Implement AudioOutputProxy.

media/audio/audio_output_dispatcher.h

+// Copyright (c) 2010 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.
+
+// AudioOutputDispatcher dispatches creation and deletion of audio
+// output streams. AudioOutputProxy objects use this class to allocate
+// and recycle actual audio output streams. When playback is started,
+// the proxy calls StreamStarted() to get an output stream that it
+// uses to play the sound. When playback is stopped, the proxy returns
+// the stream back to the dispatcher by calling StreamStopped().
+//
+// To avoid opening and closing audio devices more frequently than it
+// is neccessary, 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 in the constructor).
+//
+// AudioManagerBase creates one AudioOutputDispatcher per each
+// possible set of audio parameters, i.e. streams with different
+// parameters are managed independently.
+
+#ifndef MEDIA_AUDIO_AUDIO_OUTPUT_DISPATCHER_H_
+#define MEDIA_AUDIO_AUDIO_OUTPUT_DISPATCHER_H_
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/ref_counted.h"
+#include "base/timer.h"
+#include "media/audio/audio_manager.h"
+#include "media/audio/audio_parameters.h"
+
+class AudioOutputStream;
+class MessageLoop;
+
+class AudioOutputDispatcher
+    : public base::RefCountedThreadSafe<AudioOutputDispatcher> {
+ public:
+  // |close_delay_ms| specifies delay after the stream is paused until
+  // the audio device is closed.
+  AudioOutputDispatcher(AudioManager* audio_manager,
+                        const AudioParameters& params,
+                        int close_delay_ms);
+  ~AudioOutputDispatcher();
+
+  // Called by AudioOutputProxy when the stream is closed. Opens a new
+  // physical stream if there are no pending streams in |streams_|.
+  // Returns false, if it fails to open it.
+  bool StreamOpened();
+
+  // Called by AudioOutputProxy when the stream is started. If there
+  // are pending streams in |streams_| then it returns one of them,
+  // otherwise creates a new one. Returns a physical stream that must
+  // be used, or NULL if it fails to open audio device. Ownership of
+  // the result is passed to the caller.
+  AudioOutputStream* StreamStarted();
+
+  // Called by AudioOutputProxy when the stream is stopped. Returns
+  // |stream| to the pool of pending streams (i.e. |streams_|).
+  // Ownership of the |stream| is passed to the dispatcher.
+  void StreamStopped(AudioOutputStream* stream);
+
+  // Called by AudioOutputProxy when the stream is closed.
+  void StreamClosed();
+
+  MessageLoop* message_loop();
+
+ private:
+  friend class AudioOutputProxyTest;
+
+  // Creates a new physical output stream, opens it and pushes to
+  // |streams_|.  Returns false if the stream couldn't be created or
+  // opened.
+  bool CreateAndOpenStream();
+
+  // A task scheduled by StreamStarted(). Opens a new stream and puts
+  // it in |streams_|.
+  void OpenTask();
+
+  // Called by |close_timer_|. Closes all pending stream.
+  void ClosePendingStreams();
+
+  AudioManager* audio_manager_;
+  MessageLoop* message_loop_;
+  AudioParameters params_;
+
+  size_t paused_proxies_;
+  std::vector<AudioOutputStream*> streams_;
+  base::DelayTimer<AudioOutputDispatcher> close_timer_;
+
+  DISALLOW_COPY_AND_ASSIGN(AudioOutputDispatcher);
+};
+
+#endif  // MEDIA_AUDIO_AUDIO_OUTPUT_DISPATCHER_H_