Source/modules/webaudio/AudioDestinationNode.h

/*
 * Copyright (C) 2010, Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 *    notice, this list of conditions and the following disclaimer.
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#ifndef AudioDestinationNode_h
#define AudioDestinationNode_h

#include "platform/audio/AudioBus.h"
#include "platform/audio/AudioIOCallback.h"
#include "platform/audio/AudioSourceProvider.h"
#include "modules/webaudio/AudioBuffer.h"
#include "modules/webaudio/AudioNode.h"

namespace blink {

class AudioBus;
class AudioContext;

class AudioDestinationNode : public AudioNode, public AudioIOCallback {
    DEFINE_WRAPPERTYPEINFO();
public:
    AudioDestinationNode(AudioContext*, float sampleRate);
    virtual ~AudioDestinationNode();

    // AudioNode
    virtual void dispose() override;
    virtual void process(size_t) override final { } // we're pulled by hardware so this is never called

    // The audio hardware calls render() to get the next render quantum of audio into destinationBus.
    // It will optionally give us local/live audio input in sourceBus (if it's not 0).
    virtual void render(AudioBus* sourceBus, AudioBus* destinationBus, size_t numberOfFrames) override final;

    size_t currentSampleFrame() const { return m_currentSampleFrame; }
    double currentTime() const { return currentSampleFrame() / static_cast<double>(sampleRate()); }

    virtual unsigned long maxChannelCount() const { return 0; }

    virtual void startRendering() = 0;

protected:
    // LocalAudioInputProvider allows us to expose an AudioSourceProvider for local/live audio input.
    // If there is local/live audio input, we call set() with the audio input data every render quantum.
    class LocalAudioInputProvider final : public AudioSourceProvider {
    public:
        LocalAudioInputProvider()
            : m_sourceBus(AudioBus::create(2, AudioNode::ProcessingSizeInFrames)) // FIXME: handle non-stereo local input.
        {
        }

        void set(AudioBus* bus)
        {
            if (bus)
                m_sourceBus->copyFrom(*bus);
        }

        // AudioSourceProvider.
        virtual void provideInput(AudioBus* destinationBus, size_t numberOfFrames) override
        {
            bool isGood = destinationBus && destinationBus->length() == numberOfFrames && m_sourceBus->length() == numberOfFrames;
            ASSERT(isGood);
            if (isGood)
                destinationBus->copyFrom(*m_sourceBus);
        }

    private:
        RefPtr<AudioBus> m_sourceBus;
    };

    virtual double tailTime() const override final { return 0; }
    virtual double latencyTime() const override final { return 0; }

    // Counts the number of sample-frames processed by the destination.
    size_t m_currentSampleFrame;

    LocalAudioInputProvider m_localAudioInputProvider;
};

} // namespace blink

#endif // AudioDestinationNode_h