#include <vector>
#include <complex>

#define POCKETFFT_CACHE_SIZE (16*1024*1024)
#define POCKETFFT_NO_MULTITHREADING  // MT doesn't seem to help at small sizes
#include <pocketfft_hdronly.h>

void fft_mag(std::complex<float>* in, float* out, size_t len)
{
    pocketfft::shape_t shape{len};
    pocketfft::stride_t stride(1);
    stride[0] = sizeof(std::complex<float>);
    pocketfft::shape_t axes;
    axes.push_back(0);
    std::vector<std::complex<float>> out_rev(len);

    pocketfft::c2c(shape, stride, stride, axes, pocketfft::FORWARD, in, out_rev.data(), 1.0f);
    // negative frequencies first
    for(size_t i=0;i<len/2;i++)
        out[i] = abs(out_rev[i + len/2]);
    for(size_t i=0;i<len/2;i++)
        out[i + len/2] = abs(out_rev[i]);
}