1 files changed, 65 insertions, 0 deletions
diff --git a/dom/media/AudioCompactor.cpp b/dom/media/AudioCompactor.cpp
new file mode 100644
index 0000000000..54e723d55e
--- /dev/null
+++ b/dom/media/AudioCompactor.cpp
@@ -0,0 +1,65 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#include "AudioCompactor.h"
+#if defined(MOZ_MEMORY)
+#  include "mozmemory.h"
+#endif
+
+namespace mozilla {
+
+static size_t MallocGoodSize(size_t aSize) {
+#if defined(MOZ_MEMORY)
+  return malloc_good_size(aSize);
+#else
+  return aSize;
+#endif
+}
+
+static size_t TooMuchSlop(size_t aSize, size_t aAllocSize, size_t aMaxSlop) {
+  // If the allocated size is less then our target size, then we
+  // are chunking.  This means it will be completely filled with
+  // zero slop.
+  size_t slop = (aAllocSize > aSize) ? (aAllocSize - aSize) : 0;
+  return slop > aMaxSlop;
+}
+
+uint32_t AudioCompactor::GetChunkSamples(uint32_t aFrames, uint32_t aChannels,
+                                         size_t aMaxSlop) {
+  size_t size = AudioDataSize(aFrames, aChannels);
+  size_t chunkSize = MallocGoodSize(size);
+
+  // Reduce the chunk size until we meet our slop goal or the chunk
+  // approaches an unreasonably small size.
+  while (chunkSize > 64 && TooMuchSlop(size, chunkSize, aMaxSlop)) {
+    chunkSize = MallocGoodSize(chunkSize / 2);
+  }
+
+  // Calculate the number of samples based on expected malloc size
+  // in order to allow as many frames as possible to be packed.
+  return chunkSize / sizeof(AudioDataValue);
+}
+
+uint32_t AudioCompactor::NativeCopy::operator()(AudioDataValue* aBuffer,
+                                                uint32_t aSamples) {
+  NS_ASSERTION(aBuffer, "cannot copy to null buffer pointer");
+  NS_ASSERTION(aSamples, "cannot copy zero values");
+
+  size_t bufferBytes = aSamples * sizeof(AudioDataValue);
+  size_t maxBytes = std::min(bufferBytes, mSourceBytes - mNextByte);
+  uint32_t frames = maxBytes / BytesPerFrame(mChannels);
+  size_t bytes = frames * BytesPerFrame(mChannels);
+
+  NS_ASSERTION((mNextByte + bytes) <= mSourceBytes,
+               "tried to copy beyond source buffer");
+  NS_ASSERTION(bytes <= bufferBytes, "tried to copy beyond destination buffer");
+
+  memcpy(aBuffer, mSource + mNextByte, bytes);
+
+  mNextByte += bytes;
+  return frames;
+}
+
+}  // namespace mozilla