches(a));
+  EXPECT_TRUE(m2.Matches(b));
+}
+
+// Tests that _ describes itself properly.
+TEST(UnderscoreTest, CanDescribeSelf) {
+  Matcher<int> m = _;
+  EXPECT_EQ("is anything", Describe(m));
+}
+
+// Tests that Eq(x) matches any value equal to x.
+TEST(EqTest, MatchesEqualValue) {
+  // 2 C-strings with same content but different addresses.
+  const char a1[] = "hi";
+  const char a2[] = "hi";
+
+  Matcher<const char*> m1 = Eq(a1);
+  EXPECT_TRUE(m1.Matches(a1));
+  EXPECT_FALSE(m1.Matches(a2));
+}
+
+// Tests that Eq(v) describes itself properly.
+
+class Unprintable {
+ public:
+  Unprintable() : c_('a') {}
+
+  bool operator==(const Unprintable& /* rhs */) const { return true; }
+  // -Wunused-private-field: dummy accessor for `c_`.
+  char dummy_c() { return c_; }
+ private:
+  char c_;
+};
+
+TEST(EqTest, CanDescribeSelf) {
+  Matcher<Unprintable> m = Eq(Unprintable());
+  EXPECT_EQ("is equal to 1-byte object <61>", Describe(m));
+}
+
+// Tests that Eq(v) can be used to match any type that supports
+// comparing with type T, where T is v's type.
+TEST(EqTest, IsPolymorphic) {
+  Matcher<int> m1 = Eq(1);
+  EXPECT_TRUE(m1.Matches(1));
+  EXPECT_FALSE(m1.Matches(2));
+
+  Matcher<char> m2 = Eq(1);
+  EXPECT_TRUE(m2.Matches('\1'));
+  EXPECT_FALSE(m2.Matches('a'));
+}
+
+// Tests that TypedEq<T>(v) matches values of type T that's equal to v.
+TEST(TypedEqTest, ChecksEqualityForGivenType) {
+  Matcher<char> m1 = TypedEq<char>('a');
+  EXPECT_TRUE(m1.Matches('a'));
+  EXPECT_FALSE(m1.Matches('b'));
+
+  Matcher<int> m2 = TypedEq<int>(6);
+  EXPECT_TRUE(m2.Matches(6));
+  EXPECT_FALSE(m2.Matches(7));
+}
+
+// Tests that TypedEq(v) describes itself properly.
+TEST(TypedEqTest, CanDescribeSelf) {
+  EXPECT_EQ("is equal to 2", Describe(TypedEq<int>(2)));
+}
+
+// Tests that TypedEq<T>(v) has type Matcher<T>.
+
+// Type<T>::IsTypeOf(v) compiles if and only if the type of value v is T, where
+// T is a "bare" type (i.e. not in the form of const U or U&).  If v's type is
+// not T, the compiler will generate a message about "undefined reference".
+template <typename T>
+struct Type {
+  static bool IsTypeOf(const T& /* v */) { return true; }
+
+  template <typename T2>
+  static void IsTypeOf(T2 v);
+};
+
+TEST(TypedEqTest, HasSpecifiedType) {
+  // Verfies that the type of TypedEq<T>(v) is Matcher<T>.
+  Type<Matcher<int> >::IsTypeOf(TypedEq<int>(5));
+  Type<Matcher<double> >::IsTypeOf(TypedEq<double>(5));
+}
+
+// Tests that Ge(v) matches anything >= v.
+TEST(GeTest, ImplementsGreaterThanOrEqual) {
+  Matcher<int> m1 = Ge(0);
+  EXPECT_TRUE(m1.Matches(1));
+  EXPECT_TRUE(m1.Matches(0));
+  EXPECT_FALSE(m1.Matches(-1));
+}
+
+// Tests that Ge(v) describes itself properly.
+TEST(GeTest, CanDescribeSelf) {
+  Matcher<int> m = Ge(5);
+  EXPECT_EQ("is >= 5", Describe(m));
+}
+
+// Tests that Gt(v) matches anything > v.
+TEST(GtTest, ImplementsGreaterThan) {
+  Matcher<double> m1 = Gt(0);
+  EXPECT_TRUE(m1.Matches(1.0));
+  EXPECT_FALSE(m1.Matches(0.0));
+  EXPECT_FALSE(m1.Matches(-1.0));
+}
+
+// Tests that Gt(v) describes itself properly.
+TEST(GtTest, CanDescribeSelf) {
+  Matcher<int> m = Gt(5);
+  EXPECT_EQ("is > 5", Describe(m));
+}
+
+// Tests that Le(v) matches anything <= v.
+TEST(LeTest, ImplementsLessThanOrEqual) {
+  Matcher<char> m1 = Le('b');
+  EXPECT_TRUE(m1.Matches('a'));
+  EXPECT_TRUE(m1.Matches('b'));
+  EXPECT_FALSE(m1.Matches('c'));
+}
+
+// Tests that Le(v) describes itself properly.
+TEST(LeTest, CanDescribeSelf) {
+  Matcher<int> m = Le(5);
+  EXPECT_EQ("is <= 5", Describe(m));
+}
+
+// Tests that Lt(v) matches anything < v.
+TEST(LtTest, ImplementsLessThan) {
+  Matcher<const std::string&> m1 = Lt("Hello");
+  EXPECT_TRUE(m1.Matches("Abc"));
+  EXPECT_FALSE(m1.Matches("Hello"));
+  EXPECT_FALSE(m1.Matches("Hello, world!"));
+}
+
+// Tests that Lt(v) describes itself properly.
+TEST(LtTest, CanDescribeSelf) {
+  Matcher<int> m = Lt(5);
+  EXPECT_EQ("is < 5", Describe(m));
+}
+
+// Tests that Ne(v) matches anything != v.
+TEST(NeTest, ImplementsNotEqual) {
+  Matcher<int> m1 = Ne(0);
+  EXPECT_TRUE(m1.Matches(1));
+  EXPECT_TRUE(m1.Matches(-1));
+  EXPECT_FALSE(m1.Matches(0));
+}
+
+// Tests that Ne(v) describes itself properly.
+TEST(NeTest, CanDescribeSelf) {
+  Matcher<int> m = Ne(5);
+  EXPECT_EQ("isn't equal to 5", Describe(m));
+}
+
+class MoveOnly {
+ public:
+  explicit MoveOnly(int i) : i_(i) {}
+  MoveOnly(const MoveOnly&) = delete;
+  MoveOnly(MoveOnly&&) = default;
+  MoveOnly& operator=(const MoveOnly&) = delete;
+  MoveOnly& operator=(MoveOnly&&) = default;
+
+  bool operator==(const MoveOnly& other) const { return i_ == other.i_; }
+  bool operator!=(const MoveOnly& other) const { return i_ != other.i_; }
+  bool operator<(const MoveOnly& other) const { return i_ < other.i_; }
+  bool operator<=(const MoveOnly& other) const { return i_ <= other.i_; }
+  bool operator>(const MoveOnly& other) const { return i_ > other.i_; }
+  bool operator>=(const MoveOnly& other) const { return i_ >= other.i_; }
+
+ private:
+  int i_;
+};
+
+struct MoveHelper {
+  MOCK_METHOD1(Call, void(MoveOnly));
+};
+
+// Disable this test in VS 2015 (version 14), where it fails when SEH is enabled
+#if defined(_MSC_VER) && (_MSC_VER < 1910)
+TEST(ComparisonBaseTest, DISABLED_WorksWithMoveOnly) {
+#else
+TEST(ComparisonBaseTest, WorksWithMoveOnly) {
+#endif
+  MoveOnly m{0};
+  MoveHelper helper;
+
+  EXPECT_CALL(helper, Call(Eq(ByRef(m))));
+  helper.Call(MoveOnly(0));
+  EXPECT_CALL(helper, Call(Ne(ByRef(m))));
+  helper.Call(MoveOnly(1));
+  EXPECT_CALL(helper, Call(Le(ByRef(m))));
+  helper.Call(MoveOnly(0));
+  EXPECT_CALL(helper, Call(Lt(ByRef(m))));
+  helper.Call(MoveOnly(-1));
+  EXPECT_CALL(helper, Call(Ge(ByRef(m))));
+  helper.Call(MoveOnly(0));
+  EXPECT_CALL(helper, Call(Gt(ByRef(m))));
+  helper.Call(MoveOnly(1));
+}
+
+// Tests that IsNull() matches any NULL pointer of any type.
+TEST(IsNullTest, MatchesNullPointer) {
+  Matcher<int*> m1 = IsNull();
+  int* p1 = nullptr;
+  int n = 0;
+  EXPECT_TRUE(m1.Matches(p1));
+  EXPECT_FALSE(m1.Matches(&n));
+
+  Matcher<const char*> m2 = IsNull();
+  const char* p2 = nullptr;
+  EXPECT_TRUE(m2.Matches(p2));
+  EXPECT_FALSE(m2.Matches("hi"));
+
+  Matcher<void*> m3 = IsNull();
+  void* p3 = nullptr;
+  EXPECT_TRUE(m3.Matches(p3));
+  EXPECT_FALSE(m3.Matches(reinterpret_cast<void*>(0xbeef)));
+}
+
+TEST(IsNullTest, StdFunction) {
+  const Matcher<std::function<void()>> m = IsNull();
+
+  EXPECT_TRUE(m.Matches(std::function<void()>()));
+  EXPECT_FALSE(m.Matches([]{}));
+}
+
+// Tests that IsNull() describes itself properly.
+TEST(IsNullTest, CanDescribeSelf) {
+  Matcher<int*> m = IsNull();
+  EXPECT_EQ("is NULL", Describe(m));
+  EXPECT_EQ("isn't NULL", DescribeNegation(m));
+}
+
+// Tests that NotNull() matches any non-NULL pointer of any type.
+TEST(NotNullTest, MatchesNonNullPointer) {
+  Matcher<int*> m1 = NotNull();
+  int* p1 = nullptr;
+  int n = 0;
+  EXPECT_FALSE(m1.Matches(p1));
+  EXPECT_TRUE(m1.Matches(&n));
+
+  Matcher<const char*> m2 = NotNull();
+  const char* p2 = nullptr;
+  EXPECT_FALSE(m2.Matches(p2));
+  EXPECT_TRUE(m2.Matches("hi"));
+}
+
+TEST(NotNullTest, LinkedPtr) {
+  const Matcher<std::shared_ptr<int>> m = NotNull();
+  const std::shared_ptr<int> null_p;
+  const std::shared_ptr<int> non_null_p(new int);
+
+  EXPECT_FALSE(m.Matches(null_p));
+  EXPECT_TRUE(m.Matches(non_null_p));
+}
+
+TEST(NotNullTest, ReferenceToConstLinkedPtr) {
+  const Matcher<const std::shared_ptr<double>&> m = NotNull();
+  const std::shared_ptr<double> null_p;
+  const std::shared_ptr<double> non_null_p(new double);
+
+  EXPECT_FALSE(m.Matches(null_p));
+  EXPECT_TRUE(m.Matches(non_null_p));
+}
+
+TEST(NotNullTest, StdFunction) {
+  const Matcher<std::function<void()>> m = NotNull();
+
+  EXPECT_TRUE(m.Matches([]{}));
+  EXPECT_FALSE(m.Matches(std::function<void()>()));
+}
+
+// Tests that NotNull() describes itself properly.
+TEST(NotNullTest, CanDescribeSelf) {
+  Matcher<int*> m = NotNull();
+  EXPECT_EQ("isn't NULL", Describe(m));
+}
+
+// Tests that Ref(variable) matches an argument that references
+// 'variable'.
+TEST(RefTest, MatchesSameVariable) {
+  int a = 0;
+  int b = 0;
+  Matcher<int&> m = Ref(a);
+  EXPECT_TRUE(m.Matches(a));
+  EXPECT_FALSE(m.Matches(b));
+}
+
+// Tests that Ref(variable) describes itself properly.
+TEST(RefTest, CanDescribeSelf) {
+  int n = 5;
+  Matcher<int&> m = Ref(n);
+  stringstream ss;
+  ss << "references the variable @" << &n << " 5";
+  EXPECT_EQ(ss.str(), Describe(m));
+}
+
+// Test that Ref(non_const_varialbe) can be used as a matcher for a
+// const reference.
+TEST(RefTest, CanBeUsedAsMatcherForConstReference) {
+  int a = 0;
+  int b = 0;
+  Matcher<const int&> m = Ref(a);
+  EXPECT_TRUE(m.Matches(a));
+  EXPECT_FALSE(m.Matches(b));
+}
+
+// Tests that Ref(variable) is covariant, i.e. Ref(derived) can be
+// used wherever Ref(base) can be used (Ref(derived) is a sub-type
+// of Ref(base), but not vice versa.
+
+TEST(RefTest, IsCovariant) {
+  Base base, base2;
+  Derived derived;
+  Matcher<const Base&> m1 = Ref(base);
+  EXPECT_TRUE(m1.Matches(base));
+  EXPECT_FALSE(m1.Matches(base2));
+  EXPECT_FALSE(m1.Matches(derived));
+
+  m1 = Ref(derived);
+  EXPECT_TRUE(m1.Matches(derived));
+  EXPECT_FALSE(m1.Matches(base));
+  EXPECT_FALSE(m1.Matches(base2));
+}
+
+TEST(RefTest, ExplainsResult) {
+  int n = 0;
+  EXPECT_THAT(Explain(Matcher<const int&>(Ref(n)), n),
+              StartsWith("which is located @"));
+
+  int m = 0;
+  EXPECT_THAT(Explain(Matcher<const int&>(Ref(n)), m),
+              StartsWith("which is located @"));
+}
+
+// Tests string comparison matchers.
+
+template <typename T = std::string>
+std::string FromStringLike(internal::StringLike<T> str) {
+  return std::string(str);
+}
+
+TEST(StringLike, TestConversions) {
+  EXPECT_EQ("foo", FromStringLike("foo"));
+  EXPECT_EQ("foo", FromStringLike(std::string("foo")));
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  EXPECT_EQ("foo", FromStringLike(internal::StringView("foo")));
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+
+  // Non deducible types.
+  EXPECT_EQ("", FromStringLike({}));
+  EXPECT_EQ("foo", FromStringLike({'f', 'o', 'o'}));
+  const char buf[] = "foo";
+  EXPECT_EQ("foo", FromStringLike({buf, buf + 3}));
+}
+
+TEST(StrEqTest, MatchesEqualString) {
+  Matcher<const char*> m = StrEq(std::string("Hello"));
+  EXPECT_TRUE(m.Matches("Hello"));
+  EXPECT_FALSE(m.Matches("hello"));
+  EXPECT_FALSE(m.Matches(nullptr));
+
+  Matcher<const std::string&> m2 = StrEq("Hello");
+  EXPECT_TRUE(m2.Matches("Hello"));
+  EXPECT_FALSE(m2.Matches("Hi"));
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  Matcher<const internal::StringView&> m3 =
+      StrEq(internal::StringView("Hello"));
+  EXPECT_TRUE(m3.Matches(internal::StringView("Hello")));
+  EXPECT_FALSE(m3.Matches(internal::StringView("hello")));
+  EXPECT_FALSE(m3.Matches(internal::StringView()));
+
+  Matcher<const internal::StringView&> m_empty = StrEq("");
+  EXPECT_TRUE(m_empty.Matches(internal::StringView("")));
+  EXPECT_TRUE(m_empty.Matches(internal::StringView()));
+  EXPECT_FALSE(m_empty.Matches(internal::StringView("hello")));
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+}
+
+TEST(StrEqTest, CanDescribeSelf) {
+  Matcher<std::string> m = StrEq("Hi-\'\"?\\\a\b\f\n\r\t\v\xD3");
+  EXPECT_EQ("is equal to \"Hi-\'\\\"?\\\\\\a\\b\\f\\n\\r\\t\\v\\xD3\"",
+      Describe(m));
+
+  std::string str("01204500800");
+  str[3] = '\0';
+  Matcher<std::string> m2 = StrEq(str);
+  EXPECT_EQ("is equal to \"012\\04500800\"", Describe(m2));
+  str[0] = str[6] = str[7] = str[9] = str[10] = '\0';
+  Matcher<std::string> m3 = StrEq(str);
+  EXPECT_EQ("is equal to \"\\012\\045\\0\\08\\0\\0\"", Describe(m3));
+}
+
+TEST(StrNeTest, MatchesUnequalString) {
+  Matcher<const char*> m = StrNe("Hello");
+  EXPECT_TRUE(m.Matches(""));
+  EXPECT_TRUE(m.Matches(nullptr));
+  EXPECT_FALSE(m.Matches("Hello"));
+
+  Matcher<std::string> m2 = StrNe(std::string("Hello"));
+  EXPECT_TRUE(m2.Matches("hello"));
+  EXPECT_FALSE(m2.Matches("Hello"));
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  Matcher<const internal::StringView> m3 = StrNe(internal::StringView("Hello"));
+  EXPECT_TRUE(m3.Matches(internal::StringView("")));
+  EXPECT_TRUE(m3.Matches(internal::StringView()));
+  EXPECT_FALSE(m3.Matches(internal::StringView("Hello")));
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+}
+
+TEST(StrNeTest, CanDescribeSelf) {
+  Matcher<const char*> m = StrNe("Hi");
+  EXPECT_EQ("isn't equal to \"Hi\"", Describe(m));
+}
+
+TEST(StrCaseEqTest, MatchesEqualStringIgnoringCase) {
+  Matcher<const char*> m = StrCaseEq(std::string("Hello"));
+  EXPECT_TRUE(m.Matches("Hello"));
+  EXPECT_TRUE(m.Matches("hello"));
+  EXPECT_FALSE(m.Matches("Hi"));
+  EXPECT_FALSE(m.Matches(nullptr));
+
+  Matcher<const std::string&> m2 = StrCaseEq("Hello");
+  EXPECT_TRUE(m2.Matches("hello"));
+  EXPECT_FALSE(m2.Matches("Hi"));
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  Matcher<const internal::StringView&> m3 =
+      StrCaseEq(internal::StringView("Hello"));
+  EXPECT_TRUE(m3.Matches(internal::StringView("Hello")));
+  EXPECT_TRUE(m3.Matches(internal::StringView("hello")));
+  EXPECT_FALSE(m3.Matches(internal::StringView("Hi")));
+  EXPECT_FALSE(m3.Matches(internal::StringView()));
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+}
+
+TEST(StrCaseEqTest, MatchesEqualStringWith0IgnoringCase) {
+  std::string str1("oabocdooeoo");
+  std::string str2("OABOCDOOEOO");
+  Matcher<const std::string&> m0 = StrCaseEq(str1);
+  EXPECT_FALSE(m0.Matches(str2 + std::string(1, '\0')));
+
+  str1[3] = str2[3] = '\0';
+  Matcher<const std::string&> m1 = StrCaseEq(str1);
+  EXPECT_TRUE(m1.Matches(str2));
+
+  str1[0] = str1[6] = str1[7] = str1[10] = '\0';
+  str2[0] = str2[6] = str2[7] = str2[10] = '\0';
+  Matcher<const std::string&> m2 = StrCaseEq(str1);
+  str1[9] = str2[9] = '\0';
+  EXPECT_FALSE(m2.Matches(str2));
+
+  Matcher<const std::string&> m3 = StrCaseEq(str1);
+  EXPECT_TRUE(m3.Matches(str2));
+
+  EXPECT_FALSE(m3.Matches(str2 + "x"));
+  str2.append(1, '\0');
+  EXPECT_FALSE(m3.Matches(str2));
+  EXPECT_FALSE(m3.Matches(std::string(str2, 0, 9)));
+}
+
+TEST(StrCaseEqTest, CanDescribeSelf) {
+  Matcher<std::string> m = StrCaseEq("Hi");
+  EXPECT_EQ("is equal to (ignoring case) \"Hi\"", Describe(m));
+}
+
+TEST(StrCaseNeTest, MatchesUnequalStringIgnoringCase) {
+  Matcher<const char*> m = StrCaseNe("Hello");
+  EXPECT_TRUE(m.Matches("Hi"));
+  EXPECT_TRUE(m.Matches(nullptr));
+  EXPECT_FALSE(m.Matches("Hello"));
+  EXPECT_FALSE(m.Matches("hello"));
+
+  Matcher<std::string> m2 = StrCaseNe(std::string("Hello"));
+  EXPECT_TRUE(m2.Matches(""));
+  EXPECT_FALSE(m2.Matches("Hello"));
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  Matcher<const internal::StringView> m3 =
+      StrCaseNe(internal::StringView("Hello"));
+  EXPECT_TRUE(m3.Matches(internal::StringView("Hi")));
+  EXPECT_TRUE(m3.Matches(internal::StringView()));
+  EXPECT_FALSE(m3.Matches(internal::StringView("Hello")));
+  EXPECT_FALSE(m3.Matches(internal::StringView("hello")));
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+}
+
+TEST(StrCaseNeTest, CanDescribeSelf) {
+  Matcher<const char*> m = StrCaseNe("Hi");
+  EXPECT_EQ("isn't equal to (ignoring case) \"Hi\"", Describe(m));
+}
+
+// Tests that HasSubstr() works for matching string-typed values.
+TEST(HasSubstrTest, WorksForStringClasses) {
+  const Matcher<std::string> m1 = HasSubstr("foo");
+  EXPECT_TRUE(m1.Matches(std::string("I love food.")));
+  EXPECT_FALSE(m1.Matches(std::string("tofo")));
+
+  const Matcher<const std::string&> m2 = HasSubstr("foo");
+  EXPECT_TRUE(m2.Matches(std::string("I love food.")));
+  EXPECT_FALSE(m2.Matches(std::string("tofo")));
+
+  const Matcher<std::string> m_empty = HasSubstr("");
+  EXPECT_TRUE(m_empty.Matches(std::string()));
+  EXPECT_TRUE(m_empty.Matches(std::string("not empty")));
+}
+
+// Tests that HasSubstr() works for matching C-string-typed values.
+TEST(HasSubstrTest, WorksForCStrings) {
+  const Matcher<char*> m1 = HasSubstr("foo");
+  EXPECT_TRUE(m1.Matches(const_cast<char*>("I love food.")));
+  EXPECT_FALSE(m1.Matches(const_cast<char*>("tofo")));
+  EXPECT_FALSE(m1.Matches(nullptr));
+
+  const Matcher<const char*> m2 = HasSubstr("foo");
+  EXPECT_TRUE(m2.Matches("I love food."));
+  EXPECT_FALSE(m2.Matches("tofo"));
+  EXPECT_FALSE(m2.Matches(nullptr));
+
+  const Matcher<const char*> m_empty = HasSubstr("");
+  EXPECT_TRUE(m_empty.Matches("not empty"));
+  EXPECT_TRUE(m_empty.Matches(""));
+  EXPECT_FALSE(m_empty.Matches(nullptr));
+}
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+// Tests that HasSubstr() works for matching StringView-typed values.
+TEST(HasSubstrTest, WorksForStringViewClasses) {
+  const Matcher<internal::StringView> m1 =
+      HasSubstr(internal::StringView("foo"));
+  EXPECT_TRUE(m1.Matches(internal::StringView("I love food.")));
+  EXPECT_FALSE(m1.Matches(internal::StringView("tofo")));
+  EXPECT_FALSE(m1.Matches(internal::StringView()));
+
+  const Matcher<const internal::StringView&> m2 = HasSubstr("foo");
+  EXPECT_TRUE(m2.Matches(internal::StringView("I love food.")));
+  EXPECT_FALSE(m2.Matches(internal::StringView("tofo")));
+  EXPECT_FALSE(m2.Matches(internal::StringView()));
+
+  const Matcher<const internal::StringView&> m3 = HasSubstr("");
+  EXPECT_TRUE(m3.Matches(internal::StringView("foo")));
+  EXPECT_TRUE(m3.Matches(internal::StringView("")));
+  EXPECT_TRUE(m3.Matches(internal::StringView()));
+}
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+
+// Tests that HasSubstr(s) describes itself properly.
+TEST(HasSubstrTest, CanDescribeSelf) {
+  Matcher<std::string> m = HasSubstr("foo\n\"");
+  EXPECT_EQ("has substring \"foo\\n\\\"\"", Describe(m));
+}
+
+TEST(KeyTest, CanDescribeSelf) {
+  Matcher<const pair<std::string, int>&> m = Key("foo");
+  EXPECT_EQ("has a key that is equal to \"foo\"", Describe(m));
+  EXPECT_EQ("doesn't have a key that is equal to \"foo\"", DescribeNegation(m));
+}
+
+TEST(KeyTest, ExplainsResult) {
+  Matcher<pair<int, bool> > m = Key(GreaterThan(10));
+  EXPECT_EQ("whose first field is a value which is 5 less than 10",
+            Explain(m, make_pair(5, true)));
+  EXPECT_EQ("whose first field is a value which is 5 more than 10",
+            Explain(m, make_pair(15, true)));
+}
+
+TEST(KeyTest, MatchesCorrectly) {
+  pair<int, std::string> p(25, "foo");
+  EXPECT_THAT(p, Key(25));
+  EXPECT_THAT(p, Not(Key(42)));
+  EXPECT_THAT(p, Key(Ge(20)));
+  EXPECT_THAT(p, Not(Key(Lt(25))));
+}
+
+TEST(KeyTest, WorksWithMoveOnly) {
+  pair<std::unique_ptr<int>, std::unique_ptr<int>> p;
+  EXPECT_THAT(p, Key(Eq(nullptr)));
+}
+
+template <size_t I>
+struct Tag {};
+
+struct PairWithGet {
+  int member_1;
+  std::string member_2;
+  using first_type = int;
+  using second_type = std::string;
+
+  const int& GetImpl(Tag<0>) const { return member_1; }
+  const std::string& GetImpl(Tag<1>) const { return member_2; }
+};
+template <size_t I>
+auto get(const PairWithGet& value) -> decltype(value.GetImpl(Tag<I>())) {
+  return value.GetImpl(Tag<I>());
+}
+TEST(PairTest, MatchesPairWithGetCorrectly) {
+  PairWithGet p{25, "foo"};
+  EXPECT_THAT(p, Key(25));
+  EXPECT_THAT(p, Not(Key(42)));
+  EXPECT_THAT(p, Key(Ge(20)));
+  EXPECT_THAT(p, Not(Key(Lt(25))));
+
+  std::vector<PairWithGet> v = {{11, "Foo"}, {29, "gMockIsBestMock"}};
+  EXPECT_THAT(v, Contains(Key(29)));
+}
+
+TEST(KeyTest, SafelyCastsInnerMatcher) {
+  Matcher<int> is_positive = Gt(0);
+  Matcher<int> is_negative = Lt(0);
+  pair<char, bool> p('a', true);
+  EXPECT_THAT(p, Key(is_positive));
+  EXPECT_THAT(p, Not(Key(is_negative)));
+}
+
+TEST(KeyTest, InsideContainsUsingMap) {
+  map<int, char> container;
+  container.insert(make_pair(1, 'a'));
+  container.insert(make_pair(2, 'b'));
+  container.insert(make_pair(4, 'c'));
+  EXPECT_THAT(container, Contains(Key(1)));
+  EXPECT_THAT(container, Not(Contains(Key(3))));
+}
+
+TEST(KeyTest, InsideContainsUsingMultimap) {
+  multimap<int, char> container;
+  container.insert(make_pair(1, 'a'));
+  container.insert(make_pair(2, 'b'));
+  container.insert(make_pair(4, 'c'));
+
+  EXPECT_THAT(container, Not(Contains(Key(25))));
+  container.insert(make_pair(25, 'd'));
+  EXPECT_THAT(container, Contains(Key(25)));
+  container.insert(make_pair(25, 'e'));
+  EXPECT_THAT(container, Contains(Key(25)));
+
+  EXPECT_THAT(container, Contains(Key(1)));
+  EXPECT_THAT(container, Not(Contains(Key(3))));
+}
+
+TEST(PairTest, Typing) {
+  // Test verifies the following type conversions can be compiled.
+  Matcher<const pair<const char*, int>&> m1 = Pair("foo", 42);
+  Matcher<const pair<const char*, int> > m2 = Pair("foo", 42);
+  Matcher<pair<const char*, int> > m3 = Pair("foo", 42);
+
+  Matcher<pair<int, const std::string> > m4 = Pair(25, "42");
+  Matcher<pair<const std::string, int> > m5 = Pair("25", 42);
+}
+
+TEST(PairTest, CanDescribeSelf) {
+  Matcher<const pair<std::string, int>&> m1 = Pair("foo", 42);
+  EXPECT_EQ("has a first field that is equal to \"foo\""
+            ", and has a second field that is equal to 42",
+            Describe(m1));
+  EXPECT_EQ("has a first field that isn't equal to \"foo\""
+            ", or has a second field that isn't equal to 42",
+            DescribeNegation(m1));
+  // Double and triple negation (1 or 2 times not and description of negation).
+  Matcher<const pair<int, int>&> m2 = Not(Pair(Not(13), 42));
+  EXPECT_EQ("has a first field that isn't equal to 13"
+            ", and has a second field that is equal to 42",
+            DescribeNegation(m2));
+}
+
+TEST(PairTest, CanExplainMatchResultTo) {
+  // If neither field matches, Pair() should explain about the first
+  // field.
+  const Matcher<pair<int, int> > m = Pair(GreaterThan(0), GreaterThan(0));
+  EXPECT_EQ("whose first field does not match, which is 1 less than 0",
+            Explain(m, make_pair(-1, -2)));
+
+  // If the first field matches but the second doesn't, Pair() should
+  // explain about the second field.
+  EXPECT_EQ("whose second field does not match, which is 2 less than 0",
+            Explain(m, make_pair(1, -2)));
+
+  // If the first field doesn't match but the second does, Pair()
+  // should explain about the first field.
+  EXPECT_EQ("whose first field does not match, which is 1 less than 0",
+            Explain(m, make_pair(-1, 2)));
+
+  // If both fields match, Pair() should explain about them both.
+  EXPECT_EQ("whose both fields match, where the first field is a value "
+            "which is 1 more than 0, and the second field is a value "
+            "which is 2 more than 0",
+            Explain(m, make_pair(1, 2)));
+
+  // If only the first match has an explanation, only this explanation should
+  // be printed.
+  const Matcher<pair<int, int> > explain_first = Pair(GreaterThan(0), 0);
+  EXPECT_EQ("whose both fields match, where the first field is a value "
+            "which is 1 more than 0",
+            Explain(explain_first, make_pair(1, 0)));
+
+  // If only the second match has an explanation, only this explanation should
+  // be printed.
+  const Matcher<pair<int, int> > explain_second = Pair(0, GreaterThan(0));
+  EXPECT_EQ("whose both fields match, where the second field is a value "
+            "which is 1 more than 0",
+            Explain(explain_second, make_pair(0, 1)));
+}
+
+TEST(PairTest, MatchesCorrectly) {
+  pair<int, std::string> p(25, "foo");
+
+  // Both fields match.
+  EXPECT_THAT(p, Pair(25, "foo"));
+  EXPECT_THAT(p, Pair(Ge(20), HasSubstr("o")));
+
+  // 'first' doesnt' match, but 'second' matches.
+  EXPECT_THAT(p, Not(Pair(42, "foo")));
+  EXPECT_THAT(p, Not(Pair(Lt(25), "foo")));
+
+  // 'first' matches, but 'second' doesn't match.
+  EXPECT_THAT(p, Not(Pair(25, "bar")));
+  EXPECT_THAT(p, Not(Pair(25, Not("foo"))));
+
+  // Neither field matches.
+  EXPECT_THAT(p, Not(Pair(13, "bar")));
+  EXPECT_THAT(p, Not(Pair(Lt(13), HasSubstr("a"))));
+}
+
+TEST(PairTest, WorksWithMoveOnly) {
+  pair<std::unique_ptr<int>, std::unique_ptr<int>> p;
+  p.second.reset(new int(7));
+  EXPECT_THAT(p, Pair(Eq(nullptr), Ne(nullptr)));
+}
+
+TEST(PairTest, SafelyCastsInnerMatchers) {
+  Matcher<int> is_positive = Gt(0);
+  Matcher<int> is_negative = Lt(0);
+  pair<char, bool> p('a', true);
+  EXPECT_THAT(p, Pair(is_positive, _));
+  EXPECT_THAT(p, Not(Pair(is_negative, _)));
+  EXPECT_THAT(p, Pair(_, is_positive));
+  EXPECT_THAT(p, Not(Pair(_, is_negative)));
+}
+
+TEST(PairTest, InsideContainsUsingMap) {
+  map<int, char> container;
+  container.insert(make_pair(1, 'a'));
+  container.insert(make_pair(2, 'b'));
+  container.insert(make_pair(4, 'c'));
+  EXPECT_THAT(container, Contains(Pair(1, 'a')));
+  EXPECT_THAT(container, Contains(Pair(1, _)));
+  EXPECT_THAT(container, Contains(Pair(_, 'a')));
+  EXPECT_THAT(container, Not(Contains(Pair(3, _))));
+}
+
+TEST(FieldsAreTest, MatchesCorrectly) {
+  std::tuple<int, std::string, double> p(25, "foo", .5);
+
+  // All fields match.
+  EXPECT_THAT(p, FieldsAre(25, "foo", .5));
+  EXPECT_THAT(p, FieldsAre(Ge(20), HasSubstr("o"), DoubleEq(.5)));
+
+  // Some don't match.
+  EXPECT_THAT(p, Not(FieldsAre(26, "foo", .5)));
+  EXPECT_THAT(p, Not(FieldsAre(25, "fo", .5)));
+  EXPECT_THAT(p, Not(FieldsAre(25, "foo", .6)));
+}
+
+TEST(FieldsAreTest, CanDescribeSelf) {
+  Matcher<const pair<std::string, int>&> m1 = FieldsAre("foo", 42);
+  EXPECT_EQ(
+      "has field #0 that is equal to \"foo\""
+      ", and has field #1 that is equal to 42",
+      Describe(m1));
+  EXPECT_EQ(
+      "has field #0 that isn't equal to \"foo\""
+      ", or has field #1 that isn't equal to 42",
+      DescribeNegation(m1));
+}
+
+TEST(FieldsAreTest, CanExplainMatchResultTo) {
+  // The first one that fails is the one that gives the error.
+  Matcher<std::tuple<int, int, int>> m =
+      FieldsAre(GreaterThan(0), GreaterThan(0), GreaterThan(0));
+
+  EXPECT_EQ("whose field #0 does not match, which is 1 less than 0",
+            Explain(m, std::make_tuple(-1, -2, -3)));
+  EXPECT_EQ("whose field #1 does not match, which is 2 less than 0",
+            Explain(m, std::make_tuple(1, -2, -3)));
+  EXPECT_EQ("whose field #2 does not match, which is 3 less than 0",
+            Explain(m, std::make_tuple(1, 2, -3)));
+
+  // If they all match, we get a long explanation of success.
+  EXPECT_EQ(
+      "whose all elements match, "
+      "where field #0 is a value which is 1 more than 0"
+      ", and field #1 is a value which is 2 more than 0"
+      ", and field #2 is a value which is 3 more than 0",
+      Explain(m, std::make_tuple(1, 2, 3)));
+
+  // Only print those that have an explanation.
+  m = FieldsAre(GreaterThan(0), 0, GreaterThan(0));
+  EXPECT_EQ(
+      "whose all elements match, "
+      "where field #0 is a value which is 1 more than 0"
+      ", and field #2 is a value which is 3 more than 0",
+      Explain(m, std::make_tuple(1, 0, 3)));
+
+  // If only one has an explanation, then print that one.
+  m = FieldsAre(0, GreaterThan(0), 0);
+  EXPECT_EQ(
+      "whose all elements match, "
+      "where field #1 is a value which is 1 more than 0",
+      Explain(m, std::make_tuple(0, 1, 0)));
+}
+
+#if defined(__cpp_structured_bindings) && __cpp_structured_bindings >= 201606
+TEST(FieldsAreTest, StructuredBindings) {
+  // testing::FieldsAre can also match aggregates and such with C++17 and up.
+  struct MyType {
+    int i;
+    std::string str;
+  };
+  EXPECT_THAT((MyType{17, "foo"}), FieldsAre(Eq(17), HasSubstr("oo")));
+
+  // Test all the supported arities.
+  struct MyVarType1 {
+    int a;
+  };
+  EXPECT_THAT(MyVarType1{}, FieldsAre(0));
+  struct MyVarType2 {
+    int a, b;
+  };
+  EXPECT_THAT(MyVarType2{}, FieldsAre(0, 0));
+  struct MyVarType3 {
+    int a, b, c;
+  };
+  EXPECT_THAT(MyVarType3{}, FieldsAre(0, 0, 0));
+  struct MyVarType4 {
+    int a, b, c, d;
+  };
+  EXPECT_THAT(MyVarType4{}, FieldsAre(0, 0, 0, 0));
+  struct MyVarType5 {
+    int a, b, c, d, e;
+  };
+  EXPECT_THAT(MyVarType5{}, FieldsAre(0, 0, 0, 0, 0));
+  struct MyVarType6 {
+    int a, b, c, d, e, f;
+  };
+  EXPECT_THAT(MyVarType6{}, FieldsAre(0, 0, 0, 0, 0, 0));
+  struct MyVarType7 {
+    int a, b, c, d, e, f, g;
+  };
+  EXPECT_THAT(MyVarType7{}, FieldsAre(0, 0, 0, 0, 0, 0, 0));
+  struct MyVarType8 {
+    int a, b, c, d, e, f, g, h;
+  };
+  EXPECT_THAT(MyVarType8{}, FieldsAre(0, 0, 0, 0, 0, 0, 0, 0));
+  struct MyVarType9 {
+    int a, b, c, d, e, f, g, h, i;
+  };
+  EXPECT_THAT(MyVarType9{}, FieldsAre(0, 0, 0, 0, 0, 0, 0, 0, 0));
+  struct MyVarType10 {
+    int a, b, c, d, e, f, g, h, i, j;
+  };
+  EXPECT_THAT(MyVarType10{}, FieldsAre(0, 0, 0, 0, 0, 0, 0, 0, 0, 0));
+  struct MyVarType11 {
+    int a, b, c, d, e, f, g, h, i, j, k;
+  };
+  EXPECT_THAT(MyVarType11{}, FieldsAre(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0));
+  struct MyVarType12 {
+    int a, b, c, d, e, f, g, h, i, j, k, l;
+  };
+  EXPECT_THAT(MyVarType12{}, FieldsAre(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0));
+  struct MyVarType13 {
+    int a, b, c, d, e, f, g, h, i, j, k, l, m;
+  };
+  EXPECT_THAT(MyVarType13{}, FieldsAre(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0));
+  struct MyVarType14 {
+    int a, b, c, d, e, f, g, h, i, j, k, l, m, n;
+  };
+  EXPECT_THAT(MyVarType14{},
+              FieldsAre(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0));
+  struct MyVarType15 {
+    int a, b, c, d, e, f, g, h, i, j, k, l, m, n, o;
+  };
+  EXPECT_THAT(MyVarType15{},
+              FieldsAre(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0));
+  struct MyVarType16 {
+    int a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p;
+  };
+  EXPECT_THAT(MyVarType16{},
+              FieldsAre(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0));
+}
+#endif
+
+TEST(ContainsTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper, Call(Contains(Pointee(2))));
+  helper.Call(MakeUniquePtrs({1, 2}));
+}
+
+TEST(PairTest, UseGetInsteadOfMembers) {
+  PairWithGet pair{7, "ABC"};
+  EXPECT_THAT(pair, Pair(7, "ABC"));
+  EXPECT_THAT(pair, Pair(Ge(7), HasSubstr("AB")));
+  EXPECT_THAT(pair, Not(Pair(Lt(7), "ABC")));
+
+  std::vector<PairWithGet> v = {{11, "Foo"}, {29, "gMockIsBestMock"}};
+  EXPECT_THAT(v,
+              ElementsAre(Pair(11, std::string("Foo")), Pair(Ge(10), Not(""))));
+}
+
+// Tests StartsWith(s).
+
+TEST(StartsWithTest, MatchesStringWithGivenPrefix) {
+  const Matcher<const char*> m1 = StartsWith(std::string(""));
+  EXPECT_TRUE(m1.Matches("Hi"));
+  EXPECT_TRUE(m1.Matches(""));
+  EXPECT_FALSE(m1.Matches(nullptr));
+
+  const Matcher<const std::string&> m2 = StartsWith("Hi");
+  EXPECT_TRUE(m2.Matches("Hi"));
+  EXPECT_TRUE(m2.Matches("Hi Hi!"));
+  EXPECT_TRUE(m2.Matches("High"));
+  EXPECT_FALSE(m2.Matches("H"));
+  EXPECT_FALSE(m2.Matches(" Hi"));
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  const Matcher<internal::StringView> m_empty =
+      StartsWith(internal::StringView(""));
+  EXPECT_TRUE(m_empty.Matches(internal::StringView()));
+  EXPECT_TRUE(m_empty.Matches(internal::StringView("")));
+  EXPECT_TRUE(m_empty.Matches(internal::StringView("not empty")));
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+}
+
+TEST(StartsWithTest, CanDescribeSelf) {
+  Matcher<const std::string> m = StartsWith("Hi");
+  EXPECT_EQ("starts with \"Hi\"", Describe(m));
+}
+
+// Tests EndsWith(s).
+
+TEST(EndsWithTest, MatchesStringWithGivenSuffix) {
+  const Matcher<const char*> m1 = EndsWith("");
+  EXPECT_TRUE(m1.Matches("Hi"));
+  EXPECT_TRUE(m1.Matches(""));
+  EXPECT_FALSE(m1.Matches(nullptr));
+
+  const Matcher<const std::string&> m2 = EndsWith(std::string("Hi"));
+  EXPECT_TRUE(m2.Matches("Hi"));
+  EXPECT_TRUE(m2.Matches("Wow Hi Hi"));
+  EXPECT_TRUE(m2.Matches("Super Hi"));
+  EXPECT_FALSE(m2.Matches("i"));
+  EXPECT_FALSE(m2.Matches("Hi "));
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  const Matcher<const internal::StringView&> m4 =
+      EndsWith(internal::StringView(""));
+  EXPECT_TRUE(m4.Matches("Hi"));
+  EXPECT_TRUE(m4.Matches(""));
+  EXPECT_TRUE(m4.Matches(internal::StringView()));
+  EXPECT_TRUE(m4.Matches(internal::StringView("")));
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+}
+
+TEST(EndsWithTest, CanDescribeSelf) {
+  Matcher<const std::string> m = EndsWith("Hi");
+  EXPECT_EQ("ends with \"Hi\"", Describe(m));
+}
+
+// Tests MatchesRegex().
+
+TEST(MatchesRegexTest, MatchesStringMatchingGivenRegex) {
+  const Matcher<const char*> m1 = MatchesRegex("a.*z");
+  EXPECT_TRUE(m1.Matches("az"));
+  EXPECT_TRUE(m1.Matches("abcz"));
+  EXPECT_FALSE(m1.Matches(nullptr));
+
+  const Matcher<const std::string&> m2 = MatchesRegex(new RE("a.*z"));
+  EXPECT_TRUE(m2.Matches("azbz"));
+  EXPECT_FALSE(m2.Matches("az1"));
+  EXPECT_FALSE(m2.Matches("1az"));
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  const Matcher<const internal::StringView&> m3 = MatchesRegex("a.*z");
+  EXPECT_TRUE(m3.Matches(internal::StringView("az")));
+  EXPECT_TRUE(m3.Matches(internal::StringView("abcz")));
+  EXPECT_FALSE(m3.Matches(internal::StringView("1az")));
+  EXPECT_FALSE(m3.Matches(internal::StringView()));
+  const Matcher<const internal::StringView&> m4 =
+      MatchesRegex(internal::StringView(""));
+  EXPECT_TRUE(m4.Matches(internal::StringView("")));
+  EXPECT_TRUE(m4.Matches(internal::StringView()));
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+}
+
+TEST(MatchesRegexTest, CanDescribeSelf) {
+  Matcher<const std::string> m1 = MatchesRegex(std::string("Hi.*"));
+  EXPECT_EQ("matches regular expression \"Hi.*\"", Describe(m1));
+
+  Matcher<const char*> m2 = MatchesRegex(new RE("a.*"));
+  EXPECT_EQ("matches regular expression \"a.*\"", Describe(m2));
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  Matcher<const internal::StringView> m3 = MatchesRegex(new RE("0.*"));
+  EXPECT_EQ("matches regular expression \"0.*\"", Describe(m3));
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+}
+
+// Tests ContainsRegex().
+
+TEST(ContainsRegexTest, MatchesStringContainingGivenRegex) {
+  const Matcher<const char*> m1 = ContainsRegex(std::string("a.*z"));
+  EXPECT_TRUE(m1.Matches("az"));
+  EXPECT_TRUE(m1.Matches("0abcz1"));
+  EXPECT_FALSE(m1.Matches(nullptr));
+
+  const Matcher<const std::string&> m2 = ContainsRegex(new RE("a.*z"));
+  EXPECT_TRUE(m2.Matches("azbz"));
+  EXPECT_TRUE(m2.Matches("az1"));
+  EXPECT_FALSE(m2.Matches("1a"));
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  const Matcher<const internal::StringView&> m3 =
+      ContainsRegex(new RE("a.*z"));
+  EXPECT_TRUE(m3.Matches(internal::StringView("azbz")));
+  EXPECT_TRUE(m3.Matches(internal::StringView("az1")));
+  EXPECT_FALSE(m3.Matches(internal::StringView("1a")));
+  EXPECT_FALSE(m3.Matches(internal::StringView()));
+  const Matcher<const internal::StringView&> m4 =
+      ContainsRegex(internal::StringView(""));
+  EXPECT_TRUE(m4.Matches(internal::StringView("")));
+  EXPECT_TRUE(m4.Matches(internal::StringView()));
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+}
+
+TEST(ContainsRegexTest, CanDescribeSelf) {
+  Matcher<const std::string> m1 = ContainsRegex("Hi.*");
+  EXPECT_EQ("contains regular expression \"Hi.*\"", Describe(m1));
+
+  Matcher<const char*> m2 = ContainsRegex(new RE("a.*"));
+  EXPECT_EQ("contains regular expression \"a.*\"", Describe(m2));
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  Matcher<const internal::StringView> m3 = ContainsRegex(new RE("0.*"));
+  EXPECT_EQ("contains regular expression \"0.*\"", Describe(m3));
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+}
+
+// Tests for wide strings.
+#if GTEST_HAS_STD_WSTRING
+TEST(StdWideStrEqTest, MatchesEqual) {
+  Matcher<const wchar_t*> m = StrEq(::std::wstring(L"Hello"));
+  EXPECT_TRUE(m.Matches(L"Hello"));
+  EXPECT_FALSE(m.Matches(L"hello"));
+  EXPECT_FALSE(m.Matches(nullptr));
+
+  Matcher<const ::std::wstring&> m2 = StrEq(L"Hello");
+  EXPECT_TRUE(m2.Matches(L"Hello"));
+  EXPECT_FALSE(m2.Matches(L"Hi"));
+
+  Matcher<const ::std::wstring&> m3 = StrEq(L"\xD3\x576\x8D3\xC74D");
+  EXPECT_TRUE(m3.Matches(L"\xD3\x576\x8D3\xC74D"));
+  EXPECT_FALSE(m3.Matches(L"\xD3\x576\x8D3\xC74E"));
+
+  ::std::wstring str(L"01204500800");
+  str[3] = L'\0';
+  Matcher<const ::std::wstring&> m4 = StrEq(str);
+  EXPECT_TRUE(m4.Matches(str));
+  str[0] = str[6] = str[7] = str[9] = str[10] = L'\0';
+  Matcher<const ::std::wstring&> m5 = StrEq(str);
+  EXPECT_TRUE(m5.Matches(str));
+}
+
+TEST(StdWideStrEqTest, CanDescribeSelf) {
+  Matcher< ::std::wstring> m = StrEq(L"Hi-\'\"?\\\a\b\f\n\r\t\v");
+  EXPECT_EQ("is equal to L\"Hi-\'\\\"?\\\\\\a\\b\\f\\n\\r\\t\\v\"",
+    Describe(m));
+
+  Matcher< ::std::wstring> m2 = StrEq(L"\xD3\x576\x8D3\xC74D");
+  EXPECT_EQ("is equal to L\"\\xD3\\x576\\x8D3\\xC74D\"",
+    Describe(m2));
+
+  ::std::wstring str(L"01204500800");
+  str[3] = L'\0';
+  Matcher<const ::std::wstring&> m4 = StrEq(str);
+  EXPECT_EQ("is equal to L\"012\\04500800\"", Describe(m4));
+  str[0] = str[6] = str[7] = str[9] = str[10] = L'\0';
+  Matcher<const ::std::wstring&> m5 = StrEq(str);
+  EXPECT_EQ("is equal to L\"\\012\\045\\0\\08\\0\\0\"", Describe(m5));
+}
+
+TEST(StdWideStrNeTest, MatchesUnequalString) {
+  Matcher<const wchar_t*> m = StrNe(L"Hello");
+  EXPECT_TRUE(m.Matches(L""));
+  EXPECT_TRUE(m.Matches(nullptr));
+  EXPECT_FALSE(m.Matches(L"Hello"));
+
+  Matcher< ::std::wstring> m2 = StrNe(::std::wstring(L"Hello"));
+  EXPECT_TRUE(m2.Matches(L"hello"));
+  EXPECT_FALSE(m2.Matches(L"Hello"));
+}
+
+TEST(StdWideStrNeTest, CanDescribeSelf) {
+  Matcher<const wchar_t*> m = StrNe(L"Hi");
+  EXPECT_EQ("isn't equal to L\"Hi\"", Describe(m));
+}
+
+TEST(StdWideStrCaseEqTest, MatchesEqualStringIgnoringCase) {
+  Matcher<const wchar_t*> m = StrCaseEq(::std::wstring(L"Hello"));
+  EXPECT_TRUE(m.Matches(L"Hello"));
+  EXPECT_TRUE(m.Matches(L"hello"));
+  EXPECT_FALSE(m.Matches(L"Hi"));
+  EXPECT_FALSE(m.Matches(nullptr));
+
+  Matcher<const ::std::wstring&> m2 = StrCaseEq(L"Hello");
+  EXPECT_TRUE(m2.Matches(L"hello"));
+  EXPECT_FALSE(m2.Matches(L"Hi"));
+}
+
+TEST(StdWideStrCaseEqTest, MatchesEqualStringWith0IgnoringCase) {
+  ::std::wstring str1(L"oabocdooeoo");
+  ::std::wstring str2(L"OABOCDOOEOO");
+  Matcher<const ::std::wstring&> m0 = StrCaseEq(str1);
+  EXPECT_FALSE(m0.Matches(str2 + ::std::wstring(1, L'\0')));
+
+  str1[3] = str2[3] = L'\0';
+  Matcher<const ::std::wstring&> m1 = StrCaseEq(str1);
+  EXPECT_TRUE(m1.Matches(str2));
+
+  str1[0] = str1[6] = str1[7] = str1[10] = L'\0';
+  str2[0] = str2[6] = str2[7] = str2[10] = L'\0';
+  Matcher<const ::std::wstring&> m2 = StrCaseEq(str1);
+  str1[9] = str2[9] = L'\0';
+  EXPECT_FALSE(m2.Matches(str2));
+
+  Matcher<const ::std::wstring&> m3 = StrCaseEq(str1);
+  EXPECT_TRUE(m3.Matches(str2));
+
+  EXPECT_FALSE(m3.Matches(str2 + L"x"));
+  str2.append(1, L'\0');
+  EXPECT_FALSE(m3.Matches(str2));
+  EXPECT_FALSE(m3.Matches(::std::wstring(str2, 0, 9)));
+}
+
+TEST(StdWideStrCaseEqTest, CanDescribeSelf) {
+  Matcher< ::std::wstring> m = StrCaseEq(L"Hi");
+  EXPECT_EQ("is equal to (ignoring case) L\"Hi\"", Describe(m));
+}
+
+TEST(StdWideStrCaseNeTest, MatchesUnequalStringIgnoringCase) {
+  Matcher<const wchar_t*> m = StrCaseNe(L"Hello");
+  EXPECT_TRUE(m.Matches(L"Hi"));
+  EXPECT_TRUE(m.Matches(nullptr));
+  EXPECT_FALSE(m.Matches(L"Hello"));
+  EXPECT_FALSE(m.Matches(L"hello"));
+
+  Matcher< ::std::wstring> m2 = StrCaseNe(::std::wstring(L"Hello"));
+  EXPECT_TRUE(m2.Matches(L""));
+  EXPECT_FALSE(m2.Matches(L"Hello"));
+}
+
+TEST(StdWideStrCaseNeTest, CanDescribeSelf) {
+  Matcher<const wchar_t*> m = StrCaseNe(L"Hi");
+  EXPECT_EQ("isn't equal to (ignoring case) L\"Hi\"", Describe(m));
+}
+
+// Tests that HasSubstr() works for matching wstring-typed values.
+TEST(StdWideHasSubstrTest, WorksForStringClasses) {
+  const Matcher< ::std::wstring> m1 = HasSubstr(L"foo");
+  EXPECT_TRUE(m1.Matches(::std::wstring(L"I love food.")));
+  EXPECT_FALSE(m1.Matches(::std::wstring(L"tofo")));
+
+  const Matcher<const ::std::wstring&> m2 = HasSubstr(L"foo");
+  EXPECT_TRUE(m2.Matches(::std::wstring(L"I love food.")));
+  EXPECT_FALSE(m2.Matches(::std::wstring(L"tofo")));
+}
+
+// Tests that HasSubstr() works for matching C-wide-string-typed values.
+TEST(StdWideHasSubstrTest, WorksForCStrings) {
+  const Matcher<wchar_t*> m1 = HasSubstr(L"foo");
+  EXPECT_TRUE(m1.Matches(const_cast<wchar_t*>(L"I love food.")));
+  EXPECT_FALSE(m1.Matches(const_cast<wchar_t*>(L"tofo")));
+  EXPECT_FALSE(m1.Matches(nullptr));
+
+  const Matcher<const wchar_t*> m2 = HasSubstr(L"foo");
+  EXPECT_TRUE(m2.Matches(L"I love food."));
+  EXPECT_FALSE(m2.Matches(L"tofo"));
+  EXPECT_FALSE(m2.Matches(nullptr));
+}
+
+// Tests that HasSubstr(s) describes itself properly.
+TEST(StdWideHasSubstrTest, CanDescribeSelf) {
+  Matcher< ::std::wstring> m = HasSubstr(L"foo\n\"");
+  EXPECT_EQ("has substring L\"foo\\n\\\"\"", Describe(m));
+}
+
+// Tests StartsWith(s).
+
+TEST(StdWideStartsWithTest, MatchesStringWithGivenPrefix) {
+  const Matcher<const wchar_t*> m1 = StartsWith(::std::wstring(L""));
+  EXPECT_TRUE(m1.Matches(L"Hi"));
+  EXPECT_TRUE(m1.Matches(L""));
+  EXPECT_FALSE(m1.Matches(nullptr));
+
+  const Matcher<const ::std::wstring&> m2 = StartsWith(L"Hi");
+  EXPECT_TRUE(m2.Matches(L"Hi"));
+  EXPECT_TRUE(m2.Matches(L"Hi Hi!"));
+  EXPECT_TRUE(m2.Matches(L"High"));
+  EXPECT_FALSE(m2.Matches(L"H"));
+  EXPECT_FALSE(m2.Matches(L" Hi"));
+}
+
+TEST(StdWideStartsWithTest, CanDescribeSelf) {
+  Matcher<const ::std::wstring> m = StartsWith(L"Hi");
+  EXPECT_EQ("starts with L\"Hi\"", Describe(m));
+}
+
+// Tests EndsWith(s).
+
+TEST(StdWideEndsWithTest, MatchesStringWithGivenSuffix) {
+  const Matcher<const wchar_t*> m1 = EndsWith(L"");
+  EXPECT_TRUE(m1.Matches(L"Hi"));
+  EXPECT_TRUE(m1.Matches(L""));
+  EXPECT_FALSE(m1.Matches(nullptr));
+
+  const Matcher<const ::std::wstring&> m2 = EndsWith(::std::wstring(L"Hi"));
+  EXPECT_TRUE(m2.Matches(L"Hi"));
+  EXPECT_TRUE(m2.Matches(L"Wow Hi Hi"));
+  EXPECT_TRUE(m2.Matches(L"Super Hi"));
+  EXPECT_FALSE(m2.Matches(L"i"));
+  EXPECT_FALSE(m2.Matches(L"Hi "));
+}
+
+TEST(StdWideEndsWithTest, CanDescribeSelf) {
+  Matcher<const ::std::wstring> m = EndsWith(L"Hi");
+  EXPECT_EQ("ends with L\"Hi\"", Describe(m));
+}
+
+#endif  // GTEST_HAS_STD_WSTRING
+
+typedef ::std::tuple<long, int> Tuple2;  // NOLINT
+
+// Tests that Eq() matches a 2-tuple where the first field == the
+// second field.
+TEST(Eq2Test, MatchesEqualArguments) {
+  Matcher<const Tuple2&> m = Eq();
+  EXPECT_TRUE(m.Matches(Tuple2(5L, 5)));
+  EXPECT_FALSE(m.Matches(Tuple2(5L, 6)));
+}
+
+// Tests that Eq() describes itself properly.
+TEST(Eq2Test, CanDescribeSelf) {
+  Matcher<const Tuple2&> m = Eq();
+  EXPECT_EQ("are an equal pair", Describe(m));
+}
+
+// Tests that Ge() matches a 2-tuple where the first field >= the
+// second field.
+TEST(Ge2Test, MatchesGreaterThanOrEqualArguments) {
+  Matcher<const Tuple2&> m = Ge();
+  EXPECT_TRUE(m.Matches(Tuple2(5L, 4)));
+  EXPECT_TRUE(m.Matches(Tuple2(5L, 5)));
+  EXPECT_FALSE(m.Matches(Tuple2(5L, 6)));
+}
+
+// Tests that Ge() describes itself properly.
+TEST(Ge2Test, CanDescribeSelf) {
+  Matcher<const Tuple2&> m = Ge();
+  EXPECT_EQ("are a pair where the first >= the second", Describe(m));
+}
+
+// Tests that Gt() matches a 2-tuple where the first field > the
+// second field.
+TEST(Gt2Test, MatchesGreaterThanArguments) {
+  Matcher<const Tuple2&> m = Gt();
+  EXPECT_TRUE(m.Matches(Tuple2(5L, 4)));
+  EXPECT_FALSE(m.Matches(Tuple2(5L, 5)));
+  EXPECT_FALSE(m.Matches(Tuple2(5L, 6)));
+}
+
+// Tests that Gt() describes itself properly.
+TEST(Gt2Test, CanDescribeSelf) {
+  Matcher<const Tuple2&> m = Gt();
+  EXPECT_EQ("are a pair where the first > the second", Describe(m));
+}
+
+// Tests that Le() matches a 2-tuple where the first field <= the
+// second field.
+TEST(Le2Test, MatchesLessThanOrEqualArguments) {
+  Matcher<const Tuple2&> m = Le();
+  EXPECT_TRUE(m.Matches(Tuple2(5L, 6)));
+  EXPECT_TRUE(m.Matches(Tuple2(5L, 5)));
+  EXPECT_FALSE(m.Matches(Tuple2(5L, 4)));
+}
+
+// Tests that Le() describes itself properly.
+TEST(Le2Test, CanDescribeSelf) {
+  Matcher<const Tuple2&> m = Le();
+  EXPECT_EQ("are a pair where the first <= the second", Describe(m));
+}
+
+// Tests that Lt() matches a 2-tuple where the first field < the
+// second field.
+TEST(Lt2Test, MatchesLessThanArguments) {
+  Matcher<const Tuple2&> m = Lt();
+  EXPECT_TRUE(m.Matches(Tuple2(5L, 6)));
+  EXPECT_FALSE(m.Matches(Tuple2(5L, 5)));
+  EXPECT_FALSE(m.Matches(Tuple2(5L, 4)));
+}
+
+// Tests that Lt() describes itself properly.
+TEST(Lt2Test, CanDescribeSelf) {
+  Matcher<const Tuple2&> m = Lt();
+  EXPECT_EQ("are a pair where the first < the second", Describe(m));
+}
+
+// Tests that Ne() matches a 2-tuple where the first field != the
+// second field.
+TEST(Ne2Test, MatchesUnequalArguments) {
+  Matcher<const Tuple2&> m = Ne();
+  EXPECT_TRUE(m.Matches(Tuple2(5L, 6)));
+  EXPECT_TRUE(m.Matches(Tuple2(5L, 4)));
+  EXPECT_FALSE(m.Matches(Tuple2(5L, 5)));
+}
+
+// Tests that Ne() describes itself properly.
+TEST(Ne2Test, CanDescribeSelf) {
+  Matcher<const Tuple2&> m = Ne();
+  EXPECT_EQ("are an unequal pair", Describe(m));
+}
+
+TEST(PairMatchBaseTest, WorksWithMoveOnly) {
+  using Pointers = std::tuple<std::unique_ptr<int>, std::unique_ptr<int>>;
+  Matcher<Pointers> matcher = Eq();
+  Pointers pointers;
+  // Tested values don't matter; the point is that matcher does not copy the
+  // matched values.
+  EXPECT_TRUE(matcher.Matches(pointers));
+}
+
+// Tests that IsNan() matches a NaN, with float.
+TEST(IsNan, FloatMatchesNan) {
+  float quiet_nan = std::numeric_limits<float>::quiet_NaN();
+  float other_nan = std::nanf("1");
+  float real_value = 1.0f;
+
+  Matcher<float> m = IsNan();
+  EXPECT_TRUE(m.Matches(quiet_nan));
+  EXPECT_TRUE(m.Matches(other_nan));
+  EXPECT_FALSE(m.Matches(real_value));
+
+  Matcher<float&> m_ref = IsNan();
+  EXPECT_TRUE(m_ref.Matches(quiet_nan));
+  EXPECT_TRUE(m_ref.Matches(other_nan));
+  EXPECT_FALSE(m_ref.Matches(real_value));
+
+  Matcher<const float&> m_cref = IsNan();
+  EXPECT_TRUE(m_cref.Matches(quiet_nan));
+  EXPECT_TRUE(m_cref.Matches(other_nan));
+  EXPECT_FALSE(m_cref.Matches(real_value));
+}
+
+// Tests that IsNan() matches a NaN, with double.
+TEST(IsNan, DoubleMatchesNan) {
+  double quiet_nan = std::numeric_limits<double>::quiet_NaN();
+  double other_nan = std::nan("1");
+  double real_value = 1.0;
+
+  Matcher<double> m = IsNan();
+  EXPECT_TRUE(m.Matches(quiet_nan));
+  EXPECT_TRUE(m.Matches(other_nan));
+  EXPECT_FALSE(m.Matches(real_value));
+
+  Matcher<double&> m_ref = IsNan();
+  EXPECT_TRUE(m_ref.Matches(quiet_nan));
+  EXPECT_TRUE(m_ref.Matches(other_nan));
+  EXPECT_FALSE(m_ref.Matches(real_value));
+
+  Matcher<const double&> m_cref = IsNan();
+  EXPECT_TRUE(m_cref.Matches(quiet_nan));
+  EXPECT_TRUE(m_cref.Matches(other_nan));
+  EXPECT_FALSE(m_cref.Matches(real_value));
+}
+
+// Tests that IsNan() matches a NaN, with long double.
+TEST(IsNan, LongDoubleMatchesNan) {
+  long double quiet_nan = std::numeric_limits<long double>::quiet_NaN();
+  long double other_nan = std::nan("1");
+  long double real_value = 1.0;
+
+  Matcher<long double> m = IsNan();
+  EXPECT_TRUE(m.Matches(quiet_nan));
+  EXPECT_TRUE(m.Matches(other_nan));
+  EXPECT_FALSE(m.Matches(real_value));
+
+  Matcher<long double&> m_ref = IsNan();
+  EXPECT_TRUE(m_ref.Matches(quiet_nan));
+  EXPECT_TRUE(m_ref.Matches(other_nan));
+  EXPECT_FALSE(m_ref.Matches(real_value));
+
+  Matcher<const long double&> m_cref = IsNan();
+  EXPECT_TRUE(m_cref.Matches(quiet_nan));
+  EXPECT_TRUE(m_cref.Matches(other_nan));
+  EXPECT_FALSE(m_cref.Matches(real_value));
+}
+
+// Tests that IsNan() works with Not.
+TEST(IsNan, NotMatchesNan) {
+  Matcher<float> mf = Not(IsNan());
+  EXPECT_FALSE(mf.Matches(std::numeric_limits<float>::quiet_NaN()));
+  EXPECT_FALSE(mf.Matches(std::nanf("1")));
+  EXPECT_TRUE(mf.Matches(1.0));
+
+  Matcher<double> md = Not(IsNan());
+  EXPECT_FALSE(md.Matches(std::numeric_limits<double>::quiet_NaN()));
+  EXPECT_FALSE(md.Matches(std::nan("1")));
+  EXPECT_TRUE(md.Matches(1.0));
+
+  Matcher<long double> mld = Not(IsNan());
+  EXPECT_FALSE(mld.Matches(std::numeric_limits<long double>::quiet_NaN()));
+  EXPECT_FALSE(mld.Matches(std::nanl("1")));
+  EXPECT_TRUE(mld.Matches(1.0));
+}
+
+// Tests that IsNan() can describe itself.
+TEST(IsNan, CanDescribeSelf) {
+  Matcher<float> mf = IsNan();
+  EXPECT_EQ("is NaN", Describe(mf));
+
+  Matcher<double> md = IsNan();
+  EXPECT_EQ("is NaN", Describe(md));
+
+  Matcher<long double> mld = IsNan();
+  EXPECT_EQ("is NaN", Describe(mld));
+}
+
+// Tests that IsNan() can describe itself with Not.
+TEST(IsNan, CanDescribeSelfWithNot) {
+  Matcher<float> mf = Not(IsNan());
+  EXPECT_EQ("isn't NaN", Describe(mf));
+
+  Matcher<double> md = Not(IsNan());
+  EXPECT_EQ("isn't NaN", Describe(md));
+
+  Matcher<long double> mld = Not(IsNan());
+  EXPECT_EQ("isn't NaN", Describe(mld));
+}
+
+// Tests that FloatEq() matches a 2-tuple where
+// FloatEq(first field) matches the second field.
+TEST(FloatEq2Test, MatchesEqualArguments) {
+  typedef ::std::tuple<float, float> Tpl;
+  Matcher<const Tpl&> m = FloatEq();
+  EXPECT_TRUE(m.Matches(Tpl(1.0f, 1.0f)));
+  EXPECT_TRUE(m.Matches(Tpl(0.3f, 0.1f + 0.1f + 0.1f)));
+  EXPECT_FALSE(m.Matches(Tpl(1.1f, 1.0f)));
+}
+
+// Tests that FloatEq() describes itself properly.
+TEST(FloatEq2Test, CanDescribeSelf) {
+  Matcher<const ::std::tuple<float, float>&> m = FloatEq();
+  EXPECT_EQ("are an almost-equal pair", Describe(m));
+}
+
+// Tests that NanSensitiveFloatEq() matches a 2-tuple where
+// NanSensitiveFloatEq(first field) matches the second field.
+TEST(NanSensitiveFloatEqTest, MatchesEqualArgumentsWithNaN) {
+  typedef ::std::tuple<float, float> Tpl;
+  Matcher<const Tpl&> m = NanSensitiveFloatEq();
+  EXPECT_TRUE(m.Matches(Tpl(1.0f, 1.0f)));
+  EXPECT_TRUE(m.Matches(Tpl(std::numeric_limits<float>::quiet_NaN(),
+                            std::numeric_limits<float>::quiet_NaN())));
+  EXPECT_FALSE(m.Matches(Tpl(1.1f, 1.0f)));
+  EXPECT_FALSE(m.Matches(Tpl(1.0f, std::numeric_limits<float>::quiet_NaN())));
+  EXPECT_FALSE(m.Matches(Tpl(std::numeric_limits<float>::quiet_NaN(), 1.0f)));
+}
+
+// Tests that NanSensitiveFloatEq() describes itself properly.
+TEST(NanSensitiveFloatEqTest, CanDescribeSelfWithNaNs) {
+  Matcher<const ::std::tuple<float, float>&> m = NanSensitiveFloatEq();
+  EXPECT_EQ("are an almost-equal pair", Describe(m));
+}
+
+// Tests that DoubleEq() matches a 2-tuple where
+// DoubleEq(first field) matches the second field.
+TEST(DoubleEq2Test, MatchesEqualArguments) {
+  typedef ::std::tuple<double, double> Tpl;
+  Matcher<const Tpl&> m = DoubleEq();
+  EXPECT_TRUE(m.Matches(Tpl(1.0, 1.0)));
+  EXPECT_TRUE(m.Matches(Tpl(0.3, 0.1 + 0.1 + 0.1)));
+  EXPECT_FALSE(m.Matches(Tpl(1.1, 1.0)));
+}
+
+// Tests that DoubleEq() describes itself properly.
+TEST(DoubleEq2Test, CanDescribeSelf) {
+  Matcher<const ::std::tuple<double, double>&> m = DoubleEq();
+  EXPECT_EQ("are an almost-equal pair", Describe(m));
+}
+
+// Tests that NanSensitiveDoubleEq() matches a 2-tuple where
+// NanSensitiveDoubleEq(first field) matches the second field.
+TEST(NanSensitiveDoubleEqTest, MatchesEqualArgumentsWithNaN) {
+  typedef ::std::tuple<double, double> Tpl;
+  Matcher<const Tpl&> m = NanSensitiveDoubleEq();
+  EXPECT_TRUE(m.Matches(Tpl(1.0f, 1.0f)));
+  EXPECT_TRUE(m.Matches(Tpl(std::numeric_limits<double>::quiet_NaN(),
+                            std::numeric_limits<double>::quiet_NaN())));
+  EXPECT_FALSE(m.Matches(Tpl(1.1f, 1.0f)));
+  EXPECT_FALSE(m.Matches(Tpl(1.0f, std::numeric_limits<double>::quiet_NaN())));
+  EXPECT_FALSE(m.Matches(Tpl(std::numeric_limits<double>::quiet_NaN(), 1.0f)));
+}
+
+// Tests that DoubleEq() describes itself properly.
+TEST(NanSensitiveDoubleEqTest, CanDescribeSelfWithNaNs) {
+  Matcher<const ::std::tuple<double, double>&> m = NanSensitiveDoubleEq();
+  EXPECT_EQ("are an almost-equal pair", Describe(m));
+}
+
+// Tests that FloatEq() matches a 2-tuple where
+// FloatNear(first field, max_abs_error) matches the second field.
+TEST(FloatNear2Test, MatchesEqualArguments) {
+  typedef ::std::tuple<float, float> Tpl;
+  Matcher<const Tpl&> m = FloatNear(0.5f);
+  EXPECT_TRUE(m.Matches(Tpl(1.0f, 1.0f)));
+  EXPECT_TRUE(m.Matches(Tpl(1.3f, 1.0f)));
+  EXPECT_FALSE(m.Matches(Tpl(1.8f, 1.0f)));
+}
+
+// Tests that FloatNear() describes itself properly.
+TEST(FloatNear2Test, CanDescribeSelf) {
+  Matcher<const ::std::tuple<float, float>&> m = FloatNear(0.5f);
+  EXPECT_EQ("are an almost-equal pair", Describe(m));
+}
+
+// Tests that NanSensitiveFloatNear() matches a 2-tuple where
+// NanSensitiveFloatNear(first field) matches the second field.
+TEST(NanSensitiveFloatNearTest, MatchesNearbyArgumentsWithNaN) {
+  typedef ::std::tuple<float, float> Tpl;
+  Matcher<const Tpl&> m = NanSensitiveFloatNear(0.5f);
+  EXPECT_TRUE(m.Matches(Tpl(1.0f, 1.0f)));
+  EXPECT_TRUE(m.Matches(Tpl(1.1f, 1.0f)));
+  EXPECT_TRUE(m.Matches(Tpl(std::numeric_limits<float>::quiet_NaN(),
+                            std::numeric_limits<float>::quiet_NaN())));
+  EXPECT_FALSE(m.Matches(Tpl(1.6f, 1.0f)));
+  EXPECT_FALSE(m.Matches(Tpl(1.0f, std::numeric_limits<float>::quiet_NaN())));
+  EXPECT_FALSE(m.Matches(Tpl(std::numeric_limits<float>::quiet_NaN(), 1.0f)));
+}
+
+// Tests that NanSensitiveFloatNear() describes itself properly.
+TEST(NanSensitiveFloatNearTest, CanDescribeSelfWithNaNs) {
+  Matcher<const ::std::tuple<float, float>&> m = NanSensitiveFloatNear(0.5f);
+  EXPECT_EQ("are an almost-equal pair", Describe(m));
+}
+
+// Tests that FloatEq() matches a 2-tuple where
+// DoubleNear(first field, max_abs_error) matches the second field.
+TEST(DoubleNear2Test, MatchesEqualArguments) {
+  typedef ::std::tuple<double, double> Tpl;
+  Matcher<const Tpl&> m = DoubleNear(0.5);
+  EXPECT_TRUE(m.Matches(Tpl(1.0, 1.0)));
+  EXPECT_TRUE(m.Matches(Tpl(1.3, 1.0)));
+  EXPECT_FALSE(m.Matches(Tpl(1.8, 1.0)));
+}
+
+// Tests that DoubleNear() describes itself properly.
+TEST(DoubleNear2Test, CanDescribeSelf) {
+  Matcher<const ::std::tuple<double, double>&> m = DoubleNear(0.5);
+  EXPECT_EQ("are an almost-equal pair", Describe(m));
+}
+
+// Tests that NanSensitiveDoubleNear() matches a 2-tuple where
+// NanSensitiveDoubleNear(first field) matches the second field.
+TEST(NanSensitiveDoubleNearTest, MatchesNearbyArgumentsWithNaN) {
+  typedef ::std::tuple<double, double> Tpl;
+  Matcher<const Tpl&> m = NanSensitiveDoubleNear(0.5f);
+  EXPECT_TRUE(m.Matches(Tpl(1.0f, 1.0f)));
+  EXPECT_TRUE(m.Matches(Tpl(1.1f, 1.0f)));
+  EXPECT_TRUE(m.Matches(Tpl(std::numeric_limits<double>::quiet_NaN(),
+                            std::numeric_limits<double>::quiet_NaN())));
+  EXPECT_FALSE(m.Matches(Tpl(1.6f, 1.0f)));
+  EXPECT_FALSE(m.Matches(Tpl(1.0f, std::numeric_limits<double>::quiet_NaN())));
+  EXPECT_FALSE(m.Matches(Tpl(std::numeric_limits<double>::quiet_NaN(), 1.0f)));
+}
+
+// Tests that NanSensitiveDoubleNear() describes itself properly.
+TEST(NanSensitiveDoubleNearTest, CanDescribeSelfWithNaNs) {
+  Matcher<const ::std::tuple<double, double>&> m = NanSensitiveDoubleNear(0.5f);
+  EXPECT_EQ("are an almost-equal pair", Describe(m));
+}
+
+// Tests that Not(m) matches any value that doesn't match m.
+TEST(NotTest, NegatesMatcher) {
+  Matcher<int> m;
+  m = Not(Eq(2));
+  EXPECT_TRUE(m.Matches(3));
+  EXPECT_FALSE(m.Matches(2));
+}
+
+// Tests that Not(m) describes itself properly.
+TEST(NotTest, CanDescribeSelf) {
+  Matcher<int> m = Not(Eq(5));
+  EXPECT_EQ("isn't equal to 5", Describe(m));
+}
+
+// Tests that monomorphic matchers are safely cast by the Not matcher.
+TEST(NotTest, NotMatcherSafelyCastsMonomorphicMatchers) {
+  // greater_than_5 is a monomorphic matcher.
+  Matcher<int> greater_than_5 = Gt(5);
+
+  Matcher<const int&> m = Not(greater_than_5);
+  Matcher<int&> m2 = Not(greater_than_5);
+  Matcher<int&> m3 = Not(m);
+}
+
+// Helper to allow easy testing of AllOf matchers with num parameters.
+void AllOfMatches(int num, const Matcher<int>& m) {
+  SCOPED_TRACE(Describe(m));
+  EXPECT_TRUE(m.Matches(0));
+  for (int i = 1; i <= num; ++i) {
+    EXPECT_FALSE(m.Matches(i));
+  }
+  EXPECT_TRUE(m.Matches(num + 1));
+}
+
+// Tests that AllOf(m1, ..., mn) matches any value that matches all of
+// the given matchers.
+TEST(AllOfTest, MatchesWhenAllMatch) {
+  Matcher<int> m;
+  m = AllOf(Le(2), Ge(1));
+  EXPECT_TRUE(m.Matches(1));
+  EXPECT_TRUE(m.Matches(2));
+  EXPECT_FALSE(m.Matches(0));
+  EXPECT_FALSE(m.Matches(3));
+
+  m = AllOf(Gt(0), Ne(1), Ne(2));
+  EXPECT_TRUE(m.Matches(3));
+  EXPECT_FALSE(m.Matches(2));
+  EXPECT_FALSE(m.Matches(1));
+  EXPECT_FALSE(m.Matches(0));
+
+  m = AllOf(Gt(0), Ne(1), Ne(2), Ne(3));
+  EXPECT_TRUE(m.Matches(4));
+  EXPECT_FALSE(m.Matches(3));
+  EXPECT_FALSE(m.Matches(2));
+  EXPECT_FALSE(m.Matches(1));
+  EXPECT_FALSE(m.Matches(0));
+
+  m = AllOf(Ge(0), Lt(10), Ne(3), Ne(5), Ne(7));
+  EXPECT_TRUE(m.Matches(0));
+  EXPECT_TRUE(m.Matches(1));
+  EXPECT_FALSE(m.Matches(3));
+
+  // The following tests for varying number of sub-matchers. Due to the way
+  // the sub-matchers are handled it is enough to test every sub-matcher once
+  // with sub-matchers using the same matcher type. Varying matcher types are
+  // checked for above.
+  AllOfMatches(2, AllOf(Ne(1), Ne(2)));
+  AllOfMatches(3, AllOf(Ne(1), Ne(2), Ne(3)));
+  AllOfMatches(4, AllOf(Ne(1), Ne(2), Ne(3), Ne(4)));
+  AllOfMatches(5, AllOf(Ne(1), Ne(2), Ne(3), Ne(4), Ne(5)));
+  AllOfMatches(6, AllOf(Ne(1), Ne(2), Ne(3), Ne(4), Ne(5), Ne(6)));
+  AllOfMatches(7, AllOf(Ne(1), Ne(2), Ne(3), Ne(4), Ne(5), Ne(6), Ne(7)));
+  AllOfMatches(8, AllOf(Ne(1), Ne(2), Ne(3), Ne(4), Ne(5), Ne(6), Ne(7),
+                        Ne(8)));
+  AllOfMatches(9, AllOf(Ne(1), Ne(2), Ne(3), Ne(4), Ne(5), Ne(6), Ne(7),
+                        Ne(8), Ne(9)));
+  AllOfMatches(10, AllOf(Ne(1), Ne(2), Ne(3), Ne(4), Ne(5), Ne(6), Ne(7), Ne(8),
+                         Ne(9), Ne(10)));
+  AllOfMatches(
+      50, AllOf(Ne(1), Ne(2), Ne(3), Ne(4), Ne(5), Ne(6), Ne(7), Ne(8), Ne(9),
+                Ne(10), Ne(11), Ne(12), Ne(13), Ne(14), Ne(15), Ne(16), Ne(17),
+                Ne(18), Ne(19), Ne(20), Ne(21), Ne(22), Ne(23), Ne(24), Ne(25),
+                Ne(26), Ne(27), Ne(28), Ne(29), Ne(30), Ne(31), Ne(32), Ne(33),
+                Ne(34), Ne(35), Ne(36), Ne(37), Ne(38), Ne(39), Ne(40), Ne(41),
+                Ne(42), Ne(43), Ne(44), Ne(45), Ne(46), Ne(47), Ne(48), Ne(49),
+                Ne(50)));
+}
+
+
+// Tests that AllOf(m1, ..., mn) describes itself properly.
+TEST(AllOfTest, CanDescribeSelf) {
+  Matcher<int> m;
+  m = AllOf(Le(2), Ge(1));
+  EXPECT_EQ("(is <= 2) and (is >= 1)", Describe(m));
+
+  m = AllOf(Gt(0), Ne(1), Ne(2));
+  std::string expected_descr1 =
+      "(is > 0) and (isn't equal to 1) and (isn't equal to 2)";
+  EXPECT_EQ(expected_descr1, Describe(m));
+
+  m = AllOf(Gt(0), Ne(1), Ne(2), Ne(3));
+  std::string expected_descr2 =
+      "(is > 0) and (isn't equal to 1) and (isn't equal to 2) and (isn't equal "
+      "to 3)";
+  EXPECT_EQ(expected_descr2, Describe(m));
+
+  m = AllOf(Ge(0), Lt(10), Ne(3), Ne(5), Ne(7));
+  std::string expected_descr3 =
+      "(is >= 0) and (is < 10) and (isn't equal to 3) and (isn't equal to 5) "
+      "and (isn't equal to 7)";
+  EXPECT_EQ(expected_descr3, Describe(m));
+}
+
+// Tests that AllOf(m1, ..., mn) describes its negation properly.
+TEST(AllOfTest, CanDescribeNegation) {
+  Matcher<int> m;
+  m = AllOf(Le(2), Ge(1));
+  std::string expected_descr4 = "(isn't <= 2) or (isn't >= 1)";
+  EXPECT_EQ(expected_descr4, DescribeNegation(m));
+
+  m = AllOf(Gt(0), Ne(1), Ne(2));
+  std::string expected_descr5 =
+      "(isn't > 0) or (is equal to 1) or (is equal to 2)";
+  EXPECT_EQ(expected_descr5, DescribeNegation(m));
+
+  m = AllOf(Gt(0), Ne(1), Ne(2), Ne(3));
+  std::string expected_descr6 =
+      "(isn't > 0) or (is equal to 1) or (is equal to 2) or (is equal to 3)";
+  EXPECT_EQ(expected_descr6, DescribeNegation(m));
+
+  m = AllOf(Ge(0), Lt(10), Ne(3), Ne(5), Ne(7));
+  std::string expected_desr7 =
+      "(isn't >= 0) or (isn't < 10) or (is equal to 3) or (is equal to 5) or "
+      "(is equal to 7)";
+  EXPECT_EQ(expected_desr7, DescribeNegation(m));
+
+  m = AllOf(Ne(1), Ne(2), Ne(3), Ne(4), Ne(5), Ne(6), Ne(7), Ne(8), Ne(9),
+            Ne(10), Ne(11));
+  AllOf(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11);
+  EXPECT_THAT(Describe(m), EndsWith("and (isn't equal to 11)"));
+  AllOfMatches(11, m);
+}
+
+// Tests that monomorphic matchers are safely cast by the AllOf matcher.
+TEST(AllOfTest, AllOfMatcherSafelyCastsMonomorphicMatchers) {
+  // greater_than_5 and less_than_10 are monomorphic matchers.
+  Matcher<int> greater_than_5 = Gt(5);
+  Matcher<int> less_than_10 = Lt(10);
+
+  Matcher<const int&> m = AllOf(greater_than_5, less_than_10);
+  Matcher<int&> m2 = AllOf(greater_than_5, less_than_10);
+  Matcher<int&> m3 = AllOf(greater_than_5, m2);
+
+  // Tests that BothOf works when composing itself.
+  Matcher<const int&> m4 = AllOf(greater_than_5, less_than_10, less_than_10);
+  Matcher<int&> m5 = AllOf(greater_than_5, less_than_10, less_than_10);
+}
+
+TEST(AllOfTest, ExplainsResult) {
+  Matcher<int> m;
+
+  // Successful match.  Both matchers need to explain.  The second
+  // matcher doesn't give an explanation, so only the first matcher's
+  // explanation is printed.
+  m = AllOf(GreaterThan(10), Lt(30));
+  EXPECT_EQ("which is 15 more than 10", Explain(m, 25));
+
+  // Successful match.  Both matchers need to explain.
+  m = AllOf(GreaterThan(10), GreaterThan(20));
+  EXPECT_EQ("which is 20 more than 10, and which is 10 more than 20",
+            Explain(m, 30));
+
+  // Successful match.  All matchers need to explain.  The second
+  // matcher doesn't given an explanation.
+  m = AllOf(GreaterThan(10), Lt(30), GreaterThan(20));
+  EXPECT_EQ("which is 15 more than 10, and which is 5 more than 20",
+            Explain(m, 25));
+
+  // Successful match.  All matchers need to explain.
+  m = AllOf(GreaterThan(10), GreaterThan(20), GreaterThan(30));
+  EXPECT_EQ("which is 30 more than 10, and which is 20 more than 20, "
+            "and which is 10 more than 30",
+            Explain(m, 40));
+
+  // Failed match.  The first matcher, which failed, needs to
+  // explain.
+  m = AllOf(GreaterThan(10), GreaterThan(20));
+  EXPECT_EQ("which is 5 less than 10", Explain(m, 5));
+
+  // Failed match.  The second matcher, which failed, needs to
+  // explain.  Since it doesn't given an explanation, nothing is
+  // printed.
+  m = AllOf(GreaterThan(10), Lt(30));
+  EXPECT_EQ("", Explain(m, 40));
+
+  // Failed match.  The second matcher, which failed, needs to
+  // explain.
+  m = AllOf(GreaterThan(10), GreaterThan(20));
+  EXPECT_EQ("which is 5 less than 20", Explain(m, 15));
+}
+
+// Helper to allow easy testing of AnyOf matchers with num parameters.
+static void AnyOfMatches(int num, const Matcher<int>& m) {
+  SCOPED_TRACE(Describe(m));
+  EXPECT_FALSE(m.Matches(0));
+  for (int i = 1; i <= num; ++i) {
+    EXPECT_TRUE(m.Matches(i));
+  }
+  EXPECT_FALSE(m.Matches(num + 1));
+}
+
+static void AnyOfStringMatches(int num, const Matcher<std::string>& m) {
+  SCOPED_TRACE(Describe(m));
+  EXPECT_FALSE(m.Matches(std::to_string(0)));
+
+  for (int i = 1; i <= num; ++i) {
+    EXPECT_TRUE(m.Matches(std::to_string(i)));
+  }
+  EXPECT_FALSE(m.Matches(std::to_string(num + 1)));
+}
+
+// Tests that AnyOf(m1, ..., mn) matches any value that matches at
+// least one of the given matchers.
+TEST(AnyOfTest, MatchesWhenAnyMatches) {
+  Matcher<int> m;
+  m = AnyOf(Le(1), Ge(3));
+  EXPECT_TRUE(m.Matches(1));
+  EXPECT_TRUE(m.Matches(4));
+  EXPECT_FALSE(m.Matches(2));
+
+  m = AnyOf(Lt(0), Eq(1), Eq(2));
+  EXPECT_TRUE(m.Matches(-1));
+  EXPECT_TRUE(m.Matches(1));
+  EXPECT_TRUE(m.Matches(2));
+  EXPECT_FALSE(m.Matches(0));
+
+  m = AnyOf(Lt(0), Eq(1), Eq(2), Eq(3));
+  EXPECT_TRUE(m.Matches(-1));
+  EXPECT_TRUE(m.Matches(1));
+  EXPECT_TRUE(m.Matches(2));
+  EXPECT_TRUE(m.Matches(3));
+  EXPECT_FALSE(m.Matches(0));
+
+  m = AnyOf(Le(0), Gt(10), 3, 5, 7);
+  EXPECT_TRUE(m.Matches(0));
+  EXPECT_TRUE(m.Matches(11));
+  EXPECT_TRUE(m.Matches(3));
+  EXPECT_FALSE(m.Matches(2));
+
+  // The following tests for varying number of sub-matchers. Due to the way
+  // the sub-matchers are handled it is enough to test every sub-matcher once
+  // with sub-matchers using the same matcher type. Varying matcher types are
+  // checked for above.
+  AnyOfMatches(2, AnyOf(1, 2));
+  AnyOfMatches(3, AnyOf(1, 2, 3));
+  AnyOfMatches(4, AnyOf(1, 2, 3, 4));
+  AnyOfMatches(5, AnyOf(1, 2, 3, 4, 5));
+  AnyOfMatches(6, AnyOf(1, 2, 3, 4, 5, 6));
+  AnyOfMatches(7, AnyOf(1, 2, 3, 4, 5, 6, 7));
+  AnyOfMatches(8, AnyOf(1, 2, 3, 4, 5, 6, 7, 8));
+  AnyOfMatches(9, AnyOf(1, 2, 3, 4, 5, 6, 7, 8, 9));
+  AnyOfMatches(10, AnyOf(1, 2, 3, 4, 5, 6, 7, 8, 9, 10));
+}
+
+// Tests the variadic version of the AnyOfMatcher.
+TEST(AnyOfTest, VariadicMatchesWhenAnyMatches) {
+  // Also make sure AnyOf is defined in the right namespace and does not depend
+  // on ADL.
+  Matcher<int> m = ::testing::AnyOf(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11);
+
+  EXPECT_THAT(Describe(m), EndsWith("or (is equal to 11)"));
+  AnyOfMatches(11, m);
+  AnyOfMatches(50, AnyOf(1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
+                         11, 12, 13, 14, 15, 16, 17, 18, 19, 20,
+                         21, 22, 23, 24, 25, 26, 27, 28, 29, 30,
+                         31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
+                         41, 42, 43, 44, 45, 46, 47, 48, 49, 50));
+  AnyOfStringMatches(
+      50, AnyOf("1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12",
+                "13", "14", "15", "16", "17", "18", "19", "20", "21", "22",
+                "23", "24", "25", "26", "27", "28", "29", "30", "31", "32",
+                "33", "34", "35", "36", "37", "38", "39", "40", "41", "42",
+                "43", "44", "45", "46", "47", "48", "49", "50"));
+}
+
+// Tests the variadic version of the ElementsAreMatcher
+TEST(ElementsAreTest, HugeMatcher) {
+  vector<int> test_vector{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12};
+
+  EXPECT_THAT(test_vector,
+              ElementsAre(Eq(1), Eq(2), Lt(13), Eq(4), Eq(5), Eq(6), Eq(7),
+                          Eq(8), Eq(9), Eq(10), Gt(1), Eq(12)));
+}
+
+// Tests the variadic version of the UnorderedElementsAreMatcher
+TEST(ElementsAreTest, HugeMatcherStr) {
+  vector<std::string> test_vector{
+      "literal_string", "", "", "", "", "", "", "", "", "", "", ""};
+
+  EXPECT_THAT(test_vector, UnorderedElementsAre("literal_string", _, _, _, _, _,
+                                                _, _, _, _, _, _));
+}
+
+// Tests the variadic version of the UnorderedElementsAreMatcher
+TEST(ElementsAreTest, HugeMatcherUnordered) {
+  vector<int> test_vector{2, 1, 8, 5, 4, 6, 7, 3, 9, 12, 11, 10};
+
+  EXPECT_THAT(test_vector, UnorderedElementsAre(
+                               Eq(2), Eq(1), Gt(7), Eq(5), Eq(4), Eq(6), Eq(7),
+                               Eq(3), Eq(9), Eq(12), Eq(11), Ne(122)));
+}
+
+
+// Tests that AnyOf(m1, ..., mn) describes itself properly.
+TEST(AnyOfTest, CanDescribeSelf) {
+  Matcher<int> m;
+  m = AnyOf(Le(1), Ge(3));
+
+  EXPECT_EQ("(is <= 1) or (is >= 3)",
+            Describe(m));
+
+  m = AnyOf(Lt(0), Eq(1), Eq(2));
+  EXPECT_EQ("(is < 0) or (is equal to 1) or (is equal to 2)", Describe(m));
+
+  m = AnyOf(Lt(0), Eq(1), Eq(2), Eq(3));
+  EXPECT_EQ("(is < 0) or (is equal to 1) or (is equal to 2) or (is equal to 3)",
+            Describe(m));
+
+  m = AnyOf(Le(0), Gt(10), 3, 5, 7);
+  EXPECT_EQ(
+      "(is <= 0) or (is > 10) or (is equal to 3) or (is equal to 5) or (is "
+      "equal to 7)",
+      Describe(m));
+}
+
+// Tests that AnyOf(m1, ..., mn) describes its negation properly.
+TEST(AnyOfTest, CanDescribeNegation) {
+  Matcher<int> m;
+  m = AnyOf(Le(1), Ge(3));
+  EXPECT_EQ("(isn't <= 1) and (isn't >= 3)",
+            DescribeNegation(m));
+
+  m = AnyOf(Lt(0), Eq(1), Eq(2));
+  EXPECT_EQ("(isn't < 0) and (isn't equal to 1) and (isn't equal to 2)",
+            DescribeNegation(m));
+
+  m = AnyOf(Lt(0), Eq(1), Eq(2), Eq(3));
+  EXPECT_EQ(
+      "(isn't < 0) and (isn't equal to 1) and (isn't equal to 2) and (isn't "
+      "equal to 3)",
+      DescribeNegation(m));
+
+  m = AnyOf(Le(0), Gt(10), 3, 5, 7);
+  EXPECT_EQ(
+      "(isn't <= 0) and (isn't > 10) and (isn't equal to 3) and (isn't equal "
+      "to 5) and (isn't equal to 7)",
+      DescribeNegation(m));
+}
+
+// Tests that monomorphic matchers are safely cast by the AnyOf matcher.
+TEST(AnyOfTest, AnyOfMatcherSafelyCastsMonomorphicMatchers) {
+  // greater_than_5 and less_than_10 are monomorphic matchers.
+  Matcher<int> greater_than_5 = Gt(5);
+  Matcher<int> less_than_10 = Lt(10);
+
+  Matcher<const int&> m = AnyOf(greater_than_5, less_than_10);
+  Matcher<int&> m2 = AnyOf(greater_than_5, less_than_10);
+  Matcher<int&> m3 = AnyOf(greater_than_5, m2);
+
+  // Tests that EitherOf works when composing itself.
+  Matcher<const int&> m4 = AnyOf(greater_than_5, less_than_10, less_than_10);
+  Matcher<int&> m5 = AnyOf(greater_than_5, less_than_10, less_than_10);
+}
+
+TEST(AnyOfTest, ExplainsResult) {
+  Matcher<int> m;
+
+  // Failed match.  Both matchers need to explain.  The second
+  // matcher doesn't give an explanation, so only the first matcher's
+  // explanation is printed.
+  m = AnyOf(GreaterThan(10), Lt(0));
+  EXPECT_EQ("which is 5 less than 10", Explain(m, 5));
+
+  // Failed match.  Both matchers need to explain.
+  m = AnyOf(GreaterThan(10), GreaterThan(20));
+  EXPECT_EQ("which is 5 less than 10, and which is 15 less than 20",
+            Explain(m, 5));
+
+  // Failed match.  All matchers need to explain.  The second
+  // matcher doesn't given an explanation.
+  m = AnyOf(GreaterThan(10), Gt(20), GreaterThan(30));
+  EXPECT_EQ("which is 5 less than 10, and which is 25 less than 30",
+            Explain(m, 5));
+
+  // Failed match.  All matchers need to explain.
+  m = AnyOf(GreaterThan(10), GreaterThan(20), GreaterThan(30));
+  EXPECT_EQ("which is 5 less than 10, and which is 15 less than 20, "
+            "and which is 25 less than 30",
+            Explain(m, 5));
+
+  // Successful match.  The first matcher, which succeeded, needs to
+  // explain.
+  m = AnyOf(GreaterThan(10), GreaterThan(20));
+  EXPECT_EQ("which is 5 more than 10", Explain(m, 15));
+
+  // Successful match.  The second matcher, which succeeded, needs to
+  // explain.  Since it doesn't given an explanation, nothing is
+  // printed.
+  m = AnyOf(GreaterThan(10), Lt(30));
+  EXPECT_EQ("", Explain(m, 0));
+
+  // Successful match.  The second matcher, which succeeded, needs to
+  // explain.
+  m = AnyOf(GreaterThan(30), GreaterThan(20));
+  EXPECT_EQ("which is 5 more than 20", Explain(m, 25));
+}
+
+// The following predicate function and predicate functor are for
+// testing the Truly(predicate) matcher.
+
+// Returns non-zero if the input is positive.  Note that the return
+// type of this function is not bool.  It's OK as Truly() accepts any
+// unary function or functor whose return type can be implicitly
+// converted to bool.
+int IsPositive(double x) {
+  return x > 0 ? 1 : 0;
+}
+
+// This functor returns true if the input is greater than the given
+// number.
+class IsGreaterThan {
+ public:
+  explicit IsGreaterThan(int threshold) : threshold_(threshold) {}
+
+  bool operator()(int n) const { return n > threshold_; }
+
+ private:
+  int threshold_;
+};
+
+// For testing Truly().
+const int foo = 0;
+
+// This predicate returns true if and only if the argument references foo and
+// has a zero value.
+bool ReferencesFooAndIsZero(const int& n) {
+  return (&n == &foo) && (n == 0);
+}
+
+// Tests that Truly(predicate) matches what satisfies the given
+// predicate.
+TEST(TrulyTest, MatchesWhatSatisfiesThePredicate) {
+  Matcher<double> m = Truly(IsPositive);
+  EXPECT_TRUE(m.Matches(2.0));
+  EXPECT_FALSE(m.Matches(-1.5));
+}
+
+// Tests that Truly(predicate_functor) works too.
+TEST(TrulyTest, CanBeUsedWithFunctor) {
+  Matcher<int> m = Truly(IsGreaterThan(5));
+  EXPECT_TRUE(m.Matches(6));
+  EXPECT_FALSE(m.Matches(4));
+}
+
+// A class that can be implicitly converted to bool.
+class ConvertibleToBool {
+ public:
+  explicit ConvertibleToBool(int number) : number_(number) {}
+  operator bool() const { return number_ != 0; }
+
+ private:
+  int number_;
+};
+
+ConvertibleToBool IsNotZero(int number) {
+  return ConvertibleToBool(number);
+}
+
+// Tests that the predicate used in Truly() may return a class that's
+// implicitly convertible to bool, even when the class has no
+// operator!().
+TEST(TrulyTest, PredicateCanReturnAClassConvertibleToBool) {
+  Matcher<int> m = Truly(IsNotZero);
+  EXPECT_TRUE(m.Matches(1));
+  EXPECT_FALSE(m.Matches(0));
+}
+
+// Tests that Truly(predicate) can describe itself properly.
+TEST(TrulyTest, CanDescribeSelf) {
+  Matcher<double> m = Truly(IsPositive);
+  EXPECT_EQ("satisfies the given predicate",
+            Describe(m));
+}
+
+// Tests that Truly(predicate) works when the matcher takes its
+// argument by reference.
+TEST(TrulyTest, WorksForByRefArguments) {
+  Matcher<const int&> m = Truly(ReferencesFooAndIsZero);
+  EXPECT_TRUE(m.Matches(foo));
+  int n = 0;
+  EXPECT_FALSE(m.Matches(n));
+}
+
+// Tests that Truly(predicate) provides a helpful reason when it fails.
+TEST(TrulyTest, ExplainsFailures) {
+  StringMatchResultListener listener;
+  EXPECT_FALSE(ExplainMatchResult(Truly(IsPositive), -1, &listener));
+  EXPECT_EQ(listener.str(), "didn't satisfy the given predicate");
+}
+
+// Tests that Matches(m) is a predicate satisfied by whatever that
+// matches matcher m.
+TEST(MatchesTest, IsSatisfiedByWhatMatchesTheMatcher) {
+  EXPECT_TRUE(Matches(Ge(0))(1));
+  EXPECT_FALSE(Matches(Eq('a'))('b'));
+}
+
+// Tests that Matches(m) works when the matcher takes its argument by
+// reference.
+TEST(MatchesTest, WorksOnByRefArguments) {
+  int m = 0, n = 0;
+  EXPECT_TRUE(Matches(AllOf(Ref(n), Eq(0)))(n));
+  EXPECT_FALSE(Matches(Ref(m))(n));
+}
+
+// Tests that a Matcher on non-reference type can be used in
+// Matches().
+TEST(MatchesTest, WorksWithMatcherOnNonRefType) {
+  Matcher<int> eq5 = Eq(5);
+  EXPECT_TRUE(Matches(eq5)(5));
+  EXPECT_FALSE(Matches(eq5)(2));
+}
+
+// Tests Value(value, matcher).  Since Value() is a simple wrapper for
+// Matches(), which has been tested already, we don't spend a lot of
+// effort on testing Value().
+TEST(ValueTest, WorksWithPolymorphicMatcher) {
+  EXPECT_TRUE(Value("hi", StartsWith("h")));
+  EXPECT_FALSE(Value(5, Gt(10)));
+}
+
+TEST(ValueTest, WorksWithMonomorphicMatcher) {
+  const Matcher<int> is_zero = Eq(0);
+  EXPECT_TRUE(Value(0, is_zero));
+  EXPECT_FALSE(Value('a', is_zero));
+
+  int n = 0;
+  const Matcher<const int&> ref_n = Ref(n);
+  EXPECT_TRUE(Value(n, ref_n));
+  EXPECT_FALSE(Value(1, ref_n));
+}
+
+TEST(ExplainMatchResultTest, WorksWithPolymorphicMatcher) {
+  StringMatchResultListener listener1;
+  EXPECT_TRUE(ExplainMatchResult(PolymorphicIsEven(), 42, &listener1));
+  EXPECT_EQ("% 2 == 0", listener1.str());
+
+  StringMatchResultListener listener2;
+  EXPECT_FALSE(ExplainMatchResult(Ge(42), 1.5, &listener2));
+  EXPECT_EQ("", listener2.str());
+}
+
+TEST(ExplainMatchResultTest, WorksWithMonomorphicMatcher) {
+  const Matcher<int> is_even = PolymorphicIsEven();
+  StringMatchResultListener listener1;
+  EXPECT_TRUE(ExplainMatchResult(is_even, 42, &listener1));
+  EXPECT_EQ("% 2 == 0", listener1.str());
+
+  const Matcher<const double&> is_zero = Eq(0);
+  StringMatchResultListener listener2;
+  EXPECT_FALSE(ExplainMatchResult(is_zero, 1.5, &listener2));
+  EXPECT_EQ("", listener2.str());
+}
+
+MATCHER(ConstructNoArg, "") { return true; }
+MATCHER_P(Construct1Arg, arg1, "") { return true; }
+MATCHER_P2(Construct2Args, arg1, arg2, "") { return true; }
+
+TEST(MatcherConstruct, ExplicitVsImplicit) {
+  {
+    // No arg constructor can be constructed with empty brace.
+    ConstructNoArgMatcher m = {};
+    (void)m;
+    // And with no args
+    ConstructNoArgMatcher m2;
+    (void)m2;
+  }
+  {
+    // The one arg constructor has an explicit constructor.
+    // This is to prevent the implicit conversion.
+    using M = Construct1ArgMatcherP<int>;
+    EXPECT_TRUE((std::is_constructible<M, int>::value));
+    EXPECT_FALSE((std::is_convertible<int, M>::value));
+  }
+  {
+    // Multiple arg matchers can be constructed with an implicit construction.
+    Construct2ArgsMatcherP2<int, double> m = {1, 2.2};
+    (void)m;
+  }
+}
+
+MATCHER_P(Really, inner_matcher, "") {
+  return ExplainMatchResult(inner_matcher, arg, result_listener);
+}
+
+TEST(ExplainMatchResultTest, WorksInsideMATCHER) {
+  EXPECT_THAT(0, Really(Eq(0)));
+}
+
+TEST(DescribeMatcherTest, WorksWithValue) {
+  EXPECT_EQ("is equal to 42", DescribeMatcher<int>(42));
+  EXPECT_EQ("isn't equal to 42", DescribeMatcher<int>(42, true));
+}
+
+TEST(DescribeMatcherTest, WorksWithMonomorphicMatcher) {
+  const Matcher<int> monomorphic = Le(0);
+  EXPECT_EQ("is <= 0", DescribeMatcher<int>(monomorphic));
+  EXPECT_EQ("isn't <= 0", DescribeMatcher<int>(monomorphic, true));
+}
+
+TEST(DescribeMatcherTest, WorksWithPolymorphicMatcher) {
+  EXPECT_EQ("is even", DescribeMatcher<int>(PolymorphicIsEven()));
+  EXPECT_EQ("is odd", DescribeMatcher<int>(PolymorphicIsEven(), true));
+}
+
+TEST(AllArgsTest, WorksForTuple) {
+  EXPECT_THAT(std::make_tuple(1, 2L), AllArgs(Lt()));
+  EXPECT_THAT(std::make_tuple(2L, 1), Not(AllArgs(Lt())));
+}
+
+TEST(AllArgsTest, WorksForNonTuple) {
+  EXPECT_THAT(42, AllArgs(Gt(0)));
+  EXPECT_THAT('a', Not(AllArgs(Eq('b'))));
+}
+
+class AllArgsHelper {
+ public:
+  AllArgsHelper() {}
+
+  MOCK_METHOD2(Helper, int(char x, int y));
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(AllArgsHelper);
+};
+
+TEST(AllArgsTest, WorksInWithClause) {
+  AllArgsHelper helper;
+  ON_CALL(helper, Helper(_, _))
+      .With(AllArgs(Lt()))
+      .WillByDefault(Return(1));
+  EXPECT_CALL(helper, Helper(_, _));
+  EXPECT_CALL(helper, Helper(_, _))
+      .With(AllArgs(Gt()))
+      .WillOnce(Return(2));
+
+  EXPECT_EQ(1, helper.Helper('\1', 2));
+  EXPECT_EQ(2, helper.Helper('a', 1));
+}
+
+class OptionalMatchersHelper {
+ public:
+  OptionalMatchersHelper() {}
+
+  MOCK_METHOD0(NoArgs, int());
+
+  MOCK_METHOD1(OneArg, int(int y));
+
+  MOCK_METHOD2(TwoArgs, int(char x, int y));
+
+  MOCK_METHOD1(Overloaded, int(char x));
+  MOCK_METHOD2(Overloaded, int(char x, int y));
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(OptionalMatchersHelper);
+};
+
+TEST(AllArgsTest, WorksWithoutMatchers) {
+  OptionalMatchersHelper helper;
+
+  ON_CALL(helper, NoArgs).WillByDefault(Return(10));
+  ON_CALL(helper, OneArg).WillByDefault(Return(20));
+  ON_CALL(helper, TwoArgs).WillByDefault(Return(30));
+
+  EXPECT_EQ(10, helper.NoArgs());
+  EXPECT_EQ(20, helper.OneArg(1));
+  EXPECT_EQ(30, helper.TwoArgs('\1', 2));
+
+  EXPECT_CALL(helper, NoArgs).Times(1);
+  EXPECT_CALL(helper, OneArg).WillOnce(Return(100));
+  EXPECT_CALL(helper, OneArg(17)).WillOnce(Return(200));
+  EXPECT_CALL(helper, TwoArgs).Times(0);
+
+  EXPECT_EQ(10, helper.NoArgs());
+  EXPECT_EQ(100, helper.OneArg(1));
+  EXPECT_EQ(200, helper.OneArg(17));
+}
+
+// Tests that ASSERT_THAT() and EXPECT_THAT() work when the value
+// matches the matcher.
+TEST(MatcherAssertionTest, WorksWhenMatcherIsSatisfied) {
+  ASSERT_THAT(5, Ge(2)) << "This should succeed.";
+  ASSERT_THAT("Foo", EndsWith("oo"));
+  EXPECT_THAT(2, AllOf(Le(7), Ge(0))) << "This should succeed too.";
+  EXPECT_THAT("Hello", StartsWith("Hell"));
+}
+
+// Tests that ASSERT_THAT() and EXPECT_THAT() work when the value
+// doesn't match the matcher.
+TEST(MatcherAssertionTest, WorksWhenMatcherIsNotSatisfied) {
+  // 'n' must be static as it is used in an EXPECT_FATAL_FAILURE(),
+  // which cannot reference auto variables.
+  static unsigned short n;  // NOLINT
+  n = 5;
+
+  EXPECT_FATAL_FAILURE(ASSERT_THAT(n, Gt(10)),
+                       "Value of: n\n"
+                       "Expected: is > 10\n"
+                       "  Actual: 5" + OfType("unsigned short"));
+  n = 0;
+  EXPECT_NONFATAL_FAILURE(
+      EXPECT_THAT(n, AllOf(Le(7), Ge(5))),
+      "Value of: n\n"
+      "Expected: (is <= 7) and (is >= 5)\n"
+      "  Actual: 0" + OfType("unsigned short"));
+}
+
+// Tests that ASSERT_THAT() and EXPECT_THAT() work when the argument
+// has a reference type.
+TEST(MatcherAssertionTest, WorksForByRefArguments) {
+  // We use a static variable here as EXPECT_FATAL_FAILURE() cannot
+  // reference auto variables.
+  static int n;
+  n = 0;
+  EXPECT_THAT(n, AllOf(Le(7), Ref(n)));
+  EXPECT_FATAL_FAILURE(ASSERT_THAT(n, Not(Ref(n))),
+                       "Value of: n\n"
+                       "Expected: does not reference the variable @");
+  // Tests the "Actual" part.
+  EXPECT_FATAL_FAILURE(ASSERT_THAT(n, Not(Ref(n))),
+                       "Actual: 0" + OfType("int") + ", which is located @");
+}
+
+// Tests that ASSERT_THAT() and EXPECT_THAT() work when the matcher is
+// monomorphic.
+TEST(MatcherAssertionTest, WorksForMonomorphicMatcher) {
+  Matcher<const char*> starts_with_he = StartsWith("he");
+  ASSERT_THAT("hello", starts_with_he);
+
+  Matcher<const std::string&> ends_with_ok = EndsWith("ok");
+  ASSERT_THAT("book", ends_with_ok);
+  const std::string bad = "bad";
+  EXPECT_NONFATAL_FAILURE(EXPECT_THAT(bad, ends_with_ok),
+                          "Value of: bad\n"
+                          "Expected: ends with \"ok\"\n"
+                          "  Actual: \"bad\"");
+  Matcher<int> is_greater_than_5 = Gt(5);
+  EXPECT_NONFATAL_FAILURE(EXPECT_THAT(5, is_greater_than_5),
+                          "Value of: 5\n"
+                          "Expected: is > 5\n"
+                          "  Actual: 5" + OfType("int"));
+}
+
+// Tests floating-point matchers.
+template <typename RawType>
+class FloatingPointTest : public testing::Test {
+ protected:
+  typedef testing::internal::FloatingPoint<RawType> Floating;
+  typedef typename Floating::Bits Bits;
+
+  FloatingPointTest()
+      : max_ulps_(Floating::kMaxUlps),
+        zero_bits_(Floating(0).bits()),
+        one_bits_(Floating(1).bits()),
+        infinity_bits_(Floating(Floating::Infinity()).bits()),
+        close_to_positive_zero_(
+            Floating::ReinterpretBits(zero_bits_ + max_ulps_/2)),
+        close_to_negative_zero_(
+            -Floating::ReinterpretBits(zero_bits_ + max_ulps_ - max_ulps_/2)),
+        further_from_negative_zero_(-Floating::ReinterpretBits(
+            zero_bits_ + max_ulps_ + 1 - max_ulps_/2)),
+        close_to_one_(Floating::ReinterpretBits(one_bits_ + max_ulps_)),
+        further_from_one_(Floating::ReinterpretBits(one_bits_ + max_ulps_ + 1)),
+        infinity_(Floating::Infinity()),
+        close_to_infinity_(
+            Floating::ReinterpretBits(infinity_bits_ - max_ulps_)),
+        further_from_infinity_(
+            Floating::ReinterpretBits(infinity_bits_ - max_ulps_ - 1)),
+        max_(Floating::Max()),
+        nan1_(Floating::ReinterpretBits(Floating::kExponentBitMask | 1)),
+        nan2_(Floating::ReinterpretBits(Floating::kExponentBitMask | 200)) {
+  }
+
+  void TestSize() {
+    EXPECT_EQ(sizeof(RawType), sizeof(Bits));
+  }
+
+  // A battery of tests for FloatingEqMatcher::Matches.
+  // matcher_maker is a pointer to a function which creates a FloatingEqMatcher.
+  void TestMatches(
+      testing::internal::FloatingEqMatcher<RawType> (*matcher_maker)(RawType)) {
+    Matcher<RawType> m1 = matcher_maker(0.0);
+    EXPECT_TRUE(m1.Matches(-0.0));
+    EXPECT_TRUE(m1.Matches(close_to_positive_zero_));
+    EXPECT_TRUE(m1.Matches(close_to_negative_zero_));
+    EXPECT_FALSE(m1.Matches(1.0));
+
+    Matcher<RawType> m2 = matcher_maker(close_to_positive_zero_);
+    EXPECT_FALSE(m2.Matches(further_from_negative_zero_));
+
+    Matcher<RawType> m3 = matcher_maker(1.0);
+    EXPECT_TRUE(m3.Matches(close_to_one_));
+    EXPECT_FALSE(m3.Matches(further_from_one_));
+
+    // Test commutativity: matcher_maker(0.0).Matches(1.0) was tested above.
+    EXPECT_FALSE(m3.Matches(0.0));
+
+    Matcher<RawType> m4 = matcher_maker(-infinity_);
+    EXPECT_TRUE(m4.Matches(-close_to_infinity_));
+
+    Matcher<RawType> m5 = matcher_maker(infinity_);
+    EXPECT_TRUE(m5.Matches(close_to_infinity_));
+
+    // This is interesting as the representations of infinity_ and nan1_
+    // are only 1 DLP apart.
+    EXPECT_FALSE(m5.Matches(nan1_));
+
+    // matcher_maker can produce a Matcher<const RawType&>, which is needed in
+    // some cases.
+    Matcher<const RawType&> m6 = matcher_maker(0.0);
+    EXPECT_TRUE(m6.Matches(-0.0));
+    EXPECT_TRUE(m6.Matches(close_to_positive_zero_));
+    EXPECT_FALSE(m6.Matches(1.0));
+
+    // matcher_maker can produce a Matcher<RawType&>, which is needed in some
+    // cases.
+    Matcher<RawType&> m7 = matcher_maker(0.0);
+    RawType x = 0.0;
+    EXPECT_TRUE(m7.Matches(x));
+    x = 0.01f;
+    EXPECT_FALSE(m7.Matches(x));
+  }
+
+  // Pre-calculated numbers to be used by the tests.
+
+  const Bits max_ulps_;
+
+  const Bits zero_bits_;  // The bits that represent 0.0.
+  const Bits one_bits_;  // The bits that represent 1.0.
+  const Bits infinity_bits_;  // The bits that represent +infinity.
+
+  // Some numbers close to 0.0.
+  const RawType close_to_positive_zero_;
+  const RawType close_to_negative_zero_;
+  const RawType further_from_negative_zero_;
+
+  // Some numbers close to 1.0.
+  const RawType close_to_one_;
+  const RawType further_from_one_;
+
+  // Some numbers close to +infinity.
+  const RawType infinity_;
+  const RawType close_to_infinity_;
+  const RawType further_from_infinity_;
+
+  // Maximum representable value that's not infinity.
+  const RawType max_;
+
+  // Some NaNs.
+  const RawType nan1_;
+  const RawType nan2_;
+};
+
+// Tests floating-point matchers with fixed epsilons.
+template <typename RawType>
+class FloatingPointNearTest : public FloatingPointTest<RawType> {
+ protected:
+  typedef FloatingPointTest<RawType> ParentType;
+
+  // A battery of tests for FloatingEqMatcher::Matches with a fixed epsilon.
+  // matcher_maker is a pointer to a function which creates a FloatingEqMatcher.
+  void TestNearMatches(
+      testing::internal::FloatingEqMatcher<RawType>
+          (*matcher_maker)(RawType, RawType)) {
+    Matcher<RawType> m1 = matcher_maker(0.0, 0.0);
+    EXPECT_TRUE(m1.Matches(0.0));
+    EXPECT_TRUE(m1.Matches(-0.0));
+    EXPECT_FALSE(m1.Matches(ParentType::close_to_positive_zero_));
+    EXPECT_FALSE(m1.Matches(ParentType::close_to_negative_zero_));
+    EXPECT_FALSE(m1.Matches(1.0));
+
+    Matcher<RawType> m2 = matcher_maker(0.0, 1.0);
+    EXPECT_TRUE(m2.Matches(0.0));
+    EXPECT_TRUE(m2.Matches(-0.0));
+    EXPECT_TRUE(m2.Matches(1.0));
+    EXPECT_TRUE(m2.Matches(-1.0));
+    EXPECT_FALSE(m2.Matches(ParentType::close_to_one_));
+    EXPECT_FALSE(m2.Matches(-ParentType::close_to_one_));
+
+    // Check that inf matches inf, regardless of the of the specified max
+    // absolute error.
+    Matcher<RawType> m3 = matcher_maker(ParentType::infinity_, 0.0);
+    EXPECT_TRUE(m3.Matches(ParentType::infinity_));
+    EXPECT_FALSE(m3.Matches(ParentType::close_to_infinity_));
+    EXPECT_FALSE(m3.Matches(-ParentType::infinity_));
+
+    Matcher<RawType> m4 = matcher_maker(-ParentType::infinity_, 0.0);
+    EXPECT_TRUE(m4.Matches(-ParentType::infinity_));
+    EXPECT_FALSE(m4.Matches(-ParentType::close_to_infinity_));
+    EXPECT_FALSE(m4.Matches(ParentType::infinity_));
+
+    // Test various overflow scenarios.
+    Matcher<RawType> m5 = matcher_maker(ParentType::max_, ParentType::max_);
+    EXPECT_TRUE(m5.Matches(ParentType::max_));
+    EXPECT_FALSE(m5.Matches(-ParentType::max_));
+
+    Matcher<RawType> m6 = matcher_maker(-ParentType::max_, ParentType::max_);
+    EXPECT_FALSE(m6.Matches(ParentType::max_));
+    EXPECT_TRUE(m6.Matches(-ParentType::max_));
+
+    Matcher<RawType> m7 = matcher_maker(ParentType::max_, 0);
+    EXPECT_TRUE(m7.Matches(ParentType::max_));
+    EXPECT_FALSE(m7.Matches(-ParentType::max_));
+
+    Matcher<RawType> m8 = matcher_maker(-ParentType::max_, 0);
+    EXPECT_FALSE(m8.Matches(ParentType::max_));
+    EXPECT_TRUE(m8.Matches(-ParentType::max_));
+
+    // The difference between max() and -max() normally overflows to infinity,
+    // but it should still match if the max_abs_error is also infinity.
+    Matcher<RawType> m9 = matcher_maker(
+        ParentType::max_, ParentType::infinity_);
+    EXPECT_TRUE(m8.Matches(-ParentType::max_));
+
+    // matcher_maker can produce a Matcher<const RawType&>, which is needed in
+    // some cases.
+    Matcher<const RawType&> m10 = matcher_maker(0.0, 1.0);
+    EXPECT_TRUE(m10.Matches(-0.0));
+    EXPECT_TRUE(m10.Matches(ParentType::close_to_positive_zero_));
+    EXPECT_FALSE(m10.Matches(ParentType::close_to_one_));
+
+    // matcher_maker can produce a Matcher<RawType&>, which is needed in some
+    // cases.
+    Matcher<RawType&> m11 = matcher_maker(0.0, 1.0);
+    RawType x = 0.0;
+    EXPECT_TRUE(m11.Matches(x));
+    x = 1.0f;
+    EXPECT_TRUE(m11.Matches(x));
+    x = -1.0f;
+    EXPECT_TRUE(m11.Matches(x));
+    x = 1.1f;
+    EXPECT_FALSE(m11.Matches(x));
+    x = -1.1f;
+    EXPECT_FALSE(m11.Matches(x));
+  }
+};
+
+// Instantiate FloatingPointTest for testing floats.
+typedef FloatingPointTest<float> FloatTest;
+
+TEST_F(FloatTest, FloatEqApproximatelyMatchesFloats) {
+  TestMatches(&FloatEq);
+}
+
+TEST_F(FloatTest, NanSensitiveFloatEqApproximatelyMatchesFloats) {
+  TestMatches(&NanSensitiveFloatEq);
+}
+
+TEST_F(FloatTest, FloatEqCannotMatchNaN) {
+  // FloatEq never matches NaN.
+  Matcher<float> m = FloatEq(nan1_);
+  EXPECT_FALSE(m.Matches(nan1_));
+  EXPECT_FALSE(m.Matches(nan2_));
+  EXPECT_FALSE(m.Matches(1.0));
+}
+
+TEST_F(FloatTest, NanSensitiveFloatEqCanMatchNaN) {
+  // NanSensitiveFloatEq will match NaN.
+  Matcher<float> m = NanSensitiveFloatEq(nan1_);
+  EXPECT_TRUE(m.Matches(nan1_));
+  EXPECT_TRUE(m.Matches(nan2_));
+  EXPECT_FALSE(m.Matches(1.0));
+}
+
+TEST_F(FloatTest, FloatEqCanDescribeSelf) {
+  Matcher<float> m1 = FloatEq(2.0f);
+  EXPECT_EQ("is approximately 2", Describe(m1));
+  EXPECT_EQ("isn't approximately 2", DescribeNegation(m1));
+
+  Matcher<float> m2 = FloatEq(0.5f);
+  EXPECT_EQ("is approximately 0.5", Describe(m2));
+  EXPECT_EQ("isn't approximately 0.5", DescribeNegation(m2));
+
+  Matcher<float> m3 = FloatEq(nan1_);
+  EXPECT_EQ("never matches", Describe(m3));
+  EXPECT_EQ("is anything", DescribeNegation(m3));
+}
+
+TEST_F(FloatTest, NanSensitiveFloatEqCanDescribeSelf) {
+  Matcher<float> m1 = NanSensitiveFloatEq(2.0f);
+  EXPECT_EQ("is approximately 2", Describe(m1));
+  EXPECT_EQ("isn't approximately 2", DescribeNegation(m1));
+
+  Matcher<float> m2 = NanSensitiveFloatEq(0.5f);
+  EXPECT_EQ("is approximately 0.5", Describe(m2));
+  EXPECT_EQ("isn't approximately 0.5", DescribeNegation(m2));
+
+  Matcher<float> m3 = NanSensitiveFloatEq(nan1_);
+  EXPECT_EQ("is NaN", Describe(m3));
+  EXPECT_EQ("isn't NaN", DescribeNegation(m3));
+}
+
+// Instantiate FloatingPointTest for testing floats with a user-specified
+// max absolute error.
+typedef FloatingPointNearTest<float> FloatNearTest;
+
+TEST_F(FloatNearTest, FloatNearMatches) {
+  TestNearMatches(&FloatNear);
+}
+
+TEST_F(FloatNearTest, NanSensitiveFloatNearApproximatelyMatchesFloats) {
+  TestNearMatches(&NanSensitiveFloatNear);
+}
+
+TEST_F(FloatNearTest, FloatNearCanDescribeSelf) {
+  Matcher<float> m1 = FloatNear(2.0f, 0.5f);
+  EXPECT_EQ("is approximately 2 (absolute error <= 0.5)", Describe(m1));
+  EXPECT_EQ(
+      "isn't approximately 2 (absolute error > 0.5)", DescribeNegation(m1));
+
+  Matcher<float> m2 = FloatNear(0.5f, 0.5f);
+  EXPECT_EQ("is approximately 0.5 (absolute error <= 0.5)", Describe(m2));
+  EXPECT_EQ(
+      "isn't approximately 0.5 (absolute error > 0.5)", DescribeNegation(m2));
+
+  Matcher<float> m3 = FloatNear(nan1_, 0.0);
+  EXPECT_EQ("never matches", Describe(m3));
+  EXPECT_EQ("is anything", DescribeNegation(m3));
+}
+
+TEST_F(FloatNearTest, NanSensitiveFloatNearCanDescribeSelf) {
+  Matcher<float> m1 = NanSensitiveFloatNear(2.0f, 0.5f);
+  EXPECT_EQ("is approximately 2 (absolute error <= 0.5)", Describe(m1));
+  EXPECT_EQ(
+      "isn't approximately 2 (absolute error > 0.5)", DescribeNegation(m1));
+
+  Matcher<float> m2 = NanSensitiveFloatNear(0.5f, 0.5f);
+  EXPECT_EQ("is approximately 0.5 (absolute error <= 0.5)", Describe(m2));
+  EXPECT_EQ(
+      "isn't approximately 0.5 (absolute error > 0.5)", DescribeNegation(m2));
+
+  Matcher<float> m3 = NanSensitiveFloatNear(nan1_, 0.1f);
+  EXPECT_EQ("is NaN", Describe(m3));
+  EXPECT_EQ("isn't NaN", DescribeNegation(m3));
+}
+
+TEST_F(FloatNearTest, FloatNearCannotMatchNaN) {
+  // FloatNear never matches NaN.
+  Matcher<float> m = FloatNear(ParentType::nan1_, 0.1f);
+  EXPECT_FALSE(m.Matches(nan1_));
+  EXPECT_FALSE(m.Matches(nan2_));
+  EXPECT_FALSE(m.Matches(1.0));
+}
+
+TEST_F(FloatNearTest, NanSensitiveFloatNearCanMatchNaN) {
+  // NanSensitiveFloatNear will match NaN.
+  Matcher<float> m = NanSensitiveFloatNear(nan1_, 0.1f);
+  EXPECT_TRUE(m.Matches(nan1_));
+  EXPECT_TRUE(m.Matches(nan2_));
+  EXPECT_FALSE(m.Matches(1.0));
+}
+
+// Instantiate FloatingPointTest for testing doubles.
+typedef FloatingPointTest<double> DoubleTest;
+
+TEST_F(DoubleTest, DoubleEqApproximatelyMatchesDoubles) {
+  TestMatches(&DoubleEq);
+}
+
+TEST_F(DoubleTest, NanSensitiveDoubleEqApproximatelyMatchesDoubles) {
+  TestMatches(&NanSensitiveDoubleEq);
+}
+
+TEST_F(DoubleTest, DoubleEqCannotMatchNaN) {
+  // DoubleEq never matches NaN.
+  Matcher<double> m = DoubleEq(nan1_);
+  EXPECT_FALSE(m.Matches(nan1_));
+  EXPECT_FALSE(m.Matches(nan2_));
+  EXPECT_FALSE(m.Matches(1.0));
+}
+
+TEST_F(DoubleTest, NanSensitiveDoubleEqCanMatchNaN) {
+  // NanSensitiveDoubleEq will match NaN.
+  Matcher<double> m = NanSensitiveDoubleEq(nan1_);
+  EXPECT_TRUE(m.Matches(nan1_));
+  EXPECT_TRUE(m.Matches(nan2_));
+  EXPECT_FALSE(m.Matches(1.0));
+}
+
+TEST_F(DoubleTest, DoubleEqCanDescribeSelf) {
+  Matcher<double> m1 = DoubleEq(2.0);
+  EXPECT_EQ("is approximately 2", Describe(m1));
+  EXPECT_EQ("isn't approximately 2", DescribeNegation(m1));
+
+  Matcher<double> m2 = DoubleEq(0.5);
+  EXPECT_EQ("is approximately 0.5", Describe(m2));
+  EXPECT_EQ("isn't approximately 0.5", DescribeNegation(m2));
+
+  Matcher<double> m3 = DoubleEq(nan1_);
+  EXPECT_EQ("never matches", Describe(m3));
+  EXPECT_EQ("is anything", DescribeNegation(m3));
+}
+
+TEST_F(DoubleTest, NanSensitiveDoubleEqCanDescribeSelf) {
+  Matcher<double> m1 = NanSensitiveDoubleEq(2.0);
+  EXPECT_EQ("is approximately 2", Describe(m1));
+  EXPECT_EQ("isn't approximately 2", DescribeNegation(m1));
+
+  Matcher<double> m2 = NanSensitiveDoubleEq(0.5);
+  EXPECT_EQ("is approximately 0.5", Describe(m2));
+  EXPECT_EQ("isn't approximately 0.5", DescribeNegation(m2));
+
+  Matcher<double> m3 = NanSensitiveDoubleEq(nan1_);
+  EXPECT_EQ("is NaN", Describe(m3));
+  EXPECT_EQ("isn't NaN", DescribeNegation(m3));
+}
+
+// Instantiate FloatingPointTest for testing floats with a user-specified
+// max absolute error.
+typedef FloatingPointNearTest<double> DoubleNearTest;
+
+TEST_F(DoubleNearTest, DoubleNearMatches) {
+  TestNearMatches(&DoubleNear);
+}
+
+TEST_F(DoubleNearTest, NanSensitiveDoubleNearApproximatelyMatchesDoubles) {
+  TestNearMatches(&NanSensitiveDoubleNear);
+}
+
+TEST_F(DoubleNearTest, DoubleNearCanDescribeSelf) {
+  Matcher<double> m1 = DoubleNear(2.0, 0.5);
+  EXPECT_EQ("is approximately 2 (absolute error <= 0.5)", Describe(m1));
+  EXPECT_EQ(
+      "isn't approximately 2 (absolute error > 0.5)", DescribeNegation(m1));
+
+  Matcher<double> m2 = DoubleNear(0.5, 0.5);
+  EXPECT_EQ("is approximately 0.5 (absolute error <= 0.5)", Describe(m2));
+  EXPECT_EQ(
+      "isn't approximately 0.5 (absolute error > 0.5)", DescribeNegation(m2));
+
+  Matcher<double> m3 = DoubleNear(nan1_, 0.0);
+  EXPECT_EQ("never matches", Describe(m3));
+  EXPECT_EQ("is anything", DescribeNegation(m3));
+}
+
+TEST_F(DoubleNearTest, ExplainsResultWhenMatchFails) {
+  EXPECT_EQ("", Explain(DoubleNear(2.0, 0.1), 2.05));
+  EXPECT_EQ("which is 0.2 from 2", Explain(DoubleNear(2.0, 0.1), 2.2));
+  EXPECT_EQ("which is -0.3 from 2", Explain(DoubleNear(2.0, 0.1), 1.7));
+
+  const std::string explanation =
+      Explain(DoubleNear(2.1, 1e-10), 2.1 + 1.2e-10);
+  // Different C++ implementations may print floating-point numbers
+  // slightly differently.
+  EXPECT_TRUE(explanation == "which is 1.2e-10 from 2.1" ||  // GCC
+              explanation == "which is 1.2e-010 from 2.1")   // MSVC
+      << " where explanation is \"" << explanation << "\".";
+}
+
+TEST_F(DoubleNearTest, NanSensitiveDoubleNearCanDescribeSelf) {
+  Matcher<double> m1 = NanSensitiveDoubleNear(2.0, 0.5);
+  EXPECT_EQ("is approximately 2 (absolute error <= 0.5)", Describe(m1));
+  EXPECT_EQ(
+      "isn't approximately 2 (absolute error > 0.5)", DescribeNegation(m1));
+
+  Matcher<double> m2 = NanSensitiveDoubleNear(0.5, 0.5);
+  EXPECT_EQ("is approximately 0.5 (absolute error <= 0.5)", Describe(m2));
+  EXPECT_EQ(
+      "isn't approximately 0.5 (absolute error > 0.5)", DescribeNegation(m2));
+
+  Matcher<double> m3 = NanSensitiveDoubleNear(nan1_, 0.1);
+  EXPECT_EQ("is NaN", Describe(m3));
+  EXPECT_EQ("isn't NaN", DescribeNegation(m3));
+}
+
+TEST_F(DoubleNearTest, DoubleNearCannotMatchNaN) {
+  // DoubleNear never matches NaN.
+  Matcher<double> m = DoubleNear(ParentType::nan1_, 0.1);
+  EXPECT_FALSE(m.Matches(nan1_));
+  EXPECT_FALSE(m.Matches(nan2_));
+  EXPECT_FALSE(m.Matches(1.0));
+}
+
+TEST_F(DoubleNearTest, NanSensitiveDoubleNearCanMatchNaN) {
+  // NanSensitiveDoubleNear will match NaN.
+  Matcher<double> m = NanSensitiveDoubleNear(nan1_, 0.1);
+  EXPECT_TRUE(m.Matches(nan1_));
+  EXPECT_TRUE(m.Matches(nan2_));
+  EXPECT_FALSE(m.Matches(1.0));
+}
+
+TEST(PointeeTest, RawPointer) {
+  const Matcher<int*> m = Pointee(Ge(0));
+
+  int n = 1;
+  EXPECT_TRUE(m.Matches(&n));
+  n = -1;
+  EXPECT_FALSE(m.Matches(&n));
+  EXPECT_FALSE(m.Matches(nullptr));
+}
+
+TEST(PointeeTest, RawPointerToConst) {
+  const Matcher<const double*> m = Pointee(Ge(0));
+
+  double x = 1;
+  EXPECT_TRUE(m.Matches(&x));
+  x = -1;
+  EXPECT_FALSE(m.Matches(&x));
+  EXPECT_FALSE(m.Matches(nullptr));
+}
+
+TEST(PointeeTest, ReferenceToConstRawPointer) {
+  const Matcher<int* const &> m = Pointee(Ge(0));
+
+  int n = 1;
+  EXPECT_TRUE(m.Matches(&n));
+  n = -1;
+  EXPECT_FALSE(m.Matches(&n));
+  EXPECT_FALSE(m.Matches(nullptr));
+}
+
+TEST(PointeeTest, ReferenceToNonConstRawPointer) {
+  const Matcher<double* &> m = Pointee(Ge(0));
+
+  double x = 1.0;
+  double* p = &x;
+  EXPECT_TRUE(m.Matches(p));
+  x = -1;
+  EXPECT_FALSE(m.Matches(p));
+  p = nullptr;
+  EXPECT_FALSE(m.Matches(p));
+}
+
+TEST(PointeeTest, SmartPointer) {
+  const Matcher<std::unique_ptr<int>> m = Pointee(Ge(0));
+
+  std::unique_ptr<int> n(new int(1));
+  EXPECT_TRUE(m.Matches(n));
+}
+
+TEST(PointeeTest, SmartPointerToConst) {
+  const Matcher<std::unique_ptr<const int>> m = Pointee(Ge(0));
+
+  // There's no implicit conversion from unique_ptr<int> to const
+  // unique_ptr<const int>, so we must pass a unique_ptr<const int> into the
+  // matcher.
+  std::unique_ptr<const int> n(new int(1));
+  EXPECT_TRUE(m.Matches(n));
+}
+
+TEST(PointerTest, RawPointer) {
+  int n = 1;
+  const Matcher<int*> m = Pointer(Eq(&n));
+
+  EXPECT_TRUE(m.Matches(&n));
+
+  int* p = nullptr;
+  EXPECT_FALSE(m.Matches(p));
+  EXPECT_FALSE(m.Matches(nullptr));
+}
+
+TEST(PointerTest, RawPointerToConst) {
+  int n = 1;
+  const Matcher<const int*> m = Pointer(Eq(&n));
+
+  EXPECT_TRUE(m.Matches(&n));
+
+  int* p = nullptr;
+  EXPECT_FALSE(m.Matches(p));
+  EXPECT_FALSE(m.Matches(nullptr));
+}
+
+TEST(PointerTest, SmartPointer) {
+  std::unique_ptr<int> n(new int(10));
+  int* raw_n = n.get();
+  const Matcher<std::unique_ptr<int>> m = Pointer(Eq(raw_n));
+
+  EXPECT_TRUE(m.Matches(n));
+}
+
+TEST(PointerTest, SmartPointerToConst) {
+  std::unique_ptr<const int> n(new int(10));
+  const int* raw_n = n.get();
+  const Matcher<std::unique_ptr<const int>> m = Pointer(Eq(raw_n));
+
+  // There's no implicit conversion from unique_ptr<int> to const
+  // unique_ptr<const int>, so we must pass a unique_ptr<const int> into the
+  // matcher.
+  std::unique_ptr<const int> p(new int(10));
+  EXPECT_FALSE(m.Matches(p));
+}
+
+TEST(AddressTest, NonConst) {
+  int n = 1;
+  const Matcher<int> m = Address(Eq(&n));
+
+  EXPECT_TRUE(m.Matches(n));
+
+  int other = 5;
+
+  EXPECT_FALSE(m.Matches(other));
+
+  int& n_ref = n;
+
+  EXPECT_TRUE(m.Matches(n_ref));
+}
+
+TEST(AddressTest, Const) {
+  const int n = 1;
+  const Matcher<int> m = Address(Eq(&n));
+
+  EXPECT_TRUE(m.Matches(n));
+
+  int other = 5;
+
+  EXPECT_FALSE(m.Matches(other));
+}
+
+TEST(AddressTest, MatcherDoesntCopy) {
+  std::unique_ptr<int> n(new int(1));
+  const Matcher<std::unique_ptr<int>> m = Address(Eq(&n));
+
+  EXPECT_TRUE(m.Matches(n));
+}
+
+TEST(AddressTest, Describe) {
+  Matcher<int> matcher = Address(_);
+  EXPECT_EQ("has address that is anything", Describe(matcher));
+  EXPECT_EQ("does not have address that is anything",
+            DescribeNegation(matcher));
+}
+
+MATCHER_P(FieldIIs, inner_matcher, "") {
+  return ExplainMatchResult(inner_matcher, arg.i, result_listener);
+}
+
+#if GTEST_HAS_RTTI
+TEST(WhenDynamicCastToTest, SameType) {
+  Derived derived;
+  derived.i = 4;
+
+  // Right type. A pointer is passed down.
+  Base* as_base_ptr = &derived;
+  EXPECT_THAT(as_base_ptr, WhenDynamicCastTo<Derived*>(Not(IsNull())));
+  EXPECT_THAT(as_base_ptr, WhenDynamicCastTo<Derived*>(Pointee(FieldIIs(4))));
+  EXPECT_THAT(as_base_ptr,
+              Not(WhenDynamicCastTo<Derived*>(Pointee(FieldIIs(5)))));
+}
+
+TEST(WhenDynamicCastToTest, WrongTypes) {
+  Base base;
+  Derived derived;
+  OtherDerived other_derived;
+
+  // Wrong types. NULL is passed.
+  EXPECT_THAT(&base, Not(WhenDynamicCastTo<Derived*>(Pointee(_))));
+  EXPECT_THAT(&base, WhenDynamicCastTo<Derived*>(IsNull()));
+  Base* as_base_ptr = &derived;
+  EXPECT_THAT(as_base_ptr, Not(WhenDynamicCastTo<OtherDerived*>(Pointee(_))));
+  EXPECT_THAT(as_base_ptr, WhenDynamicCastTo<OtherDerived*>(IsNull()));
+  as_base_ptr = &other_derived;
+  EXPECT_THAT(as_base_ptr, Not(WhenDynamicCastTo<Derived*>(Pointee(_))));
+  EXPECT_THAT(as_base_ptr, WhenDynamicCastTo<Derived*>(IsNull()));
+}
+
+TEST(WhenDynamicCastToTest, AlreadyNull) {
+  // Already NULL.
+  Base* as_base_ptr = nullptr;
+  EXPECT_THAT(as_base_ptr, WhenDynamicCastTo<Derived*>(IsNull()));
+}
+
+struct AmbiguousCastTypes {
+  class VirtualDerived : public virtual Base {};
+  class DerivedSub1 : public VirtualDerived {};
+  class DerivedSub2 : public VirtualDerived {};
+  class ManyDerivedInHierarchy : public DerivedSub1, public DerivedSub2 {};
+};
+
+TEST(WhenDynamicCastToTest, AmbiguousCast) {
+  AmbiguousCastTypes::DerivedSub1 sub1;
+  AmbiguousCastTypes::ManyDerivedInHierarchy many_derived;
+  // Multiply derived from Base. dynamic_cast<> returns NULL.
+  Base* as_base_ptr =
+      static_cast<AmbiguousCastTypes::DerivedSub1*>(&many_derived);
+  EXPECT_THAT(as_base_ptr,
+              WhenDynamicCastTo<AmbiguousCastTypes::VirtualDerived*>(IsNull()));
+  as_base_ptr = &sub1;
+  EXPECT_THAT(
+      as_base_ptr,
+      WhenDynamicCastTo<AmbiguousCastTypes::VirtualDerived*>(Not(IsNull())));
+}
+
+TEST(WhenDynamicCastToTest, Describe) {
+  Matcher<Base*> matcher = WhenDynamicCastTo<Derived*>(Pointee(_));
+  const std::string prefix =
+      "when dynamic_cast to " + internal::GetTypeName<Derived*>() + ", ";
+  EXPECT_EQ(prefix + "points to a value that is anything", Describe(matcher));
+  EXPECT_EQ(prefix + "does not point to a value that is anything",
+            DescribeNegation(matcher));
+}
+
+TEST(WhenDynamicCastToTest, Explain) {
+  Matcher<Base*> matcher = WhenDynamicCastTo<Derived*>(Pointee(_));
+  Base* null = nullptr;
+  EXPECT_THAT(Explain(matcher, null), HasSubstr("NULL"));
+  Derived derived;
+  EXPECT_TRUE(matcher.Matches(&derived));
+  EXPECT_THAT(Explain(matcher, &derived), HasSubstr("which points to "));
+
+  // With references, the matcher itself can fail. Test for that one.
+  Matcher<const Base&> ref_matcher = WhenDynamicCastTo<const OtherDerived&>(_);
+  EXPECT_THAT(Explain(ref_matcher, derived),
+              HasSubstr("which cannot be dynamic_cast"));
+}
+
+TEST(WhenDynamicCastToTest, GoodReference) {
+  Derived derived;
+  derived.i = 4;
+  Base& as_base_ref = derived;
+  EXPECT_THAT(as_base_ref, WhenDynamicCastTo<const Derived&>(FieldIIs(4)));
+  EXPECT_THAT(as_base_ref, WhenDynamicCastTo<const Derived&>(Not(FieldIIs(5))));
+}
+
+TEST(WhenDynamicCastToTest, BadReference) {
+  Derived derived;
+  Base& as_base_ref = derived;
+  EXPECT_THAT(as_base_ref, Not(WhenDynamicCastTo<const OtherDerived&>(_)));
+}
+#endif  // GTEST_HAS_RTTI
+
+// Minimal const-propagating pointer.
+template <typename T>
+class ConstPropagatingPtr {
+ public:
+  typedef T element_type;
+
+  ConstPropagatingPtr() : val_() {}
+  explicit ConstPropagatingPtr(T* t) : val_(t) {}
+  ConstPropagatingPtr(const ConstPropagatingPtr& other) : val_(other.val_) {}
+
+  T* get() { return val_; }
+  T& operator*() { return *val_; }
+  // Most smart pointers return non-const T* and T& from the next methods.
+  const T* get() const { return val_; }
+  const T& operator*() const { return *val_; }
+
+ private:
+  T* val_;
+};
+
+TEST(PointeeTest, WorksWithConstPropagatingPointers) {
+  const Matcher< ConstPropagatingPtr<int> > m = Pointee(Lt(5));
+  int three = 3;
+  const ConstPropagatingPtr<int> co(&three);
+  ConstPropagatingPtr<int> o(&three);
+  EXPECT_TRUE(m.Matches(o));
+  EXPECT_TRUE(m.Matches(co));
+  *o = 6;
+  EXPECT_FALSE(m.Matches(o));
+  EXPECT_FALSE(m.Matches(ConstPropagatingPtr<int>()));
+}
+
+TEST(PointeeTest, NeverMatchesNull) {
+  const Matcher<const char*> m = Pointee(_);
+  EXPECT_FALSE(m.Matches(nullptr));
+}
+
+// Tests that we can write Pointee(value) instead of Pointee(Eq(value)).
+TEST(PointeeTest, MatchesAgainstAValue) {
+  const Matcher<int*> m = Pointee(5);
+
+  int n = 5;
+  EXPECT_TRUE(m.Matches(&n));
+  n = -1;
+  EXPECT_FALSE(m.Matches(&n));
+  EXPECT_FALSE(m.Matches(nullptr));
+}
+
+TEST(PointeeTest, CanDescribeSelf) {
+  const Matcher<int*> m = Pointee(Gt(3));
+  EXPECT_EQ("points to a value that is > 3", Describe(m));
+  EXPECT_EQ("does not point to a value that is > 3",
+            DescribeNegation(m));
+}
+
+TEST(PointeeTest, CanExplainMatchResult) {
+  const Matcher<const std::string*> m = Pointee(StartsWith("Hi"));
+
+  EXPECT_EQ("", Explain(m, static_cast<const std::string*>(nullptr)));
+
+  const Matcher<long*> m2 = Pointee(GreaterThan(1));  // NOLINT
+  long n = 3;  // NOLINT
+  EXPECT_EQ("which points to 3" + OfType("long") + ", which is 2 more than 1",
+            Explain(m2, &n));
+}
+
+TEST(PointeeTest, AlwaysExplainsPointee) {
+  const Matcher<int*> m = Pointee(0);
+  int n = 42;
+  EXPECT_EQ("which points to 42" + OfType("int"), Explain(m, &n));
+}
+
+// An uncopyable class.
+class Uncopyable {
+ public:
+  Uncopyable() : value_(-1) {}
+  explicit Uncopyable(int a_value) : value_(a_value) {}
+
+  int value() const { return value_; }
+  void set_value(int i) { value_ = i; }
+
+ private:
+  int value_;
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(Uncopyable);
+};
+
+// Returns true if and only if x.value() is positive.
+bool ValueIsPositive(const Uncopyable& x) { return x.value() > 0; }
+
+MATCHER_P(UncopyableIs, inner_matcher, "") {
+  return ExplainMatchResult(inner_matcher, arg.value(), result_listener);
+}
+
+// A user-defined struct for testing Field().
+struct AStruct {
+  AStruct() : x(0), y(1.0), z(5), p(nullptr) {}
+  AStruct(const AStruct& rhs)
+      : x(rhs.x), y(rhs.y), z(rhs.z.value()), p(rhs.p) {}
+
+  int x;           // A non-const field.
+  const double y;  // A const field.
+  Uncopyable z;    // An uncopyable field.
+  const char* p;   // A pointer field.
+};
+
+// A derived struct for testing Field().
+struct DerivedStruct : public AStruct {
+  char ch;
+};
+
+// Tests that Field(&Foo::field, ...) works when field is non-const.
+TEST(FieldTest, WorksForNonConstField) {
+  Matcher<AStruct> m = Field(&AStruct::x, Ge(0));
+  Matcher<AStruct> m_with_name = Field("x", &AStruct::x, Ge(0));
+
+  AStruct a;
+  EXPECT_TRUE(m.Matches(a));
+  EXPECT_TRUE(m_with_name.Matches(a));
+  a.x = -1;
+  EXPECT_FALSE(m.Matches(a));
+  EXPECT_FALSE(m_with_name.Matches(a));
+}
+
+// Tests that Field(&Foo::field, ...) works when field is const.
+TEST(FieldTest, WorksForConstField) {
+  AStruct a;
+
+  Matcher<AStruct> m = Field(&AStruct::y, Ge(0.0));
+  Matcher<AStruct> m_with_name = Field("y", &AStruct::y, Ge(0.0));
+  EXPECT_TRUE(m.Matches(a));
+  EXPECT_TRUE(m_with_name.Matches(a));
+  m = Field(&AStruct::y, Le(0.0));
+  m_with_name = Field("y", &AStruct::y, Le(0.0));
+  EXPECT_FALSE(m.Matches(a));
+  EXPECT_FALSE(m_with_name.Matches(a));
+}
+
+// Tests that Field(&Foo::field, ...) works when field is not copyable.
+TEST(FieldTest, WorksForUncopyableField) {
+  AStruct a;
+
+  Matcher<AStruct> m = Field(&AStruct::z, Truly(ValueIsPositive));
+  EXPECT_TRUE(m.Matches(a));
+  m = Field(&AStruct::z, Not(Truly(ValueIsPositive)));
+  EXPECT_FALSE(m.Matches(a));
+}
+
+// Tests that Field(&Foo::field, ...) works when field is a pointer.
+TEST(FieldTest, WorksForPointerField) {
+  // Matching against NULL.
+  Matcher<AStruct> m = Field(&AStruct::p, static_cast<const char*>(nullptr));
+  AStruct a;
+  EXPECT_TRUE(m.Matches(a));
+  a.p = "hi";
+  EXPECT_FALSE(m.Matches(a));
+
+  // Matching a pointer that is not NULL.
+  m = Field(&AStruct::p, StartsWith("hi"));
+  a.p = "hill";
+  EXPECT_TRUE(m.Matches(a));
+  a.p = "hole";
+  EXPECT_FALSE(m.Matches(a));
+}
+
+// Tests that Field() works when the object is passed by reference.
+TEST(FieldTest, WorksForByRefArgument) {
+  Matcher<const AStruct&> m = Field(&AStruct::x, Ge(0));
+
+  AStruct a;
+  EXPECT_TRUE(m.Matches(a));
+  a.x = -1;
+  EXPECT_FALSE(m.Matches(a));
+}
+
+// Tests that Field(&Foo::field, ...) works when the argument's type
+// is a sub-type of Foo.
+TEST(FieldTest, WorksForArgumentOfSubType) {
+  // Note that the matcher expects DerivedStruct but we say AStruct
+  // inside Field().
+  Matcher<const DerivedStruct&> m = Field(&AStruct::x, Ge(0));
+
+  DerivedStruct d;
+  EXPECT_TRUE(m.Matches(d));
+  d.x = -1;
+  EXPECT_FALSE(m.Matches(d));
+}
+
+// Tests that Field(&Foo::field, m) works when field's type and m's
+// argument type are compatible but not the same.
+TEST(FieldTest, WorksForCompatibleMatcherType) {
+  // The field is an int, but the inner matcher expects a signed char.
+  Matcher<const AStruct&> m = Field(&AStruct::x,
+                                    Matcher<signed char>(Ge(0)));
+
+  AStruct a;
+  EXPECT_TRUE(m.Matches(a));
+  a.x = -1;
+  EXPECT_FALSE(m.Matches(a));
+}
+
+// Tests that Field() can describe itself.
+TEST(FieldTest, CanDescribeSelf) {
+  Matcher<const AStruct&> m = Field(&AStruct::x, Ge(0));
+
+  EXPECT_EQ("is an object whose given field is >= 0", Describe(m));
+  EXPECT_EQ("is an object whose given field isn't >= 0", DescribeNegation(m));
+}
+
+TEST(FieldTest, CanDescribeSelfWithFieldName) {
+  Matcher<const AStruct&> m = Field("field_name", &AStruct::x, Ge(0));
+
+  EXPECT_EQ("is an object whose field `field_name` is >= 0", Describe(m));
+  EXPECT_EQ("is an object whose field `field_name` isn't >= 0",
+            DescribeNegation(m));
+}
+
+// Tests that Field() can explain the match result.
+TEST(FieldTest, CanExplainMatchResult) {
+  Matcher<const AStruct&> m = Field(&AStruct::x, Ge(0));
+
+  AStruct a;
+  a.x = 1;
+  EXPECT_EQ("whose given field is 1" + OfType("int"), Explain(m, a));
+
+  m = Field(&AStruct::x, GreaterThan(0));
+  EXPECT_EQ(
+      "whose given field is 1" + OfType("int") + ", which is 1 more than 0",
+      Explain(m, a));
+}
+
+TEST(FieldTest, CanExplainMatchResultWithFieldName) {
+  Matcher<const AStruct&> m = Field("field_name", &AStruct::x, Ge(0));
+
+  AStruct a;
+  a.x = 1;
+  EXPECT_EQ("whose field `field_name` is 1" + OfType("int"), Explain(m, a));
+
+  m = Field("field_name", &AStruct::x, GreaterThan(0));
+  EXPECT_EQ("whose field `field_name` is 1" + OfType("int") +
+                ", which is 1 more than 0",
+            Explain(m, a));
+}
+
+// Tests that Field() works when the argument is a pointer to const.
+TEST(FieldForPointerTest, WorksForPointerToConst) {
+  Matcher<const AStruct*> m = Field(&AStruct::x, Ge(0));
+
+  AStruct a;
+  EXPECT_TRUE(m.Matches(&a));
+  a.x = -1;
+  EXPECT_FALSE(m.Matches(&a));
+}
+
+// Tests that Field() works when the argument is a pointer to non-const.
+TEST(FieldForPointerTest, WorksForPointerToNonConst) {
+  Matcher<AStruct*> m = Field(&AStruct::x, Ge(0));
+
+  AStruct a;
+  EXPECT_TRUE(m.Matches(&a));
+  a.x = -1;
+  EXPECT_FALSE(m.Matches(&a));
+}
+
+// Tests that Field() works when the argument is a reference to a const pointer.
+TEST(FieldForPointerTest, WorksForReferenceToConstPointer) {
+  Matcher<AStruct* const&> m = Field(&AStruct::x, Ge(0));
+
+  AStruct a;
+  EXPECT_TRUE(m.Matches(&a));
+  a.x = -1;
+  EXPECT_FALSE(m.Matches(&a));
+}
+
+// Tests that Field() does not match the NULL pointer.
+TEST(FieldForPointerTest, DoesNotMatchNull) {
+  Matcher<const AStruct*> m = Field(&AStruct::x, _);
+  EXPECT_FALSE(m.Matches(nullptr));
+}
+
+// Tests that Field(&Foo::field, ...) works when the argument's type
+// is a sub-type of const Foo*.
+TEST(FieldForPointerTest, WorksForArgumentOfSubType) {
+  // Note that the matcher expects DerivedStruct but we say AStruct
+  // inside Field().
+  Matcher<DerivedStruct*> m = Field(&AStruct::x, Ge(0));
+
+  DerivedStruct d;
+  EXPECT_TRUE(m.Matches(&d));
+  d.x = -1;
+  EXPECT_FALSE(m.Matches(&d));
+}
+
+// Tests that Field() can describe itself when used to match a pointer.
+TEST(FieldForPointerTest, CanDescribeSelf) {
+  Matcher<const AStruct*> m = Field(&AStruct::x, Ge(0));
+
+  EXPECT_EQ("is an object whose given field is >= 0", Describe(m));
+  EXPECT_EQ("is an object whose given field isn't >= 0", DescribeNegation(m));
+}
+
+TEST(FieldForPointerTest, CanDescribeSelfWithFieldName) {
+  Matcher<const AStruct*> m = Field("field_name", &AStruct::x, Ge(0));
+
+  EXPECT_EQ("is an object whose field `field_name` is >= 0", Describe(m));
+  EXPECT_EQ("is an object whose field `field_name` isn't >= 0",
+            DescribeNegation(m));
+}
+
+// Tests that Field() can explain the result of matching a pointer.
+TEST(FieldForPointerTest, CanExplainMatchResult) {
+  Matcher<const AStruct*> m = Field(&AStruct::x, Ge(0));
+
+  AStruct a;
+  a.x = 1;
+  EXPECT_EQ("", Explain(m, static_cast<const AStruct*>(nullptr)));
+  EXPECT_EQ("which points to an object whose given field is 1" + OfType("int"),
+            Explain(m, &a));
+
+  m = Field(&AStruct::x, GreaterThan(0));
+  EXPECT_EQ("which points to an object whose given field is 1" + OfType("int") +
+            ", which is 1 more than 0", Explain(m, &a));
+}
+
+TEST(FieldForPointerTest, CanExplainMatchResultWithFieldName) {
+  Matcher<const AStruct*> m = Field("field_name", &AStruct::x, Ge(0));
+
+  AStruct a;
+  a.x = 1;
+  EXPECT_EQ("", Explain(m, static_cast<const AStruct*>(nullptr)));
+  EXPECT_EQ(
+      "which points to an object whose field `field_name` is 1" + OfType("int"),
+      Explain(m, &a));
+
+  m = Field("field_name", &AStruct::x, GreaterThan(0));
+  EXPECT_EQ("which points to an object whose field `field_name` is 1" +
+                OfType("int") + ", which is 1 more than 0",
+            Explain(m, &a));
+}
+
+// A user-defined class for testing Property().
+class AClass {
+ public:
+  AClass() : n_(0) {}
+
+  // A getter that returns a non-reference.
+  int n() const { return n_; }
+
+  void set_n(int new_n) { n_ = new_n; }
+
+  // A getter that returns a reference to const.
+  const std::string& s() const { return s_; }
+
+  const std::string& s_ref() const & { return s_; }
+
+  void set_s(const std::string& new_s) { s_ = new_s; }
+
+  // A getter that returns a reference to non-const.
+  double& x() const { return x_; }
+
+ private:
+  int n_;
+  std::string s_;
+
+  static double x_;
+};
+
+double AClass::x_ = 0.0;
+
+// A derived class for testing Property().
+class DerivedClass : public AClass {
+ public:
+  int k() const { return k_; }
+ private:
+  int k_;
+};
+
+// Tests that Property(&Foo::property, ...) works when property()
+// returns a non-reference.
+TEST(PropertyTest, WorksForNonReferenceProperty) {
+  Matcher<const AClass&> m = Property(&AClass::n, Ge(0));
+  Matcher<const AClass&> m_with_name = Property("n", &AClass::n, Ge(0));
+
+  AClass a;
+  a.set_n(1);
+  EXPECT_TRUE(m.Matches(a));
+  EXPECT_TRUE(m_with_name.Matches(a));
+
+  a.set_n(-1);
+  EXPECT_FALSE(m.Matches(a));
+  EXPECT_FALSE(m_with_name.Matches(a));
+}
+
+// Tests that Property(&Foo::property, ...) works when property()
+// returns a reference to const.
+TEST(PropertyTest, WorksForReferenceToConstProperty) {
+  Matcher<const AClass&> m = Property(&AClass::s, StartsWith("hi"));
+  Matcher<const AClass&> m_with_name =
+      Property("s", &AClass::s, StartsWith("hi"));
+
+  AClass a;
+  a.set_s("hill");
+  EXPECT_TRUE(m.Matches(a));
+  EXPECT_TRUE(m_with_name.Matches(a));
+
+  a.set_s("hole");
+  EXPECT_FALSE(m.Matches(a));
+  EXPECT_FALSE(m_with_name.Matches(a));
+}
+
+// Tests that Property(&Foo::property, ...) works when property() is
+// ref-qualified.
+TEST(PropertyTest, WorksForRefQualifiedProperty) {
+  Matcher<const AClass&> m = Property(&AClass::s_ref, StartsWith("hi"));
+  Matcher<const AClass&> m_with_name =
+      Property("s", &AClass::s_ref, StartsWith("hi"));
+
+  AClass a;
+  a.set_s("hill");
+  EXPECT_TRUE(m.Matches(a));
+  EXPECT_TRUE(m_with_name.Matches(a));
+
+  a.set_s("hole");
+  EXPECT_FALSE(m.Matches(a));
+  EXPECT_FALSE(m_with_name.Matches(a));
+}
+
+// Tests that Property(&Foo::property, ...) works when property()
+// returns a reference to non-const.
+TEST(PropertyTest, WorksForReferenceToNonConstProperty) {
+  double x = 0.0;
+  AClass a;
+
+  Matcher<const AClass&> m = Property(&AClass::x, Ref(x));
+  EXPECT_FALSE(m.Matches(a));
+
+  m = Property(&AClass::x, Not(Ref(x)));
+  EXPECT_TRUE(m.Matches(a));
+}
+
+// Tests that Property(&Foo::property, ...) works when the argument is
+// passed by value.
+TEST(PropertyTest, WorksForByValueArgument) {
+  Matcher<AClass> m = Property(&AClass::s, StartsWith("hi"));
+
+  AClass a;
+  a.set_s("hill");
+  EXPECT_TRUE(m.Matches(a));
+
+  a.set_s("hole");
+  EXPECT_FALSE(m.Matches(a));
+}
+
+// Tests that Property(&Foo::property, ...) works when the argument's
+// type is a sub-type of Foo.
+TEST(PropertyTest, WorksForArgumentOfSubType) {
+  // The matcher expects a DerivedClass, but inside the Property() we
+  // say AClass.
+  Matcher<const DerivedClass&> m = Property(&AClass::n, Ge(0));
+
+  DerivedClass d;
+  d.set_n(1);
+  EXPECT_TRUE(m.Matches(d));
+
+  d.set_n(-1);
+  EXPECT_FALSE(m.Matches(d));
+}
+
+// Tests that Property(&Foo::property, m) works when property()'s type
+// and m's argument type are compatible but different.
+TEST(PropertyTest, WorksForCompatibleMatcherType) {
+  // n() returns an int but the inner matcher expects a signed char.
+  Matcher<const AClass&> m = Property(&AClass::n,
+                                      Matcher<signed char>(Ge(0)));
+
+  Matcher<const AClass&> m_with_name =
+      Property("n", &AClass::n, Matcher<signed char>(Ge(0)));
+
+  AClass a;
+  EXPECT_TRUE(m.Matches(a));
+  EXPECT_TRUE(m_with_name.Matches(a));
+  a.set_n(-1);
+  EXPECT_FALSE(m.Matches(a));
+  EXPECT_FALSE(m_with_name.Matches(a));
+}
+
+// Tests that Property() can describe itself.
+TEST(PropertyTest, CanDescribeSelf) {
+  Matcher<const AClass&> m = Property(&AClass::n, Ge(0));
+
+  EXPECT_EQ("is an object whose given property is >= 0", Describe(m));
+  EXPECT_EQ("is an object whose given property isn't >= 0",
+            DescribeNegation(m));
+}
+
+TEST(PropertyTest, CanDescribeSelfWithPropertyName) {
+  Matcher<const AClass&> m = Property("fancy_name", &AClass::n, Ge(0));
+
+  EXPECT_EQ("is an object whose property `fancy_name` is >= 0", Describe(m));
+  EXPECT_EQ("is an object whose property `fancy_name` isn't >= 0",
+            DescribeNegation(m));
+}
+
+// Tests that Property() can explain the match result.
+TEST(PropertyTest, CanExplainMatchResult) {
+  Matcher<const AClass&> m = Property(&AClass::n, Ge(0));
+
+  AClass a;
+  a.set_n(1);
+  EXPECT_EQ("whose given property is 1" + OfType("int"), Explain(m, a));
+
+  m = Property(&AClass::n, GreaterThan(0));
+  EXPECT_EQ(
+      "whose given property is 1" + OfType("int") + ", which is 1 more than 0",
+      Explain(m, a));
+}
+
+TEST(PropertyTest, CanExplainMatchResultWithPropertyName) {
+  Matcher<const AClass&> m = Property("fancy_name", &AClass::n, Ge(0));
+
+  AClass a;
+  a.set_n(1);
+  EXPECT_EQ("whose property `fancy_name` is 1" + OfType("int"), Explain(m, a));
+
+  m = Property("fancy_name", &AClass::n, GreaterThan(0));
+  EXPECT_EQ("whose property `fancy_name` is 1" + OfType("int") +
+                ", which is 1 more than 0",
+            Explain(m, a));
+}
+
+// Tests that Property() works when the argument is a pointer to const.
+TEST(PropertyForPointerTest, WorksForPointerToConst) {
+  Matcher<const AClass*> m = Property(&AClass::n, Ge(0));
+
+  AClass a;
+  a.set_n(1);
+  EXPECT_TRUE(m.Matches(&a));
+
+  a.set_n(-1);
+  EXPECT_FALSE(m.Matches(&a));
+}
+
+// Tests that Property() works when the argument is a pointer to non-const.
+TEST(PropertyForPointerTest, WorksForPointerToNonConst) {
+  Matcher<AClass*> m = Property(&AClass::s, StartsWith("hi"));
+
+  AClass a;
+  a.set_s("hill");
+  EXPECT_TRUE(m.Matches(&a));
+
+  a.set_s("hole");
+  EXPECT_FALSE(m.Matches(&a));
+}
+
+// Tests that Property() works when the argument is a reference to a
+// const pointer.
+TEST(PropertyForPointerTest, WorksForReferenceToConstPointer) {
+  Matcher<AClass* const&> m = Property(&AClass::s, StartsWith("hi"));
+
+  AClass a;
+  a.set_s("hill");
+  EXPECT_TRUE(m.Matches(&a));
+
+  a.set_s("hole");
+  EXPECT_FALSE(m.Matches(&a));
+}
+
+// Tests that Property() does not match the NULL pointer.
+TEST(PropertyForPointerTest, WorksForReferenceToNonConstProperty) {
+  Matcher<const AClass*> m = Property(&AClass::x, _);
+  EXPECT_FALSE(m.Matches(nullptr));
+}
+
+// Tests that Property(&Foo::property, ...) works when the argument's
+// type is a sub-type of const Foo*.
+TEST(PropertyForPointerTest, WorksForArgumentOfSubType) {
+  // The matcher expects a DerivedClass, but inside the Property() we
+  // say AClass.
+  Matcher<const DerivedClass*> m = Property(&AClass::n, Ge(0));
+
+  DerivedClass d;
+  d.set_n(1);
+  EXPECT_TRUE(m.Matches(&d));
+
+  d.set_n(-1);
+  EXPECT_FALSE(m.Matches(&d));
+}
+
+// Tests that Property() can describe itself when used to match a pointer.
+TEST(PropertyForPointerTest, CanDescribeSelf) {
+  Matcher<const AClass*> m = Property(&AClass::n, Ge(0));
+
+  EXPECT_EQ("is an object whose given property is >= 0", Describe(m));
+  EXPECT_EQ("is an object whose given property isn't >= 0",
+            DescribeNegation(m));
+}
+
+TEST(PropertyForPointerTest, CanDescribeSelfWithPropertyDescription) {
+  Matcher<const AClass*> m = Property("fancy_name", &AClass::n, Ge(0));
+
+  EXPECT_EQ("is an object whose property `fancy_name` is >= 0", Describe(m));
+  EXPECT_EQ("is an object whose property `fancy_name` isn't >= 0",
+            DescribeNegation(m));
+}
+
+// Tests that Property() can explain the result of matching a pointer.
+TEST(PropertyForPointerTest, CanExplainMatchResult) {
+  Matcher<const AClass*> m = Property(&AClass::n, Ge(0));
+
+  AClass a;
+  a.set_n(1);
+  EXPECT_EQ("", Explain(m, static_cast<const AClass*>(nullptr)));
+  EXPECT_EQ(
+      "which points to an object whose given property is 1" + OfType("int"),
+      Explain(m, &a));
+
+  m = Property(&AClass::n, GreaterThan(0));
+  EXPECT_EQ("which points to an object whose given property is 1" +
+            OfType("int") + ", which is 1 more than 0",
+            Explain(m, &a));
+}
+
+TEST(PropertyForPointerTest, CanExplainMatchResultWithPropertyName) {
+  Matcher<const AClass*> m = Property("fancy_name", &AClass::n, Ge(0));
+
+  AClass a;
+  a.set_n(1);
+  EXPECT_EQ("", Explain(m, static_cast<const AClass*>(nullptr)));
+  EXPECT_EQ("which points to an object whose property `fancy_name` is 1" +
+                OfType("int"),
+            Explain(m, &a));
+
+  m = Property("fancy_name", &AClass::n, GreaterThan(0));
+  EXPECT_EQ("which points to an object whose property `fancy_name` is 1" +
+                OfType("int") + ", which is 1 more than 0",
+            Explain(m, &a));
+}
+
+// Tests ResultOf.
+
+// Tests that ResultOf(f, ...) compiles and works as expected when f is a
+// function pointer.
+std::string IntToStringFunction(int input) {
+  return input == 1 ? "foo" : "bar";
+}
+
+TEST(ResultOfTest, WorksForFunctionPointers) {
+  Matcher<int> matcher = ResultOf(&IntToStringFunction, Eq(std::string("foo")));
+
+  EXPECT_TRUE(matcher.Matches(1));
+  EXPECT_FALSE(matcher.Matches(2));
+}
+
+// Tests that ResultOf() can describe itself.
+TEST(ResultOfTest, CanDescribeItself) {
+  Matcher<int> matcher = ResultOf(&IntToStringFunction, StrEq("foo"));
+
+  EXPECT_EQ("is mapped by the given callable to a value that "
+            "is equal to \"foo\"", Describe(matcher));
+  EXPECT_EQ("is mapped by the given callable to a value that "
+            "isn't equal to \"foo\"", DescribeNegation(matcher));
+}
+
+// Tests that ResultOf() can explain the match result.
+int IntFunction(int input) { return input == 42 ? 80 : 90; }
+
+TEST(ResultOfTest, CanExplainMatchResult) {
+  Matcher<int> matcher = ResultOf(&IntFunction, Ge(85));
+  EXPECT_EQ("which is mapped by the given callable to 90" + OfType("int"),
+            Explain(matcher, 36));
+
+  matcher = ResultOf(&IntFunction, GreaterThan(85));
+  EXPECT_EQ("which is mapped by the given callable to 90" + OfType("int") +
+            ", which is 5 more than 85", Explain(matcher, 36));
+}
+
+// Tests that ResultOf(f, ...) compiles and works as expected when f(x)
+// returns a non-reference.
+TEST(ResultOfTest, WorksForNonReferenceResults) {
+  Matcher<int> matcher = ResultOf(&IntFunction, Eq(80));
+
+  EXPECT_TRUE(matcher.Matches(42));
+  EXPECT_FALSE(matcher.Matches(36));
+}
+
+// Tests that ResultOf(f, ...) compiles and works as expected when f(x)
+// returns a reference to non-const.
+double& DoubleFunction(double& input) { return input; }  // NOLINT
+
+Uncopyable& RefUncopyableFunction(Uncopyable& obj) {  // NOLINT
+  return obj;
+}
+
+TEST(ResultOfTest, WorksForReferenceToNonConstResults) {
+  double x = 3.14;
+  double x2 = x;
+  Matcher<double&> matcher = ResultOf(&DoubleFunction, Ref(x));
+
+  EXPECT_TRUE(matcher.Matches(x));
+  EXPECT_FALSE(matcher.Matches(x2));
+
+  // Test that ResultOf works with uncopyable objects
+  Uncopyable obj(0);
+  Uncopyable obj2(0);
+  Matcher<Uncopyable&> matcher2 =
+      ResultOf(&RefUncopyableFunction, Ref(obj));
+
+  EXPECT_TRUE(matcher2.Matches(obj));
+  EXPECT_FALSE(matcher2.Matches(obj2));
+}
+
+// Tests that ResultOf(f, ...) compiles and works as expected when f(x)
+// returns a reference to const.
+const std::string& StringFunction(const std::string& input) { return input; }
+
+TEST(ResultOfTest, WorksForReferenceToConstResults) {
+  std::string s = "foo";
+  std::string s2 = s;
+  Matcher<const std::string&> matcher = ResultOf(&StringFunction, Ref(s));
+
+  EXPECT_TRUE(matcher.Matches(s));
+  EXPECT_FALSE(matcher.Matches(s2));
+}
+
+// Tests that ResultOf(f, m) works when f(x) and m's
+// argument types are compatible but different.
+TEST(ResultOfTest, WorksForCompatibleMatcherTypes) {
+  // IntFunction() returns int but the inner matcher expects a signed char.
+  Matcher<int> matcher = ResultOf(IntFunction, Matcher<signed char>(Ge(85)));
+
+  EXPECT_TRUE(matcher.Matches(36));
+  EXPECT_FALSE(matcher.Matches(42));
+}
+
+// Tests that the program aborts when ResultOf is passed
+// a NULL function pointer.
+TEST(ResultOfDeathTest, DiesOnNullFunctionPointers) {
+  EXPECT_DEATH_IF_SUPPORTED(
+      ResultOf(static_cast<std::string (*)(int dummy)>(nullptr),
+               Eq(std::string("foo"))),
+      "NULL function pointer is passed into ResultOf\\(\\)\\.");
+}
+
+// Tests that ResultOf(f, ...) compiles and works as expected when f is a
+// function reference.
+TEST(ResultOfTest, WorksForFunctionReferences) {
+  Matcher<int> matcher = ResultOf(IntToStringFunction, StrEq("foo"));
+  EXPECT_TRUE(matcher.Matches(1));
+  EXPECT_FALSE(matcher.Matches(2));
+}
+
+// Tests that ResultOf(f, ...) compiles and works as expected when f is a
+// function object.
+struct Functor {
+  std::string operator()(int input) const {
+    return IntToStringFunction(input);
+  }
+};
+
+TEST(ResultOfTest, WorksForFunctors) {
+  Matcher<int> matcher = ResultOf(Functor(), Eq(std::string("foo")));
+
+  EXPECT_TRUE(matcher.Matches(1));
+  EXPECT_FALSE(matcher.Matches(2));
+}
+
+// Tests that ResultOf(f, ...) compiles and works as expected when f is a
+// functor with more than one operator() defined. ResultOf() must work
+// for each defined operator().
+struct PolymorphicFunctor {
+  typedef int result_type;
+  int operator()(int n) { return n; }
+  int operator()(const char* s) { return static_cast<int>(strlen(s)); }
+  std::string operator()(int *p) { return p ? "good ptr" : "null"; }
+};
+
+TEST(ResultOfTest, WorksForPolymorphicFunctors) {
+  Matcher<int> matcher_int = ResultOf(PolymorphicFunctor(), Ge(5));
+
+  EXPECT_TRUE(matcher_int.Matches(10));
+  EXPECT_FALSE(matcher_int.Matches(2));
+
+  Matcher<const char*> matcher_string = ResultOf(PolymorphicFunctor(), Ge(5));
+
+  EXPECT_TRUE(matcher_string.Matches("long string"));
+  EXPECT_FALSE(matcher_string.Matches("shrt"));
+}
+
+TEST(ResultOfTest, WorksForPolymorphicFunctorsIgnoringResultType) {
+  Matcher<int*> matcher = ResultOf(PolymorphicFunctor(), "good ptr");
+
+  int n = 0;
+  EXPECT_TRUE(matcher.Matches(&n));
+  EXPECT_FALSE(matcher.Matches(nullptr));
+}
+
+TEST(ResultOfTest, WorksForLambdas) {
+  Matcher<int> matcher = ResultOf(
+      [](int str_len) {
+        return std::string(static_cast<size_t>(str_len), 'x');
+      },
+      "xxx");
+  EXPECT_TRUE(matcher.Matches(3));
+  EXPECT_FALSE(matcher.Matches(1));
+}
+
+TEST(ResultOfTest, WorksForNonCopyableArguments) {
+  Matcher<std::unique_ptr<int>> matcher = ResultOf(
+      [](const std::unique_ptr<int>& str_len) {
+        return std::string(static_cast<size_t>(*str_len), 'x');
+      },
+      "xxx");
+  EXPECT_TRUE(matcher.Matches(std::unique_ptr<int>(new int(3))));
+  EXPECT_FALSE(matcher.Matches(std::unique_ptr<int>(new int(1))));
+}
+
+const int* ReferencingFunction(const int& n) { return &n; }
+
+struct ReferencingFunctor {
+  typedef const int* result_type;
+  result_type operator()(const int& n) { return &n; }
+};
+
+TEST(ResultOfTest, WorksForReferencingCallables) {
+  const int n = 1;
+  const int n2 = 1;
+  Matcher<const int&> matcher2 = ResultOf(ReferencingFunction, Eq(&n));
+  EXPECT_TRUE(matcher2.Matches(n));
+  EXPECT_FALSE(matcher2.Matches(n2));
+
+  Matcher<const int&> matcher3 = ResultOf(ReferencingFunctor(), Eq(&n));
+  EXPECT_TRUE(matcher3.Matches(n));
+  EXPECT_FALSE(matcher3.Matches(n2));
+}
+
+class DivisibleByImpl {
+ public:
+  explicit DivisibleByImpl(int a_divider) : divider_(a_divider) {}
+
+  // For testing using ExplainMatchResultTo() with polymorphic matchers.
+  template <typename T>
+  bool MatchAndExplain(const T& n, MatchResultListener* listener) const {
+    *listener << "which is " << (n % divider_) << " modulo "
+              << divider_;
+    return (n % divider_) == 0;
+  }
+
+  void DescribeTo(ostream* os) const {
+    *os << "is divisible by " << divider_;
+  }
+
+  void DescribeNegationTo(ostream* os) const {
+    *os << "is not divisible by " << divider_;
+  }
+
+  void set_divider(int a_divider) { divider_ = a_divider; }
+  int divider() const { return divider_; }
+
+ private:
+  int divider_;
+};
+
+PolymorphicMatcher<DivisibleByImpl> DivisibleBy(int n) {
+  return MakePolymorphicMatcher(DivisibleByImpl(n));
+}
+
+// Tests that when AllOf() fails, only the first failing matcher is
+// asked to explain why.
+TEST(ExplainMatchResultTest, AllOf_False_False) {
+  const Matcher<int> m = AllOf(DivisibleBy(4), DivisibleBy(3));
+  EXPECT_EQ("which is 1 modulo 4", Explain(m, 5));
+}
+
+// Tests that when AllOf() fails, only the first failing matcher is
+// asked to explain why.
+TEST(ExplainMatchResultTest, AllOf_False_True) {
+  const Matcher<int> m = AllOf(DivisibleBy(4), DivisibleBy(3));
+  EXPECT_EQ("which is 2 modulo 4", Explain(m, 6));
+}
+
+// Tests that when AllOf() fails, only the first failing matcher is
+// asked to explain why.
+TEST(ExplainMatchResultTest, AllOf_True_False) {
+  const Matcher<int> m = AllOf(Ge(1), DivisibleBy(3));
+  EXPECT_EQ("which is 2 modulo 3", Explain(m, 5));
+}
+
+// Tests that when AllOf() succeeds, all matchers are asked to explain
+// why.
+TEST(ExplainMatchResultTest, AllOf_True_True) {
+  const Matcher<int> m = AllOf(DivisibleBy(2), DivisibleBy(3));
+  EXPECT_EQ("which is 0 modulo 2, and which is 0 modulo 3", Explain(m, 6));
+}
+
+TEST(ExplainMatchResultTest, AllOf_True_True_2) {
+  const Matcher<int> m = AllOf(Ge(2), Le(3));
+  EXPECT_EQ("", Explain(m, 2));
+}
+
+TEST(ExplainmatcherResultTest, MonomorphicMatcher) {
+  const Matcher<int> m = GreaterThan(5);
+  EXPECT_EQ("which is 1 more than 5", Explain(m, 6));
+}
+
+// The following two tests verify that values without a public copy
+// ctor can be used as arguments to matchers like Eq(), Ge(), and etc
+// with the help of ByRef().
+
+class NotCopyable {
+ public:
+  explicit NotCopyable(int a_value) : value_(a_value) {}
+
+  int value() const { return value_; }
+
+  bool operator==(const NotCopyable& rhs) const {
+    return value() == rhs.value();
+  }
+
+  bool operator>=(const NotCopyable& rhs) const {
+    return value() >= rhs.value();
+  }
+ private:
+  int value_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(NotCopyable);
+};
+
+TEST(ByRefTest, AllowsNotCopyableConstValueInMatchers) {
+  const NotCopyable const_value1(1);
+  const Matcher<const NotCopyable&> m = Eq(ByRef(const_value1));
+
+  const NotCopyable n1(1), n2(2);
+  EXPECT_TRUE(m.Matches(n1));
+  EXPECT_FALSE(m.Matches(n2));
+}
+
+TEST(ByRefTest, AllowsNotCopyableValueInMatchers) {
+  NotCopyable value2(2);
+  const Matcher<NotCopyable&> m = Ge(ByRef(value2));
+
+  NotCopyable n1(1), n2(2);
+  EXPECT_FALSE(m.Matches(n1));
+  EXPECT_TRUE(m.Matches(n2));
+}
+
+TEST(IsEmptyTest, ImplementsIsEmpty) {
+  vector<int> container;
+  EXPECT_THAT(container, IsEmpty());
+  container.push_back(0);
+  EXPECT_THAT(container, Not(IsEmpty()));
+  container.push_back(1);
+  EXPECT_THAT(container, Not(IsEmpty()));
+}
+
+TEST(IsEmptyTest, WorksWithString) {
+  std::string text;
+  EXPECT_THAT(text, IsEmpty());
+  text = "foo";
+  EXPECT_THAT(text, Not(IsEmpty()));
+  text = std::string("\0", 1);
+  EXPECT_THAT(text, Not(IsEmpty()));
+}
+
+TEST(IsEmptyTest, CanDescribeSelf) {
+  Matcher<vector<int> > m = IsEmpty();
+  EXPECT_EQ("is empty", Describe(m));
+  EXPECT_EQ("isn't empty", DescribeNegation(m));
+}
+
+TEST(IsEmptyTest, ExplainsResult) {
+  Matcher<vector<int> > m = IsEmpty();
+  vector<int> container;
+  EXPECT_EQ("", Explain(m, container));
+  container.push_back(0);
+  EXPECT_EQ("whose size is 1", Explain(m, container));
+}
+
+TEST(IsEmptyTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper, Call(IsEmpty()));
+  helper.Call({});
+}
+
+TEST(IsTrueTest, IsTrueIsFalse) {
+  EXPECT_THAT(true, IsTrue());
+  EXPECT_THAT(false, IsFalse());
+  EXPECT_THAT(true, Not(IsFalse()));
+  EXPECT_THAT(false, Not(IsTrue()));
+  EXPECT_THAT(0, Not(IsTrue()));
+  EXPECT_THAT(0, IsFalse());
+  EXPECT_THAT(nullptr, Not(IsTrue()));
+  EXPECT_THAT(nullptr, IsFalse());
+  EXPECT_THAT(-1, IsTrue());
+  EXPECT_THAT(-1, Not(IsFalse()));
+  EXPECT_THAT(1, IsTrue());
+  EXPECT_THAT(1, Not(IsFalse()));
+  EXPECT_THAT(2, IsTrue());
+  EXPECT_THAT(2, Not(IsFalse()));
+  int a = 42;
+  EXPECT_THAT(a, IsTrue());
+  EXPECT_THAT(a, Not(IsFalse()));
+  EXPECT_THAT(&a, IsTrue());
+  EXPECT_THAT(&a, Not(IsFalse()));
+  EXPECT_THAT(false, Not(IsTrue()));
+  EXPECT_THAT(true, Not(IsFalse()));
+  EXPECT_THAT(std::true_type(), IsTrue());
+  EXPECT_THAT(std::true_type(), Not(IsFalse()));
+  EXPECT_THAT(std::false_type(), IsFalse());
+  EXPECT_THAT(std::false_type(), Not(IsTrue()));
+  EXPECT_THAT(nullptr, Not(IsTrue()));
+  EXPECT_THAT(nullptr, IsFalse());
+  std::unique_ptr<int> null_unique;
+  std::unique_ptr<int> nonnull_unique(new int(0));
+  EXPECT_THAT(null_unique, Not(IsTrue()));
+  EXPECT_THAT(null_unique, IsFalse());
+  EXPECT_THAT(nonnull_unique, IsTrue());
+  EXPECT_THAT(nonnull_unique, Not(IsFalse()));
+}
+
+TEST(SizeIsTest, ImplementsSizeIs) {
+  vector<int> container;
+  EXPECT_THAT(container, SizeIs(0));
+  EXPECT_THAT(container, Not(SizeIs(1)));
+  container.push_back(0);
+  EXPECT_THAT(container, Not(SizeIs(0)));
+  EXPECT_THAT(container, SizeIs(1));
+  container.push_back(0);
+  EXPECT_THAT(container, Not(SizeIs(0)));
+  EXPECT_THAT(container, SizeIs(2));
+}
+
+TEST(SizeIsTest, WorksWithMap) {
+  map<std::string, int> container;
+  EXPECT_THAT(container, SizeIs(0));
+  EXPECT_THAT(container, Not(SizeIs(1)));
+  container.insert(make_pair("foo", 1));
+  EXPECT_THAT(container, Not(SizeIs(0)));
+  EXPECT_THAT(container, SizeIs(1));
+  container.insert(make_pair("bar", 2));
+  EXPECT_THAT(container, Not(SizeIs(0)));
+  EXPECT_THAT(container, SizeIs(2));
+}
+
+TEST(SizeIsTest, WorksWithReferences) {
+  vector<int> container;
+  Matcher<const vector<int>&> m = SizeIs(1);
+  EXPECT_THAT(container, Not(m));
+  container.push_back(0);
+  EXPECT_THAT(container, m);
+}
+
+TEST(SizeIsTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper, Call(SizeIs(3)));
+  helper.Call(MakeUniquePtrs({1, 2, 3}));
+}
+
+// SizeIs should work for any type that provides a size() member function.
+// For example, a size_type member type should not need to be provided.
+struct MinimalistCustomType {
+  int size() const { return 1; }
+};
+TEST(SizeIsTest, WorksWithMinimalistCustomType) {
+  MinimalistCustomType container;
+  EXPECT_THAT(container, SizeIs(1));
+  EXPECT_THAT(container, Not(SizeIs(0)));
+}
+
+TEST(SizeIsTest, CanDescribeSelf) {
+  Matcher<vector<int> > m = SizeIs(2);
+  EXPECT_EQ("size is equal to 2", Describe(m));
+  EXPECT_EQ("size isn't equal to 2", DescribeNegation(m));
+}
+
+TEST(SizeIsTest, ExplainsResult) {
+  Matcher<vector<int> > m1 = SizeIs(2);
+  Matcher<vector<int> > m2 = SizeIs(Lt(2u));
+  Matcher<vector<int> > m3 = SizeIs(AnyOf(0, 3));
+  Matcher<vector<int> > m4 = SizeIs(Gt(1u));
+  vector<int> container;
+  EXPECT_EQ("whose size 0 doesn't match", Explain(m1, container));
+  EXPECT_EQ("whose size 0 matches", Explain(m2, container));
+  EXPECT_EQ("whose size 0 matches", Explain(m3, container));
+  EXPECT_EQ("whose size 0 doesn't match", Explain(m4, container));
+  container.push_back(0);
+  container.push_back(0);
+  EXPECT_EQ("whose size 2 matches", Explain(m1, container));
+  EXPECT_EQ("whose size 2 doesn't match", Explain(m2, container));
+  EXPECT_EQ("whose size 2 doesn't match", Explain(m3, container));
+  EXPECT_EQ("whose size 2 matches", Explain(m4, container));
+}
+
+#if GTEST_HAS_TYPED_TEST
+// Tests ContainerEq with different container types, and
+// different element types.
+
+template <typename T>
+class ContainerEqTest : public testing::Test {};
+
+typedef testing::Types<
+    set<int>,
+    vector<size_t>,
+    multiset<size_t>,
+    list<int> >
+    ContainerEqTestTypes;
+
+TYPED_TEST_SUITE(ContainerEqTest, ContainerEqTestTypes);
+
+// Tests that the filled container is equal to itself.
+TYPED_TEST(ContainerEqTest, EqualsSelf) {
+  static const int vals[] = {1, 1, 2, 3, 5, 8};
+  TypeParam my_set(vals, vals + 6);
+  const Matcher<TypeParam> m = ContainerEq(my_set);
+  EXPECT_TRUE(m.Matches(my_set));
+  EXPECT_EQ("", Explain(m, my_set));
+}
+
+// Tests that missing values are reported.
+TYPED_TEST(ContainerEqTest, ValueMissing) {
+  static const int vals[] = {1, 1, 2, 3, 5, 8};
+  static const int test_vals[] = {2, 1, 8, 5};
+  TypeParam my_set(vals, vals + 6);
+  TypeParam test_set(test_vals, test_vals + 4);
+  const Matcher<TypeParam> m = ContainerEq(my_set);
+  EXPECT_FALSE(m.Matches(test_set));
+  EXPECT_EQ("which doesn't have these expected elements: 3",
+            Explain(m, test_set));
+}
+
+// Tests that added values are reported.
+TYPED_TEST(ContainerEqTest, ValueAdded) {
+  static const int vals[] = {1, 1, 2, 3, 5, 8};
+  static const int test_vals[] = {1, 2, 3, 5, 8, 46};
+  TypeParam my_set(vals, vals + 6);
+  TypeParam test_set(test_vals, test_vals + 6);
+  const Matcher<const TypeParam&> m = ContainerEq(my_set);
+  EXPECT_FALSE(m.Matches(test_set));
+  EXPECT_EQ("which has these unexpected elements: 46", Explain(m, test_set));
+}
+
+// Tests that added and missing values are reported together.
+TYPED_TEST(ContainerEqTest, ValueAddedAndRemoved) {
+  static const int vals[] = {1, 1, 2, 3, 5, 8};
+  static const int test_vals[] = {1, 2, 3, 8, 46};
+  TypeParam my_set(vals, vals + 6);
+  TypeParam test_set(test_vals, test_vals + 5);
+  const Matcher<TypeParam> m = ContainerEq(my_set);
+  EXPECT_FALSE(m.Matches(test_set));
+  EXPECT_EQ("which has these unexpected elements: 46,\n"
+            "and doesn't have these expected elements: 5",
+            Explain(m, test_set));
+}
+
+// Tests duplicated value -- expect no explanation.
+TYPED_TEST(ContainerEqTest, DuplicateDifference) {
+  static const int vals[] = {1, 1, 2, 3, 5, 8};
+  static const int test_vals[] = {1, 2, 3, 5, 8};
+  TypeParam my_set(vals, vals + 6);
+  TypeParam test_set(test_vals, test_vals + 5);
+  const Matcher<const TypeParam&> m = ContainerEq(my_set);
+  // Depending on the container, match may be true or false
+  // But in any case there should be no explanation.
+  EXPECT_EQ("", Explain(m, test_set));
+}
+#endif  // GTEST_HAS_TYPED_TEST
+
+// Tests that multiple missing values are reported.
+// Using just vector here, so order is predictable.
+TEST(ContainerEqExtraTest, MultipleValuesMissing) {
+  static const int vals[] = {1, 1, 2, 3, 5, 8};
+  static const int test_vals[] = {2, 1, 5};
+  vector<int> my_set(vals, vals + 6);
+  vector<int> test_set(test_vals, test_vals + 3);
+  const Matcher<vector<int> > m = ContainerEq(my_set);
+  EXPECT_FALSE(m.Matches(test_set));
+  EXPECT_EQ("which doesn't have these expected elements: 3, 8",
+            Explain(m, test_set));
+}
+
+// Tests that added values are reported.
+// Using just vector here, so order is predictable.
+TEST(ContainerEqExtraTest, MultipleValuesAdded) {
+  static const int vals[] = {1, 1, 2, 3, 5, 8};
+  static const int test_vals[] = {1, 2, 92, 3, 5, 8, 46};
+  list<size_t> my_set(vals, vals + 6);
+  list<size_t> test_set(test_vals, test_vals + 7);
+  const Matcher<const list<size_t>&> m = ContainerEq(my_set);
+  EXPECT_FALSE(m.Matches(test_set));
+  EXPECT_EQ("which has these unexpected elements: 92, 46",
+            Explain(m, test_set));
+}
+
+// Tests that added and missing values are reported together.
+TEST(ContainerEqExtraTest, MultipleValuesAddedAndRemoved) {
+  static const int vals[] = {1, 1, 2, 3, 5, 8};
+  static const int test_vals[] = {1, 2, 3, 92, 46};
+  list<size_t> my_set(vals, vals + 6);
+  list<size_t> test_set(test_vals, test_vals + 5);
+  const Matcher<const list<size_t> > m = ContainerEq(my_set);
+  EXPECT_FALSE(m.Matches(test_set));
+  EXPECT_EQ("which has these unexpected elements: 92, 46,\n"
+            "and doesn't have these expected elements: 5, 8",
+            Explain(m, test_set));
+}
+
+// Tests to see that duplicate elements are detected,
+// but (as above) not reported in the explanation.
+TEST(ContainerEqExtraTest, MultiSetOfIntDuplicateDifference) {
+  static const int vals[] = {1, 1, 2, 3, 5, 8};
+  static const int test_vals[] = {1, 2, 3, 5, 8};
+  vector<int> my_set(vals, vals + 6);
+  vector<int> test_set(test_vals, test_vals + 5);
+  const Matcher<vector<int> > m = ContainerEq(my_set);
+  EXPECT_TRUE(m.Matches(my_set));
+  EXPECT_FALSE(m.Matches(test_set));
+  // There is nothing to report when both sets contain all the same values.
+  EXPECT_EQ("", Explain(m, test_set));
+}
+
+// Tests that ContainerEq works for non-trivial associative containers,
+// like maps.
+TEST(ContainerEqExtraTest, WorksForMaps) {
+  map<int, std::string> my_map;
+  my_map[0] = "a";
+  my_map[1] = "b";
+
+  map<int, std::string> test_map;
+  test_map[0] = "aa";
+  test_map[1] = "b";
+
+  const Matcher<const map<int, std::string>&> m = ContainerEq(my_map);
+  EXPECT_TRUE(m.Matches(my_map));
+  EXPECT_FALSE(m.Matches(test_map));
+
+  EXPECT_EQ("which has these unexpected elements: (0, \"aa\"),\n"
+            "and doesn't have these expected elements: (0, \"a\")",
+            Explain(m, test_map));
+}
+
+TEST(ContainerEqExtraTest, WorksForNativeArray) {
+  int a1[] = {1, 2, 3};
+  int a2[] = {1, 2, 3};
+  int b[] = {1, 2, 4};
+
+  EXPECT_THAT(a1, ContainerEq(a2));
+  EXPECT_THAT(a1, Not(ContainerEq(b)));
+}
+
+TEST(ContainerEqExtraTest, WorksForTwoDimensionalNativeArray) {
+  const char a1[][3] = {"hi", "lo"};
+  const char a2[][3] = {"hi", "lo"};
+  const char b[][3] = {"lo", "hi"};
+
+  // Tests using ContainerEq() in the first dimension.
+  EXPECT_THAT(a1, ContainerEq(a2));
+  EXPECT_THAT(a1, Not(ContainerEq(b)));
+
+  // Tests using ContainerEq() in the second dimension.
+  EXPECT_THAT(a1, ElementsAre(ContainerEq(a2[0]), ContainerEq(a2[1])));
+  EXPECT_THAT(a1, ElementsAre(Not(ContainerEq(b[0])), ContainerEq(a2[1])));
+}
+
+TEST(ContainerEqExtraTest, WorksForNativeArrayAsTuple) {
+  const int a1[] = {1, 2, 3};
+  const int a2[] = {1, 2, 3};
+  const int b[] = {1, 2, 3, 4};
+
+  const int* const p1 = a1;
+  EXPECT_THAT(std::make_tuple(p1, 3), ContainerEq(a2));
+  EXPECT_THAT(std::make_tuple(p1, 3), Not(ContainerEq(b)));
+
+  const int c[] = {1, 3, 2};
+  EXPECT_THAT(std::make_tuple(p1, 3), Not(ContainerEq(c)));
+}
+
+TEST(ContainerEqExtraTest, CopiesNativeArrayParameter) {
+  std::string a1[][3] = {
+    {"hi", "hello", "ciao"},
+    {"bye", "see you", "ciao"}
+  };
+
+  std::string a2[][3] = {
+    {"hi", "hello", "ciao"},
+    {"bye", "see you", "ciao"}
+  };
+
+  const Matcher<const std::string(&)[2][3]> m = ContainerEq(a2);
+  EXPECT_THAT(a1, m);
+
+  a2[0][0] = "ha";
+  EXPECT_THAT(a1, m);
+}
+
+TEST(WhenSortedByTest, WorksForEmptyContainer) {
+  const vector<int> numbers;
+  EXPECT_THAT(numbers, WhenSortedBy(less<int>(), ElementsAre()));
+  EXPECT_THAT(numbers, Not(WhenSortedBy(less<int>(), ElementsAre(1))));
+}
+
+TEST(WhenSortedByTest, WorksForNonEmptyContainer) {
+  vector<unsigned> numbers;
+  numbers.push_back(3);
+  numbers.push_back(1);
+  numbers.push_back(2);
+  numbers.push_back(2);
+  EXPECT_THAT(numbers, WhenSortedBy(greater<unsigned>(),
+                                    ElementsAre(3, 2, 2, 1)));
+  EXPECT_THAT(numbers, Not(WhenSortedBy(greater<unsigned>(),
+                                        ElementsAre(1, 2, 2, 3))));
+}
+
+TEST(WhenSortedByTest, WorksForNonVectorContainer) {
+  list<std::string> words;
+  words.push_back("say");
+  words.push_back("hello");
+  words.push_back("world");
+  EXPECT_THAT(words, WhenSortedBy(less<std::string>(),
+                                  ElementsAre("hello", "say", "world")));
+  EXPECT_THAT(words, Not(WhenSortedBy(less<std::string>(),
+                                      ElementsAre("say", "hello", "world"))));
+}
+
+TEST(WhenSortedByTest, WorksForNativeArray) {
+  const int numbers[] = {1, 3, 2, 4};
+  const int sorted_numbers[] = {1, 2, 3, 4};
+  EXPECT_THAT(numbers, WhenSortedBy(less<int>(), ElementsAre(1, 2, 3, 4)));
+  EXPECT_THAT(numbers, WhenSortedBy(less<int>(),
+                                    ElementsAreArray(sorted_numbers)));
+  EXPECT_THAT(numbers, Not(WhenSortedBy(less<int>(), ElementsAre(1, 3, 2, 4))));
+}
+
+TEST(WhenSortedByTest, CanDescribeSelf) {
+  const Matcher<vector<int> > m = WhenSortedBy(less<int>(), ElementsAre(1, 2));
+  EXPECT_EQ("(when sorted) has 2 elements where\n"
+            "element #0 is equal to 1,\n"
+            "element #1 is equal to 2",
+            Describe(m));
+  EXPECT_EQ("(when sorted) doesn't have 2 elements, or\n"
+            "element #0 isn't equal to 1, or\n"
+            "element #1 isn't equal to 2",
+            DescribeNegation(m));
+}
+
+TEST(WhenSortedByTest, ExplainsMatchResult) {
+  const int a[] = {2, 1};
+  EXPECT_EQ("which is { 1, 2 } when sorted, whose element #0 doesn't match",
+            Explain(WhenSortedBy(less<int>(), ElementsAre(2, 3)), a));
+  EXPECT_EQ("which is { 1, 2 } when sorted",
+            Explain(WhenSortedBy(less<int>(), ElementsAre(1, 2)), a));
+}
+
+// WhenSorted() is a simple wrapper on WhenSortedBy().  Hence we don't
+// need to test it as exhaustively as we test the latter.
+
+TEST(WhenSortedTest, WorksForEmptyContainer) {
+  const vector<int> numbers;
+  EXPECT_THAT(numbers, WhenSorted(ElementsAre()));
+  EXPECT_THAT(numbers, Not(WhenSorted(ElementsAre(1))));
+}
+
+TEST(WhenSortedTest, WorksForNonEmptyContainer) {
+  list<std::string> words;
+  words.push_back("3");
+  words.push_back("1");
+  words.push_back("2");
+  words.push_back("2");
+  EXPECT_THAT(words, WhenSorted(ElementsAre("1", "2", "2", "3")));
+  EXPECT_THAT(words, Not(WhenSorted(ElementsAre("3", "1", "2", "2"))));
+}
+
+TEST(WhenSortedTest, WorksForMapTypes) {
+  map<std::string, int> word_counts;
+  word_counts["and"] = 1;
+  word_counts["the"] = 1;
+  word_counts["buffalo"] = 2;
+  EXPECT_THAT(word_counts,
+              WhenSorted(ElementsAre(Pair("and", 1), Pair("buffalo", 2),
+                                     Pair("the", 1))));
+  EXPECT_THAT(word_counts,
+              Not(WhenSorted(ElementsAre(Pair("and", 1), Pair("the", 1),
+                                         Pair("buffalo", 2)))));
+}
+
+TEST(WhenSortedTest, WorksForMultiMapTypes) {
+    multimap<int, int> ifib;
+    ifib.insert(make_pair(8, 6));
+    ifib.insert(make_pair(2, 3));
+    ifib.insert(make_pair(1, 1));
+    ifib.insert(make_pair(3, 4));
+    ifib.insert(make_pair(1, 2));
+    ifib.insert(make_pair(5, 5));
+    EXPECT_THAT(ifib, WhenSorted(ElementsAre(Pair(1, 1),
+                                             Pair(1, 2),
+                                             Pair(2, 3),
+                                             Pair(3, 4),
+                                             Pair(5, 5),
+                                             Pair(8, 6))));
+    EXPECT_THAT(ifib, Not(WhenSorted(ElementsAre(Pair(8, 6),
+                                                 Pair(2, 3),
+                                                 Pair(1, 1),
+                                                 Pair(3, 4),
+                                                 Pair(1, 2),
+                                                 Pair(5, 5)))));
+}
+
+TEST(WhenSortedTest, WorksForPolymorphicMatcher) {
+    std::deque<int> d;
+    d.push_back(2);
+    d.push_back(1);
+    EXPECT_THAT(d, WhenSorted(ElementsAre(1, 2)));
+    EXPECT_THAT(d, Not(WhenSorted(ElementsAre(2, 1))));
+}
+
+TEST(WhenSortedTest, WorksForVectorConstRefMatcher) {
+    std::deque<int> d;
+    d.push_back(2);
+    d.push_back(1);
+    Matcher<const std::vector<int>&> vector_match = ElementsAre(1, 2);
+    EXPECT_THAT(d, WhenSorted(vector_match));
+    Matcher<const std::vector<int>&> not_vector_match = ElementsAre(2, 1);
+    EXPECT_THAT(d, Not(WhenSorted(not_vector_match)));
+}
+
+// Deliberately bare pseudo-container.
+// Offers only begin() and end() accessors, yielding InputIterator.
+template <typename T>
+class Streamlike {
+ private:
+  class ConstIter;
+ public:
+  typedef ConstIter const_iterator;
+  typedef T value_type;
+
+  template <typename InIter>
+  Streamlike(InIter first, InIter last) : remainder_(first, last) {}
+
+  const_iterator begin() const {
+    return const_iterator(this, remainder_.begin());
+  }
+  const_iterator end() const {
+    return const_iterator(this, remainder_.end());
+  }
+
+ private:
+  class ConstIter : public std::iterator<std::input_iterator_tag,
+                                         value_type,
+                                         ptrdiff_t,
+                                         const value_type*,
+                                         const value_type&> {
+   public:
+    ConstIter(const Streamlike* s,
+              typename std::list<value_type>::iterator pos)
+        : s_(s), pos_(pos) {}
+
+    const value_type& operator*() const { return *pos_; }
+    const value_type* operator->() const { return &*pos_; }
+    ConstIter& operator++() {
+      s_->remainder_.erase(pos_++);
+      return *this;
+    }
+
+    // *iter++ is required to work (see std::istreambuf_iterator).
+    // (void)iter++ is also required to work.
+    class PostIncrProxy {
+     public:
+      explicit PostIncrProxy(const value_type& value) : value_(value) {}
+      value_type operator*() const { return value_; }
+     private:
+      value_type value_;
+    };
+    PostIncrProxy operator++(int) {
+      PostIncrProxy proxy(**this);
+      ++(*this);
+      return proxy;
+    }
+
+    friend bool operator==(const ConstIter& a, const ConstIter& b) {
+      return a.s_ == b.s_ && a.pos_ == b.pos_;
+    }
+    friend bool operator!=(const ConstIter& a, const ConstIter& b) {
+      return !(a == b);
+    }
+
+   private:
+    const Streamlike* s_;
+    typename std::list<value_type>::iterator pos_;
+  };
+
+  friend std::ostream& operator<<(std::ostream& os, const Streamlike& s) {
+    os << "[";
+    typedef typename std::list<value_type>::const_iterator Iter;
+    const char* sep = "";
+    for (Iter it = s.remainder_.begin(); it != s.remainder_.end(); ++it) {
+      os << sep << *it;
+      sep = ",";
+    }
+    os << "]";
+    return os;
+  }
+
+  mutable std::list<value_type> remainder_;  // modified by iteration
+};
+
+TEST(StreamlikeTest, Iteration) {
+  const int a[5] = {2, 1, 4, 5, 3};
+  Streamlike<int> s(a, a + 5);
+  Streamlike<int>::const_iterator it = s.begin();
+  const int* ip = a;
+  while (it != s.end()) {
+    SCOPED_TRACE(ip - a);
+    EXPECT_EQ(*ip++, *it++);
+  }
+}
+
+TEST(BeginEndDistanceIsTest, WorksWithForwardList) {
+  std::forward_list<int> container;
+  EXPECT_THAT(container, BeginEndDistanceIs(0));
+  EXPECT_THAT(container, Not(BeginEndDistanceIs(1)));
+  container.push_front(0);
+  EXPECT_THAT(container, Not(BeginEndDistanceIs(0)));
+  EXPECT_THAT(container, BeginEndDistanceIs(1));
+  container.push_front(0);
+  EXPECT_THAT(container, Not(BeginEndDistanceIs(0)));
+  EXPECT_THAT(container, BeginEndDistanceIs(2));
+}
+
+TEST(BeginEndDistanceIsTest, WorksWithNonStdList) {
+  const int a[5] = {1, 2, 3, 4, 5};
+  Streamlike<int> s(a, a + 5);
+  EXPECT_THAT(s, BeginEndDistanceIs(5));
+}
+
+TEST(BeginEndDistanceIsTest, CanDescribeSelf) {
+  Matcher<vector<int> > m = BeginEndDistanceIs(2);
+  EXPECT_EQ("distance between begin() and end() is equal to 2", Describe(m));
+  EXPECT_EQ("distance between begin() and end() isn't equal to 2",
+            DescribeNegation(m));
+}
+
+TEST(BeginEndDistanceIsTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper, Call(BeginEndDistanceIs(2)));
+  helper.Call(MakeUniquePtrs({1, 2}));
+}
+
+TEST(BeginEndDistanceIsTest, ExplainsResult) {
+  Matcher<vector<int> > m1 = BeginEndDistanceIs(2);
+  Matcher<vector<int> > m2 = BeginEndDistanceIs(Lt(2));
+  Matcher<vector<int> > m3 = BeginEndDistanceIs(AnyOf(0, 3));
+  Matcher<vector<int> > m4 = BeginEndDistanceIs(GreaterThan(1));
+  vector<int> container;
+  EXPECT_EQ("whose distance between begin() and end() 0 doesn't match",
+            Explain(m1, container));
+  EXPECT_EQ("whose distance between begin() and end() 0 matches",
+            Explain(m2, container));
+  EXPECT_EQ("whose distance between begin() and end() 0 matches",
+            Explain(m3, container));
+  EXPECT_EQ(
+      "whose distance between begin() and end() 0 doesn't match, which is 1 "
+      "less than 1",
+      Explain(m4, container));
+  container.push_back(0);
+  container.push_back(0);
+  EXPECT_EQ("whose distance between begin() and end() 2 matches",
+            Explain(m1, container));
+  EXPECT_EQ("whose distance between begin() and end() 2 doesn't match",
+            Explain(m2, container));
+  EXPECT_EQ("whose distance between begin() and end() 2 doesn't match",
+            Explain(m3, container));
+  EXPECT_EQ(
+      "whose distance between begin() and end() 2 matches, which is 1 more "
+      "than 1",
+      Explain(m4, container));
+}
+
+TEST(WhenSortedTest, WorksForStreamlike) {
+  // Streamlike 'container' provides only minimal iterator support.
+  // Its iterators are tagged with input_iterator_tag.
+  const int a[5] = {2, 1, 4, 5, 3};
+  Streamlike<int> s(std::begin(a), std::end(a));
+  EXPECT_THAT(s, WhenSorted(ElementsAre(1, 2, 3, 4, 5)));
+  EXPECT_THAT(s, Not(WhenSorted(ElementsAre(2, 1, 4, 5, 3))));
+}
+
+TEST(WhenSortedTest, WorksForVectorConstRefMatcherOnStreamlike) {
+  const int a[] = {2, 1, 4, 5, 3};
+  Streamlike<int> s(std::begin(a), std::end(a));
+  Matcher<const std::vector<int>&> vector_match = ElementsAre(1, 2, 3, 4, 5);
+  EXPECT_THAT(s, WhenSorted(vector_match));
+  EXPECT_THAT(s, Not(WhenSorted(ElementsAre(2, 1, 4, 5, 3))));
+}
+
+TEST(IsSupersetOfTest, WorksForNativeArray) {
+  const int subset[] = {1, 4};
+  const int superset[] = {1, 2, 4};
+  const int disjoint[] = {1, 0, 3};
+  EXPECT_THAT(subset, IsSupersetOf(subset));
+  EXPECT_THAT(subset, Not(IsSupersetOf(superset)));
+  EXPECT_THAT(superset, IsSupersetOf(subset));
+  EXPECT_THAT(subset, Not(IsSupersetOf(disjoint)));
+  EXPECT_THAT(disjoint, Not(IsSupersetOf(subset)));
+}
+
+TEST(IsSupersetOfTest, WorksWithDuplicates) {
+  const int not_enough[] = {1, 2};
+  const int enough[] = {1, 1, 2};
+  const int expected[] = {1, 1};
+  EXPECT_THAT(not_enough, Not(IsSupersetOf(expected)));
+  EXPECT_THAT(enough, IsSupersetOf(expected));
+}
+
+TEST(IsSupersetOfTest, WorksForEmpty) {
+  vector<int> numbers;
+  vector<int> expected;
+  EXPECT_THAT(numbers, IsSupersetOf(expected));
+  expected.push_back(1);
+  EXPECT_THAT(numbers, Not(IsSupersetOf(expected)));
+  expected.clear();
+  numbers.push_back(1);
+  numbers.push_back(2);
+  EXPECT_THAT(numbers, IsSupersetOf(expected));
+  expected.push_back(1);
+  EXPECT_THAT(numbers, IsSupersetOf(expected));
+  expected.push_back(2);
+  EXPECT_THAT(numbers, IsSupersetOf(expected));
+  expected.push_back(3);
+  EXPECT_THAT(numbers, Not(IsSupersetOf(expected)));
+}
+
+TEST(IsSupersetOfTest, WorksForStreamlike) {
+  const int a[5] = {1, 2, 3, 4, 5};
+  Streamlike<int> s(std::begin(a), std::end(a));
+
+  vector<int> expected;
+  expected.push_back(1);
+  expected.push_back(2);
+  expected.push_back(5);
+  EXPECT_THAT(s, IsSupersetOf(expected));
+
+  expected.push_back(0);
+  EXPECT_THAT(s, Not(IsSupersetOf(expected)));
+}
+
+TEST(IsSupersetOfTest, TakesStlContainer) {
+  const int actual[] = {3, 1, 2};
+
+  ::std::list<int> expected;
+  expected.push_back(1);
+  expected.push_back(3);
+  EXPECT_THAT(actual, IsSupersetOf(expected));
+
+  expected.push_back(4);
+  EXPECT_THAT(actual, Not(IsSupersetOf(expected)));
+}
+
+TEST(IsSupersetOfTest, Describe) {
+  typedef std::vector<int> IntVec;
+  IntVec expected;
+  expected.push_back(111);
+  expected.push_back(222);
+  expected.push_back(333);
+  EXPECT_THAT(
+      Describe<IntVec>(IsSupersetOf(expected)),
+      Eq("a surjection from elements to requirements exists such that:\n"
+         " - an element is equal to 111\n"
+         " - an element is equal to 222\n"
+         " - an element is equal to 333"));
+}
+
+TEST(IsSupersetOfTest, DescribeNegation) {
+  typedef std::vector<int> IntVec;
+  IntVec expected;
+  expected.push_back(111);
+  expected.push_back(222);
+  expected.push_back(333);
+  EXPECT_THAT(
+      DescribeNegation<IntVec>(IsSupersetOf(expected)),
+      Eq("no surjection from elements to requirements exists such that:\n"
+         " - an element is equal to 111\n"
+         " - an element is equal to 222\n"
+         " - an element is equal to 333"));
+}
+
+TEST(IsSupersetOfTest, MatchAndExplain) {
+  std::vector<int> v;
+  v.push_back(2);
+  v.push_back(3);
+  std::vector<int> expected;
+  expected.push_back(1);
+  expected.push_back(2);
+  StringMatchResultListener listener;
+  ASSERT_FALSE(ExplainMatchResult(IsSupersetOf(expected), v, &listener))
+      << listener.str();
+  EXPECT_THAT(listener.str(),
+              Eq("where the following matchers don't match any elements:\n"
+                 "matcher #0: is equal to 1"));
+
+  v.push_back(1);
+  listener.Clear();
+  ASSERT_TRUE(ExplainMatchResult(IsSupersetOf(expected), v, &listener))
+      << listener.str();
+  EXPECT_THAT(listener.str(), Eq("where:\n"
+                                 " - element #0 is matched by matcher #1,\n"
+                                 " - element #2 is matched by matcher #0"));
+}
+
+TEST(IsSupersetOfTest, WorksForRhsInitializerList) {
+  const int numbers[] = {1, 3, 6, 2, 4, 5};
+  EXPECT_THAT(numbers, IsSupersetOf({1, 2}));
+  EXPECT_THAT(numbers, Not(IsSupersetOf({3, 0})));
+}
+
+TEST(IsSupersetOfTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper, Call(IsSupersetOf({Pointee(1)})));
+  helper.Call(MakeUniquePtrs({1, 2}));
+  EXPECT_CALL(helper, Call(Not(IsSupersetOf({Pointee(1), Pointee(2)}))));
+  helper.Call(MakeUniquePtrs({2}));
+}
+
+TEST(IsSubsetOfTest, WorksForNativeArray) {
+  const int subset[] = {1, 4};
+  const int superset[] = {1, 2, 4};
+  const int disjoint[] = {1, 0, 3};
+  EXPECT_THAT(subset, IsSubsetOf(subset));
+  EXPECT_THAT(subset, IsSubsetOf(superset));
+  EXPECT_THAT(superset, Not(IsSubsetOf(subset)));
+  EXPECT_THAT(subset, Not(IsSubsetOf(disjoint)));
+  EXPECT_THAT(disjoint, Not(IsSubsetOf(subset)));
+}
+
+TEST(IsSubsetOfTest, WorksWithDuplicates) {
+  const int not_enough[] = {1, 2};
+  const int enough[] = {1, 1, 2};
+  const int actual[] = {1, 1};
+  EXPECT_THAT(actual, Not(IsSubsetOf(not_enough)));
+  EXPECT_THAT(actual, IsSubsetOf(enough));
+}
+
+TEST(IsSubsetOfTest, WorksForEmpty) {
+  vector<int> numbers;
+  vector<int> expected;
+  EXPECT_THAT(numbers, IsSubsetOf(expected));
+  expected.push_back(1);
+  EXPECT_THAT(numbers, IsSubsetOf(expected));
+  expected.clear();
+  numbers.push_back(1);
+  numbers.push_back(2);
+  EXPECT_THAT(numbers, Not(IsSubsetOf(expected)));
+  expected.push_back(1);
+  EXPECT_THAT(numbers, Not(IsSubsetOf(expected)));
+  expected.push_back(2);
+  EXPECT_THAT(numbers, IsSubsetOf(expected));
+  expected.push_back(3);
+  EXPECT_THAT(numbers, IsSubsetOf(expected));
+}
+
+TEST(IsSubsetOfTest, WorksForStreamlike) {
+  const int a[5] = {1, 2};
+  Streamlike<int> s(std::begin(a), std::end(a));
+
+  vector<int> expected;
+  expected.push_back(1);
+  EXPECT_THAT(s, Not(IsSubsetOf(expected)));
+  expected.push_back(2);
+  expected.push_back(5);
+  EXPECT_THAT(s, IsSubsetOf(expected));
+}
+
+TEST(IsSubsetOfTest, TakesStlContainer) {
+  const int actual[] = {3, 1, 2};
+
+  ::std::list<int> expected;
+  expected.push_back(1);
+  expected.push_back(3);
+  EXPECT_THAT(actual, Not(IsSubsetOf(expected)));
+
+  expected.push_back(2);
+  expected.push_back(4);
+  EXPECT_THAT(actual, IsSubsetOf(expected));
+}
+
+TEST(IsSubsetOfTest, Describe) {
+  typedef std::vector<int> IntVec;
+  IntVec expected;
+  expected.push_back(111);
+  expected.push_back(222);
+  expected.push_back(333);
+
+  EXPECT_THAT(
+      Describe<IntVec>(IsSubsetOf(expected)),
+      Eq("an injection from elements to requirements exists such that:\n"
+         " - an element is equal to 111\n"
+         " - an element is equal to 222\n"
+         " - an element is equal to 333"));
+}
+
+TEST(IsSubsetOfTest, DescribeNegation) {
+  typedef std::vector<int> IntVec;
+  IntVec expected;
+  expected.push_back(111);
+  expected.push_back(222);
+  expected.push_back(333);
+  EXPECT_THAT(
+      DescribeNegation<IntVec>(IsSubsetOf(expected)),
+      Eq("no injection from elements to requirements exists such that:\n"
+         " - an element is equal to 111\n"
+         " - an element is equal to 222\n"
+         " - an element is equal to 333"));
+}
+
+TEST(IsSubsetOfTest, MatchAndExplain) {
+  std::vector<int> v;
+  v.push_back(2);
+  v.push_back(3);
+  std::vector<int> expected;
+  expected.push_back(1);
+  expected.push_back(2);
+  StringMatchResultListener listener;
+  ASSERT_FALSE(ExplainMatchResult(IsSubsetOf(expected), v, &listener))
+      << listener.str();
+  EXPECT_THAT(listener.str(),
+              Eq("where the following elements don't match any matchers:\n"
+                 "element #1: 3"));
+
+  expected.push_back(3);
+  listener.Clear();
+  ASSERT_TRUE(ExplainMatchResult(IsSubsetOf(expected), v, &listener))
+      << listener.str();
+  EXPECT_THAT(listener.str(), Eq("where:\n"
+                                 " - element #0 is matched by matcher #1,\n"
+                                 " - element #1 is matched by matcher #2"));
+}
+
+TEST(IsSubsetOfTest, WorksForRhsInitializerList) {
+  const int numbers[] = {1, 2, 3};
+  EXPECT_THAT(numbers, IsSubsetOf({1, 2, 3, 4}));
+  EXPECT_THAT(numbers, Not(IsSubsetOf({1, 2})));
+}
+
+TEST(IsSubsetOfTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper, Call(IsSubsetOf({Pointee(1), Pointee(2)})));
+  helper.Call(MakeUniquePtrs({1}));
+  EXPECT_CALL(helper, Call(Not(IsSubsetOf({Pointee(1)}))));
+  helper.Call(MakeUniquePtrs({2}));
+}
+
+// Tests using ElementsAre() and ElementsAreArray() with stream-like
+// "containers".
+
+TEST(ElemensAreStreamTest, WorksForStreamlike) {
+  const int a[5] = {1, 2, 3, 4, 5};
+  Streamlike<int> s(std::begin(a), std::end(a));
+  EXPECT_THAT(s, ElementsAre(1, 2, 3, 4, 5));
+  EXPECT_THAT(s, Not(ElementsAre(2, 1, 4, 5, 3)));
+}
+
+TEST(ElemensAreArrayStreamTest, WorksForStreamlike) {
+  const int a[5] = {1, 2, 3, 4, 5};
+  Streamlike<int> s(std::begin(a), std::end(a));
+
+  vector<int> expected;
+  expected.push_back(1);
+  expected.push_back(2);
+  expected.push_back(3);
+  expected.push_back(4);
+  expected.push_back(5);
+  EXPECT_THAT(s, ElementsAreArray(expected));
+
+  expected[3] = 0;
+  EXPECT_THAT(s, Not(ElementsAreArray(expected)));
+}
+
+TEST(ElementsAreTest, WorksWithUncopyable) {
+  Uncopyable objs[2];
+  objs[0].set_value(-3);
+  objs[1].set_value(1);
+  EXPECT_THAT(objs, ElementsAre(UncopyableIs(-3), Truly(ValueIsPositive)));
+}
+
+TEST(ElementsAreTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper, Call(ElementsAre(Pointee(1), Pointee(2))));
+  helper.Call(MakeUniquePtrs({1, 2}));
+
+  EXPECT_CALL(helper, Call(ElementsAreArray({Pointee(3), Pointee(4)})));
+  helper.Call(MakeUniquePtrs({3, 4}));
+}
+
+TEST(ElementsAreTest, TakesStlContainer) {
+  const int actual[] = {3, 1, 2};
+
+  ::std::list<int> expected;
+  expected.push_back(3);
+  expected.push_back(1);
+  expected.push_back(2);
+  EXPECT_THAT(actual, ElementsAreArray(expected));
+
+  expected.push_back(4);
+  EXPECT_THAT(actual, Not(ElementsAreArray(expected)));
+}
+
+// Tests for UnorderedElementsAreArray()
+
+TEST(UnorderedElementsAreArrayTest, SucceedsWhenExpected) {
+  const int a[] = {0, 1, 2, 3, 4};
+  std::vector<int> s(std::begin(a), std::end(a));
+  do {
+    StringMatchResultListener listener;
+    EXPECT_TRUE(ExplainMatchResult(UnorderedElementsAreArray(a),
+                                   s, &listener)) << listener.str();
+  } while (std::next_permutation(s.begin(), s.end()));
+}
+
+TEST(UnorderedElementsAreArrayTest, VectorBool) {
+  const bool a[] = {0, 1, 0, 1, 1};
+  const bool b[] = {1, 0, 1, 1, 0};
+  std::vector<bool> expected(std::begin(a), std::end(a));
+  std::vector<bool> actual(std::begin(b), std::end(b));
+  StringMatchResultListener listener;
+  EXPECT_TRUE(ExplainMatchResult(UnorderedElementsAreArray(expected),
+                                 actual, &listener)) << listener.str();
+}
+
+TEST(UnorderedElementsAreArrayTest, WorksForStreamlike) {
+  // Streamlike 'container' provides only minimal iterator support.
+  // Its iterators are tagged with input_iterator_tag, and it has no
+  // size() or empty() methods.
+  const int a[5] = {2, 1, 4, 5, 3};
+  Streamlike<int> s(std::begin(a), std::end(a));
+
+  ::std::vector<int> expected;
+  expected.push_back(1);
+  expected.push_back(2);
+  expected.push_back(3);
+  expected.push_back(4);
+  expected.push_back(5);
+  EXPECT_THAT(s, UnorderedElementsAreArray(expected));
+
+  expected.push_back(6);
+  EXPECT_THAT(s, Not(UnorderedElementsAreArray(expected)));
+}
+
+TEST(UnorderedElementsAreArrayTest, TakesStlContainer) {
+  const int actual[] = {3, 1, 2};
+
+  ::std::list<int> expected;
+  expected.push_back(1);
+  expected.push_back(2);
+  expected.push_back(3);
+  EXPECT_THAT(actual, UnorderedElementsAreArray(expected));
+
+  expected.push_back(4);
+  EXPECT_THAT(actual, Not(UnorderedElementsAreArray(expected)));
+}
+
+
+TEST(UnorderedElementsAreArrayTest, TakesInitializerList) {
+  const int a[5] = {2, 1, 4, 5, 3};
+  EXPECT_THAT(a, UnorderedElementsAreArray({1, 2, 3, 4, 5}));
+  EXPECT_THAT(a, Not(UnorderedElementsAreArray({1, 2, 3, 4, 6})));
+}
+
+TEST(UnorderedElementsAreArrayTest, TakesInitializerListOfCStrings) {
+  const std::string a[5] = {"a", "b", "c", "d", "e"};
+  EXPECT_THAT(a, UnorderedElementsAreArray({"a", "b", "c", "d", "e"}));
+  EXPECT_THAT(a, Not(UnorderedElementsAreArray({"a", "b", "c", "d", "ef"})));
+}
+
+TEST(UnorderedElementsAreArrayTest, TakesInitializerListOfSameTypedMatchers) {
+  const int a[5] = {2, 1, 4, 5, 3};
+  EXPECT_THAT(a, UnorderedElementsAreArray(
+      {Eq(1), Eq(2), Eq(3), Eq(4), Eq(5)}));
+  EXPECT_THAT(a, Not(UnorderedElementsAreArray(
+      {Eq(1), Eq(2), Eq(3), Eq(4), Eq(6)})));
+}
+
+TEST(UnorderedElementsAreArrayTest,
+     TakesInitializerListOfDifferentTypedMatchers) {
+  const int a[5] = {2, 1, 4, 5, 3};
+  // The compiler cannot infer the type of the initializer list if its
+  // elements have different types.  We must explicitly specify the
+  // unified element type in this case.
+  EXPECT_THAT(a, UnorderedElementsAreArray<Matcher<int> >(
+      {Eq(1), Ne(-2), Ge(3), Le(4), Eq(5)}));
+  EXPECT_THAT(a, Not(UnorderedElementsAreArray<Matcher<int> >(
+      {Eq(1), Ne(-2), Ge(3), Le(4), Eq(6)})));
+}
+
+
+TEST(UnorderedElementsAreArrayTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper,
+              Call(UnorderedElementsAreArray({Pointee(1), Pointee(2)})));
+  helper.Call(MakeUniquePtrs({2, 1}));
+}
+
+class UnorderedElementsAreTest : public testing::Test {
+ protected:
+  typedef std::vector<int> IntVec;
+};
+
+TEST_F(UnorderedElementsAreTest, WorksWithUncopyable) {
+  Uncopyable objs[2];
+  objs[0].set_value(-3);
+  objs[1].set_value(1);
+  EXPECT_THAT(objs,
+              UnorderedElementsAre(Truly(ValueIsPositive), UncopyableIs(-3)));
+}
+
+TEST_F(UnorderedElementsAreTest, SucceedsWhenExpected) {
+  const int a[] = {1, 2, 3};
+  std::vector<int> s(std::begin(a), std::end(a));
+  do {
+    StringMatchResultListener listener;
+    EXPECT_TRUE(ExplainMatchResult(UnorderedElementsAre(1, 2, 3),
+                                   s, &listener)) << listener.str();
+  } while (std::next_permutation(s.begin(), s.end()));
+}
+
+TEST_F(UnorderedElementsAreTest, FailsWhenAnElementMatchesNoMatcher) {
+  const int a[] = {1, 2, 3};
+  std::vector<int> s(std::begin(a), std::end(a));
+  std::vector<Matcher<int> > mv;
+  mv.push_back(1);
+  mv.push_back(2);
+  mv.push_back(2);
+  // The element with value '3' matches nothing: fail fast.
+  StringMatchResultListener listener;
+  EXPECT_FALSE(ExplainMatchResult(UnorderedElementsAreArray(mv),
+                                  s, &listener)) << listener.str();
+}
+
+TEST_F(UnorderedElementsAreTest, WorksForStreamlike) {
+  // Streamlike 'container' provides only minimal iterator support.
+  // Its iterators are tagged with input_iterator_tag, and it has no
+  // size() or empty() methods.
+  const int a[5] = {2, 1, 4, 5, 3};
+  Streamlike<int> s(std::begin(a), std::end(a));
+
+  EXPECT_THAT(s, UnorderedElementsAre(1, 2, 3, 4, 5));
+  EXPECT_THAT(s, Not(UnorderedElementsAre(2, 2, 3, 4, 5)));
+}
+
+TEST_F(UnorderedElementsAreTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper, Call(UnorderedElementsAre(Pointee(1), Pointee(2))));
+  helper.Call(MakeUniquePtrs({2, 1}));
+}
+
+// One naive implementation of the matcher runs in O(N!) time, which is too
+// slow for many real-world inputs. This test shows that our matcher can match
+// 100 inputs very quickly (a few milliseconds).  An O(100!) is 10^158
+// iterations and obviously effectively incomputable.
+// [ RUN      ] UnorderedElementsAreTest.Performance
+// [       OK ] UnorderedElementsAreTest.Performance (4 ms)
+TEST_F(UnorderedElementsAreTest, Performance) {
+  std::vector<int> s;
+  std::vector<Matcher<int> > mv;
+  for (int i = 0; i < 100; ++i) {
+    s.push_back(i);
+    mv.push_back(_);
+  }
+  mv[50] = Eq(0);
+  StringMatchResultListener listener;
+  EXPECT_TRUE(ExplainMatchResult(UnorderedElementsAreArray(mv),
+                                 s, &listener)) << listener.str();
+}
+
+// Another variant of 'Performance' with similar expectations.
+// [ RUN      ] UnorderedElementsAreTest.PerformanceHalfStrict
+// [       OK ] UnorderedElementsAreTest.PerformanceHalfStrict (4 ms)
+TEST_F(UnorderedElementsAreTest, PerformanceHalfStrict) {
+  std::vector<int> s;
+  std::vector<Matcher<int> > mv;
+  for (int i = 0; i < 100; ++i) {
+    s.push_back(i);
+    if (i & 1) {
+      mv.push_back(_);
+    } else {
+      mv.push_back(i);
+    }
+  }
+  StringMatchResultListener listener;
+  EXPECT_TRUE(ExplainMatchResult(UnorderedElementsAreArray(mv),
+                                 s, &listener)) << listener.str();
+}
+
+TEST_F(UnorderedElementsAreTest, FailMessageCountWrong) {
+  std::vector<int> v;
+  v.push_back(4);
+  StringMatchResultListener listener;
+  EXPECT_FALSE(ExplainMatchResult(UnorderedElementsAre(1, 2, 3),
+                                  v, &listener)) << listener.str();
+  EXPECT_THAT(listener.str(), Eq("which has 1 element"));
+}
+
+TEST_F(UnorderedElementsAreTest, FailMessageCountWrongZero) {
+  std::vector<int> v;
+  StringMatchResultListener listener;
+  EXPECT_FALSE(ExplainMatchResult(UnorderedElementsAre(1, 2, 3),
+                                  v, &listener)) << listener.str();
+  EXPECT_THAT(listener.str(), Eq(""));
+}
+
+TEST_F(UnorderedElementsAreTest, FailMessageUnmatchedMatchers) {
+  std::vector<int> v;
+  v.push_back(1);
+  v.push_back(1);
+  StringMatchResultListener listener;
+  EXPECT_FALSE(ExplainMatchResult(UnorderedElementsAre(1, 2),
+                                  v, &listener)) << listener.str();
+  EXPECT_THAT(
+      listener.str(),
+      Eq("where the following matchers don't match any elements:\n"
+         "matcher #1: is equal to 2"));
+}
+
+TEST_F(UnorderedElementsAreTest, FailMessageUnmatchedElements) {
+  std::vector<int> v;
+  v.push_back(1);
+  v.push_back(2);
+  StringMatchResultListener listener;
+  EXPECT_FALSE(ExplainMatchResult(UnorderedElementsAre(1, 1),
+                                  v, &listener)) << listener.str();
+  EXPECT_THAT(
+      listener.str(),
+      Eq("where the following elements don't match any matchers:\n"
+         "element #1: 2"));
+}
+
+TEST_F(UnorderedElementsAreTest, FailMessageUnmatchedMatcherAndElement) {
+  std::vector<int> v;
+  v.push_back(2);
+  v.push_back(3);
+  StringMatchResultListener listener;
+  EXPECT_FALSE(ExplainMatchResult(UnorderedElementsAre(1, 2),
+                                  v, &listener)) << listener.str();
+  EXPECT_THAT(
+      listener.str(),
+      Eq("where"
+         " the following matchers don't match any elements:\n"
+         "matcher #0: is equal to 1\n"
+         "and"
+         " where"
+         " the following elements don't match any matchers:\n"
+         "element #1: 3"));
+}
+
+// Test helper for formatting element, matcher index pairs in expectations.
+static std::string EMString(int element, int matcher) {
+  stringstream ss;
+  ss << "(element #" << element << ", matcher #" << matcher << ")";
+  return ss.str();
+}
+
+TEST_F(UnorderedElementsAreTest, FailMessageImperfectMatchOnly) {
+  // A situation where all elements and matchers have a match
+  // associated with them, but the max matching is not perfect.
+  std::vector<std::string> v;
+  v.push_back("a");
+  v.push_back("b");
+  v.push_back("c");
+  StringMatchResultListener listener;
+  EXPECT_FALSE(ExplainMatchResult(
+      UnorderedElementsAre("a", "a", AnyOf("b", "c")), v, &listener))
+      << listener.str();
+
+  std::string prefix =
+      "where no permutation of the elements can satisfy all matchers, "
+      "and the closest match is 2 of 3 matchers with the "
+      "pairings:\n";
+
+  // We have to be a bit loose here, because there are 4 valid max matches.
+  EXPECT_THAT(
+      listener.str(),
+      AnyOf(prefix + "{\n  " + EMString(0, 0) +
+                     ",\n  " + EMString(1, 2) + "\n}",
+            prefix + "{\n  " + EMString(0, 1) +
+                     ",\n  " + EMString(1, 2) + "\n}",
+            prefix + "{\n  " + EMString(0, 0) +
+                     ",\n  " + EMString(2, 2) + "\n}",
+            prefix + "{\n  " + EMString(0, 1) +
+                     ",\n  " + EMString(2, 2) + "\n}"));
+}
+
+TEST_F(UnorderedElementsAreTest, Describe) {
+  EXPECT_THAT(Describe<IntVec>(UnorderedElementsAre()),
+              Eq("is empty"));
+  EXPECT_THAT(
+      Describe<IntVec>(UnorderedElementsAre(345)),
+      Eq("has 1 element and that element is equal to 345"));
+  EXPECT_THAT(
+      Describe<IntVec>(UnorderedElementsAre(111, 222, 333)),
+      Eq("has 3 elements and there exists some permutation "
+         "of elements such that:\n"
+         " - element #0 is equal to 111, and\n"
+         " - element #1 is equal to 222, and\n"
+         " - element #2 is equal to 333"));
+}
+
+TEST_F(UnorderedElementsAreTest, DescribeNegation) {
+  EXPECT_THAT(DescribeNegation<IntVec>(UnorderedElementsAre()),
+              Eq("isn't empty"));
+  EXPECT_THAT(
+      DescribeNegation<IntVec>(UnorderedElementsAre(345)),
+      Eq("doesn't have 1 element, or has 1 element that isn't equal to 345"));
+  EXPECT_THAT(
+      DescribeNegation<IntVec>(UnorderedElementsAre(123, 234, 345)),
+      Eq("doesn't have 3 elements, or there exists no permutation "
+         "of elements such that:\n"
+         " - element #0 is equal to 123, and\n"
+         " - element #1 is equal to 234, and\n"
+         " - element #2 is equal to 345"));
+}
+
+namespace {
+
+// Used as a check on the more complex max flow method used in the
+// real testing::internal::FindMaxBipartiteMatching. This method is
+// compatible but runs in worst-case factorial time, so we only
+// use it in testing for small problem sizes.
+template <typename Graph>
+class BacktrackingMaxBPMState {
+ public:
+  // Does not take ownership of 'g'.
+  explicit BacktrackingMaxBPMState(const Graph* g) : graph_(g) { }
+
+  ElementMatcherPairs Compute() {
+    if (graph_->LhsSize() == 0 || graph_->RhsSize() == 0) {
+      return best_so_far_;
+    }
+    lhs_used_.assign(graph_->LhsSize(), kUnused);
+    rhs_used_.assign(graph_->RhsSize(), kUnused);
+    for (size_t irhs = 0; irhs < graph_->RhsSize(); ++irhs) {
+      matches_.clear();
+      RecurseInto(irhs);
+      if (best_so_far_.size() == graph_->RhsSize())
+        break;
+    }
+    return best_so_far_;
+  }
+
+ private:
+  static const size_t kUnused = static_cast<size_t>(-1);
+
+  void PushMatch(size_t lhs, size_t rhs) {
+    matches_.push_back(ElementMatcherPair(lhs, rhs));
+    lhs_used_[lhs] = rhs;
+    rhs_used_[rhs] = lhs;
+    if (matches_.size() > best_so_far_.size()) {
+      best_so_far_ = matches_;
+    }
+  }
+
+  void PopMatch() {
+    const ElementMatcherPair& back = matches_.back();
+    lhs_used_[back.first] = kUnused;
+    rhs_used_[back.second] = kUnused;
+    matches_.pop_back();
+  }
+
+  bool RecurseInto(size_t irhs) {
+    if (rhs_used_[irhs] != kUnused) {
+      return true;
+    }
+    for (size_t ilhs = 0; ilhs < graph_->LhsSize(); ++ilhs) {
+      if (lhs_used_[ilhs] != kUnused) {
+        continue;
+      }
+      if (!graph_->HasEdge(ilhs, irhs)) {
+        continue;
+      }
+      PushMatch(ilhs, irhs);
+      if (best_so_far_.size() == graph_->RhsSize()) {
+        return false;
+      }
+      for (size_t mi = irhs + 1; mi < graph_->RhsSize(); ++mi) {
+        if (!RecurseInto(mi)) return false;
+      }
+      PopMatch();
+    }
+    return true;
+  }
+
+  const Graph* graph_;  // not owned
+  std::vector<size_t> lhs_used_;
+  std::vector<size_t> rhs_used_;
+  ElementMatcherPairs matches_;
+  ElementMatcherPairs best_so_far_;
+};
+
+template <typename Graph>
+const size_t BacktrackingMaxBPMState<Graph>::kUnused;
+
+}  // namespace
+
+// Implement a simple backtracking algorithm to determine if it is possible
+// to find one element per matcher, without reusing elements.
+template <typename Graph>
+ElementMatcherPairs
+FindBacktrackingMaxBPM(const Graph& g) {
+  return BacktrackingMaxBPMState<Graph>(&g).Compute();
+}
+
+class BacktrackingBPMTest : public ::testing::Test { };
+
+// Tests the MaxBipartiteMatching algorithm with square matrices.
+// The single int param is the # of nodes on each of the left and right sides.
+class BipartiteTest : public ::testing::TestWithParam<size_t> {};
+
+// Verify all match graphs up to some moderate number of edges.
+TEST_P(BipartiteTest, Exhaustive) {
+  size_t nodes = GetParam();
+  MatchMatrix graph(nodes, nodes);
+  do {
+    ElementMatcherPairs matches =
+        internal::FindMaxBipartiteMatching(graph);
+    EXPECT_EQ(FindBacktrackingMaxBPM(graph).size(), matches.size())
+        << "graph: " << graph.DebugString();
+    // Check that all elements of matches are in the graph.
+    // Check that elements of first and second are unique.
+    std::vector<bool> seen_element(graph.LhsSize());
+    std::vector<bool> seen_matcher(graph.RhsSize());
+    SCOPED_TRACE(PrintToString(matches));
+    for (size_t i = 0; i < matches.size(); ++i) {
+      size_t ilhs = matches[i].first;
+      size_t irhs = matches[i].second;
+      EXPECT_TRUE(graph.HasEdge(ilhs, irhs));
+      EXPECT_FALSE(seen_element[ilhs]);
+      EXPECT_FALSE(seen_matcher[irhs]);
+      seen_element[ilhs] = true;
+      seen_matcher[irhs] = true;
+    }
+  } while (graph.NextGraph());
+}
+
+INSTANTIATE_TEST_SUITE_P(AllGraphs, BipartiteTest,
+                         ::testing::Range(size_t{0}, size_t{5}));
+
+// Parameterized by a pair interpreted as (LhsSize, RhsSize).
+class BipartiteNonSquareTest
+    : public ::testing::TestWithParam<std::pair<size_t, size_t> > {
+};
+
+TEST_F(BipartiteNonSquareTest, SimpleBacktracking) {
+  //   .......
+  // 0:-----\ :
+  // 1:---\ | :
+  // 2:---\ | :
+  // 3:-\ | | :
+  //  :.......:
+  //    0 1 2
+  MatchMatrix g(4, 3);
+  constexpr std::array<std::array<size_t, 2>, 4> kEdges = {
+      {{{0, 2}}, {{1, 1}}, {{2, 1}}, {{3, 0}}}};
+  for (size_t i = 0; i < kEdges.size(); ++i) {
+    g.SetEdge(kEdges[i][0], kEdges[i][1], true);
+  }
+  EXPECT_THAT(FindBacktrackingMaxBPM(g),
+              ElementsAre(Pair(3, 0),
+                          Pair(AnyOf(1, 2), 1),
+                          Pair(0, 2))) << g.DebugString();
+}
+
+// Verify a few nonsquare matrices.
+TEST_P(BipartiteNonSquareTest, Exhaustive) {
+  size_t nlhs = GetParam().first;
+  size_t nrhs = GetParam().second;
+  MatchMatrix graph(nlhs, nrhs);
+  do {
+    EXPECT_EQ(FindBacktrackingMaxBPM(graph).size(),
+              internal::FindMaxBipartiteMatching(graph).size())
+        << "graph: " << graph.DebugString()
+        << "\nbacktracking: "
+        << PrintToString(FindBacktrackingMaxBPM(graph))
+        << "\nmax flow: "
+        << PrintToString(internal::FindMaxBipartiteMatching(graph));
+  } while (graph.NextGraph());
+}
+
+INSTANTIATE_TEST_SUITE_P(AllGraphs, BipartiteNonSquareTest,
+    testing::Values(
+        std::make_pair(1, 2),
+        std::make_pair(2, 1),
+        std::make_pair(3, 2),
+        std::make_pair(2, 3),
+        std::make_pair(4, 1),
+        std::make_pair(1, 4),
+        std::make_pair(4, 3),
+        std::make_pair(3, 4)));
+
+class BipartiteRandomTest
+    : public ::testing::TestWithParam<std::pair<int, int> > {
+};
+
+// Verifies a large sample of larger graphs.
+TEST_P(BipartiteRandomTest, LargerNets) {
+  int nodes = GetParam().first;
+  int iters = GetParam().second;
+  MatchMatrix graph(static_cast<size_t>(nodes), static_cast<size_t>(nodes));
+
+  auto seed = static_cast<uint32_t>(GTEST_FLAG(random_seed));
+  if (seed == 0) {
+    seed = static_cast<uint32_t>(time(nullptr));
+  }
+
+  for (; iters > 0; --iters, ++seed) {
+    srand(static_cast<unsigned int>(seed));
+    graph.Randomize();
+    EXPECT_EQ(FindBacktrackingMaxBPM(graph).size(),
+              internal::FindMaxBipartiteMatching(graph).size())
+        << " graph: " << graph.DebugString()
+        << "\nTo reproduce the failure, rerun the test with the flag"
+           " --" << GTEST_FLAG_PREFIX_ << "random_seed=" << seed;
+  }
+}
+
+// Test argument is a std::pair<int, int> representing (nodes, iters).
+INSTANTIATE_TEST_SUITE_P(Samples, BipartiteRandomTest,
+    testing::Values(
+        std::make_pair(5, 10000),
+        std::make_pair(6, 5000),
+        std::make_pair(7, 2000),
+        std::make_pair(8, 500),
+        std::make_pair(9, 100)));
+
+// Tests IsReadableTypeName().
+
+TEST(IsReadableTypeNameTest, ReturnsTrueForShortNames) {
+  EXPECT_TRUE(IsReadableTypeName("int"));
+  EXPECT_TRUE(IsReadableTypeName("const unsigned char*"));
+  EXPECT_TRUE(IsReadableTypeName("MyMap<int, void*>"));
+  EXPECT_TRUE(IsReadableTypeName("void (*)(int, bool)"));
+}
+
+TEST(IsReadableTypeNameTest, ReturnsTrueForLongNonTemplateNonFunctionNames) {
+  EXPECT_TRUE(IsReadableTypeName("my_long_namespace::MyClassName"));
+  EXPECT_TRUE(IsReadableTypeName("int [5][6][7][8][9][10][11]"));
+  EXPECT_TRUE(IsReadableTypeName("my_namespace::MyOuterClass::MyInnerClass"));
+}
+
+TEST(IsReadableTypeNameTest, ReturnsFalseForLongTemplateNames) {
+  EXPECT_FALSE(
+      IsReadableTypeName("basic_string<char, std::char_traits<char> >"));
+  EXPECT_FALSE(IsReadableTypeName("std::vector<int, std::alloc_traits<int> >"));
+}
+
+TEST(IsReadableTypeNameTest, ReturnsFalseForLongFunctionTypeNames) {
+  EXPECT_FALSE(IsReadableTypeName("void (&)(int, bool, char, float)"));
+}
+
+// Tests FormatMatcherDescription().
+
+TEST(FormatMatcherDescriptionTest, WorksForEmptyDescription) {
+  EXPECT_EQ("is even",
+            FormatMatcherDescription(false, "IsEven", Strings()));
+  EXPECT_EQ("not (is even)",
+            FormatMatcherDescription(true, "IsEven", Strings()));
+
+  const char* params[] = {"5"};
+  EXPECT_EQ("equals 5",
+            FormatMatcherDescription(false, "Equals",
+                                     Strings(params, params + 1)));
+
+  const char* params2[] = {"5", "8"};
+  EXPECT_EQ("is in range (5, 8)",
+            FormatMatcherDescription(false, "IsInRange",
+                                     Strings(params2, params2 + 2)));
+}
+
+// Tests PolymorphicMatcher::mutable_impl().
+TEST(PolymorphicMatcherTest, CanAccessMutableImpl) {
+  PolymorphicMatcher<DivisibleByImpl> m(DivisibleByImpl(42));
+  DivisibleByImpl& impl = m.mutable_impl();
+  EXPECT_EQ(42, impl.divider());
+
+  impl.set_divider(0);
+  EXPECT_EQ(0, m.mutable_impl().divider());
+}
+
+// Tests PolymorphicMatcher::impl().
+TEST(PolymorphicMatcherTest, CanAccessImpl) {
+  const PolymorphicMatcher<DivisibleByImpl> m(DivisibleByImpl(42));
+  const DivisibleByImpl& impl = m.impl();
+  EXPECT_EQ(42, impl.divider());
+}
+
+TEST(MatcherTupleTest, ExplainsMatchFailure) {
+  stringstream ss1;
+  ExplainMatchFailureTupleTo(
+      std::make_tuple(Matcher<char>(Eq('a')), GreaterThan(5)),
+      std::make_tuple('a', 10), &ss1);
+  EXPECT_EQ("", ss1.str());  // Successful match.
+
+  stringstream ss2;
+  ExplainMatchFailureTupleTo(
+      std::make_tuple(GreaterThan(5), Matcher<char>(Eq('a'))),
+      std::make_tuple(2, 'b'), &ss2);
+  EXPECT_EQ("  Expected arg #0: is > 5\n"
+            "           Actual: 2, which is 3 less than 5\n"
+            "  Expected arg #1: is equal to 'a' (97, 0x61)\n"
+            "           Actual: 'b' (98, 0x62)\n",
+            ss2.str());  // Failed match where both arguments need explanation.
+
+  stringstream ss3;
+  ExplainMatchFailureTupleTo(
+      std::make_tuple(GreaterThan(5), Matcher<char>(Eq('a'))),
+      std::make_tuple(2, 'a'), &ss3);
+  EXPECT_EQ("  Expected arg #0: is > 5\n"
+            "           Actual: 2, which is 3 less than 5\n",
+            ss3.str());  // Failed match where only one argument needs
+                         // explanation.
+}
+
+// Tests Each().
+
+TEST(EachTest, ExplainsMatchResultCorrectly) {
+  set<int> a;  // empty
+
+  Matcher<set<int> > m = Each(2);
+  EXPECT_EQ("", Explain(m, a));
+
+  Matcher<const int(&)[1]> n = Each(1);  // NOLINT
+
+  const int b[1] = {1};
+  EXPECT_EQ("", Explain(n, b));
+
+  n = Each(3);
+  EXPECT_EQ("whose element #0 doesn't match", Explain(n, b));
+
+  a.insert(1);
+  a.insert(2);
+  a.insert(3);
+  m = Each(GreaterThan(0));
+  EXPECT_EQ("", Explain(m, a));
+
+  m = Each(GreaterThan(10));
+  EXPECT_EQ("whose element #0 doesn't match, which is 9 less than 10",
+            Explain(m, a));
+}
+
+TEST(EachTest, DescribesItselfCorrectly) {
+  Matcher<vector<int> > m = Each(1);
+  EXPECT_EQ("only contains elements that is equal to 1", Describe(m));
+
+  Matcher<vector<int> > m2 = Not(m);
+  EXPECT_EQ("contains some element that isn't equal to 1", Describe(m2));
+}
+
+TEST(EachTest, MatchesVectorWhenAllElementsMatch) {
+  vector<int> some_vector;
+  EXPECT_THAT(some_vector, Each(1));
+  some_vector.push_back(3);
+  EXPECT_THAT(some_vector, Not(Each(1)));
+  EXPECT_THAT(some_vector, Each(3));
+  some_vector.push_back(1);
+  some_vector.push_back(2);
+  EXPECT_THAT(some_vector, Not(Each(3)));
+  EXPECT_THAT(some_vector, Each(Lt(3.5)));
+
+  vector<std::string> another_vector;
+  another_vector.push_back("fee");
+  EXPECT_THAT(another_vector, Each(std::string("fee")));
+  another_vector.push_back("fie");
+  another_vector.push_back("foe");
+  another_vector.push_back("fum");
+  EXPECT_THAT(another_vector, Not(Each(std::string("fee"))));
+}
+
+TEST(EachTest, MatchesMapWhenAllElementsMatch) {
+  map<const char*, int> my_map;
+  const char* bar = "a string";
+  my_map[bar] = 2;
+  EXPECT_THAT(my_map, Each(make_pair(bar, 2)));
+
+  map<std::string, int> another_map;
+  EXPECT_THAT(another_map, Each(make_pair(std::string("fee"), 1)));
+  another_map["fee"] = 1;
+  EXPECT_THAT(another_map, Each(make_pair(std::string("fee"), 1)));
+  another_map["fie"] = 2;
+  another_map["foe"] = 3;
+  another_map["fum"] = 4;
+  EXPECT_THAT(another_map, Not(Each(make_pair(std::string("fee"), 1))));
+  EXPECT_THAT(another_map, Not(Each(make_pair(std::string("fum"), 1))));
+  EXPECT_THAT(another_map, Each(Pair(_, Gt(0))));
+}
+
+TEST(EachTest, AcceptsMatcher) {
+  const int a[] = {1, 2, 3};
+  EXPECT_THAT(a, Each(Gt(0)));
+  EXPECT_THAT(a, Not(Each(Gt(1))));
+}
+
+TEST(EachTest, WorksForNativeArrayAsTuple) {
+  const int a[] = {1, 2};
+  const int* const pointer = a;
+  EXPECT_THAT(std::make_tuple(pointer, 2), Each(Gt(0)));
+  EXPECT_THAT(std::make_tuple(pointer, 2), Not(Each(Gt(1))));
+}
+
+TEST(EachTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper, Call(Each(Pointee(Gt(0)))));
+  helper.Call(MakeUniquePtrs({1, 2}));
+}
+
+// For testing Pointwise().
+class IsHalfOfMatcher {
+ public:
+  template <typename T1, typename T2>
+  bool MatchAndExplain(const std::tuple<T1, T2>& a_pair,
+                       MatchResultListener* listener) const {
+    if (std::get<0>(a_pair) == std::get<1>(a_pair) / 2) {
+      *listener << "where the second is " << std::get<1>(a_pair);
+      return true;
+    } else {
+      *listener << "where the second/2 is " << std::get<1>(a_pair) / 2;
+      return false;
+    }
+  }
+
+  void DescribeTo(ostream* os) const {
+    *os << "are a pair where the first is half of the second";
+  }
+
+  void DescribeNegationTo(ostream* os) const {
+    *os << "are a pair where the first isn't half of the second";
+  }
+};
+
+PolymorphicMatcher<IsHalfOfMatcher> IsHalfOf() {
+  return MakePolymorphicMatcher(IsHalfOfMatcher());
+}
+
+TEST(PointwiseTest, DescribesSelf) {
+  vector<int> rhs;
+  rhs.push_back(1);
+  rhs.push_back(2);
+  rhs.push_back(3);
+  const Matcher<const vector<int>&> m = Pointwise(IsHalfOf(), rhs);
+  EXPECT_EQ("contains 3 values, where each value and its corresponding value "
+            "in { 1, 2, 3 } are a pair where the first is half of the second",
+            Describe(m));
+  EXPECT_EQ("doesn't contain exactly 3 values, or contains a value x at some "
+            "index i where x and the i-th value of { 1, 2, 3 } are a pair "
+            "where the first isn't half of the second",
+            DescribeNegation(m));
+}
+
+TEST(PointwiseTest, MakesCopyOfRhs) {
+  list<signed char> rhs;
+  rhs.push_back(2);
+  rhs.push_back(4);
+
+  int lhs[] = {1, 2};
+  const Matcher<const int (&)[2]> m = Pointwise(IsHalfOf(), rhs);
+  EXPECT_THAT(lhs, m);
+
+  // Changing rhs now shouldn't affect m, which made a copy of rhs.
+  rhs.push_back(6);
+  EXPECT_THAT(lhs, m);
+}
+
+TEST(PointwiseTest, WorksForLhsNativeArray) {
+  const int lhs[] = {1, 2, 3};
+  vector<int> rhs;
+  rhs.push_back(2);
+  rhs.push_back(4);
+  rhs.push_back(6);
+  EXPECT_THAT(lhs, Pointwise(Lt(), rhs));
+  EXPECT_THAT(lhs, Not(Pointwise(Gt(), rhs)));
+}
+
+TEST(PointwiseTest, WorksForRhsNativeArray) {
+  const int rhs[] = {1, 2, 3};
+  vector<int> lhs;
+  lhs.push_back(2);
+  lhs.push_back(4);
+  lhs.push_back(6);
+  EXPECT_THAT(lhs, Pointwise(Gt(), rhs));
+  EXPECT_THAT(lhs, Not(Pointwise(Lt(), rhs)));
+}
+
+// Test is effective only with sanitizers.
+TEST(PointwiseTest, WorksForVectorOfBool) {
+  vector<bool> rhs(3, false);
+  rhs[1] = true;
+  vector<bool> lhs = rhs;
+  EXPECT_THAT(lhs, Pointwise(Eq(), rhs));
+  rhs[0] = true;
+  EXPECT_THAT(lhs, Not(Pointwise(Eq(), rhs)));
+}
+
+
+TEST(PointwiseTest, WorksForRhsInitializerList) {
+  const vector<int> lhs{2, 4, 6};
+  EXPECT_THAT(lhs, Pointwise(Gt(), {1, 2, 3}));
+  EXPECT_THAT(lhs, Not(Pointwise(Lt(), {3, 3, 7})));
+}
+
+
+TEST(PointwiseTest, RejectsWrongSize) {
+  const double lhs[2] = {1, 2};
+  const int rhs[1] = {0};
+  EXPECT_THAT(lhs, Not(Pointwise(Gt(), rhs)));
+  EXPECT_EQ("which contains 2 values",
+            Explain(Pointwise(Gt(), rhs), lhs));
+
+  const int rhs2[3] = {0, 1, 2};
+  EXPECT_THAT(lhs, Not(Pointwise(Gt(), rhs2)));
+}
+
+TEST(PointwiseTest, RejectsWrongContent) {
+  const double lhs[3] = {1, 2, 3};
+  const int rhs[3] = {2, 6, 4};
+  EXPECT_THAT(lhs, Not(Pointwise(IsHalfOf(), rhs)));
+  EXPECT_EQ("where the value pair (2, 6) at index #1 don't match, "
+            "where the second/2 is 3",
+            Explain(Pointwise(IsHalfOf(), rhs), lhs));
+}
+
+TEST(PointwiseTest, AcceptsCorrectContent) {
+  const double lhs[3] = {1, 2, 3};
+  const int rhs[3] = {2, 4, 6};
+  EXPECT_THAT(lhs, Pointwise(IsHalfOf(), rhs));
+  EXPECT_EQ("", Explain(Pointwise(IsHalfOf(), rhs), lhs));
+}
+
+TEST(PointwiseTest, AllowsMonomorphicInnerMatcher) {
+  const double lhs[3] = {1, 2, 3};
+  const int rhs[3] = {2, 4, 6};
+  const Matcher<std::tuple<const double&, const int&>> m1 = IsHalfOf();
+  EXPECT_THAT(lhs, Pointwise(m1, rhs));
+  EXPECT_EQ("", Explain(Pointwise(m1, rhs), lhs));
+
+  // This type works as a std::tuple<const double&, const int&> can be
+  // implicitly cast to std::tuple<double, int>.
+  const Matcher<std::tuple<double, int>> m2 = IsHalfOf();
+  EXPECT_THAT(lhs, Pointwise(m2, rhs));
+  EXPECT_EQ("", Explain(Pointwise(m2, rhs), lhs));
+}
+
+MATCHER(PointeeEquals, "Points to an equal value") {
+  return ExplainMatchResult(::testing::Pointee(::testing::get<1>(arg)),
+                            ::testing::get<0>(arg), result_listener);
+}
+
+TEST(PointwiseTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper, Call(Pointwise(PointeeEquals(), std::vector<int>{1, 2})));
+  helper.Call(MakeUniquePtrs({1, 2}));
+}
+
+TEST(UnorderedPointwiseTest, DescribesSelf) {
+  vector<int> rhs;
+  rhs.push_back(1);
+  rhs.push_back(2);
+  rhs.push_back(3);
+  const Matcher<const vector<int>&> m = UnorderedPointwise(IsHalfOf(), rhs);
+  EXPECT_EQ(
+      "has 3 elements and there exists some permutation of elements such "
+      "that:\n"
+      " - element #0 and 1 are a pair where the first is half of the second, "
+      "and\n"
+      " - element #1 and 2 are a pair where the first is half of the second, "
+      "and\n"
+      " - element #2 and 3 are a pair where the first is half of the second",
+      Describe(m));
+  EXPECT_EQ(
+      "doesn't have 3 elements, or there exists no permutation of elements "
+      "such that:\n"
+      " - element #0 and 1 are a pair where the first is half of the second, "
+      "and\n"
+      " - element #1 and 2 are a pair where the first is half of the second, "
+      "and\n"
+      " - element #2 and 3 are a pair where the first is half of the second",
+      DescribeNegation(m));
+}
+
+TEST(UnorderedPointwiseTest, MakesCopyOfRhs) {
+  list<signed char> rhs;
+  rhs.push_back(2);
+  rhs.push_back(4);
+
+  int lhs[] = {2, 1};
+  const Matcher<const int (&)[2]> m = UnorderedPointwise(IsHalfOf(), rhs);
+  EXPECT_THAT(lhs, m);
+
+  // Changing rhs now shouldn't affect m, which made a copy of rhs.
+  rhs.push_back(6);
+  EXPECT_THAT(lhs, m);
+}
+
+TEST(UnorderedPointwiseTest, WorksForLhsNativeArray) {
+  const int lhs[] = {1, 2, 3};
+  vector<int> rhs;
+  rhs.push_back(4);
+  rhs.push_back(6);
+  rhs.push_back(2);
+  EXPECT_THAT(lhs, UnorderedPointwise(Lt(), rhs));
+  EXPECT_THAT(lhs, Not(UnorderedPointwise(Gt(), rhs)));
+}
+
+TEST(UnorderedPointwiseTest, WorksForRhsNativeArray) {
+  const int rhs[] = {1, 2, 3};
+  vector<int> lhs;
+  lhs.push_back(4);
+  lhs.push_back(2);
+  lhs.push_back(6);
+  EXPECT_THAT(lhs, UnorderedPointwise(Gt(), rhs));
+  EXPECT_THAT(lhs, Not(UnorderedPointwise(Lt(), rhs)));
+}
+
+
+TEST(UnorderedPointwiseTest, WorksForRhsInitializerList) {
+  const vector<int> lhs{2, 4, 6};
+  EXPECT_THAT(lhs, UnorderedPointwise(Gt(), {5, 1, 3}));
+  EXPECT_THAT(lhs, Not(UnorderedPointwise(Lt(), {1, 1, 7})));
+}
+
+
+TEST(UnorderedPointwiseTest, RejectsWrongSize) {
+  const double lhs[2] = {1, 2};
+  const int rhs[1] = {0};
+  EXPECT_THAT(lhs, Not(UnorderedPointwise(Gt(), rhs)));
+  EXPECT_EQ("which has 2 elements",
+            Explain(UnorderedPointwise(Gt(), rhs), lhs));
+
+  const int rhs2[3] = {0, 1, 2};
+  EXPECT_THAT(lhs, Not(UnorderedPointwise(Gt(), rhs2)));
+}
+
+TEST(UnorderedPointwiseTest, RejectsWrongContent) {
+  const double lhs[3] = {1, 2, 3};
+  const int rhs[3] = {2, 6, 6};
+  EXPECT_THAT(lhs, Not(UnorderedPointwise(IsHalfOf(), rhs)));
+  EXPECT_EQ("where the following elements don't match any matchers:\n"
+            "element #1: 2",
+            Explain(UnorderedPointwise(IsHalfOf(), rhs), lhs));
+}
+
+TEST(UnorderedPointwiseTest, AcceptsCorrectContentInSameOrder) {
+  const double lhs[3] = {1, 2, 3};
+  const int rhs[3] = {2, 4, 6};
+  EXPECT_THAT(lhs, UnorderedPointwise(IsHalfOf(), rhs));
+}
+
+TEST(UnorderedPointwiseTest, AcceptsCorrectContentInDifferentOrder) {
+  const double lhs[3] = {1, 2, 3};
+  const int rhs[3] = {6, 4, 2};
+  EXPECT_THAT(lhs, UnorderedPointwise(IsHalfOf(), rhs));
+}
+
+TEST(UnorderedPointwiseTest, AllowsMonomorphicInnerMatcher) {
+  const double lhs[3] = {1, 2, 3};
+  const int rhs[3] = {4, 6, 2};
+  const Matcher<std::tuple<const double&, const int&>> m1 = IsHalfOf();
+  EXPECT_THAT(lhs, UnorderedPointwise(m1, rhs));
+
+  // This type works as a std::tuple<const double&, const int&> can be
+  // implicitly cast to std::tuple<double, int>.
+  const Matcher<std::tuple<double, int>> m2 = IsHalfOf();
+  EXPECT_THAT(lhs, UnorderedPointwise(m2, rhs));
+}
+
+TEST(UnorderedPointwiseTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper, Call(UnorderedPointwise(PointeeEquals(),
+                                              std::vector<int>{1, 2})));
+  helper.Call(MakeUniquePtrs({2, 1}));
+}
+
+// Sample optional type implementation with minimal requirements for use with
+// Optional matcher.
+template <typename T>
+class SampleOptional {
+ public:
+  using value_type = T;
+  explicit SampleOptional(T value)
+      : value_(std::move(value)), has_value_(true) {}
+  SampleOptional() : value_(), has_value_(false) {}
+  operator bool() const { return has_value_; }
+  const T& operator*() const { return value_; }
+
+ private:
+  T value_;
+  bool has_value_;
+};
+
+TEST(OptionalTest, DescribesSelf) {
+  const Matcher<SampleOptional<int>> m = Optional(Eq(1));
+  EXPECT_EQ("value is equal to 1", Describe(m));
+}
+
+TEST(OptionalTest, ExplainsSelf) {
+  const Matcher<SampleOptional<int>> m = Optional(Eq(1));
+  EXPECT_EQ("whose value 1 matches", Explain(m, SampleOptional<int>(1)));
+  EXPECT_EQ("whose value 2 doesn't match", Explain(m, SampleOptional<int>(2)));
+}
+
+TEST(OptionalTest, MatchesNonEmptyOptional) {
+  const Matcher<SampleOptional<int>> m1 = Optional(1);
+  const Matcher<SampleOptional<int>> m2 = Optional(Eq(2));
+  const Matcher<SampleOptional<int>> m3 = Optional(Lt(3));
+  SampleOptional<int> opt(1);
+  EXPECT_TRUE(m1.Matches(opt));
+  EXPECT_FALSE(m2.Matches(opt));
+  EXPECT_TRUE(m3.Matches(opt));
+}
+
+TEST(OptionalTest, DoesNotMatchNullopt) {
+  const Matcher<SampleOptional<int>> m = Optional(1);
+  SampleOptional<int> empty;
+  EXPECT_FALSE(m.Matches(empty));
+}
+
+TEST(OptionalTest, WorksWithMoveOnly) {
+  Matcher<SampleOptional<std::unique_ptr<int>>> m = Optional(Eq(nullptr));
+  EXPECT_TRUE(m.Matches(SampleOptional<std::unique_ptr<int>>(nullptr)));
+}
+
+class SampleVariantIntString {
+ public:
+  SampleVariantIntString(int i) : i_(i), has_int_(true) {}
+  SampleVariantIntString(const std::string& s) : s_(s), has_int_(false) {}
+
+  template <typename T>
+  friend bool holds_alternative(const SampleVariantIntString& value) {
+    return value.has_int_ == std::is_same<T, int>::value;
+  }
+
+  template <typename T>
+  friend const T& get(const SampleVariantIntString& value) {
+    return value.get_impl(static_cast<T*>(nullptr));
+  }
+
+ private:
+  const int& get_impl(int*) const { return i_; }
+  const std::string& get_impl(std::string*) const { return s_; }
+
+  int i_;
+  std::string s_;
+  bool has_int_;
+};
+
+TEST(VariantTest, DescribesSelf) {
+  const Matcher<SampleVariantIntString> m = VariantWith<int>(Eq(1));
+  EXPECT_THAT(Describe(m), ContainsRegex("is a variant<> with value of type "
+                                         "'.*' and the value is equal to 1"));
+}
+
+TEST(VariantTest, ExplainsSelf) {
+  const Matcher<SampleVariantIntString> m = VariantWith<int>(Eq(1));
+  EXPECT_THAT(Explain(m, SampleVariantIntString(1)),
+              ContainsRegex("whose value 1"));
+  EXPECT_THAT(Explain(m, SampleVariantIntString("A")),
+              HasSubstr("whose value is not of type '"));
+  EXPECT_THAT(Explain(m, SampleVariantIntString(2)),
+              "whose value 2 doesn't match");
+}
+
+TEST(VariantTest, FullMatch) {
+  Matcher<SampleVariantIntString> m = VariantWith<int>(Eq(1));
+  EXPECT_TRUE(m.Matches(SampleVariantIntString(1)));
+
+  m = VariantWith<std::string>(Eq("1"));
+  EXPECT_TRUE(m.Matches(SampleVariantIntString("1")));
+}
+
+TEST(VariantTest, TypeDoesNotMatch) {
+  Matcher<SampleVariantIntString> m = VariantWith<int>(Eq(1));
+  EXPECT_FALSE(m.Matches(SampleVariantIntString("1")));
+
+  m = VariantWith<std::string>(Eq("1"));
+  EXPECT_FALSE(m.Matches(SampleVariantIntString(1)));
+}
+
+TEST(VariantTest, InnerDoesNotMatch) {
+  Matcher<SampleVariantIntString> m = VariantWith<int>(Eq(1));
+  EXPECT_FALSE(m.Matches(SampleVariantIntString(2)));
+
+  m = VariantWith<std::string>(Eq("1"));
+  EXPECT_FALSE(m.Matches(SampleVariantIntString("2")));
+}
+
+class SampleAnyType {
+ public:
+  explicit SampleAnyType(int i) : index_(0), i_(i) {}
+  explicit SampleAnyType(const std::string& s) : index_(1), s_(s) {}
+
+  template <typename T>
+  friend const T* any_cast(const SampleAnyType* any) {
+    return any->get_impl(static_cast<T*>(nullptr));
+  }
+
+ private:
+  int index_;
+  int i_;
+  std::string s_;
+
+  const int* get_impl(int*) const { return index_ == 0 ? &i_ : nullptr; }
+  const std::string* get_impl(std::string*) const {
+    return index_ == 1 ? &s_ : nullptr;
+  }
+};
+
+TEST(AnyWithTest, FullMatch) {
+  Matcher<SampleAnyType> m = AnyWith<int>(Eq(1));
+  EXPECT_TRUE(m.Matches(SampleAnyType(1)));
+}
+
+TEST(AnyWithTest, TestBadCastType) {
+  Matcher<SampleAnyType> m = AnyWith<std::string>(Eq("fail"));
+  EXPECT_FALSE(m.Matches(SampleAnyType(1)));
+}
+
+TEST(AnyWithTest, TestUseInContainers) {
+  std::vector<SampleAnyType> a;
+  a.emplace_back(1);
+  a.emplace_back(2);
+  a.emplace_back(3);
+  EXPECT_THAT(
+      a, ElementsAreArray({AnyWith<int>(1), AnyWith<int>(2), AnyWith<int>(3)}));
+
+  std::vector<SampleAnyType> b;
+  b.emplace_back("hello");
+  b.emplace_back("merhaba");
+  b.emplace_back("salut");
+  EXPECT_THAT(b, ElementsAreArray({AnyWith<std::string>("hello"),
+                                   AnyWith<std::string>("merhaba"),
+                                   AnyWith<std::string>("salut")}));
+}
+TEST(AnyWithTest, TestCompare) {
+  EXPECT_THAT(SampleAnyType(1), AnyWith<int>(Gt(0)));
+}
+
+TEST(AnyWithTest, DescribesSelf) {
+  const Matcher<const SampleAnyType&> m = AnyWith<int>(Eq(1));
+  EXPECT_THAT(Describe(m), ContainsRegex("is an 'any' type with value of type "
+                                         "'.*' and the value is equal to 1"));
+}
+
+TEST(AnyWithTest, ExplainsSelf) {
+  const Matcher<const SampleAnyType&> m = AnyWith<int>(Eq(1));
+
+  EXPECT_THAT(Explain(m, SampleAnyType(1)), ContainsRegex("whose value 1"));
+  EXPECT_THAT(Explain(m, SampleAnyType("A")),
+              HasSubstr("whose value is not of type '"));
+  EXPECT_THAT(Explain(m, SampleAnyType(2)), "whose value 2 doesn't match");
+}
+
+TEST(PointeeTest, WorksOnMoveOnlyType) {
+  std::unique_ptr<int> p(new int(3));
+  EXPECT_THAT(p, Pointee(Eq(3)));
+  EXPECT_THAT(p, Not(Pointee(Eq(2))));
+}
+
+TEST(NotTest, WorksOnMoveOnlyType) {
+  std::unique_ptr<int> p(new int(3));
+  EXPECT_THAT(p, Pointee(Eq(3)));
+  EXPECT_THAT(p, Not(Pointee(Eq(2))));
+}
+
+// Tests Args<k0, ..., kn>(m).
+
+TEST(ArgsTest, AcceptsZeroTemplateArg) {
+  const std::tuple<int, bool> t(5, true);
+  EXPECT_THAT(t, Args<>(Eq(std::tuple<>())));
+  EXPECT_THAT(t, Not(Args<>(Ne(std::tuple<>()))));
+}
+
+TEST(ArgsTest, AcceptsOneTemplateArg) {
+  const std::tuple<int, bool> t(5, true);
+  EXPECT_THAT(t, Args<0>(Eq(std::make_tuple(5))));
+  EXPECT_THAT(t, Args<1>(Eq(std::make_tuple(true))));
+  EXPECT_THAT(t, Not(Args<1>(Eq(std::make_tuple(false)))));
+}
+
+TEST(ArgsTest, AcceptsTwoTemplateArgs) {
+  const std::tuple<short, int, long> t(4, 5, 6L);  // NOLINT
+
+  EXPECT_THAT(t, (Args<0, 1>(Lt())));
+  EXPECT_THAT(t, (Args<1, 2>(Lt())));
+  EXPECT_THAT(t, Not(Args<0, 2>(Gt())));
+}
+
+TEST(ArgsTest, AcceptsRepeatedTemplateArgs) {
+  const std::tuple<short, int, long> t(4, 5, 6L);  // NOLINT
+  EXPECT_THAT(t, (Args<0, 0>(Eq())));
+  EXPECT_THAT(t, Not(Args<1, 1>(Ne())));
+}
+
+TEST(ArgsTest, AcceptsDecreasingTemplateArgs) {
+  const std::tuple<short, int, long> t(4, 5, 6L);  // NOLINT
+  EXPECT_THAT(t, (Args<2, 0>(Gt())));
+  EXPECT_THAT(t, Not(Args<2, 1>(Lt())));
+}
+
+MATCHER(SumIsZero, "") {
+  return std::get<0>(arg) + std::get<1>(arg) + std::get<2>(arg) == 0;
+}
+
+TEST(ArgsTest, AcceptsMoreTemplateArgsThanArityOfOriginalTuple) {
+  EXPECT_THAT(std::make_tuple(-1, 2), (Args<0, 0, 1>(SumIsZero())));
+  EXPECT_THAT(std::make_tuple(1, 2), Not(Args<0, 0, 1>(SumIsZero())));
+}
+
+TEST(ArgsTest, CanBeNested) {
+  const std::tuple<short, int, long, int> t(4, 5, 6L, 6);  // NOLINT
+  EXPECT_THAT(t, (Args<1, 2, 3>(Args<1, 2>(Eq()))));
+  EXPECT_THAT(t, (Args<0, 1, 3>(Args<0, 2>(Lt()))));
+}
+
+TEST(ArgsTest, CanMatchTupleByValue) {
+  typedef std::tuple<char, int, int> Tuple3;
+  const Matcher<Tuple3> m = Args<1, 2>(Lt());
+  EXPECT_TRUE(m.Matches(Tuple3('a', 1, 2)));
+  EXPECT_FALSE(m.Matches(Tuple3('b', 2, 2)));
+}
+
+TEST(ArgsTest, CanMatchTupleByReference) {
+  typedef std::tuple<char, char, int> Tuple3;
+  const Matcher<const Tuple3&> m = Args<0, 1>(Lt());
+  EXPECT_TRUE(m.Matches(Tuple3('a', 'b', 2)));
+  EXPECT_FALSE(m.Matches(Tuple3('b', 'b', 2)));
+}
+
+// Validates that arg is printed as str.
+MATCHER_P(PrintsAs, str, "") {
+  return testing::PrintToString(arg) == str;
+}
+
+TEST(ArgsTest, AcceptsTenTemplateArgs) {
+  EXPECT_THAT(std::make_tuple(0, 1L, 2, 3L, 4, 5, 6, 7, 8, 9),
+              (Args<9, 8, 7, 6, 5, 4, 3, 2, 1, 0>(
+                  PrintsAs("(9, 8, 7, 6, 5, 4, 3, 2, 1, 0)"))));
+  EXPECT_THAT(std::make_tuple(0, 1L, 2, 3L, 4, 5, 6, 7, 8, 9),
+              Not(Args<9, 8, 7, 6, 5, 4, 3, 2, 1, 0>(
+                  PrintsAs("(0, 8, 7, 6, 5, 4, 3, 2, 1, 0)"))));
+}
+
+TEST(ArgsTest, DescirbesSelfCorrectly) {
+  const Matcher<std::tuple<int, bool, char> > m = Args<2, 0>(Lt());
+  EXPECT_EQ("are a tuple whose fields (#2, #0) are a pair where "
+            "the first < the second",
+            Describe(m));
+}
+
+TEST(ArgsTest, DescirbesNestedArgsCorrectly) {
+  const Matcher<const std::tuple<int, bool, char, int>&> m =
+      Args<0, 2, 3>(Args<2, 0>(Lt()));
+  EXPECT_EQ("are a tuple whose fields (#0, #2, #3) are a tuple "
+            "whose fields (#2, #0) are a pair where the first < the second",
+            Describe(m));
+}
+
+TEST(ArgsTest, DescribesNegationCorrectly) {
+  const Matcher<std::tuple<int, char> > m = Args<1, 0>(Gt());
+  EXPECT_EQ("are a tuple whose fields (#1, #0) aren't a pair "
+            "where the first > the second",
+            DescribeNegation(m));
+}
+
+TEST(ArgsTest, ExplainsMatchResultWithoutInnerExplanation) {
+  const Matcher<std::tuple<bool, int, int> > m = Args<1, 2>(Eq());
+  EXPECT_EQ("whose fields (#1, #2) are (42, 42)",
+            Explain(m, std::make_tuple(false, 42, 42)));
+  EXPECT_EQ("whose fields (#1, #2) are (42, 43)",
+            Explain(m, std::make_tuple(false, 42, 43)));
+}
+
+// For testing Args<>'s explanation.
+class LessThanMatcher : public MatcherInterface<std::tuple<char, int> > {
+ public:
+  void DescribeTo(::std::ostream* /*os*/) const override {}
+
+  bool MatchAndExplain(std::tuple<char, int> value,
+                       MatchResultListener* listener) const override {
+    const int diff = std::get<0>(value) - std::get<1>(value);
+    if (diff > 0) {
+      *listener << "where the first value is " << diff
+                << " more than the second";
+    }
+    return diff < 0;
+  }
+};
+
+Matcher<std::tuple<char, int> > LessThan() {
+  return MakeMatcher(new LessThanMatcher);
+}
+
+TEST(ArgsTest, ExplainsMatchResultWithInnerExplanation) {
+  const Matcher<std::tuple<char, int, int> > m = Args<0, 2>(LessThan());
+  EXPECT_EQ(
+      "whose fields (#0, #2) are ('a' (97, 0x61), 42), "
+      "where the first value is 55 more than the second",
+      Explain(m, std::make_tuple('a', 42, 42)));
+  EXPECT_EQ("whose fields (#0, #2) are ('\\0', 43)",
+            Explain(m, std::make_tuple('\0', 42, 43)));
+}
+
+class PredicateFormatterFromMatcherTest : public ::testing::Test {
+ protected:
+  enum Behavior { kInitialSuccess, kAlwaysFail, kFlaky };
+
+  // A matcher that can return different results when used multiple times on the
+  // same input. No real matcher should do this; but this lets us test that we
+  // detect such behavior and fail appropriately.
+  class MockMatcher : public MatcherInterface<Behavior> {
+   public:
+    bool MatchAndExplain(Behavior behavior,
+                         MatchResultListener* listener) const override {
+      *listener << "[MatchAndExplain]";
+      switch (behavior) {
+        case kInitialSuccess:
+          // The first call to MatchAndExplain should use a "not interested"
+          // listener; so this is expected to return |true|. There should be no
+          // subsequent calls.
+          return !listener->IsInterested();
+
+        case kAlwaysFail:
+          return false;
+
+        case kFlaky:
+          // The first call to MatchAndExplain should use a "not interested"
+          // listener; so this will return |false|. Subsequent calls should have
+          // an "interested" listener; so this will return |true|, thus
+          // simulating a flaky matcher.
+          return listener->IsInterested();
+      }
+
+      GTEST_LOG_(FATAL) << "This should never be reached";
+      return false;
+    }
+
+    void DescribeTo(ostream* os) const override { *os << "[DescribeTo]"; }
+
+    void DescribeNegationTo(ostream* os) const override {
+      *os << "[DescribeNegationTo]";
+    }
+  };
+
+  AssertionResult RunPredicateFormatter(Behavior behavior) {
+    auto matcher = MakeMatcher(new MockMatcher);
+    PredicateFormatterFromMatcher<Matcher<Behavior>> predicate_formatter(
+        matcher);
+    return predicate_formatter("dummy-name", behavior);
+  }
+};
+
+TEST_F(PredicateFormatterFromMatcherTest, ShortCircuitOnSuccess) {
+  AssertionResult result = RunPredicateFormatter(kInitialSuccess);
+  EXPECT_TRUE(result);  // Implicit cast to bool.
+  std::string expect;
+  EXPECT_EQ(expect, result.message());
+}
+
+TEST_F(PredicateFormatterFromMatcherTest, NoShortCircuitOnFailure) {
+  AssertionResult result = RunPredicateFormatter(kAlwaysFail);
+  EXPECT_FALSE(result);  // Implicit cast to bool.
+  std::string expect =
+      "Value of: dummy-name\nExpected: [DescribeTo]\n"
+      "  Actual: 1" +
+      OfType(internal::GetTypeName<Behavior>()) + ", [MatchAndExplain]";
+  EXPECT_EQ(expect, result.message());
+}
+
+TEST_F(PredicateFormatterFromMatcherTest, DetectsFlakyShortCircuit) {
+  AssertionResult result = RunPredicateFormatter(kFlaky);
+  EXPECT_FALSE(result);  // Implicit cast to bool.
+  std::string expect =
+      "Value of: dummy-name\nExpected: [DescribeTo]\n"
+      "  The matcher failed on the initial attempt; but passed when rerun to "
+      "generate the explanation.\n"
+      "  Actual: 2" +
+      OfType(internal::GetTypeName<Behavior>()) + ", [MatchAndExplain]";
+  EXPECT_EQ(expect, result.message());
+}
+
+// Tests for ElementsAre().
+
+TEST(ElementsAreTest, CanDescribeExpectingNoElement) {
+  Matcher<const vector<int>&> m = ElementsAre();
+  EXPECT_EQ("is empty", Describe(m));
+}
+
+TEST(ElementsAreTest, CanDescribeExpectingOneElement) {
+  Matcher<vector<int>> m = ElementsAre(Gt(5));
+  EXPECT_EQ("has 1 element that is > 5", Describe(m));
+}
+
+TEST(ElementsAreTest, CanDescribeExpectingManyElements) {
+  Matcher<list<std::string>> m = ElementsAre(StrEq("one"), "two");
+  EXPECT_EQ(
+      "has 2 elements where\n"
+      "element #0 is equal to \"one\",\n"
+      "element #1 is equal to \"two\"",
+      Describe(m));
+}
+
+TEST(ElementsAreTest, CanDescribeNegationOfExpectingNoElement) {
+  Matcher<vector<int>> m = ElementsAre();
+  EXPECT_EQ("isn't empty", DescribeNegation(m));
+}
+
+TEST(ElementsAreTest, CanDescribeNegationOfExpectingOneElment) {
+  Matcher<const list<int>&> m = ElementsAre(Gt(5));
+  EXPECT_EQ(
+      "doesn't have 1 element, or\n"
+      "element #0 isn't > 5",
+      DescribeNegation(m));
+}
+
+TEST(ElementsAreTest, CanDescribeNegationOfExpectingManyElements) {
+  Matcher<const list<std::string>&> m = ElementsAre("one", "two");
+  EXPECT_EQ(
+      "doesn't have 2 elements, or\n"
+      "element #0 isn't equal to \"one\", or\n"
+      "element #1 isn't equal to \"two\"",
+      DescribeNegation(m));
+}
+
+TEST(ElementsAreTest, DoesNotExplainTrivialMatch) {
+  Matcher<const list<int>&> m = ElementsAre(1, Ne(2));
+
+  list<int> test_list;
+  test_list.push_back(1);
+  test_list.push_back(3);
+  EXPECT_EQ("", Explain(m, test_list));  // No need to explain anything.
+}
+
+TEST(ElementsAreTest, ExplainsNonTrivialMatch) {
+  Matcher<const vector<int>&> m =
+      ElementsAre(GreaterThan(1), 0, GreaterThan(2));
+
+  const int a[] = {10, 0, 100};
+  vector<int> test_vector(std::begin(a), std::end(a));
+  EXPECT_EQ(
+      "whose element #0 matches, which is 9 more than 1,\n"
+      "and whose element #2 matches, which is 98 more than 2",
+      Explain(m, test_vector));
+}
+
+TEST(ElementsAreTest, CanExplainMismatchWrongSize) {
+  Matcher<const list<int>&> m = ElementsAre(1, 3);
+
+  list<int> test_list;
+  // No need to explain when the container is empty.
+  EXPECT_EQ("", Explain(m, test_list));
+
+  test_list.push_back(1);
+  EXPECT_EQ("which has 1 element", Explain(m, test_list));
+}
+
+TEST(ElementsAreTest, CanExplainMismatchRightSize) {
+  Matcher<const vector<int>&> m = ElementsAre(1, GreaterThan(5));
+
+  vector<int> v;
+  v.push_back(2);
+  v.push_back(1);
+  EXPECT_EQ("whose element #0 doesn't match", Explain(m, v));
+
+  v[0] = 1;
+  EXPECT_EQ("whose element #1 doesn't match, which is 4 less than 5",
+            Explain(m, v));
+}
+
+TEST(ElementsAreTest, MatchesOneElementVector) {
+  vector<std::string> test_vector;
+  test_vector.push_back("test string");
+
+  EXPECT_THAT(test_vector, ElementsAre(StrEq("test string")));
+}
+
+TEST(ElementsAreTest, MatchesOneElementList) {
+  list<std::string> test_list;
+  test_list.push_back("test string");
+
+  EXPECT_THAT(test_list, ElementsAre("test string"));
+}
+
+TEST(ElementsAreTest, MatchesThreeElementVector) {
+  vector<std::string> test_vector;
+  test_vector.push_back("one");
+  test_vector.push_back("two");
+  test_vector.push_back("three");
+
+  EXPECT_THAT(test_vector, ElementsAre("one", StrEq("two"), _));
+}
+
+TEST(ElementsAreTest, MatchesOneElementEqMatcher) {
+  vector<int> test_vector;
+  test_vector.push_back(4);
+
+  EXPECT_THAT(test_vector, ElementsAre(Eq(4)));
+}
+
+TEST(ElementsAreTest, MatchesOneElementAnyMatcher) {
+  vector<int> test_vector;
+  test_vector.push_back(4);
+
+  EXPECT_THAT(test_vector, ElementsAre(_));
+}
+
+TEST(ElementsAreTest, MatchesOneElementValue) {
+  vector<int> test_vector;
+  test_vector.push_back(4);
+
+  EXPECT_THAT(test_vector, ElementsAre(4));
+}
+
+TEST(ElementsAreTest, MatchesThreeElementsMixedMatchers) {
+  vector<int> test_vector;
+  test_vector.push_back(1);
+  test_vector.push_back(2);
+  test_vector.push_back(3);
+
+  EXPECT_THAT(test_vector, ElementsAre(1, Eq(2), _));
+}
+
+TEST(ElementsAreTest, MatchesTenElementVector) {
+  const int a[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
+  vector<int> test_vector(std::begin(a), std::end(a));
+
+  EXPECT_THAT(test_vector,
+              // The element list can contain values and/or matchers
+              // of different types.
+              ElementsAre(0, Ge(0), _, 3, 4, Ne(2), Eq(6), 7, 8, _));
+}
+
+TEST(ElementsAreTest, DoesNotMatchWrongSize) {
+  vector<std::string> test_vector;
+  test_vector.push_back("test string");
+  test_vector.push_back("test string");
+
+  Matcher<vector<std::string>> m = ElementsAre(StrEq("test string"));
+  EXPECT_FALSE(m.Matches(test_vector));
+}
+
+TEST(ElementsAreTest, DoesNotMatchWrongValue) {
+  vector<std::string> test_vector;
+  test_vector.push_back("other string");
+
+  Matcher<vector<std::string>> m = ElementsAre(StrEq("test string"));
+  EXPECT_FALSE(m.Matches(test_vector));
+}
+
+TEST(ElementsAreTest, DoesNotMatchWrongOrder) {
+  vector<std::string> test_vector;
+  test_vector.push_back("one");
+  test_vector.push_back("three");
+  test_vector.push_back("two");
+
+  Matcher<vector<std::string>> m =
+      ElementsAre(StrEq("one"), StrEq("two"), StrEq("three"));
+  EXPECT_FALSE(m.Matches(test_vector));
+}
+
+TEST(ElementsAreTest, WorksForNestedContainer) {
+  constexpr std::array<const char*, 2> strings = {{"Hi", "world"}};
+
+  vector<list<char>> nested;
+  for (const auto& s : strings) {
+    nested.emplace_back(s, s + strlen(s));
+  }
+
+  EXPECT_THAT(nested, ElementsAre(ElementsAre('H', Ne('e')),
+                                  ElementsAre('w', 'o', _, _, 'd')));
+  EXPECT_THAT(nested, Not(ElementsAre(ElementsAre('H', 'e'),
+                                      ElementsAre('w', 'o', _, _, 'd'))));
+}
+
+TEST(ElementsAreTest, WorksWithByRefElementMatchers) {
+  int a[] = {0, 1, 2};
+  vector<int> v(std::begin(a), std::end(a));
+
+  EXPECT_THAT(v, ElementsAre(Ref(v[0]), Ref(v[1]), Ref(v[2])));
+  EXPECT_THAT(v, Not(ElementsAre(Ref(v[0]), Ref(v[1]), Ref(a[2]))));
+}
+
+TEST(ElementsAreTest, WorksWithContainerPointerUsingPointee) {
+  int a[] = {0, 1, 2};
+  vector<int> v(std::begin(a), std::end(a));
+
+  EXPECT_THAT(&v, Pointee(ElementsAre(0, 1, _)));
+  EXPECT_THAT(&v, Not(Pointee(ElementsAre(0, _, 3))));
+}
+
+TEST(ElementsAreTest, WorksWithNativeArrayPassedByReference) {
+  int array[] = {0, 1, 2};
+  EXPECT_THAT(array, ElementsAre(0, 1, _));
+  EXPECT_THAT(array, Not(ElementsAre(1, _, _)));
+  EXPECT_THAT(array, Not(ElementsAre(0, _)));
+}
+
+class NativeArrayPassedAsPointerAndSize {
+ public:
+  NativeArrayPassedAsPointerAndSize() {}
+
+  MOCK_METHOD(void, Helper, (int* array, int size));
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(NativeArrayPassedAsPointerAndSize);
+};
+
+TEST(ElementsAreTest, WorksWithNativeArrayPassedAsPointerAndSize) {
+  int array[] = {0, 1};
+  ::std::tuple<int*, size_t> array_as_tuple(array, 2);
+  EXPECT_THAT(array_as_tuple, ElementsAre(0, 1));
+  EXPECT_THAT(array_as_tuple, Not(ElementsAre(0)));
+
+  NativeArrayPassedAsPointerAndSize helper;
+  EXPECT_CALL(helper, Helper(_, _)).With(ElementsAre(0, 1));
+  helper.Helper(array, 2);
+}
+
+TEST(ElementsAreTest, WorksWithTwoDimensionalNativeArray) {
+  const char a2[][3] = {"hi", "lo"};
+  EXPECT_THAT(a2, ElementsAre(ElementsAre('h', 'i', '\0'),
+                              ElementsAre('l', 'o', '\0')));
+  EXPECT_THAT(a2, ElementsAre(StrEq("hi"), StrEq("lo")));
+  EXPECT_THAT(a2, ElementsAre(Not(ElementsAre('h', 'o', '\0')),
+                              ElementsAre('l', 'o', '\0')));
+}
+
+TEST(ElementsAreTest, AcceptsStringLiteral) {
+  std::string array[] = {"hi", "one", "two"};
+  EXPECT_THAT(array, ElementsAre("hi", "one", "two"));
+  EXPECT_THAT(array, Not(ElementsAre("hi", "one", "too")));
+}
+
+// Declared here with the size unknown.  Defined AFTER the following test.
+extern const char kHi[];
+
+TEST(ElementsAreTest, AcceptsArrayWithUnknownSize) {
+  // The size of kHi is not known in this test, but ElementsAre() should
+  // still accept it.
+
+  std::string array1[] = {"hi"};
+  EXPECT_THAT(array1, ElementsAre(kHi));
+
+  std::string array2[] = {"ho"};
+  EXPECT_THAT(array2, Not(ElementsAre(kHi)));
+}
+
+const char kHi[] = "hi";
+
+TEST(ElementsAreTest, MakesCopyOfArguments) {
+  int x = 1;
+  int y = 2;
+  // This should make a copy of x and y.
+  ::testing::internal::ElementsAreMatcher<std::tuple<int, int>>
+      polymorphic_matcher = ElementsAre(x, y);
+  // Changing x and y now shouldn't affect the meaning of the above matcher.
+  x = y = 0;
+  const int array1[] = {1, 2};
+  EXPECT_THAT(array1, polymorphic_matcher);
+  const int array2[] = {0, 0};
+  EXPECT_THAT(array2, Not(polymorphic_matcher));
+}
+
+// Tests for ElementsAreArray().  Since ElementsAreArray() shares most
+// of the implementation with ElementsAre(), we don't test it as
+// thoroughly here.
+
+TEST(ElementsAreArrayTest, CanBeCreatedWithValueArray) {
+  const int a[] = {1, 2, 3};
+
+  vector<int> test_vector(std::begin(a), std::end(a));
+  EXPECT_THAT(test_vector, ElementsAreArray(a));
+
+  test_vector[2] = 0;
+  EXPECT_THAT(test_vector, Not(ElementsAreArray(a)));
+}
+
+TEST(ElementsAreArrayTest, CanBeCreatedWithArraySize) {
+  std::array<const char*, 3> a = {{"one", "two", "three"}};
+
+  vector<std::string> test_vector(std::begin(a), std::end(a));
+  EXPECT_THAT(test_vector, ElementsAreArray(a.data(), a.size()));
+
+  const char** p = a.data();
+  test_vector[0] = "1";
+  EXPECT_THAT(test_vector, Not(ElementsAreArray(p, a.size())));
+}
+
+TEST(ElementsAreArrayTest, CanBeCreatedWithoutArraySize) {
+  const char* a[] = {"one", "two", "three"};
+
+  vector<std::string> test_vector(std::begin(a), std::end(a));
+  EXPECT_THAT(test_vector, ElementsAreArray(a));
+
+  test_vector[0] = "1";
+  EXPECT_THAT(test_vector, Not(ElementsAreArray(a)));
+}
+
+TEST(ElementsAreArrayTest, CanBeCreatedWithMatcherArray) {
+  const Matcher<std::string> kMatcherArray[] = {StrEq("one"), StrEq("two"),
+                                                StrEq("three")};
+
+  vector<std::string> test_vector;
+  test_vector.push_back("one");
+  test_vector.push_back("two");
+  test_vector.push_back("three");
+  EXPECT_THAT(test_vector, ElementsAreArray(kMatcherArray));
+
+  test_vector.push_back("three");
+  EXPECT_THAT(test_vector, Not(ElementsAreArray(kMatcherArray)));
+}
+
+TEST(ElementsAreArrayTest, CanBeCreatedWithVector) {
+  const int a[] = {1, 2, 3};
+  vector<int> test_vector(std::begin(a), std::end(a));
+  const vector<int> expected(std::begin(a), std::end(a));
+  EXPECT_THAT(test_vector, ElementsAreArray(expected));
+  test_vector.push_back(4);
+  EXPECT_THAT(test_vector, Not(ElementsAreArray(expected)));
+}
+
+TEST(ElementsAreArrayTest, TakesInitializerList) {
+  const int a[5] = {1, 2, 3, 4, 5};
+  EXPECT_THAT(a, ElementsAreArray({1, 2, 3, 4, 5}));
+  EXPECT_THAT(a, Not(ElementsAreArray({1, 2, 3, 5, 4})));
+  EXPECT_THAT(a, Not(ElementsAreArray({1, 2, 3, 4, 6})));
+}
+
+TEST(ElementsAreArrayTest, TakesInitializerListOfCStrings) {
+  const std::string a[5] = {"a", "b", "c", "d", "e"};
+  EXPECT_THAT(a, ElementsAreArray({"a", "b", "c", "d", "e"}));
+  EXPECT_THAT(a, Not(ElementsAreArray({"a", "b", "c", "e", "d"})));
+  EXPECT_THAT(a, Not(ElementsAreArray({"a", "b", "c", "d", "ef"})));
+}
+
+TEST(ElementsAreArrayTest, TakesInitializerListOfSameTypedMatchers) {
+  const int a[5] = {1, 2, 3, 4, 5};
+  EXPECT_THAT(a, ElementsAreArray({Eq(1), Eq(2), Eq(3), Eq(4), Eq(5)}));
+  EXPECT_THAT(a, Not(ElementsAreArray({Eq(1), Eq(2), Eq(3), Eq(4), Eq(6)})));
+}
+
+TEST(ElementsAreArrayTest, TakesInitializerListOfDifferentTypedMatchers) {
+  const int a[5] = {1, 2, 3, 4, 5};
+  // The compiler cannot infer the type of the initializer list if its
+  // elements have different types.  We must explicitly specify the
+  // unified element type in this case.
+  EXPECT_THAT(
+      a, ElementsAreArray<Matcher<int>>({Eq(1), Ne(-2), Ge(3), Le(4), Eq(5)}));
+  EXPECT_THAT(a, Not(ElementsAreArray<Matcher<int>>(
+                     {Eq(1), Ne(-2), Ge(3), Le(4), Eq(6)})));
+}
+
+TEST(ElementsAreArrayTest, CanBeCreatedWithMatcherVector) {
+  const int a[] = {1, 2, 3};
+  const Matcher<int> kMatchers[] = {Eq(1), Eq(2), Eq(3)};
+  vector<int> test_vector(std::begin(a), std::end(a));
+  const vector<Matcher<int>> expected(std::begin(kMatchers),
+                                      std::end(kMatchers));
+  EXPECT_THAT(test_vector, ElementsAreArray(expected));
+  test_vector.push_back(4);
+  EXPECT_THAT(test_vector, Not(ElementsAreArray(expected)));
+}
+
+TEST(ElementsAreArrayTest, CanBeCreatedWithIteratorRange) {
+  const int a[] = {1, 2, 3};
+  const vector<int> test_vector(std::begin(a), std::end(a));
+  const vector<int> expected(std::begin(a), std::end(a));
+  EXPECT_THAT(test_vector, ElementsAreArray(expected.begin(), expected.end()));
+  // Pointers are iterators, too.
+  EXPECT_THAT(test_vector, ElementsAreArray(std::begin(a), std::end(a)));
+  // The empty range of NULL pointers should also be okay.
+  int* const null_int = nullptr;
+  EXPECT_THAT(test_vector, Not(ElementsAreArray(null_int, null_int)));
+  EXPECT_THAT((vector<int>()), ElementsAreArray(null_int, null_int));
+}
+
+// Since ElementsAre() and ElementsAreArray() share much of the
+// implementation, we only do a sanity test for native arrays here.
+TEST(ElementsAreArrayTest, WorksWithNativeArray) {
+  ::std::string a[] = {"hi", "ho"};
+  ::std::string b[] = {"hi", "ho"};
+
+  EXPECT_THAT(a, ElementsAreArray(b));
+  EXPECT_THAT(a, ElementsAreArray(b, 2));
+  EXPECT_THAT(a, Not(ElementsAreArray(b, 1)));
+}
+
+TEST(ElementsAreArrayTest, SourceLifeSpan) {
+  const int a[] = {1, 2, 3};
+  vector<int> test_vector(std::begin(a), std::end(a));
+  vector<int> expect(std::begin(a), std::end(a));
+  ElementsAreArrayMatcher<int> matcher_maker =
+      ElementsAreArray(expect.begin(), expect.end());
+  EXPECT_THAT(test_vector, matcher_maker);
+  // Changing in place the values that initialized matcher_maker should not
+  // affect matcher_maker anymore. It should have made its own copy of them.
+  for (int& i : expect) {
+    i += 10;
+  }
+  EXPECT_THAT(test_vector, matcher_maker);
+  test_vector.push_back(3);
+  EXPECT_THAT(test_vector, Not(matcher_maker));
+}
+
+// Tests for the MATCHER*() macro family.
+
+// Tests that a simple MATCHER() definition works.
+
+MATCHER(IsEven, "") { return (arg % 2) == 0; }
+
+TEST(MatcherMacroTest, Works) {
+  const Matcher<int> m = IsEven();
+  EXPECT_TRUE(m.Matches(6));
+  EXPECT_FALSE(m.Matches(7));
+
+  EXPECT_EQ("is even", Describe(m));
+  EXPECT_EQ("not (is even)", DescribeNegation(m));
+  EXPECT_EQ("", Explain(m, 6));
+  EXPECT_EQ("", Explain(m, 7));
+}
+
+// This also tests that the description string can reference 'negation'.
+MATCHER(IsEven2, negation ? "is odd" : "is even") {
+  if ((arg % 2) == 0) {
+    // Verifies that we can stream to result_listener, a listener
+    // supplied by the MATCHER macro implicitly.
+    *result_listener << "OK";
+    return true;
+  } else {
+    *result_listener << "% 2 == " << (arg % 2);
+    return false;
+  }
+}
+
+// This also tests that the description string can reference matcher
+// parameters.
+MATCHER_P2(EqSumOf, x, y,
+           std::string(negation ? "doesn't equal" : "equals") + " the sum of " +
+               PrintToString(x) + " and " + PrintToString(y)) {
+  if (arg == (x + y)) {
+    *result_listener << "OK";
+    return true;
+  } else {
+    // Verifies that we can stream to the underlying stream of
+    // result_listener.
+    if (result_listener->stream() != nullptr) {
+      *result_listener->stream() << "diff == " << (x + y - arg);
+    }
+    return false;
+  }
+}
+
+// Tests that the matcher description can reference 'negation' and the
+// matcher parameters.
+TEST(MatcherMacroTest, DescriptionCanReferenceNegationAndParameters) {
+  const Matcher<int> m1 = IsEven2();
+  EXPECT_EQ("is even", Describe(m1));
+  EXPECT_EQ("is odd", DescribeNegation(m1));
+
+  const Matcher<int> m2 = EqSumOf(5, 9);
+  EXPECT_EQ("equals the sum of 5 and 9", Describe(m2));
+  EXPECT_EQ("doesn't equal the sum of 5 and 9", DescribeNegation(m2));
+}
+
+// Tests explaining match result in a MATCHER* macro.
+TEST(MatcherMacroTest, CanExplainMatchResult) {
+  const Matcher<int> m1 = IsEven2();
+  EXPECT_EQ("OK", Explain(m1, 4));
+  EXPECT_EQ("% 2 == 1", Explain(m1, 5));
+
+  const Matcher<int> m2 = EqSumOf(1, 2);
+  EXPECT_EQ("OK", Explain(m2, 3));
+  EXPECT_EQ("diff == -1", Explain(m2, 4));
+}
+
+// Tests that the body of MATCHER() can reference the type of the
+// value being matched.
+
+MATCHER(IsEmptyString, "") {
+  StaticAssertTypeEq<::std::string, arg_type>();
+  return arg.empty();
+}
+
+MATCHER(IsEmptyStringByRef, "") {
+  StaticAssertTypeEq<const ::std::string&, arg_type>();
+  return arg.empty();
+}
+
+TEST(MatcherMacroTest, CanReferenceArgType) {
+  const Matcher<::std::string> m1 = IsEmptyString();
+  EXPECT_TRUE(m1.Matches(""));
+
+  const Matcher<const ::std::string&> m2 = IsEmptyStringByRef();
+  EXPECT_TRUE(m2.Matches(""));
+}
+
+// Tests that MATCHER() can be used in a namespace.
+
+namespace matcher_test {
+MATCHER(IsOdd, "") { return (arg % 2) != 0; }
+}  // namespace matcher_test
+
+TEST(MatcherMacroTest, WorksInNamespace) {
+  Matcher<int> m = matcher_test::IsOdd();
+  EXPECT_FALSE(m.Matches(4));
+  EXPECT_TRUE(m.Matches(5));
+}
+
+// Tests that Value() can be used to compose matchers.
+MATCHER(IsPositiveOdd, "") {
+  return Value(arg, matcher_test::IsOdd()) && arg > 0;
+}
+
+TEST(MatcherMacroTest, CanBeComposedUsingValue) {
+  EXPECT_THAT(3, IsPositiveOdd());
+  EXPECT_THAT(4, Not(IsPositiveOdd()));
+  EXPECT_THAT(-1, Not(IsPositiveOdd()));
+}
+
+// Tests that a simple MATCHER_P() definition works.
+
+MATCHER_P(IsGreaterThan32And, n, "") { return arg > 32 && arg > n; }
+
+TEST(MatcherPMacroTest, Works) {
+  const Matcher<int> m = IsGreaterThan32And(5);
+  EXPECT_TRUE(m.Matches(36));
+  EXPECT_FALSE(m.Matches(5));
+
+  EXPECT_EQ("is greater than 32 and 5", Describe(m));
+  EXPECT_EQ("not (is greater than 32 and 5)", DescribeNegation(m));
+  EXPECT_EQ("", Explain(m, 36));
+  EXPECT_EQ("", Explain(m, 5));
+}
+
+// Tests that the description is calculated correctly from the matcher name.
+MATCHER_P(_is_Greater_Than32and_, n, "") { return arg > 32 && arg > n; }
+
+TEST(MatcherPMacroTest, GeneratesCorrectDescription) {
+  const Matcher<int> m = _is_Greater_Than32and_(5);
+
+  EXPECT_EQ("is greater than 32 and 5", Describe(m));
+  EXPECT_EQ("not (is greater than 32 and 5)", DescribeNegation(m));
+  EXPECT_EQ("", Explain(m, 36));
+  EXPECT_EQ("", Explain(m, 5));
+}
+
+// Tests that a MATCHER_P matcher can be explicitly instantiated with
+// a reference parameter type.
+
+class UncopyableFoo {
+ public:
+  explicit UncopyableFoo(char value) : value_(value) { (void)value_; }
+
+  UncopyableFoo(const UncopyableFoo&) = delete;
+  void operator=(const UncopyableFoo&) = delete;
+
+ private:
+  char value_;
+};
+
+MATCHER_P(ReferencesUncopyable, variable, "") { return &arg == &variable; }
+
+TEST(MatcherPMacroTest, WorksWhenExplicitlyInstantiatedWithReference) {
+  UncopyableFoo foo1('1'), foo2('2');
+  const Matcher<const UncopyableFoo&> m =
+      ReferencesUncopyable<const UncopyableFoo&>(foo1);
+
+  EXPECT_TRUE(m.Matches(foo1));
+  EXPECT_FALSE(m.Matches(foo2));
+
+  // We don't want the address of the parameter printed, as most
+  // likely it will just annoy the user.  If the address is
+  // interesting, the user should consider passing the parameter by
+  // pointer instead.
+  EXPECT_EQ("references uncopyable 1-byte object <31>", Describe(m));
+}
+
+// Tests that the body of MATCHER_Pn() can reference the parameter
+// types.
+
+MATCHER_P3(ParamTypesAreIntLongAndChar, foo, bar, baz, "") {
+  StaticAssertTypeEq<int, foo_type>();
+  StaticAssertTypeEq<long, bar_type>();  // NOLINT
+  StaticAssertTypeEq<char, baz_type>();
+  return arg == 0;
+}
+
+TEST(MatcherPnMacroTest, CanReferenceParamTypes) {
+  EXPECT_THAT(0, ParamTypesAreIntLongAndChar(10, 20L, 'a'));
+}
+
+// Tests that a MATCHER_Pn matcher can be explicitly instantiated with
+// reference parameter types.
+
+MATCHER_P2(ReferencesAnyOf, variable1, variable2, "") {
+  return &arg == &variable1 || &arg == &variable2;
+}
+
+TEST(MatcherPnMacroTest, WorksWhenExplicitlyInstantiatedWithReferences) {
+  UncopyableFoo foo1('1'), foo2('2'), foo3('3');
+  const Matcher<const UncopyableFoo&> const_m =
+      ReferencesAnyOf<const UncopyableFoo&, const UncopyableFoo&>(foo1, foo2);
+
+  EXPECT_TRUE(const_m.Matches(foo1));
+  EXPECT_TRUE(const_m.Matches(foo2));
+  EXPECT_FALSE(const_m.Matches(foo3));
+
+  const Matcher<UncopyableFoo&> m =
+      ReferencesAnyOf<UncopyableFoo&, UncopyableFoo&>(foo1, foo2);
+
+  EXPECT_TRUE(m.Matches(foo1));
+  EXPECT_TRUE(m.Matches(foo2));
+  EXPECT_FALSE(m.Matches(foo3));
+}
+
+TEST(MatcherPnMacroTest,
+     GeneratesCorretDescriptionWhenExplicitlyInstantiatedWithReferences) {
+  UncopyableFoo foo1('1'), foo2('2');
+  const Matcher<const UncopyableFoo&> m =
+      ReferencesAnyOf<const UncopyableFoo&, const UncopyableFoo&>(foo1, foo2);
+
+  // We don't want the addresses of the parameters printed, as most
+  // likely they will just annoy the user.  If the addresses are
+  // interesting, the user should consider passing the parameters by
+  // pointers instead.
+  EXPECT_EQ("references any of (1-byte object <31>, 1-byte object <32>)",
+            Describe(m));
+}
+
+// Tests that a simple MATCHER_P2() definition works.
+
+MATCHER_P2(IsNotInClosedRange, low, hi, "") { return arg < low || arg > hi; }
+
+TEST(MatcherPnMacroTest, Works) {
+  const Matcher<const long&> m = IsNotInClosedRange(10, 20);  // NOLINT
+  EXPECT_TRUE(m.Matches(36L));
+  EXPECT_FALSE(m.Matches(15L));
+
+  EXPECT_EQ("is not in closed range (10, 20)", Describe(m));
+  EXPECT_EQ("not (is not in closed range (10, 20))", DescribeNegation(m));
+  EXPECT_EQ("", Explain(m, 36L));
+  EXPECT_EQ("", Explain(m, 15L));
+}
+
+// Tests that MATCHER*() definitions can be overloaded on the number
+// of parameters; also tests MATCHER_Pn() where n >= 3.
+
+MATCHER(EqualsSumOf, "") { return arg == 0; }
+MATCHER_P(EqualsSumOf, a, "") { return arg == a; }
+MATCHER_P2(EqualsSumOf, a, b, "") { return arg == a + b; }
+MATCHER_P3(EqualsSumOf, a, b, c, "") { return arg == a + b + c; }
+MATCHER_P4(EqualsSumOf, a, b, c, d, "") { return arg == a + b + c + d; }
+MATCHER_P5(EqualsSumOf, a, b, c, d, e, "") { return arg == a + b + c + d + e; }
+MATCHER_P6(EqualsSumOf, a, b, c, d, e, f, "") {
+  return arg == a + b + c + d + e + f;
+}
+MATCHER_P7(EqualsSumOf, a, b, c, d, e, f, g, "") {
+  return arg == a + b + c + d + e + f + g;
+}
+MATCHER_P8(EqualsSumOf, a, b, c, d, e, f, g, h, "") {
+  return arg == a + b + c + d + e + f + g + h;
+}
+MATCHER_P9(EqualsSumOf, a, b, c, d, e, f, g, h, i, "") {
+  return arg == a + b + c + d + e + f + g + h + i;
+}
+MATCHER_P10(EqualsSumOf, a, b, c, d, e, f, g, h, i, j, "") {
+  return arg == a + b + c + d + e + f + g + h + i + j;
+}
+
+TEST(MatcherPnMacroTest, CanBeOverloadedOnNumberOfParameters) {
+  EXPECT_THAT(0, EqualsSumOf());
+  EXPECT_THAT(1, EqualsSumOf(1));
+  EXPECT_THAT(12, EqualsSumOf(10, 2));
+  EXPECT_THAT(123, EqualsSumOf(100, 20, 3));
+  EXPECT_THAT(1234, EqualsSumOf(1000, 200, 30, 4));
+  EXPECT_THAT(12345, EqualsSumOf(10000, 2000, 300, 40, 5));
+  EXPECT_THAT("abcdef",
+              EqualsSumOf(::std::string("a"), 'b', 'c', "d", "e", 'f'));
+  EXPECT_THAT("abcdefg",
+              EqualsSumOf(::std::string("a"), 'b', 'c', "d", "e", 'f', 'g'));
+  EXPECT_THAT("abcdefgh", EqualsSumOf(::std::string("a"), 'b', 'c', "d", "e",
+                                      'f', 'g', "h"));
+  EXPECT_THAT("abcdefghi", EqualsSumOf(::std::string("a"), 'b', 'c', "d", "e",
+                                       'f', 'g', "h", 'i'));
+  EXPECT_THAT("abcdefghij",
+              EqualsSumOf(::std::string("a"), 'b', 'c', "d", "e", 'f', 'g', "h",
+                          'i', ::std::string("j")));
+
+  EXPECT_THAT(1, Not(EqualsSumOf()));
+  EXPECT_THAT(-1, Not(EqualsSumOf(1)));
+  EXPECT_THAT(-12, Not(EqualsSumOf(10, 2)));
+  EXPECT_THAT(-123, Not(EqualsSumOf(100, 20, 3)));
+  EXPECT_THAT(-1234, Not(EqualsSumOf(1000, 200, 30, 4)));
+  EXPECT_THAT(-12345, Not(EqualsSumOf(10000, 2000, 300, 40, 5)));
+  EXPECT_THAT("abcdef ",
+              Not(EqualsSumOf(::std::string("a"), 'b', 'c', "d", "e", 'f')));
+  EXPECT_THAT("abcdefg ", Not(EqualsSumOf(::std::string("a"), 'b', 'c', "d",
+                                          "e", 'f', 'g')));
+  EXPECT_THAT("abcdefgh ", Not(EqualsSumOf(::std::string("a"), 'b', 'c', "d",
+                                           "e", 'f', 'g', "h")));
+  EXPECT_THAT("abcdefghi ", Not(EqualsSumOf(::std::string("a"), 'b', 'c', "d",
+                                            "e", 'f', 'g', "h", 'i')));
+  EXPECT_THAT("abcdefghij ",
+              Not(EqualsSumOf(::std::string("a"), 'b', 'c', "d", "e", 'f', 'g',
+                              "h", 'i', ::std::string("j"))));
+}
+
+// Tests that a MATCHER_Pn() definition can be instantiated with any
+// compatible parameter types.
+TEST(MatcherPnMacroTest, WorksForDifferentParameterTypes) {
+  EXPECT_THAT(123, EqualsSumOf(100L, 20, static_cast<char>(3)));
+  EXPECT_THAT("abcd", EqualsSumOf(::std::string("a"), "b", 'c', "d"));
+
+  EXPECT_THAT(124, Not(EqualsSumOf(100L, 20, static_cast<char>(3))));
+  EXPECT_THAT("abcde", Not(EqualsSumOf(::std::string("a"), "b", 'c', "d")));
+}
+
+// Tests that the matcher body can promote the parameter types.
+
+MATCHER_P2(EqConcat, prefix, suffix, "") {
+  // The following lines promote the two parameters to desired types.
+  std::string prefix_str(prefix);
+  char suffix_char = static_cast<char>(suffix);
+  return arg == prefix_str + suffix_char;
+}
+
+TEST(MatcherPnMacroTest, SimpleTypePromotion) {
+  Matcher<std::string> no_promo = EqConcat(std::string("foo"), 't');
+  Matcher<const std::string&> promo = EqConcat("foo", static_cast<int>('t'));
+  EXPECT_FALSE(no_promo.Matches("fool"));
+  EXPECT_FALSE(promo.Matches("fool"));
+  EXPECT_TRUE(no_promo.Matches("foot"));
+  EXPECT_TRUE(promo.Matches("foot"));
+}
+
+// Verifies the type of a MATCHER*.
+
+TEST(MatcherPnMacroTest, TypesAreCorrect) {
+  // EqualsSumOf() must be assignable to a EqualsSumOfMatcher variable.
+  EqualsSumOfMatcher a0 = EqualsSumOf();
+
+  // EqualsSumOf(1) must be assignable to a EqualsSumOfMatcherP variable.
+  EqualsSumOfMatcherP<int> a1 = EqualsSumOf(1);
+
+  // EqualsSumOf(p1, ..., pk) must be assignable to a EqualsSumOfMatcherPk
+  // variable, and so on.
+  EqualsSumOfMatcherP2<int, char> a2 = EqualsSumOf(1, '2');
+  EqualsSumOfMatcherP3<int, int, char> a3 = EqualsSumOf(1, 2, '3');
+  EqualsSumOfMatcherP4<int, int, int, char> a4 = EqualsSumOf(1, 2, 3, '4');
+  EqualsSumOfMatcherP5<int, int, int, int, char> a5 =
+      EqualsSumOf(1, 2, 3, 4, '5');
+  EqualsSumOfMatcherP6<int, int, int, int, int, char> a6 =
+      EqualsSumOf(1, 2, 3, 4, 5, '6');
+  EqualsSumOfMatcherP7<int, int, int, int, int, int, char> a7 =
+      EqualsSumOf(1, 2, 3, 4, 5, 6, '7');
+  EqualsSumOfMatcherP8<int, int, int, int, int, int, int, char> a8 =
+      EqualsSumOf(1, 2, 3, 4, 5, 6, 7, '8');
+  EqualsSumOfMatcherP9<int, int, int, int, int, int, int, int, char> a9 =
+      EqualsSumOf(1, 2, 3, 4, 5, 6, 7, 8, '9');
+  EqualsSumOfMatcherP10<int, int, int, int, int, int, int, int, int, char> a10 =
+      EqualsSumOf(1, 2, 3, 4, 5, 6, 7, 8, 9, '0');
+
+  // Avoid "unused variable" warnings.
+  (void)a0;
+  (void)a1;
+  (void)a2;
+  (void)a3;
+  (void)a4;
+  (void)a5;
+  (void)a6;
+  (void)a7;
+  (void)a8;
+  (void)a9;
+  (void)a10;
+}
+
+// Tests that matcher-typed parameters can be used in Value() inside a
+// MATCHER_Pn definition.
+
+// Succeeds if arg matches exactly 2 of the 3 matchers.
+MATCHER_P3(TwoOf, m1, m2, m3, "") {
+  const int count = static_cast<int>(Value(arg, m1)) +
+                    static_cast<int>(Value(arg, m2)) +
+                    static_cast<int>(Value(arg, m3));
+  return count == 2;
+}
+
+TEST(MatcherPnMacroTest, CanUseMatcherTypedParameterInValue) {
+  EXPECT_THAT(42, TwoOf(Gt(0), Lt(50), Eq(10)));
+  EXPECT_THAT(0, Not(TwoOf(Gt(-1), Lt(1), Eq(0))));
+}
+
+// Tests Contains().
+
+TEST(ContainsTest, ListMatchesWhenElementIsInContainer) {
+  list<int> some_list;
+  some_list.push_back(3);
+  some_list.push_back(1);
+  some_list.push_back(2);
+  EXPECT_THAT(some_list, Contains(1));
+  EXPECT_THAT(some_list, Contains(Gt(2.5)));
+  EXPECT_THAT(some_list, Contains(Eq(2.0f)));
+
+  list<std::string> another_list;
+  another_list.push_back("fee");
+  another_list.push_back("fie");
+  another_list.push_back("foe");
+  another_list.push_back("fum");
+  EXPECT_THAT(another_list, Contains(std::string("fee")));
+}
+
+TEST(ContainsTest, ListDoesNotMatchWhenElementIsNotInContainer) {
+  list<int> some_list;
+  some_list.push_back(3);
+  some_list.push_back(1);
+  EXPECT_THAT(some_list, Not(Contains(4)));
+}
+
+TEST(ContainsTest, SetMatchesWhenElementIsInContainer) {
+  set<int> some_set;
+  some_set.insert(3);
+  some_set.insert(1);
+  some_set.insert(2);
+  EXPECT_THAT(some_set, Contains(Eq(1.0)));
+  EXPECT_THAT(some_set, Contains(Eq(3.0f)));
+  EXPECT_THAT(some_set, Contains(2));
+
+  set<std::string> another_set;
+  another_set.insert("fee");
+  another_set.insert("fie");
+  another_set.insert("foe");
+  another_set.insert("fum");
+  EXPECT_THAT(another_set, Contains(Eq(std::string("fum"))));
+}
+
+TEST(ContainsTest, SetDoesNotMatchWhenElementIsNotInContainer) {
+  set<int> some_set;
+  some_set.insert(3);
+  some_set.insert(1);
+  EXPECT_THAT(some_set, Not(Contains(4)));
+
+  set<std::string> c_string_set;
+  c_string_set.insert("hello");
+  EXPECT_THAT(c_string_set, Not(Contains(std::string("goodbye"))));
+}
+
+TEST(ContainsTest, ExplainsMatchResultCorrectly) {
+  const int a[2] = {1, 2};
+  Matcher<const int(&)[2]> m = Contains(2);
+  EXPECT_EQ("whose element #1 matches", Explain(m, a));
+
+  m = Contains(3);
+  EXPECT_EQ("", Explain(m, a));
+
+  m = Contains(GreaterThan(0));
+  EXPECT_EQ("whose element #0 matches, which is 1 more than 0", Explain(m, a));
+
+  m = Contains(GreaterThan(10));
+  EXPECT_EQ("", Explain(m, a));
+}
+
+TEST(ContainsTest, DescribesItselfCorrectly) {
+  Matcher<vector<int>> m = Contains(1);
+  EXPECT_EQ("contains at least one element that is equal to 1", Describe(m));
+
+  Matcher<vector<int>> m2 = Not(m);
+  EXPECT_EQ("doesn't contain any element that is equal to 1", Describe(m2));
+}
+
+TEST(ContainsTest, MapMatchesWhenElementIsInContainer) {
+  map<std::string, int> my_map;
+  const char* bar = "a string";
+  my_map[bar] = 2;
+  EXPECT_THAT(my_map, Contains(pair<const char* const, int>(bar, 2)));
+
+  map<std::string, int> another_map;
+  another_map["fee"] = 1;
+  another_map["fie"] = 2;
+  another_map["foe"] = 3;
+  another_map["fum"] = 4;
+  EXPECT_THAT(another_map,
+              Contains(pair<const std::string, int>(std::string("fee"), 1)));
+  EXPECT_THAT(another_map, Contains(pair<const std::string, int>("fie", 2)));
+}
+
+TEST(ContainsTest, MapDoesNotMatchWhenElementIsNotInContainer) {
+  map<int, int> some_map;
+  some_map[1] = 11;
+  some_map[2] = 22;
+  EXPECT_THAT(some_map, Not(Contains(pair<const int, int>(2, 23))));
+}
+
+TEST(ContainsTest, ArrayMatchesWhenElementIsInContainer) {
+  const char* string_array[] = {"fee", "fie", "foe", "fum"};
+  EXPECT_THAT(string_array, Contains(Eq(std::string("fum"))));
+}
+
+TEST(ContainsTest, ArrayDoesNotMatchWhenElementIsNotInContainer) {
+  int int_array[] = {1, 2, 3, 4};
+  EXPECT_THAT(int_array, Not(Contains(5)));
+}
+
+TEST(ContainsTest, AcceptsMatcher) {
+  const int a[] = {1, 2, 3};
+  EXPECT_THAT(a, Contains(Gt(2)));
+  EXPECT_THAT(a, Not(Contains(Gt(4))));
+}
+
+TEST(ContainsTest, WorksForNativeArrayAsTuple) {
+  const int a[] = {1, 2};
+  const int* const pointer = a;
+  EXPECT_THAT(std::make_tuple(pointer, 2), Contains(1));
+  EXPECT_THAT(std::make_tuple(pointer, 2), Not(Contains(Gt(3))));
+}
+
+TEST(ContainsTest, WorksForTwoDimensionalNativeArray) {
+  int a[][3] = {{1, 2, 3}, {4, 5, 6}};
+  EXPECT_THAT(a, Contains(ElementsAre(4, 5, 6)));
+  EXPECT_THAT(a, Contains(Contains(5)));
+  EXPECT_THAT(a, Not(Contains(ElementsAre(3, 4, 5))));
+  EXPECT_THAT(a, Contains(Not(Contains(5))));
+}
+
+TEST(AllOfArrayTest, BasicForms) {
+  // Iterator
+  std::vector<int> v0{};
+  std::vector<int> v1{1};
+  std::vector<int> v2{2, 3};
+  std::vector<int> v3{4, 4, 4};
+  EXPECT_THAT(0, AllOfArray(v0.begin(), v0.end()));
+  EXPECT_THAT(1, AllOfArray(v1.begin(), v1.end()));
+  EXPECT_THAT(2, Not(AllOfArray(v1.begin(), v1.end())));
+  EXPECT_THAT(3, Not(AllOfArray(v2.begin(), v2.end())));
+  EXPECT_THAT(4, AllOfArray(v3.begin(), v3.end()));
+  // Pointer +  size
+  int ar[6] = {1, 2, 3, 4, 4, 4};
+  EXPECT_THAT(0, AllOfArray(ar, 0));
+  EXPECT_THAT(1, AllOfArray(ar, 1));
+  EXPECT_THAT(2, Not(AllOfArray(ar, 1)));
+  EXPECT_THAT(3, Not(AllOfArray(ar + 1, 3)));
+  EXPECT_THAT(4, AllOfArray(ar + 3, 3));
+  // Array
+  // int ar0[0];  Not usable
+  int ar1[1] = {1};
+  int ar2[2] = {2, 3};
+  int ar3[3] = {4, 4, 4};
+  // EXPECT_THAT(0, Not(AllOfArray(ar0)));  // Cannot work
+  EXPECT_THAT(1, AllOfArray(ar1));
+  EXPECT_THAT(2, Not(AllOfArray(ar1)));
+  EXPECT_THAT(3, Not(AllOfArray(ar2)));
+  EXPECT_THAT(4, AllOfArray(ar3));
+  // Container
+  EXPECT_THAT(0, AllOfArray(v0));
+  EXPECT_THAT(1, AllOfArray(v1));
+  EXPECT_THAT(2, Not(AllOfArray(v1)));
+  EXPECT_THAT(3, Not(AllOfArray(v2)));
+  EXPECT_THAT(4, AllOfArray(v3));
+  // Initializer
+  EXPECT_THAT(0, AllOfArray<int>({}));  // Requires template arg.
+  EXPECT_THAT(1, AllOfArray({1}));
+  EXPECT_THAT(2, Not(AllOfArray({1})));
+  EXPECT_THAT(3, Not(AllOfArray({2, 3})));
+  EXPECT_THAT(4, AllOfArray({4, 4, 4}));
+}
+
+TEST(AllOfArrayTest, Matchers) {
+  // vector
+  std::vector<Matcher<int>> matchers{Ge(1), Lt(2)};
+  EXPECT_THAT(0, Not(AllOfArray(matchers)));
+  EXPECT_THAT(1, AllOfArray(matchers));
+  EXPECT_THAT(2, Not(AllOfArray(matchers)));
+  // initializer_list
+  EXPECT_THAT(0, Not(AllOfArray({Ge(0), Ge(1)})));
+  EXPECT_THAT(1, AllOfArray({Ge(0), Ge(1)}));
+}
+
+TEST(AnyOfArrayTest, BasicForms) {
+  // Iterator
+  std::vector<int> v0{};
+  std::vector<int> v1{1};
+  std::vector<int> v2{2, 3};
+  EXPECT_THAT(0, Not(AnyOfArray(v0.begin(), v0.end())));
+  EXPECT_THAT(1, AnyOfArray(v1.begin(), v1.end()));
+  EXPECT_THAT(2, Not(AnyOfArray(v1.begin(), v1.end())));
+  EXPECT_THAT(3, AnyOfArray(v2.begin(), v2.end()));
+  EXPECT_THAT(4, Not(AnyOfArray(v2.begin(), v2.end())));
+  // Pointer +  size
+  int ar[3] = {1, 2, 3};
+  EXPECT_THAT(0, Not(AnyOfArray(ar, 0)));
+  EXPECT_THAT(1, AnyOfArray(ar, 1));
+  EXPECT_THAT(2, Not(AnyOfArray(ar, 1)));
+  EXPECT_THAT(3, AnyOfArray(ar + 1, 2));
+  EXPECT_THAT(4, Not(AnyOfArray(ar + 1, 2)));
+  // Array
+  // int ar0[0];  Not usable
+  int ar1[1] = {1};
+  int ar2[2] = {2, 3};
+  // EXPECT_THAT(0, Not(AnyOfArray(ar0)));  // Cannot work
+  EXPECT_THAT(1, AnyOfArray(ar1));
+  EXPECT_THAT(2, Not(AnyOfArray(ar1)));
+  EXPECT_THAT(3, AnyOfArray(ar2));
+  EXPECT_THAT(4, Not(AnyOfArray(ar2)));
+  // Container
+  EXPECT_THAT(0, Not(AnyOfArray(v0)));
+  EXPECT_THAT(1, AnyOfArray(v1));
+  EXPECT_THAT(2, Not(AnyOfArray(v1)));
+  EXPECT_THAT(3, AnyOfArray(v2));
+  EXPECT_THAT(4, Not(AnyOfArray(v2)));
+  // Initializer
+  EXPECT_THAT(0, Not(AnyOfArray<int>({})));  // Requires template arg.
+  EXPECT_THAT(1, AnyOfArray({1}));
+  EXPECT_THAT(2, Not(AnyOfArray({1})));
+  EXPECT_THAT(3, AnyOfArray({2, 3}));
+  EXPECT_THAT(4, Not(AnyOfArray({2, 3})));
+}
+
+TEST(AnyOfArrayTest, Matchers) {
+  // We negate test AllOfArrayTest.Matchers.
+  // vector
+  std::vector<Matcher<int>> matchers{Lt(1), Ge(2)};
+  EXPECT_THAT(0, AnyOfArray(matchers));
+  EXPECT_THAT(1, Not(AnyOfArray(matchers)));
+  EXPECT_THAT(2, AnyOfArray(matchers));
+  // initializer_list
+  EXPECT_THAT(0, AnyOfArray({Lt(0), Lt(1)}));
+  EXPECT_THAT(1, Not(AllOfArray({Lt(0), Lt(1)})));
+}
+
+TEST(AnyOfArrayTest, ExplainsMatchResultCorrectly) {
+  // AnyOfArray and AllOfArry use the same underlying template-template,
+  // thus it is sufficient to test one here.
+  const std::vector<int> v0{};
+  const std::vector<int> v1{1};
+  const std::vector<int> v2{2, 3};
+  const Matcher<int> m0 = AnyOfArray(v0);
+  const Matcher<int> m1 = AnyOfArray(v1);
+  const Matcher<int> m2 = AnyOfArray(v2);
+  EXPECT_EQ("", Explain(m0, 0));
+  EXPECT_EQ("", Explain(m1, 1));
+  EXPECT_EQ("", Explain(m1, 2));
+  EXPECT_EQ("", Explain(m2, 3));
+  EXPECT_EQ("", Explain(m2, 4));
+  EXPECT_EQ("()", Describe(m0));
+  EXPECT_EQ("(is equal to 1)", Describe(m1));
+  EXPECT_EQ("(is equal to 2) or (is equal to 3)", Describe(m2));
+  EXPECT_EQ("()", DescribeNegation(m0));
+  EXPECT_EQ("(isn't equal to 1)", DescribeNegation(m1));
+  EXPECT_EQ("(isn't equal to 2) and (isn't equal to 3)", DescribeNegation(m2));
+  // Explain with matchers
+  const Matcher<int> g1 = AnyOfArray({GreaterThan(1)});
+  const Matcher<int> g2 = AnyOfArray({GreaterThan(1), GreaterThan(2)});
+  // Explains the first positiv match and all prior negative matches...
+  EXPECT_EQ("which is 1 less than 1", Explain(g1, 0));
+  EXPECT_EQ("which is the same as 1", Explain(g1, 1));
+  EXPECT_EQ("which is 1 more than 1", Explain(g1, 2));
+  EXPECT_EQ("which is 1 less than 1, and which is 2 less than 2",
+            Explain(g2, 0));
+  EXPECT_EQ("which is the same as 1, and which is 1 less than 2",
+            Explain(g2, 1));
+  EXPECT_EQ("which is 1 more than 1",  // Only the first
+            Explain(g2, 2));
+}
+
+TEST(AllOfTest, HugeMatcher) {
+  // Verify that using AllOf with many arguments doesn't cause
+  // the compiler to exceed template instantiation depth limit.
+  EXPECT_THAT(0, testing::AllOf(_, _, _, _, _, _, _, _, _,
+                                testing::AllOf(_, _, _, _, _, _, _, _, _, _)));
+}
+
+TEST(AnyOfTest, HugeMatcher) {
+  // Verify that using AnyOf with many arguments doesn't cause
+  // the compiler to exceed template instantiation depth limit.
+  EXPECT_THAT(0, testing::AnyOf(_, _, _, _, _, _, _, _, _,
+                                testing::AnyOf(_, _, _, _, _, _, _, _, _, _)));
+}
+
+namespace adl_test {
+
+// Verifies that the implementation of ::testing::AllOf and ::testing::AnyOf
+// don't issue unqualified recursive calls.  If they do, the argument dependent
+// name lookup will cause AllOf/AnyOf in the 'adl_test' namespace to be found
+// as a candidate and the compilation will break due to an ambiguous overload.
+
+// The matcher must be in the same namespace as AllOf/AnyOf to make argument
+// dependent lookup find those.
+MATCHER(M, "") {
+  (void)arg;
+  return true;
+}
+
+template <typename T1, typename T2>
+bool AllOf(const T1& /*t1*/, const T2& /*t2*/) {
+  return true;
+}
+
+TEST(AllOfTest, DoesNotCallAllOfUnqualified) {
+  EXPECT_THAT(42,
+              testing::AllOf(M(), M(), M(), M(), M(), M(), M(), M(), M(), M()));
+}
+
+template <typename T1, typename T2>
+bool AnyOf(const T1&, const T2&) {
+  return true;
+}
+
+TEST(AnyOfTest, DoesNotCallAnyOfUnqualified) {
+  EXPECT_THAT(42,
+              testing::AnyOf(M(), M(), M(), M(), M(), M(), M(), M(), M(), M()));
+}
+
+}  // namespace adl_test
+
+TEST(AllOfTest, WorksOnMoveOnlyType) {
+  std::unique_ptr<int> p(new int(3));
+  EXPECT_THAT(p, AllOf(Pointee(Eq(3)), Pointee(Gt(0)), Pointee(Lt(5))));
+  EXPECT_THAT(p, Not(AllOf(Pointee(Eq(3)), Pointee(Gt(0)), Pointee(Lt(3)))));
+}
+
+TEST(AnyOfTest, WorksOnMoveOnlyType) {
+  std::unique_ptr<int> p(new int(3));
+  EXPECT_THAT(p, AnyOf(Pointee(Eq(5)), Pointee(Lt(0)), Pointee(Lt(5))));
+  EXPECT_THAT(p, Not(AnyOf(Pointee(Eq(5)), Pointee(Lt(0)), Pointee(Gt(5)))));
+}
+
+MATCHER(IsNotNull, "") { return arg != nullptr; }
+
+// Verifies that a matcher defined using MATCHER() can work on
+// move-only types.
+TEST(MatcherMacroTest, WorksOnMoveOnlyType) {
+  std::unique_ptr<int> p(new int(3));
+  EXPECT_THAT(p, IsNotNull());
+  EXPECT_THAT(std::unique_ptr<int>(), Not(IsNotNull()));
+}
+
+MATCHER_P(UniquePointee, pointee, "") { return *arg == pointee; }
+
+// Verifies that a matcher defined using MATCHER_P*() can work on
+// move-only types.
+TEST(MatcherPMacroTest, WorksOnMoveOnlyType) {
+  std::unique_ptr<int> p(new int(3));
+  EXPECT_THAT(p, UniquePointee(3));
+  EXPECT_THAT(p, Not(UniquePointee(2)));
+}
+
+#if GTEST_HAS_EXCEPTIONS
+
+// std::function<void()> is used below for compatibility with older copies of
+// GCC. Normally, a raw lambda is all that is needed.
+
+// Test that examples from documentation compile
+TEST(ThrowsTest, Examples) {
+  EXPECT_THAT(
+      std::function<void()>([]() { throw std::runtime_error("message"); }),
+      Throws<std::runtime_error>());
+
+  EXPECT_THAT(
+      std::function<void()>([]() { throw std::runtime_error("message"); }),
+      ThrowsMessage<std::runtime_error>(HasSubstr("message")));
+}
+
+TEST(ThrowsTest, DoesNotGenerateDuplicateCatchClauseWarning) {
+  EXPECT_THAT(std::function<void()>([]() { throw std::exception(); }),
+              Throws<std::exception>());
+}
+
+TEST(ThrowsTest, CallableExecutedExactlyOnce) {
+  size_t a = 0;
+
+  EXPECT_THAT(std::function<void()>([&a]() {
+                a++;
+                throw 10;
+              }),
+              Throws<int>());
+  EXPECT_EQ(a, 1u);
+
+  EXPECT_THAT(std::function<void()>([&a]() {
+                a++;
+                throw std::runtime_error("message");
+              }),
+              Throws<std::runtime_error>());
+  EXPECT_EQ(a, 2u);
+
+  EXPECT_THAT(std::function<void()>([&a]() {
+                a++;
+                throw std::runtime_error("message");
+              }),
+              ThrowsMessage<std::runtime_error>(HasSubstr("message")));
+  EXPECT_EQ(a, 3u);
+
+  EXPECT_THAT(std::function<void()>([&a]() {
+                a++;
+                throw std::runtime_error("message");
+              }),
+              Throws<std::runtime_error>(
+                  Property(&std::runtime_error::what, HasSubstr("message"))));
+  EXPECT_EQ(a, 4u);
+}
+
+TEST(ThrowsTest, Describe) {
+  Matcher<std::function<void()>> matcher = Throws<std::runtime_error>();
+  std::stringstream ss;
+  matcher.DescribeTo(&ss);
+  auto explanation = ss.str();
+  EXPECT_THAT(explanation, HasSubstr("std::runtime_error"));
+}
+
+TEST(ThrowsTest, Success) {
+  Matcher<std::function<void()>> matcher = Throws<std::runtime_error>();
+  StringMatchResultListener listener;
+  EXPECT_TRUE(matcher.MatchAndExplain(
+      []() { throw std::runtime_error("error message"); }, &listener));
+  EXPECT_THAT(listener.str(), HasSubstr("std::runtime_error"));
+}
+
+TEST(ThrowsTest, FailWrongType) {
+  Matcher<std::function<void()>> matcher = Throws<std::runtime_error>();
+  StringMatchResultListener listener;
+  EXPECT_FALSE(matcher.MatchAndExplain(
+      []() { throw std::logic_error("error message"); }, &listener));
+  EXPECT_THAT(listener.str(), HasSubstr("std::logic_error"));
+  EXPECT_THAT(listener.str(), HasSubstr("\"error message\""));
+}
+
+TEST(ThrowsTest, FailWrongTypeNonStd) {
+  Matcher<std::function<void()>> matcher = Throws<std::runtime_error>();
+  StringMatchResultListener listener;
+  EXPECT_FALSE(matcher.MatchAndExplain([]() { throw 10; }, &listener));
+  EXPECT_THAT(listener.str(),
+              HasSubstr("throws an exception of an unknown type"));
+}
+
+TEST(ThrowsTest, FailNoThrow) {
+  Matcher<std::function<void()>> matcher = Throws<std::runtime_error>();
+  StringMatchResultListener listener;
+  EXPECT_FALSE(matcher.MatchAndExplain([]() { (void)0; }, &listener));
+  EXPECT_THAT(listener.str(), HasSubstr("does not throw any exception"));
+}
+
+class ThrowsPredicateTest
+    : public TestWithParam<Matcher<std::function<void()>>> {};
+
+TEST_P(ThrowsPredicateTest, Describe) {
+  Matcher<std::function<void()>> matcher = GetParam();
+  std::stringstream ss;
+  matcher.DescribeTo(&ss);
+  auto explanation = ss.str();
+  EXPECT_THAT(explanation, HasSubstr("std::runtime_error"));
+  EXPECT_THAT(explanation, HasSubstr("error message"));
+}
+
+TEST_P(ThrowsPredicateTest, Success) {
+  Matcher<std::function<void()>> matcher = GetParam();
+  StringMatchResultListener listener;
+  EXPECT_TRUE(matcher.MatchAndExplain(
+      []() { throw std::runtime_error("error message"); }, &listener));
+  EXPECT_THAT(listener.str(), HasSubstr("std::runtime_error"));
+}
+
+TEST_P(ThrowsPredicateTest, FailWrongType) {
+  Matcher<std::function<void()>> matcher = GetParam();
+  StringMatchResultListener listener;
+  EXPECT_FALSE(matcher.MatchAndExplain(
+      []() { throw std::logic_error("error message"); }, &listener));
+  EXPECT_THAT(listener.str(), HasSubstr("std::logic_error"));
+  EXPECT_THAT(listener.str(), HasSubstr("\"error message\""));
+}
+
+TEST_P(ThrowsPredicateTest, FailWrongTypeNonStd) {
+  Matcher<std::function<void()>> matcher = GetParam();
+  StringMatchResultListener listener;
+  EXPECT_FALSE(matcher.MatchAndExplain([]() { throw 10; }, &listener));
+  EXPECT_THAT(listener.str(),
+              HasSubstr("throws an exception of an unknown type"));
+}
+
+TEST_P(ThrowsPredicateTest, FailWrongMessage) {
+  Matcher<std::function<void()>> matcher = GetParam();
+  StringMatchResultListener listener;
+  EXPECT_FALSE(matcher.MatchAndExplain(
+      []() { throw std::runtime_error("wrong message"); }, &listener));
+  EXPECT_THAT(listener.str(), HasSubstr("std::runtime_error"));
+  EXPECT_THAT(listener.str(), Not(HasSubstr("wrong message")));
+}
+
+TEST_P(ThrowsPredicateTest, FailNoThrow) {
+  Matcher<std::function<void()>> matcher = GetParam();
+  StringMatchResultListener listener;
+  EXPECT_FALSE(matcher.MatchAndExplain([]() {}, &listener));
+  EXPECT_THAT(listener.str(), HasSubstr("does not throw any exception"));
+}
+
+INSTANTIATE_TEST_SUITE_P(
+    AllMessagePredicates, ThrowsPredicateTest,
+    Values(Matcher<std::function<void()>>(
+        ThrowsMessage<std::runtime_error>(HasSubstr("error message")))));
+
+// Tests that Throws<E1>(Matcher<E2>{}) compiles even when E2 != const E1&.
+TEST(ThrowsPredicateCompilesTest, ExceptionMatcherAcceptsBroadType) {
+  {
+    Matcher<std::function<void()>> matcher =
+        ThrowsMessage<std::runtime_error>(HasSubstr("error message"));
+    EXPECT_TRUE(
+        matcher.Matches([]() { throw std::runtime_error("error message"); }));
+    EXPECT_FALSE(
+        matcher.Matches([]() { throw std::runtime_error("wrong message"); }));
+  }
+
+  {
+    Matcher<uint64_t> inner = Eq(10);
+    Matcher<std::function<void()>> matcher = Throws<uint32_t>(inner);
+    EXPECT_TRUE(matcher.Matches([]() { throw(uint32_t) 10; }));
+    EXPECT_FALSE(matcher.Matches([]() { throw(uint32_t) 11; }));
+  }
+}
+
+// Tests that ThrowsMessage("message") is equivalent
+// to ThrowsMessage(Eq<std::string>("message")).
+TEST(ThrowsPredicateCompilesTest, MessageMatcherAcceptsNonMatcher) {
+  Matcher<std::function<void()>> matcher =
+      ThrowsMessage<std::runtime_error>("error message");
+  EXPECT_TRUE(
+      matcher.Matches([]() { throw std::runtime_error("error message"); }));
+  EXPECT_FALSE(matcher.Matches(
+      []() { throw std::runtime_error("wrong error message"); }));
+}
+
+#endif  // GTEST_HAS_EXCEPTIONS
+
+}  // namespace
+}  // namespace gmock_matchers_test
+}  // namespace testing
+
+#ifdef _MSC_VER
+# pragma warning(pop)
+#endif
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock-more-actions_test.cc b/leveldb_base/third_party/googletest/googlemock/test/gmock-more-actions_test.cc
new file mode 100644
index 0000000..53bb029
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock-more-actions_test.cc
@@ -0,0 +1,1547 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests the built-in actions in gmock-actions.h.
+
+#ifdef _MSC_VER
+#pragma warning(push)
+#pragma warning(disable : 4577)
+#endif
+
+#include "gmock/gmock-more-actions.h"
+
+#include <functional>
+#include <memory>
+#include <sstream>
+#include <string>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest-spi.h"
+#include "gtest/gtest.h"
+
+namespace testing {
+namespace gmock_more_actions_test {
+
+using ::std::plus;
+using ::std::string;
+using testing::Action;
+using testing::DeleteArg;
+using testing::Invoke;
+using testing::ReturnArg;
+using testing::ReturnPointee;
+using testing::SaveArg;
+using testing::SaveArgPointee;
+using testing::SetArgReferee;
+using testing::Unused;
+using testing::WithArg;
+using testing::WithoutArgs;
+
+// For suppressing compiler warnings on conversion possibly losing precision.
+inline short Short(short n) { return n; }  // NOLINT
+inline char Char(char ch) { return ch; }
+
+// Sample functions and functors for testing Invoke() and etc.
+int Nullary() { return 1; }
+
+bool g_done = false;
+
+bool Unary(int x) { return x < 0; }
+
+bool ByConstRef(const std::string& s) { return s == "Hi"; }
+
+const double g_double = 0;
+bool ReferencesGlobalDouble(const double& x) { return &x == &g_double; }
+
+struct UnaryFunctor {
+  int operator()(bool x) { return x ? 1 : -1; }
+};
+
+const char* Binary(const char* input, short n) { return input + n; }  // NOLINT
+
+int Ternary(int x, char y, short z) { return x + y + z; }  // NOLINT
+
+int SumOf4(int a, int b, int c, int d) { return a + b + c + d; }
+
+int SumOfFirst2(int a, int b, Unused, Unused) { return a + b; }
+
+int SumOf5(int a, int b, int c, int d, int e) { return a + b + c + d + e; }
+
+struct SumOf5Functor {
+  int operator()(int a, int b, int c, int d, int e) {
+    return a + b + c + d + e;
+  }
+};
+
+int SumOf6(int a, int b, int c, int d, int e, int f) {
+  return a + b + c + d + e + f;
+}
+
+struct SumOf6Functor {
+  int operator()(int a, int b, int c, int d, int e, int f) {
+    return a + b + c + d + e + f;
+  }
+};
+
+std::string Concat7(const char* s1, const char* s2, const char* s3,
+                    const char* s4, const char* s5, const char* s6,
+                    const char* s7) {
+  return std::string(s1) + s2 + s3 + s4 + s5 + s6 + s7;
+}
+
+std::string Concat8(const char* s1, const char* s2, const char* s3,
+                    const char* s4, const char* s5, const char* s6,
+                    const char* s7, const char* s8) {
+  return std::string(s1) + s2 + s3 + s4 + s5 + s6 + s7 + s8;
+}
+
+std::string Concat9(const char* s1, const char* s2, const char* s3,
+                    const char* s4, const char* s5, const char* s6,
+                    const char* s7, const char* s8, const char* s9) {
+  return std::string(s1) + s2 + s3 + s4 + s5 + s6 + s7 + s8 + s9;
+}
+
+std::string Concat10(const char* s1, const char* s2, const char* s3,
+                     const char* s4, const char* s5, const char* s6,
+                     const char* s7, const char* s8, const char* s9,
+                     const char* s10) {
+  return std::string(s1) + s2 + s3 + s4 + s5 + s6 + s7 + s8 + s9 + s10;
+}
+
+class Foo {
+ public:
+  Foo() : value_(123) {}
+
+  int Nullary() const { return value_; }
+
+  short Unary(long x) { return static_cast<short>(value_ + x); }  // NOLINT
+
+  std::string Binary(const std::string& str, char c) const { return str + c; }
+
+  int Ternary(int x, bool y, char z) { return value_ + x + y*z; }
+
+  int SumOf4(int a, int b, int c, int d) const {
+    return a + b + c + d + value_;
+  }
+
+  int SumOfLast2(Unused, Unused, int a, int b) const { return a + b; }
+
+  int SumOf5(int a, int b, int c, int d, int e) { return a + b + c + d + e; }
+
+  int SumOf6(int a, int b, int c, int d, int e, int f) {
+    return a + b + c + d + e + f;
+  }
+
+  std::string Concat7(const char* s1, const char* s2, const char* s3,
+                      const char* s4, const char* s5, const char* s6,
+                      const char* s7) {
+    return std::string(s1) + s2 + s3 + s4 + s5 + s6 + s7;
+  }
+
+  std::string Concat8(const char* s1, const char* s2, const char* s3,
+                      const char* s4, const char* s5, const char* s6,
+                      const char* s7, const char* s8) {
+    return std::string(s1) + s2 + s3 + s4 + s5 + s6 + s7 + s8;
+  }
+
+  std::string Concat9(const char* s1, const char* s2, const char* s3,
+                      const char* s4, const char* s5, const char* s6,
+                      const char* s7, const char* s8, const char* s9) {
+    return std::string(s1) + s2 + s3 + s4 + s5 + s6 + s7 + s8 + s9;
+  }
+
+  std::string Concat10(const char* s1, const char* s2, const char* s3,
+                       const char* s4, const char* s5, const char* s6,
+                       const char* s7, const char* s8, const char* s9,
+                       const char* s10) {
+    return std::string(s1) + s2 + s3 + s4 + s5 + s6 + s7 + s8 + s9 + s10;
+  }
+
+ private:
+  int value_;
+};
+
+// Tests using Invoke() with a nullary function.
+TEST(InvokeTest, Nullary) {
+  Action<int()> a = Invoke(Nullary);  // NOLINT
+  EXPECT_EQ(1, a.Perform(std::make_tuple()));
+}
+
+// Tests using Invoke() with a unary function.
+TEST(InvokeTest, Unary) {
+  Action<bool(int)> a = Invoke(Unary);  // NOLINT
+  EXPECT_FALSE(a.Perform(std::make_tuple(1)));
+  EXPECT_TRUE(a.Perform(std::make_tuple(-1)));
+}
+
+// Tests using Invoke() with a binary function.
+TEST(InvokeTest, Binary) {
+  Action<const char*(const char*, short)> a = Invoke(Binary);  // NOLINT
+  const char* p = "Hello";
+  EXPECT_EQ(p + 2, a.Perform(std::make_tuple(p, Short(2))));
+}
+
+// Tests using Invoke() with a ternary function.
+TEST(InvokeTest, Ternary) {
+  Action<int(int, char, short)> a = Invoke(Ternary);  // NOLINT
+  EXPECT_EQ(6, a.Perform(std::make_tuple(1, '\2', Short(3))));
+}
+
+// Tests using Invoke() with a 4-argument function.
+TEST(InvokeTest, FunctionThatTakes4Arguments) {
+  Action<int(int, int, int, int)> a = Invoke(SumOf4);  // NOLINT
+  EXPECT_EQ(1234, a.Perform(std::make_tuple(1000, 200, 30, 4)));
+}
+
+// Tests using Invoke() with a 5-argument function.
+TEST(InvokeTest, FunctionThatTakes5Arguments) {
+  Action<int(int, int, int, int, int)> a = Invoke(SumOf5);  // NOLINT
+  EXPECT_EQ(12345, a.Perform(std::make_tuple(10000, 2000, 300, 40, 5)));
+}
+
+// Tests using Invoke() with a 6-argument function.
+TEST(InvokeTest, FunctionThatTakes6Arguments) {
+  Action<int(int, int, int, int, int, int)> a = Invoke(SumOf6);  // NOLINT
+  EXPECT_EQ(123456,
+            a.Perform(std::make_tuple(100000, 20000, 3000, 400, 50, 6)));
+}
+
+// A helper that turns the type of a C-string literal from const
+// char[N] to const char*.
+inline const char* CharPtr(const char* s) { return s; }
+
+// Tests using Invoke() with a 7-argument function.
+TEST(InvokeTest, FunctionThatTakes7Arguments) {
+  Action<std::string(const char*, const char*, const char*, const char*,
+                     const char*, const char*, const char*)>
+      a = Invoke(Concat7);
+  EXPECT_EQ("1234567",
+            a.Perform(std::make_tuple(CharPtr("1"), CharPtr("2"), CharPtr("3"),
+                                      CharPtr("4"), CharPtr("5"), CharPtr("6"),
+                                      CharPtr("7"))));
+}
+
+// Tests using Invoke() with a 8-argument function.
+TEST(InvokeTest, FunctionThatTakes8Arguments) {
+  Action<std::string(const char*, const char*, const char*, const char*,
+                     const char*, const char*, const char*, const char*)>
+      a = Invoke(Concat8);
+  EXPECT_EQ("12345678",
+            a.Perform(std::make_tuple(CharPtr("1"), CharPtr("2"), CharPtr("3"),
+                                      CharPtr("4"), CharPtr("5"), CharPtr("6"),
+                                      CharPtr("7"), CharPtr("8"))));
+}
+
+// Tests using Invoke() with a 9-argument function.
+TEST(InvokeTest, FunctionThatTakes9Arguments) {
+  Action<std::string(const char*, const char*, const char*, const char*,
+                     const char*, const char*, const char*, const char*,
+                     const char*)>
+      a = Invoke(Concat9);
+  EXPECT_EQ("123456789", a.Perform(std::make_tuple(
+                             CharPtr("1"), CharPtr("2"), CharPtr("3"),
+                             CharPtr("4"), CharPtr("5"), CharPtr("6"),
+                             CharPtr("7"), CharPtr("8"), CharPtr("9"))));
+}
+
+// Tests using Invoke() with a 10-argument function.
+TEST(InvokeTest, FunctionThatTakes10Arguments) {
+  Action<std::string(const char*, const char*, const char*, const char*,
+                     const char*, const char*, const char*, const char*,
+                     const char*, const char*)>
+      a = Invoke(Concat10);
+  EXPECT_EQ("1234567890",
+            a.Perform(std::make_tuple(CharPtr("1"), CharPtr("2"), CharPtr("3"),
+                                      CharPtr("4"), CharPtr("5"), CharPtr("6"),
+                                      CharPtr("7"), CharPtr("8"), CharPtr("9"),
+                                      CharPtr("0"))));
+}
+
+// Tests using Invoke() with functions with parameters declared as Unused.
+TEST(InvokeTest, FunctionWithUnusedParameters) {
+  Action<int(int, int, double, const std::string&)> a1 = Invoke(SumOfFirst2);
+  std::tuple<int, int, double, std::string> dummy =
+      std::make_tuple(10, 2, 5.6, std::string("hi"));
+  EXPECT_EQ(12, a1.Perform(dummy));
+
+  Action<int(int, int, bool, int*)> a2 =
+      Invoke(SumOfFirst2);
+  EXPECT_EQ(
+      23, a2.Perform(std::make_tuple(20, 3, true, static_cast<int*>(nullptr))));
+}
+
+// Tests using Invoke() with methods with parameters declared as Unused.
+TEST(InvokeTest, MethodWithUnusedParameters) {
+  Foo foo;
+  Action<int(std::string, bool, int, int)> a1 = Invoke(&foo, &Foo::SumOfLast2);
+  EXPECT_EQ(12, a1.Perform(std::make_tuple(CharPtr("hi"), true, 10, 2)));
+
+  Action<int(char, double, int, int)> a2 =
+      Invoke(&foo, &Foo::SumOfLast2);
+  EXPECT_EQ(23, a2.Perform(std::make_tuple('a', 2.5, 20, 3)));
+}
+
+// Tests using Invoke() with a functor.
+TEST(InvokeTest, Functor) {
+  Action<long(long, int)> a = Invoke(plus<long>());  // NOLINT
+  EXPECT_EQ(3L, a.Perform(std::make_tuple(1, 2)));
+}
+
+// Tests using Invoke(f) as an action of a compatible type.
+TEST(InvokeTest, FunctionWithCompatibleType) {
+  Action<long(int, short, char, bool)> a = Invoke(SumOf4);  // NOLINT
+  EXPECT_EQ(4321, a.Perform(std::make_tuple(4000, Short(300), Char(20), true)));
+}
+
+// Tests using Invoke() with an object pointer and a method pointer.
+
+// Tests using Invoke() with a nullary method.
+TEST(InvokeMethodTest, Nullary) {
+  Foo foo;
+  Action<int()> a = Invoke(&foo, &Foo::Nullary);  // NOLINT
+  EXPECT_EQ(123, a.Perform(std::make_tuple()));
+}
+
+// Tests using Invoke() with a unary method.
+TEST(InvokeMethodTest, Unary) {
+  Foo foo;
+  Action<short(long)> a = Invoke(&foo, &Foo::Unary);  // NOLINT
+  EXPECT_EQ(4123, a.Perform(std::make_tuple(4000)));
+}
+
+// Tests using Invoke() with a binary method.
+TEST(InvokeMethodTest, Binary) {
+  Foo foo;
+  Action<std::string(const std::string&, char)> a = Invoke(&foo, &Foo::Binary);
+  std::string s("Hell");
+  std::tuple<std::string, char> dummy = std::make_tuple(s, 'o');
+  EXPECT_EQ("Hello", a.Perform(dummy));
+}
+
+// Tests using Invoke() with a ternary method.
+TEST(InvokeMethodTest, Ternary) {
+  Foo foo;
+  Action<int(int, bool, char)> a = Invoke(&foo, &Foo::Ternary);  // NOLINT
+  EXPECT_EQ(1124, a.Perform(std::make_tuple(1000, true, Char(1))));
+}
+
+// Tests using Invoke() with a 4-argument method.
+TEST(InvokeMethodTest, MethodThatTakes4Arguments) {
+  Foo foo;
+  Action<int(int, int, int, int)> a = Invoke(&foo, &Foo::SumOf4);  // NOLINT
+  EXPECT_EQ(1357, a.Perform(std::make_tuple(1000, 200, 30, 4)));
+}
+
+// Tests using Invoke() with a 5-argument method.
+TEST(InvokeMethodTest, MethodThatTakes5Arguments) {
+  Foo foo;
+  Action<int(int, int, int, int, int)> a = Invoke(&foo, &Foo::SumOf5);  // NOLINT
+  EXPECT_EQ(12345, a.Perform(std::make_tuple(10000, 2000, 300, 40, 5)));
+}
+
+// Tests using Invoke() with a 6-argument method.
+TEST(InvokeMethodTest, MethodThatTakes6Arguments) {
+  Foo foo;
+  Action<int(int, int, int, int, int, int)> a =  // NOLINT
+      Invoke(&foo, &Foo::SumOf6);
+  EXPECT_EQ(123456,
+            a.Perform(std::make_tuple(100000, 20000, 3000, 400, 50, 6)));
+}
+
+// Tests using Invoke() with a 7-argument method.
+TEST(InvokeMethodTest, MethodThatTakes7Arguments) {
+  Foo foo;
+  Action<std::string(const char*, const char*, const char*, const char*,
+                     const char*, const char*, const char*)>
+      a = Invoke(&foo, &Foo::Concat7);
+  EXPECT_EQ("1234567",
+            a.Perform(std::make_tuple(CharPtr("1"), CharPtr("2"), CharPtr("3"),
+                                      CharPtr("4"), CharPtr("5"), CharPtr("6"),
+                                      CharPtr("7"))));
+}
+
+// Tests using Invoke() with a 8-argument method.
+TEST(InvokeMethodTest, MethodThatTakes8Arguments) {
+  Foo foo;
+  Action<std::string(const char*, const char*, const char*, const char*,
+                     const char*, const char*, const char*, const char*)>
+      a = Invoke(&foo, &Foo::Concat8);
+  EXPECT_EQ("12345678",
+            a.Perform(std::make_tuple(CharPtr("1"), CharPtr("2"), CharPtr("3"),
+                                      CharPtr("4"), CharPtr("5"), CharPtr("6"),
+                                      CharPtr("7"), CharPtr("8"))));
+}
+
+// Tests using Invoke() with a 9-argument method.
+TEST(InvokeMethodTest, MethodThatTakes9Arguments) {
+  Foo foo;
+  Action<std::string(const char*, const char*, const char*, const char*,
+                     const char*, const char*, const char*, const char*,
+                     const char*)>
+      a = Invoke(&foo, &Foo::Concat9);
+  EXPECT_EQ("123456789", a.Perform(std::make_tuple(
+                             CharPtr("1"), CharPtr("2"), CharPtr("3"),
+                             CharPtr("4"), CharPtr("5"), CharPtr("6"),
+                             CharPtr("7"), CharPtr("8"), CharPtr("9"))));
+}
+
+// Tests using Invoke() with a 10-argument method.
+TEST(InvokeMethodTest, MethodThatTakes10Arguments) {
+  Foo foo;
+  Action<std::string(const char*, const char*, const char*, const char*,
+                     const char*, const char*, const char*, const char*,
+                     const char*, const char*)>
+      a = Invoke(&foo, &Foo::Concat10);
+  EXPECT_EQ("1234567890",
+            a.Perform(std::make_tuple(CharPtr("1"), CharPtr("2"), CharPtr("3"),
+                                      CharPtr("4"), CharPtr("5"), CharPtr("6"),
+                                      CharPtr("7"), CharPtr("8"), CharPtr("9"),
+                                      CharPtr("0"))));
+}
+
+// Tests using Invoke(f) as an action of a compatible type.
+TEST(InvokeMethodTest, MethodWithCompatibleType) {
+  Foo foo;
+  Action<long(int, short, char, bool)> a =  // NOLINT
+      Invoke(&foo, &Foo::SumOf4);
+  EXPECT_EQ(4444, a.Perform(std::make_tuple(4000, Short(300), Char(20), true)));
+}
+
+// Tests using WithoutArgs with an action that takes no argument.
+TEST(WithoutArgsTest, NoArg) {
+  Action<int(int n)> a = WithoutArgs(Invoke(Nullary));  // NOLINT
+  EXPECT_EQ(1, a.Perform(std::make_tuple(2)));
+}
+
+// Tests using WithArg with an action that takes 1 argument.
+TEST(WithArgTest, OneArg) {
+  Action<bool(double x, int n)> b = WithArg<1>(Invoke(Unary));  // NOLINT
+  EXPECT_TRUE(b.Perform(std::make_tuple(1.5, -1)));
+  EXPECT_FALSE(b.Perform(std::make_tuple(1.5, 1)));
+}
+
+TEST(ReturnArgActionTest, WorksForOneArgIntArg0) {
+  const Action<int(int)> a = ReturnArg<0>();
+  EXPECT_EQ(5, a.Perform(std::make_tuple(5)));
+}
+
+TEST(ReturnArgActionTest, WorksForMultiArgBoolArg0) {
+  const Action<bool(bool, bool, bool)> a = ReturnArg<0>();
+  EXPECT_TRUE(a.Perform(std::make_tuple(true, false, false)));
+}
+
+TEST(ReturnArgActionTest, WorksForMultiArgStringArg2) {
+  const Action<std::string(int, int, std::string, int)> a = ReturnArg<2>();
+  EXPECT_EQ("seven", a.Perform(std::make_tuple(5, 6, std::string("seven"), 8)));
+}
+
+TEST(SaveArgActionTest, WorksForSameType) {
+  int result = 0;
+  const Action<void(int n)> a1 = SaveArg<0>(&result);
+  a1.Perform(std::make_tuple(5));
+  EXPECT_EQ(5, result);
+}
+
+TEST(SaveArgActionTest, WorksForCompatibleType) {
+  int result = 0;
+  const Action<void(bool, char)> a1 = SaveArg<1>(&result);
+  a1.Perform(std::make_tuple(true, 'a'));
+  EXPECT_EQ('a', result);
+}
+
+TEST(SaveArgPointeeActionTest, WorksForSameType) {
+  int result = 0;
+  const int value = 5;
+  const Action<void(const int*)> a1 = SaveArgPointee<0>(&result);
+  a1.Perform(std::make_tuple(&value));
+  EXPECT_EQ(5, result);
+}
+
+TEST(SaveArgPointeeActionTest, WorksForCompatibleType) {
+  int result = 0;
+  char value = 'a';
+  const Action<void(bool, char*)> a1 = SaveArgPointee<1>(&result);
+  a1.Perform(std::make_tuple(true, &value));
+  EXPECT_EQ('a', result);
+}
+
+TEST(SetArgRefereeActionTest, WorksForSameType) {
+  int value = 0;
+  const Action<void(int&)> a1 = SetArgReferee<0>(1);
+  a1.Perform(std::tuple<int&>(value));
+  EXPECT_EQ(1, value);
+}
+
+TEST(SetArgRefereeActionTest, WorksForCompatibleType) {
+  int value = 0;
+  const Action<void(int, int&)> a1 = SetArgReferee<1>('a');
+  a1.Perform(std::tuple<int, int&>(0, value));
+  EXPECT_EQ('a', value);
+}
+
+TEST(SetArgRefereeActionTest, WorksWithExtraArguments) {
+  int value = 0;
+  const Action<void(bool, int, int&, const char*)> a1 = SetArgReferee<2>('a');
+  a1.Perform(std::tuple<bool, int, int&, const char*>(true, 0, value, "hi"));
+  EXPECT_EQ('a', value);
+}
+
+// A class that can be used to verify that its destructor is called: it will set
+// the bool provided to the constructor to true when destroyed.
+class DeletionTester {
+ public:
+  explicit DeletionTester(bool* is_deleted)
+    : is_deleted_(is_deleted) {
+    // Make sure the bit is set to false.
+    *is_deleted_ = false;
+  }
+
+  ~DeletionTester() {
+    *is_deleted_ = true;
+  }
+
+ private:
+  bool* is_deleted_;
+};
+
+TEST(DeleteArgActionTest, OneArg) {
+  bool is_deleted = false;
+  DeletionTester* t = new DeletionTester(&is_deleted);
+  const Action<void(DeletionTester*)> a1 = DeleteArg<0>();      // NOLINT
+  EXPECT_FALSE(is_deleted);
+  a1.Perform(std::make_tuple(t));
+  EXPECT_TRUE(is_deleted);
+}
+
+TEST(DeleteArgActionTest, TenArgs) {
+  bool is_deleted = false;
+  DeletionTester* t = new DeletionTester(&is_deleted);
+  const Action<void(bool, int, int, const char*, bool,
+                    int, int, int, int, DeletionTester*)> a1 = DeleteArg<9>();
+  EXPECT_FALSE(is_deleted);
+  a1.Perform(std::make_tuple(true, 5, 6, CharPtr("hi"), false, 7, 8, 9, 10, t));
+  EXPECT_TRUE(is_deleted);
+}
+
+#if GTEST_HAS_EXCEPTIONS
+
+TEST(ThrowActionTest, ThrowsGivenExceptionInVoidFunction) {
+  const Action<void(int n)> a = Throw('a');
+  EXPECT_THROW(a.Perform(std::make_tuple(0)), char);
+}
+
+class MyException {};
+
+TEST(ThrowActionTest, ThrowsGivenExceptionInNonVoidFunction) {
+  const Action<double(char ch)> a = Throw(MyException());
+  EXPECT_THROW(a.Perform(std::make_tuple('0')), MyException);
+}
+
+TEST(ThrowActionTest, ThrowsGivenExceptionInNullaryFunction) {
+  const Action<double()> a = Throw(MyException());
+  EXPECT_THROW(a.Perform(std::make_tuple()), MyException);
+}
+
+class Object {
+ public:
+  virtual ~Object() {}
+  virtual void Func() {}
+};
+
+class MockObject : public Object {
+ public:
+  ~MockObject() override {}
+  MOCK_METHOD(void, Func, (), (override));
+};
+
+TEST(ThrowActionTest, Times0) {
+  EXPECT_NONFATAL_FAILURE(
+      [] {
+        try {
+          MockObject m;
+          ON_CALL(m, Func()).WillByDefault([] { throw "something"; });
+          EXPECT_CALL(m, Func()).Times(0);
+          m.Func();
+        } catch (...) {
+          // Exception is caught but Times(0) still triggers a failure.
+        }
+      }(),
+      "");
+}
+
+#endif  // GTEST_HAS_EXCEPTIONS
+
+// Tests that SetArrayArgument<N>(first, last) sets the elements of the array
+// pointed to by the N-th (0-based) argument to values in range [first, last).
+TEST(SetArrayArgumentTest, SetsTheNthArray) {
+  using MyFunction = void(bool, int*, char*);
+  int numbers[] = { 1, 2, 3 };
+  Action<MyFunction> a = SetArrayArgument<1>(numbers, numbers + 3);
+
+  int n[4] = {};
+  int* pn = n;
+  char ch[4] = {};
+  char* pch = ch;
+  a.Perform(std::make_tuple(true, pn, pch));
+  EXPECT_EQ(1, n[0]);
+  EXPECT_EQ(2, n[1]);
+  EXPECT_EQ(3, n[2]);
+  EXPECT_EQ(0, n[3]);
+  EXPECT_EQ('\0', ch[0]);
+  EXPECT_EQ('\0', ch[1]);
+  EXPECT_EQ('\0', ch[2]);
+  EXPECT_EQ('\0', ch[3]);
+
+  // Tests first and last are iterators.
+  std::string letters = "abc";
+  a = SetArrayArgument<2>(letters.begin(), letters.end());
+  std::fill_n(n, 4, 0);
+  std::fill_n(ch, 4, '\0');
+  a.Perform(std::make_tuple(true, pn, pch));
+  EXPECT_EQ(0, n[0]);
+  EXPECT_EQ(0, n[1]);
+  EXPECT_EQ(0, n[2]);
+  EXPECT_EQ(0, n[3]);
+  EXPECT_EQ('a', ch[0]);
+  EXPECT_EQ('b', ch[1]);
+  EXPECT_EQ('c', ch[2]);
+  EXPECT_EQ('\0', ch[3]);
+}
+
+// Tests SetArrayArgument<N>(first, last) where first == last.
+TEST(SetArrayArgumentTest, SetsTheNthArrayWithEmptyRange) {
+  using MyFunction = void(bool, int*);
+  int numbers[] = { 1, 2, 3 };
+  Action<MyFunction> a = SetArrayArgument<1>(numbers, numbers);
+
+  int n[4] = {};
+  int* pn = n;
+  a.Perform(std::make_tuple(true, pn));
+  EXPECT_EQ(0, n[0]);
+  EXPECT_EQ(0, n[1]);
+  EXPECT_EQ(0, n[2]);
+  EXPECT_EQ(0, n[3]);
+}
+
+// Tests SetArrayArgument<N>(first, last) where *first is convertible
+// (but not equal) to the argument type.
+TEST(SetArrayArgumentTest, SetsTheNthArrayWithConvertibleType) {
+  using MyFunction = void(bool, int*);
+  char chars[] = { 97, 98, 99 };
+  Action<MyFunction> a = SetArrayArgument<1>(chars, chars + 3);
+
+  int codes[4] = { 111, 222, 333, 444 };
+  int* pcodes = codes;
+  a.Perform(std::make_tuple(true, pcodes));
+  EXPECT_EQ(97, codes[0]);
+  EXPECT_EQ(98, codes[1]);
+  EXPECT_EQ(99, codes[2]);
+  EXPECT_EQ(444, codes[3]);
+}
+
+// Test SetArrayArgument<N>(first, last) with iterator as argument.
+TEST(SetArrayArgumentTest, SetsTheNthArrayWithIteratorArgument) {
+  using MyFunction = void(bool, std::back_insert_iterator<std::string>);
+  std::string letters = "abc";
+  Action<MyFunction> a = SetArrayArgument<1>(letters.begin(), letters.end());
+
+  std::string s;
+  a.Perform(std::make_tuple(true, back_inserter(s)));
+  EXPECT_EQ(letters, s);
+}
+
+TEST(ReturnPointeeTest, Works) {
+  int n = 42;
+  const Action<int()> a = ReturnPointee(&n);
+  EXPECT_EQ(42, a.Perform(std::make_tuple()));
+
+  n = 43;
+  EXPECT_EQ(43, a.Perform(std::make_tuple()));
+}
+
+// Tests InvokeArgument<N>(...).
+
+// Tests using InvokeArgument with a nullary function.
+TEST(InvokeArgumentTest, Function0) {
+  Action<int(int, int (*)())> a = InvokeArgument<1>();  // NOLINT
+  EXPECT_EQ(1, a.Perform(std::make_tuple(2, &Nullary)));
+}
+
+// Tests using InvokeArgument with a unary function.
+TEST(InvokeArgumentTest, Functor1) {
+  Action<int(UnaryFunctor)> a = InvokeArgument<0>(true);  // NOLINT
+  EXPECT_EQ(1, a.Perform(std::make_tuple(UnaryFunctor())));
+}
+
+// Tests using InvokeArgument with a 5-ary function.
+TEST(InvokeArgumentTest, Function5) {
+  Action<int(int (*)(int, int, int, int, int))> a =  // NOLINT
+      InvokeArgument<0>(10000, 2000, 300, 40, 5);
+  EXPECT_EQ(12345, a.Perform(std::make_tuple(&SumOf5)));
+}
+
+// Tests using InvokeArgument with a 5-ary functor.
+TEST(InvokeArgumentTest, Functor5) {
+  Action<int(SumOf5Functor)> a =  // NOLINT
+      InvokeArgument<0>(10000, 2000, 300, 40, 5);
+  EXPECT_EQ(12345, a.Perform(std::make_tuple(SumOf5Functor())));
+}
+
+// Tests using InvokeArgument with a 6-ary function.
+TEST(InvokeArgumentTest, Function6) {
+  Action<int(int (*)(int, int, int, int, int, int))> a =  // NOLINT
+      InvokeArgument<0>(100000, 20000, 3000, 400, 50, 6);
+  EXPECT_EQ(123456, a.Perform(std::make_tuple(&SumOf6)));
+}
+
+// Tests using InvokeArgument with a 6-ary functor.
+TEST(InvokeArgumentTest, Functor6) {
+  Action<int(SumOf6Functor)> a =  // NOLINT
+      InvokeArgument<0>(100000, 20000, 3000, 400, 50, 6);
+  EXPECT_EQ(123456, a.Perform(std::make_tuple(SumOf6Functor())));
+}
+
+// Tests using InvokeArgument with a 7-ary function.
+TEST(InvokeArgumentTest, Function7) {
+  Action<std::string(std::string(*)(const char*, const char*, const char*,
+                                    const char*, const char*, const char*,
+                                    const char*))>
+      a = InvokeArgument<0>("1", "2", "3", "4", "5", "6", "7");
+  EXPECT_EQ("1234567", a.Perform(std::make_tuple(&Concat7)));
+}
+
+// Tests using InvokeArgument with a 8-ary function.
+TEST(InvokeArgumentTest, Function8) {
+  Action<std::string(std::string(*)(const char*, const char*, const char*,
+                                    const char*, const char*, const char*,
+                                    const char*, const char*))>
+      a = InvokeArgument<0>("1", "2", "3", "4", "5", "6", "7", "8");
+  EXPECT_EQ("12345678", a.Perform(std::make_tuple(&Concat8)));
+}
+
+// Tests using InvokeArgument with a 9-ary function.
+TEST(InvokeArgumentTest, Function9) {
+  Action<std::string(std::string(*)(const char*, const char*, const char*,
+                                    const char*, const char*, const char*,
+                                    const char*, const char*, const char*))>
+      a = InvokeArgument<0>("1", "2", "3", "4", "5", "6", "7", "8", "9");
+  EXPECT_EQ("123456789", a.Perform(std::make_tuple(&Concat9)));
+}
+
+// Tests using InvokeArgument with a 10-ary function.
+TEST(InvokeArgumentTest, Function10) {
+  Action<std::string(std::string(*)(
+      const char*, const char*, const char*, const char*, const char*,
+      const char*, const char*, const char*, const char*, const char*))>
+      a = InvokeArgument<0>("1", "2", "3", "4", "5", "6", "7", "8", "9", "0");
+  EXPECT_EQ("1234567890", a.Perform(std::make_tuple(&Concat10)));
+}
+
+// Tests using InvokeArgument with a function that takes a pointer argument.
+TEST(InvokeArgumentTest, ByPointerFunction) {
+  Action<const char*(const char* (*)(const char* input, short n))>  // NOLINT
+      a = InvokeArgument<0>(static_cast<const char*>("Hi"), Short(1));
+  EXPECT_STREQ("i", a.Perform(std::make_tuple(&Binary)));
+}
+
+// Tests using InvokeArgument with a function that takes a const char*
+// by passing it a C-string literal.
+TEST(InvokeArgumentTest, FunctionWithCStringLiteral) {
+  Action<const char*(const char* (*)(const char* input, short n))>  // NOLINT
+      a = InvokeArgument<0>("Hi", Short(1));
+  EXPECT_STREQ("i", a.Perform(std::make_tuple(&Binary)));
+}
+
+// Tests using InvokeArgument with a function that takes a const reference.
+TEST(InvokeArgumentTest, ByConstReferenceFunction) {
+  Action<bool(bool (*function)(const std::string& s))> a =  // NOLINT
+      InvokeArgument<0>(std::string("Hi"));
+  // When action 'a' is constructed, it makes a copy of the temporary
+  // string object passed to it, so it's OK to use 'a' later, when the
+  // temporary object has already died.
+  EXPECT_TRUE(a.Perform(std::make_tuple(&ByConstRef)));
+}
+
+// Tests using InvokeArgument with ByRef() and a function that takes a
+// const reference.
+TEST(InvokeArgumentTest, ByExplicitConstReferenceFunction) {
+  Action<bool(bool (*)(const double& x))> a =  // NOLINT
+      InvokeArgument<0>(ByRef(g_double));
+  // The above line calls ByRef() on a const value.
+  EXPECT_TRUE(a.Perform(std::make_tuple(&ReferencesGlobalDouble)));
+
+  double x = 0;
+  a = InvokeArgument<0>(ByRef(x));  // This calls ByRef() on a non-const.
+  EXPECT_FALSE(a.Perform(std::make_tuple(&ReferencesGlobalDouble)));
+}
+
+// Tests DoAll(a1, a2).
+TEST(DoAllTest, TwoActions) {
+  int n = 0;
+  Action<int(int*)> a = DoAll(SetArgPointee<0>(1),  // NOLINT
+                              Return(2));
+  EXPECT_EQ(2, a.Perform(std::make_tuple(&n)));
+  EXPECT_EQ(1, n);
+}
+
+// Tests DoAll(a1, a2, a3).
+TEST(DoAllTest, ThreeActions) {
+  int m = 0, n = 0;
+  Action<int(int*, int*)> a = DoAll(SetArgPointee<0>(1),  // NOLINT
+                                    SetArgPointee<1>(2), Return(3));
+  EXPECT_EQ(3, a.Perform(std::make_tuple(&m, &n)));
+  EXPECT_EQ(1, m);
+  EXPECT_EQ(2, n);
+}
+
+// Tests DoAll(a1, a2, a3, a4).
+TEST(DoAllTest, FourActions) {
+  int m = 0, n = 0;
+  char ch = '\0';
+  Action<int(int*, int*, char*)> a =  // NOLINT
+      DoAll(SetArgPointee<0>(1), SetArgPointee<1>(2), SetArgPointee<2>('a'),
+            Return(3));
+  EXPECT_EQ(3, a.Perform(std::make_tuple(&m, &n, &ch)));
+  EXPECT_EQ(1, m);
+  EXPECT_EQ(2, n);
+  EXPECT_EQ('a', ch);
+}
+
+// Tests DoAll(a1, a2, a3, a4, a5).
+TEST(DoAllTest, FiveActions) {
+  int m = 0, n = 0;
+  char a = '\0', b = '\0';
+  Action<int(int*, int*, char*, char*)> action =  // NOLINT
+      DoAll(SetArgPointee<0>(1), SetArgPointee<1>(2), SetArgPointee<2>('a'),
+            SetArgPointee<3>('b'), Return(3));
+  EXPECT_EQ(3, action.Perform(std::make_tuple(&m, &n, &a, &b)));
+  EXPECT_EQ(1, m);
+  EXPECT_EQ(2, n);
+  EXPECT_EQ('a', a);
+  EXPECT_EQ('b', b);
+}
+
+// Tests DoAll(a1, a2, ..., a6).
+TEST(DoAllTest, SixActions) {
+  int m = 0, n = 0;
+  char a = '\0', b = '\0', c = '\0';
+  Action<int(int*, int*, char*, char*, char*)> action =  // NOLINT
+      DoAll(SetArgPointee<0>(1), SetArgPointee<1>(2), SetArgPointee<2>('a'),
+            SetArgPointee<3>('b'), SetArgPointee<4>('c'), Return(3));
+  EXPECT_EQ(3, action.Perform(std::make_tuple(&m, &n, &a, &b, &c)));
+  EXPECT_EQ(1, m);
+  EXPECT_EQ(2, n);
+  EXPECT_EQ('a', a);
+  EXPECT_EQ('b', b);
+  EXPECT_EQ('c', c);
+}
+
+// Tests DoAll(a1, a2, ..., a7).
+TEST(DoAllTest, SevenActions) {
+  int m = 0, n = 0;
+  char a = '\0', b = '\0', c = '\0', d = '\0';
+  Action<int(int*, int*, char*, char*, char*, char*)> action =  // NOLINT
+      DoAll(SetArgPointee<0>(1), SetArgPointee<1>(2), SetArgPointee<2>('a'),
+            SetArgPointee<3>('b'), SetArgPointee<4>('c'), SetArgPointee<5>('d'),
+            Return(3));
+  EXPECT_EQ(3, action.Perform(std::make_tuple(&m, &n, &a, &b, &c, &d)));
+  EXPECT_EQ(1, m);
+  EXPECT_EQ(2, n);
+  EXPECT_EQ('a', a);
+  EXPECT_EQ('b', b);
+  EXPECT_EQ('c', c);
+  EXPECT_EQ('d', d);
+}
+
+// Tests DoAll(a1, a2, ..., a8).
+TEST(DoAllTest, EightActions) {
+  int m = 0, n = 0;
+  char a = '\0', b = '\0', c = '\0', d = '\0', e = '\0';
+  Action<int(int*, int*, char*, char*, char*, char*,  // NOLINT
+             char*)>
+      action =
+          DoAll(SetArgPointee<0>(1), SetArgPointee<1>(2), SetArgPointee<2>('a'),
+                SetArgPointee<3>('b'), SetArgPointee<4>('c'),
+                SetArgPointee<5>('d'), SetArgPointee<6>('e'), Return(3));
+  EXPECT_EQ(3, action.Perform(std::make_tuple(&m, &n, &a, &b, &c, &d, &e)));
+  EXPECT_EQ(1, m);
+  EXPECT_EQ(2, n);
+  EXPECT_EQ('a', a);
+  EXPECT_EQ('b', b);
+  EXPECT_EQ('c', c);
+  EXPECT_EQ('d', d);
+  EXPECT_EQ('e', e);
+}
+
+// Tests DoAll(a1, a2, ..., a9).
+TEST(DoAllTest, NineActions) {
+  int m = 0, n = 0;
+  char a = '\0', b = '\0', c = '\0', d = '\0', e = '\0', f = '\0';
+  Action<int(int*, int*, char*, char*, char*, char*,  // NOLINT
+             char*, char*)>
+      action = DoAll(SetArgPointee<0>(1), SetArgPointee<1>(2),
+                     SetArgPointee<2>('a'), SetArgPointee<3>('b'),
+                     SetArgPointee<4>('c'), SetArgPointee<5>('d'),
+                     SetArgPointee<6>('e'), SetArgPointee<7>('f'), Return(3));
+  EXPECT_EQ(3, action.Perform(std::make_tuple(&m, &n, &a, &b, &c, &d, &e, &f)));
+  EXPECT_EQ(1, m);
+  EXPECT_EQ(2, n);
+  EXPECT_EQ('a', a);
+  EXPECT_EQ('b', b);
+  EXPECT_EQ('c', c);
+  EXPECT_EQ('d', d);
+  EXPECT_EQ('e', e);
+  EXPECT_EQ('f', f);
+}
+
+// Tests DoAll(a1, a2, ..., a10).
+TEST(DoAllTest, TenActions) {
+  int m = 0, n = 0;
+  char a = '\0', b = '\0', c = '\0', d = '\0';
+  char e = '\0', f = '\0', g = '\0';
+  Action<int(int*, int*, char*, char*, char*, char*,  // NOLINT
+             char*, char*, char*)>
+      action =
+          DoAll(SetArgPointee<0>(1), SetArgPointee<1>(2), SetArgPointee<2>('a'),
+                SetArgPointee<3>('b'), SetArgPointee<4>('c'),
+                SetArgPointee<5>('d'), SetArgPointee<6>('e'),
+                SetArgPointee<7>('f'), SetArgPointee<8>('g'), Return(3));
+  EXPECT_EQ(
+      3, action.Perform(std::make_tuple(&m, &n, &a, &b, &c, &d, &e, &f, &g)));
+  EXPECT_EQ(1, m);
+  EXPECT_EQ(2, n);
+  EXPECT_EQ('a', a);
+  EXPECT_EQ('b', b);
+  EXPECT_EQ('c', c);
+  EXPECT_EQ('d', d);
+  EXPECT_EQ('e', e);
+  EXPECT_EQ('f', f);
+  EXPECT_EQ('g', g);
+}
+
+TEST(DoAllTest, NoArgs) {
+  bool ran_first = false;
+  Action<bool()> a =
+      DoAll([&] { ran_first = true; }, [&] { return ran_first; });
+  EXPECT_TRUE(a.Perform({}));
+}
+
+TEST(DoAllTest, MoveOnlyArgs) {
+  bool ran_first = false;
+  Action<int(std::unique_ptr<int>)> a =
+      DoAll(InvokeWithoutArgs([&] { ran_first = true; }),
+            [](std::unique_ptr<int> p) { return *p; });
+  EXPECT_EQ(7, a.Perform(std::make_tuple(std::unique_ptr<int>(new int(7)))));
+  EXPECT_TRUE(ran_first);
+}
+
+TEST(DoAllTest, ImplicitlyConvertsActionArguments) {
+  bool ran_first = false;
+  // Action<void(std::vector<int>)> isn't an
+  // Action<void(const std::vector<int>&) but can be converted.
+  Action<void(std::vector<int>)> first = [&] { ran_first = true; };
+  Action<int(std::vector<int>)> a =
+      DoAll(first, [](std::vector<int> arg) { return arg.front(); });
+  EXPECT_EQ(7, a.Perform(std::make_tuple(std::vector<int>{7})));
+  EXPECT_TRUE(ran_first);
+}
+
+// The ACTION*() macros trigger warning C4100 (unreferenced formal
+// parameter) in MSVC with -W4.  Unfortunately they cannot be fixed in
+// the macro definition, as the warnings are generated when the macro
+// is expanded and macro expansion cannot contain #pragma.  Therefore
+// we suppress them here.
+// Also suppress C4503 decorated name length exceeded, name was truncated
+#ifdef _MSC_VER
+#pragma warning(push)
+#pragma warning(disable : 4100)
+#pragma warning(disable : 4503)
+#endif
+// Tests the ACTION*() macro family.
+
+// Tests that ACTION() can define an action that doesn't reference the
+// mock function arguments.
+ACTION(Return5) { return 5; }
+
+TEST(ActionMacroTest, WorksWhenNotReferencingArguments) {
+  Action<double()> a1 = Return5();
+  EXPECT_DOUBLE_EQ(5, a1.Perform(std::make_tuple()));
+
+  Action<int(double, bool)> a2 = Return5();
+  EXPECT_EQ(5, a2.Perform(std::make_tuple(1, true)));
+}
+
+// Tests that ACTION() can define an action that returns void.
+ACTION(IncrementArg1) { (*arg1)++; }
+
+TEST(ActionMacroTest, WorksWhenReturningVoid) {
+  Action<void(int, int*)> a1 = IncrementArg1();
+  int n = 0;
+  a1.Perform(std::make_tuple(5, &n));
+  EXPECT_EQ(1, n);
+}
+
+// Tests that the body of ACTION() can reference the type of the
+// argument.
+ACTION(IncrementArg2) {
+  StaticAssertTypeEq<int*, arg2_type>();
+  arg2_type temp = arg2;
+  (*temp)++;
+}
+
+TEST(ActionMacroTest, CanReferenceArgumentType) {
+  Action<void(int, bool, int*)> a1 = IncrementArg2();
+  int n = 0;
+  a1.Perform(std::make_tuple(5, false, &n));
+  EXPECT_EQ(1, n);
+}
+
+// Tests that the body of ACTION() can reference the argument tuple
+// via args_type and args.
+ACTION(Sum2) {
+  StaticAssertTypeEq<std::tuple<int, char, int*>, args_type>();
+  args_type args_copy = args;
+  return std::get<0>(args_copy) + std::get<1>(args_copy);
+}
+
+TEST(ActionMacroTest, CanReferenceArgumentTuple) {
+  Action<int(int, char, int*)> a1 = Sum2();
+  int dummy = 0;
+  EXPECT_EQ(11, a1.Perform(std::make_tuple(5, Char(6), &dummy)));
+}
+
+namespace {
+
+// Tests that the body of ACTION() can reference the mock function
+// type.
+int Dummy(bool flag) { return flag ? 1 : 0; }
+
+}  // namespace
+
+ACTION(InvokeDummy) {
+  StaticAssertTypeEq<int(bool), function_type>();
+  function_type* fp = &Dummy;
+  return (*fp)(true);
+}
+
+TEST(ActionMacroTest, CanReferenceMockFunctionType) {
+  Action<int(bool)> a1 = InvokeDummy();
+  EXPECT_EQ(1, a1.Perform(std::make_tuple(true)));
+  EXPECT_EQ(1, a1.Perform(std::make_tuple(false)));
+}
+
+// Tests that the body of ACTION() can reference the mock function's
+// return type.
+ACTION(InvokeDummy2) {
+  StaticAssertTypeEq<int, return_type>();
+  return_type result = Dummy(true);
+  return result;
+}
+
+TEST(ActionMacroTest, CanReferenceMockFunctionReturnType) {
+  Action<int(bool)> a1 = InvokeDummy2();
+  EXPECT_EQ(1, a1.Perform(std::make_tuple(true)));
+  EXPECT_EQ(1, a1.Perform(std::make_tuple(false)));
+}
+
+// Tests that ACTION() works for arguments passed by const reference.
+ACTION(ReturnAddrOfConstBoolReferenceArg) {
+  StaticAssertTypeEq<const bool&, arg1_type>();
+  return &arg1;
+}
+
+TEST(ActionMacroTest, WorksForConstReferenceArg) {
+  Action<const bool*(int, const bool&)> a = ReturnAddrOfConstBoolReferenceArg();
+  const bool b = false;
+  EXPECT_EQ(&b, a.Perform(std::tuple<int, const bool&>(0, b)));
+}
+
+// Tests that ACTION() works for arguments passed by non-const reference.
+ACTION(ReturnAddrOfIntReferenceArg) {
+  StaticAssertTypeEq<int&, arg0_type>();
+  return &arg0;
+}
+
+TEST(ActionMacroTest, WorksForNonConstReferenceArg) {
+  Action<int*(int&, bool, int)> a = ReturnAddrOfIntReferenceArg();
+  int n = 0;
+  EXPECT_EQ(&n, a.Perform(std::tuple<int&, bool, int>(n, true, 1)));
+}
+
+// Tests that ACTION() can be used in a namespace.
+namespace action_test {
+ACTION(Sum) { return arg0 + arg1; }
+}  // namespace action_test
+
+TEST(ActionMacroTest, WorksInNamespace) {
+  Action<int(int, int)> a1 = action_test::Sum();
+  EXPECT_EQ(3, a1.Perform(std::make_tuple(1, 2)));
+}
+
+// Tests that the same ACTION definition works for mock functions with
+// different argument numbers.
+ACTION(PlusTwo) { return arg0 + 2; }
+
+TEST(ActionMacroTest, WorksForDifferentArgumentNumbers) {
+  Action<int(int)> a1 = PlusTwo();
+  EXPECT_EQ(4, a1.Perform(std::make_tuple(2)));
+
+  Action<double(float, void*)> a2 = PlusTwo();
+  int dummy;
+  EXPECT_DOUBLE_EQ(6, a2.Perform(std::make_tuple(4.0f, &dummy)));
+}
+
+// Tests that ACTION_P can define a parameterized action.
+ACTION_P(Plus, n) { return arg0 + n; }
+
+TEST(ActionPMacroTest, DefinesParameterizedAction) {
+  Action<int(int m, bool t)> a1 = Plus(9);
+  EXPECT_EQ(10, a1.Perform(std::make_tuple(1, true)));
+}
+
+// Tests that the body of ACTION_P can reference the argument types
+// and the parameter type.
+ACTION_P(TypedPlus, n) {
+  arg0_type t1 = arg0;
+  n_type t2 = n;
+  return t1 + t2;
+}
+
+TEST(ActionPMacroTest, CanReferenceArgumentAndParameterTypes) {
+  Action<int(char m, bool t)> a1 = TypedPlus(9);
+  EXPECT_EQ(10, a1.Perform(std::make_tuple(Char(1), true)));
+}
+
+// Tests that a parameterized action can be used in any mock function
+// whose type is compatible.
+TEST(ActionPMacroTest, WorksInCompatibleMockFunction) {
+  Action<std::string(const std::string& s)> a1 = Plus("tail");
+  const std::string re = "re";
+  std::tuple<const std::string> dummy = std::make_tuple(re);
+  EXPECT_EQ("retail", a1.Perform(dummy));
+}
+
+// Tests that we can use ACTION*() to define actions overloaded on the
+// number of parameters.
+
+ACTION(OverloadedAction) { return arg0 ? arg1 : "hello"; }
+
+ACTION_P(OverloadedAction, default_value) {
+  return arg0 ? arg1 : default_value;
+}
+
+ACTION_P2(OverloadedAction, true_value, false_value) {
+  return arg0 ? true_value : false_value;
+}
+
+TEST(ActionMacroTest, CanDefineOverloadedActions) {
+  using MyAction = Action<const char*(bool, const char*)>;
+
+  const MyAction a1 = OverloadedAction();
+  EXPECT_STREQ("hello", a1.Perform(std::make_tuple(false, CharPtr("world"))));
+  EXPECT_STREQ("world", a1.Perform(std::make_tuple(true, CharPtr("world"))));
+
+  const MyAction a2 = OverloadedAction("hi");
+  EXPECT_STREQ("hi", a2.Perform(std::make_tuple(false, CharPtr("world"))));
+  EXPECT_STREQ("world", a2.Perform(std::make_tuple(true, CharPtr("world"))));
+
+  const MyAction a3 = OverloadedAction("hi", "you");
+  EXPECT_STREQ("hi", a3.Perform(std::make_tuple(true, CharPtr("world"))));
+  EXPECT_STREQ("you", a3.Perform(std::make_tuple(false, CharPtr("world"))));
+}
+
+// Tests ACTION_Pn where n >= 3.
