remoting/host/file_transfer/local_file_operations.cc - chromium/src - Git at Google

 // Copyright 2018 The Chromium Authors
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 #include "remoting/host/file_transfer/local_file_operations.h"

 #include <cstdint>

 #include "base/files/file_proxy.h"
 #include "base/files/file_util.h"
 #include "base/functional/bind.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "base/path_service.h"
 #include "base/sequence_checker.h"
 #include "base/task/sequenced_task_runner.h"
 #include "base/task/thread_pool.h"
 #include "build/build_config.h"
 #include "remoting/base/result.h"
 #include "remoting/host/file_transfer/ensure_user.h"
 #include "remoting/host/file_transfer/file_chooser.h"
 #include "remoting/host/file_transfer/get_desktop_directory.h"
 #include "remoting/protocol/file_transfer_helpers.h"
 #include "third_party/abseil-cpp/absl/types/optional.h"

 namespace remoting {

 namespace {

 constexpr char kTempFileExtension[] = ".part";

 remoting::protocol::FileTransfer_Error_Type FileErrorToResponseErrorType(
     base::File::Error file_error) {
   switch (file_error) {
     case base::File::FILE_ERROR_ACCESS_DENIED:
       return remoting::protocol::FileTransfer_Error_Type_PERMISSION_DENIED;
     case base::File::FILE_ERROR_NO_SPACE:
       return remoting::protocol::FileTransfer_Error_Type_OUT_OF_DISK_SPACE;
     default:
       return remoting::protocol::FileTransfer_Error_Type_IO_ERROR;
   }
 }

 scoped_refptr<base::SequencedTaskRunner> CreateFileTaskRunner() {
 #if BUILDFLAG(IS_WIN)
   // On Windows, we use user impersonation to write files as the currently
   // logged-in user, while the process as a whole runs as SYSTEM. Since user
   // impersonation is per-thread on Windows, we need a dedicated thread to
   // ensure that no other code is accidentally run with the wrong privileges.
   return base::ThreadPool::CreateSingleThreadTaskRunner(
       {base::MayBlock(), base::TaskPriority::BEST_EFFORT},
       base::SingleThreadTaskRunnerThreadMode::DEDICATED);
 #else
   return base::ThreadPool::CreateSequencedTaskRunner(
       {base::MayBlock(), base::TaskPriority::BEST_EFFORT});
 #endif
 }

 class LocalFileReader : public FileOperations::Reader {
  public:
   explicit LocalFileReader(
       scoped_refptr<base::SequencedTaskRunner> ui_task_runner);

   LocalFileReader(const LocalFileReader&) = delete;
   LocalFileReader& operator=(const LocalFileReader&) = delete;

   ~LocalFileReader() override;

   // FileOperations::Reader implementation.
   void Open(OpenCallback callback) override;
   void ReadChunk(std::size_t size, ReadCallback callback) override;
   const base::FilePath& filename() const override;
   std::uint64_t size() const override;
   FileOperations::State state() const override;

  private:
   void OnEnsureUserResult(OpenCallback callback,
                           protocol::FileTransferResult<absl::monostate> result);
   void OnFileChooserResult(OpenCallback callback, FileChooser::Result result);
   void OnOpenResult(OpenCallback callback, base::File::Error error);
   void OnGetInfoResult(OpenCallback callback,
                        base::File::Error error,
                        const base::File::Info& info);
   void OnReadResult(ReadCallback callback,
                     base::File::Error error,
                     const char* data,
                     int bytes_read);

   void SetState(FileOperations::State state);

   base::FilePath filename_;
   std::uint64_t size_ = 0;
   std::uint64_t offset_ = 0;
   FileOperations::State state_ = FileOperations::kCreated;

   scoped_refptr<base::SequencedTaskRunner> ui_task_runner_;
   scoped_refptr<base::SequencedTaskRunner> file_task_runner_;
   std::unique_ptr<FileChooser> file_chooser_;
   absl::optional<base::FileProxy> file_proxy_;
   SEQUENCE_CHECKER(sequence_checker_);
   base::WeakPtrFactory<LocalFileReader> weak_ptr_factory_{this};
 };

 class LocalFileWriter : public FileOperations::Writer {
  public:
   LocalFileWriter();

   LocalFileWriter(const LocalFileWriter&) = delete;
   LocalFileWriter& operator=(const LocalFileWriter&) = delete;

   ~LocalFileWriter() override;

   // FileOperations::Writer implementation.
   void Open(const base::FilePath& filename, Callback callback) override;
   void WriteChunk(std::vector<std::uint8_t> data, Callback callback) override;
   void Close(Callback callback) override;
   FileOperations::State state() const override;

  private:
   void Cancel();

   // Callbacks for Open().
   void OnGetTargetDirectoryResult(
       base::FilePath filename,
       Callback callback,
       protocol::FileTransferResult<base::FilePath> target_directory_result);
   void CreateTempFile(Callback callback, base::FilePath temp_filepath);
   void OnCreateResult(Callback callback, base::File::Error error);

   void OnWriteResult(std::vector<std::uint8_t> data,
                      Callback callback,
                      base::File::Error error,
                      int bytes_written);

