Improve and simplify AudioOutputDispatcher.

media/audio/audio_output_dispatcher_impl.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // AudioOutputDispatcherImpl is an implementation of AudioOutputDispatcher.
 //
 // To avoid opening and closing audio devices more frequently than necessary,
 // each dispatcher has a pool of inactive physical streams. A stream is closed
 // only if it hasn't been used for a certain period of time (specified via the
 // constructor).
 //
 
 #ifndef MEDIA_AUDIO_AUDIO_OUTPUT_DISPATCHER_IMPL_H_
 #define MEDIA_AUDIO_AUDIO_OUTPUT_DISPATCHER_IMPL_H_
 
-#include <list>
 #include <map>
+#include <vector>
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
-#include "base/memory/weak_ptr.h"
 #include "base/timer/timer.h"
 #include "media/audio/audio_io.h"
 #include "media/audio/audio_manager.h"
 #include "media/audio/audio_output_dispatcher.h"
 #include "media/audio/audio_parameters.h"
 
 namespace media {
 
 class AudioOutputProxy;
 
 class MEDIA_EXPORT AudioOutputDispatcherImpl : public AudioOutputDispatcher {
  public:
-  // |close_delay_ms| specifies delay after the stream is paused until
-  // the audio device is closed.
+  // |close_delay| specifies delay after the stream is idle until the audio
+  // device is closed.
   AudioOutputDispatcherImpl(AudioManager* audio_manager,
                             const AudioParameters& params,
                             const std::string& output_device_id,
                             const std::string& input_device_id,
                             const base::TimeDelta& close_delay);
 
   // Opens a new physical stream if there are no pending streams in
   // |idle_streams_|.  Do not call Close() or Stop() if this method fails.
   virtual bool OpenStream() OVERRIDE;
 
   // If there are pending streams in |idle_streams_| then it reuses one of
   // them, otherwise creates a new one.
   virtual bool StartStream(AudioOutputStream::AudioSourceCallback* callback,
                            AudioOutputProxy* stream_proxy) OVERRIDE;
 
-  // Holds the physical stream temporarily in |pausing_streams_| and then
-  // |stream| is  added to the pool of pending streams (i.e. |idle_streams_|).
+  // Stops the stream assigned to the specified proxy and moves it into
+  // |idle_streams_| for reuse by other proxies.
   virtual void StopStream(AudioOutputProxy* stream_proxy) OVERRIDE;
 
   virtual void StreamVolumeSet(AudioOutputProxy* stream_proxy,
                                double volume) OVERRIDE;
 
+  // Closes |idle_streams_| until the number of |idle_streams_| is equal to the
+  // |idle_proxies_| count.  If there are no |idle_proxies_| a single stream is
+  // kept alive until |close_timer_| fires.
   virtual void CloseStream(AudioOutputProxy* stream_proxy) OVERRIDE;
 
   virtual void Shutdown() OVERRIDE;
 
   virtual void CloseStreamsForWedgeFix() OVERRIDE;
   virtual void RestartStreamsForWedgeFix() OVERRIDE;
 
  private:
-  typedef std::map<AudioOutputProxy*, AudioOutputStream*> AudioStreamMap;
   friend class base::RefCountedThreadSafe<AudioOutputDispatcherImpl>;
   virtual ~AudioOutputDispatcherImpl();
 
-  friend class AudioOutputProxyTest;
-
   // Creates a new physical output stream, opens it and pushes to
   // |idle_streams_|.  Returns false if the stream couldn't be created or
   // opened.
   bool CreateAndOpenStream();
 
-  // Before a stream is reused, it should sit idle for a bit.  This task is
-  // called once that time has elapsed.
-  void StopStreamTask();
+  // Closes all |idle_streams_|.
+  void CloseAllIdleStreams();
+  // Similar to CloseAllIdleStreams(), but keeps |keep_alive| streams alive.
+  void CloseIdleStreams(size_t keep_alive);
 
-  // Called by |close_timer_|. Closes all pending streams.
-  void ClosePendingStreams();
+  size_t idle_proxies_;
+  std::vector<AudioOutputStream*> idle_streams_;
 
-  base::TimeDelta pause_delay_;
-  size_t paused_proxies_;
-  typedef std::list<AudioOutputStream*> AudioOutputStreamList;
-  AudioOutputStreamList idle_streams_;
-  AudioOutputStreamList pausing_streams_;
-
-  // Used to post delayed tasks to ourselves that we cancel inside Shutdown().
-  base::WeakPtrFactory<AudioOutputDispatcherImpl> weak_this_;
+  // When streams are stopped they're added to |idle_streams_|, if no stream is
+  // reused before |close_delay_| elapses |close_timer_| will run
+  // CloseIdleStreams().
   base::DelayTimer<AudioOutputDispatcherImpl> close_timer_;
 
+  typedef std::map<AudioOutputProxy*, AudioOutputStream*> AudioStreamMap;
   AudioStreamMap proxy_to_physical_map_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioOutputDispatcherImpl);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_OUTPUT_DISPATCHER_IMPL_H_