1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/content/media/AudioCompactor.cpp Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,73 @@
1.4 +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
1.5 +/* vim: set ts=8 sts=2 et sw=2 tw=80: */
1.6 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.7 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.8 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.9 +#include "AudioCompactor.h"
1.10 +#if defined(MOZ_MEMORY)
1.11 +# include "mozmemory.h"
1.12 +#endif
1.13 +
1.14 +namespace mozilla {
1.15 +
1.16 +static size_t
1.17 +MallocGoodSize(size_t aSize)
1.18 +{
1.19 +# if defined(MOZ_MEMORY)
1.20 + return malloc_good_size(aSize);
1.21 +# else
1.22 + return aSize;
1.23 +# endif
1.24 +}
1.25 +
1.26 +static size_t
1.27 +TooMuchSlop(size_t aSize, size_t aAllocSize, size_t aMaxSlop)
1.28 +{
1.29 + // If the allocated size is less then our target size, then we
1.30 + // are chunking. This means it will be completely filled with
1.31 + // zero slop.
1.32 + size_t slop = (aAllocSize > aSize) ? (aAllocSize - aSize) : 0;
1.33 + return slop > aMaxSlop;
1.34 +}
1.35 +
1.36 +uint32_t
1.37 +AudioCompactor::GetChunkSamples(uint32_t aFrames, uint32_t aChannels,
1.38 + size_t aMaxSlop)
1.39 +{
1.40 + size_t size = AudioDataSize(aFrames, aChannels);
1.41 + size_t chunkSize = MallocGoodSize(size);
1.42 +
1.43 + // Reduce the chunk size until we meet our slop goal or the chunk
1.44 + // approaches an unreasonably small size.
1.45 + while (chunkSize > 64 && TooMuchSlop(size, chunkSize, aMaxSlop)) {
1.46 + chunkSize = MallocGoodSize(chunkSize / 2);
1.47 + }
1.48 +
1.49 + // Calculate the number of samples based on expected malloc size
1.50 + // in order to allow as many frames as possible to be packed.
1.51 + return chunkSize / sizeof(AudioDataValue);
1.52 +}
1.53 +
1.54 +uint32_t
1.55 +AudioCompactor::NativeCopy::operator()(AudioDataValue *aBuffer,
1.56 + uint32_t aSamples)
1.57 +{
1.58 + NS_ASSERTION(aBuffer, "cannot copy to null buffer pointer");
1.59 + NS_ASSERTION(aSamples, "cannot copy zero values");
1.60 +
1.61 + size_t bufferBytes = aSamples * sizeof(AudioDataValue);
1.62 + size_t maxBytes = std::min(bufferBytes, mSourceBytes - mNextByte);
1.63 + uint32_t frames = maxBytes / BytesPerFrame(mChannels);
1.64 + size_t bytes = frames * BytesPerFrame(mChannels);
1.65 +
1.66 + NS_ASSERTION((mNextByte + bytes) <= mSourceBytes,
1.67 + "tried to copy beyond source buffer");
1.68 + NS_ASSERTION(bytes <= bufferBytes, "tried to copy beyond destination buffer");
1.69 +
1.70 + memcpy(aBuffer, mSource + mNextByte, bytes);
1.71 +
1.72 + mNextByte += bytes;
1.73 + return frames;
1.74 +}
1.75 +
1.76 +} // namespace mozilla
