third_party/WebKit/Source/platform/audio/mac/FFTFrameMac.cpp

/*
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// Mac OS X - specific FFTFrame implementation

#include "wtf/build_config.h"

#if OS(MACOSX)

#include "platform/audio/FFTFrame.h"

#include "platform/audio/VectorMath.h"

namespace blink {

const int kMaxFFTPow2Size = 24;

FFTSetup* FFTFrame::fftSetups = nullptr;

// Normal constructor: allocates for a given fftSize
FFTFrame::FFTFrame(unsigned fftSize)
    : m_realData(fftSize), m_imagData(fftSize) {
  m_FFTSize = fftSize;
  m_log2FFTSize = static_cast<unsigned>(log2(fftSize));

  // We only allow power of two
  ASSERT(1UL << m_log2FFTSize == m_FFTSize);

  // Lazily create and share fftSetup with other frames
  m_FFTSetup = fftSetupForSize(fftSize);

  // Setup frame data
  m_frame.realp = m_realData.data();
  m_frame.imagp = m_imagData.data();
}

// Creates a blank/empty frame (interpolate() must later be called)
FFTFrame::FFTFrame() : m_realData(0), m_imagData(0) {
  // Later will be set to correct values when interpolate() is called
  m_frame.realp = 0;
  m_frame.imagp = 0;

  m_FFTSize = 0;
  m_log2FFTSize = 0;
}

// Copy constructor
FFTFrame::FFTFrame(const FFTFrame& frame)
    : m_FFTSize(frame.m_FFTSize),
      m_log2FFTSize(frame.m_log2FFTSize),
      m_realData(frame.m_FFTSize),
      m_imagData(frame.m_FFTSize),
      m_FFTSetup(frame.m_FFTSetup) {
  // Setup frame data
  m_frame.realp = m_realData.data();
  m_frame.imagp = m_imagData.data();

  // Copy/setup frame data
  unsigned nbytes = sizeof(float) * m_FFTSize;
  memcpy(realData(), frame.m_frame.realp, nbytes);
  memcpy(imagData(), frame.m_frame.imagp, nbytes);
}

FFTFrame::~FFTFrame() {}

void FFTFrame::doFFT(const float* data) {
  AudioFloatArray scaledData(m_FFTSize);
  // veclib fft returns a result that is twice as large as would be expected.
  // Compensate for that by scaling the input by half so the FFT has the
  // correct scaling.
  float scale = 0.5f;
  VectorMath::vsmul(data, 1, &scale, scaledData.data(), 1, m_FFTSize);

  vDSP_ctoz((DSPComplex*)scaledData.data(), 2, &m_frame, 1, m_FFTSize / 2);
  vDSP_fft_zrip(m_FFTSetup, &m_frame, 1, m_log2FFTSize, FFT_FORWARD);
}

void FFTFrame::doInverseFFT(float* data) {
  vDSP_fft_zrip(m_FFTSetup, &m_frame, 1, m_log2FFTSize, FFT_INVERSE);
  vDSP_ztoc(&m_frame, 1, (DSPComplex*)data, 2, m_FFTSize / 2);

  // Do final scaling so that x == IFFT(FFT(x))
  float scale = 1.0f / m_FFTSize;
  VectorMath::vsmul(data, 1, &scale, data, 1, m_FFTSize);
}

FFTSetup FFTFrame::fftSetupForSize(unsigned fftSize) {
  if (!fftSetups) {
    fftSetups = (FFTSetup*)malloc(sizeof(FFTSetup) * kMaxFFTPow2Size);
    memset(fftSetups, 0, sizeof(FFTSetup) * kMaxFFTPow2Size);
  }

  int pow2size = static_cast<int>(log2(fftSize));
  ASSERT(pow2size < kMaxFFTPow2Size);
  if (!fftSetups[pow2size])
    fftSetups[pow2size] = vDSP_create_fftsetup(pow2size, FFT_RADIX2);

  return fftSetups[pow2size];
}

void FFTFrame::initialize() {}

void FFTFrame::cleanup() {
  if (!fftSetups)
    return;

  for (int i = 0; i < kMaxFFTPow2Size; ++i) {
    if (fftSetups[i])
      vDSP_destroy_fftsetup(fftSetups[i]);
  }

  free(fftSetups);
  fftSetups = nullptr;
}

}  // namespace blink

#endif  // #if OS(MACOSX)