// Copyright (c) 2011 The Chromium Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. #include "base/file_util_proxy.h" #include "base/message_loop_proxy.h" // TODO(jianli): Move the code from anonymous namespace to base namespace so // that all of the base:: prefixes would be unnecessary. namespace { namespace { // Performs common checks for move and copy. // This also removes the destination directory if it's non-empty and all other // checks are passed (so that the copy/move correctly overwrites the // destination). static base::PlatformFileError PerformCommonCheckAndPreparationForMoveAndCopy( const FilePath& src_file_path, const FilePath& dest_file_path) { // Exits earlier if the source path does not exist. if (!file_util::PathExists(src_file_path)) return base::PLATFORM_FILE_ERROR_NOT_FOUND; // The parent of the |dest_file_path| does not exist. if (!file_util::DirectoryExists(dest_file_path.DirName())) return base::PLATFORM_FILE_ERROR_NOT_FOUND; // It is an error to try to copy/move an entry into its child. if (src_file_path.IsParent(dest_file_path)) return base::PLATFORM_FILE_ERROR_INVALID_OPERATION; // Now it is ok to return if the |dest_file_path| does not exist. if (!file_util::PathExists(dest_file_path)) return base::PLATFORM_FILE_OK; // |src_file_path| exists and is a directory. // |dest_file_path| exists and is a file. bool src_is_directory = file_util::DirectoryExists(src_file_path); bool dest_is_directory = file_util::DirectoryExists(dest_file_path); if (src_is_directory && !dest_is_directory) return base::PLATFORM_FILE_ERROR_NOT_A_DIRECTORY; // |src_file_path| exists and is a file. // |dest_file_path| exists and is a directory. if (!src_is_directory && dest_is_directory) return base::PLATFORM_FILE_ERROR_NOT_A_FILE; // It is an error to copy/move an entry into the same path. if (src_file_path.value() == dest_file_path.value()) return base::PLATFORM_FILE_ERROR_EXISTS; if (dest_is_directory) { // It is an error to copy/move an entry to a non-empty directory. // Otherwise the copy/move attempt must overwrite the destination, but // the file_util's Copy or Move method doesn't perform overwrite // on all platforms, so we delete the destination directory here. // TODO(kinuko): may be better to change the file_util::{Copy,Move}. if (!file_util::Delete(dest_file_path, false /* recursive */)) { if (!file_util::IsDirectoryEmpty(dest_file_path)) return base::PLATFORM_FILE_ERROR_NOT_EMPTY; return base::PLATFORM_FILE_ERROR_FAILED; } } return base::PLATFORM_FILE_OK; } } // anonymous namespace class MessageLoopRelay : public base::RefCountedThreadSafe { public: MessageLoopRelay() : origin_message_loop_proxy_( base::MessageLoopProxy::CreateForCurrentThread()), error_code_(base::PLATFORM_FILE_OK) { } bool Start(scoped_refptr message_loop_proxy, const tracked_objects::Location& from_here) { return message_loop_proxy->PostTask( from_here, NewRunnableMethod(this, &MessageLoopRelay::ProcessOnTargetThread)); } protected: friend class base::RefCountedThreadSafe; virtual ~MessageLoopRelay() {} // Called to perform work on the FILE thread. virtual void RunWork() = 0; // Called to notify the callback on the origin thread. virtual void RunCallback() = 0; void set_error_code(base::PlatformFileError error_code) { error_code_ = error_code; } base::PlatformFileError error_code() const { return error_code_; } private: void ProcessOnTargetThread() { RunWork(); origin_message_loop_proxy_->PostTask( FROM_HERE, NewRunnableMethod(this, &MessageLoopRelay::RunCallback)); } scoped_refptr origin_message_loop_proxy_; base::PlatformFileError error_code_; }; class RelayCreateOrOpen : public MessageLoopRelay { public: RelayCreateOrOpen( scoped_refptr message_loop_proxy, const FilePath& file_path, int file_flags, base::FileUtilProxy::CreateOrOpenCallback* callback) : message_loop_proxy_(message_loop_proxy), file_path_(file_path), file_flags_(file_flags), callback_(callback), file_handle_(base::kInvalidPlatformFileValue), created_(false) { DCHECK(callback); } protected: