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;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#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 AudioNodeOutput;
class DeferredTaskHandler;

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

class AudioSummingJunction {
public:
    virtual ~AudioSummingJunction();

    // Can be called from any thread.
    DeferredTaskHandler& deferredTaskHandler() const { return *m_deferredTaskHandler; }

    // 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(DeferredTaskHandler&);

    RefPtr<DeferredTaskHandler> m_deferredTaskHandler;

    // 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.
    // These raw pointers are safe. Owner AudioNodes of these AudioNodeOutputs
    // manage their lifetime, and AudioNode::dispose() disconnects all of
    // connections.
    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.
    // These raw pointers are safe. Owner of this AudioSummingJunction has
    // strong references to owners of these AudioNodeOutput.
    Vector<AudioNodeOutput*> m_renderingOutputs;

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

} // namespace blink

#endif // AudioSummingJunction_h