   // Callbacks for Close().
   void OnCloseResult(Callback callback, base::File::Error error);
   void MoveToDestination(Callback callback,
                          base::FilePath destination_filepath);
   void OnMoveResult(Callback callback, bool success);

   void SetState(FileOperations::State state);

   FileOperations::State state_ = FileOperations::kCreated;

   base::FilePath destination_filepath_;
   base::FilePath temp_filepath_;
   std::uint64_t bytes_written_ = 0;

   scoped_refptr<base::SequencedTaskRunner> file_task_runner_;
   absl::optional<base::FileProxy> file_proxy_;
   SEQUENCE_CHECKER(sequence_checker_);
   base::WeakPtrFactory<LocalFileWriter> weak_ptr_factory_{this};
 };

 LocalFileReader::LocalFileReader(
     scoped_refptr<base::SequencedTaskRunner> ui_task_runner)
     : ui_task_runner_(std::move(ui_task_runner)) {}

 LocalFileReader::~LocalFileReader() = default;

 void LocalFileReader::Open(OpenCallback callback) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   DCHECK_EQ(FileOperations::kCreated, state_);
   SetState(FileOperations::kBusy);
   file_task_runner_ = CreateFileTaskRunner();
   file_proxy_.emplace(file_task_runner_.get());
   file_task_runner_->PostTaskAndReplyWithResult(
       FROM_HERE, base::BindOnce(&EnsureUserContext),
       base::BindOnce(&LocalFileReader::OnEnsureUserResult,
                      weak_ptr_factory_.GetWeakPtr(), std::move(callback)));
 }

 void LocalFileReader::ReadChunk(std::size_t size, ReadCallback callback) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   DCHECK_EQ(FileOperations::kReady, state_);
   SetState(FileOperations::kBusy);
   file_proxy_->Read(
       offset_, size,
       base::BindOnce(&LocalFileReader::OnReadResult,
                      weak_ptr_factory_.GetWeakPtr(), std::move(callback)));
 }

 const base::FilePath& LocalFileReader::filename() const {
   return filename_;
 }

 uint64_t LocalFileReader::size() const {
   return size_;
 }

 FileOperations::State LocalFileReader::state() const {
   return state_;
 }

 void LocalFileReader::OnEnsureUserResult(
     FileOperations::Reader::OpenCallback callback,
     protocol::FileTransferResult<absl::monostate> result) {
   if (!result) {
     SetState(FileOperations::kFailed);
     std::move(callback).Run(std::move(result.error()));
     return;
   }

   file_chooser_ = FileChooser::Create(
       ui_task_runner_,
       base::BindOnce(&LocalFileReader::OnFileChooserResult,
                      weak_ptr_factory_.GetWeakPtr(), std::move(callback)));
   file_chooser_->Show();
 }

 void LocalFileReader::OnFileChooserResult(OpenCallback callback,
                                           FileChooser::Result result) {
   file_chooser_.reset();
   if (!result) {
     SetState(FileOperations::kFailed);
     std::move(callback).Run(std::move(result.error()));
     return;
   }

   filename_ = result->BaseName();
   file_proxy_->CreateOrOpen(
       *result, base::File::FLAG_OPEN | base::File::FLAG_READ,
       base::BindOnce(&LocalFileReader::OnOpenResult,
                      weak_ptr_factory_.GetWeakPtr(), std::move(callback)));
 }

 void LocalFileReader::OnOpenResult(OpenCallback callback,
                                    base::File::Error error) {
   if (error != base::File::FILE_OK) {
     SetState(FileOperations::kFailed);
     std::move(callback).Run(protocol::MakeFileTransferError(
         FROM_HERE, FileErrorToResponseErrorType(error), error));
     return;
   }

   file_proxy_->GetInfo(base::BindOnce(&LocalFileReader::OnGetInfoResult,
                                       weak_ptr_factory_.GetWeakPtr(),
                                       std::move(callback)));
 }

 void LocalFileReader::OnGetInfoResult(OpenCallback callback,
                                       base::File::Error error,
                                       const base::File::Info& info) {
   if (error != base::File::FILE_OK) {
     SetState(FileOperations::kFailed);
     std::move(callback).Run(protocol::MakeFileTransferError(
         FROM_HERE, FileErrorToResponseErrorType(error), error));
     return;
   }

   size_ = info.size;

   SetState(FileOperations::kReady);
   std::move(callback).Run(kSuccessTag);
 }

 void LocalFileReader::OnReadResult(ReadCallback callback,
                                    base::File::Error error,
                                    const char* data,
                                    int bytes_read) {
   if (error != base::File::FILE_OK) {
     SetState(FileOperations::kFailed);
     std::move(callback).Run(protocol::MakeFileTransferError(
         FROM_HERE, FileErrorToResponseErrorType(error), error));
     return;
   }

   offset_ += bytes_read;
   SetState(bytes_read > 0 ? FileOperations::kReady : FileOperations::kComplete);

