media/audio/scoped_loop_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_LOOP_OBSERVER_H_
   6 #define MEDIA_AUDIO_SCOPED_LOOP_OBSERVER_H_
   7
   8 #include "base/memory/ref_counted.h"
   9 #include "base/message_loop/message_loop.h"
  10 #include "base/message_loop/message_loop_proxy.h"
  11
  12 namespace base {
  13 class WaitableEvent;
  14 }
  15
  16 namespace media {
  17
  18 // A common base class for AudioOutputDevice and AudioInputDevice that manages
  19 // a message loop pointer and monitors it for destruction. If the object goes
  20 // out of scope before the message loop, the object will automatically remove
  21 // itself from the message loop'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 ScopedLoopObserver
  25     : public base::MessageLoop::DestructionObserver {
  26  public:
  27   explicit ScopedLoopObserver(
  28       const scoped_refptr<base::MessageLoopProxy>& message_loop);
  29
  30  protected:
  31   virtual ~ScopedLoopObserver();
  32
  33   // Accessor to the loop that's used by the derived class.
  34   const scoped_refptr<base::MessageLoopProxy>& message_loop() { return loop_; }
  35
  36  private:
  37   // Call to add or remove ourselves from the list of destruction observers for
  38   // the message loop.
  39   void ObserveLoopDestruction(bool enable, base::WaitableEvent* done);
  40
  41   // A pointer to the message loop's proxy. In case the loop gets destroyed
  42   // before this object goes out of scope, PostTask etc will fail but not crash.
  43   scoped_refptr<base::MessageLoopProxy> loop_;
  44
  45   DISALLOW_COPY_AND_ASSIGN(ScopedLoopObserver);
  46 };
  47
  48 }  // namespace media.
  49
  50 #endif  // MEDIA_AUDIO_SCOPED_LOOP_OBSERVER_H_