/*
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#include "platform/audio/ReverbConvolver.h"

#include "platform/CrossThreadFunctional.h"
#include "platform/WebTaskRunner.h"
#include "platform/audio/AudioBus.h"
#include "platform/audio/VectorMath.h"
#include "public/platform/Platform.h"
#include "public/platform/WebThread.h"
#include "public/platform/WebTraceLocation.h"
#include "wtf/PtrUtil.h"
#include <memory>

namespace blink {

using namespace VectorMath;

const int InputBufferSize = 8 * 16384;

// We only process the leading portion of the impulse response in the real-time
// thread.  We don't exceed this length.  It turns out then, that the
// background thread has about 278msec of scheduling slop.  Empirically, this
// has been found to be a good compromise between giving enough time for
// scheduling slop, while still minimizing the amount of processing done in the
// primary (high-priority) thread.  This was found to be a good value on Mac OS
// X, and may work well on other platforms as well, assuming the very rough
// scheduling latencies are similar on these time-scales.  Of course, this code
// may need to be tuned for individual platforms if this assumption is found to
// be incorrect.
const size_t RealtimeFrameLimit = 8192 + 4096;  // ~278msec @ 44.1KHz

const size_t MinFFTSize = 128;
const size_t MaxRealtimeFFTSize = 2048;

ReverbConvolver::ReverbConvolver(AudioChannel* impulseResponse,
                                 size_t renderSliceSize,
                                 size_t maxFFTSize,
                                 size_t convolverRenderPhase,
                                 bool useBackgroundThreads)
    : m_impulseResponseLength(impulseResponse->length()),
      m_accumulationBuffer(impulseResponse->length() + renderSliceSize),
      m_inputBuffer(InputBufferSize),
      m_minFFTSize(MinFFTSize),  // First stage will have this size - successive
                                 // stages will double in size each time
      m_maxFFTSize(maxFFTSize)   // until we hit m_maxFFTSize
{
  // If we are using background threads then don't exceed this FFT size for the
  // stages which run in the real-time thread.  This avoids having only one or
  // two large stages (size 16384 or so) at the end which take a lot of time
  // every several processing slices.  This way we amortize the cost over more
  // processing slices.
  m_maxRealtimeFFTSize = MaxRealtimeFFTSize;

  const float* response = impulseResponse->data();
  size_t totalResponseLength = impulseResponse->length();

  // The total latency is zero because the direct-convolution is used in the
  // leading portion.
  size_t reverbTotalLatency = 0;

  size_t stageOffset = 0;
  int i = 0;
  size_t fftSize = m_minFFTSize;
  while (stageOffset < totalResponseLength) {
    size_t stageSize = fftSize / 2;

    // For the last stage, it's possible that stageOffset is such that we're
    // straddling the end of the impulse response buffer (if we use stageSize),
    // so reduce the last stage's length...
    if (stageSize + stageOffset > totalResponseLength)
      stageSize = totalResponseLength - stageOffset;

    // This "staggers" the time when each FFT happens so they don't all happen
    // at the same time
    int renderPhase = convolverRenderPhase + i * renderSliceSize;

    bool useDirectConvolver = !stageOffset;

    std::unique_ptr<ReverbConvolverStage> stage =
        WTF::wrapUnique(new ReverbConvolverStage(
            response, totalResponseLength, reverbTotalLatency, stageOffset,
            stageSize, fftSize, renderPhase, renderSliceSize,
            &m_accumulationBuffer, useDirectConvolver));

    bool isBackgroundStage = false;

    if (useBackgroundThreads && stageOffset > RealtimeFrameLimit) {
      m_backgroundStages.push_back(std::move(stage));
      isBackgroundStage = true;
    } else {
      m_stages.push_back(std::move(stage));
    }

    stageOffset += stageSize;
    ++i;

    if (!useDirectConvolver) {
      // Figure out next FFT size
      fftSize *= 2;
    }

    if (useBackgroundThreads && !isBackgroundStage &&
        fftSize > m_maxRealtimeFFTSize)
      fftSize = m_maxRealtimeFFTSize;
    if (fftSize > m_maxFFTSize)
      fftSize = m_maxFFTSize;
  }

  // Start up background thread
  // FIXME: would be better to up the thread priority here.  It doesn't need to
  // be real-time, but higher than the default...
  if (useBackgroundThreads && m_backgroundStages.size() > 0)
    m_backgroundThread = WTF::wrapUnique(Platform::current()->createThread(
        "Reverb convolution background thread"));
}

ReverbConvolver::~ReverbConvolver() {
  // Wait for background thread to stop
  m_backgroundThread.reset();
}

void ReverbConvolver::processInBackground() {
  // Process all of the stages until their read indices reach the input buffer's
  // write index
  int writeIndex = m_inputBuffer.writeIndex();

  // Even though it doesn't seem like every stage needs to maintain its own
  // version of readIndex we do this in case we want to run in more than one
  // background thread.
  int readIndex;

  while ((readIndex = m_backgroundStages[0]->inputReadIndex()) !=
         writeIndex) {  // FIXME: do better to detect buffer overrun...
    // The ReverbConvolverStages need to process in amounts which evenly divide
    // half the FFT size
    const int SliceSize = MinFFTSize / 2;

    // Accumulate contributions from each stage
    for (size_t i = 0; i < m_backgroundStages.size(); ++i)
      m_backgroundStages[i]->processInBackground(this, SliceSize);
  }
}

void ReverbConvolver::process(const AudioChannel* sourceChannel,
                              AudioChannel* destinationChannel,
                              size_t framesToProcess) {
  bool isSafe = sourceChannel && destinationChannel &&
                sourceChannel->length() >= framesToProcess &&
                destinationChannel->length() >= framesToProcess;
  ASSERT(isSafe);
  if (!isSafe)
    return;

  const float* source = sourceChannel->data();
  float* destination = destinationChannel->mutableData();
  bool isDataSafe = source && destination;
  ASSERT(isDataSafe);
  if (!isDataSafe)
    return;

  // Feed input buffer (read by all threads)
  m_inputBuffer.write(source, framesToProcess);

  // Accumulate contributions from each stage
  for (size_t i = 0; i < m_stages.size(); ++i)
    m_stages[i]->process(source, framesToProcess);

  // Finally read from accumulation buffer
  m_accumulationBuffer.readAndClear(destination, framesToProcess);

  // Now that we've buffered more input, post another task to the background
  // thread.
  if (m_backgroundThread)
    m_backgroundThread->getWebTaskRunner()->postTask(
        BLINK_FROM_HERE, crossThreadBind(&ReverbConvolver::processInBackground,
                                         crossThreadUnretained(this)));
}

void ReverbConvolver::reset() {
  for (size_t i = 0; i < m_stages.size(); ++i)
    m_stages[i]->reset();

  for (size_t i = 0; i < m_backgroundStages.size(); ++i)
    m_backgroundStages[i]->reset();

  m_accumulationBuffer.reset();
  m_inputBuffer.reset();
}

size_t ReverbConvolver::latencyFrames() const {
  return 0;
}

}  // namespace blink