bluetooth/async/async_fd_watcher.h

/*
 * Copyright 2022 The Android Open Source Project
 *
 * 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
 *
 *      http://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 <map>
#include <mutex>
#include <thread>

namespace android::hardware::bluetooth::async {

using ReadCallback = std::function<void(int)>;
using TimeoutCallback = std::function<void(void)>;

class AsyncFdWatcher {
 public:
  AsyncFdWatcher() = default;
  ~AsyncFdWatcher();

  int WatchFdForNonBlockingReads(int file_descriptor,
                                 const ReadCallback& on_read_fd_ready_callback);
  int ConfigureTimeout(const std::chrono::milliseconds timeout,
                       const TimeoutCallback& on_timeout_callback);
  void StopWatchingFileDescriptors();

 private:
  AsyncFdWatcher(const AsyncFdWatcher&) = delete;
  AsyncFdWatcher& operator=(const AsyncFdWatcher&) = delete;

  int tryStartThread();
  int stopThread();
  int notifyThread();
  void ThreadRoutine();

  std::atomic_bool running_{false};
  std::thread thread_;
  std::mutex internal_mutex_;
  std::mutex timeout_mutex_;

  std::map<int, ReadCallback> watched_fds_;
  int notification_listen_fd_;
  int notification_write_fd_;
  TimeoutCallback timeout_cb_;
  std::chrono::milliseconds timeout_ms_;
};

}  // namespace android::hardware::bluetooth::async