+
+ACTION_P3(Plus, m, n, k) { return arg0 + m + n + k; }
+
+TEST(ActionPnMacroTest, WorksFor3Parameters) {
+  Action<double(int m, bool t)> a1 = Plus(100, 20, 3.4);
+  EXPECT_DOUBLE_EQ(3123.4, a1.Perform(std::make_tuple(3000, true)));
+
+  Action<std::string(const std::string& s)> a2 = Plus("tail", "-", ">");
+  const std::string re = "re";
+  std::tuple<const std::string> dummy = std::make_tuple(re);
+  EXPECT_EQ("retail->", a2.Perform(dummy));
+}
+
+ACTION_P4(Plus, p0, p1, p2, p3) { return arg0 + p0 + p1 + p2 + p3; }
+
+TEST(ActionPnMacroTest, WorksFor4Parameters) {
+  Action<int(int)> a1 = Plus(1, 2, 3, 4);
+  EXPECT_EQ(10 + 1 + 2 + 3 + 4, a1.Perform(std::make_tuple(10)));
+}
+
+ACTION_P5(Plus, p0, p1, p2, p3, p4) { return arg0 + p0 + p1 + p2 + p3 + p4; }
+
+TEST(ActionPnMacroTest, WorksFor5Parameters) {
+  Action<int(int)> a1 = Plus(1, 2, 3, 4, 5);
+  EXPECT_EQ(10 + 1 + 2 + 3 + 4 + 5, a1.Perform(std::make_tuple(10)));
+}
+
+ACTION_P6(Plus, p0, p1, p2, p3, p4, p5) {
+  return arg0 + p0 + p1 + p2 + p3 + p4 + p5;
+}
+
+TEST(ActionPnMacroTest, WorksFor6Parameters) {
+  Action<int(int)> a1 = Plus(1, 2, 3, 4, 5, 6);
+  EXPECT_EQ(10 + 1 + 2 + 3 + 4 + 5 + 6, a1.Perform(std::make_tuple(10)));
+}
+
+ACTION_P7(Plus, p0, p1, p2, p3, p4, p5, p6) {
+  return arg0 + p0 + p1 + p2 + p3 + p4 + p5 + p6;
+}
+
+TEST(ActionPnMacroTest, WorksFor7Parameters) {
+  Action<int(int)> a1 = Plus(1, 2, 3, 4, 5, 6, 7);
+  EXPECT_EQ(10 + 1 + 2 + 3 + 4 + 5 + 6 + 7, a1.Perform(std::make_tuple(10)));
+}
+
+ACTION_P8(Plus, p0, p1, p2, p3, p4, p5, p6, p7) {
+  return arg0 + p0 + p1 + p2 + p3 + p4 + p5 + p6 + p7;
+}
+
+TEST(ActionPnMacroTest, WorksFor8Parameters) {
+  Action<int(int)> a1 = Plus(1, 2, 3, 4, 5, 6, 7, 8);
+  EXPECT_EQ(10 + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8,
+            a1.Perform(std::make_tuple(10)));
+}
+
+ACTION_P9(Plus, p0, p1, p2, p3, p4, p5, p6, p7, p8) {
+  return arg0 + p0 + p1 + p2 + p3 + p4 + p5 + p6 + p7 + p8;
+}
+
+TEST(ActionPnMacroTest, WorksFor9Parameters) {
+  Action<int(int)> a1 = Plus(1, 2, 3, 4, 5, 6, 7, 8, 9);
+  EXPECT_EQ(10 + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9,
+            a1.Perform(std::make_tuple(10)));
+}
+
+ACTION_P10(Plus, p0, p1, p2, p3, p4, p5, p6, p7, p8, last_param) {
+  arg0_type t0 = arg0;
+  last_param_type t9 = last_param;
+  return t0 + p0 + p1 + p2 + p3 + p4 + p5 + p6 + p7 + p8 + t9;
+}
+
+TEST(ActionPnMacroTest, WorksFor10Parameters) {
+  Action<int(int)> a1 = Plus(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
+  EXPECT_EQ(10 + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10,
+            a1.Perform(std::make_tuple(10)));
+}
+
+// Tests that the action body can promote the parameter types.
+
+ACTION_P2(PadArgument, prefix, suffix) {
+  // The following lines promote the two parameters to desired types.
+  std::string prefix_str(prefix);
+  char suffix_char = static_cast<char>(suffix);
+  return prefix_str + arg0 + suffix_char;
+}
+
+TEST(ActionPnMacroTest, SimpleTypePromotion) {
+  Action<std::string(const char*)> no_promo =
+      PadArgument(std::string("foo"), 'r');
+  Action<std::string(const char*)> promo =
+      PadArgument("foo", static_cast<int>('r'));
+  EXPECT_EQ("foobar", no_promo.Perform(std::make_tuple(CharPtr("ba"))));
+  EXPECT_EQ("foobar", promo.Perform(std::make_tuple(CharPtr("ba"))));
+}
+
+// Tests that we can partially restrict parameter types using a
+// straight-forward pattern.
+
+// Defines a generic action that doesn't restrict the types of its
+// parameters.
+ACTION_P3(ConcatImpl, a, b, c) {
+  std::stringstream ss;
+  ss << a << b << c;
+  return ss.str();
+}
+
+// Next, we try to restrict that either the first parameter is a
+// string, or the second parameter is an int.
+
+// Defines a partially specialized wrapper that restricts the first
+// parameter to std::string.
+template <typename T1, typename T2>
+// ConcatImplActionP3 is the class template ACTION_P3 uses to
+// implement ConcatImpl.  We shouldn't change the name as this
+// pattern requires the user to use it directly.
+ConcatImplActionP3<std::string, T1, T2> Concat(const std::string& a, T1 b,
+                                               T2 c) {
+  GTEST_INTENTIONAL_CONST_COND_PUSH_()
+  if (true) {
+    GTEST_INTENTIONAL_CONST_COND_POP_()
+    // This branch verifies that ConcatImpl() can be invoked without
+    // explicit template arguments.
+    return ConcatImpl(a, b, c);
+  } else {
+    // This branch verifies that ConcatImpl() can also be invoked with
+    // explicit template arguments.  It doesn't really need to be
+    // executed as this is a compile-time verification.
+    return ConcatImpl<std::string, T1, T2>(a, b, c);
+  }
+}
+
+// Defines another partially specialized wrapper that restricts the
+// second parameter to int.
+template <typename T1, typename T2>
+ConcatImplActionP3<T1, int, T2> Concat(T1 a, int b, T2 c) {
+  return ConcatImpl(a, b, c);
+}
+
+TEST(ActionPnMacroTest, CanPartiallyRestrictParameterTypes) {
+  Action<const std::string()> a1 = Concat("Hello", "1", 2);
+  EXPECT_EQ("Hello12", a1.Perform(std::make_tuple()));
+
+  a1 = Concat(1, 2, 3);
+  EXPECT_EQ("123", a1.Perform(std::make_tuple()));
+}
+
+// Verifies the type of an ACTION*.
+
+ACTION(DoFoo) {}
+ACTION_P(DoFoo, p) {}
+ACTION_P2(DoFoo, p0, p1) {}
+
+TEST(ActionPnMacroTest, TypesAreCorrect) {
+  // DoFoo() must be assignable to a DoFooAction variable.
+  DoFooAction a0 = DoFoo();
+
+  // DoFoo(1) must be assignable to a DoFooActionP variable.
+  DoFooActionP<int> a1 = DoFoo(1);
+
+  // DoFoo(p1, ..., pk) must be assignable to a DoFooActionPk
+  // variable, and so on.
+  DoFooActionP2<int, char> a2 = DoFoo(1, '2');
+  PlusActionP3<int, int, char> a3 = Plus(1, 2, '3');
+  PlusActionP4<int, int, int, char> a4 = Plus(1, 2, 3, '4');
+  PlusActionP5<int, int, int, int, char> a5 = Plus(1, 2, 3, 4, '5');
+  PlusActionP6<int, int, int, int, int, char> a6 = Plus(1, 2, 3, 4, 5, '6');
+  PlusActionP7<int, int, int, int, int, int, char> a7 =
+      Plus(1, 2, 3, 4, 5, 6, '7');
+  PlusActionP8<int, int, int, int, int, int, int, char> a8 =
+      Plus(1, 2, 3, 4, 5, 6, 7, '8');
+  PlusActionP9<int, int, int, int, int, int, int, int, char> a9 =
+      Plus(1, 2, 3, 4, 5, 6, 7, 8, '9');
+  PlusActionP10<int, int, int, int, int, int, int, int, int, char> a10 =
+      Plus(1, 2, 3, 4, 5, 6, 7, 8, 9, '0');
+
+  // Avoid "unused variable" warnings.
+  (void)a0;
+  (void)a1;
+  (void)a2;
+  (void)a3;
+  (void)a4;
+  (void)a5;
+  (void)a6;
+  (void)a7;
+  (void)a8;
+  (void)a9;
+  (void)a10;
+}
+
+// Tests that an ACTION_P*() action can be explicitly instantiated
+// with reference-typed parameters.
+
+ACTION_P(Plus1, x) { return x; }
+ACTION_P2(Plus2, x, y) { return x + y; }
+ACTION_P3(Plus3, x, y, z) { return x + y + z; }
+ACTION_P10(Plus10, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9) {
+  return a0 + a1 + a2 + a3 + a4 + a5 + a6 + a7 + a8 + a9;
+}
+
+TEST(ActionPnMacroTest, CanExplicitlyInstantiateWithReferenceTypes) {
+  int x = 1, y = 2, z = 3;
+  const std::tuple<> empty = std::make_tuple();
+
+  Action<int()> a = Plus1<int&>(x);
+  EXPECT_EQ(1, a.Perform(empty));
+
+  a = Plus2<const int&, int&>(x, y);
+  EXPECT_EQ(3, a.Perform(empty));
+
+  a = Plus3<int&, const int&, int&>(x, y, z);
+  EXPECT_EQ(6, a.Perform(empty));
+
+  int n[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
+  a = Plus10<const int&, int&, const int&, int&, const int&, int&, const int&,
+             int&, const int&, int&>(n[0], n[1], n[2], n[3], n[4], n[5], n[6],
+                                     n[7], n[8], n[9]);
+  EXPECT_EQ(55, a.Perform(empty));
+}
+
+class TenArgConstructorClass {
+ public:
+  TenArgConstructorClass(int a1, int a2, int a3, int a4, int a5, int a6, int a7,
+                         int a8, int a9, int a10)
+      : value_(a1 + a2 + a3 + a4 + a5 + a6 + a7 + a8 + a9 + a10) {}
+  int value_;
+};
+
+// Tests that ACTION_TEMPLATE works when there is no value parameter.
+ACTION_TEMPLATE(CreateNew, HAS_1_TEMPLATE_PARAMS(typename, T),
+                AND_0_VALUE_PARAMS()) {
+  return new T;
+}
+
+TEST(ActionTemplateTest, WorksWithoutValueParam) {
+  const Action<int*()> a = CreateNew<int>();
+  int* p = a.Perform(std::make_tuple());
+  delete p;
+}
+
+// Tests that ACTION_TEMPLATE works when there are value parameters.
+ACTION_TEMPLATE(CreateNew, HAS_1_TEMPLATE_PARAMS(typename, T),
+                AND_1_VALUE_PARAMS(a0)) {
+  return new T(a0);
+}
+
+TEST(ActionTemplateTest, WorksWithValueParams) {
+  const Action<int*()> a = CreateNew<int>(42);
+  int* p = a.Perform(std::make_tuple());
+  EXPECT_EQ(42, *p);
+  delete p;
+}
+
+// Tests that ACTION_TEMPLATE works for integral template parameters.
+ACTION_TEMPLATE(MyDeleteArg, HAS_1_TEMPLATE_PARAMS(int, k),
+                AND_0_VALUE_PARAMS()) {
+  delete std::get<k>(args);
+}
+
+// Resets a bool variable in the destructor.
+class BoolResetter {
+ public:
+  explicit BoolResetter(bool* value) : value_(value) {}
+  ~BoolResetter() { *value_ = false; }
+
+ private:
+  bool* value_;
+};
+
+TEST(ActionTemplateTest, WorksForIntegralTemplateParams) {
+  const Action<void(int*, BoolResetter*)> a = MyDeleteArg<1>();
+  int n = 0;
+  bool b = true;
+  auto* resetter = new BoolResetter(&b);
+  a.Perform(std::make_tuple(&n, resetter));
+  EXPECT_FALSE(b);  // Verifies that resetter is deleted.
+}
+
+// Tests that ACTION_TEMPLATES works for template template parameters.
+ACTION_TEMPLATE(ReturnSmartPointer,
+                HAS_1_TEMPLATE_PARAMS(template <typename Pointee> class,
+                                      Pointer),
+                AND_1_VALUE_PARAMS(pointee)) {
+  return Pointer<pointee_type>(new pointee_type(pointee));
+}
+
+TEST(ActionTemplateTest, WorksForTemplateTemplateParameters) {
+  const Action<std::shared_ptr<int>()> a =
+      ReturnSmartPointer<std::shared_ptr>(42);
+  std::shared_ptr<int> p = a.Perform(std::make_tuple());
+  EXPECT_EQ(42, *p);
+}
+
+// Tests that ACTION_TEMPLATE works for 10 template parameters.
+template <typename T1, typename T2, typename T3, int k4, bool k5,
+          unsigned int k6, typename T7, typename T8, typename T9>
+struct GiantTemplate {
+ public:
+  explicit GiantTemplate(int a_value) : value(a_value) {}
+  int value;
+};
+
+ACTION_TEMPLATE(ReturnGiant,
+                HAS_10_TEMPLATE_PARAMS(typename, T1, typename, T2, typename, T3,
+                                       int, k4, bool, k5, unsigned int, k6,
+                                       class, T7, class, T8, class, T9,
+                                       template <typename T> class, T10),
+                AND_1_VALUE_PARAMS(value)) {
+  return GiantTemplate<T10<T1>, T2, T3, k4, k5, k6, T7, T8, T9>(value);
+}
+
+TEST(ActionTemplateTest, WorksFor10TemplateParameters) {
+  using Giant = GiantTemplate<std::shared_ptr<int>, bool, double, 5, true, 6,
+                              char, unsigned, int>;
+  const Action<Giant()> a = ReturnGiant<int, bool, double, 5, true, 6, char,
+                                        unsigned, int, std::shared_ptr>(42);
+  Giant giant = a.Perform(std::make_tuple());
+  EXPECT_EQ(42, giant.value);
+}
+
+// Tests that ACTION_TEMPLATE works for 10 value parameters.
+ACTION_TEMPLATE(ReturnSum, HAS_1_TEMPLATE_PARAMS(typename, Number),
+                AND_10_VALUE_PARAMS(v1, v2, v3, v4, v5, v6, v7, v8, v9, v10)) {
+  return static_cast<Number>(v1) + v2 + v3 + v4 + v5 + v6 + v7 + v8 + v9 + v10;
+}
+
+TEST(ActionTemplateTest, WorksFor10ValueParameters) {
+  const Action<int()> a = ReturnSum<int>(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
+  EXPECT_EQ(55, a.Perform(std::make_tuple()));
+}
+
+// Tests that ACTION_TEMPLATE and ACTION/ACTION_P* can be overloaded
+// on the number of value parameters.
+
+ACTION(ReturnSum) { return 0; }
+
+ACTION_P(ReturnSum, x) { return x; }
+
+ACTION_TEMPLATE(ReturnSum, HAS_1_TEMPLATE_PARAMS(typename, Number),
+                AND_2_VALUE_PARAMS(v1, v2)) {
+  return static_cast<Number>(v1) + v2;
+}
+
+ACTION_TEMPLATE(ReturnSum, HAS_1_TEMPLATE_PARAMS(typename, Number),
+                AND_3_VALUE_PARAMS(v1, v2, v3)) {
+  return static_cast<Number>(v1) + v2 + v3;
+}
+
+ACTION_TEMPLATE(ReturnSum, HAS_2_TEMPLATE_PARAMS(typename, Number, int, k),
+                AND_4_VALUE_PARAMS(v1, v2, v3, v4)) {
+  return static_cast<Number>(v1) + v2 + v3 + v4 + k;
+}
+
+TEST(ActionTemplateTest, CanBeOverloadedOnNumberOfValueParameters) {
+  const Action<int()> a0 = ReturnSum();
+  const Action<int()> a1 = ReturnSum(1);
+  const Action<int()> a2 = ReturnSum<int>(1, 2);
+  const Action<int()> a3 = ReturnSum<int>(1, 2, 3);
+  const Action<int()> a4 = ReturnSum<int, 10000>(2000, 300, 40, 5);
+  EXPECT_EQ(0, a0.Perform(std::make_tuple()));
+  EXPECT_EQ(1, a1.Perform(std::make_tuple()));
+  EXPECT_EQ(3, a2.Perform(std::make_tuple()));
+  EXPECT_EQ(6, a3.Perform(std::make_tuple()));
+  EXPECT_EQ(12345, a4.Perform(std::make_tuple()));
+}
+
+}  // namespace gmock_more_actions_test
+}  // namespace testing
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock-nice-strict_test.cc b/leveldb_base/third_party/googletest/googlemock/test/gmock-nice-strict_test.cc
new file mode 100644
index 0000000..25558eb
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock-nice-strict_test.cc
@@ -0,0 +1,539 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "gmock/gmock-nice-strict.h"
+
+#include <string>
+#include <utility>
+#include "gmock/gmock.h"
+#include "gtest/gtest-spi.h"
+#include "gtest/gtest.h"
+
+// This must not be defined inside the ::testing namespace, or it will
+// clash with ::testing::Mock.
+class Mock {
+ public:
+  Mock() {}
+
+  MOCK_METHOD0(DoThis, void());
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(Mock);
+};
+
+namespace testing {
+namespace gmock_nice_strict_test {
+
+using testing::GMOCK_FLAG(verbose);
+using testing::HasSubstr;
+using testing::NaggyMock;
+using testing::NiceMock;
+using testing::StrictMock;
+
+#if GTEST_HAS_STREAM_REDIRECTION
+using testing::internal::CaptureStdout;
+using testing::internal::GetCapturedStdout;
+#endif
+
+// Class without default constructor.
+class NotDefaultConstructible {
+ public:
+  explicit NotDefaultConstructible(int) {}
+};
+
+class CallsMockMethodInDestructor {
+ public:
+  ~CallsMockMethodInDestructor() { OnDestroy(); }
+  MOCK_METHOD(void, OnDestroy, ());
+};
+
+// Defines some mock classes needed by the tests.
+
+class Foo {
+ public:
+  virtual ~Foo() {}
+
+  virtual void DoThis() = 0;
+  virtual int DoThat(bool flag) = 0;
+};
+
+class MockFoo : public Foo {
+ public:
+  MockFoo() {}
+  void Delete() { delete this; }
+
+  MOCK_METHOD0(DoThis, void());
+  MOCK_METHOD1(DoThat, int(bool flag));
+  MOCK_METHOD0(ReturnNonDefaultConstructible, NotDefaultConstructible());
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(MockFoo);
+};
+
+class MockBar {
+ public:
+  explicit MockBar(const std::string& s) : str_(s) {}
+
+  MockBar(char a1, char a2, std::string a3, std::string a4, int a5, int a6,
+          const std::string& a7, const std::string& a8, bool a9, bool a10) {
+    str_ = std::string() + a1 + a2 + a3 + a4 + static_cast<char>(a5) +
+        static_cast<char>(a6) + a7 + a8 + (a9 ? 'T' : 'F') + (a10 ? 'T' : 'F');
+  }
+
+  virtual ~MockBar() {}
+
+  const std::string& str() const { return str_; }
+
+  MOCK_METHOD0(This, int());
+  MOCK_METHOD2(That, std::string(int, bool));
+
+ private:
+  std::string str_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(MockBar);
+};
+
+
+class MockBaz {
+ public:
+  class MoveOnly {
+   public:
+    MoveOnly() = default;
+
+    MoveOnly(const MoveOnly&) = delete;
+    MoveOnly& operator=(const MoveOnly&) = delete;
+
+    MoveOnly(MoveOnly&&) = default;
+    MoveOnly& operator=(MoveOnly&&) = default;
+  };
+
+  MockBaz(MoveOnly) {}
+};
+
+#if GTEST_HAS_STREAM_REDIRECTION
+
+// Tests that a raw mock generates warnings for uninteresting calls.
+TEST(RawMockTest, WarningForUninterestingCall) {
+  const std::string saved_flag = GMOCK_FLAG(verbose);
+  GMOCK_FLAG(verbose) = "warning";
+
+  MockFoo raw_foo;
+
+  CaptureStdout();
+  raw_foo.DoThis();
+  raw_foo.DoThat(true);
+  EXPECT_THAT(GetCapturedStdout(),
+              HasSubstr("Uninteresting mock function call"));
+
+  GMOCK_FLAG(verbose) = saved_flag;
+}
+
+// Tests that a raw mock generates warnings for uninteresting calls
+// that delete the mock object.
+TEST(RawMockTest, WarningForUninterestingCallAfterDeath) {
+  const std::string saved_flag = GMOCK_FLAG(verbose);
+  GMOCK_FLAG(verbose) = "warning";
+
+  MockFoo* const raw_foo = new MockFoo;
+
+  ON_CALL(*raw_foo, DoThis())
+      .WillByDefault(Invoke(raw_foo, &MockFoo::Delete));
+
+  CaptureStdout();
+  raw_foo->DoThis();
+  EXPECT_THAT(GetCapturedStdout(),
+              HasSubstr("Uninteresting mock function call"));
+
+  GMOCK_FLAG(verbose) = saved_flag;
+}
+
+// Tests that a raw mock generates informational logs for
+// uninteresting calls.
+TEST(RawMockTest, InfoForUninterestingCall) {
+  MockFoo raw_foo;
+
+  const std::string saved_flag = GMOCK_FLAG(verbose);
+  GMOCK_FLAG(verbose) = "info";
+  CaptureStdout();
+  raw_foo.DoThis();
+  EXPECT_THAT(GetCapturedStdout(),
+              HasSubstr("Uninteresting mock function call"));
+
+  GMOCK_FLAG(verbose) = saved_flag;
+}
+
+TEST(RawMockTest, IsNaggy_IsNice_IsStrict) {
+  MockFoo raw_foo;
+  EXPECT_TRUE(Mock::IsNaggy(&raw_foo));
+  EXPECT_FALSE(Mock::IsNice(&raw_foo));
+  EXPECT_FALSE(Mock::IsStrict(&raw_foo));
+}
+
+// Tests that a nice mock generates no warning for uninteresting calls.
+TEST(NiceMockTest, NoWarningForUninterestingCall) {
+  NiceMock<MockFoo> nice_foo;
+
+  CaptureStdout();
+  nice_foo.DoThis();
+  nice_foo.DoThat(true);
+  EXPECT_EQ("", GetCapturedStdout());
+}
+
+// Tests that a nice mock generates no warning for uninteresting calls
+// that delete the mock object.
+TEST(NiceMockTest, NoWarningForUninterestingCallAfterDeath) {
+  NiceMock<MockFoo>* const nice_foo = new NiceMock<MockFoo>;
+
+  ON_CALL(*nice_foo, DoThis())
+      .WillByDefault(Invoke(nice_foo, &MockFoo::Delete));
+
+  CaptureStdout();
+  nice_foo->DoThis();
+  EXPECT_EQ("", GetCapturedStdout());
+}
+
+// Tests that a nice mock generates informational logs for
+// uninteresting calls.
+TEST(NiceMockTest, InfoForUninterestingCall) {
+  NiceMock<MockFoo> nice_foo;
+
+  const std::string saved_flag = GMOCK_FLAG(verbose);
+  GMOCK_FLAG(verbose) = "info";
+  CaptureStdout();
+  nice_foo.DoThis();
+  EXPECT_THAT(GetCapturedStdout(),
+              HasSubstr("Uninteresting mock function call"));
+
+  GMOCK_FLAG(verbose) = saved_flag;
+}
+
+#endif  // GTEST_HAS_STREAM_REDIRECTION
+
+// Tests that a nice mock allows expected calls.
+TEST(NiceMockTest, AllowsExpectedCall) {
+  NiceMock<MockFoo> nice_foo;
+
+  EXPECT_CALL(nice_foo, DoThis());
+  nice_foo.DoThis();
+}
+
+// Tests that an unexpected call on a nice mock which returns a
+// not-default-constructible type throws an exception and the exception contains
+// the method's name.
+TEST(NiceMockTest, ThrowsExceptionForUnknownReturnTypes) {
+  NiceMock<MockFoo> nice_foo;
+#if GTEST_HAS_EXCEPTIONS
+  try {
+    nice_foo.ReturnNonDefaultConstructible();
+    FAIL();
+  } catch (const std::runtime_error& ex) {
+    EXPECT_THAT(ex.what(), HasSubstr("ReturnNonDefaultConstructible"));
+  }
+#else
+  EXPECT_DEATH_IF_SUPPORTED({ nice_foo.ReturnNonDefaultConstructible(); }, "");
+#endif
+}
+
+// Tests that an unexpected call on a nice mock fails.
+TEST(NiceMockTest, UnexpectedCallFails) {
+  NiceMock<MockFoo> nice_foo;
+
+  EXPECT_CALL(nice_foo, DoThis()).Times(0);
+  EXPECT_NONFATAL_FAILURE(nice_foo.DoThis(), "called more times than expected");
+}
+
+// Tests that NiceMock works with a mock class that has a non-default
+// constructor.
+TEST(NiceMockTest, NonDefaultConstructor) {
+  NiceMock<MockBar> nice_bar("hi");
+  EXPECT_EQ("hi", nice_bar.str());
+
+  nice_bar.This();
+  nice_bar.That(5, true);
+}
+
+// Tests that NiceMock works with a mock class that has a 10-ary
+// non-default constructor.
+TEST(NiceMockTest, NonDefaultConstructor10) {
+  NiceMock<MockBar> nice_bar('a', 'b', "c", "d", 'e', 'f',
+                             "g", "h", true, false);
+  EXPECT_EQ("abcdefghTF", nice_bar.str());
+
+  nice_bar.This();
+  nice_bar.That(5, true);
+}
+
+TEST(NiceMockTest, AllowLeak) {
+  NiceMock<MockFoo>* leaked = new NiceMock<MockFoo>;
+  Mock::AllowLeak(leaked);
+  EXPECT_CALL(*leaked, DoThis());
+  leaked->DoThis();
+}
+
+TEST(NiceMockTest, MoveOnlyConstructor) {
+  NiceMock<MockBaz> nice_baz(MockBaz::MoveOnly{});
+}
+
+// Tests that NiceMock<Mock> compiles where Mock is a user-defined
+// class (as opposed to ::testing::Mock).
+TEST(NiceMockTest, AcceptsClassNamedMock) {
+  NiceMock< ::Mock> nice;
+  EXPECT_CALL(nice, DoThis());
+  nice.DoThis();
+}
+
+TEST(NiceMockTest, IsNiceInDestructor) {
+  {
+    NiceMock<CallsMockMethodInDestructor> nice_on_destroy;
+    // Don't add an expectation for the call before the mock goes out of scope.
+  }
+}
+
+TEST(NiceMockTest, IsNaggy_IsNice_IsStrict) {
+  NiceMock<MockFoo> nice_foo;
+  EXPECT_FALSE(Mock::IsNaggy(&nice_foo));
+  EXPECT_TRUE(Mock::IsNice(&nice_foo));
+  EXPECT_FALSE(Mock::IsStrict(&nice_foo));
+}
+
+#if GTEST_HAS_STREAM_REDIRECTION
+
+// Tests that a naggy mock generates warnings for uninteresting calls.
+TEST(NaggyMockTest, WarningForUninterestingCall) {
+  const std::string saved_flag = GMOCK_FLAG(verbose);
+  GMOCK_FLAG(verbose) = "warning";
+
+  NaggyMock<MockFoo> naggy_foo;
+
+  CaptureStdout();
+  naggy_foo.DoThis();
+  naggy_foo.DoThat(true);
+  EXPECT_THAT(GetCapturedStdout(),
+              HasSubstr("Uninteresting mock function call"));
+
+  GMOCK_FLAG(verbose) = saved_flag;
+}
+
+// Tests that a naggy mock generates a warning for an uninteresting call
+// that deletes the mock object.
+TEST(NaggyMockTest, WarningForUninterestingCallAfterDeath) {
+  const std::string saved_flag = GMOCK_FLAG(verbose);
+  GMOCK_FLAG(verbose) = "warning";
+
+  NaggyMock<MockFoo>* const naggy_foo = new NaggyMock<MockFoo>;
+
+  ON_CALL(*naggy_foo, DoThis())
+      .WillByDefault(Invoke(naggy_foo, &MockFoo::Delete));
+
+  CaptureStdout();
+  naggy_foo->DoThis();
+  EXPECT_THAT(GetCapturedStdout(),
+              HasSubstr("Uninteresting mock function call"));
+
+  GMOCK_FLAG(verbose) = saved_flag;
+}
+
+#endif  // GTEST_HAS_STREAM_REDIRECTION
+
+// Tests that a naggy mock allows expected calls.
+TEST(NaggyMockTest, AllowsExpectedCall) {
+  NaggyMock<MockFoo> naggy_foo;
+
+  EXPECT_CALL(naggy_foo, DoThis());
+  naggy_foo.DoThis();
+}
+
+// Tests that an unexpected call on a naggy mock fails.
+TEST(NaggyMockTest, UnexpectedCallFails) {
+  NaggyMock<MockFoo> naggy_foo;
+
+  EXPECT_CALL(naggy_foo, DoThis()).Times(0);
+  EXPECT_NONFATAL_FAILURE(naggy_foo.DoThis(),
+                          "called more times than expected");
+}
+
+// Tests that NaggyMock works with a mock class that has a non-default
+// constructor.
+TEST(NaggyMockTest, NonDefaultConstructor) {
+  NaggyMock<MockBar> naggy_bar("hi");
+  EXPECT_EQ("hi", naggy_bar.str());
+
+  naggy_bar.This();
+  naggy_bar.That(5, true);
+}
+
+// Tests that NaggyMock works with a mock class that has a 10-ary
+// non-default constructor.
+TEST(NaggyMockTest, NonDefaultConstructor10) {
+  NaggyMock<MockBar> naggy_bar('0', '1', "2", "3", '4', '5',
+                               "6", "7", true, false);
+  EXPECT_EQ("01234567TF", naggy_bar.str());
+
+  naggy_bar.This();
+  naggy_bar.That(5, true);
+}
+
+TEST(NaggyMockTest, AllowLeak) {
+  NaggyMock<MockFoo>* leaked = new NaggyMock<MockFoo>;
+  Mock::AllowLeak(leaked);
+  EXPECT_CALL(*leaked, DoThis());
+  leaked->DoThis();
+}
+
+TEST(NaggyMockTest, MoveOnlyConstructor) {
+  NaggyMock<MockBaz> naggy_baz(MockBaz::MoveOnly{});
+}
+
+// Tests that NaggyMock<Mock> compiles where Mock is a user-defined
+// class (as opposed to ::testing::Mock).
+TEST(NaggyMockTest, AcceptsClassNamedMock) {
+  NaggyMock< ::Mock> naggy;
+  EXPECT_CALL(naggy, DoThis());
+  naggy.DoThis();
+}
+
+TEST(NaggyMockTest, IsNaggyInDestructor) {
+  const std::string saved_flag = GMOCK_FLAG(verbose);
+  GMOCK_FLAG(verbose) = "warning";
+  CaptureStdout();
+
+  {
+    NaggyMock<CallsMockMethodInDestructor> naggy_on_destroy;
+    // Don't add an expectation for the call before the mock goes out of scope.
+  }
+
+  EXPECT_THAT(GetCapturedStdout(),
+              HasSubstr("Uninteresting mock function call"));
+
+  GMOCK_FLAG(verbose) = saved_flag;
+}
+
+TEST(NaggyMockTest, IsNaggy_IsNice_IsStrict) {
+  NaggyMock<MockFoo> naggy_foo;
+  EXPECT_TRUE(Mock::IsNaggy(&naggy_foo));
+  EXPECT_FALSE(Mock::IsNice(&naggy_foo));
+  EXPECT_FALSE(Mock::IsStrict(&naggy_foo));
+}
+
+// Tests that a strict mock allows expected calls.
+TEST(StrictMockTest, AllowsExpectedCall) {
+  StrictMock<MockFoo> strict_foo;
+
+  EXPECT_CALL(strict_foo, DoThis());
+  strict_foo.DoThis();
+}
+
+// Tests that an unexpected call on a strict mock fails.
+TEST(StrictMockTest, UnexpectedCallFails) {
+  StrictMock<MockFoo> strict_foo;
+
+  EXPECT_CALL(strict_foo, DoThis()).Times(0);
+  EXPECT_NONFATAL_FAILURE(strict_foo.DoThis(),
+                          "called more times than expected");
+}
+
+// Tests that an uninteresting call on a strict mock fails.
+TEST(StrictMockTest, UninterestingCallFails) {
+  StrictMock<MockFoo> strict_foo;
+
+  EXPECT_NONFATAL_FAILURE(strict_foo.DoThis(),
+                          "Uninteresting mock function call");
+}
+
+// Tests that an uninteresting call on a strict mock fails, even if
+// the call deletes the mock object.
+TEST(StrictMockTest, UninterestingCallFailsAfterDeath) {
+  StrictMock<MockFoo>* const strict_foo = new StrictMock<MockFoo>;
+
+  ON_CALL(*strict_foo, DoThis())
+      .WillByDefault(Invoke(strict_foo, &MockFoo::Delete));
+
+  EXPECT_NONFATAL_FAILURE(strict_foo->DoThis(),
+                          "Uninteresting mock function call");
+}
+
+// Tests that StrictMock works with a mock class that has a
+// non-default constructor.
+TEST(StrictMockTest, NonDefaultConstructor) {
+  StrictMock<MockBar> strict_bar("hi");
+  EXPECT_EQ("hi", strict_bar.str());
+
+  EXPECT_NONFATAL_FAILURE(strict_bar.That(5, true),
+                          "Uninteresting mock function call");
+}
+
+// Tests that StrictMock works with a mock class that has a 10-ary
+// non-default constructor.
+TEST(StrictMockTest, NonDefaultConstructor10) {
+  StrictMock<MockBar> strict_bar('a', 'b', "c", "d", 'e', 'f',
+                                 "g", "h", true, false);
+  EXPECT_EQ("abcdefghTF", strict_bar.str());
+
+  EXPECT_NONFATAL_FAILURE(strict_bar.That(5, true),
+                          "Uninteresting mock function call");
+}
+
+TEST(StrictMockTest, AllowLeak) {
+  StrictMock<MockFoo>* leaked = new StrictMock<MockFoo>;
+  Mock::AllowLeak(leaked);
+  EXPECT_CALL(*leaked, DoThis());
+  leaked->DoThis();
+}
+
+TEST(StrictMockTest, MoveOnlyConstructor) {
+  StrictMock<MockBaz> strict_baz(MockBaz::MoveOnly{});
+}
+
+// Tests that StrictMock<Mock> compiles where Mock is a user-defined
+// class (as opposed to ::testing::Mock).
+TEST(StrictMockTest, AcceptsClassNamedMock) {
+  StrictMock< ::Mock> strict;
+  EXPECT_CALL(strict, DoThis());
+  strict.DoThis();
+}
+
+TEST(StrictMockTest, IsStrictInDestructor) {
+  EXPECT_NONFATAL_FAILURE(
+      {
+        StrictMock<CallsMockMethodInDestructor> strict_on_destroy;
+        // Don't add an expectation for the call before the mock goes out of
+        // scope.
+      },
+      "Uninteresting mock function call");
+}
+
+TEST(StrictMockTest, IsNaggy_IsNice_IsStrict) {
+  StrictMock<MockFoo> strict_foo;
+  EXPECT_FALSE(Mock::IsNaggy(&strict_foo));
+  EXPECT_FALSE(Mock::IsNice(&strict_foo));
+  EXPECT_TRUE(Mock::IsStrict(&strict_foo));
+}
+
+}  // namespace gmock_nice_strict_test
+}  // namespace testing
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock-port_test.cc b/leveldb_base/third_party/googletest/googlemock/test/gmock-port_test.cc
new file mode 100644
index 0000000..a2c2be2
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock-port_test.cc
@@ -0,0 +1,42 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests the internal cross-platform support utilities.
+
+#include "gmock/internal/gmock-port.h"
+#include "gtest/gtest.h"
+
+// NOTE: if this file is left without tests for some reason, put a dummy
+// test here to make references to symbols in the gtest library and avoid
+// 'undefined symbol' linker errors in gmock_main:
+
+TEST(DummyTest, Dummy) {}
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock-pp-string_test.cc b/leveldb_base/third_party/googletest/googlemock/test/gmock-pp-string_test.cc
new file mode 100644
index 0000000..6f66cf1
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock-pp-string_test.cc
@@ -0,0 +1,206 @@
+// Copyright 2018, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests the internal preprocessor macro library.
+#include "gmock/internal/gmock-pp.h"
+
+#include <string>
+
+#include "gmock/gmock.h"
+
+namespace testing {
+namespace {
+
+// Matcher to verify that to strings are identical up to whitespace
+// Not 100% correct, because it treats "AB" as equal to "A B".
+::testing::Matcher<const std::string&> SameExceptSpaces(const std::string& s) {
+  auto remove_spaces = [](std::string to_split) {
+    to_split.erase(std::remove(to_split.begin(), to_split.end(), ' '),
+                   to_split.end());
+    return to_split;
+  };
+  return ::testing::ResultOf(remove_spaces, remove_spaces(s));
+}
+
+// Verify that a macro expands to a given text. Ignores whitespace difference.
+// In MSVC, GMOCK_PP_STRINGIZE() returns nothing, rather than "". So concatenate
+// with an empty string.
+#define EXPECT_EXPANSION(Result, Macro) \
+  EXPECT_THAT("" GMOCK_PP_STRINGIZE(Macro), SameExceptSpaces(Result))
+
+TEST(Macros, Cat) {
+  EXPECT_EXPANSION("14", GMOCK_PP_CAT(1, 4));
+  EXPECT_EXPANSION("+=", GMOCK_PP_CAT(+, =));
+}
+
+TEST(Macros, Narg) {
+  EXPECT_EXPANSION("1", GMOCK_PP_NARG());
+  EXPECT_EXPANSION("1", GMOCK_PP_NARG(x));
+  EXPECT_EXPANSION("2", GMOCK_PP_NARG(x, y));
+  EXPECT_EXPANSION("3", GMOCK_PP_NARG(x, y, z));
+  EXPECT_EXPANSION("4", GMOCK_PP_NARG(x, y, z, w));
+
+  EXPECT_EXPANSION("0", GMOCK_PP_NARG0());
+  EXPECT_EXPANSION("1", GMOCK_PP_NARG0(x));
+  EXPECT_EXPANSION("2", GMOCK_PP_NARG0(x, y));
+}
+
+TEST(Macros, Comma) {
+  EXPECT_EXPANSION("0", GMOCK_PP_HAS_COMMA());
+  EXPECT_EXPANSION("1", GMOCK_PP_HAS_COMMA(, ));
+  EXPECT_EXPANSION("0", GMOCK_PP_HAS_COMMA((, )));
+}
+
+TEST(Macros, IsEmpty) {
+  EXPECT_EXPANSION("1", GMOCK_PP_IS_EMPTY());
+  EXPECT_EXPANSION("0", GMOCK_PP_IS_EMPTY(, ));
+  EXPECT_EXPANSION("0", GMOCK_PP_IS_EMPTY(a));
+  EXPECT_EXPANSION("0", GMOCK_PP_IS_EMPTY(()));
+
+#define GMOCK_PP_INTERNAL_IS_EMPTY_TEST_1
+  EXPECT_EXPANSION("1", GMOCK_PP_IS_EMPTY(GMOCK_PP_INTERNAL_IS_EMPTY_TEST_1));
+}
+
+TEST(Macros, If) {
+  EXPECT_EXPANSION("1", GMOCK_PP_IF(1, 1, 2));
+  EXPECT_EXPANSION("2", GMOCK_PP_IF(0, 1, 2));
+}
+
+TEST(Macros, HeadTail) {
+  EXPECT_EXPANSION("1", GMOCK_PP_HEAD(1));
+  EXPECT_EXPANSION("1", GMOCK_PP_HEAD(1, 2));
+  EXPECT_EXPANSION("1", GMOCK_PP_HEAD(1, 2, 3));
+
+  EXPECT_EXPANSION("", GMOCK_PP_TAIL(1));
+  EXPECT_EXPANSION("2", GMOCK_PP_TAIL(1, 2));
+  EXPECT_EXPANSION("2", GMOCK_PP_HEAD(GMOCK_PP_TAIL(1, 2, 3)));
+}
+
+TEST(Macros, Parentheses) {
+  EXPECT_EXPANSION("0", GMOCK_PP_IS_BEGIN_PARENS(sss));
+  EXPECT_EXPANSION("0", GMOCK_PP_IS_BEGIN_PARENS(sss()));
+  EXPECT_EXPANSION("0", GMOCK_PP_IS_BEGIN_PARENS(sss() sss));
+  EXPECT_EXPANSION("1", GMOCK_PP_IS_BEGIN_PARENS((sss)));
+  EXPECT_EXPANSION("1", GMOCK_PP_IS_BEGIN_PARENS((sss)ss));
+
+  EXPECT_EXPANSION("0", GMOCK_PP_IS_ENCLOSED_PARENS(sss));
+  EXPECT_EXPANSION("0", GMOCK_PP_IS_ENCLOSED_PARENS(sss()));
+  EXPECT_EXPANSION("0", GMOCK_PP_IS_ENCLOSED_PARENS(sss() sss));
+  EXPECT_EXPANSION("1", GMOCK_PP_IS_ENCLOSED_PARENS((sss)));
+  EXPECT_EXPANSION("0", GMOCK_PP_IS_ENCLOSED_PARENS((sss)ss));
+
+  EXPECT_EXPANSION("1 + 1", GMOCK_PP_REMOVE_PARENS((1 + 1)));
+}
+
+TEST(Macros, Increment) {
+  EXPECT_EXPANSION("1", GMOCK_PP_INC(0));
+  EXPECT_EXPANSION("2", GMOCK_PP_INC(1));
+  EXPECT_EXPANSION("3", GMOCK_PP_INC(2));
+  EXPECT_EXPANSION("4", GMOCK_PP_INC(3));
+  EXPECT_EXPANSION("5", GMOCK_PP_INC(4));
+
+  EXPECT_EXPANSION("16", GMOCK_PP_INC(15));
+}
+
+#define JOINER_CAT(a, b) a##b
+#define JOINER(_N, _Data, _Elem) JOINER_CAT(_Data, _N) = _Elem
+
+TEST(Macros, Repeat) {
+  EXPECT_EXPANSION("", GMOCK_PP_REPEAT(JOINER, X, 0));
+  EXPECT_EXPANSION("X0=", GMOCK_PP_REPEAT(JOINER, X, 1));
+  EXPECT_EXPANSION("X0= X1=", GMOCK_PP_REPEAT(JOINER, X, 2));
+  EXPECT_EXPANSION("X0= X1= X2=", GMOCK_PP_REPEAT(JOINER, X, 3));
+  EXPECT_EXPANSION("X0= X1= X2= X3=", GMOCK_PP_REPEAT(JOINER, X, 4));
+  EXPECT_EXPANSION("X0= X1= X2= X3= X4=", GMOCK_PP_REPEAT(JOINER, X, 5));
+  EXPECT_EXPANSION("X0= X1= X2= X3= X4= X5=", GMOCK_PP_REPEAT(JOINER, X, 6));
+  EXPECT_EXPANSION("X0= X1= X2= X3= X4= X5= X6=",
+                   GMOCK_PP_REPEAT(JOINER, X, 7));
+  EXPECT_EXPANSION("X0= X1= X2= X3= X4= X5= X6= X7=",
+                   GMOCK_PP_REPEAT(JOINER, X, 8));
+  EXPECT_EXPANSION("X0= X1= X2= X3= X4= X5= X6= X7= X8=",
+                   GMOCK_PP_REPEAT(JOINER, X, 9));
+  EXPECT_EXPANSION("X0= X1= X2= X3= X4= X5= X6= X7= X8= X9=",
+                   GMOCK_PP_REPEAT(JOINER, X, 10));
+  EXPECT_EXPANSION("X0= X1= X2= X3= X4= X5= X6= X7= X8= X9= X10=",
+                   GMOCK_PP_REPEAT(JOINER, X, 11));
+  EXPECT_EXPANSION("X0= X1= X2= X3= X4= X5= X6= X7= X8= X9= X10= X11=",
+                   GMOCK_PP_REPEAT(JOINER, X, 12));
+  EXPECT_EXPANSION("X0= X1= X2= X3= X4= X5= X6= X7= X8= X9= X10= X11= X12=",
+                   GMOCK_PP_REPEAT(JOINER, X, 13));
+  EXPECT_EXPANSION(
+      "X0= X1= X2= X3= X4= X5= X6= X7= X8= X9= X10= X11= X12= X13=",
+      GMOCK_PP_REPEAT(JOINER, X, 14));
+  EXPECT_EXPANSION(
+      "X0= X1= X2= X3= X4= X5= X6= X7= X8= X9= X10= X11= X12= X13= X14=",
+      GMOCK_PP_REPEAT(JOINER, X, 15));
+}
+TEST(Macros, ForEach) {
+  EXPECT_EXPANSION("", GMOCK_PP_FOR_EACH(JOINER, X, ()));
+  EXPECT_EXPANSION("X0=a", GMOCK_PP_FOR_EACH(JOINER, X, (a)));
+  EXPECT_EXPANSION("X0=a X1=b", GMOCK_PP_FOR_EACH(JOINER, X, (a, b)));
+  EXPECT_EXPANSION("X0=a X1=b X2=c", GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c)));
+  EXPECT_EXPANSION("X0=a X1=b X2=c X3=d",
+                   GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c, d)));
+  EXPECT_EXPANSION("X0=a X1=b X2=c X3=d X4=e",
+                   GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c, d, e)));
+  EXPECT_EXPANSION("X0=a X1=b X2=c X3=d X4=e X5=f",
+                   GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c, d, e, f)));
+  EXPECT_EXPANSION("X0=a X1=b X2=c X3=d X4=e X5=f X6=g",
+                   GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c, d, e, f, g)));
+  EXPECT_EXPANSION("X0=a X1=b X2=c X3=d X4=e X5=f X6=g X7=h",
+                   GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c, d, e, f, g, h)));
+  EXPECT_EXPANSION("X0=a X1=b X2=c X3=d X4=e X5=f X6=g X7=h X8=i",
+                   GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c, d, e, f, g, h, i)));
+  EXPECT_EXPANSION(
+      "X0=a X1=b X2=c X3=d X4=e X5=f X6=g X7=h X8=i X9=j",
+      GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c, d, e, f, g, h, i, j)));
+  EXPECT_EXPANSION(
+      "X0=a X1=b X2=c X3=d X4=e X5=f X6=g X7=h X8=i X9=j X10=k",
+      GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c, d, e, f, g, h, i, j, k)));
+  EXPECT_EXPANSION(
+      "X0=a X1=b X2=c X3=d X4=e X5=f X6=g X7=h X8=i X9=j X10=k X11=l",
+      GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c, d, e, f, g, h, i, j, k, l)));
+  EXPECT_EXPANSION(
+      "X0=a X1=b X2=c X3=d X4=e X5=f X6=g X7=h X8=i X9=j X10=k X11=l X12=m",
+      GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c, d, e, f, g, h, i, j, k, l, m)));
+  EXPECT_EXPANSION(
+      "X0=a X1=b X2=c X3=d X4=e X5=f X6=g X7=h X8=i X9=j X10=k X11=l X12=m "
+      "X13=n",
+      GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c, d, e, f, g, h, i, j, k, l, m, n)));
+  EXPECT_EXPANSION(
+      "X0=a X1=b X2=c X3=d X4=e X5=f X6=g X7=h X8=i X9=j X10=k X11=l X12=m "
+      "X13=n X14=o",
+      GMOCK_PP_FOR_EACH(JOINER, X,
+                        (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o)));
+}
+
+}  // namespace
+}  // namespace testing
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock-pp_test.cc b/leveldb_base/third_party/googletest/googlemock/test/gmock-pp_test.cc
new file mode 100644
index 0000000..5d1566e
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock-pp_test.cc
@@ -0,0 +1,83 @@
+#include "gmock/internal/gmock-pp.h"
+
+// Used to test MSVC treating __VA_ARGS__ with a comma in it as one value
+#define GMOCK_TEST_REPLACE_comma_WITH_COMMA_I_comma ,
+#define GMOCK_TEST_REPLACE_comma_WITH_COMMA(x) \
+  GMOCK_PP_CAT(GMOCK_TEST_REPLACE_comma_WITH_COMMA_I_, x)
+
+// Static assertions.
+namespace testing {
+namespace internal {
+namespace gmockpp {
+
+static_assert(GMOCK_PP_CAT(1, 4) == 14, "");
+static_assert(GMOCK_PP_INTERNAL_INTERNAL_16TH(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,
+                                              12, 13, 14, 15, 16, 17, 18) == 16,
+              "");
+static_assert(GMOCK_PP_NARG() == 1, "");
+static_assert(GMOCK_PP_NARG(x) == 1, "");
+static_assert(GMOCK_PP_NARG(x, y) == 2, "");
+static_assert(GMOCK_PP_NARG(x, y, z) == 3, "");
+static_assert(GMOCK_PP_NARG(x, y, z, w) == 4, "");
+static_assert(!GMOCK_PP_HAS_COMMA(), "");
+static_assert(GMOCK_PP_HAS_COMMA(b, ), "");
+static_assert(!GMOCK_PP_HAS_COMMA((, )), "");
+static_assert(GMOCK_PP_HAS_COMMA(GMOCK_TEST_REPLACE_comma_WITH_COMMA(comma)),
+              "");
+static_assert(
+    GMOCK_PP_HAS_COMMA(GMOCK_TEST_REPLACE_comma_WITH_COMMA(comma(unrelated))),
+    "");
+static_assert(!GMOCK_PP_IS_EMPTY(, ), "");
+static_assert(!GMOCK_PP_IS_EMPTY(a), "");
+static_assert(!GMOCK_PP_IS_EMPTY(()), "");
+static_assert(GMOCK_PP_IF(1, 1, 2) == 1, "");
+static_assert(GMOCK_PP_IF(0, 1, 2) == 2, "");
+static_assert(GMOCK_PP_NARG0(x) == 1, "");
+static_assert(GMOCK_PP_NARG0(x, y) == 2, "");
+static_assert(GMOCK_PP_HEAD(1) == 1, "");
+static_assert(GMOCK_PP_HEAD(1, 2) == 1, "");
+static_assert(GMOCK_PP_HEAD(1, 2, 3) == 1, "");
+static_assert(GMOCK_PP_TAIL(1, 2) == 2, "");
+static_assert(GMOCK_PP_HEAD(GMOCK_PP_TAIL(1, 2, 3)) == 2, "");
+static_assert(!GMOCK_PP_IS_BEGIN_PARENS(sss), "");
+static_assert(!GMOCK_PP_IS_BEGIN_PARENS(sss()), "");
+static_assert(!GMOCK_PP_IS_BEGIN_PARENS(sss() sss), "");
+static_assert(GMOCK_PP_IS_BEGIN_PARENS((sss)), "");
+static_assert(GMOCK_PP_IS_BEGIN_PARENS((sss)ss), "");
+static_assert(!GMOCK_PP_IS_ENCLOSED_PARENS(sss), "");
+static_assert(!GMOCK_PP_IS_ENCLOSED_PARENS(sss()), "");
+static_assert(!GMOCK_PP_IS_ENCLOSED_PARENS(sss() sss), "");
+static_assert(!GMOCK_PP_IS_ENCLOSED_PARENS((sss)ss), "");
+static_assert(GMOCK_PP_REMOVE_PARENS((1 + 1)) * 2 == 3, "");
+static_assert(GMOCK_PP_INC(4) == 5, "");
+
+template <class... Args>
+struct Test {
+  static constexpr int kArgs = sizeof...(Args);
+};
+#define GMOCK_PP_INTERNAL_TYPE_TEST(_i, _Data, _element) \
+  GMOCK_PP_COMMA_IF(_i) _element
+static_assert(Test<GMOCK_PP_FOR_EACH(GMOCK_PP_INTERNAL_TYPE_TEST, ~,
+                                     (int, float, double, char))>::kArgs == 4,
+              "");
+#define GMOCK_PP_INTERNAL_VAR_TEST_1(_x) 1
+#define GMOCK_PP_INTERNAL_VAR_TEST_2(_x, _y) 2
+#define GMOCK_PP_INTERNAL_VAR_TEST_3(_x, _y, _z) 3
+
+#define GMOCK_PP_INTERNAL_VAR_TEST(...) \
+  GMOCK_PP_VARIADIC_CALL(GMOCK_PP_INTERNAL_VAR_TEST_, __VA_ARGS__)
+static_assert(GMOCK_PP_INTERNAL_VAR_TEST(x, y) == 2, "");
+static_assert(GMOCK_PP_INTERNAL_VAR_TEST(silly) == 1, "");
+static_assert(GMOCK_PP_INTERNAL_VAR_TEST(x, y, z) == 3, "");
+
+// TODO(iserna): The following asserts fail in --config=lexan.
+#define GMOCK_PP_INTERNAL_IS_EMPTY_TEST_1
+static_assert(GMOCK_PP_IS_EMPTY(GMOCK_PP_INTERNAL_IS_EMPTY_TEST_1), "");
+static_assert(GMOCK_PP_IS_EMPTY(), "");
+static_assert(GMOCK_PP_IS_ENCLOSED_PARENS((sss)), "");
+static_assert(GMOCK_PP_IS_EMPTY(GMOCK_PP_TAIL(1)), "");
+static_assert(GMOCK_PP_NARG0() == 0, "");
+
+}  // namespace gmockpp
+}  // namespace internal
+}  // namespace testing
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock-spec-builders_test.cc b/leveldb_base/third_party/googletest/googlemock/test/gmock-spec-builders_test.cc
new file mode 100644
index 0000000..fa97411
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock-spec-builders_test.cc
@@ -0,0 +1,2775 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests the spec builder syntax.
+
+#include "gmock/gmock-spec-builders.h"
+
+#include <memory>
+#include <ostream>  // NOLINT
+#include <sstream>
+#include <string>
+
+#include "gmock/gmock.h"
+#include "gmock/internal/gmock-port.h"
+#include "gtest/gtest.h"
+#include "gtest/gtest-spi.h"
+#include "gtest/internal/gtest-port.h"
+
+namespace testing {
+namespace internal {
+
+// Helper class for testing the Expectation class template.
+class ExpectationTester {
+ public:
+  // Sets the call count of the given expectation to the given number.
+  void SetCallCount(int n, ExpectationBase* exp) {
+    exp->call_count_ = n;
+  }
+};
+
+}  // namespace internal
+}  // namespace testing
+
+namespace {
+
+using testing::_;
+using testing::AnyNumber;
+using testing::AtLeast;
+using testing::AtMost;
+using testing::Between;
+using testing::Cardinality;
+using testing::CardinalityInterface;
+using testing::Const;
+using testing::ContainsRegex;
+using testing::DoAll;
+using testing::DoDefault;
+using testing::Eq;
+using testing::Expectation;
+using testing::ExpectationSet;
+using testing::GMOCK_FLAG(verbose);
+using testing::Gt;
+using testing::IgnoreResult;
+using testing::InSequence;
+using testing::Invoke;
+using testing::InvokeWithoutArgs;
+using testing::IsNotSubstring;
+using testing::IsSubstring;
+using testing::Lt;
+using testing::Message;
+using testing::Mock;
+using testing::NaggyMock;
+using testing::Ne;
+using testing::Return;
+using testing::SaveArg;
+using testing::Sequence;
+using testing::SetArgPointee;
+using testing::internal::ExpectationTester;
+using testing::internal::FormatFileLocation;
+using testing::internal::kAllow;
+using testing::internal::kErrorVerbosity;
+using testing::internal::kFail;
+using testing::internal::kInfoVerbosity;
+using testing::internal::kWarn;
+using testing::internal::kWarningVerbosity;
+
+#if GTEST_HAS_STREAM_REDIRECTION
+using testing::HasSubstr;
+using testing::internal::CaptureStdout;
+using testing::internal::GetCapturedStdout;
+#endif
+
+class Incomplete;
+
+class MockIncomplete {
+ public:
+  // This line verifies that a mock method can take a by-reference
+  // argument of an incomplete type.
+  MOCK_METHOD1(ByRefFunc, void(const Incomplete& x));
+};
+
+// Tells Google Mock how to print a value of type Incomplete.
+void PrintTo(const Incomplete& x, ::std::ostream* os);
+
+TEST(MockMethodTest, CanInstantiateWithIncompleteArgType) {
+  // Even though this mock class contains a mock method that takes
+  // by-reference an argument whose type is incomplete, we can still
+  // use the mock, as long as Google Mock knows how to print the
+  // argument.
+  MockIncomplete incomplete;
+  EXPECT_CALL(incomplete, ByRefFunc(_))
+      .Times(AnyNumber());
+}
+
+// The definition of the printer for the argument type doesn't have to
+// be visible where the mock is used.
+void PrintTo(const Incomplete& /* x */, ::std::ostream* os) {
+  *os << "incomplete";
+}
+
+class Result {};
+
+// A type that's not default constructible.
+class NonDefaultConstructible {
+ public:
+  explicit NonDefaultConstructible(int /* dummy */) {}
+};
+
+class MockA {
+ public:
+  MockA() {}
+
+  MOCK_METHOD1(DoA, void(int n));
+  MOCK_METHOD1(ReturnResult, Result(int n));
+  MOCK_METHOD0(ReturnNonDefaultConstructible, NonDefaultConstructible());
+  MOCK_METHOD2(Binary, bool(int x, int y));
+  MOCK_METHOD2(ReturnInt, int(int x, int y));
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(MockA);
+};
+
+class MockB {
+ public:
+  MockB() {}
+
+  MOCK_CONST_METHOD0(DoB, int());  // NOLINT
+  MOCK_METHOD1(DoB, int(int n));  // NOLINT
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(MockB);
+};
+
+class ReferenceHoldingMock {
+ public:
+  ReferenceHoldingMock() {}
+
+  MOCK_METHOD1(AcceptReference, void(std::shared_ptr<MockA>*));
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(ReferenceHoldingMock);
+};
+
+// Tests that EXPECT_CALL and ON_CALL compile in a presence of macro
+// redefining a mock method name. This could happen, for example, when
+// the tested code #includes Win32 API headers which define many APIs
+// as macros, e.g. #define TextOut TextOutW.
+
+#define Method MethodW
+
+class CC {
+ public:
+  virtual ~CC() {}
+  virtual int Method() = 0;
+};
+class MockCC : public CC {
+ public:
+  MockCC() {}
+
+  MOCK_METHOD0(Method, int());
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(MockCC);
+};
+
+// Tests that a method with expanded name compiles.
+TEST(OnCallSyntaxTest, CompilesWithMethodNameExpandedFromMacro) {
+  MockCC cc;
+  ON_CALL(cc, Method());
+}
+
+// Tests that the method with expanded name not only compiles but runs
+// and returns a correct value, too.
+TEST(OnCallSyntaxTest, WorksWithMethodNameExpandedFromMacro) {
+  MockCC cc;
+  ON_CALL(cc, Method()).WillByDefault(Return(42));
+  EXPECT_EQ(42, cc.Method());
+}
+
+// Tests that a method with expanded name compiles.
+TEST(ExpectCallSyntaxTest, CompilesWithMethodNameExpandedFromMacro) {
+  MockCC cc;
+  EXPECT_CALL(cc, Method());
+  cc.Method();
+}
+
+// Tests that it works, too.
+TEST(ExpectCallSyntaxTest, WorksWithMethodNameExpandedFromMacro) {
+  MockCC cc;
+  EXPECT_CALL(cc, Method()).WillOnce(Return(42));
+  EXPECT_EQ(42, cc.Method());
+}
+
+#undef Method  // Done with macro redefinition tests.
+
+// Tests that ON_CALL evaluates its arguments exactly once as promised
+// by Google Mock.
+TEST(OnCallSyntaxTest, EvaluatesFirstArgumentOnce) {
+  MockA a;
+  MockA* pa = &a;
+
+  ON_CALL(*pa++, DoA(_));
+  EXPECT_EQ(&a + 1, pa);
+}
+
+TEST(OnCallSyntaxTest, EvaluatesSecondArgumentOnce) {
+  MockA a;
+  int n = 0;
+
+  ON_CALL(a, DoA(n++));
+  EXPECT_EQ(1, n);
+}
+
+// Tests that the syntax of ON_CALL() is enforced at run time.
+
+TEST(OnCallSyntaxTest, WithIsOptional) {
+  MockA a;
+
+  ON_CALL(a, DoA(5))
+      .WillByDefault(Return());
+  ON_CALL(a, DoA(_))
+      .With(_)
+      .WillByDefault(Return());
+}
+
+TEST(OnCallSyntaxTest, WithCanAppearAtMostOnce) {
+  MockA a;
+
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    ON_CALL(a, ReturnResult(_))
+        .With(_)
+        .With(_)
+        .WillByDefault(Return(Result()));
+  }, ".With() cannot appear more than once in an ON_CALL()");
+}
+
+TEST(OnCallSyntaxTest, WillByDefaultIsMandatory) {
+  MockA a;
+
+  EXPECT_DEATH_IF_SUPPORTED({
+    ON_CALL(a, DoA(5));
+    a.DoA(5);
+  }, "");
+}
+
+TEST(OnCallSyntaxTest, WillByDefaultCanAppearAtMostOnce) {
+  MockA a;
+
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    ON_CALL(a, DoA(5))
+        .WillByDefault(Return())
+        .WillByDefault(Return());
+  }, ".WillByDefault() must appear exactly once in an ON_CALL()");
+}
+
+// Tests that EXPECT_CALL evaluates its arguments exactly once as
+// promised by Google Mock.
+TEST(ExpectCallSyntaxTest, EvaluatesFirstArgumentOnce) {
+  MockA a;
+  MockA* pa = &a;
+
+  EXPECT_CALL(*pa++, DoA(_));
+  a.DoA(0);
+  EXPECT_EQ(&a + 1, pa);
+}
+
+TEST(ExpectCallSyntaxTest, EvaluatesSecondArgumentOnce) {
+  MockA a;
+  int n = 0;
+
+  EXPECT_CALL(a, DoA(n++));
+  a.DoA(0);
+  EXPECT_EQ(1, n);
+}
+
+// Tests that the syntax of EXPECT_CALL() is enforced at run time.
+
+TEST(ExpectCallSyntaxTest, WithIsOptional) {
+  MockA a;
+
+  EXPECT_CALL(a, DoA(5))
+      .Times(0);
+  EXPECT_CALL(a, DoA(6))
+      .With(_)
+      .Times(0);
+}
+
+TEST(ExpectCallSyntaxTest, WithCanAppearAtMostOnce) {
+  MockA a;
+
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_CALL(a, DoA(6))
+        .With(_)
+        .With(_);
+  }, ".With() cannot appear more than once in an EXPECT_CALL()");
+
+  a.DoA(6);
+}
+
+TEST(ExpectCallSyntaxTest, WithMustBeFirstClause) {
+  MockA a;
+
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_CALL(a, DoA(1))
+        .Times(1)
+        .With(_);
+  }, ".With() must be the first clause in an EXPECT_CALL()");
+
+  a.DoA(1);
+
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_CALL(a, DoA(2))
+        .WillOnce(Return())
+        .With(_);
+  }, ".With() must be the first clause in an EXPECT_CALL()");
+
+  a.DoA(2);
+}
+
+TEST(ExpectCallSyntaxTest, TimesCanBeInferred) {
+  MockA a;
+
+  EXPECT_CALL(a, DoA(1))
+      .WillOnce(Return());
+
+  EXPECT_CALL(a, DoA(2))
+      .WillOnce(Return())
+      .WillRepeatedly(Return());
+
+  a.DoA(1);
+  a.DoA(2);
+  a.DoA(2);
+}
+
+TEST(ExpectCallSyntaxTest, TimesCanAppearAtMostOnce) {
+  MockA a;
+
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_CALL(a, DoA(1))
+        .Times(1)
+        .Times(2);
+  }, ".Times() cannot appear more than once in an EXPECT_CALL()");
+
+  a.DoA(1);
+  a.DoA(1);
+}
+
+TEST(ExpectCallSyntaxTest, TimesMustBeBeforeInSequence) {
+  MockA a;
+  Sequence s;
+
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_CALL(a, DoA(1))
+        .InSequence(s)
+        .Times(1);
+  }, ".Times() cannot appear after ");
+
+  a.DoA(1);
+}
+
+TEST(ExpectCallSyntaxTest, InSequenceIsOptional) {
+  MockA a;
+  Sequence s;
+
+  EXPECT_CALL(a, DoA(1));
+  EXPECT_CALL(a, DoA(2))
+      .InSequence(s);
+
+  a.DoA(1);
+  a.DoA(2);
+}
+
+TEST(ExpectCallSyntaxTest, InSequenceCanAppearMultipleTimes) {
+  MockA a;
+  Sequence s1, s2;
+
+  EXPECT_CALL(a, DoA(1))
+      .InSequence(s1, s2)
+      .InSequence(s1);
+
+  a.DoA(1);
+}
+
+TEST(ExpectCallSyntaxTest, InSequenceMustBeBeforeAfter) {
+  MockA a;
+  Sequence s;
+
+  Expectation e = EXPECT_CALL(a, DoA(1))
+      .Times(AnyNumber());
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_CALL(a, DoA(2))
+        .After(e)
+        .InSequence(s);
+  }, ".InSequence() cannot appear after ");
+
+  a.DoA(2);
+}
+
+TEST(ExpectCallSyntaxTest, InSequenceMustBeBeforeWillOnce) {
+  MockA a;
+  Sequence s;
+
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_CALL(a, DoA(1))
+        .WillOnce(Return())
+        .InSequence(s);
+  }, ".InSequence() cannot appear after ");
+
+  a.DoA(1);
+}
+
+TEST(ExpectCallSyntaxTest, AfterMustBeBeforeWillOnce) {
+  MockA a;
+
+  Expectation e = EXPECT_CALL(a, DoA(1));
+  EXPECT_NONFATAL_FAILURE({
+    EXPECT_CALL(a, DoA(2))
+        .WillOnce(Return())
+        .After(e);
+  }, ".After() cannot appear after ");
+
+  a.DoA(1);
+  a.DoA(2);
+}
+
+TEST(ExpectCallSyntaxTest, WillIsOptional) {
+  MockA a;
+
+  EXPECT_CALL(a, DoA(1));
+  EXPECT_CALL(a, DoA(2))
+      .WillOnce(Return());
+
+  a.DoA(1);
+  a.DoA(2);
+}
+
+TEST(ExpectCallSyntaxTest, WillCanAppearMultipleTimes) {
+  MockA a;
+
+  EXPECT_CALL(a, DoA(1))
+      .Times(AnyNumber())
+      .WillOnce(Return())
+      .WillOnce(Return())
+      .WillOnce(Return());
+}
+
+TEST(ExpectCallSyntaxTest, WillMustBeBeforeWillRepeatedly) {
+  MockA a;
+
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_CALL(a, DoA(1))
+        .WillRepeatedly(Return())
+        .WillOnce(Return());
+  }, ".WillOnce() cannot appear after ");
+
+  a.DoA(1);
+}
+
+TEST(ExpectCallSyntaxTest, WillRepeatedlyIsOptional) {
+  MockA a;
+
+  EXPECT_CALL(a, DoA(1))
+      .WillOnce(Return());
+  EXPECT_CALL(a, DoA(2))
+      .WillOnce(Return())
+      .WillRepeatedly(Return());
+
+  a.DoA(1);
+  a.DoA(2);
+  a.DoA(2);
+}
+
+TEST(ExpectCallSyntaxTest, WillRepeatedlyCannotAppearMultipleTimes) {
+  MockA a;
+
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_CALL(a, DoA(1))
+        .WillRepeatedly(Return())
+        .WillRepeatedly(Return());
+  }, ".WillRepeatedly() cannot appear more than once in an "
+     "EXPECT_CALL()");
+}
+
+TEST(ExpectCallSyntaxTest, WillRepeatedlyMustBeBeforeRetiresOnSaturation) {
+  MockA a;
+
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_CALL(a, DoA(1))
+        .RetiresOnSaturation()
+        .WillRepeatedly(Return());
+  }, ".WillRepeatedly() cannot appear after ");
+}
+
+TEST(ExpectCallSyntaxTest, RetiresOnSaturationIsOptional) {
+  MockA a;
+
+  EXPECT_CALL(a, DoA(1));
+  EXPECT_CALL(a, DoA(1))
+      .RetiresOnSaturation();
+
+  a.DoA(1);
+  a.DoA(1);
+}
+
+TEST(ExpectCallSyntaxTest, RetiresOnSaturationCannotAppearMultipleTimes) {
+  MockA a;
+
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_CALL(a, DoA(1))
+        .RetiresOnSaturation()
+        .RetiresOnSaturation();
+  }, ".RetiresOnSaturation() cannot appear more than once");
+
+  a.DoA(1);
+}
+
+TEST(ExpectCallSyntaxTest, DefaultCardinalityIsOnce) {
+  {
+    MockA a;
+    EXPECT_CALL(a, DoA(1));
+    a.DoA(1);
+  }
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    MockA a;
+    EXPECT_CALL(a, DoA(1));
+  }, "to be called once");
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    MockA a;
+    EXPECT_CALL(a, DoA(1));
+    a.DoA(1);
+    a.DoA(1);
+  }, "to be called once");
+}
+
+#if GTEST_HAS_STREAM_REDIRECTION
+
+// Tests that Google Mock doesn't print a warning when the number of
+// WillOnce() is adequate.
+TEST(ExpectCallSyntaxTest, DoesNotWarnOnAdequateActionCount) {
+  CaptureStdout();
+  {
+    MockB b;
+
+    // It's always fine to omit WillOnce() entirely.
+    EXPECT_CALL(b, DoB())
+        .Times(0);
+    EXPECT_CALL(b, DoB(1))
+        .Times(AtMost(1));
+    EXPECT_CALL(b, DoB(2))
+        .Times(1)
+        .WillRepeatedly(Return(1));
+
+    // It's fine for the number of WillOnce()s to equal the upper bound.
+    EXPECT_CALL(b, DoB(3))
+        .Times(Between(1, 2))
+        .WillOnce(Return(1))
+        .WillOnce(Return(2));
+
+    // It's fine for the number of WillOnce()s to be smaller than the
+    // upper bound when there is a WillRepeatedly().
+    EXPECT_CALL(b, DoB(4))
+        .Times(AtMost(3))
+        .WillOnce(Return(1))
+        .WillRepeatedly(Return(2));
+
+    // Satisfies the above expectations.
+    b.DoB(2);
+    b.DoB(3);
+  }
+  EXPECT_STREQ("", GetCapturedStdout().c_str());
+}
+
+// Tests that Google Mock warns on having too many actions in an
+// expectation compared to its cardinality.
+TEST(ExpectCallSyntaxTest, WarnsOnTooManyActions) {
+  CaptureStdout();
+  {
+    MockB b;
+
+    // Warns when the number of WillOnce()s is larger than the upper bound.
+    EXPECT_CALL(b, DoB())
+        .Times(0)
+        .WillOnce(Return(1));  // #1
+    EXPECT_CALL(b, DoB())
+        .Times(AtMost(1))
+        .WillOnce(Return(1))
+        .WillOnce(Return(2));  // #2
+    EXPECT_CALL(b, DoB(1))
+        .Times(1)
+        .WillOnce(Return(1))
+        .WillOnce(Return(2))
+        .RetiresOnSaturation();  // #3
+
+    // Warns when the number of WillOnce()s equals the upper bound and
+    // there is a WillRepeatedly().
+    EXPECT_CALL(b, DoB())
+        .Times(0)
+        .WillRepeatedly(Return(1));  // #4
+    EXPECT_CALL(b, DoB(2))
+        .Times(1)
+        .WillOnce(Return(1))
+        .WillRepeatedly(Return(2));  // #5
+
+    // Satisfies the above expectations.
+    b.DoB(1);
+    b.DoB(2);
+  }
+  const std::string output = GetCapturedStdout();
+  EXPECT_PRED_FORMAT2(
+      IsSubstring,
+      "Too many actions specified in EXPECT_CALL(b, DoB())...\n"
+      "Expected to be never called, but has 1 WillOnce().",
+      output);  // #1
+  EXPECT_PRED_FORMAT2(
+      IsSubstring,
+      "Too many actions specified in EXPECT_CALL(b, DoB())...\n"
+      "Expected to be called at most once, "
+      "but has 2 WillOnce()s.",
+      output);  // #2
+  EXPECT_PRED_FORMAT2(
+      IsSubstring,
+      "Too many actions specified in EXPECT_CALL(b, DoB(1))...\n"
+      "Expected to be called once, but has 2 WillOnce()s.",
+      output);  // #3
+  EXPECT_PRED_FORMAT2(
+      IsSubstring,
+      "Too many actions specified in EXPECT_CALL(b, DoB())...\n"
+      "Expected to be never called, but has 0 WillOnce()s "
+      "and a WillRepeatedly().",
+      output);  // #4
+  EXPECT_PRED_FORMAT2(
+      IsSubstring,
+      "Too many actions specified in EXPECT_CALL(b, DoB(2))...\n"
+      "Expected to be called once, but has 1 WillOnce() "
+      "and a WillRepeatedly().",
+      output);  // #5
+}
+
+// Tests that Google Mock warns on having too few actions in an
+// expectation compared to its cardinality.
+TEST(ExpectCallSyntaxTest, WarnsOnTooFewActions) {
+  MockB b;
+
+  EXPECT_CALL(b, DoB())
+      .Times(Between(2, 3))
+      .WillOnce(Return(1));
+
+  CaptureStdout();
+  b.DoB();
+  const std::string output = GetCapturedStdout();
+  EXPECT_PRED_FORMAT2(
+      IsSubstring,
+      "Too few actions specified in EXPECT_CALL(b, DoB())...\n"
+      "Expected to be called between 2 and 3 times, "
+      "but has only 1 WillOnce().",
+      output);
+  b.DoB();
+}
+
+TEST(ExpectCallSyntaxTest, WarningIsErrorWithFlag) {
+  int original_behavior = testing::GMOCK_FLAG(default_mock_behavior);
+
+  testing::GMOCK_FLAG(default_mock_behavior) = kAllow;
+  CaptureStdout();
+  {
+    MockA a;
+    a.DoA(0);
+  }
+  std::string output = GetCapturedStdout();
+  EXPECT_TRUE(output.empty()) << output;
+
+  testing::GMOCK_FLAG(default_mock_behavior) = kWarn;
+  CaptureStdout();
+  {
+    MockA a;
+    a.DoA(0);
+  }
+  std::string warning_output = GetCapturedStdout();
+  EXPECT_PRED_FORMAT2(IsSubstring, "GMOCK WARNING", warning_output);
+  EXPECT_PRED_FORMAT2(IsSubstring, "Uninteresting mock function call",
+                      warning_output);
+
+  testing::GMOCK_FLAG(default_mock_behavior) = kFail;
+  EXPECT_NONFATAL_FAILURE({
+    MockA a;
+    a.DoA(0);
+  }, "Uninteresting mock function call");
+
+  // Out of bounds values are converted to kWarn
+  testing::GMOCK_FLAG(default_mock_behavior) = -1;
+  CaptureStdout();
+  {
+    MockA a;
+    a.DoA(0);
+  }
+  warning_output = GetCapturedStdout();
+  EXPECT_PRED_FORMAT2(IsSubstring, "GMOCK WARNING", warning_output);
+  EXPECT_PRED_FORMAT2(IsSubstring, "Uninteresting mock function call",
+                      warning_output);
+  testing::GMOCK_FLAG(default_mock_behavior) = 3;
+  CaptureStdout();
+  {
+    MockA a;
+    a.DoA(0);
+  }
+  warning_output = GetCapturedStdout();
+  EXPECT_PRED_FORMAT2(IsSubstring, "GMOCK WARNING", warning_output);
+  EXPECT_PRED_FORMAT2(IsSubstring, "Uninteresting mock function call",
+                      warning_output);
+
+  testing::GMOCK_FLAG(default_mock_behavior) = original_behavior;
+}
+
+#endif  // GTEST_HAS_STREAM_REDIRECTION
+
+// Tests the semantics of ON_CALL().
+
+// Tests that the built-in default action is taken when no ON_CALL()
+// is specified.
+TEST(OnCallTest, TakesBuiltInDefaultActionWhenNoOnCall) {
+  MockB b;
+  EXPECT_CALL(b, DoB());
+
+  EXPECT_EQ(0, b.DoB());
+}
+
+// Tests that the built-in default action is taken when no ON_CALL()
+// matches the invocation.
+TEST(OnCallTest, TakesBuiltInDefaultActionWhenNoOnCallMatches) {
+  MockB b;
+  ON_CALL(b, DoB(1))
+      .WillByDefault(Return(1));
+  EXPECT_CALL(b, DoB(_));
+
+  EXPECT_EQ(0, b.DoB(2));
+}
+
+// Tests that the last matching ON_CALL() action is taken.
+TEST(OnCallTest, PicksLastMatchingOnCall) {
+  MockB b;
+  ON_CALL(b, DoB(_))
+      .WillByDefault(Return(3));
+  ON_CALL(b, DoB(2))
+      .WillByDefault(Return(2));
+  ON_CALL(b, DoB(1))
+      .WillByDefault(Return(1));
+  EXPECT_CALL(b, DoB(_));
+
+  EXPECT_EQ(2, b.DoB(2));
+}
+
+// Tests the semantics of EXPECT_CALL().
+
+// Tests that any call is allowed when no EXPECT_CALL() is specified.
+TEST(ExpectCallTest, AllowsAnyCallWhenNoSpec) {
+  MockB b;
+  EXPECT_CALL(b, DoB());
+  // There is no expectation on DoB(int).
+
+  b.DoB();
+
+  // DoB(int) can be called any number of times.
+  b.DoB(1);
+  b.DoB(2);
+}
+
+// Tests that the last matching EXPECT_CALL() fires.
+TEST(ExpectCallTest, PicksLastMatchingExpectCall) {
+  MockB b;
+  EXPECT_CALL(b, DoB(_))
+      .WillRepeatedly(Return(2));
+  EXPECT_CALL(b, DoB(1))
+      .WillRepeatedly(Return(1));
+
+  EXPECT_EQ(1, b.DoB(1));
+}
+
+// Tests lower-bound violation.
+TEST(ExpectCallTest, CatchesTooFewCalls) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    MockB b;
+    EXPECT_CALL(b, DoB(5))
+        .Times(AtLeast(2));
+
+    b.DoB(5);
+  }, "Actual function call count doesn't match EXPECT_CALL(b, DoB(5))...\n"
+     "         Expected: to be called at least twice\n"
+     "           Actual: called once - unsatisfied and active");
+}
+
+// Tests that the cardinality can be inferred when no Times(...) is
+// specified.
+TEST(ExpectCallTest, InfersCardinalityWhenThereIsNoWillRepeatedly) {
+  {
+    MockB b;
+    EXPECT_CALL(b, DoB())
+        .WillOnce(Return(1))
+        .WillOnce(Return(2));
+
+    EXPECT_EQ(1, b.DoB());
+    EXPECT_EQ(2, b.DoB());
+  }
+
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    MockB b;
+    EXPECT_CALL(b, DoB())
+        .WillOnce(Return(1))
+        .WillOnce(Return(2));
+
+    EXPECT_EQ(1, b.DoB());
+  }, "to be called twice");
+
+  {  // NOLINT
+    MockB b;
+    EXPECT_CALL(b, DoB())
+        .WillOnce(Return(1))
+        .WillOnce(Return(2));
+
+    EXPECT_EQ(1, b.DoB());
+    EXPECT_EQ(2, b.DoB());
+    EXPECT_NONFATAL_FAILURE(b.DoB(), "to be called twice");
+  }
+}
+
+TEST(ExpectCallTest, InfersCardinality1WhenThereIsWillRepeatedly) {
+  {
+    MockB b;
+    EXPECT_CALL(b, DoB())
+        .WillOnce(Return(1))
+        .WillRepeatedly(Return(2));
+
+    EXPECT_EQ(1, b.DoB());
+  }
+
+  {  // NOLINT
+    MockB b;
+    EXPECT_CALL(b, DoB())
+        .WillOnce(Return(1))
+        .WillRepeatedly(Return(2));
+
+    EXPECT_EQ(1, b.DoB());
+    EXPECT_EQ(2, b.DoB());
+    EXPECT_EQ(2, b.DoB());
+  }
+
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    MockB b;
+    EXPECT_CALL(b, DoB())
+        .WillOnce(Return(1))
+        .WillRepeatedly(Return(2));
+  }, "to be called at least once");
+}
+
+// Tests that the n-th action is taken for the n-th matching
+// invocation.
+TEST(ExpectCallTest, NthMatchTakesNthAction) {
+  MockB b;
+  EXPECT_CALL(b, DoB())
+      .WillOnce(Return(1))
+      .WillOnce(Return(2))
+      .WillOnce(Return(3));
+
+  EXPECT_EQ(1, b.DoB());
+  EXPECT_EQ(2, b.DoB());
+  EXPECT_EQ(3, b.DoB());
+}
+
+// Tests that the WillRepeatedly() action is taken when the WillOnce(...)
+// list is exhausted.
+TEST(ExpectCallTest, TakesRepeatedActionWhenWillListIsExhausted) {
+  MockB b;
+  EXPECT_CALL(b, DoB())
+      .WillOnce(Return(1))
+      .WillRepeatedly(Return(2));
+
+  EXPECT_EQ(1, b.DoB());
+  EXPECT_EQ(2, b.DoB());
+  EXPECT_EQ(2, b.DoB());
+}
+
+#if GTEST_HAS_STREAM_REDIRECTION
+
+// Tests that the default action is taken when the WillOnce(...) list is
+// exhausted and there is no WillRepeatedly().
+TEST(ExpectCallTest, TakesDefaultActionWhenWillListIsExhausted) {
+  MockB b;
+  EXPECT_CALL(b, DoB(_))
+      .Times(1);
+  EXPECT_CALL(b, DoB())
+      .Times(AnyNumber())
+      .WillOnce(Return(1))
+      .WillOnce(Return(2));
+
+  CaptureStdout();
+  EXPECT_EQ(0, b.DoB(1));  // Shouldn't generate a warning as the
+                           // expectation has no action clause at all.
+  EXPECT_EQ(1, b.DoB());
+  EXPECT_EQ(2, b.DoB());
+  const std::string output1 = GetCapturedStdout();
+  EXPECT_STREQ("", output1.c_str());
+
+  CaptureStdout();
+  EXPECT_EQ(0, b.DoB());
+  EXPECT_EQ(0, b.DoB());
+  const std::string output2 = GetCapturedStdout();
+  EXPECT_THAT(output2.c_str(),
+              HasSubstr("Actions ran out in EXPECT_CALL(b, DoB())...\n"
+                        "Called 3 times, but only 2 WillOnce()s are specified"
+                        " - returning default value."));
+  EXPECT_THAT(output2.c_str(),
+              HasSubstr("Actions ran out in EXPECT_CALL(b, DoB())...\n"
+                        "Called 4 times, but only 2 WillOnce()s are specified"
+                        " - returning default value."));
+}
+
+TEST(FunctionMockerMessageTest, ReportsExpectCallLocationForExhausedActions) {
+  MockB b;
+  std::string expect_call_location = FormatFileLocation(__FILE__, __LINE__ + 1);
+  EXPECT_CALL(b, DoB()).Times(AnyNumber()).WillOnce(Return(1));
+
+  EXPECT_EQ(1, b.DoB());
+
+  CaptureStdout();
+  EXPECT_EQ(0, b.DoB());
+  const std::string output = GetCapturedStdout();
+  // The warning message should contain the call location.
+  EXPECT_PRED_FORMAT2(IsSubstring, expect_call_location, output);
+}
+
+TEST(FunctionMockerMessageTest,
+     ReportsDefaultActionLocationOfUninterestingCallsForNaggyMock) {
+  std::string on_call_location;
+  CaptureStdout();
+  {
+    NaggyMock<MockB> b;
+    on_call_location = FormatFileLocation(__FILE__, __LINE__ + 1);
+    ON_CALL(b, DoB(_)).WillByDefault(Return(0));
+    b.DoB(0);
+  }
+  EXPECT_PRED_FORMAT2(IsSubstring, on_call_location, GetCapturedStdout());
+}
+
+#endif  // GTEST_HAS_STREAM_REDIRECTION
+
+// Tests that an uninteresting call performs the default action.
+TEST(UninterestingCallTest, DoesDefaultAction) {
+  // When there is an ON_CALL() statement, the action specified by it
+  // should be taken.
+  MockA a;
+  ON_CALL(a, Binary(_, _))
+      .WillByDefault(Return(true));
+  EXPECT_TRUE(a.Binary(1, 2));
+
+  // When there is no ON_CALL(), the default value for the return type
+  // should be returned.
+  MockB b;
+  EXPECT_EQ(0, b.DoB());
+}
+
+// Tests that an unexpected call performs the default action.
+TEST(UnexpectedCallTest, DoesDefaultAction) {
+  // When there is an ON_CALL() statement, the action specified by it
+  // should be taken.
+  MockA a;
+  ON_CALL(a, Binary(_, _))
+      .WillByDefault(Return(true));
+  EXPECT_CALL(a, Binary(0, 0));
+  a.Binary(0, 0);
+  bool result = false;
+  EXPECT_NONFATAL_FAILURE(result = a.Binary(1, 2),
+                          "Unexpected mock function call");
+  EXPECT_TRUE(result);
+
+  // When there is no ON_CALL(), the default value for the return type
+  // should be returned.
+  MockB b;
+  EXPECT_CALL(b, DoB(0))
+      .Times(0);
+  int n = -1;
+  EXPECT_NONFATAL_FAILURE(n = b.DoB(1),
+                          "Unexpected mock function call");
+  EXPECT_EQ(0, n);
+}
+
+// Tests that when an unexpected void function generates the right
+// failure message.
+TEST(UnexpectedCallTest, GeneratesFailureForVoidFunction) {
+  // First, tests the message when there is only one EXPECT_CALL().
+  MockA a1;
+  EXPECT_CALL(a1, DoA(1));
+  a1.DoA(1);
+  // Ideally we should match the failure message against a regex, but
+  // EXPECT_NONFATAL_FAILURE doesn't support that, so we test for
+  // multiple sub-strings instead.
+  EXPECT_NONFATAL_FAILURE(
+      a1.DoA(9),
+      "Unexpected mock function call - returning directly.\n"
+      "    Function call: DoA(9)\n"
+      "Google Mock tried the following 1 expectation, but it didn't match:");
+  EXPECT_NONFATAL_FAILURE(
+      a1.DoA(9),
+      "  Expected arg #0: is equal to 1\n"
+      "           Actual: 9\n"
+      "         Expected: to be called once\n"
+      "           Actual: called once - saturated and active");
+
+  // Next, tests the message when there are more than one EXPECT_CALL().
+  MockA a2;
+  EXPECT_CALL(a2, DoA(1));
+  EXPECT_CALL(a2, DoA(3));
+  a2.DoA(1);
+  EXPECT_NONFATAL_FAILURE(
+      a2.DoA(2),
+      "Unexpected mock function call - returning directly.\n"
+      "    Function call: DoA(2)\n"
+      "Google Mock tried the following 2 expectations, but none matched:");
+  EXPECT_NONFATAL_FAILURE(
+      a2.DoA(2),
+      "tried expectation #0: EXPECT_CALL(a2, DoA(1))...\n"
+      "  Expected arg #0: is equal to 1\n"
+      "           Actual: 2\n"
+      "         Expected: to be called once\n"
+      "           Actual: called once - saturated and active");
+  EXPECT_NONFATAL_FAILURE(
+      a2.DoA(2),
+      "tried expectation #1: EXPECT_CALL(a2, DoA(3))...\n"
+      "  Expected arg #0: is equal to 3\n"
+      "           Actual: 2\n"
+      "         Expected: to be called once\n"
+      "           Actual: never called - unsatisfied and active");
+  a2.DoA(3);
+}
+
+// Tests that an unexpected non-void function generates the right
+// failure message.
+TEST(UnexpectedCallTest, GeneartesFailureForNonVoidFunction) {
+  MockB b1;
+  EXPECT_CALL(b1, DoB(1));
+  b1.DoB(1);
+  EXPECT_NONFATAL_FAILURE(
+      b1.DoB(2),
+      "Unexpected mock function call - returning default value.\n"
+      "    Function call: DoB(2)\n"
+      "          Returns: 0\n"
+      "Google Mock tried the following 1 expectation, but it didn't match:");
+  EXPECT_NONFATAL_FAILURE(
+      b1.DoB(2),
+      "  Expected arg #0: is equal to 1\n"
+      "           Actual: 2\n"
+      "         Expected: to be called once\n"
+      "           Actual: called once - saturated and active");
+}
+
+// Tests that Google Mock explains that an retired expectation doesn't
+// match the call.
+TEST(UnexpectedCallTest, RetiredExpectation) {
+  MockB b;
+  EXPECT_CALL(b, DoB(1))
+      .RetiresOnSaturation();
+
+  b.DoB(1);
+  EXPECT_NONFATAL_FAILURE(
+      b.DoB(1),
+      "         Expected: the expectation is active\n"
+      "           Actual: it is retired");
+}
+
+// Tests that Google Mock explains that an expectation that doesn't
+// match the arguments doesn't match the call.
+TEST(UnexpectedCallTest, UnmatchedArguments) {
+  MockB b;
+  EXPECT_CALL(b, DoB(1));
+
+  EXPECT_NONFATAL_FAILURE(
+      b.DoB(2),
+      "  Expected arg #0: is equal to 1\n"
+      "           Actual: 2\n");
+  b.DoB(1);
+}
+
+// Tests that Google Mock explains that an expectation with
+// unsatisfied pre-requisites doesn't match the call.
+TEST(UnexpectedCallTest, UnsatisifiedPrerequisites) {
+  Sequence s1, s2;
+  MockB b;
+  EXPECT_CALL(b, DoB(1))
+      .InSequence(s1);
+  EXPECT_CALL(b, DoB(2))
+      .Times(AnyNumber())
+      .InSequence(s1);
+  EXPECT_CALL(b, DoB(3))
+      .InSequence(s2);
+  EXPECT_CALL(b, DoB(4))
+      .InSequence(s1, s2);
+
+  ::testing::TestPartResultArray failures;
+  {
+    ::testing::ScopedFakeTestPartResultReporter reporter(&failures);
+    b.DoB(4);
+    // Now 'failures' contains the Google Test failures generated by
+    // the above statement.
+  }
+
+  // There should be one non-fatal failure.
+  ASSERT_EQ(1, failures.size());
+  const ::testing::TestPartResult& r = failures.GetTestPartResult(0);
+  EXPECT_EQ(::testing::TestPartResult::kNonFatalFailure, r.type());
+
+  // Verifies that the failure message contains the two unsatisfied
+  // pre-requisites but not the satisfied one.
+#if GTEST_USES_PCRE
+  EXPECT_THAT(r.message(), ContainsRegex(
+      // PCRE has trouble using (.|\n) to match any character, but
+      // supports the (?s) prefix for using . to match any character.
+      "(?s)the following immediate pre-requisites are not satisfied:\n"
+      ".*: pre-requisite #0\n"
+      ".*: pre-requisite #1"));
+#elif GTEST_USES_POSIX_RE
+  EXPECT_THAT(r.message(), ContainsRegex(
+      // POSIX RE doesn't understand the (?s) prefix, but has no trouble
+      // with (.|\n).
+      "the following immediate pre-requisites are not satisfied:\n"
+      "(.|\n)*: pre-requisite #0\n"
+      "(.|\n)*: pre-requisite #1"));
+#else
+  // We can only use Google Test's own simple regex.
+  EXPECT_THAT(r.message(), ContainsRegex(
+      "the following immediate pre-requisites are not satisfied:"));
+  EXPECT_THAT(r.message(), ContainsRegex(": pre-requisite #0"));
+  EXPECT_THAT(r.message(), ContainsRegex(": pre-requisite #1"));
+#endif  // GTEST_USES_PCRE
+
+  b.DoB(1);
+  b.DoB(3);
+  b.DoB(4);
+}
+
+TEST(UndefinedReturnValueTest,
+     ReturnValueIsMandatoryWhenNotDefaultConstructible) {
+  MockA a;
+  // FIXME: We should really verify the output message,
+  // but we cannot yet due to that EXPECT_DEATH only captures stderr
+  // while Google Mock logs to stdout.
+#if GTEST_HAS_EXCEPTIONS
+  EXPECT_ANY_THROW(a.ReturnNonDefaultConstructible());
+#else
+  EXPECT_DEATH_IF_SUPPORTED(a.ReturnNonDefaultConstructible(), "");
+#endif
+}
+
+// Tests that an excessive call (one whose arguments match the
+// matchers but is called too many times) performs the default action.
+TEST(ExcessiveCallTest, DoesDefaultAction) {
+  // When there is an ON_CALL() statement, the action specified by it
+  // should be taken.
+  MockA a;
+  ON_CALL(a, Binary(_, _))
+      .WillByDefault(Return(true));
+  EXPECT_CALL(a, Binary(0, 0));
+  a.Binary(0, 0);
+  bool result = false;
+  EXPECT_NONFATAL_FAILURE(result = a.Binary(0, 0),
+                          "Mock function called more times than expected");
+  EXPECT_TRUE(result);
+
+  // When there is no ON_CALL(), the default value for the return type
+  // should be returned.
+  MockB b;
+  EXPECT_CALL(b, DoB(0))
+      .Times(0);
+  int n = -1;
+  EXPECT_NONFATAL_FAILURE(n = b.DoB(0),
+                          "Mock function called more times than expected");
+  EXPECT_EQ(0, n);
+}
+
+// Tests that when a void function is called too many times,
+// the failure message contains the argument values.
+TEST(ExcessiveCallTest, GeneratesFailureForVoidFunction) {
+  MockA a;
+  EXPECT_CALL(a, DoA(_))
+      .Times(0);
+  EXPECT_NONFATAL_FAILURE(
+      a.DoA(9),
+      "Mock function called more times than expected - returning directly.\n"
+      "    Function call: DoA(9)\n"
+      "         Expected: to be never called\n"
+      "           Actual: called once - over-saturated and active");
+}
+
+// Tests that when a non-void function is called too many times, the
+// failure message contains the argument values and the return value.
+TEST(ExcessiveCallTest, GeneratesFailureForNonVoidFunction) {
+  MockB b;
+  EXPECT_CALL(b, DoB(_));
+  b.DoB(1);
+  EXPECT_NONFATAL_FAILURE(
+      b.DoB(2),
+      "Mock function called more times than expected - "
+      "returning default value.\n"
+      "    Function call: DoB(2)\n"
+      "          Returns: 0\n"
+      "         Expected: to be called once\n"
+      "           Actual: called twice - over-saturated and active");
+}
+
+// Tests using sequences.
+
+TEST(InSequenceTest, AllExpectationInScopeAreInSequence) {
+  MockA a;
+  {
+    InSequence dummy;
+
+    EXPECT_CALL(a, DoA(1));
+    EXPECT_CALL(a, DoA(2));
+  }
+
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    a.DoA(2);
+  }, "Unexpected mock function call");
+
+  a.DoA(1);
+  a.DoA(2);
+}
+
+TEST(InSequenceTest, NestedInSequence) {
+  MockA a;
+  {
+    InSequence dummy;
+
+    EXPECT_CALL(a, DoA(1));
+    {
+      InSequence dummy2;
+
+      EXPECT_CALL(a, DoA(2));
+      EXPECT_CALL(a, DoA(3));
+    }
+  }
+
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    a.DoA(1);
+    a.DoA(3);
+  }, "Unexpected mock function call");
+
+  a.DoA(2);
+  a.DoA(3);
+}
+
+TEST(InSequenceTest, ExpectationsOutOfScopeAreNotAffected) {
+  MockA a;
+  {
+    InSequence dummy;
+
+    EXPECT_CALL(a, DoA(1));
+    EXPECT_CALL(a, DoA(2));
+  }
+  EXPECT_CALL(a, DoA(3));
+
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    a.DoA(2);
+  }, "Unexpected mock function call");
+
+  a.DoA(3);
+  a.DoA(1);
+  a.DoA(2);
+}
+
+// Tests that any order is allowed when no sequence is used.
+TEST(SequenceTest, AnyOrderIsOkByDefault) {
+  {
+    MockA a;
+    MockB b;
+
+    EXPECT_CALL(a, DoA(1));
+    EXPECT_CALL(b, DoB())
+        .Times(AnyNumber());
+
+    a.DoA(1);
+    b.DoB();
+  }
+
+  {  // NOLINT
+    MockA a;
+    MockB b;
+
+    EXPECT_CALL(a, DoA(1));
+    EXPECT_CALL(b, DoB())
+        .Times(AnyNumber());
+
+    b.DoB();
+    a.DoA(1);
+  }
+}
+
+// Tests that the calls must be in strict order when a complete order
+// is specified.
+TEST(SequenceTest, CallsMustBeInStrictOrderWhenSaidSo1) {
+  MockA a;
+  ON_CALL(a, ReturnResult(_))
+      .WillByDefault(Return(Result()));
+
+  Sequence s;
+  EXPECT_CALL(a, ReturnResult(1))
+      .InSequence(s);
+  EXPECT_CALL(a, ReturnResult(2))
+      .InSequence(s);
+  EXPECT_CALL(a, ReturnResult(3))
+      .InSequence(s);
+
+  a.ReturnResult(1);
+
+  // May only be called after a.ReturnResult(2).
+  EXPECT_NONFATAL_FAILURE(a.ReturnResult(3), "Unexpected mock function call");
+
+  a.ReturnResult(2);
+  a.ReturnResult(3);
+}
+
+// Tests that the calls must be in strict order when a complete order
+// is specified.
+TEST(SequenceTest, CallsMustBeInStrictOrderWhenSaidSo2) {
+  MockA a;
+  ON_CALL(a, ReturnResult(_))
+      .WillByDefault(Return(Result()));
+
+  Sequence s;
+  EXPECT_CALL(a, ReturnResult(1))
+      .InSequence(s);
+  EXPECT_CALL(a, ReturnResult(2))
+      .InSequence(s);
+
+  // May only be called after a.ReturnResult(1).
+  EXPECT_NONFATAL_FAILURE(a.ReturnResult(2), "Unexpected mock function call");
+
+  a.ReturnResult(1);
+  a.ReturnResult(2);
+}
+
+// Tests specifying a DAG using multiple sequences.
+class PartialOrderTest : public testing::Test {
+ protected:
+  PartialOrderTest() {
+    ON_CALL(a_, ReturnResult(_))
+        .WillByDefault(Return(Result()));
+
+    // Specifies this partial ordering:
+    //
+    // a.ReturnResult(1) ==>
+    //                       a.ReturnResult(2) * n  ==>  a.ReturnResult(3)
+    // b.DoB() * 2       ==>
+    Sequence x, y;
+    EXPECT_CALL(a_, ReturnResult(1))
+        .InSequence(x);
+    EXPECT_CALL(b_, DoB())
+        .Times(2)
+        .InSequence(y);
+    EXPECT_CALL(a_, ReturnResult(2))
+        .Times(AnyNumber())
+        .InSequence(x, y);
+    EXPECT_CALL(a_, ReturnResult(3))
+        .InSequence(x);
+  }
+
+  MockA a_;
+  MockB b_;
+};
+
+TEST_F(PartialOrderTest, CallsMustConformToSpecifiedDag1) {
+  a_.ReturnResult(1);
+  b_.DoB();
+
+  // May only be called after the second DoB().
+  EXPECT_NONFATAL_FAILURE(a_.ReturnResult(2), "Unexpected mock function call");
+
+  b_.DoB();
+  a_.ReturnResult(3);
+}
+
+TEST_F(PartialOrderTest, CallsMustConformToSpecifiedDag2) {
+  // May only be called after ReturnResult(1).
+  EXPECT_NONFATAL_FAILURE(a_.ReturnResult(2), "Unexpected mock function call");
+
+  a_.ReturnResult(1);
+  b_.DoB();
+  b_.DoB();
+  a_.ReturnResult(3);
+}
+
+TEST_F(PartialOrderTest, CallsMustConformToSpecifiedDag3) {
+  // May only be called last.
+  EXPECT_NONFATAL_FAILURE(a_.ReturnResult(3), "Unexpected mock function call");
+
+  a_.ReturnResult(1);
+  b_.DoB();
+  b_.DoB();
+  a_.ReturnResult(3);
+}
+
+TEST_F(PartialOrderTest, CallsMustConformToSpecifiedDag4) {
+  a_.ReturnResult(1);
+  b_.DoB();
+  b_.DoB();
+  a_.ReturnResult(3);
+
+  // May only be called before ReturnResult(3).
+  EXPECT_NONFATAL_FAILURE(a_.ReturnResult(2), "Unexpected mock function call");
+}
+
+TEST(SequenceTest, Retirement) {
+  MockA a;
+  Sequence s;
+
+  EXPECT_CALL(a, DoA(1))
+      .InSequence(s);
+  EXPECT_CALL(a, DoA(_))
+      .InSequence(s)
+      .RetiresOnSaturation();
+  EXPECT_CALL(a, DoA(1))
+      .InSequence(s);
+
+  a.DoA(1);
+  a.DoA(2);
+  a.DoA(1);
+}
+
+// Tests Expectation.
+
+TEST(ExpectationTest, ConstrutorsWork) {
+  MockA a;
+  Expectation e1;  // Default ctor.
+
+  // Ctor from various forms of EXPECT_CALL.
+  Expectation e2 = EXPECT_CALL(a, DoA(2));
+  Expectation e3 = EXPECT_CALL(a, DoA(3)).With(_);
+  {
+    Sequence s;
+    Expectation e4 = EXPECT_CALL(a, DoA(4)).Times(1);
+    Expectation e5 = EXPECT_CALL(a, DoA(5)).InSequence(s);
+  }
+  Expectation e6 = EXPECT_CALL(a, DoA(6)).After(e2);
+  Expectation e7 = EXPECT_CALL(a, DoA(7)).WillOnce(Return());
+  Expectation e8 = EXPECT_CALL(a, DoA(8)).WillRepeatedly(Return());
+  Expectation e9 = EXPECT_CALL(a, DoA(9)).RetiresOnSaturation();
+
+  Expectation e10 = e2;  // Copy ctor.
+
+  EXPECT_THAT(e1, Ne(e2));
+  EXPECT_THAT(e2, Eq(e10));
+
+  a.DoA(2);
+  a.DoA(3);
+  a.DoA(4);
+  a.DoA(5);
+  a.DoA(6);
+  a.DoA(7);
+  a.DoA(8);
+  a.DoA(9);
+}
+
+TEST(ExpectationTest, AssignmentWorks) {
+  MockA a;
+  Expectation e1;
+  Expectation e2 = EXPECT_CALL(a, DoA(1));
+
+  EXPECT_THAT(e1, Ne(e2));
+
+  e1 = e2;
+  EXPECT_THAT(e1, Eq(e2));
+
+  a.DoA(1);
+}
+
+// Tests ExpectationSet.
+
+TEST(ExpectationSetTest, MemberTypesAreCorrect) {
+  ::testing::StaticAssertTypeEq<Expectation, ExpectationSet::value_type>();
+}
+
+TEST(ExpectationSetTest, ConstructorsWork) {
+  MockA a;
+
+  Expectation e1;
+  const Expectation e2;
+  ExpectationSet es1;  // Default ctor.
+  ExpectationSet es2 = EXPECT_CALL(a, DoA(1));  // Ctor from EXPECT_CALL.
+  ExpectationSet es3 = e1;  // Ctor from Expectation.
+  ExpectationSet es4(e1);   // Ctor from Expectation; alternative syntax.
+  ExpectationSet es5 = e2;  // Ctor from const Expectation.
+  ExpectationSet es6(e2);   // Ctor from const Expectation; alternative syntax.
+  ExpectationSet es7 = es2;  // Copy ctor.
+
+  EXPECT_EQ(0, es1.size());
+  EXPECT_EQ(1, es2.size());
+  EXPECT_EQ(1, es3.size());
+  EXPECT_EQ(1, es4.size());
+  EXPECT_EQ(1, es5.size());
+  EXPECT_EQ(1, es6.size());
+  EXPECT_EQ(1, es7.size());
+
+  EXPECT_THAT(es3, Ne(es2));
+  EXPECT_THAT(es4, Eq(es3));
+  EXPECT_THAT(es5, Eq(es4));
+  EXPECT_THAT(es6, Eq(es5));
+  EXPECT_THAT(es7, Eq(es2));
+  a.DoA(1);
+}
+
+TEST(ExpectationSetTest, AssignmentWorks) {
+  ExpectationSet es1;
+  ExpectationSet es2 = Expectation();
+
+  es1 = es2;
+  EXPECT_EQ(1, es1.size());
+  EXPECT_THAT(*(es1.begin()), Eq(Expectation()));
+  EXPECT_THAT(es1, Eq(es2));
+}
+
+TEST(ExpectationSetTest, InsertionWorks) {
+  ExpectationSet es1;
+  Expectation e1;
+  es1 += e1;
+  EXPECT_EQ(1, es1.size());
+  EXPECT_THAT(*(es1.begin()), Eq(e1));
+
+  MockA a;
+  Expectation e2 = EXPECT_CALL(a, DoA(1));
+  es1 += e2;
+  EXPECT_EQ(2, es1.size());
+
+  ExpectationSet::const_iterator it1 = es1.begin();
+  ExpectationSet::const_iterator it2 = it1;
+  ++it2;
+  EXPECT_TRUE(*it1 == e1 || *it2 == e1);  // e1 must be in the set.
+  EXPECT_TRUE(*it1 == e2 || *it2 == e2);  // e2 must be in the set too.
+  a.DoA(1);
+}
+
+TEST(ExpectationSetTest, SizeWorks) {
+  ExpectationSet es;
+  EXPECT_EQ(0, es.size());
+
+  es += Expectation();
+  EXPECT_EQ(1, es.size());
+
+  MockA a;
+  es += EXPECT_CALL(a, DoA(1));
+  EXPECT_EQ(2, es.size());
+
+  a.DoA(1);
+}
+
+TEST(ExpectationSetTest, IsEnumerable) {
+  ExpectationSet es;
+  EXPECT_TRUE(es.begin() == es.end());
+
+  es += Expectation();
+  ExpectationSet::const_iterator it = es.begin();
+  EXPECT_TRUE(it != es.end());
+  EXPECT_THAT(*it, Eq(Expectation()));
+  ++it;
+  EXPECT_TRUE(it== es.end());
+}
+
+// Tests the .After() clause.
+
+TEST(AfterTest, SucceedsWhenPartialOrderIsSatisfied) {
+  MockA a;
+  ExpectationSet es;
+  es += EXPECT_CALL(a, DoA(1));
+  es += EXPECT_CALL(a, DoA(2));
+  EXPECT_CALL(a, DoA(3))
+      .After(es);
+
+  a.DoA(1);
+  a.DoA(2);
+  a.DoA(3);
+}
+
+TEST(AfterTest, SucceedsWhenTotalOrderIsSatisfied) {
+  MockA a;
+  MockB b;
+  // The following also verifies that const Expectation objects work
+  // too.  Do not remove the const modifiers.
+  const Expectation e1 = EXPECT_CALL(a, DoA(1));
+  const Expectation e2 = EXPECT_CALL(b, DoB())
+      .Times(2)
+      .After(e1);
+  EXPECT_CALL(a, DoA(2)).After(e2);
+
+  a.DoA(1);
+  b.DoB();
+  b.DoB();
+  a.DoA(2);
+}
+
+// Calls must be in strict order when specified so using .After().
+TEST(AfterTest, CallsMustBeInStrictOrderWhenSpecifiedSo1) {
+  MockA a;
+  MockB b;
+
+  // Define ordering:
+  //   a.DoA(1) ==> b.DoB() ==> a.DoA(2)
+  Expectation e1 = EXPECT_CALL(a, DoA(1));
+  Expectation e2 = EXPECT_CALL(b, DoB())
+      .After(e1);
+  EXPECT_CALL(a, DoA(2))
+      .After(e2);
+
+  a.DoA(1);
+
+  // May only be called after DoB().
+  EXPECT_NONFATAL_FAILURE(a.DoA(2), "Unexpected mock function call");
+
+  b.DoB();
+  a.DoA(2);
+}
+
+// Calls must be in strict order when specified so using .After().
+TEST(AfterTest, CallsMustBeInStrictOrderWhenSpecifiedSo2) {
+  MockA a;
+  MockB b;
+
+  // Define ordering:
+  //   a.DoA(1) ==> b.DoB() * 2 ==> a.DoA(2)
+  Expectation e1 = EXPECT_CALL(a, DoA(1));
+  Expectation e2 = EXPECT_CALL(b, DoB())
+      .Times(2)
+      .After(e1);
+  EXPECT_CALL(a, DoA(2))
+      .After(e2);
+
+  a.DoA(1);
+  b.DoB();
+
+  // May only be called after the second DoB().
+  EXPECT_NONFATAL_FAILURE(a.DoA(2), "Unexpected mock function call");
+
+  b.DoB();
+  a.DoA(2);
+}
+
+// Calls must satisfy the partial order when specified so.
+TEST(AfterTest, CallsMustSatisfyPartialOrderWhenSpecifiedSo) {
+  MockA a;
+  ON_CALL(a, ReturnResult(_))
+      .WillByDefault(Return(Result()));
+
+  // Define ordering:
+  //   a.DoA(1) ==>
+  //   a.DoA(2) ==> a.ReturnResult(3)
+  Expectation e = EXPECT_CALL(a, DoA(1));
+  const ExpectationSet es = EXPECT_CALL(a, DoA(2));
+  EXPECT_CALL(a, ReturnResult(3))
+      .After(e, es);
+
+  // May only be called last.
+  EXPECT_NONFATAL_FAILURE(a.ReturnResult(3), "Unexpected mock function call");
+
+  a.DoA(2);
+  a.DoA(1);
+  a.ReturnResult(3);
+}
+
+// Calls must satisfy the partial order when specified so.
+TEST(AfterTest, CallsMustSatisfyPartialOrderWhenSpecifiedSo2) {
+  MockA a;
+
+  // Define ordering:
+  //   a.DoA(1) ==>
+  //   a.DoA(2) ==> a.DoA(3)
+  Expectation e = EXPECT_CALL(a, DoA(1));
+  const ExpectationSet es = EXPECT_CALL(a, DoA(2));
+  EXPECT_CALL(a, DoA(3))
+      .After(e, es);
+
+  a.DoA(2);
+
+  // May only be called last.
+  EXPECT_NONFATAL_FAILURE(a.DoA(3), "Unexpected mock function call");
+
+  a.DoA(1);
+  a.DoA(3);
+}
+
+// .After() can be combined with .InSequence().
+TEST(AfterTest, CanBeUsedWithInSequence) {
+  MockA a;
+  Sequence s;
+  Expectation e = EXPECT_CALL(a, DoA(1));
+  EXPECT_CALL(a, DoA(2)).InSequence(s);
+  EXPECT_CALL(a, DoA(3))
+      .InSequence(s)
+      .After(e);
+
+  a.DoA(1);
+
+  // May only be after DoA(2).
+  EXPECT_NONFATAL_FAILURE(a.DoA(3), "Unexpected mock function call");
+
+  a.DoA(2);
+  a.DoA(3);
+}
+
+// .After() can be called multiple times.
+TEST(AfterTest, CanBeCalledManyTimes) {
+  MockA a;
+  Expectation e1 = EXPECT_CALL(a, DoA(1));
+  Expectation e2 = EXPECT_CALL(a, DoA(2));
+  Expectation e3 = EXPECT_CALL(a, DoA(3));
+  EXPECT_CALL(a, DoA(4))
+      .After(e1)
+      .After(e2)
+      .After(e3);
+
+  a.DoA(3);
+  a.DoA(1);
+  a.DoA(2);
+  a.DoA(4);
+}
+
+// .After() accepts up to 5 arguments.
+TEST(AfterTest, AcceptsUpToFiveArguments) {
+  MockA a;
+  Expectation e1 = EXPECT_CALL(a, DoA(1));
+  Expectation e2 = EXPECT_CALL(a, DoA(2));
+  Expectation e3 = EXPECT_CALL(a, DoA(3));
+  ExpectationSet es1 = EXPECT_CALL(a, DoA(4));
+  ExpectationSet es2 = EXPECT_CALL(a, DoA(5));
+  EXPECT_CALL(a, DoA(6))
+      .After(e1, e2, e3, es1, es2);
+
+  a.DoA(5);
+  a.DoA(2);
+  a.DoA(4);
+  a.DoA(1);
+  a.DoA(3);
+  a.DoA(6);
+}
+
+// .After() allows input to contain duplicated Expectations.
+TEST(AfterTest, AcceptsDuplicatedInput) {
+  MockA a;
+  ON_CALL(a, ReturnResult(_))
+      .WillByDefault(Return(Result()));
+
+  // Define ordering:
+  //   DoA(1) ==>
+  //   DoA(2) ==> ReturnResult(3)
+  Expectation e1 = EXPECT_CALL(a, DoA(1));
+  Expectation e2 = EXPECT_CALL(a, DoA(2));
+  ExpectationSet es;
+  es += e1;
+  es += e2;
+  EXPECT_CALL(a, ReturnResult(3))
+      .After(e1, e2, es, e1);
+
+  a.DoA(1);
+
+  // May only be after DoA(2).
+  EXPECT_NONFATAL_FAILURE(a.ReturnResult(3), "Unexpected mock function call");
+
+  a.DoA(2);
+  a.ReturnResult(3);
+}
+
+// An Expectation added to an ExpectationSet after it has been used in
+// an .After() has no effect.
+TEST(AfterTest, ChangesToExpectationSetHaveNoEffectAfterwards) {
+  MockA a;
+  ExpectationSet es1 = EXPECT_CALL(a, DoA(1));
+  Expectation e2 = EXPECT_CALL(a, DoA(2));
+  EXPECT_CALL(a, DoA(3))
+      .After(es1);
+  es1 += e2;
+
+  a.DoA(1);
+  a.DoA(3);
+  a.DoA(2);
+}
+
+// Tests that Google Mock correctly handles calls to mock functions
+// after a mock object owning one of their pre-requisites has died.
+
+// Tests that calls that satisfy the original spec are successful.
+TEST(DeletingMockEarlyTest, Success1) {
+  MockB* const b1 = new MockB;
+  MockA* const a = new MockA;
+  MockB* const b2 = new MockB;
+
+  {
+    InSequence dummy;
+    EXPECT_CALL(*b1, DoB(_))
+        .WillOnce(Return(1));
+    EXPECT_CALL(*a, Binary(_, _))
+        .Times(AnyNumber())
+        .WillRepeatedly(Return(true));
+    EXPECT_CALL(*b2, DoB(_))
+        .Times(AnyNumber())
+        .WillRepeatedly(Return(2));
+  }
+
+  EXPECT_EQ(1, b1->DoB(1));
+  delete b1;
+  // a's pre-requisite has died.
+  EXPECT_TRUE(a->Binary(0, 1));
+  delete b2;
+  // a's successor has died.
+  EXPECT_TRUE(a->Binary(1, 2));
+  delete a;
+}
+
+// Tests that calls that satisfy the original spec are successful.
+TEST(DeletingMockEarlyTest, Success2) {
+  MockB* const b1 = new MockB;
+  MockA* const a = new MockA;
+  MockB* const b2 = new MockB;
+
+  {
+    InSequence dummy;
+    EXPECT_CALL(*b1, DoB(_))
+        .WillOnce(Return(1));
+    EXPECT_CALL(*a, Binary(_, _))
+        .Times(AnyNumber());
+    EXPECT_CALL(*b2, DoB(_))
+        .Times(AnyNumber())
+        .WillRepeatedly(Return(2));
+  }
+
+  delete a;  // a is trivially satisfied.
+  EXPECT_EQ(1, b1->DoB(1));
+  EXPECT_EQ(2, b2->DoB(2));
+  delete b1;
+  delete b2;
+}
+
+// Tests that it's OK to delete a mock object itself in its action.
+
+// Suppresses warning on unreferenced formal parameter in MSVC with
+// -W4.
+#ifdef _MSC_VER
+# pragma warning(push)
+# pragma warning(disable:4100)
+#endif
+
+ACTION_P(Delete, ptr) { delete ptr; }
+
+#ifdef _MSC_VER
+# pragma warning(pop)
+#endif
+
+TEST(DeletingMockEarlyTest, CanDeleteSelfInActionReturningVoid) {
+  MockA* const a = new MockA;
+  EXPECT_CALL(*a, DoA(_)).WillOnce(Delete(a));
+  a->DoA(42);  // This will cause a to be deleted.
+}
+
+TEST(DeletingMockEarlyTest, CanDeleteSelfInActionReturningValue) {
+  MockA* const a = new MockA;
+  EXPECT_CALL(*a, ReturnResult(_))
+      .WillOnce(DoAll(Delete(a), Return(Result())));
+  a->ReturnResult(42);  // This will cause a to be deleted.
+}
+
+// Tests that calls that violate the original spec yield failures.
+TEST(DeletingMockEarlyTest, Failure1) {
+  MockB* const b1 = new MockB;
+  MockA* const a = new MockA;
+  MockB* const b2 = new MockB;
+
+  {
+    InSequence dummy;
+    EXPECT_CALL(*b1, DoB(_))
+        .WillOnce(Return(1));
+    EXPECT_CALL(*a, Binary(_, _))
+        .Times(AnyNumber());
+    EXPECT_CALL(*b2, DoB(_))
+        .Times(AnyNumber())
+        .WillRepeatedly(Return(2));
+  }
+
+  delete a;  // a is trivially satisfied.
+  EXPECT_NONFATAL_FAILURE({
+    b2->DoB(2);
+  }, "Unexpected mock function call");
+  EXPECT_EQ(1, b1->DoB(1));
+  delete b1;
+  delete b2;
+}
+
+// Tests that calls that violate the original spec yield failures.
+TEST(DeletingMockEarlyTest, Failure2) {
+  MockB* const b1 = new MockB;
+  MockA* const a = new MockA;
+  MockB* const b2 = new MockB;
+
+  {
+    InSequence dummy;
+    EXPECT_CALL(*b1, DoB(_));
+    EXPECT_CALL(*a, Binary(_, _))
+        .Times(AnyNumber());
+    EXPECT_CALL(*b2, DoB(_))
+        .Times(AnyNumber());
+  }
+
+  EXPECT_NONFATAL_FAILURE(delete b1,
+                          "Actual: never called");
+  EXPECT_NONFATAL_FAILURE(a->Binary(0, 1),
+                          "Unexpected mock function call");
+  EXPECT_NONFATAL_FAILURE(b2->DoB(1),
+                          "Unexpected mock function call");
+  delete a;
+  delete b2;
+}
+
+class EvenNumberCardinality : public CardinalityInterface {
+ public:
+  // Returns true if and only if call_count calls will satisfy this
+  // cardinality.
+  bool IsSatisfiedByCallCount(int call_count) const override {
+    return call_count % 2 == 0;
+  }
+
+  // Returns true if and only if call_count calls will saturate this
+  // cardinality.
+  bool IsSaturatedByCallCount(int /* call_count */) const override {
+    return false;
+  }
+
+  // Describes self to an ostream.
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "called even number of times";
+  }
+};
+
+Cardinality EvenNumber() {
+  return Cardinality(new EvenNumberCardinality);
+}
+
+TEST(ExpectationBaseTest,
+     AllPrerequisitesAreSatisfiedWorksForNonMonotonicCardinality) {
+  MockA* a = new MockA;
+  Sequence s;
+
+  EXPECT_CALL(*a, DoA(1))
+      .Times(EvenNumber())
+      .InSequence(s);
+  EXPECT_CALL(*a, DoA(2))
+      .Times(AnyNumber())
+      .InSequence(s);
+  EXPECT_CALL(*a, DoA(3))
+      .Times(AnyNumber());
+
+  a->DoA(3);
+  a->DoA(1);
+  EXPECT_NONFATAL_FAILURE(a->DoA(2), "Unexpected mock function call");
+  EXPECT_NONFATAL_FAILURE(delete a, "to be called even number of times");
+}
+
+// The following tests verify the message generated when a mock
+// function is called.
+
+struct Printable {
+};
+
+inline void operator<<(::std::ostream& os, const Printable&) {
+  os << "Printable";
+}
+
+struct Unprintable {
+  Unprintable() : value(0) {}
+  int value;
+};
+
+class MockC {
+ public:
+  MockC() {}
+
+  MOCK_METHOD6(VoidMethod, void(bool cond, int n, std::string s, void* p,
+                                const Printable& x, Unprintable y));
+  MOCK_METHOD0(NonVoidMethod, int());  // NOLINT
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(MockC);
+};
+
+class VerboseFlagPreservingFixture : public testing::Test {
+ protected:
+  VerboseFlagPreservingFixture()
+      : saved_verbose_flag_(GMOCK_FLAG(verbose)) {}
+
+  ~VerboseFlagPreservingFixture() override {
+    GMOCK_FLAG(verbose) = saved_verbose_flag_;
+  }
+
+ private:
+  const std::string saved_verbose_flag_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(VerboseFlagPreservingFixture);
+};
+
+#if GTEST_HAS_STREAM_REDIRECTION
+
+// Tests that an uninteresting mock function call on a naggy mock
+// generates a warning without the stack trace when
+// --gmock_verbose=warning is specified.
+TEST(FunctionCallMessageTest,
+     UninterestingCallOnNaggyMockGeneratesNoStackTraceWhenVerboseWarning) {
+  GMOCK_FLAG(verbose) = kWarningVerbosity;
+  NaggyMock<MockC> c;
+  CaptureStdout();
+  c.VoidMethod(false, 5, "Hi", nullptr, Printable(), Unprintable());
+  const std::string output = GetCapturedStdout();
+  EXPECT_PRED_FORMAT2(IsSubstring, "GMOCK WARNING", output);
+  EXPECT_PRED_FORMAT2(IsNotSubstring, "Stack trace:", output);
+}
+
+// Tests that an uninteresting mock function call on a naggy mock
+// generates a warning containing the stack trace when
+// --gmock_verbose=info is specified.
+TEST(FunctionCallMessageTest,
+     UninterestingCallOnNaggyMockGeneratesFyiWithStackTraceWhenVerboseInfo) {
+  GMOCK_FLAG(verbose) = kInfoVerbosity;
+  NaggyMock<MockC> c;
+  CaptureStdout();
+  c.VoidMethod(false, 5, "Hi", nullptr, Printable(), Unprintable());
+  const std::string output = GetCapturedStdout();
+  EXPECT_PRED_FORMAT2(IsSubstring, "GMOCK WARNING", output);
+  EXPECT_PRED_FORMAT2(IsSubstring, "Stack trace:", output);
+
+# ifndef NDEBUG
+
+  // We check the stack trace content in dbg-mode only, as opt-mode
+  // may inline the call we are interested in seeing.
+
+  // Verifies that a void mock function's name appears in the stack
+  // trace.
+  EXPECT_PRED_FORMAT2(IsSubstring, "VoidMethod(", output);
+
+  // Verifies that a non-void mock function's name appears in the
+  // stack trace.
+  CaptureStdout();
+  c.NonVoidMethod();
+  const std::string output2 = GetCapturedStdout();
+  EXPECT_PRED_FORMAT2(IsSubstring, "NonVoidMethod(", output2);
+
+# endif  // NDEBUG
+}
+
+// Tests that an uninteresting mock function call on a naggy mock
+// causes the function arguments and return value to be printed.
+TEST(FunctionCallMessageTest,
+     UninterestingCallOnNaggyMockPrintsArgumentsAndReturnValue) {
+  // A non-void mock function.
+  NaggyMock<MockB> b;
+  CaptureStdout();
+  b.DoB();
+  const std::string output1 = GetCapturedStdout();
+  EXPECT_PRED_FORMAT2(
+      IsSubstring,
+      "Uninteresting mock function call - returning default value.\n"
+      "    Function call: DoB()\n"
+      "          Returns: 0\n", output1.c_str());
+  // Makes sure the return value is printed.
+
+  // A void mock function.
+  NaggyMock<MockC> c;
+  CaptureStdout();
+  c.VoidMethod(false, 5, "Hi", nullptr, Printable(), Unprintable());
+  const std::string output2 = GetCapturedStdout();
+  EXPECT_THAT(output2.c_str(),
+              ContainsRegex(
+                  "Uninteresting mock function call - returning directly\\.\n"
+                  "    Function call: VoidMethod"
+                  "\\(false, 5, \"Hi\", NULL, @.+ "
+                  "Printable, 4-byte object <00-00 00-00>\\)"));
+  // A void function has no return value to print.
+}
+
+// Tests how the --gmock_verbose flag affects Google Mock's output.
+
+class GMockVerboseFlagTest : public VerboseFlagPreservingFixture {
+ public:
+  // Verifies that the given Google Mock output is correct.  (When
+  // should_print is true, the output should match the given regex and
+  // contain the given function name in the stack trace.  When it's
+  // false, the output should be empty.)
+  void VerifyOutput(const std::string& output, bool should_print,
+                    const std::string& expected_substring,
+                    const std::string& function_name) {
+    if (should_print) {
+      EXPECT_THAT(output.c_str(), HasSubstr(expected_substring));
+# ifndef NDEBUG
+      // We check the stack trace content in dbg-mode only, as opt-mode
+      // may inline the call we are interested in seeing.
+      EXPECT_THAT(output.c_str(), HasSubstr(function_name));
+# else
+      // Suppresses 'unused function parameter' warnings.
+      static_cast<void>(function_name);
+# endif  // NDEBUG
+    } else {
+      EXPECT_STREQ("", output.c_str());
+    }
+  }
+
+  // Tests how the flag affects expected calls.
+  void TestExpectedCall(bool should_print) {
+    MockA a;
+    EXPECT_CALL(a, DoA(5));
+    EXPECT_CALL(a, Binary(_, 1))
+        .WillOnce(Return(true));
+
+    // A void-returning function.
+    CaptureStdout();
+    a.DoA(5);
+    VerifyOutput(
+        GetCapturedStdout(),
+        should_print,
+        "Mock function call matches EXPECT_CALL(a, DoA(5))...\n"
+        "    Function call: DoA(5)\n"
+        "Stack trace:\n",
+        "DoA");
+
+    // A non-void-returning function.
+    CaptureStdout();
+    a.Binary(2, 1);
+    VerifyOutput(
+        GetCapturedStdout(),
+        should_print,
+        "Mock function call matches EXPECT_CALL(a, Binary(_, 1))...\n"
+        "    Function call: Binary(2, 1)\n"
+        "          Returns: true\n"
+        "Stack trace:\n",
+        "Binary");
+  }
+
+  // Tests how the flag affects uninteresting calls on a naggy mock.
+  void TestUninterestingCallOnNaggyMock(bool should_print) {
+    NaggyMock<MockA> a;
+    const std::string note =
+        "NOTE: You can safely ignore the above warning unless this "
+        "call should not happen.  Do not suppress it by blindly adding "
+        "an EXPECT_CALL() if you don't mean to enforce the call.  "
+        "See "
+        "https://github.com/google/googletest/blob/master/docs/"
+        "gmock_cook_book.md#"
+        "knowing-when-to-expect for details.";
+
+    // A void-returning function.
+    CaptureStdout();
+    a.DoA(5);
+    VerifyOutput(
+        GetCapturedStdout(),
+        should_print,
+        "\nGMOCK WARNING:\n"
+        "Uninteresting mock function call - returning directly.\n"
+        "    Function call: DoA(5)\n" +
+        note,
+        "DoA");
+
+    // A non-void-returning function.
+    CaptureStdout();
+    a.Binary(2, 1);
+    VerifyOutput(
+        GetCapturedStdout(),
+        should_print,
+        "\nGMOCK WARNING:\n"
+        "Uninteresting mock function call - returning default value.\n"
+        "    Function call: Binary(2, 1)\n"
+        "          Returns: false\n" +
+        note,
+        "Binary");
+  }
+};
+
+// Tests that --gmock_verbose=info causes both expected and
+// uninteresting calls to be reported.
+TEST_F(GMockVerboseFlagTest, Info) {
+  GMOCK_FLAG(verbose) = kInfoVerbosity;
+  TestExpectedCall(true);
+  TestUninterestingCallOnNaggyMock(true);
+}
+
+// Tests that --gmock_verbose=warning causes uninteresting calls to be
+// reported.
+TEST_F(GMockVerboseFlagTest, Warning) {
+  GMOCK_FLAG(verbose) = kWarningVerbosity;
+  TestExpectedCall(false);
+  TestUninterestingCallOnNaggyMock(true);
+}
+
+// Tests that --gmock_verbose=warning causes neither expected nor
+// uninteresting calls to be reported.
+TEST_F(GMockVerboseFlagTest, Error) {
+  GMOCK_FLAG(verbose) = kErrorVerbosity;
+  TestExpectedCall(false);
+  TestUninterestingCallOnNaggyMock(false);
+}
+
+// Tests that --gmock_verbose=SOME_INVALID_VALUE has the same effect
+// as --gmock_verbose=warning.
+TEST_F(GMockVerboseFlagTest, InvalidFlagIsTreatedAsWarning) {
+  GMOCK_FLAG(verbose) = "invalid";  // Treated as "warning".
+  TestExpectedCall(false);
+  TestUninterestingCallOnNaggyMock(true);
+}
+
+#endif  // GTEST_HAS_STREAM_REDIRECTION
+
+// A helper class that generates a failure when printed.  We use it to
+// ensure that Google Mock doesn't print a value (even to an internal
+// buffer) when it is not supposed to do so.
+class PrintMeNot {};
+
+void PrintTo(PrintMeNot /* dummy */, ::std::ostream* /* os */) {
+  ADD_FAILURE() << "Google Mock is printing a value that shouldn't be "
+                << "printed even to an internal buffer.";
+}
+
+class LogTestHelper {
+ public:
+  LogTestHelper() {}
+
+  MOCK_METHOD1(Foo, PrintMeNot(PrintMeNot));
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(LogTestHelper);
+};
+
+class GMockLogTest : public VerboseFlagPreservingFixture {
+ protected:
+  LogTestHelper helper_;
+};
+
+TEST_F(GMockLogTest, DoesNotPrintGoodCallInternallyIfVerbosityIsWarning) {
+  GMOCK_FLAG(verbose) = kWarningVerbosity;
+  EXPECT_CALL(helper_, Foo(_))
+      .WillOnce(Return(PrintMeNot()));
+  helper_.Foo(PrintMeNot());  // This is an expected call.
+}
+
+TEST_F(GMockLogTest, DoesNotPrintGoodCallInternallyIfVerbosityIsError) {
+  GMOCK_FLAG(verbose) = kErrorVerbosity;
+  EXPECT_CALL(helper_, Foo(_))
+      .WillOnce(Return(PrintMeNot()));
+  helper_.Foo(PrintMeNot());  // This is an expected call.
+}
+
+TEST_F(GMockLogTest, DoesNotPrintWarningInternallyIfVerbosityIsError) {
+  GMOCK_FLAG(verbose) = kErrorVerbosity;
+  ON_CALL(helper_, Foo(_))
+      .WillByDefault(Return(PrintMeNot()));
+  helper_.Foo(PrintMeNot());  // This should generate a warning.
+}
+
+// Tests Mock::AllowLeak().
+
+TEST(AllowLeakTest, AllowsLeakingUnusedMockObject) {
+  MockA* a = new MockA;
+  Mock::AllowLeak(a);
+}
+
+TEST(AllowLeakTest, CanBeCalledBeforeOnCall) {
+  MockA* a = new MockA;
+  Mock::AllowLeak(a);
+  ON_CALL(*a, DoA(_)).WillByDefault(Return());
+  a->DoA(0);
+}
+
+TEST(AllowLeakTest, CanBeCalledAfterOnCall) {
+  MockA* a = new MockA;
+  ON_CALL(*a, DoA(_)).WillByDefault(Return());
+  Mock::AllowLeak(a);
+}
+
+TEST(AllowLeakTest, CanBeCalledBeforeExpectCall) {
+  MockA* a = new MockA;
+  Mock::AllowLeak(a);
+  EXPECT_CALL(*a, DoA(_));
+  a->DoA(0);
+}
+
+TEST(AllowLeakTest, CanBeCalledAfterExpectCall) {
+  MockA* a = new MockA;
+  EXPECT_CALL(*a, DoA(_)).Times(AnyNumber());
+  Mock::AllowLeak(a);
+}
+
+TEST(AllowLeakTest, WorksWhenBothOnCallAndExpectCallArePresent) {
+  MockA* a = new MockA;
+  ON_CALL(*a, DoA(_)).WillByDefault(Return());
+  EXPECT_CALL(*a, DoA(_)).Times(AnyNumber());
+  Mock::AllowLeak(a);
+}
+
+// Tests that we can verify and clear a mock object's expectations
+// when none of its methods has expectations.
+TEST(VerifyAndClearExpectationsTest, NoMethodHasExpectations) {
+  MockB b;
+  ASSERT_TRUE(Mock::VerifyAndClearExpectations(&b));
+
+  // There should be no expectations on the methods now, so we can
+  // freely call them.
+  EXPECT_EQ(0, b.DoB());
+  EXPECT_EQ(0, b.DoB(1));
+}
+
+// Tests that we can verify and clear a mock object's expectations
+// when some, but not all, of its methods have expectations *and* the
+// verification succeeds.
+TEST(VerifyAndClearExpectationsTest, SomeMethodsHaveExpectationsAndSucceed) {
+  MockB b;
+  EXPECT_CALL(b, DoB())
+      .WillOnce(Return(1));
+  b.DoB();
+  ASSERT_TRUE(Mock::VerifyAndClearExpectations(&b));
+
+  // There should be no expectations on the methods now, so we can
+  // freely call them.
+  EXPECT_EQ(0, b.DoB());
+  EXPECT_EQ(0, b.DoB(1));
+}
+
+// Tests that we can verify and clear a mock object's expectations
+// when some, but not all, of its methods have expectations *and* the
+// verification fails.
+TEST(VerifyAndClearExpectationsTest, SomeMethodsHaveExpectationsAndFail) {
+  MockB b;
+  EXPECT_CALL(b, DoB())
+      .WillOnce(Return(1));
+  bool result = true;
+  EXPECT_NONFATAL_FAILURE(result = Mock::VerifyAndClearExpectations(&b),
+                          "Actual: never called");
+  ASSERT_FALSE(result);
+
+  // There should be no expectations on the methods now, so we can
+  // freely call them.
+  EXPECT_EQ(0, b.DoB());
+  EXPECT_EQ(0, b.DoB(1));
+}
+
+// Tests that we can verify and clear a mock object's expectations
+// when all of its methods have expectations.
+TEST(VerifyAndClearExpectationsTest, AllMethodsHaveExpectations) {
+  MockB b;
+  EXPECT_CALL(b, DoB())
+      .WillOnce(Return(1));
+  EXPECT_CALL(b, DoB(_))
+      .WillOnce(Return(2));
+  b.DoB();
+  b.DoB(1);
+  ASSERT_TRUE(Mock::VerifyAndClearExpectations(&b));
+
+  // There should be no expectations on the methods now, so we can
+  // freely call them.
+  EXPECT_EQ(0, b.DoB());
+  EXPECT_EQ(0, b.DoB(1));
+}
+
+// Tests that we can verify and clear a mock object's expectations
+// when a method has more than one expectation.
+TEST(VerifyAndClearExpectationsTest, AMethodHasManyExpectations) {
+  MockB b;
+  EXPECT_CALL(b, DoB(0))
+      .WillOnce(Return(1));
+  EXPECT_CALL(b, DoB(_))
+      .WillOnce(Return(2));
+  b.DoB(1);
+  bool result = true;
+  EXPECT_NONFATAL_FAILURE(result = Mock::VerifyAndClearExpectations(&b),
+                          "Actual: never called");
+  ASSERT_FALSE(result);
+
+  // There should be no expectations on the methods now, so we can
+  // freely call them.
+  EXPECT_EQ(0, b.DoB());
+  EXPECT_EQ(0, b.DoB(1));
+}
+
+// Tests that we can call VerifyAndClearExpectations() on the same
+// mock object multiple times.
+TEST(VerifyAndClearExpectationsTest, CanCallManyTimes) {
+  MockB b;
+  EXPECT_CALL(b, DoB());
+  b.DoB();
+  Mock::VerifyAndClearExpectations(&b);
+
+  EXPECT_CALL(b, DoB(_))
+      .WillOnce(Return(1));
+  b.DoB(1);
+  Mock::VerifyAndClearExpectations(&b);
+  Mock::VerifyAndClearExpectations(&b);
+
+  // There should be no expectations on the methods now, so we can
+  // freely call them.
+  EXPECT_EQ(0, b.DoB());
+  EXPECT_EQ(0, b.DoB(1));
+}
+
+// Tests that we can clear a mock object's default actions when none
+// of its methods has default actions.
+TEST(VerifyAndClearTest, NoMethodHasDefaultActions) {
+  MockB b;
+  // If this crashes or generates a failure, the test will catch it.
+  Mock::VerifyAndClear(&b);
+  EXPECT_EQ(0, b.DoB());
+}
+
+// Tests that we can clear a mock object's default actions when some,
+// but not all of its methods have default actions.
+TEST(VerifyAndClearTest, SomeMethodsHaveDefaultActions) {
+  MockB b;
+  ON_CALL(b, DoB())
+      .WillByDefault(Return(1));
+
+  Mock::VerifyAndClear(&b);
+
+  // Verifies that the default action of int DoB() was removed.
+  EXPECT_EQ(0, b.DoB());
+}
+
+// Tests that we can clear a mock object's default actions when all of
+// its methods have default actions.
+TEST(VerifyAndClearTest, AllMethodsHaveDefaultActions) {
+  MockB b;
+  ON_CALL(b, DoB())
+      .WillByDefault(Return(1));
+  ON_CALL(b, DoB(_))
+      .WillByDefault(Return(2));
+
+  Mock::VerifyAndClear(&b);
+
+  // Verifies that the default action of int DoB() was removed.
+  EXPECT_EQ(0, b.DoB());
+
+  // Verifies that the default action of int DoB(int) was removed.
+  EXPECT_EQ(0, b.DoB(0));
+}
+
+// Tests that we can clear a mock object's default actions when a
+// method has more than one ON_CALL() set on it.
+TEST(VerifyAndClearTest, AMethodHasManyDefaultActions) {
+  MockB b;
+  ON_CALL(b, DoB(0))
+      .WillByDefault(Return(1));
+  ON_CALL(b, DoB(_))
+      .WillByDefault(Return(2));
+
+  Mock::VerifyAndClear(&b);
+
+  // Verifies that the default actions (there are two) of int DoB(int)
+  // were removed.
+  EXPECT_EQ(0, b.DoB(0));
+  EXPECT_EQ(0, b.DoB(1));
+}
+
+// Tests that we can call VerifyAndClear() on a mock object multiple
+// times.
+TEST(VerifyAndClearTest, CanCallManyTimes) {
+  MockB b;
+  ON_CALL(b, DoB())
+      .WillByDefault(Return(1));
+  Mock::VerifyAndClear(&b);
+  Mock::VerifyAndClear(&b);
+
+  ON_CALL(b, DoB(_))
+      .WillByDefault(Return(1));
+  Mock::VerifyAndClear(&b);
+
+  EXPECT_EQ(0, b.DoB());
+  EXPECT_EQ(0, b.DoB(1));
+}
+
+// Tests that VerifyAndClear() works when the verification succeeds.
+TEST(VerifyAndClearTest, Success) {
+  MockB b;
+  ON_CALL(b, DoB())
+      .WillByDefault(Return(1));
+  EXPECT_CALL(b, DoB(1))
+      .WillOnce(Return(2));
+
+  b.DoB();
+  b.DoB(1);
+  ASSERT_TRUE(Mock::VerifyAndClear(&b));
+
+  // There should be no expectations on the methods now, so we can
+  // freely call them.
+  EXPECT_EQ(0, b.DoB());
+  EXPECT_EQ(0, b.DoB(1));
+}
+
+// Tests that VerifyAndClear() works when the verification fails.
+TEST(VerifyAndClearTest, Failure) {
+  MockB b;
+  ON_CALL(b, DoB(_))
+      .WillByDefault(Return(1));
+  EXPECT_CALL(b, DoB())
+      .WillOnce(Return(2));
+
+  b.DoB(1);
+  bool result = true;
+  EXPECT_NONFATAL_FAILURE(result = Mock::VerifyAndClear(&b),
+                          "Actual: never called");
+  ASSERT_FALSE(result);
+
+  // There should be no expectations on the methods now, so we can
+  // freely call them.
+  EXPECT_EQ(0, b.DoB());
+  EXPECT_EQ(0, b.DoB(1));
+}
+
+// Tests that VerifyAndClear() works when the default actions and
+// expectations are set on a const mock object.
+TEST(VerifyAndClearTest, Const) {
+  MockB b;
+  ON_CALL(Const(b), DoB())
+      .WillByDefault(Return(1));
+
+  EXPECT_CALL(Const(b), DoB())
+      .WillOnce(DoDefault())
+      .WillOnce(Return(2));
+
+  b.DoB();
+  b.DoB();
+  ASSERT_TRUE(Mock::VerifyAndClear(&b));
+
+  // There should be no expectations on the methods now, so we can
+  // freely call them.
+  EXPECT_EQ(0, b.DoB());
+  EXPECT_EQ(0, b.DoB(1));
+}
+
+// Tests that we can set default actions and expectations on a mock
+// object after VerifyAndClear() has been called on it.
+TEST(VerifyAndClearTest, CanSetDefaultActionsAndExpectationsAfterwards) {
+  MockB b;
+  ON_CALL(b, DoB())
+      .WillByDefault(Return(1));
+  EXPECT_CALL(b, DoB(_))
+      .WillOnce(Return(2));
+  b.DoB(1);
+
+  Mock::VerifyAndClear(&b);
+
+  EXPECT_CALL(b, DoB())
+      .WillOnce(Return(3));
+  ON_CALL(b, DoB(_))
+      .WillByDefault(Return(4));
+
+  EXPECT_EQ(3, b.DoB());
+  EXPECT_EQ(4, b.DoB(1));
+}
+
+// Tests that calling VerifyAndClear() on one mock object does not
+// affect other mock objects (either of the same type or not).
+TEST(VerifyAndClearTest, DoesNotAffectOtherMockObjects) {
+  MockA a;
+  MockB b1;
+  MockB b2;
+
+  ON_CALL(a, Binary(_, _))
+      .WillByDefault(Return(true));
+  EXPECT_CALL(a, Binary(_, _))
+      .WillOnce(DoDefault())
+      .WillOnce(Return(false));
+
+  ON_CALL(b1, DoB())
+      .WillByDefault(Return(1));
+  EXPECT_CALL(b1, DoB(_))
+      .WillOnce(Return(2));
+
+  ON_CALL(b2, DoB())
+      .WillByDefault(Return(3));
+  EXPECT_CALL(b2, DoB(_));
+
+  b2.DoB(0);
+  Mock::VerifyAndClear(&b2);
+
+  // Verifies that the default actions and expectations of a and b1
+  // are still in effect.
+  EXPECT_TRUE(a.Binary(0, 0));
+  EXPECT_FALSE(a.Binary(0, 0));
+
+  EXPECT_EQ(1, b1.DoB());
+  EXPECT_EQ(2, b1.DoB(0));
+}
+
+TEST(VerifyAndClearTest,
+     DestroyingChainedMocksDoesNotDeadlockThroughExpectations) {
+  std::shared_ptr<MockA> a(new MockA);
+  ReferenceHoldingMock test_mock;
+
+  // EXPECT_CALL stores a reference to a inside test_mock.
+  EXPECT_CALL(test_mock, AcceptReference(_))
+      .WillRepeatedly(SetArgPointee<0>(a));
+
+  // Throw away the reference to the mock that we have in a. After this, the
+  // only reference to it is stored by test_mock.
+  a.reset();
+
+  // When test_mock goes out of scope, it destroys the last remaining reference
+  // to the mock object originally pointed to by a. This will cause the MockA
+  // destructor to be called from inside the ReferenceHoldingMock destructor.
+  // The state of all mocks is protected by a single global lock, but there
+  // should be no deadlock.
+}
+
+TEST(VerifyAndClearTest,
+     DestroyingChainedMocksDoesNotDeadlockThroughDefaultAction) {
+  std::shared_ptr<MockA> a(new MockA);
+  ReferenceHoldingMock test_mock;
+
+  // ON_CALL stores a reference to a inside test_mock.
+  ON_CALL(test_mock, AcceptReference(_))
+      .WillByDefault(SetArgPointee<0>(a));
+
+  // Throw away the reference to the mock that we have in a. After this, the
+  // only reference to it is stored by test_mock.
+  a.reset();
+
+  // When test_mock goes out of scope, it destroys the last remaining reference
+  // to the mock object originally pointed to by a. This will cause the MockA
+  // destructor to be called from inside the ReferenceHoldingMock destructor.
+  // The state of all mocks is protected by a single global lock, but there
+  // should be no deadlock.
+}
+
+// Tests that a mock function's action can call a mock function
+// (either the same function or a different one) either as an explicit
+// action or as a default action without causing a dead lock.  It
+// verifies that the action is not performed inside the critical
+// section.
+TEST(SynchronizationTest, CanCallMockMethodInAction) {
+  MockA a;
+  MockC c;
+  ON_CALL(a, DoA(_))
+      .WillByDefault(IgnoreResult(InvokeWithoutArgs(&c,
+                                                    &MockC::NonVoidMethod)));
+  EXPECT_CALL(a, DoA(1));
+  EXPECT_CALL(a, DoA(1))
+      .WillOnce(Invoke(&a, &MockA::DoA))
+      .RetiresOnSaturation();
+  EXPECT_CALL(c, NonVoidMethod());
+
+  a.DoA(1);
+  // This will match the second EXPECT_CALL() and trigger another a.DoA(1),
+  // which will in turn match the first EXPECT_CALL() and trigger a call to
+  // c.NonVoidMethod() that was specified by the ON_CALL() since the first
+  // EXPECT_CALL() did not specify an action.
+}
+
+TEST(ParameterlessExpectationsTest, CanSetExpectationsWithoutMatchers) {
+  MockA a;
+  int do_a_arg0 = 0;
+  ON_CALL(a, DoA).WillByDefault(SaveArg<0>(&do_a_arg0));
+  int do_a_47_arg0 = 0;
+  ON_CALL(a, DoA(47)).WillByDefault(SaveArg<0>(&do_a_47_arg0));
+
+  a.DoA(17);
+  EXPECT_THAT(do_a_arg0, 17);
+  EXPECT_THAT(do_a_47_arg0, 0);
+  a.DoA(47);
+  EXPECT_THAT(do_a_arg0, 17);
+  EXPECT_THAT(do_a_47_arg0, 47);
+
+  ON_CALL(a, Binary).WillByDefault(Return(true));
+  ON_CALL(a, Binary(_, 14)).WillByDefault(Return(false));
+  EXPECT_THAT(a.Binary(14, 17), true);
+  EXPECT_THAT(a.Binary(17, 14), false);
+}
+
+TEST(ParameterlessExpectationsTest, CanSetExpectationsForOverloadedMethods) {
+  MockB b;
+  ON_CALL(b, DoB()).WillByDefault(Return(9));
+  ON_CALL(b, DoB(5)).WillByDefault(Return(11));
+
+  EXPECT_THAT(b.DoB(), 9);
+  EXPECT_THAT(b.DoB(1), 0);  // default value
+  EXPECT_THAT(b.DoB(5), 11);
+}
+
+struct MockWithConstMethods {
+ public:
+  MOCK_CONST_METHOD1(Foo, int(int));
+  MOCK_CONST_METHOD2(Bar, int(int, const char*));
+};
+
+TEST(ParameterlessExpectationsTest, CanSetExpectationsForConstMethods) {
+  MockWithConstMethods mock;
+  ON_CALL(mock, Foo).WillByDefault(Return(7));
+  ON_CALL(mock, Bar).WillByDefault(Return(33));
+
+  EXPECT_THAT(mock.Foo(17), 7);
+  EXPECT_THAT(mock.Bar(27, "purple"), 33);
+}
+
+class MockConstOverload {
+ public:
+  MOCK_METHOD1(Overloaded, int(int));
+  MOCK_CONST_METHOD1(Overloaded, int(int));
+};
+
+TEST(ParameterlessExpectationsTest,
+     CanSetExpectationsForConstOverloadedMethods) {
+  MockConstOverload mock;
+  ON_CALL(mock, Overloaded(_)).WillByDefault(Return(7));
+  ON_CALL(mock, Overloaded(5)).WillByDefault(Return(9));
+  ON_CALL(Const(mock), Overloaded(5)).WillByDefault(Return(11));
+  ON_CALL(Const(mock), Overloaded(7)).WillByDefault(Return(13));
+
+  EXPECT_THAT(mock.Overloaded(1), 7);
+  EXPECT_THAT(mock.Overloaded(5), 9);
+  EXPECT_THAT(mock.Overloaded(7), 7);
+
+  const MockConstOverload& const_mock = mock;
+  EXPECT_THAT(const_mock.Overloaded(1), 0);
+  EXPECT_THAT(const_mock.Overloaded(5), 11);
+  EXPECT_THAT(const_mock.Overloaded(7), 13);
+}
+
+}  // namespace
+
+// Allows the user to define their own main and then invoke gmock_main
+// from it. This might be necessary on some platforms which require
+// specific setup and teardown.
+#if GMOCK_RENAME_MAIN
+int gmock_main(int argc, char **argv) {
+#else
+int main(int argc, char **argv) {
+#endif  // GMOCK_RENAME_MAIN
+  testing::InitGoogleMock(&argc, argv);
+  // Ensures that the tests pass no matter what value of
+  // --gmock_catch_leaked_mocks and --gmock_verbose the user specifies.
+  testing::GMOCK_FLAG(catch_leaked_mocks) = true;
+  testing::GMOCK_FLAG(verbose) = testing::internal::kWarningVerbosity;
+
+  return RUN_ALL_TESTS();
+}
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock_all_test.cc b/leveldb_base/third_party/googletest/googlemock/test/gmock_all_test.cc
new file mode 100644
index 0000000..fffbb8b
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock_all_test.cc
@@ -0,0 +1,46 @@
+// Copyright 2009, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// Tests for Google C++ Mocking Framework (Google Mock)
+//
+// Some users use a build system that Google Mock doesn't support directly,
+// yet they still want to build and run Google Mock's own tests.  This file
+// includes most such tests, making it easier for these users to maintain
+// their build scripts (they just need to build this file, even though the
+// below list of actual *_test.cc files might change).
+#include "test/gmock-actions_test.cc"
+#include "test/gmock-cardinalities_test.cc"
+#include "test/gmock-internal-utils_test.cc"
+#include "test/gmock-matchers_test.cc"
+#include "test/gmock-more-actions_test.cc"
+#include "test/gmock-nice-strict_test.cc"
+#include "test/gmock-port_test.cc"
+#include "test/gmock-spec-builders_test.cc"
+#include "test/gmock_test.cc"
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock_ex_test.cc b/leveldb_base/third_party/googletest/googlemock/test/gmock_ex_test.cc
new file mode 100644
index 0000000..72eb43f
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock_ex_test.cc
@@ -0,0 +1,80 @@
+// Copyright 2013, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Tests Google Mock's functionality that depends on exceptions.
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+#if GTEST_HAS_EXCEPTIONS
+namespace {
+
+using testing::HasSubstr;
+
+using testing::internal::GoogleTestFailureException;
+
+// A type that cannot be default constructed.
+class NonDefaultConstructible {
+ public:
+  explicit NonDefaultConstructible(int /* dummy */) {}
+};
+
+class MockFoo {
+ public:
+  // A mock method that returns a user-defined type.  Google Mock
+  // doesn't know what the default value for this type is.
+  MOCK_METHOD0(GetNonDefaultConstructible, NonDefaultConstructible());
+};
+
+TEST(DefaultValueTest, ThrowsRuntimeErrorWhenNoDefaultValue) {
+  MockFoo mock;
+  try {
+    // No expectation is set on this method, so Google Mock must
+    // return the default value.  However, since Google Mock knows
+    // nothing about the return type, it doesn't know what to return,
+    // and has to throw (when exceptions are enabled) or abort
+    // (otherwise).
+    mock.GetNonDefaultConstructible();
+    FAIL() << "GetNonDefaultConstructible()'s return type has no default "
+           << "value, so Google Mock should have thrown.";
+  } catch (const GoogleTestFailureException& /* unused */) {
+    FAIL() << "Google Test does not try to catch an exception of type "
+           << "GoogleTestFailureException, which is used for reporting "
+           << "a failure to other testing frameworks.  Google Mock should "
+           << "not throw a GoogleTestFailureException as it will kill the "
+           << "entire test program instead of just the current TEST.";
+  } catch (const std::exception& ex) {
+    EXPECT_THAT(ex.what(), HasSubstr("has no default value"));
+  }
+}
+
+
+}  // unnamed namespace
+#endif
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock_leak_test.py b/leveldb_base/third_party/googletest/googlemock/test/gmock_leak_test.py
new file mode 100644
index 0000000..7e4b1ee
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock_leak_test.py
@@ -0,0 +1,104 @@
+#!/usr/bin/env python
+#
+# Copyright 2009, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Tests that leaked mock objects can be caught be Google Mock."""
+
+import gmock_test_utils
+
+PROGRAM_PATH = gmock_test_utils.GetTestExecutablePath('gmock_leak_test_')
+TEST_WITH_EXPECT_CALL = [PROGRAM_PATH, '--gtest_filter=*ExpectCall*']
+TEST_WITH_ON_CALL = [PROGRAM_PATH, '--gtest_filter=*OnCall*']
+TEST_MULTIPLE_LEAKS = [PROGRAM_PATH, '--gtest_filter=*MultipleLeaked*']
+
+environ = gmock_test_utils.environ
+SetEnvVar = gmock_test_utils.SetEnvVar
+
+# Tests in this file run a Google-Test-based test program and expect it
+# to terminate prematurely.  Therefore they are incompatible with
+# the premature-exit-file protocol by design.  Unset the
+# premature-exit filepath to prevent Google Test from creating
+# the file.
+SetEnvVar(gmock_test_utils.PREMATURE_EXIT_FILE_ENV_VAR, None)
+
+
+class GMockLeakTest(gmock_test_utils.TestCase):
+
+  def testCatchesLeakedMockByDefault(self):
+    self.assertNotEqual(
+        0,
+        gmock_test_utils.Subprocess(TEST_WITH_EXPECT_CALL,
+                                    env=environ).exit_code)
+    self.assertNotEqual(
+        0,
+        gmock_test_utils.Subprocess(TEST_WITH_ON_CALL,
+                                    env=environ).exit_code)
+
+  def testDoesNotCatchLeakedMockWhenDisabled(self):
+    self.assertEquals(
+        0,
+        gmock_test_utils.Subprocess(TEST_WITH_EXPECT_CALL +
+                                    ['--gmock_catch_leaked_mocks=0'],
+                                    env=environ).exit_code)
+    self.assertEquals(
+        0,
+        gmock_test_utils.Subprocess(TEST_WITH_ON_CALL +
+                                    ['--gmock_catch_leaked_mocks=0'],
+                                    env=environ).exit_code)
+
+  def testCatchesLeakedMockWhenEnabled(self):
+    self.assertNotEqual(
+        0,
+        gmock_test_utils.Subprocess(TEST_WITH_EXPECT_CALL +
+                                    ['--gmock_catch_leaked_mocks'],
+                                    env=environ).exit_code)
+    self.assertNotEqual(
+        0,
+        gmock_test_utils.Subprocess(TEST_WITH_ON_CALL +
+                                    ['--gmock_catch_leaked_mocks'],
+                                    env=environ).exit_code)
+
+  def testCatchesLeakedMockWhenEnabledWithExplictFlagValue(self):
+    self.assertNotEqual(
+        0,
+        gmock_test_utils.Subprocess(TEST_WITH_EXPECT_CALL +
+                                    ['--gmock_catch_leaked_mocks=1'],
+                                    env=environ).exit_code)
+
+  def testCatchesMultipleLeakedMocks(self):
+    self.assertNotEqual(
+        0,
+        gmock_test_utils.Subprocess(TEST_MULTIPLE_LEAKS +
+                                    ['--gmock_catch_leaked_mocks'],
+                                    env=environ).exit_code)
+
+
+if __name__ == '__main__':
+  gmock_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock_leak_test_.cc b/leveldb_base/third_party/googletest/googlemock/test/gmock_leak_test_.cc
new file mode 100644
index 0000000..2e095ab
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock_leak_test_.cc
@@ -0,0 +1,99 @@
+// Copyright 2009, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This program is for verifying that a leaked mock object can be
+// caught by Google Mock's leak detector.
+
+#include "gmock/gmock.h"
+
+namespace {
+
+using ::testing::Return;
+
+class FooInterface {
+ public:
+  virtual ~FooInterface() {}
+  virtual void DoThis() = 0;
+};
+
+class MockFoo : public FooInterface {
+ public:
+  MockFoo() {}
+
+  MOCK_METHOD0(DoThis, void());
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(MockFoo);
+};
+
+TEST(LeakTest, LeakedMockWithExpectCallCausesFailureWhenLeakCheckingIsEnabled) {
+  MockFoo* foo = new MockFoo;
+
+  EXPECT_CALL(*foo, DoThis());
+  foo->DoThis();
+
+  // In order to test the leak detector, we deliberately leak foo.
+
+  // Makes sure Google Mock's leak detector can change the exit code
+  // to 1 even when the code is already exiting with 0.
+  exit(0);
+}
+
+TEST(LeakTest, LeakedMockWithOnCallCausesFailureWhenLeakCheckingIsEnabled) {
+  MockFoo* foo = new MockFoo;
+
+  ON_CALL(*foo, DoThis()).WillByDefault(Return());
+
+  // In order to test the leak detector, we deliberately leak foo.
+
+  // Makes sure Google Mock's leak detector can change the exit code
+  // to 1 even when the code is already exiting with 0.
+  exit(0);
+}
+
+TEST(LeakTest, CatchesMultipleLeakedMockObjects) {
+  MockFoo* foo1 = new MockFoo;
+  MockFoo* foo2 = new MockFoo;
+
+  ON_CALL(*foo1, DoThis()).WillByDefault(Return());
+  EXPECT_CALL(*foo2, DoThis());
+  foo2->DoThis();
+
+  // In order to test the leak detector, we deliberately leak foo1 and
+  // foo2.
+
+  // Makes sure Google Mock's leak detector can change the exit code
+  // to 1 even when the code is already exiting with 0.
+  exit(0);
+}
+
+}  // namespace
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock_link2_test.cc b/leveldb_base/third_party/googletest/googlemock/test/gmock_link2_test.cc
new file mode 100644
index 0000000..d27ce17
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock_link2_test.cc
@@ -0,0 +1,39 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file is for verifying that various Google Mock constructs do not
+// produce linker errors when instantiated in different translation units.
+// Please see gmock_link_test.h for details.
+
+#define LinkTest LinkTest2
+
+#include "test/gmock_link_test.h"
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock_link_test.cc b/leveldb_base/third_party/googletest/googlemock/test/gmock_link_test.cc
new file mode 100644
index 0000000..e7c54cc
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock_link_test.cc
@@ -0,0 +1,39 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file is for verifying that various Google Mock constructs do not
+// produce linker errors when instantiated in different translation units.
+// Please see gmock_link_test.h for details.
+
+#define LinkTest LinkTest1
+
+#include "test/gmock_link_test.h"
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock_link_test.h b/leveldb_base/third_party/googletest/googlemock/test/gmock_link_test.h
new file mode 100644
index 0000000..5734b2e
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock_link_test.h
@@ -0,0 +1,690 @@
+// Copyright 2009, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests that:
+// a. A header file defining a mock class can be included in multiple
+//    translation units without causing a link error.
+// b. Actions and matchers can be instantiated with identical template
+//    arguments in different translation units without causing link
+//    errors.
+//    The following constructs are currently tested:
+//    Actions:
+//      Return()
+//      Return(value)
+//      ReturnNull
+//      ReturnRef
+//      Assign
+//      SetArgPointee
+//      SetArrayArgument
+//      SetErrnoAndReturn
+//      Invoke(function)
+//      Invoke(object, method)
+//      InvokeWithoutArgs(function)
+//      InvokeWithoutArgs(object, method)
+//      InvokeArgument
+//      WithArg
+//      WithArgs
+//      WithoutArgs
+//      DoAll
+//      DoDefault
+//      IgnoreResult
+//      Throw
+//      ACTION()-generated
+//      ACTION_P()-generated
+//      ACTION_P2()-generated
+//    Matchers:
+//      _
+//      A
+//      An
+//      Eq
+//      Gt, Lt, Ge, Le, Ne
+//      NotNull
+//      Ref
+//      TypedEq
+//      DoubleEq
+//      FloatEq
+//      NanSensitiveDoubleEq
+//      NanSensitiveFloatEq
+//      ContainsRegex
+//      MatchesRegex
+//      EndsWith
+//      HasSubstr
+//      StartsWith
+//      StrCaseEq
+//      StrCaseNe
+//      StrEq
+//      StrNe
+//      ElementsAre
+//      ElementsAreArray
+//      ContainerEq
+//      Field
+//      Property
+//      ResultOf(function)
+//      ResultOf(callback)
+//      Pointee
+//      Truly(predicate)
+//      AddressSatisfies
+//      AllOf
+//      AnyOf
+//      Not
+//      MatcherCast<T>
+//
+//  Please note: this test does not verify the functioning of these
+//  constructs, only that the programs using them will link successfully.
+//
+// Implementation note:
+// This test requires identical definitions of Interface and Mock to be
+// included in different translation units.  We achieve this by writing
+// them in this header and #including it in gmock_link_test.cc and
+// gmock_link2_test.cc.  Because the symbols generated by the compiler for
+// those constructs must be identical in both translation units,
+// definitions of Interface and Mock tests MUST be kept in the SAME
+// NON-ANONYMOUS namespace in this file.  The test fixture class LinkTest
+// is defined as LinkTest1 in gmock_link_test.cc and as LinkTest2 in
+// gmock_link2_test.cc to avoid producing linker errors.
+
+#ifndef GOOGLEMOCK_TEST_GMOCK_LINK_TEST_H_
+#define GOOGLEMOCK_TEST_GMOCK_LINK_TEST_H_
+
+#include "gmock/gmock.h"
+
+#if !GTEST_OS_WINDOWS_MOBILE
+# include <errno.h>
+#endif
+
+#include <iostream>
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "gtest/internal/gtest-port.h"
+
+using testing::_;
+using testing::A;
+using testing::Action;
+using testing::AllOf;
+using testing::AnyOf;
+using testing::Assign;
+using testing::ContainerEq;
+using testing::DoAll;
+using testing::DoDefault;
+using testing::DoubleEq;
+using testing::ElementsAre;
+using testing::ElementsAreArray;
+using testing::EndsWith;
+using testing::Eq;
+using testing::Field;
+using testing::FloatEq;
+using testing::Ge;
+using testing::Gt;
+using testing::HasSubstr;
+using testing::IgnoreResult;
+using testing::Invoke;
+using testing::InvokeArgument;
+using testing::InvokeWithoutArgs;
+using testing::IsNull;
+using testing::IsSubsetOf;
+using testing::IsSupersetOf;
+using testing::Le;
+using testing::Lt;
+using testing::Matcher;
+using testing::MatcherCast;
+using testing::NanSensitiveDoubleEq;
+using testing::NanSensitiveFloatEq;
+using testing::Ne;
+using testing::Not;
+using testing::NotNull;
+using testing::Pointee;
+using testing::Property;
+using testing::Ref;
+using testing::ResultOf;
+using testing::Return;
+using testing::ReturnNull;
+using testing::ReturnRef;
+using testing::SetArgPointee;
+using testing::SetArrayArgument;
+using testing::StartsWith;
+using testing::StrCaseEq;
+using testing::StrCaseNe;
+using testing::StrEq;
+using testing::StrNe;
+using testing::Truly;
+using testing::TypedEq;
+using testing::WithArg;
+using testing::WithArgs;
+using testing::WithoutArgs;
+
+#if !GTEST_OS_WINDOWS_MOBILE
+using testing::SetErrnoAndReturn;
+#endif
+
+#if GTEST_HAS_EXCEPTIONS
+using testing::Throw;
+#endif
+
+using testing::ContainsRegex;
+using testing::MatchesRegex;
+
+class Interface {
+ public:
+  virtual ~Interface() {}
+  virtual void VoidFromString(char* str) = 0;
+  virtual char* StringFromString(char* str) = 0;
+  virtual int IntFromString(char* str) = 0;
+  virtual int& IntRefFromString(char* str) = 0;
+  virtual void VoidFromFunc(void(*func)(char* str)) = 0;
+  virtual void VoidFromIntRef(int& n) = 0;  // NOLINT
+  virtual void VoidFromFloat(float n) = 0;
+  virtual void VoidFromDouble(double n) = 0;
+  virtual void VoidFromVector(const std::vector<int>& v) = 0;
+};
+
+class Mock: public Interface {
+ public:
+  Mock() {}
+
+  MOCK_METHOD1(VoidFromString, void(char* str));
+  MOCK_METHOD1(StringFromString, char*(char* str));
+  MOCK_METHOD1(IntFromString, int(char* str));
+  MOCK_METHOD1(IntRefFromString, int&(char* str));
+  MOCK_METHOD1(VoidFromFunc, void(void(*func)(char* str)));
+  MOCK_METHOD1(VoidFromIntRef, void(int& n));  // NOLINT
+  MOCK_METHOD1(VoidFromFloat, void(float n));
+  MOCK_METHOD1(VoidFromDouble, void(double n));
+  MOCK_METHOD1(VoidFromVector, void(const std::vector<int>& v));
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(Mock);
+};
+
+class InvokeHelper {
+ public:
+  static void StaticVoidFromVoid() {}
+  void VoidFromVoid() {}
+  static void StaticVoidFromString(char* /* str */) {}
+  void VoidFromString(char* /* str */) {}
+  static int StaticIntFromString(char* /* str */) { return 1; }
+  static bool StaticBoolFromString(const char* /* str */) { return true; }
+};
+
+class FieldHelper {
+ public:
+  explicit FieldHelper(int a_field) : field_(a_field) {}
+  int field() const { return field_; }
+  int field_;  // NOLINT -- need external access to field_ to test
+               //           the Field matcher.
+};
+
+// Tests the linkage of the ReturnVoid action.
+TEST(LinkTest, TestReturnVoid) {
+  Mock mock;
+
+  EXPECT_CALL(mock, VoidFromString(_)).WillOnce(Return());
+  mock.VoidFromString(nullptr);
+}
+
+// Tests the linkage of the Return action.
+TEST(LinkTest, TestReturn) {
+  Mock mock;
+  char ch = 'x';
+
+  EXPECT_CALL(mock, StringFromString(_)).WillOnce(Return(&ch));
+  mock.StringFromString(nullptr);
+}
+
+// Tests the linkage of the ReturnNull action.
+TEST(LinkTest, TestReturnNull) {
+  Mock mock;
+
+  EXPECT_CALL(mock, VoidFromString(_)).WillOnce(Return());
+  mock.VoidFromString(nullptr);
+}
+
+// Tests the linkage of the ReturnRef action.
+TEST(LinkTest, TestReturnRef) {
+  Mock mock;
+  int n = 42;
+
+  EXPECT_CALL(mock, IntRefFromString(_)).WillOnce(ReturnRef(n));
+  mock.IntRefFromString(nullptr);
+}
+
+// Tests the linkage of the Assign action.
+TEST(LinkTest, TestAssign) {
+  Mock mock;
+  char ch = 'x';
+
+  EXPECT_CALL(mock, VoidFromString(_)).WillOnce(Assign(&ch, 'y'));
+  mock.VoidFromString(nullptr);
+}
+
+// Tests the linkage of the SetArgPointee action.
+TEST(LinkTest, TestSetArgPointee) {
+  Mock mock;
+  char ch = 'x';
+
+  EXPECT_CALL(mock, VoidFromString(_)).WillOnce(SetArgPointee<0>('y'));
+  mock.VoidFromString(&ch);
+}
+
+// Tests the linkage of the SetArrayArgument action.
+TEST(LinkTest, TestSetArrayArgument) {
+  Mock mock;
+  char ch = 'x';
+  char ch2 = 'y';
+
+  EXPECT_CALL(mock, VoidFromString(_)).WillOnce(SetArrayArgument<0>(&ch2,
+                                                                    &ch2 + 1));
+  mock.VoidFromString(&ch);
+}
+
+#if !GTEST_OS_WINDOWS_MOBILE
+
+// Tests the linkage of the SetErrnoAndReturn action.
+TEST(LinkTest, TestSetErrnoAndReturn) {
+  Mock mock;
+
+  int saved_errno = errno;
+  EXPECT_CALL(mock, IntFromString(_)).WillOnce(SetErrnoAndReturn(1, -1));
+  mock.IntFromString(nullptr);
+  errno = saved_errno;
+}
+
+#endif  // !GTEST_OS_WINDOWS_MOBILE
+
+// Tests the linkage of the Invoke(function) and Invoke(object, method) actions.
+TEST(LinkTest, TestInvoke) {
+  Mock mock;
+  InvokeHelper test_invoke_helper;
+
+  EXPECT_CALL(mock, VoidFromString(_))
+      .WillOnce(Invoke(&InvokeHelper::StaticVoidFromString))
+      .WillOnce(Invoke(&test_invoke_helper, &InvokeHelper::VoidFromString));
+  mock.VoidFromString(nullptr);
+  mock.VoidFromString(nullptr);
+}
+
+// Tests the linkage of the InvokeWithoutArgs action.
+TEST(LinkTest, TestInvokeWithoutArgs) {
+  Mock mock;
+  InvokeHelper test_invoke_helper;
+
+  EXPECT_CALL(mock, VoidFromString(_))
+      .WillOnce(InvokeWithoutArgs(&InvokeHelper::StaticVoidFromVoid))
+      .WillOnce(InvokeWithoutArgs(&test_invoke_helper,
+                                  &InvokeHelper::VoidFromVoid));
+  mock.VoidFromString(nullptr);
+  mock.VoidFromString(nullptr);
+}
+
+// Tests the linkage of the InvokeArgument action.
+TEST(LinkTest, TestInvokeArgument) {
+  Mock mock;
+  char ch = 'x';
+
+  EXPECT_CALL(mock, VoidFromFunc(_)).WillOnce(InvokeArgument<0>(&ch));
+  mock.VoidFromFunc(InvokeHelper::StaticVoidFromString);
+}
+
+// Tests the linkage of the WithArg action.
+TEST(LinkTest, TestWithArg) {
+  Mock mock;
+
+  EXPECT_CALL(mock, VoidFromString(_))
+      .WillOnce(WithArg<0>(Invoke(&InvokeHelper::StaticVoidFromString)));
+  mock.VoidFromString(nullptr);
+}
+
+// Tests the linkage of the WithArgs action.
+TEST(LinkTest, TestWithArgs) {
+  Mock mock;
+
+  EXPECT_CALL(mock, VoidFromString(_))
+      .WillOnce(WithArgs<0>(Invoke(&InvokeHelper::StaticVoidFromString)));
+  mock.VoidFromString(nullptr);
+}
+
+// Tests the linkage of the WithoutArgs action.
+TEST(LinkTest, TestWithoutArgs) {
+  Mock mock;
+
+  EXPECT_CALL(mock, VoidFromString(_)).WillOnce(WithoutArgs(Return()));
+  mock.VoidFromString(nullptr);
+}
+
+// Tests the linkage of the DoAll action.
+TEST(LinkTest, TestDoAll) {
+  Mock mock;
+  char ch = 'x';
+
+  EXPECT_CALL(mock, VoidFromString(_))
+      .WillOnce(DoAll(SetArgPointee<0>('y'), Return()));
+  mock.VoidFromString(&ch);
+}
+
+// Tests the linkage of the DoDefault action.
+TEST(LinkTest, TestDoDefault) {
+  Mock mock;
+  char ch = 'x';
+
+  ON_CALL(mock, VoidFromString(_)).WillByDefault(Return());
+  EXPECT_CALL(mock, VoidFromString(_)).WillOnce(DoDefault());
+  mock.VoidFromString(&ch);
+}
+
+// Tests the linkage of the IgnoreResult action.
+TEST(LinkTest, TestIgnoreResult) {
+  Mock mock;
+
+  EXPECT_CALL(mock, VoidFromString(_)).WillOnce(IgnoreResult(Return(42)));
+  mock.VoidFromString(nullptr);
+}
+
+#if GTEST_HAS_EXCEPTIONS
+// Tests the linkage of the Throw action.
+TEST(LinkTest, TestThrow) {
+  Mock mock;
+
+  EXPECT_CALL(mock, VoidFromString(_)).WillOnce(Throw(42));
+  EXPECT_THROW(mock.VoidFromString(nullptr), int);
+}
+#endif  // GTEST_HAS_EXCEPTIONS
+
+// The ACTION*() macros trigger warning C4100 (unreferenced formal
+// parameter) in MSVC with -W4.  Unfortunately they cannot be fixed in
+// the macro definition, as the warnings are generated when the macro
+// is expanded and macro expansion cannot contain #pragma.  Therefore
+// we suppress them here.
+#ifdef _MSC_VER
+# pragma warning(push)
+# pragma warning(disable:4100)
+#endif
+
+// Tests the linkage of actions created using ACTION macro.
+namespace {
+ACTION(Return1) { return 1; }
+}
+
+TEST(LinkTest, TestActionMacro) {
+  Mock mock;
+
+  EXPECT_CALL(mock, IntFromString(_)).WillOnce(Return1());
+  mock.IntFromString(nullptr);
+}
+
+// Tests the linkage of actions created using ACTION_P macro.
+namespace {
+ACTION_P(ReturnArgument, ret_value) { return ret_value; }
+}
+
+TEST(LinkTest, TestActionPMacro) {
+  Mock mock;
+
+  EXPECT_CALL(mock, IntFromString(_)).WillOnce(ReturnArgument(42));
+  mock.IntFromString(nullptr);
+}
+
+// Tests the linkage of actions created using ACTION_P2 macro.
+namespace {
+ACTION_P2(ReturnEqualsEitherOf, first, second) {
+  return arg0 == first || arg0 == second;
+}
+}
+
+#ifdef _MSC_VER
+# pragma warning(pop)
+#endif
+
+TEST(LinkTest, TestActionP2Macro) {
+  Mock mock;
+  char ch = 'x';
+
+  EXPECT_CALL(mock, IntFromString(_))
+      .WillOnce(ReturnEqualsEitherOf("one", "two"));
+  mock.IntFromString(&ch);
+}
+
+// Tests the linkage of the "_" matcher.
+TEST(LinkTest, TestMatcherAnything) {
+  Mock mock;
+
+  ON_CALL(mock, VoidFromString(_)).WillByDefault(Return());
+}
+
+// Tests the linkage of the A matcher.
+TEST(LinkTest, TestMatcherA) {
+  Mock mock;
+
+  ON_CALL(mock, VoidFromString(A<char*>())).WillByDefault(Return());
+}
+
+// Tests the linkage of the Eq and the "bare value" matcher.
+TEST(LinkTest, TestMatchersEq) {
+  Mock mock;
+  const char* p = "x";
+
+  ON_CALL(mock, VoidFromString(Eq(p))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromString(const_cast<char*>("y")))
+      .WillByDefault(Return());
+}
+
+// Tests the linkage of the Lt, Gt, Le, Ge, and Ne matchers.
+TEST(LinkTest, TestMatchersRelations) {
+  Mock mock;
+
+  ON_CALL(mock, VoidFromFloat(Lt(1.0f))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromFloat(Gt(1.0f))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromFloat(Le(1.0f))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromFloat(Ge(1.0f))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromFloat(Ne(1.0f))).WillByDefault(Return());
+}
+
+// Tests the linkage of the NotNull matcher.
+TEST(LinkTest, TestMatcherNotNull) {
+  Mock mock;
+
+  ON_CALL(mock, VoidFromString(NotNull())).WillByDefault(Return());
+}
+
+// Tests the linkage of the IsNull matcher.
+TEST(LinkTest, TestMatcherIsNull) {
+  Mock mock;
+
+  ON_CALL(mock, VoidFromString(IsNull())).WillByDefault(Return());
+}
+
+// Tests the linkage of the Ref matcher.
+TEST(LinkTest, TestMatcherRef) {
+  Mock mock;
+  int a = 0;
+
+  ON_CALL(mock, VoidFromIntRef(Ref(a))).WillByDefault(Return());
+}
+
+// Tests the linkage of the TypedEq matcher.
+TEST(LinkTest, TestMatcherTypedEq) {
+  Mock mock;
+  long a = 0;
+
+  ON_CALL(mock, VoidFromIntRef(TypedEq<int&>(a))).WillByDefault(Return());
+}
+
+// Tests the linkage of the FloatEq, DoubleEq, NanSensitiveFloatEq and
+// NanSensitiveDoubleEq matchers.
+TEST(LinkTest, TestMatchersFloatingPoint) {
+  Mock mock;
+  float a = 0;
+
+  ON_CALL(mock, VoidFromFloat(FloatEq(a))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromDouble(DoubleEq(a))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromFloat(NanSensitiveFloatEq(a))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromDouble(NanSensitiveDoubleEq(a)))
+      .WillByDefault(Return());
+}
+
+// Tests the linkage of the ContainsRegex matcher.
+TEST(LinkTest, TestMatcherContainsRegex) {
+  Mock mock;
+
+  ON_CALL(mock, VoidFromString(ContainsRegex(".*"))).WillByDefault(Return());
+}
+
+// Tests the linkage of the MatchesRegex matcher.
+TEST(LinkTest, TestMatcherMatchesRegex) {
+  Mock mock;
+
+  ON_CALL(mock, VoidFromString(MatchesRegex(".*"))).WillByDefault(Return());
+}
+
+// Tests the linkage of the StartsWith, EndsWith, and HasSubstr matchers.
+TEST(LinkTest, TestMatchersSubstrings) {
+  Mock mock;
+
+  ON_CALL(mock, VoidFromString(StartsWith("a"))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromString(EndsWith("c"))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromString(HasSubstr("b"))).WillByDefault(Return());
+}
+
+// Tests the linkage of the StrEq, StrNe, StrCaseEq, and StrCaseNe matchers.
+TEST(LinkTest, TestMatchersStringEquality) {
+  Mock mock;
+  ON_CALL(mock, VoidFromString(StrEq("a"))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromString(StrNe("a"))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromString(StrCaseEq("a"))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromString(StrCaseNe("a"))).WillByDefault(Return());
+}
+
+// Tests the linkage of the ElementsAre matcher.
+TEST(LinkTest, TestMatcherElementsAre) {
+  Mock mock;
+
+  ON_CALL(mock, VoidFromVector(ElementsAre('a', _))).WillByDefault(Return());
+}
+
+// Tests the linkage of the ElementsAreArray matcher.
+TEST(LinkTest, TestMatcherElementsAreArray) {
+  Mock mock;
+  char arr[] = { 'a', 'b' };
+
+  ON_CALL(mock, VoidFromVector(ElementsAreArray(arr))).WillByDefault(Return());
+}
+
+// Tests the linkage of the IsSubsetOf matcher.
+TEST(LinkTest, TestMatcherIsSubsetOf) {
+  Mock mock;
+  char arr[] = {'a', 'b'};
+
+  ON_CALL(mock, VoidFromVector(IsSubsetOf(arr))).WillByDefault(Return());
+}
+
+// Tests the linkage of the IsSupersetOf matcher.
+TEST(LinkTest, TestMatcherIsSupersetOf) {
+  Mock mock;
+  char arr[] = {'a', 'b'};
+
+  ON_CALL(mock, VoidFromVector(IsSupersetOf(arr))).WillByDefault(Return());
+}
+
+// Tests the linkage of the ContainerEq matcher.
+TEST(LinkTest, TestMatcherContainerEq) {
+  Mock mock;
+  std::vector<int> v;
+
+  ON_CALL(mock, VoidFromVector(ContainerEq(v))).WillByDefault(Return());
+}
+
+// Tests the linkage of the Field matcher.
+TEST(LinkTest, TestMatcherField) {
+  FieldHelper helper(0);
+
+  Matcher<const FieldHelper&> m = Field(&FieldHelper::field_, Eq(0));
+  EXPECT_TRUE(m.Matches(helper));
+
+  Matcher<const FieldHelper*> m2 = Field(&FieldHelper::field_, Eq(0));
+  EXPECT_TRUE(m2.Matches(&helper));
+}
+
+// Tests the linkage of the Property matcher.
+TEST(LinkTest, TestMatcherProperty) {
+  FieldHelper helper(0);
+
+  Matcher<const FieldHelper&> m = Property(&FieldHelper::field, Eq(0));
+  EXPECT_TRUE(m.Matches(helper));
+
+  Matcher<const FieldHelper*> m2 = Property(&FieldHelper::field, Eq(0));
+  EXPECT_TRUE(m2.Matches(&helper));
+}
+
+// Tests the linkage of the ResultOf matcher.
+TEST(LinkTest, TestMatcherResultOf) {
+  Matcher<char*> m = ResultOf(&InvokeHelper::StaticIntFromString, Eq(1));
+  EXPECT_TRUE(m.Matches(nullptr));
+}
+
+// Tests the linkage of the ResultOf matcher.
+TEST(LinkTest, TestMatcherPointee) {
+  int n = 1;
+
+  Matcher<int*> m = Pointee(Eq(1));
+  EXPECT_TRUE(m.Matches(&n));
+}
+
+// Tests the linkage of the Truly matcher.
+TEST(LinkTest, TestMatcherTruly) {
+  Matcher<const char*> m = Truly(&InvokeHelper::StaticBoolFromString);
+  EXPECT_TRUE(m.Matches(nullptr));
+}
+
+// Tests the linkage of the AllOf matcher.
+TEST(LinkTest, TestMatcherAllOf) {
+  Matcher<int> m = AllOf(_, Eq(1));
+  EXPECT_TRUE(m.Matches(1));
+}
+
+// Tests the linkage of the AnyOf matcher.
+TEST(LinkTest, TestMatcherAnyOf) {
+  Matcher<int> m = AnyOf(_, Eq(1));
+  EXPECT_TRUE(m.Matches(1));
+}
+
+// Tests the linkage of the Not matcher.
+TEST(LinkTest, TestMatcherNot) {
+  Matcher<int> m = Not(_);
+  EXPECT_FALSE(m.Matches(1));
+}
+
+// Tests the linkage of the MatcherCast<T>() function.
+TEST(LinkTest, TestMatcherCast) {
+  Matcher<const char*> m = MatcherCast<const char*>(_);
+  EXPECT_TRUE(m.Matches(nullptr));
+}
+
+#endif  // GOOGLEMOCK_TEST_GMOCK_LINK_TEST_H_
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock_output_test.py b/leveldb_base/third_party/googletest/googlemock/test/gmock_output_test.py
new file mode 100644
index 0000000..25f99f2
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock_output_test.py
@@ -0,0 +1,183 @@
+#!/usr/bin/env python
+#
+# Copyright 2008, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+r"""Tests the text output of Google C++ Mocking Framework.
+
+To update the golden file:
+gmock_output_test.py --build_dir=BUILD/DIR --gengolden
+where BUILD/DIR contains the built gmock_output_test_ file.
+gmock_output_test.py --gengolden
+gmock_output_test.py
+
+"""
+
+from io import open    # pylint: disable=redefined-builtin, g-importing-member
+import os
+import re
+import sys
+import gmock_test_utils
+
+
+# The flag for generating the golden file
+GENGOLDEN_FLAG = '--gengolden'
+
+PROGRAM_PATH = gmock_test_utils.GetTestExecutablePath('gmock_output_test_')
+COMMAND = [PROGRAM_PATH, '--gtest_stack_trace_depth=0', '--gtest_print_time=0']
+GOLDEN_NAME = 'gmock_output_test_golden.txt'
+GOLDEN_PATH = os.path.join(gmock_test_utils.GetSourceDir(), GOLDEN_NAME)
+
+
+def ToUnixLineEnding(s):
+  """Changes all Windows/Mac line endings in s to UNIX line endings."""
+
+  return s.replace('\r\n', '\n').replace('\r', '\n')
+
+
+def RemoveReportHeaderAndFooter(output):
+  """Removes Google Test result report's header and footer from the output."""
+
+  output = re.sub(r'.*gtest_main.*\n', '', output)
+  output = re.sub(r'\[.*\d+ tests.*\n', '', output)
+  output = re.sub(r'\[.* test environment .*\n', '', output)
+  output = re.sub(r'\[=+\] \d+ tests .* ran.*', '', output)
+  output = re.sub(r'.* FAILED TESTS\n', '', output)
+  return output
+
+
+def RemoveLocations(output):
+  """Removes all file location info from a Google Test program's output.
+
+  Args:
+       output:  the output of a Google Test program.
+
+  Returns:
+       output with all file location info (in the form of
+       'DIRECTORY/FILE_NAME:LINE_NUMBER: 'or
+       'DIRECTORY\\FILE_NAME(LINE_NUMBER): ') replaced by
+       'FILE:#: '.
+  """
+
+  return re.sub(r'.*[/\\](.+)(\:\d+|\(\d+\))\:', 'FILE:#:', output)
+
+
+def NormalizeErrorMarker(output):
+  """Normalizes the error marker, which is different on Windows vs on Linux."""
+
+  return re.sub(r' error: ', ' Failure\n', output)
+
+
+def RemoveMemoryAddresses(output):
+  """Removes memory addresses from the test output."""
+
+  return re.sub(r'@\w+', '@0x#', output)
+
+
+def RemoveTestNamesOfLeakedMocks(output):
+  """Removes the test names of leaked mock objects from the test output."""
+
+  return re.sub(r'\(used in test .+\) ', '', output)
+
+
+def GetLeakyTests(output):
+  """Returns a list of test names that leak mock objects."""
+
+  # findall() returns a list of all matches of the regex in output.
+  # For example, if '(used in test FooTest.Bar)' is in output, the
+  # list will contain 'FooTest.Bar'.
+  return re.findall(r'\(used in test (.+)\)', output)
+
+
+def GetNormalizedOutputAndLeakyTests(output):
+  """Normalizes the output of gmock_output_test_.
+
+  Args:
+    output: The test output.
+
+  Returns:
+    A tuple (the normalized test output, the list of test names that have
+    leaked mocks).
+  """
+
+  output = ToUnixLineEnding(output)
+  output = RemoveReportHeaderAndFooter(output)
+  output = NormalizeErrorMarker(output)
+  output = RemoveLocations(output)
+  output = RemoveMemoryAddresses(output)
+  return (RemoveTestNamesOfLeakedMocks(output), GetLeakyTests(output))
+
+
+def GetShellCommandOutput(cmd):
+  """Runs a command in a sub-process, and returns its STDOUT in a string."""
+
+  return gmock_test_utils.Subprocess(cmd, capture_stderr=False).output
+
+
+def GetNormalizedCommandOutputAndLeakyTests(cmd):
+  """Runs a command and returns its normalized output and a list of leaky tests.
+
+  Args:
+    cmd:  the shell command.
+  """
+
+  # Disables exception pop-ups on Windows.
+  os.environ['GTEST_CATCH_EXCEPTIONS'] = '1'
+  return GetNormalizedOutputAndLeakyTests(GetShellCommandOutput(cmd))
+
+
+class GMockOutputTest(gmock_test_utils.TestCase):
+
+  def testOutput(self):
+    (output, leaky_tests) = GetNormalizedCommandOutputAndLeakyTests(COMMAND)
+    golden_file = open(GOLDEN_PATH, 'rb')
+    golden = golden_file.read().decode('utf-8')
+    golden_file.close()
+
+    # The normalized output should match the golden file.
+    self.assertEquals(golden, output)
+
+    # The raw output should contain 2 leaked mock object errors for
+    # test GMockOutputTest.CatchesLeakedMocks.
+    self.assertEquals(['GMockOutputTest.CatchesLeakedMocks',
+                       'GMockOutputTest.CatchesLeakedMocks'],
+                      leaky_tests)
+
+
+if __name__ == '__main__':
+  if sys.argv[1:] == [GENGOLDEN_FLAG]:
+    (output, _) = GetNormalizedCommandOutputAndLeakyTests(COMMAND)
+    golden_file = open(GOLDEN_PATH, 'wb')
+    golden_file.write(output)
+    golden_file.close()
+    # Suppress the error "googletest was imported but a call to its main()
+    # was never detected."
+    os._exit(0)
+  else:
+    gmock_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock_output_test_.cc b/leveldb_base/third_party/googletest/googlemock/test/gmock_output_test_.cc
new file mode 100644
index 0000000..3955c73
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock_output_test_.cc
@@ -0,0 +1,309 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Tests Google Mock's output in various scenarios.  This ensures that
+// Google Mock's messages are readable and useful.
+
+#include "gmock/gmock.h"
+
+#include <stdio.h>
+#include <string>
+
+#include "gtest/gtest.h"
+
+// Silence C4100 (unreferenced formal parameter)
+#ifdef _MSC_VER
+# pragma warning(push)
+# pragma warning(disable:4100)
+#endif
+
+using testing::_;
+using testing::AnyNumber;
+using testing::Ge;
+using testing::InSequence;
+using testing::NaggyMock;
+using testing::Ref;
+using testing::Return;
+using testing::Sequence;
+using testing::Value;
+
+class MockFoo {
+ public:
+  MockFoo() {}
+
+  MOCK_METHOD3(Bar, char(const std::string& s, int i, double x));
+  MOCK_METHOD2(Bar2, bool(int x, int y));
+  MOCK_METHOD2(Bar3, void(int x, int y));
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(MockFoo);
+};
+
+class GMockOutputTest : public testing::Test {
+ protected:
+  NaggyMock<MockFoo> foo_;
+};
+
+TEST_F(GMockOutputTest, ExpectedCall) {
+  testing::GMOCK_FLAG(verbose) = "info";
+
+  EXPECT_CALL(foo_, Bar2(0, _));
+  foo_.Bar2(0, 0);  // Expected call
+
+  testing::GMOCK_FLAG(verbose) = "warning";
+}
+
+TEST_F(GMockOutputTest, ExpectedCallToVoidFunction) {
+  testing::GMOCK_FLAG(verbose) = "info";
+
+  EXPECT_CALL(foo_, Bar3(0, _));
+  foo_.Bar3(0, 0);  // Expected call
+
+  testing::GMOCK_FLAG(verbose) = "warning";
+}
+
+TEST_F(GMockOutputTest, ExplicitActionsRunOut) {
+  EXPECT_CALL(foo_, Bar2(_, _))
+      .Times(2)
+      .WillOnce(Return(false));
+  foo_.Bar2(2, 2);
+  foo_.Bar2(1, 1);  // Explicit actions in EXPECT_CALL run out.
+}
+
+TEST_F(GMockOutputTest, UnexpectedCall) {
+  EXPECT_CALL(foo_, Bar2(0, _));
+
+  foo_.Bar2(1, 0);  // Unexpected call
+  foo_.Bar2(0, 0);  // Expected call
+}
+
+TEST_F(GMockOutputTest, UnexpectedCallToVoidFunction) {
+  EXPECT_CALL(foo_, Bar3(0, _));
+
+  foo_.Bar3(1, 0);  // Unexpected call
+  foo_.Bar3(0, 0);  // Expected call
+}
+
+TEST_F(GMockOutputTest, ExcessiveCall) {
+  EXPECT_CALL(foo_, Bar2(0, _));
+
+  foo_.Bar2(0, 0);  // Expected call
+  foo_.Bar2(0, 1);  // Excessive call
+}
+
+TEST_F(GMockOutputTest, ExcessiveCallToVoidFunction) {
+  EXPECT_CALL(foo_, Bar3(0, _));
+
+  foo_.Bar3(0, 0);  // Expected call
+  foo_.Bar3(0, 1);  // Excessive call
+}
+
+TEST_F(GMockOutputTest, UninterestingCall) {
+  foo_.Bar2(0, 1);  // Uninteresting call
+}
+
+TEST_F(GMockOutputTest, UninterestingCallToVoidFunction) {
+  foo_.Bar3(0, 1);  // Uninteresting call
+}
+
+TEST_F(GMockOutputTest, RetiredExpectation) {
+  EXPECT_CALL(foo_, Bar2(_, _))
+      .RetiresOnSaturation();
+  EXPECT_CALL(foo_, Bar2(0, 0));
+
+  foo_.Bar2(1, 1);
+  foo_.Bar2(1, 1);  // Matches a retired expectation
+  foo_.Bar2(0, 0);
+}
+
+TEST_F(GMockOutputTest, UnsatisfiedPrerequisite) {
+  {
+    InSequence s;
+    EXPECT_CALL(foo_, Bar(_, 0, _));
+    EXPECT_CALL(foo_, Bar2(0, 0));
+    EXPECT_CALL(foo_, Bar2(1, _));
+  }
+
+  foo_.Bar2(1, 0);  // Has one immediate unsatisfied pre-requisite
+  foo_.Bar("Hi", 0, 0);
+  foo_.Bar2(0, 0);
+  foo_.Bar2(1, 0);
+}
+
+TEST_F(GMockOutputTest, UnsatisfiedPrerequisites) {
+  Sequence s1, s2;
+
+  EXPECT_CALL(foo_, Bar(_, 0, _))
+      .InSequence(s1);
+  EXPECT_CALL(foo_, Bar2(0, 0))
+      .InSequence(s2);
+  EXPECT_CALL(foo_, Bar2(1, _))
+      .InSequence(s1, s2);
+
+  foo_.Bar2(1, 0);  // Has two immediate unsatisfied pre-requisites
+  foo_.Bar("Hi", 0, 0);
+  foo_.Bar2(0, 0);
+  foo_.Bar2(1, 0);
+}
+
+TEST_F(GMockOutputTest, UnsatisfiedWith) {
+  EXPECT_CALL(foo_, Bar2(_, _)).With(Ge());
+}
+
+TEST_F(GMockOutputTest, UnsatisfiedExpectation) {
+  EXPECT_CALL(foo_, Bar(_, _, _));
+  EXPECT_CALL(foo_, Bar2(0, _))
+      .Times(2);
+
+  foo_.Bar2(0, 1);
+}
+
+TEST_F(GMockOutputTest, MismatchArguments) {
+  const std::string s = "Hi";
+  EXPECT_CALL(foo_, Bar(Ref(s), _, Ge(0)));
+
+  foo_.Bar("Ho", 0, -0.1);  // Mismatch arguments
+  foo_.Bar(s, 0, 0);
+}
+
+TEST_F(GMockOutputTest, MismatchWith) {
+  EXPECT_CALL(foo_, Bar2(Ge(2), Ge(1)))
+      .With(Ge());
+
+  foo_.Bar2(2, 3);  // Mismatch With()
+  foo_.Bar2(2, 1);
+}
+
+TEST_F(GMockOutputTest, MismatchArgumentsAndWith) {
+  EXPECT_CALL(foo_, Bar2(Ge(2), Ge(1)))
+      .With(Ge());
+
+  foo_.Bar2(1, 3);  // Mismatch arguments and mismatch With()
+  foo_.Bar2(2, 1);
+}
+
+TEST_F(GMockOutputTest, UnexpectedCallWithDefaultAction) {
+  ON_CALL(foo_, Bar2(_, _))
+      .WillByDefault(Return(true));   // Default action #1
+  ON_CALL(foo_, Bar2(1, _))
+      .WillByDefault(Return(false));  // Default action #2
+
+  EXPECT_CALL(foo_, Bar2(2, 2));
+  foo_.Bar2(1, 0);  // Unexpected call, takes default action #2.
+  foo_.Bar2(0, 0);  // Unexpected call, takes default action #1.
+  foo_.Bar2(2, 2);  // Expected call.
+}
+
+TEST_F(GMockOutputTest, ExcessiveCallWithDefaultAction) {
+  ON_CALL(foo_, Bar2(_, _))
+      .WillByDefault(Return(true));   // Default action #1
+  ON_CALL(foo_, Bar2(1, _))
+      .WillByDefault(Return(false));  // Default action #2
+
+  EXPECT_CALL(foo_, Bar2(2, 2));
+  EXPECT_CALL(foo_, Bar2(1, 1));
+
+  foo_.Bar2(2, 2);  // Expected call.
+  foo_.Bar2(2, 2);  // Excessive call, takes default action #1.
+  foo_.Bar2(1, 1);  // Expected call.
+  foo_.Bar2(1, 1);  // Excessive call, takes default action #2.
+}
+
+TEST_F(GMockOutputTest, UninterestingCallWithDefaultAction) {
+  ON_CALL(foo_, Bar2(_, _))
+      .WillByDefault(Return(true));   // Default action #1
+  ON_CALL(foo_, Bar2(1, _))
+      .WillByDefault(Return(false));  // Default action #2
+
+  foo_.Bar2(2, 2);  // Uninteresting call, takes default action #1.
+  foo_.Bar2(1, 1);  // Uninteresting call, takes default action #2.
+}
+
+TEST_F(GMockOutputTest, ExplicitActionsRunOutWithDefaultAction) {
+  ON_CALL(foo_, Bar2(_, _))
+      .WillByDefault(Return(true));   // Default action #1
+
+  EXPECT_CALL(foo_, Bar2(_, _))
+      .Times(2)
+      .WillOnce(Return(false));
+  foo_.Bar2(2, 2);
+  foo_.Bar2(1, 1);  // Explicit actions in EXPECT_CALL run out.
+}
+
+TEST_F(GMockOutputTest, CatchesLeakedMocks) {
+  MockFoo* foo1 = new MockFoo;
+  MockFoo* foo2 = new MockFoo;
+
+  // Invokes ON_CALL on foo1.
+  ON_CALL(*foo1, Bar(_, _, _)).WillByDefault(Return('a'));
+
+  // Invokes EXPECT_CALL on foo2.
+  EXPECT_CALL(*foo2, Bar2(_, _));
+  EXPECT_CALL(*foo2, Bar2(1, _));
+  EXPECT_CALL(*foo2, Bar3(_, _)).Times(AnyNumber());
+  foo2->Bar2(2, 1);
+  foo2->Bar2(1, 1);
+
+  // Both foo1 and foo2 are deliberately leaked.
+}
+
+MATCHER_P2(IsPair, first, second, "") {
+  return Value(arg.first, first) && Value(arg.second, second);
+}
+
+TEST_F(GMockOutputTest, PrintsMatcher) {
+  const testing::Matcher<int> m1 = Ge(48);
+  EXPECT_THAT((std::pair<int, bool>(42, true)), IsPair(m1, true));
+}
+
+void TestCatchesLeakedMocksInAdHocTests() {
+  MockFoo* foo = new MockFoo;
+
+  // Invokes EXPECT_CALL on foo.
+  EXPECT_CALL(*foo, Bar2(_, _));
+  foo->Bar2(2, 1);
+
+  // foo is deliberately leaked.
+}
+
+int main(int argc, char **argv) {
+  testing::InitGoogleMock(&argc, argv);
+  // Ensures that the tests pass no matter what value of
+  // --gmock_catch_leaked_mocks and --gmock_verbose the user specifies.
+  testing::GMOCK_FLAG(catch_leaked_mocks) = true;
+  testing::GMOCK_FLAG(verbose) = "warning";
+
+  TestCatchesLeakedMocksInAdHocTests();
+  return RUN_ALL_TESTS();
+}
+
+#ifdef _MSC_VER
+# pragma warning(pop)
+#endif
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock_output_test_golden.txt b/leveldb_base/third_party/googletest/googlemock/test/gmock_output_test_golden.txt
new file mode 100644
index 0000000..4846c12
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock_output_test_golden.txt
@@ -0,0 +1,317 @@
+[ RUN      ] GMockOutputTest.ExpectedCall
+
+FILE:#: EXPECT_CALL(foo_, Bar2(0, _)) invoked
+Stack trace:
+
+FILE:#: Mock function call matches EXPECT_CALL(foo_, Bar2(0, _))...
+    Function call: Bar2(0, 0)
+          Returns: false
+Stack trace:
+[       OK ] GMockOutputTest.ExpectedCall
+[ RUN      ] GMockOutputTest.ExpectedCallToVoidFunction
+
+FILE:#: EXPECT_CALL(foo_, Bar3(0, _)) invoked
+Stack trace:
+
+FILE:#: Mock function call matches EXPECT_CALL(foo_, Bar3(0, _))...
+    Function call: Bar3(0, 0)
+Stack trace:
+[       OK ] GMockOutputTest.ExpectedCallToVoidFunction
+[ RUN      ] GMockOutputTest.ExplicitActionsRunOut
+
+GMOCK WARNING:
+FILE:#: Too few actions specified in EXPECT_CALL(foo_, Bar2(_, _))...
+Expected to be called twice, but has only 1 WillOnce().
+GMOCK WARNING:
+FILE:#: Actions ran out in EXPECT_CALL(foo_, Bar2(_, _))...
+Called 2 times, but only 1 WillOnce() is specified - returning default value.
+Stack trace:
+[       OK ] GMockOutputTest.ExplicitActionsRunOut
+[ RUN      ] GMockOutputTest.UnexpectedCall
+unknown file: Failure
+
+Unexpected mock function call - returning default value.
+    Function call: Bar2(1, 0)
+          Returns: false
+Google Mock tried the following 1 expectation, but it didn't match:
+
+FILE:#: EXPECT_CALL(foo_, Bar2(0, _))...
+  Expected arg #0: is equal to 0
+           Actual: 1
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+[  FAILED  ] GMockOutputTest.UnexpectedCall
+[ RUN      ] GMockOutputTest.UnexpectedCallToVoidFunction
+unknown file: Failure
+
+Unexpected mock function call - returning directly.
+    Function call: Bar3(1, 0)
+Google Mock tried the following 1 expectation, but it didn't match:
+
+FILE:#: EXPECT_CALL(foo_, Bar3(0, _))...
+  Expected arg #0: is equal to 0
+           Actual: 1
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+[  FAILED  ] GMockOutputTest.UnexpectedCallToVoidFunction
+[ RUN      ] GMockOutputTest.ExcessiveCall
+FILE:#: Failure
+Mock function called more times than expected - returning default value.
+    Function call: Bar2(0, 1)
+          Returns: false
+         Expected: to be called once
+           Actual: called twice - over-saturated and active
+[  FAILED  ] GMockOutputTest.ExcessiveCall
+[ RUN      ] GMockOutputTest.ExcessiveCallToVoidFunction
+FILE:#: Failure
+Mock function called more times than expected - returning directly.
+    Function call: Bar3(0, 1)
+         Expected: to be called once
+           Actual: called twice - over-saturated and active
+[  FAILED  ] GMockOutputTest.ExcessiveCallToVoidFunction
+[ RUN      ] GMockOutputTest.UninterestingCall
+
+GMOCK WARNING:
+Uninteresting mock function call - returning default value.
+    Function call: Bar2(0, 1)
+          Returns: false
+NOTE: You can safely ignore the above warning unless this call should not happen.  Do not suppress it by blindly adding an EXPECT_CALL() if you don't mean to enforce the call.  See https://github.com/google/googletest/blob/master/docs/gmock_cook_book.md#knowing-when-to-expect for details.
+[       OK ] GMockOutputTest.UninterestingCall
+[ RUN      ] GMockOutputTest.UninterestingCallToVoidFunction
+
+GMOCK WARNING:
+Uninteresting mock function call - returning directly.
+    Function call: Bar3(0, 1)
+NOTE: You can safely ignore the above warning unless this call should not happen.  Do not suppress it by blindly adding an EXPECT_CALL() if you don't mean to enforce the call.  See https://github.com/google/googletest/blob/master/docs/gmock_cook_book.md#knowing-when-to-expect for details.
+[       OK ] GMockOutputTest.UninterestingCallToVoidFunction
+[ RUN      ] GMockOutputTest.RetiredExpectation
+unknown file: Failure
+
+Unexpected mock function call - returning default value.
+    Function call: Bar2(1, 1)
+          Returns: false
+Google Mock tried the following 2 expectations, but none matched:
+
+FILE:#: tried expectation #0: EXPECT_CALL(foo_, Bar2(_, _))...
+         Expected: the expectation is active
+           Actual: it is retired
+         Expected: to be called once
+           Actual: called once - saturated and retired
+FILE:#: tried expectation #1: EXPECT_CALL(foo_, Bar2(0, 0))...
+  Expected arg #0: is equal to 0
+           Actual: 1
+  Expected arg #1: is equal to 0
+           Actual: 1
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+[  FAILED  ] GMockOutputTest.RetiredExpectation
+[ RUN      ] GMockOutputTest.UnsatisfiedPrerequisite
+unknown file: Failure
+
+Unexpected mock function call - returning default value.
+    Function call: Bar2(1, 0)
+          Returns: false
+Google Mock tried the following 2 expectations, but none matched:
+
+FILE:#: tried expectation #0: EXPECT_CALL(foo_, Bar2(0, 0))...
+  Expected arg #0: is equal to 0
+           Actual: 1
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+FILE:#: tried expectation #1: EXPECT_CALL(foo_, Bar2(1, _))...
+         Expected: all pre-requisites are satisfied
+           Actual: the following immediate pre-requisites are not satisfied:
+FILE:#: pre-requisite #0
+                   (end of pre-requisites)
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+[  FAILED  ] GMockOutputTest.UnsatisfiedPrerequisite
+[ RUN      ] GMockOutputTest.UnsatisfiedPrerequisites
+unknown file: Failure
+
+Unexpected mock function call - returning default value.
+    Function call: Bar2(1, 0)
+          Returns: false
+Google Mock tried the following 2 expectations, but none matched:
+
+FILE:#: tried expectation #0: EXPECT_CALL(foo_, Bar2(0, 0))...
+  Expected arg #0: is equal to 0
+           Actual: 1
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+FILE:#: tried expectation #1: EXPECT_CALL(foo_, Bar2(1, _))...
+         Expected: all pre-requisites are satisfied
+           Actual: the following immediate pre-requisites are not satisfied:
+FILE:#: pre-requisite #0
+FILE:#: pre-requisite #1
+                   (end of pre-requisites)
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+[  FAILED  ] GMockOutputTest.UnsatisfiedPrerequisites
+[ RUN      ] GMockOutputTest.UnsatisfiedWith
+FILE:#: Failure
+Actual function call count doesn't match EXPECT_CALL(foo_, Bar2(_, _))...
+    Expected args: are a pair where the first >= the second
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+[  FAILED  ] GMockOutputTest.UnsatisfiedWith
+[ RUN      ] GMockOutputTest.UnsatisfiedExpectation
+FILE:#: Failure
+Actual function call count doesn't match EXPECT_CALL(foo_, Bar2(0, _))...
+         Expected: to be called twice
+           Actual: called once - unsatisfied and active
+FILE:#: Failure
+Actual function call count doesn't match EXPECT_CALL(foo_, Bar(_, _, _))...
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+[  FAILED  ] GMockOutputTest.UnsatisfiedExpectation
+[ RUN      ] GMockOutputTest.MismatchArguments
+unknown file: Failure
+
+Unexpected mock function call - returning default value.
+    Function call: Bar(@0x# "Ho", 0, -0.1)
+          Returns: '\0'
+Google Mock tried the following 1 expectation, but it didn't match:
+
+FILE:#: EXPECT_CALL(foo_, Bar(Ref(s), _, Ge(0)))...
+  Expected arg #0: references the variable @0x# "Hi"
+           Actual: "Ho", which is located @0x#
+  Expected arg #2: is >= 0
+           Actual: -0.1
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+[  FAILED  ] GMockOutputTest.MismatchArguments
+[ RUN      ] GMockOutputTest.MismatchWith
+unknown file: Failure
+
+Unexpected mock function call - returning default value.
+    Function call: Bar2(2, 3)
+          Returns: false
+Google Mock tried the following 1 expectation, but it didn't match:
+
+FILE:#: EXPECT_CALL(foo_, Bar2(Ge(2), Ge(1)))...
+    Expected args: are a pair where the first >= the second
+           Actual: don't match
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+[  FAILED  ] GMockOutputTest.MismatchWith
+[ RUN      ] GMockOutputTest.MismatchArgumentsAndWith
+unknown file: Failure
+
+Unexpected mock function call - returning default value.
+    Function call: Bar2(1, 3)
+          Returns: false
+Google Mock tried the following 1 expectation, but it didn't match:
+
+FILE:#: EXPECT_CALL(foo_, Bar2(Ge(2), Ge(1)))...
+  Expected arg #0: is >= 2
+           Actual: 1
+    Expected args: are a pair where the first >= the second
+           Actual: don't match
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+[  FAILED  ] GMockOutputTest.MismatchArgumentsAndWith
+[ RUN      ] GMockOutputTest.UnexpectedCallWithDefaultAction
+unknown file: Failure
+
+Unexpected mock function call - taking default action specified at:
+FILE:#:
+    Function call: Bar2(1, 0)
+          Returns: false
+Google Mock tried the following 1 expectation, but it didn't match:
+
+FILE:#: EXPECT_CALL(foo_, Bar2(2, 2))...
+  Expected arg #0: is equal to 2
+           Actual: 1
+  Expected arg #1: is equal to 2
+           Actual: 0
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+unknown file: Failure
+
+Unexpected mock function call - taking default action specified at:
+FILE:#:
+    Function call: Bar2(0, 0)
+          Returns: true
+Google Mock tried the following 1 expectation, but it didn't match:
+
+FILE:#: EXPECT_CALL(foo_, Bar2(2, 2))...
+  Expected arg #0: is equal to 2
+           Actual: 0
+  Expected arg #1: is equal to 2
+           Actual: 0
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+[  FAILED  ] GMockOutputTest.UnexpectedCallWithDefaultAction
+[ RUN      ] GMockOutputTest.ExcessiveCallWithDefaultAction
+FILE:#: Failure
+Mock function called more times than expected - taking default action specified at:
+FILE:#:
+    Function call: Bar2(2, 2)
+          Returns: true
+         Expected: to be called once
+           Actual: called twice - over-saturated and active
+FILE:#: Failure
+Mock function called more times than expected - taking default action specified at:
+FILE:#:
+    Function call: Bar2(1, 1)
+          Returns: false
+         Expected: to be called once
+           Actual: called twice - over-saturated and active
+[  FAILED  ] GMockOutputTest.ExcessiveCallWithDefaultAction
+[ RUN      ] GMockOutputTest.UninterestingCallWithDefaultAction
+
+GMOCK WARNING:
+Uninteresting mock function call - taking default action specified at:
+FILE:#:
+    Function call: Bar2(2, 2)
+          Returns: true
+NOTE: You can safely ignore the above warning unless this call should not happen.  Do not suppress it by blindly adding an EXPECT_CALL() if you don't mean to enforce the call.  See https://github.com/google/googletest/blob/master/docs/gmock_cook_book.md#knowing-when-to-expect for details.
+
+GMOCK WARNING:
+Uninteresting mock function call - taking default action specified at:
+FILE:#:
+    Function call: Bar2(1, 1)
+          Returns: false
+NOTE: You can safely ignore the above warning unless this call should not happen.  Do not suppress it by blindly adding an EXPECT_CALL() if you don't mean to enforce the call.  See https://github.com/google/googletest/blob/master/docs/gmock_cook_book.md#knowing-when-to-expect for details.
+[       OK ] GMockOutputTest.UninterestingCallWithDefaultAction
+[ RUN      ] GMockOutputTest.ExplicitActionsRunOutWithDefaultAction
+
+GMOCK WARNING:
+FILE:#: Too few actions specified in EXPECT_CALL(foo_, Bar2(_, _))...
+Expected to be called twice, but has only 1 WillOnce().
+GMOCK WARNING:
+FILE:#: Actions ran out in EXPECT_CALL(foo_, Bar2(_, _))...
+Called 2 times, but only 1 WillOnce() is specified - taking default action specified at:
+FILE:#:
+Stack trace:
+[       OK ] GMockOutputTest.ExplicitActionsRunOutWithDefaultAction
+[ RUN      ] GMockOutputTest.CatchesLeakedMocks
+[       OK ] GMockOutputTest.CatchesLeakedMocks
+[ RUN      ] GMockOutputTest.PrintsMatcher
+FILE:#: Failure
+Value of: (std::pair<int, bool>(42, true))
+Expected: is pair (is >= 48, true)
+  Actual: (42, true) (of type std::pair<int, bool>)
+[  FAILED  ] GMockOutputTest.PrintsMatcher
+[  FAILED  ] GMockOutputTest.UnexpectedCall
+[  FAILED  ] GMockOutputTest.UnexpectedCallToVoidFunction
+[  FAILED  ] GMockOutputTest.ExcessiveCall
+[  FAILED  ] GMockOutputTest.ExcessiveCallToVoidFunction
+[  FAILED  ] GMockOutputTest.RetiredExpectation
+[  FAILED  ] GMockOutputTest.UnsatisfiedPrerequisite
+[  FAILED  ] GMockOutputTest.UnsatisfiedPrerequisites
+[  FAILED  ] GMockOutputTest.UnsatisfiedWith
+[  FAILED  ] GMockOutputTest.UnsatisfiedExpectation
+[  FAILED  ] GMockOutputTest.MismatchArguments
+[  FAILED  ] GMockOutputTest.MismatchWith
+[  FAILED  ] GMockOutputTest.MismatchArgumentsAndWith
+[  FAILED  ] GMockOutputTest.UnexpectedCallWithDefaultAction
+[  FAILED  ] GMockOutputTest.ExcessiveCallWithDefaultAction
+[  FAILED  ] GMockOutputTest.PrintsMatcher
+
+
+FILE:#: ERROR: this mock object should be deleted but never is. Its address is @0x#.
+FILE:#: ERROR: this mock object should be deleted but never is. Its address is @0x#.
+FILE:#: ERROR: this mock object should be deleted but never is. Its address is @0x#.
+ERROR: 3 leaked mock objects found at program exit. Expectations on a mock object are verified when the object is destructed. Leaking a mock means that its expectations aren't verified, which is usually a test bug. If you really intend to leak a mock, you can suppress this error using testing::Mock::AllowLeak(mock_object), or you may use a fake or stub instead of a mock.
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock_stress_test.cc b/leveldb_base/third_party/googletest/googlemock/test/gmock_stress_test.cc
new file mode 100644
index 0000000..20725d6
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock_stress_test.cc
@@ -0,0 +1,240 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Tests that Google Mock constructs can be used in a large number of
+// threads concurrently.
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+namespace testing {
+namespace {
+
+// From gtest-port.h.
+using ::testing::internal::ThreadWithParam;
+
+// The maximum number of test threads (not including helper threads)
+// to create.
+const int kMaxTestThreads = 50;
+
+// How many times to repeat a task in a test thread.
+const int kRepeat = 50;
+
+class MockFoo {
+ public:
+  MOCK_METHOD1(Bar, int(int n));  // NOLINT
+  MOCK_METHOD2(Baz, char(const char* s1, const std::string& s2));  // NOLINT
+};
+
+// Helper for waiting for the given thread to finish and then deleting it.
+template <typename T>
+void JoinAndDelete(ThreadWithParam<T>* t) {
+  t->Join();
+  delete t;
+}
+
+struct Dummy {};
+
+
+// Tests that different mock objects can be used in their respective
+// threads.  This should generate no Google Test failure.
+void TestConcurrentMockObjects(Dummy /* dummy */) {
+  // Creates a mock and does some typical operations on it.
+  MockFoo foo;
+  ON_CALL(foo, Bar(_))
+      .WillByDefault(Return(1));
+  ON_CALL(foo, Baz(_, _))
+      .WillByDefault(Return('b'));
+  ON_CALL(foo, Baz(_, "you"))
+      .WillByDefault(Return('a'));
+
+  EXPECT_CALL(foo, Bar(0))
+      .Times(AtMost(3));
+  EXPECT_CALL(foo, Baz(_, _));
+  EXPECT_CALL(foo, Baz("hi", "you"))
+      .WillOnce(Return('z'))
+      .WillRepeatedly(DoDefault());
+
+  EXPECT_EQ(1, foo.Bar(0));
+  EXPECT_EQ(1, foo.Bar(0));
+  EXPECT_EQ('z', foo.Baz("hi", "you"));
+  EXPECT_EQ('a', foo.Baz("hi", "you"));
+  EXPECT_EQ('b', foo.Baz("hi", "me"));
+}
+
+// Tests invoking methods of the same mock object in multiple threads.
+
+struct Helper1Param {
+  MockFoo* mock_foo;
+  int* count;
+};
+
+void Helper1(Helper1Param param) {
+  for (int i = 0; i < kRepeat; i++) {
+    const char ch = param.mock_foo->Baz("a", "b");
+    if (ch == 'a') {
+      // It was an expected call.
+      (*param.count)++;
+    } else {
+      // It was an excessive call.
+      EXPECT_EQ('\0', ch);
+    }
+
+    // An unexpected call.
+    EXPECT_EQ('\0', param.mock_foo->Baz("x", "y")) << "Expected failure.";
+
+    // An uninteresting call.
+    EXPECT_EQ(1, param.mock_foo->Bar(5));
+  }
+}
+
+// This should generate 3*kRepeat + 1 failures in total.
+void TestConcurrentCallsOnSameObject(Dummy /* dummy */) {
+  MockFoo foo;
+
+  ON_CALL(foo, Bar(_))
+      .WillByDefault(Return(1));
+  EXPECT_CALL(foo, Baz(_, "b"))
+      .Times(kRepeat)
+      .WillRepeatedly(Return('a'));
+  EXPECT_CALL(foo, Baz(_, "c"));  // Expected to be unsatisfied.
+
+  // This chunk of code should generate kRepeat failures about
+  // excessive calls, and 2*kRepeat failures about unexpected calls.
+  int count1 = 0;
+  const Helper1Param param = { &foo, &count1 };
+  ThreadWithParam<Helper1Param>* const t =
+      new ThreadWithParam<Helper1Param>(Helper1, param, nullptr);
+
+  int count2 = 0;
+  const Helper1Param param2 = { &foo, &count2 };
+  Helper1(param2);
+  JoinAndDelete(t);
+
+  EXPECT_EQ(kRepeat, count1 + count2);
+
+  // foo's destructor should generate one failure about unsatisfied
+  // expectation.
+}
+
+// Tests using the same mock object in multiple threads when the
+// expectations are partially ordered.
+
+void Helper2(MockFoo* foo) {
+  for (int i = 0; i < kRepeat; i++) {
+    foo->Bar(2);
+    foo->Bar(3);
+  }
+}
+
+// This should generate no Google Test failures.
+void TestPartiallyOrderedExpectationsWithThreads(Dummy /* dummy */) {
+  MockFoo foo;
+  Sequence s1, s2;
+
+  {
+    InSequence dummy;
+    EXPECT_CALL(foo, Bar(0));
+    EXPECT_CALL(foo, Bar(1))
+        .InSequence(s1, s2);
+  }
+
+  EXPECT_CALL(foo, Bar(2))
+      .Times(2*kRepeat)
+      .InSequence(s1)
+      .RetiresOnSaturation();
+  EXPECT_CALL(foo, Bar(3))
+      .Times(2*kRepeat)
+      .InSequence(s2);
+
+  {
+    InSequence dummy;
+    EXPECT_CALL(foo, Bar(2))
+        .InSequence(s1, s2);
+    EXPECT_CALL(foo, Bar(4));
+  }
+
+  foo.Bar(0);
+  foo.Bar(1);
+
+  ThreadWithParam<MockFoo*>* const t =
+      new ThreadWithParam<MockFoo*>(Helper2, &foo, nullptr);
+  Helper2(&foo);
+  JoinAndDelete(t);
+
+  foo.Bar(2);
+  foo.Bar(4);
+}
+
+// Tests using Google Mock constructs in many threads concurrently.
+TEST(StressTest, CanUseGMockWithThreads) {
+  void (*test_routines[])(Dummy dummy) = {
+    &TestConcurrentMockObjects,
+    &TestConcurrentCallsOnSameObject,
+    &TestPartiallyOrderedExpectationsWithThreads,
+  };
+
+  const int kRoutines = sizeof(test_routines)/sizeof(test_routines[0]);
+  const int kCopiesOfEachRoutine = kMaxTestThreads / kRoutines;
+  const int kTestThreads = kCopiesOfEachRoutine * kRoutines;
+  ThreadWithParam<Dummy>* threads[kTestThreads] = {};
+  for (int i = 0; i < kTestThreads; i++) {
+    // Creates a thread to run the test function.
+    threads[i] = new ThreadWithParam<Dummy>(test_routines[i % kRoutines],
+                                            Dummy(), nullptr);
+    GTEST_LOG_(INFO) << "Thread #" << i << " running . . .";
+  }
+
+  // At this point, we have many threads running.
+  for (int i = 0; i < kTestThreads; i++) {
+    JoinAndDelete(threads[i]);
+  }
+
+  // Ensures that the correct number of failures have been reported.
+  const TestInfo* const info = UnitTest::GetInstance()->current_test_info();
+  const TestResult& result = *info->result();
+  const int kExpectedFailures = (3*kRepeat + 1)*kCopiesOfEachRoutine;
+  GTEST_CHECK_(kExpectedFailures == result.total_part_count())
+      << "Expected " << kExpectedFailures << " failures, but got "
+      << result.total_part_count();
+}
+
+}  // namespace
+}  // namespace testing
+
+int main(int argc, char **argv) {
+  testing::InitGoogleMock(&argc, argv);
+
+  const int exit_code = RUN_ALL_TESTS();  // Expected to fail.
+  GTEST_CHECK_(exit_code != 0) << "RUN_ALL_TESTS() did not fail as expected";
+
+  printf("\nPASS\n");
+  return 0;
+}
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock_test.cc b/leveldb_base/third_party/googletest/googlemock/test/gmock_test.cc
new file mode 100644
index 0000000..e9840a3
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock_test.cc
@@ -0,0 +1,181 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests code in gmock.cc.
+
+#include "gmock/gmock.h"
+
+#include <string>
+#include "gtest/gtest.h"
+#include "gtest/internal/custom/gtest.h"
+
+#if !defined(GTEST_CUSTOM_INIT_GOOGLE_TEST_FUNCTION_)
+
+using testing::GMOCK_FLAG(default_mock_behavior);
+using testing::GMOCK_FLAG(verbose);
+using testing::InitGoogleMock;
+
+// Verifies that calling InitGoogleMock() on argv results in new_argv,
+// and the gmock_verbose flag's value is set to expected_gmock_verbose.
+template <typename Char, int M, int N>
+void TestInitGoogleMock(const Char* (&argv)[M], const Char* (&new_argv)[N],
+                        const ::std::string& expected_gmock_verbose) {
+  const ::std::string old_verbose = GMOCK_FLAG(verbose);
+
+  int argc = M - 1;
+  InitGoogleMock(&argc, const_cast<Char**>(argv));
+  ASSERT_EQ(N - 1, argc) << "The new argv has wrong number of elements.";
+
+  for (int i = 0; i < N; i++) {
+    EXPECT_STREQ(new_argv[i], argv[i]);
+  }
+
+  EXPECT_EQ(expected_gmock_verbose, GMOCK_FLAG(verbose).c_str());
+  GMOCK_FLAG(verbose) = old_verbose;  // Restores the gmock_verbose flag.
+}
+
+TEST(InitGoogleMockTest, ParsesInvalidCommandLine) {
+  const char* argv[] = {nullptr};
+
+  const char* new_argv[] = {nullptr};
+
+  TestInitGoogleMock(argv, new_argv, GMOCK_FLAG(verbose));
+}
+
+TEST(InitGoogleMockTest, ParsesEmptyCommandLine) {
+  const char* argv[] = {"foo.exe", nullptr};
+
+  const char* new_argv[] = {"foo.exe", nullptr};
+
+  TestInitGoogleMock(argv, new_argv, GMOCK_FLAG(verbose));
+}
+
+TEST(InitGoogleMockTest, ParsesSingleFlag) {
+  const char* argv[] = {"foo.exe", "--gmock_verbose=info", nullptr};
+
+  const char* new_argv[] = {"foo.exe", nullptr};
+
+  TestInitGoogleMock(argv, new_argv, "info");
+}
+
+TEST(InitGoogleMockTest, ParsesMultipleFlags) {
+  int old_default_behavior = GMOCK_FLAG(default_mock_behavior);
+  const wchar_t* argv[] = {L"foo.exe", L"--gmock_verbose=info",
+                           L"--gmock_default_mock_behavior=2", nullptr};
+
+  const wchar_t* new_argv[] = {L"foo.exe", nullptr};
+
+  TestInitGoogleMock(argv, new_argv, "info");
+  EXPECT_EQ(2, GMOCK_FLAG(default_mock_behavior));
+  EXPECT_NE(2, old_default_behavior);
+  GMOCK_FLAG(default_mock_behavior) = old_default_behavior;
+}
+
+TEST(InitGoogleMockTest, ParsesUnrecognizedFlag) {
+  const char* argv[] = {"foo.exe", "--non_gmock_flag=blah", nullptr};
+
+  const char* new_argv[] = {"foo.exe", "--non_gmock_flag=blah", nullptr};
+
+  TestInitGoogleMock(argv, new_argv, GMOCK_FLAG(verbose));
+}
+
+TEST(InitGoogleMockTest, ParsesGoogleMockFlagAndUnrecognizedFlag) {
+  const char* argv[] = {"foo.exe", "--non_gmock_flag=blah",
+                        "--gmock_verbose=error", nullptr};
+
+  const char* new_argv[] = {"foo.exe", "--non_gmock_flag=blah", nullptr};
+
+  TestInitGoogleMock(argv, new_argv, "error");
+}
+
+TEST(WideInitGoogleMockTest, ParsesInvalidCommandLine) {
+  const wchar_t* argv[] = {nullptr};
+
+  const wchar_t* new_argv[] = {nullptr};
+
+  TestInitGoogleMock(argv, new_argv, GMOCK_FLAG(verbose));
+}
+
+TEST(WideInitGoogleMockTest, ParsesEmptyCommandLine) {
+  const wchar_t* argv[] = {L"foo.exe", nullptr};
+
+  const wchar_t* new_argv[] = {L"foo.exe", nullptr};
+
+  TestInitGoogleMock(argv, new_argv, GMOCK_FLAG(verbose));
+}
+
+TEST(WideInitGoogleMockTest, ParsesSingleFlag) {
+  const wchar_t* argv[] = {L"foo.exe", L"--gmock_verbose=info", nullptr};
+
+  const wchar_t* new_argv[] = {L"foo.exe", nullptr};
+
+  TestInitGoogleMock(argv, new_argv, "info");
+}
+
+TEST(WideInitGoogleMockTest, ParsesMultipleFlags) {
+  int old_default_behavior = GMOCK_FLAG(default_mock_behavior);
+  const wchar_t* argv[] = {L"foo.exe", L"--gmock_verbose=info",
+                           L"--gmock_default_mock_behavior=2", nullptr};
+
+  const wchar_t* new_argv[] = {L"foo.exe", nullptr};
+
+  TestInitGoogleMock(argv, new_argv, "info");
+  EXPECT_EQ(2, GMOCK_FLAG(default_mock_behavior));
+  EXPECT_NE(2, old_default_behavior);
+  GMOCK_FLAG(default_mock_behavior) = old_default_behavior;
+}
+
+TEST(WideInitGoogleMockTest, ParsesUnrecognizedFlag) {
+  const wchar_t* argv[] = {L"foo.exe", L"--non_gmock_flag=blah", nullptr};
+
+  const wchar_t* new_argv[] = {L"foo.exe", L"--non_gmock_flag=blah", nullptr};
+
+  TestInitGoogleMock(argv, new_argv, GMOCK_FLAG(verbose));
+}
+
+TEST(WideInitGoogleMockTest, ParsesGoogleMockFlagAndUnrecognizedFlag) {
+  const wchar_t* argv[] = {L"foo.exe", L"--non_gmock_flag=blah",
+                           L"--gmock_verbose=error", nullptr};
+
+  const wchar_t* new_argv[] = {L"foo.exe", L"--non_gmock_flag=blah", nullptr};
+
+  TestInitGoogleMock(argv, new_argv, "error");
+}
+
+#endif  // !defined(GTEST_CUSTOM_INIT_GOOGLE_TEST_FUNCTION_)
+
+// Makes sure Google Mock flags can be accessed in code.
+TEST(FlagTest, IsAccessibleInCode) {
+  bool dummy = testing::GMOCK_FLAG(catch_leaked_mocks) &&
+      testing::GMOCK_FLAG(verbose) == "";
+  (void)dummy;  // Avoids the "unused local variable" warning.
+}
diff --git a/leveldb_base/third_party/googletest/googlemock/test/gmock_test_utils.py b/leveldb_base/third_party/googletest/googlemock/test/gmock_test_utils.py
new file mode 100644
index 0000000..7dc4e11
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googlemock/test/gmock_test_utils.py
@@ -0,0 +1,108 @@
+# Copyright 2006, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Unit test utilities for Google C++ Mocking Framework."""
+
+import os
+import sys
+
+# Determines path to gtest_test_utils and imports it.
+SCRIPT_DIR = os.path.dirname(__file__) or '.'
+
+# isdir resolves symbolic links.
+gtest_tests_util_dir = os.path.join(SCRIPT_DIR, '../../googletest/test')
+if os.path.isdir(gtest_tests_util_dir):
+  GTEST_TESTS_UTIL_DIR = gtest_tests_util_dir
+else:
+  GTEST_TESTS_UTIL_DIR = os.path.join(SCRIPT_DIR, '../../googletest/test')
+sys.path.append(GTEST_TESTS_UTIL_DIR)
+
+# pylint: disable=C6204
+import gtest_test_utils
+
+
+def GetSourceDir():
+  """Returns the absolute path of the directory where the .py files are."""
+
+  return gtest_test_utils.GetSourceDir()
+
+
+def GetTestExecutablePath(executable_name):
+  """Returns the absolute path of the test binary given its name.
+
+  The function will print a message and abort the program if the resulting file
+  doesn't exist.
+
+  Args:
+    executable_name: name of the test binary that the test script runs.
+
+  Returns:
+    The absolute path of the test binary.
+  """
+
+  return gtest_test_utils.GetTestExecutablePath(executable_name)
+
+
+def GetExitStatus(exit_code):
+  """Returns the argument to exit(), or -1 if exit() wasn't called.
+
+  Args:
+    exit_code: the result value of os.system(command).
+  """
+
+  if os.name == 'nt':
+    # On Windows, os.WEXITSTATUS() doesn't work and os.system() returns
+    # the argument to exit() directly.
+    return exit_code
+  else:
+    # On Unix, os.WEXITSTATUS() must be used to extract the exit status
+    # from the result of os.system().
+    if os.WIFEXITED(exit_code):
+      return os.WEXITSTATUS(exit_code)
+    else:
+      return -1
+
+
+# Suppresses the "Invalid const name" lint complaint
+# pylint: disable-msg=C6409
+
+# Exposes utilities from gtest_test_utils.
+Subprocess = gtest_test_utils.Subprocess
+TestCase = gtest_test_utils.TestCase
+environ = gtest_test_utils.environ
+SetEnvVar = gtest_test_utils.SetEnvVar
+PREMATURE_EXIT_FILE_ENV_VAR = gtest_test_utils.PREMATURE_EXIT_FILE_ENV_VAR
+
+# pylint: enable-msg=C6409
+
+
+def Main():
+  """Runs the unit test."""
+
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/CMakeLists.txt b/leveldb_base/third_party/googletest/googletest/CMakeLists.txt
new file mode 100644
index 0000000..abdd98b
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/CMakeLists.txt
@@ -0,0 +1,323 @@
+########################################################################
+# Note: CMake support is community-based. The maintainers do not use CMake
+# internally.
+#
+# CMake build script for Google Test.
+#
+# To run the tests for Google Test itself on Linux, use 'make test' or
+# ctest.  You can select which tests to run using 'ctest -R regex'.
+# For more options, run 'ctest --help'.
+
+# When other libraries are using a shared version of runtime libraries,
+# Google Test also has to use one.
+option(
+  gtest_force_shared_crt
+  "Use shared (DLL) run-time lib even when Google Test is built as static lib."
+  OFF)
+
+option(gtest_build_tests "Build all of gtest's own tests." OFF)
+
+option(gtest_build_samples "Build gtest's sample programs." OFF)
+
+option(gtest_disable_pthreads "Disable uses of pthreads in gtest." OFF)
+
+option(
+  gtest_hide_internal_symbols
+  "Build gtest with internal symbols hidden in shared libraries."
+  OFF)
+
+# Defines pre_project_set_up_hermetic_build() and set_up_hermetic_build().
+include(cmake/hermetic_build.cmake OPTIONAL)
+
+if (COMMAND pre_project_set_up_hermetic_build)
+  pre_project_set_up_hermetic_build()
+endif()
+
+########################################################################
+#
+# Project-wide settings
+
+# Name of the project.
+#
+# CMake files in this project can refer to the root source directory
+# as ${gtest_SOURCE_DIR} and to the root binary directory as
+# ${gtest_BINARY_DIR}.
+# Language "C" is required for find_package(Threads).
+
+# Project version:
+
+if (CMAKE_VERSION VERSION_LESS 3.0)
+  project(gtest CXX C)
+  set(PROJECT_VERSION ${GOOGLETEST_VERSION})
+else()
+  cmake_policy(SET CMP0048 NEW)
+  project(gtest VERSION ${GOOGLETEST_VERSION} LANGUAGES CXX C)
+endif()
+cmake_minimum_required(VERSION 2.8.12)
+
+if (POLICY CMP0063) # Visibility
+  cmake_policy(SET CMP0063 NEW)
+endif (POLICY CMP0063)
+
+if (COMMAND set_up_hermetic_build)
+  set_up_hermetic_build()
+endif()
+
+# These commands only run if this is the main project
+if(CMAKE_PROJECT_NAME STREQUAL "gtest" OR CMAKE_PROJECT_NAME STREQUAL "googletest-distribution")
+
+  # BUILD_SHARED_LIBS is a standard CMake variable, but we declare it here to
+  # make it prominent in the GUI.
+  option(BUILD_SHARED_LIBS "Build shared libraries (DLLs)." OFF)
+
+else()
+
+  mark_as_advanced(
+    gtest_force_shared_crt
+    gtest_build_tests
+    gtest_build_samples
+    gtest_disable_pthreads
+    gtest_hide_internal_symbols)
+
+endif()
+
+
+if (gtest_hide_internal_symbols)
+  set(CMAKE_CXX_VISIBILITY_PRESET hidden)
+  set(CMAKE_VISIBILITY_INLINES_HIDDEN 1)
+endif()
+
+# Define helper functions and macros used by Google Test.
+include(cmake/internal_utils.cmake)
+
+config_compiler_and_linker()  # Defined in internal_utils.cmake.
+
+# Needed to set the namespace for both the export targets and the
+# alias libraries
+set(cmake_package_name GTest CACHE INTERNAL "")
+
+# Create the CMake package file descriptors.
+if (INSTALL_GTEST)
+  include(CMakePackageConfigHelpers)
+  set(targets_export_name ${cmake_package_name}Targets CACHE INTERNAL "")
+  set(generated_dir "${CMAKE_CURRENT_BINARY_DIR}/generated" CACHE INTERNAL "")
+  set(cmake_files_install_dir "${CMAKE_INSTALL_LIBDIR}/cmake/${cmake_package_name}")
+  set(version_file "${generated_dir}/${cmake_package_name}ConfigVersion.cmake")
+  write_basic_package_version_file(${version_file} VERSION ${GOOGLETEST_VERSION} COMPATIBILITY AnyNewerVersion)
+  install(EXPORT ${targets_export_name}
+    NAMESPACE ${cmake_package_name}::
+    DESTINATION ${cmake_files_install_dir})
+  set(config_file "${generated_dir}/${cmake_package_name}Config.cmake")
+  configure_package_config_file("${gtest_SOURCE_DIR}/cmake/Config.cmake.in"
+    "${config_file}" INSTALL_DESTINATION ${cmake_files_install_dir})
+  install(FILES ${version_file} ${config_file}
+    DESTINATION ${cmake_files_install_dir})
+endif()
+
+# Where Google Test's .h files can be found.
+set(gtest_build_include_dirs
+  "${gtest_SOURCE_DIR}/include"
+  "${gtest_SOURCE_DIR}")
+include_directories(${gtest_build_include_dirs})
+
+########################################################################
+#
+# Defines the gtest & gtest_main libraries.  User tests should link
+# with one of them.
+
+# Google Test libraries.  We build them using more strict warnings than what
+# are used for other targets, to ensure that gtest can be compiled by a user
+# aggressive about warnings.
+cxx_library(gtest "${cxx_strict}" src/gtest-all.cc)
+set_target_properties(gtest PROPERTIES VERSION ${GOOGLETEST_VERSION})
+cxx_library(gtest_main "${cxx_strict}" src/gtest_main.cc)
+set_target_properties(gtest_main PROPERTIES VERSION ${GOOGLETEST_VERSION})
+# If the CMake version supports it, attach header directory information
+# to the targets for when we are part of a parent build (ie being pulled
+# in via add_subdirectory() rather than being a standalone build).
+if (DEFINED CMAKE_VERSION AND NOT "${CMAKE_VERSION}" VERSION_LESS "2.8.11")
+  target_include_directories(gtest SYSTEM INTERFACE
+    "$<BUILD_INTERFACE:${gtest_build_include_dirs}>"
+    "$<INSTALL_INTERFACE:$<INSTALL_PREFIX>/${CMAKE_INSTALL_INCLUDEDIR}>")
+  target_include_directories(gtest_main SYSTEM INTERFACE
+    "$<BUILD_INTERFACE:${gtest_build_include_dirs}>"
+    "$<INSTALL_INTERFACE:$<INSTALL_PREFIX>/${CMAKE_INSTALL_INCLUDEDIR}>")
+endif()
+target_link_libraries(gtest_main PUBLIC gtest)
+
+########################################################################
+#
+# Install rules
+install_project(gtest gtest_main)
+
+########################################################################
+#
+# Samples on how to link user tests with gtest or gtest_main.
+#
+# They are not built by default.  To build them, set the
+# gtest_build_samples option to ON.  You can do it by running ccmake
+# or specifying the -Dgtest_build_samples=ON flag when running cmake.
+
+if (gtest_build_samples)
+  cxx_executable(sample1_unittest samples gtest_main samples/sample1.cc)
+  cxx_executable(sample2_unittest samples gtest_main samples/sample2.cc)
+  cxx_executable(sample3_unittest samples gtest_main)
+  cxx_executable(sample4_unittest samples gtest_main samples/sample4.cc)
+  cxx_executable(sample5_unittest samples gtest_main samples/sample1.cc)
+  cxx_executable(sample6_unittest samples gtest_main)
+  cxx_executable(sample7_unittest samples gtest_main)
+  cxx_executable(sample8_unittest samples gtest_main)
+  cxx_executable(sample9_unittest samples gtest)
+  cxx_executable(sample10_unittest samples gtest)
+endif()
+
+########################################################################
+#
+# Google Test's own tests.
+#
+# You can skip this section if you aren't interested in testing
+# Google Test itself.
+#
+# The tests are not built by default.  To build them, set the
+# gtest_build_tests option to ON.  You can do it by running ccmake
+# or specifying the -Dgtest_build_tests=ON flag when running cmake.
+
+if (gtest_build_tests)
+  # This must be set in the root directory for the tests to be run by
+  # 'make test' or ctest.
+  enable_testing()
+
+  ############################################################
+  # C++ tests built with standard compiler flags.
+
+  cxx_test(googletest-death-test-test gtest_main)
+  cxx_test(gtest_environment_test gtest)
+  cxx_test(googletest-filepath-test gtest_main)
+  cxx_test(googletest-listener-test gtest_main)
+  cxx_test(gtest_main_unittest gtest_main)
+  cxx_test(googletest-message-test gtest_main)
+  cxx_test(gtest_no_test_unittest gtest)
+  cxx_test(googletest-options-test gtest_main)
+  cxx_test(googletest-param-test-test gtest
+    test/googletest-param-test2-test.cc)
+  cxx_test(googletest-port-test gtest_main)
+  cxx_test(gtest_pred_impl_unittest gtest_main)
+  cxx_test(gtest_premature_exit_test gtest
+    test/gtest_premature_exit_test.cc)
+  cxx_test(googletest-printers-test gtest_main)
+  cxx_test(gtest_prod_test gtest_main
+    test/production.cc)
+  cxx_test(gtest_repeat_test gtest)
+  cxx_test(gtest_sole_header_test gtest_main)
+  cxx_test(gtest_stress_test gtest)
+  cxx_test(googletest-test-part-test gtest_main)
+  cxx_test(gtest_throw_on_failure_ex_test gtest)
+  cxx_test(gtest-typed-test_test gtest_main
+    test/gtest-typed-test2_test.cc)
+  cxx_test(gtest_unittest gtest_main)
+  cxx_test(gtest-unittest-api_test gtest)
+  cxx_test(gtest_skip_in_environment_setup_test gtest_main)
+  cxx_test(gtest_skip_test gtest_main)
+
+  ############################################################
+  # C++ tests built with non-standard compiler flags.
+
+  # MSVC 7.1 does not support STL with exceptions disabled.
+  if (NOT MSVC OR MSVC_VERSION GREATER 1310)
+    cxx_library(gtest_no_exception "${cxx_no_exception}"
+      src/gtest-all.cc)
+    cxx_library(gtest_main_no_exception "${cxx_no_exception}"
+      src/gtest-all.cc src/gtest_main.cc)
+  endif()
+  cxx_library(gtest_main_no_rtti "${cxx_no_rtti}"
+    src/gtest-all.cc src/gtest_main.cc)
+
+  cxx_test_with_flags(gtest-death-test_ex_nocatch_test
+    "${cxx_exception} -DGTEST_ENABLE_CATCH_EXCEPTIONS_=0"
+    gtest test/googletest-death-test_ex_test.cc)
+  cxx_test_with_flags(gtest-death-test_ex_catch_test
+    "${cxx_exception} -DGTEST_ENABLE_CATCH_EXCEPTIONS_=1"
+    gtest test/googletest-death-test_ex_test.cc)
+
+  cxx_test_with_flags(gtest_no_rtti_unittest "${cxx_no_rtti}"
+    gtest_main_no_rtti test/gtest_unittest.cc)
+
+  cxx_shared_library(gtest_dll "${cxx_default}"
+    src/gtest-all.cc src/gtest_main.cc)
+
+  cxx_executable_with_flags(gtest_dll_test_ "${cxx_default}"
+    gtest_dll test/gtest_all_test.cc)
+  set_target_properties(gtest_dll_test_
+                        PROPERTIES
+                        COMPILE_DEFINITIONS "GTEST_LINKED_AS_SHARED_LIBRARY=1")
+
+  ############################################################
+  # Python tests.
+
+  cxx_executable(googletest-break-on-failure-unittest_ test gtest)
+  py_test(googletest-break-on-failure-unittest)
+
+  py_test(gtest_skip_check_output_test)
+  py_test(gtest_skip_environment_check_output_test)
+
+  # Visual Studio .NET 2003 does not support STL with exceptions disabled.
+  if (NOT MSVC OR MSVC_VERSION GREATER 1310)  # 1310 is Visual Studio .NET 2003
+    cxx_executable_with_flags(
+      googletest-catch-exceptions-no-ex-test_
+      "${cxx_no_exception}"
+      gtest_main_no_exception
+      test/googletest-catch-exceptions-test_.cc)
+  endif()
+
+  cxx_executable_with_flags(
+    googletest-catch-exceptions-ex-test_
+    "${cxx_exception}"
+    gtest_main
+    test/googletest-catch-exceptions-test_.cc)
+  py_test(googletest-catch-exceptions-test)
+
+  cxx_executable(googletest-color-test_ test gtest)
+  py_test(googletest-color-test)
+
+  cxx_executable(googletest-env-var-test_ test gtest)
+  py_test(googletest-env-var-test)
+
+  cxx_executable(googletest-filter-unittest_ test gtest)
+  py_test(googletest-filter-unittest)
+
+  cxx_executable(gtest_help_test_ test gtest_main)
+  py_test(gtest_help_test)
+
+  cxx_executable(googletest-list-tests-unittest_ test gtest)
+  py_test(googletest-list-tests-unittest)
+
+  cxx_executable(googletest-output-test_ test gtest)
+  py_test(googletest-output-test --no_stacktrace_support)
+
+  cxx_executable(googletest-shuffle-test_ test gtest)
+  py_test(googletest-shuffle-test)
+
+  # MSVC 7.1 does not support STL with exceptions disabled.
+  if (NOT MSVC OR MSVC_VERSION GREATER 1310)
+    cxx_executable(googletest-throw-on-failure-test_ test gtest_no_exception)
+    set_target_properties(googletest-throw-on-failure-test_
+      PROPERTIES
+      COMPILE_FLAGS "${cxx_no_exception}")
+    py_test(googletest-throw-on-failure-test)
+  endif()
+
+  cxx_executable(googletest-uninitialized-test_ test gtest)
+  py_test(googletest-uninitialized-test)
+
+  cxx_executable(gtest_list_output_unittest_ test gtest)
+  py_test(gtest_list_output_unittest)
+
+  cxx_executable(gtest_xml_outfile1_test_ test gtest_main)
+  cxx_executable(gtest_xml_outfile2_test_ test gtest_main)
+  py_test(gtest_xml_outfiles_test)
+  py_test(googletest-json-outfiles-test)
+
+  cxx_executable(gtest_xml_output_unittest_ test gtest)
+  py_test(gtest_xml_output_unittest --no_stacktrace_support)
+  py_test(googletest-json-output-unittest --no_stacktrace_support)
+endif()
diff --git a/leveldb_base/third_party/googletest/googletest/README.md b/leveldb_base/third_party/googletest/googletest/README.md
new file mode 100644
index 0000000..1f8b349
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/README.md
@@ -0,0 +1,215 @@
+### Generic Build Instructions
+
+#### Setup
+
+To build GoogleTest and your tests that use it, you need to tell your build
+system where to find its headers and source files. The exact way to do it
+depends on which build system you use, and is usually straightforward.
+
+### Build with CMake
+
+GoogleTest comes with a CMake build script
+([CMakeLists.txt](https://github.com/google/googletest/blob/master/CMakeLists.txt))
+that can be used on a wide range of platforms ("C" stands for cross-platform.).
+If you don't have CMake installed already, you can download it for free from
+<http://www.cmake.org/>.
+
+CMake works by generating native makefiles or build projects that can be used in
+the compiler environment of your choice. You can either build GoogleTest as a
+standalone project or it can be incorporated into an existing CMake build for
+another project.
+
+#### Standalone CMake Project
+
+When building GoogleTest as a standalone project, the typical workflow starts
+with
+
+```
+git clone https://github.com/google/googletest.git -b release-1.10.0
+cd googletest        # Main directory of the cloned repository.
+mkdir build          # Create a directory to hold the build output.
+cd build
+cmake ..             # Generate native build scripts for GoogleTest.
+```
+
+The above command also includes GoogleMock by default. And so, if you want to
+build only GoogleTest, you should replace the last command with
+
+```
+cmake .. -DBUILD_GMOCK=OFF
+```
+
+If you are on a \*nix system, you should now see a Makefile in the current
+directory. Just type `make` to build GoogleTest. And then you can simply install
+GoogleTest if you are a system administrator.
+
+```
+make
+sudo make install    # Install in /usr/local/ by default
+```
+
+If you use Windows and have Visual Studio installed, a `gtest.sln` file and
+several `.vcproj` files will be created. You can then build them using Visual
+Studio.
+
+On Mac OS X with Xcode installed, a `.xcodeproj` file will be generated.
+
+#### Incorporating Into An Existing CMake Project
+
+If you want to use GoogleTest in a project which already uses CMake, the easiest
+way is to get installed libraries and headers.
+
+*   Import GoogleTest by using `find_package` (or `pkg_check_modules`). For
+    example, if `find_package(GTest CONFIG REQUIRED)` succeeds, you can use the
+    libraries as `GTest::gtest`, `GTest::gmock`.
+
+And a more robust and flexible approach is to build GoogleTest as part of that
+project directly. This is done by making the GoogleTest source code available to
+the main build and adding it using CMake's `add_subdirectory()` command. This
+has the significant advantage that the same compiler and linker settings are
+used between GoogleTest and the rest of your project, so issues associated with
+using incompatible libraries (eg debug/release), etc. are avoided. This is
+particularly useful on Windows. Making GoogleTest's source code available to the
+main build can be done a few different ways:
+
+*   Download the GoogleTest source code manually and place it at a known
+    location. This is the least flexible approach and can make it more difficult
+    to use with continuous integration systems, etc.
+*   Embed the GoogleTest source code as a direct copy in the main project's
+    source tree. This is often the simplest approach, but is also the hardest to
+    keep up to date. Some organizations may not permit this method.
+*   Add GoogleTest as a git submodule or equivalent. This may not always be
+    possible or appropriate. Git submodules, for example, have their own set of
+    advantages and drawbacks.
+*   Use CMake to download GoogleTest as part of the build's configure step. This
+    approach doesn't have the limitations of the other methods.
+
+The last of the above methods is implemented with a small piece of CMake code
+that downloads and pulls the GoogleTest code into the main build.
+
+Just add to your `CMakeLists.txt`:
+
+```cmake
+include(FetchContent)
+FetchContent_Declare(
+  googletest
+  # Specify the commit you depend on and update it regularly.
+  URL https://github.com/google/googletest/archive/609281088cfefc76f9d0ce82e1ff6c30cc3591e5.zip
+)
+# For Windows: Prevent overriding the parent project's compiler/linker settings
+set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
+FetchContent_MakeAvailable(googletest)
+
+# Now simply link against gtest or gtest_main as needed. Eg
+add_executable(example example.cpp)
+target_link_libraries(example gtest_main)
+add_test(NAME example_test COMMAND example)
+```
+
+Note that this approach requires CMake 3.14 or later due to its use of the
+`FetchContent_MakeAvailable()` command.
+
+##### Visual Studio Dynamic vs Static Runtimes
+
+By default, new Visual Studio projects link the C runtimes dynamically but
+GoogleTest links them statically. This will generate an error that looks
+something like the following: gtest.lib(gtest-all.obj) : error LNK2038: mismatch
+detected for 'RuntimeLibrary': value 'MTd_StaticDebug' doesn't match value
+'MDd_DynamicDebug' in main.obj
+
+GoogleTest already has a CMake option for this: `gtest_force_shared_crt`
+
+Enabling this option will make gtest link the runtimes dynamically too, and
+match the project in which it is included.
+
+#### C++ Standard Version
+
+An environment that supports C++11 is required in order to successfully build
+GoogleTest. One way to ensure this is to specify the standard in the top-level
+project, for example by using the `set(CMAKE_CXX_STANDARD 11)` command. If this
+is not feasible, for example in a C project using GoogleTest for validation,
+then it can be specified by adding it to the options for cmake via the
+`DCMAKE_CXX_FLAGS` option.
+
+### Tweaking GoogleTest
+
+GoogleTest can be used in diverse environments. The default configuration may
+not work (or may not work well) out of the box in some environments. However,
+you can easily tweak GoogleTest by defining control macros on the compiler
+command line. Generally, these macros are named like `GTEST_XYZ` and you define
+them to either 1 or 0 to enable or disable a certain feature.
+
+We list the most frequently used macros below. For a complete list, see file
+[include/gtest/internal/gtest-port.h](https://github.com/google/googletest/blob/master/googletest/include/gtest/internal/gtest-port.h).
+
+### Multi-threaded Tests
+
+GoogleTest is thread-safe where the pthread library is available. After
+`#include "gtest/gtest.h"`, you can check the
+`GTEST_IS_THREADSAFE` macro to see whether this is the case (yes if the macro is
+`#defined` to 1, no if it's undefined.).
+
+If GoogleTest doesn't correctly detect whether pthread is available in your
+environment, you can force it with
+
+    -DGTEST_HAS_PTHREAD=1
+
+or
+
+    -DGTEST_HAS_PTHREAD=0
+
+When GoogleTest uses pthread, you may need to add flags to your compiler and/or
+linker to select the pthread library, or you'll get link errors. If you use the
+CMake script, this is taken care of for you. If you use your own build script,
+you'll need to read your compiler and linker's manual to figure out what flags
+to add.
+
+### As a Shared Library (DLL)
+
+GoogleTest is compact, so most users can build and link it as a static library
+for the simplicity. You can choose to use GoogleTest as a shared library (known
+as a DLL on Windows) if you prefer.
+
+To compile *gtest* as a shared library, add
+
+    -DGTEST_CREATE_SHARED_LIBRARY=1
+
+to the compiler flags. You'll also need to tell the linker to produce a shared
+library instead - consult your linker's manual for how to do it.
+
+To compile your *tests* that use the gtest shared library, add
+
+    -DGTEST_LINKED_AS_SHARED_LIBRARY=1
+
+to the compiler flags.
+
+Note: while the above steps aren't technically necessary today when using some
+compilers (e.g. GCC), they may become necessary in the future, if we decide to
+improve the speed of loading the library (see
+<http://gcc.gnu.org/wiki/Visibility> for details). Therefore you are recommended
+to always add the above flags when using GoogleTest as a shared library.
+Otherwise a future release of GoogleTest may break your build script.
+
+### Avoiding Macro Name Clashes
+
+In C++, macros don't obey namespaces. Therefore two libraries that both define a
+macro of the same name will clash if you `#include` both definitions. In case a
+GoogleTest macro clashes with another library, you can force GoogleTest to
+rename its macro to avoid the conflict.
+
+Specifically, if both GoogleTest and some other code define macro FOO, you can
+add
+
+    -DGTEST_DONT_DEFINE_FOO=1
+
+to the compiler flags to tell GoogleTest to change the macro's name from `FOO`
+to `GTEST_FOO`. Currently `FOO` can be `FAIL`, `SUCCEED`, or `TEST`. For
+example, with `-DGTEST_DONT_DEFINE_TEST=1`, you'll need to write
+
+    GTEST_TEST(SomeTest, DoesThis) { ... }
+
+instead of
+
+    TEST(SomeTest, DoesThis) { ... }
+
+in order to define a test.
diff --git a/leveldb_base/third_party/googletest/googletest/cmake/Config.cmake.in b/leveldb_base/third_party/googletest/googletest/cmake/Config.cmake.in
new file mode 100644
index 0000000..12be449
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/cmake/Config.cmake.in
@@ -0,0 +1,9 @@
+@PACKAGE_INIT@
+include(CMakeFindDependencyMacro)
+if (@GTEST_HAS_PTHREAD@)
+  set(THREADS_PREFER_PTHREAD_FLAG @THREADS_PREFER_PTHREAD_FLAG@)
+  find_dependency(Threads)
+endif()
+
+include("${CMAKE_CURRENT_LIST_DIR}/@targets_export_name@.cmake")
+check_required_components("@project_name@")
diff --git a/leveldb_base/third_party/googletest/googletest/cmake/gtest.pc.in b/leveldb_base/third_party/googletest/googletest/cmake/gtest.pc.in
new file mode 100644
index 0000000..b4148fa
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/cmake/gtest.pc.in
@@ -0,0 +1,9 @@
+libdir=@CMAKE_INSTALL_FULL_LIBDIR@
+includedir=@CMAKE_INSTALL_FULL_INCLUDEDIR@
+
+Name: gtest
+Description: GoogleTest (without main() function)
+Version: @PROJECT_VERSION@
+URL: https://github.com/google/googletest
+Libs: -L${libdir} -lgtest @CMAKE_THREAD_LIBS_INIT@
+Cflags: -I${includedir} @GTEST_HAS_PTHREAD_MACRO@
diff --git a/leveldb_base/third_party/googletest/googletest/cmake/gtest_main.pc.in b/leveldb_base/third_party/googletest/googletest/cmake/gtest_main.pc.in
new file mode 100644
index 0000000..38c88c5
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/cmake/gtest_main.pc.in
@@ -0,0 +1,10 @@
+libdir=@CMAKE_INSTALL_FULL_LIBDIR@
+includedir=@CMAKE_INSTALL_FULL_INCLUDEDIR@
+
+Name: gtest_main
+Description: GoogleTest (with main() function)
+Version: @PROJECT_VERSION@
+URL: https://github.com/google/googletest
+Requires: gtest = @PROJECT_VERSION@
+Libs: -L${libdir} -lgtest_main @CMAKE_THREAD_LIBS_INIT@
+Cflags: -I${includedir} @GTEST_HAS_PTHREAD_MACRO@
diff --git a/leveldb_base/third_party/googletest/googletest/cmake/internal_utils.cmake b/leveldb_base/third_party/googletest/googletest/cmake/internal_utils.cmake
new file mode 100644
index 0000000..8d8d60a
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/cmake/internal_utils.cmake
@@ -0,0 +1,344 @@
+# Defines functions and macros useful for building Google Test and
+# Google Mock.
+#
+# Note:
+#
+# - This file will be run twice when building Google Mock (once via
+#   Google Test's CMakeLists.txt, and once via Google Mock's).
+#   Therefore it shouldn't have any side effects other than defining
+#   the functions and macros.
+#
+# - The functions/macros defined in this file may depend on Google
+#   Test and Google Mock's option() definitions, and thus must be
+#   called *after* the options have been defined.
+
+if (POLICY CMP0054)
+  cmake_policy(SET CMP0054 NEW)
+endif (POLICY CMP0054)
+
+# Tweaks CMake's default compiler/linker settings to suit Google Test's needs.
+#
+# This must be a macro(), as inside a function string() can only
+# update variables in the function scope.
+macro(fix_default_compiler_settings_)
+  if (MSVC)
+    # For MSVC, CMake sets certain flags to defaults we want to override.
+    # This replacement code is taken from sample in the CMake Wiki at
+    # https://gitlab.kitware.com/cmake/community/wikis/FAQ#dynamic-replace.
+    foreach (flag_var
+             CMAKE_C_FLAGS CMAKE_C_FLAGS_DEBUG CMAKE_C_FLAGS_RELEASE
+             CMAKE_C_FLAGS_MINSIZEREL CMAKE_C_FLAGS_RELWITHDEBINFO
+             CMAKE_CXX_FLAGS CMAKE_CXX_FLAGS_DEBUG CMAKE_CXX_FLAGS_RELEASE
+             CMAKE_CXX_FLAGS_MINSIZEREL CMAKE_CXX_FLAGS_RELWITHDEBINFO)
+      if (NOT BUILD_SHARED_LIBS AND NOT gtest_force_shared_crt)
+        # When Google Test is built as a shared library, it should also use
+        # shared runtime libraries.  Otherwise, it may end up with multiple
+        # copies of runtime library data in different modules, resulting in
+        # hard-to-find crashes. When it is built as a static library, it is
+        # preferable to use CRT as static libraries, as we don't have to rely
+        # on CRT DLLs being available. CMake always defaults to using shared
+        # CRT libraries, so we override that default here.
+        string(REPLACE "/MD" "-MT" ${flag_var} "${${flag_var}}")
+      endif()
+
+      # We prefer more strict warning checking for building Google Test.
+      # Replaces /W3 with /W4 in defaults.
+      string(REPLACE "/W3" "/W4" ${flag_var} "${${flag_var}}")
+
+      # Prevent D9025 warning for targets that have exception handling
+      # turned off (/EHs-c- flag). Where required, exceptions are explicitly
+      # re-enabled using the cxx_exception_flags variable.
+      string(REPLACE "/EHsc" "" ${flag_var} "${${flag_var}}")
+    endforeach()
+  endif()
+endmacro()
+
+# Defines the compiler/linker flags used to build Google Test and
+# Google Mock.  You can tweak these definitions to suit your need.  A
+# variable's value is empty before it's explicitly assigned to.
+macro(config_compiler_and_linker)
+  # Note: pthreads on MinGW is not supported, even if available
+  # instead, we use windows threading primitives
+  unset(GTEST_HAS_PTHREAD)
+  if (NOT gtest_disable_pthreads AND NOT MINGW)
+    # Defines CMAKE_USE_PTHREADS_INIT and CMAKE_THREAD_LIBS_INIT.
+    find_package(Threads)
+    if (CMAKE_USE_PTHREADS_INIT)
+      set(GTEST_HAS_PTHREAD ON)
+    endif()
+  endif()
+
+  fix_default_compiler_settings_()
+  if (MSVC)
+    # Newlines inside flags variables break CMake's NMake generator.
+    # TODO(vladl@google.com): Add -RTCs and -RTCu to debug builds.
+    set(cxx_base_flags "-GS -W4 -WX -wd4251 -wd4275 -nologo -J")
+    set(cxx_base_flags "${cxx_base_flags} -D_UNICODE -DUNICODE -DWIN32 -D_WIN32")
+    set(cxx_base_flags "${cxx_base_flags} -DSTRICT -DWIN32_LEAN_AND_MEAN")
+    set(cxx_exception_flags "-EHsc -D_HAS_EXCEPTIONS=1")
+    set(cxx_no_exception_flags "-EHs-c- -D_HAS_EXCEPTIONS=0")
+    set(cxx_no_rtti_flags "-GR-")
+    # Suppress "unreachable code" warning
+    # http://stackoverflow.com/questions/3232669 explains the issue.
+    set(cxx_base_flags "${cxx_base_flags} -wd4702")
+    # Ensure MSVC treats source files as UTF-8 encoded.
+    set(cxx_base_flags "${cxx_base_flags} -utf-8")
+  elseif (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+    set(cxx_base_flags "-Wall -Wshadow -Werror -Wconversion")
+    set(cxx_exception_flags "-fexceptions")
+    set(cxx_no_exception_flags "-fno-exceptions")
+    set(cxx_strict_flags "-W -Wpointer-arith -Wreturn-type -Wcast-qual -Wwrite-strings -Wswitch -Wunused-parameter -Wcast-align -Wchar-subscripts -Winline -Wredundant-decls")
+    set(cxx_no_rtti_flags "-fno-rtti")
+  elseif (CMAKE_COMPILER_IS_GNUCXX)
+    set(cxx_base_flags "-Wall -Wshadow -Werror")
+    if(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 7.0.0)
+      set(cxx_base_flags "${cxx_base_flags} -Wno-error=dangling-else")
+    endif()
+    set(cxx_exception_flags "-fexceptions")
+    set(cxx_no_exception_flags "-fno-exceptions")
+    # Until version 4.3.2, GCC doesn't define a macro to indicate
+    # whether RTTI is enabled.  Therefore we define GTEST_HAS_RTTI
+    # explicitly.
+    set(cxx_no_rtti_flags "-fno-rtti -DGTEST_HAS_RTTI=0")
+    set(cxx_strict_flags
+      "-Wextra -Wno-unused-parameter -Wno-missing-field-initializers")
+  elseif (CMAKE_CXX_COMPILER_ID STREQUAL "SunPro")
+    set(cxx_exception_flags "-features=except")
+    # Sun Pro doesn't provide macros to indicate whether exceptions and
+    # RTTI are enabled, so we define GTEST_HAS_* explicitly.
+    set(cxx_no_exception_flags "-features=no%except -DGTEST_HAS_EXCEPTIONS=0")
+    set(cxx_no_rtti_flags "-features=no%rtti -DGTEST_HAS_RTTI=0")
+  elseif (CMAKE_CXX_COMPILER_ID STREQUAL "VisualAge" OR
+      CMAKE_CXX_COMPILER_ID STREQUAL "XL")
+    # CMake 2.8 changes Visual Age's compiler ID to "XL".
+    set(cxx_exception_flags "-qeh")
+    set(cxx_no_exception_flags "-qnoeh")
+    # Until version 9.0, Visual Age doesn't define a macro to indicate
+    # whether RTTI is enabled.  Therefore we define GTEST_HAS_RTTI
+    # explicitly.
+    set(cxx_no_rtti_flags "-qnortti -DGTEST_HAS_RTTI=0")
+  elseif (CMAKE_CXX_COMPILER_ID STREQUAL "HP")
+    set(cxx_base_flags "-AA -mt")
+    set(cxx_exception_flags "-DGTEST_HAS_EXCEPTIONS=1")
+    set(cxx_no_exception_flags "+noeh -DGTEST_HAS_EXCEPTIONS=0")
+    # RTTI can not be disabled in HP aCC compiler.
+    set(cxx_no_rtti_flags "")
+  endif()
+
+  # The pthreads library is available and allowed?
+  if (DEFINED GTEST_HAS_PTHREAD)
+    set(GTEST_HAS_PTHREAD_MACRO "-DGTEST_HAS_PTHREAD=1")
+  else()
+    set(GTEST_HAS_PTHREAD_MACRO "-DGTEST_HAS_PTHREAD=0")
+  endif()
+  set(cxx_base_flags "${cxx_base_flags} ${GTEST_HAS_PTHREAD_MACRO}")
+
+  # For building gtest's own tests and samples.
+  set(cxx_exception "${cxx_base_flags} ${cxx_exception_flags}")
+  set(cxx_no_exception
+    "${CMAKE_CXX_FLAGS} ${cxx_base_flags} ${cxx_no_exception_flags}")
+  set(cxx_default "${cxx_exception}")
+  set(cxx_no_rtti "${cxx_default} ${cxx_no_rtti_flags}")
+
+  # For building the gtest libraries.
+  set(cxx_strict "${cxx_default} ${cxx_strict_flags}")
+endmacro()
+
+# Defines the gtest & gtest_main libraries.  User tests should link
+# with one of them.
+function(cxx_library_with_type name type cxx_flags)
+  # type can be either STATIC or SHARED to denote a static or shared library.
+  # ARGN refers to additional arguments after 'cxx_flags'.
+  add_library(${name} ${type} ${ARGN})
+  add_library(${cmake_package_name}::${name} ALIAS ${name})
+  set_target_properties(${name}
+    PROPERTIES
+    COMPILE_FLAGS "${cxx_flags}")
+  # Generate debug library name with a postfix.
+  set_target_properties(${name}
+    PROPERTIES
+    DEBUG_POSTFIX "d")
+  # Set the output directory for build artifacts
+  set_target_properties(${name}
+    PROPERTIES
+    RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/bin"
+    LIBRARY_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/lib"
+    ARCHIVE_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/lib"
+    PDB_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/bin")
+  # make PDBs match library name
+  get_target_property(pdb_debug_postfix ${name} DEBUG_POSTFIX)
+  set_target_properties(${name}
+    PROPERTIES
+    PDB_NAME "${name}"
+    PDB_NAME_DEBUG "${name}${pdb_debug_postfix}"
+    COMPILE_PDB_NAME "${name}"
+    COMPILE_PDB_NAME_DEBUG "${name}${pdb_debug_postfix}")
+
+  if (BUILD_SHARED_LIBS OR type STREQUAL "SHARED")
+    set_target_properties(${name}
+      PROPERTIES
+      COMPILE_DEFINITIONS "GTEST_CREATE_SHARED_LIBRARY=1")
+    if (NOT "${CMAKE_VERSION}" VERSION_LESS "2.8.11")
+      target_compile_definitions(${name} INTERFACE
+        $<INSTALL_INTERFACE:GTEST_LINKED_AS_SHARED_LIBRARY=1>)
+    endif()
+  endif()
+  if (DEFINED GTEST_HAS_PTHREAD)
+    if ("${CMAKE_VERSION}" VERSION_LESS "3.1.0")
+      set(threads_spec ${CMAKE_THREAD_LIBS_INIT})
+    else()
+      set(threads_spec Threads::Threads)
+    endif()
+    target_link_libraries(${name} PUBLIC ${threads_spec})
+  endif()
+
+  if (NOT "${CMAKE_VERSION}" VERSION_LESS "3.8")
+    target_compile_features(${name} PUBLIC cxx_std_11)
+  endif()
+endfunction()
+
+########################################################################
+#
+# Helper functions for creating build targets.
+
+function(cxx_shared_library name cxx_flags)
+  cxx_library_with_type(${name} SHARED "${cxx_flags}" ${ARGN})
+endfunction()
+
+function(cxx_library name cxx_flags)
+  cxx_library_with_type(${name} "" "${cxx_flags}" ${ARGN})
+endfunction()
+
+# cxx_executable_with_flags(name cxx_flags libs srcs...)
+#
+# creates a named C++ executable that depends on the given libraries and
+# is built from the given source files with the given compiler flags.
+function(cxx_executable_with_flags name cxx_flags libs)
+  add_executable(${name} ${ARGN})
+  if (MSVC)
+    # BigObj required for tests.
+    set(cxx_flags "${cxx_flags} -bigobj")
+  endif()
+  if (cxx_flags)
+    set_target_properties(${name}
+      PROPERTIES
+      COMPILE_FLAGS "${cxx_flags}")
+  endif()
+  if (BUILD_SHARED_LIBS)
+    set_target_properties(${name}
+      PROPERTIES
+      COMPILE_DEFINITIONS "GTEST_LINKED_AS_SHARED_LIBRARY=1")
+  endif()
+  # To support mixing linking in static and dynamic libraries, link each
+  # library in with an extra call to target_link_libraries.
+  foreach (lib "${libs}")
+    target_link_libraries(${name} ${lib})
+  endforeach()
+endfunction()
+
+# cxx_executable(name dir lib srcs...)
+#
+# creates a named target that depends on the given libs and is built
+# from the given source files.  dir/name.cc is implicitly included in
+# the source file list.
+function(cxx_executable name dir libs)
+  cxx_executable_with_flags(
+    ${name} "${cxx_default}" "${libs}" "${dir}/${name}.cc" ${ARGN})
+endfunction()
+
+# Sets PYTHONINTERP_FOUND and PYTHON_EXECUTABLE.
+if ("${CMAKE_VERSION}" VERSION_LESS "3.12.0")
+  find_package(PythonInterp)
+else()
+  find_package(Python COMPONENTS Interpreter)
+  set(PYTHONINTERP_FOUND ${Python_Interpreter_FOUND})
+  set(PYTHON_EXECUTABLE ${Python_EXECUTABLE})
+endif()
+
+# cxx_test_with_flags(name cxx_flags libs srcs...)
+#
+# creates a named C++ test that depends on the given libs and is built
+# from the given source files with the given compiler flags.
+function(cxx_test_with_flags name cxx_flags libs)
+  cxx_executable_with_flags(${name} "${cxx_flags}" "${libs}" ${ARGN})
+    add_test(NAME ${name} COMMAND "$<TARGET_FILE:${name}>")
+endfunction()
+
+# cxx_test(name libs srcs...)
+#
+# creates a named test target that depends on the given libs and is
+# built from the given source files.  Unlike cxx_test_with_flags,
+# test/name.cc is already implicitly included in the source file list.
+function(cxx_test name libs)
+  cxx_test_with_flags("${name}" "${cxx_default}" "${libs}"
+    "test/${name}.cc" ${ARGN})
+endfunction()
+
+# py_test(name)
+#
+# creates a Python test with the given name whose main module is in
+# test/name.py.  It does nothing if Python is not installed.
+function(py_test name)
+  if (PYTHONINTERP_FOUND)
+    if ("${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION}" VERSION_GREATER 3.1)
+      if (CMAKE_CONFIGURATION_TYPES)
+        # Multi-configuration build generators as for Visual Studio save
+        # output in a subdirectory of CMAKE_CURRENT_BINARY_DIR (Debug,
+        # Release etc.), so we have to provide it here.
+        add_test(NAME ${name}
+          COMMAND ${PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/test/${name}.py
+              --build_dir=${CMAKE_CURRENT_BINARY_DIR}/$<CONFIG> ${ARGN})
+      else (CMAKE_CONFIGURATION_TYPES)
+        # Single-configuration build generators like Makefile generators
+        # don't have subdirs below CMAKE_CURRENT_BINARY_DIR.
+        add_test(NAME ${name}
+          COMMAND ${PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/test/${name}.py
+            --build_dir=${CMAKE_CURRENT_BINARY_DIR} ${ARGN})
+      endif (CMAKE_CONFIGURATION_TYPES)
+    else()
+      # ${CMAKE_CURRENT_BINARY_DIR} is known at configuration time, so we can
+      # directly bind it from cmake. ${CTEST_CONFIGURATION_TYPE} is known
+      # only at ctest runtime (by calling ctest -c <Configuration>), so
+      # we have to escape $ to delay variable substitution here.
+      add_test(NAME ${name}
+        COMMAND ${PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/test/${name}.py
+          --build_dir=${CMAKE_CURRENT_BINARY_DIR}/\${CTEST_CONFIGURATION_TYPE} ${ARGN})
+    endif()
+  endif(PYTHONINTERP_FOUND)
+endfunction()
+
+# install_project(targets...)
+#
+# Installs the specified targets and configures the associated pkgconfig files.
+function(install_project)
+  if(INSTALL_GTEST)
+    install(DIRECTORY "${PROJECT_SOURCE_DIR}/include/"
+      DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}")
+    # Install the project targets.
+    install(TARGETS ${ARGN}
+      EXPORT ${targets_export_name}
+      RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}"
+      ARCHIVE DESTINATION "${CMAKE_INSTALL_LIBDIR}"
+      LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}")
+    if(CMAKE_CXX_COMPILER_ID MATCHES "MSVC")
+      # Install PDBs
+      foreach(t ${ARGN})
+        get_target_property(t_pdb_name ${t} COMPILE_PDB_NAME)
+        get_target_property(t_pdb_name_debug ${t} COMPILE_PDB_NAME_DEBUG)
+        get_target_property(t_pdb_output_directory ${t} PDB_OUTPUT_DIRECTORY)
+        install(FILES
+          "${t_pdb_output_directory}/\${CMAKE_INSTALL_CONFIG_NAME}/$<$<CONFIG:Debug>:${t_pdb_name_debug}>$<$<NOT:$<CONFIG:Debug>>:${t_pdb_name}>.pdb"
+          DESTINATION ${CMAKE_INSTALL_LIBDIR}
+          OPTIONAL)
+      endforeach()
+    endif()
+    # Configure and install pkgconfig files.
+    foreach(t ${ARGN})
+      set(configured_pc "${generated_dir}/${t}.pc")
+      configure_file("${PROJECT_SOURCE_DIR}/cmake/${t}.pc.in"
+        "${configured_pc}" @ONLY)
+      install(FILES "${configured_pc}"
+        DESTINATION "${CMAKE_INSTALL_LIBDIR}/pkgconfig")
+    endforeach()
+  endif()
+endfunction()
diff --git a/leveldb_base/third_party/googletest/googletest/cmake/libgtest.la.in b/leveldb_base/third_party/googletest/googletest/cmake/libgtest.la.in
new file mode 100644
index 0000000..840c838
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/cmake/libgtest.la.in
@@ -0,0 +1,21 @@
+# libgtest.la - a libtool library file
+# Generated by libtool (GNU libtool) 2.4.6
+
+# Please DO NOT delete this file!
+# It is necessary for linking the library.
+
+# Names of this library.
+library_names='libgtest.so'
+
+# Is this an already installed library?
+installed=yes
+
+# Should we warn about portability when linking against -modules?
+shouldnotlink=no
+
+# Files to dlopen/dlpreopen
+dlopen=''
+dlpreopen=''
+
+# Directory that this library needs to be installed in:
+libdir='@CMAKE_INSTALL_FULL_LIBDIR@'
diff --git a/leveldb_base/third_party/googletest/googletest/docs/README.md b/leveldb_base/third_party/googletest/googletest/docs/README.md
new file mode 100644
index 0000000..1bc57b7
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/docs/README.md
@@ -0,0 +1,4 @@
+# Content Moved
+
+We are working on updates to the GoogleTest documentation, which has moved to
+the top-level [docs](../../docs) directory.
diff --git a/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-death-test.h b/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-death-test.h
new file mode 100644
index 0000000..9b4d4d1
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-death-test.h
@@ -0,0 +1,346 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// The Google C++ Testing and Mocking Framework (Google Test)
+//
+// This header file defines the public API for death tests.  It is
+// #included by gtest.h so a user doesn't need to include this
+// directly.
+// GOOGLETEST_CM0001 DO NOT DELETE
+
+#ifndef GOOGLETEST_INCLUDE_GTEST_GTEST_DEATH_TEST_H_
+#define GOOGLETEST_INCLUDE_GTEST_GTEST_DEATH_TEST_H_
+
+#include "gtest/internal/gtest-death-test-internal.h"
+
+namespace testing {
+
+// This flag controls the style of death tests.  Valid values are "threadsafe",
+// meaning that the death test child process will re-execute the test binary
+// from the start, running only a single death test, or "fast",
+// meaning that the child process will execute the test logic immediately
+// after forking.
+GTEST_DECLARE_string_(death_test_style);
+
+#if GTEST_HAS_DEATH_TEST
+
+namespace internal {
+
+// Returns a Boolean value indicating whether the caller is currently
+// executing in the context of the death test child process.  Tools such as
+// Valgrind heap checkers may need this to modify their behavior in death
+// tests.  IMPORTANT: This is an internal utility.  Using it may break the
+// implementation of death tests.  User code MUST NOT use it.
+GTEST_API_ bool InDeathTestChild();
+
+}  // namespace internal
+
+// The following macros are useful for writing death tests.
+
+// Here's what happens when an ASSERT_DEATH* or EXPECT_DEATH* is
+// executed:
+//
+//   1. It generates a warning if there is more than one active
+//   thread.  This is because it's safe to fork() or clone() only
+//   when there is a single thread.
+//
+//   2. The parent process clone()s a sub-process and runs the death
+//   test in it; the sub-process exits with code 0 at the end of the
+//   death test, if it hasn't exited already.
+//
+//   3. The parent process waits for the sub-process to terminate.
+//
+//   4. The parent process checks the exit code and error message of
+//   the sub-process.
+//
+// Examples:
+//
+//   ASSERT_DEATH(server.SendMessage(56, "Hello"), "Invalid port number");
+//   for (int i = 0; i < 5; i++) {
+//     EXPECT_DEATH(server.ProcessRequest(i),
+//                  "Invalid request .* in ProcessRequest()")
+//                  << "Failed to die on request " << i;
+//   }
+//
+//   ASSERT_EXIT(server.ExitNow(), ::testing::ExitedWithCode(0), "Exiting");
+//
+//   bool KilledBySIGHUP(int exit_code) {
+//     return WIFSIGNALED(exit_code) && WTERMSIG(exit_code) == SIGHUP;
+//   }
+//
+//   ASSERT_EXIT(client.HangUpServer(), KilledBySIGHUP, "Hanging up!");
+//
+// The final parameter to each of these macros is a matcher applied to any data
+// the sub-process wrote to stderr.  For compatibility with existing tests, a
+// bare string is interpreted as a regular expression matcher.
+//
+// On the regular expressions used in death tests:
+//
+//   GOOGLETEST_CM0005 DO NOT DELETE
+//   On POSIX-compliant systems (*nix), we use the <regex.h> library,
+//   which uses the POSIX extended regex syntax.
+//
+//   On other platforms (e.g. Windows or Mac), we only support a simple regex
+//   syntax implemented as part of Google Test.  This limited
+//   implementation should be enough most of the time when writing
+//   death tests; though it lacks many features you can find in PCRE
+//   or POSIX extended regex syntax.  For example, we don't support
+//   union ("x|y"), grouping ("(xy)"), brackets ("[xy]"), and
+//   repetition count ("x{5,7}"), among others.
+//
+//   Below is the syntax that we do support.  We chose it to be a
+//   subset of both PCRE and POSIX extended regex, so it's easy to
+//   learn wherever you come from.  In the following: 'A' denotes a
+//   literal character, period (.), or a single \\ escape sequence;
+//   'x' and 'y' denote regular expressions; 'm' and 'n' are for
+//   natural numbers.
+//
+//     c     matches any literal character c
+//     \\d   matches any decimal digit
+//     \\D   matches any character that's not a decimal digit
+//     \\f   matches \f
+//     \\n   matches \n
+//     \\r   matches \r
+//     \\s   matches any ASCII whitespace, including \n
+//     \\S   matches any character that's not a whitespace
+//     \\t   matches \t
+//     \\v   matches \v
+//     \\w   matches any letter, _, or decimal digit
+//     \\W   matches any character that \\w doesn't match
+//     \\c   matches any literal character c, which must be a punctuation
+//     .     matches any single character except \n
+//     A?    matches 0 or 1 occurrences of A
+//     A*    matches 0 or many occurrences of A
+//     A+    matches 1 or many occurrences of A
+//     ^     matches the beginning of a string (not that of each line)
+//     $     matches the end of a string (not that of each line)
+//     xy    matches x followed by y
+//
+//   If you accidentally use PCRE or POSIX extended regex features
+//   not implemented by us, you will get a run-time failure.  In that
+//   case, please try to rewrite your regular expression within the
+//   above syntax.
+//
+//   This implementation is *not* meant to be as highly tuned or robust
+//   as a compiled regex library, but should perform well enough for a
+//   death test, which already incurs significant overhead by launching
+//   a child process.
+//
+// Known caveats:
+//
+//   A "threadsafe" style death test obtains the path to the test
+//   program from argv[0] and re-executes it in the sub-process.  For
+//   simplicity, the current implementation doesn't search the PATH
+//   when launching the sub-process.  This means that the user must
+//   invoke the test program via a path that contains at least one
+//   path separator (e.g. path/to/foo_test and
+//   /absolute/path/to/bar_test are fine, but foo_test is not).  This
+//   is rarely a problem as people usually don't put the test binary
+//   directory in PATH.
+//
+
+// Asserts that a given `statement` causes the program to exit, with an
+// integer exit status that satisfies `predicate`, and emitting error output
+// that matches `matcher`.
+# define ASSERT_EXIT(statement, predicate, matcher) \
+    GTEST_DEATH_TEST_(statement, predicate, matcher, GTEST_FATAL_FAILURE_)
+
+// Like `ASSERT_EXIT`, but continues on to successive tests in the
+// test suite, if any:
+# define EXPECT_EXIT(statement, predicate, matcher) \
+    GTEST_DEATH_TEST_(statement, predicate, matcher, GTEST_NONFATAL_FAILURE_)
+
+// Asserts that a given `statement` causes the program to exit, either by
+// explicitly exiting with a nonzero exit code or being killed by a
+// signal, and emitting error output that matches `matcher`.
+# define ASSERT_DEATH(statement, matcher) \
+    ASSERT_EXIT(statement, ::testing::internal::ExitedUnsuccessfully, matcher)
+
+// Like `ASSERT_DEATH`, but continues on to successive tests in the
+// test suite, if any:
+# define EXPECT_DEATH(statement, matcher) \
+    EXPECT_EXIT(statement, ::testing::internal::ExitedUnsuccessfully, matcher)
+
+// Two predicate classes that can be used in {ASSERT,EXPECT}_EXIT*:
+
+// Tests that an exit code describes a normal exit with a given exit code.
+class GTEST_API_ ExitedWithCode {
+ public:
+  explicit ExitedWithCode(int exit_code);
+  ExitedWithCode(const ExitedWithCode&) = default;
+  void operator=(const ExitedWithCode& other) = delete;
+  bool operator()(int exit_status) const;
+ private:
+  const int exit_code_;
+};
+
+# if !GTEST_OS_WINDOWS && !GTEST_OS_FUCHSIA
+// Tests that an exit code describes an exit due to termination by a
+// given signal.
+// GOOGLETEST_CM0006 DO NOT DELETE
+class GTEST_API_ KilledBySignal {
+ public:
+  explicit KilledBySignal(int signum);
+  bool operator()(int exit_status) const;
+ private:
+  const int signum_;
+};
+# endif  // !GTEST_OS_WINDOWS
+
+// EXPECT_DEBUG_DEATH asserts that the given statements die in debug mode.
+// The death testing framework causes this to have interesting semantics,
+// since the sideeffects of the call are only visible in opt mode, and not
+// in debug mode.
+//
+// In practice, this can be used to test functions that utilize the
+// LOG(DFATAL) macro using the following style:
+//
+// int DieInDebugOr12(int* sideeffect) {
+//   if (sideeffect) {
+//     *sideeffect = 12;
+//   }
+//   LOG(DFATAL) << "death";
+//   return 12;
+// }
+//
+// TEST(TestSuite, TestDieOr12WorksInDgbAndOpt) {
+//   int sideeffect = 0;
+//   // Only asserts in dbg.
+//   EXPECT_DEBUG_DEATH(DieInDebugOr12(&sideeffect), "death");
+//
+// #ifdef NDEBUG
+//   // opt-mode has sideeffect visible.
+//   EXPECT_EQ(12, sideeffect);
+// #else
+//   // dbg-mode no visible sideeffect.
+//   EXPECT_EQ(0, sideeffect);
+// #endif
+// }
+//
+// This will assert that DieInDebugReturn12InOpt() crashes in debug
+// mode, usually due to a DCHECK or LOG(DFATAL), but returns the
+// appropriate fallback value (12 in this case) in opt mode. If you
+// need to test that a function has appropriate side-effects in opt
+// mode, include assertions against the side-effects.  A general
+// pattern for this is:
+//
+// EXPECT_DEBUG_DEATH({
+//   // Side-effects here will have an effect after this statement in
+//   // opt mode, but none in debug mode.
+//   EXPECT_EQ(12, DieInDebugOr12(&sideeffect));
+// }, "death");
+//
+# ifdef NDEBUG
+
+#  define EXPECT_DEBUG_DEATH(statement, regex) \
+  GTEST_EXECUTE_STATEMENT_(statement, regex)
+
+#  define ASSERT_DEBUG_DEATH(statement, regex) \
+  GTEST_EXECUTE_STATEMENT_(statement, regex)
+
+# else
+
+#  define EXPECT_DEBUG_DEATH(statement, regex) \
+  EXPECT_DEATH(statement, regex)
+
+#  define ASSERT_DEBUG_DEATH(statement, regex) \
+  ASSERT_DEATH(statement, regex)
+
+# endif  // NDEBUG for EXPECT_DEBUG_DEATH
+#endif  // GTEST_HAS_DEATH_TEST
+
+// This macro is used for implementing macros such as
+// EXPECT_DEATH_IF_SUPPORTED and ASSERT_DEATH_IF_SUPPORTED on systems where
+// death tests are not supported. Those macros must compile on such systems
+// if and only if EXPECT_DEATH and ASSERT_DEATH compile with the same parameters
+// on systems that support death tests. This allows one to write such a macro on
+// a system that does not support death tests and be sure that it will compile
+// on a death-test supporting system. It is exposed publicly so that systems
+// that have death-tests with stricter requirements than GTEST_HAS_DEATH_TEST
+// can write their own equivalent of EXPECT_DEATH_IF_SUPPORTED and
+// ASSERT_DEATH_IF_SUPPORTED.
+//
+// Parameters:
+//   statement -  A statement that a macro such as EXPECT_DEATH would test
+//                for program termination. This macro has to make sure this
+//                statement is compiled but not executed, to ensure that
+//                EXPECT_DEATH_IF_SUPPORTED compiles with a certain
+//                parameter if and only if EXPECT_DEATH compiles with it.
+//   regex     -  A regex that a macro such as EXPECT_DEATH would use to test
+//                the output of statement.  This parameter has to be
+//                compiled but not evaluated by this macro, to ensure that
+//                this macro only accepts expressions that a macro such as
+//                EXPECT_DEATH would accept.
+//   terminator - Must be an empty statement for EXPECT_DEATH_IF_SUPPORTED
+//                and a return statement for ASSERT_DEATH_IF_SUPPORTED.
+//                This ensures that ASSERT_DEATH_IF_SUPPORTED will not
+//                compile inside functions where ASSERT_DEATH doesn't
+//                compile.
+//
+//  The branch that has an always false condition is used to ensure that
+//  statement and regex are compiled (and thus syntactically correct) but
+//  never executed. The unreachable code macro protects the terminator
+//  statement from generating an 'unreachable code' warning in case
+//  statement unconditionally returns or throws. The Message constructor at
+//  the end allows the syntax of streaming additional messages into the
+//  macro, for compilational compatibility with EXPECT_DEATH/ASSERT_DEATH.
+# define GTEST_UNSUPPORTED_DEATH_TEST(statement, regex, terminator) \
+    GTEST_AMBIGUOUS_ELSE_BLOCKER_ \
+    if (::testing::internal::AlwaysTrue()) { \
+      GTEST_LOG_(WARNING) \
+          << "Death tests are not supported on this platform.\n" \
+          << "Statement '" #statement "' cannot be verified."; \
+    } else if (::testing::internal::AlwaysFalse()) { \
+      ::testing::internal::RE::PartialMatch(".*", (regex)); \
+      GTEST_SUPPRESS_UNREACHABLE_CODE_WARNING_BELOW_(statement); \
+      terminator; \
+    } else \
+      ::testing::Message()
+
+// EXPECT_DEATH_IF_SUPPORTED(statement, regex) and
+// ASSERT_DEATH_IF_SUPPORTED(statement, regex) expand to real death tests if
+// death tests are supported; otherwise they just issue a warning.  This is
+// useful when you are combining death test assertions with normal test
+// assertions in one test.
+#if GTEST_HAS_DEATH_TEST
+# define EXPECT_DEATH_IF_SUPPORTED(statement, regex) \
+    EXPECT_DEATH(statement, regex)
+# define ASSERT_DEATH_IF_SUPPORTED(statement, regex) \
+    ASSERT_DEATH(statement, regex)
+#else
+# define EXPECT_DEATH_IF_SUPPORTED(statement, regex) \
+    GTEST_UNSUPPORTED_DEATH_TEST(statement, regex, )
+# define ASSERT_DEATH_IF_SUPPORTED(statement, regex) \
+    GTEST_UNSUPPORTED_DEATH_TEST(statement, regex, return)
+#endif
+
+}  // namespace testing
+
+#endif  // GOOGLETEST_INCLUDE_GTEST_GTEST_DEATH_TEST_H_
diff --git a/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-matchers.h b/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-matchers.h
new file mode 100644
index 0000000..2bd3dcf
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-matchers.h
@@ -0,0 +1,930 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// The Google C++ Testing and Mocking Framework (Google Test)
+//
+// This file implements just enough of the matcher interface to allow
+// EXPECT_DEATH and friends to accept a matcher argument.
+
+#ifndef GOOGLETEST_INCLUDE_GTEST_GTEST_MATCHERS_H_
+#define GOOGLETEST_INCLUDE_GTEST_GTEST_MATCHERS_H_
+
+#include <atomic>
+#include <memory>
+#include <ostream>
+#include <string>
+#include <type_traits>
+
+#include "gtest/gtest-printers.h"
+#include "gtest/internal/gtest-internal.h"
+#include "gtest/internal/gtest-port.h"
+
+// MSVC warning C5046 is new as of VS2017 version 15.8.
+#if defined(_MSC_VER) && _MSC_VER >= 1915
+#define GTEST_MAYBE_5046_ 5046
+#else
+#define GTEST_MAYBE_5046_
+#endif
+
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(
+    4251 GTEST_MAYBE_5046_ /* class A needs to have dll-interface to be used by
+                              clients of class B */
+    /* Symbol involving type with internal linkage not defined */)
+
+namespace testing {
+
+// To implement a matcher Foo for type T, define:
+//   1. a class FooMatcherMatcher that implements the matcher interface:
+//     using is_gtest_matcher = void;
+//     bool MatchAndExplain(const T&, std::ostream*);
+//       (MatchResultListener* can also be used instead of std::ostream*)
+//     void DescribeTo(std::ostream*);
+//     void DescribeNegationTo(std::ostream*);
+//
+//   2. a factory function that creates a Matcher<T> object from a
+//      FooMatcherMatcher.
+
+class MatchResultListener {
+ public:
+  // Creates a listener object with the given underlying ostream.  The
+  // listener does not own the ostream, and does not dereference it
+  // in the constructor or destructor.
+  explicit MatchResultListener(::std::ostream* os) : stream_(os) {}
+  virtual ~MatchResultListener() = 0;  // Makes this class abstract.
+
+  // Streams x to the underlying ostream; does nothing if the ostream
+  // is NULL.
+  template <typename T>
+  MatchResultListener& operator<<(const T& x) {
+    if (stream_ != nullptr) *stream_ << x;
+    return *this;
+  }
+
+  // Returns the underlying ostream.
+  ::std::ostream* stream() { return stream_; }
+
+  // Returns true if and only if the listener is interested in an explanation
+  // of the match result.  A matcher's MatchAndExplain() method can use
+  // this information to avoid generating the explanation when no one
+  // intends to hear it.
+  bool IsInterested() const { return stream_ != nullptr; }
+
+ private:
+  ::std::ostream* const stream_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(MatchResultListener);
+};
+
+inline MatchResultListener::~MatchResultListener() {
+}
+
+// An instance of a subclass of this knows how to describe itself as a
+// matcher.
+class MatcherDescriberInterface {
+ public:
+  virtual ~MatcherDescriberInterface() {}
+
+  // Describes this matcher to an ostream.  The function should print
+  // a verb phrase that describes the property a value matching this
+  // matcher should have.  The subject of the verb phrase is the value
+  // being matched.  For example, the DescribeTo() method of the Gt(7)
+  // matcher prints "is greater than 7".
+  virtual void DescribeTo(::std::ostream* os) const = 0;
+
+  // Describes the negation of this matcher to an ostream.  For
+  // example, if the description of this matcher is "is greater than
+  // 7", the negated description could be "is not greater than 7".
+  // You are not required to override this when implementing
+  // MatcherInterface, but it is highly advised so that your matcher
+  // can produce good error messages.
+  virtual void DescribeNegationTo(::std::ostream* os) const {
+    *os << "not (";
+    DescribeTo(os);
+    *os << ")";
+  }
+};
+
+// The implementation of a matcher.
+template <typename T>
+class MatcherInterface : public MatcherDescriberInterface {
+ public:
+  // Returns true if and only if the matcher matches x; also explains the
+  // match result to 'listener' if necessary (see the next paragraph), in
+  // the form of a non-restrictive relative clause ("which ...",
+  // "whose ...", etc) that describes x.  For example, the
+  // MatchAndExplain() method of the Pointee(...) matcher should
+  // generate an explanation like "which points to ...".
+  //
+  // Implementations of MatchAndExplain() should add an explanation of
+  // the match result *if and only if* they can provide additional
+  // information that's not already present (or not obvious) in the
+  // print-out of x and the matcher's description.  Whether the match
+  // succeeds is not a factor in deciding whether an explanation is
+  // needed, as sometimes the caller needs to print a failure message
+  // when the match succeeds (e.g. when the matcher is used inside
+  // Not()).
+  //
+  // For example, a "has at least 10 elements" matcher should explain
+  // what the actual element count is, regardless of the match result,
+  // as it is useful information to the reader; on the other hand, an
+  // "is empty" matcher probably only needs to explain what the actual
+  // size is when the match fails, as it's redundant to say that the
+  // size is 0 when the value is already known to be empty.
+  //
+  // You should override this method when defining a new matcher.
+  //
+  // It's the responsibility of the caller (Google Test) to guarantee
+  // that 'listener' is not NULL.  This helps to simplify a matcher's
+  // implementation when it doesn't care about the performance, as it
+  // can talk to 'listener' without checking its validity first.
+  // However, in order to implement dummy listeners efficiently,
+  // listener->stream() may be NULL.
+  virtual bool MatchAndExplain(T x, MatchResultListener* listener) const = 0;
+
+  // Inherits these methods from MatcherDescriberInterface:
+  //   virtual void DescribeTo(::std::ostream* os) const = 0;
+  //   virtual void DescribeNegationTo(::std::ostream* os) const;
+};
+
+namespace internal {
+
+struct AnyEq {
+  template <typename A, typename B>
+  bool operator()(const A& a, const B& b) const { return a == b; }
+};
+struct AnyNe {
+  template <typename A, typename B>
+  bool operator()(const A& a, const B& b) const { return a != b; }
+};
+struct AnyLt {
+  template <typename A, typename B>
+  bool operator()(const A& a, const B& b) const { return a < b; }
+};
+struct AnyGt {
+  template <typename A, typename B>
+  bool operator()(const A& a, const B& b) const { return a > b; }
+};
+struct AnyLe {
+  template <typename A, typename B>
+  bool operator()(const A& a, const B& b) const { return a <= b; }
+};
+struct AnyGe {
+  template <typename A, typename B>
+  bool operator()(const A& a, const B& b) const { return a >= b; }
+};
+
+// A match result listener that ignores the explanation.
+class DummyMatchResultListener : public MatchResultListener {
+ public:
+  DummyMatchResultListener() : MatchResultListener(nullptr) {}
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(DummyMatchResultListener);
+};
+
+// A match result listener that forwards the explanation to a given
+// ostream.  The difference between this and MatchResultListener is
+// that the former is concrete.
+class StreamMatchResultListener : public MatchResultListener {
+ public:
+  explicit StreamMatchResultListener(::std::ostream* os)
+      : MatchResultListener(os) {}
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(StreamMatchResultListener);
+};
+
+struct SharedPayloadBase {
+  std::atomic<int> ref{1};
+  void Ref() { ref.fetch_add(1, std::memory_order_relaxed); }
+  bool Unref() { return ref.fetch_sub(1, std::memory_order_acq_rel) == 1; }
+};
+
+template <typename T>
+struct SharedPayload : SharedPayloadBase {
+  explicit SharedPayload(const T& v) : value(v) {}
+  explicit SharedPayload(T&& v) : value(std::move(v)) {}
+
+  static void Destroy(SharedPayloadBase* shared) {
+    delete static_cast<SharedPayload*>(shared);
+  }
+
+  T value;
+};
+
+// An internal class for implementing Matcher<T>, which will derive
+// from it.  We put functionalities common to all Matcher<T>
+// specializations here to avoid code duplication.
+template <typename T>
+class MatcherBase : private MatcherDescriberInterface {
+ public:
+  // Returns true if and only if the matcher matches x; also explains the
+  // match result to 'listener'.
+  bool MatchAndExplain(const T& x, MatchResultListener* listener) const {
+    GTEST_CHECK_(vtable_ != nullptr);
+    return vtable_->match_and_explain(*this, x, listener);
+  }
+
+  // Returns true if and only if this matcher matches x.
+  bool Matches(const T& x) const {
+    DummyMatchResultListener dummy;
+    return MatchAndExplain(x, &dummy);
+  }
+
+  // Describes this matcher to an ostream.
+  void DescribeTo(::std::ostream* os) const final {
+    GTEST_CHECK_(vtable_ != nullptr);
+    vtable_->describe(*this, os, false);
+  }
+
+  // Describes the negation of this matcher to an ostream.
+  void DescribeNegationTo(::std::ostream* os) const final {
+    GTEST_CHECK_(vtable_ != nullptr);
+    vtable_->describe(*this, os, true);
+  }
+
+  // Explains why x matches, or doesn't match, the matcher.
+  void ExplainMatchResultTo(const T& x, ::std::ostream* os) const {
+    StreamMatchResultListener listener(os);
+    MatchAndExplain(x, &listener);
+  }
+
+  // Returns the describer for this matcher object; retains ownership
+  // of the describer, which is only guaranteed to be alive when
+  // this matcher object is alive.
+  const MatcherDescriberInterface* GetDescriber() const {
+    if (vtable_ == nullptr) return nullptr;
+    return vtable_->get_describer(*this);
+  }
+
+ protected:
+  MatcherBase() : vtable_(nullptr) {}
+
+  // Constructs a matcher from its implementation.
+  template <typename U>
+  explicit MatcherBase(const MatcherInterface<U>* impl) {
+    Init(impl);
+  }
+
+  template <typename M, typename = typename std::remove_reference<
+                            M>::type::is_gtest_matcher>
+  MatcherBase(M&& m) {  // NOLINT
+    Init(std::forward<M>(m));
+  }
+
+  MatcherBase(const MatcherBase& other)
+      : vtable_(other.vtable_), buffer_(other.buffer_) {
+    if (IsShared()) buffer_.shared->Ref();
+  }
+
+  MatcherBase& operator=(const MatcherBase& other) {
+    if (this == &other) return *this;
+    Destroy();
+    vtable_ = other.vtable_;
+    buffer_ = other.buffer_;
+    if (IsShared()) buffer_.shared->Ref();
+    return *this;
+  }
+
+  MatcherBase(MatcherBase&& other)
+      : vtable_(other.vtable_), buffer_(other.buffer_) {
+    other.vtable_ = nullptr;
+  }
+
+  MatcherBase& operator=(MatcherBase&& other) {
+    if (this == &other) return *this;
+    Destroy();
+    vtable_ = other.vtable_;
+    buffer_ = other.buffer_;
+    other.vtable_ = nullptr;
+    return *this;
+  }
+
+  ~MatcherBase() override { Destroy(); }
+
+ private:
+  struct VTable {
+    bool (*match_and_explain)(const MatcherBase&, const T&,
+                              MatchResultListener*);
+    void (*describe)(const MatcherBase&, std::ostream*, bool negation);
+    // Returns the captured object if it implements the interface, otherwise
+    // returns the MatcherBase itself.
+    const MatcherDescriberInterface* (*get_describer)(const MatcherBase&);
+    // Called on shared instances when the reference count reaches 0.
+    void (*shared_destroy)(SharedPayloadBase*);
+  };
+
+  bool IsShared() const {
+    return vtable_ != nullptr && vtable_->shared_destroy != nullptr;
+  }
+
+  // If the implementation uses a listener, call that.
+  template <typename P>
+  static auto MatchAndExplainImpl(const MatcherBase& m, const T& value,
+                                  MatchResultListener* listener)
+      -> decltype(P::Get(m).MatchAndExplain(value, listener->stream())) {
+    return P::Get(m).MatchAndExplain(value, listener->stream());
+  }
+
+  template <typename P>
+  static auto MatchAndExplainImpl(const MatcherBase& m, const T& value,
+                                  MatchResultListener* listener)
+      -> decltype(P::Get(m).MatchAndExplain(value, listener)) {
+    return P::Get(m).MatchAndExplain(value, listener);
+  }
+
+  template <typename P>
+  static void DescribeImpl(const MatcherBase& m, std::ostream* os,
+                           bool negation) {
+    if (negation) {
+      P::Get(m).DescribeNegationTo(os);
+    } else {
+      P::Get(m).DescribeTo(os);
+    }
+  }
+
+  template <typename P>
+  static const MatcherDescriberInterface* GetDescriberImpl(
+      const MatcherBase& m) {
+    // If the impl is a MatcherDescriberInterface, then return it.
+    // Otherwise use MatcherBase itself.
+    // This allows us to implement the GetDescriber() function without support
+    // from the impl, but some users really want to get their impl back when
+    // they call GetDescriber().
+    // We use std::get on a tuple as a workaround of not having `if constexpr`.
+    return std::get<(
+        std::is_convertible<decltype(&P::Get(m)),
+                            const MatcherDescriberInterface*>::value
+            ? 1
+            : 0)>(std::make_tuple(&m, &P::Get(m)));
+  }
+
+  template <typename P>
+  const VTable* GetVTable() {
+    static constexpr VTable kVTable = {&MatchAndExplainImpl<P>,
+                                       &DescribeImpl<P>, &GetDescriberImpl<P>,
+                                       P::shared_destroy};
+    return &kVTable;
+  }
+
+  union Buffer {
+    // Add some types to give Buffer some common alignment/size use cases.
+    void* ptr;
+    double d;
+    int64_t i;
+    // And add one for the out-of-line cases.
+    SharedPayloadBase* shared;
+  };
+
+  void Destroy() {
+    if (IsShared() && buffer_.shared->Unref()) {
+      vtable_->shared_destroy(buffer_.shared);
+    }
+  }
+
+  template <typename M>
+  static constexpr bool IsInlined() {
+    return sizeof(M) <= sizeof(Buffer) && alignof(M) <= alignof(Buffer) &&
+           std::is_trivially_copy_constructible<M>::value &&
+           std::is_trivially_destructible<M>::value;
+  }
+
+  template <typename M, bool = MatcherBase::IsInlined<M>()>
+  struct ValuePolicy {
+    static const M& Get(const MatcherBase& m) {
+      // When inlined along with Init, need to be explicit to avoid violating
+      // strict aliasing rules.
+      const M *ptr = static_cast<const M*>(
+          static_cast<const void*>(&m.buffer_));
+      return *ptr;
+    }
+    static void Init(MatcherBase& m, M impl) {
+      ::new (static_cast<void*>(&m.buffer_)) M(impl);
+    }
+    static constexpr auto shared_destroy = nullptr;
+  };
+
+  template <typename M>
+  struct ValuePolicy<M, false> {
+    using Shared = SharedPayload<M>;
+    static const M& Get(const MatcherBase& m) {
+      return static_cast<Shared*>(m.buffer_.shared)->value;
+    }
+    template <typename Arg>
+    static void Init(MatcherBase& m, Arg&& arg) {
+      m.buffer_.shared = new Shared(std::forward<Arg>(arg));
+    }
+    static constexpr auto shared_destroy = &Shared::Destroy;
+  };
+
+  template <typename U, bool B>
+  struct ValuePolicy<const MatcherInterface<U>*, B> {
+    using M = const MatcherInterface<U>;
+    using Shared = SharedPayload<std::unique_ptr<M>>;
+    static const M& Get(const MatcherBase& m) {
+      return *static_cast<Shared*>(m.buffer_.shared)->value;
+    }
+    static void Init(MatcherBase& m, M* impl) {
+      m.buffer_.shared = new Shared(std::unique_ptr<M>(impl));
+    }
+
+    static constexpr auto shared_destroy = &Shared::Destroy;
+  };
+
+  template <typename M>
+  void Init(M&& m) {
+    using MM = typename std::decay<M>::type;
+    using Policy = ValuePolicy<MM>;
+    vtable_ = GetVTable<Policy>();
+    Policy::Init(*this, std::forward<M>(m));
+  }
+
+  const VTable* vtable_;
+  Buffer buffer_;
+};
+
+}  // namespace internal
+
+// A Matcher<T> is a copyable and IMMUTABLE (except by assignment)
+// object that can check whether a value of type T matches.  The
+// implementation of Matcher<T> is just a std::shared_ptr to const
+// MatcherInterface<T>.  Don't inherit from Matcher!
+template <typename T>
+class Matcher : public internal::MatcherBase<T> {
+ public:
+  // Constructs a null matcher.  Needed for storing Matcher objects in STL
+  // containers.  A default-constructed matcher is not yet initialized.  You
+  // cannot use it until a valid value has been assigned to it.
+  explicit Matcher() {}  // NOLINT
+
+  // Constructs a matcher from its implementation.
+  explicit Matcher(const MatcherInterface<const T&>* impl)
+      : internal::MatcherBase<T>(impl) {}
+
+  template <typename U>
+  explicit Matcher(
+      const MatcherInterface<U>* impl,
+      typename std::enable_if<!std::is_same<U, const U&>::value>::type* =
+          nullptr)
+      : internal::MatcherBase<T>(impl) {}
+
+  template <typename M, typename = typename std::remove_reference<
+                            M>::type::is_gtest_matcher>
+  Matcher(M&& m) : internal::MatcherBase<T>(std::forward<M>(m)) {}  // NOLINT
+
+  // Implicit constructor here allows people to write
+  // EXPECT_CALL(foo, Bar(5)) instead of EXPECT_CALL(foo, Bar(Eq(5))) sometimes
+  Matcher(T value);  // NOLINT
+};
+
+// The following two specializations allow the user to write str
+// instead of Eq(str) and "foo" instead of Eq("foo") when a std::string
+// matcher is expected.
+template <>
+class GTEST_API_ Matcher<const std::string&>
+    : public internal::MatcherBase<const std::string&> {
+ public:
+  Matcher() {}
+
+  explicit Matcher(const MatcherInterface<const std::string&>* impl)
+      : internal::MatcherBase<const std::string&>(impl) {}
+
+  template <typename M, typename = typename std::remove_reference<
+                            M>::type::is_gtest_matcher>
+  Matcher(M&& m)  // NOLINT
+      : internal::MatcherBase<const std::string&>(std::forward<M>(m)) {}
+
+  // Allows the user to write str instead of Eq(str) sometimes, where
+  // str is a std::string object.
+  Matcher(const std::string& s);  // NOLINT
+
+  // Allows the user to write "foo" instead of Eq("foo") sometimes.
+  Matcher(const char* s);  // NOLINT
+};
+
+template <>
+class GTEST_API_ Matcher<std::string>
+    : public internal::MatcherBase<std::string> {
+ public:
+  Matcher() {}
+
+  explicit Matcher(const MatcherInterface<const std::string&>* impl)
+      : internal::MatcherBase<std::string>(impl) {}
+  explicit Matcher(const MatcherInterface<std::string>* impl)
+      : internal::MatcherBase<std::string>(impl) {}
+
+  template <typename M, typename = typename std::remove_reference<
+                            M>::type::is_gtest_matcher>
+  Matcher(M&& m)  // NOLINT
+      : internal::MatcherBase<std::string>(std::forward<M>(m)) {}
+
+  // Allows the user to write str instead of Eq(str) sometimes, where
+  // str is a string object.
+  Matcher(const std::string& s);  // NOLINT
+
+  // Allows the user to write "foo" instead of Eq("foo") sometimes.
+  Matcher(const char* s);  // NOLINT
+};
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+// The following two specializations allow the user to write str
+// instead of Eq(str) and "foo" instead of Eq("foo") when a absl::string_view
+// matcher is expected.
+template <>
+class GTEST_API_ Matcher<const internal::StringView&>
+    : public internal::MatcherBase<const internal::StringView&> {
+ public:
+  Matcher() {}
+
+  explicit Matcher(const MatcherInterface<const internal::StringView&>* impl)
+      : internal::MatcherBase<const internal::StringView&>(impl) {}
+
+  template <typename M, typename = typename std::remove_reference<
+                            M>::type::is_gtest_matcher>
+  Matcher(M&& m)  // NOLINT
+      : internal::MatcherBase<const internal::StringView&>(std::forward<M>(m)) {
+  }
+
+  // Allows the user to write str instead of Eq(str) sometimes, where
+  // str is a std::string object.
+  Matcher(const std::string& s);  // NOLINT
+
+  // Allows the user to write "foo" instead of Eq("foo") sometimes.
+  Matcher(const char* s);  // NOLINT
+
+  // Allows the user to pass absl::string_views or std::string_views directly.
+  Matcher(internal::StringView s);  // NOLINT
+};
+
+template <>
+class GTEST_API_ Matcher<internal::StringView>
+    : public internal::MatcherBase<internal::StringView> {
+ public:
+  Matcher() {}
+
+  explicit Matcher(const MatcherInterface<const internal::StringView&>* impl)
+      : internal::MatcherBase<internal::StringView>(impl) {}
+  explicit Matcher(const MatcherInterface<internal::StringView>* impl)
+      : internal::MatcherBase<internal::StringView>(impl) {}
+
+  template <typename M, typename = typename std::remove_reference<
+                            M>::type::is_gtest_matcher>
+  Matcher(M&& m)  // NOLINT
+      : internal::MatcherBase<internal::StringView>(std::forward<M>(m)) {}
+
+  // Allows the user to write str instead of Eq(str) sometimes, where
+  // str is a std::string object.
+  Matcher(const std::string& s);  // NOLINT
+
+  // Allows the user to write "foo" instead of Eq("foo") sometimes.
+  Matcher(const char* s);  // NOLINT
+
+  // Allows the user to pass absl::string_views or std::string_views directly.
+  Matcher(internal::StringView s);  // NOLINT
+};
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+
+// Prints a matcher in a human-readable format.
+template <typename T>
+std::ostream& operator<<(std::ostream& os, const Matcher<T>& matcher) {
+  matcher.DescribeTo(&os);
+  return os;
+}
+
+// The PolymorphicMatcher class template makes it easy to implement a
+// polymorphic matcher (i.e. a matcher that can match values of more
+// than one type, e.g. Eq(n) and NotNull()).
+//
+// To define a polymorphic matcher, a user should provide an Impl
+// class that has a DescribeTo() method and a DescribeNegationTo()
+// method, and define a member function (or member function template)
+//
+//   bool MatchAndExplain(const Value& value,
+//                        MatchResultListener* listener) const;
+//
+// See the definition of NotNull() for a complete example.
+template <class Impl>
+class PolymorphicMatcher {
+ public:
+  explicit PolymorphicMatcher(const Impl& an_impl) : impl_(an_impl) {}
+
+  // Returns a mutable reference to the underlying matcher
+  // implementation object.
+  Impl& mutable_impl() { return impl_; }
+
+  // Returns an immutable reference to the underlying matcher
+  // implementation object.
+  const Impl& impl() const { return impl_; }
+
+  template <typename T>
+  operator Matcher<T>() const {
+    return Matcher<T>(new MonomorphicImpl<const T&>(impl_));
+  }
+
+ private:
+  template <typename T>
+  class MonomorphicImpl : public MatcherInterface<T> {
+   public:
+    explicit MonomorphicImpl(const Impl& impl) : impl_(impl) {}
+
+    void DescribeTo(::std::ostream* os) const override { impl_.DescribeTo(os); }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      impl_.DescribeNegationTo(os);
+    }
+
+    bool MatchAndExplain(T x, MatchResultListener* listener) const override {
+      return impl_.MatchAndExplain(x, listener);
+    }
+
+   private:
+    const Impl impl_;
+  };
+
+  Impl impl_;
+};
+
+// Creates a matcher from its implementation.
+// DEPRECATED: Especially in the generic code, prefer:
+//   Matcher<T>(new MyMatcherImpl<const T&>(...));
+//
+// MakeMatcher may create a Matcher that accepts its argument by value, which
+// leads to unnecessary copies & lack of support for non-copyable types.
+template <typename T>
+inline Matcher<T> MakeMatcher(const MatcherInterface<T>* impl) {
+  return Matcher<T>(impl);
+}
+
+// Creates a polymorphic matcher from its implementation.  This is
+// easier to use than the PolymorphicMatcher<Impl> constructor as it
+// doesn't require you to explicitly write the template argument, e.g.
+//
+//   MakePolymorphicMatcher(foo);
+// vs
+//   PolymorphicMatcher<TypeOfFoo>(foo);
+template <class Impl>
+inline PolymorphicMatcher<Impl> MakePolymorphicMatcher(const Impl& impl) {
+  return PolymorphicMatcher<Impl>(impl);
+}
+
+namespace internal {
+// Implements a matcher that compares a given value with a
+// pre-supplied value using one of the ==, <=, <, etc, operators.  The
+// two values being compared don't have to have the same type.
+//
+// The matcher defined here is polymorphic (for example, Eq(5) can be
+// used to match an int, a short, a double, etc).  Therefore we use
+// a template type conversion operator in the implementation.
+//
+// The following template definition assumes that the Rhs parameter is
+// a "bare" type (i.e. neither 'const T' nor 'T&').
+template <typename D, typename Rhs, typename Op>
+class ComparisonBase {
+ public:
+  explicit ComparisonBase(const Rhs& rhs) : rhs_(rhs) {}
+
+  using is_gtest_matcher = void;
+
+  template <typename Lhs>
+  bool MatchAndExplain(const Lhs& lhs, std::ostream*) const {
+    return Op()(lhs, Unwrap(rhs_));
+  }
+  void DescribeTo(std::ostream* os) const {
+    *os << D::Desc() << " ";
+    UniversalPrint(Unwrap(rhs_), os);
+  }
+  void DescribeNegationTo(std::ostream* os) const {
+    *os << D::NegatedDesc() << " ";
+    UniversalPrint(Unwrap(rhs_), os);
+  }
+
+ private:
+  template <typename T>
+  static const T& Unwrap(const T& v) {
+    return v;
+  }
+  template <typename T>
+  static const T& Unwrap(std::reference_wrapper<T> v) {
+    return v;
+  }
+
+  Rhs rhs_;
+};
+
+template <typename Rhs>
+class EqMatcher : public ComparisonBase<EqMatcher<Rhs>, Rhs, AnyEq> {
+ public:
+  explicit EqMatcher(const Rhs& rhs)
+      : ComparisonBase<EqMatcher<Rhs>, Rhs, AnyEq>(rhs) { }
+  static const char* Desc() { return "is equal to"; }
+  static const char* NegatedDesc() { return "isn't equal to"; }
+};
+template <typename Rhs>
+class NeMatcher : public ComparisonBase<NeMatcher<Rhs>, Rhs, AnyNe> {
+ public:
+  explicit NeMatcher(const Rhs& rhs)
+      : ComparisonBase<NeMatcher<Rhs>, Rhs, AnyNe>(rhs) { }
+  static const char* Desc() { return "isn't equal to"; }
+  static const char* NegatedDesc() { return "is equal to"; }
+};
+template <typename Rhs>
+class LtMatcher : public ComparisonBase<LtMatcher<Rhs>, Rhs, AnyLt> {
+ public:
+  explicit LtMatcher(const Rhs& rhs)
+      : ComparisonBase<LtMatcher<Rhs>, Rhs, AnyLt>(rhs) { }
+  static const char* Desc() { return "is <"; }
+  static const char* NegatedDesc() { return "isn't <"; }
+};
+template <typename Rhs>
+class GtMatcher : public ComparisonBase<GtMatcher<Rhs>, Rhs, AnyGt> {
+ public:
+  explicit GtMatcher(const Rhs& rhs)
+      : ComparisonBase<GtMatcher<Rhs>, Rhs, AnyGt>(rhs) { }
+  static const char* Desc() { return "is >"; }
+  static const char* NegatedDesc() { return "isn't >"; }
+};
+template <typename Rhs>
+class LeMatcher : public ComparisonBase<LeMatcher<Rhs>, Rhs, AnyLe> {
+ public:
+  explicit LeMatcher(const Rhs& rhs)
+      : ComparisonBase<LeMatcher<Rhs>, Rhs, AnyLe>(rhs) { }
+  static const char* Desc() { return "is <="; }
+  static const char* NegatedDesc() { return "isn't <="; }
+};
+template <typename Rhs>
+class GeMatcher : public ComparisonBase<GeMatcher<Rhs>, Rhs, AnyGe> {
+ public:
+  explicit GeMatcher(const Rhs& rhs)
+      : ComparisonBase<GeMatcher<Rhs>, Rhs, AnyGe>(rhs) { }
+  static const char* Desc() { return "is >="; }
+  static const char* NegatedDesc() { return "isn't >="; }
+};
+
+template <typename T, typename = typename std::enable_if<
+                          std::is_constructible<std::string, T>::value>::type>
+using StringLike = T;
+
+// Implements polymorphic matchers MatchesRegex(regex) and
+// ContainsRegex(regex), which can be used as a Matcher<T> as long as
+// T can be converted to a string.
+class MatchesRegexMatcher {
+ public:
+  MatchesRegexMatcher(const RE* regex, bool full_match)
+      : regex_(regex), full_match_(full_match) {}
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  bool MatchAndExplain(const internal::StringView& s,
+                       MatchResultListener* listener) const {
+    return MatchAndExplain(std::string(s), listener);
+  }
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+
+  // Accepts pointer types, particularly:
+  //   const char*
+  //   char*
+  //   const wchar_t*
+  //   wchar_t*
+  template <typename CharType>
+  bool MatchAndExplain(CharType* s, MatchResultListener* listener) const {
+    return s != nullptr && MatchAndExplain(std::string(s), listener);
+  }
+
+  // Matches anything that can convert to std::string.
+  //
+  // This is a template, not just a plain function with const std::string&,
+  // because absl::string_view has some interfering non-explicit constructors.
+  template <class MatcheeStringType>
+  bool MatchAndExplain(const MatcheeStringType& s,
+                       MatchResultListener* /* listener */) const {
+    const std::string& s2(s);
+    return full_match_ ? RE::FullMatch(s2, *regex_)
+                       : RE::PartialMatch(s2, *regex_);
+  }
+
+  void DescribeTo(::std::ostream* os) const {
+    *os << (full_match_ ? "matches" : "contains") << " regular expression ";
+    UniversalPrinter<std::string>::Print(regex_->pattern(), os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "doesn't " << (full_match_ ? "match" : "contain")
+        << " regular expression ";
+    UniversalPrinter<std::string>::Print(regex_->pattern(), os);
+  }
+
+ private:
+  const std::shared_ptr<const RE> regex_;
+  const bool full_match_;
+};
+}  // namespace internal
+
+// Matches a string that fully matches regular expression 'regex'.
+// The matcher takes ownership of 'regex'.
+inline PolymorphicMatcher<internal::MatchesRegexMatcher> MatchesRegex(
+    const internal::RE* regex) {
+  return MakePolymorphicMatcher(internal::MatchesRegexMatcher(regex, true));
+}
+template <typename T = std::string>
+PolymorphicMatcher<internal::MatchesRegexMatcher> MatchesRegex(
+    const internal::StringLike<T>& regex) {
+  return MatchesRegex(new internal::RE(std::string(regex)));
+}
+
+// Matches a string that contains regular expression 'regex'.
+// The matcher takes ownership of 'regex'.
+inline PolymorphicMatcher<internal::MatchesRegexMatcher> ContainsRegex(
+    const internal::RE* regex) {
+  return MakePolymorphicMatcher(internal::MatchesRegexMatcher(regex, false));
+}
+template <typename T = std::string>
+PolymorphicMatcher<internal::MatchesRegexMatcher> ContainsRegex(
+    const internal::StringLike<T>& regex) {
+  return ContainsRegex(new internal::RE(std::string(regex)));
+}
+
+// Creates a polymorphic matcher that matches anything equal to x.
+// Note: if the parameter of Eq() were declared as const T&, Eq("foo")
+// wouldn't compile.
+template <typename T>
+inline internal::EqMatcher<T> Eq(T x) { return internal::EqMatcher<T>(x); }
+
+// Constructs a Matcher<T> from a 'value' of type T.  The constructed
+// matcher matches any value that's equal to 'value'.
+template <typename T>
+Matcher<T>::Matcher(T value) { *this = Eq(value); }
+
+// Creates a monomorphic matcher that matches anything with type Lhs
+// and equal to rhs.  A user may need to use this instead of Eq(...)
+// in order to resolve an overloading ambiguity.
+//
+// TypedEq<T>(x) is just a convenient short-hand for Matcher<T>(Eq(x))
+// or Matcher<T>(x), but more readable than the latter.
+//
+// We could define similar monomorphic matchers for other comparison
+// operations (e.g. TypedLt, TypedGe, and etc), but decided not to do
+// it yet as those are used much less than Eq() in practice.  A user
+// can always write Matcher<T>(Lt(5)) to be explicit about the type,
+// for example.
+template <typename Lhs, typename Rhs>
+inline Matcher<Lhs> TypedEq(const Rhs& rhs) { return Eq(rhs); }
+
+// Creates a polymorphic matcher that matches anything >= x.
+template <typename Rhs>
+inline internal::GeMatcher<Rhs> Ge(Rhs x) {
+  return internal::GeMatcher<Rhs>(x);
+}
+
+// Creates a polymorphic matcher that matches anything > x.
+template <typename Rhs>
+inline internal::GtMatcher<Rhs> Gt(Rhs x) {
+  return internal::GtMatcher<Rhs>(x);
+}
+
+// Creates a polymorphic matcher that matches anything <= x.
+template <typename Rhs>
+inline internal::LeMatcher<Rhs> Le(Rhs x) {
+  return internal::LeMatcher<Rhs>(x);
+}
+
+// Creates a polymorphic matcher that matches anything < x.
+template <typename Rhs>
+inline internal::LtMatcher<Rhs> Lt(Rhs x) {
+  return internal::LtMatcher<Rhs>(x);
+}
+
+// Creates a polymorphic matcher that matches anything != x.
+template <typename Rhs>
+inline internal::NeMatcher<Rhs> Ne(Rhs x) {
+  return internal::NeMatcher<Rhs>(x);
+}
+}  // namespace testing
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  //  4251 5046
+
+#endif  // GOOGLETEST_INCLUDE_GTEST_GTEST_MATCHERS_H_
diff --git a/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-message.h b/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-message.h
new file mode 100644
index 0000000..becfd49
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-message.h
@@ -0,0 +1,219 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// The Google C++ Testing and Mocking Framework (Google Test)
+//
+// This header file defines the Message class.
+//
+// IMPORTANT NOTE: Due to limitation of the C++ language, we have to
+// leave some internal implementation details in this header file.
+// They are clearly marked by comments like this:
+//
+//   // INTERNAL IMPLEMENTATION - DO NOT USE IN A USER PROGRAM.
+//
+// Such code is NOT meant to be used by a user directly, and is subject
+// to CHANGE WITHOUT NOTICE.  Therefore DO NOT DEPEND ON IT in a user
+// program!
+
+// GOOGLETEST_CM0001 DO NOT DELETE
+
+#ifndef GOOGLETEST_INCLUDE_GTEST_GTEST_MESSAGE_H_
+#define GOOGLETEST_INCLUDE_GTEST_GTEST_MESSAGE_H_
+
+#include <limits>
+#include <memory>
+#include <sstream>
+
+#include "gtest/internal/gtest-port.h"
+
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4251 \
+/* class A needs to have dll-interface to be used by clients of class B */)
+
+// Ensures that there is at least one operator<< in the global namespace.
+// See Message& operator<<(...) below for why.
+void operator<<(const testing::internal::Secret&, int);
+
+namespace testing {
+
+// The Message class works like an ostream repeater.
+//
+// Typical usage:
+//
+//   1. You stream a bunch of values to a Message object.
+//      It will remember the text in a stringstream.
+//   2. Then you stream the Message object to an ostream.
+//      This causes the text in the Message to be streamed
+//      to the ostream.
+//
+// For example;
+//
+//   testing::Message foo;
+//   foo << 1 << " != " << 2;
+//   std::cout << foo;
+//
+// will print "1 != 2".
+//
+// Message is not intended to be inherited from.  In particular, its
+// destructor is not virtual.
+//
+// Note that stringstream behaves differently in gcc and in MSVC.  You
+// can stream a NULL char pointer to it in the former, but not in the
+// latter (it causes an access violation if you do).  The Message
+// class hides this difference by treating a NULL char pointer as
+// "(null)".
+class GTEST_API_ Message {
+ private:
+  // The type of basic IO manipulators (endl, ends, and flush) for
+  // narrow streams.
+  typedef std::ostream& (*BasicNarrowIoManip)(std::ostream&);
+
+ public:
+  // Constructs an empty Message.
+  Message();
+
+  // Copy constructor.
+  Message(const Message& msg) : ss_(new ::std::stringstream) {  // NOLINT
+    *ss_ << msg.GetString();
+  }
+
+  // Constructs a Message from a C-string.
+  explicit Message(const char* str) : ss_(new ::std::stringstream) {
+    *ss_ << str;
+  }
+
+  // Streams a non-pointer value to this object.
+  template <typename T>
+  inline Message& operator <<(const T& val) {
+    // Some libraries overload << for STL containers.  These
+    // overloads are defined in the global namespace instead of ::std.
+    //
+    // C++'s symbol lookup rule (i.e. Koenig lookup) says that these
+    // overloads are visible in either the std namespace or the global
+    // namespace, but not other namespaces, including the testing
+    // namespace which Google Test's Message class is in.
+    //
+    // To allow STL containers (and other types that has a << operator
+    // defined in the global namespace) to be used in Google Test
+    // assertions, testing::Message must access the custom << operator
+    // from the global namespace.  With this using declaration,
+    // overloads of << defined in the global namespace and those
+    // visible via Koenig lookup are both exposed in this function.
+    using ::operator <<;
+    *ss_ << val;
+    return *this;
+  }
+
+  // Streams a pointer value to this object.
+  //
+  // This function is an overload of the previous one.  When you
+  // stream a pointer to a Message, this definition will be used as it
+  // is more specialized.  (The C++ Standard, section
+  // [temp.func.order].)  If you stream a non-pointer, then the
+  // previous definition will be used.
+  //
+  // The reason for this overload is that streaming a NULL pointer to
+  // ostream is undefined behavior.  Depending on the compiler, you
+  // may get "0", "(nil)", "(null)", or an access violation.  To
+  // ensure consistent result across compilers, we always treat NULL
+  // as "(null)".
+  template <typename T>
+  inline Message& operator <<(T* const& pointer) {  // NOLINT
+    if (pointer == nullptr) {
+      *ss_ << "(null)";
+    } else {
+      *ss_ << pointer;
+    }
+    return *this;
+  }
+
+  // Since the basic IO manipulators are overloaded for both narrow
+  // and wide streams, we have to provide this specialized definition
+  // of operator <<, even though its body is the same as the
+  // templatized version above.  Without this definition, streaming
+  // endl or other basic IO manipulators to Message will confuse the
+  // compiler.
+  Message& operator <<(BasicNarrowIoManip val) {
+    *ss_ << val;
+    return *this;
+  }
+
+  // Instead of 1/0, we want to see true/false for bool values.
+  Message& operator <<(bool b) {
+    return *this << (b ? "true" : "false");
+  }
+
+  // These two overloads allow streaming a wide C string to a Message
+  // using the UTF-8 encoding.
+  Message& operator <<(const wchar_t* wide_c_str);
+  Message& operator <<(wchar_t* wide_c_str);
+
+#if GTEST_HAS_STD_WSTRING
+  // Converts the given wide string to a narrow string using the UTF-8
+  // encoding, and streams the result to this Message object.
+  Message& operator <<(const ::std::wstring& wstr);
+#endif  // GTEST_HAS_STD_WSTRING
+
+  // Gets the text streamed to this object so far as an std::string.
+  // Each '\0' character in the buffer is replaced with "\\0".
+  //
+  // INTERNAL IMPLEMENTATION - DO NOT USE IN A USER PROGRAM.
+  std::string GetString() const;
+
+ private:
+  // We'll hold the text streamed to this object here.
+  const std::unique_ptr< ::std::stringstream> ss_;
+
+  // We declare (but don't implement) this to prevent the compiler
+  // from implementing the assignment operator.
+  void operator=(const Message&);
+};
+
+// Streams a Message to an ostream.
+inline std::ostream& operator <<(std::ostream& os, const Message& sb) {
+  return os << sb.GetString();
+}
+
+namespace internal {
+
+// Converts a streamable value to an std::string.  A NULL pointer is
+// converted to "(null)".  When the input value is a ::string,
+// ::std::string, ::wstring, or ::std::wstring object, each NUL
+// character in it is replaced with "\\0".
+template <typename T>
+std::string StreamableToString(const T& streamable) {
+  return (Message() << streamable).GetString();
+}
+
+}  // namespace internal
+}  // namespace testing
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  //  4251
+
+#endif  // GOOGLETEST_INCLUDE_GTEST_GTEST_MESSAGE_H_
diff --git a/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-param-test.h b/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-param-test.h
new file mode 100644
index 0000000..804e702
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-param-test.h
@@ -0,0 +1,507 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// Macros and functions for implementing parameterized tests
+// in Google C++ Testing and Mocking Framework (Google Test)
+//
+// GOOGLETEST_CM0001 DO NOT DELETE
+#ifndef GOOGLETEST_INCLUDE_GTEST_GTEST_PARAM_TEST_H_
+#define GOOGLETEST_INCLUDE_GTEST_GTEST_PARAM_TEST_H_
+
+// Value-parameterized tests allow you to test your code with different
+// parameters without writing multiple copies of the same test.
+//
+// Here is how you use value-parameterized tests:
+
+#if 0
+
+// To write value-parameterized tests, first you should define a fixture
+// class. It is usually derived from testing::TestWithParam<T> (see below for
+// another inheritance scheme that's sometimes useful in more complicated
+// class hierarchies), where the type of your parameter values.
+// TestWithParam<T> is itself derived from testing::Test. T can be any
+// copyable type. If it's a raw pointer, you are responsible for managing the
+// lifespan of the pointed values.
+
+class FooTest : public ::testing::TestWithParam<const char*> {
+  // You can implement all the usual class fixture members here.
+};
+
+// Then, use the TEST_P macro to define as many parameterized tests
+// for this fixture as you want. The _P suffix is for "parameterized"
+// or "pattern", whichever you prefer to think.
+
+TEST_P(FooTest, DoesBlah) {
+  // Inside a test, access the test parameter with the GetParam() method
+  // of the TestWithParam<T> class:
+  EXPECT_TRUE(foo.Blah(GetParam()));
+  ...
+}
+
+TEST_P(FooTest, HasBlahBlah) {
+  ...
+}
+
+// Finally, you can use INSTANTIATE_TEST_SUITE_P to instantiate the test
+// case with any set of parameters you want. Google Test defines a number
+// of functions for generating test parameters. They return what we call
+// (surprise!) parameter generators. Here is a summary of them, which
+// are all in the testing namespace:
+//
+//
+//  Range(begin, end [, step]) - Yields values {begin, begin+step,
+//                               begin+step+step, ...}. The values do not
+//                               include end. step defaults to 1.
+//  Values(v1, v2, ..., vN)    - Yields values {v1, v2, ..., vN}.
+//  ValuesIn(container)        - Yields values from a C-style array, an STL
+//  ValuesIn(begin,end)          container, or an iterator range [begin, end).
+//  Bool()                     - Yields sequence {false, true}.
+//  Combine(g1, g2, ..., gN)   - Yields all combinations (the Cartesian product
+//                               for the math savvy) of the values generated
+//                               by the N generators.
+//
+// For more details, see comments at the definitions of these functions below
+// in this file.
+//
+// The following statement will instantiate tests from the FooTest test suite
+// each with parameter values "meeny", "miny", and "moe".
+
+INSTANTIATE_TEST_SUITE_P(InstantiationName,
+                         FooTest,
+                         Values("meeny", "miny", "moe"));
+
+// To distinguish different instances of the pattern, (yes, you
+// can instantiate it more than once) the first argument to the
+// INSTANTIATE_TEST_SUITE_P macro is a prefix that will be added to the
+// actual test suite name. Remember to pick unique prefixes for different
+// instantiations. The tests from the instantiation above will have
+// these names:
+//
+//    * InstantiationName/FooTest.DoesBlah/0 for "meeny"
+//    * InstantiationName/FooTest.DoesBlah/1 for "miny"
+//    * InstantiationName/FooTest.DoesBlah/2 for "moe"
+//    * InstantiationName/FooTest.HasBlahBlah/0 for "meeny"
+//    * InstantiationName/FooTest.HasBlahBlah/1 for "miny"
+//    * InstantiationName/FooTest.HasBlahBlah/2 for "moe"
+//
+// You can use these names in --gtest_filter.
+//
+// This statement will instantiate all tests from FooTest again, each
+// with parameter values "cat" and "dog":
+
+const char* pets[] = {"cat", "dog"};
+INSTANTIATE_TEST_SUITE_P(AnotherInstantiationName, FooTest, ValuesIn(pets));
+
+// The tests from the instantiation above will have these names:
+//
+//    * AnotherInstantiationName/FooTest.DoesBlah/0 for "cat"
+//    * AnotherInstantiationName/FooTest.DoesBlah/1 for "dog"
+//    * AnotherInstantiationName/FooTest.HasBlahBlah/0 for "cat"
+//    * AnotherInstantiationName/FooTest.HasBlahBlah/1 for "dog"
+//
+// Please note that INSTANTIATE_TEST_SUITE_P will instantiate all tests
+// in the given test suite, whether their definitions come before or
+// AFTER the INSTANTIATE_TEST_SUITE_P statement.
+//
+// Please also note that generator expressions (including parameters to the
+// generators) are evaluated in InitGoogleTest(), after main() has started.
+// This allows the user on one hand, to adjust generator parameters in order
+// to dynamically determine a set of tests to run and on the other hand,
+// give the user a chance to inspect the generated tests with Google Test
+// reflection API before RUN_ALL_TESTS() is executed.
+//
+// You can see samples/sample7_unittest.cc and samples/sample8_unittest.cc
+// for more examples.
+//
+// In the future, we plan to publish the API for defining new parameter
+// generators. But for now this interface remains part of the internal
+// implementation and is subject to change.
+//
+//
+// A parameterized test fixture must be derived from testing::Test and from
+// testing::WithParamInterface<T>, where T is the type of the parameter
+// values. Inheriting from TestWithParam<T> satisfies that requirement because
+// TestWithParam<T> inherits from both Test and WithParamInterface. In more
+// complicated hierarchies, however, it is occasionally useful to inherit
+// separately from Test and WithParamInterface. For example:
+
+class BaseTest : public ::testing::Test {
+  // You can inherit all the usual members for a non-parameterized test
+  // fixture here.
+};
+
+class DerivedTest : public BaseTest, public ::testing::WithParamInterface<int> {
+  // The usual test fixture members go here too.
+};
+
+TEST_F(BaseTest, HasFoo) {
+  // This is an ordinary non-parameterized test.
+}
+
+TEST_P(DerivedTest, DoesBlah) {
+  // GetParam works just the same here as if you inherit from TestWithParam.
+  EXPECT_TRUE(foo.Blah(GetParam()));
+}
+
+#endif  // 0
+
+#include <iterator>
+#include <utility>
+
+#include "gtest/internal/gtest-internal.h"
+#include "gtest/internal/gtest-param-util.h"
+#include "gtest/internal/gtest-port.h"
+
+namespace testing {
+
+// Functions producing parameter generators.
+//
+// Google Test uses these generators to produce parameters for value-
+// parameterized tests. When a parameterized test suite is instantiated
+// with a particular generator, Google Test creates and runs tests
+// for each element in the sequence produced by the generator.
+//
+// In the following sample, tests from test suite FooTest are instantiated
+// each three times with parameter values 3, 5, and 8:
+//
+// class FooTest : public TestWithParam<int> { ... };
+//
+// TEST_P(FooTest, TestThis) {
+// }
+// TEST_P(FooTest, TestThat) {
+// }
+// INSTANTIATE_TEST_SUITE_P(TestSequence, FooTest, Values(3, 5, 8));
+//
+
+// Range() returns generators providing sequences of values in a range.
+//
+// Synopsis:
+// Range(start, end)
+//   - returns a generator producing a sequence of values {start, start+1,
+//     start+2, ..., }.
+// Range(start, end, step)
+//   - returns a generator producing a sequence of values {start, start+step,
+//     start+step+step, ..., }.
+// Notes:
+//   * The generated sequences never include end. For example, Range(1, 5)
+//     returns a generator producing a sequence {1, 2, 3, 4}. Range(1, 9, 2)
+//     returns a generator producing {1, 3, 5, 7}.
+//   * start and end must have the same type. That type may be any integral or
+//     floating-point type or a user defined type satisfying these conditions:
+//     * It must be assignable (have operator=() defined).
+//     * It must have operator+() (operator+(int-compatible type) for
+//       two-operand version).
+//     * It must have operator<() defined.
+//     Elements in the resulting sequences will also have that type.
+//   * Condition start < end must be satisfied in order for resulting sequences
+//     to contain any elements.
+//
+template <typename T, typename IncrementT>
+internal::ParamGenerator<T> Range(T start, T end, IncrementT step) {
+  return internal::ParamGenerator<T>(
+      new internal::RangeGenerator<T, IncrementT>(start, end, step));
+}
+
+template <typename T>
+internal::ParamGenerator<T> Range(T start, T end) {
+  return Range(start, end, 1);
+}
+
+// ValuesIn() function allows generation of tests with parameters coming from
+// a container.
+//
+// Synopsis:
+// ValuesIn(const T (&array)[N])
+//   - returns a generator producing sequences with elements from
+//     a C-style array.
+// ValuesIn(const Container& container)
+//   - returns a generator producing sequences with elements from
+//     an STL-style container.
+// ValuesIn(Iterator begin, Iterator end)
+//   - returns a generator producing sequences with elements from
+//     a range [begin, end) defined by a pair of STL-style iterators. These
+//     iterators can also be plain C pointers.
+//
+// Please note that ValuesIn copies the values from the containers
+// passed in and keeps them to generate tests in RUN_ALL_TESTS().
+//
+// Examples:
+//
+// This instantiates tests from test suite StringTest
+// each with C-string values of "foo", "bar", and "baz":
+//
+// const char* strings[] = {"foo", "bar", "baz"};
+// INSTANTIATE_TEST_SUITE_P(StringSequence, StringTest, ValuesIn(strings));
+//
+// This instantiates tests from test suite StlStringTest
+// each with STL strings with values "a" and "b":
+//
+// ::std::vector< ::std::string> GetParameterStrings() {
+//   ::std::vector< ::std::string> v;
+//   v.push_back("a");
+//   v.push_back("b");
+//   return v;
+// }
+//
+// INSTANTIATE_TEST_SUITE_P(CharSequence,
+//                          StlStringTest,
+//                          ValuesIn(GetParameterStrings()));
+//
+//
+// This will also instantiate tests from CharTest
+// each with parameter values 'a' and 'b':
+//
+// ::std::list<char> GetParameterChars() {
+//   ::std::list<char> list;
+//   list.push_back('a');
+//   list.push_back('b');
+//   return list;
+// }
+// ::std::list<char> l = GetParameterChars();
+// INSTANTIATE_TEST_SUITE_P(CharSequence2,
+//                          CharTest,
+//                          ValuesIn(l.begin(), l.end()));
+//
+template <typename ForwardIterator>
+internal::ParamGenerator<
+    typename std::iterator_traits<ForwardIterator>::value_type>
+ValuesIn(ForwardIterator begin, ForwardIterator end) {
+  typedef typename std::iterator_traits<ForwardIterator>::value_type ParamType;
+  return internal::ParamGenerator<ParamType>(
+      new internal::ValuesInIteratorRangeGenerator<ParamType>(begin, end));
+}
+
+template <typename T, size_t N>
+internal::ParamGenerator<T> ValuesIn(const T (&array)[N]) {
+  return ValuesIn(array, array + N);
+}
+
+template <class Container>
+internal::ParamGenerator<typename Container::value_type> ValuesIn(
+    const Container& container) {
+  return ValuesIn(container.begin(), container.end());
+}
+
+// Values() allows generating tests from explicitly specified list of
+// parameters.
+//
+// Synopsis:
+// Values(T v1, T v2, ..., T vN)
+//   - returns a generator producing sequences with elements v1, v2, ..., vN.
+//
+// For example, this instantiates tests from test suite BarTest each
+// with values "one", "two", and "three":
+//
+// INSTANTIATE_TEST_SUITE_P(NumSequence,
+//                          BarTest,
+//                          Values("one", "two", "three"));
+//
+// This instantiates tests from test suite BazTest each with values 1, 2, 3.5.
+// The exact type of values will depend on the type of parameter in BazTest.
+//
+// INSTANTIATE_TEST_SUITE_P(FloatingNumbers, BazTest, Values(1, 2, 3.5));
+//
+//
+template <typename... T>
+internal::ValueArray<T...> Values(T... v) {
+  return internal::ValueArray<T...>(std::move(v)...);
+}
+
+// Bool() allows generating tests with parameters in a set of (false, true).
+//
+// Synopsis:
+// Bool()
+//   - returns a generator producing sequences with elements {false, true}.
+//
+// It is useful when testing code that depends on Boolean flags. Combinations
+// of multiple flags can be tested when several Bool()'s are combined using
+// Combine() function.
+//
+// In the following example all tests in the test suite FlagDependentTest
+// will be instantiated twice with parameters false and true.
+//
+// class FlagDependentTest : public testing::TestWithParam<bool> {
+//   virtual void SetUp() {
+//     external_flag = GetParam();
+//   }
+// }
+// INSTANTIATE_TEST_SUITE_P(BoolSequence, FlagDependentTest, Bool());
+//
+inline internal::ParamGenerator<bool> Bool() {
+  return Values(false, true);
+}
+
+// Combine() allows the user to combine two or more sequences to produce
+// values of a Cartesian product of those sequences' elements.
+//
+// Synopsis:
+// Combine(gen1, gen2, ..., genN)
+//   - returns a generator producing sequences with elements coming from
+//     the Cartesian product of elements from the sequences generated by
+//     gen1, gen2, ..., genN. The sequence elements will have a type of
+//     std::tuple<T1, T2, ..., TN> where T1, T2, ..., TN are the types
+//     of elements from sequences produces by gen1, gen2, ..., genN.
+//
+// Example:
+//
+// This will instantiate tests in test suite AnimalTest each one with
+// the parameter values tuple("cat", BLACK), tuple("cat", WHITE),
+// tuple("dog", BLACK), and tuple("dog", WHITE):
+//
+// enum Color { BLACK, GRAY, WHITE };
+// class AnimalTest
+//     : public testing::TestWithParam<std::tuple<const char*, Color> > {...};
+//
+// TEST_P(AnimalTest, AnimalLooksNice) {...}
+//
+// INSTANTIATE_TEST_SUITE_P(AnimalVariations, AnimalTest,
+//                          Combine(Values("cat", "dog"),
+//                                  Values(BLACK, WHITE)));
+//
+// This will instantiate tests in FlagDependentTest with all variations of two
+// Boolean flags:
+//
+// class FlagDependentTest
+//     : public testing::TestWithParam<std::tuple<bool, bool> > {
+//   virtual void SetUp() {
+//     // Assigns external_flag_1 and external_flag_2 values from the tuple.
+//     std::tie(external_flag_1, external_flag_2) = GetParam();
+//   }
+// };
+//
+// TEST_P(FlagDependentTest, TestFeature1) {
+//   // Test your code using external_flag_1 and external_flag_2 here.
+// }
+// INSTANTIATE_TEST_SUITE_P(TwoBoolSequence, FlagDependentTest,
+//                          Combine(Bool(), Bool()));
+//
+template <typename... Generator>
+internal::CartesianProductHolder<Generator...> Combine(const Generator&... g) {
+  return internal::CartesianProductHolder<Generator...>(g...);
+}
+
+#define TEST_P(test_suite_name, test_name)                                     \
+  class GTEST_TEST_CLASS_NAME_(test_suite_name, test_name)                     \
+      : public test_suite_name {                                               \
+   public:                                                                     \
+    GTEST_TEST_CLASS_NAME_(test_suite_name, test_name)() {}                    \
+    void TestBody() override;                                                  \
+                                                                               \
+   private:                                                                    \
+    static int AddToRegistry() {                                               \
+      ::testing::UnitTest::GetInstance()                                       \
+          ->parameterized_test_registry()                                      \
+          .GetTestSuitePatternHolder<test_suite_name>(                         \
+              GTEST_STRINGIFY_(test_suite_name),                               \
+              ::testing::internal::CodeLocation(__FILE__, __LINE__))           \
+          ->AddTestPattern(                                                    \
+              GTEST_STRINGIFY_(test_suite_name), GTEST_STRINGIFY_(test_name),  \
+              new ::testing::internal::TestMetaFactory<GTEST_TEST_CLASS_NAME_( \
+                  test_suite_name, test_name)>(),                              \
+              ::testing::internal::CodeLocation(__FILE__, __LINE__));          \
+      return 0;                                                                \
+    }                                                                          \
+    static int gtest_registering_dummy_ GTEST_ATTRIBUTE_UNUSED_;               \
+    GTEST_DISALLOW_COPY_AND_ASSIGN_(GTEST_TEST_CLASS_NAME_(test_suite_name,    \
+                                                           test_name));        \
+  };                                                                           \
+  int GTEST_TEST_CLASS_NAME_(test_suite_name,                                  \
+                             test_name)::gtest_registering_dummy_ =            \
+      GTEST_TEST_CLASS_NAME_(test_suite_name, test_name)::AddToRegistry();     \
+  void GTEST_TEST_CLASS_NAME_(test_suite_name, test_name)::TestBody()
+
+// The last argument to INSTANTIATE_TEST_SUITE_P allows the user to specify
+// generator and an optional function or functor that generates custom test name
+// suffixes based on the test parameters. Such a function or functor should
+// accept one argument of type testing::TestParamInfo<class ParamType>, and
+// return std::string.
+//
+// testing::PrintToStringParamName is a builtin test suffix generator that
+// returns the value of testing::PrintToString(GetParam()).
+//
+// Note: test names must be non-empty, unique, and may only contain ASCII
+// alphanumeric characters or underscore. Because PrintToString adds quotes
+// to std::string and C strings, it won't work for these types.
+
+#define GTEST_EXPAND_(arg) arg
+#define GTEST_GET_FIRST_(first, ...) first
+#define GTEST_GET_SECOND_(first, second, ...) second
+
+#define INSTANTIATE_TEST_SUITE_P(prefix, test_suite_name, ...)                \
+  static ::testing::internal::ParamGenerator<test_suite_name::ParamType>      \
+      gtest_##prefix##test_suite_name##_EvalGenerator_() {                    \
+    return GTEST_EXPAND_(GTEST_GET_FIRST_(__VA_ARGS__, DUMMY_PARAM_));        \
+  }                                                                           \
+  static ::std::string gtest_##prefix##test_suite_name##_EvalGenerateName_(   \
+      const ::testing::TestParamInfo<test_suite_name::ParamType>& info) {     \
+    if (::testing::internal::AlwaysFalse()) {                                 \
+      ::testing::internal::TestNotEmpty(GTEST_EXPAND_(GTEST_GET_SECOND_(      \
+          __VA_ARGS__,                                                        \
+          ::testing::internal::DefaultParamName<test_suite_name::ParamType>,  \
+          DUMMY_PARAM_)));                                                    \
+      auto t = std::make_tuple(__VA_ARGS__);                                  \
+      static_assert(std::tuple_size<decltype(t)>::value <= 2,                 \
+                    "Too Many Args!");                                        \
+    }                                                                         \
+    return ((GTEST_EXPAND_(GTEST_GET_SECOND_(                                 \
+        __VA_ARGS__,                                                          \
+        ::testing::internal::DefaultParamName<test_suite_name::ParamType>,    \
+        DUMMY_PARAM_))))(info);                                               \
+  }                                                                           \
+  static int gtest_##prefix##test_suite_name##_dummy_                         \
+      GTEST_ATTRIBUTE_UNUSED_ =                                               \
+          ::testing::UnitTest::GetInstance()                                  \
+              ->parameterized_test_registry()                                 \
+              .GetTestSuitePatternHolder<test_suite_name>(                    \
+                  GTEST_STRINGIFY_(test_suite_name),                          \
+                  ::testing::internal::CodeLocation(__FILE__, __LINE__))      \
+              ->AddTestSuiteInstantiation(                                    \
+                  GTEST_STRINGIFY_(prefix),                                   \
+                  &gtest_##prefix##test_suite_name##_EvalGenerator_,          \
+                  &gtest_##prefix##test_suite_name##_EvalGenerateName_,       \
+                  __FILE__, __LINE__)
+
+
+// Allow Marking a Parameterized test class as not needing to be instantiated.
+#define GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST(T)                   \
+  namespace gtest_do_not_use_outside_namespace_scope {}                   \
+  static const ::testing::internal::MarkAsIgnored gtest_allow_ignore_##T( \
+      GTEST_STRINGIFY_(T))
+
+// Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+#define INSTANTIATE_TEST_CASE_P                                            \
+  static_assert(::testing::internal::InstantiateTestCase_P_IsDeprecated(), \
+                "");                                                       \
+  INSTANTIATE_TEST_SUITE_P
+#endif  // GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+}  // namespace testing
+
+#endif  // GOOGLETEST_INCLUDE_GTEST_GTEST_PARAM_TEST_H_
diff --git a/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-printers.h b/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-printers.h
new file mode 100644
index 0000000..978420e
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-printers.h
@@ -0,0 +1,1029 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Test - The Google C++ Testing and Mocking Framework
+//
+// This file implements a universal value printer that can print a
+// value of any type T:
+//
+//   void ::testing::internal::UniversalPrinter<T>::Print(value, ostream_ptr);
+//
+// A user can teach this function how to print a class type T by
+// defining either operator<<() or PrintTo() in the namespace that
+// defines T.  More specifically, the FIRST defined function in the
+// following list will be used (assuming T is defined in namespace
+// foo):
+//
+//   1. foo::PrintTo(const T&, ostream*)
+//   2. operator<<(ostream&, const T&) defined in either foo or the
+//      global namespace.
+//
+// However if T is an STL-style container then it is printed element-wise
+// unless foo::PrintTo(const T&, ostream*) is defined. Note that
+// operator<<() is ignored for container types.
+//
+// If none of the above is defined, it will print the debug string of
+// the value if it is a protocol buffer, or print the raw bytes in the
+// value otherwise.
+//
+// To aid debugging: when T is a reference type, the address of the
+// value is also printed; when T is a (const) char pointer, both the
+// pointer value and the NUL-terminated string it points to are
+// printed.
+//
+// We also provide some convenient wrappers:
+//
+//   // Prints a value to a string.  For a (const or not) char
+//   // pointer, the NUL-terminated string (but not the pointer) is
+//   // printed.
+//   std::string ::testing::PrintToString(const T& value);
+//
+//   // Prints a value tersely: for a reference type, the referenced
+//   // value (but not the address) is printed; for a (const or not) char
+//   // pointer, the NUL-terminated string (but not the pointer) is
+//   // printed.
+//   void ::testing::internal::UniversalTersePrint(const T& value, ostream*);
+//
+//   // Prints value using the type inferred by the compiler.  The difference
+//   // from UniversalTersePrint() is that this function prints both the
+//   // pointer and the NUL-terminated string for a (const or not) char pointer.
+//   void ::testing::internal::UniversalPrint(const T& value, ostream*);
+//
+//   // Prints the fields of a tuple tersely to a string vector, one
+//   // element for each field. Tuple support must be enabled in
+//   // gtest-port.h.
+//   std::vector<string> UniversalTersePrintTupleFieldsToStrings(
+//       const Tuple& value);
+//
+// Known limitation:
+//
+// The print primitives print the elements of an STL-style container
+// using the compiler-inferred type of *iter where iter is a
+// const_iterator of the container.  When const_iterator is an input
+// iterator but not a forward iterator, this inferred type may not
+// match value_type, and the print output may be incorrect.  In
+// practice, this is rarely a problem as for most containers
+// const_iterator is a forward iterator.  We'll fix this if there's an
+// actual need for it.  Note that this fix cannot rely on value_type
+// being defined as many user-defined container types don't have
+// value_type.
+
+// GOOGLETEST_CM0001 DO NOT DELETE
+
+#ifndef GOOGLETEST_INCLUDE_GTEST_GTEST_PRINTERS_H_
+#define GOOGLETEST_INCLUDE_GTEST_GTEST_PRINTERS_H_
+
+#include <functional>
+#include <memory>
+#include <ostream>  // NOLINT
+#include <sstream>
+#include <string>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include "gtest/internal/gtest-internal.h"
+#include "gtest/internal/gtest-port.h"
+
+namespace testing {
+
+// Definitions in the internal* namespaces are subject to change without notice.
+// DO NOT USE THEM IN USER CODE!
+namespace internal {
+
+template <typename T>
+void UniversalPrint(const T& value, ::std::ostream* os);
+
+// Used to print an STL-style container when the user doesn't define
+// a PrintTo() for it.
+struct ContainerPrinter {
+  template <typename T,
+            typename = typename std::enable_if<
+                (sizeof(IsContainerTest<T>(0)) == sizeof(IsContainer)) &&
+                !IsRecursiveContainer<T>::value>::type>
+  static void PrintValue(const T& container, std::ostream* os) {
+    const size_t kMaxCount = 32;  // The maximum number of elements to print.
+    *os << '{';
+    size_t count = 0;
+    for (auto&& elem : container) {
+      if (count > 0) {
+        *os << ',';
+        if (count == kMaxCount) {  // Enough has been printed.
+          *os << " ...";
+          break;
+        }
+      }
+      *os << ' ';
+      // We cannot call PrintTo(elem, os) here as PrintTo() doesn't
+      // handle `elem` being a native array.
+      internal::UniversalPrint(elem, os);
+      ++count;
+    }
+
+    if (count > 0) {
+      *os << ' ';
+    }
+    *os << '}';
+  }
+};
+
+// Used to print a pointer that is neither a char pointer nor a member
+// pointer, when the user doesn't define PrintTo() for it.  (A member
+// variable pointer or member function pointer doesn't really point to
+// a location in the address space.  Their representation is
+// implementation-defined.  Therefore they will be printed as raw
+// bytes.)
+struct FunctionPointerPrinter {
+  template <typename T, typename = typename std::enable_if<
+                            std::is_function<T>::value>::type>
+  static void PrintValue(T* p, ::std::ostream* os) {
+    if (p == nullptr) {
+      *os << "NULL";
+    } else {
+      // T is a function type, so '*os << p' doesn't do what we want
+      // (it just prints p as bool).  We want to print p as a const
+      // void*.
+      *os << reinterpret_cast<const void*>(p);
+    }
+  }
+};
+
+struct PointerPrinter {
+  template <typename T>
+  static void PrintValue(T* p, ::std::ostream* os) {
+    if (p == nullptr) {
+      *os << "NULL";
+    } else {
+      // T is not a function type.  We just call << to print p,
+      // relying on ADL to pick up user-defined << for their pointer
+      // types, if any.
+      *os << p;
+    }
+  }
+};
+
+namespace internal_stream_operator_without_lexical_name_lookup {
+
+// The presence of an operator<< here will terminate lexical scope lookup
+// straight away (even though it cannot be a match because of its argument
+// types). Thus, the two operator<< calls in StreamPrinter will find only ADL
+// candidates.
+struct LookupBlocker {};
+void operator<<(LookupBlocker, LookupBlocker);
+
+struct StreamPrinter {
+  template <typename T,
+            // Don't accept member pointers here. We'd print them via implicit
+            // conversion to bool, which isn't useful.
+            typename = typename std::enable_if<
+                !std::is_member_pointer<T>::value>::type,
+            // Only accept types for which we can find a streaming operator via
+            // ADL (possibly involving implicit conversions).
+            typename = decltype(std::declval<std::ostream&>()
+                                << std::declval<const T&>())>
+  static void PrintValue(const T& value, ::std::ostream* os) {
+    // Call streaming operator found by ADL, possibly with implicit conversions
+    // of the arguments.
+    *os << value;
+  }
+};
+
+}  // namespace internal_stream_operator_without_lexical_name_lookup
+
+struct ProtobufPrinter {
+  // We print a protobuf using its ShortDebugString() when the string
+  // doesn't exceed this many characters; otherwise we print it using
+  // DebugString() for better readability.
+  static const size_t kProtobufOneLinerMaxLength = 50;
+
+  template <typename T,
+            typename = typename std::enable_if<
+                internal::HasDebugStringAndShortDebugString<T>::value>::type>
+  static void PrintValue(const T& value, ::std::ostream* os) {
+    std::string pretty_str = value.ShortDebugString();
+    if (pretty_str.length() > kProtobufOneLinerMaxLength) {
+      pretty_str = "\n" + value.DebugString();
+    }
+    *os << ("<" + pretty_str + ">");
+  }
+};
+
+struct ConvertibleToIntegerPrinter {
+  // Since T has no << operator or PrintTo() but can be implicitly
+  // converted to BiggestInt, we print it as a BiggestInt.
+  //
+  // Most likely T is an enum type (either named or unnamed), in which
+  // case printing it as an integer is the desired behavior.  In case
+  // T is not an enum, printing it as an integer is the best we can do
+  // given that it has no user-defined printer.
+  static void PrintValue(internal::BiggestInt value, ::std::ostream* os) {
+    *os << value;
+  }
+};
+
+struct ConvertibleToStringViewPrinter {
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  static void PrintValue(internal::StringView value, ::std::ostream* os) {
+    internal::UniversalPrint(value, os);
+  }
+#endif
+};
+
+
+// Prints the given number of bytes in the given object to the given
+// ostream.
+GTEST_API_ void PrintBytesInObjectTo(const unsigned char* obj_bytes,
+                                     size_t count,
+                                     ::std::ostream* os);
+struct RawBytesPrinter {
+  // SFINAE on `sizeof` to make sure we have a complete type.
+  template <typename T, size_t = sizeof(T)>
+  static void PrintValue(const T& value, ::std::ostream* os) {
+    PrintBytesInObjectTo(
+        static_cast<const unsigned char*>(
+            // Load bearing cast to void* to support iOS
+            reinterpret_cast<const void*>(std::addressof(value))),
+        sizeof(value), os);
+  }
+};
+
+struct FallbackPrinter {
+  template <typename T>
+  static void PrintValue(const T&, ::std::ostream* os) {
+    *os << "(incomplete type)";
+  }
+};
+
+// Try every printer in order and return the first one that works.
+template <typename T, typename E, typename Printer, typename... Printers>
+struct FindFirstPrinter : FindFirstPrinter<T, E, Printers...> {};
+
+template <typename T, typename Printer, typename... Printers>
+struct FindFirstPrinter<
+    T, decltype(Printer::PrintValue(std::declval<const T&>(), nullptr)),
+    Printer, Printers...> {
+  using type = Printer;
+};
+
+// Select the best printer in the following order:
+//  - Print containers (they have begin/end/etc).
+//  - Print function pointers.
+//  - Print object pointers.
+//  - Use the stream operator, if available.
+//  - Print protocol buffers.
+//  - Print types convertible to BiggestInt.
+//  - Print types convertible to StringView, if available.
+//  - Fallback to printing the raw bytes of the object.
+template <typename T>
+void PrintWithFallback(const T& value, ::std::ostream* os) {
+  using Printer = typename FindFirstPrinter<
+      T, void, ContainerPrinter, FunctionPointerPrinter, PointerPrinter,
+      internal_stream_operator_without_lexical_name_lookup::StreamPrinter,
+      ProtobufPrinter, ConvertibleToIntegerPrinter,
+      ConvertibleToStringViewPrinter, RawBytesPrinter, FallbackPrinter>::type;
+  Printer::PrintValue(value, os);
+}
+
+// FormatForComparison<ToPrint, OtherOperand>::Format(value) formats a
+// value of type ToPrint that is an operand of a comparison assertion
+// (e.g. ASSERT_EQ).  OtherOperand is the type of the other operand in
+// the comparison, and is used to help determine the best way to
+// format the value.  In particular, when the value is a C string
+// (char pointer) and the other operand is an STL string object, we
+// want to format the C string as a string, since we know it is
+// compared by value with the string object.  If the value is a char
+// pointer but the other operand is not an STL string object, we don't
+// know whether the pointer is supposed to point to a NUL-terminated
+// string, and thus want to print it as a pointer to be safe.
+//
+// INTERNAL IMPLEMENTATION - DO NOT USE IN A USER PROGRAM.
+
+// The default case.
+template <typename ToPrint, typename OtherOperand>
+class FormatForComparison {
+ public:
+  static ::std::string Format(const ToPrint& value) {
+    return ::testing::PrintToString(value);
+  }
+};
+
+// Array.
+template <typename ToPrint, size_t N, typename OtherOperand>
+class FormatForComparison<ToPrint[N], OtherOperand> {
+ public:
+  static ::std::string Format(const ToPrint* value) {
+    return FormatForComparison<const ToPrint*, OtherOperand>::Format(value);
+  }
+};
+
+// By default, print C string as pointers to be safe, as we don't know
+// whether they actually point to a NUL-terminated string.
+
+#define GTEST_IMPL_FORMAT_C_STRING_AS_POINTER_(CharType)                \
+  template <typename OtherOperand>                                      \
+  class FormatForComparison<CharType*, OtherOperand> {                  \
+   public:                                                              \
+    static ::std::string Format(CharType* value) {                      \
+      return ::testing::PrintToString(static_cast<const void*>(value)); \
+    }                                                                   \
+  }
+
+GTEST_IMPL_FORMAT_C_STRING_AS_POINTER_(char);
+GTEST_IMPL_FORMAT_C_STRING_AS_POINTER_(const char);
+GTEST_IMPL_FORMAT_C_STRING_AS_POINTER_(wchar_t);
+GTEST_IMPL_FORMAT_C_STRING_AS_POINTER_(const wchar_t);
+#ifdef __cpp_char8_t
+GTEST_IMPL_FORMAT_C_STRING_AS_POINTER_(char8_t);
+GTEST_IMPL_FORMAT_C_STRING_AS_POINTER_(const char8_t);
+#endif
+GTEST_IMPL_FORMAT_C_STRING_AS_POINTER_(char16_t);
+GTEST_IMPL_FORMAT_C_STRING_AS_POINTER_(const char16_t);
+GTEST_IMPL_FORMAT_C_STRING_AS_POINTER_(char32_t);
+GTEST_IMPL_FORMAT_C_STRING_AS_POINTER_(const char32_t);
+
+#undef GTEST_IMPL_FORMAT_C_STRING_AS_POINTER_
+
+// If a C string is compared with an STL string object, we know it's meant
+// to point to a NUL-terminated string, and thus can print it as a string.
+
+#define GTEST_IMPL_FORMAT_C_STRING_AS_STRING_(CharType, OtherStringType) \
+  template <>                                                           \
+  class FormatForComparison<CharType*, OtherStringType> {               \
+   public:                                                              \
+    static ::std::string Format(CharType* value) {                      \
+      return ::testing::PrintToString(value);                           \
+    }                                                                   \
+  }
+
+GTEST_IMPL_FORMAT_C_STRING_AS_STRING_(char, ::std::string);
+GTEST_IMPL_FORMAT_C_STRING_AS_STRING_(const char, ::std::string);
+#ifdef __cpp_char8_t
+GTEST_IMPL_FORMAT_C_STRING_AS_STRING_(char8_t, ::std::u8string);
+GTEST_IMPL_FORMAT_C_STRING_AS_STRING_(const char8_t, ::std::u8string);
+#endif
+GTEST_IMPL_FORMAT_C_STRING_AS_STRING_(char16_t, ::std::u16string);
+GTEST_IMPL_FORMAT_C_STRING_AS_STRING_(const char16_t, ::std::u16string);
+GTEST_IMPL_FORMAT_C_STRING_AS_STRING_(char32_t, ::std::u32string);
+GTEST_IMPL_FORMAT_C_STRING_AS_STRING_(const char32_t, ::std::u32string);
+
+#if GTEST_HAS_STD_WSTRING
+GTEST_IMPL_FORMAT_C_STRING_AS_STRING_(wchar_t, ::std::wstring);
+GTEST_IMPL_FORMAT_C_STRING_AS_STRING_(const wchar_t, ::std::wstring);
+#endif
+
+#undef GTEST_IMPL_FORMAT_C_STRING_AS_STRING_
+
+// Formats a comparison assertion (e.g. ASSERT_EQ, EXPECT_LT, and etc)
+// operand to be used in a failure message.  The type (but not value)
+// of the other operand may affect the format.  This allows us to
+// print a char* as a raw pointer when it is compared against another
+// char* or void*, and print it as a C string when it is compared
+// against an std::string object, for example.
+//
+// INTERNAL IMPLEMENTATION - DO NOT USE IN A USER PROGRAM.
+template <typename T1, typename T2>
+std::string FormatForComparisonFailureMessage(
+    const T1& value, const T2& /* other_operand */) {
+  return FormatForComparison<T1, T2>::Format(value);
+}
+
+// UniversalPrinter<T>::Print(value, ostream_ptr) prints the given
+// value to the given ostream.  The caller must ensure that
+// 'ostream_ptr' is not NULL, or the behavior is undefined.
+//
+// We define UniversalPrinter as a class template (as opposed to a
+// function template), as we need to partially specialize it for
+// reference types, which cannot be done with function templates.
+template <typename T>
+class UniversalPrinter;
+
+// Prints the given value using the << operator if it has one;
+// otherwise prints the bytes in it.  This is what
+// UniversalPrinter<T>::Print() does when PrintTo() is not specialized
+// or overloaded for type T.
+//
+// A user can override this behavior for a class type Foo by defining
+// an overload of PrintTo() in the namespace where Foo is defined.  We
+// give the user this option as sometimes defining a << operator for
+// Foo is not desirable (e.g. the coding style may prevent doing it,
+// or there is already a << operator but it doesn't do what the user
+// wants).
+template <typename T>
+void PrintTo(const T& value, ::std::ostream* os) {
+  internal::PrintWithFallback(value, os);
+}
+
+// The following list of PrintTo() overloads tells
+// UniversalPrinter<T>::Print() how to print standard types (built-in
+// types, strings, plain arrays, and pointers).
+
+// Overloads for various char types.
+GTEST_API_ void PrintTo(unsigned char c, ::std::ostream* os);
+GTEST_API_ void PrintTo(signed char c, ::std::ostream* os);
+inline void PrintTo(char c, ::std::ostream* os) {
+  // When printing a plain char, we always treat it as unsigned.  This
+  // way, the output won't be affected by whether the compiler thinks
+  // char is signed or not.
+  PrintTo(static_cast<unsigned char>(c), os);
+}
+
+// Overloads for other simple built-in types.
+inline void PrintTo(bool x, ::std::ostream* os) {
+  *os << (x ? "true" : "false");
+}
+
+// Overload for wchar_t type.
+// Prints a wchar_t as a symbol if it is printable or as its internal
+// code otherwise and also as its decimal code (except for L'\0').
+// The L'\0' char is printed as "L'\\0'". The decimal code is printed
+// as signed integer when wchar_t is implemented by the compiler
+// as a signed type and is printed as an unsigned integer when wchar_t
+// is implemented as an unsigned type.
+GTEST_API_ void PrintTo(wchar_t wc, ::std::ostream* os);
+
+GTEST_API_ void PrintTo(char32_t c, ::std::ostream* os);
+inline void PrintTo(char16_t c, ::std::ostream* os) {
+  PrintTo(ImplicitCast_<char32_t>(c), os);
+}
+#ifdef __cpp_char8_t
+inline void PrintTo(char8_t c, ::std::ostream* os) {
+  PrintTo(ImplicitCast_<char32_t>(c), os);
+}
+#endif
+
+// Overloads for C strings.
+GTEST_API_ void PrintTo(const char* s, ::std::ostream* os);
+inline void PrintTo(char* s, ::std::ostream* os) {
+  PrintTo(ImplicitCast_<const char*>(s), os);
+}
+
+// signed/unsigned char is often used for representing binary data, so
+// we print pointers to it as void* to be safe.
+inline void PrintTo(const signed char* s, ::std::ostream* os) {
+  PrintTo(ImplicitCast_<const void*>(s), os);
+}
+inline void PrintTo(signed char* s, ::std::ostream* os) {
+  PrintTo(ImplicitCast_<const void*>(s), os);
+}
+inline void PrintTo(const unsigned char* s, ::std::ostream* os) {
+  PrintTo(ImplicitCast_<const void*>(s), os);
+}
+inline void PrintTo(unsigned char* s, ::std::ostream* os) {
+  PrintTo(ImplicitCast_<const void*>(s), os);
+}
+#ifdef __cpp_char8_t
+// Overloads for u8 strings.
+void PrintTo(const char8_t* s, ::std::ostream* os);
+inline void PrintTo(char8_t* s, ::std::ostream* os) {
+  PrintTo(ImplicitCast_<const char8_t*>(s), os);
+}
+#endif
+// Overloads for u16 strings.
+void PrintTo(const char16_t* s, ::std::ostream* os);
+inline void PrintTo(char16_t* s, ::std::ostream* os) {
+  PrintTo(ImplicitCast_<const char16_t*>(s), os);
+}
+// Overloads for u32 strings.
+void PrintTo(const char32_t* s, ::std::ostream* os);
+inline void PrintTo(char32_t* s, ::std::ostream* os) {
+  PrintTo(ImplicitCast_<const char32_t*>(s), os);
+}
+
+// MSVC can be configured to define wchar_t as a typedef of unsigned
+// short.  It defines _NATIVE_WCHAR_T_DEFINED when wchar_t is a native
+// type.  When wchar_t is a typedef, defining an overload for const
+// wchar_t* would cause unsigned short* be printed as a wide string,
+// possibly causing invalid memory accesses.
+#if !defined(_MSC_VER) || defined(_NATIVE_WCHAR_T_DEFINED)
+// Overloads for wide C strings
+GTEST_API_ void PrintTo(const wchar_t* s, ::std::ostream* os);
+inline void PrintTo(wchar_t* s, ::std::ostream* os) {
+  PrintTo(ImplicitCast_<const wchar_t*>(s), os);
+}
+#endif
+
+// Overload for C arrays.  Multi-dimensional arrays are printed
+// properly.
+
+// Prints the given number of elements in an array, without printing
+// the curly braces.
+template <typename T>
+void PrintRawArrayTo(const T a[], size_t count, ::std::ostream* os) {
+  UniversalPrint(a[0], os);
+  for (size_t i = 1; i != count; i++) {
+    *os << ", ";
+    UniversalPrint(a[i], os);
+  }
+}
+
+// Overloads for ::std::string.
+GTEST_API_ void PrintStringTo(const ::std::string&s, ::std::ostream* os);
+inline void PrintTo(const ::std::string& s, ::std::ostream* os) {
+  PrintStringTo(s, os);
+}
+
+// Overloads for ::std::u8string
+#ifdef __cpp_char8_t
+GTEST_API_ void PrintU8StringTo(const ::std::u8string& s, ::std::ostream* os);
+inline void PrintTo(const ::std::u8string& s, ::std::ostream* os) {
+  PrintU8StringTo(s, os);
+}
+#endif
+
+// Overloads for ::std::u16string
+GTEST_API_ void PrintU16StringTo(const ::std::u16string& s, ::std::ostream* os);
+inline void PrintTo(const ::std::u16string& s, ::std::ostream* os) {
+  PrintU16StringTo(s, os);
+}
+
+// Overloads for ::std::u32string
+GTEST_API_ void PrintU32StringTo(const ::std::u32string& s, ::std::ostream* os);
+inline void PrintTo(const ::std::u32string& s, ::std::ostream* os) {
+  PrintU32StringTo(s, os);
+}
+
+// Overloads for ::std::wstring.
+#if GTEST_HAS_STD_WSTRING
+GTEST_API_ void PrintWideStringTo(const ::std::wstring&s, ::std::ostream* os);
+inline void PrintTo(const ::std::wstring& s, ::std::ostream* os) {
+  PrintWideStringTo(s, os);
+}
+#endif  // GTEST_HAS_STD_WSTRING
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+// Overload for internal::StringView.
+inline void PrintTo(internal::StringView sp, ::std::ostream* os) {
+  PrintTo(::std::string(sp), os);
+}
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+
+inline void PrintTo(std::nullptr_t, ::std::ostream* os) { *os << "(nullptr)"; }
+
+template <typename T>
+void PrintTo(std::reference_wrapper<T> ref, ::std::ostream* os) {
+  UniversalPrinter<T&>::Print(ref.get(), os);
+}
+
+inline const void* VoidifyPointer(const void* p) { return p; }
+inline const void* VoidifyPointer(volatile const void* p) {
+  return const_cast<const void*>(p);
+}
+
+template <typename T, typename Ptr>
+void PrintSmartPointer(const Ptr& ptr, std::ostream* os, char) {
+  if (ptr == nullptr) {
+    *os << "(nullptr)";
+  } else {
+    // We can't print the value. Just print the pointer..
+    *os << "(" << (VoidifyPointer)(ptr.get()) << ")";
+  }
+}
+template <typename T, typename Ptr,
+          typename = typename std::enable_if<!std::is_void<T>::value &&
+                                             !std::is_array<T>::value>::type>
+void PrintSmartPointer(const Ptr& ptr, std::ostream* os, int) {
+  if (ptr == nullptr) {
+    *os << "(nullptr)";
+  } else {
+    *os << "(ptr = " << (VoidifyPointer)(ptr.get()) << ", value = ";
+    UniversalPrinter<T>::Print(*ptr, os);
+    *os << ")";
+  }
+}
+
+template <typename T, typename D>
+void PrintTo(const std::unique_ptr<T, D>& ptr, std::ostream* os) {
+  (PrintSmartPointer<T>)(ptr, os, 0);
+}
+
+template <typename T>
+void PrintTo(const std::shared_ptr<T>& ptr, std::ostream* os) {
+  (PrintSmartPointer<T>)(ptr, os, 0);
+}
+
+// Helper function for printing a tuple.  T must be instantiated with
+// a tuple type.
+template <typename T>
+void PrintTupleTo(const T&, std::integral_constant<size_t, 0>,
+                  ::std::ostream*) {}
+
+template <typename T, size_t I>
+void PrintTupleTo(const T& t, std::integral_constant<size_t, I>,
+                  ::std::ostream* os) {
+  PrintTupleTo(t, std::integral_constant<size_t, I - 1>(), os);
+  GTEST_INTENTIONAL_CONST_COND_PUSH_()
+  if (I > 1) {
+    GTEST_INTENTIONAL_CONST_COND_POP_()
+    *os << ", ";
+  }
+  UniversalPrinter<typename std::tuple_element<I - 1, T>::type>::Print(
+      std::get<I - 1>(t), os);
+}
+
+template <typename... Types>
+void PrintTo(const ::std::tuple<Types...>& t, ::std::ostream* os) {
+  *os << "(";
+  PrintTupleTo(t, std::integral_constant<size_t, sizeof...(Types)>(), os);
+  *os << ")";
+}
+
+// Overload for std::pair.
+template <typename T1, typename T2>
+void PrintTo(const ::std::pair<T1, T2>& value, ::std::ostream* os) {
+  *os << '(';
+  // We cannot use UniversalPrint(value.first, os) here, as T1 may be
+  // a reference type.  The same for printing value.second.
+  UniversalPrinter<T1>::Print(value.first, os);
+  *os << ", ";
+  UniversalPrinter<T2>::Print(value.second, os);
+  *os << ')';
+}
+
+// Implements printing a non-reference type T by letting the compiler
+// pick the right overload of PrintTo() for T.
+template <typename T>
+class UniversalPrinter {
+ public:
+  // MSVC warns about adding const to a function type, so we want to
+  // disable the warning.
+  GTEST_DISABLE_MSC_WARNINGS_PUSH_(4180)
+
+  // Note: we deliberately don't call this PrintTo(), as that name
+  // conflicts with ::testing::internal::PrintTo in the body of the
+  // function.
+  static void Print(const T& value, ::std::ostream* os) {
+    // By default, ::testing::internal::PrintTo() is used for printing
+    // the value.
+    //
+    // Thanks to Koenig look-up, if T is a class and has its own
+    // PrintTo() function defined in its namespace, that function will
+    // be visible here.  Since it is more specific than the generic ones
+    // in ::testing::internal, it will be picked by the compiler in the
+    // following statement - exactly what we want.
+    PrintTo(value, os);
+  }
+
+  GTEST_DISABLE_MSC_WARNINGS_POP_()
+};
+
+// Remove any const-qualifiers before passing a type to UniversalPrinter.
+template <typename T>
+class UniversalPrinter<const T> : public UniversalPrinter<T> {};
+
+#if GTEST_INTERNAL_HAS_ANY
+
+// Printer for std::any / absl::any
+
+template <>
+class UniversalPrinter<Any> {
+ public:
+  static void Print(const Any& value, ::std::ostream* os) {
+    if (value.has_value()) {
+      *os << "value of type " << GetTypeName(value);
+    } else {
+      *os << "no value";
+    }
+  }
+
+ private:
+  static std::string GetTypeName(const Any& value) {
+#if GTEST_HAS_RTTI
+    return internal::GetTypeName(value.type());
+#else
+    static_cast<void>(value);  // possibly unused
+    return "<unknown_type>";
+#endif  // GTEST_HAS_RTTI
+  }
+};
+
+#endif  // GTEST_INTERNAL_HAS_ANY
+
+#if GTEST_INTERNAL_HAS_OPTIONAL
+
+// Printer for std::optional / absl::optional
+
+template <typename T>
+class UniversalPrinter<Optional<T>> {
+ public:
+  static void Print(const Optional<T>& value, ::std::ostream* os) {
+    *os << '(';
+    if (!value) {
+      *os << "nullopt";
+    } else {
+      UniversalPrint(*value, os);
+    }
+    *os << ')';
+  }
+};
+
+#endif  // GTEST_INTERNAL_HAS_OPTIONAL
+
+#if GTEST_INTERNAL_HAS_VARIANT
+
+// Printer for std::variant / absl::variant
+
+template <typename... T>
+class UniversalPrinter<Variant<T...>> {
+ public:
+  static void Print(const Variant<T...>& value, ::std::ostream* os) {
+    *os << '(';
+#if GTEST_HAS_ABSL
+    absl::visit(Visitor{os, value.index()}, value);
+#else
+    std::visit(Visitor{os, value.index()}, value);
+#endif  // GTEST_HAS_ABSL
+    *os << ')';
+  }
+
+ private:
+  struct Visitor {
+    template <typename U>
+    void operator()(const U& u) const {
+      *os << "'" << GetTypeName<U>() << "(index = " << index
+          << ")' with value ";
+      UniversalPrint(u, os);
+    }
+    ::std::ostream* os;
+    std::size_t index;
+  };
+};
+
+#endif  // GTEST_INTERNAL_HAS_VARIANT
+
+// UniversalPrintArray(begin, len, os) prints an array of 'len'
+// elements, starting at address 'begin'.
+template <typename T>
+void UniversalPrintArray(const T* begin, size_t len, ::std::ostream* os) {
+  if (len == 0) {
+    *os << "{}";
+  } else {
+    *os << "{ ";
+    const size_t kThreshold = 18;
+    const size_t kChunkSize = 8;
+    // If the array has more than kThreshold elements, we'll have to
+    // omit some details by printing only the first and the last
+    // kChunkSize elements.
+    if (len <= kThreshold) {
+      PrintRawArrayTo(begin, len, os);
+    } else {
+      PrintRawArrayTo(begin, kChunkSize, os);
+      *os << ", ..., ";
+      PrintRawArrayTo(begin + len - kChunkSize, kChunkSize, os);
+    }
+    *os << " }";
+  }
+}
+// This overload prints a (const) char array compactly.
+GTEST_API_ void UniversalPrintArray(
+    const char* begin, size_t len, ::std::ostream* os);
+
+#ifdef __cpp_char8_t
+// This overload prints a (const) char8_t array compactly.
+GTEST_API_ void UniversalPrintArray(const char8_t* begin, size_t len,
+                                    ::std::ostream* os);
+#endif
+
+// This overload prints a (const) char16_t array compactly.
+GTEST_API_ void UniversalPrintArray(const char16_t* begin, size_t len,
+                                    ::std::ostream* os);
+
+// This overload prints a (const) char32_t array compactly.
+GTEST_API_ void UniversalPrintArray(const char32_t* begin, size_t len,
+                                    ::std::ostream* os);
+
+// This overload prints a (const) wchar_t array compactly.
+GTEST_API_ void UniversalPrintArray(
+    const wchar_t* begin, size_t len, ::std::ostream* os);
+
+// Implements printing an array type T[N].
+template <typename T, size_t N>
+class UniversalPrinter<T[N]> {
+ public:
+  // Prints the given array, omitting some elements when there are too
+  // many.
+  static void Print(const T (&a)[N], ::std::ostream* os) {
+    UniversalPrintArray(a, N, os);
+  }
+};
+
+// Implements printing a reference type T&.
+template <typename T>
+class UniversalPrinter<T&> {
+ public:
+  // MSVC warns about adding const to a function type, so we want to
+  // disable the warning.
+  GTEST_DISABLE_MSC_WARNINGS_PUSH_(4180)
+
+  static void Print(const T& value, ::std::ostream* os) {
+    // Prints the address of the value.  We use reinterpret_cast here
+    // as static_cast doesn't compile when T is a function type.
+    *os << "@" << reinterpret_cast<const void*>(&value) << " ";
+
+    // Then prints the value itself.
+    UniversalPrint(value, os);
+  }
+
+  GTEST_DISABLE_MSC_WARNINGS_POP_()
+};
+
+// Prints a value tersely: for a reference type, the referenced value
+// (but not the address) is printed; for a (const) char pointer, the
+// NUL-terminated string (but not the pointer) is printed.
+
+template <typename T>
+class UniversalTersePrinter {
+ public:
+  static void Print(const T& value, ::std::ostream* os) {
+    UniversalPrint(value, os);
+  }
+};
+template <typename T>
+class UniversalTersePrinter<T&> {
+ public:
+  static void Print(const T& value, ::std::ostream* os) {
+    UniversalPrint(value, os);
+  }
+};
+template <typename T, size_t N>
+class UniversalTersePrinter<T[N]> {
+ public:
+  static void Print(const T (&value)[N], ::std::ostream* os) {
+    UniversalPrinter<T[N]>::Print(value, os);
+  }
+};
+template <>
+class UniversalTersePrinter<const char*> {
+ public:
+  static void Print(const char* str, ::std::ostream* os) {
+    if (str == nullptr) {
+      *os << "NULL";
+    } else {
+      UniversalPrint(std::string(str), os);
+    }
+  }
+};
+template <>
+class UniversalTersePrinter<char*> : public UniversalTersePrinter<const char*> {
+};
+
+#ifdef __cpp_char8_t
+template <>
+class UniversalTersePrinter<const char8_t*> {
+ public:
+  static void Print(const char8_t* str, ::std::ostream* os) {
+    if (str == nullptr) {
+      *os << "NULL";
+    } else {
+      UniversalPrint(::std::u8string(str), os);
+    }
+  }
+};
+template <>
+class UniversalTersePrinter<char8_t*>
+    : public UniversalTersePrinter<const char8_t*> {};
+#endif
+
+template <>
+class UniversalTersePrinter<const char16_t*> {
+ public:
+  static void Print(const char16_t* str, ::std::ostream* os) {
+    if (str == nullptr) {
+      *os << "NULL";
+    } else {
+      UniversalPrint(::std::u16string(str), os);
+    }
+  }
+};
+template <>
+class UniversalTersePrinter<char16_t*>
+    : public UniversalTersePrinter<const char16_t*> {};
+
+template <>
+class UniversalTersePrinter<const char32_t*> {
+ public:
+  static void Print(const char32_t* str, ::std::ostream* os) {
+    if (str == nullptr) {
+      *os << "NULL";
+    } else {
+      UniversalPrint(::std::u32string(str), os);
+    }
+  }
+};
+template <>
+class UniversalTersePrinter<char32_t*>
+    : public UniversalTersePrinter<const char32_t*> {};
+
+#if GTEST_HAS_STD_WSTRING
+template <>
+class UniversalTersePrinter<const wchar_t*> {
+ public:
+  static void Print(const wchar_t* str, ::std::ostream* os) {
+    if (str == nullptr) {
+      *os << "NULL";
+    } else {
+      UniversalPrint(::std::wstring(str), os);
+    }
+  }
+};
+#endif
+
+template <>
+class UniversalTersePrinter<wchar_t*> {
+ public:
+  static void Print(wchar_t* str, ::std::ostream* os) {
+    UniversalTersePrinter<const wchar_t*>::Print(str, os);
+  }
+};
+
+template <typename T>
+void UniversalTersePrint(const T& value, ::std::ostream* os) {
+  UniversalTersePrinter<T>::Print(value, os);
+}
+
+// Prints a value using the type inferred by the compiler.  The
+// difference between this and UniversalTersePrint() is that for a
+// (const) char pointer, this prints both the pointer and the
+// NUL-terminated string.
+template <typename T>
+void UniversalPrint(const T& value, ::std::ostream* os) {
+  // A workarond for the bug in VC++ 7.1 that prevents us from instantiating
+  // UniversalPrinter with T directly.
+  typedef T T1;
+  UniversalPrinter<T1>::Print(value, os);
+}
+
+typedef ::std::vector< ::std::string> Strings;
+
+  // Tersely prints the first N fields of a tuple to a string vector,
+  // one element for each field.
+template <typename Tuple>
+void TersePrintPrefixToStrings(const Tuple&, std::integral_constant<size_t, 0>,
+                               Strings*) {}
+template <typename Tuple, size_t I>
+void TersePrintPrefixToStrings(const Tuple& t,
+                               std::integral_constant<size_t, I>,
+                               Strings* strings) {
+  TersePrintPrefixToStrings(t, std::integral_constant<size_t, I - 1>(),
+                            strings);
+  ::std::stringstream ss;
+  UniversalTersePrint(std::get<I - 1>(t), &ss);
+  strings->push_back(ss.str());
+}
+
+// Prints the fields of a tuple tersely to a string vector, one
+// element for each field.  See the comment before
+// UniversalTersePrint() for how we define "tersely".
+template <typename Tuple>
+Strings UniversalTersePrintTupleFieldsToStrings(const Tuple& value) {
+  Strings result;
+  TersePrintPrefixToStrings(
+      value, std::integral_constant<size_t, std::tuple_size<Tuple>::value>(),
+      &result);
+  return result;
+}
+
+}  // namespace internal
+
+template <typename T>
+::std::string PrintToString(const T& value) {
+  ::std::stringstream ss;
+  internal::UniversalTersePrinter<T>::Print(value, &ss);
+  return ss.str();
+}
+
+}  // namespace testing
+
+// Include any custom printer added by the local installation.
+// We must include this header at the end to make sure it can use the
+// declarations from this file.
+#include "gtest/internal/custom/gtest-printers.h"
+
+#endif  // GOOGLETEST_INCLUDE_GTEST_GTEST_PRINTERS_H_
diff --git a/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-spi.h b/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-spi.h
new file mode 100644
index 0000000..eacef44
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-spi.h
@@ -0,0 +1,238 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// Utilities for testing Google Test itself and code that uses Google Test
+// (e.g. frameworks built on top of Google Test).
+
+// GOOGLETEST_CM0004 DO NOT DELETE
+
+#ifndef GOOGLETEST_INCLUDE_GTEST_GTEST_SPI_H_
+#define GOOGLETEST_INCLUDE_GTEST_GTEST_SPI_H_
+
+#include "gtest/gtest.h"
+
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4251 \
+/* class A needs to have dll-interface to be used by clients of class B */)
+
+namespace testing {
+
+// This helper class can be used to mock out Google Test failure reporting
+// so that we can test Google Test or code that builds on Google Test.
+//
+// An object of this class appends a TestPartResult object to the
+// TestPartResultArray object given in the constructor whenever a Google Test
+// failure is reported. It can either intercept only failures that are
+// generated in the same thread that created this object or it can intercept
+// all generated failures. The scope of this mock object can be controlled with
+// the second argument to the two arguments constructor.
+class GTEST_API_ ScopedFakeTestPartResultReporter
+    : public TestPartResultReporterInterface {
+ public:
+  // The two possible mocking modes of this object.
+  enum InterceptMode {
+    INTERCEPT_ONLY_CURRENT_THREAD,  // Intercepts only thread local failures.
+    INTERCEPT_ALL_THREADS           // Intercepts all failures.
+  };
+
+  // The c'tor sets this object as the test part result reporter used
+  // by Google Test.  The 'result' parameter specifies where to report the
+  // results. This reporter will only catch failures generated in the current
+  // thread. DEPRECATED
+  explicit ScopedFakeTestPartResultReporter(TestPartResultArray* result);
+
+  // Same as above, but you can choose the interception scope of this object.
+  ScopedFakeTestPartResultReporter(InterceptMode intercept_mode,
+                                   TestPartResultArray* result);
+
+  // The d'tor restores the previous test part result reporter.
+  ~ScopedFakeTestPartResultReporter() override;
+
+  // Appends the TestPartResult object to the TestPartResultArray
+  // received in the constructor.
+  //
+  // This method is from the TestPartResultReporterInterface
+  // interface.
+  void ReportTestPartResult(const TestPartResult& result) override;
+
+ private:
+  void Init();
+
+  const InterceptMode intercept_mode_;
+  TestPartResultReporterInterface* old_reporter_;
+  TestPartResultArray* const result_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(ScopedFakeTestPartResultReporter);
+};
+
+namespace internal {
+
+// A helper class for implementing EXPECT_FATAL_FAILURE() and
+// EXPECT_NONFATAL_FAILURE().  Its destructor verifies that the given
+// TestPartResultArray contains exactly one failure that has the given
+// type and contains the given substring.  If that's not the case, a
+// non-fatal failure will be generated.
+class GTEST_API_ SingleFailureChecker {
+ public:
+  // The constructor remembers the arguments.
+  SingleFailureChecker(const TestPartResultArray* results,
+                       TestPartResult::Type type, const std::string& substr);
+  ~SingleFailureChecker();
+ private:
+  const TestPartResultArray* const results_;
+  const TestPartResult::Type type_;
+  const std::string substr_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(SingleFailureChecker);
+};
+
+}  // namespace internal
+
+}  // namespace testing
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  //  4251
+
+// A set of macros for testing Google Test assertions or code that's expected
+// to generate Google Test fatal failures.  It verifies that the given
+// statement will cause exactly one fatal Google Test failure with 'substr'
+// being part of the failure message.
+//
+// There are two different versions of this macro. EXPECT_FATAL_FAILURE only
+// affects and considers failures generated in the current thread and
+// EXPECT_FATAL_FAILURE_ON_ALL_THREADS does the same but for all threads.
+//
+// The verification of the assertion is done correctly even when the statement
+// throws an exception or aborts the current function.
+//
+// Known restrictions:
+//   - 'statement' cannot reference local non-static variables or
+//     non-static members of the current object.
+//   - 'statement' cannot return a value.
+//   - You cannot stream a failure message to this macro.
+//
+// Note that even though the implementations of the following two
+// macros are much alike, we cannot refactor them to use a common
+// helper macro, due to some peculiarity in how the preprocessor
+// works.  The AcceptsMacroThatExpandsToUnprotectedComma test in
+// gtest_unittest.cc will fail to compile if we do that.
+#define EXPECT_FATAL_FAILURE(statement, substr) \
+  do { \
+    class GTestExpectFatalFailureHelper {\
+     public:\
+      static void Execute() { statement; }\
+    };\
+    ::testing::TestPartResultArray gtest_failures;\
+    ::testing::internal::SingleFailureChecker gtest_checker(\
+        &gtest_failures, ::testing::TestPartResult::kFatalFailure, (substr));\
+    {\
+      ::testing::ScopedFakeTestPartResultReporter gtest_reporter(\
+          ::testing::ScopedFakeTestPartResultReporter:: \
+          INTERCEPT_ONLY_CURRENT_THREAD, &gtest_failures);\
+      GTestExpectFatalFailureHelper::Execute();\
+    }\
+  } while (::testing::internal::AlwaysFalse())
+
+#define EXPECT_FATAL_FAILURE_ON_ALL_THREADS(statement, substr) \
+  do { \
+    class GTestExpectFatalFailureHelper {\
+     public:\
+      static void Execute() { statement; }\
+    };\
+    ::testing::TestPartResultArray gtest_failures;\
+    ::testing::internal::SingleFailureChecker gtest_checker(\
+        &gtest_failures, ::testing::TestPartResult::kFatalFailure, (substr));\
+    {\
+      ::testing::ScopedFakeTestPartResultReporter gtest_reporter(\
+          ::testing::ScopedFakeTestPartResultReporter:: \
+          INTERCEPT_ALL_THREADS, &gtest_failures);\
+      GTestExpectFatalFailureHelper::Execute();\
+    }\
+  } while (::testing::internal::AlwaysFalse())
+
+// A macro for testing Google Test assertions or code that's expected to
+// generate Google Test non-fatal failures.  It asserts that the given
+// statement will cause exactly one non-fatal Google Test failure with 'substr'
+// being part of the failure message.
+//
+// There are two different versions of this macro. EXPECT_NONFATAL_FAILURE only
+// affects and considers failures generated in the current thread and
+// EXPECT_NONFATAL_FAILURE_ON_ALL_THREADS does the same but for all threads.
+//
+// 'statement' is allowed to reference local variables and members of
+// the current object.
+//
+// The verification of the assertion is done correctly even when the statement
+// throws an exception or aborts the current function.
+//
+// Known restrictions:
+//   - You cannot stream a failure message to this macro.
+//
+// Note that even though the implementations of the following two
+// macros are much alike, we cannot refactor them to use a common
+// helper macro, due to some peculiarity in how the preprocessor
+// works.  If we do that, the code won't compile when the user gives
+// EXPECT_NONFATAL_FAILURE() a statement that contains a macro that
+// expands to code containing an unprotected comma.  The
+// AcceptsMacroThatExpandsToUnprotectedComma test in gtest_unittest.cc
+// catches that.
+//
+// For the same reason, we have to write
+//   if (::testing::internal::AlwaysTrue()) { statement; }
+// instead of
+//   GTEST_SUPPRESS_UNREACHABLE_CODE_WARNING_BELOW_(statement)
+// to avoid an MSVC warning on unreachable code.
