/****************** begin Pd-specific prologue ***********************/

/*
This is the file, "fftsg.c" from the OOURA FFT package.  The copyright notice
from Ooura's README is:

Copyright:
    Copyright(C) 1996-2001 Takuya OOURA
    email: ooura@mmm.t.u-tokyo.ac.jp
    download: http://momonga.t.u-tokyo.ac.jp/~ooura/fft.html
    You may use, copy, modify this code for any purpose and
    without fee. You may distribute this ORIGINAL package.

After the following prologue, the code is essentially Ooura's original, which I
believe the above notice permits me to redistribute; the only change is to
replace 'double' with a macro, 'FFTFLT', so that it can optionally
be run in single precision for greater speed.  See Ooura's website
for another, more permissive-sounding copyright notice.  -MSP
*/

/* ---------- Pd interface to OOURA FFT; imitate Mayer API ---------- */
#include "m_pd.h"
#include "m_imp.h"

#ifdef _WIN32
# include <malloc.h> /* MSVC or mingw on windows */
#elif defined(__linux__) || defined(__APPLE__)
# include <alloca.h> /* linux, mac, mingw, cygwin */
#else
# include <stdlib.h> /* BSDs for example */
#endif

#define FFTFLT double
void cdft(int, int, FFTFLT *, int *, FFTFLT *);
void rdft(int, int, FFTFLT *, int *, FFTFLT *);

int ilog2(int n);

static PERTHREAD int ooura_maxn;
static PERTHREAD int *ooura_bitrev;
static PERTHREAD int ooura_bitrevsize;
static PERTHREAD FFTFLT *ooura_costab;

static int ooura_init( int n)
{
    n = (1 << ilog2(n));
    if (n < 4)
        return (0);
    if (n > ooura_maxn)
    {
        if (n > ooura_maxn)    /* recheck in case it got set while we waited */
        {
            if (ooura_maxn)
            {
                t_freebytes(ooura_bitrev, ooura_bitrevsize);
                t_freebytes(ooura_costab, ooura_maxn * sizeof(FFTFLT) / 2);
            }
            ooura_bitrevsize = sizeof(int) * (2 + (1 << (ilog2(n)/2)));
            ooura_bitrev = (int *)t_getbytes(ooura_bitrevsize);
            ooura_bitrev[0] = 0;
            if (!ooura_bitrev)
            {
                error("out of memory allocating FFT buffer");
                ooura_maxn = 0;
                return (0);
            }
            ooura_costab = (FFTFLT *)t_getbytes(n * sizeof(FFTFLT)/2);
            if (!ooura_costab)
            {
                error("out of memory allocating FFT buffer");
                t_freebytes(ooura_bitrev, ooura_bitrevsize);
                ooura_maxn = 0;
                return (0);
            }
            ooura_maxn = n;
            ooura_bitrev[0] = 0;
        }
    }
    return (1);
}

static void ooura_term( void)
{
    if (!ooura_maxn)
        return;
    t_freebytes(ooura_bitrev, ooura_bitrevsize);
    t_freebytes(ooura_costab, ooura_maxn * sizeof(FFTFLT)/2);
    ooura_maxn = 0;
    ooura_bitrev = 0;
    ooura_bitrevsize = 0;
    ooura_costab = 0;
}

/* -------- initialization and cleanup -------- */
static int mayer_refcount = 0;

void mayer_init( void)
{
    mayer_refcount++;
}

void mayer_term( void)
{
    if (--mayer_refcount == 0)  /* clean up */
        ooura_term();
}

/* -------- public routines -------- */
EXTERN void mayer_fht(t_sample *fz, int n)
{
    post("FHT: not yet implemented");
}

EXTERN void mayer_dofft(t_sample *fz1, t_sample *fz2, int n, int sgn)
{
    FFTFLT *buf, *fp3;
    int i;
    t_sample *fp1, *fp2;
    buf = alloca(n * (2 * sizeof(FFTFLT)));
    if (!ooura_init(2*n))
        return;
    for (i = 0, fp1 = fz1, fp2 = fz2, fp3 = buf; i < n; i++)
    {
        fp3[0] = *fp1++;
        fp3[1] = *fp2++;
        fp3 += 2;
    }
    cdft(2*n, sgn, buf, ooura_bitrev, ooura_costab);
    for (i = 0, fp1 = fz1, fp2 = fz2, fp3 = buf; i < n; i++)
    {
        *fp1++ = fp3[0];
        *fp2++ = fp3[1];
        fp3 += 2;
    }
}

EXTERN void mayer_fft(int n, t_sample *fz1, t_sample *fz2)
{
    mayer_dofft(fz1, fz2, n, -1);
}

EXTERN void mayer_ifft(int n, t_sample *fz1, t_sample *fz2)
{
    mayer_dofft(fz1, fz2, n, 1);
}

EXTERN void mayer_realfft(int n, t_sample *fz)
{
    FFTFLT *buf, *fp3;
    int i, nover2 = n/2;
    t_sample *fp1, *fp2;
    buf = alloca(n * sizeof(FFTFLT));
    if (!ooura_init(n))
        return;
    for (i = 0, fp1 = fz, fp3 = buf; i < n; i++, fp1++, fp3++)
        buf[i] = fz[i];
    rdft(n, 1, buf, ooura_bitrev, ooura_costab);
    fz[0] = buf[0];
    fz[nover2] = buf[1];
    for (i = 1, fp1 = fz+1, fp2 = fz+(n-1), fp3 = buf+2; i < nover2;
        i++, fp1++, fp2--, fp3 += 2)
            *fp1 = fp3[0], *fp2 = fp3[1];
}

EXTERN void mayer_realifft(int n, t_sample *fz)
{
    FFTFLT *buf, *fp3;
    int i, nover2 = n/2;
    t_sample *fp1, *fp2;
    buf = alloca(n * sizeof(FFTFLT));
    if (!ooura_init(n))
        return;
    buf[0] = fz[0];
    buf[1] = fz[nover2];
    for (i = 1, fp1 = fz+1, fp2 = fz+(n-1), fp3 = buf+2; i < nover2;
        i++, fp1++, fp2--, fp3 += 2)
            fp3[0] = *fp1, fp3[1] = *fp2;
    rdft(n, -1, buf, ooura_bitrev, ooura_costab);
    for (i = 0, fp1 = fz, fp3 = buf; i < n; i++, fp1++, fp3++)
        fz[i] = 2*buf[i];
}

    /* ancient ISPW-like version, used in fiddle~ and perhaps other externs
    here and there. */
void pd_fft(t_float *buf, int npoints, int inverse)
{
    FFTFLT *buf2 = (FFTFLT *)alloca(2 * npoints * sizeof(FFTFLT)), *bp2;
    t_float *fp;
    int i;
    if (!ooura_init(2*npoints))
        return;
    for (i = 0, bp2 = buf2, fp = buf; i < 2 * npoints; i++, bp2++, fp++)
        *bp2 = *fp;
    cdft(2*npoints, (inverse ? 1 : -1), buf2, ooura_bitrev, ooura_costab);
    for (i = 0, bp2 = buf2, fp = buf; i < 2 * npoints; i++, bp2++, fp++)
        *fp = *bp2;
}

