pw_stream_uart_linux/public/pw_stream_uart_linux/stream.h

// Copyright 2020 The Pigweed Authors
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
#pragma once

#include <cstdint>

#include "pw_result/result.h"
#include "pw_span/span.h"
#include "pw_stream/stream.h"

namespace pw::stream {

/// `pw::stream::NonSeekableReaderWriter` implementation for UARTs on Linux.
class UartStreamLinux : public NonSeekableReaderWriter {
 public:
  constexpr UartStreamLinux() = default;

  // UartStream objects are moveable but not copyable.
  UartStreamLinux& operator=(UartStreamLinux&& other) {
    fd_ = other.fd_;
    other.fd_ = kInvalidFd;
    return *this;
  }
  UartStreamLinux(UartStreamLinux&& other) noexcept : fd_(other.fd_) {
    other.fd_ = kInvalidFd;
  }
  UartStreamLinux(const UartStreamLinux&) = delete;
  UartStreamLinux& operator=(const UartStreamLinux&) = delete;

  ~UartStreamLinux() override { Close(); }

  /// Open a UART device using the specified baud rate.
  ///
  /// @param[in] path Path to the TTY device.
  /// @param[in] baud_rate Baud rate to use for the device.
  ///
  /// @returns
  /// * @pw_status{OK} - The device was successfully opened and configured.
  /// * @pw_status{INVALID_ARGUMENT} - An unsupported baud rate was supplied.
  /// * @pw_status{FAILED_PRECONDITION} - A device was already open.
  /// * @pw_status{UNKNOWN} - An error was returned by the operating system.
  Status Open(const char* path, uint32_t baud_rate);
  void Close();

 private:
  static constexpr int kInvalidFd = -1;

  Status DoWrite(ConstByteSpan data) override;
  StatusWithSize DoRead(ByteSpan dest) override;

  int fd_ = kInvalidFd;
};

}  // namespace pw::stream