+#define EXPECT_NONFATAL_FAILURE(statement, substr) \
+  do {\
+    ::testing::TestPartResultArray gtest_failures;\
+    ::testing::internal::SingleFailureChecker gtest_checker(\
+        &gtest_failures, ::testing::TestPartResult::kNonFatalFailure, \
+        (substr));\
+    {\
+      ::testing::ScopedFakeTestPartResultReporter gtest_reporter(\
+          ::testing::ScopedFakeTestPartResultReporter:: \
+          INTERCEPT_ONLY_CURRENT_THREAD, &gtest_failures);\
+      if (::testing::internal::AlwaysTrue()) { statement; }\
+    }\
+  } while (::testing::internal::AlwaysFalse())
+
+#define EXPECT_NONFATAL_FAILURE_ON_ALL_THREADS(statement, substr) \
+  do {\
+    ::testing::TestPartResultArray gtest_failures;\
+    ::testing::internal::SingleFailureChecker gtest_checker(\
+        &gtest_failures, ::testing::TestPartResult::kNonFatalFailure, \
+        (substr));\
+    {\
+      ::testing::ScopedFakeTestPartResultReporter gtest_reporter(\
+          ::testing::ScopedFakeTestPartResultReporter::INTERCEPT_ALL_THREADS, \
+          &gtest_failures);\
+      if (::testing::internal::AlwaysTrue()) { statement; }\
+    }\
+  } while (::testing::internal::AlwaysFalse())
+
+#endif  // GOOGLETEST_INCLUDE_GTEST_GTEST_SPI_H_
diff --git a/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-test-part.h b/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-test-part.h
new file mode 100644
index 0000000..203fdf9
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-test-part.h
@@ -0,0 +1,184 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// GOOGLETEST_CM0001 DO NOT DELETE
+
+#ifndef GOOGLETEST_INCLUDE_GTEST_GTEST_TEST_PART_H_
+#define GOOGLETEST_INCLUDE_GTEST_GTEST_TEST_PART_H_
+
+#include <iosfwd>
+#include <vector>
+#include "gtest/internal/gtest-internal.h"
+#include "gtest/internal/gtest-string.h"
+
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4251 \
+/* class A needs to have dll-interface to be used by clients of class B */)
+
+namespace testing {
+
+// A copyable object representing the result of a test part (i.e. an
+// assertion or an explicit FAIL(), ADD_FAILURE(), or SUCCESS()).
+//
+// Don't inherit from TestPartResult as its destructor is not virtual.
+class GTEST_API_ TestPartResult {
+ public:
+  // The possible outcomes of a test part (i.e. an assertion or an
+  // explicit SUCCEED(), FAIL(), or ADD_FAILURE()).
+  enum Type {
+    kSuccess,          // Succeeded.
+    kNonFatalFailure,  // Failed but the test can continue.
+    kFatalFailure,     // Failed and the test should be terminated.
+    kSkip              // Skipped.
+  };
+
+  // C'tor.  TestPartResult does NOT have a default constructor.
+  // Always use this constructor (with parameters) to create a
+  // TestPartResult object.
+  TestPartResult(Type a_type, const char* a_file_name, int a_line_number,
+                 const char* a_message)
+      : type_(a_type),
+        file_name_(a_file_name == nullptr ? "" : a_file_name),
+        line_number_(a_line_number),
+        summary_(ExtractSummary(a_message)),
+        message_(a_message) {}
+
+  // Gets the outcome of the test part.
+  Type type() const { return type_; }
+
+  // Gets the name of the source file where the test part took place, or
+  // NULL if it's unknown.
+  const char* file_name() const {
+    return file_name_.empty() ? nullptr : file_name_.c_str();
+  }
+
+  // Gets the line in the source file where the test part took place,
+  // or -1 if it's unknown.
+  int line_number() const { return line_number_; }
+
+  // Gets the summary of the failure message.
+  const char* summary() const { return summary_.c_str(); }
+
+  // Gets the message associated with the test part.
+  const char* message() const { return message_.c_str(); }
+
+  // Returns true if and only if the test part was skipped.
+  bool skipped() const { return type_ == kSkip; }
+
+  // Returns true if and only if the test part passed.
+  bool passed() const { return type_ == kSuccess; }
+
+  // Returns true if and only if the test part non-fatally failed.
+  bool nonfatally_failed() const { return type_ == kNonFatalFailure; }
+
+  // Returns true if and only if the test part fatally failed.
+  bool fatally_failed() const { return type_ == kFatalFailure; }
+
+  // Returns true if and only if the test part failed.
+  bool failed() const { return fatally_failed() || nonfatally_failed(); }
+
+ private:
+  Type type_;
+
+  // Gets the summary of the failure message by omitting the stack
+  // trace in it.
+  static std::string ExtractSummary(const char* message);
+
+  // The name of the source file where the test part took place, or
+  // "" if the source file is unknown.
+  std::string file_name_;
+  // The line in the source file where the test part took place, or -1
+  // if the line number is unknown.
+  int line_number_;
+  std::string summary_;  // The test failure summary.
+  std::string message_;  // The test failure message.
+};
+
+// Prints a TestPartResult object.
+std::ostream& operator<<(std::ostream& os, const TestPartResult& result);
+
+// An array of TestPartResult objects.
+//
+// Don't inherit from TestPartResultArray as its destructor is not
+// virtual.
+class GTEST_API_ TestPartResultArray {
+ public:
+  TestPartResultArray() {}
+
+  // Appends the given TestPartResult to the array.
+  void Append(const TestPartResult& result);
+
+  // Returns the TestPartResult at the given index (0-based).
+  const TestPartResult& GetTestPartResult(int index) const;
+
+  // Returns the number of TestPartResult objects in the array.
+  int size() const;
+
+ private:
+  std::vector<TestPartResult> array_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(TestPartResultArray);
+};
+
+// This interface knows how to report a test part result.
+class GTEST_API_ TestPartResultReporterInterface {
+ public:
+  virtual ~TestPartResultReporterInterface() {}
+
+  virtual void ReportTestPartResult(const TestPartResult& result) = 0;
+};
+
+namespace internal {
+
+// This helper class is used by {ASSERT|EXPECT}_NO_FATAL_FAILURE to check if a
+// statement generates new fatal failures. To do so it registers itself as the
+// current test part result reporter. Besides checking if fatal failures were
+// reported, it only delegates the reporting to the former result reporter.
+// The original result reporter is restored in the destructor.
+// INTERNAL IMPLEMENTATION - DO NOT USE IN A USER PROGRAM.
+class GTEST_API_ HasNewFatalFailureHelper
+    : public TestPartResultReporterInterface {
+ public:
+  HasNewFatalFailureHelper();
+  ~HasNewFatalFailureHelper() override;
+  void ReportTestPartResult(const TestPartResult& result) override;
+  bool has_new_fatal_failure() const { return has_new_fatal_failure_; }
+ private:
+  bool has_new_fatal_failure_;
+  TestPartResultReporterInterface* original_reporter_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(HasNewFatalFailureHelper);
+};
+
+}  // namespace internal
+
+}  // namespace testing
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  //  4251
+
+#endif  // GOOGLETEST_INCLUDE_GTEST_GTEST_TEST_PART_H_
diff --git a/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-typed-test.h b/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-typed-test.h
new file mode 100644
index 0000000..9fdc6be
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/include/gtest/gtest-typed-test.h
@@ -0,0 +1,329 @@
+// Copyright 2008 Google Inc.
+// All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// GOOGLETEST_CM0001 DO NOT DELETE
+
+#ifndef GOOGLETEST_INCLUDE_GTEST_GTEST_TYPED_TEST_H_
+#define GOOGLETEST_INCLUDE_GTEST_GTEST_TYPED_TEST_H_
+
+// This header implements typed tests and type-parameterized tests.
+
+// Typed (aka type-driven) tests repeat the same test for types in a
+// list.  You must know which types you want to test with when writing
+// typed tests. Here's how you do it:
+
+#if 0
+
+// First, define a fixture class template.  It should be parameterized
+// by a type.  Remember to derive it from testing::Test.
+template <typename T>
+class FooTest : public testing::Test {
+ public:
+  ...
+  typedef std::list<T> List;
+  static T shared_;
+  T value_;
+};
+
+// Next, associate a list of types with the test suite, which will be
+// repeated for each type in the list.  The typedef is necessary for
+// the macro to parse correctly.
+typedef testing::Types<char, int, unsigned int> MyTypes;
+TYPED_TEST_SUITE(FooTest, MyTypes);
+
+// If the type list contains only one type, you can write that type
+// directly without Types<...>:
+//   TYPED_TEST_SUITE(FooTest, int);
+
+// Then, use TYPED_TEST() instead of TEST_F() to define as many typed
+// tests for this test suite as you want.
+TYPED_TEST(FooTest, DoesBlah) {
+  // Inside a test, refer to the special name TypeParam to get the type
+  // parameter.  Since we are inside a derived class template, C++ requires
+  // us to visit the members of FooTest via 'this'.
+  TypeParam n = this->value_;
+
+  // To visit static members of the fixture, add the TestFixture::
+  // prefix.
+  n += TestFixture::shared_;
+
+  // To refer to typedefs in the fixture, add the "typename
+  // TestFixture::" prefix.
+  typename TestFixture::List values;
+  values.push_back(n);
+  ...
+}
+
+TYPED_TEST(FooTest, HasPropertyA) { ... }
+
+// TYPED_TEST_SUITE takes an optional third argument which allows to specify a
+// class that generates custom test name suffixes based on the type. This should
+// be a class which has a static template function GetName(int index) returning
+// a string for each type. The provided integer index equals the index of the
+// type in the provided type list. In many cases the index can be ignored.
+//
+// For example:
+//   class MyTypeNames {
+//    public:
+//     template <typename T>
+//     static std::string GetName(int) {
+//       if (std::is_same<T, char>()) return "char";
+//       if (std::is_same<T, int>()) return "int";
+//       if (std::is_same<T, unsigned int>()) return "unsignedInt";
+//     }
+//   };
+//   TYPED_TEST_SUITE(FooTest, MyTypes, MyTypeNames);
+
+#endif  // 0
+
+// Type-parameterized tests are abstract test patterns parameterized
+// by a type.  Compared with typed tests, type-parameterized tests
+// allow you to define the test pattern without knowing what the type
+// parameters are.  The defined pattern can be instantiated with
+// different types any number of times, in any number of translation
+// units.
+//
+// If you are designing an interface or concept, you can define a
+// suite of type-parameterized tests to verify properties that any
+// valid implementation of the interface/concept should have.  Then,
+// each implementation can easily instantiate the test suite to verify
+// that it conforms to the requirements, without having to write
+// similar tests repeatedly.  Here's an example:
+
+#if 0
+
+// First, define a fixture class template.  It should be parameterized
+// by a type.  Remember to derive it from testing::Test.
+template <typename T>
+class FooTest : public testing::Test {
+  ...
+};
+
+// Next, declare that you will define a type-parameterized test suite
+// (the _P suffix is for "parameterized" or "pattern", whichever you
+// prefer):
+TYPED_TEST_SUITE_P(FooTest);
+
+// Then, use TYPED_TEST_P() to define as many type-parameterized tests
+// for this type-parameterized test suite as you want.
+TYPED_TEST_P(FooTest, DoesBlah) {
+  // Inside a test, refer to TypeParam to get the type parameter.
+  TypeParam n = 0;
+  ...
+}
+
+TYPED_TEST_P(FooTest, HasPropertyA) { ... }
+
+// Now the tricky part: you need to register all test patterns before
+// you can instantiate them.  The first argument of the macro is the
+// test suite name; the rest are the names of the tests in this test
+// case.
+REGISTER_TYPED_TEST_SUITE_P(FooTest,
+                            DoesBlah, HasPropertyA);
+
+// Finally, you are free to instantiate the pattern with the types you
+// want.  If you put the above code in a header file, you can #include
+// it in multiple C++ source files and instantiate it multiple times.
+//
+// To distinguish different instances of the pattern, the first
+// argument to the INSTANTIATE_* macro is a prefix that will be added
+// to the actual test suite name.  Remember to pick unique prefixes for
+// different instances.
+typedef testing::Types<char, int, unsigned int> MyTypes;
+INSTANTIATE_TYPED_TEST_SUITE_P(My, FooTest, MyTypes);
+
+// If the type list contains only one type, you can write that type
+// directly without Types<...>:
+//   INSTANTIATE_TYPED_TEST_SUITE_P(My, FooTest, int);
+//
+// Similar to the optional argument of TYPED_TEST_SUITE above,
+// INSTANTIATE_TEST_SUITE_P takes an optional fourth argument which allows to
+// generate custom names.
+//   INSTANTIATE_TYPED_TEST_SUITE_P(My, FooTest, MyTypes, MyTypeNames);
+
+#endif  // 0
+
+#include "gtest/internal/gtest-internal.h"
+#include "gtest/internal/gtest-port.h"
+#include "gtest/internal/gtest-type-util.h"
+
+// Implements typed tests.
+
+// INTERNAL IMPLEMENTATION - DO NOT USE IN USER CODE.
+//
+// Expands to the name of the typedef for the type parameters of the
+// given test suite.
+#define GTEST_TYPE_PARAMS_(TestSuiteName) gtest_type_params_##TestSuiteName##_
+
+// Expands to the name of the typedef for the NameGenerator, responsible for
+// creating the suffixes of the name.
+#define GTEST_NAME_GENERATOR_(TestSuiteName) \
+  gtest_type_params_##TestSuiteName##_NameGenerator
+
+#define TYPED_TEST_SUITE(CaseName, Types, ...)                          \
+  typedef ::testing::internal::GenerateTypeList<Types>::type            \
+      GTEST_TYPE_PARAMS_(CaseName);                                     \
+  typedef ::testing::internal::NameGeneratorSelector<__VA_ARGS__>::type \
+      GTEST_NAME_GENERATOR_(CaseName)
+
+#define TYPED_TEST(CaseName, TestName)                                        \
+  static_assert(sizeof(GTEST_STRINGIFY_(TestName)) > 1,                       \
+                "test-name must not be empty");                               \
+  template <typename gtest_TypeParam_>                                        \
+  class GTEST_TEST_CLASS_NAME_(CaseName, TestName)                            \
+      : public CaseName<gtest_TypeParam_> {                                   \
+   private:                                                                   \
+    typedef CaseName<gtest_TypeParam_> TestFixture;                           \
+    typedef gtest_TypeParam_ TypeParam;                                       \
+    void TestBody() override;                                                 \
+  };                                                                          \
+  static bool gtest_##CaseName##_##TestName##_registered_                     \
+      GTEST_ATTRIBUTE_UNUSED_ = ::testing::internal::TypeParameterizedTest<   \
+          CaseName,                                                           \
+          ::testing::internal::TemplateSel<GTEST_TEST_CLASS_NAME_(CaseName,   \
+                                                                  TestName)>, \
+          GTEST_TYPE_PARAMS_(                                                 \
+              CaseName)>::Register("",                                        \
+                                   ::testing::internal::CodeLocation(         \
+                                       __FILE__, __LINE__),                   \
+                                   GTEST_STRINGIFY_(CaseName),                \
+                                   GTEST_STRINGIFY_(TestName), 0,             \
+                                   ::testing::internal::GenerateNames<        \
+                                       GTEST_NAME_GENERATOR_(CaseName),       \
+                                       GTEST_TYPE_PARAMS_(CaseName)>());      \
+  template <typename gtest_TypeParam_>                                        \
+  void GTEST_TEST_CLASS_NAME_(CaseName,                                       \
+                              TestName)<gtest_TypeParam_>::TestBody()
+
+// Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+#define TYPED_TEST_CASE                                                \
+  static_assert(::testing::internal::TypedTestCaseIsDeprecated(), ""); \
+  TYPED_TEST_SUITE
+#endif  // GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+// Implements type-parameterized tests.
+
+// INTERNAL IMPLEMENTATION - DO NOT USE IN USER CODE.
+//
+// Expands to the namespace name that the type-parameterized tests for
+// the given type-parameterized test suite are defined in.  The exact
+// name of the namespace is subject to change without notice.
+#define GTEST_SUITE_NAMESPACE_(TestSuiteName) gtest_suite_##TestSuiteName##_
+
+// INTERNAL IMPLEMENTATION - DO NOT USE IN USER CODE.
+//
+// Expands to the name of the variable used to remember the names of
+// the defined tests in the given test suite.
+#define GTEST_TYPED_TEST_SUITE_P_STATE_(TestSuiteName) \
+  gtest_typed_test_suite_p_state_##TestSuiteName##_
+
+// INTERNAL IMPLEMENTATION - DO NOT USE IN USER CODE DIRECTLY.
+//
+// Expands to the name of the variable used to remember the names of
+// the registered tests in the given test suite.
+#define GTEST_REGISTERED_TEST_NAMES_(TestSuiteName) \
+  gtest_registered_test_names_##TestSuiteName##_
+
+// The variables defined in the type-parameterized test macros are
+// static as typically these macros are used in a .h file that can be
+// #included in multiple translation units linked together.
+#define TYPED_TEST_SUITE_P(SuiteName)              \
+  static ::testing::internal::TypedTestSuitePState \
+      GTEST_TYPED_TEST_SUITE_P_STATE_(SuiteName)
+
+// Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+#define TYPED_TEST_CASE_P                                                 \
+  static_assert(::testing::internal::TypedTestCase_P_IsDeprecated(), ""); \
+  TYPED_TEST_SUITE_P
+#endif  // GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+#define TYPED_TEST_P(SuiteName, TestName)                             \
+  namespace GTEST_SUITE_NAMESPACE_(SuiteName) {                       \
+    template <typename gtest_TypeParam_>                              \
+    class TestName : public SuiteName<gtest_TypeParam_> {             \
+     private:                                                         \
+      typedef SuiteName<gtest_TypeParam_> TestFixture;                \
+      typedef gtest_TypeParam_ TypeParam;                             \
+      void TestBody() override;                                       \
+    };                                                                \
+    static bool gtest_##TestName##_defined_ GTEST_ATTRIBUTE_UNUSED_ = \
+        GTEST_TYPED_TEST_SUITE_P_STATE_(SuiteName).AddTestName(       \
+            __FILE__, __LINE__, GTEST_STRINGIFY_(SuiteName),          \
+            GTEST_STRINGIFY_(TestName));                              \
+  }                                                                   \
+  template <typename gtest_TypeParam_>                                \
+  void GTEST_SUITE_NAMESPACE_(                                        \
+      SuiteName)::TestName<gtest_TypeParam_>::TestBody()
+
+// Note: this won't work correctly if the trailing arguments are macros.
+#define REGISTER_TYPED_TEST_SUITE_P(SuiteName, ...)                         \
+  namespace GTEST_SUITE_NAMESPACE_(SuiteName) {                             \
+    typedef ::testing::internal::Templates<__VA_ARGS__> gtest_AllTests_;    \
+  }                                                                         \
+  static const char* const GTEST_REGISTERED_TEST_NAMES_(                    \
+      SuiteName) GTEST_ATTRIBUTE_UNUSED_ =                                  \
+      GTEST_TYPED_TEST_SUITE_P_STATE_(SuiteName).VerifyRegisteredTestNames( \
+          GTEST_STRINGIFY_(SuiteName), __FILE__, __LINE__, #__VA_ARGS__)
+
+// Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+#define REGISTER_TYPED_TEST_CASE_P                                           \
+  static_assert(::testing::internal::RegisterTypedTestCase_P_IsDeprecated(), \
+                "");                                                         \
+  REGISTER_TYPED_TEST_SUITE_P
+#endif  // GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+#define INSTANTIATE_TYPED_TEST_SUITE_P(Prefix, SuiteName, Types, ...)       \
+  static_assert(sizeof(GTEST_STRINGIFY_(Prefix)) > 1,                       \
+                "test-suit-prefix must not be empty");                      \
+  static bool gtest_##Prefix##_##SuiteName GTEST_ATTRIBUTE_UNUSED_ =        \
+      ::testing::internal::TypeParameterizedTestSuite<                      \
+          SuiteName, GTEST_SUITE_NAMESPACE_(SuiteName)::gtest_AllTests_,    \
+          ::testing::internal::GenerateTypeList<Types>::type>::             \
+          Register(GTEST_STRINGIFY_(Prefix),                                \
+                   ::testing::internal::CodeLocation(__FILE__, __LINE__),   \
+                   &GTEST_TYPED_TEST_SUITE_P_STATE_(SuiteName),             \
+                   GTEST_STRINGIFY_(SuiteName),                             \
+                   GTEST_REGISTERED_TEST_NAMES_(SuiteName),                 \
+                   ::testing::internal::GenerateNames<                      \
+                       ::testing::internal::NameGeneratorSelector<          \
+                           __VA_ARGS__>::type,                              \
+                       ::testing::internal::GenerateTypeList<Types>::type>())
+
+// Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+#define INSTANTIATE_TYPED_TEST_CASE_P                                      \
+  static_assert(                                                           \
+      ::testing::internal::InstantiateTypedTestCase_P_IsDeprecated(), ""); \
+  INSTANTIATE_TYPED_TEST_SUITE_P
+#endif  // GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+#endif  // GOOGLETEST_INCLUDE_GTEST_GTEST_TYPED_TEST_H_
diff --git a/leveldb_base/third_party/googletest/googletest/include/gtest/gtest.h b/leveldb_base/third_party/googletest/googletest/include/gtest/gtest.h
new file mode 100644
index 0000000..7a5d057
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/include/gtest/gtest.h
@@ -0,0 +1,2495 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// The Google C++ Testing and Mocking Framework (Google Test)
+//
+// This header file defines the public API for Google Test.  It should be
+// included by any test program that uses Google Test.
+//
+// IMPORTANT NOTE: Due to limitation of the C++ language, we have to
+// leave some internal implementation details in this header file.
+// They are clearly marked by comments like this:
+//
+//   // INTERNAL IMPLEMENTATION - DO NOT USE IN A USER PROGRAM.
+//
+// Such code is NOT meant to be used by a user directly, and is subject
+// to CHANGE WITHOUT NOTICE.  Therefore DO NOT DEPEND ON IT in a user
+// program!
+//
+// Acknowledgment: Google Test borrowed the idea of automatic test
+// registration from Barthelemy Dagenais' (barthelemy@prologique.com)
+// easyUnit framework.
+
+// GOOGLETEST_CM0001 DO NOT DELETE
+
+#ifndef GOOGLETEST_INCLUDE_GTEST_GTEST_H_
+#define GOOGLETEST_INCLUDE_GTEST_GTEST_H_
+
+#include <cstddef>
+#include <limits>
+#include <memory>
+#include <ostream>
+#include <type_traits>
+#include <vector>
+
+#include "gtest/internal/gtest-internal.h"
+#include "gtest/internal/gtest-string.h"
+#include "gtest/gtest-death-test.h"
+#include "gtest/gtest-matchers.h"
+#include "gtest/gtest-message.h"
+#include "gtest/gtest-param-test.h"
+#include "gtest/gtest-printers.h"
+#include "gtest/gtest_prod.h"
+#include "gtest/gtest-test-part.h"
+#include "gtest/gtest-typed-test.h"
+
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4251 \
+/* class A needs to have dll-interface to be used by clients of class B */)
+
+namespace testing {
+
+// Silence C4100 (unreferenced formal parameter) and 4805
+// unsafe mix of type 'const int' and type 'const bool'
+#ifdef _MSC_VER
+# pragma warning(push)
+# pragma warning(disable:4805)
+# pragma warning(disable:4100)
+#endif
+
+
+// Declares the flags.
+
+// This flag temporary enables the disabled tests.
+GTEST_DECLARE_bool_(also_run_disabled_tests);
+
+// This flag brings the debugger on an assertion failure.
+GTEST_DECLARE_bool_(break_on_failure);
+
+// This flag controls whether Google Test catches all test-thrown exceptions
+// and logs them as failures.
+GTEST_DECLARE_bool_(catch_exceptions);
+
+// This flag enables using colors in terminal output. Available values are
+// "yes" to enable colors, "no" (disable colors), or "auto" (the default)
+// to let Google Test decide.
+GTEST_DECLARE_string_(color);
+
+// This flag controls whether the test runner should continue execution past
+// first failure.
+GTEST_DECLARE_bool_(fail_fast);
+
+// This flag sets up the filter to select by name using a glob pattern
+// the tests to run. If the filter is not given all tests are executed.
+GTEST_DECLARE_string_(filter);
+
+// This flag controls whether Google Test installs a signal handler that dumps
+// debugging information when fatal signals are raised.
+GTEST_DECLARE_bool_(install_failure_signal_handler);
+
+// This flag causes the Google Test to list tests. None of the tests listed
+// are actually run if the flag is provided.
+GTEST_DECLARE_bool_(list_tests);
+
+// This flag controls whether Google Test emits a detailed XML report to a file
+// in addition to its normal textual output.
+GTEST_DECLARE_string_(output);
+
+// This flags control whether Google Test prints only test failures.
+GTEST_DECLARE_bool_(brief);
+
+// This flags control whether Google Test prints the elapsed time for each
+// test.
+GTEST_DECLARE_bool_(print_time);
+
+// This flags control whether Google Test prints UTF8 characters as text.
+GTEST_DECLARE_bool_(print_utf8);
+
+// This flag specifies the random number seed.
+GTEST_DECLARE_int32_(random_seed);
+
+// This flag sets how many times the tests are repeated. The default value
+// is 1. If the value is -1 the tests are repeating forever.
+GTEST_DECLARE_int32_(repeat);
+
+// This flag controls whether Google Test includes Google Test internal
+// stack frames in failure stack traces.
+GTEST_DECLARE_bool_(show_internal_stack_frames);
+
+// When this flag is specified, tests' order is randomized on every iteration.
+GTEST_DECLARE_bool_(shuffle);
+
+// This flag specifies the maximum number of stack frames to be
+// printed in a failure message.
+GTEST_DECLARE_int32_(stack_trace_depth);
+
+// When this flag is specified, a failed assertion will throw an
+// exception if exceptions are enabled, or exit the program with a
+// non-zero code otherwise. For use with an external test framework.
+GTEST_DECLARE_bool_(throw_on_failure);
+
+// When this flag is set with a "host:port" string, on supported
+// platforms test results are streamed to the specified port on
+// the specified host machine.
+GTEST_DECLARE_string_(stream_result_to);
+
+#if GTEST_USE_OWN_FLAGFILE_FLAG_
+GTEST_DECLARE_string_(flagfile);
+#endif  // GTEST_USE_OWN_FLAGFILE_FLAG_
+
+// The upper limit for valid stack trace depths.
+const int kMaxStackTraceDepth = 100;
+
+namespace internal {
+
+class AssertHelper;
+class DefaultGlobalTestPartResultReporter;
+class ExecDeathTest;
+class NoExecDeathTest;
+class FinalSuccessChecker;
+class GTestFlagSaver;
+class StreamingListenerTest;
+class TestResultAccessor;
+class TestEventListenersAccessor;
+class TestEventRepeater;
+class UnitTestRecordPropertyTestHelper;
+class WindowsDeathTest;
+class FuchsiaDeathTest;
+class UnitTestImpl* GetUnitTestImpl();
+void ReportFailureInUnknownLocation(TestPartResult::Type result_type,
+                                    const std::string& message);
+std::set<std::string>* GetIgnoredParameterizedTestSuites();
+
+}  // namespace internal
+
+// The friend relationship of some of these classes is cyclic.
+// If we don't forward declare them the compiler might confuse the classes
+// in friendship clauses with same named classes on the scope.
+class Test;
+class TestSuite;
+
+// Old API is still available but deprecated
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+using TestCase = TestSuite;
+#endif
+class TestInfo;
+class UnitTest;
+
+// A class for indicating whether an assertion was successful.  When
+// the assertion wasn't successful, the AssertionResult object
+// remembers a non-empty message that describes how it failed.
+//
+// To create an instance of this class, use one of the factory functions
+// (AssertionSuccess() and AssertionFailure()).
+//
+// This class is useful for two purposes:
+//   1. Defining predicate functions to be used with Boolean test assertions
+//      EXPECT_TRUE/EXPECT_FALSE and their ASSERT_ counterparts
+//   2. Defining predicate-format functions to be
+//      used with predicate assertions (ASSERT_PRED_FORMAT*, etc).
+//
+// For example, if you define IsEven predicate:
+//
+//   testing::AssertionResult IsEven(int n) {
+//     if ((n % 2) == 0)
+//       return testing::AssertionSuccess();
+//     else
+//       return testing::AssertionFailure() << n << " is odd";
+//   }
+//
+// Then the failed expectation EXPECT_TRUE(IsEven(Fib(5)))
+// will print the message
+//
+//   Value of: IsEven(Fib(5))
+//     Actual: false (5 is odd)
+//   Expected: true
+//
+// instead of a more opaque
+//
+//   Value of: IsEven(Fib(5))
+//     Actual: false
+//   Expected: true
+//
+// in case IsEven is a simple Boolean predicate.
+//
+// If you expect your predicate to be reused and want to support informative
+// messages in EXPECT_FALSE and ASSERT_FALSE (negative assertions show up
+// about half as often as positive ones in our tests), supply messages for
+// both success and failure cases:
+//
+//   testing::AssertionResult IsEven(int n) {
+//     if ((n % 2) == 0)
+//       return testing::AssertionSuccess() << n << " is even";
+//     else
+//       return testing::AssertionFailure() << n << " is odd";
+//   }
+//
+// Then a statement EXPECT_FALSE(IsEven(Fib(6))) will print
+//
+//   Value of: IsEven(Fib(6))
+//     Actual: true (8 is even)
+//   Expected: false
+//
+// NB: Predicates that support negative Boolean assertions have reduced
+// performance in positive ones so be careful not to use them in tests
+// that have lots (tens of thousands) of positive Boolean assertions.
+//
+// To use this class with EXPECT_PRED_FORMAT assertions such as:
+//
+//   // Verifies that Foo() returns an even number.
+//   EXPECT_PRED_FORMAT1(IsEven, Foo());
+//
+// you need to define:
+//
+//   testing::AssertionResult IsEven(const char* expr, int n) {
+//     if ((n % 2) == 0)
+//       return testing::AssertionSuccess();
+//     else
+//       return testing::AssertionFailure()
+//         << "Expected: " << expr << " is even\n  Actual: it's " << n;
+//   }
+//
+// If Foo() returns 5, you will see the following message:
+//
+//   Expected: Foo() is even
+//     Actual: it's 5
+//
+class GTEST_API_ AssertionResult {
+ public:
+  // Copy constructor.
+  // Used in EXPECT_TRUE/FALSE(assertion_result).
+  AssertionResult(const AssertionResult& other);
+
+// C4800 is a level 3 warning in Visual Studio 2015 and earlier.
+// This warning is not emitted in Visual Studio 2017.
+// This warning is off by default starting in Visual Studio 2019 but can be
+// enabled with command-line options.
+#if defined(_MSC_VER) && (_MSC_VER < 1910 || _MSC_VER >= 1920)
+  GTEST_DISABLE_MSC_WARNINGS_PUSH_(4800 /* forcing value to bool */)
+#endif
+
+  // Used in the EXPECT_TRUE/FALSE(bool_expression).
+  //
+  // T must be contextually convertible to bool.
+  //
+  // The second parameter prevents this overload from being considered if
+  // the argument is implicitly convertible to AssertionResult. In that case
+  // we want AssertionResult's copy constructor to be used.
+  template <typename T>
+  explicit AssertionResult(
+      const T& success,
+      typename std::enable_if<
+          !std::is_convertible<T, AssertionResult>::value>::type*
+      /*enabler*/
+      = nullptr)
+      : success_(success) {}
+
+#if defined(_MSC_VER) && (_MSC_VER < 1910 || _MSC_VER >= 1920)
+  GTEST_DISABLE_MSC_WARNINGS_POP_()
+#endif
+
+  // Assignment operator.
+  AssertionResult& operator=(AssertionResult other) {
+    swap(other);
+    return *this;
+  }
+
+  // Returns true if and only if the assertion succeeded.
+  operator bool() const { return success_; }  // NOLINT
+
+  // Returns the assertion's negation. Used with EXPECT/ASSERT_FALSE.
+  AssertionResult operator!() const;
+
+  // Returns the text streamed into this AssertionResult. Test assertions
+  // use it when they fail (i.e., the predicate's outcome doesn't match the
+  // assertion's expectation). When nothing has been streamed into the
+  // object, returns an empty string.
+  const char* message() const {
+    return message_.get() != nullptr ? message_->c_str() : "";
+  }
+  // Deprecated; please use message() instead.
+  const char* failure_message() const { return message(); }
+
+  // Streams a custom failure message into this object.
+  template <typename T> AssertionResult& operator<<(const T& value) {
+    AppendMessage(Message() << value);
+    return *this;
+  }
+
+  // Allows streaming basic output manipulators such as endl or flush into
+  // this object.
+  AssertionResult& operator<<(
+      ::std::ostream& (*basic_manipulator)(::std::ostream& stream)) {
+    AppendMessage(Message() << basic_manipulator);
+    return *this;
+  }
+
+ private:
+  // Appends the contents of message to message_.
+  void AppendMessage(const Message& a_message) {
+    if (message_.get() == nullptr) message_.reset(new ::std::string);
+    message_->append(a_message.GetString().c_str());
+  }
+
+  // Swap the contents of this AssertionResult with other.
+  void swap(AssertionResult& other);
+
+  // Stores result of the assertion predicate.
+  bool success_;
+  // Stores the message describing the condition in case the expectation
+  // construct is not satisfied with the predicate's outcome.
+  // Referenced via a pointer to avoid taking too much stack frame space
+  // with test assertions.
+  std::unique_ptr< ::std::string> message_;
+};
+
+// Makes a successful assertion result.
+GTEST_API_ AssertionResult AssertionSuccess();
+
+// Makes a failed assertion result.
+GTEST_API_ AssertionResult AssertionFailure();
+
+// Makes a failed assertion result with the given failure message.
+// Deprecated; use AssertionFailure() << msg.
+GTEST_API_ AssertionResult AssertionFailure(const Message& msg);
+
+}  // namespace testing
+
+// Includes the auto-generated header that implements a family of generic
+// predicate assertion macros. This include comes late because it relies on
+// APIs declared above.
+#include "gtest/gtest_pred_impl.h"
+
+namespace testing {
+
+// The abstract class that all tests inherit from.
+//
+// In Google Test, a unit test program contains one or many TestSuites, and
+// each TestSuite contains one or many Tests.
+//
+// When you define a test using the TEST macro, you don't need to
+// explicitly derive from Test - the TEST macro automatically does
+// this for you.
+//
+// The only time you derive from Test is when defining a test fixture
+// to be used in a TEST_F.  For example:
+//
+//   class FooTest : public testing::Test {
+//    protected:
+//     void SetUp() override { ... }
+//     void TearDown() override { ... }
+//     ...
+//   };
+//
+//   TEST_F(FooTest, Bar) { ... }
+//   TEST_F(FooTest, Baz) { ... }
+//
+// Test is not copyable.
+class GTEST_API_ Test {
+ public:
+  friend class TestInfo;
+
+  // The d'tor is virtual as we intend to inherit from Test.
+  virtual ~Test();
+
+  // Sets up the stuff shared by all tests in this test suite.
+  //
+  // Google Test will call Foo::SetUpTestSuite() before running the first
+  // test in test suite Foo.  Hence a sub-class can define its own
+  // SetUpTestSuite() method to shadow the one defined in the super
+  // class.
+  static void SetUpTestSuite() {}
+
+  // Tears down the stuff shared by all tests in this test suite.
+  //
+  // Google Test will call Foo::TearDownTestSuite() after running the last
+  // test in test suite Foo.  Hence a sub-class can define its own
+  // TearDownTestSuite() method to shadow the one defined in the super
+  // class.
+  static void TearDownTestSuite() {}
+
+  // Legacy API is deprecated but still available. Use SetUpTestSuite and
+  // TearDownTestSuite instead.
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  static void TearDownTestCase() {}
+  static void SetUpTestCase() {}
+#endif  // GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+  // Returns true if and only if the current test has a fatal failure.
+  static bool HasFatalFailure();
+
+  // Returns true if and only if the current test has a non-fatal failure.
+  static bool HasNonfatalFailure();
+
+  // Returns true if and only if the current test was skipped.
+  static bool IsSkipped();
+
+  // Returns true if and only if the current test has a (either fatal or
+  // non-fatal) failure.
+  static bool HasFailure() { return HasFatalFailure() || HasNonfatalFailure(); }
+
+  // Logs a property for the current test, test suite, or for the entire
+  // invocation of the test program when used outside of the context of a
+  // test suite.  Only the last value for a given key is remembered.  These
+  // are public static so they can be called from utility functions that are
+  // not members of the test fixture.  Calls to RecordProperty made during
+  // lifespan of the test (from the moment its constructor starts to the
+  // moment its destructor finishes) will be output in XML as attributes of
+  // the <testcase> element.  Properties recorded from fixture's
+  // SetUpTestSuite or TearDownTestSuite are logged as attributes of the
+  // corresponding <testsuite> element.  Calls to RecordProperty made in the
+  // global context (before or after invocation of RUN_ALL_TESTS and from
+  // SetUp/TearDown method of Environment objects registered with Google
+  // Test) will be output as attributes of the <testsuites> element.
+  static void RecordProperty(const std::string& key, const std::string& value);
+  static void RecordProperty(const std::string& key, int value);
+
+ protected:
+  // Creates a Test object.
+  Test();
+
+  // Sets up the test fixture.
+  virtual void SetUp();
+
+  // Tears down the test fixture.
+  virtual void TearDown();
+
+ private:
+  // Returns true if and only if the current test has the same fixture class
+  // as the first test in the current test suite.
+  static bool HasSameFixtureClass();
+
+  // Runs the test after the test fixture has been set up.
+  //
+  // A sub-class must implement this to define the test logic.
+  //
+  // DO NOT OVERRIDE THIS FUNCTION DIRECTLY IN A USER PROGRAM.
+  // Instead, use the TEST or TEST_F macro.
+  virtual void TestBody() = 0;
+
+  // Sets up, executes, and tears down the test.
+  void Run();
+
+  // Deletes self.  We deliberately pick an unusual name for this
+  // internal method to avoid clashing with names used in user TESTs.
+  void DeleteSelf_() { delete this; }
+
+  const std::unique_ptr<GTEST_FLAG_SAVER_> gtest_flag_saver_;
+
+  // Often a user misspells SetUp() as Setup() and spends a long time
+  // wondering why it is never called by Google Test.  The declaration of
+  // the following method is solely for catching such an error at
+  // compile time:
+  //
+  //   - The return type is deliberately chosen to be not void, so it
+  //   will be a conflict if void Setup() is declared in the user's
+  //   test fixture.
+  //
+  //   - This method is private, so it will be another compiler error
+  //   if the method is called from the user's test fixture.
+  //
+  // DO NOT OVERRIDE THIS FUNCTION.
+  //
+  // If you see an error about overriding the following function or
+  // about it being private, you have mis-spelled SetUp() as Setup().
+  struct Setup_should_be_spelled_SetUp {};
+  virtual Setup_should_be_spelled_SetUp* Setup() { return nullptr; }
+
+  // We disallow copying Tests.
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(Test);
+};
+
+typedef internal::TimeInMillis TimeInMillis;
+
+// A copyable object representing a user specified test property which can be
+// output as a key/value string pair.
+//
+// Don't inherit from TestProperty as its destructor is not virtual.
+class TestProperty {
+ public:
+  // C'tor.  TestProperty does NOT have a default constructor.
+  // Always use this constructor (with parameters) to create a
+  // TestProperty object.
+  TestProperty(const std::string& a_key, const std::string& a_value) :
+    key_(a_key), value_(a_value) {
+  }
+
+  // Gets the user supplied key.
+  const char* key() const {
+    return key_.c_str();
+  }
+
+  // Gets the user supplied value.
+  const char* value() const {
+    return value_.c_str();
+  }
+
+  // Sets a new value, overriding the one supplied in the constructor.
+  void SetValue(const std::string& new_value) {
+    value_ = new_value;
+  }
+
+ private:
+  // The key supplied by the user.
+  std::string key_;
+  // The value supplied by the user.
+  std::string value_;
+};
+
+// The result of a single Test.  This includes a list of
+// TestPartResults, a list of TestProperties, a count of how many
+// death tests there are in the Test, and how much time it took to run
+// the Test.
+//
+// TestResult is not copyable.
+class GTEST_API_ TestResult {
+ public:
+  // Creates an empty TestResult.
+  TestResult();
+
+  // D'tor.  Do not inherit from TestResult.
+  ~TestResult();
+
+  // Gets the number of all test parts.  This is the sum of the number
+  // of successful test parts and the number of failed test parts.
+  int total_part_count() const;
+
+  // Returns the number of the test properties.
+  int test_property_count() const;
+
+  // Returns true if and only if the test passed (i.e. no test part failed).
+  bool Passed() const { return !Skipped() && !Failed(); }
+
+  // Returns true if and only if the test was skipped.
+  bool Skipped() const;
+
+  // Returns true if and only if the test failed.
+  bool Failed() const;
+
+  // Returns true if and only if the test fatally failed.
+  bool HasFatalFailure() const;
+
+  // Returns true if and only if the test has a non-fatal failure.
+  bool HasNonfatalFailure() const;
+
+  // Returns the elapsed time, in milliseconds.
+  TimeInMillis elapsed_time() const { return elapsed_time_; }
+
+  // Gets the time of the test case start, in ms from the start of the
+  // UNIX epoch.
+  TimeInMillis start_timestamp() const { return start_timestamp_; }
+
+  // Returns the i-th test part result among all the results. i can range from 0
+  // to total_part_count() - 1. If i is not in that range, aborts the program.
+  const TestPartResult& GetTestPartResult(int i) const;
+
+  // Returns the i-th test property. i can range from 0 to
+  // test_property_count() - 1. If i is not in that range, aborts the
+  // program.
+  const TestProperty& GetTestProperty(int i) const;
+
+ private:
+  friend class TestInfo;
+  friend class TestSuite;
+  friend class UnitTest;
+  friend class internal::DefaultGlobalTestPartResultReporter;
+  friend class internal::ExecDeathTest;
+  friend class internal::TestResultAccessor;
+  friend class internal::UnitTestImpl;
+  friend class internal::WindowsDeathTest;
+  friend class internal::FuchsiaDeathTest;
+
+  // Gets the vector of TestPartResults.
+  const std::vector<TestPartResult>& test_part_results() const {
+    return test_part_results_;
+  }
+
+  // Gets the vector of TestProperties.
+  const std::vector<TestProperty>& test_properties() const {
+    return test_properties_;
+  }
+
+  // Sets the start time.
+  void set_start_timestamp(TimeInMillis start) { start_timestamp_ = start; }
+
+  // Sets the elapsed time.
+  void set_elapsed_time(TimeInMillis elapsed) { elapsed_time_ = elapsed; }
+
+  // Adds a test property to the list. The property is validated and may add
+  // a non-fatal failure if invalid (e.g., if it conflicts with reserved
+  // key names). If a property is already recorded for the same key, the
+  // value will be updated, rather than storing multiple values for the same
+  // key.  xml_element specifies the element for which the property is being
+  // recorded and is used for validation.
+  void RecordProperty(const std::string& xml_element,
+                      const TestProperty& test_property);
+
+  // Adds a failure if the key is a reserved attribute of Google Test
+  // testsuite tags.  Returns true if the property is valid.
+  // FIXME: Validate attribute names are legal and human readable.
+  static bool ValidateTestProperty(const std::string& xml_element,
+                                   const TestProperty& test_property);
+
+  // Adds a test part result to the list.
+  void AddTestPartResult(const TestPartResult& test_part_result);
+
+  // Returns the death test count.
+  int death_test_count() const { return death_test_count_; }
+
+  // Increments the death test count, returning the new count.
+  int increment_death_test_count() { return ++death_test_count_; }
+
+  // Clears the test part results.
+  void ClearTestPartResults();
+
+  // Clears the object.
+  void Clear();
+
+  // Protects mutable state of the property vector and of owned
+  // properties, whose values may be updated.
+  internal::Mutex test_properties_mutex_;
+
+  // The vector of TestPartResults
+  std::vector<TestPartResult> test_part_results_;
+  // The vector of TestProperties
+  std::vector<TestProperty> test_properties_;
+  // Running count of death tests.
+  int death_test_count_;
+  // The start time, in milliseconds since UNIX Epoch.
+  TimeInMillis start_timestamp_;
+  // The elapsed time, in milliseconds.
+  TimeInMillis elapsed_time_;
+
+  // We disallow copying TestResult.
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(TestResult);
+};  // class TestResult
+
+// A TestInfo object stores the following information about a test:
+//
+//   Test suite name
+//   Test name
+//   Whether the test should be run
+//   A function pointer that creates the test object when invoked
+//   Test result
+//
+// The constructor of TestInfo registers itself with the UnitTest
+// singleton such that the RUN_ALL_TESTS() macro knows which tests to
+// run.
+class GTEST_API_ TestInfo {
+ public:
+  // Destructs a TestInfo object.  This function is not virtual, so
+  // don't inherit from TestInfo.
+  ~TestInfo();
+
+  // Returns the test suite name.
+  const char* test_suite_name() const { return test_suite_name_.c_str(); }
+
+// Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  const char* test_case_name() const { return test_suite_name(); }
+#endif  // GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+  // Returns the test name.
+  const char* name() const { return name_.c_str(); }
+
+  // Returns the name of the parameter type, or NULL if this is not a typed
+  // or a type-parameterized test.
+  const char* type_param() const {
+    if (type_param_.get() != nullptr) return type_param_->c_str();
+    return nullptr;
+  }
+
+  // Returns the text representation of the value parameter, or NULL if this
+  // is not a value-parameterized test.
+  const char* value_param() const {
+    if (value_param_.get() != nullptr) return value_param_->c_str();
+    return nullptr;
+  }
+
+  // Returns the file name where this test is defined.
+  const char* file() const { return location_.file.c_str(); }
+
+  // Returns the line where this test is defined.
+  int line() const { return location_.line; }
+
+  // Return true if this test should not be run because it's in another shard.
+  bool is_in_another_shard() const { return is_in_another_shard_; }
+
+  // Returns true if this test should run, that is if the test is not
+  // disabled (or it is disabled but the also_run_disabled_tests flag has
+  // been specified) and its full name matches the user-specified filter.
+  //
+  // Google Test allows the user to filter the tests by their full names.
+  // The full name of a test Bar in test suite Foo is defined as
+  // "Foo.Bar".  Only the tests that match the filter will run.
+  //
+  // A filter is a colon-separated list of glob (not regex) patterns,
+  // optionally followed by a '-' and a colon-separated list of
+  // negative patterns (tests to exclude).  A test is run if it
+  // matches one of the positive patterns and does not match any of
+  // the negative patterns.
+  //
+  // For example, *A*:Foo.* is a filter that matches any string that
+  // contains the character 'A' or starts with "Foo.".
+  bool should_run() const { return should_run_; }
+
+  // Returns true if and only if this test will appear in the XML report.
+  bool is_reportable() const {
+    // The XML report includes tests matching the filter, excluding those
+    // run in other shards.
+    return matches_filter_ && !is_in_another_shard_;
+  }
+
+  // Returns the result of the test.
+  const TestResult* result() const { return &result_; }
+
+ private:
+#if GTEST_HAS_DEATH_TEST
+  friend class internal::DefaultDeathTestFactory;
+#endif  // GTEST_HAS_DEATH_TEST
+  friend class Test;
+  friend class TestSuite;
+  friend class internal::UnitTestImpl;
+  friend class internal::StreamingListenerTest;
+  friend TestInfo* internal::MakeAndRegisterTestInfo(
+      const char* test_suite_name, const char* name, const char* type_param,
+      const char* value_param, internal::CodeLocation code_location,
+      internal::TypeId fixture_class_id, internal::SetUpTestSuiteFunc set_up_tc,
+      internal::TearDownTestSuiteFunc tear_down_tc,
+      internal::TestFactoryBase* factory);
+
+  // Constructs a TestInfo object. The newly constructed instance assumes
+  // ownership of the factory object.
+  TestInfo(const std::string& test_suite_name, const std::string& name,
+           const char* a_type_param,   // NULL if not a type-parameterized test
+           const char* a_value_param,  // NULL if not a value-parameterized test
+           internal::CodeLocation a_code_location,
+           internal::TypeId fixture_class_id,
+           internal::TestFactoryBase* factory);
+
+  // Increments the number of death tests encountered in this test so
+  // far.
+  int increment_death_test_count() {
+    return result_.increment_death_test_count();
+  }
+
+  // Creates the test object, runs it, records its result, and then
+  // deletes it.
+  void Run();
+
+  // Skip and records the test result for this object.
+  void Skip();
+
+  static void ClearTestResult(TestInfo* test_info) {
+    test_info->result_.Clear();
+  }
+
+  // These fields are immutable properties of the test.
+  const std::string test_suite_name_;    // test suite name
+  const std::string name_;               // Test name
+  // Name of the parameter type, or NULL if this is not a typed or a
+  // type-parameterized test.
+  const std::unique_ptr<const ::std::string> type_param_;
+  // Text representation of the value parameter, or NULL if this is not a
+  // value-parameterized test.
+  const std::unique_ptr<const ::std::string> value_param_;
+  internal::CodeLocation location_;
+  const internal::TypeId fixture_class_id_;  // ID of the test fixture class
+  bool should_run_;           // True if and only if this test should run
+  bool is_disabled_;          // True if and only if this test is disabled
+  bool matches_filter_;       // True if this test matches the
+                              // user-specified filter.
+  bool is_in_another_shard_;  // Will be run in another shard.
+  internal::TestFactoryBase* const factory_;  // The factory that creates
+                                              // the test object
+
+  // This field is mutable and needs to be reset before running the
+  // test for the second time.
+  TestResult result_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(TestInfo);
+};
+
+// A test suite, which consists of a vector of TestInfos.
+//
+// TestSuite is not copyable.
+class GTEST_API_ TestSuite {
+ public:
+  // Creates a TestSuite with the given name.
+  //
+  // TestSuite does NOT have a default constructor.  Always use this
+  // constructor to create a TestSuite object.
+  //
+  // Arguments:
+  //
+  //   name:         name of the test suite
+  //   a_type_param: the name of the test's type parameter, or NULL if
+  //                 this is not a type-parameterized test.
+  //   set_up_tc:    pointer to the function that sets up the test suite
+  //   tear_down_tc: pointer to the function that tears down the test suite
+  TestSuite(const char* name, const char* a_type_param,
+            internal::SetUpTestSuiteFunc set_up_tc,
+            internal::TearDownTestSuiteFunc tear_down_tc);
+
+  // Destructor of TestSuite.
+  virtual ~TestSuite();
+
+  // Gets the name of the TestSuite.
+  const char* name() const { return name_.c_str(); }
+
+  // Returns the name of the parameter type, or NULL if this is not a
+  // type-parameterized test suite.
+  const char* type_param() const {
+    if (type_param_.get() != nullptr) return type_param_->c_str();
+    return nullptr;
+  }
+
+  // Returns true if any test in this test suite should run.
+  bool should_run() const { return should_run_; }
+
+  // Gets the number of successful tests in this test suite.
+  int successful_test_count() const;
+
+  // Gets the number of skipped tests in this test suite.
+  int skipped_test_count() const;
+
+  // Gets the number of failed tests in this test suite.
+  int failed_test_count() const;
+
+  // Gets the number of disabled tests that will be reported in the XML report.
+  int reportable_disabled_test_count() const;
+
+  // Gets the number of disabled tests in this test suite.
+  int disabled_test_count() const;
+
+  // Gets the number of tests to be printed in the XML report.
+  int reportable_test_count() const;
+
+  // Get the number of tests in this test suite that should run.
+  int test_to_run_count() const;
+
+  // Gets the number of all tests in this test suite.
+  int total_test_count() const;
+
+  // Returns true if and only if the test suite passed.
+  bool Passed() const { return !Failed(); }
+
+  // Returns true if and only if the test suite failed.
+  bool Failed() const {
+    return failed_test_count() > 0 || ad_hoc_test_result().Failed();
+  }
+
+  // Returns the elapsed time, in milliseconds.
+  TimeInMillis elapsed_time() const { return elapsed_time_; }
+
+  // Gets the time of the test suite start, in ms from the start of the
+  // UNIX epoch.
+  TimeInMillis start_timestamp() const { return start_timestamp_; }
+
+  // Returns the i-th test among all the tests. i can range from 0 to
+  // total_test_count() - 1. If i is not in that range, returns NULL.
+  const TestInfo* GetTestInfo(int i) const;
+
+  // Returns the TestResult that holds test properties recorded during
+  // execution of SetUpTestSuite and TearDownTestSuite.
+  const TestResult& ad_hoc_test_result() const { return ad_hoc_test_result_; }
+
+ private:
+  friend class Test;
+  friend class internal::UnitTestImpl;
+
+  // Gets the (mutable) vector of TestInfos in this TestSuite.
+  std::vector<TestInfo*>& test_info_list() { return test_info_list_; }
+
+  // Gets the (immutable) vector of TestInfos in this TestSuite.
+  const std::vector<TestInfo*>& test_info_list() const {
+    return test_info_list_;
+  }
+
+  // Returns the i-th test among all the tests. i can range from 0 to
+  // total_test_count() - 1. If i is not in that range, returns NULL.
+  TestInfo* GetMutableTestInfo(int i);
+
+  // Sets the should_run member.
+  void set_should_run(bool should) { should_run_ = should; }
+
+  // Adds a TestInfo to this test suite.  Will delete the TestInfo upon
+  // destruction of the TestSuite object.
+  void AddTestInfo(TestInfo * test_info);
+
+  // Clears the results of all tests in this test suite.
+  void ClearResult();
+
+  // Clears the results of all tests in the given test suite.
+  static void ClearTestSuiteResult(TestSuite* test_suite) {
+    test_suite->ClearResult();
+  }
+
+  // Runs every test in this TestSuite.
+  void Run();
+
+  // Skips the execution of tests under this TestSuite
+  void Skip();
+
+  // Runs SetUpTestSuite() for this TestSuite.  This wrapper is needed
+  // for catching exceptions thrown from SetUpTestSuite().
+  void RunSetUpTestSuite() {
+    if (set_up_tc_ != nullptr) {
+      (*set_up_tc_)();
+    }
+  }
+
+  // Runs TearDownTestSuite() for this TestSuite.  This wrapper is
+  // needed for catching exceptions thrown from TearDownTestSuite().
+  void RunTearDownTestSuite() {
+    if (tear_down_tc_ != nullptr) {
+      (*tear_down_tc_)();
+    }
+  }
+
+  // Returns true if and only if test passed.
+  static bool TestPassed(const TestInfo* test_info) {
+    return test_info->should_run() && test_info->result()->Passed();
+  }
+
+  // Returns true if and only if test skipped.
+  static bool TestSkipped(const TestInfo* test_info) {
+    return test_info->should_run() && test_info->result()->Skipped();
+  }
+
+  // Returns true if and only if test failed.
+  static bool TestFailed(const TestInfo* test_info) {
+    return test_info->should_run() && test_info->result()->Failed();
+  }
+
+  // Returns true if and only if the test is disabled and will be reported in
+  // the XML report.
+  static bool TestReportableDisabled(const TestInfo* test_info) {
+    return test_info->is_reportable() && test_info->is_disabled_;
+  }
+
+  // Returns true if and only if test is disabled.
+  static bool TestDisabled(const TestInfo* test_info) {
+    return test_info->is_disabled_;
+  }
+
+  // Returns true if and only if this test will appear in the XML report.
+  static bool TestReportable(const TestInfo* test_info) {
+    return test_info->is_reportable();
+  }
+
+  // Returns true if the given test should run.
+  static bool ShouldRunTest(const TestInfo* test_info) {
+    return test_info->should_run();
+  }
+
+  // Shuffles the tests in this test suite.
+  void ShuffleTests(internal::Random* random);
+
+  // Restores the test order to before the first shuffle.
+  void UnshuffleTests();
+
+  // Name of the test suite.
+  std::string name_;
+  // Name of the parameter type, or NULL if this is not a typed or a
+  // type-parameterized test.
+  const std::unique_ptr<const ::std::string> type_param_;
+  // The vector of TestInfos in their original order.  It owns the
+  // elements in the vector.
+  std::vector<TestInfo*> test_info_list_;
+  // Provides a level of indirection for the test list to allow easy
+  // shuffling and restoring the test order.  The i-th element in this
+  // vector is the index of the i-th test in the shuffled test list.
+  std::vector<int> test_indices_;
+  // Pointer to the function that sets up the test suite.
+  internal::SetUpTestSuiteFunc set_up_tc_;
+  // Pointer to the function that tears down the test suite.
+  internal::TearDownTestSuiteFunc tear_down_tc_;
+  // True if and only if any test in this test suite should run.
+  bool should_run_;
+  // The start time, in milliseconds since UNIX Epoch.
+  TimeInMillis start_timestamp_;
+  // Elapsed time, in milliseconds.
+  TimeInMillis elapsed_time_;
+  // Holds test properties recorded during execution of SetUpTestSuite and
+  // TearDownTestSuite.
+  TestResult ad_hoc_test_result_;
+
+  // We disallow copying TestSuites.
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(TestSuite);
+};
+
+// An Environment object is capable of setting up and tearing down an
+// environment.  You should subclass this to define your own
+// environment(s).
+//
+// An Environment object does the set-up and tear-down in virtual
+// methods SetUp() and TearDown() instead of the constructor and the
+// destructor, as:
+//
+//   1. You cannot safely throw from a destructor.  This is a problem
+//      as in some cases Google Test is used where exceptions are enabled, and
+//      we may want to implement ASSERT_* using exceptions where they are
+//      available.
+//   2. You cannot use ASSERT_* directly in a constructor or
+//      destructor.
+class Environment {
+ public:
+  // The d'tor is virtual as we need to subclass Environment.
+  virtual ~Environment() {}
+
+  // Override this to define how to set up the environment.
+  virtual void SetUp() {}
+
+  // Override this to define how to tear down the environment.
+  virtual void TearDown() {}
+ private:
+  // If you see an error about overriding the following function or
+  // about it being private, you have mis-spelled SetUp() as Setup().
+  struct Setup_should_be_spelled_SetUp {};
+  virtual Setup_should_be_spelled_SetUp* Setup() { return nullptr; }
+};
+
+#if GTEST_HAS_EXCEPTIONS
+
+// Exception which can be thrown from TestEventListener::OnTestPartResult.
+class GTEST_API_ AssertionException
+    : public internal::GoogleTestFailureException {
+ public:
+  explicit AssertionException(const TestPartResult& result)
+      : GoogleTestFailureException(result) {}
+};
+
+#endif  // GTEST_HAS_EXCEPTIONS
+
+// The interface for tracing execution of tests. The methods are organized in
+// the order the corresponding events are fired.
+class TestEventListener {
+ public:
+  virtual ~TestEventListener() {}
+
+  // Fired before any test activity starts.
+  virtual void OnTestProgramStart(const UnitTest& unit_test) = 0;
+
+  // Fired before each iteration of tests starts.  There may be more than
+  // one iteration if GTEST_FLAG(repeat) is set. iteration is the iteration
+  // index, starting from 0.
+  virtual void OnTestIterationStart(const UnitTest& unit_test,
+                                    int iteration) = 0;
+
+  // Fired before environment set-up for each iteration of tests starts.
+  virtual void OnEnvironmentsSetUpStart(const UnitTest& unit_test) = 0;
+
+  // Fired after environment set-up for each iteration of tests ends.
+  virtual void OnEnvironmentsSetUpEnd(const UnitTest& unit_test) = 0;
+
+  // Fired before the test suite starts.
+  virtual void OnTestSuiteStart(const TestSuite& /*test_suite*/) {}
+
+  //  Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  virtual void OnTestCaseStart(const TestCase& /*test_case*/) {}
+#endif  //  GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+  // Fired before the test starts.
+  virtual void OnTestStart(const TestInfo& test_info) = 0;
+
+  // Fired after a failed assertion or a SUCCEED() invocation.
+  // If you want to throw an exception from this function to skip to the next
+  // TEST, it must be AssertionException defined above, or inherited from it.
+  virtual void OnTestPartResult(const TestPartResult& test_part_result) = 0;
+
+  // Fired after the test ends.
+  virtual void OnTestEnd(const TestInfo& test_info) = 0;
+
+  // Fired after the test suite ends.
+  virtual void OnTestSuiteEnd(const TestSuite& /*test_suite*/) {}
+
+//  Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  virtual void OnTestCaseEnd(const TestCase& /*test_case*/) {}
+#endif  //  GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+  // Fired before environment tear-down for each iteration of tests starts.
+  virtual void OnEnvironmentsTearDownStart(const UnitTest& unit_test) = 0;
+
+  // Fired after environment tear-down for each iteration of tests ends.
+  virtual void OnEnvironmentsTearDownEnd(const UnitTest& unit_test) = 0;
+
+  // Fired after each iteration of tests finishes.
+  virtual void OnTestIterationEnd(const UnitTest& unit_test,
+                                  int iteration) = 0;
+
+  // Fired after all test activities have ended.
+  virtual void OnTestProgramEnd(const UnitTest& unit_test) = 0;
+};
+
+// The convenience class for users who need to override just one or two
+// methods and are not concerned that a possible change to a signature of
+// the methods they override will not be caught during the build.  For
+// comments about each method please see the definition of TestEventListener
+// above.
+class EmptyTestEventListener : public TestEventListener {
+ public:
+  void OnTestProgramStart(const UnitTest& /*unit_test*/) override {}
+  void OnTestIterationStart(const UnitTest& /*unit_test*/,
+                            int /*iteration*/) override {}
+  void OnEnvironmentsSetUpStart(const UnitTest& /*unit_test*/) override {}
+  void OnEnvironmentsSetUpEnd(const UnitTest& /*unit_test*/) override {}
+  void OnTestSuiteStart(const TestSuite& /*test_suite*/) override {}
+//  Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  void OnTestCaseStart(const TestCase& /*test_case*/) override {}
+#endif  //  GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+  void OnTestStart(const TestInfo& /*test_info*/) override {}
+  void OnTestPartResult(const TestPartResult& /*test_part_result*/) override {}
+  void OnTestEnd(const TestInfo& /*test_info*/) override {}
+  void OnTestSuiteEnd(const TestSuite& /*test_suite*/) override {}
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  void OnTestCaseEnd(const TestCase& /*test_case*/) override {}
+#endif  //  GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+  void OnEnvironmentsTearDownStart(const UnitTest& /*unit_test*/) override {}
+  void OnEnvironmentsTearDownEnd(const UnitTest& /*unit_test*/) override {}
+  void OnTestIterationEnd(const UnitTest& /*unit_test*/,
+                          int /*iteration*/) override {}
+  void OnTestProgramEnd(const UnitTest& /*unit_test*/) override {}
+};
+
+// TestEventListeners lets users add listeners to track events in Google Test.
+class GTEST_API_ TestEventListeners {
+ public:
+  TestEventListeners();
+  ~TestEventListeners();
+
+  // Appends an event listener to the end of the list. Google Test assumes
+  // the ownership of the listener (i.e. it will delete the listener when
+  // the test program finishes).
+  void Append(TestEventListener* listener);
+
+  // Removes the given event listener from the list and returns it.  It then
+  // becomes the caller's responsibility to delete the listener. Returns
+  // NULL if the listener is not found in the list.
+  TestEventListener* Release(TestEventListener* listener);
+
+  // Returns the standard listener responsible for the default console
+  // output.  Can be removed from the listeners list to shut down default
+  // console output.  Note that removing this object from the listener list
+  // with Release transfers its ownership to the caller and makes this
+  // function return NULL the next time.
+  TestEventListener* default_result_printer() const {
+    return default_result_printer_;
+  }
+
+  // Returns the standard listener responsible for the default XML output
+  // controlled by the --gtest_output=xml flag.  Can be removed from the
+  // listeners list by users who want to shut down the default XML output
+  // controlled by this flag and substitute it with custom one.  Note that
+  // removing this object from the listener list with Release transfers its
+  // ownership to the caller and makes this function return NULL the next
+  // time.
+  TestEventListener* default_xml_generator() const {
+    return default_xml_generator_;
+  }
+
+ private:
+  friend class TestSuite;
+  friend class TestInfo;
+  friend class internal::DefaultGlobalTestPartResultReporter;
+  friend class internal::NoExecDeathTest;
+  friend class internal::TestEventListenersAccessor;
+  friend class internal::UnitTestImpl;
+
+  // Returns repeater that broadcasts the TestEventListener events to all
+  // subscribers.
+  TestEventListener* repeater();
+
+  // Sets the default_result_printer attribute to the provided listener.
+  // The listener is also added to the listener list and previous
+  // default_result_printer is removed from it and deleted. The listener can
+  // also be NULL in which case it will not be added to the list. Does
+  // nothing if the previous and the current listener objects are the same.
+  void SetDefaultResultPrinter(TestEventListener* listener);
+
+  // Sets the default_xml_generator attribute to the provided listener.  The
+  // listener is also added to the listener list and previous
+  // default_xml_generator is removed from it and deleted. The listener can
+  // also be NULL in which case it will not be added to the list. Does
+  // nothing if the previous and the current listener objects are the same.
+  void SetDefaultXmlGenerator(TestEventListener* listener);
+
+  // Controls whether events will be forwarded by the repeater to the
+  // listeners in the list.
+  bool EventForwardingEnabled() const;
+  void SuppressEventForwarding();
+
+  // The actual list of listeners.
+  internal::TestEventRepeater* repeater_;
+  // Listener responsible for the standard result output.
+  TestEventListener* default_result_printer_;
+  // Listener responsible for the creation of the XML output file.
+  TestEventListener* default_xml_generator_;
+
+  // We disallow copying TestEventListeners.
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(TestEventListeners);
+};
+
+// A UnitTest consists of a vector of TestSuites.
+//
+// This is a singleton class.  The only instance of UnitTest is
+// created when UnitTest::GetInstance() is first called.  This
+// instance is never deleted.
+//
+// UnitTest is not copyable.
+//
+// This class is thread-safe as long as the methods are called
+// according to their specification.
+class GTEST_API_ UnitTest {
+ public:
+  // Gets the singleton UnitTest object.  The first time this method
+  // is called, a UnitTest object is constructed and returned.
+  // Consecutive calls will return the same object.
+  static UnitTest* GetInstance();
+
+  // Runs all tests in this UnitTest object and prints the result.
+  // Returns 0 if successful, or 1 otherwise.
+  //
+  // This method can only be called from the main thread.
+  //
+  // INTERNAL IMPLEMENTATION - DO NOT USE IN A USER PROGRAM.
+  int Run() GTEST_MUST_USE_RESULT_;
+
+  // Returns the working directory when the first TEST() or TEST_F()
+  // was executed.  The UnitTest object owns the string.
+  const char* original_working_dir() const;
+
+  // Returns the TestSuite object for the test that's currently running,
+  // or NULL if no test is running.
+  const TestSuite* current_test_suite() const GTEST_LOCK_EXCLUDED_(mutex_);
+
+// Legacy API is still available but deprecated
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  const TestCase* current_test_case() const GTEST_LOCK_EXCLUDED_(mutex_);
+#endif
+
+  // Returns the TestInfo object for the test that's currently running,
+  // or NULL if no test is running.
+  const TestInfo* current_test_info() const
+      GTEST_LOCK_EXCLUDED_(mutex_);
+
+  // Returns the random seed used at the start of the current test run.
+  int random_seed() const;
+
+  // Returns the ParameterizedTestSuiteRegistry object used to keep track of
+  // value-parameterized tests and instantiate and register them.
+  //
+  // INTERNAL IMPLEMENTATION - DO NOT USE IN A USER PROGRAM.
+  internal::ParameterizedTestSuiteRegistry& parameterized_test_registry()
+      GTEST_LOCK_EXCLUDED_(mutex_);
+
+  // Gets the number of successful test suites.
+  int successful_test_suite_count() const;
+
+  // Gets the number of failed test suites.
+  int failed_test_suite_count() const;
+
+  // Gets the number of all test suites.
+  int total_test_suite_count() const;
+
+  // Gets the number of all test suites that contain at least one test
+  // that should run.
+  int test_suite_to_run_count() const;
+
+  //  Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  int successful_test_case_count() const;
+  int failed_test_case_count() const;
+  int total_test_case_count() const;
+  int test_case_to_run_count() const;
+#endif  //  GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+  // Gets the number of successful tests.
+  int successful_test_count() const;
+
+  // Gets the number of skipped tests.
+  int skipped_test_count() const;
+
+  // Gets the number of failed tests.
+  int failed_test_count() const;
+
+  // Gets the number of disabled tests that will be reported in the XML report.
+  int reportable_disabled_test_count() const;
+
+  // Gets the number of disabled tests.
+  int disabled_test_count() const;
+
+  // Gets the number of tests to be printed in the XML report.
+  int reportable_test_count() const;
+
+  // Gets the number of all tests.
+  int total_test_count() const;
+
+  // Gets the number of tests that should run.
+  int test_to_run_count() const;
+
+  // Gets the time of the test program start, in ms from the start of the
+  // UNIX epoch.
+  TimeInMillis start_timestamp() const;
+
+  // Gets the elapsed time, in milliseconds.
+  TimeInMillis elapsed_time() const;
+
+  // Returns true if and only if the unit test passed (i.e. all test suites
+  // passed).
+  bool Passed() const;
+
+  // Returns true if and only if the unit test failed (i.e. some test suite
+  // failed or something outside of all tests failed).
+  bool Failed() const;
+
+  // Gets the i-th test suite among all the test suites. i can range from 0 to
+  // total_test_suite_count() - 1. If i is not in that range, returns NULL.
+  const TestSuite* GetTestSuite(int i) const;
+
+//  Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  const TestCase* GetTestCase(int i) const;
+#endif  //  GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+  // Returns the TestResult containing information on test failures and
+  // properties logged outside of individual test suites.
+  const TestResult& ad_hoc_test_result() const;
+
+  // Returns the list of event listeners that can be used to track events
+  // inside Google Test.
+  TestEventListeners& listeners();
+
+ private:
+  // Registers and returns a global test environment.  When a test
+  // program is run, all global test environments will be set-up in
+  // the order they were registered.  After all tests in the program
+  // have finished, all global test environments will be torn-down in
+  // the *reverse* order they were registered.
+  //
+  // The UnitTest object takes ownership of the given environment.
+  //
+  // This method can only be called from the main thread.
+  Environment* AddEnvironment(Environment* env);
+
+  // Adds a TestPartResult to the current TestResult object.  All
+  // Google Test assertion macros (e.g. ASSERT_TRUE, EXPECT_EQ, etc)
+  // eventually call this to report their results.  The user code
+  // should use the assertion macros instead of calling this directly.
+  void AddTestPartResult(TestPartResult::Type result_type,
+                         const char* file_name,
+                         int line_number,
+                         const std::string& message,
+                         const std::string& os_stack_trace)
+      GTEST_LOCK_EXCLUDED_(mutex_);
+
+  // Adds a TestProperty to the current TestResult object when invoked from
+  // inside a test, to current TestSuite's ad_hoc_test_result_ when invoked
+  // from SetUpTestSuite or TearDownTestSuite, or to the global property set
+  // when invoked elsewhere.  If the result already contains a property with
+  // the same key, the value will be updated.
+  void RecordProperty(const std::string& key, const std::string& value);
+
+  // Gets the i-th test suite among all the test suites. i can range from 0 to
+  // total_test_suite_count() - 1. If i is not in that range, returns NULL.
+  TestSuite* GetMutableTestSuite(int i);
+
+  // Accessors for the implementation object.
+  internal::UnitTestImpl* impl() { return impl_; }
+  const internal::UnitTestImpl* impl() const { return impl_; }
+
+  // These classes and functions are friends as they need to access private
+  // members of UnitTest.
+  friend class ScopedTrace;
+  friend class Test;
+  friend class internal::AssertHelper;
+  friend class internal::StreamingListenerTest;
+  friend class internal::UnitTestRecordPropertyTestHelper;
+  friend Environment* AddGlobalTestEnvironment(Environment* env);
+  friend std::set<std::string>* internal::GetIgnoredParameterizedTestSuites();
+  friend internal::UnitTestImpl* internal::GetUnitTestImpl();
+  friend void internal::ReportFailureInUnknownLocation(
+      TestPartResult::Type result_type,
+      const std::string& message);
+
+  // Creates an empty UnitTest.
+  UnitTest();
+
+  // D'tor
+  virtual ~UnitTest();
+
+  // Pushes a trace defined by SCOPED_TRACE() on to the per-thread
+  // Google Test trace stack.
+  void PushGTestTrace(const internal::TraceInfo& trace)
+      GTEST_LOCK_EXCLUDED_(mutex_);
+
+  // Pops a trace from the per-thread Google Test trace stack.
+  void PopGTestTrace()
+      GTEST_LOCK_EXCLUDED_(mutex_);
+
+  // Protects mutable state in *impl_.  This is mutable as some const
+  // methods need to lock it too.
+  mutable internal::Mutex mutex_;
+
+  // Opaque implementation object.  This field is never changed once
+  // the object is constructed.  We don't mark it as const here, as
+  // doing so will cause a warning in the constructor of UnitTest.
+  // Mutable state in *impl_ is protected by mutex_.
+  internal::UnitTestImpl* impl_;
+
+  // We disallow copying UnitTest.
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(UnitTest);
+};
+
+// A convenient wrapper for adding an environment for the test
+// program.
+//
+// You should call this before RUN_ALL_TESTS() is called, probably in
+// main().  If you use gtest_main, you need to call this before main()
+// starts for it to take effect.  For example, you can define a global
+// variable like this:
+//
+//   testing::Environment* const foo_env =
+//       testing::AddGlobalTestEnvironment(new FooEnvironment);
+//
+// However, we strongly recommend you to write your own main() and
+// call AddGlobalTestEnvironment() there, as relying on initialization
+// of global variables makes the code harder to read and may cause
+// problems when you register multiple environments from different
+// translation units and the environments have dependencies among them
+// (remember that the compiler doesn't guarantee the order in which
+// global variables from different translation units are initialized).
+inline Environment* AddGlobalTestEnvironment(Environment* env) {
+  return UnitTest::GetInstance()->AddEnvironment(env);
+}
+
+// Initializes Google Test.  This must be called before calling
+// RUN_ALL_TESTS().  In particular, it parses a command line for the
+// flags that Google Test recognizes.  Whenever a Google Test flag is
+// seen, it is removed from argv, and *argc is decremented.
+//
+// No value is returned.  Instead, the Google Test flag variables are
+// updated.
+//
+// Calling the function for the second time has no user-visible effect.
+GTEST_API_ void InitGoogleTest(int* argc, char** argv);
+
+// This overloaded version can be used in Windows programs compiled in
+// UNICODE mode.
+GTEST_API_ void InitGoogleTest(int* argc, wchar_t** argv);
+
+// This overloaded version can be used on Arduino/embedded platforms where
+// there is no argc/argv.
+GTEST_API_ void InitGoogleTest();
+
+namespace internal {
+
+// Separate the error generating code from the code path to reduce the stack
+// frame size of CmpHelperEQ. This helps reduce the overhead of some sanitizers
+// when calling EXPECT_* in a tight loop.
+template <typename T1, typename T2>
+AssertionResult CmpHelperEQFailure(const char* lhs_expression,
+                                   const char* rhs_expression,
+                                   const T1& lhs, const T2& rhs) {
+  return EqFailure(lhs_expression,
+                   rhs_expression,
+                   FormatForComparisonFailureMessage(lhs, rhs),
+                   FormatForComparisonFailureMessage(rhs, lhs),
+                   false);
+}
+
+// This block of code defines operator==/!=
+// to block lexical scope lookup.
+// It prevents using invalid operator==/!= defined at namespace scope.
+struct faketype {};
+inline bool operator==(faketype, faketype) { return true; }
+inline bool operator!=(faketype, faketype) { return false; }
+
+// The helper function for {ASSERT|EXPECT}_EQ.
+template <typename T1, typename T2>
+AssertionResult CmpHelperEQ(const char* lhs_expression,
+                            const char* rhs_expression,
+                            const T1& lhs,
+                            const T2& rhs) {
+  if (lhs == rhs) {
+    return AssertionSuccess();
+  }
+
+  return CmpHelperEQFailure(lhs_expression, rhs_expression, lhs, rhs);
+}
+
+class EqHelper {
+ public:
+  // This templatized version is for the general case.
+  template <
+      typename T1, typename T2,
+      // Disable this overload for cases where one argument is a pointer
+      // and the other is the null pointer constant.
+      typename std::enable_if<!std::is_integral<T1>::value ||
+                              !std::is_pointer<T2>::value>::type* = nullptr>
+  static AssertionResult Compare(const char* lhs_expression,
+                                 const char* rhs_expression, const T1& lhs,
+                                 const T2& rhs) {
+    return CmpHelperEQ(lhs_expression, rhs_expression, lhs, rhs);
+  }
+
+  // With this overloaded version, we allow anonymous enums to be used
+  // in {ASSERT|EXPECT}_EQ when compiled with gcc 4, as anonymous
+  // enums can be implicitly cast to BiggestInt.
+  //
+  // Even though its body looks the same as the above version, we
+  // cannot merge the two, as it will make anonymous enums unhappy.
+  static AssertionResult Compare(const char* lhs_expression,
+                                 const char* rhs_expression,
+                                 BiggestInt lhs,
+                                 BiggestInt rhs) {
+    return CmpHelperEQ(lhs_expression, rhs_expression, lhs, rhs);
+  }
+
+  template <typename T>
+  static AssertionResult Compare(
+      const char* lhs_expression, const char* rhs_expression,
+      // Handle cases where '0' is used as a null pointer literal.
+      std::nullptr_t /* lhs */, T* rhs) {
+    // We already know that 'lhs' is a null pointer.
+    return CmpHelperEQ(lhs_expression, rhs_expression, static_cast<T*>(nullptr),
+                       rhs);
+  }
+};
+
+// Separate the error generating code from the code path to reduce the stack
+// frame size of CmpHelperOP. This helps reduce the overhead of some sanitizers
+// when calling EXPECT_OP in a tight loop.
+template <typename T1, typename T2>
+AssertionResult CmpHelperOpFailure(const char* expr1, const char* expr2,
+                                   const T1& val1, const T2& val2,
+                                   const char* op) {
+  return AssertionFailure()
+         << "Expected: (" << expr1 << ") " << op << " (" << expr2
+         << "), actual: " << FormatForComparisonFailureMessage(val1, val2)
+         << " vs " << FormatForComparisonFailureMessage(val2, val1);
+}
+
+// A macro for implementing the helper functions needed to implement
+// ASSERT_?? and EXPECT_??.  It is here just to avoid copy-and-paste
+// of similar code.
+//
+// INTERNAL IMPLEMENTATION - DO NOT USE IN A USER PROGRAM.
+
+#define GTEST_IMPL_CMP_HELPER_(op_name, op)\
+template <typename T1, typename T2>\
+AssertionResult CmpHelper##op_name(const char* expr1, const char* expr2, \
+                                   const T1& val1, const T2& val2) {\
+  if (val1 op val2) {\
+    return AssertionSuccess();\
+  } else {\
+    return CmpHelperOpFailure(expr1, expr2, val1, val2, #op);\
+  }\
+}
+
+// INTERNAL IMPLEMENTATION - DO NOT USE IN A USER PROGRAM.
+
+// Implements the helper function for {ASSERT|EXPECT}_NE
+GTEST_IMPL_CMP_HELPER_(NE, !=)
+// Implements the helper function for {ASSERT|EXPECT}_LE
+GTEST_IMPL_CMP_HELPER_(LE, <=)
+// Implements the helper function for {ASSERT|EXPECT}_LT
+GTEST_IMPL_CMP_HELPER_(LT, <)
+// Implements the helper function for {ASSERT|EXPECT}_GE
+GTEST_IMPL_CMP_HELPER_(GE, >=)
+// Implements the helper function for {ASSERT|EXPECT}_GT
+GTEST_IMPL_CMP_HELPER_(GT, >)
+
+#undef GTEST_IMPL_CMP_HELPER_
+
+// The helper function for {ASSERT|EXPECT}_STREQ.
+//
+// INTERNAL IMPLEMENTATION - DO NOT USE IN A USER PROGRAM.
+GTEST_API_ AssertionResult CmpHelperSTREQ(const char* s1_expression,
+                                          const char* s2_expression,
+                                          const char* s1,
+                                          const char* s2);
+
+// The helper function for {ASSERT|EXPECT}_STRCASEEQ.
+//
+// INTERNAL IMPLEMENTATION - DO NOT USE IN A USER PROGRAM.
+GTEST_API_ AssertionResult CmpHelperSTRCASEEQ(const char* s1_expression,
+                                              const char* s2_expression,
+                                              const char* s1,
+                                              const char* s2);
+
+// The helper function for {ASSERT|EXPECT}_STRNE.
+//
+// INTERNAL IMPLEMENTATION - DO NOT USE IN A USER PROGRAM.
+GTEST_API_ AssertionResult CmpHelperSTRNE(const char* s1_expression,
+                                          const char* s2_expression,
+                                          const char* s1,
+                                          const char* s2);
+
+// The helper function for {ASSERT|EXPECT}_STRCASENE.
+//
+// INTERNAL IMPLEMENTATION - DO NOT USE IN A USER PROGRAM.
+GTEST_API_ AssertionResult CmpHelperSTRCASENE(const char* s1_expression,
+                                              const char* s2_expression,
+                                              const char* s1,
+                                              const char* s2);
+
+
+// Helper function for *_STREQ on wide strings.
+//
+// INTERNAL IMPLEMENTATION - DO NOT USE IN A USER PROGRAM.
+GTEST_API_ AssertionResult CmpHelperSTREQ(const char* s1_expression,
+                                          const char* s2_expression,
+                                          const wchar_t* s1,
+                                          const wchar_t* s2);
+
+// Helper function for *_STRNE on wide strings.
+//
+// INTERNAL IMPLEMENTATION - DO NOT USE IN A USER PROGRAM.
+GTEST_API_ AssertionResult CmpHelperSTRNE(const char* s1_expression,
+                                          const char* s2_expression,
+                                          const wchar_t* s1,
+                                          const wchar_t* s2);
+
+}  // namespace internal
+
+// IsSubstring() and IsNotSubstring() are intended to be used as the
+// first argument to {EXPECT,ASSERT}_PRED_FORMAT2(), not by
+// themselves.  They check whether needle is a substring of haystack
+// (NULL is considered a substring of itself only), and return an
+// appropriate error message when they fail.
+//
+// The {needle,haystack}_expr arguments are the stringified
+// expressions that generated the two real arguments.
+GTEST_API_ AssertionResult IsSubstring(
+    const char* needle_expr, const char* haystack_expr,
+    const char* needle, const char* haystack);
+GTEST_API_ AssertionResult IsSubstring(
+    const char* needle_expr, const char* haystack_expr,
+    const wchar_t* needle, const wchar_t* haystack);
+GTEST_API_ AssertionResult IsNotSubstring(
+    const char* needle_expr, const char* haystack_expr,
+    const char* needle, const char* haystack);
+GTEST_API_ AssertionResult IsNotSubstring(
+    const char* needle_expr, const char* haystack_expr,
+    const wchar_t* needle, const wchar_t* haystack);
+GTEST_API_ AssertionResult IsSubstring(
+    const char* needle_expr, const char* haystack_expr,
+    const ::std::string& needle, const ::std::string& haystack);
+GTEST_API_ AssertionResult IsNotSubstring(
+    const char* needle_expr, const char* haystack_expr,
+    const ::std::string& needle, const ::std::string& haystack);
+
+#if GTEST_HAS_STD_WSTRING
+GTEST_API_ AssertionResult IsSubstring(
+    const char* needle_expr, const char* haystack_expr,
+    const ::std::wstring& needle, const ::std::wstring& haystack);
+GTEST_API_ AssertionResult IsNotSubstring(
+    const char* needle_expr, const char* haystack_expr,
+    const ::std::wstring& needle, const ::std::wstring& haystack);
+#endif  // GTEST_HAS_STD_WSTRING
+
+namespace internal {
+
+// Helper template function for comparing floating-points.
+//
+// Template parameter:
+//
+//   RawType: the raw floating-point type (either float or double)
+//
+// INTERNAL IMPLEMENTATION - DO NOT USE IN A USER PROGRAM.
+template <typename RawType>
+AssertionResult CmpHelperFloatingPointEQ(const char* lhs_expression,
+                                         const char* rhs_expression,
+                                         RawType lhs_value,
+                                         RawType rhs_value) {
+  const FloatingPoint<RawType> lhs(lhs_value), rhs(rhs_value);
+
+  if (lhs.AlmostEquals(rhs)) {
+    return AssertionSuccess();
+  }
+
+  ::std::stringstream lhs_ss;
+  lhs_ss << std::setprecision(std::numeric_limits<RawType>::digits10 + 2)
+         << lhs_value;
+
+  ::std::stringstream rhs_ss;
+  rhs_ss << std::setprecision(std::numeric_limits<RawType>::digits10 + 2)
+         << rhs_value;
+
+  return EqFailure(lhs_expression,
+                   rhs_expression,
+                   StringStreamToString(&lhs_ss),
+                   StringStreamToString(&rhs_ss),
+                   false);
+}
+
+// Helper function for implementing ASSERT_NEAR.
+//
+// INTERNAL IMPLEMENTATION - DO NOT USE IN A USER PROGRAM.
+GTEST_API_ AssertionResult DoubleNearPredFormat(const char* expr1,
+                                                const char* expr2,
+                                                const char* abs_error_expr,
+                                                double val1,
+                                                double val2,
+                                                double abs_error);
+
+// INTERNAL IMPLEMENTATION - DO NOT USE IN USER CODE.
+// A class that enables one to stream messages to assertion macros
+class GTEST_API_ AssertHelper {
+ public:
+  // Constructor.
+  AssertHelper(TestPartResult::Type type,
+               const char* file,
+               int line,
+               const char* message);
+  ~AssertHelper();
+
+  // Message assignment is a semantic trick to enable assertion
+  // streaming; see the GTEST_MESSAGE_ macro below.
+  void operator=(const Message& message) const;
+
+ private:
+  // We put our data in a struct so that the size of the AssertHelper class can
+  // be as small as possible.  This is important because gcc is incapable of
+  // re-using stack space even for temporary variables, so every EXPECT_EQ
+  // reserves stack space for another AssertHelper.
+  struct AssertHelperData {
+    AssertHelperData(TestPartResult::Type t,
+                     const char* srcfile,
+                     int line_num,
+                     const char* msg)
+        : type(t), file(srcfile), line(line_num), message(msg) { }
+
+    TestPartResult::Type const type;
+    const char* const file;
+    int const line;
+    std::string const message;
+
+   private:
+    GTEST_DISALLOW_COPY_AND_ASSIGN_(AssertHelperData);
+  };
+
+  AssertHelperData* const data_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(AssertHelper);
+};
+
+}  // namespace internal
+
+// The pure interface class that all value-parameterized tests inherit from.
+// A value-parameterized class must inherit from both ::testing::Test and
+// ::testing::WithParamInterface. In most cases that just means inheriting
+// from ::testing::TestWithParam, but more complicated test hierarchies
+// may need to inherit from Test and WithParamInterface at different levels.
+//
+// This interface has support for accessing the test parameter value via
+// the GetParam() method.
+//
+// Use it with one of the parameter generator defining functions, like Range(),
+// Values(), ValuesIn(), Bool(), and Combine().
+//
+// class FooTest : public ::testing::TestWithParam<int> {
+//  protected:
+//   FooTest() {
+//     // Can use GetParam() here.
+//   }
+//   ~FooTest() override {
+//     // Can use GetParam() here.
+//   }
+//   void SetUp() override {
+//     // Can use GetParam() here.
+//   }
+//   void TearDown override {
+//     // Can use GetParam() here.
+//   }
+// };
+// TEST_P(FooTest, DoesBar) {
+//   // Can use GetParam() method here.
+//   Foo foo;
+//   ASSERT_TRUE(foo.DoesBar(GetParam()));
+// }
+// INSTANTIATE_TEST_SUITE_P(OneToTenRange, FooTest, ::testing::Range(1, 10));
+
+template <typename T>
+class WithParamInterface {
+ public:
+  typedef T ParamType;
+  virtual ~WithParamInterface() {}
+
+  // The current parameter value. Is also available in the test fixture's
+  // constructor.
+  static const ParamType& GetParam() {
+    GTEST_CHECK_(parameter_ != nullptr)
+        << "GetParam() can only be called inside a value-parameterized test "
+        << "-- did you intend to write TEST_P instead of TEST_F?";
+    return *parameter_;
+  }
+
+ private:
+  // Sets parameter value. The caller is responsible for making sure the value
+  // remains alive and unchanged throughout the current test.
+  static void SetParam(const ParamType* parameter) {
+    parameter_ = parameter;
+  }
+
+  // Static value used for accessing parameter during a test lifetime.
+  static const ParamType* parameter_;
+
+  // TestClass must be a subclass of WithParamInterface<T> and Test.
+  template <class TestClass> friend class internal::ParameterizedTestFactory;
+};
+
+template <typename T>
+const T* WithParamInterface<T>::parameter_ = nullptr;
+
+// Most value-parameterized classes can ignore the existence of
+// WithParamInterface, and can just inherit from ::testing::TestWithParam.
+
+template <typename T>
+class TestWithParam : public Test, public WithParamInterface<T> {
+};
+
+// Macros for indicating success/failure in test code.
+
+// Skips test in runtime.
+// Skipping test aborts current function.
+// Skipped tests are neither successful nor failed.
+#define GTEST_SKIP() GTEST_SKIP_("")
+
+// ADD_FAILURE unconditionally adds a failure to the current test.
+// SUCCEED generates a success - it doesn't automatically make the
+// current test successful, as a test is only successful when it has
+// no failure.
+//
+// EXPECT_* verifies that a certain condition is satisfied.  If not,
+// it behaves like ADD_FAILURE.  In particular:
+//
+//   EXPECT_TRUE  verifies that a Boolean condition is true.
+//   EXPECT_FALSE verifies that a Boolean condition is false.
+//
+// FAIL and ASSERT_* are similar to ADD_FAILURE and EXPECT_*, except
+// that they will also abort the current function on failure.  People
+// usually want the fail-fast behavior of FAIL and ASSERT_*, but those
+// writing data-driven tests often find themselves using ADD_FAILURE
+// and EXPECT_* more.
+
+// Generates a nonfatal failure with a generic message.
+#define ADD_FAILURE() GTEST_NONFATAL_FAILURE_("Failed")
+
+// Generates a nonfatal failure at the given source file location with
+// a generic message.
+#define ADD_FAILURE_AT(file, line) \
+  GTEST_MESSAGE_AT_(file, line, "Failed", \
+                    ::testing::TestPartResult::kNonFatalFailure)
+
+// Generates a fatal failure with a generic message.
+#define GTEST_FAIL() GTEST_FATAL_FAILURE_("Failed")
+
+// Like GTEST_FAIL(), but at the given source file location.
+#define GTEST_FAIL_AT(file, line)         \
+  GTEST_MESSAGE_AT_(file, line, "Failed", \
+                    ::testing::TestPartResult::kFatalFailure)
+
+// Define this macro to 1 to omit the definition of FAIL(), which is a
+// generic name and clashes with some other libraries.
+#if !GTEST_DONT_DEFINE_FAIL
+# define FAIL() GTEST_FAIL()
+#endif
+
+// Generates a success with a generic message.
+#define GTEST_SUCCEED() GTEST_SUCCESS_("Succeeded")
+
+// Define this macro to 1 to omit the definition of SUCCEED(), which
+// is a generic name and clashes with some other libraries.
+#if !GTEST_DONT_DEFINE_SUCCEED
+# define SUCCEED() GTEST_SUCCEED()
+#endif
+
+// Macros for testing exceptions.
+//
+//    * {ASSERT|EXPECT}_THROW(statement, expected_exception):
+//         Tests that the statement throws the expected exception.
+//    * {ASSERT|EXPECT}_NO_THROW(statement):
+//         Tests that the statement doesn't throw any exception.
+//    * {ASSERT|EXPECT}_ANY_THROW(statement):
+//         Tests that the statement throws an exception.
+
+#define EXPECT_THROW(statement, expected_exception) \
+  GTEST_TEST_THROW_(statement, expected_exception, GTEST_NONFATAL_FAILURE_)
+#define EXPECT_NO_THROW(statement) \
+  GTEST_TEST_NO_THROW_(statement, GTEST_NONFATAL_FAILURE_)
+#define EXPECT_ANY_THROW(statement) \
+  GTEST_TEST_ANY_THROW_(statement, GTEST_NONFATAL_FAILURE_)
+#define ASSERT_THROW(statement, expected_exception) \
+  GTEST_TEST_THROW_(statement, expected_exception, GTEST_FATAL_FAILURE_)
+#define ASSERT_NO_THROW(statement) \
+  GTEST_TEST_NO_THROW_(statement, GTEST_FATAL_FAILURE_)
+#define ASSERT_ANY_THROW(statement) \
+  GTEST_TEST_ANY_THROW_(statement, GTEST_FATAL_FAILURE_)
+
+// Boolean assertions. Condition can be either a Boolean expression or an
+// AssertionResult. For more information on how to use AssertionResult with
+// these macros see comments on that class.
+#define GTEST_EXPECT_TRUE(condition) \
+  GTEST_TEST_BOOLEAN_(condition, #condition, false, true, \
+                      GTEST_NONFATAL_FAILURE_)
+#define GTEST_EXPECT_FALSE(condition) \
+  GTEST_TEST_BOOLEAN_(!(condition), #condition, true, false, \
+                      GTEST_NONFATAL_FAILURE_)
+#define GTEST_ASSERT_TRUE(condition) \
+  GTEST_TEST_BOOLEAN_(condition, #condition, false, true, \
+                      GTEST_FATAL_FAILURE_)
+#define GTEST_ASSERT_FALSE(condition) \
+  GTEST_TEST_BOOLEAN_(!(condition), #condition, true, false, \
+                      GTEST_FATAL_FAILURE_)
+
+// Define these macros to 1 to omit the definition of the corresponding
+// EXPECT or ASSERT, which clashes with some users' own code.
+
+#if !GTEST_DONT_DEFINE_EXPECT_TRUE
+#define EXPECT_TRUE(condition) GTEST_EXPECT_TRUE(condition)
+#endif
+
+#if !GTEST_DONT_DEFINE_EXPECT_FALSE
+#define EXPECT_FALSE(condition) GTEST_EXPECT_FALSE(condition)
+#endif
+
+#if !GTEST_DONT_DEFINE_ASSERT_TRUE
+#define ASSERT_TRUE(condition) GTEST_ASSERT_TRUE(condition)
+#endif
+
+#if !GTEST_DONT_DEFINE_ASSERT_FALSE
+#define ASSERT_FALSE(condition) GTEST_ASSERT_FALSE(condition)
+#endif
+
+// Macros for testing equalities and inequalities.
+//
+//    * {ASSERT|EXPECT}_EQ(v1, v2): Tests that v1 == v2
+//    * {ASSERT|EXPECT}_NE(v1, v2): Tests that v1 != v2
+//    * {ASSERT|EXPECT}_LT(v1, v2): Tests that v1 < v2
+//    * {ASSERT|EXPECT}_LE(v1, v2): Tests that v1 <= v2
+//    * {ASSERT|EXPECT}_GT(v1, v2): Tests that v1 > v2
+//    * {ASSERT|EXPECT}_GE(v1, v2): Tests that v1 >= v2
+//
+// When they are not, Google Test prints both the tested expressions and
+// their actual values.  The values must be compatible built-in types,
+// or you will get a compiler error.  By "compatible" we mean that the
+// values can be compared by the respective operator.
+//
+// Note:
+//
+//   1. It is possible to make a user-defined type work with
+//   {ASSERT|EXPECT}_??(), but that requires overloading the
+//   comparison operators and is thus discouraged by the Google C++
+//   Usage Guide.  Therefore, you are advised to use the
+//   {ASSERT|EXPECT}_TRUE() macro to assert that two objects are
+//   equal.
+//
+//   2. The {ASSERT|EXPECT}_??() macros do pointer comparisons on
+//   pointers (in particular, C strings).  Therefore, if you use it
+//   with two C strings, you are testing how their locations in memory
+//   are related, not how their content is related.  To compare two C
+//   strings by content, use {ASSERT|EXPECT}_STR*().
+//
+//   3. {ASSERT|EXPECT}_EQ(v1, v2) is preferred to
+//   {ASSERT|EXPECT}_TRUE(v1 == v2), as the former tells you
+//   what the actual value is when it fails, and similarly for the
+//   other comparisons.
+//
+//   4. Do not depend on the order in which {ASSERT|EXPECT}_??()
+//   evaluate their arguments, which is undefined.
+//
+//   5. These macros evaluate their arguments exactly once.
+//
+// Examples:
+//
+//   EXPECT_NE(Foo(), 5);
+//   EXPECT_EQ(a_pointer, NULL);
+//   ASSERT_LT(i, array_size);
+//   ASSERT_GT(records.size(), 0) << "There is no record left.";
+
+#define EXPECT_EQ(val1, val2) \
+  EXPECT_PRED_FORMAT2(::testing::internal::EqHelper::Compare, val1, val2)
+#define EXPECT_NE(val1, val2) \
+  EXPECT_PRED_FORMAT2(::testing::internal::CmpHelperNE, val1, val2)
+#define EXPECT_LE(val1, val2) \
+  EXPECT_PRED_FORMAT2(::testing::internal::CmpHelperLE, val1, val2)
+#define EXPECT_LT(val1, val2) \
+  EXPECT_PRED_FORMAT2(::testing::internal::CmpHelperLT, val1, val2)
+#define EXPECT_GE(val1, val2) \
+  EXPECT_PRED_FORMAT2(::testing::internal::CmpHelperGE, val1, val2)
+#define EXPECT_GT(val1, val2) \
+  EXPECT_PRED_FORMAT2(::testing::internal::CmpHelperGT, val1, val2)
+
+#define GTEST_ASSERT_EQ(val1, val2) \
+  ASSERT_PRED_FORMAT2(::testing::internal::EqHelper::Compare, val1, val2)
+#define GTEST_ASSERT_NE(val1, val2) \
+  ASSERT_PRED_FORMAT2(::testing::internal::CmpHelperNE, val1, val2)
+#define GTEST_ASSERT_LE(val1, val2) \
+  ASSERT_PRED_FORMAT2(::testing::internal::CmpHelperLE, val1, val2)
+#define GTEST_ASSERT_LT(val1, val2) \
+  ASSERT_PRED_FORMAT2(::testing::internal::CmpHelperLT, val1, val2)
+#define GTEST_ASSERT_GE(val1, val2) \
+  ASSERT_PRED_FORMAT2(::testing::internal::CmpHelperGE, val1, val2)
+#define GTEST_ASSERT_GT(val1, val2) \
+  ASSERT_PRED_FORMAT2(::testing::internal::CmpHelperGT, val1, val2)
+
+// Define macro GTEST_DONT_DEFINE_ASSERT_XY to 1 to omit the definition of
+// ASSERT_XY(), which clashes with some users' own code.
+
+#if !GTEST_DONT_DEFINE_ASSERT_EQ
+# define ASSERT_EQ(val1, val2) GTEST_ASSERT_EQ(val1, val2)
+#endif
+
+#if !GTEST_DONT_DEFINE_ASSERT_NE
+# define ASSERT_NE(val1, val2) GTEST_ASSERT_NE(val1, val2)
+#endif
+
+#if !GTEST_DONT_DEFINE_ASSERT_LE
+# define ASSERT_LE(val1, val2) GTEST_ASSERT_LE(val1, val2)
+#endif
+
+#if !GTEST_DONT_DEFINE_ASSERT_LT
+# define ASSERT_LT(val1, val2) GTEST_ASSERT_LT(val1, val2)
+#endif
+
+#if !GTEST_DONT_DEFINE_ASSERT_GE
+# define ASSERT_GE(val1, val2) GTEST_ASSERT_GE(val1, val2)
+#endif
+
+#if !GTEST_DONT_DEFINE_ASSERT_GT
+# define ASSERT_GT(val1, val2) GTEST_ASSERT_GT(val1, val2)
+#endif
+
+// C-string Comparisons.  All tests treat NULL and any non-NULL string
+// as different.  Two NULLs are equal.
+//
+//    * {ASSERT|EXPECT}_STREQ(s1, s2):     Tests that s1 == s2
+//    * {ASSERT|EXPECT}_STRNE(s1, s2):     Tests that s1 != s2
+//    * {ASSERT|EXPECT}_STRCASEEQ(s1, s2): Tests that s1 == s2, ignoring case
+//    * {ASSERT|EXPECT}_STRCASENE(s1, s2): Tests that s1 != s2, ignoring case
+//
+// For wide or narrow string objects, you can use the
+// {ASSERT|EXPECT}_??() macros.
+//
+// Don't depend on the order in which the arguments are evaluated,
+// which is undefined.
+//
+// These macros evaluate their arguments exactly once.
+
+#define EXPECT_STREQ(s1, s2) \
+  EXPECT_PRED_FORMAT2(::testing::internal::CmpHelperSTREQ, s1, s2)
+#define EXPECT_STRNE(s1, s2) \
+  EXPECT_PRED_FORMAT2(::testing::internal::CmpHelperSTRNE, s1, s2)
+#define EXPECT_STRCASEEQ(s1, s2) \
+  EXPECT_PRED_FORMAT2(::testing::internal::CmpHelperSTRCASEEQ, s1, s2)
+#define EXPECT_STRCASENE(s1, s2)\
+  EXPECT_PRED_FORMAT2(::testing::internal::CmpHelperSTRCASENE, s1, s2)
+
+#define ASSERT_STREQ(s1, s2) \
+  ASSERT_PRED_FORMAT2(::testing::internal::CmpHelperSTREQ, s1, s2)
+#define ASSERT_STRNE(s1, s2) \
+  ASSERT_PRED_FORMAT2(::testing::internal::CmpHelperSTRNE, s1, s2)
+#define ASSERT_STRCASEEQ(s1, s2) \
+  ASSERT_PRED_FORMAT2(::testing::internal::CmpHelperSTRCASEEQ, s1, s2)
+#define ASSERT_STRCASENE(s1, s2)\
+  ASSERT_PRED_FORMAT2(::testing::internal::CmpHelperSTRCASENE, s1, s2)
+
+// Macros for comparing floating-point numbers.
+//
+//    * {ASSERT|EXPECT}_FLOAT_EQ(val1, val2):
+//         Tests that two float values are almost equal.
+//    * {ASSERT|EXPECT}_DOUBLE_EQ(val1, val2):
+//         Tests that two double values are almost equal.
+//    * {ASSERT|EXPECT}_NEAR(v1, v2, abs_error):
+//         Tests that v1 and v2 are within the given distance to each other.
+//
+// Google Test uses ULP-based comparison to automatically pick a default
+// error bound that is appropriate for the operands.  See the
+// FloatingPoint template class in gtest-internal.h if you are
+// interested in the implementation details.
+
+#define EXPECT_FLOAT_EQ(val1, val2)\
+  EXPECT_PRED_FORMAT2(::testing::internal::CmpHelperFloatingPointEQ<float>, \
+                      val1, val2)
+
+#define EXPECT_DOUBLE_EQ(val1, val2)\
+  EXPECT_PRED_FORMAT2(::testing::internal::CmpHelperFloatingPointEQ<double>, \
+                      val1, val2)
+
+#define ASSERT_FLOAT_EQ(val1, val2)\
+  ASSERT_PRED_FORMAT2(::testing::internal::CmpHelperFloatingPointEQ<float>, \
+                      val1, val2)
+
+#define ASSERT_DOUBLE_EQ(val1, val2)\
+  ASSERT_PRED_FORMAT2(::testing::internal::CmpHelperFloatingPointEQ<double>, \
+                      val1, val2)
+
+#define EXPECT_NEAR(val1, val2, abs_error)\
+  EXPECT_PRED_FORMAT3(::testing::internal::DoubleNearPredFormat, \
+                      val1, val2, abs_error)
+
+#define ASSERT_NEAR(val1, val2, abs_error)\
+  ASSERT_PRED_FORMAT3(::testing::internal::DoubleNearPredFormat, \
+                      val1, val2, abs_error)
+
+// These predicate format functions work on floating-point values, and
+// can be used in {ASSERT|EXPECT}_PRED_FORMAT2*(), e.g.
+//
+//   EXPECT_PRED_FORMAT2(testing::DoubleLE, Foo(), 5.0);
+
+// Asserts that val1 is less than, or almost equal to, val2.  Fails
+// otherwise.  In particular, it fails if either val1 or val2 is NaN.
+GTEST_API_ AssertionResult FloatLE(const char* expr1, const char* expr2,
+                                   float val1, float val2);
+GTEST_API_ AssertionResult DoubleLE(const char* expr1, const char* expr2,
+                                    double val1, double val2);
+
+
+#if GTEST_OS_WINDOWS
+
+// Macros that test for HRESULT failure and success, these are only useful
+// on Windows, and rely on Windows SDK macros and APIs to compile.
+//
+//    * {ASSERT|EXPECT}_HRESULT_{SUCCEEDED|FAILED}(expr)
+//
+// When expr unexpectedly fails or succeeds, Google Test prints the
+// expected result and the actual result with both a human-readable
+// string representation of the error, if available, as well as the
+// hex result code.
+# define EXPECT_HRESULT_SUCCEEDED(expr) \
+    EXPECT_PRED_FORMAT1(::testing::internal::IsHRESULTSuccess, (expr))
+
+# define ASSERT_HRESULT_SUCCEEDED(expr) \
+    ASSERT_PRED_FORMAT1(::testing::internal::IsHRESULTSuccess, (expr))
+
+# define EXPECT_HRESULT_FAILED(expr) \
+    EXPECT_PRED_FORMAT1(::testing::internal::IsHRESULTFailure, (expr))
+
+# define ASSERT_HRESULT_FAILED(expr) \
+    ASSERT_PRED_FORMAT1(::testing::internal::IsHRESULTFailure, (expr))
+
+#endif  // GTEST_OS_WINDOWS
+
+// Macros that execute statement and check that it doesn't generate new fatal
+// failures in the current thread.
+//
+//   * {ASSERT|EXPECT}_NO_FATAL_FAILURE(statement);
+//
+// Examples:
+//
+//   EXPECT_NO_FATAL_FAILURE(Process());
+//   ASSERT_NO_FATAL_FAILURE(Process()) << "Process() failed";
+//
+#define ASSERT_NO_FATAL_FAILURE(statement) \
+    GTEST_TEST_NO_FATAL_FAILURE_(statement, GTEST_FATAL_FAILURE_)
+#define EXPECT_NO_FATAL_FAILURE(statement) \
+    GTEST_TEST_NO_FATAL_FAILURE_(statement, GTEST_NONFATAL_FAILURE_)
+
+// Causes a trace (including the given source file path and line number,
+// and the given message) to be included in every test failure message generated
+// by code in the scope of the lifetime of an instance of this class. The effect
+// is undone with the destruction of the instance.
+//
+// The message argument can be anything streamable to std::ostream.
+//
+// Example:
+//   testing::ScopedTrace trace("file.cc", 123, "message");
+//
+class GTEST_API_ ScopedTrace {
+ public:
+  // The c'tor pushes the given source file location and message onto
+  // a trace stack maintained by Google Test.
+
+  // Template version. Uses Message() to convert the values into strings.
+  // Slow, but flexible.
+  template <typename T>
+  ScopedTrace(const char* file, int line, const T& message) {
+    PushTrace(file, line, (Message() << message).GetString());
+  }
+
+  // Optimize for some known types.
+  ScopedTrace(const char* file, int line, const char* message) {
+    PushTrace(file, line, message ? message : "(null)");
+  }
+
+  ScopedTrace(const char* file, int line, const std::string& message) {
+    PushTrace(file, line, message);
+  }
+
+  // The d'tor pops the info pushed by the c'tor.
+  //
+  // Note that the d'tor is not virtual in order to be efficient.
+  // Don't inherit from ScopedTrace!
+  ~ScopedTrace();
+
+ private:
+  void PushTrace(const char* file, int line, std::string message);
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(ScopedTrace);
+} GTEST_ATTRIBUTE_UNUSED_;  // A ScopedTrace object does its job in its
+                            // c'tor and d'tor.  Therefore it doesn't
+                            // need to be used otherwise.
+
+// Causes a trace (including the source file path, the current line
+// number, and the given message) to be included in every test failure
+// message generated by code in the current scope.  The effect is
+// undone when the control leaves the current scope.
+//
+// The message argument can be anything streamable to std::ostream.
+//
+// In the implementation, we include the current line number as part
+// of the dummy variable name, thus allowing multiple SCOPED_TRACE()s
+// to appear in the same block - as long as they are on different
+// lines.
+//
+// Assuming that each thread maintains its own stack of traces.
+// Therefore, a SCOPED_TRACE() would (correctly) only affect the
+// assertions in its own thread.
+#define SCOPED_TRACE(message) \
+  ::testing::ScopedTrace GTEST_CONCAT_TOKEN_(gtest_trace_, __LINE__)(\
+    __FILE__, __LINE__, (message))
+
+// Compile-time assertion for type equality.
+// StaticAssertTypeEq<type1, type2>() compiles if and only if type1 and type2
+// are the same type.  The value it returns is not interesting.
+//
+// Instead of making StaticAssertTypeEq a class template, we make it a
+// function template that invokes a helper class template.  This
+// prevents a user from misusing StaticAssertTypeEq<T1, T2> by
+// defining objects of that type.
+//
+// CAVEAT:
+//
+// When used inside a method of a class template,
+// StaticAssertTypeEq<T1, T2>() is effective ONLY IF the method is
+// instantiated.  For example, given:
+//
+//   template <typename T> class Foo {
+//    public:
+//     void Bar() { testing::StaticAssertTypeEq<int, T>(); }
+//   };
+//
+// the code:
+//
+//   void Test1() { Foo<bool> foo; }
+//
+// will NOT generate a compiler error, as Foo<bool>::Bar() is never
+// actually instantiated.  Instead, you need:
+//
+//   void Test2() { Foo<bool> foo; foo.Bar(); }
+//
+// to cause a compiler error.
+template <typename T1, typename T2>
+constexpr bool StaticAssertTypeEq() noexcept {
+  static_assert(std::is_same<T1, T2>::value, "T1 and T2 are not the same type");
+  return true;
+}
+
+// Defines a test.
+//
+// The first parameter is the name of the test suite, and the second
+// parameter is the name of the test within the test suite.
+//
+// The convention is to end the test suite name with "Test".  For
+// example, a test suite for the Foo class can be named FooTest.
+//
+// Test code should appear between braces after an invocation of
+// this macro.  Example:
+//
+//   TEST(FooTest, InitializesCorrectly) {
+//     Foo foo;
+//     EXPECT_TRUE(foo.StatusIsOK());
+//   }
+
+// Note that we call GetTestTypeId() instead of GetTypeId<
+// ::testing::Test>() here to get the type ID of testing::Test.  This
+// is to work around a suspected linker bug when using Google Test as
+// a framework on Mac OS X.  The bug causes GetTypeId<
+// ::testing::Test>() to return different values depending on whether
+// the call is from the Google Test framework itself or from user test
+// code.  GetTestTypeId() is guaranteed to always return the same
+// value, as it always calls GetTypeId<>() from the Google Test
+// framework.
+#define GTEST_TEST(test_suite_name, test_name)             \
+  GTEST_TEST_(test_suite_name, test_name, ::testing::Test, \
+              ::testing::internal::GetTestTypeId())
+
+// Define this macro to 1 to omit the definition of TEST(), which
+// is a generic name and clashes with some other libraries.
+#if !GTEST_DONT_DEFINE_TEST
+#define TEST(test_suite_name, test_name) GTEST_TEST(test_suite_name, test_name)
+#endif
+
+// Defines a test that uses a test fixture.
+//
+// The first parameter is the name of the test fixture class, which
+// also doubles as the test suite name.  The second parameter is the
+// name of the test within the test suite.
+//
+// A test fixture class must be declared earlier.  The user should put
+// the test code between braces after using this macro.  Example:
+//
+//   class FooTest : public testing::Test {
+//    protected:
+//     void SetUp() override { b_.AddElement(3); }
+//
+//     Foo a_;
+//     Foo b_;
+//   };
+//
+//   TEST_F(FooTest, InitializesCorrectly) {
+//     EXPECT_TRUE(a_.StatusIsOK());
+//   }
+//
+//   TEST_F(FooTest, ReturnsElementCountCorrectly) {
+//     EXPECT_EQ(a_.size(), 0);
+//     EXPECT_EQ(b_.size(), 1);
+//   }
+//
+// GOOGLETEST_CM0011 DO NOT DELETE
+#if !GTEST_DONT_DEFINE_TEST
+#define TEST_F(test_fixture, test_name)\
+  GTEST_TEST_(test_fixture, test_name, test_fixture, \
+              ::testing::internal::GetTypeId<test_fixture>())
+#endif  // !GTEST_DONT_DEFINE_TEST
+
+// Returns a path to temporary directory.
+// Tries to determine an appropriate directory for the platform.
+GTEST_API_ std::string TempDir();
+
+#ifdef _MSC_VER
+#  pragma warning(pop)
+#endif
+
+// Dynamically registers a test with the framework.
+//
+// This is an advanced API only to be used when the `TEST` macros are
+// insufficient. The macros should be preferred when possible, as they avoid
+// most of the complexity of calling this function.
+//
+// The `factory` argument is a factory callable (move-constructible) object or
+// function pointer that creates a new instance of the Test object. It
+// handles ownership to the caller. The signature of the callable is
+// `Fixture*()`, where `Fixture` is the test fixture class for the test. All
+// tests registered with the same `test_suite_name` must return the same
+// fixture type. This is checked at runtime.
+//
+// The framework will infer the fixture class from the factory and will call
+// the `SetUpTestSuite` and `TearDownTestSuite` for it.
+//
+// Must be called before `RUN_ALL_TESTS()` is invoked, otherwise behavior is
+// undefined.
+//
+// Use case example:
+//
+// class MyFixture : public ::testing::Test {
+//  public:
+//   // All of these optional, just like in regular macro usage.
+//   static void SetUpTestSuite() { ... }
+//   static void TearDownTestSuite() { ... }
+//   void SetUp() override { ... }
+//   void TearDown() override { ... }
+// };
+//
+// class MyTest : public MyFixture {
+//  public:
+//   explicit MyTest(int data) : data_(data) {}
+//   void TestBody() override { ... }
+//
+//  private:
+//   int data_;
+// };
+//
+// void RegisterMyTests(const std::vector<int>& values) {
+//   for (int v : values) {
+//     ::testing::RegisterTest(
+//         "MyFixture", ("Test" + std::to_string(v)).c_str(), nullptr,
+//         std::to_string(v).c_str(),
+//         __FILE__, __LINE__,
+//         // Important to use the fixture type as the return type here.
+//         [=]() -> MyFixture* { return new MyTest(v); });
+//   }
+// }
+// ...
+// int main(int argc, char** argv) {
+//   std::vector<int> values_to_test = LoadValuesFromConfig();
+//   RegisterMyTests(values_to_test);
+//   ...
+//   return RUN_ALL_TESTS();
+// }
+//
+template <int&... ExplicitParameterBarrier, typename Factory>
+TestInfo* RegisterTest(const char* test_suite_name, const char* test_name,
+                       const char* type_param, const char* value_param,
+                       const char* file, int line, Factory factory) {
+  using TestT = typename std::remove_pointer<decltype(factory())>::type;
+
+  class FactoryImpl : public internal::TestFactoryBase {
+   public:
+    explicit FactoryImpl(Factory f) : factory_(std::move(f)) {}
+    Test* CreateTest() override { return factory_(); }
+
+   private:
+    Factory factory_;
+  };
+
+  return internal::MakeAndRegisterTestInfo(
+      test_suite_name, test_name, type_param, value_param,
+      internal::CodeLocation(file, line), internal::GetTypeId<TestT>(),
+      internal::SuiteApiResolver<TestT>::GetSetUpCaseOrSuite(file, line),
+      internal::SuiteApiResolver<TestT>::GetTearDownCaseOrSuite(file, line),
+      new FactoryImpl{std::move(factory)});
+}
+
+}  // namespace testing
+
+// Use this function in main() to run all tests.  It returns 0 if all
+// tests are successful, or 1 otherwise.
+//
+// RUN_ALL_TESTS() should be invoked after the command line has been
+// parsed by InitGoogleTest().
+//
+// This function was formerly a macro; thus, it is in the global
+// namespace and has an all-caps name.
+int RUN_ALL_TESTS() GTEST_MUST_USE_RESULT_;
+
+inline int RUN_ALL_TESTS() {
+  return ::testing::UnitTest::GetInstance()->Run();
+}
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  //  4251
+
+#endif  // GOOGLETEST_INCLUDE_GTEST_GTEST_H_
diff --git a/leveldb_base/third_party/googletest/googletest/include/gtest/gtest_pred_impl.h b/leveldb_base/third_party/googletest/googletest/include/gtest/gtest_pred_impl.h
new file mode 100644
index 0000000..5029a9b
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/include/gtest/gtest_pred_impl.h
@@ -0,0 +1,359 @@
+// Copyright 2006, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// This file is AUTOMATICALLY GENERATED on 01/02/2019 by command
+// 'gen_gtest_pred_impl.py 5'.  DO NOT EDIT BY HAND!
+//
+// Implements a family of generic predicate assertion macros.
+// GOOGLETEST_CM0001 DO NOT DELETE
+
+#ifndef GOOGLETEST_INCLUDE_GTEST_GTEST_PRED_IMPL_H_
+#define GOOGLETEST_INCLUDE_GTEST_GTEST_PRED_IMPL_H_
+
+#include "gtest/gtest.h"
+
+namespace testing {
+
+// This header implements a family of generic predicate assertion
+// macros:
+//
+//   ASSERT_PRED_FORMAT1(pred_format, v1)
+//   ASSERT_PRED_FORMAT2(pred_format, v1, v2)
+//   ...
+//
+// where pred_format is a function or functor that takes n (in the
+// case of ASSERT_PRED_FORMATn) values and their source expression
+// text, and returns a testing::AssertionResult.  See the definition
+// of ASSERT_EQ in gtest.h for an example.
+//
+// If you don't care about formatting, you can use the more
+// restrictive version:
+//
+//   ASSERT_PRED1(pred, v1)
+//   ASSERT_PRED2(pred, v1, v2)
+//   ...
+//
+// where pred is an n-ary function or functor that returns bool,
+// and the values v1, v2, ..., must support the << operator for
+// streaming to std::ostream.
+//
+// We also define the EXPECT_* variations.
+//
+// For now we only support predicates whose arity is at most 5.
+// Please email googletestframework@googlegroups.com if you need
+// support for higher arities.
+
+// GTEST_ASSERT_ is the basic statement to which all of the assertions
+// in this file reduce.  Don't use this in your code.
+
+#define GTEST_ASSERT_(expression, on_failure) \
+  GTEST_AMBIGUOUS_ELSE_BLOCKER_ \
+  if (const ::testing::AssertionResult gtest_ar = (expression)) \
+    ; \
+  else \
+    on_failure(gtest_ar.failure_message())
+
+
+// Helper function for implementing {EXPECT|ASSERT}_PRED1.  Don't use
+// this in your code.
+template <typename Pred,
+          typename T1>
+AssertionResult AssertPred1Helper(const char* pred_text,
+                                  const char* e1,
+                                  Pred pred,
+                                  const T1& v1) {
+  if (pred(v1)) return AssertionSuccess();
+
+  return AssertionFailure()
+         << pred_text << "(" << e1 << ") evaluates to false, where"
+         << "\n"
+         << e1 << " evaluates to " << ::testing::PrintToString(v1);
+}
+
+// Internal macro for implementing {EXPECT|ASSERT}_PRED_FORMAT1.
+// Don't use this in your code.
+#define GTEST_PRED_FORMAT1_(pred_format, v1, on_failure)\
+  GTEST_ASSERT_(pred_format(#v1, v1), \
+                on_failure)
+
+// Internal macro for implementing {EXPECT|ASSERT}_PRED1.  Don't use
+// this in your code.
+#define GTEST_PRED1_(pred, v1, on_failure)\
+  GTEST_ASSERT_(::testing::AssertPred1Helper(#pred, \
+                                             #v1, \
+                                             pred, \
+                                             v1), on_failure)
+
+// Unary predicate assertion macros.
+#define EXPECT_PRED_FORMAT1(pred_format, v1) \
+  GTEST_PRED_FORMAT1_(pred_format, v1, GTEST_NONFATAL_FAILURE_)
+#define EXPECT_PRED1(pred, v1) \
+  GTEST_PRED1_(pred, v1, GTEST_NONFATAL_FAILURE_)
+#define ASSERT_PRED_FORMAT1(pred_format, v1) \
+  GTEST_PRED_FORMAT1_(pred_format, v1, GTEST_FATAL_FAILURE_)
+#define ASSERT_PRED1(pred, v1) \
+  GTEST_PRED1_(pred, v1, GTEST_FATAL_FAILURE_)
+
+
+
+// Helper function for implementing {EXPECT|ASSERT}_PRED2.  Don't use
+// this in your code.
+template <typename Pred,
+          typename T1,
+          typename T2>
+AssertionResult AssertPred2Helper(const char* pred_text,
+                                  const char* e1,
+                                  const char* e2,
+                                  Pred pred,
+                                  const T1& v1,
+                                  const T2& v2) {
+  if (pred(v1, v2)) return AssertionSuccess();
+
+  return AssertionFailure()
+         << pred_text << "(" << e1 << ", " << e2
+         << ") evaluates to false, where"
+         << "\n"
+         << e1 << " evaluates to " << ::testing::PrintToString(v1) << "\n"
+         << e2 << " evaluates to " << ::testing::PrintToString(v2);
+}
+
+// Internal macro for implementing {EXPECT|ASSERT}_PRED_FORMAT2.
+// Don't use this in your code.
+#define GTEST_PRED_FORMAT2_(pred_format, v1, v2, on_failure)\
+  GTEST_ASSERT_(pred_format(#v1, #v2, v1, v2), \
+                on_failure)
+
+// Internal macro for implementing {EXPECT|ASSERT}_PRED2.  Don't use
+// this in your code.
+#define GTEST_PRED2_(pred, v1, v2, on_failure)\
+  GTEST_ASSERT_(::testing::AssertPred2Helper(#pred, \
+                                             #v1, \
+                                             #v2, \
+                                             pred, \
+                                             v1, \
+                                             v2), on_failure)
+
+// Binary predicate assertion macros.
+#define EXPECT_PRED_FORMAT2(pred_format, v1, v2) \
+  GTEST_PRED_FORMAT2_(pred_format, v1, v2, GTEST_NONFATAL_FAILURE_)
+#define EXPECT_PRED2(pred, v1, v2) \
+  GTEST_PRED2_(pred, v1, v2, GTEST_NONFATAL_FAILURE_)
+#define ASSERT_PRED_FORMAT2(pred_format, v1, v2) \
+  GTEST_PRED_FORMAT2_(pred_format, v1, v2, GTEST_FATAL_FAILURE_)
+#define ASSERT_PRED2(pred, v1, v2) \
+  GTEST_PRED2_(pred, v1, v2, GTEST_FATAL_FAILURE_)
+
+
+
+// Helper function for implementing {EXPECT|ASSERT}_PRED3.  Don't use
+// this in your code.
+template <typename Pred,
+          typename T1,
+          typename T2,
+          typename T3>
+AssertionResult AssertPred3Helper(const char* pred_text,
+                                  const char* e1,
+                                  const char* e2,
+                                  const char* e3,
+                                  Pred pred,
+                                  const T1& v1,
+                                  const T2& v2,
+                                  const T3& v3) {
+  if (pred(v1, v2, v3)) return AssertionSuccess();
+
+  return AssertionFailure()
+         << pred_text << "(" << e1 << ", " << e2 << ", " << e3
+         << ") evaluates to false, where"
+         << "\n"
+         << e1 << " evaluates to " << ::testing::PrintToString(v1) << "\n"
+         << e2 << " evaluates to " << ::testing::PrintToString(v2) << "\n"
+         << e3 << " evaluates to " << ::testing::PrintToString(v3);
+}
+
+// Internal macro for implementing {EXPECT|ASSERT}_PRED_FORMAT3.
+// Don't use this in your code.
+#define GTEST_PRED_FORMAT3_(pred_format, v1, v2, v3, on_failure)\
+  GTEST_ASSERT_(pred_format(#v1, #v2, #v3, v1, v2, v3), \
+                on_failure)
+
+// Internal macro for implementing {EXPECT|ASSERT}_PRED3.  Don't use
+// this in your code.
+#define GTEST_PRED3_(pred, v1, v2, v3, on_failure)\
+  GTEST_ASSERT_(::testing::AssertPred3Helper(#pred, \
+                                             #v1, \
+                                             #v2, \
+                                             #v3, \
+                                             pred, \
+                                             v1, \
+                                             v2, \
+                                             v3), on_failure)
+
+// Ternary predicate assertion macros.
+#define EXPECT_PRED_FORMAT3(pred_format, v1, v2, v3) \
+  GTEST_PRED_FORMAT3_(pred_format, v1, v2, v3, GTEST_NONFATAL_FAILURE_)
+#define EXPECT_PRED3(pred, v1, v2, v3) \
+  GTEST_PRED3_(pred, v1, v2, v3, GTEST_NONFATAL_FAILURE_)
+#define ASSERT_PRED_FORMAT3(pred_format, v1, v2, v3) \
+  GTEST_PRED_FORMAT3_(pred_format, v1, v2, v3, GTEST_FATAL_FAILURE_)
+#define ASSERT_PRED3(pred, v1, v2, v3) \
+  GTEST_PRED3_(pred, v1, v2, v3, GTEST_FATAL_FAILURE_)
+
+
+
+// Helper function for implementing {EXPECT|ASSERT}_PRED4.  Don't use
+// this in your code.
+template <typename Pred,
+          typename T1,
+          typename T2,
+          typename T3,
+          typename T4>
+AssertionResult AssertPred4Helper(const char* pred_text,
+                                  const char* e1,
+                                  const char* e2,
+                                  const char* e3,
+                                  const char* e4,
+                                  Pred pred,
+                                  const T1& v1,
+                                  const T2& v2,
+                                  const T3& v3,
+                                  const T4& v4) {
+  if (pred(v1, v2, v3, v4)) return AssertionSuccess();
+
+  return AssertionFailure()
+         << pred_text << "(" << e1 << ", " << e2 << ", " << e3 << ", " << e4
+         << ") evaluates to false, where"
+         << "\n"
+         << e1 << " evaluates to " << ::testing::PrintToString(v1) << "\n"
+         << e2 << " evaluates to " << ::testing::PrintToString(v2) << "\n"
+         << e3 << " evaluates to " << ::testing::PrintToString(v3) << "\n"
+         << e4 << " evaluates to " << ::testing::PrintToString(v4);
+}
+
+// Internal macro for implementing {EXPECT|ASSERT}_PRED_FORMAT4.
+// Don't use this in your code.
+#define GTEST_PRED_FORMAT4_(pred_format, v1, v2, v3, v4, on_failure)\
+  GTEST_ASSERT_(pred_format(#v1, #v2, #v3, #v4, v1, v2, v3, v4), \
+                on_failure)
+
+// Internal macro for implementing {EXPECT|ASSERT}_PRED4.  Don't use
+// this in your code.
+#define GTEST_PRED4_(pred, v1, v2, v3, v4, on_failure)\
+  GTEST_ASSERT_(::testing::AssertPred4Helper(#pred, \
+                                             #v1, \
+                                             #v2, \
+                                             #v3, \
+                                             #v4, \
+                                             pred, \
+                                             v1, \
+                                             v2, \
+                                             v3, \
+                                             v4), on_failure)
+
+// 4-ary predicate assertion macros.
+#define EXPECT_PRED_FORMAT4(pred_format, v1, v2, v3, v4) \
+  GTEST_PRED_FORMAT4_(pred_format, v1, v2, v3, v4, GTEST_NONFATAL_FAILURE_)
+#define EXPECT_PRED4(pred, v1, v2, v3, v4) \
+  GTEST_PRED4_(pred, v1, v2, v3, v4, GTEST_NONFATAL_FAILURE_)
+#define ASSERT_PRED_FORMAT4(pred_format, v1, v2, v3, v4) \
+  GTEST_PRED_FORMAT4_(pred_format, v1, v2, v3, v4, GTEST_FATAL_FAILURE_)
+#define ASSERT_PRED4(pred, v1, v2, v3, v4) \
+  GTEST_PRED4_(pred, v1, v2, v3, v4, GTEST_FATAL_FAILURE_)
+
+
+
+// Helper function for implementing {EXPECT|ASSERT}_PRED5.  Don't use
+// this in your code.
+template <typename Pred,
+          typename T1,
+          typename T2,
+          typename T3,
+          typename T4,
+          typename T5>
+AssertionResult AssertPred5Helper(const char* pred_text,
+                                  const char* e1,
+                                  const char* e2,
+                                  const char* e3,
+                                  const char* e4,
+                                  const char* e5,
+                                  Pred pred,
+                                  const T1& v1,
+                                  const T2& v2,
+                                  const T3& v3,
+                                  const T4& v4,
+                                  const T5& v5) {
+  if (pred(v1, v2, v3, v4, v5)) return AssertionSuccess();
+
+  return AssertionFailure()
+         << pred_text << "(" << e1 << ", " << e2 << ", " << e3 << ", " << e4
+         << ", " << e5 << ") evaluates to false, where"
+         << "\n"
+         << e1 << " evaluates to " << ::testing::PrintToString(v1) << "\n"
+         << e2 << " evaluates to " << ::testing::PrintToString(v2) << "\n"
+         << e3 << " evaluates to " << ::testing::PrintToString(v3) << "\n"
+         << e4 << " evaluates to " << ::testing::PrintToString(v4) << "\n"
+         << e5 << " evaluates to " << ::testing::PrintToString(v5);
+}
+
+// Internal macro for implementing {EXPECT|ASSERT}_PRED_FORMAT5.
+// Don't use this in your code.
+#define GTEST_PRED_FORMAT5_(pred_format, v1, v2, v3, v4, v5, on_failure)\
+  GTEST_ASSERT_(pred_format(#v1, #v2, #v3, #v4, #v5, v1, v2, v3, v4, v5), \
+                on_failure)
+
+// Internal macro for implementing {EXPECT|ASSERT}_PRED5.  Don't use
+// this in your code.
+#define GTEST_PRED5_(pred, v1, v2, v3, v4, v5, on_failure)\
+  GTEST_ASSERT_(::testing::AssertPred5Helper(#pred, \
+                                             #v1, \
+                                             #v2, \
+                                             #v3, \
+                                             #v4, \
+                                             #v5, \
+                                             pred, \
+                                             v1, \
+                                             v2, \
+                                             v3, \
+                                             v4, \
+                                             v5), on_failure)
+
+// 5-ary predicate assertion macros.
+#define EXPECT_PRED_FORMAT5(pred_format, v1, v2, v3, v4, v5) \
+  GTEST_PRED_FORMAT5_(pred_format, v1, v2, v3, v4, v5, GTEST_NONFATAL_FAILURE_)
+#define EXPECT_PRED5(pred, v1, v2, v3, v4, v5) \
+  GTEST_PRED5_(pred, v1, v2, v3, v4, v5, GTEST_NONFATAL_FAILURE_)
+#define ASSERT_PRED_FORMAT5(pred_format, v1, v2, v3, v4, v5) \
+  GTEST_PRED_FORMAT5_(pred_format, v1, v2, v3, v4, v5, GTEST_FATAL_FAILURE_)
+#define ASSERT_PRED5(pred, v1, v2, v3, v4, v5) \
+  GTEST_PRED5_(pred, v1, v2, v3, v4, v5, GTEST_FATAL_FAILURE_)
+
+
+
+}  // namespace testing
+
+#endif  // GOOGLETEST_INCLUDE_GTEST_GTEST_PRED_IMPL_H_
diff --git a/leveldb_base/third_party/googletest/googletest/include/gtest/gtest_prod.h b/leveldb_base/third_party/googletest/googletest/include/gtest/gtest_prod.h
new file mode 100644
index 0000000..38b9d85
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/include/gtest/gtest_prod.h
@@ -0,0 +1,61 @@
+// Copyright 2006, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// Google C++ Testing and Mocking Framework definitions useful in production code.
+// GOOGLETEST_CM0003 DO NOT DELETE
+
+#ifndef GOOGLETEST_INCLUDE_GTEST_GTEST_PROD_H_
+#define GOOGLETEST_INCLUDE_GTEST_GTEST_PROD_H_
+
+// When you need to test the private or protected members of a class,
+// use the FRIEND_TEST macro to declare your tests as friends of the
+// class.  For example:
+//
+// class MyClass {
+//  private:
+//   void PrivateMethod();
+//   FRIEND_TEST(MyClassTest, PrivateMethodWorks);
+// };
+//
+// class MyClassTest : public testing::Test {
+//   // ...
+// };
+//
+// TEST_F(MyClassTest, PrivateMethodWorks) {
+//   // Can call MyClass::PrivateMethod() here.
+// }
+//
+// Note: The test class must be in the same namespace as the class being tested.
+// For example, putting MyClassTest in an anonymous namespace will not work.
+
+#define FRIEND_TEST(test_case_name, test_name)\
+friend class test_case_name##_##test_name##_Test
+
+#endif  // GOOGLETEST_INCLUDE_GTEST_GTEST_PROD_H_
diff --git a/leveldb_base/third_party/googletest/googletest/include/gtest/internal/custom/README.md b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/custom/README.md
new file mode 100644
index 0000000..ff391fb
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/custom/README.md
@@ -0,0 +1,56 @@
+# Customization Points
+
+The custom directory is an injection point for custom user configurations.
+
+## Header `gtest.h`
+
+### The following macros can be defined:
+
+*   `GTEST_OS_STACK_TRACE_GETTER_` - The name of an implementation of
+    `OsStackTraceGetterInterface`.
+*   `GTEST_CUSTOM_TEMPDIR_FUNCTION_` - An override for `testing::TempDir()`. See
+    `testing::TempDir` for semantics and signature.
+
+## Header `gtest-port.h`
+
+The following macros can be defined:
+
+### Flag related macros:
+
+*   `GTEST_FLAG(flag_name)`
+*   `GTEST_USE_OWN_FLAGFILE_FLAG_` - Define to 0 when the system provides its
+    own flagfile flag parsing.
+*   `GTEST_DECLARE_bool_(name)`
+*   `GTEST_DECLARE_int32_(name)`
+*   `GTEST_DECLARE_string_(name)`
+*   `GTEST_DEFINE_bool_(name, default_val, doc)`
+*   `GTEST_DEFINE_int32_(name, default_val, doc)`
+*   `GTEST_DEFINE_string_(name, default_val, doc)`
+
+### Logging:
+
+*   `GTEST_LOG_(severity)`
+*   `GTEST_CHECK_(condition)`
+*   Functions `LogToStderr()` and `FlushInfoLog()` have to be provided too.
+
+### Threading:
+
+*   `GTEST_HAS_NOTIFICATION_` - Enabled if Notification is already provided.
+*   `GTEST_HAS_MUTEX_AND_THREAD_LOCAL_` - Enabled if `Mutex` and `ThreadLocal`
+    are already provided. Must also provide `GTEST_DECLARE_STATIC_MUTEX_(mutex)`
+    and `GTEST_DEFINE_STATIC_MUTEX_(mutex)`
+*   `GTEST_EXCLUSIVE_LOCK_REQUIRED_(locks)`
+*   `GTEST_LOCK_EXCLUDED_(locks)`
+
+### Underlying library support features
+
+*   `GTEST_HAS_CXXABI_H_`
+
+### Exporting API symbols:
+
+*   `GTEST_API_` - Specifier for exported symbols.
+
+## Header `gtest-printers.h`
+
+*   See documentation at `gtest/gtest-printers.h` for details on how to define a
+    custom printer.
diff --git a/leveldb_base/third_party/googletest/googletest/include/gtest/internal/custom/gtest-port.h b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/custom/gtest-port.h
new file mode 100644
index 0000000..db02881
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/custom/gtest-port.h
@@ -0,0 +1,37 @@
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// Injection point for custom user configurations. See README for details
+//
+// ** Custom implementation starts here **
+
+#ifndef GOOGLETEST_INCLUDE_GTEST_INTERNAL_CUSTOM_GTEST_PORT_H_
+#define GOOGLETEST_INCLUDE_GTEST_INTERNAL_CUSTOM_GTEST_PORT_H_
+
+#endif  // GOOGLETEST_INCLUDE_GTEST_INTERNAL_CUSTOM_GTEST_PORT_H_
diff --git a/leveldb_base/third_party/googletest/googletest/include/gtest/internal/custom/gtest-printers.h b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/custom/gtest-printers.h
new file mode 100644
index 0000000..b9495d8
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/custom/gtest-printers.h
@@ -0,0 +1,42 @@
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// This file provides an injection point for custom printers in a local
+// installation of gTest.
+// It will be included from gtest-printers.h and the overrides in this file
+// will be visible to everyone.
+//
+// Injection point for custom user configurations. See README for details
+//
+// ** Custom implementation starts here **
+
+#ifndef GOOGLETEST_INCLUDE_GTEST_INTERNAL_CUSTOM_GTEST_PRINTERS_H_
+#define GOOGLETEST_INCLUDE_GTEST_INTERNAL_CUSTOM_GTEST_PRINTERS_H_
+
+#endif  // GOOGLETEST_INCLUDE_GTEST_INTERNAL_CUSTOM_GTEST_PRINTERS_H_
diff --git a/leveldb_base/third_party/googletest/googletest/include/gtest/internal/custom/gtest.h b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/custom/gtest.h
new file mode 100644
index 0000000..afaaf17
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/custom/gtest.h
@@ -0,0 +1,37 @@
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// Injection point for custom user configurations. See README for details
+//
+// ** Custom implementation starts here **
+
+#ifndef GOOGLETEST_INCLUDE_GTEST_INTERNAL_CUSTOM_GTEST_H_
+#define GOOGLETEST_INCLUDE_GTEST_INTERNAL_CUSTOM_GTEST_H_
+
+#endif  // GOOGLETEST_INCLUDE_GTEST_INTERNAL_CUSTOM_GTEST_H_
diff --git a/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-death-test-internal.h b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-death-test-internal.h
new file mode 100644
index 0000000..490296d
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-death-test-internal.h
@@ -0,0 +1,304 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// The Google C++ Testing and Mocking Framework (Google Test)
+//
+// This header file defines internal utilities needed for implementing
+// death tests.  They are subject to change without notice.
+// GOOGLETEST_CM0001 DO NOT DELETE
+
+#ifndef GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_DEATH_TEST_INTERNAL_H_
+#define GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_DEATH_TEST_INTERNAL_H_
+
+#include "gtest/gtest-matchers.h"
+#include "gtest/internal/gtest-internal.h"
+
+#include <stdio.h>
+#include <memory>
+
+namespace testing {
+namespace internal {
+
+GTEST_DECLARE_string_(internal_run_death_test);
+
+// Names of the flags (needed for parsing Google Test flags).
+const char kDeathTestStyleFlag[] = "death_test_style";
+const char kDeathTestUseFork[] = "death_test_use_fork";
+const char kInternalRunDeathTestFlag[] = "internal_run_death_test";
+
+#if GTEST_HAS_DEATH_TEST
+
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4251 \
+/* class A needs to have dll-interface to be used by clients of class B */)
+
+// DeathTest is a class that hides much of the complexity of the
+// GTEST_DEATH_TEST_ macro.  It is abstract; its static Create method
+// returns a concrete class that depends on the prevailing death test
+// style, as defined by the --gtest_death_test_style and/or
+// --gtest_internal_run_death_test flags.
+
+// In describing the results of death tests, these terms are used with
+// the corresponding definitions:
+//
+// exit status:  The integer exit information in the format specified
+//               by wait(2)
+// exit code:    The integer code passed to exit(3), _exit(2), or
+//               returned from main()
+class GTEST_API_ DeathTest {
+ public:
+  // Create returns false if there was an error determining the
+  // appropriate action to take for the current death test; for example,
+  // if the gtest_death_test_style flag is set to an invalid value.
+  // The LastMessage method will return a more detailed message in that
+  // case.  Otherwise, the DeathTest pointer pointed to by the "test"
+  // argument is set.  If the death test should be skipped, the pointer
+  // is set to NULL; otherwise, it is set to the address of a new concrete
+  // DeathTest object that controls the execution of the current test.
+  static bool Create(const char* statement, Matcher<const std::string&> matcher,
+                     const char* file, int line, DeathTest** test);
+  DeathTest();
+  virtual ~DeathTest() { }
+
+  // A helper class that aborts a death test when it's deleted.
+  class ReturnSentinel {
+   public:
+    explicit ReturnSentinel(DeathTest* test) : test_(test) { }
+    ~ReturnSentinel() { test_->Abort(TEST_ENCOUNTERED_RETURN_STATEMENT); }
+   private:
+    DeathTest* const test_;
+    GTEST_DISALLOW_COPY_AND_ASSIGN_(ReturnSentinel);
+  } GTEST_ATTRIBUTE_UNUSED_;
+
+  // An enumeration of possible roles that may be taken when a death
+  // test is encountered.  EXECUTE means that the death test logic should
+  // be executed immediately.  OVERSEE means that the program should prepare
+  // the appropriate environment for a child process to execute the death
+  // test, then wait for it to complete.
+  enum TestRole { OVERSEE_TEST, EXECUTE_TEST };
+
+  // An enumeration of the three reasons that a test might be aborted.
+  enum AbortReason {
+    TEST_ENCOUNTERED_RETURN_STATEMENT,
+    TEST_THREW_EXCEPTION,
+    TEST_DID_NOT_DIE
+  };
+
+  // Assumes one of the above roles.
+  virtual TestRole AssumeRole() = 0;
+
+  // Waits for the death test to finish and returns its status.
+  virtual int Wait() = 0;
+
+  // Returns true if the death test passed; that is, the test process
+  // exited during the test, its exit status matches a user-supplied
+  // predicate, and its stderr output matches a user-supplied regular
+  // expression.
+  // The user-supplied predicate may be a macro expression rather
+  // than a function pointer or functor, or else Wait and Passed could
+  // be combined.
+  virtual bool Passed(bool exit_status_ok) = 0;
+
+  // Signals that the death test did not die as expected.
+  virtual void Abort(AbortReason reason) = 0;
+
+  // Returns a human-readable outcome message regarding the outcome of
+  // the last death test.
+  static const char* LastMessage();
+
+  static void set_last_death_test_message(const std::string& message);
+
+ private:
+  // A string containing a description of the outcome of the last death test.
+  static std::string last_death_test_message_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(DeathTest);
+};
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  //  4251
+
+// Factory interface for death tests.  May be mocked out for testing.
+class DeathTestFactory {
+ public:
+  virtual ~DeathTestFactory() { }
+  virtual bool Create(const char* statement,
+                      Matcher<const std::string&> matcher, const char* file,
+                      int line, DeathTest** test) = 0;
+};
+
+// A concrete DeathTestFactory implementation for normal use.
+class DefaultDeathTestFactory : public DeathTestFactory {
+ public:
+  bool Create(const char* statement, Matcher<const std::string&> matcher,
+              const char* file, int line, DeathTest** test) override;
+};
+
+// Returns true if exit_status describes a process that was terminated
+// by a signal, or exited normally with a nonzero exit code.
+GTEST_API_ bool ExitedUnsuccessfully(int exit_status);
+
+// A string passed to EXPECT_DEATH (etc.) is caught by one of these overloads
+// and interpreted as a regex (rather than an Eq matcher) for legacy
+// compatibility.
+inline Matcher<const ::std::string&> MakeDeathTestMatcher(
+    ::testing::internal::RE regex) {
+  return ContainsRegex(regex.pattern());
+}
+inline Matcher<const ::std::string&> MakeDeathTestMatcher(const char* regex) {
+  return ContainsRegex(regex);
+}
+inline Matcher<const ::std::string&> MakeDeathTestMatcher(
+    const ::std::string& regex) {
+  return ContainsRegex(regex);
+}
+
+// If a Matcher<const ::std::string&> is passed to EXPECT_DEATH (etc.), it's
+// used directly.
+inline Matcher<const ::std::string&> MakeDeathTestMatcher(
+    Matcher<const ::std::string&> matcher) {
+  return matcher;
+}
+
+// Traps C++ exceptions escaping statement and reports them as test
+// failures. Note that trapping SEH exceptions is not implemented here.
+# if GTEST_HAS_EXCEPTIONS
+#  define GTEST_EXECUTE_DEATH_TEST_STATEMENT_(statement, death_test) \
+  try { \
+    GTEST_SUPPRESS_UNREACHABLE_CODE_WARNING_BELOW_(statement); \
+  } catch (const ::std::exception& gtest_exception) { \
+    fprintf(\
+        stderr, \
+        "\n%s: Caught std::exception-derived exception escaping the " \
+        "death test statement. Exception message: %s\n", \
+        ::testing::internal::FormatFileLocation(__FILE__, __LINE__).c_str(), \
+        gtest_exception.what()); \
+    fflush(stderr); \
+    death_test->Abort(::testing::internal::DeathTest::TEST_THREW_EXCEPTION); \
+  } catch (...) { \
+    death_test->Abort(::testing::internal::DeathTest::TEST_THREW_EXCEPTION); \
+  }
+
+# else
+#  define GTEST_EXECUTE_DEATH_TEST_STATEMENT_(statement, death_test) \
+  GTEST_SUPPRESS_UNREACHABLE_CODE_WARNING_BELOW_(statement)
+
+# endif
+
+// This macro is for implementing ASSERT_DEATH*, EXPECT_DEATH*,
+// ASSERT_EXIT*, and EXPECT_EXIT*.
+#define GTEST_DEATH_TEST_(statement, predicate, regex_or_matcher, fail)        \
+  GTEST_AMBIGUOUS_ELSE_BLOCKER_                                                \
+  if (::testing::internal::AlwaysTrue()) {                                     \
+    ::testing::internal::DeathTest* gtest_dt;                                  \
+    if (!::testing::internal::DeathTest::Create(                               \
+            #statement,                                                        \
+            ::testing::internal::MakeDeathTestMatcher(regex_or_matcher),       \
+            __FILE__, __LINE__, &gtest_dt)) {                                  \
+      goto GTEST_CONCAT_TOKEN_(gtest_label_, __LINE__);                        \
+    }                                                                          \
+    if (gtest_dt != nullptr) {                                                 \
+      std::unique_ptr< ::testing::internal::DeathTest> gtest_dt_ptr(gtest_dt); \
+      switch (gtest_dt->AssumeRole()) {                                        \
+        case ::testing::internal::DeathTest::OVERSEE_TEST:                     \
+          if (!gtest_dt->Passed(predicate(gtest_dt->Wait()))) {                \
+            goto GTEST_CONCAT_TOKEN_(gtest_label_, __LINE__);                  \
+          }                                                                    \
+          break;                                                               \
+        case ::testing::internal::DeathTest::EXECUTE_TEST: {                   \
+          ::testing::internal::DeathTest::ReturnSentinel gtest_sentinel(       \
+              gtest_dt);                                                       \
+          GTEST_EXECUTE_DEATH_TEST_STATEMENT_(statement, gtest_dt);            \
+          gtest_dt->Abort(::testing::internal::DeathTest::TEST_DID_NOT_DIE);   \
+          break;                                                               \
+        }                                                                      \
+        default:                                                               \
+          break;                                                               \
+      }                                                                        \
+    }                                                                          \
+  } else                                                                       \
+    GTEST_CONCAT_TOKEN_(gtest_label_, __LINE__)                                \
+        : fail(::testing::internal::DeathTest::LastMessage())
+// The symbol "fail" here expands to something into which a message
+// can be streamed.
+
+// This macro is for implementing ASSERT/EXPECT_DEBUG_DEATH when compiled in
+// NDEBUG mode. In this case we need the statements to be executed and the macro
+// must accept a streamed message even though the message is never printed.
+// The regex object is not evaluated, but it is used to prevent "unused"
+// warnings and to avoid an expression that doesn't compile in debug mode.
+#define GTEST_EXECUTE_STATEMENT_(statement, regex_or_matcher)    \
+  GTEST_AMBIGUOUS_ELSE_BLOCKER_                                  \
+  if (::testing::internal::AlwaysTrue()) {                       \
+    GTEST_SUPPRESS_UNREACHABLE_CODE_WARNING_BELOW_(statement);   \
+  } else if (!::testing::internal::AlwaysTrue()) {               \
+    ::testing::internal::MakeDeathTestMatcher(regex_or_matcher); \
+  } else                                                         \
+    ::testing::Message()
+
+// A class representing the parsed contents of the
+// --gtest_internal_run_death_test flag, as it existed when
+// RUN_ALL_TESTS was called.
+class InternalRunDeathTestFlag {
+ public:
+  InternalRunDeathTestFlag(const std::string& a_file,
+                           int a_line,
+                           int an_index,
+                           int a_write_fd)
+      : file_(a_file), line_(a_line), index_(an_index),
+        write_fd_(a_write_fd) {}
+
+  ~InternalRunDeathTestFlag() {
+    if (write_fd_ >= 0)
+      posix::Close(write_fd_);
+  }
+
+  const std::string& file() const { return file_; }
+  int line() const { return line_; }
+  int index() const { return index_; }
+  int write_fd() const { return write_fd_; }
+
+ private:
+  std::string file_;
+  int line_;
+  int index_;
+  int write_fd_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(InternalRunDeathTestFlag);
+};
+
+// Returns a newly created InternalRunDeathTestFlag object with fields
+// initialized from the GTEST_FLAG(internal_run_death_test) flag if
+// the flag is specified; otherwise returns NULL.
+InternalRunDeathTestFlag* ParseInternalRunDeathTestFlag();
+
+#endif  // GTEST_HAS_DEATH_TEST
+
+}  // namespace internal
+}  // namespace testing
+
+#endif  // GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_DEATH_TEST_INTERNAL_H_
diff --git a/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-filepath.h b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-filepath.h
new file mode 100644
index 0000000..0c033ab
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-filepath.h
@@ -0,0 +1,211 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// Google Test filepath utilities
+//
+// This header file declares classes and functions used internally by
+// Google Test.  They are subject to change without notice.
+//
+// This file is #included in gtest/internal/gtest-internal.h.
+// Do not include this header file separately!
+
+// GOOGLETEST_CM0001 DO NOT DELETE
+
+#ifndef GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_FILEPATH_H_
+#define GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_FILEPATH_H_
+
+#include "gtest/internal/gtest-string.h"
+
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4251 \
+/* class A needs to have dll-interface to be used by clients of class B */)
+
+namespace testing {
+namespace internal {
+
+// FilePath - a class for file and directory pathname manipulation which
+// handles platform-specific conventions (like the pathname separator).
+// Used for helper functions for naming files in a directory for xml output.
+// Except for Set methods, all methods are const or static, which provides an
+// "immutable value object" -- useful for peace of mind.
+// A FilePath with a value ending in a path separator ("like/this/") represents
+// a directory, otherwise it is assumed to represent a file. In either case,
+// it may or may not represent an actual file or directory in the file system.
+// Names are NOT checked for syntax correctness -- no checking for illegal
+// characters, malformed paths, etc.
+
+class GTEST_API_ FilePath {
+ public:
+  FilePath() : pathname_("") { }
+  FilePath(const FilePath& rhs) : pathname_(rhs.pathname_) { }
+
+  explicit FilePath(const std::string& pathname) : pathname_(pathname) {
+    Normalize();
+  }
+
+  FilePath& operator=(const FilePath& rhs) {
+    Set(rhs);
+    return *this;
+  }
+
+  void Set(const FilePath& rhs) {
+    pathname_ = rhs.pathname_;
+  }
+
+  const std::string& string() const { return pathname_; }
+  const char* c_str() const { return pathname_.c_str(); }
+
+  // Returns the current working directory, or "" if unsuccessful.
+  static FilePath GetCurrentDir();
+
+  // Given directory = "dir", base_name = "test", number = 0,
+  // extension = "xml", returns "dir/test.xml". If number is greater
+  // than zero (e.g., 12), returns "dir/test_12.xml".
+  // On Windows platform, uses \ as the separator rather than /.
+  static FilePath MakeFileName(const FilePath& directory,
+                               const FilePath& base_name,
+                               int number,
+                               const char* extension);
+
+  // Given directory = "dir", relative_path = "test.xml",
+  // returns "dir/test.xml".
+  // On Windows, uses \ as the separator rather than /.
+  static FilePath ConcatPaths(const FilePath& directory,
+                              const FilePath& relative_path);
+
+  // Returns a pathname for a file that does not currently exist. The pathname
+  // will be directory/base_name.extension or
+  // directory/base_name_<number>.extension if directory/base_name.extension
+  // already exists. The number will be incremented until a pathname is found
+  // that does not already exist.
+  // Examples: 'dir/foo_test.xml' or 'dir/foo_test_1.xml'.
+  // There could be a race condition if two or more processes are calling this
+  // function at the same time -- they could both pick the same filename.
+  static FilePath GenerateUniqueFileName(const FilePath& directory,
+                                         const FilePath& base_name,
+                                         const char* extension);
+
+  // Returns true if and only if the path is "".
+  bool IsEmpty() const { return pathname_.empty(); }
+
+  // If input name has a trailing separator character, removes it and returns
+  // the name, otherwise return the name string unmodified.
+  // On Windows platform, uses \ as the separator, other platforms use /.
+  FilePath RemoveTrailingPathSeparator() const;
+
+  // Returns a copy of the FilePath with the directory part removed.
+  // Example: FilePath("path/to/file").RemoveDirectoryName() returns
+  // FilePath("file"). If there is no directory part ("just_a_file"), it returns
+  // the FilePath unmodified. If there is no file part ("just_a_dir/") it
+  // returns an empty FilePath ("").
+  // On Windows platform, '\' is the path separator, otherwise it is '/'.
+  FilePath RemoveDirectoryName() const;
+
+  // RemoveFileName returns the directory path with the filename removed.
+  // Example: FilePath("path/to/file").RemoveFileName() returns "path/to/".
+  // If the FilePath is "a_file" or "/a_file", RemoveFileName returns
+  // FilePath("./") or, on Windows, FilePath(".\\"). If the filepath does
+  // not have a file, like "just/a/dir/", it returns the FilePath unmodified.
+  // On Windows platform, '\' is the path separator, otherwise it is '/'.
+  FilePath RemoveFileName() const;
+
+  // Returns a copy of the FilePath with the case-insensitive extension removed.
+  // Example: FilePath("dir/file.exe").RemoveExtension("EXE") returns
+  // FilePath("dir/file"). If a case-insensitive extension is not
+  // found, returns a copy of the original FilePath.
+  FilePath RemoveExtension(const char* extension) const;
+
+  // Creates directories so that path exists. Returns true if successful or if
+  // the directories already exist; returns false if unable to create
+  // directories for any reason. Will also return false if the FilePath does
+  // not represent a directory (that is, it doesn't end with a path separator).
+  bool CreateDirectoriesRecursively() const;
+
+  // Create the directory so that path exists. Returns true if successful or
+  // if the directory already exists; returns false if unable to create the
+  // directory for any reason, including if the parent directory does not
+  // exist. Not named "CreateDirectory" because that's a macro on Windows.
+  bool CreateFolder() const;
+
+  // Returns true if FilePath describes something in the file-system,
+  // either a file, directory, or whatever, and that something exists.
+  bool FileOrDirectoryExists() const;
+
+  // Returns true if pathname describes a directory in the file-system
+  // that exists.
+  bool DirectoryExists() const;
+
+  // Returns true if FilePath ends with a path separator, which indicates that
+  // it is intended to represent a directory. Returns false otherwise.
+  // This does NOT check that a directory (or file) actually exists.
+  bool IsDirectory() const;
+
+  // Returns true if pathname describes a root directory. (Windows has one
+  // root directory per disk drive.)
+  bool IsRootDirectory() const;
+
+  // Returns true if pathname describes an absolute path.
+  bool IsAbsolutePath() const;
+
+ private:
+  // Replaces multiple consecutive separators with a single separator.
+  // For example, "bar///foo" becomes "bar/foo". Does not eliminate other
+  // redundancies that might be in a pathname involving "." or "..".
+  //
+  // A pathname with multiple consecutive separators may occur either through
+  // user error or as a result of some scripts or APIs that generate a pathname
+  // with a trailing separator. On other platforms the same API or script
+  // may NOT generate a pathname with a trailing "/". Then elsewhere that
+  // pathname may have another "/" and pathname components added to it,
+  // without checking for the separator already being there.
+  // The script language and operating system may allow paths like "foo//bar"
+  // but some of the functions in FilePath will not handle that correctly. In
+  // particular, RemoveTrailingPathSeparator() only removes one separator, and
+  // it is called in CreateDirectoriesRecursively() assuming that it will change
+  // a pathname from directory syntax (trailing separator) to filename syntax.
+  //
+  // On Windows this method also replaces the alternate path separator '/' with
+  // the primary path separator '\\', so that for example "bar\\/\\foo" becomes
+  // "bar\\foo".
+
+  void Normalize();
+
+  // Returns a pointer to the last occurrence of a valid path separator in
+  // the FilePath. On Windows, for example, both '/' and '\' are valid path
+  // separators. Returns NULL if no path separator was found.
+  const char* FindLastPathSeparator() const;
+
+  std::string pathname_;
+};  // class FilePath
+
+}  // namespace internal
+}  // namespace testing
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  //  4251
+
+#endif  // GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_FILEPATH_H_
diff --git a/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-internal.h b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-internal.h
new file mode 100644
index 0000000..f8cbdbd
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-internal.h
@@ -0,0 +1,1560 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// The Google C++ Testing and Mocking Framework (Google Test)
+//
+// This header file declares functions and macros used internally by
+// Google Test.  They are subject to change without notice.
+
+// GOOGLETEST_CM0001 DO NOT DELETE
+
+#ifndef GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_INTERNAL_H_
+#define GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_INTERNAL_H_
+
+#include "gtest/internal/gtest-port.h"
+
+#if GTEST_OS_LINUX
+# include <stdlib.h>
+# include <sys/types.h>
+# include <sys/wait.h>
+# include <unistd.h>
+#endif  // GTEST_OS_LINUX
+
+#if GTEST_HAS_EXCEPTIONS
+# include <stdexcept>
+#endif
+
+#include <ctype.h>
+#include <float.h>
+#include <string.h>
+#include <cstdint>
+#include <iomanip>
+#include <limits>
+#include <map>
+#include <set>
+#include <string>
+#include <type_traits>
+#include <vector>
+
+#include "gtest/gtest-message.h"
+#include "gtest/internal/gtest-filepath.h"
+#include "gtest/internal/gtest-string.h"
+#include "gtest/internal/gtest-type-util.h"
+
+// Due to C++ preprocessor weirdness, we need double indirection to
+// concatenate two tokens when one of them is __LINE__.  Writing
+//
+//   foo ## __LINE__
+//
+// will result in the token foo__LINE__, instead of foo followed by
+// the current line number.  For more details, see
+// http://www.parashift.com/c++-faq-lite/misc-technical-issues.html#faq-39.6
+#define GTEST_CONCAT_TOKEN_(foo, bar) GTEST_CONCAT_TOKEN_IMPL_(foo, bar)
+#define GTEST_CONCAT_TOKEN_IMPL_(foo, bar) foo ## bar
+
+// Stringifies its argument.
+// Work around a bug in visual studio which doesn't accept code like this:
+//
+//   #define GTEST_STRINGIFY_(name) #name
+//   #define MACRO(a, b, c) ... GTEST_STRINGIFY_(a) ...
+//   MACRO(, x, y)
+//
+// Complaining about the argument to GTEST_STRINGIFY_ being empty.
+// This is allowed by the spec.
+#define GTEST_STRINGIFY_HELPER_(name, ...) #name
+#define GTEST_STRINGIFY_(...) GTEST_STRINGIFY_HELPER_(__VA_ARGS__, )
+
+namespace proto2 {
+class MessageLite;
+}
+
+namespace testing {
+
+// Forward declarations.
+
+class AssertionResult;                 // Result of an assertion.
+class Message;                         // Represents a failure message.
+class Test;                            // Represents a test.
+class TestInfo;                        // Information about a test.
+class TestPartResult;                  // Result of a test part.
+class UnitTest;                        // A collection of test suites.
+
+template <typename T>
+::std::string PrintToString(const T& value);
+
+namespace internal {
+
+struct TraceInfo;                      // Information about a trace point.
+class TestInfoImpl;                    // Opaque implementation of TestInfo
+class UnitTestImpl;                    // Opaque implementation of UnitTest
+
+// The text used in failure messages to indicate the start of the
+// stack trace.
+GTEST_API_ extern const char kStackTraceMarker[];
+
+// An IgnoredValue object can be implicitly constructed from ANY value.
+class IgnoredValue {
+  struct Sink {};
+ public:
+  // This constructor template allows any value to be implicitly
+  // converted to IgnoredValue.  The object has no data member and
+  // doesn't try to remember anything about the argument.  We
+  // deliberately omit the 'explicit' keyword in order to allow the
+  // conversion to be implicit.
+  // Disable the conversion if T already has a magical conversion operator.
+  // Otherwise we get ambiguity.
+  template <typename T,
+            typename std::enable_if<!std::is_convertible<T, Sink>::value,
+                                    int>::type = 0>
+  IgnoredValue(const T& /* ignored */) {}  // NOLINT(runtime/explicit)
+};
+
+// Appends the user-supplied message to the Google-Test-generated message.
+GTEST_API_ std::string AppendUserMessage(
+    const std::string& gtest_msg, const Message& user_msg);
+
+#if GTEST_HAS_EXCEPTIONS
+
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4275 \
+/* an exported class was derived from a class that was not exported */)
+
+// This exception is thrown by (and only by) a failed Google Test
+// assertion when GTEST_FLAG(throw_on_failure) is true (if exceptions
+// are enabled).  We derive it from std::runtime_error, which is for
+// errors presumably detectable only at run time.  Since
+// std::runtime_error inherits from std::exception, many testing
+// frameworks know how to extract and print the message inside it.
+class GTEST_API_ GoogleTestFailureException : public ::std::runtime_error {
+ public:
+  explicit GoogleTestFailureException(const TestPartResult& failure);
+};
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  //  4275
+
+#endif  // GTEST_HAS_EXCEPTIONS
+
+namespace edit_distance {
+// Returns the optimal edits to go from 'left' to 'right'.
+// All edits cost the same, with replace having lower priority than
+// add/remove.
+// Simple implementation of the Wagner-Fischer algorithm.
+// See http://en.wikipedia.org/wiki/Wagner-Fischer_algorithm
+enum EditType { kMatch, kAdd, kRemove, kReplace };
+GTEST_API_ std::vector<EditType> CalculateOptimalEdits(
+    const std::vector<size_t>& left, const std::vector<size_t>& right);
+
+// Same as above, but the input is represented as strings.
+GTEST_API_ std::vector<EditType> CalculateOptimalEdits(
+    const std::vector<std::string>& left,
+    const std::vector<std::string>& right);
+
+// Create a diff of the input strings in Unified diff format.
+GTEST_API_ std::string CreateUnifiedDiff(const std::vector<std::string>& left,
+                                         const std::vector<std::string>& right,
+                                         size_t context = 2);
+
+}  // namespace edit_distance
+
+// Calculate the diff between 'left' and 'right' and return it in unified diff
+// format.
+// If not null, stores in 'total_line_count' the total number of lines found
+// in left + right.
+GTEST_API_ std::string DiffStrings(const std::string& left,
+                                   const std::string& right,
+                                   size_t* total_line_count);
+
+// Constructs and returns the message for an equality assertion
+// (e.g. ASSERT_EQ, EXPECT_STREQ, etc) failure.
+//
+// The first four parameters are the expressions used in the assertion
+// and their values, as strings.  For example, for ASSERT_EQ(foo, bar)
+// where foo is 5 and bar is 6, we have:
+//
+//   expected_expression: "foo"
+//   actual_expression:   "bar"
+//   expected_value:      "5"
+//   actual_value:        "6"
+//
+// The ignoring_case parameter is true if and only if the assertion is a
+// *_STRCASEEQ*.  When it's true, the string " (ignoring case)" will
+// be inserted into the message.
+GTEST_API_ AssertionResult EqFailure(const char* expected_expression,
+                                     const char* actual_expression,
+                                     const std::string& expected_value,
+                                     const std::string& actual_value,
+                                     bool ignoring_case);
+
+// Constructs a failure message for Boolean assertions such as EXPECT_TRUE.
+GTEST_API_ std::string GetBoolAssertionFailureMessage(
+    const AssertionResult& assertion_result,
+    const char* expression_text,
+    const char* actual_predicate_value,
+    const char* expected_predicate_value);
+
+// This template class represents an IEEE floating-point number
+// (either single-precision or double-precision, depending on the
+// template parameters).
+//
+// The purpose of this class is to do more sophisticated number
+// comparison.  (Due to round-off error, etc, it's very unlikely that
+// two floating-points will be equal exactly.  Hence a naive
+// comparison by the == operation often doesn't work.)
+//
+// Format of IEEE floating-point:
+//
+//   The most-significant bit being the leftmost, an IEEE
+//   floating-point looks like
+//
+//     sign_bit exponent_bits fraction_bits
+//
+//   Here, sign_bit is a single bit that designates the sign of the
+//   number.
+//
+//   For float, there are 8 exponent bits and 23 fraction bits.
+//
+//   For double, there are 11 exponent bits and 52 fraction bits.
+//
+//   More details can be found at
+//   http://en.wikipedia.org/wiki/IEEE_floating-point_standard.
+//
+// Template parameter:
+//
+//   RawType: the raw floating-point type (either float or double)
+template <typename RawType>
+class FloatingPoint {
+ public:
+  // Defines the unsigned integer type that has the same size as the
+  // floating point number.
+  typedef typename TypeWithSize<sizeof(RawType)>::UInt Bits;
+
+  // Constants.
+
+  // # of bits in a number.
+  static const size_t kBitCount = 8*sizeof(RawType);
+
+  // # of fraction bits in a number.
+  static const size_t kFractionBitCount =
+    std::numeric_limits<RawType>::digits - 1;
+
+  // # of exponent bits in a number.
+  static const size_t kExponentBitCount = kBitCount - 1 - kFractionBitCount;
+
+  // The mask for the sign bit.
+  static const Bits kSignBitMask = static_cast<Bits>(1) << (kBitCount - 1);
+
+  // The mask for the fraction bits.
+  static const Bits kFractionBitMask =
+    ~static_cast<Bits>(0) >> (kExponentBitCount + 1);
+
+  // The mask for the exponent bits.
+  static const Bits kExponentBitMask = ~(kSignBitMask | kFractionBitMask);
+
+  // How many ULP's (Units in the Last Place) we want to tolerate when
+  // comparing two numbers.  The larger the value, the more error we
+  // allow.  A 0 value means that two numbers must be exactly the same
+  // to be considered equal.
+  //
+  // The maximum error of a single floating-point operation is 0.5
+  // units in the last place.  On Intel CPU's, all floating-point
+  // calculations are done with 80-bit precision, while double has 64
+  // bits.  Therefore, 4 should be enough for ordinary use.
+  //
+  // See the following article for more details on ULP:
+  // http://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition/
+  static const uint32_t kMaxUlps = 4;
+
+  // Constructs a FloatingPoint from a raw floating-point number.
+  //
+  // On an Intel CPU, passing a non-normalized NAN (Not a Number)
+  // around may change its bits, although the new value is guaranteed
+  // to be also a NAN.  Therefore, don't expect this constructor to
+  // preserve the bits in x when x is a NAN.
+  explicit FloatingPoint(const RawType& x) { u_.value_ = x; }
+
+  // Static methods
+
+  // Reinterprets a bit pattern as a floating-point number.
+  //
+  // This function is needed to test the AlmostEquals() method.
+  static RawType ReinterpretBits(const Bits bits) {
+    FloatingPoint fp(0);
+    fp.u_.bits_ = bits;
+    return fp.u_.value_;
+  }
+
+  // Returns the floating-point number that represent positive infinity.
+  static RawType Infinity() {
+    return ReinterpretBits(kExponentBitMask);
+  }
+
+  // Returns the maximum representable finite floating-point number.
+  static RawType Max();
+
+  // Non-static methods
+
+  // Returns the bits that represents this number.
+  const Bits &bits() const { return u_.bits_; }
+
+  // Returns the exponent bits of this number.
+  Bits exponent_bits() const { return kExponentBitMask & u_.bits_; }
+
+  // Returns the fraction bits of this number.
+  Bits fraction_bits() const { return kFractionBitMask & u_.bits_; }
+
+  // Returns the sign bit of this number.
+  Bits sign_bit() const { return kSignBitMask & u_.bits_; }
+
+  // Returns true if and only if this is NAN (not a number).
+  bool is_nan() const {
+    // It's a NAN if the exponent bits are all ones and the fraction
+    // bits are not entirely zeros.
+    return (exponent_bits() == kExponentBitMask) && (fraction_bits() != 0);
+  }
+
+  // Returns true if and only if this number is at most kMaxUlps ULP's away
+  // from rhs.  In particular, this function:
+  //
+  //   - returns false if either number is (or both are) NAN.
+  //   - treats really large numbers as almost equal to infinity.
+  //   - thinks +0.0 and -0.0 are 0 DLP's apart.
+  bool AlmostEquals(const FloatingPoint& rhs) const {
+    // The IEEE standard says that any comparison operation involving
+    // a NAN must return false.
+    if (is_nan() || rhs.is_nan()) return false;
+
+    return DistanceBetweenSignAndMagnitudeNumbers(u_.bits_, rhs.u_.bits_)
+        <= kMaxUlps;
+  }
+
+ private:
+  // The data type used to store the actual floating-point number.
+  union FloatingPointUnion {
+    RawType value_;  // The raw floating-point number.
+    Bits bits_;      // The bits that represent the number.
+  };
+
+  // Converts an integer from the sign-and-magnitude representation to
+  // the biased representation.  More precisely, let N be 2 to the
+  // power of (kBitCount - 1), an integer x is represented by the
+  // unsigned number x + N.
+  //
+  // For instance,
+  //
+  //   -N + 1 (the most negative number representable using
+  //          sign-and-magnitude) is represented by 1;
+  //   0      is represented by N; and
+  //   N - 1  (the biggest number representable using
+  //          sign-and-magnitude) is represented by 2N - 1.
+  //
+  // Read http://en.wikipedia.org/wiki/Signed_number_representations
+  // for more details on signed number representations.
+  static Bits SignAndMagnitudeToBiased(const Bits &sam) {
+    if (kSignBitMask & sam) {
+      // sam represents a negative number.
+      return ~sam + 1;
+    } else {
+      // sam represents a positive number.
+      return kSignBitMask | sam;
+    }
+  }
+
+  // Given two numbers in the sign-and-magnitude representation,
+  // returns the distance between them as an unsigned number.
+  static Bits DistanceBetweenSignAndMagnitudeNumbers(const Bits &sam1,
+                                                     const Bits &sam2) {
+    const Bits biased1 = SignAndMagnitudeToBiased(sam1);
+    const Bits biased2 = SignAndMagnitudeToBiased(sam2);
+    return (biased1 >= biased2) ? (biased1 - biased2) : (biased2 - biased1);
+  }
+
+  FloatingPointUnion u_;
+};
+
+// We cannot use std::numeric_limits<T>::max() as it clashes with the max()
+// macro defined by <windows.h>.
+template <>
+inline float FloatingPoint<float>::Max() { return FLT_MAX; }
+template <>
+inline double FloatingPoint<double>::Max() { return DBL_MAX; }
+
+// Typedefs the instances of the FloatingPoint template class that we
+// care to use.
+typedef FloatingPoint<float> Float;
+typedef FloatingPoint<double> Double;
+
+// In order to catch the mistake of putting tests that use different
+// test fixture classes in the same test suite, we need to assign
+// unique IDs to fixture classes and compare them.  The TypeId type is
+// used to hold such IDs.  The user should treat TypeId as an opaque
+// type: the only operation allowed on TypeId values is to compare
+// them for equality using the == operator.
+typedef const void* TypeId;
+
+template <typename T>
+class TypeIdHelper {
+ public:
+  // dummy_ must not have a const type.  Otherwise an overly eager
+  // compiler (e.g. MSVC 7.1 & 8.0) may try to merge
+  // TypeIdHelper<T>::dummy_ for different Ts as an "optimization".
+  static bool dummy_;
+};
+
+template <typename T>
+bool TypeIdHelper<T>::dummy_ = false;
+
+// GetTypeId<T>() returns the ID of type T.  Different values will be
+// returned for different types.  Calling the function twice with the
+// same type argument is guaranteed to return the same ID.
+template <typename T>
+TypeId GetTypeId() {
+  // The compiler is required to allocate a different
+  // TypeIdHelper<T>::dummy_ variable for each T used to instantiate
+  // the template.  Therefore, the address of dummy_ is guaranteed to
+  // be unique.
+  return &(TypeIdHelper<T>::dummy_);
+}
+
+// Returns the type ID of ::testing::Test.  Always call this instead
+// of GetTypeId< ::testing::Test>() to get the type ID of
+// ::testing::Test, as the latter may give the wrong result due to a
+// suspected linker bug when compiling Google Test as a Mac OS X
+// framework.
+GTEST_API_ TypeId GetTestTypeId();
+
+// Defines the abstract factory interface that creates instances
+// of a Test object.
+class TestFactoryBase {
+ public:
+  virtual ~TestFactoryBase() {}
+
+  // Creates a test instance to run. The instance is both created and destroyed
+  // within TestInfoImpl::Run()
+  virtual Test* CreateTest() = 0;
+
+ protected:
+  TestFactoryBase() {}
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(TestFactoryBase);
+};
+
+// This class provides implementation of TeastFactoryBase interface.
+// It is used in TEST and TEST_F macros.
+template <class TestClass>
+class TestFactoryImpl : public TestFactoryBase {
+ public:
+  Test* CreateTest() override { return new TestClass; }
+};
+
+#if GTEST_OS_WINDOWS
+
+// Predicate-formatters for implementing the HRESULT checking macros
+// {ASSERT|EXPECT}_HRESULT_{SUCCEEDED|FAILED}
+// We pass a long instead of HRESULT to avoid causing an
+// include dependency for the HRESULT type.
+GTEST_API_ AssertionResult IsHRESULTSuccess(const char* expr,
+                                            long hr);  // NOLINT
+GTEST_API_ AssertionResult IsHRESULTFailure(const char* expr,
+                                            long hr);  // NOLINT
+
+#endif  // GTEST_OS_WINDOWS
+
+// Types of SetUpTestSuite() and TearDownTestSuite() functions.
+using SetUpTestSuiteFunc = void (*)();
+using TearDownTestSuiteFunc = void (*)();
+
+struct CodeLocation {
+  CodeLocation(const std::string& a_file, int a_line)
+      : file(a_file), line(a_line) {}
+
+  std::string file;
+  int line;
+};
+
+//  Helper to identify which setup function for TestCase / TestSuite to call.
+//  Only one function is allowed, either TestCase or TestSute but not both.
+
+// Utility functions to help SuiteApiResolver
+using SetUpTearDownSuiteFuncType = void (*)();
+
+inline SetUpTearDownSuiteFuncType GetNotDefaultOrNull(
+    SetUpTearDownSuiteFuncType a, SetUpTearDownSuiteFuncType def) {
+  return a == def ? nullptr : a;
+}
+
+template <typename T>
+//  Note that SuiteApiResolver inherits from T because
+//  SetUpTestSuite()/TearDownTestSuite() could be protected. Ths way
+//  SuiteApiResolver can access them.
+struct SuiteApiResolver : T {
+  // testing::Test is only forward declared at this point. So we make it a
+  // dependend class for the compiler to be OK with it.
+  using Test =
+      typename std::conditional<sizeof(T) != 0, ::testing::Test, void>::type;
+
+  static SetUpTearDownSuiteFuncType GetSetUpCaseOrSuite(const char* filename,
+                                                        int line_num) {
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+    SetUpTearDownSuiteFuncType test_case_fp =
+        GetNotDefaultOrNull(&T::SetUpTestCase, &Test::SetUpTestCase);
+    SetUpTearDownSuiteFuncType test_suite_fp =
+        GetNotDefaultOrNull(&T::SetUpTestSuite, &Test::SetUpTestSuite);
+
+    GTEST_CHECK_(!test_case_fp || !test_suite_fp)
+        << "Test can not provide both SetUpTestSuite and SetUpTestCase, please "
+           "make sure there is only one present at "
+        << filename << ":" << line_num;
+
+    return test_case_fp != nullptr ? test_case_fp : test_suite_fp;
+#else
+    (void)(filename);
+    (void)(line_num);
+    return &T::SetUpTestSuite;
+#endif
+  }
+
+  static SetUpTearDownSuiteFuncType GetTearDownCaseOrSuite(const char* filename,
+                                                           int line_num) {
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+    SetUpTearDownSuiteFuncType test_case_fp =
+        GetNotDefaultOrNull(&T::TearDownTestCase, &Test::TearDownTestCase);
+    SetUpTearDownSuiteFuncType test_suite_fp =
+        GetNotDefaultOrNull(&T::TearDownTestSuite, &Test::TearDownTestSuite);
+
+    GTEST_CHECK_(!test_case_fp || !test_suite_fp)
+        << "Test can not provide both TearDownTestSuite and TearDownTestCase,"
+           " please make sure there is only one present at"
+        << filename << ":" << line_num;
+
+    return test_case_fp != nullptr ? test_case_fp : test_suite_fp;
+#else
+    (void)(filename);
+    (void)(line_num);
+    return &T::TearDownTestSuite;
+#endif
+  }
+};
+
+// Creates a new TestInfo object and registers it with Google Test;
+// returns the created object.
+//
+// Arguments:
+//
+//   test_suite_name:  name of the test suite
+//   name:             name of the test
+//   type_param:       the name of the test's type parameter, or NULL if
+//                     this is not a typed or a type-parameterized test.
+//   value_param:      text representation of the test's value parameter,
+//                     or NULL if this is not a type-parameterized test.
+//   code_location:    code location where the test is defined
+//   fixture_class_id: ID of the test fixture class
+//   set_up_tc:        pointer to the function that sets up the test suite
+//   tear_down_tc:     pointer to the function that tears down the test suite
+//   factory:          pointer to the factory that creates a test object.
+//                     The newly created TestInfo instance will assume
+//                     ownership of the factory object.
+GTEST_API_ TestInfo* MakeAndRegisterTestInfo(
+    const char* test_suite_name, const char* name, const char* type_param,
+    const char* value_param, CodeLocation code_location,
+    TypeId fixture_class_id, SetUpTestSuiteFunc set_up_tc,
+    TearDownTestSuiteFunc tear_down_tc, TestFactoryBase* factory);
+
+// If *pstr starts with the given prefix, modifies *pstr to be right
+// past the prefix and returns true; otherwise leaves *pstr unchanged
+// and returns false.  None of pstr, *pstr, and prefix can be NULL.
+GTEST_API_ bool SkipPrefix(const char* prefix, const char** pstr);
+
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4251 \
+/* class A needs to have dll-interface to be used by clients of class B */)
+
+// State of the definition of a type-parameterized test suite.
+class GTEST_API_ TypedTestSuitePState {
+ public:
+  TypedTestSuitePState() : registered_(false) {}
+
+  // Adds the given test name to defined_test_names_ and return true
+  // if the test suite hasn't been registered; otherwise aborts the
+  // program.
+  bool AddTestName(const char* file, int line, const char* case_name,
+                   const char* test_name) {
+    if (registered_) {
+      fprintf(stderr,
+              "%s Test %s must be defined before "
+              "REGISTER_TYPED_TEST_SUITE_P(%s, ...).\n",
+              FormatFileLocation(file, line).c_str(), test_name, case_name);
+      fflush(stderr);
+      posix::Abort();
+    }
+    registered_tests_.insert(
+        ::std::make_pair(test_name, CodeLocation(file, line)));
+    return true;
+  }
+
+  bool TestExists(const std::string& test_name) const {
+    return registered_tests_.count(test_name) > 0;
+  }
+
+  const CodeLocation& GetCodeLocation(const std::string& test_name) const {
+    RegisteredTestsMap::const_iterator it = registered_tests_.find(test_name);
+    GTEST_CHECK_(it != registered_tests_.end());
+    return it->second;
+  }
+
+  // Verifies that registered_tests match the test names in
+  // defined_test_names_; returns registered_tests if successful, or
+  // aborts the program otherwise.
+  const char* VerifyRegisteredTestNames(const char* test_suite_name,
+                                        const char* file, int line,
+                                        const char* registered_tests);
+
+ private:
+  typedef ::std::map<std::string, CodeLocation> RegisteredTestsMap;
+
+  bool registered_;
+  RegisteredTestsMap registered_tests_;
+};
+
+//  Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+using TypedTestCasePState = TypedTestSuitePState;
+#endif  //  GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  //  4251
+
+// Skips to the first non-space char after the first comma in 'str';
+// returns NULL if no comma is found in 'str'.
+inline const char* SkipComma(const char* str) {
+  const char* comma = strchr(str, ',');
+  if (comma == nullptr) {
+    return nullptr;
+  }
+  while (IsSpace(*(++comma))) {}
+  return comma;
+}
+
+// Returns the prefix of 'str' before the first comma in it; returns
+// the entire string if it contains no comma.
+inline std::string GetPrefixUntilComma(const char* str) {
+  const char* comma = strchr(str, ',');
+  return comma == nullptr ? str : std::string(str, comma);
+}
+
+// Splits a given string on a given delimiter, populating a given
+// vector with the fields.
+void SplitString(const ::std::string& str, char delimiter,
+                 ::std::vector< ::std::string>* dest);
+
+// The default argument to the template below for the case when the user does
+// not provide a name generator.
+struct DefaultNameGenerator {
+  template <typename T>
+  static std::string GetName(int i) {
+    return StreamableToString(i);
+  }
+};
+
+template <typename Provided = DefaultNameGenerator>
+struct NameGeneratorSelector {
+  typedef Provided type;
+};
+
+template <typename NameGenerator>
+void GenerateNamesRecursively(internal::None, std::vector<std::string>*, int) {}
+
+template <typename NameGenerator, typename Types>
+void GenerateNamesRecursively(Types, std::vector<std::string>* result, int i) {
+  result->push_back(NameGenerator::template GetName<typename Types::Head>(i));
+  GenerateNamesRecursively<NameGenerator>(typename Types::Tail(), result,
+                                          i + 1);
+}
+
+template <typename NameGenerator, typename Types>
+std::vector<std::string> GenerateNames() {
+  std::vector<std::string> result;
+  GenerateNamesRecursively<NameGenerator>(Types(), &result, 0);
+  return result;
+}
+
+// TypeParameterizedTest<Fixture, TestSel, Types>::Register()
+// registers a list of type-parameterized tests with Google Test.  The
+// return value is insignificant - we just need to return something
+// such that we can call this function in a namespace scope.
+//
+// Implementation note: The GTEST_TEMPLATE_ macro declares a template
+// template parameter.  It's defined in gtest-type-util.h.
+template <GTEST_TEMPLATE_ Fixture, class TestSel, typename Types>
+class TypeParameterizedTest {
+ public:
+  // 'index' is the index of the test in the type list 'Types'
+  // specified in INSTANTIATE_TYPED_TEST_SUITE_P(Prefix, TestSuite,
+  // Types).  Valid values for 'index' are [0, N - 1] where N is the
+  // length of Types.
+  static bool Register(const char* prefix, const CodeLocation& code_location,
+                       const char* case_name, const char* test_names, int index,
+                       const std::vector<std::string>& type_names =
+                           GenerateNames<DefaultNameGenerator, Types>()) {
+    typedef typename Types::Head Type;
+    typedef Fixture<Type> FixtureClass;
+    typedef typename GTEST_BIND_(TestSel, Type) TestClass;
+
+    // First, registers the first type-parameterized test in the type
+    // list.
+    MakeAndRegisterTestInfo(
+        (std::string(prefix) + (prefix[0] == '\0' ? "" : "/") + case_name +
+         "/" + type_names[static_cast<size_t>(index)])
+            .c_str(),
+        StripTrailingSpaces(GetPrefixUntilComma(test_names)).c_str(),
+        GetTypeName<Type>().c_str(),
+        nullptr,  // No value parameter.
+        code_location, GetTypeId<FixtureClass>(),
+        SuiteApiResolver<TestClass>::GetSetUpCaseOrSuite(
+            code_location.file.c_str(), code_location.line),
+        SuiteApiResolver<TestClass>::GetTearDownCaseOrSuite(
+            code_location.file.c_str(), code_location.line),
+        new TestFactoryImpl<TestClass>);
+
+    // Next, recurses (at compile time) with the tail of the type list.
+    return TypeParameterizedTest<Fixture, TestSel,
+                                 typename Types::Tail>::Register(prefix,
+                                                                 code_location,
+                                                                 case_name,
+                                                                 test_names,
+                                                                 index + 1,
+                                                                 type_names);
+  }
+};
+
+// The base case for the compile time recursion.
+template <GTEST_TEMPLATE_ Fixture, class TestSel>
+class TypeParameterizedTest<Fixture, TestSel, internal::None> {
+ public:
+  static bool Register(const char* /*prefix*/, const CodeLocation&,
+                       const char* /*case_name*/, const char* /*test_names*/,
+                       int /*index*/,
+                       const std::vector<std::string>& =
+                           std::vector<std::string>() /*type_names*/) {
+    return true;
+  }
+};
+
+GTEST_API_ void RegisterTypeParameterizedTestSuite(const char* test_suite_name,
+                                                   CodeLocation code_location);
+GTEST_API_ void RegisterTypeParameterizedTestSuiteInstantiation(
+    const char* case_name);
+
+// TypeParameterizedTestSuite<Fixture, Tests, Types>::Register()
+// registers *all combinations* of 'Tests' and 'Types' with Google
+// Test.  The return value is insignificant - we just need to return
+// something such that we can call this function in a namespace scope.
+template <GTEST_TEMPLATE_ Fixture, typename Tests, typename Types>
+class TypeParameterizedTestSuite {
+ public:
+  static bool Register(const char* prefix, CodeLocation code_location,
+                       const TypedTestSuitePState* state, const char* case_name,
+                       const char* test_names,
+                       const std::vector<std::string>& type_names =
+                           GenerateNames<DefaultNameGenerator, Types>()) {
+    RegisterTypeParameterizedTestSuiteInstantiation(case_name);
+    std::string test_name = StripTrailingSpaces(
+        GetPrefixUntilComma(test_names));
+    if (!state->TestExists(test_name)) {
+      fprintf(stderr, "Failed to get code location for test %s.%s at %s.",
+              case_name, test_name.c_str(),
+              FormatFileLocation(code_location.file.c_str(),
+                                 code_location.line).c_str());
+      fflush(stderr);
+      posix::Abort();
+    }
+    const CodeLocation& test_location = state->GetCodeLocation(test_name);
+
+    typedef typename Tests::Head Head;
+
+    // First, register the first test in 'Test' for each type in 'Types'.
+    TypeParameterizedTest<Fixture, Head, Types>::Register(
+        prefix, test_location, case_name, test_names, 0, type_names);
+
+    // Next, recurses (at compile time) with the tail of the test list.
+    return TypeParameterizedTestSuite<Fixture, typename Tests::Tail,
+                                      Types>::Register(prefix, code_location,
+                                                       state, case_name,
+                                                       SkipComma(test_names),
+                                                       type_names);
+  }
+};
+
+// The base case for the compile time recursion.
+template <GTEST_TEMPLATE_ Fixture, typename Types>
+class TypeParameterizedTestSuite<Fixture, internal::None, Types> {
+ public:
+  static bool Register(const char* /*prefix*/, const CodeLocation&,
+                       const TypedTestSuitePState* /*state*/,
+                       const char* /*case_name*/, const char* /*test_names*/,
+                       const std::vector<std::string>& =
+                           std::vector<std::string>() /*type_names*/) {
+    return true;
+  }
+};
+
+// Returns the current OS stack trace as an std::string.
+//
+// The maximum number of stack frames to be included is specified by
+// the gtest_stack_trace_depth flag.  The skip_count parameter
+// specifies the number of top frames to be skipped, which doesn't
+// count against the number of frames to be included.
+//
+// For example, if Foo() calls Bar(), which in turn calls
+// GetCurrentOsStackTraceExceptTop(..., 1), Foo() will be included in
+// the trace but Bar() and GetCurrentOsStackTraceExceptTop() won't.
+GTEST_API_ std::string GetCurrentOsStackTraceExceptTop(
+    UnitTest* unit_test, int skip_count);
+
+// Helpers for suppressing warnings on unreachable code or constant
+// condition.
+
+// Always returns true.
+GTEST_API_ bool AlwaysTrue();
+
+// Always returns false.
+inline bool AlwaysFalse() { return !AlwaysTrue(); }
+
+// Helper for suppressing false warning from Clang on a const char*
+// variable declared in a conditional expression always being NULL in
+// the else branch.
+struct GTEST_API_ ConstCharPtr {
+  ConstCharPtr(const char* str) : value(str) {}
+  operator bool() const { return true; }
+  const char* value;
+};
+
+// Helper for declaring std::string within 'if' statement
+// in pre C++17 build environment.
+struct TrueWithString {
+  TrueWithString() = default;
+  explicit TrueWithString(const char* str) : value(str) {}
+  explicit TrueWithString(const std::string& str) : value(str) {}
+  explicit operator bool() const { return true; }
+  std::string value;
+};
+
+// A simple Linear Congruential Generator for generating random
+// numbers with a uniform distribution.  Unlike rand() and srand(), it
+// doesn't use global state (and therefore can't interfere with user
+// code).  Unlike rand_r(), it's portable.  An LCG isn't very random,
+// but it's good enough for our purposes.
+class GTEST_API_ Random {
+ public:
+  static const uint32_t kMaxRange = 1u << 31;
+
+  explicit Random(uint32_t seed) : state_(seed) {}
+
+  void Reseed(uint32_t seed) { state_ = seed; }
+
+  // Generates a random number from [0, range).  Crashes if 'range' is
+  // 0 or greater than kMaxRange.
+  uint32_t Generate(uint32_t range);
+
+ private:
+  uint32_t state_;
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(Random);
+};
+
+// Turns const U&, U&, const U, and U all into U.
+#define GTEST_REMOVE_REFERENCE_AND_CONST_(T) \
+  typename std::remove_const<typename std::remove_reference<T>::type>::type
+
+// HasDebugStringAndShortDebugString<T>::value is a compile-time bool constant
+// that's true if and only if T has methods DebugString() and ShortDebugString()
+// that return std::string.
+template <typename T>
+class HasDebugStringAndShortDebugString {
+ private:
+  template <typename C>
+  static auto CheckDebugString(C*) -> typename std::is_same<
+      std::string, decltype(std::declval<const C>().DebugString())>::type;
+  template <typename>
+  static std::false_type CheckDebugString(...);
+
+  template <typename C>
+  static auto CheckShortDebugString(C*) -> typename std::is_same<
+      std::string, decltype(std::declval<const C>().ShortDebugString())>::type;
+  template <typename>
+  static std::false_type CheckShortDebugString(...);
+
+  using HasDebugStringType = decltype(CheckDebugString<T>(nullptr));
+  using HasShortDebugStringType = decltype(CheckShortDebugString<T>(nullptr));
+
+ public:
+  static constexpr bool value =
+      HasDebugStringType::value && HasShortDebugStringType::value;
+};
+
+template <typename T>
+constexpr bool HasDebugStringAndShortDebugString<T>::value;
+
+// When the compiler sees expression IsContainerTest<C>(0), if C is an
+// STL-style container class, the first overload of IsContainerTest
+// will be viable (since both C::iterator* and C::const_iterator* are
+// valid types and NULL can be implicitly converted to them).  It will
+// be picked over the second overload as 'int' is a perfect match for
+// the type of argument 0.  If C::iterator or C::const_iterator is not
+// a valid type, the first overload is not viable, and the second
+// overload will be picked.  Therefore, we can determine whether C is
+// a container class by checking the type of IsContainerTest<C>(0).
+// The value of the expression is insignificant.
+//
+// In C++11 mode we check the existence of a const_iterator and that an
+// iterator is properly implemented for the container.
+//
+// For pre-C++11 that we look for both C::iterator and C::const_iterator.
+// The reason is that C++ injects the name of a class as a member of the
+// class itself (e.g. you can refer to class iterator as either
+// 'iterator' or 'iterator::iterator').  If we look for C::iterator
+// only, for example, we would mistakenly think that a class named
+// iterator is an STL container.
+//
+// Also note that the simpler approach of overloading
+// IsContainerTest(typename C::const_iterator*) and
+// IsContainerTest(...) doesn't work with Visual Age C++ and Sun C++.
+typedef int IsContainer;
+template <class C,
+          class Iterator = decltype(::std::declval<const C&>().begin()),
+          class = decltype(::std::declval<const C&>().end()),
+          class = decltype(++::std::declval<Iterator&>()),
+          class = decltype(*::std::declval<Iterator>()),
+          class = typename C::const_iterator>
+IsContainer IsContainerTest(int /* dummy */) {
+  return 0;
+}
+
+typedef char IsNotContainer;
+template <class C>
+IsNotContainer IsContainerTest(long /* dummy */) { return '\0'; }
+
+// Trait to detect whether a type T is a hash table.
+// The heuristic used is that the type contains an inner type `hasher` and does
+// not contain an inner type `reverse_iterator`.
+// If the container is iterable in reverse, then order might actually matter.
+template <typename T>
+struct IsHashTable {
+ private:
+  template <typename U>
+  static char test(typename U::hasher*, typename U::reverse_iterator*);
+  template <typename U>
+  static int test(typename U::hasher*, ...);
+  template <typename U>
+  static char test(...);
+
+ public:
+  static const bool value = sizeof(test<T>(nullptr, nullptr)) == sizeof(int);
+};
+
+template <typename T>
+const bool IsHashTable<T>::value;
+
+template <typename C,
+          bool = sizeof(IsContainerTest<C>(0)) == sizeof(IsContainer)>
+struct IsRecursiveContainerImpl;
+
+template <typename C>
+struct IsRecursiveContainerImpl<C, false> : public std::false_type {};
+
+// Since the IsRecursiveContainerImpl depends on the IsContainerTest we need to
+// obey the same inconsistencies as the IsContainerTest, namely check if
+// something is a container is relying on only const_iterator in C++11 and
+// is relying on both const_iterator and iterator otherwise
+template <typename C>
+struct IsRecursiveContainerImpl<C, true> {
+  using value_type = decltype(*std::declval<typename C::const_iterator>());
+  using type =
+      std::is_same<typename std::remove_const<
+                       typename std::remove_reference<value_type>::type>::type,
+                   C>;
+};
+
+// IsRecursiveContainer<Type> is a unary compile-time predicate that
+// evaluates whether C is a recursive container type. A recursive container
+// type is a container type whose value_type is equal to the container type
+// itself. An example for a recursive container type is
+// boost::filesystem::path, whose iterator has a value_type that is equal to
+// boost::filesystem::path.
+template <typename C>
+struct IsRecursiveContainer : public IsRecursiveContainerImpl<C>::type {};
+
+// Utilities for native arrays.
+
+// ArrayEq() compares two k-dimensional native arrays using the
+// elements' operator==, where k can be any integer >= 0.  When k is
+// 0, ArrayEq() degenerates into comparing a single pair of values.
+
+template <typename T, typename U>
+bool ArrayEq(const T* lhs, size_t size, const U* rhs);
+
+// This generic version is used when k is 0.
+template <typename T, typename U>
+inline bool ArrayEq(const T& lhs, const U& rhs) { return lhs == rhs; }
+
+// This overload is used when k >= 1.
+template <typename T, typename U, size_t N>
+inline bool ArrayEq(const T(&lhs)[N], const U(&rhs)[N]) {
+  return internal::ArrayEq(lhs, N, rhs);
+}
+
+// This helper reduces code bloat.  If we instead put its logic inside
+// the previous ArrayEq() function, arrays with different sizes would
+// lead to different copies of the template code.
+template <typename T, typename U>
+bool ArrayEq(const T* lhs, size_t size, const U* rhs) {
+  for (size_t i = 0; i != size; i++) {
+    if (!internal::ArrayEq(lhs[i], rhs[i]))
+      return false;
+  }
+  return true;
+}
+
+// Finds the first element in the iterator range [begin, end) that
+// equals elem.  Element may be a native array type itself.
+template <typename Iter, typename Element>
+Iter ArrayAwareFind(Iter begin, Iter end, const Element& elem) {
+  for (Iter it = begin; it != end; ++it) {
+    if (internal::ArrayEq(*it, elem))
+      return it;
+  }
+  return end;
+}
+
+// CopyArray() copies a k-dimensional native array using the elements'
+// operator=, where k can be any integer >= 0.  When k is 0,
+// CopyArray() degenerates into copying a single value.
+
+template <typename T, typename U>
+void CopyArray(const T* from, size_t size, U* to);
+
+// This generic version is used when k is 0.
+template <typename T, typename U>
+inline void CopyArray(const T& from, U* to) { *to = from; }
+
+// This overload is used when k >= 1.
+template <typename T, typename U, size_t N>
+inline void CopyArray(const T(&from)[N], U(*to)[N]) {
+  internal::CopyArray(from, N, *to);
+}
+
+// This helper reduces code bloat.  If we instead put its logic inside
+// the previous CopyArray() function, arrays with different sizes
+// would lead to different copies of the template code.
+template <typename T, typename U>
+void CopyArray(const T* from, size_t size, U* to) {
+  for (size_t i = 0; i != size; i++) {
+    internal::CopyArray(from[i], to + i);
+  }
+}
+
+// The relation between an NativeArray object (see below) and the
+// native array it represents.
+// We use 2 different structs to allow non-copyable types to be used, as long
+// as RelationToSourceReference() is passed.
+struct RelationToSourceReference {};
+struct RelationToSourceCopy {};
+
+// Adapts a native array to a read-only STL-style container.  Instead
+// of the complete STL container concept, this adaptor only implements
+// members useful for Google Mock's container matchers.  New members
+// should be added as needed.  To simplify the implementation, we only
+// support Element being a raw type (i.e. having no top-level const or
+// reference modifier).  It's the client's responsibility to satisfy
+// this requirement.  Element can be an array type itself (hence
+// multi-dimensional arrays are supported).
+template <typename Element>
+class NativeArray {
+ public:
+  // STL-style container typedefs.
+  typedef Element value_type;
+  typedef Element* iterator;
+  typedef const Element* const_iterator;
+
+  // Constructs from a native array. References the source.
+  NativeArray(const Element* array, size_t count, RelationToSourceReference) {
+    InitRef(array, count);
+  }
+
+  // Constructs from a native array. Copies the source.
+  NativeArray(const Element* array, size_t count, RelationToSourceCopy) {
+    InitCopy(array, count);
+  }
+
+  // Copy constructor.
+  NativeArray(const NativeArray& rhs) {
+    (this->*rhs.clone_)(rhs.array_, rhs.size_);
+  }
+
+  ~NativeArray() {
+    if (clone_ != &NativeArray::InitRef)
+      delete[] array_;
+  }
+
+  // STL-style container methods.
+  size_t size() const { return size_; }
+  const_iterator begin() const { return array_; }
+  const_iterator end() const { return array_ + size_; }
+  bool operator==(const NativeArray& rhs) const {
+    return size() == rhs.size() &&
+        ArrayEq(begin(), size(), rhs.begin());
+  }
+
+ private:
+  static_assert(!std::is_const<Element>::value, "Type must not be const");
+  static_assert(!std::is_reference<Element>::value,
+                "Type must not be a reference");
+
+  // Initializes this object with a copy of the input.
+  void InitCopy(const Element* array, size_t a_size) {
+    Element* const copy = new Element[a_size];
+    CopyArray(array, a_size, copy);
+    array_ = copy;
+    size_ = a_size;
+    clone_ = &NativeArray::InitCopy;
+  }
+
+  // Initializes this object with a reference of the input.
+  void InitRef(const Element* array, size_t a_size) {
+    array_ = array;
+    size_ = a_size;
+    clone_ = &NativeArray::InitRef;
+  }
+
+  const Element* array_;
+  size_t size_;
+  void (NativeArray::*clone_)(const Element*, size_t);
+};
+
+// Backport of std::index_sequence.
+template <size_t... Is>
+struct IndexSequence {
+  using type = IndexSequence;
+};
+
+// Double the IndexSequence, and one if plus_one is true.
+template <bool plus_one, typename T, size_t sizeofT>
+struct DoubleSequence;
+template <size_t... I, size_t sizeofT>
+struct DoubleSequence<true, IndexSequence<I...>, sizeofT> {
+  using type = IndexSequence<I..., (sizeofT + I)..., 2 * sizeofT>;
+};
+template <size_t... I, size_t sizeofT>
+struct DoubleSequence<false, IndexSequence<I...>, sizeofT> {
+  using type = IndexSequence<I..., (sizeofT + I)...>;
+};
+
+// Backport of std::make_index_sequence.
+// It uses O(ln(N)) instantiation depth.
+template <size_t N>
+struct MakeIndexSequenceImpl
+    : DoubleSequence<N % 2 == 1, typename MakeIndexSequenceImpl<N / 2>::type,
+                     N / 2>::type {};
+
+template <>
+struct MakeIndexSequenceImpl<0> : IndexSequence<> {};
+
+template <size_t N>
+using MakeIndexSequence = typename MakeIndexSequenceImpl<N>::type;
+
+template <typename... T>
+using IndexSequenceFor = typename MakeIndexSequence<sizeof...(T)>::type;
+
+template <size_t>
+struct Ignore {
+  Ignore(...);  // NOLINT
+};
+
+template <typename>
+struct ElemFromListImpl;
+template <size_t... I>
+struct ElemFromListImpl<IndexSequence<I...>> {
+  // We make Ignore a template to solve a problem with MSVC.
+  // A non-template Ignore would work fine with `decltype(Ignore(I))...`, but
+  // MSVC doesn't understand how to deal with that pack expansion.
+  // Use `0 * I` to have a single instantiation of Ignore.
+  template <typename R>
+  static R Apply(Ignore<0 * I>..., R (*)(), ...);
+};
+
+template <size_t N, typename... T>
+struct ElemFromList {
+  using type =
+      decltype(ElemFromListImpl<typename MakeIndexSequence<N>::type>::Apply(
+          static_cast<T (*)()>(nullptr)...));
+};
+
+struct FlatTupleConstructTag {};
+
+template <typename... T>
+class FlatTuple;
+
+template <typename Derived, size_t I>
+struct FlatTupleElemBase;
+
+template <typename... T, size_t I>
+struct FlatTupleElemBase<FlatTuple<T...>, I> {
+  using value_type = typename ElemFromList<I, T...>::type;
+  FlatTupleElemBase() = default;
+  template <typename Arg>
+  explicit FlatTupleElemBase(FlatTupleConstructTag, Arg&& t)
+      : value(std::forward<Arg>(t)) {}
+  value_type value;
+};
+
+template <typename Derived, typename Idx>
+struct FlatTupleBase;
+
+template <size_t... Idx, typename... T>
+struct FlatTupleBase<FlatTuple<T...>, IndexSequence<Idx...>>
+    : FlatTupleElemBase<FlatTuple<T...>, Idx>... {
+  using Indices = IndexSequence<Idx...>;
+  FlatTupleBase() = default;
+  template <typename... Args>
+  explicit FlatTupleBase(FlatTupleConstructTag, Args&&... args)
+      : FlatTupleElemBase<FlatTuple<T...>, Idx>(FlatTupleConstructTag{},
+                                                std::forward<Args>(args))... {}
+
+  template <size_t I>
+  const typename ElemFromList<I, T...>::type& Get() const {
+    return FlatTupleElemBase<FlatTuple<T...>, I>::value;
+  }
+
+  template <size_t I>
+  typename ElemFromList<I, T...>::type& Get() {
+    return FlatTupleElemBase<FlatTuple<T...>, I>::value;
+  }
+
+  template <typename F>
+  auto Apply(F&& f) -> decltype(std::forward<F>(f)(this->Get<Idx>()...)) {
+    return std::forward<F>(f)(Get<Idx>()...);
+  }
+
+  template <typename F>
+  auto Apply(F&& f) const -> decltype(std::forward<F>(f)(this->Get<Idx>()...)) {
+    return std::forward<F>(f)(Get<Idx>()...);
+  }
+};
+
+// Analog to std::tuple but with different tradeoffs.
+// This class minimizes the template instantiation depth, thus allowing more
+// elements than std::tuple would. std::tuple has been seen to require an
+// instantiation depth of more than 10x the number of elements in some
+// implementations.
+// FlatTuple and ElemFromList are not recursive and have a fixed depth
+// regardless of T...
+// MakeIndexSequence, on the other hand, it is recursive but with an
+// instantiation depth of O(ln(N)).
+template <typename... T>
+class FlatTuple
+    : private FlatTupleBase<FlatTuple<T...>,
+                            typename MakeIndexSequence<sizeof...(T)>::type> {
+  using Indices = typename FlatTupleBase<
+      FlatTuple<T...>, typename MakeIndexSequence<sizeof...(T)>::type>::Indices;
+
+ public:
+  FlatTuple() = default;
+  template <typename... Args>
+  explicit FlatTuple(FlatTupleConstructTag tag, Args&&... args)
+      : FlatTuple::FlatTupleBase(tag, std::forward<Args>(args)...) {}
+
+  using FlatTuple::FlatTupleBase::Apply;
+  using FlatTuple::FlatTupleBase::Get;
+};
+
+// Utility functions to be called with static_assert to induce deprecation
+// warnings.
+GTEST_INTERNAL_DEPRECATED(
+    "INSTANTIATE_TEST_CASE_P is deprecated, please use "
+    "INSTANTIATE_TEST_SUITE_P")
+constexpr bool InstantiateTestCase_P_IsDeprecated() { return true; }
+
+GTEST_INTERNAL_DEPRECATED(
+    "TYPED_TEST_CASE_P is deprecated, please use "
+    "TYPED_TEST_SUITE_P")
+constexpr bool TypedTestCase_P_IsDeprecated() { return true; }
+
+GTEST_INTERNAL_DEPRECATED(
+    "TYPED_TEST_CASE is deprecated, please use "
+    "TYPED_TEST_SUITE")
+constexpr bool TypedTestCaseIsDeprecated() { return true; }
+
+GTEST_INTERNAL_DEPRECATED(
+    "REGISTER_TYPED_TEST_CASE_P is deprecated, please use "
+    "REGISTER_TYPED_TEST_SUITE_P")
+constexpr bool RegisterTypedTestCase_P_IsDeprecated() { return true; }
+
+GTEST_INTERNAL_DEPRECATED(
+    "INSTANTIATE_TYPED_TEST_CASE_P is deprecated, please use "
+    "INSTANTIATE_TYPED_TEST_SUITE_P")
+constexpr bool InstantiateTypedTestCase_P_IsDeprecated() { return true; }
+
+}  // namespace internal
+}  // namespace testing
+
+namespace std {
+// Some standard library implementations use `struct tuple_size` and some use
+// `class tuple_size`. Clang warns about the mismatch.
+// https://reviews.llvm.org/D55466
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wmismatched-tags"
+#endif
+template <typename... Ts>
+struct tuple_size<testing::internal::FlatTuple<Ts...>>
+    : std::integral_constant<size_t, sizeof...(Ts)> {};
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif
+}  // namespace std
+
+#define GTEST_MESSAGE_AT_(file, line, message, result_type) \
+  ::testing::internal::AssertHelper(result_type, file, line, message) \
+    = ::testing::Message()
+
+#define GTEST_MESSAGE_(message, result_type) \
+  GTEST_MESSAGE_AT_(__FILE__, __LINE__, message, result_type)
+
+#define GTEST_FATAL_FAILURE_(message) \
+  return GTEST_MESSAGE_(message, ::testing::TestPartResult::kFatalFailure)
+
+#define GTEST_NONFATAL_FAILURE_(message) \
+  GTEST_MESSAGE_(message, ::testing::TestPartResult::kNonFatalFailure)
+
+#define GTEST_SUCCESS_(message) \
+  GTEST_MESSAGE_(message, ::testing::TestPartResult::kSuccess)
+
+#define GTEST_SKIP_(message) \
+  return GTEST_MESSAGE_(message, ::testing::TestPartResult::kSkip)
+
+// Suppress MSVC warning 4072 (unreachable code) for the code following
+// statement if it returns or throws (or doesn't return or throw in some
+// situations).
+// NOTE: The "else" is important to keep this expansion to prevent a top-level
+// "else" from attaching to our "if".
+#define GTEST_SUPPRESS_UNREACHABLE_CODE_WARNING_BELOW_(statement) \
+  if (::testing::internal::AlwaysTrue()) {                        \
+    statement;                                                    \
+  } else                     /* NOLINT */                         \
+    static_assert(true, "")  // User must have a semicolon after expansion.
+
+#if GTEST_HAS_EXCEPTIONS
+
+namespace testing {
+namespace internal {
+
+class NeverThrown {
+ public:
+  const char* what() const noexcept {
+    return "this exception should never be thrown";
+  }
+};
+
+}  // namespace internal
+}  // namespace testing
+
+#if GTEST_HAS_RTTI
+
+#define GTEST_EXCEPTION_TYPE_(e) ::testing::internal::GetTypeName(typeid(e))
+
+#else  // GTEST_HAS_RTTI
+
+#define GTEST_EXCEPTION_TYPE_(e) \
+  std::string { "an std::exception-derived error" }
+
+#endif  // GTEST_HAS_RTTI
+
+#define GTEST_TEST_THROW_CATCH_STD_EXCEPTION_(statement, expected_exception)   \
+  catch (typename std::conditional<                                            \
+         std::is_same<typename std::remove_cv<typename std::remove_reference<  \
+                          expected_exception>::type>::type,                    \
+                      std::exception>::value,                                  \
+         const ::testing::internal::NeverThrown&, const std::exception&>::type \
+             e) {                                                              \
+    gtest_msg.value = "Expected: " #statement                                  \
+                      " throws an exception of type " #expected_exception      \
+                      ".\n  Actual: it throws ";                               \
+    gtest_msg.value += GTEST_EXCEPTION_TYPE_(e);                               \
+    gtest_msg.value += " with description \"";                                 \
+    gtest_msg.value += e.what();                                               \
+    gtest_msg.value += "\".";                                                  \
+    goto GTEST_CONCAT_TOKEN_(gtest_label_testthrow_, __LINE__);                \
+  }
+
+#else  // GTEST_HAS_EXCEPTIONS
+
+#define GTEST_TEST_THROW_CATCH_STD_EXCEPTION_(statement, expected_exception)
+
+#endif  // GTEST_HAS_EXCEPTIONS
+
+#define GTEST_TEST_THROW_(statement, expected_exception, fail)              \
+  GTEST_AMBIGUOUS_ELSE_BLOCKER_                                             \
+  if (::testing::internal::TrueWithString gtest_msg{}) {                    \
+    bool gtest_caught_expected = false;                                     \
+    try {                                                                   \
+      GTEST_SUPPRESS_UNREACHABLE_CODE_WARNING_BELOW_(statement);            \
+    } catch (expected_exception const&) {                                   \
+      gtest_caught_expected = true;                                         \
+    }                                                                       \
+    GTEST_TEST_THROW_CATCH_STD_EXCEPTION_(statement, expected_exception)    \
+    catch (...) {                                                           \
+      gtest_msg.value = "Expected: " #statement                             \
+                        " throws an exception of type " #expected_exception \
+                        ".\n  Actual: it throws a different type.";         \
+      goto GTEST_CONCAT_TOKEN_(gtest_label_testthrow_, __LINE__);           \
+    }                                                                       \
+    if (!gtest_caught_expected) {                                           \
+      gtest_msg.value = "Expected: " #statement                             \
+                        " throws an exception of type " #expected_exception \
+                        ".\n  Actual: it throws nothing.";                  \
+      goto GTEST_CONCAT_TOKEN_(gtest_label_testthrow_, __LINE__);           \
+    }                                                                       \
+  } else /*NOLINT*/                                                         \
+    GTEST_CONCAT_TOKEN_(gtest_label_testthrow_, __LINE__)                   \
+        : fail(gtest_msg.value.c_str())
+
+#if GTEST_HAS_EXCEPTIONS
+
+#define GTEST_TEST_NO_THROW_CATCH_STD_EXCEPTION_()                \
+  catch (std::exception const& e) {                               \
+    gtest_msg.value = "it throws ";                               \
+    gtest_msg.value += GTEST_EXCEPTION_TYPE_(e);                  \
+    gtest_msg.value += " with description \"";                    \
+    gtest_msg.value += e.what();                                  \
+    gtest_msg.value += "\".";                                     \
+    goto GTEST_CONCAT_TOKEN_(gtest_label_testnothrow_, __LINE__); \
+  }
+
+#else  // GTEST_HAS_EXCEPTIONS
+
+#define GTEST_TEST_NO_THROW_CATCH_STD_EXCEPTION_()
+
+#endif  // GTEST_HAS_EXCEPTIONS
+
+#define GTEST_TEST_NO_THROW_(statement, fail) \
+  GTEST_AMBIGUOUS_ELSE_BLOCKER_ \
+  if (::testing::internal::TrueWithString gtest_msg{}) { \
+    try { \
+      GTEST_SUPPRESS_UNREACHABLE_CODE_WARNING_BELOW_(statement); \
+    } \
+    GTEST_TEST_NO_THROW_CATCH_STD_EXCEPTION_() \
+    catch (...) { \
+      gtest_msg.value = "it throws."; \
+      goto GTEST_CONCAT_TOKEN_(gtest_label_testnothrow_, __LINE__); \
+    } \
+  } else \
+    GTEST_CONCAT_TOKEN_(gtest_label_testnothrow_, __LINE__): \
+      fail(("Expected: " #statement " doesn't throw an exception.\n" \
+            "  Actual: " + gtest_msg.value).c_str())
+
+#define GTEST_TEST_ANY_THROW_(statement, fail) \
+  GTEST_AMBIGUOUS_ELSE_BLOCKER_ \
+  if (::testing::internal::AlwaysTrue()) { \
+    bool gtest_caught_any = false; \
+    try { \
+      GTEST_SUPPRESS_UNREACHABLE_CODE_WARNING_BELOW_(statement); \
+    } \
+    catch (...) { \
+      gtest_caught_any = true; \
+    } \
+    if (!gtest_caught_any) { \
+      goto GTEST_CONCAT_TOKEN_(gtest_label_testanythrow_, __LINE__); \
+    } \
+  } else \
+    GTEST_CONCAT_TOKEN_(gtest_label_testanythrow_, __LINE__): \
+      fail("Expected: " #statement " throws an exception.\n" \
+           "  Actual: it doesn't.")
+
+
+// Implements Boolean test assertions such as EXPECT_TRUE. expression can be
+// either a boolean expression or an AssertionResult. text is a textual
+// representation of expression as it was passed into the EXPECT_TRUE.
+#define GTEST_TEST_BOOLEAN_(expression, text, actual, expected, fail) \
+  GTEST_AMBIGUOUS_ELSE_BLOCKER_ \
+  if (const ::testing::AssertionResult gtest_ar_ = \
+      ::testing::AssertionResult(expression)) \
+    ; \
+  else \
+    fail(::testing::internal::GetBoolAssertionFailureMessage(\
+        gtest_ar_, text, #actual, #expected).c_str())
+
+#define GTEST_TEST_NO_FATAL_FAILURE_(statement, fail) \
+  GTEST_AMBIGUOUS_ELSE_BLOCKER_ \
+  if (::testing::internal::AlwaysTrue()) { \
+    ::testing::internal::HasNewFatalFailureHelper gtest_fatal_failure_checker; \
+    GTEST_SUPPRESS_UNREACHABLE_CODE_WARNING_BELOW_(statement); \
+    if (gtest_fatal_failure_checker.has_new_fatal_failure()) { \
+      goto GTEST_CONCAT_TOKEN_(gtest_label_testnofatal_, __LINE__); \
+    } \
+  } else \
+    GTEST_CONCAT_TOKEN_(gtest_label_testnofatal_, __LINE__): \
+      fail("Expected: " #statement " doesn't generate new fatal " \
+           "failures in the current thread.\n" \
+           "  Actual: it does.")
+
+// Expands to the name of the class that implements the given test.
+#define GTEST_TEST_CLASS_NAME_(test_suite_name, test_name) \
+  test_suite_name##_##test_name##_Test
+
+// Helper macro for defining tests.
+#define GTEST_TEST_(test_suite_name, test_name, parent_class, parent_id)      \
+  static_assert(sizeof(GTEST_STRINGIFY_(test_suite_name)) > 1,                \
+                "test_suite_name must not be empty");                         \
+  static_assert(sizeof(GTEST_STRINGIFY_(test_name)) > 1,                      \
+                "test_name must not be empty");                               \
+  class GTEST_TEST_CLASS_NAME_(test_suite_name, test_name)                    \
+      : public parent_class {                                                 \
+   public:                                                                    \
+    GTEST_TEST_CLASS_NAME_(test_suite_name, test_name)() = default;           \
+    ~GTEST_TEST_CLASS_NAME_(test_suite_name, test_name)() override = default; \
+    GTEST_DISALLOW_COPY_AND_ASSIGN_(GTEST_TEST_CLASS_NAME_(test_suite_name,   \
+                                                           test_name));       \
+    GTEST_DISALLOW_MOVE_AND_ASSIGN_(GTEST_TEST_CLASS_NAME_(test_suite_name,   \
+                                                           test_name));       \
+                                                                              \
+   private:                                                                   \
+    void TestBody() override;                                                 \
+    static ::testing::TestInfo* const test_info_ GTEST_ATTRIBUTE_UNUSED_;     \
+  };                                                                          \
+                                                                              \
+  ::testing::TestInfo* const GTEST_TEST_CLASS_NAME_(test_suite_name,          \
+                                                    test_name)::test_info_ =  \
+      ::testing::internal::MakeAndRegisterTestInfo(                           \
+          #test_suite_name, #test_name, nullptr, nullptr,                     \
+          ::testing::internal::CodeLocation(__FILE__, __LINE__), (parent_id), \
+          ::testing::internal::SuiteApiResolver<                              \
+              parent_class>::GetSetUpCaseOrSuite(__FILE__, __LINE__),         \
+          ::testing::internal::SuiteApiResolver<                              \
+              parent_class>::GetTearDownCaseOrSuite(__FILE__, __LINE__),      \
+          new ::testing::internal::TestFactoryImpl<GTEST_TEST_CLASS_NAME_(    \
+              test_suite_name, test_name)>);                                  \
+  void GTEST_TEST_CLASS_NAME_(test_suite_name, test_name)::TestBody()
+
+#endif  // GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_INTERNAL_H_
diff --git a/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-param-util.h b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-param-util.h
new file mode 100644
index 0000000..3e49a6b
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-param-util.h
@@ -0,0 +1,947 @@
+// Copyright 2008 Google Inc.
+// All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Type and function utilities for implementing parameterized tests.
+
+// GOOGLETEST_CM0001 DO NOT DELETE
+
+#ifndef GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_PARAM_UTIL_H_
+#define GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_PARAM_UTIL_H_
+
+#include <ctype.h>
+
+#include <cassert>
+#include <iterator>
+#include <memory>
+#include <set>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include "gtest/internal/gtest-internal.h"
+#include "gtest/internal/gtest-port.h"
+#include "gtest/gtest-printers.h"
+#include "gtest/gtest-test-part.h"
+
+namespace testing {
+// Input to a parameterized test name generator, describing a test parameter.
+// Consists of the parameter value and the integer parameter index.
+template <class ParamType>
+struct TestParamInfo {
+  TestParamInfo(const ParamType& a_param, size_t an_index) :
+    param(a_param),
+    index(an_index) {}
+  ParamType param;
+  size_t index;
+};
+
+// A builtin parameterized test name generator which returns the result of
+// testing::PrintToString.
+struct PrintToStringParamName {
+  template <class ParamType>
+  std::string operator()(const TestParamInfo<ParamType>& info) const {
+    return PrintToString(info.param);
+  }
+};
+
+namespace internal {
+
+// INTERNAL IMPLEMENTATION - DO NOT USE IN USER CODE.
+// Utility Functions
+
+// Outputs a message explaining invalid registration of different
+// fixture class for the same test suite. This may happen when
+// TEST_P macro is used to define two tests with the same name
+// but in different namespaces.
+GTEST_API_ void ReportInvalidTestSuiteType(const char* test_suite_name,
+                                           CodeLocation code_location);
+
+template <typename> class ParamGeneratorInterface;
+template <typename> class ParamGenerator;
+
+// Interface for iterating over elements provided by an implementation
+// of ParamGeneratorInterface<T>.
+template <typename T>
+class ParamIteratorInterface {
+ public:
+  virtual ~ParamIteratorInterface() {}
+  // A pointer to the base generator instance.
+  // Used only for the purposes of iterator comparison
+  // to make sure that two iterators belong to the same generator.
+  virtual const ParamGeneratorInterface<T>* BaseGenerator() const = 0;
+  // Advances iterator to point to the next element
+  // provided by the generator. The caller is responsible
+  // for not calling Advance() on an iterator equal to
+  // BaseGenerator()->End().
+  virtual void Advance() = 0;
+  // Clones the iterator object. Used for implementing copy semantics
+  // of ParamIterator<T>.
+  virtual ParamIteratorInterface* Clone() const = 0;
+  // Dereferences the current iterator and provides (read-only) access
+  // to the pointed value. It is the caller's responsibility not to call
+  // Current() on an iterator equal to BaseGenerator()->End().
+  // Used for implementing ParamGenerator<T>::operator*().
+  virtual const T* Current() const = 0;
+  // Determines whether the given iterator and other point to the same
+  // element in the sequence generated by the generator.
+  // Used for implementing ParamGenerator<T>::operator==().
+  virtual bool Equals(const ParamIteratorInterface& other) const = 0;
+};
+
+// Class iterating over elements provided by an implementation of
+// ParamGeneratorInterface<T>. It wraps ParamIteratorInterface<T>
+// and implements the const forward iterator concept.
+template <typename T>
+class ParamIterator {
+ public:
+  typedef T value_type;
+  typedef const T& reference;
+  typedef ptrdiff_t difference_type;
+
+  // ParamIterator assumes ownership of the impl_ pointer.
+  ParamIterator(const ParamIterator& other) : impl_(other.impl_->Clone()) {}
+  ParamIterator& operator=(const ParamIterator& other) {
+    if (this != &other)
+      impl_.reset(other.impl_->Clone());
+    return *this;
+  }
+
+  const T& operator*() const { return *impl_->Current(); }
+  const T* operator->() const { return impl_->Current(); }
+  // Prefix version of operator++.
+  ParamIterator& operator++() {
+    impl_->Advance();
+    return *this;
+  }
+  // Postfix version of operator++.
+  ParamIterator operator++(int /*unused*/) {
+    ParamIteratorInterface<T>* clone = impl_->Clone();
+    impl_->Advance();
+    return ParamIterator(clone);
+  }
+  bool operator==(const ParamIterator& other) const {
+    return impl_.get() == other.impl_.get() || impl_->Equals(*other.impl_);
+  }
+  bool operator!=(const ParamIterator& other) const {
+    return !(*this == other);
+  }
+
+ private:
+  friend class ParamGenerator<T>;
+  explicit ParamIterator(ParamIteratorInterface<T>* impl) : impl_(impl) {}
+  std::unique_ptr<ParamIteratorInterface<T> > impl_;
+};
+
+// ParamGeneratorInterface<T> is the binary interface to access generators
+// defined in other translation units.
+template <typename T>
+class ParamGeneratorInterface {
+ public:
+  typedef T ParamType;
+
+  virtual ~ParamGeneratorInterface() {}
+
+  // Generator interface definition
+  virtual ParamIteratorInterface<T>* Begin() const = 0;
+  virtual ParamIteratorInterface<T>* End() const = 0;
+};
+
+// Wraps ParamGeneratorInterface<T> and provides general generator syntax
+// compatible with the STL Container concept.
+// This class implements copy initialization semantics and the contained
+// ParamGeneratorInterface<T> instance is shared among all copies
+// of the original object. This is possible because that instance is immutable.
+template<typename T>
+class ParamGenerator {
+ public:
+  typedef ParamIterator<T> iterator;
+
+  explicit ParamGenerator(ParamGeneratorInterface<T>* impl) : impl_(impl) {}
+  ParamGenerator(const ParamGenerator& other) : impl_(other.impl_) {}
+
+  ParamGenerator& operator=(const ParamGenerator& other) {
+    impl_ = other.impl_;
+    return *this;
+  }
+
+  iterator begin() const { return iterator(impl_->Begin()); }
+  iterator end() const { return iterator(impl_->End()); }
+
+ private:
+  std::shared_ptr<const ParamGeneratorInterface<T> > impl_;
+};
+
+// Generates values from a range of two comparable values. Can be used to
+// generate sequences of user-defined types that implement operator+() and
+// operator<().
+// This class is used in the Range() function.
+template <typename T, typename IncrementT>
+class RangeGenerator : public ParamGeneratorInterface<T> {
+ public:
+  RangeGenerator(T begin, T end, IncrementT step)
+      : begin_(begin), end_(end),
+        step_(step), end_index_(CalculateEndIndex(begin, end, step)) {}
+  ~RangeGenerator() override {}
+
+  ParamIteratorInterface<T>* Begin() const override {
+    return new Iterator(this, begin_, 0, step_);
+  }
+  ParamIteratorInterface<T>* End() const override {
+    return new Iterator(this, end_, end_index_, step_);
+  }
+
+ private:
+  class Iterator : public ParamIteratorInterface<T> {
+   public:
+    Iterator(const ParamGeneratorInterface<T>* base, T value, int index,
+             IncrementT step)
+        : base_(base), value_(value), index_(index), step_(step) {}
+    ~Iterator() override {}
+
+    const ParamGeneratorInterface<T>* BaseGenerator() const override {
+      return base_;
+    }
+    void Advance() override {
+      value_ = static_cast<T>(value_ + step_);
+      index_++;
+    }
+    ParamIteratorInterface<T>* Clone() const override {
+      return new Iterator(*this);
+    }
+    const T* Current() const override { return &value_; }
+    bool Equals(const ParamIteratorInterface<T>& other) const override {
+      // Having the same base generator guarantees that the other
+      // iterator is of the same type and we can downcast.
+      GTEST_CHECK_(BaseGenerator() == other.BaseGenerator())
+          << "The program attempted to compare iterators "
+          << "from different generators." << std::endl;
+      const int other_index =
+          CheckedDowncastToActualType<const Iterator>(&other)->index_;
+      return index_ == other_index;
+    }
+
+   private:
+    Iterator(const Iterator& other)
+        : ParamIteratorInterface<T>(),
+          base_(other.base_), value_(other.value_), index_(other.index_),
+          step_(other.step_) {}
+
+    // No implementation - assignment is unsupported.
+    void operator=(const Iterator& other);
+
+    const ParamGeneratorInterface<T>* const base_;
+    T value_;
+    int index_;
+    const IncrementT step_;
+  };  // class RangeGenerator::Iterator
+
+  static int CalculateEndIndex(const T& begin,
+                               const T& end,
+                               const IncrementT& step) {
+    int end_index = 0;
+    for (T i = begin; i < end; i = static_cast<T>(i + step))
+      end_index++;
+    return end_index;
+  }
+
+  // No implementation - assignment is unsupported.
+  void operator=(const RangeGenerator& other);
+
+  const T begin_;
+  const T end_;
+  const IncrementT step_;
+  // The index for the end() iterator. All the elements in the generated
+  // sequence are indexed (0-based) to aid iterator comparison.
+  const int end_index_;
+};  // class RangeGenerator
+
+
+// Generates values from a pair of STL-style iterators. Used in the
+// ValuesIn() function. The elements are copied from the source range
+// since the source can be located on the stack, and the generator
+// is likely to persist beyond that stack frame.
+template <typename T>
+class ValuesInIteratorRangeGenerator : public ParamGeneratorInterface<T> {
+ public:
+  template <typename ForwardIterator>
+  ValuesInIteratorRangeGenerator(ForwardIterator begin, ForwardIterator end)
+      : container_(begin, end) {}
+  ~ValuesInIteratorRangeGenerator() override {}
+
+  ParamIteratorInterface<T>* Begin() const override {
+    return new Iterator(this, container_.begin());
+  }
+  ParamIteratorInterface<T>* End() const override {
+    return new Iterator(this, container_.end());
+  }
+
+ private:
+  typedef typename ::std::vector<T> ContainerType;
+
+  class Iterator : public ParamIteratorInterface<T> {
+   public:
+    Iterator(const ParamGeneratorInterface<T>* base,
+             typename ContainerType::const_iterator iterator)
+        : base_(base), iterator_(iterator) {}
+    ~Iterator() override {}
+
+    const ParamGeneratorInterface<T>* BaseGenerator() const override {
+      return base_;
+    }
+    void Advance() override {
+      ++iterator_;
+      value_.reset();
+    }
+    ParamIteratorInterface<T>* Clone() const override {
+      return new Iterator(*this);
+    }
+    // We need to use cached value referenced by iterator_ because *iterator_
+    // can return a temporary object (and of type other then T), so just
+    // having "return &*iterator_;" doesn't work.
+    // value_ is updated here and not in Advance() because Advance()
+    // can advance iterator_ beyond the end of the range, and we cannot
+    // detect that fact. The client code, on the other hand, is
+    // responsible for not calling Current() on an out-of-range iterator.
+    const T* Current() const override {
+      if (value_.get() == nullptr) value_.reset(new T(*iterator_));
+      return value_.get();
+    }
+    bool Equals(const ParamIteratorInterface<T>& other) const override {
+      // Having the same base generator guarantees that the other
+      // iterator is of the same type and we can downcast.
+      GTEST_CHECK_(BaseGenerator() == other.BaseGenerator())
+          << "The program attempted to compare iterators "
+          << "from different generators." << std::endl;
+      return iterator_ ==
+          CheckedDowncastToActualType<const Iterator>(&other)->iterator_;
+    }
+
+   private:
+    Iterator(const Iterator& other)
+          // The explicit constructor call suppresses a false warning
+          // emitted by gcc when supplied with the -Wextra option.
+        : ParamIteratorInterface<T>(),
+          base_(other.base_),
+          iterator_(other.iterator_) {}
+
+    const ParamGeneratorInterface<T>* const base_;
+    typename ContainerType::const_iterator iterator_;
+    // A cached value of *iterator_. We keep it here to allow access by
+    // pointer in the wrapping iterator's operator->().
+    // value_ needs to be mutable to be accessed in Current().
+    // Use of std::unique_ptr helps manage cached value's lifetime,
+    // which is bound by the lifespan of the iterator itself.
+    mutable std::unique_ptr<const T> value_;
+  };  // class ValuesInIteratorRangeGenerator::Iterator
+
+  // No implementation - assignment is unsupported.
+  void operator=(const ValuesInIteratorRangeGenerator& other);
+
+  const ContainerType container_;
+};  // class ValuesInIteratorRangeGenerator
+
+// INTERNAL IMPLEMENTATION - DO NOT USE IN USER CODE.
+//
+// Default parameterized test name generator, returns a string containing the
+// integer test parameter index.
+template <class ParamType>
+std::string DefaultParamName(const TestParamInfo<ParamType>& info) {
+  Message name_stream;
+  name_stream << info.index;
+  return name_stream.GetString();
+}
+
+template <typename T = int>
+void TestNotEmpty() {
+  static_assert(sizeof(T) == 0, "Empty arguments are not allowed.");
+}
+template <typename T = int>
+void TestNotEmpty(const T&) {}
+
+// INTERNAL IMPLEMENTATION - DO NOT USE IN USER CODE.
+//
+// Stores a parameter value and later creates tests parameterized with that
+// value.
+template <class TestClass>
+class ParameterizedTestFactory : public TestFactoryBase {
+ public:
+  typedef typename TestClass::ParamType ParamType;
+  explicit ParameterizedTestFactory(ParamType parameter) :
+      parameter_(parameter) {}
+  Test* CreateTest() override {
+    TestClass::SetParam(&parameter_);
+    return new TestClass();
+  }
+
+ private:
+  const ParamType parameter_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(ParameterizedTestFactory);
+};
+
+// INTERNAL IMPLEMENTATION - DO NOT USE IN USER CODE.
+//
+// TestMetaFactoryBase is a base class for meta-factories that create
+// test factories for passing into MakeAndRegisterTestInfo function.
+template <class ParamType>
+class TestMetaFactoryBase {
+ public:
+  virtual ~TestMetaFactoryBase() {}
+
+  virtual TestFactoryBase* CreateTestFactory(ParamType parameter) = 0;
+};
+
+// INTERNAL IMPLEMENTATION - DO NOT USE IN USER CODE.
+//
+// TestMetaFactory creates test factories for passing into
+// MakeAndRegisterTestInfo function. Since MakeAndRegisterTestInfo receives
+// ownership of test factory pointer, same factory object cannot be passed
+// into that method twice. But ParameterizedTestSuiteInfo is going to call
+// it for each Test/Parameter value combination. Thus it needs meta factory
+// creator class.
+template <class TestSuite>
+class TestMetaFactory
+    : public TestMetaFactoryBase<typename TestSuite::ParamType> {
+ public:
+  using ParamType = typename TestSuite::ParamType;
+
+  TestMetaFactory() {}
+
+  TestFactoryBase* CreateTestFactory(ParamType parameter) override {
+    return new ParameterizedTestFactory<TestSuite>(parameter);
+  }
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(TestMetaFactory);
+};
+
+// INTERNAL IMPLEMENTATION - DO NOT USE IN USER CODE.
+//
+// ParameterizedTestSuiteInfoBase is a generic interface
+// to ParameterizedTestSuiteInfo classes. ParameterizedTestSuiteInfoBase
+// accumulates test information provided by TEST_P macro invocations
+// and generators provided by INSTANTIATE_TEST_SUITE_P macro invocations
+// and uses that information to register all resulting test instances
+// in RegisterTests method. The ParameterizeTestSuiteRegistry class holds
+// a collection of pointers to the ParameterizedTestSuiteInfo objects
+// and calls RegisterTests() on each of them when asked.
+class ParameterizedTestSuiteInfoBase {
+ public:
+  virtual ~ParameterizedTestSuiteInfoBase() {}
+
+  // Base part of test suite name for display purposes.
+  virtual const std::string& GetTestSuiteName() const = 0;
+  // Test suite id to verify identity.
+  virtual TypeId GetTestSuiteTypeId() const = 0;
+  // UnitTest class invokes this method to register tests in this
+  // test suite right before running them in RUN_ALL_TESTS macro.
+  // This method should not be called more than once on any single
+  // instance of a ParameterizedTestSuiteInfoBase derived class.
+  virtual void RegisterTests() = 0;
+
+ protected:
+  ParameterizedTestSuiteInfoBase() {}
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(ParameterizedTestSuiteInfoBase);
+};
+
+// INTERNAL IMPLEMENTATION - DO NOT USE IN USER CODE.
+//
+// Report a the name of a test_suit as safe to ignore
+// as the side effect of construction of this type.
+struct MarkAsIgnored {
+  explicit MarkAsIgnored(const char* test_suite);
+};
+
+GTEST_API_ void InsertSyntheticTestCase(const std::string& name,
+                                        CodeLocation location, bool has_test_p);
+
+// INTERNAL IMPLEMENTATION - DO NOT USE IN USER CODE.
+//
+// ParameterizedTestSuiteInfo accumulates tests obtained from TEST_P
+// macro invocations for a particular test suite and generators
+// obtained from INSTANTIATE_TEST_SUITE_P macro invocations for that
+// test suite. It registers tests with all values generated by all
+// generators when asked.
+template <class TestSuite>
+class ParameterizedTestSuiteInfo : public ParameterizedTestSuiteInfoBase {
+ public:
+  // ParamType and GeneratorCreationFunc are private types but are required
+  // for declarations of public methods AddTestPattern() and
+  // AddTestSuiteInstantiation().
+  using ParamType = typename TestSuite::ParamType;
+  // A function that returns an instance of appropriate generator type.
+  typedef ParamGenerator<ParamType>(GeneratorCreationFunc)();
+  using ParamNameGeneratorFunc = std::string(const TestParamInfo<ParamType>&);
+
+  explicit ParameterizedTestSuiteInfo(const char* name,
+                                      CodeLocation code_location)
+      : test_suite_name_(name), code_location_(code_location) {}
+
+  // Test suite base name for display purposes.
+  const std::string& GetTestSuiteName() const override {
+    return test_suite_name_;
+  }
+  // Test suite id to verify identity.
+  TypeId GetTestSuiteTypeId() const override { return GetTypeId<TestSuite>(); }
+  // TEST_P macro uses AddTestPattern() to record information
+  // about a single test in a LocalTestInfo structure.
+  // test_suite_name is the base name of the test suite (without invocation
+  // prefix). test_base_name is the name of an individual test without
+  // parameter index. For the test SequenceA/FooTest.DoBar/1 FooTest is
+  // test suite base name and DoBar is test base name.
+  void AddTestPattern(const char* test_suite_name, const char* test_base_name,
+                      TestMetaFactoryBase<ParamType>* meta_factory,
+                      CodeLocation code_location) {
+    tests_.push_back(std::shared_ptr<TestInfo>(new TestInfo(
+        test_suite_name, test_base_name, meta_factory, code_location)));
+  }
+  // INSTANTIATE_TEST_SUITE_P macro uses AddGenerator() to record information
+  // about a generator.
+  int AddTestSuiteInstantiation(const std::string& instantiation_name,
+                                GeneratorCreationFunc* func,
+                                ParamNameGeneratorFunc* name_func,
+                                const char* file, int line) {
+    instantiations_.push_back(
+        InstantiationInfo(instantiation_name, func, name_func, file, line));
+    return 0;  // Return value used only to run this method in namespace scope.
+  }
+  // UnitTest class invokes this method to register tests in this test suite
+  // right before running tests in RUN_ALL_TESTS macro.
+  // This method should not be called more than once on any single
+  // instance of a ParameterizedTestSuiteInfoBase derived class.
+  // UnitTest has a guard to prevent from calling this method more than once.
+  void RegisterTests() override {
+    bool generated_instantiations = false;
+
+    for (typename TestInfoContainer::iterator test_it = tests_.begin();
+         test_it != tests_.end(); ++test_it) {
+      std::shared_ptr<TestInfo> test_info = *test_it;
+      for (typename InstantiationContainer::iterator gen_it =
+               instantiations_.begin(); gen_it != instantiations_.end();
+               ++gen_it) {
+        const std::string& instantiation_name = gen_it->name;
+        ParamGenerator<ParamType> generator((*gen_it->generator)());
+        ParamNameGeneratorFunc* name_func = gen_it->name_func;
+        const char* file = gen_it->file;
+        int line = gen_it->line;
+
+        std::string test_suite_name;
+        if ( !instantiation_name.empty() )
+          test_suite_name = instantiation_name + "/";
+        test_suite_name += test_info->test_suite_base_name;
+
+        size_t i = 0;
+        std::set<std::string> test_param_names;
+        for (typename ParamGenerator<ParamType>::iterator param_it =
+                 generator.begin();
+             param_it != generator.end(); ++param_it, ++i) {
+          generated_instantiations = true;
+
+          Message test_name_stream;
+
+          std::string param_name = name_func(
+              TestParamInfo<ParamType>(*param_it, i));
+
+          GTEST_CHECK_(IsValidParamName(param_name))
+              << "Parameterized test name '" << param_name
+              << "' is invalid, in " << file
+              << " line " << line << std::endl;
+
+          GTEST_CHECK_(test_param_names.count(param_name) == 0)
+              << "Duplicate parameterized test name '" << param_name
+              << "', in " << file << " line " << line << std::endl;
+
+          test_param_names.insert(param_name);
+
+          if (!test_info->test_base_name.empty()) {
+            test_name_stream << test_info->test_base_name << "/";
+          }
+          test_name_stream << param_name;
+          MakeAndRegisterTestInfo(
+              test_suite_name.c_str(), test_name_stream.GetString().c_str(),
+              nullptr,  // No type parameter.
+              PrintToString(*param_it).c_str(), test_info->code_location,
+              GetTestSuiteTypeId(),
+              SuiteApiResolver<TestSuite>::GetSetUpCaseOrSuite(file, line),
+              SuiteApiResolver<TestSuite>::GetTearDownCaseOrSuite(file, line),
+              test_info->test_meta_factory->CreateTestFactory(*param_it));
+        }  // for param_it
+      }  // for gen_it
+    }  // for test_it
+
+    if (!generated_instantiations) {
+      // There are no generaotrs, or they all generate nothing ...
+      InsertSyntheticTestCase(GetTestSuiteName(), code_location_,
+                              !tests_.empty());
+    }
+  }    // RegisterTests
+
+ private:
+  // LocalTestInfo structure keeps information about a single test registered
+  // with TEST_P macro.
+  struct TestInfo {
+    TestInfo(const char* a_test_suite_base_name, const char* a_test_base_name,
+             TestMetaFactoryBase<ParamType>* a_test_meta_factory,
+             CodeLocation a_code_location)
+        : test_suite_base_name(a_test_suite_base_name),
+          test_base_name(a_test_base_name),
+          test_meta_factory(a_test_meta_factory),
+          code_location(a_code_location) {}
+
+    const std::string test_suite_base_name;
+    const std::string test_base_name;
+    const std::unique_ptr<TestMetaFactoryBase<ParamType> > test_meta_factory;
+    const CodeLocation code_location;
+  };
+  using TestInfoContainer = ::std::vector<std::shared_ptr<TestInfo> >;
+  // Records data received from INSTANTIATE_TEST_SUITE_P macros:
+  //  <Instantiation name, Sequence generator creation function,
+  //     Name generator function, Source file, Source line>
+  struct InstantiationInfo {
+      InstantiationInfo(const std::string &name_in,
+                        GeneratorCreationFunc* generator_in,
+                        ParamNameGeneratorFunc* name_func_in,
+                        const char* file_in,
+                        int line_in)
+          : name(name_in),
+            generator(generator_in),
+            name_func(name_func_in),
+            file(file_in),
+            line(line_in) {}
+
+      std::string name;
+      GeneratorCreationFunc* generator;
+      ParamNameGeneratorFunc* name_func;
+      const char* file;
+      int line;
+  };
+  typedef ::std::vector<InstantiationInfo> InstantiationContainer;
+
+  static bool IsValidParamName(const std::string& name) {
+    // Check for empty string
+    if (name.empty())
+      return false;
+
+    // Check for invalid characters
+    for (std::string::size_type index = 0; index < name.size(); ++index) {
+      if (!isalnum(name[index]) && name[index] != '_')
+        return false;
+    }
+
+    return true;
+  }
+
+  const std::string test_suite_name_;
+  CodeLocation code_location_;
+  TestInfoContainer tests_;
+  InstantiationContainer instantiations_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(ParameterizedTestSuiteInfo);
+};  // class ParameterizedTestSuiteInfo
+
+//  Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+template <class TestCase>
+using ParameterizedTestCaseInfo = ParameterizedTestSuiteInfo<TestCase>;
+#endif  //  GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+// INTERNAL IMPLEMENTATION - DO NOT USE IN USER CODE.
+//
+// ParameterizedTestSuiteRegistry contains a map of
+// ParameterizedTestSuiteInfoBase classes accessed by test suite names. TEST_P
+// and INSTANTIATE_TEST_SUITE_P macros use it to locate their corresponding
+// ParameterizedTestSuiteInfo descriptors.
+class ParameterizedTestSuiteRegistry {
+ public:
+  ParameterizedTestSuiteRegistry() {}
+  ~ParameterizedTestSuiteRegistry() {
+    for (auto& test_suite_info : test_suite_infos_) {
+      delete test_suite_info;
+    }
+  }
+
+  // Looks up or creates and returns a structure containing information about
+  // tests and instantiations of a particular test suite.
+  template <class TestSuite>
+  ParameterizedTestSuiteInfo<TestSuite>* GetTestSuitePatternHolder(
+      const char* test_suite_name, CodeLocation code_location) {
+    ParameterizedTestSuiteInfo<TestSuite>* typed_test_info = nullptr;
+    for (auto& test_suite_info : test_suite_infos_) {
+      if (test_suite_info->GetTestSuiteName() == test_suite_name) {
+        if (test_suite_info->GetTestSuiteTypeId() != GetTypeId<TestSuite>()) {
+          // Complain about incorrect usage of Google Test facilities
+          // and terminate the program since we cannot guaranty correct
+          // test suite setup and tear-down in this case.
+          ReportInvalidTestSuiteType(test_suite_name, code_location);
+          posix::Abort();
+        } else {
+          // At this point we are sure that the object we found is of the same
+          // type we are looking for, so we downcast it to that type
+          // without further checks.
+          typed_test_info = CheckedDowncastToActualType<
+              ParameterizedTestSuiteInfo<TestSuite> >(test_suite_info);
+        }
+        break;
+      }
+    }
+    if (typed_test_info == nullptr) {
+      typed_test_info = new ParameterizedTestSuiteInfo<TestSuite>(
+          test_suite_name, code_location);
+      test_suite_infos_.push_back(typed_test_info);
+    }
+    return typed_test_info;
+  }
+  void RegisterTests() {
+    for (auto& test_suite_info : test_suite_infos_) {
+      test_suite_info->RegisterTests();
+    }
+  }
+//  Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  template <class TestCase>
+  ParameterizedTestCaseInfo<TestCase>* GetTestCasePatternHolder(
+      const char* test_case_name, CodeLocation code_location) {
+    return GetTestSuitePatternHolder<TestCase>(test_case_name, code_location);
+  }
+
+#endif  //  GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+ private:
+  using TestSuiteInfoContainer = ::std::vector<ParameterizedTestSuiteInfoBase*>;
+
+  TestSuiteInfoContainer test_suite_infos_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(ParameterizedTestSuiteRegistry);
+};
+
+// Keep track of what type-parameterized test suite are defined and
+// where as well as which are intatiated. This allows susequently
+// identifying suits that are defined but never used.
+class TypeParameterizedTestSuiteRegistry {
+ public:
+  // Add a suite definition
+  void RegisterTestSuite(const char* test_suite_name,
+                         CodeLocation code_location);
+
+  // Add an instantiation of a suit.
+  void RegisterInstantiation(const char* test_suite_name);
+
+  // For each suit repored as defined but not reported as instantiation,
+  // emit a test that reports that fact (configurably, as an error).
+  void CheckForInstantiations();
+
+ private:
+  struct TypeParameterizedTestSuiteInfo {
+    explicit TypeParameterizedTestSuiteInfo(CodeLocation c)
+        : code_location(c), instantiated(false) {}
+
+    CodeLocation code_location;
+    bool instantiated;
+  };
+
+  std::map<std::string, TypeParameterizedTestSuiteInfo> suites_;
+};
+
+}  // namespace internal
+
+// Forward declarations of ValuesIn(), which is implemented in
+// include/gtest/gtest-param-test.h.
+template <class Container>
+internal::ParamGenerator<typename Container::value_type> ValuesIn(
+    const Container& container);
+
+namespace internal {
+// Used in the Values() function to provide polymorphic capabilities.
+
+#ifdef _MSC_VER
+#pragma warning(push)
+#pragma warning(disable : 4100)
+#endif
+
+template <typename... Ts>
+class ValueArray {
+ public:
+  explicit ValueArray(Ts... v) : v_(FlatTupleConstructTag{}, std::move(v)...) {}
+
+  template <typename T>
+  operator ParamGenerator<T>() const {  // NOLINT
+    return ValuesIn(MakeVector<T>(MakeIndexSequence<sizeof...(Ts)>()));
+  }
+
+ private:
+  template <typename T, size_t... I>
+  std::vector<T> MakeVector(IndexSequence<I...>) const {
+    return std::vector<T>{static_cast<T>(v_.template Get<I>())...};
+  }
+
+  FlatTuple<Ts...> v_;
+};
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+
+template <typename... T>
+class CartesianProductGenerator
+    : public ParamGeneratorInterface<::std::tuple<T...>> {
+ public:
+  typedef ::std::tuple<T...> ParamType;
+
+  CartesianProductGenerator(const std::tuple<ParamGenerator<T>...>& g)
+      : generators_(g) {}
+  ~CartesianProductGenerator() override {}
+
+  ParamIteratorInterface<ParamType>* Begin() const override {
+    return new Iterator(this, generators_, false);
+  }
+  ParamIteratorInterface<ParamType>* End() const override {
+    return new Iterator(this, generators_, true);
+  }
+
+ private:
+  template <class I>
+  class IteratorImpl;
+  template <size_t... I>
+  class IteratorImpl<IndexSequence<I...>>
+      : public ParamIteratorInterface<ParamType> {
+   public:
+    IteratorImpl(const ParamGeneratorInterface<ParamType>* base,
+             const std::tuple<ParamGenerator<T>...>& generators, bool is_end)
+        : base_(base),
+          begin_(std::get<I>(generators).begin()...),
+          end_(std::get<I>(generators).end()...),
+          current_(is_end ? end_ : begin_) {
+      ComputeCurrentValue();
+    }
+    ~IteratorImpl() override {}
+
+    const ParamGeneratorInterface<ParamType>* BaseGenerator() const override {
+      return base_;
+    }
+    // Advance should not be called on beyond-of-range iterators
+    // so no component iterators must be beyond end of range, either.
+    void Advance() override {
+      assert(!AtEnd());
+      // Advance the last iterator.
+      ++std::get<sizeof...(T) - 1>(current_);
+      // if that reaches end, propagate that up.
+      AdvanceIfEnd<sizeof...(T) - 1>();
+      ComputeCurrentValue();
+    }
+    ParamIteratorInterface<ParamType>* Clone() const override {
+      return new IteratorImpl(*this);
+    }
+
+    const ParamType* Current() const override { return current_value_.get(); }
+
+    bool Equals(const ParamIteratorInterface<ParamType>& other) const override {
+      // Having the same base generator guarantees that the other
+      // iterator is of the same type and we can downcast.
+      GTEST_CHECK_(BaseGenerator() == other.BaseGenerator())
+          << "The program attempted to compare iterators "
+          << "from different generators." << std::endl;
+      const IteratorImpl* typed_other =
+          CheckedDowncastToActualType<const IteratorImpl>(&other);
+
+      // We must report iterators equal if they both point beyond their
+      // respective ranges. That can happen in a variety of fashions,
+      // so we have to consult AtEnd().
+      if (AtEnd() && typed_other->AtEnd()) return true;
+
+      bool same = true;
+      bool dummy[] = {
+          (same = same && std::get<I>(current_) ==
+                              std::get<I>(typed_other->current_))...};
+      (void)dummy;
+      return same;
+    }
+
+   private:
+    template <size_t ThisI>
+    void AdvanceIfEnd() {
+      if (std::get<ThisI>(current_) != std::get<ThisI>(end_)) return;
+
+      bool last = ThisI == 0;
+      if (last) {
+        // We are done. Nothing else to propagate.
+        return;
+      }
+
+      constexpr size_t NextI = ThisI - (ThisI != 0);
+      std::get<ThisI>(current_) = std::get<ThisI>(begin_);
+      ++std::get<NextI>(current_);
+      AdvanceIfEnd<NextI>();
+    }
+
+    void ComputeCurrentValue() {
+      if (!AtEnd())
+        current_value_ = std::make_shared<ParamType>(*std::get<I>(current_)...);
+    }
+    bool AtEnd() const {
+      bool at_end = false;
+      bool dummy[] = {
+          (at_end = at_end || std::get<I>(current_) == std::get<I>(end_))...};
+      (void)dummy;
+      return at_end;
+    }
+
+    const ParamGeneratorInterface<ParamType>* const base_;
+    std::tuple<typename ParamGenerator<T>::iterator...> begin_;
+    std::tuple<typename ParamGenerator<T>::iterator...> end_;
+    std::tuple<typename ParamGenerator<T>::iterator...> current_;
+    std::shared_ptr<ParamType> current_value_;
+  };
+
+  using Iterator = IteratorImpl<typename MakeIndexSequence<sizeof...(T)>::type>;
+
+  std::tuple<ParamGenerator<T>...> generators_;
+};
+
+template <class... Gen>
+class CartesianProductHolder {
+ public:
+  CartesianProductHolder(const Gen&... g) : generators_(g...) {}
+  template <typename... T>
+  operator ParamGenerator<::std::tuple<T...>>() const {
+    return ParamGenerator<::std::tuple<T...>>(
+        new CartesianProductGenerator<T...>(generators_));
+  }
+
+ private:
+  std::tuple<Gen...> generators_;
+};
+
+}  // namespace internal
+}  // namespace testing
+
+#endif  // GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_PARAM_UTIL_H_
diff --git a/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-port-arch.h b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-port-arch.h
new file mode 100644
index 0000000..dd84591
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-port-arch.h
@@ -0,0 +1,114 @@
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// The Google C++ Testing and Mocking Framework (Google Test)
+//
+// This header file defines the GTEST_OS_* macro.
+// It is separate from gtest-port.h so that custom/gtest-port.h can include it.
+
+#ifndef GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_PORT_ARCH_H_
+#define GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_PORT_ARCH_H_
+
+// Determines the platform on which Google Test is compiled.
+#ifdef __CYGWIN__
+# define GTEST_OS_CYGWIN 1
+# elif defined(__MINGW__) || defined(__MINGW32__) || defined(__MINGW64__)
+#  define GTEST_OS_WINDOWS_MINGW 1
+#  define GTEST_OS_WINDOWS 1
+#elif defined _WIN32
+# define GTEST_OS_WINDOWS 1
+# ifdef _WIN32_WCE
+#  define GTEST_OS_WINDOWS_MOBILE 1
+# elif defined(WINAPI_FAMILY)
+#  include <winapifamily.h>
+#  if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
+#   define GTEST_OS_WINDOWS_DESKTOP 1
+#  elif WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_PHONE_APP)
+#   define GTEST_OS_WINDOWS_PHONE 1
+#  elif WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_APP)
+#   define GTEST_OS_WINDOWS_RT 1
+#  elif WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_TV_TITLE)
+#   define GTEST_OS_WINDOWS_PHONE 1
+#   define GTEST_OS_WINDOWS_TV_TITLE 1
+#  else
+    // WINAPI_FAMILY defined but no known partition matched.
+    // Default to desktop.
+#   define GTEST_OS_WINDOWS_DESKTOP 1
+#  endif
+# else
+#  define GTEST_OS_WINDOWS_DESKTOP 1
+# endif  // _WIN32_WCE
+#elif defined __OS2__
+# define GTEST_OS_OS2 1
+#elif defined __APPLE__
+# define GTEST_OS_MAC 1
+# include <TargetConditionals.h>
+# if TARGET_OS_IPHONE
+#  define GTEST_OS_IOS 1
+# endif
+#elif defined __DragonFly__
+# define GTEST_OS_DRAGONFLY 1
+#elif defined __FreeBSD__
+# define GTEST_OS_FREEBSD 1
+#elif defined __Fuchsia__
+# define GTEST_OS_FUCHSIA 1
+#elif defined(__GLIBC__) && defined(__FreeBSD_kernel__)
+# define GTEST_OS_GNU_KFREEBSD 1
+#elif defined __linux__
+# define GTEST_OS_LINUX 1
+# if defined __ANDROID__
+#  define GTEST_OS_LINUX_ANDROID 1
+# endif
+#elif defined __MVS__
+# define GTEST_OS_ZOS 1
+#elif defined(__sun) && defined(__SVR4)
+# define GTEST_OS_SOLARIS 1
+#elif defined(_AIX)
+# define GTEST_OS_AIX 1
+#elif defined(__hpux)
+# define GTEST_OS_HPUX 1
+#elif defined __native_client__
+# define GTEST_OS_NACL 1
+#elif defined __NetBSD__
+# define GTEST_OS_NETBSD 1
+#elif defined __OpenBSD__
+# define GTEST_OS_OPENBSD 1
+#elif defined __QNX__
+# define GTEST_OS_QNX 1
+#elif defined(__HAIKU__)
+#define GTEST_OS_HAIKU 1
+#elif defined ESP8266
+#define GTEST_OS_ESP8266 1
+#elif defined ESP32
+#define GTEST_OS_ESP32 1
+#elif defined(__XTENSA__)
+#define GTEST_OS_XTENSA 1
+#endif  // __CYGWIN__
+
+#endif  // GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_PORT_ARCH_H_
diff --git a/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-port.h b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-port.h
new file mode 100644
index 0000000..0953a78
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-port.h
@@ -0,0 +1,2389 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// Low-level types and utilities for porting Google Test to various
+// platforms.  All macros ending with _ and symbols defined in an
+// internal namespace are subject to change without notice.  Code
+// outside Google Test MUST NOT USE THEM DIRECTLY.  Macros that don't
+// end with _ are part of Google Test's public API and can be used by
+// code outside Google Test.
+//
+// This file is fundamental to Google Test.  All other Google Test source
+// files are expected to #include this.  Therefore, it cannot #include
+// any other Google Test header.
+
+// GOOGLETEST_CM0001 DO NOT DELETE
+
+#ifndef GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_PORT_H_
+#define GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_PORT_H_
+
+// Environment-describing macros
+// -----------------------------
+//
+// Google Test can be used in many different environments.  Macros in
+// this section tell Google Test what kind of environment it is being
+// used in, such that Google Test can provide environment-specific
+// features and implementations.
+//
+// Google Test tries to automatically detect the properties of its
+// environment, so users usually don't need to worry about these
+// macros.  However, the automatic detection is not perfect.
+// Sometimes it's necessary for a user to define some of the following
+// macros in the build script to override Google Test's decisions.
+//
+// If the user doesn't define a macro in the list, Google Test will
+// provide a default definition.  After this header is #included, all
+// macros in this list will be defined to either 1 or 0.
+//
+// Notes to maintainers:
+//   - Each macro here is a user-tweakable knob; do not grow the list
+//     lightly.
+//   - Use #if to key off these macros.  Don't use #ifdef or "#if
+//     defined(...)", which will not work as these macros are ALWAYS
+//     defined.
+//
+//   GTEST_HAS_CLONE          - Define it to 1/0 to indicate that clone(2)
+//                              is/isn't available.
+//   GTEST_HAS_EXCEPTIONS     - Define it to 1/0 to indicate that exceptions
+//                              are enabled.
+//   GTEST_HAS_POSIX_RE       - Define it to 1/0 to indicate that POSIX regular
+//                              expressions are/aren't available.
+//   GTEST_HAS_PTHREAD        - Define it to 1/0 to indicate that <pthread.h>
+//                              is/isn't available.
+//   GTEST_HAS_RTTI           - Define it to 1/0 to indicate that RTTI is/isn't
+//                              enabled.
+//   GTEST_HAS_STD_WSTRING    - Define it to 1/0 to indicate that
+//                              std::wstring does/doesn't work (Google Test can
+//                              be used where std::wstring is unavailable).
+//   GTEST_HAS_SEH            - Define it to 1/0 to indicate whether the
+//                              compiler supports Microsoft's "Structured
+//                              Exception Handling".
+//   GTEST_HAS_STREAM_REDIRECTION
+//                            - Define it to 1/0 to indicate whether the
+//                              platform supports I/O stream redirection using
+//                              dup() and dup2().
+//   GTEST_LINKED_AS_SHARED_LIBRARY
+//                            - Define to 1 when compiling tests that use
+//                              Google Test as a shared library (known as
+//                              DLL on Windows).
+//   GTEST_CREATE_SHARED_LIBRARY
+//                            - Define to 1 when compiling Google Test itself
+//                              as a shared library.
+//   GTEST_DEFAULT_DEATH_TEST_STYLE
+//                            - The default value of --gtest_death_test_style.
+//                              The legacy default has been "fast" in the open
+//                              source version since 2008. The recommended value
+//                              is "threadsafe", and can be set in
+//                              custom/gtest-port.h.
+
+// Platform-indicating macros
+// --------------------------
+//
+// Macros indicating the platform on which Google Test is being used
+// (a macro is defined to 1 if compiled on the given platform;
+// otherwise UNDEFINED -- it's never defined to 0.).  Google Test
+// defines these macros automatically.  Code outside Google Test MUST
+// NOT define them.
+//
+//   GTEST_OS_AIX      - IBM AIX
+//   GTEST_OS_CYGWIN   - Cygwin
+//   GTEST_OS_DRAGONFLY - DragonFlyBSD
+//   GTEST_OS_FREEBSD  - FreeBSD
+//   GTEST_OS_FUCHSIA  - Fuchsia
+//   GTEST_OS_GNU_KFREEBSD - GNU/kFreeBSD
+//   GTEST_OS_HAIKU    - Haiku
+//   GTEST_OS_HPUX     - HP-UX
+//   GTEST_OS_LINUX    - Linux
+//     GTEST_OS_LINUX_ANDROID - Google Android
+//   GTEST_OS_MAC      - Mac OS X
+//     GTEST_OS_IOS    - iOS
+//   GTEST_OS_NACL     - Google Native Client (NaCl)
+//   GTEST_OS_NETBSD   - NetBSD
+//   GTEST_OS_OPENBSD  - OpenBSD
+//   GTEST_OS_OS2      - OS/2
+//   GTEST_OS_QNX      - QNX
+//   GTEST_OS_SOLARIS  - Sun Solaris
+//   GTEST_OS_WINDOWS  - Windows (Desktop, MinGW, or Mobile)
+//     GTEST_OS_WINDOWS_DESKTOP  - Windows Desktop
+//     GTEST_OS_WINDOWS_MINGW    - MinGW
+//     GTEST_OS_WINDOWS_MOBILE   - Windows Mobile
+//     GTEST_OS_WINDOWS_PHONE    - Windows Phone
+//     GTEST_OS_WINDOWS_RT       - Windows Store App/WinRT
+//   GTEST_OS_ZOS      - z/OS
+//
+// Among the platforms, Cygwin, Linux, Mac OS X, and Windows have the
+// most stable support.  Since core members of the Google Test project
+// don't have access to other platforms, support for them may be less
+// stable.  If you notice any problems on your platform, please notify
+// googletestframework@googlegroups.com (patches for fixing them are
+// even more welcome!).
+//
+// It is possible that none of the GTEST_OS_* macros are defined.
+
+// Feature-indicating macros
+// -------------------------
+//
+// Macros indicating which Google Test features are available (a macro
+// is defined to 1 if the corresponding feature is supported;
+// otherwise UNDEFINED -- it's never defined to 0.).  Google Test
+// defines these macros automatically.  Code outside Google Test MUST
+// NOT define them.
+//
+// These macros are public so that portable tests can be written.
+// Such tests typically surround code using a feature with an #if
+// which controls that code.  For example:
+//
+// #if GTEST_HAS_DEATH_TEST
+//   EXPECT_DEATH(DoSomethingDeadly());
+// #endif
+//
+//   GTEST_HAS_DEATH_TEST   - death tests
+//   GTEST_HAS_TYPED_TEST   - typed tests
+//   GTEST_HAS_TYPED_TEST_P - type-parameterized tests
+//   GTEST_IS_THREADSAFE    - Google Test is thread-safe.
+//   GOOGLETEST_CM0007 DO NOT DELETE
+//   GTEST_USES_POSIX_RE    - enhanced POSIX regex is used. Do not confuse with
+//                            GTEST_HAS_POSIX_RE (see above) which users can
+//                            define themselves.
+//   GTEST_USES_SIMPLE_RE   - our own simple regex is used;
+//                            the above RE\b(s) are mutually exclusive.
+
+// Misc public macros
+// ------------------
+//
+//   GTEST_FLAG(flag_name)  - references the variable corresponding to
+//                            the given Google Test flag.
+
+// Internal utilities
+// ------------------
+//
+// The following macros and utilities are for Google Test's INTERNAL
+// use only.  Code outside Google Test MUST NOT USE THEM DIRECTLY.
+//
+// Macros for basic C++ coding:
+//   GTEST_AMBIGUOUS_ELSE_BLOCKER_ - for disabling a gcc warning.
+//   GTEST_ATTRIBUTE_UNUSED_  - declares that a class' instances or a
+//                              variable don't have to be used.
+//   GTEST_DISALLOW_ASSIGN_   - disables copy operator=.
+//   GTEST_DISALLOW_COPY_AND_ASSIGN_ - disables copy ctor and operator=.
+//   GTEST_DISALLOW_MOVE_ASSIGN_   - disables move operator=.
+//   GTEST_DISALLOW_MOVE_AND_ASSIGN_ - disables move ctor and operator=.
+//   GTEST_MUST_USE_RESULT_   - declares that a function's result must be used.
+//   GTEST_INTENTIONAL_CONST_COND_PUSH_ - start code section where MSVC C4127 is
+//                                        suppressed (constant conditional).
+//   GTEST_INTENTIONAL_CONST_COND_POP_  - finish code section where MSVC C4127
+//                                        is suppressed.
+//   GTEST_INTERNAL_HAS_ANY - for enabling UniversalPrinter<std::any> or
+//                            UniversalPrinter<absl::any> specializations.
+//   GTEST_INTERNAL_HAS_OPTIONAL - for enabling UniversalPrinter<std::optional>
+//   or
+//                                 UniversalPrinter<absl::optional>
+//                                 specializations.
+//   GTEST_INTERNAL_HAS_STRING_VIEW - for enabling Matcher<std::string_view> or
+//                                    Matcher<absl::string_view>
+//                                    specializations.
+//   GTEST_INTERNAL_HAS_VARIANT - for enabling UniversalPrinter<std::variant> or
+//                                UniversalPrinter<absl::variant>
+//                                specializations.
+//
+// Synchronization:
+//   Mutex, MutexLock, ThreadLocal, GetThreadCount()
+//                            - synchronization primitives.
+//
+// Regular expressions:
+//   RE             - a simple regular expression class using the POSIX
+//                    Extended Regular Expression syntax on UNIX-like platforms
+//                    GOOGLETEST_CM0008 DO NOT DELETE
+//                    or a reduced regular exception syntax on other
+//                    platforms, including Windows.
+// Logging:
+//   GTEST_LOG_()   - logs messages at the specified severity level.
+//   LogToStderr()  - directs all log messages to stderr.
+//   FlushInfoLog() - flushes informational log messages.
+//
+// Stdout and stderr capturing:
+//   CaptureStdout()     - starts capturing stdout.
+//   GetCapturedStdout() - stops capturing stdout and returns the captured
+//                         string.
+//   CaptureStderr()     - starts capturing stderr.
+//   GetCapturedStderr() - stops capturing stderr and returns the captured
+//                         string.
+//
+// Integer types:
+//   TypeWithSize   - maps an integer to a int type.
+//   TimeInMillis   - integers of known sizes.
+//   BiggestInt     - the biggest signed integer type.
+//
+// Command-line utilities:
+//   GTEST_DECLARE_*()  - declares a flag.
+//   GTEST_DEFINE_*()   - defines a flag.
+//   GetInjectableArgvs() - returns the command line as a vector of strings.
+//
+// Environment variable utilities:
+//   GetEnv()             - gets the value of an environment variable.
+//   BoolFromGTestEnv()   - parses a bool environment variable.
+//   Int32FromGTestEnv()  - parses an int32_t environment variable.
+//   StringFromGTestEnv() - parses a string environment variable.
+//
+// Deprecation warnings:
+//   GTEST_INTERNAL_DEPRECATED(message) - attribute marking a function as
+//                                        deprecated; calling a marked function
+//                                        should generate a compiler warning
+
+#include <ctype.h>   // for isspace, etc
+#include <stddef.h>  // for ptrdiff_t
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <cerrno>
+#include <cstdint>
+#include <limits>
+#include <type_traits>
+
+#ifndef _WIN32_WCE
+# include <sys/types.h>
+# include <sys/stat.h>
+#endif  // !_WIN32_WCE
+
+#if defined __APPLE__
+# include <AvailabilityMacros.h>
+# include <TargetConditionals.h>
+#endif
+
+#include <iostream>  // NOLINT
+#include <locale>
+#include <memory>
+#include <string>  // NOLINT
+#include <tuple>
+#include <vector>  // NOLINT
+
+#include "gtest/internal/custom/gtest-port.h"
+#include "gtest/internal/gtest-port-arch.h"
+
+#if !defined(GTEST_DEV_EMAIL_)
+# define GTEST_DEV_EMAIL_ "googletestframework@@googlegroups.com"
+# define GTEST_FLAG_PREFIX_ "gtest_"
+# define GTEST_FLAG_PREFIX_DASH_ "gtest-"
+# define GTEST_FLAG_PREFIX_UPPER_ "GTEST_"
+# define GTEST_NAME_ "Google Test"
+# define GTEST_PROJECT_URL_ "https://github.com/google/googletest/"
+#endif  // !defined(GTEST_DEV_EMAIL_)
+
+#if !defined(GTEST_INIT_GOOGLE_TEST_NAME_)
+# define GTEST_INIT_GOOGLE_TEST_NAME_ "testing::InitGoogleTest"
+#endif  // !defined(GTEST_INIT_GOOGLE_TEST_NAME_)
+
+// Determines the version of gcc that is used to compile this.
+#ifdef __GNUC__
+// 40302 means version 4.3.2.
+# define GTEST_GCC_VER_ \
+    (__GNUC__*10000 + __GNUC_MINOR__*100 + __GNUC_PATCHLEVEL__)
+#endif  // __GNUC__
+
+// Macros for disabling Microsoft Visual C++ warnings.
+//
+//   GTEST_DISABLE_MSC_WARNINGS_PUSH_(4800 4385)
+//   /* code that triggers warnings C4800 and C4385 */
+//   GTEST_DISABLE_MSC_WARNINGS_POP_()
+#if defined(_MSC_VER)
+# define GTEST_DISABLE_MSC_WARNINGS_PUSH_(warnings) \
+    __pragma(warning(push))                        \
+    __pragma(warning(disable: warnings))
+# define GTEST_DISABLE_MSC_WARNINGS_POP_()          \
+    __pragma(warning(pop))
+#else
+// Not all compilers are MSVC
+# define GTEST_DISABLE_MSC_WARNINGS_PUSH_(warnings)
+# define GTEST_DISABLE_MSC_WARNINGS_POP_()
+#endif
+
+// Clang on Windows does not understand MSVC's pragma warning.
+// We need clang-specific way to disable function deprecation warning.
+#ifdef __clang__
+# define GTEST_DISABLE_MSC_DEPRECATED_PUSH_()                         \
+    _Pragma("clang diagnostic push")                                  \
+    _Pragma("clang diagnostic ignored \"-Wdeprecated-declarations\"") \
+    _Pragma("clang diagnostic ignored \"-Wdeprecated-implementations\"")
+#define GTEST_DISABLE_MSC_DEPRECATED_POP_() \
+    _Pragma("clang diagnostic pop")
+#else
+# define GTEST_DISABLE_MSC_DEPRECATED_PUSH_() \
+    GTEST_DISABLE_MSC_WARNINGS_PUSH_(4996)
+# define GTEST_DISABLE_MSC_DEPRECATED_POP_() \
+    GTEST_DISABLE_MSC_WARNINGS_POP_()
+#endif
+
+// Brings in definitions for functions used in the testing::internal::posix
+// namespace (read, write, close, chdir, isatty, stat). We do not currently
+// use them on Windows Mobile.
+#if GTEST_OS_WINDOWS
+# if !GTEST_OS_WINDOWS_MOBILE
+#  include <direct.h>
+#  include <io.h>
+# endif
+// In order to avoid having to include <windows.h>, use forward declaration
+#if GTEST_OS_WINDOWS_MINGW && !defined(__MINGW64_VERSION_MAJOR)
+// MinGW defined _CRITICAL_SECTION and _RTL_CRITICAL_SECTION as two
+// separate (equivalent) structs, instead of using typedef
+typedef struct _CRITICAL_SECTION GTEST_CRITICAL_SECTION;
+#else
+// Assume CRITICAL_SECTION is a typedef of _RTL_CRITICAL_SECTION.
+// This assumption is verified by
+// WindowsTypesTest.CRITICAL_SECTIONIs_RTL_CRITICAL_SECTION.
+typedef struct _RTL_CRITICAL_SECTION GTEST_CRITICAL_SECTION;
+#endif
+#elif GTEST_OS_XTENSA
+#include <unistd.h>
+// Xtensa toolchains define strcasecmp in the string.h header instead of
+// strings.h. string.h is already included.
+#else
+// This assumes that non-Windows OSes provide unistd.h. For OSes where this
+// is not the case, we need to include headers that provide the functions
+// mentioned above.
+# include <unistd.h>
+# include <strings.h>
+#endif  // GTEST_OS_WINDOWS
+
+#if GTEST_OS_LINUX_ANDROID
+// Used to define __ANDROID_API__ matching the target NDK API level.
+#  include <android/api-level.h>  // NOLINT
+#endif
+
+// Defines this to true if and only if Google Test can use POSIX regular
+// expressions.
+#ifndef GTEST_HAS_POSIX_RE
+# if GTEST_OS_LINUX_ANDROID
+// On Android, <regex.h> is only available starting with Gingerbread.
+#  define GTEST_HAS_POSIX_RE (__ANDROID_API__ >= 9)
+# else
+#define GTEST_HAS_POSIX_RE (!GTEST_OS_WINDOWS && !GTEST_OS_XTENSA)
+# endif
+#endif
+
+#if GTEST_USES_PCRE
+// The appropriate headers have already been included.
+
+#elif GTEST_HAS_POSIX_RE
+
+// On some platforms, <regex.h> needs someone to define size_t, and
+// won't compile otherwise.  We can #include it here as we already
+// included <stdlib.h>, which is guaranteed to define size_t through
+// <stddef.h>.
+# include <regex.h>  // NOLINT
+
+# define GTEST_USES_POSIX_RE 1
+
+#elif GTEST_OS_WINDOWS
+
+// <regex.h> is not available on Windows.  Use our own simple regex
+// implementation instead.
+# define GTEST_USES_SIMPLE_RE 1
+
+#else
+
+// <regex.h> may not be available on this platform.  Use our own
+// simple regex implementation instead.
+# define GTEST_USES_SIMPLE_RE 1
+
+#endif  // GTEST_USES_PCRE
+
+#ifndef GTEST_HAS_EXCEPTIONS
+// The user didn't tell us whether exceptions are enabled, so we need
+// to figure it out.
+# if defined(_MSC_VER) && defined(_CPPUNWIND)
+// MSVC defines _CPPUNWIND to 1 if and only if exceptions are enabled.
+#  define GTEST_HAS_EXCEPTIONS 1
+# elif defined(__BORLANDC__)
+// C++Builder's implementation of the STL uses the _HAS_EXCEPTIONS
+// macro to enable exceptions, so we'll do the same.
+// Assumes that exceptions are enabled by default.
+#  ifndef _HAS_EXCEPTIONS
+#   define _HAS_EXCEPTIONS 1
+#  endif  // _HAS_EXCEPTIONS
+#  define GTEST_HAS_EXCEPTIONS _HAS_EXCEPTIONS
+# elif defined(__clang__)
+// clang defines __EXCEPTIONS if and only if exceptions are enabled before clang
+// 220714, but if and only if cleanups are enabled after that. In Obj-C++ files,
+// there can be cleanups for ObjC exceptions which also need cleanups, even if
+// C++ exceptions are disabled. clang has __has_feature(cxx_exceptions) which
+// checks for C++ exceptions starting at clang r206352, but which checked for
+// cleanups prior to that. To reliably check for C++ exception availability with
+// clang, check for
+// __EXCEPTIONS && __has_feature(cxx_exceptions).
+#  define GTEST_HAS_EXCEPTIONS (__EXCEPTIONS && __has_feature(cxx_exceptions))
+# elif defined(__GNUC__) && __EXCEPTIONS
+// gcc defines __EXCEPTIONS to 1 if and only if exceptions are enabled.
+#  define GTEST_HAS_EXCEPTIONS 1
+# elif defined(__SUNPRO_CC)
+// Sun Pro CC supports exceptions.  However, there is no compile-time way of
+// detecting whether they are enabled or not.  Therefore, we assume that
+// they are enabled unless the user tells us otherwise.
+#  define GTEST_HAS_EXCEPTIONS 1
+# elif defined(__IBMCPP__) && __EXCEPTIONS
+// xlC defines __EXCEPTIONS to 1 if and only if exceptions are enabled.
+#  define GTEST_HAS_EXCEPTIONS 1
+# elif defined(__HP_aCC)
+// Exception handling is in effect by default in HP aCC compiler. It has to
+// be turned of by +noeh compiler option if desired.
+#  define GTEST_HAS_EXCEPTIONS 1
+# else
+// For other compilers, we assume exceptions are disabled to be
+// conservative.
+#  define GTEST_HAS_EXCEPTIONS 0
+# endif  // defined(_MSC_VER) || defined(__BORLANDC__)
+#endif  // GTEST_HAS_EXCEPTIONS
+
+#ifndef GTEST_HAS_STD_WSTRING
+// The user didn't tell us whether ::std::wstring is available, so we need
+// to figure it out.
+// Cygwin 1.7 and below doesn't support ::std::wstring.
+// Solaris' libc++ doesn't support it either.  Android has
+// no support for it at least as recent as Froyo (2.2).
+#define GTEST_HAS_STD_WSTRING                                         \
+  (!(GTEST_OS_LINUX_ANDROID || GTEST_OS_CYGWIN || GTEST_OS_SOLARIS || \
+     GTEST_OS_HAIKU || GTEST_OS_ESP32 || GTEST_OS_ESP8266 || GTEST_OS_XTENSA))
+
+#endif  // GTEST_HAS_STD_WSTRING
+
+// Determines whether RTTI is available.
+#ifndef GTEST_HAS_RTTI
+// The user didn't tell us whether RTTI is enabled, so we need to
+// figure it out.
+
+# ifdef _MSC_VER
+
+#ifdef _CPPRTTI  // MSVC defines this macro if and only if RTTI is enabled.
+#   define GTEST_HAS_RTTI 1
+#  else
+#   define GTEST_HAS_RTTI 0
+#  endif
+
+// Starting with version 4.3.2, gcc defines __GXX_RTTI if and only if RTTI is
+// enabled.
+# elif defined(__GNUC__)
+
+#  ifdef __GXX_RTTI
+// When building against STLport with the Android NDK and with
+// -frtti -fno-exceptions, the build fails at link time with undefined
+// references to __cxa_bad_typeid. Note sure if STL or toolchain bug,
+// so disable RTTI when detected.
+#   if GTEST_OS_LINUX_ANDROID && defined(_STLPORT_MAJOR) && \
+       !defined(__EXCEPTIONS)
+#    define GTEST_HAS_RTTI 0
+#   else
+#    define GTEST_HAS_RTTI 1
+#   endif  // GTEST_OS_LINUX_ANDROID && __STLPORT_MAJOR && !__EXCEPTIONS
+#  else
+#   define GTEST_HAS_RTTI 0
+#  endif  // __GXX_RTTI
+
+// Clang defines __GXX_RTTI starting with version 3.0, but its manual recommends
+// using has_feature instead. has_feature(cxx_rtti) is supported since 2.7, the
+// first version with C++ support.
+# elif defined(__clang__)
+
+#  define GTEST_HAS_RTTI __has_feature(cxx_rtti)
+
+// Starting with version 9.0 IBM Visual Age defines __RTTI_ALL__ to 1 if
+// both the typeid and dynamic_cast features are present.
+# elif defined(__IBMCPP__) && (__IBMCPP__ >= 900)
+
+#  ifdef __RTTI_ALL__
+#   define GTEST_HAS_RTTI 1
+#  else
+#   define GTEST_HAS_RTTI 0
+#  endif
+
+# else
+
+// For all other compilers, we assume RTTI is enabled.
+#  define GTEST_HAS_RTTI 1
+
+# endif  // _MSC_VER
+
+#endif  // GTEST_HAS_RTTI
+
+// It's this header's responsibility to #include <typeinfo> when RTTI
+// is enabled.
+#if GTEST_HAS_RTTI
+# include <typeinfo>
+#endif
+
+// Determines whether Google Test can use the pthreads library.
+#ifndef GTEST_HAS_PTHREAD
+// The user didn't tell us explicitly, so we make reasonable assumptions about
+// which platforms have pthreads support.
+//
+// To disable threading support in Google Test, add -DGTEST_HAS_PTHREAD=0
+// to your compiler flags.
+#define GTEST_HAS_PTHREAD                                                      \
+  (GTEST_OS_LINUX || GTEST_OS_MAC || GTEST_OS_HPUX || GTEST_OS_QNX ||          \
+   GTEST_OS_FREEBSD || GTEST_OS_NACL || GTEST_OS_NETBSD || GTEST_OS_FUCHSIA || \
+   GTEST_OS_DRAGONFLY || GTEST_OS_GNU_KFREEBSD || GTEST_OS_OPENBSD ||          \
+   GTEST_OS_HAIKU)
+#endif  // GTEST_HAS_PTHREAD
+
+#if GTEST_HAS_PTHREAD
+// gtest-port.h guarantees to #include <pthread.h> when GTEST_HAS_PTHREAD is
+// true.
+# include <pthread.h>  // NOLINT
+
+// For timespec and nanosleep, used below.
+# include <time.h>  // NOLINT
+#endif
+
+// Determines whether clone(2) is supported.
+// Usually it will only be available on Linux, excluding
+// Linux on the Itanium architecture.
+// Also see http://linux.die.net/man/2/clone.
+#ifndef GTEST_HAS_CLONE
+// The user didn't tell us, so we need to figure it out.
+
+# if GTEST_OS_LINUX && !defined(__ia64__)
+#  if GTEST_OS_LINUX_ANDROID
+// On Android, clone() became available at different API levels for each 32-bit
+// architecture.
+#    if defined(__LP64__) || \
+        (defined(__arm__) && __ANDROID_API__ >= 9) || \
+        (defined(__mips__) && __ANDROID_API__ >= 12) || \
+        (defined(__i386__) && __ANDROID_API__ >= 17)
+#     define GTEST_HAS_CLONE 1
+#    else
+#     define GTEST_HAS_CLONE 0
+#    endif
+#  else
+#   define GTEST_HAS_CLONE 1
+#  endif
+# else
+#  define GTEST_HAS_CLONE 0
+# endif  // GTEST_OS_LINUX && !defined(__ia64__)
+
+#endif  // GTEST_HAS_CLONE
+
+// Determines whether to support stream redirection. This is used to test
+// output correctness and to implement death tests.
+#ifndef GTEST_HAS_STREAM_REDIRECTION
+// By default, we assume that stream redirection is supported on all
+// platforms except known mobile ones.
+#if GTEST_OS_WINDOWS_MOBILE || GTEST_OS_WINDOWS_PHONE || \
+    GTEST_OS_WINDOWS_RT || GTEST_OS_ESP8266 || GTEST_OS_XTENSA
+#  define GTEST_HAS_STREAM_REDIRECTION 0
+# else
+#  define GTEST_HAS_STREAM_REDIRECTION 1
+# endif  // !GTEST_OS_WINDOWS_MOBILE
+#endif  // GTEST_HAS_STREAM_REDIRECTION
+
+// Determines whether to support death tests.
+// pops up a dialog window that cannot be suppressed programmatically.
+#if (GTEST_OS_LINUX || GTEST_OS_CYGWIN || GTEST_OS_SOLARIS ||             \
+     (GTEST_OS_MAC && !GTEST_OS_IOS) ||                                   \
+     (GTEST_OS_WINDOWS_DESKTOP && _MSC_VER) || GTEST_OS_WINDOWS_MINGW ||  \
+     GTEST_OS_AIX || GTEST_OS_HPUX || GTEST_OS_OPENBSD || GTEST_OS_QNX || \
+     GTEST_OS_FREEBSD || GTEST_OS_NETBSD || GTEST_OS_FUCHSIA ||           \
+     GTEST_OS_DRAGONFLY || GTEST_OS_GNU_KFREEBSD || GTEST_OS_HAIKU)
+# define GTEST_HAS_DEATH_TEST 1
+#endif
+
+// Determines whether to support type-driven tests.
+
+// Typed tests need <typeinfo> and variadic macros, which GCC, VC++ 8.0,
+// Sun Pro CC, IBM Visual Age, and HP aCC support.
+#if defined(__GNUC__) || defined(_MSC_VER) || defined(__SUNPRO_CC) || \
+    defined(__IBMCPP__) || defined(__HP_aCC)
+# define GTEST_HAS_TYPED_TEST 1
+# define GTEST_HAS_TYPED_TEST_P 1
+#endif
+
+// Determines whether the system compiler uses UTF-16 for encoding wide strings.
+#define GTEST_WIDE_STRING_USES_UTF16_ \
+  (GTEST_OS_WINDOWS || GTEST_OS_CYGWIN || GTEST_OS_AIX || GTEST_OS_OS2)
+
+// Determines whether test results can be streamed to a socket.
+#if GTEST_OS_LINUX || GTEST_OS_GNU_KFREEBSD || GTEST_OS_DRAGONFLY || \
+    GTEST_OS_FREEBSD || GTEST_OS_NETBSD || GTEST_OS_OPENBSD
+# define GTEST_CAN_STREAM_RESULTS_ 1
+#endif
+
+// Defines some utility macros.
+
+// The GNU compiler emits a warning if nested "if" statements are followed by
+// an "else" statement and braces are not used to explicitly disambiguate the
+// "else" binding.  This leads to problems with code like:
+//
+//   if (gate)
+//     ASSERT_*(condition) << "Some message";
+//
+// The "switch (0) case 0:" idiom is used to suppress this.
+#ifdef __INTEL_COMPILER
+# define GTEST_AMBIGUOUS_ELSE_BLOCKER_
+#else
+# define GTEST_AMBIGUOUS_ELSE_BLOCKER_ switch (0) case 0: default:  // NOLINT
+#endif
+
+// Use this annotation at the end of a struct/class definition to
+// prevent the compiler from optimizing away instances that are never
+// used.  This is useful when all interesting logic happens inside the
+// c'tor and / or d'tor.  Example:
+//
+//   struct Foo {
+//     Foo() { ... }
+//   } GTEST_ATTRIBUTE_UNUSED_;
+//
+// Also use it after a variable or parameter declaration to tell the
+// compiler the variable/parameter does not have to be used.
+#if defined(__GNUC__) && !defined(COMPILER_ICC)
+# define GTEST_ATTRIBUTE_UNUSED_ __attribute__ ((unused))
+#elif defined(__clang__)
+# if __has_attribute(unused)
+#  define GTEST_ATTRIBUTE_UNUSED_ __attribute__ ((unused))
+# endif
+#endif
+#ifndef GTEST_ATTRIBUTE_UNUSED_
+# define GTEST_ATTRIBUTE_UNUSED_
+#endif
+
+// Use this annotation before a function that takes a printf format string.
+#if (defined(__GNUC__) || defined(__clang__)) && !defined(COMPILER_ICC)
+# if defined(__MINGW_PRINTF_FORMAT)
+// MinGW has two different printf implementations. Ensure the format macro
+// matches the selected implementation. See
+// https://sourceforge.net/p/mingw-w64/wiki2/gnu%20printf/.
+#  define GTEST_ATTRIBUTE_PRINTF_(string_index, first_to_check) \
+       __attribute__((__format__(__MINGW_PRINTF_FORMAT, string_index, \
+                                 first_to_check)))
+# else
+#  define GTEST_ATTRIBUTE_PRINTF_(string_index, first_to_check) \
+       __attribute__((__format__(__printf__, string_index, first_to_check)))
+# endif
+#else
+# define GTEST_ATTRIBUTE_PRINTF_(string_index, first_to_check)
+#endif
+
+
+// A macro to disallow copy operator=
+// This should be used in the private: declarations for a class.
+#define GTEST_DISALLOW_ASSIGN_(type) \
+  type& operator=(type const &) = delete
+
+// A macro to disallow copy constructor and operator=
+// This should be used in the private: declarations for a class.
+#define GTEST_DISALLOW_COPY_AND_ASSIGN_(type) \
+  type(type const&) = delete;                 \
+  type& operator=(type const&) = delete
+
+// A macro to disallow move operator=
+// This should be used in the private: declarations for a class.
+#define GTEST_DISALLOW_MOVE_ASSIGN_(type) \
+  type& operator=(type &&) noexcept = delete
+
+// A macro to disallow move constructor and operator=
+// This should be used in the private: declarations for a class.
+#define GTEST_DISALLOW_MOVE_AND_ASSIGN_(type) \
+  type(type&&) noexcept = delete;             \
+  type& operator=(type&&) noexcept = delete
+
+// Tell the compiler to warn about unused return values for functions declared
+// with this macro.  The macro should be used on function declarations
+// following the argument list:
+//
+//   Sprocket* AllocateSprocket() GTEST_MUST_USE_RESULT_;
+#if defined(__GNUC__) && !defined(COMPILER_ICC)
+# define GTEST_MUST_USE_RESULT_ __attribute__ ((warn_unused_result))
+#else
+# define GTEST_MUST_USE_RESULT_
+#endif  // __GNUC__ && !COMPILER_ICC
+
+// MS C++ compiler emits warning when a conditional expression is compile time
+// constant. In some contexts this warning is false positive and needs to be
+// suppressed. Use the following two macros in such cases:
+//
+// GTEST_INTENTIONAL_CONST_COND_PUSH_()
+// while (true) {
+// GTEST_INTENTIONAL_CONST_COND_POP_()
+// }
+# define GTEST_INTENTIONAL_CONST_COND_PUSH_() \
+    GTEST_DISABLE_MSC_WARNINGS_PUSH_(4127)
+# define GTEST_INTENTIONAL_CONST_COND_POP_() \
+    GTEST_DISABLE_MSC_WARNINGS_POP_()
+
+// Determine whether the compiler supports Microsoft's Structured Exception
+// Handling.  This is supported by several Windows compilers but generally
+// does not exist on any other system.
+#ifndef GTEST_HAS_SEH
+// The user didn't tell us, so we need to figure it out.
+
+# if defined(_MSC_VER) || defined(__BORLANDC__)
+// These two compilers are known to support SEH.
+#  define GTEST_HAS_SEH 1
+# else
+// Assume no SEH.
+#  define GTEST_HAS_SEH 0
+# endif
+
+#endif  // GTEST_HAS_SEH
+
+#ifndef GTEST_IS_THREADSAFE
+
+#define GTEST_IS_THREADSAFE                                                 \
+  (GTEST_HAS_MUTEX_AND_THREAD_LOCAL_ ||                                     \
+   (GTEST_OS_WINDOWS && !GTEST_OS_WINDOWS_PHONE && !GTEST_OS_WINDOWS_RT) || \
+   GTEST_HAS_PTHREAD)
+
+#endif  // GTEST_IS_THREADSAFE
+
+// GTEST_API_ qualifies all symbols that must be exported. The definitions below
+// are guarded by #ifndef to give embedders a chance to define GTEST_API_ in
+// gtest/internal/custom/gtest-port.h
+#ifndef GTEST_API_
+
+#ifdef _MSC_VER
+# if GTEST_LINKED_AS_SHARED_LIBRARY
+#  define GTEST_API_ __declspec(dllimport)
+# elif GTEST_CREATE_SHARED_LIBRARY
+#  define GTEST_API_ __declspec(dllexport)
+# endif
+#elif __GNUC__ >= 4 || defined(__clang__)
+# define GTEST_API_ __attribute__((visibility ("default")))
+#endif  // _MSC_VER
+
+#endif  // GTEST_API_
+
+#ifndef GTEST_API_
+# define GTEST_API_
+#endif  // GTEST_API_
+
+#ifndef GTEST_DEFAULT_DEATH_TEST_STYLE
+# define GTEST_DEFAULT_DEATH_TEST_STYLE  "fast"
+#endif  // GTEST_DEFAULT_DEATH_TEST_STYLE
+
+#ifdef __GNUC__
+// Ask the compiler to never inline a given function.
+# define GTEST_NO_INLINE_ __attribute__((noinline))
+#else
+# define GTEST_NO_INLINE_
+#endif
+
+// _LIBCPP_VERSION is defined by the libc++ library from the LLVM project.
+#if !defined(GTEST_HAS_CXXABI_H_)
+# if defined(__GLIBCXX__) || (defined(_LIBCPP_VERSION) && !defined(_MSC_VER))
+#  define GTEST_HAS_CXXABI_H_ 1
+# else
+#  define GTEST_HAS_CXXABI_H_ 0
+# endif
+#endif
+
+// A function level attribute to disable checking for use of uninitialized
+// memory when built with MemorySanitizer.
+#if defined(__clang__)
+# if __has_feature(memory_sanitizer)
+#  define GTEST_ATTRIBUTE_NO_SANITIZE_MEMORY_ \
+       __attribute__((no_sanitize_memory))
+# else
+#  define GTEST_ATTRIBUTE_NO_SANITIZE_MEMORY_
+# endif  // __has_feature(memory_sanitizer)
+#else
+# define GTEST_ATTRIBUTE_NO_SANITIZE_MEMORY_
+#endif  // __clang__
+
+// A function level attribute to disable AddressSanitizer instrumentation.
+#if defined(__clang__)
+# if __has_feature(address_sanitizer)
+#  define GTEST_ATTRIBUTE_NO_SANITIZE_ADDRESS_ \
+       __attribute__((no_sanitize_address))
+# else
+#  define GTEST_ATTRIBUTE_NO_SANITIZE_ADDRESS_
+# endif  // __has_feature(address_sanitizer)
+#else
+# define GTEST_ATTRIBUTE_NO_SANITIZE_ADDRESS_
+#endif  // __clang__
+
+// A function level attribute to disable HWAddressSanitizer instrumentation.
+#if defined(__clang__)
+# if __has_feature(hwaddress_sanitizer)
+#  define GTEST_ATTRIBUTE_NO_SANITIZE_HWADDRESS_ \
+       __attribute__((no_sanitize("hwaddress")))
+# else
+#  define GTEST_ATTRIBUTE_NO_SANITIZE_HWADDRESS_
+# endif  // __has_feature(hwaddress_sanitizer)
+#else
+# define GTEST_ATTRIBUTE_NO_SANITIZE_HWADDRESS_
+#endif  // __clang__
+
+// A function level attribute to disable ThreadSanitizer instrumentation.
+#if defined(__clang__)
+# if __has_feature(thread_sanitizer)
+#  define GTEST_ATTRIBUTE_NO_SANITIZE_THREAD_ \
+       __attribute__((no_sanitize_thread))
+# else
+#  define GTEST_ATTRIBUTE_NO_SANITIZE_THREAD_
+# endif  // __has_feature(thread_sanitizer)
+#else
+# define GTEST_ATTRIBUTE_NO_SANITIZE_THREAD_
+#endif  // __clang__
+
+namespace testing {
+
+class Message;
+
+// Legacy imports for backwards compatibility.
+// New code should use std:: names directly.
+using std::get;
+using std::make_tuple;
+using std::tuple;
+using std::tuple_element;
+using std::tuple_size;
+
+namespace internal {
+
+// A secret type that Google Test users don't know about.  It has no
+// definition on purpose.  Therefore it's impossible to create a
+// Secret object, which is what we want.
+class Secret;
+
+// The GTEST_COMPILE_ASSERT_ is a legacy macro used to verify that a compile
+// time expression is true (in new code, use static_assert instead). For
+// example, you could use it to verify the size of a static array:
+//
+//   GTEST_COMPILE_ASSERT_(GTEST_ARRAY_SIZE_(names) == NUM_NAMES,
+//                         names_incorrect_size);
+//
+// The second argument to the macro must be a valid C++ identifier. If the
+// expression is false, compiler will issue an error containing this identifier.
+#define GTEST_COMPILE_ASSERT_(expr, msg) static_assert(expr, #msg)
+
+// A helper for suppressing warnings on constant condition.  It just
+// returns 'condition'.
+GTEST_API_ bool IsTrue(bool condition);
+
+// Defines RE.
+
+#if GTEST_USES_PCRE
+// if used, PCRE is injected by custom/gtest-port.h
+#elif GTEST_USES_POSIX_RE || GTEST_USES_SIMPLE_RE
+
+// A simple C++ wrapper for <regex.h>.  It uses the POSIX Extended
+// Regular Expression syntax.
+class GTEST_API_ RE {
+ public:
+  // A copy constructor is required by the Standard to initialize object
+  // references from r-values.
+  RE(const RE& other) { Init(other.pattern()); }
+
+  // Constructs an RE from a string.
+  RE(const ::std::string& regex) { Init(regex.c_str()); }  // NOLINT
+
+  RE(const char* regex) { Init(regex); }  // NOLINT
+  ~RE();
+
+  // Returns the string representation of the regex.
+  const char* pattern() const { return pattern_; }
+
+  // FullMatch(str, re) returns true if and only if regular expression re
+  // matches the entire str.
+  // PartialMatch(str, re) returns true if and only if regular expression re
+  // matches a substring of str (including str itself).
+  static bool FullMatch(const ::std::string& str, const RE& re) {
+    return FullMatch(str.c_str(), re);
+  }
+  static bool PartialMatch(const ::std::string& str, const RE& re) {
+    return PartialMatch(str.c_str(), re);
+  }
+
+  static bool FullMatch(const char* str, const RE& re);
+  static bool PartialMatch(const char* str, const RE& re);
+
+ private:
+  void Init(const char* regex);
+  const char* pattern_;
+  bool is_valid_;
+
+# if GTEST_USES_POSIX_RE
+
+  regex_t full_regex_;     // For FullMatch().
+  regex_t partial_regex_;  // For PartialMatch().
+
+# else  // GTEST_USES_SIMPLE_RE
+
+  const char* full_pattern_;  // For FullMatch();
+
+# endif
+};
+
+#endif  // GTEST_USES_PCRE
+
+// Formats a source file path and a line number as they would appear
+// in an error message from the compiler used to compile this code.
+GTEST_API_ ::std::string FormatFileLocation(const char* file, int line);
+
+// Formats a file location for compiler-independent XML output.
+// Although this function is not platform dependent, we put it next to
+// FormatFileLocation in order to contrast the two functions.
+GTEST_API_ ::std::string FormatCompilerIndependentFileLocation(const char* file,
+                                                               int line);
+
+// Defines logging utilities:
+//   GTEST_LOG_(severity) - logs messages at the specified severity level. The
+//                          message itself is streamed into the macro.
+//   LogToStderr()  - directs all log messages to stderr.
+//   FlushInfoLog() - flushes informational log messages.
+
+enum GTestLogSeverity {
+  GTEST_INFO,
+  GTEST_WARNING,
+  GTEST_ERROR,
+  GTEST_FATAL
+};
+
+// Formats log entry severity, provides a stream object for streaming the
+// log message, and terminates the message with a newline when going out of
+// scope.
+class GTEST_API_ GTestLog {
+ public:
+  GTestLog(GTestLogSeverity severity, const char* file, int line);
+
+  // Flushes the buffers and, if severity is GTEST_FATAL, aborts the program.
+  ~GTestLog();
+
+  ::std::ostream& GetStream() { return ::std::cerr; }
+
+ private:
+  const GTestLogSeverity severity_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(GTestLog);
+};
+
+#if !defined(GTEST_LOG_)
+
+# define GTEST_LOG_(severity) \
+    ::testing::internal::GTestLog(::testing::internal::GTEST_##severity, \
+                                  __FILE__, __LINE__).GetStream()
+
+inline void LogToStderr() {}
+inline void FlushInfoLog() { fflush(nullptr); }
+
+#endif  // !defined(GTEST_LOG_)
+
+#if !defined(GTEST_CHECK_)
+// INTERNAL IMPLEMENTATION - DO NOT USE.
+//
+// GTEST_CHECK_ is an all-mode assert. It aborts the program if the condition
+// is not satisfied.
+//  Synopsys:
+//    GTEST_CHECK_(boolean_condition);
+//     or
+//    GTEST_CHECK_(boolean_condition) << "Additional message";
+//
+//    This checks the condition and if the condition is not satisfied
+//    it prints message about the condition violation, including the
+//    condition itself, plus additional message streamed into it, if any,
+//    and then it aborts the program. It aborts the program irrespective of
+//    whether it is built in the debug mode or not.
+# define GTEST_CHECK_(condition) \
+    GTEST_AMBIGUOUS_ELSE_BLOCKER_ \
+    if (::testing::internal::IsTrue(condition)) \
+      ; \
+    else \
+      GTEST_LOG_(FATAL) << "Condition " #condition " failed. "
+#endif  // !defined(GTEST_CHECK_)
+
+// An all-mode assert to verify that the given POSIX-style function
+// call returns 0 (indicating success).  Known limitation: this
+// doesn't expand to a balanced 'if' statement, so enclose the macro
+// in {} if you need to use it as the only statement in an 'if'
+// branch.
+#define GTEST_CHECK_POSIX_SUCCESS_(posix_call) \
+  if (const int gtest_error = (posix_call)) \
+    GTEST_LOG_(FATAL) << #posix_call << "failed with error " \
+                      << gtest_error
+
+// Transforms "T" into "const T&" according to standard reference collapsing
+// rules (this is only needed as a backport for C++98 compilers that do not
+// support reference collapsing). Specifically, it transforms:
+//
+//   char         ==> const char&
+//   const char   ==> const char&
+//   char&        ==> char&
+//   const char&  ==> const char&
+//
+// Note that the non-const reference will not have "const" added. This is
+// standard, and necessary so that "T" can always bind to "const T&".
+template <typename T>
+struct ConstRef { typedef const T& type; };
+template <typename T>
+struct ConstRef<T&> { typedef T& type; };
+
+// The argument T must depend on some template parameters.
+#define GTEST_REFERENCE_TO_CONST_(T) \
+  typename ::testing::internal::ConstRef<T>::type
+
+// INTERNAL IMPLEMENTATION - DO NOT USE IN USER CODE.
+//
+// Use ImplicitCast_ as a safe version of static_cast for upcasting in
+// the type hierarchy (e.g. casting a Foo* to a SuperclassOfFoo* or a
+// const Foo*).  When you use ImplicitCast_, the compiler checks that
+// the cast is safe.  Such explicit ImplicitCast_s are necessary in
+// surprisingly many situations where C++ demands an exact type match
+// instead of an argument type convertable to a target type.
+//
+// The syntax for using ImplicitCast_ is the same as for static_cast:
+//
+//   ImplicitCast_<ToType>(expr)
+//
+// ImplicitCast_ would have been part of the C++ standard library,
+// but the proposal was submitted too late.  It will probably make
+// its way into the language in the future.
+//
+// This relatively ugly name is intentional. It prevents clashes with
+// similar functions users may have (e.g., implicit_cast). The internal
+// namespace alone is not enough because the function can be found by ADL.
+template<typename To>
+inline To ImplicitCast_(To x) { return x; }
+
+// When you upcast (that is, cast a pointer from type Foo to type
+// SuperclassOfFoo), it's fine to use ImplicitCast_<>, since upcasts
+// always succeed.  When you downcast (that is, cast a pointer from
+// type Foo to type SubclassOfFoo), static_cast<> isn't safe, because
+// how do you know the pointer is really of type SubclassOfFoo?  It
+// could be a bare Foo, or of type DifferentSubclassOfFoo.  Thus,
+// when you downcast, you should use this macro.  In debug mode, we
+// use dynamic_cast<> to double-check the downcast is legal (we die
+// if it's not).  In normal mode, we do the efficient static_cast<>
+// instead.  Thus, it's important to test in debug mode to make sure
+// the cast is legal!
+//    This is the only place in the code we should use dynamic_cast<>.
+// In particular, you SHOULDN'T be using dynamic_cast<> in order to
+// do RTTI (eg code like this:
+//    if (dynamic_cast<Subclass1>(foo)) HandleASubclass1Object(foo);
+//    if (dynamic_cast<Subclass2>(foo)) HandleASubclass2Object(foo);
+// You should design the code some other way not to need this.
+//
+// This relatively ugly name is intentional. It prevents clashes with
+// similar functions users may have (e.g., down_cast). The internal
+// namespace alone is not enough because the function can be found by ADL.
+template<typename To, typename From>  // use like this: DownCast_<T*>(foo);
+inline To DownCast_(From* f) {  // so we only accept pointers
+  // Ensures that To is a sub-type of From *.  This test is here only
+  // for compile-time type checking, and has no overhead in an
+  // optimized build at run-time, as it will be optimized away
+  // completely.
+  GTEST_INTENTIONAL_CONST_COND_PUSH_()
+  if (false) {
+  GTEST_INTENTIONAL_CONST_COND_POP_()
+  const To to = nullptr;
+  ::testing::internal::ImplicitCast_<From*>(to);
+  }
+
+#if GTEST_HAS_RTTI
+  // RTTI: debug mode only!
+  GTEST_CHECK_(f == nullptr || dynamic_cast<To>(f) != nullptr);
+#endif
+  return static_cast<To>(f);
+}
+
+// Downcasts the pointer of type Base to Derived.
+// Derived must be a subclass of Base. The parameter MUST
+// point to a class of type Derived, not any subclass of it.
+// When RTTI is available, the function performs a runtime
+// check to enforce this.
+template <class Derived, class Base>
+Derived* CheckedDowncastToActualType(Base* base) {
+#if GTEST_HAS_RTTI
+  GTEST_CHECK_(typeid(*base) == typeid(Derived));
+#endif
+
+#if GTEST_HAS_DOWNCAST_
+  return ::down_cast<Derived*>(base);
+#elif GTEST_HAS_RTTI
+  return dynamic_cast<Derived*>(base);  // NOLINT
+#else
+  return static_cast<Derived*>(base);  // Poor man's downcast.
+#endif
+}
+
+#if GTEST_HAS_STREAM_REDIRECTION
+
+// Defines the stderr capturer:
+//   CaptureStdout     - starts capturing stdout.
+//   GetCapturedStdout - stops capturing stdout and returns the captured string.
+//   CaptureStderr     - starts capturing stderr.
+//   GetCapturedStderr - stops capturing stderr and returns the captured string.
+//
+GTEST_API_ void CaptureStdout();
+GTEST_API_ std::string GetCapturedStdout();
+GTEST_API_ void CaptureStderr();
+GTEST_API_ std::string GetCapturedStderr();
+
+#endif  // GTEST_HAS_STREAM_REDIRECTION
+// Returns the size (in bytes) of a file.
+GTEST_API_ size_t GetFileSize(FILE* file);
+
+// Reads the entire content of a file as a string.
+GTEST_API_ std::string ReadEntireFile(FILE* file);
+
+// All command line arguments.
+GTEST_API_ std::vector<std::string> GetArgvs();
+
+#if GTEST_HAS_DEATH_TEST
+
+std::vector<std::string> GetInjectableArgvs();
+// Deprecated: pass the args vector by value instead.
+void SetInjectableArgvs(const std::vector<std::string>* new_argvs);
+void SetInjectableArgvs(const std::vector<std::string>& new_argvs);
+void ClearInjectableArgvs();
+
+#endif  // GTEST_HAS_DEATH_TEST
+
+// Defines synchronization primitives.
+#if GTEST_IS_THREADSAFE
+# if GTEST_HAS_PTHREAD
+// Sleeps for (roughly) n milliseconds.  This function is only for testing
+// Google Test's own constructs.  Don't use it in user tests, either
+// directly or indirectly.
+inline void SleepMilliseconds(int n) {
+  const timespec time = {
+    0,                  // 0 seconds.
+    n * 1000L * 1000L,  // And n ms.
+  };
+  nanosleep(&time, nullptr);
+}
+# endif  // GTEST_HAS_PTHREAD
+
+# if GTEST_HAS_NOTIFICATION_
+// Notification has already been imported into the namespace.
+// Nothing to do here.
+
+# elif GTEST_HAS_PTHREAD
+// Allows a controller thread to pause execution of newly created
+// threads until notified.  Instances of this class must be created
+// and destroyed in the controller thread.
+//
+// This class is only for testing Google Test's own constructs. Do not
+// use it in user tests, either directly or indirectly.
+class Notification {
+ public:
+  Notification() : notified_(false) {
+    GTEST_CHECK_POSIX_SUCCESS_(pthread_mutex_init(&mutex_, nullptr));
+  }
+  ~Notification() {
+    pthread_mutex_destroy(&mutex_);
+  }
+
+  // Notifies all threads created with this notification to start. Must
+  // be called from the controller thread.
+  void Notify() {
+    pthread_mutex_lock(&mutex_);
+    notified_ = true;
+    pthread_mutex_unlock(&mutex_);
+  }
+
+  // Blocks until the controller thread notifies. Must be called from a test
+  // thread.
+  void WaitForNotification() {
+    for (;;) {
+      pthread_mutex_lock(&mutex_);
+      const bool notified = notified_;
+      pthread_mutex_unlock(&mutex_);
+      if (notified)
+        break;
+      SleepMilliseconds(10);
+    }
+  }
+
+ private:
+  pthread_mutex_t mutex_;
+  bool notified_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(Notification);
+};
+
+# elif GTEST_OS_WINDOWS && !GTEST_OS_WINDOWS_PHONE && !GTEST_OS_WINDOWS_RT
+
+GTEST_API_ void SleepMilliseconds(int n);
+
+// Provides leak-safe Windows kernel handle ownership.
+// Used in death tests and in threading support.
+class GTEST_API_ AutoHandle {
+ public:
+  // Assume that Win32 HANDLE type is equivalent to void*. Doing so allows us to
+  // avoid including <windows.h> in this header file. Including <windows.h> is
+  // undesirable because it defines a lot of symbols and macros that tend to
+  // conflict with client code. This assumption is verified by
+  // WindowsTypesTest.HANDLEIsVoidStar.
+  typedef void* Handle;
+  AutoHandle();
+  explicit AutoHandle(Handle handle);
+
+  ~AutoHandle();
+
+  Handle Get() const;
+  void Reset();
+  void Reset(Handle handle);
+
+ private:
+  // Returns true if and only if the handle is a valid handle object that can be
+  // closed.
+  bool IsCloseable() const;
+
+  Handle handle_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(AutoHandle);
+};
+
+// Allows a controller thread to pause execution of newly created
+// threads until notified.  Instances of this class must be created
+// and destroyed in the controller thread.
+//
+// This class is only for testing Google Test's own constructs. Do not
+// use it in user tests, either directly or indirectly.
+class GTEST_API_ Notification {
+ public:
+  Notification();
+  void Notify();
+  void WaitForNotification();
+
+ private:
+  AutoHandle event_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(Notification);
+};
+# endif  // GTEST_HAS_NOTIFICATION_
+
+// On MinGW, we can have both GTEST_OS_WINDOWS and GTEST_HAS_PTHREAD
+// defined, but we don't want to use MinGW's pthreads implementation, which
+// has conformance problems with some versions of the POSIX standard.
+# if GTEST_HAS_PTHREAD && !GTEST_OS_WINDOWS_MINGW
+
+// As a C-function, ThreadFuncWithCLinkage cannot be templated itself.
+// Consequently, it cannot select a correct instantiation of ThreadWithParam
+// in order to call its Run(). Introducing ThreadWithParamBase as a
+// non-templated base class for ThreadWithParam allows us to bypass this
+// problem.
+class ThreadWithParamBase {
+ public:
+  virtual ~ThreadWithParamBase() {}
+  virtual void Run() = 0;
+};
+
+// pthread_create() accepts a pointer to a function type with the C linkage.
+// According to the Standard (7.5/1), function types with different linkages
+// are different even if they are otherwise identical.  Some compilers (for
+// example, SunStudio) treat them as different types.  Since class methods
+// cannot be defined with C-linkage we need to define a free C-function to
+// pass into pthread_create().
+extern "C" inline void* ThreadFuncWithCLinkage(void* thread) {
+  static_cast<ThreadWithParamBase*>(thread)->Run();
+  return nullptr;
+}
+
+// Helper class for testing Google Test's multi-threading constructs.
+// To use it, write:
+//
+//   void ThreadFunc(int param) { /* Do things with param */ }
+//   Notification thread_can_start;
+//   ...
+//   // The thread_can_start parameter is optional; you can supply NULL.
+//   ThreadWithParam<int> thread(&ThreadFunc, 5, &thread_can_start);
+//   thread_can_start.Notify();
+//
+// These classes are only for testing Google Test's own constructs. Do
+// not use them in user tests, either directly or indirectly.
+template <typename T>
+class ThreadWithParam : public ThreadWithParamBase {
+ public:
+  typedef void UserThreadFunc(T);
+
+  ThreadWithParam(UserThreadFunc* func, T param, Notification* thread_can_start)
+      : func_(func),
+        param_(param),
+        thread_can_start_(thread_can_start),
+        finished_(false) {
+    ThreadWithParamBase* const base = this;
+    // The thread can be created only after all fields except thread_
+    // have been initialized.
+    GTEST_CHECK_POSIX_SUCCESS_(
+        pthread_create(&thread_, nullptr, &ThreadFuncWithCLinkage, base));
+  }
+  ~ThreadWithParam() override { Join(); }
+
+  void Join() {
+    if (!finished_) {
+      GTEST_CHECK_POSIX_SUCCESS_(pthread_join(thread_, nullptr));
+      finished_ = true;
+    }
+  }
+
+  void Run() override {
+    if (thread_can_start_ != nullptr) thread_can_start_->WaitForNotification();
+    func_(param_);
+  }
+
+ private:
+  UserThreadFunc* const func_;  // User-supplied thread function.
+  const T param_;  // User-supplied parameter to the thread function.
+  // When non-NULL, used to block execution until the controller thread
+  // notifies.
+  Notification* const thread_can_start_;
+  bool finished_;  // true if and only if we know that the thread function has
+                   // finished.
+  pthread_t thread_;  // The native thread object.
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(ThreadWithParam);
+};
+# endif  // !GTEST_OS_WINDOWS && GTEST_HAS_PTHREAD ||
+         // GTEST_HAS_MUTEX_AND_THREAD_LOCAL_
+
+# if GTEST_HAS_MUTEX_AND_THREAD_LOCAL_
+// Mutex and ThreadLocal have already been imported into the namespace.
+// Nothing to do here.
+
+# elif GTEST_OS_WINDOWS && !GTEST_OS_WINDOWS_PHONE && !GTEST_OS_WINDOWS_RT
+
+// Mutex implements mutex on Windows platforms.  It is used in conjunction
+// with class MutexLock:
+//
+//   Mutex mutex;
+//   ...
+//   MutexLock lock(&mutex);  // Acquires the mutex and releases it at the
+//                            // end of the current scope.
+//
+// A static Mutex *must* be defined or declared using one of the following
+// macros:
+//   GTEST_DEFINE_STATIC_MUTEX_(g_some_mutex);
+//   GTEST_DECLARE_STATIC_MUTEX_(g_some_mutex);
+//
+// (A non-static Mutex is defined/declared in the usual way).
+class GTEST_API_ Mutex {
+ public:
+  enum MutexType { kStatic = 0, kDynamic = 1 };
+  // We rely on kStaticMutex being 0 as it is to what the linker initializes
+  // type_ in static mutexes.  critical_section_ will be initialized lazily
+  // in ThreadSafeLazyInit().
+  enum StaticConstructorSelector { kStaticMutex = 0 };
+
+  // This constructor intentionally does nothing.  It relies on type_ being
+  // statically initialized to 0 (effectively setting it to kStatic) and on
+  // ThreadSafeLazyInit() to lazily initialize the rest of the members.
+  explicit Mutex(StaticConstructorSelector /*dummy*/) {}
+
+  Mutex();
+  ~Mutex();
+
+  void Lock();
+
+  void Unlock();
+
+  // Does nothing if the current thread holds the mutex. Otherwise, crashes
+  // with high probability.
+  void AssertHeld();
+
+ private:
+  // Initializes owner_thread_id_ and critical_section_ in static mutexes.
+  void ThreadSafeLazyInit();
+
+  // Per https://blogs.msdn.microsoft.com/oldnewthing/20040223-00/?p=40503,
+  // we assume that 0 is an invalid value for thread IDs.
+  unsigned int owner_thread_id_;
+
+  // For static mutexes, we rely on these members being initialized to zeros
+  // by the linker.
+  MutexType type_;
+  long critical_section_init_phase_;  // NOLINT
+  GTEST_CRITICAL_SECTION* critical_section_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(Mutex);
+};
+
+# define GTEST_DECLARE_STATIC_MUTEX_(mutex) \
+    extern ::testing::internal::Mutex mutex
+
+# define GTEST_DEFINE_STATIC_MUTEX_(mutex) \
+    ::testing::internal::Mutex mutex(::testing::internal::Mutex::kStaticMutex)
+
+// We cannot name this class MutexLock because the ctor declaration would
+// conflict with a macro named MutexLock, which is defined on some
+// platforms. That macro is used as a defensive measure to prevent against
+// inadvertent misuses of MutexLock like "MutexLock(&mu)" rather than
+// "MutexLock l(&mu)".  Hence the typedef trick below.
+class GTestMutexLock {
+ public:
+  explicit GTestMutexLock(Mutex* mutex)
+      : mutex_(mutex) { mutex_->Lock(); }
+
+  ~GTestMutexLock() { mutex_->Unlock(); }
+
+ private:
+  Mutex* const mutex_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(GTestMutexLock);
+};
+
+typedef GTestMutexLock MutexLock;
+
+// Base class for ValueHolder<T>.  Allows a caller to hold and delete a value
+// without knowing its type.
+class ThreadLocalValueHolderBase {
+ public:
+  virtual ~ThreadLocalValueHolderBase() {}
+};
+
+// Provides a way for a thread to send notifications to a ThreadLocal
+// regardless of its parameter type.
+class ThreadLocalBase {
+ public:
+  // Creates a new ValueHolder<T> object holding a default value passed to
+  // this ThreadLocal<T>'s constructor and returns it.  It is the caller's
+  // responsibility not to call this when the ThreadLocal<T> instance already
+  // has a value on the current thread.
+  virtual ThreadLocalValueHolderBase* NewValueForCurrentThread() const = 0;
+
+ protected:
+  ThreadLocalBase() {}
+  virtual ~ThreadLocalBase() {}
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(ThreadLocalBase);
+};
+
+// Maps a thread to a set of ThreadLocals that have values instantiated on that
+// thread and notifies them when the thread exits.  A ThreadLocal instance is
+// expected to persist until all threads it has values on have terminated.
+class GTEST_API_ ThreadLocalRegistry {
+ public:
+  // Registers thread_local_instance as having value on the current thread.
+  // Returns a value that can be used to identify the thread from other threads.
+  static ThreadLocalValueHolderBase* GetValueOnCurrentThread(
+      const ThreadLocalBase* thread_local_instance);
+
+  // Invoked when a ThreadLocal instance is destroyed.
+  static void OnThreadLocalDestroyed(
+      const ThreadLocalBase* thread_local_instance);
+};
+
+class GTEST_API_ ThreadWithParamBase {
+ public:
+  void Join();
+
+ protected:
+  class Runnable {
+   public:
+    virtual ~Runnable() {}
+    virtual void Run() = 0;
+  };
+
+  ThreadWithParamBase(Runnable *runnable, Notification* thread_can_start);
+  virtual ~ThreadWithParamBase();
+
+ private:
+  AutoHandle thread_;
+};
+
+// Helper class for testing Google Test's multi-threading constructs.
+template <typename T>
+class ThreadWithParam : public ThreadWithParamBase {
+ public:
+  typedef void UserThreadFunc(T);
+
+  ThreadWithParam(UserThreadFunc* func, T param, Notification* thread_can_start)
+      : ThreadWithParamBase(new RunnableImpl(func, param), thread_can_start) {
+  }
+  virtual ~ThreadWithParam() {}
+
+ private:
+  class RunnableImpl : public Runnable {
+   public:
+    RunnableImpl(UserThreadFunc* func, T param)
+        : func_(func),
+          param_(param) {
+    }
+    virtual ~RunnableImpl() {}
+    virtual void Run() {
+      func_(param_);
+    }
+
+   private:
+    UserThreadFunc* const func_;
+    const T param_;
+
+    GTEST_DISALLOW_COPY_AND_ASSIGN_(RunnableImpl);
+  };
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(ThreadWithParam);
+};
+
+// Implements thread-local storage on Windows systems.
+//
+//   // Thread 1
+//   ThreadLocal<int> tl(100);  // 100 is the default value for each thread.
+//
+//   // Thread 2
+//   tl.set(150);  // Changes the value for thread 2 only.
+//   EXPECT_EQ(150, tl.get());
+//
+//   // Thread 1
+//   EXPECT_EQ(100, tl.get());  // In thread 1, tl has the original value.
+//   tl.set(200);
+//   EXPECT_EQ(200, tl.get());
+//
+// The template type argument T must have a public copy constructor.
+// In addition, the default ThreadLocal constructor requires T to have
+// a public default constructor.
+//
+// The users of a TheadLocal instance have to make sure that all but one
+// threads (including the main one) using that instance have exited before
+// destroying it. Otherwise, the per-thread objects managed for them by the
+// ThreadLocal instance are not guaranteed to be destroyed on all platforms.
+//
+// Google Test only uses global ThreadLocal objects.  That means they
+// will die after main() has returned.  Therefore, no per-thread
+// object managed by Google Test will be leaked as long as all threads
+// using Google Test have exited when main() returns.
+template <typename T>
+class ThreadLocal : public ThreadLocalBase {
+ public:
+  ThreadLocal() : default_factory_(new DefaultValueHolderFactory()) {}
+  explicit ThreadLocal(const T& value)
+      : default_factory_(new InstanceValueHolderFactory(value)) {}
+
+  ~ThreadLocal() { ThreadLocalRegistry::OnThreadLocalDestroyed(this); }
+
+  T* pointer() { return GetOrCreateValue(); }
+  const T* pointer() const { return GetOrCreateValue(); }
+  const T& get() const { return *pointer(); }
+  void set(const T& value) { *pointer() = value; }
+
+ private:
+  // Holds a value of T.  Can be deleted via its base class without the caller
+  // knowing the type of T.
+  class ValueHolder : public ThreadLocalValueHolderBase {
+   public:
+    ValueHolder() : value_() {}
+    explicit ValueHolder(const T& value) : value_(value) {}
+
+    T* pointer() { return &value_; }
+
+   private:
+    T value_;
+    GTEST_DISALLOW_COPY_AND_ASSIGN_(ValueHolder);
+  };
+
+
+  T* GetOrCreateValue() const {
+    return static_cast<ValueHolder*>(
+        ThreadLocalRegistry::GetValueOnCurrentThread(this))->pointer();
+  }
+
+  virtual ThreadLocalValueHolderBase* NewValueForCurrentThread() const {
+    return default_factory_->MakeNewHolder();
+  }
+
+  class ValueHolderFactory {
+   public:
+    ValueHolderFactory() {}
+    virtual ~ValueHolderFactory() {}
+    virtual ValueHolder* MakeNewHolder() const = 0;
+
+   private:
+    GTEST_DISALLOW_COPY_AND_ASSIGN_(ValueHolderFactory);
+  };
+
+  class DefaultValueHolderFactory : public ValueHolderFactory {
+   public:
+    DefaultValueHolderFactory() {}
+    ValueHolder* MakeNewHolder() const override { return new ValueHolder(); }
+
+   private:
+    GTEST_DISALLOW_COPY_AND_ASSIGN_(DefaultValueHolderFactory);
+  };
+
+  class InstanceValueHolderFactory : public ValueHolderFactory {
+   public:
+    explicit InstanceValueHolderFactory(const T& value) : value_(value) {}
+    ValueHolder* MakeNewHolder() const override {
+      return new ValueHolder(value_);
+    }
+
+   private:
+    const T value_;  // The value for each thread.
+
+    GTEST_DISALLOW_COPY_AND_ASSIGN_(InstanceValueHolderFactory);
+  };
+
+  std::unique_ptr<ValueHolderFactory> default_factory_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(ThreadLocal);
+};
+
+# elif GTEST_HAS_PTHREAD
+
+// MutexBase and Mutex implement mutex on pthreads-based platforms.
+class MutexBase {
+ public:
+  // Acquires this mutex.
+  void Lock() {
+    GTEST_CHECK_POSIX_SUCCESS_(pthread_mutex_lock(&mutex_));
+    owner_ = pthread_self();
+    has_owner_ = true;
+  }
+
+  // Releases this mutex.
+  void Unlock() {
+    // Since the lock is being released the owner_ field should no longer be
+    // considered valid. We don't protect writing to has_owner_ here, as it's
+    // the caller's responsibility to ensure that the current thread holds the
+    // mutex when this is called.
+    has_owner_ = false;
+    GTEST_CHECK_POSIX_SUCCESS_(pthread_mutex_unlock(&mutex_));
+  }
+
+  // Does nothing if the current thread holds the mutex. Otherwise, crashes
+  // with high probability.
+  void AssertHeld() const {
+    GTEST_CHECK_(has_owner_ && pthread_equal(owner_, pthread_self()))
+        << "The current thread is not holding the mutex @" << this;
+  }
+
+  // A static mutex may be used before main() is entered.  It may even
+  // be used before the dynamic initialization stage.  Therefore we
+  // must be able to initialize a static mutex object at link time.
+  // This means MutexBase has to be a POD and its member variables
+  // have to be public.
+ public:
+  pthread_mutex_t mutex_;  // The underlying pthread mutex.
+  // has_owner_ indicates whether the owner_ field below contains a valid thread
+  // ID and is therefore safe to inspect (e.g., to use in pthread_equal()). All
+  // accesses to the owner_ field should be protected by a check of this field.
+  // An alternative might be to memset() owner_ to all zeros, but there's no
+  // guarantee that a zero'd pthread_t is necessarily invalid or even different
+  // from pthread_self().
+  bool has_owner_;
+  pthread_t owner_;  // The thread holding the mutex.
+};
+
+// Forward-declares a static mutex.
+#  define GTEST_DECLARE_STATIC_MUTEX_(mutex) \
+     extern ::testing::internal::MutexBase mutex
+
+// Defines and statically (i.e. at link time) initializes a static mutex.
+// The initialization list here does not explicitly initialize each field,
+// instead relying on default initialization for the unspecified fields. In
+// particular, the owner_ field (a pthread_t) is not explicitly initialized.
+// This allows initialization to work whether pthread_t is a scalar or struct.
+// The flag -Wmissing-field-initializers must not be specified for this to work.
+#define GTEST_DEFINE_STATIC_MUTEX_(mutex) \
+  ::testing::internal::MutexBase mutex = {PTHREAD_MUTEX_INITIALIZER, false, 0}
+
+// The Mutex class can only be used for mutexes created at runtime. It
+// shares its API with MutexBase otherwise.
+class Mutex : public MutexBase {
+ public:
+  Mutex() {
+    GTEST_CHECK_POSIX_SUCCESS_(pthread_mutex_init(&mutex_, nullptr));
+    has_owner_ = false;
+  }
+  ~Mutex() {
+    GTEST_CHECK_POSIX_SUCCESS_(pthread_mutex_destroy(&mutex_));
+  }
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(Mutex);
+};
+
+// We cannot name this class MutexLock because the ctor declaration would
+// conflict with a macro named MutexLock, which is defined on some
+// platforms. That macro is used as a defensive measure to prevent against
+// inadvertent misuses of MutexLock like "MutexLock(&mu)" rather than
+// "MutexLock l(&mu)".  Hence the typedef trick below.
+class GTestMutexLock {
+ public:
+  explicit GTestMutexLock(MutexBase* mutex)
+      : mutex_(mutex) { mutex_->Lock(); }
+
+  ~GTestMutexLock() { mutex_->Unlock(); }
+
+ private:
+  MutexBase* const mutex_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(GTestMutexLock);
+};
+
+typedef GTestMutexLock MutexLock;
+
+// Helpers for ThreadLocal.
+
+// pthread_key_create() requires DeleteThreadLocalValue() to have
+// C-linkage.  Therefore it cannot be templatized to access
+// ThreadLocal<T>.  Hence the need for class
+// ThreadLocalValueHolderBase.
+class ThreadLocalValueHolderBase {
+ public:
+  virtual ~ThreadLocalValueHolderBase() {}
+};
+
+// Called by pthread to delete thread-local data stored by
+// pthread_setspecific().
+extern "C" inline void DeleteThreadLocalValue(void* value_holder) {
+  delete static_cast<ThreadLocalValueHolderBase*>(value_holder);
+}
+
+// Implements thread-local storage on pthreads-based systems.
+template <typename T>
+class GTEST_API_ ThreadLocal {
+ public:
+  ThreadLocal()
+      : key_(CreateKey()), default_factory_(new DefaultValueHolderFactory()) {}
+  explicit ThreadLocal(const T& value)
+      : key_(CreateKey()),
+        default_factory_(new InstanceValueHolderFactory(value)) {}
+
+  ~ThreadLocal() {
+    // Destroys the managed object for the current thread, if any.
+    DeleteThreadLocalValue(pthread_getspecific(key_));
+
+    // Releases resources associated with the key.  This will *not*
+    // delete managed objects for other threads.
+    GTEST_CHECK_POSIX_SUCCESS_(pthread_key_delete(key_));
+  }
+
+  T* pointer() { return GetOrCreateValue(); }
+  const T* pointer() const { return GetOrCreateValue(); }
+  const T& get() const { return *pointer(); }
+  void set(const T& value) { *pointer() = value; }
+
+ private:
+  // Holds a value of type T.
+  class ValueHolder : public ThreadLocalValueHolderBase {
+   public:
+    ValueHolder() : value_() {}
+    explicit ValueHolder(const T& value) : value_(value) {}
+
+    T* pointer() { return &value_; }
+
+   private:
+    T value_;
+    GTEST_DISALLOW_COPY_AND_ASSIGN_(ValueHolder);
+  };
+
+  static pthread_key_t CreateKey() {
+    pthread_key_t key;
+    // When a thread exits, DeleteThreadLocalValue() will be called on
+    // the object managed for that thread.
+    GTEST_CHECK_POSIX_SUCCESS_(
+        pthread_key_create(&key, &DeleteThreadLocalValue));
+    return key;
+  }
+
+  T* GetOrCreateValue() const {
+    ThreadLocalValueHolderBase* const holder =
+        static_cast<ThreadLocalValueHolderBase*>(pthread_getspecific(key_));
+    if (holder != nullptr) {
+      return CheckedDowncastToActualType<ValueHolder>(holder)->pointer();
+    }
+
+    ValueHolder* const new_holder = default_factory_->MakeNewHolder();
+    ThreadLocalValueHolderBase* const holder_base = new_holder;
+    GTEST_CHECK_POSIX_SUCCESS_(pthread_setspecific(key_, holder_base));
+    return new_holder->pointer();
+  }
+
+  class ValueHolderFactory {
+   public:
+    ValueHolderFactory() {}
+    virtual ~ValueHolderFactory() {}
+    virtual ValueHolder* MakeNewHolder() const = 0;
+
+   private:
+    GTEST_DISALLOW_COPY_AND_ASSIGN_(ValueHolderFactory);
+  };
+
+  class DefaultValueHolderFactory : public ValueHolderFactory {
+   public:
+    DefaultValueHolderFactory() {}
+    ValueHolder* MakeNewHolder() const override { return new ValueHolder(); }
+
+   private:
+    GTEST_DISALLOW_COPY_AND_ASSIGN_(DefaultValueHolderFactory);
+  };
+
+  class InstanceValueHolderFactory : public ValueHolderFactory {
+   public:
+    explicit InstanceValueHolderFactory(const T& value) : value_(value) {}
+    ValueHolder* MakeNewHolder() const override {
+      return new ValueHolder(value_);
+    }
+
+   private:
+    const T value_;  // The value for each thread.
+
+    GTEST_DISALLOW_COPY_AND_ASSIGN_(InstanceValueHolderFactory);
+  };
+
+  // A key pthreads uses for looking up per-thread values.
+  const pthread_key_t key_;
+  std::unique_ptr<ValueHolderFactory> default_factory_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(ThreadLocal);
+};
+
+# endif  // GTEST_HAS_MUTEX_AND_THREAD_LOCAL_
+
+#else  // GTEST_IS_THREADSAFE
+
+// A dummy implementation of synchronization primitives (mutex, lock,
+// and thread-local variable).  Necessary for compiling Google Test where
+// mutex is not supported - using Google Test in multiple threads is not
+// supported on such platforms.
+
+class Mutex {
+ public:
+  Mutex() {}
+  void Lock() {}
+  void Unlock() {}
+  void AssertHeld() const {}
+};
+
+# define GTEST_DECLARE_STATIC_MUTEX_(mutex) \
+  extern ::testing::internal::Mutex mutex
+
+# define GTEST_DEFINE_STATIC_MUTEX_(mutex) ::testing::internal::Mutex mutex
+
+// We cannot name this class MutexLock because the ctor declaration would
+// conflict with a macro named MutexLock, which is defined on some
+// platforms. That macro is used as a defensive measure to prevent against
+// inadvertent misuses of MutexLock like "MutexLock(&mu)" rather than
+// "MutexLock l(&mu)".  Hence the typedef trick below.
+class GTestMutexLock {
+ public:
+  explicit GTestMutexLock(Mutex*) {}  // NOLINT
+};
+
+typedef GTestMutexLock MutexLock;
+
+template <typename T>
+class GTEST_API_ ThreadLocal {
+ public:
+  ThreadLocal() : value_() {}
+  explicit ThreadLocal(const T& value) : value_(value) {}
+  T* pointer() { return &value_; }
+  const T* pointer() const { return &value_; }
+  const T& get() const { return value_; }
+  void set(const T& value) { value_ = value; }
+ private:
+  T value_;
+};
+
+#endif  // GTEST_IS_THREADSAFE
+
+// Returns the number of threads running in the process, or 0 to indicate that
+// we cannot detect it.
+GTEST_API_ size_t GetThreadCount();
+
+#if GTEST_OS_WINDOWS
+# define GTEST_PATH_SEP_ "\\"
+# define GTEST_HAS_ALT_PATH_SEP_ 1
+#else
+# define GTEST_PATH_SEP_ "/"
+# define GTEST_HAS_ALT_PATH_SEP_ 0
+#endif  // GTEST_OS_WINDOWS
+
+// Utilities for char.
+
+// isspace(int ch) and friends accept an unsigned char or EOF.  char
+// may be signed, depending on the compiler (or compiler flags).
+// Therefore we need to cast a char to unsigned char before calling
+// isspace(), etc.
+
+inline bool IsAlpha(char ch) {
+  return isalpha(static_cast<unsigned char>(ch)) != 0;
+}
+inline bool IsAlNum(char ch) {
+  return isalnum(static_cast<unsigned char>(ch)) != 0;
+}
+inline bool IsDigit(char ch) {
+  return isdigit(static_cast<unsigned char>(ch)) != 0;
+}
+inline bool IsLower(char ch) {
+  return islower(static_cast<unsigned char>(ch)) != 0;
+}
+inline bool IsSpace(char ch) {
+  return isspace(static_cast<unsigned char>(ch)) != 0;
+}
+inline bool IsUpper(char ch) {
+  return isupper(static_cast<unsigned char>(ch)) != 0;
+}
+inline bool IsXDigit(char ch) {
+  return isxdigit(static_cast<unsigned char>(ch)) != 0;
+}
+#ifdef __cpp_char8_t
+inline bool IsXDigit(char8_t ch) {
+  return isxdigit(static_cast<unsigned char>(ch)) != 0;
+}
+#endif
+inline bool IsXDigit(char16_t ch) {
+  const unsigned char low_byte = static_cast<unsigned char>(ch);
+  return ch == low_byte && isxdigit(low_byte) != 0;
+}
+inline bool IsXDigit(char32_t ch) {
+  const unsigned char low_byte = static_cast<unsigned char>(ch);
+  return ch == low_byte && isxdigit(low_byte) != 0;
+}
+inline bool IsXDigit(wchar_t ch) {
+  const unsigned char low_byte = static_cast<unsigned char>(ch);
+  return ch == low_byte && isxdigit(low_byte) != 0;
+}
+
+inline char ToLower(char ch) {
+  return static_cast<char>(tolower(static_cast<unsigned char>(ch)));
+}
+inline char ToUpper(char ch) {
+  return static_cast<char>(toupper(static_cast<unsigned char>(ch)));
+}
+
+inline std::string StripTrailingSpaces(std::string str) {
+  std::string::iterator it = str.end();
+  while (it != str.begin() && IsSpace(*--it))
+    it = str.erase(it);
+  return str;
+}
+
+// The testing::internal::posix namespace holds wrappers for common
+// POSIX functions.  These wrappers hide the differences between
+// Windows/MSVC and POSIX systems.  Since some compilers define these
+// standard functions as macros, the wrapper cannot have the same name
+// as the wrapped function.
+
+namespace posix {
+
+// Functions with a different name on Windows.
+
+#if GTEST_OS_WINDOWS
+
+typedef struct _stat StatStruct;
+
+# ifdef __BORLANDC__
+inline int DoIsATTY(int fd) { return isatty(fd); }
+inline int StrCaseCmp(const char* s1, const char* s2) {
+  return stricmp(s1, s2);
+}
+inline char* StrDup(const char* src) { return strdup(src); }
+# else  // !__BORLANDC__
+#  if GTEST_OS_WINDOWS_MOBILE
+inline int DoIsATTY(int /* fd */) { return 0; }
+#  else
+inline int DoIsATTY(int fd) { return _isatty(fd); }
+#  endif  // GTEST_OS_WINDOWS_MOBILE
+inline int StrCaseCmp(const char* s1, const char* s2) {
+  return _stricmp(s1, s2);
+}
+inline char* StrDup(const char* src) { return _strdup(src); }
+# endif  // __BORLANDC__
+
+# if GTEST_OS_WINDOWS_MOBILE
+inline int FileNo(FILE* file) { return reinterpret_cast<int>(_fileno(file)); }
+// Stat(), RmDir(), and IsDir() are not needed on Windows CE at this
+// time and thus not defined there.
+# else
+inline int FileNo(FILE* file) { return _fileno(file); }
+inline int Stat(const char* path, StatStruct* buf) { return _stat(path, buf); }
+inline int RmDir(const char* dir) { return _rmdir(dir); }
+inline bool IsDir(const StatStruct& st) {
+  return (_S_IFDIR & st.st_mode) != 0;
+}
+# endif  // GTEST_OS_WINDOWS_MOBILE
+
+#elif GTEST_OS_ESP8266
+typedef struct stat StatStruct;
+
+inline int FileNo(FILE* file) { return fileno(file); }
+inline int DoIsATTY(int fd) { return isatty(fd); }
+inline int Stat(const char* path, StatStruct* buf) {
+  // stat function not implemented on ESP8266
+  return 0;
+}
+inline int StrCaseCmp(const char* s1, const char* s2) {
+  return strcasecmp(s1, s2);
+}
+inline char* StrDup(const char* src) { return strdup(src); }
+inline int RmDir(const char* dir) { return rmdir(dir); }
+inline bool IsDir(const StatStruct& st) { return S_ISDIR(st.st_mode); }
+
+#else
+
+typedef struct stat StatStruct;
+
+inline int FileNo(FILE* file) { return fileno(file); }
+inline int DoIsATTY(int fd) { return isatty(fd); }
+inline int Stat(const char* path, StatStruct* buf) { return stat(path, buf); }
+inline int StrCaseCmp(const char* s1, const char* s2) {
+  return strcasecmp(s1, s2);
+}
+inline char* StrDup(const char* src) { return strdup(src); }
+inline int RmDir(const char* dir) { return rmdir(dir); }
+inline bool IsDir(const StatStruct& st) { return S_ISDIR(st.st_mode); }
+
+#endif  // GTEST_OS_WINDOWS
+
+inline int IsATTY(int fd) {
+  // DoIsATTY might change errno (for example ENOTTY in case you redirect stdout
+  // to a file on Linux), which is unexpected, so save the previous value, and
+  // restore it after the call.
+  int savedErrno = errno;
+  int isAttyValue = DoIsATTY(fd);
+  errno = savedErrno;
+
+  return isAttyValue;
+}
+
+// Functions deprecated by MSVC 8.0.
+
+GTEST_DISABLE_MSC_DEPRECATED_PUSH_()
+
+// ChDir(), FReopen(), FDOpen(), Read(), Write(), Close(), and
+// StrError() aren't needed on Windows CE at this time and thus not
+// defined there.
+
+#if !GTEST_OS_WINDOWS_MOBILE && !GTEST_OS_WINDOWS_PHONE && \
+    !GTEST_OS_WINDOWS_RT && !GTEST_OS_ESP8266 && !GTEST_OS_XTENSA
+inline int ChDir(const char* dir) { return chdir(dir); }
+#endif
+inline FILE* FOpen(const char* path, const char* mode) {
+#if GTEST_OS_WINDOWS && !GTEST_OS_WINDOWS_MINGW
+  struct wchar_codecvt : public std::codecvt<wchar_t, char, std::mbstate_t> {};
+  std::wstring_convert<wchar_codecvt> converter;
+  std::wstring wide_path = converter.from_bytes(path);
+  std::wstring wide_mode = converter.from_bytes(mode);
+  return _wfopen(wide_path.c_str(), wide_mode.c_str());
+#else  // GTEST_OS_WINDOWS && !GTEST_OS_WINDOWS_MINGW
+  return fopen(path, mode);
+#endif  // GTEST_OS_WINDOWS && !GTEST_OS_WINDOWS_MINGW
+}
+#if !GTEST_OS_WINDOWS_MOBILE
+inline FILE *FReopen(const char* path, const char* mode, FILE* stream) {
+  return freopen(path, mode, stream);
+}
+inline FILE* FDOpen(int fd, const char* mode) { return fdopen(fd, mode); }
+#endif
+inline int FClose(FILE* fp) { return fclose(fp); }
+#if !GTEST_OS_WINDOWS_MOBILE
+inline int Read(int fd, void* buf, unsigned int count) {
+  return static_cast<int>(read(fd, buf, count));
+}
+inline int Write(int fd, const void* buf, unsigned int count) {
+  return static_cast<int>(write(fd, buf, count));
+}
+inline int Close(int fd) { return close(fd); }
+inline const char* StrError(int errnum) { return strerror(errnum); }
+#endif
+inline const char* GetEnv(const char* name) {
+#if GTEST_OS_WINDOWS_MOBILE || GTEST_OS_WINDOWS_PHONE || \
+    GTEST_OS_WINDOWS_RT || GTEST_OS_ESP8266 || GTEST_OS_XTENSA
+  // We are on an embedded platform, which has no environment variables.
+  static_cast<void>(name);  // To prevent 'unused argument' warning.
+  return nullptr;
+#elif defined(__BORLANDC__) || defined(__SunOS_5_8) || defined(__SunOS_5_9)
+  // Environment variables which we programmatically clear will be set to the
+  // empty string rather than unset (NULL).  Handle that case.
+  const char* const env = getenv(name);
+  return (env != nullptr && env[0] != '\0') ? env : nullptr;
+#else
+  return getenv(name);
+#endif
+}
+
+GTEST_DISABLE_MSC_DEPRECATED_POP_()
+
+#if GTEST_OS_WINDOWS_MOBILE
+// Windows CE has no C library. The abort() function is used in
+// several places in Google Test. This implementation provides a reasonable
+// imitation of standard behaviour.
+[[noreturn]] void Abort();
+#else
+[[noreturn]] inline void Abort() { abort(); }
+#endif  // GTEST_OS_WINDOWS_MOBILE
+
+}  // namespace posix
+
+// MSVC "deprecates" snprintf and issues warnings wherever it is used.  In
+// order to avoid these warnings, we need to use _snprintf or _snprintf_s on
+// MSVC-based platforms.  We map the GTEST_SNPRINTF_ macro to the appropriate
+// function in order to achieve that.  We use macro definition here because
+// snprintf is a variadic function.
+#if _MSC_VER && !GTEST_OS_WINDOWS_MOBILE
+// MSVC 2005 and above support variadic macros.
+# define GTEST_SNPRINTF_(buffer, size, format, ...) \
+     _snprintf_s(buffer, size, size, format, __VA_ARGS__)
+#elif defined(_MSC_VER)
+// Windows CE does not define _snprintf_s
+# define GTEST_SNPRINTF_ _snprintf
+#else
+# define GTEST_SNPRINTF_ snprintf
+#endif
+
+// The biggest signed integer type the compiler supports.
+//
+// long long is guaranteed to be at least 64-bits in C++11.
+using BiggestInt = long long;  // NOLINT
+
+// The maximum number a BiggestInt can represent.
+constexpr BiggestInt kMaxBiggestInt = (std::numeric_limits<BiggestInt>::max)();
+
+// This template class serves as a compile-time function from size to
+// type.  It maps a size in bytes to a primitive type with that
+// size. e.g.
+//
+//   TypeWithSize<4>::UInt
+//
+// is typedef-ed to be unsigned int (unsigned integer made up of 4
+// bytes).
+//
+// Such functionality should belong to STL, but I cannot find it
+// there.
+//
+// Google Test uses this class in the implementation of floating-point
+// comparison.
+//
+// For now it only handles UInt (unsigned int) as that's all Google Test
+// needs.  Other types can be easily added in the future if need
+// arises.
+template <size_t size>
+class TypeWithSize {
+ public:
+  // This prevents the user from using TypeWithSize<N> with incorrect
+  // values of N.
+  using UInt = void;
+};
+
+// The specialization for size 4.
+template <>
+class TypeWithSize<4> {
+ public:
+  using Int = std::int32_t;
+  using UInt = std::uint32_t;
+};
+
+// The specialization for size 8.
+template <>
+class TypeWithSize<8> {
+ public:
+  using Int = std::int64_t;
+  using UInt = std::uint64_t;
+};
+
+// Integer types of known sizes.
+using TimeInMillis = int64_t;  // Represents time in milliseconds.
+
+// Utilities for command line flags and environment variables.
+
+// Macro for referencing flags.
+#if !defined(GTEST_FLAG)
+# define GTEST_FLAG(name) FLAGS_gtest_##name
+#endif  // !defined(GTEST_FLAG)
+
+#if !defined(GTEST_USE_OWN_FLAGFILE_FLAG_)
+# define GTEST_USE_OWN_FLAGFILE_FLAG_ 1
+#endif  // !defined(GTEST_USE_OWN_FLAGFILE_FLAG_)
+
+#if !defined(GTEST_DECLARE_bool_)
+# define GTEST_FLAG_SAVER_ ::testing::internal::GTestFlagSaver
+
+// Macros for declaring flags.
+# define GTEST_DECLARE_bool_(name) GTEST_API_ extern bool GTEST_FLAG(name)
+# define GTEST_DECLARE_int32_(name) \
+    GTEST_API_ extern std::int32_t GTEST_FLAG(name)
+# define GTEST_DECLARE_string_(name) \
+    GTEST_API_ extern ::std::string GTEST_FLAG(name)
+
+// Macros for defining flags.
+# define GTEST_DEFINE_bool_(name, default_val, doc) \
+    GTEST_API_ bool GTEST_FLAG(name) = (default_val)
+# define GTEST_DEFINE_int32_(name, default_val, doc) \
+    GTEST_API_ std::int32_t GTEST_FLAG(name) = (default_val)
+# define GTEST_DEFINE_string_(name, default_val, doc) \
+    GTEST_API_ ::std::string GTEST_FLAG(name) = (default_val)
+
+#endif  // !defined(GTEST_DECLARE_bool_)
+
+// Thread annotations
+#if !defined(GTEST_EXCLUSIVE_LOCK_REQUIRED_)
+# define GTEST_EXCLUSIVE_LOCK_REQUIRED_(locks)
+# define GTEST_LOCK_EXCLUDED_(locks)
+#endif  // !defined(GTEST_EXCLUSIVE_LOCK_REQUIRED_)
+
+// Parses 'str' for a 32-bit signed integer.  If successful, writes the result
+// to *value and returns true; otherwise leaves *value unchanged and returns
+// false.
+GTEST_API_ bool ParseInt32(const Message& src_text, const char* str,
+                           int32_t* value);
+
+// Parses a bool/int32_t/string from the environment variable
+// corresponding to the given Google Test flag.
+bool BoolFromGTestEnv(const char* flag, bool default_val);
+GTEST_API_ int32_t Int32FromGTestEnv(const char* flag, int32_t default_val);
+std::string OutputFlagAlsoCheckEnvVar();
+const char* StringFromGTestEnv(const char* flag, const char* default_val);
+
+}  // namespace internal
+}  // namespace testing
+
+#if !defined(GTEST_INTERNAL_DEPRECATED)
+
+// Internal Macro to mark an API deprecated, for googletest usage only
+// Usage: class GTEST_INTERNAL_DEPRECATED(message) MyClass or
+// GTEST_INTERNAL_DEPRECATED(message) <return_type> myFunction(); Every usage of
+// a deprecated entity will trigger a warning when compiled with
+// `-Wdeprecated-declarations` option (clang, gcc, any __GNUC__ compiler).
+// For msvc /W3 option will need to be used
+// Note that for 'other' compilers this macro evaluates to nothing to prevent
+// compilations errors.
+#if defined(_MSC_VER)
+#define GTEST_INTERNAL_DEPRECATED(message) __declspec(deprecated(message))
+#elif defined(__GNUC__)
+#define GTEST_INTERNAL_DEPRECATED(message) __attribute__((deprecated(message)))
+#else
+#define GTEST_INTERNAL_DEPRECATED(message)
+#endif
+
+#endif  // !defined(GTEST_INTERNAL_DEPRECATED)
+
+#if GTEST_HAS_ABSL
+// Always use absl::any for UniversalPrinter<> specializations if googletest
+// is built with absl support.
+#define GTEST_INTERNAL_HAS_ANY 1
+#include "absl/types/any.h"
+namespace testing {
+namespace internal {
+using Any = ::absl::any;
+}  // namespace internal
+}  // namespace testing
+#else
+#ifdef __has_include
+#if __has_include(<any>) && __cplusplus >= 201703L
+// Otherwise for C++17 and higher use std::any for UniversalPrinter<>
+// specializations.
+#define GTEST_INTERNAL_HAS_ANY 1
+#include <any>
+namespace testing {
+namespace internal {
+using Any = ::std::any;
+}  // namespace internal
+}  // namespace testing
+// The case where absl is configured NOT to alias std::any is not
+// supported.
+#endif  // __has_include(<any>) && __cplusplus >= 201703L
+#endif  // __has_include
+#endif  // GTEST_HAS_ABSL
+
+#if GTEST_HAS_ABSL
+// Always use absl::optional for UniversalPrinter<> specializations if
+// googletest is built with absl support.
+#define GTEST_INTERNAL_HAS_OPTIONAL 1
+#include "absl/types/optional.h"
+namespace testing {
+namespace internal {
+template <typename T>
+using Optional = ::absl::optional<T>;
+}  // namespace internal
+}  // namespace testing
+#else
+#ifdef __has_include
+#if __has_include(<optional>) && __cplusplus >= 201703L
+// Otherwise for C++17 and higher use std::optional for UniversalPrinter<>
+// specializations.
+#define GTEST_INTERNAL_HAS_OPTIONAL 1
+#include <optional>
+namespace testing {
+namespace internal {
+template <typename T>
+using Optional = ::std::optional<T>;
+}  // namespace internal
+}  // namespace testing
+// The case where absl is configured NOT to alias std::optional is not
+// supported.
+#endif  // __has_include(<optional>) && __cplusplus >= 201703L
+#endif  // __has_include
+#endif  // GTEST_HAS_ABSL
+
+#if GTEST_HAS_ABSL
+// Always use absl::string_view for Matcher<> specializations if googletest
+// is built with absl support.
+# define GTEST_INTERNAL_HAS_STRING_VIEW 1
+#include "absl/strings/string_view.h"
+namespace testing {
+namespace internal {
+using StringView = ::absl::string_view;
+}  // namespace internal
+}  // namespace testing
+#else
+# ifdef __has_include
+#   if __has_include(<string_view>) && __cplusplus >= 201703L
+// Otherwise for C++17 and higher use std::string_view for Matcher<>
+// specializations.
+#   define GTEST_INTERNAL_HAS_STRING_VIEW 1
+#include <string_view>
+namespace testing {
+namespace internal {
+using StringView = ::std::string_view;
+}  // namespace internal
+}  // namespace testing
+// The case where absl is configured NOT to alias std::string_view is not
+// supported.
+#  endif  // __has_include(<string_view>) && __cplusplus >= 201703L
+# endif  // __has_include
+#endif  // GTEST_HAS_ABSL
+
+#if GTEST_HAS_ABSL
+// Always use absl::variant for UniversalPrinter<> specializations if googletest
+// is built with absl support.
+#define GTEST_INTERNAL_HAS_VARIANT 1
+#include "absl/types/variant.h"
+namespace testing {
+namespace internal {
+template <typename... T>
+using Variant = ::absl::variant<T...>;
+}  // namespace internal
+}  // namespace testing
+#else
+#ifdef __has_include
+#if __has_include(<variant>) && __cplusplus >= 201703L
+// Otherwise for C++17 and higher use std::variant for UniversalPrinter<>
+// specializations.
+#define GTEST_INTERNAL_HAS_VARIANT 1
+#include <variant>
+namespace testing {
+namespace internal {
+template <typename... T>
+using Variant = ::std::variant<T...>;
+}  // namespace internal
+}  // namespace testing
+// The case where absl is configured NOT to alias std::variant is not supported.
+#endif  // __has_include(<variant>) && __cplusplus >= 201703L
+#endif  // __has_include
+#endif  // GTEST_HAS_ABSL
+
+#endif  // GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_PORT_H_
diff --git a/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-string.h b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-string.h
new file mode 100644
index 0000000..10f774f
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-string.h
@@ -0,0 +1,175 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// The Google C++ Testing and Mocking Framework (Google Test)
+//
+// This header file declares the String class and functions used internally by
+// Google Test.  They are subject to change without notice. They should not used
+// by code external to Google Test.
+//
+// This header file is #included by gtest-internal.h.
+// It should not be #included by other files.
+
+// GOOGLETEST_CM0001 DO NOT DELETE
+
+#ifndef GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_STRING_H_
+#define GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_STRING_H_
+
+#ifdef __BORLANDC__
+// string.h is not guaranteed to provide strcpy on C++ Builder.
+# include <mem.h>
+#endif
+
+#include <string.h>
+#include <cstdint>
+#include <string>
+
+#include "gtest/internal/gtest-port.h"
+
+namespace testing {
+namespace internal {
+
+// String - an abstract class holding static string utilities.
+class GTEST_API_ String {
+ public:
+  // Static utility methods
+
+  // Clones a 0-terminated C string, allocating memory using new.  The
+  // caller is responsible for deleting the return value using
+  // delete[].  Returns the cloned string, or NULL if the input is
+  // NULL.
+  //
+  // This is different from strdup() in string.h, which allocates
+  // memory using malloc().
+  static const char* CloneCString(const char* c_str);
+
+#if GTEST_OS_WINDOWS_MOBILE
+  // Windows CE does not have the 'ANSI' versions of Win32 APIs. To be
+  // able to pass strings to Win32 APIs on CE we need to convert them
+  // to 'Unicode', UTF-16.
+
+  // Creates a UTF-16 wide string from the given ANSI string, allocating
+  // memory using new. The caller is responsible for deleting the return
+  // value using delete[]. Returns the wide string, or NULL if the
+  // input is NULL.
+  //
+  // The wide string is created using the ANSI codepage (CP_ACP) to
+  // match the behaviour of the ANSI versions of Win32 calls and the
+  // C runtime.
+  static LPCWSTR AnsiToUtf16(const char* c_str);
+
+  // Creates an ANSI string from the given wide string, allocating
+  // memory using new. The caller is responsible for deleting the return
+  // value using delete[]. Returns the ANSI string, or NULL if the
+  // input is NULL.
+  //
+  // The returned string is created using the ANSI codepage (CP_ACP) to
+  // match the behaviour of the ANSI versions of Win32 calls and the
+  // C runtime.
+  static const char* Utf16ToAnsi(LPCWSTR utf16_str);
+#endif
+
+  // Compares two C strings.  Returns true if and only if they have the same
+  // content.
+  //
+  // Unlike strcmp(), this function can handle NULL argument(s).  A
+  // NULL C string is considered different to any non-NULL C string,
+  // including the empty string.
+  static bool CStringEquals(const char* lhs, const char* rhs);
+
+  // Converts a wide C string to a String using the UTF-8 encoding.
+  // NULL will be converted to "(null)".  If an error occurred during
+  // the conversion, "(failed to convert from wide string)" is
+  // returned.
+  static std::string ShowWideCString(const wchar_t* wide_c_str);
+
+  // Compares two wide C strings.  Returns true if and only if they have the
+  // same content.
+  //
+  // Unlike wcscmp(), this function can handle NULL argument(s).  A
+  // NULL C string is considered different to any non-NULL C string,
+  // including the empty string.
+  static bool WideCStringEquals(const wchar_t* lhs, const wchar_t* rhs);
+
+  // Compares two C strings, ignoring case.  Returns true if and only if
+  // they have the same content.
+  //
+  // Unlike strcasecmp(), this function can handle NULL argument(s).
+  // A NULL C string is considered different to any non-NULL C string,
+  // including the empty string.
+  static bool CaseInsensitiveCStringEquals(const char* lhs,
+                                           const char* rhs);
+
+  // Compares two wide C strings, ignoring case.  Returns true if and only if
+  // they have the same content.
+  //
+  // Unlike wcscasecmp(), this function can handle NULL argument(s).
+  // A NULL C string is considered different to any non-NULL wide C string,
+  // including the empty string.
+  // NB: The implementations on different platforms slightly differ.
+  // On windows, this method uses _wcsicmp which compares according to LC_CTYPE
+  // environment variable. On GNU platform this method uses wcscasecmp
+  // which compares according to LC_CTYPE category of the current locale.
+  // On MacOS X, it uses towlower, which also uses LC_CTYPE category of the
+  // current locale.
+  static bool CaseInsensitiveWideCStringEquals(const wchar_t* lhs,
+                                               const wchar_t* rhs);
+
+  // Returns true if and only if the given string ends with the given suffix,
+  // ignoring case. Any string is considered to end with an empty suffix.
+  static bool EndsWithCaseInsensitive(
+      const std::string& str, const std::string& suffix);
+
+  // Formats an int value as "%02d".
+  static std::string FormatIntWidth2(int value);  // "%02d" for width == 2
+
+  // Formats an int value to given width with leading zeros.
+  static std::string FormatIntWidthN(int value, int width);
+
+  // Formats an int value as "%X".
+  static std::string FormatHexInt(int value);
+
+  // Formats an int value as "%X".
+  static std::string FormatHexUInt32(uint32_t value);
+
+  // Formats a byte as "%02X".
+  static std::string FormatByte(unsigned char value);
+
+ private:
+  String();  // Not meant to be instantiated.
+};  // class String
+
+// Gets the content of the stringstream's buffer as an std::string.  Each '\0'
+// character in the buffer is replaced with "\\0".
+GTEST_API_ std::string StringStreamToString(::std::stringstream* stream);
+
+}  // namespace internal
+}  // namespace testing
+
+#endif  // GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_STRING_H_
diff --git a/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-type-util.h b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-type-util.h
new file mode 100644
index 0000000..b87a2e2
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/include/gtest/internal/gtest-type-util.h
@@ -0,0 +1,183 @@
+// Copyright 2008 Google Inc.
+// All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Type utilities needed for implementing typed and type-parameterized
+// tests.
+
+// GOOGLETEST_CM0001 DO NOT DELETE
+
+#ifndef GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_TYPE_UTIL_H_
+#define GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_TYPE_UTIL_H_
+
+#include "gtest/internal/gtest-port.h"
+
+// #ifdef __GNUC__ is too general here.  It is possible to use gcc without using
+// libstdc++ (which is where cxxabi.h comes from).
+# if GTEST_HAS_CXXABI_H_
+#  include <cxxabi.h>
+# elif defined(__HP_aCC)
+#  include <acxx_demangle.h>
+# endif  // GTEST_HASH_CXXABI_H_
+
+namespace testing {
+namespace internal {
+
+// Canonicalizes a given name with respect to the Standard C++ Library.
+// This handles removing the inline namespace within `std` that is
+// used by various standard libraries (e.g., `std::__1`).  Names outside
+// of namespace std are returned unmodified.
+inline std::string CanonicalizeForStdLibVersioning(std::string s) {
+  static const char prefix[] = "std::__";
+  if (s.compare(0, strlen(prefix), prefix) == 0) {
+    std::string::size_type end = s.find("::", strlen(prefix));
+    if (end != s.npos) {
+      // Erase everything between the initial `std` and the second `::`.
+      s.erase(strlen("std"), end - strlen("std"));
+    }
+  }
+  return s;
+}
+
+#if GTEST_HAS_RTTI
+// GetTypeName(const std::type_info&) returns a human-readable name of type T.
+inline std::string GetTypeName(const std::type_info& type) {
+  const char* const name = type.name();
+#if GTEST_HAS_CXXABI_H_ || defined(__HP_aCC)
+  int status = 0;
+  // gcc's implementation of typeid(T).name() mangles the type name,
+  // so we have to demangle it.
+#if GTEST_HAS_CXXABI_H_
+  using abi::__cxa_demangle;
+#endif  // GTEST_HAS_CXXABI_H_
+  char* const readable_name = __cxa_demangle(name, nullptr, nullptr, &status);
+  const std::string name_str(status == 0 ? readable_name : name);
+  free(readable_name);
+  return CanonicalizeForStdLibVersioning(name_str);
+#else
+  return name;
+#endif  // GTEST_HAS_CXXABI_H_ || __HP_aCC
+}
+#endif  // GTEST_HAS_RTTI
+
+// GetTypeName<T>() returns a human-readable name of type T if and only if
+// RTTI is enabled, otherwise it returns a dummy type name.
+// NB: This function is also used in Google Mock, so don't move it inside of
+// the typed-test-only section below.
+template <typename T>
+std::string GetTypeName() {
+#if GTEST_HAS_RTTI
+  return GetTypeName(typeid(T));
+#else
+  return "<type>";
+#endif  // GTEST_HAS_RTTI
+}
+
+// A unique type indicating an empty node
+struct None {};
+
+# define GTEST_TEMPLATE_ template <typename T> class
+
+// The template "selector" struct TemplateSel<Tmpl> is used to
+// represent Tmpl, which must be a class template with one type
+// parameter, as a type.  TemplateSel<Tmpl>::Bind<T>::type is defined
+// as the type Tmpl<T>.  This allows us to actually instantiate the
+// template "selected" by TemplateSel<Tmpl>.
+//
+// This trick is necessary for simulating typedef for class templates,
+// which C++ doesn't support directly.
+template <GTEST_TEMPLATE_ Tmpl>
+struct TemplateSel {
+  template <typename T>
+  struct Bind {
+    typedef Tmpl<T> type;
+  };
+};
+
+# define GTEST_BIND_(TmplSel, T) \
+  TmplSel::template Bind<T>::type
+
+template <GTEST_TEMPLATE_ Head_, GTEST_TEMPLATE_... Tail_>
+struct Templates {
+  using Head = TemplateSel<Head_>;
+  using Tail = Templates<Tail_...>;
+};
+
+template <GTEST_TEMPLATE_ Head_>
+struct Templates<Head_> {
+  using Head = TemplateSel<Head_>;
+  using Tail = None;
+};
+
+// Tuple-like type lists
+template <typename Head_, typename... Tail_>
+struct Types {
+  using Head = Head_;
+  using Tail = Types<Tail_...>;
+};
+
+template <typename Head_>
+struct Types<Head_> {
+  using Head = Head_;
+  using Tail = None;
+};
+
+// Helper metafunctions to tell apart a single type from types
+// generated by ::testing::Types
+template <typename... Ts>
+struct ProxyTypeList {
+  using type = Types<Ts...>;
+};
+
+template <typename>
+struct is_proxy_type_list : std::false_type {};
+
+template <typename... Ts>
+struct is_proxy_type_list<ProxyTypeList<Ts...>> : std::true_type {};
+
+// Generator which conditionally creates type lists.
+// It recognizes if a requested type list should be created
+// and prevents creating a new type list nested within another one.
+template <typename T>
+struct GenerateTypeList {
+ private:
+  using proxy = typename std::conditional<is_proxy_type_list<T>::value, T,
+                                          ProxyTypeList<T>>::type;
+
+ public:
+  using type = typename proxy::type;
+};
+
+}  // namespace internal
+
+template <typename... Ts>
+using Types = internal::ProxyTypeList<Ts...>;
+
+}  // namespace testing
+
+#endif  // GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_TYPE_UTIL_H_
diff --git a/leveldb_base/third_party/googletest/googletest/samples/prime_tables.h b/leveldb_base/third_party/googletest/googletest/samples/prime_tables.h
new file mode 100644
index 0000000..3a10352
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/samples/prime_tables.h
@@ -0,0 +1,126 @@
+// Copyright 2008 Google Inc.
+// All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+
+// This provides interface PrimeTable that determines whether a number is a
+// prime and determines a next prime number. This interface is used
+// in Google Test samples demonstrating use of parameterized tests.
+
+#ifndef GOOGLETEST_SAMPLES_PRIME_TABLES_H_
+#define GOOGLETEST_SAMPLES_PRIME_TABLES_H_
+
+#include <algorithm>
+
+// The prime table interface.
+class PrimeTable {
+ public:
+  virtual ~PrimeTable() {}
+
+  // Returns true if and only if n is a prime number.
+  virtual bool IsPrime(int n) const = 0;
+
+  // Returns the smallest prime number greater than p; or returns -1
+  // if the next prime is beyond the capacity of the table.
+  virtual int GetNextPrime(int p) const = 0;
+};
+
+// Implementation #1 calculates the primes on-the-fly.
+class OnTheFlyPrimeTable : public PrimeTable {
+ public:
+  bool IsPrime(int n) const override {
+    if (n <= 1) return false;
+
+    for (int i = 2; i*i <= n; i++) {
+      // n is divisible by an integer other than 1 and itself.
+      if ((n % i) == 0) return false;
+    }
+
+    return true;
+  }
+
+  int GetNextPrime(int p) const override {
+    if (p < 0) return -1;
+
+    for (int n = p + 1;; n++) {
+      if (IsPrime(n)) return n;
+    }
+  }
+};
+
+// Implementation #2 pre-calculates the primes and stores the result
+// in an array.
+class PreCalculatedPrimeTable : public PrimeTable {
+ public:
+  // 'max' specifies the maximum number the prime table holds.
+  explicit PreCalculatedPrimeTable(int max)
+      : is_prime_size_(max + 1), is_prime_(new bool[max + 1]) {
+    CalculatePrimesUpTo(max);
+  }
+  ~PreCalculatedPrimeTable() override { delete[] is_prime_; }
+
+  bool IsPrime(int n) const override {
+    return 0 <= n && n < is_prime_size_ && is_prime_[n];
+  }
+
+  int GetNextPrime(int p) const override {
+    for (int n = p + 1; n < is_prime_size_; n++) {
+      if (is_prime_[n]) return n;
+    }
+
+    return -1;
+  }
+
+ private:
+  void CalculatePrimesUpTo(int max) {
+    ::std::fill(is_prime_, is_prime_ + is_prime_size_, true);
+    is_prime_[0] = is_prime_[1] = false;
+
+    // Checks every candidate for prime number (we know that 2 is the only even
+    // prime).
+    for (int i = 2; i*i <= max; i += i%2+1) {
+      if (!is_prime_[i]) continue;
+
+      // Marks all multiples of i (except i itself) as non-prime.
+      // We are starting here from i-th multiplier, because all smaller
+      // complex numbers were already marked.
+      for (int j = i*i; j <= max; j += i) {
+        is_prime_[j] = false;
+      }
+    }
+  }
+
+  const int is_prime_size_;
+  bool* const is_prime_;
+
+  // Disables compiler warning "assignment operator could not be generated."
+  void operator=(const PreCalculatedPrimeTable& rhs);
+};
+
+#endif  // GOOGLETEST_SAMPLES_PRIME_TABLES_H_
diff --git a/leveldb_base/third_party/googletest/googletest/samples/sample1.cc b/leveldb_base/third_party/googletest/googletest/samples/sample1.cc
new file mode 100644
index 0000000..1d42759
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/samples/sample1.cc
@@ -0,0 +1,66 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// A sample program demonstrating using Google C++ testing framework.
+
+#include "sample1.h"
+
+// Returns n! (the factorial of n).  For negative n, n! is defined to be 1.
+int Factorial(int n) {
+  int result = 1;
+  for (int i = 1; i <= n; i++) {
+    result *= i;
+  }
+
+  return result;
+}
+
+// Returns true if and only if n is a prime number.
+bool IsPrime(int n) {
+  // Trivial case 1: small numbers
+  if (n <= 1) return false;
+
+  // Trivial case 2: even numbers
+  if (n % 2 == 0) return n == 2;
+
+  // Now, we have that n is odd and n >= 3.
+
+  // Try to divide n by every odd number i, starting from 3
+  for (int i = 3; ; i += 2) {
+    // We only have to try i up to the square root of n
+    if (i > n/i) break;
+
+    // Now, we have i <= n/i < n.
+    // If n is divisible by i, n is not prime.
+    if (n % i == 0) return false;
+  }
+
+  // n has no integer factor in the range (1, n), and thus is prime.
+  return true;
+}
diff --git a/leveldb_base/third_party/googletest/googletest/samples/sample1.h b/leveldb_base/third_party/googletest/googletest/samples/sample1.h
new file mode 100644
index 0000000..ba392cf
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/samples/sample1.h
@@ -0,0 +1,41 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// A sample program demonstrating using Google C++ testing framework.
+
+#ifndef GOOGLETEST_SAMPLES_SAMPLE1_H_
+#define GOOGLETEST_SAMPLES_SAMPLE1_H_
+
+// Returns n! (the factorial of n).  For negative n, n! is defined to be 1.
+int Factorial(int n);
+
+// Returns true if and only if n is a prime number.
+bool IsPrime(int n);
+
+#endif  // GOOGLETEST_SAMPLES_SAMPLE1_H_
diff --git a/leveldb_base/third_party/googletest/googletest/samples/sample10_unittest.cc b/leveldb_base/third_party/googletest/googletest/samples/sample10_unittest.cc
new file mode 100644
index 0000000..36cdac2
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/samples/sample10_unittest.cc
@@ -0,0 +1,139 @@
+// Copyright 2009 Google Inc. All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// This sample shows how to use Google Test listener API to implement
+// a primitive leak checker.
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "gtest/gtest.h"
+using ::testing::EmptyTestEventListener;
+using ::testing::InitGoogleTest;
+using ::testing::Test;
+using ::testing::TestEventListeners;
+using ::testing::TestInfo;
+using ::testing::TestPartResult;
+using ::testing::UnitTest;
+
+namespace {
+// We will track memory used by this class.
+class Water {
+ public:
+  // Normal Water declarations go here.
+
+  // operator new and operator delete help us control water allocation.
+  void* operator new(size_t allocation_size) {
+    allocated_++;
+    return malloc(allocation_size);
+  }
+
+  void operator delete(void* block, size_t /* allocation_size */) {
+    allocated_--;
+    free(block);
+  }
+
+  static int allocated() { return allocated_; }
+
+ private:
+  static int allocated_;
+};
+
+int Water::allocated_ = 0;
+
+// This event listener monitors how many Water objects are created and
+// destroyed by each test, and reports a failure if a test leaks some Water
+// objects. It does this by comparing the number of live Water objects at
+// the beginning of a test and at the end of a test.
+class LeakChecker : public EmptyTestEventListener {
+ private:
+  // Called before a test starts.
+  void OnTestStart(const TestInfo& /* test_info */) override {
+    initially_allocated_ = Water::allocated();
+  }
+
+  // Called after a test ends.
+  void OnTestEnd(const TestInfo& /* test_info */) override {
+    int difference = Water::allocated() - initially_allocated_;
+
+    // You can generate a failure in any event handler except
+    // OnTestPartResult. Just use an appropriate Google Test assertion to do
+    // it.
+    EXPECT_LE(difference, 0) << "Leaked " << difference << " unit(s) of Water!";
+  }
+
+  int initially_allocated_;
+};
+
+TEST(ListenersTest, DoesNotLeak) {
+  Water* water = new Water;
+  delete water;
+}
+
+// This should fail when the --check_for_leaks command line flag is
+// specified.
+TEST(ListenersTest, LeaksWater) {
+  Water* water = new Water;
+  EXPECT_TRUE(water != nullptr);
+}
+}  // namespace
+
+int main(int argc, char **argv) {
+  InitGoogleTest(&argc, argv);
+
+  bool check_for_leaks = false;
+  if (argc > 1 && strcmp(argv[1], "--check_for_leaks") == 0 )
+    check_for_leaks = true;
+  else
+    printf("%s\n", "Run this program with --check_for_leaks to enable "
+           "custom leak checking in the tests.");
+
+  // If we are given the --check_for_leaks command line flag, installs the
+  // leak checker.
+  if (check_for_leaks) {
+    TestEventListeners& listeners = UnitTest::GetInstance()->listeners();
+
+    // Adds the leak checker to the end of the test event listener list,
+    // after the default text output printer and the default XML report
+    // generator.
+    //
+    // The order is important - it ensures that failures generated in the
+    // leak checker's OnTestEnd() method are processed by the text and XML
+    // printers *before* their OnTestEnd() methods are called, such that
+    // they are attributed to the right test. Remember that a listener
+    // receives an OnXyzStart event *after* listeners preceding it in the
+    // list received that event, and receives an OnXyzEnd event *before*
+    // listeners preceding it.
+    //
+    // We don't need to worry about deleting the new listener later, as
+    // Google Test will do it.
+    listeners.Append(new LeakChecker);
+  }
+  return RUN_ALL_TESTS();
+}
diff --git a/leveldb_base/third_party/googletest/googletest/samples/sample1_unittest.cc b/leveldb_base/third_party/googletest/googletest/samples/sample1_unittest.cc
new file mode 100644
index 0000000..cb08b61
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/samples/sample1_unittest.cc
@@ -0,0 +1,151 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// A sample program demonstrating using Google C++ testing framework.
+
+// This sample shows how to write a simple unit test for a function,
+// using Google C++ testing framework.
+//
+// Writing a unit test using Google C++ testing framework is easy as 1-2-3:
+
+
+// Step 1. Include necessary header files such that the stuff your
+// test logic needs is declared.
+//
+// Don't forget gtest.h, which declares the testing framework.
+
+#include <limits.h>
+#include "sample1.h"
+#include "gtest/gtest.h"
+namespace {
+
+// Step 2. Use the TEST macro to define your tests.
+//
+// TEST has two parameters: the test case name and the test name.
+// After using the macro, you should define your test logic between a
+// pair of braces.  You can use a bunch of macros to indicate the
+// success or failure of a test.  EXPECT_TRUE and EXPECT_EQ are
+// examples of such macros.  For a complete list, see gtest.h.
+//
+// <TechnicalDetails>
+//
+// In Google Test, tests are grouped into test cases.  This is how we
+// keep test code organized.  You should put logically related tests
+// into the same test case.
+//
+// The test case name and the test name should both be valid C++
+// identifiers.  And you should not use underscore (_) in the names.
+//
+// Google Test guarantees that each test you define is run exactly
+// once, but it makes no guarantee on the order the tests are
+// executed.  Therefore, you should write your tests in such a way
+// that their results don't depend on their order.
+//
+// </TechnicalDetails>
+
+
+// Tests Factorial().
+
+// Tests factorial of negative numbers.
+TEST(FactorialTest, Negative) {
+  // This test is named "Negative", and belongs to the "FactorialTest"
+  // test case.
+  EXPECT_EQ(1, Factorial(-5));
+  EXPECT_EQ(1, Factorial(-1));
+  EXPECT_GT(Factorial(-10), 0);
+
+  // <TechnicalDetails>
+  //
+  // EXPECT_EQ(expected, actual) is the same as
+  //
+  //   EXPECT_TRUE((expected) == (actual))
+  //
+  // except that it will print both the expected value and the actual
+  // value when the assertion fails.  This is very helpful for
+  // debugging.  Therefore in this case EXPECT_EQ is preferred.
+  //
+  // On the other hand, EXPECT_TRUE accepts any Boolean expression,
+  // and is thus more general.
+  //
+  // </TechnicalDetails>
+}
+
+// Tests factorial of 0.
+TEST(FactorialTest, Zero) {
+  EXPECT_EQ(1, Factorial(0));
+}
+
+// Tests factorial of positive numbers.
+TEST(FactorialTest, Positive) {
+  EXPECT_EQ(1, Factorial(1));
+  EXPECT_EQ(2, Factorial(2));
+  EXPECT_EQ(6, Factorial(3));
+  EXPECT_EQ(40320, Factorial(8));
+}
+
+
+// Tests IsPrime()
+
+// Tests negative input.
+TEST(IsPrimeTest, Negative) {
+  // This test belongs to the IsPrimeTest test case.
+
+  EXPECT_FALSE(IsPrime(-1));
+  EXPECT_FALSE(IsPrime(-2));
+  EXPECT_FALSE(IsPrime(INT_MIN));
+}
+
+// Tests some trivial cases.
+TEST(IsPrimeTest, Trivial) {
+  EXPECT_FALSE(IsPrime(0));
+  EXPECT_FALSE(IsPrime(1));
+  EXPECT_TRUE(IsPrime(2));
+  EXPECT_TRUE(IsPrime(3));
+}
+
+// Tests positive input.
+TEST(IsPrimeTest, Positive) {
+  EXPECT_FALSE(IsPrime(4));
+  EXPECT_TRUE(IsPrime(5));
+  EXPECT_FALSE(IsPrime(6));
+  EXPECT_TRUE(IsPrime(23));
+}
+}  // namespace
+
+// Step 3. Call RUN_ALL_TESTS() in main().
+//
+// We do this by linking in src/gtest_main.cc file, which consists of
+// a main() function which calls RUN_ALL_TESTS() for us.
+//
+// This runs all the tests you've defined, prints the result, and
+// returns 0 if successful, or 1 otherwise.
+//
+// Did you notice that we didn't register the tests?  The
+// RUN_ALL_TESTS() macro magically knows about all the tests we
+// defined.  Isn't this convenient?
diff --git a/leveldb_base/third_party/googletest/googletest/samples/sample2.cc b/leveldb_base/third_party/googletest/googletest/samples/sample2.cc
new file mode 100644
index 0000000..d8e8723
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/samples/sample2.cc
@@ -0,0 +1,54 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// A sample program demonstrating using Google C++ testing framework.
+
+#include "sample2.h"
+
+#include <string.h>
+
+// Clones a 0-terminated C string, allocating memory using new.
+const char* MyString::CloneCString(const char* a_c_string) {
+  if (a_c_string == nullptr) return nullptr;
+
+  const size_t len = strlen(a_c_string);
+  char* const clone = new char[ len + 1 ];
+  memcpy(clone, a_c_string, len + 1);
+
+  return clone;
+}
+
+// Sets the 0-terminated C string this MyString object
+// represents.
+void MyString::Set(const char* a_c_string) {
+  // Makes sure this works when c_string == c_string_
+  const char* const temp = MyString::CloneCString(a_c_string);
+  delete[] c_string_;
+  c_string_ = temp;
+}
diff --git a/leveldb_base/third_party/googletest/googletest/samples/sample2.h b/leveldb_base/third_party/googletest/googletest/samples/sample2.h
new file mode 100644
index 0000000..0f98689
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/samples/sample2.h
@@ -0,0 +1,80 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// A sample program demonstrating using Google C++ testing framework.
+
+#ifndef GOOGLETEST_SAMPLES_SAMPLE2_H_
+#define GOOGLETEST_SAMPLES_SAMPLE2_H_
+
+#include <string.h>
+
+
+// A simple string class.
+class MyString {
+ private:
+  const char* c_string_;
+  const MyString& operator=(const MyString& rhs);
+
+ public:
+  // Clones a 0-terminated C string, allocating memory using new.
+  static const char* CloneCString(const char* a_c_string);
+
+  ////////////////////////////////////////////////////////////
+  //
+  // C'tors
+
+  // The default c'tor constructs a NULL string.
+  MyString() : c_string_(nullptr) {}
+
+  // Constructs a MyString by cloning a 0-terminated C string.
+  explicit MyString(const char* a_c_string) : c_string_(nullptr) {
+    Set(a_c_string);
+  }
+
+  // Copy c'tor
+  MyString(const MyString& string) : c_string_(nullptr) {
+    Set(string.c_string_);
+  }
+
+  ////////////////////////////////////////////////////////////
+  //
+  // D'tor.  MyString is intended to be a final class, so the d'tor
+  // doesn't need to be virtual.
+  ~MyString() { delete[] c_string_; }
+
+  // Gets the 0-terminated C string this MyString object represents.
+  const char* c_string() const { return c_string_; }
+
+  size_t Length() const { return c_string_ == nullptr ? 0 : strlen(c_string_); }
+
+  // Sets the 0-terminated C string this MyString object represents.
+  void Set(const char* c_string);
+};
+
+#endif  // GOOGLETEST_SAMPLES_SAMPLE2_H_
diff --git a/leveldb_base/third_party/googletest/googletest/samples/sample2_unittest.cc b/leveldb_base/third_party/googletest/googletest/samples/sample2_unittest.cc
new file mode 100644
index 0000000..41e31c1
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/samples/sample2_unittest.cc
@@ -0,0 +1,107 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// A sample program demonstrating using Google C++ testing framework.
+
+// This sample shows how to write a more complex unit test for a class
+// that has multiple member functions.
+//
+// Usually, it's a good idea to have one test for each method in your
+// class.  You don't have to do that exactly, but it helps to keep
+// your tests organized.  You may also throw in additional tests as
+// needed.
+
+#include "sample2.h"
+#include "gtest/gtest.h"
+namespace {
+// In this example, we test the MyString class (a simple string).
+
+// Tests the default c'tor.
+TEST(MyString, DefaultConstructor) {
+  const MyString s;
+
+  // Asserts that s.c_string() returns NULL.
+  //
+  // <TechnicalDetails>
+  //
+  // If we write NULL instead of
+  //
+  //   static_cast<const char *>(NULL)
+  //
+  // in this assertion, it will generate a warning on gcc 3.4.  The
+  // reason is that EXPECT_EQ needs to know the types of its
+  // arguments in order to print them when it fails.  Since NULL is
+  // #defined as 0, the compiler will use the formatter function for
+  // int to print it.  However, gcc thinks that NULL should be used as
+  // a pointer, not an int, and therefore complains.
+  //
+  // The root of the problem is C++'s lack of distinction between the
+  // integer number 0 and the null pointer constant.  Unfortunately,
+  // we have to live with this fact.
+  //
+  // </TechnicalDetails>
+  EXPECT_STREQ(nullptr, s.c_string());
+
+  EXPECT_EQ(0u, s.Length());
+}
+
+const char kHelloString[] = "Hello, world!";
+
+// Tests the c'tor that accepts a C string.
+TEST(MyString, ConstructorFromCString) {
+  const MyString s(kHelloString);
+  EXPECT_EQ(0, strcmp(s.c_string(), kHelloString));
+  EXPECT_EQ(sizeof(kHelloString)/sizeof(kHelloString[0]) - 1,
+            s.Length());
+}
+
+// Tests the copy c'tor.
+TEST(MyString, CopyConstructor) {
+  const MyString s1(kHelloString);
+  const MyString s2 = s1;
+  EXPECT_EQ(0, strcmp(s2.c_string(), kHelloString));
+}
+
+// Tests the Set method.
+TEST(MyString, Set) {
+  MyString s;
+
+  s.Set(kHelloString);
+  EXPECT_EQ(0, strcmp(s.c_string(), kHelloString));
+
+  // Set should work when the input pointer is the same as the one
+  // already in the MyString object.
+  s.Set(s.c_string());
+  EXPECT_EQ(0, strcmp(s.c_string(), kHelloString));
+
+  // Can we set the MyString to NULL?
+  s.Set(nullptr);
+  EXPECT_STREQ(nullptr, s.c_string());
+}
+}  // namespace
diff --git a/leveldb_base/third_party/googletest/googletest/samples/sample3-inl.h b/leveldb_base/third_party/googletest/googletest/samples/sample3-inl.h
new file mode 100644
index 0000000..659e0f0
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/samples/sample3-inl.h
@@ -0,0 +1,172 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// A sample program demonstrating using Google C++ testing framework.
+
+#ifndef GOOGLETEST_SAMPLES_SAMPLE3_INL_H_
+#define GOOGLETEST_SAMPLES_SAMPLE3_INL_H_
+
+#include <stddef.h>
+
+
+// Queue is a simple queue implemented as a singled-linked list.
+//
+// The element type must support copy constructor.
+template <typename E>  // E is the element type
+class Queue;
+
+// QueueNode is a node in a Queue, which consists of an element of
+// type E and a pointer to the next node.
+template <typename E>  // E is the element type
+class QueueNode {
+  friend class Queue<E>;
+
+ public:
+  // Gets the element in this node.
+  const E& element() const { return element_; }
+
+  // Gets the next node in the queue.
+  QueueNode* next() { return next_; }
+  const QueueNode* next() const { return next_; }
+
+ private:
+  // Creates a node with a given element value.  The next pointer is
+  // set to NULL.
+  explicit QueueNode(const E& an_element)
+      : element_(an_element), next_(nullptr) {}
+
+  // We disable the default assignment operator and copy c'tor.
+  const QueueNode& operator = (const QueueNode&);
+  QueueNode(const QueueNode&);
+
+  E element_;
+  QueueNode* next_;
+};
+
+template <typename E>  // E is the element type.
+class Queue {
+ public:
+  // Creates an empty queue.
+  Queue() : head_(nullptr), last_(nullptr), size_(0) {}
+
+  // D'tor.  Clears the queue.
+  ~Queue() { Clear(); }
+
+  // Clears the queue.
+  void Clear() {
+    if (size_ > 0) {
+      // 1. Deletes every node.
+      QueueNode<E>* node = head_;
+      QueueNode<E>* next = node->next();
+      for (; ;) {
+        delete node;
+        node = next;
+        if (node == nullptr) break;
+        next = node->next();
+      }
+
+      // 2. Resets the member variables.
+      head_ = last_ = nullptr;
+      size_ = 0;
+    }
+  }
+
+  // Gets the number of elements.
+  size_t Size() const { return size_; }
+
+  // Gets the first element of the queue, or NULL if the queue is empty.
+  QueueNode<E>* Head() { return head_; }
+  const QueueNode<E>* Head() const { return head_; }
+
+  // Gets the last element of the queue, or NULL if the queue is empty.
+  QueueNode<E>* Last() { return last_; }
+  const QueueNode<E>* Last() const { return last_; }
+
+  // Adds an element to the end of the queue.  A copy of the element is
+  // created using the copy constructor, and then stored in the queue.
+  // Changes made to the element in the queue doesn't affect the source
+  // object, and vice versa.
+  void Enqueue(const E& element) {
+    QueueNode<E>* new_node = new QueueNode<E>(element);
+
+    if (size_ == 0) {
+      head_ = last_ = new_node;
+      size_ = 1;
+    } else {
+      last_->next_ = new_node;
+      last_ = new_node;
+      size_++;
+    }
+  }
+
+  // Removes the head of the queue and returns it.  Returns NULL if
+  // the queue is empty.
+  E* Dequeue() {
+    if (size_ == 0) {
+      return nullptr;
+    }
+
+    const QueueNode<E>* const old_head = head_;
+    head_ = head_->next_;
+    size_--;
+    if (size_ == 0) {
+      last_ = nullptr;
+    }
+
+    E* element = new E(old_head->element());
+    delete old_head;
+
+    return element;
+  }
+
+  // Applies a function/functor on each element of the queue, and
+  // returns the result in a new queue.  The original queue is not
+  // affected.
+  template <typename F>
+  Queue* Map(F function) const {
+    Queue* new_queue = new Queue();
+    for (const QueueNode<E>* node = head_; node != nullptr;
+         node = node->next_) {
+      new_queue->Enqueue(function(node->element()));
+    }
+
+    return new_queue;
+  }
+
+ private:
+  QueueNode<E>* head_;  // The first node of the queue.
+  QueueNode<E>* last_;  // The last node of the queue.
+  size_t size_;  // The number of elements in the queue.
+
+  // We disallow copying a queue.
+  Queue(const Queue&);
+  const Queue& operator = (const Queue&);
+};
+
+#endif  // GOOGLETEST_SAMPLES_SAMPLE3_INL_H_
diff --git a/leveldb_base/third_party/googletest/googletest/samples/sample3_unittest.cc b/leveldb_base/third_party/googletest/googletest/samples/sample3_unittest.cc
new file mode 100644
index 0000000..b19416d
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/samples/sample3_unittest.cc
@@ -0,0 +1,149 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// A sample program demonstrating using Google C++ testing framework.
+
+// In this example, we use a more advanced feature of Google Test called
+// test fixture.
+//
+// A test fixture is a place to hold objects and functions shared by
+// all tests in a test case.  Using a test fixture avoids duplicating
+// the test code necessary to initialize and cleanup those common
+// objects for each test.  It is also useful for defining sub-routines
+// that your tests need to invoke a lot.
+//
+// <TechnicalDetails>
+//
+// The tests share the test fixture in the sense of code sharing, not
+// data sharing.  Each test is given its own fresh copy of the
+// fixture.  You cannot expect the data modified by one test to be
+// passed on to another test, which is a bad idea.
+//
+// The reason for this design is that tests should be independent and
+// repeatable.  In particular, a test should not fail as the result of
+// another test's failure.  If one test depends on info produced by
+// another test, then the two tests should really be one big test.
+//
+// The macros for indicating the success/failure of a test
+// (EXPECT_TRUE, FAIL, etc) need to know what the current test is
+// (when Google Test prints the test result, it tells you which test
+// each failure belongs to).  Technically, these macros invoke a
+// member function of the Test class.  Therefore, you cannot use them
+// in a global function.  That's why you should put test sub-routines
+// in a test fixture.
+//
+// </TechnicalDetails>
+
+#include "sample3-inl.h"
+#include "gtest/gtest.h"
+namespace {
+// To use a test fixture, derive a class from testing::Test.
+class QueueTestSmpl3 : public testing::Test {
+ protected:  // You should make the members protected s.t. they can be
+             // accessed from sub-classes.
+
+  // virtual void SetUp() will be called before each test is run.  You
+  // should define it if you need to initialize the variables.
+  // Otherwise, this can be skipped.
+  void SetUp() override {
+    q1_.Enqueue(1);
+    q2_.Enqueue(2);
+    q2_.Enqueue(3);
+  }
+
+  // virtual void TearDown() will be called after each test is run.
+  // You should define it if there is cleanup work to do.  Otherwise,
+  // you don't have to provide it.
+  //
+  // virtual void TearDown() {
+  // }
+
+  // A helper function that some test uses.
+  static int Double(int n) {
+    return 2*n;
+  }
+
+  // A helper function for testing Queue::Map().
+  void MapTester(const Queue<int> * q) {
+    // Creates a new queue, where each element is twice as big as the
+    // corresponding one in q.
+    const Queue<int> * const new_q = q->Map(Double);
+
+    // Verifies that the new queue has the same size as q.
+    ASSERT_EQ(q->Size(), new_q->Size());
+
+    // Verifies the relationship between the elements of the two queues.
+    for (const QueueNode<int>*n1 = q->Head(), *n2 = new_q->Head();
+         n1 != nullptr; n1 = n1->next(), n2 = n2->next()) {
+      EXPECT_EQ(2 * n1->element(), n2->element());
+    }
+
+    delete new_q;
+  }
+
+  // Declares the variables your tests want to use.
+  Queue<int> q0_;
+  Queue<int> q1_;
+  Queue<int> q2_;
+};
+
+// When you have a test fixture, you define a test using TEST_F
+// instead of TEST.
+
+// Tests the default c'tor.
+TEST_F(QueueTestSmpl3, DefaultConstructor) {
+  // You can access data in the test fixture here.
+  EXPECT_EQ(0u, q0_.Size());
+}
+
+// Tests Dequeue().
+TEST_F(QueueTestSmpl3, Dequeue) {
+  int * n = q0_.Dequeue();
+  EXPECT_TRUE(n == nullptr);
+
+  n = q1_.Dequeue();
+  ASSERT_TRUE(n != nullptr);
+  EXPECT_EQ(1, *n);
+  EXPECT_EQ(0u, q1_.Size());
+  delete n;
+
+  n = q2_.Dequeue();
+  ASSERT_TRUE(n != nullptr);
+  EXPECT_EQ(2, *n);
+  EXPECT_EQ(1u, q2_.Size());
+  delete n;
+}
+
+// Tests the Queue::Map() function.
+TEST_F(QueueTestSmpl3, Map) {
+  MapTester(&q0_);
+  MapTester(&q1_);
+  MapTester(&q2_);
+}
+}  // namespace
diff --git a/leveldb_base/third_party/googletest/googletest/samples/sample4.cc b/leveldb_base/third_party/googletest/googletest/samples/sample4.cc
new file mode 100644
index 0000000..b0ee609
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/samples/sample4.cc
@@ -0,0 +1,54 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// A sample program demonstrating using Google C++ testing framework.
+
+#include <stdio.h>
+
+#include "sample4.h"
+
+// Returns the current counter value, and increments it.
+int Counter::Increment() {
+  return counter_++;
+}
+
+// Returns the current counter value, and decrements it.
+// counter can not be less than 0, return 0 in this case
+int Counter::Decrement() {
+  if (counter_ == 0) {
+    return counter_;
+  } else  {
+    return counter_--;
+  }
+}
+
+// Prints the current counter value to STDOUT.
+void Counter::Print() const {
+  printf("%d", counter_);
+}
diff --git a/leveldb_base/third_party/googletest/googletest/samples/sample4.h b/leveldb_base/third_party/googletest/googletest/samples/sample4.h
new file mode 100644
index 0000000..0c4ed92
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/samples/sample4.h
@@ -0,0 +1,53 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// A sample program demonstrating using Google C++ testing framework.
+#ifndef GOOGLETEST_SAMPLES_SAMPLE4_H_
+#define GOOGLETEST_SAMPLES_SAMPLE4_H_
+
+// A simple monotonic counter.
+class Counter {
+ private:
+  int counter_;
+
+ public:
+  // Creates a counter that starts at 0.
+  Counter() : counter_(0) {}
+
+  // Returns the current counter value, and increments it.
+  int Increment();
+
+  // Returns the current counter value, and decrements it.
+  int Decrement();
+
+  // Prints the current counter value to STDOUT.
