Source/modules/webaudio/AudioNodeInput.h

/*
 * Copyright (C) 2010, Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
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 *
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 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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#ifndef AudioNodeInput_h
#define AudioNodeInput_h

#include "platform/audio/AudioBus.h"
#include "modules/webaudio/AudioNode.h"
#include "modules/webaudio/AudioSummingJunction.h"
#include "wtf/HashSet.h"

namespace blink {

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 final : public AudioSummingJunction {
public:
    static AudioNodeInput* create(AudioNode&);

    // AudioSummingJunction
    virtual void trace(Visitor*) override;
    virtual void didUpdate() override;

    // Can be called from any thread.
    AudioNode& node() const { return *m_node; }

    // 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();

    // updateInternalBus() updates m_internalSummingBus appropriately for the number of channels.
    // 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 updateInternalBus();

    // The number of channels of the connection with the largest number of channels.
    unsigned numberOfChannels() const;

private:
    explicit AudioNodeInput(AudioNode&);

    Member<AudioNode> m_node;

    // 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.
    // Oilpan: Since items are added to the hash set by the audio thread (not registered to Oilpan),
    // we cannot use a HeapHashSet.
    GC_PLUGIN_IGNORE("http://crbug.com/404527")
    HashSet<AudioNodeOutput*> m_disabledOutputs;

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

    RefPtr<AudioBus> m_internalSummingBus;
};

} // namespace blink

#endif // AudioNodeInput_h