/****************** end Pd-specific prologue ***********************/
/*
Fast Fourier/Cosine/Sine Transform
    dimension   :one
    data length :power of 2
    decimation  :frequency
    radix       :split-radix
    data        :inplace
    table       :use
functions
    cdft: Complex Discrete Fourier Transform
    rdft: Real Discrete Fourier Transform
    ddct: Discrete Cosine Transform
    ddst: Discrete Sine Transform
    dfct: Cosine Transform of RDFT (Real Symmetric DFT)
    dfst: Sine Transform of RDFT (Real Anti-symmetric DFT)
function prototypes
    void cdft(int, int, FFTFLT *, int *, FFTFLT *);
    void rdft(int, int, FFTFLT *, int *, FFTFLT *);
    void ddct(int, int, FFTFLT *, int *, FFTFLT *);
    void ddst(int, int, FFTFLT *, int *, FFTFLT *);
    void dfct(int, FFTFLT *, FFTFLT *, int *, FFTFLT *);
    void dfst(int, FFTFLT *, FFTFLT *, int *, FFTFLT *);
macro definitions
    USE_CDFT_PTHREADS : default=not defined
        CDFT_THREADS_BEGIN_N  : must be >= 512, default=8192
        CDFT_4THREADS_BEGIN_N : must be >= 512, default=65536
    USE_CDFT_WINTHREADS : default=not defined
        CDFT_THREADS_BEGIN_N  : must be >= 512, default=32768
        CDFT_4THREADS_BEGIN_N : must be >= 512, default=524288


-------- Complex DFT (Discrete Fourier Transform) --------
    [definition]
        <case1>
            X[k] = sum_j=0^n-1 x[j]*exp(2*pi*i*j*k/n), 0<=k<n
        <case2>
            X[k] = sum_j=0^n-1 x[j]*exp(-2*pi*i*j*k/n), 0<=k<n
        (notes: sum_j=0^n-1 is a summation from j=0 to n-1)
    [usage]
        <case1>
            ip[0] = 0; // first time only
            cdft(2*n, 1, a, ip, w);
        <case2>
            ip[0] = 0; // first time only
            cdft(2*n, -1, a, ip, w);
    [parameters]
        2*n            :data length (int)
                        n >= 1, n = power of 2
        a[0...2*n-1]   :input/output data (FFTFLT *)
                        input data
                            a[2*j] = Re(x[j]),
                            a[2*j+1] = Im(x[j]), 0<=j<n
                        output data
                            a[2*k] = Re(X[k]),
                            a[2*k+1] = Im(X[k]), 0<=k<n
        ip[0...*]      :work area for bit reversal (int *)
                        length of ip >= 2+sqrt(n)
                        strictly,
                        length of ip >=
                            2+(1<<(int)(log(n+0.5)/log(2))/2).
                        ip[0],ip[1] are pointers of the cos/sin table.
        w[0...n/2-1]   :cos/sin table (FFTFLT *)
                        w[],ip[] are initialized if ip[0] == 0.
    [remark]
        Inverse of
            cdft(2*n, -1, a, ip, w);
        is
            cdft(2*n, 1, a, ip, w);
            for (j = 0; j <= 2 * n - 1; j++) {
                a[j] *= 1.0 / n;
            }
        .


-------- Real DFT / Inverse of Real DFT --------
    [definition]
        <case1> RDFT
            R[k] = sum_j=0^n-1 a[j]*cos(2*pi*j*k/n), 0<=k<=n/2
            I[k] = sum_j=0^n-1 a[j]*sin(2*pi*j*k/n), 0<k<n/2
        <case2> IRDFT (excluding scale)
            a[k] = (R[0] + R[n/2]*cos(pi*k))/2 +
                   sum_j=1^n/2-1 R[j]*cos(2*pi*j*k/n) +
                   sum_j=1^n/2-1 I[j]*sin(2*pi*j*k/n), 0<=k<n
    [usage]
        <case1>
            ip[0] = 0; // first time only
            rdft(n, 1, a, ip, w);
        <case2>
            ip[0] = 0; // first time only
            rdft(n, -1, a, ip, w);
    [parameters]
        n              :data length (int)
                        n >= 2, n = power of 2
        a[0...n-1]     :input/output data (FFTFLT *)
                        <case1>
                            output data
                                a[2*k] = R[k], 0<=k<n/2
                                a[2*k+1] = I[k], 0<k<n/2
                                a[1] = R[n/2]
                        <case2>
                            input data
                                a[2*j] = R[j], 0<=j<n/2
                                a[2*j+1] = I[j], 0<j<n/2
                                a[1] = R[n/2]
        ip[0...*]      :work area for bit reversal (int *)
                        length of ip >= 2+sqrt(n/2)
                        strictly,
                        length of ip >=
                            2+(1<<(int)(log(n/2+0.5)/log(2))/2).
                        ip[0],ip[1] are pointers of the cos/sin table.
        w[0...n/2-1]   :cos/sin table (FFTFLT *)
                        w[],ip[] are initialized if ip[0] == 0.
    [remark]
        Inverse of
            rdft(n, 1, a, ip, w);
        is
            rdft(n, -1, a, ip, w);
            for (j = 0; j <= n - 1; j++) {
                a[j] *= 2.0 / n;
            }
        .


-------- DCT (Discrete Cosine Transform) / Inverse of DCT --------
    [definition]
        <case1> IDCT (excluding scale)
            C[k] = sum_j=0^n-1 a[j]*cos(pi*j*(k+1/2)/n), 0<=k<n
        <case2> DCT
            C[k] = sum_j=0^n-1 a[j]*cos(pi*(j+1/2)*k/n), 0<=k<n
    [usage]
        <case1>
            ip[0] = 0; // first time only
            ddct(n, 1, a, ip, w);
        <case2>
            ip[0] = 0; // first time only
            ddct(n, -1, a, ip, w);
    [parameters]
        n              :data length (int)
                        n >= 2, n = power of 2
        a[0...n-1]     :input/output data (FFTFLT *)
                        output data
                            a[k] = C[k], 0<=k<n
        ip[0...*]      :work area for bit reversal (int *)
                        length of ip >= 2+sqrt(n/2)
                        strictly,
                        length of ip >=
                            2+(1<<(int)(log(n/2+0.5)/log(2))/2).
                        ip[0],ip[1] are pointers of the cos/sin table.
        w[0...n*5/4-1] :cos/sin table (FFTFLT *)
                        w[],ip[] are initialized if ip[0] == 0.
    [remark]
        Inverse of
            ddct(n, -1, a, ip, w);
        is
            a[0] *= 0.5;
            ddct(n, 1, a, ip, w);
            for (j = 0; j <= n - 1; j++) {
                a[j] *= 2.0 / n;
            }
        .