+  void Print() const;
+};
+
+#endif  // GOOGLETEST_SAMPLES_SAMPLE4_H_
diff --git a/leveldb_base/third_party/googletest/googletest/samples/sample4_unittest.cc b/leveldb_base/third_party/googletest/googletest/samples/sample4_unittest.cc
new file mode 100644
index 0000000..d5144c0
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/samples/sample4_unittest.cc
@@ -0,0 +1,53 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+#include "sample4.h"
+#include "gtest/gtest.h"
+
+namespace {
+// Tests the Increment() method.
+
+TEST(Counter, Increment) {
+  Counter c;
+
+  // Test that counter 0 returns 0
+  EXPECT_EQ(0, c.Decrement());
+
+  // EXPECT_EQ() evaluates its arguments exactly once, so they
+  // can have side effects.
+
+  EXPECT_EQ(0, c.Increment());
+  EXPECT_EQ(1, c.Increment());
+  EXPECT_EQ(2, c.Increment());
+
+  EXPECT_EQ(3, c.Decrement());
+}
+
+}  // namespace
diff --git a/leveldb_base/third_party/googletest/googletest/samples/sample5_unittest.cc b/leveldb_base/third_party/googletest/googletest/samples/sample5_unittest.cc
new file mode 100644
index 0000000..0a21dd2
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/samples/sample5_unittest.cc
@@ -0,0 +1,196 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// This sample teaches how to reuse a test fixture in multiple test
+// cases by deriving sub-fixtures from it.
+//
+// When you define a test fixture, you specify the name of the test
+// case that will use this fixture.  Therefore, a test fixture can
+// be used by only one test case.
+//
+// Sometimes, more than one test cases may want to use the same or
+// slightly different test fixtures.  For example, you may want to
+// make sure that all tests for a GUI library don't leak important
+// system resources like fonts and brushes.  In Google Test, you do
+// this by putting the shared logic in a super (as in "super class")
+// test fixture, and then have each test case use a fixture derived
+// from this super fixture.
+
+#include <limits.h>
+#include <time.h>
+#include "gtest/gtest.h"
+#include "sample1.h"
+#include "sample3-inl.h"
+namespace {
+// In this sample, we want to ensure that every test finishes within
+// ~5 seconds.  If a test takes longer to run, we consider it a
+// failure.
+//
+// We put the code for timing a test in a test fixture called
+// "QuickTest".  QuickTest is intended to be the super fixture that
+// other fixtures derive from, therefore there is no test case with
+// the name "QuickTest".  This is OK.
+//
+// Later, we will derive multiple test fixtures from QuickTest.
+class QuickTest : public testing::Test {
+ protected:
+  // Remember that SetUp() is run immediately before a test starts.
+  // This is a good place to record the start time.
+  void SetUp() override { start_time_ = time(nullptr); }
+
+  // TearDown() is invoked immediately after a test finishes.  Here we
+  // check if the test was too slow.
+  void TearDown() override {
+    // Gets the time when the test finishes
+    const time_t end_time = time(nullptr);
+
+    // Asserts that the test took no more than ~5 seconds.  Did you
+    // know that you can use assertions in SetUp() and TearDown() as
+    // well?
+    EXPECT_TRUE(end_time - start_time_ <= 5) << "The test took too long.";
+  }
+
+  // The UTC time (in seconds) when the test starts
+  time_t start_time_;
+};
+
+
+// We derive a fixture named IntegerFunctionTest from the QuickTest
+// fixture.  All tests using this fixture will be automatically
+// required to be quick.
+class IntegerFunctionTest : public QuickTest {
+  // We don't need any more logic than already in the QuickTest fixture.
+  // Therefore the body is empty.
+};
+
+
+// Now we can write tests in the IntegerFunctionTest test case.
+
+// Tests Factorial()
+TEST_F(IntegerFunctionTest, Factorial) {
+  // Tests factorial of negative numbers.
+  EXPECT_EQ(1, Factorial(-5));
+  EXPECT_EQ(1, Factorial(-1));
+  EXPECT_GT(Factorial(-10), 0);
+
+  // Tests factorial of 0.
+  EXPECT_EQ(1, Factorial(0));
+
+  // Tests factorial of positive numbers.
+  EXPECT_EQ(1, Factorial(1));
+  EXPECT_EQ(2, Factorial(2));
+  EXPECT_EQ(6, Factorial(3));
+  EXPECT_EQ(40320, Factorial(8));
+}
+
+
+// Tests IsPrime()
+TEST_F(IntegerFunctionTest, IsPrime) {
+  // Tests negative input.
+  EXPECT_FALSE(IsPrime(-1));
+  EXPECT_FALSE(IsPrime(-2));
+  EXPECT_FALSE(IsPrime(INT_MIN));
+
+  // Tests some trivial cases.
+  EXPECT_FALSE(IsPrime(0));
+  EXPECT_FALSE(IsPrime(1));
+  EXPECT_TRUE(IsPrime(2));
+  EXPECT_TRUE(IsPrime(3));
+
+  // Tests positive input.
+  EXPECT_FALSE(IsPrime(4));
+  EXPECT_TRUE(IsPrime(5));
+  EXPECT_FALSE(IsPrime(6));
+  EXPECT_TRUE(IsPrime(23));
+}
+
+
+// The next test case (named "QueueTest") also needs to be quick, so
+// we derive another fixture from QuickTest.
+//
+// The QueueTest test fixture has some logic and shared objects in
+// addition to what's in QuickTest already.  We define the additional
+// stuff inside the body of the test fixture, as usual.
+class QueueTest : public QuickTest {
+ protected:
+  void SetUp() override {
+    // First, we need to set up the super fixture (QuickTest).
+    QuickTest::SetUp();
+
+    // Second, some additional setup for this fixture.
+    q1_.Enqueue(1);
+    q2_.Enqueue(2);
+    q2_.Enqueue(3);
+  }
+
+  // By default, TearDown() inherits the behavior of
+  // QuickTest::TearDown().  As we have no additional cleaning work
+  // for QueueTest, we omit it here.
+  //
+  // virtual void TearDown() {
+  //   QuickTest::TearDown();
+  // }
+
+  Queue<int> q0_;
+  Queue<int> q1_;
+  Queue<int> q2_;
+};
+
+
+// Now, let's write tests using the QueueTest fixture.
+
+// Tests the default constructor.
+TEST_F(QueueTest, DefaultConstructor) {
+  EXPECT_EQ(0u, q0_.Size());
+}
+
+// Tests Dequeue().
+TEST_F(QueueTest, Dequeue) {
+  int* n = q0_.Dequeue();
+  EXPECT_TRUE(n == nullptr);
+
+  n = q1_.Dequeue();
+  EXPECT_TRUE(n != nullptr);
+  EXPECT_EQ(1, *n);
+  EXPECT_EQ(0u, q1_.Size());
+  delete n;
+
+  n = q2_.Dequeue();
+  EXPECT_TRUE(n != nullptr);
+  EXPECT_EQ(2, *n);
+  EXPECT_EQ(1u, q2_.Size());
+  delete n;
+}
+}  // namespace
+// If necessary, you can derive further test fixtures from a derived
+// fixture itself.  For example, you can derive another fixture from
+// QueueTest.  Google Test imposes no limit on how deep the hierarchy
+// can be.  In practice, however, you probably don't want it to be too
+// deep as to be confusing.
diff --git a/leveldb_base/third_party/googletest/googletest/samples/sample6_unittest.cc b/leveldb_base/third_party/googletest/googletest/samples/sample6_unittest.cc
new file mode 100644
index 0000000..da317ee
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/samples/sample6_unittest.cc
@@ -0,0 +1,217 @@
+// Copyright 2008 Google Inc.
+// All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// This sample shows how to test common properties of multiple
+// implementations of the same interface (aka interface tests).
+
+// The interface and its implementations are in this header.
+#include "prime_tables.h"
+
+#include "gtest/gtest.h"
+namespace {
+// First, we define some factory functions for creating instances of
+// the implementations.  You may be able to skip this step if all your
+// implementations can be constructed the same way.
+
+template <class T>
+PrimeTable* CreatePrimeTable();
+
+template <>
+PrimeTable* CreatePrimeTable<OnTheFlyPrimeTable>() {
+  return new OnTheFlyPrimeTable;
+}
+
+template <>
+PrimeTable* CreatePrimeTable<PreCalculatedPrimeTable>() {
+  return new PreCalculatedPrimeTable(10000);
+}
+
+// Then we define a test fixture class template.
+template <class T>
+class PrimeTableTest : public testing::Test {
+ protected:
+  // The ctor calls the factory function to create a prime table
+  // implemented by T.
+  PrimeTableTest() : table_(CreatePrimeTable<T>()) {}
+
+  ~PrimeTableTest() override { delete table_; }
+
+  // Note that we test an implementation via the base interface
+  // instead of the actual implementation class.  This is important
+  // for keeping the tests close to the real world scenario, where the
+  // implementation is invoked via the base interface.  It avoids
+  // got-yas where the implementation class has a method that shadows
+  // a method with the same name (but slightly different argument
+  // types) in the base interface, for example.
+  PrimeTable* const table_;
+};
+
+using testing::Types;
+
+// Google Test offers two ways for reusing tests for different types.
+// The first is called "typed tests".  You should use it if you
+// already know *all* the types you are gonna exercise when you write
+// the tests.
+
+// To write a typed test case, first use
+//
+//   TYPED_TEST_SUITE(TestCaseName, TypeList);
+//
+// to declare it and specify the type parameters.  As with TEST_F,
+// TestCaseName must match the test fixture name.
+
+// The list of types we want to test.
+typedef Types<OnTheFlyPrimeTable, PreCalculatedPrimeTable> Implementations;
+
+TYPED_TEST_SUITE(PrimeTableTest, Implementations);
+
+// Then use TYPED_TEST(TestCaseName, TestName) to define a typed test,
+// similar to TEST_F.
+TYPED_TEST(PrimeTableTest, ReturnsFalseForNonPrimes) {
+  // Inside the test body, you can refer to the type parameter by
+  // TypeParam, and refer to the fixture class by TestFixture.  We
+  // don't need them in this example.
+
+  // Since we are in the template world, C++ requires explicitly
+  // writing 'this->' when referring to members of the fixture class.
+  // This is something you have to learn to live with.
+  EXPECT_FALSE(this->table_->IsPrime(-5));
+  EXPECT_FALSE(this->table_->IsPrime(0));
+  EXPECT_FALSE(this->table_->IsPrime(1));
+  EXPECT_FALSE(this->table_->IsPrime(4));
+  EXPECT_FALSE(this->table_->IsPrime(6));
+  EXPECT_FALSE(this->table_->IsPrime(100));
+}
+
+TYPED_TEST(PrimeTableTest, ReturnsTrueForPrimes) {
+  EXPECT_TRUE(this->table_->IsPrime(2));
+  EXPECT_TRUE(this->table_->IsPrime(3));
+  EXPECT_TRUE(this->table_->IsPrime(5));
+  EXPECT_TRUE(this->table_->IsPrime(7));
+  EXPECT_TRUE(this->table_->IsPrime(11));
+  EXPECT_TRUE(this->table_->IsPrime(131));
+}
+
+TYPED_TEST(PrimeTableTest, CanGetNextPrime) {
+  EXPECT_EQ(2, this->table_->GetNextPrime(0));
+  EXPECT_EQ(3, this->table_->GetNextPrime(2));
+  EXPECT_EQ(5, this->table_->GetNextPrime(3));
+  EXPECT_EQ(7, this->table_->GetNextPrime(5));
+  EXPECT_EQ(11, this->table_->GetNextPrime(7));
+  EXPECT_EQ(131, this->table_->GetNextPrime(128));
+}
+
+// That's it!  Google Test will repeat each TYPED_TEST for each type
+// in the type list specified in TYPED_TEST_SUITE.  Sit back and be
+// happy that you don't have to define them multiple times.
+
+using testing::Types;
+
+// Sometimes, however, you don't yet know all the types that you want
+// to test when you write the tests.  For example, if you are the
+// author of an interface and expect other people to implement it, you
+// might want to write a set of tests to make sure each implementation
+// conforms to some basic requirements, but you don't know what
+// implementations will be written in the future.
+//
+// How can you write the tests without committing to the type
+// parameters?  That's what "type-parameterized tests" can do for you.
+// It is a bit more involved than typed tests, but in return you get a
+// test pattern that can be reused in many contexts, which is a big
+// win.  Here's how you do it:
+
+// First, define a test fixture class template.  Here we just reuse
+// the PrimeTableTest fixture defined earlier:
+
+template <class T>
+class PrimeTableTest2 : public PrimeTableTest<T> {
+};
+
+// Then, declare the test case.  The argument is the name of the test
+// fixture, and also the name of the test case (as usual).  The _P
+// suffix is for "parameterized" or "pattern".
+TYPED_TEST_SUITE_P(PrimeTableTest2);
+
+// Next, use TYPED_TEST_P(TestCaseName, TestName) to define a test,
+// similar to what you do with TEST_F.
+TYPED_TEST_P(PrimeTableTest2, ReturnsFalseForNonPrimes) {
+  EXPECT_FALSE(this->table_->IsPrime(-5));
+  EXPECT_FALSE(this->table_->IsPrime(0));
+  EXPECT_FALSE(this->table_->IsPrime(1));
+  EXPECT_FALSE(this->table_->IsPrime(4));
+  EXPECT_FALSE(this->table_->IsPrime(6));
+  EXPECT_FALSE(this->table_->IsPrime(100));
+}
+
+TYPED_TEST_P(PrimeTableTest2, ReturnsTrueForPrimes) {
+  EXPECT_TRUE(this->table_->IsPrime(2));
+  EXPECT_TRUE(this->table_->IsPrime(3));
+  EXPECT_TRUE(this->table_->IsPrime(5));
+  EXPECT_TRUE(this->table_->IsPrime(7));
+  EXPECT_TRUE(this->table_->IsPrime(11));
+  EXPECT_TRUE(this->table_->IsPrime(131));
+}
+
+TYPED_TEST_P(PrimeTableTest2, CanGetNextPrime) {
+  EXPECT_EQ(2, this->table_->GetNextPrime(0));
+  EXPECT_EQ(3, this->table_->GetNextPrime(2));
+  EXPECT_EQ(5, this->table_->GetNextPrime(3));
+  EXPECT_EQ(7, this->table_->GetNextPrime(5));
+  EXPECT_EQ(11, this->table_->GetNextPrime(7));
+  EXPECT_EQ(131, this->table_->GetNextPrime(128));
+}
+
+// Type-parameterized tests involve one extra step: you have to
+// enumerate the tests you defined:
+REGISTER_TYPED_TEST_SUITE_P(
+    PrimeTableTest2,  // The first argument is the test case name.
+    // The rest of the arguments are the test names.
+    ReturnsFalseForNonPrimes, ReturnsTrueForPrimes, CanGetNextPrime);
+
+// At this point the test pattern is done.  However, you don't have
+// any real test yet as you haven't said which types you want to run
+// the tests with.
+
+// To turn the abstract test pattern into real tests, you instantiate
+// it with a list of types.  Usually the test pattern will be defined
+// in a .h file, and anyone can #include and instantiate it.  You can
+// even instantiate it more than once in the same program.  To tell
+// different instances apart, you give each of them a name, which will
+// become part of the test case name and can be used in test filters.
+
+// The list of types we want to test.  Note that it doesn't have to be
+// defined at the time we write the TYPED_TEST_P()s.
+typedef Types<OnTheFlyPrimeTable, PreCalculatedPrimeTable>
+    PrimeTableImplementations;
+INSTANTIATE_TYPED_TEST_SUITE_P(OnTheFlyAndPreCalculated,    // Instance name
+                               PrimeTableTest2,             // Test case name
+                               PrimeTableImplementations);  // Type list
+
+}  // namespace
diff --git a/leveldb_base/third_party/googletest/googletest/samples/sample7_unittest.cc b/leveldb_base/third_party/googletest/googletest/samples/sample7_unittest.cc
new file mode 100644
index 0000000..e0efc29
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/samples/sample7_unittest.cc
@@ -0,0 +1,117 @@
+// Copyright 2008 Google Inc.
+// All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// This sample shows how to test common properties of multiple
+// implementations of an interface (aka interface tests) using
+// value-parameterized tests. Each test in the test case has
+// a parameter that is an interface pointer to an implementation
+// tested.
+
+// The interface and its implementations are in this header.
+#include "prime_tables.h"
+
+#include "gtest/gtest.h"
+namespace {
+
+using ::testing::TestWithParam;
+using ::testing::Values;
+
+// As a general rule, to prevent a test from affecting the tests that come
+// after it, you should create and destroy the tested objects for each test
+// instead of reusing them.  In this sample we will define a simple factory
+// function for PrimeTable objects.  We will instantiate objects in test's
+// SetUp() method and delete them in TearDown() method.
+typedef PrimeTable* CreatePrimeTableFunc();
+
+PrimeTable* CreateOnTheFlyPrimeTable() {
+  return new OnTheFlyPrimeTable();
+}
+
+template <size_t max_precalculated>
+PrimeTable* CreatePreCalculatedPrimeTable() {
+  return new PreCalculatedPrimeTable(max_precalculated);
+}
+
+// Inside the test body, fixture constructor, SetUp(), and TearDown() you
+// can refer to the test parameter by GetParam().  In this case, the test
+// parameter is a factory function which we call in fixture's SetUp() to
+// create and store an instance of PrimeTable.
+class PrimeTableTestSmpl7 : public TestWithParam<CreatePrimeTableFunc*> {
+ public:
+  ~PrimeTableTestSmpl7() override { delete table_; }
+  void SetUp() override { table_ = (*GetParam())(); }
+  void TearDown() override {
+    delete table_;
+    table_ = nullptr;
+  }
+
+ protected:
+  PrimeTable* table_;
+};
+
+TEST_P(PrimeTableTestSmpl7, ReturnsFalseForNonPrimes) {
+  EXPECT_FALSE(table_->IsPrime(-5));
+  EXPECT_FALSE(table_->IsPrime(0));
+  EXPECT_FALSE(table_->IsPrime(1));
+  EXPECT_FALSE(table_->IsPrime(4));
+  EXPECT_FALSE(table_->IsPrime(6));
+  EXPECT_FALSE(table_->IsPrime(100));
+}
+
+TEST_P(PrimeTableTestSmpl7, ReturnsTrueForPrimes) {
+  EXPECT_TRUE(table_->IsPrime(2));
+  EXPECT_TRUE(table_->IsPrime(3));
+  EXPECT_TRUE(table_->IsPrime(5));
+  EXPECT_TRUE(table_->IsPrime(7));
+  EXPECT_TRUE(table_->IsPrime(11));
+  EXPECT_TRUE(table_->IsPrime(131));
+}
+
+TEST_P(PrimeTableTestSmpl7, CanGetNextPrime) {
+  EXPECT_EQ(2, table_->GetNextPrime(0));
+  EXPECT_EQ(3, table_->GetNextPrime(2));
+  EXPECT_EQ(5, table_->GetNextPrime(3));
+  EXPECT_EQ(7, table_->GetNextPrime(5));
+  EXPECT_EQ(11, table_->GetNextPrime(7));
+  EXPECT_EQ(131, table_->GetNextPrime(128));
+}
+
+// In order to run value-parameterized tests, you need to instantiate them,
+// or bind them to a list of values which will be used as test parameters.
+// You can instantiate them in a different translation module, or even
+// instantiate them several times.
+//
+// Here, we instantiate our tests with a list of two PrimeTable object
+// factory functions:
+INSTANTIATE_TEST_SUITE_P(OnTheFlyAndPreCalculated, PrimeTableTestSmpl7,
+                         Values(&CreateOnTheFlyPrimeTable,
+                                &CreatePreCalculatedPrimeTable<1000>));
+
+}  // namespace
diff --git a/leveldb_base/third_party/googletest/googletest/samples/sample8_unittest.cc b/leveldb_base/third_party/googletest/googletest/samples/sample8_unittest.cc
new file mode 100644
index 0000000..10488b0
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/samples/sample8_unittest.cc
@@ -0,0 +1,154 @@
+// Copyright 2008 Google Inc.
+// All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// This sample shows how to test code relying on some global flag variables.
+// Combine() helps with generating all possible combinations of such flags,
+// and each test is given one combination as a parameter.
+
+// Use class definitions to test from this header.
+#include "prime_tables.h"
+
+#include "gtest/gtest.h"
+namespace {
+
+// Suppose we want to introduce a new, improved implementation of PrimeTable
+// which combines speed of PrecalcPrimeTable and versatility of
+// OnTheFlyPrimeTable (see prime_tables.h). Inside it instantiates both
+// PrecalcPrimeTable and OnTheFlyPrimeTable and uses the one that is more
+// appropriate under the circumstances. But in low memory conditions, it can be
+// told to instantiate without PrecalcPrimeTable instance at all and use only
+// OnTheFlyPrimeTable.
+class HybridPrimeTable : public PrimeTable {
+ public:
+  HybridPrimeTable(bool force_on_the_fly, int max_precalculated)
+      : on_the_fly_impl_(new OnTheFlyPrimeTable),
+        precalc_impl_(force_on_the_fly
+                          ? nullptr
+                          : new PreCalculatedPrimeTable(max_precalculated)),
+        max_precalculated_(max_precalculated) {}
+  ~HybridPrimeTable() override {
+    delete on_the_fly_impl_;
+    delete precalc_impl_;
+  }
+
+  bool IsPrime(int n) const override {
+    if (precalc_impl_ != nullptr && n < max_precalculated_)
+      return precalc_impl_->IsPrime(n);
+    else
+      return on_the_fly_impl_->IsPrime(n);
+  }
+
+  int GetNextPrime(int p) const override {
+    int next_prime = -1;
+    if (precalc_impl_ != nullptr && p < max_precalculated_)
+      next_prime = precalc_impl_->GetNextPrime(p);
+
+    return next_prime != -1 ? next_prime : on_the_fly_impl_->GetNextPrime(p);
+  }
+
+ private:
+  OnTheFlyPrimeTable* on_the_fly_impl_;
+  PreCalculatedPrimeTable* precalc_impl_;
+  int max_precalculated_;
+};
+
+using ::testing::TestWithParam;
+using ::testing::Bool;
+using ::testing::Values;
+using ::testing::Combine;
+
+// To test all code paths for HybridPrimeTable we must test it with numbers
+// both within and outside PreCalculatedPrimeTable's capacity and also with
+// PreCalculatedPrimeTable disabled. We do this by defining fixture which will
+// accept different combinations of parameters for instantiating a
+// HybridPrimeTable instance.
+class PrimeTableTest : public TestWithParam< ::std::tuple<bool, int> > {
+ protected:
+  void SetUp() override {
+    bool force_on_the_fly;
+    int max_precalculated;
+    std::tie(force_on_the_fly, max_precalculated) = GetParam();
+    table_ = new HybridPrimeTable(force_on_the_fly, max_precalculated);
+  }
+  void TearDown() override {
+    delete table_;
+    table_ = nullptr;
+  }
+  HybridPrimeTable* table_;
+};
+
+TEST_P(PrimeTableTest, ReturnsFalseForNonPrimes) {
+  // Inside the test body, you can refer to the test parameter by GetParam().
+  // In this case, the test parameter is a PrimeTable interface pointer which
+  // we can use directly.
+  // Please note that you can also save it in the fixture's SetUp() method
+  // or constructor and use saved copy in the tests.
+
+  EXPECT_FALSE(table_->IsPrime(-5));
+  EXPECT_FALSE(table_->IsPrime(0));
+  EXPECT_FALSE(table_->IsPrime(1));
+  EXPECT_FALSE(table_->IsPrime(4));
+  EXPECT_FALSE(table_->IsPrime(6));
+  EXPECT_FALSE(table_->IsPrime(100));
+}
+
+TEST_P(PrimeTableTest, ReturnsTrueForPrimes) {
+  EXPECT_TRUE(table_->IsPrime(2));
+  EXPECT_TRUE(table_->IsPrime(3));
+  EXPECT_TRUE(table_->IsPrime(5));
+  EXPECT_TRUE(table_->IsPrime(7));
+  EXPECT_TRUE(table_->IsPrime(11));
+  EXPECT_TRUE(table_->IsPrime(131));
+}
+
+TEST_P(PrimeTableTest, CanGetNextPrime) {
+  EXPECT_EQ(2, table_->GetNextPrime(0));
+  EXPECT_EQ(3, table_->GetNextPrime(2));
+  EXPECT_EQ(5, table_->GetNextPrime(3));
+  EXPECT_EQ(7, table_->GetNextPrime(5));
+  EXPECT_EQ(11, table_->GetNextPrime(7));
+  EXPECT_EQ(131, table_->GetNextPrime(128));
+}
+
+// In order to run value-parameterized tests, you need to instantiate them,
+// or bind them to a list of values which will be used as test parameters.
+// You can instantiate them in a different translation module, or even
+// instantiate them several times.
+//
+// Here, we instantiate our tests with a list of parameters. We must combine
+// all variations of the boolean flag suppressing PrecalcPrimeTable and some
+// meaningful values for tests. We choose a small value (1), and a value that
+// will put some of the tested numbers beyond the capability of the
+// PrecalcPrimeTable instance and some inside it (10). Combine will produce all
+// possible combinations.
+INSTANTIATE_TEST_SUITE_P(MeaningfulTestParameters, PrimeTableTest,
+                         Combine(Bool(), Values(1, 10)));
+
+}  // namespace
diff --git a/leveldb_base/third_party/googletest/googletest/samples/sample9_unittest.cc b/leveldb_base/third_party/googletest/googletest/samples/sample9_unittest.cc
new file mode 100644
index 0000000..e502d08
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/samples/sample9_unittest.cc
@@ -0,0 +1,156 @@
+// Copyright 2009 Google Inc. All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// This sample shows how to use Google Test listener API to implement
+// an alternative console output and how to use the UnitTest reflection API
+// to enumerate test cases and tests and to inspect their results.
+
+#include <stdio.h>
+
+#include "gtest/gtest.h"
+
+using ::testing::EmptyTestEventListener;
+using ::testing::InitGoogleTest;
+using ::testing::Test;
+using ::testing::TestCase;
+using ::testing::TestEventListeners;
+using ::testing::TestInfo;
+using ::testing::TestPartResult;
+using ::testing::UnitTest;
+namespace {
+// Provides alternative output mode which produces minimal amount of
+// information about tests.
+class TersePrinter : public EmptyTestEventListener {
+ private:
+  // Called before any test activity starts.
+  void OnTestProgramStart(const UnitTest& /* unit_test */) override {}
+
+  // Called after all test activities have ended.
+  void OnTestProgramEnd(const UnitTest& unit_test) override {
+    fprintf(stdout, "TEST %s\n", unit_test.Passed() ? "PASSED" : "FAILED");
+    fflush(stdout);
+  }
+
+  // Called before a test starts.
+  void OnTestStart(const TestInfo& test_info) override {
+    fprintf(stdout,
+            "*** Test %s.%s starting.\n",
+            test_info.test_case_name(),
+            test_info.name());
+    fflush(stdout);
+  }
+
+  // Called after a failed assertion or a SUCCEED() invocation.
+  void OnTestPartResult(const TestPartResult& test_part_result) override {
+    fprintf(stdout,
+            "%s in %s:%d\n%s\n",
+            test_part_result.failed() ? "*** Failure" : "Success",
+            test_part_result.file_name(),
+            test_part_result.line_number(),
+            test_part_result.summary());
+    fflush(stdout);
+  }
+
+  // Called after a test ends.
+  void OnTestEnd(const TestInfo& test_info) override {
+    fprintf(stdout,
+            "*** Test %s.%s ending.\n",
+            test_info.test_case_name(),
+            test_info.name());
+    fflush(stdout);
+  }
+};  // class TersePrinter
+
+TEST(CustomOutputTest, PrintsMessage) {
+  printf("Printing something from the test body...\n");
+}
+
+TEST(CustomOutputTest, Succeeds) {
+  SUCCEED() << "SUCCEED() has been invoked from here";
+}
+
+TEST(CustomOutputTest, Fails) {
+  EXPECT_EQ(1, 2)
+      << "This test fails in order to demonstrate alternative failure messages";
+}
+}  // namespace
+
+int main(int argc, char **argv) {
+  InitGoogleTest(&argc, argv);
+
+  bool terse_output = false;
+  if (argc > 1 && strcmp(argv[1], "--terse_output") == 0 )
+    terse_output = true;
+  else
+    printf("%s\n", "Run this program with --terse_output to change the way "
+           "it prints its output.");
+
+  UnitTest& unit_test = *UnitTest::GetInstance();
+
+  // If we are given the --terse_output command line flag, suppresses the
+  // standard output and attaches own result printer.
+  if (terse_output) {
+    TestEventListeners& listeners = unit_test.listeners();
+
+    // Removes the default console output listener from the list so it will
+    // not receive events from Google Test and won't print any output. Since
+    // this operation transfers ownership of the listener to the caller we
+    // have to delete it as well.
+    delete listeners.Release(listeners.default_result_printer());
+
+    // Adds the custom output listener to the list. It will now receive
+    // events from Google Test and print the alternative output. We don't
+    // have to worry about deleting it since Google Test assumes ownership
+    // over it after adding it to the list.
+    listeners.Append(new TersePrinter);
+  }
+  int ret_val = RUN_ALL_TESTS();
+
+  // This is an example of using the UnitTest reflection API to inspect test
+  // results. Here we discount failures from the tests we expected to fail.
+  int unexpectedly_failed_tests = 0;
+  for (int i = 0; i < unit_test.total_test_suite_count(); ++i) {
+    const testing::TestSuite& test_suite = *unit_test.GetTestSuite(i);
+    for (int j = 0; j < test_suite.total_test_count(); ++j) {
+      const TestInfo& test_info = *test_suite.GetTestInfo(j);
+      // Counts failed tests that were not meant to fail (those without
+      // 'Fails' in the name).
+      if (test_info.result()->Failed() &&
+          strcmp(test_info.name(), "Fails") != 0) {
+        unexpectedly_failed_tests++;
+      }
+    }
+  }
+
+  // Test that were meant to fail should not affect the test program outcome.
+  if (unexpectedly_failed_tests == 0)
+    ret_val = 0;
+
+  return ret_val;
+}
diff --git a/leveldb_base/third_party/googletest/googletest/scripts/README.md b/leveldb_base/third_party/googletest/googletest/scripts/README.md
new file mode 100644
index 0000000..fa359fe
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/scripts/README.md
@@ -0,0 +1,5 @@
+# Please Note:
+
+Files in this directory are no longer supported by the maintainers. They
+represent mosty historical artifacts and supported by the community only. There
+is no guarantee whatsoever that these scripts still work.
diff --git a/leveldb_base/third_party/googletest/googletest/scripts/common.py b/leveldb_base/third_party/googletest/googletest/scripts/common.py
new file mode 100644
index 0000000..3c0347a
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/scripts/common.py
@@ -0,0 +1,83 @@
+# Copyright 2013 Google Inc. All Rights Reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Shared utilities for writing scripts for Google Test/Mock."""
+
+__author__ = 'wan@google.com (Zhanyong Wan)'
+
+
+import os
+import re
+
+
+# Matches the line from 'svn info .' output that describes what SVN
+# path the current local directory corresponds to.  For example, in
+# a googletest SVN workspace's trunk/test directory, the output will be:
+#
+# URL: https://googletest.googlecode.com/svn/trunk/test
+_SVN_INFO_URL_RE = re.compile(r'^URL: https://(\w+)\.googlecode\.com/svn(.*)')
+
+
+def GetCommandOutput(command):
+  """Runs the shell command and returns its stdout as a list of lines."""
+
+  f = os.popen(command, 'r')
+  lines = [line.strip() for line in f.readlines()]
+  f.close()
+  return lines
+
+
+def GetSvnInfo():
+  """Returns the project name and the current SVN workspace's root path."""
+
+  for line in GetCommandOutput('svn info .'):
+    m = _SVN_INFO_URL_RE.match(line)
+    if m:
+      project = m.group(1)  # googletest or googlemock
+      rel_path = m.group(2)
+      root = os.path.realpath(rel_path.count('/') * '../')
+      return project, root
+
+  return None, None
+
+
+def GetSvnTrunk():
+  """Returns the current SVN workspace's trunk root path."""
+
+  _, root = GetSvnInfo()
+  return root + '/trunk' if root else None
+
+
+def IsInGTestSvn():
+  project, _ = GetSvnInfo()
+  return project == 'googletest'
+
+
+def IsInGMockSvn():
+  project, _ = GetSvnInfo()
+  return project == 'googlemock'
diff --git a/leveldb_base/third_party/googletest/googletest/scripts/fuse_gtest_files.py b/leveldb_base/third_party/googletest/googletest/scripts/fuse_gtest_files.py
new file mode 100644
index 0000000..d0dd464
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/scripts/fuse_gtest_files.py
@@ -0,0 +1,253 @@
+#!/usr/bin/env python
+#
+# Copyright 2009, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""fuse_gtest_files.py v0.2.0
+Fuses Google Test source code into a .h file and a .cc file.
+
+SYNOPSIS
+       fuse_gtest_files.py [GTEST_ROOT_DIR] OUTPUT_DIR
+
+       Scans GTEST_ROOT_DIR for Google Test source code, and generates
+       two files: OUTPUT_DIR/gtest/gtest.h and OUTPUT_DIR/gtest/gtest-all.cc.
+       Then you can build your tests by adding OUTPUT_DIR to the include
+       search path and linking with OUTPUT_DIR/gtest/gtest-all.cc.  These
+       two files contain everything you need to use Google Test.  Hence
+       you can "install" Google Test by copying them to wherever you want.
+
+       GTEST_ROOT_DIR can be omitted and defaults to the parent
+       directory of the directory holding this script.
+
+EXAMPLES
+       ./fuse_gtest_files.py fused_gtest
+       ./fuse_gtest_files.py path/to/unpacked/gtest fused_gtest
+
+This tool is experimental.  In particular, it assumes that there is no
+conditional inclusion of Google Test headers.  Please report any
+problems to googletestframework@googlegroups.com.  You can read
+https://github.com/google/googletest/blob/master/googletest/docs/advanced.md for
+more information.
+"""
+
+__author__ = 'wan@google.com (Zhanyong Wan)'
+
+import os
+import re
+try:
+  from sets import Set as set  # For Python 2.3 compatibility
+except ImportError:
+  pass
+import sys
+
+# We assume that this file is in the scripts/ directory in the Google
+# Test root directory.
+DEFAULT_GTEST_ROOT_DIR = os.path.join(os.path.dirname(__file__), '..')
+
+# Regex for matching '#include "gtest/..."'.
+INCLUDE_GTEST_FILE_REGEX = re.compile(r'^\s*#\s*include\s*"(gtest/.+)"')
+
+# Regex for matching '#include "src/..."'.
+INCLUDE_SRC_FILE_REGEX = re.compile(r'^\s*#\s*include\s*"(src/.+)"')
+
+# Where to find the source seed files.
+GTEST_H_SEED = 'include/gtest/gtest.h'
+GTEST_SPI_H_SEED = 'include/gtest/gtest-spi.h'
+GTEST_ALL_CC_SEED = 'src/gtest-all.cc'
+
+# Where to put the generated files.
+GTEST_H_OUTPUT = 'gtest/gtest.h'
+GTEST_ALL_CC_OUTPUT = 'gtest/gtest-all.cc'
+
+
+def VerifyFileExists(directory, relative_path):
+  """Verifies that the given file exists; aborts on failure.
+
+  relative_path is the file path relative to the given directory.
+  """
+
+  if not os.path.isfile(os.path.join(directory, relative_path)):
+    print('ERROR: Cannot find %s in directory %s.' % (relative_path,
+                                                      directory))
+    print('Please either specify a valid project root directory '
+          'or omit it on the command line.')
+    sys.exit(1)
+
+
+def ValidateGTestRootDir(gtest_root):
+  """Makes sure gtest_root points to a valid gtest root directory.
+
+  The function aborts the program on failure.
+  """
+
+  VerifyFileExists(gtest_root, GTEST_H_SEED)
+  VerifyFileExists(gtest_root, GTEST_ALL_CC_SEED)
+
+
+def VerifyOutputFile(output_dir, relative_path):
+  """Verifies that the given output file path is valid.
+
+  relative_path is relative to the output_dir directory.
+  """
+
+  # Makes sure the output file either doesn't exist or can be overwritten.
+  output_file = os.path.join(output_dir, relative_path)
+  if os.path.exists(output_file):
+    # TODO(wan@google.com): The following user-interaction doesn't
+    # work with automated processes.  We should provide a way for the
+    # Makefile to force overwriting the files.
+    print('%s already exists in directory %s - overwrite it? (y/N) ' %
+          (relative_path, output_dir))
+    answer = sys.stdin.readline().strip()
+    if answer not in ['y', 'Y']:
+      print('ABORTED.')
+      sys.exit(1)
+
+  # Makes sure the directory holding the output file exists; creates
+  # it and all its ancestors if necessary.
+  parent_directory = os.path.dirname(output_file)
+  if not os.path.isdir(parent_directory):
+    os.makedirs(parent_directory)
+
+
+def ValidateOutputDir(output_dir):
+  """Makes sure output_dir points to a valid output directory.
+
+  The function aborts the program on failure.
+  """
+
+  VerifyOutputFile(output_dir, GTEST_H_OUTPUT)
+  VerifyOutputFile(output_dir, GTEST_ALL_CC_OUTPUT)
+
+
+def FuseGTestH(gtest_root, output_dir):
+  """Scans folder gtest_root to generate gtest/gtest.h in output_dir."""
+
+  output_file = open(os.path.join(output_dir, GTEST_H_OUTPUT), 'w')
+  processed_files = set()  # Holds all gtest headers we've processed.
+
+  def ProcessFile(gtest_header_path):
+    """Processes the given gtest header file."""
+
+    # We don't process the same header twice.
+    if gtest_header_path in processed_files:
+      return
+
+    processed_files.add(gtest_header_path)
+
+    # Reads each line in the given gtest header.
+    for line in open(os.path.join(gtest_root, gtest_header_path), 'r'):
+      m = INCLUDE_GTEST_FILE_REGEX.match(line)
+      if m:
+        # It's '#include "gtest/..."' - let's process it recursively.
+        ProcessFile('include/' + m.group(1))
+      else:
+        # Otherwise we copy the line unchanged to the output file.
+        output_file.write(line)
+
+  ProcessFile(GTEST_H_SEED)
+  output_file.close()
+
+
+def FuseGTestAllCcToFile(gtest_root, output_file):
+  """Scans folder gtest_root to generate gtest/gtest-all.cc in output_file."""
+
+  processed_files = set()
+
+  def ProcessFile(gtest_source_file):
+    """Processes the given gtest source file."""
+
+    # We don't process the same #included file twice.
+    if gtest_source_file in processed_files:
+      return
+
+    processed_files.add(gtest_source_file)
+
+    # Reads each line in the given gtest source file.
+    for line in open(os.path.join(gtest_root, gtest_source_file), 'r'):
+      m = INCLUDE_GTEST_FILE_REGEX.match(line)
+      if m:
+        if 'include/' + m.group(1) == GTEST_SPI_H_SEED:
+          # It's '#include "gtest/gtest-spi.h"'.  This file is not
+          # #included by "gtest/gtest.h", so we need to process it.
+          ProcessFile(GTEST_SPI_H_SEED)
+        else:
+          # It's '#include "gtest/foo.h"' where foo is not gtest-spi.
+          # We treat it as '#include "gtest/gtest.h"', as all other
+          # gtest headers are being fused into gtest.h and cannot be
+          # #included directly.
+
+          # There is no need to #include "gtest/gtest.h" more than once.
+          if not GTEST_H_SEED in processed_files:
+            processed_files.add(GTEST_H_SEED)
+            output_file.write('#include "%s"\n' % (GTEST_H_OUTPUT,))
+      else:
+        m = INCLUDE_SRC_FILE_REGEX.match(line)
+        if m:
+          # It's '#include "src/foo"' - let's process it recursively.
+          ProcessFile(m.group(1))
+        else:
+          output_file.write(line)
+
+  ProcessFile(GTEST_ALL_CC_SEED)
+
+
+def FuseGTestAllCc(gtest_root, output_dir):
+  """Scans folder gtest_root to generate gtest/gtest-all.cc in output_dir."""
+
+  output_file = open(os.path.join(output_dir, GTEST_ALL_CC_OUTPUT), 'w')
+  FuseGTestAllCcToFile(gtest_root, output_file)
+  output_file.close()
+
+
+def FuseGTest(gtest_root, output_dir):
+  """Fuses gtest.h and gtest-all.cc."""
+
+  ValidateGTestRootDir(gtest_root)
+  ValidateOutputDir(output_dir)
+
+  FuseGTestH(gtest_root, output_dir)
+  FuseGTestAllCc(gtest_root, output_dir)
+
+
+def main():
+  argc = len(sys.argv)
+  if argc == 2:
+    # fuse_gtest_files.py OUTPUT_DIR
+    FuseGTest(DEFAULT_GTEST_ROOT_DIR, sys.argv[1])
+  elif argc == 3:
+    # fuse_gtest_files.py GTEST_ROOT_DIR OUTPUT_DIR
+    FuseGTest(sys.argv[1], sys.argv[2])
+  else:
+    print(__doc__)
+    sys.exit(1)
+
+
+if __name__ == '__main__':
+  main()
diff --git a/leveldb_base/third_party/googletest/googletest/scripts/gen_gtest_pred_impl.py b/leveldb_base/third_party/googletest/googletest/scripts/gen_gtest_pred_impl.py
new file mode 100644
index 0000000..e09a6e0
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/scripts/gen_gtest_pred_impl.py
@@ -0,0 +1,733 @@
+#!/usr/bin/env python
+#
+# Copyright 2006, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""gen_gtest_pred_impl.py v0.1
+
+Generates the implementation of Google Test predicate assertions and
+accompanying tests.
+
+Usage:
+
+  gen_gtest_pred_impl.py MAX_ARITY
+
+where MAX_ARITY is a positive integer.
+
+The command generates the implementation of up-to MAX_ARITY-ary
+predicate assertions, and writes it to file gtest_pred_impl.h in the
+directory where the script is.  It also generates the accompanying
+unit test in file gtest_pred_impl_unittest.cc.
+"""
+
+__author__ = 'wan@google.com (Zhanyong Wan)'
+
+import os
+import sys
+import time
+
+# Where this script is.
+SCRIPT_DIR = os.path.dirname(sys.argv[0])
+
+# Where to store the generated header.
+HEADER = os.path.join(SCRIPT_DIR, '../include/gtest/gtest_pred_impl.h')
+
+# Where to store the generated unit test.
+UNIT_TEST = os.path.join(SCRIPT_DIR, '../test/gtest_pred_impl_unittest.cc')
+
+
+def HeaderPreamble(n):
+  """Returns the preamble for the header file.
+
+  Args:
+    n:  the maximum arity of the predicate macros to be generated.
+  """
+
+  # A map that defines the values used in the preamble template.
+  DEFS = {
+    'today' : time.strftime('%m/%d/%Y'),
+    'year' : time.strftime('%Y'),
+    'command' : '%s %s' % (os.path.basename(sys.argv[0]), n),
+    'n' : n
+    }
+
+  return (
+  """// Copyright 2006, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// This file is AUTOMATICALLY GENERATED on %(today)s by command
+// '%(command)s'.  DO NOT EDIT BY HAND!
+//
+// Implements a family of generic predicate assertion macros.
+// GOOGLETEST_CM0001 DO NOT DELETE
+
+
+#ifndef GTEST_INCLUDE_GTEST_GTEST_PRED_IMPL_H_
+#define GTEST_INCLUDE_GTEST_GTEST_PRED_IMPL_H_
+
+#include "gtest/gtest.h"
+
+namespace testing {
+
+// This header implements a family of generic predicate assertion
+// macros:
+//
+//   ASSERT_PRED_FORMAT1(pred_format, v1)
+//   ASSERT_PRED_FORMAT2(pred_format, v1, v2)
+//   ...
+//
+// where pred_format is a function or functor that takes n (in the
+// case of ASSERT_PRED_FORMATn) values and their source expression
+// text, and returns a testing::AssertionResult.  See the definition
+// of ASSERT_EQ in gtest.h for an example.
+//
+// If you don't care about formatting, you can use the more
+// restrictive version:
+//
+//   ASSERT_PRED1(pred, v1)
+//   ASSERT_PRED2(pred, v1, v2)
+//   ...
+//
+// where pred is an n-ary function or functor that returns bool,
+// and the values v1, v2, ..., must support the << operator for
+// streaming to std::ostream.
+//
+// We also define the EXPECT_* variations.
+//
+// For now we only support predicates whose arity is at most %(n)s.
+// Please email googletestframework@googlegroups.com if you need
+// support for higher arities.
+
+// GTEST_ASSERT_ is the basic statement to which all of the assertions
+// in this file reduce.  Don't use this in your code.
+
+#define GTEST_ASSERT_(expression, on_failure) \\
+  GTEST_AMBIGUOUS_ELSE_BLOCKER_ \\
+  if (const ::testing::AssertionResult gtest_ar = (expression)) \\
+    ; \\
+  else \\
+    on_failure(gtest_ar.failure_message())
+""" % DEFS)
+
+
+def Arity(n):
+  """Returns the English name of the given arity."""
+
+  if n < 0:
+    return None
+  elif n <= 3:
+    return ['nullary', 'unary', 'binary', 'ternary'][n]
+  else:
+    return '%s-ary' % n
+
+
+def Title(word):
+  """Returns the given word in title case.  The difference between
+  this and string's title() method is that Title('4-ary') is '4-ary'
+  while '4-ary'.title() is '4-Ary'."""
+
+  return word[0].upper() + word[1:]
+
+
+def OneTo(n):
+  """Returns the list [1, 2, 3, ..., n]."""
+
+  return range(1, n + 1)
+
+
+def Iter(n, format, sep=''):
+  """Given a positive integer n, a format string that contains 0 or
+  more '%s' format specs, and optionally a separator string, returns
+  the join of n strings, each formatted with the format string on an
+  iterator ranged from 1 to n.
+
+  Example:
+
+  Iter(3, 'v%s', sep=', ') returns 'v1, v2, v3'.
+  """
+
+  # How many '%s' specs are in format?
+  spec_count = len(format.split('%s')) - 1
+  return sep.join([format % (spec_count * (i,)) for i in OneTo(n)])
+
+
+def ImplementationForArity(n):
+  """Returns the implementation of n-ary predicate assertions."""
+
+  # A map the defines the values used in the implementation template.
+  DEFS = {
+    'n' : str(n),
+    'vs' : Iter(n, 'v%s', sep=', '),
+    'vts' : Iter(n, '#v%s', sep=', '),
+    'arity' : Arity(n),
+    'Arity' : Title(Arity(n))
+    }
+
+  impl = """
+
+// Helper function for implementing {EXPECT|ASSERT}_PRED%(n)s.  Don't use
+// this in your code.
+template <typename Pred""" % DEFS
+
+  impl += Iter(n, """,
+          typename T%s""")
+
+  impl += """>
+AssertionResult AssertPred%(n)sHelper(const char* pred_text""" % DEFS
+
+  impl += Iter(n, """,
+                                  const char* e%s""")
+
+  impl += """,
+                                  Pred pred"""
+
+  impl += Iter(n, """,
+                                  const T%s& v%s""")
+
+  impl += """) {
+  if (pred(%(vs)s)) return AssertionSuccess();
+
+""" % DEFS
+
+  impl += '  return AssertionFailure() << pred_text << "("'
+
+  impl += Iter(n, """
+                            << e%s""", sep=' << ", "')
+
+  impl += ' << ") evaluates to false, where"'
+
+  impl += Iter(
+      n, """
+      << "\\n" << e%s << " evaluates to " << ::testing::PrintToString(v%s)"""
+  )
+
+  impl += """;
+}
+
+// Internal macro for implementing {EXPECT|ASSERT}_PRED_FORMAT%(n)s.
+// Don't use this in your code.
+#define GTEST_PRED_FORMAT%(n)s_(pred_format, %(vs)s, on_failure)\\
+  GTEST_ASSERT_(pred_format(%(vts)s, %(vs)s), \\
+                on_failure)
+
+// Internal macro for implementing {EXPECT|ASSERT}_PRED%(n)s.  Don't use
+// this in your code.
+#define GTEST_PRED%(n)s_(pred, %(vs)s, on_failure)\\
+  GTEST_ASSERT_(::testing::AssertPred%(n)sHelper(#pred""" % DEFS
+
+  impl += Iter(n, """, \\
+                                             #v%s""")
+
+  impl += """, \\
+                                             pred"""
+
+  impl += Iter(n, """, \\
+                                             v%s""")
+
+  impl += """), on_failure)
+
+// %(Arity)s predicate assertion macros.
+#define EXPECT_PRED_FORMAT%(n)s(pred_format, %(vs)s) \\
+  GTEST_PRED_FORMAT%(n)s_(pred_format, %(vs)s, GTEST_NONFATAL_FAILURE_)
+#define EXPECT_PRED%(n)s(pred, %(vs)s) \\
+  GTEST_PRED%(n)s_(pred, %(vs)s, GTEST_NONFATAL_FAILURE_)
+#define ASSERT_PRED_FORMAT%(n)s(pred_format, %(vs)s) \\
+  GTEST_PRED_FORMAT%(n)s_(pred_format, %(vs)s, GTEST_FATAL_FAILURE_)
+#define ASSERT_PRED%(n)s(pred, %(vs)s) \\
+  GTEST_PRED%(n)s_(pred, %(vs)s, GTEST_FATAL_FAILURE_)
+
+""" % DEFS
+
+  return impl
+
+
+def HeaderPostamble():
+  """Returns the postamble for the header file."""
+
+  return """
+
+}  // namespace testing
+
+#endif  // GTEST_INCLUDE_GTEST_GTEST_PRED_IMPL_H_
+"""
+
+
+def GenerateFile(path, content):
+  """Given a file path and a content string
+     overwrites it with the given content.
+  """
+  print 'Updating file %s . . .' % path
+  f = file(path, 'w+')
+  print >>f, content,
+  f.close()
+
+  print 'File %s has been updated.' % path
+
+
+def GenerateHeader(n):
+  """Given the maximum arity n, updates the header file that implements
+  the predicate assertions.
+  """
+  GenerateFile(HEADER,
+               HeaderPreamble(n)
+               + ''.join([ImplementationForArity(i) for i in OneTo(n)])
+               + HeaderPostamble())
+
+
+def UnitTestPreamble():
+  """Returns the preamble for the unit test file."""
+
+  # A map that defines the values used in the preamble template.
+  DEFS = {
+    'today' : time.strftime('%m/%d/%Y'),
+    'year' : time.strftime('%Y'),
+    'command' : '%s %s' % (os.path.basename(sys.argv[0]), sys.argv[1]),
+    }
+
+  return (
+  """// Copyright 2006, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// This file is AUTOMATICALLY GENERATED on %(today)s by command
+// '%(command)s'.  DO NOT EDIT BY HAND!
+
+// Regression test for gtest_pred_impl.h
+//
+// This file is generated by a script and quite long.  If you intend to
+// learn how Google Test works by reading its unit tests, read
+// gtest_unittest.cc instead.
+//
+// This is intended as a regression test for the Google Test predicate
+// assertions.  We compile it as part of the gtest_unittest target
+// only to keep the implementation tidy and compact, as it is quite
+// involved to set up the stage for testing Google Test using Google
+// Test itself.
+//
+// Currently, gtest_unittest takes ~11 seconds to run in the testing
+// daemon.  In the future, if it grows too large and needs much more
+// time to finish, we should consider separating this file into a
+// stand-alone regression test.
+
+#include <iostream>
+
+#include "gtest/gtest.h"
+#include "gtest/gtest-spi.h"
+
+// A user-defined data type.
+struct Bool {
+  explicit Bool(int val) : value(val != 0) {}
+
+  bool operator>(int n) const { return value > Bool(n).value; }
+
+  Bool operator+(const Bool& rhs) const { return Bool(value + rhs.value); }
+
+  bool operator==(const Bool& rhs) const { return value == rhs.value; }
+
+  bool value;
+};
+
+// Enables Bool to be used in assertions.
+std::ostream& operator<<(std::ostream& os, const Bool& x) {
+  return os << (x.value ? "true" : "false");
+}
+
+""" % DEFS)
+
+
+def TestsForArity(n):
+  """Returns the tests for n-ary predicate assertions."""
+
+  # A map that defines the values used in the template for the tests.
+  DEFS = {
+    'n' : n,
+    'es' : Iter(n, 'e%s', sep=', '),
+    'vs' : Iter(n, 'v%s', sep=', '),
+    'vts' : Iter(n, '#v%s', sep=', '),
+    'tvs' : Iter(n, 'T%s v%s', sep=', '),
+    'int_vs' : Iter(n, 'int v%s', sep=', '),
+    'Bool_vs' : Iter(n, 'Bool v%s', sep=', '),
+    'types' : Iter(n, 'typename T%s', sep=', '),
+    'v_sum' : Iter(n, 'v%s', sep=' + '),
+    'arity' : Arity(n),
+    'Arity' : Title(Arity(n)),
+    }
+
+  tests = (
+  """// Sample functions/functors for testing %(arity)s predicate assertions.
+
+// A %(arity)s predicate function.
+template <%(types)s>
+bool PredFunction%(n)s(%(tvs)s) {
+  return %(v_sum)s > 0;
+}
+
+// The following two functions are needed because a compiler doesn't have
+// a context yet to know which template function must be instantiated.
+bool PredFunction%(n)sInt(%(int_vs)s) {
+  return %(v_sum)s > 0;
+}
+bool PredFunction%(n)sBool(%(Bool_vs)s) {
+  return %(v_sum)s > 0;
+}
+""" % DEFS)
+
+  tests += """
+// A %(arity)s predicate functor.
+struct PredFunctor%(n)s {
+  template <%(types)s>
+  bool operator()(""" % DEFS
+
+  tests += Iter(n, 'const T%s& v%s', sep=""",
+                  """)
+
+  tests += """) {
+    return %(v_sum)s > 0;
+  }
+};
+""" % DEFS
+
+  tests += """
+// A %(arity)s predicate-formatter function.
+template <%(types)s>
+testing::AssertionResult PredFormatFunction%(n)s(""" % DEFS
+
+  tests += Iter(n, 'const char* e%s', sep=""",
+                                             """)
+
+  tests += Iter(n, """,
+                                             const T%s& v%s""")
+
+  tests += """) {
+  if (PredFunction%(n)s(%(vs)s))
+    return testing::AssertionSuccess();
+
+  return testing::AssertionFailure()
+      << """ % DEFS
+
+  tests += Iter(n, 'e%s', sep=' << " + " << ')
+
+  tests += """
+      << " is expected to be positive, but evaluates to "
+      << %(v_sum)s << ".";
+}
+""" % DEFS
+
+  tests += """
+// A %(arity)s predicate-formatter functor.
+struct PredFormatFunctor%(n)s {
+  template <%(types)s>
+  testing::AssertionResult operator()(""" % DEFS
+
+  tests += Iter(n, 'const char* e%s', sep=""",
+                                      """)
+
+  tests += Iter(n, """,
+                                      const T%s& v%s""")
+
+  tests += """) const {
+    return PredFormatFunction%(n)s(%(es)s, %(vs)s);
+  }
+};
+""" % DEFS
+
+  tests += """
+// Tests for {EXPECT|ASSERT}_PRED_FORMAT%(n)s.
+
+class Predicate%(n)sTest : public testing::Test {
+ protected:
+  void SetUp() override {
+    expected_to_finish_ = true;
+    finished_ = false;""" % DEFS
+
+  tests += """
+    """ + Iter(n, 'n%s_ = ') + """0;
+  }
+"""
+
+  tests += """
+  void TearDown() override {
+    // Verifies that each of the predicate's arguments was evaluated
+    // exactly once."""
+
+  tests += ''.join(["""
+    EXPECT_EQ(1, n%s_) <<
+        "The predicate assertion didn't evaluate argument %s "
+        "exactly once.";""" % (i, i + 1) for i in OneTo(n)])
+
+  tests += """
+
+    // Verifies that the control flow in the test function is expected.
+    if (expected_to_finish_ && !finished_) {
+      FAIL() << "The predicate assertion unexpactedly aborted the test.";
+    } else if (!expected_to_finish_ && finished_) {
+      FAIL() << "The failed predicate assertion didn't abort the test "
+                "as expected.";
+    }
+  }
+
+  // true if and only if the test function is expected to run to finish.
+  static bool expected_to_finish_;
+
+  // true if and only if the test function did run to finish.
+  static bool finished_;
+""" % DEFS
+
+  tests += Iter(n, """
+  static int n%s_;""")
+
+  tests += """
+};
+
+bool Predicate%(n)sTest::expected_to_finish_;
+bool Predicate%(n)sTest::finished_;
+""" % DEFS
+
+  tests += Iter(n, """int Predicate%%(n)sTest::n%s_;
+""") % DEFS
+
+  tests += """
+typedef Predicate%(n)sTest EXPECT_PRED_FORMAT%(n)sTest;
+typedef Predicate%(n)sTest ASSERT_PRED_FORMAT%(n)sTest;
+typedef Predicate%(n)sTest EXPECT_PRED%(n)sTest;
+typedef Predicate%(n)sTest ASSERT_PRED%(n)sTest;
+""" % DEFS
+
+  def GenTest(use_format, use_assert, expect_failure,
+              use_functor, use_user_type):
+    """Returns the test for a predicate assertion macro.
+
+    Args:
+      use_format:     true if and only if the assertion is a *_PRED_FORMAT*.
+      use_assert:     true if and only if the assertion is a ASSERT_*.
+      expect_failure: true if and only if the assertion is expected to fail.
+      use_functor:    true if and only if the first argument of the assertion is
+                      a functor (as opposed to a function)
+      use_user_type:  true if and only if the predicate functor/function takes
+                      argument(s) of a user-defined type.
+
+    Example:
+
+      GenTest(1, 0, 0, 1, 0) returns a test that tests the behavior
+      of a successful EXPECT_PRED_FORMATn() that takes a functor
+      whose arguments have built-in types."""
+
+    if use_assert:
+      assrt = 'ASSERT'  # 'assert' is reserved, so we cannot use
+      # that identifier here.
+    else:
+      assrt = 'EXPECT'
+
+    assertion = assrt + '_PRED'
+
+    if use_format:
+      pred_format = 'PredFormat'
+      assertion += '_FORMAT'
+    else:
+      pred_format = 'Pred'
+
+    assertion += '%(n)s' % DEFS
+
+    if use_functor:
+      pred_format_type = 'functor'
+      pred_format += 'Functor%(n)s()'
+    else:
+      pred_format_type = 'function'
+      pred_format += 'Function%(n)s'
+      if not use_format:
+        if use_user_type:
+          pred_format += 'Bool'
+        else:
+          pred_format += 'Int'
+
+    test_name = pred_format_type.title()
+
+    if use_user_type:
+      arg_type = 'user-defined type (Bool)'
+      test_name += 'OnUserType'
+      if expect_failure:
+        arg = 'Bool(n%s_++)'
+      else:
+        arg = 'Bool(++n%s_)'
+    else:
+      arg_type = 'built-in type (int)'
+      test_name += 'OnBuiltInType'
+      if expect_failure:
+        arg = 'n%s_++'
+      else:
+        arg = '++n%s_'
+
+    if expect_failure:
+      successful_or_failed = 'failed'
+      expected_or_not = 'expected.'
+      test_name +=  'Failure'
+    else:
+      successful_or_failed = 'successful'
+      expected_or_not = 'UNEXPECTED!'
+      test_name +=  'Success'
+
+    # A map that defines the values used in the test template.
+    defs = DEFS.copy()
+    defs.update({
+      'assert' : assrt,
+      'assertion' : assertion,
+      'test_name' : test_name,
+      'pf_type' : pred_format_type,
+      'pf' : pred_format,
+      'arg_type' : arg_type,
+      'arg' : arg,
+      'successful' : successful_or_failed,
+      'expected' : expected_or_not,
+      })
+
+    test = """
+// Tests a %(successful)s %(assertion)s where the
+// predicate-formatter is a %(pf_type)s on a %(arg_type)s.
+TEST_F(%(assertion)sTest, %(test_name)s) {""" % defs
+
+    indent = (len(assertion) + 3)*' '
+    extra_indent = ''
+
+    if expect_failure:
+      extra_indent = '  '
+      if use_assert:
+        test += """
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT"""
+      else:
+        test += """
+  EXPECT_NONFATAL_FAILURE({  // NOLINT"""
+
+    test += '\n' + extra_indent + """  %(assertion)s(%(pf)s""" % defs
+
+    test = test % defs
+    test += Iter(n, ',\n' + indent + extra_indent + '%(arg)s' % defs)
+    test += ');\n' + extra_indent + '  finished_ = true;\n'
+
+    if expect_failure:
+      test += '  }, "");\n'
+
+    test += '}\n'
+    return test
+
+  # Generates tests for all 2**6 = 64 combinations.
+  tests += ''.join([GenTest(use_format, use_assert, expect_failure,
+                            use_functor, use_user_type)
+                    for use_format in [0, 1]
+                    for use_assert in [0, 1]
+                    for expect_failure in [0, 1]
+                    for use_functor in [0, 1]
+                    for use_user_type in [0, 1]
+                    ])
+
+  return tests
+
+
+def UnitTestPostamble():
+  """Returns the postamble for the tests."""
+
+  return ''
+
+
+def GenerateUnitTest(n):
+  """Returns the tests for up-to n-ary predicate assertions."""
+
+  GenerateFile(UNIT_TEST,
+               UnitTestPreamble()
+               + ''.join([TestsForArity(i) for i in OneTo(n)])
+               + UnitTestPostamble())
+
+
+def _Main():
+  """The entry point of the script.  Generates the header file and its
+  unit test."""
+
+  if len(sys.argv) != 2:
+    print __doc__
+    print 'Author: ' + __author__
+    sys.exit(1)
+
+  n = int(sys.argv[1])
+  GenerateHeader(n)
+  GenerateUnitTest(n)
+
+
+if __name__ == '__main__':
+  _Main()
diff --git a/leveldb_base/third_party/googletest/googletest/scripts/gtest-config.in b/leveldb_base/third_party/googletest/googletest/scripts/gtest-config.in
new file mode 100644
index 0000000..780f843
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/scripts/gtest-config.in
@@ -0,0 +1,274 @@
+#!/bin/sh
+
+# These variables are automatically filled in by the configure script.
+name="@PACKAGE_TARNAME@"
+version="@PACKAGE_VERSION@"
+
+show_usage()
+{
+  echo "Usage: gtest-config [OPTIONS...]"
+}
+
+show_help()
+{
+  show_usage
+  cat <<\EOF
+
+The `gtest-config' script provides access to the necessary compile and linking
+flags to connect with Google C++ Testing Framework, both in a build prior to
+installation, and on the system proper after installation. The installation
+overrides may be issued in combination with any other queries, but will only
+affect installation queries if called on a built but not installed gtest. The
+installation queries may not be issued with any other types of queries, and
+only one installation query may be made at a time. The version queries and
+compiler flag queries may be combined as desired but not mixed. Different
+version queries are always combined with logical "and" semantics, and only the
+last of any particular query is used while all previous ones ignored. All
+versions must be specified as a sequence of numbers separated by periods.
+Compiler flag queries output the union of the sets of flags when combined.
+
+ Examples:
+  gtest-config --min-version=1.0 || echo "Insufficient Google Test version."
+
+  g++ $(gtest-config --cppflags --cxxflags) -o foo.o -c foo.cpp
+  g++ $(gtest-config --ldflags --libs) -o foo foo.o
+
+  # When using a built but not installed Google Test:
+  g++ $(../../my_gtest_build/scripts/gtest-config ...) ...
+
+  # When using an installed Google Test, but with installation overrides:
+  export GTEST_PREFIX="/opt"
+  g++ $(gtest-config --libdir="/opt/lib64" ...) ...
+
+ Help:
+  --usage                    brief usage information
+  --help                     display this help message
+
+ Installation Overrides:
+  --prefix=<dir>             overrides the installation prefix
+  --exec-prefix=<dir>        overrides the executable installation prefix
+  --libdir=<dir>             overrides the library installation prefix
+  --includedir=<dir>         overrides the header file installation prefix
+
+ Installation Queries:
+  --prefix                   installation prefix
+  --exec-prefix              executable installation prefix
+  --libdir                   library installation directory
+  --includedir               header file installation directory
+  --version                  the version of the Google Test installation
+
+ Version Queries:
+  --min-version=VERSION      return 0 if the version is at least VERSION
+  --exact-version=VERSION    return 0 if the version is exactly VERSION
+  --max-version=VERSION      return 0 if the version is at most VERSION
+
+ Compilation Flag Queries:
+  --cppflags                 compile flags specific to the C-like preprocessors
+  --cxxflags                 compile flags appropriate for C++ programs
+  --ldflags                  linker flags
+  --libs                     libraries for linking
+
+EOF
+}
+
+# This function bounds our version with a min and a max. It uses some clever
+# POSIX-compliant variable expansion to portably do all the work in the shell
+# and avoid any dependency on a particular "sed" or "awk" implementation.
+# Notable is that it will only ever compare the first 3 components of versions.
+# Further components will be cleanly stripped off. All versions must be
+# unadorned, so "v1.0" will *not* work. The minimum version must be in $1, and
+# the max in $2. TODO(chandlerc@google.com): If this ever breaks, we should
+# investigate expanding this via autom4te from AS_VERSION_COMPARE rather than
+# continuing to maintain our own shell version.
+check_versions()
+{
+  major_version=${version%%.*}
+  minor_version="0"
+  point_version="0"
+  if test "${version#*.}" != "${version}"; then
+    minor_version=${version#*.}
+    minor_version=${minor_version%%.*}
+  fi
+  if test "${version#*.*.}" != "${version}"; then
+    point_version=${version#*.*.}
+    point_version=${point_version%%.*}
+  fi
+
+  min_version="$1"
+  min_major_version=${min_version%%.*}
+  min_minor_version="0"
+  min_point_version="0"
+  if test "${min_version#*.}" != "${min_version}"; then
+    min_minor_version=${min_version#*.}
+    min_minor_version=${min_minor_version%%.*}
+  fi
+  if test "${min_version#*.*.}" != "${min_version}"; then
+    min_point_version=${min_version#*.*.}
+    min_point_version=${min_point_version%%.*}
+  fi
+
+  max_version="$2"
+  max_major_version=${max_version%%.*}
+  max_minor_version="0"
+  max_point_version="0"
+  if test "${max_version#*.}" != "${max_version}"; then
+    max_minor_version=${max_version#*.}
+    max_minor_version=${max_minor_version%%.*}
+  fi
+  if test "${max_version#*.*.}" != "${max_version}"; then
+    max_point_version=${max_version#*.*.}
+    max_point_version=${max_point_version%%.*}
+  fi
+
+  test $(($major_version)) -lt $(($min_major_version)) && exit 1
+  if test $(($major_version)) -eq $(($min_major_version)); then
+    test $(($minor_version)) -lt $(($min_minor_version)) && exit 1
+    if test $(($minor_version)) -eq $(($min_minor_version)); then
+      test $(($point_version)) -lt $(($min_point_version)) && exit 1
+    fi
+  fi
+
+  test $(($major_version)) -gt $(($max_major_version)) && exit 1
+  if test $(($major_version)) -eq $(($max_major_version)); then
+    test $(($minor_version)) -gt $(($max_minor_version)) && exit 1
+    if test $(($minor_version)) -eq $(($max_minor_version)); then
+      test $(($point_version)) -gt $(($max_point_version)) && exit 1
+    fi
+  fi
+
+  exit 0
+}
+
+# Show the usage line when no arguments are specified.
+if test $# -eq 0; then
+  show_usage
+  exit 1
+fi
+
+while test $# -gt 0; do
+  case $1 in
+    --usage)          show_usage;         exit 0;;
+    --help)           show_help;          exit 0;;
+
+    # Installation overrides
+    --prefix=*)       GTEST_PREFIX=${1#--prefix=};;
+    --exec-prefix=*)  GTEST_EXEC_PREFIX=${1#--exec-prefix=};;
+    --libdir=*)       GTEST_LIBDIR=${1#--libdir=};;
+    --includedir=*)   GTEST_INCLUDEDIR=${1#--includedir=};;
+
+    # Installation queries
+    --prefix|--exec-prefix|--libdir|--includedir|--version)
+      if test -n "${do_query}"; then
+        show_usage
+        exit 1
+      fi
+      do_query=${1#--}
+      ;;
+
+    # Version checking
+    --min-version=*)
+      do_check_versions=yes
+      min_version=${1#--min-version=}
+      ;;
+    --max-version=*)
+      do_check_versions=yes
+      max_version=${1#--max-version=}
+      ;;
+    --exact-version=*)
+      do_check_versions=yes
+      exact_version=${1#--exact-version=}
+      ;;
+
+    # Compiler flag output
+    --cppflags)       echo_cppflags=yes;;
+    --cxxflags)       echo_cxxflags=yes;;
+    --ldflags)        echo_ldflags=yes;;
+    --libs)           echo_libs=yes;;
+
+    # Everything else is an error
+    *)                show_usage;         exit 1;;
+  esac
+  shift
+done
+
+# These have defaults filled in by the configure script but can also be
+# overridden by environment variables or command line parameters.
+prefix="${GTEST_PREFIX:-@prefix@}"
+exec_prefix="${GTEST_EXEC_PREFIX:-@exec_prefix@}"
+libdir="${GTEST_LIBDIR:-@libdir@}"
+includedir="${GTEST_INCLUDEDIR:-@includedir@}"
+
+# We try and detect if our binary is not located at its installed location. If
+# it's not, we provide variables pointing to the source and build tree rather
+# than to the install tree. This allows building against a just-built gtest
+# rather than an installed gtest.
+bindir="@bindir@"
+this_relative_bindir=`dirname $0`
+this_bindir=`cd ${this_relative_bindir}; pwd -P`
+if test "${this_bindir}" = "${this_bindir%${bindir}}"; then
+  # The path to the script doesn't end in the bindir sequence from Autoconf,
+  # assume that we are in a build tree.
+  build_dir=`dirname ${this_bindir}`
+  src_dir=`cd ${this_bindir}; cd @top_srcdir@; pwd -P`
+
+  # TODO(chandlerc@google.com): This is a dangerous dependency on libtool, we
+  # should work to remove it, and/or remove libtool altogether, replacing it
+  # with direct references to the library and a link path.
+  gtest_libs="${build_dir}/lib/libgtest.la @PTHREAD_CFLAGS@ @PTHREAD_LIBS@"
+  gtest_ldflags=""
+
+  # We provide hooks to include from either the source or build dir, where the
+  # build dir is always preferred. This will potentially allow us to write
+  # build rules for generated headers and have them automatically be preferred
+  # over provided versions.
+  gtest_cppflags="-I${build_dir}/include -I${src_dir}/include"
+  gtest_cxxflags="@PTHREAD_CFLAGS@"
+else
+  # We're using an installed gtest, although it may be staged under some
+  # prefix. Assume (as our own libraries do) that we can resolve the prefix,
+  # and are present in the dynamic link paths.
+  gtest_ldflags="-L${libdir}"
+  gtest_libs="-l${name} @PTHREAD_CFLAGS@ @PTHREAD_LIBS@"
+  gtest_cppflags="-I${includedir}"
+  gtest_cxxflags="@PTHREAD_CFLAGS@"
+fi
+
+# Do an installation query if requested.
+if test -n "$do_query"; then
+  case $do_query in
+    prefix)           echo $prefix;       exit 0;;
+    exec-prefix)      echo $exec_prefix;  exit 0;;
+    libdir)           echo $libdir;       exit 0;;
+    includedir)       echo $includedir;   exit 0;;
+    version)          echo $version;      exit 0;;
+    *)                show_usage;         exit 1;;
+  esac
+fi
+
+# Do a version check if requested.
+if test "$do_check_versions" = "yes"; then
+  # Make sure we didn't receive a bad combination of parameters.
+  test "$echo_cppflags" = "yes" && show_usage && exit 1
+  test "$echo_cxxflags" = "yes" && show_usage && exit 1
+  test "$echo_ldflags" = "yes"  && show_usage && exit 1
+  test "$echo_libs" = "yes"     && show_usage && exit 1
+
+  if test "$exact_version" != ""; then
+    check_versions $exact_version $exact_version
+    # unreachable
+  else
+    check_versions ${min_version:-0.0.0} ${max_version:-9999.9999.9999}
+    # unreachable
+  fi
+fi
+
+# Do the output in the correct order so that these can be used in-line of
+# a compiler invocation.
+output=""
+test "$echo_cppflags" = "yes" && output="$output $gtest_cppflags"
+test "$echo_cxxflags" = "yes" && output="$output $gtest_cxxflags"
+test "$echo_ldflags" = "yes"  && output="$output $gtest_ldflags"
+test "$echo_libs" = "yes"     && output="$output $gtest_libs"
+echo $output
+
+exit 0
diff --git a/leveldb_base/third_party/googletest/googletest/scripts/release_docs.py b/leveldb_base/third_party/googletest/googletest/scripts/release_docs.py
new file mode 100644
index 0000000..8d24f28
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/scripts/release_docs.py
@@ -0,0 +1,158 @@
+#!/usr/bin/env python
+#
+# Copyright 2013 Google Inc. All Rights Reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Script for branching Google Test/Mock wiki pages for a new version.
+
+SYNOPSIS
+       release_docs.py NEW_RELEASE_VERSION
+
+       Google Test and Google Mock's external user documentation is in
+       interlinked wiki files.  When we release a new version of
+       Google Test or Google Mock, we need to branch the wiki files
+       such that users of a specific version of Google Test/Mock can
+       look up documentation relevant for that version.  This script
+       automates that process by:
+
+         - branching the current wiki pages (which document the
+           behavior of the SVN trunk head) to pages for the specified
+           version (e.g. branching FAQ.wiki to V2_6_FAQ.wiki when
+           NEW_RELEASE_VERSION is 2.6);
+         - updating the links in the branched files to point to the branched
+           version (e.g. a link in V2_6_FAQ.wiki that pointed to
+           Primer.wiki#Anchor will now point to V2_6_Primer.wiki#Anchor).
+
+       NOTE: NEW_RELEASE_VERSION must be a NEW version number for
+       which the wiki pages don't yet exist; otherwise you'll get SVN
+       errors like "svn: Path 'V1_7_PumpManual.wiki' is not a
+       directory" when running the script.
+
+EXAMPLE
+       $ cd PATH/TO/GTEST_SVN_WORKSPACE/trunk
+       $ scripts/release_docs.py 2.6  # create wiki pages for v2.6
+       $ svn status                   # verify the file list
+       $ svn diff                     # verify the file contents
+       $ svn commit -m "release wiki pages for v2.6"
+"""
+
+__author__ = 'wan@google.com (Zhanyong Wan)'
+
+import os
+import re
+import sys
+
+import common
+
+
+# Wiki pages that shouldn't be branched for every gtest/gmock release.
+GTEST_UNVERSIONED_WIKIS = ['DevGuide.wiki']
+GMOCK_UNVERSIONED_WIKIS = [
+    'DesignDoc.wiki',
+    'DevGuide.wiki',
+    'KnownIssues.wiki'
+    ]
+
+
+def DropWikiSuffix(wiki_filename):
+  """Removes the .wiki suffix (if any) from the given filename."""
+
+  return (wiki_filename[:-len('.wiki')] if wiki_filename.endswith('.wiki')
+          else wiki_filename)
+
+
+class WikiBrancher(object):
+  """Branches ..."""
+
+  def __init__(self, dot_version):
+    self.project, svn_root_path = common.GetSvnInfo()
+    if self.project not in ('googletest', 'googlemock'):
+      sys.exit('This script must be run in a gtest or gmock SVN workspace.')
+    self.wiki_dir = svn_root_path + '/wiki'
+    # Turn '2.6' to 'V2_6_'.
+    self.version_prefix = 'V' + dot_version.replace('.', '_') + '_'
+    self.files_to_branch = self.GetFilesToBranch()
+    page_names = [DropWikiSuffix(f) for f in self.files_to_branch]
+    # A link to Foo.wiki is in one of the following forms:
+    #   [Foo words]
+    #   [Foo#Anchor words]
+    #   [http://code.google.com/.../wiki/Foo words]
+    #   [http://code.google.com/.../wiki/Foo#Anchor words]
+    # We want to replace 'Foo' with 'V2_6_Foo' in the above cases.
+    self.search_for_re = re.compile(
+        # This regex matches either
+        #   [Foo
+        # or
+        #   /wiki/Foo
+        # followed by a space or a #, where Foo is the name of an
+        # unversioned wiki page.
+        r'(\[|/wiki/)(%s)([ #])' % '|'.join(page_names))
+    self.replace_with = r'\1%s\2\3' % (self.version_prefix,)
+
+  def GetFilesToBranch(self):
+    """Returns a list of .wiki file names that need to be branched."""
+
+    unversioned_wikis = (GTEST_UNVERSIONED_WIKIS if self.project == 'googletest'
+                         else GMOCK_UNVERSIONED_WIKIS)
+    return [f for f in os.listdir(self.wiki_dir)
+            if (f.endswith('.wiki') and
+                not re.match(r'^V\d', f) and  # Excluded versioned .wiki files.
+                f not in unversioned_wikis)]
+
+  def BranchFiles(self):
+    """Branches the .wiki files needed to be branched."""
+
+    print 'Branching %d .wiki files:' % (len(self.files_to_branch),)
+    os.chdir(self.wiki_dir)
+    for f in self.files_to_branch:
+      command = 'svn cp %s %s%s' % (f, self.version_prefix, f)
+      print command
+      os.system(command)
+
+  def UpdateLinksInBranchedFiles(self):
+
+    for f in self.files_to_branch:
+      source_file = os.path.join(self.wiki_dir, f)
+      versioned_file = os.path.join(self.wiki_dir, self.version_prefix + f)
+      print 'Updating links in %s.' % (versioned_file,)
+      text = file(source_file, 'r').read()
+      new_text = self.search_for_re.sub(self.replace_with, text)
+      file(versioned_file, 'w').write(new_text)
+
+
+def main():
+  if len(sys.argv) != 2:
+    sys.exit(__doc__)
+
+  brancher = WikiBrancher(sys.argv[1])
+  brancher.BranchFiles()
+  brancher.UpdateLinksInBranchedFiles()
+
+
+if __name__ == '__main__':
+  main()
diff --git a/leveldb_base/third_party/googletest/googletest/scripts/run_with_path.py b/leveldb_base/third_party/googletest/googletest/scripts/run_with_path.py
new file mode 100644
index 0000000..d46ab4d
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/scripts/run_with_path.py
@@ -0,0 +1,32 @@
+#!/usr/bin/env python
+#
+# Copyright 2010 Google Inc. All Rights Reserved.
+
+"""Runs program specified in the command line with the substituted PATH.
+
+   This script is needed for to support building under Pulse which is unable
+   to override the existing PATH variable.
+"""
+
+import os
+import subprocess
+import sys
+
+SUBST_PATH_ENV_VAR_NAME = "SUBST_PATH"
+
+def main():
+  if SUBST_PATH_ENV_VAR_NAME in os.environ:
+    os.environ["PATH"] = os.environ[SUBST_PATH_ENV_VAR_NAME]
+
+  exit_code = subprocess.Popen(sys.argv[1:]).wait()
+
+  # exit_code is negative (-signal) if the process has been terminated by
+  # a signal. Returning negative exit code is not portable and so we return
+  # 100 instead.
+  if exit_code < 0:
+    exit_code = 100
+
+  sys.exit(exit_code)
+
+if __name__ == "__main__":
+  main()
diff --git a/leveldb_base/third_party/googletest/googletest/scripts/upload.py b/leveldb_base/third_party/googletest/googletest/scripts/upload.py
new file mode 100644
index 0000000..eba5711
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/scripts/upload.py
@@ -0,0 +1,1402 @@
+#!/usr/bin/env python
+#
+# Copyright 2007, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Tool for uploading diffs from a version control system to the codereview app.
+
+Usage summary: upload.py [options] [-- diff_options]
+
+Diff options are passed to the diff command of the underlying system.
+
+Supported version control systems:
+  Git
+  Mercurial
+  Subversion
+
+It is important for Git/Mercurial users to specify a tree/node/branch to diff
+against by using the '--rev' option.
+"""
+# This code is derived from appcfg.py in the App Engine SDK (open source),
+# and from ASPN recipe #146306.
+
+import cookielib
+import getpass
+import logging
+import md5
+import mimetypes
+import optparse
+import os
+import re
+import socket
+import subprocess
+import sys
+import urllib
+import urllib2
+import urlparse
+
+try:
+  import readline
+except ImportError:
+  pass
+
+# The logging verbosity:
+#  0: Errors only.
+#  1: Status messages.
+#  2: Info logs.
+#  3: Debug logs.
+verbosity = 1
+
+# Max size of patch or base file.
+MAX_UPLOAD_SIZE = 900 * 1024
+
+
+def GetEmail(prompt):
+  """Prompts the user for their email address and returns it.
+
+  The last used email address is saved to a file and offered up as a suggestion
+  to the user. If the user presses enter without typing in anything the last
+  used email address is used. If the user enters a new address, it is saved
+  for next time we prompt.
+
+  """
+  last_email_file_name = os.path.expanduser("~/.last_codereview_email_address")
+  last_email = ""
+  if os.path.exists(last_email_file_name):
+    try:
+      last_email_file = open(last_email_file_name, "r")
+      last_email = last_email_file.readline().strip("\n")
+      last_email_file.close()
+      prompt += " [%s]" % last_email
+    except IOError, e:
+      pass
+  email = raw_input(prompt + ": ").strip()
+  if email:
+    try:
+      last_email_file = open(last_email_file_name, "w")
+      last_email_file.write(email)
+      last_email_file.close()
+    except IOError, e:
+      pass
+  else:
+    email = last_email
+  return email
+
+
+def StatusUpdate(msg):
+  """Print a status message to stdout.
+
+  If 'verbosity' is greater than 0, print the message.
+
+  Args:
+    msg: The string to print.
+  """
+  if verbosity > 0:
+    print msg
+
+
+def ErrorExit(msg):
+  """Print an error message to stderr and exit."""
+  print >>sys.stderr, msg
+  sys.exit(1)
+
+
+class ClientLoginError(urllib2.HTTPError):
+  """Raised to indicate there was an error authenticating with ClientLogin."""
+
+  def __init__(self, url, code, msg, headers, args):
+    urllib2.HTTPError.__init__(self, url, code, msg, headers, None)
+    self.args = args
+    self.reason = args["Error"]
+
+
+class AbstractRpcServer(object):
+  """Provides a common interface for a simple RPC server."""
+
+  def __init__(self, host, auth_function, host_override=None, extra_headers={},
+               save_cookies=False):
+    """Creates a new HttpRpcServer.
+
+    Args:
+      host: The host to send requests to.
+      auth_function: A function that takes no arguments and returns an
+        (email, password) tuple when called. Will be called if authentication
+        is required.
+      host_override: The host header to send to the server (defaults to host).
+      extra_headers: A dict of extra headers to append to every request.
+      save_cookies: If True, save the authentication cookies to local disk.
+        If False, use an in-memory cookiejar instead.  Subclasses must
+        implement this functionality.  Defaults to False.
+    """
+    self.host = host
+    self.host_override = host_override
+    self.auth_function = auth_function
+    self.authenticated = False
+    self.extra_headers = extra_headers
+    self.save_cookies = save_cookies
+    self.opener = self._GetOpener()
+    if self.host_override:
+      logging.info("Server: %s; Host: %s", self.host, self.host_override)
+    else:
+      logging.info("Server: %s", self.host)
+
+  def _GetOpener(self):
+    """Returns an OpenerDirector for making HTTP requests.
+
+    Returns:
+      A urllib2.OpenerDirector object.
+    """
+    raise NotImplementedError()
+
+  def _CreateRequest(self, url, data=None):
+    """Creates a new urllib request."""
+    logging.debug("Creating request for: '%s' with payload:\n%s", url, data)
+    req = urllib2.Request(url, data=data)
+    if self.host_override:
+      req.add_header("Host", self.host_override)
+    for key, value in self.extra_headers.iteritems():
+      req.add_header(key, value)
+    return req
+
+  def _GetAuthToken(self, email, password):
+    """Uses ClientLogin to authenticate the user, returning an auth token.
+
+    Args:
+      email:    The user's email address
+      password: The user's password
+
+    Raises:
+      ClientLoginError: If there was an error authenticating with ClientLogin.
+      HTTPError: If there was some other form of HTTP error.
+
+    Returns:
+      The authentication token returned by ClientLogin.
+    """
+    account_type = "GOOGLE"
+    if self.host.endswith(".google.com"):
+      # Needed for use inside Google.
+      account_type = "HOSTED"
+    req = self._CreateRequest(
+        url="https://www.google.com/accounts/ClientLogin",
+        data=urllib.urlencode({
+            "Email": email,
+            "Passwd": password,
+            "service": "ah",
+            "source": "rietveld-codereview-upload",
+            "accountType": account_type,
+        }),
+    )
+    try:
+      response = self.opener.open(req)
+      response_body = response.read()
+      response_dict = dict(x.split("=")
+                           for x in response_body.split("\n") if x)
+      return response_dict["Auth"]
+    except urllib2.HTTPError, e:
+      if e.code == 403:
+        body = e.read()
+        response_dict = dict(x.split("=", 1) for x in body.split("\n") if x)
+        raise ClientLoginError(req.get_full_url(), e.code, e.msg,
+                               e.headers, response_dict)
+      else:
+        raise
+
+  def _GetAuthCookie(self, auth_token):
+    """Fetches authentication cookies for an authentication token.
+
+    Args:
+      auth_token: The authentication token returned by ClientLogin.
+
+    Raises:
+      HTTPError: If there was an error fetching the authentication cookies.
+    """
+    # This is a dummy value to allow us to identify when we're successful.
+    continue_location = "http://localhost/"
+    args = {"continue": continue_location, "auth": auth_token}
+    req = self._CreateRequest("http://%s/_ah/login?%s" %
+                              (self.host, urllib.urlencode(args)))
+    try:
+      response = self.opener.open(req)
+    except urllib2.HTTPError, e:
+      response = e
+    if (response.code != 302 or
+        response.info()["location"] != continue_location):
+      raise urllib2.HTTPError(req.get_full_url(), response.code, response.msg,
+                              response.headers, response.fp)
+    self.authenticated = True
+
+  def _Authenticate(self):
+    """Authenticates the user.
+
+    The authentication process works as follows:
+     1) We get a username and password from the user
+     2) We use ClientLogin to obtain an AUTH token for the user
+        (see https://developers.google.com/identity/protocols/AuthForInstalledApps).
+     3) We pass the auth token to /_ah/login on the server to obtain an
+        authentication cookie. If login was successful, it tries to redirect
+        us to the URL we provided.
+
+    If we attempt to access the upload API without first obtaining an
+    authentication cookie, it returns a 401 response and directs us to
+    authenticate ourselves with ClientLogin.
+    """
+    for i in range(3):
+      credentials = self.auth_function()
+      try:
+        auth_token = self._GetAuthToken(credentials[0], credentials[1])
+      except ClientLoginError, e:
+        if e.reason == "BadAuthentication":
+          print >>sys.stderr, "Invalid username or password."
+          continue
+        if e.reason == "CaptchaRequired":
+          print >>sys.stderr, (
+              "Please go to\n"
+              "https://www.google.com/accounts/DisplayUnlockCaptcha\n"
+              "and verify you are a human.  Then try again.")
+          break
+        if e.reason == "NotVerified":
+          print >>sys.stderr, "Account not verified."
+          break
+        if e.reason == "TermsNotAgreed":
+          print >>sys.stderr, "User has not agreed to TOS."
+          break
+        if e.reason == "AccountDeleted":
+          print >>sys.stderr, "The user account has been deleted."
+          break
+        if e.reason == "AccountDisabled":
+          print >>sys.stderr, "The user account has been disabled."
+          break
+        if e.reason == "ServiceDisabled":
+          print >>sys.stderr, ("The user's access to the service has been "
+                               "disabled.")
+          break
+        if e.reason == "ServiceUnavailable":
+          print >>sys.stderr, "The service is not available; try again later."
+          break
+        raise
+      self._GetAuthCookie(auth_token)
+      return
+
+  def Send(self, request_path, payload=None,
+           content_type="application/octet-stream",
+           timeout=None,
+           **kwargs):
+    """Sends an RPC and returns the response.
+
+    Args:
+      request_path: The path to send the request to, eg /api/appversion/create.
+      payload: The body of the request, or None to send an empty request.
+      content_type: The Content-Type header to use.
+      timeout: timeout in seconds; default None i.e. no timeout.
+        (Note: for large requests on OS X, the timeout doesn't work right.)
+      kwargs: Any keyword arguments are converted into query string parameters.
+
+    Returns:
+      The response body, as a string.
+    """
+    # TODO: Don't require authentication.  Let the server say
+    # whether it is necessary.
+    if not self.authenticated:
+      self._Authenticate()
+
+    old_timeout = socket.getdefaulttimeout()
+    socket.setdefaulttimeout(timeout)
+    try:
+      tries = 0
+      while True:
+        tries += 1
+        args = dict(kwargs)
+        url = "http://%s%s" % (self.host, request_path)
+        if args:
+          url += "?" + urllib.urlencode(args)
+        req = self._CreateRequest(url=url, data=payload)
+        req.add_header("Content-Type", content_type)
+        try:
+          f = self.opener.open(req)
+          response = f.read()
+          f.close()
+          return response
+        except urllib2.HTTPError, e:
+          if tries > 3:
+            raise
+          elif e.code == 401:
+            self._Authenticate()
+##           elif e.code >= 500 and e.code < 600:
+##             # Server Error - try again.
+##             continue
+          else:
+            raise
+    finally:
+      socket.setdefaulttimeout(old_timeout)
+
+
+class HttpRpcServer(AbstractRpcServer):
+  """Provides a simplified RPC-style interface for HTTP requests."""
+
+  def _Authenticate(self):
+    """Save the cookie jar after authentication."""
+    super(HttpRpcServer, self)._Authenticate()
+    if self.save_cookies:
+      StatusUpdate("Saving authentication cookies to %s" % self.cookie_file)
+      self.cookie_jar.save()
+
+  def _GetOpener(self):
+    """Returns an OpenerDirector that supports cookies and ignores redirects.
+
+    Returns:
+      A urllib2.OpenerDirector object.
+    """
+    opener = urllib2.OpenerDirector()
+    opener.add_handler(urllib2.ProxyHandler())
+    opener.add_handler(urllib2.UnknownHandler())
+    opener.add_handler(urllib2.HTTPHandler())
+    opener.add_handler(urllib2.HTTPDefaultErrorHandler())
+    opener.add_handler(urllib2.HTTPSHandler())
+    opener.add_handler(urllib2.HTTPErrorProcessor())
+    if self.save_cookies:
+      self.cookie_file = os.path.expanduser("~/.codereview_upload_cookies")
+      self.cookie_jar = cookielib.MozillaCookieJar(self.cookie_file)
+      if os.path.exists(self.cookie_file):
+        try:
+          self.cookie_jar.load()
+          self.authenticated = True
+          StatusUpdate("Loaded authentication cookies from %s" %
+                       self.cookie_file)
+        except (cookielib.LoadError, IOError):
+          # Failed to load cookies - just ignore them.
+          pass
+      else:
+        # Create an empty cookie file with mode 600
+        fd = os.open(self.cookie_file, os.O_CREAT, 0600)
+        os.close(fd)
+      # Always chmod the cookie file
+      os.chmod(self.cookie_file, 0600)
+    else:
+      # Don't save cookies across runs of update.py.
+      self.cookie_jar = cookielib.CookieJar()
+    opener.add_handler(urllib2.HTTPCookieProcessor(self.cookie_jar))
+    return opener
+
+
+parser = optparse.OptionParser(usage="%prog [options] [-- diff_options]")
+parser.add_option("-y", "--assume_yes", action="store_true",
+                  dest="assume_yes", default=False,
+                  help="Assume that the answer to yes/no questions is 'yes'.")
+# Logging
+group = parser.add_option_group("Logging options")
+group.add_option("-q", "--quiet", action="store_const", const=0,
+                 dest="verbose", help="Print errors only.")
+group.add_option("-v", "--verbose", action="store_const", const=2,
+                 dest="verbose", default=1,
+                 help="Print info level logs (default).")
+group.add_option("--noisy", action="store_const", const=3,
+                 dest="verbose", help="Print all logs.")
+# Review server
+group = parser.add_option_group("Review server options")
+group.add_option("-s", "--server", action="store", dest="server",
+                 default="codereview.appspot.com",
+                 metavar="SERVER",
+                 help=("The server to upload to. The format is host[:port]. "
+                       "Defaults to 'codereview.appspot.com'."))
+group.add_option("-e", "--email", action="store", dest="email",
+                 metavar="EMAIL", default=None,
+                 help="The username to use. Will prompt if omitted.")
+group.add_option("-H", "--host", action="store", dest="host",
+                 metavar="HOST", default=None,
+                 help="Overrides the Host header sent with all RPCs.")
+group.add_option("--no_cookies", action="store_false",
+                 dest="save_cookies", default=True,
+                 help="Do not save authentication cookies to local disk.")
+# Issue
+group = parser.add_option_group("Issue options")
+group.add_option("-d", "--description", action="store", dest="description",
+                 metavar="DESCRIPTION", default=None,
+                 help="Optional description when creating an issue.")
+group.add_option("-f", "--description_file", action="store",
+                 dest="description_file", metavar="DESCRIPTION_FILE",
+                 default=None,
+                 help="Optional path of a file that contains "
+                      "the description when creating an issue.")
+group.add_option("-r", "--reviewers", action="store", dest="reviewers",
+                 metavar="REVIEWERS", default=None,
+                 help="Add reviewers (comma separated email addresses).")
+group.add_option("--cc", action="store", dest="cc",
+                 metavar="CC", default=None,
+                 help="Add CC (comma separated email addresses).")
+# Upload options
+group = parser.add_option_group("Patch options")
+group.add_option("-m", "--message", action="store", dest="message",
+                 metavar="MESSAGE", default=None,
+                 help="A message to identify the patch. "
+                      "Will prompt if omitted.")
+group.add_option("-i", "--issue", type="int", action="store",
+                 metavar="ISSUE", default=None,
+                 help="Issue number to which to add. Defaults to new issue.")
+group.add_option("--download_base", action="store_true",
+                 dest="download_base", default=False,
+                 help="Base files will be downloaded by the server "
+                 "(side-by-side diffs may not work on files with CRs).")
+group.add_option("--rev", action="store", dest="revision",
+                 metavar="REV", default=None,
+                 help="Branch/tree/revision to diff against (used by DVCS).")
+group.add_option("--send_mail", action="store_true",
+                 dest="send_mail", default=False,
+                 help="Send notification email to reviewers.")
+
+
+def GetRpcServer(options):
+  """Returns an instance of an AbstractRpcServer.
+
+  Returns:
+    A new AbstractRpcServer, on which RPC calls can be made.
+  """
+
+  rpc_server_class = HttpRpcServer
+
+  def GetUserCredentials():
+    """Prompts the user for a username and password."""
+    email = options.email
+    if email is None:
+      email = GetEmail("Email (login for uploading to %s)" % options.server)
+    password = getpass.getpass("Password for %s: " % email)
+    return (email, password)
+
+  # If this is the dev_appserver, use fake authentication.
+  host = (options.host or options.server).lower()
+  if host == "localhost" or host.startswith("localhost:"):
+    email = options.email
+    if email is None:
+      email = "test@example.com"
+      logging.info("Using debug user %s.  Override with --email" % email)
+    server = rpc_server_class(
+        options.server,
+        lambda: (email, "password"),
+        host_override=options.host,
+        extra_headers={"Cookie":
+                       'dev_appserver_login="%s:False"' % email},
+        save_cookies=options.save_cookies)
+    # Don't try to talk to ClientLogin.
+    server.authenticated = True
+    return server
+
+  return rpc_server_class(options.server, GetUserCredentials,
+                          host_override=options.host,
+                          save_cookies=options.save_cookies)
+
+
+def EncodeMultipartFormData(fields, files):
+  """Encode form fields for multipart/form-data.
+
+  Args:
+    fields: A sequence of (name, value) elements for regular form fields.
+    files: A sequence of (name, filename, value) elements for data to be
+           uploaded as files.
+  Returns:
+    (content_type, body) ready for httplib.HTTP instance.
+
+  Source:
+    https://web.archive.org/web/20160116052001/code.activestate.com/recipes/146306
+  """
+  BOUNDARY = '-M-A-G-I-C---B-O-U-N-D-A-R-Y-'
+  CRLF = '\r\n'
+  lines = []
+  for (key, value) in fields:
+    lines.append('--' + BOUNDARY)
+    lines.append('Content-Disposition: form-data; name="%s"' % key)
+    lines.append('')
+    lines.append(value)
+  for (key, filename, value) in files:
+    lines.append('--' + BOUNDARY)
+    lines.append('Content-Disposition: form-data; name="%s"; filename="%s"' %
+             (key, filename))
+    lines.append('Content-Type: %s' % GetContentType(filename))
+    lines.append('')
+    lines.append(value)
+  lines.append('--' + BOUNDARY + '--')
+  lines.append('')
+  body = CRLF.join(lines)
+  content_type = 'multipart/form-data; boundary=%s' % BOUNDARY
+  return content_type, body
+
+
+def GetContentType(filename):
+  """Helper to guess the content-type from the filename."""
+  return mimetypes.guess_type(filename)[0] or 'application/octet-stream'
+
+
+# Use a shell for subcommands on Windows to get a PATH search.
+use_shell = sys.platform.startswith("win")
+
+def RunShellWithReturnCode(command, print_output=False,
+                           universal_newlines=True):
+  """Executes a command and returns the output from stdout and the return code.
+
+  Args:
+    command: Command to execute.
+    print_output: If True, the output is printed to stdout.
+                  If False, both stdout and stderr are ignored.
+    universal_newlines: Use universal_newlines flag (default: True).
+
+  Returns:
+    Tuple (output, return code)
+  """
+  logging.info("Running %s", command)
+  p = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE,
+                       shell=use_shell, universal_newlines=universal_newlines)
+  if print_output:
+    output_array = []
+    while True:
+      line = p.stdout.readline()
+      if not line:
+        break
+      print line.strip("\n")
+      output_array.append(line)
+    output = "".join(output_array)
+  else:
+    output = p.stdout.read()
+  p.wait()
+  errout = p.stderr.read()
+  if print_output and errout:
+    print >>sys.stderr, errout
+  p.stdout.close()
+  p.stderr.close()
+  return output, p.returncode
+
+
+def RunShell(command, silent_ok=False, universal_newlines=True,
+             print_output=False):
+  data, retcode = RunShellWithReturnCode(command, print_output,
+                                         universal_newlines)
+  if retcode:
+    ErrorExit("Got error status from %s:\n%s" % (command, data))
+  if not silent_ok and not data:
+    ErrorExit("No output from %s" % command)
+  return data
+
+
+class VersionControlSystem(object):
+  """Abstract base class providing an interface to the VCS."""
+
+  def __init__(self, options):
+    """Constructor.
+
+    Args:
+      options: Command line options.
+    """
+    self.options = options
+
+  def GenerateDiff(self, args):
+    """Return the current diff as a string.
+
+    Args:
+      args: Extra arguments to pass to the diff command.
+    """
+    raise NotImplementedError(
+        "abstract method -- subclass %s must override" % self.__class__)
+
+  def GetUnknownFiles(self):
+    """Return a list of files unknown to the VCS."""
+    raise NotImplementedError(
+        "abstract method -- subclass %s must override" % self.__class__)
+
+  def CheckForUnknownFiles(self):
+    """Show an "are you sure?" prompt if there are unknown files."""
+    unknown_files = self.GetUnknownFiles()
+    if unknown_files:
+      print "The following files are not added to version control:"
+      for line in unknown_files:
+        print line
+      prompt = "Are you sure to continue?(y/N) "
+      answer = raw_input(prompt).strip()
+      if answer != "y":
+        ErrorExit("User aborted")
+
+  def GetBaseFile(self, filename):
+    """Get the content of the upstream version of a file.
+
+    Returns:
+      A tuple (base_content, new_content, is_binary, status)
+        base_content: The contents of the base file.
+        new_content: For text files, this is empty.  For binary files, this is
+          the contents of the new file, since the diff output won't contain
+          information to reconstruct the current file.
+        is_binary: True iff the file is binary.
+        status: The status of the file.
+    """
+
+    raise NotImplementedError(
+        "abstract method -- subclass %s must override" % self.__class__)
+
+
+  def GetBaseFiles(self, diff):
+    """Helper that calls GetBase file for each file in the patch.
+
+    Returns:
+      A dictionary that maps from filename to GetBaseFile's tuple.  Filenames
+      are retrieved based on lines that start with "Index:" or
+      "Property changes on:".
+    """
+    files = {}
+    for line in diff.splitlines(True):
+      if line.startswith('Index:') or line.startswith('Property changes on:'):
+        unused, filename = line.split(':', 1)
+        # On Windows if a file has property changes its filename uses '\'
+        # instead of '/'.
+        filename = filename.strip().replace('\\', '/')
+        files[filename] = self.GetBaseFile(filename)
+    return files
+
+
+  def UploadBaseFiles(self, issue, rpc_server, patch_list, patchset, options,
+                      files):
+    """Uploads the base files (and if necessary, the current ones as well)."""
+
+    def UploadFile(filename, file_id, content, is_binary, status, is_base):
+      """Uploads a file to the server."""
+      file_too_large = False
+      if is_base:
+        type = "base"
+      else:
+        type = "current"
+      if len(content) > MAX_UPLOAD_SIZE:
+        print ("Not uploading the %s file for %s because it's too large." %
+               (type, filename))
+        file_too_large = True
+        content = ""
+      checksum = md5.new(content).hexdigest()
+      if options.verbose > 0 and not file_too_large:
+        print "Uploading %s file for %s" % (type, filename)
+      url = "/%d/upload_content/%d/%d" % (int(issue), int(patchset), file_id)
+      form_fields = [("filename", filename),
+                     ("status", status),
+                     ("checksum", checksum),
+                     ("is_binary", str(is_binary)),
+                     ("is_current", str(not is_base)),
+                    ]
+      if file_too_large:
+        form_fields.append(("file_too_large", "1"))
+      if options.email:
+        form_fields.append(("user", options.email))
+      ctype, body = EncodeMultipartFormData(form_fields,
+                                            [("data", filename, content)])
+      response_body = rpc_server.Send(url, body,
+                                      content_type=ctype)
+      if not response_body.startswith("OK"):
+        StatusUpdate("  --> %s" % response_body)
+        sys.exit(1)
+
+    patches = dict()
+    [patches.setdefault(v, k) for k, v in patch_list]
+    for filename in patches.keys():
+      base_content, new_content, is_binary, status = files[filename]
+      file_id_str = patches.get(filename)
+      if file_id_str.find("nobase") != -1:
+        base_content = None
+        file_id_str = file_id_str[file_id_str.rfind("_") + 1:]
+      file_id = int(file_id_str)
+      if base_content != None:
+        UploadFile(filename, file_id, base_content, is_binary, status, True)
+      if new_content != None:
+        UploadFile(filename, file_id, new_content, is_binary, status, False)
+
+  def IsImage(self, filename):
+    """Returns true if the filename has an image extension."""
+    mimetype =  mimetypes.guess_type(filename)[0]
+    if not mimetype:
+      return False
+    return mimetype.startswith("image/")
+
+
+class SubversionVCS(VersionControlSystem):
+  """Implementation of the VersionControlSystem interface for Subversion."""
+
+  def __init__(self, options):
+    super(SubversionVCS, self).__init__(options)
+    if self.options.revision:
+      match = re.match(r"(\d+)(:(\d+))?", self.options.revision)
+      if not match:
+        ErrorExit("Invalid Subversion revision %s." % self.options.revision)
+      self.rev_start = match.group(1)
+      self.rev_end = match.group(3)
+    else:
+      self.rev_start = self.rev_end = None
+    # Cache output from "svn list -r REVNO dirname".
+    # Keys: dirname, Values: 2-tuple (output for start rev and end rev).
+    self.svnls_cache = {}
+    # SVN base URL is required to fetch files deleted in an older revision.
+    # Result is cached to not guess it over and over again in GetBaseFile().
+    required = self.options.download_base or self.options.revision is not None
+    self.svn_base = self._GuessBase(required)
+
+  def GuessBase(self, required):
+    """Wrapper for _GuessBase."""
+    return self.svn_base
+
+  def _GuessBase(self, required):
+    """Returns the SVN base URL.
+
+    Args:
+      required: If true, exits if the url can't be guessed, otherwise None is
+        returned.
+    """
+    info = RunShell(["svn", "info"])
+    for line in info.splitlines():
+      words = line.split()
+      if len(words) == 2 and words[0] == "URL:":
+        url = words[1]
+        scheme, netloc, path, params, query, fragment = urlparse.urlparse(url)
+        username, netloc = urllib.splituser(netloc)
+        if username:
+          logging.info("Removed username from base URL")
+        if netloc.endswith("svn.python.org"):
+          if netloc == "svn.python.org":
+            if path.startswith("/projects/"):
+              path = path[9:]
+          elif netloc != "pythondev@svn.python.org":
+            ErrorExit("Unrecognized Python URL: %s" % url)
+          base = "http://svn.python.org/view/*checkout*%s/" % path
+          logging.info("Guessed Python base = %s", base)
+        elif netloc.endswith("svn.collab.net"):
+          if path.startswith("/repos/"):
+            path = path[6:]
+          base = "http://svn.collab.net/viewvc/*checkout*%s/" % path
+          logging.info("Guessed CollabNet base = %s", base)
+        elif netloc.endswith(".googlecode.com"):
+          path = path + "/"
+          base = urlparse.urlunparse(("http", netloc, path, params,
+                                      query, fragment))
+          logging.info("Guessed Google Code base = %s", base)
+        else:
+          path = path + "/"
+          base = urlparse.urlunparse((scheme, netloc, path, params,
+                                      query, fragment))
+          logging.info("Guessed base = %s", base)
+        return base
+    if required:
+      ErrorExit("Can't find URL in output from svn info")
+    return None
+
+  def GenerateDiff(self, args):
+    cmd = ["svn", "diff"]
+    if self.options.revision:
+      cmd += ["-r", self.options.revision]
+    cmd.extend(args)
+    data = RunShell(cmd)
+    count = 0
+    for line in data.splitlines():
+      if line.startswith("Index:") or line.startswith("Property changes on:"):
+        count += 1
+        logging.info(line)
+    if not count:
+      ErrorExit("No valid patches found in output from svn diff")
+    return data
+
+  def _CollapseKeywords(self, content, keyword_str):
+    """Collapses SVN keywords."""
+    # svn cat translates keywords but svn diff doesn't. As a result of this
+    # behavior patching.PatchChunks() fails with a chunk mismatch error.
+    # This part was originally written by the Review Board development team
+    # who had the same problem (https://reviews.reviewboard.org/r/276/).
+    # Mapping of keywords to known aliases
+    svn_keywords = {
+      # Standard keywords
+      'Date':                ['Date', 'LastChangedDate'],
+      'Revision':            ['Revision', 'LastChangedRevision', 'Rev'],
+      'Author':              ['Author', 'LastChangedBy'],
+      'HeadURL':             ['HeadURL', 'URL'],
+      'Id':                  ['Id'],
+
+      # Aliases
+      'LastChangedDate':     ['LastChangedDate', 'Date'],
+      'LastChangedRevision': ['LastChangedRevision', 'Rev', 'Revision'],
+      'LastChangedBy':       ['LastChangedBy', 'Author'],
+      'URL':                 ['URL', 'HeadURL'],
+    }
+
+    def repl(m):
+       if m.group(2):
+         return "$%s::%s$" % (m.group(1), " " * len(m.group(3)))
+       return "$%s$" % m.group(1)
+    keywords = [keyword
+                for name in keyword_str.split(" ")
+                for keyword in svn_keywords.get(name, [])]
+    return re.sub(r"\$(%s):(:?)([^\$]+)\$" % '|'.join(keywords), repl, content)
+
+  def GetUnknownFiles(self):
+    status = RunShell(["svn", "status", "--ignore-externals"], silent_ok=True)
+    unknown_files = []
+    for line in status.split("\n"):
+      if line and line[0] == "?":
+        unknown_files.append(line)
+    return unknown_files
+
+  def ReadFile(self, filename):
+    """Returns the contents of a file."""
+    file = open(filename, 'rb')
+    result = ""
+    try:
+      result = file.read()
+    finally:
+      file.close()
+    return result
+
+  def GetStatus(self, filename):
+    """Returns the status of a file."""
+    if not self.options.revision:
+      status = RunShell(["svn", "status", "--ignore-externals", filename])
+      if not status:
+        ErrorExit("svn status returned no output for %s" % filename)
+      status_lines = status.splitlines()
+      # If file is in a cl, the output will begin with
+      # "\n--- Changelist 'cl_name':\n".  See
+      # https://web.archive.org/web/20090918234815/svn.collab.net/repos/svn/trunk/notes/changelist-design.txt
+      if (len(status_lines) == 3 and
+          not status_lines[0] and
+          status_lines[1].startswith("--- Changelist")):
+        status = status_lines[2]
+      else:
+        status = status_lines[0]
+    # If we have a revision to diff against we need to run "svn list"
+    # for the old and the new revision and compare the results to get
+    # the correct status for a file.
+    else:
+      dirname, relfilename = os.path.split(filename)
+      if dirname not in self.svnls_cache:
+        cmd = ["svn", "list", "-r", self.rev_start, dirname or "."]
+        out, returncode = RunShellWithReturnCode(cmd)
+        if returncode:
+          ErrorExit("Failed to get status for %s." % filename)
+        old_files = out.splitlines()
+        args = ["svn", "list"]
+        if self.rev_end:
+          args += ["-r", self.rev_end]
+        cmd = args + [dirname or "."]
+        out, returncode = RunShellWithReturnCode(cmd)
+        if returncode:
+          ErrorExit("Failed to run command %s" % cmd)
+        self.svnls_cache[dirname] = (old_files, out.splitlines())
+      old_files, new_files = self.svnls_cache[dirname]
+      if relfilename in old_files and relfilename not in new_files:
+        status = "D   "
+      elif relfilename in old_files and relfilename in new_files:
+        status = "M   "
+      else:
+        status = "A   "
+    return status
+
+  def GetBaseFile(self, filename):
+    status = self.GetStatus(filename)
+    base_content = None
+    new_content = None
+
+    # If a file is copied its status will be "A  +", which signifies
+    # "addition-with-history".  See "svn st" for more information.  We need to
+    # upload the original file or else diff parsing will fail if the file was
+    # edited.
+    if status[0] == "A" and status[3] != "+":
+      # We'll need to upload the new content if we're adding a binary file
+      # since diff's output won't contain it.
+      mimetype = RunShell(["svn", "propget", "svn:mime-type", filename],
+                          silent_ok=True)
+      base_content = ""
+      is_binary = mimetype and not mimetype.startswith("text/")
+      if is_binary and self.IsImage(filename):
+        new_content = self.ReadFile(filename)
+    elif (status[0] in ("M", "D", "R") or
+          (status[0] == "A" and status[3] == "+") or  # Copied file.
+          (status[0] == " " and status[1] == "M")):  # Property change.
+      args = []
+      if self.options.revision:
+        url = "%s/%s@%s" % (self.svn_base, filename, self.rev_start)
+      else:
+        # Don't change filename, it's needed later.
+        url = filename
+        args += ["-r", "BASE"]
+      cmd = ["svn"] + args + ["propget", "svn:mime-type", url]
+      mimetype, returncode = RunShellWithReturnCode(cmd)
+      if returncode:
+        # File does not exist in the requested revision.
+        # Reset mimetype, it contains an error message.
+        mimetype = ""
+      get_base = False
+      is_binary = mimetype and not mimetype.startswith("text/")
+      if status[0] == " ":
+        # Empty base content just to force an upload.
+        base_content = ""
+      elif is_binary:
+        if self.IsImage(filename):
+          get_base = True
+          if status[0] == "M":
+            if not self.rev_end:
+              new_content = self.ReadFile(filename)
+            else:
+              url = "%s/%s@%s" % (self.svn_base, filename, self.rev_end)
+              new_content = RunShell(["svn", "cat", url],
+                                     universal_newlines=True, silent_ok=True)
+        else:
+          base_content = ""
+      else:
+        get_base = True
+
+      if get_base:
+        if is_binary:
+          universal_newlines = False
+        else:
+          universal_newlines = True
+        if self.rev_start:
+          # "svn cat -r REV delete_file.txt" doesn't work. cat requires
+          # the full URL with "@REV" appended instead of using "-r" option.
+          url = "%s/%s@%s" % (self.svn_base, filename, self.rev_start)
+          base_content = RunShell(["svn", "cat", url],
+                                  universal_newlines=universal_newlines,
+                                  silent_ok=True)
+        else:
+          base_content = RunShell(["svn", "cat", filename],
+                                  universal_newlines=universal_newlines,
+                                  silent_ok=True)
+        if not is_binary:
+          args = []
+          if self.rev_start:
+            url = "%s/%s@%s" % (self.svn_base, filename, self.rev_start)
+          else:
+            url = filename
+            args += ["-r", "BASE"]
+          cmd = ["svn"] + args + ["propget", "svn:keywords", url]
+          keywords, returncode = RunShellWithReturnCode(cmd)
+          if keywords and not returncode:
+            base_content = self._CollapseKeywords(base_content, keywords)
+    else:
+      StatusUpdate("svn status returned unexpected output: %s" % status)
+      sys.exit(1)
+    return base_content, new_content, is_binary, status[0:5]
+
+
+class GitVCS(VersionControlSystem):
+  """Implementation of the VersionControlSystem interface for Git."""
+
+  def __init__(self, options):
+    super(GitVCS, self).__init__(options)
+    # Map of filename -> hash of base file.
+    self.base_hashes = {}
+
+  def GenerateDiff(self, extra_args):
+    # This is more complicated than svn's GenerateDiff because we must convert
+    # the diff output to include an svn-style "Index:" line as well as record
+    # the hashes of the base files, so we can upload them along with our diff.
+    if self.options.revision:
+      extra_args = [self.options.revision] + extra_args
+    gitdiff = RunShell(["git", "diff", "--full-index"] + extra_args)
+    svndiff = []
+    filecount = 0
+    filename = None
+    for line in gitdiff.splitlines():
+      match = re.match(r"diff --git a/(.*) b/.*$", line)
+      if match:
+        filecount += 1
+        filename = match.group(1)
+        svndiff.append("Index: %s\n" % filename)
+      else:
+        # The "index" line in a git diff looks like this (long hashes elided):
+        #   index 82c0d44..b2cee3f 100755
+        # We want to save the left hash, as that identifies the base file.
+        match = re.match(r"index (\w+)\.\.", line)
+        if match:
+          self.base_hashes[filename] = match.group(1)
+      svndiff.append(line + "\n")
+    if not filecount:
+      ErrorExit("No valid patches found in output from git diff")
+    return "".join(svndiff)
+
+  def GetUnknownFiles(self):
+    status = RunShell(["git", "ls-files", "--exclude-standard", "--others"],
+                      silent_ok=True)
+    return status.splitlines()
+
+  def GetBaseFile(self, filename):
+    hash = self.base_hashes[filename]
+    base_content = None
+    new_content = None
+    is_binary = False
+    if hash == "0" * 40:  # All-zero hash indicates no base file.
+      status = "A"
+      base_content = ""
+    else:
+      status = "M"
+      base_content, returncode = RunShellWithReturnCode(["git", "show", hash])
+      if returncode:
+        ErrorExit("Got error status from 'git show %s'" % hash)
+    return (base_content, new_content, is_binary, status)
+
+
+class MercurialVCS(VersionControlSystem):
+  """Implementation of the VersionControlSystem interface for Mercurial."""
+
+  def __init__(self, options, repo_dir):
+    super(MercurialVCS, self).__init__(options)
+    # Absolute path to repository (we can be in a subdir)
+    self.repo_dir = os.path.normpath(repo_dir)
+    # Compute the subdir
+    cwd = os.path.normpath(os.getcwd())
+    assert cwd.startswith(self.repo_dir)
+    self.subdir = cwd[len(self.repo_dir):].lstrip(r"\/")
+    if self.options.revision:
+      self.base_rev = self.options.revision
+    else:
+      self.base_rev = RunShell(["hg", "parent", "-q"]).split(':')[1].strip()
+
+  def _GetRelPath(self, filename):
+    """Get relative path of a file according to the current directory,
+    given its logical path in the repo."""
+    assert filename.startswith(self.subdir), filename
+    return filename[len(self.subdir):].lstrip(r"\/")
+
+  def GenerateDiff(self, extra_args):
+    # If no file specified, restrict to the current subdir
+    extra_args = extra_args or ["."]
+    cmd = ["hg", "diff", "--git", "-r", self.base_rev] + extra_args
+    data = RunShell(cmd, silent_ok=True)
+    svndiff = []
+    filecount = 0
+    for line in data.splitlines():
+      m = re.match("diff --git a/(\S+) b/(\S+)", line)
+      if m:
+        # Modify line to make it look like as it comes from svn diff.
+        # With this modification no changes on the server side are required
+        # to make upload.py work with Mercurial repos.
+        # NOTE: for proper handling of moved/copied files, we have to use
+        # the second filename.
+        filename = m.group(2)
+        svndiff.append("Index: %s" % filename)
+        svndiff.append("=" * 67)
+        filecount += 1
+        logging.info(line)
+      else:
+        svndiff.append(line)
+    if not filecount:
+      ErrorExit("No valid patches found in output from hg diff")
+    return "\n".join(svndiff) + "\n"
+
+  def GetUnknownFiles(self):
+    """Return a list of files unknown to the VCS."""
+    args = []
+    status = RunShell(["hg", "status", "--rev", self.base_rev, "-u", "."],
+        silent_ok=True)
+    unknown_files = []
+    for line in status.splitlines():
+      st, fn = line.split(" ", 1)
+      if st == "?":
+        unknown_files.append(fn)
+    return unknown_files
+
+  def GetBaseFile(self, filename):
+    # "hg status" and "hg cat" both take a path relative to the current subdir
+    # rather than to the repo root, but "hg diff" has given us the full path
+    # to the repo root.
+    base_content = ""
+    new_content = None
+    is_binary = False
+    oldrelpath = relpath = self._GetRelPath(filename)
+    # "hg status -C" returns two lines for moved/copied files, one otherwise
+    out = RunShell(["hg", "status", "-C", "--rev", self.base_rev, relpath])
+    out = out.splitlines()
+    # HACK: strip error message about missing file/directory if it isn't in
+    # the working copy
+    if out[0].startswith('%s: ' % relpath):
+      out = out[1:]
+    if len(out) > 1:
+      # Moved/copied => considered as modified, use old filename to
+      # retrieve base contents
+      oldrelpath = out[1].strip()
+      status = "M"
+    else:
+      status, _ = out[0].split(' ', 1)
+    if status != "A":
+      base_content = RunShell(["hg", "cat", "-r", self.base_rev, oldrelpath],
+        silent_ok=True)
+      is_binary = "\0" in base_content  # Mercurial's heuristic
+    if status != "R":
+      new_content = open(relpath, "rb").read()
+      is_binary = is_binary or "\0" in new_content
+    if is_binary and base_content:
+      # Fetch again without converting newlines
+      base_content = RunShell(["hg", "cat", "-r", self.base_rev, oldrelpath],
+        silent_ok=True, universal_newlines=False)
+    if not is_binary or not self.IsImage(relpath):
+      new_content = None
+    return base_content, new_content, is_binary, status
+
+
+# NOTE: The SplitPatch function is duplicated in engine.py, keep them in sync.
+def SplitPatch(data):
+  """Splits a patch into separate pieces for each file.
+
+  Args:
+    data: A string containing the output of svn diff.
+
+  Returns:
+    A list of 2-tuple (filename, text) where text is the svn diff output
+      pertaining to filename.
+  """
+  patches = []
+  filename = None
+  diff = []
+  for line in data.splitlines(True):
+    new_filename = None
+    if line.startswith('Index:'):
+      unused, new_filename = line.split(':', 1)
+      new_filename = new_filename.strip()
+    elif line.startswith('Property changes on:'):
+      unused, temp_filename = line.split(':', 1)
+      # When a file is modified, paths use '/' between directories, however
+      # when a property is modified '\' is used on Windows.  Make them the same
+      # otherwise the file shows up twice.
+      temp_filename = temp_filename.strip().replace('\\', '/')
+      if temp_filename != filename:
+        # File has property changes but no modifications, create a new diff.
+        new_filename = temp_filename
+    if new_filename:
+      if filename and diff:
+        patches.append((filename, ''.join(diff)))
+      filename = new_filename
+      diff = [line]
+      continue
+    if diff is not None:
+      diff.append(line)
+  if filename and diff:
+    patches.append((filename, ''.join(diff)))
+  return patches
+
+
+def UploadSeparatePatches(issue, rpc_server, patchset, data, options):
+  """Uploads a separate patch for each file in the diff output.
+
+  Returns a list of [patch_key, filename] for each file.
+  """
+  patches = SplitPatch(data)
+  rv = []
+  for patch in patches:
+    if len(patch[1]) > MAX_UPLOAD_SIZE:
+      print ("Not uploading the patch for " + patch[0] +
+             " because the file is too large.")
+      continue
+    form_fields = [("filename", patch[0])]
+    if not options.download_base:
+      form_fields.append(("content_upload", "1"))
+    files = [("data", "data.diff", patch[1])]
+    ctype, body = EncodeMultipartFormData(form_fields, files)
+    url = "/%d/upload_patch/%d" % (int(issue), int(patchset))
+    print "Uploading patch for " + patch[0]
+    response_body = rpc_server.Send(url, body, content_type=ctype)
+    lines = response_body.splitlines()
+    if not lines or lines[0] != "OK":
+      StatusUpdate("  --> %s" % response_body)
+      sys.exit(1)
+    rv.append([lines[1], patch[0]])
+  return rv
+
+
+def GuessVCS(options):
+  """Helper to guess the version control system.
+
+  This examines the current directory, guesses which VersionControlSystem
+  we're using, and returns an instance of the appropriate class.  Exit with an
+  error if we can't figure it out.
+
+  Returns:
+    A VersionControlSystem instance. Exits if the VCS can't be guessed.
+  """
+  # Mercurial has a command to get the base directory of a repository
+  # Try running it, but don't die if we don't have hg installed.
+  # NOTE: we try Mercurial first as it can sit on top of an SVN working copy.
+  try:
+    out, returncode = RunShellWithReturnCode(["hg", "root"])
+    if returncode == 0:
+      return MercurialVCS(options, out.strip())
+  except OSError, (errno, message):
+    if errno != 2:  # ENOENT -- they don't have hg installed.
+      raise
+
+  # Subversion has a .svn in all working directories.
+  if os.path.isdir('.svn'):
+    logging.info("Guessed VCS = Subversion")
+    return SubversionVCS(options)
+
+  # Git has a command to test if you're in a git tree.
+  # Try running it, but don't die if we don't have git installed.
+  try:
+    out, returncode = RunShellWithReturnCode(["git", "rev-parse",
+                                              "--is-inside-work-tree"])
+    if returncode == 0:
+      return GitVCS(options)
+  except OSError, (errno, message):
+    if errno != 2:  # ENOENT -- they don't have git installed.
+      raise
+
+  ErrorExit(("Could not guess version control system. "
+             "Are you in a working copy directory?"))
+
+
+def RealMain(argv, data=None):
+  """The real main function.
+
+  Args:
+    argv: Command line arguments.
+    data: Diff contents. If None (default) the diff is generated by
+      the VersionControlSystem implementation returned by GuessVCS().
+
+  Returns:
+    A 2-tuple (issue id, patchset id).
+    The patchset id is None if the base files are not uploaded by this
+    script (applies only to SVN checkouts).
+  """
+  logging.basicConfig(format=("%(asctime).19s %(levelname)s %(filename)s:"
+                              "%(lineno)s %(message)s "))
+  os.environ['LC_ALL'] = 'C'
+  options, args = parser.parse_args(argv[1:])
+  global verbosity
+  verbosity = options.verbose
+  if verbosity >= 3:
+    logging.getLogger().setLevel(logging.DEBUG)
+  elif verbosity >= 2:
+    logging.getLogger().setLevel(logging.INFO)
+  vcs = GuessVCS(options)
+  if isinstance(vcs, SubversionVCS):
+    # base field is only allowed for Subversion.
+    # Note: Fetching base files may become deprecated in future releases.
+    base = vcs.GuessBase(options.download_base)
+  else:
+    base = None
+  if not base and options.download_base:
+    options.download_base = True
+    logging.info("Enabled upload of base file")
+  if not options.assume_yes:
+    vcs.CheckForUnknownFiles()
+  if data is None:
+    data = vcs.GenerateDiff(args)
+  files = vcs.GetBaseFiles(data)
+  if verbosity >= 1:
+    print "Upload server:", options.server, "(change with -s/--server)"
+  if options.issue:
+    prompt = "Message describing this patch set: "
+  else:
+    prompt = "New issue subject: "
+  message = options.message or raw_input(prompt).strip()
+  if not message:
+    ErrorExit("A non-empty message is required")
+  rpc_server = GetRpcServer(options)
+  form_fields = [("subject", message)]
+  if base:
+    form_fields.append(("base", base))
+  if options.issue:
+    form_fields.append(("issue", str(options.issue)))
+  if options.email:
+    form_fields.append(("user", options.email))
+  if options.reviewers:
+    for reviewer in options.reviewers.split(','):
+      if "@" in reviewer and not reviewer.split("@")[1].count(".") == 1:
+        ErrorExit("Invalid email address: %s" % reviewer)
+    form_fields.append(("reviewers", options.reviewers))
+  if options.cc:
+    for cc in options.cc.split(','):
+      if "@" in cc and not cc.split("@")[1].count(".") == 1:
+        ErrorExit("Invalid email address: %s" % cc)
+    form_fields.append(("cc", options.cc))
+  description = options.description
+  if options.description_file:
+    if options.description:
+      ErrorExit("Can't specify description and description_file")
+    file = open(options.description_file, 'r')
+    description = file.read()
+    file.close()
+  if description:
+    form_fields.append(("description", description))
+  # Send a hash of all the base file so the server can determine if a copy
+  # already exists in an earlier patchset.
+  base_hashes = ""
+  for file, info in files.iteritems():
+    if not info[0] is None:
+      checksum = md5.new(info[0]).hexdigest()
+      if base_hashes:
+        base_hashes += "|"
+      base_hashes += checksum + ":" + file
+  form_fields.append(("base_hashes", base_hashes))
+  # If we're uploading base files, don't send the email before the uploads, so
+  # that it contains the file status.
+  if options.send_mail and options.download_base:
+    form_fields.append(("send_mail", "1"))
+  if not options.download_base:
+    form_fields.append(("content_upload", "1"))
+  if len(data) > MAX_UPLOAD_SIZE:
+    print "Patch is large, so uploading file patches separately."
+    uploaded_diff_file = []
+    form_fields.append(("separate_patches", "1"))
+  else:
+    uploaded_diff_file = [("data", "data.diff", data)]
+  ctype, body = EncodeMultipartFormData(form_fields, uploaded_diff_file)
+  response_body = rpc_server.Send("/upload", body, content_type=ctype)
+  patchset = None
+  if not options.download_base or not uploaded_diff_file:
+    lines = response_body.splitlines()
+    if len(lines) >= 2:
+      msg = lines[0]
+      patchset = lines[1].strip()
+      patches = [x.split(" ", 1) for x in lines[2:]]
+    else:
+      msg = response_body
+  else:
+    msg = response_body
+  StatusUpdate(msg)
+  if not response_body.startswith("Issue created.") and \
+  not response_body.startswith("Issue updated."):
+    sys.exit(0)
+  issue = msg[msg.rfind("/")+1:]
+
+  if not uploaded_diff_file:
+    result = UploadSeparatePatches(issue, rpc_server, patchset, data, options)
+    if not options.download_base:
+      patches = result
+
+  if not options.download_base:
+    vcs.UploadBaseFiles(issue, rpc_server, patches, patchset, options, files)
+    if options.send_mail:
+      rpc_server.Send("/" + issue + "/mail", payload="")
+  return issue, patchset
+
+
+def main():
+  try:
+    RealMain(sys.argv)
+  except KeyboardInterrupt:
+    print
+    StatusUpdate("Interrupted.")
+    sys.exit(1)
+
+
+if __name__ == "__main__":
+  main()
diff --git a/leveldb_base/third_party/googletest/googletest/scripts/upload_gtest.py b/leveldb_base/third_party/googletest/googletest/scripts/upload_gtest.py
new file mode 100644
index 0000000..be19ae8
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/scripts/upload_gtest.py
@@ -0,0 +1,78 @@
+#!/usr/bin/env python
+#
+# Copyright 2009, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""upload_gtest.py v0.1.0 -- uploads a Google Test patch for review.
+
+This simple wrapper passes all command line flags and
+--cc=googletestframework@googlegroups.com to upload.py.
+
+USAGE: upload_gtest.py [options for upload.py]
+"""
+
+__author__ = 'wan@google.com (Zhanyong Wan)'
+
+import os
+import sys
+
+CC_FLAG = '--cc='
+GTEST_GROUP = 'googletestframework@googlegroups.com'
+
+
+def main():
+  # Finds the path to upload.py, assuming it is in the same directory
+  # as this file.
+  my_dir = os.path.dirname(os.path.abspath(__file__))
+  upload_py_path = os.path.join(my_dir, 'upload.py')
+
+  # Adds Google Test discussion group to the cc line if it's not there
+  # already.
+  upload_py_argv = [upload_py_path]
+  found_cc_flag = False
+  for arg in sys.argv[1:]:
+    if arg.startswith(CC_FLAG):
+      found_cc_flag = True
+      cc_line = arg[len(CC_FLAG):]
+      cc_list = [addr for addr in cc_line.split(',') if addr]
+      if GTEST_GROUP not in cc_list:
+        cc_list.append(GTEST_GROUP)
+      upload_py_argv.append(CC_FLAG + ','.join(cc_list))
+    else:
+      upload_py_argv.append(arg)
+
+  if not found_cc_flag:
+    upload_py_argv.append(CC_FLAG + GTEST_GROUP)
+
+  # Invokes upload.py with the modified command line flags.
+  os.execv(upload_py_path, upload_py_argv)
+
+
+if __name__ == '__main__':
+  main()
diff --git a/leveldb_base/third_party/googletest/googletest/src/gtest-all.cc b/leveldb_base/third_party/googletest/googletest/src/gtest-all.cc
new file mode 100644
index 0000000..ad29290
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/src/gtest-all.cc
@@ -0,0 +1,48 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// Google C++ Testing and Mocking Framework (Google Test)
+//
+// Sometimes it's desirable to build Google Test by compiling a single file.
+// This file serves this purpose.
+
+// This line ensures that gtest.h can be compiled on its own, even
+// when it's fused.
+#include "gtest/gtest.h"
+
+// The following lines pull in the real gtest *.cc files.
+#include "src/gtest.cc"
+#include "src/gtest-death-test.cc"
+#include "src/gtest-filepath.cc"
+#include "src/gtest-matchers.cc"
+#include "src/gtest-port.cc"
+#include "src/gtest-printers.cc"
+#include "src/gtest-test-part.cc"
+#include "src/gtest-typed-test.cc"
diff --git a/leveldb_base/third_party/googletest/googletest/src/gtest-death-test.cc b/leveldb_base/third_party/googletest/googletest/src/gtest-death-test.cc
new file mode 100644
index 0000000..bf4f633
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/src/gtest-death-test.cc
@@ -0,0 +1,1644 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// This file implements death tests.
+
+#include "gtest/gtest-death-test.h"
+
+#include <functional>
+#include <utility>
+
+#include "gtest/internal/gtest-port.h"
+#include "gtest/internal/custom/gtest.h"
+
+#if GTEST_HAS_DEATH_TEST
+
+# if GTEST_OS_MAC
+#  include <crt_externs.h>
+# endif  // GTEST_OS_MAC
+
+# include <errno.h>
+# include <fcntl.h>
+# include <limits.h>
+
+# if GTEST_OS_LINUX
+#  include <signal.h>
+# endif  // GTEST_OS_LINUX
+
+# include <stdarg.h>
+
+# if GTEST_OS_WINDOWS
+#  include <windows.h>
+# else
+#  include <sys/mman.h>
+#  include <sys/wait.h>
+# endif  // GTEST_OS_WINDOWS
+
+# if GTEST_OS_QNX
+#  include <spawn.h>
+# endif  // GTEST_OS_QNX
+
+# if GTEST_OS_FUCHSIA
+#  include <lib/fdio/fd.h>
+#  include <lib/fdio/io.h>
+#  include <lib/fdio/spawn.h>
+#  include <lib/zx/channel.h>
+#  include <lib/zx/port.h>
+#  include <lib/zx/process.h>
+#  include <lib/zx/socket.h>
+#  include <zircon/processargs.h>
+#  include <zircon/syscalls.h>
+#  include <zircon/syscalls/policy.h>
+#  include <zircon/syscalls/port.h>
+# endif  // GTEST_OS_FUCHSIA
+
+#endif  // GTEST_HAS_DEATH_TEST
+
+#include "gtest/gtest-message.h"
+#include "gtest/internal/gtest-string.h"
+#include "src/gtest-internal-inl.h"
+
+namespace testing {
+
+// Constants.
+
+// The default death test style.
+//
+// This is defined in internal/gtest-port.h as "fast", but can be overridden by
+// a definition in internal/custom/gtest-port.h. The recommended value, which is
+// used internally at Google, is "threadsafe".
+static const char kDefaultDeathTestStyle[] = GTEST_DEFAULT_DEATH_TEST_STYLE;
+
+GTEST_DEFINE_string_(
+    death_test_style,
+    internal::StringFromGTestEnv("death_test_style", kDefaultDeathTestStyle),
+    "Indicates how to run a death test in a forked child process: "
+    "\"threadsafe\" (child process re-executes the test binary "
+    "from the beginning, running only the specific death test) or "
+    "\"fast\" (child process runs the death test immediately "
+    "after forking).");
+
+GTEST_DEFINE_bool_(
+    death_test_use_fork,
+    internal::BoolFromGTestEnv("death_test_use_fork", false),
+    "Instructs to use fork()/_exit() instead of clone() in death tests. "
+    "Ignored and always uses fork() on POSIX systems where clone() is not "
+    "implemented. Useful when running under valgrind or similar tools if "
+    "those do not support clone(). Valgrind 3.3.1 will just fail if "
+    "it sees an unsupported combination of clone() flags. "
+    "It is not recommended to use this flag w/o valgrind though it will "
+    "work in 99% of the cases. Once valgrind is fixed, this flag will "
+    "most likely be removed.");
+
+namespace internal {
+GTEST_DEFINE_string_(
+    internal_run_death_test, "",
+    "Indicates the file, line number, temporal index of "
+    "the single death test to run, and a file descriptor to "
+    "which a success code may be sent, all separated by "
+    "the '|' characters.  This flag is specified if and only if the "
+    "current process is a sub-process launched for running a thread-safe "
+    "death test.  FOR INTERNAL USE ONLY.");
+}  // namespace internal
+
+#if GTEST_HAS_DEATH_TEST
+
+namespace internal {
+
+// Valid only for fast death tests. Indicates the code is running in the
+// child process of a fast style death test.
+# if !GTEST_OS_WINDOWS && !GTEST_OS_FUCHSIA
+static bool g_in_fast_death_test_child = false;
+# endif
+
+// Returns a Boolean value indicating whether the caller is currently
+// executing in the context of the death test child process.  Tools such as
+// Valgrind heap checkers may need this to modify their behavior in death
+// tests.  IMPORTANT: This is an internal utility.  Using it may break the
+// implementation of death tests.  User code MUST NOT use it.
+bool InDeathTestChild() {
+# if GTEST_OS_WINDOWS || GTEST_OS_FUCHSIA
+
+  // On Windows and Fuchsia, death tests are thread-safe regardless of the value
+  // of the death_test_style flag.
+  return !GTEST_FLAG(internal_run_death_test).empty();
+
+# else
+
+  if (GTEST_FLAG(death_test_style) == "threadsafe")
+    return !GTEST_FLAG(internal_run_death_test).empty();
+  else
+    return g_in_fast_death_test_child;
+#endif
+}
+
+}  // namespace internal
+
+// ExitedWithCode constructor.
+ExitedWithCode::ExitedWithCode(int exit_code) : exit_code_(exit_code) {
+}
+
+// ExitedWithCode function-call operator.
+bool ExitedWithCode::operator()(int exit_status) const {
+# if GTEST_OS_WINDOWS || GTEST_OS_FUCHSIA
+
+  return exit_status == exit_code_;
+
+# else
+
+  return WIFEXITED(exit_status) && WEXITSTATUS(exit_status) == exit_code_;
+
+# endif  // GTEST_OS_WINDOWS || GTEST_OS_FUCHSIA
+}
+
+# if !GTEST_OS_WINDOWS && !GTEST_OS_FUCHSIA
+// KilledBySignal constructor.
+KilledBySignal::KilledBySignal(int signum) : signum_(signum) {
+}
+
+// KilledBySignal function-call operator.
+bool KilledBySignal::operator()(int exit_status) const {
+#  if defined(GTEST_KILLED_BY_SIGNAL_OVERRIDE_)
+  {
+    bool result;
+    if (GTEST_KILLED_BY_SIGNAL_OVERRIDE_(signum_, exit_status, &result)) {
+      return result;
+    }
+  }
+#  endif  // defined(GTEST_KILLED_BY_SIGNAL_OVERRIDE_)
+  return WIFSIGNALED(exit_status) && WTERMSIG(exit_status) == signum_;
+}
+# endif  // !GTEST_OS_WINDOWS && !GTEST_OS_FUCHSIA
+
+namespace internal {
+
+// Utilities needed for death tests.
+
+// Generates a textual description of a given exit code, in the format
+// specified by wait(2).
+static std::string ExitSummary(int exit_code) {
+  Message m;
+
+# if GTEST_OS_WINDOWS || GTEST_OS_FUCHSIA
+
+  m << "Exited with exit status " << exit_code;
+
+# else
+
+  if (WIFEXITED(exit_code)) {
+    m << "Exited with exit status " << WEXITSTATUS(exit_code);
+  } else if (WIFSIGNALED(exit_code)) {
+    m << "Terminated by signal " << WTERMSIG(exit_code);
+  }
+#  ifdef WCOREDUMP
+  if (WCOREDUMP(exit_code)) {
+    m << " (core dumped)";
+  }
+#  endif
+# endif  // GTEST_OS_WINDOWS || GTEST_OS_FUCHSIA
+
+  return m.GetString();
+}
+
+// Returns true if exit_status describes a process that was terminated
+// by a signal, or exited normally with a nonzero exit code.
+bool ExitedUnsuccessfully(int exit_status) {
+  return !ExitedWithCode(0)(exit_status);
+}
+
+# if !GTEST_OS_WINDOWS && !GTEST_OS_FUCHSIA
+// Generates a textual failure message when a death test finds more than
+// one thread running, or cannot determine the number of threads, prior
+// to executing the given statement.  It is the responsibility of the
+// caller not to pass a thread_count of 1.
+static std::string DeathTestThreadWarning(size_t thread_count) {
+  Message msg;
+  msg << "Death tests use fork(), which is unsafe particularly"
+      << " in a threaded context. For this test, " << GTEST_NAME_ << " ";
+  if (thread_count == 0) {
+    msg << "couldn't detect the number of threads.";
+  } else {
+    msg << "detected " << thread_count << " threads.";
+  }
+  msg << " See "
+         "https://github.com/google/googletest/blob/master/docs/"
+         "advanced.md#death-tests-and-threads"
+      << " for more explanation and suggested solutions, especially if"
+      << " this is the last message you see before your test times out.";
+  return msg.GetString();
+}
+# endif  // !GTEST_OS_WINDOWS && !GTEST_OS_FUCHSIA
+
+// Flag characters for reporting a death test that did not die.
+static const char kDeathTestLived = 'L';
+static const char kDeathTestReturned = 'R';
+static const char kDeathTestThrew = 'T';
+static const char kDeathTestInternalError = 'I';
+
+#if GTEST_OS_FUCHSIA
+
+// File descriptor used for the pipe in the child process.
+static const int kFuchsiaReadPipeFd = 3;
+
+#endif
+
+// An enumeration describing all of the possible ways that a death test can
+// conclude.  DIED means that the process died while executing the test
+// code; LIVED means that process lived beyond the end of the test code;
+// RETURNED means that the test statement attempted to execute a return
+// statement, which is not allowed; THREW means that the test statement
+// returned control by throwing an exception.  IN_PROGRESS means the test
+// has not yet concluded.
+enum DeathTestOutcome { IN_PROGRESS, DIED, LIVED, RETURNED, THREW };
+
+// Routine for aborting the program which is safe to call from an
+// exec-style death test child process, in which case the error
+// message is propagated back to the parent process.  Otherwise, the
+// message is simply printed to stderr.  In either case, the program
+// then exits with status 1.
+static void DeathTestAbort(const std::string& message) {
+  // On a POSIX system, this function may be called from a threadsafe-style
+  // death test child process, which operates on a very small stack.  Use
+  // the heap for any additional non-minuscule memory requirements.
+  const InternalRunDeathTestFlag* const flag =
+      GetUnitTestImpl()->internal_run_death_test_flag();
+  if (flag != nullptr) {
+    FILE* parent = posix::FDOpen(flag->write_fd(), "w");
+    fputc(kDeathTestInternalError, parent);
+    fprintf(parent, "%s", message.c_str());
+    fflush(parent);
+    _exit(1);
+  } else {
+    fprintf(stderr, "%s", message.c_str());
+    fflush(stderr);
+    posix::Abort();
+  }
+}
+
+// A replacement for CHECK that calls DeathTestAbort if the assertion
+// fails.
+# define GTEST_DEATH_TEST_CHECK_(expression) \
+  do { \
+    if (!::testing::internal::IsTrue(expression)) { \
+      DeathTestAbort( \
+          ::std::string("CHECK failed: File ") + __FILE__ +  ", line " \
+          + ::testing::internal::StreamableToString(__LINE__) + ": " \
+          + #expression); \
+    } \
+  } while (::testing::internal::AlwaysFalse())
+
+// This macro is similar to GTEST_DEATH_TEST_CHECK_, but it is meant for
+// evaluating any system call that fulfills two conditions: it must return
+// -1 on failure, and set errno to EINTR when it is interrupted and
+// should be tried again.  The macro expands to a loop that repeatedly
+// evaluates the expression as long as it evaluates to -1 and sets
+// errno to EINTR.  If the expression evaluates to -1 but errno is
+// something other than EINTR, DeathTestAbort is called.
+# define GTEST_DEATH_TEST_CHECK_SYSCALL_(expression) \
+  do { \
+    int gtest_retval; \
+    do { \
+      gtest_retval = (expression); \
+    } while (gtest_retval == -1 && errno == EINTR); \
+    if (gtest_retval == -1) { \
+      DeathTestAbort( \
+          ::std::string("CHECK failed: File ") + __FILE__ + ", line " \
+          + ::testing::internal::StreamableToString(__LINE__) + ": " \
+          + #expression + " != -1"); \
+    } \
+  } while (::testing::internal::AlwaysFalse())
+
+// Returns the message describing the last system error in errno.
+std::string GetLastErrnoDescription() {
+    return errno == 0 ? "" : posix::StrError(errno);
+}
+
+// This is called from a death test parent process to read a failure
+// message from the death test child process and log it with the FATAL
+// severity. On Windows, the message is read from a pipe handle. On other
+// platforms, it is read from a file descriptor.
+static void FailFromInternalError(int fd) {
+  Message error;
+  char buffer[256];
+  int num_read;
+
+  do {
+    while ((num_read = posix::Read(fd, buffer, 255)) > 0) {
+      buffer[num_read] = '\0';
+      error << buffer;
+    }
+  } while (num_read == -1 && errno == EINTR);
+
+  if (num_read == 0) {
+    GTEST_LOG_(FATAL) << error.GetString();
+  } else {
+    const int last_error = errno;
+    GTEST_LOG_(FATAL) << "Error while reading death test internal: "
+                      << GetLastErrnoDescription() << " [" << last_error << "]";
+  }
+}
+
+// Death test constructor.  Increments the running death test count
+// for the current test.
+DeathTest::DeathTest() {
+  TestInfo* const info = GetUnitTestImpl()->current_test_info();
+  if (info == nullptr) {
+    DeathTestAbort("Cannot run a death test outside of a TEST or "
+                   "TEST_F construct");
+  }
+}
+
+// Creates and returns a death test by dispatching to the current
+// death test factory.
+bool DeathTest::Create(const char* statement,
+                       Matcher<const std::string&> matcher, const char* file,
+                       int line, DeathTest** test) {
+  return GetUnitTestImpl()->death_test_factory()->Create(
+      statement, std::move(matcher), file, line, test);
+}
+
+const char* DeathTest::LastMessage() {
+  return last_death_test_message_.c_str();
+}
+
+void DeathTest::set_last_death_test_message(const std::string& message) {
+  last_death_test_message_ = message;
+}
+
+std::string DeathTest::last_death_test_message_;
+
+// Provides cross platform implementation for some death functionality.
+class DeathTestImpl : public DeathTest {
+ protected:
+  DeathTestImpl(const char* a_statement, Matcher<const std::string&> matcher)
+      : statement_(a_statement),
+        matcher_(std::move(matcher)),
+        spawned_(false),
+        status_(-1),
+        outcome_(IN_PROGRESS),
+        read_fd_(-1),
+        write_fd_(-1) {}
+
+  // read_fd_ is expected to be closed and cleared by a derived class.
+  ~DeathTestImpl() override { GTEST_DEATH_TEST_CHECK_(read_fd_ == -1); }
+
+  void Abort(AbortReason reason) override;
+  bool Passed(bool status_ok) override;
+
+  const char* statement() const { return statement_; }
+  bool spawned() const { return spawned_; }
+  void set_spawned(bool is_spawned) { spawned_ = is_spawned; }
+  int status() const { return status_; }
+  void set_status(int a_status) { status_ = a_status; }
+  DeathTestOutcome outcome() const { return outcome_; }
+  void set_outcome(DeathTestOutcome an_outcome) { outcome_ = an_outcome; }
+  int read_fd() const { return read_fd_; }
+  void set_read_fd(int fd) { read_fd_ = fd; }
+  int write_fd() const { return write_fd_; }
+  void set_write_fd(int fd) { write_fd_ = fd; }
+
+  // Called in the parent process only. Reads the result code of the death
+  // test child process via a pipe, interprets it to set the outcome_
+  // member, and closes read_fd_.  Outputs diagnostics and terminates in
+  // case of unexpected codes.
+  void ReadAndInterpretStatusByte();
+
+  // Returns stderr output from the child process.
+  virtual std::string GetErrorLogs();
+
+ private:
+  // The textual content of the code this object is testing.  This class
+  // doesn't own this string and should not attempt to delete it.
+  const char* const statement_;
+  // A matcher that's expected to match the stderr output by the child process.
+  Matcher<const std::string&> matcher_;
+  // True if the death test child process has been successfully spawned.
+  bool spawned_;
+  // The exit status of the child process.
+  int status_;
+  // How the death test concluded.
+  DeathTestOutcome outcome_;
+  // Descriptor to the read end of the pipe to the child process.  It is
+  // always -1 in the child process.  The child keeps its write end of the
+  // pipe in write_fd_.
+  int read_fd_;
+  // Descriptor to the child's write end of the pipe to the parent process.
+  // It is always -1 in the parent process.  The parent keeps its end of the
+  // pipe in read_fd_.
+  int write_fd_;
+};
+
+// Called in the parent process only. Reads the result code of the death
+// test child process via a pipe, interprets it to set the outcome_
+// member, and closes read_fd_.  Outputs diagnostics and terminates in
+// case of unexpected codes.
+void DeathTestImpl::ReadAndInterpretStatusByte() {
+  char flag;
+  int bytes_read;
+
+  // The read() here blocks until data is available (signifying the
+  // failure of the death test) or until the pipe is closed (signifying
+  // its success), so it's okay to call this in the parent before
+  // the child process has exited.
+  do {
+    bytes_read = posix::Read(read_fd(), &flag, 1);
+  } while (bytes_read == -1 && errno == EINTR);
+
+  if (bytes_read == 0) {
+    set_outcome(DIED);
+  } else if (bytes_read == 1) {
+    switch (flag) {
+      case kDeathTestReturned:
+        set_outcome(RETURNED);
+        break;
+      case kDeathTestThrew:
+        set_outcome(THREW);
+        break;
+      case kDeathTestLived:
+        set_outcome(LIVED);
+        break;
+      case kDeathTestInternalError:
+        FailFromInternalError(read_fd());  // Does not return.
+        break;
+      default:
+        GTEST_LOG_(FATAL) << "Death test child process reported "
+                          << "unexpected status byte ("
+                          << static_cast<unsigned int>(flag) << ")";
+    }
+  } else {
+    GTEST_LOG_(FATAL) << "Read from death test child process failed: "
+                      << GetLastErrnoDescription();
+  }
+  GTEST_DEATH_TEST_CHECK_SYSCALL_(posix::Close(read_fd()));
+  set_read_fd(-1);
+}
+
+std::string DeathTestImpl::GetErrorLogs() {
+  return GetCapturedStderr();
+}
+
+// Signals that the death test code which should have exited, didn't.
+// Should be called only in a death test child process.
+// Writes a status byte to the child's status file descriptor, then
+// calls _exit(1).
+void DeathTestImpl::Abort(AbortReason reason) {
+  // The parent process considers the death test to be a failure if
+  // it finds any data in our pipe.  So, here we write a single flag byte
+  // to the pipe, then exit.
+  const char status_ch =
+      reason == TEST_DID_NOT_DIE ? kDeathTestLived :
+      reason == TEST_THREW_EXCEPTION ? kDeathTestThrew : kDeathTestReturned;
+
+  GTEST_DEATH_TEST_CHECK_SYSCALL_(posix::Write(write_fd(), &status_ch, 1));
+  // We are leaking the descriptor here because on some platforms (i.e.,
+  // when built as Windows DLL), destructors of global objects will still
+  // run after calling _exit(). On such systems, write_fd_ will be
+  // indirectly closed from the destructor of UnitTestImpl, causing double
+  // close if it is also closed here. On debug configurations, double close
+  // may assert. As there are no in-process buffers to flush here, we are
+  // relying on the OS to close the descriptor after the process terminates
+  // when the destructors are not run.
+  _exit(1);  // Exits w/o any normal exit hooks (we were supposed to crash)
+}
+
+// Returns an indented copy of stderr output for a death test.
+// This makes distinguishing death test output lines from regular log lines
+// much easier.
+static ::std::string FormatDeathTestOutput(const ::std::string& output) {
+  ::std::string ret;
+  for (size_t at = 0; ; ) {
+    const size_t line_end = output.find('\n', at);
+    ret += "[  DEATH   ] ";
+    if (line_end == ::std::string::npos) {
+      ret += output.substr(at);
+      break;
+    }
+    ret += output.substr(at, line_end + 1 - at);
+    at = line_end + 1;
+  }
+  return ret;
+}
+
+// Assesses the success or failure of a death test, using both private
+// members which have previously been set, and one argument:
+//
+// Private data members:
+//   outcome:  An enumeration describing how the death test
+//             concluded: DIED, LIVED, THREW, or RETURNED.  The death test
+//             fails in the latter three cases.
+//   status:   The exit status of the child process. On *nix, it is in the
+//             in the format specified by wait(2). On Windows, this is the
+//             value supplied to the ExitProcess() API or a numeric code
+//             of the exception that terminated the program.
+//   matcher_: A matcher that's expected to match the stderr output by the child
+//             process.
+//
+// Argument:
+//   status_ok: true if exit_status is acceptable in the context of
+//              this particular death test, which fails if it is false
+//
+// Returns true if and only if all of the above conditions are met.  Otherwise,
+// the first failing condition, in the order given above, is the one that is
+// reported. Also sets the last death test message string.
+bool DeathTestImpl::Passed(bool status_ok) {
+  if (!spawned())
+    return false;
+
+  const std::string error_message = GetErrorLogs();
+
+  bool success = false;
+  Message buffer;
+
+  buffer << "Death test: " << statement() << "\n";
+  switch (outcome()) {
+    case LIVED:
+      buffer << "    Result: failed to die.\n"
+             << " Error msg:\n" << FormatDeathTestOutput(error_message);
+      break;
+    case THREW:
+      buffer << "    Result: threw an exception.\n"
+             << " Error msg:\n" << FormatDeathTestOutput(error_message);
+      break;
+    case RETURNED:
+      buffer << "    Result: illegal return in test statement.\n"
+             << " Error msg:\n" << FormatDeathTestOutput(error_message);
+      break;
+    case DIED:
+      if (status_ok) {
+        if (matcher_.Matches(error_message)) {
+          success = true;
+        } else {
+          std::ostringstream stream;
+          matcher_.DescribeTo(&stream);
+          buffer << "    Result: died but not with expected error.\n"
+                 << "  Expected: " << stream.str() << "\n"
+                 << "Actual msg:\n"
+                 << FormatDeathTestOutput(error_message);
+        }
+      } else {
+        buffer << "    Result: died but not with expected exit code:\n"
+               << "            " << ExitSummary(status()) << "\n"
+               << "Actual msg:\n" << FormatDeathTestOutput(error_message);
+      }
+      break;
+    case IN_PROGRESS:
+    default:
+      GTEST_LOG_(FATAL)
+          << "DeathTest::Passed somehow called before conclusion of test";
+  }
+
+  DeathTest::set_last_death_test_message(buffer.GetString());
+  return success;
+}
+
+# if GTEST_OS_WINDOWS
+// WindowsDeathTest implements death tests on Windows. Due to the
+// specifics of starting new processes on Windows, death tests there are
+// always threadsafe, and Google Test considers the
+// --gtest_death_test_style=fast setting to be equivalent to
+// --gtest_death_test_style=threadsafe there.
+//
+// A few implementation notes:  Like the Linux version, the Windows
+// implementation uses pipes for child-to-parent communication. But due to
+// the specifics of pipes on Windows, some extra steps are required:
+//
+// 1. The parent creates a communication pipe and stores handles to both
+//    ends of it.
+// 2. The parent starts the child and provides it with the information
+//    necessary to acquire the handle to the write end of the pipe.
+// 3. The child acquires the write end of the pipe and signals the parent
+//    using a Windows event.
+// 4. Now the parent can release the write end of the pipe on its side. If
+//    this is done before step 3, the object's reference count goes down to
+//    0 and it is destroyed, preventing the child from acquiring it. The
+//    parent now has to release it, or read operations on the read end of
+//    the pipe will not return when the child terminates.
+// 5. The parent reads child's output through the pipe (outcome code and
+//    any possible error messages) from the pipe, and its stderr and then
+//    determines whether to fail the test.
+//
+// Note: to distinguish Win32 API calls from the local method and function
+// calls, the former are explicitly resolved in the global namespace.
+//
+class WindowsDeathTest : public DeathTestImpl {
+ public:
+  WindowsDeathTest(const char* a_statement, Matcher<const std::string&> matcher,
+                   const char* file, int line)
+      : DeathTestImpl(a_statement, std::move(matcher)),
+        file_(file),
+        line_(line) {}
+
+  // All of these virtual functions are inherited from DeathTest.
+  virtual int Wait();
+  virtual TestRole AssumeRole();
+
+ private:
+  // The name of the file in which the death test is located.
+  const char* const file_;
+  // The line number on which the death test is located.
+  const int line_;
+  // Handle to the write end of the pipe to the child process.
+  AutoHandle write_handle_;
+  // Child process handle.
+  AutoHandle child_handle_;
+  // Event the child process uses to signal the parent that it has
+  // acquired the handle to the write end of the pipe. After seeing this
+  // event the parent can release its own handles to make sure its
+  // ReadFile() calls return when the child terminates.
+  AutoHandle event_handle_;
+};
+
+// Waits for the child in a death test to exit, returning its exit
+// status, or 0 if no child process exists.  As a side effect, sets the
+// outcome data member.
+int WindowsDeathTest::Wait() {
+  if (!spawned())
+    return 0;
+
+  // Wait until the child either signals that it has acquired the write end
+  // of the pipe or it dies.
+  const HANDLE wait_handles[2] = { child_handle_.Get(), event_handle_.Get() };
+  switch (::WaitForMultipleObjects(2,
+                                   wait_handles,
+                                   FALSE,  // Waits for any of the handles.
+                                   INFINITE)) {
+    case WAIT_OBJECT_0:
+    case WAIT_OBJECT_0 + 1:
+      break;
+    default:
+      GTEST_DEATH_TEST_CHECK_(false);  // Should not get here.
+  }
+
+  // The child has acquired the write end of the pipe or exited.
+  // We release the handle on our side and continue.
+  write_handle_.Reset();
+  event_handle_.Reset();
+
+  ReadAndInterpretStatusByte();
+
+  // Waits for the child process to exit if it haven't already. This
+  // returns immediately if the child has already exited, regardless of
+  // whether previous calls to WaitForMultipleObjects synchronized on this
+  // handle or not.
+  GTEST_DEATH_TEST_CHECK_(
+      WAIT_OBJECT_0 == ::WaitForSingleObject(child_handle_.Get(),
+                                             INFINITE));
+  DWORD status_code;
+  GTEST_DEATH_TEST_CHECK_(
+      ::GetExitCodeProcess(child_handle_.Get(), &status_code) != FALSE);
+  child_handle_.Reset();
+  set_status(static_cast<int>(status_code));
+  return status();
+}
+
+// The AssumeRole process for a Windows death test.  It creates a child
+// process with the same executable as the current process to run the
+// death test.  The child process is given the --gtest_filter and
+// --gtest_internal_run_death_test flags such that it knows to run the
+// current death test only.
+DeathTest::TestRole WindowsDeathTest::AssumeRole() {
+  const UnitTestImpl* const impl = GetUnitTestImpl();
+  const InternalRunDeathTestFlag* const flag =
+      impl->internal_run_death_test_flag();
+  const TestInfo* const info = impl->current_test_info();
+  const int death_test_index = info->result()->death_test_count();
+
+  if (flag != nullptr) {
+    // ParseInternalRunDeathTestFlag() has performed all the necessary
+    // processing.
+    set_write_fd(flag->write_fd());
+    return EXECUTE_TEST;
+  }
+
+  // WindowsDeathTest uses an anonymous pipe to communicate results of
+  // a death test.
+  SECURITY_ATTRIBUTES handles_are_inheritable = {sizeof(SECURITY_ATTRIBUTES),
+                                                 nullptr, TRUE};
+  HANDLE read_handle, write_handle;
+  GTEST_DEATH_TEST_CHECK_(
+      ::CreatePipe(&read_handle, &write_handle, &handles_are_inheritable,
+                   0)  // Default buffer size.
+      != FALSE);
+  set_read_fd(::_open_osfhandle(reinterpret_cast<intptr_t>(read_handle),
+                                O_RDONLY));
+  write_handle_.Reset(write_handle);
+  event_handle_.Reset(::CreateEvent(
+      &handles_are_inheritable,
+      TRUE,       // The event will automatically reset to non-signaled state.
+      FALSE,      // The initial state is non-signalled.
+      nullptr));  // The even is unnamed.
+  GTEST_DEATH_TEST_CHECK_(event_handle_.Get() != nullptr);
+  const std::string filter_flag = std::string("--") + GTEST_FLAG_PREFIX_ +
+                                  kFilterFlag + "=" + info->test_suite_name() +
+                                  "." + info->name();
+  const std::string internal_flag =
+      std::string("--") + GTEST_FLAG_PREFIX_ + kInternalRunDeathTestFlag +
+      "=" + file_ + "|" + StreamableToString(line_) + "|" +
+      StreamableToString(death_test_index) + "|" +
+      StreamableToString(static_cast<unsigned int>(::GetCurrentProcessId())) +
+      // size_t has the same width as pointers on both 32-bit and 64-bit
+      // Windows platforms.
+      // See http://msdn.microsoft.com/en-us/library/tcxf1dw6.aspx.
+      "|" + StreamableToString(reinterpret_cast<size_t>(write_handle)) +
+      "|" + StreamableToString(reinterpret_cast<size_t>(event_handle_.Get()));
+
+  char executable_path[_MAX_PATH + 1];  // NOLINT
+  GTEST_DEATH_TEST_CHECK_(_MAX_PATH + 1 != ::GetModuleFileNameA(nullptr,
+                                                                executable_path,
+                                                                _MAX_PATH));
+
+  std::string command_line =
+      std::string(::GetCommandLineA()) + " " + filter_flag + " \"" +
+      internal_flag + "\"";
+
+  DeathTest::set_last_death_test_message("");
+
+  CaptureStderr();
+  // Flush the log buffers since the log streams are shared with the child.
+  FlushInfoLog();
+
+  // The child process will share the standard handles with the parent.
+  STARTUPINFOA startup_info;
+  memset(&startup_info, 0, sizeof(STARTUPINFO));
+  startup_info.dwFlags = STARTF_USESTDHANDLES;
+  startup_info.hStdInput = ::GetStdHandle(STD_INPUT_HANDLE);
+  startup_info.hStdOutput = ::GetStdHandle(STD_OUTPUT_HANDLE);
+  startup_info.hStdError = ::GetStdHandle(STD_ERROR_HANDLE);
+
+  PROCESS_INFORMATION process_info;
+  GTEST_DEATH_TEST_CHECK_(
+      ::CreateProcessA(
+          executable_path, const_cast<char*>(command_line.c_str()),
+          nullptr,  // Retuned process handle is not inheritable.
+          nullptr,  // Retuned thread handle is not inheritable.
+          TRUE,  // Child inherits all inheritable handles (for write_handle_).
+          0x0,   // Default creation flags.
+          nullptr,  // Inherit the parent's environment.
+          UnitTest::GetInstance()->original_working_dir(), &startup_info,
+          &process_info) != FALSE);
+  child_handle_.Reset(process_info.hProcess);
+  ::CloseHandle(process_info.hThread);
+  set_spawned(true);
+  return OVERSEE_TEST;
+}
+
+# elif GTEST_OS_FUCHSIA
+
+class FuchsiaDeathTest : public DeathTestImpl {
+ public:
+  FuchsiaDeathTest(const char* a_statement, Matcher<const std::string&> matcher,
+                   const char* file, int line)
+      : DeathTestImpl(a_statement, std::move(matcher)),
+        file_(file),
+        line_(line) {}
+
+  // All of these virtual functions are inherited from DeathTest.
+  int Wait() override;
+  TestRole AssumeRole() override;
+  std::string GetErrorLogs() override;
+
+ private:
+  // The name of the file in which the death test is located.
+  const char* const file_;
+  // The line number on which the death test is located.
+  const int line_;
+  // The stderr data captured by the child process.
+  std::string captured_stderr_;
+
+  zx::process child_process_;
+  zx::channel exception_channel_;
+  zx::socket stderr_socket_;
+};
+
+// Utility class for accumulating command-line arguments.
+class Arguments {
+ public:
+  Arguments() { args_.push_back(nullptr); }
+
+  ~Arguments() {
+    for (std::vector<char*>::iterator i = args_.begin(); i != args_.end();
+         ++i) {
+      free(*i);
+    }
+  }
+  void AddArgument(const char* argument) {
+    args_.insert(args_.end() - 1, posix::StrDup(argument));
+  }
+
+  template <typename Str>
+  void AddArguments(const ::std::vector<Str>& arguments) {
+    for (typename ::std::vector<Str>::const_iterator i = arguments.begin();
+         i != arguments.end();
+         ++i) {
+      args_.insert(args_.end() - 1, posix::StrDup(i->c_str()));
+    }
+  }
+  char* const* Argv() {
+    return &args_[0];
+  }
+
+  int size() {
+    return static_cast<int>(args_.size()) - 1;
+  }
+
+ private:
+  std::vector<char*> args_;
+};
+
+// Waits for the child in a death test to exit, returning its exit
+// status, or 0 if no child process exists.  As a side effect, sets the
+// outcome data member.
+int FuchsiaDeathTest::Wait() {
+  const int kProcessKey = 0;
+  const int kSocketKey = 1;
+  const int kExceptionKey = 2;
+
+  if (!spawned())
+    return 0;
+
+  // Create a port to wait for socket/task/exception events.
+  zx_status_t status_zx;
+  zx::port port;
+  status_zx = zx::port::create(0, &port);
+  GTEST_DEATH_TEST_CHECK_(status_zx == ZX_OK);
+
+  // Register to wait for the child process to terminate.
+  status_zx = child_process_.wait_async(
+      port, kProcessKey, ZX_PROCESS_TERMINATED, 0);
+  GTEST_DEATH_TEST_CHECK_(status_zx == ZX_OK);
+
+  // Register to wait for the socket to be readable or closed.
+  status_zx = stderr_socket_.wait_async(
+      port, kSocketKey, ZX_SOCKET_READABLE | ZX_SOCKET_PEER_CLOSED, 0);
+  GTEST_DEATH_TEST_CHECK_(status_zx == ZX_OK);
+
+  // Register to wait for an exception.
+  status_zx = exception_channel_.wait_async(
+      port, kExceptionKey, ZX_CHANNEL_READABLE, 0);
+  GTEST_DEATH_TEST_CHECK_(status_zx == ZX_OK);
+
+  bool process_terminated = false;
+  bool socket_closed = false;
+  do {
+    zx_port_packet_t packet = {};
+    status_zx = port.wait(zx::time::infinite(), &packet);
+    GTEST_DEATH_TEST_CHECK_(status_zx == ZX_OK);
+
+    if (packet.key == kExceptionKey) {
+      // Process encountered an exception. Kill it directly rather than
+      // letting other handlers process the event. We will get a kProcessKey
+      // event when the process actually terminates.
+      status_zx = child_process_.kill();
+      GTEST_DEATH_TEST_CHECK_(status_zx == ZX_OK);
+    } else if (packet.key == kProcessKey) {
+      // Process terminated.
+      GTEST_DEATH_TEST_CHECK_(ZX_PKT_IS_SIGNAL_ONE(packet.type));
+      GTEST_DEATH_TEST_CHECK_(packet.signal.observed & ZX_PROCESS_TERMINATED);
+      process_terminated = true;
+    } else if (packet.key == kSocketKey) {
+      GTEST_DEATH_TEST_CHECK_(ZX_PKT_IS_SIGNAL_ONE(packet.type));
+      if (packet.signal.observed & ZX_SOCKET_READABLE) {
+        // Read data from the socket.
+        constexpr size_t kBufferSize = 1024;
+        do {
+          size_t old_length = captured_stderr_.length();
+          size_t bytes_read = 0;
+          captured_stderr_.resize(old_length + kBufferSize);
+          status_zx = stderr_socket_.read(
+              0, &captured_stderr_.front() + old_length, kBufferSize,
+              &bytes_read);
+          captured_stderr_.resize(old_length + bytes_read);
+        } while (status_zx == ZX_OK);
+        if (status_zx == ZX_ERR_PEER_CLOSED) {
+          socket_closed = true;
+        } else {
+          GTEST_DEATH_TEST_CHECK_(status_zx == ZX_ERR_SHOULD_WAIT);
+          status_zx = stderr_socket_.wait_async(
+              port, kSocketKey, ZX_SOCKET_READABLE | ZX_SOCKET_PEER_CLOSED, 0);
+          GTEST_DEATH_TEST_CHECK_(status_zx == ZX_OK);
+        }
+      } else {
+        GTEST_DEATH_TEST_CHECK_(packet.signal.observed & ZX_SOCKET_PEER_CLOSED);
+        socket_closed = true;
+      }
+    }
+  } while (!process_terminated && !socket_closed);
+
+  ReadAndInterpretStatusByte();
+
+  zx_info_process_t buffer;
+  status_zx = child_process_.get_info(ZX_INFO_PROCESS, &buffer, sizeof(buffer),
+                                      nullptr, nullptr);
+  GTEST_DEATH_TEST_CHECK_(status_zx == ZX_OK);
+
+  GTEST_DEATH_TEST_CHECK_(buffer.flags & ZX_INFO_PROCESS_FLAG_EXITED);
+  set_status(static_cast<int>(buffer.return_code));
+  return status();
+}
+
+// The AssumeRole process for a Fuchsia death test.  It creates a child
+// process with the same executable as the current process to run the
+// death test.  The child process is given the --gtest_filter and
+// --gtest_internal_run_death_test flags such that it knows to run the
+// current death test only.
+DeathTest::TestRole FuchsiaDeathTest::AssumeRole() {
+  const UnitTestImpl* const impl = GetUnitTestImpl();
+  const InternalRunDeathTestFlag* const flag =
+      impl->internal_run_death_test_flag();
+  const TestInfo* const info = impl->current_test_info();
+  const int death_test_index = info->result()->death_test_count();
+
+  if (flag != nullptr) {
+    // ParseInternalRunDeathTestFlag() has performed all the necessary
+    // processing.
+    set_write_fd(kFuchsiaReadPipeFd);
+    return EXECUTE_TEST;
+  }
+
+  // Flush the log buffers since the log streams are shared with the child.
+  FlushInfoLog();
+
+  // Build the child process command line.
+  const std::string filter_flag = std::string("--") + GTEST_FLAG_PREFIX_ +
+                                  kFilterFlag + "=" + info->test_suite_name() +
+                                  "." + info->name();
+  const std::string internal_flag =
+      std::string("--") + GTEST_FLAG_PREFIX_ + kInternalRunDeathTestFlag + "="
+      + file_ + "|"
+      + StreamableToString(line_) + "|"
+      + StreamableToString(death_test_index);
+  Arguments args;
+  args.AddArguments(GetInjectableArgvs());
+  args.AddArgument(filter_flag.c_str());
+  args.AddArgument(internal_flag.c_str());
+
+  // Build the pipe for communication with the child.
+  zx_status_t status;
+  zx_handle_t child_pipe_handle;
+  int child_pipe_fd;
+  status = fdio_pipe_half(&child_pipe_fd, &child_pipe_handle);
+  GTEST_DEATH_TEST_CHECK_(status == ZX_OK);
+  set_read_fd(child_pipe_fd);
+
+  // Set the pipe handle for the child.
+  fdio_spawn_action_t spawn_actions[2] = {};
+  fdio_spawn_action_t* add_handle_action = &spawn_actions[0];
+  add_handle_action->action = FDIO_SPAWN_ACTION_ADD_HANDLE;
+  add_handle_action->h.id = PA_HND(PA_FD, kFuchsiaReadPipeFd);
+  add_handle_action->h.handle = child_pipe_handle;
+
+  // Create a socket pair will be used to receive the child process' stderr.
+  zx::socket stderr_producer_socket;
+  status =
+      zx::socket::create(0, &stderr_producer_socket, &stderr_socket_);
+  GTEST_DEATH_TEST_CHECK_(status >= 0);
+  int stderr_producer_fd = -1;
+  status =
+      fdio_fd_create(stderr_producer_socket.release(), &stderr_producer_fd);
+  GTEST_DEATH_TEST_CHECK_(status >= 0);
+
+  // Make the stderr socket nonblocking.
+  GTEST_DEATH_TEST_CHECK_(fcntl(stderr_producer_fd, F_SETFL, 0) == 0);
+
+  fdio_spawn_action_t* add_stderr_action = &spawn_actions[1];
+  add_stderr_action->action = FDIO_SPAWN_ACTION_CLONE_FD;
+  add_stderr_action->fd.local_fd = stderr_producer_fd;
+  add_stderr_action->fd.target_fd = STDERR_FILENO;
+
+  // Create a child job.
+  zx_handle_t child_job = ZX_HANDLE_INVALID;
+  status = zx_job_create(zx_job_default(), 0, & child_job);
+  GTEST_DEATH_TEST_CHECK_(status == ZX_OK);
+  zx_policy_basic_t policy;
+  policy.condition = ZX_POL_NEW_ANY;
+  policy.policy = ZX_POL_ACTION_ALLOW;
+  status = zx_job_set_policy(
+      child_job, ZX_JOB_POL_RELATIVE, ZX_JOB_POL_BASIC, &policy, 1);
+  GTEST_DEATH_TEST_CHECK_(status == ZX_OK);
+
+  // Create an exception channel attached to the |child_job|, to allow
+  // us to suppress the system default exception handler from firing.
+  status =
+      zx_task_create_exception_channel(
+          child_job, 0, exception_channel_.reset_and_get_address());
+  GTEST_DEATH_TEST_CHECK_(status == ZX_OK);
+
+  // Spawn the child process.
+  status = fdio_spawn_etc(
+      child_job, FDIO_SPAWN_CLONE_ALL, args.Argv()[0], args.Argv(), nullptr,
+      2, spawn_actions, child_process_.reset_and_get_address(), nullptr);
+  GTEST_DEATH_TEST_CHECK_(status == ZX_OK);
+
+  set_spawned(true);
+  return OVERSEE_TEST;
+}
+
+std::string FuchsiaDeathTest::GetErrorLogs() {
+  return captured_stderr_;
+}
+
+#else  // We are neither on Windows, nor on Fuchsia.
+
+// ForkingDeathTest provides implementations for most of the abstract
+// methods of the DeathTest interface.  Only the AssumeRole method is
+// left undefined.
+class ForkingDeathTest : public DeathTestImpl {
+ public:
+  ForkingDeathTest(const char* statement, Matcher<const std::string&> matcher);
+
+  // All of these virtual functions are inherited from DeathTest.
+  int Wait() override;
+
+ protected:
+  void set_child_pid(pid_t child_pid) { child_pid_ = child_pid; }
+
+ private:
+  // PID of child process during death test; 0 in the child process itself.
+  pid_t child_pid_;
+};
+
+// Constructs a ForkingDeathTest.
+ForkingDeathTest::ForkingDeathTest(const char* a_statement,
+                                   Matcher<const std::string&> matcher)
+    : DeathTestImpl(a_statement, std::move(matcher)), child_pid_(-1) {}
+
+// Waits for the child in a death test to exit, returning its exit
+// status, or 0 if no child process exists.  As a side effect, sets the
+// outcome data member.
+int ForkingDeathTest::Wait() {
+  if (!spawned())
+    return 0;
+
+  ReadAndInterpretStatusByte();
+
+  int status_value;
+  GTEST_DEATH_TEST_CHECK_SYSCALL_(waitpid(child_pid_, &status_value, 0));
+  set_status(status_value);
+  return status_value;
+}
+
+// A concrete death test class that forks, then immediately runs the test
+// in the child process.
+class NoExecDeathTest : public ForkingDeathTest {
+ public:
+  NoExecDeathTest(const char* a_statement, Matcher<const std::string&> matcher)
+      : ForkingDeathTest(a_statement, std::move(matcher)) {}
+  TestRole AssumeRole() override;
+};
+
+// The AssumeRole process for a fork-and-run death test.  It implements a
+// straightforward fork, with a simple pipe to transmit the status byte.
+DeathTest::TestRole NoExecDeathTest::AssumeRole() {
+  const size_t thread_count = GetThreadCount();
+  if (thread_count != 1) {
+    GTEST_LOG_(WARNING) << DeathTestThreadWarning(thread_count);
+  }
+
+  int pipe_fd[2];
+  GTEST_DEATH_TEST_CHECK_(pipe(pipe_fd) != -1);
+
+  DeathTest::set_last_death_test_message("");
+  CaptureStderr();
+  // When we fork the process below, the log file buffers are copied, but the
+  // file descriptors are shared.  We flush all log files here so that closing
+  // the file descriptors in the child process doesn't throw off the
+  // synchronization between descriptors and buffers in the parent process.
+  // This is as close to the fork as possible to avoid a race condition in case
+  // there are multiple threads running before the death test, and another
+  // thread writes to the log file.
+  FlushInfoLog();
+
+  const pid_t child_pid = fork();
+  GTEST_DEATH_TEST_CHECK_(child_pid != -1);
+  set_child_pid(child_pid);
+  if (child_pid == 0) {
+    GTEST_DEATH_TEST_CHECK_SYSCALL_(close(pipe_fd[0]));
+    set_write_fd(pipe_fd[1]);
+    // Redirects all logging to stderr in the child process to prevent
+    // concurrent writes to the log files.  We capture stderr in the parent
+    // process and append the child process' output to a log.
+    LogToStderr();
+    // Event forwarding to the listeners of event listener API mush be shut
+    // down in death test subprocesses.
+    GetUnitTestImpl()->listeners()->SuppressEventForwarding();
+    g_in_fast_death_test_child = true;
+    return EXECUTE_TEST;
+  } else {
+    GTEST_DEATH_TEST_CHECK_SYSCALL_(close(pipe_fd[1]));
+    set_read_fd(pipe_fd[0]);
+    set_spawned(true);
+    return OVERSEE_TEST;
+  }
+}
+
+// A concrete death test class that forks and re-executes the main
+// program from the beginning, with command-line flags set that cause
+// only this specific death test to be run.
+class ExecDeathTest : public ForkingDeathTest {
+ public:
+  ExecDeathTest(const char* a_statement, Matcher<const std::string&> matcher,
+                const char* file, int line)
+      : ForkingDeathTest(a_statement, std::move(matcher)),
+        file_(file),
+        line_(line) {}
+  TestRole AssumeRole() override;
+
+ private:
+  static ::std::vector<std::string> GetArgvsForDeathTestChildProcess() {
+    ::std::vector<std::string> args = GetInjectableArgvs();
+#  if defined(GTEST_EXTRA_DEATH_TEST_COMMAND_LINE_ARGS_)
+    ::std::vector<std::string> extra_args =
+        GTEST_EXTRA_DEATH_TEST_COMMAND_LINE_ARGS_();
+    args.insert(args.end(), extra_args.begin(), extra_args.end());
+#  endif  // defined(GTEST_EXTRA_DEATH_TEST_COMMAND_LINE_ARGS_)
+    return args;
+  }
+  // The name of the file in which the death test is located.
+  const char* const file_;
+  // The line number on which the death test is located.
+  const int line_;
+};
+
+// Utility class for accumulating command-line arguments.
+class Arguments {
+ public:
+  Arguments() { args_.push_back(nullptr); }
+
+  ~Arguments() {
+    for (std::vector<char*>::iterator i = args_.begin(); i != args_.end();
+         ++i) {
+      free(*i);
+    }
+  }
+  void AddArgument(const char* argument) {
+    args_.insert(args_.end() - 1, posix::StrDup(argument));
+  }
+
+  template <typename Str>
+  void AddArguments(const ::std::vector<Str>& arguments) {
+    for (typename ::std::vector<Str>::const_iterator i = arguments.begin();
+         i != arguments.end();
+         ++i) {
+      args_.insert(args_.end() - 1, posix::StrDup(i->c_str()));
+    }
+  }
+  char* const* Argv() {
+    return &args_[0];
+  }
+
+ private:
+  std::vector<char*> args_;
+};
+
+// A struct that encompasses the arguments to the child process of a
+// threadsafe-style death test process.
+struct ExecDeathTestArgs {
+  char* const* argv;  // Command-line arguments for the child's call to exec
+  int close_fd;       // File descriptor to close; the read end of a pipe
+};
+
+#  if GTEST_OS_QNX
+extern "C" char** environ;
+#  else  // GTEST_OS_QNX
+// The main function for a threadsafe-style death test child process.
+// This function is called in a clone()-ed process and thus must avoid
+// any potentially unsafe operations like malloc or libc functions.
+static int ExecDeathTestChildMain(void* child_arg) {
+  ExecDeathTestArgs* const args = static_cast<ExecDeathTestArgs*>(child_arg);
+  GTEST_DEATH_TEST_CHECK_SYSCALL_(close(args->close_fd));
+
+  // We need to execute the test program in the same environment where
+  // it was originally invoked.  Therefore we change to the original
+  // working directory first.
+  const char* const original_dir =
+      UnitTest::GetInstance()->original_working_dir();
+  // We can safely call chdir() as it's a direct system call.
+  if (chdir(original_dir) != 0) {
+    DeathTestAbort(std::string("chdir(\"") + original_dir + "\") failed: " +
+                   GetLastErrnoDescription());
+    return EXIT_FAILURE;
+  }
+
+  // We can safely call execv() as it's almost a direct system call. We
+  // cannot use execvp() as it's a libc function and thus potentially
+  // unsafe.  Since execv() doesn't search the PATH, the user must
+  // invoke the test program via a valid path that contains at least
+  // one path separator.
+  execv(args->argv[0], args->argv);
+  DeathTestAbort(std::string("execv(") + args->argv[0] + ", ...) in " +
+                 original_dir + " failed: " +
+                 GetLastErrnoDescription());
+  return EXIT_FAILURE;
+}
+#  endif  // GTEST_OS_QNX
+
+#  if GTEST_HAS_CLONE
+// Two utility routines that together determine the direction the stack
+// grows.
+// This could be accomplished more elegantly by a single recursive
+// function, but we want to guard against the unlikely possibility of
+// a smart compiler optimizing the recursion away.
+//
+// GTEST_NO_INLINE_ is required to prevent GCC 4.6 from inlining
+// StackLowerThanAddress into StackGrowsDown, which then doesn't give
+// correct answer.
+static void StackLowerThanAddress(const void* ptr,
+                                  bool* result) GTEST_NO_INLINE_;
+// Make sure sanitizers do not tamper with the stack here.
+// Ideally, we want to use `__builtin_frame_address` instead of a local variable
+// address with sanitizer disabled, but it does not work when the
+// compiler optimizes the stack frame out, which happens on PowerPC targets.
+// HWAddressSanitizer add a random tag to the MSB of the local variable address,
+// making comparison result unpredictable.
+GTEST_ATTRIBUTE_NO_SANITIZE_ADDRESS_
+GTEST_ATTRIBUTE_NO_SANITIZE_HWADDRESS_
+static void StackLowerThanAddress(const void* ptr, bool* result) {
+  int dummy = 0;
+  *result = std::less<const void*>()(&dummy, ptr);
+}
+
+// Make sure AddressSanitizer does not tamper with the stack here.
+GTEST_ATTRIBUTE_NO_SANITIZE_ADDRESS_
+GTEST_ATTRIBUTE_NO_SANITIZE_HWADDRESS_
+static bool StackGrowsDown() {
+  int dummy = 0;
+  bool result;
+  StackLowerThanAddress(&dummy, &result);
+  return result;
+}
+#  endif  // GTEST_HAS_CLONE
+
+// Spawns a child process with the same executable as the current process in
+// a thread-safe manner and instructs it to run the death test.  The
+// implementation uses fork(2) + exec.  On systems where clone(2) is
+// available, it is used instead, being slightly more thread-safe.  On QNX,
+// fork supports only single-threaded environments, so this function uses
+// spawn(2) there instead.  The function dies with an error message if
+// anything goes wrong.
+static pid_t ExecDeathTestSpawnChild(char* const* argv, int close_fd) {
+  ExecDeathTestArgs args = { argv, close_fd };
+  pid_t child_pid = -1;
+
+#  if GTEST_OS_QNX
+  // Obtains the current directory and sets it to be closed in the child
+  // process.
+  const int cwd_fd = open(".", O_RDONLY);
+  GTEST_DEATH_TEST_CHECK_(cwd_fd != -1);
+  GTEST_DEATH_TEST_CHECK_SYSCALL_(fcntl(cwd_fd, F_SETFD, FD_CLOEXEC));
+  // We need to execute the test program in the same environment where
+  // it was originally invoked.  Therefore we change to the original
+  // working directory first.
+  const char* const original_dir =
+      UnitTest::GetInstance()->original_working_dir();
+  // We can safely call chdir() as it's a direct system call.
+  if (chdir(original_dir) != 0) {
+    DeathTestAbort(std::string("chdir(\"") + original_dir + "\") failed: " +
+                   GetLastErrnoDescription());
+    return EXIT_FAILURE;
+  }
+
+  int fd_flags;
+  // Set close_fd to be closed after spawn.
+  GTEST_DEATH_TEST_CHECK_SYSCALL_(fd_flags = fcntl(close_fd, F_GETFD));
+  GTEST_DEATH_TEST_CHECK_SYSCALL_(fcntl(close_fd, F_SETFD,
+                                        fd_flags | FD_CLOEXEC));
+  struct inheritance inherit = {0};
+  // spawn is a system call.
+  child_pid = spawn(args.argv[0], 0, nullptr, &inherit, args.argv, environ);
+  // Restores the current working directory.
+  GTEST_DEATH_TEST_CHECK_(fchdir(cwd_fd) != -1);
+  GTEST_DEATH_TEST_CHECK_SYSCALL_(close(cwd_fd));
+
+#  else   // GTEST_OS_QNX
+#   if GTEST_OS_LINUX
+  // When a SIGPROF signal is received while fork() or clone() are executing,
+  // the process may hang. To avoid this, we ignore SIGPROF here and re-enable
+  // it after the call to fork()/clone() is complete.
+  struct sigaction saved_sigprof_action;
+  struct sigaction ignore_sigprof_action;
+  memset(&ignore_sigprof_action, 0, sizeof(ignore_sigprof_action));
+  sigemptyset(&ignore_sigprof_action.sa_mask);
+  ignore_sigprof_action.sa_handler = SIG_IGN;
+  GTEST_DEATH_TEST_CHECK_SYSCALL_(sigaction(
+      SIGPROF, &ignore_sigprof_action, &saved_sigprof_action));
+#   endif  // GTEST_OS_LINUX
+
+#   if GTEST_HAS_CLONE
+  const bool use_fork = GTEST_FLAG(death_test_use_fork);
+
+  if (!use_fork) {
+    static const bool stack_grows_down = StackGrowsDown();
+    const auto stack_size = static_cast<size_t>(getpagesize() * 2);
+    // MMAP_ANONYMOUS is not defined on Mac, so we use MAP_ANON instead.
+    void* const stack = mmap(nullptr, stack_size, PROT_READ | PROT_WRITE,
+                             MAP_ANON | MAP_PRIVATE, -1, 0);
+    GTEST_DEATH_TEST_CHECK_(stack != MAP_FAILED);
+
+    // Maximum stack alignment in bytes:  For a downward-growing stack, this
+    // amount is subtracted from size of the stack space to get an address
+    // that is within the stack space and is aligned on all systems we care
+    // about.  As far as I know there is no ABI with stack alignment greater
+    // than 64.  We assume stack and stack_size already have alignment of
+    // kMaxStackAlignment.
+    const size_t kMaxStackAlignment = 64;
+    void* const stack_top =
+        static_cast<char*>(stack) +
+            (stack_grows_down ? stack_size - kMaxStackAlignment : 0);
+    GTEST_DEATH_TEST_CHECK_(
+        static_cast<size_t>(stack_size) > kMaxStackAlignment &&
+        reinterpret_cast<uintptr_t>(stack_top) % kMaxStackAlignment == 0);
+
+    child_pid = clone(&ExecDeathTestChildMain, stack_top, SIGCHLD, &args);
+
+    GTEST_DEATH_TEST_CHECK_(munmap(stack, stack_size) != -1);
+  }
+#   else
+  const bool use_fork = true;
+#   endif  // GTEST_HAS_CLONE
+
+  if (use_fork && (child_pid = fork()) == 0) {
+      ExecDeathTestChildMain(&args);
+      _exit(0);
+  }
+#  endif  // GTEST_OS_QNX
+#  if GTEST_OS_LINUX
+  GTEST_DEATH_TEST_CHECK_SYSCALL_(
+      sigaction(SIGPROF, &saved_sigprof_action, nullptr));
+#  endif  // GTEST_OS_LINUX
+
+  GTEST_DEATH_TEST_CHECK_(child_pid != -1);
+  return child_pid;
+}
+
+// The AssumeRole process for a fork-and-exec death test.  It re-executes the
+// main program from the beginning, setting the --gtest_filter
+// and --gtest_internal_run_death_test flags to cause only the current
+// death test to be re-run.
+DeathTest::TestRole ExecDeathTest::AssumeRole() {
+  const UnitTestImpl* const impl = GetUnitTestImpl();
+  const InternalRunDeathTestFlag* const flag =
+      impl->internal_run_death_test_flag();
+  const TestInfo* const info = impl->current_test_info();
+  const int death_test_index = info->result()->death_test_count();
+
+  if (flag != nullptr) {
+    set_write_fd(flag->write_fd());
+    return EXECUTE_TEST;
+  }
+
+  int pipe_fd[2];
+  GTEST_DEATH_TEST_CHECK_(pipe(pipe_fd) != -1);
+  // Clear the close-on-exec flag on the write end of the pipe, lest
+  // it be closed when the child process does an exec:
+  GTEST_DEATH_TEST_CHECK_(fcntl(pipe_fd[1], F_SETFD, 0) != -1);
+
+  const std::string filter_flag = std::string("--") + GTEST_FLAG_PREFIX_ +
+                                  kFilterFlag + "=" + info->test_suite_name() +
+                                  "." + info->name();
+  const std::string internal_flag =
+      std::string("--") + GTEST_FLAG_PREFIX_ + kInternalRunDeathTestFlag + "="
+      + file_ + "|" + StreamableToString(line_) + "|"
+      + StreamableToString(death_test_index) + "|"
+      + StreamableToString(pipe_fd[1]);
+  Arguments args;
+  args.AddArguments(GetArgvsForDeathTestChildProcess());
+  args.AddArgument(filter_flag.c_str());
+  args.AddArgument(internal_flag.c_str());
+
+  DeathTest::set_last_death_test_message("");
+
+  CaptureStderr();
+  // See the comment in NoExecDeathTest::AssumeRole for why the next line
+  // is necessary.
+  FlushInfoLog();
+
+  const pid_t child_pid = ExecDeathTestSpawnChild(args.Argv(), pipe_fd[0]);
+  GTEST_DEATH_TEST_CHECK_SYSCALL_(close(pipe_fd[1]));
+  set_child_pid(child_pid);
+  set_read_fd(pipe_fd[0]);
+  set_spawned(true);
+  return OVERSEE_TEST;
+}
+
+# endif  // !GTEST_OS_WINDOWS
+
+// Creates a concrete DeathTest-derived class that depends on the
+// --gtest_death_test_style flag, and sets the pointer pointed to
+// by the "test" argument to its address.  If the test should be
+// skipped, sets that pointer to NULL.  Returns true, unless the
+// flag is set to an invalid value.
+bool DefaultDeathTestFactory::Create(const char* statement,
+                                     Matcher<const std::string&> matcher,
+                                     const char* file, int line,
+                                     DeathTest** test) {
+  UnitTestImpl* const impl = GetUnitTestImpl();
+  const InternalRunDeathTestFlag* const flag =
+      impl->internal_run_death_test_flag();
+  const int death_test_index = impl->current_test_info()
+      ->increment_death_test_count();
+
+  if (flag != nullptr) {
+    if (death_test_index > flag->index()) {
+      DeathTest::set_last_death_test_message(
+          "Death test count (" + StreamableToString(death_test_index)
+          + ") somehow exceeded expected maximum ("
+          + StreamableToString(flag->index()) + ")");
+      return false;
+    }
+
+    if (!(flag->file() == file && flag->line() == line &&
+          flag->index() == death_test_index)) {
+      *test = nullptr;
+      return true;
+    }
+  }
+
+# if GTEST_OS_WINDOWS
+
+  if (GTEST_FLAG(death_test_style) == "threadsafe" ||
+      GTEST_FLAG(death_test_style) == "fast") {
+    *test = new WindowsDeathTest(statement, std::move(matcher), file, line);
+  }
+
+# elif GTEST_OS_FUCHSIA
+
+  if (GTEST_FLAG(death_test_style) == "threadsafe" ||
+      GTEST_FLAG(death_test_style) == "fast") {
+    *test = new FuchsiaDeathTest(statement, std::move(matcher), file, line);
+  }
+
+# else
+
+  if (GTEST_FLAG(death_test_style) == "threadsafe") {
+    *test = new ExecDeathTest(statement, std::move(matcher), file, line);
+  } else if (GTEST_FLAG(death_test_style) == "fast") {
+    *test = new NoExecDeathTest(statement, std::move(matcher));
+  }
+
+# endif  // GTEST_OS_WINDOWS
+
+  else {  // NOLINT - this is more readable than unbalanced brackets inside #if.
+    DeathTest::set_last_death_test_message(
+        "Unknown death test style \"" + GTEST_FLAG(death_test_style)
+        + "\" encountered");
+    return false;
+  }
+
+  return true;
+}
+
+# if GTEST_OS_WINDOWS
+// Recreates the pipe and event handles from the provided parameters,
+// signals the event, and returns a file descriptor wrapped around the pipe
+// handle. This function is called in the child process only.
+static int GetStatusFileDescriptor(unsigned int parent_process_id,
+                            size_t write_handle_as_size_t,
+                            size_t event_handle_as_size_t) {
+  AutoHandle parent_process_handle(::OpenProcess(PROCESS_DUP_HANDLE,
+                                                   FALSE,  // Non-inheritable.
+                                                   parent_process_id));
+  if (parent_process_handle.Get() == INVALID_HANDLE_VALUE) {
+    DeathTestAbort("Unable to open parent process " +
+                   StreamableToString(parent_process_id));
+  }
+
+  GTEST_CHECK_(sizeof(HANDLE) <= sizeof(size_t));
+
+  const HANDLE write_handle =
+      reinterpret_cast<HANDLE>(write_handle_as_size_t);
+  HANDLE dup_write_handle;
+
+  // The newly initialized handle is accessible only in the parent
+  // process. To obtain one accessible within the child, we need to use
+  // DuplicateHandle.
+  if (!::DuplicateHandle(parent_process_handle.Get(), write_handle,
+                         ::GetCurrentProcess(), &dup_write_handle,
+                         0x0,    // Requested privileges ignored since
+                                 // DUPLICATE_SAME_ACCESS is used.
+                         FALSE,  // Request non-inheritable handler.
+                         DUPLICATE_SAME_ACCESS)) {
+    DeathTestAbort("Unable to duplicate the pipe handle " +
+                   StreamableToString(write_handle_as_size_t) +
+                   " from the parent process " +
+                   StreamableToString(parent_process_id));
+  }
+
+  const HANDLE event_handle = reinterpret_cast<HANDLE>(event_handle_as_size_t);
+  HANDLE dup_event_handle;
+
+  if (!::DuplicateHandle(parent_process_handle.Get(), event_handle,
+                         ::GetCurrentProcess(), &dup_event_handle,
+                         0x0,
+                         FALSE,
+                         DUPLICATE_SAME_ACCESS)) {
+    DeathTestAbort("Unable to duplicate the event handle " +
+                   StreamableToString(event_handle_as_size_t) +
+                   " from the parent process " +
+                   StreamableToString(parent_process_id));
+  }
+
+  const int write_fd =
+      ::_open_osfhandle(reinterpret_cast<intptr_t>(dup_write_handle), O_APPEND);
+  if (write_fd == -1) {
+    DeathTestAbort("Unable to convert pipe handle " +
+                   StreamableToString(write_handle_as_size_t) +
+                   " to a file descriptor");
+  }
+
+  // Signals the parent that the write end of the pipe has been acquired
+  // so the parent can release its own write end.
+  ::SetEvent(dup_event_handle);
+
+  return write_fd;
+}
+# endif  // GTEST_OS_WINDOWS
+
+// Returns a newly created InternalRunDeathTestFlag object with fields
+// initialized from the GTEST_FLAG(internal_run_death_test) flag if
+// the flag is specified; otherwise returns NULL.
+InternalRunDeathTestFlag* ParseInternalRunDeathTestFlag() {
+  if (GTEST_FLAG(internal_run_death_test) == "") return nullptr;
+
+  // GTEST_HAS_DEATH_TEST implies that we have ::std::string, so we
+  // can use it here.
+  int line = -1;
+  int index = -1;
+  ::std::vector< ::std::string> fields;
+  SplitString(GTEST_FLAG(internal_run_death_test).c_str(), '|', &fields);
+  int write_fd = -1;
+
+# if GTEST_OS_WINDOWS
+
+  unsigned int parent_process_id = 0;
+  size_t write_handle_as_size_t = 0;
+  size_t event_handle_as_size_t = 0;
+
+  if (fields.size() != 6
+      || !ParseNaturalNumber(fields[1], &line)
+      || !ParseNaturalNumber(fields[2], &index)
+      || !ParseNaturalNumber(fields[3], &parent_process_id)
+      || !ParseNaturalNumber(fields[4], &write_handle_as_size_t)
+      || !ParseNaturalNumber(fields[5], &event_handle_as_size_t)) {
+    DeathTestAbort("Bad --gtest_internal_run_death_test flag: " +
+                   GTEST_FLAG(internal_run_death_test));
+  }
+  write_fd = GetStatusFileDescriptor(parent_process_id,
+                                     write_handle_as_size_t,
+                                     event_handle_as_size_t);
+
+# elif GTEST_OS_FUCHSIA
+
+  if (fields.size() != 3
+      || !ParseNaturalNumber(fields[1], &line)
+      || !ParseNaturalNumber(fields[2], &index)) {
+    DeathTestAbort("Bad --gtest_internal_run_death_test flag: "
+        + GTEST_FLAG(internal_run_death_test));
+  }
+
+# else
+
+  if (fields.size() != 4
+      || !ParseNaturalNumber(fields[1], &line)
+      || !ParseNaturalNumber(fields[2], &index)
+      || !ParseNaturalNumber(fields[3], &write_fd)) {
+    DeathTestAbort("Bad --gtest_internal_run_death_test flag: "
+        + GTEST_FLAG(internal_run_death_test));
+  }
+
+# endif  // GTEST_OS_WINDOWS
+
+  return new InternalRunDeathTestFlag(fields[0], line, index, write_fd);
+}
+
+}  // namespace internal
+
+#endif  // GTEST_HAS_DEATH_TEST
+
+}  // namespace testing
diff --git a/leveldb_base/third_party/googletest/googletest/src/gtest-filepath.cc b/leveldb_base/third_party/googletest/googletest/src/gtest-filepath.cc
new file mode 100644
index 0000000..9504f0f
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/src/gtest-filepath.cc
@@ -0,0 +1,369 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "gtest/internal/gtest-filepath.h"
+
+#include <stdlib.h>
+#include "gtest/internal/gtest-port.h"
+#include "gtest/gtest-message.h"
+
+#if GTEST_OS_WINDOWS_MOBILE
+# include <windows.h>
+#elif GTEST_OS_WINDOWS
+# include <direct.h>
+# include <io.h>
+#else
+# include <limits.h>
+# include <climits>  // Some Linux distributions define PATH_MAX here.
+#endif  // GTEST_OS_WINDOWS_MOBILE
+
+#include "gtest/internal/gtest-string.h"
+
+#if GTEST_OS_WINDOWS
+# define GTEST_PATH_MAX_ _MAX_PATH
+#elif defined(PATH_MAX)
+# define GTEST_PATH_MAX_ PATH_MAX
+#elif defined(_XOPEN_PATH_MAX)
+# define GTEST_PATH_MAX_ _XOPEN_PATH_MAX
+#else
+# define GTEST_PATH_MAX_ _POSIX_PATH_MAX
+#endif  // GTEST_OS_WINDOWS
+
+namespace testing {
+namespace internal {
+
+#if GTEST_OS_WINDOWS
+// On Windows, '\\' is the standard path separator, but many tools and the
+// Windows API also accept '/' as an alternate path separator. Unless otherwise
+// noted, a file path can contain either kind of path separators, or a mixture
+// of them.
+const char kPathSeparator = '\\';
+const char kAlternatePathSeparator = '/';
+const char kAlternatePathSeparatorString[] = "/";
+# if GTEST_OS_WINDOWS_MOBILE
+// Windows CE doesn't have a current directory. You should not use
+// the current directory in tests on Windows CE, but this at least
+// provides a reasonable fallback.
+const char kCurrentDirectoryString[] = "\\";
+// Windows CE doesn't define INVALID_FILE_ATTRIBUTES
+const DWORD kInvalidFileAttributes = 0xffffffff;
+# else
+const char kCurrentDirectoryString[] = ".\\";
+# endif  // GTEST_OS_WINDOWS_MOBILE
+#else
+const char kPathSeparator = '/';
+const char kCurrentDirectoryString[] = "./";
+#endif  // GTEST_OS_WINDOWS
+
+// Returns whether the given character is a valid path separator.
+static bool IsPathSeparator(char c) {
+#if GTEST_HAS_ALT_PATH_SEP_
+  return (c == kPathSeparator) || (c == kAlternatePathSeparator);
+#else
+  return c == kPathSeparator;
+#endif
+}
+
+// Returns the current working directory, or "" if unsuccessful.
+FilePath FilePath::GetCurrentDir() {
+#if GTEST_OS_WINDOWS_MOBILE || GTEST_OS_WINDOWS_PHONE ||         \
+    GTEST_OS_WINDOWS_RT || GTEST_OS_ESP8266 || GTEST_OS_ESP32 || \
+    GTEST_OS_XTENSA
+  // These platforms do not have a current directory, so we just return
+  // something reasonable.
+  return FilePath(kCurrentDirectoryString);
+#elif GTEST_OS_WINDOWS
+  char cwd[GTEST_PATH_MAX_ + 1] = { '\0' };
+  return FilePath(_getcwd(cwd, sizeof(cwd)) == nullptr ? "" : cwd);
+#else
+  char cwd[GTEST_PATH_MAX_ + 1] = { '\0' };
+  char* result = getcwd(cwd, sizeof(cwd));
+# if GTEST_OS_NACL
+  // getcwd will likely fail in NaCl due to the sandbox, so return something
+  // reasonable. The user may have provided a shim implementation for getcwd,
+  // however, so fallback only when failure is detected.
+  return FilePath(result == nullptr ? kCurrentDirectoryString : cwd);
+# endif  // GTEST_OS_NACL
+  return FilePath(result == nullptr ? "" : cwd);
+#endif  // GTEST_OS_WINDOWS_MOBILE
+}
+
+// Returns a copy of the FilePath with the case-insensitive extension removed.
+// Example: FilePath("dir/file.exe").RemoveExtension("EXE") returns
+// FilePath("dir/file"). If a case-insensitive extension is not
+// found, returns a copy of the original FilePath.
+FilePath FilePath::RemoveExtension(const char* extension) const {
+  const std::string dot_extension = std::string(".") + extension;
+  if (String::EndsWithCaseInsensitive(pathname_, dot_extension)) {
+    return FilePath(pathname_.substr(
+        0, pathname_.length() - dot_extension.length()));
+  }
+  return *this;
+}
+
+// Returns a pointer to the last occurrence of a valid path separator in
+// the FilePath. On Windows, for example, both '/' and '\' are valid path
+// separators. Returns NULL if no path separator was found.
+const char* FilePath::FindLastPathSeparator() const {
+  const char* const last_sep = strrchr(c_str(), kPathSeparator);
+#if GTEST_HAS_ALT_PATH_SEP_
+  const char* const last_alt_sep = strrchr(c_str(), kAlternatePathSeparator);
+  // Comparing two pointers of which only one is NULL is undefined.
+  if (last_alt_sep != nullptr &&
+      (last_sep == nullptr || last_alt_sep > last_sep)) {
+    return last_alt_sep;
+  }
+#endif
+  return last_sep;
+}
+
+// Returns a copy of the FilePath with the directory part removed.
+// Example: FilePath("path/to/file").RemoveDirectoryName() returns
+// FilePath("file"). If there is no directory part ("just_a_file"), it returns
+// the FilePath unmodified. If there is no file part ("just_a_dir/") it
+// returns an empty FilePath ("").
+// On Windows platform, '\' is the path separator, otherwise it is '/'.
+FilePath FilePath::RemoveDirectoryName() const {
+  const char* const last_sep = FindLastPathSeparator();
+  return last_sep ? FilePath(last_sep + 1) : *this;
+}
+
+// RemoveFileName returns the directory path with the filename removed.
+// Example: FilePath("path/to/file").RemoveFileName() returns "path/to/".
+// If the FilePath is "a_file" or "/a_file", RemoveFileName returns
+// FilePath("./") or, on Windows, FilePath(".\\"). If the filepath does
+// not have a file, like "just/a/dir/", it returns the FilePath unmodified.
+// On Windows platform, '\' is the path separator, otherwise it is '/'.
+FilePath FilePath::RemoveFileName() const {
+  const char* const last_sep = FindLastPathSeparator();
+  std::string dir;
+  if (last_sep) {
+    dir = std::string(c_str(), static_cast<size_t>(last_sep + 1 - c_str()));
+  } else {
+    dir = kCurrentDirectoryString;
+  }
+  return FilePath(dir);
+}
+
+// Helper functions for naming files in a directory for xml output.
+
+// Given directory = "dir", base_name = "test", number = 0,
+// extension = "xml", returns "dir/test.xml". If number is greater
+// than zero (e.g., 12), returns "dir/test_12.xml".
+// On Windows platform, uses \ as the separator rather than /.
+FilePath FilePath::MakeFileName(const FilePath& directory,
+                                const FilePath& base_name,
+                                int number,
+                                const char* extension) {
+  std::string file;
+  if (number == 0) {
+    file = base_name.string() + "." + extension;
+  } else {
+    file = base_name.string() + "_" + StreamableToString(number)
+        + "." + extension;
+  }
+  return ConcatPaths(directory, FilePath(file));
+}
+
+// Given directory = "dir", relative_path = "test.xml", returns "dir/test.xml".
+// On Windows, uses \ as the separator rather than /.
+FilePath FilePath::ConcatPaths(const FilePath& directory,
+                               const FilePath& relative_path) {
+  if (directory.IsEmpty())
+    return relative_path;
+  const FilePath dir(directory.RemoveTrailingPathSeparator());
+  return FilePath(dir.string() + kPathSeparator + relative_path.string());
+}
+
+// Returns true if pathname describes something findable in the file-system,
+// either a file, directory, or whatever.
+bool FilePath::FileOrDirectoryExists() const {
+#if GTEST_OS_WINDOWS_MOBILE
+  LPCWSTR unicode = String::AnsiToUtf16(pathname_.c_str());
+  const DWORD attributes = GetFileAttributes(unicode);
+  delete [] unicode;
+  return attributes != kInvalidFileAttributes;
+#else
+  posix::StatStruct file_stat;
+  return posix::Stat(pathname_.c_str(), &file_stat) == 0;
+#endif  // GTEST_OS_WINDOWS_MOBILE
+}
+
+// Returns true if pathname describes a directory in the file-system
+// that exists.
+bool FilePath::DirectoryExists() const {
+  bool result = false;
+#if GTEST_OS_WINDOWS
+  // Don't strip off trailing separator if path is a root directory on
+  // Windows (like "C:\\").
+  const FilePath& path(IsRootDirectory() ? *this :
+                                           RemoveTrailingPathSeparator());
+#else
+  const FilePath& path(*this);
+#endif
+
+#if GTEST_OS_WINDOWS_MOBILE
+  LPCWSTR unicode = String::AnsiToUtf16(path.c_str());
+  const DWORD attributes = GetFileAttributes(unicode);
+  delete [] unicode;
+  if ((attributes != kInvalidFileAttributes) &&
+      (attributes & FILE_ATTRIBUTE_DIRECTORY)) {
+    result = true;
+  }
+#else
+  posix::StatStruct file_stat;
+  result = posix::Stat(path.c_str(), &file_stat) == 0 &&
+      posix::IsDir(file_stat);
+#endif  // GTEST_OS_WINDOWS_MOBILE
+
+  return result;
+}
+
+// Returns true if pathname describes a root directory. (Windows has one
+// root directory per disk drive.)
+bool FilePath::IsRootDirectory() const {
+#if GTEST_OS_WINDOWS
+  return pathname_.length() == 3 && IsAbsolutePath();
+#else
+  return pathname_.length() == 1 && IsPathSeparator(pathname_.c_str()[0]);
+#endif
+}
+
+// Returns true if pathname describes an absolute path.
+bool FilePath::IsAbsolutePath() const {
+  const char* const name = pathname_.c_str();
+#if GTEST_OS_WINDOWS
+  return pathname_.length() >= 3 &&
+     ((name[0] >= 'a' && name[0] <= 'z') ||
+      (name[0] >= 'A' && name[0] <= 'Z')) &&
+     name[1] == ':' &&
+     IsPathSeparator(name[2]);
+#else
+  return IsPathSeparator(name[0]);
+#endif
+}
+
+// Returns a pathname for a file that does not currently exist. The pathname
+// will be directory/base_name.extension or
+// directory/base_name_<number>.extension if directory/base_name.extension
+// already exists. The number will be incremented until a pathname is found
+// that does not already exist.
+// Examples: 'dir/foo_test.xml' or 'dir/foo_test_1.xml'.
+// There could be a race condition if two or more processes are calling this
+// function at the same time -- they could both pick the same filename.
+FilePath FilePath::GenerateUniqueFileName(const FilePath& directory,
+                                          const FilePath& base_name,
+                                          const char* extension) {
+  FilePath full_pathname;
+  int number = 0;
+  do {
+    full_pathname.Set(MakeFileName(directory, base_name, number++, extension));
+  } while (full_pathname.FileOrDirectoryExists());
+  return full_pathname;
+}
+
+// Returns true if FilePath ends with a path separator, which indicates that
+// it is intended to represent a directory. Returns false otherwise.
+// This does NOT check that a directory (or file) actually exists.
+bool FilePath::IsDirectory() const {
+  return !pathname_.empty() &&
+         IsPathSeparator(pathname_.c_str()[pathname_.length() - 1]);
+}
+
+// Create directories so that path exists. Returns true if successful or if
+// the directories already exist; returns false if unable to create directories
+// for any reason.
+bool FilePath::CreateDirectoriesRecursively() const {
+  if (!this->IsDirectory()) {
+    return false;
+  }
+
+  if (pathname_.length() == 0 || this->DirectoryExists()) {
+    return true;
+  }
+
+  const FilePath parent(this->RemoveTrailingPathSeparator().RemoveFileName());
+  return parent.CreateDirectoriesRecursively() && this->CreateFolder();
+}
+
+// Create the directory so that path exists. Returns true if successful or
+// if the directory already exists; returns false if unable to create the
+// directory for any reason, including if the parent directory does not
+// exist. Not named "CreateDirectory" because that's a macro on Windows.
+bool FilePath::CreateFolder() const {
+#if GTEST_OS_WINDOWS_MOBILE
+  FilePath removed_sep(this->RemoveTrailingPathSeparator());
+  LPCWSTR unicode = String::AnsiToUtf16(removed_sep.c_str());
+  int result = CreateDirectory(unicode, nullptr) ? 0 : -1;
+  delete [] unicode;
+#elif GTEST_OS_WINDOWS
+  int result = _mkdir(pathname_.c_str());
+#elif GTEST_OS_ESP8266 || GTEST_OS_XTENSA
+  // do nothing
+  int result = 0;
+#else
+  int result = mkdir(pathname_.c_str(), 0777);
+#endif  // GTEST_OS_WINDOWS_MOBILE
+
+  if (result == -1) {
+    return this->DirectoryExists();  // An error is OK if the directory exists.
+  }
+  return true;  // No error.
+}
+
+// If input name has a trailing separator character, remove it and return the
+// name, otherwise return the name string unmodified.
+// On Windows platform, uses \ as the separator, other platforms use /.
+FilePath FilePath::RemoveTrailingPathSeparator() const {
+  return IsDirectory()
+      ? FilePath(pathname_.substr(0, pathname_.length() - 1))
+      : *this;
+}
+
+// Removes any redundant separators that might be in the pathname.
+// For example, "bar///foo" becomes "bar/foo". Does not eliminate other
+// redundancies that might be in a pathname involving "." or "..".
+void FilePath::Normalize() {
+  auto out = pathname_.begin();
+
+  for (const char character : pathname_) {
+    if (!IsPathSeparator(character)) {
+      *(out++) = character;
+    } else if (out == pathname_.begin() || *std::prev(out) != kPathSeparator) {
+      *(out++) = kPathSeparator;
+    } else {
+      continue;
+    }
+  }
+
+  pathname_.erase(out, pathname_.end());
+}
+
+}  // namespace internal
+}  // namespace testing
diff --git a/leveldb_base/third_party/googletest/googletest/src/gtest-internal-inl.h b/leveldb_base/third_party/googletest/googletest/src/gtest-internal-inl.h
new file mode 100644
index 0000000..6d8cecb
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/src/gtest-internal-inl.h
@@ -0,0 +1,1221 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Utility functions and classes used by the Google C++ testing framework.//
+// This file contains purely Google Test's internal implementation.  Please
+// DO NOT #INCLUDE IT IN A USER PROGRAM.
+
+#ifndef GOOGLETEST_SRC_GTEST_INTERNAL_INL_H_
+#define GOOGLETEST_SRC_GTEST_INTERNAL_INL_H_
+
+#ifndef _WIN32_WCE
+# include <errno.h>
+#endif  // !_WIN32_WCE
+#include <stddef.h>
+#include <stdlib.h>  // For strtoll/_strtoul64/malloc/free.
+#include <string.h>  // For memmove.
+
+#include <algorithm>
+#include <cstdint>
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "gtest/internal/gtest-port.h"
+
+#if GTEST_CAN_STREAM_RESULTS_
+# include <arpa/inet.h>  // NOLINT
+# include <netdb.h>  // NOLINT
+#endif
+
+#if GTEST_OS_WINDOWS
+# include <windows.h>  // NOLINT
+#endif  // GTEST_OS_WINDOWS
+
+#include "gtest/gtest.h"
+#include "gtest/gtest-spi.h"
+
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4251 \
+/* class A needs to have dll-interface to be used by clients of class B */)
+
+namespace testing {
+
+// Declares the flags.
+//
+// We don't want the users to modify this flag in the code, but want
+// Google Test's own unit tests to be able to access it. Therefore we
+// declare it here as opposed to in gtest.h.
+GTEST_DECLARE_bool_(death_test_use_fork);
+
+namespace internal {
+
+// The value of GetTestTypeId() as seen from within the Google Test
+// library.  This is solely for testing GetTestTypeId().
+GTEST_API_ extern const TypeId kTestTypeIdInGoogleTest;
+
+// Names of the flags (needed for parsing Google Test flags).
+const char kAlsoRunDisabledTestsFlag[] = "also_run_disabled_tests";
+const char kBreakOnFailureFlag[] = "break_on_failure";
+const char kCatchExceptionsFlag[] = "catch_exceptions";
+const char kColorFlag[] = "color";
+const char kFailFast[] = "fail_fast";
+const char kFilterFlag[] = "filter";
+const char kListTestsFlag[] = "list_tests";
+const char kOutputFlag[] = "output";
+const char kBriefFlag[] = "brief";
+const char kPrintTimeFlag[] = "print_time";
+const char kPrintUTF8Flag[] = "print_utf8";
+const char kRandomSeedFlag[] = "random_seed";
+const char kRepeatFlag[] = "repeat";
+const char kShuffleFlag[] = "shuffle";
+const char kStackTraceDepthFlag[] = "stack_trace_depth";
+const char kStreamResultToFlag[] = "stream_result_to";
+const char kThrowOnFailureFlag[] = "throw_on_failure";
+const char kFlagfileFlag[] = "flagfile";
+
+// A valid random seed must be in [1, kMaxRandomSeed].
+const int kMaxRandomSeed = 99999;
+
+// g_help_flag is true if and only if the --help flag or an equivalent form
+// is specified on the command line.
+GTEST_API_ extern bool g_help_flag;
+
+// Returns the current time in milliseconds.
+GTEST_API_ TimeInMillis GetTimeInMillis();
+
+// Returns true if and only if Google Test should use colors in the output.
+GTEST_API_ bool ShouldUseColor(bool stdout_is_tty);
+
+// Formats the given time in milliseconds as seconds.
+GTEST_API_ std::string FormatTimeInMillisAsSeconds(TimeInMillis ms);
+
+// Converts the given time in milliseconds to a date string in the ISO 8601
+// format, without the timezone information.  N.B.: due to the use the
+// non-reentrant localtime() function, this function is not thread safe.  Do
+// not use it in any code that can be called from multiple threads.
+GTEST_API_ std::string FormatEpochTimeInMillisAsIso8601(TimeInMillis ms);
+
+// Parses a string for an Int32 flag, in the form of "--flag=value".
+//
+// On success, stores the value of the flag in *value, and returns
+// true.  On failure, returns false without changing *value.
+GTEST_API_ bool ParseInt32Flag(
+    const char* str, const char* flag, int32_t* value);
+
+// Returns a random seed in range [1, kMaxRandomSeed] based on the
+// given --gtest_random_seed flag value.
+inline int GetRandomSeedFromFlag(int32_t random_seed_flag) {
+  const unsigned int raw_seed = (random_seed_flag == 0) ?
+      static_cast<unsigned int>(GetTimeInMillis()) :
+      static_cast<unsigned int>(random_seed_flag);
+
+  // Normalizes the actual seed to range [1, kMaxRandomSeed] such that
+  // it's easy to type.
+  const int normalized_seed =
+      static_cast<int>((raw_seed - 1U) %
+                       static_cast<unsigned int>(kMaxRandomSeed)) + 1;
+  return normalized_seed;
+}
+
+// Returns the first valid random seed after 'seed'.  The behavior is
+// undefined if 'seed' is invalid.  The seed after kMaxRandomSeed is
+// considered to be 1.
+inline int GetNextRandomSeed(int seed) {
+  GTEST_CHECK_(1 <= seed && seed <= kMaxRandomSeed)
+      << "Invalid random seed " << seed << " - must be in [1, "
+      << kMaxRandomSeed << "].";
+  const int next_seed = seed + 1;
+  return (next_seed > kMaxRandomSeed) ? 1 : next_seed;
+}
+
+// This class saves the values of all Google Test flags in its c'tor, and
+// restores them in its d'tor.
+class GTestFlagSaver {
+ public:
+  // The c'tor.
+  GTestFlagSaver() {
+    also_run_disabled_tests_ = GTEST_FLAG(also_run_disabled_tests);
+    break_on_failure_ = GTEST_FLAG(break_on_failure);
+    catch_exceptions_ = GTEST_FLAG(catch_exceptions);
+    color_ = GTEST_FLAG(color);
+    death_test_style_ = GTEST_FLAG(death_test_style);
+    death_test_use_fork_ = GTEST_FLAG(death_test_use_fork);
+    fail_fast_ = GTEST_FLAG(fail_fast);
+    filter_ = GTEST_FLAG(filter);
+    internal_run_death_test_ = GTEST_FLAG(internal_run_death_test);
+    list_tests_ = GTEST_FLAG(list_tests);
+    output_ = GTEST_FLAG(output);
+    brief_ = GTEST_FLAG(brief);
+    print_time_ = GTEST_FLAG(print_time);
+    print_utf8_ = GTEST_FLAG(print_utf8);
+    random_seed_ = GTEST_FLAG(random_seed);
+    repeat_ = GTEST_FLAG(repeat);
+    shuffle_ = GTEST_FLAG(shuffle);
+    stack_trace_depth_ = GTEST_FLAG(stack_trace_depth);
+    stream_result_to_ = GTEST_FLAG(stream_result_to);
+    throw_on_failure_ = GTEST_FLAG(throw_on_failure);
+  }
+
+  // The d'tor is not virtual.  DO NOT INHERIT FROM THIS CLASS.
+  ~GTestFlagSaver() {
+    GTEST_FLAG(also_run_disabled_tests) = also_run_disabled_tests_;
+    GTEST_FLAG(break_on_failure) = break_on_failure_;
+    GTEST_FLAG(catch_exceptions) = catch_exceptions_;
+    GTEST_FLAG(color) = color_;
+    GTEST_FLAG(death_test_style) = death_test_style_;
+    GTEST_FLAG(death_test_use_fork) = death_test_use_fork_;
+    GTEST_FLAG(filter) = filter_;
+    GTEST_FLAG(fail_fast) = fail_fast_;
+    GTEST_FLAG(internal_run_death_test) = internal_run_death_test_;
+    GTEST_FLAG(list_tests) = list_tests_;
+    GTEST_FLAG(output) = output_;
+    GTEST_FLAG(brief) = brief_;
+    GTEST_FLAG(print_time) = print_time_;
+    GTEST_FLAG(print_utf8) = print_utf8_;
+    GTEST_FLAG(random_seed) = random_seed_;
+    GTEST_FLAG(repeat) = repeat_;
+    GTEST_FLAG(shuffle) = shuffle_;
+    GTEST_FLAG(stack_trace_depth) = stack_trace_depth_;
+    GTEST_FLAG(stream_result_to) = stream_result_to_;
+    GTEST_FLAG(throw_on_failure) = throw_on_failure_;
+  }
+
+ private:
+  // Fields for saving the original values of flags.
+  bool also_run_disabled_tests_;
+  bool break_on_failure_;
+  bool catch_exceptions_;
+  std::string color_;
+  std::string death_test_style_;
+  bool death_test_use_fork_;
+  bool fail_fast_;
+  std::string filter_;
+  std::string internal_run_death_test_;
+  bool list_tests_;
+  std::string output_;
+  bool brief_;
+  bool print_time_;
+  bool print_utf8_;
+  int32_t random_seed_;
+  int32_t repeat_;
+  bool shuffle_;
+  int32_t stack_trace_depth_;
+  std::string stream_result_to_;
+  bool throw_on_failure_;
+} GTEST_ATTRIBUTE_UNUSED_;
+
+// Converts a Unicode code point to a narrow string in UTF-8 encoding.
+// code_point parameter is of type UInt32 because wchar_t may not be
+// wide enough to contain a code point.
+// If the code_point is not a valid Unicode code point
+// (i.e. outside of Unicode range U+0 to U+10FFFF) it will be converted
+// to "(Invalid Unicode 0xXXXXXXXX)".
+GTEST_API_ std::string CodePointToUtf8(uint32_t code_point);
+
+// Converts a wide string to a narrow string in UTF-8 encoding.
+// The wide string is assumed to have the following encoding:
+//   UTF-16 if sizeof(wchar_t) == 2 (on Windows, Cygwin)
+//   UTF-32 if sizeof(wchar_t) == 4 (on Linux)
+// Parameter str points to a null-terminated wide string.
+// Parameter num_chars may additionally limit the number
+// of wchar_t characters processed. -1 is used when the entire string
+// should be processed.
+// If the string contains code points that are not valid Unicode code points
+// (i.e. outside of Unicode range U+0 to U+10FFFF) they will be output
+// as '(Invalid Unicode 0xXXXXXXXX)'. If the string is in UTF16 encoding
+// and contains invalid UTF-16 surrogate pairs, values in those pairs
+// will be encoded as individual Unicode characters from Basic Normal Plane.
+GTEST_API_ std::string WideStringToUtf8(const wchar_t* str, int num_chars);
+
+// Reads the GTEST_SHARD_STATUS_FILE environment variable, and creates the file
+// if the variable is present. If a file already exists at this location, this
+// function will write over it. If the variable is present, but the file cannot
+// be created, prints an error and exits.
+void WriteToShardStatusFileIfNeeded();
+
+// Checks whether sharding is enabled by examining the relevant
+// environment variable values. If the variables are present,
+// but inconsistent (e.g., shard_index >= total_shards), prints
+// an error and exits. If in_subprocess_for_death_test, sharding is
+// disabled because it must only be applied to the original test
+// process. Otherwise, we could filter out death tests we intended to execute.
+GTEST_API_ bool ShouldShard(const char* total_shards_str,
+                            const char* shard_index_str,
+                            bool in_subprocess_for_death_test);
+
+// Parses the environment variable var as a 32-bit integer. If it is unset,
+// returns default_val. If it is not a 32-bit integer, prints an error and
+// and aborts.
+GTEST_API_ int32_t Int32FromEnvOrDie(const char* env_var, int32_t default_val);
+
+// Given the total number of shards, the shard index, and the test id,
+// returns true if and only if the test should be run on this shard. The test id
+// is some arbitrary but unique non-negative integer assigned to each test
+// method. Assumes that 0 <= shard_index < total_shards.
+GTEST_API_ bool ShouldRunTestOnShard(
+    int total_shards, int shard_index, int test_id);
+
+// STL container utilities.
+
+// Returns the number of elements in the given container that satisfy
+// the given predicate.
+template <class Container, typename Predicate>
+inline int CountIf(const Container& c, Predicate predicate) {
+  // Implemented as an explicit loop since std::count_if() in libCstd on
+  // Solaris has a non-standard signature.
+  int count = 0;
+  for (typename Container::const_iterator it = c.begin(); it != c.end(); ++it) {
+    if (predicate(*it))
+      ++count;
+  }
+  return count;
+}
+
+// Applies a function/functor to each element in the container.
+template <class Container, typename Functor>
+void ForEach(const Container& c, Functor functor) {
+  std::for_each(c.begin(), c.end(), functor);
+}
+
+// Returns the i-th element of the vector, or default_value if i is not
+// in range [0, v.size()).
+template <typename E>
+inline E GetElementOr(const std::vector<E>& v, int i, E default_value) {
+  return (i < 0 || i >= static_cast<int>(v.size())) ? default_value
+                                                    : v[static_cast<size_t>(i)];
+}
+
+// Performs an in-place shuffle of a range of the vector's elements.
+// 'begin' and 'end' are element indices as an STL-style range;
+// i.e. [begin, end) are shuffled, where 'end' == size() means to
+// shuffle to the end of the vector.
+template <typename E>
+void ShuffleRange(internal::Random* random, int begin, int end,
+                  std::vector<E>* v) {
+  const int size = static_cast<int>(v->size());
+  GTEST_CHECK_(0 <= begin && begin <= size)
+      << "Invalid shuffle range start " << begin << ": must be in range [0, "
+      << size << "].";
+  GTEST_CHECK_(begin <= end && end <= size)
+      << "Invalid shuffle range finish " << end << ": must be in range ["
+      << begin << ", " << size << "].";
+
+  // Fisher-Yates shuffle, from
+  // http://en.wikipedia.org/wiki/Fisher-Yates_shuffle
+  for (int range_width = end - begin; range_width >= 2; range_width--) {
+    const int last_in_range = begin + range_width - 1;
+    const int selected =
+        begin +
+        static_cast<int>(random->Generate(static_cast<uint32_t>(range_width)));
+    std::swap((*v)[static_cast<size_t>(selected)],
+              (*v)[static_cast<size_t>(last_in_range)]);
+  }
+}
+
+// Performs an in-place shuffle of the vector's elements.
+template <typename E>
+inline void Shuffle(internal::Random* random, std::vector<E>* v) {
+  ShuffleRange(random, 0, static_cast<int>(v->size()), v);
+}
+
+// A function for deleting an object.  Handy for being used as a
+// functor.
+template <typename T>
+static void Delete(T* x) {
+  delete x;
+}
+
+// A predicate that checks the key of a TestProperty against a known key.
+//
+// TestPropertyKeyIs is copyable.
+class TestPropertyKeyIs {
+ public:
+  // Constructor.
+  //
+  // TestPropertyKeyIs has NO default constructor.
+  explicit TestPropertyKeyIs(const std::string& key) : key_(key) {}
+
+  // Returns true if and only if the test name of test property matches on key_.
+  bool operator()(const TestProperty& test_property) const {
+    return test_property.key() == key_;
+  }
+
+ private:
+  std::string key_;
+};
+
+// Class UnitTestOptions.
+//
+// This class contains functions for processing options the user
+// specifies when running the tests.  It has only static members.
+//
+// In most cases, the user can specify an option using either an
+// environment variable or a command line flag.  E.g. you can set the
+// test filter using either GTEST_FILTER or --gtest_filter.  If both
+// the variable and the flag are present, the latter overrides the
+// former.
+class GTEST_API_ UnitTestOptions {
+ public:
+  // Functions for processing the gtest_output flag.
+
+  // Returns the output format, or "" for normal printed output.
+  static std::string GetOutputFormat();
+
+  // Returns the absolute path of the requested output file, or the
+  // default (test_detail.xml in the original working directory) if
+  // none was explicitly specified.
+  static std::string GetAbsolutePathToOutputFile();
+
+  // Functions for processing the gtest_filter flag.
+
+  // Returns true if and only if the user-specified filter matches the test
+  // suite name and the test name.
+  static bool FilterMatchesTest(const std::string& test_suite_name,
+                                const std::string& test_name);
+
+#if GTEST_OS_WINDOWS
+  // Function for supporting the gtest_catch_exception flag.
+
+  // Returns EXCEPTION_EXECUTE_HANDLER if Google Test should handle the
+  // given SEH exception, or EXCEPTION_CONTINUE_SEARCH otherwise.
+  // This function is useful as an __except condition.
+  static int GTestShouldProcessSEH(DWORD exception_code);
+#endif  // GTEST_OS_WINDOWS
+
+  // Returns true if "name" matches the ':' separated list of glob-style
+  // filters in "filter".
+  static bool MatchesFilter(const std::string& name, const char* filter);
+};
+
+// Returns the current application's name, removing directory path if that
+// is present.  Used by UnitTestOptions::GetOutputFile.
+GTEST_API_ FilePath GetCurrentExecutableName();
+
+// The role interface for getting the OS stack trace as a string.
+class OsStackTraceGetterInterface {
+ public:
+  OsStackTraceGetterInterface() {}
+  virtual ~OsStackTraceGetterInterface() {}
+
+  // Returns the current OS stack trace as an std::string.  Parameters:
+  //
+  //   max_depth  - the maximum number of stack frames to be included
+  //                in the trace.
+  //   skip_count - the number of top frames to be skipped; doesn't count
+  //                against max_depth.
+  virtual std::string CurrentStackTrace(int max_depth, int skip_count) = 0;
+
+  // UponLeavingGTest() should be called immediately before Google Test calls
+  // user code. It saves some information about the current stack that
+  // CurrentStackTrace() will use to find and hide Google Test stack frames.
+  virtual void UponLeavingGTest() = 0;
+
+  // This string is inserted in place of stack frames that are part of
+  // Google Test's implementation.
+  static const char* const kElidedFramesMarker;
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(OsStackTraceGetterInterface);
+};
+
+// A working implementation of the OsStackTraceGetterInterface interface.
+class OsStackTraceGetter : public OsStackTraceGetterInterface {
+ public:
+  OsStackTraceGetter() {}
+
+  std::string CurrentStackTrace(int max_depth, int skip_count) override;
+  void UponLeavingGTest() override;
+
+ private:
+#if GTEST_HAS_ABSL
+  Mutex mutex_;  // Protects all internal state.
+
+  // We save the stack frame below the frame that calls user code.
+  // We do this because the address of the frame immediately below
+  // the user code changes between the call to UponLeavingGTest()
+  // and any calls to the stack trace code from within the user code.
+  void* caller_frame_ = nullptr;
+#endif  // GTEST_HAS_ABSL
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(OsStackTraceGetter);
+};
+
+// Information about a Google Test trace point.
+struct TraceInfo {
+  const char* file;
+  int line;
+  std::string message;
+};
+
+// This is the default global test part result reporter used in UnitTestImpl.
+// This class should only be used by UnitTestImpl.
+class DefaultGlobalTestPartResultReporter
+  : public TestPartResultReporterInterface {
+ public:
+  explicit DefaultGlobalTestPartResultReporter(UnitTestImpl* unit_test);
+  // Implements the TestPartResultReporterInterface. Reports the test part
+  // result in the current test.
+  void ReportTestPartResult(const TestPartResult& result) override;
+
+ private:
+  UnitTestImpl* const unit_test_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(DefaultGlobalTestPartResultReporter);
+};
+
+// This is the default per thread test part result reporter used in
+// UnitTestImpl. This class should only be used by UnitTestImpl.
+class DefaultPerThreadTestPartResultReporter
+    : public TestPartResultReporterInterface {
+ public:
+  explicit DefaultPerThreadTestPartResultReporter(UnitTestImpl* unit_test);
+  // Implements the TestPartResultReporterInterface. The implementation just
+  // delegates to the current global test part result reporter of *unit_test_.
+  void ReportTestPartResult(const TestPartResult& result) override;
+
+ private:
+  UnitTestImpl* const unit_test_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(DefaultPerThreadTestPartResultReporter);
+};
+
+// The private implementation of the UnitTest class.  We don't protect
+// the methods under a mutex, as this class is not accessible by a
+// user and the UnitTest class that delegates work to this class does
+// proper locking.
+class GTEST_API_ UnitTestImpl {
+ public:
+  explicit UnitTestImpl(UnitTest* parent);
+  virtual ~UnitTestImpl();
+
+  // There are two different ways to register your own TestPartResultReporter.
+  // You can register your own repoter to listen either only for test results
+  // from the current thread or for results from all threads.
+  // By default, each per-thread test result repoter just passes a new
+  // TestPartResult to the global test result reporter, which registers the
+  // test part result for the currently running test.
+
+  // Returns the global test part result reporter.
+  TestPartResultReporterInterface* GetGlobalTestPartResultReporter();
+
+  // Sets the global test part result reporter.
+  void SetGlobalTestPartResultReporter(
+      TestPartResultReporterInterface* reporter);
+
+  // Returns the test part result reporter for the current thread.
+  TestPartResultReporterInterface* GetTestPartResultReporterForCurrentThread();
+
+  // Sets the test part result reporter for the current thread.
+  void SetTestPartResultReporterForCurrentThread(
+      TestPartResultReporterInterface* reporter);
+
+  // Gets the number of successful test suites.
+  int successful_test_suite_count() const;
+
+  // Gets the number of failed test suites.
+  int failed_test_suite_count() const;
+
+  // Gets the number of all test suites.
+  int total_test_suite_count() const;
+
+  // Gets the number of all test suites that contain at least one test
+  // that should run.
+  int test_suite_to_run_count() const;
+
+  // Gets the number of successful tests.
+  int successful_test_count() const;
+
+  // Gets the number of skipped tests.
+  int skipped_test_count() const;
+
+  // Gets the number of failed tests.
+  int failed_test_count() const;
+
+  // Gets the number of disabled tests that will be reported in the XML report.
+  int reportable_disabled_test_count() const;
+
+  // Gets the number of disabled tests.
+  int disabled_test_count() const;
+
+  // Gets the number of tests to be printed in the XML report.
+  int reportable_test_count() const;
+
+  // Gets the number of all tests.
+  int total_test_count() const;
+
+  // Gets the number of tests that should run.
+  int test_to_run_count() const;
+
+  // Gets the time of the test program start, in ms from the start of the
+  // UNIX epoch.
+  TimeInMillis start_timestamp() const { return start_timestamp_; }
+
+  // Gets the elapsed time, in milliseconds.
+  TimeInMillis elapsed_time() const { return elapsed_time_; }
+
+  // Returns true if and only if the unit test passed (i.e. all test suites
+  // passed).
+  bool Passed() const { return !Failed(); }
+
+  // Returns true if and only if the unit test failed (i.e. some test suite
+  // failed or something outside of all tests failed).
+  bool Failed() const {
+    return failed_test_suite_count() > 0 || ad_hoc_test_result()->Failed();
+  }
+
+  // Gets the i-th test suite among all the test suites. i can range from 0 to
+  // total_test_suite_count() - 1. If i is not in that range, returns NULL.
+  const TestSuite* GetTestSuite(int i) const {
+    const int index = GetElementOr(test_suite_indices_, i, -1);
+    return index < 0 ? nullptr : test_suites_[static_cast<size_t>(i)];
+  }
+
+  //  Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  const TestCase* GetTestCase(int i) const { return GetTestSuite(i); }
+#endif  //  GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+  // Gets the i-th test suite among all the test suites. i can range from 0 to
+  // total_test_suite_count() - 1. If i is not in that range, returns NULL.
+  TestSuite* GetMutableSuiteCase(int i) {
+    const int index = GetElementOr(test_suite_indices_, i, -1);
+    return index < 0 ? nullptr : test_suites_[static_cast<size_t>(index)];
+  }
+
+  // Provides access to the event listener list.
+  TestEventListeners* listeners() { return &listeners_; }
+
+  // Returns the TestResult for the test that's currently running, or
+  // the TestResult for the ad hoc test if no test is running.
+  TestResult* current_test_result();
+
+  // Returns the TestResult for the ad hoc test.
+  const TestResult* ad_hoc_test_result() const { return &ad_hoc_test_result_; }
+
+  // Sets the OS stack trace getter.
+  //
+  // Does nothing if the input and the current OS stack trace getter
+  // are the same; otherwise, deletes the old getter and makes the
+  // input the current getter.
+  void set_os_stack_trace_getter(OsStackTraceGetterInterface* getter);
+
+  // Returns the current OS stack trace getter if it is not NULL;
+  // otherwise, creates an OsStackTraceGetter, makes it the current
+  // getter, and returns it.
+  OsStackTraceGetterInterface* os_stack_trace_getter();
+
+  // Returns the current OS stack trace as an std::string.
+  //
+  // The maximum number of stack frames to be included is specified by
+  // the gtest_stack_trace_depth flag.  The skip_count parameter
+  // specifies the number of top frames to be skipped, which doesn't
+  // count against the number of frames to be included.
+  //
+  // For example, if Foo() calls Bar(), which in turn calls
+  // CurrentOsStackTraceExceptTop(1), Foo() will be included in the
+  // trace but Bar() and CurrentOsStackTraceExceptTop() won't.
+  std::string CurrentOsStackTraceExceptTop(int skip_count) GTEST_NO_INLINE_;
+
+  // Finds and returns a TestSuite with the given name.  If one doesn't
+  // exist, creates one and returns it.
+  //
+  // Arguments:
+  //
+  //   test_suite_name: name of the test suite
+  //   type_param:      the name of the test's type parameter, or NULL if
+  //                    this is not a typed or a type-parameterized test.
+  //   set_up_tc:       pointer to the function that sets up the test suite
+  //   tear_down_tc:    pointer to the function that tears down the test suite
+  TestSuite* GetTestSuite(const char* test_suite_name, const char* type_param,
+                          internal::SetUpTestSuiteFunc set_up_tc,
+                          internal::TearDownTestSuiteFunc tear_down_tc);
+
+//  Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  TestCase* GetTestCase(const char* test_case_name, const char* type_param,
+                        internal::SetUpTestSuiteFunc set_up_tc,
+                        internal::TearDownTestSuiteFunc tear_down_tc) {
+    return GetTestSuite(test_case_name, type_param, set_up_tc, tear_down_tc);
+  }
+#endif  //  GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+  // Adds a TestInfo to the unit test.
+  //
+  // Arguments:
+  //
+  //   set_up_tc:    pointer to the function that sets up the test suite
+  //   tear_down_tc: pointer to the function that tears down the test suite
+  //   test_info:    the TestInfo object
+  void AddTestInfo(internal::SetUpTestSuiteFunc set_up_tc,
+                   internal::TearDownTestSuiteFunc tear_down_tc,
+                   TestInfo* test_info) {
+#if GTEST_HAS_DEATH_TEST
+    // In order to support thread-safe death tests, we need to
+    // remember the original working directory when the test program
+    // was first invoked.  We cannot do this in RUN_ALL_TESTS(), as
+    // the user may have changed the current directory before calling
+    // RUN_ALL_TESTS().  Therefore we capture the current directory in
+    // AddTestInfo(), which is called to register a TEST or TEST_F
+    // before main() is reached.
+    if (original_working_dir_.IsEmpty()) {
+      original_working_dir_.Set(FilePath::GetCurrentDir());
+      GTEST_CHECK_(!original_working_dir_.IsEmpty())
+          << "Failed to get the current working directory.";
+    }
+#endif  // GTEST_HAS_DEATH_TEST
+
+    GetTestSuite(test_info->test_suite_name(), test_info->type_param(),
+                 set_up_tc, tear_down_tc)
+        ->AddTestInfo(test_info);
+  }
+
+  // Returns ParameterizedTestSuiteRegistry object used to keep track of
+  // value-parameterized tests and instantiate and register them.
+  internal::ParameterizedTestSuiteRegistry& parameterized_test_registry() {
+    return parameterized_test_registry_;
+  }
+
+  std::set<std::string>* ignored_parameterized_test_suites() {
+    return &ignored_parameterized_test_suites_;
+  }
+
+  // Returns TypeParameterizedTestSuiteRegistry object used to keep track of
+  // type-parameterized tests and instantiations of them.
+  internal::TypeParameterizedTestSuiteRegistry&
+  type_parameterized_test_registry() {
+    return type_parameterized_test_registry_;
+  }
+
+  // Sets the TestSuite object for the test that's currently running.
+  void set_current_test_suite(TestSuite* a_current_test_suite) {
+    current_test_suite_ = a_current_test_suite;
+  }
+
+  // Sets the TestInfo object for the test that's currently running.  If
+  // current_test_info is NULL, the assertion results will be stored in
+  // ad_hoc_test_result_.
+  void set_current_test_info(TestInfo* a_current_test_info) {
+    current_test_info_ = a_current_test_info;
+  }
+
+  // Registers all parameterized tests defined using TEST_P and
+  // INSTANTIATE_TEST_SUITE_P, creating regular tests for each test/parameter
+  // combination. This method can be called more then once; it has guards
+  // protecting from registering the tests more then once.  If
+  // value-parameterized tests are disabled, RegisterParameterizedTests is
+  // present but does nothing.
+  void RegisterParameterizedTests();
+
+  // Runs all tests in this UnitTest object, prints the result, and
+  // returns true if all tests are successful.  If any exception is
+  // thrown during a test, this test is considered to be failed, but
+  // the rest of the tests will still be run.
+  bool RunAllTests();
+
+  // Clears the results of all tests, except the ad hoc tests.
+  void ClearNonAdHocTestResult() {
+    ForEach(test_suites_, TestSuite::ClearTestSuiteResult);
+  }
+
+  // Clears the results of ad-hoc test assertions.
+  void ClearAdHocTestResult() {
+    ad_hoc_test_result_.Clear();
+  }
+
+  // Adds a TestProperty to the current TestResult object when invoked in a
+  // context of a test or a test suite, or to the global property set. If the
+  // result already contains a property with the same key, the value will be
+  // updated.
+  void RecordProperty(const TestProperty& test_property);
+
+  enum ReactionToSharding {
+    HONOR_SHARDING_PROTOCOL,
+    IGNORE_SHARDING_PROTOCOL
+  };
+
+  // Matches the full name of each test against the user-specified
+  // filter to decide whether the test should run, then records the
+  // result in each TestSuite and TestInfo object.
+  // If shard_tests == HONOR_SHARDING_PROTOCOL, further filters tests
+  // based on sharding variables in the environment.
+  // Returns the number of tests that should run.
+  int FilterTests(ReactionToSharding shard_tests);
+
+  // Prints the names of the tests matching the user-specified filter flag.
+  void ListTestsMatchingFilter();
+
+  const TestSuite* current_test_suite() const { return current_test_suite_; }
+  TestInfo* current_test_info() { return current_test_info_; }
+  const TestInfo* current_test_info() const { return current_test_info_; }
+
+  // Returns the vector of environments that need to be set-up/torn-down
+  // before/after the tests are run.
+  std::vector<Environment*>& environments() { return environments_; }
+
+  // Getters for the per-thread Google Test trace stack.
+  std::vector<TraceInfo>& gtest_trace_stack() {
+    return *(gtest_trace_stack_.pointer());
+  }
+  const std::vector<TraceInfo>& gtest_trace_stack() const {
+    return gtest_trace_stack_.get();
+  }
+
+#if GTEST_HAS_DEATH_TEST
+  void InitDeathTestSubprocessControlInfo() {
+    internal_run_death_test_flag_.reset(ParseInternalRunDeathTestFlag());
+  }
+  // Returns a pointer to the parsed --gtest_internal_run_death_test
+  // flag, or NULL if that flag was not specified.
+  // This information is useful only in a death test child process.
+  // Must not be called before a call to InitGoogleTest.
+  const InternalRunDeathTestFlag* internal_run_death_test_flag() const {
+    return internal_run_death_test_flag_.get();
+  }
+
+  // Returns a pointer to the current death test factory.
+  internal::DeathTestFactory* death_test_factory() {
+    return death_test_factory_.get();
+  }
+
+  void SuppressTestEventsIfInSubprocess();
+
+  friend class ReplaceDeathTestFactory;
+#endif  // GTEST_HAS_DEATH_TEST
+
+  // Initializes the event listener performing XML output as specified by
+  // UnitTestOptions. Must not be called before InitGoogleTest.
+  void ConfigureXmlOutput();
+
+#if GTEST_CAN_STREAM_RESULTS_
+  // Initializes the event listener for streaming test results to a socket.
+  // Must not be called before InitGoogleTest.
+  void ConfigureStreamingOutput();
+#endif
+
+  // Performs initialization dependent upon flag values obtained in
+  // ParseGoogleTestFlagsOnly.  Is called from InitGoogleTest after the call to
+  // ParseGoogleTestFlagsOnly.  In case a user neglects to call InitGoogleTest
+  // this function is also called from RunAllTests.  Since this function can be
+  // called more than once, it has to be idempotent.
+  void PostFlagParsingInit();
+
+  // Gets the random seed used at the start of the current test iteration.
+  int random_seed() const { return random_seed_; }
+
+  // Gets the random number generator.
+  internal::Random* random() { return &random_; }
+
+  // Shuffles all test suites, and the tests within each test suite,
+  // making sure that death tests are still run first.
+  void ShuffleTests();
+
+  // Restores the test suites and tests to their order before the first shuffle.
+  void UnshuffleTests();
+
+  // Returns the value of GTEST_FLAG(catch_exceptions) at the moment
+  // UnitTest::Run() starts.
+  bool catch_exceptions() const { return catch_exceptions_; }
+
+ private:
+  friend class ::testing::UnitTest;
+
+  // Used by UnitTest::Run() to capture the state of
+  // GTEST_FLAG(catch_exceptions) at the moment it starts.
+  void set_catch_exceptions(bool value) { catch_exceptions_ = value; }
+
+  // The UnitTest object that owns this implementation object.
+  UnitTest* const parent_;
+
+  // The working directory when the first TEST() or TEST_F() was
+  // executed.
+  internal::FilePath original_working_dir_;
+
+  // The default test part result reporters.
+  DefaultGlobalTestPartResultReporter default_global_test_part_result_reporter_;
+  DefaultPerThreadTestPartResultReporter
+      default_per_thread_test_part_result_reporter_;
+
+  // Points to (but doesn't own) the global test part result reporter.
+  TestPartResultReporterInterface* global_test_part_result_repoter_;
+
+  // Protects read and write access to global_test_part_result_reporter_.
+  internal::Mutex global_test_part_result_reporter_mutex_;
+
+  // Points to (but doesn't own) the per-thread test part result reporter.
+  internal::ThreadLocal<TestPartResultReporterInterface*>
+      per_thread_test_part_result_reporter_;
+
+  // The vector of environments that need to be set-up/torn-down
+  // before/after the tests are run.
+  std::vector<Environment*> environments_;
+
+  // The vector of TestSuites in their original order.  It owns the
+  // elements in the vector.
+  std::vector<TestSuite*> test_suites_;
+
+  // Provides a level of indirection for the test suite list to allow
+  // easy shuffling and restoring the test suite order.  The i-th
+  // element of this vector is the index of the i-th test suite in the
+  // shuffled order.
+  std::vector<int> test_suite_indices_;
+
+  // ParameterizedTestRegistry object used to register value-parameterized
+  // tests.
+  internal::ParameterizedTestSuiteRegistry parameterized_test_registry_;
+  internal::TypeParameterizedTestSuiteRegistry
+      type_parameterized_test_registry_;
+
+  // The set holding the name of parameterized
+  // test suites that may go uninstantiated.
+  std::set<std::string> ignored_parameterized_test_suites_;
+
+  // Indicates whether RegisterParameterizedTests() has been called already.
+  bool parameterized_tests_registered_;
+
+  // Index of the last death test suite registered.  Initially -1.
+  int last_death_test_suite_;
+
+  // This points to the TestSuite for the currently running test.  It
+  // changes as Google Test goes through one test suite after another.
+  // When no test is running, this is set to NULL and Google Test
+  // stores assertion results in ad_hoc_test_result_.  Initially NULL.
+  TestSuite* current_test_suite_;
+
+  // This points to the TestInfo for the currently running test.  It
+  // changes as Google Test goes through one test after another.  When
+  // no test is running, this is set to NULL and Google Test stores
+  // assertion results in ad_hoc_test_result_.  Initially NULL.
+  TestInfo* current_test_info_;
+
+  // Normally, a user only writes assertions inside a TEST or TEST_F,
+  // or inside a function called by a TEST or TEST_F.  Since Google
+  // Test keeps track of which test is current running, it can
+  // associate such an assertion with the test it belongs to.
+  //
+  // If an assertion is encountered when no TEST or TEST_F is running,
+  // Google Test attributes the assertion result to an imaginary "ad hoc"
+  // test, and records the result in ad_hoc_test_result_.
+  TestResult ad_hoc_test_result_;
+
+  // The list of event listeners that can be used to track events inside
+  // Google Test.
+  TestEventListeners listeners_;
+
+  // The OS stack trace getter.  Will be deleted when the UnitTest
+  // object is destructed.  By default, an OsStackTraceGetter is used,
+  // but the user can set this field to use a custom getter if that is
+  // desired.
+  OsStackTraceGetterInterface* os_stack_trace_getter_;
+
+  // True if and only if PostFlagParsingInit() has been called.
+  bool post_flag_parse_init_performed_;
+
+  // The random number seed used at the beginning of the test run.
+  int random_seed_;
+
+  // Our random number generator.
+  internal::Random random_;
+
+  // The time of the test program start, in ms from the start of the
+  // UNIX epoch.
+  TimeInMillis start_timestamp_;
+
+  // How long the test took to run, in milliseconds.
+  TimeInMillis elapsed_time_;
+
+#if GTEST_HAS_DEATH_TEST
+  // The decomposed components of the gtest_internal_run_death_test flag,
+  // parsed when RUN_ALL_TESTS is called.
+  std::unique_ptr<InternalRunDeathTestFlag> internal_run_death_test_flag_;
+  std::unique_ptr<internal::DeathTestFactory> death_test_factory_;
+#endif  // GTEST_HAS_DEATH_TEST
+
+  // A per-thread stack of traces created by the SCOPED_TRACE() macro.
+  internal::ThreadLocal<std::vector<TraceInfo> > gtest_trace_stack_;
+
+  // The value of GTEST_FLAG(catch_exceptions) at the moment RunAllTests()
+  // starts.
+  bool catch_exceptions_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(UnitTestImpl);
+};  // class UnitTestImpl
+
+// Convenience function for accessing the global UnitTest
+// implementation object.
+inline UnitTestImpl* GetUnitTestImpl() {
+  return UnitTest::GetInstance()->impl();
+}
+
+#if GTEST_USES_SIMPLE_RE
+
+// Internal helper functions for implementing the simple regular
+// expression matcher.
+GTEST_API_ bool IsInSet(char ch, const char* str);
+GTEST_API_ bool IsAsciiDigit(char ch);
+GTEST_API_ bool IsAsciiPunct(char ch);
+GTEST_API_ bool IsRepeat(char ch);
+GTEST_API_ bool IsAsciiWhiteSpace(char ch);
+GTEST_API_ bool IsAsciiWordChar(char ch);
+GTEST_API_ bool IsValidEscape(char ch);
+GTEST_API_ bool AtomMatchesChar(bool escaped, char pattern, char ch);
+GTEST_API_ bool ValidateRegex(const char* regex);
+GTEST_API_ bool MatchRegexAtHead(const char* regex, const char* str);
+GTEST_API_ bool MatchRepetitionAndRegexAtHead(
+    bool escaped, char ch, char repeat, const char* regex, const char* str);
+GTEST_API_ bool MatchRegexAnywhere(const char* regex, const char* str);
+
+#endif  // GTEST_USES_SIMPLE_RE
+
+// Parses the command line for Google Test flags, without initializing
+// other parts of Google Test.
+GTEST_API_ void ParseGoogleTestFlagsOnly(int* argc, char** argv);
+GTEST_API_ void ParseGoogleTestFlagsOnly(int* argc, wchar_t** argv);
+
+#if GTEST_HAS_DEATH_TEST
+
+// Returns the message describing the last system error, regardless of the
+// platform.
+GTEST_API_ std::string GetLastErrnoDescription();
+
+// Attempts to parse a string into a positive integer pointed to by the
+// number parameter.  Returns true if that is possible.
+// GTEST_HAS_DEATH_TEST implies that we have ::std::string, so we can use
+// it here.
+template <typename Integer>
+bool ParseNaturalNumber(const ::std::string& str, Integer* number) {
+  // Fail fast if the given string does not begin with a digit;
+  // this bypasses strtoXXX's "optional leading whitespace and plus
+  // or minus sign" semantics, which are undesirable here.
+  if (str.empty() || !IsDigit(str[0])) {
+    return false;
+  }
+  errno = 0;
+
+  char* end;
+  // BiggestConvertible is the largest integer type that system-provided
+  // string-to-number conversion routines can return.
+  using BiggestConvertible = unsigned long long;  // NOLINT
+
+  const BiggestConvertible parsed = strtoull(str.c_str(), &end, 10);  // NOLINT
+  const bool parse_success = *end == '\0' && errno == 0;
+
+  GTEST_CHECK_(sizeof(Integer) <= sizeof(parsed));
+
+  const Integer result = static_cast<Integer>(parsed);
+  if (parse_success && static_cast<BiggestConvertible>(result) == parsed) {
+    *number = result;
+    return true;
+  }
+  return false;
+}
+#endif  // GTEST_HAS_DEATH_TEST
+
+// TestResult contains some private methods that should be hidden from
+// Google Test user but are required for testing. This class allow our tests
+// to access them.
+//
+// This class is supplied only for the purpose of testing Google Test's own
+// constructs. Do not use it in user tests, either directly or indirectly.
+class TestResultAccessor {
+ public:
+  static void RecordProperty(TestResult* test_result,
+                             const std::string& xml_element,
+                             const TestProperty& property) {
+    test_result->RecordProperty(xml_element, property);
+  }
+
+  static void ClearTestPartResults(TestResult* test_result) {
+    test_result->ClearTestPartResults();
+  }
+
+  static const std::vector<testing::TestPartResult>& test_part_results(
+      const TestResult& test_result) {
+    return test_result.test_part_results();
+  }
+};
+
+#if GTEST_CAN_STREAM_RESULTS_
+
+// Streams test results to the given port on the given host machine.
+class StreamingListener : public EmptyTestEventListener {
+ public:
+  // Abstract base class for writing strings to a socket.
+  class AbstractSocketWriter {
+   public:
+    virtual ~AbstractSocketWriter() {}
+
+    // Sends a string to the socket.
+    virtual void Send(const std::string& message) = 0;
+
+    // Closes the socket.
+    virtual void CloseConnection() {}
+
+    // Sends a string and a newline to the socket.
+    void SendLn(const std::string& message) { Send(message + "\n"); }
+  };
+
+  // Concrete class for actually writing strings to a socket.
+  class SocketWriter : public AbstractSocketWriter {
+   public:
+    SocketWriter(const std::string& host, const std::string& port)
+        : sockfd_(-1), host_name_(host), port_num_(port) {
+      MakeConnection();
+    }
+
+    ~SocketWriter() override {
+      if (sockfd_ != -1)
+        CloseConnection();
+    }
+
+    // Sends a string to the socket.
+    void Send(const std::string& message) override {
+      GTEST_CHECK_(sockfd_ != -1)
+          << "Send() can be called only when there is a connection.";
+
+      const auto len = static_cast<size_t>(message.length());
+      if (write(sockfd_, message.c_str(), len) != static_cast<ssize_t>(len)) {
+        GTEST_LOG_(WARNING)
+            << "stream_result_to: failed to stream to "
+            << host_name_ << ":" << port_num_;
+      }
+    }
+
+   private:
+    // Creates a client socket and connects to the server.
+    void MakeConnection();
+
+    // Closes the socket.
+    void CloseConnection() override {
+      GTEST_CHECK_(sockfd_ != -1)
+          << "CloseConnection() can be called only when there is a connection.";
+
+      close(sockfd_);
+      sockfd_ = -1;
+    }
+
+    int sockfd_;  // socket file descriptor
+    const std::string host_name_;
+    const std::string port_num_;
+
+    GTEST_DISALLOW_COPY_AND_ASSIGN_(SocketWriter);
+  };  // class SocketWriter
+
+  // Escapes '=', '&', '%', and '\n' characters in str as "%xx".
+  static std::string UrlEncode(const char* str);
+
+  StreamingListener(const std::string& host, const std::string& port)
+      : socket_writer_(new SocketWriter(host, port)) {
+    Start();
+  }
+
+  explicit StreamingListener(AbstractSocketWriter* socket_writer)
+      : socket_writer_(socket_writer) { Start(); }
+
+  void OnTestProgramStart(const UnitTest& /* unit_test */) override {
+    SendLn("event=TestProgramStart");
+  }
+
+  void OnTestProgramEnd(const UnitTest& unit_test) override {
+    // Note that Google Test current only report elapsed time for each
+    // test iteration, not for the entire test program.
+    SendLn("event=TestProgramEnd&passed=" + FormatBool(unit_test.Passed()));
+
+    // Notify the streaming server to stop.
+    socket_writer_->CloseConnection();
+  }
+
+  void OnTestIterationStart(const UnitTest& /* unit_test */,
+                            int iteration) override {
+    SendLn("event=TestIterationStart&iteration=" +
+           StreamableToString(iteration));
+  }
+
+  void OnTestIterationEnd(const UnitTest& unit_test,
+                          int /* iteration */) override {
+    SendLn("event=TestIterationEnd&passed=" +
+           FormatBool(unit_test.Passed()) + "&elapsed_time=" +
+           StreamableToString(unit_test.elapsed_time()) + "ms");
+  }
+
+  // Note that "event=TestCaseStart" is a wire format and has to remain
+  // "case" for compatibility
+  void OnTestCaseStart(const TestCase& test_case) override {
+    SendLn(std::string("event=TestCaseStart&name=") + test_case.name());
+  }
+
+  // Note that "event=TestCaseEnd" is a wire format and has to remain
+  // "case" for compatibility
+  void OnTestCaseEnd(const TestCase& test_case) override {
+    SendLn("event=TestCaseEnd&passed=" + FormatBool(test_case.Passed()) +
+           "&elapsed_time=" + StreamableToString(test_case.elapsed_time()) +
+           "ms");
+  }
+
+  void OnTestStart(const TestInfo& test_info) override {
+    SendLn(std::string("event=TestStart&name=") + test_info.name());
+  }
+
+  void OnTestEnd(const TestInfo& test_info) override {
+    SendLn("event=TestEnd&passed=" +
+           FormatBool((test_info.result())->Passed()) +
+           "&elapsed_time=" +
+           StreamableToString((test_info.result())->elapsed_time()) + "ms");
+  }
+
+  void OnTestPartResult(const TestPartResult& test_part_result) override {
+    const char* file_name = test_part_result.file_name();
+    if (file_name == nullptr) file_name = "";
+    SendLn("event=TestPartResult&file=" + UrlEncode(file_name) +
+           "&line=" + StreamableToString(test_part_result.line_number()) +
+           "&message=" + UrlEncode(test_part_result.message()));
+  }
+
+ private:
+  // Sends the given message and a newline to the socket.
+  void SendLn(const std::string& message) { socket_writer_->SendLn(message); }
+
+  // Called at the start of streaming to notify the receiver what
+  // protocol we are using.
+  void Start() { SendLn("gtest_streaming_protocol_version=1.0"); }
+
+  std::string FormatBool(bool value) { return value ? "1" : "0"; }
+
+  const std::unique_ptr<AbstractSocketWriter> socket_writer_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(StreamingListener);
+};  // class StreamingListener
+
+#endif  // GTEST_CAN_STREAM_RESULTS_
+
+}  // namespace internal
+}  // namespace testing
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  //  4251
+
+#endif  // GOOGLETEST_SRC_GTEST_INTERNAL_INL_H_
diff --git a/leveldb_base/third_party/googletest/googletest/src/gtest-matchers.cc b/leveldb_base/third_party/googletest/googletest/src/gtest-matchers.cc
new file mode 100644
index 0000000..65104eb
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/src/gtest-matchers.cc
@@ -0,0 +1,97 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// The Google C++ Testing and Mocking Framework (Google Test)
+//
+// This file implements just enough of the matcher interface to allow
+// EXPECT_DEATH and friends to accept a matcher argument.
+
+#include "gtest/internal/gtest-internal.h"
+#include "gtest/internal/gtest-port.h"
+#include "gtest/gtest-matchers.h"
+
+#include <string>
+
+namespace testing {
+
+// Constructs a matcher that matches a const std::string& whose value is
+// equal to s.
+Matcher<const std::string&>::Matcher(const std::string& s) { *this = Eq(s); }
+
+// Constructs a matcher that matches a const std::string& whose value is
+// equal to s.
+Matcher<const std::string&>::Matcher(const char* s) {
+  *this = Eq(std::string(s));
+}
+
+// Constructs a matcher that matches a std::string whose value is equal to
+// s.
+Matcher<std::string>::Matcher(const std::string& s) { *this = Eq(s); }
+
+// Constructs a matcher that matches a std::string whose value is equal to
+// s.
+Matcher<std::string>::Matcher(const char* s) { *this = Eq(std::string(s)); }
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+// Constructs a matcher that matches a const StringView& whose value is
+// equal to s.
+Matcher<const internal::StringView&>::Matcher(const std::string& s) {
+  *this = Eq(s);
+}
+
+// Constructs a matcher that matches a const StringView& whose value is
+// equal to s.
+Matcher<const internal::StringView&>::Matcher(const char* s) {
+  *this = Eq(std::string(s));
+}
+
+// Constructs a matcher that matches a const StringView& whose value is
+// equal to s.
+Matcher<const internal::StringView&>::Matcher(internal::StringView s) {
+  *this = Eq(std::string(s));
+}
+
+// Constructs a matcher that matches a StringView whose value is equal to
+// s.
+Matcher<internal::StringView>::Matcher(const std::string& s) { *this = Eq(s); }
+
+// Constructs a matcher that matches a StringView whose value is equal to
+// s.
+Matcher<internal::StringView>::Matcher(const char* s) {
+  *this = Eq(std::string(s));
+}
+
+// Constructs a matcher that matches a StringView whose value is equal to
+// s.
+Matcher<internal::StringView>::Matcher(internal::StringView s) {
+  *this = Eq(std::string(s));
+}
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+
+}  // namespace testing
diff --git a/leveldb_base/third_party/googletest/googletest/src/gtest-port.cc b/leveldb_base/third_party/googletest/googletest/src/gtest-port.cc
new file mode 100644
index 0000000..26bc857
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/src/gtest-port.cc
@@ -0,0 +1,1414 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+#include "gtest/internal/gtest-port.h"
+
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <cstdint>
+#include <fstream>
+#include <memory>
+
+#if GTEST_OS_WINDOWS
+# include <windows.h>
+# include <io.h>
+# include <sys/stat.h>
+# include <map>  // Used in ThreadLocal.
+# ifdef _MSC_VER
+#  include <crtdbg.h>
+# endif  // _MSC_VER
+#else
+# include <unistd.h>
+#endif  // GTEST_OS_WINDOWS
+
+#if GTEST_OS_MAC
+# include <mach/mach_init.h>
+# include <mach/task.h>
+# include <mach/vm_map.h>
+#endif  // GTEST_OS_MAC
+
+#if GTEST_OS_DRAGONFLY || GTEST_OS_FREEBSD || GTEST_OS_GNU_KFREEBSD || \
+    GTEST_OS_NETBSD || GTEST_OS_OPENBSD
+# include <sys/sysctl.h>
+# if GTEST_OS_DRAGONFLY || GTEST_OS_FREEBSD || GTEST_OS_GNU_KFREEBSD
+#  include <sys/user.h>
+# endif
+#endif
+
+#if GTEST_OS_QNX
+# include <devctl.h>
+# include <fcntl.h>
+# include <sys/procfs.h>
+#endif  // GTEST_OS_QNX
+
+#if GTEST_OS_AIX
+# include <procinfo.h>
+# include <sys/types.h>
+#endif  // GTEST_OS_AIX
+
+#if GTEST_OS_FUCHSIA
+# include <zircon/process.h>
+# include <zircon/syscalls.h>
+#endif  // GTEST_OS_FUCHSIA
+
+#if GTEST_OS_IOS
+#import <Foundation/Foundation.h>
+#endif  // GTEST_OS_IOS
+
+#include "gtest/gtest-spi.h"
+#include "gtest/gtest-message.h"
+#include "gtest/internal/gtest-internal.h"
+#include "gtest/internal/gtest-string.h"
+#include "src/gtest-internal-inl.h"
+
+namespace testing {
+namespace internal {
+
+#if defined(_MSC_VER) || defined(__BORLANDC__)
+// MSVC and C++Builder do not provide a definition of STDERR_FILENO.
+const int kStdOutFileno = 1;
+const int kStdErrFileno = 2;
+#else
+const int kStdOutFileno = STDOUT_FILENO;
+const int kStdErrFileno = STDERR_FILENO;
+#endif  // _MSC_VER
+
+#if GTEST_OS_LINUX
+
+namespace {
+template <typename T>
+T ReadProcFileField(const std::string& filename, int field) {
+  std::string dummy;
+  std::ifstream file(filename.c_str());
+  while (field-- > 0) {
+    file >> dummy;
+  }
+  T output = 0;
+  file >> output;
+  return output;
+}
+}  // namespace
+
+// Returns the number of active threads, or 0 when there is an error.
+size_t GetThreadCount() {
+  const std::string filename =
+      (Message() << "/proc/" << getpid() << "/stat").GetString();
+  return ReadProcFileField<size_t>(filename, 19);
+}
+
+#elif GTEST_OS_MAC
+
+size_t GetThreadCount() {
+  const task_t task = mach_task_self();
+  mach_msg_type_number_t thread_count;
+  thread_act_array_t thread_list;
+  const kern_return_t status = task_threads(task, &thread_list, &thread_count);
+  if (status == KERN_SUCCESS) {
+    // task_threads allocates resources in thread_list and we need to free them
+    // to avoid leaks.
+    vm_deallocate(task,
+                  reinterpret_cast<vm_address_t>(thread_list),
+                  sizeof(thread_t) * thread_count);
+    return static_cast<size_t>(thread_count);
+  } else {
+    return 0;
+  }
+}
+
+#elif GTEST_OS_DRAGONFLY || GTEST_OS_FREEBSD || GTEST_OS_GNU_KFREEBSD || \
+      GTEST_OS_NETBSD
+
+#if GTEST_OS_NETBSD
+#undef KERN_PROC
+#define KERN_PROC KERN_PROC2
+#define kinfo_proc kinfo_proc2
+#endif
+
+#if GTEST_OS_DRAGONFLY
+#define KP_NLWP(kp) (kp.kp_nthreads)
+#elif GTEST_OS_FREEBSD || GTEST_OS_GNU_KFREEBSD
+#define KP_NLWP(kp) (kp.ki_numthreads)
+#elif GTEST_OS_NETBSD
+#define KP_NLWP(kp) (kp.p_nlwps)
+#endif
+
+// Returns the number of threads running in the process, or 0 to indicate that
+// we cannot detect it.
+size_t GetThreadCount() {
+  int mib[] = {
+    CTL_KERN,
+    KERN_PROC,
+    KERN_PROC_PID,
+    getpid(),
+#if GTEST_OS_NETBSD
+    sizeof(struct kinfo_proc),
+    1,
+#endif
+  };
+  u_int miblen = sizeof(mib) / sizeof(mib[0]);
+  struct kinfo_proc info;
+  size_t size = sizeof(info);
+  if (sysctl(mib, miblen, &info, &size, NULL, 0)) {
+    return 0;
+  }
+  return static_cast<size_t>(KP_NLWP(info));
+}
+#elif GTEST_OS_OPENBSD
+
+// Returns the number of threads running in the process, or 0 to indicate that
+// we cannot detect it.
+size_t GetThreadCount() {
+  int mib[] = {
+    CTL_KERN,
+    KERN_PROC,
+    KERN_PROC_PID | KERN_PROC_SHOW_THREADS,
+    getpid(),
+    sizeof(struct kinfo_proc),
+    0,
+  };
+  u_int miblen = sizeof(mib) / sizeof(mib[0]);
+
+  // get number of structs
+  size_t size;
+  if (sysctl(mib, miblen, NULL, &size, NULL, 0)) {
+    return 0;
+  }
+
+  mib[5] = static_cast<int>(size / static_cast<size_t>(mib[4]));
+
+  // populate array of structs
+  struct kinfo_proc info[mib[5]];
+  if (sysctl(mib, miblen, &info, &size, NULL, 0)) {
+    return 0;
+  }
+
+  // exclude empty members
+  size_t nthreads = 0;
+  for (size_t i = 0; i < size / static_cast<size_t>(mib[4]); i++) {
+    if (info[i].p_tid != -1)
+      nthreads++;
+  }
+  return nthreads;
+}
+
+#elif GTEST_OS_QNX
+
+// Returns the number of threads running in the process, or 0 to indicate that
+// we cannot detect it.
+size_t GetThreadCount() {
+  const int fd = open("/proc/self/as", O_RDONLY);
+  if (fd < 0) {
+    return 0;
+  }
+  procfs_info process_info;
+  const int status =
+      devctl(fd, DCMD_PROC_INFO, &process_info, sizeof(process_info), nullptr);
+  close(fd);
+  if (status == EOK) {
+    return static_cast<size_t>(process_info.num_threads);
+  } else {
+    return 0;
+  }
+}
+
+#elif GTEST_OS_AIX
+
+size_t GetThreadCount() {
+  struct procentry64 entry;
+  pid_t pid = getpid();
+  int status = getprocs64(&entry, sizeof(entry), nullptr, 0, &pid, 1);
+  if (status == 1) {
+    return entry.pi_thcount;
+  } else {
+    return 0;
+  }
+}
+
+#elif GTEST_OS_FUCHSIA
+
+size_t GetThreadCount() {
+  int dummy_buffer;
+  size_t avail;
+  zx_status_t status = zx_object_get_info(
+      zx_process_self(),
+      ZX_INFO_PROCESS_THREADS,
+      &dummy_buffer,
+      0,
+      nullptr,
+      &avail);
+  if (status == ZX_OK) {
+    return avail;
+  } else {
+    return 0;
+  }
+}
+
+#else
+
+size_t GetThreadCount() {
+  // There's no portable way to detect the number of threads, so we just
+  // return 0 to indicate that we cannot detect it.
+  return 0;
+}
+
+#endif  // GTEST_OS_LINUX
+
+#if GTEST_IS_THREADSAFE && GTEST_OS_WINDOWS
+
+void SleepMilliseconds(int n) {
+  ::Sleep(static_cast<DWORD>(n));
+}
+
+AutoHandle::AutoHandle()
+    : handle_(INVALID_HANDLE_VALUE) {}
+
+AutoHandle::AutoHandle(Handle handle)
+    : handle_(handle) {}
+
+AutoHandle::~AutoHandle() {
+  Reset();
+}
+
+AutoHandle::Handle AutoHandle::Get() const {
+  return handle_;
+}
+
+void AutoHandle::Reset() {
+  Reset(INVALID_HANDLE_VALUE);
+}
+
+void AutoHandle::Reset(HANDLE handle) {
+  // Resetting with the same handle we already own is invalid.
+  if (handle_ != handle) {
+    if (IsCloseable()) {
+      ::CloseHandle(handle_);
+    }
+    handle_ = handle;
+  } else {
+    GTEST_CHECK_(!IsCloseable())
+        << "Resetting a valid handle to itself is likely a programmer error "
+            "and thus not allowed.";
+  }
+}
+
+bool AutoHandle::IsCloseable() const {
+  // Different Windows APIs may use either of these values to represent an
+  // invalid handle.
+  return handle_ != nullptr && handle_ != INVALID_HANDLE_VALUE;
+}
+
+Notification::Notification()
+    : event_(::CreateEvent(nullptr,     // Default security attributes.
+                           TRUE,        // Do not reset automatically.
+                           FALSE,       // Initially unset.
+                           nullptr)) {  // Anonymous event.
+  GTEST_CHECK_(event_.Get() != nullptr);
+}
+
+void Notification::Notify() {
+  GTEST_CHECK_(::SetEvent(event_.Get()) != FALSE);
+}
+
+void Notification::WaitForNotification() {
+  GTEST_CHECK_(
+      ::WaitForSingleObject(event_.Get(), INFINITE) == WAIT_OBJECT_0);
+}
+
+Mutex::Mutex()
+    : owner_thread_id_(0),
+      type_(kDynamic),
+      critical_section_init_phase_(0),
+      critical_section_(new CRITICAL_SECTION) {
+  ::InitializeCriticalSection(critical_section_);
+}
+
+Mutex::~Mutex() {
+  // Static mutexes are leaked intentionally. It is not thread-safe to try
+  // to clean them up.
+  if (type_ == kDynamic) {
+    ::DeleteCriticalSection(critical_section_);
+    delete critical_section_;
+    critical_section_ = nullptr;
+  }
+}
+
+void Mutex::Lock() {
+  ThreadSafeLazyInit();
+  ::EnterCriticalSection(critical_section_);
+  owner_thread_id_ = ::GetCurrentThreadId();
+}
+
+void Mutex::Unlock() {
+  ThreadSafeLazyInit();
+  // We don't protect writing to owner_thread_id_ here, as it's the
+  // caller's responsibility to ensure that the current thread holds the
+  // mutex when this is called.
+  owner_thread_id_ = 0;
+  ::LeaveCriticalSection(critical_section_);
+}
+
+// Does nothing if the current thread holds the mutex. Otherwise, crashes
+// with high probability.
+void Mutex::AssertHeld() {
+  ThreadSafeLazyInit();
+  GTEST_CHECK_(owner_thread_id_ == ::GetCurrentThreadId())
+      << "The current thread is not holding the mutex @" << this;
+}
+
+namespace {
+
+#ifdef _MSC_VER
+// Use the RAII idiom to flag mem allocs that are intentionally never
+// deallocated. The motivation is to silence the false positive mem leaks
+// that are reported by the debug version of MS's CRT which can only detect
+// if an alloc is missing a matching deallocation.
+// Example:
+//    MemoryIsNotDeallocated memory_is_not_deallocated;
+//    critical_section_ = new CRITICAL_SECTION;
+//
+class MemoryIsNotDeallocated
+{
+ public:
+  MemoryIsNotDeallocated() : old_crtdbg_flag_(0) {
+    old_crtdbg_flag_ = _CrtSetDbgFlag(_CRTDBG_REPORT_FLAG);
+    // Set heap allocation block type to _IGNORE_BLOCK so that MS debug CRT
+    // doesn't report mem leak if there's no matching deallocation.
+    _CrtSetDbgFlag(old_crtdbg_flag_ & ~_CRTDBG_ALLOC_MEM_DF);
+  }
+
+  ~MemoryIsNotDeallocated() {
+    // Restore the original _CRTDBG_ALLOC_MEM_DF flag
+    _CrtSetDbgFlag(old_crtdbg_flag_);
+  }
+
+ private:
+  int old_crtdbg_flag_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(MemoryIsNotDeallocated);
+};
+#endif  // _MSC_VER
+
+}  // namespace
+
+// Initializes owner_thread_id_ and critical_section_ in static mutexes.
+void Mutex::ThreadSafeLazyInit() {
+  // Dynamic mutexes are initialized in the constructor.
+  if (type_ == kStatic) {
+    switch (
+        ::InterlockedCompareExchange(&critical_section_init_phase_, 1L, 0L)) {
+      case 0:
+        // If critical_section_init_phase_ was 0 before the exchange, we
+        // are the first to test it and need to perform the initialization.
+        owner_thread_id_ = 0;
+        {
+          // Use RAII to flag that following mem alloc is never deallocated.
+#ifdef _MSC_VER
+          MemoryIsNotDeallocated memory_is_not_deallocated;
+#endif  // _MSC_VER
+          critical_section_ = new CRITICAL_SECTION;
+        }
+        ::InitializeCriticalSection(critical_section_);
+        // Updates the critical_section_init_phase_ to 2 to signal
+        // initialization complete.
+        GTEST_CHECK_(::InterlockedCompareExchange(
+                          &critical_section_init_phase_, 2L, 1L) ==
+                      1L);
+        break;
+      case 1:
+        // Somebody else is already initializing the mutex; spin until they
+        // are done.
+        while (::InterlockedCompareExchange(&critical_section_init_phase_,
+                                            2L,
+                                            2L) != 2L) {
+          // Possibly yields the rest of the thread's time slice to other
+          // threads.
+          ::Sleep(0);
+        }
+        break;
+
+      case 2:
+        break;  // The mutex is already initialized and ready for use.
+
+      default:
+        GTEST_CHECK_(false)
+            << "Unexpected value of critical_section_init_phase_ "
+            << "while initializing a static mutex.";
+    }
+  }
+}
+
+namespace {
+
+class ThreadWithParamSupport : public ThreadWithParamBase {
+ public:
+  static HANDLE CreateThread(Runnable* runnable,
+                             Notification* thread_can_start) {
+    ThreadMainParam* param = new ThreadMainParam(runnable, thread_can_start);
+    DWORD thread_id;
+    HANDLE thread_handle = ::CreateThread(
+        nullptr,  // Default security.
+        0,        // Default stack size.
+        &ThreadWithParamSupport::ThreadMain,
+        param,        // Parameter to ThreadMainStatic
+        0x0,          // Default creation flags.
+        &thread_id);  // Need a valid pointer for the call to work under Win98.
+    GTEST_CHECK_(thread_handle != nullptr)
+        << "CreateThread failed with error " << ::GetLastError() << ".";
+    if (thread_handle == nullptr) {
+      delete param;
+    }
+    return thread_handle;
+  }
+
+ private:
+  struct ThreadMainParam {
+    ThreadMainParam(Runnable* runnable, Notification* thread_can_start)
+        : runnable_(runnable),
+          thread_can_start_(thread_can_start) {
+    }
+    std::unique_ptr<Runnable> runnable_;
+    // Does not own.
+    Notification* thread_can_start_;
+  };
+
+  static DWORD WINAPI ThreadMain(void* ptr) {
+    // Transfers ownership.
+    std::unique_ptr<ThreadMainParam> param(static_cast<ThreadMainParam*>(ptr));
+    if (param->thread_can_start_ != nullptr)
+      param->thread_can_start_->WaitForNotification();
+    param->runnable_->Run();
+    return 0;
+  }
+
+  // Prohibit instantiation.
+  ThreadWithParamSupport();
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(ThreadWithParamSupport);
+};
+
+}  // namespace
+
+ThreadWithParamBase::ThreadWithParamBase(Runnable *runnable,
+                                         Notification* thread_can_start)
+      : thread_(ThreadWithParamSupport::CreateThread(runnable,
+                                                     thread_can_start)) {
+}
+
+ThreadWithParamBase::~ThreadWithParamBase() {
+  Join();
+}
+
+void ThreadWithParamBase::Join() {
+  GTEST_CHECK_(::WaitForSingleObject(thread_.Get(), INFINITE) == WAIT_OBJECT_0)
+      << "Failed to join the thread with error " << ::GetLastError() << ".";
+}
+
+// Maps a thread to a set of ThreadIdToThreadLocals that have values
+// instantiated on that thread and notifies them when the thread exits.  A
+// ThreadLocal instance is expected to persist until all threads it has
+// values on have terminated.
+class ThreadLocalRegistryImpl {
+ public:
+  // Registers thread_local_instance as having value on the current thread.
+  // Returns a value that can be used to identify the thread from other threads.
+  static ThreadLocalValueHolderBase* GetValueOnCurrentThread(
+      const ThreadLocalBase* thread_local_instance) {
+#ifdef _MSC_VER
+    MemoryIsNotDeallocated memory_is_not_deallocated;
+#endif  // _MSC_VER
+    DWORD current_thread = ::GetCurrentThreadId();
+    MutexLock lock(&mutex_);
+    ThreadIdToThreadLocals* const thread_to_thread_locals =
+        GetThreadLocalsMapLocked();
+    ThreadIdToThreadLocals::iterator thread_local_pos =
+        thread_to_thread_locals->find(current_thread);
+    if (thread_local_pos == thread_to_thread_locals->end()) {
+      thread_local_pos = thread_to_thread_locals->insert(
+          std::make_pair(current_thread, ThreadLocalValues())).first;
+      StartWatcherThreadFor(current_thread);
+    }
+    ThreadLocalValues& thread_local_values = thread_local_pos->second;
+    ThreadLocalValues::iterator value_pos =
+        thread_local_values.find(thread_local_instance);
+    if (value_pos == thread_local_values.end()) {
+      value_pos =
+          thread_local_values
+              .insert(std::make_pair(
+                  thread_local_instance,
+                  std::shared_ptr<ThreadLocalValueHolderBase>(
+                      thread_local_instance->NewValueForCurrentThread())))
+              .first;
+    }
+    return value_pos->second.get();
+  }
+
+  static void OnThreadLocalDestroyed(
+      const ThreadLocalBase* thread_local_instance) {
+    std::vector<std::shared_ptr<ThreadLocalValueHolderBase> > value_holders;
+    // Clean up the ThreadLocalValues data structure while holding the lock, but
+    // defer the destruction of the ThreadLocalValueHolderBases.
+    {
+      MutexLock lock(&mutex_);
+      ThreadIdToThreadLocals* const thread_to_thread_locals =
+          GetThreadLocalsMapLocked();
+      for (ThreadIdToThreadLocals::iterator it =
+          thread_to_thread_locals->begin();
+          it != thread_to_thread_locals->end();
+          ++it) {
+        ThreadLocalValues& thread_local_values = it->second;
+        ThreadLocalValues::iterator value_pos =
+            thread_local_values.find(thread_local_instance);
+        if (value_pos != thread_local_values.end()) {
+          value_holders.push_back(value_pos->second);
+          thread_local_values.erase(value_pos);
+          // This 'if' can only be successful at most once, so theoretically we
+          // could break out of the loop here, but we don't bother doing so.
+        }
+      }
+    }
+    // Outside the lock, let the destructor for 'value_holders' deallocate the
+    // ThreadLocalValueHolderBases.
+  }
+
+  static void OnThreadExit(DWORD thread_id) {
+    GTEST_CHECK_(thread_id != 0) << ::GetLastError();
+    std::vector<std::shared_ptr<ThreadLocalValueHolderBase> > value_holders;
+    // Clean up the ThreadIdToThreadLocals data structure while holding the
+    // lock, but defer the destruction of the ThreadLocalValueHolderBases.
+    {
+      MutexLock lock(&mutex_);
+      ThreadIdToThreadLocals* const thread_to_thread_locals =
+          GetThreadLocalsMapLocked();
+      ThreadIdToThreadLocals::iterator thread_local_pos =
+          thread_to_thread_locals->find(thread_id);
+      if (thread_local_pos != thread_to_thread_locals->end()) {
+        ThreadLocalValues& thread_local_values = thread_local_pos->second;
+        for (ThreadLocalValues::iterator value_pos =
+            thread_local_values.begin();
+            value_pos != thread_local_values.end();
+            ++value_pos) {
+          value_holders.push_back(value_pos->second);
+        }
+        thread_to_thread_locals->erase(thread_local_pos);
+      }
+    }
+    // Outside the lock, let the destructor for 'value_holders' deallocate the
+    // ThreadLocalValueHolderBases.
+  }
+
+ private:
+  // In a particular thread, maps a ThreadLocal object to its value.
+  typedef std::map<const ThreadLocalBase*,
+                   std::shared_ptr<ThreadLocalValueHolderBase> >
+      ThreadLocalValues;
+  // Stores all ThreadIdToThreadLocals having values in a thread, indexed by
+  // thread's ID.
+  typedef std::map<DWORD, ThreadLocalValues> ThreadIdToThreadLocals;
+
+  // Holds the thread id and thread handle that we pass from
+  // StartWatcherThreadFor to WatcherThreadFunc.
+  typedef std::pair<DWORD, HANDLE> ThreadIdAndHandle;
+
+  static void StartWatcherThreadFor(DWORD thread_id) {
+    // The returned handle will be kept in thread_map and closed by
+    // watcher_thread in WatcherThreadFunc.
+    HANDLE thread = ::OpenThread(SYNCHRONIZE | THREAD_QUERY_INFORMATION,
+                                 FALSE,
+                                 thread_id);
+    GTEST_CHECK_(thread != nullptr);
+    // We need to pass a valid thread ID pointer into CreateThread for it
+    // to work correctly under Win98.
+    DWORD watcher_thread_id;
+    HANDLE watcher_thread = ::CreateThread(
+        nullptr,  // Default security.
+        0,        // Default stack size
+        &ThreadLocalRegistryImpl::WatcherThreadFunc,
+        reinterpret_cast<LPVOID>(new ThreadIdAndHandle(thread_id, thread)),
+        CREATE_SUSPENDED, &watcher_thread_id);
+    GTEST_CHECK_(watcher_thread != nullptr);
+    // Give the watcher thread the same priority as ours to avoid being
+    // blocked by it.
+    ::SetThreadPriority(watcher_thread,
+                        ::GetThreadPriority(::GetCurrentThread()));
+    ::ResumeThread(watcher_thread);
+    ::CloseHandle(watcher_thread);
+  }
+
+  // Monitors exit from a given thread and notifies those
+  // ThreadIdToThreadLocals about thread termination.
+  static DWORD WINAPI WatcherThreadFunc(LPVOID param) {
+    const ThreadIdAndHandle* tah =
+        reinterpret_cast<const ThreadIdAndHandle*>(param);
+    GTEST_CHECK_(
+        ::WaitForSingleObject(tah->second, INFINITE) == WAIT_OBJECT_0);
+    OnThreadExit(tah->first);
+    ::CloseHandle(tah->second);
+    delete tah;
+    return 0;
+  }
+
+  // Returns map of thread local instances.
+  static ThreadIdToThreadLocals* GetThreadLocalsMapLocked() {
+    mutex_.AssertHeld();
+#ifdef _MSC_VER
+    MemoryIsNotDeallocated memory_is_not_deallocated;
+#endif  // _MSC_VER
+    static ThreadIdToThreadLocals* map = new ThreadIdToThreadLocals();
+    return map;
+  }
+
+  // Protects access to GetThreadLocalsMapLocked() and its return value.
+  static Mutex mutex_;
+  // Protects access to GetThreadMapLocked() and its return value.
+  static Mutex thread_map_mutex_;
+};
+
+Mutex ThreadLocalRegistryImpl::mutex_(Mutex::kStaticMutex);
+Mutex ThreadLocalRegistryImpl::thread_map_mutex_(Mutex::kStaticMutex);
+
+ThreadLocalValueHolderBase* ThreadLocalRegistry::GetValueOnCurrentThread(
+      const ThreadLocalBase* thread_local_instance) {
+  return ThreadLocalRegistryImpl::GetValueOnCurrentThread(
+      thread_local_instance);
+}
+
+void ThreadLocalRegistry::OnThreadLocalDestroyed(
+      const ThreadLocalBase* thread_local_instance) {
+  ThreadLocalRegistryImpl::OnThreadLocalDestroyed(thread_local_instance);
+}
+
+#endif  // GTEST_IS_THREADSAFE && GTEST_OS_WINDOWS
+
+#if GTEST_USES_POSIX_RE
+
+// Implements RE.  Currently only needed for death tests.
+
+RE::~RE() {
+  if (is_valid_) {
+    // regfree'ing an invalid regex might crash because the content
+    // of the regex is undefined. Since the regex's are essentially
+    // the same, one cannot be valid (or invalid) without the other
+    // being so too.
+    regfree(&partial_regex_);
+    regfree(&full_regex_);
+  }
+  free(const_cast<char*>(pattern_));
+}
+
+// Returns true if and only if regular expression re matches the entire str.
+bool RE::FullMatch(const char* str, const RE& re) {
+  if (!re.is_valid_) return false;
+
+  regmatch_t match;
+  return regexec(&re.full_regex_, str, 1, &match, 0) == 0;
+}
+
+// Returns true if and only if regular expression re matches a substring of
+// str (including str itself).
+bool RE::PartialMatch(const char* str, const RE& re) {
+  if (!re.is_valid_) return false;
+
+  regmatch_t match;
+  return regexec(&re.partial_regex_, str, 1, &match, 0) == 0;
+}
+
+// Initializes an RE from its string representation.
+void RE::Init(const char* regex) {
+  pattern_ = posix::StrDup(regex);
+
+  // Reserves enough bytes to hold the regular expression used for a
+  // full match.
+  const size_t full_regex_len = strlen(regex) + 10;
+  char* const full_pattern = new char[full_regex_len];
+
+  snprintf(full_pattern, full_regex_len, "^(%s)$", regex);
+  is_valid_ = regcomp(&full_regex_, full_pattern, REG_EXTENDED) == 0;
+  // We want to call regcomp(&partial_regex_, ...) even if the
+  // previous expression returns false.  Otherwise partial_regex_ may
+  // not be properly initialized can may cause trouble when it's
+  // freed.
+  //
+  // Some implementation of POSIX regex (e.g. on at least some
+  // versions of Cygwin) doesn't accept the empty string as a valid
+  // regex.  We change it to an equivalent form "()" to be safe.
+  if (is_valid_) {
+    const char* const partial_regex = (*regex == '\0') ? "()" : regex;
+    is_valid_ = regcomp(&partial_regex_, partial_regex, REG_EXTENDED) == 0;
+  }
+  EXPECT_TRUE(is_valid_)
+      << "Regular expression \"" << regex
+      << "\" is not a valid POSIX Extended regular expression.";
+
+  delete[] full_pattern;
+}
+
+#elif GTEST_USES_SIMPLE_RE
+
+// Returns true if and only if ch appears anywhere in str (excluding the
+// terminating '\0' character).
+bool IsInSet(char ch, const char* str) {
+  return ch != '\0' && strchr(str, ch) != nullptr;
+}
+
+// Returns true if and only if ch belongs to the given classification.
+// Unlike similar functions in <ctype.h>, these aren't affected by the
+// current locale.
+bool IsAsciiDigit(char ch) { return '0' <= ch && ch <= '9'; }
+bool IsAsciiPunct(char ch) {
+  return IsInSet(ch, "^-!\"#$%&'()*+,./:;<=>?@[\\]_`{|}~");
+}
+bool IsRepeat(char ch) { return IsInSet(ch, "?*+"); }
+bool IsAsciiWhiteSpace(char ch) { return IsInSet(ch, " \f\n\r\t\v"); }
+bool IsAsciiWordChar(char ch) {
+  return ('a' <= ch && ch <= 'z') || ('A' <= ch && ch <= 'Z') ||
+      ('0' <= ch && ch <= '9') || ch == '_';
+}
+
+// Returns true if and only if "\\c" is a supported escape sequence.
+bool IsValidEscape(char c) {
+  return (IsAsciiPunct(c) || IsInSet(c, "dDfnrsStvwW"));
+}
+
+// Returns true if and only if the given atom (specified by escaped and
+// pattern) matches ch.  The result is undefined if the atom is invalid.
+bool AtomMatchesChar(bool escaped, char pattern_char, char ch) {
+  if (escaped) {  // "\\p" where p is pattern_char.
+    switch (pattern_char) {
+      case 'd': return IsAsciiDigit(ch);
+      case 'D': return !IsAsciiDigit(ch);
+      case 'f': return ch == '\f';
+      case 'n': return ch == '\n';
+      case 'r': return ch == '\r';
+      case 's': return IsAsciiWhiteSpace(ch);
+      case 'S': return !IsAsciiWhiteSpace(ch);
+      case 't': return ch == '\t';
+      case 'v': return ch == '\v';
+      case 'w': return IsAsciiWordChar(ch);
+      case 'W': return !IsAsciiWordChar(ch);
+    }
+    return IsAsciiPunct(pattern_char) && pattern_char == ch;
+  }
+
+  return (pattern_char == '.' && ch != '\n') || pattern_char == ch;
+}
+
+// Helper function used by ValidateRegex() to format error messages.
+static std::string FormatRegexSyntaxError(const char* regex, int index) {
+  return (Message() << "Syntax error at index " << index
+          << " in simple regular expression \"" << regex << "\": ").GetString();
+}
+
+// Generates non-fatal failures and returns false if regex is invalid;
+// otherwise returns true.
+bool ValidateRegex(const char* regex) {
+  if (regex == nullptr) {
+    ADD_FAILURE() << "NULL is not a valid simple regular expression.";
+    return false;
+  }
+
+  bool is_valid = true;
+
+  // True if and only if ?, *, or + can follow the previous atom.
+  bool prev_repeatable = false;
+  for (int i = 0; regex[i]; i++) {
+    if (regex[i] == '\\') {  // An escape sequence
+      i++;
+      if (regex[i] == '\0') {
+        ADD_FAILURE() << FormatRegexSyntaxError(regex, i - 1)
+                      << "'\\' cannot appear at the end.";
+        return false;
+      }
+
+      if (!IsValidEscape(regex[i])) {
+        ADD_FAILURE() << FormatRegexSyntaxError(regex, i - 1)
+                      << "invalid escape sequence \"\\" << regex[i] << "\".";
+        is_valid = false;
+      }
+      prev_repeatable = true;
+    } else {  // Not an escape sequence.
+      const char ch = regex[i];
+
+      if (ch == '^' && i > 0) {
+        ADD_FAILURE() << FormatRegexSyntaxError(regex, i)
+                      << "'^' can only appear at the beginning.";
+        is_valid = false;
+      } else if (ch == '$' && regex[i + 1] != '\0') {
+        ADD_FAILURE() << FormatRegexSyntaxError(regex, i)
+                      << "'$' can only appear at the end.";
+        is_valid = false;
+      } else if (IsInSet(ch, "()[]{}|")) {
+        ADD_FAILURE() << FormatRegexSyntaxError(regex, i)
+                      << "'" << ch << "' is unsupported.";
+        is_valid = false;
+      } else if (IsRepeat(ch) && !prev_repeatable) {
+        ADD_FAILURE() << FormatRegexSyntaxError(regex, i)
+                      << "'" << ch << "' can only follow a repeatable token.";
+        is_valid = false;
+      }
+
+      prev_repeatable = !IsInSet(ch, "^$?*+");
+    }
+  }
+
+  return is_valid;
+}
+
+// Matches a repeated regex atom followed by a valid simple regular
+// expression.  The regex atom is defined as c if escaped is false,
+// or \c otherwise.  repeat is the repetition meta character (?, *,
+// or +).  The behavior is undefined if str contains too many
+// characters to be indexable by size_t, in which case the test will
+// probably time out anyway.  We are fine with this limitation as
+// std::string has it too.
+bool MatchRepetitionAndRegexAtHead(
+    bool escaped, char c, char repeat, const char* regex,
+    const char* str) {
+  const size_t min_count = (repeat == '+') ? 1 : 0;
+  const size_t max_count = (repeat == '?') ? 1 :
+      static_cast<size_t>(-1) - 1;
+  // We cannot call numeric_limits::max() as it conflicts with the
+  // max() macro on Windows.
+
+  for (size_t i = 0; i <= max_count; ++i) {
+    // We know that the atom matches each of the first i characters in str.
+    if (i >= min_count && MatchRegexAtHead(regex, str + i)) {
+      // We have enough matches at the head, and the tail matches too.
+      // Since we only care about *whether* the pattern matches str
+      // (as opposed to *how* it matches), there is no need to find a
+      // greedy match.
+      return true;
+    }
+    if (str[i] == '\0' || !AtomMatchesChar(escaped, c, str[i]))
+      return false;
+  }
+  return false;
+}
+
+// Returns true if and only if regex matches a prefix of str. regex must
+// be a valid simple regular expression and not start with "^", or the
+// result is undefined.
+bool MatchRegexAtHead(const char* regex, const char* str) {
+  if (*regex == '\0')  // An empty regex matches a prefix of anything.
+    return true;
+
+  // "$" only matches the end of a string.  Note that regex being
+  // valid guarantees that there's nothing after "$" in it.
+  if (*regex == '$')
+    return *str == '\0';
+
+  // Is the first thing in regex an escape sequence?
+  const bool escaped = *regex == '\\';
+  if (escaped)
+    ++regex;
+  if (IsRepeat(regex[1])) {
+    // MatchRepetitionAndRegexAtHead() calls MatchRegexAtHead(), so
+    // here's an indirect recursion.  It terminates as the regex gets
+    // shorter in each recursion.
+    return MatchRepetitionAndRegexAtHead(
+        escaped, regex[0], regex[1], regex + 2, str);
+  } else {
+    // regex isn't empty, isn't "$", and doesn't start with a
+    // repetition.  We match the first atom of regex with the first
+    // character of str and recurse.
+    return (*str != '\0') && AtomMatchesChar(escaped, *regex, *str) &&
+        MatchRegexAtHead(regex + 1, str + 1);
+  }
+}
+
+// Returns true if and only if regex matches any substring of str.  regex must
+// be a valid simple regular expression, or the result is undefined.
+//
+// The algorithm is recursive, but the recursion depth doesn't exceed
+// the regex length, so we won't need to worry about running out of
+// stack space normally.  In rare cases the time complexity can be
+// exponential with respect to the regex length + the string length,
+// but usually it's must faster (often close to linear).
+bool MatchRegexAnywhere(const char* regex, const char* str) {
+  if (regex == nullptr || str == nullptr) return false;
+
+  if (*regex == '^')
+    return MatchRegexAtHead(regex + 1, str);
+
+  // A successful match can be anywhere in str.
+  do {
+    if (MatchRegexAtHead(regex, str))
+      return true;
+  } while (*str++ != '\0');
+  return false;
+}
+
+// Implements the RE class.
+
+RE::~RE() {
+  free(const_cast<char*>(pattern_));
+  free(const_cast<char*>(full_pattern_));
+}
+
+// Returns true if and only if regular expression re matches the entire str.
+bool RE::FullMatch(const char* str, const RE& re) {
+  return re.is_valid_ && MatchRegexAnywhere(re.full_pattern_, str);
+}
+
+// Returns true if and only if regular expression re matches a substring of
+// str (including str itself).
+bool RE::PartialMatch(const char* str, const RE& re) {
+  return re.is_valid_ && MatchRegexAnywhere(re.pattern_, str);
+}
+
+// Initializes an RE from its string representation.
+void RE::Init(const char* regex) {
+  pattern_ = full_pattern_ = nullptr;
+  if (regex != nullptr) {
+    pattern_ = posix::StrDup(regex);
+  }
+
+  is_valid_ = ValidateRegex(regex);
+  if (!is_valid_) {
+    // No need to calculate the full pattern when the regex is invalid.
+    return;
+  }
+
+  const size_t len = strlen(regex);
+  // Reserves enough bytes to hold the regular expression used for a
+  // full match: we need space to prepend a '^', append a '$', and
+  // terminate the string with '\0'.
+  char* buffer = static_cast<char*>(malloc(len + 3));
+  full_pattern_ = buffer;
+
+  if (*regex != '^')
+    *buffer++ = '^';  // Makes sure full_pattern_ starts with '^'.
+
+  // We don't use snprintf or strncpy, as they trigger a warning when
+  // compiled with VC++ 8.0.
+  memcpy(buffer, regex, len);
+  buffer += len;
+
+  if (len == 0 || regex[len - 1] != '$')
+    *buffer++ = '$';  // Makes sure full_pattern_ ends with '$'.
+
+  *buffer = '\0';
+}
+
+#endif  // GTEST_USES_POSIX_RE
+
+const char kUnknownFile[] = "unknown file";
+
+// Formats a source file path and a line number as they would appear
+// in an error message from the compiler used to compile this code.
+GTEST_API_ ::std::string FormatFileLocation(const char* file, int line) {
+  const std::string file_name(file == nullptr ? kUnknownFile : file);
+
+  if (line < 0) {
+    return file_name + ":";
+  }
+#ifdef _MSC_VER
+  return file_name + "(" + StreamableToString(line) + "):";
+#else
+  return file_name + ":" + StreamableToString(line) + ":";
+#endif  // _MSC_VER
+}
+
+// Formats a file location for compiler-independent XML output.
+// Although this function is not platform dependent, we put it next to
+// FormatFileLocation in order to contrast the two functions.
+// Note that FormatCompilerIndependentFileLocation() does NOT append colon
+// to the file location it produces, unlike FormatFileLocation().
+GTEST_API_ ::std::string FormatCompilerIndependentFileLocation(
+    const char* file, int line) {
+  const std::string file_name(file == nullptr ? kUnknownFile : file);
+
+  if (line < 0)
+    return file_name;
+  else
+    return file_name + ":" + StreamableToString(line);
+}
+
+GTestLog::GTestLog(GTestLogSeverity severity, const char* file, int line)
+    : severity_(severity) {
+  const char* const marker =
+      severity == GTEST_INFO ?    "[  INFO ]" :
+      severity == GTEST_WARNING ? "[WARNING]" :
+      severity == GTEST_ERROR ?   "[ ERROR ]" : "[ FATAL ]";
+  GetStream() << ::std::endl << marker << " "
+              << FormatFileLocation(file, line).c_str() << ": ";
+}
+
+// Flushes the buffers and, if severity is GTEST_FATAL, aborts the program.
+GTestLog::~GTestLog() {
+  GetStream() << ::std::endl;
+  if (severity_ == GTEST_FATAL) {
+    fflush(stderr);
+    posix::Abort();
+  }
+}
+
+// Disable Microsoft deprecation warnings for POSIX functions called from
+// this class (creat, dup, dup2, and close)
+GTEST_DISABLE_MSC_DEPRECATED_PUSH_()
+
+#if GTEST_HAS_STREAM_REDIRECTION
+
+// Object that captures an output stream (stdout/stderr).
+class CapturedStream {
+ public:
+  // The ctor redirects the stream to a temporary file.
+  explicit CapturedStream(int fd) : fd_(fd), uncaptured_fd_(dup(fd)) {
+# if GTEST_OS_WINDOWS
+    char temp_dir_path[MAX_PATH + 1] = { '\0' };  // NOLINT
+    char temp_file_path[MAX_PATH + 1] = { '\0' };  // NOLINT
+
+    ::GetTempPathA(sizeof(temp_dir_path), temp_dir_path);
+    const UINT success = ::GetTempFileNameA(temp_dir_path,
+                                            "gtest_redir",
+                                            0,  // Generate unique file name.
+                                            temp_file_path);
+    GTEST_CHECK_(success != 0)
+        << "Unable to create a temporary file in " << temp_dir_path;
+    const int captured_fd = creat(temp_file_path, _S_IREAD | _S_IWRITE);
+    GTEST_CHECK_(captured_fd != -1) << "Unable to open temporary file "
+                                    << temp_file_path;
+    filename_ = temp_file_path;
+# else
+    // There's no guarantee that a test has write access to the current
+    // directory, so we create the temporary file in the /tmp directory
+    // instead. We use /tmp on most systems, and /sdcard on Android.
+    // That's because Android doesn't have /tmp.
+#  if GTEST_OS_LINUX_ANDROID
+    // Note: Android applications are expected to call the framework's
+    // Context.getExternalStorageDirectory() method through JNI to get
+    // the location of the world-writable SD Card directory. However,
+    // this requires a Context handle, which cannot be retrieved
+    // globally from native code. Doing so also precludes running the
+    // code as part of a regular standalone executable, which doesn't
+    // run in a Dalvik process (e.g. when running it through 'adb shell').
+    //
+    // The location /data/local/tmp is directly accessible from native code.
+    // '/sdcard' and other variants cannot be relied on, as they are not
+    // guaranteed to be mounted, or may have a delay in mounting.
+    char name_template[] = "/data/local/tmp/gtest_captured_stream.XXXXXX";
+#  elif GTEST_OS_IOS
+    NSString* temp_path = [NSTemporaryDirectory()
+        stringByAppendingPathComponent:@"gtest_captured_stream.XXXXXX"];
+
+    char name_template[PATH_MAX + 1];
+    strncpy(name_template, [temp_path UTF8String], PATH_MAX);
+#  else
+    char name_template[] = "/tmp/captured_stream.XXXXXX";
+#  endif
+    const int captured_fd = mkstemp(name_template);
+    if (captured_fd == -1) {
+      GTEST_LOG_(WARNING)
+          << "Failed to create tmp file " << name_template
+          << " for test; does the test have access to the /tmp directory?";
+    }
+    filename_ = name_template;
+# endif  // GTEST_OS_WINDOWS
+    fflush(nullptr);
+    dup2(captured_fd, fd_);
+    close(captured_fd);
+  }
+
+  ~CapturedStream() {
+    remove(filename_.c_str());
+  }
+
+  std::string GetCapturedString() {
+    if (uncaptured_fd_ != -1) {
+      // Restores the original stream.
+      fflush(nullptr);
+      dup2(uncaptured_fd_, fd_);
+      close(uncaptured_fd_);
+      uncaptured_fd_ = -1;
+    }
+
+    FILE* const file = posix::FOpen(filename_.c_str(), "r");
+    if (file == nullptr) {
+      GTEST_LOG_(FATAL) << "Failed to open tmp file " << filename_
+                        << " for capturing stream.";
+    }
+    const std::string content = ReadEntireFile(file);
+    posix::FClose(file);
+    return content;
+  }
+
+ private:
+  const int fd_;  // A stream to capture.
+  int uncaptured_fd_;
+  // Name of the temporary file holding the stderr output.
+  ::std::string filename_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(CapturedStream);
+};
+
+GTEST_DISABLE_MSC_DEPRECATED_POP_()
+
+static CapturedStream* g_captured_stderr = nullptr;
+static CapturedStream* g_captured_stdout = nullptr;
+
+// Starts capturing an output stream (stdout/stderr).
+static void CaptureStream(int fd, const char* stream_name,
+                          CapturedStream** stream) {
+  if (*stream != nullptr) {
+    GTEST_LOG_(FATAL) << "Only one " << stream_name
+                      << " capturer can exist at a time.";
+  }
+  *stream = new CapturedStream(fd);
+}
+
+// Stops capturing the output stream and returns the captured string.
+static std::string GetCapturedStream(CapturedStream** captured_stream) {
+  const std::string content = (*captured_stream)->GetCapturedString();
+
+  delete *captured_stream;
+  *captured_stream = nullptr;
+
+  return content;
+}
+
+// Starts capturing stdout.
+void CaptureStdout() {
+  CaptureStream(kStdOutFileno, "stdout", &g_captured_stdout);
+}
+
+// Starts capturing stderr.
+void CaptureStderr() {
+  CaptureStream(kStdErrFileno, "stderr", &g_captured_stderr);
+}
+
+// Stops capturing stdout and returns the captured string.
+std::string GetCapturedStdout() {
+  return GetCapturedStream(&g_captured_stdout);
+}
+
+// Stops capturing stderr and returns the captured string.
+std::string GetCapturedStderr() {
+  return GetCapturedStream(&g_captured_stderr);
+}
+
+#endif  // GTEST_HAS_STREAM_REDIRECTION
+
+
+
+
+
+size_t GetFileSize(FILE* file) {
+  fseek(file, 0, SEEK_END);
+  return static_cast<size_t>(ftell(file));
+}
+
+std::string ReadEntireFile(FILE* file) {
+  const size_t file_size = GetFileSize(file);
+  char* const buffer = new char[file_size];
+
+  size_t bytes_last_read = 0;  // # of bytes read in the last fread()
+  size_t bytes_read = 0;       // # of bytes read so far
+
+  fseek(file, 0, SEEK_SET);
+
+  // Keeps reading the file until we cannot read further or the
+  // pre-determined file size is reached.
+  do {
+    bytes_last_read = fread(buffer+bytes_read, 1, file_size-bytes_read, file);
+    bytes_read += bytes_last_read;
+  } while (bytes_last_read > 0 && bytes_read < file_size);
+
+  const std::string content(buffer, bytes_read);
+  delete[] buffer;
+
+  return content;
+}
+
+#if GTEST_HAS_DEATH_TEST
+static const std::vector<std::string>* g_injected_test_argvs =
+    nullptr;  // Owned.
+
+std::vector<std::string> GetInjectableArgvs() {
+  if (g_injected_test_argvs != nullptr) {
+    return *g_injected_test_argvs;
+  }
+  return GetArgvs();
+}
+
+void SetInjectableArgvs(const std::vector<std::string>* new_argvs) {
+  if (g_injected_test_argvs != new_argvs) delete g_injected_test_argvs;
+  g_injected_test_argvs = new_argvs;
+}
+
+void SetInjectableArgvs(const std::vector<std::string>& new_argvs) {
+  SetInjectableArgvs(
+      new std::vector<std::string>(new_argvs.begin(), new_argvs.end()));
+}
+
+void ClearInjectableArgvs() {
+  delete g_injected_test_argvs;
+  g_injected_test_argvs = nullptr;
+}
+#endif  // GTEST_HAS_DEATH_TEST
+
+#if GTEST_OS_WINDOWS_MOBILE
+namespace posix {
+void Abort() {
+  DebugBreak();
+  TerminateProcess(GetCurrentProcess(), 1);
+}
+}  // namespace posix
+#endif  // GTEST_OS_WINDOWS_MOBILE
+
+// Returns the name of the environment variable corresponding to the
+// given flag.  For example, FlagToEnvVar("foo") will return
+// "GTEST_FOO" in the open-source version.
+static std::string FlagToEnvVar(const char* flag) {
+  const std::string full_flag =
+      (Message() << GTEST_FLAG_PREFIX_ << flag).GetString();
+
+  Message env_var;
+  for (size_t i = 0; i != full_flag.length(); i++) {
+    env_var << ToUpper(full_flag.c_str()[i]);
+  }
+
+  return env_var.GetString();
+}
+
+// Parses 'str' for a 32-bit signed integer.  If successful, writes
+// the result to *value and returns true; otherwise leaves *value
+// unchanged and returns false.
+bool ParseInt32(const Message& src_text, const char* str, int32_t* value) {
+  // Parses the environment variable as a decimal integer.
+  char* end = nullptr;
+  const long long_value = strtol(str, &end, 10);  // NOLINT
+
+  // Has strtol() consumed all characters in the string?
+  if (*end != '\0') {
+    // No - an invalid character was encountered.
+    Message msg;
+    msg << "WARNING: " << src_text
+        << " is expected to be a 32-bit integer, but actually"
+        << " has value \"" << str << "\".\n";
+    printf("%s", msg.GetString().c_str());
+    fflush(stdout);
+    return false;
+  }
+
+  // Is the parsed value in the range of an int32_t?
+  const auto result = static_cast<int32_t>(long_value);
+  if (long_value == LONG_MAX || long_value == LONG_MIN ||
+      // The parsed value overflows as a long.  (strtol() returns
+      // LONG_MAX or LONG_MIN when the input overflows.)
+      result != long_value
+      // The parsed value overflows as an int32_t.
+      ) {
+    Message msg;
+    msg << "WARNING: " << src_text
+        << " is expected to be a 32-bit integer, but actually"
+        << " has value " << str << ", which overflows.\n";
+    printf("%s", msg.GetString().c_str());
+    fflush(stdout);
+    return false;
+  }
+
+  *value = result;
+  return true;
+}
+
+// Reads and returns the Boolean environment variable corresponding to
+// the given flag; if it's not set, returns default_value.
+//
+// The value is considered true if and only if it's not "0".
+bool BoolFromGTestEnv(const char* flag, bool default_value) {
+#if defined(GTEST_GET_BOOL_FROM_ENV_)
+  return GTEST_GET_BOOL_FROM_ENV_(flag, default_value);
+#else
+  const std::string env_var = FlagToEnvVar(flag);
+  const char* const string_value = posix::GetEnv(env_var.c_str());
+  return string_value == nullptr ? default_value
+                                 : strcmp(string_value, "0") != 0;
+#endif  // defined(GTEST_GET_BOOL_FROM_ENV_)
+}
+
+// Reads and returns a 32-bit integer stored in the environment
+// variable corresponding to the given flag; if it isn't set or
+// doesn't represent a valid 32-bit integer, returns default_value.
+int32_t Int32FromGTestEnv(const char* flag, int32_t default_value) {
+#if defined(GTEST_GET_INT32_FROM_ENV_)
+  return GTEST_GET_INT32_FROM_ENV_(flag, default_value);
+#else
+  const std::string env_var = FlagToEnvVar(flag);
+  const char* const string_value = posix::GetEnv(env_var.c_str());
+  if (string_value == nullptr) {
+    // The environment variable is not set.
+    return default_value;
+  }
+
+  int32_t result = default_value;
+  if (!ParseInt32(Message() << "Environment variable " << env_var,
+                  string_value, &result)) {
+    printf("The default value %s is used.\n",
+           (Message() << default_value).GetString().c_str());
+    fflush(stdout);
+    return default_value;
+  }
+
+  return result;
+#endif  // defined(GTEST_GET_INT32_FROM_ENV_)
+}
+
+// As a special case for the 'output' flag, if GTEST_OUTPUT is not
+// set, we look for XML_OUTPUT_FILE, which is set by the Bazel build
+// system.  The value of XML_OUTPUT_FILE is a filename without the
+// "xml:" prefix of GTEST_OUTPUT.
+// Note that this is meant to be called at the call site so it does
+// not check that the flag is 'output'
+// In essence this checks an env variable called XML_OUTPUT_FILE
+// and if it is set we prepend "xml:" to its value, if it not set we return ""
+std::string OutputFlagAlsoCheckEnvVar(){
+  std::string default_value_for_output_flag = "";
+  const char* xml_output_file_env = posix::GetEnv("XML_OUTPUT_FILE");
+  if (nullptr != xml_output_file_env) {
+    default_value_for_output_flag = std::string("xml:") + xml_output_file_env;
+  }
+  return default_value_for_output_flag;
+}
+
+// Reads and returns the string environment variable corresponding to
+// the given flag; if it's not set, returns default_value.
+const char* StringFromGTestEnv(const char* flag, const char* default_value) {
+#if defined(GTEST_GET_STRING_FROM_ENV_)
+  return GTEST_GET_STRING_FROM_ENV_(flag, default_value);
+#else
+  const std::string env_var = FlagToEnvVar(flag);
+  const char* const value = posix::GetEnv(env_var.c_str());
+  return value == nullptr ? default_value : value;
+#endif  // defined(GTEST_GET_STRING_FROM_ENV_)
+}
+
+}  // namespace internal
+}  // namespace testing
diff --git a/leveldb_base/third_party/googletest/googletest/src/gtest-printers.cc b/leveldb_base/third_party/googletest/googletest/src/gtest-printers.cc
new file mode 100644
index 0000000..1b68fcb
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/src/gtest-printers.cc
@@ -0,0 +1,533 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Test - The Google C++ Testing and Mocking Framework
+//
+// This file implements a universal value printer that can print a
+// value of any type T:
+//
+//   void ::testing::internal::UniversalPrinter<T>::Print(value, ostream_ptr);
+//
+// It uses the << operator when possible, and prints the bytes in the
+// object otherwise.  A user can override its behavior for a class
+// type Foo by defining either operator<<(::std::ostream&, const Foo&)
+// or void PrintTo(const Foo&, ::std::ostream*) in the namespace that
+// defines Foo.
+
+#include "gtest/gtest-printers.h"
+
+#include <stdio.h>
+
+#include <cctype>
+#include <cstdint>
+#include <cwchar>
+#include <ostream>  // NOLINT
+#include <string>
+#include <type_traits>
+
+#include "gtest/internal/gtest-port.h"
+#include "src/gtest-internal-inl.h"
+
+namespace testing {
+
+namespace {
+
+using ::std::ostream;
+
+// Prints a segment of bytes in the given object.
+GTEST_ATTRIBUTE_NO_SANITIZE_MEMORY_
+GTEST_ATTRIBUTE_NO_SANITIZE_ADDRESS_
+GTEST_ATTRIBUTE_NO_SANITIZE_HWADDRESS_
+GTEST_ATTRIBUTE_NO_SANITIZE_THREAD_
+void PrintByteSegmentInObjectTo(const unsigned char* obj_bytes, size_t start,
+                                size_t count, ostream* os) {
+  char text[5] = "";
+  for (size_t i = 0; i != count; i++) {
+    const size_t j = start + i;
+    if (i != 0) {
+      // Organizes the bytes into groups of 2 for easy parsing by
+      // human.
+      if ((j % 2) == 0)
+        *os << ' ';
+      else
+        *os << '-';
+    }
+    GTEST_SNPRINTF_(text, sizeof(text), "%02X", obj_bytes[j]);
+    *os << text;
+  }
+}
+
+// Prints the bytes in the given value to the given ostream.
+void PrintBytesInObjectToImpl(const unsigned char* obj_bytes, size_t count,
+                              ostream* os) {
+  // Tells the user how big the object is.
+  *os << count << "-byte object <";
+
+  const size_t kThreshold = 132;
+  const size_t kChunkSize = 64;
+  // If the object size is bigger than kThreshold, we'll have to omit
+  // some details by printing only the first and the last kChunkSize
+  // bytes.
+  if (count < kThreshold) {
+    PrintByteSegmentInObjectTo(obj_bytes, 0, count, os);
+  } else {
+    PrintByteSegmentInObjectTo(obj_bytes, 0, kChunkSize, os);
+    *os << " ... ";
+    // Rounds up to 2-byte boundary.
+    const size_t resume_pos = (count - kChunkSize + 1)/2*2;
+    PrintByteSegmentInObjectTo(obj_bytes, resume_pos, count - resume_pos, os);
+  }
+  *os << ">";
+}
+
+// Helpers for widening a character to char32_t. Since the standard does not
+// specify if char / wchar_t is signed or unsigned, it is important to first
+// convert it to the unsigned type of the same width before widening it to
+// char32_t.
+template <typename CharType>
+char32_t ToChar32(CharType in) {
+  return static_cast<char32_t>(
+      static_cast<typename std::make_unsigned<CharType>::type>(in));
+}
+
+}  // namespace
+
+namespace internal {
+
+// Delegates to PrintBytesInObjectToImpl() to print the bytes in the
+// given object.  The delegation simplifies the implementation, which
+// uses the << operator and thus is easier done outside of the
+// ::testing::internal namespace, which contains a << operator that
+// sometimes conflicts with the one in STL.
+void PrintBytesInObjectTo(const unsigned char* obj_bytes, size_t count,
+                          ostream* os) {
+  PrintBytesInObjectToImpl(obj_bytes, count, os);
+}
+
+// Depending on the value of a char (or wchar_t), we print it in one
+// of three formats:
+//   - as is if it's a printable ASCII (e.g. 'a', '2', ' '),
+//   - as a hexadecimal escape sequence (e.g. '\x7F'), or
+//   - as a special escape sequence (e.g. '\r', '\n').
+enum CharFormat {
+  kAsIs,
+  kHexEscape,
+  kSpecialEscape
+};
+
+// Returns true if c is a printable ASCII character.  We test the
+// value of c directly instead of calling isprint(), which is buggy on
+// Windows Mobile.
+inline bool IsPrintableAscii(char32_t c) { return 0x20 <= c && c <= 0x7E; }
+
+// Prints c (of type char, char8_t, char16_t, char32_t, or wchar_t) as a
+// character literal without the quotes, escaping it when necessary; returns how
+// c was formatted.
+template <typename Char>
+static CharFormat PrintAsCharLiteralTo(Char c, ostream* os) {
+  const char32_t u_c = ToChar32(c);
+  switch (u_c) {
+    case L'\0':
+      *os << "\\0";
+      break;
+    case L'\'':
+      *os << "\\'";
+      break;
+    case L'\\':
+      *os << "\\\\";
+      break;
+    case L'\a':
+      *os << "\\a";
+      break;
+    case L'\b':
+      *os << "\\b";
+      break;
+    case L'\f':
+      *os << "\\f";
+      break;
+    case L'\n':
+      *os << "\\n";
+      break;
+    case L'\r':
+      *os << "\\r";
+      break;
+    case L'\t':
+      *os << "\\t";
+      break;
+    case L'\v':
+      *os << "\\v";
+      break;
+    default:
+      if (IsPrintableAscii(u_c)) {
+        *os << static_cast<char>(c);
+        return kAsIs;
+      } else {
+        ostream::fmtflags flags = os->flags();
+        *os << "\\x" << std::hex << std::uppercase << static_cast<int>(u_c);
+        os->flags(flags);
+        return kHexEscape;
+      }
+  }
+  return kSpecialEscape;
+}
+
+// Prints a char32_t c as if it's part of a string literal, escaping it when
+// necessary; returns how c was formatted.
+static CharFormat PrintAsStringLiteralTo(char32_t c, ostream* os) {
+  switch (c) {
+    case L'\'':
+      *os << "'";
+      return kAsIs;
+    case L'"':
+      *os << "\\\"";
+      return kSpecialEscape;
+    default:
+      return PrintAsCharLiteralTo(c, os);
+  }
+}
+
+static const char* GetCharWidthPrefix(char) {
+  return "";
+}
+
+static const char* GetCharWidthPrefix(signed char) {
+  return "";
+}
+
+static const char* GetCharWidthPrefix(unsigned char) {
+  return "";
+}
+
+#ifdef __cpp_char8_t
+static const char* GetCharWidthPrefix(char8_t) {
+  return "u8";
+}
+#endif
+
+static const char* GetCharWidthPrefix(char16_t) {
+  return "u";
+}
+
+static const char* GetCharWidthPrefix(char32_t) {
+  return "U";
+}
+
+static const char* GetCharWidthPrefix(wchar_t) {
+  return "L";
+}
+
+// Prints a char c as if it's part of a string literal, escaping it when
+// necessary; returns how c was formatted.
+static CharFormat PrintAsStringLiteralTo(char c, ostream* os) {
+  return PrintAsStringLiteralTo(ToChar32(c), os);
+}
+
+#ifdef __cpp_char8_t
+static CharFormat PrintAsStringLiteralTo(char8_t c, ostream* os) {
+  return PrintAsStringLiteralTo(ToChar32(c), os);
+}
+#endif
+
+static CharFormat PrintAsStringLiteralTo(char16_t c, ostream* os) {
+  return PrintAsStringLiteralTo(ToChar32(c), os);
+}
+
+static CharFormat PrintAsStringLiteralTo(wchar_t c, ostream* os) {
+  return PrintAsStringLiteralTo(ToChar32(c), os);
+}
+
+// Prints a character c (of type char, char8_t, char16_t, char32_t, or wchar_t)
+// and its code. '\0' is printed as "'\\0'", other unprintable characters are
+// also properly escaped using the standard C++ escape sequence.
+template <typename Char>
+void PrintCharAndCodeTo(Char c, ostream* os) {
+  // First, print c as a literal in the most readable form we can find.
+  *os << GetCharWidthPrefix(c) << "'";
+  const CharFormat format = PrintAsCharLiteralTo(c, os);
+  *os << "'";
+
+  // To aid user debugging, we also print c's code in decimal, unless
+  // it's 0 (in which case c was printed as '\\0', making the code
+  // obvious).
+  if (c == 0)
+    return;
+  *os << " (" << static_cast<int>(c);
+
+  // For more convenience, we print c's code again in hexadecimal,
+  // unless c was already printed in the form '\x##' or the code is in
+  // [1, 9].
+  if (format == kHexEscape || (1 <= c && c <= 9)) {
+    // Do nothing.
+  } else {
+    *os << ", 0x" << String::FormatHexInt(static_cast<int>(c));
+  }
+  *os << ")";
+}
+
+void PrintTo(unsigned char c, ::std::ostream* os) { PrintCharAndCodeTo(c, os); }
+void PrintTo(signed char c, ::std::ostream* os) { PrintCharAndCodeTo(c, os); }
+
+// Prints a wchar_t as a symbol if it is printable or as its internal
+// code otherwise and also as its code.  L'\0' is printed as "L'\\0'".
+void PrintTo(wchar_t wc, ostream* os) { PrintCharAndCodeTo(wc, os); }
+
+// TODO(dcheng): Consider making this delegate to PrintCharAndCodeTo() as well.
+void PrintTo(char32_t c, ::std::ostream* os) {
+  *os << std::hex << "U+" << std::uppercase << std::setfill('0') << std::setw(4)
+      << static_cast<uint32_t>(c);
+}
+
+// Prints the given array of characters to the ostream.  CharType must be either
+// char, char8_t, char16_t, char32_t, or wchar_t.
+// The array starts at begin, the length is len, it may include '\0' characters
+// and may not be NUL-terminated.
+template <typename CharType>
+GTEST_ATTRIBUTE_NO_SANITIZE_MEMORY_
+GTEST_ATTRIBUTE_NO_SANITIZE_ADDRESS_
+GTEST_ATTRIBUTE_NO_SANITIZE_HWADDRESS_
+GTEST_ATTRIBUTE_NO_SANITIZE_THREAD_
+static CharFormat PrintCharsAsStringTo(
+    const CharType* begin, size_t len, ostream* os) {
+  const char* const quote_prefix = GetCharWidthPrefix(*begin);
+  *os << quote_prefix << "\"";
+  bool is_previous_hex = false;
+  CharFormat print_format = kAsIs;
+  for (size_t index = 0; index < len; ++index) {
+    const CharType cur = begin[index];
+    if (is_previous_hex && IsXDigit(cur)) {
+      // Previous character is of '\x..' form and this character can be
+      // interpreted as another hexadecimal digit in its number. Break string to
+      // disambiguate.
+      *os << "\" " << quote_prefix << "\"";
+    }
+    is_previous_hex = PrintAsStringLiteralTo(cur, os) == kHexEscape;
+    // Remember if any characters required hex escaping.
+    if (is_previous_hex) {
+      print_format = kHexEscape;
+    }
+  }
+  *os << "\"";
+  return print_format;
+}
+
+// Prints a (const) char/wchar_t array of 'len' elements, starting at address
+// 'begin'.  CharType must be either char or wchar_t.
+template <typename CharType>
+GTEST_ATTRIBUTE_NO_SANITIZE_MEMORY_
+GTEST_ATTRIBUTE_NO_SANITIZE_ADDRESS_
+GTEST_ATTRIBUTE_NO_SANITIZE_HWADDRESS_
+GTEST_ATTRIBUTE_NO_SANITIZE_THREAD_
+static void UniversalPrintCharArray(
+    const CharType* begin, size_t len, ostream* os) {
+  // The code
+  //   const char kFoo[] = "foo";
+  // generates an array of 4, not 3, elements, with the last one being '\0'.
+  //
+  // Therefore when printing a char array, we don't print the last element if
+  // it's '\0', such that the output matches the string literal as it's
+  // written in the source code.
+  if (len > 0 && begin[len - 1] == '\0') {
+    PrintCharsAsStringTo(begin, len - 1, os);
+    return;
+  }
+
+  // If, however, the last element in the array is not '\0', e.g.
+  //    const char kFoo[] = { 'f', 'o', 'o' };
+  // we must print the entire array.  We also print a message to indicate
+  // that the array is not NUL-terminated.
+  PrintCharsAsStringTo(begin, len, os);
+  *os << " (no terminating NUL)";
+}
+
+// Prints a (const) char array of 'len' elements, starting at address 'begin'.
+void UniversalPrintArray(const char* begin, size_t len, ostream* os) {
+  UniversalPrintCharArray(begin, len, os);
+}
+
+#ifdef __cpp_char8_t
+// Prints a (const) char8_t array of 'len' elements, starting at address
+// 'begin'.
+void UniversalPrintArray(const char8_t* begin, size_t len, ostream* os) {
+  UniversalPrintCharArray(begin, len, os);
+}
+#endif
+
+// Prints a (const) char16_t array of 'len' elements, starting at address
+// 'begin'.
+void UniversalPrintArray(const char16_t* begin, size_t len, ostream* os) {
+  UniversalPrintCharArray(begin, len, os);
+}
+
+// Prints a (const) char32_t array of 'len' elements, starting at address
+// 'begin'.
+void UniversalPrintArray(const char32_t* begin, size_t len, ostream* os) {
+  UniversalPrintCharArray(begin, len, os);
+}
+
+// Prints a (const) wchar_t array of 'len' elements, starting at address
+// 'begin'.
+void UniversalPrintArray(const wchar_t* begin, size_t len, ostream* os) {
+  UniversalPrintCharArray(begin, len, os);
+}
+
+namespace {
+
+// Prints a null-terminated C-style string to the ostream.
+template <typename Char>
+void PrintCStringTo(const Char* s, ostream* os) {
+  if (s == nullptr) {
+    *os << "NULL";
+  } else {
+    *os << ImplicitCast_<const void*>(s) << " pointing to ";
+    PrintCharsAsStringTo(s, std::char_traits<Char>::length(s), os);
+  }
+}
+
+}  // anonymous namespace
+
+void PrintTo(const char* s, ostream* os) { PrintCStringTo(s, os); }
+
+#ifdef __cpp_char8_t
+void PrintTo(const char8_t* s, ostream* os) { PrintCStringTo(s, os); }
+#endif
+
+void PrintTo(const char16_t* s, ostream* os) { PrintCStringTo(s, os); }
+
+void PrintTo(const char32_t* s, ostream* os) { PrintCStringTo(s, os); }
+
+// MSVC compiler can be configured to define whar_t as a typedef
+// of unsigned short. Defining an overload for const wchar_t* in that case
+// would cause pointers to unsigned shorts be printed as wide strings,
+// possibly accessing more memory than intended and causing invalid
+// memory accesses. MSVC defines _NATIVE_WCHAR_T_DEFINED symbol when
+// wchar_t is implemented as a native type.
+#if !defined(_MSC_VER) || defined(_NATIVE_WCHAR_T_DEFINED)
+// Prints the given wide C string to the ostream.
+void PrintTo(const wchar_t* s, ostream* os) { PrintCStringTo(s, os); }
+#endif  // wchar_t is native
+
+namespace {
+
+bool ContainsUnprintableControlCodes(const char* str, size_t length) {
+  const unsigned char *s = reinterpret_cast<const unsigned char *>(str);
+
+  for (size_t i = 0; i < length; i++) {
+    unsigned char ch = *s++;
+    if (std::iscntrl(ch)) {
+        switch (ch) {
+        case '\t':
+        case '\n':
+        case '\r':
+          break;
+        default:
+          return true;
+        }
+      }
+  }
+  return false;
+}
+
+bool IsUTF8TrailByte(unsigned char t) { return 0x80 <= t && t<= 0xbf; }
+
+bool IsValidUTF8(const char* str, size_t length) {
+  const unsigned char *s = reinterpret_cast<const unsigned char *>(str);
+
+  for (size_t i = 0; i < length;) {
+    unsigned char lead = s[i++];
+
+    if (lead <= 0x7f) {
+      continue;  // single-byte character (ASCII) 0..7F
+    }
+    if (lead < 0xc2) {
+      return false;  // trail byte or non-shortest form
+    } else if (lead <= 0xdf && (i + 1) <= length && IsUTF8TrailByte(s[i])) {
+      ++i;  // 2-byte character
+    } else if (0xe0 <= lead && lead <= 0xef && (i + 2) <= length &&
+               IsUTF8TrailByte(s[i]) &&
+               IsUTF8TrailByte(s[i + 1]) &&
+               // check for non-shortest form and surrogate
+               (lead != 0xe0 || s[i] >= 0xa0) &&
+               (lead != 0xed || s[i] < 0xa0)) {
+      i += 2;  // 3-byte character
+    } else if (0xf0 <= lead && lead <= 0xf4 && (i + 3) <= length &&
+               IsUTF8TrailByte(s[i]) &&
+               IsUTF8TrailByte(s[i + 1]) &&
+               IsUTF8TrailByte(s[i + 2]) &&
+               // check for non-shortest form
+               (lead != 0xf0 || s[i] >= 0x90) &&
+               (lead != 0xf4 || s[i] < 0x90)) {
+      i += 3;  // 4-byte character
+    } else {
+      return false;
+    }
+  }
+  return true;
+}
+
+void ConditionalPrintAsText(const char* str, size_t length, ostream* os) {
+  if (!ContainsUnprintableControlCodes(str, length) &&
+      IsValidUTF8(str, length)) {
+    *os << "\n    As Text: \"" << str << "\"";
+  }
+}
+
+}  // anonymous namespace
+
+void PrintStringTo(const ::std::string& s, ostream* os) {
+  if (PrintCharsAsStringTo(s.data(), s.size(), os) == kHexEscape) {
+    if (GTEST_FLAG(print_utf8)) {
+      ConditionalPrintAsText(s.data(), s.size(), os);
+    }
+  }
+}
+
+#ifdef __cpp_char8_t
+void PrintU8StringTo(const ::std::u8string& s, ostream* os) {
+  PrintCharsAsStringTo(s.data(), s.size(), os);
+}
+#endif
+
+void PrintU16StringTo(const ::std::u16string& s, ostream* os) {
+  PrintCharsAsStringTo(s.data(), s.size(), os);
+}
+
+void PrintU32StringTo(const ::std::u32string& s, ostream* os) {
+  PrintCharsAsStringTo(s.data(), s.size(), os);
+}
+
+#if GTEST_HAS_STD_WSTRING
+void PrintWideStringTo(const ::std::wstring& s, ostream* os) {
+  PrintCharsAsStringTo(s.data(), s.size(), os);
+}
+#endif  // GTEST_HAS_STD_WSTRING
+
+}  // namespace internal
+
+}  // namespace testing
diff --git a/leveldb_base/third_party/googletest/googletest/src/gtest-test-part.cc b/leveldb_base/third_party/googletest/googletest/src/gtest-test-part.cc
new file mode 100644
index 0000000..a938683
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/src/gtest-test-part.cc
@@ -0,0 +1,108 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// The Google C++ Testing and Mocking Framework (Google Test)
+
+#include "gtest/gtest-test-part.h"
+
+#include "gtest/internal/gtest-port.h"
+#include "src/gtest-internal-inl.h"
+
+namespace testing {
+
+using internal::GetUnitTestImpl;
+
+// Gets the summary of the failure message by omitting the stack trace
+// in it.
+std::string TestPartResult::ExtractSummary(const char* message) {
+  const char* const stack_trace = strstr(message, internal::kStackTraceMarker);
+  return stack_trace == nullptr ? message : std::string(message, stack_trace);
+}
+
+// Prints a TestPartResult object.
+std::ostream& operator<<(std::ostream& os, const TestPartResult& result) {
+  return os << internal::FormatFileLocation(result.file_name(),
+                                            result.line_number())
+            << " "
+            << (result.type() == TestPartResult::kSuccess
+                    ? "Success"
+                    : result.type() == TestPartResult::kSkip
+                          ? "Skipped"
+                          : result.type() == TestPartResult::kFatalFailure
+                                ? "Fatal failure"
+                                : "Non-fatal failure")
+            << ":\n"
+            << result.message() << std::endl;
+}
+
+// Appends a TestPartResult to the array.
+void TestPartResultArray::Append(const TestPartResult& result) {
+  array_.push_back(result);
+}
+
+// Returns the TestPartResult at the given index (0-based).
+const TestPartResult& TestPartResultArray::GetTestPartResult(int index) const {
+  if (index < 0 || index >= size()) {
+    printf("\nInvalid index (%d) into TestPartResultArray.\n", index);
+    internal::posix::Abort();
+  }
+
+  return array_[static_cast<size_t>(index)];
+}
+
+// Returns the number of TestPartResult objects in the array.
+int TestPartResultArray::size() const {
+  return static_cast<int>(array_.size());
+}
+
+namespace internal {
+
+HasNewFatalFailureHelper::HasNewFatalFailureHelper()
+    : has_new_fatal_failure_(false),
+      original_reporter_(GetUnitTestImpl()->
+                         GetTestPartResultReporterForCurrentThread()) {
+  GetUnitTestImpl()->SetTestPartResultReporterForCurrentThread(this);
+}
+
+HasNewFatalFailureHelper::~HasNewFatalFailureHelper() {
+  GetUnitTestImpl()->SetTestPartResultReporterForCurrentThread(
+      original_reporter_);
+}
+
+void HasNewFatalFailureHelper::ReportTestPartResult(
+    const TestPartResult& result) {
+  if (result.fatally_failed())
+    has_new_fatal_failure_ = true;
+  original_reporter_->ReportTestPartResult(result);
+}
+
+}  // namespace internal
+
+}  // namespace testing
diff --git a/leveldb_base/third_party/googletest/googletest/src/gtest-typed-test.cc b/leveldb_base/third_party/googletest/googletest/src/gtest-typed-test.cc
new file mode 100644
index 0000000..c02c3df
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/src/gtest-typed-test.cc
@@ -0,0 +1,107 @@
+// Copyright 2008 Google Inc.
+// All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+#include "gtest/gtest-typed-test.h"
+
+#include "gtest/gtest.h"
+
+namespace testing {
+namespace internal {
+
+// Skips to the first non-space char in str. Returns an empty string if str
+// contains only whitespace characters.
+static const char* SkipSpaces(const char* str) {
+  while (IsSpace(*str))
+    str++;
+  return str;
+}
+
+static std::vector<std::string> SplitIntoTestNames(const char* src) {
+  std::vector<std::string> name_vec;
+  src = SkipSpaces(src);
+  for (; src != nullptr; src = SkipComma(src)) {
+    name_vec.push_back(StripTrailingSpaces(GetPrefixUntilComma(src)));
+  }
+  return name_vec;
+}
+
+// Verifies that registered_tests match the test names in
+// registered_tests_; returns registered_tests if successful, or
+// aborts the program otherwise.
+const char* TypedTestSuitePState::VerifyRegisteredTestNames(
+    const char* test_suite_name, const char* file, int line,
+    const char* registered_tests) {
+  RegisterTypeParameterizedTestSuite(test_suite_name, CodeLocation(file, line));
+
+  typedef RegisteredTestsMap::const_iterator RegisteredTestIter;
+  registered_ = true;
+
+  std::vector<std::string> name_vec = SplitIntoTestNames(registered_tests);
+
+  Message errors;
+
+  std::set<std::string> tests;
+  for (std::vector<std::string>::const_iterator name_it = name_vec.begin();
+       name_it != name_vec.end(); ++name_it) {
+    const std::string& name = *name_it;
+    if (tests.count(name) != 0) {
+      errors << "Test " << name << " is listed more than once.\n";
+      continue;
+    }
+
+    if (registered_tests_.count(name) != 0) {
+      tests.insert(name);
+    } else {
+      errors << "No test named " << name
+             << " can be found in this test suite.\n";
+    }
+  }
+
+  for (RegisteredTestIter it = registered_tests_.begin();
+       it != registered_tests_.end();
+       ++it) {
+    if (tests.count(it->first) == 0) {
+      errors << "You forgot to list test " << it->first << ".\n";
+    }
+  }
+
+  const std::string& errors_str = errors.GetString();
+  if (errors_str != "") {
+    fprintf(stderr, "%s %s", FormatFileLocation(file, line).c_str(),
+            errors_str.c_str());
+    fflush(stderr);
+    posix::Abort();
+  }
+
+  return registered_tests;
+}
+
+}  // namespace internal
+}  // namespace testing
diff --git a/leveldb_base/third_party/googletest/googletest/src/gtest.cc b/leveldb_base/third_party/googletest/googletest/src/gtest.cc
new file mode 100644
index 0000000..21c611a
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/src/gtest.cc
@@ -0,0 +1,6746 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// The Google C++ Testing and Mocking Framework (Google Test)
+
+#include "gtest/gtest.h"
+#include "gtest/internal/custom/gtest.h"
+#include "gtest/gtest-spi.h"
+
+#include <ctype.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <wchar.h>
+#include <wctype.h>
+
+#include <algorithm>
+#include <chrono>  // NOLINT
+#include <cmath>
+#include <cstdint>
+#include <iomanip>
+#include <limits>
+#include <list>
+#include <map>
+#include <ostream>  // NOLINT
+#include <sstream>
+#include <vector>
+
+#if GTEST_OS_LINUX
+
+# include <fcntl.h>  // NOLINT
+# include <limits.h>  // NOLINT
+# include <sched.h>  // NOLINT
+// Declares vsnprintf().  This header is not available on Windows.
+# include <strings.h>  // NOLINT
+# include <sys/mman.h>  // NOLINT
+# include <sys/time.h>  // NOLINT
+# include <unistd.h>  // NOLINT
+# include <string>
+
+#elif GTEST_OS_ZOS
+# include <sys/time.h>  // NOLINT
+
+// On z/OS we additionally need strings.h for strcasecmp.
+# include <strings.h>  // NOLINT
+
+#elif GTEST_OS_WINDOWS_MOBILE  // We are on Windows CE.
+
+# include <windows.h>  // NOLINT
+# undef min
+
+#elif GTEST_OS_WINDOWS  // We are on Windows proper.
+
+# include <windows.h>  // NOLINT
+# undef min
+
+#ifdef _MSC_VER
+# include <crtdbg.h>  // NOLINT
+#endif
+
+# include <io.h>  // NOLINT
+# include <sys/timeb.h>  // NOLINT
+# include <sys/types.h>  // NOLINT
+# include <sys/stat.h>  // NOLINT
+
+# if GTEST_OS_WINDOWS_MINGW
+#  include <sys/time.h>  // NOLINT
+# endif  // GTEST_OS_WINDOWS_MINGW
+
+#else
+
+// cpplint thinks that the header is already included, so we want to
+// silence it.
+# include <sys/time.h>  // NOLINT
+# include <unistd.h>  // NOLINT
+
+#endif  // GTEST_OS_LINUX
+
+#if GTEST_HAS_EXCEPTIONS
+# include <stdexcept>
+#endif
+
+#if GTEST_CAN_STREAM_RESULTS_
+# include <arpa/inet.h>  // NOLINT
+# include <netdb.h>  // NOLINT
+# include <sys/socket.h>  // NOLINT
+# include <sys/types.h>  // NOLINT
+#endif
+
+#include "src/gtest-internal-inl.h"
+
+#if GTEST_OS_WINDOWS
+# define vsnprintf _vsnprintf
+#endif  // GTEST_OS_WINDOWS
+
+#if GTEST_OS_MAC
+#ifndef GTEST_OS_IOS
+#include <crt_externs.h>
+#endif
+#endif
+
+#if GTEST_HAS_ABSL
+#include "absl/debugging/failure_signal_handler.h"
+#include "absl/debugging/stacktrace.h"
+#include "absl/debugging/symbolize.h"
+#include "absl/strings/str_cat.h"
+#endif  // GTEST_HAS_ABSL
+
+namespace testing {
+
+using internal::CountIf;
+using internal::ForEach;
+using internal::GetElementOr;
+using internal::Shuffle;
+
+// Constants.
+
+// A test whose test suite name or test name matches this filter is
+// disabled and not run.
+static const char kDisableTestFilter[] = "DISABLED_*:*/DISABLED_*";
+
+// A test suite whose name matches this filter is considered a death
+// test suite and will be run before test suites whose name doesn't
+// match this filter.
+static const char kDeathTestSuiteFilter[] = "*DeathTest:*DeathTest/*";
+
+// A test filter that matches everything.
+static const char kUniversalFilter[] = "*";
+
+// The default output format.
+static const char kDefaultOutputFormat[] = "xml";
+// The default output file.
+static const char kDefaultOutputFile[] = "test_detail";
+
+// The environment variable name for the test shard index.
+static const char kTestShardIndex[] = "GTEST_SHARD_INDEX";
+// The environment variable name for the total number of test shards.
+static const char kTestTotalShards[] = "GTEST_TOTAL_SHARDS";
+// The environment variable name for the test shard status file.
+static const char kTestShardStatusFile[] = "GTEST_SHARD_STATUS_FILE";
+
+namespace internal {
+
+// The text used in failure messages to indicate the start of the
+// stack trace.
+const char kStackTraceMarker[] = "\nStack trace:\n";
+
+// g_help_flag is true if and only if the --help flag or an equivalent form
+// is specified on the command line.
+bool g_help_flag = false;
+
+// Utilty function to Open File for Writing
+static FILE* OpenFileForWriting(const std::string& output_file) {
+  FILE* fileout = nullptr;
+  FilePath output_file_path(output_file);
+  FilePath output_dir(output_file_path.RemoveFileName());
+
+  if (output_dir.CreateDirectoriesRecursively()) {
+    fileout = posix::FOpen(output_file.c_str(), "w");
+  }
+  if (fileout == nullptr) {
+    GTEST_LOG_(FATAL) << "Unable to open file \"" << output_file << "\"";
+  }
+  return fileout;
+}
+
+}  // namespace internal
+
+// Bazel passes in the argument to '--test_filter' via the TESTBRIDGE_TEST_ONLY
+// environment variable.
+static const char* GetDefaultFilter() {
+  const char* const testbridge_test_only =
+      internal::posix::GetEnv("TESTBRIDGE_TEST_ONLY");
+  if (testbridge_test_only != nullptr) {
+    return testbridge_test_only;
+  }
+  return kUniversalFilter;
+}
+
+// Bazel passes in the argument to '--test_runner_fail_fast' via the
+// TESTBRIDGE_TEST_RUNNER_FAIL_FAST environment variable.
+static bool GetDefaultFailFast() {
+  const char* const testbridge_test_runner_fail_fast =
+      internal::posix::GetEnv("TESTBRIDGE_TEST_RUNNER_FAIL_FAST");
+  if (testbridge_test_runner_fail_fast != nullptr) {
+    return strcmp(testbridge_test_runner_fail_fast, "1") == 0;
+  }
+  return false;
+}
+
+GTEST_DEFINE_bool_(
+    fail_fast, internal::BoolFromGTestEnv("fail_fast", GetDefaultFailFast()),
+    "True if and only if a test failure should stop further test execution.");
+
+GTEST_DEFINE_bool_(
+    also_run_disabled_tests,
+    internal::BoolFromGTestEnv("also_run_disabled_tests", false),
+    "Run disabled tests too, in addition to the tests normally being run.");
+
+GTEST_DEFINE_bool_(
+    break_on_failure, internal::BoolFromGTestEnv("break_on_failure", false),
+    "True if and only if a failed assertion should be a debugger "
+    "break-point.");
+
+GTEST_DEFINE_bool_(catch_exceptions,
+                   internal::BoolFromGTestEnv("catch_exceptions", true),
+                   "True if and only if " GTEST_NAME_
+                   " should catch exceptions and treat them as test failures.");
+
+GTEST_DEFINE_string_(
+    color,
+    internal::StringFromGTestEnv("color", "auto"),
+    "Whether to use colors in the output.  Valid values: yes, no, "
+    "and auto.  'auto' means to use colors if the output is "
+    "being sent to a terminal and the TERM environment variable "
+    "is set to a terminal type that supports colors.");
+
+GTEST_DEFINE_string_(
+    filter,
+    internal::StringFromGTestEnv("filter", GetDefaultFilter()),
+    "A colon-separated list of glob (not regex) patterns "
+    "for filtering the tests to run, optionally followed by a "
+    "'-' and a : separated list of negative patterns (tests to "
+    "exclude).  A test is run if it matches one of the positive "
+    "patterns and does not match any of the negative patterns.");
+
+GTEST_DEFINE_bool_(
+    install_failure_signal_handler,
+    internal::BoolFromGTestEnv("install_failure_signal_handler", false),
+    "If true and supported on the current platform, " GTEST_NAME_ " should "
+    "install a signal handler that dumps debugging information when fatal "
+    "signals are raised.");
+
+GTEST_DEFINE_bool_(list_tests, false,
+                   "List all tests without running them.");
+
+// The net priority order after flag processing is thus:
+//   --gtest_output command line flag
+//   GTEST_OUTPUT environment variable
+//   XML_OUTPUT_FILE environment variable
+//   ''
+GTEST_DEFINE_string_(
+    output,
+    internal::StringFromGTestEnv("output",
+      internal::OutputFlagAlsoCheckEnvVar().c_str()),
+    "A format (defaults to \"xml\" but can be specified to be \"json\"), "
+    "optionally followed by a colon and an output file name or directory. "
+    "A directory is indicated by a trailing pathname separator. "
+    "Examples: \"xml:filename.xml\", \"xml::directoryname/\". "
+    "If a directory is specified, output files will be created "
+    "within that directory, with file-names based on the test "
+    "executable's name and, if necessary, made unique by adding "
+    "digits.");
+
+GTEST_DEFINE_bool_(
+    brief, internal::BoolFromGTestEnv("brief", false),
+    "True if only test failures should be displayed in text output.");
+
+GTEST_DEFINE_bool_(print_time, internal::BoolFromGTestEnv("print_time", true),
+                   "True if and only if " GTEST_NAME_
+                   " should display elapsed time in text output.");
+
+GTEST_DEFINE_bool_(print_utf8, internal::BoolFromGTestEnv("print_utf8", true),
+                   "True if and only if " GTEST_NAME_
+                   " prints UTF8 characters as text.");
+
+GTEST_DEFINE_int32_(
+    random_seed,
+    internal::Int32FromGTestEnv("random_seed", 0),
+    "Random number seed to use when shuffling test orders.  Must be in range "
+    "[1, 99999], or 0 to use a seed based on the current time.");
+
+GTEST_DEFINE_int32_(
+    repeat,
+    internal::Int32FromGTestEnv("repeat", 1),
+    "How many times to repeat each test.  Specify a negative number "
+    "for repeating forever.  Useful for shaking out flaky tests.");
+
+GTEST_DEFINE_bool_(show_internal_stack_frames, false,
+                   "True if and only if " GTEST_NAME_
+                   " should include internal stack frames when "
+                   "printing test failure stack traces.");
+
+GTEST_DEFINE_bool_(shuffle, internal::BoolFromGTestEnv("shuffle", false),
+                   "True if and only if " GTEST_NAME_
+                   " should randomize tests' order on every run.");
+
+GTEST_DEFINE_int32_(
+    stack_trace_depth,
+    internal::Int32FromGTestEnv("stack_trace_depth", kMaxStackTraceDepth),
+    "The maximum number of stack frames to print when an "
+    "assertion fails.  The valid range is 0 through 100, inclusive.");
+
+GTEST_DEFINE_string_(
+    stream_result_to,
+    internal::StringFromGTestEnv("stream_result_to", ""),
+    "This flag specifies the host name and the port number on which to stream "
+    "test results. Example: \"localhost:555\". The flag is effective only on "
+    "Linux.");
+
+GTEST_DEFINE_bool_(
+    throw_on_failure,
+    internal::BoolFromGTestEnv("throw_on_failure", false),
+    "When this flag is specified, a failed assertion will throw an exception "
+    "if exceptions are enabled or exit the program with a non-zero code "
+    "otherwise. For use with an external test framework.");
+
+#if GTEST_USE_OWN_FLAGFILE_FLAG_
+GTEST_DEFINE_string_(
+    flagfile,
+    internal::StringFromGTestEnv("flagfile", ""),
+    "This flag specifies the flagfile to read command-line flags from.");
+#endif  // GTEST_USE_OWN_FLAGFILE_FLAG_
+
+namespace internal {
+
+// Generates a random number from [0, range), using a Linear
+// Congruential Generator (LCG).  Crashes if 'range' is 0 or greater
+// than kMaxRange.
+uint32_t Random::Generate(uint32_t range) {
+  // These constants are the same as are used in glibc's rand(3).
+  // Use wider types than necessary to prevent unsigned overflow diagnostics.
+  state_ = static_cast<uint32_t>(1103515245ULL*state_ + 12345U) % kMaxRange;
+
+  GTEST_CHECK_(range > 0)
+      << "Cannot generate a number in the range [0, 0).";
+  GTEST_CHECK_(range <= kMaxRange)
+      << "Generation of a number in [0, " << range << ") was requested, "
+      << "but this can only generate numbers in [0, " << kMaxRange << ").";
+
+  // Converting via modulus introduces a bit of downward bias, but
+  // it's simple, and a linear congruential generator isn't too good
+  // to begin with.
+  return state_ % range;
+}
+
+// GTestIsInitialized() returns true if and only if the user has initialized
+// Google Test.  Useful for catching the user mistake of not initializing
+// Google Test before calling RUN_ALL_TESTS().
+static bool GTestIsInitialized() { return GetArgvs().size() > 0; }
+
+// Iterates over a vector of TestSuites, keeping a running sum of the
+// results of calling a given int-returning method on each.
+// Returns the sum.
+static int SumOverTestSuiteList(const std::vector<TestSuite*>& case_list,
+                                int (TestSuite::*method)() const) {
+  int sum = 0;
+  for (size_t i = 0; i < case_list.size(); i++) {
+    sum += (case_list[i]->*method)();
+  }
+  return sum;
+}
+
+// Returns true if and only if the test suite passed.
+static bool TestSuitePassed(const TestSuite* test_suite) {
+  return test_suite->should_run() && test_suite->Passed();
+}
+
+// Returns true if and only if the test suite failed.
+static bool TestSuiteFailed(const TestSuite* test_suite) {
+  return test_suite->should_run() && test_suite->Failed();
+}
+
+// Returns true if and only if test_suite contains at least one test that
+// should run.
+static bool ShouldRunTestSuite(const TestSuite* test_suite) {
+  return test_suite->should_run();
+}
+
+// AssertHelper constructor.
+AssertHelper::AssertHelper(TestPartResult::Type type,
+                           const char* file,
+                           int line,
+                           const char* message)
+    : data_(new AssertHelperData(type, file, line, message)) {
+}
+
+AssertHelper::~AssertHelper() {
+  delete data_;
+}
+
+// Message assignment, for assertion streaming support.
+void AssertHelper::operator=(const Message& message) const {
+  UnitTest::GetInstance()->
+    AddTestPartResult(data_->type, data_->file, data_->line,
+                      AppendUserMessage(data_->message, message),
+                      UnitTest::GetInstance()->impl()
+                      ->CurrentOsStackTraceExceptTop(1)
+                      // Skips the stack frame for this function itself.
+                      );  // NOLINT
+}
+
+namespace {
+
+// When TEST_P is found without a matching INSTANTIATE_TEST_SUITE_P
+// to creates test cases for it, a syntetic test case is
+// inserted to report ether an error or a log message.
+//
+// This configuration bit will likely be removed at some point.
+constexpr bool kErrorOnUninstantiatedParameterizedTest = true;
+constexpr bool kErrorOnUninstantiatedTypeParameterizedTest = true;
+
+// A test that fails at a given file/line location with a given message.
+class FailureTest : public Test {
+ public:
+  explicit FailureTest(const CodeLocation& loc, std::string error_message,
+                       bool as_error)
+      : loc_(loc),
+        error_message_(std::move(error_message)),
+        as_error_(as_error) {}
+
+  void TestBody() override {
+    if (as_error_) {
+      AssertHelper(TestPartResult::kNonFatalFailure, loc_.file.c_str(),
+                   loc_.line, "") = Message() << error_message_;
+    } else {
+      std::cout << error_message_ << std::endl;
+    }
+  }
+
+ private:
+  const CodeLocation loc_;
+  const std::string error_message_;
+  const bool as_error_;
+};
+
+
+}  // namespace
+
+std::set<std::string>* GetIgnoredParameterizedTestSuites() {
+  return UnitTest::GetInstance()->impl()->ignored_parameterized_test_suites();
+}
+
+// Add a given test_suit to the list of them allow to go un-instantiated.
+MarkAsIgnored::MarkAsIgnored(const char* test_suite) {
+  GetIgnoredParameterizedTestSuites()->insert(test_suite);
+}
+
+// If this parameterized test suite has no instantiations (and that
+// has not been marked as okay), emit a test case reporting that.
+void InsertSyntheticTestCase(const std::string& name, CodeLocation location,
+                             bool has_test_p) {
+  const auto& ignored = *GetIgnoredParameterizedTestSuites();
+  if (ignored.find(name) != ignored.end()) return;
+
+  const char kMissingInstantiation[] =  //
+      " is defined via TEST_P, but never instantiated. None of the test cases "
+      "will run. Either no INSTANTIATE_TEST_SUITE_P is provided or the only "
+      "ones provided expand to nothing."
+      "\n\n"
+      "Ideally, TEST_P definitions should only ever be included as part of "
+      "binaries that intend to use them. (As opposed to, for example, being "
+      "placed in a library that may be linked in to get other utilities.)";
+
+  const char kMissingTestCase[] =  //
+      " is instantiated via INSTANTIATE_TEST_SUITE_P, but no tests are "
+      "defined via TEST_P . No test cases will run."
+      "\n\n"
+      "Ideally, INSTANTIATE_TEST_SUITE_P should only ever be invoked from "
+      "code that always depend on code that provides TEST_P. Failing to do "
+      "so is often an indication of dead code, e.g. the last TEST_P was "
+      "removed but the rest got left behind.";
+
+  std::string message =
+      "Parameterized test suite " + name +
+      (has_test_p ? kMissingInstantiation : kMissingTestCase) +
+      "\n\n"
+      "To suppress this error for this test suite, insert the following line "
+      "(in a non-header) in the namespace it is defined in:"
+      "\n\n"
+      "GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST(" + name + ");";
+
+  std::string full_name = "UninstantiatedParameterizedTestSuite<" + name + ">";
+  RegisterTest(  //
+      "GoogleTestVerification", full_name.c_str(),
+      nullptr,  // No type parameter.
+      nullptr,  // No value parameter.
+      location.file.c_str(), location.line, [message, location] {
+        return new FailureTest(location, message,
+                               kErrorOnUninstantiatedParameterizedTest);
+      });
+}
+
+void RegisterTypeParameterizedTestSuite(const char* test_suite_name,
+                                        CodeLocation code_location) {
+  GetUnitTestImpl()->type_parameterized_test_registry().RegisterTestSuite(
+      test_suite_name, code_location);
+}
+
+void RegisterTypeParameterizedTestSuiteInstantiation(const char* case_name) {
+  GetUnitTestImpl()
+      ->type_parameterized_test_registry()
+      .RegisterInstantiation(case_name);
+}
+
+void TypeParameterizedTestSuiteRegistry::RegisterTestSuite(
+    const char* test_suite_name, CodeLocation code_location) {
+  suites_.emplace(std::string(test_suite_name),
+                 TypeParameterizedTestSuiteInfo(code_location));
+}
+
+void TypeParameterizedTestSuiteRegistry::RegisterInstantiation(
+        const char* test_suite_name) {
+  auto it = suites_.find(std::string(test_suite_name));
+  if (it != suites_.end()) {
+    it->second.instantiated = true;
+  } else {
+    GTEST_LOG_(ERROR) << "Unknown type parameterized test suit '"
+                      << test_suite_name << "'";
+  }
+}
+
+void TypeParameterizedTestSuiteRegistry::CheckForInstantiations() {
+  const auto& ignored = *GetIgnoredParameterizedTestSuites();
+  for (const auto& testcase : suites_) {
+    if (testcase.second.instantiated) continue;
+    if (ignored.find(testcase.first) != ignored.end()) continue;
+
+    std::string message =
+        "Type parameterized test suite " + testcase.first +
+        " is defined via REGISTER_TYPED_TEST_SUITE_P, but never instantiated "
+        "via INSTANTIATE_TYPED_TEST_SUITE_P. None of the test cases will run."
+        "\n\n"
+        "Ideally, TYPED_TEST_P definitions should only ever be included as "
+        "part of binaries that intend to use them. (As opposed to, for "
+        "example, being placed in a library that may be linked in to get other "
+        "utilities.)"
+        "\n\n"
+        "To suppress this error for this test suite, insert the following line "
+        "(in a non-header) in the namespace it is defined in:"
+        "\n\n"
+        "GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST(" +
+        testcase.first + ");";
+
+    std::string full_name =
+        "UninstantiatedTypeParameterizedTestSuite<" + testcase.first + ">";
+    RegisterTest(  //
+        "GoogleTestVerification", full_name.c_str(),
+        nullptr,  // No type parameter.
+        nullptr,  // No value parameter.
+        testcase.second.code_location.file.c_str(),
+        testcase.second.code_location.line, [message, testcase] {
+          return new FailureTest(testcase.second.code_location, message,
+                                 kErrorOnUninstantiatedTypeParameterizedTest);
+        });
+  }
+}
+
+// A copy of all command line arguments.  Set by InitGoogleTest().
+static ::std::vector<std::string> g_argvs;
+
+::std::vector<std::string> GetArgvs() {
+#if defined(GTEST_CUSTOM_GET_ARGVS_)
+  // GTEST_CUSTOM_GET_ARGVS_() may return a container of std::string or
+  // ::string. This code converts it to the appropriate type.
+  const auto& custom = GTEST_CUSTOM_GET_ARGVS_();
+  return ::std::vector<std::string>(custom.begin(), custom.end());
+#else   // defined(GTEST_CUSTOM_GET_ARGVS_)
+  return g_argvs;
+#endif  // defined(GTEST_CUSTOM_GET_ARGVS_)
+}
+
+// Returns the current application's name, removing directory path if that
+// is present.
+FilePath GetCurrentExecutableName() {
+  FilePath result;
+
+#if GTEST_OS_WINDOWS || GTEST_OS_OS2
+  result.Set(FilePath(GetArgvs()[0]).RemoveExtension("exe"));
+#else
+  result.Set(FilePath(GetArgvs()[0]));
+#endif  // GTEST_OS_WINDOWS
+
+  return result.RemoveDirectoryName();
+}
+
+// Functions for processing the gtest_output flag.
+
+// Returns the output format, or "" for normal printed output.
+std::string UnitTestOptions::GetOutputFormat() {
+  const char* const gtest_output_flag = GTEST_FLAG(output).c_str();
+  const char* const colon = strchr(gtest_output_flag, ':');
+  return (colon == nullptr)
+             ? std::string(gtest_output_flag)
+             : std::string(gtest_output_flag,
+                           static_cast<size_t>(colon - gtest_output_flag));
+}
+
+// Returns the name of the requested output file, or the default if none
+// was explicitly specified.
+std::string UnitTestOptions::GetAbsolutePathToOutputFile() {
+  const char* const gtest_output_flag = GTEST_FLAG(output).c_str();
+
+  std::string format = GetOutputFormat();
+  if (format.empty())
+    format = std::string(kDefaultOutputFormat);
+
+  const char* const colon = strchr(gtest_output_flag, ':');
+  if (colon == nullptr)
+    return internal::FilePath::MakeFileName(
+        internal::FilePath(
+            UnitTest::GetInstance()->original_working_dir()),
+        internal::FilePath(kDefaultOutputFile), 0,
+        format.c_str()).string();
+
+  internal::FilePath output_name(colon + 1);
+  if (!output_name.IsAbsolutePath())
+    output_name = internal::FilePath::ConcatPaths(
+        internal::FilePath(UnitTest::GetInstance()->original_working_dir()),
+        internal::FilePath(colon + 1));
+
+  if (!output_name.IsDirectory())
+    return output_name.string();
+
+  internal::FilePath result(internal::FilePath::GenerateUniqueFileName(
+      output_name, internal::GetCurrentExecutableName(),
+      GetOutputFormat().c_str()));
+  return result.string();
+}
+
+// Returns true if and only if the wildcard pattern matches the string. Each
+// pattern consists of regular characters, single-character wildcards (?), and
+// multi-character wildcards (*).
+//
+// This function implements a linear-time string globbing algorithm based on
+// https://research.swtch.com/glob.
+static bool PatternMatchesString(const std::string& name_str,
+                                 const char* pattern, const char* pattern_end) {
+  const char* name = name_str.c_str();
+  const char* const name_begin = name;
+  const char* const name_end = name + name_str.size();
+
+  const char* pattern_next = pattern;
+  const char* name_next = name;
+
+  while (pattern < pattern_end || name < name_end) {
+    if (pattern < pattern_end) {
+      switch (*pattern) {
+        default:  // Match an ordinary character.
+          if (name < name_end && *name == *pattern) {
+            ++pattern;
+            ++name;
+            continue;
+          }
+          break;
+        case '?':  // Match any single character.
+          if (name < name_end) {
+            ++pattern;
+            ++name;
+            continue;
+          }
+          break;
+        case '*':
+          // Match zero or more characters. Start by skipping over the wildcard
+          // and matching zero characters from name. If that fails, restart and
+          // match one more character than the last attempt.
+          pattern_next = pattern;
+          name_next = name + 1;
+          ++pattern;
+          continue;
+      }
+    }
+    // Failed to match a character. Restart if possible.
+    if (name_begin < name_next && name_next <= name_end) {
+      pattern = pattern_next;
+      name = name_next;
+      continue;
+    }
+    return false;
+  }
+  return true;
+}
+
+bool UnitTestOptions::MatchesFilter(const std::string& name_str,
+                                    const char* filter) {
+  // The filter is a list of patterns separated by colons (:).
+  const char* pattern = filter;
+  while (true) {
+    // Find the bounds of this pattern.
+    const char* const next_sep = strchr(pattern, ':');
+    const char* const pattern_end =
+        next_sep != nullptr ? next_sep : pattern + strlen(pattern);
+
+    // Check if this pattern matches name_str.
+    if (PatternMatchesString(name_str, pattern, pattern_end)) {
+      return true;
+    }
+
+    // Give up on this pattern. However, if we found a pattern separator (:),
+    // advance to the next pattern (skipping over the separator) and restart.
+    if (next_sep == nullptr) {
+      return false;
+    }
+    pattern = next_sep + 1;
+  }
+  return true;
+}
+
+// Returns true if and only if the user-specified filter matches the test
+// suite name and the test name.
+bool UnitTestOptions::FilterMatchesTest(const std::string& test_suite_name,
+                                        const std::string& test_name) {
+  const std::string& full_name = test_suite_name + "." + test_name.c_str();
+
+  // Split --gtest_filter at '-', if there is one, to separate into
+  // positive filter and negative filter portions
+  const char* const p = GTEST_FLAG(filter).c_str();
+  const char* const dash = strchr(p, '-');
+  std::string positive;
+  std::string negative;
+  if (dash == nullptr) {
+    positive = GTEST_FLAG(filter).c_str();  // Whole string is a positive filter
+    negative = "";
+  } else {
+    positive = std::string(p, dash);   // Everything up to the dash
+    negative = std::string(dash + 1);  // Everything after the dash
+    if (positive.empty()) {
+      // Treat '-test1' as the same as '*-test1'
+      positive = kUniversalFilter;
+    }
+  }
+
+  // A filter is a colon-separated list of patterns.  It matches a
+  // test if any pattern in it matches the test.
+  return (MatchesFilter(full_name, positive.c_str()) &&
+          !MatchesFilter(full_name, negative.c_str()));
+}
+
+#if GTEST_HAS_SEH
+// Returns EXCEPTION_EXECUTE_HANDLER if Google Test should handle the
+// given SEH exception, or EXCEPTION_CONTINUE_SEARCH otherwise.
+// This function is useful as an __except condition.
+int UnitTestOptions::GTestShouldProcessSEH(DWORD exception_code) {
+  // Google Test should handle a SEH exception if:
+  //   1. the user wants it to, AND
+  //   2. this is not a breakpoint exception, AND
+  //   3. this is not a C++ exception (VC++ implements them via SEH,
+  //      apparently).
+  //
+  // SEH exception code for C++ exceptions.
+  // (see http://support.microsoft.com/kb/185294 for more information).
+  const DWORD kCxxExceptionCode = 0xe06d7363;
+
+  bool should_handle = true;
+
+  if (!GTEST_FLAG(catch_exceptions))
+    should_handle = false;
+  else if (exception_code == EXCEPTION_BREAKPOINT)
+    should_handle = false;
+  else if (exception_code == kCxxExceptionCode)
+    should_handle = false;
+
+  return should_handle ? EXCEPTION_EXECUTE_HANDLER : EXCEPTION_CONTINUE_SEARCH;
+}
+#endif  // GTEST_HAS_SEH
+
+}  // namespace internal
+
+// The c'tor sets this object as the test part result reporter used by
+// Google Test.  The 'result' parameter specifies where to report the
+// results. Intercepts only failures from the current thread.
+ScopedFakeTestPartResultReporter::ScopedFakeTestPartResultReporter(
+    TestPartResultArray* result)
+    : intercept_mode_(INTERCEPT_ONLY_CURRENT_THREAD),
+      result_(result) {
+  Init();
+}
+
+// The c'tor sets this object as the test part result reporter used by
+// Google Test.  The 'result' parameter specifies where to report the
+// results.
+ScopedFakeTestPartResultReporter::ScopedFakeTestPartResultReporter(
+    InterceptMode intercept_mode, TestPartResultArray* result)
+    : intercept_mode_(intercept_mode),
+      result_(result) {
+  Init();
+}
+
+void ScopedFakeTestPartResultReporter::Init() {
+  internal::UnitTestImpl* const impl = internal::GetUnitTestImpl();
+  if (intercept_mode_ == INTERCEPT_ALL_THREADS) {
+    old_reporter_ = impl->GetGlobalTestPartResultReporter();
+    impl->SetGlobalTestPartResultReporter(this);
+  } else {
+    old_reporter_ = impl->GetTestPartResultReporterForCurrentThread();
+    impl->SetTestPartResultReporterForCurrentThread(this);
+  }
+}
+
+// The d'tor restores the test part result reporter used by Google Test
+// before.
+ScopedFakeTestPartResultReporter::~ScopedFakeTestPartResultReporter() {
+  internal::UnitTestImpl* const impl = internal::GetUnitTestImpl();
+  if (intercept_mode_ == INTERCEPT_ALL_THREADS) {
+    impl->SetGlobalTestPartResultReporter(old_reporter_);
+  } else {
+    impl->SetTestPartResultReporterForCurrentThread(old_reporter_);
+  }
+}
+
+// Increments the test part result count and remembers the result.
+// This method is from the TestPartResultReporterInterface interface.
+void ScopedFakeTestPartResultReporter::ReportTestPartResult(
+    const TestPartResult& result) {
+  result_->Append(result);
+}
+
+namespace internal {
+
+// Returns the type ID of ::testing::Test.  We should always call this
+// instead of GetTypeId< ::testing::Test>() to get the type ID of
+// testing::Test.  This is to work around a suspected linker bug when
+// using Google Test as a framework on Mac OS X.  The bug causes
+// GetTypeId< ::testing::Test>() to return different values depending
+// on whether the call is from the Google Test framework itself or
+// from user test code.  GetTestTypeId() is guaranteed to always
+// return the same value, as it always calls GetTypeId<>() from the
+// gtest.cc, which is within the Google Test framework.
+TypeId GetTestTypeId() {
+  return GetTypeId<Test>();
+}
+
+// The value of GetTestTypeId() as seen from within the Google Test
+// library.  This is solely for testing GetTestTypeId().
+extern const TypeId kTestTypeIdInGoogleTest = GetTestTypeId();
+
+// This predicate-formatter checks that 'results' contains a test part
+// failure of the given type and that the failure message contains the
+// given substring.
+static AssertionResult HasOneFailure(const char* /* results_expr */,
+                                     const char* /* type_expr */,
+                                     const char* /* substr_expr */,
+                                     const TestPartResultArray& results,
+                                     TestPartResult::Type type,
+                                     const std::string& substr) {
+  const std::string expected(type == TestPartResult::kFatalFailure ?
+                        "1 fatal failure" :
+                        "1 non-fatal failure");
+  Message msg;
+  if (results.size() != 1) {
+    msg << "Expected: " << expected << "\n"
+        << "  Actual: " << results.size() << " failures";
+    for (int i = 0; i < results.size(); i++) {
+      msg << "\n" << results.GetTestPartResult(i);
+    }
+    return AssertionFailure() << msg;
+  }
+
+  const TestPartResult& r = results.GetTestPartResult(0);
+  if (r.type() != type) {
+    return AssertionFailure() << "Expected: " << expected << "\n"
+                              << "  Actual:\n"
+                              << r;
+  }
+
+  if (strstr(r.message(), substr.c_str()) == nullptr) {
+    return AssertionFailure() << "Expected: " << expected << " containing \""
+                              << substr << "\"\n"
+                              << "  Actual:\n"
+                              << r;
+  }
+
+  return AssertionSuccess();
+}
+
+// The constructor of SingleFailureChecker remembers where to look up
+// test part results, what type of failure we expect, and what
+// substring the failure message should contain.
+SingleFailureChecker::SingleFailureChecker(const TestPartResultArray* results,
+                                           TestPartResult::Type type,
+                                           const std::string& substr)
+    : results_(results), type_(type), substr_(substr) {}
+
+// The destructor of SingleFailureChecker verifies that the given
+// TestPartResultArray contains exactly one failure that has the given
+// type and contains the given substring.  If that's not the case, a
+// non-fatal failure will be generated.
+SingleFailureChecker::~SingleFailureChecker() {
+  EXPECT_PRED_FORMAT3(HasOneFailure, *results_, type_, substr_);
+}
+
+DefaultGlobalTestPartResultReporter::DefaultGlobalTestPartResultReporter(
+    UnitTestImpl* unit_test) : unit_test_(unit_test) {}
+
+void DefaultGlobalTestPartResultReporter::ReportTestPartResult(
+    const TestPartResult& result) {
+  unit_test_->current_test_result()->AddTestPartResult(result);
+  unit_test_->listeners()->repeater()->OnTestPartResult(result);
+}
+
+DefaultPerThreadTestPartResultReporter::DefaultPerThreadTestPartResultReporter(
+    UnitTestImpl* unit_test) : unit_test_(unit_test) {}
+
+void DefaultPerThreadTestPartResultReporter::ReportTestPartResult(
+    const TestPartResult& result) {
+  unit_test_->GetGlobalTestPartResultReporter()->ReportTestPartResult(result);
+}
+
+// Returns the global test part result reporter.
+TestPartResultReporterInterface*
+UnitTestImpl::GetGlobalTestPartResultReporter() {
+  internal::MutexLock lock(&global_test_part_result_reporter_mutex_);
+  return global_test_part_result_repoter_;
+}
+
+// Sets the global test part result reporter.
+void UnitTestImpl::SetGlobalTestPartResultReporter(
+    TestPartResultReporterInterface* reporter) {
+  internal::MutexLock lock(&global_test_part_result_reporter_mutex_);
+  global_test_part_result_repoter_ = reporter;
+}
+
+// Returns the test part result reporter for the current thread.
+TestPartResultReporterInterface*
+UnitTestImpl::GetTestPartResultReporterForCurrentThread() {
+  return per_thread_test_part_result_reporter_.get();
+}
+
+// Sets the test part result reporter for the current thread.
+void UnitTestImpl::SetTestPartResultReporterForCurrentThread(
+    TestPartResultReporterInterface* reporter) {
+  per_thread_test_part_result_reporter_.set(reporter);
+}
+
+// Gets the number of successful test suites.
+int UnitTestImpl::successful_test_suite_count() const {
+  return CountIf(test_suites_, TestSuitePassed);
+}
+
+// Gets the number of failed test suites.
+int UnitTestImpl::failed_test_suite_count() const {
+  return CountIf(test_suites_, TestSuiteFailed);
+}
+
+// Gets the number of all test suites.
+int UnitTestImpl::total_test_suite_count() const {
+  return static_cast<int>(test_suites_.size());
+}
+
+// Gets the number of all test suites that contain at least one test
+// that should run.
+int UnitTestImpl::test_suite_to_run_count() const {
+  return CountIf(test_suites_, ShouldRunTestSuite);
+}
+
+// Gets the number of successful tests.
+int UnitTestImpl::successful_test_count() const {
+  return SumOverTestSuiteList(test_suites_, &TestSuite::successful_test_count);
+}
+
+// Gets the number of skipped tests.
+int UnitTestImpl::skipped_test_count() const {
+  return SumOverTestSuiteList(test_suites_, &TestSuite::skipped_test_count);
+}
+
+// Gets the number of failed tests.
+int UnitTestImpl::failed_test_count() const {
+  return SumOverTestSuiteList(test_suites_, &TestSuite::failed_test_count);
+}
+
+// Gets the number of disabled tests that will be reported in the XML report.
+int UnitTestImpl::reportable_disabled_test_count() const {
+  return SumOverTestSuiteList(test_suites_,
+                              &TestSuite::reportable_disabled_test_count);
+}
+
+// Gets the number of disabled tests.
+int UnitTestImpl::disabled_test_count() const {
+  return SumOverTestSuiteList(test_suites_, &TestSuite::disabled_test_count);
+}
+
+// Gets the number of tests to be printed in the XML report.
+int UnitTestImpl::reportable_test_count() const {
+  return SumOverTestSuiteList(test_suites_, &TestSuite::reportable_test_count);
+}
+
+// Gets the number of all tests.
+int UnitTestImpl::total_test_count() const {
+  return SumOverTestSuiteList(test_suites_, &TestSuite::total_test_count);
+}
+
+// Gets the number of tests that should run.
+int UnitTestImpl::test_to_run_count() const {
+  return SumOverTestSuiteList(test_suites_, &TestSuite::test_to_run_count);
+}
+
+// Returns the current OS stack trace as an std::string.
+//
+// The maximum number of stack frames to be included is specified by
+// the gtest_stack_trace_depth flag.  The skip_count parameter
+// specifies the number of top frames to be skipped, which doesn't
+// count against the number of frames to be included.
+//
+// For example, if Foo() calls Bar(), which in turn calls
+// CurrentOsStackTraceExceptTop(1), Foo() will be included in the
+// trace but Bar() and CurrentOsStackTraceExceptTop() won't.
+std::string UnitTestImpl::CurrentOsStackTraceExceptTop(int skip_count) {
+  return os_stack_trace_getter()->CurrentStackTrace(
+      static_cast<int>(GTEST_FLAG(stack_trace_depth)),
+      skip_count + 1
+      // Skips the user-specified number of frames plus this function
+      // itself.
+      );  // NOLINT
+}
+
+// A helper class for measuring elapsed times.
+class Timer {
+ public:
+  Timer() : start_(std::chrono::steady_clock::now()) {}
+
+  // Return time elapsed in milliseconds since the timer was created.
+  TimeInMillis Elapsed() {
+    return std::chrono::duration_cast<std::chrono::milliseconds>(
+               std::chrono::steady_clock::now() - start_)
+        .count();
+  }
+
+ private:
+  std::chrono::steady_clock::time_point start_;
+};
+
+// Returns a timestamp as milliseconds since the epoch. Note this time may jump
+// around subject to adjustments by the system, to measure elapsed time use
+// Timer instead.
+TimeInMillis GetTimeInMillis() {
+  return std::chrono::duration_cast<std::chrono::milliseconds>(
+             std::chrono::system_clock::now() -
+             std::chrono::system_clock::from_time_t(0))
+      .count();
+}
+
+// Utilities
+
+// class String.
+
+#if GTEST_OS_WINDOWS_MOBILE
+// Creates a UTF-16 wide string from the given ANSI string, allocating
+// memory using new. The caller is responsible for deleting the return
+// value using delete[]. Returns the wide string, or NULL if the
+// input is NULL.
+LPCWSTR String::AnsiToUtf16(const char* ansi) {
+  if (!ansi) return nullptr;
+  const int length = strlen(ansi);
+  const int unicode_length =
+      MultiByteToWideChar(CP_ACP, 0, ansi, length, nullptr, 0);
+  WCHAR* unicode = new WCHAR[unicode_length + 1];
+  MultiByteToWideChar(CP_ACP, 0, ansi, length,
+                      unicode, unicode_length);
+  unicode[unicode_length] = 0;
+  return unicode;
+}
+
+// Creates an ANSI string from the given wide string, allocating
+// memory using new. The caller is responsible for deleting the return
+// value using delete[]. Returns the ANSI string, or NULL if the
+// input is NULL.
+const char* String::Utf16ToAnsi(LPCWSTR utf16_str)  {
+  if (!utf16_str) return nullptr;
+  const int ansi_length = WideCharToMultiByte(CP_ACP, 0, utf16_str, -1, nullptr,
+                                              0, nullptr, nullptr);
+  char* ansi = new char[ansi_length + 1];
+  WideCharToMultiByte(CP_ACP, 0, utf16_str, -1, ansi, ansi_length, nullptr,
+                      nullptr);
+  ansi[ansi_length] = 0;
+  return ansi;
+}
+
+#endif  // GTEST_OS_WINDOWS_MOBILE
+
+// Compares two C strings.  Returns true if and only if they have the same
+// content.
+//
+// Unlike strcmp(), this function can handle NULL argument(s).  A NULL
+// C string is considered different to any non-NULL C string,
+// including the empty string.
+bool String::CStringEquals(const char * lhs, const char * rhs) {
+  if (lhs == nullptr) return rhs == nullptr;
+
+  if (rhs == nullptr) return false;
+
+  return strcmp(lhs, rhs) == 0;
+}
+
+#if GTEST_HAS_STD_WSTRING
+
+// Converts an array of wide chars to a narrow string using the UTF-8
+// encoding, and streams the result to the given Message object.
+static void StreamWideCharsToMessage(const wchar_t* wstr, size_t length,
+                                     Message* msg) {
+  for (size_t i = 0; i != length; ) {  // NOLINT
+    if (wstr[i] != L'\0') {
+      *msg << WideStringToUtf8(wstr + i, static_cast<int>(length - i));
+      while (i != length && wstr[i] != L'\0')
+        i++;
+    } else {
+      *msg << '\0';
+      i++;
+    }
+  }
+}
+
+#endif  // GTEST_HAS_STD_WSTRING
+
+void SplitString(const ::std::string& str, char delimiter,
+                 ::std::vector< ::std::string>* dest) {
+  ::std::vector< ::std::string> parsed;
+  ::std::string::size_type pos = 0;
+  while (::testing::internal::AlwaysTrue()) {
+    const ::std::string::size_type colon = str.find(delimiter, pos);
+    if (colon == ::std::string::npos) {
+      parsed.push_back(str.substr(pos));
+      break;
+    } else {
+      parsed.push_back(str.substr(pos, colon - pos));
+      pos = colon + 1;
+    }
+  }
+  dest->swap(parsed);
+}
+
+}  // namespace internal
+
+// Constructs an empty Message.
+// We allocate the stringstream separately because otherwise each use of
+// ASSERT/EXPECT in a procedure adds over 200 bytes to the procedure's
+// stack frame leading to huge stack frames in some cases; gcc does not reuse
+// the stack space.
+Message::Message() : ss_(new ::std::stringstream) {
+  // By default, we want there to be enough precision when printing
+  // a double to a Message.
+  *ss_ << std::setprecision(std::numeric_limits<double>::digits10 + 2);
+}
+
+// These two overloads allow streaming a wide C string to a Message
+// using the UTF-8 encoding.
+Message& Message::operator <<(const wchar_t* wide_c_str) {
+  return *this << internal::String::ShowWideCString(wide_c_str);
+}
+Message& Message::operator <<(wchar_t* wide_c_str) {
+  return *this << internal::String::ShowWideCString(wide_c_str);
+}
+
+#if GTEST_HAS_STD_WSTRING
+// Converts the given wide string to a narrow string using the UTF-8
+// encoding, and streams the result to this Message object.
+Message& Message::operator <<(const ::std::wstring& wstr) {
+  internal::StreamWideCharsToMessage(wstr.c_str(), wstr.length(), this);
+  return *this;
+}
+#endif  // GTEST_HAS_STD_WSTRING
+
+// Gets the text streamed to this object so far as an std::string.
+// Each '\0' character in the buffer is replaced with "\\0".
+std::string Message::GetString() const {
+  return internal::StringStreamToString(ss_.get());
+}
+
+// AssertionResult constructors.
+// Used in EXPECT_TRUE/FALSE(assertion_result).
+AssertionResult::AssertionResult(const AssertionResult& other)
+    : success_(other.success_),
+      message_(other.message_.get() != nullptr
+                   ? new ::std::string(*other.message_)
+                   : static_cast< ::std::string*>(nullptr)) {}
+
+// Swaps two AssertionResults.
+void AssertionResult::swap(AssertionResult& other) {
+  using std::swap;
+  swap(success_, other.success_);
+  swap(message_, other.message_);
+}
+
+// Returns the assertion's negation. Used with EXPECT/ASSERT_FALSE.
+AssertionResult AssertionResult::operator!() const {
+  AssertionResult negation(!success_);
+  if (message_.get() != nullptr) negation << *message_;
+  return negation;
+}
+
+// Makes a successful assertion result.
+AssertionResult AssertionSuccess() {
+  return AssertionResult(true);
+}
+
+// Makes a failed assertion result.
+AssertionResult AssertionFailure() {
+  return AssertionResult(false);
+}
+
+// Makes a failed assertion result with the given failure message.
+// Deprecated; use AssertionFailure() << message.
+AssertionResult AssertionFailure(const Message& message) {
+  return AssertionFailure() << message;
+}
+
+namespace internal {
+
+namespace edit_distance {
+std::vector<EditType> CalculateOptimalEdits(const std::vector<size_t>& left,
+                                            const std::vector<size_t>& right) {
+  std::vector<std::vector<double> > costs(
+      left.size() + 1, std::vector<double>(right.size() + 1));
+  std::vector<std::vector<EditType> > best_move(
+      left.size() + 1, std::vector<EditType>(right.size() + 1));
+
+  // Populate for empty right.
+  for (size_t l_i = 0; l_i < costs.size(); ++l_i) {
+    costs[l_i][0] = static_cast<double>(l_i);
+    best_move[l_i][0] = kRemove;
+  }
+  // Populate for empty left.
+  for (size_t r_i = 1; r_i < costs[0].size(); ++r_i) {
+    costs[0][r_i] = static_cast<double>(r_i);
+    best_move[0][r_i] = kAdd;
+  }
+
+  for (size_t l_i = 0; l_i < left.size(); ++l_i) {
+    for (size_t r_i = 0; r_i < right.size(); ++r_i) {
+      if (left[l_i] == right[r_i]) {
+        // Found a match. Consume it.
+        costs[l_i + 1][r_i + 1] = costs[l_i][r_i];
+        best_move[l_i + 1][r_i + 1] = kMatch;
+        continue;
+      }
+
+      const double add = costs[l_i + 1][r_i];
+      const double remove = costs[l_i][r_i + 1];
+      const double replace = costs[l_i][r_i];
+      if (add < remove && add < replace) {
+        costs[l_i + 1][r_i + 1] = add + 1;
+        best_move[l_i + 1][r_i + 1] = kAdd;
+      } else if (remove < add && remove < replace) {
+        costs[l_i + 1][r_i + 1] = remove + 1;
+        best_move[l_i + 1][r_i + 1] = kRemove;
+      } else {
+        // We make replace a little more expensive than add/remove to lower
+        // their priority.
+        costs[l_i + 1][r_i + 1] = replace + 1.00001;
+        best_move[l_i + 1][r_i + 1] = kReplace;
+      }
+    }
+  }
+
+  // Reconstruct the best path. We do it in reverse order.
+  std::vector<EditType> best_path;
+  for (size_t l_i = left.size(), r_i = right.size(); l_i > 0 || r_i > 0;) {
+    EditType move = best_move[l_i][r_i];
+    best_path.push_back(move);
+    l_i -= move != kAdd;
+    r_i -= move != kRemove;
+  }
+  std::reverse(best_path.begin(), best_path.end());
+  return best_path;
+}
+
+namespace {
+
+// Helper class to convert string into ids with deduplication.
+class InternalStrings {
+ public:
+  size_t GetId(const std::string& str) {
+    IdMap::iterator it = ids_.find(str);
+    if (it != ids_.end()) return it->second;
+    size_t id = ids_.size();
+    return ids_[str] = id;
+  }
+
+ private:
+  typedef std::map<std::string, size_t> IdMap;
+  IdMap ids_;
+};
+
+}  // namespace
+
+std::vector<EditType> CalculateOptimalEdits(
+    const std::vector<std::string>& left,
+    const std::vector<std::string>& right) {
+  std::vector<size_t> left_ids, right_ids;
+  {
+    InternalStrings intern_table;
+    for (size_t i = 0; i < left.size(); ++i) {
+      left_ids.push_back(intern_table.GetId(left[i]));
+    }
+    for (size_t i = 0; i < right.size(); ++i) {
+      right_ids.push_back(intern_table.GetId(right[i]));
+    }
+  }
+  return CalculateOptimalEdits(left_ids, right_ids);
+}
+
+namespace {
+
+// Helper class that holds the state for one hunk and prints it out to the
+// stream.
+// It reorders adds/removes when possible to group all removes before all
+// adds. It also adds the hunk header before printint into the stream.
+class Hunk {
+ public:
+  Hunk(size_t left_start, size_t right_start)
+      : left_start_(left_start),
+        right_start_(right_start),
+        adds_(),
+        removes_(),
+        common_() {}
+
+  void PushLine(char edit, const char* line) {
+    switch (edit) {
+      case ' ':
+        ++common_;
+        FlushEdits();
+        hunk_.push_back(std::make_pair(' ', line));
+        break;
+      case '-':
+        ++removes_;
+        hunk_removes_.push_back(std::make_pair('-', line));
+        break;
+      case '+':
+        ++adds_;
+        hunk_adds_.push_back(std::make_pair('+', line));
+        break;
+    }
+  }
+
+  void PrintTo(std::ostream* os) {
+    PrintHeader(os);
+    FlushEdits();
+    for (std::list<std::pair<char, const char*> >::const_iterator it =
+             hunk_.begin();
+         it != hunk_.end(); ++it) {
+      *os << it->first << it->second << "\n";
+    }
+  }
+
+  bool has_edits() const { return adds_ || removes_; }
+
+ private:
+  void FlushEdits() {
+    hunk_.splice(hunk_.end(), hunk_removes_);
+    hunk_.splice(hunk_.end(), hunk_adds_);
+  }
+
+  // Print a unified diff header for one hunk.
+  // The format is
+  //   "@@ -<left_start>,<left_length> +<right_start>,<right_length> @@"
+  // where the left/right parts are omitted if unnecessary.
+  void PrintHeader(std::ostream* ss) const {
+    *ss << "@@ ";
+    if (removes_) {
+      *ss << "-" << left_start_ << "," << (removes_ + common_);
+    }
+    if (removes_ && adds_) {
+      *ss << " ";
+    }
+    if (adds_) {
+      *ss << "+" << right_start_ << "," << (adds_ + common_);
+    }
+    *ss << " @@\n";
+  }
+
+  size_t left_start_, right_start_;
+  size_t adds_, removes_, common_;
+  std::list<std::pair<char, const char*> > hunk_, hunk_adds_, hunk_removes_;
+};
+
+}  // namespace
+
+// Create a list of diff hunks in Unified diff format.
+// Each hunk has a header generated by PrintHeader above plus a body with
+// lines prefixed with ' ' for no change, '-' for deletion and '+' for
+// addition.
+// 'context' represents the desired unchanged prefix/suffix around the diff.
+// If two hunks are close enough that their contexts overlap, then they are
+// joined into one hunk.
+std::string CreateUnifiedDiff(const std::vector<std::string>& left,
+                              const std::vector<std::string>& right,
+                              size_t context) {
+  const std::vector<EditType> edits = CalculateOptimalEdits(left, right);
+
+  size_t l_i = 0, r_i = 0, edit_i = 0;
+  std::stringstream ss;
+  while (edit_i < edits.size()) {
+    // Find first edit.
+    while (edit_i < edits.size() && edits[edit_i] == kMatch) {
+      ++l_i;
+      ++r_i;
+      ++edit_i;
+    }
+
+    // Find the first line to include in the hunk.
+    const size_t prefix_context = std::min(l_i, context);
+    Hunk hunk(l_i - prefix_context + 1, r_i - prefix_context + 1);
+    for (size_t i = prefix_context; i > 0; --i) {
+      hunk.PushLine(' ', left[l_i - i].c_str());
+    }
+
+    // Iterate the edits until we found enough suffix for the hunk or the input
+    // is over.
+    size_t n_suffix = 0;
+    for (; edit_i < edits.size(); ++edit_i) {
+      if (n_suffix >= context) {
+        // Continue only if the next hunk is very close.
+        auto it = edits.begin() + static_cast<int>(edit_i);
+        while (it != edits.end() && *it == kMatch) ++it;
+        if (it == edits.end() ||
+            static_cast<size_t>(it - edits.begin()) - edit_i >= context) {
+          // There is no next edit or it is too far away.
+          break;
+        }
+      }
+
+      EditType edit = edits[edit_i];
+      // Reset count when a non match is found.
+      n_suffix = edit == kMatch ? n_suffix + 1 : 0;
+
+      if (edit == kMatch || edit == kRemove || edit == kReplace) {
+        hunk.PushLine(edit == kMatch ? ' ' : '-', left[l_i].c_str());
+      }
+      if (edit == kAdd || edit == kReplace) {
+        hunk.PushLine('+', right[r_i].c_str());
+      }
+
+      // Advance indices, depending on edit type.
+      l_i += edit != kAdd;
+      r_i += edit != kRemove;
+    }
+
+    if (!hunk.has_edits()) {
+      // We are done. We don't want this hunk.
+      break;
+    }
+
+    hunk.PrintTo(&ss);
+  }
+  return ss.str();
+}
+
+}  // namespace edit_distance
+
+namespace {
+
+// The string representation of the values received in EqFailure() are already
+// escaped. Split them on escaped '\n' boundaries. Leave all other escaped
+// characters the same.
+std::vector<std::string> SplitEscapedString(const std::string& str) {
+  std::vector<std::string> lines;
+  size_t start = 0, end = str.size();
+  if (end > 2 && str[0] == '"' && str[end - 1] == '"') {
+    ++start;
+    --end;
+  }
+  bool escaped = false;
+  for (size_t i = start; i + 1 < end; ++i) {
+    if (escaped) {
+      escaped = false;
+      if (str[i] == 'n') {
+        lines.push_back(str.substr(start, i - start - 1));
+        start = i + 1;
+      }
+    } else {
+      escaped = str[i] == '\\';
+    }
+  }
+  lines.push_back(str.substr(start, end - start));
+  return lines;
+}
+
+}  // namespace
+
+// Constructs and returns the message for an equality assertion
+// (e.g. ASSERT_EQ, EXPECT_STREQ, etc) failure.
+//
+// The first four parameters are the expressions used in the assertion
+// and their values, as strings.  For example, for ASSERT_EQ(foo, bar)
+// where foo is 5 and bar is 6, we have:
+//
+//   lhs_expression: "foo"
+//   rhs_expression: "bar"
+//   lhs_value:      "5"
+//   rhs_value:      "6"
+//
+// The ignoring_case parameter is true if and only if the assertion is a
+// *_STRCASEEQ*.  When it's true, the string "Ignoring case" will
+// be inserted into the message.
+AssertionResult EqFailure(const char* lhs_expression,
+                          const char* rhs_expression,
+                          const std::string& lhs_value,
+                          const std::string& rhs_value,
+                          bool ignoring_case) {
+  Message msg;
+  msg << "Expected equality of these values:";
+  msg << "\n  " << lhs_expression;
+  if (lhs_value != lhs_expression) {
+    msg << "\n    Which is: " << lhs_value;
+  }
+  msg << "\n  " << rhs_expression;
+  if (rhs_value != rhs_expression) {
+    msg << "\n    Which is: " << rhs_value;
+  }
+
+  if (ignoring_case) {
+    msg << "\nIgnoring case";
+  }
+
+  if (!lhs_value.empty() && !rhs_value.empty()) {
+    const std::vector<std::string> lhs_lines =
+        SplitEscapedString(lhs_value);
+    const std::vector<std::string> rhs_lines =
+        SplitEscapedString(rhs_value);
+    if (lhs_lines.size() > 1 || rhs_lines.size() > 1) {
+      msg << "\nWith diff:\n"
+          << edit_distance::CreateUnifiedDiff(lhs_lines, rhs_lines);
+    }
+  }
+
+  return AssertionFailure() << msg;
+}
+
+// Constructs a failure message for Boolean assertions such as EXPECT_TRUE.
