#include <math.h>
#include "fftease.h"

/* forward declarations */
static void rftsub(int n, t_float *a, int nc, t_float *c);
static void fftease_bitrv2(int n, int *ip, t_float *a);
static void fftease_cftsub(int n, t_float *a, t_float *w);

void fftease_init_rdft(int n, int *ip, t_float *w)
{
	
	int	nw,
	nc;
	
	void	fftease_makewt(int nw, int *ip, t_float *w);
	void	fftease_makect(int nc, int *ip, t_float *c);
	nw = n >> 2;
	fftease_makewt(nw, ip, w);
	
	nc = n >> 2;
	fftease_makect(nc, ip, w + nw);
	
	return;
}


void fftease_rdft(t_fftease *fft, int isgn)
{
	int n = fft->N;
	t_float *a = fft->buffer;
	int *ip = fft->bitshuffle;
	t_float *w = fft->trigland; 
	
	int j, nw, nc;
	
	t_float	xi;

    
	nw = ip[0];
	nc = ip[1];
	
	if (isgn < 0) {
		a[1] = 0.5 * (a[1] - a[0]);
		a[0] += a[1];
		
		for (j = 3; j <= n - 1; j += 2) {
			a[j] = -a[j];
		}
		
		if (n > 4) {
			rftsub(n, a, nc, w + nw);
			fftease_bitrv2(n, ip + 2, a);
		}
		
		fftease_cftsub(n, a, w);
		
		for (j = 1; j <= n - 1; j += 2) {
			a[j] = -a[j];
		}
	}
	
	else {
		
		if (n > 4) {
			fftease_bitrv2(n, ip + 2, a);
		}
		
		fftease_cftsub(n, a, w);
		
		if (n > 4) {
			rftsub(n, a, nc, w + nw);
		}
		
		xi = a[0] - a[1];
		a[0] += a[1];
		a[1] = xi;
	}
}


void fftease_bitrv2(int n, int *ip, t_float *a)
{
	int j, j1, k, k1, l, m, m2;
	t_float xr, xi;
    
	ip[0] = 0;
	l = n;
	m = 1;
	
	while ((m << 2) < l) {
		l >>= 1;
		for (j = 0; j <= m - 1; j++) {
			ip[m + j] = ip[j] + l;
		}
		m <<= 1;
	}
	
	if ((m << 2) > l) {
		
		for (k = 1; k <= m - 1; k++) {
			
			for (j = 0; j <= k - 1; j++) {
				j1 = (j << 1) + ip[k];
				k1 = (k << 1) + ip[j];
				xr = a[j1];
				xi = a[j1 + 1];
				a[j1] = a[k1];
				a[j1 + 1] = a[k1 + 1];
				a[k1] = xr;
				a[k1 + 1] = xi;
			}
		}
	}
	
	else {
		m2 = m << 1;
		
		for (k = 1; k <= m - 1; k++) {
			
			for (j = 0; j <= k - 1; j++) {
				j1 = (j << 1) + ip[k];
				k1 = (k << 1) + ip[j];
				xr = a[j1];
				xi = a[j1 + 1];
				a[j1] = a[k1];
				a[j1 + 1] = a[k1 + 1];
				a[k1] = xr;
				a[k1 + 1] = xi;
				j1 += m2;
				k1 += m2;
				xr = a[j1];
				xi = a[j1 + 1];
				a[j1] = a[k1];
				a[j1 + 1] = a[k1 + 1];
				a[k1] = xr;
				a[k1 + 1] = xi;
			}
		}
	}
}


void fftease_cftsub(int n, t_float *a, t_float *w)
{
	int j, j1, j2, j3, k, k1, ks, l, m;
	t_float wk1r, wk1i, wk2r, wk2i, wk3r, wk3i;
	t_float x0r, x0i, x1r, x1i, x2r, x2i, x3r, x3i;
    
	l = 2;
	
	while ((l << 1) < n) {
		m = l << 2;
		
		for (j = 0; j <= l - 2; j += 2) {
			j1 = j + l;
			j2 = j1 + l;
			j3 = j2 + l;
			x0r = a[j] + a[j1];
			x0i = a[j + 1] + a[j1 + 1];
			x1r = a[j] - a[j1];
			x1i = a[j + 1] - a[j1 + 1];
			x2r = a[j2] + a[j3];
			x2i = a[j2 + 1] + a[j3 + 1];
			x3r = a[j2] - a[j3];
			x3i = a[j2 + 1] - a[j3 + 1];
			a[j] = x0r + x2r;
			a[j + 1] = x0i + x2i;
			a[j2] = x0r - x2r;
			a[j2 + 1] = x0i - x2i;
			a[j1] = x1r - x3i;
			a[j1 + 1] = x1i + x3r;
			a[j3] = x1r + x3i;
			a[j3 + 1] = x1i - x3r;
		}
		