virtual ~RelayCreateOrOpen() { if (file_handle_ != base::kInvalidPlatformFileValue) base::FileUtilProxy::Close(message_loop_proxy_, file_handle_, NULL); } virtual void RunWork() { if (!file_util::DirectoryExists(file_path_.DirName())) { // If its parent does not exist, should return NOT_FOUND error. set_error_code(base::PLATFORM_FILE_ERROR_NOT_FOUND); return; } base::PlatformFileError error_code = base::PLATFORM_FILE_OK; file_handle_ = base::CreatePlatformFile(file_path_, file_flags_, &created_, &error_code); set_error_code(error_code); } virtual void RunCallback() { callback_->Run(error_code(), base::PassPlatformFile(&file_handle_), created_); delete callback_; } private: scoped_refptr message_loop_proxy_; FilePath file_path_; int file_flags_; base::FileUtilProxy::CreateOrOpenCallback* callback_; base::PlatformFile file_handle_; bool created_; }; class RelayCreateTemporary : public MessageLoopRelay { public: RelayCreateTemporary( scoped_refptr message_loop_proxy, base::FileUtilProxy::CreateTemporaryCallback* callback) : message_loop_proxy_(message_loop_proxy), callback_(callback), file_handle_(base::kInvalidPlatformFileValue) { DCHECK(callback); } protected: virtual ~RelayCreateTemporary() { if (file_handle_ != base::kInvalidPlatformFileValue) base::FileUtilProxy::Close(message_loop_proxy_, file_handle_, NULL); } virtual void RunWork() { // TODO(darin): file_util should have a variant of CreateTemporaryFile // that returns a FilePath and a PlatformFile. file_util::CreateTemporaryFile(&file_path_); // Use a fixed set of flags that are appropriate for writing to a temporary // file from the IO thread using a net::FileStream. int file_flags = base::PLATFORM_FILE_CREATE_ALWAYS | base::PLATFORM_FILE_WRITE | base::PLATFORM_FILE_ASYNC | base::PLATFORM_FILE_TEMPORARY; base::PlatformFileError error_code = base::PLATFORM_FILE_OK; file_handle_ = base::CreatePlatformFile(file_path_, file_flags, NULL, &error_code); set_error_code(error_code); } virtual void RunCallback() { callback_->Run(error_code(), base::PassPlatformFile(&file_handle_), file_path_); delete callback_; } private: scoped_refptr message_loop_proxy_; base::FileUtilProxy::CreateTemporaryCallback* callback_; base::PlatformFile file_handle_; FilePath file_path_; }; class RelayWithStatusCallback : public MessageLoopRelay { public: explicit RelayWithStatusCallback( base::FileUtilProxy::StatusCallback* callback) : callback_(callback) { // It is OK for callback to be NULL. } protected: virtual void RunCallback() { // The caller may not have been interested in the result. if (callback_) { callback_->Run(error_code()); delete callback_; } } private: base::FileUtilProxy::StatusCallback* callback_; }; class RelayClose : public RelayWithStatusCallback { public: RelayClose(base::PlatformFile file_handle, base::FileUtilProxy::StatusCallback* callback) : RelayWithStatusCallback(callback), file_handle_(file_handle) { } protected: virtual void RunWork() { if (!base::ClosePlatformFile(file_handle_)) set_error_code(base::PLATFORM_FILE_ERROR_FAILED); } private: base::PlatformFile file_handle_; }; class RelayEnsureFileExists : public MessageLoopRelay { public: RelayEnsureFileExists( scoped_refptr message_loop_proxy, const FilePath& file_path, base::FileUtilProxy::EnsureFileExistsCallback* callback) : message_loop_proxy_(message_loop_proxy), file_path_(file_path), callback_(callback), created_(false) { DCHECK(callback); } protected: virtual void RunWork() { if (!file_util::DirectoryExists(file_path_.DirName())) { // If its parent does not exist, should return NOT_FOUND error. set_error_code(base::PLATFORM_FILE_ERROR_NOT_FOUND); return; } base::PlatformFileError error_code = base::PLATFORM_FILE_OK; // Tries to create the |file_path_| exclusively. This should fail // with PLATFORM_FILE_ERROR_EXISTS