Add the copresence DirectiveHandler.

components/copresence/handlers/audio/audio_directive_handler.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 COMPONENTS_COPRESENCE_HANDLERS_AUDIO_DIRECTIVE_HANDLER_
+#define COMPONENTS_COPRESENCE_HANDLERS_AUDIO_DIRECTIVE_HANDLER_
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/time/time.h"
+#include "base/timer/timer.h"
+#include "components/copresence/handlers/audio/audio_directive_list.h"
+#include "components/copresence/mediums/audio/audio_recorder.h"
+#include "components/copresence/proto/data.pb.h"
+
+namespace media {
+class AudioBusRefCounted;
+}
+
+namespace copresence {
+
+class AudioPlayer;
+class AudioRecorder;
+
+class AudioDirectiveHandler {
+ public:
+  AudioDirectiveHandler(
+      const AudioRecorder::DecodeSamplesCallback& decode_cb,
+      const AudioDirectiveList::EncodeTokenCallback& encode_cb);
+  // Use this constructor ONLY for testing.
+  explicit AudioDirectiveHandler(

[xiyuan, 2014/07/25 21:02:09]

nit: If we only want to expose it for testing, maybe we should put this ctor in
private section and add a class factory method that ends with 'ForTesting'. This
way presubmit script would catch misuse.

[Daniel Erat, 2014/07/25 23:09:01]

what about just having a single c'tor and documenting that passing a null
|decode_cb| will prevent |player_| and |recorder_| from being initialized?

[rkc, 2014/07/28 21:02:01]

Made this protected, so only the Mock that overrides the class can actually use
this constructor.

[rkc, 2014/07/28 21:02:01]

Keeping a separate constructor makes it explicit that this is being instantiated
for testing. Plus moving it into protected: allows us to make sure that we
aren't accidentally using the incorrect constructor by passing in a null value
for decode_cb.

+      const AudioDirectiveList::EncodeTokenCallback& encode_cb);
+  virtual ~AudioDirectiveHandler();
+
+  void AddInstruction(const copresence::TokenInstruction& instruction,

[Daniel Erat, 2014/07/25 23:09:01]

document what this does

[rkc, 2014/07/28 21:02:01]

Done.

+                      base::TimeDelta ttl_ms);
+
+ protected:
+  virtual void PlayAudio(

[xiyuan, 2014/07/25 21:02:09]

It seems that these are made "virtual" because we need to mock them in tests.
Could you add a comment?

[rkc, 2014/07/28 21:02:01]

Done.

+      const scoped_refptr<media::AudioBusRefCounted>& samples,
+      base::TimeDelta duration);

[xiyuan, 2014/07/25 21:02:09]

nit: const base::TimeDelta& ?

[Daniel Erat, 2014/07/25 23:09:01]

(not really necessary; time structs are just int64s and there's a bunch of code
that passes them by value)

[rkc, 2014/07/28 21:02:02]

time.h specifies that these can be efficiently passed by value.

[rkc, 2014/07/28 21:02:02]

Acknowledged.

+  virtual void RecordAudio(base::TimeDelta duration);

[xiyuan, 2014/07/25 21:02:09]

nit: const base::TimeDelta& ?

[rkc, 2014/07/28 21:02:02]

ditto.

+
+  virtual void StopPlayback();
+  virtual void StopRecording();
+
+  // For testing, we want to override base::Time::Now().
+  base::Time Now();

[Daniel Erat, 2014/07/25 23:09:01]

i don't think you define this anywhere

[rkc, 2014/07/28 21:02:01]

Leftover code, removed.
Done.

+
+ private:
+  void ExecuteNextTransmit();

[Daniel Erat, 2014/07/25 23:09:01]

add a comment documenting what these do

[rkc, 2014/07/28 21:02:01]

Done.

+  void ExecuteNextReceive();
+
+  AudioDirectiveList directive_list_;
+
+  AudioPlayer* player_;

[Daniel Erat, 2014/07/25 23:09:01]

document that these are owned by this class but destroyed on another thread.
(actually, i would very strongly prefer that they were scoped_ptr or
scoped_refptrs or something; haven't gotten to these classes yet to see if
that's possible.)

[rkc, 2014/07/28 21:02:01]

These objects delete themselves on the audio thread (after we call Finalize on
them). We can't delete them from the UI thread.

+  AudioRecorder* recorder_;
+
+  base::OneShotTimer<AudioDirectiveHandler> stop_playback_timer_;
+  base::OneShotTimer<AudioDirectiveHandler> stop_recording_timer_;
+
+  DISALLOW_COPY_AND_ASSIGN(AudioDirectiveHandler);
+};
+
+}  // namespace copresence
+
+#endif  // COMPONENTS_COPRESENCE_HANDLERS_AUDIO_DIRECTIVE_HANDLER_