Adds media::AudioPullFifo class to Chrome.

media/base/audio_pull_fifo.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 MEDIA_BASE_AUDIO_PULL_FIFO_H_
+#define MEDIA_BASE_AUDIO_PULL_FIFO_H_
+
+#include "base/callback.h"
+#include "media/base/audio_fifo.h"
+#include "media/base/media_export.h"
+
+namespace media {
+
+// A FIFO (First In First Out) buffer to handle mismatches in buffer sizes
+// between a provider and consumer. The consumer will pull data from this FIFO.

[scherkus (not reviewing), 2012/09/07 14:19:03]

s/provider/producer/

[henrika (OOO until Aug 14), 2012/09/10 07:23:04]

OK. Can be discussed I guess but it sounds better. Will change.

+// If data is already available in the FIFO, it is provided to the consumer.
+// If insufficient data is available to satisfy the request, the FIFO will ask
+// the provider for more data to fulfill a request.
+class MEDIA_EXPORT AudioPullFifo {
+ public:
+  // Callback type for providing more data into the FIFO.  Expects AudioBus
+  // to be completely filled with data upon return; zero padded if not enough
+  // frames are available to satisfy the request.
+  typedef base::Callback<void(AudioBus* audio_bus)> ReadCB;
+
+  // Constructs an AudioPullFifo with the specified |read_cb|, which is used to
+  // read audio data of size |read_frames| to the FIFO if data is not already
+  // available. The internal FIFO can contain |channel| number of channels,
+  // where each channel is of length |frames| audio frames.
+  AudioPullFifo(int channels, int frames,
+                const ReadCB& read_cb, int read_frames);
+  virtual ~AudioPullFifo();
+
+  // Consumes |frames_to_consume| audio frames from the FIFO and copies
+  // them to |destination|.
+  // If the FIFO does not have enough data, we ask the provider to give us more
+  // data to fulfill the request using the ReadCB implementation.
+  void Consume(AudioBus* destination, int frames_to_consume);
+
+ private:
+  // Fill the FIFO buffer with at least |frames| number of audio frames.
+  void FillBuffer(int frames);
+
+  // Source of data to the FIFO.
+  ReadCB read_cb_;
+
+  // The actual FIFO.
+  scoped_ptr<AudioFifo> audio_fifo_;
+
+  // Temporary audio bus to hold the data from the provider.
+  scoped_ptr<AudioBus> audio_bus_;
+
+  DISALLOW_COPY_AND_ASSIGN(AudioPullFifo);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_AUDIO_PULL_FIFO_H_