   // The read buffer is provided and owned by FileProxy, so there's no way to
   // avoid a copy, here.
   std::move(callback).Run(std::vector<std::uint8_t>(data, data + bytes_read));
 }

 void LocalFileReader::SetState(FileOperations::State state) {
   switch (state) {
     case FileOperations::kCreated:
       NOTREACHED();  // Can never return to initial state.
       break;
     case FileOperations::kReady:
       DCHECK_EQ(FileOperations::kBusy, state_);
       break;
     case FileOperations::kBusy:
       DCHECK(state_ == FileOperations::kCreated ||
              state_ == FileOperations::kReady);
       break;
     case FileOperations::kComplete:
       DCHECK_EQ(FileOperations::kBusy, state_);
       break;
     case FileOperations::kFailed:
       // Any state can change to kFailed.
       break;
   }

   state_ = state;
 }

 LocalFileWriter::LocalFileWriter() {}

 LocalFileWriter::~LocalFileWriter() {
   Cancel();
 }

 void LocalFileWriter::Open(const base::FilePath& filename, Callback callback) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   DCHECK_EQ(FileOperations::kCreated, state_);
   SetState(FileOperations::kBusy);
   file_task_runner_ = CreateFileTaskRunner();
   file_proxy_.emplace(file_task_runner_.get());
   file_task_runner_->PostTaskAndReplyWithResult(
       FROM_HERE, base::BindOnce([] {
         return EnsureUserContext().AndThen(
             [](absl::monostate) { return GetDesktopDirectory(); });
       }),
       base::BindOnce(&LocalFileWriter::OnGetTargetDirectoryResult,
                      weak_ptr_factory_.GetWeakPtr(), filename,
                      std::move(callback)));
 }

 void LocalFileWriter::WriteChunk(std::vector<std::uint8_t> data,
                                  Callback callback) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   DCHECK_EQ(FileOperations::kReady, state_);
   SetState(FileOperations::kBusy);
   // TODO(rkjnsn): Under what circumstances can posting the task fail? Is it
   //               worth checking for? If so, what should we do in that case,
   //               given that callback is moved into the task and not returned
   //               on error?

   // Ensure buffer pointer is obtained before data is moved.
   const std::uint8_t* buffer = data.data();
   const std::size_t size = data.size();
   file_proxy_->Write(bytes_written_, reinterpret_cast<const char*>(buffer),
                      size,
                      base::BindOnce(&LocalFileWriter::OnWriteResult,
                                     weak_ptr_factory_.GetWeakPtr(),
                                     std::move(data), std::move(callback)));
 }

 void LocalFileWriter::Close(Callback callback) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   DCHECK_EQ(FileOperations::kReady, state_);
   SetState(FileOperations::kBusy);
   file_proxy_->Close(base::BindOnce(&LocalFileWriter::OnCloseResult,
                                     weak_ptr_factory_.GetWeakPtr(),
                                     std::move(callback)));
 }

 void LocalFileWriter::Cancel() {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (state_ == FileOperations::kCreated ||
       state_ == FileOperations::kComplete ||
       state_ == FileOperations::kFailed) {
     return;
   }

   // Ensure we don't receive further callbacks.
   weak_ptr_factory_.InvalidateWeakPtrs();
   // Drop FileProxy, which will close the underlying file on the file
   // sequence after any possible pending operation is complete.
   file_proxy_.reset();
   // And finally, queue deletion of the temp file.
   if (!temp_filepath_.empty()) {
     file_task_runner_->PostTask(FROM_HERE,
                                 base::GetDeleteFileCallback(temp_filepath_));
   }
   SetState(FileOperations::kFailed);
 }

 FileOperations::State LocalFileWriter::state() const {
   return state_;
 }

 void LocalFileWriter::OnGetTargetDirectoryResult(
     base::FilePath filename,
     Callback callback,
     protocol::FileTransferResult<base::FilePath> target_directory) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!target_directory) {
     LOG(ERROR) << "Failed to get target directory.";
     SetState(FileOperations::kFailed);
     std::move(callback).Run(std::move(target_directory.error()));
     return;
   }

   destination_filepath_ =
       target_directory.success().Append(filename.BaseName());
   // Don't store in temp_filepath_ until we have the final path to make sure
   // Cancel can never delete the wrong file.
   base::FilePath temp_filepath =
       destination_filepath_.AddExtensionASCII(kTempFileExtension);

   file_task_runner_->PostTaskAndReplyWithResult(
       FROM_HERE, base::BindOnce(&base::GetUniquePath, temp_filepath),
       base::BindOnce(&LocalFileWriter::CreateTempFile,
                      weak_ptr_factory_.GetWeakPtr(), std::move(callback)));
 }

 void LocalFileWriter::CreateTempFile(Callback callback,
                                      base::FilePath temp_filepath) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (temp_filepath.empty()) {
     LOG(ERROR) << "Failed to get unique path number.";
     SetState(FileOperations::kFailed);
     std::move(callback).Run(protocol::MakeFileTransferError(
         FROM_HERE, protocol::FileTransfer_Error_Type_IO_ERROR));
     return;
   }

   temp_filepath_ = std::move(temp_filepath);

