Implement StereoPannerNode for robust stereo panning

Source/modules/webaudio/StereoPannerNode.h

-// Copyright (C) 2013 Google Inc. All rights reserved.
+// Copyright 2014 The Chromium Authors. All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //    * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //    * 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.
 //    * Neither the name of Google Inc. nor the names of its
 // contributors may be used to endorse or promote products derived from
 // this software without specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND 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 THE COPYRIGHT
 // OWNER OR 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 TextRunIterator_h
-#define TextRunIterator_h
+#ifndef StereoPannerNode_h
+#define StereoPannerNode_h
 
-#include "platform/text/TextRun.h"
+#include "modules/webaudio/AudioNode.h"
+#include "modules/webaudio/AudioParam.h"
+#include "platform/audio/AudioBus.h"
+#include "platform/audio/Spatializer.h"
 
 namespace blink {
 
-class TextRunIterator {
+// StereoPannerNode is an AudioNode with one input and one output. It is
+// specifically designed for equal-power stereo panning.
+class StereoPannerNode final : public AudioNode {
+    DEFINE_WRAPPERTYPEINFO();
 public:
-    TextRunIterator()
-        : m_textRun(0)
-        , m_offset(0)
+    static StereoPannerNode* create(AudioContext* context, float sampleRate)
     {
+        return new StereoPannerNode(context, sampleRate);
     }
 
-    TextRunIterator(const TextRun* textRun, unsigned offset)
-        : m_textRun(textRun)
-        , m_offset(offset)
-    {
-    }
+    virtual ~StereoPannerNode();
 
-    TextRunIterator(const TextRunIterator& other)
-        : m_textRun(other.m_textRun)
-        , m_offset(other.m_offset)
-    {
-    }
+    virtual void dispose() override;
+    virtual void process(size_t framesToProcess) override;
+    virtual void initialize() override;
+    virtual void uninitialize() override;
 
-    unsigned offset() const { return m_offset; }
-    void increment() { m_offset++; }
-    bool atEnd() const { return !m_textRun || m_offset >= m_textRun->length(); }
-    UChar current() const { return (*m_textRun)[m_offset]; }
-    WTF::Unicode::Direction direction() const { return atEnd() ? WTF::Unicode::OtherNeutral : WTF::Unicode::direction(current()); }
-    bool atParagraphSeparator() const { return current() == '\n'; }
+    virtual double tailTime() const override { return 0; }
+    virtual double latencyTime() const override { return 0; }
 
-    bool operator==(const TextRunIterator& other)
-    {
-        return m_offset == other.m_offset && m_textRun == other.m_textRun;
-    }
+    virtual void setChannelCount(unsigned long, ExceptionState&) final;
+    virtual void setChannelCountMode(const String&, ExceptionState&) final;
 
-    bool operator!=(const TextRunIterator& other) { return !operator==(other); }
+    virtual void trace(Visitor*) override;
+
+    AudioParam* pan() { return m_pan.get(); }
 
 private:
-    const TextRun* m_textRun;
-    int m_offset;
+    StereoPannerNode(AudioContext*, float sampleRate);
+
+    Member<Spatializer> m_stereoPanner;
+    Member<AudioParam> m_pan;
+
+    AudioFloatArray m_sampleAccuratePanValues;
 };
 
-
 } // namespace blink
 
-#endif // TextRunIterator_h
+#endif // StereoPannerNode_h