Add an initial revision of an audio server.

services/media/audio/audio_track_impl.h

Index: services/media/audio/audio_track_impl.h
diff --git a/services/media/audio/audio_track_impl.h b/services/media/audio/audio_track_impl.h
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+// 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_TRACK_IMPL_H_
+#define SERVICES_MEDIA_AUDIO_AUDIO_TRACK_IMPL_H_
+
+#include <deque>
+#include <set>
+
+#include "base/synchronization/lock.h"
+#include "mojo/public/cpp/bindings/binding.h"
+#include "mojo/public/cpp/bindings/callback.h"
+#include "mojo/services/media/audio/interfaces/audio_track.mojom.h"
+#include "mojo/services/media/common/cpp/linear_transform.h"
+#include "services/media/audio/audio_pipe.h"
+#include "services/media/audio/fwd_decls.h"
+#include "services/media/common/rate_control_base.h"
+
+namespace mojo {
+namespace media {
+namespace audio {
+
+class AudioTrackImpl : public AudioTrack {
+ public:
+  // TODO(johngro): Find a better place for this constant.  It affects the
+  // behavior of more than just the Audio Track implementation.
+  static constexpr size_t PTS_FRACTIONAL_BITS = 12;
+
+  ~AudioTrackImpl() override;
+  static AudioTrackImplPtr Create(InterfaceRequest<AudioTrack> iface,
+                                 AudioServerImpl* owner);
+
+  // Methods used by the output manager to link this track to different outputs.
+  void AddOutput(AudioTrackToOutputLinkPtr link);
+  void RemoveOutput(AudioTrackToOutputLinkPtr link);
+
+  // Accessors used by AudioOutputs during mixing to access parameters which are
+  // important for the mixing process.
+  void SnapshotRateTrans(LinearTransform* out, uint32_t* generation = nullptr) {
+    rate_control_.SnapshotCurrentTransform(out, generation);
+  }
+
+  const LinearTransform::Ratio& FractionalFrameToMediaTimeRatio() const {
+    return frame_to_media_ratio_;
+  }
+
+  uint32_t BytesPerFrame() const { return bytes_per_frame_; }
+  const LpcmMediaTypeDetailsPtr& Format() const { return format_; }
+
+ private:
+  friend class AudioPipe;
+
+  AudioTrackImpl(InterfaceRequest<AudioTrack> track,
+                AudioServerImpl* owner);
+
+  // Implementation of AudioTrack interface.
+  void Describe(const DescribeCallback& cbk) override;
+  void Configure(AudioTrackConfigurationPtr configuration,
+                 InterfaceRequest<MediaPipe> req,
+                 const ConfigureCallback& cbk) override;
+  void GetRateControl(InterfaceRequest<RateControl> req,
+                      const GetRateControlCallback& cbk) override;
+
+  // Methods called by our AudioPipe.
+  //
+  // TODO(johngro): MI is banned by style, but multiple interface inheritance
+  // (inheriting for one or more base classes consisting only of pure virtual
+  // methods) is allowed.  Consider defining an interface for AudioPipe
+  // encapsulation so that AudioPipe does not have to know that we are an
+  // AudioTrackImpl (just that we implement its interface).
+  void OnPacketReceived(AudioPipe::AudioPacketRefPtr packet);
+  void OnFlushRequested(const MediaPipe::FlushCallback& cbk);
+
+  AudioTrackImplWeakPtr     weak_this_;
+  AudioServerImpl*          owner_;
+  Binding<AudioTrack>       binding_;
+  AudioPipe                 pipe_;
+  RateControlBase           rate_control_;
+  LinearTransform::Ratio    frame_to_media_ratio_;
+  uint32_t                  bytes_per_frame_ = 1;
+  LpcmMediaTypeDetailsPtr   format_;
+  AudioTrackToOutputLinkSet outputs_;
+};
+
+}  // namespace audio
+}  // namespace media
+}  // namespace mojo
+
+#endif  // SERVICES_MEDIA_AUDIO_AUDIO_TRACK_IMPL_H_