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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/. */
+#ifndef MOZILLA_AUDIOBLOCK_H_
+#define MOZILLA_AUDIOBLOCK_H_
+
+#include "AudioSegment.h"
+
+namespace mozilla {
+
+/**
+ * An AudioChunk whose buffer contents need to be valid only for one
+ * processing block iteration, after which contents can be overwritten if the
+ * buffer has not been passed to longer term storage or to another thread,
+ * which may happen though AsAudioChunk() or AsMutableChunk().
+ *
+ * Use on graph thread only.
+ */
+class AudioBlock : private AudioChunk
+{
+public:
+ AudioBlock() {
+ mDuration = WEBAUDIO_BLOCK_SIZE;
+ mBufferFormat = AUDIO_FORMAT_SILENCE;
+ }
+ // No effort is made in constructors to ensure that mBufferIsDownstreamRef
+ // is set because the block is expected to be a temporary and so the
+ // reference will be released before the next iteration.
+ // The custom copy constructor is required so as not to set
+ // mBufferIsDownstreamRef without notifying AudioBlockBuffer.
+ AudioBlock(const AudioBlock& aBlock) : AudioChunk(aBlock.AsAudioChunk()) {}
+ explicit AudioBlock(const AudioChunk& aChunk)
+ : AudioChunk(aChunk)
+ {
+ MOZ_ASSERT(aChunk.mDuration == WEBAUDIO_BLOCK_SIZE);
+ }
+ ~AudioBlock();
+
+ using AudioChunk::GetDuration;
+ using AudioChunk::IsNull;
+ using AudioChunk::ChannelCount;
+ using AudioChunk::ChannelData;
+ using AudioChunk::SizeOfExcludingThisIfUnshared;
+ using AudioChunk::SizeOfExcludingThis;
+ // mDuration is not exposed. Use GetDuration().
+ // mBuffer is not exposed. Use SetBuffer().
+ using AudioChunk::mChannelData;
+ using AudioChunk::mVolume;
+ using AudioChunk::mBufferFormat;
+
+ const AudioChunk& AsAudioChunk() const { return *this; }
+ AudioChunk* AsMutableChunk() {
+ ClearDownstreamMark();
+ return this;
+ }
+
+ /**
+ * Allocates, if necessary, aChannelCount buffers of WEBAUDIO_BLOCK_SIZE float
+ * samples for writing.
+ */
+ void AllocateChannels(uint32_t aChannelCount);
+
+ /**
+ * ChannelFloatsForWrite() should only be used when the buffers have been
+ * created with AllocateChannels().
+ */
+ float* ChannelFloatsForWrite(size_t aChannel)
+ {
+ MOZ_ASSERT(mBufferFormat == AUDIO_FORMAT_FLOAT32);
+ MOZ_ASSERT(CanWrite());
+ return static_cast<float*>(const_cast<void*>(mChannelData[aChannel]));
+ }
+
+ void SetBuffer(ThreadSharedObject* aNewBuffer);
+ void SetNull(StreamTime aDuration) {
+ MOZ_ASSERT(aDuration == WEBAUDIO_BLOCK_SIZE);
+ SetBuffer(nullptr);
+ mChannelData.Clear();
+ mVolume = 1.0f;
+ mBufferFormat = AUDIO_FORMAT_SILENCE;
+ }
+
+ AudioBlock& operator=(const AudioBlock& aBlock) {
+ // Instead of just copying, mBufferIsDownstreamRef must be first cleared
+ // if set. It is set again for the new mBuffer if possible. This happens
+ // in SetBuffer().
+ return *this = aBlock.AsAudioChunk();
+ }
+ AudioBlock& operator=(const AudioChunk& aChunk) {
+ MOZ_ASSERT(aChunk.mDuration == WEBAUDIO_BLOCK_SIZE);
+ SetBuffer(aChunk.mBuffer);
+ mChannelData = aChunk.mChannelData;
+ mVolume = aChunk.mVolume;
+ mBufferFormat = aChunk.mBufferFormat;
+ return *this;
+ }
+
+ bool IsMuted() const { return mVolume == 0.0f; }
+
+ bool IsSilentOrSubnormal() const
+ {
+ if (!mBuffer) {
+ return true;
+ }
+
+ for (uint32_t i = 0, length = mChannelData.Length(); i < length; ++i) {
+ const float* channel = static_cast<const float*>(mChannelData[i]);
+ for (StreamTime frame = 0; frame < mDuration; ++frame) {
+ if (fabs(channel[frame]) >= FLT_MIN) {
+ return false;
+ }
+ }
+ }
+
+ return true;
+ }
+
+private:
+ void ClearDownstreamMark();
+ bool CanWrite();
+
+ // mBufferIsDownstreamRef is set only when mBuffer references an
+ // AudioBlockBuffer created in a different AudioBlock. That can happen when
+ // this AudioBlock is on a node downstream from the node which created the
+ // buffer. When this is set, the AudioBlockBuffer is notified that this
+ // reference does prevent the upstream node from re-using the buffer next
+ // iteration and modifying its contents. The AudioBlockBuffer is also
+ // notified when mBuffer releases this reference.
+ bool mBufferIsDownstreamRef = false;
+};
+
+} // namespace mozilla
+
+#endif // MOZILLA_AUDIOBLOCK_H_