Add an initial revision of an audio server.

services/media/audio/audio_server_impl.h

+// Copyright 2015 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 SERVICES_MEDIA_AUDIO_AUDIO_SERVER_IMPL_H_
+#define SERVICES_MEDIA_AUDIO_AUDIO_SERVER_IMPL_H_
+
+#include <list>
+#include <set>
+
+#include "base/callback.h"
+#include "base/synchronization/lock.h"
+#include "base/task_runner.h"
+#include "mojo/services/media/audio/interfaces/audio_server.mojom.h"
+#include "mojo/services/media/audio/interfaces/audio_track.mojom.h"
+#include "services/media/audio/audio_output_manager.h"
+#include "services/media/audio/fwd_decls.h"
+#include "services/media/common/media_pipe_base.h"
+
+namespace mojo {
+namespace media {
+namespace audio {
+
+class AudioServerImpl : public AudioServer {
+ public:
+  AudioServerImpl();
+  ~AudioServerImpl() override;
+
+  void Initialize();
+
+  // AudioServer
+  void CreateTrack(mojo::InterfaceRequest<AudioTrack> track) override;
+
+  // Called (indirectly) by AudioOutputs to schedule the callback for a
+  // MediaPacked which was queued to an AudioTrack via. a media pipe.
+  //
+  // TODO(johngro): This bouncing through thread contexts is inefficient and
+  // will increase the latency requirements for clients (its going to take them
+  // some extra time to discover that their media has been completely consumed).
+  // When mojo exposes a way to safely invoke interface method callbacks from
+  // threads other than the thread which executed the method itself, we will
+  // want to switch to creating the callback message directly, instead of
+  // indirecting through the server.
+  void SchedulePacketCleanup(MediaPipeBase::MediaPacketStatePtr state);
+
+  // Schedule a closure to run on the server's main message loop.
+  void ScheduleMessageLoopTask(const tracked_objects::Location& from_here,
+                               const base::Closure& task) {
+    DCHECK(task_runner_);
+    bool success = task_runner_->PostTask(from_here, task);
+    DCHECK(success);
+  }
+
+
+  // Accessor for our encapsulated output manager.
+  AudioOutputManager& GetOutputManager() { return output_manager_; }
+
+ private:
+  using CleanupQueue = std::list<MediaPipeBase::MediaPacketStatePtr>;
+
+  void Shutdown();
+  void DoPacketCleanup();
+
+  // A reference to our message loop's task runner.  Allows us to post events to
+  // be handled by our main application thread from things like the output
+  // manager's thread pool.
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+
+  // State for dealing with outputs.
+  AudioOutputManager output_manager_;
+
+  // State for dealing with tracks.
+  base::Lock track_lock_;
+  std::set<AudioTrackImplPtr> tracks_;
+
+  // State for dealing with cleanup tasks.
+  base::Lock cleanup_queue_lock_;
+  std::unique_ptr<CleanupQueue> cleanup_queue_;
+  bool cleanup_scheduled_ = false;
+  bool shutting_down_ = false;
+  base::Closure cleanup_closure_;
+};
+
+}  // namespace audio
+}  // namespace media
+}  // namespace mojo
+
+#endif  // SERVICES_MEDIA_AUDIO_AUDIO_SERVER_IMPL_H_