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 * Copyright (C) 2010, Google Inc. All rights reserved.
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#ifndef AudioNodeOutput_h
#define AudioNodeOutput_h

#include "platform/audio/AudioBus.h"
#include "modules/webaudio/AudioNode.h"
#include "modules/webaudio/AudioParam.h"
#include "wtf/HashSet.h"
#include "wtf/RefPtr.h"
#include "wtf/Vector.h"

namespace WebCore {

class AudioContext;
class AudioNodeInput;

// AudioNodeOutput represents a single output for an AudioNode.
// It may be connected to one or more AudioNodeInputs.

class AudioNodeOutput {
public:
    // It's OK to pass 0 for numberOfChannels in which case setNumberOfChannels() must be called later on.
    AudioNodeOutput(AudioNode*, unsigned numberOfChannels);

    // Can be called from any thread.
    AudioNode* node() const { return m_node; }
    AudioContext* context() { return m_node->context(); }

    // Causes our AudioNode to process if it hasn't already for this render quantum.
    // It returns the bus containing the processed audio for this output, returning inPlaceBus if in-place processing was possible.
    // Called from context's audio thread.
    AudioBus* pull(AudioBus* inPlaceBus, size_t framesToProcess);

    // bus() will contain the rendered audio after pull() is called for each rendering time quantum.
    // Called from context's audio thread.
    AudioBus* bus() const;

    // renderingFanOutCount() is the number of AudioNodeInputs that we're connected to during rendering.
    // Unlike fanOutCount() it will not change during the course of a render quantum.
    unsigned renderingFanOutCount() const;

    // renderingParamFanOutCount() is the number of AudioParams that we're connected to during rendering.
    // Unlike paramFanOutCount() it will not change during the course of a render quantum.
    unsigned renderingParamFanOutCount() const;

    // Must be called with the context's graph lock.
    void disconnectAll();

    void setNumberOfChannels(unsigned);
    unsigned numberOfChannels() const { return m_numberOfChannels; }
    bool isChannelCountKnown() const { return numberOfChannels() > 0; }

    bool isConnected() { return fanOutCount() > 0 || paramFanOutCount() > 0; }

    // Disable/Enable happens when there are still JavaScript references to a node, but it has otherwise "finished" its work.
    // For example, when a note has finished playing.  It is kept around, because it may be played again at a later time.
    // They must be called with the context's graph lock.
    void disable();
    void enable();

    // updateRenderingState() is called in the audio thread at the start or end of the render quantum to handle any recent changes to the graph state.
    // It must be called with the context's graph lock.
    void updateRenderingState();

private:
    AudioNode* m_node;

    friend class AudioNodeInput;
    friend class AudioParam;

    // These are called from AudioNodeInput.
    // They must be called with the context's graph lock.
    void addInput(AudioNodeInput*);
    void removeInput(AudioNodeInput*);
    void addParam(AudioParam*);
    void removeParam(AudioParam*);

    // fanOutCount() is the number of AudioNodeInputs that we're connected to.
    // This method should not be called in audio thread rendering code, instead renderingFanOutCount() should be used.
    // It must be called with the context's graph lock.
    unsigned fanOutCount();

    // Similar to fanOutCount(), paramFanOutCount() is the number of AudioParams that we're connected to.
    // This method should not be called in audio thread rendering code, instead renderingParamFanOutCount() should be used.
    // It must be called with the context's graph lock.
    unsigned paramFanOutCount();

    // Must be called with the context's graph lock.
    void disconnectAllInputs();
    void disconnectAllParams();

    // updateInternalBus() updates m_internalBus appropriately for the number of channels.
    // It is called in the constructor or in the audio thread with the context's graph lock.
    void updateInternalBus();

    // Announce to any nodes we're connected to that we changed our channel count for its input.
    // It must be called in the audio thread with the context's graph lock.
    void propagateChannelCount();

    // updateNumberOfChannels() is called in the audio thread at the start or end of the render quantum to pick up channel changes.
    // It must be called with the context's graph lock.
    void updateNumberOfChannels();

    // m_numberOfChannels will only be changed in the audio thread.
    // The main thread sets m_desiredNumberOfChannels which will later get picked up in the audio thread in updateNumberOfChannels().
    unsigned m_numberOfChannels;
    unsigned m_desiredNumberOfChannels;

    // m_internalBus and m_inPlaceBus must only be changed in the audio thread with the context's graph lock (or constructor).
    RefPtr<AudioBus> m_internalBus;
    RefPtr<AudioBus> m_inPlaceBus;
    // If m_isInPlace is true, use m_inPlaceBus as the valid AudioBus; If false, use the default m_internalBus.
    bool m_isInPlace;

    HashSet<AudioNodeInput*> m_inputs;
    typedef HashSet<AudioNodeInput*>::iterator InputsIterator;
    bool m_isEnabled;

    // For the purposes of rendering, keeps track of the number of inputs and AudioParams we're connected to.
    // These value should only be changed at the very start or end of the rendering quantum.
    unsigned m_renderingFanOutCount;
    unsigned m_renderingParamFanOutCount;

    HashSet<RefPtr<AudioParam> > m_params;
    typedef HashSet<RefPtr<AudioParam> >::iterator ParamsIterator;
};

} // namespace WebCore

#endif // AudioNodeOutput_h