if the path already exists. base::PlatformFile handle = base::CreatePlatformFile( file_path_, base::PLATFORM_FILE_CREATE | base::PLATFORM_FILE_READ, &created_, &error_code); if (error_code == base::PLATFORM_FILE_ERROR_EXISTS) { // Make sure created_ is false. created_ = false; error_code = base::PLATFORM_FILE_OK; } if (handle != base::kInvalidPlatformFileValue) base::ClosePlatformFile(handle); set_error_code(error_code); } virtual void RunCallback() { callback_->Run(error_code(), created_); delete callback_; } private: scoped_refptr message_loop_proxy_; FilePath file_path_; base::FileUtilProxy::EnsureFileExistsCallback* callback_; bool created_; }; class RelayDelete : public RelayWithStatusCallback { public: RelayDelete(const FilePath& file_path, bool recursive, base::FileUtilProxy::StatusCallback* callback) : RelayWithStatusCallback(callback), file_path_(file_path), recursive_(recursive) { } protected: virtual void RunWork() { if (!file_util::PathExists(file_path_)) { set_error_code(base::PLATFORM_FILE_ERROR_NOT_FOUND); return; } if (!file_util::Delete(file_path_, recursive_)) { if (!recursive_ && !file_util::IsDirectoryEmpty(file_path_)) { set_error_code(base::PLATFORM_FILE_ERROR_NOT_EMPTY); return; } set_error_code(base::PLATFORM_FILE_ERROR_FAILED); } } private: FilePath file_path_; bool recursive_; }; class RelayCopy : public RelayWithStatusCallback { public: RelayCopy(const FilePath& src_file_path, const FilePath& dest_file_path, base::FileUtilProxy::StatusCallback* callback) : RelayWithStatusCallback(callback), src_file_path_(src_file_path), dest_file_path_(dest_file_path) { } protected: virtual void RunWork() { set_error_code(PerformCommonCheckAndPreparationForMoveAndCopy( src_file_path_, dest_file_path_)); if (error_code() != base::PLATFORM_FILE_OK) return; if (!file_util::CopyDirectory(src_file_path_, dest_file_path_, true /* recursive */)) set_error_code(base::PLATFORM_FILE_ERROR_FAILED); } private: FilePath src_file_path_; FilePath dest_file_path_; }; class RelayMove : public RelayWithStatusCallback { public: RelayMove(const FilePath& src_file_path, const FilePath& dest_file_path, base::FileUtilProxy::StatusCallback* callback) : RelayWithStatusCallback(callback), src_file_path_(src_file_path), dest_file_path_(dest_file_path) { } protected: virtual void RunWork() { set_error_code(PerformCommonCheckAndPreparationForMoveAndCopy( src_file_path_, dest_file_path_)); if (error_code() != base::PLATFORM_FILE_OK) return; if (!file_util::Move(src_file_path_, dest_file_path_)) set_error_code(base::PLATFORM_FILE_ERROR_FAILED); } private: FilePath src_file_path_; FilePath dest_file_path_; }; class RelayCreateDirectory : public RelayWithStatusCallback { public: RelayCreateDirectory( const FilePath& file_path, bool exclusive, bool recursive, base::FileUtilProxy::StatusCallback* callback) : RelayWithStatusCallback(callback), file_path_(file_path), exclusive_(exclusive), recursive_(recursive) { } protected: virtual void RunWork() { bool path_exists = file_util::PathExists(file_path_); // If parent dir of file doesn't exist. if (!recursive_ && !file_util::PathExists(file_path_.DirName())) { set_error_code(base::PLATFORM_FILE_ERROR_NOT_FOUND); return; } if (exclusive_ && path_exists) { set_error_code(base::PLATFORM_FILE_ERROR_EXISTS); return; } // If file exists at the path. if (path_exists && !file_util::DirectoryExists(file_path_)) { set_error_code(base::PLATFORM_FILE_ERROR_EXISTS); return; } if (!file_util::CreateDirectory(file_path_)) set_error_code(base::PLATFORM_FILE_ERROR_FAILED); } private: FilePath file_path_; bool exclusive_; bool recursive_; }; class RelayReadDirectory : public MessageLoopRelay { public: RelayReadDirectory(const FilePath& file_path, base::FileUtilProxy::ReadDirectoryCallback* callback) : callback_(callback), file_path_(file_path) { DCHECK(callback); } protected: virtual void RunWork() { // TODO(kkanetkar): Implement directory read in multiple chunks. if (!file_util::DirectoryExists(file_path_)) { set_error_code(base::PLATFORM_FILE_ERROR_NOT_FOUND); return; } file_util::FileEnumerator file_enum( file_path_, false, static_cast( file_util::FileEnumerator::FILES | file_util::FileEnumerator::DIRECTORIES)); FilePath current; while (!