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Diffstat (limited to 'src/leveldb/util/env_windows.cc')
| -rw-r--r-- | src/leveldb/util/env_windows.cc | 849 |
1 files changed, 849 insertions, 0 deletions
diff --git a/src/leveldb/util/env_windows.cc b/src/leveldb/util/env_windows.cc new file mode 100644 index 0000000000..1834206562 --- /dev/null +++ b/src/leveldb/util/env_windows.cc @@ -0,0 +1,849 @@ +// 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" + +#if defined(DeleteFile) +#undef DeleteFile +#endif // defined(DeleteFile) + +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(); + } + + std::string GetName() const override { return filename_; } + + 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(); + } + + std::string GetName() const override { return filename_; } + + 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(); + } + + std::string GetName() const override { return filename_; } + + 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(); + } + + std::string GetName() const override { return filename_; } + + 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; + auto wFilename = toUtf16(filename); + ScopedHandle handle = ::CreateFileW( + wFilename.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; + auto wFilename = toUtf16(filename); + ScopedHandle handle = + ::CreateFileW(wFilename.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 = + ::CreateFileMappingW(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. + auto wFilename = toUtf16(filename); + ScopedHandle handle = ::CreateFileW( + wFilename.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. + auto wFilename = toUtf16(filename); + ScopedHandle handle = ::CreateFileW( + wFilename.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 { + auto wFilename = toUtf16(filename); + return GetFileAttributesW(wFilename.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_DATAW find_data; + auto wFind_pattern = toUtf16(find_pattern); + HANDLE dir_handle = ::FindFirstFileW(wFind_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]; + + auto find_data_filename = toUtf8(find_data.cFileName); + if (!_splitpath_s(find_data_filename.c_str(), nullptr, 0, nullptr, 0, + base_name, ARRAYSIZE(base_name), ext, ARRAYSIZE(ext))) { + result->emplace_back(std::string(base_name) + ext); + } + } while (::FindNextFileW(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 DeleteFile(const std::string& filename) override { + auto wFilename = toUtf16(filename); + if (!::DeleteFileW(wFilename.c_str())) { + return WindowsError(filename, ::GetLastError()); + } + return Status::OK(); + } + + Status CreateDir(const std::string& dirname) override { + auto wDirname = toUtf16(dirname); + if (!::CreateDirectoryW(wDirname.c_str(), nullptr)) { + return WindowsError(dirname, ::GetLastError()); + } + return Status::OK(); + } + + Status DeleteDir(const std::string& dirname) override { + auto wDirname = toUtf16(dirname); + if (!::RemoveDirectoryW(wDirname.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; + auto wFilename = toUtf16(filename); + if (!::GetFileAttributesExW(wFilename.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. + auto wFrom = toUtf16(from); + auto wTo = toUtf16(to); + if (::MoveFileW(wFrom.c_str(), wTo.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 (::ReplaceFileW(wTo.c_str(), wFrom.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; + auto wFilename = toUtf16(filename); + ScopedHandle handle = ::CreateFileW( + wFilename.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(); + } + + wchar_t wtmp_path[MAX_PATH]; + if (!GetTempPathW(ARRAYSIZE(wtmp_path), wtmp_path)) { + return WindowsError("GetTempPath", ::GetLastError()); + } + std::string tmp_path = toUtf8(std::wstring(wtmp_path)); + 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 { + auto wFilename = toUtf16(filename); + std::FILE* fp = _wfopen(wFilename.c_str(), L"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. + + // Converts a Windows wide multi-byte UTF-16 string to a UTF-8 string. + // See http://utf8everywhere.org/#windows + std::string toUtf8(const std::wstring& wstr) { + if (wstr.empty()) return std::string(); + int size_needed = WideCharToMultiByte( + CP_UTF8, 0, &wstr[0], (int)wstr.size(), NULL, 0, NULL, NULL); + std::string strTo(size_needed, 0); + WideCharToMultiByte(CP_UTF8, 0, &wstr[0], (int)wstr.size(), &strTo[0], + size_needed, NULL, NULL); + return strTo; + } + + // Converts a UTF-8 string to a Windows UTF-16 multi-byte wide character + // string. + // See http://utf8everywhere.org/#windows + std::wstring toUtf16(const std::string& str) { + if (str.empty()) return std::wstring(); + int size_needed = + MultiByteToWideChar(CP_UTF8, 0, &str[0], (int)str.size(), NULL, 0); + std::wstring strTo(size_needed, 0); + MultiByteToWideChar(CP_UTF8, 0, &str[0], (int)str.size(), &strTo[0], + size_needed); + return strTo; + } +}; + +// 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 |