		if (m < n) {
			wk1r = w[2];
			
			for (j = m; j <= l + m - 2; j += 2) {
				j1 = j + l;
				j2 = j1 + l;
				j3 = j2 + l;
				x0r = a[j] + a[j1];
				x0i = a[j + 1] + a[j1 + 1];
				x1r = a[j] - a[j1];
				x1i = a[j + 1] - a[j1 + 1];
				x2r = a[j2] + a[j3];
				x2i = a[j2 + 1] + a[j3 + 1];
				x3r = a[j2] - a[j3];
				x3i = a[j2 + 1] - a[j3 + 1];
				a[j] = x0r + x2r;
				a[j + 1] = x0i + x2i;
				a[j2] = x2i - x0i;
				a[j2 + 1] = x0r - x2r;
				x0r = x1r - x3i;
				x0i = x1i + x3r;
				a[j1] = wk1r * (x0r - x0i);
				a[j1 + 1] = wk1r * (x0r + x0i);
				x0r = x3i + x1r;
				x0i = x3r - x1i;
				a[j3] = wk1r * (x0i - x0r);
				a[j3 + 1] = wk1r * (x0i + x0r);
			}
			
			k1 = 1;
			ks = -1;
			
			for (k = (m << 1); k <= n - m; k += m) {
				k1++;
				ks = -ks;
				wk1r = w[k1 << 1];
				wk1i = w[(k1 << 1) + 1];
				wk2r = ks * w[k1];
				wk2i = w[k1 + ks];
				wk3r = wk1r - 2 * wk2i * wk1i;
				wk3i = 2 * wk2i * wk1r - wk1i;
				
				for (j = k; j <= l + k - 2; j += 2) {
					j1 = j + l;
					j2 = j1 + l;
					j3 = j2 + l;
					x0r = a[j] + a[j1];
					x0i = a[j + 1] + a[j1 + 1];
					x1r = a[j] - a[j1];
					x1i = a[j + 1] - a[j1 + 1];
					x2r = a[j2] + a[j3];
					x2i = a[j2 + 1] + a[j3 + 1];
					x3r = a[j2] - a[j3];
					x3i = a[j2 + 1] - a[j3 + 1];
					a[j] = x0r + x2r;
					a[j + 1] = x0i + x2i;
					x0r -= x2r;
					x0i -= x2i;
					a[j2] = wk2r * x0r - wk2i * x0i;
					a[j2 + 1] = wk2r * x0i + wk2i * x0r;
					x0r = x1r - x3i;
					x0i = x1i + x3r;
					a[j1] = wk1r * x0r - wk1i * x0i;
					a[j1 + 1] = wk1r * x0i + wk1i * x0r;
					x0r = x1r + x3i;
					x0i = x1i - x3r;
					a[j3] = wk3r * x0r - wk3i * x0i;
					a[j3 + 1] = wk3r * x0i + wk3i * x0r;
				}
			}
		}
		
		l = m;
	}
	
	if (l < n) {
		
		for (j = 0; j <= l - 2; j += 2) {
			j1 = j + l;
			x0r = a[j] - a[j1];
			x0i = a[j + 1] - a[j1 + 1];
			a[j] += a[j1];
			a[j + 1] += a[j1 + 1];
			a[j1] = x0r;
			a[j1 + 1] = x0i;
		}
	}
}


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


void fftease_makewt(int nw, int *ip, t_float *w)
{
    void fftease_bitrv2(int n, int *ip, t_float *a);
    int nwh, j;
    t_float delta, x, y;
    
    ip[0] = nw;
    ip[1] = 1;
    if (nw > 2) {
        nwh = nw >> 1;
        delta = atan(1.0) / nwh;
        w[0] = 1;
        w[1] = 0;
        w[nwh] = cos(delta * nwh);
        w[nwh + 1] = w[nwh];
        for (j = 2; j <= nwh - 2; j += 2) {
            x = cos(delta * j);
            y = sin(delta * j);
            w[j] = x;
            w[j + 1] = y;
            w[nw - j] = y;
            w[nw - j + 1] = x;
        }
        fftease_bitrv2(nw, ip + 2, w);
    }
}


void fftease_makect(int nc, int *ip, t_float *c)
{
    int nch, j;
    t_float delta;
    
    ip[1] = nc;
    if (nc > 1) {
        nch = nc >> 1;
        delta = atan(1.0) / nch;
        c[0] = 0.5;
        c[nch] = 0.5 * cos(delta * nch);
        for (j = 1; j <= nch - 1; j++) {
            c[j] = 0.5 * cos(delta * j);
            c[nc - j] = 0.5 * sin(delta * j);
        }
    }
}

