1/*
2 * Copyright (C) 2012, Google Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1.  Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2.  Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
15 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
16 * DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
17 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
18 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
19 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
20 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
22 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23 */
24
25#ifndef AudioSummingJunction_h
26#define AudioSummingJunction_h
27
28#include "AudioBus.h"
29#include <wtf/HashSet.h>
30#include <wtf/Vector.h>
31
32namespace WebCore {
33
34class AudioContext;
35class AudioNodeOutput;
36
37// An AudioSummingJunction represents a point where zero, one, or more AudioNodeOutputs connect.
38
39class AudioSummingJunction {
40public:
41    explicit AudioSummingJunction(AudioContext*);
42    virtual ~AudioSummingJunction();
43
44    // Can be called from any thread.
45    AudioContext* context() { return m_context.get(); }
46
47    // This must be called whenever we modify m_outputs.
48    void changedOutputs();
49
50    // This copies m_outputs to m_renderingOutputs. Please see comments for these lists below.
51    // 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.
52    void updateRenderingState();
53
54    // Rendering code accesses its version of the current connections here.
55    unsigned numberOfRenderingConnections() const { return m_renderingOutputs.size(); }
56    AudioNodeOutput* renderingOutput(unsigned i) { return m_renderingOutputs[i]; }
57    const AudioNodeOutput* renderingOutput(unsigned i) const { return m_renderingOutputs[i]; }
58    bool isConnected() const { return numberOfRenderingConnections() > 0; }
59
60    virtual bool canUpdateState() = 0;
61    virtual void didUpdate() = 0;
62
63protected:
64    RefPtr<AudioContext> m_context;
65
66    // m_outputs contains the AudioNodeOutputs representing current connections which are not disabled.
67    // The rendering code should never use this directly, but instead uses m_renderingOutputs.
68    HashSet<AudioNodeOutput*> m_outputs;
69
70    // numberOfConnections() should never be called from the audio rendering thread.
71    // Instead numberOfRenderingConnections() and renderingOutput() should be used.
72    unsigned numberOfConnections() const { return m_outputs.size(); }
73
74    // m_renderingOutputs is a copy of m_outputs which will never be modified during the graph rendering on the audio thread.
75    // This is the list which is used by the rendering code.
76    // Whenever m_outputs is modified, the context is told so it can later update m_renderingOutputs from m_outputs at a safe time.
77    // Most of the time, m_renderingOutputs is identical to m_outputs.
78    Vector<AudioNodeOutput*> m_renderingOutputs;
79
80    // m_renderingStateNeedUpdating keeps track if m_outputs is modified.
81    bool m_renderingStateNeedUpdating;
82};
83
84} // namespace WebCore
85
86#endif // AudioSummingJunction_h
87