/* -*- 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; };

  uint32_t ChannelsAllocated() const { return mChannelsAllocated; }

  float* ChannelData(uint32_t aChannel) const

  {

    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 = operator new(size.value());

    RefPtr<AudioBlockBuffer> p = new (m) AudioBlockBuffer(aChannelCount);

    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() const

  {

    // 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:

  explicit AudioBlockBuffer(uint32_t aChannelsAllocated)

    : mChannelsAllocated(aChannelsAllocated) {}

  ~AudioBlockBuffer() override { MOZ_ASSERT(mDownstreamRefCount == 0); }

  nsAutoRefCnt mDownstreamRefCount;

  const uint32_t mChannelsAllocated;

};

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) {

    AudioBlockBuffer* buffer = mBuffer->AsAudioBlockBuffer();

    if (buffer && !buffer->HasLastingShares() &&

        buffer->ChannelsAllocated() >= aChannelCount) {

      MOZ_ASSERT(mBufferFormat == AUDIO_FORMAT_FLOAT32);

      // No need to allocate again.

      uint32_t previousChannelCount = ChannelCount();

      mChannelData.SetLength(aChannelCount);

      for (uint32_t i = previousChannelCount; i < aChannelCount; ++i) {

        mChannelData[i] = buffer->ChannelData(i);

      }

      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