-------- DST (Discrete Sine Transform) / Inverse of DST --------
    [definition]
        <case1> IDST (excluding scale)
            S[k] = sum_j=1^n A[j]*sin(pi*j*(k+1/2)/n), 0<=k<n
        <case2> DST
            S[k] = sum_j=0^n-1 a[j]*sin(pi*(j+1/2)*k/n), 0<k<=n
    [usage]
        <case1>
            ip[0] = 0; // first time only
            ddst(n, 1, a, ip, w);
        <case2>
            ip[0] = 0; // first time only
            ddst(n, -1, a, ip, w);
    [parameters]
        n              :data length (int)
                        n >= 2, n = power of 2
        a[0...n-1]     :input/output data (FFTFLT *)
                        <case1>
                            input data
                                a[j] = A[j], 0<j<n
                                a[0] = A[n]
                            output data
                                a[k] = S[k], 0<=k<n
                        <case2>
                            output data
                                a[k] = S[k], 0<k<n
                                a[0] = S[n]
        ip[0...*]      :work area for bit reversal (int *)
                        length of ip >= 2+sqrt(n/2)
                        strictly,
                        length of ip >=
                            2+(1<<(int)(log(n/2+0.5)/log(2))/2).
                        ip[0],ip[1] are pointers of the cos/sin table.
        w[0...n*5/4-1] :cos/sin table (FFTFLT *)
                        w[],ip[] are initialized if ip[0] == 0.
    [remark]
        Inverse of
            ddst(n, -1, a, ip, w);
        is
            a[0] *= 0.5;
            ddst(n, 1, a, ip, w);
            for (j = 0; j <= n - 1; j++) {
                a[j] *= 2.0 / n;
            }
        .


-------- Cosine Transform of RDFT (Real Symmetric DFT) --------
    [definition]
        C[k] = sum_j=0^n a[j]*cos(pi*j*k/n), 0<=k<=n
    [usage]
        ip[0] = 0; // first time only
        dfct(n, a, t, ip, w);
    [parameters]
        n              :data length - 1 (int)
                        n >= 2, n = power of 2
        a[0...n]       :input/output data (FFTFLT *)
                        output data
                            a[k] = C[k], 0<=k<=n
        t[0...n/2]     :work area (FFTFLT *)
        ip[0...*]      :work area for bit reversal (int *)
                        length of ip >= 2+sqrt(n/4)
                        strictly,
                        length of ip >=
                            2+(1<<(int)(log(n/4+0.5)/log(2))/2).
                        ip[0],ip[1] are pointers of the cos/sin table.
        w[0...n*5/8-1] :cos/sin table (FFTFLT *)
                        w[],ip[] are initialized if ip[0] == 0.
    [remark]
        Inverse of
            a[0] *= 0.5;
            a[n] *= 0.5;
            dfct(n, a, t, ip, w);
        is
            a[0] *= 0.5;
            a[n] *= 0.5;
            dfct(n, a, t, ip, w);
            for (j = 0; j <= n; j++) {
                a[j] *= 2.0 / n;
            }
        .


-------- Sine Transform of RDFT (Real Anti-symmetric DFT) --------
    [definition]
        S[k] = sum_j=1^n-1 a[j]*sin(pi*j*k/n), 0<k<n
    [usage]
        ip[0] = 0; // first time only
        dfst(n, a, t, ip, w);
    [parameters]
        n              :data length + 1 (int)
                        n >= 2, n = power of 2
        a[0...n-1]     :input/output data (FFTFLT *)
                        output data
                            a[k] = S[k], 0<k<n
                        (a[0] is used for work area)
        t[0...n/2-1]   :work area (FFTFLT *)
        ip[0...*]      :work area for bit reversal (int *)
                        length of ip >= 2+sqrt(n/4)
                        strictly,
                        length of ip >=
                            2+(1<<(int)(log(n/4+0.5)/log(2))/2).
                        ip[0],ip[1] are pointers of the cos/sin table.
        w[0...n*5/8-1] :cos/sin table (FFTFLT *)
                        w[],ip[] are initialized if ip[0] == 0.
    [remark]
        Inverse of
            dfst(n, a, t, ip, w);
        is
            dfst(n, a, t, ip, w);
            for (j = 1; j <= n - 1; j++) {
                a[j] *= 2.0 / n;
            }
        .


Appendix :
    The cos/sin table is recalculated when the larger table required.
    w[] and ip[] are compatible with all routines.
*/


void cdft(int n, int isgn, FFTFLT *a, int *ip, FFTFLT *w)
{
    void makewt(int nw, int *ip, FFTFLT *w);
    void cftfsub(int n, FFTFLT *a, int *ip, int nw, FFTFLT *w);
    void cftbsub(int n, FFTFLT *a, int *ip, int nw, FFTFLT *w);
    int nw;

    nw = ip[0];
    if (n > (nw << 2)) {
        nw = n >> 2;
        makewt(nw, ip, w);
    }
    if (isgn >= 0) {
        cftfsub(n, a, ip, nw, w);
    } else {
        cftbsub(n, a, ip, nw, w);
    }
}


void rdft(int n, int isgn, FFTFLT *a, int *ip, FFTFLT *w)
{
    void makewt(int nw, int *ip, FFTFLT *w);
    void makect(int nc, int *ip, FFTFLT *c);
    void cftfsub(int n, FFTFLT *a, int *ip, int nw, FFTFLT *w);
    void cftbsub(int n, FFTFLT *a, int *ip, int nw, FFTFLT *w);
    void rftfsub(int n, FFTFLT *a, int nc, FFTFLT *c);
    void rftbsub(int n, FFTFLT *a, int nc, FFTFLT *c);
    int nw, nc;
    FFTFLT xi;

    nw = ip[0];
    if (n > (nw << 2)) {
        nw = n >> 2;
        makewt(nw, ip, w);
    }
    nc = ip[1];
    if (n > (nc << 2)) {
        nc = n >> 2;
        makect(nc, ip, w + nw);
    }
    if (isgn >= 0) {
        if (n > 4) {
            cftfsub(n, a, ip, nw, w);
            rftfsub(n, a, nc, w + nw);
        } else if (n == 4) {
            cftfsub(n, a, ip, nw, w);
        }
        xi = a[0] - a[1];
        a[0] += a[1];
        a[1] = xi;
    } else {
        a[1] = 0.5 * (a[0] - a[1]);
        a[0] -= a[1];
        if (n > 4) {
            rftbsub(n, a, nc, w + nw);
            cftbsub(n, a, ip, nw, w);
        } else if (n == 4) {
            cftbsub(n, a, ip, nw, w);
        }
    }
}


