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diff --git a/Source/WebCore/platform/audio/Distance.cpp b/Source/WebCore/platform/audio/Distance.cpp
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+++ b/Source/WebCore/platform/audio/Distance.cpp
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+/*
+ * 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
+ * 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.
+ * 3.  Neither the name of Apple Computer, Inc. ("Apple") 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 APPLE 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 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.
+ */
+
+#include "config.h"
+
+#if ENABLE(WEB_AUDIO)
+
+#include "Distance.h"
+
+#include <algorithm>
+#include <math.h>
+
+using namespace std;
+
+namespace WebCore {
+
+DistanceEffect::DistanceEffect()
+    : m_model(ModelInverse)
+    , m_isClamped(true)
+    , m_refDistance(1.0)
+    , m_maxDistance(10000.0)
+    , m_rolloffFactor(1.0)
+{
+}
+
+double DistanceEffect::gain(double distance)
+{
+    // don't go beyond maximum distance
+    distance = min(distance, m_maxDistance);
+
+    // if clamped, don't get closer than reference distance
+    if (m_isClamped)
+        distance = max(distance, m_refDistance);
+
+    switch (m_model) {
+    case ModelLinear:
+        return linearGain(distance);
+        break;
+    case ModelInverse:
+        return inverseGain(distance);
+        break;
+    case ModelExponential:
+        return exponentialGain(distance);
+        break;
+
+    default:
+        return 0.0;
+    }
+}
+
+double DistanceEffect::linearGain(double distance)
+{
+    return (1.0 - m_rolloffFactor * (distance - m_refDistance)) / (m_maxDistance - m_refDistance);
+}
+
+double DistanceEffect::inverseGain(double distance)
+{
+    return m_refDistance / (m_refDistance + m_rolloffFactor * (distance - m_refDistance));
+}
+
+double DistanceEffect::exponentialGain(double distance)
+{
+    return pow(distance / m_refDistance, -m_rolloffFactor);
+}
+
+} // namespace WebCore
+
+#endif // ENABLE(WEB_AUDIO)