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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim:set ts=2 sw=2 sts=2 et cindent: */
/* 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 "AudioBlock.h"
#include "AlignmentUtils.h"
namespace mozilla {
/**
* Heap-allocated buffer of channels of 128-sample float arrays, with
* threadsafe refcounting. Typically you would allocate one of these, fill it
* in, and then treat it as immutable while it's shared.
*
* Downstream references are accounted specially so that the creator of the
* buffer can reuse and modify its contents next iteration if other references
* are all downstream temporary references held by AudioBlock.
*
* We guarantee 16 byte alignment of the channel data.
*/
class AudioBlockBuffer final : public ThreadSharedObject {
public:
virtual AudioBlockBuffer* AsAudioBlockBuffer() override { return this; };
float* ChannelData(uint32_t aChannel)
{
float* base = reinterpret_cast<float*>(((uintptr_t)(this + 1) + 15) & ~0x0F);
ASSERT_ALIGNED16(base);
return base + aChannel * WEBAUDIO_BLOCK_SIZE;
}
static already_AddRefed<AudioBlockBuffer> Create(uint32_t aChannelCount)
{
CheckedInt<size_t> size = WEBAUDIO_BLOCK_SIZE;
size *= aChannelCount;
size *= sizeof(float);
size += sizeof(AudioBlockBuffer);
size += 15; //padding for alignment
if (!size.isValid()) {
MOZ_CRASH();
}
void* m = moz_xmalloc(size.value());
RefPtr<AudioBlockBuffer> p = new (m) AudioBlockBuffer();
NS_ASSERTION((reinterpret_cast<char*>(p.get() + 1) - reinterpret_cast<char*>(p.get())) % 4 == 0,
"AudioBlockBuffers should be at least 4-byte aligned");
return p.forget();
}
// Graph thread only.
void DownstreamRefAdded() { ++mDownstreamRefCount; }
void DownstreamRefRemoved() {
MOZ_ASSERT(mDownstreamRefCount > 0);
--mDownstreamRefCount;
}
// Whether this is shared by any owners that are not downstream.
// Called only from owners with a reference that is not a downstream
// reference. Graph thread only.
bool HasLastingShares()
{
// mRefCnt is atomic and so reading its value is defined even when
// modifications may happen on other threads. mDownstreamRefCount is
// not modified on any other thread.
//
// If all other references are downstream references (managed on this, the
// graph thread), then other threads are not using this buffer and cannot
// add further references. This method can safely return false. The
// buffer contents can be modified.
//
// If there are other references that are not downstream references, then
// this method will return true. The buffer will be assumed to be still
// in use and so will not be reused.
nsrefcnt count = mRefCnt;
// This test is strictly less than because the caller has a reference
// that is not a downstream reference.
MOZ_ASSERT(mDownstreamRefCount < count);
return count != mDownstreamRefCount + 1;
}
virtual size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const override
{
return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
}
private:
AudioBlockBuffer() {}
~AudioBlockBuffer() override { MOZ_ASSERT(mDownstreamRefCount == 0); }
nsAutoRefCnt mDownstreamRefCount;
};
AudioBlock::~AudioBlock()
{
ClearDownstreamMark();
}
void
AudioBlock::SetBuffer(ThreadSharedObject* aNewBuffer)
{
if (aNewBuffer == mBuffer) {
return;
}
ClearDownstreamMark();
mBuffer = aNewBuffer;
if (!aNewBuffer) {
return;
}
AudioBlockBuffer* buffer = aNewBuffer->AsAudioBlockBuffer();
if (buffer) {
buffer->DownstreamRefAdded();
mBufferIsDownstreamRef = true;
}
}
void
AudioBlock::ClearDownstreamMark() {
if (mBufferIsDownstreamRef) {
mBuffer->AsAudioBlockBuffer()->DownstreamRefRemoved();
mBufferIsDownstreamRef = false;
}
}
bool
AudioBlock::CanWrite() {
// If mBufferIsDownstreamRef is set then the buffer is not ours to use.
// It may be in use by another node which is not downstream.
return !mBufferIsDownstreamRef &&
!mBuffer->AsAudioBlockBuffer()->HasLastingShares();
}
void
AudioBlock::AllocateChannels(uint32_t aChannelCount)
{
MOZ_ASSERT(mDuration == WEBAUDIO_BLOCK_SIZE);
if (mBufferIsDownstreamRef) {
// This is not our buffer to re-use.
ClearDownstreamMark();
} else if (mBuffer && ChannelCount() == aChannelCount) {
AudioBlockBuffer* buffer = mBuffer->AsAudioBlockBuffer();
if (buffer && !buffer->HasLastingShares()) {
MOZ_ASSERT(mBufferFormat == AUDIO_FORMAT_FLOAT32);
// No need to allocate again.
mVolume = 1.0f;
return;
}
}
RefPtr<AudioBlockBuffer> buffer = AudioBlockBuffer::Create(aChannelCount);
mChannelData.SetLength(aChannelCount);
for (uint32_t i = 0; i < aChannelCount; ++i) {
mChannelData[i] = buffer->ChannelData(i);
}
mBuffer = buffer.forget();
mVolume = 1.0f;
mBufferFormat = AUDIO_FORMAT_FLOAT32;
}
} // namespace mozilla
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