+std::string GetBoolAssertionFailureMessage(
+    const AssertionResult& assertion_result,
+    const char* expression_text,
+    const char* actual_predicate_value,
+    const char* expected_predicate_value) {
+  const char* actual_message = assertion_result.message();
+  Message msg;
+  msg << "Value of: " << expression_text
+      << "\n  Actual: " << actual_predicate_value;
+  if (actual_message[0] != '\0')
+    msg << " (" << actual_message << ")";
+  msg << "\nExpected: " << expected_predicate_value;
+  return msg.GetString();
+}
+
+// Helper function for implementing ASSERT_NEAR.
+AssertionResult DoubleNearPredFormat(const char* expr1,
+                                     const char* expr2,
+                                     const char* abs_error_expr,
+                                     double val1,
+                                     double val2,
+                                     double abs_error) {
+  const double diff = fabs(val1 - val2);
+  if (diff <= abs_error) return AssertionSuccess();
+
+  // Find the value which is closest to zero.
+  const double min_abs = std::min(fabs(val1), fabs(val2));
+  // Find the distance to the next double from that value.
+  const double epsilon =
+      nextafter(min_abs, std::numeric_limits<double>::infinity()) - min_abs;
+  // Detect the case where abs_error is so small that EXPECT_NEAR is
+  // effectively the same as EXPECT_EQUAL, and give an informative error
+  // message so that the situation can be more easily understood without
+  // requiring exotic floating-point knowledge.
+  // Don't do an epsilon check if abs_error is zero because that implies
+  // that an equality check was actually intended.
+  if (!(std::isnan)(val1) && !(std::isnan)(val2) && abs_error > 0 &&
+      abs_error < epsilon) {
+    return AssertionFailure()
+           << "The difference between " << expr1 << " and " << expr2 << " is "
+           << diff << ", where\n"
+           << expr1 << " evaluates to " << val1 << ",\n"
+           << expr2 << " evaluates to " << val2 << ".\nThe abs_error parameter "
+           << abs_error_expr << " evaluates to " << abs_error
+           << " which is smaller than the minimum distance between doubles for "
+              "numbers of this magnitude which is "
+           << epsilon
+           << ", thus making this EXPECT_NEAR check equivalent to "
+              "EXPECT_EQUAL. Consider using EXPECT_DOUBLE_EQ instead.";
+  }
+  return AssertionFailure()
+      << "The difference between " << expr1 << " and " << expr2
+      << " is " << diff << ", which exceeds " << abs_error_expr << ", where\n"
+      << expr1 << " evaluates to " << val1 << ",\n"
+      << expr2 << " evaluates to " << val2 << ", and\n"
+      << abs_error_expr << " evaluates to " << abs_error << ".";
+}
+
+
+// Helper template for implementing FloatLE() and DoubleLE().
+template <typename RawType>
+AssertionResult FloatingPointLE(const char* expr1,
+                                const char* expr2,
+                                RawType val1,
+                                RawType val2) {
+  // Returns success if val1 is less than val2,
+  if (val1 < val2) {
+    return AssertionSuccess();
+  }
+
+  // or if val1 is almost equal to val2.
+  const FloatingPoint<RawType> lhs(val1), rhs(val2);
+  if (lhs.AlmostEquals(rhs)) {
+    return AssertionSuccess();
+  }
+
+  // Note that the above two checks will both fail if either val1 or
+  // val2 is NaN, as the IEEE floating-point standard requires that
+  // any predicate involving a NaN must return false.
+
+  ::std::stringstream val1_ss;
+  val1_ss << std::setprecision(std::numeric_limits<RawType>::digits10 + 2)
+          << val1;
+
+  ::std::stringstream val2_ss;
+  val2_ss << std::setprecision(std::numeric_limits<RawType>::digits10 + 2)
+          << val2;
+
+  return AssertionFailure()
+      << "Expected: (" << expr1 << ") <= (" << expr2 << ")\n"
+      << "  Actual: " << StringStreamToString(&val1_ss) << " vs "
+      << StringStreamToString(&val2_ss);
+}
+
+}  // namespace internal
+
+// Asserts that val1 is less than, or almost equal to, val2.  Fails
+// otherwise.  In particular, it fails if either val1 or val2 is NaN.
+AssertionResult FloatLE(const char* expr1, const char* expr2,
+                        float val1, float val2) {
+  return internal::FloatingPointLE<float>(expr1, expr2, val1, val2);
+}
+
+// Asserts that val1 is less than, or almost equal to, val2.  Fails
+// otherwise.  In particular, it fails if either val1 or val2 is NaN.
+AssertionResult DoubleLE(const char* expr1, const char* expr2,
+                         double val1, double val2) {
+  return internal::FloatingPointLE<double>(expr1, expr2, val1, val2);
+}
+
+namespace internal {
+
+// The helper function for {ASSERT|EXPECT}_STREQ.
+AssertionResult CmpHelperSTREQ(const char* lhs_expression,
+                               const char* rhs_expression,
+                               const char* lhs,
+                               const char* rhs) {
+  if (String::CStringEquals(lhs, rhs)) {
+    return AssertionSuccess();
+  }
+
+  return EqFailure(lhs_expression,
+                   rhs_expression,
+                   PrintToString(lhs),
+                   PrintToString(rhs),
+                   false);
+}
+
+// The helper function for {ASSERT|EXPECT}_STRCASEEQ.
+AssertionResult CmpHelperSTRCASEEQ(const char* lhs_expression,
+                                   const char* rhs_expression,
+                                   const char* lhs,
+                                   const char* rhs) {
+  if (String::CaseInsensitiveCStringEquals(lhs, rhs)) {
+    return AssertionSuccess();
+  }
+
+  return EqFailure(lhs_expression,
+                   rhs_expression,
+                   PrintToString(lhs),
+                   PrintToString(rhs),
+                   true);
+}
+
+// The helper function for {ASSERT|EXPECT}_STRNE.
+AssertionResult CmpHelperSTRNE(const char* s1_expression,
+                               const char* s2_expression,
+                               const char* s1,
+                               const char* s2) {
+  if (!String::CStringEquals(s1, s2)) {
+    return AssertionSuccess();
+  } else {
+    return AssertionFailure() << "Expected: (" << s1_expression << ") != ("
+                              << s2_expression << "), actual: \""
+                              << s1 << "\" vs \"" << s2 << "\"";
+  }
+}
+
+// The helper function for {ASSERT|EXPECT}_STRCASENE.
+AssertionResult CmpHelperSTRCASENE(const char* s1_expression,
+                                   const char* s2_expression,
+                                   const char* s1,
+                                   const char* s2) {
+  if (!String::CaseInsensitiveCStringEquals(s1, s2)) {
+    return AssertionSuccess();
+  } else {
+    return AssertionFailure()
+        << "Expected: (" << s1_expression << ") != ("
+        << s2_expression << ") (ignoring case), actual: \""
+        << s1 << "\" vs \"" << s2 << "\"";
+  }
+}
+
+}  // namespace internal
+
+namespace {
+
+// Helper functions for implementing IsSubString() and IsNotSubstring().
+
+// This group of overloaded functions return true if and only if needle
+// is a substring of haystack.  NULL is considered a substring of
+// itself only.
+
+bool IsSubstringPred(const char* needle, const char* haystack) {
+  if (needle == nullptr || haystack == nullptr) return needle == haystack;
+
+  return strstr(haystack, needle) != nullptr;
+}
+
+bool IsSubstringPred(const wchar_t* needle, const wchar_t* haystack) {
+  if (needle == nullptr || haystack == nullptr) return needle == haystack;
+
+  return wcsstr(haystack, needle) != nullptr;
+}
+
+// StringType here can be either ::std::string or ::std::wstring.
+template <typename StringType>
+bool IsSubstringPred(const StringType& needle,
+                     const StringType& haystack) {
+  return haystack.find(needle) != StringType::npos;
+}
+
+// This function implements either IsSubstring() or IsNotSubstring(),
+// depending on the value of the expected_to_be_substring parameter.
+// StringType here can be const char*, const wchar_t*, ::std::string,
+// or ::std::wstring.
+template <typename StringType>
+AssertionResult IsSubstringImpl(
+    bool expected_to_be_substring,
+    const char* needle_expr, const char* haystack_expr,
+    const StringType& needle, const StringType& haystack) {
+  if (IsSubstringPred(needle, haystack) == expected_to_be_substring)
+    return AssertionSuccess();
+
+  const bool is_wide_string = sizeof(needle[0]) > 1;
+  const char* const begin_string_quote = is_wide_string ? "L\"" : "\"";
+  return AssertionFailure()
+      << "Value of: " << needle_expr << "\n"
+      << "  Actual: " << begin_string_quote << needle << "\"\n"
+      << "Expected: " << (expected_to_be_substring ? "" : "not ")
+      << "a substring of " << haystack_expr << "\n"
+      << "Which is: " << begin_string_quote << haystack << "\"";
+}
+
+}  // namespace
+
+// IsSubstring() and IsNotSubstring() check whether needle is a
+// substring of haystack (NULL is considered a substring of itself
+// only), and return an appropriate error message when they fail.
+
+AssertionResult IsSubstring(
+    const char* needle_expr, const char* haystack_expr,
+    const char* needle, const char* haystack) {
+  return IsSubstringImpl(true, needle_expr, haystack_expr, needle, haystack);
+}
+
+AssertionResult IsSubstring(
+    const char* needle_expr, const char* haystack_expr,
+    const wchar_t* needle, const wchar_t* haystack) {
+  return IsSubstringImpl(true, needle_expr, haystack_expr, needle, haystack);
+}
+
+AssertionResult IsNotSubstring(
+    const char* needle_expr, const char* haystack_expr,
+    const char* needle, const char* haystack) {
+  return IsSubstringImpl(false, needle_expr, haystack_expr, needle, haystack);
+}
+
+AssertionResult IsNotSubstring(
+    const char* needle_expr, const char* haystack_expr,
+    const wchar_t* needle, const wchar_t* haystack) {
+  return IsSubstringImpl(false, needle_expr, haystack_expr, needle, haystack);
+}
+
+AssertionResult IsSubstring(
+    const char* needle_expr, const char* haystack_expr,
+    const ::std::string& needle, const ::std::string& haystack) {
+  return IsSubstringImpl(true, needle_expr, haystack_expr, needle, haystack);
+}
+
+AssertionResult IsNotSubstring(
+    const char* needle_expr, const char* haystack_expr,
+    const ::std::string& needle, const ::std::string& haystack) {
+  return IsSubstringImpl(false, needle_expr, haystack_expr, needle, haystack);
+}
+
+#if GTEST_HAS_STD_WSTRING
+AssertionResult IsSubstring(
+    const char* needle_expr, const char* haystack_expr,
+    const ::std::wstring& needle, const ::std::wstring& haystack) {
+  return IsSubstringImpl(true, needle_expr, haystack_expr, needle, haystack);
+}
+
+AssertionResult IsNotSubstring(
+    const char* needle_expr, const char* haystack_expr,
+    const ::std::wstring& needle, const ::std::wstring& haystack) {
+  return IsSubstringImpl(false, needle_expr, haystack_expr, needle, haystack);
+}
+#endif  // GTEST_HAS_STD_WSTRING
+
+namespace internal {
+
+#if GTEST_OS_WINDOWS
+
+namespace {
+
+// Helper function for IsHRESULT{SuccessFailure} predicates
+AssertionResult HRESULTFailureHelper(const char* expr,
+                                     const char* expected,
+                                     long hr) {  // NOLINT
+# if GTEST_OS_WINDOWS_MOBILE || GTEST_OS_WINDOWS_TV_TITLE
+
+  // Windows CE doesn't support FormatMessage.
+  const char error_text[] = "";
+
+# else
+
+  // Looks up the human-readable system message for the HRESULT code
+  // and since we're not passing any params to FormatMessage, we don't
+  // want inserts expanded.
+  const DWORD kFlags = FORMAT_MESSAGE_FROM_SYSTEM |
+                       FORMAT_MESSAGE_IGNORE_INSERTS;
+  const DWORD kBufSize = 4096;
+  // Gets the system's human readable message string for this HRESULT.
+  char error_text[kBufSize] = { '\0' };
+  DWORD message_length = ::FormatMessageA(kFlags,
+                                          0,   // no source, we're asking system
+                                          static_cast<DWORD>(hr),  // the error
+                                          0,   // no line width restrictions
+                                          error_text,  // output buffer
+                                          kBufSize,    // buf size
+                                          nullptr);  // no arguments for inserts
+  // Trims tailing white space (FormatMessage leaves a trailing CR-LF)
+  for (; message_length && IsSpace(error_text[message_length - 1]);
+          --message_length) {
+    error_text[message_length - 1] = '\0';
+  }
+
+# endif  // GTEST_OS_WINDOWS_MOBILE
+
+  const std::string error_hex("0x" + String::FormatHexInt(hr));
+  return ::testing::AssertionFailure()
+      << "Expected: " << expr << " " << expected << ".\n"
+      << "  Actual: " << error_hex << " " << error_text << "\n";
+}
+
+}  // namespace
+
+AssertionResult IsHRESULTSuccess(const char* expr, long hr) {  // NOLINT
+  if (SUCCEEDED(hr)) {
+    return AssertionSuccess();
+  }
+  return HRESULTFailureHelper(expr, "succeeds", hr);
+}
+
+AssertionResult IsHRESULTFailure(const char* expr, long hr) {  // NOLINT
+  if (FAILED(hr)) {
+    return AssertionSuccess();
+  }
+  return HRESULTFailureHelper(expr, "fails", hr);
+}
+
+#endif  // GTEST_OS_WINDOWS
+
+// Utility functions for encoding Unicode text (wide strings) in
+// UTF-8.
+
+// A Unicode code-point can have up to 21 bits, and is encoded in UTF-8
+// like this:
+//
+// Code-point length   Encoding
+//   0 -  7 bits       0xxxxxxx
+//   8 - 11 bits       110xxxxx 10xxxxxx
+//  12 - 16 bits       1110xxxx 10xxxxxx 10xxxxxx
+//  17 - 21 bits       11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
+
+// The maximum code-point a one-byte UTF-8 sequence can represent.
+constexpr uint32_t kMaxCodePoint1 = (static_cast<uint32_t>(1) <<  7) - 1;
+
+// The maximum code-point a two-byte UTF-8 sequence can represent.
+constexpr uint32_t kMaxCodePoint2 = (static_cast<uint32_t>(1) << (5 + 6)) - 1;
+
+// The maximum code-point a three-byte UTF-8 sequence can represent.
+constexpr uint32_t kMaxCodePoint3 = (static_cast<uint32_t>(1) << (4 + 2*6)) - 1;
+
+// The maximum code-point a four-byte UTF-8 sequence can represent.
+constexpr uint32_t kMaxCodePoint4 = (static_cast<uint32_t>(1) << (3 + 3*6)) - 1;
+
+// Chops off the n lowest bits from a bit pattern.  Returns the n
+// lowest bits.  As a side effect, the original bit pattern will be
+// shifted to the right by n bits.
+inline uint32_t ChopLowBits(uint32_t* bits, int n) {
+  const uint32_t low_bits = *bits & ((static_cast<uint32_t>(1) << n) - 1);
+  *bits >>= n;
+  return low_bits;
+}
+
+// Converts a Unicode code point to a narrow string in UTF-8 encoding.
+// code_point parameter is of type uint32_t because wchar_t may not be
+// wide enough to contain a code point.
+// If the code_point is not a valid Unicode code point
+// (i.e. outside of Unicode range U+0 to U+10FFFF) it will be converted
+// to "(Invalid Unicode 0xXXXXXXXX)".
+std::string CodePointToUtf8(uint32_t code_point) {
+  if (code_point > kMaxCodePoint4) {
+    return "(Invalid Unicode 0x" + String::FormatHexUInt32(code_point) + ")";
+  }
+
+  char str[5];  // Big enough for the largest valid code point.
+  if (code_point <= kMaxCodePoint1) {
+    str[1] = '\0';
+    str[0] = static_cast<char>(code_point);                          // 0xxxxxxx
+  } else if (code_point <= kMaxCodePoint2) {
+    str[2] = '\0';
+    str[1] = static_cast<char>(0x80 | ChopLowBits(&code_point, 6));  // 10xxxxxx
+    str[0] = static_cast<char>(0xC0 | code_point);                   // 110xxxxx
+  } else if (code_point <= kMaxCodePoint3) {
+    str[3] = '\0';
+    str[2] = static_cast<char>(0x80 | ChopLowBits(&code_point, 6));  // 10xxxxxx
+    str[1] = static_cast<char>(0x80 | ChopLowBits(&code_point, 6));  // 10xxxxxx
+    str[0] = static_cast<char>(0xE0 | code_point);                   // 1110xxxx
+  } else {  // code_point <= kMaxCodePoint4
+    str[4] = '\0';
+    str[3] = static_cast<char>(0x80 | ChopLowBits(&code_point, 6));  // 10xxxxxx
+    str[2] = static_cast<char>(0x80 | ChopLowBits(&code_point, 6));  // 10xxxxxx
+    str[1] = static_cast<char>(0x80 | ChopLowBits(&code_point, 6));  // 10xxxxxx
+    str[0] = static_cast<char>(0xF0 | code_point);                   // 11110xxx
+  }
+  return str;
+}
+
+// The following two functions only make sense if the system
+// uses UTF-16 for wide string encoding. All supported systems
+// with 16 bit wchar_t (Windows, Cygwin) do use UTF-16.
+
+// Determines if the arguments constitute UTF-16 surrogate pair
+// and thus should be combined into a single Unicode code point
+// using CreateCodePointFromUtf16SurrogatePair.
+inline bool IsUtf16SurrogatePair(wchar_t first, wchar_t second) {
+  return sizeof(wchar_t) == 2 &&
+      (first & 0xFC00) == 0xD800 && (second & 0xFC00) == 0xDC00;
+}
+
+// Creates a Unicode code point from UTF16 surrogate pair.
+inline uint32_t CreateCodePointFromUtf16SurrogatePair(wchar_t first,
+                                                      wchar_t second) {
+  const auto first_u = static_cast<uint32_t>(first);
+  const auto second_u = static_cast<uint32_t>(second);
+  const uint32_t mask = (1 << 10) - 1;
+  return (sizeof(wchar_t) == 2)
+             ? (((first_u & mask) << 10) | (second_u & mask)) + 0x10000
+             :
+             // This function should not be called when the condition is
+             // false, but we provide a sensible default in case it is.
+             first_u;
+}
+
+// Converts a wide string to a narrow string in UTF-8 encoding.
+// The wide string is assumed to have the following encoding:
+//   UTF-16 if sizeof(wchar_t) == 2 (on Windows, Cygwin)
+//   UTF-32 if sizeof(wchar_t) == 4 (on Linux)
+// Parameter str points to a null-terminated wide string.
+// Parameter num_chars may additionally limit the number
+// of wchar_t characters processed. -1 is used when the entire string
+// should be processed.
+// If the string contains code points that are not valid Unicode code points
+// (i.e. outside of Unicode range U+0 to U+10FFFF) they will be output
+// as '(Invalid Unicode 0xXXXXXXXX)'. If the string is in UTF16 encoding
+// and contains invalid UTF-16 surrogate pairs, values in those pairs
+// will be encoded as individual Unicode characters from Basic Normal Plane.
+std::string WideStringToUtf8(const wchar_t* str, int num_chars) {
+  if (num_chars == -1)
+    num_chars = static_cast<int>(wcslen(str));
+
+  ::std::stringstream stream;
+  for (int i = 0; i < num_chars; ++i) {
+    uint32_t unicode_code_point;
+
+    if (str[i] == L'\0') {
+      break;
+    } else if (i + 1 < num_chars && IsUtf16SurrogatePair(str[i], str[i + 1])) {
+      unicode_code_point = CreateCodePointFromUtf16SurrogatePair(str[i],
+                                                                 str[i + 1]);
+      i++;
+    } else {
+      unicode_code_point = static_cast<uint32_t>(str[i]);
+    }
+
+    stream << CodePointToUtf8(unicode_code_point);
+  }
+  return StringStreamToString(&stream);
+}
+
+// Converts a wide C string to an std::string using the UTF-8 encoding.
+// NULL will be converted to "(null)".
+std::string String::ShowWideCString(const wchar_t * wide_c_str) {
+  if (wide_c_str == nullptr) return "(null)";
+
+  return internal::WideStringToUtf8(wide_c_str, -1);
+}
+
+// Compares two wide C strings.  Returns true if and only if they have the
+// same content.
+//
+// Unlike wcscmp(), this function can handle NULL argument(s).  A NULL
+// C string is considered different to any non-NULL C string,
+// including the empty string.
+bool String::WideCStringEquals(const wchar_t * lhs, const wchar_t * rhs) {
+  if (lhs == nullptr) return rhs == nullptr;
+
+  if (rhs == nullptr) return false;
+
+  return wcscmp(lhs, rhs) == 0;
+}
+
+// Helper function for *_STREQ on wide strings.
+AssertionResult CmpHelperSTREQ(const char* lhs_expression,
+                               const char* rhs_expression,
+                               const wchar_t* lhs,
+                               const wchar_t* rhs) {
+  if (String::WideCStringEquals(lhs, rhs)) {
+    return AssertionSuccess();
+  }
+
+  return EqFailure(lhs_expression,
+                   rhs_expression,
+                   PrintToString(lhs),
+                   PrintToString(rhs),
+                   false);
+}
+
+// Helper function for *_STRNE on wide strings.
+AssertionResult CmpHelperSTRNE(const char* s1_expression,
+                               const char* s2_expression,
+                               const wchar_t* s1,
+                               const wchar_t* s2) {
+  if (!String::WideCStringEquals(s1, s2)) {
+    return AssertionSuccess();
+  }
+
+  return AssertionFailure() << "Expected: (" << s1_expression << ") != ("
+                            << s2_expression << "), actual: "
+                            << PrintToString(s1)
+                            << " vs " << PrintToString(s2);
+}
+
+// Compares two C strings, ignoring case.  Returns true if and only if they have
+// the same content.
+//
+// Unlike strcasecmp(), this function can handle NULL argument(s).  A
+// NULL C string is considered different to any non-NULL C string,
+// including the empty string.
+bool String::CaseInsensitiveCStringEquals(const char * lhs, const char * rhs) {
+  if (lhs == nullptr) return rhs == nullptr;
+  if (rhs == nullptr) return false;
+  return posix::StrCaseCmp(lhs, rhs) == 0;
+}
+
+// Compares two wide C strings, ignoring case.  Returns true if and only if they
+// have the same content.
+//
+// Unlike wcscasecmp(), this function can handle NULL argument(s).
+// A NULL C string is considered different to any non-NULL wide C string,
+// including the empty string.
+// NB: The implementations on different platforms slightly differ.
+// On windows, this method uses _wcsicmp which compares according to LC_CTYPE
+// environment variable. On GNU platform this method uses wcscasecmp
+// which compares according to LC_CTYPE category of the current locale.
+// On MacOS X, it uses towlower, which also uses LC_CTYPE category of the
+// current locale.
+bool String::CaseInsensitiveWideCStringEquals(const wchar_t* lhs,
+                                              const wchar_t* rhs) {
+  if (lhs == nullptr) return rhs == nullptr;
+
+  if (rhs == nullptr) return false;
+
+#if GTEST_OS_WINDOWS
+  return _wcsicmp(lhs, rhs) == 0;
+#elif GTEST_OS_LINUX && !GTEST_OS_LINUX_ANDROID
+  return wcscasecmp(lhs, rhs) == 0;
+#else
+  // Android, Mac OS X and Cygwin don't define wcscasecmp.
+  // Other unknown OSes may not define it either.
+  wint_t left, right;
+  do {
+    left = towlower(static_cast<wint_t>(*lhs++));
+    right = towlower(static_cast<wint_t>(*rhs++));
+  } while (left && left == right);
+  return left == right;
+#endif  // OS selector
+}
+
+// Returns true if and only if str ends with the given suffix, ignoring case.
+// Any string is considered to end with an empty suffix.
+bool String::EndsWithCaseInsensitive(
+    const std::string& str, const std::string& suffix) {
+  const size_t str_len = str.length();
+  const size_t suffix_len = suffix.length();
+  return (str_len >= suffix_len) &&
+         CaseInsensitiveCStringEquals(str.c_str() + str_len - suffix_len,
+                                      suffix.c_str());
+}
+
+// Formats an int value as "%02d".
+std::string String::FormatIntWidth2(int value) {
+  return FormatIntWidthN(value, 2);
+}
+
+// Formats an int value to given width with leading zeros.
+std::string String::FormatIntWidthN(int value, int width) {
+  std::stringstream ss;
+  ss << std::setfill('0') << std::setw(width) << value;
+  return ss.str();
+}
+
+// Formats an int value as "%X".
+std::string String::FormatHexUInt32(uint32_t value) {
+  std::stringstream ss;
+  ss << std::hex << std::uppercase << value;
+  return ss.str();
+}
+
+// Formats an int value as "%X".
+std::string String::FormatHexInt(int value) {
+  return FormatHexUInt32(static_cast<uint32_t>(value));
+}
+
+// Formats a byte as "%02X".
+std::string String::FormatByte(unsigned char value) {
+  std::stringstream ss;
+  ss << std::setfill('0') << std::setw(2) << std::hex << std::uppercase
+     << static_cast<unsigned int>(value);
+  return ss.str();
+}
+
+// Converts the buffer in a stringstream to an std::string, converting NUL
+// bytes to "\\0" along the way.
+std::string StringStreamToString(::std::stringstream* ss) {
+  const ::std::string& str = ss->str();
+  const char* const start = str.c_str();
+  const char* const end = start + str.length();
+
+  std::string result;
+  result.reserve(static_cast<size_t>(2 * (end - start)));
+  for (const char* ch = start; ch != end; ++ch) {
+    if (*ch == '\0') {
+      result += "\\0";  // Replaces NUL with "\\0";
+    } else {
+      result += *ch;
+    }
+  }
+
+  return result;
+}
+
+// Appends the user-supplied message to the Google-Test-generated message.
+std::string AppendUserMessage(const std::string& gtest_msg,
+                              const Message& user_msg) {
+  // Appends the user message if it's non-empty.
+  const std::string user_msg_string = user_msg.GetString();
+  if (user_msg_string.empty()) {
+    return gtest_msg;
+  }
+  if (gtest_msg.empty()) {
+    return user_msg_string;
+  }
+  return gtest_msg + "\n" + user_msg_string;
+}
+
+}  // namespace internal
+
+// class TestResult
+
+// Creates an empty TestResult.
+TestResult::TestResult()
+    : death_test_count_(0), start_timestamp_(0), elapsed_time_(0) {}
+
+// D'tor.
+TestResult::~TestResult() {
+}
+
+// Returns the i-th test part result among all the results. i can
+// range from 0 to total_part_count() - 1. If i is not in that range,
+// aborts the program.
+const TestPartResult& TestResult::GetTestPartResult(int i) const {
+  if (i < 0 || i >= total_part_count())
+    internal::posix::Abort();
+  return test_part_results_.at(static_cast<size_t>(i));
+}
+
+// Returns the i-th test property. i can range from 0 to
+// test_property_count() - 1. If i is not in that range, aborts the
+// program.
+const TestProperty& TestResult::GetTestProperty(int i) const {
+  if (i < 0 || i >= test_property_count())
+    internal::posix::Abort();
+  return test_properties_.at(static_cast<size_t>(i));
+}
+
+// Clears the test part results.
+void TestResult::ClearTestPartResults() {
+  test_part_results_.clear();
+}
+
+// Adds a test part result to the list.
+void TestResult::AddTestPartResult(const TestPartResult& test_part_result) {
+  test_part_results_.push_back(test_part_result);
+}
+
+// Adds a test property to the list. If a property with the same key as the
+// supplied property is already represented, the value of this test_property
+// replaces the old value for that key.
+void TestResult::RecordProperty(const std::string& xml_element,
+                                const TestProperty& test_property) {
+  if (!ValidateTestProperty(xml_element, test_property)) {
+    return;
+  }
+  internal::MutexLock lock(&test_properties_mutex_);
+  const std::vector<TestProperty>::iterator property_with_matching_key =
+      std::find_if(test_properties_.begin(), test_properties_.end(),
+                   internal::TestPropertyKeyIs(test_property.key()));
+  if (property_with_matching_key == test_properties_.end()) {
+    test_properties_.push_back(test_property);
+    return;
+  }
+  property_with_matching_key->SetValue(test_property.value());
+}
+
+// The list of reserved attributes used in the <testsuites> element of XML
+// output.
+static const char* const kReservedTestSuitesAttributes[] = {
+  "disabled",
+  "errors",
+  "failures",
+  "name",
+  "random_seed",
+  "tests",
+  "time",
+  "timestamp"
+};
+
+// The list of reserved attributes used in the <testsuite> element of XML
+// output.
+static const char* const kReservedTestSuiteAttributes[] = {
+    "disabled", "errors", "failures",  "name",
+    "tests",    "time",   "timestamp", "skipped"};
+
+// The list of reserved attributes used in the <testcase> element of XML output.
+static const char* const kReservedTestCaseAttributes[] = {
+    "classname",   "name", "status", "time",  "type_param",
+    "value_param", "file", "line"};
+
+// Use a slightly different set for allowed output to ensure existing tests can
+// still RecordProperty("result") or "RecordProperty(timestamp")
+static const char* const kReservedOutputTestCaseAttributes[] = {
+    "classname",   "name", "status", "time",   "type_param",
+    "value_param", "file", "line",   "result", "timestamp"};
+
+template <size_t kSize>
+std::vector<std::string> ArrayAsVector(const char* const (&array)[kSize]) {
+  return std::vector<std::string>(array, array + kSize);
+}
+
+static std::vector<std::string> GetReservedAttributesForElement(
+    const std::string& xml_element) {
+  if (xml_element == "testsuites") {
+    return ArrayAsVector(kReservedTestSuitesAttributes);
+  } else if (xml_element == "testsuite") {
+    return ArrayAsVector(kReservedTestSuiteAttributes);
+  } else if (xml_element == "testcase") {
+    return ArrayAsVector(kReservedTestCaseAttributes);
+  } else {
+    GTEST_CHECK_(false) << "Unrecognized xml_element provided: " << xml_element;
+  }
+  // This code is unreachable but some compilers may not realizes that.
+  return std::vector<std::string>();
+}
+
+// TODO(jdesprez): Merge the two getReserved attributes once skip is improved
+static std::vector<std::string> GetReservedOutputAttributesForElement(
+    const std::string& xml_element) {
+  if (xml_element == "testsuites") {
+    return ArrayAsVector(kReservedTestSuitesAttributes);
+  } else if (xml_element == "testsuite") {
+    return ArrayAsVector(kReservedTestSuiteAttributes);
+  } else if (xml_element == "testcase") {
+    return ArrayAsVector(kReservedOutputTestCaseAttributes);
+  } else {
+    GTEST_CHECK_(false) << "Unrecognized xml_element provided: " << xml_element;
+  }
+  // This code is unreachable but some compilers may not realizes that.
+  return std::vector<std::string>();
+}
+
+static std::string FormatWordList(const std::vector<std::string>& words) {
+  Message word_list;
+  for (size_t i = 0; i < words.size(); ++i) {
+    if (i > 0 && words.size() > 2) {
+      word_list << ", ";
+    }
+    if (i == words.size() - 1) {
+      word_list << "and ";
+    }
+    word_list << "'" << words[i] << "'";
+  }
+  return word_list.GetString();
+}
+
+static bool ValidateTestPropertyName(
+    const std::string& property_name,
+    const std::vector<std::string>& reserved_names) {
+  if (std::find(reserved_names.begin(), reserved_names.end(), property_name) !=
+          reserved_names.end()) {
+    ADD_FAILURE() << "Reserved key used in RecordProperty(): " << property_name
+                  << " (" << FormatWordList(reserved_names)
+                  << " are reserved by " << GTEST_NAME_ << ")";
+    return false;
+  }
+  return true;
+}
+
+// Adds a failure if the key is a reserved attribute of the element named
+// xml_element.  Returns true if the property is valid.
+bool TestResult::ValidateTestProperty(const std::string& xml_element,
+                                      const TestProperty& test_property) {
+  return ValidateTestPropertyName(test_property.key(),
+                                  GetReservedAttributesForElement(xml_element));
+}
+
+// Clears the object.
+void TestResult::Clear() {
+  test_part_results_.clear();
+  test_properties_.clear();
+  death_test_count_ = 0;
+  elapsed_time_ = 0;
+}
+
+// Returns true off the test part was skipped.
+static bool TestPartSkipped(const TestPartResult& result) {
+  return result.skipped();
+}
+
+// Returns true if and only if the test was skipped.
+bool TestResult::Skipped() const {
+  return !Failed() && CountIf(test_part_results_, TestPartSkipped) > 0;
+}
+
+// Returns true if and only if the test failed.
+bool TestResult::Failed() const {
+  for (int i = 0; i < total_part_count(); ++i) {
+    if (GetTestPartResult(i).failed())
+      return true;
+  }
+  return false;
+}
+
+// Returns true if and only if the test part fatally failed.
+static bool TestPartFatallyFailed(const TestPartResult& result) {
+  return result.fatally_failed();
+}
+
+// Returns true if and only if the test fatally failed.
+bool TestResult::HasFatalFailure() const {
+  return CountIf(test_part_results_, TestPartFatallyFailed) > 0;
+}
+
+// Returns true if and only if the test part non-fatally failed.
+static bool TestPartNonfatallyFailed(const TestPartResult& result) {
+  return result.nonfatally_failed();
+}
+
+// Returns true if and only if the test has a non-fatal failure.
+bool TestResult::HasNonfatalFailure() const {
+  return CountIf(test_part_results_, TestPartNonfatallyFailed) > 0;
+}
+
+// Gets the number of all test parts.  This is the sum of the number
+// of successful test parts and the number of failed test parts.
+int TestResult::total_part_count() const {
+  return static_cast<int>(test_part_results_.size());
+}
+
+// Returns the number of the test properties.
+int TestResult::test_property_count() const {
+  return static_cast<int>(test_properties_.size());
+}
+
+// class Test
+
+// Creates a Test object.
+
+// The c'tor saves the states of all flags.
+Test::Test()
+    : gtest_flag_saver_(new GTEST_FLAG_SAVER_) {
+}
+
+// The d'tor restores the states of all flags.  The actual work is
+// done by the d'tor of the gtest_flag_saver_ field, and thus not
+// visible here.
+Test::~Test() {
+}
+
+// Sets up the test fixture.
+//
+// A sub-class may override this.
+void Test::SetUp() {
+}
+
+// Tears down the test fixture.
+//
+// A sub-class may override this.
+void Test::TearDown() {
+}
+
+// Allows user supplied key value pairs to be recorded for later output.
+void Test::RecordProperty(const std::string& key, const std::string& value) {
+  UnitTest::GetInstance()->RecordProperty(key, value);
+}
+
+// Allows user supplied key value pairs to be recorded for later output.
+void Test::RecordProperty(const std::string& key, int value) {
+  Message value_message;
+  value_message << value;
+  RecordProperty(key, value_message.GetString().c_str());
+}
+
+namespace internal {
+
+void ReportFailureInUnknownLocation(TestPartResult::Type result_type,
+                                    const std::string& message) {
+  // This function is a friend of UnitTest and as such has access to
+  // AddTestPartResult.
+  UnitTest::GetInstance()->AddTestPartResult(
+      result_type,
+      nullptr,  // No info about the source file where the exception occurred.
+      -1,       // We have no info on which line caused the exception.
+      message,
+      "");  // No stack trace, either.
+}
+
+}  // namespace internal
+
+// Google Test requires all tests in the same test suite to use the same test
+// fixture class.  This function checks if the current test has the
+// same fixture class as the first test in the current test suite.  If
+// yes, it returns true; otherwise it generates a Google Test failure and
+// returns false.
+bool Test::HasSameFixtureClass() {
+  internal::UnitTestImpl* const impl = internal::GetUnitTestImpl();
+  const TestSuite* const test_suite = impl->current_test_suite();
+
+  // Info about the first test in the current test suite.
+  const TestInfo* const first_test_info = test_suite->test_info_list()[0];
+  const internal::TypeId first_fixture_id = first_test_info->fixture_class_id_;
+  const char* const first_test_name = first_test_info->name();
+
+  // Info about the current test.
+  const TestInfo* const this_test_info = impl->current_test_info();
+  const internal::TypeId this_fixture_id = this_test_info->fixture_class_id_;
+  const char* const this_test_name = this_test_info->name();
+
+  if (this_fixture_id != first_fixture_id) {
+    // Is the first test defined using TEST?
+    const bool first_is_TEST = first_fixture_id == internal::GetTestTypeId();
+    // Is this test defined using TEST?
+    const bool this_is_TEST = this_fixture_id == internal::GetTestTypeId();
+
+    if (first_is_TEST || this_is_TEST) {
+      // Both TEST and TEST_F appear in same test suite, which is incorrect.
+      // Tell the user how to fix this.
+
+      // Gets the name of the TEST and the name of the TEST_F.  Note
+      // that first_is_TEST and this_is_TEST cannot both be true, as
+      // the fixture IDs are different for the two tests.
+      const char* const TEST_name =
+          first_is_TEST ? first_test_name : this_test_name;
+      const char* const TEST_F_name =
+          first_is_TEST ? this_test_name : first_test_name;
+
+      ADD_FAILURE()
+          << "All tests in the same test suite must use the same test fixture\n"
+          << "class, so mixing TEST_F and TEST in the same test suite is\n"
+          << "illegal.  In test suite " << this_test_info->test_suite_name()
+          << ",\n"
+          << "test " << TEST_F_name << " is defined using TEST_F but\n"
+          << "test " << TEST_name << " is defined using TEST.  You probably\n"
+          << "want to change the TEST to TEST_F or move it to another test\n"
+          << "case.";
+    } else {
+      // Two fixture classes with the same name appear in two different
+      // namespaces, which is not allowed. Tell the user how to fix this.
+      ADD_FAILURE()
+          << "All tests in the same test suite must use the same test fixture\n"
+          << "class.  However, in test suite "
+          << this_test_info->test_suite_name() << ",\n"
+          << "you defined test " << first_test_name << " and test "
+          << this_test_name << "\n"
+          << "using two different test fixture classes.  This can happen if\n"
+          << "the two classes are from different namespaces or translation\n"
+          << "units and have the same name.  You should probably rename one\n"
+          << "of the classes to put the tests into different test suites.";
+    }
+    return false;
+  }
+
+  return true;
+}
+
+#if GTEST_HAS_SEH
+
+// Adds an "exception thrown" fatal failure to the current test.  This
+// function returns its result via an output parameter pointer because VC++
+// prohibits creation of objects with destructors on stack in functions
+// using __try (see error C2712).
+static std::string* FormatSehExceptionMessage(DWORD exception_code,
+                                              const char* location) {
+  Message message;
+  message << "SEH exception with code 0x" << std::setbase(16) <<
+    exception_code << std::setbase(10) << " thrown in " << location << ".";
+
+  return new std::string(message.GetString());
+}
+
+#endif  // GTEST_HAS_SEH
+
+namespace internal {
+
+#if GTEST_HAS_EXCEPTIONS
+
+// Adds an "exception thrown" fatal failure to the current test.
+static std::string FormatCxxExceptionMessage(const char* description,
+                                             const char* location) {
+  Message message;
+  if (description != nullptr) {
+    message << "C++ exception with description \"" << description << "\"";
+  } else {
+    message << "Unknown C++ exception";
+  }
+  message << " thrown in " << location << ".";
+
+  return message.GetString();
+}
+
+static std::string PrintTestPartResultToString(
+    const TestPartResult& test_part_result);
+
+GoogleTestFailureException::GoogleTestFailureException(
+    const TestPartResult& failure)
+    : ::std::runtime_error(PrintTestPartResultToString(failure).c_str()) {}
+
+#endif  // GTEST_HAS_EXCEPTIONS
+
+// We put these helper functions in the internal namespace as IBM's xlC
+// compiler rejects the code if they were declared static.
+
+// Runs the given method and handles SEH exceptions it throws, when
+// SEH is supported; returns the 0-value for type Result in case of an
+// SEH exception.  (Microsoft compilers cannot handle SEH and C++
+// exceptions in the same function.  Therefore, we provide a separate
+// wrapper function for handling SEH exceptions.)
+template <class T, typename Result>
+Result HandleSehExceptionsInMethodIfSupported(
+    T* object, Result (T::*method)(), const char* location) {
+#if GTEST_HAS_SEH
+  __try {
+    return (object->*method)();
+  } __except (internal::UnitTestOptions::GTestShouldProcessSEH(  // NOLINT
+      GetExceptionCode())) {
+    // We create the exception message on the heap because VC++ prohibits
+    // creation of objects with destructors on stack in functions using __try
+    // (see error C2712).
+    std::string* exception_message = FormatSehExceptionMessage(
+        GetExceptionCode(), location);
+    internal::ReportFailureInUnknownLocation(TestPartResult::kFatalFailure,
+                                             *exception_message);
+    delete exception_message;
+    return static_cast<Result>(0);
+  }
+#else
+  (void)location;
+  return (object->*method)();
+#endif  // GTEST_HAS_SEH
+}
+
+// Runs the given method and catches and reports C++ and/or SEH-style
+// exceptions, if they are supported; returns the 0-value for type
+// Result in case of an SEH exception.
+template <class T, typename Result>
+Result HandleExceptionsInMethodIfSupported(
+    T* object, Result (T::*method)(), const char* location) {
+  // NOTE: The user code can affect the way in which Google Test handles
+  // exceptions by setting GTEST_FLAG(catch_exceptions), but only before
+  // RUN_ALL_TESTS() starts. It is technically possible to check the flag
+  // after the exception is caught and either report or re-throw the
+  // exception based on the flag's value:
+  //
+  // try {
+  //   // Perform the test method.
+  // } catch (...) {
+  //   if (GTEST_FLAG(catch_exceptions))
+  //     // Report the exception as failure.
+  //   else
+  //     throw;  // Re-throws the original exception.
+  // }
+  //
+  // However, the purpose of this flag is to allow the program to drop into
+  // the debugger when the exception is thrown. On most platforms, once the
+  // control enters the catch block, the exception origin information is
+  // lost and the debugger will stop the program at the point of the
+  // re-throw in this function -- instead of at the point of the original
+  // throw statement in the code under test.  For this reason, we perform
+  // the check early, sacrificing the ability to affect Google Test's
+  // exception handling in the method where the exception is thrown.
+  if (internal::GetUnitTestImpl()->catch_exceptions()) {
+#if GTEST_HAS_EXCEPTIONS
+    try {
+      return HandleSehExceptionsInMethodIfSupported(object, method, location);
+    } catch (const AssertionException&) {  // NOLINT
+      // This failure was reported already.
+    } catch (const internal::GoogleTestFailureException&) {  // NOLINT
+      // This exception type can only be thrown by a failed Google
+      // Test assertion with the intention of letting another testing
+      // framework catch it.  Therefore we just re-throw it.
+      throw;
+    } catch (const std::exception& e) {  // NOLINT
+      internal::ReportFailureInUnknownLocation(
+          TestPartResult::kFatalFailure,
+          FormatCxxExceptionMessage(e.what(), location));
+    } catch (...) {  // NOLINT
+      internal::ReportFailureInUnknownLocation(
+          TestPartResult::kFatalFailure,
+          FormatCxxExceptionMessage(nullptr, location));
+    }
+    return static_cast<Result>(0);
+#else
+    return HandleSehExceptionsInMethodIfSupported(object, method, location);
+#endif  // GTEST_HAS_EXCEPTIONS
+  } else {
+    return (object->*method)();
+  }
+}
+
+}  // namespace internal
+
+// Runs the test and updates the test result.
+void Test::Run() {
+  if (!HasSameFixtureClass()) return;
+
+  internal::UnitTestImpl* const impl = internal::GetUnitTestImpl();
+  impl->os_stack_trace_getter()->UponLeavingGTest();
+  internal::HandleExceptionsInMethodIfSupported(this, &Test::SetUp, "SetUp()");
+  // We will run the test only if SetUp() was successful and didn't call
+  // GTEST_SKIP().
+  if (!HasFatalFailure() && !IsSkipped()) {
+    impl->os_stack_trace_getter()->UponLeavingGTest();
+    internal::HandleExceptionsInMethodIfSupported(
+        this, &Test::TestBody, "the test body");
+  }
+
+  // However, we want to clean up as much as possible.  Hence we will
+  // always call TearDown(), even if SetUp() or the test body has
+  // failed.
+  impl->os_stack_trace_getter()->UponLeavingGTest();
+  internal::HandleExceptionsInMethodIfSupported(
+      this, &Test::TearDown, "TearDown()");
+}
+
+// Returns true if and only if the current test has a fatal failure.
+bool Test::HasFatalFailure() {
+  return internal::GetUnitTestImpl()->current_test_result()->HasFatalFailure();
+}
+
+// Returns true if and only if the current test has a non-fatal failure.
+bool Test::HasNonfatalFailure() {
+  return internal::GetUnitTestImpl()->current_test_result()->
+      HasNonfatalFailure();
+}
+
+// Returns true if and only if the current test was skipped.
+bool Test::IsSkipped() {
+  return internal::GetUnitTestImpl()->current_test_result()->Skipped();
+}
+
+// class TestInfo
+
+// Constructs a TestInfo object. It assumes ownership of the test factory
+// object.
+TestInfo::TestInfo(const std::string& a_test_suite_name,
+                   const std::string& a_name, const char* a_type_param,
+                   const char* a_value_param,
+                   internal::CodeLocation a_code_location,
+                   internal::TypeId fixture_class_id,
+                   internal::TestFactoryBase* factory)
+    : test_suite_name_(a_test_suite_name),
+      name_(a_name),
+      type_param_(a_type_param ? new std::string(a_type_param) : nullptr),
+      value_param_(a_value_param ? new std::string(a_value_param) : nullptr),
+      location_(a_code_location),
+      fixture_class_id_(fixture_class_id),
+      should_run_(false),
+      is_disabled_(false),
+      matches_filter_(false),
+      is_in_another_shard_(false),
+      factory_(factory),
+      result_() {}
+
+// Destructs a TestInfo object.
+TestInfo::~TestInfo() { delete factory_; }
+
+namespace internal {
+
+// Creates a new TestInfo object and registers it with Google Test;
+// returns the created object.
+//
+// Arguments:
+//
+//   test_suite_name:  name of the test suite
+//   name:             name of the test
+//   type_param:       the name of the test's type parameter, or NULL if
+//                     this is not a typed or a type-parameterized test.
+//   value_param:      text representation of the test's value parameter,
+//                     or NULL if this is not a value-parameterized test.
+//   code_location:    code location where the test is defined
+//   fixture_class_id: ID of the test fixture class
+//   set_up_tc:        pointer to the function that sets up the test suite
+//   tear_down_tc:     pointer to the function that tears down the test suite
+//   factory:          pointer to the factory that creates a test object.
+//                     The newly created TestInfo instance will assume
+//                     ownership of the factory object.
+TestInfo* MakeAndRegisterTestInfo(
+    const char* test_suite_name, const char* name, const char* type_param,
+    const char* value_param, CodeLocation code_location,
+    TypeId fixture_class_id, SetUpTestSuiteFunc set_up_tc,
+    TearDownTestSuiteFunc tear_down_tc, TestFactoryBase* factory) {
+  TestInfo* const test_info =
+      new TestInfo(test_suite_name, name, type_param, value_param,
+                   code_location, fixture_class_id, factory);
+  GetUnitTestImpl()->AddTestInfo(set_up_tc, tear_down_tc, test_info);
+  return test_info;
+}
+
+void ReportInvalidTestSuiteType(const char* test_suite_name,
+                                CodeLocation code_location) {
+  Message errors;
+  errors
+      << "Attempted redefinition of test suite " << test_suite_name << ".\n"
+      << "All tests in the same test suite must use the same test fixture\n"
+      << "class.  However, in test suite " << test_suite_name << ", you tried\n"
+      << "to define a test using a fixture class different from the one\n"
+      << "used earlier. This can happen if the two fixture classes are\n"
+      << "from different namespaces and have the same name. You should\n"
+      << "probably rename one of the classes to put the tests into different\n"
+      << "test suites.";
+
+  GTEST_LOG_(ERROR) << FormatFileLocation(code_location.file.c_str(),
+                                          code_location.line)
+                    << " " << errors.GetString();
+}
+}  // namespace internal
+
+namespace {
+
+// A predicate that checks the test name of a TestInfo against a known
+// value.
+//
+// This is used for implementation of the TestSuite class only.  We put
+// it in the anonymous namespace to prevent polluting the outer
+// namespace.
+//
+// TestNameIs is copyable.
+class TestNameIs {
+ public:
+  // Constructor.
+  //
+  // TestNameIs has NO default constructor.
+  explicit TestNameIs(const char* name)
+      : name_(name) {}
+
+  // Returns true if and only if the test name of test_info matches name_.
+  bool operator()(const TestInfo * test_info) const {
+    return test_info && test_info->name() == name_;
+  }
+
+ private:
+  std::string name_;
+};
+
+}  // namespace
+
+namespace internal {
+
+// This method expands all parameterized tests registered with macros TEST_P
+// and INSTANTIATE_TEST_SUITE_P into regular tests and registers those.
+// This will be done just once during the program runtime.
+void UnitTestImpl::RegisterParameterizedTests() {
+  if (!parameterized_tests_registered_) {
+    parameterized_test_registry_.RegisterTests();
+    type_parameterized_test_registry_.CheckForInstantiations();
+    parameterized_tests_registered_ = true;
+  }
+}
+
+}  // namespace internal
+
+// Creates the test object, runs it, records its result, and then
+// deletes it.
+void TestInfo::Run() {
+  if (!should_run_) return;
+
+  // Tells UnitTest where to store test result.
+  internal::UnitTestImpl* const impl = internal::GetUnitTestImpl();
+  impl->set_current_test_info(this);
+
+  TestEventListener* repeater = UnitTest::GetInstance()->listeners().repeater();
+
+  // Notifies the unit test event listeners that a test is about to start.
+  repeater->OnTestStart(*this);
+
+  result_.set_start_timestamp(internal::GetTimeInMillis());
+  internal::Timer timer;
+
+  impl->os_stack_trace_getter()->UponLeavingGTest();
+
+  // Creates the test object.
+  Test* const test = internal::HandleExceptionsInMethodIfSupported(
+      factory_, &internal::TestFactoryBase::CreateTest,
+      "the test fixture's constructor");
+
+  // Runs the test if the constructor didn't generate a fatal failure or invoke
+  // GTEST_SKIP().
+  // Note that the object will not be null
+  if (!Test::HasFatalFailure() && !Test::IsSkipped()) {
+    // This doesn't throw as all user code that can throw are wrapped into
+    // exception handling code.
+    test->Run();
+  }
+
+  if (test != nullptr) {
+    // Deletes the test object.
+    impl->os_stack_trace_getter()->UponLeavingGTest();
+    internal::HandleExceptionsInMethodIfSupported(
+        test, &Test::DeleteSelf_, "the test fixture's destructor");
+  }
+
+  result_.set_elapsed_time(timer.Elapsed());
+
+  // Notifies the unit test event listener that a test has just finished.
+  repeater->OnTestEnd(*this);
+
+  // Tells UnitTest to stop associating assertion results to this
+  // test.
+  impl->set_current_test_info(nullptr);
+}
+
+// Skip and records a skipped test result for this object.
+void TestInfo::Skip() {
+  if (!should_run_) return;
+
+  internal::UnitTestImpl* const impl = internal::GetUnitTestImpl();
+  impl->set_current_test_info(this);
+
+  TestEventListener* repeater = UnitTest::GetInstance()->listeners().repeater();
+
+  // Notifies the unit test event listeners that a test is about to start.
+  repeater->OnTestStart(*this);
+
+  const TestPartResult test_part_result =
+      TestPartResult(TestPartResult::kSkip, this->file(), this->line(), "");
+  impl->GetTestPartResultReporterForCurrentThread()->ReportTestPartResult(
+      test_part_result);
+
+  // Notifies the unit test event listener that a test has just finished.
+  repeater->OnTestEnd(*this);
+  impl->set_current_test_info(nullptr);
+}
+
+// class TestSuite
+
+// Gets the number of successful tests in this test suite.
+int TestSuite::successful_test_count() const {
+  return CountIf(test_info_list_, TestPassed);
+}
+
+// Gets the number of successful tests in this test suite.
+int TestSuite::skipped_test_count() const {
+  return CountIf(test_info_list_, TestSkipped);
+}
+
+// Gets the number of failed tests in this test suite.
+int TestSuite::failed_test_count() const {
+  return CountIf(test_info_list_, TestFailed);
+}
+
+// Gets the number of disabled tests that will be reported in the XML report.
+int TestSuite::reportable_disabled_test_count() const {
+  return CountIf(test_info_list_, TestReportableDisabled);
+}
+
+// Gets the number of disabled tests in this test suite.
+int TestSuite::disabled_test_count() const {
+  return CountIf(test_info_list_, TestDisabled);
+}
+
+// Gets the number of tests to be printed in the XML report.
+int TestSuite::reportable_test_count() const {
+  return CountIf(test_info_list_, TestReportable);
+}
+
+// Get the number of tests in this test suite that should run.
+int TestSuite::test_to_run_count() const {
+  return CountIf(test_info_list_, ShouldRunTest);
+}
+
+// Gets the number of all tests.
+int TestSuite::total_test_count() const {
+  return static_cast<int>(test_info_list_.size());
+}
+
+// Creates a TestSuite with the given name.
+//
+// Arguments:
+//
+//   a_name:       name of the test suite
+//   a_type_param: the name of the test suite's type parameter, or NULL if
+//                 this is not a typed or a type-parameterized test suite.
+//   set_up_tc:    pointer to the function that sets up the test suite
+//   tear_down_tc: pointer to the function that tears down the test suite
+TestSuite::TestSuite(const char* a_name, const char* a_type_param,
+                     internal::SetUpTestSuiteFunc set_up_tc,
+                     internal::TearDownTestSuiteFunc tear_down_tc)
+    : name_(a_name),
+      type_param_(a_type_param ? new std::string(a_type_param) : nullptr),
+      set_up_tc_(set_up_tc),
+      tear_down_tc_(tear_down_tc),
+      should_run_(false),
+      start_timestamp_(0),
+      elapsed_time_(0) {}
+
+// Destructor of TestSuite.
+TestSuite::~TestSuite() {
+  // Deletes every Test in the collection.
+  ForEach(test_info_list_, internal::Delete<TestInfo>);
+}
+
+// Returns the i-th test among all the tests. i can range from 0 to
+// total_test_count() - 1. If i is not in that range, returns NULL.
+const TestInfo* TestSuite::GetTestInfo(int i) const {
+  const int index = GetElementOr(test_indices_, i, -1);
+  return index < 0 ? nullptr : test_info_list_[static_cast<size_t>(index)];
+}
+
+// Returns the i-th test among all the tests. i can range from 0 to
+// total_test_count() - 1. If i is not in that range, returns NULL.
+TestInfo* TestSuite::GetMutableTestInfo(int i) {
+  const int index = GetElementOr(test_indices_, i, -1);
+  return index < 0 ? nullptr : test_info_list_[static_cast<size_t>(index)];
+}
+
+// Adds a test to this test suite.  Will delete the test upon
+// destruction of the TestSuite object.
+void TestSuite::AddTestInfo(TestInfo* test_info) {
+  test_info_list_.push_back(test_info);
+  test_indices_.push_back(static_cast<int>(test_indices_.size()));
+}
+
+// Runs every test in this TestSuite.
+void TestSuite::Run() {
+  if (!should_run_) return;
+
+  internal::UnitTestImpl* const impl = internal::GetUnitTestImpl();
+  impl->set_current_test_suite(this);
+
+  TestEventListener* repeater = UnitTest::GetInstance()->listeners().repeater();
+
+  // Call both legacy and the new API
+  repeater->OnTestSuiteStart(*this);
+//  Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  repeater->OnTestCaseStart(*this);
+#endif  //  GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+  impl->os_stack_trace_getter()->UponLeavingGTest();
+  internal::HandleExceptionsInMethodIfSupported(
+      this, &TestSuite::RunSetUpTestSuite, "SetUpTestSuite()");
+
+  start_timestamp_ = internal::GetTimeInMillis();
+  internal::Timer timer;
+  for (int i = 0; i < total_test_count(); i++) {
+    GetMutableTestInfo(i)->Run();
+    if (GTEST_FLAG(fail_fast) && GetMutableTestInfo(i)->result()->Failed()) {
+      for (int j = i + 1; j < total_test_count(); j++) {
+        GetMutableTestInfo(j)->Skip();
+      }
+      break;
+    }
+  }
+  elapsed_time_ = timer.Elapsed();
+
+  impl->os_stack_trace_getter()->UponLeavingGTest();
+  internal::HandleExceptionsInMethodIfSupported(
+      this, &TestSuite::RunTearDownTestSuite, "TearDownTestSuite()");
+
+  // Call both legacy and the new API
+  repeater->OnTestSuiteEnd(*this);
+//  Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  repeater->OnTestCaseEnd(*this);
+#endif  //  GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+  impl->set_current_test_suite(nullptr);
+}
+
+// Skips all tests under this TestSuite.
+void TestSuite::Skip() {
+  if (!should_run_) return;
+
+  internal::UnitTestImpl* const impl = internal::GetUnitTestImpl();
+  impl->set_current_test_suite(this);
+
+  TestEventListener* repeater = UnitTest::GetInstance()->listeners().repeater();
+
+  // Call both legacy and the new API
+  repeater->OnTestSuiteStart(*this);
+//  Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  repeater->OnTestCaseStart(*this);
+#endif  //  GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+  for (int i = 0; i < total_test_count(); i++) {
+    GetMutableTestInfo(i)->Skip();
+  }
+
+  // Call both legacy and the new API
+  repeater->OnTestSuiteEnd(*this);
+  // Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  repeater->OnTestCaseEnd(*this);
+#endif  //  GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+  impl->set_current_test_suite(nullptr);
+}
+
+// Clears the results of all tests in this test suite.
+void TestSuite::ClearResult() {
+  ad_hoc_test_result_.Clear();
+  ForEach(test_info_list_, TestInfo::ClearTestResult);
+}
+
+// Shuffles the tests in this test suite.
+void TestSuite::ShuffleTests(internal::Random* random) {
+  Shuffle(random, &test_indices_);
+}
+
+// Restores the test order to before the first shuffle.
+void TestSuite::UnshuffleTests() {
+  for (size_t i = 0; i < test_indices_.size(); i++) {
+    test_indices_[i] = static_cast<int>(i);
+  }
+}
+
+// Formats a countable noun.  Depending on its quantity, either the
+// singular form or the plural form is used. e.g.
+//
+// FormatCountableNoun(1, "formula", "formuli") returns "1 formula".
+// FormatCountableNoun(5, "book", "books") returns "5 books".
+static std::string FormatCountableNoun(int count,
+                                       const char * singular_form,
+                                       const char * plural_form) {
+  return internal::StreamableToString(count) + " " +
+      (count == 1 ? singular_form : plural_form);
+}
+
+// Formats the count of tests.
+static std::string FormatTestCount(int test_count) {
+  return FormatCountableNoun(test_count, "test", "tests");
+}
+
+// Formats the count of test suites.
+static std::string FormatTestSuiteCount(int test_suite_count) {
+  return FormatCountableNoun(test_suite_count, "test suite", "test suites");
+}
+
+// Converts a TestPartResult::Type enum to human-friendly string
+// representation.  Both kNonFatalFailure and kFatalFailure are translated
+// to "Failure", as the user usually doesn't care about the difference
+// between the two when viewing the test result.
+static const char * TestPartResultTypeToString(TestPartResult::Type type) {
+  switch (type) {
+    case TestPartResult::kSkip:
+      return "Skipped\n";
+    case TestPartResult::kSuccess:
+      return "Success";
+
+    case TestPartResult::kNonFatalFailure:
+    case TestPartResult::kFatalFailure:
+#ifdef _MSC_VER
+      return "error: ";
+#else
+      return "Failure\n";
+#endif
+    default:
+      return "Unknown result type";
+  }
+}
+
+namespace internal {
+namespace {
+enum class GTestColor { kDefault, kRed, kGreen, kYellow };
+}  // namespace
+
+// Prints a TestPartResult to an std::string.
+static std::string PrintTestPartResultToString(
+    const TestPartResult& test_part_result) {
+  return (Message()
+          << internal::FormatFileLocation(test_part_result.file_name(),
+                                          test_part_result.line_number())
+          << " " << TestPartResultTypeToString(test_part_result.type())
+          << test_part_result.message()).GetString();
+}
+
+// Prints a TestPartResult.
+static void PrintTestPartResult(const TestPartResult& test_part_result) {
+  const std::string& result =
+      PrintTestPartResultToString(test_part_result);
+  printf("%s\n", result.c_str());
+  fflush(stdout);
+  // If the test program runs in Visual Studio or a debugger, the
+  // following statements add the test part result message to the Output
+  // window such that the user can double-click on it to jump to the
+  // corresponding source code location; otherwise they do nothing.
+#if GTEST_OS_WINDOWS && !GTEST_OS_WINDOWS_MOBILE
+  // We don't call OutputDebugString*() on Windows Mobile, as printing
+  // to stdout is done by OutputDebugString() there already - we don't
+  // want the same message printed twice.
+  ::OutputDebugStringA(result.c_str());
+  ::OutputDebugStringA("\n");
+#endif
+}
+
+// class PrettyUnitTestResultPrinter
+#if GTEST_OS_WINDOWS && !GTEST_OS_WINDOWS_MOBILE && \
+    !GTEST_OS_WINDOWS_PHONE && !GTEST_OS_WINDOWS_RT && !GTEST_OS_WINDOWS_MINGW
+
+// Returns the character attribute for the given color.
+static WORD GetColorAttribute(GTestColor color) {
+  switch (color) {
+    case GTestColor::kRed:
+      return FOREGROUND_RED;
+    case GTestColor::kGreen:
+      return FOREGROUND_GREEN;
+    case GTestColor::kYellow:
+      return FOREGROUND_RED | FOREGROUND_GREEN;
+    default:           return 0;
+  }
+}
+
+static int GetBitOffset(WORD color_mask) {
+  if (color_mask == 0) return 0;
+
+  int bitOffset = 0;
+  while ((color_mask & 1) == 0) {
+    color_mask >>= 1;
+    ++bitOffset;
+  }
+  return bitOffset;
+}
+
+static WORD GetNewColor(GTestColor color, WORD old_color_attrs) {
+  // Let's reuse the BG
+  static const WORD background_mask = BACKGROUND_BLUE | BACKGROUND_GREEN |
+                                      BACKGROUND_RED | BACKGROUND_INTENSITY;
+  static const WORD foreground_mask = FOREGROUND_BLUE | FOREGROUND_GREEN |
+                                      FOREGROUND_RED | FOREGROUND_INTENSITY;
+  const WORD existing_bg = old_color_attrs & background_mask;
+
+  WORD new_color =
+      GetColorAttribute(color) | existing_bg | FOREGROUND_INTENSITY;
+  static const int bg_bitOffset = GetBitOffset(background_mask);
+  static const int fg_bitOffset = GetBitOffset(foreground_mask);
+
+  if (((new_color & background_mask) >> bg_bitOffset) ==
+      ((new_color & foreground_mask) >> fg_bitOffset)) {
+    new_color ^= FOREGROUND_INTENSITY;  // invert intensity
+  }
+  return new_color;
+}
+
+#else
+
+// Returns the ANSI color code for the given color. GTestColor::kDefault is
+// an invalid input.
+static const char* GetAnsiColorCode(GTestColor color) {
+  switch (color) {
+    case GTestColor::kRed:
+      return "1";
+    case GTestColor::kGreen:
+      return "2";
+    case GTestColor::kYellow:
+      return "3";
+    default:
+      return nullptr;
+  }
+}
+
+#endif  // GTEST_OS_WINDOWS && !GTEST_OS_WINDOWS_MOBILE
+
+// Returns true if and only if Google Test should use colors in the output.
+bool ShouldUseColor(bool stdout_is_tty) {
+  const char* const gtest_color = GTEST_FLAG(color).c_str();
+
+  if (String::CaseInsensitiveCStringEquals(gtest_color, "auto")) {
+#if GTEST_OS_WINDOWS && !GTEST_OS_WINDOWS_MINGW
+    // On Windows the TERM variable is usually not set, but the
+    // console there does support colors.
+    return stdout_is_tty;
+#else
+    // On non-Windows platforms, we rely on the TERM variable.
+    const char* const term = posix::GetEnv("TERM");
+    const bool term_supports_color =
+        String::CStringEquals(term, "xterm") ||
+        String::CStringEquals(term, "xterm-color") ||
+        String::CStringEquals(term, "xterm-256color") ||
+        String::CStringEquals(term, "screen") ||
+        String::CStringEquals(term, "screen-256color") ||
+        String::CStringEquals(term, "tmux") ||
+        String::CStringEquals(term, "tmux-256color") ||
+        String::CStringEquals(term, "rxvt-unicode") ||
+        String::CStringEquals(term, "rxvt-unicode-256color") ||
+        String::CStringEquals(term, "linux") ||
+        String::CStringEquals(term, "cygwin");
+    return stdout_is_tty && term_supports_color;
+#endif  // GTEST_OS_WINDOWS
+  }
+
+  return String::CaseInsensitiveCStringEquals(gtest_color, "yes") ||
+      String::CaseInsensitiveCStringEquals(gtest_color, "true") ||
+      String::CaseInsensitiveCStringEquals(gtest_color, "t") ||
+      String::CStringEquals(gtest_color, "1");
+  // We take "yes", "true", "t", and "1" as meaning "yes".  If the
+  // value is neither one of these nor "auto", we treat it as "no" to
+  // be conservative.
+}
+
+// Helpers for printing colored strings to stdout. Note that on Windows, we
+// cannot simply emit special characters and have the terminal change colors.
+// This routine must actually emit the characters rather than return a string
+// that would be colored when printed, as can be done on Linux.
+
+GTEST_ATTRIBUTE_PRINTF_(2, 3)
+static void ColoredPrintf(GTestColor color, const char *fmt, ...) {
+  va_list args;
+  va_start(args, fmt);
+
+#if GTEST_OS_WINDOWS_MOBILE || GTEST_OS_ZOS || GTEST_OS_IOS || \
+    GTEST_OS_WINDOWS_PHONE || GTEST_OS_WINDOWS_RT || defined(ESP_PLATFORM)
+  const bool use_color = AlwaysFalse();
+#else
+  static const bool in_color_mode =
+      ShouldUseColor(posix::IsATTY(posix::FileNo(stdout)) != 0);
+  const bool use_color = in_color_mode && (color != GTestColor::kDefault);
+#endif  // GTEST_OS_WINDOWS_MOBILE || GTEST_OS_ZOS
+
+  if (!use_color) {
+    vprintf(fmt, args);
+    va_end(args);
+    return;
+  }
+
+#if GTEST_OS_WINDOWS && !GTEST_OS_WINDOWS_MOBILE && \
+    !GTEST_OS_WINDOWS_PHONE && !GTEST_OS_WINDOWS_RT && !GTEST_OS_WINDOWS_MINGW
+  const HANDLE stdout_handle = GetStdHandle(STD_OUTPUT_HANDLE);
+
+  // Gets the current text color.
+  CONSOLE_SCREEN_BUFFER_INFO buffer_info;
+  GetConsoleScreenBufferInfo(stdout_handle, &buffer_info);
+  const WORD old_color_attrs = buffer_info.wAttributes;
+  const WORD new_color = GetNewColor(color, old_color_attrs);
+
+  // We need to flush the stream buffers into the console before each
+  // SetConsoleTextAttribute call lest it affect the text that is already
+  // printed but has not yet reached the console.
+  fflush(stdout);
+  SetConsoleTextAttribute(stdout_handle, new_color);
+
+  vprintf(fmt, args);
+
+  fflush(stdout);
+  // Restores the text color.
+  SetConsoleTextAttribute(stdout_handle, old_color_attrs);
+#else
+  printf("\033[0;3%sm", GetAnsiColorCode(color));
+  vprintf(fmt, args);
+  printf("\033[m");  // Resets the terminal to default.
+#endif  // GTEST_OS_WINDOWS && !GTEST_OS_WINDOWS_MOBILE
+  va_end(args);
+}
+
+// Text printed in Google Test's text output and --gtest_list_tests
+// output to label the type parameter and value parameter for a test.
+static const char kTypeParamLabel[] = "TypeParam";
+static const char kValueParamLabel[] = "GetParam()";
+
+static void PrintFullTestCommentIfPresent(const TestInfo& test_info) {
+  const char* const type_param = test_info.type_param();
+  const char* const value_param = test_info.value_param();
+
+  if (type_param != nullptr || value_param != nullptr) {
+    printf(", where ");
+    if (type_param != nullptr) {
+      printf("%s = %s", kTypeParamLabel, type_param);
+      if (value_param != nullptr) printf(" and ");
+    }
+    if (value_param != nullptr) {
+      printf("%s = %s", kValueParamLabel, value_param);
+    }
+  }
+}
+
+// This class implements the TestEventListener interface.
+//
+// Class PrettyUnitTestResultPrinter is copyable.
+class PrettyUnitTestResultPrinter : public TestEventListener {
+ public:
+  PrettyUnitTestResultPrinter() {}
+  static void PrintTestName(const char* test_suite, const char* test) {
+    printf("%s.%s", test_suite, test);
+  }
+
+  // The following methods override what's in the TestEventListener class.
+  void OnTestProgramStart(const UnitTest& /*unit_test*/) override {}
+  void OnTestIterationStart(const UnitTest& unit_test, int iteration) override;
+  void OnEnvironmentsSetUpStart(const UnitTest& unit_test) override;
+  void OnEnvironmentsSetUpEnd(const UnitTest& /*unit_test*/) override {}
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  void OnTestCaseStart(const TestCase& test_case) override;
+#else
+  void OnTestSuiteStart(const TestSuite& test_suite) override;
+#endif  // OnTestCaseStart
+
+  void OnTestStart(const TestInfo& test_info) override;
+
+  void OnTestPartResult(const TestPartResult& result) override;
+  void OnTestEnd(const TestInfo& test_info) override;
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  void OnTestCaseEnd(const TestCase& test_case) override;
+#else
+  void OnTestSuiteEnd(const TestSuite& test_suite) override;
+#endif  // GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+  void OnEnvironmentsTearDownStart(const UnitTest& unit_test) override;
+  void OnEnvironmentsTearDownEnd(const UnitTest& /*unit_test*/) override {}
+  void OnTestIterationEnd(const UnitTest& unit_test, int iteration) override;
+  void OnTestProgramEnd(const UnitTest& /*unit_test*/) override {}
+
+ private:
+  static void PrintFailedTests(const UnitTest& unit_test);
+  static void PrintFailedTestSuites(const UnitTest& unit_test);
+  static void PrintSkippedTests(const UnitTest& unit_test);
+};
+
+  // Fired before each iteration of tests starts.
+void PrettyUnitTestResultPrinter::OnTestIterationStart(
+    const UnitTest& unit_test, int iteration) {
+  if (GTEST_FLAG(repeat) != 1)
+    printf("\nRepeating all tests (iteration %d) . . .\n\n", iteration + 1);
+
+  const char* const filter = GTEST_FLAG(filter).c_str();
+
+  // Prints the filter if it's not *.  This reminds the user that some
+  // tests may be skipped.
+  if (!String::CStringEquals(filter, kUniversalFilter)) {
+    ColoredPrintf(GTestColor::kYellow, "Note: %s filter = %s\n", GTEST_NAME_,
+                  filter);
+  }
+
+  if (internal::ShouldShard(kTestTotalShards, kTestShardIndex, false)) {
+    const int32_t shard_index = Int32FromEnvOrDie(kTestShardIndex, -1);
+    ColoredPrintf(GTestColor::kYellow, "Note: This is test shard %d of %s.\n",
+                  static_cast<int>(shard_index) + 1,
+                  internal::posix::GetEnv(kTestTotalShards));
+  }
+
+  if (GTEST_FLAG(shuffle)) {
+    ColoredPrintf(GTestColor::kYellow,
+                  "Note: Randomizing tests' orders with a seed of %d .\n",
+                  unit_test.random_seed());
+  }
+
+  ColoredPrintf(GTestColor::kGreen, "[==========] ");
+  printf("Running %s from %s.\n",
+         FormatTestCount(unit_test.test_to_run_count()).c_str(),
+         FormatTestSuiteCount(unit_test.test_suite_to_run_count()).c_str());
+  fflush(stdout);
+}
+
+void PrettyUnitTestResultPrinter::OnEnvironmentsSetUpStart(
+    const UnitTest& /*unit_test*/) {
+  ColoredPrintf(GTestColor::kGreen, "[----------] ");
+  printf("Global test environment set-up.\n");
+  fflush(stdout);
+}
+
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+void PrettyUnitTestResultPrinter::OnTestCaseStart(const TestCase& test_case) {
+  const std::string counts =
+      FormatCountableNoun(test_case.test_to_run_count(), "test", "tests");
+  ColoredPrintf(GTestColor::kGreen, "[----------] ");
+  printf("%s from %s", counts.c_str(), test_case.name());
+  if (test_case.type_param() == nullptr) {
+    printf("\n");
+  } else {
+    printf(", where %s = %s\n", kTypeParamLabel, test_case.type_param());
+  }
+  fflush(stdout);
+}
+#else
+void PrettyUnitTestResultPrinter::OnTestSuiteStart(
+    const TestSuite& test_suite) {
+  const std::string counts =
+      FormatCountableNoun(test_suite.test_to_run_count(), "test", "tests");
+  ColoredPrintf(GTestColor::kGreen, "[----------] ");
+  printf("%s from %s", counts.c_str(), test_suite.name());
+  if (test_suite.type_param() == nullptr) {
+    printf("\n");
+  } else {
+    printf(", where %s = %s\n", kTypeParamLabel, test_suite.type_param());
+  }
+  fflush(stdout);
+}
+#endif  // GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+void PrettyUnitTestResultPrinter::OnTestStart(const TestInfo& test_info) {
+  ColoredPrintf(GTestColor::kGreen, "[ RUN      ] ");
+  PrintTestName(test_info.test_suite_name(), test_info.name());
+  printf("\n");
+  fflush(stdout);
+}
+
+// Called after an assertion failure.
+void PrettyUnitTestResultPrinter::OnTestPartResult(
+    const TestPartResult& result) {
+  switch (result.type()) {
+    // If the test part succeeded, we don't need to do anything.
+    case TestPartResult::kSuccess:
+      return;
+    default:
+      // Print failure message from the assertion
+      // (e.g. expected this and got that).
+      PrintTestPartResult(result);
+      fflush(stdout);
+  }
+}
+
+void PrettyUnitTestResultPrinter::OnTestEnd(const TestInfo& test_info) {
+  if (test_info.result()->Passed()) {
+    ColoredPrintf(GTestColor::kGreen, "[       OK ] ");
+  } else if (test_info.result()->Skipped()) {
+    ColoredPrintf(GTestColor::kGreen, "[  SKIPPED ] ");
+  } else {
+    ColoredPrintf(GTestColor::kRed, "[  FAILED  ] ");
+  }
+  PrintTestName(test_info.test_suite_name(), test_info.name());
+  if (test_info.result()->Failed())
+    PrintFullTestCommentIfPresent(test_info);
+
+  if (GTEST_FLAG(print_time)) {
+    printf(" (%s ms)\n", internal::StreamableToString(
+           test_info.result()->elapsed_time()).c_str());
+  } else {
+    printf("\n");
+  }
+  fflush(stdout);
+}
+
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+void PrettyUnitTestResultPrinter::OnTestCaseEnd(const TestCase& test_case) {
+  if (!GTEST_FLAG(print_time)) return;
+
+  const std::string counts =
+      FormatCountableNoun(test_case.test_to_run_count(), "test", "tests");
+  ColoredPrintf(GTestColor::kGreen, "[----------] ");
+  printf("%s from %s (%s ms total)\n\n", counts.c_str(), test_case.name(),
+         internal::StreamableToString(test_case.elapsed_time()).c_str());
+  fflush(stdout);
+}
+#else
+void PrettyUnitTestResultPrinter::OnTestSuiteEnd(const TestSuite& test_suite) {
+  if (!GTEST_FLAG(print_time)) return;
+
+  const std::string counts =
+      FormatCountableNoun(test_suite.test_to_run_count(), "test", "tests");
+  ColoredPrintf(GTestColor::kGreen, "[----------] ");
+  printf("%s from %s (%s ms total)\n\n", counts.c_str(), test_suite.name(),
+         internal::StreamableToString(test_suite.elapsed_time()).c_str());
+  fflush(stdout);
+}
+#endif  // GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+void PrettyUnitTestResultPrinter::OnEnvironmentsTearDownStart(
+    const UnitTest& /*unit_test*/) {
+  ColoredPrintf(GTestColor::kGreen, "[----------] ");
+  printf("Global test environment tear-down\n");
+  fflush(stdout);
+}
+
+// Internal helper for printing the list of failed tests.
+void PrettyUnitTestResultPrinter::PrintFailedTests(const UnitTest& unit_test) {
+  const int failed_test_count = unit_test.failed_test_count();
+  ColoredPrintf(GTestColor::kRed, "[  FAILED  ] ");
+  printf("%s, listed below:\n", FormatTestCount(failed_test_count).c_str());
+
+  for (int i = 0; i < unit_test.total_test_suite_count(); ++i) {
+    const TestSuite& test_suite = *unit_test.GetTestSuite(i);
+    if (!test_suite.should_run() || (test_suite.failed_test_count() == 0)) {
+      continue;
+    }
+    for (int j = 0; j < test_suite.total_test_count(); ++j) {
+      const TestInfo& test_info = *test_suite.GetTestInfo(j);
+      if (!test_info.should_run() || !test_info.result()->Failed()) {
+        continue;
+      }
+      ColoredPrintf(GTestColor::kRed, "[  FAILED  ] ");
+      printf("%s.%s", test_suite.name(), test_info.name());
+      PrintFullTestCommentIfPresent(test_info);
+      printf("\n");
+    }
+  }
+  printf("\n%2d FAILED %s\n", failed_test_count,
+         failed_test_count == 1 ? "TEST" : "TESTS");
+}
+
+// Internal helper for printing the list of test suite failures not covered by
+// PrintFailedTests.
+void PrettyUnitTestResultPrinter::PrintFailedTestSuites(
+    const UnitTest& unit_test) {
+  int suite_failure_count = 0;
+  for (int i = 0; i < unit_test.total_test_suite_count(); ++i) {
+    const TestSuite& test_suite = *unit_test.GetTestSuite(i);
+    if (!test_suite.should_run()) {
+      continue;
+    }
+    if (test_suite.ad_hoc_test_result().Failed()) {
+      ColoredPrintf(GTestColor::kRed, "[  FAILED  ] ");
+      printf("%s: SetUpTestSuite or TearDownTestSuite\n", test_suite.name());
+      ++suite_failure_count;
+    }
+  }
+  if (suite_failure_count > 0) {
+    printf("\n%2d FAILED TEST %s\n", suite_failure_count,
+           suite_failure_count == 1 ? "SUITE" : "SUITES");
+  }
+}
+
+// Internal helper for printing the list of skipped tests.
+void PrettyUnitTestResultPrinter::PrintSkippedTests(const UnitTest& unit_test) {
+  const int skipped_test_count = unit_test.skipped_test_count();
+  if (skipped_test_count == 0) {
+    return;
+  }
+
+  for (int i = 0; i < unit_test.total_test_suite_count(); ++i) {
+    const TestSuite& test_suite = *unit_test.GetTestSuite(i);
+    if (!test_suite.should_run() || (test_suite.skipped_test_count() == 0)) {
+      continue;
+    }
+    for (int j = 0; j < test_suite.total_test_count(); ++j) {
+      const TestInfo& test_info = *test_suite.GetTestInfo(j);
+      if (!test_info.should_run() || !test_info.result()->Skipped()) {
+        continue;
+      }
+      ColoredPrintf(GTestColor::kGreen, "[  SKIPPED ] ");
+      printf("%s.%s", test_suite.name(), test_info.name());
+      printf("\n");
+    }
+  }
+}
+
+void PrettyUnitTestResultPrinter::OnTestIterationEnd(const UnitTest& unit_test,
+                                                     int /*iteration*/) {
+  ColoredPrintf(GTestColor::kGreen, "[==========] ");
+  printf("%s from %s ran.",
+         FormatTestCount(unit_test.test_to_run_count()).c_str(),
+         FormatTestSuiteCount(unit_test.test_suite_to_run_count()).c_str());
+  if (GTEST_FLAG(print_time)) {
+    printf(" (%s ms total)",
+           internal::StreamableToString(unit_test.elapsed_time()).c_str());
+  }
+  printf("\n");
+  ColoredPrintf(GTestColor::kGreen, "[  PASSED  ] ");
+  printf("%s.\n", FormatTestCount(unit_test.successful_test_count()).c_str());
+
+  const int skipped_test_count = unit_test.skipped_test_count();
+  if (skipped_test_count > 0) {
+    ColoredPrintf(GTestColor::kGreen, "[  SKIPPED ] ");
+    printf("%s, listed below:\n", FormatTestCount(skipped_test_count).c_str());
+    PrintSkippedTests(unit_test);
+  }
+
+  if (!unit_test.Passed()) {
+    PrintFailedTests(unit_test);
+    PrintFailedTestSuites(unit_test);
+  }
+
+  int num_disabled = unit_test.reportable_disabled_test_count();
+  if (num_disabled && !GTEST_FLAG(also_run_disabled_tests)) {
+    if (unit_test.Passed()) {
+      printf("\n");  // Add a spacer if no FAILURE banner is displayed.
+    }
+    ColoredPrintf(GTestColor::kYellow, "  YOU HAVE %d DISABLED %s\n\n",
+                  num_disabled, num_disabled == 1 ? "TEST" : "TESTS");
+  }
+  // Ensure that Google Test output is printed before, e.g., heapchecker output.
+  fflush(stdout);
+}
+
+// End PrettyUnitTestResultPrinter
+
+// This class implements the TestEventListener interface.
+//
+// Class BriefUnitTestResultPrinter is copyable.
+class BriefUnitTestResultPrinter : public TestEventListener {
+ public:
+  BriefUnitTestResultPrinter() {}
+  static void PrintTestName(const char* test_suite, const char* test) {
+    printf("%s.%s", test_suite, test);
+  }
+
+  // The following methods override what's in the TestEventListener class.
+  void OnTestProgramStart(const UnitTest& /*unit_test*/) override {}
+  void OnTestIterationStart(const UnitTest& /*unit_test*/,
+                            int /*iteration*/) override {}
+  void OnEnvironmentsSetUpStart(const UnitTest& /*unit_test*/) override {}
+  void OnEnvironmentsSetUpEnd(const UnitTest& /*unit_test*/) override {}
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  void OnTestCaseStart(const TestCase& /*test_case*/) override {}
+#else
+  void OnTestSuiteStart(const TestSuite& /*test_suite*/) override {}
+#endif  // OnTestCaseStart
+
+  void OnTestStart(const TestInfo& /*test_info*/) override {}
+
+  void OnTestPartResult(const TestPartResult& result) override;
+  void OnTestEnd(const TestInfo& test_info) override;
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  void OnTestCaseEnd(const TestCase& /*test_case*/) override {}
+#else
+  void OnTestSuiteEnd(const TestSuite& /*test_suite*/) override {}
+#endif  // GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+  void OnEnvironmentsTearDownStart(const UnitTest& /*unit_test*/) override {}
+  void OnEnvironmentsTearDownEnd(const UnitTest& /*unit_test*/) override {}
+  void OnTestIterationEnd(const UnitTest& unit_test, int iteration) override;
+  void OnTestProgramEnd(const UnitTest& /*unit_test*/) override {}
+};
+
+// Called after an assertion failure.
+void BriefUnitTestResultPrinter::OnTestPartResult(
+    const TestPartResult& result) {
+  switch (result.type()) {
+    // If the test part succeeded, we don't need to do anything.
+    case TestPartResult::kSuccess:
+      return;
+    default:
+      // Print failure message from the assertion
+      // (e.g. expected this and got that).
+      PrintTestPartResult(result);
+      fflush(stdout);
+  }
+}
+
+void BriefUnitTestResultPrinter::OnTestEnd(const TestInfo& test_info) {
+  if (test_info.result()->Failed()) {
+    ColoredPrintf(GTestColor::kRed, "[  FAILED  ] ");
+    PrintTestName(test_info.test_suite_name(), test_info.name());
+    PrintFullTestCommentIfPresent(test_info);
+
+    if (GTEST_FLAG(print_time)) {
+      printf(" (%s ms)\n",
+             internal::StreamableToString(test_info.result()->elapsed_time())
+                 .c_str());
+    } else {
+      printf("\n");
+    }
+    fflush(stdout);
+  }
+}
+
+void BriefUnitTestResultPrinter::OnTestIterationEnd(const UnitTest& unit_test,
+                                                    int /*iteration*/) {
+  ColoredPrintf(GTestColor::kGreen, "[==========] ");
+  printf("%s from %s ran.",
+         FormatTestCount(unit_test.test_to_run_count()).c_str(),
+         FormatTestSuiteCount(unit_test.test_suite_to_run_count()).c_str());
+  if (GTEST_FLAG(print_time)) {
+    printf(" (%s ms total)",
+           internal::StreamableToString(unit_test.elapsed_time()).c_str());
+  }
+  printf("\n");
+  ColoredPrintf(GTestColor::kGreen, "[  PASSED  ] ");
+  printf("%s.\n", FormatTestCount(unit_test.successful_test_count()).c_str());
+
+  const int skipped_test_count = unit_test.skipped_test_count();
+  if (skipped_test_count > 0) {
+    ColoredPrintf(GTestColor::kGreen, "[  SKIPPED ] ");
+    printf("%s.\n", FormatTestCount(skipped_test_count).c_str());
+  }
+
+  int num_disabled = unit_test.reportable_disabled_test_count();
+  if (num_disabled && !GTEST_FLAG(also_run_disabled_tests)) {
+    if (unit_test.Passed()) {
+      printf("\n");  // Add a spacer if no FAILURE banner is displayed.
+    }
+    ColoredPrintf(GTestColor::kYellow, "  YOU HAVE %d DISABLED %s\n\n",
+                  num_disabled, num_disabled == 1 ? "TEST" : "TESTS");
+  }
+  // Ensure that Google Test output is printed before, e.g., heapchecker output.
+  fflush(stdout);
+}
+
+// End BriefUnitTestResultPrinter
+
+// class TestEventRepeater
+//
+// This class forwards events to other event listeners.
+class TestEventRepeater : public TestEventListener {
+ public:
+  TestEventRepeater() : forwarding_enabled_(true) {}
+  ~TestEventRepeater() override;
+  void Append(TestEventListener *listener);
+  TestEventListener* Release(TestEventListener* listener);
+
+  // Controls whether events will be forwarded to listeners_. Set to false
+  // in death test child processes.
+  bool forwarding_enabled() const { return forwarding_enabled_; }
+  void set_forwarding_enabled(bool enable) { forwarding_enabled_ = enable; }
+
+  void OnTestProgramStart(const UnitTest& unit_test) override;
+  void OnTestIterationStart(const UnitTest& unit_test, int iteration) override;
+  void OnEnvironmentsSetUpStart(const UnitTest& unit_test) override;
+  void OnEnvironmentsSetUpEnd(const UnitTest& unit_test) override;
+//  Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  void OnTestCaseStart(const TestSuite& parameter) override;
+#endif  //  GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  void OnTestSuiteStart(const TestSuite& parameter) override;
+  void OnTestStart(const TestInfo& test_info) override;
+  void OnTestPartResult(const TestPartResult& result) override;
+  void OnTestEnd(const TestInfo& test_info) override;
+//  Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  void OnTestCaseEnd(const TestCase& parameter) override;
+#endif  //  GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  void OnTestSuiteEnd(const TestSuite& parameter) override;
+  void OnEnvironmentsTearDownStart(const UnitTest& unit_test) override;
+  void OnEnvironmentsTearDownEnd(const UnitTest& unit_test) override;
+  void OnTestIterationEnd(const UnitTest& unit_test, int iteration) override;
+  void OnTestProgramEnd(const UnitTest& unit_test) override;
+
+ private:
+  // Controls whether events will be forwarded to listeners_. Set to false
+  // in death test child processes.
+  bool forwarding_enabled_;
+  // The list of listeners that receive events.
+  std::vector<TestEventListener*> listeners_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(TestEventRepeater);
+};
+
+TestEventRepeater::~TestEventRepeater() {
+  ForEach(listeners_, Delete<TestEventListener>);
+}
+
+void TestEventRepeater::Append(TestEventListener *listener) {
+  listeners_.push_back(listener);
+}
+
+TestEventListener* TestEventRepeater::Release(TestEventListener *listener) {
+  for (size_t i = 0; i < listeners_.size(); ++i) {
+    if (listeners_[i] == listener) {
+      listeners_.erase(listeners_.begin() + static_cast<int>(i));
+      return listener;
+    }
+  }
+
+  return nullptr;
+}
+
+// Since most methods are very similar, use macros to reduce boilerplate.
+// This defines a member that forwards the call to all listeners.
+#define GTEST_REPEATER_METHOD_(Name, Type) \
+void TestEventRepeater::Name(const Type& parameter) { \
+  if (forwarding_enabled_) { \
+    for (size_t i = 0; i < listeners_.size(); i++) { \
+      listeners_[i]->Name(parameter); \
+    } \
+  } \
+}
+// This defines a member that forwards the call to all listeners in reverse
+// order.
+#define GTEST_REVERSE_REPEATER_METHOD_(Name, Type)      \
+  void TestEventRepeater::Name(const Type& parameter) { \
+    if (forwarding_enabled_) {                          \
+      for (size_t i = listeners_.size(); i != 0; i--) { \
+        listeners_[i - 1]->Name(parameter);             \
+      }                                                 \
+    }                                                   \
+  }
+
+GTEST_REPEATER_METHOD_(OnTestProgramStart, UnitTest)
+GTEST_REPEATER_METHOD_(OnEnvironmentsSetUpStart, UnitTest)
+//  Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+GTEST_REPEATER_METHOD_(OnTestCaseStart, TestSuite)
+#endif  //  GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+GTEST_REPEATER_METHOD_(OnTestSuiteStart, TestSuite)
+GTEST_REPEATER_METHOD_(OnTestStart, TestInfo)
+GTEST_REPEATER_METHOD_(OnTestPartResult, TestPartResult)
+GTEST_REPEATER_METHOD_(OnEnvironmentsTearDownStart, UnitTest)
+GTEST_REVERSE_REPEATER_METHOD_(OnEnvironmentsSetUpEnd, UnitTest)
+GTEST_REVERSE_REPEATER_METHOD_(OnEnvironmentsTearDownEnd, UnitTest)
+GTEST_REVERSE_REPEATER_METHOD_(OnTestEnd, TestInfo)
+//  Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+GTEST_REVERSE_REPEATER_METHOD_(OnTestCaseEnd, TestSuite)
+#endif  //  GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+GTEST_REVERSE_REPEATER_METHOD_(OnTestSuiteEnd, TestSuite)
+GTEST_REVERSE_REPEATER_METHOD_(OnTestProgramEnd, UnitTest)
+
+#undef GTEST_REPEATER_METHOD_
+#undef GTEST_REVERSE_REPEATER_METHOD_
+
+void TestEventRepeater::OnTestIterationStart(const UnitTest& unit_test,
+                                             int iteration) {
+  if (forwarding_enabled_) {
+    for (size_t i = 0; i < listeners_.size(); i++) {
+      listeners_[i]->OnTestIterationStart(unit_test, iteration);
+    }
+  }
+}
+
+void TestEventRepeater::OnTestIterationEnd(const UnitTest& unit_test,
+                                           int iteration) {
+  if (forwarding_enabled_) {
+    for (size_t i = listeners_.size(); i > 0; i--) {
+      listeners_[i - 1]->OnTestIterationEnd(unit_test, iteration);
+    }
+  }
+}
+
+// End TestEventRepeater
+
+// This class generates an XML output file.
+class XmlUnitTestResultPrinter : public EmptyTestEventListener {
+ public:
+  explicit XmlUnitTestResultPrinter(const char* output_file);
+
+  void OnTestIterationEnd(const UnitTest& unit_test, int iteration) override;
+  void ListTestsMatchingFilter(const std::vector<TestSuite*>& test_suites);
+
+  // Prints an XML summary of all unit tests.
+  static void PrintXmlTestsList(std::ostream* stream,
+                                const std::vector<TestSuite*>& test_suites);
+
+ private:
+  // Is c a whitespace character that is normalized to a space character
+  // when it appears in an XML attribute value?
+  static bool IsNormalizableWhitespace(char c) {
+    return c == 0x9 || c == 0xA || c == 0xD;
+  }
+
+  // May c appear in a well-formed XML document?
+  static bool IsValidXmlCharacter(char c) {
+    return IsNormalizableWhitespace(c) || c >= 0x20;
+  }
+
+  // Returns an XML-escaped copy of the input string str.  If
+  // is_attribute is true, the text is meant to appear as an attribute
+  // value, and normalizable whitespace is preserved by replacing it
+  // with character references.
+  static std::string EscapeXml(const std::string& str, bool is_attribute);
+
+  // Returns the given string with all characters invalid in XML removed.
+  static std::string RemoveInvalidXmlCharacters(const std::string& str);
+
+  // Convenience wrapper around EscapeXml when str is an attribute value.
+  static std::string EscapeXmlAttribute(const std::string& str) {
+    return EscapeXml(str, true);
+  }
+
+  // Convenience wrapper around EscapeXml when str is not an attribute value.
+  static std::string EscapeXmlText(const char* str) {
+    return EscapeXml(str, false);
+  }
+
+  // Verifies that the given attribute belongs to the given element and
+  // streams the attribute as XML.
+  static void OutputXmlAttribute(std::ostream* stream,
+                                 const std::string& element_name,
+                                 const std::string& name,
+                                 const std::string& value);
+
+  // Streams an XML CDATA section, escaping invalid CDATA sequences as needed.
+  static void OutputXmlCDataSection(::std::ostream* stream, const char* data);
+
+  // Streams a test suite XML stanza containing the given test result.
+  //
+  // Requires: result.Failed()
+  static void OutputXmlTestSuiteForTestResult(::std::ostream* stream,
+                                              const TestResult& result);
+
+  // Streams an XML representation of a TestResult object.
+  static void OutputXmlTestResult(::std::ostream* stream,
+                                  const TestResult& result);
+
+  // Streams an XML representation of a TestInfo object.
+  static void OutputXmlTestInfo(::std::ostream* stream,
+                                const char* test_suite_name,
+                                const TestInfo& test_info);
+
+  // Prints an XML representation of a TestSuite object
+  static void PrintXmlTestSuite(::std::ostream* stream,
+                                const TestSuite& test_suite);
+
+  // Prints an XML summary of unit_test to output stream out.
+  static void PrintXmlUnitTest(::std::ostream* stream,
+                               const UnitTest& unit_test);
+
+  // Produces a string representing the test properties in a result as space
+  // delimited XML attributes based on the property key="value" pairs.
+  // When the std::string is not empty, it includes a space at the beginning,
+  // to delimit this attribute from prior attributes.
+  static std::string TestPropertiesAsXmlAttributes(const TestResult& result);
+
+  // Streams an XML representation of the test properties of a TestResult
+  // object.
+  static void OutputXmlTestProperties(std::ostream* stream,
+                                      const TestResult& result);
+
+  // The output file.
+  const std::string output_file_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(XmlUnitTestResultPrinter);
+};
+
+// Creates a new XmlUnitTestResultPrinter.
+XmlUnitTestResultPrinter::XmlUnitTestResultPrinter(const char* output_file)
+    : output_file_(output_file) {
+  if (output_file_.empty()) {
+    GTEST_LOG_(FATAL) << "XML output file may not be null";
+  }
+}
+
+// Called after the unit test ends.
+void XmlUnitTestResultPrinter::OnTestIterationEnd(const UnitTest& unit_test,
+                                                  int /*iteration*/) {
+  FILE* xmlout = OpenFileForWriting(output_file_);
+  std::stringstream stream;
+  PrintXmlUnitTest(&stream, unit_test);
+  fprintf(xmlout, "%s", StringStreamToString(&stream).c_str());
+  fclose(xmlout);
+}
+
+void XmlUnitTestResultPrinter::ListTestsMatchingFilter(
+    const std::vector<TestSuite*>& test_suites) {
+  FILE* xmlout = OpenFileForWriting(output_file_);
+  std::stringstream stream;
+  PrintXmlTestsList(&stream, test_suites);
+  fprintf(xmlout, "%s", StringStreamToString(&stream).c_str());
+  fclose(xmlout);
+}
+
+// Returns an XML-escaped copy of the input string str.  If is_attribute
+// is true, the text is meant to appear as an attribute value, and
+// normalizable whitespace is preserved by replacing it with character
+// references.
+//
+// Invalid XML characters in str, if any, are stripped from the output.
+// It is expected that most, if not all, of the text processed by this
+// module will consist of ordinary English text.
+// If this module is ever modified to produce version 1.1 XML output,
+// most invalid characters can be retained using character references.
+std::string XmlUnitTestResultPrinter::EscapeXml(
+    const std::string& str, bool is_attribute) {
+  Message m;
+
+  for (size_t i = 0; i < str.size(); ++i) {
+    const char ch = str[i];
+    switch (ch) {
+      case '<':
+        m << "&lt;";
+        break;
+      case '>':
+        m << "&gt;";
+        break;
+      case '&':
+        m << "&amp;";
+        break;
+      case '\'':
+        if (is_attribute)
+          m << "&apos;";
+        else
+          m << '\'';
+        break;
+      case '"':
+        if (is_attribute)
+          m << "&quot;";
+        else
+          m << '"';
+        break;
+      default:
+        if (IsValidXmlCharacter(ch)) {
+          if (is_attribute && IsNormalizableWhitespace(ch))
+            m << "&#x" << String::FormatByte(static_cast<unsigned char>(ch))
+              << ";";
+          else
+            m << ch;
+        }
+        break;
+    }
+  }
+
+  return m.GetString();
+}
+
+// Returns the given string with all characters invalid in XML removed.
+// Currently invalid characters are dropped from the string. An
+// alternative is to replace them with certain characters such as . or ?.
+std::string XmlUnitTestResultPrinter::RemoveInvalidXmlCharacters(
+    const std::string& str) {
+  std::string output;
+  output.reserve(str.size());
+  for (std::string::const_iterator it = str.begin(); it != str.end(); ++it)
+    if (IsValidXmlCharacter(*it))
+      output.push_back(*it);
+
+  return output;
+}
+
+// The following routines generate an XML representation of a UnitTest
+// object.
+// GOOGLETEST_CM0009 DO NOT DELETE
+//
+// This is how Google Test concepts map to the DTD:
+//
+// <testsuites name="AllTests">        <-- corresponds to a UnitTest object
+//   <testsuite name="testcase-name">  <-- corresponds to a TestSuite object
+//     <testcase name="test-name">     <-- corresponds to a TestInfo object
+//       <failure message="...">...</failure>
+//       <failure message="...">...</failure>
+//       <failure message="...">...</failure>
+//                                     <-- individual assertion failures
+//     </testcase>
+//   </testsuite>
+// </testsuites>
+
+// Formats the given time in milliseconds as seconds.
+std::string FormatTimeInMillisAsSeconds(TimeInMillis ms) {
+  ::std::stringstream ss;
+  ss << (static_cast<double>(ms) * 1e-3);
+  return ss.str();
+}
+
+static bool PortableLocaltime(time_t seconds, struct tm* out) {
+#if defined(_MSC_VER)
+  return localtime_s(out, &seconds) == 0;
+#elif defined(__MINGW32__) || defined(__MINGW64__)
+  // MINGW <time.h> provides neither localtime_r nor localtime_s, but uses
+  // Windows' localtime(), which has a thread-local tm buffer.
+  struct tm* tm_ptr = localtime(&seconds);  // NOLINT
+  if (tm_ptr == nullptr) return false;
+  *out = *tm_ptr;
+  return true;
+#elif defined(__STDC_LIB_EXT1__)
+  // Uses localtime_s when available as localtime_r is only available from
+  // C23 standard.
+  return localtime_s(&seconds, out) != nullptr;
+#else
+  return localtime_r(&seconds, out) != nullptr;
+#endif
+}
+
+// Converts the given epoch time in milliseconds to a date string in the ISO
+// 8601 format, without the timezone information.
+std::string FormatEpochTimeInMillisAsIso8601(TimeInMillis ms) {
+  struct tm time_struct;
+  if (!PortableLocaltime(static_cast<time_t>(ms / 1000), &time_struct))
+    return "";
+  // YYYY-MM-DDThh:mm:ss.sss
+  return StreamableToString(time_struct.tm_year + 1900) + "-" +
+      String::FormatIntWidth2(time_struct.tm_mon + 1) + "-" +
+      String::FormatIntWidth2(time_struct.tm_mday) + "T" +
+      String::FormatIntWidth2(time_struct.tm_hour) + ":" +
+      String::FormatIntWidth2(time_struct.tm_min) + ":" +
+      String::FormatIntWidth2(time_struct.tm_sec) + "." +
+      String::FormatIntWidthN(static_cast<int>(ms % 1000), 3);
+}
+
+// Streams an XML CDATA section, escaping invalid CDATA sequences as needed.
+void XmlUnitTestResultPrinter::OutputXmlCDataSection(::std::ostream* stream,
+                                                     const char* data) {
+  const char* segment = data;
+  *stream << "<![CDATA[";
+  for (;;) {
+    const char* const next_segment = strstr(segment, "]]>");
+    if (next_segment != nullptr) {
+      stream->write(
+          segment, static_cast<std::streamsize>(next_segment - segment));
+      *stream << "]]>]]&gt;<![CDATA[";
+      segment = next_segment + strlen("]]>");
+    } else {
+      *stream << segment;
+      break;
+    }
+  }
+  *stream << "]]>";
+}
+
+void XmlUnitTestResultPrinter::OutputXmlAttribute(
+    std::ostream* stream,
+    const std::string& element_name,
+    const std::string& name,
+    const std::string& value) {
+  const std::vector<std::string>& allowed_names =
+      GetReservedOutputAttributesForElement(element_name);
+
+  GTEST_CHECK_(std::find(allowed_names.begin(), allowed_names.end(), name) !=
+                   allowed_names.end())
+      << "Attribute " << name << " is not allowed for element <" << element_name
+      << ">.";
+
+  *stream << " " << name << "=\"" << EscapeXmlAttribute(value) << "\"";
+}
+
+// Streams a test suite XML stanza containing the given test result.
+void XmlUnitTestResultPrinter::OutputXmlTestSuiteForTestResult(
+    ::std::ostream* stream, const TestResult& result) {
+  // Output the boilerplate for a minimal test suite with one test.
+  *stream << "  <testsuite";
+  OutputXmlAttribute(stream, "testsuite", "name", "NonTestSuiteFailure");
+  OutputXmlAttribute(stream, "testsuite", "tests", "1");
+  OutputXmlAttribute(stream, "testsuite", "failures", "1");
+  OutputXmlAttribute(stream, "testsuite", "disabled", "0");
+  OutputXmlAttribute(stream, "testsuite", "skipped", "0");
+  OutputXmlAttribute(stream, "testsuite", "errors", "0");
+  OutputXmlAttribute(stream, "testsuite", "time",
+                     FormatTimeInMillisAsSeconds(result.elapsed_time()));
+  OutputXmlAttribute(
+      stream, "testsuite", "timestamp",
+      FormatEpochTimeInMillisAsIso8601(result.start_timestamp()));
+  *stream << ">";
+
+  // Output the boilerplate for a minimal test case with a single test.
+  *stream << "    <testcase";
+  OutputXmlAttribute(stream, "testcase", "name", "");
+  OutputXmlAttribute(stream, "testcase", "status", "run");
+  OutputXmlAttribute(stream, "testcase", "result", "completed");
+  OutputXmlAttribute(stream, "testcase", "classname", "");
+  OutputXmlAttribute(stream, "testcase", "time",
+                     FormatTimeInMillisAsSeconds(result.elapsed_time()));
+  OutputXmlAttribute(
+      stream, "testcase", "timestamp",
+      FormatEpochTimeInMillisAsIso8601(result.start_timestamp()));
+
+  // Output the actual test result.
+  OutputXmlTestResult(stream, result);
+
+  // Complete the test suite.
+  *stream << "  </testsuite>\n";
+}
+
+// Prints an XML representation of a TestInfo object.
+void XmlUnitTestResultPrinter::OutputXmlTestInfo(::std::ostream* stream,
+                                                 const char* test_suite_name,
+                                                 const TestInfo& test_info) {
+  const TestResult& result = *test_info.result();
+  const std::string kTestsuite = "testcase";
+
+  if (test_info.is_in_another_shard()) {
+    return;
+  }
+
+  *stream << "    <testcase";
+  OutputXmlAttribute(stream, kTestsuite, "name", test_info.name());
+
+  if (test_info.value_param() != nullptr) {
+    OutputXmlAttribute(stream, kTestsuite, "value_param",
+                       test_info.value_param());
+  }
+  if (test_info.type_param() != nullptr) {
+    OutputXmlAttribute(stream, kTestsuite, "type_param",
+                       test_info.type_param());
+  }
+  if (GTEST_FLAG(list_tests)) {
+    OutputXmlAttribute(stream, kTestsuite, "file", test_info.file());
+    OutputXmlAttribute(stream, kTestsuite, "line",
+                       StreamableToString(test_info.line()));
+    *stream << " />\n";
+    return;
+  }
+
+  OutputXmlAttribute(stream, kTestsuite, "status",
+                     test_info.should_run() ? "run" : "notrun");
+  OutputXmlAttribute(stream, kTestsuite, "result",
+                     test_info.should_run()
+                         ? (result.Skipped() ? "skipped" : "completed")
+                         : "suppressed");
+  OutputXmlAttribute(stream, kTestsuite, "time",
+                     FormatTimeInMillisAsSeconds(result.elapsed_time()));
+  OutputXmlAttribute(
+      stream, kTestsuite, "timestamp",
+      FormatEpochTimeInMillisAsIso8601(result.start_timestamp()));
+  OutputXmlAttribute(stream, kTestsuite, "classname", test_suite_name);
+
+  OutputXmlTestResult(stream, result);
+}
+
+void XmlUnitTestResultPrinter::OutputXmlTestResult(::std::ostream* stream,
+                                                   const TestResult& result) {
+  int failures = 0;
+  int skips = 0;
+  for (int i = 0; i < result.total_part_count(); ++i) {
+    const TestPartResult& part = result.GetTestPartResult(i);
+    if (part.failed()) {
+      if (++failures == 1 && skips == 0) {
+        *stream << ">\n";
+      }
+      const std::string location =
+          internal::FormatCompilerIndependentFileLocation(part.file_name(),
+                                                          part.line_number());
+      const std::string summary = location + "\n" + part.summary();
+      *stream << "      <failure message=\""
+              << EscapeXmlAttribute(summary)
+              << "\" type=\"\">";
+      const std::string detail = location + "\n" + part.message();
+      OutputXmlCDataSection(stream, RemoveInvalidXmlCharacters(detail).c_str());
+      *stream << "</failure>\n";
+    } else if (part.skipped()) {
+      if (++skips == 1 && failures == 0) {
+        *stream << ">\n";
+      }
+      const std::string location =
+          internal::FormatCompilerIndependentFileLocation(part.file_name(),
+                                                          part.line_number());
+      const std::string summary = location + "\n" + part.summary();
+      *stream << "      <skipped message=\""
+              << EscapeXmlAttribute(summary.c_str()) << "\">";
+      const std::string detail = location + "\n" + part.message();
+      OutputXmlCDataSection(stream, RemoveInvalidXmlCharacters(detail).c_str());
+      *stream << "</skipped>\n";
+    }
+  }
+
+  if (failures == 0 && skips == 0 && result.test_property_count() == 0) {
+    *stream << " />\n";
+  } else {
+    if (failures == 0 && skips == 0) {
+      *stream << ">\n";
+    }
+    OutputXmlTestProperties(stream, result);
+    *stream << "    </testcase>\n";
+  }
+}
+
+// Prints an XML representation of a TestSuite object
+void XmlUnitTestResultPrinter::PrintXmlTestSuite(std::ostream* stream,
+                                                 const TestSuite& test_suite) {
+  const std::string kTestsuite = "testsuite";
+  *stream << "  <" << kTestsuite;
+  OutputXmlAttribute(stream, kTestsuite, "name", test_suite.name());
+  OutputXmlAttribute(stream, kTestsuite, "tests",
+                     StreamableToString(test_suite.reportable_test_count()));
+  if (!GTEST_FLAG(list_tests)) {
+    OutputXmlAttribute(stream, kTestsuite, "failures",
+                       StreamableToString(test_suite.failed_test_count()));
+    OutputXmlAttribute(
+        stream, kTestsuite, "disabled",
+        StreamableToString(test_suite.reportable_disabled_test_count()));
+    OutputXmlAttribute(stream, kTestsuite, "skipped",
+                       StreamableToString(test_suite.skipped_test_count()));
+
+    OutputXmlAttribute(stream, kTestsuite, "errors", "0");
+
+    OutputXmlAttribute(stream, kTestsuite, "time",
+                       FormatTimeInMillisAsSeconds(test_suite.elapsed_time()));
+    OutputXmlAttribute(
+        stream, kTestsuite, "timestamp",
+        FormatEpochTimeInMillisAsIso8601(test_suite.start_timestamp()));
+    *stream << TestPropertiesAsXmlAttributes(test_suite.ad_hoc_test_result());
+  }
+  *stream << ">\n";
+  for (int i = 0; i < test_suite.total_test_count(); ++i) {
+    if (test_suite.GetTestInfo(i)->is_reportable())
+      OutputXmlTestInfo(stream, test_suite.name(), *test_suite.GetTestInfo(i));
+  }
+  *stream << "  </" << kTestsuite << ">\n";
+}
+
+// Prints an XML summary of unit_test to output stream out.
+void XmlUnitTestResultPrinter::PrintXmlUnitTest(std::ostream* stream,
+                                                const UnitTest& unit_test) {
+  const std::string kTestsuites = "testsuites";
+
+  *stream << "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n";
+  *stream << "<" << kTestsuites;
+
+  OutputXmlAttribute(stream, kTestsuites, "tests",
+                     StreamableToString(unit_test.reportable_test_count()));
+  OutputXmlAttribute(stream, kTestsuites, "failures",
+                     StreamableToString(unit_test.failed_test_count()));
+  OutputXmlAttribute(
+      stream, kTestsuites, "disabled",
+      StreamableToString(unit_test.reportable_disabled_test_count()));
+  OutputXmlAttribute(stream, kTestsuites, "errors", "0");
+  OutputXmlAttribute(stream, kTestsuites, "time",
+                     FormatTimeInMillisAsSeconds(unit_test.elapsed_time()));
+  OutputXmlAttribute(
+      stream, kTestsuites, "timestamp",
+      FormatEpochTimeInMillisAsIso8601(unit_test.start_timestamp()));
+
+  if (GTEST_FLAG(shuffle)) {
+    OutputXmlAttribute(stream, kTestsuites, "random_seed",
+                       StreamableToString(unit_test.random_seed()));
+  }
+  *stream << TestPropertiesAsXmlAttributes(unit_test.ad_hoc_test_result());
+
+  OutputXmlAttribute(stream, kTestsuites, "name", "AllTests");
+  *stream << ">\n";
+
+  for (int i = 0; i < unit_test.total_test_suite_count(); ++i) {
+    if (unit_test.GetTestSuite(i)->reportable_test_count() > 0)
+      PrintXmlTestSuite(stream, *unit_test.GetTestSuite(i));
+  }
+
+  // If there was a test failure outside of one of the test suites (like in a
+  // test environment) include that in the output.
+  if (unit_test.ad_hoc_test_result().Failed()) {
+    OutputXmlTestSuiteForTestResult(stream, unit_test.ad_hoc_test_result());
+  }
+
+  *stream << "</" << kTestsuites << ">\n";
+}
+
+void XmlUnitTestResultPrinter::PrintXmlTestsList(
+    std::ostream* stream, const std::vector<TestSuite*>& test_suites) {
+  const std::string kTestsuites = "testsuites";
+
+  *stream << "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n";
+  *stream << "<" << kTestsuites;
+
+  int total_tests = 0;
+  for (auto test_suite : test_suites) {
+    total_tests += test_suite->total_test_count();
+  }
+  OutputXmlAttribute(stream, kTestsuites, "tests",
+                     StreamableToString(total_tests));
+  OutputXmlAttribute(stream, kTestsuites, "name", "AllTests");
+  *stream << ">\n";
+
+  for (auto test_suite : test_suites) {
+    PrintXmlTestSuite(stream, *test_suite);
+  }
+  *stream << "</" << kTestsuites << ">\n";
+}
+
+// Produces a string representing the test properties in a result as space
+// delimited XML attributes based on the property key="value" pairs.
+std::string XmlUnitTestResultPrinter::TestPropertiesAsXmlAttributes(
+    const TestResult& result) {
+  Message attributes;
+  for (int i = 0; i < result.test_property_count(); ++i) {
+    const TestProperty& property = result.GetTestProperty(i);
+    attributes << " " << property.key() << "="
+        << "\"" << EscapeXmlAttribute(property.value()) << "\"";
+  }
+  return attributes.GetString();
+}
+
+void XmlUnitTestResultPrinter::OutputXmlTestProperties(
+    std::ostream* stream, const TestResult& result) {
+  const std::string kProperties = "properties";
+  const std::string kProperty = "property";
+
+  if (result.test_property_count() <= 0) {
+    return;
+  }
+
+  *stream << "<" << kProperties << ">\n";
+  for (int i = 0; i < result.test_property_count(); ++i) {
+    const TestProperty& property = result.GetTestProperty(i);
+    *stream << "<" << kProperty;
+    *stream << " name=\"" << EscapeXmlAttribute(property.key()) << "\"";
+    *stream << " value=\"" << EscapeXmlAttribute(property.value()) << "\"";
+    *stream << "/>\n";
+  }
+  *stream << "</" << kProperties << ">\n";
+}
+
+// End XmlUnitTestResultPrinter
+
+// This class generates an JSON output file.
+class JsonUnitTestResultPrinter : public EmptyTestEventListener {
+ public:
+  explicit JsonUnitTestResultPrinter(const char* output_file);
+
+  void OnTestIterationEnd(const UnitTest& unit_test, int iteration) override;
+
+  // Prints an JSON summary of all unit tests.
+  static void PrintJsonTestList(::std::ostream* stream,
+                                const std::vector<TestSuite*>& test_suites);
+
+ private:
+  // Returns an JSON-escaped copy of the input string str.
+  static std::string EscapeJson(const std::string& str);
+
+  //// Verifies that the given attribute belongs to the given element and
+  //// streams the attribute as JSON.
+  static void OutputJsonKey(std::ostream* stream,
+                            const std::string& element_name,
+                            const std::string& name,
+                            const std::string& value,
+                            const std::string& indent,
+                            bool comma = true);
+  static void OutputJsonKey(std::ostream* stream,
+                            const std::string& element_name,
+                            const std::string& name,
+                            int value,
+                            const std::string& indent,
+                            bool comma = true);
+
+  // Streams a test suite JSON stanza containing the given test result.
+  //
+  // Requires: result.Failed()
+  static void OutputJsonTestSuiteForTestResult(::std::ostream* stream,
+                                               const TestResult& result);
+
+  // Streams a JSON representation of a TestResult object.
+  static void OutputJsonTestResult(::std::ostream* stream,
+                                   const TestResult& result);
+
+  // Streams a JSON representation of a TestInfo object.
+  static void OutputJsonTestInfo(::std::ostream* stream,
+                                 const char* test_suite_name,
+                                 const TestInfo& test_info);
+
+  // Prints a JSON representation of a TestSuite object
+  static void PrintJsonTestSuite(::std::ostream* stream,
+                                 const TestSuite& test_suite);
+
+  // Prints a JSON summary of unit_test to output stream out.
+  static void PrintJsonUnitTest(::std::ostream* stream,
+                                const UnitTest& unit_test);
+
+  // Produces a string representing the test properties in a result as
+  // a JSON dictionary.
+  static std::string TestPropertiesAsJson(const TestResult& result,
+                                          const std::string& indent);
+
+  // The output file.
+  const std::string output_file_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(JsonUnitTestResultPrinter);
+};
+
+// Creates a new JsonUnitTestResultPrinter.
+JsonUnitTestResultPrinter::JsonUnitTestResultPrinter(const char* output_file)
+    : output_file_(output_file) {
+  if (output_file_.empty()) {
+    GTEST_LOG_(FATAL) << "JSON output file may not be null";
+  }
+}
+
+void JsonUnitTestResultPrinter::OnTestIterationEnd(const UnitTest& unit_test,
+                                                  int /*iteration*/) {
+  FILE* jsonout = OpenFileForWriting(output_file_);
+  std::stringstream stream;
+  PrintJsonUnitTest(&stream, unit_test);
+  fprintf(jsonout, "%s", StringStreamToString(&stream).c_str());
+  fclose(jsonout);
+}
+
+// Returns an JSON-escaped copy of the input string str.
+std::string JsonUnitTestResultPrinter::EscapeJson(const std::string& str) {
+  Message m;
+
+  for (size_t i = 0; i < str.size(); ++i) {
+    const char ch = str[i];
+    switch (ch) {
+      case '\\':
+      case '"':
+      case '/':
+        m << '\\' << ch;
+        break;
+      case '\b':
+        m << "\\b";
+        break;
+      case '\t':
+        m << "\\t";
+        break;
+      case '\n':
+        m << "\\n";
+        break;
+      case '\f':
+        m << "\\f";
+        break;
+      case '\r':
+        m << "\\r";
+        break;
+      default:
+        if (ch < ' ') {
+          m << "\\u00" << String::FormatByte(static_cast<unsigned char>(ch));
+        } else {
+          m << ch;
+        }
+        break;
+    }
+  }
+
+  return m.GetString();
+}
+
+// The following routines generate an JSON representation of a UnitTest
+// object.
+
+// Formats the given time in milliseconds as seconds.
+static std::string FormatTimeInMillisAsDuration(TimeInMillis ms) {
+  ::std::stringstream ss;
+  ss << (static_cast<double>(ms) * 1e-3) << "s";
+  return ss.str();
+}
+
+// Converts the given epoch time in milliseconds to a date string in the
+// RFC3339 format, without the timezone information.
+static std::string FormatEpochTimeInMillisAsRFC3339(TimeInMillis ms) {
+  struct tm time_struct;
+  if (!PortableLocaltime(static_cast<time_t>(ms / 1000), &time_struct))
+    return "";
+  // YYYY-MM-DDThh:mm:ss
+  return StreamableToString(time_struct.tm_year + 1900) + "-" +
+      String::FormatIntWidth2(time_struct.tm_mon + 1) + "-" +
+      String::FormatIntWidth2(time_struct.tm_mday) + "T" +
+      String::FormatIntWidth2(time_struct.tm_hour) + ":" +
+      String::FormatIntWidth2(time_struct.tm_min) + ":" +
+      String::FormatIntWidth2(time_struct.tm_sec) + "Z";
+}
+
+static inline std::string Indent(size_t width) {
+  return std::string(width, ' ');
+}
+
+void JsonUnitTestResultPrinter::OutputJsonKey(
+    std::ostream* stream,
+    const std::string& element_name,
+    const std::string& name,
+    const std::string& value,
+    const std::string& indent,
+    bool comma) {
+  const std::vector<std::string>& allowed_names =
+      GetReservedOutputAttributesForElement(element_name);
+
+  GTEST_CHECK_(std::find(allowed_names.begin(), allowed_names.end(), name) !=
+                   allowed_names.end())
+      << "Key \"" << name << "\" is not allowed for value \"" << element_name
+      << "\".";
+
+  *stream << indent << "\"" << name << "\": \"" << EscapeJson(value) << "\"";
+  if (comma)
+    *stream << ",\n";
+}
+
+void JsonUnitTestResultPrinter::OutputJsonKey(
+    std::ostream* stream,
+    const std::string& element_name,
+    const std::string& name,
+    int value,
+    const std::string& indent,
+    bool comma) {
+  const std::vector<std::string>& allowed_names =
+      GetReservedOutputAttributesForElement(element_name);
+
+  GTEST_CHECK_(std::find(allowed_names.begin(), allowed_names.end(), name) !=
+                   allowed_names.end())
+      << "Key \"" << name << "\" is not allowed for value \"" << element_name
+      << "\".";
+
+  *stream << indent << "\"" << name << "\": " << StreamableToString(value);
+  if (comma)
+    *stream << ",\n";
+}
+
+// Streams a test suite JSON stanza containing the given test result.
+void JsonUnitTestResultPrinter::OutputJsonTestSuiteForTestResult(
+    ::std::ostream* stream, const TestResult& result) {
+  // Output the boilerplate for a new test suite.
+  *stream << Indent(4) << "{\n";
+  OutputJsonKey(stream, "testsuite", "name", "NonTestSuiteFailure", Indent(6));
+  OutputJsonKey(stream, "testsuite", "tests", 1, Indent(6));
+  if (!GTEST_FLAG(list_tests)) {
+    OutputJsonKey(stream, "testsuite", "failures", 1, Indent(6));
+    OutputJsonKey(stream, "testsuite", "disabled", 0, Indent(6));
+    OutputJsonKey(stream, "testsuite", "skipped", 0, Indent(6));
+    OutputJsonKey(stream, "testsuite", "errors", 0, Indent(6));
+    OutputJsonKey(stream, "testsuite", "time",
+                  FormatTimeInMillisAsDuration(result.elapsed_time()),
+                  Indent(6));
+    OutputJsonKey(stream, "testsuite", "timestamp",
+                  FormatEpochTimeInMillisAsRFC3339(result.start_timestamp()),
+                  Indent(6));
+  }
+  *stream << Indent(6) << "\"testsuite\": [\n";
+
+  // Output the boilerplate for a new test case.
+  *stream << Indent(8) << "{\n";
+  OutputJsonKey(stream, "testcase", "name", "", Indent(10));
+  OutputJsonKey(stream, "testcase", "status", "RUN", Indent(10));
+  OutputJsonKey(stream, "testcase", "result", "COMPLETED", Indent(10));
+  OutputJsonKey(stream, "testcase", "timestamp",
+                FormatEpochTimeInMillisAsRFC3339(result.start_timestamp()),
+                Indent(10));
+  OutputJsonKey(stream, "testcase", "time",
+                FormatTimeInMillisAsDuration(result.elapsed_time()),
+                Indent(10));
+  OutputJsonKey(stream, "testcase", "classname", "", Indent(10), false);
+  *stream << TestPropertiesAsJson(result, Indent(10));
+
+  // Output the actual test result.
+  OutputJsonTestResult(stream, result);
+
+  // Finish the test suite.
+  *stream << "\n" << Indent(6) << "]\n" << Indent(4) << "}";
+}
+
+// Prints a JSON representation of a TestInfo object.
+void JsonUnitTestResultPrinter::OutputJsonTestInfo(::std::ostream* stream,
+                                                   const char* test_suite_name,
+                                                   const TestInfo& test_info) {
+  const TestResult& result = *test_info.result();
+  const std::string kTestsuite = "testcase";
+  const std::string kIndent = Indent(10);
+
+  *stream << Indent(8) << "{\n";
+  OutputJsonKey(stream, kTestsuite, "name", test_info.name(), kIndent);
+
+  if (test_info.value_param() != nullptr) {
+    OutputJsonKey(stream, kTestsuite, "value_param", test_info.value_param(),
+                  kIndent);
+  }
+  if (test_info.type_param() != nullptr) {
+    OutputJsonKey(stream, kTestsuite, "type_param", test_info.type_param(),
+                  kIndent);
+  }
+  if (GTEST_FLAG(list_tests)) {
+    OutputJsonKey(stream, kTestsuite, "file", test_info.file(), kIndent);
+    OutputJsonKey(stream, kTestsuite, "line", test_info.line(), kIndent, false);
+    *stream << "\n" << Indent(8) << "}";
+    return;
+  }
+
+  OutputJsonKey(stream, kTestsuite, "status",
+                test_info.should_run() ? "RUN" : "NOTRUN", kIndent);
+  OutputJsonKey(stream, kTestsuite, "result",
+                test_info.should_run()
+                    ? (result.Skipped() ? "SKIPPED" : "COMPLETED")
+                    : "SUPPRESSED",
+                kIndent);
+  OutputJsonKey(stream, kTestsuite, "timestamp",
+                FormatEpochTimeInMillisAsRFC3339(result.start_timestamp()),
+                kIndent);
+  OutputJsonKey(stream, kTestsuite, "time",
+                FormatTimeInMillisAsDuration(result.elapsed_time()), kIndent);
+  OutputJsonKey(stream, kTestsuite, "classname", test_suite_name, kIndent,
+                false);
+  *stream << TestPropertiesAsJson(result, kIndent);
+
+  OutputJsonTestResult(stream, result);
+}
+
+void JsonUnitTestResultPrinter::OutputJsonTestResult(::std::ostream* stream,
+                                                     const TestResult& result) {
+  const std::string kIndent = Indent(10);
+
+  int failures = 0;
+  for (int i = 0; i < result.total_part_count(); ++i) {
+    const TestPartResult& part = result.GetTestPartResult(i);
+    if (part.failed()) {
+      *stream << ",\n";
+      if (++failures == 1) {
+        *stream << kIndent << "\"" << "failures" << "\": [\n";
+      }
+      const std::string location =
+          internal::FormatCompilerIndependentFileLocation(part.file_name(),
+                                                          part.line_number());
+      const std::string message = EscapeJson(location + "\n" + part.message());
+      *stream << kIndent << "  {\n"
+              << kIndent << "    \"failure\": \"" << message << "\",\n"
+              << kIndent << "    \"type\": \"\"\n"
+              << kIndent << "  }";
+    }
+  }
+
+  if (failures > 0)
+    *stream << "\n" << kIndent << "]";
+  *stream << "\n" << Indent(8) << "}";
+}
+
+// Prints an JSON representation of a TestSuite object
+void JsonUnitTestResultPrinter::PrintJsonTestSuite(
+    std::ostream* stream, const TestSuite& test_suite) {
+  const std::string kTestsuite = "testsuite";
+  const std::string kIndent = Indent(6);
+
+  *stream << Indent(4) << "{\n";
+  OutputJsonKey(stream, kTestsuite, "name", test_suite.name(), kIndent);
+  OutputJsonKey(stream, kTestsuite, "tests", test_suite.reportable_test_count(),
+                kIndent);
+  if (!GTEST_FLAG(list_tests)) {
+    OutputJsonKey(stream, kTestsuite, "failures",
+                  test_suite.failed_test_count(), kIndent);
+    OutputJsonKey(stream, kTestsuite, "disabled",
+                  test_suite.reportable_disabled_test_count(), kIndent);
+    OutputJsonKey(stream, kTestsuite, "errors", 0, kIndent);
+    OutputJsonKey(
+        stream, kTestsuite, "timestamp",
+        FormatEpochTimeInMillisAsRFC3339(test_suite.start_timestamp()),
+        kIndent);
+    OutputJsonKey(stream, kTestsuite, "time",
+                  FormatTimeInMillisAsDuration(test_suite.elapsed_time()),
+                  kIndent, false);
+    *stream << TestPropertiesAsJson(test_suite.ad_hoc_test_result(), kIndent)
+            << ",\n";
+  }
+
+  *stream << kIndent << "\"" << kTestsuite << "\": [\n";
+
+  bool comma = false;
+  for (int i = 0; i < test_suite.total_test_count(); ++i) {
+    if (test_suite.GetTestInfo(i)->is_reportable()) {
+      if (comma) {
+        *stream << ",\n";
+      } else {
+        comma = true;
+      }
+      OutputJsonTestInfo(stream, test_suite.name(), *test_suite.GetTestInfo(i));
+    }
+  }
+  *stream << "\n" << kIndent << "]\n" << Indent(4) << "}";
+}
+
+// Prints a JSON summary of unit_test to output stream out.
+void JsonUnitTestResultPrinter::PrintJsonUnitTest(std::ostream* stream,
+                                                  const UnitTest& unit_test) {
+  const std::string kTestsuites = "testsuites";
+  const std::string kIndent = Indent(2);
+  *stream << "{\n";
+
+  OutputJsonKey(stream, kTestsuites, "tests", unit_test.reportable_test_count(),
+                kIndent);
+  OutputJsonKey(stream, kTestsuites, "failures", unit_test.failed_test_count(),
+                kIndent);
+  OutputJsonKey(stream, kTestsuites, "disabled",
+                unit_test.reportable_disabled_test_count(), kIndent);
+  OutputJsonKey(stream, kTestsuites, "errors", 0, kIndent);
+  if (GTEST_FLAG(shuffle)) {
+    OutputJsonKey(stream, kTestsuites, "random_seed", unit_test.random_seed(),
+                  kIndent);
+  }
+  OutputJsonKey(stream, kTestsuites, "timestamp",
+                FormatEpochTimeInMillisAsRFC3339(unit_test.start_timestamp()),
+                kIndent);
+  OutputJsonKey(stream, kTestsuites, "time",
+                FormatTimeInMillisAsDuration(unit_test.elapsed_time()), kIndent,
+                false);
+
+  *stream << TestPropertiesAsJson(unit_test.ad_hoc_test_result(), kIndent)
+          << ",\n";
+
+  OutputJsonKey(stream, kTestsuites, "name", "AllTests", kIndent);
+  *stream << kIndent << "\"" << kTestsuites << "\": [\n";
+
+  bool comma = false;
+  for (int i = 0; i < unit_test.total_test_suite_count(); ++i) {
+    if (unit_test.GetTestSuite(i)->reportable_test_count() > 0) {
+      if (comma) {
+        *stream << ",\n";
+      } else {
+        comma = true;
+      }
+      PrintJsonTestSuite(stream, *unit_test.GetTestSuite(i));
+    }
+  }
+
+  // If there was a test failure outside of one of the test suites (like in a
+  // test environment) include that in the output.
+  if (unit_test.ad_hoc_test_result().Failed()) {
+    OutputJsonTestSuiteForTestResult(stream, unit_test.ad_hoc_test_result());
+  }
+
+  *stream << "\n" << kIndent << "]\n" << "}\n";
+}
+
+void JsonUnitTestResultPrinter::PrintJsonTestList(
+    std::ostream* stream, const std::vector<TestSuite*>& test_suites) {
+  const std::string kTestsuites = "testsuites";
+  const std::string kIndent = Indent(2);
+  *stream << "{\n";
+  int total_tests = 0;
+  for (auto test_suite : test_suites) {
+    total_tests += test_suite->total_test_count();
+  }
+  OutputJsonKey(stream, kTestsuites, "tests", total_tests, kIndent);
+
+  OutputJsonKey(stream, kTestsuites, "name", "AllTests", kIndent);
+  *stream << kIndent << "\"" << kTestsuites << "\": [\n";
+
+  for (size_t i = 0; i < test_suites.size(); ++i) {
+    if (i != 0) {
+      *stream << ",\n";
+    }
+    PrintJsonTestSuite(stream, *test_suites[i]);
+  }
+
+  *stream << "\n"
+          << kIndent << "]\n"
+          << "}\n";
+}
+// Produces a string representing the test properties in a result as
+// a JSON dictionary.
+std::string JsonUnitTestResultPrinter::TestPropertiesAsJson(
+    const TestResult& result, const std::string& indent) {
+  Message attributes;
+  for (int i = 0; i < result.test_property_count(); ++i) {
+    const TestProperty& property = result.GetTestProperty(i);
+    attributes << ",\n" << indent << "\"" << property.key() << "\": "
+               << "\"" << EscapeJson(property.value()) << "\"";
+  }
+  return attributes.GetString();
+}
+
+// End JsonUnitTestResultPrinter
+
+#if GTEST_CAN_STREAM_RESULTS_
+
+// Checks if str contains '=', '&', '%' or '\n' characters. If yes,
+// replaces them by "%xx" where xx is their hexadecimal value. For
+// example, replaces "=" with "%3D".  This algorithm is O(strlen(str))
+// in both time and space -- important as the input str may contain an
+// arbitrarily long test failure message and stack trace.
+std::string StreamingListener::UrlEncode(const char* str) {
+  std::string result;
+  result.reserve(strlen(str) + 1);
+  for (char ch = *str; ch != '\0'; ch = *++str) {
+    switch (ch) {
+      case '%':
+      case '=':
+      case '&':
+      case '\n':
+        result.append("%" + String::FormatByte(static_cast<unsigned char>(ch)));
+        break;
+      default:
+        result.push_back(ch);
+        break;
+    }
+  }
+  return result;
+}
+
+void StreamingListener::SocketWriter::MakeConnection() {
+  GTEST_CHECK_(sockfd_ == -1)
+      << "MakeConnection() can't be called when there is already a connection.";
+
+  addrinfo hints;
+  memset(&hints, 0, sizeof(hints));
+  hints.ai_family = AF_UNSPEC;    // To allow both IPv4 and IPv6 addresses.
+  hints.ai_socktype = SOCK_STREAM;
+  addrinfo* servinfo = nullptr;
+
+  // Use the getaddrinfo() to get a linked list of IP addresses for
+  // the given host name.
+  const int error_num = getaddrinfo(
+      host_name_.c_str(), port_num_.c_str(), &hints, &servinfo);
+  if (error_num != 0) {
+    GTEST_LOG_(WARNING) << "stream_result_to: getaddrinfo() failed: "
+                        << gai_strerror(error_num);
+  }
+
+  // Loop through all the results and connect to the first we can.
+  for (addrinfo* cur_addr = servinfo; sockfd_ == -1 && cur_addr != nullptr;
+       cur_addr = cur_addr->ai_next) {
+    sockfd_ = socket(
+        cur_addr->ai_family, cur_addr->ai_socktype, cur_addr->ai_protocol);
+    if (sockfd_ != -1) {
+      // Connect the client socket to the server socket.
+      if (connect(sockfd_, cur_addr->ai_addr, cur_addr->ai_addrlen) == -1) {
+        close(sockfd_);
+        sockfd_ = -1;
+      }
+    }
+  }
+
+  freeaddrinfo(servinfo);  // all done with this structure
+
+  if (sockfd_ == -1) {
+    GTEST_LOG_(WARNING) << "stream_result_to: failed to connect to "
+                        << host_name_ << ":" << port_num_;
+  }
+}
+
+// End of class Streaming Listener
+#endif  // GTEST_CAN_STREAM_RESULTS__
+
+// class OsStackTraceGetter
+
+const char* const OsStackTraceGetterInterface::kElidedFramesMarker =
+    "... " GTEST_NAME_ " internal frames ...";
+
+std::string OsStackTraceGetter::CurrentStackTrace(int max_depth, int skip_count)
+    GTEST_LOCK_EXCLUDED_(mutex_) {
+#if GTEST_HAS_ABSL
+  std::string result;
+
+  if (max_depth <= 0) {
+    return result;
+  }
+
+  max_depth = std::min(max_depth, kMaxStackTraceDepth);
+
+  std::vector<void*> raw_stack(max_depth);
+  // Skips the frames requested by the caller, plus this function.
+  const int raw_stack_size =
+      absl::GetStackTrace(&raw_stack[0], max_depth, skip_count + 1);
+
+  void* caller_frame = nullptr;
+  {
+    MutexLock lock(&mutex_);
+    caller_frame = caller_frame_;
+  }
+
+  for (int i = 0; i < raw_stack_size; ++i) {
+    if (raw_stack[i] == caller_frame &&
+        !GTEST_FLAG(show_internal_stack_frames)) {
+      // Add a marker to the trace and stop adding frames.
+      absl::StrAppend(&result, kElidedFramesMarker, "\n");
+      break;
+    }
+
+    char tmp[1024];
+    const char* symbol = "(unknown)";
+    if (absl::Symbolize(raw_stack[i], tmp, sizeof(tmp))) {
+      symbol = tmp;
+    }
+
+    char line[1024];
+    snprintf(line, sizeof(line), "  %p: %s\n", raw_stack[i], symbol);
+    result += line;
+  }
+
+  return result;
+
+#else  // !GTEST_HAS_ABSL
+  static_cast<void>(max_depth);
+  static_cast<void>(skip_count);
+  return "";
+#endif  // GTEST_HAS_ABSL
+}
+
+void OsStackTraceGetter::UponLeavingGTest() GTEST_LOCK_EXCLUDED_(mutex_) {
+#if GTEST_HAS_ABSL
+  void* caller_frame = nullptr;
+  if (absl::GetStackTrace(&caller_frame, 1, 3) <= 0) {
+    caller_frame = nullptr;
+  }
+
+  MutexLock lock(&mutex_);
+  caller_frame_ = caller_frame;
+#endif  // GTEST_HAS_ABSL
+}
+
+// A helper class that creates the premature-exit file in its
+// constructor and deletes the file in its destructor.
+class ScopedPrematureExitFile {
+ public:
+  explicit ScopedPrematureExitFile(const char* premature_exit_filepath)
+      : premature_exit_filepath_(premature_exit_filepath ?
+                                 premature_exit_filepath : "") {
+    // If a path to the premature-exit file is specified...
+    if (!premature_exit_filepath_.empty()) {
+      // create the file with a single "0" character in it.  I/O
+      // errors are ignored as there's nothing better we can do and we
+      // don't want to fail the test because of this.
+      FILE* pfile = posix::FOpen(premature_exit_filepath, "w");
+      fwrite("0", 1, 1, pfile);
+      fclose(pfile);
+    }
+  }
+
+  ~ScopedPrematureExitFile() {
+#if !defined GTEST_OS_ESP8266
+    if (!premature_exit_filepath_.empty()) {
+      int retval = remove(premature_exit_filepath_.c_str());
+      if (retval) {
+        GTEST_LOG_(ERROR) << "Failed to remove premature exit filepath \""
+                          << premature_exit_filepath_ << "\" with error "
+                          << retval;
+      }
+    }
+#endif
+  }
+
+ private:
+  const std::string premature_exit_filepath_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(ScopedPrematureExitFile);
+};
+
+}  // namespace internal
+
+// class TestEventListeners
+
+TestEventListeners::TestEventListeners()
+    : repeater_(new internal::TestEventRepeater()),
+      default_result_printer_(nullptr),
+      default_xml_generator_(nullptr) {}
+
+TestEventListeners::~TestEventListeners() { delete repeater_; }
+
+// Returns the standard listener responsible for the default console
+// output.  Can be removed from the listeners list to shut down default
+// console output.  Note that removing this object from the listener list
+// with Release transfers its ownership to the user.
+void TestEventListeners::Append(TestEventListener* listener) {
+  repeater_->Append(listener);
+}
+
+// Removes the given event listener from the list and returns it.  It then
+// becomes the caller's responsibility to delete the listener. Returns
+// NULL if the listener is not found in the list.
+TestEventListener* TestEventListeners::Release(TestEventListener* listener) {
+  if (listener == default_result_printer_)
+    default_result_printer_ = nullptr;
+  else if (listener == default_xml_generator_)
+    default_xml_generator_ = nullptr;
+  return repeater_->Release(listener);
+}
+
+// Returns repeater that broadcasts the TestEventListener events to all
+// subscribers.
+TestEventListener* TestEventListeners::repeater() { return repeater_; }
+
+// Sets the default_result_printer attribute to the provided listener.
+// The listener is also added to the listener list and previous
+// default_result_printer is removed from it and deleted. The listener can
+// also be NULL in which case it will not be added to the list. Does
+// nothing if the previous and the current listener objects are the same.
+void TestEventListeners::SetDefaultResultPrinter(TestEventListener* listener) {
+  if (default_result_printer_ != listener) {
+    // It is an error to pass this method a listener that is already in the
+    // list.
+    delete Release(default_result_printer_);
+    default_result_printer_ = listener;
+    if (listener != nullptr) Append(listener);
+  }
+}
+
+// Sets the default_xml_generator attribute to the provided listener.  The
+// listener is also added to the listener list and previous
+// default_xml_generator is removed from it and deleted. The listener can
+// also be NULL in which case it will not be added to the list. Does
+// nothing if the previous and the current listener objects are the same.
+void TestEventListeners::SetDefaultXmlGenerator(TestEventListener* listener) {
+  if (default_xml_generator_ != listener) {
+    // It is an error to pass this method a listener that is already in the
+    // list.
+    delete Release(default_xml_generator_);
+    default_xml_generator_ = listener;
+    if (listener != nullptr) Append(listener);
+  }
+}
+
+// Controls whether events will be forwarded by the repeater to the
+// listeners in the list.
+bool TestEventListeners::EventForwardingEnabled() const {
+  return repeater_->forwarding_enabled();
+}
+
+void TestEventListeners::SuppressEventForwarding() {
+  repeater_->set_forwarding_enabled(false);
+}
+
+// class UnitTest
+
+// Gets the singleton UnitTest object.  The first time this method is
+// called, a UnitTest object is constructed and returned.  Consecutive
+// calls will return the same object.
+//
+// We don't protect this under mutex_ as a user is not supposed to
+// call this before main() starts, from which point on the return
+// value will never change.
+UnitTest* UnitTest::GetInstance() {
+  // CodeGear C++Builder insists on a public destructor for the
+  // default implementation.  Use this implementation to keep good OO
+  // design with private destructor.
+
+#if defined(__BORLANDC__)
+  static UnitTest* const instance = new UnitTest;
+  return instance;
+#else
+  static UnitTest instance;
+  return &instance;
+#endif  // defined(__BORLANDC__)
+}
+
+// Gets the number of successful test suites.
+int UnitTest::successful_test_suite_count() const {
+  return impl()->successful_test_suite_count();
+}
+
+// Gets the number of failed test suites.
+int UnitTest::failed_test_suite_count() const {
+  return impl()->failed_test_suite_count();
+}
+
+// Gets the number of all test suites.
+int UnitTest::total_test_suite_count() const {
+  return impl()->total_test_suite_count();
+}
+
+// Gets the number of all test suites that contain at least one test
+// that should run.
+int UnitTest::test_suite_to_run_count() const {
+  return impl()->test_suite_to_run_count();
+}
+
+//  Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+int UnitTest::successful_test_case_count() const {
+  return impl()->successful_test_suite_count();
+}
+int UnitTest::failed_test_case_count() const {
+  return impl()->failed_test_suite_count();
+}
+int UnitTest::total_test_case_count() const {
+  return impl()->total_test_suite_count();
+}
+int UnitTest::test_case_to_run_count() const {
+  return impl()->test_suite_to_run_count();
+}
+#endif  //  GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+// Gets the number of successful tests.
+int UnitTest::successful_test_count() const {
+  return impl()->successful_test_count();
+}
+
+// Gets the number of skipped tests.
+int UnitTest::skipped_test_count() const {
+  return impl()->skipped_test_count();
+}
+
+// Gets the number of failed tests.
+int UnitTest::failed_test_count() const { return impl()->failed_test_count(); }
+
+// Gets the number of disabled tests that will be reported in the XML report.
+int UnitTest::reportable_disabled_test_count() const {
+  return impl()->reportable_disabled_test_count();
+}
+
+// Gets the number of disabled tests.
+int UnitTest::disabled_test_count() const {
+  return impl()->disabled_test_count();
+}
+
+// Gets the number of tests to be printed in the XML report.
+int UnitTest::reportable_test_count() const {
+  return impl()->reportable_test_count();
+}
+
+// Gets the number of all tests.
+int UnitTest::total_test_count() const { return impl()->total_test_count(); }
+
+// Gets the number of tests that should run.
+int UnitTest::test_to_run_count() const { return impl()->test_to_run_count(); }
+
+// Gets the time of the test program start, in ms from the start of the
+// UNIX epoch.
+internal::TimeInMillis UnitTest::start_timestamp() const {
+    return impl()->start_timestamp();
+}
+
+// Gets the elapsed time, in milliseconds.
+internal::TimeInMillis UnitTest::elapsed_time() const {
+  return impl()->elapsed_time();
+}
+
+// Returns true if and only if the unit test passed (i.e. all test suites
+// passed).
+bool UnitTest::Passed() const { return impl()->Passed(); }
+
+// Returns true if and only if the unit test failed (i.e. some test suite
+// failed or something outside of all tests failed).
+bool UnitTest::Failed() const { return impl()->Failed(); }
+
+// Gets the i-th test suite among all the test suites. i can range from 0 to
+// total_test_suite_count() - 1. If i is not in that range, returns NULL.
+const TestSuite* UnitTest::GetTestSuite(int i) const {
+  return impl()->GetTestSuite(i);
+}
+
+//  Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+const TestCase* UnitTest::GetTestCase(int i) const {
+  return impl()->GetTestCase(i);
+}
+#endif  //  GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+// Returns the TestResult containing information on test failures and
+// properties logged outside of individual test suites.
+const TestResult& UnitTest::ad_hoc_test_result() const {
+  return *impl()->ad_hoc_test_result();
+}
+
+// Gets the i-th test suite among all the test suites. i can range from 0 to
+// total_test_suite_count() - 1. If i is not in that range, returns NULL.
+TestSuite* UnitTest::GetMutableTestSuite(int i) {
+  return impl()->GetMutableSuiteCase(i);
+}
+
+// Returns the list of event listeners that can be used to track events
+// inside Google Test.
+TestEventListeners& UnitTest::listeners() {
+  return *impl()->listeners();
+}
+
+// Registers and returns a global test environment.  When a test
+// program is run, all global test environments will be set-up in the
+// order they were registered.  After all tests in the program have
+// finished, all global test environments will be torn-down in the
+// *reverse* order they were registered.
+//
+// The UnitTest object takes ownership of the given environment.
+//
+// We don't protect this under mutex_, as we only support calling it
+// from the main thread.
+Environment* UnitTest::AddEnvironment(Environment* env) {
+  if (env == nullptr) {
+    return nullptr;
+  }
+
+  impl_->environments().push_back(env);
+  return env;
+}
+
+// Adds a TestPartResult to the current TestResult object.  All Google Test
+// assertion macros (e.g. ASSERT_TRUE, EXPECT_EQ, etc) eventually call
+// this to report their results.  The user code should use the
+// assertion macros instead of calling this directly.
+void UnitTest::AddTestPartResult(
+    TestPartResult::Type result_type,
+    const char* file_name,
+    int line_number,
+    const std::string& message,
+    const std::string& os_stack_trace) GTEST_LOCK_EXCLUDED_(mutex_) {
+  Message msg;
+  msg << message;
+
+  internal::MutexLock lock(&mutex_);
+  if (impl_->gtest_trace_stack().size() > 0) {
+    msg << "\n" << GTEST_NAME_ << " trace:";
+
+    for (size_t i = impl_->gtest_trace_stack().size(); i > 0; --i) {
+      const internal::TraceInfo& trace = impl_->gtest_trace_stack()[i - 1];
+      msg << "\n" << internal::FormatFileLocation(trace.file, trace.line)
+          << " " << trace.message;
+    }
+  }
+
+  if (os_stack_trace.c_str() != nullptr && !os_stack_trace.empty()) {
+    msg << internal::kStackTraceMarker << os_stack_trace;
+  }
+
+  const TestPartResult result = TestPartResult(
+      result_type, file_name, line_number, msg.GetString().c_str());
+  impl_->GetTestPartResultReporterForCurrentThread()->
+      ReportTestPartResult(result);
+
+  if (result_type != TestPartResult::kSuccess &&
+      result_type != TestPartResult::kSkip) {
+    // gtest_break_on_failure takes precedence over
+    // gtest_throw_on_failure.  This allows a user to set the latter
+    // in the code (perhaps in order to use Google Test assertions
+    // with another testing framework) and specify the former on the
+    // command line for debugging.
+    if (GTEST_FLAG(break_on_failure)) {
+#if GTEST_OS_WINDOWS && !GTEST_OS_WINDOWS_PHONE && !GTEST_OS_WINDOWS_RT
+      // Using DebugBreak on Windows allows gtest to still break into a debugger
+      // when a failure happens and both the --gtest_break_on_failure and
+      // the --gtest_catch_exceptions flags are specified.
+      DebugBreak();
+#elif (!defined(__native_client__)) &&            \
+    ((defined(__clang__) || defined(__GNUC__)) && \
+     (defined(__x86_64__) || defined(__i386__)))
+      // with clang/gcc we can achieve the same effect on x86 by invoking int3
+      asm("int3");
+#else
+      // Dereference nullptr through a volatile pointer to prevent the compiler
+      // from removing. We use this rather than abort() or __builtin_trap() for
+      // portability: some debuggers don't correctly trap abort().
+      *static_cast<volatile int*>(nullptr) = 1;
+#endif  // GTEST_OS_WINDOWS
+    } else if (GTEST_FLAG(throw_on_failure)) {
+#if GTEST_HAS_EXCEPTIONS
+      throw internal::GoogleTestFailureException(result);
+#else
+      // We cannot call abort() as it generates a pop-up in debug mode
+      // that cannot be suppressed in VC 7.1 or below.
+      exit(1);
+#endif
+    }
+  }
+}
+
+// Adds a TestProperty to the current TestResult object when invoked from
+// inside a test, to current TestSuite's ad_hoc_test_result_ when invoked
+// from SetUpTestSuite or TearDownTestSuite, or to the global property set
+// when invoked elsewhere.  If the result already contains a property with
+// the same key, the value will be updated.
+void UnitTest::RecordProperty(const std::string& key,
+                              const std::string& value) {
+  impl_->RecordProperty(TestProperty(key, value));
+}
+
+// Runs all tests in this UnitTest object and prints the result.
+// Returns 0 if successful, or 1 otherwise.
+//
+// We don't protect this under mutex_, as we only support calling it
+// from the main thread.
+int UnitTest::Run() {
+  const bool in_death_test_child_process =
+      internal::GTEST_FLAG(internal_run_death_test).length() > 0;
+
+  // Google Test implements this protocol for catching that a test
+  // program exits before returning control to Google Test:
+  //
+  //   1. Upon start, Google Test creates a file whose absolute path
+  //      is specified by the environment variable
+  //      TEST_PREMATURE_EXIT_FILE.
+  //   2. When Google Test has finished its work, it deletes the file.
+  //
+  // This allows a test runner to set TEST_PREMATURE_EXIT_FILE before
+  // running a Google-Test-based test program and check the existence
+  // of the file at the end of the test execution to see if it has
+  // exited prematurely.
+
+  // If we are in the child process of a death test, don't
+  // create/delete the premature exit file, as doing so is unnecessary
+  // and will confuse the parent process.  Otherwise, create/delete
+  // the file upon entering/leaving this function.  If the program
+  // somehow exits before this function has a chance to return, the
+  // premature-exit file will be left undeleted, causing a test runner
+  // that understands the premature-exit-file protocol to report the
+  // test as having failed.
+  const internal::ScopedPrematureExitFile premature_exit_file(
+      in_death_test_child_process
+          ? nullptr
+          : internal::posix::GetEnv("TEST_PREMATURE_EXIT_FILE"));
+
+  // Captures the value of GTEST_FLAG(catch_exceptions).  This value will be
+  // used for the duration of the program.
+  impl()->set_catch_exceptions(GTEST_FLAG(catch_exceptions));
+
+#if GTEST_OS_WINDOWS
+  // Either the user wants Google Test to catch exceptions thrown by the
+  // tests or this is executing in the context of death test child
+  // process. In either case the user does not want to see pop-up dialogs
+  // about crashes - they are expected.
+  if (impl()->catch_exceptions() || in_death_test_child_process) {
+# if !GTEST_OS_WINDOWS_MOBILE && !GTEST_OS_WINDOWS_PHONE && !GTEST_OS_WINDOWS_RT
+    // SetErrorMode doesn't exist on CE.
+    SetErrorMode(SEM_FAILCRITICALERRORS | SEM_NOALIGNMENTFAULTEXCEPT |
+                 SEM_NOGPFAULTERRORBOX | SEM_NOOPENFILEERRORBOX);
+# endif  // !GTEST_OS_WINDOWS_MOBILE
+
+# if (defined(_MSC_VER) || GTEST_OS_WINDOWS_MINGW) && !GTEST_OS_WINDOWS_MOBILE
+    // Death test children can be terminated with _abort().  On Windows,
+    // _abort() can show a dialog with a warning message.  This forces the
+    // abort message to go to stderr instead.
+    _set_error_mode(_OUT_TO_STDERR);
+# endif
+
+# if defined(_MSC_VER) && !GTEST_OS_WINDOWS_MOBILE
+    // In the debug version, Visual Studio pops up a separate dialog
+    // offering a choice to debug the aborted program. We need to suppress
+    // this dialog or it will pop up for every EXPECT/ASSERT_DEATH statement
+    // executed. Google Test will notify the user of any unexpected
+    // failure via stderr.
+    if (!GTEST_FLAG(break_on_failure))
+      _set_abort_behavior(
+          0x0,                                    // Clear the following flags:
+          _WRITE_ABORT_MSG | _CALL_REPORTFAULT);  // pop-up window, core dump.
+
+    // In debug mode, the Windows CRT can crash with an assertion over invalid
+    // input (e.g. passing an invalid file descriptor).  The default handling
+    // for these assertions is to pop up a dialog and wait for user input.
+    // Instead ask the CRT to dump such assertions to stderr non-interactively.
+    if (!IsDebuggerPresent()) {
+      (void)_CrtSetReportMode(_CRT_ASSERT,
+                              _CRTDBG_MODE_FILE | _CRTDBG_MODE_DEBUG);
+      (void)_CrtSetReportFile(_CRT_ASSERT, _CRTDBG_FILE_STDERR);
+    }
+# endif
+  }
+#endif  // GTEST_OS_WINDOWS
+
+  return internal::HandleExceptionsInMethodIfSupported(
+      impl(),
+      &internal::UnitTestImpl::RunAllTests,
+      "auxiliary test code (environments or event listeners)") ? 0 : 1;
+}
+
+// Returns the working directory when the first TEST() or TEST_F() was
+// executed.
+const char* UnitTest::original_working_dir() const {
+  return impl_->original_working_dir_.c_str();
+}
+
+// Returns the TestSuite object for the test that's currently running,
+// or NULL if no test is running.
+const TestSuite* UnitTest::current_test_suite() const
+    GTEST_LOCK_EXCLUDED_(mutex_) {
+  internal::MutexLock lock(&mutex_);
+  return impl_->current_test_suite();
+}
+
+// Legacy API is still available but deprecated
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+const TestCase* UnitTest::current_test_case() const
+    GTEST_LOCK_EXCLUDED_(mutex_) {
+  internal::MutexLock lock(&mutex_);
+  return impl_->current_test_suite();
+}
+#endif
+
+// Returns the TestInfo object for the test that's currently running,
+// or NULL if no test is running.
+const TestInfo* UnitTest::current_test_info() const
+    GTEST_LOCK_EXCLUDED_(mutex_) {
+  internal::MutexLock lock(&mutex_);
+  return impl_->current_test_info();
+}
+
+// Returns the random seed used at the start of the current test run.
+int UnitTest::random_seed() const { return impl_->random_seed(); }
+
+// Returns ParameterizedTestSuiteRegistry object used to keep track of
+// value-parameterized tests and instantiate and register them.
+internal::ParameterizedTestSuiteRegistry&
+UnitTest::parameterized_test_registry() GTEST_LOCK_EXCLUDED_(mutex_) {
+  return impl_->parameterized_test_registry();
+}
+
+// Creates an empty UnitTest.
+UnitTest::UnitTest() {
+  impl_ = new internal::UnitTestImpl(this);
+}
+
+// Destructor of UnitTest.
+UnitTest::~UnitTest() {
+  delete impl_;
+}
+
+// Pushes a trace defined by SCOPED_TRACE() on to the per-thread
+// Google Test trace stack.
+void UnitTest::PushGTestTrace(const internal::TraceInfo& trace)
+    GTEST_LOCK_EXCLUDED_(mutex_) {
+  internal::MutexLock lock(&mutex_);
+  impl_->gtest_trace_stack().push_back(trace);
+}
+
+// Pops a trace from the per-thread Google Test trace stack.
+void UnitTest::PopGTestTrace()
+    GTEST_LOCK_EXCLUDED_(mutex_) {
+  internal::MutexLock lock(&mutex_);
+  impl_->gtest_trace_stack().pop_back();
+}
+
+namespace internal {
+
+UnitTestImpl::UnitTestImpl(UnitTest* parent)
+    : parent_(parent),
+      GTEST_DISABLE_MSC_WARNINGS_PUSH_(4355 /* using this in initializer */)
+          default_global_test_part_result_reporter_(this),
+      default_per_thread_test_part_result_reporter_(this),
+      GTEST_DISABLE_MSC_WARNINGS_POP_() global_test_part_result_repoter_(
+          &default_global_test_part_result_reporter_),
+      per_thread_test_part_result_reporter_(
+          &default_per_thread_test_part_result_reporter_),
+      parameterized_test_registry_(),
+      parameterized_tests_registered_(false),
+      last_death_test_suite_(-1),
+      current_test_suite_(nullptr),
+      current_test_info_(nullptr),
+      ad_hoc_test_result_(),
+      os_stack_trace_getter_(nullptr),
+      post_flag_parse_init_performed_(false),
+      random_seed_(0),  // Will be overridden by the flag before first use.
+      random_(0),       // Will be reseeded before first use.
+      start_timestamp_(0),
+      elapsed_time_(0),
+#if GTEST_HAS_DEATH_TEST
+      death_test_factory_(new DefaultDeathTestFactory),
+#endif
+      // Will be overridden by the flag before first use.
+      catch_exceptions_(false) {
+  listeners()->SetDefaultResultPrinter(new PrettyUnitTestResultPrinter);
+}
+
+UnitTestImpl::~UnitTestImpl() {
+  // Deletes every TestSuite.
+  ForEach(test_suites_, internal::Delete<TestSuite>);
+
+  // Deletes every Environment.
+  ForEach(environments_, internal::Delete<Environment>);
+
+  delete os_stack_trace_getter_;
+}
+
+// Adds a TestProperty to the current TestResult object when invoked in a
+// context of a test, to current test suite's ad_hoc_test_result when invoke
+// from SetUpTestSuite/TearDownTestSuite, or to the global property set
+// otherwise.  If the result already contains a property with the same key,
+// the value will be updated.
+void UnitTestImpl::RecordProperty(const TestProperty& test_property) {
+  std::string xml_element;
+  TestResult* test_result;  // TestResult appropriate for property recording.
+
+  if (current_test_info_ != nullptr) {
+    xml_element = "testcase";
+    test_result = &(current_test_info_->result_);
+  } else if (current_test_suite_ != nullptr) {
+    xml_element = "testsuite";
+    test_result = &(current_test_suite_->ad_hoc_test_result_);
+  } else {
+    xml_element = "testsuites";
+    test_result = &ad_hoc_test_result_;
+  }
+  test_result->RecordProperty(xml_element, test_property);
+}
+
+#if GTEST_HAS_DEATH_TEST
+// Disables event forwarding if the control is currently in a death test
+// subprocess. Must not be called before InitGoogleTest.
+void UnitTestImpl::SuppressTestEventsIfInSubprocess() {
+  if (internal_run_death_test_flag_.get() != nullptr)
+    listeners()->SuppressEventForwarding();
+}
+#endif  // GTEST_HAS_DEATH_TEST
+
+// Initializes event listeners performing XML output as specified by
+// UnitTestOptions. Must not be called before InitGoogleTest.
+void UnitTestImpl::ConfigureXmlOutput() {
+  const std::string& output_format = UnitTestOptions::GetOutputFormat();
+  if (output_format == "xml") {
+    listeners()->SetDefaultXmlGenerator(new XmlUnitTestResultPrinter(
+        UnitTestOptions::GetAbsolutePathToOutputFile().c_str()));
+  } else if (output_format == "json") {
+    listeners()->SetDefaultXmlGenerator(new JsonUnitTestResultPrinter(
+        UnitTestOptions::GetAbsolutePathToOutputFile().c_str()));
+  } else if (output_format != "") {
+    GTEST_LOG_(WARNING) << "WARNING: unrecognized output format \""
+                        << output_format << "\" ignored.";
+  }
+}
+
+#if GTEST_CAN_STREAM_RESULTS_
+// Initializes event listeners for streaming test results in string form.
+// Must not be called before InitGoogleTest.
+void UnitTestImpl::ConfigureStreamingOutput() {
+  const std::string& target = GTEST_FLAG(stream_result_to);
+  if (!target.empty()) {
+    const size_t pos = target.find(':');
+    if (pos != std::string::npos) {
+      listeners()->Append(new StreamingListener(target.substr(0, pos),
+                                                target.substr(pos+1)));
+    } else {
+      GTEST_LOG_(WARNING) << "unrecognized streaming target \"" << target
+                          << "\" ignored.";
+    }
+  }
+}
+#endif  // GTEST_CAN_STREAM_RESULTS_
+
+// Performs initialization dependent upon flag values obtained in
+// ParseGoogleTestFlagsOnly.  Is called from InitGoogleTest after the call to
+// ParseGoogleTestFlagsOnly.  In case a user neglects to call InitGoogleTest
+// this function is also called from RunAllTests.  Since this function can be
+// called more than once, it has to be idempotent.
+void UnitTestImpl::PostFlagParsingInit() {
+  // Ensures that this function does not execute more than once.
+  if (!post_flag_parse_init_performed_) {
+    post_flag_parse_init_performed_ = true;
+
+#if defined(GTEST_CUSTOM_TEST_EVENT_LISTENER_)
+    // Register to send notifications about key process state changes.
+    listeners()->Append(new GTEST_CUSTOM_TEST_EVENT_LISTENER_());
+#endif  // defined(GTEST_CUSTOM_TEST_EVENT_LISTENER_)
+
+#if GTEST_HAS_DEATH_TEST
+    InitDeathTestSubprocessControlInfo();
+    SuppressTestEventsIfInSubprocess();
+#endif  // GTEST_HAS_DEATH_TEST
+
+    // Registers parameterized tests. This makes parameterized tests
+    // available to the UnitTest reflection API without running
+    // RUN_ALL_TESTS.
+    RegisterParameterizedTests();
+
+    // Configures listeners for XML output. This makes it possible for users
+    // to shut down the default XML output before invoking RUN_ALL_TESTS.
+    ConfigureXmlOutput();
+
+    if (GTEST_FLAG(brief)) {
+      listeners()->SetDefaultResultPrinter(new BriefUnitTestResultPrinter);
+    }
+
+#if GTEST_CAN_STREAM_RESULTS_
+    // Configures listeners for streaming test results to the specified server.
+    ConfigureStreamingOutput();
+#endif  // GTEST_CAN_STREAM_RESULTS_
+
+#if GTEST_HAS_ABSL
+    if (GTEST_FLAG(install_failure_signal_handler)) {
+      absl::FailureSignalHandlerOptions options;
+      absl::InstallFailureSignalHandler(options);
+    }
+#endif  // GTEST_HAS_ABSL
+  }
+}
+
+// A predicate that checks the name of a TestSuite against a known
+// value.
+//
+// This is used for implementation of the UnitTest class only.  We put
+// it in the anonymous namespace to prevent polluting the outer
+// namespace.
+//
+// TestSuiteNameIs is copyable.
+class TestSuiteNameIs {
+ public:
+  // Constructor.
+  explicit TestSuiteNameIs(const std::string& name) : name_(name) {}
+
+  // Returns true if and only if the name of test_suite matches name_.
+  bool operator()(const TestSuite* test_suite) const {
+    return test_suite != nullptr &&
+           strcmp(test_suite->name(), name_.c_str()) == 0;
+  }
+
+ private:
+  std::string name_;
+};
+
+// Finds and returns a TestSuite with the given name.  If one doesn't
+// exist, creates one and returns it.  It's the CALLER'S
+// RESPONSIBILITY to ensure that this function is only called WHEN THE
+// TESTS ARE NOT SHUFFLED.
+//
+// Arguments:
+//
+//   test_suite_name: name of the test suite
+//   type_param:      the name of the test suite's type parameter, or NULL if
+//                    this is not a typed or a type-parameterized test suite.
+//   set_up_tc:       pointer to the function that sets up the test suite
+//   tear_down_tc:    pointer to the function that tears down the test suite
+TestSuite* UnitTestImpl::GetTestSuite(
+    const char* test_suite_name, const char* type_param,
+    internal::SetUpTestSuiteFunc set_up_tc,
+    internal::TearDownTestSuiteFunc tear_down_tc) {
+  // Can we find a TestSuite with the given name?
+  const auto test_suite =
+      std::find_if(test_suites_.rbegin(), test_suites_.rend(),
+                   TestSuiteNameIs(test_suite_name));
+
+  if (test_suite != test_suites_.rend()) return *test_suite;
+
+  // No.  Let's create one.
+  auto* const new_test_suite =
+      new TestSuite(test_suite_name, type_param, set_up_tc, tear_down_tc);
+
+  // Is this a death test suite?
+  if (internal::UnitTestOptions::MatchesFilter(test_suite_name,
+                                               kDeathTestSuiteFilter)) {
+    // Yes.  Inserts the test suite after the last death test suite
+    // defined so far.  This only works when the test suites haven't
+    // been shuffled.  Otherwise we may end up running a death test
+    // after a non-death test.
+    ++last_death_test_suite_;
+    test_suites_.insert(test_suites_.begin() + last_death_test_suite_,
+                        new_test_suite);
+  } else {
+    // No.  Appends to the end of the list.
+    test_suites_.push_back(new_test_suite);
+  }
+
+  test_suite_indices_.push_back(static_cast<int>(test_suite_indices_.size()));
+  return new_test_suite;
+}
+
+// Helpers for setting up / tearing down the given environment.  They
+// are for use in the ForEach() function.
+static void SetUpEnvironment(Environment* env) { env->SetUp(); }
+static void TearDownEnvironment(Environment* env) { env->TearDown(); }
+
+// Runs all tests in this UnitTest object, prints the result, and
+// returns true if all tests are successful.  If any exception is
+// thrown during a test, the test is considered to be failed, but the
+// rest of the tests will still be run.
+//
+// When parameterized tests are enabled, it expands and registers
+// parameterized tests first in RegisterParameterizedTests().
+// All other functions called from RunAllTests() may safely assume that
+// parameterized tests are ready to be counted and run.
+bool UnitTestImpl::RunAllTests() {
+  // True if and only if Google Test is initialized before RUN_ALL_TESTS() is
+  // called.
+  const bool gtest_is_initialized_before_run_all_tests = GTestIsInitialized();
+
+  // Do not run any test if the --help flag was specified.
+  if (g_help_flag)
+    return true;
+
+  // Repeats the call to the post-flag parsing initialization in case the
+  // user didn't call InitGoogleTest.
+  PostFlagParsingInit();
+
+  // Even if sharding is not on, test runners may want to use the
+  // GTEST_SHARD_STATUS_FILE to query whether the test supports the sharding
+  // protocol.
+  internal::WriteToShardStatusFileIfNeeded();
+
+  // True if and only if we are in a subprocess for running a thread-safe-style
+  // death test.
+  bool in_subprocess_for_death_test = false;
+
+#if GTEST_HAS_DEATH_TEST
+  in_subprocess_for_death_test =
+      (internal_run_death_test_flag_.get() != nullptr);
+# if defined(GTEST_EXTRA_DEATH_TEST_CHILD_SETUP_)
+  if (in_subprocess_for_death_test) {
+    GTEST_EXTRA_DEATH_TEST_CHILD_SETUP_();
+  }
+# endif  // defined(GTEST_EXTRA_DEATH_TEST_CHILD_SETUP_)
+#endif  // GTEST_HAS_DEATH_TEST
+
+  const bool should_shard = ShouldShard(kTestTotalShards, kTestShardIndex,
+                                        in_subprocess_for_death_test);
+
+  // Compares the full test names with the filter to decide which
+  // tests to run.
+  const bool has_tests_to_run = FilterTests(should_shard
+                                              ? HONOR_SHARDING_PROTOCOL
+                                              : IGNORE_SHARDING_PROTOCOL) > 0;
+
+  // Lists the tests and exits if the --gtest_list_tests flag was specified.
+  if (GTEST_FLAG(list_tests)) {
+    // This must be called *after* FilterTests() has been called.
+    ListTestsMatchingFilter();
+    return true;
+  }
+
+  random_seed_ = GTEST_FLAG(shuffle) ?
+      GetRandomSeedFromFlag(GTEST_FLAG(random_seed)) : 0;
+
+  // True if and only if at least one test has failed.
+  bool failed = false;
+
+  TestEventListener* repeater = listeners()->repeater();
+
+  start_timestamp_ = GetTimeInMillis();
+  repeater->OnTestProgramStart(*parent_);
+
+  // How many times to repeat the tests?  We don't want to repeat them
+  // when we are inside the subprocess of a death test.
+  const int repeat = in_subprocess_for_death_test ? 1 : GTEST_FLAG(repeat);
+  // Repeats forever if the repeat count is negative.
+  const bool gtest_repeat_forever = repeat < 0;
+  for (int i = 0; gtest_repeat_forever || i != repeat; i++) {
+    // We want to preserve failures generated by ad-hoc test
+    // assertions executed before RUN_ALL_TESTS().
+    ClearNonAdHocTestResult();
+
+    Timer timer;
+
+    // Shuffles test suites and tests if requested.
+    if (has_tests_to_run && GTEST_FLAG(shuffle)) {
+      random()->Reseed(static_cast<uint32_t>(random_seed_));
+      // This should be done before calling OnTestIterationStart(),
+      // such that a test event listener can see the actual test order
+      // in the event.
+      ShuffleTests();
+    }
+
+    // Tells the unit test event listeners that the tests are about to start.
+    repeater->OnTestIterationStart(*parent_, i);
+
+    // Runs each test suite if there is at least one test to run.
+    if (has_tests_to_run) {
+      // Sets up all environments beforehand.
+      repeater->OnEnvironmentsSetUpStart(*parent_);
+      ForEach(environments_, SetUpEnvironment);
+      repeater->OnEnvironmentsSetUpEnd(*parent_);
+
+      // Runs the tests only if there was no fatal failure or skip triggered
+      // during global set-up.
+      if (Test::IsSkipped()) {
+        // Emit diagnostics when global set-up calls skip, as it will not be
+        // emitted by default.
+        TestResult& test_result =
+            *internal::GetUnitTestImpl()->current_test_result();
+        for (int j = 0; j < test_result.total_part_count(); ++j) {
+          const TestPartResult& test_part_result =
+              test_result.GetTestPartResult(j);
+          if (test_part_result.type() == TestPartResult::kSkip) {
+            const std::string& result = test_part_result.message();
+            printf("%s\n", result.c_str());
+          }
+        }
+        fflush(stdout);
+      } else if (!Test::HasFatalFailure()) {
+        for (int test_index = 0; test_index < total_test_suite_count();
+             test_index++) {
+          GetMutableSuiteCase(test_index)->Run();
+          if (GTEST_FLAG(fail_fast) &&
+              GetMutableSuiteCase(test_index)->Failed()) {
+            for (int j = test_index + 1; j < total_test_suite_count(); j++) {
+              GetMutableSuiteCase(j)->Skip();
+            }
+            break;
+          }
+        }
+      } else if (Test::HasFatalFailure()) {
+        // If there was a fatal failure during the global setup then we know we
+        // aren't going to run any tests. Explicitly mark all of the tests as
+        // skipped to make this obvious in the output.
+        for (int test_index = 0; test_index < total_test_suite_count();
+             test_index++) {
+          GetMutableSuiteCase(test_index)->Skip();
+        }
+      }
+
+      // Tears down all environments in reverse order afterwards.
+      repeater->OnEnvironmentsTearDownStart(*parent_);
+      std::for_each(environments_.rbegin(), environments_.rend(),
+                    TearDownEnvironment);
+      repeater->OnEnvironmentsTearDownEnd(*parent_);
+    }
+
+    elapsed_time_ = timer.Elapsed();
+
+    // Tells the unit test event listener that the tests have just finished.
+    repeater->OnTestIterationEnd(*parent_, i);
+
+    // Gets the result and clears it.
+    if (!Passed()) {
+      failed = true;
+    }
+
+    // Restores the original test order after the iteration.  This
+    // allows the user to quickly repro a failure that happens in the
+    // N-th iteration without repeating the first (N - 1) iterations.
+    // This is not enclosed in "if (GTEST_FLAG(shuffle)) { ... }", in
+    // case the user somehow changes the value of the flag somewhere
+    // (it's always safe to unshuffle the tests).
+    UnshuffleTests();
+
+    if (GTEST_FLAG(shuffle)) {
+      // Picks a new random seed for each iteration.
+      random_seed_ = GetNextRandomSeed(random_seed_);
+    }
+  }
+
+  repeater->OnTestProgramEnd(*parent_);
+
+  if (!gtest_is_initialized_before_run_all_tests) {
+    ColoredPrintf(
+        GTestColor::kRed,
+        "\nIMPORTANT NOTICE - DO NOT IGNORE:\n"
+        "This test program did NOT call " GTEST_INIT_GOOGLE_TEST_NAME_
+        "() before calling RUN_ALL_TESTS(). This is INVALID. Soon " GTEST_NAME_
+        " will start to enforce the valid usage. "
+        "Please fix it ASAP, or IT WILL START TO FAIL.\n");  // NOLINT
+#if GTEST_FOR_GOOGLE_
+    ColoredPrintf(GTestColor::kRed,
+                  "For more details, see http://wiki/Main/ValidGUnitMain.\n");
+#endif  // GTEST_FOR_GOOGLE_
+  }
+
+  return !failed;
+}
+
+// Reads the GTEST_SHARD_STATUS_FILE environment variable, and creates the file
+// if the variable is present. If a file already exists at this location, this
+// function will write over it. If the variable is present, but the file cannot
+// be created, prints an error and exits.
+void WriteToShardStatusFileIfNeeded() {
+  const char* const test_shard_file = posix::GetEnv(kTestShardStatusFile);
+  if (test_shard_file != nullptr) {
+    FILE* const file = posix::FOpen(test_shard_file, "w");
+    if (file == nullptr) {
+      ColoredPrintf(GTestColor::kRed,
+                    "Could not write to the test shard status file \"%s\" "
+                    "specified by the %s environment variable.\n",
+                    test_shard_file, kTestShardStatusFile);
+      fflush(stdout);
+      exit(EXIT_FAILURE);
+    }
+    fclose(file);
+  }
+}
+
+// Checks whether sharding is enabled by examining the relevant
+// environment variable values. If the variables are present,
+// but inconsistent (i.e., shard_index >= total_shards), prints
+// an error and exits. If in_subprocess_for_death_test, sharding is
+// disabled because it must only be applied to the original test
+// process. Otherwise, we could filter out death tests we intended to execute.
+bool ShouldShard(const char* total_shards_env,
+                 const char* shard_index_env,
+                 bool in_subprocess_for_death_test) {
+  if (in_subprocess_for_death_test) {
+    return false;
+  }
+
+  const int32_t total_shards = Int32FromEnvOrDie(total_shards_env, -1);
+  const int32_t shard_index = Int32FromEnvOrDie(shard_index_env, -1);
+
+  if (total_shards == -1 && shard_index == -1) {
+    return false;
+  } else if (total_shards == -1 && shard_index != -1) {
+    const Message msg = Message()
+      << "Invalid environment variables: you have "
+      << kTestShardIndex << " = " << shard_index
+      << ", but have left " << kTestTotalShards << " unset.\n";
+    ColoredPrintf(GTestColor::kRed, "%s", msg.GetString().c_str());
+    fflush(stdout);
+    exit(EXIT_FAILURE);
+  } else if (total_shards != -1 && shard_index == -1) {
+    const Message msg = Message()
+      << "Invalid environment variables: you have "
+      << kTestTotalShards << " = " << total_shards
+      << ", but have left " << kTestShardIndex << " unset.\n";
+    ColoredPrintf(GTestColor::kRed, "%s", msg.GetString().c_str());
+    fflush(stdout);
+    exit(EXIT_FAILURE);
+  } else if (shard_index < 0 || shard_index >= total_shards) {
+    const Message msg = Message()
+      << "Invalid environment variables: we require 0 <= "
+      << kTestShardIndex << " < " << kTestTotalShards
+      << ", but you have " << kTestShardIndex << "=" << shard_index
+      << ", " << kTestTotalShards << "=" << total_shards << ".\n";
+    ColoredPrintf(GTestColor::kRed, "%s", msg.GetString().c_str());
+    fflush(stdout);
+    exit(EXIT_FAILURE);
+  }
+
+  return total_shards > 1;
+}
+
+// Parses the environment variable var as an Int32. If it is unset,
+// returns default_val. If it is not an Int32, prints an error
+// and aborts.
+int32_t Int32FromEnvOrDie(const char* var, int32_t default_val) {
+  const char* str_val = posix::GetEnv(var);
+  if (str_val == nullptr) {
+    return default_val;
+  }
+
+  int32_t result;
+  if (!ParseInt32(Message() << "The value of environment variable " << var,
+                  str_val, &result)) {
+    exit(EXIT_FAILURE);
+  }
+  return result;
+}
+
+// Given the total number of shards, the shard index, and the test id,
+// returns true if and only if the test should be run on this shard. The test id
+// is some arbitrary but unique non-negative integer assigned to each test
+// method. Assumes that 0 <= shard_index < total_shards.
+bool ShouldRunTestOnShard(int total_shards, int shard_index, int test_id) {
+  return (test_id % total_shards) == shard_index;
+}
+
+// Compares the name of each test with the user-specified filter to
+// decide whether the test should be run, then records the result in
+// each TestSuite and TestInfo object.
+// If shard_tests == true, further filters tests based on sharding
+// variables in the environment - see
+// https://github.com/google/googletest/blob/master/googletest/docs/advanced.md
+// . Returns the number of tests that should run.
+int UnitTestImpl::FilterTests(ReactionToSharding shard_tests) {
+  const int32_t total_shards = shard_tests == HONOR_SHARDING_PROTOCOL ?
+      Int32FromEnvOrDie(kTestTotalShards, -1) : -1;
+  const int32_t shard_index = shard_tests == HONOR_SHARDING_PROTOCOL ?
+      Int32FromEnvOrDie(kTestShardIndex, -1) : -1;
+
+  // num_runnable_tests are the number of tests that will
+  // run across all shards (i.e., match filter and are not disabled).
+  // num_selected_tests are the number of tests to be run on
+  // this shard.
+  int num_runnable_tests = 0;
+  int num_selected_tests = 0;
+  for (auto* test_suite : test_suites_) {
+    const std::string& test_suite_name = test_suite->name();
+    test_suite->set_should_run(false);
+
+    for (size_t j = 0; j < test_suite->test_info_list().size(); j++) {
+      TestInfo* const test_info = test_suite->test_info_list()[j];
+      const std::string test_name(test_info->name());
+      // A test is disabled if test suite name or test name matches
+      // kDisableTestFilter.
+      const bool is_disabled = internal::UnitTestOptions::MatchesFilter(
+                                   test_suite_name, kDisableTestFilter) ||
+                               internal::UnitTestOptions::MatchesFilter(
+                                   test_name, kDisableTestFilter);
+      test_info->is_disabled_ = is_disabled;
+
+      const bool matches_filter = internal::UnitTestOptions::FilterMatchesTest(
+          test_suite_name, test_name);
+      test_info->matches_filter_ = matches_filter;
+
+      const bool is_runnable =
+          (GTEST_FLAG(also_run_disabled_tests) || !is_disabled) &&
+          matches_filter;
+
+      const bool is_in_another_shard =
+          shard_tests != IGNORE_SHARDING_PROTOCOL &&
+          !ShouldRunTestOnShard(total_shards, shard_index, num_runnable_tests);
+      test_info->is_in_another_shard_ = is_in_another_shard;
+      const bool is_selected = is_runnable && !is_in_another_shard;
+
+      num_runnable_tests += is_runnable;
+      num_selected_tests += is_selected;
+
+      test_info->should_run_ = is_selected;
+      test_suite->set_should_run(test_suite->should_run() || is_selected);
+    }
+  }
+  return num_selected_tests;
+}
+
+// Prints the given C-string on a single line by replacing all '\n'
+// characters with string "\\n".  If the output takes more than
+// max_length characters, only prints the first max_length characters
+// and "...".
+static void PrintOnOneLine(const char* str, int max_length) {
+  if (str != nullptr) {
+    for (int i = 0; *str != '\0'; ++str) {
+      if (i >= max_length) {
+        printf("...");
+        break;
+      }
+      if (*str == '\n') {
+        printf("\\n");
+        i += 2;
+      } else {
+        printf("%c", *str);
+        ++i;
+      }
+    }
+  }
+}
+
+// Prints the names of the tests matching the user-specified filter flag.
+void UnitTestImpl::ListTestsMatchingFilter() {
+  // Print at most this many characters for each type/value parameter.
+  const int kMaxParamLength = 250;
+
+  for (auto* test_suite : test_suites_) {
+    bool printed_test_suite_name = false;
+
+    for (size_t j = 0; j < test_suite->test_info_list().size(); j++) {
+      const TestInfo* const test_info = test_suite->test_info_list()[j];
+      if (test_info->matches_filter_) {
+        if (!printed_test_suite_name) {
+          printed_test_suite_name = true;
+          printf("%s.", test_suite->name());
+          if (test_suite->type_param() != nullptr) {
+            printf("  # %s = ", kTypeParamLabel);
+            // We print the type parameter on a single line to make
+            // the output easy to parse by a program.
+            PrintOnOneLine(test_suite->type_param(), kMaxParamLength);
+          }
+          printf("\n");
+        }
+        printf("  %s", test_info->name());
+        if (test_info->value_param() != nullptr) {
+          printf("  # %s = ", kValueParamLabel);
+          // We print the value parameter on a single line to make the
+          // output easy to parse by a program.
+          PrintOnOneLine(test_info->value_param(), kMaxParamLength);
+        }
+        printf("\n");
+      }
+    }
+  }
+  fflush(stdout);
+  const std::string& output_format = UnitTestOptions::GetOutputFormat();
+  if (output_format == "xml" || output_format == "json") {
+    FILE* fileout = OpenFileForWriting(
+        UnitTestOptions::GetAbsolutePathToOutputFile().c_str());
+    std::stringstream stream;
+    if (output_format == "xml") {
+      XmlUnitTestResultPrinter(
+          UnitTestOptions::GetAbsolutePathToOutputFile().c_str())
+          .PrintXmlTestsList(&stream, test_suites_);
+    } else if (output_format == "json") {
+      JsonUnitTestResultPrinter(
+          UnitTestOptions::GetAbsolutePathToOutputFile().c_str())
+          .PrintJsonTestList(&stream, test_suites_);
+    }
+    fprintf(fileout, "%s", StringStreamToString(&stream).c_str());
+    fclose(fileout);
+  }
+}
+
+// Sets the OS stack trace getter.
+//
+// Does nothing if the input and the current OS stack trace getter are
+// the same; otherwise, deletes the old getter and makes the input the
+// current getter.
+void UnitTestImpl::set_os_stack_trace_getter(
+    OsStackTraceGetterInterface* getter) {
+  if (os_stack_trace_getter_ != getter) {
+    delete os_stack_trace_getter_;
+    os_stack_trace_getter_ = getter;
+  }
+}
+
+// Returns the current OS stack trace getter if it is not NULL;
+// otherwise, creates an OsStackTraceGetter, makes it the current
+// getter, and returns it.
+OsStackTraceGetterInterface* UnitTestImpl::os_stack_trace_getter() {
+  if (os_stack_trace_getter_ == nullptr) {
+#ifdef GTEST_OS_STACK_TRACE_GETTER_
+    os_stack_trace_getter_ = new GTEST_OS_STACK_TRACE_GETTER_;
+#else
+    os_stack_trace_getter_ = new OsStackTraceGetter;
+#endif  // GTEST_OS_STACK_TRACE_GETTER_
+  }
+
+  return os_stack_trace_getter_;
+}
+
+// Returns the most specific TestResult currently running.
+TestResult* UnitTestImpl::current_test_result() {
+  if (current_test_info_ != nullptr) {
+    return &current_test_info_->result_;
+  }
+  if (current_test_suite_ != nullptr) {
+    return &current_test_suite_->ad_hoc_test_result_;
+  }
+  return &ad_hoc_test_result_;
+}
+
+// Shuffles all test suites, and the tests within each test suite,
+// making sure that death tests are still run first.
+void UnitTestImpl::ShuffleTests() {
+  // Shuffles the death test suites.
+  ShuffleRange(random(), 0, last_death_test_suite_ + 1, &test_suite_indices_);
+
+  // Shuffles the non-death test suites.
+  ShuffleRange(random(), last_death_test_suite_ + 1,
+               static_cast<int>(test_suites_.size()), &test_suite_indices_);
+
+  // Shuffles the tests inside each test suite.
+  for (auto& test_suite : test_suites_) {
+    test_suite->ShuffleTests(random());
+  }
+}
+
+// Restores the test suites and tests to their order before the first shuffle.
+void UnitTestImpl::UnshuffleTests() {
+  for (size_t i = 0; i < test_suites_.size(); i++) {
+    // Unshuffles the tests in each test suite.
+    test_suites_[i]->UnshuffleTests();
+    // Resets the index of each test suite.
+    test_suite_indices_[i] = static_cast<int>(i);
+  }
+}
+
+// Returns the current OS stack trace as an std::string.
+//
+// The maximum number of stack frames to be included is specified by
+// the gtest_stack_trace_depth flag.  The skip_count parameter
+// specifies the number of top frames to be skipped, which doesn't
+// count against the number of frames to be included.
+//
+// For example, if Foo() calls Bar(), which in turn calls
+// GetCurrentOsStackTraceExceptTop(..., 1), Foo() will be included in
+// the trace but Bar() and GetCurrentOsStackTraceExceptTop() won't.
+std::string GetCurrentOsStackTraceExceptTop(UnitTest* /*unit_test*/,
+                                            int skip_count) {
+  // We pass skip_count + 1 to skip this wrapper function in addition
+  // to what the user really wants to skip.
+  return GetUnitTestImpl()->CurrentOsStackTraceExceptTop(skip_count + 1);
+}
+
+// Used by the GTEST_SUPPRESS_UNREACHABLE_CODE_WARNING_BELOW_ macro to
+// suppress unreachable code warnings.
+namespace {
+class ClassUniqueToAlwaysTrue {};
+}
+
+bool IsTrue(bool condition) { return condition; }
+
+bool AlwaysTrue() {
+#if GTEST_HAS_EXCEPTIONS
+  // This condition is always false so AlwaysTrue() never actually throws,
+  // but it makes the compiler think that it may throw.
+  if (IsTrue(false))
+    throw ClassUniqueToAlwaysTrue();
+#endif  // GTEST_HAS_EXCEPTIONS
+  return true;
+}
+
+// If *pstr starts with the given prefix, modifies *pstr to be right
+// past the prefix and returns true; otherwise leaves *pstr unchanged
+// and returns false.  None of pstr, *pstr, and prefix can be NULL.
+bool SkipPrefix(const char* prefix, const char** pstr) {
+  const size_t prefix_len = strlen(prefix);
+  if (strncmp(*pstr, prefix, prefix_len) == 0) {
+    *pstr += prefix_len;
+    return true;
+  }
+  return false;
+}
+
+// Parses a string as a command line flag.  The string should have
+// the format "--flag=value".  When def_optional is true, the "=value"
+// part can be omitted.
+//
+// Returns the value of the flag, or NULL if the parsing failed.
+static const char* ParseFlagValue(const char* str, const char* flag,
+                                  bool def_optional) {
+  // str and flag must not be NULL.
+  if (str == nullptr || flag == nullptr) return nullptr;
+
+  // The flag must start with "--" followed by GTEST_FLAG_PREFIX_.
+  const std::string flag_str = std::string("--") + GTEST_FLAG_PREFIX_ + flag;
+  const size_t flag_len = flag_str.length();
+  if (strncmp(str, flag_str.c_str(), flag_len) != 0) return nullptr;
+
+  // Skips the flag name.
+  const char* flag_end = str + flag_len;
+
+  // When def_optional is true, it's OK to not have a "=value" part.
+  if (def_optional && (flag_end[0] == '\0')) {
+    return flag_end;
+  }
+
+  // If def_optional is true and there are more characters after the
+  // flag name, or if def_optional is false, there must be a '=' after
+  // the flag name.
+  if (flag_end[0] != '=') return nullptr;
+
+  // Returns the string after "=".
+  return flag_end + 1;
+}
+
+// Parses a string for a bool flag, in the form of either
+// "--flag=value" or "--flag".
+//
+// In the former case, the value is taken as true as long as it does
+// not start with '0', 'f', or 'F'.
+//
+// In the latter case, the value is taken as true.
+//
+// On success, stores the value of the flag in *value, and returns
+// true.  On failure, returns false without changing *value.
+static bool ParseBoolFlag(const char* str, const char* flag, bool* value) {
+  // Gets the value of the flag as a string.
+  const char* const value_str = ParseFlagValue(str, flag, true);
+
+  // Aborts if the parsing failed.
+  if (value_str == nullptr) return false;
+
+  // Converts the string value to a bool.
+  *value = !(*value_str == '0' || *value_str == 'f' || *value_str == 'F');
+  return true;
+}
+
+// Parses a string for an int32_t flag, in the form of "--flag=value".
+//
+// On success, stores the value of the flag in *value, and returns
+// true.  On failure, returns false without changing *value.
+bool ParseInt32Flag(const char* str, const char* flag, int32_t* value) {
+  // Gets the value of the flag as a string.
+  const char* const value_str = ParseFlagValue(str, flag, false);
+
+  // Aborts if the parsing failed.
+  if (value_str == nullptr) return false;
+
+  // Sets *value to the value of the flag.
+  return ParseInt32(Message() << "The value of flag --" << flag,
+                    value_str, value);
+}
+
+// Parses a string for a string flag, in the form of "--flag=value".
+//
+// On success, stores the value of the flag in *value, and returns
+// true.  On failure, returns false without changing *value.
+template <typename String>
+static bool ParseStringFlag(const char* str, const char* flag, String* value) {
+  // Gets the value of the flag as a string.
+  const char* const value_str = ParseFlagValue(str, flag, false);
+
+  // Aborts if the parsing failed.
+  if (value_str == nullptr) return false;
+
+  // Sets *value to the value of the flag.
+  *value = value_str;
+  return true;
+}
+
+// Determines whether a string has a prefix that Google Test uses for its
+// flags, i.e., starts with GTEST_FLAG_PREFIX_ or GTEST_FLAG_PREFIX_DASH_.
+// If Google Test detects that a command line flag has its prefix but is not
+// recognized, it will print its help message. Flags starting with
+// GTEST_INTERNAL_PREFIX_ followed by "internal_" are considered Google Test
+// internal flags and do not trigger the help message.
+static bool HasGoogleTestFlagPrefix(const char* str) {
+  return (SkipPrefix("--", &str) ||
+          SkipPrefix("-", &str) ||
+          SkipPrefix("/", &str)) &&
+         !SkipPrefix(GTEST_FLAG_PREFIX_ "internal_", &str) &&
+         (SkipPrefix(GTEST_FLAG_PREFIX_, &str) ||
+          SkipPrefix(GTEST_FLAG_PREFIX_DASH_, &str));
+}
+
+// Prints a string containing code-encoded text.  The following escape
+// sequences can be used in the string to control the text color:
+//
+//   @@    prints a single '@' character.
+//   @R    changes the color to red.
+//   @G    changes the color to green.
+//   @Y    changes the color to yellow.
+//   @D    changes to the default terminal text color.
+//
+static void PrintColorEncoded(const char* str) {
+  GTestColor color = GTestColor::kDefault;  // The current color.
+
+  // Conceptually, we split the string into segments divided by escape
+  // sequences.  Then we print one segment at a time.  At the end of
+  // each iteration, the str pointer advances to the beginning of the
+  // next segment.
+  for (;;) {
+    const char* p = strchr(str, '@');
+    if (p == nullptr) {
+      ColoredPrintf(color, "%s", str);
+      return;
+    }
+
+    ColoredPrintf(color, "%s", std::string(str, p).c_str());
+
+    const char ch = p[1];
+    str = p + 2;
+    if (ch == '@') {
+      ColoredPrintf(color, "@");
+    } else if (ch == 'D') {
+      color = GTestColor::kDefault;
+    } else if (ch == 'R') {
+      color = GTestColor::kRed;
+    } else if (ch == 'G') {
+      color = GTestColor::kGreen;
+    } else if (ch == 'Y') {
+      color = GTestColor::kYellow;
+    } else {
+      --str;
+    }
+  }
+}
+
+static const char kColorEncodedHelpMessage[] =
+    "This program contains tests written using " GTEST_NAME_
+    ". You can use the\n"
+    "following command line flags to control its behavior:\n"
+    "\n"
+    "Test Selection:\n"
+    "  @G--" GTEST_FLAG_PREFIX_
+    "list_tests@D\n"
+    "      List the names of all tests instead of running them. The name of\n"
+    "      TEST(Foo, Bar) is \"Foo.Bar\".\n"
+    "  @G--" GTEST_FLAG_PREFIX_
+    "filter=@YPOSITIVE_PATTERNS"
+    "[@G-@YNEGATIVE_PATTERNS]@D\n"
+    "      Run only the tests whose name matches one of the positive patterns "
+    "but\n"
+    "      none of the negative patterns. '?' matches any single character; "
+    "'*'\n"
+    "      matches any substring; ':' separates two patterns.\n"
+    "  @G--" GTEST_FLAG_PREFIX_
+    "also_run_disabled_tests@D\n"
+    "      Run all disabled tests too.\n"
+    "\n"
+    "Test Execution:\n"
+    "  @G--" GTEST_FLAG_PREFIX_
+    "repeat=@Y[COUNT]@D\n"
+    "      Run the tests repeatedly; use a negative count to repeat forever.\n"
+    "  @G--" GTEST_FLAG_PREFIX_
+    "shuffle@D\n"
+    "      Randomize tests' orders on every iteration.\n"
+    "  @G--" GTEST_FLAG_PREFIX_
+    "random_seed=@Y[NUMBER]@D\n"
+    "      Random number seed to use for shuffling test orders (between 1 and\n"
+    "      99999, or 0 to use a seed based on the current time).\n"
+    "\n"
+    "Test Output:\n"
+    "  @G--" GTEST_FLAG_PREFIX_
+    "color=@Y(@Gyes@Y|@Gno@Y|@Gauto@Y)@D\n"
+    "      Enable/disable colored output. The default is @Gauto@D.\n"
+    "  @G--" GTEST_FLAG_PREFIX_
+    "brief=1@D\n"
+    "      Only print test failures.\n"
+    "  @G--" GTEST_FLAG_PREFIX_
+    "print_time=0@D\n"
+    "      Don't print the elapsed time of each test.\n"
+    "  @G--" GTEST_FLAG_PREFIX_
+    "output=@Y(@Gjson@Y|@Gxml@Y)[@G:@YDIRECTORY_PATH@G" GTEST_PATH_SEP_
+    "@Y|@G:@YFILE_PATH]@D\n"
+    "      Generate a JSON or XML report in the given directory or with the "
+    "given\n"
+    "      file name. @YFILE_PATH@D defaults to @Gtest_detail.xml@D.\n"
+# if GTEST_CAN_STREAM_RESULTS_
+    "  @G--" GTEST_FLAG_PREFIX_
+    "stream_result_to=@YHOST@G:@YPORT@D\n"
+    "      Stream test results to the given server.\n"
+# endif  // GTEST_CAN_STREAM_RESULTS_
+    "\n"
+    "Assertion Behavior:\n"
+# if GTEST_HAS_DEATH_TEST && !GTEST_OS_WINDOWS
+    "  @G--" GTEST_FLAG_PREFIX_
+    "death_test_style=@Y(@Gfast@Y|@Gthreadsafe@Y)@D\n"
+    "      Set the default death test style.\n"
+# endif  // GTEST_HAS_DEATH_TEST && !GTEST_OS_WINDOWS
+    "  @G--" GTEST_FLAG_PREFIX_
+    "break_on_failure@D\n"
+    "      Turn assertion failures into debugger break-points.\n"
+    "  @G--" GTEST_FLAG_PREFIX_
+    "throw_on_failure@D\n"
+    "      Turn assertion failures into C++ exceptions for use by an external\n"
+    "      test framework.\n"
+    "  @G--" GTEST_FLAG_PREFIX_
+    "catch_exceptions=0@D\n"
+    "      Do not report exceptions as test failures. Instead, allow them\n"
+    "      to crash the program or throw a pop-up (on Windows).\n"
+    "\n"
+    "Except for @G--" GTEST_FLAG_PREFIX_
+    "list_tests@D, you can alternatively set "
+    "the corresponding\n"
+    "environment variable of a flag (all letters in upper-case). For example, "
+    "to\n"
+    "disable colored text output, you can either specify "
+    "@G--" GTEST_FLAG_PREFIX_
+    "color=no@D or set\n"
+    "the @G" GTEST_FLAG_PREFIX_UPPER_
+    "COLOR@D environment variable to @Gno@D.\n"
+    "\n"
+    "For more information, please read the " GTEST_NAME_
+    " documentation at\n"
+    "@G" GTEST_PROJECT_URL_ "@D. If you find a bug in " GTEST_NAME_
+    "\n"
+    "(not one in your own code or tests), please report it to\n"
+    "@G<" GTEST_DEV_EMAIL_ ">@D.\n";
+
+static bool ParseGoogleTestFlag(const char* const arg) {
+  return ParseBoolFlag(arg, kAlsoRunDisabledTestsFlag,
+                       &GTEST_FLAG(also_run_disabled_tests)) ||
+         ParseBoolFlag(arg, kBreakOnFailureFlag,
+                       &GTEST_FLAG(break_on_failure)) ||
+         ParseBoolFlag(arg, kCatchExceptionsFlag,
+                       &GTEST_FLAG(catch_exceptions)) ||
+         ParseStringFlag(arg, kColorFlag, &GTEST_FLAG(color)) ||
+         ParseStringFlag(arg, kDeathTestStyleFlag,
+                         &GTEST_FLAG(death_test_style)) ||
+         ParseBoolFlag(arg, kDeathTestUseFork,
+                       &GTEST_FLAG(death_test_use_fork)) ||
+         ParseBoolFlag(arg, kFailFast, &GTEST_FLAG(fail_fast)) ||
+         ParseStringFlag(arg, kFilterFlag, &GTEST_FLAG(filter)) ||
+         ParseStringFlag(arg, kInternalRunDeathTestFlag,
+                         &GTEST_FLAG(internal_run_death_test)) ||
+         ParseBoolFlag(arg, kListTestsFlag, &GTEST_FLAG(list_tests)) ||
+         ParseStringFlag(arg, kOutputFlag, &GTEST_FLAG(output)) ||
+         ParseBoolFlag(arg, kBriefFlag, &GTEST_FLAG(brief)) ||
+         ParseBoolFlag(arg, kPrintTimeFlag, &GTEST_FLAG(print_time)) ||
+         ParseBoolFlag(arg, kPrintUTF8Flag, &GTEST_FLAG(print_utf8)) ||
+         ParseInt32Flag(arg, kRandomSeedFlag, &GTEST_FLAG(random_seed)) ||
+         ParseInt32Flag(arg, kRepeatFlag, &GTEST_FLAG(repeat)) ||
+         ParseBoolFlag(arg, kShuffleFlag, &GTEST_FLAG(shuffle)) ||
+         ParseInt32Flag(arg, kStackTraceDepthFlag,
+                        &GTEST_FLAG(stack_trace_depth)) ||
+         ParseStringFlag(arg, kStreamResultToFlag,
+                         &GTEST_FLAG(stream_result_to)) ||
+         ParseBoolFlag(arg, kThrowOnFailureFlag, &GTEST_FLAG(throw_on_failure));
+}
+
+#if GTEST_USE_OWN_FLAGFILE_FLAG_
+static void LoadFlagsFromFile(const std::string& path) {
+  FILE* flagfile = posix::FOpen(path.c_str(), "r");
+  if (!flagfile) {
+    GTEST_LOG_(FATAL) << "Unable to open file \"" << GTEST_FLAG(flagfile)
+                      << "\"";
+  }
+  std::string contents(ReadEntireFile(flagfile));
+  posix::FClose(flagfile);
+  std::vector<std::string> lines;
+  SplitString(contents, '\n', &lines);
+  for (size_t i = 0; i < lines.size(); ++i) {
+    if (lines[i].empty())
+      continue;
+    if (!ParseGoogleTestFlag(lines[i].c_str()))
+      g_help_flag = true;
+  }
+}
+#endif  // GTEST_USE_OWN_FLAGFILE_FLAG_
+
+// Parses the command line for Google Test flags, without initializing
+// other parts of Google Test.  The type parameter CharType can be
+// instantiated to either char or wchar_t.
+template <typename CharType>
+void ParseGoogleTestFlagsOnlyImpl(int* argc, CharType** argv) {
+  for (int i = 1; i < *argc; i++) {
+    const std::string arg_string = StreamableToString(argv[i]);
+    const char* const arg = arg_string.c_str();
+
+    using internal::ParseBoolFlag;
+    using internal::ParseInt32Flag;
+    using internal::ParseStringFlag;
+
+    bool remove_flag = false;
+    if (ParseGoogleTestFlag(arg)) {
+      remove_flag = true;
+#if GTEST_USE_OWN_FLAGFILE_FLAG_
+    } else if (ParseStringFlag(arg, kFlagfileFlag, &GTEST_FLAG(flagfile))) {
+      LoadFlagsFromFile(GTEST_FLAG(flagfile));
+      remove_flag = true;
+#endif  // GTEST_USE_OWN_FLAGFILE_FLAG_
+    } else if (arg_string == "--help" || arg_string == "-h" ||
+               arg_string == "-?" || arg_string == "/?" ||
+               HasGoogleTestFlagPrefix(arg)) {
+      // Both help flag and unrecognized Google Test flags (excluding
+      // internal ones) trigger help display.
+      g_help_flag = true;
+    }
+
+    if (remove_flag) {
+      // Shift the remainder of the argv list left by one.  Note
+      // that argv has (*argc + 1) elements, the last one always being
+      // NULL.  The following loop moves the trailing NULL element as
+      // well.
+      for (int j = i; j != *argc; j++) {
+        argv[j] = argv[j + 1];
+      }
+
+      // Decrements the argument count.
+      (*argc)--;
+
+      // We also need to decrement the iterator as we just removed
+      // an element.
+      i--;
+    }
+  }
+
+  if (g_help_flag) {
+    // We print the help here instead of in RUN_ALL_TESTS(), as the
+    // latter may not be called at all if the user is using Google
+    // Test with another testing framework.
+    PrintColorEncoded(kColorEncodedHelpMessage);
+  }
+}
+
+// Parses the command line for Google Test flags, without initializing
+// other parts of Google Test.
+void ParseGoogleTestFlagsOnly(int* argc, char** argv) {
+  ParseGoogleTestFlagsOnlyImpl(argc, argv);
+
+  // Fix the value of *_NSGetArgc() on macOS, but if and only if
+  // *_NSGetArgv() == argv
+  // Only applicable to char** version of argv
+#if GTEST_OS_MAC
+#ifndef GTEST_OS_IOS
+  if (*_NSGetArgv() == argv) {
+    *_NSGetArgc() = *argc;
+  }
+#endif
+#endif
+}
+void ParseGoogleTestFlagsOnly(int* argc, wchar_t** argv) {
+  ParseGoogleTestFlagsOnlyImpl(argc, argv);
+}
+
+// The internal implementation of InitGoogleTest().
+//
+// The type parameter CharType can be instantiated to either char or
+// wchar_t.
+template <typename CharType>
+void InitGoogleTestImpl(int* argc, CharType** argv) {
+  // We don't want to run the initialization code twice.
+  if (GTestIsInitialized()) return;
+
+  if (*argc <= 0) return;
+
+  g_argvs.clear();
+  for (int i = 0; i != *argc; i++) {
+    g_argvs.push_back(StreamableToString(argv[i]));
+  }
+
+#if GTEST_HAS_ABSL
+  absl::InitializeSymbolizer(g_argvs[0].c_str());
+#endif  // GTEST_HAS_ABSL
+
+  ParseGoogleTestFlagsOnly(argc, argv);
+  GetUnitTestImpl()->PostFlagParsingInit();
+}
+
+}  // namespace internal
+
+// Initializes Google Test.  This must be called before calling
+// RUN_ALL_TESTS().  In particular, it parses a command line for the
+// flags that Google Test recognizes.  Whenever a Google Test flag is
+// seen, it is removed from argv, and *argc is decremented.
+//
+// No value is returned.  Instead, the Google Test flag variables are
+// updated.
+//
+// Calling the function for the second time has no user-visible effect.
+void InitGoogleTest(int* argc, char** argv) {
+#if defined(GTEST_CUSTOM_INIT_GOOGLE_TEST_FUNCTION_)
+  GTEST_CUSTOM_INIT_GOOGLE_TEST_FUNCTION_(argc, argv);
+#else  // defined(GTEST_CUSTOM_INIT_GOOGLE_TEST_FUNCTION_)
+  internal::InitGoogleTestImpl(argc, argv);
+#endif  // defined(GTEST_CUSTOM_INIT_GOOGLE_TEST_FUNCTION_)
+}
+
+// This overloaded version can be used in Windows programs compiled in
+// UNICODE mode.
+void InitGoogleTest(int* argc, wchar_t** argv) {
+#if defined(GTEST_CUSTOM_INIT_GOOGLE_TEST_FUNCTION_)
+  GTEST_CUSTOM_INIT_GOOGLE_TEST_FUNCTION_(argc, argv);
+#else  // defined(GTEST_CUSTOM_INIT_GOOGLE_TEST_FUNCTION_)
+  internal::InitGoogleTestImpl(argc, argv);
+#endif  // defined(GTEST_CUSTOM_INIT_GOOGLE_TEST_FUNCTION_)
+}
+
+// This overloaded version can be used on Arduino/embedded platforms where
+// there is no argc/argv.
+void InitGoogleTest() {
+  // Since Arduino doesn't have a command line, fake out the argc/argv arguments
+  int argc = 1;
+  const auto arg0 = "dummy";
+  char* argv0 = const_cast<char*>(arg0);
+  char** argv = &argv0;
+
+#if defined(GTEST_CUSTOM_INIT_GOOGLE_TEST_FUNCTION_)
+  GTEST_CUSTOM_INIT_GOOGLE_TEST_FUNCTION_(&argc, argv);
+#else  // defined(GTEST_CUSTOM_INIT_GOOGLE_TEST_FUNCTION_)
+  internal::InitGoogleTestImpl(&argc, argv);
+#endif  // defined(GTEST_CUSTOM_INIT_GOOGLE_TEST_FUNCTION_)
+}
+
+std::string TempDir() {
+#if defined(GTEST_CUSTOM_TEMPDIR_FUNCTION_)
+  return GTEST_CUSTOM_TEMPDIR_FUNCTION_();
+#elif GTEST_OS_WINDOWS_MOBILE
+  return "\\temp\\";
+#elif GTEST_OS_WINDOWS
+  const char* temp_dir = internal::posix::GetEnv("TEMP");
+  if (temp_dir == nullptr || temp_dir[0] == '\0') {
+    return "\\temp\\";
+  } else if (temp_dir[strlen(temp_dir) - 1] == '\\') {
+    return temp_dir;
+  } else {
+    return std::string(temp_dir) + "\\";
+  }
+#elif GTEST_OS_LINUX_ANDROID
+  const char* temp_dir = internal::posix::GetEnv("TEST_TMPDIR");
+  if (temp_dir == nullptr || temp_dir[0] == '\0') {
+    return "/data/local/tmp/";
+  } else {
+    return temp_dir;
+  }
+#elif GTEST_OS_LINUX
+  const char* temp_dir = internal::posix::GetEnv("TEST_TMPDIR");
+  if (temp_dir == nullptr || temp_dir[0] == '\0') {
+    return "/tmp/";
+  } else {
+    return temp_dir;
+  }
+#else
+  return "/tmp/";
+#endif  // GTEST_OS_WINDOWS_MOBILE
+}
+
+// Class ScopedTrace
+
+// Pushes the given source file location and message onto a per-thread
+// trace stack maintained by Google Test.
+void ScopedTrace::PushTrace(const char* file, int line, std::string message) {
+  internal::TraceInfo trace;
+  trace.file = file;
+  trace.line = line;
+  trace.message.swap(message);
+
+  UnitTest::GetInstance()->PushGTestTrace(trace);
+}
+
+// Pops the info pushed by the c'tor.
+ScopedTrace::~ScopedTrace()
+    GTEST_LOCK_EXCLUDED_(&UnitTest::mutex_) {
+  UnitTest::GetInstance()->PopGTestTrace();
+}
+
+}  // namespace testing
diff --git a/leveldb_base/third_party/googletest/googletest/src/gtest_main.cc b/leveldb_base/third_party/googletest/googletest/src/gtest_main.cc
new file mode 100644
index 0000000..46b27c3
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/src/gtest_main.cc
@@ -0,0 +1,54 @@
+// Copyright 2006, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <cstdio>
+#include "gtest/gtest.h"
+
+#if GTEST_OS_ESP8266 || GTEST_OS_ESP32
+#if GTEST_OS_ESP8266
+extern "C" {
+#endif
+void setup() {
+  testing::InitGoogleTest();
+}
+
+void loop() { RUN_ALL_TESTS(); }
+
+#if GTEST_OS_ESP8266
+}
+#endif
+
+#else
+
+GTEST_API_ int main(int argc, char **argv) {
+  printf("Running main() from %s\n", __FILE__);
+  testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
+#endif
diff --git a/leveldb_base/third_party/googletest/googletest/test/BUILD.bazel b/leveldb_base/third_party/googletest/googletest/test/BUILD.bazel
new file mode 100644
index 0000000..b06a00a
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/BUILD.bazel
@@ -0,0 +1,590 @@
+# Copyright 2017 Google Inc.
+# All Rights Reserved.
+#
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#
+# Bazel BUILD for The Google C++ Testing Framework (Google Test)
+
+load("@rules_cc//cc:defs.bzl", "cc_binary", "cc_test")
+load("@rules_python//python:defs.bzl", "py_library", "py_test")
+
+licenses(["notice"])
+
+package(default_visibility = ["//:__subpackages__"])
+
+#on windows exclude gtest-tuple.h
+cc_test(
+    name = "gtest_all_test",
+    size = "small",
+    srcs = glob(
+        include = [
+            "gtest-*.cc",
+            "googletest-*.cc",
+            "*.h",
+            "googletest/include/gtest/**/*.h",
+        ],
+        exclude = [
+            "gtest-unittest-api_test.cc",
+            "googletest/src/gtest-all.cc",
+            "gtest_all_test.cc",
+            "gtest-death-test_ex_test.cc",
+            "gtest-listener_test.cc",
+            "gtest-unittest-api_test.cc",
+            "googletest-param-test-test.cc",
+            "googletest-param-test2-test.cc",
+            "googletest-catch-exceptions-test_.cc",
+            "googletest-color-test_.cc",
+            "googletest-env-var-test_.cc",
+            "googletest-failfast-unittest_.cc",
+            "googletest-filter-unittest_.cc",
+            "googletest-global-environment-unittest_.cc",
+            "googletest-break-on-failure-unittest_.cc",
+            "googletest-listener-test.cc",
+            "googletest-output-test_.cc",
+            "googletest-list-tests-unittest_.cc",
+            "googletest-shuffle-test_.cc",
+            "googletest-setuptestsuite-test_.cc",
+            "googletest-uninitialized-test_.cc",
+            "googletest-death-test_ex_test.cc",
+            "googletest-param-test-test",
+            "googletest-throw-on-failure-test_.cc",
+            "googletest-param-test-invalid-name1-test_.cc",
+            "googletest-param-test-invalid-name2-test_.cc",
+        ],
+    ) + select({
+        "//:windows": [],
+        "//conditions:default": [],
+    }),
+    copts = select({
+        "//:windows": ["-DGTEST_USE_OWN_TR1_TUPLE=0"],
+        "//conditions:default": ["-DGTEST_USE_OWN_TR1_TUPLE=1"],
+    }) + select({
+        # Ensure MSVC treats source files as UTF-8 encoded.
+        "//:msvc_compiler": ["-utf-8"],
+        "//conditions:default": [],
+    }),
+    includes = [
+        "googletest",
+        "googletest/include",
+        "googletest/include/internal",
+        "googletest/test",
+    ],
+    linkopts = select({
+        "//:windows": [],
+        "//conditions:default": ["-pthread"],
+    }),
+    deps = ["//:gtest_main"],
+)
+
+# Tests death tests.
+cc_test(
+    name = "googletest-death-test-test",
+    size = "medium",
+    srcs = ["googletest-death-test-test.cc"],
+    deps = ["//:gtest_main"],
+)
+
+cc_test(
+    name = "gtest_test_macro_stack_footprint_test",
+    size = "small",
+    srcs = ["gtest_test_macro_stack_footprint_test.cc"],
+    deps = ["//:gtest"],
+)
+
+#These googletest tests have their own main()
+cc_test(
+    name = "googletest-listener-test",
+    size = "small",
+    srcs = ["googletest-listener-test.cc"],
+    deps = ["//:gtest_main"],
+)
+
+cc_test(
+    name = "gtest-unittest-api_test",
+    size = "small",
+    srcs = [
+        "gtest-unittest-api_test.cc",
+    ],
+    deps = [
+        "//:gtest",
+    ],
+)
+
+cc_test(
+    name = "googletest-param-test-test",
+    size = "small",
+    srcs = [
+        "googletest-param-test-test.cc",
+        "googletest-param-test-test.h",
+        "googletest-param-test2-test.cc",
+    ],
+    deps = ["//:gtest"],
+)
+
+cc_test(
+    name = "gtest_unittest",
+    size = "small",
+    srcs = ["gtest_unittest.cc"],
+    shard_count = 2,
+    deps = ["//:gtest_main"],
+)
+
+#  Py tests
+
+py_library(
+    name = "gtest_test_utils",
+    testonly = 1,
+    srcs = ["gtest_test_utils.py"],
+    imports = ["."],
+)
+
+cc_binary(
+    name = "gtest_help_test_",
+    testonly = 1,
+    srcs = ["gtest_help_test_.cc"],
+    deps = ["//:gtest_main"],
+)
+
+py_test(
+    name = "gtest_help_test",
+    size = "small",
+    srcs = ["gtest_help_test.py"],
+    data = [":gtest_help_test_"],
+    deps = [":gtest_test_utils"],
+)
+
+cc_binary(
+    name = "googletest-output-test_",
+    testonly = 1,
+    srcs = ["googletest-output-test_.cc"],
+    deps = ["//:gtest"],
+)
+
+py_test(
+    name = "googletest-output-test",
+    size = "small",
+    srcs = ["googletest-output-test.py"],
+    args = select({
+        "//:has_absl": [],
+        "//conditions:default": ["--no_stacktrace_support"],
+    }),
+    data = [
+        "googletest-output-test-golden-lin.txt",
+        ":googletest-output-test_",
+    ],
+    deps = [":gtest_test_utils"],
+)
+
+cc_binary(
+    name = "googletest-color-test_",
+    testonly = 1,
+    srcs = ["googletest-color-test_.cc"],
+    deps = ["//:gtest"],
+)
+
+py_test(
+    name = "googletest-color-test",
+    size = "small",
+    srcs = ["googletest-color-test.py"],
+    data = [":googletest-color-test_"],
+    deps = [":gtest_test_utils"],
+)
+
+cc_binary(
+    name = "googletest-env-var-test_",
+    testonly = 1,
+    srcs = ["googletest-env-var-test_.cc"],
+    deps = ["//:gtest"],
+)
+
+py_test(
+    name = "googletest-env-var-test",
+    size = "medium",
+    srcs = ["googletest-env-var-test.py"],
+    data = [":googletest-env-var-test_"],
+    deps = [":gtest_test_utils"],
+)
+
+cc_binary(
+    name = "googletest-failfast-unittest_",
+    testonly = 1,
+    srcs = ["googletest-failfast-unittest_.cc"],
+    deps = ["//:gtest"],
+)
+
+py_test(
+    name = "googletest-failfast-unittest",
+    size = "medium",
+    srcs = ["googletest-failfast-unittest.py"],
+    data = [":googletest-failfast-unittest_"],
+    deps = [":gtest_test_utils"],
+)
+
+cc_binary(
+    name = "googletest-filter-unittest_",
+    testonly = 1,
+    srcs = ["googletest-filter-unittest_.cc"],
+    deps = ["//:gtest"],
+)
+
+py_test(
+    name = "googletest-filter-unittest",
+    size = "medium",
+    srcs = ["googletest-filter-unittest.py"],
+    data = [":googletest-filter-unittest_"],
+    deps = [":gtest_test_utils"],
+)
+
+cc_binary(
+    name = "googletest-global-environment-unittest_",
+    testonly = 1,
+    srcs = ["googletest-global-environment-unittest_.cc"],
+    deps = ["//:gtest"],
+)
+
+py_test(
+    name = "googletest-global-environment-unittest",
+    size = "medium",
+    srcs = ["googletest-global-environment-unittest.py"],
+    data = [":googletest-global-environment-unittest_"],
+    deps = [":gtest_test_utils"],
+)
+
+cc_binary(
+    name = "googletest-break-on-failure-unittest_",
+    testonly = 1,
+    srcs = ["googletest-break-on-failure-unittest_.cc"],
+    deps = ["//:gtest"],
+)
+
+py_test(
+    name = "googletest-break-on-failure-unittest",
+    size = "small",
+    srcs = ["googletest-break-on-failure-unittest.py"],
+    data = [":googletest-break-on-failure-unittest_"],
+    deps = [":gtest_test_utils"],
+)
+
+cc_test(
+    name = "gtest_assert_by_exception_test",
+    size = "small",
+    srcs = ["gtest_assert_by_exception_test.cc"],
+    deps = ["//:gtest"],
+)
+
+cc_binary(
+    name = "googletest-throw-on-failure-test_",
+    testonly = 1,
+    srcs = ["googletest-throw-on-failure-test_.cc"],
+    deps = ["//:gtest"],
+)
+
+py_test(
+    name = "googletest-throw-on-failure-test",
+    size = "small",
+    srcs = ["googletest-throw-on-failure-test.py"],
+    data = [":googletest-throw-on-failure-test_"],
+    deps = [":gtest_test_utils"],
+)
+
+cc_binary(
+    name = "googletest-list-tests-unittest_",
+    testonly = 1,
+    srcs = ["googletest-list-tests-unittest_.cc"],
+    deps = ["//:gtest"],
+)
+
+cc_test(
+    name = "gtest_skip_test",
+    size = "small",
+    srcs = ["gtest_skip_test.cc"],
+    deps = ["//:gtest_main"],
+)
+
+cc_test(
+    name = "gtest_skip_in_environment_setup_test",
+    size = "small",
+    srcs = ["gtest_skip_in_environment_setup_test.cc"],
+    deps = ["//:gtest_main"],
+)
+
+py_test(
+    name = "gtest_skip_check_output_test",
+    size = "small",
+    srcs = ["gtest_skip_check_output_test.py"],
+    data = [":gtest_skip_test"],
+    deps = [":gtest_test_utils"],
+)
+
+py_test(
+    name = "gtest_skip_environment_check_output_test",
+    size = "small",
+    srcs = ["gtest_skip_environment_check_output_test.py"],
+    data = [
+        ":gtest_skip_in_environment_setup_test",
+    ],
+    deps = [":gtest_test_utils"],
+)
+
+py_test(
+    name = "googletest-list-tests-unittest",
+    size = "small",
+    srcs = ["googletest-list-tests-unittest.py"],
+    data = [":googletest-list-tests-unittest_"],
+    deps = [":gtest_test_utils"],
+)
+
+cc_binary(
+    name = "googletest-shuffle-test_",
+    srcs = ["googletest-shuffle-test_.cc"],
+    deps = ["//:gtest"],
+)
+
+py_test(
+    name = "googletest-shuffle-test",
+    size = "small",
+    srcs = ["googletest-shuffle-test.py"],
+    data = [":googletest-shuffle-test_"],
+    deps = [":gtest_test_utils"],
+)
+
+cc_binary(
+    name = "googletest-catch-exceptions-no-ex-test_",
+    testonly = 1,
+    srcs = ["googletest-catch-exceptions-test_.cc"],
+    deps = ["//:gtest_main"],
+)
+
+cc_binary(
+    name = "googletest-catch-exceptions-ex-test_",
+    testonly = 1,
+    srcs = ["googletest-catch-exceptions-test_.cc"],
+    copts = ["-fexceptions"],
+    deps = ["//:gtest_main"],
+)
+
+py_test(
+    name = "googletest-catch-exceptions-test",
+    size = "small",
+    srcs = ["googletest-catch-exceptions-test.py"],
+    data = [
+        ":googletest-catch-exceptions-ex-test_",
+        ":googletest-catch-exceptions-no-ex-test_",
+    ],
+    deps = [":gtest_test_utils"],
+)
+
+cc_binary(
+    name = "gtest_xml_output_unittest_",
+    testonly = 1,
+    srcs = ["gtest_xml_output_unittest_.cc"],
+    deps = ["//:gtest"],
+)
+
+cc_test(
+    name = "gtest_no_test_unittest",
+    size = "small",
+    srcs = ["gtest_no_test_unittest.cc"],
+    deps = ["//:gtest"],
+)
+
+py_test(
+    name = "gtest_xml_output_unittest",
+    size = "small",
+    srcs = [
+        "gtest_xml_output_unittest.py",
+        "gtest_xml_test_utils.py",
+    ],
+    args = select({
+        "//:has_absl": [],
+        "//conditions:default": ["--no_stacktrace_support"],
+    }),
+    data = [
+        # We invoke gtest_no_test_unittest to verify the XML output
+        # when the test program contains no test definition.
+        ":gtest_no_test_unittest",
+        ":gtest_xml_output_unittest_",
+    ],
+    deps = [":gtest_test_utils"],
+)
+
+cc_binary(
+    name = "gtest_xml_outfile1_test_",
+    testonly = 1,
+    srcs = ["gtest_xml_outfile1_test_.cc"],
+    deps = ["//:gtest_main"],
+)
+
+cc_binary(
+    name = "gtest_xml_outfile2_test_",
+    testonly = 1,
+    srcs = ["gtest_xml_outfile2_test_.cc"],
+    deps = ["//:gtest_main"],
+)
+
+py_test(
+    name = "gtest_xml_outfiles_test",
+    size = "small",
+    srcs = [
+        "gtest_xml_outfiles_test.py",
+        "gtest_xml_test_utils.py",
+    ],
+    data = [
+        ":gtest_xml_outfile1_test_",
+        ":gtest_xml_outfile2_test_",
+    ],
+    deps = [":gtest_test_utils"],
+)
+
+cc_binary(
+    name = "googletest-setuptestsuite-test_",
+    testonly = 1,
+    srcs = ["googletest-setuptestsuite-test_.cc"],
+    deps = ["//:gtest_main"],
+)
+
+py_test(
+    name = "googletest-setuptestsuite-test",
+    size = "medium",
+    srcs = ["googletest-setuptestsuite-test.py"],
+    data = [":googletest-setuptestsuite-test_"],
+    deps = [":gtest_test_utils"],
+)
+
+cc_binary(
+    name = "googletest-uninitialized-test_",
+    testonly = 1,
+    srcs = ["googletest-uninitialized-test_.cc"],
+    deps = ["//:gtest"],
+)
+
+py_test(
+    name = "googletest-uninitialized-test",
+    size = "medium",
+    srcs = ["googletest-uninitialized-test.py"],
+    data = ["googletest-uninitialized-test_"],
+    deps = [":gtest_test_utils"],
+)
+
+cc_binary(
+    name = "gtest_testbridge_test_",
+    testonly = 1,
+    srcs = ["gtest_testbridge_test_.cc"],
+    deps = ["//:gtest_main"],
+)
+
+# Tests that filtering via testbridge works
+py_test(
+    name = "gtest_testbridge_test",
+    size = "small",
+    srcs = ["gtest_testbridge_test.py"],
+    data = [":gtest_testbridge_test_"],
+    deps = [":gtest_test_utils"],
+)
+
+py_test(
+    name = "googletest-json-outfiles-test",
+    size = "small",
+    srcs = [
+        "googletest-json-outfiles-test.py",
+        "gtest_json_test_utils.py",
+    ],
+    data = [
+        ":gtest_xml_outfile1_test_",
+        ":gtest_xml_outfile2_test_",
+    ],
+    deps = [":gtest_test_utils"],
+)
+
+py_test(
+    name = "googletest-json-output-unittest",
+    size = "medium",
+    srcs = [
+        "googletest-json-output-unittest.py",
+        "gtest_json_test_utils.py",
+    ],
+    args = select({
+        "//:has_absl": [],
+        "//conditions:default": ["--no_stacktrace_support"],
+    }),
+    data = [
+        # We invoke gtest_no_test_unittest to verify the JSON output
+        # when the test program contains no test definition.
+        ":gtest_no_test_unittest",
+        ":gtest_xml_output_unittest_",
+    ],
+    deps = [":gtest_test_utils"],
+)
+
+# Verifies interaction of death tests and exceptions.
+cc_test(
+    name = "googletest-death-test_ex_catch_test",
+    size = "medium",
+    srcs = ["googletest-death-test_ex_test.cc"],
+    copts = ["-fexceptions"],
+    defines = ["GTEST_ENABLE_CATCH_EXCEPTIONS_=1"],
+    deps = ["//:gtest"],
+)
+
+cc_binary(
+    name = "googletest-param-test-invalid-name1-test_",
+    testonly = 1,
+    srcs = ["googletest-param-test-invalid-name1-test_.cc"],
+    deps = ["//:gtest"],
+)
+
+cc_binary(
+    name = "googletest-param-test-invalid-name2-test_",
+    testonly = 1,
+    srcs = ["googletest-param-test-invalid-name2-test_.cc"],
+    deps = ["//:gtest"],
+)
+
+py_test(
+    name = "googletest-param-test-invalid-name1-test",
+    size = "small",
+    srcs = ["googletest-param-test-invalid-name1-test.py"],
+    data = [":googletest-param-test-invalid-name1-test_"],
+    tags = [
+        "no_test_msvc2015",
+        "no_test_msvc2017",
+    ],
+    deps = [":gtest_test_utils"],
+)
+
+py_test(
+    name = "googletest-param-test-invalid-name2-test",
+    size = "small",
+    srcs = ["googletest-param-test-invalid-name2-test.py"],
+    data = [":googletest-param-test-invalid-name2-test_"],
+    tags = [
+        "no_test_msvc2015",
+        "no_test_msvc2017",
+    ],
+    deps = [":gtest_test_utils"],
+)
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-break-on-failure-unittest.py b/leveldb_base/third_party/googletest/googletest/test/googletest-break-on-failure-unittest.py
new file mode 100644
index 0000000..a5dfbc6
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-break-on-failure-unittest.py
@@ -0,0 +1,208 @@
+#!/usr/bin/env python
+#
+# Copyright 2006, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Unit test for Google Test's break-on-failure mode.
+
+A user can ask Google Test to seg-fault when an assertion fails, using
+either the GTEST_BREAK_ON_FAILURE environment variable or the
+--gtest_break_on_failure flag.  This script tests such functionality
+by invoking googletest-break-on-failure-unittest_ (a program written with
+Google Test) with different environments and command line flags.
+"""
+
+import os
+import gtest_test_utils
+
+# Constants.
+
+IS_WINDOWS = os.name == 'nt'
+
+# The environment variable for enabling/disabling the break-on-failure mode.
+BREAK_ON_FAILURE_ENV_VAR = 'GTEST_BREAK_ON_FAILURE'
+
+# The command line flag for enabling/disabling the break-on-failure mode.
+BREAK_ON_FAILURE_FLAG = 'gtest_break_on_failure'
+
+# The environment variable for enabling/disabling the throw-on-failure mode.
+THROW_ON_FAILURE_ENV_VAR = 'GTEST_THROW_ON_FAILURE'
+
+# The environment variable for enabling/disabling the catch-exceptions mode.
+CATCH_EXCEPTIONS_ENV_VAR = 'GTEST_CATCH_EXCEPTIONS'
+
+# Path to the googletest-break-on-failure-unittest_ program.
+EXE_PATH = gtest_test_utils.GetTestExecutablePath(
+    'googletest-break-on-failure-unittest_')
+
+
+environ = gtest_test_utils.environ
+SetEnvVar = gtest_test_utils.SetEnvVar
+
+# Tests in this file run a Google-Test-based test program and expect it
+# to terminate prematurely.  Therefore they are incompatible with
+# the premature-exit-file protocol by design.  Unset the
+# premature-exit filepath to prevent Google Test from creating
+# the file.
+SetEnvVar(gtest_test_utils.PREMATURE_EXIT_FILE_ENV_VAR, None)
+
+
+def Run(command):
+  """Runs a command; returns 1 if it was killed by a signal, or 0 otherwise."""
+
+  p = gtest_test_utils.Subprocess(command, env=environ)
+  if p.terminated_by_signal:
+    return 1
+  else:
+    return 0
+
+
+# The tests.
+
+
+class GTestBreakOnFailureUnitTest(gtest_test_utils.TestCase):
+  """Tests using the GTEST_BREAK_ON_FAILURE environment variable or
+  the --gtest_break_on_failure flag to turn assertion failures into
+  segmentation faults.
+  """
+
+  def RunAndVerify(self, env_var_value, flag_value, expect_seg_fault):
+    """Runs googletest-break-on-failure-unittest_ and verifies that it does
+    (or does not) have a seg-fault.
+
+    Args:
+      env_var_value:    value of the GTEST_BREAK_ON_FAILURE environment
+                        variable; None if the variable should be unset.
+      flag_value:       value of the --gtest_break_on_failure flag;
+                        None if the flag should not be present.
+      expect_seg_fault: 1 if the program is expected to generate a seg-fault;
+                        0 otherwise.
+    """
+
+    SetEnvVar(BREAK_ON_FAILURE_ENV_VAR, env_var_value)
+
+    if env_var_value is None:
+      env_var_value_msg = ' is not set'
+    else:
+      env_var_value_msg = '=' + env_var_value
+
+    if flag_value is None:
+      flag = ''
+    elif flag_value == '0':
+      flag = '--%s=0' % BREAK_ON_FAILURE_FLAG
+    else:
+      flag = '--%s' % BREAK_ON_FAILURE_FLAG
+
+    command = [EXE_PATH]
+    if flag:
+      command.append(flag)
+
+    if expect_seg_fault:
+      should_or_not = 'should'
+    else:
+      should_or_not = 'should not'
+
+    has_seg_fault = Run(command)
+
+    SetEnvVar(BREAK_ON_FAILURE_ENV_VAR, None)
+
+    msg = ('when %s%s, an assertion failure in "%s" %s cause a seg-fault.' %
+           (BREAK_ON_FAILURE_ENV_VAR, env_var_value_msg, ' '.join(command),
+            should_or_not))
+    self.assert_(has_seg_fault == expect_seg_fault, msg)
+
+  def testDefaultBehavior(self):
+    """Tests the behavior of the default mode."""
+
+    self.RunAndVerify(env_var_value=None,
+                      flag_value=None,
+                      expect_seg_fault=0)
+
+  def testEnvVar(self):
+    """Tests using the GTEST_BREAK_ON_FAILURE environment variable."""
+
+    self.RunAndVerify(env_var_value='0',
+                      flag_value=None,
+                      expect_seg_fault=0)
+    self.RunAndVerify(env_var_value='1',
+                      flag_value=None,
+                      expect_seg_fault=1)
+
+  def testFlag(self):
+    """Tests using the --gtest_break_on_failure flag."""
+
+    self.RunAndVerify(env_var_value=None,
+                      flag_value='0',
+                      expect_seg_fault=0)
+    self.RunAndVerify(env_var_value=None,
+                      flag_value='1',
+                      expect_seg_fault=1)
+
+  def testFlagOverridesEnvVar(self):
+    """Tests that the flag overrides the environment variable."""
+
+    self.RunAndVerify(env_var_value='0',
+                      flag_value='0',
+                      expect_seg_fault=0)
+    self.RunAndVerify(env_var_value='0',
+                      flag_value='1',
+                      expect_seg_fault=1)
+    self.RunAndVerify(env_var_value='1',
+                      flag_value='0',
+                      expect_seg_fault=0)
+    self.RunAndVerify(env_var_value='1',
+                      flag_value='1',
+                      expect_seg_fault=1)
+
+  def testBreakOnFailureOverridesThrowOnFailure(self):
+    """Tests that gtest_break_on_failure overrides gtest_throw_on_failure."""
+
+    SetEnvVar(THROW_ON_FAILURE_ENV_VAR, '1')
+    try:
+      self.RunAndVerify(env_var_value=None,
+                        flag_value='1',
+                        expect_seg_fault=1)
+    finally:
+      SetEnvVar(THROW_ON_FAILURE_ENV_VAR, None)
+
+  if IS_WINDOWS:
+    def testCatchExceptionsDoesNotInterfere(self):
+      """Tests that gtest_catch_exceptions doesn't interfere."""
+
+      SetEnvVar(CATCH_EXCEPTIONS_ENV_VAR, '1')
+      try:
+        self.RunAndVerify(env_var_value='1',
+                          flag_value='1',
+                          expect_seg_fault=1)
+      finally:
+        SetEnvVar(CATCH_EXCEPTIONS_ENV_VAR, None)
+
+
+if __name__ == '__main__':
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-break-on-failure-unittest_.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-break-on-failure-unittest_.cc
new file mode 100644
index 0000000..f84957a
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-break-on-failure-unittest_.cc
@@ -0,0 +1,86 @@
+// Copyright 2006, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Unit test for Google Test's break-on-failure mode.
+//
+// A user can ask Google Test to seg-fault when an assertion fails, using
+// either the GTEST_BREAK_ON_FAILURE environment variable or the
+// --gtest_break_on_failure flag.  This file is used for testing such
+// functionality.
+//
+// This program will be invoked from a Python unit test.  It is
+// expected to fail.  Don't run it directly.
+
+#include "gtest/gtest.h"
+
+#if GTEST_OS_WINDOWS
+# include <windows.h>
+# include <stdlib.h>
+#endif
+
+namespace {
+
+// A test that's expected to fail.
+TEST(Foo, Bar) {
+  EXPECT_EQ(2, 3);
+}
+
+#if GTEST_HAS_SEH && !GTEST_OS_WINDOWS_MOBILE
+// On Windows Mobile global exception handlers are not supported.
+LONG WINAPI ExitWithExceptionCode(
+    struct _EXCEPTION_POINTERS* exception_pointers) {
+  exit(exception_pointers->ExceptionRecord->ExceptionCode);
+}
+#endif
+
+}  // namespace
+
+int main(int argc, char **argv) {
+#if GTEST_OS_WINDOWS
+  // Suppresses display of the Windows error dialog upon encountering
+  // a general protection fault (segment violation).
+  SetErrorMode(SEM_NOGPFAULTERRORBOX | SEM_FAILCRITICALERRORS);
+
+# if GTEST_HAS_SEH && !GTEST_OS_WINDOWS_MOBILE
+
+  // The default unhandled exception filter does not always exit
+  // with the exception code as exit code - for example it exits with
+  // 0 for EXCEPTION_ACCESS_VIOLATION and 1 for EXCEPTION_BREAKPOINT
+  // if the application is compiled in debug mode. Thus we use our own
+  // filter which always exits with the exception code for unhandled
+  // exceptions.
+  SetUnhandledExceptionFilter(ExitWithExceptionCode);
+
+# endif
+#endif  // GTEST_OS_WINDOWS
+  testing::InitGoogleTest(&argc, argv);
+
+  return RUN_ALL_TESTS();
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-catch-exceptions-test.py b/leveldb_base/third_party/googletest/googletest/test/googletest-catch-exceptions-test.py
new file mode 100644
index 0000000..94a5b33
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-catch-exceptions-test.py
@@ -0,0 +1,236 @@
+#!/usr/bin/env python
+#
+# Copyright 2010 Google Inc.  All Rights Reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Tests Google Test's exception catching behavior.
+
+This script invokes googletest-catch-exceptions-test_ and
+googletest-catch-exceptions-ex-test_ (programs written with
+Google Test) and verifies their output.
+"""
+
+import gtest_test_utils
+
+# Constants.
+FLAG_PREFIX = '--gtest_'
+LIST_TESTS_FLAG = FLAG_PREFIX + 'list_tests'
+NO_CATCH_EXCEPTIONS_FLAG = FLAG_PREFIX + 'catch_exceptions=0'
+FILTER_FLAG = FLAG_PREFIX + 'filter'
+
+# Path to the googletest-catch-exceptions-ex-test_ binary, compiled with
+# exceptions enabled.
+EX_EXE_PATH = gtest_test_utils.GetTestExecutablePath(
+    'googletest-catch-exceptions-ex-test_')
+
+# Path to the googletest-catch-exceptions-test_ binary, compiled with
+# exceptions disabled.
+EXE_PATH = gtest_test_utils.GetTestExecutablePath(
+    'googletest-catch-exceptions-no-ex-test_')
+
+environ = gtest_test_utils.environ
+SetEnvVar = gtest_test_utils.SetEnvVar
+
+# Tests in this file run a Google-Test-based test program and expect it
+# to terminate prematurely.  Therefore they are incompatible with
+# the premature-exit-file protocol by design.  Unset the
+# premature-exit filepath to prevent Google Test from creating
+# the file.
+SetEnvVar(gtest_test_utils.PREMATURE_EXIT_FILE_ENV_VAR, None)
+
+TEST_LIST = gtest_test_utils.Subprocess(
+    [EXE_PATH, LIST_TESTS_FLAG], env=environ).output
+
+SUPPORTS_SEH_EXCEPTIONS = 'ThrowsSehException' in TEST_LIST
+
+if SUPPORTS_SEH_EXCEPTIONS:
+  BINARY_OUTPUT = gtest_test_utils.Subprocess([EXE_PATH], env=environ).output
+
+EX_BINARY_OUTPUT = gtest_test_utils.Subprocess(
+    [EX_EXE_PATH], env=environ).output
+
+
+# The tests.
+if SUPPORTS_SEH_EXCEPTIONS:
+  # pylint:disable-msg=C6302
+  class CatchSehExceptionsTest(gtest_test_utils.TestCase):
+    """Tests exception-catching behavior."""
+
+
+    def TestSehExceptions(self, test_output):
+      self.assert_('SEH exception with code 0x2a thrown '
+                   'in the test fixture\'s constructor'
+                   in test_output)
+      self.assert_('SEH exception with code 0x2a thrown '
+                   'in the test fixture\'s destructor'
+                   in test_output)
+      self.assert_('SEH exception with code 0x2a thrown in SetUpTestSuite()'
+                   in test_output)
+      self.assert_('SEH exception with code 0x2a thrown in TearDownTestSuite()'
+                   in test_output)
+      self.assert_('SEH exception with code 0x2a thrown in SetUp()'
+                   in test_output)
+      self.assert_('SEH exception with code 0x2a thrown in TearDown()'
+                   in test_output)
+      self.assert_('SEH exception with code 0x2a thrown in the test body'
+                   in test_output)
+
+    def testCatchesSehExceptionsWithCxxExceptionsEnabled(self):
+      self.TestSehExceptions(EX_BINARY_OUTPUT)
+
+    def testCatchesSehExceptionsWithCxxExceptionsDisabled(self):
+      self.TestSehExceptions(BINARY_OUTPUT)
+
+
+class CatchCxxExceptionsTest(gtest_test_utils.TestCase):
+  """Tests C++ exception-catching behavior.
+
+     Tests in this test case verify that:
+     * C++ exceptions are caught and logged as C++ (not SEH) exceptions
+     * Exception thrown affect the remainder of the test work flow in the
+       expected manner.
+  """
+
+  def testCatchesCxxExceptionsInFixtureConstructor(self):
+    self.assertTrue(
+        'C++ exception with description '
+        '"Standard C++ exception" thrown '
+        'in the test fixture\'s constructor' in EX_BINARY_OUTPUT,
+        EX_BINARY_OUTPUT)
+    self.assert_('unexpected' not in EX_BINARY_OUTPUT,
+                 'This failure belongs in this test only if '
+                 '"CxxExceptionInConstructorTest" (no quotes) '
+                 'appears on the same line as words "called unexpectedly"')
+
+  if ('CxxExceptionInDestructorTest.ThrowsExceptionInDestructor' in
+      EX_BINARY_OUTPUT):
+
+    def testCatchesCxxExceptionsInFixtureDestructor(self):
+      self.assertTrue(
+          'C++ exception with description '
+          '"Standard C++ exception" thrown '
+          'in the test fixture\'s destructor' in EX_BINARY_OUTPUT,
+          EX_BINARY_OUTPUT)
+      self.assertTrue(
+          'CxxExceptionInDestructorTest::TearDownTestSuite() '
+          'called as expected.' in EX_BINARY_OUTPUT, EX_BINARY_OUTPUT)
+
+  def testCatchesCxxExceptionsInSetUpTestCase(self):
+    self.assertTrue(
+        'C++ exception with description "Standard C++ exception"'
+        ' thrown in SetUpTestSuite()' in EX_BINARY_OUTPUT, EX_BINARY_OUTPUT)
+    self.assertTrue(
+        'CxxExceptionInConstructorTest::TearDownTestSuite() '
+        'called as expected.' in EX_BINARY_OUTPUT, EX_BINARY_OUTPUT)
+    self.assertTrue(
+        'CxxExceptionInSetUpTestSuiteTest constructor '
+        'called as expected.' in EX_BINARY_OUTPUT, EX_BINARY_OUTPUT)
+    self.assertTrue(
+        'CxxExceptionInSetUpTestSuiteTest destructor '
+        'called as expected.' in EX_BINARY_OUTPUT, EX_BINARY_OUTPUT)
+    self.assertTrue(
+        'CxxExceptionInSetUpTestSuiteTest::SetUp() '
+        'called as expected.' in EX_BINARY_OUTPUT, EX_BINARY_OUTPUT)
+    self.assertTrue(
+        'CxxExceptionInSetUpTestSuiteTest::TearDown() '
+        'called as expected.' in EX_BINARY_OUTPUT, EX_BINARY_OUTPUT)
+    self.assertTrue(
+        'CxxExceptionInSetUpTestSuiteTest test body '
+        'called as expected.' in EX_BINARY_OUTPUT, EX_BINARY_OUTPUT)
+
+  def testCatchesCxxExceptionsInTearDownTestCase(self):
+    self.assertTrue(
+        'C++ exception with description "Standard C++ exception"'
+        ' thrown in TearDownTestSuite()' in EX_BINARY_OUTPUT, EX_BINARY_OUTPUT)
+
+  def testCatchesCxxExceptionsInSetUp(self):
+    self.assertTrue(
+        'C++ exception with description "Standard C++ exception"'
+        ' thrown in SetUp()' in EX_BINARY_OUTPUT, EX_BINARY_OUTPUT)
+    self.assertTrue(
+        'CxxExceptionInSetUpTest::TearDownTestSuite() '
+        'called as expected.' in EX_BINARY_OUTPUT, EX_BINARY_OUTPUT)
+    self.assertTrue(
+        'CxxExceptionInSetUpTest destructor '
+        'called as expected.' in EX_BINARY_OUTPUT, EX_BINARY_OUTPUT)
+    self.assertTrue(
+        'CxxExceptionInSetUpTest::TearDown() '
+        'called as expected.' in EX_BINARY_OUTPUT, EX_BINARY_OUTPUT)
+    self.assert_('unexpected' not in EX_BINARY_OUTPUT,
+                 'This failure belongs in this test only if '
+                 '"CxxExceptionInSetUpTest" (no quotes) '
+                 'appears on the same line as words "called unexpectedly"')
+
+  def testCatchesCxxExceptionsInTearDown(self):
+    self.assertTrue(
+        'C++ exception with description "Standard C++ exception"'
+        ' thrown in TearDown()' in EX_BINARY_OUTPUT, EX_BINARY_OUTPUT)
+    self.assertTrue(
+        'CxxExceptionInTearDownTest::TearDownTestSuite() '
+        'called as expected.' in EX_BINARY_OUTPUT, EX_BINARY_OUTPUT)
+    self.assertTrue(
+        'CxxExceptionInTearDownTest destructor '
+        'called as expected.' in EX_BINARY_OUTPUT, EX_BINARY_OUTPUT)
+
+  def testCatchesCxxExceptionsInTestBody(self):
+    self.assertTrue(
+        'C++ exception with description "Standard C++ exception"'
+        ' thrown in the test body' in EX_BINARY_OUTPUT, EX_BINARY_OUTPUT)
+    self.assertTrue(
+        'CxxExceptionInTestBodyTest::TearDownTestSuite() '
+        'called as expected.' in EX_BINARY_OUTPUT, EX_BINARY_OUTPUT)
+    self.assertTrue(
+        'CxxExceptionInTestBodyTest destructor '
+        'called as expected.' in EX_BINARY_OUTPUT, EX_BINARY_OUTPUT)
+    self.assertTrue(
+        'CxxExceptionInTestBodyTest::TearDown() '
+        'called as expected.' in EX_BINARY_OUTPUT, EX_BINARY_OUTPUT)
+
+  def testCatchesNonStdCxxExceptions(self):
+    self.assertTrue(
+        'Unknown C++ exception thrown in the test body' in EX_BINARY_OUTPUT,
+        EX_BINARY_OUTPUT)
+
+  def testUnhandledCxxExceptionsAbortTheProgram(self):
+    # Filters out SEH exception tests on Windows. Unhandled SEH exceptions
+    # cause tests to show pop-up windows there.
+    FITLER_OUT_SEH_TESTS_FLAG = FILTER_FLAG + '=-*Seh*'
+    # By default, Google Test doesn't catch the exceptions.
+    uncaught_exceptions_ex_binary_output = gtest_test_utils.Subprocess(
+        [EX_EXE_PATH,
+         NO_CATCH_EXCEPTIONS_FLAG,
+         FITLER_OUT_SEH_TESTS_FLAG],
+        env=environ).output
+
+    self.assert_('Unhandled C++ exception terminating the program'
+                 in uncaught_exceptions_ex_binary_output)
+    self.assert_('unexpected' not in uncaught_exceptions_ex_binary_output)
+
+
+if __name__ == '__main__':
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-catch-exceptions-test_.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-catch-exceptions-test_.cc
new file mode 100644
index 0000000..8c127d4
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-catch-exceptions-test_.cc
@@ -0,0 +1,293 @@
+// Copyright 2010, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// Tests for Google Test itself. Tests in this file throw C++ or SEH
+// exceptions, and the output is verified by
+// googletest-catch-exceptions-test.py.
+
+#include <stdio.h>  // NOLINT
+#include <stdlib.h>  // For exit().
+
+#include "gtest/gtest.h"
+
+#if GTEST_HAS_SEH
+# include <windows.h>
+#endif
+
+#if GTEST_HAS_EXCEPTIONS
+# include <exception>  // For set_terminate().
+# include <stdexcept>
+#endif
+
+using testing::Test;
+
+#if GTEST_HAS_SEH
+
+class SehExceptionInConstructorTest : public Test {
+ public:
+  SehExceptionInConstructorTest() { RaiseException(42, 0, 0, NULL); }
+};
+
+TEST_F(SehExceptionInConstructorTest, ThrowsExceptionInConstructor) {}
+
+class SehExceptionInDestructorTest : public Test {
+ public:
+  ~SehExceptionInDestructorTest() { RaiseException(42, 0, 0, NULL); }
+};
+
+TEST_F(SehExceptionInDestructorTest, ThrowsExceptionInDestructor) {}
+
+class SehExceptionInSetUpTestSuiteTest : public Test {
+ public:
+  static void SetUpTestSuite() { RaiseException(42, 0, 0, NULL); }
+};
+
+TEST_F(SehExceptionInSetUpTestSuiteTest, ThrowsExceptionInSetUpTestSuite) {}
+
+class SehExceptionInTearDownTestSuiteTest : public Test {
+ public:
+  static void TearDownTestSuite() { RaiseException(42, 0, 0, NULL); }
+};
+
+TEST_F(SehExceptionInTearDownTestSuiteTest,
+       ThrowsExceptionInTearDownTestSuite) {}
+
+class SehExceptionInSetUpTest : public Test {
+ protected:
+  virtual void SetUp() { RaiseException(42, 0, 0, NULL); }
+};
+
+TEST_F(SehExceptionInSetUpTest, ThrowsExceptionInSetUp) {}
+
+class SehExceptionInTearDownTest : public Test {
+ protected:
+  virtual void TearDown() { RaiseException(42, 0, 0, NULL); }
+};
+
+TEST_F(SehExceptionInTearDownTest, ThrowsExceptionInTearDown) {}
+
+TEST(SehExceptionTest, ThrowsSehException) {
+  RaiseException(42, 0, 0, NULL);
+}
+
+#endif  // GTEST_HAS_SEH
+
+#if GTEST_HAS_EXCEPTIONS
+
+class CxxExceptionInConstructorTest : public Test {
+ public:
+  CxxExceptionInConstructorTest() {
+    // Without this macro VC++ complains about unreachable code at the end of
+    // the constructor.
+    GTEST_SUPPRESS_UNREACHABLE_CODE_WARNING_BELOW_(
+        throw std::runtime_error("Standard C++ exception"));
+  }
+
+  static void TearDownTestSuite() {
+    printf("%s",
+           "CxxExceptionInConstructorTest::TearDownTestSuite() "
+           "called as expected.\n");
+  }
+
+ protected:
+  ~CxxExceptionInConstructorTest() override {
+    ADD_FAILURE() << "CxxExceptionInConstructorTest destructor "
+                  << "called unexpectedly.";
+  }
+
+  void SetUp() override {
+    ADD_FAILURE() << "CxxExceptionInConstructorTest::SetUp() "
+                  << "called unexpectedly.";
+  }
+
+  void TearDown() override {
+    ADD_FAILURE() << "CxxExceptionInConstructorTest::TearDown() "
+                  << "called unexpectedly.";
+  }
+};
+
+TEST_F(CxxExceptionInConstructorTest, ThrowsExceptionInConstructor) {
+  ADD_FAILURE() << "CxxExceptionInConstructorTest test body "
+                << "called unexpectedly.";
+}
+
+class CxxExceptionInSetUpTestSuiteTest : public Test {
+ public:
+  CxxExceptionInSetUpTestSuiteTest() {
+    printf("%s",
+           "CxxExceptionInSetUpTestSuiteTest constructor "
+           "called as expected.\n");
+  }
+
+  static void SetUpTestSuite() {
+    throw std::runtime_error("Standard C++ exception");
+  }
+
+  static void TearDownTestSuite() {
+    printf("%s",
+           "CxxExceptionInSetUpTestSuiteTest::TearDownTestSuite() "
+           "called as expected.\n");
+  }
+
+ protected:
+  ~CxxExceptionInSetUpTestSuiteTest() override {
+    printf("%s",
+           "CxxExceptionInSetUpTestSuiteTest destructor "
+           "called as expected.\n");
+  }
+
+  void SetUp() override {
+    printf("%s",
+           "CxxExceptionInSetUpTestSuiteTest::SetUp() "
+           "called as expected.\n");
+  }
+
+  void TearDown() override {
+    printf("%s",
+           "CxxExceptionInSetUpTestSuiteTest::TearDown() "
+           "called as expected.\n");
+  }
+};
+
+TEST_F(CxxExceptionInSetUpTestSuiteTest, ThrowsExceptionInSetUpTestSuite) {
+  printf("%s",
+         "CxxExceptionInSetUpTestSuiteTest test body "
+         "called as expected.\n");
+}
+
+class CxxExceptionInTearDownTestSuiteTest : public Test {
+ public:
+  static void TearDownTestSuite() {
+    throw std::runtime_error("Standard C++ exception");
+  }
+};
+
+TEST_F(CxxExceptionInTearDownTestSuiteTest,
+       ThrowsExceptionInTearDownTestSuite) {}
+
+class CxxExceptionInSetUpTest : public Test {
+ public:
+  static void TearDownTestSuite() {
+    printf("%s",
+           "CxxExceptionInSetUpTest::TearDownTestSuite() "
+           "called as expected.\n");
+  }
+
+ protected:
+  ~CxxExceptionInSetUpTest() override {
+    printf("%s",
+           "CxxExceptionInSetUpTest destructor "
+           "called as expected.\n");
+  }
+
+  void SetUp() override { throw std::runtime_error("Standard C++ exception"); }
+
+  void TearDown() override {
+    printf("%s",
+           "CxxExceptionInSetUpTest::TearDown() "
+           "called as expected.\n");
+  }
+};
+
+TEST_F(CxxExceptionInSetUpTest, ThrowsExceptionInSetUp) {
+  ADD_FAILURE() << "CxxExceptionInSetUpTest test body "
+                << "called unexpectedly.";
+}
+
+class CxxExceptionInTearDownTest : public Test {
+ public:
+  static void TearDownTestSuite() {
+    printf("%s",
+           "CxxExceptionInTearDownTest::TearDownTestSuite() "
+           "called as expected.\n");
+  }
+
+ protected:
+  ~CxxExceptionInTearDownTest() override {
+    printf("%s",
+           "CxxExceptionInTearDownTest destructor "
+           "called as expected.\n");
+  }
+
+  void TearDown() override {
+    throw std::runtime_error("Standard C++ exception");
+  }
+};
+
+TEST_F(CxxExceptionInTearDownTest, ThrowsExceptionInTearDown) {}
+
+class CxxExceptionInTestBodyTest : public Test {
+ public:
+  static void TearDownTestSuite() {
+    printf("%s",
+           "CxxExceptionInTestBodyTest::TearDownTestSuite() "
+           "called as expected.\n");
+  }
+
+ protected:
+  ~CxxExceptionInTestBodyTest() override {
+    printf("%s",
+           "CxxExceptionInTestBodyTest destructor "
+           "called as expected.\n");
+  }
+
+  void TearDown() override {
+    printf("%s",
+           "CxxExceptionInTestBodyTest::TearDown() "
+           "called as expected.\n");
+  }
+};
+
+TEST_F(CxxExceptionInTestBodyTest, ThrowsStdCxxException) {
+  throw std::runtime_error("Standard C++ exception");
+}
+
+TEST(CxxExceptionTest, ThrowsNonStdCxxException) {
+  throw "C-string";
+}
+
+// This terminate handler aborts the program using exit() rather than abort().
+// This avoids showing pop-ups on Windows systems and core dumps on Unix-like
+// ones.
+void TerminateHandler() {
+  fprintf(stderr, "%s\n", "Unhandled C++ exception terminating the program.");
+  fflush(nullptr);
+  exit(3);
+}
+
+#endif  // GTEST_HAS_EXCEPTIONS
+
+int main(int argc, char** argv) {
+#if GTEST_HAS_EXCEPTIONS
+  std::set_terminate(&TerminateHandler);
+#endif
+  testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-color-test.py b/leveldb_base/third_party/googletest/googletest/test/googletest-color-test.py
new file mode 100644
index 0000000..f3b7c99
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-color-test.py
@@ -0,0 +1,127 @@
+#!/usr/bin/env python
+#
+# Copyright 2008, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Verifies that Google Test correctly determines whether to use colors."""
+
+import os
+import gtest_test_utils
+
+IS_WINDOWS = os.name == 'nt'
+
+COLOR_ENV_VAR = 'GTEST_COLOR'
+COLOR_FLAG = 'gtest_color'
+COMMAND = gtest_test_utils.GetTestExecutablePath('googletest-color-test_')
+
+
+def SetEnvVar(env_var, value):
+  """Sets the env variable to 'value'; unsets it when 'value' is None."""
+
+  if value is not None:
+    os.environ[env_var] = value
+  elif env_var in os.environ:
+    del os.environ[env_var]
+
+
+def UsesColor(term, color_env_var, color_flag):
+  """Runs googletest-color-test_ and returns its exit code."""
+
+  SetEnvVar('TERM', term)
+  SetEnvVar(COLOR_ENV_VAR, color_env_var)
+
+  if color_flag is None:
+    args = []
+  else:
+    args = ['--%s=%s' % (COLOR_FLAG, color_flag)]
+  p = gtest_test_utils.Subprocess([COMMAND] + args)
+  return not p.exited or p.exit_code
+
+
+class GTestColorTest(gtest_test_utils.TestCase):
+  def testNoEnvVarNoFlag(self):
+    """Tests the case when there's neither GTEST_COLOR nor --gtest_color."""
+
+    if not IS_WINDOWS:
+      self.assert_(not UsesColor('dumb', None, None))
+      self.assert_(not UsesColor('emacs', None, None))
+      self.assert_(not UsesColor('xterm-mono', None, None))
+      self.assert_(not UsesColor('unknown', None, None))
+      self.assert_(not UsesColor(None, None, None))
+    self.assert_(UsesColor('linux', None, None))
+    self.assert_(UsesColor('cygwin', None, None))
+    self.assert_(UsesColor('xterm', None, None))
+    self.assert_(UsesColor('xterm-color', None, None))
+    self.assert_(UsesColor('xterm-256color', None, None))
+
+  def testFlagOnly(self):
+    """Tests the case when there's --gtest_color but not GTEST_COLOR."""
+
+    self.assert_(not UsesColor('dumb', None, 'no'))
+    self.assert_(not UsesColor('xterm-color', None, 'no'))
+    if not IS_WINDOWS:
+      self.assert_(not UsesColor('emacs', None, 'auto'))
+    self.assert_(UsesColor('xterm', None, 'auto'))
+    self.assert_(UsesColor('dumb', None, 'yes'))
+    self.assert_(UsesColor('xterm', None, 'yes'))
+
+  def testEnvVarOnly(self):
+    """Tests the case when there's GTEST_COLOR but not --gtest_color."""
+
+    self.assert_(not UsesColor('dumb', 'no', None))
+    self.assert_(not UsesColor('xterm-color', 'no', None))
+    if not IS_WINDOWS:
+      self.assert_(not UsesColor('dumb', 'auto', None))
+    self.assert_(UsesColor('xterm-color', 'auto', None))
+    self.assert_(UsesColor('dumb', 'yes', None))
+    self.assert_(UsesColor('xterm-color', 'yes', None))
+
+  def testEnvVarAndFlag(self):
+    """Tests the case when there are both GTEST_COLOR and --gtest_color."""
+
+    self.assert_(not UsesColor('xterm-color', 'no', 'no'))
+    self.assert_(UsesColor('dumb', 'no', 'yes'))
+    self.assert_(UsesColor('xterm-color', 'no', 'auto'))
+
+  def testAliasesOfYesAndNo(self):
+    """Tests using aliases in specifying --gtest_color."""
+
+    self.assert_(UsesColor('dumb', None, 'true'))
+    self.assert_(UsesColor('dumb', None, 'YES'))
+    self.assert_(UsesColor('dumb', None, 'T'))
+    self.assert_(UsesColor('dumb', None, '1'))
+
+    self.assert_(not UsesColor('xterm', None, 'f'))
+    self.assert_(not UsesColor('xterm', None, 'false'))
+    self.assert_(not UsesColor('xterm', None, '0'))
+    self.assert_(not UsesColor('xterm', None, 'unknown'))
+
+
+if __name__ == '__main__':
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-color-test_.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-color-test_.cc
new file mode 100644
index 0000000..220a3a0
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-color-test_.cc
@@ -0,0 +1,62 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// A helper program for testing how Google Test determines whether to use
+// colors in the output.  It prints "YES" and returns 1 if Google Test
+// decides to use colors, and prints "NO" and returns 0 otherwise.
+
+#include <stdio.h>
+
+#include "gtest/gtest.h"
+#include "src/gtest-internal-inl.h"
+
+using testing::internal::ShouldUseColor;
+
+// The purpose of this is to ensure that the UnitTest singleton is
+// created before main() is entered, and thus that ShouldUseColor()
+// works the same way as in a real Google-Test-based test.  We don't actual
+// run the TEST itself.
+TEST(GTestColorTest, Dummy) {
+}
+
+int main(int argc, char** argv) {
+  testing::InitGoogleTest(&argc, argv);
+
+  if (ShouldUseColor(true)) {
+    // Google Test decides to use colors in the output (assuming it
+    // goes to a TTY).
+    printf("YES\n");
+    return 1;
+  } else {
+    // Google Test decides not to use colors in the output.
+    printf("NO\n");
+    return 0;
+  }
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-death-test-test.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-death-test-test.cc
new file mode 100644
index 0000000..c0b3d1f
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-death-test-test.cc
@@ -0,0 +1,1542 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// Tests for death tests.
+
+#include "gtest/gtest-death-test.h"
+
+#include "gtest/gtest.h"
+#include "gtest/internal/gtest-filepath.h"
+
+using testing::internal::AlwaysFalse;
+using testing::internal::AlwaysTrue;
+
+#if GTEST_HAS_DEATH_TEST
+
+# if GTEST_OS_WINDOWS
+#  include <fcntl.h>           // For O_BINARY
+#  include <direct.h>          // For chdir().
+#  include <io.h>
+# else
+#  include <unistd.h>
+#  include <sys/wait.h>        // For waitpid.
+# endif  // GTEST_OS_WINDOWS
+
+# include <limits.h>
+# include <signal.h>
+# include <stdio.h>
+
+# if GTEST_OS_LINUX
+#  include <sys/time.h>
+# endif  // GTEST_OS_LINUX
+
+# include "gtest/gtest-spi.h"
+# include "src/gtest-internal-inl.h"
+
+namespace posix = ::testing::internal::posix;
+
+using testing::ContainsRegex;
+using testing::Matcher;
+using testing::Message;
+using testing::internal::DeathTest;
+using testing::internal::DeathTestFactory;
+using testing::internal::FilePath;
+using testing::internal::GetLastErrnoDescription;
+using testing::internal::GetUnitTestImpl;
+using testing::internal::InDeathTestChild;
+using testing::internal::ParseNaturalNumber;
+
+namespace testing {
+namespace internal {
+
+// A helper class whose objects replace the death test factory for a
+// single UnitTest object during their lifetimes.
+class ReplaceDeathTestFactory {
+ public:
+  explicit ReplaceDeathTestFactory(DeathTestFactory* new_factory)
+      : unit_test_impl_(GetUnitTestImpl()) {
+    old_factory_ = unit_test_impl_->death_test_factory_.release();
+    unit_test_impl_->death_test_factory_.reset(new_factory);
+  }
+
+  ~ReplaceDeathTestFactory() {
+    unit_test_impl_->death_test_factory_.release();
+    unit_test_impl_->death_test_factory_.reset(old_factory_);
+  }
+ private:
+  // Prevents copying ReplaceDeathTestFactory objects.
+  ReplaceDeathTestFactory(const ReplaceDeathTestFactory&);
+  void operator=(const ReplaceDeathTestFactory&);
+
+  UnitTestImpl* unit_test_impl_;
+  DeathTestFactory* old_factory_;
+};
+
+}  // namespace internal
+}  // namespace testing
+
+namespace {
+
+void DieWithMessage(const ::std::string& message) {
+  fprintf(stderr, "%s", message.c_str());
+  fflush(stderr);  // Make sure the text is printed before the process exits.
+
+  // We call _exit() instead of exit(), as the former is a direct
+  // system call and thus safer in the presence of threads.  exit()
+  // will invoke user-defined exit-hooks, which may do dangerous
+  // things that conflict with death tests.
+  //
+  // Some compilers can recognize that _exit() never returns and issue the
+  // 'unreachable code' warning for code following this function, unless
+  // fooled by a fake condition.
+  if (AlwaysTrue())
+    _exit(1);
+}
+
+void DieInside(const ::std::string& function) {
+  DieWithMessage("death inside " + function + "().");
+}
+
+// Tests that death tests work.
+
+class TestForDeathTest : public testing::Test {
+ protected:
+  TestForDeathTest() : original_dir_(FilePath::GetCurrentDir()) {}
+
+  ~TestForDeathTest() override { posix::ChDir(original_dir_.c_str()); }
+
+  // A static member function that's expected to die.
+  static void StaticMemberFunction() { DieInside("StaticMemberFunction"); }
+
+  // A method of the test fixture that may die.
+  void MemberFunction() {
+    if (should_die_)
+      DieInside("MemberFunction");
+  }
+
+  // True if and only if MemberFunction() should die.
+  bool should_die_;
+  const FilePath original_dir_;
+};
+
+// A class with a member function that may die.
+class MayDie {
+ public:
+  explicit MayDie(bool should_die) : should_die_(should_die) {}
+
+  // A member function that may die.
+  void MemberFunction() const {
+    if (should_die_)
+      DieInside("MayDie::MemberFunction");
+  }
+
+ private:
+  // True if and only if MemberFunction() should die.
+  bool should_die_;
+};
+
+// A global function that's expected to die.
+void GlobalFunction() { DieInside("GlobalFunction"); }
+
+// A non-void function that's expected to die.
+int NonVoidFunction() {
+  DieInside("NonVoidFunction");
+  return 1;
+}
+
+// A unary function that may die.
+void DieIf(bool should_die) {
+  if (should_die)
+    DieInside("DieIf");
+}
+
+// A binary function that may die.
+bool DieIfLessThan(int x, int y) {
+  if (x < y) {
+    DieInside("DieIfLessThan");
+  }
+  return true;
+}
+
+// Tests that ASSERT_DEATH can be used outside a TEST, TEST_F, or test fixture.
+void DeathTestSubroutine() {
+  EXPECT_DEATH(GlobalFunction(), "death.*GlobalFunction");
+  ASSERT_DEATH(GlobalFunction(), "death.*GlobalFunction");
+}
+
+// Death in dbg, not opt.
+int DieInDebugElse12(int* sideeffect) {
+  if (sideeffect) *sideeffect = 12;
+
+# ifndef NDEBUG
+
+  DieInside("DieInDebugElse12");
+
+# endif  // NDEBUG
+
+  return 12;
+}
+
+# if GTEST_OS_WINDOWS
+
+// Death in dbg due to Windows CRT assertion failure, not opt.
+int DieInCRTDebugElse12(int* sideeffect) {
+  if (sideeffect) *sideeffect = 12;
+
+  // Create an invalid fd by closing a valid one
+  int fdpipe[2];
+  EXPECT_EQ(_pipe(fdpipe, 256, O_BINARY), 0);
+  EXPECT_EQ(_close(fdpipe[0]), 0);
+  EXPECT_EQ(_close(fdpipe[1]), 0);
+
+  // _dup() should crash in debug mode
+  EXPECT_EQ(_dup(fdpipe[0]), -1);
+
+  return 12;
+}
+
+#endif  // GTEST_OS_WINDOWS
+
+# if GTEST_OS_WINDOWS || GTEST_OS_FUCHSIA
+
+// Tests the ExitedWithCode predicate.
+TEST(ExitStatusPredicateTest, ExitedWithCode) {
+  // On Windows, the process's exit code is the same as its exit status,
+  // so the predicate just compares the its input with its parameter.
+  EXPECT_TRUE(testing::ExitedWithCode(0)(0));
+  EXPECT_TRUE(testing::ExitedWithCode(1)(1));
+  EXPECT_TRUE(testing::ExitedWithCode(42)(42));
+  EXPECT_FALSE(testing::ExitedWithCode(0)(1));
+  EXPECT_FALSE(testing::ExitedWithCode(1)(0));
+}
+
+# else
+
+// Returns the exit status of a process that calls _exit(2) with a
+// given exit code.  This is a helper function for the
+// ExitStatusPredicateTest test suite.
+static int NormalExitStatus(int exit_code) {
+  pid_t child_pid = fork();
+  if (child_pid == 0) {
+    _exit(exit_code);
+  }
+  int status;
+  waitpid(child_pid, &status, 0);
+  return status;
+}
+
+// Returns the exit status of a process that raises a given signal.
+// If the signal does not cause the process to die, then it returns
+// instead the exit status of a process that exits normally with exit
+// code 1.  This is a helper function for the ExitStatusPredicateTest
+// test suite.
+static int KilledExitStatus(int signum) {
+  pid_t child_pid = fork();
+  if (child_pid == 0) {
+    raise(signum);
+    _exit(1);
+  }
+  int status;
+  waitpid(child_pid, &status, 0);
+  return status;
+}
+
+// Tests the ExitedWithCode predicate.
+TEST(ExitStatusPredicateTest, ExitedWithCode) {
+  const int status0  = NormalExitStatus(0);
+  const int status1  = NormalExitStatus(1);
+  const int status42 = NormalExitStatus(42);
+  const testing::ExitedWithCode pred0(0);
+  const testing::ExitedWithCode pred1(1);
+  const testing::ExitedWithCode pred42(42);
+  EXPECT_PRED1(pred0,  status0);
+  EXPECT_PRED1(pred1,  status1);
+  EXPECT_PRED1(pred42, status42);
+  EXPECT_FALSE(pred0(status1));
+  EXPECT_FALSE(pred42(status0));
+  EXPECT_FALSE(pred1(status42));
+}
+
+// Tests the KilledBySignal predicate.
+TEST(ExitStatusPredicateTest, KilledBySignal) {
+  const int status_segv = KilledExitStatus(SIGSEGV);
+  const int status_kill = KilledExitStatus(SIGKILL);
+  const testing::KilledBySignal pred_segv(SIGSEGV);
+  const testing::KilledBySignal pred_kill(SIGKILL);
+  EXPECT_PRED1(pred_segv, status_segv);
+  EXPECT_PRED1(pred_kill, status_kill);
+  EXPECT_FALSE(pred_segv(status_kill));
+  EXPECT_FALSE(pred_kill(status_segv));
+}
+
+# endif  // GTEST_OS_WINDOWS || GTEST_OS_FUCHSIA
+
+// The following code intentionally tests a suboptimal syntax.
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdangling-else"
+#pragma GCC diagnostic ignored "-Wempty-body"
+#pragma GCC diagnostic ignored "-Wpragmas"
+#endif
+// Tests that the death test macros expand to code which may or may not
+// be followed by operator<<, and that in either case the complete text
+// comprises only a single C++ statement.
+TEST_F(TestForDeathTest, SingleStatement) {
+  if (AlwaysFalse())
+    // This would fail if executed; this is a compilation test only
+    ASSERT_DEATH(return, "");
+
+  if (AlwaysTrue())
+    EXPECT_DEATH(_exit(1), "");
+  else
+    // This empty "else" branch is meant to ensure that EXPECT_DEATH
+    // doesn't expand into an "if" statement without an "else"
+    ;
+
+  if (AlwaysFalse())
+    ASSERT_DEATH(return, "") << "did not die";
+
+  if (AlwaysFalse())
+    ;
+  else
+    EXPECT_DEATH(_exit(1), "") << 1 << 2 << 3;
+}
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif
+
+# if GTEST_USES_PCRE
+
+void DieWithEmbeddedNul() {
+  fprintf(stderr, "Hello%cmy null world.\n", '\0');
+  fflush(stderr);
+  _exit(1);
+}
+
+// Tests that EXPECT_DEATH and ASSERT_DEATH work when the error
+// message has a NUL character in it.
+TEST_F(TestForDeathTest, EmbeddedNulInMessage) {
+  EXPECT_DEATH(DieWithEmbeddedNul(), "my null world");
+  ASSERT_DEATH(DieWithEmbeddedNul(), "my null world");
+}
+
+# endif  // GTEST_USES_PCRE
+
+// Tests that death test macros expand to code which interacts well with switch
+// statements.
+TEST_F(TestForDeathTest, SwitchStatement) {
+  // Microsoft compiler usually complains about switch statements without
+  // case labels. We suppress that warning for this test.
+  GTEST_DISABLE_MSC_WARNINGS_PUSH_(4065)
+
+  switch (0)
+    default:
+      ASSERT_DEATH(_exit(1), "") << "exit in default switch handler";
+
+  switch (0)
+    case 0:
+      EXPECT_DEATH(_exit(1), "") << "exit in switch case";
+
+  GTEST_DISABLE_MSC_WARNINGS_POP_()
+}
+
+// Tests that a static member function can be used in a "fast" style
+// death test.
+TEST_F(TestForDeathTest, StaticMemberFunctionFastStyle) {
+  testing::GTEST_FLAG(death_test_style) = "fast";
+  ASSERT_DEATH(StaticMemberFunction(), "death.*StaticMember");
+}
+
+// Tests that a method of the test fixture can be used in a "fast"
+// style death test.
+TEST_F(TestForDeathTest, MemberFunctionFastStyle) {
+  testing::GTEST_FLAG(death_test_style) = "fast";
+  should_die_ = true;
+  EXPECT_DEATH(MemberFunction(), "inside.*MemberFunction");
+}
+
+void ChangeToRootDir() { posix::ChDir(GTEST_PATH_SEP_); }
+
+// Tests that death tests work even if the current directory has been
+// changed.
+TEST_F(TestForDeathTest, FastDeathTestInChangedDir) {
+  testing::GTEST_FLAG(death_test_style) = "fast";
+
+  ChangeToRootDir();
+  EXPECT_EXIT(_exit(1), testing::ExitedWithCode(1), "");
+
+  ChangeToRootDir();
+  ASSERT_DEATH(_exit(1), "");
+}
+
+# if GTEST_OS_LINUX
+void SigprofAction(int, siginfo_t*, void*) { /* no op */ }
+
+// Sets SIGPROF action and ITIMER_PROF timer (interval: 1ms).
+void SetSigprofActionAndTimer() {
+  struct sigaction signal_action;
+  memset(&signal_action, 0, sizeof(signal_action));
+  sigemptyset(&signal_action.sa_mask);
+  signal_action.sa_sigaction = SigprofAction;
+  signal_action.sa_flags = SA_RESTART | SA_SIGINFO;
+  ASSERT_EQ(0, sigaction(SIGPROF, &signal_action, nullptr));
+  // timer comes second, to avoid SIGPROF premature delivery, as suggested at
+  // https://www.gnu.org/software/libc/manual/html_node/Setting-an-Alarm.html
+  struct itimerval timer;
+  timer.it_interval.tv_sec = 0;
+  timer.it_interval.tv_usec = 1;
+  timer.it_value = timer.it_interval;
+  ASSERT_EQ(0, setitimer(ITIMER_PROF, &timer, nullptr));
+}
+
+// Disables ITIMER_PROF timer and ignores SIGPROF signal.
+void DisableSigprofActionAndTimer(struct sigaction* old_signal_action) {
+  struct itimerval timer;
+  timer.it_interval.tv_sec = 0;
+  timer.it_interval.tv_usec = 0;
+  timer.it_value = timer.it_interval;
+  ASSERT_EQ(0, setitimer(ITIMER_PROF, &timer, nullptr));
+  struct sigaction signal_action;
+  memset(&signal_action, 0, sizeof(signal_action));
+  sigemptyset(&signal_action.sa_mask);
+  signal_action.sa_handler = SIG_IGN;
+  ASSERT_EQ(0, sigaction(SIGPROF, &signal_action, old_signal_action));
+}
+
+// Tests that death tests work when SIGPROF handler and timer are set.
+TEST_F(TestForDeathTest, FastSigprofActionSet) {
+  testing::GTEST_FLAG(death_test_style) = "fast";
+  SetSigprofActionAndTimer();
+  EXPECT_DEATH(_exit(1), "");
+  struct sigaction old_signal_action;
+  DisableSigprofActionAndTimer(&old_signal_action);
+  EXPECT_TRUE(old_signal_action.sa_sigaction == SigprofAction);
+}
+
+TEST_F(TestForDeathTest, ThreadSafeSigprofActionSet) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+  SetSigprofActionAndTimer();
+  EXPECT_DEATH(_exit(1), "");
+  struct sigaction old_signal_action;
+  DisableSigprofActionAndTimer(&old_signal_action);
+  EXPECT_TRUE(old_signal_action.sa_sigaction == SigprofAction);
+}
+# endif  // GTEST_OS_LINUX
+
+// Repeats a representative sample of death tests in the "threadsafe" style:
+
+TEST_F(TestForDeathTest, StaticMemberFunctionThreadsafeStyle) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+  ASSERT_DEATH(StaticMemberFunction(), "death.*StaticMember");
+}
+
+TEST_F(TestForDeathTest, MemberFunctionThreadsafeStyle) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+  should_die_ = true;
+  EXPECT_DEATH(MemberFunction(), "inside.*MemberFunction");
+}
+
+TEST_F(TestForDeathTest, ThreadsafeDeathTestInLoop) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
+  for (int i = 0; i < 3; ++i)
+    EXPECT_EXIT(_exit(i), testing::ExitedWithCode(i), "") << ": i = " << i;
+}
+
+TEST_F(TestForDeathTest, ThreadsafeDeathTestInChangedDir) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
+  ChangeToRootDir();
+  EXPECT_EXIT(_exit(1), testing::ExitedWithCode(1), "");
+
+  ChangeToRootDir();
+  ASSERT_DEATH(_exit(1), "");
+}
+
+TEST_F(TestForDeathTest, MixedStyles) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+  EXPECT_DEATH(_exit(1), "");
+  testing::GTEST_FLAG(death_test_style) = "fast";
+  EXPECT_DEATH(_exit(1), "");
+}
+
+# if GTEST_HAS_CLONE && GTEST_HAS_PTHREAD
+
+bool pthread_flag;
+
+void SetPthreadFlag() {
+  pthread_flag = true;
+}
+
+TEST_F(TestForDeathTest, DoesNotExecuteAtforkHooks) {
+  if (!testing::GTEST_FLAG(death_test_use_fork)) {
+    testing::GTEST_FLAG(death_test_style) = "threadsafe";
+    pthread_flag = false;
+    ASSERT_EQ(0, pthread_atfork(&SetPthreadFlag, nullptr, nullptr));
+    ASSERT_DEATH(_exit(1), "");
+    ASSERT_FALSE(pthread_flag);
+  }
+}
+
+# endif  // GTEST_HAS_CLONE && GTEST_HAS_PTHREAD
+
+// Tests that a method of another class can be used in a death test.
+TEST_F(TestForDeathTest, MethodOfAnotherClass) {
+  const MayDie x(true);
+  ASSERT_DEATH(x.MemberFunction(), "MayDie\\:\\:MemberFunction");
+}
+
+// Tests that a global function can be used in a death test.
+TEST_F(TestForDeathTest, GlobalFunction) {
+  EXPECT_DEATH(GlobalFunction(), "GlobalFunction");
+}
+
+// Tests that any value convertible to an RE works as a second
+// argument to EXPECT_DEATH.
+TEST_F(TestForDeathTest, AcceptsAnythingConvertibleToRE) {
+  static const char regex_c_str[] = "GlobalFunction";
+  EXPECT_DEATH(GlobalFunction(), regex_c_str);
+
+  const testing::internal::RE regex(regex_c_str);
+  EXPECT_DEATH(GlobalFunction(), regex);
+
+# if !GTEST_USES_PCRE
+
+  const ::std::string regex_std_str(regex_c_str);
+  EXPECT_DEATH(GlobalFunction(), regex_std_str);
+
+  // This one is tricky; a temporary pointer into another temporary.  Reference
+  // lifetime extension of the pointer is not sufficient.
+  EXPECT_DEATH(GlobalFunction(), ::std::string(regex_c_str).c_str());
+
+# endif  // !GTEST_USES_PCRE
+}
+
+// Tests that a non-void function can be used in a death test.
+TEST_F(TestForDeathTest, NonVoidFunction) {
+  ASSERT_DEATH(NonVoidFunction(), "NonVoidFunction");
+}
+
+// Tests that functions that take parameter(s) can be used in a death test.
+TEST_F(TestForDeathTest, FunctionWithParameter) {
+  EXPECT_DEATH(DieIf(true), "DieIf\\(\\)");
+  EXPECT_DEATH(DieIfLessThan(2, 3), "DieIfLessThan");
+}
+
+// Tests that ASSERT_DEATH can be used outside a TEST, TEST_F, or test fixture.
+TEST_F(TestForDeathTest, OutsideFixture) {
+  DeathTestSubroutine();
+}
+
+// Tests that death tests can be done inside a loop.
+TEST_F(TestForDeathTest, InsideLoop) {
+  for (int i = 0; i < 5; i++) {
+    EXPECT_DEATH(DieIfLessThan(-1, i), "DieIfLessThan") << "where i == " << i;
+  }
+}
+
+// Tests that a compound statement can be used in a death test.
+TEST_F(TestForDeathTest, CompoundStatement) {
+  EXPECT_DEATH({  // NOLINT
+    const int x = 2;
+    const int y = x + 1;
+    DieIfLessThan(x, y);
+  },
+  "DieIfLessThan");
+}
+
+// Tests that code that doesn't die causes a death test to fail.
+TEST_F(TestForDeathTest, DoesNotDie) {
+  EXPECT_NONFATAL_FAILURE(EXPECT_DEATH(DieIf(false), "DieIf"),
+                          "failed to die");
+}
+
+// Tests that a death test fails when the error message isn't expected.
+TEST_F(TestForDeathTest, ErrorMessageMismatch) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_DEATH(DieIf(true), "DieIfLessThan") << "End of death test message.";
+  }, "died but not with expected error");
+}
+
+// On exit, *aborted will be true if and only if the EXPECT_DEATH()
+// statement aborted the function.
+void ExpectDeathTestHelper(bool* aborted) {
+  *aborted = true;
+  EXPECT_DEATH(DieIf(false), "DieIf");  // This assertion should fail.
+  *aborted = false;
+}
+
+// Tests that EXPECT_DEATH doesn't abort the test on failure.
+TEST_F(TestForDeathTest, EXPECT_DEATH) {
+  bool aborted = true;
+  EXPECT_NONFATAL_FAILURE(ExpectDeathTestHelper(&aborted),
+                          "failed to die");
+  EXPECT_FALSE(aborted);
+}
+
+// Tests that ASSERT_DEATH does abort the test on failure.
+TEST_F(TestForDeathTest, ASSERT_DEATH) {
+  static bool aborted;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    aborted = true;
+    ASSERT_DEATH(DieIf(false), "DieIf");  // This assertion should fail.
+    aborted = false;
+  }, "failed to die");
+  EXPECT_TRUE(aborted);
+}
+
+// Tests that EXPECT_DEATH evaluates the arguments exactly once.
+TEST_F(TestForDeathTest, SingleEvaluation) {
+  int x = 3;
+  EXPECT_DEATH(DieIf((++x) == 4), "DieIf");
+
+  const char* regex = "DieIf";
+  const char* regex_save = regex;
+  EXPECT_DEATH(DieIfLessThan(3, 4), regex++);
+  EXPECT_EQ(regex_save + 1, regex);
+}
+
+// Tests that run-away death tests are reported as failures.
+TEST_F(TestForDeathTest, RunawayIsFailure) {
+  EXPECT_NONFATAL_FAILURE(EXPECT_DEATH(static_cast<void>(0), "Foo"),
+                          "failed to die.");
+}
+
+// Tests that death tests report executing 'return' in the statement as
+// failure.
+TEST_F(TestForDeathTest, ReturnIsFailure) {
+  EXPECT_FATAL_FAILURE(ASSERT_DEATH(return, "Bar"),
+                       "illegal return in test statement.");
+}
+
+// Tests that EXPECT_DEBUG_DEATH works as expected, that is, you can stream a
+// message to it, and in debug mode it:
+// 1. Asserts on death.
+// 2. Has no side effect.
+//
+// And in opt mode, it:
+// 1.  Has side effects but does not assert.
+TEST_F(TestForDeathTest, TestExpectDebugDeath) {
+  int sideeffect = 0;
+
+  // Put the regex in a local variable to make sure we don't get an "unused"
+  // warning in opt mode.
+  const char* regex = "death.*DieInDebugElse12";
+
+  EXPECT_DEBUG_DEATH(DieInDebugElse12(&sideeffect), regex)
+      << "Must accept a streamed message";
+
+# ifdef NDEBUG
+
+  // Checks that the assignment occurs in opt mode (sideeffect).
+  EXPECT_EQ(12, sideeffect);
+
+# else
+
+  // Checks that the assignment does not occur in dbg mode (no sideeffect).
+  EXPECT_EQ(0, sideeffect);
+
+# endif
+}
+
+# if GTEST_OS_WINDOWS
+
+// Tests that EXPECT_DEBUG_DEATH works as expected when in debug mode
+// the Windows CRT crashes the process with an assertion failure.
+// 1. Asserts on death.
+// 2. Has no side effect (doesn't pop up a window or wait for user input).
+//
+// And in opt mode, it:
+// 1.  Has side effects but does not assert.
+TEST_F(TestForDeathTest, CRTDebugDeath) {
+  int sideeffect = 0;
+
+  // Put the regex in a local variable to make sure we don't get an "unused"
+  // warning in opt mode.
+  const char* regex = "dup.* : Assertion failed";
+
+  EXPECT_DEBUG_DEATH(DieInCRTDebugElse12(&sideeffect), regex)
+      << "Must accept a streamed message";
+
+# ifdef NDEBUG
+
+  // Checks that the assignment occurs in opt mode (sideeffect).
+  EXPECT_EQ(12, sideeffect);
+
+# else
+
+  // Checks that the assignment does not occur in dbg mode (no sideeffect).
+  EXPECT_EQ(0, sideeffect);
+
+# endif
+}
+
+# endif  // GTEST_OS_WINDOWS
+
+// Tests that ASSERT_DEBUG_DEATH works as expected, that is, you can stream a
+// message to it, and in debug mode it:
+// 1. Asserts on death.
+// 2. Has no side effect.
+//
+// And in opt mode, it:
+// 1.  Has side effects but does not assert.
+TEST_F(TestForDeathTest, TestAssertDebugDeath) {
+  int sideeffect = 0;
+
+  ASSERT_DEBUG_DEATH(DieInDebugElse12(&sideeffect), "death.*DieInDebugElse12")
+      << "Must accept a streamed message";
+
+# ifdef NDEBUG
+
+  // Checks that the assignment occurs in opt mode (sideeffect).
+  EXPECT_EQ(12, sideeffect);
+
+# else
+
+  // Checks that the assignment does not occur in dbg mode (no sideeffect).
+  EXPECT_EQ(0, sideeffect);
+
+# endif
+}
+
+# ifndef NDEBUG
+
+void ExpectDebugDeathHelper(bool* aborted) {
+  *aborted = true;
+  EXPECT_DEBUG_DEATH(return, "") << "This is expected to fail.";
+  *aborted = false;
+}
+
+#  if GTEST_OS_WINDOWS
+TEST(PopUpDeathTest, DoesNotShowPopUpOnAbort) {
+  printf("This test should be considered failing if it shows "
+         "any pop-up dialogs.\n");
+  fflush(stdout);
+
+  EXPECT_DEATH({
+    testing::GTEST_FLAG(catch_exceptions) = false;
+    abort();
+  }, "");
+}
+#  endif  // GTEST_OS_WINDOWS
+
+// Tests that EXPECT_DEBUG_DEATH in debug mode does not abort
+// the function.
+TEST_F(TestForDeathTest, ExpectDebugDeathDoesNotAbort) {
+  bool aborted = true;
+  EXPECT_NONFATAL_FAILURE(ExpectDebugDeathHelper(&aborted), "");
+  EXPECT_FALSE(aborted);
+}
+
+void AssertDebugDeathHelper(bool* aborted) {
+  *aborted = true;
+  GTEST_LOG_(INFO) << "Before ASSERT_DEBUG_DEATH";
+  ASSERT_DEBUG_DEATH(GTEST_LOG_(INFO) << "In ASSERT_DEBUG_DEATH"; return, "")
+      << "This is expected to fail.";
+  GTEST_LOG_(INFO) << "After ASSERT_DEBUG_DEATH";
+  *aborted = false;
+}
+
+// Tests that ASSERT_DEBUG_DEATH in debug mode aborts the function on
+// failure.
+TEST_F(TestForDeathTest, AssertDebugDeathAborts) {
+  static bool aborted;
+  aborted = false;
+  EXPECT_FATAL_FAILURE(AssertDebugDeathHelper(&aborted), "");
+  EXPECT_TRUE(aborted);
+}
+
+TEST_F(TestForDeathTest, AssertDebugDeathAborts2) {
+  static bool aborted;
+  aborted = false;
+  EXPECT_FATAL_FAILURE(AssertDebugDeathHelper(&aborted), "");
+  EXPECT_TRUE(aborted);
+}
+
+TEST_F(TestForDeathTest, AssertDebugDeathAborts3) {
+  static bool aborted;
+  aborted = false;
+  EXPECT_FATAL_FAILURE(AssertDebugDeathHelper(&aborted), "");
+  EXPECT_TRUE(aborted);
+}
+
+TEST_F(TestForDeathTest, AssertDebugDeathAborts4) {
+  static bool aborted;
+  aborted = false;
+  EXPECT_FATAL_FAILURE(AssertDebugDeathHelper(&aborted), "");
+  EXPECT_TRUE(aborted);
+}
+
+TEST_F(TestForDeathTest, AssertDebugDeathAborts5) {
+  static bool aborted;
+  aborted = false;
+  EXPECT_FATAL_FAILURE(AssertDebugDeathHelper(&aborted), "");
+  EXPECT_TRUE(aborted);
+}
+
+TEST_F(TestForDeathTest, AssertDebugDeathAborts6) {
+  static bool aborted;
+  aborted = false;
+  EXPECT_FATAL_FAILURE(AssertDebugDeathHelper(&aborted), "");
+  EXPECT_TRUE(aborted);
+}
+
+TEST_F(TestForDeathTest, AssertDebugDeathAborts7) {
+  static bool aborted;
+  aborted = false;
+  EXPECT_FATAL_FAILURE(AssertDebugDeathHelper(&aborted), "");
+  EXPECT_TRUE(aborted);
+}
+
+TEST_F(TestForDeathTest, AssertDebugDeathAborts8) {
+  static bool aborted;
+  aborted = false;
+  EXPECT_FATAL_FAILURE(AssertDebugDeathHelper(&aborted), "");
+  EXPECT_TRUE(aborted);
+}
+
+TEST_F(TestForDeathTest, AssertDebugDeathAborts9) {
+  static bool aborted;
+  aborted = false;
+  EXPECT_FATAL_FAILURE(AssertDebugDeathHelper(&aborted), "");
+  EXPECT_TRUE(aborted);
+}
+
+TEST_F(TestForDeathTest, AssertDebugDeathAborts10) {
+  static bool aborted;
+  aborted = false;
+  EXPECT_FATAL_FAILURE(AssertDebugDeathHelper(&aborted), "");
+  EXPECT_TRUE(aborted);
+}
+
+# endif  // _NDEBUG
+
+// Tests the *_EXIT family of macros, using a variety of predicates.
+static void TestExitMacros() {
+  EXPECT_EXIT(_exit(1),  testing::ExitedWithCode(1),  "");
+  ASSERT_EXIT(_exit(42), testing::ExitedWithCode(42), "");
+
+# if GTEST_OS_WINDOWS
+
+  // Of all signals effects on the process exit code, only those of SIGABRT
+  // are documented on Windows.
+  // See https://msdn.microsoft.com/en-us/query-bi/m/dwwzkt4c.
+  EXPECT_EXIT(raise(SIGABRT), testing::ExitedWithCode(3), "") << "b_ar";
+
+# elif !GTEST_OS_FUCHSIA
+
+  // Fuchsia has no unix signals.
+  EXPECT_EXIT(raise(SIGKILL), testing::KilledBySignal(SIGKILL), "") << "foo";
+  ASSERT_EXIT(raise(SIGUSR2), testing::KilledBySignal(SIGUSR2), "") << "bar";
+
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_EXIT(_exit(0), testing::KilledBySignal(SIGSEGV), "")
+      << "This failure is expected, too.";
+  }, "This failure is expected, too.");
+
+# endif  // GTEST_OS_WINDOWS
+
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_EXIT(raise(SIGSEGV), testing::ExitedWithCode(0), "")
+      << "This failure is expected.";
+  }, "This failure is expected.");
+}
+
+TEST_F(TestForDeathTest, ExitMacros) {
+  TestExitMacros();
+}
+
+TEST_F(TestForDeathTest, ExitMacrosUsingFork) {
+  testing::GTEST_FLAG(death_test_use_fork) = true;
+  TestExitMacros();
+}
+
+TEST_F(TestForDeathTest, InvalidStyle) {
+  testing::GTEST_FLAG(death_test_style) = "rococo";
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_DEATH(_exit(0), "") << "This failure is expected.";
+  }, "This failure is expected.");
+}
+
+TEST_F(TestForDeathTest, DeathTestFailedOutput) {
+  testing::GTEST_FLAG(death_test_style) = "fast";
+  EXPECT_NONFATAL_FAILURE(
+      EXPECT_DEATH(DieWithMessage("death\n"),
+                   "expected message"),
+      "Actual msg:\n"
+      "[  DEATH   ] death\n");
+}
+
+TEST_F(TestForDeathTest, DeathTestUnexpectedReturnOutput) {
+  testing::GTEST_FLAG(death_test_style) = "fast";
+  EXPECT_NONFATAL_FAILURE(
+      EXPECT_DEATH({
+          fprintf(stderr, "returning\n");
+          fflush(stderr);
+          return;
+        }, ""),
+      "    Result: illegal return in test statement.\n"
+      " Error msg:\n"
+      "[  DEATH   ] returning\n");
+}
+
+TEST_F(TestForDeathTest, DeathTestBadExitCodeOutput) {
+  testing::GTEST_FLAG(death_test_style) = "fast";
+  EXPECT_NONFATAL_FAILURE(
+      EXPECT_EXIT(DieWithMessage("exiting with rc 1\n"),
+                  testing::ExitedWithCode(3),
+                  "expected message"),
+      "    Result: died but not with expected exit code:\n"
+      "            Exited with exit status 1\n"
+      "Actual msg:\n"
+      "[  DEATH   ] exiting with rc 1\n");
+}
+
+TEST_F(TestForDeathTest, DeathTestMultiLineMatchFail) {
+  testing::GTEST_FLAG(death_test_style) = "fast";
+  EXPECT_NONFATAL_FAILURE(
+      EXPECT_DEATH(DieWithMessage("line 1\nline 2\nline 3\n"),
+                   "line 1\nxyz\nline 3\n"),
+      "Actual msg:\n"
+      "[  DEATH   ] line 1\n"
+      "[  DEATH   ] line 2\n"
+      "[  DEATH   ] line 3\n");
+}
+
+TEST_F(TestForDeathTest, DeathTestMultiLineMatchPass) {
+  testing::GTEST_FLAG(death_test_style) = "fast";
+  EXPECT_DEATH(DieWithMessage("line 1\nline 2\nline 3\n"),
+               "line 1\nline 2\nline 3\n");
+}
+
+// A DeathTestFactory that returns MockDeathTests.
+class MockDeathTestFactory : public DeathTestFactory {
+ public:
+  MockDeathTestFactory();
+  bool Create(const char* statement,
+              testing::Matcher<const std::string&> matcher, const char* file,
+              int line, DeathTest** test) override;
+
+  // Sets the parameters for subsequent calls to Create.
+  void SetParameters(bool create, DeathTest::TestRole role,
+                     int status, bool passed);
+
+  // Accessors.
+  int AssumeRoleCalls() const { return assume_role_calls_; }
+  int WaitCalls() const { return wait_calls_; }
+  size_t PassedCalls() const { return passed_args_.size(); }
+  bool PassedArgument(int n) const {
+    return passed_args_[static_cast<size_t>(n)];
+  }
+  size_t AbortCalls() const { return abort_args_.size(); }
+  DeathTest::AbortReason AbortArgument(int n) const {
+    return abort_args_[static_cast<size_t>(n)];
+  }
+  bool TestDeleted() const { return test_deleted_; }
+
+ private:
+  friend class MockDeathTest;
+  // If true, Create will return a MockDeathTest; otherwise it returns
+  // NULL.
+  bool create_;
+  // The value a MockDeathTest will return from its AssumeRole method.
+  DeathTest::TestRole role_;
+  // The value a MockDeathTest will return from its Wait method.
+  int status_;
+  // The value a MockDeathTest will return from its Passed method.
+  bool passed_;
+
+  // Number of times AssumeRole was called.
+  int assume_role_calls_;
+  // Number of times Wait was called.
+  int wait_calls_;
+  // The arguments to the calls to Passed since the last call to
+  // SetParameters.
+  std::vector<bool> passed_args_;
+  // The arguments to the calls to Abort since the last call to
+  // SetParameters.
+  std::vector<DeathTest::AbortReason> abort_args_;
+  // True if the last MockDeathTest returned by Create has been
+  // deleted.
+  bool test_deleted_;
+};
+
+
+// A DeathTest implementation useful in testing.  It returns values set
+// at its creation from its various inherited DeathTest methods, and
+// reports calls to those methods to its parent MockDeathTestFactory
+// object.
+class MockDeathTest : public DeathTest {
+ public:
+  MockDeathTest(MockDeathTestFactory *parent,
+                TestRole role, int status, bool passed) :
+      parent_(parent), role_(role), status_(status), passed_(passed) {
+  }
+  ~MockDeathTest() override { parent_->test_deleted_ = true; }
+  TestRole AssumeRole() override {
+    ++parent_->assume_role_calls_;
+    return role_;
+  }
+  int Wait() override {
+    ++parent_->wait_calls_;
+    return status_;
+  }
+  bool Passed(bool exit_status_ok) override {
+    parent_->passed_args_.push_back(exit_status_ok);
+    return passed_;
+  }
+  void Abort(AbortReason reason) override {
+    parent_->abort_args_.push_back(reason);
+  }
+
+ private:
+  MockDeathTestFactory* const parent_;
+  const TestRole role_;
+  const int status_;
+  const bool passed_;
+};
+
+
+// MockDeathTestFactory constructor.
+MockDeathTestFactory::MockDeathTestFactory()
+    : create_(true),
+      role_(DeathTest::OVERSEE_TEST),
+      status_(0),
+      passed_(true),
+      assume_role_calls_(0),
+      wait_calls_(0),
+      passed_args_(),
+      abort_args_() {
+}
+
+
+// Sets the parameters for subsequent calls to Create.
+void MockDeathTestFactory::SetParameters(bool create,
+                                         DeathTest::TestRole role,
+                                         int status, bool passed) {
+  create_ = create;
+  role_ = role;
+  status_ = status;
+  passed_ = passed;
+
+  assume_role_calls_ = 0;
+  wait_calls_ = 0;
+  passed_args_.clear();
+  abort_args_.clear();
+}
+
+
+// Sets test to NULL (if create_ is false) or to the address of a new
+// MockDeathTest object with parameters taken from the last call
+// to SetParameters (if create_ is true).  Always returns true.
+bool MockDeathTestFactory::Create(
+    const char* /*statement*/, testing::Matcher<const std::string&> /*matcher*/,
+    const char* /*file*/, int /*line*/, DeathTest** test) {
+  test_deleted_ = false;
+  if (create_) {
+    *test = new MockDeathTest(this, role_, status_, passed_);
+  } else {
+    *test = nullptr;
+  }
+  return true;
+}
+
+// A test fixture for testing the logic of the GTEST_DEATH_TEST_ macro.
+// It installs a MockDeathTestFactory that is used for the duration
+// of the test case.
+class MacroLogicDeathTest : public testing::Test {
+ protected:
+  static testing::internal::ReplaceDeathTestFactory* replacer_;
+  static MockDeathTestFactory* factory_;
+
+  static void SetUpTestSuite() {
+    factory_ = new MockDeathTestFactory;
+    replacer_ = new testing::internal::ReplaceDeathTestFactory(factory_);
+  }
+
+  static void TearDownTestSuite() {
+    delete replacer_;
+    replacer_ = nullptr;
+    delete factory_;
+    factory_ = nullptr;
+  }
+
+  // Runs a death test that breaks the rules by returning.  Such a death
+  // test cannot be run directly from a test routine that uses a
+  // MockDeathTest, or the remainder of the routine will not be executed.
+  static void RunReturningDeathTest(bool* flag) {
+    ASSERT_DEATH({  // NOLINT
+      *flag = true;
+      return;
+    }, "");
+  }
+};
+
+testing::internal::ReplaceDeathTestFactory* MacroLogicDeathTest::replacer_ =
+    nullptr;
+MockDeathTestFactory* MacroLogicDeathTest::factory_ = nullptr;
+
+// Test that nothing happens when the factory doesn't return a DeathTest:
+TEST_F(MacroLogicDeathTest, NothingHappens) {
+  bool flag = false;
+  factory_->SetParameters(false, DeathTest::OVERSEE_TEST, 0, true);
+  EXPECT_DEATH(flag = true, "");
+  EXPECT_FALSE(flag);
+  EXPECT_EQ(0, factory_->AssumeRoleCalls());
+  EXPECT_EQ(0, factory_->WaitCalls());
+  EXPECT_EQ(0U, factory_->PassedCalls());
+  EXPECT_EQ(0U, factory_->AbortCalls());
+  EXPECT_FALSE(factory_->TestDeleted());
+}
+
+// Test that the parent process doesn't run the death test code,
+// and that the Passed method returns false when the (simulated)
+// child process exits with status 0:
+TEST_F(MacroLogicDeathTest, ChildExitsSuccessfully) {
+  bool flag = false;
+  factory_->SetParameters(true, DeathTest::OVERSEE_TEST, 0, true);
+  EXPECT_DEATH(flag = true, "");
+  EXPECT_FALSE(flag);
+  EXPECT_EQ(1, factory_->AssumeRoleCalls());
+  EXPECT_EQ(1, factory_->WaitCalls());
+  ASSERT_EQ(1U, factory_->PassedCalls());
+  EXPECT_FALSE(factory_->PassedArgument(0));
+  EXPECT_EQ(0U, factory_->AbortCalls());
+  EXPECT_TRUE(factory_->TestDeleted());
+}
+
+// Tests that the Passed method was given the argument "true" when
+// the (simulated) child process exits with status 1:
+TEST_F(MacroLogicDeathTest, ChildExitsUnsuccessfully) {
+  bool flag = false;
+  factory_->SetParameters(true, DeathTest::OVERSEE_TEST, 1, true);
+  EXPECT_DEATH(flag = true, "");
+  EXPECT_FALSE(flag);
+  EXPECT_EQ(1, factory_->AssumeRoleCalls());
+  EXPECT_EQ(1, factory_->WaitCalls());
+  ASSERT_EQ(1U, factory_->PassedCalls());
+  EXPECT_TRUE(factory_->PassedArgument(0));
+  EXPECT_EQ(0U, factory_->AbortCalls());
+  EXPECT_TRUE(factory_->TestDeleted());
+}
+
+// Tests that the (simulated) child process executes the death test
+// code, and is aborted with the correct AbortReason if it
+// executes a return statement.
+TEST_F(MacroLogicDeathTest, ChildPerformsReturn) {
+  bool flag = false;
+  factory_->SetParameters(true, DeathTest::EXECUTE_TEST, 0, true);
+  RunReturningDeathTest(&flag);
+  EXPECT_TRUE(flag);
+  EXPECT_EQ(1, factory_->AssumeRoleCalls());
+  EXPECT_EQ(0, factory_->WaitCalls());
+  EXPECT_EQ(0U, factory_->PassedCalls());
+  EXPECT_EQ(1U, factory_->AbortCalls());
+  EXPECT_EQ(DeathTest::TEST_ENCOUNTERED_RETURN_STATEMENT,
+            factory_->AbortArgument(0));
+  EXPECT_TRUE(factory_->TestDeleted());
+}
+
+// Tests that the (simulated) child process is aborted with the
+// correct AbortReason if it does not die.
+TEST_F(MacroLogicDeathTest, ChildDoesNotDie) {
+  bool flag = false;
+  factory_->SetParameters(true, DeathTest::EXECUTE_TEST, 0, true);
+  EXPECT_DEATH(flag = true, "");
+  EXPECT_TRUE(flag);
+  EXPECT_EQ(1, factory_->AssumeRoleCalls());
+  EXPECT_EQ(0, factory_->WaitCalls());
+  EXPECT_EQ(0U, factory_->PassedCalls());
+  // This time there are two calls to Abort: one since the test didn't
+  // die, and another from the ReturnSentinel when it's destroyed.  The
+  // sentinel normally isn't destroyed if a test doesn't die, since
+  // _exit(2) is called in that case by ForkingDeathTest, but not by
+  // our MockDeathTest.
+  ASSERT_EQ(2U, factory_->AbortCalls());
+  EXPECT_EQ(DeathTest::TEST_DID_NOT_DIE,
+            factory_->AbortArgument(0));
+  EXPECT_EQ(DeathTest::TEST_ENCOUNTERED_RETURN_STATEMENT,
+            factory_->AbortArgument(1));
+  EXPECT_TRUE(factory_->TestDeleted());
+}
+
+// Tests that a successful death test does not register a successful
+// test part.
+TEST(SuccessRegistrationDeathTest, NoSuccessPart) {
+  EXPECT_DEATH(_exit(1), "");
+  EXPECT_EQ(0, GetUnitTestImpl()->current_test_result()->total_part_count());
+}
+
+TEST(StreamingAssertionsDeathTest, DeathTest) {
+  EXPECT_DEATH(_exit(1), "") << "unexpected failure";
+  ASSERT_DEATH(_exit(1), "") << "unexpected failure";
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_DEATH(_exit(0), "") << "expected failure";
+  }, "expected failure");
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_DEATH(_exit(0), "") << "expected failure";
+  }, "expected failure");
+}
+
+// Tests that GetLastErrnoDescription returns an empty string when the
+// last error is 0 and non-empty string when it is non-zero.
+TEST(GetLastErrnoDescription, GetLastErrnoDescriptionWorks) {
+  errno = ENOENT;
+  EXPECT_STRNE("", GetLastErrnoDescription().c_str());
+  errno = 0;
+  EXPECT_STREQ("", GetLastErrnoDescription().c_str());
+}
+
+# if GTEST_OS_WINDOWS
+TEST(AutoHandleTest, AutoHandleWorks) {
+  HANDLE handle = ::CreateEvent(NULL, FALSE, FALSE, NULL);
+  ASSERT_NE(INVALID_HANDLE_VALUE, handle);
+
+  // Tests that the AutoHandle is correctly initialized with a handle.
+  testing::internal::AutoHandle auto_handle(handle);
+  EXPECT_EQ(handle, auto_handle.Get());
+
+  // Tests that Reset assigns INVALID_HANDLE_VALUE.
+  // Note that this cannot verify whether the original handle is closed.
+  auto_handle.Reset();
+  EXPECT_EQ(INVALID_HANDLE_VALUE, auto_handle.Get());
+
+  // Tests that Reset assigns the new handle.
+  // Note that this cannot verify whether the original handle is closed.
+  handle = ::CreateEvent(NULL, FALSE, FALSE, NULL);
+  ASSERT_NE(INVALID_HANDLE_VALUE, handle);
+  auto_handle.Reset(handle);
+  EXPECT_EQ(handle, auto_handle.Get());
+
+  // Tests that AutoHandle contains INVALID_HANDLE_VALUE by default.
+  testing::internal::AutoHandle auto_handle2;
+  EXPECT_EQ(INVALID_HANDLE_VALUE, auto_handle2.Get());
+}
+# endif  // GTEST_OS_WINDOWS
+
+# if GTEST_OS_WINDOWS
+typedef unsigned __int64 BiggestParsable;
+typedef signed __int64 BiggestSignedParsable;
+# else
+typedef unsigned long long BiggestParsable;
+typedef signed long long BiggestSignedParsable;
+# endif  // GTEST_OS_WINDOWS
+
+// We cannot use std::numeric_limits<T>::max() as it clashes with the
+// max() macro defined by <windows.h>.
+const BiggestParsable kBiggestParsableMax = ULLONG_MAX;
+const BiggestSignedParsable kBiggestSignedParsableMax = LLONG_MAX;
+
+TEST(ParseNaturalNumberTest, RejectsInvalidFormat) {
+  BiggestParsable result = 0;
+
+  // Rejects non-numbers.
+  EXPECT_FALSE(ParseNaturalNumber("non-number string", &result));
+
+  // Rejects numbers with whitespace prefix.
+  EXPECT_FALSE(ParseNaturalNumber(" 123", &result));
+
+  // Rejects negative numbers.
+  EXPECT_FALSE(ParseNaturalNumber("-123", &result));
+
+  // Rejects numbers starting with a plus sign.
+  EXPECT_FALSE(ParseNaturalNumber("+123", &result));
+  errno = 0;
+}
+
+TEST(ParseNaturalNumberTest, RejectsOverflownNumbers) {
+  BiggestParsable result = 0;
+
+  EXPECT_FALSE(ParseNaturalNumber("99999999999999999999999", &result));
+
+  signed char char_result = 0;
+  EXPECT_FALSE(ParseNaturalNumber("200", &char_result));
+  errno = 0;
+}
+
+TEST(ParseNaturalNumberTest, AcceptsValidNumbers) {
+  BiggestParsable result = 0;
+
+  result = 0;
+  ASSERT_TRUE(ParseNaturalNumber("123", &result));
+  EXPECT_EQ(123U, result);
+
+  // Check 0 as an edge case.
+  result = 1;
+  ASSERT_TRUE(ParseNaturalNumber("0", &result));
+  EXPECT_EQ(0U, result);
+
+  result = 1;
+  ASSERT_TRUE(ParseNaturalNumber("00000", &result));
+  EXPECT_EQ(0U, result);
+}
+
+TEST(ParseNaturalNumberTest, AcceptsTypeLimits) {
+  Message msg;
+  msg << kBiggestParsableMax;
+
+  BiggestParsable result = 0;
+  EXPECT_TRUE(ParseNaturalNumber(msg.GetString(), &result));
+  EXPECT_EQ(kBiggestParsableMax, result);
+
+  Message msg2;
+  msg2 << kBiggestSignedParsableMax;
+
+  BiggestSignedParsable signed_result = 0;
+  EXPECT_TRUE(ParseNaturalNumber(msg2.GetString(), &signed_result));
+  EXPECT_EQ(kBiggestSignedParsableMax, signed_result);
+
+  Message msg3;
+  msg3 << INT_MAX;
+
+  int int_result = 0;
+  EXPECT_TRUE(ParseNaturalNumber(msg3.GetString(), &int_result));
+  EXPECT_EQ(INT_MAX, int_result);
+
+  Message msg4;
+  msg4 << UINT_MAX;
+
+  unsigned int uint_result = 0;
+  EXPECT_TRUE(ParseNaturalNumber(msg4.GetString(), &uint_result));
+  EXPECT_EQ(UINT_MAX, uint_result);
+}
+
+TEST(ParseNaturalNumberTest, WorksForShorterIntegers) {
+  short short_result = 0;
+  ASSERT_TRUE(ParseNaturalNumber("123", &short_result));
+  EXPECT_EQ(123, short_result);
+
+  signed char char_result = 0;
+  ASSERT_TRUE(ParseNaturalNumber("123", &char_result));
+  EXPECT_EQ(123, char_result);
+}
+
+# if GTEST_OS_WINDOWS
+TEST(EnvironmentTest, HandleFitsIntoSizeT) {
+  ASSERT_TRUE(sizeof(HANDLE) <= sizeof(size_t));
+}
+# endif  // GTEST_OS_WINDOWS
+
+// Tests that EXPECT_DEATH_IF_SUPPORTED/ASSERT_DEATH_IF_SUPPORTED trigger
+// failures when death tests are available on the system.
+TEST(ConditionalDeathMacrosDeathTest, ExpectsDeathWhenDeathTestsAvailable) {
+  EXPECT_DEATH_IF_SUPPORTED(DieInside("CondDeathTestExpectMacro"),
+                            "death inside CondDeathTestExpectMacro");
+  ASSERT_DEATH_IF_SUPPORTED(DieInside("CondDeathTestAssertMacro"),
+                            "death inside CondDeathTestAssertMacro");
+
+  // Empty statement will not crash, which must trigger a failure.
+  EXPECT_NONFATAL_FAILURE(EXPECT_DEATH_IF_SUPPORTED(;, ""), "");
+  EXPECT_FATAL_FAILURE(ASSERT_DEATH_IF_SUPPORTED(;, ""), "");
+}
+
+TEST(InDeathTestChildDeathTest, ReportsDeathTestCorrectlyInFastStyle) {
+  testing::GTEST_FLAG(death_test_style) = "fast";
+  EXPECT_FALSE(InDeathTestChild());
+  EXPECT_DEATH({
+    fprintf(stderr, InDeathTestChild() ? "Inside" : "Outside");
+    fflush(stderr);
+    _exit(1);
+  }, "Inside");
+}
+
+TEST(InDeathTestChildDeathTest, ReportsDeathTestCorrectlyInThreadSafeStyle) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+  EXPECT_FALSE(InDeathTestChild());
+  EXPECT_DEATH({
+    fprintf(stderr, InDeathTestChild() ? "Inside" : "Outside");
+    fflush(stderr);
+    _exit(1);
+  }, "Inside");
+}
+
+void DieWithMessage(const char* message) {
+  fputs(message, stderr);
+  fflush(stderr);  // Make sure the text is printed before the process exits.
+  _exit(1);
+}
+
+TEST(MatcherDeathTest, DoesNotBreakBareRegexMatching) {
+  // googletest tests this, of course; here we ensure that including googlemock
+  // has not broken it.
+#if GTEST_USES_POSIX_RE
+  EXPECT_DEATH(DieWithMessage("O, I die, Horatio."), "I d[aeiou]e");
+#else
+  EXPECT_DEATH(DieWithMessage("O, I die, Horatio."), "I di?e");
+#endif
+}
+
+TEST(MatcherDeathTest, MonomorphicMatcherMatches) {
+  EXPECT_DEATH(DieWithMessage("Behind O, I am slain!"),
+               Matcher<const std::string&>(ContainsRegex("I am slain")));
+}
+
+TEST(MatcherDeathTest, MonomorphicMatcherDoesNotMatch) {
+  EXPECT_NONFATAL_FAILURE(
+      EXPECT_DEATH(
+          DieWithMessage("Behind O, I am slain!"),
+          Matcher<const std::string&>(ContainsRegex("Ow, I am slain"))),
+      "Expected: contains regular expression \"Ow, I am slain\"");
+}
+
+TEST(MatcherDeathTest, PolymorphicMatcherMatches) {
+  EXPECT_DEATH(DieWithMessage("The rest is silence."),
+               ContainsRegex("rest is silence"));
+}
+
+TEST(MatcherDeathTest, PolymorphicMatcherDoesNotMatch) {
+  EXPECT_NONFATAL_FAILURE(
+      EXPECT_DEATH(DieWithMessage("The rest is silence."),
+                   ContainsRegex("rest is science")),
+      "Expected: contains regular expression \"rest is science\"");
+}
+
+}  // namespace
+
+#else  // !GTEST_HAS_DEATH_TEST follows
+
+namespace {
+
+using testing::internal::CaptureStderr;
+using testing::internal::GetCapturedStderr;
+
+// Tests that EXPECT_DEATH_IF_SUPPORTED/ASSERT_DEATH_IF_SUPPORTED are still
+// defined but do not trigger failures when death tests are not available on
+// the system.
+TEST(ConditionalDeathMacrosTest, WarnsWhenDeathTestsNotAvailable) {
+  // Empty statement will not crash, but that should not trigger a failure
+  // when death tests are not supported.
+  CaptureStderr();
+  EXPECT_DEATH_IF_SUPPORTED(;, "");
+  std::string output = GetCapturedStderr();
+  ASSERT_TRUE(NULL != strstr(output.c_str(),
+                             "Death tests are not supported on this platform"));
+  ASSERT_TRUE(NULL != strstr(output.c_str(), ";"));
+
+  // The streamed message should not be printed as there is no test failure.
+  CaptureStderr();
+  EXPECT_DEATH_IF_SUPPORTED(;, "") << "streamed message";
+  output = GetCapturedStderr();
+  ASSERT_TRUE(NULL == strstr(output.c_str(), "streamed message"));
+
+  CaptureStderr();
+  ASSERT_DEATH_IF_SUPPORTED(;, "");  // NOLINT
+  output = GetCapturedStderr();
+  ASSERT_TRUE(NULL != strstr(output.c_str(),
+                             "Death tests are not supported on this platform"));
+  ASSERT_TRUE(NULL != strstr(output.c_str(), ";"));
+
+  CaptureStderr();
+  ASSERT_DEATH_IF_SUPPORTED(;, "") << "streamed message";  // NOLINT
+  output = GetCapturedStderr();
+  ASSERT_TRUE(NULL == strstr(output.c_str(), "streamed message"));
+}
+
+void FuncWithAssert(int* n) {
+  ASSERT_DEATH_IF_SUPPORTED(return;, "");
+  (*n)++;
+}
+
+// Tests that ASSERT_DEATH_IF_SUPPORTED does not return from the current
+// function (as ASSERT_DEATH does) if death tests are not supported.
+TEST(ConditionalDeathMacrosTest, AssertDeatDoesNotReturnhIfUnsupported) {
+  int n = 0;
+  FuncWithAssert(&n);
+  EXPECT_EQ(1, n);
+}
+
+}  // namespace
+
+#endif  // !GTEST_HAS_DEATH_TEST
+
+namespace {
+
+// The following code intentionally tests a suboptimal syntax.
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdangling-else"
+#pragma GCC diagnostic ignored "-Wempty-body"
+#pragma GCC diagnostic ignored "-Wpragmas"
+#endif
+// Tests that the death test macros expand to code which may or may not
+// be followed by operator<<, and that in either case the complete text
+// comprises only a single C++ statement.
+//
+// The syntax should work whether death tests are available or not.
+TEST(ConditionalDeathMacrosSyntaxDeathTest, SingleStatement) {
+  if (AlwaysFalse())
+    // This would fail if executed; this is a compilation test only
+    ASSERT_DEATH_IF_SUPPORTED(return, "");
+
+  if (AlwaysTrue())
+    EXPECT_DEATH_IF_SUPPORTED(_exit(1), "");
+  else
+    // This empty "else" branch is meant to ensure that EXPECT_DEATH
+    // doesn't expand into an "if" statement without an "else"
+    ;  // NOLINT
+
+  if (AlwaysFalse())
+    ASSERT_DEATH_IF_SUPPORTED(return, "") << "did not die";
+
+  if (AlwaysFalse())
+    ;  // NOLINT
+  else
+    EXPECT_DEATH_IF_SUPPORTED(_exit(1), "") << 1 << 2 << 3;
+}
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif
+
+// Tests that conditional death test macros expand to code which interacts
+// well with switch statements.
+TEST(ConditionalDeathMacrosSyntaxDeathTest, SwitchStatement) {
+  // Microsoft compiler usually complains about switch statements without
+  // case labels. We suppress that warning for this test.
+  GTEST_DISABLE_MSC_WARNINGS_PUSH_(4065)
+
+  switch (0)
+    default:
+      ASSERT_DEATH_IF_SUPPORTED(_exit(1), "")
+          << "exit in default switch handler";
+
+  switch (0)
+    case 0:
+      EXPECT_DEATH_IF_SUPPORTED(_exit(1), "") << "exit in switch case";
+
+  GTEST_DISABLE_MSC_WARNINGS_POP_()
+}
+
+// Tests that a test case whose name ends with "DeathTest" works fine
+// on Windows.
+TEST(NotADeathTest, Test) {
+  SUCCEED();
+}
+
+}  // namespace
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-death-test_ex_test.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-death-test_ex_test.cc
new file mode 100644
index 0000000..7219680
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-death-test_ex_test.cc
@@ -0,0 +1,92 @@
+// Copyright 2010, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// Tests that verify interaction of exceptions and death tests.
+
+#include "gtest/gtest-death-test.h"
+#include "gtest/gtest.h"
+
+#if GTEST_HAS_DEATH_TEST
+
+# if GTEST_HAS_SEH
+#  include <windows.h>          // For RaiseException().
+# endif
+
+# include "gtest/gtest-spi.h"
+
+# if GTEST_HAS_EXCEPTIONS
+
+#  include <exception>  // For std::exception.
+
+// Tests that death tests report thrown exceptions as failures and that the
+// exceptions do not escape death test macros.
+TEST(CxxExceptionDeathTest, ExceptionIsFailure) {
+  try {
+    EXPECT_NONFATAL_FAILURE(EXPECT_DEATH(throw 1, ""), "threw an exception");
+  } catch (...) {  // NOLINT
+    FAIL() << "An exception escaped a death test macro invocation "
+           << "with catch_exceptions "
+           << (testing::GTEST_FLAG(catch_exceptions) ? "enabled" : "disabled");
+  }
+}
+
+class TestException : public std::exception {
+ public:
+  const char* what() const noexcept override { return "exceptional message"; }
+};
+
+TEST(CxxExceptionDeathTest, PrintsMessageForStdExceptions) {
+  // Verifies that the exception message is quoted in the failure text.
+  EXPECT_NONFATAL_FAILURE(EXPECT_DEATH(throw TestException(), ""),
+                          "exceptional message");
+  // Verifies that the location is mentioned in the failure text.
+  EXPECT_NONFATAL_FAILURE(EXPECT_DEATH(throw TestException(), ""),
+                          __FILE__);
+}
+# endif  // GTEST_HAS_EXCEPTIONS
+
+# if GTEST_HAS_SEH
+// Tests that enabling interception of SEH exceptions with the
+// catch_exceptions flag does not interfere with SEH exceptions being
+// treated as death by death tests.
+TEST(SehExceptionDeasTest, CatchExceptionsDoesNotInterfere) {
+  EXPECT_DEATH(RaiseException(42, 0x0, 0, NULL), "")
+      << "with catch_exceptions "
+      << (testing::GTEST_FLAG(catch_exceptions) ? "enabled" : "disabled");
+}
+# endif
+
+#endif  // GTEST_HAS_DEATH_TEST
+
+int main(int argc, char** argv) {
+  testing::InitGoogleTest(&argc, argv);
+  testing::GTEST_FLAG(catch_exceptions) = GTEST_ENABLE_CATCH_EXCEPTIONS_ != 0;
+  return RUN_ALL_TESTS();
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-env-var-test.py b/leveldb_base/third_party/googletest/googletest/test/googletest-env-var-test.py
new file mode 100644
index 0000000..02c3655
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-env-var-test.py
@@ -0,0 +1,120 @@
+#!/usr/bin/env python
+#
+# Copyright 2008, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Verifies that Google Test correctly parses environment variables."""
+
+import os
+import gtest_test_utils
+
+
+IS_WINDOWS = os.name == 'nt'
+IS_LINUX = os.name == 'posix' and os.uname()[0] == 'Linux'
+
+COMMAND = gtest_test_utils.GetTestExecutablePath('googletest-env-var-test_')
+
+environ = os.environ.copy()
+
+
+def AssertEq(expected, actual):
+  if expected != actual:
+    print('Expected: %s' % (expected,))
+    print('  Actual: %s' % (actual,))
+    raise AssertionError
+
+
+def SetEnvVar(env_var, value):
+  """Sets the env variable to 'value'; unsets it when 'value' is None."""
+
+  if value is not None:
+    environ[env_var] = value
+  elif env_var in environ:
+    del environ[env_var]
+
+
+def GetFlag(flag):
+  """Runs googletest-env-var-test_ and returns its output."""
+
+  args = [COMMAND]
+  if flag is not None:
+    args += [flag]
+  return gtest_test_utils.Subprocess(args, env=environ).output
+
+
+def TestFlag(flag, test_val, default_val):
+  """Verifies that the given flag is affected by the corresponding env var."""
+
+  env_var = 'GTEST_' + flag.upper()
+  SetEnvVar(env_var, test_val)
+  AssertEq(test_val, GetFlag(flag))
+  SetEnvVar(env_var, None)
+  AssertEq(default_val, GetFlag(flag))
+
+
+class GTestEnvVarTest(gtest_test_utils.TestCase):
+
+  def testEnvVarAffectsFlag(self):
+    """Tests that environment variable should affect the corresponding flag."""
+
+    TestFlag('break_on_failure', '1', '0')
+    TestFlag('color', 'yes', 'auto')
+    SetEnvVar('TESTBRIDGE_TEST_RUNNER_FAIL_FAST', None)  # For 'fail_fast' test
+    TestFlag('fail_fast', '1', '0')
+    TestFlag('filter', 'FooTest.Bar', '*')
+    SetEnvVar('XML_OUTPUT_FILE', None)  # For 'output' test
+    TestFlag('output', 'xml:tmp/foo.xml', '')
+    TestFlag('brief', '1', '0')
+    TestFlag('print_time', '0', '1')
+    TestFlag('repeat', '999', '1')
+    TestFlag('throw_on_failure', '1', '0')
+    TestFlag('death_test_style', 'threadsafe', 'fast')
+    TestFlag('catch_exceptions', '0', '1')
+
+    if IS_LINUX:
+      TestFlag('death_test_use_fork', '1', '0')
+      TestFlag('stack_trace_depth', '0', '100')
+
+
+  def testXmlOutputFile(self):
+    """Tests that $XML_OUTPUT_FILE affects the output flag."""
+
+    SetEnvVar('GTEST_OUTPUT', None)
+    SetEnvVar('XML_OUTPUT_FILE', 'tmp/bar.xml')
+    AssertEq('xml:tmp/bar.xml', GetFlag('output'))
+
+  def testXmlOutputFileOverride(self):
+    """Tests that $XML_OUTPUT_FILE is overridden by $GTEST_OUTPUT."""
+
+    SetEnvVar('GTEST_OUTPUT', 'xml:tmp/foo.xml')
+    SetEnvVar('XML_OUTPUT_FILE', 'tmp/bar.xml')
+    AssertEq('xml:tmp/foo.xml', GetFlag('output'))
+
+if __name__ == '__main__':
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-env-var-test_.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-env-var-test_.cc
new file mode 100644
index 0000000..52f9586
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-env-var-test_.cc
@@ -0,0 +1,132 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// A helper program for testing that Google Test parses the environment
+// variables correctly.
+
+#include <iostream>
+
+#include "gtest/gtest.h"
+#include "src/gtest-internal-inl.h"
+
+using ::std::cout;
+
+namespace testing {
+
+// The purpose of this is to make the test more realistic by ensuring
+// that the UnitTest singleton is created before main() is entered.
+// We don't actual run the TEST itself.
+TEST(GTestEnvVarTest, Dummy) {
+}
+
+void PrintFlag(const char* flag) {
+  if (strcmp(flag, "break_on_failure") == 0) {
+    cout << GTEST_FLAG(break_on_failure);
+    return;
+  }
+
+  if (strcmp(flag, "catch_exceptions") == 0) {
+    cout << GTEST_FLAG(catch_exceptions);
+    return;
+  }
+
+  if (strcmp(flag, "color") == 0) {
+    cout << GTEST_FLAG(color);
+    return;
+  }
+
+  if (strcmp(flag, "death_test_style") == 0) {
+    cout << GTEST_FLAG(death_test_style);
+    return;
+  }
+
+  if (strcmp(flag, "death_test_use_fork") == 0) {
+    cout << GTEST_FLAG(death_test_use_fork);
+    return;
+  }
+
+  if (strcmp(flag, "fail_fast") == 0) {
+    cout << GTEST_FLAG(fail_fast);
+    return;
+  }
+
+  if (strcmp(flag, "filter") == 0) {
+    cout << GTEST_FLAG(filter);
+    return;
+  }
+
+  if (strcmp(flag, "output") == 0) {
+    cout << GTEST_FLAG(output);
+    return;
+  }
+
+  if (strcmp(flag, "brief") == 0) {
+    cout << GTEST_FLAG(brief);
+    return;
+  }
+
+  if (strcmp(flag, "print_time") == 0) {
+    cout << GTEST_FLAG(print_time);
+    return;
+  }
+
+  if (strcmp(flag, "repeat") == 0) {
+    cout << GTEST_FLAG(repeat);
+    return;
+  }
+
+  if (strcmp(flag, "stack_trace_depth") == 0) {
+    cout << GTEST_FLAG(stack_trace_depth);
+    return;
+  }
+
+  if (strcmp(flag, "throw_on_failure") == 0) {
+    cout << GTEST_FLAG(throw_on_failure);
+    return;
+  }
+
+  cout << "Invalid flag name " << flag
+       << ".  Valid names are break_on_failure, color, filter, etc.\n";
+  exit(1);
+}
+
+}  // namespace testing
+
+int main(int argc, char** argv) {
+  testing::InitGoogleTest(&argc, argv);
+
+  if (argc != 2) {
+    cout << "Usage: googletest-env-var-test_ NAME_OF_FLAG\n";
+    return 1;
+  }
+
+  testing::PrintFlag(argv[1]);
+  return 0;
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-failfast-unittest.py b/leveldb_base/third_party/googletest/googletest/test/googletest-failfast-unittest.py
new file mode 100644
index 0000000..3aeb2df
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-failfast-unittest.py
@@ -0,0 +1,410 @@
+#!/usr/bin/env python
+#
+# Copyright 2020 Google Inc. All Rights Reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Unit test for Google Test fail_fast.
+
+A user can specify if a Google Test program should continue test execution
+after a test failure via the GTEST_FAIL_FAST environment variable or the
+--gtest_fail_fast flag. The default value of the flag can also be changed
+by Bazel fail fast environment variable TESTBRIDGE_TEST_RUNNER_FAIL_FAST.
+
+This script tests such functionality by invoking googletest-failfast-unittest_
+(a program written with Google Test) with different environments and command
+line flags.
+"""
+
+import os
+import gtest_test_utils
+
+# Constants.
+
+# Bazel testbridge environment variable for fail fast
+BAZEL_FAIL_FAST_ENV_VAR = 'TESTBRIDGE_TEST_RUNNER_FAIL_FAST'
+
+# The environment variable for specifying fail fast.
+FAIL_FAST_ENV_VAR = 'GTEST_FAIL_FAST'
+
+# The command line flag for specifying fail fast.
+FAIL_FAST_FLAG = 'gtest_fail_fast'
+
+# The command line flag to run disabled tests.
+RUN_DISABLED_FLAG = 'gtest_also_run_disabled_tests'
+
+# The command line flag for specifying a filter.
+FILTER_FLAG = 'gtest_filter'
+
+# Command to run the googletest-failfast-unittest_ program.
+COMMAND = gtest_test_utils.GetTestExecutablePath(
+    'googletest-failfast-unittest_')
+
+# The command line flag to tell Google Test to output the list of tests it
+# will run.
+LIST_TESTS_FLAG = '--gtest_list_tests'
+
+# Indicates whether Google Test supports death tests.
+SUPPORTS_DEATH_TESTS = 'HasDeathTest' in gtest_test_utils.Subprocess(
+    [COMMAND, LIST_TESTS_FLAG]).output
+
+# Utilities.
+
+environ = os.environ.copy()
+
+
+def SetEnvVar(env_var, value):
+  """Sets the env variable to 'value'; unsets it when 'value' is None."""
+
+  if value is not None:
+    environ[env_var] = value
+  elif env_var in environ:
+    del environ[env_var]
+
+
+def RunAndReturnOutput(test_suite=None, fail_fast=None, run_disabled=False):
+  """Runs the test program and returns its output."""
+
+  args = []
+  xml_path = os.path.join(gtest_test_utils.GetTempDir(),
+                          '.GTestFailFastUnitTest.xml')
+  args += ['--gtest_output=xml:' + xml_path]
+  if fail_fast is not None:
+    if isinstance(fail_fast, str):
+      args += ['--%s=%s' % (FAIL_FAST_FLAG, fail_fast)]
+    elif fail_fast:
+      args += ['--%s' % FAIL_FAST_FLAG]
+    else:
+      args += ['--no%s' % FAIL_FAST_FLAG]
+  if test_suite:
+    args += ['--%s=%s.*' % (FILTER_FLAG, test_suite)]
+  if run_disabled:
+    args += ['--%s' % RUN_DISABLED_FLAG]
+  txt_out = gtest_test_utils.Subprocess([COMMAND] + args, env=environ).output
+  with open(xml_path) as xml_file:
+    return txt_out, xml_file.read()
+
+
+# The unit test.
+class GTestFailFastUnitTest(gtest_test_utils.TestCase):
+  """Tests the env variable or the command line flag for fail_fast."""
+
+  def testDefaultBehavior(self):
+    """Tests the behavior of not specifying the fail_fast."""
+
+    txt, _ = RunAndReturnOutput()
+    self.assertIn('22 FAILED TEST', txt)
+
+  def testGoogletestFlag(self):
+    txt, _ = RunAndReturnOutput(test_suite='HasSimpleTest', fail_fast=True)
+    self.assertIn('1 FAILED TEST', txt)
+    self.assertIn('[  SKIPPED ] 3 tests', txt)
+
+    txt, _ = RunAndReturnOutput(test_suite='HasSimpleTest', fail_fast=False)
+    self.assertIn('4 FAILED TEST', txt)
+    self.assertNotIn('[  SKIPPED ]', txt)
+
+  def testGoogletestEnvVar(self):
+    """Tests the behavior of specifying fail_fast via Googletest env var."""
+
+    try:
+      SetEnvVar(FAIL_FAST_ENV_VAR, '1')
+      txt, _ = RunAndReturnOutput('HasSimpleTest')
+      self.assertIn('1 FAILED TEST', txt)
+      self.assertIn('[  SKIPPED ] 3 tests', txt)
+
+      SetEnvVar(FAIL_FAST_ENV_VAR, '0')
+      txt, _ = RunAndReturnOutput('HasSimpleTest')
+      self.assertIn('4 FAILED TEST', txt)
+      self.assertNotIn('[  SKIPPED ]', txt)
+    finally:
+      SetEnvVar(FAIL_FAST_ENV_VAR, None)
+
+  def testBazelEnvVar(self):
+    """Tests the behavior of specifying fail_fast via Bazel testbridge."""
+
+    try:
+      SetEnvVar(BAZEL_FAIL_FAST_ENV_VAR, '1')
+      txt, _ = RunAndReturnOutput('HasSimpleTest')
+      self.assertIn('1 FAILED TEST', txt)
+      self.assertIn('[  SKIPPED ] 3 tests', txt)
+
+      SetEnvVar(BAZEL_FAIL_FAST_ENV_VAR, '0')
+      txt, _ = RunAndReturnOutput('HasSimpleTest')
+      self.assertIn('4 FAILED TEST', txt)
+      self.assertNotIn('[  SKIPPED ]', txt)
+    finally:
+      SetEnvVar(BAZEL_FAIL_FAST_ENV_VAR, None)
+
+  def testFlagOverridesEnvVar(self):
+    """Tests precedence of flag over env var."""
+
+    try:
+      SetEnvVar(FAIL_FAST_ENV_VAR, '0')
+      txt, _ = RunAndReturnOutput('HasSimpleTest', True)
+      self.assertIn('1 FAILED TEST', txt)
+      self.assertIn('[  SKIPPED ] 3 tests', txt)
+    finally:
+      SetEnvVar(FAIL_FAST_ENV_VAR, None)
+
+  def testGoogletestEnvVarOverridesBazelEnvVar(self):
+    """Tests that the Googletest native env var over Bazel testbridge."""
+
+    try:
+      SetEnvVar(BAZEL_FAIL_FAST_ENV_VAR, '0')
+      SetEnvVar(FAIL_FAST_ENV_VAR, '1')
+      txt, _ = RunAndReturnOutput('HasSimpleTest')
+      self.assertIn('1 FAILED TEST', txt)
+      self.assertIn('[  SKIPPED ] 3 tests', txt)
+    finally:
+      SetEnvVar(FAIL_FAST_ENV_VAR, None)
+      SetEnvVar(BAZEL_FAIL_FAST_ENV_VAR, None)
+
+  def testEventListener(self):
+    txt, _ = RunAndReturnOutput(test_suite='HasSkipTest', fail_fast=True)
+    self.assertIn('1 FAILED TEST', txt)
+    self.assertIn('[  SKIPPED ] 3 tests', txt)
+    for expected_count, callback in [(1, 'OnTestSuiteStart'),
+                                     (5, 'OnTestStart'),
+                                     (5, 'OnTestEnd'),
+                                     (5, 'OnTestPartResult'),
+                                     (1, 'OnTestSuiteEnd')]:
+      self.assertEqual(
+          expected_count, txt.count(callback),
+          'Expected %d calls to callback %s match count on output: %s ' %
+          (expected_count, callback, txt))
+
+    txt, _ = RunAndReturnOutput(test_suite='HasSkipTest', fail_fast=False)
+    self.assertIn('3 FAILED TEST', txt)
+    self.assertIn('[  SKIPPED ] 1 test', txt)
+    for expected_count, callback in [(1, 'OnTestSuiteStart'),
+                                     (5, 'OnTestStart'),
+                                     (5, 'OnTestEnd'),
+                                     (5, 'OnTestPartResult'),
+                                     (1, 'OnTestSuiteEnd')]:
+      self.assertEqual(
+          expected_count, txt.count(callback),
+          'Expected %d calls to callback %s match count on output: %s ' %
+          (expected_count, callback, txt))
+
+  def assertXmlResultCount(self, result, count, xml):
+    self.assertEqual(
+        count, xml.count('result="%s"' % result),
+        'Expected \'result="%s"\' match count of %s: %s ' %
+        (result, count, xml))
+
+  def assertXmlStatusCount(self, status, count, xml):
+    self.assertEqual(
+        count, xml.count('status="%s"' % status),
+        'Expected \'status="%s"\' match count of %s: %s ' %
+        (status, count, xml))
+
+  def assertFailFastXmlAndTxtOutput(self,
+                                    fail_fast,
+                                    test_suite,
+                                    passed_count,
+                                    failure_count,
+                                    skipped_count,
+                                    suppressed_count,
+                                    run_disabled=False):
+    """Assert XML and text output of a test execution."""
+
+    txt, xml = RunAndReturnOutput(test_suite, fail_fast, run_disabled)
+    if failure_count > 0:
+      self.assertIn('%s FAILED TEST' % failure_count, txt)
+    if suppressed_count > 0:
+      self.assertIn('%s DISABLED TEST' % suppressed_count, txt)
+    if skipped_count > 0:
+      self.assertIn('[  SKIPPED ] %s tests' % skipped_count, txt)
+    self.assertXmlStatusCount('run',
+                              passed_count + failure_count + skipped_count, xml)
+    self.assertXmlStatusCount('notrun', suppressed_count, xml)
+    self.assertXmlResultCount('completed', passed_count + failure_count, xml)
+    self.assertXmlResultCount('skipped', skipped_count, xml)
+    self.assertXmlResultCount('suppressed', suppressed_count, xml)
+
+  def assertFailFastBehavior(self,
+                             test_suite,
+                             passed_count,
+                             failure_count,
+                             skipped_count,
+                             suppressed_count,
+                             run_disabled=False):
+    """Assert --fail_fast via flag."""
+
+    for fail_fast in ('true', '1', 't', True):
+      self.assertFailFastXmlAndTxtOutput(fail_fast, test_suite, passed_count,
+                                         failure_count, skipped_count,
+                                         suppressed_count, run_disabled)
+
+  def assertNotFailFastBehavior(self,
+                                test_suite,
+                                passed_count,
+                                failure_count,
+                                skipped_count,
+                                suppressed_count,
+                                run_disabled=False):
+    """Assert --nofail_fast via flag."""
+
+    for fail_fast in ('false', '0', 'f', False):
+      self.assertFailFastXmlAndTxtOutput(fail_fast, test_suite, passed_count,
+                                         failure_count, skipped_count,
+                                         suppressed_count, run_disabled)
+
+  def testFlag_HasFixtureTest(self):
+    """Tests the behavior of fail_fast and TEST_F."""
+    self.assertFailFastBehavior(
+        test_suite='HasFixtureTest',
+        passed_count=1,
+        failure_count=1,
+        skipped_count=3,
+        suppressed_count=0)
+    self.assertNotFailFastBehavior(
+        test_suite='HasFixtureTest',
+        passed_count=1,
+        failure_count=4,
+        skipped_count=0,
+        suppressed_count=0)
+
+  def testFlag_HasSimpleTest(self):
+    """Tests the behavior of fail_fast and TEST."""
+    self.assertFailFastBehavior(
+        test_suite='HasSimpleTest',
+        passed_count=1,
+        failure_count=1,
+        skipped_count=3,
+        suppressed_count=0)
+    self.assertNotFailFastBehavior(
+        test_suite='HasSimpleTest',
+        passed_count=1,
+        failure_count=4,
+        skipped_count=0,
+        suppressed_count=0)
+
+  def testFlag_HasParametersTest(self):
+    """Tests the behavior of fail_fast and TEST_P."""
+    self.assertFailFastBehavior(
+        test_suite='HasParametersSuite/HasParametersTest',
+        passed_count=0,
+        failure_count=1,
+        skipped_count=3,
+        suppressed_count=0)
+    self.assertNotFailFastBehavior(
+        test_suite='HasParametersSuite/HasParametersTest',
+        passed_count=0,
+        failure_count=4,
+        skipped_count=0,
+        suppressed_count=0)
+
+  def testFlag_HasDisabledTest(self):
+    """Tests the behavior of fail_fast and Disabled test cases."""
+    self.assertFailFastBehavior(
+        test_suite='HasDisabledTest',
+        passed_count=1,
+        failure_count=1,
+        skipped_count=2,
+        suppressed_count=1,
+        run_disabled=False)
+    self.assertNotFailFastBehavior(
+        test_suite='HasDisabledTest',
+        passed_count=1,
+        failure_count=3,
+        skipped_count=0,
+        suppressed_count=1,
+        run_disabled=False)
+
+  def testFlag_HasDisabledRunDisabledTest(self):
+    """Tests the behavior of fail_fast and Disabled test cases enabled."""
+    self.assertFailFastBehavior(
+        test_suite='HasDisabledTest',
+        passed_count=1,
+        failure_count=1,
+        skipped_count=3,
+        suppressed_count=0,
+        run_disabled=True)
+    self.assertNotFailFastBehavior(
+        test_suite='HasDisabledTest',
+        passed_count=1,
+        failure_count=4,
+        skipped_count=0,
+        suppressed_count=0,
+        run_disabled=True)
+
+  def testFlag_HasDisabledSuiteTest(self):
+    """Tests the behavior of fail_fast and Disabled test suites."""
+    self.assertFailFastBehavior(
+        test_suite='DISABLED_HasDisabledSuite',
+        passed_count=0,
+        failure_count=0,
+        skipped_count=0,
+        suppressed_count=5,
+        run_disabled=False)
+    self.assertNotFailFastBehavior(
+        test_suite='DISABLED_HasDisabledSuite',
+        passed_count=0,
+        failure_count=0,
+        skipped_count=0,
+        suppressed_count=5,
+        run_disabled=False)
+
+  def testFlag_HasDisabledSuiteRunDisabledTest(self):
+    """Tests the behavior of fail_fast and Disabled test suites enabled."""
+    self.assertFailFastBehavior(
+        test_suite='DISABLED_HasDisabledSuite',
+        passed_count=1,
+        failure_count=1,
+        skipped_count=3,
+        suppressed_count=0,
+        run_disabled=True)
+    self.assertNotFailFastBehavior(
+        test_suite='DISABLED_HasDisabledSuite',
+        passed_count=1,
+        failure_count=4,
+        skipped_count=0,
+        suppressed_count=0,
+        run_disabled=True)
+
+  if SUPPORTS_DEATH_TESTS:
+
+    def testFlag_HasDeathTest(self):
+      """Tests the behavior of fail_fast and death tests."""
+      self.assertFailFastBehavior(
+          test_suite='HasDeathTest',
+          passed_count=1,
+          failure_count=1,
+          skipped_count=3,
+          suppressed_count=0)
+      self.assertNotFailFastBehavior(
+          test_suite='HasDeathTest',
+          passed_count=1,
+          failure_count=4,
+          skipped_count=0,
+          suppressed_count=0)
+
+
+if __name__ == '__main__':
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-failfast-unittest_.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-failfast-unittest_.cc
new file mode 100644
index 0000000..0b2c951
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-failfast-unittest_.cc
@@ -0,0 +1,167 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Unit test for Google Test test filters.
+//
+// A user can specify which test(s) in a Google Test program to run via
+// either the GTEST_FILTER environment variable or the --gtest_filter
+// flag.  This is used for testing such functionality.
+//
+// The program will be invoked from a Python unit test.  Don't run it
+// directly.
+
+#include "gtest/gtest.h"
+
+namespace {
+
+// Test HasFixtureTest.
+
+class HasFixtureTest : public testing::Test {};
+
+TEST_F(HasFixtureTest, Test0) {}
+
+TEST_F(HasFixtureTest, Test1) { FAIL() << "Expected failure."; }
+
+TEST_F(HasFixtureTest, Test2) { FAIL() << "Expected failure."; }
+
+TEST_F(HasFixtureTest, Test3) { FAIL() << "Expected failure."; }
+
+TEST_F(HasFixtureTest, Test4) { FAIL() << "Expected failure."; }
+
+// Test HasSimpleTest.
+
+TEST(HasSimpleTest, Test0) {}
+
+TEST(HasSimpleTest, Test1) { FAIL() << "Expected failure."; }
+
+TEST(HasSimpleTest, Test2) { FAIL() << "Expected failure."; }
+
+TEST(HasSimpleTest, Test3) { FAIL() << "Expected failure."; }
+
+TEST(HasSimpleTest, Test4) { FAIL() << "Expected failure."; }
+
+// Test HasDisabledTest.
+
+TEST(HasDisabledTest, Test0) {}
+
+TEST(HasDisabledTest, DISABLED_Test1) { FAIL() << "Expected failure."; }
+
+TEST(HasDisabledTest, Test2) { FAIL() << "Expected failure."; }
+
+TEST(HasDisabledTest, Test3) { FAIL() << "Expected failure."; }
+
+TEST(HasDisabledTest, Test4) { FAIL() << "Expected failure."; }
+
+// Test HasDeathTest
+
+TEST(HasDeathTest, Test0) { EXPECT_DEATH_IF_SUPPORTED(exit(1), ".*"); }
+
+TEST(HasDeathTest, Test1) {
+  EXPECT_DEATH_IF_SUPPORTED(FAIL() << "Expected failure.", ".*");
+}
+
+TEST(HasDeathTest, Test2) {
+  EXPECT_DEATH_IF_SUPPORTED(FAIL() << "Expected failure.", ".*");
+}
+
+TEST(HasDeathTest, Test3) {
+  EXPECT_DEATH_IF_SUPPORTED(FAIL() << "Expected failure.", ".*");
+}
+
+TEST(HasDeathTest, Test4) {
+  EXPECT_DEATH_IF_SUPPORTED(FAIL() << "Expected failure.", ".*");
+}
+
+// Test DISABLED_HasDisabledSuite
+
+TEST(DISABLED_HasDisabledSuite, Test0) {}
+
+TEST(DISABLED_HasDisabledSuite, Test1) { FAIL() << "Expected failure."; }
+
+TEST(DISABLED_HasDisabledSuite, Test2) { FAIL() << "Expected failure."; }
+
+TEST(DISABLED_HasDisabledSuite, Test3) { FAIL() << "Expected failure."; }
+
+TEST(DISABLED_HasDisabledSuite, Test4) { FAIL() << "Expected failure."; }
+
+// Test HasParametersTest
+
+class HasParametersTest : public testing::TestWithParam<int> {};
+
+TEST_P(HasParametersTest, Test1) { FAIL() << "Expected failure."; }
+
+TEST_P(HasParametersTest, Test2) { FAIL() << "Expected failure."; }
+
+INSTANTIATE_TEST_SUITE_P(HasParametersSuite, HasParametersTest,
+                         testing::Values(1, 2));
+
+class MyTestListener : public ::testing::EmptyTestEventListener {
+  void OnTestSuiteStart(const ::testing::TestSuite& test_suite) override {
+    printf("We are in OnTestSuiteStart of %s.\n", test_suite.name());
+  }
+
+  void OnTestStart(const ::testing::TestInfo& test_info) override {
+    printf("We are in OnTestStart of %s.%s.\n", test_info.test_suite_name(),
+           test_info.name());
+  }
+
+  void OnTestPartResult(
+      const ::testing::TestPartResult& test_part_result) override {
+    printf("We are in OnTestPartResult %s:%d.\n", test_part_result.file_name(),
+           test_part_result.line_number());
+  }
+
+  void OnTestEnd(const ::testing::TestInfo& test_info) override {
+    printf("We are in OnTestEnd of %s.%s.\n", test_info.test_suite_name(),
+           test_info.name());
+  }
+
+  void OnTestSuiteEnd(const ::testing::TestSuite& test_suite) override {
+    printf("We are in OnTestSuiteEnd of %s.\n", test_suite.name());
+  }
+};
+
+TEST(HasSkipTest, Test0) { SUCCEED() << "Expected success."; }
+
+TEST(HasSkipTest, Test1) { GTEST_SKIP() << "Expected skip."; }
+
+TEST(HasSkipTest, Test2) { FAIL() << "Expected failure."; }
+
+TEST(HasSkipTest, Test3) { FAIL() << "Expected failure."; }
+
+TEST(HasSkipTest, Test4) { FAIL() << "Expected failure."; }
+
+}  // namespace
+
+int main(int argc, char **argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+  ::testing::UnitTest::GetInstance()->listeners().Append(new MyTestListener());
+  return RUN_ALL_TESTS();
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-filepath-test.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-filepath-test.cc
new file mode 100644
index 0000000..aafad36
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-filepath-test.cc
@@ -0,0 +1,649 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// Google Test filepath utilities
+//
+// This file tests classes and functions used internally by
+// Google Test.  They are subject to change without notice.
+//
+// This file is #included from gtest-internal.h.
+// Do not #include this file anywhere else!
+
+#include "gtest/internal/gtest-filepath.h"
+#include "gtest/gtest.h"
+#include "src/gtest-internal-inl.h"
+
+#if GTEST_OS_WINDOWS_MOBILE
+# include <windows.h>  // NOLINT
+#elif GTEST_OS_WINDOWS
+# include <direct.h>  // NOLINT
+#endif  // GTEST_OS_WINDOWS_MOBILE
+
+namespace testing {
+namespace internal {
+namespace {
+
+#if GTEST_OS_WINDOWS_MOBILE
+
+// Windows CE doesn't have the remove C function.
+int remove(const char* path) {
+  LPCWSTR wpath = String::AnsiToUtf16(path);
+  int ret = DeleteFile(wpath) ? 0 : -1;
+  delete [] wpath;
+  return ret;
+}
+// Windows CE doesn't have the _rmdir C function.
+int _rmdir(const char* path) {
+  FilePath filepath(path);
+  LPCWSTR wpath = String::AnsiToUtf16(
+      filepath.RemoveTrailingPathSeparator().c_str());
+  int ret = RemoveDirectory(wpath) ? 0 : -1;
+  delete [] wpath;
+  return ret;
+}
+
+#else
+
+TEST(GetCurrentDirTest, ReturnsCurrentDir) {
+  const FilePath original_dir = FilePath::GetCurrentDir();
+  EXPECT_FALSE(original_dir.IsEmpty());
+
+  posix::ChDir(GTEST_PATH_SEP_);
+  const FilePath cwd = FilePath::GetCurrentDir();
+  posix::ChDir(original_dir.c_str());
+
+# if GTEST_OS_WINDOWS || GTEST_OS_OS2
+
+  // Skips the ":".
+  const char* const cwd_without_drive = strchr(cwd.c_str(), ':');
+  ASSERT_TRUE(cwd_without_drive != NULL);
+  EXPECT_STREQ(GTEST_PATH_SEP_, cwd_without_drive + 1);
+
+# else
+
+  EXPECT_EQ(GTEST_PATH_SEP_, cwd.string());
+
+# endif
+}
+
+#endif  // GTEST_OS_WINDOWS_MOBILE
+
+TEST(IsEmptyTest, ReturnsTrueForEmptyPath) {
+  EXPECT_TRUE(FilePath("").IsEmpty());
+}
+
+TEST(IsEmptyTest, ReturnsFalseForNonEmptyPath) {
+  EXPECT_FALSE(FilePath("a").IsEmpty());
+  EXPECT_FALSE(FilePath(".").IsEmpty());
+  EXPECT_FALSE(FilePath("a/b").IsEmpty());
+  EXPECT_FALSE(FilePath("a\\b\\").IsEmpty());
+}
+
+// RemoveDirectoryName "" -> ""
+TEST(RemoveDirectoryNameTest, WhenEmptyName) {
+  EXPECT_EQ("", FilePath("").RemoveDirectoryName().string());
+}
+
+// RemoveDirectoryName "afile" -> "afile"
+TEST(RemoveDirectoryNameTest, ButNoDirectory) {
+  EXPECT_EQ("afile",
+      FilePath("afile").RemoveDirectoryName().string());
+}
+
+// RemoveDirectoryName "/afile" -> "afile"
+TEST(RemoveDirectoryNameTest, RootFileShouldGiveFileName) {
+  EXPECT_EQ("afile",
+      FilePath(GTEST_PATH_SEP_ "afile").RemoveDirectoryName().string());
+}
+
+// RemoveDirectoryName "adir/" -> ""
+TEST(RemoveDirectoryNameTest, WhereThereIsNoFileName) {
+  EXPECT_EQ("",
+      FilePath("adir" GTEST_PATH_SEP_).RemoveDirectoryName().string());
+}
+
+// RemoveDirectoryName "adir/afile" -> "afile"
+TEST(RemoveDirectoryNameTest, ShouldGiveFileName) {
+  EXPECT_EQ("afile",
+      FilePath("adir" GTEST_PATH_SEP_ "afile").RemoveDirectoryName().string());
+}
+
+// RemoveDirectoryName "adir/subdir/afile" -> "afile"
+TEST(RemoveDirectoryNameTest, ShouldAlsoGiveFileName) {
+  EXPECT_EQ("afile",
+      FilePath("adir" GTEST_PATH_SEP_ "subdir" GTEST_PATH_SEP_ "afile")
+      .RemoveDirectoryName().string());
+}
+
+#if GTEST_HAS_ALT_PATH_SEP_
+
+// Tests that RemoveDirectoryName() works with the alternate separator
+// on Windows.
+
+// RemoveDirectoryName("/afile") -> "afile"
+TEST(RemoveDirectoryNameTest, RootFileShouldGiveFileNameForAlternateSeparator) {
+  EXPECT_EQ("afile", FilePath("/afile").RemoveDirectoryName().string());
+}
+
+// RemoveDirectoryName("adir/") -> ""
+TEST(RemoveDirectoryNameTest, WhereThereIsNoFileNameForAlternateSeparator) {
+  EXPECT_EQ("", FilePath("adir/").RemoveDirectoryName().string());
+}
+
+// RemoveDirectoryName("adir/afile") -> "afile"
+TEST(RemoveDirectoryNameTest, ShouldGiveFileNameForAlternateSeparator) {
+  EXPECT_EQ("afile", FilePath("adir/afile").RemoveDirectoryName().string());
+}
+
+// RemoveDirectoryName("adir/subdir/afile") -> "afile"
+TEST(RemoveDirectoryNameTest, ShouldAlsoGiveFileNameForAlternateSeparator) {
+  EXPECT_EQ("afile",
+            FilePath("adir/subdir/afile").RemoveDirectoryName().string());
+}
+
+#endif
+
+// RemoveFileName "" -> "./"
+TEST(RemoveFileNameTest, EmptyName) {
+#if GTEST_OS_WINDOWS_MOBILE
+  // On Windows CE, we use the root as the current directory.
+  EXPECT_EQ(GTEST_PATH_SEP_, FilePath("").RemoveFileName().string());
+#else
+  EXPECT_EQ("." GTEST_PATH_SEP_, FilePath("").RemoveFileName().string());
+#endif
+}
+
+// RemoveFileName "adir/" -> "adir/"
+TEST(RemoveFileNameTest, ButNoFile) {
+  EXPECT_EQ("adir" GTEST_PATH_SEP_,
+      FilePath("adir" GTEST_PATH_SEP_).RemoveFileName().string());
+}
+
+// RemoveFileName "adir/afile" -> "adir/"
+TEST(RemoveFileNameTest, GivesDirName) {
+  EXPECT_EQ("adir" GTEST_PATH_SEP_,
+            FilePath("adir" GTEST_PATH_SEP_ "afile").RemoveFileName().string());
+}
+
+// RemoveFileName "adir/subdir/afile" -> "adir/subdir/"
+TEST(RemoveFileNameTest, GivesDirAndSubDirName) {
+  EXPECT_EQ("adir" GTEST_PATH_SEP_ "subdir" GTEST_PATH_SEP_,
+      FilePath("adir" GTEST_PATH_SEP_ "subdir" GTEST_PATH_SEP_ "afile")
+      .RemoveFileName().string());
+}
+
+// RemoveFileName "/afile" -> "/"
+TEST(RemoveFileNameTest, GivesRootDir) {
+  EXPECT_EQ(GTEST_PATH_SEP_,
+      FilePath(GTEST_PATH_SEP_ "afile").RemoveFileName().string());
+}
+
+#if GTEST_HAS_ALT_PATH_SEP_
+
+// Tests that RemoveFileName() works with the alternate separator on
+// Windows.
+
+// RemoveFileName("adir/") -> "adir/"
+TEST(RemoveFileNameTest, ButNoFileForAlternateSeparator) {
+  EXPECT_EQ("adir" GTEST_PATH_SEP_,
+            FilePath("adir/").RemoveFileName().string());
+}
+
+// RemoveFileName("adir/afile") -> "adir/"
+TEST(RemoveFileNameTest, GivesDirNameForAlternateSeparator) {
+  EXPECT_EQ("adir" GTEST_PATH_SEP_,
+            FilePath("adir/afile").RemoveFileName().string());
+}
+
+// RemoveFileName("adir/subdir/afile") -> "adir/subdir/"
+TEST(RemoveFileNameTest, GivesDirAndSubDirNameForAlternateSeparator) {
+  EXPECT_EQ("adir" GTEST_PATH_SEP_ "subdir" GTEST_PATH_SEP_,
+            FilePath("adir/subdir/afile").RemoveFileName().string());
+}
+
+// RemoveFileName("/afile") -> "\"
+TEST(RemoveFileNameTest, GivesRootDirForAlternateSeparator) {
+  EXPECT_EQ(GTEST_PATH_SEP_, FilePath("/afile").RemoveFileName().string());
+}
+
+#endif
+
+TEST(MakeFileNameTest, GenerateWhenNumberIsZero) {
+  FilePath actual = FilePath::MakeFileName(FilePath("foo"), FilePath("bar"),
+      0, "xml");
+  EXPECT_EQ("foo" GTEST_PATH_SEP_ "bar.xml", actual.string());
+}
+
+TEST(MakeFileNameTest, GenerateFileNameNumberGtZero) {
+  FilePath actual = FilePath::MakeFileName(FilePath("foo"), FilePath("bar"),
+      12, "xml");
+  EXPECT_EQ("foo" GTEST_PATH_SEP_ "bar_12.xml", actual.string());
+}
+
+TEST(MakeFileNameTest, GenerateFileNameWithSlashNumberIsZero) {
+  FilePath actual = FilePath::MakeFileName(FilePath("foo" GTEST_PATH_SEP_),
+      FilePath("bar"), 0, "xml");
+  EXPECT_EQ("foo" GTEST_PATH_SEP_ "bar.xml", actual.string());
+}
+
+TEST(MakeFileNameTest, GenerateFileNameWithSlashNumberGtZero) {
+  FilePath actual = FilePath::MakeFileName(FilePath("foo" GTEST_PATH_SEP_),
+      FilePath("bar"), 12, "xml");
+  EXPECT_EQ("foo" GTEST_PATH_SEP_ "bar_12.xml", actual.string());
+}
+
+TEST(MakeFileNameTest, GenerateWhenNumberIsZeroAndDirIsEmpty) {
+  FilePath actual = FilePath::MakeFileName(FilePath(""), FilePath("bar"),
+      0, "xml");
+  EXPECT_EQ("bar.xml", actual.string());
+}
+
+TEST(MakeFileNameTest, GenerateWhenNumberIsNotZeroAndDirIsEmpty) {
+  FilePath actual = FilePath::MakeFileName(FilePath(""), FilePath("bar"),
+      14, "xml");
+  EXPECT_EQ("bar_14.xml", actual.string());
+}
+
+TEST(ConcatPathsTest, WorksWhenDirDoesNotEndWithPathSep) {
+  FilePath actual = FilePath::ConcatPaths(FilePath("foo"),
+                                          FilePath("bar.xml"));
+  EXPECT_EQ("foo" GTEST_PATH_SEP_ "bar.xml", actual.string());
+}
+
+TEST(ConcatPathsTest, WorksWhenPath1EndsWithPathSep) {
+  FilePath actual = FilePath::ConcatPaths(FilePath("foo" GTEST_PATH_SEP_),
+                                          FilePath("bar.xml"));
+  EXPECT_EQ("foo" GTEST_PATH_SEP_ "bar.xml", actual.string());
+}
+
+TEST(ConcatPathsTest, Path1BeingEmpty) {
+  FilePath actual = FilePath::ConcatPaths(FilePath(""),
+                                          FilePath("bar.xml"));
+  EXPECT_EQ("bar.xml", actual.string());
+}
+
+TEST(ConcatPathsTest, Path2BeingEmpty) {
+  FilePath actual = FilePath::ConcatPaths(FilePath("foo"), FilePath(""));
+  EXPECT_EQ("foo" GTEST_PATH_SEP_, actual.string());
+}
+
+TEST(ConcatPathsTest, BothPathBeingEmpty) {
+  FilePath actual = FilePath::ConcatPaths(FilePath(""),
+                                          FilePath(""));
+  EXPECT_EQ("", actual.string());
+}
+
+TEST(ConcatPathsTest, Path1ContainsPathSep) {
+  FilePath actual = FilePath::ConcatPaths(FilePath("foo" GTEST_PATH_SEP_ "bar"),
+                                          FilePath("foobar.xml"));
+  EXPECT_EQ("foo" GTEST_PATH_SEP_ "bar" GTEST_PATH_SEP_ "foobar.xml",
+            actual.string());
+}
+
+TEST(ConcatPathsTest, Path2ContainsPathSep) {
+  FilePath actual = FilePath::ConcatPaths(
+      FilePath("foo" GTEST_PATH_SEP_),
+      FilePath("bar" GTEST_PATH_SEP_ "bar.xml"));
+  EXPECT_EQ("foo" GTEST_PATH_SEP_ "bar" GTEST_PATH_SEP_ "bar.xml",
+            actual.string());
+}
+
+TEST(ConcatPathsTest, Path2EndsWithPathSep) {
+  FilePath actual = FilePath::ConcatPaths(FilePath("foo"),
+                                          FilePath("bar" GTEST_PATH_SEP_));
+  EXPECT_EQ("foo" GTEST_PATH_SEP_ "bar" GTEST_PATH_SEP_, actual.string());
+}
+
+// RemoveTrailingPathSeparator "" -> ""
+TEST(RemoveTrailingPathSeparatorTest, EmptyString) {
+  EXPECT_EQ("", FilePath("").RemoveTrailingPathSeparator().string());
+}
+
+// RemoveTrailingPathSeparator "foo" -> "foo"
+TEST(RemoveTrailingPathSeparatorTest, FileNoSlashString) {
+  EXPECT_EQ("foo", FilePath("foo").RemoveTrailingPathSeparator().string());
+}
+
+// RemoveTrailingPathSeparator "foo/" -> "foo"
+TEST(RemoveTrailingPathSeparatorTest, ShouldRemoveTrailingSeparator) {
+  EXPECT_EQ("foo",
+      FilePath("foo" GTEST_PATH_SEP_).RemoveTrailingPathSeparator().string());
+#if GTEST_HAS_ALT_PATH_SEP_
+  EXPECT_EQ("foo", FilePath("foo/").RemoveTrailingPathSeparator().string());
+#endif
+}
+
+// RemoveTrailingPathSeparator "foo/bar/" -> "foo/bar/"
+TEST(RemoveTrailingPathSeparatorTest, ShouldRemoveLastSeparator) {
+  EXPECT_EQ("foo" GTEST_PATH_SEP_ "bar",
+            FilePath("foo" GTEST_PATH_SEP_ "bar" GTEST_PATH_SEP_)
+                .RemoveTrailingPathSeparator().string());
+}
+
+// RemoveTrailingPathSeparator "foo/bar" -> "foo/bar"
+TEST(RemoveTrailingPathSeparatorTest, ShouldReturnUnmodified) {
+  EXPECT_EQ("foo" GTEST_PATH_SEP_ "bar",
+            FilePath("foo" GTEST_PATH_SEP_ "bar")
+                .RemoveTrailingPathSeparator().string());
+}
+
+TEST(DirectoryTest, RootDirectoryExists) {
+#if GTEST_OS_WINDOWS  // We are on Windows.
+  char current_drive[_MAX_PATH];  // NOLINT
+  current_drive[0] = static_cast<char>(_getdrive() + 'A' - 1);
+  current_drive[1] = ':';
+  current_drive[2] = '\\';
+  current_drive[3] = '\0';
+  EXPECT_TRUE(FilePath(current_drive).DirectoryExists());
+#else
+  EXPECT_TRUE(FilePath("/").DirectoryExists());
+#endif  // GTEST_OS_WINDOWS
+}
+
+#if GTEST_OS_WINDOWS
+TEST(DirectoryTest, RootOfWrongDriveDoesNotExists) {
+  const int saved_drive_ = _getdrive();
+  // Find a drive that doesn't exist. Start with 'Z' to avoid common ones.
+  for (char drive = 'Z'; drive >= 'A'; drive--)
+    if (_chdrive(drive - 'A' + 1) == -1) {
+      char non_drive[_MAX_PATH];  // NOLINT
+      non_drive[0] = drive;
+      non_drive[1] = ':';
+      non_drive[2] = '\\';
+      non_drive[3] = '\0';
+      EXPECT_FALSE(FilePath(non_drive).DirectoryExists());
+      break;
+    }
+  _chdrive(saved_drive_);
+}
+#endif  // GTEST_OS_WINDOWS
+
+#if !GTEST_OS_WINDOWS_MOBILE
+// Windows CE _does_ consider an empty directory to exist.
+TEST(DirectoryTest, EmptyPathDirectoryDoesNotExist) {
+  EXPECT_FALSE(FilePath("").DirectoryExists());
+}
+#endif  // !GTEST_OS_WINDOWS_MOBILE
+
+TEST(DirectoryTest, CurrentDirectoryExists) {
+#if GTEST_OS_WINDOWS  // We are on Windows.
+# ifndef _WIN32_CE  // Windows CE doesn't have a current directory.
+
+  EXPECT_TRUE(FilePath(".").DirectoryExists());
+  EXPECT_TRUE(FilePath(".\\").DirectoryExists());
+
+# endif  // _WIN32_CE
+#else
+  EXPECT_TRUE(FilePath(".").DirectoryExists());
+  EXPECT_TRUE(FilePath("./").DirectoryExists());
+#endif  // GTEST_OS_WINDOWS
+}
+
+// "foo/bar" == foo//bar" == "foo///bar"
+TEST(NormalizeTest, MultipleConsecutiveSepaparatorsInMidstring) {
+  EXPECT_EQ("foo" GTEST_PATH_SEP_ "bar",
+            FilePath("foo" GTEST_PATH_SEP_ "bar").string());
+  EXPECT_EQ("foo" GTEST_PATH_SEP_ "bar",
+            FilePath("foo" GTEST_PATH_SEP_ GTEST_PATH_SEP_ "bar").string());
+  EXPECT_EQ("foo" GTEST_PATH_SEP_ "bar",
+            FilePath("foo" GTEST_PATH_SEP_ GTEST_PATH_SEP_
+                     GTEST_PATH_SEP_ "bar").string());
+}
+
+// "/bar" == //bar" == "///bar"
+TEST(NormalizeTest, MultipleConsecutiveSepaparatorsAtStringStart) {
+  EXPECT_EQ(GTEST_PATH_SEP_ "bar",
+    FilePath(GTEST_PATH_SEP_ "bar").string());
+  EXPECT_EQ(GTEST_PATH_SEP_ "bar",
+    FilePath(GTEST_PATH_SEP_ GTEST_PATH_SEP_ "bar").string());
+  EXPECT_EQ(GTEST_PATH_SEP_ "bar",
+    FilePath(GTEST_PATH_SEP_ GTEST_PATH_SEP_ GTEST_PATH_SEP_ "bar").string());
+}
+
+// "foo/" == foo//" == "foo///"
+TEST(NormalizeTest, MultipleConsecutiveSepaparatorsAtStringEnd) {
+  EXPECT_EQ("foo" GTEST_PATH_SEP_,
+    FilePath("foo" GTEST_PATH_SEP_).string());
+  EXPECT_EQ("foo" GTEST_PATH_SEP_,
+    FilePath("foo" GTEST_PATH_SEP_ GTEST_PATH_SEP_).string());
+  EXPECT_EQ("foo" GTEST_PATH_SEP_,
+    FilePath("foo" GTEST_PATH_SEP_ GTEST_PATH_SEP_ GTEST_PATH_SEP_).string());
+}
+
+#if GTEST_HAS_ALT_PATH_SEP_
+
+// Tests that separators at the end of the string are normalized
+// regardless of their combination (e.g. "foo\" =="foo/\" ==
+// "foo\\/").
+TEST(NormalizeTest, MixAlternateSeparatorAtStringEnd) {
+  EXPECT_EQ("foo" GTEST_PATH_SEP_,
+            FilePath("foo/").string());
+  EXPECT_EQ("foo" GTEST_PATH_SEP_,
+            FilePath("foo" GTEST_PATH_SEP_ "/").string());
+  EXPECT_EQ("foo" GTEST_PATH_SEP_,
+            FilePath("foo//" GTEST_PATH_SEP_).string());
+}
+
+#endif
+
+TEST(AssignmentOperatorTest, DefaultAssignedToNonDefault) {
+  FilePath default_path;
+  FilePath non_default_path("path");
+  non_default_path = default_path;
+  EXPECT_EQ("", non_default_path.string());
+  EXPECT_EQ("", default_path.string());  // RHS var is unchanged.
+}
+
+TEST(AssignmentOperatorTest, NonDefaultAssignedToDefault) {
+  FilePath non_default_path("path");
+  FilePath default_path;
+  default_path = non_default_path;
+  EXPECT_EQ("path", default_path.string());
+  EXPECT_EQ("path", non_default_path.string());  // RHS var is unchanged.
+}
+
+TEST(AssignmentOperatorTest, ConstAssignedToNonConst) {
+  const FilePath const_default_path("const_path");
+  FilePath non_default_path("path");
+  non_default_path = const_default_path;
+  EXPECT_EQ("const_path", non_default_path.string());
+}
+
+class DirectoryCreationTest : public Test {
+ protected:
+  void SetUp() override {
+    testdata_path_.Set(FilePath(
+        TempDir() + GetCurrentExecutableName().string() +
+        "_directory_creation" GTEST_PATH_SEP_ "test" GTEST_PATH_SEP_));
+    testdata_file_.Set(testdata_path_.RemoveTrailingPathSeparator());
+
+    unique_file0_.Set(FilePath::MakeFileName(testdata_path_, FilePath("unique"),
+        0, "txt"));
+    unique_file1_.Set(FilePath::MakeFileName(testdata_path_, FilePath("unique"),
+        1, "txt"));
+
+    remove(testdata_file_.c_str());
+    remove(unique_file0_.c_str());
+    remove(unique_file1_.c_str());
+    posix::RmDir(testdata_path_.c_str());
+  }
+
+  void TearDown() override {
+    remove(testdata_file_.c_str());
+    remove(unique_file0_.c_str());
+    remove(unique_file1_.c_str());
+    posix::RmDir(testdata_path_.c_str());
+  }
+
+  void CreateTextFile(const char* filename) {
+    FILE* f = posix::FOpen(filename, "w");
+    fprintf(f, "text\n");
+    fclose(f);
+  }
+
+  // Strings representing a directory and a file, with identical paths
+  // except for the trailing separator character that distinquishes
+  // a directory named 'test' from a file named 'test'. Example names:
+  FilePath testdata_path_;  // "/tmp/directory_creation/test/"
+  FilePath testdata_file_;  // "/tmp/directory_creation/test"
+  FilePath unique_file0_;  // "/tmp/directory_creation/test/unique.txt"
+  FilePath unique_file1_;  // "/tmp/directory_creation/test/unique_1.txt"
+};
+
+TEST_F(DirectoryCreationTest, CreateDirectoriesRecursively) {
+  EXPECT_FALSE(testdata_path_.DirectoryExists()) << testdata_path_.string();
+  EXPECT_TRUE(testdata_path_.CreateDirectoriesRecursively());
+  EXPECT_TRUE(testdata_path_.DirectoryExists());
+}
+
+TEST_F(DirectoryCreationTest, CreateDirectoriesForAlreadyExistingPath) {
+  EXPECT_FALSE(testdata_path_.DirectoryExists()) << testdata_path_.string();
+  EXPECT_TRUE(testdata_path_.CreateDirectoriesRecursively());
+  // Call 'create' again... should still succeed.
+  EXPECT_TRUE(testdata_path_.CreateDirectoriesRecursively());
+}
+
+TEST_F(DirectoryCreationTest, CreateDirectoriesAndUniqueFilename) {
+  FilePath file_path(FilePath::GenerateUniqueFileName(testdata_path_,
+      FilePath("unique"), "txt"));
+  EXPECT_EQ(unique_file0_.string(), file_path.string());
+  EXPECT_FALSE(file_path.FileOrDirectoryExists());  // file not there
+
+  testdata_path_.CreateDirectoriesRecursively();
+  EXPECT_FALSE(file_path.FileOrDirectoryExists());  // file still not there
+  CreateTextFile(file_path.c_str());
+  EXPECT_TRUE(file_path.FileOrDirectoryExists());
+
+  FilePath file_path2(FilePath::GenerateUniqueFileName(testdata_path_,
+      FilePath("unique"), "txt"));
+  EXPECT_EQ(unique_file1_.string(), file_path2.string());
+  EXPECT_FALSE(file_path2.FileOrDirectoryExists());  // file not there
+  CreateTextFile(file_path2.c_str());
+  EXPECT_TRUE(file_path2.FileOrDirectoryExists());
+}
+
+TEST_F(DirectoryCreationTest, CreateDirectoriesFail) {
+  // force a failure by putting a file where we will try to create a directory.
+  CreateTextFile(testdata_file_.c_str());
+  EXPECT_TRUE(testdata_file_.FileOrDirectoryExists());
+  EXPECT_FALSE(testdata_file_.DirectoryExists());
+  EXPECT_FALSE(testdata_file_.CreateDirectoriesRecursively());
+}
+
+TEST(NoDirectoryCreationTest, CreateNoDirectoriesForDefaultXmlFile) {
+  const FilePath test_detail_xml("test_detail.xml");
+  EXPECT_FALSE(test_detail_xml.CreateDirectoriesRecursively());
+}
+
+TEST(FilePathTest, DefaultConstructor) {
+  FilePath fp;
+  EXPECT_EQ("", fp.string());
+}
+
+TEST(FilePathTest, CharAndCopyConstructors) {
+  const FilePath fp("spicy");
+  EXPECT_EQ("spicy", fp.string());
+
+  const FilePath fp_copy(fp);
+  EXPECT_EQ("spicy", fp_copy.string());
+}
+
+TEST(FilePathTest, StringConstructor) {
+  const FilePath fp(std::string("cider"));
+  EXPECT_EQ("cider", fp.string());
+}
+
+TEST(FilePathTest, Set) {
+  const FilePath apple("apple");
+  FilePath mac("mac");
+  mac.Set(apple);  // Implement Set() since overloading operator= is forbidden.
+  EXPECT_EQ("apple", mac.string());
+  EXPECT_EQ("apple", apple.string());
+}
+
+TEST(FilePathTest, ToString) {
+  const FilePath file("drink");
+  EXPECT_EQ("drink", file.string());
+}
+
+TEST(FilePathTest, RemoveExtension) {
+  EXPECT_EQ("app", FilePath("app.cc").RemoveExtension("cc").string());
+  EXPECT_EQ("app", FilePath("app.exe").RemoveExtension("exe").string());
+  EXPECT_EQ("APP", FilePath("APP.EXE").RemoveExtension("exe").string());
+}
+
+TEST(FilePathTest, RemoveExtensionWhenThereIsNoExtension) {
+  EXPECT_EQ("app", FilePath("app").RemoveExtension("exe").string());
+}
+
+TEST(FilePathTest, IsDirectory) {
+  EXPECT_FALSE(FilePath("cola").IsDirectory());
+  EXPECT_TRUE(FilePath("koala" GTEST_PATH_SEP_).IsDirectory());
+#if GTEST_HAS_ALT_PATH_SEP_
+  EXPECT_TRUE(FilePath("koala/").IsDirectory());
+#endif
+}
+
+TEST(FilePathTest, IsAbsolutePath) {
+  EXPECT_FALSE(FilePath("is" GTEST_PATH_SEP_ "relative").IsAbsolutePath());
+  EXPECT_FALSE(FilePath("").IsAbsolutePath());
+#if GTEST_OS_WINDOWS
+  EXPECT_TRUE(FilePath("c:\\" GTEST_PATH_SEP_ "is_not"
+                       GTEST_PATH_SEP_ "relative").IsAbsolutePath());
+  EXPECT_FALSE(FilePath("c:foo" GTEST_PATH_SEP_ "bar").IsAbsolutePath());
+  EXPECT_TRUE(FilePath("c:/" GTEST_PATH_SEP_ "is_not"
+                       GTEST_PATH_SEP_ "relative").IsAbsolutePath());
+#else
+  EXPECT_TRUE(FilePath(GTEST_PATH_SEP_ "is_not" GTEST_PATH_SEP_ "relative")
+              .IsAbsolutePath());
+#endif  // GTEST_OS_WINDOWS
+}
+
+TEST(FilePathTest, IsRootDirectory) {
+#if GTEST_OS_WINDOWS
+  EXPECT_TRUE(FilePath("a:\\").IsRootDirectory());
+  EXPECT_TRUE(FilePath("Z:/").IsRootDirectory());
+  EXPECT_TRUE(FilePath("e://").IsRootDirectory());
+  EXPECT_FALSE(FilePath("").IsRootDirectory());
+  EXPECT_FALSE(FilePath("b:").IsRootDirectory());
+  EXPECT_FALSE(FilePath("b:a").IsRootDirectory());
+  EXPECT_FALSE(FilePath("8:/").IsRootDirectory());
+  EXPECT_FALSE(FilePath("c|/").IsRootDirectory());
+#else
+  EXPECT_TRUE(FilePath("/").IsRootDirectory());
+  EXPECT_TRUE(FilePath("//").IsRootDirectory());
+  EXPECT_FALSE(FilePath("").IsRootDirectory());
+  EXPECT_FALSE(FilePath("\\").IsRootDirectory());
+  EXPECT_FALSE(FilePath("/x").IsRootDirectory());
+#endif
+}
+
+}  // namespace
+}  // namespace internal
+}  // namespace testing
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-filter-unittest.py b/leveldb_base/third_party/googletest/googletest/test/googletest-filter-unittest.py
new file mode 100644
index 0000000..6b32f2d
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-filter-unittest.py
@@ -0,0 +1,639 @@
+#!/usr/bin/env python
+#
+# Copyright 2005 Google Inc. All Rights Reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Unit test for Google Test test filters.
+
+A user can specify which test(s) in a Google Test program to run via either
+the GTEST_FILTER environment variable or the --gtest_filter flag.
+This script tests such functionality by invoking
+googletest-filter-unittest_ (a program written with Google Test) with different
+environments and command line flags.
+
+Note that test sharding may also influence which tests are filtered. Therefore,
+we test that here also.
+"""
+
+import os
+import re
+try:
+  from sets import Set as set  # For Python 2.3 compatibility
+except ImportError:
+  pass
+import sys
+import gtest_test_utils
+
+# Constants.
+
+# Checks if this platform can pass empty environment variables to child
+# processes.  We set an env variable to an empty string and invoke a python
+# script in a subprocess to print whether the variable is STILL in
+# os.environ.  We then use 'eval' to parse the child's output so that an
+# exception is thrown if the input is anything other than 'True' nor 'False'.
+CAN_PASS_EMPTY_ENV = False
+if sys.executable:
+  os.environ['EMPTY_VAR'] = ''
+  child = gtest_test_utils.Subprocess(
+      [sys.executable, '-c', 'import os; print(\'EMPTY_VAR\' in os.environ)'])
+  CAN_PASS_EMPTY_ENV = eval(child.output)
+
+
+# Check if this platform can unset environment variables in child processes.
+# We set an env variable to a non-empty string, unset it, and invoke
+# a python script in a subprocess to print whether the variable
+# is NO LONGER in os.environ.
+# We use 'eval' to parse the child's output so that an exception
+# is thrown if the input is neither 'True' nor 'False'.
+CAN_UNSET_ENV = False
+if sys.executable:
+  os.environ['UNSET_VAR'] = 'X'
+  del os.environ['UNSET_VAR']
+  child = gtest_test_utils.Subprocess(
+      [sys.executable, '-c', 'import os; print(\'UNSET_VAR\' not in os.environ)'
+      ])
+  CAN_UNSET_ENV = eval(child.output)
+
+
+# Checks if we should test with an empty filter. This doesn't
+# make sense on platforms that cannot pass empty env variables (Win32)
+# and on platforms that cannot unset variables (since we cannot tell
+# the difference between "" and NULL -- Borland and Solaris < 5.10)
+CAN_TEST_EMPTY_FILTER = (CAN_PASS_EMPTY_ENV and CAN_UNSET_ENV)
+
+
+# The environment variable for specifying the test filters.
+FILTER_ENV_VAR = 'GTEST_FILTER'
+
+# The environment variables for test sharding.
+TOTAL_SHARDS_ENV_VAR = 'GTEST_TOTAL_SHARDS'
+SHARD_INDEX_ENV_VAR = 'GTEST_SHARD_INDEX'
+SHARD_STATUS_FILE_ENV_VAR = 'GTEST_SHARD_STATUS_FILE'
+
+# The command line flag for specifying the test filters.
+FILTER_FLAG = 'gtest_filter'
+
+# The command line flag for including disabled tests.
+ALSO_RUN_DISABLED_TESTS_FLAG = 'gtest_also_run_disabled_tests'
+
+# Command to run the googletest-filter-unittest_ program.
+COMMAND = gtest_test_utils.GetTestExecutablePath('googletest-filter-unittest_')
+
+# Regex for determining whether parameterized tests are enabled in the binary.
+PARAM_TEST_REGEX = re.compile(r'/ParamTest')
+
+# Regex for parsing test case names from Google Test's output.
+TEST_CASE_REGEX = re.compile(r'^\[\-+\] \d+ tests? from (\w+(/\w+)?)')
+
+# Regex for parsing test names from Google Test's output.
+TEST_REGEX = re.compile(r'^\[\s*RUN\s*\].*\.(\w+(/\w+)?)')
+
+# The command line flag to tell Google Test to output the list of tests it
+# will run.
+LIST_TESTS_FLAG = '--gtest_list_tests'
+
+# Indicates whether Google Test supports death tests.
+SUPPORTS_DEATH_TESTS = 'HasDeathTest' in gtest_test_utils.Subprocess(
+    [COMMAND, LIST_TESTS_FLAG]).output
+
+# Full names of all tests in googletest-filter-unittests_.
+PARAM_TESTS = [
+    'SeqP/ParamTest.TestX/0',
+    'SeqP/ParamTest.TestX/1',
+    'SeqP/ParamTest.TestY/0',
+    'SeqP/ParamTest.TestY/1',
+    'SeqQ/ParamTest.TestX/0',
+    'SeqQ/ParamTest.TestX/1',
+    'SeqQ/ParamTest.TestY/0',
+    'SeqQ/ParamTest.TestY/1',
+    ]
+
+DISABLED_TESTS = [
+    'BarTest.DISABLED_TestFour',
+    'BarTest.DISABLED_TestFive',
+    'BazTest.DISABLED_TestC',
+    'DISABLED_FoobarTest.Test1',
+    'DISABLED_FoobarTest.DISABLED_Test2',
+    'DISABLED_FoobarbazTest.TestA',
+    ]
+
+if SUPPORTS_DEATH_TESTS:
+  DEATH_TESTS = [
+    'HasDeathTest.Test1',
+    'HasDeathTest.Test2',
+    ]
+else:
+  DEATH_TESTS = []
+
+# All the non-disabled tests.
+ACTIVE_TESTS = [
+    'FooTest.Abc',
+    'FooTest.Xyz',
+
+    'BarTest.TestOne',
+    'BarTest.TestTwo',
+    'BarTest.TestThree',
+
+    'BazTest.TestOne',
+    'BazTest.TestA',
+    'BazTest.TestB',
+    ] + DEATH_TESTS + PARAM_TESTS
+
+param_tests_present = None
+
+# Utilities.
+
+environ = os.environ.copy()
+
+
+def SetEnvVar(env_var, value):
+  """Sets the env variable to 'value'; unsets it when 'value' is None."""
+
+  if value is not None:
+    environ[env_var] = value
+  elif env_var in environ:
+    del environ[env_var]
+
+
+def RunAndReturnOutput(args = None):
+  """Runs the test program and returns its output."""
+
+  return gtest_test_utils.Subprocess([COMMAND] + (args or []),
+                                     env=environ).output
+
+
+def RunAndExtractTestList(args = None):
+  """Runs the test program and returns its exit code and a list of tests run."""
+
+  p = gtest_test_utils.Subprocess([COMMAND] + (args or []), env=environ)
+  tests_run = []
+  test_case = ''
+  test = ''
+  for line in p.output.split('\n'):
+    match = TEST_CASE_REGEX.match(line)
+    if match is not None:
+      test_case = match.group(1)
+    else:
+      match = TEST_REGEX.match(line)
+      if match is not None:
+        test = match.group(1)
+        tests_run.append(test_case + '.' + test)
+  return (tests_run, p.exit_code)
+
+
+def InvokeWithModifiedEnv(extra_env, function, *args, **kwargs):
+  """Runs the given function and arguments in a modified environment."""
+  try:
+    original_env = environ.copy()
+    environ.update(extra_env)
+    return function(*args, **kwargs)
+  finally:
+    environ.clear()
+    environ.update(original_env)
+
+
+def RunWithSharding(total_shards, shard_index, command):
+  """Runs a test program shard and returns exit code and a list of tests run."""
+
+  extra_env = {SHARD_INDEX_ENV_VAR: str(shard_index),
+               TOTAL_SHARDS_ENV_VAR: str(total_shards)}
+  return InvokeWithModifiedEnv(extra_env, RunAndExtractTestList, command)
+
+# The unit test.
+
+
+class GTestFilterUnitTest(gtest_test_utils.TestCase):
+  """Tests the env variable or the command line flag to filter tests."""
+
+  # Utilities.
+
+  def AssertSetEqual(self, lhs, rhs):
+    """Asserts that two sets are equal."""
+
+    for elem in lhs:
+      self.assert_(elem in rhs, '%s in %s' % (elem, rhs))
+
+    for elem in rhs:
+      self.assert_(elem in lhs, '%s in %s' % (elem, lhs))
+
+  def AssertPartitionIsValid(self, set_var, list_of_sets):
+    """Asserts that list_of_sets is a valid partition of set_var."""
+
+    full_partition = []
+    for slice_var in list_of_sets:
+      full_partition.extend(slice_var)
+    self.assertEqual(len(set_var), len(full_partition))
+    self.assertEqual(set(set_var), set(full_partition))
+
+  def AdjustForParameterizedTests(self, tests_to_run):
+    """Adjust tests_to_run in case value parameterized tests are disabled."""
+
+    global param_tests_present
+    if not param_tests_present:
+      return list(set(tests_to_run) - set(PARAM_TESTS))
+    else:
+      return tests_to_run
+
+  def RunAndVerify(self, gtest_filter, tests_to_run):
+    """Checks that the binary runs correct set of tests for a given filter."""
+
+    tests_to_run = self.AdjustForParameterizedTests(tests_to_run)
+
+    # First, tests using the environment variable.
+
+    # Windows removes empty variables from the environment when passing it
+    # to a new process.  This means it is impossible to pass an empty filter
+    # into a process using the environment variable.  However, we can still
+    # test the case when the variable is not supplied (i.e., gtest_filter is
+    # None).
+    # pylint: disable-msg=C6403
+    if CAN_TEST_EMPTY_FILTER or gtest_filter != '':
+      SetEnvVar(FILTER_ENV_VAR, gtest_filter)
+      tests_run = RunAndExtractTestList()[0]
+      SetEnvVar(FILTER_ENV_VAR, None)
+      self.AssertSetEqual(tests_run, tests_to_run)
+    # pylint: enable-msg=C6403
+
+    # Next, tests using the command line flag.
+
+    if gtest_filter is None:
+      args = []
+    else:
+      args = ['--%s=%s' % (FILTER_FLAG, gtest_filter)]
+
+    tests_run = RunAndExtractTestList(args)[0]
+    self.AssertSetEqual(tests_run, tests_to_run)
+
+  def RunAndVerifyWithSharding(self, gtest_filter, total_shards, tests_to_run,
+                               args=None, check_exit_0=False):
+    """Checks that binary runs correct tests for the given filter and shard.
+
+    Runs all shards of googletest-filter-unittest_ with the given filter, and
+    verifies that the right set of tests were run. The union of tests run
+    on each shard should be identical to tests_to_run, without duplicates.
+    If check_exit_0, .
+
+    Args:
+      gtest_filter: A filter to apply to the tests.
+      total_shards: A total number of shards to split test run into.
+      tests_to_run: A set of tests expected to run.
+      args   :      Arguments to pass to the to the test binary.
+      check_exit_0: When set to a true value, make sure that all shards
+                    return 0.
+    """
+
+    tests_to_run = self.AdjustForParameterizedTests(tests_to_run)
+
+    # Windows removes empty variables from the environment when passing it
+    # to a new process.  This means it is impossible to pass an empty filter
+    # into a process using the environment variable.  However, we can still
+    # test the case when the variable is not supplied (i.e., gtest_filter is
+    # None).
+    # pylint: disable-msg=C6403
+    if CAN_TEST_EMPTY_FILTER or gtest_filter != '':
+      SetEnvVar(FILTER_ENV_VAR, gtest_filter)
+      partition = []
+      for i in range(0, total_shards):
+        (tests_run, exit_code) = RunWithSharding(total_shards, i, args)
+        if check_exit_0:
+          self.assertEqual(0, exit_code)
+        partition.append(tests_run)
+
+      self.AssertPartitionIsValid(tests_to_run, partition)
+      SetEnvVar(FILTER_ENV_VAR, None)
+    # pylint: enable-msg=C6403
+
+  def RunAndVerifyAllowingDisabled(self, gtest_filter, tests_to_run):
+    """Checks that the binary runs correct set of tests for the given filter.
+
+    Runs googletest-filter-unittest_ with the given filter, and enables
+    disabled tests. Verifies that the right set of tests were run.
+
+    Args:
+      gtest_filter: A filter to apply to the tests.
+      tests_to_run: A set of tests expected to run.
+    """
+
+    tests_to_run = self.AdjustForParameterizedTests(tests_to_run)
+
+    # Construct the command line.
+    args = ['--%s' % ALSO_RUN_DISABLED_TESTS_FLAG]
+    if gtest_filter is not None:
+      args.append('--%s=%s' % (FILTER_FLAG, gtest_filter))
+
+    tests_run = RunAndExtractTestList(args)[0]
+    self.AssertSetEqual(tests_run, tests_to_run)
+
+  def setUp(self):
+    """Sets up test case.
+
+    Determines whether value-parameterized tests are enabled in the binary and
+    sets the flags accordingly.
+    """
+
+    global param_tests_present
+    if param_tests_present is None:
+      param_tests_present = PARAM_TEST_REGEX.search(
+          RunAndReturnOutput()) is not None
+
+  def testDefaultBehavior(self):
+    """Tests the behavior of not specifying the filter."""
+
+    self.RunAndVerify(None, ACTIVE_TESTS)
+
+  def testDefaultBehaviorWithShards(self):
+    """Tests the behavior without the filter, with sharding enabled."""
+
+    self.RunAndVerifyWithSharding(None, 1, ACTIVE_TESTS)
+    self.RunAndVerifyWithSharding(None, 2, ACTIVE_TESTS)
+    self.RunAndVerifyWithSharding(None, len(ACTIVE_TESTS) - 1, ACTIVE_TESTS)
+    self.RunAndVerifyWithSharding(None, len(ACTIVE_TESTS), ACTIVE_TESTS)
+    self.RunAndVerifyWithSharding(None, len(ACTIVE_TESTS) + 1, ACTIVE_TESTS)
+
+  def testEmptyFilter(self):
+    """Tests an empty filter."""
+
+    self.RunAndVerify('', [])
+    self.RunAndVerifyWithSharding('', 1, [])
+    self.RunAndVerifyWithSharding('', 2, [])
+
+  def testBadFilter(self):
+    """Tests a filter that matches nothing."""
+
+    self.RunAndVerify('BadFilter', [])
+    self.RunAndVerifyAllowingDisabled('BadFilter', [])
+
+  def testFullName(self):
+    """Tests filtering by full name."""
+
+    self.RunAndVerify('FooTest.Xyz', ['FooTest.Xyz'])
+    self.RunAndVerifyAllowingDisabled('FooTest.Xyz', ['FooTest.Xyz'])
+    self.RunAndVerifyWithSharding('FooTest.Xyz', 5, ['FooTest.Xyz'])
+
+  def testUniversalFilters(self):
+    """Tests filters that match everything."""
+
+    self.RunAndVerify('*', ACTIVE_TESTS)
+    self.RunAndVerify('*.*', ACTIVE_TESTS)
+    self.RunAndVerifyWithSharding('*.*', len(ACTIVE_TESTS) - 3, ACTIVE_TESTS)
+    self.RunAndVerifyAllowingDisabled('*', ACTIVE_TESTS + DISABLED_TESTS)
+    self.RunAndVerifyAllowingDisabled('*.*', ACTIVE_TESTS + DISABLED_TESTS)
+
+  def testFilterByTestCase(self):
+    """Tests filtering by test case name."""
+
+    self.RunAndVerify('FooTest.*', ['FooTest.Abc', 'FooTest.Xyz'])
+
+    BAZ_TESTS = ['BazTest.TestOne', 'BazTest.TestA', 'BazTest.TestB']
+    self.RunAndVerify('BazTest.*', BAZ_TESTS)
+    self.RunAndVerifyAllowingDisabled('BazTest.*',
+                                      BAZ_TESTS + ['BazTest.DISABLED_TestC'])
+
+  def testFilterByTest(self):
+    """Tests filtering by test name."""