void ddct(int n, int isgn, FFTFLT *a, int *ip, FFTFLT *w)
{
    void makewt(int nw, int *ip, FFTFLT *w);
    void makect(int nc, int *ip, FFTFLT *c);
    void cftfsub(int n, FFTFLT *a, int *ip, int nw, FFTFLT *w);
    void cftbsub(int n, FFTFLT *a, int *ip, int nw, FFTFLT *w);
    void rftfsub(int n, FFTFLT *a, int nc, FFTFLT *c);
    void rftbsub(int n, FFTFLT *a, int nc, FFTFLT *c);
    void dctsub(int n, FFTFLT *a, int nc, FFTFLT *c);
    int j, nw, nc;
    FFTFLT xr;

    nw = ip[0];
    if (n > (nw << 2)) {
        nw = n >> 2;
        makewt(nw, ip, w);
    }
    nc = ip[1];
    if (n > nc) {
        nc = n;
        makect(nc, ip, w + nw);
    }
    if (isgn < 0) {
        xr = a[n - 1];
        for (j = n - 2; j >= 2; j -= 2) {
            a[j + 1] = a[j] - a[j - 1];
            a[j] += a[j - 1];
        }
        a[1] = a[0] - xr;
        a[0] += xr;
        if (n > 4) {
            rftbsub(n, a, nc, w + nw);
            cftbsub(n, a, ip, nw, w);
        } else if (n == 4) {
            cftbsub(n, a, ip, nw, w);
        }
    }
    dctsub(n, a, nc, w + nw);
    if (isgn >= 0) {
        if (n > 4) {
            cftfsub(n, a, ip, nw, w);
            rftfsub(n, a, nc, w + nw);
        } else if (n == 4) {
            cftfsub(n, a, ip, nw, w);
        }
        xr = a[0] - a[1];
        a[0] += a[1];
        for (j = 2; j < n; j += 2) {
            a[j - 1] = a[j] - a[j + 1];
            a[j] += a[j + 1];
        }
        a[n - 1] = xr;
    }
}


void ddst(int n, int isgn, FFTFLT *a, int *ip, FFTFLT *w)
{
    void makewt(int nw, int *ip, FFTFLT *w);
    void makect(int nc, int *ip, FFTFLT *c);
    void cftfsub(int n, FFTFLT *a, int *ip, int nw, FFTFLT *w);
    void cftbsub(int n, FFTFLT *a, int *ip, int nw, FFTFLT *w);
    void rftfsub(int n, FFTFLT *a, int nc, FFTFLT *c);
    void rftbsub(int n, FFTFLT *a, int nc, FFTFLT *c);
    void dstsub(int n, FFTFLT *a, int nc, FFTFLT *c);
    int j, nw, nc;
    FFTFLT xr;

    nw = ip[0];
    if (n > (nw << 2)) {
        nw = n >> 2;
        makewt(nw, ip, w);
    }
    nc = ip[1];
    if (n > nc) {
        nc = n;
        makect(nc, ip, w + nw);
    }
    if (isgn < 0) {
        xr = a[n - 1];
        for (j = n - 2; j >= 2; j -= 2) {
            a[j + 1] = -a[j] - a[j - 1];
            a[j] -= a[j - 1];
        }
        a[1] = a[0] + xr;
        a[0] -= xr;
        if (n > 4) {
            rftbsub(n, a, nc, w + nw);
            cftbsub(n, a, ip, nw, w);
        } else if (n == 4) {
            cftbsub(n, a, ip, nw, w);
        }
    }
    dstsub(n, a, nc, w + nw);
    if (isgn >= 0) {
        if (n > 4) {
            cftfsub(n, a, ip, nw, w);
            rftfsub(n, a, nc, w + nw);
        } else if (n == 4) {
            cftfsub(n, a, ip, nw, w);
        }
        xr = a[0] - a[1];
        a[0] += a[1];
        for (j = 2; j < n; j += 2) {
            a[j - 1] = -a[j] - a[j + 1];
            a[j] -= a[j + 1];
        }
        a[n - 1] = -xr;
    }
}


void dfct(int n, FFTFLT *a, FFTFLT *t, int *ip, FFTFLT *w)
{
    void makewt(int nw, int *ip, FFTFLT *w);
    void makect(int nc, int *ip, FFTFLT *c);
    void cftfsub(int n, FFTFLT *a, int *ip, int nw, FFTFLT *w);
    void rftfsub(int n, FFTFLT *a, int nc, FFTFLT *c);
    void dctsub(int n, FFTFLT *a, int nc, FFTFLT *c);
    int j, k, l, m, mh, nw, nc;
    FFTFLT xr, xi, yr, yi;

    nw = ip[0];
    if (n > (nw << 3)) {
        nw = n >> 3;
        makewt(nw, ip, w);
    }
    nc = ip[1];
    if (n > (nc << 1)) {
        nc = n >> 1;
        makect(nc, ip, w + nw);
    }
    m = n >> 1;
    yi = a[m];
    xi = a[0] + a[n];
    a[0] -= a[n];
    t[0] = xi - yi;
    t[m] = xi + yi;
    if (n > 2) {
        mh = m >> 1;
        for (j = 1; j < mh; j++) {
            k = m - j;
            xr = a[j] - a[n - j];
            xi = a[j] + a[n - j];
            yr = a[k] - a[n - k];
            yi = a[k] + a[n - k];
            a[j] = xr;
            a[k] = yr;
            t[j] = xi - yi;
            t[k] = xi + yi;
        }
        t[mh] = a[mh] + a[n - mh];
        a[mh] -= a[n - mh];
        dctsub(m, a, nc, w + nw);
        if (m > 4) {
            cftfsub(m, a, ip, nw, w);
            rftfsub(m, a, nc, w + nw);
        } else if (m == 4) {
            cftfsub(m, a, ip, nw, w);
        }
        a[n - 1] = a[0] - a[1];
        a[1] = a[0] + a[1];
        for (j = m - 2; j >= 2; j -= 2) {
            a[2 * j + 1] = a[j] + a[j + 1];
            a[2 * j - 1] = a[j] - a[j + 1];
        }
        l = 2;
        m = mh;
        while (m >= 2) {
            dctsub(m, t, nc, w + nw);
            if (m > 4) {
                cftfsub(m, t, ip, nw, w);
                rftfsub(m, t, nc, w + nw);
            } else if (m == 4) {
                cftfsub(m, t, ip, nw, w);
            }
            a[n - l] = t[0] - t[1];
            a[l] = t[0] + t[1];
            k = 0;
            for (j = 2; j < m; j += 2) {
                k += l << 2;
                a[k - l] = t[j] - t[j + 1];
                a[k + l] = t[j] + t[j + 1];
            }
            l <<= 1;
            mh = m >> 1;
            for (j = 0; j < mh; j++) {
                k = m - j;
                t[j] = t[m + k] - t[m + j];
                t[k] = t[m + k] + t[m + j];
            }
            t[mh] = t[m + mh];
            m = mh;
        }
        a[l] = t[0];
        a[n] = t[2] - t[1];
        a[0] = t[2] + t[1];
    } else {
        a[1] = a[0];
        a[2] = t[0];
        a[0] = t[1];
    }
}


