Require use of AudioBus::create() to avoid ref-counting issues

Source/core/platform/audio/AudioBus.cpp

 /*
  * 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
@@ skipping 30 matching lines @@
 #include "core/platform/audio/VectorMath.h"
 #include <wtf/OwnPtr.h>
 #include <wtf/PassOwnPtr.h>
 
 namespace WebCore {
 
 using namespace VectorMath;
 
 const unsigned MaxBusChannels = 32;
 
+PassRefPtr<AudioBus> AudioBus::create(unsigned numberOfChannels, size_t length, bool allocate)
+{
+    ASSERT(numberOfChannels <= MaxBusChannels);
+    if (numberOfChannels > MaxBusChannels)
+        return 0;
+
+    return adoptRef(new AudioBus(numberOfChannels, length, allocate));
+}
+
 AudioBus::AudioBus(unsigned numberOfChannels, size_t length, bool allocate)
     : m_length(length)
     , m_busGain(1)
     , m_isFirstTime(true)
     , m_sampleRate(0)
 {
-    ASSERT(numberOfChannels <= MaxBusChannels);
-    if (numberOfChannels > MaxBusChannels)
-        return;
-
     m_channels.reserveInitialCapacity(numberOfChannels);
 
     for (unsigned i = 0; i < numberOfChannels; ++i) {
         PassOwnPtr<AudioChannel> channel = allocate ? adoptPtr(new AudioChannel(length)) : adoptPtr(new AudioChannel(0, length));
         m_channels.append(channel);
     }
 
     m_layout = LayoutCanonical; // for now this is the only layout we define
 }
 
@@ skipping 99 matching lines @@
     unsigned numberOfChannels = sourceBuffer->numberOfChannels();
 
     // Sanity checking
     bool isRangeSafe = startFrame < endFrame && endFrame <= numberOfSourceFrames;
     ASSERT(isRangeSafe);
     if (!isRangeSafe)
         return 0;
 
     size_t rangeLength = endFrame - startFrame;
 
-    RefPtr<AudioBus> audioBus = adoptRef(new AudioBus(numberOfChannels, rangeLength));
+    RefPtr<AudioBus> audioBus = create(numberOfChannels, rangeLength);
     audioBus->setSampleRate(sourceBuffer->sampleRate());
 
     for (unsigned i = 0; i < numberOfChannels; ++i)
         audioBus->channel(i)->copyFromRange(sourceBuffer->channel(i), startFrame, endFrame);
 
     return audioBus;
 }
 
 float AudioBus::maxAbsValue() const
 {
@@ skipping 345 matching lines @@
     if (sourceSampleRate == destinationSampleRate) {
         // No sample-rate conversion is necessary.
         if (mixToMono)
             return AudioBus::createByMixingToMono(sourceBus);
 
         // Return exact copy.
         return AudioBus::createBufferFromRange(sourceBus, 0, sourceBus->length());
     }
 
     if (sourceBus->isSilent()) {
-        RefPtr<AudioBus> silentBus = adoptRef(new AudioBus(numberOfSourceChannels, sourceBus->length() / sampleRateRatio));
+        RefPtr<AudioBus> silentBus = create(numberOfSourceChannels, sourceBus->length() / sampleRateRatio);
         silentBus->setSampleRate(newSampleRate);
         return silentBus;
     }
 
     // First, mix to mono (if necessary) then sample-rate convert.
     const AudioBus* resamplerSourceBus;
     RefPtr<AudioBus> mixedMonoBus;
     if (mixToMono) {
         mixedMonoBus = AudioBus::createByMixingToMono(sourceBus);
         resamplerSourceBus = mixedMonoBus.get();
     } else {
         // Directly resample without down-mixing.
         resamplerSourceBus = sourceBus;
     }
 
     // Calculate destination length based on the sample-rates.
     int sourceLength = resamplerSourceBus->length();
     int destinationLength = sourceLength / sampleRateRatio;
 
     // Create destination bus with same number of channels.
     unsigned numberOfDestinationChannels = resamplerSourceBus->numberOfChannels();
-    RefPtr<AudioBus> destinationBus(adoptRef(new AudioBus(numberOfDestinationChannels, destinationLength)));
+    RefPtr<AudioBus> destinationBus = create(numberOfDestinationChannels, destinationLength);
 
     // Sample-rate convert each channel.
     for (unsigned i = 0; i < numberOfDestinationChannels; ++i) {
         const float* source = resamplerSourceBus->channel(i)->data();
         float* destination = destinationBus->channel(i)->mutableData();
 
         SincResampler resampler(sampleRateRatio);
         resampler.process(source, destination, sourceLength);
     }
 
     destinationBus->clearSilentFlag();
     destinationBus->setSampleRate(newSampleRate);    
     return destinationBus;
 }
 
 PassRefPtr<AudioBus> AudioBus::createByMixingToMono(const AudioBus* sourceBus)
 {
     if (sourceBus->isSilent())
-        return adoptRef(new AudioBus(1, sourceBus->length()));
+        return create(1, sourceBus->length());
 
     switch (sourceBus->numberOfChannels()) {
     case 1:
         // Simply create an exact copy.
         return AudioBus::createBufferFromRange(sourceBus, 0, sourceBus->length());
     case 2:
         {
             unsigned n = sourceBus->length();
-            RefPtr<AudioBus> destinationBus(adoptRef(new AudioBus(1, n)));
+            RefPtr<AudioBus> destinationBus = create(1, n);
 
             const float* sourceL = sourceBus->channel(0)->data();
             const float* sourceR = sourceBus->channel(1)->data();
             float* destination = destinationBus->channel(0)->mutableData();
         
             // Do the mono mixdown.
             for (unsigned i = 0; i < n; ++i)
                 destination[i] = (sourceL[i] + sourceR[i]) / 2;
 
             destinationBus->clearSilentFlag();
@@ skipping 17 matching lines @@
 
 void AudioBus::clearSilentFlag()
 {
     for (size_t i = 0; i < m_channels.size(); ++i)
         m_channels[i]->clearSilentFlag();
 }
 
 } // WebCore
 
 #endif // ENABLE(WEB_AUDIO)