services/device/serial/serial_io_handler_posix.h

// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef SERVICES_DEVICE_SERIAL_SERIAL_IO_HANDLER_POSIX_H_
#define SERVICES_DEVICE_SERIAL_SERIAL_IO_HANDLER_POSIX_H_

#include <array>
#include <memory>

#include "base/files/file_descriptor_watcher_posix.h"
#include "base/task/single_thread_task_runner.h"
#include "services/device/serial/serial_io_handler.h"

namespace device {

// Linux reports breaks and parity errors by inserting the sequence '\377\0x'
// into the byte stream where 'x' is '\0' for a break and the corrupted byte for
// a parity error.
enum class ErrorDetectState { NO_ERROR, MARK_377_SEEN, MARK_0_SEEN };

class SerialIoHandlerPosix : public SerialIoHandler {
 public:
  SerialIoHandlerPosix(const SerialIoHandlerPosix&) = delete;
  SerialIoHandlerPosix& operator=(const SerialIoHandlerPosix&) = delete;

 protected:
  // SerialIoHandler impl.
  void ReadImpl() override;
  void WriteImpl() override;
  void CancelReadImpl() override;
  void CancelWriteImpl() override;
  bool ConfigurePortImpl() override;
  bool PostOpen() override;
  void PreClose() override;
  void Flush(mojom::SerialPortFlushMode mode) const override;
  void Drain() override;
  mojom::SerialPortControlSignalsPtr GetControlSignals() const override;
  bool SetControlSignals(
      const mojom::SerialHostControlSignals& control_signals) override;
  mojom::SerialConnectionInfoPtr GetPortInfo() const override;
  size_t CheckReceiveError(base::span<uint8_t> buffer,
                           size_t bytes_read,
                           bool& break_detected,
                           bool& parity_error_detected);

 private:
  friend class SerialIoHandler;
  friend class SerialIoHandlerPosixTest;

  SerialIoHandlerPosix(
      const base::FilePath& port,
      scoped_refptr<base::SingleThreadTaskRunner> ui_thread_task_runner);
  ~SerialIoHandlerPosix() override;

  void AttemptRead();

  // Called when file() is writable without blocking.
  void OnFileCanWriteWithoutBlocking();

  void EnsureWatchingReads();
  void EnsureWatchingWrites();

  void StopWatchingFileRead();
  void StopWatchingFileWrite();

  std::unique_ptr<base::FileDescriptorWatcher::Controller> file_read_watcher_;
  std::unique_ptr<base::FileDescriptorWatcher::Controller> file_write_watcher_;

  ErrorDetectState error_detect_state_;
  bool parity_check_enabled_;
  std::array<uint8_t, 2> chars_stashed_;
  size_t num_chars_stashed_;
};

}  // namespace device

#endif  // SERVICES_DEVICE_SERIAL_SERIAL_IO_HANDLER_POSIX_H_