void dfst(int n, FFTFLT *a, FFTFLT *t, int *ip, FFTFLT *w)
{
    void makewt(int nw, int *ip, FFTFLT *w);
    void makect(int nc, int *ip, FFTFLT *c);
    void cftfsub(int n, FFTFLT *a, int *ip, int nw, FFTFLT *w);
    void rftfsub(int n, FFTFLT *a, int nc, FFTFLT *c);
    void dstsub(int n, FFTFLT *a, int nc, FFTFLT *c);
    int j, k, l, m, mh, nw, nc;
    FFTFLT xr, xi, yr, yi;

    nw = ip[0];
    if (n > (nw << 3)) {
        nw = n >> 3;
        makewt(nw, ip, w);
    }
    nc = ip[1];
    if (n > (nc << 1)) {
        nc = n >> 1;
        makect(nc, ip, w + nw);
    }
    if (n > 2) {
        m = n >> 1;
        mh = m >> 1;
        for (j = 1; j < mh; j++) {
            k = m - j;
            xr = a[j] + a[n - j];
            xi = a[j] - a[n - j];
            yr = a[k] + a[n - k];
            yi = a[k] - a[n - k];
            a[j] = xr;
            a[k] = yr;
            t[j] = xi + yi;
            t[k] = xi - yi;
        }
        t[0] = a[mh] - a[n - mh];
        a[mh] += a[n - mh];
        a[0] = a[m];
        dstsub(m, a, nc, w + nw);
        if (m > 4) {
            cftfsub(m, a, ip, nw, w);
            rftfsub(m, a, nc, w + nw);
        } else if (m == 4) {
            cftfsub(m, a, ip, nw, w);
        }
        a[n - 1] = a[1] - a[0];
        a[1] = a[0] + a[1];
        for (j = m - 2; j >= 2; j -= 2) {
            a[2 * j + 1] = a[j] - a[j + 1];
            a[2 * j - 1] = -a[j] - a[j + 1];
        }
        l = 2;
        m = mh;
        while (m >= 2) {
            dstsub(m, t, nc, w + nw);
            if (m > 4) {
                cftfsub(m, t, ip, nw, w);
                rftfsub(m, t, nc, w + nw);
            } else if (m == 4) {
                cftfsub(m, t, ip, nw, w);
            }
            a[n - l] = t[1] - t[0];
            a[l] = t[0] + t[1];
            k = 0;
            for (j = 2; j < m; j += 2) {
                k += l << 2;
                a[k - l] = -t[j] - t[j + 1];
                a[k + l] = t[j] - t[j + 1];
            }
            l <<= 1;
            mh = m >> 1;
            for (j = 1; j < mh; j++) {
                k = m - j;
                t[j] = t[m + k] + t[m + j];
                t[k] = t[m + k] - t[m + j];
            }
            t[0] = t[m + mh];
            m = mh;
        }
        a[l] = t[0];
    }
    a[0] = 0;
}


/* -------- initializing routines -------- */


#include <math.h>

void makewt(int nw, int *ip, FFTFLT *w)
{
    void makeipt(int nw, int *ip);
    int j, nwh, nw0, nw1;
    FFTFLT delta, wn4r, wk1r, wk1i, wk3r, wk3i;

    ip[0] = nw;
    ip[1] = 1;
    if (nw > 2) {
        nwh = nw >> 1;
        delta = atan(1.0) / nwh;
        wn4r = cos(delta * nwh);
        w[0] = 1;
        w[1] = wn4r;
        if (nwh == 4) {
            w[2] = cos(delta * 2);
            w[3] = sin(delta * 2);
        } else if (nwh > 4) {
            makeipt(nw, ip);
            w[2] = 0.5 / cos(delta * 2);
            w[3] = 0.5 / cos(delta * 6);
            for (j = 4; j < nwh; j += 4) {
                w[j] = cos(delta * j);
                w[j + 1] = sin(delta * j);
                w[j + 2] = cos(3 * delta * j);
                w[j + 3] = -sin(3 * delta * j);
            }
        }
        nw0 = 0;
        while (nwh > 2) {
            nw1 = nw0 + nwh;
            nwh >>= 1;
            w[nw1] = 1;
            w[nw1 + 1] = wn4r;
            if (nwh == 4) {
                wk1r = w[nw0 + 4];
                wk1i = w[nw0 + 5];
                w[nw1 + 2] = wk1r;
                w[nw1 + 3] = wk1i;
            } else if (nwh > 4) {
                wk1r = w[nw0 + 4];
                wk3r = w[nw0 + 6];
                w[nw1 + 2] = 0.5 / wk1r;
                w[nw1 + 3] = 0.5 / wk3r;
                for (j = 4; j < nwh; j += 4) {
                    wk1r = w[nw0 + 2 * j];
                    wk1i = w[nw0 + 2 * j + 1];
                    wk3r = w[nw0 + 2 * j + 2];
                    wk3i = w[nw0 + 2 * j + 3];
                    w[nw1 + j] = wk1r;
                    w[nw1 + j + 1] = wk1i;
                    w[nw1 + j + 2] = wk3r;
                    w[nw1 + j + 3] = wk3i;
                }
            }
            nw0 = nw1;
        }
    }
}


void makeipt(int nw, int *ip)
{
    int j, l, m, m2, p, q;

    ip[2] = 0;
    ip[3] = 16;
    m = 2;
    for (l = nw; l > 32; l >>= 2) {
        m2 = m << 1;
        q = m2 << 3;
        for (j = m; j < m2; j++) {
            p = ip[j] << 2;
            ip[m + j] = p;
            ip[m2 + j] = p + q;
        }
        m = m2;
    }
}


void makect(int nc, int *ip, FFTFLT *c)
{
    int j, nch;
    FFTFLT delta;

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


/* -------- child routines -------- */


#ifdef USE_CDFT_PTHREADS
#define USE_CDFT_THREADS
#ifndef CDFT_THREADS_BEGIN_N
#define CDFT_THREADS_BEGIN_N 8192
#endif
#ifndef CDFT_4THREADS_BEGIN_N
#define CDFT_4THREADS_BEGIN_N 65536
#endif
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#define cdft_thread_t pthread_t
#define cdft_thread_create(thp,func,argp) { \
    if (pthread_create(thp, NULL, func, (void *) argp) != 0) { \
        fprintf(stderr, "cdft thread error\n"); \
        exit(1); \
    } \
}
#define cdft_thread_wait(th) { \
    if (pthread_join(th, NULL) != 0) { \
        fprintf(stderr, "cdft thread error\n"); \
        exit(1); \
    } \
}
#endif /* USE_CDFT_PTHREADS */


