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816 行
26 KiB
816 行
26 KiB
// Copyright (c) 2018 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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// Prevent Windows headers from defining min/max macros and instead
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// use STL.
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#ifndef NOMINMAX
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#define NOMINMAX
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#endif // ifndef NOMINMAX
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#include <windows.h>
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#include <algorithm>
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#include <atomic>
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#include <chrono>
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#include <condition_variable>
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#include <cstddef>
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#include <cstdint>
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#include <cstdlib>
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#include <cstring>
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#include <memory>
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#include <mutex>
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#include <queue>
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#include <sstream>
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#include <string>
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#include <vector>
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#include "leveldb/env.h"
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#include "leveldb/slice.h"
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#include "port/port.h"
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#include "port/thread_annotations.h"
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#include "util/env_windows_test_helper.h"
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#include "util/logging.h"
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#include "util/mutexlock.h"
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#include "util/windows_logger.h"
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namespace leveldb {
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namespace {
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constexpr const size_t kWritableFileBufferSize = 65536;
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// Up to 1000 mmaps for 64-bit binaries; none for 32-bit.
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constexpr int kDefaultMmapLimit = (sizeof(void*) >= 8) ? 1000 : 0;
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// Can be set by by EnvWindowsTestHelper::SetReadOnlyMMapLimit().
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int g_mmap_limit = kDefaultMmapLimit;
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std::string GetWindowsErrorMessage(DWORD error_code) {
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std::string message;
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char* error_text = nullptr;
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// Use MBCS version of FormatMessage to match return value.
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size_t error_text_size = ::FormatMessageA(
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FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ALLOCATE_BUFFER |
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FORMAT_MESSAGE_IGNORE_INSERTS,
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nullptr, error_code, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
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reinterpret_cast<char*>(&error_text), 0, nullptr);
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if (!error_text) {
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return message;
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}
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message.assign(error_text, error_text_size);
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::LocalFree(error_text);
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return message;
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}
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Status WindowsError(const std::string& context, DWORD error_code) {
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if (error_code == ERROR_FILE_NOT_FOUND || error_code == ERROR_PATH_NOT_FOUND)
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return Status::NotFound(context, GetWindowsErrorMessage(error_code));
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return Status::IOError(context, GetWindowsErrorMessage(error_code));
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}
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class ScopedHandle {
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public:
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ScopedHandle(HANDLE handle) : handle_(handle) {}
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ScopedHandle(const ScopedHandle&) = delete;
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ScopedHandle(ScopedHandle&& other) noexcept : handle_(other.Release()) {}
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~ScopedHandle() { Close(); }
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ScopedHandle& operator=(const ScopedHandle&) = delete;
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ScopedHandle& operator=(ScopedHandle&& rhs) noexcept {
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if (this != &rhs) handle_ = rhs.Release();
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return *this;
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}
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bool Close() {
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if (!is_valid()) {
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return true;
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}
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HANDLE h = handle_;
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handle_ = INVALID_HANDLE_VALUE;
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return ::CloseHandle(h);
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}
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bool is_valid() const {
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return handle_ != INVALID_HANDLE_VALUE && handle_ != nullptr;
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}
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HANDLE get() const { return handle_; }
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HANDLE Release() {
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HANDLE h = handle_;
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handle_ = INVALID_HANDLE_VALUE;
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return h;
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}
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private:
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HANDLE handle_;
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};
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// Helper class to limit resource usage to avoid exhaustion.
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// Currently used to limit read-only file descriptors and mmap file usage
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// so that we do not run out of file descriptors or virtual memory, or run into
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// kernel performance problems for very large databases.
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class Limiter {
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public:
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// Limit maximum number of resources to |max_acquires|.
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Limiter(int max_acquires)
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:
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#if !defined(NDEBUG)
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max_acquires_(max_acquires),
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#endif // !defined(NDEBUG)
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acquires_allowed_(max_acquires) {
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assert(max_acquires >= 0);
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}
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Limiter(const Limiter&) = delete;
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Limiter operator=(const Limiter&) = delete;
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// If another resource is available, acquire it and return true.
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// Else return false.
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bool Acquire() {
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int old_acquires_allowed =
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acquires_allowed_.fetch_sub(1, std::memory_order_relaxed);
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if (old_acquires_allowed > 0) return true;
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acquires_allowed_.fetch_add(1, std::memory_order_relaxed);
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return false;
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}
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// Release a resource acquired by a previous call to Acquire() that returned
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// true.