+
+    self.RunAndVerify('*.TestOne', ['BarTest.TestOne', 'BazTest.TestOne'])
+
+  def testFilterDisabledTests(self):
+    """Select only the disabled tests to run."""
+
+    self.RunAndVerify('DISABLED_FoobarTest.Test1', [])
+    self.RunAndVerifyAllowingDisabled('DISABLED_FoobarTest.Test1',
+                                      ['DISABLED_FoobarTest.Test1'])
+
+    self.RunAndVerify('*DISABLED_*', [])
+    self.RunAndVerifyAllowingDisabled('*DISABLED_*', DISABLED_TESTS)
+
+    self.RunAndVerify('*.DISABLED_*', [])
+    self.RunAndVerifyAllowingDisabled('*.DISABLED_*', [
+        'BarTest.DISABLED_TestFour',
+        'BarTest.DISABLED_TestFive',
+        'BazTest.DISABLED_TestC',
+        'DISABLED_FoobarTest.DISABLED_Test2',
+        ])
+
+    self.RunAndVerify('DISABLED_*', [])
+    self.RunAndVerifyAllowingDisabled('DISABLED_*', [
+        'DISABLED_FoobarTest.Test1',
+        'DISABLED_FoobarTest.DISABLED_Test2',
+        'DISABLED_FoobarbazTest.TestA',
+        ])
+
+  def testWildcardInTestCaseName(self):
+    """Tests using wildcard in the test case name."""
+
+    self.RunAndVerify('*a*.*', [
+        'BarTest.TestOne',
+        'BarTest.TestTwo',
+        'BarTest.TestThree',
+
+        'BazTest.TestOne',
+        'BazTest.TestA',
+        'BazTest.TestB', ] + DEATH_TESTS + PARAM_TESTS)
+
+  def testWildcardInTestName(self):
+    """Tests using wildcard in the test name."""
+
+    self.RunAndVerify('*.*A*', ['FooTest.Abc', 'BazTest.TestA'])
+
+  def testFilterWithoutDot(self):
+    """Tests a filter that has no '.' in it."""
+
+    self.RunAndVerify('*z*', [
+        'FooTest.Xyz',
+
+        'BazTest.TestOne',
+        'BazTest.TestA',
+        'BazTest.TestB',
+        ])
+
+  def testTwoPatterns(self):
+    """Tests filters that consist of two patterns."""
+
+    self.RunAndVerify('Foo*.*:*A*', [
+        'FooTest.Abc',
+        'FooTest.Xyz',
+
+        'BazTest.TestA',
+        ])
+
+    # An empty pattern + a non-empty one
+    self.RunAndVerify(':*A*', ['FooTest.Abc', 'BazTest.TestA'])
+
+  def testThreePatterns(self):
+    """Tests filters that consist of three patterns."""
+
+    self.RunAndVerify('*oo*:*A*:*One', [
+        'FooTest.Abc',
+        'FooTest.Xyz',
+
+        'BarTest.TestOne',
+
+        'BazTest.TestOne',
+        'BazTest.TestA',
+        ])
+
+    # The 2nd pattern is empty.
+    self.RunAndVerify('*oo*::*One', [
+        'FooTest.Abc',
+        'FooTest.Xyz',
+
+        'BarTest.TestOne',
+
+        'BazTest.TestOne',
+        ])
+
+    # The last 2 patterns are empty.
+    self.RunAndVerify('*oo*::', [
+        'FooTest.Abc',
+        'FooTest.Xyz',
+        ])
+
+  def testNegativeFilters(self):
+    self.RunAndVerify('*-BazTest.TestOne', [
+        'FooTest.Abc',
+        'FooTest.Xyz',
+
+        'BarTest.TestOne',
+        'BarTest.TestTwo',
+        'BarTest.TestThree',
+
+        'BazTest.TestA',
+        'BazTest.TestB',
+        ] + DEATH_TESTS + PARAM_TESTS)
+
+    self.RunAndVerify('*-FooTest.Abc:BazTest.*', [
+        'FooTest.Xyz',
+
+        'BarTest.TestOne',
+        'BarTest.TestTwo',
+        'BarTest.TestThree',
+        ] + DEATH_TESTS + PARAM_TESTS)
+
+    self.RunAndVerify('BarTest.*-BarTest.TestOne', [
+        'BarTest.TestTwo',
+        'BarTest.TestThree',
+        ])
+
+    # Tests without leading '*'.
+    self.RunAndVerify('-FooTest.Abc:FooTest.Xyz:BazTest.*', [
+        'BarTest.TestOne',
+        'BarTest.TestTwo',
+        'BarTest.TestThree',
+        ] + DEATH_TESTS + PARAM_TESTS)
+
+    # Value parameterized tests.
+    self.RunAndVerify('*/*', PARAM_TESTS)
+
+    # Value parameterized tests filtering by the sequence name.
+    self.RunAndVerify('SeqP/*', [
+        'SeqP/ParamTest.TestX/0',
+        'SeqP/ParamTest.TestX/1',
+        'SeqP/ParamTest.TestY/0',
+        'SeqP/ParamTest.TestY/1',
+        ])
+
+    # Value parameterized tests filtering by the test name.
+    self.RunAndVerify('*/0', [
+        'SeqP/ParamTest.TestX/0',
+        'SeqP/ParamTest.TestY/0',
+        'SeqQ/ParamTest.TestX/0',
+        'SeqQ/ParamTest.TestY/0',
+        ])
+
+  def testFlagOverridesEnvVar(self):
+    """Tests that the filter flag overrides the filtering env. variable."""
+
+    SetEnvVar(FILTER_ENV_VAR, 'Foo*')
+    args = ['--%s=%s' % (FILTER_FLAG, '*One')]
+    tests_run = RunAndExtractTestList(args)[0]
+    SetEnvVar(FILTER_ENV_VAR, None)
+
+    self.AssertSetEqual(tests_run, ['BarTest.TestOne', 'BazTest.TestOne'])
+
+  def testShardStatusFileIsCreated(self):
+    """Tests that the shard file is created if specified in the environment."""
+
+    shard_status_file = os.path.join(gtest_test_utils.GetTempDir(),
+                                     'shard_status_file')
+    self.assert_(not os.path.exists(shard_status_file))
+
+    extra_env = {SHARD_STATUS_FILE_ENV_VAR: shard_status_file}
+    try:
+      InvokeWithModifiedEnv(extra_env, RunAndReturnOutput)
+    finally:
+      self.assert_(os.path.exists(shard_status_file))
+      os.remove(shard_status_file)
+
+  def testShardStatusFileIsCreatedWithListTests(self):
+    """Tests that the shard file is created with the "list_tests" flag."""
+
+    shard_status_file = os.path.join(gtest_test_utils.GetTempDir(),
+                                     'shard_status_file2')
+    self.assert_(not os.path.exists(shard_status_file))
+
+    extra_env = {SHARD_STATUS_FILE_ENV_VAR: shard_status_file}
+    try:
+      output = InvokeWithModifiedEnv(extra_env,
+                                     RunAndReturnOutput,
+                                     [LIST_TESTS_FLAG])
+    finally:
+      # This assertion ensures that Google Test enumerated the tests as
+      # opposed to running them.
+      self.assert_('[==========]' not in output,
+                   'Unexpected output during test enumeration.\n'
+                   'Please ensure that LIST_TESTS_FLAG is assigned the\n'
+                   'correct flag value for listing Google Test tests.')
+
+      self.assert_(os.path.exists(shard_status_file))
+      os.remove(shard_status_file)
+
+  if SUPPORTS_DEATH_TESTS:
+    def testShardingWorksWithDeathTests(self):
+      """Tests integration with death tests and sharding."""
+
+      gtest_filter = 'HasDeathTest.*:SeqP/*'
+      expected_tests = [
+          'HasDeathTest.Test1',
+          'HasDeathTest.Test2',
+
+          'SeqP/ParamTest.TestX/0',
+          'SeqP/ParamTest.TestX/1',
+          'SeqP/ParamTest.TestY/0',
+          'SeqP/ParamTest.TestY/1',
+          ]
+
+      for flag in ['--gtest_death_test_style=threadsafe',
+                   '--gtest_death_test_style=fast']:
+        self.RunAndVerifyWithSharding(gtest_filter, 3, expected_tests,
+                                      check_exit_0=True, args=[flag])
+        self.RunAndVerifyWithSharding(gtest_filter, 5, expected_tests,
+                                      check_exit_0=True, args=[flag])
+
+if __name__ == '__main__':
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-filter-unittest_.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-filter-unittest_.cc
new file mode 100644
index 0000000..d30ec9c
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-filter-unittest_.cc
@@ -0,0 +1,137 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Unit test for Google Test test filters.
+//
+// A user can specify which test(s) in a Google Test program to run via
+// either the GTEST_FILTER environment variable or the --gtest_filter
+// flag.  This is used for testing such functionality.
+//
+// The program will be invoked from a Python unit test.  Don't run it
+// directly.
+
+#include "gtest/gtest.h"
+
+namespace {
+
+// Test case FooTest.
+
+class FooTest : public testing::Test {
+};
+
+TEST_F(FooTest, Abc) {
+}
+
+TEST_F(FooTest, Xyz) {
+  FAIL() << "Expected failure.";
+}
+
+// Test case BarTest.
+
+TEST(BarTest, TestOne) {
+}
+
+TEST(BarTest, TestTwo) {
+}
+
+TEST(BarTest, TestThree) {
+}
+
+TEST(BarTest, DISABLED_TestFour) {
+  FAIL() << "Expected failure.";
+}
+
+TEST(BarTest, DISABLED_TestFive) {
+  FAIL() << "Expected failure.";
+}
+
+// Test case BazTest.
+
+TEST(BazTest, TestOne) {
+  FAIL() << "Expected failure.";
+}
+
+TEST(BazTest, TestA) {
+}
+
+TEST(BazTest, TestB) {
+}
+
+TEST(BazTest, DISABLED_TestC) {
+  FAIL() << "Expected failure.";
+}
+
+// Test case HasDeathTest
+
+TEST(HasDeathTest, Test1) {
+  EXPECT_DEATH_IF_SUPPORTED(exit(1), ".*");
+}
+
+// We need at least two death tests to make sure that the all death tests
+// aren't on the first shard.
+TEST(HasDeathTest, Test2) {
+  EXPECT_DEATH_IF_SUPPORTED(exit(1), ".*");
+}
+
+// Test case FoobarTest
+
+TEST(DISABLED_FoobarTest, Test1) {
+  FAIL() << "Expected failure.";
+}
+
+TEST(DISABLED_FoobarTest, DISABLED_Test2) {
+  FAIL() << "Expected failure.";
+}
+
+// Test case FoobarbazTest
+
+TEST(DISABLED_FoobarbazTest, TestA) {
+  FAIL() << "Expected failure.";
+}
+
+class ParamTest : public testing::TestWithParam<int> {
+};
+
+TEST_P(ParamTest, TestX) {
+}
+
+TEST_P(ParamTest, TestY) {
+}
+
+INSTANTIATE_TEST_SUITE_P(SeqP, ParamTest, testing::Values(1, 2));
+INSTANTIATE_TEST_SUITE_P(SeqQ, ParamTest, testing::Values(5, 6));
+
+}  // namespace
+
+int main(int argc, char **argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+
+  return RUN_ALL_TESTS();
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-global-environment-unittest.py b/leveldb_base/third_party/googletest/googletest/test/googletest-global-environment-unittest.py
new file mode 100644
index 0000000..32ba628
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-global-environment-unittest.py
@@ -0,0 +1,72 @@
+# Copyright 2021 Google Inc. All Rights Reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+"""Unit test for Google Test's global test environment behavior.
+
+A user can specify a global test environment via
+testing::AddGlobalTestEnvironment. Failures in the global environment should
+result in all unit tests being skipped.
+
+This script tests such functionality by invoking
+googletest-global-environment-unittest_ (a program written with Google Test).
+"""
+
+import gtest_test_utils
+
+
+def RunAndReturnOutput():
+  """Runs the test program and returns its output."""
+
+  return gtest_test_utils.Subprocess([
+      gtest_test_utils.GetTestExecutablePath(
+          'googletest-global-environment-unittest_')
+  ]).output
+
+
+class GTestGlobalEnvironmentUnitTest(gtest_test_utils.TestCase):
+  """Tests global test environment failures."""
+
+  def testEnvironmentSetUpFails(self):
+    """Tests the behavior of not specifying the fail_fast."""
+
+    # Run the test.
+    txt = RunAndReturnOutput()
+
+    # We should see the text of the global environment setup error.
+    self.assertIn('Canned environment setup error', txt)
+
+    # Our test should have been skipped due to the error, and not treated as a
+    # pass.
+    self.assertIn('[  SKIPPED ] 1 test', txt)
+    self.assertIn('[  PASSED  ] 0 tests', txt)
+
+    # The test case shouldn't have been run.
+    self.assertNotIn('Unexpected call', txt)
+
+
+if __name__ == '__main__':
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-global-environment-unittest_.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-global-environment-unittest_.cc
new file mode 100644
index 0000000..f401b2f
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-global-environment-unittest_.cc
@@ -0,0 +1,58 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Unit test for Google Test global test environments.
+//
+// The program will be invoked from a Python unit test.  Don't run it
+// directly.
+
+#include "gtest/gtest.h"
+
+namespace {
+
+// An environment that always fails in its SetUp method.
+class FailingEnvironment final : public ::testing::Environment {
+ public:
+  void SetUp() override { FAIL() << "Canned environment setup error"; }
+};
+
+// Register the environment.
+auto* const g_environment_ =
+    ::testing::AddGlobalTestEnvironment(new FailingEnvironment);
+
+// A test that doesn't actually run.
+TEST(SomeTest, DoesFoo) { FAIL() << "Unexpected call"; }
+
+}  // namespace
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+
+  return RUN_ALL_TESTS();
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-json-outfiles-test.py b/leveldb_base/third_party/googletest/googletest/test/googletest-json-outfiles-test.py
new file mode 100644
index 0000000..8ef47b8
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-json-outfiles-test.py
@@ -0,0 +1,191 @@
+#!/usr/bin/env python
+# Copyright 2018, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Unit test for the gtest_json_output module."""
+
+import json
+import os
+import gtest_json_test_utils
+import gtest_test_utils
+
+GTEST_OUTPUT_SUBDIR = 'json_outfiles'
+GTEST_OUTPUT_1_TEST = 'gtest_xml_outfile1_test_'
+GTEST_OUTPUT_2_TEST = 'gtest_xml_outfile2_test_'
+
+EXPECTED_1 = {
+    u'tests':
+        1,
+    u'failures':
+        0,
+    u'disabled':
+        0,
+    u'errors':
+        0,
+    u'time':
+        u'*',
+    u'timestamp':
+        u'*',
+    u'name':
+        u'AllTests',
+    u'testsuites': [{
+        u'name':
+            u'PropertyOne',
+        u'tests':
+            1,
+        u'failures':
+            0,
+        u'disabled':
+            0,
+        u'errors':
+            0,
+        u'time':
+            u'*',
+        u'timestamp':
+            u'*',
+        u'testsuite': [{
+            u'name': u'TestSomeProperties',
+            u'status': u'RUN',
+            u'result': u'COMPLETED',
+            u'time': u'*',
+            u'timestamp': u'*',
+            u'classname': u'PropertyOne',
+            u'SetUpProp': u'1',
+            u'TestSomeProperty': u'1',
+            u'TearDownProp': u'1',
+        }],
+    }],
+}
+
+EXPECTED_2 = {
+    u'tests':
+        1,
+    u'failures':
+        0,
+    u'disabled':
+        0,
+    u'errors':
+        0,
+    u'time':
+        u'*',
+    u'timestamp':
+        u'*',
+    u'name':
+        u'AllTests',
+    u'testsuites': [{
+        u'name':
+            u'PropertyTwo',
+        u'tests':
+            1,
+        u'failures':
+            0,
+        u'disabled':
+            0,
+        u'errors':
+            0,
+        u'time':
+            u'*',
+        u'timestamp':
+            u'*',
+        u'testsuite': [{
+            u'name': u'TestSomeProperties',
+            u'status': u'RUN',
+            u'result': u'COMPLETED',
+            u'timestamp': u'*',
+            u'time': u'*',
+            u'classname': u'PropertyTwo',
+            u'SetUpProp': u'2',
+            u'TestSomeProperty': u'2',
+            u'TearDownProp': u'2',
+        }],
+    }],
+}
+
+
+class GTestJsonOutFilesTest(gtest_test_utils.TestCase):
+  """Unit test for Google Test's JSON output functionality."""
+
+  def setUp(self):
+    # We want the trailing '/' that the last "" provides in os.path.join, for
+    # telling Google Test to create an output directory instead of a single file
+    # for xml output.
+    self.output_dir_ = os.path.join(gtest_test_utils.GetTempDir(),
+                                    GTEST_OUTPUT_SUBDIR, '')
+    self.DeleteFilesAndDir()
+
+  def tearDown(self):
+    self.DeleteFilesAndDir()
+
+  def DeleteFilesAndDir(self):
+    try:
+      os.remove(os.path.join(self.output_dir_, GTEST_OUTPUT_1_TEST + '.json'))
+    except os.error:
+      pass
+    try:
+      os.remove(os.path.join(self.output_dir_, GTEST_OUTPUT_2_TEST + '.json'))
+    except os.error:
+      pass
+    try:
+      os.rmdir(self.output_dir_)
+    except os.error:
+      pass
+
+  def testOutfile1(self):
+    self._TestOutFile(GTEST_OUTPUT_1_TEST, EXPECTED_1)
+
+  def testOutfile2(self):
+    self._TestOutFile(GTEST_OUTPUT_2_TEST, EXPECTED_2)
+
+  def _TestOutFile(self, test_name, expected):
+    gtest_prog_path = gtest_test_utils.GetTestExecutablePath(test_name)
+    command = [gtest_prog_path, '--gtest_output=json:%s' % self.output_dir_]
+    p = gtest_test_utils.Subprocess(command,
+                                    working_dir=gtest_test_utils.GetTempDir())
+    self.assert_(p.exited)
+    self.assertEquals(0, p.exit_code)
+
+    output_file_name1 = test_name + '.json'
+    output_file1 = os.path.join(self.output_dir_, output_file_name1)
+    output_file_name2 = 'lt-' + output_file_name1
+    output_file2 = os.path.join(self.output_dir_, output_file_name2)
+    self.assert_(os.path.isfile(output_file1) or os.path.isfile(output_file2),
+                 output_file1)
+
+    if os.path.isfile(output_file1):
+      with open(output_file1) as f:
+        actual = json.load(f)
+    else:
+      with open(output_file2) as f:
+        actual = json.load(f)
+    self.assertEqual(expected, gtest_json_test_utils.normalize(actual))
+
+
+if __name__ == '__main__':
+  os.environ['GTEST_STACK_TRACE_DEPTH'] = '0'
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-json-output-unittest.py b/leveldb_base/third_party/googletest/googletest/test/googletest-json-output-unittest.py
new file mode 100644
index 0000000..41c8565
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-json-output-unittest.py
@@ -0,0 +1,848 @@
+#!/usr/bin/env python
+# Copyright 2018, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Unit test for the gtest_json_output module."""
+
+import datetime
+import errno
+import json
+import os
+import re
+import sys
+
+import gtest_json_test_utils
+import gtest_test_utils
+
+GTEST_FILTER_FLAG = '--gtest_filter'
+GTEST_LIST_TESTS_FLAG = '--gtest_list_tests'
+GTEST_OUTPUT_FLAG = '--gtest_output'
+GTEST_DEFAULT_OUTPUT_FILE = 'test_detail.json'
+GTEST_PROGRAM_NAME = 'gtest_xml_output_unittest_'
+
+# The flag indicating stacktraces are not supported
+NO_STACKTRACE_SUPPORT_FLAG = '--no_stacktrace_support'
+
+SUPPORTS_STACK_TRACES = NO_STACKTRACE_SUPPORT_FLAG not in sys.argv
+
+if SUPPORTS_STACK_TRACES:
+  STACK_TRACE_TEMPLATE = '\nStack trace:\n*'
+else:
+  STACK_TRACE_TEMPLATE = ''
+
+EXPECTED_NON_EMPTY = {
+    u'tests':
+        26,
+    u'failures':
+        5,
+    u'disabled':
+        2,
+    u'errors':
+        0,
+    u'timestamp':
+        u'*',
+    u'time':
+        u'*',
+    u'ad_hoc_property':
+        u'42',
+    u'name':
+        u'AllTests',
+    u'testsuites': [{
+        u'name':
+            u'SuccessfulTest',
+        u'tests':
+            1,
+        u'failures':
+            0,
+        u'disabled':
+            0,
+        u'errors':
+            0,
+        u'time':
+            u'*',
+        u'timestamp':
+            u'*',
+        u'testsuite': [{
+            u'name': u'Succeeds',
+            u'status': u'RUN',
+            u'result': u'COMPLETED',
+            u'time': u'*',
+            u'timestamp': u'*',
+            u'classname': u'SuccessfulTest'
+        }]
+    }, {
+        u'name':
+            u'FailedTest',
+        u'tests':
+            1,
+        u'failures':
+            1,
+        u'disabled':
+            0,
+        u'errors':
+            0,
+        u'time':
+            u'*',
+        u'timestamp':
+            u'*',
+        u'testsuite': [{
+            u'name':
+                u'Fails',
+            u'status':
+                u'RUN',
+            u'result':
+                u'COMPLETED',
+            u'time':
+                u'*',
+            u'timestamp':
+                u'*',
+            u'classname':
+                u'FailedTest',
+            u'failures': [{
+                u'failure': u'gtest_xml_output_unittest_.cc:*\n'
+                            u'Expected equality of these values:\n'
+                            u'  1\n  2' + STACK_TRACE_TEMPLATE,
+                u'type': u''
+            }]
+        }]
+    }, {
+        u'name':
+            u'DisabledTest',
+        u'tests':
+            1,
+        u'failures':
+            0,
+        u'disabled':
+            1,
+        u'errors':
+            0,
+        u'time':
+            u'*',
+        u'timestamp':
+            u'*',
+        u'testsuite': [{
+            u'name': u'DISABLED_test_not_run',
+            u'status': u'NOTRUN',
+            u'result': u'SUPPRESSED',
+            u'time': u'*',
+            u'timestamp': u'*',
+            u'classname': u'DisabledTest'
+        }]
+    }, {
+        u'name':
+            u'SkippedTest',
+        u'tests':
+            3,
+        u'failures':
+            1,
+        u'disabled':
+            0,
+        u'errors':
+            0,
+        u'time':
+            u'*',
+        u'timestamp':
+            u'*',
+        u'testsuite': [{
+            u'name': u'Skipped',
+            u'status': u'RUN',
+            u'result': u'SKIPPED',
+            u'time': u'*',
+            u'timestamp': u'*',
+            u'classname': u'SkippedTest'
+        }, {
+            u'name': u'SkippedWithMessage',
+            u'status': u'RUN',
+            u'result': u'SKIPPED',
+            u'time': u'*',
+            u'timestamp': u'*',
+            u'classname': u'SkippedTest'
+        }, {
+            u'name':
+                u'SkippedAfterFailure',
+            u'status':
+                u'RUN',
+            u'result':
+                u'COMPLETED',
+            u'time':
+                u'*',
+            u'timestamp':
+                u'*',
+            u'classname':
+                u'SkippedTest',
+            u'failures': [{
+                u'failure': u'gtest_xml_output_unittest_.cc:*\n'
+                            u'Expected equality of these values:\n'
+                            u'  1\n  2' + STACK_TRACE_TEMPLATE,
+                u'type': u''
+            }]
+        }]
+    }, {
+        u'name':
+            u'MixedResultTest',
+        u'tests':
+            3,
+        u'failures':
+            1,
+        u'disabled':
+            1,
+        u'errors':
+            0,
+        u'time':
+            u'*',
+        u'timestamp':
+            u'*',
+        u'testsuite': [{
+            u'name': u'Succeeds',
+            u'status': u'RUN',
+            u'result': u'COMPLETED',
+            u'time': u'*',
+            u'timestamp': u'*',
+            u'classname': u'MixedResultTest'
+        }, {
+            u'name':
+                u'Fails',
+            u'status':
+                u'RUN',
+            u'result':
+                u'COMPLETED',
+            u'time':
+                u'*',
+            u'timestamp':
+                u'*',
+            u'classname':
+                u'MixedResultTest',
+            u'failures': [{
+                u'failure': u'gtest_xml_output_unittest_.cc:*\n'
+                            u'Expected equality of these values:\n'
+                            u'  1\n  2' + STACK_TRACE_TEMPLATE,
+                u'type': u''
+            }, {
+                u'failure': u'gtest_xml_output_unittest_.cc:*\n'
+                            u'Expected equality of these values:\n'
+                            u'  2\n  3' + STACK_TRACE_TEMPLATE,
+                u'type': u''
+            }]
+        }, {
+            u'name': u'DISABLED_test',
+            u'status': u'NOTRUN',
+            u'result': u'SUPPRESSED',
+            u'time': u'*',
+            u'timestamp': u'*',
+            u'classname': u'MixedResultTest'
+        }]
+    }, {
+        u'name':
+            u'XmlQuotingTest',
+        u'tests':
+            1,
+        u'failures':
+            1,
+        u'disabled':
+            0,
+        u'errors':
+            0,
+        u'time':
+            u'*',
+        u'timestamp':
+            u'*',
+        u'testsuite': [{
+            u'name':
+                u'OutputsCData',
+            u'status':
+                u'RUN',
+            u'result':
+                u'COMPLETED',
+            u'time':
+                u'*',
+            u'timestamp':
+                u'*',
+            u'classname':
+                u'XmlQuotingTest',
+            u'failures': [{
+                u'failure': u'gtest_xml_output_unittest_.cc:*\n'
+                            u'Failed\nXML output: <?xml encoding="utf-8">'
+                            u'<top><![CDATA[cdata text]]></top>' +
+                            STACK_TRACE_TEMPLATE,
+                u'type': u''
+            }]
+        }]
+    }, {
+        u'name':
+            u'InvalidCharactersTest',
+        u'tests':
+            1,
+        u'failures':
+            1,
+        u'disabled':
+            0,
+        u'errors':
+            0,
+        u'time':
+            u'*',
+        u'timestamp':
+            u'*',
+        u'testsuite': [{
+            u'name':
+                u'InvalidCharactersInMessage',
+            u'status':
+                u'RUN',
+            u'result':
+                u'COMPLETED',
+            u'time':
+                u'*',
+            u'timestamp':
+                u'*',
+            u'classname':
+                u'InvalidCharactersTest',
+            u'failures': [{
+                u'failure': u'gtest_xml_output_unittest_.cc:*\n'
+                            u'Failed\nInvalid characters in brackets'
+                            u' [\x01\x02]' + STACK_TRACE_TEMPLATE,
+                u'type': u''
+            }]
+        }]
+    }, {
+        u'name':
+            u'PropertyRecordingTest',
+        u'tests':
+            4,
+        u'failures':
+            0,
+        u'disabled':
+            0,
+        u'errors':
+            0,
+        u'time':
+            u'*',
+        u'timestamp':
+            u'*',
+        u'SetUpTestSuite':
+            u'yes',
+        u'TearDownTestSuite':
+            u'aye',
+        u'testsuite': [{
+            u'name': u'OneProperty',
+            u'status': u'RUN',
+            u'result': u'COMPLETED',
+            u'time': u'*',
+            u'timestamp': u'*',
+            u'classname': u'PropertyRecordingTest',
+            u'key_1': u'1'
+        }, {
+            u'name': u'IntValuedProperty',
+            u'status': u'RUN',
+            u'result': u'COMPLETED',
+            u'time': u'*',
+            u'timestamp': u'*',
+            u'classname': u'PropertyRecordingTest',
+            u'key_int': u'1'
+        }, {
+            u'name': u'ThreeProperties',
+            u'status': u'RUN',
+            u'result': u'COMPLETED',
+            u'time': u'*',
+            u'timestamp': u'*',
+            u'classname': u'PropertyRecordingTest',
+            u'key_1': u'1',
+            u'key_2': u'2',
+            u'key_3': u'3'
+        }, {
+            u'name': u'TwoValuesForOneKeyUsesLastValue',
+            u'status': u'RUN',
+            u'result': u'COMPLETED',
+            u'time': u'*',
+            u'timestamp': u'*',
+            u'classname': u'PropertyRecordingTest',
+            u'key_1': u'2'
+        }]
+    }, {
+        u'name':
+            u'NoFixtureTest',
+        u'tests':
+            3,
+        u'failures':
+            0,
+        u'disabled':
+            0,
+        u'errors':
+            0,
+        u'time':
+            u'*',
+        u'timestamp':
+            u'*',
+        u'testsuite': [{
+            u'name': u'RecordProperty',
+            u'status': u'RUN',
+            u'result': u'COMPLETED',
+            u'time': u'*',
+            u'timestamp': u'*',
+            u'classname': u'NoFixtureTest',
+            u'key': u'1'
+        }, {
+            u'name': u'ExternalUtilityThatCallsRecordIntValuedProperty',
+            u'status': u'RUN',
+            u'result': u'COMPLETED',
+            u'time': u'*',
+            u'timestamp': u'*',
+            u'classname': u'NoFixtureTest',
+            u'key_for_utility_int': u'1'
+        }, {
+            u'name': u'ExternalUtilityThatCallsRecordStringValuedProperty',
+            u'status': u'RUN',
+            u'result': u'COMPLETED',
+            u'time': u'*',
+            u'timestamp': u'*',
+            u'classname': u'NoFixtureTest',
+            u'key_for_utility_string': u'1'
+        }]
+    }, {
+        u'name':
+            u'TypedTest/0',
+        u'tests':
+            1,
+        u'failures':
+            0,
+        u'disabled':
+            0,
+        u'errors':
+            0,
+        u'time':
+            u'*',
+        u'timestamp':
+            u'*',
+        u'testsuite': [{
+            u'name': u'HasTypeParamAttribute',
+            u'type_param': u'int',
+            u'status': u'RUN',
+            u'result': u'COMPLETED',
+            u'time': u'*',
+            u'timestamp': u'*',
+            u'classname': u'TypedTest/0'
+        }]
+    }, {
+        u'name':
+            u'TypedTest/1',
+        u'tests':
+            1,
+        u'failures':
+            0,
+        u'disabled':
+            0,
+        u'errors':
+            0,
+        u'time':
+            u'*',
+        u'timestamp':
+            u'*',
+        u'testsuite': [{
+            u'name': u'HasTypeParamAttribute',
+            u'type_param': u'long',
+            u'status': u'RUN',
+            u'result': u'COMPLETED',
+            u'time': u'*',
+            u'timestamp': u'*',
+            u'classname': u'TypedTest/1'
+        }]
+    }, {
+        u'name':
+            u'Single/TypeParameterizedTestSuite/0',
+        u'tests':
+            1,
+        u'failures':
+            0,
+        u'disabled':
+            0,
+        u'errors':
+            0,
+        u'time':
+            u'*',
+        u'timestamp':
+            u'*',
+        u'testsuite': [{
+            u'name': u'HasTypeParamAttribute',
+            u'type_param': u'int',
+            u'status': u'RUN',
+            u'result': u'COMPLETED',
+            u'time': u'*',
+            u'timestamp': u'*',
+            u'classname': u'Single/TypeParameterizedTestSuite/0'
+        }]
+    }, {
+        u'name':
+            u'Single/TypeParameterizedTestSuite/1',
+        u'tests':
+            1,
+        u'failures':
+            0,
+        u'disabled':
+            0,
+        u'errors':
+            0,
+        u'time':
+            u'*',
+        u'timestamp':
+            u'*',
+        u'testsuite': [{
+            u'name': u'HasTypeParamAttribute',
+            u'type_param': u'long',
+            u'status': u'RUN',
+            u'result': u'COMPLETED',
+            u'time': u'*',
+            u'timestamp': u'*',
+            u'classname': u'Single/TypeParameterizedTestSuite/1'
+        }]
+    }, {
+        u'name':
+            u'Single/ValueParamTest',
+        u'tests':
+            4,
+        u'failures':
+            0,
+        u'disabled':
+            0,
+        u'errors':
+            0,
+        u'time':
+            u'*',
+        u'timestamp':
+            u'*',
+        u'testsuite': [{
+            u'name': u'HasValueParamAttribute/0',
+            u'value_param': u'33',
+            u'status': u'RUN',
+            u'result': u'COMPLETED',
+            u'time': u'*',
+            u'timestamp': u'*',
+            u'classname': u'Single/ValueParamTest'
+        }, {
+            u'name': u'HasValueParamAttribute/1',
+            u'value_param': u'42',
+            u'status': u'RUN',
+            u'result': u'COMPLETED',
+            u'time': u'*',
+            u'timestamp': u'*',
+            u'classname': u'Single/ValueParamTest'
+        }, {
+            u'name': u'AnotherTestThatHasValueParamAttribute/0',
+            u'value_param': u'33',
+            u'status': u'RUN',
+            u'result': u'COMPLETED',
+            u'time': u'*',
+            u'timestamp': u'*',
+            u'classname': u'Single/ValueParamTest'
+        }, {
+            u'name': u'AnotherTestThatHasValueParamAttribute/1',
+            u'value_param': u'42',
+            u'status': u'RUN',
+            u'result': u'COMPLETED',
+            u'time': u'*',
+            u'timestamp': u'*',
+            u'classname': u'Single/ValueParamTest'
+        }]
+    }]
+}
+
+EXPECTED_FILTERED = {
+    u'tests':
+        1,
+    u'failures':
+        0,
+    u'disabled':
+        0,
+    u'errors':
+        0,
+    u'time':
+        u'*',
+    u'timestamp':
+        u'*',
+    u'name':
+        u'AllTests',
+    u'ad_hoc_property':
+        u'42',
+    u'testsuites': [{
+        u'name':
+            u'SuccessfulTest',
+        u'tests':
+            1,
+        u'failures':
+            0,
+        u'disabled':
+            0,
+        u'errors':
+            0,
+        u'time':
+            u'*',
+        u'timestamp':
+            u'*',
+        u'testsuite': [{
+            u'name': u'Succeeds',
+            u'status': u'RUN',
+            u'result': u'COMPLETED',
+            u'time': u'*',
+            u'timestamp': u'*',
+            u'classname': u'SuccessfulTest',
+        }]
+    }],
+}
+
+EXPECTED_NO_TEST = {
+    u'tests':
+        0,
+    u'failures':
+        0,
+    u'disabled':
+        0,
+    u'errors':
+        0,
+    u'time':
+        u'*',
+    u'timestamp':
+        u'*',
+    u'name':
+        u'AllTests',
+    u'testsuites': [{
+        u'name':
+            u'NonTestSuiteFailure',
+        u'tests':
+            1,
+        u'failures':
+            1,
+        u'disabled':
+            0,
+        u'skipped':
+            0,
+        u'errors':
+            0,
+        u'time':
+            u'*',
+        u'timestamp':
+            u'*',
+        u'testsuite': [{
+            u'name':
+                u'',
+            u'status':
+                u'RUN',
+            u'result':
+                u'COMPLETED',
+            u'time':
+                u'*',
+            u'timestamp':
+                u'*',
+            u'classname':
+                u'',
+            u'failures': [{
+                u'failure': u'gtest_no_test_unittest.cc:*\n'
+                            u'Expected equality of these values:\n'
+                            u'  1\n  2' + STACK_TRACE_TEMPLATE,
+                u'type': u'',
+            }]
+        }]
+    }],
+}
+
+GTEST_PROGRAM_PATH = gtest_test_utils.GetTestExecutablePath(GTEST_PROGRAM_NAME)
+
+SUPPORTS_TYPED_TESTS = 'TypedTest' in gtest_test_utils.Subprocess(
+    [GTEST_PROGRAM_PATH, GTEST_LIST_TESTS_FLAG], capture_stderr=False).output
+
+
+class GTestJsonOutputUnitTest(gtest_test_utils.TestCase):
+  """Unit test for Google Test's JSON output functionality.
+  """
+
+  # This test currently breaks on platforms that do not support typed and
+  # type-parameterized tests, so we don't run it under them.
+  if SUPPORTS_TYPED_TESTS:
+
+    def testNonEmptyJsonOutput(self):
+      """Verifies JSON output for a Google Test binary with non-empty output.
+
+      Runs a test program that generates a non-empty JSON output, and
+      tests that the JSON output is expected.
+      """
+      self._TestJsonOutput(GTEST_PROGRAM_NAME, EXPECTED_NON_EMPTY, 1)
+
+  def testNoTestJsonOutput(self):
+    """Verifies JSON output for a Google Test binary without actual tests.
+
+    Runs a test program that generates an JSON output for a binary with no
+    tests, and tests that the JSON output is expected.
+    """
+
+    self._TestJsonOutput('gtest_no_test_unittest', EXPECTED_NO_TEST, 0)
+
+  def testTimestampValue(self):
+    """Checks whether the timestamp attribute in the JSON output is valid.
+
+    Runs a test program that generates an empty JSON output, and checks if
+    the timestamp attribute in the testsuites tag is valid.
+    """
+    actual = self._GetJsonOutput('gtest_no_test_unittest', [], 0)
+    date_time_str = actual['timestamp']
+    # datetime.strptime() is only available in Python 2.5+ so we have to
+    # parse the expected datetime manually.
+    match = re.match(r'(\d+)-(\d\d)-(\d\d)T(\d\d):(\d\d):(\d\d)', date_time_str)
+    self.assertTrue(
+        re.match,
+        'JSON datettime string %s has incorrect format' % date_time_str)
+    date_time_from_json = datetime.datetime(
+        year=int(match.group(1)), month=int(match.group(2)),
+        day=int(match.group(3)), hour=int(match.group(4)),
+        minute=int(match.group(5)), second=int(match.group(6)))
+
+    time_delta = abs(datetime.datetime.now() - date_time_from_json)
+    # timestamp value should be near the current local time
+    self.assertTrue(time_delta < datetime.timedelta(seconds=600),
+                    'time_delta is %s' % time_delta)
+
+  def testDefaultOutputFile(self):
+    """Verifies the default output file name.
+
+    Confirms that Google Test produces an JSON output file with the expected
+    default name if no name is explicitly specified.
+    """
+    output_file = os.path.join(gtest_test_utils.GetTempDir(),
+                               GTEST_DEFAULT_OUTPUT_FILE)
+    gtest_prog_path = gtest_test_utils.GetTestExecutablePath(
+        'gtest_no_test_unittest')
+    try:
+      os.remove(output_file)
+    except OSError:
+      e = sys.exc_info()[1]
+      if e.errno != errno.ENOENT:
+        raise
+
+    p = gtest_test_utils.Subprocess(
+        [gtest_prog_path, '%s=json' % GTEST_OUTPUT_FLAG],
+        working_dir=gtest_test_utils.GetTempDir())
+    self.assert_(p.exited)
+    self.assertEquals(0, p.exit_code)
+    self.assert_(os.path.isfile(output_file))
+
+  def testSuppressedJsonOutput(self):
+    """Verifies that no JSON output is generated.
+
+    Tests that no JSON file is generated if the default JSON listener is
+    shut down before RUN_ALL_TESTS is invoked.
+    """
+
+    json_path = os.path.join(gtest_test_utils.GetTempDir(),
+                             GTEST_PROGRAM_NAME + 'out.json')
+    if os.path.isfile(json_path):
+      os.remove(json_path)
+
+    command = [GTEST_PROGRAM_PATH,
+               '%s=json:%s' % (GTEST_OUTPUT_FLAG, json_path),
+               '--shut_down_xml']
+    p = gtest_test_utils.Subprocess(command)
+    if p.terminated_by_signal:
+      # p.signal is available only if p.terminated_by_signal is True.
+      self.assertFalse(
+          p.terminated_by_signal,
+          '%s was killed by signal %d' % (GTEST_PROGRAM_NAME, p.signal))
+    else:
+      self.assert_(p.exited)
+      self.assertEquals(1, p.exit_code,
+                        "'%s' exited with code %s, which doesn't match "
+                        'the expected exit code %s.'
+                        % (command, p.exit_code, 1))
+
+    self.assert_(not os.path.isfile(json_path))
+
+  def testFilteredTestJsonOutput(self):
+    """Verifies JSON output when a filter is applied.
+
+    Runs a test program that executes only some tests and verifies that
+    non-selected tests do not show up in the JSON output.
+    """
+
+    self._TestJsonOutput(GTEST_PROGRAM_NAME, EXPECTED_FILTERED, 0,
+                         extra_args=['%s=SuccessfulTest.*' % GTEST_FILTER_FLAG])
+
+  def _GetJsonOutput(self, gtest_prog_name, extra_args, expected_exit_code):
+    """Returns the JSON output generated by running the program gtest_prog_name.
+
+    Furthermore, the program's exit code must be expected_exit_code.
+
+    Args:
+      gtest_prog_name: Google Test binary name.
+      extra_args: extra arguments to binary invocation.
+      expected_exit_code: program's exit code.
+    """
+    json_path = os.path.join(gtest_test_utils.GetTempDir(),
+                             gtest_prog_name + 'out.json')
+    gtest_prog_path = gtest_test_utils.GetTestExecutablePath(gtest_prog_name)
+
+    command = (
+        [gtest_prog_path, '%s=json:%s' % (GTEST_OUTPUT_FLAG, json_path)] +
+        extra_args
+    )
+    p = gtest_test_utils.Subprocess(command)
+    if p.terminated_by_signal:
+      self.assert_(False,
+                   '%s was killed by signal %d' % (gtest_prog_name, p.signal))
+    else:
+      self.assert_(p.exited)
+      self.assertEquals(expected_exit_code, p.exit_code,
+                        "'%s' exited with code %s, which doesn't match "
+                        'the expected exit code %s.'
+                        % (command, p.exit_code, expected_exit_code))
+    with open(json_path) as f:
+      actual = json.load(f)
+    return actual
+
+  def _TestJsonOutput(self, gtest_prog_name, expected,
+                      expected_exit_code, extra_args=None):
+    """Checks the JSON output generated by the Google Test binary.
+
+    Asserts that the JSON document generated by running the program
+    gtest_prog_name matches expected_json, a string containing another
+    JSON document.  Furthermore, the program's exit code must be
+    expected_exit_code.
+
+    Args:
+      gtest_prog_name: Google Test binary name.
+      expected: expected output.
+      expected_exit_code: program's exit code.
+      extra_args: extra arguments to binary invocation.
+    """
+
+    actual = self._GetJsonOutput(gtest_prog_name, extra_args or [],
+                                 expected_exit_code)
+    self.assertEqual(expected, gtest_json_test_utils.normalize(actual))
+
+
+if __name__ == '__main__':
+  if NO_STACKTRACE_SUPPORT_FLAG in sys.argv:
+    # unittest.main() can't handle unknown flags
+    sys.argv.remove(NO_STACKTRACE_SUPPORT_FLAG)
+
+  os.environ['GTEST_STACK_TRACE_DEPTH'] = '1'
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-list-tests-unittest.py b/leveldb_base/third_party/googletest/googletest/test/googletest-list-tests-unittest.py
new file mode 100644
index 0000000..81423a3
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-list-tests-unittest.py
@@ -0,0 +1,205 @@
+#!/usr/bin/env python
+#
+# Copyright 2006, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Unit test for Google Test's --gtest_list_tests flag.
+
+A user can ask Google Test to list all tests by specifying the
+--gtest_list_tests flag.  This script tests such functionality
+by invoking googletest-list-tests-unittest_ (a program written with
+Google Test) the command line flags.
+"""
+
+import re
+import gtest_test_utils
+
+# Constants.
+
+# The command line flag for enabling/disabling listing all tests.
+LIST_TESTS_FLAG = 'gtest_list_tests'
+
+# Path to the googletest-list-tests-unittest_ program.
+EXE_PATH = gtest_test_utils.GetTestExecutablePath('googletest-list-tests-unittest_')
+
+# The expected output when running googletest-list-tests-unittest_ with
+# --gtest_list_tests
+EXPECTED_OUTPUT_NO_FILTER_RE = re.compile(r"""FooDeathTest\.
+  Test1
+Foo\.
+  Bar1
+  Bar2
+  DISABLED_Bar3
+Abc\.
+  Xyz
+  Def
+FooBar\.
+  Baz
+FooTest\.
+  Test1
+  DISABLED_Test2
+  Test3
+TypedTest/0\.  # TypeParam = (VeryLo{245}|class VeryLo{239})\.\.\.
+  TestA
+  TestB
+TypedTest/1\.  # TypeParam = int\s*\*( __ptr64)?
+  TestA
+  TestB
+TypedTest/2\.  # TypeParam = .*MyArray<bool,\s*42>
+  TestA
+  TestB
+My/TypeParamTest/0\.  # TypeParam = (VeryLo{245}|class VeryLo{239})\.\.\.
+  TestA
+  TestB
+My/TypeParamTest/1\.  # TypeParam = int\s*\*( __ptr64)?
+  TestA
+  TestB
+My/TypeParamTest/2\.  # TypeParam = .*MyArray<bool,\s*42>
+  TestA
+  TestB
+MyInstantiation/ValueParamTest\.
+  TestA/0  # GetParam\(\) = one line
+  TestA/1  # GetParam\(\) = two\\nlines
+  TestA/2  # GetParam\(\) = a very\\nlo{241}\.\.\.
+  TestB/0  # GetParam\(\) = one line
+  TestB/1  # GetParam\(\) = two\\nlines
+  TestB/2  # GetParam\(\) = a very\\nlo{241}\.\.\.
+""")
+
+# The expected output when running googletest-list-tests-unittest_ with
+# --gtest_list_tests and --gtest_filter=Foo*.
+EXPECTED_OUTPUT_FILTER_FOO_RE = re.compile(r"""FooDeathTest\.
+  Test1
+Foo\.
+  Bar1
+  Bar2
+  DISABLED_Bar3
+FooBar\.
+  Baz
+FooTest\.
+  Test1
+  DISABLED_Test2
+  Test3
+""")
+
+# Utilities.
+
+
+def Run(args):
+  """Runs googletest-list-tests-unittest_ and returns the list of tests printed."""
+
+  return gtest_test_utils.Subprocess([EXE_PATH] + args,
+                                     capture_stderr=False).output
+
+
+# The unit test.
+
+
+class GTestListTestsUnitTest(gtest_test_utils.TestCase):
+  """Tests using the --gtest_list_tests flag to list all tests."""
+
+  def RunAndVerify(self, flag_value, expected_output_re, other_flag):
+    """Runs googletest-list-tests-unittest_ and verifies that it prints
+    the correct tests.
+
+    Args:
+      flag_value:         value of the --gtest_list_tests flag;
+                          None if the flag should not be present.
+      expected_output_re: regular expression that matches the expected
+                          output after running command;
+      other_flag:         a different flag to be passed to command
+                          along with gtest_list_tests;
+                          None if the flag should not be present.
+    """
+
+    if flag_value is None:
+      flag = ''
+      flag_expression = 'not set'
+    elif flag_value == '0':
+      flag = '--%s=0' % LIST_TESTS_FLAG
+      flag_expression = '0'
+    else:
+      flag = '--%s' % LIST_TESTS_FLAG
+      flag_expression = '1'
+
+    args = [flag]
+
+    if other_flag is not None:
+      args += [other_flag]
+
+    output = Run(args)
+
+    if expected_output_re:
+      self.assert_(
+          expected_output_re.match(output),
+          ('when %s is %s, the output of "%s" is "%s",\n'
+           'which does not match regex "%s"' %
+           (LIST_TESTS_FLAG, flag_expression, ' '.join(args), output,
+            expected_output_re.pattern)))
+    else:
+      self.assert_(
+          not EXPECTED_OUTPUT_NO_FILTER_RE.match(output),
+          ('when %s is %s, the output of "%s" is "%s"'%
+           (LIST_TESTS_FLAG, flag_expression, ' '.join(args), output)))
+
+  def testDefaultBehavior(self):
+    """Tests the behavior of the default mode."""
+
+    self.RunAndVerify(flag_value=None,
+                      expected_output_re=None,
+                      other_flag=None)
+
+  def testFlag(self):
+    """Tests using the --gtest_list_tests flag."""
+
+    self.RunAndVerify(flag_value='0',
+                      expected_output_re=None,
+                      other_flag=None)
+    self.RunAndVerify(flag_value='1',
+                      expected_output_re=EXPECTED_OUTPUT_NO_FILTER_RE,
+                      other_flag=None)
+
+  def testOverrideNonFilterFlags(self):
+    """Tests that --gtest_list_tests overrides the non-filter flags."""
+
+    self.RunAndVerify(flag_value='1',
+                      expected_output_re=EXPECTED_OUTPUT_NO_FILTER_RE,
+                      other_flag='--gtest_break_on_failure')
+
+  def testWithFilterFlags(self):
+    """Tests that --gtest_list_tests takes into account the
+    --gtest_filter flag."""
+
+    self.RunAndVerify(flag_value='1',
+                      expected_output_re=EXPECTED_OUTPUT_FILTER_FOO_RE,
+                      other_flag='--gtest_filter=Foo*')
+
+
+if __name__ == '__main__':
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-list-tests-unittest_.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-list-tests-unittest_.cc
new file mode 100644
index 0000000..493c6f0
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-list-tests-unittest_.cc
@@ -0,0 +1,156 @@
+// Copyright 2006, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Unit test for Google Test's --gtest_list_tests flag.
+//
+// A user can ask Google Test to list all tests that will run
+// so that when using a filter, a user will know what
+// tests to look for. The tests will not be run after listing.
+//
+// This program will be invoked from a Python unit test.
+// Don't run it directly.
+
+#include "gtest/gtest.h"
+
+// Several different test cases and tests that will be listed.
+TEST(Foo, Bar1) {
+}
+
+TEST(Foo, Bar2) {
+}
+
+TEST(Foo, DISABLED_Bar3) {
+}
+
+TEST(Abc, Xyz) {
+}
+
+TEST(Abc, Def) {
+}
+
+TEST(FooBar, Baz) {
+}
+
+class FooTest : public testing::Test {
+};
+
+TEST_F(FooTest, Test1) {
+}
+
+TEST_F(FooTest, DISABLED_Test2) {
+}
+
+TEST_F(FooTest, Test3) {
+}
+
+TEST(FooDeathTest, Test1) {
+}
+
+// A group of value-parameterized tests.
+
+class MyType {
+ public:
+  explicit MyType(const std::string& a_value) : value_(a_value) {}
+
+  const std::string& value() const { return value_; }
+
+ private:
+  std::string value_;
+};
+
+// Teaches Google Test how to print a MyType.
+void PrintTo(const MyType& x, std::ostream* os) {
+  *os << x.value();
+}
+
+class ValueParamTest : public testing::TestWithParam<MyType> {
+};
+
+TEST_P(ValueParamTest, TestA) {
+}
+
+TEST_P(ValueParamTest, TestB) {
+}
+
+INSTANTIATE_TEST_SUITE_P(
+    MyInstantiation, ValueParamTest,
+    testing::Values(MyType("one line"),
+                    MyType("two\nlines"),
+                    MyType("a very\nloooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong line")));  // NOLINT
+
+// A group of typed tests.
+
+// A deliberately long type name for testing the line-truncating
+// behavior when printing a type parameter.
+class VeryLoooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooogName {  // NOLINT
+};
+
+template <typename T>
+class TypedTest : public testing::Test {
+};
+
+template <typename T, int kSize>
+class MyArray {
+};
+
+typedef testing::Types<VeryLoooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooogName,  // NOLINT
+                       int*, MyArray<bool, 42> > MyTypes;
+
+TYPED_TEST_SUITE(TypedTest, MyTypes);
+
+TYPED_TEST(TypedTest, TestA) {
+}
+
+TYPED_TEST(TypedTest, TestB) {
+}
+
+// A group of type-parameterized tests.
+
+template <typename T>
+class TypeParamTest : public testing::Test {
+};
+
+TYPED_TEST_SUITE_P(TypeParamTest);
+
+TYPED_TEST_P(TypeParamTest, TestA) {
+}
+
+TYPED_TEST_P(TypeParamTest, TestB) {
+}
+
+REGISTER_TYPED_TEST_SUITE_P(TypeParamTest, TestA, TestB);
+
+INSTANTIATE_TYPED_TEST_SUITE_P(My, TypeParamTest, MyTypes);
+
+int main(int argc, char **argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+
+  return RUN_ALL_TESTS();
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-listener-test.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-listener-test.cc
new file mode 100644
index 0000000..10457af
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-listener-test.cc
@@ -0,0 +1,518 @@
+// Copyright 2009 Google Inc. All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// The Google C++ Testing and Mocking Framework (Google Test)
+//
+// This file verifies Google Test event listeners receive events at the
+// right times.
+
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "gtest/internal/custom/gtest.h"
+
+using ::testing::AddGlobalTestEnvironment;
+using ::testing::Environment;
+using ::testing::InitGoogleTest;
+using ::testing::Test;
+using ::testing::TestSuite;
+using ::testing::TestEventListener;
+using ::testing::TestInfo;
+using ::testing::TestPartResult;
+using ::testing::UnitTest;
+
+// Used by tests to register their events.
+std::vector<std::string>* g_events = nullptr;
+
+namespace testing {
+namespace internal {
+
+class EventRecordingListener : public TestEventListener {
+ public:
+  explicit EventRecordingListener(const char* name) : name_(name) {}
+
+ protected:
+  void OnTestProgramStart(const UnitTest& /*unit_test*/) override {
+    g_events->push_back(GetFullMethodName("OnTestProgramStart"));
+  }
+
+  void OnTestIterationStart(const UnitTest& /*unit_test*/,
+                            int iteration) override {
+    Message message;
+    message << GetFullMethodName("OnTestIterationStart")
+            << "(" << iteration << ")";
+    g_events->push_back(message.GetString());
+  }
+
+  void OnEnvironmentsSetUpStart(const UnitTest& /*unit_test*/) override {
+    g_events->push_back(GetFullMethodName("OnEnvironmentsSetUpStart"));
+  }
+
+  void OnEnvironmentsSetUpEnd(const UnitTest& /*unit_test*/) override {
+    g_events->push_back(GetFullMethodName("OnEnvironmentsSetUpEnd"));
+  }
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  void OnTestCaseStart(const TestCase& /*test_case*/) override {
+    g_events->push_back(GetFullMethodName("OnTestCaseStart"));
+  }
+#endif  // GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+  void OnTestStart(const TestInfo& /*test_info*/) override {
+    g_events->push_back(GetFullMethodName("OnTestStart"));
+  }
+
+  void OnTestPartResult(const TestPartResult& /*test_part_result*/) override {
+    g_events->push_back(GetFullMethodName("OnTestPartResult"));
+  }
+
+  void OnTestEnd(const TestInfo& /*test_info*/) override {
+    g_events->push_back(GetFullMethodName("OnTestEnd"));
+  }
+
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+  void OnTestCaseEnd(const TestCase& /*test_case*/) override {
+    g_events->push_back(GetFullMethodName("OnTestCaseEnd"));
+  }
+#endif  // GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+  void OnEnvironmentsTearDownStart(const UnitTest& /*unit_test*/) override {
+    g_events->push_back(GetFullMethodName("OnEnvironmentsTearDownStart"));
+  }
+
+  void OnEnvironmentsTearDownEnd(const UnitTest& /*unit_test*/) override {
+    g_events->push_back(GetFullMethodName("OnEnvironmentsTearDownEnd"));
+  }
+
+  void OnTestIterationEnd(const UnitTest& /*unit_test*/,
+                          int iteration) override {
+    Message message;
+    message << GetFullMethodName("OnTestIterationEnd")
+            << "("  << iteration << ")";
+    g_events->push_back(message.GetString());
+  }
+
+  void OnTestProgramEnd(const UnitTest& /*unit_test*/) override {
+    g_events->push_back(GetFullMethodName("OnTestProgramEnd"));
+  }
+
+ private:
+  std::string GetFullMethodName(const char* name) {
+    return name_ + "." + name;
+  }
+
+  std::string name_;
+};
+
+// This listener is using OnTestSuiteStart, OnTestSuiteEnd API
+class EventRecordingListener2 : public TestEventListener {
+ public:
+  explicit EventRecordingListener2(const char* name) : name_(name) {}
+
+ protected:
+  void OnTestProgramStart(const UnitTest& /*unit_test*/) override {
+    g_events->push_back(GetFullMethodName("OnTestProgramStart"));
+  }
+
+  void OnTestIterationStart(const UnitTest& /*unit_test*/,
+                            int iteration) override {
+    Message message;
+    message << GetFullMethodName("OnTestIterationStart") << "(" << iteration
+            << ")";
+    g_events->push_back(message.GetString());
+  }
+
+  void OnEnvironmentsSetUpStart(const UnitTest& /*unit_test*/) override {
+    g_events->push_back(GetFullMethodName("OnEnvironmentsSetUpStart"));
+  }
+
+  void OnEnvironmentsSetUpEnd(const UnitTest& /*unit_test*/) override {
+    g_events->push_back(GetFullMethodName("OnEnvironmentsSetUpEnd"));
+  }
+
+  void OnTestSuiteStart(const TestSuite& /*test_suite*/) override {
+    g_events->push_back(GetFullMethodName("OnTestSuiteStart"));
+  }
+
+  void OnTestStart(const TestInfo& /*test_info*/) override {
+    g_events->push_back(GetFullMethodName("OnTestStart"));
+  }
+
+  void OnTestPartResult(const TestPartResult& /*test_part_result*/) override {
+    g_events->push_back(GetFullMethodName("OnTestPartResult"));
+  }
+
+  void OnTestEnd(const TestInfo& /*test_info*/) override {
+    g_events->push_back(GetFullMethodName("OnTestEnd"));
+  }
+
+  void OnTestSuiteEnd(const TestSuite& /*test_suite*/) override {
+    g_events->push_back(GetFullMethodName("OnTestSuiteEnd"));
+  }
+
+  void OnEnvironmentsTearDownStart(const UnitTest& /*unit_test*/) override {
+    g_events->push_back(GetFullMethodName("OnEnvironmentsTearDownStart"));
+  }
+
+  void OnEnvironmentsTearDownEnd(const UnitTest& /*unit_test*/) override {
+    g_events->push_back(GetFullMethodName("OnEnvironmentsTearDownEnd"));
+  }
+
+  void OnTestIterationEnd(const UnitTest& /*unit_test*/,
+                          int iteration) override {
+    Message message;
+    message << GetFullMethodName("OnTestIterationEnd") << "(" << iteration
+            << ")";
+    g_events->push_back(message.GetString());
+  }
+
+  void OnTestProgramEnd(const UnitTest& /*unit_test*/) override {
+    g_events->push_back(GetFullMethodName("OnTestProgramEnd"));
+  }
+
+ private:
+  std::string GetFullMethodName(const char* name) { return name_ + "." + name; }
+
+  std::string name_;
+};
+
+class EnvironmentInvocationCatcher : public Environment {
+ protected:
+  void SetUp() override { g_events->push_back("Environment::SetUp"); }
+
+  void TearDown() override { g_events->push_back("Environment::TearDown"); }
+};
+
+class ListenerTest : public Test {
+ protected:
+  static void SetUpTestSuite() {
+    g_events->push_back("ListenerTest::SetUpTestSuite");
+  }
+
+  static void TearDownTestSuite() {
+    g_events->push_back("ListenerTest::TearDownTestSuite");
+  }
+
+  void SetUp() override { g_events->push_back("ListenerTest::SetUp"); }
+
+  void TearDown() override { g_events->push_back("ListenerTest::TearDown"); }
+};
+
+TEST_F(ListenerTest, DoesFoo) {
+  // Test execution order within a test case is not guaranteed so we are not
+  // recording the test name.
+  g_events->push_back("ListenerTest::* Test Body");
+  SUCCEED();  // Triggers OnTestPartResult.
+}
+
+TEST_F(ListenerTest, DoesBar) {
+  g_events->push_back("ListenerTest::* Test Body");
+  SUCCEED();  // Triggers OnTestPartResult.
+}
+
+}  // namespace internal
+
+}  // namespace testing
+
+using ::testing::internal::EnvironmentInvocationCatcher;
+using ::testing::internal::EventRecordingListener;
+using ::testing::internal::EventRecordingListener2;
+
+void VerifyResults(const std::vector<std::string>& data,
+                   const char* const* expected_data,
+                   size_t expected_data_size) {
+  const size_t actual_size = data.size();
+  // If the following assertion fails, a new entry will be appended to
+  // data.  Hence we save data.size() first.
+  EXPECT_EQ(expected_data_size, actual_size);
+
+  // Compares the common prefix.
+  const size_t shorter_size = expected_data_size <= actual_size ?
+      expected_data_size : actual_size;
+  size_t i = 0;
+  for (; i < shorter_size; ++i) {
+    ASSERT_STREQ(expected_data[i], data[i].c_str())
+        << "at position " << i;
+  }
+
+  // Prints extra elements in the actual data.
+  for (; i < actual_size; ++i) {
+    printf("  Actual event #%lu: %s\n",
+        static_cast<unsigned long>(i), data[i].c_str());
+  }
+}
+
+int main(int argc, char **argv) {
+  std::vector<std::string> events;
+  g_events = &events;
+  InitGoogleTest(&argc, argv);
+
+  UnitTest::GetInstance()->listeners().Append(
+      new EventRecordingListener("1st"));
+  UnitTest::GetInstance()->listeners().Append(
+      new EventRecordingListener("2nd"));
+  UnitTest::GetInstance()->listeners().Append(
+      new EventRecordingListener2("3rd"));
+
+  AddGlobalTestEnvironment(new EnvironmentInvocationCatcher);
+
+  GTEST_CHECK_(events.size() == 0)
+      << "AddGlobalTestEnvironment should not generate any events itself.";
+
+  ::testing::GTEST_FLAG(repeat) = 2;
+  int ret_val = RUN_ALL_TESTS();
+
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+  // The deprecated OnTestSuiteStart/OnTestCaseStart events are included
+  const char* const expected_events[] = {"1st.OnTestProgramStart",
+                                         "2nd.OnTestProgramStart",
+                                         "3rd.OnTestProgramStart",
+                                         "1st.OnTestIterationStart(0)",
+                                         "2nd.OnTestIterationStart(0)",
+                                         "3rd.OnTestIterationStart(0)",
+                                         "1st.OnEnvironmentsSetUpStart",
+                                         "2nd.OnEnvironmentsSetUpStart",
+                                         "3rd.OnEnvironmentsSetUpStart",
+                                         "Environment::SetUp",
+                                         "3rd.OnEnvironmentsSetUpEnd",
+                                         "2nd.OnEnvironmentsSetUpEnd",
+                                         "1st.OnEnvironmentsSetUpEnd",
+                                         "3rd.OnTestSuiteStart",
+                                         "1st.OnTestCaseStart",
+                                         "2nd.OnTestCaseStart",
+                                         "ListenerTest::SetUpTestSuite",
+                                         "1st.OnTestStart",
+                                         "2nd.OnTestStart",
+                                         "3rd.OnTestStart",
+                                         "ListenerTest::SetUp",
+                                         "ListenerTest::* Test Body",
+                                         "1st.OnTestPartResult",
+                                         "2nd.OnTestPartResult",
+                                         "3rd.OnTestPartResult",
+                                         "ListenerTest::TearDown",
+                                         "3rd.OnTestEnd",
+                                         "2nd.OnTestEnd",
+                                         "1st.OnTestEnd",
+                                         "1st.OnTestStart",
+                                         "2nd.OnTestStart",
+                                         "3rd.OnTestStart",
+                                         "ListenerTest::SetUp",
+                                         "ListenerTest::* Test Body",
+                                         "1st.OnTestPartResult",
+                                         "2nd.OnTestPartResult",
+                                         "3rd.OnTestPartResult",
+                                         "ListenerTest::TearDown",
+                                         "3rd.OnTestEnd",
+                                         "2nd.OnTestEnd",
+                                         "1st.OnTestEnd",
+                                         "ListenerTest::TearDownTestSuite",
+                                         "3rd.OnTestSuiteEnd",
+                                         "2nd.OnTestCaseEnd",
+                                         "1st.OnTestCaseEnd",
+                                         "1st.OnEnvironmentsTearDownStart",
+                                         "2nd.OnEnvironmentsTearDownStart",
+                                         "3rd.OnEnvironmentsTearDownStart",
+                                         "Environment::TearDown",
+                                         "3rd.OnEnvironmentsTearDownEnd",
+                                         "2nd.OnEnvironmentsTearDownEnd",
+                                         "1st.OnEnvironmentsTearDownEnd",
+                                         "3rd.OnTestIterationEnd(0)",
+                                         "2nd.OnTestIterationEnd(0)",
+                                         "1st.OnTestIterationEnd(0)",
+                                         "1st.OnTestIterationStart(1)",
+                                         "2nd.OnTestIterationStart(1)",
+                                         "3rd.OnTestIterationStart(1)",
+                                         "1st.OnEnvironmentsSetUpStart",
+                                         "2nd.OnEnvironmentsSetUpStart",
+                                         "3rd.OnEnvironmentsSetUpStart",
+                                         "Environment::SetUp",
+                                         "3rd.OnEnvironmentsSetUpEnd",
+                                         "2nd.OnEnvironmentsSetUpEnd",
+                                         "1st.OnEnvironmentsSetUpEnd",
+                                         "3rd.OnTestSuiteStart",
+                                         "1st.OnTestCaseStart",
+                                         "2nd.OnTestCaseStart",
+                                         "ListenerTest::SetUpTestSuite",
+                                         "1st.OnTestStart",
+                                         "2nd.OnTestStart",
+                                         "3rd.OnTestStart",
+                                         "ListenerTest::SetUp",
+                                         "ListenerTest::* Test Body",
+                                         "1st.OnTestPartResult",
+                                         "2nd.OnTestPartResult",
+                                         "3rd.OnTestPartResult",
+                                         "ListenerTest::TearDown",
+                                         "3rd.OnTestEnd",
+                                         "2nd.OnTestEnd",
+                                         "1st.OnTestEnd",
+                                         "1st.OnTestStart",
+                                         "2nd.OnTestStart",
+                                         "3rd.OnTestStart",
+                                         "ListenerTest::SetUp",
+                                         "ListenerTest::* Test Body",
+                                         "1st.OnTestPartResult",
+                                         "2nd.OnTestPartResult",
+                                         "3rd.OnTestPartResult",
+                                         "ListenerTest::TearDown",
+                                         "3rd.OnTestEnd",
+                                         "2nd.OnTestEnd",
+                                         "1st.OnTestEnd",
+                                         "ListenerTest::TearDownTestSuite",
+                                         "3rd.OnTestSuiteEnd",
+                                         "2nd.OnTestCaseEnd",
+                                         "1st.OnTestCaseEnd",
+                                         "1st.OnEnvironmentsTearDownStart",
+                                         "2nd.OnEnvironmentsTearDownStart",
+                                         "3rd.OnEnvironmentsTearDownStart",
+                                         "Environment::TearDown",
+                                         "3rd.OnEnvironmentsTearDownEnd",
+                                         "2nd.OnEnvironmentsTearDownEnd",
+                                         "1st.OnEnvironmentsTearDownEnd",
+                                         "3rd.OnTestIterationEnd(1)",
+                                         "2nd.OnTestIterationEnd(1)",
+                                         "1st.OnTestIterationEnd(1)",
+                                         "3rd.OnTestProgramEnd",
+                                         "2nd.OnTestProgramEnd",
+                                         "1st.OnTestProgramEnd"};
+#else
+  const char* const expected_events[] = {"1st.OnTestProgramStart",
+                                         "2nd.OnTestProgramStart",
+                                         "3rd.OnTestProgramStart",
+                                         "1st.OnTestIterationStart(0)",
+                                         "2nd.OnTestIterationStart(0)",
+                                         "3rd.OnTestIterationStart(0)",
+                                         "1st.OnEnvironmentsSetUpStart",
+                                         "2nd.OnEnvironmentsSetUpStart",
+                                         "3rd.OnEnvironmentsSetUpStart",
+                                         "Environment::SetUp",
+                                         "3rd.OnEnvironmentsSetUpEnd",
+                                         "2nd.OnEnvironmentsSetUpEnd",
+                                         "1st.OnEnvironmentsSetUpEnd",
+                                         "3rd.OnTestSuiteStart",
+                                         "ListenerTest::SetUpTestSuite",
+                                         "1st.OnTestStart",
+                                         "2nd.OnTestStart",
+                                         "3rd.OnTestStart",
+                                         "ListenerTest::SetUp",
+                                         "ListenerTest::* Test Body",
+                                         "1st.OnTestPartResult",
+                                         "2nd.OnTestPartResult",
+                                         "3rd.OnTestPartResult",
+                                         "ListenerTest::TearDown",
+                                         "3rd.OnTestEnd",
+                                         "2nd.OnTestEnd",
+                                         "1st.OnTestEnd",
+                                         "1st.OnTestStart",
+                                         "2nd.OnTestStart",
+                                         "3rd.OnTestStart",
+                                         "ListenerTest::SetUp",
+                                         "ListenerTest::* Test Body",
+                                         "1st.OnTestPartResult",
+                                         "2nd.OnTestPartResult",
+                                         "3rd.OnTestPartResult",
+                                         "ListenerTest::TearDown",
+                                         "3rd.OnTestEnd",
+                                         "2nd.OnTestEnd",
+                                         "1st.OnTestEnd",
+                                         "ListenerTest::TearDownTestSuite",
+                                         "3rd.OnTestSuiteEnd",
+                                         "1st.OnEnvironmentsTearDownStart",
+                                         "2nd.OnEnvironmentsTearDownStart",
+                                         "3rd.OnEnvironmentsTearDownStart",
+                                         "Environment::TearDown",
+                                         "3rd.OnEnvironmentsTearDownEnd",
+                                         "2nd.OnEnvironmentsTearDownEnd",
+                                         "1st.OnEnvironmentsTearDownEnd",
+                                         "3rd.OnTestIterationEnd(0)",
+                                         "2nd.OnTestIterationEnd(0)",
+                                         "1st.OnTestIterationEnd(0)",
+                                         "1st.OnTestIterationStart(1)",
+                                         "2nd.OnTestIterationStart(1)",
+                                         "3rd.OnTestIterationStart(1)",
+                                         "1st.OnEnvironmentsSetUpStart",
+                                         "2nd.OnEnvironmentsSetUpStart",
+                                         "3rd.OnEnvironmentsSetUpStart",
+                                         "Environment::SetUp",
+                                         "3rd.OnEnvironmentsSetUpEnd",
+                                         "2nd.OnEnvironmentsSetUpEnd",
+                                         "1st.OnEnvironmentsSetUpEnd",
+                                         "3rd.OnTestSuiteStart",
+                                         "ListenerTest::SetUpTestSuite",
+                                         "1st.OnTestStart",
+                                         "2nd.OnTestStart",
+                                         "3rd.OnTestStart",
+                                         "ListenerTest::SetUp",
+                                         "ListenerTest::* Test Body",
+                                         "1st.OnTestPartResult",
+                                         "2nd.OnTestPartResult",
+                                         "3rd.OnTestPartResult",
+                                         "ListenerTest::TearDown",
+                                         "3rd.OnTestEnd",
+                                         "2nd.OnTestEnd",
+                                         "1st.OnTestEnd",
+                                         "1st.OnTestStart",
+                                         "2nd.OnTestStart",
+                                         "3rd.OnTestStart",
+                                         "ListenerTest::SetUp",
+                                         "ListenerTest::* Test Body",
+                                         "1st.OnTestPartResult",
+                                         "2nd.OnTestPartResult",
+                                         "3rd.OnTestPartResult",
+                                         "ListenerTest::TearDown",
+                                         "3rd.OnTestEnd",
+                                         "2nd.OnTestEnd",
+                                         "1st.OnTestEnd",
+                                         "ListenerTest::TearDownTestSuite",
+                                         "3rd.OnTestSuiteEnd",
+                                         "1st.OnEnvironmentsTearDownStart",
+                                         "2nd.OnEnvironmentsTearDownStart",
+                                         "3rd.OnEnvironmentsTearDownStart",
+                                         "Environment::TearDown",
+                                         "3rd.OnEnvironmentsTearDownEnd",
+                                         "2nd.OnEnvironmentsTearDownEnd",
+                                         "1st.OnEnvironmentsTearDownEnd",
+                                         "3rd.OnTestIterationEnd(1)",
+                                         "2nd.OnTestIterationEnd(1)",
+                                         "1st.OnTestIterationEnd(1)",
+                                         "3rd.OnTestProgramEnd",
+                                         "2nd.OnTestProgramEnd",
+                                         "1st.OnTestProgramEnd"};
+#endif  // GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+  VerifyResults(events,
+                expected_events,
+                sizeof(expected_events)/sizeof(expected_events[0]));
+
+  // We need to check manually for ad hoc test failures that happen after
+  // RUN_ALL_TESTS finishes.
+  if (UnitTest::GetInstance()->Failed())
+    ret_val = 1;
+
+  return ret_val;
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-message-test.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-message-test.cc
new file mode 100644
index 0000000..962d519
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-message-test.cc
@@ -0,0 +1,158 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// Tests for the Message class.
+
+#include "gtest/gtest-message.h"
+
+#include "gtest/gtest.h"
+
+namespace {
+
+using ::testing::Message;
+
+// Tests the testing::Message class
+
+// Tests the default constructor.
+TEST(MessageTest, DefaultConstructor) {
+  const Message msg;
+  EXPECT_EQ("", msg.GetString());
+}
+
+// Tests the copy constructor.
+TEST(MessageTest, CopyConstructor) {
+  const Message msg1("Hello");
+  const Message msg2(msg1);
+  EXPECT_EQ("Hello", msg2.GetString());
+}
+
+// Tests constructing a Message from a C-string.
+TEST(MessageTest, ConstructsFromCString) {
+  Message msg("Hello");
+  EXPECT_EQ("Hello", msg.GetString());
+}
+
+// Tests streaming a float.
+TEST(MessageTest, StreamsFloat) {
+  const std::string s = (Message() << 1.23456F << " " << 2.34567F).GetString();
+  // Both numbers should be printed with enough precision.
+  EXPECT_PRED_FORMAT2(testing::IsSubstring, "1.234560", s.c_str());
+  EXPECT_PRED_FORMAT2(testing::IsSubstring, " 2.345669", s.c_str());
+}
+
+// Tests streaming a double.
+TEST(MessageTest, StreamsDouble) {
+  const std::string s = (Message() << 1260570880.4555497 << " "
+                                  << 1260572265.1954534).GetString();
+  // Both numbers should be printed with enough precision.
+  EXPECT_PRED_FORMAT2(testing::IsSubstring, "1260570880.45", s.c_str());
+  EXPECT_PRED_FORMAT2(testing::IsSubstring, " 1260572265.19", s.c_str());
+}
+
+// Tests streaming a non-char pointer.
+TEST(MessageTest, StreamsPointer) {
+  int n = 0;
+  int* p = &n;
+  EXPECT_NE("(null)", (Message() << p).GetString());
+}
+
+// Tests streaming a NULL non-char pointer.
+TEST(MessageTest, StreamsNullPointer) {
+  int* p = nullptr;
+  EXPECT_EQ("(null)", (Message() << p).GetString());
+}
+
+// Tests streaming a C string.
+TEST(MessageTest, StreamsCString) {
+  EXPECT_EQ("Foo", (Message() << "Foo").GetString());
+}
+
+// Tests streaming a NULL C string.
+TEST(MessageTest, StreamsNullCString) {
+  char* p = nullptr;
+  EXPECT_EQ("(null)", (Message() << p).GetString());
+}
+
+// Tests streaming std::string.
+TEST(MessageTest, StreamsString) {
+  const ::std::string str("Hello");
+  EXPECT_EQ("Hello", (Message() << str).GetString());
+}
+
+// Tests that we can output strings containing embedded NULs.
+TEST(MessageTest, StreamsStringWithEmbeddedNUL) {
+  const char char_array_with_nul[] =
+      "Here's a NUL\0 and some more string";
+  const ::std::string string_with_nul(char_array_with_nul,
+                                      sizeof(char_array_with_nul) - 1);
+  EXPECT_EQ("Here's a NUL\\0 and some more string",
+            (Message() << string_with_nul).GetString());
+}
+
+// Tests streaming a NUL char.
+TEST(MessageTest, StreamsNULChar) {
+  EXPECT_EQ("\\0", (Message() << '\0').GetString());
+}
+
+// Tests streaming int.
+TEST(MessageTest, StreamsInt) {
+  EXPECT_EQ("123", (Message() << 123).GetString());
+}
+
+// Tests that basic IO manipulators (endl, ends, and flush) can be
+// streamed to Message.
+TEST(MessageTest, StreamsBasicIoManip) {
+  EXPECT_EQ("Line 1.\nA NUL char \\0 in line 2.",
+               (Message() << "Line 1." << std::endl
+                         << "A NUL char " << std::ends << std::flush
+                         << " in line 2.").GetString());
+}
+
+// Tests Message::GetString()
+TEST(MessageTest, GetString) {
+  Message msg;
+  msg << 1 << " lamb";
+  EXPECT_EQ("1 lamb", msg.GetString());
+}
+
+// Tests streaming a Message object to an ostream.
+TEST(MessageTest, StreamsToOStream) {
+  Message msg("Hello");
+  ::std::stringstream ss;
+  ss << msg;
+  EXPECT_EQ("Hello", testing::internal::StringStreamToString(&ss));
+}
+
+// Tests that a Message object doesn't take up too much stack space.
+TEST(MessageTest, DoesNotTakeUpMuchStackSpace) {
+  EXPECT_LE(sizeof(Message), 16U);
+}
+
+}  // namespace
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-options-test.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-options-test.cc
new file mode 100644
index 0000000..11fb1f2
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-options-test.cc
@@ -0,0 +1,219 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// Google Test UnitTestOptions tests
+//
+// This file tests classes and functions used internally by
+// Google Test.  They are subject to change without notice.
+//
+// This file is #included from gtest.cc, to avoid changing build or
+// make-files on Windows and other platforms. Do not #include this file
+// anywhere else!
+
+#include "gtest/gtest.h"
+
+#if GTEST_OS_WINDOWS_MOBILE
+# include <windows.h>
+#elif GTEST_OS_WINDOWS
+# include <direct.h>
+#elif GTEST_OS_OS2
+// For strcasecmp on OS/2
+#include <strings.h>
+#endif  // GTEST_OS_WINDOWS_MOBILE
+
+#include "src/gtest-internal-inl.h"
+
+namespace testing {
+namespace internal {
+namespace {
+
+// Turns the given relative path into an absolute path.
+FilePath GetAbsolutePathOf(const FilePath& relative_path) {
+  return FilePath::ConcatPaths(FilePath::GetCurrentDir(), relative_path);
+}
+
+// Testing UnitTestOptions::GetOutputFormat/GetOutputFile.
+
+TEST(XmlOutputTest, GetOutputFormatDefault) {
+  GTEST_FLAG(output) = "";
+  EXPECT_STREQ("", UnitTestOptions::GetOutputFormat().c_str());
+}
+
+TEST(XmlOutputTest, GetOutputFormat) {
+  GTEST_FLAG(output) = "xml:filename";
+  EXPECT_STREQ("xml", UnitTestOptions::GetOutputFormat().c_str());
+}
+
+TEST(XmlOutputTest, GetOutputFileDefault) {
+  GTEST_FLAG(output) = "";
+  EXPECT_EQ(GetAbsolutePathOf(FilePath("test_detail.xml")).string(),
+            UnitTestOptions::GetAbsolutePathToOutputFile());
+}
+
+TEST(XmlOutputTest, GetOutputFileSingleFile) {
+  GTEST_FLAG(output) = "xml:filename.abc";
+  EXPECT_EQ(GetAbsolutePathOf(FilePath("filename.abc")).string(),
+            UnitTestOptions::GetAbsolutePathToOutputFile());
+}
+
+TEST(XmlOutputTest, GetOutputFileFromDirectoryPath) {
+  GTEST_FLAG(output) = "xml:path" GTEST_PATH_SEP_;
+  const std::string expected_output_file =
+      GetAbsolutePathOf(
+          FilePath(std::string("path") + GTEST_PATH_SEP_ +
+                   GetCurrentExecutableName().string() + ".xml")).string();
+  const std::string& output_file =
+      UnitTestOptions::GetAbsolutePathToOutputFile();
+#if GTEST_OS_WINDOWS
+  EXPECT_STRCASEEQ(expected_output_file.c_str(), output_file.c_str());
+#else
+  EXPECT_EQ(expected_output_file, output_file.c_str());
+#endif
+}
+
+TEST(OutputFileHelpersTest, GetCurrentExecutableName) {
+  const std::string exe_str = GetCurrentExecutableName().string();
+#if GTEST_OS_WINDOWS
+  const bool success =
+      _strcmpi("googletest-options-test", exe_str.c_str()) == 0 ||
+      _strcmpi("gtest-options-ex_test", exe_str.c_str()) == 0 ||
+      _strcmpi("gtest_all_test", exe_str.c_str()) == 0 ||
+      _strcmpi("gtest_dll_test", exe_str.c_str()) == 0;
+#elif GTEST_OS_OS2
+  const bool success =
+      strcasecmp("googletest-options-test", exe_str.c_str()) == 0 ||
+      strcasecmp("gtest-options-ex_test", exe_str.c_str()) == 0 ||
+      strcasecmp("gtest_all_test", exe_str.c_str()) == 0 ||
+      strcasecmp("gtest_dll_test", exe_str.c_str()) == 0;
+#elif GTEST_OS_FUCHSIA
+  const bool success = exe_str == "app";
+#else
+  const bool success =
+      exe_str == "googletest-options-test" ||
+      exe_str == "gtest_all_test" ||
+      exe_str == "lt-gtest_all_test" ||
+      exe_str == "gtest_dll_test";
+#endif  // GTEST_OS_WINDOWS
+  if (!success)
+    FAIL() << "GetCurrentExecutableName() returns " << exe_str;
+}
+
+#if !GTEST_OS_FUCHSIA
+
+class XmlOutputChangeDirTest : public Test {
+ protected:
+  void SetUp() override {
+    original_working_dir_ = FilePath::GetCurrentDir();
+    posix::ChDir("..");
+    // This will make the test fail if run from the root directory.
+    EXPECT_NE(original_working_dir_.string(),
+              FilePath::GetCurrentDir().string());
+  }
+
+  void TearDown() override {
+    posix::ChDir(original_working_dir_.string().c_str());
+  }
+
+  FilePath original_working_dir_;
+};
+
+TEST_F(XmlOutputChangeDirTest, PreserveOriginalWorkingDirWithDefault) {
+  GTEST_FLAG(output) = "";
+  EXPECT_EQ(FilePath::ConcatPaths(original_working_dir_,
+                                  FilePath("test_detail.xml")).string(),
+            UnitTestOptions::GetAbsolutePathToOutputFile());
+}
+
+TEST_F(XmlOutputChangeDirTest, PreserveOriginalWorkingDirWithDefaultXML) {
+  GTEST_FLAG(output) = "xml";
+  EXPECT_EQ(FilePath::ConcatPaths(original_working_dir_,
+                                  FilePath("test_detail.xml")).string(),
+            UnitTestOptions::GetAbsolutePathToOutputFile());
+}
+
+TEST_F(XmlOutputChangeDirTest, PreserveOriginalWorkingDirWithRelativeFile) {
+  GTEST_FLAG(output) = "xml:filename.abc";
+  EXPECT_EQ(FilePath::ConcatPaths(original_working_dir_,
+                                  FilePath("filename.abc")).string(),
+            UnitTestOptions::GetAbsolutePathToOutputFile());
+}
+
+TEST_F(XmlOutputChangeDirTest, PreserveOriginalWorkingDirWithRelativePath) {
+  GTEST_FLAG(output) = "xml:path" GTEST_PATH_SEP_;
+  const std::string expected_output_file =
+      FilePath::ConcatPaths(
+          original_working_dir_,
+          FilePath(std::string("path") + GTEST_PATH_SEP_ +
+                   GetCurrentExecutableName().string() + ".xml")).string();
+  const std::string& output_file =
+      UnitTestOptions::GetAbsolutePathToOutputFile();
+#if GTEST_OS_WINDOWS
+  EXPECT_STRCASEEQ(expected_output_file.c_str(), output_file.c_str());
+#else
+  EXPECT_EQ(expected_output_file, output_file.c_str());
+#endif
+}
+
+TEST_F(XmlOutputChangeDirTest, PreserveOriginalWorkingDirWithAbsoluteFile) {
+#if GTEST_OS_WINDOWS
+  GTEST_FLAG(output) = "xml:c:\\tmp\\filename.abc";
+  EXPECT_EQ(FilePath("c:\\tmp\\filename.abc").string(),
+            UnitTestOptions::GetAbsolutePathToOutputFile());
+#else
+  GTEST_FLAG(output) ="xml:/tmp/filename.abc";
+  EXPECT_EQ(FilePath("/tmp/filename.abc").string(),
+            UnitTestOptions::GetAbsolutePathToOutputFile());
+#endif
+}
+
+TEST_F(XmlOutputChangeDirTest, PreserveOriginalWorkingDirWithAbsolutePath) {
+#if GTEST_OS_WINDOWS
+  const std::string path = "c:\\tmp\\";
+#else
+  const std::string path = "/tmp/";
+#endif
+
+  GTEST_FLAG(output) = "xml:" + path;
+  const std::string expected_output_file =
+      path + GetCurrentExecutableName().string() + ".xml";
+  const std::string& output_file =
+      UnitTestOptions::GetAbsolutePathToOutputFile();
+
+#if GTEST_OS_WINDOWS
+  EXPECT_STRCASEEQ(expected_output_file.c_str(), output_file.c_str());
+#else
+  EXPECT_EQ(expected_output_file, output_file.c_str());
+#endif
+}
+
+#endif  // !GTEST_OS_FUCHSIA
+
+}  // namespace
+}  // namespace internal
+}  // namespace testing
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-output-test-golden-lin.txt b/leveldb_base/third_party/googletest/googletest/test/googletest-output-test-golden-lin.txt
new file mode 100644
index 0000000..3fab3b9
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-output-test-golden-lin.txt
@@ -0,0 +1,1180 @@
+The non-test part of the code is expected to have 2 failures.
+
+googletest-output-test_.cc:#: Failure
+Value of: false
+  Actual: false
+Expected: true
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Expected equality of these values:
+  2
+  3
+Stack trace: (omitted)
+
+[==========] Running 88 tests from 41 test suites.
+[----------] Global test environment set-up.
+FooEnvironment::SetUp() called.
+BarEnvironment::SetUp() called.
+[----------] 1 test from ADeathTest
+[ RUN      ] ADeathTest.ShouldRunFirst
+[       OK ] ADeathTest.ShouldRunFirst
+[----------] 1 test from ATypedDeathTest/0, where TypeParam = int
+[ RUN      ] ATypedDeathTest/0.ShouldRunFirst
+[       OK ] ATypedDeathTest/0.ShouldRunFirst
+[----------] 1 test from ATypedDeathTest/1, where TypeParam = double
+[ RUN      ] ATypedDeathTest/1.ShouldRunFirst
+[       OK ] ATypedDeathTest/1.ShouldRunFirst
+[----------] 1 test from My/ATypeParamDeathTest/0, where TypeParam = int
+[ RUN      ] My/ATypeParamDeathTest/0.ShouldRunFirst
+[       OK ] My/ATypeParamDeathTest/0.ShouldRunFirst
+[----------] 1 test from My/ATypeParamDeathTest/1, where TypeParam = double
+[ RUN      ] My/ATypeParamDeathTest/1.ShouldRunFirst
+[       OK ] My/ATypeParamDeathTest/1.ShouldRunFirst
+[----------] 2 tests from PassingTest
+[ RUN      ] PassingTest.PassingTest1
+[       OK ] PassingTest.PassingTest1
+[ RUN      ] PassingTest.PassingTest2
+[       OK ] PassingTest.PassingTest2
+[----------] 2 tests from NonfatalFailureTest
+[ RUN      ] NonfatalFailureTest.EscapesStringOperands
+googletest-output-test_.cc:#: Failure
+Expected equality of these values:
+  kGoldenString
+    Which is: "\"Line"
+  actual
+    Which is: "actual \"string\""
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Expected equality of these values:
+  golden
+    Which is: "\"Line"
+  actual
+    Which is: "actual \"string\""
+Stack trace: (omitted)
+
+[  FAILED  ] NonfatalFailureTest.EscapesStringOperands
+[ RUN      ] NonfatalFailureTest.DiffForLongStrings
+googletest-output-test_.cc:#: Failure
+Expected equality of these values:
+  golden_str
+    Which is: "\"Line\0 1\"\nLine 2"
+  "Line 2"
+With diff:
+@@ -1,2 @@
+-\"Line\0 1\"
+ Line 2
+
+Stack trace: (omitted)
+
+[  FAILED  ] NonfatalFailureTest.DiffForLongStrings
+[----------] 3 tests from FatalFailureTest
+[ RUN      ] FatalFailureTest.FatalFailureInSubroutine
+(expecting a failure that x should be 1)
+googletest-output-test_.cc:#: Failure
+Expected equality of these values:
+  1
+  x
+    Which is: 2
+Stack trace: (omitted)
+
+[  FAILED  ] FatalFailureTest.FatalFailureInSubroutine
+[ RUN      ] FatalFailureTest.FatalFailureInNestedSubroutine
+(expecting a failure that x should be 1)
+googletest-output-test_.cc:#: Failure
+Expected equality of these values:
+  1
+  x
+    Which is: 2
+Stack trace: (omitted)
+
+[  FAILED  ] FatalFailureTest.FatalFailureInNestedSubroutine
+[ RUN      ] FatalFailureTest.NonfatalFailureInSubroutine
+(expecting a failure on false)
+googletest-output-test_.cc:#: Failure
+Value of: false
+  Actual: false
+Expected: true
+Stack trace: (omitted)
+
+[  FAILED  ] FatalFailureTest.NonfatalFailureInSubroutine
+[----------] 1 test from LoggingTest
+[ RUN      ] LoggingTest.InterleavingLoggingAndAssertions
+(expecting 2 failures on (3) >= (a[i]))
+i == 0
+i == 1
+googletest-output-test_.cc:#: Failure
+Expected: (3) >= (a[i]), actual: 3 vs 9
+Stack trace: (omitted)
+
+i == 2
+i == 3
+googletest-output-test_.cc:#: Failure
+Expected: (3) >= (a[i]), actual: 3 vs 6
+Stack trace: (omitted)
+
+[  FAILED  ] LoggingTest.InterleavingLoggingAndAssertions
+[----------] 7 tests from SCOPED_TRACETest
+[ RUN      ] SCOPED_TRACETest.AcceptedValues
+googletest-output-test_.cc:#: Failure
+Failed
+Just checking that all these values work fine.
+Google Test trace:
+googletest-output-test_.cc:#: (null)
+googletest-output-test_.cc:#: 1337
+googletest-output-test_.cc:#: std::string
+googletest-output-test_.cc:#: literal string
+Stack trace: (omitted)
+
+[  FAILED  ] SCOPED_TRACETest.AcceptedValues
+[ RUN      ] SCOPED_TRACETest.ObeysScopes
+(expected to fail)
+googletest-output-test_.cc:#: Failure
+Failed
+This failure is expected, and shouldn't have a trace.
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Failed
+This failure is expected, and should have a trace.
+Google Test trace:
+googletest-output-test_.cc:#: Expected trace
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Failed
+This failure is expected, and shouldn't have a trace.
+Stack trace: (omitted)
+
+[  FAILED  ] SCOPED_TRACETest.ObeysScopes
+[ RUN      ] SCOPED_TRACETest.WorksInLoop
+(expected to fail)
+googletest-output-test_.cc:#: Failure
+Expected equality of these values:
+  2
+  n
+    Which is: 1
+Google Test trace:
+googletest-output-test_.cc:#: i = 1
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Expected equality of these values:
+  1
+  n
+    Which is: 2
+Google Test trace:
+googletest-output-test_.cc:#: i = 2
+Stack trace: (omitted)
+
+[  FAILED  ] SCOPED_TRACETest.WorksInLoop
+[ RUN      ] SCOPED_TRACETest.WorksInSubroutine
+(expected to fail)
+googletest-output-test_.cc:#: Failure
+Expected equality of these values:
+  2
+  n
+    Which is: 1
+Google Test trace:
+googletest-output-test_.cc:#: n = 1
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Expected equality of these values:
+  1
+  n
+    Which is: 2
+Google Test trace:
+googletest-output-test_.cc:#: n = 2
+Stack trace: (omitted)
+
+[  FAILED  ] SCOPED_TRACETest.WorksInSubroutine
+[ RUN      ] SCOPED_TRACETest.CanBeNested
+(expected to fail)
+googletest-output-test_.cc:#: Failure
+Expected equality of these values:
+  1
+  n
+    Which is: 2
+Google Test trace:
+googletest-output-test_.cc:#: n = 2
+googletest-output-test_.cc:#: 
+Stack trace: (omitted)
+
+[  FAILED  ] SCOPED_TRACETest.CanBeNested
+[ RUN      ] SCOPED_TRACETest.CanBeRepeated
+(expected to fail)
+googletest-output-test_.cc:#: Failure
+Failed
+This failure is expected, and should contain trace point A.
+Google Test trace:
+googletest-output-test_.cc:#: A
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Failed
+This failure is expected, and should contain trace point A and B.
+Google Test trace:
+googletest-output-test_.cc:#: B
+googletest-output-test_.cc:#: A
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Failed
+This failure is expected, and should contain trace point A, B, and C.
+Google Test trace:
+googletest-output-test_.cc:#: C
+googletest-output-test_.cc:#: B
+googletest-output-test_.cc:#: A
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Failed
+This failure is expected, and should contain trace point A, B, and D.
+Google Test trace:
+googletest-output-test_.cc:#: D
+googletest-output-test_.cc:#: B
+googletest-output-test_.cc:#: A
+Stack trace: (omitted)
+
+[  FAILED  ] SCOPED_TRACETest.CanBeRepeated
+[ RUN      ] SCOPED_TRACETest.WorksConcurrently
+(expecting 6 failures)
+googletest-output-test_.cc:#: Failure
+Failed
+Expected failure #1 (in thread B, only trace B alive).
+Google Test trace:
+googletest-output-test_.cc:#: Trace B
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Failed
+Expected failure #2 (in thread A, trace A & B both alive).
+Google Test trace:
+googletest-output-test_.cc:#: Trace A
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Failed
+Expected failure #3 (in thread B, trace A & B both alive).
+Google Test trace:
+googletest-output-test_.cc:#: Trace B
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Failed
+Expected failure #4 (in thread B, only trace A alive).
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Failed
+Expected failure #5 (in thread A, only trace A alive).
+Google Test trace:
+googletest-output-test_.cc:#: Trace A
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Failed
+Expected failure #6 (in thread A, no trace alive).
+Stack trace: (omitted)
+
+[  FAILED  ] SCOPED_TRACETest.WorksConcurrently
+[----------] 1 test from ScopedTraceTest
+[ RUN      ] ScopedTraceTest.WithExplicitFileAndLine
+googletest-output-test_.cc:#: Failure
+Failed
+Check that the trace is attached to a particular location.
+Google Test trace:
+explicit_file.cc:123: expected trace message
+Stack trace: (omitted)
+
+[  FAILED  ] ScopedTraceTest.WithExplicitFileAndLine
+[----------] 1 test from NonFatalFailureInFixtureConstructorTest
+[ RUN      ] NonFatalFailureInFixtureConstructorTest.FailureInConstructor
+(expecting 5 failures)
+googletest-output-test_.cc:#: Failure
+Failed
+Expected failure #1, in the test fixture c'tor.
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Failed
+Expected failure #2, in SetUp().
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Failed
+Expected failure #3, in the test body.
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Failed
+Expected failure #4, in TearDown.
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Failed
+Expected failure #5, in the test fixture d'tor.
+Stack trace: (omitted)
+
+[  FAILED  ] NonFatalFailureInFixtureConstructorTest.FailureInConstructor
+[----------] 1 test from FatalFailureInFixtureConstructorTest
+[ RUN      ] FatalFailureInFixtureConstructorTest.FailureInConstructor
+(expecting 2 failures)
+googletest-output-test_.cc:#: Failure
+Failed
+Expected failure #1, in the test fixture c'tor.
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Failed
+Expected failure #2, in the test fixture d'tor.
+Stack trace: (omitted)
+
+[  FAILED  ] FatalFailureInFixtureConstructorTest.FailureInConstructor
+[----------] 1 test from NonFatalFailureInSetUpTest
+[ RUN      ] NonFatalFailureInSetUpTest.FailureInSetUp
+(expecting 4 failures)
+googletest-output-test_.cc:#: Failure
+Failed
+Expected failure #1, in SetUp().
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Failed
+Expected failure #2, in the test function.
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Failed
+Expected failure #3, in TearDown().
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Failed
+Expected failure #4, in the test fixture d'tor.
+Stack trace: (omitted)
+
+[  FAILED  ] NonFatalFailureInSetUpTest.FailureInSetUp
+[----------] 1 test from FatalFailureInSetUpTest
+[ RUN      ] FatalFailureInSetUpTest.FailureInSetUp
+(expecting 3 failures)
+googletest-output-test_.cc:#: Failure
+Failed
+Expected failure #1, in SetUp().
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Failed
+Expected failure #2, in TearDown().
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Failed
+Expected failure #3, in the test fixture d'tor.
+Stack trace: (omitted)
+
+[  FAILED  ] FatalFailureInSetUpTest.FailureInSetUp
+[----------] 1 test from AddFailureAtTest
+[ RUN      ] AddFailureAtTest.MessageContainsSpecifiedFileAndLineNumber
+foo.cc:42: Failure
+Failed
+Expected nonfatal failure in foo.cc
+Stack trace: (omitted)
+
+[  FAILED  ] AddFailureAtTest.MessageContainsSpecifiedFileAndLineNumber
+[----------] 1 test from GtestFailAtTest
+[ RUN      ] GtestFailAtTest.MessageContainsSpecifiedFileAndLineNumber
+foo.cc:42: Failure
+Failed
+Expected fatal failure in foo.cc
+Stack trace: (omitted)
+
+[  FAILED  ] GtestFailAtTest.MessageContainsSpecifiedFileAndLineNumber
+[----------] 4 tests from MixedUpTestSuiteTest
+[ RUN      ] MixedUpTestSuiteTest.FirstTestFromNamespaceFoo
+[       OK ] MixedUpTestSuiteTest.FirstTestFromNamespaceFoo
+[ RUN      ] MixedUpTestSuiteTest.SecondTestFromNamespaceFoo
+[       OK ] MixedUpTestSuiteTest.SecondTestFromNamespaceFoo
+[ RUN      ] MixedUpTestSuiteTest.ThisShouldFail
+gtest.cc:#: Failure
+Failed
+All tests in the same test suite must use the same test fixture
+class.  However, in test suite MixedUpTestSuiteTest,
+you defined test FirstTestFromNamespaceFoo and test ThisShouldFail
+using two different test fixture classes.  This can happen if
+the two classes are from different namespaces or translation
+units and have the same name.  You should probably rename one
+of the classes to put the tests into different test suites.
+Stack trace: (omitted)
+
+[  FAILED  ] MixedUpTestSuiteTest.ThisShouldFail
+[ RUN      ] MixedUpTestSuiteTest.ThisShouldFailToo
+gtest.cc:#: Failure
+Failed
+All tests in the same test suite must use the same test fixture
+class.  However, in test suite MixedUpTestSuiteTest,
+you defined test FirstTestFromNamespaceFoo and test ThisShouldFailToo
+using two different test fixture classes.  This can happen if
+the two classes are from different namespaces or translation
+units and have the same name.  You should probably rename one
+of the classes to put the tests into different test suites.
+Stack trace: (omitted)
+
+[  FAILED  ] MixedUpTestSuiteTest.ThisShouldFailToo
+[----------] 2 tests from MixedUpTestSuiteWithSameTestNameTest
+[ RUN      ] MixedUpTestSuiteWithSameTestNameTest.TheSecondTestWithThisNameShouldFail
+[       OK ] MixedUpTestSuiteWithSameTestNameTest.TheSecondTestWithThisNameShouldFail
+[ RUN      ] MixedUpTestSuiteWithSameTestNameTest.TheSecondTestWithThisNameShouldFail
+gtest.cc:#: Failure
+Failed
+All tests in the same test suite must use the same test fixture
+class.  However, in test suite MixedUpTestSuiteWithSameTestNameTest,
+you defined test TheSecondTestWithThisNameShouldFail and test TheSecondTestWithThisNameShouldFail
+using two different test fixture classes.  This can happen if
+the two classes are from different namespaces or translation
+units and have the same name.  You should probably rename one
+of the classes to put the tests into different test suites.
+Stack trace: (omitted)
+
+[  FAILED  ] MixedUpTestSuiteWithSameTestNameTest.TheSecondTestWithThisNameShouldFail
+[----------] 2 tests from TEST_F_before_TEST_in_same_test_case
+[ RUN      ] TEST_F_before_TEST_in_same_test_case.DefinedUsingTEST_F
+[       OK ] TEST_F_before_TEST_in_same_test_case.DefinedUsingTEST_F
+[ RUN      ] TEST_F_before_TEST_in_same_test_case.DefinedUsingTESTAndShouldFail
+gtest.cc:#: Failure
+Failed
+All tests in the same test suite must use the same test fixture
+class, so mixing TEST_F and TEST in the same test suite is
+illegal.  In test suite TEST_F_before_TEST_in_same_test_case,
+test DefinedUsingTEST_F is defined using TEST_F but
+test DefinedUsingTESTAndShouldFail is defined using TEST.  You probably
+want to change the TEST to TEST_F or move it to another test
+case.
+Stack trace: (omitted)
+
+[  FAILED  ] TEST_F_before_TEST_in_same_test_case.DefinedUsingTESTAndShouldFail
+[----------] 2 tests from TEST_before_TEST_F_in_same_test_case
+[ RUN      ] TEST_before_TEST_F_in_same_test_case.DefinedUsingTEST
+[       OK ] TEST_before_TEST_F_in_same_test_case.DefinedUsingTEST
+[ RUN      ] TEST_before_TEST_F_in_same_test_case.DefinedUsingTEST_FAndShouldFail
+gtest.cc:#: Failure
+Failed
+All tests in the same test suite must use the same test fixture
+class, so mixing TEST_F and TEST in the same test suite is
+illegal.  In test suite TEST_before_TEST_F_in_same_test_case,
+test DefinedUsingTEST_FAndShouldFail is defined using TEST_F but
+test DefinedUsingTEST is defined using TEST.  You probably
+want to change the TEST to TEST_F or move it to another test
+case.
+Stack trace: (omitted)
+
+[  FAILED  ] TEST_before_TEST_F_in_same_test_case.DefinedUsingTEST_FAndShouldFail
+[----------] 8 tests from ExpectNonfatalFailureTest
+[ RUN      ] ExpectNonfatalFailureTest.CanReferenceGlobalVariables
+[       OK ] ExpectNonfatalFailureTest.CanReferenceGlobalVariables
+[ RUN      ] ExpectNonfatalFailureTest.CanReferenceLocalVariables
+[       OK ] ExpectNonfatalFailureTest.CanReferenceLocalVariables
+[ RUN      ] ExpectNonfatalFailureTest.SucceedsWhenThereIsOneNonfatalFailure
+[       OK ] ExpectNonfatalFailureTest.SucceedsWhenThereIsOneNonfatalFailure
+[ RUN      ] ExpectNonfatalFailureTest.FailsWhenThereIsNoNonfatalFailure
+(expecting a failure)
+gtest.cc:#: Failure
+Expected: 1 non-fatal failure
+  Actual: 0 failures
+Stack trace: (omitted)
+
+[  FAILED  ] ExpectNonfatalFailureTest.FailsWhenThereIsNoNonfatalFailure
+[ RUN      ] ExpectNonfatalFailureTest.FailsWhenThereAreTwoNonfatalFailures
+(expecting a failure)
+gtest.cc:#: Failure
+Expected: 1 non-fatal failure
+  Actual: 2 failures
+googletest-output-test_.cc:#: Non-fatal failure:
+Failed
+Expected non-fatal failure 1.
+Stack trace: (omitted)
+
+
+googletest-output-test_.cc:#: Non-fatal failure:
+Failed
+Expected non-fatal failure 2.
+Stack trace: (omitted)
+
+
+Stack trace: (omitted)
+
+[  FAILED  ] ExpectNonfatalFailureTest.FailsWhenThereAreTwoNonfatalFailures
+[ RUN      ] ExpectNonfatalFailureTest.FailsWhenThereIsOneFatalFailure
+(expecting a failure)
+gtest.cc:#: Failure
+Expected: 1 non-fatal failure
+  Actual:
+googletest-output-test_.cc:#: Fatal failure:
+Failed
+Expected fatal failure.
+Stack trace: (omitted)
+
+
+Stack trace: (omitted)
+
+[  FAILED  ] ExpectNonfatalFailureTest.FailsWhenThereIsOneFatalFailure
+[ RUN      ] ExpectNonfatalFailureTest.FailsWhenStatementReturns
+(expecting a failure)
+gtest.cc:#: Failure
+Expected: 1 non-fatal failure
+  Actual: 0 failures
+Stack trace: (omitted)
+
+[  FAILED  ] ExpectNonfatalFailureTest.FailsWhenStatementReturns
+[ RUN      ] ExpectNonfatalFailureTest.FailsWhenStatementThrows
+(expecting a failure)
+gtest.cc:#: Failure
+Expected: 1 non-fatal failure
+  Actual: 0 failures
+Stack trace: (omitted)
+
+[  FAILED  ] ExpectNonfatalFailureTest.FailsWhenStatementThrows
+[----------] 8 tests from ExpectFatalFailureTest
+[ RUN      ] ExpectFatalFailureTest.CanReferenceGlobalVariables
+[       OK ] ExpectFatalFailureTest.CanReferenceGlobalVariables
+[ RUN      ] ExpectFatalFailureTest.CanReferenceLocalStaticVariables
+[       OK ] ExpectFatalFailureTest.CanReferenceLocalStaticVariables
+[ RUN      ] ExpectFatalFailureTest.SucceedsWhenThereIsOneFatalFailure
+[       OK ] ExpectFatalFailureTest.SucceedsWhenThereIsOneFatalFailure
+[ RUN      ] ExpectFatalFailureTest.FailsWhenThereIsNoFatalFailure
+(expecting a failure)
+gtest.cc:#: Failure
+Expected: 1 fatal failure
+  Actual: 0 failures
+Stack trace: (omitted)
+
+[  FAILED  ] ExpectFatalFailureTest.FailsWhenThereIsNoFatalFailure
+[ RUN      ] ExpectFatalFailureTest.FailsWhenThereAreTwoFatalFailures
+(expecting a failure)
+gtest.cc:#: Failure
+Expected: 1 fatal failure
+  Actual: 2 failures
+googletest-output-test_.cc:#: Fatal failure:
+Failed
+Expected fatal failure.
+Stack trace: (omitted)
+
+
+googletest-output-test_.cc:#: Fatal failure:
+Failed
+Expected fatal failure.
+Stack trace: (omitted)
+
+
+Stack trace: (omitted)
+
+[  FAILED  ] ExpectFatalFailureTest.FailsWhenThereAreTwoFatalFailures
+[ RUN      ] ExpectFatalFailureTest.FailsWhenThereIsOneNonfatalFailure
+(expecting a failure)
+gtest.cc:#: Failure
+Expected: 1 fatal failure
+  Actual:
+googletest-output-test_.cc:#: Non-fatal failure:
+Failed
+Expected non-fatal failure.
+Stack trace: (omitted)
+
+
+Stack trace: (omitted)
+
+[  FAILED  ] ExpectFatalFailureTest.FailsWhenThereIsOneNonfatalFailure
+[ RUN      ] ExpectFatalFailureTest.FailsWhenStatementReturns
+(expecting a failure)
+gtest.cc:#: Failure
+Expected: 1 fatal failure
+  Actual: 0 failures
+Stack trace: (omitted)
+
+[  FAILED  ] ExpectFatalFailureTest.FailsWhenStatementReturns
+[ RUN      ] ExpectFatalFailureTest.FailsWhenStatementThrows
+(expecting a failure)
+gtest.cc:#: Failure
+Expected: 1 fatal failure
+  Actual: 0 failures
+Stack trace: (omitted)
+
+[  FAILED  ] ExpectFatalFailureTest.FailsWhenStatementThrows
+[----------] 2 tests from TypedTest/0, where TypeParam = int
+[ RUN      ] TypedTest/0.Success
+[       OK ] TypedTest/0.Success
+[ RUN      ] TypedTest/0.Failure
+googletest-output-test_.cc:#: Failure
+Expected equality of these values:
+  1
+  TypeParam()
+    Which is: 0
+Expected failure
+Stack trace: (omitted)
+
+[  FAILED  ] TypedTest/0.Failure, where TypeParam = int
+[----------] 2 tests from TypedTestWithNames/char0, where TypeParam = char
+[ RUN      ] TypedTestWithNames/char0.Success
+[       OK ] TypedTestWithNames/char0.Success
+[ RUN      ] TypedTestWithNames/char0.Failure
+googletest-output-test_.cc:#: Failure
+Failed
+Stack trace: (omitted)
+
+[  FAILED  ] TypedTestWithNames/char0.Failure, where TypeParam = char
+[----------] 2 tests from TypedTestWithNames/int1, where TypeParam = int
+[ RUN      ] TypedTestWithNames/int1.Success
+[       OK ] TypedTestWithNames/int1.Success
+[ RUN      ] TypedTestWithNames/int1.Failure
+googletest-output-test_.cc:#: Failure
+Failed
+Stack trace: (omitted)
+
+[  FAILED  ] TypedTestWithNames/int1.Failure, where TypeParam = int
+[----------] 2 tests from Unsigned/TypedTestP/0, where TypeParam = unsigned char
+[ RUN      ] Unsigned/TypedTestP/0.Success
+[       OK ] Unsigned/TypedTestP/0.Success
+[ RUN      ] Unsigned/TypedTestP/0.Failure
+googletest-output-test_.cc:#: Failure
+Expected equality of these values:
+  1U
+    Which is: 1
+  TypeParam()
+    Which is: '\0'
+Expected failure
+Stack trace: (omitted)
+
+[  FAILED  ] Unsigned/TypedTestP/0.Failure, where TypeParam = unsigned char
+[----------] 2 tests from Unsigned/TypedTestP/1, where TypeParam = unsigned int
+[ RUN      ] Unsigned/TypedTestP/1.Success
+[       OK ] Unsigned/TypedTestP/1.Success
+[ RUN      ] Unsigned/TypedTestP/1.Failure
+googletest-output-test_.cc:#: Failure
+Expected equality of these values:
+  1U
+    Which is: 1
+  TypeParam()
+    Which is: 0
+Expected failure
+Stack trace: (omitted)
+
+[  FAILED  ] Unsigned/TypedTestP/1.Failure, where TypeParam = unsigned int
+[----------] 2 tests from UnsignedCustomName/TypedTestP/unsignedChar0, where TypeParam = unsigned char
+[ RUN      ] UnsignedCustomName/TypedTestP/unsignedChar0.Success
+[       OK ] UnsignedCustomName/TypedTestP/unsignedChar0.Success
+[ RUN      ] UnsignedCustomName/TypedTestP/unsignedChar0.Failure
+googletest-output-test_.cc:#: Failure
+Expected equality of these values:
+  1U
+    Which is: 1
+  TypeParam()
+    Which is: '\0'
+Expected failure
+Stack trace: (omitted)
+
+[  FAILED  ] UnsignedCustomName/TypedTestP/unsignedChar0.Failure, where TypeParam = unsigned char
+[----------] 2 tests from UnsignedCustomName/TypedTestP/unsignedInt1, where TypeParam = unsigned int
+[ RUN      ] UnsignedCustomName/TypedTestP/unsignedInt1.Success
+[       OK ] UnsignedCustomName/TypedTestP/unsignedInt1.Success
+[ RUN      ] UnsignedCustomName/TypedTestP/unsignedInt1.Failure
+googletest-output-test_.cc:#: Failure
+Expected equality of these values:
+  1U
+    Which is: 1
+  TypeParam()
+    Which is: 0
+Expected failure
+Stack trace: (omitted)
+
+[  FAILED  ] UnsignedCustomName/TypedTestP/unsignedInt1.Failure, where TypeParam = unsigned int
+[----------] 4 tests from ExpectFailureTest
+[ RUN      ] ExpectFailureTest.ExpectFatalFailure
+(expecting 1 failure)
+gtest.cc:#: Failure
+Expected: 1 fatal failure
+  Actual:
+googletest-output-test_.cc:#: Success:
+Succeeded
+Stack trace: (omitted)
+
+
+Stack trace: (omitted)
+
+(expecting 1 failure)
+gtest.cc:#: Failure
+Expected: 1 fatal failure
+  Actual:
+googletest-output-test_.cc:#: Non-fatal failure:
+Failed
+Expected non-fatal failure.
+Stack trace: (omitted)
+
+
+Stack trace: (omitted)
+
+(expecting 1 failure)
+gtest.cc:#: Failure
+Expected: 1 fatal failure containing "Some other fatal failure expected."
+  Actual:
+googletest-output-test_.cc:#: Fatal failure:
+Failed
+Expected fatal failure.
+Stack trace: (omitted)
+
+
+Stack trace: (omitted)
+
+[  FAILED  ] ExpectFailureTest.ExpectFatalFailure
+[ RUN      ] ExpectFailureTest.ExpectNonFatalFailure
+(expecting 1 failure)
+gtest.cc:#: Failure
+Expected: 1 non-fatal failure
+  Actual:
+googletest-output-test_.cc:#: Success:
+Succeeded
+Stack trace: (omitted)
+
+
+Stack trace: (omitted)
+
+(expecting 1 failure)
+gtest.cc:#: Failure
+Expected: 1 non-fatal failure
+  Actual:
+googletest-output-test_.cc:#: Fatal failure:
+Failed
+Expected fatal failure.
+Stack trace: (omitted)
+
+
+Stack trace: (omitted)
+
+(expecting 1 failure)
+gtest.cc:#: Failure
+Expected: 1 non-fatal failure containing "Some other non-fatal failure."
+  Actual:
+googletest-output-test_.cc:#: Non-fatal failure:
+Failed
+Expected non-fatal failure.
+Stack trace: (omitted)
+
+
+Stack trace: (omitted)
+
+[  FAILED  ] ExpectFailureTest.ExpectNonFatalFailure
+[ RUN      ] ExpectFailureTest.ExpectFatalFailureOnAllThreads
+(expecting 1 failure)
+gtest.cc:#: Failure
+Expected: 1 fatal failure
+  Actual:
+googletest-output-test_.cc:#: Success:
+Succeeded
+Stack trace: (omitted)
+
+
+Stack trace: (omitted)
+
+(expecting 1 failure)
+gtest.cc:#: Failure
+Expected: 1 fatal failure
+  Actual:
+googletest-output-test_.cc:#: Non-fatal failure:
+Failed
+Expected non-fatal failure.
+Stack trace: (omitted)
+
+
+Stack trace: (omitted)
+
+(expecting 1 failure)
+gtest.cc:#: Failure
+Expected: 1 fatal failure containing "Some other fatal failure expected."
+  Actual:
+googletest-output-test_.cc:#: Fatal failure:
+Failed
+Expected fatal failure.
+Stack trace: (omitted)
+
+
+Stack trace: (omitted)
+
+[  FAILED  ] ExpectFailureTest.ExpectFatalFailureOnAllThreads
+[ RUN      ] ExpectFailureTest.ExpectNonFatalFailureOnAllThreads
+(expecting 1 failure)
+gtest.cc:#: Failure
+Expected: 1 non-fatal failure
+  Actual:
+googletest-output-test_.cc:#: Success:
+Succeeded
+Stack trace: (omitted)
+
+
+Stack trace: (omitted)
+
+(expecting 1 failure)
+gtest.cc:#: Failure
+Expected: 1 non-fatal failure
+  Actual:
+googletest-output-test_.cc:#: Fatal failure:
+Failed
+Expected fatal failure.
+Stack trace: (omitted)
+
+
+Stack trace: (omitted)
+
+(expecting 1 failure)
+gtest.cc:#: Failure
+Expected: 1 non-fatal failure containing "Some other non-fatal failure."
+  Actual:
+googletest-output-test_.cc:#: Non-fatal failure:
+Failed
+Expected non-fatal failure.
+Stack trace: (omitted)
+
+
+Stack trace: (omitted)
+
+[  FAILED  ] ExpectFailureTest.ExpectNonFatalFailureOnAllThreads
+[----------] 2 tests from ExpectFailureWithThreadsTest
+[ RUN      ] ExpectFailureWithThreadsTest.ExpectFatalFailure
+(expecting 2 failures)
+googletest-output-test_.cc:#: Failure
+Failed
+Expected fatal failure.
+Stack trace: (omitted)
+
+gtest.cc:#: Failure
+Expected: 1 fatal failure
+  Actual: 0 failures
+Stack trace: (omitted)
+
+[  FAILED  ] ExpectFailureWithThreadsTest.ExpectFatalFailure
+[ RUN      ] ExpectFailureWithThreadsTest.ExpectNonFatalFailure
+(expecting 2 failures)
+googletest-output-test_.cc:#: Failure
+Failed
+Expected non-fatal failure.
+Stack trace: (omitted)
+
+gtest.cc:#: Failure
+Expected: 1 non-fatal failure
+  Actual: 0 failures
+Stack trace: (omitted)
+
+[  FAILED  ] ExpectFailureWithThreadsTest.ExpectNonFatalFailure
+[----------] 1 test from ScopedFakeTestPartResultReporterTest
+[ RUN      ] ScopedFakeTestPartResultReporterTest.InterceptOnlyCurrentThread
+(expecting 2 failures)
+googletest-output-test_.cc:#: Failure
+Failed
+Expected fatal failure.
+Stack trace: (omitted)
+
+googletest-output-test_.cc:#: Failure
+Failed
+Expected non-fatal failure.
+Stack trace: (omitted)
+
+[  FAILED  ] ScopedFakeTestPartResultReporterTest.InterceptOnlyCurrentThread
+[----------] 2 tests from DynamicFixture
+DynamicFixture::SetUpTestSuite
+[ RUN      ] DynamicFixture.DynamicTestPass
+DynamicFixture()
+DynamicFixture::SetUp
+DynamicFixture::TearDown
+~DynamicFixture()
+[       OK ] DynamicFixture.DynamicTestPass
+[ RUN      ] DynamicFixture.DynamicTestFail
+DynamicFixture()
+DynamicFixture::SetUp
+googletest-output-test_.cc:#: Failure
+Value of: Pass
+  Actual: false
+Expected: true
+Stack trace: (omitted)
+
+DynamicFixture::TearDown
+~DynamicFixture()
+[  FAILED  ] DynamicFixture.DynamicTestFail
+DynamicFixture::TearDownTestSuite
+[----------] 1 test from DynamicFixtureAnotherName
+DynamicFixture::SetUpTestSuite
+[ RUN      ] DynamicFixtureAnotherName.DynamicTestPass
+DynamicFixture()
+DynamicFixture::SetUp
+DynamicFixture::TearDown
+~DynamicFixture()
+[       OK ] DynamicFixtureAnotherName.DynamicTestPass
+DynamicFixture::TearDownTestSuite
+[----------] 2 tests from BadDynamicFixture1
+DynamicFixture::SetUpTestSuite
+[ RUN      ] BadDynamicFixture1.FixtureBase
+DynamicFixture()
+DynamicFixture::SetUp
+DynamicFixture::TearDown
+~DynamicFixture()
+[       OK ] BadDynamicFixture1.FixtureBase
+[ RUN      ] BadDynamicFixture1.TestBase
+DynamicFixture()
+gtest.cc:#: Failure
+Failed
+All tests in the same test suite must use the same test fixture
+class, so mixing TEST_F and TEST in the same test suite is
+illegal.  In test suite BadDynamicFixture1,
+test FixtureBase is defined using TEST_F but
+test TestBase is defined using TEST.  You probably
+want to change the TEST to TEST_F or move it to another test
+case.
+Stack trace: (omitted)
+
+~DynamicFixture()
+[  FAILED  ] BadDynamicFixture1.TestBase
+DynamicFixture::TearDownTestSuite
+[----------] 2 tests from BadDynamicFixture2
+DynamicFixture::SetUpTestSuite
+[ RUN      ] BadDynamicFixture2.FixtureBase
+DynamicFixture()
+DynamicFixture::SetUp
+DynamicFixture::TearDown
+~DynamicFixture()
+[       OK ] BadDynamicFixture2.FixtureBase
+[ RUN      ] BadDynamicFixture2.Derived
+DynamicFixture()
+gtest.cc:#: Failure
+Failed
+All tests in the same test suite must use the same test fixture
+class.  However, in test suite BadDynamicFixture2,
+you defined test FixtureBase and test Derived
+using two different test fixture classes.  This can happen if
+the two classes are from different namespaces or translation
+units and have the same name.  You should probably rename one
+of the classes to put the tests into different test suites.
+Stack trace: (omitted)
+
+~DynamicFixture()
+[  FAILED  ] BadDynamicFixture2.Derived
+DynamicFixture::TearDownTestSuite
+[----------] 1 test from PrintingFailingParams/FailingParamTest
+[ RUN      ] PrintingFailingParams/FailingParamTest.Fails/0
+googletest-output-test_.cc:#: Failure
+Expected equality of these values:
+  1
+  GetParam()
+    Which is: 2
+Stack trace: (omitted)
+
+[  FAILED  ] PrintingFailingParams/FailingParamTest.Fails/0, where GetParam() = 2
+[----------] 1 test from EmptyBasenameParamInst
+[ RUN      ] EmptyBasenameParamInst.Passes/0
+[       OK ] EmptyBasenameParamInst.Passes/0
+[----------] 2 tests from PrintingStrings/ParamTest
+[ RUN      ] PrintingStrings/ParamTest.Success/a
+[       OK ] PrintingStrings/ParamTest.Success/a
+[ RUN      ] PrintingStrings/ParamTest.Failure/a
+googletest-output-test_.cc:#: Failure
+Expected equality of these values:
+  "b"
+  GetParam()
+    Which is: "a"
+Expected failure
+Stack trace: (omitted)
+
+[  FAILED  ] PrintingStrings/ParamTest.Failure/a, where GetParam() = "a"
+[----------] 3 tests from GoogleTestVerification
+[ RUN      ] GoogleTestVerification.UninstantiatedParameterizedTestSuite<NoTests>
+googletest-output-test_.cc:#: Failure
+Parameterized test suite NoTests is instantiated via INSTANTIATE_TEST_SUITE_P, but no tests are defined via TEST_P . No test cases will run.
+
+Ideally, INSTANTIATE_TEST_SUITE_P should only ever be invoked from code that always depend on code that provides TEST_P. Failing to do so is often an indication of dead code, e.g. the last TEST_P was removed but the rest got left behind.
+
+To suppress this error for this test suite, insert the following line (in a non-header) in the namespace it is defined in:
+
+GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST(NoTests);
+Stack trace: (omitted)
+
+[  FAILED  ] GoogleTestVerification.UninstantiatedParameterizedTestSuite<NoTests>
+[ RUN      ] GoogleTestVerification.UninstantiatedParameterizedTestSuite<DetectNotInstantiatedTest>
+googletest-output-test_.cc:#: Failure
+Parameterized test suite DetectNotInstantiatedTest is defined via TEST_P, but never instantiated. None of the test cases will run. Either no INSTANTIATE_TEST_SUITE_P is provided or the only ones provided expand to nothing.
+
+Ideally, TEST_P definitions should only ever be included as part of binaries that intend to use them. (As opposed to, for example, being placed in a library that may be linked in to get other utilities.)
+
+To suppress this error for this test suite, insert the following line (in a non-header) in the namespace it is defined in:
+
+GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST(DetectNotInstantiatedTest);
+Stack trace: (omitted)
+
+[  FAILED  ] GoogleTestVerification.UninstantiatedParameterizedTestSuite<DetectNotInstantiatedTest>
+[ RUN      ] GoogleTestVerification.UninstantiatedTypeParameterizedTestSuite<DetectNotInstantiatedTypesTest>
+googletest-output-test_.cc:#: Failure
+Type parameterized test suite DetectNotInstantiatedTypesTest is defined via REGISTER_TYPED_TEST_SUITE_P, but never instantiated via INSTANTIATE_TYPED_TEST_SUITE_P. None of the test cases will run.
+
+Ideally, TYPED_TEST_P definitions should only ever be included as part of binaries that intend to use them. (As opposed to, for example, being placed in a library that may be linked in to get other utilities.)
+
+To suppress this error for this test suite, insert the following line (in a non-header) in the namespace it is defined in:
+
+GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST(DetectNotInstantiatedTypesTest);
+Stack trace: (omitted)
+
+[  FAILED  ] GoogleTestVerification.UninstantiatedTypeParameterizedTestSuite<DetectNotInstantiatedTypesTest>
+[----------] Global test environment tear-down
+BarEnvironment::TearDown() called.
+googletest-output-test_.cc:#: Failure
+Failed
+Expected non-fatal failure.
+Stack trace: (omitted)
+
+FooEnvironment::TearDown() called.
+googletest-output-test_.cc:#: Failure
+Failed
+Expected fatal failure.
+Stack trace: (omitted)
+
+[==========] 88 tests from 41 test suites ran.
+[  PASSED  ] 31 tests.
+[  FAILED  ] 57 tests, listed below:
+[  FAILED  ] NonfatalFailureTest.EscapesStringOperands
+[  FAILED  ] NonfatalFailureTest.DiffForLongStrings
+[  FAILED  ] FatalFailureTest.FatalFailureInSubroutine
+[  FAILED  ] FatalFailureTest.FatalFailureInNestedSubroutine
+[  FAILED  ] FatalFailureTest.NonfatalFailureInSubroutine
+[  FAILED  ] LoggingTest.InterleavingLoggingAndAssertions
+[  FAILED  ] SCOPED_TRACETest.AcceptedValues
+[  FAILED  ] SCOPED_TRACETest.ObeysScopes
+[  FAILED  ] SCOPED_TRACETest.WorksInLoop
+[  FAILED  ] SCOPED_TRACETest.WorksInSubroutine
+[  FAILED  ] SCOPED_TRACETest.CanBeNested
+[  FAILED  ] SCOPED_TRACETest.CanBeRepeated
+[  FAILED  ] SCOPED_TRACETest.WorksConcurrently
+[  FAILED  ] ScopedTraceTest.WithExplicitFileAndLine
+[  FAILED  ] NonFatalFailureInFixtureConstructorTest.FailureInConstructor
+[  FAILED  ] FatalFailureInFixtureConstructorTest.FailureInConstructor
+[  FAILED  ] NonFatalFailureInSetUpTest.FailureInSetUp
+[  FAILED  ] FatalFailureInSetUpTest.FailureInSetUp
+[  FAILED  ] AddFailureAtTest.MessageContainsSpecifiedFileAndLineNumber
+[  FAILED  ] GtestFailAtTest.MessageContainsSpecifiedFileAndLineNumber
+[  FAILED  ] MixedUpTestSuiteTest.ThisShouldFail
+[  FAILED  ] MixedUpTestSuiteTest.ThisShouldFailToo
+[  FAILED  ] MixedUpTestSuiteWithSameTestNameTest.TheSecondTestWithThisNameShouldFail
+[  FAILED  ] TEST_F_before_TEST_in_same_test_case.DefinedUsingTESTAndShouldFail
+[  FAILED  ] TEST_before_TEST_F_in_same_test_case.DefinedUsingTEST_FAndShouldFail
+[  FAILED  ] ExpectNonfatalFailureTest.FailsWhenThereIsNoNonfatalFailure
+[  FAILED  ] ExpectNonfatalFailureTest.FailsWhenThereAreTwoNonfatalFailures
+[  FAILED  ] ExpectNonfatalFailureTest.FailsWhenThereIsOneFatalFailure
+[  FAILED  ] ExpectNonfatalFailureTest.FailsWhenStatementReturns
+[  FAILED  ] ExpectNonfatalFailureTest.FailsWhenStatementThrows
+[  FAILED  ] ExpectFatalFailureTest.FailsWhenThereIsNoFatalFailure
+[  FAILED  ] ExpectFatalFailureTest.FailsWhenThereAreTwoFatalFailures
+[  FAILED  ] ExpectFatalFailureTest.FailsWhenThereIsOneNonfatalFailure
+[  FAILED  ] ExpectFatalFailureTest.FailsWhenStatementReturns
+[  FAILED  ] ExpectFatalFailureTest.FailsWhenStatementThrows
+[  FAILED  ] TypedTest/0.Failure, where TypeParam = int
+[  FAILED  ] TypedTestWithNames/char0.Failure, where TypeParam = char
+[  FAILED  ] TypedTestWithNames/int1.Failure, where TypeParam = int
+[  FAILED  ] Unsigned/TypedTestP/0.Failure, where TypeParam = unsigned char
+[  FAILED  ] Unsigned/TypedTestP/1.Failure, where TypeParam = unsigned int
+[  FAILED  ] UnsignedCustomName/TypedTestP/unsignedChar0.Failure, where TypeParam = unsigned char
+[  FAILED  ] UnsignedCustomName/TypedTestP/unsignedInt1.Failure, where TypeParam = unsigned int
+[  FAILED  ] ExpectFailureTest.ExpectFatalFailure
+[  FAILED  ] ExpectFailureTest.ExpectNonFatalFailure
+[  FAILED  ] ExpectFailureTest.ExpectFatalFailureOnAllThreads
+[  FAILED  ] ExpectFailureTest.ExpectNonFatalFailureOnAllThreads
+[  FAILED  ] ExpectFailureWithThreadsTest.ExpectFatalFailure
+[  FAILED  ] ExpectFailureWithThreadsTest.ExpectNonFatalFailure
+[  FAILED  ] ScopedFakeTestPartResultReporterTest.InterceptOnlyCurrentThread
+[  FAILED  ] DynamicFixture.DynamicTestFail
+[  FAILED  ] BadDynamicFixture1.TestBase
+[  FAILED  ] BadDynamicFixture2.Derived
+[  FAILED  ] PrintingFailingParams/FailingParamTest.Fails/0, where GetParam() = 2
+[  FAILED  ] PrintingStrings/ParamTest.Failure/a, where GetParam() = "a"
+[  FAILED  ] GoogleTestVerification.UninstantiatedParameterizedTestSuite<NoTests>
+[  FAILED  ] GoogleTestVerification.UninstantiatedParameterizedTestSuite<DetectNotInstantiatedTest>
+[  FAILED  ] GoogleTestVerification.UninstantiatedTypeParameterizedTestSuite<DetectNotInstantiatedTypesTest>
+
+57 FAILED TESTS
+  YOU HAVE 1 DISABLED TEST
+
+Note: Google Test filter = FatalFailureTest.*:LoggingTest.*
+[==========] Running 4 tests from 2 test suites.
+[----------] Global test environment set-up.
+[----------] 3 tests from FatalFailureTest
+[ RUN      ] FatalFailureTest.FatalFailureInSubroutine
+(expecting a failure that x should be 1)
+googletest-output-test_.cc:#: Failure
+Expected equality of these values:
+  1
+  x
+    Which is: 2
+Stack trace: (omitted)
+
+[  FAILED  ] FatalFailureTest.FatalFailureInSubroutine (? ms)
+[ RUN      ] FatalFailureTest.FatalFailureInNestedSubroutine
+(expecting a failure that x should be 1)
+googletest-output-test_.cc:#: Failure
+Expected equality of these values:
+  1
+  x
+    Which is: 2
+Stack trace: (omitted)
+
+[  FAILED  ] FatalFailureTest.FatalFailureInNestedSubroutine (? ms)
+[ RUN      ] FatalFailureTest.NonfatalFailureInSubroutine
+(expecting a failure on false)
+googletest-output-test_.cc:#: Failure
+Value of: false
+  Actual: false
+Expected: true
+Stack trace: (omitted)
+
+[  FAILED  ] FatalFailureTest.NonfatalFailureInSubroutine (? ms)
+[----------] 3 tests from FatalFailureTest (? ms total)
+
+[----------] 1 test from LoggingTest
+[ RUN      ] LoggingTest.InterleavingLoggingAndAssertions
+(expecting 2 failures on (3) >= (a[i]))
+i == 0
+i == 1
+googletest-output-test_.cc:#: Failure
+Expected: (3) >= (a[i]), actual: 3 vs 9
+Stack trace: (omitted)
+
+i == 2
+i == 3
+googletest-output-test_.cc:#: Failure
+Expected: (3) >= (a[i]), actual: 3 vs 6
+Stack trace: (omitted)
+
+[  FAILED  ] LoggingTest.InterleavingLoggingAndAssertions (? ms)
+[----------] 1 test from LoggingTest (? ms total)
+
+[----------] Global test environment tear-down
+[==========] 4 tests from 2 test suites ran. (? ms total)
+[  PASSED  ] 0 tests.
+[  FAILED  ] 4 tests, listed below:
+[  FAILED  ] FatalFailureTest.FatalFailureInSubroutine
+[  FAILED  ] FatalFailureTest.FatalFailureInNestedSubroutine
+[  FAILED  ] FatalFailureTest.NonfatalFailureInSubroutine
+[  FAILED  ] LoggingTest.InterleavingLoggingAndAssertions
+
+ 4 FAILED TESTS
+Note: Google Test filter = *DISABLED_*
+[==========] Running 1 test from 1 test suite.
+[----------] Global test environment set-up.
+[----------] 1 test from DisabledTestsWarningTest
+[ RUN      ] DisabledTestsWarningTest.DISABLED_AlsoRunDisabledTestsFlagSuppressesWarning
+[       OK ] DisabledTestsWarningTest.DISABLED_AlsoRunDisabledTestsFlagSuppressesWarning
+[----------] Global test environment tear-down
+[==========] 1 test from 1 test suite ran.
+[  PASSED  ] 1 test.
+Note: Google Test filter = PassingTest.*
+Note: This is test shard 2 of 2.
+[==========] Running 1 test from 1 test suite.
+[----------] Global test environment set-up.
+[----------] 1 test from PassingTest
+[ RUN      ] PassingTest.PassingTest2
+[       OK ] PassingTest.PassingTest2
+[----------] Global test environment tear-down
+[==========] 1 test from 1 test suite ran.
+[  PASSED  ] 1 test.
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-output-test.py b/leveldb_base/third_party/googletest/googletest/test/googletest-output-test.py
new file mode 100644
index 0000000..09028f6
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-output-test.py
@@ -0,0 +1,346 @@
+#!/usr/bin/env python
+#
+# Copyright 2008, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+r"""Tests the text output of Google C++ Testing and Mocking Framework.
+
+To update the golden file:
+googletest_output_test.py --build_dir=BUILD/DIR --gengolden
+where BUILD/DIR contains the built googletest-output-test_ file.
+googletest_output_test.py --gengolden
+googletest_output_test.py
+"""
+
+import difflib
+import os
+import re
+import sys
+import gtest_test_utils
+
+
+# The flag for generating the golden file
+GENGOLDEN_FLAG = '--gengolden'
+CATCH_EXCEPTIONS_ENV_VAR_NAME = 'GTEST_CATCH_EXCEPTIONS'
+
+# The flag indicating stacktraces are not supported
+NO_STACKTRACE_SUPPORT_FLAG = '--no_stacktrace_support'
+
+IS_LINUX = os.name == 'posix' and os.uname()[0] == 'Linux'
+IS_WINDOWS = os.name == 'nt'
+
+GOLDEN_NAME = 'googletest-output-test-golden-lin.txt'
+
+PROGRAM_PATH = gtest_test_utils.GetTestExecutablePath('googletest-output-test_')
+
+# At least one command we exercise must not have the
+# 'internal_skip_environment_and_ad_hoc_tests' argument.
+COMMAND_LIST_TESTS = ({}, [PROGRAM_PATH, '--gtest_list_tests'])
+COMMAND_WITH_COLOR = ({}, [PROGRAM_PATH, '--gtest_color=yes'])
+COMMAND_WITH_TIME = ({}, [PROGRAM_PATH,
+                          '--gtest_print_time',
+                          'internal_skip_environment_and_ad_hoc_tests',
+                          '--gtest_filter=FatalFailureTest.*:LoggingTest.*'])
+COMMAND_WITH_DISABLED = (
+    {}, [PROGRAM_PATH,
+         '--gtest_also_run_disabled_tests',
+         'internal_skip_environment_and_ad_hoc_tests',
+         '--gtest_filter=*DISABLED_*'])
+COMMAND_WITH_SHARDING = (
+    {'GTEST_SHARD_INDEX': '1', 'GTEST_TOTAL_SHARDS': '2'},
+    [PROGRAM_PATH,
+     'internal_skip_environment_and_ad_hoc_tests',
+     '--gtest_filter=PassingTest.*'])
+
+GOLDEN_PATH = os.path.join(gtest_test_utils.GetSourceDir(), GOLDEN_NAME)
+
+
+def ToUnixLineEnding(s):
+  """Changes all Windows/Mac line endings in s to UNIX line endings."""
+
+  return s.replace('\r\n', '\n').replace('\r', '\n')
+
+
+def RemoveLocations(test_output):
+  """Removes all file location info from a Google Test program's output.
+
+  Args:
+       test_output:  the output of a Google Test program.
+
+  Returns:
+       output with all file location info (in the form of
+       'DIRECTORY/FILE_NAME:LINE_NUMBER: 'or
+       'DIRECTORY\\FILE_NAME(LINE_NUMBER): ') replaced by
+       'FILE_NAME:#: '.
+  """
+
+  return re.sub(r'.*[/\\]((googletest-output-test_|gtest).cc)(\:\d+|\(\d+\))\: ',
+                r'\1:#: ', test_output)
+
+
+def RemoveStackTraceDetails(output):
+  """Removes all stack traces from a Google Test program's output."""
+
+  # *? means "find the shortest string that matches".
+  return re.sub(r'Stack trace:(.|\n)*?\n\n',
+                'Stack trace: (omitted)\n\n', output)
+
+
+def RemoveStackTraces(output):
+  """Removes all traces of stack traces from a Google Test program's output."""
+
+  # *? means "find the shortest string that matches".
+  return re.sub(r'Stack trace:(.|\n)*?\n\n', '', output)
+
+
+def RemoveTime(output):
+  """Removes all time information from a Google Test program's output."""
+
+  return re.sub(r'\(\d+ ms', '(? ms', output)
+
+
+def RemoveTypeInfoDetails(test_output):
+  """Removes compiler-specific type info from Google Test program's output.
+
+  Args:
+       test_output:  the output of a Google Test program.
+
+  Returns:
+       output with type information normalized to canonical form.
+  """
+
+  # some compilers output the name of type 'unsigned int' as 'unsigned'
+  return re.sub(r'unsigned int', 'unsigned', test_output)
+
+
+def NormalizeToCurrentPlatform(test_output):
+  """Normalizes platform specific output details for easier comparison."""
+
+  if IS_WINDOWS:
+    # Removes the color information that is not present on Windows.
+    test_output = re.sub('\x1b\\[(0;3\d)?m', '', test_output)
+    # Changes failure message headers into the Windows format.
+    test_output = re.sub(r': Failure\n', r': error: ', test_output)
+    # Changes file(line_number) to file:line_number.
+    test_output = re.sub(r'((\w|\.)+)\((\d+)\):', r'\1:\3:', test_output)
+
+  return test_output
+
+
+def RemoveTestCounts(output):
+  """Removes test counts from a Google Test program's output."""
+
+  output = re.sub(r'\d+ tests?, listed below',
+                  '? tests, listed below', output)
+  output = re.sub(r'\d+ FAILED TESTS',
+                  '? FAILED TESTS', output)
+  output = re.sub(r'\d+ tests? from \d+ test cases?',
+                  '? tests from ? test cases', output)
+  output = re.sub(r'\d+ tests? from ([a-zA-Z_])',
+                  r'? tests from \1', output)
+  return re.sub(r'\d+ tests?\.', '? tests.', output)
+
+
+def RemoveMatchingTests(test_output, pattern):
+  """Removes output of specified tests from a Google Test program's output.
+
+  This function strips not only the beginning and the end of a test but also
+  all output in between.
+
+  Args:
+    test_output:       A string containing the test output.
+    pattern:           A regex string that matches names of test cases or
+                       tests to remove.
+
+  Returns:
+    Contents of test_output with tests whose names match pattern removed.
+  """
+
+  test_output = re.sub(
+      r'.*\[ RUN      \] .*%s(.|\n)*?\[(  FAILED  |       OK )\] .*%s.*\n' % (
+          pattern, pattern),
+      '',
+      test_output)
+  return re.sub(r'.*%s.*\n' % pattern, '', test_output)
+
+
+def NormalizeOutput(output):
+  """Normalizes output (the output of googletest-output-test_.exe)."""
+
+  output = ToUnixLineEnding(output)
+  output = RemoveLocations(output)
+  output = RemoveStackTraceDetails(output)
+  output = RemoveTime(output)
+  return output
+
+
+def GetShellCommandOutput(env_cmd):
+  """Runs a command in a sub-process, and returns its output in a string.
+
+  Args:
+    env_cmd: The shell command. A 2-tuple where element 0 is a dict of extra
+             environment variables to set, and element 1 is a string with
+             the command and any flags.
+
+  Returns:
+    A string with the command's combined standard and diagnostic output.
+  """
+
+  # Spawns cmd in a sub-process, and gets its standard I/O file objects.
+  # Set and save the environment properly.
+  environ = os.environ.copy()
+  environ.update(env_cmd[0])
+  p = gtest_test_utils.Subprocess(env_cmd[1], env=environ)
+
+  return p.output
+
+
+def GetCommandOutput(env_cmd):
+  """Runs a command and returns its output with all file location
+  info stripped off.
+
+  Args:
+    env_cmd:  The shell command. A 2-tuple where element 0 is a dict of extra
+              environment variables to set, and element 1 is a string with
+              the command and any flags.
+  """
+
+  # Disables exception pop-ups on Windows.
+  environ, cmdline = env_cmd
+  environ = dict(environ)  # Ensures we are modifying a copy.
+  environ[CATCH_EXCEPTIONS_ENV_VAR_NAME] = '1'
+  return NormalizeOutput(GetShellCommandOutput((environ, cmdline)))
+
+
+def GetOutputOfAllCommands():
+  """Returns concatenated output from several representative commands."""
+
+  return (GetCommandOutput(COMMAND_WITH_COLOR) +
+          GetCommandOutput(COMMAND_WITH_TIME) +
+          GetCommandOutput(COMMAND_WITH_DISABLED) +
+          GetCommandOutput(COMMAND_WITH_SHARDING))
+
+
+test_list = GetShellCommandOutput(COMMAND_LIST_TESTS)
+SUPPORTS_DEATH_TESTS = 'DeathTest' in test_list
+SUPPORTS_TYPED_TESTS = 'TypedTest' in test_list
+SUPPORTS_THREADS = 'ExpectFailureWithThreadsTest' in test_list
+SUPPORTS_STACK_TRACES = NO_STACKTRACE_SUPPORT_FLAG not in sys.argv
+
+CAN_GENERATE_GOLDEN_FILE = (SUPPORTS_DEATH_TESTS and
+                            SUPPORTS_TYPED_TESTS and
+                            SUPPORTS_THREADS and
+                            SUPPORTS_STACK_TRACES)
+
+class GTestOutputTest(gtest_test_utils.TestCase):
+  def RemoveUnsupportedTests(self, test_output):
+    if not SUPPORTS_DEATH_TESTS:
+      test_output = RemoveMatchingTests(test_output, 'DeathTest')
+    if not SUPPORTS_TYPED_TESTS:
+      test_output = RemoveMatchingTests(test_output, 'TypedTest')
+      test_output = RemoveMatchingTests(test_output, 'TypedDeathTest')
+      test_output = RemoveMatchingTests(test_output, 'TypeParamDeathTest')
+    if not SUPPORTS_THREADS:
+      test_output = RemoveMatchingTests(test_output,
+                                        'ExpectFailureWithThreadsTest')
+      test_output = RemoveMatchingTests(test_output,
+                                        'ScopedFakeTestPartResultReporterTest')
+      test_output = RemoveMatchingTests(test_output,
+                                        'WorksConcurrently')
+    if not SUPPORTS_STACK_TRACES:
+      test_output = RemoveStackTraces(test_output)
+
+    return test_output
+
+  def testOutput(self):
+    output = GetOutputOfAllCommands()
+
+    golden_file = open(GOLDEN_PATH, 'rb')
+    # A mis-configured source control system can cause \r appear in EOL
+    # sequences when we read the golden file irrespective of an operating
+    # system used. Therefore, we need to strip those \r's from newlines
+    # unconditionally.
+    golden = ToUnixLineEnding(golden_file.read().decode())
+    golden_file.close()
+
+    # We want the test to pass regardless of certain features being
+    # supported or not.
+
+    # We still have to remove type name specifics in all cases.
+    normalized_actual = RemoveTypeInfoDetails(output)
+    normalized_golden = RemoveTypeInfoDetails(golden)
+
+    if CAN_GENERATE_GOLDEN_FILE:
+      self.assertEqual(normalized_golden, normalized_actual,
+                       '\n'.join(difflib.unified_diff(
+                           normalized_golden.split('\n'),
+                           normalized_actual.split('\n'),
+                           'golden', 'actual')))
+    else:
+      normalized_actual = NormalizeToCurrentPlatform(
+          RemoveTestCounts(normalized_actual))
+      normalized_golden = NormalizeToCurrentPlatform(
+          RemoveTestCounts(self.RemoveUnsupportedTests(normalized_golden)))
+
+      # This code is very handy when debugging golden file differences:
+      if os.getenv('DEBUG_GTEST_OUTPUT_TEST'):
+        open(os.path.join(
+            gtest_test_utils.GetSourceDir(),
+            '_googletest-output-test_normalized_actual.txt'), 'wb').write(
+                normalized_actual)
+        open(os.path.join(
+            gtest_test_utils.GetSourceDir(),
+            '_googletest-output-test_normalized_golden.txt'), 'wb').write(
+                normalized_golden)
+
+      self.assertEqual(normalized_golden, normalized_actual)
+
+
+if __name__ == '__main__':
+  if NO_STACKTRACE_SUPPORT_FLAG in sys.argv:
+    # unittest.main() can't handle unknown flags
+    sys.argv.remove(NO_STACKTRACE_SUPPORT_FLAG)
+
+  if GENGOLDEN_FLAG in sys.argv:
+    if CAN_GENERATE_GOLDEN_FILE:
+      output = GetOutputOfAllCommands()
+      golden_file = open(GOLDEN_PATH, 'wb')
+      golden_file.write(output.encode())
+      golden_file.close()
+    else:
+      message = (
+          """Unable to write a golden file when compiled in an environment
+that does not support all the required features (death tests,
+typed tests, stack traces, and multiple threads).
+Please build this test and generate the golden file using Blaze on Linux.""")
+
+      sys.stderr.write(message)
+      sys.exit(1)
+  else:
+    gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-output-test_.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-output-test_.cc
new file mode 100644
index 0000000..074f64e
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-output-test_.cc
@@ -0,0 +1,1108 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// The purpose of this file is to generate Google Test output under
+// various conditions.  The output will then be verified by
+// googletest-output-test.py to ensure that Google Test generates the
+// desired messages.  Therefore, most tests in this file are MEANT TO
+// FAIL.
+
+#include "gtest/gtest-spi.h"
+#include "gtest/gtest.h"
+#include "src/gtest-internal-inl.h"
+
+#include <stdlib.h>
+
+#if _MSC_VER
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4127 /* conditional expression is constant */)
+#endif  //  _MSC_VER
+
+#if GTEST_IS_THREADSAFE
+using testing::ScopedFakeTestPartResultReporter;
+using testing::TestPartResultArray;
+
+using testing::internal::Notification;
+using testing::internal::ThreadWithParam;
+#endif
+
+namespace posix = ::testing::internal::posix;
+
+// Tests catching fatal failures.
+
+// A subroutine used by the following test.
+void TestEq1(int x) {
+  ASSERT_EQ(1, x);
+}
+
+// This function calls a test subroutine, catches the fatal failure it
+// generates, and then returns early.
+void TryTestSubroutine() {
+  // Calls a subrountine that yields a fatal failure.
+  TestEq1(2);
+
+  // Catches the fatal failure and aborts the test.
+  //
+  // The testing::Test:: prefix is necessary when calling
+  // HasFatalFailure() outside of a TEST, TEST_F, or test fixture.
+  if (testing::Test::HasFatalFailure()) return;
+
+  // If we get here, something is wrong.
+  FAIL() << "This should never be reached.";
+}
+
+TEST(PassingTest, PassingTest1) {
+}
+
+TEST(PassingTest, PassingTest2) {
+}
+
+// Tests that parameters of failing parameterized tests are printed in the
+// failing test summary.
+class FailingParamTest : public testing::TestWithParam<int> {};
+
+TEST_P(FailingParamTest, Fails) {
+  EXPECT_EQ(1, GetParam());
+}
+
+// This generates a test which will fail. Google Test is expected to print
+// its parameter when it outputs the list of all failed tests.
+INSTANTIATE_TEST_SUITE_P(PrintingFailingParams,
+                         FailingParamTest,
+                         testing::Values(2));
+
+// Tests that an empty value for the test suite basename yields just
+// the test name without any prior /
+class EmptyBasenameParamInst : public testing::TestWithParam<int> {};
+
+TEST_P(EmptyBasenameParamInst, Passes) { EXPECT_EQ(1, GetParam()); }
+
+INSTANTIATE_TEST_SUITE_P(, EmptyBasenameParamInst, testing::Values(1));
+
+static const char kGoldenString[] = "\"Line\0 1\"\nLine 2";
+
+TEST(NonfatalFailureTest, EscapesStringOperands) {
+  std::string actual = "actual \"string\"";
+  EXPECT_EQ(kGoldenString, actual);
+
+  const char* golden = kGoldenString;
+  EXPECT_EQ(golden, actual);
+}
+
+TEST(NonfatalFailureTest, DiffForLongStrings) {
+  std::string golden_str(kGoldenString, sizeof(kGoldenString) - 1);
+  EXPECT_EQ(golden_str, "Line 2");
+}
+
+// Tests catching a fatal failure in a subroutine.
+TEST(FatalFailureTest, FatalFailureInSubroutine) {
+  printf("(expecting a failure that x should be 1)\n");
+
+  TryTestSubroutine();
+}
+
+// Tests catching a fatal failure in a nested subroutine.
+TEST(FatalFailureTest, FatalFailureInNestedSubroutine) {
+  printf("(expecting a failure that x should be 1)\n");
+
+  // Calls a subrountine that yields a fatal failure.
+  TryTestSubroutine();
+
+  // Catches the fatal failure and aborts the test.
+  //
+  // When calling HasFatalFailure() inside a TEST, TEST_F, or test
+  // fixture, the testing::Test:: prefix is not needed.
+  if (HasFatalFailure()) return;
+
+  // If we get here, something is wrong.
+  FAIL() << "This should never be reached.";
+}
+
+// Tests HasFatalFailure() after a failed EXPECT check.
+TEST(FatalFailureTest, NonfatalFailureInSubroutine) {
+  printf("(expecting a failure on false)\n");
+  EXPECT_TRUE(false);  // Generates a nonfatal failure
+  ASSERT_FALSE(HasFatalFailure());  // This should succeed.
+}
+
+// Tests interleaving user logging and Google Test assertions.
+TEST(LoggingTest, InterleavingLoggingAndAssertions) {
+  static const int a[4] = {
+    3, 9, 2, 6
+  };
+
+  printf("(expecting 2 failures on (3) >= (a[i]))\n");
+  for (int i = 0; i < static_cast<int>(sizeof(a)/sizeof(*a)); i++) {
+    printf("i == %d\n", i);
+    EXPECT_GE(3, a[i]);
+  }
+}
+
+// Tests the SCOPED_TRACE macro.
+
+// A helper function for testing SCOPED_TRACE.
+void SubWithoutTrace(int n) {
+  EXPECT_EQ(1, n);
+  ASSERT_EQ(2, n);
+}
+
+// Another helper function for testing SCOPED_TRACE.
+void SubWithTrace(int n) {
+  SCOPED_TRACE(testing::Message() << "n = " << n);
+
+  SubWithoutTrace(n);
+}
+
+TEST(SCOPED_TRACETest, AcceptedValues) {
+  SCOPED_TRACE("literal string");
+  SCOPED_TRACE(std::string("std::string"));
+  SCOPED_TRACE(1337);  // streamable type
+  const char* null_value = nullptr;
+  SCOPED_TRACE(null_value);
+
+  ADD_FAILURE() << "Just checking that all these values work fine.";
+}
+
+// Tests that SCOPED_TRACE() obeys lexical scopes.
+TEST(SCOPED_TRACETest, ObeysScopes) {
+  printf("(expected to fail)\n");
+
+  // There should be no trace before SCOPED_TRACE() is invoked.
+  ADD_FAILURE() << "This failure is expected, and shouldn't have a trace.";
+
+  {
+    SCOPED_TRACE("Expected trace");
+    // After SCOPED_TRACE(), a failure in the current scope should contain
+    // the trace.
+    ADD_FAILURE() << "This failure is expected, and should have a trace.";
+  }
+
+  // Once the control leaves the scope of the SCOPED_TRACE(), there
+  // should be no trace again.
+  ADD_FAILURE() << "This failure is expected, and shouldn't have a trace.";
+}
+
+// Tests that SCOPED_TRACE works inside a loop.
+TEST(SCOPED_TRACETest, WorksInLoop) {
+  printf("(expected to fail)\n");
+
+  for (int i = 1; i <= 2; i++) {
+    SCOPED_TRACE(testing::Message() << "i = " << i);
+
+    SubWithoutTrace(i);
+  }
+}
+
+// Tests that SCOPED_TRACE works in a subroutine.
+TEST(SCOPED_TRACETest, WorksInSubroutine) {
+  printf("(expected to fail)\n");
+
+  SubWithTrace(1);
+  SubWithTrace(2);
+}
+
+// Tests that SCOPED_TRACE can be nested.
+TEST(SCOPED_TRACETest, CanBeNested) {
+  printf("(expected to fail)\n");
+
+  SCOPED_TRACE("");  // A trace without a message.
+
+  SubWithTrace(2);
+}
+
+// Tests that multiple SCOPED_TRACEs can be used in the same scope.
+TEST(SCOPED_TRACETest, CanBeRepeated) {
+  printf("(expected to fail)\n");
+
+  SCOPED_TRACE("A");
+  ADD_FAILURE()
+      << "This failure is expected, and should contain trace point A.";
+
+  SCOPED_TRACE("B");
+  ADD_FAILURE()
+      << "This failure is expected, and should contain trace point A and B.";
+
+  {
+    SCOPED_TRACE("C");
+    ADD_FAILURE() << "This failure is expected, and should "
+                  << "contain trace point A, B, and C.";
+  }
+
+  SCOPED_TRACE("D");
+  ADD_FAILURE() << "This failure is expected, and should "
+                << "contain trace point A, B, and D.";
+}
+
+#if GTEST_IS_THREADSAFE
+// Tests that SCOPED_TRACE()s can be used concurrently from multiple
+// threads.  Namely, an assertion should be affected by
+// SCOPED_TRACE()s in its own thread only.
+
+// Here's the sequence of actions that happen in the test:
+//
+//   Thread A (main)                | Thread B (spawned)
+//   ===============================|================================
+//   spawns thread B                |
+//   -------------------------------+--------------------------------
+//   waits for n1                   | SCOPED_TRACE("Trace B");
+//                                  | generates failure #1
+//                                  | notifies n1
+//   -------------------------------+--------------------------------
+//   SCOPED_TRACE("Trace A");       | waits for n2
+//   generates failure #2           |
+//   notifies n2                    |
+//   -------------------------------|--------------------------------
+//   waits for n3                   | generates failure #3
+//                                  | trace B dies
+//                                  | generates failure #4
+//                                  | notifies n3
+//   -------------------------------|--------------------------------
+//   generates failure #5           | finishes
+//   trace A dies                   |
+//   generates failure #6           |
+//   -------------------------------|--------------------------------
+//   waits for thread B to finish   |
+
+struct CheckPoints {
+  Notification n1;
+  Notification n2;
+  Notification n3;
+};
+
+static void ThreadWithScopedTrace(CheckPoints* check_points) {
+  {
+    SCOPED_TRACE("Trace B");
+    ADD_FAILURE()
+        << "Expected failure #1 (in thread B, only trace B alive).";
+    check_points->n1.Notify();
+    check_points->n2.WaitForNotification();
+
+    ADD_FAILURE()
+        << "Expected failure #3 (in thread B, trace A & B both alive).";
+  }  // Trace B dies here.
+  ADD_FAILURE()
+      << "Expected failure #4 (in thread B, only trace A alive).";
+  check_points->n3.Notify();
+}
+
+TEST(SCOPED_TRACETest, WorksConcurrently) {
+  printf("(expecting 6 failures)\n");
+
+  CheckPoints check_points;
+  ThreadWithParam<CheckPoints*> thread(&ThreadWithScopedTrace, &check_points,
+                                       nullptr);
+  check_points.n1.WaitForNotification();
+
+  {
+    SCOPED_TRACE("Trace A");
+    ADD_FAILURE()
+        << "Expected failure #2 (in thread A, trace A & B both alive).";
+    check_points.n2.Notify();
+    check_points.n3.WaitForNotification();
+
+    ADD_FAILURE()
+        << "Expected failure #5 (in thread A, only trace A alive).";
+  }  // Trace A dies here.
+  ADD_FAILURE()
+      << "Expected failure #6 (in thread A, no trace alive).";
+  thread.Join();
+}
+#endif  // GTEST_IS_THREADSAFE
+
+// Tests basic functionality of the ScopedTrace utility (most of its features
+// are already tested in SCOPED_TRACETest).
+TEST(ScopedTraceTest, WithExplicitFileAndLine) {
+  testing::ScopedTrace trace("explicit_file.cc", 123, "expected trace message");
+  ADD_FAILURE() << "Check that the trace is attached to a particular location.";
+}
+
+TEST(DisabledTestsWarningTest,
+     DISABLED_AlsoRunDisabledTestsFlagSuppressesWarning) {
+  // This test body is intentionally empty.  Its sole purpose is for
+  // verifying that the --gtest_also_run_disabled_tests flag
+  // suppresses the "YOU HAVE 12 DISABLED TESTS" warning at the end of
+  // the test output.
+}
+
+// Tests using assertions outside of TEST and TEST_F.
+//
+// This function creates two failures intentionally.
+void AdHocTest() {
+  printf("The non-test part of the code is expected to have 2 failures.\n\n");
+  EXPECT_TRUE(false);
+  EXPECT_EQ(2, 3);
+}
+
+// Runs all TESTs, all TEST_Fs, and the ad hoc test.
+int RunAllTests() {
+  AdHocTest();
+  return RUN_ALL_TESTS();
+}
+
+// Tests non-fatal failures in the fixture constructor.
+class NonFatalFailureInFixtureConstructorTest : public testing::Test {
+ protected:
+  NonFatalFailureInFixtureConstructorTest() {
+    printf("(expecting 5 failures)\n");
+    ADD_FAILURE() << "Expected failure #1, in the test fixture c'tor.";
+  }
+
+  ~NonFatalFailureInFixtureConstructorTest() override {
+    ADD_FAILURE() << "Expected failure #5, in the test fixture d'tor.";
+  }
+
+  void SetUp() override { ADD_FAILURE() << "Expected failure #2, in SetUp()."; }
+
+  void TearDown() override {
+    ADD_FAILURE() << "Expected failure #4, in TearDown.";
+  }
+};
+
+TEST_F(NonFatalFailureInFixtureConstructorTest, FailureInConstructor) {
+  ADD_FAILURE() << "Expected failure #3, in the test body.";
+}
+
+// Tests fatal failures in the fixture constructor.
+class FatalFailureInFixtureConstructorTest : public testing::Test {
+ protected:
+  FatalFailureInFixtureConstructorTest() {
+    printf("(expecting 2 failures)\n");
+    Init();
+  }
+
+  ~FatalFailureInFixtureConstructorTest() override {
+    ADD_FAILURE() << "Expected failure #2, in the test fixture d'tor.";
+  }
+
+  void SetUp() override {
+    ADD_FAILURE() << "UNEXPECTED failure in SetUp().  "
+                  << "We should never get here, as the test fixture c'tor "
+                  << "had a fatal failure.";
+  }
+
+  void TearDown() override {
+    ADD_FAILURE() << "UNEXPECTED failure in TearDown().  "
+                  << "We should never get here, as the test fixture c'tor "
+                  << "had a fatal failure.";
+  }
+
+ private:
+  void Init() {
+    FAIL() << "Expected failure #1, in the test fixture c'tor.";
+  }
+};
+
+TEST_F(FatalFailureInFixtureConstructorTest, FailureInConstructor) {
+  ADD_FAILURE() << "UNEXPECTED failure in the test body.  "
+                << "We should never get here, as the test fixture c'tor "
+                << "had a fatal failure.";
+}
+
+// Tests non-fatal failures in SetUp().
+class NonFatalFailureInSetUpTest : public testing::Test {
+ protected:
+  ~NonFatalFailureInSetUpTest() override { Deinit(); }
+
+  void SetUp() override {
+    printf("(expecting 4 failures)\n");
+    ADD_FAILURE() << "Expected failure #1, in SetUp().";
+  }
+
+  void TearDown() override { FAIL() << "Expected failure #3, in TearDown()."; }
+
+ private:
+  void Deinit() {
+    FAIL() << "Expected failure #4, in the test fixture d'tor.";
+  }
+};
+
+TEST_F(NonFatalFailureInSetUpTest, FailureInSetUp) {
+  FAIL() << "Expected failure #2, in the test function.";
+}
+
+// Tests fatal failures in SetUp().
+class FatalFailureInSetUpTest : public testing::Test {
+ protected:
+  ~FatalFailureInSetUpTest() override { Deinit(); }
+
+  void SetUp() override {
+    printf("(expecting 3 failures)\n");
+    FAIL() << "Expected failure #1, in SetUp().";
+  }
+
+  void TearDown() override { FAIL() << "Expected failure #2, in TearDown()."; }
+
+ private:
+  void Deinit() {
+    FAIL() << "Expected failure #3, in the test fixture d'tor.";
+  }
+};
+
+TEST_F(FatalFailureInSetUpTest, FailureInSetUp) {
+  FAIL() << "UNEXPECTED failure in the test function.  "
+         << "We should never get here, as SetUp() failed.";
+}
+
+TEST(AddFailureAtTest, MessageContainsSpecifiedFileAndLineNumber) {
+  ADD_FAILURE_AT("foo.cc", 42) << "Expected nonfatal failure in foo.cc";
+}
+
+TEST(GtestFailAtTest, MessageContainsSpecifiedFileAndLineNumber) {
+  GTEST_FAIL_AT("foo.cc", 42) << "Expected fatal failure in foo.cc";
+}
+
+// The MixedUpTestSuiteTest test case verifies that Google Test will fail a
+// test if it uses a different fixture class than what other tests in
+// the same test case use.  It deliberately contains two fixture
+// classes with the same name but defined in different namespaces.
+
+// The MixedUpTestSuiteWithSameTestNameTest test case verifies that
+// when the user defines two tests with the same test case name AND
+// same test name (but in different namespaces), the second test will
+// fail.
+
+namespace foo {
+
+class MixedUpTestSuiteTest : public testing::Test {
+};
+
+TEST_F(MixedUpTestSuiteTest, FirstTestFromNamespaceFoo) {}
+TEST_F(MixedUpTestSuiteTest, SecondTestFromNamespaceFoo) {}
+
+class MixedUpTestSuiteWithSameTestNameTest : public testing::Test {
+};
+
+TEST_F(MixedUpTestSuiteWithSameTestNameTest,
+       TheSecondTestWithThisNameShouldFail) {}
+
+}  // namespace foo
+
+namespace bar {
+
+class MixedUpTestSuiteTest : public testing::Test {
+};
+
+// The following two tests are expected to fail.  We rely on the
+// golden file to check that Google Test generates the right error message.
+TEST_F(MixedUpTestSuiteTest, ThisShouldFail) {}
+TEST_F(MixedUpTestSuiteTest, ThisShouldFailToo) {}
+
+class MixedUpTestSuiteWithSameTestNameTest : public testing::Test {
+};
+
+// Expected to fail.  We rely on the golden file to check that Google Test
+// generates the right error message.
+TEST_F(MixedUpTestSuiteWithSameTestNameTest,
+       TheSecondTestWithThisNameShouldFail) {}
+
+}  // namespace bar
+
+// The following two test cases verify that Google Test catches the user
+// error of mixing TEST and TEST_F in the same test case.  The first
+// test case checks the scenario where TEST_F appears before TEST, and
+// the second one checks where TEST appears before TEST_F.
+
+class TEST_F_before_TEST_in_same_test_case : public testing::Test {
+};
+
+TEST_F(TEST_F_before_TEST_in_same_test_case, DefinedUsingTEST_F) {}
+
+// Expected to fail.  We rely on the golden file to check that Google Test
+// generates the right error message.
+TEST(TEST_F_before_TEST_in_same_test_case, DefinedUsingTESTAndShouldFail) {}
+
+class TEST_before_TEST_F_in_same_test_case : public testing::Test {
+};
+
+TEST(TEST_before_TEST_F_in_same_test_case, DefinedUsingTEST) {}
+
+// Expected to fail.  We rely on the golden file to check that Google Test
+// generates the right error message.
+TEST_F(TEST_before_TEST_F_in_same_test_case, DefinedUsingTEST_FAndShouldFail) {
+}
+
+// Used for testing EXPECT_NONFATAL_FAILURE() and EXPECT_FATAL_FAILURE().
+int global_integer = 0;
+
+// Tests that EXPECT_NONFATAL_FAILURE() can reference global variables.
+TEST(ExpectNonfatalFailureTest, CanReferenceGlobalVariables) {
+  global_integer = 0;
+  EXPECT_NONFATAL_FAILURE({
+    EXPECT_EQ(1, global_integer) << "Expected non-fatal failure.";
+  }, "Expected non-fatal failure.");
+}
+
+// Tests that EXPECT_NONFATAL_FAILURE() can reference local variables
+// (static or not).
+TEST(ExpectNonfatalFailureTest, CanReferenceLocalVariables) {
+  int m = 0;
+  static int n;
+  n = 1;
+  EXPECT_NONFATAL_FAILURE({
+    EXPECT_EQ(m, n) << "Expected non-fatal failure.";
+  }, "Expected non-fatal failure.");
+}
+
+// Tests that EXPECT_NONFATAL_FAILURE() succeeds when there is exactly
+// one non-fatal failure and no fatal failure.
+TEST(ExpectNonfatalFailureTest, SucceedsWhenThereIsOneNonfatalFailure) {
+  EXPECT_NONFATAL_FAILURE({
+    ADD_FAILURE() << "Expected non-fatal failure.";
+  }, "Expected non-fatal failure.");
+}
+
+// Tests that EXPECT_NONFATAL_FAILURE() fails when there is no
+// non-fatal failure.
+TEST(ExpectNonfatalFailureTest, FailsWhenThereIsNoNonfatalFailure) {
+  printf("(expecting a failure)\n");
+  EXPECT_NONFATAL_FAILURE({
+  }, "");
+}
+
+// Tests that EXPECT_NONFATAL_FAILURE() fails when there are two
+// non-fatal failures.
+TEST(ExpectNonfatalFailureTest, FailsWhenThereAreTwoNonfatalFailures) {
+  printf("(expecting a failure)\n");
+  EXPECT_NONFATAL_FAILURE({
+    ADD_FAILURE() << "Expected non-fatal failure 1.";
+    ADD_FAILURE() << "Expected non-fatal failure 2.";
+  }, "");
+}
+
+// Tests that EXPECT_NONFATAL_FAILURE() fails when there is one fatal
+// failure.
+TEST(ExpectNonfatalFailureTest, FailsWhenThereIsOneFatalFailure) {
+  printf("(expecting a failure)\n");
+  EXPECT_NONFATAL_FAILURE({
+    FAIL() << "Expected fatal failure.";
+  }, "");
+}
+
+// Tests that EXPECT_NONFATAL_FAILURE() fails when the statement being
+// tested returns.
+TEST(ExpectNonfatalFailureTest, FailsWhenStatementReturns) {
+  printf("(expecting a failure)\n");
+  EXPECT_NONFATAL_FAILURE({
+    return;
+  }, "");
+}
+
+#if GTEST_HAS_EXCEPTIONS
+
+// Tests that EXPECT_NONFATAL_FAILURE() fails when the statement being
+// tested throws.
+TEST(ExpectNonfatalFailureTest, FailsWhenStatementThrows) {
+  printf("(expecting a failure)\n");
+  try {
+    EXPECT_NONFATAL_FAILURE({
+      throw 0;
+    }, "");
+  } catch(int) {  // NOLINT
+  }
+}
+
+#endif  // GTEST_HAS_EXCEPTIONS
+
+// Tests that EXPECT_FATAL_FAILURE() can reference global variables.
+TEST(ExpectFatalFailureTest, CanReferenceGlobalVariables) {
+  global_integer = 0;
+  EXPECT_FATAL_FAILURE({
+    ASSERT_EQ(1, global_integer) << "Expected fatal failure.";
+  }, "Expected fatal failure.");
+}
+
+// Tests that EXPECT_FATAL_FAILURE() can reference local static
+// variables.
+TEST(ExpectFatalFailureTest, CanReferenceLocalStaticVariables) {
+  static int n;
+  n = 1;
+  EXPECT_FATAL_FAILURE({
+    ASSERT_EQ(0, n) << "Expected fatal failure.";
+  }, "Expected fatal failure.");
+}
+
+// Tests that EXPECT_FATAL_FAILURE() succeeds when there is exactly
+// one fatal failure and no non-fatal failure.
+TEST(ExpectFatalFailureTest, SucceedsWhenThereIsOneFatalFailure) {
+  EXPECT_FATAL_FAILURE({
+    FAIL() << "Expected fatal failure.";
+  }, "Expected fatal failure.");
+}
+
+// Tests that EXPECT_FATAL_FAILURE() fails when there is no fatal
+// failure.
+TEST(ExpectFatalFailureTest, FailsWhenThereIsNoFatalFailure) {
+  printf("(expecting a failure)\n");
+  EXPECT_FATAL_FAILURE({
+  }, "");
+}
+
+// A helper for generating a fatal failure.
+void FatalFailure() {
+  FAIL() << "Expected fatal failure.";
+}
+
+// Tests that EXPECT_FATAL_FAILURE() fails when there are two
+// fatal failures.
+TEST(ExpectFatalFailureTest, FailsWhenThereAreTwoFatalFailures) {
+  printf("(expecting a failure)\n");
+  EXPECT_FATAL_FAILURE({
+    FatalFailure();
+    FatalFailure();
+  }, "");
+}
+
+// Tests that EXPECT_FATAL_FAILURE() fails when there is one non-fatal
+// failure.
+TEST(ExpectFatalFailureTest, FailsWhenThereIsOneNonfatalFailure) {
+  printf("(expecting a failure)\n");
+  EXPECT_FATAL_FAILURE({
+    ADD_FAILURE() << "Expected non-fatal failure.";
+  }, "");
+}
+
+// Tests that EXPECT_FATAL_FAILURE() fails when the statement being
+// tested returns.
+TEST(ExpectFatalFailureTest, FailsWhenStatementReturns) {
+  printf("(expecting a failure)\n");
+  EXPECT_FATAL_FAILURE({
+    return;
+  }, "");
+}
+
+#if GTEST_HAS_EXCEPTIONS
+
+// Tests that EXPECT_FATAL_FAILURE() fails when the statement being
+// tested throws.
+TEST(ExpectFatalFailureTest, FailsWhenStatementThrows) {
+  printf("(expecting a failure)\n");
+  try {
+    EXPECT_FATAL_FAILURE({
+      throw 0;
+    }, "");
+  } catch(int) {  // NOLINT
+  }
+}
+
+#endif  // GTEST_HAS_EXCEPTIONS
+
+// This #ifdef block tests the output of value-parameterized tests.
+
+std::string ParamNameFunc(const testing::TestParamInfo<std::string>& info) {
+  return info.param;
+}
+
+class ParamTest : public testing::TestWithParam<std::string> {
+};
+
+TEST_P(ParamTest, Success) {
+  EXPECT_EQ("a", GetParam());
+}
+
+TEST_P(ParamTest, Failure) {
+  EXPECT_EQ("b", GetParam()) << "Expected failure";
+}
+
+INSTANTIATE_TEST_SUITE_P(PrintingStrings,
+                         ParamTest,
+                         testing::Values(std::string("a")),
+                         ParamNameFunc);
+
+// The case where a suite has INSTANTIATE_TEST_SUITE_P but not TEST_P.
+using NoTests = ParamTest;
+INSTANTIATE_TEST_SUITE_P(ThisIsOdd, NoTests, ::testing::Values("Hello"));
+
+// fails under kErrorOnUninstantiatedParameterizedTest=true
+class DetectNotInstantiatedTest : public testing::TestWithParam<int> {};
+TEST_P(DetectNotInstantiatedTest, Used) { }
+
+// This would make the test failure from the above go away.
+// INSTANTIATE_TEST_SUITE_P(Fix, DetectNotInstantiatedTest, testing::Values(1));
+
+template <typename T>
+class TypedTest : public testing::Test {
+};
+
+TYPED_TEST_SUITE(TypedTest, testing::Types<int>);
+
+TYPED_TEST(TypedTest, Success) {
+  EXPECT_EQ(0, TypeParam());
+}
+
+TYPED_TEST(TypedTest, Failure) {
+  EXPECT_EQ(1, TypeParam()) << "Expected failure";
+}
+
+typedef testing::Types<char, int> TypesForTestWithNames;
+
+template <typename T>
+class TypedTestWithNames : public testing::Test {};
+
+class TypedTestNames {
+ public:
+  template <typename T>
+  static std::string GetName(int i) {
+    if (std::is_same<T, char>::value)
+      return std::string("char") + ::testing::PrintToString(i);
+    if (std::is_same<T, int>::value)
+      return std::string("int") + ::testing::PrintToString(i);
+  }
+};
+
+TYPED_TEST_SUITE(TypedTestWithNames, TypesForTestWithNames, TypedTestNames);
+
+TYPED_TEST(TypedTestWithNames, Success) {}
+
+TYPED_TEST(TypedTestWithNames, Failure) { FAIL(); }
+
+template <typename T>
+class TypedTestP : public testing::Test {
+};
+
+TYPED_TEST_SUITE_P(TypedTestP);
+
+TYPED_TEST_P(TypedTestP, Success) {
+  EXPECT_EQ(0U, TypeParam());
+}
+
+TYPED_TEST_P(TypedTestP, Failure) {
+  EXPECT_EQ(1U, TypeParam()) << "Expected failure";
+}
+
+REGISTER_TYPED_TEST_SUITE_P(TypedTestP, Success, Failure);
+
+typedef testing::Types<unsigned char, unsigned int> UnsignedTypes;
+INSTANTIATE_TYPED_TEST_SUITE_P(Unsigned, TypedTestP, UnsignedTypes);
+
+class TypedTestPNames {
+ public:
+  template <typename T>
+  static std::string GetName(int i) {
+    if (std::is_same<T, unsigned char>::value) {
+      return std::string("unsignedChar") + ::testing::PrintToString(i);
+    }
+    if (std::is_same<T, unsigned int>::value) {
+      return std::string("unsignedInt") + ::testing::PrintToString(i);
+    }
+  }
+};
+
+INSTANTIATE_TYPED_TEST_SUITE_P(UnsignedCustomName, TypedTestP, UnsignedTypes,
+                              TypedTestPNames);
+
+template <typename T>
+class DetectNotInstantiatedTypesTest : public testing::Test {};
+TYPED_TEST_SUITE_P(DetectNotInstantiatedTypesTest);
+TYPED_TEST_P(DetectNotInstantiatedTypesTest, Used) {
+  TypeParam instantiate;
+  (void)instantiate;
+}
+REGISTER_TYPED_TEST_SUITE_P(DetectNotInstantiatedTypesTest, Used);
+
+// kErrorOnUninstantiatedTypeParameterizedTest=true would make the above fail.
+// Adding the following would make that test failure go away.
+//
+// typedef ::testing::Types<char, int, unsigned int> MyTypes;
+// INSTANTIATE_TYPED_TEST_SUITE_P(All, DetectNotInstantiatedTypesTest, MyTypes);
+
+#if GTEST_HAS_DEATH_TEST
+
+// We rely on the golden file to verify that tests whose test case
+// name ends with DeathTest are run first.
+
+TEST(ADeathTest, ShouldRunFirst) {
+}
+
+// We rely on the golden file to verify that typed tests whose test
+// case name ends with DeathTest are run first.
+
+template <typename T>
+class ATypedDeathTest : public testing::Test {
+};
+
+typedef testing::Types<int, double> NumericTypes;
+TYPED_TEST_SUITE(ATypedDeathTest, NumericTypes);
+
+TYPED_TEST(ATypedDeathTest, ShouldRunFirst) {
+}
+
+
+// We rely on the golden file to verify that type-parameterized tests
+// whose test case name ends with DeathTest are run first.
+
+template <typename T>
+class ATypeParamDeathTest : public testing::Test {
+};
+
+TYPED_TEST_SUITE_P(ATypeParamDeathTest);
+
+TYPED_TEST_P(ATypeParamDeathTest, ShouldRunFirst) {
+}
+
+REGISTER_TYPED_TEST_SUITE_P(ATypeParamDeathTest, ShouldRunFirst);
+
+INSTANTIATE_TYPED_TEST_SUITE_P(My, ATypeParamDeathTest, NumericTypes);
+
+#endif  // GTEST_HAS_DEATH_TEST
+
+// Tests various failure conditions of
+// EXPECT_{,NON}FATAL_FAILURE{,_ON_ALL_THREADS}.
+class ExpectFailureTest : public testing::Test {
+ public:  // Must be public and not protected due to a bug in g++ 3.4.2.
+  enum FailureMode {
+    FATAL_FAILURE,
+    NONFATAL_FAILURE
+  };
+  static void AddFailure(FailureMode failure) {
+    if (failure == FATAL_FAILURE) {
+      FAIL() << "Expected fatal failure.";
+    } else {
+      ADD_FAILURE() << "Expected non-fatal failure.";
+    }
+  }
+};
+
+TEST_F(ExpectFailureTest, ExpectFatalFailure) {
+  // Expected fatal failure, but succeeds.
+  printf("(expecting 1 failure)\n");
+  EXPECT_FATAL_FAILURE(SUCCEED(), "Expected fatal failure.");
+  // Expected fatal failure, but got a non-fatal failure.
+  printf("(expecting 1 failure)\n");
+  EXPECT_FATAL_FAILURE(AddFailure(NONFATAL_FAILURE), "Expected non-fatal "
+                       "failure.");
+  // Wrong message.
+  printf("(expecting 1 failure)\n");
+  EXPECT_FATAL_FAILURE(AddFailure(FATAL_FAILURE), "Some other fatal failure "
+                       "expected.");
+}
+
+TEST_F(ExpectFailureTest, ExpectNonFatalFailure) {
+  // Expected non-fatal failure, but succeeds.
+  printf("(expecting 1 failure)\n");
+  EXPECT_NONFATAL_FAILURE(SUCCEED(), "Expected non-fatal failure.");
+  // Expected non-fatal failure, but got a fatal failure.
+  printf("(expecting 1 failure)\n");
+  EXPECT_NONFATAL_FAILURE(AddFailure(FATAL_FAILURE), "Expected fatal failure.");
+  // Wrong message.
+  printf("(expecting 1 failure)\n");
+  EXPECT_NONFATAL_FAILURE(AddFailure(NONFATAL_FAILURE), "Some other non-fatal "
+                          "failure.");
+}
+
+#if GTEST_IS_THREADSAFE
+
+class ExpectFailureWithThreadsTest : public ExpectFailureTest {
+ protected:
+  static void AddFailureInOtherThread(FailureMode failure) {
+    ThreadWithParam<FailureMode> thread(&AddFailure, failure, nullptr);
+    thread.Join();
+  }
+};
+
+TEST_F(ExpectFailureWithThreadsTest, ExpectFatalFailure) {
+  // We only intercept the current thread.
+  printf("(expecting 2 failures)\n");
+  EXPECT_FATAL_FAILURE(AddFailureInOtherThread(FATAL_FAILURE),
+                       "Expected fatal failure.");
+}
+
+TEST_F(ExpectFailureWithThreadsTest, ExpectNonFatalFailure) {
+  // We only intercept the current thread.
+  printf("(expecting 2 failures)\n");
+  EXPECT_NONFATAL_FAILURE(AddFailureInOtherThread(NONFATAL_FAILURE),
+                          "Expected non-fatal failure.");
+}
+
+typedef ExpectFailureWithThreadsTest ScopedFakeTestPartResultReporterTest;
+
+// Tests that the ScopedFakeTestPartResultReporter only catches failures from
+// the current thread if it is instantiated with INTERCEPT_ONLY_CURRENT_THREAD.
+TEST_F(ScopedFakeTestPartResultReporterTest, InterceptOnlyCurrentThread) {
+  printf("(expecting 2 failures)\n");
+  TestPartResultArray results;
+  {
+    ScopedFakeTestPartResultReporter reporter(
+        ScopedFakeTestPartResultReporter::INTERCEPT_ONLY_CURRENT_THREAD,
+        &results);
+    AddFailureInOtherThread(FATAL_FAILURE);
+    AddFailureInOtherThread(NONFATAL_FAILURE);
+  }
+  // The two failures should not have been intercepted.
+  EXPECT_EQ(0, results.size()) << "This shouldn't fail.";
+}
+
+#endif  // GTEST_IS_THREADSAFE
+
+TEST_F(ExpectFailureTest, ExpectFatalFailureOnAllThreads) {
+  // Expected fatal failure, but succeeds.
+  printf("(expecting 1 failure)\n");
+  EXPECT_FATAL_FAILURE_ON_ALL_THREADS(SUCCEED(), "Expected fatal failure.");
+  // Expected fatal failure, but got a non-fatal failure.
+  printf("(expecting 1 failure)\n");
+  EXPECT_FATAL_FAILURE_ON_ALL_THREADS(AddFailure(NONFATAL_FAILURE),
+                                      "Expected non-fatal failure.");
+  // Wrong message.
+  printf("(expecting 1 failure)\n");
+  EXPECT_FATAL_FAILURE_ON_ALL_THREADS(AddFailure(FATAL_FAILURE),
+                                      "Some other fatal failure expected.");
+}
+
+TEST_F(ExpectFailureTest, ExpectNonFatalFailureOnAllThreads) {
+  // Expected non-fatal failure, but succeeds.
+  printf("(expecting 1 failure)\n");
+  EXPECT_NONFATAL_FAILURE_ON_ALL_THREADS(SUCCEED(), "Expected non-fatal "
+                                         "failure.");
+  // Expected non-fatal failure, but got a fatal failure.
+  printf("(expecting 1 failure)\n");
+  EXPECT_NONFATAL_FAILURE_ON_ALL_THREADS(AddFailure(FATAL_FAILURE),
+                                         "Expected fatal failure.");
+  // Wrong message.
+  printf("(expecting 1 failure)\n");
+  EXPECT_NONFATAL_FAILURE_ON_ALL_THREADS(AddFailure(NONFATAL_FAILURE),
+                                         "Some other non-fatal failure.");
+}
+
+class DynamicFixture : public testing::Test {
+ protected:
+  DynamicFixture() { printf("DynamicFixture()\n"); }
+  ~DynamicFixture() override { printf("~DynamicFixture()\n"); }
+  void SetUp() override { printf("DynamicFixture::SetUp\n"); }
+  void TearDown() override { printf("DynamicFixture::TearDown\n"); }
+
+  static void SetUpTestSuite() { printf("DynamicFixture::SetUpTestSuite\n"); }
+  static void TearDownTestSuite() {
+    printf("DynamicFixture::TearDownTestSuite\n");
+  }
+};
+
+template <bool Pass>
+class DynamicTest : public DynamicFixture {
+ public:
+  void TestBody() override { EXPECT_TRUE(Pass); }
+};
+
+auto dynamic_test = (
+    // Register two tests with the same fixture correctly.
+    testing::RegisterTest(
+        "DynamicFixture", "DynamicTestPass", nullptr, nullptr, __FILE__,
+        __LINE__, []() -> DynamicFixture* { return new DynamicTest<true>; }),
+    testing::RegisterTest(
+        "DynamicFixture", "DynamicTestFail", nullptr, nullptr, __FILE__,
+        __LINE__, []() -> DynamicFixture* { return new DynamicTest<false>; }),
+
+    // Register the same fixture with another name. That's fine.
+    testing::RegisterTest(
+        "DynamicFixtureAnotherName", "DynamicTestPass", nullptr, nullptr,
+        __FILE__, __LINE__,
+        []() -> DynamicFixture* { return new DynamicTest<true>; }),
+
+    // Register two tests with the same fixture incorrectly.
+    testing::RegisterTest(
+        "BadDynamicFixture1", "FixtureBase", nullptr, nullptr, __FILE__,
+        __LINE__, []() -> DynamicFixture* { return new DynamicTest<true>; }),
+    testing::RegisterTest(
+        "BadDynamicFixture1", "TestBase", nullptr, nullptr, __FILE__, __LINE__,
+        []() -> testing::Test* { return new DynamicTest<true>; }),
+
+    // Register two tests with the same fixture incorrectly by omitting the
+    // return type.
+    testing::RegisterTest(
+        "BadDynamicFixture2", "FixtureBase", nullptr, nullptr, __FILE__,
+        __LINE__, []() -> DynamicFixture* { return new DynamicTest<true>; }),
+    testing::RegisterTest("BadDynamicFixture2", "Derived", nullptr, nullptr,
+                          __FILE__, __LINE__,
+                          []() { return new DynamicTest<true>; }));
+
+// Two test environments for testing testing::AddGlobalTestEnvironment().
+
+class FooEnvironment : public testing::Environment {
+ public:
+  void SetUp() override { printf("%s", "FooEnvironment::SetUp() called.\n"); }
+
+  void TearDown() override {
+    printf("%s", "FooEnvironment::TearDown() called.\n");
+    FAIL() << "Expected fatal failure.";
+  }
+};
+
+class BarEnvironment : public testing::Environment {
+ public:
+  void SetUp() override { printf("%s", "BarEnvironment::SetUp() called.\n"); }
+
+  void TearDown() override {
+    printf("%s", "BarEnvironment::TearDown() called.\n");
+    ADD_FAILURE() << "Expected non-fatal failure.";
+  }
+};
+
+// The main function.
+//
+// The idea is to use Google Test to run all the tests we have defined (some
+// of them are intended to fail), and then compare the test results
+// with the "golden" file.
+int main(int argc, char **argv) {
+  testing::GTEST_FLAG(print_time) = false;
+
+  // We just run the tests, knowing some of them are intended to fail.
+  // We will use a separate Python script to compare the output of
+  // this program with the golden file.
+
+  // It's hard to test InitGoogleTest() directly, as it has many
+  // global side effects.  The following line serves as a sanity test
+  // for it.
+  testing::InitGoogleTest(&argc, argv);
+  bool internal_skip_environment_and_ad_hoc_tests =
+      std::count(argv, argv + argc,
+                 std::string("internal_skip_environment_and_ad_hoc_tests")) > 0;
+
+#if GTEST_HAS_DEATH_TEST
+  if (testing::internal::GTEST_FLAG(internal_run_death_test) != "") {
+    // Skip the usual output capturing if we're running as the child
+    // process of an threadsafe-style death test.
+# if GTEST_OS_WINDOWS
+    posix::FReopen("nul:", "w", stdout);
+# else
+    posix::FReopen("/dev/null", "w", stdout);
+# endif  // GTEST_OS_WINDOWS
+    return RUN_ALL_TESTS();
+  }
+#endif  // GTEST_HAS_DEATH_TEST
+
+  if (internal_skip_environment_and_ad_hoc_tests)
+    return RUN_ALL_TESTS();
+
+  // Registers two global test environments.
+  // The golden file verifies that they are set up in the order they
+  // are registered, and torn down in the reverse order.
+  testing::AddGlobalTestEnvironment(new FooEnvironment);
+  testing::AddGlobalTestEnvironment(new BarEnvironment);
+#if _MSC_VER
+GTEST_DISABLE_MSC_WARNINGS_POP_()  //  4127
+#endif  //  _MSC_VER
+  return RunAllTests();
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-param-test-invalid-name1-test.py b/leveldb_base/third_party/googletest/googletest/test/googletest-param-test-invalid-name1-test.py
new file mode 100644
index 0000000..2a08477
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-param-test-invalid-name1-test.py
@@ -0,0 +1,63 @@
+#!/usr/bin/env python
+#
+# Copyright 2015 Google Inc. All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Verifies that Google Test warns the user when not initialized properly."""
+
+import gtest_test_utils
+
+binary_name = 'googletest-param-test-invalid-name1-test_'
+COMMAND = gtest_test_utils.GetTestExecutablePath(binary_name)
+
+
+def Assert(condition):
+  if not condition:
+    raise AssertionError
+
+
+def TestExitCodeAndOutput(command):
+  """Runs the given command and verifies its exit code and output."""
+
+  err = ('Parameterized test name \'"InvalidWithQuotes"\' is invalid')
+
+  p = gtest_test_utils.Subprocess(command)
+  Assert(p.terminated_by_signal)
+
+  # Verify the output message contains appropriate output
+  Assert(err in p.output)
+
+
+class GTestParamTestInvalidName1Test(gtest_test_utils.TestCase):
+
+  def testExitCodeAndOutput(self):
+    TestExitCodeAndOutput(COMMAND)
+
+
+if __name__ == '__main__':
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-param-test-invalid-name1-test_.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-param-test-invalid-name1-test_.cc
new file mode 100644
index 0000000..955d699
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-param-test-invalid-name1-test_.cc
@@ -0,0 +1,50 @@
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+#include "gtest/gtest.h"
+
+namespace {
+class DummyTest : public ::testing::TestWithParam<const char *> {};
+
+TEST_P(DummyTest, Dummy) {
+}
+
+INSTANTIATE_TEST_SUITE_P(InvalidTestName,
+                         DummyTest,
+                         ::testing::Values("InvalidWithQuotes"),
+                         ::testing::PrintToStringParamName());
+
+}  // namespace
+
+int main(int argc, char *argv[]) {
+  testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
+
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-param-test-invalid-name2-test.py b/leveldb_base/third_party/googletest/googletest/test/googletest-param-test-invalid-name2-test.py
new file mode 100644
index 0000000..ab838f4
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-param-test-invalid-name2-test.py
@@ -0,0 +1,62 @@
+#!/usr/bin/env python
+#
+# Copyright 2015 Google Inc. All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Verifies that Google Test warns the user when not initialized properly."""
+
+import gtest_test_utils
+
+binary_name = 'googletest-param-test-invalid-name2-test_'
+COMMAND = gtest_test_utils.GetTestExecutablePath(binary_name)
+
+
+def Assert(condition):
+  if not condition:
+    raise AssertionError
+
+
+def TestExitCodeAndOutput(command):
+  """Runs the given command and verifies its exit code and output."""
+
+  err = ('Duplicate parameterized test name \'a\'')
+
+  p = gtest_test_utils.Subprocess(command)
+  Assert(p.terminated_by_signal)
+
+  # Check for appropriate output
+  Assert(err in p.output)
+
+
+class GTestParamTestInvalidName2Test(gtest_test_utils.TestCase):
+
+  def testExitCodeAndOutput(self):
+    TestExitCodeAndOutput(COMMAND)
+
+if __name__ == '__main__':
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-param-test-invalid-name2-test_.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-param-test-invalid-name2-test_.cc
new file mode 100644
index 0000000..76371df
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-param-test-invalid-name2-test_.cc
@@ -0,0 +1,55 @@
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+#include "gtest/gtest.h"
+
+namespace {
+class DummyTest : public ::testing::TestWithParam<const char *> {};
+
+std::string StringParamTestSuffix(
+    const testing::TestParamInfo<const char*>& info) {
+  return std::string(info.param);
+}
+
+TEST_P(DummyTest, Dummy) {
+}
+
+INSTANTIATE_TEST_SUITE_P(DuplicateTestNames,
+                         DummyTest,
+                         ::testing::Values("a", "b", "a", "c"),
+                         StringParamTestSuffix);
+}  // namespace
+
+int main(int argc, char *argv[]) {
+  testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
+
+
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-param-test-test.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-param-test-test.cc
new file mode 100644
index 0000000..023aa46
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-param-test-test.cc
@@ -0,0 +1,1119 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// Tests for Google Test itself. This file verifies that the parameter
+// generators objects produce correct parameter sequences and that
+// Google Test runtime instantiates correct tests from those sequences.
+
+#include "gtest/gtest.h"
+
+# include <algorithm>
+# include <iostream>
+# include <list>
+# include <set>
+# include <sstream>
+# include <string>
+# include <vector>
+
+# include "src/gtest-internal-inl.h"  // for UnitTestOptions
+# include "test/googletest-param-test-test.h"
+
+using ::std::vector;
+using ::std::sort;
+
+using ::testing::AddGlobalTestEnvironment;
+using ::testing::Bool;
+using ::testing::Combine;
+using ::testing::Message;
+using ::testing::Range;
+using ::testing::TestWithParam;
+using ::testing::Values;
+using ::testing::ValuesIn;
+
+using ::testing::internal::ParamGenerator;
+using ::testing::internal::UnitTestOptions;
+
+// Prints a value to a string.
+//
+// FIXME: remove PrintValue() when we move matchers and
+// EXPECT_THAT() from Google Mock to Google Test.  At that time, we
+// can write EXPECT_THAT(x, Eq(y)) to compare two tuples x and y, as
+// EXPECT_THAT() and the matchers know how to print tuples.
+template <typename T>
+::std::string PrintValue(const T& value) {
+  return testing::PrintToString(value);
+}
+
+// Verifies that a sequence generated by the generator and accessed
+// via the iterator object matches the expected one using Google Test
+// assertions.
+template <typename T, size_t N>
+void VerifyGenerator(const ParamGenerator<T>& generator,
+                     const T (&expected_values)[N]) {
+  typename ParamGenerator<T>::iterator it = generator.begin();
+  for (size_t i = 0; i < N; ++i) {
+    ASSERT_FALSE(it == generator.end())
+        << "At element " << i << " when accessing via an iterator "
+        << "created with the copy constructor.\n";
+    // We cannot use EXPECT_EQ() here as the values may be tuples,
+    // which don't support <<.
+    EXPECT_TRUE(expected_values[i] == *it)
+        << "where i is " << i
+        << ", expected_values[i] is " << PrintValue(expected_values[i])
+        << ", *it is " << PrintValue(*it)
+        << ", and 'it' is an iterator created with the copy constructor.\n";
+    ++it;
+  }
+  EXPECT_TRUE(it == generator.end())
+        << "At the presumed end of sequence when accessing via an iterator "
+        << "created with the copy constructor.\n";
+
+  // Test the iterator assignment. The following lines verify that
+  // the sequence accessed via an iterator initialized via the
+  // assignment operator (as opposed to a copy constructor) matches
+  // just the same.
+  it = generator.begin();
+  for (size_t i = 0; i < N; ++i) {
+    ASSERT_FALSE(it == generator.end())
+        << "At element " << i << " when accessing via an iterator "
+        << "created with the assignment operator.\n";
+    EXPECT_TRUE(expected_values[i] == *it)
+        << "where i is " << i
+        << ", expected_values[i] is " << PrintValue(expected_values[i])
+        << ", *it is " << PrintValue(*it)
+        << ", and 'it' is an iterator created with the copy constructor.\n";
+    ++it;
+  }
+  EXPECT_TRUE(it == generator.end())
+        << "At the presumed end of sequence when accessing via an iterator "
+        << "created with the assignment operator.\n";
+}
+
+template <typename T>
+void VerifyGeneratorIsEmpty(const ParamGenerator<T>& generator) {
+  typename ParamGenerator<T>::iterator it = generator.begin();
+  EXPECT_TRUE(it == generator.end());
+
+  it = generator.begin();
+  EXPECT_TRUE(it == generator.end());
+}
+
+// Generator tests. They test that each of the provided generator functions
+// generates an expected sequence of values. The general test pattern
+// instantiates a generator using one of the generator functions,
+// checks the sequence produced by the generator using its iterator API,
+// and then resets the iterator back to the beginning of the sequence
+// and checks the sequence again.
+
+// Tests that iterators produced by generator functions conform to the
+// ForwardIterator concept.
+TEST(IteratorTest, ParamIteratorConformsToForwardIteratorConcept) {
+  const ParamGenerator<int> gen = Range(0, 10);
+  ParamGenerator<int>::iterator it = gen.begin();
+
+  // Verifies that iterator initialization works as expected.
+  ParamGenerator<int>::iterator it2 = it;
+  EXPECT_TRUE(*it == *it2) << "Initialized iterators must point to the "
+                           << "element same as its source points to";
+
+  // Verifies that iterator assignment works as expected.
+  ++it;
+  EXPECT_FALSE(*it == *it2);
+  it2 = it;
+  EXPECT_TRUE(*it == *it2) << "Assigned iterators must point to the "
+                           << "element same as its source points to";
+
+  // Verifies that prefix operator++() returns *this.
+  EXPECT_EQ(&it, &(++it)) << "Result of the prefix operator++ must be "
+                          << "refer to the original object";
+
+  // Verifies that the result of the postfix operator++ points to the value
+  // pointed to by the original iterator.
+  int original_value = *it;  // Have to compute it outside of macro call to be
+                             // unaffected by the parameter evaluation order.
+  EXPECT_EQ(original_value, *(it++));
+
+  // Verifies that prefix and postfix operator++() advance an iterator
+  // all the same.
+  it2 = it;
+  ++it;
+  ++it2;
+  EXPECT_TRUE(*it == *it2);
+}
+
+// Tests that Range() generates the expected sequence.
+TEST(RangeTest, IntRangeWithDefaultStep) {
+  const ParamGenerator<int> gen = Range(0, 3);
+  const int expected_values[] = {0, 1, 2};
+  VerifyGenerator(gen, expected_values);
+}
+
+// Edge case. Tests that Range() generates the single element sequence
+// as expected when provided with range limits that are equal.
+TEST(RangeTest, IntRangeSingleValue) {
+  const ParamGenerator<int> gen = Range(0, 1);
+  const int expected_values[] = {0};
+  VerifyGenerator(gen, expected_values);
+}
+
+// Edge case. Tests that Range() with generates empty sequence when
+// supplied with an empty range.
+TEST(RangeTest, IntRangeEmpty) {
+  const ParamGenerator<int> gen = Range(0, 0);
+  VerifyGeneratorIsEmpty(gen);
+}
+
+// Tests that Range() with custom step (greater then one) generates
+// the expected sequence.
+TEST(RangeTest, IntRangeWithCustomStep) {
+  const ParamGenerator<int> gen = Range(0, 9, 3);
+  const int expected_values[] = {0, 3, 6};
+  VerifyGenerator(gen, expected_values);
+}
+
+// Tests that Range() with custom step (greater then one) generates
+// the expected sequence when the last element does not fall on the
+// upper range limit. Sequences generated by Range() must not have
+// elements beyond the range limits.
+TEST(RangeTest, IntRangeWithCustomStepOverUpperBound) {
+  const ParamGenerator<int> gen = Range(0, 4, 3);
+  const int expected_values[] = {0, 3};
+  VerifyGenerator(gen, expected_values);
+}
+
+// Verifies that Range works with user-defined types that define
+// copy constructor, operator=(), operator+(), and operator<().
+class DogAdder {
+ public:
+  explicit DogAdder(const char* a_value) : value_(a_value) {}
+  DogAdder(const DogAdder& other) : value_(other.value_.c_str()) {}
+
+  DogAdder operator=(const DogAdder& other) {
+    if (this != &other)
+      value_ = other.value_;
+    return *this;
+  }
+  DogAdder operator+(const DogAdder& other) const {
+    Message msg;
+    msg << value_.c_str() << other.value_.c_str();
+    return DogAdder(msg.GetString().c_str());
+  }
+  bool operator<(const DogAdder& other) const {
+    return value_ < other.value_;
+  }
+  const std::string& value() const { return value_; }
+
+ private:
+  std::string value_;
+};
+
+TEST(RangeTest, WorksWithACustomType) {
+  const ParamGenerator<DogAdder> gen =
+      Range(DogAdder("cat"), DogAdder("catdogdog"), DogAdder("dog"));
+  ParamGenerator<DogAdder>::iterator it = gen.begin();
+
+  ASSERT_FALSE(it == gen.end());
+  EXPECT_STREQ("cat", it->value().c_str());
+
+  ASSERT_FALSE(++it == gen.end());
+  EXPECT_STREQ("catdog", it->value().c_str());
+
+  EXPECT_TRUE(++it == gen.end());
+}
+
+class IntWrapper {
+ public:
+  explicit IntWrapper(int a_value) : value_(a_value) {}
+  IntWrapper(const IntWrapper& other) : value_(other.value_) {}
+
+  IntWrapper operator=(const IntWrapper& other) {
+    value_ = other.value_;
+    return *this;
+  }
+  // operator+() adds a different type.
+  IntWrapper operator+(int other) const { return IntWrapper(value_ + other); }
+  bool operator<(const IntWrapper& other) const {
+    return value_ < other.value_;
+  }
+  int value() const { return value_; }
+
+ private:
+  int value_;
+};
+
+TEST(RangeTest, WorksWithACustomTypeWithDifferentIncrementType) {
+  const ParamGenerator<IntWrapper> gen = Range(IntWrapper(0), IntWrapper(2));
+  ParamGenerator<IntWrapper>::iterator it = gen.begin();
+
+  ASSERT_FALSE(it == gen.end());
+  EXPECT_EQ(0, it->value());
+
+  ASSERT_FALSE(++it == gen.end());
+  EXPECT_EQ(1, it->value());
+
+  EXPECT_TRUE(++it == gen.end());
+}
+
+// Tests that ValuesIn() with an array parameter generates
+// the expected sequence.
+TEST(ValuesInTest, ValuesInArray) {
+  int array[] = {3, 5, 8};
+  const ParamGenerator<int> gen = ValuesIn(array);
+  VerifyGenerator(gen, array);
+}
+
+// Tests that ValuesIn() with a const array parameter generates
+// the expected sequence.
+TEST(ValuesInTest, ValuesInConstArray) {
+  const int array[] = {3, 5, 8};
+  const ParamGenerator<int> gen = ValuesIn(array);
+  VerifyGenerator(gen, array);
+}
+
+// Edge case. Tests that ValuesIn() with an array parameter containing a
+// single element generates the single element sequence.
+TEST(ValuesInTest, ValuesInSingleElementArray) {
+  int array[] = {42};
+  const ParamGenerator<int> gen = ValuesIn(array);
+  VerifyGenerator(gen, array);
+}
+
+// Tests that ValuesIn() generates the expected sequence for an STL
+// container (vector).
+TEST(ValuesInTest, ValuesInVector) {
+  typedef ::std::vector<int> ContainerType;
+  ContainerType values;
+  values.push_back(3);
+  values.push_back(5);
+  values.push_back(8);
+  const ParamGenerator<int> gen = ValuesIn(values);
+
+  const int expected_values[] = {3, 5, 8};
+  VerifyGenerator(gen, expected_values);
+}
+
+// Tests that ValuesIn() generates the expected sequence.
+TEST(ValuesInTest, ValuesInIteratorRange) {
+  typedef ::std::vector<int> ContainerType;
+  ContainerType values;
+  values.push_back(3);
+  values.push_back(5);
+  values.push_back(8);
+  const ParamGenerator<int> gen = ValuesIn(values.begin(), values.end());
+
+  const int expected_values[] = {3, 5, 8};
+  VerifyGenerator(gen, expected_values);
+}
+
+// Edge case. Tests that ValuesIn() provided with an iterator range specifying a
+// single value generates a single-element sequence.
+TEST(ValuesInTest, ValuesInSingleElementIteratorRange) {
+  typedef ::std::vector<int> ContainerType;
+  ContainerType values;
+  values.push_back(42);
+  const ParamGenerator<int> gen = ValuesIn(values.begin(), values.end());
+
+  const int expected_values[] = {42};
+  VerifyGenerator(gen, expected_values);
+}
+
+// Edge case. Tests that ValuesIn() provided with an empty iterator range
+// generates an empty sequence.
+TEST(ValuesInTest, ValuesInEmptyIteratorRange) {
+  typedef ::std::vector<int> ContainerType;
+  ContainerType values;
+  const ParamGenerator<int> gen = ValuesIn(values.begin(), values.end());
+
+  VerifyGeneratorIsEmpty(gen);
+}
+
+// Tests that the Values() generates the expected sequence.
+TEST(ValuesTest, ValuesWorks) {
+  const ParamGenerator<int> gen = Values(3, 5, 8);
+
+  const int expected_values[] = {3, 5, 8};
+  VerifyGenerator(gen, expected_values);
+}
+
+// Tests that Values() generates the expected sequences from elements of
+// different types convertible to ParamGenerator's parameter type.
+TEST(ValuesTest, ValuesWorksForValuesOfCompatibleTypes) {
+  const ParamGenerator<double> gen = Values(3, 5.0f, 8.0);
+
+  const double expected_values[] = {3.0, 5.0, 8.0};
+  VerifyGenerator(gen, expected_values);
+}
+
+TEST(ValuesTest, ValuesWorksForMaxLengthList) {
+  const ParamGenerator<int> gen = Values(
+      10, 20, 30, 40, 50, 60, 70, 80, 90, 100,
+      110, 120, 130, 140, 150, 160, 170, 180, 190, 200,
+      210, 220, 230, 240, 250, 260, 270, 280, 290, 300,
+      310, 320, 330, 340, 350, 360, 370, 380, 390, 400,
+      410, 420, 430, 440, 450, 460, 470, 480, 490, 500);
+
+  const int expected_values[] = {
+      10, 20, 30, 40, 50, 60, 70, 80, 90, 100,
+      110, 120, 130, 140, 150, 160, 170, 180, 190, 200,
+      210, 220, 230, 240, 250, 260, 270, 280, 290, 300,
+      310, 320, 330, 340, 350, 360, 370, 380, 390, 400,
+      410, 420, 430, 440, 450, 460, 470, 480, 490, 500};
+  VerifyGenerator(gen, expected_values);
+}
+
+// Edge case test. Tests that single-parameter Values() generates the sequence
+// with the single value.
+TEST(ValuesTest, ValuesWithSingleParameter) {
+  const ParamGenerator<int> gen = Values(42);
+
+  const int expected_values[] = {42};
+  VerifyGenerator(gen, expected_values);
+}
+
+// Tests that Bool() generates sequence (false, true).
+TEST(BoolTest, BoolWorks) {
+  const ParamGenerator<bool> gen = Bool();
+
+  const bool expected_values[] = {false, true};
+  VerifyGenerator(gen, expected_values);
+}
+
+// Tests that Combine() with two parameters generates the expected sequence.
+TEST(CombineTest, CombineWithTwoParameters) {
+  const char* foo = "foo";
+  const char* bar = "bar";
+  const ParamGenerator<std::tuple<const char*, int> > gen =
+      Combine(Values(foo, bar), Values(3, 4));
+
+  std::tuple<const char*, int> expected_values[] = {
+      std::make_tuple(foo, 3), std::make_tuple(foo, 4), std::make_tuple(bar, 3),
+      std::make_tuple(bar, 4)};
+  VerifyGenerator(gen, expected_values);
+}
+
+// Tests that Combine() with three parameters generates the expected sequence.
+TEST(CombineTest, CombineWithThreeParameters) {
+  const ParamGenerator<std::tuple<int, int, int> > gen =
+      Combine(Values(0, 1), Values(3, 4), Values(5, 6));
+  std::tuple<int, int, int> expected_values[] = {
+      std::make_tuple(0, 3, 5), std::make_tuple(0, 3, 6),
+      std::make_tuple(0, 4, 5), std::make_tuple(0, 4, 6),
+      std::make_tuple(1, 3, 5), std::make_tuple(1, 3, 6),
+      std::make_tuple(1, 4, 5), std::make_tuple(1, 4, 6)};
+  VerifyGenerator(gen, expected_values);
+}
+
+// Tests that the Combine() with the first parameter generating a single value
+// sequence generates a sequence with the number of elements equal to the
+// number of elements in the sequence generated by the second parameter.
+TEST(CombineTest, CombineWithFirstParameterSingleValue) {
+  const ParamGenerator<std::tuple<int, int> > gen =
+      Combine(Values(42), Values(0, 1));
+
+  std::tuple<int, int> expected_values[] = {std::make_tuple(42, 0),
+                                            std::make_tuple(42, 1)};
+  VerifyGenerator(gen, expected_values);
+}
+
+// Tests that the Combine() with the second parameter generating a single value
+// sequence generates a sequence with the number of elements equal to the
+// number of elements in the sequence generated by the first parameter.
+TEST(CombineTest, CombineWithSecondParameterSingleValue) {
+  const ParamGenerator<std::tuple<int, int> > gen =
+      Combine(Values(0, 1), Values(42));
+
+  std::tuple<int, int> expected_values[] = {std::make_tuple(0, 42),
+                                            std::make_tuple(1, 42)};
+  VerifyGenerator(gen, expected_values);
+}
+
+// Tests that when the first parameter produces an empty sequence,
+// Combine() produces an empty sequence, too.
+TEST(CombineTest, CombineWithFirstParameterEmptyRange) {
+  const ParamGenerator<std::tuple<int, int> > gen =
+      Combine(Range(0, 0), Values(0, 1));
+  VerifyGeneratorIsEmpty(gen);
+}
+
+// Tests that when the second parameter produces an empty sequence,
+// Combine() produces an empty sequence, too.
+TEST(CombineTest, CombineWithSecondParameterEmptyRange) {
+  const ParamGenerator<std::tuple<int, int> > gen =
+      Combine(Values(0, 1), Range(1, 1));
+  VerifyGeneratorIsEmpty(gen);
+}
+
+// Edge case. Tests that combine works with the maximum number
+// of parameters supported by Google Test (currently 10).
+TEST(CombineTest, CombineWithMaxNumberOfParameters) {
+  const char* foo = "foo";
+  const char* bar = "bar";
+  const ParamGenerator<
+      std::tuple<const char*, int, int, int, int, int, int, int, int, int> >
+      gen =
+          Combine(Values(foo, bar), Values(1), Values(2), Values(3), Values(4),
+                  Values(5), Values(6), Values(7), Values(8), Values(9));
+
+  std::tuple<const char*, int, int, int, int, int, int, int, int, int>
+      expected_values[] = {std::make_tuple(foo, 1, 2, 3, 4, 5, 6, 7, 8, 9),
+                           std::make_tuple(bar, 1, 2, 3, 4, 5, 6, 7, 8, 9)};
+  VerifyGenerator(gen, expected_values);
+}
+
+class NonDefaultConstructAssignString {
+ public:
+  NonDefaultConstructAssignString(const std::string& s) : str_(s) {}
+  NonDefaultConstructAssignString() = delete;
+  NonDefaultConstructAssignString(const NonDefaultConstructAssignString&) =
+      default;
+  NonDefaultConstructAssignString& operator=(
+      const NonDefaultConstructAssignString&) = delete;
+  ~NonDefaultConstructAssignString() = default;
+
+  const std::string& str() const { return str_; }
+
+ private:
+  std::string str_;
+};
+
+TEST(CombineTest, NonDefaultConstructAssign) {
+  const ParamGenerator<std::tuple<int, NonDefaultConstructAssignString> > gen =
+      Combine(Values(0, 1), Values(NonDefaultConstructAssignString("A"),
+                                   NonDefaultConstructAssignString("B")));
+
+  ParamGenerator<std::tuple<int, NonDefaultConstructAssignString> >::iterator
+      it = gen.begin();
+
+  EXPECT_EQ(0, std::get<0>(*it));
+  EXPECT_EQ("A", std::get<1>(*it).str());
+  ++it;
+
+  EXPECT_EQ(0, std::get<0>(*it));
+  EXPECT_EQ("B", std::get<1>(*it).str());
+  ++it;
+
+  EXPECT_EQ(1, std::get<0>(*it));
+  EXPECT_EQ("A", std::get<1>(*it).str());
+  ++it;
+
+  EXPECT_EQ(1, std::get<0>(*it));
+  EXPECT_EQ("B", std::get<1>(*it).str());
+  ++it;
+
+  EXPECT_TRUE(it == gen.end());
+}
+
+
+// Tests that an generator produces correct sequence after being
+// assigned from another generator.
+TEST(ParamGeneratorTest, AssignmentWorks) {
+  ParamGenerator<int> gen = Values(1, 2);
+  const ParamGenerator<int> gen2 = Values(3, 4);
+  gen = gen2;
+
+  const int expected_values[] = {3, 4};
+  VerifyGenerator(gen, expected_values);
+}
+
+// This test verifies that the tests are expanded and run as specified:
+// one test per element from the sequence produced by the generator
+// specified in INSTANTIATE_TEST_SUITE_P. It also verifies that the test's
+// fixture constructor, SetUp(), and TearDown() have run and have been
+// supplied with the correct parameters.
+
+// The use of environment object allows detection of the case where no test
+// case functionality is run at all. In this case TearDownTestSuite will not
+// be able to detect missing tests, naturally.
+template <int kExpectedCalls>
+class TestGenerationEnvironment : public ::testing::Environment {
+ public:
+  static TestGenerationEnvironment* Instance() {
+    static TestGenerationEnvironment* instance = new TestGenerationEnvironment;
+    return instance;
+  }
+
+  void FixtureConstructorExecuted() { fixture_constructor_count_++; }
+  void SetUpExecuted() { set_up_count_++; }
+  void TearDownExecuted() { tear_down_count_++; }
+  void TestBodyExecuted() { test_body_count_++; }
+
+  void TearDown() override {
+    // If all MultipleTestGenerationTest tests have been de-selected
+    // by the filter flag, the following checks make no sense.
+    bool perform_check = false;
+
+    for (int i = 0; i < kExpectedCalls; ++i) {
+      Message msg;
+      msg << "TestsExpandedAndRun/" << i;
+      if (UnitTestOptions::FilterMatchesTest(
+             "TestExpansionModule/MultipleTestGenerationTest",
+              msg.GetString().c_str())) {
+        perform_check = true;
+      }
+    }
+    if (perform_check) {
+      EXPECT_EQ(kExpectedCalls, fixture_constructor_count_)
+          << "Fixture constructor of ParamTestGenerationTest test case "
+          << "has not been run as expected.";
+      EXPECT_EQ(kExpectedCalls, set_up_count_)
+          << "Fixture SetUp method of ParamTestGenerationTest test case "
+          << "has not been run as expected.";
+      EXPECT_EQ(kExpectedCalls, tear_down_count_)
+          << "Fixture TearDown method of ParamTestGenerationTest test case "
+          << "has not been run as expected.";
+      EXPECT_EQ(kExpectedCalls, test_body_count_)
+          << "Test in ParamTestGenerationTest test case "
+          << "has not been run as expected.";
+    }
+  }
+
+ private:
+  TestGenerationEnvironment() : fixture_constructor_count_(0), set_up_count_(0),
+                                tear_down_count_(0), test_body_count_(0) {}
+
+  int fixture_constructor_count_;
+  int set_up_count_;
+  int tear_down_count_;
+  int test_body_count_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(TestGenerationEnvironment);
+};
+
+const int test_generation_params[] = {36, 42, 72};
+
+class TestGenerationTest : public TestWithParam<int> {
+ public:
+  enum {
+    PARAMETER_COUNT =
+        sizeof(test_generation_params)/sizeof(test_generation_params[0])
+  };
+
+  typedef TestGenerationEnvironment<PARAMETER_COUNT> Environment;
+
+  TestGenerationTest() {
+    Environment::Instance()->FixtureConstructorExecuted();
+    current_parameter_ = GetParam();
+  }
+  void SetUp() override {
+    Environment::Instance()->SetUpExecuted();
+    EXPECT_EQ(current_parameter_, GetParam());
+  }
+  void TearDown() override {
+    Environment::Instance()->TearDownExecuted();
+    EXPECT_EQ(current_parameter_, GetParam());
+  }
+
+  static void SetUpTestSuite() {
+    bool all_tests_in_test_case_selected = true;
+
+    for (int i = 0; i < PARAMETER_COUNT; ++i) {
+      Message test_name;
+      test_name << "TestsExpandedAndRun/" << i;
+      if ( !UnitTestOptions::FilterMatchesTest(
+                "TestExpansionModule/MultipleTestGenerationTest",
+                test_name.GetString())) {
+        all_tests_in_test_case_selected = false;
+      }
+    }
+    EXPECT_TRUE(all_tests_in_test_case_selected)
+        << "When running the TestGenerationTest test case all of its tests\n"
+        << "must be selected by the filter flag for the test case to pass.\n"
+        << "If not all of them are enabled, we can't reliably conclude\n"
+        << "that the correct number of tests have been generated.";
+
+    collected_parameters_.clear();
+  }
+
+  static void TearDownTestSuite() {
+    vector<int> expected_values(test_generation_params,
+                                test_generation_params + PARAMETER_COUNT);
+    // Test execution order is not guaranteed by Google Test,
+    // so the order of values in collected_parameters_ can be
+    // different and we have to sort to compare.
+    sort(expected_values.begin(), expected_values.end());
+    sort(collected_parameters_.begin(), collected_parameters_.end());
+
+    EXPECT_TRUE(collected_parameters_ == expected_values);
+  }
+
+ protected:
+  int current_parameter_;
+  static vector<int> collected_parameters_;
+
+ private:
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(TestGenerationTest);
+};
+vector<int> TestGenerationTest::collected_parameters_;
+
+TEST_P(TestGenerationTest, TestsExpandedAndRun) {
+  Environment::Instance()->TestBodyExecuted();
+  EXPECT_EQ(current_parameter_, GetParam());
+  collected_parameters_.push_back(GetParam());
+}
+INSTANTIATE_TEST_SUITE_P(TestExpansionModule, TestGenerationTest,
+                         ValuesIn(test_generation_params));
+
+// This test verifies that the element sequence (third parameter of
+// INSTANTIATE_TEST_SUITE_P) is evaluated in InitGoogleTest() and neither at
+// the call site of INSTANTIATE_TEST_SUITE_P nor in RUN_ALL_TESTS().  For
+// that, we declare param_value_ to be a static member of
+// GeneratorEvaluationTest and initialize it to 0.  We set it to 1 in
+// main(), just before invocation of InitGoogleTest().  After calling
+// InitGoogleTest(), we set the value to 2.  If the sequence is evaluated
+// before or after InitGoogleTest, INSTANTIATE_TEST_SUITE_P will create a
+// test with parameter other than 1, and the test body will fail the
+// assertion.
+class GeneratorEvaluationTest : public TestWithParam<int> {
+ public:
+  static int param_value() { return param_value_; }
+  static void set_param_value(int param_value) { param_value_ = param_value; }
+
+ private:
+  static int param_value_;
+};
+int GeneratorEvaluationTest::param_value_ = 0;
+
+TEST_P(GeneratorEvaluationTest, GeneratorsEvaluatedInMain) {
+  EXPECT_EQ(1, GetParam());
+}
+INSTANTIATE_TEST_SUITE_P(GenEvalModule, GeneratorEvaluationTest,
+                         Values(GeneratorEvaluationTest::param_value()));
+
+// Tests that generators defined in a different translation unit are
+// functional. Generator extern_gen is defined in gtest-param-test_test2.cc.
+extern ParamGenerator<int> extern_gen;
+class ExternalGeneratorTest : public TestWithParam<int> {};
+TEST_P(ExternalGeneratorTest, ExternalGenerator) {
+  // Sequence produced by extern_gen contains only a single value
+  // which we verify here.
+  EXPECT_EQ(GetParam(), 33);
+}
+INSTANTIATE_TEST_SUITE_P(ExternalGeneratorModule, ExternalGeneratorTest,
+                         extern_gen);
+
+// Tests that a parameterized test case can be defined in one translation
+// unit and instantiated in another. This test will be instantiated in
+// gtest-param-test_test2.cc. ExternalInstantiationTest fixture class is
+// defined in gtest-param-test_test.h.
+TEST_P(ExternalInstantiationTest, IsMultipleOf33) {
+  EXPECT_EQ(0, GetParam() % 33);
+}
+
+// Tests that a parameterized test case can be instantiated with multiple
+// generators.
+class MultipleInstantiationTest : public TestWithParam<int> {};
+TEST_P(MultipleInstantiationTest, AllowsMultipleInstances) {
+}
+INSTANTIATE_TEST_SUITE_P(Sequence1, MultipleInstantiationTest, Values(1, 2));
+INSTANTIATE_TEST_SUITE_P(Sequence2, MultipleInstantiationTest, Range(3, 5));
+
+// Tests that a parameterized test case can be instantiated
+// in multiple translation units. This test will be instantiated
+// here and in gtest-param-test_test2.cc.
+// InstantiationInMultipleTranslationUnitsTest fixture class
+// is defined in gtest-param-test_test.h.
+TEST_P(InstantiationInMultipleTranslationUnitsTest, IsMultipleOf42) {
+  EXPECT_EQ(0, GetParam() % 42);
+}
+INSTANTIATE_TEST_SUITE_P(Sequence1, InstantiationInMultipleTranslationUnitsTest,
+                         Values(42, 42 * 2));
+
+// Tests that each iteration of parameterized test runs in a separate test
+// object.
+class SeparateInstanceTest : public TestWithParam<int> {
+ public:
+  SeparateInstanceTest() : count_(0) {}
+
+  static void TearDownTestSuite() {
+    EXPECT_GE(global_count_, 2)
+        << "If some (but not all) SeparateInstanceTest tests have been "
+        << "filtered out this test will fail. Make sure that all "
+        << "GeneratorEvaluationTest are selected or de-selected together "
+        << "by the test filter.";
+  }
+
+ protected:
+  int count_;
+  static int global_count_;
+};
+int SeparateInstanceTest::global_count_ = 0;
+
+TEST_P(SeparateInstanceTest, TestsRunInSeparateInstances) {
+  EXPECT_EQ(0, count_++);
+  global_count_++;
+}
+INSTANTIATE_TEST_SUITE_P(FourElemSequence, SeparateInstanceTest, Range(1, 4));
+
+// Tests that all instantiations of a test have named appropriately. Test
+// defined with TEST_P(TestSuiteName, TestName) and instantiated with
+// INSTANTIATE_TEST_SUITE_P(SequenceName, TestSuiteName, generator) must be
+// named SequenceName/TestSuiteName.TestName/i, where i is the 0-based index of
+// the sequence element used to instantiate the test.
+class NamingTest : public TestWithParam<int> {};
+
+TEST_P(NamingTest, TestsReportCorrectNamesAndParameters) {
+  const ::testing::TestInfo* const test_info =
+     ::testing::UnitTest::GetInstance()->current_test_info();
+
+  EXPECT_STREQ("ZeroToFiveSequence/NamingTest", test_info->test_suite_name());
+
+  Message index_stream;
+  index_stream << "TestsReportCorrectNamesAndParameters/" << GetParam();
+  EXPECT_STREQ(index_stream.GetString().c_str(), test_info->name());
+
+  EXPECT_EQ(::testing::PrintToString(GetParam()), test_info->value_param());
+}
+
+INSTANTIATE_TEST_SUITE_P(ZeroToFiveSequence, NamingTest, Range(0, 5));
+
+// Tests that macros in test names are expanded correctly.
+class MacroNamingTest : public TestWithParam<int> {};
+
+#define PREFIX_WITH_FOO(test_name) Foo##test_name
+#define PREFIX_WITH_MACRO(test_name) Macro##test_name
+
+TEST_P(PREFIX_WITH_MACRO(NamingTest), PREFIX_WITH_FOO(SomeTestName)) {
+  const ::testing::TestInfo* const test_info =
+     ::testing::UnitTest::GetInstance()->current_test_info();
+
+  EXPECT_STREQ("FortyTwo/MacroNamingTest", test_info->test_suite_name());
+  EXPECT_STREQ("FooSomeTestName/0", test_info->name());
+}
+
+INSTANTIATE_TEST_SUITE_P(FortyTwo, MacroNamingTest, Values(42));
+
+// Tests the same thing for non-parametrized tests.
+class MacroNamingTestNonParametrized : public ::testing::Test {};
+
+TEST_F(PREFIX_WITH_MACRO(NamingTestNonParametrized),
+       PREFIX_WITH_FOO(SomeTestName)) {
+  const ::testing::TestInfo* const test_info =
+     ::testing::UnitTest::GetInstance()->current_test_info();
+
+  EXPECT_STREQ("MacroNamingTestNonParametrized", test_info->test_suite_name());
+  EXPECT_STREQ("FooSomeTestName", test_info->name());
+}
+
+TEST(MacroNameing, LookupNames) {
+  std::set<std::string> know_suite_names, know_test_names;
+
+  auto ins = testing::UnitTest::GetInstance();
+  int ts = 0;
+  while (const testing::TestSuite* suite = ins->GetTestSuite(ts++)) {
+    know_suite_names.insert(suite->name());
+
+    int ti = 0;
+    while (const testing::TestInfo* info = suite->GetTestInfo(ti++)) {
+      know_test_names.insert(std::string(suite->name()) + "." + info->name());
+    }
+  }
+
+  // Check that the expected form of the test suit name actually exists.
+  EXPECT_NE(  //
+      know_suite_names.find("FortyTwo/MacroNamingTest"),
+      know_suite_names.end());
+  EXPECT_NE(
+      know_suite_names.find("MacroNamingTestNonParametrized"),
+      know_suite_names.end());
+  // Check that the expected form of the test name actually exists.
+  EXPECT_NE(  //
+      know_test_names.find("FortyTwo/MacroNamingTest.FooSomeTestName/0"),
+      know_test_names.end());
+  EXPECT_NE(
+      know_test_names.find("MacroNamingTestNonParametrized.FooSomeTestName"),
+      know_test_names.end());
+}
+
+// Tests that user supplied custom parameter names are working correctly.
+// Runs the test with a builtin helper method which uses PrintToString,
+// as well as a custom function and custom functor to ensure all possible
+// uses work correctly.
+class CustomFunctorNamingTest : public TestWithParam<std::string> {};
+TEST_P(CustomFunctorNamingTest, CustomTestNames) {}
+
+struct CustomParamNameFunctor {
+  std::string operator()(const ::testing::TestParamInfo<std::string>& inf) {
+    return inf.param;
+  }
+};
+
+INSTANTIATE_TEST_SUITE_P(CustomParamNameFunctor, CustomFunctorNamingTest,
+                         Values(std::string("FunctorName")),
+                         CustomParamNameFunctor());
+
+INSTANTIATE_TEST_SUITE_P(AllAllowedCharacters, CustomFunctorNamingTest,
+                         Values("abcdefghijklmnopqrstuvwxyz",
+                                "ABCDEFGHIJKLMNOPQRSTUVWXYZ", "01234567890_"),
+                         CustomParamNameFunctor());
+
+inline std::string CustomParamNameFunction(
+    const ::testing::TestParamInfo<std::string>& inf) {
+  return inf.param;
+}
+
+class CustomFunctionNamingTest : public TestWithParam<std::string> {};
+TEST_P(CustomFunctionNamingTest, CustomTestNames) {}
+
+INSTANTIATE_TEST_SUITE_P(CustomParamNameFunction, CustomFunctionNamingTest,
+                         Values(std::string("FunctionName")),
+                         CustomParamNameFunction);
+
+INSTANTIATE_TEST_SUITE_P(CustomParamNameFunctionP, CustomFunctionNamingTest,
+                         Values(std::string("FunctionNameP")),
+                         &CustomParamNameFunction);
+
+// Test custom naming with a lambda
+
+class CustomLambdaNamingTest : public TestWithParam<std::string> {};
+TEST_P(CustomLambdaNamingTest, CustomTestNames) {}
+
+INSTANTIATE_TEST_SUITE_P(CustomParamNameLambda, CustomLambdaNamingTest,
+                         Values(std::string("LambdaName")),
+                         [](const ::testing::TestParamInfo<std::string>& inf) {
+                           return inf.param;
+                         });
+
+TEST(CustomNamingTest, CheckNameRegistry) {
+  ::testing::UnitTest* unit_test = ::testing::UnitTest::GetInstance();
+  std::set<std::string> test_names;
+  for (int suite_num = 0; suite_num < unit_test->total_test_suite_count();
+       ++suite_num) {
+    const ::testing::TestSuite* test_suite = unit_test->GetTestSuite(suite_num);
+    for (int test_num = 0; test_num < test_suite->total_test_count();
+         ++test_num) {
+      const ::testing::TestInfo* test_info = test_suite->GetTestInfo(test_num);
+      test_names.insert(std::string(test_info->name()));
+    }
+  }
+  EXPECT_EQ(1u, test_names.count("CustomTestNames/FunctorName"));
+  EXPECT_EQ(1u, test_names.count("CustomTestNames/FunctionName"));
+  EXPECT_EQ(1u, test_names.count("CustomTestNames/FunctionNameP"));
+  EXPECT_EQ(1u, test_names.count("CustomTestNames/LambdaName"));
+}
+
+// Test a numeric name to ensure PrintToStringParamName works correctly.
+
+class CustomIntegerNamingTest : public TestWithParam<int> {};
+
+TEST_P(CustomIntegerNamingTest, TestsReportCorrectNames) {
+  const ::testing::TestInfo* const test_info =
+     ::testing::UnitTest::GetInstance()->current_test_info();
+  Message test_name_stream;
+  test_name_stream << "TestsReportCorrectNames/" << GetParam();
+  EXPECT_STREQ(test_name_stream.GetString().c_str(), test_info->name());
+}
+
+INSTANTIATE_TEST_SUITE_P(PrintToString, CustomIntegerNamingTest, Range(0, 5),
+                         ::testing::PrintToStringParamName());
+
+// Test a custom struct with PrintToString.
+
+struct CustomStruct {
+  explicit CustomStruct(int value) : x(value) {}
+  int x;
+};
+
+std::ostream& operator<<(std::ostream& stream, const CustomStruct& val) {
+  stream << val.x;
+  return stream;
+}
+
+class CustomStructNamingTest : public TestWithParam<CustomStruct> {};
+
+TEST_P(CustomStructNamingTest, TestsReportCorrectNames) {
+  const ::testing::TestInfo* const test_info =
+     ::testing::UnitTest::GetInstance()->current_test_info();
+  Message test_name_stream;
+  test_name_stream << "TestsReportCorrectNames/" << GetParam();
+  EXPECT_STREQ(test_name_stream.GetString().c_str(), test_info->name());
+}
+
+INSTANTIATE_TEST_SUITE_P(PrintToString, CustomStructNamingTest,
+                         Values(CustomStruct(0), CustomStruct(1)),
+                         ::testing::PrintToStringParamName());
+
+// Test that using a stateful parameter naming function works as expected.
+
+struct StatefulNamingFunctor {
+  StatefulNamingFunctor() : sum(0) {}
+  std::string operator()(const ::testing::TestParamInfo<int>& info) {
+    int value = info.param + sum;
+    sum += info.param;
+    return ::testing::PrintToString(value);
+  }
+  int sum;
+};
+
+class StatefulNamingTest : public ::testing::TestWithParam<int> {
+ protected:
+  StatefulNamingTest() : sum_(0) {}
+  int sum_;
+};
+
+TEST_P(StatefulNamingTest, TestsReportCorrectNames) {
+  const ::testing::TestInfo* const test_info =
+     ::testing::UnitTest::GetInstance()->current_test_info();
+  sum_ += GetParam();
+  Message test_name_stream;
+  test_name_stream << "TestsReportCorrectNames/" << sum_;
+  EXPECT_STREQ(test_name_stream.GetString().c_str(), test_info->name());
+}
+
+INSTANTIATE_TEST_SUITE_P(StatefulNamingFunctor, StatefulNamingTest, Range(0, 5),
+                         StatefulNamingFunctor());
+
+// Class that cannot be streamed into an ostream.  It needs to be copyable
+// (and, in case of MSVC, also assignable) in order to be a test parameter
+// type.  Its default copy constructor and assignment operator do exactly
+// what we need.
+class Unstreamable {
+ public:
+  explicit Unstreamable(int value) : value_(value) {}
+  // -Wunused-private-field: dummy accessor for `value_`.
+  const int& dummy_value() const { return value_; }
+
+ private:
+  int value_;
+};
+
+class CommentTest : public TestWithParam<Unstreamable> {};
+
+TEST_P(CommentTest, TestsCorrectlyReportUnstreamableParams) {
+  const ::testing::TestInfo* const test_info =
+     ::testing::UnitTest::GetInstance()->current_test_info();
+
+  EXPECT_EQ(::testing::PrintToString(GetParam()), test_info->value_param());
+}
+
+INSTANTIATE_TEST_SUITE_P(InstantiationWithComments, CommentTest,
+                         Values(Unstreamable(1)));
+
+// Verify that we can create a hierarchy of test fixtures, where the base
+// class fixture is not parameterized and the derived class is. In this case
+// ParameterizedDerivedTest inherits from NonParameterizedBaseTest.  We
+// perform simple tests on both.
+class NonParameterizedBaseTest : public ::testing::Test {
+ public:
+  NonParameterizedBaseTest() : n_(17) { }
+ protected:
+  int n_;
+};
+
+class ParameterizedDerivedTest : public NonParameterizedBaseTest,
+                                 public ::testing::WithParamInterface<int> {
+ protected:
+  ParameterizedDerivedTest() : count_(0) { }
+  int count_;
+  static int global_count_;
+};
+
+int ParameterizedDerivedTest::global_count_ = 0;
+
+TEST_F(NonParameterizedBaseTest, FixtureIsInitialized) {
+  EXPECT_EQ(17, n_);
+}
+
+TEST_P(ParameterizedDerivedTest, SeesSequence) {
+  EXPECT_EQ(17, n_);
+  EXPECT_EQ(0, count_++);
+  EXPECT_EQ(GetParam(), global_count_++);
+}
+
+class ParameterizedDeathTest : public ::testing::TestWithParam<int> { };
+
+TEST_F(ParameterizedDeathTest, GetParamDiesFromTestF) {
+  EXPECT_DEATH_IF_SUPPORTED(GetParam(),
+                            ".* value-parameterized test .*");
+}
+
+INSTANTIATE_TEST_SUITE_P(RangeZeroToFive, ParameterizedDerivedTest,
+                         Range(0, 5));
+
+// Tests param generator working with Enums
+enum MyEnums {
+  ENUM1 = 1,
+  ENUM2 = 3,
+  ENUM3 = 8,
+};
+
+class MyEnumTest : public testing::TestWithParam<MyEnums> {};
+
+TEST_P(MyEnumTest, ChecksParamMoreThanZero) { EXPECT_GE(10, GetParam()); }
+INSTANTIATE_TEST_SUITE_P(MyEnumTests, MyEnumTest,
+                         ::testing::Values(ENUM1, ENUM2, 0));
+
+namespace works_here {
+// Never used not instantiated, this should work.
+class NotUsedTest : public testing::TestWithParam<int> {};
+
+///////
+// Never used not instantiated, this should work.
+template <typename T>
+class NotUsedTypeTest : public testing::Test {};
+TYPED_TEST_SUITE_P(NotUsedTypeTest);
+
+// Used but not instantiated, this would fail. but...
+class NotInstantiatedTest : public testing::TestWithParam<int> {};
+// ... we mark is as allowed.
+GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST(NotInstantiatedTest);
+
+TEST_P(NotInstantiatedTest, Used) { }
+
+using OtherName = NotInstantiatedTest;
+GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST(OtherName);
+TEST_P(OtherName, Used) { }
+
+// Used but not instantiated, this would fail. but...
+template <typename T>
+class NotInstantiatedTypeTest : public testing::Test {};
+TYPED_TEST_SUITE_P(NotInstantiatedTypeTest);
+// ... we mark is as allowed.
+GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST(NotInstantiatedTypeTest);
+
+TYPED_TEST_P(NotInstantiatedTypeTest, Used) { }
+REGISTER_TYPED_TEST_SUITE_P(NotInstantiatedTypeTest, Used);
+}  // namespace works_here
+
+int main(int argc, char **argv) {
+  // Used in TestGenerationTest test suite.
+  AddGlobalTestEnvironment(TestGenerationTest::Environment::Instance());
+  // Used in GeneratorEvaluationTest test suite. Tests that the updated value
+  // will be picked up for instantiating tests in GeneratorEvaluationTest.
+  GeneratorEvaluationTest::set_param_value(1);
+
+  ::testing::InitGoogleTest(&argc, argv);
+
+  // Used in GeneratorEvaluationTest test suite. Tests that value updated
+  // here will NOT be used for instantiating tests in
+  // GeneratorEvaluationTest.
+  GeneratorEvaluationTest::set_param_value(2);
+
+  return RUN_ALL_TESTS();
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-param-test-test.h b/leveldb_base/third_party/googletest/googletest/test/googletest-param-test-test.h
new file mode 100644
index 0000000..8919375
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-param-test-test.h
@@ -0,0 +1,51 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// The Google C++ Testing and Mocking Framework (Google Test)
+//
+// This header file provides classes and functions used internally
+// for testing Google Test itself.
+
+#ifndef GOOGLETEST_TEST_GOOGLETEST_PARAM_TEST_TEST_H_
+#define GOOGLETEST_TEST_GOOGLETEST_PARAM_TEST_TEST_H_
+
+#include "gtest/gtest.h"
+
+// Test fixture for testing definition and instantiation of a test
+// in separate translation units.
+class ExternalInstantiationTest : public ::testing::TestWithParam<int> {
+};
+
+// Test fixture for testing instantiation of a test in multiple
+// translation units.
+class InstantiationInMultipleTranslationUnitsTest
+    : public ::testing::TestWithParam<int> {
+};
+
+#endif  // GOOGLETEST_TEST_GOOGLETEST_PARAM_TEST_TEST_H_
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-param-test2-test.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-param-test2-test.cc
new file mode 100644
index 0000000..2a29fb1
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-param-test2-test.cc
@@ -0,0 +1,61 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// Tests for Google Test itself.  This verifies that the basic constructs of
+// Google Test work.
+
+#include "gtest/gtest.h"
+#include "test/googletest-param-test-test.h"
+
+using ::testing::Values;
+using ::testing::internal::ParamGenerator;
+
+// Tests that generators defined in a different translation unit
+// are functional. The test using extern_gen is defined
+// in googletest-param-test-test.cc.
+ParamGenerator<int> extern_gen = Values(33);
+
+// Tests that a parameterized test case can be defined in one translation unit
+// and instantiated in another. The test is defined in
+// googletest-param-test-test.cc and ExternalInstantiationTest fixture class is
+// defined in gtest-param-test_test.h.
+INSTANTIATE_TEST_SUITE_P(MultiplesOf33,
+                         ExternalInstantiationTest,
+                         Values(33, 66));
+
+// Tests that a parameterized test case can be instantiated
+// in multiple translation units. Another instantiation is defined
+// in googletest-param-test-test.cc and
+// InstantiationInMultipleTranslationUnitsTest fixture is defined in
+// gtest-param-test_test.h
+INSTANTIATE_TEST_SUITE_P(Sequence2,
+                         InstantiationInMultipleTranslationUnitsTest,
+                         Values(42*3, 42*4, 42*5));
+
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-port-test.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-port-test.cc
new file mode 100644
index 0000000..1e0c861
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-port-test.cc
@@ -0,0 +1,1276 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// This file tests the internal cross-platform support utilities.
+#include <stdio.h>
+
+#include "gtest/internal/gtest-port.h"
+
+#if GTEST_OS_MAC
+# include <time.h>
+#endif  // GTEST_OS_MAC
+
+#include <list>
+#include <memory>
+#include <utility>  // For std::pair and std::make_pair.
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "gtest/gtest-spi.h"
+#include "src/gtest-internal-inl.h"
+
+using std::make_pair;
+using std::pair;
+
+namespace testing {
+namespace internal {
+
+TEST(IsXDigitTest, WorksForNarrowAscii) {
+  EXPECT_TRUE(IsXDigit('0'));
+  EXPECT_TRUE(IsXDigit('9'));
+  EXPECT_TRUE(IsXDigit('A'));
+  EXPECT_TRUE(IsXDigit('F'));
+  EXPECT_TRUE(IsXDigit('a'));
+  EXPECT_TRUE(IsXDigit('f'));
+
+  EXPECT_FALSE(IsXDigit('-'));
+  EXPECT_FALSE(IsXDigit('g'));
+  EXPECT_FALSE(IsXDigit('G'));
+}
+
+TEST(IsXDigitTest, ReturnsFalseForNarrowNonAscii) {
+  EXPECT_FALSE(IsXDigit(static_cast<char>('\x80')));
+  EXPECT_FALSE(IsXDigit(static_cast<char>('0' | '\x80')));
+}
+
+TEST(IsXDigitTest, WorksForWideAscii) {
+  EXPECT_TRUE(IsXDigit(L'0'));
+  EXPECT_TRUE(IsXDigit(L'9'));
+  EXPECT_TRUE(IsXDigit(L'A'));
+  EXPECT_TRUE(IsXDigit(L'F'));
+  EXPECT_TRUE(IsXDigit(L'a'));
+  EXPECT_TRUE(IsXDigit(L'f'));
+
+  EXPECT_FALSE(IsXDigit(L'-'));
+  EXPECT_FALSE(IsXDigit(L'g'));
+  EXPECT_FALSE(IsXDigit(L'G'));
+}
+
+TEST(IsXDigitTest, ReturnsFalseForWideNonAscii) {
+  EXPECT_FALSE(IsXDigit(static_cast<wchar_t>(0x80)));
+  EXPECT_FALSE(IsXDigit(static_cast<wchar_t>(L'0' | 0x80)));
+  EXPECT_FALSE(IsXDigit(static_cast<wchar_t>(L'0' | 0x100)));
+}
+
+class Base {
+ public:
+  Base() : member_(0) {}
+  explicit Base(int n) : member_(n) {}
+  Base(const Base&) = default;
+  Base& operator=(const Base&) = default;
+  virtual ~Base() {}
+  int member() { return member_; }
+
+ private:
+  int member_;
+};
+
+class Derived : public Base {
+ public:
+  explicit Derived(int n) : Base(n) {}
+};
+
+TEST(ImplicitCastTest, ConvertsPointers) {
+  Derived derived(0);
+  EXPECT_TRUE(&derived == ::testing::internal::ImplicitCast_<Base*>(&derived));
+}
+
+TEST(ImplicitCastTest, CanUseInheritance) {
+  Derived derived(1);
+  Base base = ::testing::internal::ImplicitCast_<Base>(derived);
+  EXPECT_EQ(derived.member(), base.member());
+}
+
+class Castable {
+ public:
+  explicit Castable(bool* converted) : converted_(converted) {}
+  operator Base() {
+    *converted_ = true;
+    return Base();
+  }
+
+ private:
+  bool* converted_;
+};
+
+TEST(ImplicitCastTest, CanUseNonConstCastOperator) {
+  bool converted = false;
+  Castable castable(&converted);
+  Base base = ::testing::internal::ImplicitCast_<Base>(castable);
+  EXPECT_TRUE(converted);
+}
+
+class ConstCastable {
+ public:
+  explicit ConstCastable(bool* converted) : converted_(converted) {}
+  operator Base() const {
+    *converted_ = true;
+    return Base();
+  }
+
+ private:
+  bool* converted_;
+};
+
+TEST(ImplicitCastTest, CanUseConstCastOperatorOnConstValues) {
+  bool converted = false;
+  const ConstCastable const_castable(&converted);
+  Base base = ::testing::internal::ImplicitCast_<Base>(const_castable);
+  EXPECT_TRUE(converted);
+}
+
+class ConstAndNonConstCastable {
+ public:
+  ConstAndNonConstCastable(bool* converted, bool* const_converted)
+      : converted_(converted), const_converted_(const_converted) {}
+  operator Base() {
+    *converted_ = true;
+    return Base();
+  }
+  operator Base() const {
+    *const_converted_ = true;
+    return Base();
+  }
+
+ private:
+  bool* converted_;
+  bool* const_converted_;
+};
+
+TEST(ImplicitCastTest, CanSelectBetweenConstAndNonConstCasrAppropriately) {
+  bool converted = false;
+  bool const_converted = false;
+  ConstAndNonConstCastable castable(&converted, &const_converted);
+  Base base = ::testing::internal::ImplicitCast_<Base>(castable);
+  EXPECT_TRUE(converted);
+  EXPECT_FALSE(const_converted);
+
+  converted = false;
+  const_converted = false;
+  const ConstAndNonConstCastable const_castable(&converted, &const_converted);
+  base = ::testing::internal::ImplicitCast_<Base>(const_castable);
+  EXPECT_FALSE(converted);
+  EXPECT_TRUE(const_converted);
+}
+
+class To {
+ public:
+  To(bool* converted) { *converted = true; }  // NOLINT
+};
+
+TEST(ImplicitCastTest, CanUseImplicitConstructor) {
+  bool converted = false;
+  To to = ::testing::internal::ImplicitCast_<To>(&converted);
+  (void)to;
+  EXPECT_TRUE(converted);
+}
+
+// The following code intentionally tests a suboptimal syntax.
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdangling-else"
+#pragma GCC diagnostic ignored "-Wempty-body"
+#pragma GCC diagnostic ignored "-Wpragmas"
+#endif
+TEST(GtestCheckSyntaxTest, BehavesLikeASingleStatement) {
+  if (AlwaysFalse())
+    GTEST_CHECK_(false) << "This should never be executed; "
+                           "It's a compilation test only.";
+
+  if (AlwaysTrue())
+    GTEST_CHECK_(true);
+  else
+    ;  // NOLINT
+
+  if (AlwaysFalse())
+    ;  // NOLINT
+  else
+    GTEST_CHECK_(true) << "";
+}
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif
+
+TEST(GtestCheckSyntaxTest, WorksWithSwitch) {
+  switch (0) {
+    case 1:
+      break;
+    default:
+      GTEST_CHECK_(true);
+  }
+
+  switch (0)
+    case 0:
+      GTEST_CHECK_(true) << "Check failed in switch case";
+}
+
+// Verifies behavior of FormatFileLocation.
+TEST(FormatFileLocationTest, FormatsFileLocation) {
+  EXPECT_PRED_FORMAT2(IsSubstring, "foo.cc", FormatFileLocation("foo.cc", 42));
+  EXPECT_PRED_FORMAT2(IsSubstring, "42", FormatFileLocation("foo.cc", 42));
+}
+
+TEST(FormatFileLocationTest, FormatsUnknownFile) {
+  EXPECT_PRED_FORMAT2(IsSubstring, "unknown file",
+                      FormatFileLocation(nullptr, 42));
+  EXPECT_PRED_FORMAT2(IsSubstring, "42", FormatFileLocation(nullptr, 42));
+}
+
+TEST(FormatFileLocationTest, FormatsUknownLine) {
+  EXPECT_EQ("foo.cc:", FormatFileLocation("foo.cc", -1));
+}
+
+TEST(FormatFileLocationTest, FormatsUknownFileAndLine) {
+  EXPECT_EQ("unknown file:", FormatFileLocation(nullptr, -1));
+}
+
+// Verifies behavior of FormatCompilerIndependentFileLocation.
+TEST(FormatCompilerIndependentFileLocationTest, FormatsFileLocation) {
+  EXPECT_EQ("foo.cc:42", FormatCompilerIndependentFileLocation("foo.cc", 42));
+}
+
+TEST(FormatCompilerIndependentFileLocationTest, FormatsUknownFile) {
+  EXPECT_EQ("unknown file:42",
+            FormatCompilerIndependentFileLocation(nullptr, 42));
+}
+
+TEST(FormatCompilerIndependentFileLocationTest, FormatsUknownLine) {
+  EXPECT_EQ("foo.cc", FormatCompilerIndependentFileLocation("foo.cc", -1));
+}
+
+TEST(FormatCompilerIndependentFileLocationTest, FormatsUknownFileAndLine) {
+  EXPECT_EQ("unknown file", FormatCompilerIndependentFileLocation(nullptr, -1));
+}
+
+#if GTEST_OS_LINUX || GTEST_OS_MAC || GTEST_OS_QNX || GTEST_OS_FUCHSIA || \
+    GTEST_OS_DRAGONFLY || GTEST_OS_FREEBSD || GTEST_OS_GNU_KFREEBSD || \
+    GTEST_OS_NETBSD || GTEST_OS_OPENBSD
+void* ThreadFunc(void* data) {
+  internal::Mutex* mutex = static_cast<internal::Mutex*>(data);
+  mutex->Lock();
+  mutex->Unlock();
+  return nullptr;
+}
+
+TEST(GetThreadCountTest, ReturnsCorrectValue) {
+  const size_t starting_count = GetThreadCount();
+  pthread_t       thread_id;
+
+  internal::Mutex mutex;
+  {
+    internal::MutexLock lock(&mutex);
+    pthread_attr_t  attr;
+    ASSERT_EQ(0, pthread_attr_init(&attr));
+    ASSERT_EQ(0, pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE));
+
+    const int status = pthread_create(&thread_id, &attr, &ThreadFunc, &mutex);
+    ASSERT_EQ(0, pthread_attr_destroy(&attr));
+    ASSERT_EQ(0, status);
+    EXPECT_EQ(starting_count + 1, GetThreadCount());
+  }
+
+  void* dummy;
+  ASSERT_EQ(0, pthread_join(thread_id, &dummy));
+
+  // The OS may not immediately report the updated thread count after
+  // joining a thread, causing flakiness in this test. To counter that, we
+  // wait for up to .5 seconds for the OS to report the correct value.
+  for (int i = 0; i < 5; ++i) {
+    if (GetThreadCount() == starting_count)
+      break;
+
+    SleepMilliseconds(100);
+  }
+
+  EXPECT_EQ(starting_count, GetThreadCount());
+}
+#else
+TEST(GetThreadCountTest, ReturnsZeroWhenUnableToCountThreads) {
+  EXPECT_EQ(0U, GetThreadCount());
+}
+#endif  // GTEST_OS_LINUX || GTEST_OS_MAC || GTEST_OS_QNX || GTEST_OS_FUCHSIA
+
+TEST(GtestCheckDeathTest, DiesWithCorrectOutputOnFailure) {
+  const bool a_false_condition = false;
+  const char regex[] =
+#ifdef _MSC_VER
+     "googletest-port-test\\.cc\\(\\d+\\):"
+#elif GTEST_USES_POSIX_RE
+     "googletest-port-test\\.cc:[0-9]+"
+#else
+     "googletest-port-test\\.cc:\\d+"
+#endif  // _MSC_VER
+     ".*a_false_condition.*Extra info.*";
+
+  EXPECT_DEATH_IF_SUPPORTED(GTEST_CHECK_(a_false_condition) << "Extra info",
+                            regex);
+}
+
+#if GTEST_HAS_DEATH_TEST
+
+TEST(GtestCheckDeathTest, LivesSilentlyOnSuccess) {
+  EXPECT_EXIT({
+      GTEST_CHECK_(true) << "Extra info";
+      ::std::cerr << "Success\n";
+      exit(0); },
+      ::testing::ExitedWithCode(0), "Success");
+}
+
+#endif  // GTEST_HAS_DEATH_TEST
+
+// Verifies that Google Test choose regular expression engine appropriate to
+// the platform. The test will produce compiler errors in case of failure.
+// For simplicity, we only cover the most important platforms here.
+TEST(RegexEngineSelectionTest, SelectsCorrectRegexEngine) {
+#if !GTEST_USES_PCRE
+# if GTEST_HAS_POSIX_RE
+
+  EXPECT_TRUE(GTEST_USES_POSIX_RE);
+
+# else
+
+  EXPECT_TRUE(GTEST_USES_SIMPLE_RE);
+
+# endif
+#endif  // !GTEST_USES_PCRE
+}
+
+#if GTEST_USES_POSIX_RE
+
+template <typename Str>
+class RETest : public ::testing::Test {};
+
+// Defines StringTypes as the list of all string types that class RE
+// supports.
+typedef testing::Types< ::std::string, const char*> StringTypes;
+
+TYPED_TEST_SUITE(RETest, StringTypes);
+
+// Tests RE's implicit constructors.
+TYPED_TEST(RETest, ImplicitConstructorWorks) {
+  const RE empty(TypeParam(""));
+  EXPECT_STREQ("", empty.pattern());
+
+  const RE simple(TypeParam("hello"));
+  EXPECT_STREQ("hello", simple.pattern());
+
+  const RE normal(TypeParam(".*(\\w+)"));
+  EXPECT_STREQ(".*(\\w+)", normal.pattern());
+}
+
+// Tests that RE's constructors reject invalid regular expressions.
+TYPED_TEST(RETest, RejectsInvalidRegex) {
+  EXPECT_NONFATAL_FAILURE({
+    const RE invalid(TypeParam("?"));
+  }, "\"?\" is not a valid POSIX Extended regular expression.");
+}
+
+// Tests RE::FullMatch().
+TYPED_TEST(RETest, FullMatchWorks) {
+  const RE empty(TypeParam(""));
+  EXPECT_TRUE(RE::FullMatch(TypeParam(""), empty));
+  EXPECT_FALSE(RE::FullMatch(TypeParam("a"), empty));
+
+  const RE re(TypeParam("a.*z"));
+  EXPECT_TRUE(RE::FullMatch(TypeParam("az"), re));
+  EXPECT_TRUE(RE::FullMatch(TypeParam("axyz"), re));
+  EXPECT_FALSE(RE::FullMatch(TypeParam("baz"), re));
+  EXPECT_FALSE(RE::FullMatch(TypeParam("azy"), re));
+}
+
+// Tests RE::PartialMatch().
+TYPED_TEST(RETest, PartialMatchWorks) {
+  const RE empty(TypeParam(""));
+  EXPECT_TRUE(RE::PartialMatch(TypeParam(""), empty));
+  EXPECT_TRUE(RE::PartialMatch(TypeParam("a"), empty));
+
+  const RE re(TypeParam("a.*z"));
+  EXPECT_TRUE(RE::PartialMatch(TypeParam("az"), re));
+  EXPECT_TRUE(RE::PartialMatch(TypeParam("axyz"), re));
+  EXPECT_TRUE(RE::PartialMatch(TypeParam("baz"), re));
+  EXPECT_TRUE(RE::PartialMatch(TypeParam("azy"), re));
+  EXPECT_FALSE(RE::PartialMatch(TypeParam("zza"), re));
+}
+
+#elif GTEST_USES_SIMPLE_RE
+
+TEST(IsInSetTest, NulCharIsNotInAnySet) {
+  EXPECT_FALSE(IsInSet('\0', ""));
+  EXPECT_FALSE(IsInSet('\0', "\0"));
+  EXPECT_FALSE(IsInSet('\0', "a"));
+}
+
+TEST(IsInSetTest, WorksForNonNulChars) {
+  EXPECT_FALSE(IsInSet('a', "Ab"));
+  EXPECT_FALSE(IsInSet('c', ""));
+
+  EXPECT_TRUE(IsInSet('b', "bcd"));
+  EXPECT_TRUE(IsInSet('b', "ab"));
+}
+
+TEST(IsAsciiDigitTest, IsFalseForNonDigit) {
+  EXPECT_FALSE(IsAsciiDigit('\0'));
+  EXPECT_FALSE(IsAsciiDigit(' '));
+  EXPECT_FALSE(IsAsciiDigit('+'));
+  EXPECT_FALSE(IsAsciiDigit('-'));
+  EXPECT_FALSE(IsAsciiDigit('.'));
+  EXPECT_FALSE(IsAsciiDigit('a'));
+}
+
+TEST(IsAsciiDigitTest, IsTrueForDigit) {
+  EXPECT_TRUE(IsAsciiDigit('0'));
+  EXPECT_TRUE(IsAsciiDigit('1'));
+  EXPECT_TRUE(IsAsciiDigit('5'));
+  EXPECT_TRUE(IsAsciiDigit('9'));
+}
+
+TEST(IsAsciiPunctTest, IsFalseForNonPunct) {
+  EXPECT_FALSE(IsAsciiPunct('\0'));
+  EXPECT_FALSE(IsAsciiPunct(' '));
+  EXPECT_FALSE(IsAsciiPunct('\n'));
+  EXPECT_FALSE(IsAsciiPunct('a'));
+  EXPECT_FALSE(IsAsciiPunct('0'));
+}
+
+TEST(IsAsciiPunctTest, IsTrueForPunct) {
+  for (const char* p = "^-!\"#$%&'()*+,./:;<=>?@[\\]_`{|}~"; *p; p++) {
+    EXPECT_PRED1(IsAsciiPunct, *p);
+  }
+}
+
+TEST(IsRepeatTest, IsFalseForNonRepeatChar) {
+  EXPECT_FALSE(IsRepeat('\0'));
+  EXPECT_FALSE(IsRepeat(' '));
+  EXPECT_FALSE(IsRepeat('a'));
+  EXPECT_FALSE(IsRepeat('1'));
+  EXPECT_FALSE(IsRepeat('-'));
+}
+
+TEST(IsRepeatTest, IsTrueForRepeatChar) {
+  EXPECT_TRUE(IsRepeat('?'));
+  EXPECT_TRUE(IsRepeat('*'));
+  EXPECT_TRUE(IsRepeat('+'));
+}
+
+TEST(IsAsciiWhiteSpaceTest, IsFalseForNonWhiteSpace) {
+  EXPECT_FALSE(IsAsciiWhiteSpace('\0'));
+  EXPECT_FALSE(IsAsciiWhiteSpace('a'));
+  EXPECT_FALSE(IsAsciiWhiteSpace('1'));
+  EXPECT_FALSE(IsAsciiWhiteSpace('+'));
+  EXPECT_FALSE(IsAsciiWhiteSpace('_'));
+}
+
+TEST(IsAsciiWhiteSpaceTest, IsTrueForWhiteSpace) {
+  EXPECT_TRUE(IsAsciiWhiteSpace(' '));
+  EXPECT_TRUE(IsAsciiWhiteSpace('\n'));
+  EXPECT_TRUE(IsAsciiWhiteSpace('\r'));
+  EXPECT_TRUE(IsAsciiWhiteSpace('\t'));
+  EXPECT_TRUE(IsAsciiWhiteSpace('\v'));
+  EXPECT_TRUE(IsAsciiWhiteSpace('\f'));
+}
+
+TEST(IsAsciiWordCharTest, IsFalseForNonWordChar) {
+  EXPECT_FALSE(IsAsciiWordChar('\0'));
+  EXPECT_FALSE(IsAsciiWordChar('+'));
+  EXPECT_FALSE(IsAsciiWordChar('.'));
+  EXPECT_FALSE(IsAsciiWordChar(' '));
+  EXPECT_FALSE(IsAsciiWordChar('\n'));
+}
+
+TEST(IsAsciiWordCharTest, IsTrueForLetter) {
+  EXPECT_TRUE(IsAsciiWordChar('a'));
+  EXPECT_TRUE(IsAsciiWordChar('b'));
+  EXPECT_TRUE(IsAsciiWordChar('A'));
+  EXPECT_TRUE(IsAsciiWordChar('Z'));
+}
+
+TEST(IsAsciiWordCharTest, IsTrueForDigit) {
+  EXPECT_TRUE(IsAsciiWordChar('0'));
+  EXPECT_TRUE(IsAsciiWordChar('1'));
+  EXPECT_TRUE(IsAsciiWordChar('7'));
+  EXPECT_TRUE(IsAsciiWordChar('9'));
+}
+
+TEST(IsAsciiWordCharTest, IsTrueForUnderscore) {
+  EXPECT_TRUE(IsAsciiWordChar('_'));
+}
+
+TEST(IsValidEscapeTest, IsFalseForNonPrintable) {
+  EXPECT_FALSE(IsValidEscape('\0'));
+  EXPECT_FALSE(IsValidEscape('\007'));
+}
+
+TEST(IsValidEscapeTest, IsFalseForDigit) {
+  EXPECT_FALSE(IsValidEscape('0'));
+  EXPECT_FALSE(IsValidEscape('9'));
+}
+
+TEST(IsValidEscapeTest, IsFalseForWhiteSpace) {
+  EXPECT_FALSE(IsValidEscape(' '));
+  EXPECT_FALSE(IsValidEscape('\n'));
+}
+
+TEST(IsValidEscapeTest, IsFalseForSomeLetter) {
+  EXPECT_FALSE(IsValidEscape('a'));
+  EXPECT_FALSE(IsValidEscape('Z'));
+}
+
+TEST(IsValidEscapeTest, IsTrueForPunct) {
+  EXPECT_TRUE(IsValidEscape('.'));
+  EXPECT_TRUE(IsValidEscape('-'));
+  EXPECT_TRUE(IsValidEscape('^'));
+  EXPECT_TRUE(IsValidEscape('$'));
+  EXPECT_TRUE(IsValidEscape('('));
+  EXPECT_TRUE(IsValidEscape(']'));
+  EXPECT_TRUE(IsValidEscape('{'));
+  EXPECT_TRUE(IsValidEscape('|'));
+}
+
+TEST(IsValidEscapeTest, IsTrueForSomeLetter) {
+  EXPECT_TRUE(IsValidEscape('d'));
+  EXPECT_TRUE(IsValidEscape('D'));
+  EXPECT_TRUE(IsValidEscape('s'));
+  EXPECT_TRUE(IsValidEscape('S'));
+  EXPECT_TRUE(IsValidEscape('w'));
+  EXPECT_TRUE(IsValidEscape('W'));
+}
+
+TEST(AtomMatchesCharTest, EscapedPunct) {
+  EXPECT_FALSE(AtomMatchesChar(true, '\\', '\0'));
+  EXPECT_FALSE(AtomMatchesChar(true, '\\', ' '));
+  EXPECT_FALSE(AtomMatchesChar(true, '_', '.'));
+  EXPECT_FALSE(AtomMatchesChar(true, '.', 'a'));
+
+  EXPECT_TRUE(AtomMatchesChar(true, '\\', '\\'));
+  EXPECT_TRUE(AtomMatchesChar(true, '_', '_'));
+  EXPECT_TRUE(AtomMatchesChar(true, '+', '+'));
+  EXPECT_TRUE(AtomMatchesChar(true, '.', '.'));
+}
+
+TEST(AtomMatchesCharTest, Escaped_d) {
+  EXPECT_FALSE(AtomMatchesChar(true, 'd', '\0'));
+  EXPECT_FALSE(AtomMatchesChar(true, 'd', 'a'));
+  EXPECT_FALSE(AtomMatchesChar(true, 'd', '.'));
+
+  EXPECT_TRUE(AtomMatchesChar(true, 'd', '0'));
+  EXPECT_TRUE(AtomMatchesChar(true, 'd', '9'));
+}
+
+TEST(AtomMatchesCharTest, Escaped_D) {
+  EXPECT_FALSE(AtomMatchesChar(true, 'D', '0'));
+  EXPECT_FALSE(AtomMatchesChar(true, 'D', '9'));
+
+  EXPECT_TRUE(AtomMatchesChar(true, 'D', '\0'));
+  EXPECT_TRUE(AtomMatchesChar(true, 'D', 'a'));
+  EXPECT_TRUE(AtomMatchesChar(true, 'D', '-'));
+}
+
+TEST(AtomMatchesCharTest, Escaped_s) {
+  EXPECT_FALSE(AtomMatchesChar(true, 's', '\0'));
+  EXPECT_FALSE(AtomMatchesChar(true, 's', 'a'));
+  EXPECT_FALSE(AtomMatchesChar(true, 's', '.'));
+  EXPECT_FALSE(AtomMatchesChar(true, 's', '9'));
+
+  EXPECT_TRUE(AtomMatchesChar(true, 's', ' '));
+  EXPECT_TRUE(AtomMatchesChar(true, 's', '\n'));
+  EXPECT_TRUE(AtomMatchesChar(true, 's', '\t'));
+}
+
+TEST(AtomMatchesCharTest, Escaped_S) {
+  EXPECT_FALSE(AtomMatchesChar(true, 'S', ' '));
+  EXPECT_FALSE(AtomMatchesChar(true, 'S', '\r'));
+
+  EXPECT_TRUE(AtomMatchesChar(true, 'S', '\0'));
+  EXPECT_TRUE(AtomMatchesChar(true, 'S', 'a'));
+  EXPECT_TRUE(AtomMatchesChar(true, 'S', '9'));
+}
+
+TEST(AtomMatchesCharTest, Escaped_w) {
+  EXPECT_FALSE(AtomMatchesChar(true, 'w', '\0'));
+  EXPECT_FALSE(AtomMatchesChar(true, 'w', '+'));
+  EXPECT_FALSE(AtomMatchesChar(true, 'w', ' '));
+  EXPECT_FALSE(AtomMatchesChar(true, 'w', '\n'));
+
+  EXPECT_TRUE(AtomMatchesChar(true, 'w', '0'));
+  EXPECT_TRUE(AtomMatchesChar(true, 'w', 'b'));
+  EXPECT_TRUE(AtomMatchesChar(true, 'w', 'C'));
+  EXPECT_TRUE(AtomMatchesChar(true, 'w', '_'));
+}
+
+TEST(AtomMatchesCharTest, Escaped_W) {
+  EXPECT_FALSE(AtomMatchesChar(true, 'W', 'A'));
+  EXPECT_FALSE(AtomMatchesChar(true, 'W', 'b'));
+  EXPECT_FALSE(AtomMatchesChar(true, 'W', '9'));
+  EXPECT_FALSE(AtomMatchesChar(true, 'W', '_'));
+
+  EXPECT_TRUE(AtomMatchesChar(true, 'W', '\0'));
+  EXPECT_TRUE(AtomMatchesChar(true, 'W', '*'));
+  EXPECT_TRUE(AtomMatchesChar(true, 'W', '\n'));
+}
+
+TEST(AtomMatchesCharTest, EscapedWhiteSpace) {
+  EXPECT_FALSE(AtomMatchesChar(true, 'f', '\0'));
+  EXPECT_FALSE(AtomMatchesChar(true, 'f', '\n'));
+  EXPECT_FALSE(AtomMatchesChar(true, 'n', '\0'));
+  EXPECT_FALSE(AtomMatchesChar(true, 'n', '\r'));
+  EXPECT_FALSE(AtomMatchesChar(true, 'r', '\0'));
+  EXPECT_FALSE(AtomMatchesChar(true, 'r', 'a'));
+  EXPECT_FALSE(AtomMatchesChar(true, 't', '\0'));
+  EXPECT_FALSE(AtomMatchesChar(true, 't', 't'));
+  EXPECT_FALSE(AtomMatchesChar(true, 'v', '\0'));
+  EXPECT_FALSE(AtomMatchesChar(true, 'v', '\f'));
+
+  EXPECT_TRUE(AtomMatchesChar(true, 'f', '\f'));
+  EXPECT_TRUE(AtomMatchesChar(true, 'n', '\n'));
+  EXPECT_TRUE(AtomMatchesChar(true, 'r', '\r'));
+  EXPECT_TRUE(AtomMatchesChar(true, 't', '\t'));
+  EXPECT_TRUE(AtomMatchesChar(true, 'v', '\v'));
+}
+
+TEST(AtomMatchesCharTest, UnescapedDot) {
+  EXPECT_FALSE(AtomMatchesChar(false, '.', '\n'));
+
+  EXPECT_TRUE(AtomMatchesChar(false, '.', '\0'));
+  EXPECT_TRUE(AtomMatchesChar(false, '.', '.'));
+  EXPECT_TRUE(AtomMatchesChar(false, '.', 'a'));
+  EXPECT_TRUE(AtomMatchesChar(false, '.', ' '));
+}
+
+TEST(AtomMatchesCharTest, UnescapedChar) {
+  EXPECT_FALSE(AtomMatchesChar(false, 'a', '\0'));
+  EXPECT_FALSE(AtomMatchesChar(false, 'a', 'b'));
+  EXPECT_FALSE(AtomMatchesChar(false, '$', 'a'));
+
+  EXPECT_TRUE(AtomMatchesChar(false, '$', '$'));
+  EXPECT_TRUE(AtomMatchesChar(false, '5', '5'));
+  EXPECT_TRUE(AtomMatchesChar(false, 'Z', 'Z'));
+}
+
+TEST(ValidateRegexTest, GeneratesFailureAndReturnsFalseForInvalid) {
+  EXPECT_NONFATAL_FAILURE(ASSERT_FALSE(ValidateRegex(NULL)),
+                          "NULL is not a valid simple regular expression");
+  EXPECT_NONFATAL_FAILURE(
+      ASSERT_FALSE(ValidateRegex("a\\")),
+      "Syntax error at index 1 in simple regular expression \"a\\\": ");
+  EXPECT_NONFATAL_FAILURE(ASSERT_FALSE(ValidateRegex("a\\")),
+                          "'\\' cannot appear at the end");
+  EXPECT_NONFATAL_FAILURE(ASSERT_FALSE(ValidateRegex("\\n\\")),
+                          "'\\' cannot appear at the end");
+  EXPECT_NONFATAL_FAILURE(ASSERT_FALSE(ValidateRegex("\\s\\hb")),
+                          "invalid escape sequence \"\\h\"");
+  EXPECT_NONFATAL_FAILURE(ASSERT_FALSE(ValidateRegex("^^")),
+                          "'^' can only appear at the beginning");
+  EXPECT_NONFATAL_FAILURE(ASSERT_FALSE(ValidateRegex(".*^b")),
+                          "'^' can only appear at the beginning");
+  EXPECT_NONFATAL_FAILURE(ASSERT_FALSE(ValidateRegex("$$")),
+                          "'$' can only appear at the end");
+  EXPECT_NONFATAL_FAILURE(ASSERT_FALSE(ValidateRegex("^$a")),
+                          "'$' can only appear at the end");
+  EXPECT_NONFATAL_FAILURE(ASSERT_FALSE(ValidateRegex("a(b")),
+                          "'(' is unsupported");
+  EXPECT_NONFATAL_FAILURE(ASSERT_FALSE(ValidateRegex("ab)")),
+                          "')' is unsupported");
+  EXPECT_NONFATAL_FAILURE(ASSERT_FALSE(ValidateRegex("[ab")),
+                          "'[' is unsupported");
+  EXPECT_NONFATAL_FAILURE(ASSERT_FALSE(ValidateRegex("a{2")),
+                          "'{' is unsupported");
+  EXPECT_NONFATAL_FAILURE(ASSERT_FALSE(ValidateRegex("?")),
+                          "'?' can only follow a repeatable token");
+  EXPECT_NONFATAL_FAILURE(ASSERT_FALSE(ValidateRegex("^*")),
+                          "'*' can only follow a repeatable token");
+  EXPECT_NONFATAL_FAILURE(ASSERT_FALSE(ValidateRegex("5*+")),
+                          "'+' can only follow a repeatable token");
+}
+
+TEST(ValidateRegexTest, ReturnsTrueForValid) {
+  EXPECT_TRUE(ValidateRegex(""));
+  EXPECT_TRUE(ValidateRegex("a"));
+  EXPECT_TRUE(ValidateRegex(".*"));
+  EXPECT_TRUE(ValidateRegex("^a_+"));
+  EXPECT_TRUE(ValidateRegex("^a\\t\\&?"));
+  EXPECT_TRUE(ValidateRegex("09*$"));
+  EXPECT_TRUE(ValidateRegex("^Z$"));
+  EXPECT_TRUE(ValidateRegex("a\\^Z\\$\\(\\)\\|\\[\\]\\{\\}"));
+}
+
+TEST(MatchRepetitionAndRegexAtHeadTest, WorksForZeroOrOne) {
+  EXPECT_FALSE(MatchRepetitionAndRegexAtHead(false, 'a', '?', "a", "ba"));
+  // Repeating more than once.
+  EXPECT_FALSE(MatchRepetitionAndRegexAtHead(false, 'a', '?', "b", "aab"));
+
+  // Repeating zero times.
+  EXPECT_TRUE(MatchRepetitionAndRegexAtHead(false, 'a', '?', "b", "ba"));
+  // Repeating once.
+  EXPECT_TRUE(MatchRepetitionAndRegexAtHead(false, 'a', '?', "b", "ab"));
+  EXPECT_TRUE(MatchRepetitionAndRegexAtHead(false, '#', '?', ".", "##"));
+}
+
+TEST(MatchRepetitionAndRegexAtHeadTest, WorksForZeroOrMany) {
+  EXPECT_FALSE(MatchRepetitionAndRegexAtHead(false, '.', '*', "a$", "baab"));
+
+  // Repeating zero times.
+  EXPECT_TRUE(MatchRepetitionAndRegexAtHead(false, '.', '*', "b", "bc"));
+  // Repeating once.
+  EXPECT_TRUE(MatchRepetitionAndRegexAtHead(false, '.', '*', "b", "abc"));
+  // Repeating more than once.
+  EXPECT_TRUE(MatchRepetitionAndRegexAtHead(true, 'w', '*', "-", "ab_1-g"));
+}
+
+TEST(MatchRepetitionAndRegexAtHeadTest, WorksForOneOrMany) {
+  EXPECT_FALSE(MatchRepetitionAndRegexAtHead(false, '.', '+', "a$", "baab"));
+  // Repeating zero times.
+  EXPECT_FALSE(MatchRepetitionAndRegexAtHead(false, '.', '+', "b", "bc"));
+
+  // Repeating once.
+  EXPECT_TRUE(MatchRepetitionAndRegexAtHead(false, '.', '+', "b", "abc"));
+  // Repeating more than once.
+  EXPECT_TRUE(MatchRepetitionAndRegexAtHead(true, 'w', '+', "-", "ab_1-g"));
+}
+
+TEST(MatchRegexAtHeadTest, ReturnsTrueForEmptyRegex) {
+  EXPECT_TRUE(MatchRegexAtHead("", ""));
+  EXPECT_TRUE(MatchRegexAtHead("", "ab"));
+}
+
+TEST(MatchRegexAtHeadTest, WorksWhenDollarIsInRegex) {
+  EXPECT_FALSE(MatchRegexAtHead("$", "a"));
+
+  EXPECT_TRUE(MatchRegexAtHead("$", ""));
+  EXPECT_TRUE(MatchRegexAtHead("a$", "a"));
+}
+
+TEST(MatchRegexAtHeadTest, WorksWhenRegexStartsWithEscapeSequence) {
+  EXPECT_FALSE(MatchRegexAtHead("\\w", "+"));
+  EXPECT_FALSE(MatchRegexAtHead("\\W", "ab"));
+
+  EXPECT_TRUE(MatchRegexAtHead("\\sa", "\nab"));
+  EXPECT_TRUE(MatchRegexAtHead("\\d", "1a"));
+}
+
+TEST(MatchRegexAtHeadTest, WorksWhenRegexStartsWithRepetition) {
+  EXPECT_FALSE(MatchRegexAtHead(".+a", "abc"));
+  EXPECT_FALSE(MatchRegexAtHead("a?b", "aab"));
+
+  EXPECT_TRUE(MatchRegexAtHead(".*a", "bc12-ab"));
+  EXPECT_TRUE(MatchRegexAtHead("a?b", "b"));
+  EXPECT_TRUE(MatchRegexAtHead("a?b", "ab"));
+}
+
+TEST(MatchRegexAtHeadTest,
+     WorksWhenRegexStartsWithRepetionOfEscapeSequence) {
+  EXPECT_FALSE(MatchRegexAtHead("\\.+a", "abc"));
+  EXPECT_FALSE(MatchRegexAtHead("\\s?b", "  b"));
+
+  EXPECT_TRUE(MatchRegexAtHead("\\(*a", "((((ab"));
+  EXPECT_TRUE(MatchRegexAtHead("\\^?b", "^b"));
+  EXPECT_TRUE(MatchRegexAtHead("\\\\?b", "b"));
+  EXPECT_TRUE(MatchRegexAtHead("\\\\?b", "\\b"));
+}
+
+TEST(MatchRegexAtHeadTest, MatchesSequentially) {
+  EXPECT_FALSE(MatchRegexAtHead("ab.*c", "acabc"));
+
+  EXPECT_TRUE(MatchRegexAtHead("ab.*c", "ab-fsc"));
+}
+
+TEST(MatchRegexAnywhereTest, ReturnsFalseWhenStringIsNull) {
+  EXPECT_FALSE(MatchRegexAnywhere("", NULL));
+}
+
+TEST(MatchRegexAnywhereTest, WorksWhenRegexStartsWithCaret) {
+  EXPECT_FALSE(MatchRegexAnywhere("^a", "ba"));
+  EXPECT_FALSE(MatchRegexAnywhere("^$", "a"));
+
+  EXPECT_TRUE(MatchRegexAnywhere("^a", "ab"));
+  EXPECT_TRUE(MatchRegexAnywhere("^", "ab"));
+  EXPECT_TRUE(MatchRegexAnywhere("^$", ""));
+}
+
+TEST(MatchRegexAnywhereTest, ReturnsFalseWhenNoMatch) {
+  EXPECT_FALSE(MatchRegexAnywhere("a", "bcde123"));
+  EXPECT_FALSE(MatchRegexAnywhere("a.+a", "--aa88888888"));
+}
+
+TEST(MatchRegexAnywhereTest, ReturnsTrueWhenMatchingPrefix) {
+  EXPECT_TRUE(MatchRegexAnywhere("\\w+", "ab1_ - 5"));
+  EXPECT_TRUE(MatchRegexAnywhere(".*=", "="));
+  EXPECT_TRUE(MatchRegexAnywhere("x.*ab?.*bc", "xaaabc"));
+}
+
+TEST(MatchRegexAnywhereTest, ReturnsTrueWhenMatchingNonPrefix) {
+  EXPECT_TRUE(MatchRegexAnywhere("\\w+", "$$$ ab1_ - 5"));
+  EXPECT_TRUE(MatchRegexAnywhere("\\.+=", "=  ...="));
+}
+
+// Tests RE's implicit constructors.
+TEST(RETest, ImplicitConstructorWorks) {
+  const RE empty("");
+  EXPECT_STREQ("", empty.pattern());
+
+  const RE simple("hello");
+  EXPECT_STREQ("hello", simple.pattern());
+}
+
+// Tests that RE's constructors reject invalid regular expressions.
+TEST(RETest, RejectsInvalidRegex) {
+  EXPECT_NONFATAL_FAILURE({
+    const RE normal(NULL);
+  }, "NULL is not a valid simple regular expression");
+
+  EXPECT_NONFATAL_FAILURE({
+    const RE normal(".*(\\w+");
+  }, "'(' is unsupported");
+
+  EXPECT_NONFATAL_FAILURE({
+    const RE invalid("^?");
+  }, "'?' can only follow a repeatable token");
+}
+
+// Tests RE::FullMatch().
+TEST(RETest, FullMatchWorks) {
+  const RE empty("");
+  EXPECT_TRUE(RE::FullMatch("", empty));
+  EXPECT_FALSE(RE::FullMatch("a", empty));
+
+  const RE re1("a");
+  EXPECT_TRUE(RE::FullMatch("a", re1));
+
+  const RE re("a.*z");
+  EXPECT_TRUE(RE::FullMatch("az", re));
+  EXPECT_TRUE(RE::FullMatch("axyz", re));
+  EXPECT_FALSE(RE::FullMatch("baz", re));
+  EXPECT_FALSE(RE::FullMatch("azy", re));
+}
+
+// Tests RE::PartialMatch().
+TEST(RETest, PartialMatchWorks) {
+  const RE empty("");
+  EXPECT_TRUE(RE::PartialMatch("", empty));
+  EXPECT_TRUE(RE::PartialMatch("a", empty));
+
+  const RE re("a.*z");
+  EXPECT_TRUE(RE::PartialMatch("az", re));
+  EXPECT_TRUE(RE::PartialMatch("axyz", re));
+  EXPECT_TRUE(RE::PartialMatch("baz", re));
+  EXPECT_TRUE(RE::PartialMatch("azy", re));
+  EXPECT_FALSE(RE::PartialMatch("zza", re));
+}
+
+#endif  // GTEST_USES_POSIX_RE
+
+#if !GTEST_OS_WINDOWS_MOBILE
+
+TEST(CaptureTest, CapturesStdout) {
+  CaptureStdout();
+  fprintf(stdout, "abc");
+  EXPECT_STREQ("abc", GetCapturedStdout().c_str());
+
+  CaptureStdout();
+  fprintf(stdout, "def%cghi", '\0');
+  EXPECT_EQ(::std::string("def\0ghi", 7), ::std::string(GetCapturedStdout()));
+}
+
+TEST(CaptureTest, CapturesStderr) {
+  CaptureStderr();
+  fprintf(stderr, "jkl");
+  EXPECT_STREQ("jkl", GetCapturedStderr().c_str());
+
+  CaptureStderr();
+  fprintf(stderr, "jkl%cmno", '\0');
+  EXPECT_EQ(::std::string("jkl\0mno", 7), ::std::string(GetCapturedStderr()));
+}
+
+// Tests that stdout and stderr capture don't interfere with each other.
+TEST(CaptureTest, CapturesStdoutAndStderr) {
+  CaptureStdout();
+  CaptureStderr();
+  fprintf(stdout, "pqr");
+  fprintf(stderr, "stu");
+  EXPECT_STREQ("pqr", GetCapturedStdout().c_str());
+  EXPECT_STREQ("stu", GetCapturedStderr().c_str());
+}
+
+TEST(CaptureDeathTest, CannotReenterStdoutCapture) {
+  CaptureStdout();
+  EXPECT_DEATH_IF_SUPPORTED(CaptureStdout(),
+                            "Only one stdout capturer can exist at a time");
+  GetCapturedStdout();
+
+  // We cannot test stderr capturing using death tests as they use it
+  // themselves.
+}
+
+#endif  // !GTEST_OS_WINDOWS_MOBILE
+
+TEST(ThreadLocalTest, DefaultConstructorInitializesToDefaultValues) {
+  ThreadLocal<int> t1;
+  EXPECT_EQ(0, t1.get());
+
+  ThreadLocal<void*> t2;
+  EXPECT_TRUE(t2.get() == nullptr);
+}
+
+TEST(ThreadLocalTest, SingleParamConstructorInitializesToParam) {
+  ThreadLocal<int> t1(123);
+  EXPECT_EQ(123, t1.get());
+
+  int i = 0;
+  ThreadLocal<int*> t2(&i);
+  EXPECT_EQ(&i, t2.get());
+}
+
+class NoDefaultContructor {
+ public:
+  explicit NoDefaultContructor(const char*) {}
+  NoDefaultContructor(const NoDefaultContructor&) {}
+};
+
+TEST(ThreadLocalTest, ValueDefaultContructorIsNotRequiredForParamVersion) {
+  ThreadLocal<NoDefaultContructor> bar(NoDefaultContructor("foo"));
+  bar.pointer();
+}
+
+TEST(ThreadLocalTest, GetAndPointerReturnSameValue) {
+  ThreadLocal<std::string> thread_local_string;
+
+  EXPECT_EQ(thread_local_string.pointer(), &(thread_local_string.get()));
+
+  // Verifies the condition still holds after calling set.
+  thread_local_string.set("foo");
+  EXPECT_EQ(thread_local_string.pointer(), &(thread_local_string.get()));
+}
+
+TEST(ThreadLocalTest, PointerAndConstPointerReturnSameValue) {
+  ThreadLocal<std::string> thread_local_string;
+  const ThreadLocal<std::string>& const_thread_local_string =
+      thread_local_string;
+
+  EXPECT_EQ(thread_local_string.pointer(), const_thread_local_string.pointer());
+
+  thread_local_string.set("foo");
+  EXPECT_EQ(thread_local_string.pointer(), const_thread_local_string.pointer());
+}
+
+#if GTEST_IS_THREADSAFE
+
+void AddTwo(int* param) { *param += 2; }
+
+TEST(ThreadWithParamTest, ConstructorExecutesThreadFunc) {
+  int i = 40;
+  ThreadWithParam<int*> thread(&AddTwo, &i, nullptr);
+  thread.Join();
+  EXPECT_EQ(42, i);
+}
+
+TEST(MutexDeathTest, AssertHeldShouldAssertWhenNotLocked) {
+  // AssertHeld() is flaky only in the presence of multiple threads accessing
+  // the lock. In this case, the test is robust.
+  EXPECT_DEATH_IF_SUPPORTED({
+    Mutex m;
+    { MutexLock lock(&m); }
+    m.AssertHeld();
+  },
+  "thread .*hold");
+}
+
+TEST(MutexTest, AssertHeldShouldNotAssertWhenLocked) {
+  Mutex m;
+  MutexLock lock(&m);
+  m.AssertHeld();
+}
+
+class AtomicCounterWithMutex {
+ public:
+  explicit AtomicCounterWithMutex(Mutex* mutex) :
+    value_(0), mutex_(mutex), random_(42) {}
+
+  void Increment() {
+    MutexLock lock(mutex_);
+    int temp = value_;
+    {
+      // We need to put up a memory barrier to prevent reads and writes to
+      // value_ rearranged with the call to SleepMilliseconds when observed
+      // from other threads.
+#if GTEST_HAS_PTHREAD
+      // On POSIX, locking a mutex puts up a memory barrier.  We cannot use
+      // Mutex and MutexLock here or rely on their memory barrier
+      // functionality as we are testing them here.
+      pthread_mutex_t memory_barrier_mutex;
+      GTEST_CHECK_POSIX_SUCCESS_(
+          pthread_mutex_init(&memory_barrier_mutex, nullptr));
+      GTEST_CHECK_POSIX_SUCCESS_(pthread_mutex_lock(&memory_barrier_mutex));
+
+      SleepMilliseconds(static_cast<int>(random_.Generate(30)));
+
+      GTEST_CHECK_POSIX_SUCCESS_(pthread_mutex_unlock(&memory_barrier_mutex));
+      GTEST_CHECK_POSIX_SUCCESS_(pthread_mutex_destroy(&memory_barrier_mutex));
+#elif GTEST_OS_WINDOWS
+      // On Windows, performing an interlocked access puts up a memory barrier.
+      volatile LONG dummy = 0;
+      ::InterlockedIncrement(&dummy);
+      SleepMilliseconds(static_cast<int>(random_.Generate(30)));
+      ::InterlockedIncrement(&dummy);
+#else
+# error "Memory barrier not implemented on this platform."
+#endif  // GTEST_HAS_PTHREAD
+    }
+    value_ = temp + 1;
+  }
+  int value() const { return value_; }
+
+ private:
+  volatile int value_;
+  Mutex* const mutex_;  // Protects value_.
+  Random       random_;
+};
+
+void CountingThreadFunc(pair<AtomicCounterWithMutex*, int> param) {
+  for (int i = 0; i < param.second; ++i)
+      param.first->Increment();
+}
+
+// Tests that the mutex only lets one thread at a time to lock it.
+TEST(MutexTest, OnlyOneThreadCanLockAtATime) {
+  Mutex mutex;
+  AtomicCounterWithMutex locked_counter(&mutex);
+
+  typedef ThreadWithParam<pair<AtomicCounterWithMutex*, int> > ThreadType;
+  const int kCycleCount = 20;
+  const int kThreadCount = 7;
+  std::unique_ptr<ThreadType> counting_threads[kThreadCount];
+  Notification threads_can_start;
+  // Creates and runs kThreadCount threads that increment locked_counter
+  // kCycleCount times each.
+  for (int i = 0; i < kThreadCount; ++i) {
+    counting_threads[i].reset(new ThreadType(&CountingThreadFunc,
+                                             make_pair(&locked_counter,
+                                                       kCycleCount),
+                                             &threads_can_start));
+  }
+  threads_can_start.Notify();
+  for (int i = 0; i < kThreadCount; ++i)
+    counting_threads[i]->Join();
+
+  // If the mutex lets more than one thread to increment the counter at a
+  // time, they are likely to encounter a race condition and have some
+  // increments overwritten, resulting in the lower then expected counter
+  // value.
+  EXPECT_EQ(kCycleCount * kThreadCount, locked_counter.value());
+}
+
+template <typename T>
+void RunFromThread(void (func)(T), T param) {
+  ThreadWithParam<T> thread(func, param, nullptr);
+  thread.Join();
+}
+
+void RetrieveThreadLocalValue(
+    pair<ThreadLocal<std::string>*, std::string*> param) {
+  *param.second = param.first->get();
+}
+
+TEST(ThreadLocalTest, ParameterizedConstructorSetsDefault) {
+  ThreadLocal<std::string> thread_local_string("foo");
+  EXPECT_STREQ("foo", thread_local_string.get().c_str());
+
+  thread_local_string.set("bar");
+  EXPECT_STREQ("bar", thread_local_string.get().c_str());
+
+  std::string result;
+  RunFromThread(&RetrieveThreadLocalValue,
+                make_pair(&thread_local_string, &result));
+  EXPECT_STREQ("foo", result.c_str());
+}
+
+// Keeps track of whether of destructors being called on instances of
+// DestructorTracker.  On Windows, waits for the destructor call reports.
+class DestructorCall {
+ public:
+  DestructorCall() {
+    invoked_ = false;
+#if GTEST_OS_WINDOWS
+    wait_event_.Reset(::CreateEvent(NULL, TRUE, FALSE, NULL));
+    GTEST_CHECK_(wait_event_.Get() != NULL);
+#endif
+  }
+
+  bool CheckDestroyed() const {
+#if GTEST_OS_WINDOWS
+    if (::WaitForSingleObject(wait_event_.Get(), 1000) != WAIT_OBJECT_0)
+      return false;
+#endif
+    return invoked_;
+  }
+
+  void ReportDestroyed() {
+    invoked_ = true;
+#if GTEST_OS_WINDOWS
+    ::SetEvent(wait_event_.Get());
+#endif
+  }
+
+  static std::vector<DestructorCall*>& List() { return *list_; }
+
+  static void ResetList() {
+    for (size_t i = 0; i < list_->size(); ++i) {
+      delete list_->at(i);
+    }
+    list_->clear();
+  }
+
+ private:
+  bool invoked_;
+#if GTEST_OS_WINDOWS
+  AutoHandle wait_event_;
+#endif
+  static std::vector<DestructorCall*>* const list_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(DestructorCall);
+};
+
+std::vector<DestructorCall*>* const DestructorCall::list_ =
+    new std::vector<DestructorCall*>;
+
+// DestructorTracker keeps track of whether its instances have been
+// destroyed.
+class DestructorTracker {
+ public:
+  DestructorTracker() : index_(GetNewIndex()) {}
+  DestructorTracker(const DestructorTracker& /* rhs */)
+      : index_(GetNewIndex()) {}
+  ~DestructorTracker() {
+    // We never access DestructorCall::List() concurrently, so we don't need
+    // to protect this access with a mutex.
+    DestructorCall::List()[index_]->ReportDestroyed();
+  }
+
+ private:
+  static size_t GetNewIndex() {
+    DestructorCall::List().push_back(new DestructorCall);
+    return DestructorCall::List().size() - 1;
+  }
+  const size_t index_;
+};
+
+typedef ThreadLocal<DestructorTracker>* ThreadParam;
+
+void CallThreadLocalGet(ThreadParam thread_local_param) {
+  thread_local_param->get();
+}
+
+// Tests that when a ThreadLocal object dies in a thread, it destroys
+// the managed object for that thread.
+TEST(ThreadLocalTest, DestroysManagedObjectForOwnThreadWhenDying) {
+  DestructorCall::ResetList();
+
+  {
+    ThreadLocal<DestructorTracker> thread_local_tracker;
+    ASSERT_EQ(0U, DestructorCall::List().size());
+
+    // This creates another DestructorTracker object for the main thread.
+    thread_local_tracker.get();
+    ASSERT_EQ(1U, DestructorCall::List().size());
+    ASSERT_FALSE(DestructorCall::List()[0]->CheckDestroyed());
+  }
+
+  // Now thread_local_tracker has died.
+  ASSERT_EQ(1U, DestructorCall::List().size());
+  EXPECT_TRUE(DestructorCall::List()[0]->CheckDestroyed());
+
+  DestructorCall::ResetList();
+}
+
+// Tests that when a thread exits, the thread-local object for that
+// thread is destroyed.
+TEST(ThreadLocalTest, DestroysManagedObjectAtThreadExit) {
+  DestructorCall::ResetList();
+
+  {
+    ThreadLocal<DestructorTracker> thread_local_tracker;
+    ASSERT_EQ(0U, DestructorCall::List().size());
+
+    // This creates another DestructorTracker object in the new thread.
+    ThreadWithParam<ThreadParam> thread(&CallThreadLocalGet,
+                                        &thread_local_tracker, nullptr);
+    thread.Join();
+
+    // The thread has exited, and we should have a DestroyedTracker
+    // instance created for it. But it may not have been destroyed yet.
+    ASSERT_EQ(1U, DestructorCall::List().size());
+  }
+
+  // The thread has exited and thread_local_tracker has died.
+  ASSERT_EQ(1U, DestructorCall::List().size());
+  EXPECT_TRUE(DestructorCall::List()[0]->CheckDestroyed());
+
+  DestructorCall::ResetList();
+}
+
+TEST(ThreadLocalTest, ThreadLocalMutationsAffectOnlyCurrentThread) {
+  ThreadLocal<std::string> thread_local_string;
+  thread_local_string.set("Foo");
+  EXPECT_STREQ("Foo", thread_local_string.get().c_str());
+
+  std::string result;
+  RunFromThread(&RetrieveThreadLocalValue,
+                make_pair(&thread_local_string, &result));
+  EXPECT_TRUE(result.empty());
+}
+
+#endif  // GTEST_IS_THREADSAFE
+
+#if GTEST_OS_WINDOWS
+TEST(WindowsTypesTest, HANDLEIsVoidStar) {
+  StaticAssertTypeEq<HANDLE, void*>();
+}
+
+#if GTEST_OS_WINDOWS_MINGW && !defined(__MINGW64_VERSION_MAJOR)
+TEST(WindowsTypesTest, _CRITICAL_SECTIONIs_CRITICAL_SECTION) {
+  StaticAssertTypeEq<CRITICAL_SECTION, _CRITICAL_SECTION>();
+}
+#else
+TEST(WindowsTypesTest, CRITICAL_SECTIONIs_RTL_CRITICAL_SECTION) {
+  StaticAssertTypeEq<CRITICAL_SECTION, _RTL_CRITICAL_SECTION>();
+}
+#endif
+
+#endif  // GTEST_OS_WINDOWS
+
+}  // namespace internal
+}  // namespace testing
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-printers-test.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-printers-test.cc
new file mode 100644
index 0000000..e1e8e1c
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-printers-test.cc
@@ -0,0 +1,1962 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Google Test - The Google C++ Testing and Mocking Framework
+//
+// This file tests the universal value printer.
+
+#include <algorithm>
+#include <cctype>
+#include <cstdint>
+#include <cstring>
+#include <deque>
+#include <forward_list>
+#include <limits>
+#include <list>
+#include <map>
+#include <memory>
+#include <set>
+#include <sstream>
+#include <string>
+#include <unordered_map>
+#include <unordered_set>
+#include <utility>
+#include <vector>
+
+#include "gtest/gtest-printers.h"
+#include "gtest/gtest.h"
+
+// Some user-defined types for testing the universal value printer.
+
+// An anonymous enum type.
+enum AnonymousEnum {
+  kAE1 = -1,
+  kAE2 = 1
+};
+
+// An enum without a user-defined printer.
+enum EnumWithoutPrinter {
+  kEWP1 = -2,
+  kEWP2 = 42
+};
+
+// An enum with a << operator.
+enum EnumWithStreaming {
+  kEWS1 = 10
+};
+
+std::ostream& operator<<(std::ostream& os, EnumWithStreaming e) {
+  return os << (e == kEWS1 ? "kEWS1" : "invalid");
+}
+
+// An enum with a PrintTo() function.
+enum EnumWithPrintTo {
+  kEWPT1 = 1
+};
+
+void PrintTo(EnumWithPrintTo e, std::ostream* os) {
+  *os << (e == kEWPT1 ? "kEWPT1" : "invalid");
+}
+
+// A class implicitly convertible to BiggestInt.
+class BiggestIntConvertible {
+ public:
+  operator ::testing::internal::BiggestInt() const { return 42; }
+};
+
+// A parent class with two child classes. The parent and one of the kids have
+// stream operators.
+class ParentClass {};
+class ChildClassWithStreamOperator : public ParentClass {};
+class ChildClassWithoutStreamOperator : public ParentClass {};
+static void operator<<(std::ostream& os, const ParentClass&) {
+  os << "ParentClass";
+}
+static void operator<<(std::ostream& os, const ChildClassWithStreamOperator&) {
+  os << "ChildClassWithStreamOperator";
+}
+
+// A user-defined unprintable class template in the global namespace.
+template <typename T>
+class UnprintableTemplateInGlobal {
+ public:
+  UnprintableTemplateInGlobal() : value_() {}
+ private:
+  T value_;
+};
+
+// A user-defined streamable type in the global namespace.
+class StreamableInGlobal {
+ public:
+  virtual ~StreamableInGlobal() {}
+};
+
+inline void operator<<(::std::ostream& os, const StreamableInGlobal& /* x */) {
+  os << "StreamableInGlobal";
+}
+
+void operator<<(::std::ostream& os, const StreamableInGlobal* /* x */) {
+  os << "StreamableInGlobal*";
+}
+
+namespace foo {
+
+// A user-defined unprintable type in a user namespace.
+class UnprintableInFoo {
+ public:
+  UnprintableInFoo() : z_(0) { memcpy(xy_, "\xEF\x12\x0\x0\x34\xAB\x0\x0", 8); }
+  double z() const { return z_; }
+ private:
+  char xy_[8];
+  double z_;
+};
+
+// A user-defined printable type in a user-chosen namespace.
+struct PrintableViaPrintTo {
+  PrintableViaPrintTo() : value() {}
+  int value;
+};
+
+void PrintTo(const PrintableViaPrintTo& x, ::std::ostream* os) {
+  *os << "PrintableViaPrintTo: " << x.value;
+}
+
+// A type with a user-defined << for printing its pointer.
+struct PointerPrintable {
+};
+
+::std::ostream& operator<<(::std::ostream& os,
+                           const PointerPrintable* /* x */) {
+  return os << "PointerPrintable*";
+}
+
+// A user-defined printable class template in a user-chosen namespace.
+template <typename T>
+class PrintableViaPrintToTemplate {
+ public:
+  explicit PrintableViaPrintToTemplate(const T& a_value) : value_(a_value) {}
+
+  const T& value() const { return value_; }
+ private:
+  T value_;
+};
+
+template <typename T>
+void PrintTo(const PrintableViaPrintToTemplate<T>& x, ::std::ostream* os) {
+  *os << "PrintableViaPrintToTemplate: " << x.value();
+}
+
+// A user-defined streamable class template in a user namespace.
+template <typename T>
+class StreamableTemplateInFoo {
+ public:
+  StreamableTemplateInFoo() : value_() {}
+
+  const T& value() const { return value_; }
+ private:
+  T value_;
+};
+
+template <typename T>
+inline ::std::ostream& operator<<(::std::ostream& os,
+                                  const StreamableTemplateInFoo<T>& x) {
+  return os << "StreamableTemplateInFoo: " << x.value();
+}
+
+// A user-defined streamable type in a user namespace whose operator<< is
+// templated on the type of the output stream.
+struct TemplatedStreamableInFoo {};
+
+template <typename OutputStream>
+OutputStream& operator<<(OutputStream& os,
+                         const TemplatedStreamableInFoo& /*ts*/) {
+  os << "TemplatedStreamableInFoo";
+  return os;
+}
+
+// A user-defined streamable but recursively-defined container type in
+// a user namespace, it mimics therefore std::filesystem::path or
+// boost::filesystem::path.
+class PathLike {
+ public:
+  struct iterator {
+    typedef PathLike value_type;
+
+    iterator& operator++();
+    PathLike& operator*();
+  };
+
+  using value_type = char;
+  using const_iterator = iterator;
+
+  PathLike() {}
+
+  iterator begin() const { return iterator(); }
+  iterator end() const { return iterator(); }
+
+  friend ::std::ostream& operator<<(::std::ostream& os, const PathLike&) {
+    return os << "Streamable-PathLike";
+  }
+};
+
+}  // namespace foo
+
+namespace testing {
+namespace {
+template <typename T>
+class Wrapper {
+ public:
+  explicit Wrapper(T&& value) : value_(std::forward<T>(value)) {}
+
+  const T& value() const { return value_; }
+
+ private:
+  T value_;
+};
+
+}  // namespace
+
+namespace internal {
+template <typename T>
+class UniversalPrinter<Wrapper<T>> {
+ public:
+  static void Print(const Wrapper<T>& w, ::std::ostream* os) {
+    *os << "Wrapper(";
+    UniversalPrint(w.value(), os);
+    *os << ')';
+  }
+};
+}  // namespace internal
+
+
+namespace gtest_printers_test {
+
+using ::std::deque;
+using ::std::list;
+using ::std::make_pair;
+using ::std::map;
+using ::std::multimap;
+using ::std::multiset;
+using ::std::pair;
+using ::std::set;
+using ::std::vector;
+using ::testing::PrintToString;
+using ::testing::internal::FormatForComparisonFailureMessage;
+using ::testing::internal::ImplicitCast_;
+using ::testing::internal::NativeArray;
+using ::testing::internal::RelationToSourceReference;
+using ::testing::internal::Strings;
+using ::testing::internal::UniversalPrint;
+using ::testing::internal::UniversalPrinter;
+using ::testing::internal::UniversalTersePrint;
+using ::testing::internal::UniversalTersePrintTupleFieldsToStrings;
+
+// Prints a value to a string using the universal value printer.  This
+// is a helper for testing UniversalPrinter<T>::Print() for various types.
+template <typename T>
+std::string Print(const T& value) {
+  ::std::stringstream ss;
+  UniversalPrinter<T>::Print(value, &ss);
+  return ss.str();
+}
+
+// Prints a value passed by reference to a string, using the universal
+// value printer.  This is a helper for testing
+// UniversalPrinter<T&>::Print() for various types.
+template <typename T>
+std::string PrintByRef(const T& value) {
+  ::std::stringstream ss;
+  UniversalPrinter<T&>::Print(value, &ss);
+  return ss.str();
+}
+
+// Tests printing various enum types.
+
+TEST(PrintEnumTest, AnonymousEnum) {
+  EXPECT_EQ("-1", Print(kAE1));
+  EXPECT_EQ("1", Print(kAE2));
+}
+
+TEST(PrintEnumTest, EnumWithoutPrinter) {
+  EXPECT_EQ("-2", Print(kEWP1));
+  EXPECT_EQ("42", Print(kEWP2));
+}
+
+TEST(PrintEnumTest, EnumWithStreaming) {
+  EXPECT_EQ("kEWS1", Print(kEWS1));
+  EXPECT_EQ("invalid", Print(static_cast<EnumWithStreaming>(0)));
+}
+
+TEST(PrintEnumTest, EnumWithPrintTo) {
+  EXPECT_EQ("kEWPT1", Print(kEWPT1));
+  EXPECT_EQ("invalid", Print(static_cast<EnumWithPrintTo>(0)));
+}
+
+// Tests printing a class implicitly convertible to BiggestInt.
+
+TEST(PrintClassTest, BiggestIntConvertible) {
+  EXPECT_EQ("42", Print(BiggestIntConvertible()));
+}
+
+// Tests printing various char types.
+
+// char.
+TEST(PrintCharTest, PlainChar) {
+  EXPECT_EQ("'\\0'", Print('\0'));
+  EXPECT_EQ("'\\'' (39, 0x27)", Print('\''));
+  EXPECT_EQ("'\"' (34, 0x22)", Print('"'));
+  EXPECT_EQ("'?' (63, 0x3F)", Print('?'));
+  EXPECT_EQ("'\\\\' (92, 0x5C)", Print('\\'));
+  EXPECT_EQ("'\\a' (7)", Print('\a'));
+  EXPECT_EQ("'\\b' (8)", Print('\b'));
+  EXPECT_EQ("'\\f' (12, 0xC)", Print('\f'));
+  EXPECT_EQ("'\\n' (10, 0xA)", Print('\n'));
+  EXPECT_EQ("'\\r' (13, 0xD)", Print('\r'));
+  EXPECT_EQ("'\\t' (9)", Print('\t'));
+  EXPECT_EQ("'\\v' (11, 0xB)", Print('\v'));
+  EXPECT_EQ("'\\x7F' (127)", Print('\x7F'));
+  EXPECT_EQ("'\\xFF' (255)", Print('\xFF'));
+  EXPECT_EQ("' ' (32, 0x20)", Print(' '));
+  EXPECT_EQ("'a' (97, 0x61)", Print('a'));
+}
+
+// signed char.
+TEST(PrintCharTest, SignedChar) {
+  EXPECT_EQ("'\\0'", Print(static_cast<signed char>('\0')));
+  EXPECT_EQ("'\\xCE' (-50)",
+            Print(static_cast<signed char>(-50)));
+}
+
+// unsigned char.
+TEST(PrintCharTest, UnsignedChar) {
+  EXPECT_EQ("'\\0'", Print(static_cast<unsigned char>('\0')));
+  EXPECT_EQ("'b' (98, 0x62)",
+            Print(static_cast<unsigned char>('b')));
+}
+
+TEST(PrintCharTest, Char16) {
+  EXPECT_EQ("U+0041", Print(u'A'));
+}
+
+TEST(PrintCharTest, Char32) {
+  EXPECT_EQ("U+0041", Print(U'A'));
+}
+
+#ifdef __cpp_char8_t
+TEST(PrintCharTest, Char8) {
+  EXPECT_EQ("U+0041", Print(u8'A'));
+}
+#endif
+
+// Tests printing other simple, built-in types.
+
+// bool.
+TEST(PrintBuiltInTypeTest, Bool) {
+  EXPECT_EQ("false", Print(false));
+  EXPECT_EQ("true", Print(true));
+}
+
+// wchar_t.
+TEST(PrintBuiltInTypeTest, Wchar_t) {
+  EXPECT_EQ("L'\\0'", Print(L'\0'));
+  EXPECT_EQ("L'\\'' (39, 0x27)", Print(L'\''));
+  EXPECT_EQ("L'\"' (34, 0x22)", Print(L'"'));
+  EXPECT_EQ("L'?' (63, 0x3F)", Print(L'?'));
+  EXPECT_EQ("L'\\\\' (92, 0x5C)", Print(L'\\'));
+  EXPECT_EQ("L'\\a' (7)", Print(L'\a'));
+  EXPECT_EQ("L'\\b' (8)", Print(L'\b'));
+  EXPECT_EQ("L'\\f' (12, 0xC)", Print(L'\f'));
+  EXPECT_EQ("L'\\n' (10, 0xA)", Print(L'\n'));
+  EXPECT_EQ("L'\\r' (13, 0xD)", Print(L'\r'));
+  EXPECT_EQ("L'\\t' (9)", Print(L'\t'));
+  EXPECT_EQ("L'\\v' (11, 0xB)", Print(L'\v'));
+  EXPECT_EQ("L'\\x7F' (127)", Print(L'\x7F'));
+  EXPECT_EQ("L'\\xFF' (255)", Print(L'\xFF'));
+  EXPECT_EQ("L' ' (32, 0x20)", Print(L' '));
+  EXPECT_EQ("L'a' (97, 0x61)", Print(L'a'));
+  EXPECT_EQ("L'\\x576' (1398)", Print(static_cast<wchar_t>(0x576)));
+  EXPECT_EQ("L'\\xC74D' (51021)", Print(static_cast<wchar_t>(0xC74D)));
+}
+
+// Test that int64_t provides more storage than wchar_t.
+TEST(PrintTypeSizeTest, Wchar_t) {
+  EXPECT_LT(sizeof(wchar_t), sizeof(int64_t));
+}
+
+// Various integer types.
+TEST(PrintBuiltInTypeTest, Integer) {
+  EXPECT_EQ("'\\xFF' (255)", Print(static_cast<unsigned char>(255)));  // uint8
+  EXPECT_EQ("'\\x80' (-128)", Print(static_cast<signed char>(-128)));  // int8
+  EXPECT_EQ("65535", Print(std::numeric_limits<uint16_t>::max()));  // uint16
+  EXPECT_EQ("-32768", Print(std::numeric_limits<int16_t>::min()));  // int16
+  EXPECT_EQ("4294967295",
+            Print(std::numeric_limits<uint32_t>::max()));  // uint32
+  EXPECT_EQ("-2147483648",
+            Print(std::numeric_limits<int32_t>::min()));  // int32
+  EXPECT_EQ("18446744073709551615",
+            Print(std::numeric_limits<uint64_t>::max()));  // uint64
+  EXPECT_EQ("-9223372036854775808",
+            Print(std::numeric_limits<int64_t>::min()));  // int64
+#ifdef __cpp_char8_t
+  EXPECT_EQ("U+0000",
+            Print(std::numeric_limits<char8_t>::min()));  // char8_t
+  EXPECT_EQ("U+00FF",
+            Print(std::numeric_limits<char8_t>::max()));  // char8_t
+#endif
+  EXPECT_EQ("U+0000",
+            Print(std::numeric_limits<char16_t>::min()));  // char16_t
+  EXPECT_EQ("U+FFFF",
+            Print(std::numeric_limits<char16_t>::max()));  // char16_t
+  EXPECT_EQ("U+0000",
+            Print(std::numeric_limits<char32_t>::min()));  // char32_t
+  EXPECT_EQ("U+FFFFFFFF",
+            Print(std::numeric_limits<char32_t>::max()));  // char32_t
+}
+
+// Size types.
+TEST(PrintBuiltInTypeTest, Size_t) {
+  EXPECT_EQ("1", Print(sizeof('a')));  // size_t.
+#if !GTEST_OS_WINDOWS
+  // Windows has no ssize_t type.
+  EXPECT_EQ("-2", Print(static_cast<ssize_t>(-2)));  // ssize_t.
+#endif  // !GTEST_OS_WINDOWS
+}
+
+// Floating-points.
+TEST(PrintBuiltInTypeTest, FloatingPoints) {
+  EXPECT_EQ("1.5", Print(1.5f));   // float
+  EXPECT_EQ("-2.5", Print(-2.5));  // double
+}
+
+// Since ::std::stringstream::operator<<(const void *) formats the pointer
+// output differently with different compilers, we have to create the expected
+// output first and use it as our expectation.
+static std::string PrintPointer(const void* p) {
+  ::std::stringstream expected_result_stream;
+  expected_result_stream << p;
+  return expected_result_stream.str();
+}
+
+// Tests printing C strings.
+
+// const char*.
+TEST(PrintCStringTest, Const) {
+  const char* p = "World";
+  EXPECT_EQ(PrintPointer(p) + " pointing to \"World\"", Print(p));
+}
+
+// char*.
+TEST(PrintCStringTest, NonConst) {
+  char p[] = "Hi";
+  EXPECT_EQ(PrintPointer(p) + " pointing to \"Hi\"",
+            Print(static_cast<char*>(p)));
+}
+
+// NULL C string.
+TEST(PrintCStringTest, Null) {
+  const char* p = nullptr;
+  EXPECT_EQ("NULL", Print(p));
+}
+
+// Tests that C strings are escaped properly.
+TEST(PrintCStringTest, EscapesProperly) {
+  const char* p = "'\"?\\\a\b\f\n\r\t\v\x7F\xFF a";
+  EXPECT_EQ(PrintPointer(p) + " pointing to \"'\\\"?\\\\\\a\\b\\f"
+            "\\n\\r\\t\\v\\x7F\\xFF a\"",
+            Print(p));
+}
+
+#ifdef __cpp_char8_t
+// const char8_t*.
+TEST(PrintU8StringTest, Const) {
+  const char8_t* p = u8"界";
+  EXPECT_EQ(PrintPointer(p) + " pointing to u8\"\\xE7\\x95\\x8C\"", Print(p));
+}
+
+// char8_t*.
+TEST(PrintU8StringTest, NonConst) {
+  char8_t p[] = u8"世";
+  EXPECT_EQ(PrintPointer(p) + " pointing to u8\"\\xE4\\xB8\\x96\"",
+            Print(static_cast<char8_t*>(p)));
+}
+
+// NULL u8 string.
+TEST(PrintU8StringTest, Null) {
+  const char8_t* p = nullptr;
+  EXPECT_EQ("NULL", Print(p));
+}
+
+// Tests that u8 strings are escaped properly.
+TEST(PrintU8StringTest, EscapesProperly) {
+  const char8_t* p = u8"'\"?\\\a\b\f\n\r\t\v\x7F\xFF hello 世界";
+  EXPECT_EQ(PrintPointer(p) +
+                " pointing to u8\"'\\\"?\\\\\\a\\b\\f\\n\\r\\t\\v\\x7F\\xFF "
+                "hello \\xE4\\xB8\\x96\\xE7\\x95\\x8C\"",
+            Print(p));
+}
+#endif
+
+// const char16_t*.
+TEST(PrintU16StringTest, Const) {
+  const char16_t* p = u"界";
+  EXPECT_EQ(PrintPointer(p) + " pointing to u\"\\x754C\"", Print(p));
+}
+
+// char16_t*.
+TEST(PrintU16StringTest, NonConst) {
+  char16_t p[] = u"世";
+  EXPECT_EQ(PrintPointer(p) + " pointing to u\"\\x4E16\"",
+            Print(static_cast<char16_t*>(p)));
+}
+
+// NULL u16 string.
+TEST(PrintU16StringTest, Null) {
+  const char16_t* p = nullptr;
+  EXPECT_EQ("NULL", Print(p));
+}
+
+// Tests that u16 strings are escaped properly.
+TEST(PrintU16StringTest, EscapesProperly) {
+  const char16_t* p = u"'\"?\\\a\b\f\n\r\t\v\x7F\xFF hello 世界";
+  EXPECT_EQ(PrintPointer(p) +
+                " pointing to u\"'\\\"?\\\\\\a\\b\\f\\n\\r\\t\\v\\x7F\\xFF "
+                "hello \\x4E16\\x754C\"",
+            Print(p));
+}
+
+// const char32_t*.
+TEST(PrintU32StringTest, Const) {
+  const char32_t* p = U"🗺️";
+  EXPECT_EQ(PrintPointer(p) + " pointing to U\"\\x1F5FA\\xFE0F\"", Print(p));
+}
+
+// char32_t*.
+TEST(PrintU32StringTest, NonConst) {
+  char32_t p[] = U"🌌";
+  EXPECT_EQ(PrintPointer(p) + " pointing to U\"\\x1F30C\"",
+            Print(static_cast<char32_t*>(p)));
+}
+
+// NULL u32 string.
+TEST(PrintU32StringTest, Null) {
+  const char32_t* p = nullptr;
+  EXPECT_EQ("NULL", Print(p));
+}
+
+// Tests that u32 strings are escaped properly.
+TEST(PrintU32StringTest, EscapesProperly) {
+  const char32_t* p = U"'\"?\\\a\b\f\n\r\t\v\x7F\xFF hello 🗺️";
+  EXPECT_EQ(PrintPointer(p) +
+                " pointing to U\"'\\\"?\\\\\\a\\b\\f\\n\\r\\t\\v\\x7F\\xFF "
+                "hello \\x1F5FA\\xFE0F\"",
+            Print(p));
+}
+
+// MSVC compiler can be configured to define whar_t as a typedef
+// of unsigned short. Defining an overload for const wchar_t* in that case
+// would cause pointers to unsigned shorts be printed as wide strings,
+// possibly accessing more memory than intended and causing invalid
+// memory accesses. MSVC defines _NATIVE_WCHAR_T_DEFINED symbol when
+// wchar_t is implemented as a native type.
+#if !defined(_MSC_VER) || defined(_NATIVE_WCHAR_T_DEFINED)
+
+// const wchar_t*.
+TEST(PrintWideCStringTest, Const) {
+  const wchar_t* p = L"World";
+  EXPECT_EQ(PrintPointer(p) + " pointing to L\"World\"", Print(p));
+}
+
+// wchar_t*.
+TEST(PrintWideCStringTest, NonConst) {
+  wchar_t p[] = L"Hi";
+  EXPECT_EQ(PrintPointer(p) + " pointing to L\"Hi\"",
+            Print(static_cast<wchar_t*>(p)));
+}
+
+// NULL wide C string.
+TEST(PrintWideCStringTest, Null) {
+  const wchar_t* p = nullptr;
+  EXPECT_EQ("NULL", Print(p));
+}
+
+// Tests that wide C strings are escaped properly.
+TEST(PrintWideCStringTest, EscapesProperly) {
+  const wchar_t s[] = {'\'', '"', '?', '\\', '\a', '\b', '\f', '\n', '\r',
+                       '\t', '\v', 0xD3, 0x576, 0x8D3, 0xC74D, ' ', 'a', '\0'};
+  EXPECT_EQ(PrintPointer(s) + " pointing to L\"'\\\"?\\\\\\a\\b\\f"
+            "\\n\\r\\t\\v\\xD3\\x576\\x8D3\\xC74D a\"",
+            Print(static_cast<const wchar_t*>(s)));
+}
+#endif  // native wchar_t
+
+// Tests printing pointers to other char types.
+
+// signed char*.
+TEST(PrintCharPointerTest, SignedChar) {
+  signed char* p = reinterpret_cast<signed char*>(0x1234);
+  EXPECT_EQ(PrintPointer(p), Print(p));
+  p = nullptr;
+  EXPECT_EQ("NULL", Print(p));
+}
+
+// const signed char*.
+TEST(PrintCharPointerTest, ConstSignedChar) {
+  signed char* p = reinterpret_cast<signed char*>(0x1234);
+  EXPECT_EQ(PrintPointer(p), Print(p));
+  p = nullptr;
+  EXPECT_EQ("NULL", Print(p));
+}
+
+// unsigned char*.
+TEST(PrintCharPointerTest, UnsignedChar) {
+  unsigned char* p = reinterpret_cast<unsigned char*>(0x1234);
+  EXPECT_EQ(PrintPointer(p), Print(p));
+  p = nullptr;
+  EXPECT_EQ("NULL", Print(p));
+}
+
+// const unsigned char*.
+TEST(PrintCharPointerTest, ConstUnsignedChar) {
+  const unsigned char* p = reinterpret_cast<const unsigned char*>(0x1234);
+  EXPECT_EQ(PrintPointer(p), Print(p));
+  p = nullptr;
+  EXPECT_EQ("NULL", Print(p));
+}
+
+// Tests printing pointers to simple, built-in types.
+
+// bool*.
+TEST(PrintPointerToBuiltInTypeTest, Bool) {
+  bool* p = reinterpret_cast<bool*>(0xABCD);
+  EXPECT_EQ(PrintPointer(p), Print(p));
+  p = nullptr;
+  EXPECT_EQ("NULL", Print(p));
+}
+
+// void*.
+TEST(PrintPointerToBuiltInTypeTest, Void) {
+  void* p = reinterpret_cast<void*>(0xABCD);
+  EXPECT_EQ(PrintPointer(p), Print(p));
+  p = nullptr;
+  EXPECT_EQ("NULL", Print(p));
+}
+
+// const void*.
+TEST(PrintPointerToBuiltInTypeTest, ConstVoid) {
+  const void* p = reinterpret_cast<const void*>(0xABCD);
+  EXPECT_EQ(PrintPointer(p), Print(p));
+  p = nullptr;
+  EXPECT_EQ("NULL", Print(p));
+}
+
+// Tests printing pointers to pointers.
+TEST(PrintPointerToPointerTest, IntPointerPointer) {
+  int** p = reinterpret_cast<int**>(0xABCD);
+  EXPECT_EQ(PrintPointer(p), Print(p));
+  p = nullptr;
+  EXPECT_EQ("NULL", Print(p));
+}
+
+// Tests printing (non-member) function pointers.
+
+void MyFunction(int /* n */) {}
+
+TEST(PrintPointerTest, NonMemberFunctionPointer) {
+  // We cannot directly cast &MyFunction to const void* because the
+  // standard disallows casting between pointers to functions and
+  // pointers to objects, and some compilers (e.g. GCC 3.4) enforce
+  // this limitation.
+  EXPECT_EQ(
+      PrintPointer(reinterpret_cast<const void*>(
+          reinterpret_cast<internal::BiggestInt>(&MyFunction))),
+      Print(&MyFunction));
+  int (*p)(bool) = NULL;  // NOLINT
+  EXPECT_EQ("NULL", Print(p));
+}
+
+// An assertion predicate determining whether a one string is a prefix for
+// another.
+template <typename StringType>
+AssertionResult HasPrefix(const StringType& str, const StringType& prefix) {
+  if (str.find(prefix, 0) == 0)
+    return AssertionSuccess();
+
+  const bool is_wide_string = sizeof(prefix[0]) > 1;
+  const char* const begin_string_quote = is_wide_string ? "L\"" : "\"";
+  return AssertionFailure()
+      << begin_string_quote << prefix << "\" is not a prefix of "
+      << begin_string_quote << str << "\"\n";
+}
+
+// Tests printing member variable pointers.  Although they are called
+// pointers, they don't point to a location in the address space.
+// Their representation is implementation-defined.  Thus they will be
+// printed as raw bytes.
+
+struct Foo {
+ public:
+  virtual ~Foo() {}
+  int MyMethod(char x) { return x + 1; }
+  virtual char MyVirtualMethod(int /* n */) { return 'a'; }
+
+  int value;
+};
+
+TEST(PrintPointerTest, MemberVariablePointer) {
+  EXPECT_TRUE(HasPrefix(Print(&Foo::value),
+                        Print(sizeof(&Foo::value)) + "-byte object "));
+  int Foo::*p = NULL;  // NOLINT
+  EXPECT_TRUE(HasPrefix(Print(p),
+                        Print(sizeof(p)) + "-byte object "));
+}
+
+// Tests printing member function pointers.  Although they are called
+// pointers, they don't point to a location in the address space.
+// Their representation is implementation-defined.  Thus they will be
+// printed as raw bytes.
+TEST(PrintPointerTest, MemberFunctionPointer) {
+  EXPECT_TRUE(HasPrefix(Print(&Foo::MyMethod),
+                        Print(sizeof(&Foo::MyMethod)) + "-byte object "));
+  EXPECT_TRUE(
+      HasPrefix(Print(&Foo::MyVirtualMethod),
+                Print(sizeof((&Foo::MyVirtualMethod))) + "-byte object "));
+  int (Foo::*p)(char) = NULL;  // NOLINT
+  EXPECT_TRUE(HasPrefix(Print(p),
+                        Print(sizeof(p)) + "-byte object "));
+}
+
+// Tests printing C arrays.
+
+// The difference between this and Print() is that it ensures that the
+// argument is a reference to an array.
+template <typename T, size_t N>
+std::string PrintArrayHelper(T (&a)[N]) {
+  return Print(a);
+}
+
+// One-dimensional array.
+TEST(PrintArrayTest, OneDimensionalArray) {
+  int a[5] = { 1, 2, 3, 4, 5 };
+  EXPECT_EQ("{ 1, 2, 3, 4, 5 }", PrintArrayHelper(a));
+}
+
+// Two-dimensional array.
+TEST(PrintArrayTest, TwoDimensionalArray) {
+  int a[2][5] = {
+    { 1, 2, 3, 4, 5 },
+    { 6, 7, 8, 9, 0 }
+  };
+  EXPECT_EQ("{ { 1, 2, 3, 4, 5 }, { 6, 7, 8, 9, 0 } }", PrintArrayHelper(a));
+}
+
+// Array of const elements.
+TEST(PrintArrayTest, ConstArray) {
+  const bool a[1] = { false };
+  EXPECT_EQ("{ false }", PrintArrayHelper(a));
+}
+
+// char array without terminating NUL.
+TEST(PrintArrayTest, CharArrayWithNoTerminatingNul) {
+  // Array a contains '\0' in the middle and doesn't end with '\0'.
+  char a[] = { 'H', '\0', 'i' };
+  EXPECT_EQ("\"H\\0i\" (no terminating NUL)", PrintArrayHelper(a));
+}
+
+// char array with terminating NUL.
+TEST(PrintArrayTest, CharArrayWithTerminatingNul) {
+  const char a[] = "\0Hi";
+  EXPECT_EQ("\"\\0Hi\"", PrintArrayHelper(a));
+}
+
+#ifdef __cpp_char8_t
+// char_t array without terminating NUL.
+TEST(PrintArrayTest, Char8ArrayWithNoTerminatingNul) {
+  // Array a contains '\0' in the middle and doesn't end with '\0'.
+  const char8_t a[] = {u8'H', u8'\0', u8'i'};
+  EXPECT_EQ("u8\"H\\0i\" (no terminating NUL)", PrintArrayHelper(a));
+}
+
+// char8_t array with terminating NUL.
+TEST(PrintArrayTest, Char8ArrayWithTerminatingNul) {
+  const char8_t a[] = u8"\0世界";
+  EXPECT_EQ(
+      "u8\"\\0\\xE4\\xB8\\x96\\xE7\\x95\\x8C\"",
+      PrintArrayHelper(a));
+}
+#endif
+
+// const char16_t array without terminating NUL.
+TEST(PrintArrayTest, Char16ArrayWithNoTerminatingNul) {
+  // Array a contains '\0' in the middle and doesn't end with '\0'.
+  const char16_t a[] = {u'こ', u'\0', u'ん', u'に', u'ち', u'は'};
+  EXPECT_EQ("u\"\\x3053\\0\\x3093\\x306B\\x3061\\x306F\" (no terminating NUL)",
+            PrintArrayHelper(a));
+}
+
+// char16_t array with terminating NUL.
+TEST(PrintArrayTest, Char16ArrayWithTerminatingNul) {
+  const char16_t a[] = u"\0こんにちは";
+  EXPECT_EQ("u\"\\0\\x3053\\x3093\\x306B\\x3061\\x306F\"", PrintArrayHelper(a));
+}
+
+// char32_t array without terminating NUL.
+TEST(PrintArrayTest, Char32ArrayWithNoTerminatingNul) {
+  // Array a contains '\0' in the middle and doesn't end with '\0'.
+  const char32_t a[] = {U'👋', U'\0', U'🌌'};
+  EXPECT_EQ("U\"\\x1F44B\\0\\x1F30C\" (no terminating NUL)",
+            PrintArrayHelper(a));
+}
+
+// char32_t array with terminating NUL.
+TEST(PrintArrayTest, Char32ArrayWithTerminatingNul) {
+  const char32_t a[] = U"\0👋🌌";
+  EXPECT_EQ("U\"\\0\\x1F44B\\x1F30C\"", PrintArrayHelper(a));
+}
+
+// wchar_t array without terminating NUL.
+TEST(PrintArrayTest, WCharArrayWithNoTerminatingNul) {
+  // Array a contains '\0' in the middle and doesn't end with '\0'.
+  const wchar_t a[] = {L'H', L'\0', L'i'};
+  EXPECT_EQ("L\"H\\0i\" (no terminating NUL)", PrintArrayHelper(a));
+}
+
+// wchar_t array with terminating NUL.
+TEST(PrintArrayTest, WCharArrayWithTerminatingNul) {
+  const wchar_t a[] = L"\0Hi";
+  EXPECT_EQ("L\"\\0Hi\"", PrintArrayHelper(a));
+}
+
+// Array of objects.
+TEST(PrintArrayTest, ObjectArray) {
+  std::string a[3] = {"Hi", "Hello", "Ni hao"};
+  EXPECT_EQ("{ \"Hi\", \"Hello\", \"Ni hao\" }", PrintArrayHelper(a));
+}
+
+// Array with many elements.
+TEST(PrintArrayTest, BigArray) {
+  int a[100] = { 1, 2, 3 };
+  EXPECT_EQ("{ 1, 2, 3, 0, 0, 0, 0, 0, ..., 0, 0, 0, 0, 0, 0, 0, 0 }",
+            PrintArrayHelper(a));
+}
+
+// Tests printing ::string and ::std::string.
+
+// ::std::string.
+TEST(PrintStringTest, StringInStdNamespace) {
+  const char s[] = "'\"?\\\a\b\f\n\0\r\t\v\x7F\xFF a";
+  const ::std::string str(s, sizeof(s));
+  EXPECT_EQ("\"'\\\"?\\\\\\a\\b\\f\\n\\0\\r\\t\\v\\x7F\\xFF a\\0\"",
+            Print(str));
+}
+
+TEST(PrintStringTest, StringAmbiguousHex) {
+  // "\x6BANANA" is ambiguous, it can be interpreted as starting with either of:
+  // '\x6', '\x6B', or '\x6BA'.
+
+  // a hex escaping sequence following by a decimal digit
+  EXPECT_EQ("\"0\\x12\" \"3\"", Print(::std::string("0\x12" "3")));
+  // a hex escaping sequence following by a hex digit (lower-case)
+  EXPECT_EQ("\"mm\\x6\" \"bananas\"", Print(::std::string("mm\x6" "bananas")));
+  // a hex escaping sequence following by a hex digit (upper-case)
+  EXPECT_EQ("\"NOM\\x6\" \"BANANA\"", Print(::std::string("NOM\x6" "BANANA")));
+  // a hex escaping sequence following by a non-xdigit
+  EXPECT_EQ("\"!\\x5-!\"", Print(::std::string("!\x5-!")));
+}
+
+// Tests printing ::std::wstring.
+#if GTEST_HAS_STD_WSTRING
+// ::std::wstring.
+TEST(PrintWideStringTest, StringInStdNamespace) {
+  const wchar_t s[] = L"'\"?\\\a\b\f\n\0\r\t\v\xD3\x576\x8D3\xC74D a";
+  const ::std::wstring str(s, sizeof(s)/sizeof(wchar_t));
+  EXPECT_EQ("L\"'\\\"?\\\\\\a\\b\\f\\n\\0\\r\\t\\v"
+            "\\xD3\\x576\\x8D3\\xC74D a\\0\"",
+            Print(str));
+}
+
+TEST(PrintWideStringTest, StringAmbiguousHex) {
+  // same for wide strings.
+  EXPECT_EQ("L\"0\\x12\" L\"3\"", Print(::std::wstring(L"0\x12" L"3")));
+  EXPECT_EQ("L\"mm\\x6\" L\"bananas\"",
+            Print(::std::wstring(L"mm\x6" L"bananas")));
+  EXPECT_EQ("L\"NOM\\x6\" L\"BANANA\"",
+            Print(::std::wstring(L"NOM\x6" L"BANANA")));
+  EXPECT_EQ("L\"!\\x5-!\"", Print(::std::wstring(L"!\x5-!")));
+}
+#endif  // GTEST_HAS_STD_WSTRING
+
+#ifdef __cpp_char8_t
+TEST(PrintStringTest, U8String) {
+  std::u8string str = u8"Hello, 世界";
+  EXPECT_EQ(str, str);  // Verify EXPECT_EQ compiles with this type.
+  EXPECT_EQ("u8\"Hello, \\xE4\\xB8\\x96\\xE7\\x95\\x8C\"", Print(str));
+}
+#endif
+
+TEST(PrintStringTest, U16String) {
+  std::u16string str = u"Hello, 世界";
+  EXPECT_EQ(str, str);  // Verify EXPECT_EQ compiles with this type.
+  EXPECT_EQ("u\"Hello, \\x4E16\\x754C\"", Print(str));
+}
+
+TEST(PrintStringTest, U32String) {
+  std::u32string str = U"Hello, 🗺️";
+  EXPECT_EQ(str, str);  // Verify EXPECT_EQ compiles with this type
+  EXPECT_EQ("U\"Hello, \\x1F5FA\\xFE0F\"", Print(str));
+}
+
+// Tests printing types that support generic streaming (i.e. streaming
+// to std::basic_ostream<Char, CharTraits> for any valid Char and
+// CharTraits types).
+
+// Tests printing a non-template type that supports generic streaming.
+
+class AllowsGenericStreaming {};
+
+template <typename Char, typename CharTraits>
+std::basic_ostream<Char, CharTraits>& operator<<(
+    std::basic_ostream<Char, CharTraits>& os,
+    const AllowsGenericStreaming& /* a */) {
+  return os << "AllowsGenericStreaming";
+}
+
+TEST(PrintTypeWithGenericStreamingTest, NonTemplateType) {
+  AllowsGenericStreaming a;
+  EXPECT_EQ("AllowsGenericStreaming", Print(a));
+}
+
+// Tests printing a template type that supports generic streaming.
+
+template <typename T>
+class AllowsGenericStreamingTemplate {};
+
+template <typename Char, typename CharTraits, typename T>
+std::basic_ostream<Char, CharTraits>& operator<<(
+    std::basic_ostream<Char, CharTraits>& os,
+    const AllowsGenericStreamingTemplate<T>& /* a */) {
+  return os << "AllowsGenericStreamingTemplate";
+}
+
+TEST(PrintTypeWithGenericStreamingTest, TemplateType) {
+  AllowsGenericStreamingTemplate<int> a;
+  EXPECT_EQ("AllowsGenericStreamingTemplate", Print(a));
+}
+
+// Tests printing a type that supports generic streaming and can be
+// implicitly converted to another printable type.
+
+template <typename T>
+class AllowsGenericStreamingAndImplicitConversionTemplate {
+ public:
+  operator bool() const { return false; }
+};
+
+template <typename Char, typename CharTraits, typename T>
+std::basic_ostream<Char, CharTraits>& operator<<(
+    std::basic_ostream<Char, CharTraits>& os,
+    const AllowsGenericStreamingAndImplicitConversionTemplate<T>& /* a */) {
+  return os << "AllowsGenericStreamingAndImplicitConversionTemplate";
+}
+
+TEST(PrintTypeWithGenericStreamingTest, TypeImplicitlyConvertible) {
+  AllowsGenericStreamingAndImplicitConversionTemplate<int> a;
+  EXPECT_EQ("AllowsGenericStreamingAndImplicitConversionTemplate", Print(a));
+}
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+
+// Tests printing internal::StringView.
+
+TEST(PrintStringViewTest, SimpleStringView) {
+  const internal::StringView sp = "Hello";
+  EXPECT_EQ("\"Hello\"", Print(sp));
+}
+
+TEST(PrintStringViewTest, UnprintableCharacters) {
+  const char str[] = "NUL (\0) and \r\t";
+  const internal::StringView sp(str, sizeof(str) - 1);
+  EXPECT_EQ("\"NUL (\\0) and \\r\\t\"", Print(sp));
+}
+
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+
+// Tests printing STL containers.
+
+TEST(PrintStlContainerTest, EmptyDeque) {
+  deque<char> empty;
+  EXPECT_EQ("{}", Print(empty));
+}
+
+TEST(PrintStlContainerTest, NonEmptyDeque) {
+  deque<int> non_empty;
+  non_empty.push_back(1);
+  non_empty.push_back(3);
+  EXPECT_EQ("{ 1, 3 }", Print(non_empty));
+}
+
+
+TEST(PrintStlContainerTest, OneElementHashMap) {
+  ::std::unordered_map<int, char> map1;
+  map1[1] = 'a';
+  EXPECT_EQ("{ (1, 'a' (97, 0x61)) }", Print(map1));
+}
+
+TEST(PrintStlContainerTest, HashMultiMap) {
+  ::std::unordered_multimap<int, bool> map1;
+  map1.insert(make_pair(5, true));
+  map1.insert(make_pair(5, false));
+
+  // Elements of hash_multimap can be printed in any order.
+  const std::string result = Print(map1);
+  EXPECT_TRUE(result == "{ (5, true), (5, false) }" ||
+              result == "{ (5, false), (5, true) }")
+                  << " where Print(map1) returns \"" << result << "\".";
+}
+
+
+
+TEST(PrintStlContainerTest, HashSet) {
+  ::std::unordered_set<int> set1;
+  set1.insert(1);
+  EXPECT_EQ("{ 1 }", Print(set1));
+}
+
+TEST(PrintStlContainerTest, HashMultiSet) {
+  const int kSize = 5;
+  int a[kSize] = { 1, 1, 2, 5, 1 };
+  ::std::unordered_multiset<int> set1(a, a + kSize);
+
+  // Elements of hash_multiset can be printed in any order.
+  const std::string result = Print(set1);
+  const std::string expected_pattern = "{ d, d, d, d, d }";  // d means a digit.
+
+  // Verifies the result matches the expected pattern; also extracts
+  // the numbers in the result.
+  ASSERT_EQ(expected_pattern.length(), result.length());
+  std::vector<int> numbers;
+  for (size_t i = 0; i != result.length(); i++) {
+    if (expected_pattern[i] == 'd') {
+      ASSERT_NE(isdigit(static_cast<unsigned char>(result[i])), 0);
+      numbers.push_back(result[i] - '0');
+    } else {
+      EXPECT_EQ(expected_pattern[i], result[i]) << " where result is "
+                                                << result;
+    }
+  }
+
+  // Makes sure the result contains the right numbers.
+  std::sort(numbers.begin(), numbers.end());
+  std::sort(a, a + kSize);
+  EXPECT_TRUE(std::equal(a, a + kSize, numbers.begin()));
+}
+
+
+TEST(PrintStlContainerTest, List) {
+  const std::string a[] = {"hello", "world"};
+  const list<std::string> strings(a, a + 2);
+  EXPECT_EQ("{ \"hello\", \"world\" }", Print(strings));
+}
+
+TEST(PrintStlContainerTest, Map) {
+  map<int, bool> map1;
+  map1[1] = true;
+  map1[5] = false;
+  map1[3] = true;
+  EXPECT_EQ("{ (1, true), (3, true), (5, false) }", Print(map1));
+}
+
+TEST(PrintStlContainerTest, MultiMap) {
+  multimap<bool, int> map1;
+  // The make_pair template function would deduce the type as
+  // pair<bool, int> here, and since the key part in a multimap has to
+  // be constant, without a templated ctor in the pair class (as in
+  // libCstd on Solaris), make_pair call would fail to compile as no
+  // implicit conversion is found.  Thus explicit typename is used
+  // here instead.
+  map1.insert(pair<const bool, int>(true, 0));
+  map1.insert(pair<const bool, int>(true, 1));
+  map1.insert(pair<const bool, int>(false, 2));
+  EXPECT_EQ("{ (false, 2), (true, 0), (true, 1) }", Print(map1));
+}
+
+TEST(PrintStlContainerTest, Set) {
+  const unsigned int a[] = { 3, 0, 5 };
+  set<unsigned int> set1(a, a + 3);
+  EXPECT_EQ("{ 0, 3, 5 }", Print(set1));
+}
+
+TEST(PrintStlContainerTest, MultiSet) {
+  const int a[] = { 1, 1, 2, 5, 1 };
+  multiset<int> set1(a, a + 5);
+  EXPECT_EQ("{ 1, 1, 1, 2, 5 }", Print(set1));
+}
+
+
+TEST(PrintStlContainerTest, SinglyLinkedList) {
+  int a[] = { 9, 2, 8 };
+  const std::forward_list<int> ints(a, a + 3);
+  EXPECT_EQ("{ 9, 2, 8 }", Print(ints));
+}
+
+TEST(PrintStlContainerTest, Pair) {
+  pair<const bool, int> p(true, 5);
+  EXPECT_EQ("(true, 5)", Print(p));
+}
+
+TEST(PrintStlContainerTest, Vector) {
+  vector<int> v;
+  v.push_back(1);
+  v.push_back(2);
+  EXPECT_EQ("{ 1, 2 }", Print(v));
+}
+
+TEST(PrintStlContainerTest, LongSequence) {
+  const int a[100] = { 1, 2, 3 };
+  const vector<int> v(a, a + 100);
+  EXPECT_EQ("{ 1, 2, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, "
+            "0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ... }", Print(v));
+}
+
+TEST(PrintStlContainerTest, NestedContainer) {
+  const int a1[] = { 1, 2 };
+  const int a2[] = { 3, 4, 5 };
+  const list<int> l1(a1, a1 + 2);
+  const list<int> l2(a2, a2 + 3);
+
+  vector<list<int> > v;
+  v.push_back(l1);
+  v.push_back(l2);
+  EXPECT_EQ("{ { 1, 2 }, { 3, 4, 5 } }", Print(v));
+}
+
+TEST(PrintStlContainerTest, OneDimensionalNativeArray) {
+  const int a[3] = { 1, 2, 3 };
+  NativeArray<int> b(a, 3, RelationToSourceReference());
+  EXPECT_EQ("{ 1, 2, 3 }", Print(b));
+}
+
+TEST(PrintStlContainerTest, TwoDimensionalNativeArray) {
+  const int a[2][3] = { { 1, 2, 3 }, { 4, 5, 6 } };
+  NativeArray<int[3]> b(a, 2, RelationToSourceReference());
+  EXPECT_EQ("{ { 1, 2, 3 }, { 4, 5, 6 } }", Print(b));
+}
+
+// Tests that a class named iterator isn't treated as a container.
+
+struct iterator {
+  char x;
+};
+
+TEST(PrintStlContainerTest, Iterator) {
+  iterator it = {};
+  EXPECT_EQ("1-byte object <00>", Print(it));
+}
+
+// Tests that a class named const_iterator isn't treated as a container.
+
+struct const_iterator {
+  char x;
+};
+
+TEST(PrintStlContainerTest, ConstIterator) {
+  const_iterator it = {};
+  EXPECT_EQ("1-byte object <00>", Print(it));
+}
+
+// Tests printing ::std::tuples.
+
+// Tuples of various arities.
+TEST(PrintStdTupleTest, VariousSizes) {
+  ::std::tuple<> t0;
+  EXPECT_EQ("()", Print(t0));
+
+  ::std::tuple<int> t1(5);
+  EXPECT_EQ("(5)", Print(t1));
+
+  ::std::tuple<char, bool> t2('a', true);
+  EXPECT_EQ("('a' (97, 0x61), true)", Print(t2));
+
+  ::std::tuple<bool, int, int> t3(false, 2, 3);
+  EXPECT_EQ("(false, 2, 3)", Print(t3));
+
+  ::std::tuple<bool, int, int, int> t4(false, 2, 3, 4);
+  EXPECT_EQ("(false, 2, 3, 4)", Print(t4));
+
+  const char* const str = "8";
+  ::std::tuple<bool, char, short, int32_t, int64_t, float, double,  // NOLINT
+               const char*, void*, std::string>
+      t10(false, 'a', static_cast<short>(3), 4, 5, 1.5F, -2.5, str,  // NOLINT
+          nullptr, "10");
+  EXPECT_EQ("(false, 'a' (97, 0x61), 3, 4, 5, 1.5, -2.5, " + PrintPointer(str) +
+            " pointing to \"8\", NULL, \"10\")",
+            Print(t10));
+}
+
+// Nested tuples.
+TEST(PrintStdTupleTest, NestedTuple) {
+  ::std::tuple< ::std::tuple<int, bool>, char> nested(
+      ::std::make_tuple(5, true), 'a');
+  EXPECT_EQ("((5, true), 'a' (97, 0x61))", Print(nested));
+}
+
+TEST(PrintNullptrT, Basic) {
+  EXPECT_EQ("(nullptr)", Print(nullptr));
+}
+
+TEST(PrintReferenceWrapper, Printable) {
+  int x = 5;
+  EXPECT_EQ("@" + PrintPointer(&x) + " 5", Print(std::ref(x)));
+  EXPECT_EQ("@" + PrintPointer(&x) + " 5", Print(std::cref(x)));
+}
+
+TEST(PrintReferenceWrapper, Unprintable) {
+  ::foo::UnprintableInFoo up;
+  EXPECT_EQ(
+      "@" + PrintPointer(&up) +
+          " 16-byte object <EF-12 00-00 34-AB 00-00 00-00 00-00 00-00 00-00>",
+      Print(std::ref(up)));
+  EXPECT_EQ(
+      "@" + PrintPointer(&up) +
+          " 16-byte object <EF-12 00-00 34-AB 00-00 00-00 00-00 00-00 00-00>",
+      Print(std::cref(up)));
+}
+
+// Tests printing user-defined unprintable types.
+
+// Unprintable types in the global namespace.
+TEST(PrintUnprintableTypeTest, InGlobalNamespace) {
+  EXPECT_EQ("1-byte object <00>",
+            Print(UnprintableTemplateInGlobal<char>()));
+}
+
+// Unprintable types in a user namespace.
+TEST(PrintUnprintableTypeTest, InUserNamespace) {
+  EXPECT_EQ("16-byte object <EF-12 00-00 34-AB 00-00 00-00 00-00 00-00 00-00>",
+            Print(::foo::UnprintableInFoo()));
+}
+
+// Unprintable types are that too big to be printed completely.
+
+struct Big {
+  Big() { memset(array, 0, sizeof(array)); }
+  char array[257];
+};
+
+TEST(PrintUnpritableTypeTest, BigObject) {
+  EXPECT_EQ("257-byte object <00-00 00-00 00-00 00-00 00-00 00-00 "
+            "00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 "
+            "00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 "
+            "00-00 00-00 00-00 00-00 00-00 00-00 ... 00-00 00-00 00-00 "
+            "00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 "
+            "00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 "
+            "00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00>",
+            Print(Big()));
+}
+
+// Tests printing user-defined streamable types.
+
+// Streamable types in the global namespace.
+TEST(PrintStreamableTypeTest, InGlobalNamespace) {
+  StreamableInGlobal x;
+  EXPECT_EQ("StreamableInGlobal", Print(x));
+  EXPECT_EQ("StreamableInGlobal*", Print(&x));
+}
+
+// Printable template types in a user namespace.
+TEST(PrintStreamableTypeTest, TemplateTypeInUserNamespace) {
+  EXPECT_EQ("StreamableTemplateInFoo: 0",
+            Print(::foo::StreamableTemplateInFoo<int>()));
+}
+
+TEST(PrintStreamableTypeTest, TypeInUserNamespaceWithTemplatedStreamOperator) {
+  EXPECT_EQ("TemplatedStreamableInFoo",
+            Print(::foo::TemplatedStreamableInFoo()));
+}
+
+TEST(PrintStreamableTypeTest, SubclassUsesSuperclassStreamOperator) {
+  ParentClass parent;
+  ChildClassWithStreamOperator child_stream;
+  ChildClassWithoutStreamOperator child_no_stream;
+  EXPECT_EQ("ParentClass", Print(parent));
+  EXPECT_EQ("ChildClassWithStreamOperator", Print(child_stream));
+  EXPECT_EQ("ParentClass", Print(child_no_stream));
+}
+
+// Tests printing a user-defined recursive container type that has a <<
+// operator.
+TEST(PrintStreamableTypeTest, PathLikeInUserNamespace) {
+  ::foo::PathLike x;
+  EXPECT_EQ("Streamable-PathLike", Print(x));
+  const ::foo::PathLike cx;
+  EXPECT_EQ("Streamable-PathLike", Print(cx));
+}
+
+// Tests printing user-defined types that have a PrintTo() function.
+TEST(PrintPrintableTypeTest, InUserNamespace) {
+  EXPECT_EQ("PrintableViaPrintTo: 0",
+            Print(::foo::PrintableViaPrintTo()));
+}
+
+// Tests printing a pointer to a user-defined type that has a <<
+// operator for its pointer.
+TEST(PrintPrintableTypeTest, PointerInUserNamespace) {
+  ::foo::PointerPrintable x;
+  EXPECT_EQ("PointerPrintable*", Print(&x));
+}
+
+// Tests printing user-defined class template that have a PrintTo() function.
+TEST(PrintPrintableTypeTest, TemplateInUserNamespace) {
+  EXPECT_EQ("PrintableViaPrintToTemplate: 5",
+            Print(::foo::PrintableViaPrintToTemplate<int>(5)));
+}
+
+// Tests that the universal printer prints both the address and the
+// value of a reference.
+TEST(PrintReferenceTest, PrintsAddressAndValue) {
+  int n = 5;
+  EXPECT_EQ("@" + PrintPointer(&n) + " 5", PrintByRef(n));
+
+  int a[2][3] = {
+    { 0, 1, 2 },
+    { 3, 4, 5 }
+  };
+  EXPECT_EQ("@" + PrintPointer(a) + " { { 0, 1, 2 }, { 3, 4, 5 } }",
+            PrintByRef(a));
+
+  const ::foo::UnprintableInFoo x;
+  EXPECT_EQ("@" + PrintPointer(&x) + " 16-byte object "
+            "<EF-12 00-00 34-AB 00-00 00-00 00-00 00-00 00-00>",
+            PrintByRef(x));
+}
+
+// Tests that the universal printer prints a function pointer passed by
+// reference.
+TEST(PrintReferenceTest, HandlesFunctionPointer) {
+  void (*fp)(int n) = &MyFunction;
+  const std::string fp_pointer_string =
+      PrintPointer(reinterpret_cast<const void*>(&fp));
+  // We cannot directly cast &MyFunction to const void* because the
+  // standard disallows casting between pointers to functions and
+  // pointers to objects, and some compilers (e.g. GCC 3.4) enforce
+  // this limitation.
+  const std::string fp_string = PrintPointer(reinterpret_cast<const void*>(
+      reinterpret_cast<internal::BiggestInt>(fp)));
+  EXPECT_EQ("@" + fp_pointer_string + " " + fp_string,
+            PrintByRef(fp));
+}
+
+// Tests that the universal printer prints a member function pointer
+// passed by reference.
+TEST(PrintReferenceTest, HandlesMemberFunctionPointer) {
+  int (Foo::*p)(char ch) = &Foo::MyMethod;
+  EXPECT_TRUE(HasPrefix(
+      PrintByRef(p),
+      "@" + PrintPointer(reinterpret_cast<const void*>(&p)) + " " +
+          Print(sizeof(p)) + "-byte object "));
+
+  char (Foo::*p2)(int n) = &Foo::MyVirtualMethod;
+  EXPECT_TRUE(HasPrefix(
+      PrintByRef(p2),
+      "@" + PrintPointer(reinterpret_cast<const void*>(&p2)) + " " +
+          Print(sizeof(p2)) + "-byte object "));
+}
+
+// Tests that the universal printer prints a member variable pointer
+// passed by reference.
+TEST(PrintReferenceTest, HandlesMemberVariablePointer) {
+  int Foo::*p = &Foo::value;  // NOLINT
+  EXPECT_TRUE(HasPrefix(
+      PrintByRef(p),
+      "@" + PrintPointer(&p) + " " + Print(sizeof(p)) + "-byte object "));
+}
+
+// Tests that FormatForComparisonFailureMessage(), which is used to print
+// an operand in a comparison assertion (e.g. ASSERT_EQ) when the assertion
+// fails, formats the operand in the desired way.
+
+// scalar
+TEST(FormatForComparisonFailureMessageTest, WorksForScalar) {
+  EXPECT_STREQ("123",
+               FormatForComparisonFailureMessage(123, 124).c_str());
+}
+
+// non-char pointer
+TEST(FormatForComparisonFailureMessageTest, WorksForNonCharPointer) {
+  int n = 0;
+  EXPECT_EQ(PrintPointer(&n),
+            FormatForComparisonFailureMessage(&n, &n).c_str());
+}
+
+// non-char array
+TEST(FormatForComparisonFailureMessageTest, FormatsNonCharArrayAsPointer) {
+  // In expression 'array == x', 'array' is compared by pointer.
+  // Therefore we want to print an array operand as a pointer.
+  int n[] = { 1, 2, 3 };
+  EXPECT_EQ(PrintPointer(n),
+            FormatForComparisonFailureMessage(n, n).c_str());
+}
+
+// Tests formatting a char pointer when it's compared with another pointer.
+// In this case we want to print it as a raw pointer, as the comparison is by
+// pointer.
+
+// char pointer vs pointer
+TEST(FormatForComparisonFailureMessageTest, WorksForCharPointerVsPointer) {
+  // In expression 'p == x', where 'p' and 'x' are (const or not) char
+  // pointers, the operands are compared by pointer.  Therefore we
+  // want to print 'p' as a pointer instead of a C string (we don't
+  // even know if it's supposed to point to a valid C string).
+
+  // const char*
+  const char* s = "hello";
+  EXPECT_EQ(PrintPointer(s),
+            FormatForComparisonFailureMessage(s, s).c_str());
+
+  // char*
+  char ch = 'a';
+  EXPECT_EQ(PrintPointer(&ch),
+            FormatForComparisonFailureMessage(&ch, &ch).c_str());
+}
+
+// wchar_t pointer vs pointer
+TEST(FormatForComparisonFailureMessageTest, WorksForWCharPointerVsPointer) {
+  // In expression 'p == x', where 'p' and 'x' are (const or not) char
+  // pointers, the operands are compared by pointer.  Therefore we
+  // want to print 'p' as a pointer instead of a wide C string (we don't
+  // even know if it's supposed to point to a valid wide C string).
+
+  // const wchar_t*
+  const wchar_t* s = L"hello";
+  EXPECT_EQ(PrintPointer(s),
+            FormatForComparisonFailureMessage(s, s).c_str());
+
+  // wchar_t*
+  wchar_t ch = L'a';
+  EXPECT_EQ(PrintPointer(&ch),
+            FormatForComparisonFailureMessage(&ch, &ch).c_str());
+}
+
+// Tests formatting a char pointer when it's compared to a string object.
+// In this case we want to print the char pointer as a C string.
+
+// char pointer vs std::string
+TEST(FormatForComparisonFailureMessageTest, WorksForCharPointerVsStdString) {
+  const char* s = "hello \"world";
+  EXPECT_STREQ("\"hello \\\"world\"",  // The string content should be escaped.
+               FormatForComparisonFailureMessage(s, ::std::string()).c_str());
+
+  // char*
+  char str[] = "hi\1";
+  char* p = str;
+  EXPECT_STREQ("\"hi\\x1\"",  // The string content should be escaped.
+               FormatForComparisonFailureMessage(p, ::std::string()).c_str());
+}
+
+#if GTEST_HAS_STD_WSTRING
+// wchar_t pointer vs std::wstring
+TEST(FormatForComparisonFailureMessageTest, WorksForWCharPointerVsStdWString) {
+  const wchar_t* s = L"hi \"world";
+  EXPECT_STREQ("L\"hi \\\"world\"",  // The string content should be escaped.
+               FormatForComparisonFailureMessage(s, ::std::wstring()).c_str());
+
+  // wchar_t*
+  wchar_t str[] = L"hi\1";
+  wchar_t* p = str;
+  EXPECT_STREQ("L\"hi\\x1\"",  // The string content should be escaped.
+               FormatForComparisonFailureMessage(p, ::std::wstring()).c_str());
+}
+#endif
+
+// Tests formatting a char array when it's compared with a pointer or array.
+// In this case we want to print the array as a row pointer, as the comparison
+// is by pointer.
+
+// char array vs pointer
+TEST(FormatForComparisonFailureMessageTest, WorksForCharArrayVsPointer) {
+  char str[] = "hi \"world\"";
+  char* p = nullptr;
+  EXPECT_EQ(PrintPointer(str),
+            FormatForComparisonFailureMessage(str, p).c_str());
+}
+
+// char array vs char array
+TEST(FormatForComparisonFailureMessageTest, WorksForCharArrayVsCharArray) {
+  const char str[] = "hi \"world\"";
+  EXPECT_EQ(PrintPointer(str),
+            FormatForComparisonFailureMessage(str, str).c_str());
+}
+
+// wchar_t array vs pointer
+TEST(FormatForComparisonFailureMessageTest, WorksForWCharArrayVsPointer) {
+  wchar_t str[] = L"hi \"world\"";
+  wchar_t* p = nullptr;
+  EXPECT_EQ(PrintPointer(str),
+            FormatForComparisonFailureMessage(str, p).c_str());
+}
+
+// wchar_t array vs wchar_t array
+TEST(FormatForComparisonFailureMessageTest, WorksForWCharArrayVsWCharArray) {
+  const wchar_t str[] = L"hi \"world\"";
+  EXPECT_EQ(PrintPointer(str),
+            FormatForComparisonFailureMessage(str, str).c_str());
+}
+
+// Tests formatting a char array when it's compared with a string object.
+// In this case we want to print the array as a C string.
+
+// char array vs std::string
+TEST(FormatForComparisonFailureMessageTest, WorksForCharArrayVsStdString) {
+  const char str[] = "hi \"world\"";
+  EXPECT_STREQ("\"hi \\\"world\\\"\"",  // The content should be escaped.
+               FormatForComparisonFailureMessage(str, ::std::string()).c_str());
+}
+
+#if GTEST_HAS_STD_WSTRING
+// wchar_t array vs std::wstring
+TEST(FormatForComparisonFailureMessageTest, WorksForWCharArrayVsStdWString) {
+  const wchar_t str[] = L"hi \"w\0rld\"";
+  EXPECT_STREQ(
+      "L\"hi \\\"w\"",  // The content should be escaped.
+                        // Embedded NUL terminates the string.
+      FormatForComparisonFailureMessage(str, ::std::wstring()).c_str());
+}
+#endif
+
+// Useful for testing PrintToString().  We cannot use EXPECT_EQ()
+// there as its implementation uses PrintToString().  The caller must
+// ensure that 'value' has no side effect.
+#define EXPECT_PRINT_TO_STRING_(value, expected_string)         \
+  EXPECT_TRUE(PrintToString(value) == (expected_string))        \
+      << " where " #value " prints as " << (PrintToString(value))
+
+TEST(PrintToStringTest, WorksForScalar) {
+  EXPECT_PRINT_TO_STRING_(123, "123");
+}
+
+TEST(PrintToStringTest, WorksForPointerToConstChar) {
+  const char* p = "hello";
+  EXPECT_PRINT_TO_STRING_(p, "\"hello\"");
+}
+
+TEST(PrintToStringTest, WorksForPointerToNonConstChar) {
+  char s[] = "hello";
+  char* p = s;
+  EXPECT_PRINT_TO_STRING_(p, "\"hello\"");
+}
+
+TEST(PrintToStringTest, EscapesForPointerToConstChar) {
+  const char* p = "hello\n";
+  EXPECT_PRINT_TO_STRING_(p, "\"hello\\n\"");
+}
+
+TEST(PrintToStringTest, EscapesForPointerToNonConstChar) {
+  char s[] = "hello\1";
+  char* p = s;
+  EXPECT_PRINT_TO_STRING_(p, "\"hello\\x1\"");
+}
+
+TEST(PrintToStringTest, WorksForArray) {
+  int n[3] = { 1, 2, 3 };
+  EXPECT_PRINT_TO_STRING_(n, "{ 1, 2, 3 }");
+}
+
+TEST(PrintToStringTest, WorksForCharArray) {
+  char s[] = "hello";
+  EXPECT_PRINT_TO_STRING_(s, "\"hello\"");
+}
+
+TEST(PrintToStringTest, WorksForCharArrayWithEmbeddedNul) {
+  const char str_with_nul[] = "hello\0 world";
+  EXPECT_PRINT_TO_STRING_(str_with_nul, "\"hello\\0 world\"");
+
+  char mutable_str_with_nul[] = "hello\0 world";
+  EXPECT_PRINT_TO_STRING_(mutable_str_with_nul, "\"hello\\0 world\"");
+}
+
+  TEST(PrintToStringTest, ContainsNonLatin) {
+  // Sanity test with valid UTF-8. Prints both in hex and as text.
+  std::string non_ascii_str = ::std::string("오전 4:30");
+  EXPECT_PRINT_TO_STRING_(non_ascii_str,
+                          "\"\\xEC\\x98\\xA4\\xEC\\xA0\\x84 4:30\"\n"
+                          "    As Text: \"오전 4:30\"");
+  non_ascii_str = ::std::string("From ä — ẑ");
+  EXPECT_PRINT_TO_STRING_(non_ascii_str,
+                          "\"From \\xC3\\xA4 \\xE2\\x80\\x94 \\xE1\\xBA\\x91\""
+                          "\n    As Text: \"From ä — ẑ\"");
+}
+
+TEST(IsValidUTF8Test, IllFormedUTF8) {
+  // The following test strings are ill-formed UTF-8 and are printed
+  // as hex only (or ASCII, in case of ASCII bytes) because IsValidUTF8() is
+  // expected to fail, thus output does not contain "As Text:".
+
+  static const char *const kTestdata[][2] = {
+    // 2-byte lead byte followed by a single-byte character.
+    {"\xC3\x74", "\"\\xC3t\""},
+    // Valid 2-byte character followed by an orphan trail byte.
+    {"\xC3\x84\xA4", "\"\\xC3\\x84\\xA4\""},
+    // Lead byte without trail byte.
+    {"abc\xC3", "\"abc\\xC3\""},
+    // 3-byte lead byte, single-byte character, orphan trail byte.
+    {"x\xE2\x70\x94", "\"x\\xE2p\\x94\""},
+    // Truncated 3-byte character.
+    {"\xE2\x80", "\"\\xE2\\x80\""},
+    // Truncated 3-byte character followed by valid 2-byte char.
+    {"\xE2\x80\xC3\x84", "\"\\xE2\\x80\\xC3\\x84\""},
+    // Truncated 3-byte character followed by a single-byte character.
+    {"\xE2\x80\x7A", "\"\\xE2\\x80z\""},
+    // 3-byte lead byte followed by valid 3-byte character.
+    {"\xE2\xE2\x80\x94", "\"\\xE2\\xE2\\x80\\x94\""},
+    // 4-byte lead byte followed by valid 3-byte character.
+    {"\xF0\xE2\x80\x94", "\"\\xF0\\xE2\\x80\\x94\""},
+    // Truncated 4-byte character.
+    {"\xF0\xE2\x80", "\"\\xF0\\xE2\\x80\""},
+     // Invalid UTF-8 byte sequences embedded in other chars.
+    {"abc\xE2\x80\x94\xC3\x74xyc", "\"abc\\xE2\\x80\\x94\\xC3txyc\""},
+    {"abc\xC3\x84\xE2\x80\xC3\x84xyz",
+     "\"abc\\xC3\\x84\\xE2\\x80\\xC3\\x84xyz\""},
+    // Non-shortest UTF-8 byte sequences are also ill-formed.
+    // The classics: xC0, xC1 lead byte.
+    {"\xC0\x80", "\"\\xC0\\x80\""},
+    {"\xC1\x81", "\"\\xC1\\x81\""},
+    // Non-shortest sequences.
+    {"\xE0\x80\x80", "\"\\xE0\\x80\\x80\""},
+    {"\xf0\x80\x80\x80", "\"\\xF0\\x80\\x80\\x80\""},
+    // Last valid code point before surrogate range, should be printed as text,
+    // too.
+    {"\xED\x9F\xBF", "\"\\xED\\x9F\\xBF\"\n    As Text: \"퟿\""},
+    // Start of surrogate lead. Surrogates are not printed as text.
+    {"\xED\xA0\x80", "\"\\xED\\xA0\\x80\""},
+    // Last non-private surrogate lead.
+    {"\xED\xAD\xBF", "\"\\xED\\xAD\\xBF\""},
+    // First private-use surrogate lead.
+    {"\xED\xAE\x80", "\"\\xED\\xAE\\x80\""},
+    // Last private-use surrogate lead.
+    {"\xED\xAF\xBF", "\"\\xED\\xAF\\xBF\""},
+    // Mid-point of surrogate trail.
+    {"\xED\xB3\xBF", "\"\\xED\\xB3\\xBF\""},
+    // First valid code point after surrogate range, should be printed as text,
+    // too.
+    {"\xEE\x80\x80", "\"\\xEE\\x80\\x80\"\n    As Text: \"\""}
+  };
+
+  for (int i = 0; i < int(sizeof(kTestdata)/sizeof(kTestdata[0])); ++i) {
+    EXPECT_PRINT_TO_STRING_(kTestdata[i][0], kTestdata[i][1]);
+  }
+}
+
+#undef EXPECT_PRINT_TO_STRING_
+
+TEST(UniversalTersePrintTest, WorksForNonReference) {
+  ::std::stringstream ss;
+  UniversalTersePrint(123, &ss);
+  EXPECT_EQ("123", ss.str());
+}
+
+TEST(UniversalTersePrintTest, WorksForReference) {
+  const int& n = 123;
+  ::std::stringstream ss;
+  UniversalTersePrint(n, &ss);
+  EXPECT_EQ("123", ss.str());
+}
+
+TEST(UniversalTersePrintTest, WorksForCString) {
+  const char* s1 = "abc";
+  ::std::stringstream ss1;
+  UniversalTersePrint(s1, &ss1);
+  EXPECT_EQ("\"abc\"", ss1.str());
+
+  char* s2 = const_cast<char*>(s1);
+  ::std::stringstream ss2;
+  UniversalTersePrint(s2, &ss2);
+  EXPECT_EQ("\"abc\"", ss2.str());
+
+  const char* s3 = nullptr;
+  ::std::stringstream ss3;
+  UniversalTersePrint(s3, &ss3);
+  EXPECT_EQ("NULL", ss3.str());
+}
+
+TEST(UniversalPrintTest, WorksForNonReference) {
+  ::std::stringstream ss;
+  UniversalPrint(123, &ss);
+  EXPECT_EQ("123", ss.str());
+}
+
+TEST(UniversalPrintTest, WorksForReference) {
+  const int& n = 123;
+  ::std::stringstream ss;
+  UniversalPrint(n, &ss);
+  EXPECT_EQ("123", ss.str());
+}
+
+TEST(UniversalPrintTest, WorksForPairWithConst) {
+  std::pair<const Wrapper<std::string>, int> p(Wrapper<std::string>("abc"), 1);
+  ::std::stringstream ss;
+  UniversalPrint(p, &ss);
+  EXPECT_EQ("(Wrapper(\"abc\"), 1)", ss.str());
+}
+
+TEST(UniversalPrintTest, WorksForCString) {
+  const char* s1 = "abc";
+  ::std::stringstream ss1;
+  UniversalPrint(s1, &ss1);
+  EXPECT_EQ(PrintPointer(s1) + " pointing to \"abc\"", std::string(ss1.str()));
+
+  char* s2 = const_cast<char*>(s1);
+  ::std::stringstream ss2;
+  UniversalPrint(s2, &ss2);
+  EXPECT_EQ(PrintPointer(s2) + " pointing to \"abc\"", std::string(ss2.str()));
+
+  const char* s3 = nullptr;
+  ::std::stringstream ss3;
+  UniversalPrint(s3, &ss3);
+  EXPECT_EQ("NULL", ss3.str());
+}
+
+TEST(UniversalPrintTest, WorksForCharArray) {
+  const char str[] = "\"Line\0 1\"\nLine 2";
+  ::std::stringstream ss1;
+  UniversalPrint(str, &ss1);
+  EXPECT_EQ("\"\\\"Line\\0 1\\\"\\nLine 2\"", ss1.str());
+
+  const char mutable_str[] = "\"Line\0 1\"\nLine 2";
+  ::std::stringstream ss2;
+  UniversalPrint(mutable_str, &ss2);
+  EXPECT_EQ("\"\\\"Line\\0 1\\\"\\nLine 2\"", ss2.str());
+}
+
+TEST(UniversalPrintTest, IncompleteType) {
+  struct Incomplete;
+  char some_object = 0;
+  EXPECT_EQ("(incomplete type)",
+            PrintToString(reinterpret_cast<Incomplete&>(some_object)));
+}
+
+TEST(UniversalPrintTest, SmartPointers) {
+  EXPECT_EQ("(nullptr)", PrintToString(std::unique_ptr<int>()));
+  std::unique_ptr<int> p(new int(17));
+  EXPECT_EQ("(ptr = " + PrintPointer(p.get()) + ", value = 17)",
+            PrintToString(p));
+  std::unique_ptr<int[]> p2(new int[2]);
+  EXPECT_EQ("(" + PrintPointer(p2.get()) + ")", PrintToString(p2));
+
+  EXPECT_EQ("(nullptr)", PrintToString(std::shared_ptr<int>()));
+  std::shared_ptr<int> p3(new int(1979));
+  EXPECT_EQ("(ptr = " + PrintPointer(p3.get()) + ", value = 1979)",
+            PrintToString(p3));
+#if __cpp_lib_shared_ptr_arrays >= 201611L
+  std::shared_ptr<int[]> p4(new int[2]);
+  EXPECT_EQ("(" + PrintPointer(p4.get()) + ")", PrintToString(p4));
+#endif
+
+  // modifiers
+  EXPECT_EQ("(nullptr)", PrintToString(std::unique_ptr<int>()));
+  EXPECT_EQ("(nullptr)", PrintToString(std::unique_ptr<const int>()));
+  EXPECT_EQ("(nullptr)", PrintToString(std::unique_ptr<volatile int>()));
+  EXPECT_EQ("(nullptr)", PrintToString(std::unique_ptr<volatile const int>()));
+  EXPECT_EQ("(nullptr)", PrintToString(std::unique_ptr<int[]>()));
+  EXPECT_EQ("(nullptr)", PrintToString(std::unique_ptr<const int[]>()));
+  EXPECT_EQ("(nullptr)", PrintToString(std::unique_ptr<volatile int[]>()));
+  EXPECT_EQ("(nullptr)",
+            PrintToString(std::unique_ptr<volatile const int[]>()));
+  EXPECT_EQ("(nullptr)", PrintToString(std::shared_ptr<int>()));
+  EXPECT_EQ("(nullptr)", PrintToString(std::shared_ptr<const int>()));
+  EXPECT_EQ("(nullptr)", PrintToString(std::shared_ptr<volatile int>()));
+  EXPECT_EQ("(nullptr)", PrintToString(std::shared_ptr<volatile const int>()));
+#if __cpp_lib_shared_ptr_arrays >= 201611L
+  EXPECT_EQ("(nullptr)", PrintToString(std::shared_ptr<int[]>()));
+  EXPECT_EQ("(nullptr)", PrintToString(std::shared_ptr<const int[]>()));
+  EXPECT_EQ("(nullptr)", PrintToString(std::shared_ptr<volatile int[]>()));
+  EXPECT_EQ("(nullptr)",
+            PrintToString(std::shared_ptr<volatile const int[]>()));
+#endif
+
+  // void
+  EXPECT_EQ("(nullptr)", PrintToString(std::unique_ptr<void, void (*)(void*)>(
+                             nullptr, nullptr)));
+  EXPECT_EQ("(" + PrintPointer(p.get()) + ")",
+            PrintToString(
+                std::unique_ptr<void, void (*)(void*)>(p.get(), [](void*) {})));
+  EXPECT_EQ("(nullptr)", PrintToString(std::shared_ptr<void>()));
+  EXPECT_EQ("(" + PrintPointer(p.get()) + ")",
+            PrintToString(std::shared_ptr<void>(p.get(), [](void*) {})));
+}
+
+TEST(UniversalTersePrintTupleFieldsToStringsTestWithStd, PrintsEmptyTuple) {
+  Strings result = UniversalTersePrintTupleFieldsToStrings(::std::make_tuple());
+  EXPECT_EQ(0u, result.size());
+}
+
+TEST(UniversalTersePrintTupleFieldsToStringsTestWithStd, PrintsOneTuple) {
+  Strings result = UniversalTersePrintTupleFieldsToStrings(
+      ::std::make_tuple(1));
+  ASSERT_EQ(1u, result.size());
+  EXPECT_EQ("1", result[0]);
+}
+
+TEST(UniversalTersePrintTupleFieldsToStringsTestWithStd, PrintsTwoTuple) {
+  Strings result = UniversalTersePrintTupleFieldsToStrings(
+      ::std::make_tuple(1, 'a'));
+  ASSERT_EQ(2u, result.size());
+  EXPECT_EQ("1", result[0]);
+  EXPECT_EQ("'a' (97, 0x61)", result[1]);
+}
+
+TEST(UniversalTersePrintTupleFieldsToStringsTestWithStd, PrintsTersely) {
+  const int n = 1;
+  Strings result = UniversalTersePrintTupleFieldsToStrings(
+      ::std::tuple<const int&, const char*>(n, "a"));
+  ASSERT_EQ(2u, result.size());
+  EXPECT_EQ("1", result[0]);
+  EXPECT_EQ("\"a\"", result[1]);
+}
+
+#if GTEST_INTERNAL_HAS_ANY
+class PrintAnyTest : public ::testing::Test {
+ protected:
+  template <typename T>
+  static std::string ExpectedTypeName() {
+#if GTEST_HAS_RTTI
+    return internal::GetTypeName<T>();
+#else
+    return "<unknown_type>";
+#endif  // GTEST_HAS_RTTI
+  }
+};
+
+TEST_F(PrintAnyTest, Empty) {
+  internal::Any any;
+  EXPECT_EQ("no value", PrintToString(any));
+}
+
+TEST_F(PrintAnyTest, NonEmpty) {
+  internal::Any any;
+  constexpr int val1 = 10;
+  const std::string val2 = "content";
+
+  any = val1;
+  EXPECT_EQ("value of type " + ExpectedTypeName<int>(), PrintToString(any));
+
+  any = val2;
+  EXPECT_EQ("value of type " + ExpectedTypeName<std::string>(),
+            PrintToString(any));
+}
+#endif  // GTEST_INTERNAL_HAS_ANY
+
+#if GTEST_INTERNAL_HAS_OPTIONAL
+TEST(PrintOptionalTest, Basic) {
+  internal::Optional<int> value;
+  EXPECT_EQ("(nullopt)", PrintToString(value));
+  value = {7};
+  EXPECT_EQ("(7)", PrintToString(value));
+  EXPECT_EQ("(1.1)", PrintToString(internal::Optional<double>{1.1}));
+  EXPECT_EQ("(\"A\")", PrintToString(internal::Optional<std::string>{"A"}));
+}
+#endif  // GTEST_INTERNAL_HAS_OPTIONAL
+
+#if GTEST_INTERNAL_HAS_VARIANT
+struct NonPrintable {
+  unsigned char contents = 17;
+};
+
+TEST(PrintOneofTest, Basic) {
+  using Type = internal::Variant<int, StreamableInGlobal, NonPrintable>;
+  EXPECT_EQ("('int(index = 0)' with value 7)", PrintToString(Type(7)));
+  EXPECT_EQ("('StreamableInGlobal(index = 1)' with value StreamableInGlobal)",
+            PrintToString(Type(StreamableInGlobal{})));
+  EXPECT_EQ(
+      "('testing::gtest_printers_test::NonPrintable(index = 2)' with value "
+      "1-byte object <11>)",
+      PrintToString(Type(NonPrintable{})));
+}
+#endif  // GTEST_INTERNAL_HAS_VARIANT
+namespace {
+class string_ref;
+
+/**
+ * This is a synthetic pointer to a fixed size string.
+ */
+class string_ptr {
+ public:
+  string_ptr(const char* data, size_t size) : data_(data), size_(size) {}
+
+  string_ptr& operator++() noexcept {
+    data_ += size_;
+    return *this;
+  }
+
+  string_ref operator*() const noexcept;
+
+ private:
+  const char* data_;
+  size_t size_;
+};
+
+/**
+ * This is a synthetic reference of a fixed size string.
+ */
+class string_ref {
+ public:
+  string_ref(const char* data, size_t size) : data_(data), size_(size) {}
+
+  string_ptr operator&() const noexcept { return {data_, size_}; }  // NOLINT
+
+  bool operator==(const char* s) const noexcept {
+    if (size_ > 0 && data_[size_ - 1] != 0) {
+      return std::string(data_, size_) == std::string(s);
+    } else {
+      return std::string(data_) == std::string(s);
+    }
+  }
+
+ private:
+  const char* data_;
+  size_t size_;
+};
+
+string_ref string_ptr::operator*() const noexcept { return {data_, size_}; }
+
+TEST(string_ref, compare) {
+  const char* s = "alex\0davidjohn\0";
+  string_ptr ptr(s, 5);
+  EXPECT_EQ(*ptr, "alex");
+  EXPECT_TRUE(*ptr == "alex");
+  ++ptr;
+  EXPECT_EQ(*ptr, "david");
+  EXPECT_TRUE(*ptr == "david");
+  ++ptr;
+  EXPECT_EQ(*ptr, "john");
+}
+
+}  // namespace
+
+}  // namespace gtest_printers_test
+}  // namespace testing
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-setuptestsuite-test.py b/leveldb_base/third_party/googletest/googletest/test/googletest-setuptestsuite-test.py
new file mode 100644
index 0000000..c82162f
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-setuptestsuite-test.py
@@ -0,0 +1,54 @@
+#!/usr/bin/env python
+#
+# Copyright 2019, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Verifies that SetUpTestSuite and TearDownTestSuite errors are noticed."""
+
+import gtest_test_utils
+
+COMMAND = gtest_test_utils.GetTestExecutablePath(
+    'googletest-setuptestsuite-test_')
+
+
+class GTestSetUpTestSuiteTest(gtest_test_utils.TestCase):
+
+  def testSetupErrorAndTearDownError(self):
+    p = gtest_test_utils.Subprocess(COMMAND)
+    self.assertNotEqual(p.exit_code, 0, msg=p.output)
+
+    self.assertIn(
+        '[  FAILED  ] SetupFailTest: SetUpTestSuite or TearDownTestSuite\n'
+        '[  FAILED  ] TearDownFailTest: SetUpTestSuite or TearDownTestSuite\n'
+        '\n'
+        ' 2 FAILED TEST SUITES\n',
+        p.output)
+
+if __name__ == '__main__':
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-setuptestsuite-test_.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-setuptestsuite-test_.cc
new file mode 100644
index 0000000..a4bc4ef
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-setuptestsuite-test_.cc
@@ -0,0 +1,49 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+#include "gtest/gtest.h"
+
+class SetupFailTest : public ::testing::Test {
+ protected:
+  static void SetUpTestSuite() {
+    ASSERT_EQ("", "SET_UP_FAIL");
+  }
+};
+
+TEST_F(SetupFailTest, NoopPassingTest) {}
+
+class TearDownFailTest : public ::testing::Test {
+ protected:
+  static void TearDownTestSuite() {
+    ASSERT_EQ("", "TEAR_DOWN_FAIL");
+  }
+};
+
+TEST_F(TearDownFailTest, NoopPassingTest) {}
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-shuffle-test.py b/leveldb_base/third_party/googletest/googletest/test/googletest-shuffle-test.py
new file mode 100644
index 0000000..573cc5e
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-shuffle-test.py
@@ -0,0 +1,323 @@
+#!/usr/bin/env python
+#
+# Copyright 2009 Google Inc. All Rights Reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Verifies that test shuffling works."""
+
+import os
+import gtest_test_utils
+
+# Command to run the googletest-shuffle-test_ program.
+COMMAND = gtest_test_utils.GetTestExecutablePath('googletest-shuffle-test_')
+
+# The environment variables for test sharding.
+TOTAL_SHARDS_ENV_VAR = 'GTEST_TOTAL_SHARDS'
+SHARD_INDEX_ENV_VAR = 'GTEST_SHARD_INDEX'
+
+TEST_FILTER = 'A*.A:A*.B:C*'
+
+ALL_TESTS = []
+ACTIVE_TESTS = []
+FILTERED_TESTS = []
+SHARDED_TESTS = []
+
+SHUFFLED_ALL_TESTS = []
+SHUFFLED_ACTIVE_TESTS = []
+SHUFFLED_FILTERED_TESTS = []
+SHUFFLED_SHARDED_TESTS = []
+
+
+def AlsoRunDisabledTestsFlag():
+  return '--gtest_also_run_disabled_tests'
+
+
+def FilterFlag(test_filter):
+  return '--gtest_filter=%s' % (test_filter,)
+
+
+def RepeatFlag(n):
+  return '--gtest_repeat=%s' % (n,)
+
+
+def ShuffleFlag():
+  return '--gtest_shuffle'
+
+
+def RandomSeedFlag(n):
+  return '--gtest_random_seed=%s' % (n,)
+
+
+def RunAndReturnOutput(extra_env, args):
+  """Runs the test program and returns its output."""
+
+  environ_copy = os.environ.copy()
+  environ_copy.update(extra_env)
+
+  return gtest_test_utils.Subprocess([COMMAND] + args, env=environ_copy).output
+
+
+def GetTestsForAllIterations(extra_env, args):
+  """Runs the test program and returns a list of test lists.
+
+  Args:
+    extra_env: a map from environment variables to their values
+    args: command line flags to pass to googletest-shuffle-test_
+
+  Returns:
+    A list where the i-th element is the list of tests run in the i-th
+    test iteration.
+  """
+
+  test_iterations = []
+  for line in RunAndReturnOutput(extra_env, args).split('\n'):
+    if line.startswith('----'):
+      tests = []
+      test_iterations.append(tests)
+    elif line.strip():
+      tests.append(line.strip())  # 'TestCaseName.TestName'
+
+  return test_iterations
+
+
+def GetTestCases(tests):
+  """Returns a list of test cases in the given full test names.
+
+  Args:
+    tests: a list of full test names
+
+  Returns:
+    A list of test cases from 'tests', in their original order.
+    Consecutive duplicates are removed.
+  """
+
+  test_cases = []
+  for test in tests:
+    test_case = test.split('.')[0]
+    if not test_case in test_cases:
+      test_cases.append(test_case)
+
+  return test_cases
+
+
+def CalculateTestLists():
+  """Calculates the list of tests run under different flags."""
+
+  if not ALL_TESTS:
+    ALL_TESTS.extend(
+        GetTestsForAllIterations({}, [AlsoRunDisabledTestsFlag()])[0])
+
+  if not ACTIVE_TESTS:
+    ACTIVE_TESTS.extend(GetTestsForAllIterations({}, [])[0])
+
+  if not FILTERED_TESTS:
+    FILTERED_TESTS.extend(
+        GetTestsForAllIterations({}, [FilterFlag(TEST_FILTER)])[0])
+
+  if not SHARDED_TESTS:
+    SHARDED_TESTS.extend(
+        GetTestsForAllIterations({TOTAL_SHARDS_ENV_VAR: '3',
+                                  SHARD_INDEX_ENV_VAR: '1'},
+                                 [])[0])
+
+  if not SHUFFLED_ALL_TESTS:
+    SHUFFLED_ALL_TESTS.extend(GetTestsForAllIterations(
+        {}, [AlsoRunDisabledTestsFlag(), ShuffleFlag(), RandomSeedFlag(1)])[0])
+
+  if not SHUFFLED_ACTIVE_TESTS:
+    SHUFFLED_ACTIVE_TESTS.extend(GetTestsForAllIterations(
+        {}, [ShuffleFlag(), RandomSeedFlag(1)])[0])
+
+  if not SHUFFLED_FILTERED_TESTS:
+    SHUFFLED_FILTERED_TESTS.extend(GetTestsForAllIterations(
+        {}, [ShuffleFlag(), RandomSeedFlag(1), FilterFlag(TEST_FILTER)])[0])
+
+  if not SHUFFLED_SHARDED_TESTS:
+    SHUFFLED_SHARDED_TESTS.extend(
+        GetTestsForAllIterations({TOTAL_SHARDS_ENV_VAR: '3',
+                                  SHARD_INDEX_ENV_VAR: '1'},
+                                 [ShuffleFlag(), RandomSeedFlag(1)])[0])
+
+
+class GTestShuffleUnitTest(gtest_test_utils.TestCase):
+  """Tests test shuffling."""
+
+  def setUp(self):
+    CalculateTestLists()
+
+  def testShufflePreservesNumberOfTests(self):
+    self.assertEqual(len(ALL_TESTS), len(SHUFFLED_ALL_TESTS))
+    self.assertEqual(len(ACTIVE_TESTS), len(SHUFFLED_ACTIVE_TESTS))
+    self.assertEqual(len(FILTERED_TESTS), len(SHUFFLED_FILTERED_TESTS))
+    self.assertEqual(len(SHARDED_TESTS), len(SHUFFLED_SHARDED_TESTS))
+
+  def testShuffleChangesTestOrder(self):
+    self.assert_(SHUFFLED_ALL_TESTS != ALL_TESTS, SHUFFLED_ALL_TESTS)
+    self.assert_(SHUFFLED_ACTIVE_TESTS != ACTIVE_TESTS, SHUFFLED_ACTIVE_TESTS)
+    self.assert_(SHUFFLED_FILTERED_TESTS != FILTERED_TESTS,
+                 SHUFFLED_FILTERED_TESTS)
+    self.assert_(SHUFFLED_SHARDED_TESTS != SHARDED_TESTS,
+                 SHUFFLED_SHARDED_TESTS)
+
+  def testShuffleChangesTestCaseOrder(self):
+    self.assert_(GetTestCases(SHUFFLED_ALL_TESTS) != GetTestCases(ALL_TESTS),
+                 GetTestCases(SHUFFLED_ALL_TESTS))
+    self.assert_(
+        GetTestCases(SHUFFLED_ACTIVE_TESTS) != GetTestCases(ACTIVE_TESTS),
+        GetTestCases(SHUFFLED_ACTIVE_TESTS))
+    self.assert_(
+        GetTestCases(SHUFFLED_FILTERED_TESTS) != GetTestCases(FILTERED_TESTS),
+        GetTestCases(SHUFFLED_FILTERED_TESTS))
+    self.assert_(
+        GetTestCases(SHUFFLED_SHARDED_TESTS) != GetTestCases(SHARDED_TESTS),
+        GetTestCases(SHUFFLED_SHARDED_TESTS))
+
+  def testShuffleDoesNotRepeatTest(self):
+    for test in SHUFFLED_ALL_TESTS:
+      self.assertEqual(1, SHUFFLED_ALL_TESTS.count(test),
+                       '%s appears more than once' % (test,))
+    for test in SHUFFLED_ACTIVE_TESTS:
+      self.assertEqual(1, SHUFFLED_ACTIVE_TESTS.count(test),
+                       '%s appears more than once' % (test,))
+    for test in SHUFFLED_FILTERED_TESTS:
+      self.assertEqual(1, SHUFFLED_FILTERED_TESTS.count(test),
+                       '%s appears more than once' % (test,))
+    for test in SHUFFLED_SHARDED_TESTS:
+      self.assertEqual(1, SHUFFLED_SHARDED_TESTS.count(test),
+                       '%s appears more than once' % (test,))
+
+  def testShuffleDoesNotCreateNewTest(self):
+    for test in SHUFFLED_ALL_TESTS:
+      self.assert_(test in ALL_TESTS, '%s is an invalid test' % (test,))
+    for test in SHUFFLED_ACTIVE_TESTS:
+      self.assert_(test in ACTIVE_TESTS, '%s is an invalid test' % (test,))
+    for test in SHUFFLED_FILTERED_TESTS:
+      self.assert_(test in FILTERED_TESTS, '%s is an invalid test' % (test,))
+    for test in SHUFFLED_SHARDED_TESTS:
+      self.assert_(test in SHARDED_TESTS, '%s is an invalid test' % (test,))
+
+  def testShuffleIncludesAllTests(self):
+    for test in ALL_TESTS:
+      self.assert_(test in SHUFFLED_ALL_TESTS, '%s is missing' % (test,))
+    for test in ACTIVE_TESTS:
+      self.assert_(test in SHUFFLED_ACTIVE_TESTS, '%s is missing' % (test,))
+    for test in FILTERED_TESTS:
+      self.assert_(test in SHUFFLED_FILTERED_TESTS, '%s is missing' % (test,))
+    for test in SHARDED_TESTS:
+      self.assert_(test in SHUFFLED_SHARDED_TESTS, '%s is missing' % (test,))
+
+  def testShuffleLeavesDeathTestsAtFront(self):
+    non_death_test_found = False
+    for test in SHUFFLED_ACTIVE_TESTS:
+      if 'DeathTest.' in test:
+        self.assert_(not non_death_test_found,
+                     '%s appears after a non-death test' % (test,))
+      else:
+        non_death_test_found = True
+
+  def _VerifyTestCasesDoNotInterleave(self, tests):
+    test_cases = []
+    for test in tests:
+      [test_case, _] = test.split('.')
+      if test_cases and test_cases[-1] != test_case:
+        test_cases.append(test_case)
+        self.assertEqual(1, test_cases.count(test_case),
+                         'Test case %s is not grouped together in %s' %
+                         (test_case, tests))
+
+  def testShuffleDoesNotInterleaveTestCases(self):
+    self._VerifyTestCasesDoNotInterleave(SHUFFLED_ALL_TESTS)
+    self._VerifyTestCasesDoNotInterleave(SHUFFLED_ACTIVE_TESTS)
+    self._VerifyTestCasesDoNotInterleave(SHUFFLED_FILTERED_TESTS)
+    self._VerifyTestCasesDoNotInterleave(SHUFFLED_SHARDED_TESTS)
+
+  def testShuffleRestoresOrderAfterEachIteration(self):
+    # Get the test lists in all 3 iterations, using random seed 1, 2,
+    # and 3 respectively.  Google Test picks a different seed in each
+    # iteration, and this test depends on the current implementation
+    # picking successive numbers.  This dependency is not ideal, but
+    # makes the test much easier to write.
+    [tests_in_iteration1, tests_in_iteration2, tests_in_iteration3] = (
+        GetTestsForAllIterations(
+            {}, [ShuffleFlag(), RandomSeedFlag(1), RepeatFlag(3)]))
+
+    # Make sure running the tests with random seed 1 gets the same
+    # order as in iteration 1 above.
+    [tests_with_seed1] = GetTestsForAllIterations(
+        {}, [ShuffleFlag(), RandomSeedFlag(1)])
+    self.assertEqual(tests_in_iteration1, tests_with_seed1)
+
+    # Make sure running the tests with random seed 2 gets the same
+    # order as in iteration 2 above.  Success means that Google Test
+    # correctly restores the test order before re-shuffling at the
+    # beginning of iteration 2.
+    [tests_with_seed2] = GetTestsForAllIterations(
+        {}, [ShuffleFlag(), RandomSeedFlag(2)])
+    self.assertEqual(tests_in_iteration2, tests_with_seed2)
+
+    # Make sure running the tests with random seed 3 gets the same
+    # order as in iteration 3 above.  Success means that Google Test
+    # correctly restores the test order before re-shuffling at the
+    # beginning of iteration 3.
+    [tests_with_seed3] = GetTestsForAllIterations(
+        {}, [ShuffleFlag(), RandomSeedFlag(3)])
+    self.assertEqual(tests_in_iteration3, tests_with_seed3)
+
+  def testShuffleGeneratesNewOrderInEachIteration(self):
+    [tests_in_iteration1, tests_in_iteration2, tests_in_iteration3] = (
+        GetTestsForAllIterations(
+            {}, [ShuffleFlag(), RandomSeedFlag(1), RepeatFlag(3)]))
+
+    self.assert_(tests_in_iteration1 != tests_in_iteration2,
+                 tests_in_iteration1)
+    self.assert_(tests_in_iteration1 != tests_in_iteration3,
+                 tests_in_iteration1)
+    self.assert_(tests_in_iteration2 != tests_in_iteration3,
+                 tests_in_iteration2)
+
+  def testShuffleShardedTestsPreservesPartition(self):
+    # If we run M tests on N shards, the same M tests should be run in
+    # total, regardless of the random seeds used by the shards.
+    [tests1] = GetTestsForAllIterations({TOTAL_SHARDS_ENV_VAR: '3',
+                                         SHARD_INDEX_ENV_VAR: '0'},
+                                        [ShuffleFlag(), RandomSeedFlag(1)])
+    [tests2] = GetTestsForAllIterations({TOTAL_SHARDS_ENV_VAR: '3',
+                                         SHARD_INDEX_ENV_VAR: '1'},
+                                        [ShuffleFlag(), RandomSeedFlag(20)])
+    [tests3] = GetTestsForAllIterations({TOTAL_SHARDS_ENV_VAR: '3',
+                                         SHARD_INDEX_ENV_VAR: '2'},
+                                        [ShuffleFlag(), RandomSeedFlag(25)])
+    sorted_sharded_tests = tests1 + tests2 + tests3
+    sorted_sharded_tests.sort()
+    sorted_active_tests = []
+    sorted_active_tests.extend(ACTIVE_TESTS)
+    sorted_active_tests.sort()
+    self.assertEqual(sorted_active_tests, sorted_sharded_tests)
+
+if __name__ == '__main__':
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-shuffle-test_.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-shuffle-test_.cc
new file mode 100644
index 0000000..4505663
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-shuffle-test_.cc
@@ -0,0 +1,101 @@
+// Copyright 2009, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Verifies that test shuffling works.
+
+#include "gtest/gtest.h"
+
+namespace {
+
+using ::testing::EmptyTestEventListener;
+using ::testing::InitGoogleTest;
+using ::testing::Message;
+using ::testing::Test;
+using ::testing::TestEventListeners;
+using ::testing::TestInfo;
+using ::testing::UnitTest;
+
+// The test methods are empty, as the sole purpose of this program is
+// to print the test names before/after shuffling.
+
+class A : public Test {};
+TEST_F(A, A) {}
+TEST_F(A, B) {}
+
+TEST(ADeathTest, A) {}
+TEST(ADeathTest, B) {}
+TEST(ADeathTest, C) {}
+
+TEST(B, A) {}
+TEST(B, B) {}
+TEST(B, C) {}
+TEST(B, DISABLED_D) {}
+TEST(B, DISABLED_E) {}
+
+TEST(BDeathTest, A) {}
+TEST(BDeathTest, B) {}
+
+TEST(C, A) {}
+TEST(C, B) {}
+TEST(C, C) {}
+TEST(C, DISABLED_D) {}
+
+TEST(CDeathTest, A) {}
+
+TEST(DISABLED_D, A) {}
+TEST(DISABLED_D, DISABLED_B) {}
+
+// This printer prints the full test names only, starting each test
+// iteration with a "----" marker.
+class TestNamePrinter : public EmptyTestEventListener {
+ public:
+  void OnTestIterationStart(const UnitTest& /* unit_test */,
+                            int /* iteration */) override {
+    printf("----\n");
+  }
+
+  void OnTestStart(const TestInfo& test_info) override {
+    printf("%s.%s\n", test_info.test_suite_name(), test_info.name());
+  }
+};
+
+}  // namespace
+
+int main(int argc, char **argv) {
+  InitGoogleTest(&argc, argv);
+
+  // Replaces the default printer with TestNamePrinter, which prints
+  // the test name only.
+  TestEventListeners& listeners = UnitTest::GetInstance()->listeners();
+  delete listeners.Release(listeners.default_result_printer());
+  listeners.Append(new TestNamePrinter);
+
+  return RUN_ALL_TESTS();
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-test-part-test.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-test-part-test.cc
new file mode 100644
index 0000000..44cf7ca
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-test-part-test.cc
@@ -0,0 +1,230 @@
+// Copyright 2008 Google Inc.
+// All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "gtest/gtest-test-part.h"
+
+#include "gtest/gtest.h"
+
+using testing::Message;
+using testing::Test;
+using testing::TestPartResult;
+using testing::TestPartResultArray;
+
+namespace {
+
+// Tests the TestPartResult class.
+
+// The test fixture for testing TestPartResult.
