Source/WebCore/webaudio/AudioNodeInput.h

/*
 * Copyright (C) 2010, Google Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
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#ifndef AudioNodeInput_h
#define AudioNodeInput_h

#include "AudioBus.h"
#include "AudioNode.h"
#include <wtf/HashSet.h>
#include <wtf/Vector.h>

namespace WebCore {

class AudioNode;
class AudioNodeOutput;

// An AudioNodeInput represents an input to an AudioNode and can be connected from one or more AudioNodeOutputs.
// In the case of multiple connections, the input will act as a unity-gain summing junction, mixing all the outputs.
// The number of channels of the input's bus is the maximum of the number of channels of all its connections.

class AudioNodeInput {
public:
    AudioNodeInput(AudioNode*);

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

    // Must be called with the context's graph lock.
    void connect(AudioNodeOutput*);
    void disconnect(AudioNodeOutput*);

    // disable() will take the output out of the active connections list and set aside in a disabled list.
    // enable() will put the output back into the active connections list.
    // Must be called with the context's graph lock.
    void enable(AudioNodeOutput*);
    void disable(AudioNodeOutput*);

    // pull() processes all of the AudioNodes connected to us.
    // In the case of multiple connections it sums the result into an internal summing bus.
    // In the single connection case, it allows in-place processing where possible using inPlaceBus.
    // It returns the bus which it rendered into, returning inPlaceBus if in-place processing was performed.
    // Called from context's audio thread.
    AudioBus* pull(AudioBus* inPlaceBus, size_t framesToProcess);

    // bus() contains the rendered audio after pull() has been called for each time quantum.
    // Called from context's audio thread.
    AudioBus* bus();
    
    // This copies m_outputs to m_renderingOutputs.  Please see comments for these lists below.
    // This must be called when we own the context's graph lock in the audio thread at the very start or end of the render quantum.
    void updateRenderingState();

    // Rendering code accesses its version of the current connections here.
    unsigned numberOfRenderingConnections() const { return m_renderingOutputs.size(); }
    AudioNodeOutput* renderingOutput(unsigned i) { return m_renderingOutputs[i]; }
    const AudioNodeOutput* renderingOutput(unsigned i) const { return m_renderingOutputs[i]; }
    bool isConnected() const { return numberOfRenderingConnections() > 0; }

    // The number of channels of the connection with the largest number of channels.
    unsigned numberOfChannels() const;        
    
private:
    AudioNode* m_node;

    // m_outputs contains the AudioNodeOutputs representing current connections which are not disabled.
    // The rendering code should never use this directly, but instead uses m_renderingOutputs.
    HashSet<AudioNodeOutput*> m_outputs;

    // numberOfConnections() should never be called from the audio rendering thread.
    // Instead numberOfRenderingConnections() and renderingOutput() should be used.
    unsigned numberOfConnections() const { return m_outputs.size(); }

    // This must be called whenever we modify m_outputs.
    void changedOutputs();
    
    // m_renderingOutputs is a copy of m_outputs which will never be modified during the graph rendering on the audio thread.
    // This is the list which is used by the rendering code.
    // Whenever m_outputs is modified, the context is told so it can later update m_renderingOutputs from m_outputs at a safe time.
    // Most of the time, m_renderingOutputs is identical to m_outputs.
    Vector<AudioNodeOutput*> m_renderingOutputs;

    // m_renderingStateNeedUpdating keeps track if m_outputs is modified.
    bool m_renderingStateNeedUpdating;

    // The number of channels of the rendering connection with the largest number of channels.
    unsigned numberOfRenderingChannels();

    // m_disabledOutputs contains the AudioNodeOutputs which are disabled (will not be processed) by the audio graph rendering.
    // But, from JavaScript's perspective, these outputs are still connected to us.
    // Generally, these represent disabled connections from "notes" which have finished playing but are not yet garbage collected.
    HashSet<AudioNodeOutput*> m_disabledOutputs;

    // Called from context's audio thread.
    AudioBus* internalSummingBus();
    void sumAllConnections(AudioBus* summingBus, size_t framesToProcess);

    OwnPtr<AudioBus> m_monoSummingBus;
    OwnPtr<AudioBus> m_stereoSummingBus;
};

} // namespace WebCore

#endif // AudioNodeInput_h