cadencii.fft.rftfsub C# (CSharp) Method

        static void rftfsub( int n, double* a, int nc, double* c ) {
            int j, k, kk, ks, m;
            double wkr, wki, xr, xi, yr, yi;

            m = n >> 1;
            ks = 2 * nc / m;
            kk = 0;
            for ( j = 2; j < m; j += 2 ) {
                k = n - j;
                kk += ks;
                wkr = 0.5 - c[nc - kk];
                wki = c[kk];
                xr = a[j] - a[k];
                xi = a[j + 1] + a[k + 1];
                yr = wkr * xr - wki * xi;
                yi = wkr * xi + wki * xr;
                a[j] -= yr;
                a[j + 1] -= yi;
                a[k] += yr;
                a[k + 1] -= yi;
            }
        }