static void cftf1st( int n, double* a, double* w ) {
int j, j0, j1, j2, j3, k, m, mh;
double wn4r, csc1, csc3, wk1r, wk1i, wk3r, wk3i,
wd1r, wd1i, wd3r, wd3i;
double x0r, x0i, x1r, x1i, x2r, x2i, x3r, x3i,
y0r, y0i, y1r, y1i, y2r, y2i, y3r, y3i;
mh = n >> 3;
m = 2 * mh;
j1 = m;
j2 = j1 + m;
j3 = j2 + m;
x0r = a[0] + a[j2];
x0i = a[1] + a[j2 + 1];
x1r = a[0] - a[j2];
x1i = a[1] - a[j2 + 1];
x2r = a[j1] + a[j3];
x2i = a[j1 + 1] + a[j3 + 1];
x3r = a[j1] - a[j3];
x3i = a[j1 + 1] - a[j3 + 1];
a[0] = x0r + x2r;
a[1] = x0i + x2i;
a[j1] = x0r - x2r;
a[j1 + 1] = x0i - x2i;
a[j2] = x1r - x3i;
a[j2 + 1] = x1i + x3r;
a[j3] = x1r + x3i;
a[j3 + 1] = x1i - x3r;
wn4r = w[1];
csc1 = w[2];
csc3 = w[3];
wd1r = 1;
wd1i = 0;
wd3r = 1;
wd3i = 0;
k = 0;
for ( j = 2; j < mh - 2; j += 4 ) {
k += 4;
wk1r = csc1 * (wd1r + w[k]);
wk1i = csc1 * (wd1i + w[k + 1]);
wk3r = csc3 * (wd3r + w[k + 2]);
wk3i = csc3 * (wd3i + w[k + 3]);
wd1r = w[k];
wd1i = w[k + 1];
wd3r = w[k + 2];
wd3i = w[k + 3];
j1 = j + m;
j2 = j1 + m;
j3 = j2 + m;
x0r = a[j] + a[j2];
x0i = a[j + 1] + a[j2 + 1];
x1r = a[j] - a[j2];
x1i = a[j + 1] - a[j2 + 1];
y0r = a[j + 2] + a[j2 + 2];
y0i = a[j + 3] + a[j2 + 3];
y1r = a[j + 2] - a[j2 + 2];
y1i = a[j + 3] - a[j2 + 3];
x2r = a[j1] + a[j3];
x2i = a[j1 + 1] + a[j3 + 1];
x3r = a[j1] - a[j3];
x3i = a[j1 + 1] - a[j3 + 1];
y2r = a[j1 + 2] + a[j3 + 2];
y2i = a[j1 + 3] + a[j3 + 3];
y3r = a[j1 + 2] - a[j3 + 2];
y3i = a[j1 + 3] - a[j3 + 3];
a[j] = x0r + x2r;
a[j + 1] = x0i + x2i;
a[j + 2] = y0r + y2r;
a[j + 3] = y0i + y2i;
a[j1] = x0r - x2r;
a[j1 + 1] = x0i - x2i;
a[j1 + 2] = y0r - y2r;
a[j1 + 3] = y0i - y2i;
x0r = x1r - x3i;
x0i = x1i + x3r;
a[j2] = wk1r * x0r - wk1i * x0i;
a[j2 + 1] = wk1r * x0i + wk1i * x0r;
x0r = y1r - y3i;
x0i = y1i + y3r;
a[j2 + 2] = wd1r * x0r - wd1i * x0i;
a[j2 + 3] = wd1r * x0i + wd1i * x0r;
x0r = x1r + x3i;
x0i = x1i - x3r;
a[j3] = wk3r * x0r + wk3i * x0i;
a[j3 + 1] = wk3r * x0i - wk3i * x0r;
x0r = y1r + y3i;
x0i = y1i - y3r;
a[j3 + 2] = wd3r * x0r + wd3i * x0i;
a[j3 + 3] = wd3r * x0i - wd3i * x0r;
j0 = m - j;
j1 = j0 + m;
j2 = j1 + m;
j3 = j2 + m;
x0r = a[j0] + a[j2];
x0i = a[j0 + 1] + a[j2 + 1];
x1r = a[j0] - a[j2];
x1i = a[j0 + 1] - a[j2 + 1];
y0r = a[j0 - 2] + a[j2 - 2];
y0i = a[j0 - 1] + a[j2 - 1];
y1r = a[j0 - 2] - a[j2 - 2];
y1i = a[j0 - 1] - a[j2 - 1];
x2r = a[j1] + a[j3];
x2i = a[j1 + 1] + a[j3 + 1];
x3r = a[j1] - a[j3];
x3i = a[j1 + 1] - a[j3 + 1];
y2r = a[j1 - 2] + a[j3 - 2];