#ifdef USE_CDFT_WINTHREADS
#define USE_CDFT_THREADS
#ifndef CDFT_THREADS_BEGIN_N
#define CDFT_THREADS_BEGIN_N 32768
#endif
#ifndef CDFT_4THREADS_BEGIN_N
#define CDFT_4THREADS_BEGIN_N 524288
#endif
#include <windows.h>
#include <stdio.h>
#include <stdlib.h>
#define cdft_thread_t HANDLE
#define cdft_thread_create(thp,func,argp) { \
    DWORD thid; \
    *(thp) = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE) func, (LPVOID) argp, 0, &thid); \
    if (*(thp) == 0) { \
        fprintf(stderr, "cdft thread error\n"); \
        exit(1); \
    } \
}
#define cdft_thread_wait(th) { \
    WaitForSingleObject(th, INFINITE); \
    CloseHandle(th); \
}
#endif /* USE_CDFT_WINTHREADS */


void cftfsub(int n, FFTFLT *a, int *ip, int nw, FFTFLT *w)
{
    void bitrv2(int n, int *ip, FFTFLT *a);
    void bitrv216(FFTFLT *a);
    void bitrv208(FFTFLT *a);
    void cftf1st(int n, FFTFLT *a, FFTFLT *w);
    void cftrec4(int n, FFTFLT *a, int nw, FFTFLT *w);
    void cftleaf(int n, int isplt, FFTFLT *a, int nw, FFTFLT *w);
    void cftfx41(int n, FFTFLT *a, int nw, FFTFLT *w);
    void cftf161(FFTFLT *a, FFTFLT *w);
    void cftf081(FFTFLT *a, FFTFLT *w);
    void cftf040(FFTFLT *a);
    void cftx020(FFTFLT *a);
#ifdef USE_CDFT_THREADS
    void cftrec4_th(int n, FFTFLT *a, int nw, FFTFLT *w);
#endif /* USE_CDFT_THREADS */

    if (n > 8) {
        if (n > 32) {
            cftf1st(n, a, &w[nw - (n >> 2)]);
#ifdef USE_CDFT_THREADS
            if (n > CDFT_THREADS_BEGIN_N) {
                cftrec4_th(n, a, nw, w);
            } else
#endif /* USE_CDFT_THREADS */
            if (n > 512) {
                cftrec4(n, a, nw, w);
            } else if (n > 128) {
                cftleaf(n, 1, a, nw, w);
            } else {
                cftfx41(n, a, nw, w);
            }
            bitrv2(n, ip, a);
        } else if (n == 32) {
            cftf161(a, &w[nw - 8]);
            bitrv216(a);
        } else {
            cftf081(a, w);
            bitrv208(a);
        }
    } else if (n == 8) {
        cftf040(a);
    } else if (n == 4) {
        cftx020(a);
    }
}


void cftbsub(int n, FFTFLT *a, int *ip, int nw, FFTFLT *w)
{
    void bitrv2conj(int n, int *ip, FFTFLT *a);
    void bitrv216neg(FFTFLT *a);
    void bitrv208neg(FFTFLT *a);
    void cftb1st(int n, FFTFLT *a, FFTFLT *w);
    void cftrec4(int n, FFTFLT *a, int nw, FFTFLT *w);
    void cftleaf(int n, int isplt, FFTFLT *a, int nw, FFTFLT *w);
    void cftfx41(int n, FFTFLT *a, int nw, FFTFLT *w);
    void cftf161(FFTFLT *a, FFTFLT *w);
    void cftf081(FFTFLT *a, FFTFLT *w);
    void cftb040(FFTFLT *a);
    void cftx020(FFTFLT *a);
#ifdef USE_CDFT_THREADS
    void cftrec4_th(int n, FFTFLT *a, int nw, FFTFLT *w);
#endif /* USE_CDFT_THREADS */

    if (n > 8) {
        if (n > 32) {
            cftb1st(n, a, &w[nw - (n >> 2)]);
#ifdef USE_CDFT_THREADS
            if (n > CDFT_THREADS_BEGIN_N) {
                cftrec4_th(n, a, nw, w);
            } else
#endif /* USE_CDFT_THREADS */
            if (n > 512) {
                cftrec4(n, a, nw, w);
            } else if (n > 128) {
                cftleaf(n, 1, a, nw, w);
            } else {
                cftfx41(n, a, nw, w);
            }
            bitrv2conj(n, ip, a);
        } else if (n == 32) {
            cftf161(a, &w[nw - 8]);
            bitrv216neg(a);
        } else {
            cftf081(a, w);
            bitrv208neg(a);
        }
    } else if (n == 8) {
        cftb040(a);
    } else if (n == 4) {
        cftx020(a);
    }
}


void bitrv2(int n, int *ip, FFTFLT *a)
{
    int j, j1, k, k1, l, m, nh, nm;
    FFTFLT xr, xi, yr, yi;

    m = 1;
    for (l = n >> 2; l > 8; l >>= 2) {
        m <<= 1;
    }
    nh = n >> 1;
    nm = 4 * m;
    if (l == 8) {
        for (k = 0; k < m; k++) {
            for (j = 0; j < k; j++) {
                j1 = 4 * j + 2 * ip[m + k];
                k1 = 4 * k + 2 * ip[m + j];
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += nm;
                k1 += 2 * nm;
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += nm;
                k1 -= nm;
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += nm;
                k1 += 2 * nm;
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += nh;
                k1 += 2;
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 -= nm;
                k1 -= 2 * nm;
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 -= nm;
                k1 += nm;
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 -= nm;
                k1 -= 2 * nm;
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += 2;
                k1 += nh;
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += nm;
                k1 += 2 * nm;
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += nm;
                k1 -= nm;
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += nm;
                k1 += 2 * nm;
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 -= nh;
                k1 -= 2;
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 -= nm;
                k1 -= 2 * nm;
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 -= nm;
                k1 += nm;
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 -= nm;
                k1 -= 2 * nm;
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
            }
            k1 = 4 * k + 2 * ip[m + k];
            j1 = k1 + 2;
            k1 += nh;
            xr = a[j1];
            xi = a[j1 + 1];
            yr = a[k1];
            yi = a[k1 + 1];
            a[j1] = yr;
            a[j1 + 1] = yi;
            a[k1] = xr;
            a[k1 + 1] = xi;
            j1 += nm;
            k1 += 2 * nm;
            xr = a[j1];
            xi = a[j1 + 1];
            yr = a[k1];
            yi = a[k1 + 1];
            a[j1] = yr;
            a[j1 + 1] = yi;
            a[k1] = xr;
            a[k1 + 1] = xi;
            j1 += nm;
            k1 -= nm;
            xr = a[j1];
            xi = a[j1 + 1];
            yr = a[k1];
            yi = a[k1 + 1];
            a[j1] = yr;
            a[j1 + 1] = yi;
            a[k1] = xr;
            a[k1 + 1] = xi;
            j1 -= 2;
            k1 -= nh;
            xr = a[j1];
            xi = a[j1 + 1];
            yr = a[k1];
            yi = a[k1 + 1];
            a[j1] = yr;
            a[j1 + 1] = yi;
            a[k1] = xr;
            a[k1 + 1] = xi;
            j1 += nh + 2;
            k1 += nh + 2;
            xr = a[j1];
            xi = a[j1 + 1];
            yr = a[k1];
            yi = a[k1 + 1];
            a[j1] = yr;
            a[j1 + 1] = yi;
            a[k1] = xr;
            a[k1 + 1] = xi;
            j1 -= nh - nm;
            k1 += 2 * nm - 2;
            xr = a[j1];
            xi = a[j1 + 1];
            yr = a[k1];
            yi = a[k1 + 1];
            a[j1] = yr;
            a[j1 + 1] = yi;
            a[k1] = xr;
            a[k1 + 1] = xi;
        }
    } else {
        for (k = 0; k < m; k++) {
            for (j = 0; j < k; j++) {
                j1 = 4 * j + ip[m + k];
                k1 = 4 * k + ip[m + j];
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += nm;
                k1 += nm;
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += nh;
                k1 += 2;
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 -= nm;
                k1 -= nm;
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += 2;
                k1 += nh;
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += nm;
                k1 += nm;
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 -= nh;
                k1 -= 2;
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 -= nm;
                k1 -= nm;
                xr = a[j1];
                xi = a[j1 + 1];
                yr = a[k1];
                yi = a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
            }
            k1 = 4 * k + ip[m + k];
            j1 = k1 + 2;
            k1 += nh;
            xr = a[j1];
            xi = a[j1 + 1];
            yr = a[k1];
            yi = a[k1 + 1];
            a[j1] = yr;
            a[j1 + 1] = yi;
            a[k1] = xr;
            a[k1 + 1] = xi;
            j1 += nm;
            k1 += nm;
            xr = a[j1];
            xi = a[j1 + 1];
            yr = a[k1];
            yi = a[k1 + 1];
            a[j1] = yr;
            a[j1 + 1] = yi;
            a[k1] = xr;
            a[k1 + 1] = xi;
        }
    }
}


