AudioCompactor.cpp (2329B)
1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ 2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */ 3 /* This Source Code Form is subject to the terms of the Mozilla Public 4 * License, v. 2.0. If a copy of the MPL was not distributed with this 5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ 6 #include "AudioCompactor.h" 7 #if defined(MOZ_MEMORY) 8 # include "mozmemory.h" 9 #endif 10 11 namespace mozilla { 12 13 static size_t MallocGoodSize(size_t aSize) { 14 #if defined(MOZ_MEMORY) 15 return malloc_good_size(aSize); 16 #else 17 return aSize; 18 #endif 19 } 20 21 static size_t TooMuchSlop(size_t aSize, size_t aAllocSize, size_t aMaxSlop) { 22 // If the allocated size is less then our target size, then we 23 // are chunking. This means it will be completely filled with 24 // zero slop. 25 size_t slop = (aAllocSize > aSize) ? (aAllocSize - aSize) : 0; 26 return slop > aMaxSlop; 27 } 28 29 uint32_t AudioCompactor::GetChunkSamples(uint32_t aFrames, uint32_t aChannels, 30 size_t aMaxSlop) { 31 size_t size = AudioDataSize(aFrames, aChannels); 32 size_t chunkSize = MallocGoodSize(size); 33 34 // Reduce the chunk size until we meet our slop goal or the chunk 35 // approaches an unreasonably small size. 36 while (chunkSize > 64 && TooMuchSlop(size, chunkSize, aMaxSlop)) { 37 chunkSize = MallocGoodSize(chunkSize / 2); 38 } 39 40 // Calculate the number of samples based on expected malloc size 41 // in order to allow as many frames as possible to be packed. 42 return chunkSize / sizeof(AudioDataValue); 43 } 44 45 uint32_t AudioCompactor::NativeCopy::operator()(AudioDataValue* aBuffer, 46 uint32_t aSamples) { 47 NS_ASSERTION(aBuffer, "cannot copy to null buffer pointer"); 48 NS_ASSERTION(aSamples, "cannot copy zero values"); 49 50 size_t bufferBytes = aSamples * sizeof(AudioDataValue); 51 size_t maxBytes = std::min(bufferBytes, mSourceBytes - mNextByte); 52 uint32_t frames = maxBytes / BytesPerFrame(mChannels); 53 size_t bytes = frames * BytesPerFrame(mChannels); 54 55 NS_ASSERTION((mNextByte + bytes) <= mSourceBytes, 56 "tried to copy beyond source buffer"); 57 NS_ASSERTION(bytes <= bufferBytes, "tried to copy beyond destination buffer"); 58 59 memcpy(aBuffer, mSource + mNextByte, bytes); 60 61 mNextByte += bytes; 62 return frames; 63 } 64 65 } // namespace mozilla