Adds AudioDevice factory for all audio clients in Chrome

content/renderer/media/audio_device_factory.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.
+
+#ifndef CONTENT_RENDERER_MEDIA_AUDIO_DEVICE_FACTORY_H_
+#define CONTENT_RENDERER_MEDIA_AUDIO_DEVICE_FACTORY_H_
+#pragma once
+
+#include "base/compiler_specific.h"
+#include "base/logging.h"
+#include "content/common/content_export.h"
+#include "media/base/audio_renderer_sink.h"
+
+// Factory interface for AudioRendererSink implementations.
+class AudioDeviceFactoryInterface {
+ public:
+  virtual media::AudioRendererSink* Create() = 0;
+  virtual ~AudioDeviceFactoryInterface() {}
+};
+
+// AudioDeviceFactoryInterface implementation.
+// A reference to an instance of this class can be provided to users/clients
+// of audio devices. The user can then create the specified audio device.
+//
+// Pseudo code:
+//
+//  scoped_ptr<AudioDeviceFactoryInterface> factory_;
+//  scoped_ptr<MockedAudioMessageFilter> filter_;
+//  scoped_ptr<AudioDeviceClient> client_;
+//
+//  filter_.reset(new MockedAudioMessageFilter());
+//  factory_.reset(
+//      new media::AudioDeviceFactory<AudioDevice, MockedAudioMessageFilter>(
+//          filter_));
+//  client_.reset(new AudioDeviceClient(audio_params, factory_.get()));
+//
+//  class AudioDeviceClient : public media::AudioRendererSink::RenderCallback {
+//   public:
+//    AudioDeviceClient::AudioDeviceClient(const AudioParameters& params,
+//        AudioDeviceFactoryInterface* factory)
+//        : audio_device_(factory->Create()) {
+//      audio_device_->Initialize(params, this);
+//    }
+//
+//   private:
+//    scoped_refptr<media::AudioRendererSink> audio_device_;
+//  }
+//
+template<typename AudioDeviceImplementation,
+         typename AudioMessageFilterImplementation>
+class AudioDeviceFactory
+    : public AudioDeviceFactoryInterface {
+ public:
+  explicit AudioDeviceFactory(AudioMessageFilterImplementation* filter)
+    : filter_(filter) {
+    CHECK(filter_);
+  }
+  virtual ~AudioDeviceFactory() {}
+
+  // Creates the AudioRendererSink implementation and injects the cached
+  // audio message filter.
+  virtual media::AudioRendererSink* Create() OVERRIDE {
+    return new AudioDeviceImplementation(filter_);
+  }
+
+ private:
+  AudioMessageFilterImplementation* filter_;
+  DISALLOW_COPY_AND_ASSIGN(AudioDeviceFactory);
+};
+
+#endif  // CONTENT_RENDERER_MEDIA_AUDIO_DEVICE_FACTORY_H_