void bitrv2conj(int n, int *ip, FFTFLT *a)
{
    int j, j1, k, k1, l, m, nh, nm;
    FFTFLT xr, xi, yr, yi;

    m = 1;
    for (l = n >> 2; l > 8; l >>= 2) {
        m <<= 1;
    }
    nh = n >> 1;
    nm = 4 * m;
    if (l == 8) {
        for (k = 0; k < m; k++) {
            for (j = 0; j < k; j++) {
                j1 = 4 * j + 2 * ip[m + k];
                k1 = 4 * k + 2 * ip[m + j];
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += nm;
                k1 += 2 * nm;
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += nm;
                k1 -= nm;
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += nm;
                k1 += 2 * nm;
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += nh;
                k1 += 2;
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 -= nm;
                k1 -= 2 * nm;
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 -= nm;
                k1 += nm;
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 -= nm;
                k1 -= 2 * nm;
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += 2;
                k1 += nh;
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += nm;
                k1 += 2 * nm;
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += nm;
                k1 -= nm;
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += nm;
                k1 += 2 * nm;
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 -= nh;
                k1 -= 2;
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 -= nm;
                k1 -= 2 * nm;
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 -= nm;
                k1 += nm;
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 -= nm;
                k1 -= 2 * nm;
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
            }
            k1 = 4 * k + 2 * ip[m + k];
            j1 = k1 + 2;
            k1 += nh;
            a[j1 - 1] = -a[j1 - 1];
            xr = a[j1];
            xi = -a[j1 + 1];
            yr = a[k1];
            yi = -a[k1 + 1];
            a[j1] = yr;
            a[j1 + 1] = yi;
            a[k1] = xr;
            a[k1 + 1] = xi;
            a[k1 + 3] = -a[k1 + 3];
            j1 += nm;
            k1 += 2 * nm;
            xr = a[j1];
            xi = -a[j1 + 1];
            yr = a[k1];
            yi = -a[k1 + 1];
            a[j1] = yr;
            a[j1 + 1] = yi;
            a[k1] = xr;
            a[k1 + 1] = xi;
            j1 += nm;
            k1 -= nm;
            xr = a[j1];
            xi = -a[j1 + 1];
            yr = a[k1];
            yi = -a[k1 + 1];
            a[j1] = yr;
            a[j1 + 1] = yi;
            a[k1] = xr;
            a[k1 + 1] = xi;
            j1 -= 2;
            k1 -= nh;
            xr = a[j1];
            xi = -a[j1 + 1];
            yr = a[k1];
            yi = -a[k1 + 1];
            a[j1] = yr;
            a[j1 + 1] = yi;
            a[k1] = xr;
            a[k1 + 1] = xi;
            j1 += nh + 2;
            k1 += nh + 2;
            xr = a[j1];
            xi = -a[j1 + 1];
            yr = a[k1];
            yi = -a[k1 + 1];
            a[j1] = yr;
            a[j1 + 1] = yi;
            a[k1] = xr;
            a[k1 + 1] = xi;
            j1 -= nh - nm;
            k1 += 2 * nm - 2;
            a[j1 - 1] = -a[j1 - 1];
            xr = a[j1];
            xi = -a[j1 + 1];
            yr = a[k1];
            yi = -a[k1 + 1];
            a[j1] = yr;
            a[j1 + 1] = yi;
            a[k1] = xr;
            a[k1 + 1] = xi;
            a[k1 + 3] = -a[k1 + 3];
        }
    } else {
        for (k = 0; k < m; k++) {
            for (j = 0; j < k; j++) {
                j1 = 4 * j + ip[m + k];
                k1 = 4 * k + ip[m + j];
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += nm;
                k1 += nm;
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += nh;
                k1 += 2;
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 -= nm;
                k1 -= nm;
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += 2;
                k1 += nh;
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 += nm;
                k1 += nm;
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 -= nh;
                k1 -= 2;
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
                j1 -= nm;
                k1 -= nm;
                xr = a[j1];
                xi = -a[j1 + 1];
                yr = a[k1];
                yi = -a[k1 + 1];
                a[j1] = yr;
                a[j1 + 1] = yi;
                a[k1] = xr;
                a[k1 + 1] = xi;
            }
            k1 = 4 * k + ip[m + k];
            j1 = k1 + 2;
            k1 += nh;
            a[j1 - 1] = -a[j1 - 1];
            xr = a[j1];
            xi = -a[j1 + 1];
            yr = a[k1];
            yi = -a[k1 + 1];
            a[j1] = yr;
            a[j1 + 1] = yi;
            a[k1] = xr;
            a[k1 + 1] = xi;
            a[k1 + 3] = -a[k1 + 3];
            j1 += nm;
            k1 += nm;
            a[j1 - 1] = -a[j1 - 1];
            xr = a[j1];
            xi = -a[j1 + 1];
            yr = a[k1];
            yi = -a[k1 + 1];
            a[j1] = yr;
            a[j1 + 1] = yi;
            a[k1] = xr;
            a[k1 + 1] = xi;
            a[k1 + 3] = -a[k1 + 3];
        }
    }
}