(current = file_enum.Next()).empty()) { base::FileUtilProxy::Entry entry; file_util::FileEnumerator::FindInfo info; file_enum.GetFindInfo(&info); entry.is_directory = file_enum.IsDirectory(info); // This will just give the entry's name instead of entire path // if we use current.value(). entry.name = file_util::FileEnumerator::GetFilename(info).value(); entries_.push_back(entry); } } virtual void RunCallback() { callback_->Run(error_code(), entries_); delete callback_; } private: base::FileUtilProxy::ReadDirectoryCallback* callback_; FilePath file_path_; std::vector entries_; }; class RelayGetFileInfo : public MessageLoopRelay { public: RelayGetFileInfo(const FilePath& file_path, base::FileUtilProxy::GetFileInfoCallback* callback) : callback_(callback), file_path_(file_path) { DCHECK(callback); } protected: virtual void RunWork() { if (!file_util::PathExists(file_path_)) { set_error_code(base::PLATFORM_FILE_ERROR_NOT_FOUND); return; } if (!file_util::GetFileInfo(file_path_, &file_info_)) set_error_code(base::PLATFORM_FILE_ERROR_FAILED); } virtual void RunCallback() { callback_->Run(error_code(), file_info_); delete callback_; } private: base::FileUtilProxy::GetFileInfoCallback* callback_; FilePath file_path_; base::PlatformFileInfo file_info_; }; class RelayGetFileInfoFromPlatformFile : public MessageLoopRelay { public: RelayGetFileInfoFromPlatformFile( base::PlatformFile file, base::FileUtilProxy::GetFileInfoCallback* callback) : callback_(callback), file_(file) { DCHECK(callback); } protected: virtual void RunWork() { if (!base::GetPlatformFileInfo(file_, &file_info_)) set_error_code(base::PLATFORM_FILE_ERROR_FAILED); } virtual void RunCallback() { callback_->Run(error_code(), file_info_); delete callback_; } private: base::FileUtilProxy::GetFileInfoCallback* callback_; base::PlatformFile file_; base::PlatformFileInfo file_info_; }; class RelayRead : public MessageLoopRelay { public: RelayRead(base::PlatformFile file, int64 offset, int bytes_to_read, base::FileUtilProxy::ReadCallback* callback) : file_(file), offset_(offset), buffer_(new char[bytes_to_read]), bytes_to_read_(bytes_to_read), callback_(callback), bytes_read_(0) { } protected: virtual void RunWork() { bytes_read_ = base::ReadPlatformFile(file_, offset_, buffer_.get(), bytes_to_read_); if (bytes_read_ < 0) set_error_code(base::PLATFORM_FILE_ERROR_FAILED); } virtual void RunCallback() { if (callback_) { callback_->Run(error_code(), buffer_.get(), bytes_read_); delete callback_; } } private: base::PlatformFile file_; int64 offset_; scoped_array buffer_; int bytes_to_read_; base::FileUtilProxy::ReadCallback* callback_; int bytes_read_; }; class RelayWrite : public MessageLoopRelay { public: RelayWrite(base::PlatformFile file, int64 offset, const char* buffer, int bytes_to_write, base::FileUtilProxy::WriteCallback* callback) : file_(file), offset_(offset), buffer_(new char[bytes_to_write]), bytes_to_write_(bytes_to_write), callback_(callback), bytes_written_(0) { memcpy(buffer_.get(), buffer, bytes_to_write); } protected: virtual void RunWork() { bytes_written_ = base::WritePlatformFile(file_, offset_, buffer_.get(), bytes_to_write_); if (bytes_written_ < 0) set_error_code(base::PLATFORM_FILE_ERROR_FAILED); } virtual void RunCallback() { if (callback_) { callback_->Run(error_code(), bytes_written_); delete callback_; } } private: base::PlatformFile file_; int64 offset_; scoped_array buffer_; int bytes_to_write_; base::FileUtilProxy::WriteCallback* callback_; int bytes_written_; }; class RelayTouch : public RelayWithStatusCallback { public: