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_ 51
