AudioPullFIFO.cpp   [plain text]

/*
 * Copyright (C) 2012 Google Inc. All rights reserved.
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 *     its contributors may be used to endorse or promote products derived
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#include "config.h"

#if ENABLE(WEB_AUDIO)

#include "AudioPullFIFO.h"

namespace WebCore {

AudioPullFIFO::AudioPullFIFO(AudioSourceProvider& audioProvider, unsigned numberOfChannels, size_t fifoLength, size_t providerSize)
    : m_provider(audioProvider)
    , m_fifoAudioBus(numberOfChannels, fifoLength)
    , m_fifoLength(fifoLength)
    , m_framesInFifo(0)
    , m_readIndex(0)
    , m_writeIndex(0)
    , m_providerSize(providerSize)
    , m_tempBus(numberOfChannels, providerSize)
{
}

void AudioPullFIFO::consume(AudioBus* destination, size_t framesToConsume)
{
    bool isGood = destination && (framesToConsume <= m_fifoLength);
    ASSERT(isGood);
    if (!isGood)
        return;

    if (framesToConsume > m_framesInFifo) {
        // We don't have enough data in the FIFO to fulfill the request. Ask for more data.
        fillBuffer(framesToConsume - m_framesInFifo);
    }

    // We have enough data now. Copy the requested number of samples to the destination.

    size_t part1Length;
    size_t part2Length;
    findWrapLengths(m_readIndex, framesToConsume, part1Length, part2Length);

    size_t numberOfChannels = m_fifoAudioBus.numberOfChannels();

    for (size_t channelIndex = 0; channelIndex < numberOfChannels; ++channelIndex) {
        float* destinationData = destination->channel(channelIndex)->mutableData();
        const float* sourceData = m_fifoAudioBus.channel(channelIndex)->data();

        bool isCopyGood = ((m_readIndex < m_fifoLength)
                           && (m_readIndex + part1Length) <= m_fifoLength
                           && (part1Length <= destination->length())
                           && (part1Length + part2Length) <= destination->length());
        ASSERT(isCopyGood);
        if (!isCopyGood)
            return;

        memcpy(destinationData, sourceData + m_readIndex, part1Length * sizeof(*sourceData));
        // Handle wrap around of the FIFO, if needed.
        if (part2Length > 0)
            memcpy(destinationData + part1Length, sourceData, part2Length * sizeof(*sourceData));
    }
    m_readIndex = updateIndex(m_readIndex, framesToConsume);
    m_framesInFifo -= framesToConsume;
    ASSERT(m_framesInFifo >= 0);
}

void AudioPullFIFO::findWrapLengths(size_t index, size_t size, size_t& part1Length, size_t& part2Length)
{
    ASSERT(index < m_fifoLength && size <= m_fifoLength);
    if (index < m_fifoLength && size <= m_fifoLength) {
        if (index + size > m_fifoLength) {
            // Need to wrap. Figure out the length of each piece.
            part1Length = m_fifoLength - index;
            part2Length = size - part1Length;
        } else {
            // No wrap needed.
            part1Length = size;
            part2Length = 0;
        }
    } else {
        // Invalid values for index or size. Set the part lengths to zero so nothing is copied.
        part1Length = 0;
        part2Length = 0;
    }
}

void AudioPullFIFO::fillBuffer(size_t numberOfFrames)
{
    // Keep asking the provider to give us data until we have received at least |numberOfFrames| of
    // data. Stuff the data into the FIFO.
    size_t framesProvided = 0;

    while (framesProvided < numberOfFrames) {
        m_provider.provideInput(&m_tempBus, m_providerSize);

        size_t part1Length;
        size_t part2Length;
        findWrapLengths(m_writeIndex, m_providerSize, part1Length, part2Length);

        size_t numberOfChannels = m_fifoAudioBus.numberOfChannels();
        
        for (size_t channelIndex = 0; channelIndex < numberOfChannels; ++channelIndex) {
            float* destination = m_fifoAudioBus.channel(channelIndex)->mutableData();
            const float* source = m_tempBus.channel(channelIndex)->data();

            bool isCopyGood = (part1Length <= m_providerSize
                               && (part1Length + part2Length) <= m_providerSize
                               && (m_writeIndex < m_fifoLength)
                               && (m_writeIndex + part1Length) <= m_fifoLength
                               && part2Length < m_fifoLength);
            ASSERT(isCopyGood);
            if (!isCopyGood)
                return;

            memcpy(destination + m_writeIndex, source, part1Length * sizeof(*destination));
            // Handle wrap around of the FIFO, if needed.
            if (part2Length > 0)
                memcpy(destination, source + part1Length, part2Length * sizeof(*destination));
        }

        m_framesInFifo += m_providerSize;
        ASSERT(m_framesInFifo <= m_fifoLength);
        m_writeIndex = updateIndex(m_writeIndex, m_providerSize);
        framesProvided += m_providerSize;
    }
}

} // namespace WebCore

#endif // ENABLE(WEB_AUDIO)