cadencii.fft.dstsub C# (CSharp) Method

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

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