Source/WebCore/Modules/webaudio/AudioNodeInput.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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 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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 * DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
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#pragma once

#include "AudioBus.h"
#include "AudioNode.h"
#include "AudioSummingJunction.h"
#include <wtf/HashSet.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 final : public AudioSummingJunction {
    WTF_MAKE_NONCOPYABLE(AudioNodeInput);
    WTF_MAKE_FAST_ALLOCATED;
public:
    explicit AudioNodeInput(AudioNode*);

    // AudioSummingJunction
    bool canUpdateState() override { return !node()->isMarkedForDeletion(); }
    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:
    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.
    HashSet<AudioNodeOutput*> m_disabledOutputs;

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

    RefPtr<AudioBus> m_internalSummingBus;
};

} // namespace WebCore