RelayTouch(base::PlatformFile file, const base::Time& last_access_time, const base::Time& last_modified_time, base::FileUtilProxy::StatusCallback* callback) : RelayWithStatusCallback(callback), file_(file), last_access_time_(last_access_time), last_modified_time_(last_modified_time) { } protected: virtual void RunWork() { if (!base::TouchPlatformFile(file_, last_access_time_, last_modified_time_)) set_error_code(base::PLATFORM_FILE_ERROR_FAILED); } private: base::PlatformFile file_; base::Time last_access_time_; base::Time last_modified_time_; }; class RelayTouchFilePath : public RelayWithStatusCallback { public: RelayTouchFilePath(const FilePath& file_path, const base::Time& last_access_time, const base::Time& last_modified_time, base::FileUtilProxy::StatusCallback* callback) : RelayWithStatusCallback(callback), file_path_(file_path), last_access_time_(last_access_time), last_modified_time_(last_modified_time) { } protected: virtual void RunWork() { if (!file_util::TouchFile( file_path_, last_access_time_, last_modified_time_)) set_error_code(base::PLATFORM_FILE_ERROR_FAILED); } private: FilePath file_path_; base::Time last_access_time_; base::Time last_modified_time_; }; class RelayTruncatePlatformFile : public RelayWithStatusCallback { public: RelayTruncatePlatformFile(base::PlatformFile file, int64 length, base::FileUtilProxy::StatusCallback* callback) : RelayWithStatusCallback(callback), file_(file), length_(length) { } protected: virtual void RunWork() { if (!base::TruncatePlatformFile(file_, length_)) set_error_code(base::PLATFORM_FILE_ERROR_FAILED); } private: base::PlatformFile file_; int64 length_; }; class RelayTruncate : public RelayWithStatusCallback { public: RelayTruncate(const FilePath& path, int64 length, base::FileUtilProxy::StatusCallback* callback) : RelayWithStatusCallback(callback), path_(path), length_(length) { } protected: virtual void RunWork() { base::PlatformFileError error_code(base::PLATFORM_FILE_ERROR_FAILED); base::PlatformFile file = base::CreatePlatformFile( path_, base::PLATFORM_FILE_OPEN | base::PLATFORM_FILE_WRITE, NULL, &error_code); if (error_code != base::PLATFORM_FILE_OK) { set_error_code(error_code); return; } if (!base::TruncatePlatformFile(file, length_)) set_error_code(base::PLATFORM_FILE_ERROR_FAILED); base::ClosePlatformFile(file); } private: FilePath path_; int64 length_; }; class RelayFlush : public RelayWithStatusCallback { public: RelayFlush(base::PlatformFile file, base::FileUtilProxy::StatusCallback* callback) : RelayWithStatusCallback(callback), file_(file) { } protected: virtual void RunWork() { if (!base::FlushPlatformFile(file_)) set_error_code(base::PLATFORM_FILE_ERROR_FAILED); } private: base::PlatformFile file_; }; bool Start(const tracked_objects::Location& from_here, scoped_refptr message_loop_proxy, scoped_refptr relay) { return relay->Start(message_loop_proxy, from_here); } } // namespace namespace base { // static bool FileUtilProxy::CreateOrOpen( scoped_refptr message_loop_proxy, const FilePath& file_path, int file_flags, CreateOrOpenCallback* callback) { return Start(FROM_HERE, message_loop_proxy, new RelayCreateOrOpen( message_loop_proxy, file_path, file_flags, callback)); } // static bool FileUtilProxy::CreateTemporary( scoped_refptr message_loop_proxy, CreateTemporaryCallback* callback) { return Start(FROM_HERE, message_loop_proxy, new RelayCreateTemporary(message_loop_proxy, callback)); } // static bool FileUtilProxy::Close(scoped_refptr message_loop_proxy, base::PlatformFile file_handle, StatusCallback* callback) { return Start(FROM_HERE, message_loop_proxy, new RelayClose(file_handle, callback)); } // static bool FileUtilProxy::EnsureFileExists( scoped_refptr message_loop_proxy, const FilePath& file_path, EnsureFileExistsCallback* callback) { return Start(FROM_HERE, message_loop_proxy, new RelayEnsureFileExists( message_loop_proxy, file_path, callback)); } // Retrieves