   // FLAG_WIN_SHARE_DELETE allows the file to be marked as deleted on Windows
   // while the handle is still open. (Other OS's allow this by default.) This
   // allows Cancel to clean up the temporary file even if there are writes
   // pending.
   file_proxy_->CreateOrOpen(
       temp_filepath_,
       base::File::FLAG_CREATE | base::File::FLAG_WRITE |
           base::File::FLAG_WIN_SHARE_DELETE,
       base::BindOnce(&LocalFileWriter::OnCreateResult,
                      weak_ptr_factory_.GetWeakPtr(), std::move(callback)));
 }

 void LocalFileWriter::OnCreateResult(Callback callback,
                                      base::File::Error error) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (error != base::File::FILE_OK) {
     LOG(ERROR) << "Creating temp file failed with error: " << error;
     SetState(FileOperations::kFailed);
     std::move(callback).Run(protocol::MakeFileTransferError(
         FROM_HERE, FileErrorToResponseErrorType(error), error));
     return;
   }

   SetState(FileOperations::kReady);
   // Now that the temp file has been created successfully, we could lock it
   // using base::File::Lock(), but this would not prevent the file from being
   // deleted. When the file is deleted, WriteChunk() will continue to write to
   // the file as if the file was still there, and an error will occur when
   // calling base::Move() to move the temp file. Chrome exhibits the same
   // behavior with its downloads.
   std::move(callback).Run(kSuccessTag);
 }

 void LocalFileWriter::OnWriteResult(std::vector<std::uint8_t> data,
                                     Callback callback,
                                     base::File::Error error,
                                     int bytes_written) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (error != base::File::FILE_OK) {
     LOG(ERROR) << "Write failed with error: " << error;
     Cancel();
     std::move(callback).Run(protocol::MakeFileTransferError(
         FROM_HERE, FileErrorToResponseErrorType(error), error));
     return;
   }

   SetState(FileOperations::kReady);
   bytes_written_ += bytes_written;

   // bytes_written should never be negative if error is FILE_OK.
   if (static_cast<std::size_t>(bytes_written) != data.size()) {
     // Write already makes a "best effort" to write all of the data, so this
     // probably means that an error occurred. Unfortunately, the only way to
     // find out what went wrong is to try again.
     // TODO(rkjnsn): Would it be better just to return a generic error, here?
     WriteChunk(
         std::vector<std::uint8_t>(data.begin() + bytes_written, data.end()),
         std::move(callback));
     return;
   }

   std::move(callback).Run(kSuccessTag);
 }

 void LocalFileWriter::OnCloseResult(Callback callback,
                                     base::File::Error error) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (error != base::File::FILE_OK) {
     LOG(ERROR) << "Close failed with error: " << error;
     Cancel();
     std::move(callback).Run(protocol::MakeFileTransferError(
         FROM_HERE, FileErrorToResponseErrorType(error), error));
     return;
   }

   file_task_runner_->PostTaskAndReplyWithResult(
       FROM_HERE, base::BindOnce(&base::GetUniquePath, destination_filepath_),
       base::BindOnce(&LocalFileWriter::MoveToDestination,
                      weak_ptr_factory_.GetWeakPtr(), std::move(callback)));
 }

 void LocalFileWriter::MoveToDestination(Callback callback,
                                         base::FilePath destination_filepath) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (destination_filepath.empty()) {
     LOG(ERROR) << "Failed to get unique path number.";
     SetState(FileOperations::kFailed);
     std::move(callback).Run(protocol::MakeFileTransferError(
         FROM_HERE, protocol::FileTransfer_Error_Type_IO_ERROR));
     return;
   }

   destination_filepath_ = std::move(destination_filepath);

   file_task_runner_->PostTaskAndReplyWithResult(
       FROM_HERE,
       base::BindOnce(&base::Move, temp_filepath_, destination_filepath_),
       base::BindOnce(&LocalFileWriter::OnMoveResult,
                      weak_ptr_factory_.GetWeakPtr(), std::move(callback)));
 }

 void LocalFileWriter::OnMoveResult(Callback callback, bool success) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (success) {
     SetState(FileOperations::kComplete);
     std::move(callback).Run(kSuccessTag);
   } else {
     LOG(ERROR) << "Failed to move file to final destination.";
     Cancel();
     std::move(callback).Run(protocol::MakeFileTransferError(
         FROM_HERE, protocol::FileTransfer_Error_Type_IO_ERROR));
   }
 }

 void LocalFileWriter::SetState(FileOperations::State state) {
   switch (state) {
     case FileOperations::kCreated:
       NOTREACHED();  // Can never return to initial state.
       break;
     case FileOperations::kReady:
       DCHECK(state_ == FileOperations::kBusy);
       break;
     case FileOperations::kBusy:
       DCHECK(state_ == FileOperations::kCreated ||
              state_ == FileOperations::kReady);
       break;
     case FileOperations::kComplete:
       DCHECK(state_ == FileOperations::kBusy);
       break;
     case FileOperations::kFailed:
       // Any state can change to kFailed.
       break;
   }

   state_ = state;
 }

 }  // namespace

 LocalFileOperations::LocalFileOperations(
     scoped_refptr<base::SequencedTaskRunner> ui_task_runner)
     : ui_task_runner_(std::move(ui_task_runner)) {}

 LocalFileOperations::~LocalFileOperations() = default;

 std::unique_ptr<FileOperations::Reader> LocalFileOperations::CreateReader() {
   return std::make_unique<LocalFileReader>(ui_task_runner_);
 }

 std::unique_ptr<FileOperations::Writer> LocalFileOperations::CreateWriter() {
   return std::make_unique<LocalFileWriter>();
 }

