scoped_task_runner_observer.h revision 5d1f7b1de12d16ceb2c938c56701a3e8bfa558f7 
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
11namespace base {
12class SingleThreadTaskRunner;
13class WaitableEvent;
14}
15
16namespace 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.
24class ScopedTaskRunnerObserver
25    : public base::MessageLoop::DestructionObserver {
26 public:
27  explicit ScopedTaskRunnerObserver(
28      const scoped_refptr<base::SingleThreadTaskRunner>& task_runner);
29
30 protected:
31  virtual ~ScopedTaskRunnerObserver();
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_
53