y2i = a[j1 - 1] + a[j3 - 1];
y3r = a[j1 - 2] - a[j3 - 2];
y3i = a[j1 - 1] - a[j3 - 1];
a[j0] = x0r + x2r;
a[j0 + 1] = x0i + x2i;
a[j0 - 2] = y0r + y2r;
a[j0 - 1] = y0i + y2i;
a[j1] = x0r - x2r;
a[j1 + 1] = x0i - x2i;
a[j1 - 2] = y0r - y2r;
a[j1 - 1] = y0i - y2i;
x0r = x1r - x3i;
x0i = x1i + x3r;
a[j2] = wk1i * x0r - wk1r * x0i;
a[j2 + 1] = wk1i * x0i + wk1r * x0r;
x0r = y1r - y3i;
x0i = y1i + y3r;
a[j2 - 2] = wd1i * x0r - wd1r * x0i;
a[j2 - 1] = wd1i * x0i + wd1r * x0r;
x0r = x1r + x3i;
x0i = x1i - x3r;
a[j3] = wk3i * x0r + wk3r * x0i;
a[j3 + 1] = wk3i * x0i - wk3r * x0r;
x0r = y1r + y3i;
x0i = y1i - y3r;
a[j3 - 2] = wd3i * x0r + wd3r * x0i;
a[j3 - 1] = wd3i * x0i - wd3r * x0r;
}
wk1r = csc1 * (wd1r + wn4r);
wk1i = csc1 * (wd1i + wn4r);
wk3r = csc3 * (wd3r - wn4r);
wk3i = csc3 * (wd3i - wn4r);
j0 = mh;
j1 = j0 + m;
j2 = j1 + m;
j3 = j2 + m;
x0r = a[j0 - 2] + a[j2 - 2];
x0i = a[j0 - 1] + a[j2 - 1];
x1r = a[j0 - 2] - a[j2 - 2];
x1i = a[j0 - 1] - a[j2 - 1];
x2r = a[j1 - 2] + a[j3 - 2];
x2i = a[j1 - 1] + a[j3 - 1];
x3r = a[j1 - 2] - a[j3 - 2];
x3i = a[j1 - 1] - a[j3 - 1];
a[j0 - 2] = x0r + x2r;
a[j0 - 1] = x0i + x2i;
a[j1 - 2] = x0r - x2r;
a[j1 - 1] = x0i - x2i;
x0r = x1r - x3i;
x0i = x1i + x3r;
a[j2 - 2] = wk1r * x0r - wk1i * x0i;
a[j2 - 1] = wk1r * x0i + wk1i * x0r;
x0r = x1r + x3i;
x0i = x1i - x3r;
a[j3 - 2] = wk3r * x0r + wk3i * x0i;
a[j3 - 1] = wk3r * x0i - wk3i * x0r;
x0r = a[j0] + a[j2];
x0i = a[j0 + 1] + a[j2 + 1];
x1r = a[j0] - a[j2];
x1i = a[j0 + 1] - a[j2 + 1];
x2r = a[j1] + a[j3];
x2i = a[j1 + 1] + a[j3 + 1];
x3r = a[j1] - a[j3];
x3i = a[j1 + 1] - a[j3 + 1];
a[j0] = x0r + x2r;
a[j0 + 1] = x0i + x2i;
a[j1] = x0r - x2r;
a[j1 + 1] = x0i - x2i;
x0r = x1r - x3i;
x0i = x1i + x3r;
a[j2] = wn4r * (x0r - x0i);
a[j2 + 1] = wn4r * (x0i + x0r);
x0r = x1r + x3i;
x0i = x1i - x3r;
a[j3] = -wn4r * (x0r + x0i);
a[j3 + 1] = -wn4r * (x0i - x0r);
x0r = a[j0 + 2] + a[j2 + 2];
x0i = a[j0 + 3] + a[j2 + 3];
x1r = a[j0 + 2] - a[j2 + 2];
x1i = a[j0 + 3] - a[j2 + 3];
x2r = a[j1 + 2] + a[j3 + 2];
x2i = a[j1 + 3] + a[j3 + 3];
x3r = a[j1 + 2] - a[j3 + 2];
x3i = a[j1 + 3] - a[j3 + 3];
a[j0 + 2] = x0r + x2r;
a[j0 + 3] = x0i + x2i;
a[j1 + 2] = x0r - x2r;
a[j1 + 3] = x0i - x2i;
x0r = x1r - x3i;
x0i = x1i + x3r;
a[j2 + 2] = wk1i * x0r - wk1r * x0i;
a[j2 + 3] = wk1i * x0i + wk1r * x0r;
x0r = x1r + x3i;
x0i = x1i - x3r;
a[j3 + 2] = wk3i * x0r + wk3r * x0i;
a[j3 + 3] = wk3i * x0i - wk3r * x0r;
}