 }  // namespace remoting
	// Copyright 2018 The Chromium Authors
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	#include "remoting/host/file_transfer/local_file_operations.h"

	#include <cstdint>

	#include "base/files/file_proxy.h"
	#include "base/files/file_util.h"
	#include "base/functional/bind.h"
	#include "base/logging.h"
	#include "base/memory/ptr_util.h"
	#include "base/path_service.h"
	#include "base/sequence_checker.h"
	#include "base/task/sequenced_task_runner.h"
	#include "base/task/thread_pool.h"
	#include "build/build_config.h"
	#include "remoting/base/result.h"
	#include "remoting/host/file_transfer/ensure_user.h"
	#include "remoting/host/file_transfer/file_chooser.h"
	#include "remoting/host/file_transfer/get_desktop_directory.h"
	#include "remoting/protocol/file_transfer_helpers.h"
	#include "third_party/abseil-cpp/absl/types/optional.h"

	namespace remoting {

	namespace {

	constexpr char kTempFileExtension[] = ".part";

	remoting::protocol::FileTransfer_Error_Type FileErrorToResponseErrorType(
	base::File::Error file_error) {
	switch (file_error) {
	case base::File::FILE_ERROR_ACCESS_DENIED:
	return remoting::protocol::FileTransfer_Error_Type_PERMISSION_DENIED;
	case base::File::FILE_ERROR_NO_SPACE:
	return remoting::protocol::FileTransfer_Error_Type_OUT_OF_DISK_SPACE;
	default:
	return remoting::protocol::FileTransfer_Error_Type_IO_ERROR;
	}
	}

	scoped_refptr<base::SequencedTaskRunner> CreateFileTaskRunner() {
	#if BUILDFLAG(IS_WIN)
	// On Windows, we use user impersonation to write files as the currently
	// logged-in user, while the process as a whole runs as SYSTEM. Since user
	// impersonation is per-thread on Windows, we need a dedicated thread to
	// ensure that no other code is accidentally run with the wrong privileges.
	return base::ThreadPool::CreateSingleThreadTaskRunner(
	{base::MayBlock(), base::TaskPriority::BEST_EFFORT},
	base::SingleThreadTaskRunnerThreadMode::DEDICATED);
	#else
	return base::ThreadPool::CreateSequencedTaskRunner(
	{base::MayBlock(), base::TaskPriority::BEST_EFFORT});
	#endif
	}

	class LocalFileReader : public FileOperations::Reader {
	public:
	explicit LocalFileReader(
	scoped_refptr<base::SequencedTaskRunner> ui_task_runner);

	LocalFileReader(const LocalFileReader&) = delete;
	LocalFileReader& operator=(const LocalFileReader&) = delete;

	~LocalFileReader() override;

	// FileOperations::Reader implementation.
	void Open(OpenCallback callback) override;
	void ReadChunk(std::size_t size, ReadCallback callback) override;
	const base::FilePath& filename() const override;
	std::uint64_t size() const override;
	FileOperations::State state() const override;

	private:
	void OnEnsureUserResult(OpenCallback callback,
	protocol::FileTransferResult<absl::monostate> result);
	void OnFileChooserResult(OpenCallback callback, FileChooser::Result result);
	void OnOpenResult(OpenCallback callback, base::File::Error error);
	void OnGetInfoResult(OpenCallback callback,
	base::File::Error error,
	const base::File::Info& info);
	void OnReadResult(ReadCallback callback,
	base::File::Error error,
	const char* data,
	int bytes_read);

	void SetState(FileOperations::State state);

	base::FilePath filename_;
	std::uint64_t size_ = 0;
	std::uint64_t offset_ = 0;
	FileOperations::State state_ = FileOperations::kCreated;

	scoped_refptr<base::SequencedTaskRunner> ui_task_runner_;
	scoped_refptr<base::SequencedTaskRunner> file_task_runner_;
	std::unique_ptr<FileChooser> file_chooser_;
	absl::optional<base::FileProxy> file_proxy_;
	SEQUENCE_CHECKER(sequence_checker_);
	base::WeakPtrFactory<LocalFileReader> weak_ptr_factory_{this};
	};

	class LocalFileWriter : public FileOperations::Writer {
	public:
	LocalFileWriter();

	LocalFileWriter(const LocalFileWriter&) = delete;
	LocalFileWriter& operator=(const LocalFileWriter&) = delete;

	~LocalFileWriter() override;

	// FileOperations::Writer implementation.
	void Open(const base::FilePath& filename, Callback callback) override;
	void WriteChunk(std::vector<std::uint8_t> data, Callback callback) override;
	void Close(Callback callback) override;
	FileOperations::State state() const override;

	private:
	void Cancel();

	// Callbacks for Open().
	void OnGetTargetDirectoryResult(
	base::FilePath filename,
	Callback callback,
	protocol::FileTransferResult<base::FilePath> target_directory_result);
	void CreateTempFile(Callback callback, base::FilePath temp_filepath);
	void OnCreateResult(Callback callback, base::File::Error error);

	void OnWriteResult(std::vector<std::uint8_t> data,
	Callback callback,
	base::File::Error error,
	int bytes_written);

	// Callbacks for Close().
	void OnCloseResult(Callback callback, base::File::Error error);
	void MoveToDestination(Callback callback,
	base::FilePath destination_filepath);
	void OnMoveResult(Callback callback, bool success);

	void SetState(FileOperations::State state);

