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 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