+class TestPartResultTest : public Test {
+ protected:
+  TestPartResultTest()
+      : r1_(TestPartResult::kSuccess, "foo/bar.cc", 10, "Success!"),
+        r2_(TestPartResult::kNonFatalFailure, "foo/bar.cc", -1, "Failure!"),
+        r3_(TestPartResult::kFatalFailure, nullptr, -1, "Failure!"),
+        r4_(TestPartResult::kSkip, "foo/bar.cc", 2, "Skipped!") {}
+
+  TestPartResult r1_, r2_, r3_, r4_;
+};
+
+
+TEST_F(TestPartResultTest, ConstructorWorks) {
+  Message message;
+  message << "something is terribly wrong";
+  message << static_cast<const char*>(testing::internal::kStackTraceMarker);
+  message << "some unimportant stack trace";
+
+  const TestPartResult result(TestPartResult::kNonFatalFailure,
+                              "some_file.cc",
+                              42,
+                              message.GetString().c_str());
+
+  EXPECT_EQ(TestPartResult::kNonFatalFailure, result.type());
+  EXPECT_STREQ("some_file.cc", result.file_name());
+  EXPECT_EQ(42, result.line_number());
+  EXPECT_STREQ(message.GetString().c_str(), result.message());
+  EXPECT_STREQ("something is terribly wrong", result.summary());
+}
+
+TEST_F(TestPartResultTest, ResultAccessorsWork) {
+  const TestPartResult success(TestPartResult::kSuccess,
+                               "file.cc",
+                               42,
+                               "message");
+  EXPECT_TRUE(success.passed());
+  EXPECT_FALSE(success.failed());
+  EXPECT_FALSE(success.nonfatally_failed());
+  EXPECT_FALSE(success.fatally_failed());
+  EXPECT_FALSE(success.skipped());
+
+  const TestPartResult nonfatal_failure(TestPartResult::kNonFatalFailure,
+                                        "file.cc",
+                                        42,
+                                        "message");
+  EXPECT_FALSE(nonfatal_failure.passed());
+  EXPECT_TRUE(nonfatal_failure.failed());
+  EXPECT_TRUE(nonfatal_failure.nonfatally_failed());
+  EXPECT_FALSE(nonfatal_failure.fatally_failed());
+  EXPECT_FALSE(nonfatal_failure.skipped());
+
+  const TestPartResult fatal_failure(TestPartResult::kFatalFailure,
+                                     "file.cc",
+                                     42,
+                                     "message");
+  EXPECT_FALSE(fatal_failure.passed());
+  EXPECT_TRUE(fatal_failure.failed());
+  EXPECT_FALSE(fatal_failure.nonfatally_failed());
+  EXPECT_TRUE(fatal_failure.fatally_failed());
+  EXPECT_FALSE(fatal_failure.skipped());
+
+  const TestPartResult skip(TestPartResult::kSkip, "file.cc", 42, "message");
+  EXPECT_FALSE(skip.passed());
+  EXPECT_FALSE(skip.failed());
+  EXPECT_FALSE(skip.nonfatally_failed());
+  EXPECT_FALSE(skip.fatally_failed());
+  EXPECT_TRUE(skip.skipped());
+}
+
+// Tests TestPartResult::type().
+TEST_F(TestPartResultTest, type) {
+  EXPECT_EQ(TestPartResult::kSuccess, r1_.type());
+  EXPECT_EQ(TestPartResult::kNonFatalFailure, r2_.type());
+  EXPECT_EQ(TestPartResult::kFatalFailure, r3_.type());
+  EXPECT_EQ(TestPartResult::kSkip, r4_.type());
+}
+
+// Tests TestPartResult::file_name().
+TEST_F(TestPartResultTest, file_name) {
+  EXPECT_STREQ("foo/bar.cc", r1_.file_name());
+  EXPECT_STREQ(nullptr, r3_.file_name());
+  EXPECT_STREQ("foo/bar.cc", r4_.file_name());
+}
+
+// Tests TestPartResult::line_number().
+TEST_F(TestPartResultTest, line_number) {
+  EXPECT_EQ(10, r1_.line_number());
+  EXPECT_EQ(-1, r2_.line_number());
+  EXPECT_EQ(2, r4_.line_number());
+}
+
+// Tests TestPartResult::message().
+TEST_F(TestPartResultTest, message) {
+  EXPECT_STREQ("Success!", r1_.message());
+  EXPECT_STREQ("Skipped!", r4_.message());
+}
+
+// Tests TestPartResult::passed().
+TEST_F(TestPartResultTest, Passed) {
+  EXPECT_TRUE(r1_.passed());
+  EXPECT_FALSE(r2_.passed());
+  EXPECT_FALSE(r3_.passed());
+  EXPECT_FALSE(r4_.passed());
+}
+
+// Tests TestPartResult::failed().
+TEST_F(TestPartResultTest, Failed) {
+  EXPECT_FALSE(r1_.failed());
+  EXPECT_TRUE(r2_.failed());
+  EXPECT_TRUE(r3_.failed());
+  EXPECT_FALSE(r4_.failed());
+}
+
+// Tests TestPartResult::failed().
+TEST_F(TestPartResultTest, Skipped) {
+  EXPECT_FALSE(r1_.skipped());
+  EXPECT_FALSE(r2_.skipped());
+  EXPECT_FALSE(r3_.skipped());
+  EXPECT_TRUE(r4_.skipped());
+}
+
+// Tests TestPartResult::fatally_failed().
+TEST_F(TestPartResultTest, FatallyFailed) {
+  EXPECT_FALSE(r1_.fatally_failed());
+  EXPECT_FALSE(r2_.fatally_failed());
+  EXPECT_TRUE(r3_.fatally_failed());
+  EXPECT_FALSE(r4_.fatally_failed());
+}
+
+// Tests TestPartResult::nonfatally_failed().
+TEST_F(TestPartResultTest, NonfatallyFailed) {
+  EXPECT_FALSE(r1_.nonfatally_failed());
+  EXPECT_TRUE(r2_.nonfatally_failed());
+  EXPECT_FALSE(r3_.nonfatally_failed());
+  EXPECT_FALSE(r4_.nonfatally_failed());
+}
+
+// Tests the TestPartResultArray class.
+
+class TestPartResultArrayTest : public Test {
+ protected:
+  TestPartResultArrayTest()
+      : r1_(TestPartResult::kNonFatalFailure, "foo/bar.cc", -1, "Failure 1"),
+        r2_(TestPartResult::kFatalFailure, "foo/bar.cc", -1, "Failure 2") {}
+
+  const TestPartResult r1_, r2_;
+};
+
+// Tests that TestPartResultArray initially has size 0.
+TEST_F(TestPartResultArrayTest, InitialSizeIsZero) {
+  TestPartResultArray results;
+  EXPECT_EQ(0, results.size());
+}
+
+// Tests that TestPartResultArray contains the given TestPartResult
+// after one Append() operation.
+TEST_F(TestPartResultArrayTest, ContainsGivenResultAfterAppend) {
+  TestPartResultArray results;
+  results.Append(r1_);
+  EXPECT_EQ(1, results.size());
+  EXPECT_STREQ("Failure 1", results.GetTestPartResult(0).message());
+}
+
+// Tests that TestPartResultArray contains the given TestPartResults
+// after two Append() operations.
+TEST_F(TestPartResultArrayTest, ContainsGivenResultsAfterTwoAppends) {
+  TestPartResultArray results;
+  results.Append(r1_);
+  results.Append(r2_);
+  EXPECT_EQ(2, results.size());
+  EXPECT_STREQ("Failure 1", results.GetTestPartResult(0).message());
+  EXPECT_STREQ("Failure 2", results.GetTestPartResult(1).message());
+}
+
+typedef TestPartResultArrayTest TestPartResultArrayDeathTest;
+
+// Tests that the program dies when GetTestPartResult() is called with
+// an invalid index.
+TEST_F(TestPartResultArrayDeathTest, DiesWhenIndexIsOutOfBound) {
+  TestPartResultArray results;
+  results.Append(r1_);
+
+  EXPECT_DEATH_IF_SUPPORTED(results.GetTestPartResult(-1), "");
+  EXPECT_DEATH_IF_SUPPORTED(results.GetTestPartResult(1), "");
+}
+
+}  // namespace
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-throw-on-failure-test.py b/leveldb_base/third_party/googletest/googletest/test/googletest-throw-on-failure-test.py
new file mode 100644
index 0000000..ea627c4
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-throw-on-failure-test.py
@@ -0,0 +1,168 @@
+#!/usr/bin/env python
+#
+# Copyright 2009, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Tests Google Test's throw-on-failure mode with exceptions disabled.
+
+This script invokes googletest-throw-on-failure-test_ (a program written with
+Google Test) with different environments and command line flags.
+"""
+
+import os
+import gtest_test_utils
+
+
+# Constants.
+
+# The command line flag for enabling/disabling the throw-on-failure mode.
+THROW_ON_FAILURE = 'gtest_throw_on_failure'
+
+# Path to the googletest-throw-on-failure-test_ program, compiled with
+# exceptions disabled.
+EXE_PATH = gtest_test_utils.GetTestExecutablePath(
+    'googletest-throw-on-failure-test_')
+
+
+# Utilities.
+
+
+def SetEnvVar(env_var, value):
+  """Sets an environment variable to a given value; unsets it when the
+  given value is None.
+  """
+
+  env_var = env_var.upper()
+  if value is not None:
+    os.environ[env_var] = value
+  elif env_var in os.environ:
+    del os.environ[env_var]
+
+
+def Run(command):
+  """Runs a command; returns True/False if its exit code is/isn't 0."""
+
+  print('Running "%s". . .' % ' '.join(command))
+  p = gtest_test_utils.Subprocess(command)
+  return p.exited and p.exit_code == 0
+
+
+# The tests.
+class ThrowOnFailureTest(gtest_test_utils.TestCase):
+  """Tests the throw-on-failure mode."""
+
+  def RunAndVerify(self, env_var_value, flag_value, should_fail):
+    """Runs googletest-throw-on-failure-test_ and verifies that it does
+    (or does not) exit with a non-zero code.
+
+    Args:
+      env_var_value:    value of the GTEST_BREAK_ON_FAILURE environment
+                        variable; None if the variable should be unset.
+      flag_value:       value of the --gtest_break_on_failure flag;
+                        None if the flag should not be present.
+      should_fail:      True if and only if the program is expected to fail.
+    """
+
+    SetEnvVar(THROW_ON_FAILURE, env_var_value)
+
+    if env_var_value is None:
+      env_var_value_msg = ' is not set'
+    else:
+      env_var_value_msg = '=' + env_var_value
+
+    if flag_value is None:
+      flag = ''
+    elif flag_value == '0':
+      flag = '--%s=0' % THROW_ON_FAILURE
+    else:
+      flag = '--%s' % THROW_ON_FAILURE
+
+    command = [EXE_PATH]
+    if flag:
+      command.append(flag)
+
+    if should_fail:
+      should_or_not = 'should'
+    else:
+      should_or_not = 'should not'
+
+    failed = not Run(command)
+
+    SetEnvVar(THROW_ON_FAILURE, None)
+
+    msg = ('when %s%s, an assertion failure in "%s" %s cause a non-zero '
+           'exit code.' %
+           (THROW_ON_FAILURE, env_var_value_msg, ' '.join(command),
+            should_or_not))
+    self.assert_(failed == should_fail, msg)
+
+  def testDefaultBehavior(self):
+    """Tests the behavior of the default mode."""
+
+    self.RunAndVerify(env_var_value=None, flag_value=None, should_fail=False)
+
+  def testThrowOnFailureEnvVar(self):
+    """Tests using the GTEST_THROW_ON_FAILURE environment variable."""
+
+    self.RunAndVerify(env_var_value='0',
+                      flag_value=None,
+                      should_fail=False)
+    self.RunAndVerify(env_var_value='1',
+                      flag_value=None,
+                      should_fail=True)
+
+  def testThrowOnFailureFlag(self):
+    """Tests using the --gtest_throw_on_failure flag."""
+
+    self.RunAndVerify(env_var_value=None,
+                      flag_value='0',
+                      should_fail=False)
+    self.RunAndVerify(env_var_value=None,
+                      flag_value='1',
+                      should_fail=True)
+
+  def testThrowOnFailureFlagOverridesEnvVar(self):
+    """Tests that --gtest_throw_on_failure overrides GTEST_THROW_ON_FAILURE."""
+
+    self.RunAndVerify(env_var_value='0',
+                      flag_value='0',
+                      should_fail=False)
+    self.RunAndVerify(env_var_value='0',
+                      flag_value='1',
+                      should_fail=True)
+    self.RunAndVerify(env_var_value='1',
+                      flag_value='0',
+                      should_fail=False)
+    self.RunAndVerify(env_var_value='1',
+                      flag_value='1',
+                      should_fail=True)
+
+
+if __name__ == '__main__':
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-throw-on-failure-test_.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-throw-on-failure-test_.cc
new file mode 100644
index 0000000..83bb914
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-throw-on-failure-test_.cc
@@ -0,0 +1,71 @@
+// Copyright 2009, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Tests Google Test's throw-on-failure mode with exceptions disabled.
+//
+// This program must be compiled with exceptions disabled.  It will be
+// invoked by googletest-throw-on-failure-test.py, and is expected to exit
+// with non-zero in the throw-on-failure mode or 0 otherwise.
+
+#include "gtest/gtest.h"
+
+#include <stdio.h>                      // for fflush, fprintf, NULL, etc.
+#include <stdlib.h>                     // for exit
+#include <exception>                    // for set_terminate
+
+// This terminate handler aborts the program using exit() rather than abort().
+// This avoids showing pop-ups on Windows systems and core dumps on Unix-like
+// ones.
+void TerminateHandler() {
+  fprintf(stderr, "%s\n", "Unhandled C++ exception terminating the program.");
+  fflush(nullptr);
+  exit(1);
+}
+
+int main(int argc, char** argv) {
+#if GTEST_HAS_EXCEPTIONS
+  std::set_terminate(&TerminateHandler);
+#endif
+  testing::InitGoogleTest(&argc, argv);
+
+  // We want to ensure that people can use Google Test assertions in
+  // other testing frameworks, as long as they initialize Google Test
+  // properly and set the throw-on-failure mode.  Therefore, we don't
+  // use Google Test's constructs for defining and running tests
+  // (e.g. TEST and RUN_ALL_TESTS) here.
+
+  // In the throw-on-failure mode with exceptions disabled, this
+  // assertion will cause the program to exit with a non-zero code.
+  EXPECT_EQ(2, 3);
+
+  // When not in the throw-on-failure mode, the control will reach
+  // here.
+  return 0;
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-uninitialized-test.py b/leveldb_base/third_party/googletest/googletest/test/googletest-uninitialized-test.py
new file mode 100644
index 0000000..69595a0
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-uninitialized-test.py
@@ -0,0 +1,67 @@
+#!/usr/bin/env python
+#
+# Copyright 2008, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Verifies that Google Test warns the user when not initialized properly."""
+
+import gtest_test_utils
+
+COMMAND = gtest_test_utils.GetTestExecutablePath('googletest-uninitialized-test_')
+
+
+def Assert(condition):
+  if not condition:
+    raise AssertionError
+
+
+def AssertEq(expected, actual):
+  if expected != actual:
+    print('Expected: %s' % (expected,))
+    print('  Actual: %s' % (actual,))
+    raise AssertionError
+
+
+def TestExitCodeAndOutput(command):
+  """Runs the given command and verifies its exit code and output."""
+
+  # Verifies that 'command' exits with code 1.
+  p = gtest_test_utils.Subprocess(command)
+  if p.exited and p.exit_code == 0:
+    Assert('IMPORTANT NOTICE' in p.output);
+  Assert('InitGoogleTest' in p.output)
+
+
+class GTestUninitializedTest(gtest_test_utils.TestCase):
+  def testExitCodeAndOutput(self):
+    TestExitCodeAndOutput(COMMAND)
+
+
+if __name__ == '__main__':
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/googletest-uninitialized-test_.cc b/leveldb_base/third_party/googletest/googletest/test/googletest-uninitialized-test_.cc
new file mode 100644
index 0000000..b4434d5
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/googletest-uninitialized-test_.cc
@@ -0,0 +1,42 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+#include "gtest/gtest.h"
+
+TEST(DummyTest, Dummy) {
+  // This test doesn't verify anything.  We just need it to create a
+  // realistic stage for testing the behavior of Google Test when
+  // RUN_ALL_TESTS() is called without
+  // testing::InitGoogleTest() being called first.
+}
+
+int main() {
+  return RUN_ALL_TESTS();
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest-typed-test2_test.cc b/leveldb_base/third_party/googletest/googletest/test/gtest-typed-test2_test.cc
new file mode 100644
index 0000000..e83ca2e
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest-typed-test2_test.cc
@@ -0,0 +1,40 @@
+// Copyright 2008 Google Inc.
+// All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+#include <vector>
+
+#include "test/gtest-typed-test_test.h"
+#include "gtest/gtest.h"
+
+// Tests that the same type-parameterized test case can be
+// instantiated in different translation units linked together.
+// (ContainerTest is also instantiated in gtest-typed-test_test.cc.)
+INSTANTIATE_TYPED_TEST_SUITE_P(Vector, ContainerTest,
+                               testing::Types<std::vector<int> >);
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest-typed-test_test.cc b/leveldb_base/third_party/googletest/googletest/test/gtest-typed-test_test.cc
new file mode 100644
index 0000000..5fc678c
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest-typed-test_test.cc
@@ -0,0 +1,437 @@
+// Copyright 2008 Google Inc.
+// All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+#include "test/gtest-typed-test_test.h"
+
+#include <set>
+#include <type_traits>
+#include <vector>
+
+#include "gtest/gtest.h"
+
+#if _MSC_VER
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4127 /* conditional expression is constant */)
+#endif  //  _MSC_VER
+
+using testing::Test;
+
+// Used for testing that SetUpTestSuite()/TearDownTestSuite(), fixture
+// ctor/dtor, and SetUp()/TearDown() work correctly in typed tests and
+// type-parameterized test.
+template <typename T>
+class CommonTest : public Test {
+  // For some technical reason, SetUpTestSuite() and TearDownTestSuite()
+  // must be public.
+ public:
+  static void SetUpTestSuite() {
+    shared_ = new T(5);
+  }
+
+  static void TearDownTestSuite() {
+    delete shared_;
+    shared_ = nullptr;
+  }
+
+  // This 'protected:' is optional.  There's no harm in making all
+  // members of this fixture class template public.
+ protected:
+  // We used to use std::list here, but switched to std::vector since
+  // MSVC's <list> doesn't compile cleanly with /W4.
+  typedef std::vector<T> Vector;
+  typedef std::set<int> IntSet;
+
+  CommonTest() : value_(1) {}
+
+  ~CommonTest() override { EXPECT_EQ(3, value_); }
+
+  void SetUp() override {
+    EXPECT_EQ(1, value_);
+    value_++;
+  }
+
+  void TearDown() override {
+    EXPECT_EQ(2, value_);
+    value_++;
+  }
+
+  T value_;
+  static T* shared_;
+};
+
+template <typename T>
+T* CommonTest<T>::shared_ = nullptr;
+
+using testing::Types;
+
+// Tests that SetUpTestSuite()/TearDownTestSuite(), fixture ctor/dtor,
+// and SetUp()/TearDown() work correctly in typed tests
+
+typedef Types<char, int> TwoTypes;
+TYPED_TEST_SUITE(CommonTest, TwoTypes);
+
+TYPED_TEST(CommonTest, ValuesAreCorrect) {
+  // Static members of the fixture class template can be visited via
+  // the TestFixture:: prefix.
+  EXPECT_EQ(5, *TestFixture::shared_);
+
+  // Typedefs in the fixture class template can be visited via the
+  // "typename TestFixture::" prefix.
+  typename TestFixture::Vector empty;
+  EXPECT_EQ(0U, empty.size());
+
+  typename TestFixture::IntSet empty2;
+  EXPECT_EQ(0U, empty2.size());
+
+  // Non-static members of the fixture class must be visited via
+  // 'this', as required by C++ for class templates.
+  EXPECT_EQ(2, this->value_);
+}
+
+// The second test makes sure shared_ is not deleted after the first
+// test.
+TYPED_TEST(CommonTest, ValuesAreStillCorrect) {
+  // Static members of the fixture class template can also be visited
+  // via 'this'.
+  ASSERT_TRUE(this->shared_ != nullptr);
+  EXPECT_EQ(5, *this->shared_);
+
+  // TypeParam can be used to refer to the type parameter.
+  EXPECT_EQ(static_cast<TypeParam>(2), this->value_);
+}
+
+// Tests that multiple TYPED_TEST_SUITE's can be defined in the same
+// translation unit.
+
+template <typename T>
+class TypedTest1 : public Test {
+};
+
+// Verifies that the second argument of TYPED_TEST_SUITE can be a
+// single type.
+TYPED_TEST_SUITE(TypedTest1, int);
+TYPED_TEST(TypedTest1, A) {}
+
+template <typename T>
+class TypedTest2 : public Test {
+};
+
+// Verifies that the second argument of TYPED_TEST_SUITE can be a
+// Types<...> type list.
+TYPED_TEST_SUITE(TypedTest2, Types<int>);
+
+// This also verifies that tests from different typed test cases can
+// share the same name.
+TYPED_TEST(TypedTest2, A) {}
+
+// Tests that a typed test case can be defined in a namespace.
+
+namespace library1 {
+
+template <typename T>
+class NumericTest : public Test {
+};
+
+typedef Types<int, long> NumericTypes;
+TYPED_TEST_SUITE(NumericTest, NumericTypes);
+
+TYPED_TEST(NumericTest, DefaultIsZero) {
+  EXPECT_EQ(0, TypeParam());
+}
+
+}  // namespace library1
+
+// Tests that custom names work.
+template <typename T>
+class TypedTestWithNames : public Test {};
+
+class TypedTestNames {
+ public:
+  template <typename T>
+  static std::string GetName(int i) {
+    if (std::is_same<T, char>::value) {
+      return std::string("char") + ::testing::PrintToString(i);
+    }
+    if (std::is_same<T, int>::value) {
+      return std::string("int") + ::testing::PrintToString(i);
+    }
+  }
+};
+
+TYPED_TEST_SUITE(TypedTestWithNames, TwoTypes, TypedTestNames);
+
+TYPED_TEST(TypedTestWithNames, TestSuiteName) {
+  if (std::is_same<TypeParam, char>::value) {
+    EXPECT_STREQ(::testing::UnitTest::GetInstance()
+                     ->current_test_info()
+                     ->test_suite_name(),
+                 "TypedTestWithNames/char0");
+  }
+  if (std::is_same<TypeParam, int>::value) {
+    EXPECT_STREQ(::testing::UnitTest::GetInstance()
+                     ->current_test_info()
+                     ->test_suite_name(),
+                 "TypedTestWithNames/int1");
+  }
+}
+
+using testing::Types;
+using testing::internal::TypedTestSuitePState;
+
+// Tests TypedTestSuitePState.
+
+class TypedTestSuitePStateTest : public Test {
+ protected:
+  void SetUp() override {
+    state_.AddTestName("foo.cc", 0, "FooTest", "A");
+    state_.AddTestName("foo.cc", 0, "FooTest", "B");
+    state_.AddTestName("foo.cc", 0, "FooTest", "C");
+  }
+
+  TypedTestSuitePState state_;
+};
+
+TEST_F(TypedTestSuitePStateTest, SucceedsForMatchingList) {
+  const char* tests = "A, B, C";
+  EXPECT_EQ(tests,
+            state_.VerifyRegisteredTestNames("Suite", "foo.cc", 1, tests));
+}
+
+// Makes sure that the order of the tests and spaces around the names
+// don't matter.
+TEST_F(TypedTestSuitePStateTest, IgnoresOrderAndSpaces) {
+  const char* tests = "A,C,   B";
+  EXPECT_EQ(tests,
+            state_.VerifyRegisteredTestNames("Suite", "foo.cc", 1, tests));
+}
+
+using TypedTestSuitePStateDeathTest = TypedTestSuitePStateTest;
+
+TEST_F(TypedTestSuitePStateDeathTest, DetectsDuplicates) {
+  EXPECT_DEATH_IF_SUPPORTED(
+      state_.VerifyRegisteredTestNames("Suite", "foo.cc", 1, "A, B, A, C"),
+      "foo\\.cc.1.?: Test A is listed more than once\\.");
+}
+
+TEST_F(TypedTestSuitePStateDeathTest, DetectsExtraTest) {
+  EXPECT_DEATH_IF_SUPPORTED(
+      state_.VerifyRegisteredTestNames("Suite", "foo.cc", 1, "A, B, C, D"),
+      "foo\\.cc.1.?: No test named D can be found in this test suite\\.");
+}
+
+TEST_F(TypedTestSuitePStateDeathTest, DetectsMissedTest) {
+  EXPECT_DEATH_IF_SUPPORTED(
+      state_.VerifyRegisteredTestNames("Suite", "foo.cc", 1, "A, C"),
+      "foo\\.cc.1.?: You forgot to list test B\\.");
+}
+
+// Tests that defining a test for a parameterized test case generates
+// a run-time error if the test case has been registered.
+TEST_F(TypedTestSuitePStateDeathTest, DetectsTestAfterRegistration) {
+  state_.VerifyRegisteredTestNames("Suite", "foo.cc", 1, "A, B, C");
+  EXPECT_DEATH_IF_SUPPORTED(
+      state_.AddTestName("foo.cc", 2, "FooTest", "D"),
+      "foo\\.cc.2.?: Test D must be defined before REGISTER_TYPED_TEST_SUITE_P"
+      "\\(FooTest, \\.\\.\\.\\)\\.");
+}
+
+// Tests that SetUpTestSuite()/TearDownTestSuite(), fixture ctor/dtor,
+// and SetUp()/TearDown() work correctly in type-parameterized tests.
+
+template <typename T>
+class DerivedTest : public CommonTest<T> {
+};
+
+TYPED_TEST_SUITE_P(DerivedTest);
+
+TYPED_TEST_P(DerivedTest, ValuesAreCorrect) {
+  // Static members of the fixture class template can be visited via
+  // the TestFixture:: prefix.
+  EXPECT_EQ(5, *TestFixture::shared_);
+
+  // Non-static members of the fixture class must be visited via
+  // 'this', as required by C++ for class templates.
+  EXPECT_EQ(2, this->value_);
+}
+
+// The second test makes sure shared_ is not deleted after the first
+// test.
+TYPED_TEST_P(DerivedTest, ValuesAreStillCorrect) {
+  // Static members of the fixture class template can also be visited
+  // via 'this'.
+  ASSERT_TRUE(this->shared_ != nullptr);
+  EXPECT_EQ(5, *this->shared_);
+  EXPECT_EQ(2, this->value_);
+}
+
+REGISTER_TYPED_TEST_SUITE_P(DerivedTest,
+                           ValuesAreCorrect, ValuesAreStillCorrect);
+
+typedef Types<short, long> MyTwoTypes;
+INSTANTIATE_TYPED_TEST_SUITE_P(My, DerivedTest, MyTwoTypes);
+
+// Tests that custom names work with type parametrized tests. We reuse the
+// TwoTypes from above here.
+template <typename T>
+class TypeParametrizedTestWithNames : public Test {};
+
+TYPED_TEST_SUITE_P(TypeParametrizedTestWithNames);
+
+TYPED_TEST_P(TypeParametrizedTestWithNames, TestSuiteName) {
+  if (std::is_same<TypeParam, char>::value) {
+    EXPECT_STREQ(::testing::UnitTest::GetInstance()
+                     ->current_test_info()
+                     ->test_suite_name(),
+                 "CustomName/TypeParametrizedTestWithNames/parChar0");
+  }
+  if (std::is_same<TypeParam, int>::value) {
+    EXPECT_STREQ(::testing::UnitTest::GetInstance()
+                     ->current_test_info()
+                     ->test_suite_name(),
+                 "CustomName/TypeParametrizedTestWithNames/parInt1");
+  }
+}
+
+REGISTER_TYPED_TEST_SUITE_P(TypeParametrizedTestWithNames, TestSuiteName);
+
+class TypeParametrizedTestNames {
+ public:
+  template <typename T>
+  static std::string GetName(int i) {
+    if (std::is_same<T, char>::value) {
+      return std::string("parChar") + ::testing::PrintToString(i);
+    }
+    if (std::is_same<T, int>::value) {
+      return std::string("parInt") + ::testing::PrintToString(i);
+    }
+  }
+};
+
+INSTANTIATE_TYPED_TEST_SUITE_P(CustomName, TypeParametrizedTestWithNames,
+                              TwoTypes, TypeParametrizedTestNames);
+
+// Tests that multiple TYPED_TEST_SUITE_P's can be defined in the same
+// translation unit.
+
+template <typename T>
+class TypedTestP1 : public Test {
+};
+
+TYPED_TEST_SUITE_P(TypedTestP1);
+
+// For testing that the code between TYPED_TEST_SUITE_P() and
+// TYPED_TEST_P() is not enclosed in a namespace.
+using IntAfterTypedTestSuiteP = int;
+
+TYPED_TEST_P(TypedTestP1, A) {}
+TYPED_TEST_P(TypedTestP1, B) {}
+
+// For testing that the code between TYPED_TEST_P() and
+// REGISTER_TYPED_TEST_SUITE_P() is not enclosed in a namespace.
+using IntBeforeRegisterTypedTestSuiteP = int;
+
+REGISTER_TYPED_TEST_SUITE_P(TypedTestP1, A, B);
+
+template <typename T>
+class TypedTestP2 : public Test {
+};
+
+TYPED_TEST_SUITE_P(TypedTestP2);
+
+// This also verifies that tests from different type-parameterized
+// test cases can share the same name.
+TYPED_TEST_P(TypedTestP2, A) {}
+
+REGISTER_TYPED_TEST_SUITE_P(TypedTestP2, A);
+
+// Verifies that the code between TYPED_TEST_SUITE_P() and
+// REGISTER_TYPED_TEST_SUITE_P() is not enclosed in a namespace.
+IntAfterTypedTestSuiteP after = 0;
+IntBeforeRegisterTypedTestSuiteP before = 0;
+
+// Verifies that the last argument of INSTANTIATE_TYPED_TEST_SUITE_P()
+// can be either a single type or a Types<...> type list.
+INSTANTIATE_TYPED_TEST_SUITE_P(Int, TypedTestP1, int);
+INSTANTIATE_TYPED_TEST_SUITE_P(Int, TypedTestP2, Types<int>);
+
+// Tests that the same type-parameterized test case can be
+// instantiated more than once in the same translation unit.
+INSTANTIATE_TYPED_TEST_SUITE_P(Double, TypedTestP2, Types<double>);
+
+// Tests that the same type-parameterized test case can be
+// instantiated in different translation units linked together.
+// (ContainerTest is also instantiated in gtest-typed-test_test.cc.)
+typedef Types<std::vector<double>, std::set<char> > MyContainers;
+INSTANTIATE_TYPED_TEST_SUITE_P(My, ContainerTest, MyContainers);
+
+// Tests that a type-parameterized test case can be defined and
+// instantiated in a namespace.
+
+namespace library2 {
+
+template <typename T>
+class NumericTest : public Test {
+};
+
+TYPED_TEST_SUITE_P(NumericTest);
+
+TYPED_TEST_P(NumericTest, DefaultIsZero) {
+  EXPECT_EQ(0, TypeParam());
+}
+
+TYPED_TEST_P(NumericTest, ZeroIsLessThanOne) {
+  EXPECT_LT(TypeParam(0), TypeParam(1));
+}
+
+REGISTER_TYPED_TEST_SUITE_P(NumericTest,
+                           DefaultIsZero, ZeroIsLessThanOne);
+typedef Types<int, double> NumericTypes;
+INSTANTIATE_TYPED_TEST_SUITE_P(My, NumericTest, NumericTypes);
+
+static const char* GetTestName() {
+  return testing::UnitTest::GetInstance()->current_test_info()->name();
+}
+// Test the stripping of space from test names
+template <typename T> class TrimmedTest : public Test { };
+TYPED_TEST_SUITE_P(TrimmedTest);
+TYPED_TEST_P(TrimmedTest, Test1) { EXPECT_STREQ("Test1", GetTestName()); }
+TYPED_TEST_P(TrimmedTest, Test2) { EXPECT_STREQ("Test2", GetTestName()); }
+TYPED_TEST_P(TrimmedTest, Test3) { EXPECT_STREQ("Test3", GetTestName()); }
+TYPED_TEST_P(TrimmedTest, Test4) { EXPECT_STREQ("Test4", GetTestName()); }
+TYPED_TEST_P(TrimmedTest, Test5) { EXPECT_STREQ("Test5", GetTestName()); }
+REGISTER_TYPED_TEST_SUITE_P(
+    TrimmedTest,
+    Test1, Test2,Test3 , Test4 ,Test5 );  // NOLINT
+template <typename T1, typename T2> struct MyPair {};
+// Be sure to try a type with a comma in its name just in case it matters.
+typedef Types<int, double, MyPair<int, int> > TrimTypes;
+INSTANTIATE_TYPED_TEST_SUITE_P(My, TrimmedTest, TrimTypes);
+
+}  // namespace library2
+
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest-typed-test_test.h b/leveldb_base/third_party/googletest/googletest/test/gtest-typed-test_test.h
new file mode 100644
index 0000000..8ce559c
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest-typed-test_test.h
@@ -0,0 +1,60 @@
+// Copyright 2008 Google Inc.
+// All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLETEST_TEST_GTEST_TYPED_TEST_TEST_H_
+#define GOOGLETEST_TEST_GTEST_TYPED_TEST_TEST_H_
+
+#include "gtest/gtest.h"
+
+using testing::Test;
+
+// For testing that the same type-parameterized test case can be
+// instantiated in different translation units linked together.
+// ContainerTest will be instantiated in both gtest-typed-test_test.cc
+// and gtest-typed-test2_test.cc.
+
+template <typename T>
+class ContainerTest : public Test {
+};
+
+TYPED_TEST_SUITE_P(ContainerTest);
+
+TYPED_TEST_P(ContainerTest, CanBeDefaultConstructed) {
+  TypeParam container;
+}
+
+TYPED_TEST_P(ContainerTest, InitialSizeIsZero) {
+  TypeParam container;
+  EXPECT_EQ(0U, container.size());
+}
+
+REGISTER_TYPED_TEST_SUITE_P(ContainerTest,
+                            CanBeDefaultConstructed, InitialSizeIsZero);
+
+#endif  // GOOGLETEST_TEST_GTEST_TYPED_TEST_TEST_H_
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest-unittest-api_test.cc b/leveldb_base/third_party/googletest/googletest/test/gtest-unittest-api_test.cc
new file mode 100644
index 0000000..8ef5058
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest-unittest-api_test.cc
@@ -0,0 +1,328 @@
+// Copyright 2009 Google Inc.  All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// The Google C++ Testing and Mocking Framework (Google Test)
+//
+// This file contains tests verifying correctness of data provided via
+// UnitTest's public methods.
+
+#include "gtest/gtest.h"
+
+#include <string.h>  // For strcmp.
+#include <algorithm>
+
+using ::testing::InitGoogleTest;
+
+namespace testing {
+namespace internal {
+
+template <typename T>
+struct LessByName {
+  bool operator()(const T* a, const T* b) {
+    return strcmp(a->name(), b->name()) < 0;
+  }
+};
+
+class UnitTestHelper {
+ public:
+  // Returns the array of pointers to all test suites sorted by the test suite
+  // name.  The caller is responsible for deleting the array.
+  static TestSuite const** GetSortedTestSuites() {
+    UnitTest& unit_test = *UnitTest::GetInstance();
+    auto const** const test_suites = new const TestSuite*[static_cast<size_t>(
+      unit_test.total_test_suite_count())];
+
+    for (int i = 0; i < unit_test.total_test_suite_count(); ++i)
+      test_suites[i] = unit_test.GetTestSuite(i);
+
+    std::sort(test_suites,
+              test_suites + unit_test.total_test_suite_count(),
+              LessByName<TestSuite>());
+    return test_suites;
+  }
+
+  // Returns the test suite by its name.  The caller doesn't own the returned
+  // pointer.
+  static const TestSuite* FindTestSuite(const char* name) {
+    UnitTest& unit_test = *UnitTest::GetInstance();
+    for (int i = 0; i < unit_test.total_test_suite_count(); ++i) {
+      const TestSuite* test_suite = unit_test.GetTestSuite(i);
+      if (0 == strcmp(test_suite->name(), name))
+        return test_suite;
+    }
+    return nullptr;
+  }
+
+  // Returns the array of pointers to all tests in a particular test suite
+  // sorted by the test name.  The caller is responsible for deleting the
+  // array.
+  static TestInfo const** GetSortedTests(const TestSuite* test_suite) {
+    TestInfo const** const tests = new const TestInfo*[static_cast<size_t>(
+      test_suite->total_test_count())];
+
+    for (int i = 0; i < test_suite->total_test_count(); ++i)
+      tests[i] = test_suite->GetTestInfo(i);
+
+    std::sort(tests, tests + test_suite->total_test_count(),
+              LessByName<TestInfo>());
+    return tests;
+  }
+};
+
+template <typename T> class TestSuiteWithCommentTest : public Test {};
+TYPED_TEST_SUITE(TestSuiteWithCommentTest, Types<int>);
+TYPED_TEST(TestSuiteWithCommentTest, Dummy) {}
+
+const int kTypedTestSuites = 1;
+const int kTypedTests = 1;
+
+// We can only test the accessors that do not change value while tests run.
+// Since tests can be run in any order, the values the accessors that track
+// test execution (such as failed_test_count) can not be predicted.
+TEST(ApiTest, UnitTestImmutableAccessorsWork) {
+  UnitTest* unit_test = UnitTest::GetInstance();
+
+  ASSERT_EQ(2 + kTypedTestSuites, unit_test->total_test_suite_count());
+  EXPECT_EQ(1 + kTypedTestSuites, unit_test->test_suite_to_run_count());
+  EXPECT_EQ(2, unit_test->disabled_test_count());
+  EXPECT_EQ(5 + kTypedTests, unit_test->total_test_count());
+  EXPECT_EQ(3 + kTypedTests, unit_test->test_to_run_count());
+
+  const TestSuite** const test_suites = UnitTestHelper::GetSortedTestSuites();
+
+  EXPECT_STREQ("ApiTest", test_suites[0]->name());
+  EXPECT_STREQ("DISABLED_Test", test_suites[1]->name());
+  EXPECT_STREQ("TestSuiteWithCommentTest/0", test_suites[2]->name());
+
+  delete[] test_suites;
+
+  // The following lines initiate actions to verify certain methods in
+  // FinalSuccessChecker::TearDown.
+
+  // Records a test property to verify TestResult::GetTestProperty().
+  RecordProperty("key", "value");
+}
+
+AssertionResult IsNull(const char* str) {
+  if (str != nullptr) {
+    return testing::AssertionFailure() << "argument is " << str;
+  }
+  return AssertionSuccess();
+}
+
+TEST(ApiTest, TestSuiteImmutableAccessorsWork) {
+  const TestSuite* test_suite = UnitTestHelper::FindTestSuite("ApiTest");
+  ASSERT_TRUE(test_suite != nullptr);
+
+  EXPECT_STREQ("ApiTest", test_suite->name());
+  EXPECT_TRUE(IsNull(test_suite->type_param()));
+  EXPECT_TRUE(test_suite->should_run());
+  EXPECT_EQ(1, test_suite->disabled_test_count());
+  EXPECT_EQ(3, test_suite->test_to_run_count());
+  ASSERT_EQ(4, test_suite->total_test_count());
+
+  const TestInfo** tests = UnitTestHelper::GetSortedTests(test_suite);
+
+  EXPECT_STREQ("DISABLED_Dummy1", tests[0]->name());
+  EXPECT_STREQ("ApiTest", tests[0]->test_suite_name());
+  EXPECT_TRUE(IsNull(tests[0]->value_param()));
+  EXPECT_TRUE(IsNull(tests[0]->type_param()));
+  EXPECT_FALSE(tests[0]->should_run());
+
+  EXPECT_STREQ("TestSuiteDisabledAccessorsWork", tests[1]->name());
+  EXPECT_STREQ("ApiTest", tests[1]->test_suite_name());
+  EXPECT_TRUE(IsNull(tests[1]->value_param()));
+  EXPECT_TRUE(IsNull(tests[1]->type_param()));
+  EXPECT_TRUE(tests[1]->should_run());
+
+  EXPECT_STREQ("TestSuiteImmutableAccessorsWork", tests[2]->name());
+  EXPECT_STREQ("ApiTest", tests[2]->test_suite_name());
+  EXPECT_TRUE(IsNull(tests[2]->value_param()));
+  EXPECT_TRUE(IsNull(tests[2]->type_param()));
+  EXPECT_TRUE(tests[2]->should_run());
+
+  EXPECT_STREQ("UnitTestImmutableAccessorsWork", tests[3]->name());
+  EXPECT_STREQ("ApiTest", tests[3]->test_suite_name());
+  EXPECT_TRUE(IsNull(tests[3]->value_param()));
+  EXPECT_TRUE(IsNull(tests[3]->type_param()));
+  EXPECT_TRUE(tests[3]->should_run());
+
+  delete[] tests;
+  tests = nullptr;
+
+  test_suite = UnitTestHelper::FindTestSuite("TestSuiteWithCommentTest/0");
+  ASSERT_TRUE(test_suite != nullptr);
+
+  EXPECT_STREQ("TestSuiteWithCommentTest/0", test_suite->name());
+  EXPECT_STREQ(GetTypeName<Types<int>>().c_str(), test_suite->type_param());
+  EXPECT_TRUE(test_suite->should_run());
+  EXPECT_EQ(0, test_suite->disabled_test_count());
+  EXPECT_EQ(1, test_suite->test_to_run_count());
+  ASSERT_EQ(1, test_suite->total_test_count());
+
+  tests = UnitTestHelper::GetSortedTests(test_suite);
+
+  EXPECT_STREQ("Dummy", tests[0]->name());
+  EXPECT_STREQ("TestSuiteWithCommentTest/0", tests[0]->test_suite_name());
+  EXPECT_TRUE(IsNull(tests[0]->value_param()));
+  EXPECT_STREQ(GetTypeName<Types<int>>().c_str(), tests[0]->type_param());
+  EXPECT_TRUE(tests[0]->should_run());
+
+  delete[] tests;
+}
+
+TEST(ApiTest, TestSuiteDisabledAccessorsWork) {
+  const TestSuite* test_suite = UnitTestHelper::FindTestSuite("DISABLED_Test");
+  ASSERT_TRUE(test_suite != nullptr);
+
+  EXPECT_STREQ("DISABLED_Test", test_suite->name());
+  EXPECT_TRUE(IsNull(test_suite->type_param()));
+  EXPECT_FALSE(test_suite->should_run());
+  EXPECT_EQ(1, test_suite->disabled_test_count());
+  EXPECT_EQ(0, test_suite->test_to_run_count());
+  ASSERT_EQ(1, test_suite->total_test_count());
+
+  const TestInfo* const test_info = test_suite->GetTestInfo(0);
+  EXPECT_STREQ("Dummy2", test_info->name());
+  EXPECT_STREQ("DISABLED_Test", test_info->test_suite_name());
+  EXPECT_TRUE(IsNull(test_info->value_param()));
+  EXPECT_TRUE(IsNull(test_info->type_param()));
+  EXPECT_FALSE(test_info->should_run());
+}
+
+// These two tests are here to provide support for testing
+// test_suite_to_run_count, disabled_test_count, and test_to_run_count.
+TEST(ApiTest, DISABLED_Dummy1) {}
+TEST(DISABLED_Test, Dummy2) {}
+
+class FinalSuccessChecker : public Environment {
+ protected:
+  void TearDown() override {
+    UnitTest* unit_test = UnitTest::GetInstance();
+
+    EXPECT_EQ(1 + kTypedTestSuites, unit_test->successful_test_suite_count());
+    EXPECT_EQ(3 + kTypedTests, unit_test->successful_test_count());
+    EXPECT_EQ(0, unit_test->failed_test_suite_count());
+    EXPECT_EQ(0, unit_test->failed_test_count());
+    EXPECT_TRUE(unit_test->Passed());
+    EXPECT_FALSE(unit_test->Failed());
+    ASSERT_EQ(2 + kTypedTestSuites, unit_test->total_test_suite_count());
+
+    const TestSuite** const test_suites = UnitTestHelper::GetSortedTestSuites();
+
+    EXPECT_STREQ("ApiTest", test_suites[0]->name());
+    EXPECT_TRUE(IsNull(test_suites[0]->type_param()));
+    EXPECT_TRUE(test_suites[0]->should_run());
+    EXPECT_EQ(1, test_suites[0]->disabled_test_count());
+    ASSERT_EQ(4, test_suites[0]->total_test_count());
+    EXPECT_EQ(3, test_suites[0]->successful_test_count());
+    EXPECT_EQ(0, test_suites[0]->failed_test_count());
+    EXPECT_TRUE(test_suites[0]->Passed());
+    EXPECT_FALSE(test_suites[0]->Failed());
+
+    EXPECT_STREQ("DISABLED_Test", test_suites[1]->name());
+    EXPECT_TRUE(IsNull(test_suites[1]->type_param()));
+    EXPECT_FALSE(test_suites[1]->should_run());
+    EXPECT_EQ(1, test_suites[1]->disabled_test_count());
+    ASSERT_EQ(1, test_suites[1]->total_test_count());
+    EXPECT_EQ(0, test_suites[1]->successful_test_count());
+    EXPECT_EQ(0, test_suites[1]->failed_test_count());
+
+    EXPECT_STREQ("TestSuiteWithCommentTest/0", test_suites[2]->name());
+    EXPECT_STREQ(GetTypeName<Types<int>>().c_str(),
+                 test_suites[2]->type_param());
+    EXPECT_TRUE(test_suites[2]->should_run());
+    EXPECT_EQ(0, test_suites[2]->disabled_test_count());
+    ASSERT_EQ(1, test_suites[2]->total_test_count());
+    EXPECT_EQ(1, test_suites[2]->successful_test_count());
+    EXPECT_EQ(0, test_suites[2]->failed_test_count());
+    EXPECT_TRUE(test_suites[2]->Passed());
+    EXPECT_FALSE(test_suites[2]->Failed());
+
+    const TestSuite* test_suite = UnitTestHelper::FindTestSuite("ApiTest");
+    const TestInfo** tests = UnitTestHelper::GetSortedTests(test_suite);
+    EXPECT_STREQ("DISABLED_Dummy1", tests[0]->name());
+    EXPECT_STREQ("ApiTest", tests[0]->test_suite_name());
+    EXPECT_FALSE(tests[0]->should_run());
+
+    EXPECT_STREQ("TestSuiteDisabledAccessorsWork", tests[1]->name());
+    EXPECT_STREQ("ApiTest", tests[1]->test_suite_name());
+    EXPECT_TRUE(IsNull(tests[1]->value_param()));
+    EXPECT_TRUE(IsNull(tests[1]->type_param()));
+    EXPECT_TRUE(tests[1]->should_run());
+    EXPECT_TRUE(tests[1]->result()->Passed());
+    EXPECT_EQ(0, tests[1]->result()->test_property_count());
+
+    EXPECT_STREQ("TestSuiteImmutableAccessorsWork", tests[2]->name());
+    EXPECT_STREQ("ApiTest", tests[2]->test_suite_name());
+    EXPECT_TRUE(IsNull(tests[2]->value_param()));
+    EXPECT_TRUE(IsNull(tests[2]->type_param()));
+    EXPECT_TRUE(tests[2]->should_run());
+    EXPECT_TRUE(tests[2]->result()->Passed());
+    EXPECT_EQ(0, tests[2]->result()->test_property_count());
+
+    EXPECT_STREQ("UnitTestImmutableAccessorsWork", tests[3]->name());
+    EXPECT_STREQ("ApiTest", tests[3]->test_suite_name());
+    EXPECT_TRUE(IsNull(tests[3]->value_param()));
+    EXPECT_TRUE(IsNull(tests[3]->type_param()));
+    EXPECT_TRUE(tests[3]->should_run());
+    EXPECT_TRUE(tests[3]->result()->Passed());
+    EXPECT_EQ(1, tests[3]->result()->test_property_count());
+    const TestProperty& property = tests[3]->result()->GetTestProperty(0);
+    EXPECT_STREQ("key", property.key());
+    EXPECT_STREQ("value", property.value());
+
+    delete[] tests;
+
+    test_suite = UnitTestHelper::FindTestSuite("TestSuiteWithCommentTest/0");
+    tests = UnitTestHelper::GetSortedTests(test_suite);
+
+    EXPECT_STREQ("Dummy", tests[0]->name());
+    EXPECT_STREQ("TestSuiteWithCommentTest/0", tests[0]->test_suite_name());
+    EXPECT_TRUE(IsNull(tests[0]->value_param()));
+    EXPECT_STREQ(GetTypeName<Types<int>>().c_str(), tests[0]->type_param());
+    EXPECT_TRUE(tests[0]->should_run());
+    EXPECT_TRUE(tests[0]->result()->Passed());
+    EXPECT_EQ(0, tests[0]->result()->test_property_count());
+
+    delete[] tests;
+    delete[] test_suites;
+  }
+};
+
+}  // namespace internal
+}  // namespace testing
+
+int main(int argc, char **argv) {
+  InitGoogleTest(&argc, argv);
+
+  AddGlobalTestEnvironment(new testing::internal::FinalSuccessChecker());
+
+  return RUN_ALL_TESTS();
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_all_test.cc b/leveldb_base/third_party/googletest/googletest/test/gtest_all_test.cc
new file mode 100644
index 0000000..615b29b
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_all_test.cc
@@ -0,0 +1,46 @@
+// Copyright 2009, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// Tests for Google C++ Testing and Mocking Framework (Google Test)
+//
+// Sometimes it's desirable to build most of Google Test's own tests
+// by compiling a single file.  This file serves this purpose.
+#include "test/googletest-filepath-test.cc"
+#include "test/googletest-message-test.cc"
+#include "test/googletest-options-test.cc"
+#include "test/googletest-port-test.cc"
+#include "test/googletest-test-part-test.cc"
+#include "test/gtest-typed-test2_test.cc"
+#include "test/gtest-typed-test_test.cc"
+#include "test/gtest_pred_impl_unittest.cc"
+#include "test/gtest_prod_test.cc"
+#include "test/gtest_skip_test.cc"
+#include "test/gtest_unittest.cc"
+#include "test/production.cc"
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_assert_by_exception_test.cc b/leveldb_base/third_party/googletest/googletest/test/gtest_assert_by_exception_test.cc
new file mode 100644
index 0000000..ada4cb3
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_assert_by_exception_test.cc
@@ -0,0 +1,116 @@
+// Copyright 2009, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Tests Google Test's assert-by-exception mode with exceptions enabled.
+
+#include "gtest/gtest.h"
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdexcept>
+
+class ThrowListener : public testing::EmptyTestEventListener {
+  void OnTestPartResult(const testing::TestPartResult& result) override {
+    if (result.type() == testing::TestPartResult::kFatalFailure) {
+      throw testing::AssertionException(result);
+    }
+  }
+};
+
+// Prints the given failure message and exits the program with
+// non-zero.  We use this instead of a Google Test assertion to
+// indicate a failure, as the latter is been tested and cannot be
+// relied on.
+void Fail(const char* msg) {
+  printf("FAILURE: %s\n", msg);
+  fflush(stdout);
+  exit(1);
+}
+
+static void AssertFalse() {
+  ASSERT_EQ(2, 3) << "Expected failure";
+}
+
+// Tests that an assertion failure throws a subclass of
+// std::runtime_error.
+TEST(Test, Test) {
+  // A successful assertion shouldn't throw.
+  try {
+    EXPECT_EQ(3, 3);
+  } catch(...) {
+    Fail("A successful assertion wrongfully threw.");
+  }
+
+  // A successful assertion shouldn't throw.
+  try {
+    EXPECT_EQ(3, 4);
+  } catch(...) {
+    Fail("A failed non-fatal assertion wrongfully threw.");
+  }
+
+  // A failed assertion should throw.
+  try {
+    AssertFalse();
+  } catch(const testing::AssertionException& e) {
+    if (strstr(e.what(), "Expected failure") != nullptr) throw;
+
+    printf("%s",
+           "A failed assertion did throw an exception of the right type, "
+           "but the message is incorrect.  Instead of containing \"Expected "
+           "failure\", it is:\n");
+    Fail(e.what());
+  } catch(...) {
+    Fail("A failed assertion threw the wrong type of exception.");
+  }
+  Fail("A failed assertion should've thrown but didn't.");
+}
+
+int kTestForContinuingTest = 0;
+
+TEST(Test, Test2) {
+  kTestForContinuingTest = 1;
+}
+
+int main(int argc, char** argv) {
+  testing::InitGoogleTest(&argc, argv);
+  testing::UnitTest::GetInstance()->listeners().Append(new ThrowListener);
+
+  int result = RUN_ALL_TESTS();
+  if (result == 0) {
+    printf("RUN_ALL_TESTS returned %d\n", result);
+    Fail("Expected failure instead.");
+  }
+
+  if (kTestForContinuingTest == 0) {
+    Fail("Should have continued with other tests, but did not.");
+  }
+  return 0;
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_environment_test.cc b/leveldb_base/third_party/googletest/googletest/test/gtest_environment_test.cc
new file mode 100644
index 0000000..064bfc5
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_environment_test.cc
@@ -0,0 +1,188 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// Tests using global test environments.
+
+#include <stdlib.h>
+#include <stdio.h>
+#include "gtest/gtest.h"
+#include "src/gtest-internal-inl.h"
+
+namespace testing {
+GTEST_DECLARE_string_(filter);
+}
+
+namespace {
+
+enum FailureType {
+  NO_FAILURE, NON_FATAL_FAILURE, FATAL_FAILURE
+};
+
+// For testing using global test environments.
+class MyEnvironment : public testing::Environment {
+ public:
+  MyEnvironment() { Reset(); }
+
+  // Depending on the value of failure_in_set_up_, SetUp() will
+  // generate a non-fatal failure, generate a fatal failure, or
+  // succeed.
+  void SetUp() override {
+    set_up_was_run_ = true;
+
+    switch (failure_in_set_up_) {
+      case NON_FATAL_FAILURE:
+        ADD_FAILURE() << "Expected non-fatal failure in global set-up.";
+        break;
+      case FATAL_FAILURE:
+        FAIL() << "Expected fatal failure in global set-up.";
+        break;
+      default:
+        break;
+    }
+  }
+
+  // Generates a non-fatal failure.
+  void TearDown() override {
+    tear_down_was_run_ = true;
+    ADD_FAILURE() << "Expected non-fatal failure in global tear-down.";
+  }
+
+  // Resets the state of the environment s.t. it can be reused.
+  void Reset() {
+    failure_in_set_up_ = NO_FAILURE;
+    set_up_was_run_ = false;
+    tear_down_was_run_ = false;
+  }
+
+  // We call this function to set the type of failure SetUp() should
+  // generate.
+  void set_failure_in_set_up(FailureType type) {
+    failure_in_set_up_ = type;
+  }
+
+  // Was SetUp() run?
+  bool set_up_was_run() const { return set_up_was_run_; }
+
+  // Was TearDown() run?
+  bool tear_down_was_run() const { return tear_down_was_run_; }
+
+ private:
+  FailureType failure_in_set_up_;
+  bool set_up_was_run_;
+  bool tear_down_was_run_;
+};
+
+// Was the TEST run?
+bool test_was_run;
+
+// The sole purpose of this TEST is to enable us to check whether it
+// was run.
+TEST(FooTest, Bar) {
+  test_was_run = true;
+}
+
+// Prints the message and aborts the program if condition is false.
+void Check(bool condition, const char* msg) {
+  if (!condition) {
+    printf("FAILED: %s\n", msg);
+    testing::internal::posix::Abort();
+  }
+}
+
+// Runs the tests.  Return true if and only if successful.
+//
+// The 'failure' parameter specifies the type of failure that should
+// be generated by the global set-up.
+int RunAllTests(MyEnvironment* env, FailureType failure) {
+  env->Reset();
+  env->set_failure_in_set_up(failure);
+  test_was_run = false;
+  testing::internal::GetUnitTestImpl()->ClearAdHocTestResult();
+  return RUN_ALL_TESTS();
+}
+
+}  // namespace
+
+int main(int argc, char **argv) {
+  testing::InitGoogleTest(&argc, argv);
+
+  // Registers a global test environment, and verifies that the
+  // registration function returns its argument.
+  MyEnvironment* const env = new MyEnvironment;
+  Check(testing::AddGlobalTestEnvironment(env) == env,
+        "AddGlobalTestEnvironment() should return its argument.");
+
+  // Verifies that RUN_ALL_TESTS() runs the tests when the global
+  // set-up is successful.
+  Check(RunAllTests(env, NO_FAILURE) != 0,
+        "RUN_ALL_TESTS() should return non-zero, as the global tear-down "
+        "should generate a failure.");
+  Check(test_was_run,
+        "The tests should run, as the global set-up should generate no "
+        "failure");
+  Check(env->tear_down_was_run(),
+        "The global tear-down should run, as the global set-up was run.");
+
+  // Verifies that RUN_ALL_TESTS() runs the tests when the global
+  // set-up generates no fatal failure.
+  Check(RunAllTests(env, NON_FATAL_FAILURE) != 0,
+        "RUN_ALL_TESTS() should return non-zero, as both the global set-up "
+        "and the global tear-down should generate a non-fatal failure.");
+  Check(test_was_run,
+        "The tests should run, as the global set-up should generate no "
+        "fatal failure.");
+  Check(env->tear_down_was_run(),
+        "The global tear-down should run, as the global set-up was run.");
+
+  // Verifies that RUN_ALL_TESTS() runs no test when the global set-up
+  // generates a fatal failure.
+  Check(RunAllTests(env, FATAL_FAILURE) != 0,
+        "RUN_ALL_TESTS() should return non-zero, as the global set-up "
+        "should generate a fatal failure.");
+  Check(!test_was_run,
+        "The tests should not run, as the global set-up should generate "
+        "a fatal failure.");
+  Check(env->tear_down_was_run(),
+        "The global tear-down should run, as the global set-up was run.");
+
+  // Verifies that RUN_ALL_TESTS() doesn't do global set-up or
+  // tear-down when there is no test to run.
+  testing::GTEST_FLAG(filter) = "-*";
+  Check(RunAllTests(env, NO_FAILURE) == 0,
+        "RUN_ALL_TESTS() should return zero, as there is no test to run.");
+  Check(!env->set_up_was_run(),
+        "The global set-up should not run, as there is no test to run.");
+  Check(!env->tear_down_was_run(),
+        "The global tear-down should not run, "
+        "as the global set-up was not run.");
+
+  printf("PASS\n");
+  return 0;
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_help_test.py b/leveldb_base/third_party/googletest/googletest/test/gtest_help_test.py
new file mode 100644
index 0000000..8d953bb
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_help_test.py
@@ -0,0 +1,172 @@
+#!/usr/bin/env python
+#
+# Copyright 2009, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Tests the --help flag of Google C++ Testing and Mocking Framework.
+
+SYNOPSIS
+       gtest_help_test.py --build_dir=BUILD/DIR
+         # where BUILD/DIR contains the built gtest_help_test_ file.
+       gtest_help_test.py
+"""
+
+import os
+import re
+import gtest_test_utils
+
+
+IS_LINUX = os.name == 'posix' and os.uname()[0] == 'Linux'
+IS_GNUKFREEBSD = os.name == 'posix' and os.uname()[0] == 'GNU/kFreeBSD'
+IS_WINDOWS = os.name == 'nt'
+
+PROGRAM_PATH = gtest_test_utils.GetTestExecutablePath('gtest_help_test_')
+FLAG_PREFIX = '--gtest_'
+DEATH_TEST_STYLE_FLAG = FLAG_PREFIX + 'death_test_style'
+STREAM_RESULT_TO_FLAG = FLAG_PREFIX + 'stream_result_to'
+UNKNOWN_FLAG = FLAG_PREFIX + 'unknown_flag_for_testing'
+LIST_TESTS_FLAG = FLAG_PREFIX + 'list_tests'
+INCORRECT_FLAG_VARIANTS = [re.sub('^--', '-', LIST_TESTS_FLAG),
+                           re.sub('^--', '/', LIST_TESTS_FLAG),
+                           re.sub('_', '-', LIST_TESTS_FLAG)]
+INTERNAL_FLAG_FOR_TESTING = FLAG_PREFIX + 'internal_flag_for_testing'
+
+SUPPORTS_DEATH_TESTS = "DeathTest" in gtest_test_utils.Subprocess(
+    [PROGRAM_PATH, LIST_TESTS_FLAG]).output
+
+# The help message must match this regex.
+HELP_REGEX = re.compile(
+    FLAG_PREFIX + r'list_tests.*' +
+    FLAG_PREFIX + r'filter=.*' +
+    FLAG_PREFIX + r'also_run_disabled_tests.*' +
+    FLAG_PREFIX + r'repeat=.*' +
+    FLAG_PREFIX + r'shuffle.*' +
+    FLAG_PREFIX + r'random_seed=.*' +
+    FLAG_PREFIX + r'color=.*' +
+    FLAG_PREFIX + r'brief.*' +
+    FLAG_PREFIX + r'print_time.*' +
+    FLAG_PREFIX + r'output=.*' +
+    FLAG_PREFIX + r'break_on_failure.*' +
+    FLAG_PREFIX + r'throw_on_failure.*' +
+    FLAG_PREFIX + r'catch_exceptions=0.*',
+    re.DOTALL)
+
+
+def RunWithFlag(flag):
+  """Runs gtest_help_test_ with the given flag.
+
+  Returns:
+    the exit code and the text output as a tuple.
+  Args:
+    flag: the command-line flag to pass to gtest_help_test_, or None.
+  """
+
+  if flag is None:
+    command = [PROGRAM_PATH]
+  else:
+    command = [PROGRAM_PATH, flag]
+  child = gtest_test_utils.Subprocess(command)
+  return child.exit_code, child.output
+
+
+class GTestHelpTest(gtest_test_utils.TestCase):
+  """Tests the --help flag and its equivalent forms."""
+
+  def TestHelpFlag(self, flag):
+    """Verifies correct behavior when help flag is specified.
+
+    The right message must be printed and the tests must
+    skipped when the given flag is specified.
+
+    Args:
+      flag:  A flag to pass to the binary or None.
+    """
+
+    exit_code, output = RunWithFlag(flag)
+    self.assertEquals(0, exit_code)
+    self.assert_(HELP_REGEX.search(output), output)
+
+    if IS_LINUX or IS_GNUKFREEBSD:
+      self.assert_(STREAM_RESULT_TO_FLAG in output, output)
+    else:
+      self.assert_(STREAM_RESULT_TO_FLAG not in output, output)
+
+    if SUPPORTS_DEATH_TESTS and not IS_WINDOWS:
+      self.assert_(DEATH_TEST_STYLE_FLAG in output, output)
+    else:
+      self.assert_(DEATH_TEST_STYLE_FLAG not in output, output)
+
+  def TestNonHelpFlag(self, flag):
+    """Verifies correct behavior when no help flag is specified.
+
+    Verifies that when no help flag is specified, the tests are run
+    and the help message is not printed.
+
+    Args:
+      flag:  A flag to pass to the binary or None.
+    """
+
+    exit_code, output = RunWithFlag(flag)
+    self.assert_(exit_code != 0)
+    self.assert_(not HELP_REGEX.search(output), output)
+
+  def testPrintsHelpWithFullFlag(self):
+    self.TestHelpFlag('--help')
+
+  def testPrintsHelpWithShortFlag(self):
+    self.TestHelpFlag('-h')
+
+  def testPrintsHelpWithQuestionFlag(self):
+    self.TestHelpFlag('-?')
+
+  def testPrintsHelpWithWindowsStyleQuestionFlag(self):
+    self.TestHelpFlag('/?')
+
+  def testPrintsHelpWithUnrecognizedGoogleTestFlag(self):
+    self.TestHelpFlag(UNKNOWN_FLAG)
+
+  def testPrintsHelpWithIncorrectFlagStyle(self):
+    for incorrect_flag in INCORRECT_FLAG_VARIANTS:
+      self.TestHelpFlag(incorrect_flag)
+
+  def testRunsTestsWithoutHelpFlag(self):
+    """Verifies that when no help flag is specified, the tests are run
+    and the help message is not printed."""
+
+    self.TestNonHelpFlag(None)
+
+  def testRunsTestsWithGtestInternalFlag(self):
+    """Verifies that the tests are run and no help message is printed when
+    a flag starting with Google Test prefix and 'internal_' is supplied."""
+
+    self.TestNonHelpFlag(INTERNAL_FLAG_FOR_TESTING)
+
+
+if __name__ == '__main__':
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_help_test_.cc b/leveldb_base/third_party/googletest/googletest/test/gtest_help_test_.cc
new file mode 100644
index 0000000..750ae6c
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_help_test_.cc
@@ -0,0 +1,45 @@
+// Copyright 2009, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// This program is meant to be run by gtest_help_test.py.  Do not run
+// it directly.
+
+#include "gtest/gtest.h"
+
+// When a help flag is specified, this program should skip the tests
+// and exit with 0; otherwise the following test will be executed,
+// causing this program to exit with a non-zero code.
+TEST(HelpFlagTest, ShouldNotBeRun) {
+  ASSERT_TRUE(false) << "Tests shouldn't be run when --help is specified.";
+}
+
+#if GTEST_HAS_DEATH_TEST
+TEST(DeathTest, UsedByPythonScriptToDetectSupportForDeathTestsInThisBinary) {}
+#endif
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_json_test_utils.py b/leveldb_base/third_party/googletest/googletest/test/gtest_json_test_utils.py
new file mode 100644
index 0000000..62bbfc2
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_json_test_utils.py
@@ -0,0 +1,60 @@
+# Copyright 2018, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Unit test utilities for gtest_json_output."""
+
+import re
+
+
+def normalize(obj):
+  """Normalize output object.
+
+  Args:
+     obj: Google Test's JSON output object to normalize.
+
+  Returns:
+     Normalized output without any references to transient information that may
+     change from run to run.
+  """
+  def _normalize(key, value):
+    if key == 'time':
+      return re.sub(r'^\d+(\.\d+)?s$', '*', value)
+    elif key == 'timestamp':
+      return re.sub(r'^\d{4}-\d\d-\d\dT\d\d:\d\d:\d\dZ$', '*', value)
+    elif key == 'failure':
+      value = re.sub(r'^.*[/\\](.*:)\d+\n', '\\1*\n', value)
+      return re.sub(r'Stack trace:\n(.|\n)*', 'Stack trace:\n*', value)
+    else:
+      return normalize(value)
+  if isinstance(obj, dict):
+    return {k: _normalize(k, v) for k, v in obj.items()}
+  if isinstance(obj, list):
+    return [normalize(x) for x in obj]
+  else:
+    return obj
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_list_output_unittest.py b/leveldb_base/third_party/googletest/googletest/test/gtest_list_output_unittest.py
new file mode 100644
index 0000000..a442fc1
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_list_output_unittest.py
@@ -0,0 +1,286 @@
+#!/usr/bin/env python
+#
+# Copyright 2006, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+"""Unit test for Google Test's --gtest_list_tests flag.
+
+A user can ask Google Test to list all tests by specifying the
+--gtest_list_tests flag. If output is requested, via --gtest_output=xml
+or --gtest_output=json, the tests are listed, with extra information in the
+output file.
+This script tests such functionality by invoking gtest_list_output_unittest_
+ (a program written with Google Test) the command line flags.
+"""
+
+import os
+import re
+import gtest_test_utils
+
+GTEST_LIST_TESTS_FLAG = '--gtest_list_tests'
+GTEST_OUTPUT_FLAG = '--gtest_output'
+
+EXPECTED_XML = """<\?xml version="1.0" encoding="UTF-8"\?>
+<testsuites tests="16" name="AllTests">
+  <testsuite name="FooTest" tests="2">
+    <testcase name="Test1" file=".*gtest_list_output_unittest_.cc" line="43" />
+    <testcase name="Test2" file=".*gtest_list_output_unittest_.cc" line="45" />
+  </testsuite>
+  <testsuite name="FooTestFixture" tests="2">
+    <testcase name="Test3" file=".*gtest_list_output_unittest_.cc" line="48" />
+    <testcase name="Test4" file=".*gtest_list_output_unittest_.cc" line="49" />
+  </testsuite>
+  <testsuite name="TypedTest/0" tests="2">
+    <testcase name="Test7" type_param="int" file=".*gtest_list_output_unittest_.cc" line="60" />
+    <testcase name="Test8" type_param="int" file=".*gtest_list_output_unittest_.cc" line="61" />
+  </testsuite>
+  <testsuite name="TypedTest/1" tests="2">
+    <testcase name="Test7" type_param="bool" file=".*gtest_list_output_unittest_.cc" line="60" />
+    <testcase name="Test8" type_param="bool" file=".*gtest_list_output_unittest_.cc" line="61" />
+  </testsuite>
+  <testsuite name="Single/TypeParameterizedTestSuite/0" tests="2">
+    <testcase name="Test9" type_param="int" file=".*gtest_list_output_unittest_.cc" line="66" />
+    <testcase name="Test10" type_param="int" file=".*gtest_list_output_unittest_.cc" line="67" />
+  </testsuite>
+  <testsuite name="Single/TypeParameterizedTestSuite/1" tests="2">
+    <testcase name="Test9" type_param="bool" file=".*gtest_list_output_unittest_.cc" line="66" />
+    <testcase name="Test10" type_param="bool" file=".*gtest_list_output_unittest_.cc" line="67" />
+  </testsuite>
+  <testsuite name="ValueParam/ValueParamTest" tests="4">
+    <testcase name="Test5/0" value_param="33" file=".*gtest_list_output_unittest_.cc" line="52" />
+    <testcase name="Test5/1" value_param="42" file=".*gtest_list_output_unittest_.cc" line="52" />
+    <testcase name="Test6/0" value_param="33" file=".*gtest_list_output_unittest_.cc" line="53" />
+    <testcase name="Test6/1" value_param="42" file=".*gtest_list_output_unittest_.cc" line="53" />
+  </testsuite>
+</testsuites>
+"""
+
+EXPECTED_JSON = """{
+  "tests": 16,
+  "name": "AllTests",
+  "testsuites": \[
+    {
+      "name": "FooTest",
+      "tests": 2,
+      "testsuite": \[
+        {
+          "name": "Test1",
+          "file": ".*gtest_list_output_unittest_.cc",
+          "line": 43
+        },
+        {
+          "name": "Test2",
+          "file": ".*gtest_list_output_unittest_.cc",
+          "line": 45
+        }
+      \]
+    },
+    {
+      "name": "FooTestFixture",
+      "tests": 2,
+      "testsuite": \[
+        {
+          "name": "Test3",
+          "file": ".*gtest_list_output_unittest_.cc",
+          "line": 48
+        },
+        {
+          "name": "Test4",
+          "file": ".*gtest_list_output_unittest_.cc",
+          "line": 49
+        }
+      \]
+    },
+    {
+      "name": "TypedTest\\\\/0",
+      "tests": 2,
+      "testsuite": \[
+        {
+          "name": "Test7",
+          "type_param": "int",
+          "file": ".*gtest_list_output_unittest_.cc",
+          "line": 60
+        },
+        {
+          "name": "Test8",
+          "type_param": "int",
+          "file": ".*gtest_list_output_unittest_.cc",
+          "line": 61
+        }
+      \]
+    },
+    {
+      "name": "TypedTest\\\\/1",
+      "tests": 2,
+      "testsuite": \[
+        {
+          "name": "Test7",
+          "type_param": "bool",
+          "file": ".*gtest_list_output_unittest_.cc",
+          "line": 60
+        },
+        {
+          "name": "Test8",
+          "type_param": "bool",
+          "file": ".*gtest_list_output_unittest_.cc",
+          "line": 61
+        }
+      \]
+    },
+    {
+      "name": "Single\\\\/TypeParameterizedTestSuite\\\\/0",
+      "tests": 2,
+      "testsuite": \[
+        {
+          "name": "Test9",
+          "type_param": "int",
+          "file": ".*gtest_list_output_unittest_.cc",
+          "line": 66
+        },
+        {
+          "name": "Test10",
+          "type_param": "int",
+          "file": ".*gtest_list_output_unittest_.cc",
+          "line": 67
+        }
+      \]
+    },
+    {
+      "name": "Single\\\\/TypeParameterizedTestSuite\\\\/1",
+      "tests": 2,
+      "testsuite": \[
+        {
+          "name": "Test9",
+          "type_param": "bool",
+          "file": ".*gtest_list_output_unittest_.cc",
+          "line": 66
+        },
+        {
+          "name": "Test10",
+          "type_param": "bool",
+          "file": ".*gtest_list_output_unittest_.cc",
+          "line": 67
+        }
+      \]
+    },
+    {
+      "name": "ValueParam\\\\/ValueParamTest",
+      "tests": 4,
+      "testsuite": \[
+        {
+          "name": "Test5\\\\/0",
+          "value_param": "33",
+          "file": ".*gtest_list_output_unittest_.cc",
+          "line": 52
+        },
+        {
+          "name": "Test5\\\\/1",
+          "value_param": "42",
+          "file": ".*gtest_list_output_unittest_.cc",
+          "line": 52
+        },
+        {
+          "name": "Test6\\\\/0",
+          "value_param": "33",
+          "file": ".*gtest_list_output_unittest_.cc",
+          "line": 53
+        },
+        {
+          "name": "Test6\\\\/1",
+          "value_param": "42",
+          "file": ".*gtest_list_output_unittest_.cc",
+          "line": 53
+        }
+      \]
+    }
+  \]
+}
+"""
+
+
+class GTestListTestsOutputUnitTest(gtest_test_utils.TestCase):
+  """Unit test for Google Test's list tests with output to file functionality.
+  """
+
+  def testXml(self):
+    """Verifies XML output for listing tests in a Google Test binary.
+
+    Runs a test program that generates an empty XML output, and
+    tests that the XML output is expected.
+    """
+    self._TestOutput('xml', EXPECTED_XML)
+
+  def testJSON(self):
+    """Verifies XML output for listing tests in a Google Test binary.
+
+    Runs a test program that generates an empty XML output, and
+    tests that the XML output is expected.
+    """
+    self._TestOutput('json', EXPECTED_JSON)
+
+  def _GetOutput(self, out_format):
+    file_path = os.path.join(gtest_test_utils.GetTempDir(),
+                             'test_out.' + out_format)
+    gtest_prog_path = gtest_test_utils.GetTestExecutablePath(
+        'gtest_list_output_unittest_')
+
+    command = ([
+        gtest_prog_path,
+        '%s=%s:%s' % (GTEST_OUTPUT_FLAG, out_format, file_path),
+        '--gtest_list_tests'
+    ])
+    environ_copy = os.environ.copy()
+    p = gtest_test_utils.Subprocess(
+        command, env=environ_copy, working_dir=gtest_test_utils.GetTempDir())
+
+    self.assertTrue(p.exited)
+    self.assertEqual(0, p.exit_code)
+    self.assertTrue(os.path.isfile(file_path))
+    with open(file_path) as f:
+      result = f.read()
+    return result
+
+  def _TestOutput(self, test_format, expected_output):
+    actual = self._GetOutput(test_format)
+    actual_lines = actual.splitlines()
+    expected_lines = expected_output.splitlines()
+    line_count = 0
+    for actual_line in actual_lines:
+      expected_line = expected_lines[line_count]
+      expected_line_re = re.compile(expected_line.strip())
+      self.assertTrue(
+          expected_line_re.match(actual_line.strip()),
+          ('actual output of "%s",\n'
+           'which does not match expected regex of "%s"\n'
+           'on line %d' % (actual, expected_output, line_count)))
+      line_count = line_count + 1
+
+
+if __name__ == '__main__':
+  os.environ['GTEST_STACK_TRACE_DEPTH'] = '1'
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_list_output_unittest_.cc b/leveldb_base/third_party/googletest/googletest/test/gtest_list_output_unittest_.cc
new file mode 100644
index 0000000..92b9d4f
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_list_output_unittest_.cc
@@ -0,0 +1,77 @@
+// Copyright 2018, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// Author: david.schuldenfrei@gmail.com (David Schuldenfrei)
+
+// Unit test for Google Test's --gtest_list_tests and --gtest_output flag.
+//
+// A user can ask Google Test to list all tests that will run,
+// and have the output saved in a Json/Xml file.
+// The tests will not be run after listing.
+//
+// This program will be invoked from a Python unit test.
+// Don't run it directly.
+
+#include "gtest/gtest.h"
+
+TEST(FooTest, Test1) {}
+
+TEST(FooTest, Test2) {}
+
+class FooTestFixture : public ::testing::Test {};
+TEST_F(FooTestFixture, Test3) {}
+TEST_F(FooTestFixture, Test4) {}
+
+class ValueParamTest : public ::testing::TestWithParam<int> {};
+TEST_P(ValueParamTest, Test5) {}
+TEST_P(ValueParamTest, Test6) {}
+INSTANTIATE_TEST_SUITE_P(ValueParam, ValueParamTest, ::testing::Values(33, 42));
+
+template <typename T>
+class TypedTest : public ::testing::Test {};
+typedef testing::Types<int, bool> TypedTestTypes;
+TYPED_TEST_SUITE(TypedTest, TypedTestTypes);
+TYPED_TEST(TypedTest, Test7) {}
+TYPED_TEST(TypedTest, Test8) {}
+
+template <typename T>
+class TypeParameterizedTestSuite : public ::testing::Test {};
+TYPED_TEST_SUITE_P(TypeParameterizedTestSuite);
+TYPED_TEST_P(TypeParameterizedTestSuite, Test9) {}
+TYPED_TEST_P(TypeParameterizedTestSuite, Test10) {}
+REGISTER_TYPED_TEST_SUITE_P(TypeParameterizedTestSuite, Test9, Test10);
+typedef testing::Types<int, bool> TypeParameterizedTestSuiteTypes;  // NOLINT
+INSTANTIATE_TYPED_TEST_SUITE_P(Single, TypeParameterizedTestSuite,
+                               TypeParameterizedTestSuiteTypes);
+
+int main(int argc, char **argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+
+  return RUN_ALL_TESTS();
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_main_unittest.cc b/leveldb_base/third_party/googletest/googletest/test/gtest_main_unittest.cc
new file mode 100644
index 0000000..eddedea
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_main_unittest.cc
@@ -0,0 +1,44 @@
+// Copyright 2006, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+#include "gtest/gtest.h"
+
+// Tests that we don't have to define main() when we link to
+// gtest_main instead of gtest.
+
+namespace {
+
+TEST(GTestMainTest, ShouldSucceed) {
+}
+
+}  // namespace
+
+// We are using the main() function defined in gtest_main.cc, so we
+// don't define it here.
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_no_test_unittest.cc b/leveldb_base/third_party/googletest/googletest/test/gtest_no_test_unittest.cc
new file mode 100644
index 0000000..d4f88db
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_no_test_unittest.cc
@@ -0,0 +1,54 @@
+// Copyright 2006, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Tests that a Google Test program that has no test defined can run
+// successfully.
+
+#include "gtest/gtest.h"
+
+int main(int argc, char **argv) {
+  testing::InitGoogleTest(&argc, argv);
+
+  // An ad-hoc assertion outside of all tests.
+  //
+  // This serves three purposes:
+  //
+  // 1. It verifies that an ad-hoc assertion can be executed even if
+  //    no test is defined.
+  // 2. It verifies that a failed ad-hoc assertion causes the test
+  //    program to fail.
+  // 3. We had a bug where the XML output won't be generated if an
+  //    assertion is executed before RUN_ALL_TESTS() is called, even
+  //    though --gtest_output=xml is specified.  This makes sure the
+  //    bug is fixed and doesn't regress.
+  EXPECT_EQ(1, 2);
+
+  // The above EXPECT_EQ() should cause RUN_ALL_TESTS() to return non-zero.
+  return RUN_ALL_TESTS() ? 0 : 1;
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_pred_impl_unittest.cc b/leveldb_base/third_party/googletest/googletest/test/gtest_pred_impl_unittest.cc
new file mode 100644
index 0000000..bbef994
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_pred_impl_unittest.cc
@@ -0,0 +1,2422 @@
+// Copyright 2006, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// This file is AUTOMATICALLY GENERATED on 11/05/2019 by command
+// 'gen_gtest_pred_impl.py 5'.  DO NOT EDIT BY HAND!
+
+// Regression test for gtest_pred_impl.h
+//
+// This file is generated by a script and quite long.  If you intend to
+// learn how Google Test works by reading its unit tests, read
+// gtest_unittest.cc instead.
+//
+// This is intended as a regression test for the Google Test predicate
+// assertions.  We compile it as part of the gtest_unittest target
+// only to keep the implementation tidy and compact, as it is quite
+// involved to set up the stage for testing Google Test using Google
+// Test itself.
+//
+// Currently, gtest_unittest takes ~11 seconds to run in the testing
+// daemon.  In the future, if it grows too large and needs much more
+// time to finish, we should consider separating this file into a
+// stand-alone regression test.
+
+#include <iostream>
+
+#include "gtest/gtest.h"
+#include "gtest/gtest-spi.h"
+
+// A user-defined data type.
+struct Bool {
+  explicit Bool(int val) : value(val != 0) {}
+
+  bool operator>(int n) const { return value > Bool(n).value; }
+
+  Bool operator+(const Bool& rhs) const { return Bool(value + rhs.value); }
+
+  bool operator==(const Bool& rhs) const { return value == rhs.value; }
+
+  bool value;
+};
+
+// Enables Bool to be used in assertions.
+std::ostream& operator<<(std::ostream& os, const Bool& x) {
+  return os << (x.value ? "true" : "false");
+}
+
+// Sample functions/functors for testing unary predicate assertions.
+
+// A unary predicate function.
+template <typename T1>
+bool PredFunction1(T1 v1) {
+  return v1 > 0;
+}
+
+// The following two functions are needed because a compiler doesn't have
+// a context yet to know which template function must be instantiated.
+bool PredFunction1Int(int v1) {
+  return v1 > 0;
+}
+bool PredFunction1Bool(Bool v1) {
+  return v1 > 0;
+}
+
+// A unary predicate functor.
+struct PredFunctor1 {
+  template <typename T1>
+  bool operator()(const T1& v1) {
+    return v1 > 0;
+  }
+};
+
+// A unary predicate-formatter function.
+template <typename T1>
+testing::AssertionResult PredFormatFunction1(const char* e1,
+                                             const T1& v1) {
+  if (PredFunction1(v1))
+    return testing::AssertionSuccess();
+
+  return testing::AssertionFailure()
+      << e1
+      << " is expected to be positive, but evaluates to "
+      << v1 << ".";
+}
+
+// A unary predicate-formatter functor.
+struct PredFormatFunctor1 {
+  template <typename T1>
+  testing::AssertionResult operator()(const char* e1,
+                                      const T1& v1) const {
+    return PredFormatFunction1(e1, v1);
+  }
+};
+
+// Tests for {EXPECT|ASSERT}_PRED_FORMAT1.
+
+class Predicate1Test : public testing::Test {
+ protected:
+  void SetUp() override {
+    expected_to_finish_ = true;
+    finished_ = false;
+    n1_ = 0;
+  }
+
+  void TearDown() override {
+    // Verifies that each of the predicate's arguments was evaluated
+    // exactly once.
+    EXPECT_EQ(1, n1_) <<
+        "The predicate assertion didn't evaluate argument 2 "
+        "exactly once.";
+
+    // Verifies that the control flow in the test function is expected.
+    if (expected_to_finish_ && !finished_) {
+      FAIL() << "The predicate assertion unexpactedly aborted the test.";
+    } else if (!expected_to_finish_ && finished_) {
+      FAIL() << "The failed predicate assertion didn't abort the test "
+                "as expected.";
+    }
+  }
+
+  // true if and only if the test function is expected to run to finish.
+  static bool expected_to_finish_;
+
+  // true if and only if the test function did run to finish.
+  static bool finished_;
+
+  static int n1_;
+};
+
+bool Predicate1Test::expected_to_finish_;
+bool Predicate1Test::finished_;
+int Predicate1Test::n1_;
+
+typedef Predicate1Test EXPECT_PRED_FORMAT1Test;
+typedef Predicate1Test ASSERT_PRED_FORMAT1Test;
+typedef Predicate1Test EXPECT_PRED1Test;
+typedef Predicate1Test ASSERT_PRED1Test;
+
+// Tests a successful EXPECT_PRED1 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(EXPECT_PRED1Test, FunctionOnBuiltInTypeSuccess) {
+  EXPECT_PRED1(PredFunction1Int,
+               ++n1_);
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED1 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(EXPECT_PRED1Test, FunctionOnUserTypeSuccess) {
+  EXPECT_PRED1(PredFunction1Bool,
+               Bool(++n1_));
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED1 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(EXPECT_PRED1Test, FunctorOnBuiltInTypeSuccess) {
+  EXPECT_PRED1(PredFunctor1(),
+               ++n1_);
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED1 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(EXPECT_PRED1Test, FunctorOnUserTypeSuccess) {
+  EXPECT_PRED1(PredFunctor1(),
+               Bool(++n1_));
+  finished_ = true;
+}
+
+// Tests a failed EXPECT_PRED1 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(EXPECT_PRED1Test, FunctionOnBuiltInTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED1(PredFunction1Int,
+                 n1_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED1 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(EXPECT_PRED1Test, FunctionOnUserTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED1(PredFunction1Bool,
+                 Bool(n1_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED1 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(EXPECT_PRED1Test, FunctorOnBuiltInTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED1(PredFunctor1(),
+                 n1_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED1 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(EXPECT_PRED1Test, FunctorOnUserTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED1(PredFunctor1(),
+                 Bool(n1_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a successful ASSERT_PRED1 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(ASSERT_PRED1Test, FunctionOnBuiltInTypeSuccess) {
+  ASSERT_PRED1(PredFunction1Int,
+               ++n1_);
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED1 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(ASSERT_PRED1Test, FunctionOnUserTypeSuccess) {
+  ASSERT_PRED1(PredFunction1Bool,
+               Bool(++n1_));
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED1 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(ASSERT_PRED1Test, FunctorOnBuiltInTypeSuccess) {
+  ASSERT_PRED1(PredFunctor1(),
+               ++n1_);
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED1 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(ASSERT_PRED1Test, FunctorOnUserTypeSuccess) {
+  ASSERT_PRED1(PredFunctor1(),
+               Bool(++n1_));
+  finished_ = true;
+}
+
+// Tests a failed ASSERT_PRED1 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(ASSERT_PRED1Test, FunctionOnBuiltInTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED1(PredFunction1Int,
+                 n1_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED1 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(ASSERT_PRED1Test, FunctionOnUserTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED1(PredFunction1Bool,
+                 Bool(n1_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED1 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(ASSERT_PRED1Test, FunctorOnBuiltInTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED1(PredFunctor1(),
+                 n1_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED1 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(ASSERT_PRED1Test, FunctorOnUserTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED1(PredFunctor1(),
+                 Bool(n1_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a successful EXPECT_PRED_FORMAT1 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(EXPECT_PRED_FORMAT1Test, FunctionOnBuiltInTypeSuccess) {
+  EXPECT_PRED_FORMAT1(PredFormatFunction1,
+                      ++n1_);
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED_FORMAT1 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(EXPECT_PRED_FORMAT1Test, FunctionOnUserTypeSuccess) {
+  EXPECT_PRED_FORMAT1(PredFormatFunction1,
+                      Bool(++n1_));
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED_FORMAT1 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(EXPECT_PRED_FORMAT1Test, FunctorOnBuiltInTypeSuccess) {
+  EXPECT_PRED_FORMAT1(PredFormatFunctor1(),
+                      ++n1_);
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED_FORMAT1 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(EXPECT_PRED_FORMAT1Test, FunctorOnUserTypeSuccess) {
+  EXPECT_PRED_FORMAT1(PredFormatFunctor1(),
+                      Bool(++n1_));
+  finished_ = true;
+}
+
+// Tests a failed EXPECT_PRED_FORMAT1 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(EXPECT_PRED_FORMAT1Test, FunctionOnBuiltInTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT1(PredFormatFunction1,
+                        n1_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED_FORMAT1 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(EXPECT_PRED_FORMAT1Test, FunctionOnUserTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT1(PredFormatFunction1,
+                        Bool(n1_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED_FORMAT1 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(EXPECT_PRED_FORMAT1Test, FunctorOnBuiltInTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT1(PredFormatFunctor1(),
+                        n1_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED_FORMAT1 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(EXPECT_PRED_FORMAT1Test, FunctorOnUserTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT1(PredFormatFunctor1(),
+                        Bool(n1_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a successful ASSERT_PRED_FORMAT1 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(ASSERT_PRED_FORMAT1Test, FunctionOnBuiltInTypeSuccess) {
+  ASSERT_PRED_FORMAT1(PredFormatFunction1,
+                      ++n1_);
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED_FORMAT1 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(ASSERT_PRED_FORMAT1Test, FunctionOnUserTypeSuccess) {
+  ASSERT_PRED_FORMAT1(PredFormatFunction1,
+                      Bool(++n1_));
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED_FORMAT1 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(ASSERT_PRED_FORMAT1Test, FunctorOnBuiltInTypeSuccess) {
+  ASSERT_PRED_FORMAT1(PredFormatFunctor1(),
+                      ++n1_);
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED_FORMAT1 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(ASSERT_PRED_FORMAT1Test, FunctorOnUserTypeSuccess) {
+  ASSERT_PRED_FORMAT1(PredFormatFunctor1(),
+                      Bool(++n1_));
+  finished_ = true;
+}
+
+// Tests a failed ASSERT_PRED_FORMAT1 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(ASSERT_PRED_FORMAT1Test, FunctionOnBuiltInTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT1(PredFormatFunction1,
+                        n1_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED_FORMAT1 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(ASSERT_PRED_FORMAT1Test, FunctionOnUserTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT1(PredFormatFunction1,
+                        Bool(n1_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED_FORMAT1 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(ASSERT_PRED_FORMAT1Test, FunctorOnBuiltInTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT1(PredFormatFunctor1(),
+                        n1_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED_FORMAT1 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(ASSERT_PRED_FORMAT1Test, FunctorOnUserTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT1(PredFormatFunctor1(),
+                        Bool(n1_++));
+    finished_ = true;
+  }, "");
+}
+// Sample functions/functors for testing binary predicate assertions.
+
+// A binary predicate function.
+template <typename T1, typename T2>
+bool PredFunction2(T1 v1, T2 v2) {
+  return v1 + v2 > 0;
+}
+
+// The following two functions are needed because a compiler doesn't have
+// a context yet to know which template function must be instantiated.
+bool PredFunction2Int(int v1, int v2) {
+  return v1 + v2 > 0;
+}
+bool PredFunction2Bool(Bool v1, Bool v2) {
+  return v1 + v2 > 0;
+}
+
+// A binary predicate functor.
+struct PredFunctor2 {
+  template <typename T1, typename T2>
+  bool operator()(const T1& v1,
+                  const T2& v2) {
+    return v1 + v2 > 0;
+  }
+};
+
+// A binary predicate-formatter function.
+template <typename T1, typename T2>
+testing::AssertionResult PredFormatFunction2(const char* e1,
+                                             const char* e2,
+                                             const T1& v1,
+                                             const T2& v2) {
+  if (PredFunction2(v1, v2))
+    return testing::AssertionSuccess();
+
+  return testing::AssertionFailure()
+      << e1 << " + " << e2
+      << " is expected to be positive, but evaluates to "
+      << v1 + v2 << ".";
+}
+
+// A binary predicate-formatter functor.
+struct PredFormatFunctor2 {
+  template <typename T1, typename T2>
+  testing::AssertionResult operator()(const char* e1,
+                                      const char* e2,
+                                      const T1& v1,
+                                      const T2& v2) const {
+    return PredFormatFunction2(e1, e2, v1, v2);
+  }
+};
+
+// Tests for {EXPECT|ASSERT}_PRED_FORMAT2.
+
+class Predicate2Test : public testing::Test {
+ protected:
+  void SetUp() override {
+    expected_to_finish_ = true;
+    finished_ = false;
+    n1_ = n2_ = 0;
+  }
+
+  void TearDown() override {
+    // Verifies that each of the predicate's arguments was evaluated
+    // exactly once.
+    EXPECT_EQ(1, n1_) <<
+        "The predicate assertion didn't evaluate argument 2 "
+        "exactly once.";
+    EXPECT_EQ(1, n2_) <<
+        "The predicate assertion didn't evaluate argument 3 "
+        "exactly once.";
+
+    // Verifies that the control flow in the test function is expected.
+    if (expected_to_finish_ && !finished_) {
+      FAIL() << "The predicate assertion unexpactedly aborted the test.";
+    } else if (!expected_to_finish_ && finished_) {
+      FAIL() << "The failed predicate assertion didn't abort the test "
+                "as expected.";
+    }
+  }
+
+  // true if and only if the test function is expected to run to finish.
+  static bool expected_to_finish_;
+
+  // true if and only if the test function did run to finish.
+  static bool finished_;
+
+  static int n1_;
+  static int n2_;
+};
+
+bool Predicate2Test::expected_to_finish_;
+bool Predicate2Test::finished_;
+int Predicate2Test::n1_;
+int Predicate2Test::n2_;
+
+typedef Predicate2Test EXPECT_PRED_FORMAT2Test;
+typedef Predicate2Test ASSERT_PRED_FORMAT2Test;
+typedef Predicate2Test EXPECT_PRED2Test;
+typedef Predicate2Test ASSERT_PRED2Test;
+
+// Tests a successful EXPECT_PRED2 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(EXPECT_PRED2Test, FunctionOnBuiltInTypeSuccess) {
+  EXPECT_PRED2(PredFunction2Int,
+               ++n1_,
+               ++n2_);
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED2 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(EXPECT_PRED2Test, FunctionOnUserTypeSuccess) {
+  EXPECT_PRED2(PredFunction2Bool,
+               Bool(++n1_),
+               Bool(++n2_));
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED2 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(EXPECT_PRED2Test, FunctorOnBuiltInTypeSuccess) {
+  EXPECT_PRED2(PredFunctor2(),
+               ++n1_,
+               ++n2_);
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED2 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(EXPECT_PRED2Test, FunctorOnUserTypeSuccess) {
+  EXPECT_PRED2(PredFunctor2(),
+               Bool(++n1_),
+               Bool(++n2_));
+  finished_ = true;
+}
+
+// Tests a failed EXPECT_PRED2 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(EXPECT_PRED2Test, FunctionOnBuiltInTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED2(PredFunction2Int,
+                 n1_++,
+                 n2_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED2 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(EXPECT_PRED2Test, FunctionOnUserTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED2(PredFunction2Bool,
+                 Bool(n1_++),
+                 Bool(n2_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED2 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(EXPECT_PRED2Test, FunctorOnBuiltInTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED2(PredFunctor2(),
+                 n1_++,
+                 n2_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED2 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(EXPECT_PRED2Test, FunctorOnUserTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED2(PredFunctor2(),
+                 Bool(n1_++),
+                 Bool(n2_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a successful ASSERT_PRED2 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(ASSERT_PRED2Test, FunctionOnBuiltInTypeSuccess) {
+  ASSERT_PRED2(PredFunction2Int,
+               ++n1_,
+               ++n2_);
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED2 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(ASSERT_PRED2Test, FunctionOnUserTypeSuccess) {
+  ASSERT_PRED2(PredFunction2Bool,
+               Bool(++n1_),
+               Bool(++n2_));
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED2 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(ASSERT_PRED2Test, FunctorOnBuiltInTypeSuccess) {
+  ASSERT_PRED2(PredFunctor2(),
+               ++n1_,
+               ++n2_);
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED2 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(ASSERT_PRED2Test, FunctorOnUserTypeSuccess) {
+  ASSERT_PRED2(PredFunctor2(),
+               Bool(++n1_),
+               Bool(++n2_));
+  finished_ = true;
+}
+
+// Tests a failed ASSERT_PRED2 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(ASSERT_PRED2Test, FunctionOnBuiltInTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED2(PredFunction2Int,
+                 n1_++,
+                 n2_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED2 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(ASSERT_PRED2Test, FunctionOnUserTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED2(PredFunction2Bool,
+                 Bool(n1_++),
+                 Bool(n2_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED2 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(ASSERT_PRED2Test, FunctorOnBuiltInTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED2(PredFunctor2(),
+                 n1_++,
+                 n2_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED2 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(ASSERT_PRED2Test, FunctorOnUserTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED2(PredFunctor2(),
+                 Bool(n1_++),
+                 Bool(n2_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a successful EXPECT_PRED_FORMAT2 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(EXPECT_PRED_FORMAT2Test, FunctionOnBuiltInTypeSuccess) {
+  EXPECT_PRED_FORMAT2(PredFormatFunction2,
+                      ++n1_,
+                      ++n2_);
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED_FORMAT2 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(EXPECT_PRED_FORMAT2Test, FunctionOnUserTypeSuccess) {
+  EXPECT_PRED_FORMAT2(PredFormatFunction2,
+                      Bool(++n1_),
+                      Bool(++n2_));
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED_FORMAT2 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(EXPECT_PRED_FORMAT2Test, FunctorOnBuiltInTypeSuccess) {
+  EXPECT_PRED_FORMAT2(PredFormatFunctor2(),
+                      ++n1_,
+                      ++n2_);
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED_FORMAT2 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(EXPECT_PRED_FORMAT2Test, FunctorOnUserTypeSuccess) {
+  EXPECT_PRED_FORMAT2(PredFormatFunctor2(),
+                      Bool(++n1_),
+                      Bool(++n2_));
+  finished_ = true;
+}
+
+// Tests a failed EXPECT_PRED_FORMAT2 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(EXPECT_PRED_FORMAT2Test, FunctionOnBuiltInTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT2(PredFormatFunction2,
+                        n1_++,
+                        n2_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED_FORMAT2 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(EXPECT_PRED_FORMAT2Test, FunctionOnUserTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT2(PredFormatFunction2,
+                        Bool(n1_++),
+                        Bool(n2_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED_FORMAT2 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(EXPECT_PRED_FORMAT2Test, FunctorOnBuiltInTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT2(PredFormatFunctor2(),
+                        n1_++,
+                        n2_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED_FORMAT2 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(EXPECT_PRED_FORMAT2Test, FunctorOnUserTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT2(PredFormatFunctor2(),
+                        Bool(n1_++),
+                        Bool(n2_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a successful ASSERT_PRED_FORMAT2 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(ASSERT_PRED_FORMAT2Test, FunctionOnBuiltInTypeSuccess) {
+  ASSERT_PRED_FORMAT2(PredFormatFunction2,
+                      ++n1_,
+                      ++n2_);
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED_FORMAT2 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(ASSERT_PRED_FORMAT2Test, FunctionOnUserTypeSuccess) {
+  ASSERT_PRED_FORMAT2(PredFormatFunction2,
+                      Bool(++n1_),
+                      Bool(++n2_));
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED_FORMAT2 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(ASSERT_PRED_FORMAT2Test, FunctorOnBuiltInTypeSuccess) {
+  ASSERT_PRED_FORMAT2(PredFormatFunctor2(),
+                      ++n1_,
+                      ++n2_);
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED_FORMAT2 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(ASSERT_PRED_FORMAT2Test, FunctorOnUserTypeSuccess) {
+  ASSERT_PRED_FORMAT2(PredFormatFunctor2(),
+                      Bool(++n1_),
+                      Bool(++n2_));
+  finished_ = true;
+}
+
+// Tests a failed ASSERT_PRED_FORMAT2 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(ASSERT_PRED_FORMAT2Test, FunctionOnBuiltInTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT2(PredFormatFunction2,
+                        n1_++,
+                        n2_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED_FORMAT2 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(ASSERT_PRED_FORMAT2Test, FunctionOnUserTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT2(PredFormatFunction2,
+                        Bool(n1_++),
+                        Bool(n2_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED_FORMAT2 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(ASSERT_PRED_FORMAT2Test, FunctorOnBuiltInTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT2(PredFormatFunctor2(),
+                        n1_++,
+                        n2_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED_FORMAT2 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(ASSERT_PRED_FORMAT2Test, FunctorOnUserTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT2(PredFormatFunctor2(),
+                        Bool(n1_++),
+                        Bool(n2_++));
+    finished_ = true;
+  }, "");
+}
+// Sample functions/functors for testing ternary predicate assertions.
+
+// A ternary predicate function.
+template <typename T1, typename T2, typename T3>
+bool PredFunction3(T1 v1, T2 v2, T3 v3) {
+  return v1 + v2 + v3 > 0;
+}
+
+// The following two functions are needed because a compiler doesn't have
+// a context yet to know which template function must be instantiated.
+bool PredFunction3Int(int v1, int v2, int v3) {
+  return v1 + v2 + v3 > 0;
+}
+bool PredFunction3Bool(Bool v1, Bool v2, Bool v3) {
+  return v1 + v2 + v3 > 0;
+}
+
+// A ternary predicate functor.
+struct PredFunctor3 {
+  template <typename T1, typename T2, typename T3>
+  bool operator()(const T1& v1,
+                  const T2& v2,
+                  const T3& v3) {
+    return v1 + v2 + v3 > 0;
+  }
+};
+
+// A ternary predicate-formatter function.
+template <typename T1, typename T2, typename T3>
+testing::AssertionResult PredFormatFunction3(const char* e1,
+                                             const char* e2,
+                                             const char* e3,
+                                             const T1& v1,
+                                             const T2& v2,
+                                             const T3& v3) {
+  if (PredFunction3(v1, v2, v3))
+    return testing::AssertionSuccess();
+
+  return testing::AssertionFailure()
+      << e1 << " + " << e2 << " + " << e3
+      << " is expected to be positive, but evaluates to "
+      << v1 + v2 + v3 << ".";
+}
+
+// A ternary predicate-formatter functor.
+struct PredFormatFunctor3 {
+  template <typename T1, typename T2, typename T3>
+  testing::AssertionResult operator()(const char* e1,
+                                      const char* e2,
+                                      const char* e3,
+                                      const T1& v1,
+                                      const T2& v2,
+                                      const T3& v3) const {
+    return PredFormatFunction3(e1, e2, e3, v1, v2, v3);
+  }
+};
+
+// Tests for {EXPECT|ASSERT}_PRED_FORMAT3.
+
+class Predicate3Test : public testing::Test {
+ protected:
+  void SetUp() override {
+    expected_to_finish_ = true;
+    finished_ = false;
+    n1_ = n2_ = n3_ = 0;
+  }
+
+  void TearDown() override {
+    // Verifies that each of the predicate's arguments was evaluated
+    // exactly once.
+    EXPECT_EQ(1, n1_) <<
+        "The predicate assertion didn't evaluate argument 2 "
+        "exactly once.";
+    EXPECT_EQ(1, n2_) <<
+        "The predicate assertion didn't evaluate argument 3 "
+        "exactly once.";
+    EXPECT_EQ(1, n3_) <<
+        "The predicate assertion didn't evaluate argument 4 "
+        "exactly once.";
+
+    // Verifies that the control flow in the test function is expected.
+    if (expected_to_finish_ && !finished_) {
+      FAIL() << "The predicate assertion unexpactedly aborted the test.";
+    } else if (!expected_to_finish_ && finished_) {
+      FAIL() << "The failed predicate assertion didn't abort the test "
+                "as expected.";
+    }
+  }
+
+  // true if and only if the test function is expected to run to finish.
+  static bool expected_to_finish_;
+
+  // true if and only if the test function did run to finish.
+  static bool finished_;
+
+  static int n1_;
+  static int n2_;
+  static int n3_;
+};
+
+bool Predicate3Test::expected_to_finish_;
+bool Predicate3Test::finished_;
+int Predicate3Test::n1_;
+int Predicate3Test::n2_;
+int Predicate3Test::n3_;
+
+typedef Predicate3Test EXPECT_PRED_FORMAT3Test;
+typedef Predicate3Test ASSERT_PRED_FORMAT3Test;
+typedef Predicate3Test EXPECT_PRED3Test;
+typedef Predicate3Test ASSERT_PRED3Test;
+
+// Tests a successful EXPECT_PRED3 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(EXPECT_PRED3Test, FunctionOnBuiltInTypeSuccess) {
+  EXPECT_PRED3(PredFunction3Int,
+               ++n1_,
+               ++n2_,
+               ++n3_);
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED3 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(EXPECT_PRED3Test, FunctionOnUserTypeSuccess) {
+  EXPECT_PRED3(PredFunction3Bool,
+               Bool(++n1_),
+               Bool(++n2_),
+               Bool(++n3_));
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED3 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(EXPECT_PRED3Test, FunctorOnBuiltInTypeSuccess) {
+  EXPECT_PRED3(PredFunctor3(),
+               ++n1_,
+               ++n2_,
+               ++n3_);
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED3 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(EXPECT_PRED3Test, FunctorOnUserTypeSuccess) {
+  EXPECT_PRED3(PredFunctor3(),
+               Bool(++n1_),
+               Bool(++n2_),
+               Bool(++n3_));
+  finished_ = true;
+}
+
+// Tests a failed EXPECT_PRED3 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(EXPECT_PRED3Test, FunctionOnBuiltInTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED3(PredFunction3Int,
+                 n1_++,
+                 n2_++,
+                 n3_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED3 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(EXPECT_PRED3Test, FunctionOnUserTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED3(PredFunction3Bool,
+                 Bool(n1_++),
+                 Bool(n2_++),
+                 Bool(n3_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED3 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(EXPECT_PRED3Test, FunctorOnBuiltInTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED3(PredFunctor3(),
+                 n1_++,
+                 n2_++,
+                 n3_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED3 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(EXPECT_PRED3Test, FunctorOnUserTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED3(PredFunctor3(),
+                 Bool(n1_++),
+                 Bool(n2_++),
+                 Bool(n3_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a successful ASSERT_PRED3 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(ASSERT_PRED3Test, FunctionOnBuiltInTypeSuccess) {
+  ASSERT_PRED3(PredFunction3Int,
+               ++n1_,
+               ++n2_,
+               ++n3_);
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED3 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(ASSERT_PRED3Test, FunctionOnUserTypeSuccess) {
+  ASSERT_PRED3(PredFunction3Bool,
+               Bool(++n1_),
+               Bool(++n2_),
+               Bool(++n3_));
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED3 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(ASSERT_PRED3Test, FunctorOnBuiltInTypeSuccess) {
+  ASSERT_PRED3(PredFunctor3(),
+               ++n1_,
+               ++n2_,
+               ++n3_);
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED3 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(ASSERT_PRED3Test, FunctorOnUserTypeSuccess) {
+  ASSERT_PRED3(PredFunctor3(),
+               Bool(++n1_),
+               Bool(++n2_),
+               Bool(++n3_));
+  finished_ = true;
+}
+
+// Tests a failed ASSERT_PRED3 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(ASSERT_PRED3Test, FunctionOnBuiltInTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED3(PredFunction3Int,
+                 n1_++,
+                 n2_++,
+                 n3_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED3 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(ASSERT_PRED3Test, FunctionOnUserTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED3(PredFunction3Bool,
+                 Bool(n1_++),
+                 Bool(n2_++),
+                 Bool(n3_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED3 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(ASSERT_PRED3Test, FunctorOnBuiltInTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED3(PredFunctor3(),
+                 n1_++,
+                 n2_++,
+                 n3_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED3 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(ASSERT_PRED3Test, FunctorOnUserTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED3(PredFunctor3(),
+                 Bool(n1_++),
+                 Bool(n2_++),
+                 Bool(n3_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a successful EXPECT_PRED_FORMAT3 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(EXPECT_PRED_FORMAT3Test, FunctionOnBuiltInTypeSuccess) {
+  EXPECT_PRED_FORMAT3(PredFormatFunction3,
+                      ++n1_,
+                      ++n2_,
+                      ++n3_);
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED_FORMAT3 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(EXPECT_PRED_FORMAT3Test, FunctionOnUserTypeSuccess) {
+  EXPECT_PRED_FORMAT3(PredFormatFunction3,
+                      Bool(++n1_),
+                      Bool(++n2_),
+                      Bool(++n3_));
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED_FORMAT3 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(EXPECT_PRED_FORMAT3Test, FunctorOnBuiltInTypeSuccess) {
+  EXPECT_PRED_FORMAT3(PredFormatFunctor3(),
+                      ++n1_,
+                      ++n2_,
+                      ++n3_);
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED_FORMAT3 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(EXPECT_PRED_FORMAT3Test, FunctorOnUserTypeSuccess) {
+  EXPECT_PRED_FORMAT3(PredFormatFunctor3(),
+                      Bool(++n1_),
+                      Bool(++n2_),
+                      Bool(++n3_));
+  finished_ = true;
+}
+
+// Tests a failed EXPECT_PRED_FORMAT3 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(EXPECT_PRED_FORMAT3Test, FunctionOnBuiltInTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT3(PredFormatFunction3,
+                        n1_++,
+                        n2_++,
+                        n3_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED_FORMAT3 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(EXPECT_PRED_FORMAT3Test, FunctionOnUserTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT3(PredFormatFunction3,
+                        Bool(n1_++),
+                        Bool(n2_++),
+                        Bool(n3_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED_FORMAT3 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(EXPECT_PRED_FORMAT3Test, FunctorOnBuiltInTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT3(PredFormatFunctor3(),
+                        n1_++,
+                        n2_++,
+                        n3_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED_FORMAT3 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(EXPECT_PRED_FORMAT3Test, FunctorOnUserTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT3(PredFormatFunctor3(),
+                        Bool(n1_++),
+                        Bool(n2_++),
+                        Bool(n3_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a successful ASSERT_PRED_FORMAT3 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(ASSERT_PRED_FORMAT3Test, FunctionOnBuiltInTypeSuccess) {
+  ASSERT_PRED_FORMAT3(PredFormatFunction3,
+                      ++n1_,
+                      ++n2_,
+                      ++n3_);
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED_FORMAT3 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(ASSERT_PRED_FORMAT3Test, FunctionOnUserTypeSuccess) {
+  ASSERT_PRED_FORMAT3(PredFormatFunction3,
+                      Bool(++n1_),
+                      Bool(++n2_),
+                      Bool(++n3_));
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED_FORMAT3 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(ASSERT_PRED_FORMAT3Test, FunctorOnBuiltInTypeSuccess) {
+  ASSERT_PRED_FORMAT3(PredFormatFunctor3(),
+                      ++n1_,
+                      ++n2_,
+                      ++n3_);
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED_FORMAT3 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(ASSERT_PRED_FORMAT3Test, FunctorOnUserTypeSuccess) {
+  ASSERT_PRED_FORMAT3(PredFormatFunctor3(),
+                      Bool(++n1_),
+                      Bool(++n2_),
+                      Bool(++n3_));
+  finished_ = true;
+}
+
+// Tests a failed ASSERT_PRED_FORMAT3 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(ASSERT_PRED_FORMAT3Test, FunctionOnBuiltInTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT3(PredFormatFunction3,
+                        n1_++,
+                        n2_++,
+                        n3_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED_FORMAT3 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(ASSERT_PRED_FORMAT3Test, FunctionOnUserTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT3(PredFormatFunction3,
+                        Bool(n1_++),
+                        Bool(n2_++),
+                        Bool(n3_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED_FORMAT3 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(ASSERT_PRED_FORMAT3Test, FunctorOnBuiltInTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT3(PredFormatFunctor3(),
+                        n1_++,
+                        n2_++,
+                        n3_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED_FORMAT3 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(ASSERT_PRED_FORMAT3Test, FunctorOnUserTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT3(PredFormatFunctor3(),
+                        Bool(n1_++),
+                        Bool(n2_++),
+                        Bool(n3_++));
+    finished_ = true;
+  }, "");
+}
+// Sample functions/functors for testing 4-ary predicate assertions.
+
+// A 4-ary predicate function.
+template <typename T1, typename T2, typename T3, typename T4>
+bool PredFunction4(T1 v1, T2 v2, T3 v3, T4 v4) {
+  return v1 + v2 + v3 + v4 > 0;
+}
+
+// The following two functions are needed because a compiler doesn't have
+// a context yet to know which template function must be instantiated.
+bool PredFunction4Int(int v1, int v2, int v3, int v4) {
+  return v1 + v2 + v3 + v4 > 0;
+}
+bool PredFunction4Bool(Bool v1, Bool v2, Bool v3, Bool v4) {
+  return v1 + v2 + v3 + v4 > 0;
+}
+
+// A 4-ary predicate functor.
+struct PredFunctor4 {
+  template <typename T1, typename T2, typename T3, typename T4>
+  bool operator()(const T1& v1,
+                  const T2& v2,
+                  const T3& v3,
+                  const T4& v4) {
+    return v1 + v2 + v3 + v4 > 0;
+  }
+};
+
+// A 4-ary predicate-formatter function.
+template <typename T1, typename T2, typename T3, typename T4>
+testing::AssertionResult PredFormatFunction4(const char* e1,
+                                             const char* e2,
+                                             const char* e3,
+                                             const char* e4,
+                                             const T1& v1,
+                                             const T2& v2,
+                                             const T3& v3,
+                                             const T4& v4) {
+  if (PredFunction4(v1, v2, v3, v4))
+    return testing::AssertionSuccess();
+
+  return testing::AssertionFailure()
+      << e1 << " + " << e2 << " + " << e3 << " + " << e4
+      << " is expected to be positive, but evaluates to "
+      << v1 + v2 + v3 + v4 << ".";
+}
+
+// A 4-ary predicate-formatter functor.
+struct PredFormatFunctor4 {
+  template <typename T1, typename T2, typename T3, typename T4>
+  testing::AssertionResult operator()(const char* e1,
+                                      const char* e2,
+                                      const char* e3,
+                                      const char* e4,
+                                      const T1& v1,
+                                      const T2& v2,
+                                      const T3& v3,
+                                      const T4& v4) const {
+    return PredFormatFunction4(e1, e2, e3, e4, v1, v2, v3, v4);
+  }
+};
+
+// Tests for {EXPECT|ASSERT}_PRED_FORMAT4.
+
+class Predicate4Test : public testing::Test {
+ protected:
+  void SetUp() override {
+    expected_to_finish_ = true;
+    finished_ = false;
+    n1_ = n2_ = n3_ = n4_ = 0;
+  }
+
+  void TearDown() override {
+    // Verifies that each of the predicate's arguments was evaluated
+    // exactly once.
+    EXPECT_EQ(1, n1_) <<
+        "The predicate assertion didn't evaluate argument 2 "
+        "exactly once.";
+    EXPECT_EQ(1, n2_) <<
+        "The predicate assertion didn't evaluate argument 3 "
+        "exactly once.";
+    EXPECT_EQ(1, n3_) <<
+        "The predicate assertion didn't evaluate argument 4 "
+        "exactly once.";
+    EXPECT_EQ(1, n4_) <<
+        "The predicate assertion didn't evaluate argument 5 "
+        "exactly once.";
+
+    // Verifies that the control flow in the test function is expected.
+    if (expected_to_finish_ && !finished_) {
+      FAIL() << "The predicate assertion unexpactedly aborted the test.";
+    } else if (!expected_to_finish_ && finished_) {
+      FAIL() << "The failed predicate assertion didn't abort the test "
+                "as expected.";
+    }
+  }
+
+  // true if and only if the test function is expected to run to finish.
+  static bool expected_to_finish_;
+
+  // true if and only if the test function did run to finish.
+  static bool finished_;
+
+  static int n1_;
+  static int n2_;
+  static int n3_;
+  static int n4_;
+};
+
+bool Predicate4Test::expected_to_finish_;
+bool Predicate4Test::finished_;
+int Predicate4Test::n1_;
+int Predicate4Test::n2_;
+int Predicate4Test::n3_;
+int Predicate4Test::n4_;
+
+typedef Predicate4Test EXPECT_PRED_FORMAT4Test;
+typedef Predicate4Test ASSERT_PRED_FORMAT4Test;
+typedef Predicate4Test EXPECT_PRED4Test;
+typedef Predicate4Test ASSERT_PRED4Test;
+
+// Tests a successful EXPECT_PRED4 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(EXPECT_PRED4Test, FunctionOnBuiltInTypeSuccess) {
+  EXPECT_PRED4(PredFunction4Int,
+               ++n1_,
+               ++n2_,
+               ++n3_,
+               ++n4_);
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED4 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(EXPECT_PRED4Test, FunctionOnUserTypeSuccess) {
+  EXPECT_PRED4(PredFunction4Bool,
+               Bool(++n1_),
+               Bool(++n2_),
+               Bool(++n3_),
+               Bool(++n4_));
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED4 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(EXPECT_PRED4Test, FunctorOnBuiltInTypeSuccess) {
+  EXPECT_PRED4(PredFunctor4(),
+               ++n1_,
+               ++n2_,
+               ++n3_,
+               ++n4_);
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED4 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(EXPECT_PRED4Test, FunctorOnUserTypeSuccess) {
+  EXPECT_PRED4(PredFunctor4(),
+               Bool(++n1_),
+               Bool(++n2_),
+               Bool(++n3_),
+               Bool(++n4_));
+  finished_ = true;
+}
+
+// Tests a failed EXPECT_PRED4 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(EXPECT_PRED4Test, FunctionOnBuiltInTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED4(PredFunction4Int,
+                 n1_++,
+                 n2_++,
+                 n3_++,
+                 n4_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED4 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(EXPECT_PRED4Test, FunctionOnUserTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED4(PredFunction4Bool,
+                 Bool(n1_++),
+                 Bool(n2_++),
+                 Bool(n3_++),
+                 Bool(n4_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED4 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(EXPECT_PRED4Test, FunctorOnBuiltInTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED4(PredFunctor4(),
+                 n1_++,
+                 n2_++,
+                 n3_++,
+                 n4_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED4 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(EXPECT_PRED4Test, FunctorOnUserTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED4(PredFunctor4(),
+                 Bool(n1_++),
+                 Bool(n2_++),
+                 Bool(n3_++),
+                 Bool(n4_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a successful ASSERT_PRED4 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(ASSERT_PRED4Test, FunctionOnBuiltInTypeSuccess) {
+  ASSERT_PRED4(PredFunction4Int,
+               ++n1_,
+               ++n2_,
+               ++n3_,
+               ++n4_);
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED4 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(ASSERT_PRED4Test, FunctionOnUserTypeSuccess) {
+  ASSERT_PRED4(PredFunction4Bool,
+               Bool(++n1_),
+               Bool(++n2_),
+               Bool(++n3_),
+               Bool(++n4_));
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED4 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(ASSERT_PRED4Test, FunctorOnBuiltInTypeSuccess) {
+  ASSERT_PRED4(PredFunctor4(),
+               ++n1_,
+               ++n2_,
+               ++n3_,
+               ++n4_);
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED4 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(ASSERT_PRED4Test, FunctorOnUserTypeSuccess) {
+  ASSERT_PRED4(PredFunctor4(),
+               Bool(++n1_),
+               Bool(++n2_),
+               Bool(++n3_),
+               Bool(++n4_));
+  finished_ = true;
+}
+
+// Tests a failed ASSERT_PRED4 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(ASSERT_PRED4Test, FunctionOnBuiltInTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED4(PredFunction4Int,
+                 n1_++,
+                 n2_++,
+                 n3_++,
+                 n4_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED4 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(ASSERT_PRED4Test, FunctionOnUserTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED4(PredFunction4Bool,
+                 Bool(n1_++),
+                 Bool(n2_++),
+                 Bool(n3_++),
+                 Bool(n4_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED4 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(ASSERT_PRED4Test, FunctorOnBuiltInTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED4(PredFunctor4(),
+                 n1_++,
+                 n2_++,
+                 n3_++,
+                 n4_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED4 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(ASSERT_PRED4Test, FunctorOnUserTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED4(PredFunctor4(),
+                 Bool(n1_++),
+                 Bool(n2_++),
+                 Bool(n3_++),
+                 Bool(n4_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a successful EXPECT_PRED_FORMAT4 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(EXPECT_PRED_FORMAT4Test, FunctionOnBuiltInTypeSuccess) {
+  EXPECT_PRED_FORMAT4(PredFormatFunction4,
+                      ++n1_,
+                      ++n2_,
+                      ++n3_,
+                      ++n4_);
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED_FORMAT4 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(EXPECT_PRED_FORMAT4Test, FunctionOnUserTypeSuccess) {
+  EXPECT_PRED_FORMAT4(PredFormatFunction4,
+                      Bool(++n1_),
+                      Bool(++n2_),
+                      Bool(++n3_),
+                      Bool(++n4_));
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED_FORMAT4 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(EXPECT_PRED_FORMAT4Test, FunctorOnBuiltInTypeSuccess) {
+  EXPECT_PRED_FORMAT4(PredFormatFunctor4(),
+                      ++n1_,
+                      ++n2_,
+                      ++n3_,
+                      ++n4_);
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED_FORMAT4 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(EXPECT_PRED_FORMAT4Test, FunctorOnUserTypeSuccess) {
+  EXPECT_PRED_FORMAT4(PredFormatFunctor4(),
+                      Bool(++n1_),
+                      Bool(++n2_),
+                      Bool(++n3_),
+                      Bool(++n4_));
+  finished_ = true;
+}
+
+// Tests a failed EXPECT_PRED_FORMAT4 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(EXPECT_PRED_FORMAT4Test, FunctionOnBuiltInTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT4(PredFormatFunction4,
+                        n1_++,
+                        n2_++,
+                        n3_++,
+                        n4_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED_FORMAT4 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(EXPECT_PRED_FORMAT4Test, FunctionOnUserTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT4(PredFormatFunction4,
+                        Bool(n1_++),
+                        Bool(n2_++),
+                        Bool(n3_++),
+                        Bool(n4_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED_FORMAT4 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(EXPECT_PRED_FORMAT4Test, FunctorOnBuiltInTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT4(PredFormatFunctor4(),
+                        n1_++,
+                        n2_++,
+                        n3_++,
+                        n4_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED_FORMAT4 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(EXPECT_PRED_FORMAT4Test, FunctorOnUserTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT4(PredFormatFunctor4(),
+                        Bool(n1_++),
+                        Bool(n2_++),
+                        Bool(n3_++),
+                        Bool(n4_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a successful ASSERT_PRED_FORMAT4 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(ASSERT_PRED_FORMAT4Test, FunctionOnBuiltInTypeSuccess) {
+  ASSERT_PRED_FORMAT4(PredFormatFunction4,
+                      ++n1_,
+                      ++n2_,
+                      ++n3_,
+                      ++n4_);
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED_FORMAT4 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(ASSERT_PRED_FORMAT4Test, FunctionOnUserTypeSuccess) {
+  ASSERT_PRED_FORMAT4(PredFormatFunction4,
+                      Bool(++n1_),
+                      Bool(++n2_),
+                      Bool(++n3_),
+                      Bool(++n4_));
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED_FORMAT4 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(ASSERT_PRED_FORMAT4Test, FunctorOnBuiltInTypeSuccess) {
+  ASSERT_PRED_FORMAT4(PredFormatFunctor4(),
+                      ++n1_,
+                      ++n2_,
+                      ++n3_,
+                      ++n4_);
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED_FORMAT4 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(ASSERT_PRED_FORMAT4Test, FunctorOnUserTypeSuccess) {
+  ASSERT_PRED_FORMAT4(PredFormatFunctor4(),
+                      Bool(++n1_),
+                      Bool(++n2_),
+                      Bool(++n3_),
+                      Bool(++n4_));
+  finished_ = true;
+}
+
+// Tests a failed ASSERT_PRED_FORMAT4 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(ASSERT_PRED_FORMAT4Test, FunctionOnBuiltInTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT4(PredFormatFunction4,
+                        n1_++,
+                        n2_++,
+                        n3_++,
+                        n4_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED_FORMAT4 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(ASSERT_PRED_FORMAT4Test, FunctionOnUserTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT4(PredFormatFunction4,
+                        Bool(n1_++),
+                        Bool(n2_++),
+                        Bool(n3_++),
+                        Bool(n4_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED_FORMAT4 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(ASSERT_PRED_FORMAT4Test, FunctorOnBuiltInTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT4(PredFormatFunctor4(),
+                        n1_++,
+                        n2_++,
+                        n3_++,
+                        n4_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED_FORMAT4 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(ASSERT_PRED_FORMAT4Test, FunctorOnUserTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT4(PredFormatFunctor4(),
+                        Bool(n1_++),
+                        Bool(n2_++),
+                        Bool(n3_++),
+                        Bool(n4_++));
+    finished_ = true;
+  }, "");
+}
+// Sample functions/functors for testing 5-ary predicate assertions.
+
+// A 5-ary predicate function.
+template <typename T1, typename T2, typename T3, typename T4, typename T5>
+bool PredFunction5(T1 v1, T2 v2, T3 v3, T4 v4, T5 v5) {
+  return v1 + v2 + v3 + v4 + v5 > 0;
+}
+
+// The following two functions are needed because a compiler doesn't have
+// a context yet to know which template function must be instantiated.
+bool PredFunction5Int(int v1, int v2, int v3, int v4, int v5) {
+  return v1 + v2 + v3 + v4 + v5 > 0;
+}
+bool PredFunction5Bool(Bool v1, Bool v2, Bool v3, Bool v4, Bool v5) {
+  return v1 + v2 + v3 + v4 + v5 > 0;
+}
+
+// A 5-ary predicate functor.
+struct PredFunctor5 {
+  template <typename T1, typename T2, typename T3, typename T4, typename T5>
+  bool operator()(const T1& v1,
+                  const T2& v2,
+                  const T3& v3,
+                  const T4& v4,
+                  const T5& v5) {
+    return v1 + v2 + v3 + v4 + v5 > 0;
+  }
+};
+
+// A 5-ary predicate-formatter function.
+template <typename T1, typename T2, typename T3, typename T4, typename T5>
+testing::AssertionResult PredFormatFunction5(const char* e1,
+                                             const char* e2,
+                                             const char* e3,
+                                             const char* e4,
+                                             const char* e5,
+                                             const T1& v1,
+                                             const T2& v2,
+                                             const T3& v3,
+                                             const T4& v4,
+                                             const T5& v5) {
+  if (PredFunction5(v1, v2, v3, v4, v5))
+    return testing::AssertionSuccess();
+
+  return testing::AssertionFailure()
+      << e1 << " + " << e2 << " + " << e3 << " + " << e4 << " + " << e5
+      << " is expected to be positive, but evaluates to "
+      << v1 + v2 + v3 + v4 + v5 << ".";
+}
+
+// A 5-ary predicate-formatter functor.
+struct PredFormatFunctor5 {
+  template <typename T1, typename T2, typename T3, typename T4, typename T5>
+  testing::AssertionResult operator()(const char* e1,
+                                      const char* e2,
+                                      const char* e3,
+                                      const char* e4,
+                                      const char* e5,
+                                      const T1& v1,
+                                      const T2& v2,
+                                      const T3& v3,
+                                      const T4& v4,
+                                      const T5& v5) const {
+    return PredFormatFunction5(e1, e2, e3, e4, e5, v1, v2, v3, v4, v5);
+  }
+};
+
+// Tests for {EXPECT|ASSERT}_PRED_FORMAT5.
+
+class Predicate5Test : public testing::Test {
+ protected:
+  void SetUp() override {
+    expected_to_finish_ = true;
+    finished_ = false;
+    n1_ = n2_ = n3_ = n4_ = n5_ = 0;
+  }
+
+  void TearDown() override {
+    // Verifies that each of the predicate's arguments was evaluated
+    // exactly once.
+    EXPECT_EQ(1, n1_) <<
+        "The predicate assertion didn't evaluate argument 2 "
+        "exactly once.";
+    EXPECT_EQ(1, n2_) <<
+        "The predicate assertion didn't evaluate argument 3 "
+        "exactly once.";
+    EXPECT_EQ(1, n3_) <<
+        "The predicate assertion didn't evaluate argument 4 "
+        "exactly once.";
+    EXPECT_EQ(1, n4_) <<
+        "The predicate assertion didn't evaluate argument 5 "
+        "exactly once.";
+    EXPECT_EQ(1, n5_) <<
+        "The predicate assertion didn't evaluate argument 6 "
+        "exactly once.";
+
+    // Verifies that the control flow in the test function is expected.
+    if (expected_to_finish_ && !finished_) {
+      FAIL() << "The predicate assertion unexpactedly aborted the test.";
+    } else if (!expected_to_finish_ && finished_) {
+      FAIL() << "The failed predicate assertion didn't abort the test "
+                "as expected.";
+    }
+  }
+
+  // true if and only if the test function is expected to run to finish.
+  static bool expected_to_finish_;
+
+  // true if and only if the test function did run to finish.
+  static bool finished_;
+
+  static int n1_;
+  static int n2_;
+  static int n3_;
+  static int n4_;
+  static int n5_;
+};
+
+bool Predicate5Test::expected_to_finish_;
+bool Predicate5Test::finished_;
+int Predicate5Test::n1_;
+int Predicate5Test::n2_;
+int Predicate5Test::n3_;
+int Predicate5Test::n4_;
+int Predicate5Test::n5_;
+
+typedef Predicate5Test EXPECT_PRED_FORMAT5Test;
+typedef Predicate5Test ASSERT_PRED_FORMAT5Test;
+typedef Predicate5Test EXPECT_PRED5Test;
+typedef Predicate5Test ASSERT_PRED5Test;
+
+// Tests a successful EXPECT_PRED5 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(EXPECT_PRED5Test, FunctionOnBuiltInTypeSuccess) {
+  EXPECT_PRED5(PredFunction5Int,
+               ++n1_,
+               ++n2_,
+               ++n3_,
+               ++n4_,
+               ++n5_);
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED5 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(EXPECT_PRED5Test, FunctionOnUserTypeSuccess) {
+  EXPECT_PRED5(PredFunction5Bool,
+               Bool(++n1_),
+               Bool(++n2_),
+               Bool(++n3_),
+               Bool(++n4_),
+               Bool(++n5_));
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED5 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(EXPECT_PRED5Test, FunctorOnBuiltInTypeSuccess) {
+  EXPECT_PRED5(PredFunctor5(),
+               ++n1_,
+               ++n2_,
+               ++n3_,
+               ++n4_,
+               ++n5_);
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED5 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(EXPECT_PRED5Test, FunctorOnUserTypeSuccess) {
+  EXPECT_PRED5(PredFunctor5(),
+               Bool(++n1_),
+               Bool(++n2_),
+               Bool(++n3_),
+               Bool(++n4_),
+               Bool(++n5_));
+  finished_ = true;
+}
+
+// Tests a failed EXPECT_PRED5 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(EXPECT_PRED5Test, FunctionOnBuiltInTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED5(PredFunction5Int,
+                 n1_++,
+                 n2_++,
+                 n3_++,
+                 n4_++,
+                 n5_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED5 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(EXPECT_PRED5Test, FunctionOnUserTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED5(PredFunction5Bool,
+                 Bool(n1_++),
+                 Bool(n2_++),
+                 Bool(n3_++),
+                 Bool(n4_++),
+                 Bool(n5_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED5 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(EXPECT_PRED5Test, FunctorOnBuiltInTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED5(PredFunctor5(),
+                 n1_++,
+                 n2_++,
+                 n3_++,
+                 n4_++,
+                 n5_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED5 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(EXPECT_PRED5Test, FunctorOnUserTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED5(PredFunctor5(),
+                 Bool(n1_++),
+                 Bool(n2_++),
+                 Bool(n3_++),
+                 Bool(n4_++),
+                 Bool(n5_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a successful ASSERT_PRED5 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(ASSERT_PRED5Test, FunctionOnBuiltInTypeSuccess) {
+  ASSERT_PRED5(PredFunction5Int,
+               ++n1_,
+               ++n2_,
+               ++n3_,
+               ++n4_,
+               ++n5_);
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED5 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(ASSERT_PRED5Test, FunctionOnUserTypeSuccess) {
+  ASSERT_PRED5(PredFunction5Bool,
+               Bool(++n1_),
+               Bool(++n2_),
+               Bool(++n3_),
+               Bool(++n4_),
+               Bool(++n5_));
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED5 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(ASSERT_PRED5Test, FunctorOnBuiltInTypeSuccess) {
+  ASSERT_PRED5(PredFunctor5(),
+               ++n1_,
+               ++n2_,
+               ++n3_,
+               ++n4_,
+               ++n5_);
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED5 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(ASSERT_PRED5Test, FunctorOnUserTypeSuccess) {
+  ASSERT_PRED5(PredFunctor5(),
+               Bool(++n1_),
+               Bool(++n2_),
+               Bool(++n3_),
+               Bool(++n4_),
+               Bool(++n5_));
+  finished_ = true;
+}
+
+// Tests a failed ASSERT_PRED5 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(ASSERT_PRED5Test, FunctionOnBuiltInTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED5(PredFunction5Int,
+                 n1_++,
+                 n2_++,
+                 n3_++,
+                 n4_++,
+                 n5_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED5 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(ASSERT_PRED5Test, FunctionOnUserTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED5(PredFunction5Bool,
+                 Bool(n1_++),
+                 Bool(n2_++),
+                 Bool(n3_++),
+                 Bool(n4_++),
+                 Bool(n5_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED5 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(ASSERT_PRED5Test, FunctorOnBuiltInTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED5(PredFunctor5(),
+                 n1_++,
+                 n2_++,
+                 n3_++,
+                 n4_++,
+                 n5_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED5 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(ASSERT_PRED5Test, FunctorOnUserTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED5(PredFunctor5(),
+                 Bool(n1_++),
+                 Bool(n2_++),
+                 Bool(n3_++),
+                 Bool(n4_++),
+                 Bool(n5_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a successful EXPECT_PRED_FORMAT5 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(EXPECT_PRED_FORMAT5Test, FunctionOnBuiltInTypeSuccess) {
+  EXPECT_PRED_FORMAT5(PredFormatFunction5,
+                      ++n1_,
+                      ++n2_,
+                      ++n3_,
+                      ++n4_,
+                      ++n5_);
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED_FORMAT5 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(EXPECT_PRED_FORMAT5Test, FunctionOnUserTypeSuccess) {
+  EXPECT_PRED_FORMAT5(PredFormatFunction5,
+                      Bool(++n1_),
+                      Bool(++n2_),
+                      Bool(++n3_),
+                      Bool(++n4_),
+                      Bool(++n5_));
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED_FORMAT5 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(EXPECT_PRED_FORMAT5Test, FunctorOnBuiltInTypeSuccess) {
+  EXPECT_PRED_FORMAT5(PredFormatFunctor5(),
+                      ++n1_,
+                      ++n2_,
+                      ++n3_,
+                      ++n4_,
+                      ++n5_);
+  finished_ = true;
+}
+
+// Tests a successful EXPECT_PRED_FORMAT5 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(EXPECT_PRED_FORMAT5Test, FunctorOnUserTypeSuccess) {
+  EXPECT_PRED_FORMAT5(PredFormatFunctor5(),
+                      Bool(++n1_),
+                      Bool(++n2_),
+                      Bool(++n3_),
+                      Bool(++n4_),
+                      Bool(++n5_));
+  finished_ = true;
+}
+
+// Tests a failed EXPECT_PRED_FORMAT5 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(EXPECT_PRED_FORMAT5Test, FunctionOnBuiltInTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT5(PredFormatFunction5,
+                        n1_++,
+                        n2_++,
+                        n3_++,
+                        n4_++,
+                        n5_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED_FORMAT5 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(EXPECT_PRED_FORMAT5Test, FunctionOnUserTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT5(PredFormatFunction5,
+                        Bool(n1_++),
+                        Bool(n2_++),
+                        Bool(n3_++),
+                        Bool(n4_++),
+                        Bool(n5_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED_FORMAT5 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(EXPECT_PRED_FORMAT5Test, FunctorOnBuiltInTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT5(PredFormatFunctor5(),
+                        n1_++,
+                        n2_++,
+                        n3_++,
+                        n4_++,
+                        n5_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed EXPECT_PRED_FORMAT5 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(EXPECT_PRED_FORMAT5Test, FunctorOnUserTypeFailure) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT5(PredFormatFunctor5(),
+                        Bool(n1_++),
+                        Bool(n2_++),
+                        Bool(n3_++),
+                        Bool(n4_++),
+                        Bool(n5_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a successful ASSERT_PRED_FORMAT5 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(ASSERT_PRED_FORMAT5Test, FunctionOnBuiltInTypeSuccess) {
+  ASSERT_PRED_FORMAT5(PredFormatFunction5,
+                      ++n1_,
+                      ++n2_,
+                      ++n3_,
+                      ++n4_,
+                      ++n5_);
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED_FORMAT5 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(ASSERT_PRED_FORMAT5Test, FunctionOnUserTypeSuccess) {
+  ASSERT_PRED_FORMAT5(PredFormatFunction5,
+                      Bool(++n1_),
+                      Bool(++n2_),
+                      Bool(++n3_),
+                      Bool(++n4_),
+                      Bool(++n5_));
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED_FORMAT5 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(ASSERT_PRED_FORMAT5Test, FunctorOnBuiltInTypeSuccess) {
+  ASSERT_PRED_FORMAT5(PredFormatFunctor5(),
+                      ++n1_,
+                      ++n2_,
+                      ++n3_,
+                      ++n4_,
+                      ++n5_);
+  finished_ = true;
+}
+
+// Tests a successful ASSERT_PRED_FORMAT5 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(ASSERT_PRED_FORMAT5Test, FunctorOnUserTypeSuccess) {
+  ASSERT_PRED_FORMAT5(PredFormatFunctor5(),
+                      Bool(++n1_),
+                      Bool(++n2_),
+                      Bool(++n3_),
+                      Bool(++n4_),
+                      Bool(++n5_));
+  finished_ = true;
+}
+
+// Tests a failed ASSERT_PRED_FORMAT5 where the
+// predicate-formatter is a function on a built-in type (int).
+TEST_F(ASSERT_PRED_FORMAT5Test, FunctionOnBuiltInTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT5(PredFormatFunction5,
+                        n1_++,
+                        n2_++,
+                        n3_++,
+                        n4_++,
+                        n5_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED_FORMAT5 where the
+// predicate-formatter is a function on a user-defined type (Bool).
+TEST_F(ASSERT_PRED_FORMAT5Test, FunctionOnUserTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT5(PredFormatFunction5,
+                        Bool(n1_++),
+                        Bool(n2_++),
+                        Bool(n3_++),
+                        Bool(n4_++),
+                        Bool(n5_++));
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED_FORMAT5 where the
+// predicate-formatter is a functor on a built-in type (int).
+TEST_F(ASSERT_PRED_FORMAT5Test, FunctorOnBuiltInTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT5(PredFormatFunctor5(),
+                        n1_++,
+                        n2_++,
+                        n3_++,
+                        n4_++,
+                        n5_++);
+    finished_ = true;
+  }, "");
+}
+
+// Tests a failed ASSERT_PRED_FORMAT5 where the
+// predicate-formatter is a functor on a user-defined type (Bool).
+TEST_F(ASSERT_PRED_FORMAT5Test, FunctorOnUserTypeFailure) {
+  expected_to_finish_ = false;
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT5(PredFormatFunctor5(),
+                        Bool(n1_++),
+                        Bool(n2_++),
+                        Bool(n3_++),
+                        Bool(n4_++),
+                        Bool(n5_++));
+    finished_ = true;
+  }, "");
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_premature_exit_test.cc b/leveldb_base/third_party/googletest/googletest/test/gtest_premature_exit_test.cc
new file mode 100644
index 0000000..1d1187e
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_premature_exit_test.cc
@@ -0,0 +1,126 @@
+// Copyright 2013, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// Tests that Google Test manipulates the premature-exit-detection
+// file correctly.
+
+#include <stdio.h>
+
+#include "gtest/gtest.h"
+
+using ::testing::InitGoogleTest;
+using ::testing::Test;
+using ::testing::internal::posix::GetEnv;
+using ::testing::internal::posix::Stat;
+using ::testing::internal::posix::StatStruct;
+
+namespace {
+
+class PrematureExitTest : public Test {
+ public:
+  // Returns true if and only if the given file exists.
+  static bool FileExists(const char* filepath) {
+    StatStruct stat;
+    return Stat(filepath, &stat) == 0;
+  }
+
+ protected:
+  PrematureExitTest() {
+    premature_exit_file_path_ = GetEnv("TEST_PREMATURE_EXIT_FILE");
+
+    // Normalize NULL to "" for ease of handling.
+    if (premature_exit_file_path_ == nullptr) {
+      premature_exit_file_path_ = "";
+    }
+  }
+
+  // Returns true if and only if the premature-exit file exists.
+  bool PrematureExitFileExists() const {
+    return FileExists(premature_exit_file_path_);
+  }
+
+  const char* premature_exit_file_path_;
+};
+
+typedef PrematureExitTest PrematureExitDeathTest;
+
+// Tests that:
+//   - the premature-exit file exists during the execution of a
+//     death test (EXPECT_DEATH*), and
+//   - a death test doesn't interfere with the main test process's
+//     handling of the premature-exit file.
+TEST_F(PrematureExitDeathTest, FileExistsDuringExecutionOfDeathTest) {
+  if (*premature_exit_file_path_ == '\0') {
+    return;
+  }
+
+  EXPECT_DEATH_IF_SUPPORTED({
+      // If the file exists, crash the process such that the main test
+      // process will catch the (expected) crash and report a success;
+      // otherwise don't crash, which will cause the main test process
+      // to report that the death test has failed.
+      if (PrematureExitFileExists()) {
+        exit(1);
+      }
+    }, "");
+}
+
+// Tests that the premature-exit file exists during the execution of a
+// normal (non-death) test.
+TEST_F(PrematureExitTest, PrematureExitFileExistsDuringTestExecution) {
+  if (*premature_exit_file_path_ == '\0') {
+    return;
+  }
+
+  EXPECT_TRUE(PrematureExitFileExists())
+      << " file " << premature_exit_file_path_
+      << " should exist during test execution, but doesn't.";
+}
+
+}  // namespace
+
+int main(int argc, char **argv) {
+  InitGoogleTest(&argc, argv);
+  const int exit_code = RUN_ALL_TESTS();
+
+  // Test that the premature-exit file is deleted upon return from
+  // RUN_ALL_TESTS().
+  const char* const filepath = GetEnv("TEST_PREMATURE_EXIT_FILE");
+  if (filepath != nullptr && *filepath != '\0') {
+    if (PrematureExitTest::FileExists(filepath)) {
+      printf(
+          "File %s shouldn't exist after the test program finishes, but does.",
+          filepath);
+      return 1;
+    }
+  }
+
+  return exit_code;
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_prod_test.cc b/leveldb_base/third_party/googletest/googletest/test/gtest_prod_test.cc
new file mode 100644
index 0000000..ede81a0
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_prod_test.cc
@@ -0,0 +1,56 @@
+// Copyright 2006, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// Unit test for gtest_prod.h.
+
+#include "production.h"
+#include "gtest/gtest.h"
+
+// Tests that private members can be accessed from a TEST declared as
+// a friend of the class.
+TEST(PrivateCodeTest, CanAccessPrivateMembers) {
+  PrivateCode a;
+  EXPECT_EQ(0, a.x_);
+
+  a.set_x(1);
+  EXPECT_EQ(1, a.x_);
+}
+
+typedef testing::Test PrivateCodeFixtureTest;
+
+// Tests that private members can be accessed from a TEST_F declared
+// as a friend of the class.
+TEST_F(PrivateCodeFixtureTest, CanAccessPrivateMembers) {
+  PrivateCode a;
+  EXPECT_EQ(0, a.x_);
+
+  a.set_x(2);
+  EXPECT_EQ(2, a.x_);
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_repeat_test.cc b/leveldb_base/third_party/googletest/googletest/test/gtest_repeat_test.cc
new file mode 100644
index 0000000..7da4a15
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_repeat_test.cc
@@ -0,0 +1,233 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Tests the --gtest_repeat=number flag.
+
+#include <stdlib.h>
+#include <iostream>
+#include "gtest/gtest.h"
+#include "src/gtest-internal-inl.h"
+
+namespace testing {
+
+GTEST_DECLARE_string_(death_test_style);
+GTEST_DECLARE_string_(filter);
+GTEST_DECLARE_int32_(repeat);
+
+}  // namespace testing
+
+using testing::GTEST_FLAG(death_test_style);
+using testing::GTEST_FLAG(filter);
+using testing::GTEST_FLAG(repeat);
+
+namespace {
+
+// We need this when we are testing Google Test itself and therefore
+// cannot use Google Test assertions.
+#define GTEST_CHECK_INT_EQ_(expected, actual) \
+  do {\
+    const int expected_val = (expected);\
+    const int actual_val = (actual);\
+    if (::testing::internal::IsTrue(expected_val != actual_val)) {\
+      ::std::cout << "Value of: " #actual "\n"\
+                  << "  Actual: " << actual_val << "\n"\
+                  << "Expected: " #expected "\n"\
+                  << "Which is: " << expected_val << "\n";\
+      ::testing::internal::posix::Abort();\
+    }\
+  } while (::testing::internal::AlwaysFalse())
+
+
+// Used for verifying that global environment set-up and tear-down are
+// inside the --gtest_repeat loop.
+
+int g_environment_set_up_count = 0;
+int g_environment_tear_down_count = 0;
+
+class MyEnvironment : public testing::Environment {
+ public:
+  MyEnvironment() {}
+  void SetUp() override { g_environment_set_up_count++; }
+  void TearDown() override { g_environment_tear_down_count++; }
+};
+
+// A test that should fail.
+
+int g_should_fail_count = 0;
+
+TEST(FooTest, ShouldFail) {
+  g_should_fail_count++;
+  EXPECT_EQ(0, 1) << "Expected failure.";
+}
+
+// A test that should pass.
+
+int g_should_pass_count = 0;
+
+TEST(FooTest, ShouldPass) {
+  g_should_pass_count++;
+}
+
+// A test that contains a thread-safe death test and a fast death
+// test.  It should pass.
+
+int g_death_test_count = 0;
+
+TEST(BarDeathTest, ThreadSafeAndFast) {
+  g_death_test_count++;
+
+  GTEST_FLAG(death_test_style) = "threadsafe";
+  EXPECT_DEATH_IF_SUPPORTED(::testing::internal::posix::Abort(), "");
+
+  GTEST_FLAG(death_test_style) = "fast";
+  EXPECT_DEATH_IF_SUPPORTED(::testing::internal::posix::Abort(), "");
+}
+
+int g_param_test_count = 0;
+
+const int kNumberOfParamTests = 10;
+
+class MyParamTest : public testing::TestWithParam<int> {};
+
+TEST_P(MyParamTest, ShouldPass) {
+  GTEST_CHECK_INT_EQ_(g_param_test_count % kNumberOfParamTests, GetParam());
+  g_param_test_count++;
+}
+INSTANTIATE_TEST_SUITE_P(MyParamSequence,
+                         MyParamTest,
+                         testing::Range(0, kNumberOfParamTests));
+
+// Resets the count for each test.
+void ResetCounts() {
+  g_environment_set_up_count = 0;
+  g_environment_tear_down_count = 0;
+  g_should_fail_count = 0;
+  g_should_pass_count = 0;
+  g_death_test_count = 0;
+  g_param_test_count = 0;
+}
+
+// Checks that the count for each test is expected.
+void CheckCounts(int expected) {
+  GTEST_CHECK_INT_EQ_(expected, g_environment_set_up_count);
+  GTEST_CHECK_INT_EQ_(expected, g_environment_tear_down_count);
+  GTEST_CHECK_INT_EQ_(expected, g_should_fail_count);
+  GTEST_CHECK_INT_EQ_(expected, g_should_pass_count);
+  GTEST_CHECK_INT_EQ_(expected, g_death_test_count);
+  GTEST_CHECK_INT_EQ_(expected * kNumberOfParamTests, g_param_test_count);
+}
+
+// Tests the behavior of Google Test when --gtest_repeat is not specified.
+void TestRepeatUnspecified() {
+  ResetCounts();
+  GTEST_CHECK_INT_EQ_(1, RUN_ALL_TESTS());
+  CheckCounts(1);
+}
+
+// Tests the behavior of Google Test when --gtest_repeat has the given value.
+void TestRepeat(int repeat) {
+  GTEST_FLAG(repeat) = repeat;
+
+  ResetCounts();
+  GTEST_CHECK_INT_EQ_(repeat > 0 ? 1 : 0, RUN_ALL_TESTS());
+  CheckCounts(repeat);
+}
+
+// Tests using --gtest_repeat when --gtest_filter specifies an empty
+// set of tests.
+void TestRepeatWithEmptyFilter(int repeat) {
+  GTEST_FLAG(repeat) = repeat;
+  GTEST_FLAG(filter) = "None";
+
+  ResetCounts();
+  GTEST_CHECK_INT_EQ_(0, RUN_ALL_TESTS());
+  CheckCounts(0);
+}
+
+// Tests using --gtest_repeat when --gtest_filter specifies a set of
+// successful tests.
+void TestRepeatWithFilterForSuccessfulTests(int repeat) {
+  GTEST_FLAG(repeat) = repeat;
+  GTEST_FLAG(filter) = "*-*ShouldFail";
+
+  ResetCounts();
+  GTEST_CHECK_INT_EQ_(0, RUN_ALL_TESTS());
+  GTEST_CHECK_INT_EQ_(repeat, g_environment_set_up_count);
+  GTEST_CHECK_INT_EQ_(repeat, g_environment_tear_down_count);
+  GTEST_CHECK_INT_EQ_(0, g_should_fail_count);
+  GTEST_CHECK_INT_EQ_(repeat, g_should_pass_count);
+  GTEST_CHECK_INT_EQ_(repeat, g_death_test_count);
+  GTEST_CHECK_INT_EQ_(repeat * kNumberOfParamTests, g_param_test_count);
+}
+
+// Tests using --gtest_repeat when --gtest_filter specifies a set of
+// failed tests.
+void TestRepeatWithFilterForFailedTests(int repeat) {
+  GTEST_FLAG(repeat) = repeat;
+  GTEST_FLAG(filter) = "*ShouldFail";
+
+  ResetCounts();
+  GTEST_CHECK_INT_EQ_(1, RUN_ALL_TESTS());
+  GTEST_CHECK_INT_EQ_(repeat, g_environment_set_up_count);
+  GTEST_CHECK_INT_EQ_(repeat, g_environment_tear_down_count);
+  GTEST_CHECK_INT_EQ_(repeat, g_should_fail_count);
+  GTEST_CHECK_INT_EQ_(0, g_should_pass_count);
+  GTEST_CHECK_INT_EQ_(0, g_death_test_count);
+  GTEST_CHECK_INT_EQ_(0, g_param_test_count);
+}
+
+}  // namespace
+
+int main(int argc, char **argv) {
+  testing::InitGoogleTest(&argc, argv);
+
+  testing::AddGlobalTestEnvironment(new MyEnvironment);
+
+  TestRepeatUnspecified();
+  TestRepeat(0);
+  TestRepeat(1);
+  TestRepeat(5);
+
+  TestRepeatWithEmptyFilter(2);
+  TestRepeatWithEmptyFilter(3);
+
+  TestRepeatWithFilterForSuccessfulTests(3);
+
+  TestRepeatWithFilterForFailedTests(4);
+
+  // It would be nice to verify that the tests indeed loop forever
+  // when GTEST_FLAG(repeat) is negative, but this test will be quite
+  // complicated to write.  Since this flag is for interactive
+  // debugging only and doesn't affect the normal test result, such a
+  // test would be an overkill.
+
+  printf("PASS\n");
+  return 0;
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_skip_check_output_test.py b/leveldb_base/third_party/googletest/googletest/test/gtest_skip_check_output_test.py
new file mode 100644
index 0000000..14e63ab
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_skip_check_output_test.py
@@ -0,0 +1,59 @@
+#!/usr/bin/env python
+#
+# Copyright 2019 Google LLC.  All Rights Reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+"""Tests Google Test's gtest skip in environment setup  behavior.
+
+This script invokes gtest_skip_in_environment_setup_test_ and verifies its
+output.
+"""
+
+import re
+
+import gtest_test_utils
+
+# Path to the gtest_skip_in_environment_setup_test binary
+EXE_PATH = gtest_test_utils.GetTestExecutablePath('gtest_skip_test')
+
+OUTPUT = gtest_test_utils.Subprocess([EXE_PATH]).output
+
+
+# Test.
+class SkipEntireEnvironmentTest(gtest_test_utils.TestCase):
+
+  def testSkipEntireEnvironmentTest(self):
+    self.assertIn('Skipped\nskipping single test\n', OUTPUT)
+    skip_fixture = 'Skipped\nskipping all tests for this fixture\n'
+    self.assertIsNotNone(
+        re.search(skip_fixture + '.*' + skip_fixture, OUTPUT, flags=re.DOTALL),
+        repr(OUTPUT))
+    self.assertNotIn('FAILED', OUTPUT)
+
+
+if __name__ == '__main__':
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_skip_environment_check_output_test.py b/leveldb_base/third_party/googletest/googletest/test/gtest_skip_environment_check_output_test.py
new file mode 100644
index 0000000..6e79155
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_skip_environment_check_output_test.py
@@ -0,0 +1,54 @@
+#!/usr/bin/env python
+#
+# Copyright 2019 Google LLC.  All Rights Reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+"""Tests Google Test's gtest skip in environment setup  behavior.
+
+This script invokes gtest_skip_in_environment_setup_test_ and verifies its
+output.
+"""
+
+import gtest_test_utils
+
+# Path to the gtest_skip_in_environment_setup_test binary
+EXE_PATH = gtest_test_utils.GetTestExecutablePath(
+    'gtest_skip_in_environment_setup_test')
+
+OUTPUT = gtest_test_utils.Subprocess([EXE_PATH]).output
+
+
+# Test.
+class SkipEntireEnvironmentTest(gtest_test_utils.TestCase):
+
+  def testSkipEntireEnvironmentTest(self):
+    self.assertIn('Skipping the entire environment', OUTPUT)
+    self.assertNotIn('FAILED', OUTPUT)
+
+
+if __name__ == '__main__':
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_skip_in_environment_setup_test.cc b/leveldb_base/third_party/googletest/googletest/test/gtest_skip_in_environment_setup_test.cc
new file mode 100644
index 0000000..9372310
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_skip_in_environment_setup_test.cc
@@ -0,0 +1,49 @@
+// Copyright 2019, Google LLC.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google LLC. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// This test verifies that skipping in the environment results in the
+// testcases being skipped.
+
+#include <iostream>
+#include "gtest/gtest.h"
+
+class SetupEnvironment : public testing::Environment {
+ public:
+  void SetUp() override { GTEST_SKIP() << "Skipping the entire environment"; }
+};
+
+TEST(Test, AlwaysFails) { EXPECT_EQ(true, false); }
+
+int main(int argc, char **argv) {
+  testing::InitGoogleTest(&argc, argv);
+
+  testing::AddGlobalTestEnvironment(new SetupEnvironment());
+
+  return RUN_ALL_TESTS();
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_skip_test.cc b/leveldb_base/third_party/googletest/googletest/test/gtest_skip_test.cc
new file mode 100644
index 0000000..4a23004
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_skip_test.cc
@@ -0,0 +1,55 @@
+// Copyright 2008 Google Inc.
+// All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// Author: arseny.aprelev@gmail.com (Arseny Aprelev)
+//
+
+#include "gtest/gtest.h"
+
+using ::testing::Test;
+
+TEST(SkipTest, DoesSkip) {
+  GTEST_SKIP() << "skipping single test";
+  EXPECT_EQ(0, 1);
+}
+
+class Fixture : public Test {
+ protected:
+  void SetUp() override {
+    GTEST_SKIP() << "skipping all tests for this fixture";
+  }
+};
+
+TEST_F(Fixture, SkipsOneTest) {
+  EXPECT_EQ(5, 7);
+}
+
+TEST_F(Fixture, SkipsAnotherTest) {
+  EXPECT_EQ(99, 100);
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_sole_header_test.cc b/leveldb_base/third_party/googletest/googletest/test/gtest_sole_header_test.cc
new file mode 100644
index 0000000..1d94ac6
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_sole_header_test.cc
@@ -0,0 +1,56 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// This test verifies that it's possible to use Google Test by including
+// the gtest.h header file alone.
+
+#include "gtest/gtest.h"
+
+namespace {
+
+void Subroutine() {
+  EXPECT_EQ(42, 42);
+}
+
+TEST(NoFatalFailureTest, ExpectNoFatalFailure) {
+  EXPECT_NO_FATAL_FAILURE(;);
+  EXPECT_NO_FATAL_FAILURE(SUCCEED());
+  EXPECT_NO_FATAL_FAILURE(Subroutine());
+  EXPECT_NO_FATAL_FAILURE({ SUCCEED(); });
+}
+
+TEST(NoFatalFailureTest, AssertNoFatalFailure) {
+  ASSERT_NO_FATAL_FAILURE(;);
+  ASSERT_NO_FATAL_FAILURE(SUCCEED());
+  ASSERT_NO_FATAL_FAILURE(Subroutine());
+  ASSERT_NO_FATAL_FAILURE({ SUCCEED(); });
+}
+
+}  // namespace
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_stress_test.cc b/leveldb_base/third_party/googletest/googletest/test/gtest_stress_test.cc
new file mode 100644
index 0000000..8434819
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_stress_test.cc
@@ -0,0 +1,248 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Tests that SCOPED_TRACE() and various Google Test assertions can be
+// used in a large number of threads concurrently.
+
+#include "gtest/gtest.h"
+
+#include <vector>
+
+#include "src/gtest-internal-inl.h"
+
+#if GTEST_IS_THREADSAFE
+
+namespace testing {
+namespace {
+
+using internal::Notification;
+using internal::TestPropertyKeyIs;
+using internal::ThreadWithParam;
+
+// In order to run tests in this file, for platforms where Google Test is
+// thread safe, implement ThreadWithParam. See the description of its API
+// in gtest-port.h, where it is defined for already supported platforms.
+
+// How many threads to create?
+const int kThreadCount = 50;
+
+std::string IdToKey(int id, const char* suffix) {
+  Message key;
+  key << "key_" << id << "_" << suffix;
+  return key.GetString();
+}
+
+std::string IdToString(int id) {
+  Message id_message;
+  id_message << id;
+  return id_message.GetString();
+}
+
+void ExpectKeyAndValueWereRecordedForId(
+    const std::vector<TestProperty>& properties,
+    int id, const char* suffix) {
+  TestPropertyKeyIs matches_key(IdToKey(id, suffix).c_str());
+  const std::vector<TestProperty>::const_iterator property =
+      std::find_if(properties.begin(), properties.end(), matches_key);
+  ASSERT_TRUE(property != properties.end())
+      << "expecting " << suffix << " value for id " << id;
+  EXPECT_STREQ(IdToString(id).c_str(), property->value());
+}
+
+// Calls a large number of Google Test assertions, where exactly one of them
+// will fail.
+void ManyAsserts(int id) {
+  GTEST_LOG_(INFO) << "Thread #" << id << " running...";
+
+  SCOPED_TRACE(Message() << "Thread #" << id);
+
+  for (int i = 0; i < kThreadCount; i++) {
+    SCOPED_TRACE(Message() << "Iteration #" << i);
+
+    // A bunch of assertions that should succeed.
+    EXPECT_TRUE(true);
+    ASSERT_FALSE(false) << "This shouldn't fail.";
+    EXPECT_STREQ("a", "a");
+    ASSERT_LE(5, 6);
+    EXPECT_EQ(i, i) << "This shouldn't fail.";
+
+    // RecordProperty() should interact safely with other threads as well.
+    // The shared_key forces property updates.
+    Test::RecordProperty(IdToKey(id, "string").c_str(), IdToString(id).c_str());
+    Test::RecordProperty(IdToKey(id, "int").c_str(), id);
+    Test::RecordProperty("shared_key", IdToString(id).c_str());
+
+    // This assertion should fail kThreadCount times per thread.  It
+    // is for testing whether Google Test can handle failed assertions in a
+    // multi-threaded context.
+    EXPECT_LT(i, 0) << "This should always fail.";
+  }
+}
+
+void CheckTestFailureCount(int expected_failures) {
+  const TestInfo* const info = UnitTest::GetInstance()->current_test_info();
+  const TestResult* const result = info->result();
+  GTEST_CHECK_(expected_failures == result->total_part_count())
+      << "Logged " << result->total_part_count() << " failures "
+      << " vs. " << expected_failures << " expected";
+}
+
+// Tests using SCOPED_TRACE() and Google Test assertions in many threads
+// concurrently.
+TEST(StressTest, CanUseScopedTraceAndAssertionsInManyThreads) {
+  {
+    std::unique_ptr<ThreadWithParam<int> > threads[kThreadCount];
+    Notification threads_can_start;
+    for (int i = 0; i != kThreadCount; i++)
+      threads[i].reset(new ThreadWithParam<int>(&ManyAsserts,
+                                                i,
+                                                &threads_can_start));
+
+    threads_can_start.Notify();
+
+    // Blocks until all the threads are done.
+    for (int i = 0; i != kThreadCount; i++)
+      threads[i]->Join();
+  }
+
+  // Ensures that kThreadCount*kThreadCount failures have been reported.
+  const TestInfo* const info = UnitTest::GetInstance()->current_test_info();
+  const TestResult* const result = info->result();
+
+  std::vector<TestProperty> properties;
+  // We have no access to the TestResult's list of properties but we can
+  // copy them one by one.
+  for (int i = 0; i < result->test_property_count(); ++i)
+    properties.push_back(result->GetTestProperty(i));
+
+  EXPECT_EQ(kThreadCount * 2 + 1, result->test_property_count())
+      << "String and int values recorded on each thread, "
+      << "as well as one shared_key";
+  for (int i = 0; i < kThreadCount; ++i) {
+    ExpectKeyAndValueWereRecordedForId(properties, i, "string");
+    ExpectKeyAndValueWereRecordedForId(properties, i, "int");
+  }
+  CheckTestFailureCount(kThreadCount*kThreadCount);
+}
+
+void FailingThread(bool is_fatal) {
+  if (is_fatal)
+    FAIL() << "Fatal failure in some other thread. "
+           << "(This failure is expected.)";
+  else
+    ADD_FAILURE() << "Non-fatal failure in some other thread. "
+                  << "(This failure is expected.)";
+}
+
+void GenerateFatalFailureInAnotherThread(bool is_fatal) {
+  ThreadWithParam<bool> thread(&FailingThread, is_fatal, nullptr);
+  thread.Join();
+}
+
+TEST(NoFatalFailureTest, ExpectNoFatalFailureIgnoresFailuresInOtherThreads) {
+  EXPECT_NO_FATAL_FAILURE(GenerateFatalFailureInAnotherThread(true));
+  // We should only have one failure (the one from
+  // GenerateFatalFailureInAnotherThread()), since the EXPECT_NO_FATAL_FAILURE
+  // should succeed.
+  CheckTestFailureCount(1);
+}
+
+void AssertNoFatalFailureIgnoresFailuresInOtherThreads() {
+  ASSERT_NO_FATAL_FAILURE(GenerateFatalFailureInAnotherThread(true));
+}
+TEST(NoFatalFailureTest, AssertNoFatalFailureIgnoresFailuresInOtherThreads) {
+  // Using a subroutine, to make sure, that the test continues.
+  AssertNoFatalFailureIgnoresFailuresInOtherThreads();
+  // We should only have one failure (the one from
+  // GenerateFatalFailureInAnotherThread()), since the EXPECT_NO_FATAL_FAILURE
+  // should succeed.
+  CheckTestFailureCount(1);
+}
+
+TEST(FatalFailureTest, ExpectFatalFailureIgnoresFailuresInOtherThreads) {
+  // This statement should fail, since the current thread doesn't generate a
+  // fatal failure, only another one does.
+  EXPECT_FATAL_FAILURE(GenerateFatalFailureInAnotherThread(true), "expected");
+  CheckTestFailureCount(2);
+}
+
+TEST(FatalFailureOnAllThreadsTest, ExpectFatalFailureOnAllThreads) {
+  // This statement should succeed, because failures in all threads are
+  // considered.
+  EXPECT_FATAL_FAILURE_ON_ALL_THREADS(
+      GenerateFatalFailureInAnotherThread(true), "expected");
+  CheckTestFailureCount(0);
+  // We need to add a failure, because main() checks that there are failures.
+  // But when only this test is run, we shouldn't have any failures.
+  ADD_FAILURE() << "This is an expected non-fatal failure.";
+}
+
+TEST(NonFatalFailureTest, ExpectNonFatalFailureIgnoresFailuresInOtherThreads) {
+  // This statement should fail, since the current thread doesn't generate a
+  // fatal failure, only another one does.
+  EXPECT_NONFATAL_FAILURE(GenerateFatalFailureInAnotherThread(false),
+                          "expected");
+  CheckTestFailureCount(2);
+}
+
+TEST(NonFatalFailureOnAllThreadsTest, ExpectNonFatalFailureOnAllThreads) {
+  // This statement should succeed, because failures in all threads are
+  // considered.
+  EXPECT_NONFATAL_FAILURE_ON_ALL_THREADS(
+      GenerateFatalFailureInAnotherThread(false), "expected");
+  CheckTestFailureCount(0);
+  // We need to add a failure, because main() checks that there are failures,
+  // But when only this test is run, we shouldn't have any failures.
+  ADD_FAILURE() << "This is an expected non-fatal failure.";
+}
+
+}  // namespace
+}  // namespace testing
+
+int main(int argc, char **argv) {
+  testing::InitGoogleTest(&argc, argv);
+
+  const int result = RUN_ALL_TESTS();  // Expected to fail.
+  GTEST_CHECK_(result == 1) << "RUN_ALL_TESTS() did not fail as expected";
+
+  printf("\nPASS\n");
+  return 0;
+}
+
+#else
+TEST(StressTest,
+     DISABLED_ThreadSafetyTestsAreSkippedWhenGoogleTestIsNotThreadSafe) {
+}
+
+int main(int argc, char **argv) {
+  testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
+#endif  // GTEST_IS_THREADSAFE
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_test_macro_stack_footprint_test.cc b/leveldb_base/third_party/googletest/googletest/test/gtest_test_macro_stack_footprint_test.cc
new file mode 100644
index 0000000..a48db05
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_test_macro_stack_footprint_test.cc
@@ -0,0 +1,89 @@
+// Copyright 2013, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// Each TEST() expands to some static registration logic.  GCC puts all
+// such static initialization logic for a translation unit in a common,
+// internal function.  Since Google's build system restricts how much
+// stack space a function can use, there's a limit on how many TEST()s
+// one can put in a single C++ test file.  This test ensures that a large
+// number of TEST()s can be defined in the same translation unit.
+
+#include "gtest/gtest.h"
+
+// This macro defines 10 dummy tests.
+#define TEN_TESTS_(test_case_name) \
+  TEST(test_case_name, T0) {} \
+  TEST(test_case_name, T1) {} \
+  TEST(test_case_name, T2) {} \
+  TEST(test_case_name, T3) {} \
+  TEST(test_case_name, T4) {} \
+  TEST(test_case_name, T5) {} \
+  TEST(test_case_name, T6) {} \
+  TEST(test_case_name, T7) {} \
+  TEST(test_case_name, T8) {} \
+  TEST(test_case_name, T9) {}
+
+// This macro defines 100 dummy tests.
+#define HUNDRED_TESTS_(test_case_name_prefix) \
+  TEN_TESTS_(test_case_name_prefix ## 0) \
+  TEN_TESTS_(test_case_name_prefix ## 1) \
+  TEN_TESTS_(test_case_name_prefix ## 2) \
+  TEN_TESTS_(test_case_name_prefix ## 3) \
+  TEN_TESTS_(test_case_name_prefix ## 4) \
+  TEN_TESTS_(test_case_name_prefix ## 5) \
+  TEN_TESTS_(test_case_name_prefix ## 6) \
+  TEN_TESTS_(test_case_name_prefix ## 7) \
+  TEN_TESTS_(test_case_name_prefix ## 8) \
+  TEN_TESTS_(test_case_name_prefix ## 9)
+
+// This macro defines 1000 dummy tests.
+#define THOUSAND_TESTS_(test_case_name_prefix) \
+  HUNDRED_TESTS_(test_case_name_prefix ## 0) \
+  HUNDRED_TESTS_(test_case_name_prefix ## 1) \
+  HUNDRED_TESTS_(test_case_name_prefix ## 2) \
+  HUNDRED_TESTS_(test_case_name_prefix ## 3) \
+  HUNDRED_TESTS_(test_case_name_prefix ## 4) \
+  HUNDRED_TESTS_(test_case_name_prefix ## 5) \
+  HUNDRED_TESTS_(test_case_name_prefix ## 6) \
+  HUNDRED_TESTS_(test_case_name_prefix ## 7) \
+  HUNDRED_TESTS_(test_case_name_prefix ## 8) \
+  HUNDRED_TESTS_(test_case_name_prefix ## 9)
+
+// Ensures that we can define 1000 TEST()s in the same translation
+// unit.
+THOUSAND_TESTS_(T)
+
+int main(int argc, char **argv) {
+  testing::InitGoogleTest(&argc, argv);
+
+  // We don't actually need to run the dummy tests - the purpose is to
+  // ensure that they compile.
+  return 0;
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_test_utils.py b/leveldb_base/third_party/googletest/googletest/test/gtest_test_utils.py
new file mode 100644
index 0000000..d0c2446
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_test_utils.py
@@ -0,0 +1,312 @@
+# Copyright 2006, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Unit test utilities for Google C++ Testing and Mocking Framework."""
+# Suppresses the 'Import not at the top of the file' lint complaint.
+# pylint: disable-msg=C6204
+
+import os
+import sys
+
+IS_WINDOWS = os.name == 'nt'
+IS_CYGWIN = os.name == 'posix' and 'CYGWIN' in os.uname()[0]
+IS_OS2 = os.name == 'os2'
+
+import atexit
+import shutil
+import tempfile
+import unittest as _test_module
+
+try:
+  import subprocess
+  _SUBPROCESS_MODULE_AVAILABLE = True
+except:
+  import popen2
+  _SUBPROCESS_MODULE_AVAILABLE = False
+# pylint: enable-msg=C6204
+
+GTEST_OUTPUT_VAR_NAME = 'GTEST_OUTPUT'
+
+# The environment variable for specifying the path to the premature-exit file.
+PREMATURE_EXIT_FILE_ENV_VAR = 'TEST_PREMATURE_EXIT_FILE'
+
+environ = os.environ.copy()
+
+
+def SetEnvVar(env_var, value):
+  """Sets/unsets an environment variable to a given value."""
+
+  if value is not None:
+    environ[env_var] = value
+  elif env_var in environ:
+    del environ[env_var]
+
+
+# Here we expose a class from a particular module, depending on the
+# environment. The comment suppresses the 'Invalid variable name' lint
+# complaint.
+TestCase = _test_module.TestCase  # pylint: disable=C6409
+
+# Initially maps a flag to its default value. After
+# _ParseAndStripGTestFlags() is called, maps a flag to its actual value.
+_flag_map = {'source_dir': os.path.dirname(sys.argv[0]),
+             'build_dir': os.path.dirname(sys.argv[0])}
+_gtest_flags_are_parsed = False
+
+
+def _ParseAndStripGTestFlags(argv):
+  """Parses and strips Google Test flags from argv.  This is idempotent."""
+
+  # Suppresses the lint complaint about a global variable since we need it
+  # here to maintain module-wide state.
+  global _gtest_flags_are_parsed  # pylint: disable=W0603
+  if _gtest_flags_are_parsed:
+    return
+
+  _gtest_flags_are_parsed = True
+  for flag in _flag_map:
+    # The environment variable overrides the default value.
+    if flag.upper() in os.environ:
+      _flag_map[flag] = os.environ[flag.upper()]
+
+    # The command line flag overrides the environment variable.
+    i = 1  # Skips the program name.
+    while i < len(argv):
+      prefix = '--' + flag + '='
+      if argv[i].startswith(prefix):
+        _flag_map[flag] = argv[i][len(prefix):]
+        del argv[i]
+        break
+      else:
+        # We don't increment i in case we just found a --gtest_* flag
+        # and removed it from argv.
+        i += 1
+
+
+def GetFlag(flag):
+  """Returns the value of the given flag."""
+
+  # In case GetFlag() is called before Main(), we always call
+  # _ParseAndStripGTestFlags() here to make sure the --gtest_* flags
+  # are parsed.
+  _ParseAndStripGTestFlags(sys.argv)
+
+  return _flag_map[flag]
+
+
+def GetSourceDir():
+  """Returns the absolute path of the directory where the .py files are."""
+
+  return os.path.abspath(GetFlag('source_dir'))
+
+
+def GetBuildDir():
+  """Returns the absolute path of the directory where the test binaries are."""
+
+  return os.path.abspath(GetFlag('build_dir'))
+
+
+_temp_dir = None
+
+def _RemoveTempDir():
+  if _temp_dir:
+    shutil.rmtree(_temp_dir, ignore_errors=True)
+
+atexit.register(_RemoveTempDir)
+
+
+def GetTempDir():
+  global _temp_dir
+  if not _temp_dir:
+    _temp_dir = tempfile.mkdtemp()
+  return _temp_dir
+
+
+def GetTestExecutablePath(executable_name, build_dir=None):
+  """Returns the absolute path of the test binary given its name.
+
+  The function will print a message and abort the program if the resulting file
+  doesn't exist.
+
+  Args:
+    executable_name: name of the test binary that the test script runs.
+    build_dir:       directory where to look for executables, by default
+                     the result of GetBuildDir().
+
+  Returns:
+    The absolute path of the test binary.
+  """
+
+  path = os.path.abspath(os.path.join(build_dir or GetBuildDir(),
+                                      executable_name))
+  if (IS_WINDOWS or IS_CYGWIN or IS_OS2) and not path.endswith('.exe'):
+    path += '.exe'
+
+  if not os.path.exists(path):
+    message = (
+        'Unable to find the test binary "%s". Please make sure to provide\n'
+        'a path to the binary via the --build_dir flag or the BUILD_DIR\n'
+        'environment variable.' % path)
+    print >> sys.stderr, message
+    sys.exit(1)
+
+  return path
+
+
+def GetExitStatus(exit_code):
+  """Returns the argument to exit(), or -1 if exit() wasn't called.
+
+  Args:
+    exit_code: the result value of os.system(command).
+  """
+
+  if os.name == 'nt':
+    # On Windows, os.WEXITSTATUS() doesn't work and os.system() returns
+    # the argument to exit() directly.
+    return exit_code
+  else:
+    # On Unix, os.WEXITSTATUS() must be used to extract the exit status
+    # from the result of os.system().
+    if os.WIFEXITED(exit_code):
+      return os.WEXITSTATUS(exit_code)
+    else:
+      return -1
+
+
+class Subprocess:
+  def __init__(self, command, working_dir=None, capture_stderr=True, env=None):
+    """Changes into a specified directory, if provided, and executes a command.
+
+    Restores the old directory afterwards.
+
+    Args:
+      command:        The command to run, in the form of sys.argv.
+      working_dir:    The directory to change into.
+      capture_stderr: Determines whether to capture stderr in the output member
+                      or to discard it.
+      env:            Dictionary with environment to pass to the subprocess.
+
+    Returns:
+      An object that represents outcome of the executed process. It has the
+      following attributes:
+        terminated_by_signal   True if and only if the child process has been
+                               terminated by a signal.
+        exited                 True if and only if the child process exited
+                               normally.
+        exit_code              The code with which the child process exited.
+        output                 Child process's stdout and stderr output
+                               combined in a string.
+    """
+
+    # The subprocess module is the preferrable way of running programs
+    # since it is available and behaves consistently on all platforms,
+    # including Windows. But it is only available starting in python 2.4.
+    # In earlier python versions, we revert to the popen2 module, which is
+    # available in python 2.0 and later but doesn't provide required
+    # functionality (Popen4) under Windows. This allows us to support Mac
+    # OS X 10.4 Tiger, which has python 2.3 installed.
+    if _SUBPROCESS_MODULE_AVAILABLE:
+      if capture_stderr:
+        stderr = subprocess.STDOUT
+      else:
+        stderr = subprocess.PIPE
+
+      p = subprocess.Popen(command,
+                           stdout=subprocess.PIPE, stderr=stderr,
+                           cwd=working_dir, universal_newlines=True, env=env)
+      # communicate returns a tuple with the file object for the child's
+      # output.
+      self.output = p.communicate()[0]
+      self._return_code = p.returncode
+    else:
+      old_dir = os.getcwd()
+
+      def _ReplaceEnvDict(dest, src):
+        # Changes made by os.environ.clear are not inheritable by child
+        # processes until Python 2.6. To produce inheritable changes we have
+        # to delete environment items with the del statement.
+        for key in dest.keys():
+          del dest[key]
+        dest.update(src)
+
+      # When 'env' is not None, backup the environment variables and replace
+      # them with the passed 'env'. When 'env' is None, we simply use the
+      # current 'os.environ' for compatibility with the subprocess.Popen
+      # semantics used above.
+      if env is not None:
+        old_environ = os.environ.copy()
+        _ReplaceEnvDict(os.environ, env)
+
+      try:
+        if working_dir is not None:
+          os.chdir(working_dir)
+        if capture_stderr:
+          p = popen2.Popen4(command)
+        else:
+          p = popen2.Popen3(command)
+        p.tochild.close()
+        self.output = p.fromchild.read()
+        ret_code = p.wait()
+      finally:
+        os.chdir(old_dir)
+
+        # Restore the old environment variables
+        # if they were replaced.
+        if env is not None:
+          _ReplaceEnvDict(os.environ, old_environ)
+
+      # Converts ret_code to match the semantics of
+      # subprocess.Popen.returncode.
+      if os.WIFSIGNALED(ret_code):
+        self._return_code = -os.WTERMSIG(ret_code)
+      else:  # os.WIFEXITED(ret_code) should return True here.
+        self._return_code = os.WEXITSTATUS(ret_code)
+
+    if bool(self._return_code & 0x80000000):
+      self.terminated_by_signal = True
+      self.exited = False
+    else:
+      self.terminated_by_signal = False
+      self.exited = True
+      self.exit_code = self._return_code
+
+
+def Main():
+  """Runs the unit test."""
+
+  # We must call _ParseAndStripGTestFlags() before calling
+  # unittest.main().  Otherwise the latter will be confused by the
+  # --gtest_* flags.
+  _ParseAndStripGTestFlags(sys.argv)
+  # The tested binaries should not be writing XML output files unless the
+  # script explicitly instructs them to.
+  if GTEST_OUTPUT_VAR_NAME in os.environ:
+    del os.environ[GTEST_OUTPUT_VAR_NAME]
+
+  _test_module.main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_testbridge_test.py b/leveldb_base/third_party/googletest/googletest/test/gtest_testbridge_test.py
new file mode 100644
index 0000000..87ffad7
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_testbridge_test.py
@@ -0,0 +1,63 @@
+#!/usr/bin/env python
+#
+# Copyright 2018 Google LLC. All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+"""Verifies that Google Test uses filter provided via testbridge."""
+
+import os
+
+import gtest_test_utils
+
+binary_name = 'gtest_testbridge_test_'
+COMMAND = gtest_test_utils.GetTestExecutablePath(binary_name)
+TESTBRIDGE_NAME = 'TESTBRIDGE_TEST_ONLY'
+
+
+def Assert(condition):
+  if not condition:
+    raise AssertionError
+
+
+class GTestTestFilterTest(gtest_test_utils.TestCase):
+
+  def testTestExecutionIsFiltered(self):
+    """Tests that the test filter is picked up from the testbridge env var."""
+    subprocess_env = os.environ.copy()
+
+    subprocess_env[TESTBRIDGE_NAME] = '*.TestThatSucceeds'
+    p = gtest_test_utils.Subprocess(COMMAND, env=subprocess_env)
+
+    self.assertEquals(0, p.exit_code)
+
+    Assert('filter = *.TestThatSucceeds' in p.output)
+    Assert('[       OK ] TestFilterTest.TestThatSucceeds' in p.output)
+    Assert('[  PASSED  ] 1 test.' in p.output)
+
+
+if __name__ == '__main__':
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_testbridge_test_.cc b/leveldb_base/third_party/googletest/googletest/test/gtest_testbridge_test_.cc
new file mode 100644
index 0000000..24617b2
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_testbridge_test_.cc
@@ -0,0 +1,43 @@
+// Copyright 2018, Google LLC.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// This program is meant to be run by gtest_test_filter_test.py.  Do not run
+// it directly.
+
+#include "gtest/gtest.h"
+
+// These tests are used to detect if filtering is working. Only
+// 'TestThatSucceeds' should ever run.
+
+TEST(TestFilterTest, TestThatSucceeds) {}
+
+TEST(TestFilterTest, TestThatFails) {
+  ASSERT_TRUE(false) << "This test should never be run.";
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_throw_on_failure_ex_test.cc b/leveldb_base/third_party/googletest/googletest/test/gtest_throw_on_failure_ex_test.cc
new file mode 100644
index 0000000..1d95adb
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_throw_on_failure_ex_test.cc
@@ -0,0 +1,90 @@
+// Copyright 2009, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+// Tests Google Test's throw-on-failure mode with exceptions enabled.
+
+#include "gtest/gtest.h"
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdexcept>
+
+// Prints the given failure message and exits the program with
+// non-zero.  We use this instead of a Google Test assertion to
+// indicate a failure, as the latter is been tested and cannot be
+// relied on.
+void Fail(const char* msg) {
+  printf("FAILURE: %s\n", msg);
+  fflush(stdout);
+  exit(1);
+}
+
+// Tests that an assertion failure throws a subclass of
+// std::runtime_error.
+void TestFailureThrowsRuntimeError() {
+  testing::GTEST_FLAG(throw_on_failure) = true;
+
+  // A successful assertion shouldn't throw.
+  try {
+    EXPECT_EQ(3, 3);
+  } catch(...) {
+    Fail("A successful assertion wrongfully threw.");
+  }
+
+  // A failed assertion should throw a subclass of std::runtime_error.
+  try {
+    EXPECT_EQ(2, 3) << "Expected failure";
+  } catch(const std::runtime_error& e) {
+    if (strstr(e.what(), "Expected failure") != nullptr) return;
+
+    printf("%s",
+           "A failed assertion did throw an exception of the right type, "
+           "but the message is incorrect.  Instead of containing \"Expected "
+           "failure\", it is:\n");
+    Fail(e.what());
+  } catch(...) {
+    Fail("A failed assertion threw the wrong type of exception.");
+  }
+  Fail("A failed assertion should've thrown but didn't.");
+}
+
+int main(int argc, char** argv) {
+  testing::InitGoogleTest(&argc, argv);
+
+  // We want to ensure that people can use Google Test assertions in
+  // other testing frameworks, as long as they initialize Google Test
+  // properly and set the thrown-on-failure mode.  Therefore, we don't
+  // use Google Test's constructs for defining and running tests
+  // (e.g. TEST and RUN_ALL_TESTS) here.
+
+  TestFailureThrowsRuntimeError();
+  return 0;
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_unittest.cc b/leveldb_base/third_party/googletest/googletest/test/gtest_unittest.cc
new file mode 100644
index 0000000..1730e8b
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_unittest.cc
@@ -0,0 +1,7784 @@
+// Copyright 2005, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// Tests for Google Test itself.  This verifies that the basic constructs of
+// Google Test work.
+
+#include "gtest/gtest.h"
+
+// Verifies that the command line flag variables can be accessed in
+// code once "gtest.h" has been #included.
+// Do not move it after other gtest #includes.
+TEST(CommandLineFlagsTest, CanBeAccessedInCodeOnceGTestHIsIncluded) {
+  bool dummy = testing::GTEST_FLAG(also_run_disabled_tests) ||
+               testing::GTEST_FLAG(break_on_failure) ||
+               testing::GTEST_FLAG(catch_exceptions) ||
+               testing::GTEST_FLAG(color) != "unknown" ||
+               testing::GTEST_FLAG(fail_fast) ||
+               testing::GTEST_FLAG(filter) != "unknown" ||
+               testing::GTEST_FLAG(list_tests) ||
+               testing::GTEST_FLAG(output) != "unknown" ||
+               testing::GTEST_FLAG(brief) || testing::GTEST_FLAG(print_time) ||
+               testing::GTEST_FLAG(random_seed) ||
+               testing::GTEST_FLAG(repeat) > 0 ||
+               testing::GTEST_FLAG(show_internal_stack_frames) ||
+               testing::GTEST_FLAG(shuffle) ||
+               testing::GTEST_FLAG(stack_trace_depth) > 0 ||
+               testing::GTEST_FLAG(stream_result_to) != "unknown" ||
+               testing::GTEST_FLAG(throw_on_failure);
+  EXPECT_TRUE(dummy || !dummy);  // Suppresses warning that dummy is unused.
+}
+
+#include <limits.h>  // For INT_MAX.
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+
+#include <cstdint>
+#include <map>
+#include <ostream>
+#include <string>
+#include <type_traits>
+#include <unordered_set>
+#include <vector>
+
+#include "gtest/gtest-spi.h"
+#include "src/gtest-internal-inl.h"
+
+namespace testing {
+namespace internal {
+
+#if GTEST_CAN_STREAM_RESULTS_
+
+class StreamingListenerTest : public Test {
+ public:
+  class FakeSocketWriter : public StreamingListener::AbstractSocketWriter {
+   public:
+    // Sends a string to the socket.
+    void Send(const std::string& message) override { output_ += message; }
+
+    std::string output_;
+  };
+
+  StreamingListenerTest()
+      : fake_sock_writer_(new FakeSocketWriter),
+        streamer_(fake_sock_writer_),
+        test_info_obj_("FooTest", "Bar", nullptr, nullptr,
+                       CodeLocation(__FILE__, __LINE__), nullptr, nullptr) {}
+
+ protected:
+  std::string* output() { return &(fake_sock_writer_->output_); }
+
+  FakeSocketWriter* const fake_sock_writer_;
+  StreamingListener streamer_;
+  UnitTest unit_test_;
+  TestInfo test_info_obj_;  // The name test_info_ was taken by testing::Test.
+};
+
+TEST_F(StreamingListenerTest, OnTestProgramEnd) {
+  *output() = "";
+  streamer_.OnTestProgramEnd(unit_test_);
+  EXPECT_EQ("event=TestProgramEnd&passed=1\n", *output());
+}
+
+TEST_F(StreamingListenerTest, OnTestIterationEnd) {
+  *output() = "";
+  streamer_.OnTestIterationEnd(unit_test_, 42);
+  EXPECT_EQ("event=TestIterationEnd&passed=1&elapsed_time=0ms\n", *output());
+}
+
+TEST_F(StreamingListenerTest, OnTestCaseStart) {
+  *output() = "";
+  streamer_.OnTestCaseStart(TestCase("FooTest", "Bar", nullptr, nullptr));
+  EXPECT_EQ("event=TestCaseStart&name=FooTest\n", *output());
+}
+
+TEST_F(StreamingListenerTest, OnTestCaseEnd) {
+  *output() = "";
+  streamer_.OnTestCaseEnd(TestCase("FooTest", "Bar", nullptr, nullptr));
+  EXPECT_EQ("event=TestCaseEnd&passed=1&elapsed_time=0ms\n", *output());
+}
+
+TEST_F(StreamingListenerTest, OnTestStart) {
+  *output() = "";
+  streamer_.OnTestStart(test_info_obj_);
+  EXPECT_EQ("event=TestStart&name=Bar\n", *output());
+}
+
+TEST_F(StreamingListenerTest, OnTestEnd) {
+  *output() = "";
+  streamer_.OnTestEnd(test_info_obj_);
+  EXPECT_EQ("event=TestEnd&passed=1&elapsed_time=0ms\n", *output());
+}
+
+TEST_F(StreamingListenerTest, OnTestPartResult) {
+  *output() = "";
+  streamer_.OnTestPartResult(TestPartResult(
+      TestPartResult::kFatalFailure, "foo.cc", 42, "failed=\n&%"));
+
+  // Meta characters in the failure message should be properly escaped.
+  EXPECT_EQ(
+      "event=TestPartResult&file=foo.cc&line=42&message=failed%3D%0A%26%25\n",
+      *output());
+}
+
+#endif  // GTEST_CAN_STREAM_RESULTS_
+
+// Provides access to otherwise private parts of the TestEventListeners class
+// that are needed to test it.
+class TestEventListenersAccessor {
+ public:
+  static TestEventListener* GetRepeater(TestEventListeners* listeners) {
+    return listeners->repeater();
+  }
+
+  static void SetDefaultResultPrinter(TestEventListeners* listeners,
+                                      TestEventListener* listener) {
+    listeners->SetDefaultResultPrinter(listener);
+  }
+  static void SetDefaultXmlGenerator(TestEventListeners* listeners,
+                                     TestEventListener* listener) {
+    listeners->SetDefaultXmlGenerator(listener);
+  }
+
+  static bool EventForwardingEnabled(const TestEventListeners& listeners) {
+    return listeners.EventForwardingEnabled();
+  }
+
+  static void SuppressEventForwarding(TestEventListeners* listeners) {
+    listeners->SuppressEventForwarding();
+  }
+};
+
+class UnitTestRecordPropertyTestHelper : public Test {
+ protected:
+  UnitTestRecordPropertyTestHelper() {}
+
+  // Forwards to UnitTest::RecordProperty() to bypass access controls.
+  void UnitTestRecordProperty(const char* key, const std::string& value) {
+    unit_test_.RecordProperty(key, value);
+  }
+
+  UnitTest unit_test_;
+};
+
+}  // namespace internal
+}  // namespace testing
+
+using testing::AssertionFailure;
+using testing::AssertionResult;
+using testing::AssertionSuccess;
+using testing::DoubleLE;
+using testing::EmptyTestEventListener;
+using testing::Environment;
+using testing::FloatLE;
+using testing::GTEST_FLAG(also_run_disabled_tests);
+using testing::GTEST_FLAG(break_on_failure);
+using testing::GTEST_FLAG(catch_exceptions);
+using testing::GTEST_FLAG(color);
+using testing::GTEST_FLAG(death_test_use_fork);
+using testing::GTEST_FLAG(fail_fast);
+using testing::GTEST_FLAG(filter);
+using testing::GTEST_FLAG(list_tests);
+using testing::GTEST_FLAG(output);
+using testing::GTEST_FLAG(brief);
+using testing::GTEST_FLAG(print_time);
+using testing::GTEST_FLAG(random_seed);
+using testing::GTEST_FLAG(repeat);
+using testing::GTEST_FLAG(show_internal_stack_frames);
+using testing::GTEST_FLAG(shuffle);
+using testing::GTEST_FLAG(stack_trace_depth);
+using testing::GTEST_FLAG(stream_result_to);
+using testing::GTEST_FLAG(throw_on_failure);
+using testing::IsNotSubstring;
+using testing::IsSubstring;
+using testing::kMaxStackTraceDepth;
+using testing::Message;
+using testing::ScopedFakeTestPartResultReporter;
+using testing::StaticAssertTypeEq;
+using testing::Test;
+using testing::TestEventListeners;
+using testing::TestInfo;
+using testing::TestPartResult;
+using testing::TestPartResultArray;
+using testing::TestProperty;
+using testing::TestResult;
+using testing::TestSuite;
+using testing::TimeInMillis;
+using testing::UnitTest;
+using testing::internal::AlwaysFalse;
+using testing::internal::AlwaysTrue;
+using testing::internal::AppendUserMessage;
+using testing::internal::ArrayAwareFind;
+using testing::internal::ArrayEq;
+using testing::internal::CodePointToUtf8;
+using testing::internal::CopyArray;
+using testing::internal::CountIf;
+using testing::internal::EqFailure;
+using testing::internal::FloatingPoint;
+using testing::internal::ForEach;
+using testing::internal::FormatEpochTimeInMillisAsIso8601;
+using testing::internal::FormatTimeInMillisAsSeconds;
+using testing::internal::GetCurrentOsStackTraceExceptTop;
+using testing::internal::GetElementOr;
+using testing::internal::GetNextRandomSeed;
+using testing::internal::GetRandomSeedFromFlag;
+using testing::internal::GetTestTypeId;
+using testing::internal::GetTimeInMillis;
+using testing::internal::GetTypeId;
+using testing::internal::GetUnitTestImpl;
+using testing::internal::GTestFlagSaver;
+using testing::internal::HasDebugStringAndShortDebugString;
+using testing::internal::Int32FromEnvOrDie;
+using testing::internal::IsContainer;
+using testing::internal::IsContainerTest;
+using testing::internal::IsNotContainer;
+using testing::internal::kMaxRandomSeed;
+using testing::internal::kTestTypeIdInGoogleTest;
+using testing::internal::NativeArray;
+using testing::internal::OsStackTraceGetter;
+using testing::internal::OsStackTraceGetterInterface;
+using testing::internal::ParseInt32Flag;
+using testing::internal::RelationToSourceCopy;
+using testing::internal::RelationToSourceReference;
+using testing::internal::ShouldRunTestOnShard;
+using testing::internal::ShouldShard;
+using testing::internal::ShouldUseColor;
+using testing::internal::Shuffle;
+using testing::internal::ShuffleRange;
+using testing::internal::SkipPrefix;
+using testing::internal::StreamableToString;
+using testing::internal::String;
+using testing::internal::TestEventListenersAccessor;
+using testing::internal::TestResultAccessor;
+using testing::internal::UnitTestImpl;
+using testing::internal::WideStringToUtf8;
+using testing::internal::edit_distance::CalculateOptimalEdits;
+using testing::internal::edit_distance::CreateUnifiedDiff;
+using testing::internal::edit_distance::EditType;
+
+#if GTEST_HAS_STREAM_REDIRECTION
+using testing::internal::CaptureStdout;
+using testing::internal::GetCapturedStdout;
+#endif
+
+#if GTEST_IS_THREADSAFE
+using testing::internal::ThreadWithParam;
+#endif
+
+class TestingVector : public std::vector<int> {
+};
+
+::std::ostream& operator<<(::std::ostream& os,
+                           const TestingVector& vector) {
+  os << "{ ";
+  for (size_t i = 0; i < vector.size(); i++) {
+    os << vector[i] << " ";
+  }
+  os << "}";
+  return os;
+}
+
+// This line tests that we can define tests in an unnamed namespace.
+namespace {
+
+TEST(GetRandomSeedFromFlagTest, HandlesZero) {
+  const int seed = GetRandomSeedFromFlag(0);
+  EXPECT_LE(1, seed);
+  EXPECT_LE(seed, static_cast<int>(kMaxRandomSeed));
+}
+
+TEST(GetRandomSeedFromFlagTest, PreservesValidSeed) {
+  EXPECT_EQ(1, GetRandomSeedFromFlag(1));
+  EXPECT_EQ(2, GetRandomSeedFromFlag(2));
+  EXPECT_EQ(kMaxRandomSeed - 1, GetRandomSeedFromFlag(kMaxRandomSeed - 1));
+  EXPECT_EQ(static_cast<int>(kMaxRandomSeed),
+            GetRandomSeedFromFlag(kMaxRandomSeed));
+}
+
+TEST(GetRandomSeedFromFlagTest, NormalizesInvalidSeed) {
+  const int seed1 = GetRandomSeedFromFlag(-1);
+  EXPECT_LE(1, seed1);
+  EXPECT_LE(seed1, static_cast<int>(kMaxRandomSeed));
+
+  const int seed2 = GetRandomSeedFromFlag(kMaxRandomSeed + 1);
+  EXPECT_LE(1, seed2);
+  EXPECT_LE(seed2, static_cast<int>(kMaxRandomSeed));
+}
+
+TEST(GetNextRandomSeedTest, WorksForValidInput) {
+  EXPECT_EQ(2, GetNextRandomSeed(1));
+  EXPECT_EQ(3, GetNextRandomSeed(2));
+  EXPECT_EQ(static_cast<int>(kMaxRandomSeed),
+            GetNextRandomSeed(kMaxRandomSeed - 1));
+  EXPECT_EQ(1, GetNextRandomSeed(kMaxRandomSeed));
+
+  // We deliberately don't test GetNextRandomSeed() with invalid
+  // inputs, as that requires death tests, which are expensive.  This
+  // is fine as GetNextRandomSeed() is internal and has a
+  // straightforward definition.
+}
+
+static void ClearCurrentTestPartResults() {
+  TestResultAccessor::ClearTestPartResults(
+      GetUnitTestImpl()->current_test_result());
+}
+
+// Tests GetTypeId.
+
+TEST(GetTypeIdTest, ReturnsSameValueForSameType) {
+  EXPECT_EQ(GetTypeId<int>(), GetTypeId<int>());
+  EXPECT_EQ(GetTypeId<Test>(), GetTypeId<Test>());
+}
+
+class SubClassOfTest : public Test {};
+class AnotherSubClassOfTest : public Test {};
+
+TEST(GetTypeIdTest, ReturnsDifferentValuesForDifferentTypes) {
+  EXPECT_NE(GetTypeId<int>(), GetTypeId<const int>());
+  EXPECT_NE(GetTypeId<int>(), GetTypeId<char>());
+  EXPECT_NE(GetTypeId<int>(), GetTestTypeId());
+  EXPECT_NE(GetTypeId<SubClassOfTest>(), GetTestTypeId());
+  EXPECT_NE(GetTypeId<AnotherSubClassOfTest>(), GetTestTypeId());
+  EXPECT_NE(GetTypeId<AnotherSubClassOfTest>(), GetTypeId<SubClassOfTest>());
+}
+
+// Verifies that GetTestTypeId() returns the same value, no matter it
+// is called from inside Google Test or outside of it.
+TEST(GetTestTypeIdTest, ReturnsTheSameValueInsideOrOutsideOfGoogleTest) {
+  EXPECT_EQ(kTestTypeIdInGoogleTest, GetTestTypeId());
+}
+
+// Tests CanonicalizeForStdLibVersioning.
+
+using ::testing::internal::CanonicalizeForStdLibVersioning;
+
+TEST(CanonicalizeForStdLibVersioning, LeavesUnversionedNamesUnchanged) {
+  EXPECT_EQ("std::bind", CanonicalizeForStdLibVersioning("std::bind"));
+  EXPECT_EQ("std::_", CanonicalizeForStdLibVersioning("std::_"));
+  EXPECT_EQ("std::__foo", CanonicalizeForStdLibVersioning("std::__foo"));
+  EXPECT_EQ("gtl::__1::x", CanonicalizeForStdLibVersioning("gtl::__1::x"));
+  EXPECT_EQ("__1::x", CanonicalizeForStdLibVersioning("__1::x"));
+  EXPECT_EQ("::__1::x", CanonicalizeForStdLibVersioning("::__1::x"));
+}
+
+TEST(CanonicalizeForStdLibVersioning, ElidesDoubleUnderNames) {
+  EXPECT_EQ("std::bind", CanonicalizeForStdLibVersioning("std::__1::bind"));
+  EXPECT_EQ("std::_", CanonicalizeForStdLibVersioning("std::__1::_"));
+
+  EXPECT_EQ("std::bind", CanonicalizeForStdLibVersioning("std::__g::bind"));
+  EXPECT_EQ("std::_", CanonicalizeForStdLibVersioning("std::__g::_"));
+
+  EXPECT_EQ("std::bind",
+            CanonicalizeForStdLibVersioning("std::__google::bind"));
+  EXPECT_EQ("std::_", CanonicalizeForStdLibVersioning("std::__google::_"));
+}
+
+// Tests FormatTimeInMillisAsSeconds().
+
+TEST(FormatTimeInMillisAsSecondsTest, FormatsZero) {
+  EXPECT_EQ("0", FormatTimeInMillisAsSeconds(0));
+}
+
+TEST(FormatTimeInMillisAsSecondsTest, FormatsPositiveNumber) {
+  EXPECT_EQ("0.003", FormatTimeInMillisAsSeconds(3));
+  EXPECT_EQ("0.01", FormatTimeInMillisAsSeconds(10));
+  EXPECT_EQ("0.2", FormatTimeInMillisAsSeconds(200));
+  EXPECT_EQ("1.2", FormatTimeInMillisAsSeconds(1200));
+  EXPECT_EQ("3", FormatTimeInMillisAsSeconds(3000));
+}
+
+TEST(FormatTimeInMillisAsSecondsTest, FormatsNegativeNumber) {
+  EXPECT_EQ("-0.003", FormatTimeInMillisAsSeconds(-3));
+  EXPECT_EQ("-0.01", FormatTimeInMillisAsSeconds(-10));
+  EXPECT_EQ("-0.2", FormatTimeInMillisAsSeconds(-200));
+  EXPECT_EQ("-1.2", FormatTimeInMillisAsSeconds(-1200));
+  EXPECT_EQ("-3", FormatTimeInMillisAsSeconds(-3000));
+}
+
+// Tests FormatEpochTimeInMillisAsIso8601().  The correctness of conversion
+// for particular dates below was verified in Python using
+// datetime.datetime.fromutctimestamp(<timetamp>/1000).
+
+// FormatEpochTimeInMillisAsIso8601 depends on the current timezone, so we
+// have to set up a particular timezone to obtain predictable results.
+class FormatEpochTimeInMillisAsIso8601Test : public Test {
+ public:
+  // On Cygwin, GCC doesn't allow unqualified integer literals to exceed
+  // 32 bits, even when 64-bit integer types are available.  We have to
+  // force the constants to have a 64-bit type here.
+  static const TimeInMillis kMillisPerSec = 1000;
+
+ private:
+  void SetUp() override {
+    saved_tz_ = nullptr;
+
+    GTEST_DISABLE_MSC_DEPRECATED_PUSH_(/* getenv, strdup: deprecated */)
+    if (getenv("TZ"))
+      saved_tz_ = strdup(getenv("TZ"));
+    GTEST_DISABLE_MSC_DEPRECATED_POP_()
+
+    // Set up the time zone for FormatEpochTimeInMillisAsIso8601 to use.  We
+    // cannot use the local time zone because the function's output depends
+    // on the time zone.
+    SetTimeZone("UTC+00");
+  }
+
+  void TearDown() override {
+    SetTimeZone(saved_tz_);
+    free(const_cast<char*>(saved_tz_));
+    saved_tz_ = nullptr;
+  }
+
+  static void SetTimeZone(const char* time_zone) {
+    // tzset() distinguishes between the TZ variable being present and empty
+    // and not being present, so we have to consider the case of time_zone
+    // being NULL.
+#if _MSC_VER || GTEST_OS_WINDOWS_MINGW
+    // ...Unless it's MSVC, whose standard library's _putenv doesn't
+    // distinguish between an empty and a missing variable.
+    const std::string env_var =
+        std::string("TZ=") + (time_zone ? time_zone : "");
+    _putenv(env_var.c_str());
+    GTEST_DISABLE_MSC_WARNINGS_PUSH_(4996 /* deprecated function */)
+    tzset();
+    GTEST_DISABLE_MSC_WARNINGS_POP_()
+#else
+    if (time_zone) {
+      setenv(("TZ"), time_zone, 1);
+    } else {
+      unsetenv("TZ");
+    }
+    tzset();
+#endif
+  }
+
+  const char* saved_tz_;
+};
+
+const TimeInMillis FormatEpochTimeInMillisAsIso8601Test::kMillisPerSec;
+
+TEST_F(FormatEpochTimeInMillisAsIso8601Test, PrintsTwoDigitSegments) {
+  EXPECT_EQ("2011-10-31T18:52:42.000",
+            FormatEpochTimeInMillisAsIso8601(1320087162 * kMillisPerSec));
+}
+
+TEST_F(FormatEpochTimeInMillisAsIso8601Test, IncludesMillisecondsAfterDot) {
+  EXPECT_EQ(
+      "2011-10-31T18:52:42.234",
+      FormatEpochTimeInMillisAsIso8601(1320087162 * kMillisPerSec + 234));
+}
+
+TEST_F(FormatEpochTimeInMillisAsIso8601Test, PrintsLeadingZeroes) {
+  EXPECT_EQ("2011-09-03T05:07:02.000",
+            FormatEpochTimeInMillisAsIso8601(1315026422 * kMillisPerSec));
+}
+
+TEST_F(FormatEpochTimeInMillisAsIso8601Test, Prints24HourTime) {
+  EXPECT_EQ("2011-09-28T17:08:22.000",
+            FormatEpochTimeInMillisAsIso8601(1317229702 * kMillisPerSec));
+}
+
+TEST_F(FormatEpochTimeInMillisAsIso8601Test, PrintsEpochStart) {
+  EXPECT_EQ("1970-01-01T00:00:00.000", FormatEpochTimeInMillisAsIso8601(0));
+}
+
+# ifdef __BORLANDC__
+// Silences warnings: "Condition is always true", "Unreachable code"
+#  pragma option push -w-ccc -w-rch
+# endif
+
+// Tests that the LHS of EXPECT_EQ or ASSERT_EQ can be used as a null literal
+// when the RHS is a pointer type.
+TEST(NullLiteralTest, LHSAllowsNullLiterals) {
+  EXPECT_EQ(0, static_cast<void*>(nullptr));     // NOLINT
+  ASSERT_EQ(0, static_cast<void*>(nullptr));     // NOLINT
+  EXPECT_EQ(NULL, static_cast<void*>(nullptr));  // NOLINT
+  ASSERT_EQ(NULL, static_cast<void*>(nullptr));  // NOLINT
+  EXPECT_EQ(nullptr, static_cast<void*>(nullptr));
+  ASSERT_EQ(nullptr, static_cast<void*>(nullptr));
+
+  const int* const p = nullptr;
+  EXPECT_EQ(0, p);     // NOLINT
+  ASSERT_EQ(0, p);     // NOLINT
+  EXPECT_EQ(NULL, p);  // NOLINT
+  ASSERT_EQ(NULL, p);  // NOLINT
+  EXPECT_EQ(nullptr, p);
+  ASSERT_EQ(nullptr, p);
+}
+
+struct ConvertToAll {
+  template <typename T>
+  operator T() const {  // NOLINT
+    return T();
+  }
+};
+
+struct ConvertToPointer {
+  template <class T>
+  operator T*() const {  // NOLINT
+    return nullptr;
+  }
+};
+
+struct ConvertToAllButNoPointers {
+  template <typename T,
+            typename std::enable_if<!std::is_pointer<T>::value, int>::type = 0>
+  operator T() const {  // NOLINT
+    return T();
+  }
+};
+
+struct MyType {};
+inline bool operator==(MyType const&, MyType const&) { return true; }
+
+TEST(NullLiteralTest, ImplicitConversion) {
+  EXPECT_EQ(ConvertToPointer{}, static_cast<void*>(nullptr));
+#if !defined(__GNUC__) || defined(__clang__)
+  // Disabled due to GCC bug gcc.gnu.org/PR89580
+  EXPECT_EQ(ConvertToAll{}, static_cast<void*>(nullptr));
+#endif
+  EXPECT_EQ(ConvertToAll{}, MyType{});
+  EXPECT_EQ(ConvertToAllButNoPointers{}, MyType{});
+}
+
+#ifdef __clang__
+#pragma clang diagnostic push
+#if __has_warning("-Wzero-as-null-pointer-constant")
+#pragma clang diagnostic error "-Wzero-as-null-pointer-constant"
+#endif
+#endif
+
+TEST(NullLiteralTest, NoConversionNoWarning) {
+  // Test that gtests detection and handling of null pointer constants
+  // doesn't trigger a warning when '0' isn't actually used as null.
+  EXPECT_EQ(0, 0);
+  ASSERT_EQ(0, 0);
+}
+
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif
+
+# ifdef __BORLANDC__
+// Restores warnings after previous "#pragma option push" suppressed them.
+#  pragma option pop
+# endif
+
+//
+// Tests CodePointToUtf8().
+
+// Tests that the NUL character L'\0' is encoded correctly.
+TEST(CodePointToUtf8Test, CanEncodeNul) {
+  EXPECT_EQ("", CodePointToUtf8(L'\0'));
+}
+
+// Tests that ASCII characters are encoded correctly.
+TEST(CodePointToUtf8Test, CanEncodeAscii) {
+  EXPECT_EQ("a", CodePointToUtf8(L'a'));
+  EXPECT_EQ("Z", CodePointToUtf8(L'Z'));
+  EXPECT_EQ("&", CodePointToUtf8(L'&'));
+  EXPECT_EQ("\x7F", CodePointToUtf8(L'\x7F'));
+}
+
+// Tests that Unicode code-points that have 8 to 11 bits are encoded
+// as 110xxxxx 10xxxxxx.
+TEST(CodePointToUtf8Test, CanEncode8To11Bits) {
+  // 000 1101 0011 => 110-00011 10-010011
+  EXPECT_EQ("\xC3\x93", CodePointToUtf8(L'\xD3'));
+
+  // 101 0111 0110 => 110-10101 10-110110
+  // Some compilers (e.g., GCC on MinGW) cannot handle non-ASCII codepoints
+  // in wide strings and wide chars. In order to accommodate them, we have to
+  // introduce such character constants as integers.
+  EXPECT_EQ("\xD5\xB6",
+            CodePointToUtf8(static_cast<wchar_t>(0x576)));
+}
+
+// Tests that Unicode code-points that have 12 to 16 bits are encoded
+// as 1110xxxx 10xxxxxx 10xxxxxx.
+TEST(CodePointToUtf8Test, CanEncode12To16Bits) {
+  // 0000 1000 1101 0011 => 1110-0000 10-100011 10-010011
+  EXPECT_EQ("\xE0\xA3\x93",
+            CodePointToUtf8(static_cast<wchar_t>(0x8D3)));
+
+  // 1100 0111 0100 1101 => 1110-1100 10-011101 10-001101
+  EXPECT_EQ("\xEC\x9D\x8D",
+            CodePointToUtf8(static_cast<wchar_t>(0xC74D)));
+}
+
+#if !GTEST_WIDE_STRING_USES_UTF16_
+// Tests in this group require a wchar_t to hold > 16 bits, and thus
+// are skipped on Windows, and Cygwin, where a wchar_t is
+// 16-bit wide. This code may not compile on those systems.
+
+// Tests that Unicode code-points that have 17 to 21 bits are encoded
+// as 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx.
+TEST(CodePointToUtf8Test, CanEncode17To21Bits) {
+  // 0 0001 0000 1000 1101 0011 => 11110-000 10-010000 10-100011 10-010011
+  EXPECT_EQ("\xF0\x90\xA3\x93", CodePointToUtf8(L'\x108D3'));
+
+  // 0 0001 0000 0100 0000 0000 => 11110-000 10-010000 10-010000 10-000000
+  EXPECT_EQ("\xF0\x90\x90\x80", CodePointToUtf8(L'\x10400'));
+
+  // 1 0000 1000 0110 0011 0100 => 11110-100 10-001000 10-011000 10-110100
+  EXPECT_EQ("\xF4\x88\x98\xB4", CodePointToUtf8(L'\x108634'));
+}
+
+// Tests that encoding an invalid code-point generates the expected result.
+TEST(CodePointToUtf8Test, CanEncodeInvalidCodePoint) {
+  EXPECT_EQ("(Invalid Unicode 0x1234ABCD)", CodePointToUtf8(L'\x1234ABCD'));
+}
+
+#endif  // !GTEST_WIDE_STRING_USES_UTF16_
+
+// Tests WideStringToUtf8().
+
+// Tests that the NUL character L'\0' is encoded correctly.
+TEST(WideStringToUtf8Test, CanEncodeNul) {
+  EXPECT_STREQ("", WideStringToUtf8(L"", 0).c_str());
+  EXPECT_STREQ("", WideStringToUtf8(L"", -1).c_str());
+}
+
+// Tests that ASCII strings are encoded correctly.
+TEST(WideStringToUtf8Test, CanEncodeAscii) {
+  EXPECT_STREQ("a", WideStringToUtf8(L"a", 1).c_str());
+  EXPECT_STREQ("ab", WideStringToUtf8(L"ab", 2).c_str());
+  EXPECT_STREQ("a", WideStringToUtf8(L"a", -1).c_str());
+  EXPECT_STREQ("ab", WideStringToUtf8(L"ab", -1).c_str());
+}
+
+// Tests that Unicode code-points that have 8 to 11 bits are encoded
+// as 110xxxxx 10xxxxxx.
+TEST(WideStringToUtf8Test, CanEncode8To11Bits) {
+  // 000 1101 0011 => 110-00011 10-010011
+  EXPECT_STREQ("\xC3\x93", WideStringToUtf8(L"\xD3", 1).c_str());
+  EXPECT_STREQ("\xC3\x93", WideStringToUtf8(L"\xD3", -1).c_str());
+
+  // 101 0111 0110 => 110-10101 10-110110
+  const wchar_t s[] = { 0x576, '\0' };
+  EXPECT_STREQ("\xD5\xB6", WideStringToUtf8(s, 1).c_str());
+  EXPECT_STREQ("\xD5\xB6", WideStringToUtf8(s, -1).c_str());
+}
+
+// Tests that Unicode code-points that have 12 to 16 bits are encoded
+// as 1110xxxx 10xxxxxx 10xxxxxx.
+TEST(WideStringToUtf8Test, CanEncode12To16Bits) {
+  // 0000 1000 1101 0011 => 1110-0000 10-100011 10-010011
+  const wchar_t s1[] = { 0x8D3, '\0' };
+  EXPECT_STREQ("\xE0\xA3\x93", WideStringToUtf8(s1, 1).c_str());
+  EXPECT_STREQ("\xE0\xA3\x93", WideStringToUtf8(s1, -1).c_str());
+
+  // 1100 0111 0100 1101 => 1110-1100 10-011101 10-001101
+  const wchar_t s2[] = { 0xC74D, '\0' };
+  EXPECT_STREQ("\xEC\x9D\x8D", WideStringToUtf8(s2, 1).c_str());
+  EXPECT_STREQ("\xEC\x9D\x8D", WideStringToUtf8(s2, -1).c_str());
+}
+
+// Tests that the conversion stops when the function encounters \0 character.
+TEST(WideStringToUtf8Test, StopsOnNulCharacter) {
+  EXPECT_STREQ("ABC", WideStringToUtf8(L"ABC\0XYZ", 100).c_str());
+}
+
+// Tests that the conversion stops when the function reaches the limit
+// specified by the 'length' parameter.
+TEST(WideStringToUtf8Test, StopsWhenLengthLimitReached) {
+  EXPECT_STREQ("ABC", WideStringToUtf8(L"ABCDEF", 3).c_str());
+}
+
+#if !GTEST_WIDE_STRING_USES_UTF16_
+// Tests that Unicode code-points that have 17 to 21 bits are encoded
+// as 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx. This code may not compile
+// on the systems using UTF-16 encoding.
+TEST(WideStringToUtf8Test, CanEncode17To21Bits) {
+  // 0 0001 0000 1000 1101 0011 => 11110-000 10-010000 10-100011 10-010011
+  EXPECT_STREQ("\xF0\x90\xA3\x93", WideStringToUtf8(L"\x108D3", 1).c_str());
+  EXPECT_STREQ("\xF0\x90\xA3\x93", WideStringToUtf8(L"\x108D3", -1).c_str());
+
+  // 1 0000 1000 0110 0011 0100 => 11110-100 10-001000 10-011000 10-110100
+  EXPECT_STREQ("\xF4\x88\x98\xB4", WideStringToUtf8(L"\x108634", 1).c_str());
+  EXPECT_STREQ("\xF4\x88\x98\xB4", WideStringToUtf8(L"\x108634", -1).c_str());
+}
+
+// Tests that encoding an invalid code-point generates the expected result.
+TEST(WideStringToUtf8Test, CanEncodeInvalidCodePoint) {
+  EXPECT_STREQ("(Invalid Unicode 0xABCDFF)",
+               WideStringToUtf8(L"\xABCDFF", -1).c_str());
+}
+#else  // !GTEST_WIDE_STRING_USES_UTF16_
+// Tests that surrogate pairs are encoded correctly on the systems using
+// UTF-16 encoding in the wide strings.
+TEST(WideStringToUtf8Test, CanEncodeValidUtf16SUrrogatePairs) {
+  const wchar_t s[] = { 0xD801, 0xDC00, '\0' };
+  EXPECT_STREQ("\xF0\x90\x90\x80", WideStringToUtf8(s, -1).c_str());
+}
+
+// Tests that encoding an invalid UTF-16 surrogate pair
+// generates the expected result.
+TEST(WideStringToUtf8Test, CanEncodeInvalidUtf16SurrogatePair) {
+  // Leading surrogate is at the end of the string.
+  const wchar_t s1[] = { 0xD800, '\0' };
+  EXPECT_STREQ("\xED\xA0\x80", WideStringToUtf8(s1, -1).c_str());
+  // Leading surrogate is not followed by the trailing surrogate.
+  const wchar_t s2[] = { 0xD800, 'M', '\0' };
+  EXPECT_STREQ("\xED\xA0\x80M", WideStringToUtf8(s2, -1).c_str());
+  // Trailing surrogate appearas without a leading surrogate.
+  const wchar_t s3[] = { 0xDC00, 'P', 'Q', 'R', '\0' };
+  EXPECT_STREQ("\xED\xB0\x80PQR", WideStringToUtf8(s3, -1).c_str());
+}
+#endif  // !GTEST_WIDE_STRING_USES_UTF16_
+
+// Tests that codepoint concatenation works correctly.
+#if !GTEST_WIDE_STRING_USES_UTF16_
+TEST(WideStringToUtf8Test, ConcatenatesCodepointsCorrectly) {
+  const wchar_t s[] = { 0x108634, 0xC74D, '\n', 0x576, 0x8D3, 0x108634, '\0'};
+  EXPECT_STREQ(
+      "\xF4\x88\x98\xB4"
+          "\xEC\x9D\x8D"
+          "\n"
+          "\xD5\xB6"
+          "\xE0\xA3\x93"
+          "\xF4\x88\x98\xB4",
+      WideStringToUtf8(s, -1).c_str());
+}
+#else
+TEST(WideStringToUtf8Test, ConcatenatesCodepointsCorrectly) {
+  const wchar_t s[] = { 0xC74D, '\n', 0x576, 0x8D3, '\0'};
+  EXPECT_STREQ(
+      "\xEC\x9D\x8D" "\n" "\xD5\xB6" "\xE0\xA3\x93",
+      WideStringToUtf8(s, -1).c_str());
+}
+#endif  // !GTEST_WIDE_STRING_USES_UTF16_
+
+// Tests the Random class.
+
+TEST(RandomDeathTest, GeneratesCrashesOnInvalidRange) {
+  testing::internal::Random random(42);
+  EXPECT_DEATH_IF_SUPPORTED(
+      random.Generate(0),
+      "Cannot generate a number in the range \\[0, 0\\)");
+  EXPECT_DEATH_IF_SUPPORTED(
+      random.Generate(testing::internal::Random::kMaxRange + 1),
+      "Generation of a number in \\[0, 2147483649\\) was requested, "
+      "but this can only generate numbers in \\[0, 2147483648\\)");
+}
+
+TEST(RandomTest, GeneratesNumbersWithinRange) {
+  constexpr uint32_t kRange = 10000;
+  testing::internal::Random random(12345);
+  for (int i = 0; i < 10; i++) {
+    EXPECT_LT(random.Generate(kRange), kRange) << " for iteration " << i;
+  }
+
+  testing::internal::Random random2(testing::internal::Random::kMaxRange);
+  for (int i = 0; i < 10; i++) {
+    EXPECT_LT(random2.Generate(kRange), kRange) << " for iteration " << i;
+  }
+}
+
+TEST(RandomTest, RepeatsWhenReseeded) {
+  constexpr int kSeed = 123;
+  constexpr int kArraySize = 10;
+  constexpr uint32_t kRange = 10000;
+  uint32_t values[kArraySize];
+
+  testing::internal::Random random(kSeed);
+  for (int i = 0; i < kArraySize; i++) {
+    values[i] = random.Generate(kRange);
+  }
+
+  random.Reseed(kSeed);
+  for (int i = 0; i < kArraySize; i++) {
+    EXPECT_EQ(values[i], random.Generate(kRange)) << " for iteration " << i;
+  }
+}
+
+// Tests STL container utilities.
+
+// Tests CountIf().
+
+static bool IsPositive(int n) { return n > 0; }
+
+TEST(ContainerUtilityTest, CountIf) {
+  std::vector<int> v;
+  EXPECT_EQ(0, CountIf(v, IsPositive));  // Works for an empty container.
+
+  v.push_back(-1);
+  v.push_back(0);
+  EXPECT_EQ(0, CountIf(v, IsPositive));  // Works when no value satisfies.
+
+  v.push_back(2);
+  v.push_back(-10);
+  v.push_back(10);
+  EXPECT_EQ(2, CountIf(v, IsPositive));
+}
+
+// Tests ForEach().
+
+static int g_sum = 0;
+static void Accumulate(int n) { g_sum += n; }
+
+TEST(ContainerUtilityTest, ForEach) {
+  std::vector<int> v;
+  g_sum = 0;
+  ForEach(v, Accumulate);
+  EXPECT_EQ(0, g_sum);  // Works for an empty container;
+
+  g_sum = 0;
+  v.push_back(1);
+  ForEach(v, Accumulate);
+  EXPECT_EQ(1, g_sum);  // Works for a container with one element.
+
+  g_sum = 0;
+  v.push_back(20);
+  v.push_back(300);
+  ForEach(v, Accumulate);
+  EXPECT_EQ(321, g_sum);
+}
+
+// Tests GetElementOr().
+TEST(ContainerUtilityTest, GetElementOr) {
+  std::vector<char> a;
+  EXPECT_EQ('x', GetElementOr(a, 0, 'x'));
+
+  a.push_back('a');
+  a.push_back('b');
+  EXPECT_EQ('a', GetElementOr(a, 0, 'x'));
+  EXPECT_EQ('b', GetElementOr(a, 1, 'x'));
+  EXPECT_EQ('x', GetElementOr(a, -2, 'x'));
+  EXPECT_EQ('x', GetElementOr(a, 2, 'x'));
+}
+
+TEST(ContainerUtilityDeathTest, ShuffleRange) {
+  std::vector<int> a;
+  a.push_back(0);
+  a.push_back(1);
+  a.push_back(2);
+  testing::internal::Random random(1);
+
+  EXPECT_DEATH_IF_SUPPORTED(
+      ShuffleRange(&random, -1, 1, &a),
+      "Invalid shuffle range start -1: must be in range \\[0, 3\\]");
+  EXPECT_DEATH_IF_SUPPORTED(
+      ShuffleRange(&random, 4, 4, &a),
+      "Invalid shuffle range start 4: must be in range \\[0, 3\\]");
+  EXPECT_DEATH_IF_SUPPORTED(
+      ShuffleRange(&random, 3, 2, &a),
+      "Invalid shuffle range finish 2: must be in range \\[3, 3\\]");
+  EXPECT_DEATH_IF_SUPPORTED(
+      ShuffleRange(&random, 3, 4, &a),
+      "Invalid shuffle range finish 4: must be in range \\[3, 3\\]");
+}
+
+class VectorShuffleTest : public Test {
+ protected:
+  static const size_t kVectorSize = 20;
+
+  VectorShuffleTest() : random_(1) {
+    for (int i = 0; i < static_cast<int>(kVectorSize); i++) {
+      vector_.push_back(i);
+    }
+  }
+
+  static bool VectorIsCorrupt(const TestingVector& vector) {
+    if (kVectorSize != vector.size()) {
+      return true;
+    }
+
+    bool found_in_vector[kVectorSize] = { false };
+    for (size_t i = 0; i < vector.size(); i++) {
+      const int e = vector[i];
+      if (e < 0 || e >= static_cast<int>(kVectorSize) || found_in_vector[e]) {
+        return true;
+      }
+      found_in_vector[e] = true;
+    }
+
+    // Vector size is correct, elements' range is correct, no
+    // duplicate elements.  Therefore no corruption has occurred.
+    return false;
+  }
+
+  static bool VectorIsNotCorrupt(const TestingVector& vector) {
+    return !VectorIsCorrupt(vector);
+  }
+
+  static bool RangeIsShuffled(const TestingVector& vector, int begin, int end) {
+    for (int i = begin; i < end; i++) {
+      if (i != vector[static_cast<size_t>(i)]) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  static bool RangeIsUnshuffled(
+      const TestingVector& vector, int begin, int end) {
+    return !RangeIsShuffled(vector, begin, end);
+  }
+
+  static bool VectorIsShuffled(const TestingVector& vector) {
+    return RangeIsShuffled(vector, 0, static_cast<int>(vector.size()));
+  }
+
+  static bool VectorIsUnshuffled(const TestingVector& vector) {
+    return !VectorIsShuffled(vector);
+  }
+
+  testing::internal::Random random_;
+  TestingVector vector_;
+};  // class VectorShuffleTest
+
+const size_t VectorShuffleTest::kVectorSize;
+
+TEST_F(VectorShuffleTest, HandlesEmptyRange) {
+  // Tests an empty range at the beginning...
+  ShuffleRange(&random_, 0, 0, &vector_);
+  ASSERT_PRED1(VectorIsNotCorrupt, vector_);
+  ASSERT_PRED1(VectorIsUnshuffled, vector_);
+
+  // ...in the middle...
+  ShuffleRange(&random_, kVectorSize/2, kVectorSize/2, &vector_);
+  ASSERT_PRED1(VectorIsNotCorrupt, vector_);
+  ASSERT_PRED1(VectorIsUnshuffled, vector_);
+
+  // ...at the end...
+  ShuffleRange(&random_, kVectorSize - 1, kVectorSize - 1, &vector_);
+  ASSERT_PRED1(VectorIsNotCorrupt, vector_);
+  ASSERT_PRED1(VectorIsUnshuffled, vector_);
+
+  // ...and past the end.
+  ShuffleRange(&random_, kVectorSize, kVectorSize, &vector_);
+  ASSERT_PRED1(VectorIsNotCorrupt, vector_);
+  ASSERT_PRED1(VectorIsUnshuffled, vector_);
+}
+
+TEST_F(VectorShuffleTest, HandlesRangeOfSizeOne) {
+  // Tests a size one range at the beginning...
+  ShuffleRange(&random_, 0, 1, &vector_);
+  ASSERT_PRED1(VectorIsNotCorrupt, vector_);
+  ASSERT_PRED1(VectorIsUnshuffled, vector_);
+
+  // ...in the middle...
+  ShuffleRange(&random_, kVectorSize/2, kVectorSize/2 + 1, &vector_);
+  ASSERT_PRED1(VectorIsNotCorrupt, vector_);
+  ASSERT_PRED1(VectorIsUnshuffled, vector_);
+
+  // ...and at the end.
+  ShuffleRange(&random_, kVectorSize - 1, kVectorSize, &vector_);
+  ASSERT_PRED1(VectorIsNotCorrupt, vector_);
+  ASSERT_PRED1(VectorIsUnshuffled, vector_);
+}
+
+// Because we use our own random number generator and a fixed seed,
+// we can guarantee that the following "random" tests will succeed.
+
+TEST_F(VectorShuffleTest, ShufflesEntireVector) {
+  Shuffle(&random_, &vector_);
+  ASSERT_PRED1(VectorIsNotCorrupt, vector_);
+  EXPECT_FALSE(VectorIsUnshuffled(vector_)) << vector_;
+
+  // Tests the first and last elements in particular to ensure that
+  // there are no off-by-one problems in our shuffle algorithm.
+  EXPECT_NE(0, vector_[0]);
+  EXPECT_NE(static_cast<int>(kVectorSize - 1), vector_[kVectorSize - 1]);
+}
+
+TEST_F(VectorShuffleTest, ShufflesStartOfVector) {
+  const int kRangeSize = kVectorSize/2;
+
+  ShuffleRange(&random_, 0, kRangeSize, &vector_);
+
+  ASSERT_PRED1(VectorIsNotCorrupt, vector_);
+  EXPECT_PRED3(RangeIsShuffled, vector_, 0, kRangeSize);
+  EXPECT_PRED3(RangeIsUnshuffled, vector_, kRangeSize,
+               static_cast<int>(kVectorSize));
+}
+
+TEST_F(VectorShuffleTest, ShufflesEndOfVector) {
+  const int kRangeSize = kVectorSize / 2;
+  ShuffleRange(&random_, kRangeSize, kVectorSize, &vector_);
+
+  ASSERT_PRED1(VectorIsNotCorrupt, vector_);
+  EXPECT_PRED3(RangeIsUnshuffled, vector_, 0, kRangeSize);
+  EXPECT_PRED3(RangeIsShuffled, vector_, kRangeSize,
+               static_cast<int>(kVectorSize));
+}
+
+TEST_F(VectorShuffleTest, ShufflesMiddleOfVector) {
+  const int kRangeSize = static_cast<int>(kVectorSize) / 3;
+  ShuffleRange(&random_, kRangeSize, 2*kRangeSize, &vector_);
+
+  ASSERT_PRED1(VectorIsNotCorrupt, vector_);
+  EXPECT_PRED3(RangeIsUnshuffled, vector_, 0, kRangeSize);
+  EXPECT_PRED3(RangeIsShuffled, vector_, kRangeSize, 2*kRangeSize);
+  EXPECT_PRED3(RangeIsUnshuffled, vector_, 2 * kRangeSize,
+               static_cast<int>(kVectorSize));
+}
+
+TEST_F(VectorShuffleTest, ShufflesRepeatably) {
+  TestingVector vector2;
+  for (size_t i = 0; i < kVectorSize; i++) {
+    vector2.push_back(static_cast<int>(i));
+  }
+
+  random_.Reseed(1234);
+  Shuffle(&random_, &vector_);
+  random_.Reseed(1234);
+  Shuffle(&random_, &vector2);
+
+  ASSERT_PRED1(VectorIsNotCorrupt, vector_);
+  ASSERT_PRED1(VectorIsNotCorrupt, vector2);
+
+  for (size_t i = 0; i < kVectorSize; i++) {
+    EXPECT_EQ(vector_[i], vector2[i]) << " where i is " << i;
+  }
+}
+
+// Tests the size of the AssertHelper class.
+
+TEST(AssertHelperTest, AssertHelperIsSmall) {
+  // To avoid breaking clients that use lots of assertions in one
+  // function, we cannot grow the size of AssertHelper.
+  EXPECT_LE(sizeof(testing::internal::AssertHelper), sizeof(void*));
+}
+
+// Tests String::EndsWithCaseInsensitive().
+TEST(StringTest, EndsWithCaseInsensitive) {
+  EXPECT_TRUE(String::EndsWithCaseInsensitive("foobar", "BAR"));
+  EXPECT_TRUE(String::EndsWithCaseInsensitive("foobaR", "bar"));
+  EXPECT_TRUE(String::EndsWithCaseInsensitive("foobar", ""));
+  EXPECT_TRUE(String::EndsWithCaseInsensitive("", ""));
+
+  EXPECT_FALSE(String::EndsWithCaseInsensitive("Foobar", "foo"));
+  EXPECT_FALSE(String::EndsWithCaseInsensitive("foobar", "Foo"));
+  EXPECT_FALSE(String::EndsWithCaseInsensitive("", "foo"));
+}
+
+// C++Builder's preprocessor is buggy; it fails to expand macros that
+// appear in macro parameters after wide char literals.  Provide an alias
+// for NULL as a workaround.
+static const wchar_t* const kNull = nullptr;
+
+// Tests String::CaseInsensitiveWideCStringEquals
+TEST(StringTest, CaseInsensitiveWideCStringEquals) {
+  EXPECT_TRUE(String::CaseInsensitiveWideCStringEquals(nullptr, nullptr));
+  EXPECT_FALSE(String::CaseInsensitiveWideCStringEquals(kNull, L""));
+  EXPECT_FALSE(String::CaseInsensitiveWideCStringEquals(L"", kNull));
+  EXPECT_FALSE(String::CaseInsensitiveWideCStringEquals(kNull, L"foobar"));
+  EXPECT_FALSE(String::CaseInsensitiveWideCStringEquals(L"foobar", kNull));
+  EXPECT_TRUE(String::CaseInsensitiveWideCStringEquals(L"foobar", L"foobar"));
+  EXPECT_TRUE(String::CaseInsensitiveWideCStringEquals(L"foobar", L"FOOBAR"));
+  EXPECT_TRUE(String::CaseInsensitiveWideCStringEquals(L"FOOBAR", L"foobar"));
+}
+
+#if GTEST_OS_WINDOWS
+
+// Tests String::ShowWideCString().
+TEST(StringTest, ShowWideCString) {
+  EXPECT_STREQ("(null)",
+               String::ShowWideCString(NULL).c_str());
+  EXPECT_STREQ("", String::ShowWideCString(L"").c_str());
+  EXPECT_STREQ("foo", String::ShowWideCString(L"foo").c_str());
+}
+
+# if GTEST_OS_WINDOWS_MOBILE
+TEST(StringTest, AnsiAndUtf16Null) {
+  EXPECT_EQ(NULL, String::AnsiToUtf16(NULL));
+  EXPECT_EQ(NULL, String::Utf16ToAnsi(NULL));
+}
+
+TEST(StringTest, AnsiAndUtf16ConvertBasic) {
+  const char* ansi = String::Utf16ToAnsi(L"str");
+  EXPECT_STREQ("str", ansi);
+  delete [] ansi;
+  const WCHAR* utf16 = String::AnsiToUtf16("str");
+  EXPECT_EQ(0, wcsncmp(L"str", utf16, 3));
+  delete [] utf16;
+}
+
+TEST(StringTest, AnsiAndUtf16ConvertPathChars) {
+  const char* ansi = String::Utf16ToAnsi(L".:\\ \"*?");
+  EXPECT_STREQ(".:\\ \"*?", ansi);
+  delete [] ansi;
+  const WCHAR* utf16 = String::AnsiToUtf16(".:\\ \"*?");
+  EXPECT_EQ(0, wcsncmp(L".:\\ \"*?", utf16, 3));
+  delete [] utf16;
+}
+# endif  // GTEST_OS_WINDOWS_MOBILE
+
+#endif  // GTEST_OS_WINDOWS
+
+// Tests TestProperty construction.
+TEST(TestPropertyTest, StringValue) {
+  TestProperty property("key", "1");
+  EXPECT_STREQ("key", property.key());
+  EXPECT_STREQ("1", property.value());
+}
+
+// Tests TestProperty replacing a value.
+TEST(TestPropertyTest, ReplaceStringValue) {
+  TestProperty property("key", "1");
+  EXPECT_STREQ("1", property.value());
+  property.SetValue("2");
+  EXPECT_STREQ("2", property.value());
+}
+
+// AddFatalFailure() and AddNonfatalFailure() must be stand-alone
+// functions (i.e. their definitions cannot be inlined at the call
+// sites), or C++Builder won't compile the code.
+static void AddFatalFailure() {
+  FAIL() << "Expected fatal failure.";
+}
+
+static void AddNonfatalFailure() {
+  ADD_FAILURE() << "Expected non-fatal failure.";
+}
+
+class ScopedFakeTestPartResultReporterTest : public Test {
+ public:  // Must be public and not protected due to a bug in g++ 3.4.2.
+  enum FailureMode {
+    FATAL_FAILURE,
+    NONFATAL_FAILURE
+  };
+  static void AddFailure(FailureMode failure) {
+    if (failure == FATAL_FAILURE) {
+      AddFatalFailure();
+    } else {
+      AddNonfatalFailure();
+    }
+  }
+};
+
+// Tests that ScopedFakeTestPartResultReporter intercepts test
+// failures.
+TEST_F(ScopedFakeTestPartResultReporterTest, InterceptsTestFailures) {
+  TestPartResultArray results;
+  {
+    ScopedFakeTestPartResultReporter reporter(
+        ScopedFakeTestPartResultReporter::INTERCEPT_ONLY_CURRENT_THREAD,
+        &results);
+    AddFailure(NONFATAL_FAILURE);
+    AddFailure(FATAL_FAILURE);
+  }
+
+  EXPECT_EQ(2, results.size());
+  EXPECT_TRUE(results.GetTestPartResult(0).nonfatally_failed());
+  EXPECT_TRUE(results.GetTestPartResult(1).fatally_failed());
+}
+
+TEST_F(ScopedFakeTestPartResultReporterTest, DeprecatedConstructor) {
+  TestPartResultArray results;
+  {
+    // Tests, that the deprecated constructor still works.
+    ScopedFakeTestPartResultReporter reporter(&results);
+    AddFailure(NONFATAL_FAILURE);
+  }
+  EXPECT_EQ(1, results.size());
+}
+
+#if GTEST_IS_THREADSAFE
+
+class ScopedFakeTestPartResultReporterWithThreadsTest
+  : public ScopedFakeTestPartResultReporterTest {
+ protected:
+  static void AddFailureInOtherThread(FailureMode failure) {
+    ThreadWithParam<FailureMode> thread(&AddFailure, failure, nullptr);
+    thread.Join();
+  }
+};
+
+TEST_F(ScopedFakeTestPartResultReporterWithThreadsTest,
+       InterceptsTestFailuresInAllThreads) {
+  TestPartResultArray results;
+  {
+    ScopedFakeTestPartResultReporter reporter(
+        ScopedFakeTestPartResultReporter::INTERCEPT_ALL_THREADS, &results);
+    AddFailure(NONFATAL_FAILURE);
+    AddFailure(FATAL_FAILURE);
+    AddFailureInOtherThread(NONFATAL_FAILURE);
+    AddFailureInOtherThread(FATAL_FAILURE);
+  }
+
+  EXPECT_EQ(4, results.size());
+  EXPECT_TRUE(results.GetTestPartResult(0).nonfatally_failed());
+  EXPECT_TRUE(results.GetTestPartResult(1).fatally_failed());
+  EXPECT_TRUE(results.GetTestPartResult(2).nonfatally_failed());
+  EXPECT_TRUE(results.GetTestPartResult(3).fatally_failed());
+}
+
+#endif  // GTEST_IS_THREADSAFE
+
+// Tests EXPECT_FATAL_FAILURE{,ON_ALL_THREADS}.  Makes sure that they
+// work even if the failure is generated in a called function rather than
+// the current context.
+
+typedef ScopedFakeTestPartResultReporterTest ExpectFatalFailureTest;
+
+TEST_F(ExpectFatalFailureTest, CatchesFatalFaliure) {
+  EXPECT_FATAL_FAILURE(AddFatalFailure(), "Expected fatal failure.");
+}
+
+TEST_F(ExpectFatalFailureTest, AcceptsStdStringObject) {
+  EXPECT_FATAL_FAILURE(AddFatalFailure(),
+                       ::std::string("Expected fatal failure."));
+}
+
+TEST_F(ExpectFatalFailureTest, CatchesFatalFailureOnAllThreads) {
+  // We have another test below to verify that the macro catches fatal
+  // failures generated on another thread.
+  EXPECT_FATAL_FAILURE_ON_ALL_THREADS(AddFatalFailure(),
+                                      "Expected fatal failure.");
+}
+
+#ifdef __BORLANDC__
+// Silences warnings: "Condition is always true"
+# pragma option push -w-ccc
+#endif
+
+// Tests that EXPECT_FATAL_FAILURE() can be used in a non-void
+// function even when the statement in it contains ASSERT_*.
+
+int NonVoidFunction() {
+  EXPECT_FATAL_FAILURE(ASSERT_TRUE(false), "");
+  EXPECT_FATAL_FAILURE_ON_ALL_THREADS(FAIL(), "");
+  return 0;
+}
+
+TEST_F(ExpectFatalFailureTest, CanBeUsedInNonVoidFunction) {
+  NonVoidFunction();
+}
+
+// Tests that EXPECT_FATAL_FAILURE(statement, ...) doesn't abort the
+// current function even though 'statement' generates a fatal failure.
+
+void DoesNotAbortHelper(bool* aborted) {
+  EXPECT_FATAL_FAILURE(ASSERT_TRUE(false), "");
+  EXPECT_FATAL_FAILURE_ON_ALL_THREADS(FAIL(), "");
+
+  *aborted = false;
+}
+
+#ifdef __BORLANDC__
+// Restores warnings after previous "#pragma option push" suppressed them.
+# pragma option pop
+#endif
+
+TEST_F(ExpectFatalFailureTest, DoesNotAbort) {
+  bool aborted = true;
+  DoesNotAbortHelper(&aborted);
+  EXPECT_FALSE(aborted);
+}
+
+// Tests that the EXPECT_FATAL_FAILURE{,_ON_ALL_THREADS} accepts a
+// statement that contains a macro which expands to code containing an
+// unprotected comma.
+
+static int global_var = 0;
+#define GTEST_USE_UNPROTECTED_COMMA_ global_var++, global_var++
+
+TEST_F(ExpectFatalFailureTest, AcceptsMacroThatExpandsToUnprotectedComma) {
+#ifndef __BORLANDC__
+  // ICE's in C++Builder.
+  EXPECT_FATAL_FAILURE({
+    GTEST_USE_UNPROTECTED_COMMA_;
+    AddFatalFailure();
+  }, "");
+#endif
+
+  EXPECT_FATAL_FAILURE_ON_ALL_THREADS({
+    GTEST_USE_UNPROTECTED_COMMA_;
+    AddFatalFailure();
+  }, "");
+}
+
+// Tests EXPECT_NONFATAL_FAILURE{,ON_ALL_THREADS}.
+
+typedef ScopedFakeTestPartResultReporterTest ExpectNonfatalFailureTest;
+
+TEST_F(ExpectNonfatalFailureTest, CatchesNonfatalFailure) {
+  EXPECT_NONFATAL_FAILURE(AddNonfatalFailure(),
+                          "Expected non-fatal failure.");
+}
+
+TEST_F(ExpectNonfatalFailureTest, AcceptsStdStringObject) {
+  EXPECT_NONFATAL_FAILURE(AddNonfatalFailure(),
+                          ::std::string("Expected non-fatal failure."));
+}
+
+TEST_F(ExpectNonfatalFailureTest, CatchesNonfatalFailureOnAllThreads) {
+  // We have another test below to verify that the macro catches
+  // non-fatal failures generated on another thread.
+  EXPECT_NONFATAL_FAILURE_ON_ALL_THREADS(AddNonfatalFailure(),
+                                         "Expected non-fatal failure.");
+}
+
+// Tests that the EXPECT_NONFATAL_FAILURE{,_ON_ALL_THREADS} accepts a
+// statement that contains a macro which expands to code containing an
+// unprotected comma.
+TEST_F(ExpectNonfatalFailureTest, AcceptsMacroThatExpandsToUnprotectedComma) {
+  EXPECT_NONFATAL_FAILURE({
+    GTEST_USE_UNPROTECTED_COMMA_;
+    AddNonfatalFailure();
+  }, "");
+
+  EXPECT_NONFATAL_FAILURE_ON_ALL_THREADS({
+    GTEST_USE_UNPROTECTED_COMMA_;
+    AddNonfatalFailure();
+  }, "");
+}
+
+#if GTEST_IS_THREADSAFE
+
+typedef ScopedFakeTestPartResultReporterWithThreadsTest
+    ExpectFailureWithThreadsTest;
+
+TEST_F(ExpectFailureWithThreadsTest, ExpectFatalFailureOnAllThreads) {
+  EXPECT_FATAL_FAILURE_ON_ALL_THREADS(AddFailureInOtherThread(FATAL_FAILURE),
+                                      "Expected fatal failure.");
+}
+
+TEST_F(ExpectFailureWithThreadsTest, ExpectNonFatalFailureOnAllThreads) {
+  EXPECT_NONFATAL_FAILURE_ON_ALL_THREADS(
+      AddFailureInOtherThread(NONFATAL_FAILURE), "Expected non-fatal failure.");
+}
+
+#endif  // GTEST_IS_THREADSAFE
+
+// Tests the TestProperty class.
+
+TEST(TestPropertyTest, ConstructorWorks) {
+  const TestProperty property("key", "value");
+  EXPECT_STREQ("key", property.key());
+  EXPECT_STREQ("value", property.value());
+}
+
+TEST(TestPropertyTest, SetValue) {
+  TestProperty property("key", "value_1");
+  EXPECT_STREQ("key", property.key());
+  property.SetValue("value_2");
+  EXPECT_STREQ("key", property.key());
+  EXPECT_STREQ("value_2", property.value());
+}
+
+// Tests the TestResult class
+
+// The test fixture for testing TestResult.
+class TestResultTest : public Test {
+ protected:
+  typedef std::vector<TestPartResult> TPRVector;
+
+  // We make use of 2 TestPartResult objects,
+  TestPartResult * pr1, * pr2;
+
+  // ... and 3 TestResult objects.
+  TestResult * r0, * r1, * r2;
+
+  void SetUp() override {
+    // pr1 is for success.
+    pr1 = new TestPartResult(TestPartResult::kSuccess,
+                             "foo/bar.cc",
+                             10,
+                             "Success!");
+
+    // pr2 is for fatal failure.
+    pr2 = new TestPartResult(TestPartResult::kFatalFailure,
+                             "foo/bar.cc",
+                             -1,  // This line number means "unknown"
+                             "Failure!");
+
+    // Creates the TestResult objects.
+    r0 = new TestResult();
+    r1 = new TestResult();
+    r2 = new TestResult();
+
+    // In order to test TestResult, we need to modify its internal
+    // state, in particular the TestPartResult vector it holds.
+    // test_part_results() returns a const reference to this vector.
+    // We cast it to a non-const object s.t. it can be modified
+    TPRVector* results1 = const_cast<TPRVector*>(
+        &TestResultAccessor::test_part_results(*r1));
+    TPRVector* results2 = const_cast<TPRVector*>(
+        &TestResultAccessor::test_part_results(*r2));
+
+    // r0 is an empty TestResult.
+
+    // r1 contains a single SUCCESS TestPartResult.
+    results1->push_back(*pr1);
+
+    // r2 contains a SUCCESS, and a FAILURE.
+    results2->push_back(*pr1);
+    results2->push_back(*pr2);
+  }
+
+  void TearDown() override {
+    delete pr1;
+    delete pr2;
+
+    delete r0;
+    delete r1;
+    delete r2;
+  }
+
+  // Helper that compares two TestPartResults.
+  static void CompareTestPartResult(const TestPartResult& expected,
+                                    const TestPartResult& actual) {
+    EXPECT_EQ(expected.type(), actual.type());
+    EXPECT_STREQ(expected.file_name(), actual.file_name());
+    EXPECT_EQ(expected.line_number(), actual.line_number());
+    EXPECT_STREQ(expected.summary(), actual.summary());
+    EXPECT_STREQ(expected.message(), actual.message());
+    EXPECT_EQ(expected.passed(), actual.passed());
+    EXPECT_EQ(expected.failed(), actual.failed());
+    EXPECT_EQ(expected.nonfatally_failed(), actual.nonfatally_failed());
+    EXPECT_EQ(expected.fatally_failed(), actual.fatally_failed());
+  }
+};
+
+// Tests TestResult::total_part_count().
+TEST_F(TestResultTest, total_part_count) {
+  ASSERT_EQ(0, r0->total_part_count());
+  ASSERT_EQ(1, r1->total_part_count());
+  ASSERT_EQ(2, r2->total_part_count());
+}
+
+// Tests TestResult::Passed().
+TEST_F(TestResultTest, Passed) {
+  ASSERT_TRUE(r0->Passed());
+  ASSERT_TRUE(r1->Passed());
+  ASSERT_FALSE(r2->Passed());
+}
+
+// Tests TestResult::Failed().
+TEST_F(TestResultTest, Failed) {
+  ASSERT_FALSE(r0->Failed());
+  ASSERT_FALSE(r1->Failed());
+  ASSERT_TRUE(r2->Failed());
+}
+
+// Tests TestResult::GetTestPartResult().
+
+typedef TestResultTest TestResultDeathTest;
+
+TEST_F(TestResultDeathTest, GetTestPartResult) {
+  CompareTestPartResult(*pr1, r2->GetTestPartResult(0));
+  CompareTestPartResult(*pr2, r2->GetTestPartResult(1));
+  EXPECT_DEATH_IF_SUPPORTED(r2->GetTestPartResult(2), "");
+  EXPECT_DEATH_IF_SUPPORTED(r2->GetTestPartResult(-1), "");
+}
+
+// Tests TestResult has no properties when none are added.
+TEST(TestResultPropertyTest, NoPropertiesFoundWhenNoneAreAdded) {
+  TestResult test_result;
+  ASSERT_EQ(0, test_result.test_property_count());
+}
+
+// Tests TestResult has the expected property when added.
+TEST(TestResultPropertyTest, OnePropertyFoundWhenAdded) {
+  TestResult test_result;
+  TestProperty property("key_1", "1");
+  TestResultAccessor::RecordProperty(&test_result, "testcase", property);
+  ASSERT_EQ(1, test_result.test_property_count());
+  const TestProperty& actual_property = test_result.GetTestProperty(0);
+  EXPECT_STREQ("key_1", actual_property.key());
+  EXPECT_STREQ("1", actual_property.value());
+}
+
+// Tests TestResult has multiple properties when added.
+TEST(TestResultPropertyTest, MultiplePropertiesFoundWhenAdded) {
+  TestResult test_result;
+  TestProperty property_1("key_1", "1");
+  TestProperty property_2("key_2", "2");
+  TestResultAccessor::RecordProperty(&test_result, "testcase", property_1);
+  TestResultAccessor::RecordProperty(&test_result, "testcase", property_2);
+  ASSERT_EQ(2, test_result.test_property_count());
+  const TestProperty& actual_property_1 = test_result.GetTestProperty(0);
+  EXPECT_STREQ("key_1", actual_property_1.key());
+  EXPECT_STREQ("1", actual_property_1.value());
+
+  const TestProperty& actual_property_2 = test_result.GetTestProperty(1);
+  EXPECT_STREQ("key_2", actual_property_2.key());
+  EXPECT_STREQ("2", actual_property_2.value());
+}
+
+// Tests TestResult::RecordProperty() overrides values for duplicate keys.
+TEST(TestResultPropertyTest, OverridesValuesForDuplicateKeys) {
+  TestResult test_result;
+  TestProperty property_1_1("key_1", "1");
+  TestProperty property_2_1("key_2", "2");
+  TestProperty property_1_2("key_1", "12");
+  TestProperty property_2_2("key_2", "22");
+  TestResultAccessor::RecordProperty(&test_result, "testcase", property_1_1);
+  TestResultAccessor::RecordProperty(&test_result, "testcase", property_2_1);
+  TestResultAccessor::RecordProperty(&test_result, "testcase", property_1_2);
+  TestResultAccessor::RecordProperty(&test_result, "testcase", property_2_2);
+
+  ASSERT_EQ(2, test_result.test_property_count());
+  const TestProperty& actual_property_1 = test_result.GetTestProperty(0);
+  EXPECT_STREQ("key_1", actual_property_1.key());
+  EXPECT_STREQ("12", actual_property_1.value());
+
+  const TestProperty& actual_property_2 = test_result.GetTestProperty(1);
+  EXPECT_STREQ("key_2", actual_property_2.key());
+  EXPECT_STREQ("22", actual_property_2.value());
+}
+
+// Tests TestResult::GetTestProperty().
+TEST(TestResultPropertyTest, GetTestProperty) {
+  TestResult test_result;
+  TestProperty property_1("key_1", "1");
+  TestProperty property_2("key_2", "2");
+  TestProperty property_3("key_3", "3");
+  TestResultAccessor::RecordProperty(&test_result, "testcase", property_1);
+  TestResultAccessor::RecordProperty(&test_result, "testcase", property_2);
+  TestResultAccessor::RecordProperty(&test_result, "testcase", property_3);
+
+  const TestProperty& fetched_property_1 = test_result.GetTestProperty(0);
+  const TestProperty& fetched_property_2 = test_result.GetTestProperty(1);
+  const TestProperty& fetched_property_3 = test_result.GetTestProperty(2);
+
+  EXPECT_STREQ("key_1", fetched_property_1.key());
+  EXPECT_STREQ("1", fetched_property_1.value());
+
+  EXPECT_STREQ("key_2", fetched_property_2.key());
+  EXPECT_STREQ("2", fetched_property_2.value());
+
+  EXPECT_STREQ("key_3", fetched_property_3.key());
+  EXPECT_STREQ("3", fetched_property_3.value());
+
+  EXPECT_DEATH_IF_SUPPORTED(test_result.GetTestProperty(3), "");
+  EXPECT_DEATH_IF_SUPPORTED(test_result.GetTestProperty(-1), "");
+}
+
+// Tests the Test class.
+//
+// It's difficult to test every public method of this class (we are
+// already stretching the limit of Google Test by using it to test itself!).
+// Fortunately, we don't have to do that, as we are already testing
+// the functionalities of the Test class extensively by using Google Test
+// alone.
+//
+// Therefore, this section only contains one test.
+
+// Tests that GTestFlagSaver works on Windows and Mac.
+
+class GTestFlagSaverTest : public Test {
+ protected:
+  // Saves the Google Test flags such that we can restore them later, and
+  // then sets them to their default values.  This will be called
+  // before the first test in this test case is run.
+  static void SetUpTestSuite() {
+    saver_ = new GTestFlagSaver;
+
+    GTEST_FLAG(also_run_disabled_tests) = false;
+    GTEST_FLAG(break_on_failure) = false;
+    GTEST_FLAG(catch_exceptions) = false;
+    GTEST_FLAG(death_test_use_fork) = false;
+    GTEST_FLAG(color) = "auto";
+    GTEST_FLAG(fail_fast) = false;
+    GTEST_FLAG(filter) = "";
+    GTEST_FLAG(list_tests) = false;
+    GTEST_FLAG(output) = "";
+    GTEST_FLAG(brief) = false;
+    GTEST_FLAG(print_time) = true;
+    GTEST_FLAG(random_seed) = 0;
+    GTEST_FLAG(repeat) = 1;
+    GTEST_FLAG(shuffle) = false;
+    GTEST_FLAG(stack_trace_depth) = kMaxStackTraceDepth;
+    GTEST_FLAG(stream_result_to) = "";
+    GTEST_FLAG(throw_on_failure) = false;
+  }
+
+  // Restores the Google Test flags that the tests have modified.  This will
+  // be called after the last test in this test case is run.
+  static void TearDownTestSuite() {
+    delete saver_;
+    saver_ = nullptr;
+  }
+
+  // Verifies that the Google Test flags have their default values, and then
+  // modifies each of them.
+  void VerifyAndModifyFlags() {
+    EXPECT_FALSE(GTEST_FLAG(also_run_disabled_tests));
+    EXPECT_FALSE(GTEST_FLAG(break_on_failure));
+    EXPECT_FALSE(GTEST_FLAG(catch_exceptions));
+    EXPECT_STREQ("auto", GTEST_FLAG(color).c_str());
+    EXPECT_FALSE(GTEST_FLAG(death_test_use_fork));
+    EXPECT_FALSE(GTEST_FLAG(fail_fast));
+    EXPECT_STREQ("", GTEST_FLAG(filter).c_str());
+    EXPECT_FALSE(GTEST_FLAG(list_tests));
+    EXPECT_STREQ("", GTEST_FLAG(output).c_str());
+    EXPECT_FALSE(GTEST_FLAG(brief));
+    EXPECT_TRUE(GTEST_FLAG(print_time));
+    EXPECT_EQ(0, GTEST_FLAG(random_seed));
+    EXPECT_EQ(1, GTEST_FLAG(repeat));
+    EXPECT_FALSE(GTEST_FLAG(shuffle));
+    EXPECT_EQ(kMaxStackTraceDepth, GTEST_FLAG(stack_trace_depth));
+    EXPECT_STREQ("", GTEST_FLAG(stream_result_to).c_str());
+    EXPECT_FALSE(GTEST_FLAG(throw_on_failure));
+
+    GTEST_FLAG(also_run_disabled_tests) = true;
+    GTEST_FLAG(break_on_failure) = true;
+    GTEST_FLAG(catch_exceptions) = true;
+    GTEST_FLAG(color) = "no";
+    GTEST_FLAG(death_test_use_fork) = true;
+    GTEST_FLAG(fail_fast) = true;
+    GTEST_FLAG(filter) = "abc";
+    GTEST_FLAG(list_tests) = true;
+    GTEST_FLAG(output) = "xml:foo.xml";
+    GTEST_FLAG(brief) = true;
+    GTEST_FLAG(print_time) = false;
+    GTEST_FLAG(random_seed) = 1;
+    GTEST_FLAG(repeat) = 100;
+    GTEST_FLAG(shuffle) = true;
+    GTEST_FLAG(stack_trace_depth) = 1;
+    GTEST_FLAG(stream_result_to) = "localhost:1234";
+    GTEST_FLAG(throw_on_failure) = true;
+  }
+
+ private:
+  // For saving Google Test flags during this test case.
+  static GTestFlagSaver* saver_;
+};
+
+GTestFlagSaver* GTestFlagSaverTest::saver_ = nullptr;
+
+// Google Test doesn't guarantee the order of tests.  The following two
+// tests are designed to work regardless of their order.
+
+// Modifies the Google Test flags in the test body.
+TEST_F(GTestFlagSaverTest, ModifyGTestFlags) {
+  VerifyAndModifyFlags();
+}
+
+// Verifies that the Google Test flags in the body of the previous test were
+// restored to their original values.
+TEST_F(GTestFlagSaverTest, VerifyGTestFlags) {
+  VerifyAndModifyFlags();
+}
+
+// Sets an environment variable with the given name to the given
+// value.  If the value argument is "", unsets the environment
+// variable.  The caller must ensure that both arguments are not NULL.
+static void SetEnv(const char* name, const char* value) {
+#if GTEST_OS_WINDOWS_MOBILE
+  // Environment variables are not supported on Windows CE.
+  return;
+#elif defined(__BORLANDC__) || defined(__SunOS_5_8) || defined(__SunOS_5_9)
+  // C++Builder's putenv only stores a pointer to its parameter; we have to
+  // ensure that the string remains valid as long as it might be needed.
+  // We use an std::map to do so.
+  static std::map<std::string, std::string*> added_env;
+
+  // Because putenv stores a pointer to the string buffer, we can't delete the
+  // previous string (if present) until after it's replaced.
+  std::string *prev_env = NULL;
+  if (added_env.find(name) != added_env.end()) {
+    prev_env = added_env[name];
+  }
+  added_env[name] = new std::string(
+      (Message() << name << "=" << value).GetString());
+
+  // The standard signature of putenv accepts a 'char*' argument. Other
+  // implementations, like C++Builder's, accept a 'const char*'.
+  // We cast away the 'const' since that would work for both variants.
+  putenv(const_cast<char*>(added_env[name]->c_str()));
+  delete prev_env;
+#elif GTEST_OS_WINDOWS  // If we are on Windows proper.
+  _putenv((Message() << name << "=" << value).GetString().c_str());
+#else
+  if (*value == '\0') {
+    unsetenv(name);
+  } else {
+    setenv(name, value, 1);
+  }
+#endif  // GTEST_OS_WINDOWS_MOBILE
+}
+
+#if !GTEST_OS_WINDOWS_MOBILE
+// Environment variables are not supported on Windows CE.
+
+using testing::internal::Int32FromGTestEnv;
+
+// Tests Int32FromGTestEnv().
+
+// Tests that Int32FromGTestEnv() returns the default value when the
+// environment variable is not set.
+TEST(Int32FromGTestEnvTest, ReturnsDefaultWhenVariableIsNotSet) {
+  SetEnv(GTEST_FLAG_PREFIX_UPPER_ "TEMP", "");
+  EXPECT_EQ(10, Int32FromGTestEnv("temp", 10));
+}
+
+# if !defined(GTEST_GET_INT32_FROM_ENV_)
+
+// Tests that Int32FromGTestEnv() returns the default value when the
+// environment variable overflows as an Int32.
+TEST(Int32FromGTestEnvTest, ReturnsDefaultWhenValueOverflows) {
+  printf("(expecting 2 warnings)\n");
+
+  SetEnv(GTEST_FLAG_PREFIX_UPPER_ "TEMP", "12345678987654321");
+  EXPECT_EQ(20, Int32FromGTestEnv("temp", 20));
+
+  SetEnv(GTEST_FLAG_PREFIX_UPPER_ "TEMP", "-12345678987654321");
+  EXPECT_EQ(30, Int32FromGTestEnv("temp", 30));
+}
+
+// Tests that Int32FromGTestEnv() returns the default value when the
+// environment variable does not represent a valid decimal integer.
+TEST(Int32FromGTestEnvTest, ReturnsDefaultWhenValueIsInvalid) {
+  printf("(expecting 2 warnings)\n");
+
+  SetEnv(GTEST_FLAG_PREFIX_UPPER_ "TEMP", "A1");
+  EXPECT_EQ(40, Int32FromGTestEnv("temp", 40));
+
+  SetEnv(GTEST_FLAG_PREFIX_UPPER_ "TEMP", "12X");
+  EXPECT_EQ(50, Int32FromGTestEnv("temp", 50));
+}
+
+# endif  // !defined(GTEST_GET_INT32_FROM_ENV_)
+
+// Tests that Int32FromGTestEnv() parses and returns the value of the
+// environment variable when it represents a valid decimal integer in
+// the range of an Int32.
+TEST(Int32FromGTestEnvTest, ParsesAndReturnsValidValue) {
+  SetEnv(GTEST_FLAG_PREFIX_UPPER_ "TEMP", "123");
+  EXPECT_EQ(123, Int32FromGTestEnv("temp", 0));
+
+  SetEnv(GTEST_FLAG_PREFIX_UPPER_ "TEMP", "-321");
+  EXPECT_EQ(-321, Int32FromGTestEnv("temp", 0));
+}
+#endif  // !GTEST_OS_WINDOWS_MOBILE
+
+// Tests ParseInt32Flag().
+
+// Tests that ParseInt32Flag() returns false and doesn't change the
+// output value when the flag has wrong format
+TEST(ParseInt32FlagTest, ReturnsFalseForInvalidFlag) {
+  int32_t value = 123;
+  EXPECT_FALSE(ParseInt32Flag("--a=100", "b", &value));
+  EXPECT_EQ(123, value);
+
+  EXPECT_FALSE(ParseInt32Flag("a=100", "a", &value));
+  EXPECT_EQ(123, value);
+}
+
+// Tests that ParseInt32Flag() returns false and doesn't change the
+// output value when the flag overflows as an Int32.
+TEST(ParseInt32FlagTest, ReturnsDefaultWhenValueOverflows) {
+  printf("(expecting 2 warnings)\n");
+
+  int32_t value = 123;
+  EXPECT_FALSE(ParseInt32Flag("--abc=12345678987654321", "abc", &value));
+  EXPECT_EQ(123, value);
+
+  EXPECT_FALSE(ParseInt32Flag("--abc=-12345678987654321", "abc", &value));
+  EXPECT_EQ(123, value);
+}
+
+// Tests that ParseInt32Flag() returns false and doesn't change the
+// output value when the flag does not represent a valid decimal
+// integer.
+TEST(ParseInt32FlagTest, ReturnsDefaultWhenValueIsInvalid) {
+  printf("(expecting 2 warnings)\n");
+
+  int32_t value = 123;
+  EXPECT_FALSE(ParseInt32Flag("--abc=A1", "abc", &value));
+  EXPECT_EQ(123, value);
+
+  EXPECT_FALSE(ParseInt32Flag("--abc=12X", "abc", &value));
+  EXPECT_EQ(123, value);
+}
+
+// Tests that ParseInt32Flag() parses the value of the flag and
+// returns true when the flag represents a valid decimal integer in
+// the range of an Int32.
+TEST(ParseInt32FlagTest, ParsesAndReturnsValidValue) {
+  int32_t value = 123;
+  EXPECT_TRUE(ParseInt32Flag("--" GTEST_FLAG_PREFIX_ "abc=456", "abc", &value));
+  EXPECT_EQ(456, value);
+
+  EXPECT_TRUE(ParseInt32Flag("--" GTEST_FLAG_PREFIX_ "abc=-789",
+                             "abc", &value));
+  EXPECT_EQ(-789, value);
+}
+
+// Tests that Int32FromEnvOrDie() parses the value of the var or
+// returns the correct default.
+// Environment variables are not supported on Windows CE.
+#if !GTEST_OS_WINDOWS_MOBILE
+TEST(Int32FromEnvOrDieTest, ParsesAndReturnsValidValue) {
+  EXPECT_EQ(333, Int32FromEnvOrDie(GTEST_FLAG_PREFIX_UPPER_ "UnsetVar", 333));
+  SetEnv(GTEST_FLAG_PREFIX_UPPER_ "UnsetVar", "123");
+  EXPECT_EQ(123, Int32FromEnvOrDie(GTEST_FLAG_PREFIX_UPPER_ "UnsetVar", 333));
+  SetEnv(GTEST_FLAG_PREFIX_UPPER_ "UnsetVar", "-123");
+  EXPECT_EQ(-123, Int32FromEnvOrDie(GTEST_FLAG_PREFIX_UPPER_ "UnsetVar", 333));
+}
+#endif  // !GTEST_OS_WINDOWS_MOBILE
+
+// Tests that Int32FromEnvOrDie() aborts with an error message
+// if the variable is not an int32_t.
+TEST(Int32FromEnvOrDieDeathTest, AbortsOnFailure) {
+  SetEnv(GTEST_FLAG_PREFIX_UPPER_ "VAR", "xxx");
+  EXPECT_DEATH_IF_SUPPORTED(
+      Int32FromEnvOrDie(GTEST_FLAG_PREFIX_UPPER_ "VAR", 123),
+      ".*");
+}
+
+// Tests that Int32FromEnvOrDie() aborts with an error message
+// if the variable cannot be represented by an int32_t.
+TEST(Int32FromEnvOrDieDeathTest, AbortsOnInt32Overflow) {
+  SetEnv(GTEST_FLAG_PREFIX_UPPER_ "VAR", "1234567891234567891234");
+  EXPECT_DEATH_IF_SUPPORTED(
+      Int32FromEnvOrDie(GTEST_FLAG_PREFIX_UPPER_ "VAR", 123),
+      ".*");
+}
+
+// Tests that ShouldRunTestOnShard() selects all tests
+// where there is 1 shard.
+TEST(ShouldRunTestOnShardTest, IsPartitionWhenThereIsOneShard) {
+  EXPECT_TRUE(ShouldRunTestOnShard(1, 0, 0));
+  EXPECT_TRUE(ShouldRunTestOnShard(1, 0, 1));
+  EXPECT_TRUE(ShouldRunTestOnShard(1, 0, 2));
+  EXPECT_TRUE(ShouldRunTestOnShard(1, 0, 3));
+  EXPECT_TRUE(ShouldRunTestOnShard(1, 0, 4));
+}
+
+class ShouldShardTest : public testing::Test {
+ protected:
+  void SetUp() override {
+    index_var_ = GTEST_FLAG_PREFIX_UPPER_ "INDEX";
+    total_var_ = GTEST_FLAG_PREFIX_UPPER_ "TOTAL";
+  }
+
+  void TearDown() override {
+    SetEnv(index_var_, "");
+    SetEnv(total_var_, "");
+  }
+
+  const char* index_var_;
+  const char* total_var_;
+};
+
+// Tests that sharding is disabled if neither of the environment variables
+// are set.
+TEST_F(ShouldShardTest, ReturnsFalseWhenNeitherEnvVarIsSet) {
+  SetEnv(index_var_, "");
+  SetEnv(total_var_, "");
+
+  EXPECT_FALSE(ShouldShard(total_var_, index_var_, false));
+  EXPECT_FALSE(ShouldShard(total_var_, index_var_, true));
+}
+
+// Tests that sharding is not enabled if total_shards  == 1.
+TEST_F(ShouldShardTest, ReturnsFalseWhenTotalShardIsOne) {
+  SetEnv(index_var_, "0");
+  SetEnv(total_var_, "1");
+  EXPECT_FALSE(ShouldShard(total_var_, index_var_, false));
+  EXPECT_FALSE(ShouldShard(total_var_, index_var_, true));
+}
+
+// Tests that sharding is enabled if total_shards > 1 and
+// we are not in a death test subprocess.
+// Environment variables are not supported on Windows CE.
+#if !GTEST_OS_WINDOWS_MOBILE
+TEST_F(ShouldShardTest, WorksWhenShardEnvVarsAreValid) {
+  SetEnv(index_var_, "4");
+  SetEnv(total_var_, "22");
+  EXPECT_TRUE(ShouldShard(total_var_, index_var_, false));
+  EXPECT_FALSE(ShouldShard(total_var_, index_var_, true));
+
+  SetEnv(index_var_, "8");
+  SetEnv(total_var_, "9");
+  EXPECT_TRUE(ShouldShard(total_var_, index_var_, false));
+  EXPECT_FALSE(ShouldShard(total_var_, index_var_, true));
+
+  SetEnv(index_var_, "0");
+  SetEnv(total_var_, "9");
+  EXPECT_TRUE(ShouldShard(total_var_, index_var_, false));
+  EXPECT_FALSE(ShouldShard(total_var_, index_var_, true));
+}
+#endif  // !GTEST_OS_WINDOWS_MOBILE
+
+// Tests that we exit in error if the sharding values are not valid.
+
+typedef ShouldShardTest ShouldShardDeathTest;
+
+TEST_F(ShouldShardDeathTest, AbortsWhenShardingEnvVarsAreInvalid) {
+  SetEnv(index_var_, "4");
+  SetEnv(total_var_, "4");
+  EXPECT_DEATH_IF_SUPPORTED(ShouldShard(total_var_, index_var_, false), ".*");
+
+  SetEnv(index_var_, "4");
+  SetEnv(total_var_, "-2");
+  EXPECT_DEATH_IF_SUPPORTED(ShouldShard(total_var_, index_var_, false), ".*");
+
+  SetEnv(index_var_, "5");
+  SetEnv(total_var_, "");
+  EXPECT_DEATH_IF_SUPPORTED(ShouldShard(total_var_, index_var_, false), ".*");
+
+  SetEnv(index_var_, "");
+  SetEnv(total_var_, "5");
+  EXPECT_DEATH_IF_SUPPORTED(ShouldShard(total_var_, index_var_, false), ".*");
+}
+
+// Tests that ShouldRunTestOnShard is a partition when 5
+// shards are used.
+TEST(ShouldRunTestOnShardTest, IsPartitionWhenThereAreFiveShards) {
+  // Choose an arbitrary number of tests and shards.
+  const int num_tests = 17;
+  const int num_shards = 5;
+
+  // Check partitioning: each test should be on exactly 1 shard.
+  for (int test_id = 0; test_id < num_tests; test_id++) {
+    int prev_selected_shard_index = -1;
+    for (int shard_index = 0; shard_index < num_shards; shard_index++) {
+      if (ShouldRunTestOnShard(num_shards, shard_index, test_id)) {
+        if (prev_selected_shard_index < 0) {
+          prev_selected_shard_index = shard_index;
+        } else {
+          ADD_FAILURE() << "Shard " << prev_selected_shard_index << " and "
+            << shard_index << " are both selected to run test " << test_id;
+        }
+      }
+    }
+  }
+
+  // Check balance: This is not required by the sharding protocol, but is a
+  // desirable property for performance.
+  for (int shard_index = 0; shard_index < num_shards; shard_index++) {
+    int num_tests_on_shard = 0;
+    for (int test_id = 0; test_id < num_tests; test_id++) {
+      num_tests_on_shard +=
+        ShouldRunTestOnShard(num_shards, shard_index, test_id);
+    }
+    EXPECT_GE(num_tests_on_shard, num_tests / num_shards);
+  }
+}
+
+// For the same reason we are not explicitly testing everything in the
+// Test class, there are no separate tests for the following classes
+// (except for some trivial cases):
+//
+//   TestSuite, UnitTest, UnitTestResultPrinter.
+//
+// Similarly, there are no separate tests for the following macros:
+//
+//   TEST, TEST_F, RUN_ALL_TESTS
+
+TEST(UnitTestTest, CanGetOriginalWorkingDir) {
+  ASSERT_TRUE(UnitTest::GetInstance()->original_working_dir() != nullptr);
+  EXPECT_STRNE(UnitTest::GetInstance()->original_working_dir(), "");
+}
+
+TEST(UnitTestTest, ReturnsPlausibleTimestamp) {
+  EXPECT_LT(0, UnitTest::GetInstance()->start_timestamp());
+  EXPECT_LE(UnitTest::GetInstance()->start_timestamp(), GetTimeInMillis());
+}
+
+// When a property using a reserved key is supplied to this function, it
+// tests that a non-fatal failure is added, a fatal failure is not added,
+// and that the property is not recorded.
+void ExpectNonFatalFailureRecordingPropertyWithReservedKey(
+    const TestResult& test_result, const char* key) {
+  EXPECT_NONFATAL_FAILURE(Test::RecordProperty(key, "1"), "Reserved key");
+  ASSERT_EQ(0, test_result.test_property_count()) << "Property for key '" << key
+                                                  << "' recorded unexpectedly.";
+}
+
+void ExpectNonFatalFailureRecordingPropertyWithReservedKeyForCurrentTest(
+    const char* key) {
+  const TestInfo* test_info = UnitTest::GetInstance()->current_test_info();
+  ASSERT_TRUE(test_info != nullptr);
+  ExpectNonFatalFailureRecordingPropertyWithReservedKey(*test_info->result(),
+                                                        key);
+}
+
+void ExpectNonFatalFailureRecordingPropertyWithReservedKeyForCurrentTestSuite(
+    const char* key) {
+  const testing::TestSuite* test_suite =
+      UnitTest::GetInstance()->current_test_suite();
+  ASSERT_TRUE(test_suite != nullptr);
+  ExpectNonFatalFailureRecordingPropertyWithReservedKey(
+      test_suite->ad_hoc_test_result(), key);
+}
+
+void ExpectNonFatalFailureRecordingPropertyWithReservedKeyOutsideOfTestSuite(
+    const char* key) {
+  ExpectNonFatalFailureRecordingPropertyWithReservedKey(
+      UnitTest::GetInstance()->ad_hoc_test_result(), key);
+}
+
+// Tests that property recording functions in UnitTest outside of tests
+// functions correcly.  Creating a separate instance of UnitTest ensures it
+// is in a state similar to the UnitTest's singleton's between tests.
+class UnitTestRecordPropertyTest :
+    public testing::internal::UnitTestRecordPropertyTestHelper {
+ public:
+  static void SetUpTestSuite() {
+    ExpectNonFatalFailureRecordingPropertyWithReservedKeyForCurrentTestSuite(
+        "disabled");
+    ExpectNonFatalFailureRecordingPropertyWithReservedKeyForCurrentTestSuite(
+        "errors");
+    ExpectNonFatalFailureRecordingPropertyWithReservedKeyForCurrentTestSuite(
+        "failures");
+    ExpectNonFatalFailureRecordingPropertyWithReservedKeyForCurrentTestSuite(
+        "name");
+    ExpectNonFatalFailureRecordingPropertyWithReservedKeyForCurrentTestSuite(
+        "tests");
+    ExpectNonFatalFailureRecordingPropertyWithReservedKeyForCurrentTestSuite(
+        "time");
+
+    Test::RecordProperty("test_case_key_1", "1");
+
+    const testing::TestSuite* test_suite =
+        UnitTest::GetInstance()->current_test_suite();
+
+    ASSERT_TRUE(test_suite != nullptr);
+
+    ASSERT_EQ(1, test_suite->ad_hoc_test_result().test_property_count());
+    EXPECT_STREQ("test_case_key_1",
+                 test_suite->ad_hoc_test_result().GetTestProperty(0).key());
+    EXPECT_STREQ("1",
+                 test_suite->ad_hoc_test_result().GetTestProperty(0).value());
+  }
+};
+
+// Tests TestResult has the expected property when added.
+TEST_F(UnitTestRecordPropertyTest, OnePropertyFoundWhenAdded) {
+  UnitTestRecordProperty("key_1", "1");
+
+  ASSERT_EQ(1, unit_test_.ad_hoc_test_result().test_property_count());
+
+  EXPECT_STREQ("key_1",
+               unit_test_.ad_hoc_test_result().GetTestProperty(0).key());
+  EXPECT_STREQ("1",
+               unit_test_.ad_hoc_test_result().GetTestProperty(0).value());
+}
+
+// Tests TestResult has multiple properties when added.
+TEST_F(UnitTestRecordPropertyTest, MultiplePropertiesFoundWhenAdded) {
+  UnitTestRecordProperty("key_1", "1");
+  UnitTestRecordProperty("key_2", "2");
+
+  ASSERT_EQ(2, unit_test_.ad_hoc_test_result().test_property_count());
+
+  EXPECT_STREQ("key_1",
+               unit_test_.ad_hoc_test_result().GetTestProperty(0).key());
+  EXPECT_STREQ("1", unit_test_.ad_hoc_test_result().GetTestProperty(0).value());
+
+  EXPECT_STREQ("key_2",
+               unit_test_.ad_hoc_test_result().GetTestProperty(1).key());
+  EXPECT_STREQ("2", unit_test_.ad_hoc_test_result().GetTestProperty(1).value());
+}
+
+// Tests TestResult::RecordProperty() overrides values for duplicate keys.
+TEST_F(UnitTestRecordPropertyTest, OverridesValuesForDuplicateKeys) {
+  UnitTestRecordProperty("key_1", "1");
+  UnitTestRecordProperty("key_2", "2");
+  UnitTestRecordProperty("key_1", "12");
+  UnitTestRecordProperty("key_2", "22");
+
+  ASSERT_EQ(2, unit_test_.ad_hoc_test_result().test_property_count());
+
+  EXPECT_STREQ("key_1",
+               unit_test_.ad_hoc_test_result().GetTestProperty(0).key());
+  EXPECT_STREQ("12",
+               unit_test_.ad_hoc_test_result().GetTestProperty(0).value());
+
+  EXPECT_STREQ("key_2",
+               unit_test_.ad_hoc_test_result().GetTestProperty(1).key());
+  EXPECT_STREQ("22",
+               unit_test_.ad_hoc_test_result().GetTestProperty(1).value());
+}
+
+TEST_F(UnitTestRecordPropertyTest,
+       AddFailureInsideTestsWhenUsingTestSuiteReservedKeys) {
+  ExpectNonFatalFailureRecordingPropertyWithReservedKeyForCurrentTest(
+      "name");
+  ExpectNonFatalFailureRecordingPropertyWithReservedKeyForCurrentTest(
+      "value_param");
+  ExpectNonFatalFailureRecordingPropertyWithReservedKeyForCurrentTest(
+      "type_param");
+  ExpectNonFatalFailureRecordingPropertyWithReservedKeyForCurrentTest(
+      "status");
+  ExpectNonFatalFailureRecordingPropertyWithReservedKeyForCurrentTest(
+      "time");
+  ExpectNonFatalFailureRecordingPropertyWithReservedKeyForCurrentTest(
+      "classname");
+}
+
+TEST_F(UnitTestRecordPropertyTest,
+       AddRecordWithReservedKeysGeneratesCorrectPropertyList) {
+  EXPECT_NONFATAL_FAILURE(
+      Test::RecordProperty("name", "1"),
+      "'classname', 'name', 'status', 'time', 'type_param', 'value_param',"
+      " 'file', and 'line' are reserved");
+}
+
+class UnitTestRecordPropertyTestEnvironment : public Environment {
+ public:
+  void TearDown() override {
+    ExpectNonFatalFailureRecordingPropertyWithReservedKeyOutsideOfTestSuite(
+        "tests");
+    ExpectNonFatalFailureRecordingPropertyWithReservedKeyOutsideOfTestSuite(
+        "failures");
+    ExpectNonFatalFailureRecordingPropertyWithReservedKeyOutsideOfTestSuite(
+        "disabled");
+    ExpectNonFatalFailureRecordingPropertyWithReservedKeyOutsideOfTestSuite(
+        "errors");
+    ExpectNonFatalFailureRecordingPropertyWithReservedKeyOutsideOfTestSuite(
+        "name");
+    ExpectNonFatalFailureRecordingPropertyWithReservedKeyOutsideOfTestSuite(
+        "timestamp");
+    ExpectNonFatalFailureRecordingPropertyWithReservedKeyOutsideOfTestSuite(
+        "time");
+    ExpectNonFatalFailureRecordingPropertyWithReservedKeyOutsideOfTestSuite(
+        "random_seed");
+  }
+};
+
+// This will test property recording outside of any test or test case.
+static Environment* record_property_env GTEST_ATTRIBUTE_UNUSED_ =
+    AddGlobalTestEnvironment(new UnitTestRecordPropertyTestEnvironment);
+
+// This group of tests is for predicate assertions (ASSERT_PRED*, etc)
+// of various arities.  They do not attempt to be exhaustive.  Rather,
+// view them as smoke tests that can be easily reviewed and verified.
+// A more complete set of tests for predicate assertions can be found
+// in gtest_pred_impl_unittest.cc.
+
+// First, some predicates and predicate-formatters needed by the tests.
+
+// Returns true if and only if the argument is an even number.
+bool IsEven(int n) {
+  return (n % 2) == 0;
+}
+
+// A functor that returns true if and only if the argument is an even number.
+struct IsEvenFunctor {
+  bool operator()(int n) { return IsEven(n); }
+};
+
+// A predicate-formatter function that asserts the argument is an even
+// number.
+AssertionResult AssertIsEven(const char* expr, int n) {
+  if (IsEven(n)) {
+    return AssertionSuccess();
+  }
+
+  Message msg;
+  msg << expr << " evaluates to " << n << ", which is not even.";
+  return AssertionFailure(msg);
+}
+
+// A predicate function that returns AssertionResult for use in
+// EXPECT/ASSERT_TRUE/FALSE.
+AssertionResult ResultIsEven(int n) {
+  if (IsEven(n))
+    return AssertionSuccess() << n << " is even";
+  else
+    return AssertionFailure() << n << " is odd";
+}
+
+// A predicate function that returns AssertionResult but gives no
+// explanation why it succeeds. Needed for testing that
+// EXPECT/ASSERT_FALSE handles such functions correctly.
+AssertionResult ResultIsEvenNoExplanation(int n) {
+  if (IsEven(n))
+    return AssertionSuccess();
+  else
+    return AssertionFailure() << n << " is odd";
+}
+
+// A predicate-formatter functor that asserts the argument is an even
+// number.
+struct AssertIsEvenFunctor {
+  AssertionResult operator()(const char* expr, int n) {
+    return AssertIsEven(expr, n);
+  }
+};
+
+// Returns true if and only if the sum of the arguments is an even number.
+bool SumIsEven2(int n1, int n2) {
+  return IsEven(n1 + n2);
+}
+
+// A functor that returns true if and only if the sum of the arguments is an
+// even number.
+struct SumIsEven3Functor {
+  bool operator()(int n1, int n2, int n3) {
+    return IsEven(n1 + n2 + n3);
+  }
+};
+
+// A predicate-formatter function that asserts the sum of the
+// arguments is an even number.
+AssertionResult AssertSumIsEven4(
+    const char* e1, const char* e2, const char* e3, const char* e4,
+    int n1, int n2, int n3, int n4) {
+  const int sum = n1 + n2 + n3 + n4;
+  if (IsEven(sum)) {
+    return AssertionSuccess();
+  }
+
+  Message msg;
+  msg << e1 << " + " << e2 << " + " << e3 << " + " << e4
+      << " (" << n1 << " + " << n2 << " + " << n3 << " + " << n4
+      << ") evaluates to " << sum << ", which is not even.";
+  return AssertionFailure(msg);
+}
+
+// A predicate-formatter functor that asserts the sum of the arguments
+// is an even number.
+struct AssertSumIsEven5Functor {
+  AssertionResult operator()(
+      const char* e1, const char* e2, const char* e3, const char* e4,
+      const char* e5, int n1, int n2, int n3, int n4, int n5) {
+    const int sum = n1 + n2 + n3 + n4 + n5;
+    if (IsEven(sum)) {
+      return AssertionSuccess();
+    }
+
+    Message msg;
+    msg << e1 << " + " << e2 << " + " << e3 << " + " << e4 << " + " << e5
+        << " ("
+        << n1 << " + " << n2 << " + " << n3 << " + " << n4 << " + " << n5
+        << ") evaluates to " << sum << ", which is not even.";
+    return AssertionFailure(msg);
+  }
+};
+
+
+// Tests unary predicate assertions.
+
+// Tests unary predicate assertions that don't use a custom formatter.
+TEST(Pred1Test, WithoutFormat) {
+  // Success cases.
+  EXPECT_PRED1(IsEvenFunctor(), 2) << "This failure is UNEXPECTED!";
+  ASSERT_PRED1(IsEven, 4);
+
+  // Failure cases.
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED1(IsEven, 5) << "This failure is expected.";
+  }, "This failure is expected.");
+  EXPECT_FATAL_FAILURE(ASSERT_PRED1(IsEvenFunctor(), 5),
+                       "evaluates to false");
+}
+
+// Tests unary predicate assertions that use a custom formatter.
+TEST(Pred1Test, WithFormat) {
+  // Success cases.
+  EXPECT_PRED_FORMAT1(AssertIsEven, 2);
+  ASSERT_PRED_FORMAT1(AssertIsEvenFunctor(), 4)
+    << "This failure is UNEXPECTED!";
+
+  // Failure cases.
+  const int n = 5;
+  EXPECT_NONFATAL_FAILURE(EXPECT_PRED_FORMAT1(AssertIsEvenFunctor(), n),
+                          "n evaluates to 5, which is not even.");
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT1(AssertIsEven, 5) << "This failure is expected.";
+  }, "This failure is expected.");
+}
+
+// Tests that unary predicate assertions evaluates their arguments
+// exactly once.
+TEST(Pred1Test, SingleEvaluationOnFailure) {
+  // A success case.
+  static int n = 0;
+  EXPECT_PRED1(IsEven, n++);
+  EXPECT_EQ(1, n) << "The argument is not evaluated exactly once.";
+
+  // A failure case.
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT1(AssertIsEvenFunctor(), n++)
+        << "This failure is expected.";
+  }, "This failure is expected.");
+  EXPECT_EQ(2, n) << "The argument is not evaluated exactly once.";
+}
+
+
+// Tests predicate assertions whose arity is >= 2.
+
+// Tests predicate assertions that don't use a custom formatter.
+TEST(PredTest, WithoutFormat) {
+  // Success cases.
+  ASSERT_PRED2(SumIsEven2, 2, 4) << "This failure is UNEXPECTED!";
+  EXPECT_PRED3(SumIsEven3Functor(), 4, 6, 8);
+
+  // Failure cases.
+  const int n1 = 1;
+  const int n2 = 2;
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED2(SumIsEven2, n1, n2) << "This failure is expected.";
+  }, "This failure is expected.");
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED3(SumIsEven3Functor(), 1, 2, 4);
+  }, "evaluates to false");
+}
+
+// Tests predicate assertions that use a custom formatter.
+TEST(PredTest, WithFormat) {
+  // Success cases.
+  ASSERT_PRED_FORMAT4(AssertSumIsEven4, 4, 6, 8, 10) <<
+    "This failure is UNEXPECTED!";
+  EXPECT_PRED_FORMAT5(AssertSumIsEven5Functor(), 2, 4, 6, 8, 10);
+
+  // Failure cases.
+  const int n1 = 1;
+  const int n2 = 2;
+  const int n3 = 4;
+  const int n4 = 6;
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT4(AssertSumIsEven4, n1, n2, n3, n4);
+  }, "evaluates to 13, which is not even.");
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT5(AssertSumIsEven5Functor(), 1, 2, 4, 6, 8)
+        << "This failure is expected.";
+  }, "This failure is expected.");
+}
+
+// Tests that predicate assertions evaluates their arguments
+// exactly once.
+TEST(PredTest, SingleEvaluationOnFailure) {
+  // A success case.
+  int n1 = 0;
+  int n2 = 0;
+  EXPECT_PRED2(SumIsEven2, n1++, n2++);
+  EXPECT_EQ(1, n1) << "Argument 1 is not evaluated exactly once.";
+  EXPECT_EQ(1, n2) << "Argument 2 is not evaluated exactly once.";
+
+  // Another success case.
+  n1 = n2 = 0;
+  int n3 = 0;
+  int n4 = 0;
+  int n5 = 0;
+  ASSERT_PRED_FORMAT5(AssertSumIsEven5Functor(),
+                      n1++, n2++, n3++, n4++, n5++)
+                        << "This failure is UNEXPECTED!";
+  EXPECT_EQ(1, n1) << "Argument 1 is not evaluated exactly once.";
+  EXPECT_EQ(1, n2) << "Argument 2 is not evaluated exactly once.";
+  EXPECT_EQ(1, n3) << "Argument 3 is not evaluated exactly once.";
+  EXPECT_EQ(1, n4) << "Argument 4 is not evaluated exactly once.";
+  EXPECT_EQ(1, n5) << "Argument 5 is not evaluated exactly once.";
+
+  // A failure case.
+  n1 = n2 = n3 = 0;
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED3(SumIsEven3Functor(), ++n1, n2++, n3++)
+        << "This failure is expected.";
+  }, "This failure is expected.");
+  EXPECT_EQ(1, n1) << "Argument 1 is not evaluated exactly once.";
+  EXPECT_EQ(1, n2) << "Argument 2 is not evaluated exactly once.";
+  EXPECT_EQ(1, n3) << "Argument 3 is not evaluated exactly once.";
+
+  // Another failure case.
+  n1 = n2 = n3 = n4 = 0;
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT4(AssertSumIsEven4, ++n1, n2++, n3++, n4++);
+  }, "evaluates to 1, which is not even.");
+  EXPECT_EQ(1, n1) << "Argument 1 is not evaluated exactly once.";
+  EXPECT_EQ(1, n2) << "Argument 2 is not evaluated exactly once.";
+  EXPECT_EQ(1, n3) << "Argument 3 is not evaluated exactly once.";
+  EXPECT_EQ(1, n4) << "Argument 4 is not evaluated exactly once.";
+}
+
+// Test predicate assertions for sets
+TEST(PredTest, ExpectPredEvalFailure) {
+  std::set<int> set_a = {2, 1, 3, 4, 5};
+  std::set<int> set_b = {0, 4, 8};
+  const auto compare_sets = [] (std::set<int>, std::set<int>) { return false; };
+  EXPECT_NONFATAL_FAILURE(
+      EXPECT_PRED2(compare_sets, set_a, set_b),
+      "compare_sets(set_a, set_b) evaluates to false, where\nset_a evaluates "
+      "to { 1, 2, 3, 4, 5 }\nset_b evaluates to { 0, 4, 8 }");
+}
+
+// Some helper functions for testing using overloaded/template
+// functions with ASSERT_PREDn and EXPECT_PREDn.
+
+bool IsPositive(double x) {
+  return x > 0;
+}
+
+template <typename T>
+bool IsNegative(T x) {
+  return x < 0;
+}
+
+template <typename T1, typename T2>
+bool GreaterThan(T1 x1, T2 x2) {
+  return x1 > x2;
+}
+
+// Tests that overloaded functions can be used in *_PRED* as long as
+// their types are explicitly specified.
+TEST(PredicateAssertionTest, AcceptsOverloadedFunction) {
+  // C++Builder requires C-style casts rather than static_cast.
+  EXPECT_PRED1((bool (*)(int))(IsPositive), 5);  // NOLINT
+  ASSERT_PRED1((bool (*)(double))(IsPositive), 6.0);  // NOLINT
+}
+
+// Tests that template functions can be used in *_PRED* as long as
+// their types are explicitly specified.
+TEST(PredicateAssertionTest, AcceptsTemplateFunction) {
+  EXPECT_PRED1(IsNegative<int>, -5);
+  // Makes sure that we can handle templates with more than one
+  // parameter.
+  ASSERT_PRED2((GreaterThan<int, int>), 5, 0);
+}
+
+
+// Some helper functions for testing using overloaded/template
+// functions with ASSERT_PRED_FORMATn and EXPECT_PRED_FORMATn.
+
+AssertionResult IsPositiveFormat(const char* /* expr */, int n) {
+  return n > 0 ? AssertionSuccess() :
+      AssertionFailure(Message() << "Failure");
+}
+
+AssertionResult IsPositiveFormat(const char* /* expr */, double x) {
+  return x > 0 ? AssertionSuccess() :
+      AssertionFailure(Message() << "Failure");
+}
+
+template <typename T>
+AssertionResult IsNegativeFormat(const char* /* expr */, T x) {
+  return x < 0 ? AssertionSuccess() :
+      AssertionFailure(Message() << "Failure");
+}
+
+template <typename T1, typename T2>
+AssertionResult EqualsFormat(const char* /* expr1 */, const char* /* expr2 */,
+                             const T1& x1, const T2& x2) {
+  return x1 == x2 ? AssertionSuccess() :
+      AssertionFailure(Message() << "Failure");
+}
+
+// Tests that overloaded functions can be used in *_PRED_FORMAT*
+// without explicitly specifying their types.
+TEST(PredicateFormatAssertionTest, AcceptsOverloadedFunction) {
+  EXPECT_PRED_FORMAT1(IsPositiveFormat, 5);
+  ASSERT_PRED_FORMAT1(IsPositiveFormat, 6.0);
+}
+
+// Tests that template functions can be used in *_PRED_FORMAT* without
+// explicitly specifying their types.
+TEST(PredicateFormatAssertionTest, AcceptsTemplateFunction) {
+  EXPECT_PRED_FORMAT1(IsNegativeFormat, -5);
+  ASSERT_PRED_FORMAT2(EqualsFormat, 3, 3);
+}
+
+
+// Tests string assertions.
+
+// Tests ASSERT_STREQ with non-NULL arguments.
+TEST(StringAssertionTest, ASSERT_STREQ) {
+  const char * const p1 = "good";
+  ASSERT_STREQ(p1, p1);
+
+  // Let p2 have the same content as p1, but be at a different address.
+  const char p2[] = "good";
+  ASSERT_STREQ(p1, p2);
+
+  EXPECT_FATAL_FAILURE(ASSERT_STREQ("bad", "good"),
+                       "  \"bad\"\n  \"good\"");
+}
+
+// Tests ASSERT_STREQ with NULL arguments.
+TEST(StringAssertionTest, ASSERT_STREQ_Null) {
+  ASSERT_STREQ(static_cast<const char*>(nullptr), nullptr);
+  EXPECT_FATAL_FAILURE(ASSERT_STREQ(nullptr, "non-null"), "non-null");
+}
+
+// Tests ASSERT_STREQ with NULL arguments.
+TEST(StringAssertionTest, ASSERT_STREQ_Null2) {
+  EXPECT_FATAL_FAILURE(ASSERT_STREQ("non-null", nullptr), "non-null");
+}
+
+// Tests ASSERT_STRNE.
+TEST(StringAssertionTest, ASSERT_STRNE) {
+  ASSERT_STRNE("hi", "Hi");
+  ASSERT_STRNE("Hi", nullptr);
+  ASSERT_STRNE(nullptr, "Hi");
+  ASSERT_STRNE("", nullptr);
+  ASSERT_STRNE(nullptr, "");
+  ASSERT_STRNE("", "Hi");
+  ASSERT_STRNE("Hi", "");
+  EXPECT_FATAL_FAILURE(ASSERT_STRNE("Hi", "Hi"),
+                       "\"Hi\" vs \"Hi\"");
+}
+
+// Tests ASSERT_STRCASEEQ.
+TEST(StringAssertionTest, ASSERT_STRCASEEQ) {
+  ASSERT_STRCASEEQ("hi", "Hi");
+  ASSERT_STRCASEEQ(static_cast<const char*>(nullptr), nullptr);
+
+  ASSERT_STRCASEEQ("", "");
+  EXPECT_FATAL_FAILURE(ASSERT_STRCASEEQ("Hi", "hi2"),
+                       "Ignoring case");
+}
+
+// Tests ASSERT_STRCASENE.
+TEST(StringAssertionTest, ASSERT_STRCASENE) {
+  ASSERT_STRCASENE("hi1", "Hi2");
+  ASSERT_STRCASENE("Hi", nullptr);
+  ASSERT_STRCASENE(nullptr, "Hi");
+  ASSERT_STRCASENE("", nullptr);
+  ASSERT_STRCASENE(nullptr, "");
+  ASSERT_STRCASENE("", "Hi");
+  ASSERT_STRCASENE("Hi", "");
+  EXPECT_FATAL_FAILURE(ASSERT_STRCASENE("Hi", "hi"),
+                       "(ignoring case)");
+}
+
+// Tests *_STREQ on wide strings.
+TEST(StringAssertionTest, STREQ_Wide) {
+  // NULL strings.
+  ASSERT_STREQ(static_cast<const wchar_t*>(nullptr), nullptr);
+
+  // Empty strings.
+  ASSERT_STREQ(L"", L"");
+
+  // Non-null vs NULL.
+  EXPECT_NONFATAL_FAILURE(EXPECT_STREQ(L"non-null", nullptr), "non-null");
+
+  // Equal strings.
+  EXPECT_STREQ(L"Hi", L"Hi");
+
+  // Unequal strings.
+  EXPECT_NONFATAL_FAILURE(EXPECT_STREQ(L"abc", L"Abc"),
+                          "Abc");
+
+  // Strings containing wide characters.
+  EXPECT_NONFATAL_FAILURE(EXPECT_STREQ(L"abc\x8119", L"abc\x8120"),
+                          "abc");
+
+  // The streaming variation.
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_STREQ(L"abc\x8119", L"abc\x8121") << "Expected failure";
+  }, "Expected failure");
+}
+
+// Tests *_STRNE on wide strings.
+TEST(StringAssertionTest, STRNE_Wide) {
+  // NULL strings.
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        EXPECT_STRNE(static_cast<const wchar_t*>(nullptr), nullptr);
+      },
+      "");
+
+  // Empty strings.
+  EXPECT_NONFATAL_FAILURE(EXPECT_STRNE(L"", L""),
+                          "L\"\"");
+
+  // Non-null vs NULL.
+  ASSERT_STRNE(L"non-null", nullptr);
+
+  // Equal strings.
+  EXPECT_NONFATAL_FAILURE(EXPECT_STRNE(L"Hi", L"Hi"),
+                          "L\"Hi\"");
+
+  // Unequal strings.
+  EXPECT_STRNE(L"abc", L"Abc");
+
+  // Strings containing wide characters.
+  EXPECT_NONFATAL_FAILURE(EXPECT_STRNE(L"abc\x8119", L"abc\x8119"),
+                          "abc");
+
+  // The streaming variation.
+  ASSERT_STRNE(L"abc\x8119", L"abc\x8120") << "This shouldn't happen";
+}
+
+// Tests for ::testing::IsSubstring().
+
+// Tests that IsSubstring() returns the correct result when the input
+// argument type is const char*.
+TEST(IsSubstringTest, ReturnsCorrectResultForCString) {
+  EXPECT_FALSE(IsSubstring("", "", nullptr, "a"));
+  EXPECT_FALSE(IsSubstring("", "", "b", nullptr));
+  EXPECT_FALSE(IsSubstring("", "", "needle", "haystack"));
+
+  EXPECT_TRUE(IsSubstring("", "", static_cast<const char*>(nullptr), nullptr));
+  EXPECT_TRUE(IsSubstring("", "", "needle", "two needles"));
+}
+
+// Tests that IsSubstring() returns the correct result when the input
+// argument type is const wchar_t*.
+TEST(IsSubstringTest, ReturnsCorrectResultForWideCString) {
+  EXPECT_FALSE(IsSubstring("", "", kNull, L"a"));
+  EXPECT_FALSE(IsSubstring("", "", L"b", kNull));
+  EXPECT_FALSE(IsSubstring("", "", L"needle", L"haystack"));
+
+  EXPECT_TRUE(
+      IsSubstring("", "", static_cast<const wchar_t*>(nullptr), nullptr));
+  EXPECT_TRUE(IsSubstring("", "", L"needle", L"two needles"));
+}
+
+// Tests that IsSubstring() generates the correct message when the input
+// argument type is const char*.
+TEST(IsSubstringTest, GeneratesCorrectMessageForCString) {
+  EXPECT_STREQ("Value of: needle_expr\n"
+               "  Actual: \"needle\"\n"
+               "Expected: a substring of haystack_expr\n"
+               "Which is: \"haystack\"",
+               IsSubstring("needle_expr", "haystack_expr",
+                           "needle", "haystack").failure_message());
+}
+
+// Tests that IsSubstring returns the correct result when the input
+// argument type is ::std::string.
+TEST(IsSubstringTest, ReturnsCorrectResultsForStdString) {
+  EXPECT_TRUE(IsSubstring("", "", std::string("hello"), "ahellob"));
+  EXPECT_FALSE(IsSubstring("", "", "hello", std::string("world")));
+}
+
+#if GTEST_HAS_STD_WSTRING
+// Tests that IsSubstring returns the correct result when the input
+// argument type is ::std::wstring.
+TEST(IsSubstringTest, ReturnsCorrectResultForStdWstring) {
+  EXPECT_TRUE(IsSubstring("", "", ::std::wstring(L"needle"), L"two needles"));
+  EXPECT_FALSE(IsSubstring("", "", L"needle", ::std::wstring(L"haystack")));
+}
+
+// Tests that IsSubstring() generates the correct message when the input
+// argument type is ::std::wstring.
+TEST(IsSubstringTest, GeneratesCorrectMessageForWstring) {
+  EXPECT_STREQ("Value of: needle_expr\n"
+               "  Actual: L\"needle\"\n"
+               "Expected: a substring of haystack_expr\n"
+               "Which is: L\"haystack\"",
+               IsSubstring(
+                   "needle_expr", "haystack_expr",
+                   ::std::wstring(L"needle"), L"haystack").failure_message());
+}
+
+#endif  // GTEST_HAS_STD_WSTRING
+
+// Tests for ::testing::IsNotSubstring().
+
+// Tests that IsNotSubstring() returns the correct result when the input
+// argument type is const char*.
+TEST(IsNotSubstringTest, ReturnsCorrectResultForCString) {
+  EXPECT_TRUE(IsNotSubstring("", "", "needle", "haystack"));
+  EXPECT_FALSE(IsNotSubstring("", "", "needle", "two needles"));
+}
+
+// Tests that IsNotSubstring() returns the correct result when the input
+// argument type is const wchar_t*.
+TEST(IsNotSubstringTest, ReturnsCorrectResultForWideCString) {
+  EXPECT_TRUE(IsNotSubstring("", "", L"needle", L"haystack"));
+  EXPECT_FALSE(IsNotSubstring("", "", L"needle", L"two needles"));
+}
+
+// Tests that IsNotSubstring() generates the correct message when the input
+// argument type is const wchar_t*.
+TEST(IsNotSubstringTest, GeneratesCorrectMessageForWideCString) {
+  EXPECT_STREQ("Value of: needle_expr\n"
+               "  Actual: L\"needle\"\n"
+               "Expected: not a substring of haystack_expr\n"
+               "Which is: L\"two needles\"",
+               IsNotSubstring(
+                   "needle_expr", "haystack_expr",
+                   L"needle", L"two needles").failure_message());
+}
+
+// Tests that IsNotSubstring returns the correct result when the input
+// argument type is ::std::string.
+TEST(IsNotSubstringTest, ReturnsCorrectResultsForStdString) {
+  EXPECT_FALSE(IsNotSubstring("", "", std::string("hello"), "ahellob"));
+  EXPECT_TRUE(IsNotSubstring("", "", "hello", std::string("world")));
+}
+
+// Tests that IsNotSubstring() generates the correct message when the input
+// argument type is ::std::string.
+TEST(IsNotSubstringTest, GeneratesCorrectMessageForStdString) {
+  EXPECT_STREQ("Value of: needle_expr\n"
+               "  Actual: \"needle\"\n"
+               "Expected: not a substring of haystack_expr\n"
+               "Which is: \"two needles\"",
+               IsNotSubstring(
+                   "needle_expr", "haystack_expr",
+                   ::std::string("needle"), "two needles").failure_message());
+}
+
+#if GTEST_HAS_STD_WSTRING
+
+// Tests that IsNotSubstring returns the correct result when the input
+// argument type is ::std::wstring.
+TEST(IsNotSubstringTest, ReturnsCorrectResultForStdWstring) {
+  EXPECT_FALSE(
+      IsNotSubstring("", "", ::std::wstring(L"needle"), L"two needles"));
+  EXPECT_TRUE(IsNotSubstring("", "", L"needle", ::std::wstring(L"haystack")));
+}
+
+#endif  // GTEST_HAS_STD_WSTRING
+
+// Tests floating-point assertions.
+
+template <typename RawType>
+class FloatingPointTest : public Test {
+ protected:
+  // Pre-calculated numbers to be used by the tests.
+  struct TestValues {
+    RawType close_to_positive_zero;
+    RawType close_to_negative_zero;
+    RawType further_from_negative_zero;
+
+    RawType close_to_one;
+    RawType further_from_one;
+
+    RawType infinity;
+    RawType close_to_infinity;
+    RawType further_from_infinity;
+
+    RawType nan1;
+    RawType nan2;
+  };
+
+  typedef typename testing::internal::FloatingPoint<RawType> Floating;
+  typedef typename Floating::Bits Bits;
+
+  void SetUp() override {
+    const uint32_t max_ulps = Floating::kMaxUlps;
+
+    // The bits that represent 0.0.
+    const Bits zero_bits = Floating(0).bits();
+
+    // Makes some numbers close to 0.0.
+    values_.close_to_positive_zero = Floating::ReinterpretBits(
+        zero_bits + max_ulps/2);
+    values_.close_to_negative_zero = -Floating::ReinterpretBits(
+        zero_bits + max_ulps - max_ulps/2);
+    values_.further_from_negative_zero = -Floating::ReinterpretBits(
+        zero_bits + max_ulps + 1 - max_ulps/2);
+
+    // The bits that represent 1.0.
+    const Bits one_bits = Floating(1).bits();
+
+    // Makes some numbers close to 1.0.
+    values_.close_to_one = Floating::ReinterpretBits(one_bits + max_ulps);
+    values_.further_from_one = Floating::ReinterpretBits(
+        one_bits + max_ulps + 1);
+
+    // +infinity.
+    values_.infinity = Floating::Infinity();
+
+    // The bits that represent +infinity.
+    const Bits infinity_bits = Floating(values_.infinity).bits();
+
+    // Makes some numbers close to infinity.
+    values_.close_to_infinity = Floating::ReinterpretBits(
+        infinity_bits - max_ulps);
+    values_.further_from_infinity = Floating::ReinterpretBits(
+        infinity_bits - max_ulps - 1);
+
+    // Makes some NAN's.  Sets the most significant bit of the fraction so that
+    // our NaN's are quiet; trying to process a signaling NaN would raise an
+    // exception if our environment enables floating point exceptions.
+    values_.nan1 = Floating::ReinterpretBits(Floating::kExponentBitMask
+        | (static_cast<Bits>(1) << (Floating::kFractionBitCount - 1)) | 1);
+    values_.nan2 = Floating::ReinterpretBits(Floating::kExponentBitMask
+        | (static_cast<Bits>(1) << (Floating::kFractionBitCount - 1)) | 200);
+  }
+
+  void TestSize() {
+    EXPECT_EQ(sizeof(RawType), sizeof(Bits));
+  }
+
+  static TestValues values_;
+};
+
+template <typename RawType>
+typename FloatingPointTest<RawType>::TestValues
+    FloatingPointTest<RawType>::values_;
+
+// Instantiates FloatingPointTest for testing *_FLOAT_EQ.
+typedef FloatingPointTest<float> FloatTest;
+
+// Tests that the size of Float::Bits matches the size of float.
+TEST_F(FloatTest, Size) {
+  TestSize();
+}
+
+// Tests comparing with +0 and -0.
+TEST_F(FloatTest, Zeros) {
+  EXPECT_FLOAT_EQ(0.0, -0.0);
+  EXPECT_NONFATAL_FAILURE(EXPECT_FLOAT_EQ(-0.0, 1.0),
+                          "1.0");
+  EXPECT_FATAL_FAILURE(ASSERT_FLOAT_EQ(0.0, 1.5),
+                       "1.5");
+}
+
+// Tests comparing numbers close to 0.
+//
+// This ensures that *_FLOAT_EQ handles the sign correctly and no
+// overflow occurs when comparing numbers whose absolute value is very
+// small.
+TEST_F(FloatTest, AlmostZeros) {
+  // In C++Builder, names within local classes (such as used by
+  // EXPECT_FATAL_FAILURE) cannot be resolved against static members of the
+  // scoping class.  Use a static local alias as a workaround.
+  // We use the assignment syntax since some compilers, like Sun Studio,
+  // don't allow initializing references using construction syntax
+  // (parentheses).
+  static const FloatTest::TestValues& v = this->values_;
+
+  EXPECT_FLOAT_EQ(0.0, v.close_to_positive_zero);
+  EXPECT_FLOAT_EQ(-0.0, v.close_to_negative_zero);
+  EXPECT_FLOAT_EQ(v.close_to_positive_zero, v.close_to_negative_zero);
+
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_FLOAT_EQ(v.close_to_positive_zero,
+                    v.further_from_negative_zero);
+  }, "v.further_from_negative_zero");
+}
+
+// Tests comparing numbers close to each other.
+TEST_F(FloatTest, SmallDiff) {
+  EXPECT_FLOAT_EQ(1.0, values_.close_to_one);
+  EXPECT_NONFATAL_FAILURE(EXPECT_FLOAT_EQ(1.0, values_.further_from_one),
+                          "values_.further_from_one");
+}
+
+// Tests comparing numbers far apart.
+TEST_F(FloatTest, LargeDiff) {
+  EXPECT_NONFATAL_FAILURE(EXPECT_FLOAT_EQ(2.5, 3.0),
+                          "3.0");
+}
+
+// Tests comparing with infinity.
+//
+// This ensures that no overflow occurs when comparing numbers whose
+// absolute value is very large.
+TEST_F(FloatTest, Infinity) {
+  EXPECT_FLOAT_EQ(values_.infinity, values_.close_to_infinity);
+  EXPECT_FLOAT_EQ(-values_.infinity, -values_.close_to_infinity);
+  EXPECT_NONFATAL_FAILURE(EXPECT_FLOAT_EQ(values_.infinity, -values_.infinity),
+                          "-values_.infinity");
+
+  // This is interesting as the representations of infinity and nan1
+  // are only 1 DLP apart.
+  EXPECT_NONFATAL_FAILURE(EXPECT_FLOAT_EQ(values_.infinity, values_.nan1),
+                          "values_.nan1");
+}
+
+// Tests that comparing with NAN always returns false.
+TEST_F(FloatTest, NaN) {
+  // In C++Builder, names within local classes (such as used by
+  // EXPECT_FATAL_FAILURE) cannot be resolved against static members of the
+  // scoping class.  Use a static local alias as a workaround.
+  // We use the assignment syntax since some compilers, like Sun Studio,
+  // don't allow initializing references using construction syntax
+  // (parentheses).
+  static const FloatTest::TestValues& v = this->values_;
+
+  EXPECT_NONFATAL_FAILURE(EXPECT_FLOAT_EQ(v.nan1, v.nan1),
+                          "v.nan1");
+  EXPECT_NONFATAL_FAILURE(EXPECT_FLOAT_EQ(v.nan1, v.nan2),
+                          "v.nan2");
+  EXPECT_NONFATAL_FAILURE(EXPECT_FLOAT_EQ(1.0, v.nan1),
+                          "v.nan1");
+
+  EXPECT_FATAL_FAILURE(ASSERT_FLOAT_EQ(v.nan1, v.infinity),
+                       "v.infinity");
+}
+
+// Tests that *_FLOAT_EQ are reflexive.
+TEST_F(FloatTest, Reflexive) {
+  EXPECT_FLOAT_EQ(0.0, 0.0);
+  EXPECT_FLOAT_EQ(1.0, 1.0);
+  ASSERT_FLOAT_EQ(values_.infinity, values_.infinity);
+}
+
+// Tests that *_FLOAT_EQ are commutative.
+TEST_F(FloatTest, Commutative) {
+  // We already tested EXPECT_FLOAT_EQ(1.0, values_.close_to_one).
+  EXPECT_FLOAT_EQ(values_.close_to_one, 1.0);
+
+  // We already tested EXPECT_FLOAT_EQ(1.0, values_.further_from_one).
+  EXPECT_NONFATAL_FAILURE(EXPECT_FLOAT_EQ(values_.further_from_one, 1.0),
+                          "1.0");
+}
+
+// Tests EXPECT_NEAR.
+TEST_F(FloatTest, EXPECT_NEAR) {
+  EXPECT_NEAR(-1.0f, -1.1f, 0.2f);
+  EXPECT_NEAR(2.0f, 3.0f, 1.0f);
+  EXPECT_NONFATAL_FAILURE(EXPECT_NEAR(1.0f, 1.5f, 0.25f),  // NOLINT
+                          "The difference between 1.0f and 1.5f is 0.5, "
+                          "which exceeds 0.25f");
+}
+
+// Tests ASSERT_NEAR.
+TEST_F(FloatTest, ASSERT_NEAR) {
+  ASSERT_NEAR(-1.0f, -1.1f, 0.2f);
+  ASSERT_NEAR(2.0f, 3.0f, 1.0f);
+  EXPECT_FATAL_FAILURE(ASSERT_NEAR(1.0f, 1.5f, 0.25f),  // NOLINT
+                       "The difference between 1.0f and 1.5f is 0.5, "
+                       "which exceeds 0.25f");
+}
+
+// Tests the cases where FloatLE() should succeed.
+TEST_F(FloatTest, FloatLESucceeds) {
+  EXPECT_PRED_FORMAT2(FloatLE, 1.0f, 2.0f);  // When val1 < val2,
+  ASSERT_PRED_FORMAT2(FloatLE, 1.0f, 1.0f);  // val1 == val2,
+
+  // or when val1 is greater than, but almost equals to, val2.
+  EXPECT_PRED_FORMAT2(FloatLE, values_.close_to_positive_zero, 0.0f);
+}
+
+// Tests the cases where FloatLE() should fail.
+TEST_F(FloatTest, FloatLEFails) {
+  // When val1 is greater than val2 by a large margin,
+  EXPECT_NONFATAL_FAILURE(EXPECT_PRED_FORMAT2(FloatLE, 2.0f, 1.0f),
+                          "(2.0f) <= (1.0f)");
+
+  // or by a small yet non-negligible margin,
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT2(FloatLE, values_.further_from_one, 1.0f);
+  }, "(values_.further_from_one) <= (1.0f)");
+
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT2(FloatLE, values_.nan1, values_.infinity);
+  }, "(values_.nan1) <= (values_.infinity)");
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT2(FloatLE, -values_.infinity, values_.nan1);
+  }, "(-values_.infinity) <= (values_.nan1)");
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT2(FloatLE, values_.nan1, values_.nan1);
+  }, "(values_.nan1) <= (values_.nan1)");
+}
+
+// Instantiates FloatingPointTest for testing *_DOUBLE_EQ.
+typedef FloatingPointTest<double> DoubleTest;
+
+// Tests that the size of Double::Bits matches the size of double.
+TEST_F(DoubleTest, Size) {
+  TestSize();
+}
+
+// Tests comparing with +0 and -0.
+TEST_F(DoubleTest, Zeros) {
+  EXPECT_DOUBLE_EQ(0.0, -0.0);
+  EXPECT_NONFATAL_FAILURE(EXPECT_DOUBLE_EQ(-0.0, 1.0),
+                          "1.0");
+  EXPECT_FATAL_FAILURE(ASSERT_DOUBLE_EQ(0.0, 1.0),
+                       "1.0");
+}
+
+// Tests comparing numbers close to 0.
+//
+// This ensures that *_DOUBLE_EQ handles the sign correctly and no
+// overflow occurs when comparing numbers whose absolute value is very
+// small.
+TEST_F(DoubleTest, AlmostZeros) {
+  // In C++Builder, names within local classes (such as used by
+  // EXPECT_FATAL_FAILURE) cannot be resolved against static members of the
+  // scoping class.  Use a static local alias as a workaround.
+  // We use the assignment syntax since some compilers, like Sun Studio,
+  // don't allow initializing references using construction syntax
+  // (parentheses).
+  static const DoubleTest::TestValues& v = this->values_;
+
+  EXPECT_DOUBLE_EQ(0.0, v.close_to_positive_zero);
+  EXPECT_DOUBLE_EQ(-0.0, v.close_to_negative_zero);
+  EXPECT_DOUBLE_EQ(v.close_to_positive_zero, v.close_to_negative_zero);
+
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_DOUBLE_EQ(v.close_to_positive_zero,
+                     v.further_from_negative_zero);
+  }, "v.further_from_negative_zero");
+}
+
+// Tests comparing numbers close to each other.
+TEST_F(DoubleTest, SmallDiff) {
+  EXPECT_DOUBLE_EQ(1.0, values_.close_to_one);
+  EXPECT_NONFATAL_FAILURE(EXPECT_DOUBLE_EQ(1.0, values_.further_from_one),
+                          "values_.further_from_one");
+}
+
+// Tests comparing numbers far apart.
+TEST_F(DoubleTest, LargeDiff) {
+  EXPECT_NONFATAL_FAILURE(EXPECT_DOUBLE_EQ(2.0, 3.0),
+                          "3.0");
+}
+
+// Tests comparing with infinity.
+//
+// This ensures that no overflow occurs when comparing numbers whose
+// absolute value is very large.
+TEST_F(DoubleTest, Infinity) {
+  EXPECT_DOUBLE_EQ(values_.infinity, values_.close_to_infinity);
+  EXPECT_DOUBLE_EQ(-values_.infinity, -values_.close_to_infinity);
+  EXPECT_NONFATAL_FAILURE(EXPECT_DOUBLE_EQ(values_.infinity, -values_.infinity),
+                          "-values_.infinity");
+
+  // This is interesting as the representations of infinity_ and nan1_
+  // are only 1 DLP apart.
+  EXPECT_NONFATAL_FAILURE(EXPECT_DOUBLE_EQ(values_.infinity, values_.nan1),
+                          "values_.nan1");
+}
+
+// Tests that comparing with NAN always returns false.
+TEST_F(DoubleTest, NaN) {
+  static const DoubleTest::TestValues& v = this->values_;
+
+  // Nokia's STLport crashes if we try to output infinity or NaN.
+  EXPECT_NONFATAL_FAILURE(EXPECT_DOUBLE_EQ(v.nan1, v.nan1),
+                          "v.nan1");
+  EXPECT_NONFATAL_FAILURE(EXPECT_DOUBLE_EQ(v.nan1, v.nan2), "v.nan2");
+  EXPECT_NONFATAL_FAILURE(EXPECT_DOUBLE_EQ(1.0, v.nan1), "v.nan1");
+  EXPECT_FATAL_FAILURE(ASSERT_DOUBLE_EQ(v.nan1, v.infinity),
+                       "v.infinity");
+}
+
+// Tests that *_DOUBLE_EQ are reflexive.
+TEST_F(DoubleTest, Reflexive) {
+  EXPECT_DOUBLE_EQ(0.0, 0.0);
+  EXPECT_DOUBLE_EQ(1.0, 1.0);
+  ASSERT_DOUBLE_EQ(values_.infinity, values_.infinity);
+}
+
+// Tests that *_DOUBLE_EQ are commutative.
+TEST_F(DoubleTest, Commutative) {
+  // We already tested EXPECT_DOUBLE_EQ(1.0, values_.close_to_one).
+  EXPECT_DOUBLE_EQ(values_.close_to_one, 1.0);
+
+  // We already tested EXPECT_DOUBLE_EQ(1.0, values_.further_from_one).
+  EXPECT_NONFATAL_FAILURE(EXPECT_DOUBLE_EQ(values_.further_from_one, 1.0),
+                          "1.0");
+}
+
+// Tests EXPECT_NEAR.
+TEST_F(DoubleTest, EXPECT_NEAR) {
+  EXPECT_NEAR(-1.0, -1.1, 0.2);
+  EXPECT_NEAR(2.0, 3.0, 1.0);
+  EXPECT_NONFATAL_FAILURE(EXPECT_NEAR(1.0, 1.5, 0.25),  // NOLINT
+                          "The difference between 1.0 and 1.5 is 0.5, "
+                          "which exceeds 0.25");
+  // At this magnitude adjacent doubles are 512.0 apart, so this triggers a
+  // slightly different failure reporting path.
+  EXPECT_NONFATAL_FAILURE(
+      EXPECT_NEAR(4.2934311416234112e+18, 4.2934311416234107e+18, 1.0),
+      "The abs_error parameter 1.0 evaluates to 1 which is smaller than the "
+      "minimum distance between doubles for numbers of this magnitude which is "
+      "512");
+}
+
+// Tests ASSERT_NEAR.
+TEST_F(DoubleTest, ASSERT_NEAR) {
+  ASSERT_NEAR(-1.0, -1.1, 0.2);
+  ASSERT_NEAR(2.0, 3.0, 1.0);
+  EXPECT_FATAL_FAILURE(ASSERT_NEAR(1.0, 1.5, 0.25),  // NOLINT
+                       "The difference between 1.0 and 1.5 is 0.5, "
+                       "which exceeds 0.25");
+}
+
+// Tests the cases where DoubleLE() should succeed.
+TEST_F(DoubleTest, DoubleLESucceeds) {
+  EXPECT_PRED_FORMAT2(DoubleLE, 1.0, 2.0);  // When val1 < val2,
+  ASSERT_PRED_FORMAT2(DoubleLE, 1.0, 1.0);  // val1 == val2,
+
+  // or when val1 is greater than, but almost equals to, val2.
+  EXPECT_PRED_FORMAT2(DoubleLE, values_.close_to_positive_zero, 0.0);
+}
+
+// Tests the cases where DoubleLE() should fail.
+TEST_F(DoubleTest, DoubleLEFails) {
+  // When val1 is greater than val2 by a large margin,
+  EXPECT_NONFATAL_FAILURE(EXPECT_PRED_FORMAT2(DoubleLE, 2.0, 1.0),
+                          "(2.0) <= (1.0)");
+
+  // or by a small yet non-negligible margin,
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT2(DoubleLE, values_.further_from_one, 1.0);
+  }, "(values_.further_from_one) <= (1.0)");
+
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT2(DoubleLE, values_.nan1, values_.infinity);
+  }, "(values_.nan1) <= (values_.infinity)");
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_PRED_FORMAT2(DoubleLE, -values_.infinity, values_.nan1);
+  }, " (-values_.infinity) <= (values_.nan1)");
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_PRED_FORMAT2(DoubleLE, values_.nan1, values_.nan1);
+  }, "(values_.nan1) <= (values_.nan1)");
+}
+
+
+// Verifies that a test or test case whose name starts with DISABLED_ is
+// not run.
+
+// A test whose name starts with DISABLED_.
+// Should not run.
+TEST(DisabledTest, DISABLED_TestShouldNotRun) {
+  FAIL() << "Unexpected failure: Disabled test should not be run.";
+}
+
+// A test whose name does not start with DISABLED_.
+// Should run.
+TEST(DisabledTest, NotDISABLED_TestShouldRun) {
+  EXPECT_EQ(1, 1);
+}
+
+// A test case whose name starts with DISABLED_.
+// Should not run.
+TEST(DISABLED_TestSuite, TestShouldNotRun) {
+  FAIL() << "Unexpected failure: Test in disabled test case should not be run.";
+}
+
+// A test case and test whose names start with DISABLED_.
+// Should not run.
+TEST(DISABLED_TestSuite, DISABLED_TestShouldNotRun) {
+  FAIL() << "Unexpected failure: Test in disabled test case should not be run.";
+}
+
+// Check that when all tests in a test case are disabled, SetUpTestSuite() and
+// TearDownTestSuite() are not called.
+class DisabledTestsTest : public Test {
+ protected:
+  static void SetUpTestSuite() {
+    FAIL() << "Unexpected failure: All tests disabled in test case. "
+              "SetUpTestSuite() should not be called.";
+  }
+
+  static void TearDownTestSuite() {
+    FAIL() << "Unexpected failure: All tests disabled in test case. "
+              "TearDownTestSuite() should not be called.";
+  }
+};
+
+TEST_F(DisabledTestsTest, DISABLED_TestShouldNotRun_1) {
+  FAIL() << "Unexpected failure: Disabled test should not be run.";
+}
+
+TEST_F(DisabledTestsTest, DISABLED_TestShouldNotRun_2) {
+  FAIL() << "Unexpected failure: Disabled test should not be run.";
+}
+
+// Tests that disabled typed tests aren't run.
+
+template <typename T>
+class TypedTest : public Test {
+};
+
+typedef testing::Types<int, double> NumericTypes;
+TYPED_TEST_SUITE(TypedTest, NumericTypes);
+
+TYPED_TEST(TypedTest, DISABLED_ShouldNotRun) {
+  FAIL() << "Unexpected failure: Disabled typed test should not run.";
+}
+
+template <typename T>
+class DISABLED_TypedTest : public Test {
+};
+
+TYPED_TEST_SUITE(DISABLED_TypedTest, NumericTypes);
+
+TYPED_TEST(DISABLED_TypedTest, ShouldNotRun) {
+  FAIL() << "Unexpected failure: Disabled typed test should not run.";
+}
+
+// Tests that disabled type-parameterized tests aren't run.
+
+template <typename T>
+class TypedTestP : public Test {
+};
+
+TYPED_TEST_SUITE_P(TypedTestP);
+
+TYPED_TEST_P(TypedTestP, DISABLED_ShouldNotRun) {
+  FAIL() << "Unexpected failure: "
+         << "Disabled type-parameterized test should not run.";
+}
+
+REGISTER_TYPED_TEST_SUITE_P(TypedTestP, DISABLED_ShouldNotRun);
+
+INSTANTIATE_TYPED_TEST_SUITE_P(My, TypedTestP, NumericTypes);
+
+template <typename T>
+class DISABLED_TypedTestP : public Test {
+};
+
+TYPED_TEST_SUITE_P(DISABLED_TypedTestP);
+
+TYPED_TEST_P(DISABLED_TypedTestP, ShouldNotRun) {
+  FAIL() << "Unexpected failure: "
+         << "Disabled type-parameterized test should not run.";
+}
+
+REGISTER_TYPED_TEST_SUITE_P(DISABLED_TypedTestP, ShouldNotRun);
+
+INSTANTIATE_TYPED_TEST_SUITE_P(My, DISABLED_TypedTestP, NumericTypes);
+
+// Tests that assertion macros evaluate their arguments exactly once.
+
+class SingleEvaluationTest : public Test {
+ public:  // Must be public and not protected due to a bug in g++ 3.4.2.
+  // This helper function is needed by the FailedASSERT_STREQ test
+  // below.  It's public to work around C++Builder's bug with scoping local
+  // classes.
+  static void CompareAndIncrementCharPtrs() {
+    ASSERT_STREQ(p1_++, p2_++);
+  }
+
+  // This helper function is needed by the FailedASSERT_NE test below.  It's
+  // public to work around C++Builder's bug with scoping local classes.
+  static void CompareAndIncrementInts() {
+    ASSERT_NE(a_++, b_++);
+  }
+
+ protected:
+  SingleEvaluationTest() {
+    p1_ = s1_;
+    p2_ = s2_;
+    a_ = 0;
+    b_ = 0;
+  }
+
+  static const char* const s1_;
+  static const char* const s2_;
+  static const char* p1_;
+  static const char* p2_;
+
+  static int a_;
+  static int b_;
+};
+
+const char* const SingleEvaluationTest::s1_ = "01234";
+const char* const SingleEvaluationTest::s2_ = "abcde";
+const char* SingleEvaluationTest::p1_;
+const char* SingleEvaluationTest::p2_;
+int SingleEvaluationTest::a_;
+int SingleEvaluationTest::b_;
+
+// Tests that when ASSERT_STREQ fails, it evaluates its arguments
+// exactly once.
+TEST_F(SingleEvaluationTest, FailedASSERT_STREQ) {
+  EXPECT_FATAL_FAILURE(SingleEvaluationTest::CompareAndIncrementCharPtrs(),
+                       "p2_++");
+  EXPECT_EQ(s1_ + 1, p1_);
+  EXPECT_EQ(s2_ + 1, p2_);
+}
+
+// Tests that string assertion arguments are evaluated exactly once.
+TEST_F(SingleEvaluationTest, ASSERT_STR) {
+  // successful EXPECT_STRNE
+  EXPECT_STRNE(p1_++, p2_++);
+  EXPECT_EQ(s1_ + 1, p1_);
+  EXPECT_EQ(s2_ + 1, p2_);
+
+  // failed EXPECT_STRCASEEQ
+  EXPECT_NONFATAL_FAILURE(EXPECT_STRCASEEQ(p1_++, p2_++),
+                          "Ignoring case");
+  EXPECT_EQ(s1_ + 2, p1_);
+  EXPECT_EQ(s2_ + 2, p2_);
+}
+
+// Tests that when ASSERT_NE fails, it evaluates its arguments exactly
+// once.
+TEST_F(SingleEvaluationTest, FailedASSERT_NE) {
+  EXPECT_FATAL_FAILURE(SingleEvaluationTest::CompareAndIncrementInts(),
+                       "(a_++) != (b_++)");
+  EXPECT_EQ(1, a_);
+  EXPECT_EQ(1, b_);
+}
+
+// Tests that assertion arguments are evaluated exactly once.
+TEST_F(SingleEvaluationTest, OtherCases) {
+  // successful EXPECT_TRUE
+  EXPECT_TRUE(0 == a_++);  // NOLINT
+  EXPECT_EQ(1, a_);
+
+  // failed EXPECT_TRUE
+  EXPECT_NONFATAL_FAILURE(EXPECT_TRUE(-1 == a_++), "-1 == a_++");
+  EXPECT_EQ(2, a_);
+
+  // successful EXPECT_GT
+  EXPECT_GT(a_++, b_++);
+  EXPECT_EQ(3, a_);
+  EXPECT_EQ(1, b_);
+
+  // failed EXPECT_LT
+  EXPECT_NONFATAL_FAILURE(EXPECT_LT(a_++, b_++), "(a_++) < (b_++)");
+  EXPECT_EQ(4, a_);
+  EXPECT_EQ(2, b_);
+
+  // successful ASSERT_TRUE
+  ASSERT_TRUE(0 < a_++);  // NOLINT
+  EXPECT_EQ(5, a_);
+
+  // successful ASSERT_GT
+  ASSERT_GT(a_++, b_++);
+  EXPECT_EQ(6, a_);
+  EXPECT_EQ(3, b_);
+}
+
+#if GTEST_HAS_EXCEPTIONS
+
+#if GTEST_HAS_RTTI
+
+#ifdef _MSC_VER
+#define ERROR_DESC "class std::runtime_error"
+#else
+#define ERROR_DESC "std::runtime_error"
+#endif
+
+#else  // GTEST_HAS_RTTI
+
+#define ERROR_DESC "an std::exception-derived error"
+
+#endif  // GTEST_HAS_RTTI
+
+void ThrowAnInteger() {
+  throw 1;
+}
+void ThrowRuntimeError(const char* what) {
+  throw std::runtime_error(what);
+}
+
+// Tests that assertion arguments are evaluated exactly once.
+TEST_F(SingleEvaluationTest, ExceptionTests) {
+  // successful EXPECT_THROW
+  EXPECT_THROW({  // NOLINT
+    a_++;
+    ThrowAnInteger();
+  }, int);
+  EXPECT_EQ(1, a_);
+
+  // failed EXPECT_THROW, throws different
+  EXPECT_NONFATAL_FAILURE(EXPECT_THROW({  // NOLINT
+    a_++;
+    ThrowAnInteger();
+  }, bool), "throws a different type");
+  EXPECT_EQ(2, a_);
+
+  // failed EXPECT_THROW, throws runtime error
+  EXPECT_NONFATAL_FAILURE(EXPECT_THROW({  // NOLINT
+    a_++;
+    ThrowRuntimeError("A description");
+  }, bool), "throws " ERROR_DESC " with description \"A description\"");
+  EXPECT_EQ(3, a_);
+
+  // failed EXPECT_THROW, throws nothing
+  EXPECT_NONFATAL_FAILURE(EXPECT_THROW(a_++, bool), "throws nothing");
+  EXPECT_EQ(4, a_);
+
+  // successful EXPECT_NO_THROW
+  EXPECT_NO_THROW(a_++);
+  EXPECT_EQ(5, a_);
+
+  // failed EXPECT_NO_THROW
+  EXPECT_NONFATAL_FAILURE(EXPECT_NO_THROW({  // NOLINT
+    a_++;
+    ThrowAnInteger();
+  }), "it throws");
+  EXPECT_EQ(6, a_);
+
+  // successful EXPECT_ANY_THROW
+  EXPECT_ANY_THROW({  // NOLINT
+    a_++;
+    ThrowAnInteger();
+  });
+  EXPECT_EQ(7, a_);
+
+  // failed EXPECT_ANY_THROW
+  EXPECT_NONFATAL_FAILURE(EXPECT_ANY_THROW(a_++), "it doesn't");
+  EXPECT_EQ(8, a_);
+}
+
+#endif  // GTEST_HAS_EXCEPTIONS
+
+// Tests {ASSERT|EXPECT}_NO_FATAL_FAILURE.
+class NoFatalFailureTest : public Test {
+ protected:
+  void Succeeds() {}
+  void FailsNonFatal() {
+    ADD_FAILURE() << "some non-fatal failure";
+  }
+  void Fails() {
+    FAIL() << "some fatal failure";
+  }
+
+  void DoAssertNoFatalFailureOnFails() {
+    ASSERT_NO_FATAL_FAILURE(Fails());
+    ADD_FAILURE() << "should not reach here.";
+  }
+
+  void DoExpectNoFatalFailureOnFails() {
+    EXPECT_NO_FATAL_FAILURE(Fails());
+    ADD_FAILURE() << "other failure";
+  }
+};
+
+TEST_F(NoFatalFailureTest, NoFailure) {
+  EXPECT_NO_FATAL_FAILURE(Succeeds());
+  ASSERT_NO_FATAL_FAILURE(Succeeds());
+}
+
+TEST_F(NoFatalFailureTest, NonFatalIsNoFailure) {
+  EXPECT_NONFATAL_FAILURE(
+      EXPECT_NO_FATAL_FAILURE(FailsNonFatal()),
+      "some non-fatal failure");
+  EXPECT_NONFATAL_FAILURE(
+      ASSERT_NO_FATAL_FAILURE(FailsNonFatal()),
+      "some non-fatal failure");
+}
+
+TEST_F(NoFatalFailureTest, AssertNoFatalFailureOnFatalFailure) {
+  TestPartResultArray gtest_failures;
+  {
+    ScopedFakeTestPartResultReporter gtest_reporter(&gtest_failures);
+    DoAssertNoFatalFailureOnFails();
+  }
+  ASSERT_EQ(2, gtest_failures.size());
+  EXPECT_EQ(TestPartResult::kFatalFailure,
+            gtest_failures.GetTestPartResult(0).type());
+  EXPECT_EQ(TestPartResult::kFatalFailure,
+            gtest_failures.GetTestPartResult(1).type());
+  EXPECT_PRED_FORMAT2(testing::IsSubstring, "some fatal failure",
+                      gtest_failures.GetTestPartResult(0).message());
+  EXPECT_PRED_FORMAT2(testing::IsSubstring, "it does",
+                      gtest_failures.GetTestPartResult(1).message());
+}
+
+TEST_F(NoFatalFailureTest, ExpectNoFatalFailureOnFatalFailure) {
+  TestPartResultArray gtest_failures;
+  {
+    ScopedFakeTestPartResultReporter gtest_reporter(&gtest_failures);
+    DoExpectNoFatalFailureOnFails();
+  }
+  ASSERT_EQ(3, gtest_failures.size());
+  EXPECT_EQ(TestPartResult::kFatalFailure,
+            gtest_failures.GetTestPartResult(0).type());
+  EXPECT_EQ(TestPartResult::kNonFatalFailure,
+            gtest_failures.GetTestPartResult(1).type());
+  EXPECT_EQ(TestPartResult::kNonFatalFailure,
+            gtest_failures.GetTestPartResult(2).type());
+  EXPECT_PRED_FORMAT2(testing::IsSubstring, "some fatal failure",
+                      gtest_failures.GetTestPartResult(0).message());
+  EXPECT_PRED_FORMAT2(testing::IsSubstring, "it does",
+                      gtest_failures.GetTestPartResult(1).message());
+  EXPECT_PRED_FORMAT2(testing::IsSubstring, "other failure",
+                      gtest_failures.GetTestPartResult(2).message());
+}
+
+TEST_F(NoFatalFailureTest, MessageIsStreamable) {
+  TestPartResultArray gtest_failures;
+  {
+    ScopedFakeTestPartResultReporter gtest_reporter(&gtest_failures);
+    EXPECT_NO_FATAL_FAILURE(FAIL() << "foo") << "my message";
+  }
+  ASSERT_EQ(2, gtest_failures.size());
+  EXPECT_EQ(TestPartResult::kNonFatalFailure,
+            gtest_failures.GetTestPartResult(0).type());
+  EXPECT_EQ(TestPartResult::kNonFatalFailure,
+            gtest_failures.GetTestPartResult(1).type());
+  EXPECT_PRED_FORMAT2(testing::IsSubstring, "foo",
+                      gtest_failures.GetTestPartResult(0).message());
+  EXPECT_PRED_FORMAT2(testing::IsSubstring, "my message",
+                      gtest_failures.GetTestPartResult(1).message());
+}
+
+// Tests non-string assertions.
+
+std::string EditsToString(const std::vector<EditType>& edits) {
+  std::string out;
+  for (size_t i = 0; i < edits.size(); ++i) {
+    static const char kEdits[] = " +-/";
+    out.append(1, kEdits[edits[i]]);
+  }
+  return out;
+}
+
+std::vector<size_t> CharsToIndices(const std::string& str) {
+  std::vector<size_t> out;
+  for (size_t i = 0; i < str.size(); ++i) {
+    out.push_back(static_cast<size_t>(str[i]));
+  }
+  return out;
+}
+
+std::vector<std::string> CharsToLines(const std::string& str) {
+  std::vector<std::string> out;
+  for (size_t i = 0; i < str.size(); ++i) {
+    out.push_back(str.substr(i, 1));
+  }
+  return out;
+}
+
+TEST(EditDistance, TestSuites) {
+  struct Case {
+    int line;
+    const char* left;
+    const char* right;
+    const char* expected_edits;
+    const char* expected_diff;
+  };
+  static const Case kCases[] = {
+      // No change.
+      {__LINE__, "A", "A", " ", ""},
+      {__LINE__, "ABCDE", "ABCDE", "     ", ""},
+      // Simple adds.
+      {__LINE__, "X", "XA", " +", "@@ +1,2 @@\n X\n+A\n"},
+      {__LINE__, "X", "XABCD", " ++++", "@@ +1,5 @@\n X\n+A\n+B\n+C\n+D\n"},
+      // Simple removes.
+      {__LINE__, "XA", "X", " -", "@@ -1,2 @@\n X\n-A\n"},
+      {__LINE__, "XABCD", "X", " ----", "@@ -1,5 @@\n X\n-A\n-B\n-C\n-D\n"},
+      // Simple replaces.
+      {__LINE__, "A", "a", "/", "@@ -1,1 +1,1 @@\n-A\n+a\n"},
+      {__LINE__, "ABCD", "abcd", "////",
+       "@@ -1,4 +1,4 @@\n-A\n-B\n-C\n-D\n+a\n+b\n+c\n+d\n"},
+      // Path finding.
+      {__LINE__, "ABCDEFGH", "ABXEGH1", "  -/ -  +",
+       "@@ -1,8 +1,7 @@\n A\n B\n-C\n-D\n+X\n E\n-F\n G\n H\n+1\n"},
+      {__LINE__, "AAAABCCCC", "ABABCDCDC", "- /   + / ",
+       "@@ -1,9 +1,9 @@\n-A\n A\n-A\n+B\n A\n B\n C\n+D\n C\n-C\n+D\n C\n"},
+      {__LINE__, "ABCDE", "BCDCD", "-   +/",
+       "@@ -1,5 +1,5 @@\n-A\n B\n C\n D\n-E\n+C\n+D\n"},
+      {__LINE__, "ABCDEFGHIJKL", "BCDCDEFGJKLJK", "- ++     --   ++",
+       "@@ -1,4 +1,5 @@\n-A\n B\n+C\n+D\n C\n D\n"
+       "@@ -6,7 +7,7 @@\n F\n G\n-H\n-I\n J\n K\n L\n+J\n+K\n"},
+      {}};
+  for (const Case* c = kCases; c->left; ++c) {
+    EXPECT_TRUE(c->expected_edits ==
+                EditsToString(CalculateOptimalEdits(CharsToIndices(c->left),
+                                                    CharsToIndices(c->right))))
+        << "Left <" << c->left << "> Right <" << c->right << "> Edits <"
+        << EditsToString(CalculateOptimalEdits(
+               CharsToIndices(c->left), CharsToIndices(c->right))) << ">";
+    EXPECT_TRUE(c->expected_diff == CreateUnifiedDiff(CharsToLines(c->left),
+                                                      CharsToLines(c->right)))
+        << "Left <" << c->left << "> Right <" << c->right << "> Diff <"
+        << CreateUnifiedDiff(CharsToLines(c->left), CharsToLines(c->right))
+        << ">";
+  }
+}
+
+// Tests EqFailure(), used for implementing *EQ* assertions.
+TEST(AssertionTest, EqFailure) {
+  const std::string foo_val("5"), bar_val("6");
+  const std::string msg1(
+      EqFailure("foo", "bar", foo_val, bar_val, false)
+      .failure_message());
+  EXPECT_STREQ(
+      "Expected equality of these values:\n"
+      "  foo\n"
+      "    Which is: 5\n"
+      "  bar\n"
+      "    Which is: 6",
+      msg1.c_str());
+
+  const std::string msg2(
+      EqFailure("foo", "6", foo_val, bar_val, false)
+      .failure_message());
+  EXPECT_STREQ(
+      "Expected equality of these values:\n"
+      "  foo\n"
+      "    Which is: 5\n"
+      "  6",
+      msg2.c_str());
+
+  const std::string msg3(
+      EqFailure("5", "bar", foo_val, bar_val, false)
+      .failure_message());
+  EXPECT_STREQ(
+      "Expected equality of these values:\n"
+      "  5\n"
+      "  bar\n"
+      "    Which is: 6",
+      msg3.c_str());
+
+  const std::string msg4(
+      EqFailure("5", "6", foo_val, bar_val, false).failure_message());
+  EXPECT_STREQ(
+      "Expected equality of these values:\n"
+      "  5\n"
+      "  6",
+      msg4.c_str());
+
+  const std::string msg5(
+      EqFailure("foo", "bar",
+                std::string("\"x\""), std::string("\"y\""),
+                true).failure_message());
+  EXPECT_STREQ(
+      "Expected equality of these values:\n"
+      "  foo\n"
+      "    Which is: \"x\"\n"
+      "  bar\n"
+      "    Which is: \"y\"\n"
+      "Ignoring case",
+      msg5.c_str());
+}
+
+TEST(AssertionTest, EqFailureWithDiff) {
+  const std::string left(
+      "1\\n2XXX\\n3\\n5\\n6\\n7\\n8\\n9\\n10\\n11\\n12XXX\\n13\\n14\\n15");
+  const std::string right(
+      "1\\n2\\n3\\n4\\n5\\n6\\n7\\n8\\n9\\n11\\n12\\n13\\n14");
+  const std::string msg1(
+      EqFailure("left", "right", left, right, false).failure_message());
+  EXPECT_STREQ(
+      "Expected equality of these values:\n"
+      "  left\n"
+      "    Which is: "
+      "1\\n2XXX\\n3\\n5\\n6\\n7\\n8\\n9\\n10\\n11\\n12XXX\\n13\\n14\\n15\n"
+      "  right\n"
+      "    Which is: 1\\n2\\n3\\n4\\n5\\n6\\n7\\n8\\n9\\n11\\n12\\n13\\n14\n"
+      "With diff:\n@@ -1,5 +1,6 @@\n 1\n-2XXX\n+2\n 3\n+4\n 5\n 6\n"
+      "@@ -7,8 +8,6 @@\n 8\n 9\n-10\n 11\n-12XXX\n+12\n 13\n 14\n-15\n",
+      msg1.c_str());
+}
+
+// Tests AppendUserMessage(), used for implementing the *EQ* macros.
+TEST(AssertionTest, AppendUserMessage) {
+  const std::string foo("foo");
+
+  Message msg;
+  EXPECT_STREQ("foo",
+               AppendUserMessage(foo, msg).c_str());
+
+  msg << "bar";
+  EXPECT_STREQ("foo\nbar",
+               AppendUserMessage(foo, msg).c_str());
+}
+
+#ifdef __BORLANDC__
+// Silences warnings: "Condition is always true", "Unreachable code"
+# pragma option push -w-ccc -w-rch
+#endif
+
+// Tests ASSERT_TRUE.
+TEST(AssertionTest, ASSERT_TRUE) {
+  ASSERT_TRUE(2 > 1);  // NOLINT
+  EXPECT_FATAL_FAILURE(ASSERT_TRUE(2 < 1),
+                       "2 < 1");
+}
+
+// Tests ASSERT_TRUE(predicate) for predicates returning AssertionResult.
+TEST(AssertionTest, AssertTrueWithAssertionResult) {
+  ASSERT_TRUE(ResultIsEven(2));
+#ifndef __BORLANDC__
+  // ICE's in C++Builder.
+  EXPECT_FATAL_FAILURE(ASSERT_TRUE(ResultIsEven(3)),
+                       "Value of: ResultIsEven(3)\n"
+                       "  Actual: false (3 is odd)\n"
+                       "Expected: true");
+#endif
+  ASSERT_TRUE(ResultIsEvenNoExplanation(2));
+  EXPECT_FATAL_FAILURE(ASSERT_TRUE(ResultIsEvenNoExplanation(3)),
+                       "Value of: ResultIsEvenNoExplanation(3)\n"
+                       "  Actual: false (3 is odd)\n"
+                       "Expected: true");
+}
+
+// Tests ASSERT_FALSE.
+TEST(AssertionTest, ASSERT_FALSE) {
+  ASSERT_FALSE(2 < 1);  // NOLINT
+  EXPECT_FATAL_FAILURE(ASSERT_FALSE(2 > 1),
+                       "Value of: 2 > 1\n"
+                       "  Actual: true\n"
+                       "Expected: false");
+}
+
+// Tests ASSERT_FALSE(predicate) for predicates returning AssertionResult.
+TEST(AssertionTest, AssertFalseWithAssertionResult) {
+  ASSERT_FALSE(ResultIsEven(3));
+#ifndef __BORLANDC__
+  // ICE's in C++Builder.
+  EXPECT_FATAL_FAILURE(ASSERT_FALSE(ResultIsEven(2)),
+                       "Value of: ResultIsEven(2)\n"
+                       "  Actual: true (2 is even)\n"
+                       "Expected: false");
+#endif
+  ASSERT_FALSE(ResultIsEvenNoExplanation(3));
+  EXPECT_FATAL_FAILURE(ASSERT_FALSE(ResultIsEvenNoExplanation(2)),
+                       "Value of: ResultIsEvenNoExplanation(2)\n"
+                       "  Actual: true\n"
+                       "Expected: false");
+}
+
+#ifdef __BORLANDC__
+// Restores warnings after previous "#pragma option push" suppressed them
+# pragma option pop
+#endif
+
+// Tests using ASSERT_EQ on double values.  The purpose is to make
+// sure that the specialization we did for integer and anonymous enums
+// isn't used for double arguments.
+TEST(ExpectTest, ASSERT_EQ_Double) {
+  // A success.
+  ASSERT_EQ(5.6, 5.6);
+
+  // A failure.
+  EXPECT_FATAL_FAILURE(ASSERT_EQ(5.1, 5.2),
+                       "5.1");
+}
+
+// Tests ASSERT_EQ.
+TEST(AssertionTest, ASSERT_EQ) {
+  ASSERT_EQ(5, 2 + 3);
+  EXPECT_FATAL_FAILURE(ASSERT_EQ(5, 2*3),
+                       "Expected equality of these values:\n"
+                       "  5\n"
+                       "  2*3\n"
+                       "    Which is: 6");
+}
+
+// Tests ASSERT_EQ(NULL, pointer).
+TEST(AssertionTest, ASSERT_EQ_NULL) {
+  // A success.
+  const char* p = nullptr;
+  ASSERT_EQ(nullptr, p);
+
+  // A failure.
+  static int n = 0;
+  EXPECT_FATAL_FAILURE(ASSERT_EQ(nullptr, &n), "  &n\n    Which is:");
+}
+
+// Tests ASSERT_EQ(0, non_pointer).  Since the literal 0 can be
+// treated as a null pointer by the compiler, we need to make sure
+// that ASSERT_EQ(0, non_pointer) isn't interpreted by Google Test as
+// ASSERT_EQ(static_cast<void*>(NULL), non_pointer).
+TEST(ExpectTest, ASSERT_EQ_0) {
+  int n = 0;
+
+  // A success.
+  ASSERT_EQ(0, n);
+
+  // A failure.
+  EXPECT_FATAL_FAILURE(ASSERT_EQ(0, 5.6),
+                       "  0\n  5.6");
+}
+
+// Tests ASSERT_NE.
+TEST(AssertionTest, ASSERT_NE) {
+  ASSERT_NE(6, 7);
+  EXPECT_FATAL_FAILURE(ASSERT_NE('a', 'a'),
+                       "Expected: ('a') != ('a'), "
+                       "actual: 'a' (97, 0x61) vs 'a' (97, 0x61)");
+}
+
+// Tests ASSERT_LE.
+TEST(AssertionTest, ASSERT_LE) {
+  ASSERT_LE(2, 3);
+  ASSERT_LE(2, 2);
+  EXPECT_FATAL_FAILURE(ASSERT_LE(2, 0),
+                       "Expected: (2) <= (0), actual: 2 vs 0");
+}
+
+// Tests ASSERT_LT.
+TEST(AssertionTest, ASSERT_LT) {
+  ASSERT_LT(2, 3);
+  EXPECT_FATAL_FAILURE(ASSERT_LT(2, 2),
+                       "Expected: (2) < (2), actual: 2 vs 2");
+}
+
+// Tests ASSERT_GE.
+TEST(AssertionTest, ASSERT_GE) {
+  ASSERT_GE(2, 1);
+  ASSERT_GE(2, 2);
+  EXPECT_FATAL_FAILURE(ASSERT_GE(2, 3),
+                       "Expected: (2) >= (3), actual: 2 vs 3");
+}
+
+// Tests ASSERT_GT.
+TEST(AssertionTest, ASSERT_GT) {
+  ASSERT_GT(2, 1);
+  EXPECT_FATAL_FAILURE(ASSERT_GT(2, 2),
+                       "Expected: (2) > (2), actual: 2 vs 2");
+}
+
+#if GTEST_HAS_EXCEPTIONS
+
+void ThrowNothing() {}
+
+// Tests ASSERT_THROW.
+TEST(AssertionTest, ASSERT_THROW) {
+  ASSERT_THROW(ThrowAnInteger(), int);
+
+# ifndef __BORLANDC__
+
+  // ICE's in C++Builder 2007 and 2009.
+  EXPECT_FATAL_FAILURE(
+      ASSERT_THROW(ThrowAnInteger(), bool),
+      "Expected: ThrowAnInteger() throws an exception of type bool.\n"
+      "  Actual: it throws a different type.");
+  EXPECT_FATAL_FAILURE(
+      ASSERT_THROW(ThrowRuntimeError("A description"), std::logic_error),
+      "Expected: ThrowRuntimeError(\"A description\") "
+      "throws an exception of type std::logic_error.\n  "
+      "Actual: it throws " ERROR_DESC " "
+      "with description \"A description\".");
+# endif
+
+  EXPECT_FATAL_FAILURE(
+      ASSERT_THROW(ThrowNothing(), bool),
+      "Expected: ThrowNothing() throws an exception of type bool.\n"
+      "  Actual: it throws nothing.");
+}
+
+// Tests ASSERT_NO_THROW.
+TEST(AssertionTest, ASSERT_NO_THROW) {
+  ASSERT_NO_THROW(ThrowNothing());
+  EXPECT_FATAL_FAILURE(ASSERT_NO_THROW(ThrowAnInteger()),
+                       "Expected: ThrowAnInteger() doesn't throw an exception."
+                       "\n  Actual: it throws.");
+  EXPECT_FATAL_FAILURE(ASSERT_NO_THROW(ThrowRuntimeError("A description")),
+                       "Expected: ThrowRuntimeError(\"A description\") "
+                       "doesn't throw an exception.\n  "
+                       "Actual: it throws " ERROR_DESC " "
+                       "with description \"A description\".");
+}
+
+// Tests ASSERT_ANY_THROW.
+TEST(AssertionTest, ASSERT_ANY_THROW) {
+  ASSERT_ANY_THROW(ThrowAnInteger());
+  EXPECT_FATAL_FAILURE(
+      ASSERT_ANY_THROW(ThrowNothing()),
+      "Expected: ThrowNothing() throws an exception.\n"
+      "  Actual: it doesn't.");
+}
+
+#endif  // GTEST_HAS_EXCEPTIONS
+
+// Makes sure we deal with the precedence of <<.  This test should
+// compile.
+TEST(AssertionTest, AssertPrecedence) {
+  ASSERT_EQ(1 < 2, true);
+  bool false_value = false;
+  ASSERT_EQ(true && false_value, false);
+}
+
+// A subroutine used by the following test.
+void TestEq1(int x) {
+  ASSERT_EQ(1, x);
+}
+
+// Tests calling a test subroutine that's not part of a fixture.
+TEST(AssertionTest, NonFixtureSubroutine) {
+  EXPECT_FATAL_FAILURE(TestEq1(2),
+                       "  x\n    Which is: 2");
+}
+
+// An uncopyable class.
+class Uncopyable {
+ public:
+  explicit Uncopyable(int a_value) : value_(a_value) {}
+
+  int value() const { return value_; }
+  bool operator==(const Uncopyable& rhs) const {
+    return value() == rhs.value();
+  }
+ private:
+  // This constructor deliberately has no implementation, as we don't
+  // want this class to be copyable.
+  Uncopyable(const Uncopyable&);  // NOLINT
+
+  int value_;
+};
+
+::std::ostream& operator<<(::std::ostream& os, const Uncopyable& value) {
+  return os << value.value();
+}
+
+
+bool IsPositiveUncopyable(const Uncopyable& x) {
+  return x.value() > 0;
+}
+
+// A subroutine used by the following test.
+void TestAssertNonPositive() {
+  Uncopyable y(-1);
+  ASSERT_PRED1(IsPositiveUncopyable, y);
+}
+// A subroutine used by the following test.
+void TestAssertEqualsUncopyable() {
+  Uncopyable x(5);
+  Uncopyable y(-1);
+  ASSERT_EQ(x, y);
+}
+
+// Tests that uncopyable objects can be used in assertions.
+TEST(AssertionTest, AssertWorksWithUncopyableObject) {
+  Uncopyable x(5);
+  ASSERT_PRED1(IsPositiveUncopyable, x);
+  ASSERT_EQ(x, x);
+  EXPECT_FATAL_FAILURE(TestAssertNonPositive(),
+    "IsPositiveUncopyable(y) evaluates to false, where\ny evaluates to -1");
+  EXPECT_FATAL_FAILURE(TestAssertEqualsUncopyable(),
+                       "Expected equality of these values:\n"
+                       "  x\n    Which is: 5\n  y\n    Which is: -1");
+}
+
+// Tests that uncopyable objects can be used in expects.
+TEST(AssertionTest, ExpectWorksWithUncopyableObject) {
+  Uncopyable x(5);
+  EXPECT_PRED1(IsPositiveUncopyable, x);
+  Uncopyable y(-1);
+  EXPECT_NONFATAL_FAILURE(EXPECT_PRED1(IsPositiveUncopyable, y),
+    "IsPositiveUncopyable(y) evaluates to false, where\ny evaluates to -1");
+  EXPECT_EQ(x, x);
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(x, y),
+                          "Expected equality of these values:\n"
+                          "  x\n    Which is: 5\n  y\n    Which is: -1");
+}
+
+enum NamedEnum {
+  kE1 = 0,
+  kE2 = 1
+};
+
+TEST(AssertionTest, NamedEnum) {
+  EXPECT_EQ(kE1, kE1);
+  EXPECT_LT(kE1, kE2);
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(kE1, kE2), "Which is: 0");
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(kE1, kE2), "Which is: 1");
+}
+
+// Sun Studio and HP aCC2reject this code.
+#if !defined(__SUNPRO_CC) && !defined(__HP_aCC)
+
+// Tests using assertions with anonymous enums.
+enum {
+  kCaseA = -1,
+
+# if GTEST_OS_LINUX
+
+  // We want to test the case where the size of the anonymous enum is
+  // larger than sizeof(int), to make sure our implementation of the
+  // assertions doesn't truncate the enums.  However, MSVC
+  // (incorrectly) doesn't allow an enum value to exceed the range of
+  // an int, so this has to be conditionally compiled.
+  //
+  // On Linux, kCaseB and kCaseA have the same value when truncated to
+  // int size.  We want to test whether this will confuse the
+  // assertions.
+  kCaseB = testing::internal::kMaxBiggestInt,
+
+# else
+
+  kCaseB = INT_MAX,
+
+# endif  // GTEST_OS_LINUX
+
+  kCaseC = 42
+};
+
+TEST(AssertionTest, AnonymousEnum) {
+# if GTEST_OS_LINUX
+
+  EXPECT_EQ(static_cast<int>(kCaseA), static_cast<int>(kCaseB));
+
+# endif  // GTEST_OS_LINUX
+
+  EXPECT_EQ(kCaseA, kCaseA);
+  EXPECT_NE(kCaseA, kCaseB);
+  EXPECT_LT(kCaseA, kCaseB);
+  EXPECT_LE(kCaseA, kCaseB);
+  EXPECT_GT(kCaseB, kCaseA);
+  EXPECT_GE(kCaseA, kCaseA);
+  EXPECT_NONFATAL_FAILURE(EXPECT_GE(kCaseA, kCaseB),
+                          "(kCaseA) >= (kCaseB)");
+  EXPECT_NONFATAL_FAILURE(EXPECT_GE(kCaseA, kCaseC),
+                          "-1 vs 42");
+
+  ASSERT_EQ(kCaseA, kCaseA);
+  ASSERT_NE(kCaseA, kCaseB);
+  ASSERT_LT(kCaseA, kCaseB);
+  ASSERT_LE(kCaseA, kCaseB);
+  ASSERT_GT(kCaseB, kCaseA);
+  ASSERT_GE(kCaseA, kCaseA);
+
+# ifndef __BORLANDC__
+
+  // ICE's in C++Builder.
+  EXPECT_FATAL_FAILURE(ASSERT_EQ(kCaseA, kCaseB),
+                       "  kCaseB\n    Which is: ");
+  EXPECT_FATAL_FAILURE(ASSERT_EQ(kCaseA, kCaseC),
+                       "\n    Which is: 42");
+# endif
+
+  EXPECT_FATAL_FAILURE(ASSERT_EQ(kCaseA, kCaseC),
+                       "\n    Which is: -1");
+}
+
+#endif  // !GTEST_OS_MAC && !defined(__SUNPRO_CC)
+
+#if GTEST_OS_WINDOWS
+
+static HRESULT UnexpectedHRESULTFailure() {
+  return E_UNEXPECTED;
+}
+
+static HRESULT OkHRESULTSuccess() {
+  return S_OK;
+}
+
+static HRESULT FalseHRESULTSuccess() {
+  return S_FALSE;
+}
+
+// HRESULT assertion tests test both zero and non-zero
+// success codes as well as failure message for each.
+//
+// Windows CE doesn't support message texts.
+TEST(HRESULTAssertionTest, EXPECT_HRESULT_SUCCEEDED) {
+  EXPECT_HRESULT_SUCCEEDED(S_OK);
+  EXPECT_HRESULT_SUCCEEDED(S_FALSE);
+
+  EXPECT_NONFATAL_FAILURE(EXPECT_HRESULT_SUCCEEDED(UnexpectedHRESULTFailure()),
+    "Expected: (UnexpectedHRESULTFailure()) succeeds.\n"
+    "  Actual: 0x8000FFFF");
+}
+
+TEST(HRESULTAssertionTest, ASSERT_HRESULT_SUCCEEDED) {
+  ASSERT_HRESULT_SUCCEEDED(S_OK);
+  ASSERT_HRESULT_SUCCEEDED(S_FALSE);
+
+  EXPECT_FATAL_FAILURE(ASSERT_HRESULT_SUCCEEDED(UnexpectedHRESULTFailure()),
+    "Expected: (UnexpectedHRESULTFailure()) succeeds.\n"
+    "  Actual: 0x8000FFFF");
+}
+
+TEST(HRESULTAssertionTest, EXPECT_HRESULT_FAILED) {
+  EXPECT_HRESULT_FAILED(E_UNEXPECTED);
+
+  EXPECT_NONFATAL_FAILURE(EXPECT_HRESULT_FAILED(OkHRESULTSuccess()),
+    "Expected: (OkHRESULTSuccess()) fails.\n"
+    "  Actual: 0x0");
+  EXPECT_NONFATAL_FAILURE(EXPECT_HRESULT_FAILED(FalseHRESULTSuccess()),
+    "Expected: (FalseHRESULTSuccess()) fails.\n"
+    "  Actual: 0x1");
+}
+
+TEST(HRESULTAssertionTest, ASSERT_HRESULT_FAILED) {
+  ASSERT_HRESULT_FAILED(E_UNEXPECTED);
+
+# ifndef __BORLANDC__
+
+  // ICE's in C++Builder 2007 and 2009.
+  EXPECT_FATAL_FAILURE(ASSERT_HRESULT_FAILED(OkHRESULTSuccess()),
+    "Expected: (OkHRESULTSuccess()) fails.\n"
+    "  Actual: 0x0");
+# endif
+
+  EXPECT_FATAL_FAILURE(ASSERT_HRESULT_FAILED(FalseHRESULTSuccess()),
+    "Expected: (FalseHRESULTSuccess()) fails.\n"
+    "  Actual: 0x1");
+}
+
+// Tests that streaming to the HRESULT macros works.
+TEST(HRESULTAssertionTest, Streaming) {
+  EXPECT_HRESULT_SUCCEEDED(S_OK) << "unexpected failure";
+  ASSERT_HRESULT_SUCCEEDED(S_OK) << "unexpected failure";
+  EXPECT_HRESULT_FAILED(E_UNEXPECTED) << "unexpected failure";
+  ASSERT_HRESULT_FAILED(E_UNEXPECTED) << "unexpected failure";
+
+  EXPECT_NONFATAL_FAILURE(
+      EXPECT_HRESULT_SUCCEEDED(E_UNEXPECTED) << "expected failure",
+      "expected failure");
+
+# ifndef __BORLANDC__
+
+  // ICE's in C++Builder 2007 and 2009.
+  EXPECT_FATAL_FAILURE(
+      ASSERT_HRESULT_SUCCEEDED(E_UNEXPECTED) << "expected failure",
+      "expected failure");
+# endif
+
+  EXPECT_NONFATAL_FAILURE(
+      EXPECT_HRESULT_FAILED(S_OK) << "expected failure",
+      "expected failure");
+
+  EXPECT_FATAL_FAILURE(
+      ASSERT_HRESULT_FAILED(S_OK) << "expected failure",
+      "expected failure");
+}
+
+#endif  // GTEST_OS_WINDOWS
+
+// The following code intentionally tests a suboptimal syntax.
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdangling-else"
+#pragma GCC diagnostic ignored "-Wempty-body"
+#pragma GCC diagnostic ignored "-Wpragmas"
+#endif
+// Tests that the assertion macros behave like single statements.
+TEST(AssertionSyntaxTest, BasicAssertionsBehavesLikeSingleStatement) {
+  if (AlwaysFalse())
+    ASSERT_TRUE(false) << "This should never be executed; "
+                          "It's a compilation test only.";
+
+  if (AlwaysTrue())
+    EXPECT_FALSE(false);
+  else
+    ;  // NOLINT
+
+  if (AlwaysFalse())
+    ASSERT_LT(1, 3);
+
+  if (AlwaysFalse())
+    ;  // NOLINT
+  else
+    EXPECT_GT(3, 2) << "";
+}
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif
+
+#if GTEST_HAS_EXCEPTIONS
+// Tests that the compiler will not complain about unreachable code in the
+// EXPECT_THROW/EXPECT_ANY_THROW/EXPECT_NO_THROW macros.
+TEST(ExpectThrowTest, DoesNotGenerateUnreachableCodeWarning) {
+  int n = 0;
+
+  EXPECT_THROW(throw 1, int);
+  EXPECT_NONFATAL_FAILURE(EXPECT_THROW(n++, int), "");
+  EXPECT_NONFATAL_FAILURE(EXPECT_THROW(throw 1, const char*), "");
+  EXPECT_NO_THROW(n++);
+  EXPECT_NONFATAL_FAILURE(EXPECT_NO_THROW(throw 1), "");
+  EXPECT_ANY_THROW(throw 1);
+  EXPECT_NONFATAL_FAILURE(EXPECT_ANY_THROW(n++), "");
+}
+
+TEST(ExpectThrowTest, DoesNotGenerateDuplicateCatchClauseWarning) {
+  EXPECT_THROW(throw std::exception(), std::exception);
+}
+
+// The following code intentionally tests a suboptimal syntax.
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdangling-else"
+#pragma GCC diagnostic ignored "-Wempty-body"
+#pragma GCC diagnostic ignored "-Wpragmas"
+#endif
+TEST(AssertionSyntaxTest, ExceptionAssertionsBehavesLikeSingleStatement) {
+  if (AlwaysFalse())
+    EXPECT_THROW(ThrowNothing(), bool);
+
+  if (AlwaysTrue())
+    EXPECT_THROW(ThrowAnInteger(), int);
+  else
+    ;  // NOLINT
+
+  if (AlwaysFalse())
+    EXPECT_NO_THROW(ThrowAnInteger());
+
+  if (AlwaysTrue())
+    EXPECT_NO_THROW(ThrowNothing());
+  else
+    ;  // NOLINT
+
+  if (AlwaysFalse())
+    EXPECT_ANY_THROW(ThrowNothing());
+
+  if (AlwaysTrue())
+    EXPECT_ANY_THROW(ThrowAnInteger());
+  else
+    ;  // NOLINT
+}
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif
+
+#endif  // GTEST_HAS_EXCEPTIONS
+
+// The following code intentionally tests a suboptimal syntax.
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdangling-else"
+#pragma GCC diagnostic ignored "-Wempty-body"
+#pragma GCC diagnostic ignored "-Wpragmas"
+#endif
+TEST(AssertionSyntaxTest, NoFatalFailureAssertionsBehavesLikeSingleStatement) {
+  if (AlwaysFalse())
+    EXPECT_NO_FATAL_FAILURE(FAIL()) << "This should never be executed. "
+                                    << "It's a compilation test only.";
+  else
+    ;  // NOLINT
+
+  if (AlwaysFalse())
+    ASSERT_NO_FATAL_FAILURE(FAIL()) << "";
+  else
+    ;  // NOLINT
+
+  if (AlwaysTrue())
+    EXPECT_NO_FATAL_FAILURE(SUCCEED());
+  else
+    ;  // NOLINT
+
+  if (AlwaysFalse())
+    ;  // NOLINT
+  else
+    ASSERT_NO_FATAL_FAILURE(SUCCEED());
+}
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif
+
+// Tests that the assertion macros work well with switch statements.
+TEST(AssertionSyntaxTest, WorksWithSwitch) {
+  switch (0) {
+    case 1:
+      break;
+    default:
+      ASSERT_TRUE(true);
+  }
+
+  switch (0)
+    case 0:
+      EXPECT_FALSE(false) << "EXPECT_FALSE failed in switch case";
+
+  // Binary assertions are implemented using a different code path
+  // than the Boolean assertions.  Hence we test them separately.
+  switch (0) {
+    case 1:
+    default:
+      ASSERT_EQ(1, 1) << "ASSERT_EQ failed in default switch handler";
+  }
+
+  switch (0)
+    case 0:
+      EXPECT_NE(1, 2);
+}
+
+#if GTEST_HAS_EXCEPTIONS
+
+void ThrowAString() {
+    throw "std::string";
+}
+
+// Test that the exception assertion macros compile and work with const
+// type qualifier.
+TEST(AssertionSyntaxTest, WorksWithConst) {
+    ASSERT_THROW(ThrowAString(), const char*);
+
+    EXPECT_THROW(ThrowAString(), const char*);
+}
+
+#endif  // GTEST_HAS_EXCEPTIONS
+
+}  // namespace
+
+namespace testing {
+
+// Tests that Google Test tracks SUCCEED*.
+TEST(SuccessfulAssertionTest, SUCCEED) {
+  SUCCEED();
+  SUCCEED() << "OK";
+  EXPECT_EQ(2, GetUnitTestImpl()->current_test_result()->total_part_count());
+}
+
+// Tests that Google Test doesn't track successful EXPECT_*.
+TEST(SuccessfulAssertionTest, EXPECT) {
+  EXPECT_TRUE(true);
+  EXPECT_EQ(0, GetUnitTestImpl()->current_test_result()->total_part_count());
+}
+
+// Tests that Google Test doesn't track successful EXPECT_STR*.
+TEST(SuccessfulAssertionTest, EXPECT_STR) {
+  EXPECT_STREQ("", "");
+  EXPECT_EQ(0, GetUnitTestImpl()->current_test_result()->total_part_count());
+}
+
+// Tests that Google Test doesn't track successful ASSERT_*.
+TEST(SuccessfulAssertionTest, ASSERT) {
+  ASSERT_TRUE(true);
+  EXPECT_EQ(0, GetUnitTestImpl()->current_test_result()->total_part_count());
+}
+
+// Tests that Google Test doesn't track successful ASSERT_STR*.
+TEST(SuccessfulAssertionTest, ASSERT_STR) {
+  ASSERT_STREQ("", "");
+  EXPECT_EQ(0, GetUnitTestImpl()->current_test_result()->total_part_count());
+}
+
+}  // namespace testing
+
+namespace {
+
+// Tests the message streaming variation of assertions.
+
+TEST(AssertionWithMessageTest, EXPECT) {
+  EXPECT_EQ(1, 1) << "This should succeed.";
+  EXPECT_NONFATAL_FAILURE(EXPECT_NE(1, 1) << "Expected failure #1.",
+                          "Expected failure #1");
+  EXPECT_LE(1, 2) << "This should succeed.";
+  EXPECT_NONFATAL_FAILURE(EXPECT_LT(1, 0) << "Expected failure #2.",
+                          "Expected failure #2.");
+  EXPECT_GE(1, 0) << "This should succeed.";
+  EXPECT_NONFATAL_FAILURE(EXPECT_GT(1, 2) << "Expected failure #3.",
+                          "Expected failure #3.");
+
+  EXPECT_STREQ("1", "1") << "This should succeed.";
+  EXPECT_NONFATAL_FAILURE(EXPECT_STRNE("1", "1") << "Expected failure #4.",
+                          "Expected failure #4.");
+  EXPECT_STRCASEEQ("a", "A") << "This should succeed.";
+  EXPECT_NONFATAL_FAILURE(EXPECT_STRCASENE("a", "A") << "Expected failure #5.",
+                          "Expected failure #5.");
+
+  EXPECT_FLOAT_EQ(1, 1) << "This should succeed.";
+  EXPECT_NONFATAL_FAILURE(EXPECT_DOUBLE_EQ(1, 1.2) << "Expected failure #6.",
+                          "Expected failure #6.");
+  EXPECT_NEAR(1, 1.1, 0.2) << "This should succeed.";
+}
+
+TEST(AssertionWithMessageTest, ASSERT) {
+  ASSERT_EQ(1, 1) << "This should succeed.";
+  ASSERT_NE(1, 2) << "This should succeed.";
+  ASSERT_LE(1, 2) << "This should succeed.";
+  ASSERT_LT(1, 2) << "This should succeed.";
+  ASSERT_GE(1, 0) << "This should succeed.";
+  EXPECT_FATAL_FAILURE(ASSERT_GT(1, 2) << "Expected failure.",
+                       "Expected failure.");
+}
+
+TEST(AssertionWithMessageTest, ASSERT_STR) {
+  ASSERT_STREQ("1", "1") << "This should succeed.";
+  ASSERT_STRNE("1", "2") << "This should succeed.";
+  ASSERT_STRCASEEQ("a", "A") << "This should succeed.";
+  EXPECT_FATAL_FAILURE(ASSERT_STRCASENE("a", "A") << "Expected failure.",
+                       "Expected failure.");
+}
+
+TEST(AssertionWithMessageTest, ASSERT_FLOATING) {
+  ASSERT_FLOAT_EQ(1, 1) << "This should succeed.";
+  ASSERT_DOUBLE_EQ(1, 1) << "This should succeed.";
+  EXPECT_FATAL_FAILURE(ASSERT_NEAR(1, 1.2, 0.1) << "Expect failure.",  // NOLINT
+                       "Expect failure.");
+}
+
+// Tests using ASSERT_FALSE with a streamed message.
+TEST(AssertionWithMessageTest, ASSERT_FALSE) {
+  ASSERT_FALSE(false) << "This shouldn't fail.";
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_FALSE(true) << "Expected failure: " << 2 << " > " << 1
+                       << " evaluates to " << true;
+  }, "Expected failure");
+}
+
+// Tests using FAIL with a streamed message.
+TEST(AssertionWithMessageTest, FAIL) {
+  EXPECT_FATAL_FAILURE(FAIL() << 0,
+                       "0");
+}
+
+// Tests using SUCCEED with a streamed message.
+TEST(AssertionWithMessageTest, SUCCEED) {
+  SUCCEED() << "Success == " << 1;
+}
+
+// Tests using ASSERT_TRUE with a streamed message.
+TEST(AssertionWithMessageTest, ASSERT_TRUE) {
+  ASSERT_TRUE(true) << "This should succeed.";
+  ASSERT_TRUE(true) << true;
+  EXPECT_FATAL_FAILURE(
+      {  // NOLINT
+        ASSERT_TRUE(false) << static_cast<const char*>(nullptr)
+                           << static_cast<char*>(nullptr);
+      },
+      "(null)(null)");
+}
+
+#if GTEST_OS_WINDOWS
+// Tests using wide strings in assertion messages.
+TEST(AssertionWithMessageTest, WideStringMessage) {
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_TRUE(false) << L"This failure is expected.\x8119";
+  }, "This failure is expected.");
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_EQ(1, 2) << "This failure is "
+                    << L"expected too.\x8120";
+  }, "This failure is expected too.");
+}
+#endif  // GTEST_OS_WINDOWS
+
+// Tests EXPECT_TRUE.
+TEST(ExpectTest, EXPECT_TRUE) {
+  EXPECT_TRUE(true) << "Intentional success";
+  EXPECT_NONFATAL_FAILURE(EXPECT_TRUE(false) << "Intentional failure #1.",
+                          "Intentional failure #1.");
+  EXPECT_NONFATAL_FAILURE(EXPECT_TRUE(false) << "Intentional failure #2.",
+                          "Intentional failure #2.");
+  EXPECT_TRUE(2 > 1);  // NOLINT
+  EXPECT_NONFATAL_FAILURE(EXPECT_TRUE(2 < 1),
+                          "Value of: 2 < 1\n"
+                          "  Actual: false\n"
+                          "Expected: true");
+  EXPECT_NONFATAL_FAILURE(EXPECT_TRUE(2 > 3),
+                          "2 > 3");
+}
+
+// Tests EXPECT_TRUE(predicate) for predicates returning AssertionResult.
+TEST(ExpectTest, ExpectTrueWithAssertionResult) {
+  EXPECT_TRUE(ResultIsEven(2));
+  EXPECT_NONFATAL_FAILURE(EXPECT_TRUE(ResultIsEven(3)),
+                          "Value of: ResultIsEven(3)\n"
+                          "  Actual: false (3 is odd)\n"
+                          "Expected: true");
+  EXPECT_TRUE(ResultIsEvenNoExplanation(2));
+  EXPECT_NONFATAL_FAILURE(EXPECT_TRUE(ResultIsEvenNoExplanation(3)),
+                          "Value of: ResultIsEvenNoExplanation(3)\n"
+                          "  Actual: false (3 is odd)\n"
+                          "Expected: true");
+}
+
+// Tests EXPECT_FALSE with a streamed message.
+TEST(ExpectTest, EXPECT_FALSE) {
+  EXPECT_FALSE(2 < 1);  // NOLINT
+  EXPECT_FALSE(false) << "Intentional success";
+  EXPECT_NONFATAL_FAILURE(EXPECT_FALSE(true) << "Intentional failure #1.",
+                          "Intentional failure #1.");
+  EXPECT_NONFATAL_FAILURE(EXPECT_FALSE(true) << "Intentional failure #2.",
+                          "Intentional failure #2.");
+  EXPECT_NONFATAL_FAILURE(EXPECT_FALSE(2 > 1),
+                          "Value of: 2 > 1\n"
+                          "  Actual: true\n"
+                          "Expected: false");
+  EXPECT_NONFATAL_FAILURE(EXPECT_FALSE(2 < 3),
+                          "2 < 3");
+}
+
+// Tests EXPECT_FALSE(predicate) for predicates returning AssertionResult.
+TEST(ExpectTest, ExpectFalseWithAssertionResult) {
+  EXPECT_FALSE(ResultIsEven(3));
+  EXPECT_NONFATAL_FAILURE(EXPECT_FALSE(ResultIsEven(2)),
+                          "Value of: ResultIsEven(2)\n"
+                          "  Actual: true (2 is even)\n"
+                          "Expected: false");
+  EXPECT_FALSE(ResultIsEvenNoExplanation(3));
+  EXPECT_NONFATAL_FAILURE(EXPECT_FALSE(ResultIsEvenNoExplanation(2)),
+                          "Value of: ResultIsEvenNoExplanation(2)\n"
+                          "  Actual: true\n"
+                          "Expected: false");
+}
+
+#ifdef __BORLANDC__
+// Restores warnings after previous "#pragma option push" suppressed them
+# pragma option pop
+#endif
+
+// Tests EXPECT_EQ.
+TEST(ExpectTest, EXPECT_EQ) {
+  EXPECT_EQ(5, 2 + 3);
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(5, 2*3),
+                          "Expected equality of these values:\n"
+                          "  5\n"
+                          "  2*3\n"
+                          "    Which is: 6");
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(5, 2 - 3),
+                          "2 - 3");
+}
+
+// Tests using EXPECT_EQ on double values.  The purpose is to make
+// sure that the specialization we did for integer and anonymous enums
+// isn't used for double arguments.
+TEST(ExpectTest, EXPECT_EQ_Double) {
+  // A success.
+  EXPECT_EQ(5.6, 5.6);
+
+  // A failure.
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(5.1, 5.2),
+                          "5.1");
+}
+
+// Tests EXPECT_EQ(NULL, pointer).
+TEST(ExpectTest, EXPECT_EQ_NULL) {
+  // A success.
+  const char* p = nullptr;
+  EXPECT_EQ(nullptr, p);
+
+  // A failure.
+  int n = 0;
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(nullptr, &n), "  &n\n    Which is:");
+}
+
+// Tests EXPECT_EQ(0, non_pointer).  Since the literal 0 can be
+// treated as a null pointer by the compiler, we need to make sure
+// that EXPECT_EQ(0, non_pointer) isn't interpreted by Google Test as
+// EXPECT_EQ(static_cast<void*>(NULL), non_pointer).
+TEST(ExpectTest, EXPECT_EQ_0) {
+  int n = 0;
+
+  // A success.
+  EXPECT_EQ(0, n);
+
+  // A failure.
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(0, 5.6),
+                          "  0\n  5.6");
+}
+
+// Tests EXPECT_NE.
+TEST(ExpectTest, EXPECT_NE) {
+  EXPECT_NE(6, 7);
+
+  EXPECT_NONFATAL_FAILURE(EXPECT_NE('a', 'a'),
+                          "Expected: ('a') != ('a'), "
+                          "actual: 'a' (97, 0x61) vs 'a' (97, 0x61)");
+  EXPECT_NONFATAL_FAILURE(EXPECT_NE(2, 2),
+                          "2");
+  char* const p0 = nullptr;
+  EXPECT_NONFATAL_FAILURE(EXPECT_NE(p0, p0),
+                          "p0");
+  // Only way to get the Nokia compiler to compile the cast
+  // is to have a separate void* variable first. Putting
+  // the two casts on the same line doesn't work, neither does
+  // a direct C-style to char*.
+  void* pv1 = (void*)0x1234;  // NOLINT
+  char* const p1 = reinterpret_cast<char*>(pv1);
+  EXPECT_NONFATAL_FAILURE(EXPECT_NE(p1, p1),
+                          "p1");
+}
+
+// Tests EXPECT_LE.
+TEST(ExpectTest, EXPECT_LE) {
+  EXPECT_LE(2, 3);
+  EXPECT_LE(2, 2);
+  EXPECT_NONFATAL_FAILURE(EXPECT_LE(2, 0),
+                          "Expected: (2) <= (0), actual: 2 vs 0");
+  EXPECT_NONFATAL_FAILURE(EXPECT_LE(1.1, 0.9),
+                          "(1.1) <= (0.9)");
+}
+
+// Tests EXPECT_LT.
+TEST(ExpectTest, EXPECT_LT) {
+  EXPECT_LT(2, 3);
+  EXPECT_NONFATAL_FAILURE(EXPECT_LT(2, 2),
+                          "Expected: (2) < (2), actual: 2 vs 2");
+  EXPECT_NONFATAL_FAILURE(EXPECT_LT(2, 1),
+                          "(2) < (1)");
+}
+
+// Tests EXPECT_GE.
+TEST(ExpectTest, EXPECT_GE) {
+  EXPECT_GE(2, 1);
+  EXPECT_GE(2, 2);
+  EXPECT_NONFATAL_FAILURE(EXPECT_GE(2, 3),
+                          "Expected: (2) >= (3), actual: 2 vs 3");
+  EXPECT_NONFATAL_FAILURE(EXPECT_GE(0.9, 1.1),
+                          "(0.9) >= (1.1)");
+}
+
+// Tests EXPECT_GT.
+TEST(ExpectTest, EXPECT_GT) {
+  EXPECT_GT(2, 1);
+  EXPECT_NONFATAL_FAILURE(EXPECT_GT(2, 2),
+                          "Expected: (2) > (2), actual: 2 vs 2");
+  EXPECT_NONFATAL_FAILURE(EXPECT_GT(2, 3),
+                          "(2) > (3)");
+}
+
+#if GTEST_HAS_EXCEPTIONS
+
+// Tests EXPECT_THROW.
+TEST(ExpectTest, EXPECT_THROW) {
+  EXPECT_THROW(ThrowAnInteger(), int);
+  EXPECT_NONFATAL_FAILURE(EXPECT_THROW(ThrowAnInteger(), bool),
+                          "Expected: ThrowAnInteger() throws an exception of "
+                          "type bool.\n  Actual: it throws a different type.");
+  EXPECT_NONFATAL_FAILURE(EXPECT_THROW(ThrowRuntimeError("A description"),
+                                       std::logic_error),
+                          "Expected: ThrowRuntimeError(\"A description\") "
+                          "throws an exception of type std::logic_error.\n  "
+                          "Actual: it throws " ERROR_DESC " "
+                          "with description \"A description\".");
+  EXPECT_NONFATAL_FAILURE(
+      EXPECT_THROW(ThrowNothing(), bool),
+      "Expected: ThrowNothing() throws an exception of type bool.\n"
+      "  Actual: it throws nothing.");
+}
+
+// Tests EXPECT_NO_THROW.
+TEST(ExpectTest, EXPECT_NO_THROW) {
+  EXPECT_NO_THROW(ThrowNothing());
+  EXPECT_NONFATAL_FAILURE(EXPECT_NO_THROW(ThrowAnInteger()),
+                          "Expected: ThrowAnInteger() doesn't throw an "
+                          "exception.\n  Actual: it throws.");
+  EXPECT_NONFATAL_FAILURE(EXPECT_NO_THROW(ThrowRuntimeError("A description")),
+                          "Expected: ThrowRuntimeError(\"A description\") "
+                          "doesn't throw an exception.\n  "
+                          "Actual: it throws " ERROR_DESC " "
+                          "with description \"A description\".");
+}
+
+// Tests EXPECT_ANY_THROW.
+TEST(ExpectTest, EXPECT_ANY_THROW) {
+  EXPECT_ANY_THROW(ThrowAnInteger());
+  EXPECT_NONFATAL_FAILURE(
+      EXPECT_ANY_THROW(ThrowNothing()),
+      "Expected: ThrowNothing() throws an exception.\n"
+      "  Actual: it doesn't.");
+}
+
+#endif  // GTEST_HAS_EXCEPTIONS
+
+// Make sure we deal with the precedence of <<.
+TEST(ExpectTest, ExpectPrecedence) {
+  EXPECT_EQ(1 < 2, true);
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(true, true && false),
+                          "  true && false\n    Which is: false");
+}
+
+
+// Tests the StreamableToString() function.
+
+// Tests using StreamableToString() on a scalar.
+TEST(StreamableToStringTest, Scalar) {
+  EXPECT_STREQ("5", StreamableToString(5).c_str());
+}
+
+// Tests using StreamableToString() on a non-char pointer.
+TEST(StreamableToStringTest, Pointer) {
+  int n = 0;
+  int* p = &n;
+  EXPECT_STRNE("(null)", StreamableToString(p).c_str());
+}
+
+// Tests using StreamableToString() on a NULL non-char pointer.
+TEST(StreamableToStringTest, NullPointer) {
+  int* p = nullptr;
+  EXPECT_STREQ("(null)", StreamableToString(p).c_str());
+}
+
+// Tests using StreamableToString() on a C string.
+TEST(StreamableToStringTest, CString) {
+  EXPECT_STREQ("Foo", StreamableToString("Foo").c_str());
+}
+
+// Tests using StreamableToString() on a NULL C string.
+TEST(StreamableToStringTest, NullCString) {
+  char* p = nullptr;
+  EXPECT_STREQ("(null)", StreamableToString(p).c_str());
+}
+
+// Tests using streamable values as assertion messages.
+
+// Tests using std::string as an assertion message.
+TEST(StreamableTest, string) {
+  static const std::string str(
+      "This failure message is a std::string, and is expected.");
+  EXPECT_FATAL_FAILURE(FAIL() << str,
+                       str.c_str());
+}
+
+// Tests that we can output strings containing embedded NULs.
+// Limited to Linux because we can only do this with std::string's.
+TEST(StreamableTest, stringWithEmbeddedNUL) {
+  static const char char_array_with_nul[] =
+      "Here's a NUL\0 and some more string";
+  static const std::string string_with_nul(char_array_with_nul,
+                                           sizeof(char_array_with_nul)
+                                           - 1);  // drops the trailing NUL
+  EXPECT_FATAL_FAILURE(FAIL() << string_with_nul,
+                       "Here's a NUL\\0 and some more string");
+}
+
+// Tests that we can output a NUL char.
+TEST(StreamableTest, NULChar) {
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    FAIL() << "A NUL" << '\0' << " and some more string";
+  }, "A NUL\\0 and some more string");
+}
+
+// Tests using int as an assertion message.
+TEST(StreamableTest, int) {
+  EXPECT_FATAL_FAILURE(FAIL() << 900913,
+                       "900913");
+}
+
+// Tests using NULL char pointer as an assertion message.
+//
+// In MSVC, streaming a NULL char * causes access violation.  Google Test
+// implemented a workaround (substituting "(null)" for NULL).  This
+// tests whether the workaround works.
+TEST(StreamableTest, NullCharPtr) {
+  EXPECT_FATAL_FAILURE(FAIL() << static_cast<const char*>(nullptr), "(null)");
+}
+
+// Tests that basic IO manipulators (endl, ends, and flush) can be
+// streamed to testing::Message.
+TEST(StreamableTest, BasicIoManip) {
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    FAIL() << "Line 1." << std::endl
+           << "A NUL char " << std::ends << std::flush << " in line 2.";
+  }, "Line 1.\nA NUL char \\0 in line 2.");
+}
+
+// Tests the macros that haven't been covered so far.
+
+void AddFailureHelper(bool* aborted) {
+  *aborted = true;
+  ADD_FAILURE() << "Intentional failure.";
+  *aborted = false;
+}
+
+// Tests ADD_FAILURE.
+TEST(MacroTest, ADD_FAILURE) {
+  bool aborted = true;
+  EXPECT_NONFATAL_FAILURE(AddFailureHelper(&aborted),
+                          "Intentional failure.");
+  EXPECT_FALSE(aborted);
+}
+
+// Tests ADD_FAILURE_AT.
+TEST(MacroTest, ADD_FAILURE_AT) {
+  // Verifies that ADD_FAILURE_AT does generate a nonfatal failure and
+  // the failure message contains the user-streamed part.
+  EXPECT_NONFATAL_FAILURE(ADD_FAILURE_AT("foo.cc", 42) << "Wrong!", "Wrong!");
+
+  // Verifies that the user-streamed part is optional.
+  EXPECT_NONFATAL_FAILURE(ADD_FAILURE_AT("foo.cc", 42), "Failed");
+
+  // Unfortunately, we cannot verify that the failure message contains
+  // the right file path and line number the same way, as
+  // EXPECT_NONFATAL_FAILURE() doesn't get to see the file path and
+  // line number.  Instead, we do that in googletest-output-test_.cc.
+}
+
+// Tests FAIL.
+TEST(MacroTest, FAIL) {
+  EXPECT_FATAL_FAILURE(FAIL(),
+                       "Failed");
+  EXPECT_FATAL_FAILURE(FAIL() << "Intentional failure.",
+                       "Intentional failure.");
+}
+
+// Tests GTEST_FAIL_AT.
+TEST(MacroTest, GTEST_FAIL_AT) {
+  // Verifies that GTEST_FAIL_AT does generate a fatal failure and
+  // the failure message contains the user-streamed part.
+  EXPECT_FATAL_FAILURE(GTEST_FAIL_AT("foo.cc", 42) << "Wrong!", "Wrong!");
+
+  // Verifies that the user-streamed part is optional.
+  EXPECT_FATAL_FAILURE(GTEST_FAIL_AT("foo.cc", 42), "Failed");
+
+  // See the ADD_FAIL_AT test above to see how we test that the failure message
+  // contains the right filename and line number -- the same applies here.
+}
+
+// Tests SUCCEED
+TEST(MacroTest, SUCCEED) {
+  SUCCEED();
+  SUCCEED() << "Explicit success.";
+}
+
+// Tests for EXPECT_EQ() and ASSERT_EQ().
+//
+// These tests fail *intentionally*, s.t. the failure messages can be
+// generated and tested.
+//
+// We have different tests for different argument types.
+
+// Tests using bool values in {EXPECT|ASSERT}_EQ.
+TEST(EqAssertionTest, Bool) {
+  EXPECT_EQ(true,  true);
+  EXPECT_FATAL_FAILURE({
+      bool false_value = false;
+      ASSERT_EQ(false_value, true);
+    }, "  false_value\n    Which is: false\n  true");
+}
+
+// Tests using int values in {EXPECT|ASSERT}_EQ.
+TEST(EqAssertionTest, Int) {
+  ASSERT_EQ(32, 32);
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(32, 33),
+                          "  32\n  33");
+}
+
+// Tests using time_t values in {EXPECT|ASSERT}_EQ.
+TEST(EqAssertionTest, Time_T) {
+  EXPECT_EQ(static_cast<time_t>(0),
+            static_cast<time_t>(0));
+  EXPECT_FATAL_FAILURE(ASSERT_EQ(static_cast<time_t>(0),
+                                 static_cast<time_t>(1234)),
+                       "1234");
+}
+
+// Tests using char values in {EXPECT|ASSERT}_EQ.
+TEST(EqAssertionTest, Char) {
+  ASSERT_EQ('z', 'z');
+  const char ch = 'b';
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ('\0', ch),
+                          "  ch\n    Which is: 'b'");
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ('a', ch),
+                          "  ch\n    Which is: 'b'");
+}
+
+// Tests using wchar_t values in {EXPECT|ASSERT}_EQ.
+TEST(EqAssertionTest, WideChar) {
+  EXPECT_EQ(L'b', L'b');
+
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(L'\0', L'x'),
+                          "Expected equality of these values:\n"
+                          "  L'\0'\n"
+                          "    Which is: L'\0' (0, 0x0)\n"
+                          "  L'x'\n"
+                          "    Which is: L'x' (120, 0x78)");
+
+  static wchar_t wchar;
+  wchar = L'b';
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(L'a', wchar),
+                          "wchar");
+  wchar = 0x8119;
+  EXPECT_FATAL_FAILURE(ASSERT_EQ(static_cast<wchar_t>(0x8120), wchar),
+                       "  wchar\n    Which is: L'");
+}
+
+// Tests using ::std::string values in {EXPECT|ASSERT}_EQ.
+TEST(EqAssertionTest, StdString) {
+  // Compares a const char* to an std::string that has identical
+  // content.
+  ASSERT_EQ("Test", ::std::string("Test"));
+
+  // Compares two identical std::strings.
+  static const ::std::string str1("A * in the middle");
+  static const ::std::string str2(str1);
+  EXPECT_EQ(str1, str2);
+
+  // Compares a const char* to an std::string that has different
+  // content
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ("Test", ::std::string("test")),
+                          "\"test\"");
+
+  // Compares an std::string to a char* that has different content.
+  char* const p1 = const_cast<char*>("foo");
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(::std::string("bar"), p1),
+                          "p1");
+
+  // Compares two std::strings that have different contents, one of
+  // which having a NUL character in the middle.  This should fail.
+  static ::std::string str3(str1);
+  str3.at(2) = '\0';
+  EXPECT_FATAL_FAILURE(ASSERT_EQ(str1, str3),
+                       "  str3\n    Which is: \"A \\0 in the middle\"");
+}
+
+#if GTEST_HAS_STD_WSTRING
+
+// Tests using ::std::wstring values in {EXPECT|ASSERT}_EQ.
+TEST(EqAssertionTest, StdWideString) {
+  // Compares two identical std::wstrings.
+  const ::std::wstring wstr1(L"A * in the middle");
+  const ::std::wstring wstr2(wstr1);
+  ASSERT_EQ(wstr1, wstr2);
+
+  // Compares an std::wstring to a const wchar_t* that has identical
+  // content.
+  const wchar_t kTestX8119[] = { 'T', 'e', 's', 't', 0x8119, '\0' };
+  EXPECT_EQ(::std::wstring(kTestX8119), kTestX8119);
+
+  // Compares an std::wstring to a const wchar_t* that has different
+  // content.