	FileOperations::State state_ = FileOperations::kCreated;

	base::FilePath destination_filepath_;
	base::FilePath temp_filepath_;
	std::uint64_t bytes_written_ = 0;

	scoped_refptr<base::SequencedTaskRunner> file_task_runner_;
	absl::optional<base::FileProxy> file_proxy_;
	SEQUENCE_CHECKER(sequence_checker_);
	base::WeakPtrFactory<LocalFileWriter> weak_ptr_factory_{this};
	};

	LocalFileReader::LocalFileReader(
	scoped_refptr<base::SequencedTaskRunner> ui_task_runner)
	: ui_task_runner_(std::move(ui_task_runner)) {}

	LocalFileReader::~LocalFileReader() = default;

	void LocalFileReader::Open(OpenCallback callback) {
	DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
	DCHECK_EQ(FileOperations::kCreated, state_);
	SetState(FileOperations::kBusy);
	file_task_runner_ = CreateFileTaskRunner();
	file_proxy_.emplace(file_task_runner_.get());
	file_task_runner_->PostTaskAndReplyWithResult(
	FROM_HERE, base::BindOnce(&EnsureUserContext),
	base::BindOnce(&LocalFileReader::OnEnsureUserResult,
	weak_ptr_factory_.GetWeakPtr(), std::move(callback)));
	}

	void LocalFileReader::ReadChunk(std::size_t size, ReadCallback callback) {
	DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
	DCHECK_EQ(FileOperations::kReady, state_);
	SetState(FileOperations::kBusy);
	file_proxy_->Read(
	offset_, size,
	base::BindOnce(&LocalFileReader::OnReadResult,
	weak_ptr_factory_.GetWeakPtr(), std::move(callback)));
	}

	const base::FilePath& LocalFileReader::filename() const {
	return filename_;
	}

	uint64_t LocalFileReader::size() const {
	return size_;
	}

	FileOperations::State LocalFileReader::state() const {
	return state_;
	}

	void LocalFileReader::OnEnsureUserResult(
	FileOperations::Reader::OpenCallback callback,
	protocol::FileTransferResult<absl::monostate> result) {
	if (!result) {
	SetState(FileOperations::kFailed);
	std::move(callback).Run(std::move(result.error()));
	return;
	}

	file_chooser_ = FileChooser::Create(
	ui_task_runner_,
	base::BindOnce(&LocalFileReader::OnFileChooserResult,
	weak_ptr_factory_.GetWeakPtr(), std::move(callback)));
	file_chooser_->Show();
	}

	void LocalFileReader::OnFileChooserResult(OpenCallback callback,
	FileChooser::Result result) {
	file_chooser_.reset();
	if (!result) {
	SetState(FileOperations::kFailed);
	std::move(callback).Run(std::move(result.error()));
	return;
	}

	filename_ = result->BaseName();
	file_proxy_->CreateOrOpen(
	*result, base::File::FLAG_OPEN \| base::File::FLAG_READ,
	base::BindOnce(&LocalFileReader::OnOpenResult,
	weak_ptr_factory_.GetWeakPtr(), std::move(callback)));
	}

	void LocalFileReader::OnOpenResult(OpenCallback callback,
	base::File::Error error) {
	if (error != base::File::FILE_OK) {
	SetState(FileOperations::kFailed);
	std::move(callback).Run(protocol::MakeFileTransferError(
	FROM_HERE, FileErrorToResponseErrorType(error), error));
	return;
	}

	file_proxy_->GetInfo(base::BindOnce(&LocalFileReader::OnGetInfoResult,
	weak_ptr_factory_.GetWeakPtr(),
	std::move(callback)));
	}

	void LocalFileReader::OnGetInfoResult(OpenCallback callback,
	base::File::Error error,
	const base::File::Info& info) {
	if (error != base::File::FILE_OK) {
	SetState(FileOperations::kFailed);
	std::move(callback).Run(protocol::MakeFileTransferError(
	FROM_HERE, FileErrorToResponseErrorType(error), error));
	return;
	}

	size_ = info.size;

	SetState(FileOperations::kReady);
	std::move(callback).Run(kSuccessTag);
	}

	void LocalFileReader::OnReadResult(ReadCallback callback,
	base::File::Error error,
	const char* data,
	int bytes_read) {
	if (error != base::File::FILE_OK) {
	SetState(FileOperations::kFailed);
	std::move(callback).Run(protocol::MakeFileTransferError(
	FROM_HERE, FileErrorToResponseErrorType(error), error));
	return;
	}

	offset_ += bytes_read;
	SetState(bytes_read > 0 ? FileOperations::kReady : FileOperations::kComplete);