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void Release() {
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int old_acquires_allowed =
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acquires_allowed_.fetch_add(1, std::memory_order_relaxed);
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// Silence compiler warnings about unused arguments when NDEBUG is defined.
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(void)old_acquires_allowed;
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// If the check below fails, Release() was called more times than acquire.
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assert(old_acquires_allowed < max_acquires_);
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}
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private:
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#if !defined(NDEBUG)
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// Catches an excessive number of Release() calls.
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const int max_acquires_;
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#endif // !defined(NDEBUG)
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// The number of available resources.
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//
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// This is a counter and is not tied to the invariants of any other class, so
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// it can be operated on safely using std::memory_order_relaxed.
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std::atomic<int> acquires_allowed_;
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};
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class WindowsSequentialFile : public SequentialFile {
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public:
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WindowsSequentialFile(std::string filename, ScopedHandle handle)
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: handle_(std::move(handle)), filename_(std::move(filename)) {}
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~WindowsSequentialFile() override {}
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Status Read(size_t n, Slice* result, char* scratch) override {
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DWORD bytes_read;
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// DWORD is 32-bit, but size_t could technically be larger. However leveldb
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// files are limited to leveldb::Options::max_file_size which is clamped to
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// 1<<30 or 1 GiB.
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assert(n <= std::numeric_limits<DWORD>::max());
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if (!::ReadFile(handle_.get(), scratch, static_cast<DWORD>(n), &bytes_read,
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nullptr)) {
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return WindowsError(filename_, ::GetLastError());
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}
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*result = Slice(scratch, bytes_read);
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return Status::OK();
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}
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Status Skip(uint64_t n) override {
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LARGE_INTEGER distance;
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distance.QuadPart = n;
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if (!::SetFilePointerEx(handle_.get(), distance, nullptr, FILE_CURRENT)) {
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return WindowsError(filename_, ::GetLastError());
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}
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return Status::OK();
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}
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private:
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const ScopedHandle handle_;
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const std::string filename_;
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};
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class WindowsRandomAccessFile : public RandomAccessFile {
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public:
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WindowsRandomAccessFile(std::string filename, ScopedHandle handle)
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: handle_(std::move(handle)), filename_(std::move(filename)) {}
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~WindowsRandomAccessFile() override = default;
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Status Read(uint64_t offset, size_t n, Slice* result,
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char* scratch) const override {
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DWORD bytes_read = 0;
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OVERLAPPED overlapped = {0};
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overlapped.OffsetHigh = static_cast<DWORD>(offset >> 32);
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overlapped.Offset = static_cast<DWORD>(offset);
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if (!::ReadFile(handle_.get(), scratch, static_cast<DWORD>(n), &bytes_read,
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&overlapped)) {
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DWORD error_code = ::GetLastError();
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if (error_code != ERROR_HANDLE_EOF) {
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*result = Slice(scratch, 0);
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return Status::IOError(filename_, GetWindowsErrorMessage(error_code));
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}
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}
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*result = Slice(scratch, bytes_read);
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return Status::OK();
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}
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private:
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const ScopedHandle handle_;
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const std::string filename_;
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};
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class WindowsMmapReadableFile : public RandomAccessFile {
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public:
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// base[0,length-1] contains the mmapped contents of the file.
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WindowsMmapReadableFile(std::string filename, char* mmap_base, size_t length,
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Limiter* mmap_limiter)
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: mmap_base_(mmap_base),
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length_(length),
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mmap_limiter_(mmap_limiter),
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filename_(std::move(filename)) {}
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~WindowsMmapReadableFile() override {
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::UnmapViewOfFile(mmap_base_);
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mmap_limiter_->Release();
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}
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Status Read(uint64_t offset, size_t n, Slice* result,
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char* scratch) const override {
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if (offset + n > length_) {
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*result = Slice();
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return WindowsError(filename_, ERROR_INVALID_PARAMETER);
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}
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*result = Slice(mmap_base_ + offset, n);
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return Status::OK();
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}
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private:
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char* const mmap_base_;
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const size_t length_;
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Limiter* const mmap_limiter_;
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const std::string filename_;
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};
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class WindowsWritableFile : public WritableFile {
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public:
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WindowsWritableFile(std::string filename, ScopedHandle handle)
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: pos_(0), handle_(std::move(handle)), filename_(std::move(filename)) {}
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~WindowsWritableFile() override = default;
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Status Append(const Slice& data) override {
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size_t write_size = data.size();
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const char* write_data = data.data();
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// Fit as much as possible into buffer.
