device/bluetooth: Add Bluetooth Audio Sink base class.

device/bluetooth/bluetooth_audio_sink.h

+// Copyright 2014 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 DEVICE_BLUETOOTH_BLUETOOTH_AUDIO_SINK_H_
+#define DEVICE_BLUETOOTH_BLUETOOTH_AUDIO_SINK_H_
+
+#include <string>
+#include <vector>
+
+#include "base/callback.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+
+namespace device {
+
+// TODO(mcchou): Define a BluetoothAudioSink specific socket stream abstraction.
+
+// BluetoothAudioSink represents a local A2DP audio sink where a remote device
+// can stream audio data. Once a BluetoothAudioSink is successfully registered.

[armansito, 2014/12/03 23:34:52]

nit: "Once a BluetoothAudioSink is successfully registered, user applications
can..."

[Miao, 2014/12/04 02:34:06]

Done.

+// User applications can obtain a pointer to a BluetoothAudioSink object via
+// the interface provided by BluetoothAdapter. The validity of a
+// BluetoothAudioSink depends on whether BluetoothAdapter is present and whether
+// it is powered.
+class BluetoothAudioSink : public base::RefCounted<BluetoothAudioSink> {
+ public:
+  // Possible values indicating the connection states between the
+  // BluetoothAudioSink and the remote device.
+  enum State {
+    STATE_INVALID,  // BluetoothAdapter not presented or not powered.
+    STATE_DISCONNECTED,  // Not connected.
+    STATE_IDLE,  // Connected but not streaming.
+    STATE_PENDING,  // Connected, streaming but not acquired.
+    STATE_ACTIVE,  // Co[MaÂnnected, streaming and acquired.
+  };
+
+  // Options to configure an A2DP audio sink.
+  struct Options {
+    Options();
+    ~Options();
+
+    uint8_t codec;
+    std::vector<uint8_t> capabilities;
+  };
+
+  // Interface for observing changes from a BluetoothAudioSink.
+  class Observer {
+   public:
+    virtual ~Observer() {}
+
+    // Called when the state of the BluetoothAudioSink object is changed.
+    // |audio_sink| indicates the object being changed, and |audio_sink_state|

[armansito, 2014/12/03 23:34:53]

nit: s/audio_sink_state/state/

[Miao, 2014/12/04 02:34:06]

Done.

+    // indicates the new state of that object.
+    virtual void BluetoothAudioSinkStateChanged(
+        BluetoothAudioSink* audio_sink,
+        BluetoothAudioSink::State audio_sink_state) = 0;

[armansito, 2014/12/03 23:34:52]

nit: s/audio_sink_state/state/

[Miao, 2014/12/04 02:34:06]

Done.

+
+    // Called when the volume of the BluetoothAudioSink object is changed.
+    // |audio_sink| indicates the object being changed, and |audio_sink_volume|

[armansito, 2014/12/03 23:34:53]

nit: s/audio_sink_volume/volume/

[Miao, 2014/12/04 02:34:06]

Done.

+    // indicates the new volume level of that object.
+    virtual void BluetoothAudioSinkVolumeChanged(
+        BluetoothAudioSink* audio_sink,
+        uint16_t audio_sink_volume) = 0;

[armansito, 2014/12/03 23:34:53]

nit: s/audio_sink_volume/volume/

[Miao, 2014/12/04 02:34:06]

Done.

+
+    // TODO(mcchou): Add method to monitor the availability of audio data during
+    // the streaming. This method should associate with BluetoothAudioSink
+    // specific IOBuffer wrapping fd, read_mtu and write_mtu.
+  };
+
+  // The AudioSinkAcquiredCallback is used to return a BluetoothAudioSink object
+  // after it is registered successfully.
+  typedef base::Callback<void(
+      scoped_refptr<BluetoothAudioSink>)> AudioSinkAcquiredCallback;
+
+  // The ErrorCallback is used for the methods that can fail in which case it
+  // is called.
+  typedef base::Callback<void(const std::string& error_message)> ErrorCallback;
+
+  virtual ~BluetoothAudioSink();
+
+  // Adds and removes a observer for events on the BluetoothAudioSink object. If
+  // monitoring multiple audio sinks, check the |audio_sink| parameter of
+  // observer methods to determine which audio sink is issuing the event.
+  virtual void AddObserver(Observer* observer) = 0;
+  virtual void RemoveObserver(Observer* observer) = 0;
+

[armansito, 2014/12/03 23:34:53]

I would add getters for volume and state:

virtual State GetState() const = 0;
virtual uint16_t GetVolume() const = 0;

[Miao, 2014/12/04 02:34:06]

Done.

+ protected:
+  BluetoothAudioSink();
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(BluetoothAudioSink);
+};
+
+}  // namespace device
+
+#endif  // DEVICE_BLUETOOTH_BLUETOOTH_AUDIO_SINK_H_