	// The read buffer is provided and owned by FileProxy, so there's no way to
	// avoid a copy, here.
	std::move(callback).Run(std::vector<std::uint8_t>(data, data + bytes_read));
	}

	void LocalFileReader::SetState(FileOperations::State state) {
	switch (state) {
	case FileOperations::kCreated:
	NOTREACHED(); // Can never return to initial state.
	break;
	case FileOperations::kReady:
	DCHECK_EQ(FileOperations::kBusy, state_);
	break;
	case FileOperations::kBusy:
	DCHECK(state_ == FileOperations::kCreated \|\|
	state_ == FileOperations::kReady);
	break;
	case FileOperations::kComplete:
	DCHECK_EQ(FileOperations::kBusy, state_);
	break;
	case FileOperations::kFailed:
	// Any state can change to kFailed.
	break;
	}

	state_ = state;
	}

	LocalFileWriter::LocalFileWriter() {}

	LocalFileWriter::~LocalFileWriter() {
	Cancel();
	}

	void LocalFileWriter::Open(const base::FilePath& filename, Callback callback) {
	DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
	DCHECK_EQ(FileOperations::kCreated, state_);
	SetState(FileOperations::kBusy);
	file_task_runner_ = CreateFileTaskRunner();
	file_proxy_.emplace(file_task_runner_.get());
	file_task_runner_->PostTaskAndReplyWithResult(
	FROM_HERE, base::BindOnce([] {
	return EnsureUserContext().AndThen(
	[](absl::monostate) { return GetDesktopDirectory(); });
	}),
	base::BindOnce(&LocalFileWriter::OnGetTargetDirectoryResult,
	weak_ptr_factory_.GetWeakPtr(), filename,
	std::move(callback)));
	}

	void LocalFileWriter::WriteChunk(std::vector<std::uint8_t> data,
	Callback callback) {
	DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
	DCHECK_EQ(FileOperations::kReady, state_);
	SetState(FileOperations::kBusy);
	// TODO(rkjnsn): Under what circumstances can posting the task fail? Is it
	// worth checking for? If so, what should we do in that case,
	// given that callback is moved into the task and not returned
	// on error?

	// Ensure buffer pointer is obtained before data is moved.
	const std::uint8_t* buffer = data.data();
	const std::size_t size = data.size();
	file_proxy_->Write(bytes_written_, reinterpret_cast<const char*>(buffer),
	size,
	base::BindOnce(&LocalFileWriter::OnWriteResult,
	weak_ptr_factory_.GetWeakPtr(),
	std::move(data), std::move(callback)));
	}

	void LocalFileWriter::Close(Callback callback) {
	DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
	DCHECK_EQ(FileOperations::kReady, state_);
	SetState(FileOperations::kBusy);
	file_proxy_->Close(base::BindOnce(&LocalFileWriter::OnCloseResult,
	weak_ptr_factory_.GetWeakPtr(),
	std::move(callback)));
	}

	void LocalFileWriter::Cancel() {
	DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
	if (state_ == FileOperations::kCreated \|\|
	state_ == FileOperations::kComplete \|\|
	state_ == FileOperations::kFailed) {
	return;
	}

	// Ensure we don't receive further callbacks.
	weak_ptr_factory_.InvalidateWeakPtrs();
	// Drop FileProxy, which will close the underlying file on the file
	// sequence after any possible pending operation is complete.
	file_proxy_.reset();
	// And finally, queue deletion of the temp file.
	if (!temp_filepath_.empty()) {
	file_task_runner_->PostTask(FROM_HERE,
	base::GetDeleteFileCallback(temp_filepath_));
	}
	SetState(FileOperations::kFailed);
	}

	FileOperations::State LocalFileWriter::state() const {
	return state_;
	}

	void LocalFileWriter::OnGetTargetDirectoryResult(
	base::FilePath filename,
	Callback callback,
	protocol::FileTransferResult<base::FilePath> target_directory) {
	DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
	if (!target_directory) {
	LOG(ERROR) << "Failed to get target directory.";
	SetState(FileOperations::kFailed);
	std::move(callback).Run(std::move(target_directory.error()));
	return;
	}

	destination_filepath_ =
	target_directory.success().Append(filename.BaseName());
	// Don't store in temp_filepath_ until we have the final path to make sure
	// Cancel can never delete the wrong file.
	base::FilePath temp_filepath =
	destination_filepath_.AddExtensionASCII(kTempFileExtension);

	file_task_runner_->PostTaskAndReplyWithResult(
	FROM_HERE, base::BindOnce(&base::GetUniquePath, temp_filepath),
	base::BindOnce(&LocalFileWriter::CreateTempFile,
	weak_ptr_factory_.GetWeakPtr(), std::move(callback)));
	}

	void LocalFileWriter::CreateTempFile(Callback callback,
	base::FilePath temp_filepath) {
	DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
	if (temp_filepath.empty()) {
	LOG(ERROR) << "Failed to get unique path number.";
	SetState(FileOperations::kFailed);
	std::move(callback).Run(protocol::MakeFileTransferError(
	FROM_HERE, protocol::FileTransfer_Error_Type_IO_ERROR));
	return;
	}

	temp_filepath_ = std::move(temp_filepath);

	// FLAG_WIN_SHARE_DELETE allows the file to be marked as deleted on Windows
	// while the handle is still open. (Other OS's allow this by default.) This
	// allows Cancel to clean up the temporary file even if there are writes
	// pending.
	file_proxy_->CreateOrOpen(
	temp_filepath_,
	base::File::FLAG_CREATE \| base::File::FLAG_WRITE \|
	base::File::FLAG_WIN_SHARE_DELETE,
	base::BindOnce(&LocalFileWriter::OnCreateResult,
	weak_ptr_factory_.GetWeakPtr(), std::move(callback)));
	}

	void LocalFileWriter::OnCreateResult(Callback callback,
	base::File::Error error) {
	DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
	if (error != base::File::FILE_OK) {
	LOG(ERROR) << "Creating temp file failed with error: " << error;
	SetState(FileOperations::kFailed);
	std::move(callback).Run(protocol::MakeFileTransferError(
	FROM_HERE, FileErrorToResponseErrorType(error), error));
	return;
	}

