#include "StdAfx.h"
#include "IppFourier.h"

#include  <math.h>

const double PI = 3.14159265358979323846;

void DFT1d(double* re, double* im, int N, int dir)
{
    double* tr = new double[N];
    double* ti = new double[N];
    memcpy(tr, re, sizeof(double) * N);
    memcpy(ti, im, sizeof(double) * N);

    register int i, x;
    double sum_re, sum_im, temp;

    for (i = 0; i < N; i++)
    {
        sum_re = sum_im = 0;
  
        for (x = 0; x < N; x++)
        {
            temp = 2 * dir * PI * ((double)i * x / N);

            sum_re += (tr[x] * cos(temp) + ti[x] * sin(temp));
            sum_im += (ti[x] * cos(temp) - tr[x] * sin(temp));
        }

        re[i] = sum_re;
        im[i] = sum_im;
    }
  
    if (dir == -1) // IDFT
    {
        for (i = 0; i < N; i++)
        {
            re[i] /= (double)N;
            im[i] /= (double)N;
        }
    }

    delete[] tr;
    delete[] ti;
}