mirror of
https://github.com/classilla/tenfourfox.git
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166 lines
5.1 KiB
C++
166 lines
5.1 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim:set ts=2 sw=2 sts=2 et cindent: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "AudioBlock.h"
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namespace mozilla {
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/**
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* Heap-allocated buffer of channels of 128-sample float arrays, with
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* threadsafe refcounting. Typically you would allocate one of these, fill it
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* in, and then treat it as immutable while it's shared.
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*
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* Downstream references are accounted specially so that the creator of the
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* buffer can reuse and modify its contents next iteration if other references
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* are all downstream temporary references held by AudioBlock.
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*
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* This only guarantees 4-byte alignment of the data. For alignment we simply
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* assume that the memory from malloc is at least 4-byte aligned and that
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* AudioBlockBuffer's size is divisible by 4.
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*/
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class AudioBlockBuffer final : public ThreadSharedObject {
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public:
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virtual AudioBlockBuffer* AsAudioBlockBuffer() override { return this; };
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float* ChannelData(uint32_t aChannel)
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{
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return reinterpret_cast<float*>(this + 1) + aChannel * WEBAUDIO_BLOCK_SIZE;
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}
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static already_AddRefed<AudioBlockBuffer> Create(uint32_t aChannelCount)
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{
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CheckedInt<size_t> size = WEBAUDIO_BLOCK_SIZE;
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size *= aChannelCount;
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size *= sizeof(float);
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size += sizeof(AudioBlockBuffer);
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if (!size.isValid()) {
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MOZ_CRASH();
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}
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void* m = moz_xmalloc(size.value());
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RefPtr<AudioBlockBuffer> p = new (m) AudioBlockBuffer();
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NS_ASSERTION((reinterpret_cast<char*>(p.get() + 1) - reinterpret_cast<char*>(p.get())) % 4 == 0,
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"AudioBlockBuffers should be at least 4-byte aligned");
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return p.forget();
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}
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// Graph thread only.
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void DownstreamRefAdded() { ++mDownstreamRefCount; }
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void DownstreamRefRemoved() {
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MOZ_ASSERT(mDownstreamRefCount > 0);
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--mDownstreamRefCount;
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}
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// Whether this is shared by any owners that are not downstream.
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// Called only from owners with a reference that is not a downstream
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// reference. Graph thread only.
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bool HasLastingShares()
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{
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// mRefCnt is atomic and so reading its value is defined even when
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// modifications may happen on other threads. mDownstreamRefCount is
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// not modified on any other thread.
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//
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// If all other references are downstream references (managed on this, the
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// graph thread), then other threads are not using this buffer and cannot
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// add further references. This method can safely return false. The
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// buffer contents can be modified.
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//
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// If there are other references that are not downstream references, then
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// this method will return true. The buffer will be assumed to be still
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// in use and so will not be reused.
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nsrefcnt count = mRefCnt;
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// This test is strictly less than because the caller has a reference
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// that is not a downstream reference.
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MOZ_ASSERT(mDownstreamRefCount < count);
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return count != mDownstreamRefCount + 1;
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}
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virtual size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const override
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{
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return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
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}
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private:
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AudioBlockBuffer() {}
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~AudioBlockBuffer() override { MOZ_ASSERT(mDownstreamRefCount == 0); }
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nsAutoRefCnt mDownstreamRefCount;
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};
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AudioBlock::~AudioBlock()
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{
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ClearDownstreamMark();
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}
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void
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AudioBlock::SetBuffer(ThreadSharedObject* aNewBuffer)
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{
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if (aNewBuffer == mBuffer) {
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return;
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}
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ClearDownstreamMark();
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mBuffer = aNewBuffer;
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if (!aNewBuffer) {
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return;
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}
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AudioBlockBuffer* buffer = aNewBuffer->AsAudioBlockBuffer();
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if (buffer) {
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buffer->DownstreamRefAdded();
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mBufferIsDownstreamRef = true;
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}
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}
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void
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AudioBlock::ClearDownstreamMark() {
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if (mBufferIsDownstreamRef) {
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mBuffer->AsAudioBlockBuffer()->DownstreamRefRemoved();
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mBufferIsDownstreamRef = false;
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}
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}
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bool
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AudioBlock::CanWrite() {
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// If mBufferIsDownstreamRef is set then the buffer is not ours to use.
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// It may be in use by another node which is not downstream.
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return !mBufferIsDownstreamRef &&
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!mBuffer->AsAudioBlockBuffer()->HasLastingShares();
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}
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void
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AudioBlock::AllocateChannels(uint32_t aChannelCount)
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{
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MOZ_ASSERT(mDuration == WEBAUDIO_BLOCK_SIZE);
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if (mBufferIsDownstreamRef) {
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// This is not our buffer to re-use.
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ClearDownstreamMark();
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} else if (mBuffer && ChannelCount() == aChannelCount) {
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AudioBlockBuffer* buffer = mBuffer->AsAudioBlockBuffer();
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if (buffer && !buffer->HasLastingShares()) {
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MOZ_ASSERT(mBufferFormat == AUDIO_FORMAT_FLOAT32);
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// No need to allocate again.
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mVolume = 1.0f;
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return;
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}
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}
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// XXX for SIMD purposes we should do something here to make sure the
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// channel buffers are 16-byte aligned.
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RefPtr<AudioBlockBuffer> buffer = AudioBlockBuffer::Create(aChannelCount);
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mChannelData.SetLength(aChannelCount);
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for (uint32_t i = 0; i < aChannelCount; ++i) {
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mChannelData[i] = buffer->ChannelData(i);
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}
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mBuffer = buffer.forget();
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mVolume = 1.0f;
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mBufferFormat = AUDIO_FORMAT_FLOAT32;
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}
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} // namespace mozilla
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