+  const wchar_t kTestX8120[] = { 'T', 'e', 's', 't', 0x8120, '\0' };
+  EXPECT_NONFATAL_FAILURE({  // NOLINT
+    EXPECT_EQ(::std::wstring(kTestX8119), kTestX8120);
+  }, "kTestX8120");
+
+  // Compares two std::wstrings that have different contents, one of
+  // which having a NUL character in the middle.
+  ::std::wstring wstr3(wstr1);
+  wstr3.at(2) = L'\0';
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(wstr1, wstr3),
+                          "wstr3");
+
+  // Compares a wchar_t* to an std::wstring that has different
+  // content.
+  EXPECT_FATAL_FAILURE({  // NOLINT
+    ASSERT_EQ(const_cast<wchar_t*>(L"foo"), ::std::wstring(L"bar"));
+  }, "");
+}
+
+#endif  // GTEST_HAS_STD_WSTRING
+
+// Tests using char pointers in {EXPECT|ASSERT}_EQ.
+TEST(EqAssertionTest, CharPointer) {
+  char* const p0 = nullptr;
+  // Only way to get the Nokia compiler to compile the cast
+  // is to have a separate void* variable first. Putting
+  // the two casts on the same line doesn't work, neither does
+  // a direct C-style to char*.
+  void* pv1 = (void*)0x1234;  // NOLINT
+  void* pv2 = (void*)0xABC0;  // NOLINT
+  char* const p1 = reinterpret_cast<char*>(pv1);
+  char* const p2 = reinterpret_cast<char*>(pv2);
+  ASSERT_EQ(p1, p1);
+
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(p0, p2),
+                          "  p2\n    Which is:");
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(p1, p2),
+                          "  p2\n    Which is:");
+  EXPECT_FATAL_FAILURE(ASSERT_EQ(reinterpret_cast<char*>(0x1234),
+                                 reinterpret_cast<char*>(0xABC0)),
+                       "ABC0");
+}
+
+// Tests using wchar_t pointers in {EXPECT|ASSERT}_EQ.
+TEST(EqAssertionTest, WideCharPointer) {
+  wchar_t* const p0 = nullptr;
+  // Only way to get the Nokia compiler to compile the cast
+  // is to have a separate void* variable first. Putting
+  // the two casts on the same line doesn't work, neither does
+  // a direct C-style to char*.
+  void* pv1 = (void*)0x1234;  // NOLINT
+  void* pv2 = (void*)0xABC0;  // NOLINT
+  wchar_t* const p1 = reinterpret_cast<wchar_t*>(pv1);
+  wchar_t* const p2 = reinterpret_cast<wchar_t*>(pv2);
+  EXPECT_EQ(p0, p0);
+
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(p0, p2),
+                          "  p2\n    Which is:");
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(p1, p2),
+                          "  p2\n    Which is:");
+  void* pv3 = (void*)0x1234;  // NOLINT
+  void* pv4 = (void*)0xABC0;  // NOLINT
+  const wchar_t* p3 = reinterpret_cast<const wchar_t*>(pv3);
+  const wchar_t* p4 = reinterpret_cast<const wchar_t*>(pv4);
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(p3, p4),
+                          "p4");
+}
+
+// Tests using other types of pointers in {EXPECT|ASSERT}_EQ.
+TEST(EqAssertionTest, OtherPointer) {
+  ASSERT_EQ(static_cast<const int*>(nullptr), static_cast<const int*>(nullptr));
+  EXPECT_FATAL_FAILURE(ASSERT_EQ(static_cast<const int*>(nullptr),
+                                 reinterpret_cast<const int*>(0x1234)),
+                       "0x1234");
+}
+
+// A class that supports binary comparison operators but not streaming.
+class UnprintableChar {
+ public:
+  explicit UnprintableChar(char ch) : char_(ch) {}
+
+  bool operator==(const UnprintableChar& rhs) const {
+    return char_ == rhs.char_;
+  }
+  bool operator!=(const UnprintableChar& rhs) const {
+    return char_ != rhs.char_;
+  }
+  bool operator<(const UnprintableChar& rhs) const {
+    return char_ < rhs.char_;
+  }
+  bool operator<=(const UnprintableChar& rhs) const {
+    return char_ <= rhs.char_;
+  }
+  bool operator>(const UnprintableChar& rhs) const {
+    return char_ > rhs.char_;
+  }
+  bool operator>=(const UnprintableChar& rhs) const {
+    return char_ >= rhs.char_;
+  }
+
+ private:
+  char char_;
+};
+
+// Tests that ASSERT_EQ() and friends don't require the arguments to
+// be printable.
+TEST(ComparisonAssertionTest, AcceptsUnprintableArgs) {
+  const UnprintableChar x('x'), y('y');
+  ASSERT_EQ(x, x);
+  EXPECT_NE(x, y);
+  ASSERT_LT(x, y);
+  EXPECT_LE(x, y);
+  ASSERT_GT(y, x);
+  EXPECT_GE(x, x);
+
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(x, y), "1-byte object <78>");
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(x, y), "1-byte object <79>");
+  EXPECT_NONFATAL_FAILURE(EXPECT_LT(y, y), "1-byte object <79>");
+  EXPECT_NONFATAL_FAILURE(EXPECT_GT(x, y), "1-byte object <78>");
+  EXPECT_NONFATAL_FAILURE(EXPECT_GT(x, y), "1-byte object <79>");
+
+  // Code tested by EXPECT_FATAL_FAILURE cannot reference local
+  // variables, so we have to write UnprintableChar('x') instead of x.
+#ifndef __BORLANDC__
+  // ICE's in C++Builder.
+  EXPECT_FATAL_FAILURE(ASSERT_NE(UnprintableChar('x'), UnprintableChar('x')),
+                       "1-byte object <78>");
+  EXPECT_FATAL_FAILURE(ASSERT_LE(UnprintableChar('y'), UnprintableChar('x')),
+                       "1-byte object <78>");
+#endif
+  EXPECT_FATAL_FAILURE(ASSERT_LE(UnprintableChar('y'), UnprintableChar('x')),
+                       "1-byte object <79>");
+  EXPECT_FATAL_FAILURE(ASSERT_GE(UnprintableChar('x'), UnprintableChar('y')),
+                       "1-byte object <78>");
+  EXPECT_FATAL_FAILURE(ASSERT_GE(UnprintableChar('x'), UnprintableChar('y')),
+                       "1-byte object <79>");
+}
+
+// Tests the FRIEND_TEST macro.
+
+// This class has a private member we want to test.  We will test it
+// both in a TEST and in a TEST_F.
+class Foo {
+ public:
+  Foo() {}
+
+ private:
+  int Bar() const { return 1; }
+
+  // Declares the friend tests that can access the private member
+  // Bar().
+  FRIEND_TEST(FRIEND_TEST_Test, TEST);
+  FRIEND_TEST(FRIEND_TEST_Test2, TEST_F);
+};
+
+// Tests that the FRIEND_TEST declaration allows a TEST to access a
+// class's private members.  This should compile.
+TEST(FRIEND_TEST_Test, TEST) {
+  ASSERT_EQ(1, Foo().Bar());
+}
+
+// The fixture needed to test using FRIEND_TEST with TEST_F.
+class FRIEND_TEST_Test2 : public Test {
+ protected:
+  Foo foo;
+};
+
+// Tests that the FRIEND_TEST declaration allows a TEST_F to access a
+// class's private members.  This should compile.
+TEST_F(FRIEND_TEST_Test2, TEST_F) {
+  ASSERT_EQ(1, foo.Bar());
+}
+
+// Tests the life cycle of Test objects.
+
+// The test fixture for testing the life cycle of Test objects.
+//
+// This class counts the number of live test objects that uses this
+// fixture.
+class TestLifeCycleTest : public Test {
+ protected:
+  // Constructor.  Increments the number of test objects that uses
+  // this fixture.
+  TestLifeCycleTest() { count_++; }
+
+  // Destructor.  Decrements the number of test objects that uses this
+  // fixture.
+  ~TestLifeCycleTest() override { count_--; }
+
+  // Returns the number of live test objects that uses this fixture.
+  int count() const { return count_; }
+
+ private:
+  static int count_;
+};
+
+int TestLifeCycleTest::count_ = 0;
+
+// Tests the life cycle of test objects.
+TEST_F(TestLifeCycleTest, Test1) {
+  // There should be only one test object in this test case that's
+  // currently alive.
+  ASSERT_EQ(1, count());
+}
+
+// Tests the life cycle of test objects.
+TEST_F(TestLifeCycleTest, Test2) {
+  // After Test1 is done and Test2 is started, there should still be
+  // only one live test object, as the object for Test1 should've been
+  // deleted.
+  ASSERT_EQ(1, count());
+}
+
+}  // namespace
+
+// Tests that the copy constructor works when it is NOT optimized away by
+// the compiler.
+TEST(AssertionResultTest, CopyConstructorWorksWhenNotOptimied) {
+  // Checks that the copy constructor doesn't try to dereference NULL pointers
+  // in the source object.
+  AssertionResult r1 = AssertionSuccess();
+  AssertionResult r2 = r1;
+  // The following line is added to prevent the compiler from optimizing
+  // away the constructor call.
+  r1 << "abc";
+
+  AssertionResult r3 = r1;
+  EXPECT_EQ(static_cast<bool>(r3), static_cast<bool>(r1));
+  EXPECT_STREQ("abc", r1.message());
+}
+
+// Tests that AssertionSuccess and AssertionFailure construct
+// AssertionResult objects as expected.
+TEST(AssertionResultTest, ConstructionWorks) {
+  AssertionResult r1 = AssertionSuccess();
+  EXPECT_TRUE(r1);
+  EXPECT_STREQ("", r1.message());
+
+  AssertionResult r2 = AssertionSuccess() << "abc";
+  EXPECT_TRUE(r2);
+  EXPECT_STREQ("abc", r2.message());
+
+  AssertionResult r3 = AssertionFailure();
+  EXPECT_FALSE(r3);
+  EXPECT_STREQ("", r3.message());
+
+  AssertionResult r4 = AssertionFailure() << "def";
+  EXPECT_FALSE(r4);
+  EXPECT_STREQ("def", r4.message());
+
+  AssertionResult r5 = AssertionFailure(Message() << "ghi");
+  EXPECT_FALSE(r5);
+  EXPECT_STREQ("ghi", r5.message());
+}
+
+// Tests that the negation flips the predicate result but keeps the message.
+TEST(AssertionResultTest, NegationWorks) {
+  AssertionResult r1 = AssertionSuccess() << "abc";
+  EXPECT_FALSE(!r1);
+  EXPECT_STREQ("abc", (!r1).message());
+
+  AssertionResult r2 = AssertionFailure() << "def";
+  EXPECT_TRUE(!r2);
+  EXPECT_STREQ("def", (!r2).message());
+}
+
+TEST(AssertionResultTest, StreamingWorks) {
+  AssertionResult r = AssertionSuccess();
+  r << "abc" << 'd' << 0 << true;
+  EXPECT_STREQ("abcd0true", r.message());
+}
+
+TEST(AssertionResultTest, CanStreamOstreamManipulators) {
+  AssertionResult r = AssertionSuccess();
+  r << "Data" << std::endl << std::flush << std::ends << "Will be visible";
+  EXPECT_STREQ("Data\n\\0Will be visible", r.message());
+}
+
+// The next test uses explicit conversion operators
+
+TEST(AssertionResultTest, ConstructibleFromContextuallyConvertibleToBool) {
+  struct ExplicitlyConvertibleToBool {
+    explicit operator bool() const { return value; }
+    bool value;
+  };
+  ExplicitlyConvertibleToBool v1 = {false};
+  ExplicitlyConvertibleToBool v2 = {true};
+  EXPECT_FALSE(v1);
+  EXPECT_TRUE(v2);
+}
+
+struct ConvertibleToAssertionResult {
+  operator AssertionResult() const { return AssertionResult(true); }
+};
+
+TEST(AssertionResultTest, ConstructibleFromImplicitlyConvertible) {
+  ConvertibleToAssertionResult obj;
+  EXPECT_TRUE(obj);
+}
+
+// Tests streaming a user type whose definition and operator << are
+// both in the global namespace.
+class Base {
+ public:
+  explicit Base(int an_x) : x_(an_x) {}
+  int x() const { return x_; }
+ private:
+  int x_;
+};
+std::ostream& operator<<(std::ostream& os,
+                         const Base& val) {
+  return os << val.x();
+}
+std::ostream& operator<<(std::ostream& os,
+                         const Base* pointer) {
+  return os << "(" << pointer->x() << ")";
+}
+
+TEST(MessageTest, CanStreamUserTypeInGlobalNameSpace) {
+  Message msg;
+  Base a(1);
+
+  msg << a << &a;  // Uses ::operator<<.
+  EXPECT_STREQ("1(1)", msg.GetString().c_str());
+}
+
+// Tests streaming a user type whose definition and operator<< are
+// both in an unnamed namespace.
+namespace {
+class MyTypeInUnnamedNameSpace : public Base {
+ public:
+  explicit MyTypeInUnnamedNameSpace(int an_x): Base(an_x) {}
+};
+std::ostream& operator<<(std::ostream& os,
+                         const MyTypeInUnnamedNameSpace& val) {
+  return os << val.x();
+}
+std::ostream& operator<<(std::ostream& os,
+                         const MyTypeInUnnamedNameSpace* pointer) {
+  return os << "(" << pointer->x() << ")";
+}
+}  // namespace
+
+TEST(MessageTest, CanStreamUserTypeInUnnamedNameSpace) {
+  Message msg;
+  MyTypeInUnnamedNameSpace a(1);
+
+  msg << a << &a;  // Uses <unnamed_namespace>::operator<<.
+  EXPECT_STREQ("1(1)", msg.GetString().c_str());
+}
+
+// Tests streaming a user type whose definition and operator<< are
+// both in a user namespace.
+namespace namespace1 {
+class MyTypeInNameSpace1 : public Base {
+ public:
+  explicit MyTypeInNameSpace1(int an_x): Base(an_x) {}
+};
+std::ostream& operator<<(std::ostream& os,
+                         const MyTypeInNameSpace1& val) {
+  return os << val.x();
+}
+std::ostream& operator<<(std::ostream& os,
+                         const MyTypeInNameSpace1* pointer) {
+  return os << "(" << pointer->x() << ")";
+}
+}  // namespace namespace1
+
+TEST(MessageTest, CanStreamUserTypeInUserNameSpace) {
+  Message msg;
+  namespace1::MyTypeInNameSpace1 a(1);
+
+  msg << a << &a;  // Uses namespace1::operator<<.
+  EXPECT_STREQ("1(1)", msg.GetString().c_str());
+}
+
+// Tests streaming a user type whose definition is in a user namespace
+// but whose operator<< is in the global namespace.
+namespace namespace2 {
+class MyTypeInNameSpace2 : public ::Base {
+ public:
+  explicit MyTypeInNameSpace2(int an_x): Base(an_x) {}
+};
+}  // namespace namespace2
+std::ostream& operator<<(std::ostream& os,
+                         const namespace2::MyTypeInNameSpace2& val) {
+  return os << val.x();
+}
+std::ostream& operator<<(std::ostream& os,
+                         const namespace2::MyTypeInNameSpace2* pointer) {
+  return os << "(" << pointer->x() << ")";
+}
+
+TEST(MessageTest, CanStreamUserTypeInUserNameSpaceWithStreamOperatorInGlobal) {
+  Message msg;
+  namespace2::MyTypeInNameSpace2 a(1);
+
+  msg << a << &a;  // Uses ::operator<<.
+  EXPECT_STREQ("1(1)", msg.GetString().c_str());
+}
+
+// Tests streaming NULL pointers to testing::Message.
+TEST(MessageTest, NullPointers) {
+  Message msg;
+  char* const p1 = nullptr;
+  unsigned char* const p2 = nullptr;
+  int* p3 = nullptr;
+  double* p4 = nullptr;
+  bool* p5 = nullptr;
+  Message* p6 = nullptr;
+
+  msg << p1 << p2 << p3 << p4 << p5 << p6;
+  ASSERT_STREQ("(null)(null)(null)(null)(null)(null)",
+               msg.GetString().c_str());
+}
+
+// Tests streaming wide strings to testing::Message.
+TEST(MessageTest, WideStrings) {
+  // Streams a NULL of type const wchar_t*.
+  const wchar_t* const_wstr = nullptr;
+  EXPECT_STREQ("(null)",
+               (Message() << const_wstr).GetString().c_str());
+
+  // Streams a NULL of type wchar_t*.
+  wchar_t* wstr = nullptr;
+  EXPECT_STREQ("(null)",
+               (Message() << wstr).GetString().c_str());
+
+  // Streams a non-NULL of type const wchar_t*.
+  const_wstr = L"abc\x8119";
+  EXPECT_STREQ("abc\xe8\x84\x99",
+               (Message() << const_wstr).GetString().c_str());
+
+  // Streams a non-NULL of type wchar_t*.
+  wstr = const_cast<wchar_t*>(const_wstr);
+  EXPECT_STREQ("abc\xe8\x84\x99",
+               (Message() << wstr).GetString().c_str());
+}
+
+
+// This line tests that we can define tests in the testing namespace.
+namespace testing {
+
+// Tests the TestInfo class.
+
+class TestInfoTest : public Test {
+ protected:
+  static const TestInfo* GetTestInfo(const char* test_name) {
+    const TestSuite* const test_suite =
+        GetUnitTestImpl()->GetTestSuite("TestInfoTest", "", nullptr, nullptr);
+
+    for (int i = 0; i < test_suite->total_test_count(); ++i) {
+      const TestInfo* const test_info = test_suite->GetTestInfo(i);
+      if (strcmp(test_name, test_info->name()) == 0)
+        return test_info;
+    }
+    return nullptr;
+  }
+
+  static const TestResult* GetTestResult(
+      const TestInfo* test_info) {
+    return test_info->result();
+  }
+};
+
+// Tests TestInfo::test_case_name() and TestInfo::name().
+TEST_F(TestInfoTest, Names) {
+  const TestInfo* const test_info = GetTestInfo("Names");
+
+  ASSERT_STREQ("TestInfoTest", test_info->test_suite_name());
+  ASSERT_STREQ("Names", test_info->name());
+}
+
+// Tests TestInfo::result().
+TEST_F(TestInfoTest, result) {
+  const TestInfo* const test_info = GetTestInfo("result");
+
+  // Initially, there is no TestPartResult for this test.
+  ASSERT_EQ(0, GetTestResult(test_info)->total_part_count());
+
+  // After the previous assertion, there is still none.
+  ASSERT_EQ(0, GetTestResult(test_info)->total_part_count());
+}
+
+#define VERIFY_CODE_LOCATION \
+  const int expected_line = __LINE__ - 1; \
+  const TestInfo* const test_info = GetUnitTestImpl()->current_test_info(); \
+  ASSERT_TRUE(test_info); \
+  EXPECT_STREQ(__FILE__, test_info->file()); \
+  EXPECT_EQ(expected_line, test_info->line())
+
+TEST(CodeLocationForTEST, Verify) {
+  VERIFY_CODE_LOCATION;
+}
+
+class CodeLocationForTESTF : public Test {
+};
+
+TEST_F(CodeLocationForTESTF, Verify) {
+  VERIFY_CODE_LOCATION;
+}
+
+class CodeLocationForTESTP : public TestWithParam<int> {
+};
+
+TEST_P(CodeLocationForTESTP, Verify) {
+  VERIFY_CODE_LOCATION;
+}
+
+INSTANTIATE_TEST_SUITE_P(, CodeLocationForTESTP, Values(0));
+
+template <typename T>
+class CodeLocationForTYPEDTEST : public Test {
+};
+
+TYPED_TEST_SUITE(CodeLocationForTYPEDTEST, int);
+
+TYPED_TEST(CodeLocationForTYPEDTEST, Verify) {
+  VERIFY_CODE_LOCATION;
+}
+
+template <typename T>
+class CodeLocationForTYPEDTESTP : public Test {
+};
+
+TYPED_TEST_SUITE_P(CodeLocationForTYPEDTESTP);
+
+TYPED_TEST_P(CodeLocationForTYPEDTESTP, Verify) {
+  VERIFY_CODE_LOCATION;
+}
+
+REGISTER_TYPED_TEST_SUITE_P(CodeLocationForTYPEDTESTP, Verify);
+
+INSTANTIATE_TYPED_TEST_SUITE_P(My, CodeLocationForTYPEDTESTP, int);
+
+#undef VERIFY_CODE_LOCATION
+
+// Tests setting up and tearing down a test case.
+// Legacy API is deprecated but still available
+#ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+class SetUpTestCaseTest : public Test {
+ protected:
+  // This will be called once before the first test in this test case
+  // is run.
+  static void SetUpTestCase() {
+    printf("Setting up the test case . . .\n");
+
+    // Initializes some shared resource.  In this simple example, we
+    // just create a C string.  More complex stuff can be done if
+    // desired.
+    shared_resource_ = "123";
+
+    // Increments the number of test cases that have been set up.
+    counter_++;
+
+    // SetUpTestCase() should be called only once.
+    EXPECT_EQ(1, counter_);
+  }
+
+  // This will be called once after the last test in this test case is
+  // run.
+  static void TearDownTestCase() {
+    printf("Tearing down the test case . . .\n");
+
+    // Decrements the number of test cases that have been set up.
+    counter_--;
+
+    // TearDownTestCase() should be called only once.
+    EXPECT_EQ(0, counter_);
+
+    // Cleans up the shared resource.
+    shared_resource_ = nullptr;
+  }
+
+  // This will be called before each test in this test case.
+  void SetUp() override {
+    // SetUpTestCase() should be called only once, so counter_ should
+    // always be 1.
+    EXPECT_EQ(1, counter_);
+  }
+
+  // Number of test cases that have been set up.
+  static int counter_;
+
+  // Some resource to be shared by all tests in this test case.
+  static const char* shared_resource_;
+};
+
+int SetUpTestCaseTest::counter_ = 0;
+const char* SetUpTestCaseTest::shared_resource_ = nullptr;
+
+// A test that uses the shared resource.
+TEST_F(SetUpTestCaseTest, Test1) { EXPECT_STRNE(nullptr, shared_resource_); }
+
+// Another test that uses the shared resource.
+TEST_F(SetUpTestCaseTest, Test2) {
+  EXPECT_STREQ("123", shared_resource_);
+}
+#endif  //  GTEST_REMOVE_LEGACY_TEST_CASEAPI_
+
+// Tests SetupTestSuite/TearDown TestSuite
+class SetUpTestSuiteTest : public Test {
+ protected:
+  // This will be called once before the first test in this test case
+  // is run.
+  static void SetUpTestSuite() {
+    printf("Setting up the test suite . . .\n");
+
+    // Initializes some shared resource.  In this simple example, we
+    // just create a C string.  More complex stuff can be done if
+    // desired.
+    shared_resource_ = "123";
+
+    // Increments the number of test cases that have been set up.
+    counter_++;
+
+    // SetUpTestSuite() should be called only once.
+    EXPECT_EQ(1, counter_);
+  }
+
+  // This will be called once after the last test in this test case is
+  // run.
+  static void TearDownTestSuite() {
+    printf("Tearing down the test suite . . .\n");
+
+    // Decrements the number of test suites that have been set up.
+    counter_--;
+
+    // TearDownTestSuite() should be called only once.
+    EXPECT_EQ(0, counter_);
+
+    // Cleans up the shared resource.
+    shared_resource_ = nullptr;
+  }
+
+  // This will be called before each test in this test case.
+  void SetUp() override {
+    // SetUpTestSuite() should be called only once, so counter_ should
+    // always be 1.
+    EXPECT_EQ(1, counter_);
+  }
+
+  // Number of test suites that have been set up.
+  static int counter_;
+
+  // Some resource to be shared by all tests in this test case.
+  static const char* shared_resource_;
+};
+
+int SetUpTestSuiteTest::counter_ = 0;
+const char* SetUpTestSuiteTest::shared_resource_ = nullptr;
+
+// A test that uses the shared resource.
+TEST_F(SetUpTestSuiteTest, TestSetupTestSuite1) {
+  EXPECT_STRNE(nullptr, shared_resource_);
+}
+
+// Another test that uses the shared resource.
+TEST_F(SetUpTestSuiteTest, TestSetupTestSuite2) {
+  EXPECT_STREQ("123", shared_resource_);
+}
+
+// The ParseFlagsTest test case tests ParseGoogleTestFlagsOnly.
+
+// The Flags struct stores a copy of all Google Test flags.
+struct Flags {
+  // Constructs a Flags struct where each flag has its default value.
+  Flags()
+      : also_run_disabled_tests(false),
+        break_on_failure(false),
+        catch_exceptions(false),
+        death_test_use_fork(false),
+        fail_fast(false),
+        filter(""),
+        list_tests(false),
+        output(""),
+        brief(false),
+        print_time(true),
+        random_seed(0),
+        repeat(1),
+        shuffle(false),
+        stack_trace_depth(kMaxStackTraceDepth),
+        stream_result_to(""),
+        throw_on_failure(false) {}
+
+  // Factory methods.
+
+  // Creates a Flags struct where the gtest_also_run_disabled_tests flag has
+  // the given value.
+  static Flags AlsoRunDisabledTests(bool also_run_disabled_tests) {
+    Flags flags;
+    flags.also_run_disabled_tests = also_run_disabled_tests;
+    return flags;
+  }
+
+  // Creates a Flags struct where the gtest_break_on_failure flag has
+  // the given value.
+  static Flags BreakOnFailure(bool break_on_failure) {
+    Flags flags;
+    flags.break_on_failure = break_on_failure;
+    return flags;
+  }
+
+  // Creates a Flags struct where the gtest_catch_exceptions flag has
+  // the given value.
+  static Flags CatchExceptions(bool catch_exceptions) {
+    Flags flags;
+    flags.catch_exceptions = catch_exceptions;
+    return flags;
+  }
+
+  // Creates a Flags struct where the gtest_death_test_use_fork flag has
+  // the given value.
+  static Flags DeathTestUseFork(bool death_test_use_fork) {
+    Flags flags;
+    flags.death_test_use_fork = death_test_use_fork;
+    return flags;
+  }
+
+  // Creates a Flags struct where the gtest_fail_fast flag has
+  // the given value.
+  static Flags FailFast(bool fail_fast) {
+    Flags flags;
+    flags.fail_fast = fail_fast;
+    return flags;
+  }
+
+  // Creates a Flags struct where the gtest_filter flag has the given
+  // value.
+  static Flags Filter(const char* filter) {
+    Flags flags;
+    flags.filter = filter;
+    return flags;
+  }
+
+  // Creates a Flags struct where the gtest_list_tests flag has the
+  // given value.
+  static Flags ListTests(bool list_tests) {
+    Flags flags;
+    flags.list_tests = list_tests;
+    return flags;
+  }
+
+  // Creates a Flags struct where the gtest_output flag has the given
+  // value.
+  static Flags Output(const char* output) {
+    Flags flags;
+    flags.output = output;
+    return flags;
+  }
+
+  // Creates a Flags struct where the gtest_brief flag has the given
+  // value.
+  static Flags Brief(bool brief) {
+    Flags flags;
+    flags.brief = brief;
+    return flags;
+  }
+
+  // Creates a Flags struct where the gtest_print_time flag has the given
+  // value.
+  static Flags PrintTime(bool print_time) {
+    Flags flags;
+    flags.print_time = print_time;
+    return flags;
+  }
+
+  // Creates a Flags struct where the gtest_random_seed flag has the given
+  // value.
+  static Flags RandomSeed(int32_t random_seed) {
+    Flags flags;
+    flags.random_seed = random_seed;
+    return flags;
+  }
+
+  // Creates a Flags struct where the gtest_repeat flag has the given
+  // value.
+  static Flags Repeat(int32_t repeat) {
+    Flags flags;
+    flags.repeat = repeat;
+    return flags;
+  }
+
+  // Creates a Flags struct where the gtest_shuffle flag has the given
+  // value.
+  static Flags Shuffle(bool shuffle) {
+    Flags flags;
+    flags.shuffle = shuffle;
+    return flags;
+  }
+
+  // Creates a Flags struct where the GTEST_FLAG(stack_trace_depth) flag has
+  // the given value.
+  static Flags StackTraceDepth(int32_t stack_trace_depth) {
+    Flags flags;
+    flags.stack_trace_depth = stack_trace_depth;
+    return flags;
+  }
+
+  // Creates a Flags struct where the GTEST_FLAG(stream_result_to) flag has
+  // the given value.
+  static Flags StreamResultTo(const char* stream_result_to) {
+    Flags flags;
+    flags.stream_result_to = stream_result_to;
+    return flags;
+  }
+
+  // Creates a Flags struct where the gtest_throw_on_failure flag has
+  // the given value.
+  static Flags ThrowOnFailure(bool throw_on_failure) {
+    Flags flags;
+    flags.throw_on_failure = throw_on_failure;
+    return flags;
+  }
+
+  // These fields store the flag values.
+  bool also_run_disabled_tests;
+  bool break_on_failure;
+  bool catch_exceptions;
+  bool death_test_use_fork;
+  bool fail_fast;
+  const char* filter;
+  bool list_tests;
+  const char* output;
+  bool brief;
+  bool print_time;
+  int32_t random_seed;
+  int32_t repeat;
+  bool shuffle;
+  int32_t stack_trace_depth;
+  const char* stream_result_to;
+  bool throw_on_failure;
+};
+
+// Fixture for testing ParseGoogleTestFlagsOnly().
+class ParseFlagsTest : public Test {
+ protected:
+  // Clears the flags before each test.
+  void SetUp() override {
+    GTEST_FLAG(also_run_disabled_tests) = false;
+    GTEST_FLAG(break_on_failure) = false;
+    GTEST_FLAG(catch_exceptions) = false;
+    GTEST_FLAG(death_test_use_fork) = false;
+    GTEST_FLAG(fail_fast) = false;
+    GTEST_FLAG(filter) = "";
+    GTEST_FLAG(list_tests) = false;
+    GTEST_FLAG(output) = "";
+    GTEST_FLAG(brief) = false;
+    GTEST_FLAG(print_time) = true;
+    GTEST_FLAG(random_seed) = 0;
+    GTEST_FLAG(repeat) = 1;
+    GTEST_FLAG(shuffle) = false;
+    GTEST_FLAG(stack_trace_depth) = kMaxStackTraceDepth;
+    GTEST_FLAG(stream_result_to) = "";
+    GTEST_FLAG(throw_on_failure) = false;
+  }
+
+  // Asserts that two narrow or wide string arrays are equal.
+  template <typename CharType>
+  static void AssertStringArrayEq(int size1, CharType** array1, int size2,
+                                  CharType** array2) {
+    ASSERT_EQ(size1, size2) << " Array sizes different.";
+
+    for (int i = 0; i != size1; i++) {
+      ASSERT_STREQ(array1[i], array2[i]) << " where i == " << i;
+    }
+  }
+
+  // Verifies that the flag values match the expected values.
+  static void CheckFlags(const Flags& expected) {
+    EXPECT_EQ(expected.also_run_disabled_tests,
+              GTEST_FLAG(also_run_disabled_tests));
+    EXPECT_EQ(expected.break_on_failure, GTEST_FLAG(break_on_failure));
+    EXPECT_EQ(expected.catch_exceptions, GTEST_FLAG(catch_exceptions));
+    EXPECT_EQ(expected.death_test_use_fork, GTEST_FLAG(death_test_use_fork));
+    EXPECT_EQ(expected.fail_fast, GTEST_FLAG(fail_fast));
+    EXPECT_STREQ(expected.filter, GTEST_FLAG(filter).c_str());
+    EXPECT_EQ(expected.list_tests, GTEST_FLAG(list_tests));
+    EXPECT_STREQ(expected.output, GTEST_FLAG(output).c_str());
+    EXPECT_EQ(expected.brief, GTEST_FLAG(brief));
+    EXPECT_EQ(expected.print_time, GTEST_FLAG(print_time));
+    EXPECT_EQ(expected.random_seed, GTEST_FLAG(random_seed));
+    EXPECT_EQ(expected.repeat, GTEST_FLAG(repeat));
+    EXPECT_EQ(expected.shuffle, GTEST_FLAG(shuffle));
+    EXPECT_EQ(expected.stack_trace_depth, GTEST_FLAG(stack_trace_depth));
+    EXPECT_STREQ(expected.stream_result_to,
+                 GTEST_FLAG(stream_result_to).c_str());
+    EXPECT_EQ(expected.throw_on_failure, GTEST_FLAG(throw_on_failure));
+  }
+
+  // Parses a command line (specified by argc1 and argv1), then
+  // verifies that the flag values are expected and that the
+  // recognized flags are removed from the command line.
+  template <typename CharType>
+  static void TestParsingFlags(int argc1, const CharType** argv1,
+                               int argc2, const CharType** argv2,
+                               const Flags& expected, bool should_print_help) {
+    const bool saved_help_flag = ::testing::internal::g_help_flag;
+    ::testing::internal::g_help_flag = false;
+
+# if GTEST_HAS_STREAM_REDIRECTION
+    CaptureStdout();
+# endif
+
+    // Parses the command line.
+    internal::ParseGoogleTestFlagsOnly(&argc1, const_cast<CharType**>(argv1));
+
+# if GTEST_HAS_STREAM_REDIRECTION
+    const std::string captured_stdout = GetCapturedStdout();
+# endif
+
+    // Verifies the flag values.
+    CheckFlags(expected);
+
+    // Verifies that the recognized flags are removed from the command
+    // line.
+    AssertStringArrayEq(argc1 + 1, argv1, argc2 + 1, argv2);
+
+    // ParseGoogleTestFlagsOnly should neither set g_help_flag nor print the
+    // help message for the flags it recognizes.
+    EXPECT_EQ(should_print_help, ::testing::internal::g_help_flag);
+
+# if GTEST_HAS_STREAM_REDIRECTION
+    const char* const expected_help_fragment =
+        "This program contains tests written using";
+    if (should_print_help) {
+      EXPECT_PRED_FORMAT2(IsSubstring, expected_help_fragment, captured_stdout);
+    } else {
+      EXPECT_PRED_FORMAT2(IsNotSubstring,
+                          expected_help_fragment, captured_stdout);
+    }
+# endif  // GTEST_HAS_STREAM_REDIRECTION
+
+    ::testing::internal::g_help_flag = saved_help_flag;
+  }
+
+  // This macro wraps TestParsingFlags s.t. the user doesn't need
+  // to specify the array sizes.
+
+# define GTEST_TEST_PARSING_FLAGS_(argv1, argv2, expected, should_print_help) \
+  TestParsingFlags(sizeof(argv1)/sizeof(*argv1) - 1, argv1, \
+                   sizeof(argv2)/sizeof(*argv2) - 1, argv2, \
+                   expected, should_print_help)
+};
+
+// Tests parsing an empty command line.
+TEST_F(ParseFlagsTest, Empty) {
+  const char* argv[] = {nullptr};
+
+  const char* argv2[] = {nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags(), false);
+}
+
+// Tests parsing a command line that has no flag.
+TEST_F(ParseFlagsTest, NoFlag) {
+  const char* argv[] = {"foo.exe", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags(), false);
+}
+
+// Tests parsing --gtest_fail_fast.
+TEST_F(ParseFlagsTest, FailFast) {
+  const char* argv[] = {"foo.exe", "--gtest_fail_fast", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::FailFast(true), false);
+}
+
+// Tests parsing a bad --gtest_filter flag.
+TEST_F(ParseFlagsTest, FilterBad) {
+  const char* argv[] = {"foo.exe", "--gtest_filter", nullptr};
+
+  const char* argv2[] = {"foo.exe", "--gtest_filter", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::Filter(""), true);
+}
+
+// Tests parsing an empty --gtest_filter flag.
+TEST_F(ParseFlagsTest, FilterEmpty) {
+  const char* argv[] = {"foo.exe", "--gtest_filter=", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::Filter(""), false);
+}
+
+// Tests parsing a non-empty --gtest_filter flag.
+TEST_F(ParseFlagsTest, FilterNonEmpty) {
+  const char* argv[] = {"foo.exe", "--gtest_filter=abc", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::Filter("abc"), false);
+}
+
+// Tests parsing --gtest_break_on_failure.
+TEST_F(ParseFlagsTest, BreakOnFailureWithoutValue) {
+  const char* argv[] = {"foo.exe", "--gtest_break_on_failure", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::BreakOnFailure(true), false);
+}
+
+// Tests parsing --gtest_break_on_failure=0.
+TEST_F(ParseFlagsTest, BreakOnFailureFalse_0) {
+  const char* argv[] = {"foo.exe", "--gtest_break_on_failure=0", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::BreakOnFailure(false), false);
+}
+
+// Tests parsing --gtest_break_on_failure=f.
+TEST_F(ParseFlagsTest, BreakOnFailureFalse_f) {
+  const char* argv[] = {"foo.exe", "--gtest_break_on_failure=f", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::BreakOnFailure(false), false);
+}
+
+// Tests parsing --gtest_break_on_failure=F.
+TEST_F(ParseFlagsTest, BreakOnFailureFalse_F) {
+  const char* argv[] = {"foo.exe", "--gtest_break_on_failure=F", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::BreakOnFailure(false), false);
+}
+
+// Tests parsing a --gtest_break_on_failure flag that has a "true"
+// definition.
+TEST_F(ParseFlagsTest, BreakOnFailureTrue) {
+  const char* argv[] = {"foo.exe", "--gtest_break_on_failure=1", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::BreakOnFailure(true), false);
+}
+
+// Tests parsing --gtest_catch_exceptions.
+TEST_F(ParseFlagsTest, CatchExceptions) {
+  const char* argv[] = {"foo.exe", "--gtest_catch_exceptions", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::CatchExceptions(true), false);
+}
+
+// Tests parsing --gtest_death_test_use_fork.
+TEST_F(ParseFlagsTest, DeathTestUseFork) {
+  const char* argv[] = {"foo.exe", "--gtest_death_test_use_fork", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::DeathTestUseFork(true), false);
+}
+
+// Tests having the same flag twice with different values.  The
+// expected behavior is that the one coming last takes precedence.
+TEST_F(ParseFlagsTest, DuplicatedFlags) {
+  const char* argv[] = {"foo.exe", "--gtest_filter=a", "--gtest_filter=b",
+                        nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::Filter("b"), false);
+}
+
+// Tests having an unrecognized flag on the command line.
+TEST_F(ParseFlagsTest, UnrecognizedFlag) {
+  const char* argv[] = {"foo.exe", "--gtest_break_on_failure",
+                        "bar",  // Unrecognized by Google Test.
+                        "--gtest_filter=b", nullptr};
+
+  const char* argv2[] = {"foo.exe", "bar", nullptr};
+
+  Flags flags;
+  flags.break_on_failure = true;
+  flags.filter = "b";
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, flags, false);
+}
+
+// Tests having a --gtest_list_tests flag
+TEST_F(ParseFlagsTest, ListTestsFlag) {
+  const char* argv[] = {"foo.exe", "--gtest_list_tests", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::ListTests(true), false);
+}
+
+// Tests having a --gtest_list_tests flag with a "true" value
+TEST_F(ParseFlagsTest, ListTestsTrue) {
+  const char* argv[] = {"foo.exe", "--gtest_list_tests=1", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::ListTests(true), false);
+}
+
+// Tests having a --gtest_list_tests flag with a "false" value
+TEST_F(ParseFlagsTest, ListTestsFalse) {
+  const char* argv[] = {"foo.exe", "--gtest_list_tests=0", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::ListTests(false), false);
+}
+
+// Tests parsing --gtest_list_tests=f.
+TEST_F(ParseFlagsTest, ListTestsFalse_f) {
+  const char* argv[] = {"foo.exe", "--gtest_list_tests=f", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::ListTests(false), false);
+}
+
+// Tests parsing --gtest_list_tests=F.
+TEST_F(ParseFlagsTest, ListTestsFalse_F) {
+  const char* argv[] = {"foo.exe", "--gtest_list_tests=F", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::ListTests(false), false);
+}
+
+// Tests parsing --gtest_output (invalid).
+TEST_F(ParseFlagsTest, OutputEmpty) {
+  const char* argv[] = {"foo.exe", "--gtest_output", nullptr};
+
+  const char* argv2[] = {"foo.exe", "--gtest_output", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags(), true);
+}
+
+// Tests parsing --gtest_output=xml
+TEST_F(ParseFlagsTest, OutputXml) {
+  const char* argv[] = {"foo.exe", "--gtest_output=xml", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::Output("xml"), false);
+}
+
+// Tests parsing --gtest_output=xml:file
+TEST_F(ParseFlagsTest, OutputXmlFile) {
+  const char* argv[] = {"foo.exe", "--gtest_output=xml:file", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::Output("xml:file"), false);
+}
+
+// Tests parsing --gtest_output=xml:directory/path/
+TEST_F(ParseFlagsTest, OutputXmlDirectory) {
+  const char* argv[] = {"foo.exe", "--gtest_output=xml:directory/path/",
+                        nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2,
+                            Flags::Output("xml:directory/path/"), false);
+}
+
+// Tests having a --gtest_brief flag
+TEST_F(ParseFlagsTest, BriefFlag) {
+  const char* argv[] = {"foo.exe", "--gtest_brief", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::Brief(true), false);
+}
+
+// Tests having a --gtest_brief flag with a "true" value
+TEST_F(ParseFlagsTest, BriefFlagTrue) {
+  const char* argv[] = {"foo.exe", "--gtest_brief=1", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::Brief(true), false);
+}
+
+// Tests having a --gtest_brief flag with a "false" value
+TEST_F(ParseFlagsTest, BriefFlagFalse) {
+  const char* argv[] = {"foo.exe", "--gtest_brief=0", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::Brief(false), false);
+}
+
+// Tests having a --gtest_print_time flag
+TEST_F(ParseFlagsTest, PrintTimeFlag) {
+  const char* argv[] = {"foo.exe", "--gtest_print_time", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::PrintTime(true), false);
+}
+
+// Tests having a --gtest_print_time flag with a "true" value
+TEST_F(ParseFlagsTest, PrintTimeTrue) {
+  const char* argv[] = {"foo.exe", "--gtest_print_time=1", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::PrintTime(true), false);
+}
+
+// Tests having a --gtest_print_time flag with a "false" value
+TEST_F(ParseFlagsTest, PrintTimeFalse) {
+  const char* argv[] = {"foo.exe", "--gtest_print_time=0", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::PrintTime(false), false);
+}
+
+// Tests parsing --gtest_print_time=f.
+TEST_F(ParseFlagsTest, PrintTimeFalse_f) {
+  const char* argv[] = {"foo.exe", "--gtest_print_time=f", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::PrintTime(false), false);
+}
+
+// Tests parsing --gtest_print_time=F.
+TEST_F(ParseFlagsTest, PrintTimeFalse_F) {
+  const char* argv[] = {"foo.exe", "--gtest_print_time=F", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::PrintTime(false), false);
+}
+
+// Tests parsing --gtest_random_seed=number
+TEST_F(ParseFlagsTest, RandomSeed) {
+  const char* argv[] = {"foo.exe", "--gtest_random_seed=1000", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::RandomSeed(1000), false);
+}
+
+// Tests parsing --gtest_repeat=number
+TEST_F(ParseFlagsTest, Repeat) {
+  const char* argv[] = {"foo.exe", "--gtest_repeat=1000", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::Repeat(1000), false);
+}
+
+// Tests having a --gtest_also_run_disabled_tests flag
+TEST_F(ParseFlagsTest, AlsoRunDisabledTestsFlag) {
+  const char* argv[] = {"foo.exe", "--gtest_also_run_disabled_tests", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::AlsoRunDisabledTests(true),
+                            false);
+}
+
+// Tests having a --gtest_also_run_disabled_tests flag with a "true" value
+TEST_F(ParseFlagsTest, AlsoRunDisabledTestsTrue) {
+  const char* argv[] = {"foo.exe", "--gtest_also_run_disabled_tests=1",
+                        nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::AlsoRunDisabledTests(true),
+                            false);
+}
+
+// Tests having a --gtest_also_run_disabled_tests flag with a "false" value
+TEST_F(ParseFlagsTest, AlsoRunDisabledTestsFalse) {
+  const char* argv[] = {"foo.exe", "--gtest_also_run_disabled_tests=0",
+                        nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::AlsoRunDisabledTests(false),
+                            false);
+}
+
+// Tests parsing --gtest_shuffle.
+TEST_F(ParseFlagsTest, ShuffleWithoutValue) {
+  const char* argv[] = {"foo.exe", "--gtest_shuffle", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::Shuffle(true), false);
+}
+
+// Tests parsing --gtest_shuffle=0.
+TEST_F(ParseFlagsTest, ShuffleFalse_0) {
+  const char* argv[] = {"foo.exe", "--gtest_shuffle=0", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::Shuffle(false), false);
+}
+
+// Tests parsing a --gtest_shuffle flag that has a "true" definition.
+TEST_F(ParseFlagsTest, ShuffleTrue) {
+  const char* argv[] = {"foo.exe", "--gtest_shuffle=1", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::Shuffle(true), false);
+}
+
+// Tests parsing --gtest_stack_trace_depth=number.
+TEST_F(ParseFlagsTest, StackTraceDepth) {
+  const char* argv[] = {"foo.exe", "--gtest_stack_trace_depth=5", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::StackTraceDepth(5), false);
+}
+
+TEST_F(ParseFlagsTest, StreamResultTo) {
+  const char* argv[] = {"foo.exe", "--gtest_stream_result_to=localhost:1234",
+                        nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(
+      argv, argv2, Flags::StreamResultTo("localhost:1234"), false);
+}
+
+// Tests parsing --gtest_throw_on_failure.
+TEST_F(ParseFlagsTest, ThrowOnFailureWithoutValue) {
+  const char* argv[] = {"foo.exe", "--gtest_throw_on_failure", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::ThrowOnFailure(true), false);
+}
+
+// Tests parsing --gtest_throw_on_failure=0.
+TEST_F(ParseFlagsTest, ThrowOnFailureFalse_0) {
+  const char* argv[] = {"foo.exe", "--gtest_throw_on_failure=0", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::ThrowOnFailure(false), false);
+}
+
+// Tests parsing a --gtest_throw_on_failure flag that has a "true"
+// definition.
+TEST_F(ParseFlagsTest, ThrowOnFailureTrue) {
+  const char* argv[] = {"foo.exe", "--gtest_throw_on_failure=1", nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::ThrowOnFailure(true), false);
+}
+
+# if GTEST_OS_WINDOWS
+// Tests parsing wide strings.
+TEST_F(ParseFlagsTest, WideStrings) {
+  const wchar_t* argv[] = {
+    L"foo.exe",
+    L"--gtest_filter=Foo*",
+    L"--gtest_list_tests=1",
+    L"--gtest_break_on_failure",
+    L"--non_gtest_flag",
+    NULL
+  };
+
+  const wchar_t* argv2[] = {
+    L"foo.exe",
+    L"--non_gtest_flag",
+    NULL
+  };
+
+  Flags expected_flags;
+  expected_flags.break_on_failure = true;
+  expected_flags.filter = "Foo*";
+  expected_flags.list_tests = true;
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, expected_flags, false);
+}
+# endif  // GTEST_OS_WINDOWS
+
+#if GTEST_USE_OWN_FLAGFILE_FLAG_
+class FlagfileTest : public ParseFlagsTest {
+ public:
+  void SetUp() override {
+    ParseFlagsTest::SetUp();
+
+    testdata_path_.Set(internal::FilePath(
+        testing::TempDir() + internal::GetCurrentExecutableName().string() +
+        "_flagfile_test"));
+    testing::internal::posix::RmDir(testdata_path_.c_str());
+    EXPECT_TRUE(testdata_path_.CreateFolder());
+  }
+
+  void TearDown() override {
+    testing::internal::posix::RmDir(testdata_path_.c_str());
+    ParseFlagsTest::TearDown();
+  }
+
+  internal::FilePath CreateFlagfile(const char* contents) {
+    internal::FilePath file_path(internal::FilePath::GenerateUniqueFileName(
+        testdata_path_, internal::FilePath("unique"), "txt"));
+    FILE* f = testing::internal::posix::FOpen(file_path.c_str(), "w");
+    fprintf(f, "%s", contents);
+    fclose(f);
+    return file_path;
+  }
+
+ private:
+  internal::FilePath testdata_path_;
+};
+
+// Tests an empty flagfile.
+TEST_F(FlagfileTest, Empty) {
+  internal::FilePath flagfile_path(CreateFlagfile(""));
+  std::string flagfile_flag =
+      std::string("--" GTEST_FLAG_PREFIX_ "flagfile=") + flagfile_path.c_str();
+
+  const char* argv[] = {"foo.exe", flagfile_flag.c_str(), nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags(), false);
+}
+
+// Tests passing a non-empty --gtest_filter flag via --gtest_flagfile.
+TEST_F(FlagfileTest, FilterNonEmpty) {
+  internal::FilePath flagfile_path(CreateFlagfile(
+      "--"  GTEST_FLAG_PREFIX_  "filter=abc"));
+  std::string flagfile_flag =
+      std::string("--" GTEST_FLAG_PREFIX_ "flagfile=") + flagfile_path.c_str();
+
+  const char* argv[] = {"foo.exe", flagfile_flag.c_str(), nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, Flags::Filter("abc"), false);
+}
+
+// Tests passing several flags via --gtest_flagfile.
+TEST_F(FlagfileTest, SeveralFlags) {
+  internal::FilePath flagfile_path(CreateFlagfile(
+      "--"  GTEST_FLAG_PREFIX_  "filter=abc\n"
+      "--"  GTEST_FLAG_PREFIX_  "break_on_failure\n"
+      "--"  GTEST_FLAG_PREFIX_  "list_tests"));
+  std::string flagfile_flag =
+      std::string("--" GTEST_FLAG_PREFIX_ "flagfile=") + flagfile_path.c_str();
+
+  const char* argv[] = {"foo.exe", flagfile_flag.c_str(), nullptr};
+
+  const char* argv2[] = {"foo.exe", nullptr};
+
+  Flags expected_flags;
+  expected_flags.break_on_failure = true;
+  expected_flags.filter = "abc";
+  expected_flags.list_tests = true;
+
+  GTEST_TEST_PARSING_FLAGS_(argv, argv2, expected_flags, false);
+}
+#endif  // GTEST_USE_OWN_FLAGFILE_FLAG_
+
+// Tests current_test_info() in UnitTest.
+class CurrentTestInfoTest : public Test {
+ protected:
+  // Tests that current_test_info() returns NULL before the first test in
+  // the test case is run.
+  static void SetUpTestSuite() {
+    // There should be no tests running at this point.
+    const TestInfo* test_info =
+      UnitTest::GetInstance()->current_test_info();
+    EXPECT_TRUE(test_info == nullptr)
+        << "There should be no tests running at this point.";
+  }
+
+  // Tests that current_test_info() returns NULL after the last test in
+  // the test case has run.
+  static void TearDownTestSuite() {
+    const TestInfo* test_info =
+      UnitTest::GetInstance()->current_test_info();
+    EXPECT_TRUE(test_info == nullptr)
+        << "There should be no tests running at this point.";
+  }
+};
+
+// Tests that current_test_info() returns TestInfo for currently running
+// test by checking the expected test name against the actual one.
+TEST_F(CurrentTestInfoTest, WorksForFirstTestInATestSuite) {
+  const TestInfo* test_info =
+    UnitTest::GetInstance()->current_test_info();
+  ASSERT_TRUE(nullptr != test_info)
+      << "There is a test running so we should have a valid TestInfo.";
+  EXPECT_STREQ("CurrentTestInfoTest", test_info->test_suite_name())
+      << "Expected the name of the currently running test suite.";
+  EXPECT_STREQ("WorksForFirstTestInATestSuite", test_info->name())
+      << "Expected the name of the currently running test.";
+}
+
+// Tests that current_test_info() returns TestInfo for currently running
+// test by checking the expected test name against the actual one.  We
+// use this test to see that the TestInfo object actually changed from
+// the previous invocation.
+TEST_F(CurrentTestInfoTest, WorksForSecondTestInATestSuite) {
+  const TestInfo* test_info =
+    UnitTest::GetInstance()->current_test_info();
+  ASSERT_TRUE(nullptr != test_info)
+      << "There is a test running so we should have a valid TestInfo.";
+  EXPECT_STREQ("CurrentTestInfoTest", test_info->test_suite_name())
+      << "Expected the name of the currently running test suite.";
+  EXPECT_STREQ("WorksForSecondTestInATestSuite", test_info->name())
+      << "Expected the name of the currently running test.";
+}
+
+}  // namespace testing
+
+
+// These two lines test that we can define tests in a namespace that
+// has the name "testing" and is nested in another namespace.
+namespace my_namespace {
+namespace testing {
+
+// Makes sure that TEST knows to use ::testing::Test instead of
+// ::my_namespace::testing::Test.
+class Test {};
+
+// Makes sure that an assertion knows to use ::testing::Message instead of
+// ::my_namespace::testing::Message.
+class Message {};
+
+// Makes sure that an assertion knows to use
+// ::testing::AssertionResult instead of
+// ::my_namespace::testing::AssertionResult.
+class AssertionResult {};
+
+// Tests that an assertion that should succeed works as expected.
+TEST(NestedTestingNamespaceTest, Success) {
+  EXPECT_EQ(1, 1) << "This shouldn't fail.";
+}
+
+// Tests that an assertion that should fail works as expected.
+TEST(NestedTestingNamespaceTest, Failure) {
+  EXPECT_FATAL_FAILURE(FAIL() << "This failure is expected.",
+                       "This failure is expected.");
+}
+
+}  // namespace testing
+}  // namespace my_namespace
+
+// Tests that one can call superclass SetUp and TearDown methods--
+// that is, that they are not private.
+// No tests are based on this fixture; the test "passes" if it compiles
+// successfully.
+class ProtectedFixtureMethodsTest : public Test {
+ protected:
+  void SetUp() override { Test::SetUp(); }
+  void TearDown() override { Test::TearDown(); }
+};
+
+// StreamingAssertionsTest tests the streaming versions of a representative
+// sample of assertions.
+TEST(StreamingAssertionsTest, Unconditional) {
+  SUCCEED() << "expected success";
+  EXPECT_NONFATAL_FAILURE(ADD_FAILURE() << "expected failure",
+                          "expected failure");
+  EXPECT_FATAL_FAILURE(FAIL() << "expected failure",
+                       "expected failure");
+}
+
+#ifdef __BORLANDC__
+// Silences warnings: "Condition is always true", "Unreachable code"
+# pragma option push -w-ccc -w-rch
+#endif
+
+TEST(StreamingAssertionsTest, Truth) {
+  EXPECT_TRUE(true) << "unexpected failure";
+  ASSERT_TRUE(true) << "unexpected failure";
+  EXPECT_NONFATAL_FAILURE(EXPECT_TRUE(false) << "expected failure",
+                          "expected failure");
+  EXPECT_FATAL_FAILURE(ASSERT_TRUE(false) << "expected failure",
+                       "expected failure");
+}
+
+TEST(StreamingAssertionsTest, Truth2) {
+  EXPECT_FALSE(false) << "unexpected failure";
+  ASSERT_FALSE(false) << "unexpected failure";
+  EXPECT_NONFATAL_FAILURE(EXPECT_FALSE(true) << "expected failure",
+                          "expected failure");
+  EXPECT_FATAL_FAILURE(ASSERT_FALSE(true) << "expected failure",
+                       "expected failure");
+}
+
+#ifdef __BORLANDC__
+// Restores warnings after previous "#pragma option push" suppressed them
+# pragma option pop
+#endif
+
+TEST(StreamingAssertionsTest, IntegerEquals) {
+  EXPECT_EQ(1, 1) << "unexpected failure";
+  ASSERT_EQ(1, 1) << "unexpected failure";
+  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(1, 2) << "expected failure",
+                          "expected failure");
+  EXPECT_FATAL_FAILURE(ASSERT_EQ(1, 2) << "expected failure",
+                       "expected failure");
+}
+
+TEST(StreamingAssertionsTest, IntegerLessThan) {
+  EXPECT_LT(1, 2) << "unexpected failure";
+  ASSERT_LT(1, 2) << "unexpected failure";
+  EXPECT_NONFATAL_FAILURE(EXPECT_LT(2, 1) << "expected failure",
+                          "expected failure");
+  EXPECT_FATAL_FAILURE(ASSERT_LT(2, 1) << "expected failure",
+                       "expected failure");
+}
+
+TEST(StreamingAssertionsTest, StringsEqual) {
+  EXPECT_STREQ("foo", "foo") << "unexpected failure";
+  ASSERT_STREQ("foo", "foo") << "unexpected failure";
+  EXPECT_NONFATAL_FAILURE(EXPECT_STREQ("foo", "bar") << "expected failure",
+                          "expected failure");
+  EXPECT_FATAL_FAILURE(ASSERT_STREQ("foo", "bar") << "expected failure",
+                       "expected failure");
+}
+
+TEST(StreamingAssertionsTest, StringsNotEqual) {
+  EXPECT_STRNE("foo", "bar") << "unexpected failure";
+  ASSERT_STRNE("foo", "bar") << "unexpected failure";
+  EXPECT_NONFATAL_FAILURE(EXPECT_STRNE("foo", "foo") << "expected failure",
+                          "expected failure");
+  EXPECT_FATAL_FAILURE(ASSERT_STRNE("foo", "foo") << "expected failure",
+                       "expected failure");
+}
+
+TEST(StreamingAssertionsTest, StringsEqualIgnoringCase) {
+  EXPECT_STRCASEEQ("foo", "FOO") << "unexpected failure";
+  ASSERT_STRCASEEQ("foo", "FOO") << "unexpected failure";
+  EXPECT_NONFATAL_FAILURE(EXPECT_STRCASEEQ("foo", "bar") << "expected failure",
+                          "expected failure");
+  EXPECT_FATAL_FAILURE(ASSERT_STRCASEEQ("foo", "bar") << "expected failure",
+                       "expected failure");
+}
+
+TEST(StreamingAssertionsTest, StringNotEqualIgnoringCase) {
+  EXPECT_STRCASENE("foo", "bar") << "unexpected failure";
+  ASSERT_STRCASENE("foo", "bar") << "unexpected failure";
+  EXPECT_NONFATAL_FAILURE(EXPECT_STRCASENE("foo", "FOO") << "expected failure",
+                          "expected failure");
+  EXPECT_FATAL_FAILURE(ASSERT_STRCASENE("bar", "BAR") << "expected failure",
+                       "expected failure");
+}
+
+TEST(StreamingAssertionsTest, FloatingPointEquals) {
+  EXPECT_FLOAT_EQ(1.0, 1.0) << "unexpected failure";
+  ASSERT_FLOAT_EQ(1.0, 1.0) << "unexpected failure";
+  EXPECT_NONFATAL_FAILURE(EXPECT_FLOAT_EQ(0.0, 1.0) << "expected failure",
+                          "expected failure");
+  EXPECT_FATAL_FAILURE(ASSERT_FLOAT_EQ(0.0, 1.0) << "expected failure",
+                       "expected failure");
+}
+
+#if GTEST_HAS_EXCEPTIONS
+
+TEST(StreamingAssertionsTest, Throw) {
+  EXPECT_THROW(ThrowAnInteger(), int) << "unexpected failure";
+  ASSERT_THROW(ThrowAnInteger(), int) << "unexpected failure";
+  EXPECT_NONFATAL_FAILURE(EXPECT_THROW(ThrowAnInteger(), bool) <<
+                          "expected failure", "expected failure");
+  EXPECT_FATAL_FAILURE(ASSERT_THROW(ThrowAnInteger(), bool) <<
+                       "expected failure", "expected failure");
+}
+
+TEST(StreamingAssertionsTest, NoThrow) {
+  EXPECT_NO_THROW(ThrowNothing()) << "unexpected failure";
+  ASSERT_NO_THROW(ThrowNothing()) << "unexpected failure";
+  EXPECT_NONFATAL_FAILURE(EXPECT_NO_THROW(ThrowAnInteger()) <<
+                          "expected failure", "expected failure");
+  EXPECT_FATAL_FAILURE(ASSERT_NO_THROW(ThrowAnInteger()) <<
+                       "expected failure", "expected failure");
+}
+
+TEST(StreamingAssertionsTest, AnyThrow) {
+  EXPECT_ANY_THROW(ThrowAnInteger()) << "unexpected failure";
+  ASSERT_ANY_THROW(ThrowAnInteger()) << "unexpected failure";
+  EXPECT_NONFATAL_FAILURE(EXPECT_ANY_THROW(ThrowNothing()) <<
+                          "expected failure", "expected failure");
+  EXPECT_FATAL_FAILURE(ASSERT_ANY_THROW(ThrowNothing()) <<
+                       "expected failure", "expected failure");
+}
+
+#endif  // GTEST_HAS_EXCEPTIONS
+
+// Tests that Google Test correctly decides whether to use colors in the output.
+
+TEST(ColoredOutputTest, UsesColorsWhenGTestColorFlagIsYes) {
+  GTEST_FLAG(color) = "yes";
+
+  SetEnv("TERM", "xterm");  // TERM supports colors.
+  EXPECT_TRUE(ShouldUseColor(true));  // Stdout is a TTY.
+  EXPECT_TRUE(ShouldUseColor(false));  // Stdout is not a TTY.
+
+  SetEnv("TERM", "dumb");  // TERM doesn't support colors.
+  EXPECT_TRUE(ShouldUseColor(true));  // Stdout is a TTY.
+  EXPECT_TRUE(ShouldUseColor(false));  // Stdout is not a TTY.
+}
+
+TEST(ColoredOutputTest, UsesColorsWhenGTestColorFlagIsAliasOfYes) {
+  SetEnv("TERM", "dumb");  // TERM doesn't support colors.
+
+  GTEST_FLAG(color) = "True";
+  EXPECT_TRUE(ShouldUseColor(false));  // Stdout is not a TTY.
+
+  GTEST_FLAG(color) = "t";
+  EXPECT_TRUE(ShouldUseColor(false));  // Stdout is not a TTY.
+
+  GTEST_FLAG(color) = "1";
+  EXPECT_TRUE(ShouldUseColor(false));  // Stdout is not a TTY.
+}
+
+TEST(ColoredOutputTest, UsesNoColorWhenGTestColorFlagIsNo) {
+  GTEST_FLAG(color) = "no";
+
+  SetEnv("TERM", "xterm");  // TERM supports colors.
+  EXPECT_FALSE(ShouldUseColor(true));  // Stdout is a TTY.
+  EXPECT_FALSE(ShouldUseColor(false));  // Stdout is not a TTY.
+
+  SetEnv("TERM", "dumb");  // TERM doesn't support colors.
+  EXPECT_FALSE(ShouldUseColor(true));  // Stdout is a TTY.
+  EXPECT_FALSE(ShouldUseColor(false));  // Stdout is not a TTY.
+}
+
+TEST(ColoredOutputTest, UsesNoColorWhenGTestColorFlagIsInvalid) {
+  SetEnv("TERM", "xterm");  // TERM supports colors.
+
+  GTEST_FLAG(color) = "F";
+  EXPECT_FALSE(ShouldUseColor(true));  // Stdout is a TTY.
+
+  GTEST_FLAG(color) = "0";
+  EXPECT_FALSE(ShouldUseColor(true));  // Stdout is a TTY.
+
+  GTEST_FLAG(color) = "unknown";
+  EXPECT_FALSE(ShouldUseColor(true));  // Stdout is a TTY.
+}
+
+TEST(ColoredOutputTest, UsesColorsWhenStdoutIsTty) {
+  GTEST_FLAG(color) = "auto";
+
+  SetEnv("TERM", "xterm");  // TERM supports colors.
+  EXPECT_FALSE(ShouldUseColor(false));  // Stdout is not a TTY.
+  EXPECT_TRUE(ShouldUseColor(true));    // Stdout is a TTY.
+}
+
+TEST(ColoredOutputTest, UsesColorsWhenTermSupportsColors) {
+  GTEST_FLAG(color) = "auto";
+
+#if GTEST_OS_WINDOWS && !GTEST_OS_WINDOWS_MINGW
+  // On Windows, we ignore the TERM variable as it's usually not set.
+
+  SetEnv("TERM", "dumb");
+  EXPECT_TRUE(ShouldUseColor(true));  // Stdout is a TTY.
+
+  SetEnv("TERM", "");
+  EXPECT_TRUE(ShouldUseColor(true));  // Stdout is a TTY.
+
+  SetEnv("TERM", "xterm");
+  EXPECT_TRUE(ShouldUseColor(true));  // Stdout is a TTY.
+#else
+  // On non-Windows platforms, we rely on TERM to determine if the
+  // terminal supports colors.
+
+  SetEnv("TERM", "dumb");  // TERM doesn't support colors.
+  EXPECT_FALSE(ShouldUseColor(true));  // Stdout is a TTY.
+
+  SetEnv("TERM", "emacs");  // TERM doesn't support colors.
+  EXPECT_FALSE(ShouldUseColor(true));  // Stdout is a TTY.
+
+  SetEnv("TERM", "vt100");  // TERM doesn't support colors.
+  EXPECT_FALSE(ShouldUseColor(true));  // Stdout is a TTY.
+
+  SetEnv("TERM", "xterm-mono");  // TERM doesn't support colors.
+  EXPECT_FALSE(ShouldUseColor(true));  // Stdout is a TTY.
+
+  SetEnv("TERM", "xterm");  // TERM supports colors.
+  EXPECT_TRUE(ShouldUseColor(true));  // Stdout is a TTY.
+
+  SetEnv("TERM", "xterm-color");  // TERM supports colors.
+  EXPECT_TRUE(ShouldUseColor(true));  // Stdout is a TTY.
+
+  SetEnv("TERM", "xterm-256color");  // TERM supports colors.
+  EXPECT_TRUE(ShouldUseColor(true));  // Stdout is a TTY.
+
+  SetEnv("TERM", "screen");  // TERM supports colors.
+  EXPECT_TRUE(ShouldUseColor(true));  // Stdout is a TTY.
+
+  SetEnv("TERM", "screen-256color");  // TERM supports colors.
+  EXPECT_TRUE(ShouldUseColor(true));  // Stdout is a TTY.
+
+  SetEnv("TERM", "tmux");  // TERM supports colors.
+  EXPECT_TRUE(ShouldUseColor(true));  // Stdout is a TTY.
+
+  SetEnv("TERM", "tmux-256color");  // TERM supports colors.
+  EXPECT_TRUE(ShouldUseColor(true));  // Stdout is a TTY.
+
+  SetEnv("TERM", "rxvt-unicode");  // TERM supports colors.
+  EXPECT_TRUE(ShouldUseColor(true));  // Stdout is a TTY.
+
+  SetEnv("TERM", "rxvt-unicode-256color");  // TERM supports colors.
+  EXPECT_TRUE(ShouldUseColor(true));  // Stdout is a TTY.
+
+  SetEnv("TERM", "linux");  // TERM supports colors.
+  EXPECT_TRUE(ShouldUseColor(true));  // Stdout is a TTY.
+
+  SetEnv("TERM", "cygwin");  // TERM supports colors.
+  EXPECT_TRUE(ShouldUseColor(true));  // Stdout is a TTY.
+#endif  // GTEST_OS_WINDOWS
+}
+
+// Verifies that StaticAssertTypeEq works in a namespace scope.
+
+static bool dummy1 GTEST_ATTRIBUTE_UNUSED_ = StaticAssertTypeEq<bool, bool>();
+static bool dummy2 GTEST_ATTRIBUTE_UNUSED_ =
+    StaticAssertTypeEq<const int, const int>();
+
+// Verifies that StaticAssertTypeEq works in a class.
+
+template <typename T>
+class StaticAssertTypeEqTestHelper {
+ public:
+  StaticAssertTypeEqTestHelper() { StaticAssertTypeEq<bool, T>(); }
+};
+
+TEST(StaticAssertTypeEqTest, WorksInClass) {
+  StaticAssertTypeEqTestHelper<bool>();
+}
+
+// Verifies that StaticAssertTypeEq works inside a function.
+
+typedef int IntAlias;
+
+TEST(StaticAssertTypeEqTest, CompilesForEqualTypes) {
+  StaticAssertTypeEq<int, IntAlias>();
+  StaticAssertTypeEq<int*, IntAlias*>();
+}
+
+TEST(HasNonfatalFailureTest, ReturnsFalseWhenThereIsNoFailure) {
+  EXPECT_FALSE(HasNonfatalFailure());
+}
+
+static void FailFatally() { FAIL(); }
+
+TEST(HasNonfatalFailureTest, ReturnsFalseWhenThereIsOnlyFatalFailure) {
+  FailFatally();
+  const bool has_nonfatal_failure = HasNonfatalFailure();
+  ClearCurrentTestPartResults();
+  EXPECT_FALSE(has_nonfatal_failure);
+}
+
+TEST(HasNonfatalFailureTest, ReturnsTrueWhenThereIsNonfatalFailure) {
+  ADD_FAILURE();
+  const bool has_nonfatal_failure = HasNonfatalFailure();
+  ClearCurrentTestPartResults();
+  EXPECT_TRUE(has_nonfatal_failure);
+}
+
+TEST(HasNonfatalFailureTest, ReturnsTrueWhenThereAreFatalAndNonfatalFailures) {
+  FailFatally();
+  ADD_FAILURE();
+  const bool has_nonfatal_failure = HasNonfatalFailure();
+  ClearCurrentTestPartResults();
+  EXPECT_TRUE(has_nonfatal_failure);
+}
+
+// A wrapper for calling HasNonfatalFailure outside of a test body.
+static bool HasNonfatalFailureHelper() {
+  return testing::Test::HasNonfatalFailure();
+}
+
+TEST(HasNonfatalFailureTest, WorksOutsideOfTestBody) {
+  EXPECT_FALSE(HasNonfatalFailureHelper());
+}
+
+TEST(HasNonfatalFailureTest, WorksOutsideOfTestBody2) {
+  ADD_FAILURE();
+  const bool has_nonfatal_failure = HasNonfatalFailureHelper();
+  ClearCurrentTestPartResults();
+  EXPECT_TRUE(has_nonfatal_failure);
+}
+
+TEST(HasFailureTest, ReturnsFalseWhenThereIsNoFailure) {
+  EXPECT_FALSE(HasFailure());
+}
+
+TEST(HasFailureTest, ReturnsTrueWhenThereIsFatalFailure) {
+  FailFatally();
+  const bool has_failure = HasFailure();
+  ClearCurrentTestPartResults();
+  EXPECT_TRUE(has_failure);
+}
+
+TEST(HasFailureTest, ReturnsTrueWhenThereIsNonfatalFailure) {
+  ADD_FAILURE();
+  const bool has_failure = HasFailure();
+  ClearCurrentTestPartResults();
+  EXPECT_TRUE(has_failure);
+}
+
+TEST(HasFailureTest, ReturnsTrueWhenThereAreFatalAndNonfatalFailures) {
+  FailFatally();
+  ADD_FAILURE();
+  const bool has_failure = HasFailure();
+  ClearCurrentTestPartResults();
+  EXPECT_TRUE(has_failure);
+}
+
+// A wrapper for calling HasFailure outside of a test body.
+static bool HasFailureHelper() { return testing::Test::HasFailure(); }
+
+TEST(HasFailureTest, WorksOutsideOfTestBody) {
+  EXPECT_FALSE(HasFailureHelper());
+}
+
+TEST(HasFailureTest, WorksOutsideOfTestBody2) {
+  ADD_FAILURE();
+  const bool has_failure = HasFailureHelper();
+  ClearCurrentTestPartResults();
+  EXPECT_TRUE(has_failure);
+}
+
+class TestListener : public EmptyTestEventListener {
+ public:
+  TestListener() : on_start_counter_(nullptr), is_destroyed_(nullptr) {}
+  TestListener(int* on_start_counter, bool* is_destroyed)
+      : on_start_counter_(on_start_counter),
+        is_destroyed_(is_destroyed) {}
+
+  ~TestListener() override {
+    if (is_destroyed_)
+      *is_destroyed_ = true;
+  }
+
+ protected:
+  void OnTestProgramStart(const UnitTest& /*unit_test*/) override {
+    if (on_start_counter_ != nullptr) (*on_start_counter_)++;
+  }
+
+ private:
+  int* on_start_counter_;
+  bool* is_destroyed_;
+};
+
+// Tests the constructor.
+TEST(TestEventListenersTest, ConstructionWorks) {
+  TestEventListeners listeners;
+
+  EXPECT_TRUE(TestEventListenersAccessor::GetRepeater(&listeners) != nullptr);
+  EXPECT_TRUE(listeners.default_result_printer() == nullptr);
+  EXPECT_TRUE(listeners.default_xml_generator() == nullptr);
+}
+
+// Tests that the TestEventListeners destructor deletes all the listeners it
+// owns.
+TEST(TestEventListenersTest, DestructionWorks) {
+  bool default_result_printer_is_destroyed = false;
+  bool default_xml_printer_is_destroyed = false;
+  bool extra_listener_is_destroyed = false;
+  TestListener* default_result_printer =
+      new TestListener(nullptr, &default_result_printer_is_destroyed);
+  TestListener* default_xml_printer =
+      new TestListener(nullptr, &default_xml_printer_is_destroyed);
+  TestListener* extra_listener =
+      new TestListener(nullptr, &extra_listener_is_destroyed);
+
+  {
+    TestEventListeners listeners;
+    TestEventListenersAccessor::SetDefaultResultPrinter(&listeners,
+                                                        default_result_printer);
+    TestEventListenersAccessor::SetDefaultXmlGenerator(&listeners,
+                                                       default_xml_printer);
+    listeners.Append(extra_listener);
+  }
+  EXPECT_TRUE(default_result_printer_is_destroyed);
+  EXPECT_TRUE(default_xml_printer_is_destroyed);
+  EXPECT_TRUE(extra_listener_is_destroyed);
+}
+
+// Tests that a listener Append'ed to a TestEventListeners list starts
+// receiving events.
+TEST(TestEventListenersTest, Append) {
+  int on_start_counter = 0;
+  bool is_destroyed = false;
+  TestListener* listener = new TestListener(&on_start_counter, &is_destroyed);
+  {
+    TestEventListeners listeners;
+    listeners.Append(listener);
+    TestEventListenersAccessor::GetRepeater(&listeners)->OnTestProgramStart(
+        *UnitTest::GetInstance());
+    EXPECT_EQ(1, on_start_counter);
+  }
+  EXPECT_TRUE(is_destroyed);
+}
+
+// Tests that listeners receive events in the order they were appended to
+// the list, except for *End requests, which must be received in the reverse
+// order.
+class SequenceTestingListener : public EmptyTestEventListener {
+ public:
+  SequenceTestingListener(std::vector<std::string>* vector, const char* id)
+      : vector_(vector), id_(id) {}
+
+ protected:
+  void OnTestProgramStart(const UnitTest& /*unit_test*/) override {
+    vector_->push_back(GetEventDescription("OnTestProgramStart"));
+  }
+
+  void OnTestProgramEnd(const UnitTest& /*unit_test*/) override {
+    vector_->push_back(GetEventDescription("OnTestProgramEnd"));
+  }
+
+  void OnTestIterationStart(const UnitTest& /*unit_test*/,
+                            int /*iteration*/) override {
+    vector_->push_back(GetEventDescription("OnTestIterationStart"));
+  }
+
+  void OnTestIterationEnd(const UnitTest& /*unit_test*/,
+                          int /*iteration*/) override {
+    vector_->push_back(GetEventDescription("OnTestIterationEnd"));
+  }
+
+ private:
+  std::string GetEventDescription(const char* method) {
+    Message message;
+    message << id_ << "." << method;
+    return message.GetString();
+  }
+
+  std::vector<std::string>* vector_;
+  const char* const id_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(SequenceTestingListener);
+};
+
+TEST(EventListenerTest, AppendKeepsOrder) {
+  std::vector<std::string> vec;
+  TestEventListeners listeners;
+  listeners.Append(new SequenceTestingListener(&vec, "1st"));
+  listeners.Append(new SequenceTestingListener(&vec, "2nd"));
+  listeners.Append(new SequenceTestingListener(&vec, "3rd"));
+
+  TestEventListenersAccessor::GetRepeater(&listeners)->OnTestProgramStart(
+      *UnitTest::GetInstance());
+  ASSERT_EQ(3U, vec.size());
+  EXPECT_STREQ("1st.OnTestProgramStart", vec[0].c_str());
+  EXPECT_STREQ("2nd.OnTestProgramStart", vec[1].c_str());
+  EXPECT_STREQ("3rd.OnTestProgramStart", vec[2].c_str());
+
+  vec.clear();
+  TestEventListenersAccessor::GetRepeater(&listeners)->OnTestProgramEnd(
+      *UnitTest::GetInstance());
+  ASSERT_EQ(3U, vec.size());
+  EXPECT_STREQ("3rd.OnTestProgramEnd", vec[0].c_str());
+  EXPECT_STREQ("2nd.OnTestProgramEnd", vec[1].c_str());
+  EXPECT_STREQ("1st.OnTestProgramEnd", vec[2].c_str());
+
+  vec.clear();
+  TestEventListenersAccessor::GetRepeater(&listeners)->OnTestIterationStart(
+      *UnitTest::GetInstance(), 0);
+  ASSERT_EQ(3U, vec.size());
+  EXPECT_STREQ("1st.OnTestIterationStart", vec[0].c_str());
+  EXPECT_STREQ("2nd.OnTestIterationStart", vec[1].c_str());
+  EXPECT_STREQ("3rd.OnTestIterationStart", vec[2].c_str());
+
+  vec.clear();
+  TestEventListenersAccessor::GetRepeater(&listeners)->OnTestIterationEnd(
+      *UnitTest::GetInstance(), 0);
+  ASSERT_EQ(3U, vec.size());
+  EXPECT_STREQ("3rd.OnTestIterationEnd", vec[0].c_str());
+  EXPECT_STREQ("2nd.OnTestIterationEnd", vec[1].c_str());
+  EXPECT_STREQ("1st.OnTestIterationEnd", vec[2].c_str());
+}
+
+// Tests that a listener removed from a TestEventListeners list stops receiving
+// events and is not deleted when the list is destroyed.
+TEST(TestEventListenersTest, Release) {
+  int on_start_counter = 0;
+  bool is_destroyed = false;
+  // Although Append passes the ownership of this object to the list,
+  // the following calls release it, and we need to delete it before the
+  // test ends.
+  TestListener* listener = new TestListener(&on_start_counter, &is_destroyed);
+  {
+    TestEventListeners listeners;
+    listeners.Append(listener);
+    EXPECT_EQ(listener, listeners.Release(listener));
+    TestEventListenersAccessor::GetRepeater(&listeners)->OnTestProgramStart(
+        *UnitTest::GetInstance());
+    EXPECT_TRUE(listeners.Release(listener) == nullptr);
+  }
+  EXPECT_EQ(0, on_start_counter);
+  EXPECT_FALSE(is_destroyed);
+  delete listener;
+}
+
+// Tests that no events are forwarded when event forwarding is disabled.
+TEST(EventListenerTest, SuppressEventForwarding) {
+  int on_start_counter = 0;
+  TestListener* listener = new TestListener(&on_start_counter, nullptr);
+
+  TestEventListeners listeners;
+  listeners.Append(listener);
+  ASSERT_TRUE(TestEventListenersAccessor::EventForwardingEnabled(listeners));
+  TestEventListenersAccessor::SuppressEventForwarding(&listeners);
+  ASSERT_FALSE(TestEventListenersAccessor::EventForwardingEnabled(listeners));
+  TestEventListenersAccessor::GetRepeater(&listeners)->OnTestProgramStart(
+      *UnitTest::GetInstance());
+  EXPECT_EQ(0, on_start_counter);
+}
+
+// Tests that events generated by Google Test are not forwarded in
+// death test subprocesses.
+TEST(EventListenerDeathTest, EventsNotForwardedInDeathTestSubprecesses) {
+  EXPECT_DEATH_IF_SUPPORTED({
+      GTEST_CHECK_(TestEventListenersAccessor::EventForwardingEnabled(
+          *GetUnitTestImpl()->listeners())) << "expected failure";},
+      "expected failure");
+}
+
+// Tests that a listener installed via SetDefaultResultPrinter() starts
+// receiving events and is returned via default_result_printer() and that
+// the previous default_result_printer is removed from the list and deleted.
+TEST(EventListenerTest, default_result_printer) {
+  int on_start_counter = 0;
+  bool is_destroyed = false;
+  TestListener* listener = new TestListener(&on_start_counter, &is_destroyed);
+
+  TestEventListeners listeners;
+  TestEventListenersAccessor::SetDefaultResultPrinter(&listeners, listener);
+
+  EXPECT_EQ(listener, listeners.default_result_printer());
+
+  TestEventListenersAccessor::GetRepeater(&listeners)->OnTestProgramStart(
+      *UnitTest::GetInstance());
+
+  EXPECT_EQ(1, on_start_counter);
+
+  // Replacing default_result_printer with something else should remove it
+  // from the list and destroy it.
+  TestEventListenersAccessor::SetDefaultResultPrinter(&listeners, nullptr);
+
+  EXPECT_TRUE(listeners.default_result_printer() == nullptr);
+  EXPECT_TRUE(is_destroyed);
+
+  // After broadcasting an event the counter is still the same, indicating
+  // the listener is not in the list anymore.
+  TestEventListenersAccessor::GetRepeater(&listeners)->OnTestProgramStart(
+      *UnitTest::GetInstance());
+  EXPECT_EQ(1, on_start_counter);
+}
+
+// Tests that the default_result_printer listener stops receiving events
+// when removed via Release and that is not owned by the list anymore.
+TEST(EventListenerTest, RemovingDefaultResultPrinterWorks) {
+  int on_start_counter = 0;
+  bool is_destroyed = false;
+  // Although Append passes the ownership of this object to the list,
+  // the following calls release it, and we need to delete it before the
+  // test ends.
+  TestListener* listener = new TestListener(&on_start_counter, &is_destroyed);
+  {
+    TestEventListeners listeners;
+    TestEventListenersAccessor::SetDefaultResultPrinter(&listeners, listener);
+
+    EXPECT_EQ(listener, listeners.Release(listener));
+    EXPECT_TRUE(listeners.default_result_printer() == nullptr);
+    EXPECT_FALSE(is_destroyed);
+
+    // Broadcasting events now should not affect default_result_printer.
+    TestEventListenersAccessor::GetRepeater(&listeners)->OnTestProgramStart(
+        *UnitTest::GetInstance());
+    EXPECT_EQ(0, on_start_counter);
+  }
+  // Destroying the list should not affect the listener now, too.
+  EXPECT_FALSE(is_destroyed);
+  delete listener;
+}
+
+// Tests that a listener installed via SetDefaultXmlGenerator() starts
+// receiving events and is returned via default_xml_generator() and that
+// the previous default_xml_generator is removed from the list and deleted.
+TEST(EventListenerTest, default_xml_generator) {
+  int on_start_counter = 0;
+  bool is_destroyed = false;
+  TestListener* listener = new TestListener(&on_start_counter, &is_destroyed);
+
+  TestEventListeners listeners;
+  TestEventListenersAccessor::SetDefaultXmlGenerator(&listeners, listener);
+
+  EXPECT_EQ(listener, listeners.default_xml_generator());
+
+  TestEventListenersAccessor::GetRepeater(&listeners)->OnTestProgramStart(
+      *UnitTest::GetInstance());
+
+  EXPECT_EQ(1, on_start_counter);
+
+  // Replacing default_xml_generator with something else should remove it
+  // from the list and destroy it.
+  TestEventListenersAccessor::SetDefaultXmlGenerator(&listeners, nullptr);
+
+  EXPECT_TRUE(listeners.default_xml_generator() == nullptr);
+  EXPECT_TRUE(is_destroyed);
+
+  // After broadcasting an event the counter is still the same, indicating
+  // the listener is not in the list anymore.
+  TestEventListenersAccessor::GetRepeater(&listeners)->OnTestProgramStart(
+      *UnitTest::GetInstance());
+  EXPECT_EQ(1, on_start_counter);
+}
+
+// Tests that the default_xml_generator listener stops receiving events
+// when removed via Release and that is not owned by the list anymore.
+TEST(EventListenerTest, RemovingDefaultXmlGeneratorWorks) {
+  int on_start_counter = 0;
+  bool is_destroyed = false;
+  // Although Append passes the ownership of this object to the list,
+  // the following calls release it, and we need to delete it before the
+  // test ends.
+  TestListener* listener = new TestListener(&on_start_counter, &is_destroyed);
+  {
+    TestEventListeners listeners;
+    TestEventListenersAccessor::SetDefaultXmlGenerator(&listeners, listener);
+
+    EXPECT_EQ(listener, listeners.Release(listener));
+    EXPECT_TRUE(listeners.default_xml_generator() == nullptr);
+    EXPECT_FALSE(is_destroyed);
+
+    // Broadcasting events now should not affect default_xml_generator.
+    TestEventListenersAccessor::GetRepeater(&listeners)->OnTestProgramStart(
+        *UnitTest::GetInstance());
+    EXPECT_EQ(0, on_start_counter);
+  }
+  // Destroying the list should not affect the listener now, too.
+  EXPECT_FALSE(is_destroyed);
+  delete listener;
+}
+
+// Sanity tests to ensure that the alternative, verbose spellings of
+// some of the macros work.  We don't test them thoroughly as that
+// would be quite involved.  Since their implementations are
+// straightforward, and they are rarely used, we'll just rely on the
+// users to tell us when they are broken.
+GTEST_TEST(AlternativeNameTest, Works) {  // GTEST_TEST is the same as TEST.
+  GTEST_SUCCEED() << "OK";  // GTEST_SUCCEED is the same as SUCCEED.
+
+  // GTEST_FAIL is the same as FAIL.
+  EXPECT_FATAL_FAILURE(GTEST_FAIL() << "An expected failure",
+                       "An expected failure");
+
+  // GTEST_ASSERT_XY is the same as ASSERT_XY.
+
+  GTEST_ASSERT_EQ(0, 0);
+  EXPECT_FATAL_FAILURE(GTEST_ASSERT_EQ(0, 1) << "An expected failure",
+                       "An expected failure");
+  EXPECT_FATAL_FAILURE(GTEST_ASSERT_EQ(1, 0) << "An expected failure",
+                       "An expected failure");
+
+  GTEST_ASSERT_NE(0, 1);
+  GTEST_ASSERT_NE(1, 0);
+  EXPECT_FATAL_FAILURE(GTEST_ASSERT_NE(0, 0) << "An expected failure",
+                       "An expected failure");
+
+  GTEST_ASSERT_LE(0, 0);
+  GTEST_ASSERT_LE(0, 1);
+  EXPECT_FATAL_FAILURE(GTEST_ASSERT_LE(1, 0) << "An expected failure",
+                       "An expected failure");
+
+  GTEST_ASSERT_LT(0, 1);
+  EXPECT_FATAL_FAILURE(GTEST_ASSERT_LT(0, 0) << "An expected failure",
+                       "An expected failure");
+  EXPECT_FATAL_FAILURE(GTEST_ASSERT_LT(1, 0) << "An expected failure",
+                       "An expected failure");
+
+  GTEST_ASSERT_GE(0, 0);
+  GTEST_ASSERT_GE(1, 0);
+  EXPECT_FATAL_FAILURE(GTEST_ASSERT_GE(0, 1) << "An expected failure",
+                       "An expected failure");
+
+  GTEST_ASSERT_GT(1, 0);
+  EXPECT_FATAL_FAILURE(GTEST_ASSERT_GT(0, 1) << "An expected failure",
+                       "An expected failure");
+  EXPECT_FATAL_FAILURE(GTEST_ASSERT_GT(1, 1) << "An expected failure",
+                       "An expected failure");
+}
+
+// Tests for internal utilities necessary for implementation of the universal
+// printing.
+
+class ConversionHelperBase {};
+class ConversionHelperDerived : public ConversionHelperBase {};
+
+struct HasDebugStringMethods {
+  std::string DebugString() const { return ""; }
+  std::string ShortDebugString() const { return ""; }
+};
+
+struct InheritsDebugStringMethods : public HasDebugStringMethods {};
+
+struct WrongTypeDebugStringMethod {
+  std::string DebugString() const { return ""; }
+  int ShortDebugString() const { return 1; }
+};
+
+struct NotConstDebugStringMethod {
+  std::string DebugString() { return ""; }
+  std::string ShortDebugString() const { return ""; }
+};
+
+struct MissingDebugStringMethod {
+  std::string DebugString() { return ""; }
+};
+
+struct IncompleteType;
+
+// Tests that HasDebugStringAndShortDebugString<T>::value is a compile-time
+// constant.
+TEST(HasDebugStringAndShortDebugStringTest, ValueIsCompileTimeConstant) {
+  GTEST_COMPILE_ASSERT_(
+      HasDebugStringAndShortDebugString<HasDebugStringMethods>::value,
+      const_true);
+  GTEST_COMPILE_ASSERT_(
+      HasDebugStringAndShortDebugString<InheritsDebugStringMethods>::value,
+      const_true);
+  GTEST_COMPILE_ASSERT_(HasDebugStringAndShortDebugString<
+                            const InheritsDebugStringMethods>::value,
+                        const_true);
+  GTEST_COMPILE_ASSERT_(
+      !HasDebugStringAndShortDebugString<WrongTypeDebugStringMethod>::value,
+      const_false);
+  GTEST_COMPILE_ASSERT_(
+      !HasDebugStringAndShortDebugString<NotConstDebugStringMethod>::value,
+      const_false);
+  GTEST_COMPILE_ASSERT_(
+      !HasDebugStringAndShortDebugString<MissingDebugStringMethod>::value,
+      const_false);
+  GTEST_COMPILE_ASSERT_(
+      !HasDebugStringAndShortDebugString<IncompleteType>::value, const_false);
+  GTEST_COMPILE_ASSERT_(!HasDebugStringAndShortDebugString<int>::value,
+                        const_false);
+}
+
+// Tests that HasDebugStringAndShortDebugString<T>::value is true when T has
+// needed methods.
+TEST(HasDebugStringAndShortDebugStringTest,
+     ValueIsTrueWhenTypeHasDebugStringAndShortDebugString) {
+  EXPECT_TRUE(
+      HasDebugStringAndShortDebugString<InheritsDebugStringMethods>::value);
+}
+
+// Tests that HasDebugStringAndShortDebugString<T>::value is false when T
+// doesn't have needed methods.
+TEST(HasDebugStringAndShortDebugStringTest,
+     ValueIsFalseWhenTypeIsNotAProtocolMessage) {
+  EXPECT_FALSE(HasDebugStringAndShortDebugString<int>::value);
+  EXPECT_FALSE(
+      HasDebugStringAndShortDebugString<const ConversionHelperBase>::value);
+}
+
+// Tests GTEST_REMOVE_REFERENCE_AND_CONST_.
+
+template <typename T1, typename T2>
+void TestGTestRemoveReferenceAndConst() {
+  static_assert(std::is_same<T1, GTEST_REMOVE_REFERENCE_AND_CONST_(T2)>::value,
+                "GTEST_REMOVE_REFERENCE_AND_CONST_ failed.");
+}
+
+TEST(RemoveReferenceToConstTest, Works) {
+  TestGTestRemoveReferenceAndConst<int, int>();
+  TestGTestRemoveReferenceAndConst<double, double&>();
+  TestGTestRemoveReferenceAndConst<char, const char>();
+  TestGTestRemoveReferenceAndConst<char, const char&>();
+  TestGTestRemoveReferenceAndConst<const char*, const char*>();
+}
+
+// Tests GTEST_REFERENCE_TO_CONST_.
+
+template <typename T1, typename T2>
+void TestGTestReferenceToConst() {
+  static_assert(std::is_same<T1, GTEST_REFERENCE_TO_CONST_(T2)>::value,
+                "GTEST_REFERENCE_TO_CONST_ failed.");
+}
+
+TEST(GTestReferenceToConstTest, Works) {
+  TestGTestReferenceToConst<const char&, char>();
+  TestGTestReferenceToConst<const int&, const int>();
+  TestGTestReferenceToConst<const double&, double>();
+  TestGTestReferenceToConst<const std::string&, const std::string&>();
+}
+
+
+// Tests IsContainerTest.
+
+class NonContainer {};
+
+TEST(IsContainerTestTest, WorksForNonContainer) {
+  EXPECT_EQ(sizeof(IsNotContainer), sizeof(IsContainerTest<int>(0)));
+  EXPECT_EQ(sizeof(IsNotContainer), sizeof(IsContainerTest<char[5]>(0)));
+  EXPECT_EQ(sizeof(IsNotContainer), sizeof(IsContainerTest<NonContainer>(0)));
+}
+
+TEST(IsContainerTestTest, WorksForContainer) {
+  EXPECT_EQ(sizeof(IsContainer),
+            sizeof(IsContainerTest<std::vector<bool> >(0)));
+  EXPECT_EQ(sizeof(IsContainer),
+            sizeof(IsContainerTest<std::map<int, double> >(0)));
+}
+
+struct ConstOnlyContainerWithPointerIterator {
+  using const_iterator = int*;
+  const_iterator begin() const;
+  const_iterator end() const;
+};
+
+struct ConstOnlyContainerWithClassIterator {
+  struct const_iterator {
+    const int& operator*() const;
+    const_iterator& operator++(/* pre-increment */);
+  };
+  const_iterator begin() const;
+  const_iterator end() const;
+};
+
+TEST(IsContainerTestTest, ConstOnlyContainer) {
+  EXPECT_EQ(sizeof(IsContainer),
+            sizeof(IsContainerTest<ConstOnlyContainerWithPointerIterator>(0)));
+  EXPECT_EQ(sizeof(IsContainer),
+            sizeof(IsContainerTest<ConstOnlyContainerWithClassIterator>(0)));
+}
+
+// Tests IsHashTable.
+struct AHashTable {
+  typedef void hasher;
+};
+struct NotReallyAHashTable {
+  typedef void hasher;
+  typedef void reverse_iterator;
+};
+TEST(IsHashTable, Basic) {
+  EXPECT_TRUE(testing::internal::IsHashTable<AHashTable>::value);
+  EXPECT_FALSE(testing::internal::IsHashTable<NotReallyAHashTable>::value);
+  EXPECT_FALSE(testing::internal::IsHashTable<std::vector<int>>::value);
+  EXPECT_TRUE(testing::internal::IsHashTable<std::unordered_set<int>>::value);
+}
+
+// Tests ArrayEq().
+
+TEST(ArrayEqTest, WorksForDegeneratedArrays) {
+  EXPECT_TRUE(ArrayEq(5, 5L));
+  EXPECT_FALSE(ArrayEq('a', 0));
+}
+
+TEST(ArrayEqTest, WorksForOneDimensionalArrays) {
+  // Note that a and b are distinct but compatible types.
+  const int a[] = { 0, 1 };
+  long b[] = { 0, 1 };
+  EXPECT_TRUE(ArrayEq(a, b));
+  EXPECT_TRUE(ArrayEq(a, 2, b));
+
+  b[0] = 2;
+  EXPECT_FALSE(ArrayEq(a, b));
+  EXPECT_FALSE(ArrayEq(a, 1, b));
+}
+
+TEST(ArrayEqTest, WorksForTwoDimensionalArrays) {
+  const char a[][3] = { "hi", "lo" };
+  const char b[][3] = { "hi", "lo" };
+  const char c[][3] = { "hi", "li" };
+
+  EXPECT_TRUE(ArrayEq(a, b));
+  EXPECT_TRUE(ArrayEq(a, 2, b));
+
+  EXPECT_FALSE(ArrayEq(a, c));
+  EXPECT_FALSE(ArrayEq(a, 2, c));
+}
+
+// Tests ArrayAwareFind().
+
+TEST(ArrayAwareFindTest, WorksForOneDimensionalArray) {
+  const char a[] = "hello";
+  EXPECT_EQ(a + 4, ArrayAwareFind(a, a + 5, 'o'));
+  EXPECT_EQ(a + 5, ArrayAwareFind(a, a + 5, 'x'));
+}
+
+TEST(ArrayAwareFindTest, WorksForTwoDimensionalArray) {
+  int a[][2] = { { 0, 1 }, { 2, 3 }, { 4, 5 } };
+  const int b[2] = { 2, 3 };
+  EXPECT_EQ(a + 1, ArrayAwareFind(a, a + 3, b));
+
+  const int c[2] = { 6, 7 };
+  EXPECT_EQ(a + 3, ArrayAwareFind(a, a + 3, c));
+}
+
+// Tests CopyArray().
+
+TEST(CopyArrayTest, WorksForDegeneratedArrays) {
+  int n = 0;
+  CopyArray('a', &n);
+  EXPECT_EQ('a', n);
+}
+
+TEST(CopyArrayTest, WorksForOneDimensionalArrays) {
+  const char a[3] = "hi";
+  int b[3];
+#ifndef __BORLANDC__  // C++Builder cannot compile some array size deductions.
+  CopyArray(a, &b);
+  EXPECT_TRUE(ArrayEq(a, b));
+#endif
+
+  int c[3];
+  CopyArray(a, 3, c);
+  EXPECT_TRUE(ArrayEq(a, c));
+}
+
+TEST(CopyArrayTest, WorksForTwoDimensionalArrays) {
+  const int a[2][3] = { { 0, 1, 2 }, { 3, 4, 5 } };
+  int b[2][3];
+#ifndef __BORLANDC__  // C++Builder cannot compile some array size deductions.
+  CopyArray(a, &b);
+  EXPECT_TRUE(ArrayEq(a, b));
+#endif
+
+  int c[2][3];
+  CopyArray(a, 2, c);
+  EXPECT_TRUE(ArrayEq(a, c));
+}
+
+// Tests NativeArray.
+
+TEST(NativeArrayTest, ConstructorFromArrayWorks) {
+  const int a[3] = { 0, 1, 2 };
+  NativeArray<int> na(a, 3, RelationToSourceReference());
+  EXPECT_EQ(3U, na.size());
+  EXPECT_EQ(a, na.begin());
+}
+
+TEST(NativeArrayTest, CreatesAndDeletesCopyOfArrayWhenAskedTo) {
+  typedef int Array[2];
+  Array* a = new Array[1];
+  (*a)[0] = 0;
+  (*a)[1] = 1;
+  NativeArray<int> na(*a, 2, RelationToSourceCopy());
+  EXPECT_NE(*a, na.begin());
+  delete[] a;
+  EXPECT_EQ(0, na.begin()[0]);
+  EXPECT_EQ(1, na.begin()[1]);
+
+  // We rely on the heap checker to verify that na deletes the copy of
+  // array.
+}
+
+TEST(NativeArrayTest, TypeMembersAreCorrect) {
+  StaticAssertTypeEq<char, NativeArray<char>::value_type>();
+  StaticAssertTypeEq<int[2], NativeArray<int[2]>::value_type>();
+
+  StaticAssertTypeEq<const char*, NativeArray<char>::const_iterator>();
+  StaticAssertTypeEq<const bool(*)[2], NativeArray<bool[2]>::const_iterator>();
+}
+
+TEST(NativeArrayTest, MethodsWork) {
+  const int a[3] = { 0, 1, 2 };
+  NativeArray<int> na(a, 3, RelationToSourceCopy());
+  ASSERT_EQ(3U, na.size());
+  EXPECT_EQ(3, na.end() - na.begin());
+
+  NativeArray<int>::const_iterator it = na.begin();
+  EXPECT_EQ(0, *it);
+  ++it;
+  EXPECT_EQ(1, *it);
+  it++;
+  EXPECT_EQ(2, *it);
+  ++it;
+  EXPECT_EQ(na.end(), it);
+
+  EXPECT_TRUE(na == na);
+
+  NativeArray<int> na2(a, 3, RelationToSourceReference());
+  EXPECT_TRUE(na == na2);
+
+  const int b1[3] = { 0, 1, 1 };
+  const int b2[4] = { 0, 1, 2, 3 };
+  EXPECT_FALSE(na == NativeArray<int>(b1, 3, RelationToSourceReference()));
+  EXPECT_FALSE(na == NativeArray<int>(b2, 4, RelationToSourceCopy()));
+}
+
+TEST(NativeArrayTest, WorksForTwoDimensionalArray) {
+  const char a[2][3] = { "hi", "lo" };
+  NativeArray<char[3]> na(a, 2, RelationToSourceReference());
+  ASSERT_EQ(2U, na.size());
+  EXPECT_EQ(a, na.begin());
+}
+
+// IndexSequence
+TEST(IndexSequence, MakeIndexSequence) {
+  using testing::internal::IndexSequence;
+  using testing::internal::MakeIndexSequence;
+  EXPECT_TRUE(
+      (std::is_same<IndexSequence<>, MakeIndexSequence<0>::type>::value));
+  EXPECT_TRUE(
+      (std::is_same<IndexSequence<0>, MakeIndexSequence<1>::type>::value));
+  EXPECT_TRUE(
+      (std::is_same<IndexSequence<0, 1>, MakeIndexSequence<2>::type>::value));
+  EXPECT_TRUE((
+      std::is_same<IndexSequence<0, 1, 2>, MakeIndexSequence<3>::type>::value));
+  EXPECT_TRUE(
+      (std::is_base_of<IndexSequence<0, 1, 2>, MakeIndexSequence<3>>::value));
+}
+
+// ElemFromList
+TEST(ElemFromList, Basic) {
+  using testing::internal::ElemFromList;
+  EXPECT_TRUE(
+      (std::is_same<int, ElemFromList<0, int, double, char>::type>::value));
+  EXPECT_TRUE(
+      (std::is_same<double, ElemFromList<1, int, double, char>::type>::value));
+  EXPECT_TRUE(
+      (std::is_same<char, ElemFromList<2, int, double, char>::type>::value));
+  EXPECT_TRUE((
+      std::is_same<char, ElemFromList<7, int, int, int, int, int, int, int,
+                                      char, int, int, int, int>::type>::value));
+}
+
+// FlatTuple
+TEST(FlatTuple, Basic) {
+  using testing::internal::FlatTuple;
+
+  FlatTuple<int, double, const char*> tuple = {};
+  EXPECT_EQ(0, tuple.Get<0>());
+  EXPECT_EQ(0.0, tuple.Get<1>());
+  EXPECT_EQ(nullptr, tuple.Get<2>());
+
+  tuple = FlatTuple<int, double, const char*>(
+      testing::internal::FlatTupleConstructTag{}, 7, 3.2, "Foo");
+  EXPECT_EQ(7, tuple.Get<0>());
+  EXPECT_EQ(3.2, tuple.Get<1>());
+  EXPECT_EQ(std::string("Foo"), tuple.Get<2>());
+
+  tuple.Get<1>() = 5.1;
+  EXPECT_EQ(5.1, tuple.Get<1>());
+}
+
+namespace {
+std::string AddIntToString(int i, const std::string& s) {
+  return s + std::to_string(i);
+}
+}  // namespace
+
+TEST(FlatTuple, Apply) {
+  using testing::internal::FlatTuple;
+
+  FlatTuple<int, std::string> tuple{testing::internal::FlatTupleConstructTag{},
+                                    5, "Hello"};
+
+  // Lambda.
+  EXPECT_TRUE(tuple.Apply([](int i, const std::string& s) -> bool {
+    return i == static_cast<int>(s.size());
+  }));
+
+  // Function.
+  EXPECT_EQ(tuple.Apply(AddIntToString), "Hello5");
+
+  // Mutating operations.
+  tuple.Apply([](int& i, std::string& s) {
+    ++i;
+    s += s;
+  });
+  EXPECT_EQ(tuple.Get<0>(), 6);
+  EXPECT_EQ(tuple.Get<1>(), "HelloHello");
+}
+
+struct ConstructionCounting {
+  ConstructionCounting() { ++default_ctor_calls; }
+  ~ConstructionCounting() { ++dtor_calls; }
+  ConstructionCounting(const ConstructionCounting&) { ++copy_ctor_calls; }
+  ConstructionCounting(ConstructionCounting&&) noexcept { ++move_ctor_calls; }
+  ConstructionCounting& operator=(const ConstructionCounting&) {
+    ++copy_assignment_calls;
+    return *this;
+  }
+  ConstructionCounting& operator=(ConstructionCounting&&) noexcept {
+    ++move_assignment_calls;
+    return *this;
+  }
+
+  static void Reset() {
+    default_ctor_calls = 0;
+    dtor_calls = 0;
+    copy_ctor_calls = 0;
+    move_ctor_calls = 0;
+    copy_assignment_calls = 0;
+    move_assignment_calls = 0;
+  }
+
+  static int default_ctor_calls;
+  static int dtor_calls;
+  static int copy_ctor_calls;
+  static int move_ctor_calls;
+  static int copy_assignment_calls;
+  static int move_assignment_calls;
+};
+
+int ConstructionCounting::default_ctor_calls = 0;
+int ConstructionCounting::dtor_calls = 0;
+int ConstructionCounting::copy_ctor_calls = 0;
+int ConstructionCounting::move_ctor_calls = 0;
+int ConstructionCounting::copy_assignment_calls = 0;
+int ConstructionCounting::move_assignment_calls = 0;
+
+TEST(FlatTuple, ConstructorCalls) {
+  using testing::internal::FlatTuple;
+
+  // Default construction.
+  ConstructionCounting::Reset();
+  { FlatTuple<ConstructionCounting> tuple; }
+  EXPECT_EQ(ConstructionCounting::default_ctor_calls, 1);
+  EXPECT_EQ(ConstructionCounting::dtor_calls, 1);
+  EXPECT_EQ(ConstructionCounting::copy_ctor_calls, 0);
+  EXPECT_EQ(ConstructionCounting::move_ctor_calls, 0);
+  EXPECT_EQ(ConstructionCounting::copy_assignment_calls, 0);
+  EXPECT_EQ(ConstructionCounting::move_assignment_calls, 0);
+
+  // Copy construction.
+  ConstructionCounting::Reset();
+  {
+    ConstructionCounting elem;
+    FlatTuple<ConstructionCounting> tuple{
+        testing::internal::FlatTupleConstructTag{}, elem};
+  }
+  EXPECT_EQ(ConstructionCounting::default_ctor_calls, 1);
+  EXPECT_EQ(ConstructionCounting::dtor_calls, 2);
+  EXPECT_EQ(ConstructionCounting::copy_ctor_calls, 1);
+  EXPECT_EQ(ConstructionCounting::move_ctor_calls, 0);
+  EXPECT_EQ(ConstructionCounting::copy_assignment_calls, 0);
+  EXPECT_EQ(ConstructionCounting::move_assignment_calls, 0);
+
+  // Move construction.
+  ConstructionCounting::Reset();
+  {
+    FlatTuple<ConstructionCounting> tuple{
+        testing::internal::FlatTupleConstructTag{}, ConstructionCounting{}};
+  }
+  EXPECT_EQ(ConstructionCounting::default_ctor_calls, 1);
+  EXPECT_EQ(ConstructionCounting::dtor_calls, 2);
+  EXPECT_EQ(ConstructionCounting::copy_ctor_calls, 0);
+  EXPECT_EQ(ConstructionCounting::move_ctor_calls, 1);
+  EXPECT_EQ(ConstructionCounting::copy_assignment_calls, 0);
+  EXPECT_EQ(ConstructionCounting::move_assignment_calls, 0);
+
+  // Copy assignment.
+  // TODO(ofats): it should be testing assignment operator of FlatTuple, not its
+  // elements
+  ConstructionCounting::Reset();
+  {
+    FlatTuple<ConstructionCounting> tuple;
+    ConstructionCounting elem;
+    tuple.Get<0>() = elem;
+  }
+  EXPECT_EQ(ConstructionCounting::default_ctor_calls, 2);
+  EXPECT_EQ(ConstructionCounting::dtor_calls, 2);
+  EXPECT_EQ(ConstructionCounting::copy_ctor_calls, 0);
+  EXPECT_EQ(ConstructionCounting::move_ctor_calls, 0);
+  EXPECT_EQ(ConstructionCounting::copy_assignment_calls, 1);
+  EXPECT_EQ(ConstructionCounting::move_assignment_calls, 0);
+
+  // Move assignment.
+  // TODO(ofats): it should be testing assignment operator of FlatTuple, not its
+  // elements
+  ConstructionCounting::Reset();
+  {
+    FlatTuple<ConstructionCounting> tuple;
+    tuple.Get<0>() = ConstructionCounting{};
+  }
+  EXPECT_EQ(ConstructionCounting::default_ctor_calls, 2);
+  EXPECT_EQ(ConstructionCounting::dtor_calls, 2);
+  EXPECT_EQ(ConstructionCounting::copy_ctor_calls, 0);
+  EXPECT_EQ(ConstructionCounting::move_ctor_calls, 0);
+  EXPECT_EQ(ConstructionCounting::copy_assignment_calls, 0);
+  EXPECT_EQ(ConstructionCounting::move_assignment_calls, 1);
+
+  ConstructionCounting::Reset();
+}
+
+TEST(FlatTuple, ManyTypes) {
+  using testing::internal::FlatTuple;
+
+  // Instantiate FlatTuple with 257 ints.
+  // Tests show that we can do it with thousands of elements, but very long
+  // compile times makes it unusuitable for this test.
+#define GTEST_FLAT_TUPLE_INT8 int, int, int, int, int, int, int, int,
+#define GTEST_FLAT_TUPLE_INT16 GTEST_FLAT_TUPLE_INT8 GTEST_FLAT_TUPLE_INT8
+#define GTEST_FLAT_TUPLE_INT32 GTEST_FLAT_TUPLE_INT16 GTEST_FLAT_TUPLE_INT16
+#define GTEST_FLAT_TUPLE_INT64 GTEST_FLAT_TUPLE_INT32 GTEST_FLAT_TUPLE_INT32
+#define GTEST_FLAT_TUPLE_INT128 GTEST_FLAT_TUPLE_INT64 GTEST_FLAT_TUPLE_INT64
+#define GTEST_FLAT_TUPLE_INT256 GTEST_FLAT_TUPLE_INT128 GTEST_FLAT_TUPLE_INT128
+
+  // Let's make sure that we can have a very long list of types without blowing
+  // up the template instantiation depth.
+  FlatTuple<GTEST_FLAT_TUPLE_INT256 int> tuple;
+
+  tuple.Get<0>() = 7;
+  tuple.Get<99>() = 17;
+  tuple.Get<256>() = 1000;
+  EXPECT_EQ(7, tuple.Get<0>());
+  EXPECT_EQ(17, tuple.Get<99>());
+  EXPECT_EQ(1000, tuple.Get<256>());
+}
+
+// Tests SkipPrefix().
+
+TEST(SkipPrefixTest, SkipsWhenPrefixMatches) {
+  const char* const str = "hello";
+
+  const char* p = str;
+  EXPECT_TRUE(SkipPrefix("", &p));
+  EXPECT_EQ(str, p);
+
+  p = str;
+  EXPECT_TRUE(SkipPrefix("hell", &p));
+  EXPECT_EQ(str + 4, p);
+}
+
+TEST(SkipPrefixTest, DoesNotSkipWhenPrefixDoesNotMatch) {
+  const char* const str = "world";
+
+  const char* p = str;
+  EXPECT_FALSE(SkipPrefix("W", &p));
+  EXPECT_EQ(str, p);
+
+  p = str;
+  EXPECT_FALSE(SkipPrefix("world!", &p));
+  EXPECT_EQ(str, p);
+}
+
+// Tests ad_hoc_test_result().
+TEST(AdHocTestResultTest, AdHocTestResultForUnitTestDoesNotShowFailure) {
+  const testing::TestResult& test_result =
+      testing::UnitTest::GetInstance()->ad_hoc_test_result();
+  EXPECT_FALSE(test_result.Failed());
+}
+
+class DynamicUnitTestFixture : public testing::Test {};
+
+class DynamicTest : public DynamicUnitTestFixture {
+  void TestBody() override { EXPECT_TRUE(true); }
+};
+
+auto* dynamic_test = testing::RegisterTest(
+    "DynamicUnitTestFixture", "DynamicTest", "TYPE", "VALUE", __FILE__,
+    __LINE__, []() -> DynamicUnitTestFixture* { return new DynamicTest; });
+
+TEST(RegisterTest, WasRegistered) {
+  auto* unittest = testing::UnitTest::GetInstance();
+  for (int i = 0; i < unittest->total_test_suite_count(); ++i) {
+    auto* tests = unittest->GetTestSuite(i);
+    if (tests->name() != std::string("DynamicUnitTestFixture")) continue;
+    for (int j = 0; j < tests->total_test_count(); ++j) {
+      if (tests->GetTestInfo(j)->name() != std::string("DynamicTest")) continue;
+      // Found it.
+      EXPECT_STREQ(tests->GetTestInfo(j)->value_param(), "VALUE");
+      EXPECT_STREQ(tests->GetTestInfo(j)->type_param(), "TYPE");
+      return;
+    }
+  }
+
+  FAIL() << "Didn't find the test!";
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_xml_outfile1_test_.cc b/leveldb_base/third_party/googletest/googletest/test/gtest_xml_outfile1_test_.cc
new file mode 100644
index 0000000..19aa252
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_xml_outfile1_test_.cc
@@ -0,0 +1,43 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// gtest_xml_outfile1_test_ writes some xml via TestProperty used by
+// gtest_xml_outfiles_test.py
+
+#include "gtest/gtest.h"
+
+class PropertyOne : public testing::Test {
+ protected:
+  void SetUp() override { RecordProperty("SetUpProp", 1); }
+  void TearDown() override { RecordProperty("TearDownProp", 1); }
+};
+
+TEST_F(PropertyOne, TestSomeProperties) {
+  RecordProperty("TestSomeProperty", 1);
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_xml_outfile2_test_.cc b/leveldb_base/third_party/googletest/googletest/test/gtest_xml_outfile2_test_.cc
new file mode 100644
index 0000000..f9a2a6e
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_xml_outfile2_test_.cc
@@ -0,0 +1,43 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// gtest_xml_outfile2_test_ writes some xml via TestProperty used by
+// gtest_xml_outfiles_test.py
+
+#include "gtest/gtest.h"
+
+class PropertyTwo : public testing::Test {
+ protected:
+  void SetUp() override { RecordProperty("SetUpProp", 2); }
+  void TearDown() override { RecordProperty("TearDownProp", 2); }
+};
+
+TEST_F(PropertyTwo, TestSomeProperties) {
+  RecordProperty("TestSomeProperty", 2);
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_xml_outfiles_test.py b/leveldb_base/third_party/googletest/googletest/test/gtest_xml_outfiles_test.py
new file mode 100644
index 0000000..ac66feb
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_xml_outfiles_test.py
@@ -0,0 +1,135 @@
+#!/usr/bin/env python
+#
+# Copyright 2008, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Unit test for the gtest_xml_output module."""
+
+import os
+from xml.dom import minidom, Node
+import gtest_test_utils
+import gtest_xml_test_utils
+
+GTEST_OUTPUT_SUBDIR = "xml_outfiles"
+GTEST_OUTPUT_1_TEST = "gtest_xml_outfile1_test_"
+GTEST_OUTPUT_2_TEST = "gtest_xml_outfile2_test_"
+
+EXPECTED_XML_1 = """<?xml version="1.0" encoding="UTF-8"?>
+<testsuites tests="1" failures="0" disabled="0" errors="0" time="*" timestamp="*" name="AllTests">
+  <testsuite name="PropertyOne" tests="1" failures="0" skipped="0" disabled="0" errors="0" time="*" timestamp="*">
+    <testcase name="TestSomeProperties" status="run" result="completed" time="*" timestamp="*" classname="PropertyOne">
+      <properties>
+        <property name="SetUpProp" value="1"/>
+        <property name="TestSomeProperty" value="1"/>
+        <property name="TearDownProp" value="1"/>
+      </properties>
+    </testcase>
+  </testsuite>
+</testsuites>
+"""
+
+EXPECTED_XML_2 = """<?xml version="1.0" encoding="UTF-8"?>
+<testsuites tests="1" failures="0" disabled="0" errors="0" time="*" timestamp="*" name="AllTests">
+  <testsuite name="PropertyTwo" tests="1" failures="0" skipped="0" disabled="0" errors="0" time="*" timestamp="*">
+    <testcase name="TestSomeProperties" status="run" result="completed" time="*" timestamp="*" classname="PropertyTwo">
+      <properties>
+        <property name="SetUpProp" value="2"/>
+        <property name="TestSomeProperty" value="2"/>
+        <property name="TearDownProp" value="2"/>
+      </properties>
+    </testcase>
+  </testsuite>
+</testsuites>
+"""
+
+
+class GTestXMLOutFilesTest(gtest_xml_test_utils.GTestXMLTestCase):
+  """Unit test for Google Test's XML output functionality."""
+
+  def setUp(self):
+    # We want the trailing '/' that the last "" provides in os.path.join, for
+    # telling Google Test to create an output directory instead of a single file
+    # for xml output.
+    self.output_dir_ = os.path.join(gtest_test_utils.GetTempDir(),
+                                    GTEST_OUTPUT_SUBDIR, "")
+    self.DeleteFilesAndDir()
+
+  def tearDown(self):
+    self.DeleteFilesAndDir()
+
+  def DeleteFilesAndDir(self):
+    try:
+      os.remove(os.path.join(self.output_dir_, GTEST_OUTPUT_1_TEST + ".xml"))
+    except os.error:
+      pass
+    try:
+      os.remove(os.path.join(self.output_dir_, GTEST_OUTPUT_2_TEST + ".xml"))
+    except os.error:
+      pass
+    try:
+      os.rmdir(self.output_dir_)
+    except os.error:
+      pass
+
+  def testOutfile1(self):
+    self._TestOutFile(GTEST_OUTPUT_1_TEST, EXPECTED_XML_1)
+
+  def testOutfile2(self):
+    self._TestOutFile(GTEST_OUTPUT_2_TEST, EXPECTED_XML_2)
+
+  def _TestOutFile(self, test_name, expected_xml):
+    gtest_prog_path = gtest_test_utils.GetTestExecutablePath(test_name)
+    command = [gtest_prog_path, "--gtest_output=xml:%s" % self.output_dir_]
+    p = gtest_test_utils.Subprocess(command,
+                                    working_dir=gtest_test_utils.GetTempDir())
+    self.assert_(p.exited)
+    self.assertEquals(0, p.exit_code)
+
+    output_file_name1 = test_name + ".xml"
+    output_file1 = os.path.join(self.output_dir_, output_file_name1)
+    output_file_name2 = 'lt-' + output_file_name1
+    output_file2 = os.path.join(self.output_dir_, output_file_name2)
+    self.assert_(os.path.isfile(output_file1) or os.path.isfile(output_file2),
+                 output_file1)
+
+    expected = minidom.parseString(expected_xml)
+    if os.path.isfile(output_file1):
+      actual = minidom.parse(output_file1)
+    else:
+      actual = minidom.parse(output_file2)
+    self.NormalizeXml(actual.documentElement)
+    self.AssertEquivalentNodes(expected.documentElement,
+                               actual.documentElement)
+    expected.unlink()
+    actual.unlink()
+
+
+if __name__ == "__main__":
+  os.environ["GTEST_STACK_TRACE_DEPTH"] = "0"
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_xml_output_unittest.py b/leveldb_base/third_party/googletest/googletest/test/gtest_xml_output_unittest.py
new file mode 100644
index 0000000..eade7aa
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_xml_output_unittest.py
@@ -0,0 +1,415 @@
+#!/usr/bin/env python
+#
+# Copyright 2006, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Unit test for the gtest_xml_output module"""
+
+import datetime
+import errno
+import os
+import re
+import sys
+from xml.dom import minidom, Node
+
+import gtest_test_utils
+import gtest_xml_test_utils
+
+GTEST_FILTER_FLAG = '--gtest_filter'
+GTEST_LIST_TESTS_FLAG = '--gtest_list_tests'
+GTEST_OUTPUT_FLAG = '--gtest_output'
+GTEST_DEFAULT_OUTPUT_FILE = 'test_detail.xml'
+GTEST_PROGRAM_NAME = 'gtest_xml_output_unittest_'
+
+# The flag indicating stacktraces are not supported
+NO_STACKTRACE_SUPPORT_FLAG = '--no_stacktrace_support'
+
+# The environment variables for test sharding.
+TOTAL_SHARDS_ENV_VAR = 'GTEST_TOTAL_SHARDS'
+SHARD_INDEX_ENV_VAR = 'GTEST_SHARD_INDEX'
+SHARD_STATUS_FILE_ENV_VAR = 'GTEST_SHARD_STATUS_FILE'
+
+SUPPORTS_STACK_TRACES = NO_STACKTRACE_SUPPORT_FLAG not in sys.argv
+
+if SUPPORTS_STACK_TRACES:
+  STACK_TRACE_TEMPLATE = '\nStack trace:\n*'
+else:
+  STACK_TRACE_TEMPLATE = ''
+  # unittest.main() can't handle unknown flags
+  sys.argv.remove(NO_STACKTRACE_SUPPORT_FLAG)
+
+EXPECTED_NON_EMPTY_XML = """<?xml version="1.0" encoding="UTF-8"?>
+<testsuites tests="26" failures="5" disabled="2" errors="0" time="*" timestamp="*" name="AllTests" ad_hoc_property="42">
+  <testsuite name="SuccessfulTest" tests="1" failures="0" disabled="0" skipped="0" errors="0" time="*" timestamp="*">
+    <testcase name="Succeeds" status="run" result="completed" time="*" timestamp="*" classname="SuccessfulTest"/>
+  </testsuite>
+  <testsuite name="FailedTest" tests="1" failures="1" disabled="0" skipped="0" errors="0" time="*" timestamp="*">
+    <testcase name="Fails" status="run" result="completed" time="*" timestamp="*" classname="FailedTest">
+      <failure message="gtest_xml_output_unittest_.cc:*&#x0A;Expected equality of these values:&#x0A;  1&#x0A;  2" type=""><![CDATA[gtest_xml_output_unittest_.cc:*
+Expected equality of these values:
+  1
+  2%(stack)s]]></failure>
+    </testcase>
+  </testsuite>
+  <testsuite name="MixedResultTest" tests="3" failures="1" disabled="1" skipped="0" errors="0" time="*" timestamp="*">
+    <testcase name="Succeeds" status="run" result="completed" time="*" timestamp="*" classname="MixedResultTest"/>
+    <testcase name="Fails" status="run" result="completed" time="*" timestamp="*" classname="MixedResultTest">
+      <failure message="gtest_xml_output_unittest_.cc:*&#x0A;Expected equality of these values:&#x0A;  1&#x0A;  2" type=""><![CDATA[gtest_xml_output_unittest_.cc:*
+Expected equality of these values:
+  1
+  2%(stack)s]]></failure>
+      <failure message="gtest_xml_output_unittest_.cc:*&#x0A;Expected equality of these values:&#x0A;  2&#x0A;  3" type=""><![CDATA[gtest_xml_output_unittest_.cc:*
+Expected equality of these values:
+  2
+  3%(stack)s]]></failure>
+    </testcase>
+    <testcase name="DISABLED_test" status="notrun" result="suppressed" time="*" timestamp="*" classname="MixedResultTest"/>
+  </testsuite>
+  <testsuite name="XmlQuotingTest" tests="1" failures="1" disabled="0" skipped="0" errors="0" time="*" timestamp="*">
+    <testcase name="OutputsCData" status="run" result="completed" time="*" timestamp="*" classname="XmlQuotingTest">
+      <failure message="gtest_xml_output_unittest_.cc:*&#x0A;Failed&#x0A;XML output: &lt;?xml encoding=&quot;utf-8&quot;&gt;&lt;top&gt;&lt;![CDATA[cdata text]]&gt;&lt;/top&gt;" type=""><![CDATA[gtest_xml_output_unittest_.cc:*
+Failed
+XML output: <?xml encoding="utf-8"><top><![CDATA[cdata text]]>]]&gt;<![CDATA[</top>%(stack)s]]></failure>
+    </testcase>
+  </testsuite>
+  <testsuite name="InvalidCharactersTest" tests="1" failures="1" disabled="0" skipped="0" errors="0" time="*" timestamp="*">
+    <testcase name="InvalidCharactersInMessage" status="run" result="completed" time="*" timestamp="*" classname="InvalidCharactersTest">
+      <failure message="gtest_xml_output_unittest_.cc:*&#x0A;Failed&#x0A;Invalid characters in brackets []" type=""><![CDATA[gtest_xml_output_unittest_.cc:*
+Failed
+Invalid characters in brackets []%(stack)s]]></failure>
+    </testcase>
+  </testsuite>
+  <testsuite name="DisabledTest" tests="1" failures="0" disabled="1" skipped="0" errors="0" time="*" timestamp="*">
+    <testcase name="DISABLED_test_not_run" status="notrun" result="suppressed" time="*" timestamp="*" classname="DisabledTest"/>
+  </testsuite>
+  <testsuite name="SkippedTest" tests="3" failures="1" disabled="0" skipped="2" errors="0" time="*" timestamp="*">
+    <testcase name="Skipped" status="run" result="skipped" time="*" timestamp="*" classname="SkippedTest">
+      <skipped message="gtest_xml_output_unittest_.cc:*&#x0A;"><![CDATA[gtest_xml_output_unittest_.cc:*
+%(stack)s]]></skipped>
+    </testcase>
+    <testcase name="SkippedWithMessage" status="run" result="skipped" time="*" timestamp="*" classname="SkippedTest">
+      <skipped message="gtest_xml_output_unittest_.cc:*&#x0A;It is good practice to tell why you skip a test."><![CDATA[gtest_xml_output_unittest_.cc:*
+It is good practice to tell why you skip a test.%(stack)s]]></skipped>
+    </testcase>
+    <testcase name="SkippedAfterFailure" status="run" result="completed" time="*" timestamp="*" classname="SkippedTest">
+      <failure message="gtest_xml_output_unittest_.cc:*&#x0A;Expected equality of these values:&#x0A;  1&#x0A;  2" type=""><![CDATA[gtest_xml_output_unittest_.cc:*
+Expected equality of these values:
+  1
+  2%(stack)s]]></failure>
+      <skipped message="gtest_xml_output_unittest_.cc:*&#x0A;It is good practice to tell why you skip a test."><![CDATA[gtest_xml_output_unittest_.cc:*
+It is good practice to tell why you skip a test.%(stack)s]]></skipped>
+    </testcase>
+
+  </testsuite>
+  <testsuite name="PropertyRecordingTest" tests="4" failures="0" disabled="0" skipped="0" errors="0" time="*" timestamp="*" SetUpTestSuite="yes" TearDownTestSuite="aye">
+    <testcase name="OneProperty" status="run" result="completed" time="*" timestamp="*" classname="PropertyRecordingTest">
+      <properties>
+        <property name="key_1" value="1"/>
+      </properties>
+    </testcase>
+    <testcase name="IntValuedProperty" status="run" result="completed" time="*" timestamp="*" classname="PropertyRecordingTest">
+      <properties>
+        <property name="key_int" value="1"/>
+      </properties>
+    </testcase>
+    <testcase name="ThreeProperties" status="run" result="completed" time="*" timestamp="*" classname="PropertyRecordingTest">
+      <properties>
+        <property name="key_1" value="1"/>
+        <property name="key_2" value="2"/>
+        <property name="key_3" value="3"/>
+      </properties>
+    </testcase>
+    <testcase name="TwoValuesForOneKeyUsesLastValue" status="run" result="completed" time="*" timestamp="*" classname="PropertyRecordingTest">
+      <properties>
+        <property name="key_1" value="2"/>
+      </properties>
+    </testcase>
+  </testsuite>
+  <testsuite name="NoFixtureTest" tests="3" failures="0" disabled="0" skipped="0" errors="0" time="*" timestamp="*">
+     <testcase name="RecordProperty" status="run" result="completed" time="*" timestamp="*" classname="NoFixtureTest">
+       <properties>
+         <property name="key" value="1"/>
+       </properties>
+     </testcase>
+     <testcase name="ExternalUtilityThatCallsRecordIntValuedProperty" status="run" result="completed" time="*" timestamp="*" classname="NoFixtureTest">
+       <properties>
+         <property name="key_for_utility_int" value="1"/>
+       </properties>
+     </testcase>
+     <testcase name="ExternalUtilityThatCallsRecordStringValuedProperty" status="run" result="completed" time="*" timestamp="*" classname="NoFixtureTest">
+       <properties>
+         <property name="key_for_utility_string" value="1"/>
+       </properties>
+     </testcase>
+  </testsuite>
+  <testsuite name="Single/ValueParamTest" tests="4" failures="0" disabled="0" skipped="0" errors="0" time="*" timestamp="*">
+    <testcase name="HasValueParamAttribute/0" value_param="33" status="run" result="completed" time="*" timestamp="*" classname="Single/ValueParamTest" />
+    <testcase name="HasValueParamAttribute/1" value_param="42" status="run" result="completed" time="*" timestamp="*" classname="Single/ValueParamTest" />
+    <testcase name="AnotherTestThatHasValueParamAttribute/0" value_param="33" status="run" result="completed" time="*" timestamp="*" classname="Single/ValueParamTest" />
+    <testcase name="AnotherTestThatHasValueParamAttribute/1" value_param="42" status="run" result="completed" time="*" timestamp="*" classname="Single/ValueParamTest" />
+  </testsuite>
+  <testsuite name="TypedTest/0" tests="1" failures="0" disabled="0" skipped="0" errors="0" time="*" timestamp="*">
+    <testcase name="HasTypeParamAttribute" type_param="*" status="run" result="completed" time="*" timestamp="*" classname="TypedTest/0" />
+  </testsuite>
+  <testsuite name="TypedTest/1" tests="1" failures="0" disabled="0" skipped="0" errors="0" time="*" timestamp="*">
+    <testcase name="HasTypeParamAttribute" type_param="*" status="run" result="completed" time="*" timestamp="*" classname="TypedTest/1" />
+  </testsuite>
+  <testsuite name="Single/TypeParameterizedTestSuite/0" tests="1" failures="0" disabled="0" skipped="0" errors="0" time="*" timestamp="*">
+    <testcase name="HasTypeParamAttribute" type_param="*" status="run" result="completed" time="*" timestamp="*" classname="Single/TypeParameterizedTestSuite/0" />
+  </testsuite>
+  <testsuite name="Single/TypeParameterizedTestSuite/1" tests="1" failures="0" disabled="0" skipped="0" errors="0" time="*" timestamp="*">
+    <testcase name="HasTypeParamAttribute" type_param="*" status="run" result="completed" time="*" timestamp="*" classname="Single/TypeParameterizedTestSuite/1" />
+  </testsuite>
+</testsuites>""" % {
+    'stack': STACK_TRACE_TEMPLATE
+}
+
+EXPECTED_FILTERED_TEST_XML = """<?xml version="1.0" encoding="UTF-8"?>
+<testsuites tests="1" failures="0" disabled="0" errors="0" time="*"
+            timestamp="*" name="AllTests" ad_hoc_property="42">
+  <testsuite name="SuccessfulTest" tests="1" failures="0" disabled="0" skipped="0"
+             errors="0" time="*" timestamp="*">
+    <testcase name="Succeeds" status="run" result="completed" time="*" timestamp="*" classname="SuccessfulTest"/>
+  </testsuite>
+</testsuites>"""
+
+EXPECTED_SHARDED_TEST_XML = """<?xml version="1.0" encoding="UTF-8"?>
+<testsuites tests="3" failures="0" disabled="0" errors="0" time="*" timestamp="*" name="AllTests" ad_hoc_property="42">
+  <testsuite name="SuccessfulTest" tests="1" failures="0" disabled="0" skipped="0" errors="0" time="*" timestamp="*">
+    <testcase name="Succeeds" status="run" result="completed" time="*" timestamp="*" classname="SuccessfulTest"/>
+  </testsuite>
+  <testsuite name="PropertyRecordingTest" tests="1" failures="0" disabled="0" skipped="0" errors="0" time="*" timestamp="*" SetUpTestSuite="yes" TearDownTestSuite="aye">
+    <testcase name="IntValuedProperty" status="run" result="completed" time="*" timestamp="*" classname="PropertyRecordingTest">
+      <properties>
+        <property name="key_int" value="1"/>
+      </properties>
+    </testcase>
+  </testsuite>
+  <testsuite name="Single/ValueParamTest" tests="1" failures="0" disabled="0" skipped="0" errors="0" time="*" timestamp="*">
+    <testcase name="HasValueParamAttribute/0" value_param="33" status="run" result="completed" time="*" timestamp="*" classname="Single/ValueParamTest" />
+  </testsuite>
+</testsuites>"""
+
+EXPECTED_NO_TEST_XML = """<?xml version="1.0" encoding="UTF-8"?>
+<testsuites tests="0" failures="0" disabled="0" errors="0" time="*"
+            timestamp="*" name="AllTests">
+  <testsuite name="NonTestSuiteFailure" tests="1" failures="1" disabled="0" skipped="0" errors="0" time="*" timestamp="*">
+    <testcase name="" status="run" result="completed" time="*" timestamp="*" classname="">
+      <failure message="gtest_no_test_unittest.cc:*&#x0A;Expected equality of these values:&#x0A;  1&#x0A;  2" type=""><![CDATA[gtest_no_test_unittest.cc:*
+Expected equality of these values:
+  1
+  2%(stack)s]]></failure>
+    </testcase>
+  </testsuite>
+</testsuites>""" % {
+    'stack': STACK_TRACE_TEMPLATE
+}
+
+GTEST_PROGRAM_PATH = gtest_test_utils.GetTestExecutablePath(GTEST_PROGRAM_NAME)
+
+SUPPORTS_TYPED_TESTS = 'TypedTest' in gtest_test_utils.Subprocess(
+    [GTEST_PROGRAM_PATH, GTEST_LIST_TESTS_FLAG], capture_stderr=False).output
+
+
+class GTestXMLOutputUnitTest(gtest_xml_test_utils.GTestXMLTestCase):
+  """
+  Unit test for Google Test's XML output functionality.
+  """
+
+  # This test currently breaks on platforms that do not support typed and
+  # type-parameterized tests, so we don't run it under them.
+  if SUPPORTS_TYPED_TESTS:
+    def testNonEmptyXmlOutput(self):
+      """
+      Runs a test program that generates a non-empty XML output, and
+      tests that the XML output is expected.
+      """
+      self._TestXmlOutput(GTEST_PROGRAM_NAME, EXPECTED_NON_EMPTY_XML, 1)
+
+  def testNoTestXmlOutput(self):
+    """Verifies XML output for a Google Test binary without actual tests.
+
+    Runs a test program that generates an XML output for a binary without tests,
+    and tests that the XML output is expected.
+    """
+
+    self._TestXmlOutput('gtest_no_test_unittest', EXPECTED_NO_TEST_XML, 0)
+
+  def testTimestampValue(self):
+    """Checks whether the timestamp attribute in the XML output is valid.
+
+    Runs a test program that generates an empty XML output, and checks if
+    the timestamp attribute in the testsuites tag is valid.
+    """
+    actual = self._GetXmlOutput('gtest_no_test_unittest', [], {}, 0)
+    date_time_str = actual.documentElement.getAttributeNode('timestamp').value
+    # datetime.strptime() is only available in Python 2.5+ so we have to
+    # parse the expected datetime manually.
+    match = re.match(r'(\d+)-(\d\d)-(\d\d)T(\d\d):(\d\d):(\d\d)', date_time_str)
+    self.assertTrue(
+        re.match,
+        'XML datettime string %s has incorrect format' % date_time_str)
+    date_time_from_xml = datetime.datetime(
+        year=int(match.group(1)), month=int(match.group(2)),
+        day=int(match.group(3)), hour=int(match.group(4)),
+        minute=int(match.group(5)), second=int(match.group(6)))
+
+    time_delta = abs(datetime.datetime.now() - date_time_from_xml)
+    # timestamp value should be near the current local time
+    self.assertTrue(time_delta < datetime.timedelta(seconds=600),
+                    'time_delta is %s' % time_delta)
+    actual.unlink()
+
+  def testDefaultOutputFile(self):
+    """
+    Confirms that Google Test produces an XML output file with the expected
+    default name if no name is explicitly specified.
+    """
+    output_file = os.path.join(gtest_test_utils.GetTempDir(),
+                               GTEST_DEFAULT_OUTPUT_FILE)
+    gtest_prog_path = gtest_test_utils.GetTestExecutablePath(
+        'gtest_no_test_unittest')
+    try:
+      os.remove(output_file)
+    except OSError:
+      e = sys.exc_info()[1]
+      if e.errno != errno.ENOENT:
+        raise
+
+    p = gtest_test_utils.Subprocess(
+        [gtest_prog_path, '%s=xml' % GTEST_OUTPUT_FLAG],
+        working_dir=gtest_test_utils.GetTempDir())
+    self.assert_(p.exited)
+    self.assertEquals(0, p.exit_code)
+    self.assert_(os.path.isfile(output_file))
+
+  def testSuppressedXmlOutput(self):
+    """
+    Tests that no XML file is generated if the default XML listener is
+    shut down before RUN_ALL_TESTS is invoked.
+    """
+
+    xml_path = os.path.join(gtest_test_utils.GetTempDir(),
+                            GTEST_PROGRAM_NAME + 'out.xml')
+    if os.path.isfile(xml_path):
+      os.remove(xml_path)
+
+    command = [GTEST_PROGRAM_PATH,
+               '%s=xml:%s' % (GTEST_OUTPUT_FLAG, xml_path),
+               '--shut_down_xml']
+    p = gtest_test_utils.Subprocess(command)
+    if p.terminated_by_signal:
+      # p.signal is available only if p.terminated_by_signal is True.
+      self.assertFalse(
+          p.terminated_by_signal,
+          '%s was killed by signal %d' % (GTEST_PROGRAM_NAME, p.signal))
+    else:
+      self.assert_(p.exited)
+      self.assertEquals(1, p.exit_code,
+                        "'%s' exited with code %s, which doesn't match "
+                        'the expected exit code %s.'
+                        % (command, p.exit_code, 1))
+
+    self.assert_(not os.path.isfile(xml_path))
+
+  def testFilteredTestXmlOutput(self):
+    """Verifies XML output when a filter is applied.
+
+    Runs a test program that executes only some tests and verifies that
+    non-selected tests do not show up in the XML output.
+    """
+
+    self._TestXmlOutput(GTEST_PROGRAM_NAME, EXPECTED_FILTERED_TEST_XML, 0,
+                        extra_args=['%s=SuccessfulTest.*' % GTEST_FILTER_FLAG])
+
+  def testShardedTestXmlOutput(self):
+    """Verifies XML output when run using multiple shards.
+
+    Runs a test program that executes only one shard and verifies that tests
+    from other shards do not show up in the XML output.
+    """
+
+    self._TestXmlOutput(
+        GTEST_PROGRAM_NAME,
+        EXPECTED_SHARDED_TEST_XML,
+        0,
+        extra_env={SHARD_INDEX_ENV_VAR: '0',
+                   TOTAL_SHARDS_ENV_VAR: '10'})
+
+  def _GetXmlOutput(self, gtest_prog_name, extra_args, extra_env,
+                    expected_exit_code):
+    """
+    Returns the xml output generated by running the program gtest_prog_name.
+    Furthermore, the program's exit code must be expected_exit_code.
+    """
+    xml_path = os.path.join(gtest_test_utils.GetTempDir(),
+                            gtest_prog_name + 'out.xml')
+    gtest_prog_path = gtest_test_utils.GetTestExecutablePath(gtest_prog_name)
+
+    command = ([gtest_prog_path, '%s=xml:%s' % (GTEST_OUTPUT_FLAG, xml_path)] +
+               extra_args)
+    environ_copy = os.environ.copy()
+    if extra_env:
+      environ_copy.update(extra_env)
+    p = gtest_test_utils.Subprocess(command, env=environ_copy)
+
+    if p.terminated_by_signal:
+      self.assert_(False,
+                   '%s was killed by signal %d' % (gtest_prog_name, p.signal))
+    else:
+      self.assert_(p.exited)
+      self.assertEquals(expected_exit_code, p.exit_code,
+                        "'%s' exited with code %s, which doesn't match "
+                        'the expected exit code %s.'
+                        % (command, p.exit_code, expected_exit_code))
+    actual = minidom.parse(xml_path)
+    return actual
+
+  def _TestXmlOutput(self, gtest_prog_name, expected_xml,
+                     expected_exit_code, extra_args=None, extra_env=None):
+    """
+    Asserts that the XML document generated by running the program
+    gtest_prog_name matches expected_xml, a string containing another
+    XML document.  Furthermore, the program's exit code must be
+    expected_exit_code.
+    """
+
+    actual = self._GetXmlOutput(gtest_prog_name, extra_args or [],
+                                extra_env or {}, expected_exit_code)
+    expected = minidom.parseString(expected_xml)
+    self.NormalizeXml(actual.documentElement)
+    self.AssertEquivalentNodes(expected.documentElement,
+                               actual.documentElement)
+    expected.unlink()
+    actual.unlink()
+
+
+if __name__ == '__main__':
+  os.environ['GTEST_STACK_TRACE_DEPTH'] = '1'
+  gtest_test_utils.Main()
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_xml_output_unittest_.cc b/leveldb_base/third_party/googletest/googletest/test/gtest_xml_output_unittest_.cc
new file mode 100644
index 0000000..c0036aa
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_xml_output_unittest_.cc
@@ -0,0 +1,193 @@
+// Copyright 2006, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Unit test for Google Test XML output.
+//
+// A user can specify XML output in a Google Test program to run via
+// either the GTEST_OUTPUT environment variable or the --gtest_output
+// flag.  This is used for testing such functionality.
+//
+// This program will be invoked from a Python unit test.  Don't run it
+// directly.
+
+#include "gtest/gtest.h"
+
+using ::testing::InitGoogleTest;
+using ::testing::TestEventListeners;
+using ::testing::TestWithParam;
+using ::testing::UnitTest;
+using ::testing::Test;
+using ::testing::Values;
+
+class SuccessfulTest : public Test {
+};
+
+TEST_F(SuccessfulTest, Succeeds) {
+  SUCCEED() << "This is a success.";
+  ASSERT_EQ(1, 1);
+}
+
+class FailedTest : public Test {
+};
+
+TEST_F(FailedTest, Fails) {
+  ASSERT_EQ(1, 2);
+}
+
+class DisabledTest : public Test {
+};
+
+TEST_F(DisabledTest, DISABLED_test_not_run) {
+  FAIL() << "Unexpected failure: Disabled test should not be run";
+}
+
+class SkippedTest : public Test {
+};
+
+TEST_F(SkippedTest, Skipped) {
+  GTEST_SKIP();
+}
+
+TEST_F(SkippedTest, SkippedWithMessage) {
+  GTEST_SKIP() << "It is good practice to tell why you skip a test.";
+}
+
+TEST_F(SkippedTest, SkippedAfterFailure) {
+  EXPECT_EQ(1, 2);
+  GTEST_SKIP() << "It is good practice to tell why you skip a test.";
+}
+
+TEST(MixedResultTest, Succeeds) {
+  EXPECT_EQ(1, 1);
+  ASSERT_EQ(1, 1);
+}
+
+TEST(MixedResultTest, Fails) {
+  EXPECT_EQ(1, 2);
+  ASSERT_EQ(2, 3);
+}
+
+TEST(MixedResultTest, DISABLED_test) {
+  FAIL() << "Unexpected failure: Disabled test should not be run";
+}
+
+TEST(XmlQuotingTest, OutputsCData) {
+  FAIL() << "XML output: "
+            "<?xml encoding=\"utf-8\"><top><![CDATA[cdata text]]></top>";
+}
+
+// Helps to test that invalid characters produced by test code do not make
+// it into the XML file.
+TEST(InvalidCharactersTest, InvalidCharactersInMessage) {
+  FAIL() << "Invalid characters in brackets [\x1\x2]";
+}
+
+class PropertyRecordingTest : public Test {
+ public:
+  static void SetUpTestSuite() { RecordProperty("SetUpTestSuite", "yes"); }
+  static void TearDownTestSuite() {
+    RecordProperty("TearDownTestSuite", "aye");
+  }
+};
+
+TEST_F(PropertyRecordingTest, OneProperty) {
+  RecordProperty("key_1", "1");
+}
+
+TEST_F(PropertyRecordingTest, IntValuedProperty) {
+  RecordProperty("key_int", 1);
+}
+
+TEST_F(PropertyRecordingTest, ThreeProperties) {
+  RecordProperty("key_1", "1");
+  RecordProperty("key_2", "2");
+  RecordProperty("key_3", "3");
+}
+
+TEST_F(PropertyRecordingTest, TwoValuesForOneKeyUsesLastValue) {
+  RecordProperty("key_1", "1");
+  RecordProperty("key_1", "2");
+}
+
+TEST(NoFixtureTest, RecordProperty) {
+  RecordProperty("key", "1");
+}
+
+void ExternalUtilityThatCallsRecordProperty(const std::string& key, int value) {
+  testing::Test::RecordProperty(key, value);
+}
+
+void ExternalUtilityThatCallsRecordProperty(const std::string& key,
+                                            const std::string& value) {
+  testing::Test::RecordProperty(key, value);
+}
+
+TEST(NoFixtureTest, ExternalUtilityThatCallsRecordIntValuedProperty) {
+  ExternalUtilityThatCallsRecordProperty("key_for_utility_int", 1);
+}
+
+TEST(NoFixtureTest, ExternalUtilityThatCallsRecordStringValuedProperty) {
+  ExternalUtilityThatCallsRecordProperty("key_for_utility_string", "1");
+}
+
+// Verifies that the test parameter value is output in the 'value_param'
+// XML attribute for value-parameterized tests.
+class ValueParamTest : public TestWithParam<int> {};
+TEST_P(ValueParamTest, HasValueParamAttribute) {}
+TEST_P(ValueParamTest, AnotherTestThatHasValueParamAttribute) {}
+INSTANTIATE_TEST_SUITE_P(Single, ValueParamTest, Values(33, 42));
+
+// Verifies that the type parameter name is output in the 'type_param'
+// XML attribute for typed tests.
+template <typename T> class TypedTest : public Test {};
+typedef testing::Types<int, long> TypedTestTypes;
+TYPED_TEST_SUITE(TypedTest, TypedTestTypes);
+TYPED_TEST(TypedTest, HasTypeParamAttribute) {}
+
+// Verifies that the type parameter name is output in the 'type_param'
+// XML attribute for type-parameterized tests.
+template <typename T>
+class TypeParameterizedTestSuite : public Test {};
+TYPED_TEST_SUITE_P(TypeParameterizedTestSuite);
+TYPED_TEST_P(TypeParameterizedTestSuite, HasTypeParamAttribute) {}
+REGISTER_TYPED_TEST_SUITE_P(TypeParameterizedTestSuite, HasTypeParamAttribute);
+typedef testing::Types<int, long> TypeParameterizedTestSuiteTypes;  // NOLINT
+INSTANTIATE_TYPED_TEST_SUITE_P(Single, TypeParameterizedTestSuite,
+                               TypeParameterizedTestSuiteTypes);
+
+int main(int argc, char** argv) {
+  InitGoogleTest(&argc, argv);
+
+  if (argc > 1 && strcmp(argv[1], "--shut_down_xml") == 0) {
+    TestEventListeners& listeners = UnitTest::GetInstance()->listeners();
+    delete listeners.Release(listeners.default_xml_generator());
+  }
+  testing::Test::RecordProperty("ad_hoc_property", "42");
+  return RUN_ALL_TESTS();
+}
diff --git a/leveldb_base/third_party/googletest/googletest/test/gtest_xml_test_utils.py b/leveldb_base/third_party/googletest/googletest/test/gtest_xml_test_utils.py
new file mode 100644
index 0000000..ec42c62
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/gtest_xml_test_utils.py
@@ -0,0 +1,197 @@
+# Copyright 2006, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Unit test utilities for gtest_xml_output"""
+
+import re
+from xml.dom import minidom, Node
+import gtest_test_utils
+
+GTEST_DEFAULT_OUTPUT_FILE = 'test_detail.xml'
+
+class GTestXMLTestCase(gtest_test_utils.TestCase):
+  """
+  Base class for tests of Google Test's XML output functionality.
+  """
+
+
+  def AssertEquivalentNodes(self, expected_node, actual_node):
+    """
+    Asserts that actual_node (a DOM node object) is equivalent to
+    expected_node (another DOM node object), in that either both of
+    them are CDATA nodes and have the same value, or both are DOM
+    elements and actual_node meets all of the following conditions:
+
+    *  It has the same tag name as expected_node.
+    *  It has the same set of attributes as expected_node, each with
+       the same value as the corresponding attribute of expected_node.
+       Exceptions are any attribute named "time", which needs only be
+       convertible to a floating-point number and any attribute named
+       "type_param" which only has to be non-empty.
+    *  It has an equivalent set of child nodes (including elements and
+       CDATA sections) as expected_node.  Note that we ignore the
+       order of the children as they are not guaranteed to be in any
+       particular order.
+    """
+
+    if expected_node.nodeType == Node.CDATA_SECTION_NODE:
+      self.assertEquals(Node.CDATA_SECTION_NODE, actual_node.nodeType)
+      self.assertEquals(expected_node.nodeValue, actual_node.nodeValue)
+      return
+
+    self.assertEquals(Node.ELEMENT_NODE, actual_node.nodeType)
+    self.assertEquals(Node.ELEMENT_NODE, expected_node.nodeType)
+    self.assertEquals(expected_node.tagName, actual_node.tagName)
+
+    expected_attributes = expected_node.attributes
+    actual_attributes = actual_node.attributes
+    self.assertEquals(
+        expected_attributes.length, actual_attributes.length,
+        'attribute numbers differ in element %s:\nExpected: %r\nActual: %r' % (
+            actual_node.tagName, expected_attributes.keys(),
+            actual_attributes.keys()))
+    for i in range(expected_attributes.length):
+      expected_attr = expected_attributes.item(i)
+      actual_attr = actual_attributes.get(expected_attr.name)
+      self.assert_(
+          actual_attr is not None,
+          'expected attribute %s not found in element %s' %
+          (expected_attr.name, actual_node.tagName))
+      self.assertEquals(
+          expected_attr.value, actual_attr.value,
+          ' values of attribute %s in element %s differ: %s vs %s' %
+          (expected_attr.name, actual_node.tagName,
+           expected_attr.value, actual_attr.value))
+
+    expected_children = self._GetChildren(expected_node)
+    actual_children = self._GetChildren(actual_node)
+    self.assertEquals(
+        len(expected_children), len(actual_children),
+        'number of child elements differ in element ' + actual_node.tagName)
+    for child_id, child in expected_children.items():
+      self.assert_(child_id in actual_children,
+                   '<%s> is not in <%s> (in element %s)' %
+                   (child_id, actual_children, actual_node.tagName))
+      self.AssertEquivalentNodes(child, actual_children[child_id])
+
+  identifying_attribute = {
+      'testsuites': 'name',
+      'testsuite': 'name',
+      'testcase': 'name',
+      'failure': 'message',
+      'skipped': 'message',
+      'property': 'name',
+  }
+
+  def _GetChildren(self, element):
+    """
+    Fetches all of the child nodes of element, a DOM Element object.
+    Returns them as the values of a dictionary keyed by the IDs of the
+    children.  For <testsuites>, <testsuite>, <testcase>, and <property>
+    elements, the ID is the value of their "name" attribute; for <failure>
+    elements, it is the value of the "message" attribute; for <properties>
+    elements, it is the value of their parent's "name" attribute plus the
+    literal string "properties"; CDATA sections and non-whitespace
+    text nodes are concatenated into a single CDATA section with ID
+    "detail".  An exception is raised if any element other than the above
+    four is encountered, if two child elements with the same identifying
+    attributes are encountered, or if any other type of node is encountered.
+    """
+
+    children = {}
+    for child in element.childNodes:
+      if child.nodeType == Node.ELEMENT_NODE:
+        if child.tagName == 'properties':
+          self.assert_(child.parentNode is not None,
+                       'Encountered <properties> element without a parent')
+          child_id = child.parentNode.getAttribute('name') + '-properties'
+        else:
+          self.assert_(child.tagName in self.identifying_attribute,
+                       'Encountered unknown element <%s>' % child.tagName)
+          child_id = child.getAttribute(
+              self.identifying_attribute[child.tagName])
+        self.assert_(child_id not in children)
+        children[child_id] = child
+      elif child.nodeType in [Node.TEXT_NODE, Node.CDATA_SECTION_NODE]:
+        if 'detail' not in children:
+          if (child.nodeType == Node.CDATA_SECTION_NODE or
+              not child.nodeValue.isspace()):
+            children['detail'] = child.ownerDocument.createCDATASection(
+                child.nodeValue)
+        else:
+          children['detail'].nodeValue += child.nodeValue
+      else:
+        self.fail('Encountered unexpected node type %d' % child.nodeType)
+    return children
+
+  def NormalizeXml(self, element):
+    """
+    Normalizes Google Test's XML output to eliminate references to transient
+    information that may change from run to run.
+
+    *  The "time" attribute of <testsuites>, <testsuite> and <testcase>
+       elements is replaced with a single asterisk, if it contains
+       only digit characters.
+    *  The "timestamp" attribute of <testsuites> elements is replaced with a
+       single asterisk, if it contains a valid ISO8601 datetime value.
+    *  The "type_param" attribute of <testcase> elements is replaced with a
+       single asterisk (if it sn non-empty) as it is the type name returned
+       by the compiler and is platform dependent.
+    *  The line info reported in the first line of the "message"
+       attribute and CDATA section of <failure> elements is replaced with the
+       file's basename and a single asterisk for the line number.
+    *  The directory names in file paths are removed.
+    *  The stack traces are removed.
+    """
+
+    if element.tagName in ('testsuites', 'testsuite', 'testcase'):
+      timestamp = element.getAttributeNode('timestamp')
+      timestamp.value = re.sub(r'^\d{4}-\d\d-\d\dT\d\d:\d\d:\d\d\.\d\d\d$',
+                               '*', timestamp.value)
+    if element.tagName in ('testsuites', 'testsuite', 'testcase'):
+      time = element.getAttributeNode('time')
+      time.value = re.sub(r'^\d+(\.\d+)?$', '*', time.value)
+      type_param = element.getAttributeNode('type_param')
+      if type_param and type_param.value:
+        type_param.value = '*'
+    elif element.tagName == 'failure' or element.tagName == 'skipped':
+      source_line_pat = r'^.*[/\\](.*:)\d+\n'
+      # Replaces the source line information with a normalized form.
+      message = element.getAttributeNode('message')
+      message.value = re.sub(source_line_pat, '\\1*\n', message.value)
+      for child in element.childNodes:
+        if child.nodeType == Node.CDATA_SECTION_NODE:
+          # Replaces the source line information with a normalized form.
+          cdata = re.sub(source_line_pat, '\\1*\n', child.nodeValue)
+          # Removes the actual stack trace.
+          child.nodeValue = re.sub(r'Stack trace:\n(.|\n)*',
+                                   'Stack trace:\n*', cdata)
+    for child in element.childNodes:
+      if child.nodeType == Node.ELEMENT_NODE:
+        self.NormalizeXml(child)
diff --git a/leveldb_base/third_party/googletest/googletest/test/production.cc b/leveldb_base/third_party/googletest/googletest/test/production.cc
new file mode 100644
index 0000000..0f69f6d
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/production.cc
@@ -0,0 +1,35 @@
+// Copyright 2006, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// This is part of the unit test for gtest_prod.h.
+
+#include "production.h"
+
+PrivateCode::PrivateCode() : x_(0) {}
diff --git a/leveldb_base/third_party/googletest/googletest/test/production.h b/leveldb_base/third_party/googletest/googletest/test/production.h
new file mode 100644
index 0000000..41a5472
--- /dev/null
+++ b/leveldb_base/third_party/googletest/googletest/test/production.h
@@ -0,0 +1,54 @@
+// Copyright 2006, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// This is part of the unit test for gtest_prod.h.
+
+#ifndef GOOGLETEST_TEST_PRODUCTION_H_
+#define GOOGLETEST_TEST_PRODUCTION_H_
+
+#include "gtest/gtest_prod.h"
+
+class PrivateCode {
+ public:
+  // Declares a friend test that does not use a fixture.
+  FRIEND_TEST(PrivateCodeTest, CanAccessPrivateMembers);
+
+  // Declares a friend test that uses a fixture.
+  FRIEND_TEST(PrivateCodeFixtureTest, CanAccessPrivateMembers);
+
+  PrivateCode();
+
+  int x() const { return x_; }
+ private:
+  void set_x(int an_x) { x_ = an_x; }
+  int x_;
+};
+
+#endif  // GOOGLETEST_TEST_PRODUCTION_H_
diff --git a/leveldb_base/third_party/googletest/library.json b/leveldb_base/third_party/googletest/library.json
new file mode 100644
index 0000000..f61bf00
--- /dev/null
+++ b/leveldb_base/third_party/googletest/library.json
@@ -0,0 +1,62 @@
+{
+  "name": "googletest",
+  "keywords": "unittest, unit, test, gtest, gmock",
+  "description": "googletest is a testing framework developed by the Testing Technology team with Google's specific requirements and constraints in mind. No matter whether you work on Linux, Windows, or a Mac, if you write C++ code, googletest can help you. And it supports any kind of tests, not just unit tests.",
+   "license": "BSD-3-Clause",
+  "homepage": "https://github.com/google/googletest/blob/master/README.md",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/google/googletest.git"
+  },
+  "version": "1.10.0",
+  "frameworks": "arduino",
+  "platforms": [
+        "espressif32",
+        "espressif8266"
+  ],
+  "export": {
+        "include": [
+            "googlemock/include/*",
+            "googlemock/src/*",
+            "googletest/include/*",
+            "googletest/src/*"
+        ],
+        "exclude": [
+            "ci",
+            "googlemock/cmake",
+            "googlemock/scripts",
+            "googlemock/test",
+            "googlemock/CMakeLists.txt",
+            "googletest/cmake",
+            "googletest/scripts",
+            "googletest/test",
+            "googletest/CMakeLists.txt"
+          ]
+  },
+  "build": {
+        "flags": [
+            "-Igooglemock/include",
+            "-Igooglemock",
+            "-Igoogletest/include",
+            "-Igoogletest"
+        ],
+        "srcFilter": [
+          "+<*>",
+          "-<.git/>",
+          "-<googlemock>",
+          "-<googlemock/test/>",
+          "-<googlemock/src>",
+          "+<googlemock/src/gmock-all.cc>",
+          "+<googletest/src/gtest-all.cc>",
+          "+<googlemock/src/gmock_main.cc>",
+          "-<googletest>",
+          "-<googletest/codegear/>",
+          "-<googletest/samples>",
+          "-<googletest/test/>",
+          "-<googletest/xcode>",
+          "-<googletest/src>",
+          "+<googletest/src/gtest-all.cc>",
+          "+<googletest/src/gtest_main.cc>"
+        ]
+  }
+}
diff --git a/leveldb_base/util/arena.cc b/leveldb_base/util/arena.cc
new file mode 100644
index 0000000..46e3b2e
--- /dev/null
+++ b/leveldb_base/util/arena.cc
@@ -0,0 +1,66 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "util/arena.h"
+
+namespace leveldb {
+
+static const int kBlockSize = 4096;
+
+Arena::Arena()
+    : alloc_ptr_(nullptr), alloc_bytes_remaining_(0), memory_usage_(0) {}
+
+Arena::~Arena() {
+  for (size_t i = 0; i < blocks_.size(); i++) {
+    delete[] blocks_[i];
+  }
+}
+
+char* Arena::AllocateFallback(size_t bytes) {
+  if (bytes > kBlockSize / 4) {
+    // Object is more than a quarter of our block size.  Allocate it separately
+    // to avoid wasting too much space in leftover bytes.
+    char* result = AllocateNewBlock(bytes);
+    return result;
+  }
+
+  // We waste the remaining space in the current block.
+  alloc_ptr_ = AllocateNewBlock(kBlockSize);
+  alloc_bytes_remaining_ = kBlockSize;
+
+  char* result = alloc_ptr_;
+  alloc_ptr_ += bytes;
+  alloc_bytes_remaining_ -= bytes;
+  return result;
+}
+
+char* Arena::AllocateAligned(size_t bytes) {
+  const int align = (sizeof(void*) > 8) ? sizeof(void*) : 8;
+  static_assert((align & (align - 1)) == 0,
+                "Pointer size should be a power of 2");
+  size_t current_mod = reinterpret_cast<uintptr_t>(alloc_ptr_) & (align - 1);
+  size_t slop = (current_mod == 0 ? 0 : align - current_mod);
+  size_t needed = bytes + slop;
+  char* result;
+  if (needed <= alloc_bytes_remaining_) {
+    result = alloc_ptr_ + slop;
+    alloc_ptr_ += needed;
+    alloc_bytes_remaining_ -= needed;
+  } else {
+    // AllocateFallback always returned aligned memory
+    result = AllocateFallback(bytes);
+  }
+  assert((reinterpret_cast<uintptr_t>(result) & (align - 1)) == 0);
+  return result;
+}
+
+char* Arena::AllocateNewBlock(size_t block_bytes) {
+  char* result = new char[block_bytes];
+  blocks_.push_back(result);
+  memory_usage_.fetch_add(block_bytes + sizeof(char*),
+                          std::memory_order_relaxed);
+  return result;
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/util/arena.h b/leveldb_base/util/arena.h
new file mode 100644
index 0000000..68fc55d
--- /dev/null
+++ b/leveldb_base/util/arena.h
@@ -0,0 +1,71 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_UTIL_ARENA_H_
+#define STORAGE_LEVELDB_UTIL_ARENA_H_
+
+#include <atomic>
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <vector>
+
+namespace leveldb {
+
+class Arena {
+ public:
+  Arena();
+
+  Arena(const Arena&) = delete;
+  Arena& operator=(const Arena&) = delete;
+
+  ~Arena();
+
+  // Return a pointer to a newly allocated memory block of "bytes" bytes.
+  char* Allocate(size_t bytes);
+
+  // Allocate memory with the normal alignment guarantees provided by malloc.
+  char* AllocateAligned(size_t bytes);
+
+  // Returns an estimate of the total memory usage of data allocated
+  // by the arena.
+  size_t MemoryUsage() const {
+    return memory_usage_.load(std::memory_order_relaxed);
+  }
+
+ private:
+  char* AllocateFallback(size_t bytes);
+  char* AllocateNewBlock(size_t block_bytes);
+
+  // Allocation state
+  char* alloc_ptr_;
+  size_t alloc_bytes_remaining_;
+
+  // Array of new[] allocated memory blocks
+  std::vector<char*> blocks_;
+
+  // Total memory usage of the arena.
+  //
+  // TODO(costan): This member is accessed via atomics, but the others are
+  //               accessed without any locking. Is this OK?
+  std::atomic<size_t> memory_usage_;
+};
+
+inline char* Arena::Allocate(size_t bytes) {
+  // The semantics of what to return are a bit messy if we allow
+  // 0-byte allocations, so we disallow them here (we don't need
+  // them for our internal use).
+  assert(bytes > 0);
+  if (bytes <= alloc_bytes_remaining_) {
+    char* result = alloc_ptr_;
+    alloc_ptr_ += bytes;
+    alloc_bytes_remaining_ -= bytes;
+    return result;
+  }
+  return AllocateFallback(bytes);
+}
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_UTIL_ARENA_H_
diff --git a/leveldb_base/util/arena_test.cc b/leveldb_base/util/arena_test.cc
new file mode 100644
index 0000000..3e2011e
--- /dev/null
+++ b/leveldb_base/util/arena_test.cc
@@ -0,0 +1,61 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "util/arena.h"
+
+#include "gtest/gtest.h"
+#include "util/random.h"
+
+namespace leveldb {
+
+TEST(ArenaTest, Empty) { Arena arena; }
+
+TEST(ArenaTest, Simple) {
+  std::vector<std::pair<size_t, char*>> allocated;
+  Arena arena;
+  const int N = 100000;
+  size_t bytes = 0;
+  Random rnd(301);
+  for (int i = 0; i < N; i++) {
+    size_t s;
+    if (i % (N / 10) == 0) {
+      s = i;
+    } else {
+      s = rnd.OneIn(4000)
+              ? rnd.Uniform(6000)
+              : (rnd.OneIn(10) ? rnd.Uniform(100) : rnd.Uniform(20));
+    }
+    if (s == 0) {
+      // Our arena disallows size 0 allocations.
+      s = 1;
+    }
+    char* r;
+    if (rnd.OneIn(10)) {
+      r = arena.AllocateAligned(s);
+    } else {
+      r = arena.Allocate(s);
+    }
+
+    for (size_t b = 0; b < s; b++) {
+      // Fill the "i"th allocation with a known bit pattern
+      r[b] = i % 256;
+    }
+    bytes += s;
+    allocated.push_back(std::make_pair(s, r));
+    ASSERT_GE(arena.MemoryUsage(), bytes);
+    if (i > N / 10) {
+      ASSERT_LE(arena.MemoryUsage(), bytes * 1.10);
+    }
+  }
+  for (size_t i = 0; i < allocated.size(); i++) {
+    size_t num_bytes = allocated[i].first;
+    const char* p = allocated[i].second;
+    for (size_t b = 0; b < num_bytes; b++) {
+      // Check the "i"th allocation for the known bit pattern
+      ASSERT_EQ(int(p[b]) & 0xff, i % 256);
+    }
+  }
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/util/bloom.cc b/leveldb_base/util/bloom.cc
new file mode 100644
index 0000000..87547a7
--- /dev/null
+++ b/leveldb_base/util/bloom.cc
@@ -0,0 +1,92 @@
+// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "leveldb/filter_policy.h"
+
+#include "leveldb/slice.h"
+#include "util/hash.h"
+
+namespace leveldb {
+
+namespace {
+static uint32_t BloomHash(const Slice& key) {
+  return Hash(key.data(), key.size(), 0xbc9f1d34);
+}
+
+class BloomFilterPolicy : public FilterPolicy {
+ public:
+  explicit BloomFilterPolicy(int bits_per_key) : bits_per_key_(bits_per_key) {
+    // We intentionally round down to reduce probing cost a little bit
+    k_ = static_cast<size_t>(bits_per_key * 0.69);  // 0.69 =~ ln(2)
+    if (k_ < 1) k_ = 1;
+    if (k_ > 30) k_ = 30;
+  }
+
+  const char* Name() const override { return "leveldb.BuiltinBloomFilter2"; }
+
+  void CreateFilter(const Slice* keys, int n, std::string* dst) const override {
+    // Compute bloom filter size (in both bits and bytes)
+    size_t bits = n * bits_per_key_;
+
+    // For small n, we can see a very high false positive rate.  Fix it
+    // by enforcing a minimum bloom filter length.
+    if (bits < 64) bits = 64;
+
+    size_t bytes = (bits + 7) / 8;
+    bits = bytes * 8;
+
+    const size_t init_size = dst->size();
+    dst->resize(init_size + bytes, 0);
+    dst->push_back(static_cast<char>(k_));  // Remember # of probes in filter
+    char* array = &(*dst)[init_size];
+    for (int i = 0; i < n; i++) {
+      // Use double-hashing to generate a sequence of hash values.
+      // See analysis in [Kirsch,Mitzenmacher 2006].
+      uint32_t h = BloomHash(keys[i]);
+      const uint32_t delta = (h >> 17) | (h << 15);  // Rotate right 17 bits
+      for (size_t j = 0; j < k_; j++) {
+        const uint32_t bitpos = h % bits;
+        array[bitpos / 8] |= (1 << (bitpos % 8));
+        h += delta;
+      }
+    }
+  }
+
+  bool KeyMayMatch(const Slice& key, const Slice& bloom_filter) const override {
+    const size_t len = bloom_filter.size();
+    if (len < 2) return false;
+
+    const char* array = bloom_filter.data();
+    const size_t bits = (len - 1) * 8;
+
+    // Use the encoded k so that we can read filters generated by
+    // bloom filters created using different parameters.
+    const size_t k = array[len - 1];
+    if (k > 30) {
+      // Reserved for potentially new encodings for short bloom filters.
+      // Consider it a match.
+      return true;
+    }
+
+    uint32_t h = BloomHash(key);
+    const uint32_t delta = (h >> 17) | (h << 15);  // Rotate right 17 bits
+    for (size_t j = 0; j < k; j++) {
+      const uint32_t bitpos = h % bits;
+      if ((array[bitpos / 8] & (1 << (bitpos % 8))) == 0) return false;
+      h += delta;
+    }
+    return true;
+  }
+
+ private:
+  size_t bits_per_key_;
+  size_t k_;
+};
+}  // namespace
+
+const FilterPolicy* NewBloomFilterPolicy(int bits_per_key) {
+  return new BloomFilterPolicy(bits_per_key);
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/util/bloom_test.cc b/leveldb_base/util/bloom_test.cc
new file mode 100644
index 0000000..9f11108
--- /dev/null
+++ b/leveldb_base/util/bloom_test.cc
@@ -0,0 +1,154 @@
+// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "gtest/gtest.h"
+#include "leveldb/filter_policy.h"
+#include "util/coding.h"
+#include "util/logging.h"
+#include "util/testutil.h"
+
+namespace leveldb {
+
+static const int kVerbose = 1;
+
+static Slice Key(int i, char* buffer) {
+  EncodeFixed32(buffer, i);
+  return Slice(buffer, sizeof(uint32_t));
+}
+
+class BloomTest : public testing::Test {
+ public:
+  BloomTest() : policy_(NewBloomFilterPolicy(10)) {}
+
+  ~BloomTest() { delete policy_; }
+
+  void Reset() {
+    keys_.clear();
+    filter_.clear();
+  }
+
+  void Add(const Slice& s) { keys_.push_back(s.ToString()); }
+
+  void Build() {
+    std::vector<Slice> key_slices;
+    for (size_t i = 0; i < keys_.size(); i++) {
+      key_slices.push_back(Slice(keys_[i]));
+    }
+    filter_.clear();
+    policy_->CreateFilter(&key_slices[0], static_cast<int>(key_slices.size()),
+                          &filter_);
+    keys_.clear();
+    if (kVerbose >= 2) DumpFilter();
+  }
+
+  size_t FilterSize() const { return filter_.size(); }
+
+  void DumpFilter() {
+    std::fprintf(stderr, "F(");
+    for (size_t i = 0; i + 1 < filter_.size(); i++) {
+      const unsigned int c = static_cast<unsigned int>(filter_[i]);
+      for (int j = 0; j < 8; j++) {
+        std::fprintf(stderr, "%c", (c & (1 << j)) ? '1' : '.');
+      }
+    }
+    std::fprintf(stderr, ")\n");
+  }
+
+  bool Matches(const Slice& s) {
+    if (!keys_.empty()) {
+      Build();
+    }
+    return policy_->KeyMayMatch(s, filter_);
+  }
+
+  double FalsePositiveRate() {
+    char buffer[sizeof(int)];
+    int result = 0;
+    for (int i = 0; i < 10000; i++) {
+      if (Matches(Key(i + 1000000000, buffer))) {
+        result++;
+      }
+    }
+    return result / 10000.0;
+  }
+
+ private:
+  const FilterPolicy* policy_;
+  std::string filter_;
+  std::vector<std::string> keys_;
+};
+
+TEST_F(BloomTest, EmptyFilter) {
+  ASSERT_TRUE(!Matches("hello"));
+  ASSERT_TRUE(!Matches("world"));
+}
+
+TEST_F(BloomTest, Small) {
+  Add("hello");
+  Add("world");
+  ASSERT_TRUE(Matches("hello"));
+  ASSERT_TRUE(Matches("world"));
+  ASSERT_TRUE(!Matches("x"));
+  ASSERT_TRUE(!Matches("foo"));
+}
+
+static int NextLength(int length) {
+  if (length < 10) {
+    length += 1;
+  } else if (length < 100) {
+    length += 10;
+  } else if (length < 1000) {
+    length += 100;
+  } else {
+    length += 1000;
+  }
+  return length;
+}
+
+TEST_F(BloomTest, VaryingLengths) {
+  char buffer[sizeof(int)];
+
+  // Count number of filters that significantly exceed the false positive rate
+  int mediocre_filters = 0;
+  int good_filters = 0;
+
+  for (int length = 1; length <= 10000; length = NextLength(length)) {
+    Reset();
+    for (int i = 0; i < length; i++) {
+      Add(Key(i, buffer));
+    }
+    Build();
+
+    ASSERT_LE(FilterSize(), static_cast<size_t>((length * 10 / 8) + 40))
+        << length;
+
+    // All added keys must match
+    for (int i = 0; i < length; i++) {
+      ASSERT_TRUE(Matches(Key(i, buffer)))
+          << "Length " << length << "; key " << i;
+    }
+
+    // Check false positive rate
+    double rate = FalsePositiveRate();
+    if (kVerbose >= 1) {
+      std::fprintf(stderr,
+                   "False positives: %5.2f%% @ length = %6d ; bytes = %6d\n",
+                   rate * 100.0, length, static_cast<int>(FilterSize()));
+    }
+    ASSERT_LE(rate, 0.02);  // Must not be over 2%
+    if (rate > 0.0125)
+      mediocre_filters++;  // Allowed, but not too often
+    else
+      good_filters++;
+  }
+  if (kVerbose >= 1) {
+    std::fprintf(stderr, "Filters: %d good, %d mediocre\n", good_filters,
+                 mediocre_filters);
+  }
+  ASSERT_LE(mediocre_filters, good_filters / 5);
+}
+
+// Different bits-per-byte
+
+}  // namespace leveldb
diff --git a/leveldb_base/util/cache.cc b/leveldb_base/util/cache.cc
new file mode 100644
index 0000000..fc3d154
--- /dev/null
+++ b/leveldb_base/util/cache.cc
@@ -0,0 +1,401 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "leveldb/cache.h"
+
+#include <cassert>
+#include <cstdio>
+#include <cstdlib>
+
+#include "port/port.h"
+#include "port/thread_annotations.h"
+#include "util/hash.h"
+#include "util/mutexlock.h"
+
+namespace leveldb {
+
+Cache::~Cache() {}
+
+namespace {
+
+// LRU cache implementation
+//
+// Cache entries have an "in_cache" boolean indicating whether the cache has a
+// reference on the entry.  The only ways that this can become false without the
+// entry being passed to its "deleter" are via Erase(), via Insert() when
+// an element with a duplicate key is inserted, or on destruction of the cache.
+//
+// The cache keeps two linked lists of items in the cache.  All items in the
+// cache are in one list or the other, and never both.  Items still referenced
+// by clients but erased from the cache are in neither list.  The lists are:
+// - in-use:  contains the items currently referenced by clients, in no
+//   particular order.  (This list is used for invariant checking.  If we
+//   removed the check, elements that would otherwise be on this list could be
+//   left as disconnected singleton lists.)
+// - LRU:  contains the items not currently referenced by clients, in LRU order
+// Elements are moved between these lists by the Ref() and Unref() methods,
+// when they detect an element in the cache acquiring or losing its only
+// external reference.
+
+// An entry is a variable length heap-allocated structure.  Entries
+// are kept in a circular doubly linked list ordered by access time.
+struct LRUHandle {
+  void* value;
+  void (*deleter)(const Slice&, void* value);
+  LRUHandle* next_hash;
+  LRUHandle* next;
+  LRUHandle* prev;
+  size_t charge;  // TODO(opt): Only allow uint32_t?
+  size_t key_length;
+  bool in_cache;     // Whether entry is in the cache.
+  uint32_t refs;     // References, including cache reference, if present.
+  uint32_t hash;     // Hash of key(); used for fast sharding and comparisons
+  char key_data[1];  // Beginning of key
+
+  Slice key() const {
+    // next is only equal to this if the LRU handle is the list head of an
+    // empty list. List heads never have meaningful keys.
+    assert(next != this);
+
+    return Slice(key_data, key_length);
+  }
+};
+
+// We provide our own simple hash table since it removes a whole bunch
+// of porting hacks and is also faster than some of the built-in hash
+// table implementations in some of the compiler/runtime combinations
+// we have tested.  E.g., readrandom speeds up by ~5% over the g++
+// 4.4.3's builtin hashtable.
+class HandleTable {
+ public:
+  HandleTable() : length_(0), elems_(0), list_(nullptr) { Resize(); }
+  ~HandleTable() { delete[] list_; }
+
+  LRUHandle* Lookup(const Slice& key, uint32_t hash) {
+    return *FindPointer(key, hash);
+  }
+
+  LRUHandle* Insert(LRUHandle* h) {
+    LRUHandle** ptr = FindPointer(h->key(), h->hash);
+    LRUHandle* old = *ptr;
+    h->next_hash = (old == nullptr ? nullptr : old->next_hash);
+    *ptr = h;
+    if (old == nullptr) {
+      ++elems_;
+      if (elems_ > length_) {
+        // Since each cache entry is fairly large, we aim for a small
+        // average linked list length (<= 1).
+        Resize();
+      }
+    }
+    return old;
+  }
+
+  LRUHandle* Remove(const Slice& key, uint32_t hash) {
+    LRUHandle** ptr = FindPointer(key, hash);
+    LRUHandle* result = *ptr;
+    if (result != nullptr) {
+      *ptr = result->next_hash;
+      --elems_;
+    }
+    return result;
+  }
+
+ private:
+  // The table consists of an array of buckets where each bucket is
+  // a linked list of cache entries that hash into the bucket.
+  uint32_t length_;
+  uint32_t elems_;
+  LRUHandle** list_;
+
+  // Return a pointer to slot that points to a cache entry that
+  // matches key/hash.  If there is no such cache entry, return a
+  // pointer to the trailing slot in the corresponding linked list.
+  LRUHandle** FindPointer(const Slice& key, uint32_t hash) {
+    LRUHandle** ptr = &list_[hash & (length_ - 1)];
+    while (*ptr != nullptr && ((*ptr)->hash != hash || key != (*ptr)->key())) {
+      ptr = &(*ptr)->next_hash;
+    }
+    return ptr;
+  }
+
+  void Resize() {
+    uint32_t new_length = 4;
+    while (new_length < elems_) {
+      new_length *= 2;
+    }
+    LRUHandle** new_list = new LRUHandle*[new_length];
+    memset(new_list, 0, sizeof(new_list[0]) * new_length);
+    uint32_t count = 0;
+    for (uint32_t i = 0; i < length_; i++) {
+      LRUHandle* h = list_[i];
+      while (h != nullptr) {
+        LRUHandle* next = h->next_hash;
+        uint32_t hash = h->hash;
+        LRUHandle** ptr = &new_list[hash & (new_length - 1)];
+        h->next_hash = *ptr;
+        *ptr = h;
+        h = next;
+        count++;
+      }
+    }
+    assert(elems_ == count);
+    delete[] list_;
+    list_ = new_list;
+    length_ = new_length;
+  }
+};
+
+// A single shard of sharded cache.
+class LRUCache {
+ public:
+  LRUCache();
+  ~LRUCache();
+
+  // Separate from constructor so caller can easily make an array of LRUCache
+  void SetCapacity(size_t capacity) { capacity_ = capacity; }
+
+  // Like Cache methods, but with an extra "hash" parameter.
+  Cache::Handle* Insert(const Slice& key, uint32_t hash, void* value,
+                        size_t charge,
+                        void (*deleter)(const Slice& key, void* value));
+  Cache::Handle* Lookup(const Slice& key, uint32_t hash);
+  void Release(Cache::Handle* handle);
+  void Erase(const Slice& key, uint32_t hash);
+  void Prune();
+  size_t TotalCharge() const {
+    MutexLock l(&mutex_);
+    return usage_;
+  }
+
+ private:
+  void LRU_Remove(LRUHandle* e);
+  void LRU_Append(LRUHandle* list, LRUHandle* e);
+  void Ref(LRUHandle* e);
+  void Unref(LRUHandle* e);
+  bool FinishErase(LRUHandle* e) EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+
+  // Initialized before use.
+  size_t capacity_;
+
+  // mutex_ protects the following state.
+  mutable port::Mutex mutex_;
+  size_t usage_ GUARDED_BY(mutex_);
+
+  // Dummy head of LRU list.
+  // lru.prev is newest entry, lru.next is oldest entry.
+  // Entries have refs==1 and in_cache==true.
+  LRUHandle lru_ GUARDED_BY(mutex_);
+
+  // Dummy head of in-use list.
+  // Entries are in use by clients, and have refs >= 2 and in_cache==true.
+  LRUHandle in_use_ GUARDED_BY(mutex_);
+
+  HandleTable table_ GUARDED_BY(mutex_);
+};
+
+LRUCache::LRUCache() : capacity_(0), usage_(0) {
+  // Make empty circular linked lists.
+  lru_.next = &lru_;
+  lru_.prev = &lru_;
+  in_use_.next = &in_use_;
+  in_use_.prev = &in_use_;
+}
+
+LRUCache::~LRUCache() {
+  assert(in_use_.next == &in_use_);  // Error if caller has an unreleased handle
+  for (LRUHandle* e = lru_.next; e != &lru_;) {
+    LRUHandle* next = e->next;
+    assert(e->in_cache);
+    e->in_cache = false;
+    assert(e->refs == 1);  // Invariant of lru_ list.
+    Unref(e);
+    e = next;
+  }
+}
+
+void LRUCache::Ref(LRUHandle* e) {
+  if (e->refs == 1 && e->in_cache) {  // If on lru_ list, move to in_use_ list.
+    LRU_Remove(e);
+    LRU_Append(&in_use_, e);
+  }
+  e->refs++;
+}
+
+void LRUCache::Unref(LRUHandle* e) {
+  assert(e->refs > 0);
+  e->refs--;
+  if (e->refs == 0) {  // Deallocate.
+    assert(!e->in_cache);
+    (*e->deleter)(e->key(), e->value);
+    free(e);
+  } else if (e->in_cache && e->refs == 1) {
+    // No longer in use; move to lru_ list.
+    LRU_Remove(e);
+    LRU_Append(&lru_, e);
+  }
+}
+
+void LRUCache::LRU_Remove(LRUHandle* e) {
+  e->next->prev = e->prev;
+  e->prev->next = e->next;
+}
+
+void LRUCache::LRU_Append(LRUHandle* list, LRUHandle* e) {
+  // Make "e" newest entry by inserting just before *list
+  e->next = list;
+  e->prev = list->prev;
+  e->prev->next = e;
+  e->next->prev = e;
+}
+
+Cache::Handle* LRUCache::Lookup(const Slice& key, uint32_t hash) {
+  MutexLock l(&mutex_);
+  LRUHandle* e = table_.Lookup(key, hash);
+  if (e != nullptr) {
+    Ref(e);
+  }
+  return reinterpret_cast<Cache::Handle*>(e);
+}
+
+void LRUCache::Release(Cache::Handle* handle) {
+  MutexLock l(&mutex_);
+  Unref(reinterpret_cast<LRUHandle*>(handle));
+}
+
+Cache::Handle* LRUCache::Insert(const Slice& key, uint32_t hash, void* value,
+                                size_t charge,
+                                void (*deleter)(const Slice& key,
+                                                void* value)) {
+  MutexLock l(&mutex_);
+
+  LRUHandle* e =
+      reinterpret_cast<LRUHandle*>(malloc(sizeof(LRUHandle) - 1 + key.size()));
+  e->value = value;
+  e->deleter = deleter;
+  e->charge = charge;
+  e->key_length = key.size();
+  e->hash = hash;
+  e->in_cache = false;
+  e->refs = 1;  // for the returned handle.
+  std::memcpy(e->key_data, key.data(), key.size());
+
+  if (capacity_ > 0) {
+    e->refs++;  // for the cache's reference.
+    e->in_cache = true;
+    LRU_Append(&in_use_, e);
+    usage_ += charge;
+    FinishErase(table_.Insert(e));
+  } else {  // don't cache. (capacity_==0 is supported and turns off caching.)
+    // next is read by key() in an assert, so it must be initialized
+    e->next = nullptr;
+  }
+  while (usage_ > capacity_ && lru_.next != &lru_) {
+    LRUHandle* old = lru_.next;
+    assert(old->refs == 1);
+    bool erased = FinishErase(table_.Remove(old->key(), old->hash));
+    if (!erased) {  // to avoid unused variable when compiled NDEBUG
+      assert(erased);
+    }
+  }
+
+  return reinterpret_cast<Cache::Handle*>(e);
+}
+
+// If e != nullptr, finish removing *e from the cache; it has already been
+// removed from the hash table.  Return whether e != nullptr.
+bool LRUCache::FinishErase(LRUHandle* e) {
+  if (e != nullptr) {
+    assert(e->in_cache);
+    LRU_Remove(e);
+    e->in_cache = false;
+    usage_ -= e->charge;
+    Unref(e);
+  }
+  return e != nullptr;
+}
+
+void LRUCache::Erase(const Slice& key, uint32_t hash) {
+  MutexLock l(&mutex_);
+  FinishErase(table_.Remove(key, hash));
+}
+
+void LRUCache::Prune() {
+  MutexLock l(&mutex_);
+  while (lru_.next != &lru_) {
+    LRUHandle* e = lru_.next;
+    assert(e->refs == 1);
+    bool erased = FinishErase(table_.Remove(e->key(), e->hash));
+    if (!erased) {  // to avoid unused variable when compiled NDEBUG
+      assert(erased);
+    }
+  }
+}
+
+static const int kNumShardBits = 4;
+static const int kNumShards = 1 << kNumShardBits;
+
+class ShardedLRUCache : public Cache {
+ private:
+  LRUCache shard_[kNumShards];
+  port::Mutex id_mutex_;
+  uint64_t last_id_;
+
+  static inline uint32_t HashSlice(const Slice& s) {
+    return Hash(s.data(), s.size(), 0);
+  }
+
+  static uint32_t Shard(uint32_t hash) { return hash >> (32 - kNumShardBits); }
+
+ public:
+  explicit ShardedLRUCache(size_t capacity) : last_id_(0) {
+    const size_t per_shard = (capacity + (kNumShards - 1)) / kNumShards;
+    for (int s = 0; s < kNumShards; s++) {
+      shard_[s].SetCapacity(per_shard);
+    }
+  }
+  ~ShardedLRUCache() override {}
+  Handle* Insert(const Slice& key, void* value, size_t charge,
+                 void (*deleter)(const Slice& key, void* value)) override {
+    const uint32_t hash = HashSlice(key);
+    return shard_[Shard(hash)].Insert(key, hash, value, charge, deleter);
+  }
+  Handle* Lookup(const Slice& key) override {
+    const uint32_t hash = HashSlice(key);
+    return shard_[Shard(hash)].Lookup(key, hash);
+  }
+  void Release(Handle* handle) override {
+    LRUHandle* h = reinterpret_cast<LRUHandle*>(handle);
+    shard_[Shard(h->hash)].Release(handle);
+  }
+  void Erase(const Slice& key) override {
+    const uint32_t hash = HashSlice(key);
+    shard_[Shard(hash)].Erase(key, hash);
+  }
+  void* Value(Handle* handle) override {
+    return reinterpret_cast<LRUHandle*>(handle)->value;
+  }
+  uint64_t NewId() override {
+    MutexLock l(&id_mutex_);
+    return ++(last_id_);
+  }
+  void Prune() override {
+    for (int s = 0; s < kNumShards; s++) {
+      shard_[s].Prune();
+    }
+  }
+  size_t TotalCharge() const override {
+    size_t total = 0;
+    for (int s = 0; s < kNumShards; s++) {
+      total += shard_[s].TotalCharge();
+    }
+    return total;
+  }
+};
+
+}  // end anonymous namespace
+
+Cache* NewLRUCache(size_t capacity) { return new ShardedLRUCache(capacity); }
+
+}  // namespace leveldb
diff --git a/leveldb_base/util/cache_test.cc b/leveldb_base/util/cache_test.cc
new file mode 100644
index 0000000..e68da34
--- /dev/null
+++ b/leveldb_base/util/cache_test.cc
@@ -0,0 +1,224 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "leveldb/cache.h"
+
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "util/coding.h"
+
+namespace leveldb {
+
+// Conversions between numeric keys/values and the types expected by Cache.
+static std::string EncodeKey(int k) {
+  std::string result;
+  PutFixed32(&result, k);
+  return result;
+}
+static int DecodeKey(const Slice& k) {
+  assert(k.size() == 4);
+  return DecodeFixed32(k.data());
+}
+static void* EncodeValue(uintptr_t v) { return reinterpret_cast<void*>(v); }
+static int DecodeValue(void* v) { return reinterpret_cast<uintptr_t>(v); }
+
+class CacheTest : public testing::Test {
+ public:
+  static void Deleter(const Slice& key, void* v) {
+    current_->deleted_keys_.push_back(DecodeKey(key));
+    current_->deleted_values_.push_back(DecodeValue(v));
+  }
+
+  static constexpr int kCacheSize = 1000;
+  std::vector<int> deleted_keys_;
+  std::vector<int> deleted_values_;
+  Cache* cache_;
+
+  CacheTest() : cache_(NewLRUCache(kCacheSize)) { current_ = this; }
+
+  ~CacheTest() { delete cache_; }
+
+  int Lookup(int key) {
+    Cache::Handle* handle = cache_->Lookup(EncodeKey(key));
+    const int r = (handle == nullptr) ? -1 : DecodeValue(cache_->Value(handle));
+    if (handle != nullptr) {
+      cache_->Release(handle);
+    }
+    return r;
+  }
+
+  void Insert(int key, int value, int charge = 1) {
+    cache_->Release(cache_->Insert(EncodeKey(key), EncodeValue(value), charge,
+                                   &CacheTest::Deleter));
+  }
+
+  Cache::Handle* InsertAndReturnHandle(int key, int value, int charge = 1) {
+    return cache_->Insert(EncodeKey(key), EncodeValue(value), charge,
+                          &CacheTest::Deleter);
+  }
+
+  void Erase(int key) { cache_->Erase(EncodeKey(key)); }
+  static CacheTest* current_;
+};
+CacheTest* CacheTest::current_;
+
+TEST_F(CacheTest, HitAndMiss) {
+  ASSERT_EQ(-1, Lookup(100));
+
+  Insert(100, 101);
+  ASSERT_EQ(101, Lookup(100));
+  ASSERT_EQ(-1, Lookup(200));
+  ASSERT_EQ(-1, Lookup(300));
+
+  Insert(200, 201);
+  ASSERT_EQ(101, Lookup(100));
+  ASSERT_EQ(201, Lookup(200));
+  ASSERT_EQ(-1, Lookup(300));
+
+  Insert(100, 102);
+  ASSERT_EQ(102, Lookup(100));
+  ASSERT_EQ(201, Lookup(200));
+  ASSERT_EQ(-1, Lookup(300));
+
+  ASSERT_EQ(1, deleted_keys_.size());
+  ASSERT_EQ(100, deleted_keys_[0]);
+  ASSERT_EQ(101, deleted_values_[0]);
+}
+
+TEST_F(CacheTest, Erase) {
+  Erase(200);
+  ASSERT_EQ(0, deleted_keys_.size());
+
+  Insert(100, 101);
+  Insert(200, 201);
+  Erase(100);
+  ASSERT_EQ(-1, Lookup(100));
+  ASSERT_EQ(201, Lookup(200));
+  ASSERT_EQ(1, deleted_keys_.size());
+  ASSERT_EQ(100, deleted_keys_[0]);
+  ASSERT_EQ(101, deleted_values_[0]);
+
+  Erase(100);
+  ASSERT_EQ(-1, Lookup(100));
+  ASSERT_EQ(201, Lookup(200));
+  ASSERT_EQ(1, deleted_keys_.size());
+}
+
+TEST_F(CacheTest, EntriesArePinned) {
+  Insert(100, 101);
+  Cache::Handle* h1 = cache_->Lookup(EncodeKey(100));
+  ASSERT_EQ(101, DecodeValue(cache_->Value(h1)));
+
+  Insert(100, 102);
+  Cache::Handle* h2 = cache_->Lookup(EncodeKey(100));
+  ASSERT_EQ(102, DecodeValue(cache_->Value(h2)));
+  ASSERT_EQ(0, deleted_keys_.size());
+
+  cache_->Release(h1);
+  ASSERT_EQ(1, deleted_keys_.size());
+  ASSERT_EQ(100, deleted_keys_[0]);
+  ASSERT_EQ(101, deleted_values_[0]);
+
+  Erase(100);
+  ASSERT_EQ(-1, Lookup(100));
+  ASSERT_EQ(1, deleted_keys_.size());
+
+  cache_->Release(h2);
+  ASSERT_EQ(2, deleted_keys_.size());
+  ASSERT_EQ(100, deleted_keys_[1]);
+  ASSERT_EQ(102, deleted_values_[1]);
+}
+
+TEST_F(CacheTest, EvictionPolicy) {
+  Insert(100, 101);
+  Insert(200, 201);
+  Insert(300, 301);
+  Cache::Handle* h = cache_->Lookup(EncodeKey(300));
+
+  // Frequently used entry must be kept around,
+  // as must things that are still in use.
+  for (int i = 0; i < kCacheSize + 100; i++) {
+    Insert(1000 + i, 2000 + i);
+    ASSERT_EQ(2000 + i, Lookup(1000 + i));
+    ASSERT_EQ(101, Lookup(100));
+  }
+  ASSERT_EQ(101, Lookup(100));
+  ASSERT_EQ(-1, Lookup(200));
+  ASSERT_EQ(301, Lookup(300));
+  cache_->Release(h);
+}
+
+TEST_F(CacheTest, UseExceedsCacheSize) {
+  // Overfill the cache, keeping handles on all inserted entries.
+  std::vector<Cache::Handle*> h;
+  for (int i = 0; i < kCacheSize + 100; i++) {
+    h.push_back(InsertAndReturnHandle(1000 + i, 2000 + i));
+  }
+
+  // Check that all the entries can be found in the cache.
+  for (int i = 0; i < h.size(); i++) {
+    ASSERT_EQ(2000 + i, Lookup(1000 + i));
+  }
+
+  for (int i = 0; i < h.size(); i++) {
+    cache_->Release(h[i]);
+  }
+}
+
+TEST_F(CacheTest, HeavyEntries) {
+  // Add a bunch of light and heavy entries and then count the combined
+  // size of items still in the cache, which must be approximately the
+  // same as the total capacity.
+  const int kLight = 1;
+  const int kHeavy = 10;
+  int added = 0;
+  int index = 0;
+  while (added < 2 * kCacheSize) {
+    const int weight = (index & 1) ? kLight : kHeavy;
+    Insert(index, 1000 + index, weight);
+    added += weight;
+    index++;
+  }
+
+  int cached_weight = 0;
+  for (int i = 0; i < index; i++) {
+    const int weight = (i & 1 ? kLight : kHeavy);
+    int r = Lookup(i);
+    if (r >= 0) {
+      cached_weight += weight;
+      ASSERT_EQ(1000 + i, r);
+    }
+  }
+  ASSERT_LE(cached_weight, kCacheSize + kCacheSize / 10);
+}
+
+TEST_F(CacheTest, NewId) {
+  uint64_t a = cache_->NewId();
+  uint64_t b = cache_->NewId();
+  ASSERT_NE(a, b);
+}
+
+TEST_F(CacheTest, Prune) {
+  Insert(1, 100);
+  Insert(2, 200);
+
+  Cache::Handle* handle = cache_->Lookup(EncodeKey(1));
+  ASSERT_TRUE(handle);
+  cache_->Prune();
+  cache_->Release(handle);
+
+  ASSERT_EQ(100, Lookup(1));
+  ASSERT_EQ(-1, Lookup(2));
+}
+
+TEST_F(CacheTest, ZeroSizeCache) {
+  delete cache_;
+  cache_ = NewLRUCache(0);
+
+  Insert(1, 100);
+  ASSERT_EQ(-1, Lookup(1));
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/util/coding.cc b/leveldb_base/util/coding.cc
new file mode 100644
index 0000000..a8f8af8
--- /dev/null
+++ b/leveldb_base/util/coding.cc
@@ -0,0 +1,156 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "util/coding.h"
+
+namespace leveldb {
+
+void PutFixed32(std::string* dst, uint32_t value) {
+  char buf[sizeof(value)];
+  EncodeFixed32(buf, value);
+  dst->append(buf, sizeof(buf));
+}
+
+void PutFixed64(std::string* dst, uint64_t value) {
+  char buf[sizeof(value)];
+  EncodeFixed64(buf, value);
+  dst->append(buf, sizeof(buf));
+}
+
+char* EncodeVarint32(char* dst, uint32_t v) {
+  // Operate on characters as unsigneds
+  uint8_t* ptr = reinterpret_cast<uint8_t*>(dst);
+  static const int B = 128;
+  if (v < (1 << 7)) {
+    *(ptr++) = v;
+  } else if (v < (1 << 14)) {
+    *(ptr++) = v | B;
+    *(ptr++) = v >> 7;
+  } else if (v < (1 << 21)) {
+    *(ptr++) = v | B;
+    *(ptr++) = (v >> 7) | B;
+    *(ptr++) = v >> 14;
+  } else if (v < (1 << 28)) {
+    *(ptr++) = v | B;
+    *(ptr++) = (v >> 7) | B;
+    *(ptr++) = (v >> 14) | B;
+    *(ptr++) = v >> 21;
+  } else {
+    *(ptr++) = v | B;
+    *(ptr++) = (v >> 7) | B;
+    *(ptr++) = (v >> 14) | B;
+    *(ptr++) = (v >> 21) | B;
+    *(ptr++) = v >> 28;
+  }
+  return reinterpret_cast<char*>(ptr);
+}
+
+void PutVarint32(std::string* dst, uint32_t v) {
+  char buf[5];
+  char* ptr = EncodeVarint32(buf, v);
+  dst->append(buf, ptr - buf);
+}
+
+char* EncodeVarint64(char* dst, uint64_t v) {
+  static const int B = 128;
+  uint8_t* ptr = reinterpret_cast<uint8_t*>(dst);
+  while (v >= B) {
+    *(ptr++) = v | B;
+    v >>= 7;
+  }
+  *(ptr++) = static_cast<uint8_t>(v);
+  return reinterpret_cast<char*>(ptr);
+}
+
+void PutVarint64(std::string* dst, uint64_t v) {
+  char buf[10];
+  char* ptr = EncodeVarint64(buf, v);
+  dst->append(buf, ptr - buf);
+}
+
+void PutLengthPrefixedSlice(std::string* dst, const Slice& value) {
+  PutVarint32(dst, value.size());
+  dst->append(value.data(), value.size());
+}
+
+int VarintLength(uint64_t v) {
+  int len = 1;
+  while (v >= 128) {
+    v >>= 7;
+    len++;
+  }
+  return len;
+}
+
+const char* GetVarint32PtrFallback(const char* p, const char* limit,
+                                   uint32_t* value) {
+  uint32_t result = 0;
+  for (uint32_t shift = 0; shift <= 28 && p < limit; shift += 7) {
+    uint32_t byte = *(reinterpret_cast<const uint8_t*>(p));
+    p++;
+    if (byte & 128) {
+      // More bytes are present
+      result |= ((byte & 127) << shift);
+    } else {
+      result |= (byte << shift);
+      *value = result;
+      return reinterpret_cast<const char*>(p);
+    }
+  }
+  return nullptr;
+}
+
+bool GetVarint32(Slice* input, uint32_t* value) {
+  const char* p = input->data();
+  const char* limit = p + input->size();
+  const char* q = GetVarint32Ptr(p, limit, value);
+  if (q == nullptr) {
+    return false;
+  } else {
+    *input = Slice(q, limit - q);
+    return true;
+  }
+}
+
+const char* GetVarint64Ptr(const char* p, const char* limit, uint64_t* value) {
+  uint64_t result = 0;
+  for (uint32_t shift = 0; shift <= 63 && p < limit; shift += 7) {
+    uint64_t byte = *(reinterpret_cast<const uint8_t*>(p));
+    p++;
+    if (byte & 128) {
+      // More bytes are present
+      result |= ((byte & 127) << shift);
+    } else {
+      result |= (byte << shift);
+      *value = result;
+      return reinterpret_cast<const char*>(p);
+    }
+  }
+  return nullptr;
+}
+
+bool GetVarint64(Slice* input, uint64_t* value) {
+  const char* p = input->data();
+  const char* limit = p + input->size();
+  const char* q = GetVarint64Ptr(p, limit, value);
+  if (q == nullptr) {
+    return false;
+  } else {
+    *input = Slice(q, limit - q);
+    return true;
+  }
+}
+
+bool GetLengthPrefixedSlice(Slice* input, Slice* result) {
+  uint32_t len;
+  if (GetVarint32(input, &len) && input->size() >= len) {
+    *result = Slice(input->data(), len);
+    input->remove_prefix(len);
+    return true;
+  } else {
+    return false;
+  }
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/util/coding.h b/leveldb_base/util/coding.h
new file mode 100644
index 0000000..f0bb57b
--- /dev/null
+++ b/leveldb_base/util/coding.h
@@ -0,0 +1,122 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// Endian-neutral encoding:
+// * Fixed-length numbers are encoded with least-significant byte first
+// * In addition we support variable length "varint" encoding
+// * Strings are encoded prefixed by their length in varint format
+
+#ifndef STORAGE_LEVELDB_UTIL_CODING_H_
+#define STORAGE_LEVELDB_UTIL_CODING_H_
+
+#include <cstdint>
+#include <cstring>
+#include <string>
+
+#include "leveldb/slice.h"
+#include "port/port.h"
+
+namespace leveldb {
+
+// Standard Put... routines append to a string
+void PutFixed32(std::string* dst, uint32_t value);
+void PutFixed64(std::string* dst, uint64_t value);
+void PutVarint32(std::string* dst, uint32_t value);
+void PutVarint64(std::string* dst, uint64_t value);
+void PutLengthPrefixedSlice(std::string* dst, const Slice& value);
+
+// Standard Get... routines parse a value from the beginning of a Slice
+// and advance the slice past the parsed value.
+bool GetVarint32(Slice* input, uint32_t* value);
+bool GetVarint64(Slice* input, uint64_t* value);
+bool GetLengthPrefixedSlice(Slice* input, Slice* result);
+
+// Pointer-based variants of GetVarint...  These either store a value
+// in *v and return a pointer just past the parsed value, or return
+// nullptr on error.  These routines only look at bytes in the range
+// [p..limit-1]
+const char* GetVarint32Ptr(const char* p, const char* limit, uint32_t* v);
+const char* GetVarint64Ptr(const char* p, const char* limit, uint64_t* v);
+
+// Returns the length of the varint32 or varint64 encoding of "v"
+int VarintLength(uint64_t v);
+
+// Lower-level versions of Put... that write directly into a character buffer
+// and return a pointer just past the last byte written.
+// REQUIRES: dst has enough space for the value being written
+char* EncodeVarint32(char* dst, uint32_t value);
+char* EncodeVarint64(char* dst, uint64_t value);
+
+// Lower-level versions of Put... that write directly into a character buffer
+// REQUIRES: dst has enough space for the value being written
+
+inline void EncodeFixed32(char* dst, uint32_t value) {
+  uint8_t* const buffer = reinterpret_cast<uint8_t*>(dst);
+
+  // Recent clang and gcc optimize this to a single mov / str instruction.
+  buffer[0] = static_cast<uint8_t>(value);
+  buffer[1] = static_cast<uint8_t>(value >> 8);
+  buffer[2] = static_cast<uint8_t>(value >> 16);
+  buffer[3] = static_cast<uint8_t>(value >> 24);
+}
+
+inline void EncodeFixed64(char* dst, uint64_t value) {
+  uint8_t* const buffer = reinterpret_cast<uint8_t*>(dst);
+
+  // Recent clang and gcc optimize this to a single mov / str instruction.
+  buffer[0] = static_cast<uint8_t>(value);
+  buffer[1] = static_cast<uint8_t>(value >> 8);
+  buffer[2] = static_cast<uint8_t>(value >> 16);
+  buffer[3] = static_cast<uint8_t>(value >> 24);
+  buffer[4] = static_cast<uint8_t>(value >> 32);
+  buffer[5] = static_cast<uint8_t>(value >> 40);
+  buffer[6] = static_cast<uint8_t>(value >> 48);
+  buffer[7] = static_cast<uint8_t>(value >> 56);
+}
+
+// Lower-level versions of Get... that read directly from a character buffer
+// without any bounds checking.
+
+inline uint32_t DecodeFixed32(const char* ptr) {
+  const uint8_t* const buffer = reinterpret_cast<const uint8_t*>(ptr);
+
+  // Recent clang and gcc optimize this to a single mov / ldr instruction.
+  return (static_cast<uint32_t>(buffer[0])) |
+         (static_cast<uint32_t>(buffer[1]) << 8) |
+         (static_cast<uint32_t>(buffer[2]) << 16) |
+         (static_cast<uint32_t>(buffer[3]) << 24);
+}
+
+inline uint64_t DecodeFixed64(const char* ptr) {
+  const uint8_t* const buffer = reinterpret_cast<const uint8_t*>(ptr);
+
+  // Recent clang and gcc optimize this to a single mov / ldr instruction.
+  return (static_cast<uint64_t>(buffer[0])) |
+         (static_cast<uint64_t>(buffer[1]) << 8) |
+         (static_cast<uint64_t>(buffer[2]) << 16) |
+         (static_cast<uint64_t>(buffer[3]) << 24) |
+         (static_cast<uint64_t>(buffer[4]) << 32) |
+         (static_cast<uint64_t>(buffer[5]) << 40) |
+         (static_cast<uint64_t>(buffer[6]) << 48) |
+         (static_cast<uint64_t>(buffer[7]) << 56);
+}
+
+// Internal routine for use by fallback path of GetVarint32Ptr
+const char* GetVarint32PtrFallback(const char* p, const char* limit,
+                                   uint32_t* value);
+inline const char* GetVarint32Ptr(const char* p, const char* limit,
+                                  uint32_t* value) {
+  if (p < limit) {
+    uint32_t result = *(reinterpret_cast<const uint8_t*>(p));
+    if ((result & 128) == 0) {
+      *value = result;
+      return p + 1;
+    }
+  }
+  return GetVarint32PtrFallback(p, limit, value);
+}
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_UTIL_CODING_H_
diff --git a/leveldb_base/util/coding_test.cc b/leveldb_base/util/coding_test.cc
new file mode 100644
index 0000000..cceda14
--- /dev/null
+++ b/leveldb_base/util/coding_test.cc
@@ -0,0 +1,193 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "util/coding.h"
+
+#include <vector>
+
+#include "gtest/gtest.h"
+
+namespace leveldb {
+
+TEST(Coding, Fixed32) {
+  std::string s;
+  for (uint32_t v = 0; v < 100000; v++) {
+    PutFixed32(&s, v);
+  }
+
+  const char* p = s.data();
+  for (uint32_t v = 0; v < 100000; v++) {
+    uint32_t actual = DecodeFixed32(p);
+    ASSERT_EQ(v, actual);
+    p += sizeof(uint32_t);
+  }
+}
+
+TEST(Coding, Fixed64) {
+  std::string s;
+  for (int power = 0; power <= 63; power++) {
+    uint64_t v = static_cast<uint64_t>(1) << power;
+    PutFixed64(&s, v - 1);
+    PutFixed64(&s, v + 0);
+    PutFixed64(&s, v + 1);
+  }
+
+  const char* p = s.data();
+  for (int power = 0; power <= 63; power++) {
+    uint64_t v = static_cast<uint64_t>(1) << power;
+    uint64_t actual;
+    actual = DecodeFixed64(p);
+    ASSERT_EQ(v - 1, actual);
+    p += sizeof(uint64_t);
+
+    actual = DecodeFixed64(p);
+    ASSERT_EQ(v + 0, actual);
+    p += sizeof(uint64_t);
+
+    actual = DecodeFixed64(p);
+    ASSERT_EQ(v + 1, actual);
+    p += sizeof(uint64_t);
+  }
+}
+
+// Test that encoding routines generate little-endian encodings
+TEST(Coding, EncodingOutput) {
+  std::string dst;
+  PutFixed32(&dst, 0x04030201);
+  ASSERT_EQ(4, dst.size());
+  ASSERT_EQ(0x01, static_cast<int>(dst[0]));
+  ASSERT_EQ(0x02, static_cast<int>(dst[1]));
+  ASSERT_EQ(0x03, static_cast<int>(dst[2]));
+  ASSERT_EQ(0x04, static_cast<int>(dst[3]));
+
+  dst.clear();
+  PutFixed64(&dst, 0x0807060504030201ull);
+  ASSERT_EQ(8, dst.size());
+  ASSERT_EQ(0x01, static_cast<int>(dst[0]));
+  ASSERT_EQ(0x02, static_cast<int>(dst[1]));
+  ASSERT_EQ(0x03, static_cast<int>(dst[2]));
+  ASSERT_EQ(0x04, static_cast<int>(dst[3]));
+  ASSERT_EQ(0x05, static_cast<int>(dst[4]));
+  ASSERT_EQ(0x06, static_cast<int>(dst[5]));
+  ASSERT_EQ(0x07, static_cast<int>(dst[6]));
+  ASSERT_EQ(0x08, static_cast<int>(dst[7]));
+}
+
+TEST(Coding, Varint32) {
+  std::string s;
+  for (uint32_t i = 0; i < (32 * 32); i++) {
+    uint32_t v = (i / 32) << (i % 32);
+    PutVarint32(&s, v);
+  }
+
+  const char* p = s.data();
+  const char* limit = p + s.size();
+  for (uint32_t i = 0; i < (32 * 32); i++) {
+    uint32_t expected = (i / 32) << (i % 32);
+    uint32_t actual;
+    const char* start = p;
+    p = GetVarint32Ptr(p, limit, &actual);
+    ASSERT_TRUE(p != nullptr);
+    ASSERT_EQ(expected, actual);
+    ASSERT_EQ(VarintLength(actual), p - start);
+  }
+  ASSERT_EQ(p, s.data() + s.size());
+}
+
+TEST(Coding, Varint64) {
+  // Construct the list of values to check
+  std::vector<uint64_t> values;
+  // Some special values
+  values.push_back(0);
+  values.push_back(100);
+  values.push_back(~static_cast<uint64_t>(0));
+  values.push_back(~static_cast<uint64_t>(0) - 1);
+  for (uint32_t k = 0; k < 64; k++) {
+    // Test values near powers of two
+    const uint64_t power = 1ull << k;
+    values.push_back(power);
+    values.push_back(power - 1);
+    values.push_back(power + 1);
+  }
+
+  std::string s;
+  for (size_t i = 0; i < values.size(); i++) {
+    PutVarint64(&s, values[i]);
+  }
+
+  const char* p = s.data();
+  const char* limit = p + s.size();
+  for (size_t i = 0; i < values.size(); i++) {
+    ASSERT_TRUE(p < limit);
+    uint64_t actual;
+    const char* start = p;
+    p = GetVarint64Ptr(p, limit, &actual);
+    ASSERT_TRUE(p != nullptr);
+    ASSERT_EQ(values[i], actual);
+    ASSERT_EQ(VarintLength(actual), p - start);
+  }
+  ASSERT_EQ(p, limit);
+}
+
+TEST(Coding, Varint32Overflow) {
+  uint32_t result;
+  std::string input("\x81\x82\x83\x84\x85\x11");
+  ASSERT_TRUE(GetVarint32Ptr(input.data(), input.data() + input.size(),
+                             &result) == nullptr);
+}
+
+TEST(Coding, Varint32Truncation) {
+  uint32_t large_value = (1u << 31) + 100;
+  std::string s;
+  PutVarint32(&s, large_value);
+  uint32_t result;
+  for (size_t len = 0; len < s.size() - 1; len++) {
+    ASSERT_TRUE(GetVarint32Ptr(s.data(), s.data() + len, &result) == nullptr);
+  }
+  ASSERT_TRUE(GetVarint32Ptr(s.data(), s.data() + s.size(), &result) !=
+              nullptr);
+  ASSERT_EQ(large_value, result);
+}
+
+TEST(Coding, Varint64Overflow) {
+  uint64_t result;
+  std::string input("\x81\x82\x83\x84\x85\x81\x82\x83\x84\x85\x11");
+  ASSERT_TRUE(GetVarint64Ptr(input.data(), input.data() + input.size(),
+                             &result) == nullptr);
+}
+
+TEST(Coding, Varint64Truncation) {
+  uint64_t large_value = (1ull << 63) + 100ull;
+  std::string s;
+  PutVarint64(&s, large_value);
+  uint64_t result;
+  for (size_t len = 0; len < s.size() - 1; len++) {
+    ASSERT_TRUE(GetVarint64Ptr(s.data(), s.data() + len, &result) == nullptr);
+  }
+  ASSERT_TRUE(GetVarint64Ptr(s.data(), s.data() + s.size(), &result) !=
+              nullptr);
+  ASSERT_EQ(large_value, result);
+}
+
+TEST(Coding, Strings) {
+  std::string s;
+  PutLengthPrefixedSlice(&s, Slice(""));
+  PutLengthPrefixedSlice(&s, Slice("foo"));
+  PutLengthPrefixedSlice(&s, Slice("bar"));
+  PutLengthPrefixedSlice(&s, Slice(std::string(200, 'x')));
+
+  Slice input(s);
+  Slice v;
+  ASSERT_TRUE(GetLengthPrefixedSlice(&input, &v));
+  ASSERT_EQ("", v.ToString());
+  ASSERT_TRUE(GetLengthPrefixedSlice(&input, &v));
+  ASSERT_EQ("foo", v.ToString());
+  ASSERT_TRUE(GetLengthPrefixedSlice(&input, &v));
+  ASSERT_EQ("bar", v.ToString());
+  ASSERT_TRUE(GetLengthPrefixedSlice(&input, &v));
+  ASSERT_EQ(std::string(200, 'x'), v.ToString());
+  ASSERT_EQ("", input.ToString());
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/util/comparator.cc b/leveldb_base/util/comparator.cc
new file mode 100644
index 0000000..c5766e9
--- /dev/null
+++ b/leveldb_base/util/comparator.cc
@@ -0,0 +1,75 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "leveldb/comparator.h"
+
+#include <algorithm>
+#include <cstdint>
+#include <string>
+#include <type_traits>
+
+#include "leveldb/slice.h"
+#include "util/logging.h"
+#include "util/no_destructor.h"
+
+namespace leveldb {
+
+Comparator::~Comparator() = default;
+
+namespace {
+class BytewiseComparatorImpl : public Comparator {
+ public:
+  BytewiseComparatorImpl() = default;
+
+  const char* Name() const override { return "leveldb.BytewiseComparator"; }
+
+  int Compare(const Slice& a, const Slice& b) const override {
+    return a.compare(b);
+  }
+
+  void FindShortestSeparator(std::string* start,
+                             const Slice& limit) const override {
+    // Find length of common prefix
+    size_t min_length = std::min(start->size(), limit.size());
+    size_t diff_index = 0;
+    while ((diff_index < min_length) &&
+           ((*start)[diff_index] == limit[diff_index])) {
+      diff_index++;
+    }
+
+    if (diff_index >= min_length) {
+      // Do not shorten if one string is a prefix of the other
+    } else {
+      uint8_t diff_byte = static_cast<uint8_t>((*start)[diff_index]);
+      if (diff_byte < static_cast<uint8_t>(0xff) &&
+          diff_byte + 1 < static_cast<uint8_t>(limit[diff_index])) {
+        (*start)[diff_index]++;
+        start->resize(diff_index + 1);
+        assert(Compare(*start, limit) < 0);
+      }
+    }
+  }
+
+  void FindShortSuccessor(std::string* key) const override {
+    // Find first character that can be incremented
+    size_t n = key->size();
+    for (size_t i = 0; i < n; i++) {
+      const uint8_t byte = (*key)[i];
+      if (byte != static_cast<uint8_t>(0xff)) {
+        (*key)[i] = byte + 1;
+        key->resize(i + 1);
+        return;
+      }
+    }
+    // *key is a run of 0xffs.  Leave it alone.
+  }
+};
+}  // namespace
+
+const Comparator* BytewiseComparator() {
+  static NoDestructor<BytewiseComparatorImpl> singleton;
+  return singleton.get();
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/util/crc32c.cc b/leveldb_base/util/crc32c.cc
new file mode 100644
index 0000000..3f18908
--- /dev/null
+++ b/leveldb_base/util/crc32c.cc
@@ -0,0 +1,380 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// A portable implementation of crc32c.
+
+#include "util/crc32c.h"
+
+#include <cstddef>
+#include <cstdint>
+
+#include "port/port.h"
+#include "util/coding.h"
+
+namespace leveldb {
+namespace crc32c {
+
+namespace {
+
+const uint32_t kByteExtensionTable[256] = {
+    0x00000000, 0xf26b8303, 0xe13b70f7, 0x1350f3f4, 0xc79a971f, 0x35f1141c,
+    0x26a1e7e8, 0xd4ca64eb, 0x8ad958cf, 0x78b2dbcc, 0x6be22838, 0x9989ab3b,
+    0x4d43cfd0, 0xbf284cd3, 0xac78bf27, 0x5e133c24, 0x105ec76f, 0xe235446c,
+    0xf165b798, 0x030e349b, 0xd7c45070, 0x25afd373, 0x36ff2087, 0xc494a384,
+    0x9a879fa0, 0x68ec1ca3, 0x7bbcef57, 0x89d76c54, 0x5d1d08bf, 0xaf768bbc,
+    0xbc267848, 0x4e4dfb4b, 0x20bd8ede, 0xd2d60ddd, 0xc186fe29, 0x33ed7d2a,
+    0xe72719c1, 0x154c9ac2, 0x061c6936, 0xf477ea35, 0xaa64d611, 0x580f5512,
+    0x4b5fa6e6, 0xb93425e5, 0x6dfe410e, 0x9f95c20d, 0x8cc531f9, 0x7eaeb2fa,
+    0x30e349b1, 0xc288cab2, 0xd1d83946, 0x23b3ba45, 0xf779deae, 0x05125dad,
+    0x1642ae59, 0xe4292d5a, 0xba3a117e, 0x4851927d, 0x5b016189, 0xa96ae28a,
+    0x7da08661, 0x8fcb0562, 0x9c9bf696, 0x6ef07595, 0x417b1dbc, 0xb3109ebf,
+    0xa0406d4b, 0x522bee48, 0x86e18aa3, 0x748a09a0, 0x67dafa54, 0x95b17957,
+    0xcba24573, 0x39c9c670, 0x2a993584, 0xd8f2b687, 0x0c38d26c, 0xfe53516f,
+    0xed03a29b, 0x1f682198, 0x5125dad3, 0xa34e59d0, 0xb01eaa24, 0x42752927,
+    0x96bf4dcc, 0x64d4cecf, 0x77843d3b, 0x85efbe38, 0xdbfc821c, 0x2997011f,
+    0x3ac7f2eb, 0xc8ac71e8, 0x1c661503, 0xee0d9600, 0xfd5d65f4, 0x0f36e6f7,
+    0x61c69362, 0x93ad1061, 0x80fde395, 0x72966096, 0xa65c047d, 0x5437877e,
+    0x4767748a, 0xb50cf789, 0xeb1fcbad, 0x197448ae, 0x0a24bb5a, 0xf84f3859,
+    0x2c855cb2, 0xdeeedfb1, 0xcdbe2c45, 0x3fd5af46, 0x7198540d, 0x83f3d70e,
+    0x90a324fa, 0x62c8a7f9, 0xb602c312, 0x44694011, 0x5739b3e5, 0xa55230e6,
+    0xfb410cc2, 0x092a8fc1, 0x1a7a7c35, 0xe811ff36, 0x3cdb9bdd, 0xceb018de,
+    0xdde0eb2a, 0x2f8b6829, 0x82f63b78, 0x709db87b, 0x63cd4b8f, 0x91a6c88c,
+    0x456cac67, 0xb7072f64, 0xa457dc90, 0x563c5f93, 0x082f63b7, 0xfa44e0b4,
+    0xe9141340, 0x1b7f9043, 0xcfb5f4a8, 0x3dde77ab, 0x2e8e845f, 0xdce5075c,
+    0x92a8fc17, 0x60c37f14, 0x73938ce0, 0x81f80fe3, 0x55326b08, 0xa759e80b,
+    0xb4091bff, 0x466298fc, 0x1871a4d8, 0xea1a27db, 0xf94ad42f, 0x0b21572c,
+    0xdfeb33c7, 0x2d80b0c4, 0x3ed04330, 0xccbbc033, 0xa24bb5a6, 0x502036a5,
+    0x4370c551, 0xb11b4652, 0x65d122b9, 0x97baa1ba, 0x84ea524e, 0x7681d14d,
+    0x2892ed69, 0xdaf96e6a, 0xc9a99d9e, 0x3bc21e9d, 0xef087a76, 0x1d63f975,
+    0x0e330a81, 0xfc588982, 0xb21572c9, 0x407ef1ca, 0x532e023e, 0xa145813d,
+    0x758fe5d6, 0x87e466d5, 0x94b49521, 0x66df1622, 0x38cc2a06, 0xcaa7a905,
+    0xd9f75af1, 0x2b9cd9f2, 0xff56bd19, 0x0d3d3e1a, 0x1e6dcdee, 0xec064eed,
+    0xc38d26c4, 0x31e6a5c7, 0x22b65633, 0xd0ddd530, 0x0417b1db, 0xf67c32d8,
+    0xe52cc12c, 0x1747422f, 0x49547e0b, 0xbb3ffd08, 0xa86f0efc, 0x5a048dff,
+    0x8ecee914, 0x7ca56a17, 0x6ff599e3, 0x9d9e1ae0, 0xd3d3e1ab, 0x21b862a8,
+    0x32e8915c, 0xc083125f, 0x144976b4, 0xe622f5b7, 0xf5720643, 0x07198540,
+    0x590ab964, 0xab613a67, 0xb831c993, 0x4a5a4a90, 0x9e902e7b, 0x6cfbad78,
+    0x7fab5e8c, 0x8dc0dd8f, 0xe330a81a, 0x115b2b19, 0x020bd8ed, 0xf0605bee,
+    0x24aa3f05, 0xd6c1bc06, 0xc5914ff2, 0x37faccf1, 0x69e9f0d5, 0x9b8273d6,
+    0x88d28022, 0x7ab90321, 0xae7367ca, 0x5c18e4c9, 0x4f48173d, 0xbd23943e,
+    0xf36e6f75, 0x0105ec76, 0x12551f82, 0xe03e9c81, 0x34f4f86a, 0xc69f7b69,
+    0xd5cf889d, 0x27a40b9e, 0x79b737ba, 0x8bdcb4b9, 0x988c474d, 0x6ae7c44e,
+    0xbe2da0a5, 0x4c4623a6, 0x5f16d052, 0xad7d5351};
+
+const uint32_t kStrideExtensionTable0[256] = {
+    0x00000000, 0x30d23865, 0x61a470ca, 0x517648af, 0xc348e194, 0xf39ad9f1,
+    0xa2ec915e, 0x923ea93b, 0x837db5d9, 0xb3af8dbc, 0xe2d9c513, 0xd20bfd76,
+    0x4035544d, 0x70e76c28, 0x21912487, 0x11431ce2, 0x03171d43, 0x33c52526,
+    0x62b36d89, 0x526155ec, 0xc05ffcd7, 0xf08dc4b2, 0xa1fb8c1d, 0x9129b478,
+    0x806aa89a, 0xb0b890ff, 0xe1ced850, 0xd11ce035, 0x4322490e, 0x73f0716b,
+    0x228639c4, 0x125401a1, 0x062e3a86, 0x36fc02e3, 0x678a4a4c, 0x57587229,
+    0xc566db12, 0xf5b4e377, 0xa4c2abd8, 0x941093bd, 0x85538f5f, 0xb581b73a,
+    0xe4f7ff95, 0xd425c7f0, 0x461b6ecb, 0x76c956ae, 0x27bf1e01, 0x176d2664,
+    0x053927c5, 0x35eb1fa0, 0x649d570f, 0x544f6f6a, 0xc671c651, 0xf6a3fe34,
+    0xa7d5b69b, 0x97078efe, 0x8644921c, 0xb696aa79, 0xe7e0e2d6, 0xd732dab3,
+    0x450c7388, 0x75de4bed, 0x24a80342, 0x147a3b27, 0x0c5c750c, 0x3c8e4d69,
+    0x6df805c6, 0x5d2a3da3, 0xcf149498, 0xffc6acfd, 0xaeb0e452, 0x9e62dc37,
+    0x8f21c0d5, 0xbff3f8b0, 0xee85b01f, 0xde57887a, 0x4c692141, 0x7cbb1924,
+    0x2dcd518b, 0x1d1f69ee, 0x0f4b684f, 0x3f99502a, 0x6eef1885, 0x5e3d20e0,
+    0xcc0389db, 0xfcd1b1be, 0xada7f911, 0x9d75c174, 0x8c36dd96, 0xbce4e5f3,
+    0xed92ad5c, 0xdd409539, 0x4f7e3c02, 0x7fac0467, 0x2eda4cc8, 0x1e0874ad,
+    0x0a724f8a, 0x3aa077ef, 0x6bd63f40, 0x5b040725, 0xc93aae1e, 0xf9e8967b,
+    0xa89eded4, 0x984ce6b1, 0x890ffa53, 0xb9ddc236, 0xe8ab8a99, 0xd879b2fc,
+    0x4a471bc7, 0x7a9523a2, 0x2be36b0d, 0x1b315368, 0x096552c9, 0x39b76aac,
+    0x68c12203, 0x58131a66, 0xca2db35d, 0xfaff8b38, 0xab89c397, 0x9b5bfbf2,
+    0x8a18e710, 0xbacadf75, 0xebbc97da, 0xdb6eafbf, 0x49500684, 0x79823ee1,
+    0x28f4764e, 0x18264e2b, 0x18b8ea18, 0x286ad27d, 0x791c9ad2, 0x49cea2b7,
+    0xdbf00b8c, 0xeb2233e9, 0xba547b46, 0x8a864323, 0x9bc55fc1, 0xab1767a4,
+    0xfa612f0b, 0xcab3176e, 0x588dbe55, 0x685f8630, 0x3929ce9f, 0x09fbf6fa,
+    0x1baff75b, 0x2b7dcf3e, 0x7a0b8791, 0x4ad9bff4, 0xd8e716cf, 0xe8352eaa,
+    0xb9436605, 0x89915e60, 0x98d24282, 0xa8007ae7, 0xf9763248, 0xc9a40a2d,
+    0x5b9aa316, 0x6b489b73, 0x3a3ed3dc, 0x0aecebb9, 0x1e96d09e, 0x2e44e8fb,
+    0x7f32a054, 0x4fe09831, 0xddde310a, 0xed0c096f, 0xbc7a41c0, 0x8ca879a5,
+    0x9deb6547, 0xad395d22, 0xfc4f158d, 0xcc9d2de8, 0x5ea384d3, 0x6e71bcb6,
+    0x3f07f419, 0x0fd5cc7c, 0x1d81cddd, 0x2d53f5b8, 0x7c25bd17, 0x4cf78572,
+    0xdec92c49, 0xee1b142c, 0xbf6d5c83, 0x8fbf64e6, 0x9efc7804, 0xae2e4061,
+    0xff5808ce, 0xcf8a30ab, 0x5db49990, 0x6d66a1f5, 0x3c10e95a, 0x0cc2d13f,
+    0x14e49f14, 0x2436a771, 0x7540efde, 0x4592d7bb, 0xd7ac7e80, 0xe77e46e5,
+    0xb6080e4a, 0x86da362f, 0x97992acd, 0xa74b12a8, 0xf63d5a07, 0xc6ef6262,
+    0x54d1cb59, 0x6403f33c, 0x3575bb93, 0x05a783f6, 0x17f38257, 0x2721ba32,
+    0x7657f29d, 0x4685caf8, 0xd4bb63c3, 0xe4695ba6, 0xb51f1309, 0x85cd2b6c,
+    0x948e378e, 0xa45c0feb, 0xf52a4744, 0xc5f87f21, 0x57c6d61a, 0x6714ee7f,
+    0x3662a6d0, 0x06b09eb5, 0x12caa592, 0x22189df7, 0x736ed558, 0x43bced3d,
+    0xd1824406, 0xe1507c63, 0xb02634cc, 0x80f40ca9, 0x91b7104b, 0xa165282e,
+    0xf0136081, 0xc0c158e4, 0x52fff1df, 0x622dc9ba, 0x335b8115, 0x0389b970,
+    0x11ddb8d1, 0x210f80b4, 0x7079c81b, 0x40abf07e, 0xd2955945, 0xe2476120,
+    0xb331298f, 0x83e311ea, 0x92a00d08, 0xa272356d, 0xf3047dc2, 0xc3d645a7,
+    0x51e8ec9c, 0x613ad4f9, 0x304c9c56, 0x009ea433};
+
+const uint32_t kStrideExtensionTable1[256] = {
+    0x00000000, 0x54075546, 0xa80eaa8c, 0xfc09ffca, 0x55f123e9, 0x01f676af,
+    0xfdff8965, 0xa9f8dc23, 0xabe247d2, 0xffe51294, 0x03eced5e, 0x57ebb818,
+    0xfe13643b, 0xaa14317d, 0x561dceb7, 0x021a9bf1, 0x5228f955, 0x062fac13,
+    0xfa2653d9, 0xae21069f, 0x07d9dabc, 0x53de8ffa, 0xafd77030, 0xfbd02576,
+    0xf9cabe87, 0xadcdebc1, 0x51c4140b, 0x05c3414d, 0xac3b9d6e, 0xf83cc828,
+    0x043537e2, 0x503262a4, 0xa451f2aa, 0xf056a7ec, 0x0c5f5826, 0x58580d60,
+    0xf1a0d143, 0xa5a78405, 0x59ae7bcf, 0x0da92e89, 0x0fb3b578, 0x5bb4e03e,
+    0xa7bd1ff4, 0xf3ba4ab2, 0x5a429691, 0x0e45c3d7, 0xf24c3c1d, 0xa64b695b,
+    0xf6790bff, 0xa27e5eb9, 0x5e77a173, 0x0a70f435, 0xa3882816, 0xf78f7d50,
+    0x0b86829a, 0x5f81d7dc, 0x5d9b4c2d, 0x099c196b, 0xf595e6a1, 0xa192b3e7,
+    0x086a6fc4, 0x5c6d3a82, 0xa064c548, 0xf463900e, 0x4d4f93a5, 0x1948c6e3,
+    0xe5413929, 0xb1466c6f, 0x18beb04c, 0x4cb9e50a, 0xb0b01ac0, 0xe4b74f86,
+    0xe6add477, 0xb2aa8131, 0x4ea37efb, 0x1aa42bbd, 0xb35cf79e, 0xe75ba2d8,
+    0x1b525d12, 0x4f550854, 0x1f676af0, 0x4b603fb6, 0xb769c07c, 0xe36e953a,
+    0x4a964919, 0x1e911c5f, 0xe298e395, 0xb69fb6d3, 0xb4852d22, 0xe0827864,
+    0x1c8b87ae, 0x488cd2e8, 0xe1740ecb, 0xb5735b8d, 0x497aa447, 0x1d7df101,
+    0xe91e610f, 0xbd193449, 0x4110cb83, 0x15179ec5, 0xbcef42e6, 0xe8e817a0,
+    0x14e1e86a, 0x40e6bd2c, 0x42fc26dd, 0x16fb739b, 0xeaf28c51, 0xbef5d917,
+    0x170d0534, 0x430a5072, 0xbf03afb8, 0xeb04fafe, 0xbb36985a, 0xef31cd1c,
+    0x133832d6, 0x473f6790, 0xeec7bbb3, 0xbac0eef5, 0x46c9113f, 0x12ce4479,
+    0x10d4df88, 0x44d38ace, 0xb8da7504, 0xecdd2042, 0x4525fc61, 0x1122a927,
+    0xed2b56ed, 0xb92c03ab, 0x9a9f274a, 0xce98720c, 0x32918dc6, 0x6696d880,
+    0xcf6e04a3, 0x9b6951e5, 0x6760ae2f, 0x3367fb69, 0x317d6098, 0x657a35de,
+    0x9973ca14, 0xcd749f52, 0x648c4371, 0x308b1637, 0xcc82e9fd, 0x9885bcbb,
+    0xc8b7de1f, 0x9cb08b59, 0x60b97493, 0x34be21d5, 0x9d46fdf6, 0xc941a8b0,
+    0x3548577a, 0x614f023c, 0x635599cd, 0x3752cc8b, 0xcb5b3341, 0x9f5c6607,
+    0x36a4ba24, 0x62a3ef62, 0x9eaa10a8, 0xcaad45ee, 0x3eced5e0, 0x6ac980a6,
+    0x96c07f6c, 0xc2c72a2a, 0x6b3ff609, 0x3f38a34f, 0xc3315c85, 0x973609c3,
+    0x952c9232, 0xc12bc774, 0x3d2238be, 0x69256df8, 0xc0ddb1db, 0x94dae49d,
+    0x68d31b57, 0x3cd44e11, 0x6ce62cb5, 0x38e179f3, 0xc4e88639, 0x90efd37f,
+    0x39170f5c, 0x6d105a1a, 0x9119a5d0, 0xc51ef096, 0xc7046b67, 0x93033e21,
+    0x6f0ac1eb, 0x3b0d94ad, 0x92f5488e, 0xc6f21dc8, 0x3afbe202, 0x6efcb744,
+    0xd7d0b4ef, 0x83d7e1a9, 0x7fde1e63, 0x2bd94b25, 0x82219706, 0xd626c240,
+    0x2a2f3d8a, 0x7e2868cc, 0x7c32f33d, 0x2835a67b, 0xd43c59b1, 0x803b0cf7,
+    0x29c3d0d4, 0x7dc48592, 0x81cd7a58, 0xd5ca2f1e, 0x85f84dba, 0xd1ff18fc,
+    0x2df6e736, 0x79f1b270, 0xd0096e53, 0x840e3b15, 0x7807c4df, 0x2c009199,
+    0x2e1a0a68, 0x7a1d5f2e, 0x8614a0e4, 0xd213f5a2, 0x7beb2981, 0x2fec7cc7,
+    0xd3e5830d, 0x87e2d64b, 0x73814645, 0x27861303, 0xdb8fecc9, 0x8f88b98f,
+    0x267065ac, 0x727730ea, 0x8e7ecf20, 0xda799a66, 0xd8630197, 0x8c6454d1,
+    0x706dab1b, 0x246afe5d, 0x8d92227e, 0xd9957738, 0x259c88f2, 0x719bddb4,
+    0x21a9bf10, 0x75aeea56, 0x89a7159c, 0xdda040da, 0x74589cf9, 0x205fc9bf,
+    0xdc563675, 0x88516333, 0x8a4bf8c2, 0xde4cad84, 0x2245524e, 0x76420708,
+    0xdfbadb2b, 0x8bbd8e6d, 0x77b471a7, 0x23b324e1};
+
+const uint32_t kStrideExtensionTable2[256] = {
+    0x00000000, 0x678efd01, 0xcf1dfa02, 0xa8930703, 0x9bd782f5, 0xfc597ff4,
+    0x54ca78f7, 0x334485f6, 0x3243731b, 0x55cd8e1a, 0xfd5e8919, 0x9ad07418,
+    0xa994f1ee, 0xce1a0cef, 0x66890bec, 0x0107f6ed, 0x6486e636, 0x03081b37,
+    0xab9b1c34, 0xcc15e135, 0xff5164c3, 0x98df99c2, 0x304c9ec1, 0x57c263c0,
+    0x56c5952d, 0x314b682c, 0x99d86f2f, 0xfe56922e, 0xcd1217d8, 0xaa9cead9,
+    0x020fedda, 0x658110db, 0xc90dcc6c, 0xae83316d, 0x0610366e, 0x619ecb6f,
+    0x52da4e99, 0x3554b398, 0x9dc7b49b, 0xfa49499a, 0xfb4ebf77, 0x9cc04276,
+    0x34534575, 0x53ddb874, 0x60993d82, 0x0717c083, 0xaf84c780, 0xc80a3a81,
+    0xad8b2a5a, 0xca05d75b, 0x6296d058, 0x05182d59, 0x365ca8af, 0x51d255ae,
+    0xf94152ad, 0x9ecfafac, 0x9fc85941, 0xf846a440, 0x50d5a343, 0x375b5e42,
+    0x041fdbb4, 0x639126b5, 0xcb0221b6, 0xac8cdcb7, 0x97f7ee29, 0xf0791328,
+    0x58ea142b, 0x3f64e92a, 0x0c206cdc, 0x6bae91dd, 0xc33d96de, 0xa4b36bdf,
+    0xa5b49d32, 0xc23a6033, 0x6aa96730, 0x0d279a31, 0x3e631fc7, 0x59ede2c6,
+    0xf17ee5c5, 0x96f018c4, 0xf371081f, 0x94fff51e, 0x3c6cf21d, 0x5be20f1c,
+    0x68a68aea, 0x0f2877eb, 0xa7bb70e8, 0xc0358de9, 0xc1327b04, 0xa6bc8605,
+    0x0e2f8106, 0x69a17c07, 0x5ae5f9f1, 0x3d6b04f0, 0x95f803f3, 0xf276fef2,
+    0x5efa2245, 0x3974df44, 0x91e7d847, 0xf6692546, 0xc52da0b0, 0xa2a35db1,
+    0x0a305ab2, 0x6dbea7b3, 0x6cb9515e, 0x0b37ac5f, 0xa3a4ab5c, 0xc42a565d,
+    0xf76ed3ab, 0x90e02eaa, 0x387329a9, 0x5ffdd4a8, 0x3a7cc473, 0x5df23972,
+    0xf5613e71, 0x92efc370, 0xa1ab4686, 0xc625bb87, 0x6eb6bc84, 0x09384185,
+    0x083fb768, 0x6fb14a69, 0xc7224d6a, 0xa0acb06b, 0x93e8359d, 0xf466c89c,
+    0x5cf5cf9f, 0x3b7b329e, 0x2a03aaa3, 0x4d8d57a2, 0xe51e50a1, 0x8290ada0,
+    0xb1d42856, 0xd65ad557, 0x7ec9d254, 0x19472f55, 0x1840d9b8, 0x7fce24b9,
+    0xd75d23ba, 0xb0d3debb, 0x83975b4d, 0xe419a64c, 0x4c8aa14f, 0x2b045c4e,
+    0x4e854c95, 0x290bb194, 0x8198b697, 0xe6164b96, 0xd552ce60, 0xb2dc3361,
+    0x1a4f3462, 0x7dc1c963, 0x7cc63f8e, 0x1b48c28f, 0xb3dbc58c, 0xd455388d,
+    0xe711bd7b, 0x809f407a, 0x280c4779, 0x4f82ba78, 0xe30e66cf, 0x84809bce,
+    0x2c139ccd, 0x4b9d61cc, 0x78d9e43a, 0x1f57193b, 0xb7c41e38, 0xd04ae339,
+    0xd14d15d4, 0xb6c3e8d5, 0x1e50efd6, 0x79de12d7, 0x4a9a9721, 0x2d146a20,
+    0x85876d23, 0xe2099022, 0x878880f9, 0xe0067df8, 0x48957afb, 0x2f1b87fa,
+    0x1c5f020c, 0x7bd1ff0d, 0xd342f80e, 0xb4cc050f, 0xb5cbf3e2, 0xd2450ee3,
+    0x7ad609e0, 0x1d58f4e1, 0x2e1c7117, 0x49928c16, 0xe1018b15, 0x868f7614,
+    0xbdf4448a, 0xda7ab98b, 0x72e9be88, 0x15674389, 0x2623c67f, 0x41ad3b7e,
+    0xe93e3c7d, 0x8eb0c17c, 0x8fb73791, 0xe839ca90, 0x40aacd93, 0x27243092,
+    0x1460b564, 0x73ee4865, 0xdb7d4f66, 0xbcf3b267, 0xd972a2bc, 0xbefc5fbd,
+    0x166f58be, 0x71e1a5bf, 0x42a52049, 0x252bdd48, 0x8db8da4b, 0xea36274a,
+    0xeb31d1a7, 0x8cbf2ca6, 0x242c2ba5, 0x43a2d6a4, 0x70e65352, 0x1768ae53,
+    0xbffba950, 0xd8755451, 0x74f988e6, 0x137775e7, 0xbbe472e4, 0xdc6a8fe5,
+    0xef2e0a13, 0x88a0f712, 0x2033f011, 0x47bd0d10, 0x46bafbfd, 0x213406fc,
+    0x89a701ff, 0xee29fcfe, 0xdd6d7908, 0xbae38409, 0x1270830a, 0x75fe7e0b,
+    0x107f6ed0, 0x77f193d1, 0xdf6294d2, 0xb8ec69d3, 0x8ba8ec25, 0xec261124,
+    0x44b51627, 0x233beb26, 0x223c1dcb, 0x45b2e0ca, 0xed21e7c9, 0x8aaf1ac8,
+    0xb9eb9f3e, 0xde65623f, 0x76f6653c, 0x1178983d};
+
+const uint32_t kStrideExtensionTable3[256] = {
+    0x00000000, 0xf20c0dfe, 0xe1f46d0d, 0x13f860f3, 0xc604aceb, 0x3408a115,
+    0x27f0c1e6, 0xd5fccc18, 0x89e52f27, 0x7be922d9, 0x6811422a, 0x9a1d4fd4,
+    0x4fe183cc, 0xbded8e32, 0xae15eec1, 0x5c19e33f, 0x162628bf, 0xe42a2541,
+    0xf7d245b2, 0x05de484c, 0xd0228454, 0x222e89aa, 0x31d6e959, 0xc3dae4a7,
+    0x9fc30798, 0x6dcf0a66, 0x7e376a95, 0x8c3b676b, 0x59c7ab73, 0xabcba68d,
+    0xb833c67e, 0x4a3fcb80, 0x2c4c517e, 0xde405c80, 0xcdb83c73, 0x3fb4318d,
+    0xea48fd95, 0x1844f06b, 0x0bbc9098, 0xf9b09d66, 0xa5a97e59, 0x57a573a7,
+    0x445d1354, 0xb6511eaa, 0x63add2b2, 0x91a1df4c, 0x8259bfbf, 0x7055b241,
+    0x3a6a79c1, 0xc866743f, 0xdb9e14cc, 0x29921932, 0xfc6ed52a, 0x0e62d8d4,
+    0x1d9ab827, 0xef96b5d9, 0xb38f56e6, 0x41835b18, 0x527b3beb, 0xa0773615,
+    0x758bfa0d, 0x8787f7f3, 0x947f9700, 0x66739afe, 0x5898a2fc, 0xaa94af02,
+    0xb96ccff1, 0x4b60c20f, 0x9e9c0e17, 0x6c9003e9, 0x7f68631a, 0x8d646ee4,
+    0xd17d8ddb, 0x23718025, 0x3089e0d6, 0xc285ed28, 0x17792130, 0xe5752cce,
+    0xf68d4c3d, 0x048141c3, 0x4ebe8a43, 0xbcb287bd, 0xaf4ae74e, 0x5d46eab0,
+    0x88ba26a8, 0x7ab62b56, 0x694e4ba5, 0x9b42465b, 0xc75ba564, 0x3557a89a,
+    0x26afc869, 0xd4a3c597, 0x015f098f, 0xf3530471, 0xe0ab6482, 0x12a7697c,
+    0x74d4f382, 0x86d8fe7c, 0x95209e8f, 0x672c9371, 0xb2d05f69, 0x40dc5297,
+    0x53243264, 0xa1283f9a, 0xfd31dca5, 0x0f3dd15b, 0x1cc5b1a8, 0xeec9bc56,
+    0x3b35704e, 0xc9397db0, 0xdac11d43, 0x28cd10bd, 0x62f2db3d, 0x90fed6c3,
+    0x8306b630, 0x710abbce, 0xa4f677d6, 0x56fa7a28, 0x45021adb, 0xb70e1725,
+    0xeb17f41a, 0x191bf9e4, 0x0ae39917, 0xf8ef94e9, 0x2d1358f1, 0xdf1f550f,
+    0xcce735fc, 0x3eeb3802, 0xb13145f8, 0x433d4806, 0x50c528f5, 0xa2c9250b,
+    0x7735e913, 0x8539e4ed, 0x96c1841e, 0x64cd89e0, 0x38d46adf, 0xcad86721,
+    0xd92007d2, 0x2b2c0a2c, 0xfed0c634, 0x0cdccbca, 0x1f24ab39, 0xed28a6c7,
+    0xa7176d47, 0x551b60b9, 0x46e3004a, 0xb4ef0db4, 0x6113c1ac, 0x931fcc52,
+    0x80e7aca1, 0x72eba15f, 0x2ef24260, 0xdcfe4f9e, 0xcf062f6d, 0x3d0a2293,
+    0xe8f6ee8b, 0x1afae375, 0x09028386, 0xfb0e8e78, 0x9d7d1486, 0x6f711978,
+    0x7c89798b, 0x8e857475, 0x5b79b86d, 0xa975b593, 0xba8dd560, 0x4881d89e,
+    0x14983ba1, 0xe694365f, 0xf56c56ac, 0x07605b52, 0xd29c974a, 0x20909ab4,
+    0x3368fa47, 0xc164f7b9, 0x8b5b3c39, 0x795731c7, 0x6aaf5134, 0x98a35cca,
+    0x4d5f90d2, 0xbf539d2c, 0xacabfddf, 0x5ea7f021, 0x02be131e, 0xf0b21ee0,
+    0xe34a7e13, 0x114673ed, 0xc4babff5, 0x36b6b20b, 0x254ed2f8, 0xd742df06,
+    0xe9a9e704, 0x1ba5eafa, 0x085d8a09, 0xfa5187f7, 0x2fad4bef, 0xdda14611,
+    0xce5926e2, 0x3c552b1c, 0x604cc823, 0x9240c5dd, 0x81b8a52e, 0x73b4a8d0,
+    0xa64864c8, 0x54446936, 0x47bc09c5, 0xb5b0043b, 0xff8fcfbb, 0x0d83c245,
+    0x1e7ba2b6, 0xec77af48, 0x398b6350, 0xcb876eae, 0xd87f0e5d, 0x2a7303a3,
+    0x766ae09c, 0x8466ed62, 0x979e8d91, 0x6592806f, 0xb06e4c77, 0x42624189,
+    0x519a217a, 0xa3962c84, 0xc5e5b67a, 0x37e9bb84, 0x2411db77, 0xd61dd689,
+    0x03e11a91, 0xf1ed176f, 0xe215779c, 0x10197a62, 0x4c00995d, 0xbe0c94a3,
+    0xadf4f450, 0x5ff8f9ae, 0x8a0435b6, 0x78083848, 0x6bf058bb, 0x99fc5545,
+    0xd3c39ec5, 0x21cf933b, 0x3237f3c8, 0xc03bfe36, 0x15c7322e, 0xe7cb3fd0,
+    0xf4335f23, 0x063f52dd, 0x5a26b1e2, 0xa82abc1c, 0xbbd2dcef, 0x49ded111,
+    0x9c221d09, 0x6e2e10f7, 0x7dd67004, 0x8fda7dfa};
+
+// CRCs are pre- and post- conditioned by xoring with all ones.
+static constexpr const uint32_t kCRC32Xor = static_cast<uint32_t>(0xffffffffU);
+
+// Reads a little-endian 32-bit integer from a 32-bit-aligned buffer.
+inline uint32_t ReadUint32LE(const uint8_t* buffer) {
+  return DecodeFixed32(reinterpret_cast<const char*>(buffer));
+}
+
+// Returns the smallest address >= the given address that is aligned to N bytes.
+//
+// N must be a power of two.
+template <int N>
+constexpr inline const uint8_t* RoundUp(const uint8_t* pointer) {
+  return reinterpret_cast<uint8_t*>(
+      (reinterpret_cast<uintptr_t>(pointer) + (N - 1)) &
+      ~static_cast<uintptr_t>(N - 1));
+}
+
+}  // namespace
+
+// Determine if the CPU running this program can accelerate the CRC32C
+// calculation.
+static bool CanAccelerateCRC32C() {
+  // port::AcceleretedCRC32C returns zero when unable to accelerate.
+  static const char kTestCRCBuffer[] = "TestCRCBuffer";
+  static const char kBufSize = sizeof(kTestCRCBuffer) - 1;
+  static const uint32_t kTestCRCValue = 0xdcbc59fa;
+
+  return port::AcceleratedCRC32C(0, kTestCRCBuffer, kBufSize) == kTestCRCValue;
+}
+
+uint32_t Extend(uint32_t crc, const char* data, size_t n) {
+  static bool accelerate = CanAccelerateCRC32C();
+  if (accelerate) {
+    return port::AcceleratedCRC32C(crc, data, n);
+  }
+
+  const uint8_t* p = reinterpret_cast<const uint8_t*>(data);
+  const uint8_t* e = p + n;
+  uint32_t l = crc ^ kCRC32Xor;
+
+// Process one byte at a time.
+#define STEP1                              \
+  do {                                     \
+    int c = (l & 0xff) ^ *p++;             \
+    l = kByteExtensionTable[c] ^ (l >> 8); \
+  } while (0)
+
+// Process one of the 4 strides of 4-byte data.
+#define STEP4(s)                                                               \
+  do {                                                                         \
+    crc##s = ReadUint32LE(p + s * 4) ^ kStrideExtensionTable3[crc##s & 0xff] ^ \
+             kStrideExtensionTable2[(crc##s >> 8) & 0xff] ^                    \
+             kStrideExtensionTable1[(crc##s >> 16) & 0xff] ^                   \
+             kStrideExtensionTable0[crc##s >> 24];                             \
+  } while (0)
+
+// Process a 16-byte swath of 4 strides, each of which has 4 bytes of data.
+#define STEP16 \
+  do {         \
+    STEP4(0);  \
+    STEP4(1);  \
+    STEP4(2);  \
+    STEP4(3);  \
+    p += 16;   \
+  } while (0)
+
+// Process 4 bytes that were already loaded into a word.
+#define STEP4W(w)                                   \
+  do {                                              \
+    w ^= l;                                         \
+    for (size_t i = 0; i < 4; ++i) {                \
+      w = (w >> 8) ^ kByteExtensionTable[w & 0xff]; \
+    }                                               \
+    l = w;                                          \
+  } while (0)
+
+  // Point x at first 4-byte aligned byte in the buffer. This might be past the
+  // end of the buffer.
+  const uint8_t* x = RoundUp<4>(p);
+  if (x <= e) {
+    // Process bytes p is 4-byte aligned.
+    while (p != x) {
+      STEP1;
+    }
+  }
+
+  if ((e - p) >= 16) {
+    // Load a 16-byte swath into the stride partial results.
+    uint32_t crc0 = ReadUint32LE(p + 0 * 4) ^ l;
+    uint32_t crc1 = ReadUint32LE(p + 1 * 4);
+    uint32_t crc2 = ReadUint32LE(p + 2 * 4);
+    uint32_t crc3 = ReadUint32LE(p + 3 * 4);
+    p += 16;
+
+    // It is possible to get better speeds (at least on x86) by interleaving
+    // prefetching 256 bytes ahead with processing 64 bytes at a time. See the
+    // portable implementation in https://github.com/google/crc32c/.
+
+    // Process one 16-byte swath at a time.
+    while ((e - p) >= 16) {
+      STEP16;
+    }
+
+    // Advance one word at a time as far as possible.
+    while ((e - p) >= 4) {
+      STEP4(0);
+      uint32_t tmp = crc0;
+      crc0 = crc1;
+      crc1 = crc2;
+      crc2 = crc3;
+      crc3 = tmp;
+      p += 4;
+    }
+
+    // Combine the 4 partial stride results.
+    l = 0;
+    STEP4W(crc0);
+    STEP4W(crc1);
+    STEP4W(crc2);
+    STEP4W(crc3);
+  }
+
+  // Process the last few bytes.
+  while (p != e) {
+    STEP1;
+  }
+#undef STEP4W
+#undef STEP16
+#undef STEP4
+#undef STEP1
+  return l ^ kCRC32Xor;
+}
+
+}  // namespace crc32c
+}  // namespace leveldb
diff --git a/leveldb_base/util/crc32c.h b/leveldb_base/util/crc32c.h
new file mode 100644
index 0000000..b420b5f
--- /dev/null
+++ b/leveldb_base/util/crc32c.h
@@ -0,0 +1,43 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_UTIL_CRC32C_H_
+#define STORAGE_LEVELDB_UTIL_CRC32C_H_
+
+#include <cstddef>
+#include <cstdint>
+
+namespace leveldb {
+namespace crc32c {
+
+// Return the crc32c of concat(A, data[0,n-1]) where init_crc is the
+// crc32c of some string A.  Extend() is often used to maintain the
+// crc32c of a stream of data.
+uint32_t Extend(uint32_t init_crc, const char* data, size_t n);
+
+// Return the crc32c of data[0,n-1]
+inline uint32_t Value(const char* data, size_t n) { return Extend(0, data, n); }
+
+static const uint32_t kMaskDelta = 0xa282ead8ul;
+
+// Return a masked representation of crc.
+//
+// Motivation: it is problematic to compute the CRC of a string that
+// contains embedded CRCs.  Therefore we recommend that CRCs stored
+// somewhere (e.g., in files) should be masked before being stored.
+inline uint32_t Mask(uint32_t crc) {
+  // Rotate right by 15 bits and add a constant.
+  return ((crc >> 15) | (crc << 17)) + kMaskDelta;
+}
+
+// Return the crc whose masked representation is masked_crc.
+inline uint32_t Unmask(uint32_t masked_crc) {
+  uint32_t rot = masked_crc - kMaskDelta;
+  return ((rot >> 17) | (rot << 15));
+}
+
+}  // namespace crc32c
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_UTIL_CRC32C_H_
diff --git a/leveldb_base/util/crc32c_test.cc b/leveldb_base/util/crc32c_test.cc
new file mode 100644
index 0000000..2fe1c41
--- /dev/null
+++ b/leveldb_base/util/crc32c_test.cc
@@ -0,0 +1,56 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "util/crc32c.h"
+
+#include "gtest/gtest.h"
+
+namespace leveldb {
+namespace crc32c {
+
+TEST(CRC, StandardResults) {
+  // From rfc3720 section B.4.
+  char buf[32];
+
+  memset(buf, 0, sizeof(buf));
+  ASSERT_EQ(0x8a9136aa, Value(buf, sizeof(buf)));
+
+  memset(buf, 0xff, sizeof(buf));
+  ASSERT_EQ(0x62a8ab43, Value(buf, sizeof(buf)));
+
+  for (int i = 0; i < 32; i++) {
+    buf[i] = i;
+  }
+  ASSERT_EQ(0x46dd794e, Value(buf, sizeof(buf)));
+
+  for (int i = 0; i < 32; i++) {
+    buf[i] = 31 - i;
+  }
+  ASSERT_EQ(0x113fdb5c, Value(buf, sizeof(buf)));
+
+  uint8_t data[48] = {
+      0x01, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00,
+      0x00, 0x00, 0x00, 0x14, 0x00, 0x00, 0x00, 0x18, 0x28, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  };
+  ASSERT_EQ(0xd9963a56, Value(reinterpret_cast<char*>(data), sizeof(data)));
+}
+
+TEST(CRC, Values) { ASSERT_NE(Value("a", 1), Value("foo", 3)); }
+
+TEST(CRC, Extend) {
+  ASSERT_EQ(Value("hello world", 11), Extend(Value("hello ", 6), "world", 5));
+}
+
+TEST(CRC, Mask) {
+  uint32_t crc = Value("foo", 3);
+  ASSERT_NE(crc, Mask(crc));
+  ASSERT_NE(crc, Mask(Mask(crc)));
+  ASSERT_EQ(crc, Unmask(Mask(crc)));
+  ASSERT_EQ(crc, Unmask(Unmask(Mask(Mask(crc)))));
+}
+
+}  // namespace crc32c
+}  // namespace leveldb
diff --git a/leveldb_base/util/env.cc b/leveldb_base/util/env.cc
new file mode 100644
index 0000000..a53b230
--- /dev/null
+++ b/leveldb_base/util/env.cc
@@ -0,0 +1,108 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "leveldb/env.h"
+
+#include <cstdarg>
+
+// This workaround can be removed when leveldb::Env::DeleteFile is removed.
+// See env.h for justification.
+#if defined(_WIN32) && defined(LEVELDB_DELETEFILE_UNDEFINED)
+#undef DeleteFile
+#endif
+
+namespace leveldb {
+
+Env::Env() = default;
+
+Env::~Env() = default;
+
+Status Env::NewAppendableFile(const std::string& fname, WritableFile** result) {
+  return Status::NotSupported("NewAppendableFile", fname);
+}
+
+Status Env::RemoveDir(const std::string& dirname) { return DeleteDir(dirname); }
+Status Env::DeleteDir(const std::string& dirname) { return RemoveDir(dirname); }
+
+Status Env::RemoveFile(const std::string& fname) { return DeleteFile(fname); }
+Status Env::DeleteFile(const std::string& fname) { return RemoveFile(fname); }
+
+SequentialFile::~SequentialFile() = default;
+
+RandomAccessFile::~RandomAccessFile() = default;
+
+WritableFile::~WritableFile() = default;
+
+Logger::~Logger() = default;
+
+FileLock::~FileLock() = default;
+
+void Log(Logger* info_log, const char* format, ...) {
+  if (info_log != nullptr) {
+    std::va_list ap;
+    va_start(ap, format);
+    info_log->Logv(format, ap);
+    va_end(ap);
+  }
+}
+
+static Status DoWriteStringToFile(Env* env, const Slice& data,
+                                  const std::string& fname, bool should_sync) {
+  WritableFile* file;
+  Status s = env->NewWritableFile(fname, &file);
+  if (!s.ok()) {
+    return s;
+  }
+  s = file->Append(data);
+  if (s.ok() && should_sync) {
+    s = file->Sync();
+  }
+  if (s.ok()) {
+    s = file->Close();
+  }
+  delete file;  // Will auto-close if we did not close above
+  if (!s.ok()) {
+    env->RemoveFile(fname);
+  }
+  return s;
+}
+
+Status WriteStringToFile(Env* env, const Slice& data,
+                         const std::string& fname) {
+  return DoWriteStringToFile(env, data, fname, false);
+}
+
+Status WriteStringToFileSync(Env* env, const Slice& data,
+                             const std::string& fname) {
+  return DoWriteStringToFile(env, data, fname, true);
+}
+
+Status ReadFileToString(Env* env, const std::string& fname, std::string* data) {
+  data->clear();
+  SequentialFile* file;
+  Status s = env->NewSequentialFile(fname, &file);
+  if (!s.ok()) {
+    return s;
+  }
+  static const int kBufferSize = 8192;
+  char* space = new char[kBufferSize];
+  while (true) {
+    Slice fragment;
+    s = file->Read(kBufferSize, &fragment, space);
+    if (!s.ok()) {
+      break;
+    }
+    data->append(fragment.data(), fragment.size());
+    if (fragment.empty()) {
+      break;
+    }
+  }
+  delete[] space;
+  delete file;
+  return s;
+}
+
+EnvWrapper::~EnvWrapper() {}
+
+}  // namespace leveldb
diff --git a/leveldb_base/util/env_posix.cc b/leveldb_base/util/env_posix.cc
new file mode 100644
index 0000000..ffd06c4
--- /dev/null
+++ b/leveldb_base/util/env_posix.cc
@@ -0,0 +1,926 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include <dirent.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+#ifndef __Fuchsia__
+#include <sys/resource.h>
+#endif
+#include <sys/stat.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <atomic>
+#include <cerrno>
+#include <cstddef>
+#include <cstdint>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <limits>
+#include <queue>
+#include <set>
+#include <string>
+#include <thread>
+#include <type_traits>
+#include <utility>
+
+#include "leveldb/env.h"
+#include "leveldb/slice.h"
+#include "leveldb/status.h"
+#include "port/port.h"
+#include "port/thread_annotations.h"
+#include "util/env_posix_test_helper.h"
+#include "util/posix_logger.h"
+
+namespace leveldb {
+
+namespace {
+
+// Set by EnvPosixTestHelper::SetReadOnlyMMapLimit() and MaxOpenFiles().
+int g_open_read_only_file_limit = -1;
+
+// Up to 1000 mmap regions for 64-bit binaries; none for 32-bit.
+constexpr const int kDefaultMmapLimit = (sizeof(void*) >= 8) ? 1000 : 0;
+
+// Can be set using EnvPosixTestHelper::SetReadOnlyMMapLimit().
+int g_mmap_limit = kDefaultMmapLimit;
+
+// Common flags defined for all posix open operations
+#if defined(HAVE_O_CLOEXEC)
+constexpr const int kOpenBaseFlags = O_CLOEXEC;
+#else
+constexpr const int kOpenBaseFlags = 0;
+#endif  // defined(HAVE_O_CLOEXEC)
+
+constexpr const size_t kWritableFileBufferSize = 65536;
+
+Status PosixError(const std::string& context, int error_number) {
+  if (error_number == ENOENT) {
+    return Status::NotFound(context, std::strerror(error_number));
+  } else {
+    return Status::IOError(context, std::strerror(error_number));
+  }
+}
+
+// Helper class to limit resource usage to avoid exhaustion.
+// Currently used to limit read-only file descriptors and mmap file usage
+// so that we do not run out of file descriptors or virtual memory, or run into
+// kernel performance problems for very large databases.
+class Limiter {
+ public:
+  // Limit maximum number of resources to |max_acquires|.
+  Limiter(int max_acquires)
+      :
+#if !defined(NDEBUG)
+        max_acquires_(max_acquires),
+#endif  // !defined(NDEBUG)
+        acquires_allowed_(max_acquires) {
+    assert(max_acquires >= 0);
+  }
+
+  Limiter(const Limiter&) = delete;
+  Limiter operator=(const Limiter&) = delete;
+
+  // If another resource is available, acquire it and return true.
+  // Else return false.
+  bool Acquire() {
+    int old_acquires_allowed =
+        acquires_allowed_.fetch_sub(1, std::memory_order_relaxed);
+
+    if (old_acquires_allowed > 0) return true;
+
+    int pre_increment_acquires_allowed =
+        acquires_allowed_.fetch_add(1, std::memory_order_relaxed);
+
+    // Silence compiler warnings about unused arguments when NDEBUG is defined.
+    (void)pre_increment_acquires_allowed;
+    // If the check below fails, Release() was called more times than acquire.
+    assert(pre_increment_acquires_allowed < max_acquires_);
+
+    return false;
+  }
+
+  // Release a resource acquired by a previous call to Acquire() that returned
+  // true.
+  void Release() {
+    int old_acquires_allowed =
+        acquires_allowed_.fetch_add(1, std::memory_order_relaxed);
+
+    // Silence compiler warnings about unused arguments when NDEBUG is defined.
+    (void)old_acquires_allowed;
+    // If the check below fails, Release() was called more times than acquire.
+    assert(old_acquires_allowed < max_acquires_);
+  }
+
+ private:
+#if !defined(NDEBUG)
+  // Catches an excessive number of Release() calls.
+  const int max_acquires_;
+#endif  // !defined(NDEBUG)
+
+  // The number of available resources.
+  //
+  // This is a counter and is not tied to the invariants of any other class, so
+  // it can be operated on safely using std::memory_order_relaxed.
+  std::atomic<int> acquires_allowed_;
+};
+
+// Implements sequential read access in a file using read().
+//
+// Instances of this class are thread-friendly but not thread-safe, as required
+// by the SequentialFile API.
+class PosixSequentialFile final : public SequentialFile {
+ public:
+  PosixSequentialFile(std::string filename, int fd)
+      : fd_(fd), filename_(std::move(filename)) {}
+  ~PosixSequentialFile() override { close(fd_); }
+
+  Status Read(size_t n, Slice* result, char* scratch) override {
+    Status status;
+    while (true) {
+      ::ssize_t read_size = ::read(fd_, scratch, n);
+      if (read_size < 0) {  // Read error.
+        if (errno == EINTR) {
+          continue;  // Retry
+        }
+        status = PosixError(filename_, errno);
+        break;
+      }
+      *result = Slice(scratch, read_size);
+      break;
+    }
+    return status;
+  }
+
+  Status Skip(uint64_t n) override {
+    if (::lseek(fd_, n, SEEK_CUR) == static_cast<off_t>(-1)) {
+      return PosixError(filename_, errno);
+    }
+    return Status::OK();
+  }
+
+ private:
+  const int fd_;
+  const std::string filename_;
+};
+
+// Implements random read access in a file using pread().
+//
+// Instances of this class are thread-safe, as required by the RandomAccessFile
+// API. Instances are immutable and Read() only calls thread-safe library
+// functions.
+class PosixRandomAccessFile final : public RandomAccessFile {
+ public:
+  // The new instance takes ownership of |fd|. |fd_limiter| must outlive this
+  // instance, and will be used to determine if .
+  PosixRandomAccessFile(std::string filename, int fd, Limiter* fd_limiter)
+      : has_permanent_fd_(fd_limiter->Acquire()),
+        fd_(has_permanent_fd_ ? fd : -1),
+        fd_limiter_(fd_limiter),
+        filename_(std::move(filename)) {
+    if (!has_permanent_fd_) {
+      assert(fd_ == -1);
+      ::close(fd);  // The file will be opened on every read.
+    }
+  }
+
+  ~PosixRandomAccessFile() override {
+    if (has_permanent_fd_) {
+      assert(fd_ != -1);
+      ::close(fd_);
+      fd_limiter_->Release();
+    }
+  }
+
+  Status Read(uint64_t offset, size_t n, Slice* result,
+              char* scratch) const override {
+    int fd = fd_;
+    if (!has_permanent_fd_) {
+      fd = ::open(filename_.c_str(), O_RDONLY | kOpenBaseFlags);
+      if (fd < 0) {
+        return PosixError(filename_, errno);
+      }
+    }
+
+    assert(fd != -1);
+
+    Status status;
+    ssize_t read_size = ::pread(fd, scratch, n, static_cast<off_t>(offset));
+    *result = Slice(scratch, (read_size < 0) ? 0 : read_size);
+    if (read_size < 0) {
+      // An error: return a non-ok status.
+      status = PosixError(filename_, errno);
+    }
+    if (!has_permanent_fd_) {
+      // Close the temporary file descriptor opened earlier.
+      assert(fd != fd_);
+      ::close(fd);
+    }
+    return status;
+  }
+
+ private:
+  const bool has_permanent_fd_;  // If false, the file is opened on every read.
+  const int fd_;                 // -1 if has_permanent_fd_ is false.
+  Limiter* const fd_limiter_;
+  const std::string filename_;
+};
+
+// Implements random read access in a file using mmap().
+//
+// Instances of this class are thread-safe, as required by the RandomAccessFile
+// API. Instances are immutable and Read() only calls thread-safe library
+// functions.
+class PosixMmapReadableFile final : public RandomAccessFile {
+ public:
+  // mmap_base[0, length-1] points to the memory-mapped contents of the file. It
+  // must be the result of a successful call to mmap(). This instances takes
+  // over the ownership of the region.
+  //
+  // |mmap_limiter| must outlive this instance. The caller must have already
+  // acquired the right to use one mmap region, which will be released when this
+  // instance is destroyed.
+  PosixMmapReadableFile(std::string filename, char* mmap_base, size_t length,
+                        Limiter* mmap_limiter)
+      : mmap_base_(mmap_base),
+        length_(length),
+        mmap_limiter_(mmap_limiter),
+        filename_(std::move(filename)) {}
+
+  ~PosixMmapReadableFile() override {
+    ::munmap(static_cast<void*>(mmap_base_), length_);
+    mmap_limiter_->Release();
+  }
+
+  Status Read(uint64_t offset, size_t n, Slice* result,
+              char* scratch) const override {
+    if (offset + n > length_) {
+      *result = Slice();
+      return PosixError(filename_, EINVAL);
+    }
+
+    *result = Slice(mmap_base_ + offset, n);
+    return Status::OK();
+  }
+
+ private:
+  char* const mmap_base_;
+  const size_t length_;
+  Limiter* const mmap_limiter_;
+  const std::string filename_;
+};
+
+class PosixWritableFile final : public WritableFile {
+ public:
+  PosixWritableFile(std::string filename, int fd)
+      : pos_(0),
+        fd_(fd),
+        is_manifest_(IsManifest(filename)),
+        filename_(std::move(filename)),
+        dirname_(Dirname(filename_)) {}
+
+  ~PosixWritableFile() override {
+    if (fd_ >= 0) {
+      // Ignoring any potential errors
+      Close();
+    }
+  }
+
+  Status Append(const Slice& data) override {
+    size_t write_size = data.size();
+    const char* write_data = data.data();
+
+    // Fit as much as possible into buffer.
+    size_t copy_size = std::min(write_size, kWritableFileBufferSize - pos_);
+    std::memcpy(buf_ + pos_, write_data, copy_size);
+    write_data += copy_size;
+    write_size -= copy_size;
+    pos_ += copy_size;
+    if (write_size == 0) {
+      return Status::OK();
+    }
+
+    // Can't fit in buffer, so need to do at least one write.
+    Status status = FlushBuffer();
+    if (!status.ok()) {
+      return status;
+    }
+
+    // Small writes go to buffer, large writes are written directly.
+    if (write_size < kWritableFileBufferSize) {
+      std::memcpy(buf_, write_data, write_size);
+      pos_ = write_size;
+      return Status::OK();
+    }
+    return WriteUnbuffered(write_data, write_size);
+  }
+
+  Status Close() override {
+    Status status = FlushBuffer();
+    const int close_result = ::close(fd_);
+    if (close_result < 0 && status.ok()) {
+      status = PosixError(filename_, errno);
+    }
+    fd_ = -1;
+    return status;
+  }
+
+  Status Flush() override { return FlushBuffer(); }
+
+  Status Sync() override {
+    // Ensure new files referred to by the manifest are in the filesystem.
+    //
+    // This needs to happen before the manifest file is flushed to disk, to
+    // avoid crashing in a state where the manifest refers to files that are not
+    // yet on disk.
+    Status status = SyncDirIfManifest();
+    if (!status.ok()) {
+      return status;
+    }
+
+    status = FlushBuffer();
+    if (!status.ok()) {
+      return status;
+    }
+
+    return SyncFd(fd_, filename_);
+  }
+
+ private:
+  Status FlushBuffer() {
+    Status status = WriteUnbuffered(buf_, pos_);
+    pos_ = 0;
+    return status;
+  }
+
+  Status WriteUnbuffered(const char* data, size_t size) {
+    while (size > 0) {
+      ssize_t write_result = ::write(fd_, data, size);
+      if (write_result < 0) {
+        if (errno == EINTR) {
+          continue;  // Retry
+        }
+        return PosixError(filename_, errno);
+      }
+      data += write_result;
+      size -= write_result;
+    }
+    return Status::OK();
+  }
+
+  Status SyncDirIfManifest() {
+    Status status;
+    if (!is_manifest_) {
+      return status;
+    }
+
+    int fd = ::open(dirname_.c_str(), O_RDONLY | kOpenBaseFlags);
+    if (fd < 0) {
+      status = PosixError(dirname_, errno);
+    } else {
+      status = SyncFd(fd, dirname_);
+      ::close(fd);
+    }
+    return status;
+  }
+
+  // Ensures that all the caches associated with the given file descriptor's
+  // data are flushed all the way to durable media, and can withstand power
+  // failures.
+  //
+  // The path argument is only used to populate the description string in the
+  // returned Status if an error occurs.
+  static Status SyncFd(int fd, const std::string& fd_path) {
+#if HAVE_FULLFSYNC
+    // On macOS and iOS, fsync() doesn't guarantee durability past power
+    // failures. fcntl(F_FULLFSYNC) is required for that purpose. Some
+    // filesystems don't support fcntl(F_FULLFSYNC), and require a fallback to
+    // fsync().
+    if (::fcntl(fd, F_FULLFSYNC) == 0) {
+      return Status::OK();
+    }
+#endif  // HAVE_FULLFSYNC
+
+#if HAVE_FDATASYNC
+    bool sync_success = ::fdatasync(fd) == 0;
+#else
+    bool sync_success = ::fsync(fd) == 0;
+#endif  // HAVE_FDATASYNC
+
+    if (sync_success) {
+      return Status::OK();
+    }
+    return PosixError(fd_path, errno);
+  }
+
+  // Returns the directory name in a path pointing to a file.
+  //
+  // Returns "." if the path does not contain any directory separator.
+  static std::string Dirname(const std::string& filename) {
+    std::string::size_type separator_pos = filename.rfind('/');
+    if (separator_pos == std::string::npos) {
+      return std::string(".");
+    }
+    // The filename component should not contain a path separator. If it does,
+    // the splitting was done incorrectly.
+    assert(filename.find('/', separator_pos + 1) == std::string::npos);
+
+    return filename.substr(0, separator_pos);
+  }
+
+  // Extracts the file name from a path pointing to a file.
+  //
+  // The returned Slice points to |filename|'s data buffer, so it is only valid
+  // while |filename| is alive and unchanged.
+  static Slice Basename(const std::string& filename) {
+    std::string::size_type separator_pos = filename.rfind('/');
+    if (separator_pos == std::string::npos) {
+      return Slice(filename);
+    }
+    // The filename component should not contain a path separator. If it does,
+    // the splitting was done incorrectly.
+    assert(filename.find('/', separator_pos + 1) == std::string::npos);
+
+    return Slice(filename.data() + separator_pos + 1,
+                 filename.length() - separator_pos - 1);
+  }
+
+  // True if the given file is a manifest file.
+  static bool IsManifest(const std::string& filename) {
+    return Basename(filename).starts_with("MANIFEST");
+  }
+
+  // buf_[0, pos_ - 1] contains data to be written to fd_.
+  char buf_[kWritableFileBufferSize];
+  size_t pos_;
+  int fd_;
+
+  const bool is_manifest_;  // True if the file's name starts with MANIFEST.
+  const std::string filename_;
+  const std::string dirname_;  // The directory of filename_.
+};
+
+int LockOrUnlock(int fd, bool lock) {
+  errno = 0;
+  struct ::flock file_lock_info;
+  std::memset(&file_lock_info, 0, sizeof(file_lock_info));
+  file_lock_info.l_type = (lock ? F_WRLCK : F_UNLCK);
+  file_lock_info.l_whence = SEEK_SET;
+  file_lock_info.l_start = 0;
+  file_lock_info.l_len = 0;  // Lock/unlock entire file.
+  return ::fcntl(fd, F_SETLK, &file_lock_info);
+}
+
+// Instances are thread-safe because they are immutable.
+class PosixFileLock : public FileLock {
+ public:
+  PosixFileLock(int fd, std::string filename)
+      : fd_(fd), filename_(std::move(filename)) {}
+
+  int fd() const { return fd_; }
+  const std::string& filename() const { return filename_; }
+
+ private:
+  const int fd_;
+  const std::string filename_;
+};
+
+// Tracks the files locked by PosixEnv::LockFile().
+//
+// We maintain a separate set instead of relying on fcntl(F_SETLK) because
+// fcntl(F_SETLK) does not provide any protection against multiple uses from the
+// same process.
+//
+// Instances are thread-safe because all member data is guarded by a mutex.
+class PosixLockTable {
+ public:
+  bool Insert(const std::string& fname) LOCKS_EXCLUDED(mu_) {
+    mu_.Lock();
+    bool succeeded = locked_files_.insert(fname).second;
+    mu_.Unlock();
+    return succeeded;
+  }
+  void Remove(const std::string& fname) LOCKS_EXCLUDED(mu_) {
+    mu_.Lock();
+    locked_files_.erase(fname);
+    mu_.Unlock();
+  }
+
+ private:
+  port::Mutex mu_;
+  std::set<std::string> locked_files_ GUARDED_BY(mu_);
+};
+
+class PosixEnv : public Env {
+ public:
+  PosixEnv();
+  ~PosixEnv() override {
+    static const char msg[] =
+        "PosixEnv singleton destroyed. Unsupported behavior!\n";
+    std::fwrite(msg, 1, sizeof(msg), stderr);
+    std::abort();
+  }
+
+  Status NewSequentialFile(const std::string& filename,
+                           SequentialFile** result) override {
+    int fd = ::open(filename.c_str(), O_RDONLY | kOpenBaseFlags);
+    if (fd < 0) {
+      *result = nullptr;
+      return PosixError(filename, errno);
+    }
+
+    *result = new PosixSequentialFile(filename, fd);
+    return Status::OK();
+  }
+
+  Status NewRandomAccessFile(const std::string& filename,
+                             RandomAccessFile** result) override {
+    *result = nullptr;
+    int fd = ::open(filename.c_str(), O_RDONLY | kOpenBaseFlags);
+    if (fd < 0) {
+      return PosixError(filename, errno);
+    }
+
+    if (!mmap_limiter_.Acquire()) {
+      *result = new PosixRandomAccessFile(filename, fd, &fd_limiter_);
+      return Status::OK();
+    }
+
+    uint64_t file_size;
+    Status status = GetFileSize(filename, &file_size);
+    if (status.ok()) {
+      void* mmap_base =
+          ::mmap(/*addr=*/nullptr, file_size, PROT_READ, MAP_SHARED, fd, 0);
+      if (mmap_base != MAP_FAILED) {
+        *result = new PosixMmapReadableFile(filename,
+                                            reinterpret_cast<char*>(mmap_base),
+                                            file_size, &mmap_limiter_);
+      } else {
+        status = PosixError(filename, errno);
+      }
+    }
+    ::close(fd);
+    if (!status.ok()) {
+      mmap_limiter_.Release();
+    }
+    return status;
+  }
+
+  Status NewWritableFile(const std::string& filename,
+                         WritableFile** result) override {
+    int fd = ::open(filename.c_str(),
+                    O_TRUNC | O_WRONLY | O_CREAT | kOpenBaseFlags, 0644);
+    if (fd < 0) {
+      *result = nullptr;
+      return PosixError(filename, errno);
+    }
+
+    *result = new PosixWritableFile(filename, fd);
+    return Status::OK();
+  }
+
+  Status NewAppendableFile(const std::string& filename,
+                           WritableFile** result) override {
+    int fd = ::open(filename.c_str(),
+                    O_APPEND | O_WRONLY | O_CREAT | kOpenBaseFlags, 0644);
+    if (fd < 0) {
+      *result = nullptr;
+      return PosixError(filename, errno);
+    }
+
+    *result = new PosixWritableFile(filename, fd);
+    return Status::OK();
+  }
+
+  bool FileExists(const std::string& filename) override {
+    return ::access(filename.c_str(), F_OK) == 0;
+  }
+
+  Status GetChildren(const std::string& directory_path,
+                     std::vector<std::string>* result) override {
+    result->clear();
+    ::DIR* dir = ::opendir(directory_path.c_str());
+    if (dir == nullptr) {
+      return PosixError(directory_path, errno);
+    }
+    struct ::dirent* entry;
+    while ((entry = ::readdir(dir)) != nullptr) {
+      result->emplace_back(entry->d_name);
+    }
+    ::closedir(dir);
+    return Status::OK();
+  }
+
+  Status RemoveFile(const std::string& filename) override {
+    if (::unlink(filename.c_str()) != 0) {
+      return PosixError(filename, errno);
+    }
+    return Status::OK();
+  }
+
+  Status CreateDir(const std::string& dirname) override {
+    if (::mkdir(dirname.c_str(), 0755) != 0) {
+      return PosixError(dirname, errno);
+    }
+    return Status::OK();
+  }
+
+  Status RemoveDir(const std::string& dirname) override {
+    if (::rmdir(dirname.c_str()) != 0) {
+      return PosixError(dirname, errno);
+    }
+    return Status::OK();
+  }
+
+  Status GetFileSize(const std::string& filename, uint64_t* size) override {
+    struct ::stat file_stat;
+    if (::stat(filename.c_str(), &file_stat) != 0) {
+      *size = 0;
+      return PosixError(filename, errno);
+    }
+    *size = file_stat.st_size;
+    return Status::OK();
+  }
+
+  Status RenameFile(const std::string& from, const std::string& to) override {
+    if (std::rename(from.c_str(), to.c_str()) != 0) {
+      return PosixError(from, errno);
+    }
+    return Status::OK();
+  }
+
+  Status LockFile(const std::string& filename, FileLock** lock) override {
+    *lock = nullptr;
+
+    int fd = ::open(filename.c_str(), O_RDWR | O_CREAT | kOpenBaseFlags, 0644);
+    if (fd < 0) {
+      return PosixError(filename, errno);
+    }
+
+    if (!locks_.Insert(filename)) {
+      ::close(fd);
+      return Status::IOError("lock " + filename, "already held by process");
+    }
+
+    if (LockOrUnlock(fd, true) == -1) {
+      int lock_errno = errno;
+      ::close(fd);
+      locks_.Remove(filename);
+      return PosixError("lock " + filename, lock_errno);
+    }
+
+    *lock = new PosixFileLock(fd, filename);
+    return Status::OK();
+  }
+
+  Status UnlockFile(FileLock* lock) override {
+    PosixFileLock* posix_file_lock = static_cast<PosixFileLock*>(lock);
+    if (LockOrUnlock(posix_file_lock->fd(), false) == -1) {
+      return PosixError("unlock " + posix_file_lock->filename(), errno);
+    }
+    locks_.Remove(posix_file_lock->filename());
+    ::close(posix_file_lock->fd());
+    delete posix_file_lock;
+    return Status::OK();
+  }
+
+  void Schedule(void (*background_work_function)(void* background_work_arg),
+                void* background_work_arg) override;
+
+  void StartThread(void (*thread_main)(void* thread_main_arg),
+                   void* thread_main_arg) override {
+    std::thread new_thread(thread_main, thread_main_arg);
+    new_thread.detach();
+  }
+
+  Status GetTestDirectory(std::string* result) override {
+    const char* env = std::getenv("TEST_TMPDIR");
+    if (env && env[0] != '\0') {
+      *result = env;
+    } else {
+      char buf[100];
+      std::snprintf(buf, sizeof(buf), "/tmp/leveldbtest-%d",
+                    static_cast<int>(::geteuid()));
+      *result = buf;
+    }
+
+    // The CreateDir status is ignored because the directory may already exist.
+    CreateDir(*result);
+
+    return Status::OK();
+  }
+
+  Status NewLogger(const std::string& filename, Logger** result) override {
+    int fd = ::open(filename.c_str(),
+                    O_APPEND | O_WRONLY | O_CREAT | kOpenBaseFlags, 0644);
+    if (fd < 0) {
+      *result = nullptr;
+      return PosixError(filename, errno);
+    }
+
+    std::FILE* fp = ::fdopen(fd, "w");
+    if (fp == nullptr) {
+      ::close(fd);
+      *result = nullptr;
+      return PosixError(filename, errno);
+    } else {
+      *result = new PosixLogger(fp);
+      return Status::OK();
+    }
+  }
+
+  uint64_t NowMicros() override {
+    static constexpr uint64_t kUsecondsPerSecond = 1000000;
+    struct ::timeval tv;
+    ::gettimeofday(&tv, nullptr);
+    return static_cast<uint64_t>(tv.tv_sec) * kUsecondsPerSecond + tv.tv_usec;
+  }
+
+  void SleepForMicroseconds(int micros) override {
+    std::this_thread::sleep_for(std::chrono::microseconds(micros));
+  }
+
+ private:
+  void BackgroundThreadMain();
+
+  static void BackgroundThreadEntryPoint(PosixEnv* env) {
+    env->BackgroundThreadMain();
+  }
+
+  // Stores the work item data in a Schedule() call.
+  //
+  // Instances are constructed on the thread calling Schedule() and used on the
+  // background thread.
+  //
+  // This structure is thread-safe because it is immutable.
+  struct BackgroundWorkItem {
+    explicit BackgroundWorkItem(void (*function)(void* arg), void* arg)
+        : function(function), arg(arg) {}
+
+    void (*const function)(void*);
+    void* const arg;
+  };
+
+  port::Mutex background_work_mutex_;
+  port::CondVar background_work_cv_ GUARDED_BY(background_work_mutex_);
+  bool started_background_thread_ GUARDED_BY(background_work_mutex_);
+
+  std::queue<BackgroundWorkItem> background_work_queue_
+      GUARDED_BY(background_work_mutex_);
+
+  PosixLockTable locks_;  // Thread-safe.
+  Limiter mmap_limiter_;  // Thread-safe.
+  Limiter fd_limiter_;    // Thread-safe.
+};
+
+// Return the maximum number of concurrent mmaps.
+int MaxMmaps() { return g_mmap_limit; }
+
+// Return the maximum number of read-only files to keep open.
+int MaxOpenFiles() {
+  if (g_open_read_only_file_limit >= 0) {
+    return g_open_read_only_file_limit;
+  }
+#ifdef __Fuchsia__
+  // Fuchsia doesn't implement getrlimit.
+  g_open_read_only_file_limit = 50;
+#else
+  struct ::rlimit rlim;
+  if (::getrlimit(RLIMIT_NOFILE, &rlim)) {
+    // getrlimit failed, fallback to hard-coded default.
+    g_open_read_only_file_limit = 50;
+  } else if (rlim.rlim_cur == RLIM_INFINITY) {
+    g_open_read_only_file_limit = std::numeric_limits<int>::max();
+  } else {
+    // Allow use of 20% of available file descriptors for read-only files.
+    g_open_read_only_file_limit = rlim.rlim_cur / 5;
+  }
+#endif
+  return g_open_read_only_file_limit;
+}
+
+}  // namespace
+
+PosixEnv::PosixEnv()
+    : background_work_cv_(&background_work_mutex_),
+      started_background_thread_(false),
+      mmap_limiter_(MaxMmaps()),
+      fd_limiter_(MaxOpenFiles()) {}
+
+void PosixEnv::Schedule(
+    void (*background_work_function)(void* background_work_arg),
+    void* background_work_arg) {
+  background_work_mutex_.Lock();
+
+  // Start the background thread, if we haven't done so already.
+  if (!started_background_thread_) {
+    started_background_thread_ = true;
+    std::thread background_thread(PosixEnv::BackgroundThreadEntryPoint, this);
+    background_thread.detach();
+  }
+
+  // If the queue is empty, the background thread may be waiting for work.
+  if (background_work_queue_.empty()) {
+    background_work_cv_.Signal();
+  }
+
+  background_work_queue_.emplace(background_work_function, background_work_arg);
+  background_work_mutex_.Unlock();
+}
+
+void PosixEnv::BackgroundThreadMain() {
+  while (true) {
+    background_work_mutex_.Lock();
+
+    // Wait until there is work to be done.
+    while (background_work_queue_.empty()) {
+      background_work_cv_.Wait();
+    }
+
+    assert(!background_work_queue_.empty());
+    auto background_work_function = background_work_queue_.front().function;
+    void* background_work_arg = background_work_queue_.front().arg;
+    background_work_queue_.pop();
+
+    background_work_mutex_.Unlock();
+    background_work_function(background_work_arg);
+  }
+}
+
+namespace {
+
+// Wraps an Env instance whose destructor is never created.
+//
+// Intended usage:
+//   using PlatformSingletonEnv = SingletonEnv<PlatformEnv>;
+//   void ConfigurePosixEnv(int param) {
+//     PlatformSingletonEnv::AssertEnvNotInitialized();
+//     // set global configuration flags.
+//   }
+//   Env* Env::Default() {
+//     static PlatformSingletonEnv default_env;
+//     return default_env.env();
+//   }
+template <typename EnvType>
+class SingletonEnv {
+ public:
+  SingletonEnv() {
+#if !defined(NDEBUG)
+    env_initialized_.store(true, std::memory_order_relaxed);
+#endif  // !defined(NDEBUG)
+    static_assert(sizeof(env_storage_) >= sizeof(EnvType),
+                  "env_storage_ will not fit the Env");
+    static_assert(alignof(decltype(env_storage_)) >= alignof(EnvType),
+                  "env_storage_ does not meet the Env's alignment needs");
+    new (&env_storage_) EnvType();
+  }
+  ~SingletonEnv() = default;
+
+  SingletonEnv(const SingletonEnv&) = delete;
+  SingletonEnv& operator=(const SingletonEnv&) = delete;
+
+  Env* env() { return reinterpret_cast<Env*>(&env_storage_); }
+
+  static void AssertEnvNotInitialized() {
+#if !defined(NDEBUG)
+    assert(!env_initialized_.load(std::memory_order_relaxed));
+#endif  // !defined(NDEBUG)
+  }
+
+ private:
+  typename std::aligned_storage<sizeof(EnvType), alignof(EnvType)>::type
+      env_storage_;
+#if !defined(NDEBUG)
+  static std::atomic<bool> env_initialized_;
+#endif  // !defined(NDEBUG)
+};
+
+#if !defined(NDEBUG)
+template <typename EnvType>
+std::atomic<bool> SingletonEnv<EnvType>::env_initialized_;
+#endif  // !defined(NDEBUG)
+
+using PosixDefaultEnv = SingletonEnv<PosixEnv>;
+
+}  // namespace
+
+void EnvPosixTestHelper::SetReadOnlyFDLimit(int limit) {
+  PosixDefaultEnv::AssertEnvNotInitialized();
+  g_open_read_only_file_limit = limit;
+}
+
+void EnvPosixTestHelper::SetReadOnlyMMapLimit(int limit) {
+  PosixDefaultEnv::AssertEnvNotInitialized();
+  g_mmap_limit = limit;
+}
+
+Env* Env::Default() {
+  static PosixDefaultEnv env_container;
+  return env_container.env();
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/util/env_posix_test.cc b/leveldb_base/util/env_posix_test.cc
new file mode 100644
index 0000000..34bda62
--- /dev/null
+++ b/leveldb_base/util/env_posix_test.cc
@@ -0,0 +1,353 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include <sys/resource.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <string>
+#include <unordered_set>
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "leveldb/env.h"
+#include "port/port.h"
+#include "util/env_posix_test_helper.h"
+#include "util/testutil.h"
+
+#if HAVE_O_CLOEXEC
+
+namespace {
+
+// Exit codes for the helper process spawned by TestCloseOnExec* tests.
+// Useful for debugging test failures.
+constexpr int kTextCloseOnExecHelperExecFailedCode = 61;
+constexpr int kTextCloseOnExecHelperDup2FailedCode = 62;
+constexpr int kTextCloseOnExecHelperFoundOpenFdCode = 63;
+
+// Global set by main() and read in TestCloseOnExec.
+//
+// The argv[0] value is stored in a std::vector instead of a std::string because
+// std::string does not return a mutable pointer to its buffer until C++17.
+//
+// The vector stores the string pointed to by argv[0], plus the trailing null.
+std::vector<char>* GetArgvZero() {
+  static std::vector<char> program_name;
+  return &program_name;
+}
+
+// Command-line switch used to run this test as the CloseOnExecSwitch helper.
+static const char kTestCloseOnExecSwitch[] = "--test-close-on-exec-helper";
+
+// Executed in a separate process by TestCloseOnExec* tests.
+//
+// main() delegates to this function when the test executable is launched with
+// a special command-line switch. TestCloseOnExec* tests fork()+exec() the test
+// executable and pass the special command-line switch.
+//
+
+// main() delegates to this function when the test executable is launched with
+// a special command-line switch. TestCloseOnExec* tests fork()+exec() the test
+// executable and pass the special command-line switch.
+//
+// When main() delegates to this function, the process probes whether a given
+// file descriptor is open, and communicates the result via its exit code.
+int TestCloseOnExecHelperMain(char* pid_arg) {
+  int fd = std::atoi(pid_arg);
+  // When given the same file descriptor twice, dup2() returns -1 if the
+  // file descriptor is closed, or the given file descriptor if it is open.
+  if (::dup2(fd, fd) == fd) {
+    std::fprintf(stderr, "Unexpected open fd %d\n", fd);
+    return kTextCloseOnExecHelperFoundOpenFdCode;
+  }
+  // Double-check that dup2() is saying the file descriptor is closed.
+  if (errno != EBADF) {
+    std::fprintf(stderr, "Unexpected errno after calling dup2 on fd %d: %s\n",
+                 fd, std::strerror(errno));
+    return kTextCloseOnExecHelperDup2FailedCode;
+  }
+  return 0;
+}
+
+// File descriptors are small non-negative integers.
+//
+// Returns void so the implementation can use ASSERT_EQ.
+void GetMaxFileDescriptor(int* result_fd) {
+  // Get the maximum file descriptor number.
+  ::rlimit fd_rlimit;
+  ASSERT_EQ(0, ::getrlimit(RLIMIT_NOFILE, &fd_rlimit));
+  *result_fd = fd_rlimit.rlim_cur;
+}
+
+// Iterates through all possible FDs and returns the currently open ones.
+//
+// Returns void so the implementation can use ASSERT_EQ.
+void GetOpenFileDescriptors(std::unordered_set<int>* open_fds) {
+  int max_fd = 0;
+  GetMaxFileDescriptor(&max_fd);
+
+  for (int fd = 0; fd < max_fd; ++fd) {
+    if (::dup2(fd, fd) != fd) {
+      // When given the same file descriptor twice, dup2() returns -1 if the
+      // file descriptor is closed, or the given file descriptor if it is open.
+      //
+      // Double-check that dup2() is saying the fd is closed.
+      ASSERT_EQ(EBADF, errno)
+          << "dup2() should set errno to EBADF on closed file descriptors";
+      continue;
+    }
+    open_fds->insert(fd);
+  }
+}
+
+// Finds an FD open since a previous call to GetOpenFileDescriptors().
+//
+// |baseline_open_fds| is the result of a previous GetOpenFileDescriptors()
+// call. Assumes that exactly one FD was opened since that call.
+//
+// Returns void so the implementation can use ASSERT_EQ.
+void GetNewlyOpenedFileDescriptor(
+    const std::unordered_set<int>& baseline_open_fds, int* result_fd) {
+  std::unordered_set<int> open_fds;
+  GetOpenFileDescriptors(&open_fds);
+  for (int fd : baseline_open_fds) {
+    ASSERT_EQ(1, open_fds.count(fd))
+        << "Previously opened file descriptor was closed during test setup";
+    open_fds.erase(fd);
+  }
+  ASSERT_EQ(1, open_fds.size())
+      << "Expected exactly one newly opened file descriptor during test setup";
+  *result_fd = *open_fds.begin();
+}
+
+// Check that a fork()+exec()-ed child process does not have an extra open FD.
+void CheckCloseOnExecDoesNotLeakFDs(
+    const std::unordered_set<int>& baseline_open_fds) {
+  // Prepare the argument list for the child process.
+  // execv() wants mutable buffers.
+  char switch_buffer[sizeof(kTestCloseOnExecSwitch)];
+  std::memcpy(switch_buffer, kTestCloseOnExecSwitch,
+              sizeof(kTestCloseOnExecSwitch));
+
+  int probed_fd;
+  GetNewlyOpenedFileDescriptor(baseline_open_fds, &probed_fd);
+  std::string fd_string = std::to_string(probed_fd);
+  std::vector<char> fd_buffer(fd_string.begin(), fd_string.end());
+  fd_buffer.emplace_back('\0');
+
+  // The helper process is launched with the command below.
+  //      env_posix_tests --test-close-on-exec-helper 3
+  char* child_argv[] = {GetArgvZero()->data(), switch_buffer, fd_buffer.data(),
+                        nullptr};
+
+  constexpr int kForkInChildProcessReturnValue = 0;
+  int child_pid = fork();
+  if (child_pid == kForkInChildProcessReturnValue) {
+    ::execv(child_argv[0], child_argv);
+    std::fprintf(stderr, "Error spawning child process: %s\n", strerror(errno));
+    std::exit(kTextCloseOnExecHelperExecFailedCode);
+  }
+
+  int child_status = 0;
+  ASSERT_EQ(child_pid, ::waitpid(child_pid, &child_status, 0));
+  ASSERT_TRUE(WIFEXITED(child_status))
+      << "The helper process did not exit with an exit code";
+  ASSERT_EQ(0, WEXITSTATUS(child_status))
+      << "The helper process encountered an error";
+}
+
+}  // namespace
+
+#endif  // HAVE_O_CLOEXEC
+
+namespace leveldb {
+
+static const int kReadOnlyFileLimit = 4;
+static const int kMMapLimit = 4;
+
+class EnvPosixTest : public testing::Test {
+ public:
+  static void SetFileLimits(int read_only_file_limit, int mmap_limit) {
+    EnvPosixTestHelper::SetReadOnlyFDLimit(read_only_file_limit);
+    EnvPosixTestHelper::SetReadOnlyMMapLimit(mmap_limit);
+  }
+
+  EnvPosixTest() : env_(Env::Default()) {}
+
+  Env* env_;
+};
+
+TEST_F(EnvPosixTest, TestOpenOnRead) {
+  // Write some test data to a single file that will be opened |n| times.
+  std::string test_dir;
+  ASSERT_LEVELDB_OK(env_->GetTestDirectory(&test_dir));
+  std::string test_file = test_dir + "/open_on_read.txt";
+
+  FILE* f = std::fopen(test_file.c_str(), "we");
+  ASSERT_TRUE(f != nullptr);
+  const char kFileData[] = "abcdefghijklmnopqrstuvwxyz";
+  fputs(kFileData, f);
+  std::fclose(f);
+
+  // Open test file some number above the sum of the two limits to force
+  // open-on-read behavior of POSIX Env leveldb::RandomAccessFile.
+  const int kNumFiles = kReadOnlyFileLimit + kMMapLimit + 5;
+  leveldb::RandomAccessFile* files[kNumFiles] = {0};
+  for (int i = 0; i < kNumFiles; i++) {
+    ASSERT_LEVELDB_OK(env_->NewRandomAccessFile(test_file, &files[i]));
+  }
+  char scratch;
+  Slice read_result;
+  for (int i = 0; i < kNumFiles; i++) {
+    ASSERT_LEVELDB_OK(files[i]->Read(i, 1, &read_result, &scratch));
+    ASSERT_EQ(kFileData[i], read_result[0]);
+  }
+  for (int i = 0; i < kNumFiles; i++) {
+    delete files[i];
+  }
+  ASSERT_LEVELDB_OK(env_->RemoveFile(test_file));
+}
+
+#if HAVE_O_CLOEXEC
+
+TEST_F(EnvPosixTest, TestCloseOnExecSequentialFile) {
+  std::unordered_set<int> open_fds;
+  GetOpenFileDescriptors(&open_fds);
+
+  std::string test_dir;
+  ASSERT_LEVELDB_OK(env_->GetTestDirectory(&test_dir));
+  std::string file_path = test_dir + "/close_on_exec_sequential.txt";
+  ASSERT_LEVELDB_OK(WriteStringToFile(env_, "0123456789", file_path));
+
+  leveldb::SequentialFile* file = nullptr;
+  ASSERT_LEVELDB_OK(env_->NewSequentialFile(file_path, &file));
+  CheckCloseOnExecDoesNotLeakFDs(open_fds);
+  delete file;
+
+  ASSERT_LEVELDB_OK(env_->RemoveFile(file_path));
+}
+
+TEST_F(EnvPosixTest, TestCloseOnExecRandomAccessFile) {
+  std::unordered_set<int> open_fds;
+  GetOpenFileDescriptors(&open_fds);
+
+  std::string test_dir;
+  ASSERT_LEVELDB_OK(env_->GetTestDirectory(&test_dir));
+  std::string file_path = test_dir + "/close_on_exec_random_access.txt";
+  ASSERT_LEVELDB_OK(WriteStringToFile(env_, "0123456789", file_path));
+
+  // Exhaust the RandomAccessFile mmap limit. This way, the test
+  // RandomAccessFile instance below is backed by a file descriptor, not by an
+  // mmap region.
+  leveldb::RandomAccessFile* mmapped_files[kMMapLimit];
+  for (int i = 0; i < kMMapLimit; i++) {
+    ASSERT_LEVELDB_OK(env_->NewRandomAccessFile(file_path, &mmapped_files[i]));
+  }
+
+  leveldb::RandomAccessFile* file = nullptr;
+  ASSERT_LEVELDB_OK(env_->NewRandomAccessFile(file_path, &file));
+  CheckCloseOnExecDoesNotLeakFDs(open_fds);
+  delete file;
+
+  for (int i = 0; i < kMMapLimit; i++) {
+    delete mmapped_files[i];
+  }
+  ASSERT_LEVELDB_OK(env_->RemoveFile(file_path));
+}
+
+TEST_F(EnvPosixTest, TestCloseOnExecWritableFile) {
+  std::unordered_set<int> open_fds;
+  GetOpenFileDescriptors(&open_fds);
+
+  std::string test_dir;
+  ASSERT_LEVELDB_OK(env_->GetTestDirectory(&test_dir));
+  std::string file_path = test_dir + "/close_on_exec_writable.txt";
+  ASSERT_LEVELDB_OK(WriteStringToFile(env_, "0123456789", file_path));
+
+  leveldb::WritableFile* file = nullptr;
+  ASSERT_LEVELDB_OK(env_->NewWritableFile(file_path, &file));
+  CheckCloseOnExecDoesNotLeakFDs(open_fds);
+  delete file;
+
+  ASSERT_LEVELDB_OK(env_->RemoveFile(file_path));
+}
+
+TEST_F(EnvPosixTest, TestCloseOnExecAppendableFile) {
+  std::unordered_set<int> open_fds;
+  GetOpenFileDescriptors(&open_fds);
+
+  std::string test_dir;
+  ASSERT_LEVELDB_OK(env_->GetTestDirectory(&test_dir));
+  std::string file_path = test_dir + "/close_on_exec_appendable.txt";
+  ASSERT_LEVELDB_OK(WriteStringToFile(env_, "0123456789", file_path));
+
+  leveldb::WritableFile* file = nullptr;
+  ASSERT_LEVELDB_OK(env_->NewAppendableFile(file_path, &file));
+  CheckCloseOnExecDoesNotLeakFDs(open_fds);
+  delete file;
+
+  ASSERT_LEVELDB_OK(env_->RemoveFile(file_path));
+}
+
+TEST_F(EnvPosixTest, TestCloseOnExecLockFile) {
+  std::unordered_set<int> open_fds;
+  GetOpenFileDescriptors(&open_fds);
+
+  std::string test_dir;
+  ASSERT_LEVELDB_OK(env_->GetTestDirectory(&test_dir));
+  std::string file_path = test_dir + "/close_on_exec_lock.txt";
+  ASSERT_LEVELDB_OK(WriteStringToFile(env_, "0123456789", file_path));
+
+  leveldb::FileLock* lock = nullptr;
+  ASSERT_LEVELDB_OK(env_->LockFile(file_path, &lock));
+  CheckCloseOnExecDoesNotLeakFDs(open_fds);
+  ASSERT_LEVELDB_OK(env_->UnlockFile(lock));
+
+  ASSERT_LEVELDB_OK(env_->RemoveFile(file_path));
+}
+
+TEST_F(EnvPosixTest, TestCloseOnExecLogger) {
+  std::unordered_set<int> open_fds;
+  GetOpenFileDescriptors(&open_fds);
+
+  std::string test_dir;
+  ASSERT_LEVELDB_OK(env_->GetTestDirectory(&test_dir));
+  std::string file_path = test_dir + "/close_on_exec_logger.txt";
+  ASSERT_LEVELDB_OK(WriteStringToFile(env_, "0123456789", file_path));
+
+  leveldb::Logger* file = nullptr;
+  ASSERT_LEVELDB_OK(env_->NewLogger(file_path, &file));
+  CheckCloseOnExecDoesNotLeakFDs(open_fds);
+  delete file;
+
+  ASSERT_LEVELDB_OK(env_->RemoveFile(file_path));
+}
+
+#endif  // HAVE_O_CLOEXEC
+
+}  // namespace leveldb
+
+int main(int argc, char** argv) {
+#if HAVE_O_CLOEXEC
+  // Check if we're invoked as a helper program, or as the test suite.
+  for (int i = 1; i < argc; ++i) {
+    if (!std::strcmp(argv[i], kTestCloseOnExecSwitch)) {
+      return TestCloseOnExecHelperMain(argv[i + 1]);
+    }
+  }
+
+  // Save argv[0] early, because googletest may modify argv.
+  GetArgvZero()->assign(argv[0], argv[0] + std::strlen(argv[0]) + 1);
+#endif  // HAVE_O_CLOEXEC
+
+  // All tests currently run with the same read-only file limits.
+  leveldb::EnvPosixTest::SetFileLimits(leveldb::kReadOnlyFileLimit,
+                                       leveldb::kMMapLimit);
+
+  testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
diff --git a/leveldb_base/util/env_posix_test_helper.h b/leveldb_base/util/env_posix_test_helper.h
new file mode 100644
index 0000000..0386960
--- /dev/null
+++ b/leveldb_base/util/env_posix_test_helper.h
@@ -0,0 +1,28 @@
+// Copyright 2017 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_UTIL_ENV_POSIX_TEST_HELPER_H_
+#define STORAGE_LEVELDB_UTIL_ENV_POSIX_TEST_HELPER_H_
+
+namespace leveldb {
+
+class EnvPosixTest;
+
+// A helper for the POSIX Env to facilitate testing.
+class EnvPosixTestHelper {
+ private:
+  friend class EnvPosixTest;
+
+  // Set the maximum number of read-only files that will be opened.
+  // Must be called before creating an Env.
+  static void SetReadOnlyFDLimit(int limit);
+
+  // Set the maximum number of read-only files that will be mapped via mmap.
+  // Must be called before creating an Env.
+  static void SetReadOnlyMMapLimit(int limit);
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_UTIL_ENV_POSIX_TEST_HELPER_H_
diff --git a/leveldb_base/util/env_test.cc b/leveldb_base/util/env_test.cc
new file mode 100644
index 0000000..e5c30fe
--- /dev/null
+++ b/leveldb_base/util/env_test.cc
@@ -0,0 +1,248 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "leveldb/env.h"
+
+#include <algorithm>
+
+#include "gtest/gtest.h"
+#include "port/port.h"
+#include "port/thread_annotations.h"
+#include "util/mutexlock.h"
+#include "util/testutil.h"
+
+namespace leveldb {
+
+class EnvTest : public testing::Test {
+ public:
+  EnvTest() : env_(Env::Default()) {}
+
+  Env* env_;
+};
+
+TEST_F(EnvTest, ReadWrite) {
+  Random rnd(test::RandomSeed());
+
+  // Get file to use for testing.
+  std::string test_dir;
+  ASSERT_LEVELDB_OK(env_->GetTestDirectory(&test_dir));
+  std::string test_file_name = test_dir + "/open_on_read.txt";
+  WritableFile* writable_file;
+  ASSERT_LEVELDB_OK(env_->NewWritableFile(test_file_name, &writable_file));
+
+  // Fill a file with data generated via a sequence of randomly sized writes.
+  static const size_t kDataSize = 10 * 1048576;
+  std::string data;
+  while (data.size() < kDataSize) {
+    int len = rnd.Skewed(18);  // Up to 2^18 - 1, but typically much smaller
+    std::string r;
+    test::RandomString(&rnd, len, &r);
+    ASSERT_LEVELDB_OK(writable_file->Append(r));
+    data += r;
+    if (rnd.OneIn(10)) {
+      ASSERT_LEVELDB_OK(writable_file->Flush());
+    }
+  }
+  ASSERT_LEVELDB_OK(writable_file->Sync());
+  ASSERT_LEVELDB_OK(writable_file->Close());
+  delete writable_file;
+
+  // Read all data using a sequence of randomly sized reads.
+  SequentialFile* sequential_file;
+  ASSERT_LEVELDB_OK(env_->NewSequentialFile(test_file_name, &sequential_file));
+  std::string read_result;
+  std::string scratch;
+  while (read_result.size() < data.size()) {
+    int len = std::min<int>(rnd.Skewed(18), data.size() - read_result.size());
+    scratch.resize(std::max(len, 1));  // at least 1 so &scratch[0] is legal
+    Slice read;
+    ASSERT_LEVELDB_OK(sequential_file->Read(len, &read, &scratch[0]));
+    if (len > 0) {
+      ASSERT_GT(read.size(), 0);
+    }
+    ASSERT_LE(read.size(), len);
+    read_result.append(read.data(), read.size());
+  }
+  ASSERT_EQ(read_result, data);
+  delete sequential_file;
+}
+
+TEST_F(EnvTest, RunImmediately) {
+  struct RunState {
+    port::Mutex mu;
+    port::CondVar cvar{&mu};
+    bool called = false;
+
+    static void Run(void* arg) {
+      RunState* state = reinterpret_cast<RunState*>(arg);
+      MutexLock l(&state->mu);
+      ASSERT_EQ(state->called, false);
+      state->called = true;
+      state->cvar.Signal();
+    }
+  };
+
+  RunState state;
+  env_->Schedule(&RunState::Run, &state);
+
+  MutexLock l(&state.mu);
+  while (!state.called) {
+    state.cvar.Wait();
+  }
+}
+
+TEST_F(EnvTest, RunMany) {
+  struct RunState {
+    port::Mutex mu;
+    port::CondVar cvar{&mu};
+    int run_count = 0;
+  };
+
+  struct Callback {
+    RunState* const state_;  // Pointer to shared state.
+    bool run = false;
+
+    Callback(RunState* s) : state_(s) {}
+
+    static void Run(void* arg) {
+      Callback* callback = reinterpret_cast<Callback*>(arg);
+      RunState* state = callback->state_;
+
+      MutexLock l(&state->mu);
+      state->run_count++;
+      callback->run = true;
+      state->cvar.Signal();
+    }
+  };
+
+  RunState state;
+  Callback callback1(&state);
+  Callback callback2(&state);
+  Callback callback3(&state);
+  Callback callback4(&state);
+  env_->Schedule(&Callback::Run, &callback1);
+  env_->Schedule(&Callback::Run, &callback2);
+  env_->Schedule(&Callback::Run, &callback3);
+  env_->Schedule(&Callback::Run, &callback4);
+
+  MutexLock l(&state.mu);
+  while (state.run_count != 4) {
+    state.cvar.Wait();
+  }
+
+  ASSERT_TRUE(callback1.run);
+  ASSERT_TRUE(callback2.run);
+  ASSERT_TRUE(callback3.run);
+  ASSERT_TRUE(callback4.run);
+}
+
+struct State {
+  port::Mutex mu;
+  port::CondVar cvar{&mu};
+
+  int val GUARDED_BY(mu);
+  int num_running GUARDED_BY(mu);
+
+  State(int val, int num_running) : val(val), num_running(num_running) {}
+};
+
+static void ThreadBody(void* arg) {
+  State* s = reinterpret_cast<State*>(arg);
+  s->mu.Lock();
+  s->val += 1;
+  s->num_running -= 1;
+  s->cvar.Signal();
+  s->mu.Unlock();
+}
+
+TEST_F(EnvTest, StartThread) {
+  State state(0, 3);
+  for (int i = 0; i < 3; i++) {
+    env_->StartThread(&ThreadBody, &state);
+  }
+
+  MutexLock l(&state.mu);
+  while (state.num_running != 0) {
+    state.cvar.Wait();
+  }
+  ASSERT_EQ(state.val, 3);
+}
+
+TEST_F(EnvTest, TestOpenNonExistentFile) {
+  // Write some test data to a single file that will be opened |n| times.
+  std::string test_dir;
+  ASSERT_LEVELDB_OK(env_->GetTestDirectory(&test_dir));
+
+  std::string non_existent_file = test_dir + "/non_existent_file";
+  ASSERT_TRUE(!env_->FileExists(non_existent_file));
+
+  RandomAccessFile* random_access_file;
+  Status status =
+      env_->NewRandomAccessFile(non_existent_file, &random_access_file);
+#if defined(LEVELDB_PLATFORM_CHROMIUM)
+  // TODO(crbug.com/760362): See comment in MakeIOError() from env_chromium.cc.
+  ASSERT_TRUE(status.IsIOError());
+#else
+  ASSERT_TRUE(status.IsNotFound());
+#endif  // defined(LEVELDB_PLATFORM_CHROMIUM)
+
+  SequentialFile* sequential_file;
+  status = env_->NewSequentialFile(non_existent_file, &sequential_file);
+#if defined(LEVELDB_PLATFORM_CHROMIUM)
+  // TODO(crbug.com/760362): See comment in MakeIOError() from env_chromium.cc.
+  ASSERT_TRUE(status.IsIOError());
+#else
+  ASSERT_TRUE(status.IsNotFound());
+#endif  // defined(LEVELDB_PLATFORM_CHROMIUM)
+}
+
+TEST_F(EnvTest, ReopenWritableFile) {
+  std::string test_dir;
+  ASSERT_LEVELDB_OK(env_->GetTestDirectory(&test_dir));
+  std::string test_file_name = test_dir + "/reopen_writable_file.txt";
+  env_->RemoveFile(test_file_name);
+
+  WritableFile* writable_file;
+  ASSERT_LEVELDB_OK(env_->NewWritableFile(test_file_name, &writable_file));
+  std::string data("hello world!");
+  ASSERT_LEVELDB_OK(writable_file->Append(data));
+  ASSERT_LEVELDB_OK(writable_file->Close());
+  delete writable_file;
+
+  ASSERT_LEVELDB_OK(env_->NewWritableFile(test_file_name, &writable_file));
+  data = "42";
+  ASSERT_LEVELDB_OK(writable_file->Append(data));
+  ASSERT_LEVELDB_OK(writable_file->Close());
+  delete writable_file;
+
+  ASSERT_LEVELDB_OK(ReadFileToString(env_, test_file_name, &data));
+  ASSERT_EQ(std::string("42"), data);
+  env_->RemoveFile(test_file_name);
+}
+
+TEST_F(EnvTest, ReopenAppendableFile) {
+  std::string test_dir;
+  ASSERT_LEVELDB_OK(env_->GetTestDirectory(&test_dir));
+  std::string test_file_name = test_dir + "/reopen_appendable_file.txt";
+  env_->RemoveFile(test_file_name);
+
+  WritableFile* appendable_file;
+  ASSERT_LEVELDB_OK(env_->NewAppendableFile(test_file_name, &appendable_file));
+  std::string data("hello world!");
+  ASSERT_LEVELDB_OK(appendable_file->Append(data));
+  ASSERT_LEVELDB_OK(appendable_file->Close());
+  delete appendable_file;
+
+  ASSERT_LEVELDB_OK(env_->NewAppendableFile(test_file_name, &appendable_file));
+  data = "42";
+  ASSERT_LEVELDB_OK(appendable_file->Append(data));
+  ASSERT_LEVELDB_OK(appendable_file->Close());
+  delete appendable_file;
+
+  ASSERT_LEVELDB_OK(ReadFileToString(env_, test_file_name, &data));
+  ASSERT_EQ(std::string("hello world!42"), data);
+  env_->RemoveFile(test_file_name);
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/util/env_windows.cc b/leveldb_base/util/env_windows.cc
new file mode 100644
index 0000000..1c74b02
--- /dev/null
+++ b/leveldb_base/util/env_windows.cc
@@ -0,0 +1,816 @@
+// Copyright (c) 2018 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+// Prevent Windows headers from defining min/max macros and instead
+// use STL.
+#ifndef NOMINMAX
+#define NOMINMAX
+#endif  // ifndef NOMINMAX
+#include <windows.h>
+
+#include <algorithm>
+#include <atomic>
+#include <chrono>
+#include <condition_variable>
+#include <cstddef>
+#include <cstdint>
+#include <cstdlib>
+#include <cstring>
+#include <memory>
+#include <mutex>
+#include <queue>
+#include <sstream>
+#include <string>
+#include <vector>
+
+#include "leveldb/env.h"
+#include "leveldb/slice.h"
+#include "port/port.h"
+#include "port/thread_annotations.h"
+#include "util/env_windows_test_helper.h"
+#include "util/logging.h"
+#include "util/mutexlock.h"
+#include "util/windows_logger.h"
+
+namespace leveldb {
+
+namespace {
+
+constexpr const size_t kWritableFileBufferSize = 65536;
+
+// Up to 1000 mmaps for 64-bit binaries; none for 32-bit.
+constexpr int kDefaultMmapLimit = (sizeof(void*) >= 8) ? 1000 : 0;
+
+// Can be set by by EnvWindowsTestHelper::SetReadOnlyMMapLimit().
+int g_mmap_limit = kDefaultMmapLimit;
+
+std::string GetWindowsErrorMessage(DWORD error_code) {
+  std::string message;
+  char* error_text = nullptr;
+  // Use MBCS version of FormatMessage to match return value.
+  size_t error_text_size = ::FormatMessageA(
+      FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ALLOCATE_BUFFER |
+          FORMAT_MESSAGE_IGNORE_INSERTS,
+      nullptr, error_code, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+      reinterpret_cast<char*>(&error_text), 0, nullptr);
+  if (!error_text) {
+    return message;
+  }
+  message.assign(error_text, error_text_size);
+  ::LocalFree(error_text);
+  return message;
+}
+
+Status WindowsError(const std::string& context, DWORD error_code) {
+  if (error_code == ERROR_FILE_NOT_FOUND || error_code == ERROR_PATH_NOT_FOUND)
+    return Status::NotFound(context, GetWindowsErrorMessage(error_code));
+  return Status::IOError(context, GetWindowsErrorMessage(error_code));
+}
+
+class ScopedHandle {
+ public:
+  ScopedHandle(HANDLE handle) : handle_(handle) {}
+  ScopedHandle(const ScopedHandle&) = delete;
+  ScopedHandle(ScopedHandle&& other) noexcept : handle_(other.Release()) {}
+  ~ScopedHandle() { Close(); }
+
+  ScopedHandle& operator=(const ScopedHandle&) = delete;
+
+  ScopedHandle& operator=(ScopedHandle&& rhs) noexcept {
+    if (this != &rhs) handle_ = rhs.Release();
+    return *this;
+  }
+
+  bool Close() {
+    if (!is_valid()) {
+      return true;
+    }
+    HANDLE h = handle_;
+    handle_ = INVALID_HANDLE_VALUE;
+    return ::CloseHandle(h);
+  }
+
+  bool is_valid() const {
+    return handle_ != INVALID_HANDLE_VALUE && handle_ != nullptr;
+  }
+
+  HANDLE get() const { return handle_; }
+
+  HANDLE Release() {
+    HANDLE h = handle_;
+    handle_ = INVALID_HANDLE_VALUE;
+    return h;
+  }
+
+ private:
+  HANDLE handle_;
+};
+
+// Helper class to limit resource usage to avoid exhaustion.
+// Currently used to limit read-only file descriptors and mmap file usage
+// so that we do not run out of file descriptors or virtual memory, or run into
+// kernel performance problems for very large databases.
+class Limiter {
+ public:
+  // Limit maximum number of resources to |max_acquires|.
+  Limiter(int max_acquires)
+      :
+#if !defined(NDEBUG)
+        max_acquires_(max_acquires),
+#endif  // !defined(NDEBUG)
+        acquires_allowed_(max_acquires) {
+    assert(max_acquires >= 0);
+  }
+
+  Limiter(const Limiter&) = delete;
+  Limiter operator=(const Limiter&) = delete;
+
+  // If another resource is available, acquire it and return true.
+  // Else return false.
+  bool Acquire() {
+    int old_acquires_allowed =
+        acquires_allowed_.fetch_sub(1, std::memory_order_relaxed);
+
+    if (old_acquires_allowed > 0) return true;
+
+    acquires_allowed_.fetch_add(1, std::memory_order_relaxed);
+    return false;
+  }
+
+  // Release a resource acquired by a previous call to Acquire() that returned
+  // true.
+  void Release() {
+    int old_acquires_allowed =
+        acquires_allowed_.fetch_add(1, std::memory_order_relaxed);
+
+    // Silence compiler warnings about unused arguments when NDEBUG is defined.
+    (void)old_acquires_allowed;
+    // If the check below fails, Release() was called more times than acquire.
+    assert(old_acquires_allowed < max_acquires_);
+  }
+
+ private:
+#if !defined(NDEBUG)
+  // Catches an excessive number of Release() calls.
+  const int max_acquires_;
+#endif  // !defined(NDEBUG)
+
+  // The number of available resources.
+  //
+  // This is a counter and is not tied to the invariants of any other class, so
+  // it can be operated on safely using std::memory_order_relaxed.
+  std::atomic<int> acquires_allowed_;
+};
+
+class WindowsSequentialFile : public SequentialFile {
+ public:
+  WindowsSequentialFile(std::string filename, ScopedHandle handle)
+      : handle_(std::move(handle)), filename_(std::move(filename)) {}
+  ~WindowsSequentialFile() override {}
+
+  Status Read(size_t n, Slice* result, char* scratch) override {
+    DWORD bytes_read;
+    // DWORD is 32-bit, but size_t could technically be larger. However leveldb
+    // files are limited to leveldb::Options::max_file_size which is clamped to
+    // 1<<30 or 1 GiB.
+    assert(n <= std::numeric_limits<DWORD>::max());
+    if (!::ReadFile(handle_.get(), scratch, static_cast<DWORD>(n), &bytes_read,
+                    nullptr)) {
+      return WindowsError(filename_, ::GetLastError());
+    }
+
+    *result = Slice(scratch, bytes_read);
+    return Status::OK();
+  }
+
+  Status Skip(uint64_t n) override {
+    LARGE_INTEGER distance;
+    distance.QuadPart = n;
+    if (!::SetFilePointerEx(handle_.get(), distance, nullptr, FILE_CURRENT)) {
+      return WindowsError(filename_, ::GetLastError());
+    }
+    return Status::OK();
+  }
+
+ private:
+  const ScopedHandle handle_;
+  const std::string filename_;
+};
+
+class WindowsRandomAccessFile : public RandomAccessFile {
+ public:
+  WindowsRandomAccessFile(std::string filename, ScopedHandle handle)
+      : handle_(std::move(handle)), filename_(std::move(filename)) {}
+
+  ~WindowsRandomAccessFile() override = default;
+
+  Status Read(uint64_t offset, size_t n, Slice* result,
+              char* scratch) const override {
+    DWORD bytes_read = 0;
+    OVERLAPPED overlapped = {0};
+
+    overlapped.OffsetHigh = static_cast<DWORD>(offset >> 32);
+    overlapped.Offset = static_cast<DWORD>(offset);
+    if (!::ReadFile(handle_.get(), scratch, static_cast<DWORD>(n), &bytes_read,
+                    &overlapped)) {
+      DWORD error_code = ::GetLastError();
+      if (error_code != ERROR_HANDLE_EOF) {
+        *result = Slice(scratch, 0);
+        return Status::IOError(filename_, GetWindowsErrorMessage(error_code));
+      }
+    }
+
+    *result = Slice(scratch, bytes_read);
+    return Status::OK();
+  }
+
+ private:
+  const ScopedHandle handle_;
+  const std::string filename_;
+};
+
+class WindowsMmapReadableFile : public RandomAccessFile {
+ public:
+  // base[0,length-1] contains the mmapped contents of the file.
+  WindowsMmapReadableFile(std::string filename, char* mmap_base, size_t length,
+                          Limiter* mmap_limiter)
+      : mmap_base_(mmap_base),
+        length_(length),
+        mmap_limiter_(mmap_limiter),
+        filename_(std::move(filename)) {}
+
+  ~WindowsMmapReadableFile() override {
+    ::UnmapViewOfFile(mmap_base_);
+    mmap_limiter_->Release();
+  }
+
+  Status Read(uint64_t offset, size_t n, Slice* result,
+              char* scratch) const override {
+    if (offset + n > length_) {
+      *result = Slice();
+      return WindowsError(filename_, ERROR_INVALID_PARAMETER);
+    }
+
+    *result = Slice(mmap_base_ + offset, n);
+    return Status::OK();
+  }
+
+ private:
+  char* const mmap_base_;
+  const size_t length_;
+  Limiter* const mmap_limiter_;
+  const std::string filename_;
+};
+
+class WindowsWritableFile : public WritableFile {
+ public:
+  WindowsWritableFile(std::string filename, ScopedHandle handle)
+      : pos_(0), handle_(std::move(handle)), filename_(std::move(filename)) {}
+
+  ~WindowsWritableFile() override = default;
+
+  Status Append(const Slice& data) override {
+    size_t write_size = data.size();
+    const char* write_data = data.data();
+
+    // Fit as much as possible into buffer.
+    size_t copy_size = std::min(write_size, kWritableFileBufferSize - pos_);
+    std::memcpy(buf_ + pos_, write_data, copy_size);
+    write_data += copy_size;
+    write_size -= copy_size;
+    pos_ += copy_size;
+    if (write_size == 0) {
+      return Status::OK();
+    }
+
+    // Can't fit in buffer, so need to do at least one write.
+    Status status = FlushBuffer();
+    if (!status.ok()) {
+      return status;
+    }
+
+    // Small writes go to buffer, large writes are written directly.
+    if (write_size < kWritableFileBufferSize) {
+      std::memcpy(buf_, write_data, write_size);
+      pos_ = write_size;
+      return Status::OK();
+    }
+    return WriteUnbuffered(write_data, write_size);
+  }
+
+  Status Close() override {
+    Status status = FlushBuffer();
+    if (!handle_.Close() && status.ok()) {
+      status = WindowsError(filename_, ::GetLastError());
+    }
+    return status;
+  }
+
+  Status Flush() override { return FlushBuffer(); }
+
+  Status Sync() override {
+    // On Windows no need to sync parent directory. Its metadata will be updated
+    // via the creation of the new file, without an explicit sync.
+
+    Status status = FlushBuffer();
+    if (!status.ok()) {
+      return status;
+    }
+
+    if (!::FlushFileBuffers(handle_.get())) {
+      return Status::IOError(filename_,
+                             GetWindowsErrorMessage(::GetLastError()));
+    }
+    return Status::OK();
+  }
+
+ private:
+  Status FlushBuffer() {
+    Status status = WriteUnbuffered(buf_, pos_);
+    pos_ = 0;
+    return status;
+  }
+
+  Status WriteUnbuffered(const char* data, size_t size) {
+    DWORD bytes_written;
+    if (!::WriteFile(handle_.get(), data, static_cast<DWORD>(size),
+                     &bytes_written, nullptr)) {
+      return Status::IOError(filename_,
+                             GetWindowsErrorMessage(::GetLastError()));
+    }
+    return Status::OK();
+  }
+
+  // buf_[0, pos_-1] contains data to be written to handle_.
+  char buf_[kWritableFileBufferSize];
+  size_t pos_;
+
+  ScopedHandle handle_;
+  const std::string filename_;
+};
+
+// Lock or unlock the entire file as specified by |lock|. Returns true
+// when successful, false upon failure. Caller should call ::GetLastError()
+// to determine cause of failure
+bool LockOrUnlock(HANDLE handle, bool lock) {
+  if (lock) {
+    return ::LockFile(handle,
+                      /*dwFileOffsetLow=*/0, /*dwFileOffsetHigh=*/0,
+                      /*nNumberOfBytesToLockLow=*/MAXDWORD,
+                      /*nNumberOfBytesToLockHigh=*/MAXDWORD);
+  } else {
+    return ::UnlockFile(handle,
+                        /*dwFileOffsetLow=*/0, /*dwFileOffsetHigh=*/0,
+                        /*nNumberOfBytesToLockLow=*/MAXDWORD,
+                        /*nNumberOfBytesToLockHigh=*/MAXDWORD);
+  }
+}
+
+class WindowsFileLock : public FileLock {
+ public:
+  WindowsFileLock(ScopedHandle handle, std::string filename)
+      : handle_(std::move(handle)), filename_(std::move(filename)) {}
+
+  const ScopedHandle& handle() const { return handle_; }
+  const std::string& filename() const { return filename_; }
+
+ private:
+  const ScopedHandle handle_;
+  const std::string filename_;
+};
+
+class WindowsEnv : public Env {
+ public:
+  WindowsEnv();
+  ~WindowsEnv() override {
+    static const char msg[] =
+        "WindowsEnv singleton destroyed. Unsupported behavior!\n";
+    std::fwrite(msg, 1, sizeof(msg), stderr);
+    std::abort();
+  }
+
+  Status NewSequentialFile(const std::string& filename,
+                           SequentialFile** result) override {
+    *result = nullptr;
+    DWORD desired_access = GENERIC_READ;
+    DWORD share_mode = FILE_SHARE_READ;
+    ScopedHandle handle = ::CreateFileA(
+        filename.c_str(), desired_access, share_mode,
+        /*lpSecurityAttributes=*/nullptr, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL,
+        /*hTemplateFile=*/nullptr);
+    if (!handle.is_valid()) {
+      return WindowsError(filename, ::GetLastError());
+    }
+
+    *result = new WindowsSequentialFile(filename, std::move(handle));
+    return Status::OK();
+  }
+
+  Status NewRandomAccessFile(const std::string& filename,
+                             RandomAccessFile** result) override {
+    *result = nullptr;
+    DWORD desired_access = GENERIC_READ;
+    DWORD share_mode = FILE_SHARE_READ;
+    ScopedHandle handle =
+        ::CreateFileA(filename.c_str(), desired_access, share_mode,
+                      /*lpSecurityAttributes=*/nullptr, OPEN_EXISTING,
+                      FILE_ATTRIBUTE_READONLY,
+                      /*hTemplateFile=*/nullptr);
+    if (!handle.is_valid()) {
+      return WindowsError(filename, ::GetLastError());
+    }
+    if (!mmap_limiter_.Acquire()) {
+      *result = new WindowsRandomAccessFile(filename, std::move(handle));
+      return Status::OK();
+    }
+
+    LARGE_INTEGER file_size;
+    Status status;
+    if (!::GetFileSizeEx(handle.get(), &file_size)) {
+      mmap_limiter_.Release();
+      return WindowsError(filename, ::GetLastError());
+    }
+
+    ScopedHandle mapping =
+        ::CreateFileMappingA(handle.get(),
+                             /*security attributes=*/nullptr, PAGE_READONLY,
+                             /*dwMaximumSizeHigh=*/0,
+                             /*dwMaximumSizeLow=*/0,
+                             /*lpName=*/nullptr);
+    if (mapping.is_valid()) {
+      void* mmap_base = ::MapViewOfFile(mapping.get(), FILE_MAP_READ,
+                                        /*dwFileOffsetHigh=*/0,
+                                        /*dwFileOffsetLow=*/0,
+                                        /*dwNumberOfBytesToMap=*/0);
+      if (mmap_base) {
+        *result = new WindowsMmapReadableFile(
+            filename, reinterpret_cast<char*>(mmap_base),
+            static_cast<size_t>(file_size.QuadPart), &mmap_limiter_);
+        return Status::OK();
+      }
+    }
+    mmap_limiter_.Release();
+    return WindowsError(filename, ::GetLastError());
+  }
+
+  Status NewWritableFile(const std::string& filename,
+                         WritableFile** result) override {
+    DWORD desired_access = GENERIC_WRITE;
+    DWORD share_mode = 0;  // Exclusive access.
+    ScopedHandle handle = ::CreateFileA(
+        filename.c_str(), desired_access, share_mode,
+        /*lpSecurityAttributes=*/nullptr, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL,
+        /*hTemplateFile=*/nullptr);
+    if (!handle.is_valid()) {
+      *result = nullptr;
+      return WindowsError(filename, ::GetLastError());
+    }
+
+    *result = new WindowsWritableFile(filename, std::move(handle));
+    return Status::OK();
+  }
+
+  Status NewAppendableFile(const std::string& filename,
+                           WritableFile** result) override {
+    DWORD desired_access = FILE_APPEND_DATA;
+    DWORD share_mode = 0;  // Exclusive access.
+    ScopedHandle handle = ::CreateFileA(
+        filename.c_str(), desired_access, share_mode,
+        /*lpSecurityAttributes=*/nullptr, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL,
+        /*hTemplateFile=*/nullptr);
+    if (!handle.is_valid()) {
+      *result = nullptr;
+      return WindowsError(filename, ::GetLastError());
+    }
+
+    *result = new WindowsWritableFile(filename, std::move(handle));
+    return Status::OK();
+  }
+
+  bool FileExists(const std::string& filename) override {
+    return GetFileAttributesA(filename.c_str()) != INVALID_FILE_ATTRIBUTES;
+  }
+
+  Status GetChildren(const std::string& directory_path,
+                     std::vector<std::string>* result) override {
+    const std::string find_pattern = directory_path + "\\*";
+    WIN32_FIND_DATAA find_data;
+    HANDLE dir_handle = ::FindFirstFileA(find_pattern.c_str(), &find_data);
+    if (dir_handle == INVALID_HANDLE_VALUE) {
+      DWORD last_error = ::GetLastError();
+      if (last_error == ERROR_FILE_NOT_FOUND) {
+        return Status::OK();
+      }
+      return WindowsError(directory_path, last_error);
+    }
+    do {
+      char base_name[_MAX_FNAME];
+      char ext[_MAX_EXT];
+
+      if (!_splitpath_s(find_data.cFileName, nullptr, 0, nullptr, 0, base_name,
+                        ARRAYSIZE(base_name), ext, ARRAYSIZE(ext))) {
+        result->emplace_back(std::string(base_name) + ext);
+      }
+    } while (::FindNextFileA(dir_handle, &find_data));
+    DWORD last_error = ::GetLastError();
+    ::FindClose(dir_handle);
+    if (last_error != ERROR_NO_MORE_FILES) {
+      return WindowsError(directory_path, last_error);
+    }
+    return Status::OK();
+  }
+
+  Status RemoveFile(const std::string& filename) override {
+    if (!::DeleteFileA(filename.c_str())) {
+      return WindowsError(filename, ::GetLastError());
+    }
+    return Status::OK();
+  }
+
+  Status CreateDir(const std::string& dirname) override {
+    if (!::CreateDirectoryA(dirname.c_str(), nullptr)) {
+      return WindowsError(dirname, ::GetLastError());
+    }
+    return Status::OK();
+  }
+
+  Status RemoveDir(const std::string& dirname) override {
+    if (!::RemoveDirectoryA(dirname.c_str())) {
+      return WindowsError(dirname, ::GetLastError());
+    }
+    return Status::OK();
+  }
+
+  Status GetFileSize(const std::string& filename, uint64_t* size) override {
+    WIN32_FILE_ATTRIBUTE_DATA file_attributes;
+    if (!::GetFileAttributesExA(filename.c_str(), GetFileExInfoStandard,
+                                &file_attributes)) {
+      return WindowsError(filename, ::GetLastError());
+    }
+    ULARGE_INTEGER file_size;
+    file_size.HighPart = file_attributes.nFileSizeHigh;
+    file_size.LowPart = file_attributes.nFileSizeLow;
+    *size = file_size.QuadPart;
+    return Status::OK();
+  }
+
+  Status RenameFile(const std::string& from, const std::string& to) override {
+    // Try a simple move first. It will only succeed when |to| doesn't already
+    // exist.
+    if (::MoveFileA(from.c_str(), to.c_str())) {
+      return Status::OK();
+    }
+    DWORD move_error = ::GetLastError();
+
+    // Try the full-blown replace if the move fails, as ReplaceFile will only
+    // succeed when |to| does exist. When writing to a network share, we may not
+    // be able to change the ACLs. Ignore ACL errors then
+    // (REPLACEFILE_IGNORE_MERGE_ERRORS).
+    if (::ReplaceFileA(to.c_str(), from.c_str(), /*lpBackupFileName=*/nullptr,
+                       REPLACEFILE_IGNORE_MERGE_ERRORS,
+                       /*lpExclude=*/nullptr, /*lpReserved=*/nullptr)) {
+      return Status::OK();
+    }
+    DWORD replace_error = ::GetLastError();
+    // In the case of FILE_ERROR_NOT_FOUND from ReplaceFile, it is likely that
+    // |to| does not exist. In this case, the more relevant error comes from the
+    // call to MoveFile.
+    if (replace_error == ERROR_FILE_NOT_FOUND ||
+        replace_error == ERROR_PATH_NOT_FOUND) {
+      return WindowsError(from, move_error);
+    } else {
+      return WindowsError(from, replace_error);
+    }
+  }
+
+  Status LockFile(const std::string& filename, FileLock** lock) override {
+    *lock = nullptr;
+    Status result;
+    ScopedHandle handle = ::CreateFileA(
+        filename.c_str(), GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ,
+        /*lpSecurityAttributes=*/nullptr, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL,
+        nullptr);
+    if (!handle.is_valid()) {
+      result = WindowsError(filename, ::GetLastError());
+    } else if (!LockOrUnlock(handle.get(), true)) {
+      result = WindowsError("lock " + filename, ::GetLastError());
+    } else {
+      *lock = new WindowsFileLock(std::move(handle), filename);
+    }
+    return result;
+  }
+
+  Status UnlockFile(FileLock* lock) override {
+    WindowsFileLock* windows_file_lock =
+        reinterpret_cast<WindowsFileLock*>(lock);
+    if (!LockOrUnlock(windows_file_lock->handle().get(), false)) {
+      return WindowsError("unlock " + windows_file_lock->filename(),
+                          ::GetLastError());
+    }
+    delete windows_file_lock;
+    return Status::OK();
+  }
+
+  void Schedule(void (*background_work_function)(void* background_work_arg),
+                void* background_work_arg) override;
+
+  void StartThread(void (*thread_main)(void* thread_main_arg),
+                   void* thread_main_arg) override {
+    std::thread new_thread(thread_main, thread_main_arg);
+    new_thread.detach();
+  }
+
+  Status GetTestDirectory(std::string* result) override {
+    const char* env = getenv("TEST_TMPDIR");
+    if (env && env[0] != '\0') {
+      *result = env;
+      return Status::OK();
+    }
+
+    char tmp_path[MAX_PATH];
+    if (!GetTempPathA(ARRAYSIZE(tmp_path), tmp_path)) {
+      return WindowsError("GetTempPath", ::GetLastError());
+    }
+    std::stringstream ss;
+    ss << tmp_path << "leveldbtest-" << std::this_thread::get_id();
+    *result = ss.str();
+
+    // Directory may already exist
+    CreateDir(*result);
+    return Status::OK();
+  }
+
+  Status NewLogger(const std::string& filename, Logger** result) override {
+    std::FILE* fp = std::fopen(filename.c_str(), "wN");
+    if (fp == nullptr) {
+      *result = nullptr;
+      return WindowsError(filename, ::GetLastError());
+    } else {
+      *result = new WindowsLogger(fp);
+      return Status::OK();
+    }
+  }
+
+  uint64_t NowMicros() override {
+    // GetSystemTimeAsFileTime typically has a resolution of 10-20 msec.
+    // TODO(cmumford): Switch to GetSystemTimePreciseAsFileTime which is
+    // available in Windows 8 and later.
+    FILETIME ft;
+    ::GetSystemTimeAsFileTime(&ft);
+    // Each tick represents a 100-nanosecond intervals since January 1, 1601
+    // (UTC).
+    uint64_t num_ticks =
+        (static_cast<uint64_t>(ft.dwHighDateTime) << 32) + ft.dwLowDateTime;
+    return num_ticks / 10;
+  }
+
+  void SleepForMicroseconds(int micros) override {
+    std::this_thread::sleep_for(std::chrono::microseconds(micros));
+  }
+
+ private:
+  void BackgroundThreadMain();
+
+  static void BackgroundThreadEntryPoint(WindowsEnv* env) {
+    env->BackgroundThreadMain();
+  }
+
+  // Stores the work item data in a Schedule() call.
+  //
+  // Instances are constructed on the thread calling Schedule() and used on the
+  // background thread.
+  //
+  // This structure is thread-safe because it is immutable.
+  struct BackgroundWorkItem {
+    explicit BackgroundWorkItem(void (*function)(void* arg), void* arg)
+        : function(function), arg(arg) {}
+
+    void (*const function)(void*);
+    void* const arg;
+  };
+
+  port::Mutex background_work_mutex_;
+  port::CondVar background_work_cv_ GUARDED_BY(background_work_mutex_);
+  bool started_background_thread_ GUARDED_BY(background_work_mutex_);
+
+  std::queue<BackgroundWorkItem> background_work_queue_
+      GUARDED_BY(background_work_mutex_);
+
+  Limiter mmap_limiter_;  // Thread-safe.
+};
+
+// Return the maximum number of concurrent mmaps.
+int MaxMmaps() { return g_mmap_limit; }
+
+WindowsEnv::WindowsEnv()
+    : background_work_cv_(&background_work_mutex_),
+      started_background_thread_(false),
+      mmap_limiter_(MaxMmaps()) {}
+
+void WindowsEnv::Schedule(
+    void (*background_work_function)(void* background_work_arg),
+    void* background_work_arg) {
+  background_work_mutex_.Lock();
+
+  // Start the background thread, if we haven't done so already.
+  if (!started_background_thread_) {
+    started_background_thread_ = true;
+    std::thread background_thread(WindowsEnv::BackgroundThreadEntryPoint, this);
+    background_thread.detach();
+  }
+
+  // If the queue is empty, the background thread may be waiting for work.
+  if (background_work_queue_.empty()) {
+    background_work_cv_.Signal();
+  }
+
+  background_work_queue_.emplace(background_work_function, background_work_arg);
+  background_work_mutex_.Unlock();
+}
+
+void WindowsEnv::BackgroundThreadMain() {
+  while (true) {
+    background_work_mutex_.Lock();
+
+    // Wait until there is work to be done.
+    while (background_work_queue_.empty()) {
+      background_work_cv_.Wait();
+    }
+
+    assert(!background_work_queue_.empty());
+    auto background_work_function = background_work_queue_.front().function;
+    void* background_work_arg = background_work_queue_.front().arg;
+    background_work_queue_.pop();
+
+    background_work_mutex_.Unlock();
+    background_work_function(background_work_arg);
+  }
+}
+
+// Wraps an Env instance whose destructor is never created.
+//
+// Intended usage:
+//   using PlatformSingletonEnv = SingletonEnv<PlatformEnv>;
+//   void ConfigurePosixEnv(int param) {
+//     PlatformSingletonEnv::AssertEnvNotInitialized();
+//     // set global configuration flags.
+//   }
+//   Env* Env::Default() {
+//     static PlatformSingletonEnv default_env;
+//     return default_env.env();
+//   }
+template <typename EnvType>
+class SingletonEnv {
+ public:
+  SingletonEnv() {
+#if !defined(NDEBUG)
+    env_initialized_.store(true, std::memory_order_relaxed);
+#endif  // !defined(NDEBUG)
+    static_assert(sizeof(env_storage_) >= sizeof(EnvType),
+                  "env_storage_ will not fit the Env");
+    static_assert(alignof(decltype(env_storage_)) >= alignof(EnvType),
+                  "env_storage_ does not meet the Env's alignment needs");
+    new (&env_storage_) EnvType();
+  }
+  ~SingletonEnv() = default;
+
+  SingletonEnv(const SingletonEnv&) = delete;
+  SingletonEnv& operator=(const SingletonEnv&) = delete;
+
+  Env* env() { return reinterpret_cast<Env*>(&env_storage_); }
+
+  static void AssertEnvNotInitialized() {
+#if !defined(NDEBUG)
+    assert(!env_initialized_.load(std::memory_order_relaxed));
+#endif  // !defined(NDEBUG)
+  }
+
+ private:
+  typename std::aligned_storage<sizeof(EnvType), alignof(EnvType)>::type
+      env_storage_;
+#if !defined(NDEBUG)
+  static std::atomic<bool> env_initialized_;
+#endif  // !defined(NDEBUG)
+};
+
+#if !defined(NDEBUG)
+template <typename EnvType>
+std::atomic<bool> SingletonEnv<EnvType>::env_initialized_;
+#endif  // !defined(NDEBUG)
+
+using WindowsDefaultEnv = SingletonEnv<WindowsEnv>;
+
+}  // namespace
+
+void EnvWindowsTestHelper::SetReadOnlyMMapLimit(int limit) {
+  WindowsDefaultEnv::AssertEnvNotInitialized();
+  g_mmap_limit = limit;
+}
+
+Env* Env::Default() {
+  static WindowsDefaultEnv env_container;
+  return env_container.env();
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/util/env_windows_test.cc b/leveldb_base/util/env_windows_test.cc
new file mode 100644
index 0000000..d6822d2
--- /dev/null
+++ b/leveldb_base/util/env_windows_test.cc
@@ -0,0 +1,65 @@
+// Copyright (c) 2018 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "gtest/gtest.h"
+#include "leveldb/env.h"
+#include "port/port.h"
+#include "util/env_windows_test_helper.h"
+#include "util/testutil.h"
+
+namespace leveldb {
+
+static const int kMMapLimit = 4;
+
+class EnvWindowsTest : public testing::Test {
+ public:
+  static void SetFileLimits(int mmap_limit) {
+    EnvWindowsTestHelper::SetReadOnlyMMapLimit(mmap_limit);
+  }
+
+  EnvWindowsTest() : env_(Env::Default()) {}
+
+  Env* env_;
+};
+
+TEST_F(EnvWindowsTest, TestOpenOnRead) {
+  // Write some test data to a single file that will be opened |n| times.
+  std::string test_dir;
+  ASSERT_LEVELDB_OK(env_->GetTestDirectory(&test_dir));
+  std::string test_file = test_dir + "/open_on_read.txt";
+
+  FILE* f = std::fopen(test_file.c_str(), "w");
+  ASSERT_TRUE(f != nullptr);
+  const char kFileData[] = "abcdefghijklmnopqrstuvwxyz";
+  fputs(kFileData, f);
+  std::fclose(f);
+
+  // Open test file some number above the sum of the two limits to force
+  // leveldb::WindowsEnv to switch from mapping the file into memory
+  // to basic file reading.
+  const int kNumFiles = kMMapLimit + 5;
+  leveldb::RandomAccessFile* files[kNumFiles] = {0};
+  for (int i = 0; i < kNumFiles; i++) {
+    ASSERT_LEVELDB_OK(env_->NewRandomAccessFile(test_file, &files[i]));
+  }
+  char scratch;
+  Slice read_result;
+  for (int i = 0; i < kNumFiles; i++) {
+    ASSERT_LEVELDB_OK(files[i]->Read(i, 1, &read_result, &scratch));
+    ASSERT_EQ(kFileData[i], read_result[0]);
+  }
+  for (int i = 0; i < kNumFiles; i++) {
+    delete files[i];
+  }
+  ASSERT_LEVELDB_OK(env_->RemoveFile(test_file));
+}
+
+}  // namespace leveldb
+
+int main(int argc, char** argv) {
+  // All tests currently run with the same read-only file limits.
+  leveldb::EnvWindowsTest::SetFileLimits(leveldb::kMMapLimit);
+  testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
diff --git a/leveldb_base/util/env_windows_test_helper.h b/leveldb_base/util/env_windows_test_helper.h
new file mode 100644
index 0000000..e6f6020
--- /dev/null
+++ b/leveldb_base/util/env_windows_test_helper.h
@@ -0,0 +1,25 @@
+// Copyright 2018 (c) The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_UTIL_ENV_WINDOWS_TEST_HELPER_H_
+#define STORAGE_LEVELDB_UTIL_ENV_WINDOWS_TEST_HELPER_H_
+
+namespace leveldb {
+
+class EnvWindowsTest;
+
+// A helper for the Windows Env to facilitate testing.
+class EnvWindowsTestHelper {
+ private:
+  friend class CorruptionTest;
+  friend class EnvWindowsTest;
+
+  // Set the maximum number of read-only files that will be mapped via mmap.
+  // Must be called before creating an Env.
+  static void SetReadOnlyMMapLimit(int limit);
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_UTIL_ENV_WINDOWS_TEST_HELPER_H_
diff --git a/leveldb_base/util/filter_policy.cc b/leveldb_base/util/filter_policy.cc
new file mode 100644
index 0000000..90fd754
--- /dev/null
+++ b/leveldb_base/util/filter_policy.cc
@@ -0,0 +1,11 @@
+// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "leveldb/filter_policy.h"
+
+namespace leveldb {
+
+FilterPolicy::~FilterPolicy() {}
+
+}  // namespace leveldb
diff --git a/leveldb_base/util/hash.cc b/leveldb_base/util/hash.cc
new file mode 100644
index 0000000..8122fa8
--- /dev/null
+++ b/leveldb_base/util/hash.cc
@@ -0,0 +1,55 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "util/hash.h"
+
+#include <cstring>
+
+#include "util/coding.h"
+
+// The FALLTHROUGH_INTENDED macro can be used to annotate implicit fall-through
+// between switch labels. The real definition should be provided externally.
+// This one is a fallback version for unsupported compilers.
+#ifndef FALLTHROUGH_INTENDED
+#define FALLTHROUGH_INTENDED \
+  do {                       \
+  } while (0)
+#endif
+
+namespace leveldb {
+
+uint32_t Hash(const char* data, size_t n, uint32_t seed) {
+  // Similar to murmur hash
+  const uint32_t m = 0xc6a4a793;
+  const uint32_t r = 24;
+  const char* limit = data + n;
+  uint32_t h = seed ^ (n * m);
+
+  // Pick up four bytes at a time
+  while (data + 4 <= limit) {
+    uint32_t w = DecodeFixed32(data);
+    data += 4;
+    h += w;
+    h *= m;
+    h ^= (h >> 16);
+  }
+
+  // Pick up remaining bytes
+  switch (limit - data) {
+    case 3:
+      h += static_cast<uint8_t>(data[2]) << 16;
+      FALLTHROUGH_INTENDED;
+    case 2:
+      h += static_cast<uint8_t>(data[1]) << 8;
+      FALLTHROUGH_INTENDED;
+    case 1:
+      h += static_cast<uint8_t>(data[0]);
+      h *= m;
+      h ^= (h >> r);
+      break;
+  }
+  return h;
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/util/hash.h b/leveldb_base/util/hash.h
new file mode 100644
index 0000000..87ab279
--- /dev/null
+++ b/leveldb_base/util/hash.h
@@ -0,0 +1,19 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// Simple hash function used for internal data structures
+
+#ifndef STORAGE_LEVELDB_UTIL_HASH_H_
+#define STORAGE_LEVELDB_UTIL_HASH_H_
+
+#include <cstddef>
+#include <cstdint>
+
+namespace leveldb {
+
+uint32_t Hash(const char* data, size_t n, uint32_t seed);
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_UTIL_HASH_H_
diff --git a/leveldb_base/util/hash_test.cc b/leveldb_base/util/hash_test.cc
new file mode 100644
index 0000000..0ea5977
--- /dev/null
+++ b/leveldb_base/util/hash_test.cc
@@ -0,0 +1,41 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "util/hash.h"
+
+#include "gtest/gtest.h"
+
+namespace leveldb {
+
+TEST(HASH, SignedUnsignedIssue) {
+  const uint8_t data1[1] = {0x62};
+  const uint8_t data2[2] = {0xc3, 0x97};
+  const uint8_t data3[3] = {0xe2, 0x99, 0xa5};
+  const uint8_t data4[4] = {0xe1, 0x80, 0xb9, 0x32};
+  const uint8_t data5[48] = {
+      0x01, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00,
+      0x00, 0x00, 0x00, 0x14, 0x00, 0x00, 0x00, 0x18, 0x28, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  };
+
+  ASSERT_EQ(Hash(0, 0, 0xbc9f1d34), 0xbc9f1d34);
+  ASSERT_EQ(
+      Hash(reinterpret_cast<const char*>(data1), sizeof(data1), 0xbc9f1d34),
+      0xef1345c4);
+  ASSERT_EQ(
+      Hash(reinterpret_cast<const char*>(data2), sizeof(data2), 0xbc9f1d34),
+      0x5b663814);
+  ASSERT_EQ(
+      Hash(reinterpret_cast<const char*>(data3), sizeof(data3), 0xbc9f1d34),
+      0x323c078f);
+  ASSERT_EQ(
+      Hash(reinterpret_cast<const char*>(data4), sizeof(data4), 0xbc9f1d34),
+      0xed21633a);
+  ASSERT_EQ(
+      Hash(reinterpret_cast<const char*>(data5), sizeof(data5), 0x12345678),
+      0xf333dabb);
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/util/histogram.cc b/leveldb_base/util/histogram.cc
new file mode 100644
index 0000000..7af4030
--- /dev/null
+++ b/leveldb_base/util/histogram.cc
@@ -0,0 +1,272 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "util/histogram.h"
+
+#include <cmath>
+#include <cstdio>
+
+#include "port/port.h"
+
+namespace leveldb {
+
+const double Histogram::kBucketLimit[kNumBuckets] = {
+    1,
+    2,
+    3,
+    4,
+    5,
+    6,
+    7,
+    8,
+    9,
+    10,
+    12,
+    14,
+    16,
+    18,
+    20,
+    25,
+    30,
+    35,
+    40,
+    45,
+    50,
+    60,
+    70,
+    80,
+    90,
+    100,
+    120,
+    140,
+    160,
+    180,
+    200,
+    250,
+    300,
+    350,
+    400,
+    450,
+    500,
+    600,
+    700,
+    800,
+    900,
+    1000,
+    1200,
+    1400,
+    1600,
+    1800,
+    2000,
+    2500,
+    3000,
+    3500,
+    4000,
+    4500,
+    5000,
+    6000,
+    7000,
+    8000,
+    9000,
+    10000,
+    12000,
+    14000,
+    16000,
+    18000,
+    20000,
+    25000,
+    30000,
+    35000,
+    40000,
+    45000,
+    50000,
+    60000,
+    70000,
+    80000,
+    90000,
+    100000,
+    120000,
+    140000,
+    160000,
+    180000,
+    200000,
+    250000,
+    300000,
+    350000,
+    400000,
+    450000,
+    500000,
+    600000,
+    700000,
+    800000,
+    900000,
+    1000000,
+    1200000,
+    1400000,
+    1600000,
+    1800000,
+    2000000,
+    2500000,
+    3000000,
+    3500000,
+    4000000,
+    4500000,
+    5000000,
+    6000000,
+    7000000,
+    8000000,
+    9000000,
+    10000000,
+    12000000,
+    14000000,
+    16000000,
+    18000000,
+    20000000,
+    25000000,
+    30000000,
+    35000000,
+    40000000,
+    45000000,
+    50000000,
+    60000000,
+    70000000,
+    80000000,
+    90000000,
+    100000000,
+    120000000,
+    140000000,
+    160000000,
+    180000000,
+    200000000,
+    250000000,
+    300000000,
+    350000000,
+    400000000,
+    450000000,
+    500000000,
+    600000000,
+    700000000,
+    800000000,
+    900000000,
+    1000000000,
+    1200000000,
+    1400000000,
+    1600000000,
+    1800000000,
+    2000000000,
+    2500000000.0,
+    3000000000.0,
+    3500000000.0,
+    4000000000.0,
+    4500000000.0,
+    5000000000.0,
+    6000000000.0,
+    7000000000.0,
+    8000000000.0,
+    9000000000.0,
+    1e200,
+};
+
+void Histogram::Clear() {
+  min_ = kBucketLimit[kNumBuckets - 1];
+  max_ = 0;
+  num_ = 0;
+  sum_ = 0;
+  sum_squares_ = 0;
+  for (int i = 0; i < kNumBuckets; i++) {
+    buckets_[i] = 0;
+  }
+}
+
+void Histogram::Add(double value) {
+  // Linear search is fast enough for our usage in db_bench
+  int b = 0;
+  while (b < kNumBuckets - 1 && kBucketLimit[b] <= value) {
+    b++;
+  }
+  buckets_[b] += 1.0;
+  if (min_ > value) min_ = value;
+  if (max_ < value) max_ = value;
+  num_++;
+  sum_ += value;
+  sum_squares_ += (value * value);
+}
+
+void Histogram::Merge(const Histogram& other) {
+  if (other.min_ < min_) min_ = other.min_;
+  if (other.max_ > max_) max_ = other.max_;
+  num_ += other.num_;
+  sum_ += other.sum_;
+  sum_squares_ += other.sum_squares_;
+  for (int b = 0; b < kNumBuckets; b++) {
+    buckets_[b] += other.buckets_[b];
+  }
+}
+
+double Histogram::Median() const { return Percentile(50.0); }
+
+double Histogram::Percentile(double p) const {
+  double threshold = num_ * (p / 100.0);
+  double sum = 0;
+  for (int b = 0; b < kNumBuckets; b++) {
+    sum += buckets_[b];
+    if (sum >= threshold) {
+      // Scale linearly within this bucket
+      double left_point = (b == 0) ? 0 : kBucketLimit[b - 1];
+      double right_point = kBucketLimit[b];
+      double left_sum = sum - buckets_[b];
+      double right_sum = sum;
+      double pos = (threshold - left_sum) / (right_sum - left_sum);
+      double r = left_point + (right_point - left_point) * pos;
+      if (r < min_) r = min_;
+      if (r > max_) r = max_;
+      return r;
+    }
+  }
+  return max_;
+}
+
+double Histogram::Average() const {
+  if (num_ == 0.0) return 0;
+  return sum_ / num_;
+}
+
+double Histogram::StandardDeviation() const {
+  if (num_ == 0.0) return 0;
+  double variance = (sum_squares_ * num_ - sum_ * sum_) / (num_ * num_);
+  return sqrt(variance);
+}
+
+std::string Histogram::ToString() const {
+  std::string r;
+  char buf[200];
+  std::snprintf(buf, sizeof(buf), "Count: %.0f  Average: %.4f  StdDev: %.2f\n",
+                num_, Average(), StandardDeviation());
+  r.append(buf);
+  std::snprintf(buf, sizeof(buf), "Min: %.4f  Median: %.4f  Max: %.4f\n",
+                (num_ == 0.0 ? 0.0 : min_), Median(), max_);
+  r.append(buf);
+  r.append("------------------------------------------------------\n");
+  const double mult = 100.0 / num_;
+  double sum = 0;
+  for (int b = 0; b < kNumBuckets; b++) {
+    if (buckets_[b] <= 0.0) continue;
+    sum += buckets_[b];
+    std::snprintf(buf, sizeof(buf), "[ %7.0f, %7.0f ) %7.0f %7.3f%% %7.3f%% ",
+                  ((b == 0) ? 0.0 : kBucketLimit[b - 1]),  // left
+                  kBucketLimit[b],                         // right
+                  buckets_[b],                             // count
+                  mult * buckets_[b],                      // percentage
+                  mult * sum);  // cumulative percentage
+    r.append(buf);
+
+    // Add hash marks based on percentage; 20 marks for 100%.
+    int marks = static_cast<int>(20 * (buckets_[b] / num_) + 0.5);
+    r.append(marks, '#');
+    r.push_back('\n');
+  }
+  return r;
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/util/histogram.h b/leveldb_base/util/histogram.h
new file mode 100644
index 0000000..4da60fb
--- /dev/null
+++ b/leveldb_base/util/histogram.h
@@ -0,0 +1,44 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_UTIL_HISTOGRAM_H_
+#define STORAGE_LEVELDB_UTIL_HISTOGRAM_H_
+
+#include <string>
+
+namespace leveldb {
+
+class Histogram {
+ public:
+  Histogram() {}
+  ~Histogram() {}
+
+  void Clear();
+  void Add(double value);
+  void Merge(const Histogram& other);
+
+  std::string ToString() const;
+
+ private:
+  enum { kNumBuckets = 154 };
+
+  double Median() const;
+  double Percentile(double p) const;
+  double Average() const;
+  double StandardDeviation() const;
+
+  static const double kBucketLimit[kNumBuckets];
+
+  double min_;
+  double max_;
+  double num_;
+  double sum_;
+  double sum_squares_;
+
+  double buckets_[kNumBuckets];
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_UTIL_HISTOGRAM_H_
diff --git a/leveldb_base/util/logging.cc b/leveldb_base/util/logging.cc
new file mode 100644
index 0000000..8d6fb5b
--- /dev/null
+++ b/leveldb_base/util/logging.cc
@@ -0,0 +1,82 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "util/logging.h"
+
+#include <cstdarg>
+#include <cstdio>
+#include <cstdlib>
+#include <limits>
+
+#include "leveldb/env.h"
+#include "leveldb/slice.h"
+
+namespace leveldb {
+
+void AppendNumberTo(std::string* str, uint64_t num) {
+  char buf[30];
+  std::snprintf(buf, sizeof(buf), "%llu", static_cast<unsigned long long>(num));
+  str->append(buf);
+}
+
+void AppendEscapedStringTo(std::string* str, const Slice& value) {
+  for (size_t i = 0; i < value.size(); i++) {
+    char c = value[i];
+    if (c >= ' ' && c <= '~') {
+      str->push_back(c);
+    } else {
+      char buf[10];
+      std::snprintf(buf, sizeof(buf), "\\x%02x",
+                    static_cast<unsigned int>(c) & 0xff);
+      str->append(buf);
+    }
+  }
+}
+
+std::string NumberToString(uint64_t num) {
+  std::string r;
+  AppendNumberTo(&r, num);
+  return r;
+}
+
+std::string EscapeString(const Slice& value) {
+  std::string r;
+  AppendEscapedStringTo(&r, value);
+  return r;
+}
+
+bool ConsumeDecimalNumber(Slice* in, uint64_t* val) {
+  // Constants that will be optimized away.
+  constexpr const uint64_t kMaxUint64 = std::numeric_limits<uint64_t>::max();
+  constexpr const char kLastDigitOfMaxUint64 =
+      '0' + static_cast<char>(kMaxUint64 % 10);
+
+  uint64_t value = 0;
+
+  // reinterpret_cast-ing from char* to uint8_t* to avoid signedness.
+  const uint8_t* start = reinterpret_cast<const uint8_t*>(in->data());
+
+  const uint8_t* end = start + in->size();
+  const uint8_t* current = start;
+  for (; current != end; ++current) {
+    const uint8_t ch = *current;
+    if (ch < '0' || ch > '9') break;
+
+    // Overflow check.
+    // kMaxUint64 / 10 is also constant and will be optimized away.
+    if (value > kMaxUint64 / 10 ||
+        (value == kMaxUint64 / 10 && ch > kLastDigitOfMaxUint64)) {
+      return false;
+    }
+
+    value = (value * 10) + (ch - '0');
+  }
+
+  *val = value;
+  const size_t digits_consumed = current - start;
+  in->remove_prefix(digits_consumed);
+  return digits_consumed != 0;
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/util/logging.h b/leveldb_base/util/logging.h
new file mode 100644
index 0000000..a0394b2
--- /dev/null
+++ b/leveldb_base/util/logging.h
@@ -0,0 +1,44 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// Must not be included from any .h files to avoid polluting the namespace
+// with macros.
+
+#ifndef STORAGE_LEVELDB_UTIL_LOGGING_H_
+#define STORAGE_LEVELDB_UTIL_LOGGING_H_
+
+#include <cstdint>
+#include <cstdio>
+#include <string>
+
+#include "port/port.h"
+
+namespace leveldb {
+
+class Slice;
+class WritableFile;
+
+// Append a human-readable printout of "num" to *str
+void AppendNumberTo(std::string* str, uint64_t num);
+
+// Append a human-readable printout of "value" to *str.
+// Escapes any non-printable characters found in "value".
+void AppendEscapedStringTo(std::string* str, const Slice& value);
+
+// Return a human-readable printout of "num"
+std::string NumberToString(uint64_t num);
+
+// Return a human-readable version of "value".
+// Escapes any non-printable characters found in "value".
+std::string EscapeString(const Slice& value);
+
+// Parse a human-readable number from "*in" into *value.  On success,
+// advances "*in" past the consumed number and sets "*val" to the
+// numeric value.  Otherwise, returns false and leaves *in in an
+// unspecified state.
+bool ConsumeDecimalNumber(Slice* in, uint64_t* val);
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_UTIL_LOGGING_H_
diff --git a/leveldb_base/util/logging_test.cc b/leveldb_base/util/logging_test.cc
new file mode 100644
index 0000000..1746c57
--- /dev/null
+++ b/leveldb_base/util/logging_test.cc
@@ -0,0 +1,140 @@
+// Copyright (c) 2018 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "util/logging.h"
+
+#include <limits>
+#include <string>
+
+#include "gtest/gtest.h"
+#include "leveldb/slice.h"
+
+namespace leveldb {
+
+TEST(Logging, NumberToString) {
+  ASSERT_EQ("0", NumberToString(0));
+  ASSERT_EQ("1", NumberToString(1));
+  ASSERT_EQ("9", NumberToString(9));
+
+  ASSERT_EQ("10", NumberToString(10));
+  ASSERT_EQ("11", NumberToString(11));
+  ASSERT_EQ("19", NumberToString(19));
+  ASSERT_EQ("99", NumberToString(99));
+
+  ASSERT_EQ("100", NumberToString(100));
+  ASSERT_EQ("109", NumberToString(109));
+  ASSERT_EQ("190", NumberToString(190));
+  ASSERT_EQ("123", NumberToString(123));
+  ASSERT_EQ("12345678", NumberToString(12345678));
+
+  static_assert(std::numeric_limits<uint64_t>::max() == 18446744073709551615U,
+                "Test consistency check");
+  ASSERT_EQ("18446744073709551000", NumberToString(18446744073709551000U));
+  ASSERT_EQ("18446744073709551600", NumberToString(18446744073709551600U));
+  ASSERT_EQ("18446744073709551610", NumberToString(18446744073709551610U));
+  ASSERT_EQ("18446744073709551614", NumberToString(18446744073709551614U));
+  ASSERT_EQ("18446744073709551615", NumberToString(18446744073709551615U));
+}
+
+void ConsumeDecimalNumberRoundtripTest(uint64_t number,
+                                       const std::string& padding = "") {
+  std::string decimal_number = NumberToString(number);
+  std::string input_string = decimal_number + padding;
+  Slice input(input_string);
+  Slice output = input;
+  uint64_t result;
+  ASSERT_TRUE(ConsumeDecimalNumber(&output, &result));
+  ASSERT_EQ(number, result);
+  ASSERT_EQ(decimal_number.size(), output.data() - input.data());
+  ASSERT_EQ(padding.size(), output.size());
+}
+
+TEST(Logging, ConsumeDecimalNumberRoundtrip) {
+  ConsumeDecimalNumberRoundtripTest(0);
+  ConsumeDecimalNumberRoundtripTest(1);
+  ConsumeDecimalNumberRoundtripTest(9);
+
+  ConsumeDecimalNumberRoundtripTest(10);
+  ConsumeDecimalNumberRoundtripTest(11);
+  ConsumeDecimalNumberRoundtripTest(19);
+  ConsumeDecimalNumberRoundtripTest(99);
+
+  ConsumeDecimalNumberRoundtripTest(100);
+  ConsumeDecimalNumberRoundtripTest(109);
+  ConsumeDecimalNumberRoundtripTest(190);
+  ConsumeDecimalNumberRoundtripTest(123);
+  ASSERT_EQ("12345678", NumberToString(12345678));
+
+  for (uint64_t i = 0; i < 100; ++i) {
+    uint64_t large_number = std::numeric_limits<uint64_t>::max() - i;
+    ConsumeDecimalNumberRoundtripTest(large_number);
+  }
+}
+
+TEST(Logging, ConsumeDecimalNumberRoundtripWithPadding) {
+  ConsumeDecimalNumberRoundtripTest(0, " ");
+  ConsumeDecimalNumberRoundtripTest(1, "abc");
+  ConsumeDecimalNumberRoundtripTest(9, "x");
+
+  ConsumeDecimalNumberRoundtripTest(10, "_");
+  ConsumeDecimalNumberRoundtripTest(11, std::string("\0\0\0", 3));
+  ConsumeDecimalNumberRoundtripTest(19, "abc");
+  ConsumeDecimalNumberRoundtripTest(99, "padding");
+
+  ConsumeDecimalNumberRoundtripTest(100, " ");
+
+  for (uint64_t i = 0; i < 100; ++i) {
+    uint64_t large_number = std::numeric_limits<uint64_t>::max() - i;
+    ConsumeDecimalNumberRoundtripTest(large_number, "pad");
+  }
+}
+
+void ConsumeDecimalNumberOverflowTest(const std::string& input_string) {
+  Slice input(input_string);
+  Slice output = input;
+  uint64_t result;
+  ASSERT_EQ(false, ConsumeDecimalNumber(&output, &result));
+}
+
+TEST(Logging, ConsumeDecimalNumberOverflow) {
+  static_assert(std::numeric_limits<uint64_t>::max() == 18446744073709551615U,
+                "Test consistency check");
+  ConsumeDecimalNumberOverflowTest("18446744073709551616");
+  ConsumeDecimalNumberOverflowTest("18446744073709551617");
+  ConsumeDecimalNumberOverflowTest("18446744073709551618");
+  ConsumeDecimalNumberOverflowTest("18446744073709551619");
+  ConsumeDecimalNumberOverflowTest("18446744073709551620");
+  ConsumeDecimalNumberOverflowTest("18446744073709551621");
+  ConsumeDecimalNumberOverflowTest("18446744073709551622");
+  ConsumeDecimalNumberOverflowTest("18446744073709551623");
+  ConsumeDecimalNumberOverflowTest("18446744073709551624");
+  ConsumeDecimalNumberOverflowTest("18446744073709551625");
+  ConsumeDecimalNumberOverflowTest("18446744073709551626");
+
+  ConsumeDecimalNumberOverflowTest("18446744073709551700");
+
+  ConsumeDecimalNumberOverflowTest("99999999999999999999");
+}
+
+void ConsumeDecimalNumberNoDigitsTest(const std::string& input_string) {
+  Slice input(input_string);
+  Slice output = input;
+  uint64_t result;
+  ASSERT_EQ(false, ConsumeDecimalNumber(&output, &result));
+  ASSERT_EQ(input.data(), output.data());
+  ASSERT_EQ(input.size(), output.size());
+}
+
+TEST(Logging, ConsumeDecimalNumberNoDigits) {
+  ConsumeDecimalNumberNoDigitsTest("");
+  ConsumeDecimalNumberNoDigitsTest(" ");
+  ConsumeDecimalNumberNoDigitsTest("a");
+  ConsumeDecimalNumberNoDigitsTest(" 123");
+  ConsumeDecimalNumberNoDigitsTest("a123");
+  ConsumeDecimalNumberNoDigitsTest(std::string("\000123", 4));
+  ConsumeDecimalNumberNoDigitsTest(std::string("\177123", 4));
+  ConsumeDecimalNumberNoDigitsTest(std::string("\377123", 4));
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/util/mutexlock.h b/leveldb_base/util/mutexlock.h
new file mode 100644
index 0000000..0cb2e25
--- /dev/null
+++ b/leveldb_base/util/mutexlock.h
@@ -0,0 +1,39 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_UTIL_MUTEXLOCK_H_
+#define STORAGE_LEVELDB_UTIL_MUTEXLOCK_H_
+
+#include "port/port.h"
+#include "port/thread_annotations.h"
+
+namespace leveldb {
+
+// Helper class that locks a mutex on construction and unlocks the mutex when
+// the destructor of the MutexLock object is invoked.
+//
+// Typical usage:
+//
+//   void MyClass::MyMethod() {
+//     MutexLock l(&mu_);       // mu_ is an instance variable
+//     ... some complex code, possibly with multiple return paths ...
+//   }
+
+class SCOPED_LOCKABLE MutexLock {
+ public:
+  explicit MutexLock(port::Mutex* mu) EXCLUSIVE_LOCK_FUNCTION(mu) : mu_(mu) {
+    this->mu_->Lock();
+  }
+  ~MutexLock() UNLOCK_FUNCTION() { this->mu_->Unlock(); }
+
+  MutexLock(const MutexLock&) = delete;
+  MutexLock& operator=(const MutexLock&) = delete;
+
+ private:
+  port::Mutex* const mu_;
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_UTIL_MUTEXLOCK_H_
diff --git a/leveldb_base/util/no_destructor.h b/leveldb_base/util/no_destructor.h
new file mode 100644
index 0000000..a0d3b87
--- /dev/null
+++ b/leveldb_base/util/no_destructor.h
@@ -0,0 +1,46 @@
+// Copyright (c) 2018 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_UTIL_NO_DESTRUCTOR_H_
+#define STORAGE_LEVELDB_UTIL_NO_DESTRUCTOR_H_
+
+#include <type_traits>
+#include <utility>
+
+namespace leveldb {
+
+// Wraps an instance whose destructor is never called.
+//
+// This is intended for use with function-level static variables.
+template <typename InstanceType>
+class NoDestructor {
+ public:
+  template <typename... ConstructorArgTypes>
+  explicit NoDestructor(ConstructorArgTypes&&... constructor_args) {
+    static_assert(sizeof(instance_storage_) >= sizeof(InstanceType),
+                  "instance_storage_ is not large enough to hold the instance");
+    static_assert(
+        alignof(decltype(instance_storage_)) >= alignof(InstanceType),
+        "instance_storage_ does not meet the instance's alignment requirement");
+    new (&instance_storage_)
+        InstanceType(std::forward<ConstructorArgTypes>(constructor_args)...);
+  }
+
+  ~NoDestructor() = default;
+
+  NoDestructor(const NoDestructor&) = delete;
+  NoDestructor& operator=(const NoDestructor&) = delete;
+
+  InstanceType* get() {
+    return reinterpret_cast<InstanceType*>(&instance_storage_);
+  }
+
+ private:
+  typename std::aligned_storage<sizeof(InstanceType),
+                                alignof(InstanceType)>::type instance_storage_;
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_UTIL_NO_DESTRUCTOR_H_
diff --git a/leveldb_base/util/no_destructor_test.cc b/leveldb_base/util/no_destructor_test.cc
new file mode 100644
index 0000000..e3602cc
--- /dev/null
+++ b/leveldb_base/util/no_destructor_test.cc
@@ -0,0 +1,44 @@
+// Copyright (c) 2018 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "util/no_destructor.h"
+
+#include <cstdint>
+#include <cstdlib>
+#include <utility>
+
+#include "gtest/gtest.h"
+
+namespace leveldb {
+
+namespace {
+
+struct DoNotDestruct {
+ public:
+  DoNotDestruct(uint32_t a, uint64_t b) : a(a), b(b) {}
+  ~DoNotDestruct() { std::abort(); }
+
+  // Used to check constructor argument forwarding.
+  uint32_t a;
+  uint64_t b;
+};
+
+constexpr const uint32_t kGoldenA = 0xdeadbeef;
+constexpr const uint64_t kGoldenB = 0xaabbccddeeffaabb;
+
+}  // namespace
+
+TEST(NoDestructorTest, StackInstance) {
+  NoDestructor<DoNotDestruct> instance(kGoldenA, kGoldenB);
+  ASSERT_EQ(kGoldenA, instance.get()->a);
+  ASSERT_EQ(kGoldenB, instance.get()->b);
+}
+
+TEST(NoDestructorTest, StaticInstance) {
+  static NoDestructor<DoNotDestruct> instance(kGoldenA, kGoldenB);
+  ASSERT_EQ(kGoldenA, instance.get()->a);
+  ASSERT_EQ(kGoldenB, instance.get()->b);
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/util/options.cc b/leveldb_base/util/options.cc
new file mode 100644
index 0000000..62de5bf
--- /dev/null
+++ b/leveldb_base/util/options.cc
@@ -0,0 +1,14 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "leveldb/options.h"
+
+#include "leveldb/comparator.h"
+#include "leveldb/env.h"
+
+namespace leveldb {
+
+Options::Options() : comparator(BytewiseComparator()), env(Env::Default()) {}
+
+}  // namespace leveldb
diff --git a/leveldb_base/util/posix_logger.h b/leveldb_base/util/posix_logger.h
new file mode 100644
index 0000000..6bbc1a0
--- /dev/null
+++ b/leveldb_base/util/posix_logger.h
@@ -0,0 +1,130 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// Logger implementation that can be shared by all environments
+// where enough posix functionality is available.
+
+#ifndef STORAGE_LEVELDB_UTIL_POSIX_LOGGER_H_
+#define STORAGE_LEVELDB_UTIL_POSIX_LOGGER_H_
+
+#include <sys/time.h>
+
+#include <cassert>
+#include <cstdarg>
+#include <cstdio>
+#include <ctime>
+#include <sstream>
+#include <thread>
+
+#include "leveldb/env.h"
+
+namespace leveldb {
+
+class PosixLogger final : public Logger {
+ public:
+  // Creates a logger that writes to the given file.
+  //
+  // The PosixLogger instance takes ownership of the file handle.
+  explicit PosixLogger(std::FILE* fp) : fp_(fp) { assert(fp != nullptr); }
+
+  ~PosixLogger() override { std::fclose(fp_); }
+
+  void Logv(const char* format, std::va_list arguments) override {
+    // Record the time as close to the Logv() call as possible.
+    struct ::timeval now_timeval;
+    ::gettimeofday(&now_timeval, nullptr);
+    const std::time_t now_seconds = now_timeval.tv_sec;
+    struct std::tm now_components;
+    ::localtime_r(&now_seconds, &now_components);
+
+    // Record the thread ID.
+    constexpr const int kMaxThreadIdSize = 32;
+    std::ostringstream thread_stream;
+    thread_stream << std::this_thread::get_id();
+    std::string thread_id = thread_stream.str();
+    if (thread_id.size() > kMaxThreadIdSize) {
+      thread_id.resize(kMaxThreadIdSize);
+    }
+
+    // We first attempt to print into a stack-allocated buffer. If this attempt
+    // fails, we make a second attempt with a dynamically allocated buffer.
+    constexpr const int kStackBufferSize = 512;
+    char stack_buffer[kStackBufferSize];
+    static_assert(sizeof(stack_buffer) == static_cast<size_t>(kStackBufferSize),
+                  "sizeof(char) is expected to be 1 in C++");
+
+    int dynamic_buffer_size = 0;  // Computed in the first iteration.
+    for (int iteration = 0; iteration < 2; ++iteration) {
+      const int buffer_size =
+          (iteration == 0) ? kStackBufferSize : dynamic_buffer_size;
+      char* const buffer =
+          (iteration == 0) ? stack_buffer : new char[dynamic_buffer_size];
+
+      // Print the header into the buffer.
+      int buffer_offset = std::snprintf(
+          buffer, buffer_size, "%04d/%02d/%02d-%02d:%02d:%02d.%06d %s ",
+          now_components.tm_year + 1900, now_components.tm_mon + 1,
+          now_components.tm_mday, now_components.tm_hour, now_components.tm_min,
+          now_components.tm_sec, static_cast<int>(now_timeval.tv_usec),
+          thread_id.c_str());
+
+      // The header can be at most 28 characters (10 date + 15 time +
+      // 3 delimiters) plus the thread ID, which should fit comfortably into the
+      // static buffer.
+      assert(buffer_offset <= 28 + kMaxThreadIdSize);
+      static_assert(28 + kMaxThreadIdSize < kStackBufferSize,
+                    "stack-allocated buffer may not fit the message header");
+      assert(buffer_offset < buffer_size);
+
+      // Print the message into the buffer.
+      std::va_list arguments_copy;
+      va_copy(arguments_copy, arguments);
+      buffer_offset +=
+          std::vsnprintf(buffer + buffer_offset, buffer_size - buffer_offset,
+                         format, arguments_copy);
+      va_end(arguments_copy);
+
+      // The code below may append a newline at the end of the buffer, which
+      // requires an extra character.
+      if (buffer_offset >= buffer_size - 1) {
+        // The message did not fit into the buffer.
+        if (iteration == 0) {
+          // Re-run the loop and use a dynamically-allocated buffer. The buffer
+          // will be large enough for the log message, an extra newline and a
+          // null terminator.
+          dynamic_buffer_size = buffer_offset + 2;
+          continue;
+        }
+
+        // The dynamically-allocated buffer was incorrectly sized. This should
+        // not happen, assuming a correct implementation of std::(v)snprintf.
+        // Fail in tests, recover by truncating the log message in production.
+        assert(false);
+        buffer_offset = buffer_size - 1;
+      }
+
+      // Add a newline if necessary.
+      if (buffer[buffer_offset - 1] != '\n') {
+        buffer[buffer_offset] = '\n';
+        ++buffer_offset;
+      }
+
+      assert(buffer_offset <= buffer_size);
+      std::fwrite(buffer, 1, buffer_offset, fp_);
+      std::fflush(fp_);
+
+      if (iteration != 0) {
+        delete[] buffer;
+      }
+      break;
+    }
+  }
+
+ private:
+  std::FILE* const fp_;
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_UTIL_POSIX_LOGGER_H_
diff --git a/leveldb_base/util/random.h b/leveldb_base/util/random.h
new file mode 100644
index 0000000..fe76ab4
--- /dev/null
+++ b/leveldb_base/util/random.h
@@ -0,0 +1,63 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_UTIL_RANDOM_H_
+#define STORAGE_LEVELDB_UTIL_RANDOM_H_
+
+#include <cstdint>
+
+namespace leveldb {
+
+// A very simple random number generator.  Not especially good at
+// generating truly random bits, but good enough for our needs in this
+// package.
+class Random {
+ private:
+  uint32_t seed_;
+
+ public:
+  explicit Random(uint32_t s) : seed_(s & 0x7fffffffu) {
+    // Avoid bad seeds.
+    if (seed_ == 0 || seed_ == 2147483647L) {
+      seed_ = 1;
+    }
+  }
+  uint32_t Next() {
+    static const uint32_t M = 2147483647L;  // 2^31-1
+    static const uint64_t A = 16807;        // bits 14, 8, 7, 5, 2, 1, 0
+    // We are computing
+    //       seed_ = (seed_ * A) % M,    where M = 2^31-1
+    //
+    // seed_ must not be zero or M, or else all subsequent computed values
+    // will be zero or M respectively.  For all other values, seed_ will end
+    // up cycling through every number in [1,M-1]
+    uint64_t product = seed_ * A;
+
+    // Compute (product % M) using the fact that ((x << 31) % M) == x.
+    seed_ = static_cast<uint32_t>((product >> 31) + (product & M));
+    // The first reduction may overflow by 1 bit, so we may need to
+    // repeat.  mod == M is not possible; using > allows the faster
+    // sign-bit-based test.
+    if (seed_ > M) {
+      seed_ -= M;
+    }
+    return seed_;
+  }
+  // Returns a uniformly distributed value in the range [0..n-1]
+  // REQUIRES: n > 0
+  uint32_t Uniform(int n) { return Next() % n; }
+
+  // Randomly returns true ~"1/n" of the time, and false otherwise.
+  // REQUIRES: n > 0
+  bool OneIn(int n) { return (Next() % n) == 0; }
+
+  // Skewed: pick "base" uniformly from range [0,max_log] and then
+  // return "base" random bits.  The effect is to pick a number in the
+  // range [0,2^max_log-1] with exponential bias towards smaller numbers.
+  uint32_t Skewed(int max_log) { return Uniform(1 << Uniform(max_log + 1)); }
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_UTIL_RANDOM_H_
diff --git a/leveldb_base/util/status.cc b/leveldb_base/util/status.cc
new file mode 100644
index 0000000..0559f5b
--- /dev/null
+++ b/leveldb_base/util/status.cc
@@ -0,0 +1,77 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "leveldb/status.h"
+
+#include <cstdio>
+
+#include "port/port.h"
+
+namespace leveldb {
+
+const char* Status::CopyState(const char* state) {
+  uint32_t size;
+  std::memcpy(&size, state, sizeof(size));
+  char* result = new char[size + 5];
+  std::memcpy(result, state, size + 5);
+  return result;
+}
+
+Status::Status(Code code, const Slice& msg, const Slice& msg2) {
+  assert(code != kOk);
+  const uint32_t len1 = static_cast<uint32_t>(msg.size());
+  const uint32_t len2 = static_cast<uint32_t>(msg2.size());
+  const uint32_t size = len1 + (len2 ? (2 + len2) : 0);
+  char* result = new char[size + 5];
+  std::memcpy(result, &size, sizeof(size));
+  result[4] = static_cast<char>(code);
+  std::memcpy(result + 5, msg.data(), len1);
+  if (len2) {
+    result[5 + len1] = ':';
+    result[6 + len1] = ' ';
+    std::memcpy(result + 7 + len1, msg2.data(), len2);
+  }
+  state_ = result;
+}
+
+std::string Status::ToString() const {
+  if (state_ == nullptr) {
+    return "OK";
+  } else {
+    char tmp[30];
+    const char* type;
+    switch (code()) {
+      case kOk:
+        type = "OK";
+        break;
+      case kNotFound:
+        type = "NotFound: ";
+        break;
+      case kCorruption:
+        type = "Corruption: ";
+        break;
+      case kNotSupported:
+        type = "Not implemented: ";
+        break;
+      case kInvalidArgument:
+        type = "Invalid argument: ";
+        break;
+      case kIOError:
+        type = "IO error: ";
+        break;
+      default:
+        std::snprintf(tmp, sizeof(tmp),
+                      "Unknown code(%d): ", static_cast<int>(code()));
+        type = tmp;
+        break;
+    }
+    std::string result(type);
+    uint32_t length;
+    std::memcpy(&length, state_, sizeof(length));
+    result.append(state_ + 5, length);
+    return result;
+  }
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/util/status_test.cc b/leveldb_base/util/status_test.cc
new file mode 100644
index 0000000..dbf5faa
--- /dev/null
+++ b/leveldb_base/util/status_test.cc
@@ -0,0 +1,39 @@
+// Copyright (c) 2018 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "leveldb/status.h"
+
+#include <utility>
+
+#include "gtest/gtest.h"
+#include "leveldb/slice.h"
+
+namespace leveldb {
+
+TEST(Status, MoveConstructor) {
+  {
+    Status ok = Status::OK();
+    Status ok2 = std::move(ok);
+
+    ASSERT_TRUE(ok2.ok());
+  }
+
+  {
+    Status status = Status::NotFound("custom NotFound status message");
+    Status status2 = std::move(status);
+
+    ASSERT_TRUE(status2.IsNotFound());
+    ASSERT_EQ("NotFound: custom NotFound status message", status2.ToString());
+  }
+
+  {
+    Status self_moved = Status::IOError("custom IOError status message");
+
+    // Needed to bypass compiler warning about explicit move-assignment.
+    Status& self_moved_reference = self_moved;
+    self_moved_reference = std::move(self_moved);
+  }
+}
+
+}  // namespace leveldb
diff --git a/leveldb_base/util/testutil.cc b/leveldb_base/util/testutil.cc
new file mode 100644
index 0000000..5f77b08
--- /dev/null
+++ b/leveldb_base/util/testutil.cc
@@ -0,0 +1,51 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "util/testutil.h"
+
+#include <string>
+
+#include "util/random.h"
+
+namespace leveldb {
+namespace test {
+
+Slice RandomString(Random* rnd, int len, std::string* dst) {
+  dst->resize(len);
+  for (int i = 0; i < len; i++) {
+    (*dst)[i] = static_cast<char>(' ' + rnd->Uniform(95));  // ' ' .. '~'
+  }
+  return Slice(*dst);
+}
+
+std::string RandomKey(Random* rnd, int len) {
+  // Make sure to generate a wide variety of characters so we
+  // test the boundary conditions for short-key optimizations.
+  static const char kTestChars[] = {'\0', '\1', 'a',    'b',    'c',
+                                    'd',  'e',  '\xfd', '\xfe', '\xff'};
+  std::string result;
+  for (int i = 0; i < len; i++) {
+    result += kTestChars[rnd->Uniform(sizeof(kTestChars))];
+  }
+  return result;
+}
+
+Slice CompressibleString(Random* rnd, double compressed_fraction, size_t len,
+                         std::string* dst) {
+  int raw = static_cast<int>(len * compressed_fraction);
+  if (raw < 1) raw = 1;
+  std::string raw_data;
+  RandomString(rnd, raw, &raw_data);
+
+  // Duplicate the random data until we have filled "len" bytes
+  dst->clear();
+  while (dst->size() < len) {
+    dst->append(raw_data);
+  }
+  dst->resize(len);
+  return Slice(*dst);
+}
+
+}  // namespace test
+}  // namespace leveldb
diff --git a/leveldb_base/util/testutil.h b/leveldb_base/util/testutil.h
new file mode 100644
index 0000000..e0e2d64
--- /dev/null
+++ b/leveldb_base/util/testutil.h
@@ -0,0 +1,82 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_UTIL_TESTUTIL_H_
+#define STORAGE_LEVELDB_UTIL_TESTUTIL_H_
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "helpers/memenv/memenv.h"
+#include "leveldb/env.h"
+#include "leveldb/slice.h"
+#include "util/random.h"
+
+namespace leveldb {
+namespace test {
+
+MATCHER(IsOK, "") { return arg.ok(); }
+
+// Macros for testing the results of functions that return leveldb::Status or
+// absl::StatusOr<T> (for any type T).
+#define EXPECT_LEVELDB_OK(expression) \
+  EXPECT_THAT(expression, leveldb::test::IsOK())
+#define ASSERT_LEVELDB_OK(expression) \
+  ASSERT_THAT(expression, leveldb::test::IsOK())
+
+// Returns the random seed used at the start of the current test run.
+inline int RandomSeed() {
+  return testing::UnitTest::GetInstance()->random_seed();
+}
+
+// Store in *dst a random string of length "len" and return a Slice that
+// references the generated data.
+Slice RandomString(Random* rnd, int len, std::string* dst);
+
+// Return a random key with the specified length that may contain interesting
+// characters (e.g. \x00, \xff, etc.).
+std::string RandomKey(Random* rnd, int len);
+
+// Store in *dst a string of length "len" that will compress to
+// "N*compressed_fraction" bytes and return a Slice that references
+// the generated data.
+Slice CompressibleString(Random* rnd, double compressed_fraction, size_t len,
+                         std::string* dst);
+
+// A wrapper that allows injection of errors.
+class ErrorEnv : public EnvWrapper {
+ public:
+  bool writable_file_error_;
+  int num_writable_file_errors_;
+
+  ErrorEnv()
+      : EnvWrapper(NewMemEnv(Env::Default())),
+        writable_file_error_(false),
+        num_writable_file_errors_(0) {}
+  ~ErrorEnv() override { delete target(); }
+
+  Status NewWritableFile(const std::string& fname,
+                         WritableFile** result) override {
+    if (writable_file_error_) {
+      ++num_writable_file_errors_;
+      *result = nullptr;
+      return Status::IOError(fname, "fake error");
+    }
+    return target()->NewWritableFile(fname, result);
+  }
+
+  Status NewAppendableFile(const std::string& fname,
+                           WritableFile** result) override {
+    if (writable_file_error_) {
+      ++num_writable_file_errors_;
+      *result = nullptr;
+      return Status::IOError(fname, "fake error");
+    }
+    return target()->NewAppendableFile(fname, result);
+  }
+};
+
+}  // namespace test
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_UTIL_TESTUTIL_H_
diff --git a/leveldb_base/util/windows_logger.h b/leveldb_base/util/windows_logger.h
new file mode 100644
index 0000000..26e6c7b
--- /dev/null
+++ b/leveldb_base/util/windows_logger.h
@@ -0,0 +1,124 @@
+// Copyright (c) 2018 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// Logger implementation for the Windows platform.
+
+#ifndef STORAGE_LEVELDB_UTIL_WINDOWS_LOGGER_H_
+#define STORAGE_LEVELDB_UTIL_WINDOWS_LOGGER_H_
+
+#include <cassert>
+#include <cstdarg>
+#include <cstdio>
+#include <ctime>
+#include <sstream>
+#include <thread>
+
+#include "leveldb/env.h"
+
+namespace leveldb {
+
+class WindowsLogger final : public Logger {
+ public:
+  // Creates a logger that writes to the given file.
+  //
+  // The PosixLogger instance takes ownership of the file handle.
+  explicit WindowsLogger(std::FILE* fp) : fp_(fp) { assert(fp != nullptr); }
+
+  ~WindowsLogger() override { std::fclose(fp_); }
+
+  void Logv(const char* format, std::va_list arguments) override {
+    // Record the time as close to the Logv() call as possible.
+    SYSTEMTIME now_components;
+    ::GetLocalTime(&now_components);
+
+    // Record the thread ID.
+    constexpr const int kMaxThreadIdSize = 32;
+    std::ostringstream thread_stream;
+    thread_stream << std::this_thread::get_id();
+    std::string thread_id = thread_stream.str();
+    if (thread_id.size() > kMaxThreadIdSize) {
+      thread_id.resize(kMaxThreadIdSize);
+    }
+
+    // We first attempt to print into a stack-allocated buffer. If this attempt
+    // fails, we make a second attempt with a dynamically allocated buffer.
+    constexpr const int kStackBufferSize = 512;
+    char stack_buffer[kStackBufferSize];
+    static_assert(sizeof(stack_buffer) == static_cast<size_t>(kStackBufferSize),
+                  "sizeof(char) is expected to be 1 in C++");
+
+    int dynamic_buffer_size = 0;  // Computed in the first iteration.
+    for (int iteration = 0; iteration < 2; ++iteration) {
+      const int buffer_size =
+          (iteration == 0) ? kStackBufferSize : dynamic_buffer_size;
+      char* const buffer =
+          (iteration == 0) ? stack_buffer : new char[dynamic_buffer_size];
+
+      // Print the header into the buffer.
+      int buffer_offset = std::snprintf(
+          buffer, buffer_size, "%04d/%02d/%02d-%02d:%02d:%02d.%06d %s ",
+          now_components.wYear, now_components.wMonth, now_components.wDay,
+          now_components.wHour, now_components.wMinute, now_components.wSecond,
+          static_cast<int>(now_components.wMilliseconds * 1000),
+          thread_id.c_str());
+
+      // The header can be at most 28 characters (10 date + 15 time +
+      // 3 delimiters) plus the thread ID, which should fit comfortably into the
+      // static buffer.
+      assert(buffer_offset <= 28 + kMaxThreadIdSize);
+      static_assert(28 + kMaxThreadIdSize < kStackBufferSize,
+                    "stack-allocated buffer may not fit the message header");
+      assert(buffer_offset < buffer_size);
+
+      // Print the message into the buffer.
+      std::va_list arguments_copy;
+      va_copy(arguments_copy, arguments);
+      buffer_offset +=
+          std::vsnprintf(buffer + buffer_offset, buffer_size - buffer_offset,
+                         format, arguments_copy);
+      va_end(arguments_copy);
+
+      // The code below may append a newline at the end of the buffer, which
+      // requires an extra character.
+      if (buffer_offset >= buffer_size - 1) {
+        // The message did not fit into the buffer.
+        if (iteration == 0) {
+          // Re-run the loop and use a dynamically-allocated buffer. The buffer
+          // will be large enough for the log message, an extra newline and a
+          // null terminator.
+          dynamic_buffer_size = buffer_offset + 2;
+          continue;
+        }
+
+        // The dynamically-allocated buffer was incorrectly sized. This should
+        // not happen, assuming a correct implementation of std::(v)snprintf.
+        // Fail in tests, recover by truncating the log message in production.
+        assert(false);
+        buffer_offset = buffer_size - 1;
+      }
+
+      // Add a newline if necessary.
+      if (buffer[buffer_offset - 1] != '\n') {
+        buffer[buffer_offset] = '\n';
+        ++buffer_offset;
+      }
+
+      assert(buffer_offset <= buffer_size);
+      std::fwrite(buffer, 1, buffer_offset, fp_);
+      std::fflush(fp_);
+
+      if (iteration != 0) {
+        delete[] buffer;
+      }
+      break;
+    }
+  }
+
+ private:
+  std::FILE* const fp_;
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_UTIL_WINDOWS_LOGGER_H_