	SetState(FileOperations::kReady);
	// Now that the temp file has been created successfully, we could lock it
	// using base::File::Lock(), but this would not prevent the file from being
	// deleted. When the file is deleted, WriteChunk() will continue to write to
	// the file as if the file was still there, and an error will occur when
	// calling base::Move() to move the temp file. Chrome exhibits the same
	// behavior with its downloads.
	std::move(callback).Run(kSuccessTag);
	}

	void LocalFileWriter::OnWriteResult(std::vector<std::uint8_t> data,
	Callback callback,
	base::File::Error error,
	int bytes_written) {
	DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
	if (error != base::File::FILE_OK) {
	LOG(ERROR) << "Write failed with error: " << error;
	Cancel();
	std::move(callback).Run(protocol::MakeFileTransferError(
	FROM_HERE, FileErrorToResponseErrorType(error), error));
	return;
	}

	SetState(FileOperations::kReady);
	bytes_written_ += bytes_written;

	// bytes_written should never be negative if error is FILE_OK.
	if (static_cast<std::size_t>(bytes_written) != data.size()) {
	// Write already makes a "best effort" to write all of the data, so this
	// probably means that an error occurred. Unfortunately, the only way to
	// find out what went wrong is to try again.
	// TODO(rkjnsn): Would it be better just to return a generic error, here?
	WriteChunk(
	std::vector<std::uint8_t>(data.begin() + bytes_written, data.end()),
	std::move(callback));
	return;
	}

	std::move(callback).Run(kSuccessTag);
	}

	void LocalFileWriter::OnCloseResult(Callback callback,
	base::File::Error error) {
	DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
	if (error != base::File::FILE_OK) {
	LOG(ERROR) << "Close failed with error: " << error;
	Cancel();
	std::move(callback).Run(protocol::MakeFileTransferError(
	FROM_HERE, FileErrorToResponseErrorType(error), error));
	return;
	}

	file_task_runner_->PostTaskAndReplyWithResult(
	FROM_HERE, base::BindOnce(&base::GetUniquePath, destination_filepath_),
	base::BindOnce(&LocalFileWriter::MoveToDestination,
	weak_ptr_factory_.GetWeakPtr(), std::move(callback)));
	}

	void LocalFileWriter::MoveToDestination(Callback callback,
	base::FilePath destination_filepath) {
	DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
	if (destination_filepath.empty()) {
	LOG(ERROR) << "Failed to get unique path number.";
	SetState(FileOperations::kFailed);
	std::move(callback).Run(protocol::MakeFileTransferError(
	FROM_HERE, protocol::FileTransfer_Error_Type_IO_ERROR));
	return;
	}

	destination_filepath_ = std::move(destination_filepath);

	file_task_runner_->PostTaskAndReplyWithResult(
	FROM_HERE,
	base::BindOnce(&base::Move, temp_filepath_, destination_filepath_),
	base::BindOnce(&LocalFileWriter::OnMoveResult,
	weak_ptr_factory_.GetWeakPtr(), std::move(callback)));
	}

	void LocalFileWriter::OnMoveResult(Callback callback, bool success) {
	DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
	if (success) {
	SetState(FileOperations::kComplete);
	std::move(callback).Run(kSuccessTag);
	} else {
	LOG(ERROR) << "Failed to move file to final destination.";
	Cancel();
	std::move(callback).Run(protocol::MakeFileTransferError(
	FROM_HERE, protocol::FileTransfer_Error_Type_IO_ERROR));
	}
	}

	void LocalFileWriter::SetState(FileOperations::State state) {
	switch (state) {
	case FileOperations::kCreated:
	NOTREACHED(); // Can never return to initial state.
	break;
	case FileOperations::kReady:
	DCHECK(state_ == FileOperations::kBusy);
	break;
	case FileOperations::kBusy:
	DCHECK(state_ == FileOperations::kCreated \|\|
	state_ == FileOperations::kReady);
	break;
	case FileOperations::kComplete:
	DCHECK(state_ == FileOperations::kBusy);
	break;
	case FileOperations::kFailed:
	// Any state can change to kFailed.
	break;
	}

	state_ = state;
	}

	} // namespace

	LocalFileOperations::LocalFileOperations(
	scoped_refptr<base::SequencedTaskRunner> ui_task_runner)
	: ui_task_runner_(std::move(ui_task_runner)) {}

	LocalFileOperations::~LocalFileOperations() = default;

	std::unique_ptr<FileOperations::Reader> LocalFileOperations::CreateReader() {
	return std::make_unique<LocalFileReader>(ui_task_runner_);
	}

	std::unique_ptr<FileOperations::Writer> LocalFileOperations::CreateWriter() {
	return std::make_unique<LocalFileWriter>();
	}

	} // namespace remoting