1/*
2 * Copyright (C) 2012 Google Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 *
8 * 1.  Redistributions of source code must retain the above copyright
9 *     notice, this list of conditions and the following disclaimer.
10 * 2.  Redistributions in binary form must reproduce the above copyright
11 *     notice, this list of conditions and the following disclaimer in the
12 *     documentation and/or other materials provided with the distribution.
13 * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
14 *     its contributors may be used to endorse or promote products derived
15 *     from this software without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
18 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
19 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
20 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
21 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
22 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
23 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
24 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29#ifndef AudioFIFO_h
30#define AudioFIFO_h
31
32#include "platform/audio/AudioBus.h"
33
34namespace blink {
35
36class AudioFIFO {
37public:
38    // Create a FIFO large enough to hold |fifoLength| frames of data of |numberOfChannels| channels.
39    AudioFIFO(unsigned numberOfChannels, size_t fifoLength);
40
41    // Push the data from the bus into the FIFO.
42    void push(const AudioBus*);
43
44    // Consume |framesToConsume| frames of data from the FIFO and put them in |destination|. The
45    // corresponding frames are removed from the FIFO.
46    void consume(AudioBus* destination, size_t framesToConsume);
47
48    // Number of frames of data that are currently in the FIFO.
49    size_t framesInFifo() const { return m_framesInFifo; }
50
51private:
52    // Update the FIFO index by the step, with appropriate wrapping around the endpoint.
53    int updateIndex(int index, int step) { return (index + step) % m_fifoLength; }
54
55    void findWrapLengths(size_t index, size_t providerSize, size_t& part1Length, size_t& part2Length);
56
57    // The FIFO itself. In reality, the FIFO is a circular buffer.
58    RefPtr<AudioBus> m_fifoAudioBus;
59
60    // The total available space in the FIFO.
61    size_t m_fifoLength;
62
63    // The number of actual elements in the FIFO
64    size_t m_framesInFifo;
65
66    // Where to start reading from the FIFO.
67    size_t m_readIndex;
68
69    // Where to start writing to the FIFO.
70    size_t m_writeIndex;
71};
72
73} // namespace blink
74
75#endif // AudioFIFO.h
76