Source/modules/webaudio/AudioSummingJunction.h

/*
 * Copyright (C) 2012, Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1.  Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2.  Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * 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
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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#ifndef AudioSummingJunction_h
#define AudioSummingJunction_h

#include "platform/audio/AudioBus.h"
#include "platform/heap/Handle.h"
#include "wtf/HashSet.h"
#include "wtf/Vector.h"

namespace blink {

class AudioContext;
class AudioNodeOutput;

// An AudioSummingJunction represents a point where zero, one, or more AudioNodeOutputs connect.

class AudioSummingJunction : public GarbageCollectedFinalized<AudioSummingJunction> {
public:
    virtual ~AudioSummingJunction();
    virtual void trace(Visitor*);
    void dispose();

    // Can be called from any thread.
    AudioContext* context() { return m_context.get(); }

    // This must be called whenever we modify m_outputs.
    void changedOutputs();

    // 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]; }
    bool isConnected() const { return numberOfRenderingConnections() > 0; }

    virtual void didUpdate() = 0;

protected:
    explicit AudioSummingJunction(AudioContext*);

    Member<AudioContext> m_context;

    // 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.
    // 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_outputs;

    // 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.
    // Oilpan: Since items are added to the vector by the audio thread (not registered to Oilpan),
    // we cannot use a HeapVector.
    GC_PLUGIN_IGNORE("http://crbug.com/404527")
    Vector<AudioNodeOutput*> m_renderingOutputs;

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

    bool m_didCallDispose;
};

} // namespace blink

#endif // AudioSummingJunction_h