作者: 韩晨旭 10225101440 李畅 10225102463
 
 

796 рядки
25 KiB

// 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) : acquires_allowed_(max_acquires) {}
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() { acquires_allowed_.fetch_add(1, std::memory_order_relaxed); }
private:
// 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(), "w");
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 beacuse 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::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::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