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size_t copy_size = std::min(write_size, kWritableFileBufferSize - pos_);
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std::memcpy(buf_ + pos_, write_data, copy_size);
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write_data += copy_size;
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write_size -= copy_size;
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pos_ += copy_size;
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if (write_size == 0) {
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return Status::OK();
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}
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// Can't fit in buffer, so need to do at least one write.
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Status status = FlushBuffer();
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if (!status.ok()) {
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return status;
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}
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// Small writes go to buffer, large writes are written directly.
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if (write_size < kWritableFileBufferSize) {
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std::memcpy(buf_, write_data, write_size);
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pos_ = write_size;
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return Status::OK();
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}
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return WriteUnbuffered(write_data, write_size);
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}
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Status Close() override {
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Status status = FlushBuffer();
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if (!handle_.Close() && status.ok()) {
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status = WindowsError(filename_, ::GetLastError());
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}
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return status;
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}
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Status Flush() override { return FlushBuffer(); }
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Status Sync() override {
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// On Windows no need to sync parent directory. Its metadata will be updated
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// via the creation of the new file, without an explicit sync.
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Status status = FlushBuffer();
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if (!status.ok()) {
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return status;
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}
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if (!::FlushFileBuffers(handle_.get())) {
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return Status::IOError(filename_,
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GetWindowsErrorMessage(::GetLastError()));
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}
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return Status::OK();
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}
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private:
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Status FlushBuffer() {
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Status status = WriteUnbuffered(buf_, pos_);
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pos_ = 0;
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return status;
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}
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Status WriteUnbuffered(const char* data, size_t size) {
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DWORD bytes_written;
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if (!::WriteFile(handle_.get(), data, static_cast<DWORD>(size),
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&bytes_written, nullptr)) {
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return Status::IOError(filename_,
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GetWindowsErrorMessage(::GetLastError()));
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}
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return Status::OK();
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}
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// buf_[0, pos_-1] contains data to be written to handle_.
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char buf_[kWritableFileBufferSize];
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size_t pos_;
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ScopedHandle handle_;
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const std::string filename_;
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};
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// Lock or unlock the entire file as specified by |lock|. Returns true
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// when successful, false upon failure. Caller should call ::GetLastError()
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// to determine cause of failure
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bool LockOrUnlock(HANDLE handle, bool lock) {
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if (lock) {
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return ::LockFile(handle,
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/*dwFileOffsetLow=*/0, /*dwFileOffsetHigh=*/0,
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/*nNumberOfBytesToLockLow=*/MAXDWORD,
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/*nNumberOfBytesToLockHigh=*/MAXDWORD);
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} else {
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return ::UnlockFile(handle,
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/*dwFileOffsetLow=*/0, /*dwFileOffsetHigh=*/0,
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/*nNumberOfBytesToLockLow=*/MAXDWORD,
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/*nNumberOfBytesToLockHigh=*/MAXDWORD);
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}
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}
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class WindowsFileLock : public FileLock {
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public:
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WindowsFileLock(ScopedHandle handle, std::string filename)
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: handle_(std::move(handle)), filename_(std::move(filename)) {}
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const ScopedHandle& handle() const { return handle_; }
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const std::string& filename() const { return filename_; }
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private:
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const ScopedHandle handle_;
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const std::string filename_;
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};
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class WindowsEnv : public Env {
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public:
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WindowsEnv();
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~WindowsEnv() override {
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static const char msg[] =
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"WindowsEnv singleton destroyed. Unsupported behavior!\n";
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std::fwrite(msg, 1, sizeof(msg), stderr);
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std::abort();
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}
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Status NewSequentialFile(const std::string& filename,
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SequentialFile** result) override {
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*result = nullptr;
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DWORD desired_access = GENERIC_READ;
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DWORD share_mode = FILE_SHARE_READ;
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ScopedHandle handle = ::CreateFileA(
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filename.c_str(), desired_access, share_mode,
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/*lpSecurityAttributes=*/nullptr, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL,
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/*hTemplateFile=*/nullptr);
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if (!handle.is_valid()) {
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return WindowsError(filename, ::GetLastError());
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}
