media/audio/scoped_task_runner_observer.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef MEDIA_AUDIO_SCOPED_TASK_RUNNER_OBSERVER_H_
   6 #define MEDIA_AUDIO_SCOPED_TASK_RUNNER_OBSERVER_H_
   7
   8 #include "base/memory/ref_counted.h"
   9 #include "base/message_loop/message_loop.h"
  10
  11 namespace base {
  12 class SingleThreadTaskRunner;
  13 class WaitableEvent;
  14 }
  15
  16 namespace media {
  17
  18 // A common base class for AudioOutputDevice and AudioInputDevice that manages
  19 // a task runner and monitors it for destruction. If the object goes out of
  20 // scope before the task runner, the object will automatically remove itself
  21 // from the task runner's list of destruction observers.
  22 // NOTE: The class that inherits from this class must implement the
  23 // WillDestroyCurrentMessageLoop virtual method from DestructionObserver.
  24 class ScopedTaskRunnerObserver
  25     : public base::MessageLoop::DestructionObserver {
  26  public:
  27   explicit ScopedTaskRunnerObserver(
  28       const scoped_refptr<base::SingleThreadTaskRunner>& task_runner);
  29
  30  protected:
  31   ~ScopedTaskRunnerObserver() override;
  32
  33   // Accessor to the loop that's used by the derived class.
  34   const scoped_refptr<base::SingleThreadTaskRunner>& task_runner() {
  35     return task_runner_;
  36   }
  37
  38  private:
  39   // Call to add or remove ourselves from the list of destruction observers for
  40   // the message loop.
  41   void ObserveLoopDestruction(bool enable, base::WaitableEvent* done);
  42
  43   // A pointer to the task runner. In case it gets destroyed before this object
  44   // goes out of scope, PostTask() etc will fail but not crash.
  45   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
  46
  47   DISALLOW_COPY_AND_ASSIGN(ScopedTaskRunnerObserver);
  48 };
  49
  50 }  // namespace media.
  51
  52 #endif  // MEDIA_AUDIO_SCOPED_TASK_RUNNER_OBSERVER_H_