the information about a file. It is invalid to pass NULL for the // callback. bool FileUtilProxy::GetFileInfo( scoped_refptr message_loop_proxy, const FilePath& file_path, GetFileInfoCallback* callback) { return Start(FROM_HERE, message_loop_proxy, new RelayGetFileInfo( file_path, callback)); } // static bool FileUtilProxy::GetFileInfoFromPlatformFile( scoped_refptr message_loop_proxy, PlatformFile file, GetFileInfoCallback* callback) { return Start(FROM_HERE, message_loop_proxy, new RelayGetFileInfoFromPlatformFile(file, callback)); } // static bool FileUtilProxy::ReadDirectory( scoped_refptr message_loop_proxy, const FilePath& file_path, ReadDirectoryCallback* callback) { return Start(FROM_HERE, message_loop_proxy, new RelayReadDirectory( file_path, callback)); } // static bool FileUtilProxy::CreateDirectory( scoped_refptr message_loop_proxy, const FilePath& file_path, bool exclusive, bool recursive, StatusCallback* callback) { return Start(FROM_HERE, message_loop_proxy, new RelayCreateDirectory( file_path, exclusive, recursive, callback)); } // static bool FileUtilProxy::Copy(scoped_refptr message_loop_proxy, const FilePath& src_file_path, const FilePath& dest_file_path, StatusCallback* callback) { return Start(FROM_HERE, message_loop_proxy, new RelayCopy(src_file_path, dest_file_path, callback)); } // static bool FileUtilProxy::Move(scoped_refptr message_loop_proxy, const FilePath& src_file_path, const FilePath& dest_file_path, StatusCallback* callback) { return Start(FROM_HERE, message_loop_proxy, new RelayMove(src_file_path, dest_file_path, callback)); } // static bool FileUtilProxy::Delete(scoped_refptr message_loop_proxy, const FilePath& file_path, bool recursive, StatusCallback* callback) { return Start(FROM_HERE, message_loop_proxy, new RelayDelete(file_path, recursive, callback)); } // static bool FileUtilProxy::RecursiveDelete( scoped_refptr message_loop_proxy, const FilePath& file_path, StatusCallback* callback) { return Start(FROM_HERE, message_loop_proxy, new RelayDelete(file_path, true, callback)); } // static bool FileUtilProxy::Read( scoped_refptr message_loop_proxy, PlatformFile file, int64 offset, int bytes_to_read, ReadCallback* callback) { return Start(FROM_HERE, message_loop_proxy, new RelayRead(file, offset, bytes_to_read, callback)); } // static bool FileUtilProxy::Write( scoped_refptr message_loop_proxy, PlatformFile file, int64 offset, const char* buffer, int bytes_to_write, WriteCallback* callback) { return Start(FROM_HERE, message_loop_proxy, new RelayWrite(file, offset, buffer, bytes_to_write, callback)); } // static bool FileUtilProxy::Touch( scoped_refptr message_loop_proxy, PlatformFile file, const base::Time& last_access_time, const base::Time& last_modified_time, StatusCallback* callback) { return Start(FROM_HERE, message_loop_proxy, new RelayTouch(file, last_access_time, last_modified_time, callback)); } // static bool FileUtilProxy::Touch( scoped_refptr message_loop_proxy, const FilePath& file_path, const base::Time& last_access_time, const base::Time& last_modified_time, StatusCallback* callback) { return Start(FROM_HERE, message_loop_proxy, new RelayTouchFilePath(file_path, last_access_time, last_modified_time, callback)); } // static bool FileUtilProxy::Truncate( scoped_refptr message_loop_proxy, PlatformFile file, int64 length, StatusCallback* callback) { return Start(FROM_HERE, message_loop_proxy, new RelayTruncatePlatformFile(file, length, callback)); } // static bool FileUtilProxy::Truncate( scoped_refptr message_loop_proxy, const FilePath& path, int64 length, StatusCallback* callback) { return Start(FROM_HERE, message_loop_proxy, new RelayTruncate(path, length, callback)); } // static bool FileUtilProxy::Flush( scoped_refptr message_loop_proxy, PlatformFile file, StatusCallback* callback) { return Start(FROM_HERE, message_loop_proxy, new RelayFlush(file, callback)); } } // namespace base