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*result = new WindowsSequentialFile(filename, std::move(handle));
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return Status::OK();
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}
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Status NewRandomAccessFile(const std::string& filename,
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RandomAccessFile** result) override {
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*result = nullptr;
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DWORD desired_access = GENERIC_READ;
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DWORD share_mode = FILE_SHARE_READ;
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ScopedHandle handle =
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::CreateFileA(filename.c_str(), desired_access, share_mode,
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/*lpSecurityAttributes=*/nullptr, OPEN_EXISTING,
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FILE_ATTRIBUTE_READONLY,
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/*hTemplateFile=*/nullptr);
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if (!handle.is_valid()) {
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return WindowsError(filename, ::GetLastError());
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}
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if (!mmap_limiter_.Acquire()) {
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*result = new WindowsRandomAccessFile(filename, std::move(handle));
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return Status::OK();
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}
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LARGE_INTEGER file_size;
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Status status;
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if (!::GetFileSizeEx(handle.get(), &file_size)) {
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mmap_limiter_.Release();
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return WindowsError(filename, ::GetLastError());
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}
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ScopedHandle mapping =
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::CreateFileMappingA(handle.get(),
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/*security attributes=*/nullptr, PAGE_READONLY,
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/*dwMaximumSizeHigh=*/0,
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/*dwMaximumSizeLow=*/0,
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/*lpName=*/nullptr);
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if (mapping.is_valid()) {
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void* mmap_base = ::MapViewOfFile(mapping.get(), FILE_MAP_READ,
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/*dwFileOffsetHigh=*/0,
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/*dwFileOffsetLow=*/0,
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/*dwNumberOfBytesToMap=*/0);
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if (mmap_base) {
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*result = new WindowsMmapReadableFile(
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filename, reinterpret_cast<char*>(mmap_base),
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static_cast<size_t>(file_size.QuadPart), &mmap_limiter_);
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return Status::OK();
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}
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}
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mmap_limiter_.Release();
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return WindowsError(filename, ::GetLastError());
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}
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Status NewWritableFile(const std::string& filename,
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WritableFile** result) override {
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DWORD desired_access = GENERIC_WRITE;
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DWORD share_mode = 0; // Exclusive access.
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ScopedHandle handle = ::CreateFileA(
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filename.c_str(), desired_access, share_mode,
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/*lpSecurityAttributes=*/nullptr, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL,
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/*hTemplateFile=*/nullptr);
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if (!handle.is_valid()) {
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*result = nullptr;
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return WindowsError(filename, ::GetLastError());
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}
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*result = new WindowsWritableFile(filename, std::move(handle));
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return Status::OK();
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}
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Status NewAppendableFile(const std::string& filename,
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WritableFile** result) override {
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DWORD desired_access = FILE_APPEND_DATA;
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DWORD share_mode = 0; // Exclusive access.
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ScopedHandle handle = ::CreateFileA(
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filename.c_str(), desired_access, share_mode,
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/*lpSecurityAttributes=*/nullptr, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL,
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/*hTemplateFile=*/nullptr);
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if (!handle.is_valid()) {
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*result = nullptr;
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return WindowsError(filename, ::GetLastError());
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}
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*result = new WindowsWritableFile(filename, std::move(handle));
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return Status::OK();
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}
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bool FileExists(const std::string& filename) override {
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return GetFileAttributesA(filename.c_str()) != INVALID_FILE_ATTRIBUTES;
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}
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Status GetChildren(const std::string& directory_path,
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std::vector<std::string>* result) override {
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const std::string find_pattern = directory_path + "\\*";
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WIN32_FIND_DATAA find_data;
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HANDLE dir_handle = ::FindFirstFileA(find_pattern.c_str(), &find_data);
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if (dir_handle == INVALID_HANDLE_VALUE) {
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DWORD last_error = ::GetLastError();
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if (last_error == ERROR_FILE_NOT_FOUND) {
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return Status::OK();
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}
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return WindowsError(directory_path, last_error);
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}
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do {
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char base_name[_MAX_FNAME];
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char ext[_MAX_EXT];
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if (!_splitpath_s(find_data.cFileName, nullptr, 0, nullptr, 0, base_name,
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ARRAYSIZE(base_name), ext, ARRAYSIZE(ext))) {
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result->emplace_back(std::string(base_name) + ext);
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}
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} while (::FindNextFileA(dir_handle, &find_data));
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DWORD last_error = ::GetLastError();
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::FindClose(dir_handle);
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if (last_error != ERROR_NO_MORE_FILES) {
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return WindowsError(directory_path, last_error);
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}
|
|
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
|