modules/utility/source/process_thread_impl.h

/*
 *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#ifndef MODULES_UTILITY_SOURCE_PROCESS_THREAD_IMPL_H_
#define MODULES_UTILITY_SOURCE_PROCESS_THREAD_IMPL_H_

#include <stdint.h>

#include <list>
#include <memory>
#include <queue>

#include "api/task_queue/queued_task.h"
#include "modules/include/module.h"
#include "modules/utility/include/process_thread.h"
#include "rtc_base/deprecated/recursive_critical_section.h"
#include "rtc_base/event.h"
#include "rtc_base/location.h"
#include "rtc_base/platform_thread.h"
#include "rtc_base/synchronization/sequence_checker.h"

namespace webrtc {

class ProcessThreadImpl : public ProcessThread {
 public:
  explicit ProcessThreadImpl(const char* thread_name);
  ~ProcessThreadImpl() override;

  void Start() override;
  void Stop() override;

  void WakeUp(Module* module) override;
  void PostTask(std::unique_ptr<QueuedTask> task) override;
  void PostDelayedTask(std::unique_ptr<QueuedTask> task,
                       uint32_t milliseconds) override;

  void RegisterModule(Module* module, const rtc::Location& from) override;
  void DeRegisterModule(Module* module) override;

 protected:
  static void Run(void* obj);
  bool Process();

 private:
  struct ModuleCallback {
    ModuleCallback() = delete;
    ModuleCallback(ModuleCallback&& cb) = default;
    ModuleCallback(const ModuleCallback& cb) = default;
    ModuleCallback(Module* module, const rtc::Location& location)
        : module(module), location(location) {}
    bool operator==(const ModuleCallback& cb) const {
      return cb.module == module;
    }

    Module* const module;
    int64_t next_callback = 0;  // Absolute timestamp.
    const rtc::Location location;

   private:
    ModuleCallback& operator=(ModuleCallback&);
  };
  struct DelayedTask {
    DelayedTask(int64_t run_at_ms, std::unique_ptr<QueuedTask> task)
        : run_at_ms(run_at_ms), task(task.release()) {}
    friend bool operator<(const DelayedTask& lhs, const DelayedTask& rhs) {
      // Earliest DelayedTask should be at the top of the priority queue.
      return lhs.run_at_ms > rhs.run_at_ms;
    }

    int64_t run_at_ms;
    // DelayedTask owns the |task|, but some delayed tasks must be removed from
    // the std::priority_queue, but mustn't be deleted. std::priority_queue does
    // not give non-const access to the values, so storing unique_ptr would
    // delete the task as soon as it is remove from the priority queue.
    // Thus lifetime of the |task| is managed manually.
    QueuedTask* task;
  };
  typedef std::list<ModuleCallback> ModuleList;

  void Delete() override;

  // Warning: For some reason, if |lock_| comes immediately before |modules_|
  // with the current class layout, we will  start to have mysterious crashes
  // on Mac 10.9 debug.  I (Tommi) suspect we're hitting some obscure alignemnt
  // issues, but I haven't figured out what they are, if there are alignment
  // requirements for mutexes on Mac or if there's something else to it.
  // So be careful with changing the layout.
  rtc::RecursiveCriticalSection
      lock_;  // Used to guard modules_, tasks_ and stop_.

  SequenceChecker thread_checker_;
  rtc::Event wake_up_;
  // TODO(pbos): Remove unique_ptr and stop recreating the thread.
  std::unique_ptr<rtc::PlatformThread> thread_;

  ModuleList modules_;
  std::queue<QueuedTask*> queue_;
  std::priority_queue<DelayedTask> delayed_tasks_ RTC_GUARDED_BY(lock_);
  bool stop_;
  const char* thread_name_;
};

}  // namespace webrtc

#endif  // MODULES_UTILITY_SOURCE_PROCESS_THREAD_IMPL_H_