void bitrv216(FFTFLT *a)
{
    FFTFLT x1r, x1i, x2r, x2i, x3r, x3i, x4r, x4i,
        x5r, x5i, x7r, x7i, x8r, x8i, x10r, x10i,
        x11r, x11i, x12r, x12i, x13r, x13i, x14r, x14i;

    x1r = a[2];
    x1i = a[3];
    x2r = a[4];
    x2i = a[5];
    x3r = a[6];
    x3i = a[7];
    x4r = a[8];
    x4i = a[9];
    x5r = a[10];
    x5i = a[11];
    x7r = a[14];
    x7i = a[15];
    x8r = a[16];
    x8i = a[17];
    x10r = a[20];
    x10i = a[21];
    x11r = a[22];
    x11i = a[23];
    x12r = a[24];
    x12i = a[25];
    x13r = a[26];
    x13i = a[27];
    x14r = a[28];
    x14i = a[29];
    a[2] = x8r;
    a[3] = x8i;
    a[4] = x4r;
    a[5] = x4i;
    a[6] = x12r;
    a[7] = x12i;
    a[8] = x2r;
    a[9] = x2i;
    a[10] = x10r;
    a[11] = x10i;
    a[14] = x14r;
    a[15] = x14i;
    a[16] = x1r;
    a[17] = x1i;
    a[20] = x5r;
    a[21] = x5i;
    a[22] = x13r;
    a[23] = x13i;
    a[24] = x3r;
    a[25] = x3i;
    a[26] = x11r;
    a[27] = x11i;
    a[28] = x7r;
    a[29] = x7i;
}


void bitrv216neg(FFTFLT *a)
{
    FFTFLT x1r, x1i, x2r, x2i, x3r, x3i, x4r, x4i,
        x5r, x5i, x6r, x6i, x7r, x7i, x8r, x8i,
        x9r, x9i, x10r, x10i, x11r, x11i, x12r, x12i,
        x13r, x13i, x14r, x14i, x15r, x15i;

    x1r = a[2];
    x1i = a[3];
    x2r = a[4];
    x2i = a[5];
    x3r = a[6];
    x3i = a[7];
    x4r = a[8];
    x4i = a[9];
    x5r = a[10];
    x5i = a[11];
    x6r = a[12];
    x6i = a[13];
    x7r = a[14];
    x7i = a[15];
    x8r = a[16];
    x8i = a[17];
    x9r = a[18];
    x9i = a[19];
    x10r = a[20];
    x10i = a[21];
    x11r = a[22];
    x11i = a[23];
    x12r = a[24];
    x12i = a[25];
    x13r = a[26];
    x13i = a[27];
    x14r = a[28];
    x14i = a[29];
    x15r = a[30];
    x15i = a[31];
    a[2] = x15r;
    a[3] = x15i;
    a[4] = x7r;
    a[5] = x7i;
    a[6] = x11r;
    a[7] = x11i;
    a[8] = x3r;
    a[9] = x3i;
    a[10] = x13r;
    a[11] = x13i;
    a[12] = x5r;
    a[13] = x5i;
    a[14] = x9r;
    a[15] = x9i;
    a[16] = x1r;
    a[17] = x1i;
    a[18] = x14r;
    a[19] = x14i;
    a[20] = x6r;
    a[21] = x6i;
    a[22] = x10r;
    a[23] = x10i;
    a[24] = x2r;
    a[25] = x2i;
    a[26] = x12r;
    a[27] = x12i;
    a[28] = x4r;
    a[29] = x4i;
    a[30] = x8r;
    a[31] = x8i;
}


void bitrv208(FFTFLT *a)
{
    FFTFLT x1r, x1i, x3r, x3i, x4r, x4i, x6r, x6i;

    x1r = a[2];
    x1i = a[3];
    x3r = a[6];
    x3i = a[7];
    x4r = a[8];
    x4i = a[9];
    x6r = a[12];
    x6i = a[13];
    a[2] = x4r;
    a[3] = x4i;
    a[6] = x6r;
    a[7] = x6i;
    a[8] = x1r;
    a[9] = x1i;
    a[12] = x3r;
    a[13] = x3i;
}


void bitrv208neg(FFTFLT *a)
{
    FFTFLT x1r, x1i, x2r, x2i, x3r, x3i, x4r, x4i,
        x5r, x5i, x6r, x6i, x7r, x7i;

    x1r = a[2];
    x1i = a[3];
    x2r = a[4];
    x2i = a[5];
    x3r = a[6];
    x3i = a[7];
    x4r = a[8];
    x4i = a[9];
    x5r = a[10];
    x5i = a[11];
    x6r = a[12];
    x6i = a[13];
    x7r = a[14];
    x7i = a[15];
    a[2] = x7r;
    a[3] = x7i;
    a[4] = x3r;
    a[5] = x3i;
    a[6] = x5r;
    a[7] = x5i;
    a[8] = x1r;
    a[9] = x1i;
    a[10] = x6r;
    a[11] = x6i;
    a[12] = x2r;
    a[13] = x2i;
    a[14] = x4r;
    a[15] = x4i;
}


void cftf1st(int n, FFTFLT *a, FFTFLT *w)
{
    int j, j0, j1, j2, j3, k, m, mh;
    FFTFLT wn4r, csc1, csc3, wk1r, wk1i, wk3r, wk3i,
        wd1r, wd1i, wd3r, wd3i;
    FFTFLT 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;
}


void cftb1st(int n, FFTFLT *a, FFTFLT *w)
{
    int j, j0, j1, j2, j3, k, m, mh;
    FFTFLT wn4r, csc1, csc3, wk1r, wk1i, wk3r, wk3i,
        wd1r, wd1i, wd3r, wd3i;
    FFTFLT 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;
}


#ifdef USE_CDFT_THREADS
struct cdft_arg_st {
    int n0;
    int n;
    FFTFLT *a;
    int nw;
    FFTFLT *w;
};
typedef struct cdft_arg_st cdft_arg_t;


void cftrec4_th(int n, FFTFLT *a, int nw, FFTFLT *w)
{
    void *cftrec1_th(void *p);
    void *cftrec2_th(void *p);
    int i, idiv4, m, nthread;
    cdft_thread_t th[4];
    cdft_arg_t ag[4];

    nthread = 2;
    idiv4 = 0;
    m = n >> 1;
    if (n > CDFT_4THREADS_BEGIN_N) {
        nthread = 4;
        idiv4 = 1;
        m >>= 1;
    }
    for (i = 0; i < nthread; i++) {
        ag[i].n0 = n;
        ag[i].n = m;
        ag[i].a = &a[i * m];
        ag[i].nw = nw;
        ag[i].w = w;
        if (i != idiv4) {
            cdft_thread_create(&th[i], cftrec1_th, &ag[i]);
        } else {
            cdft_thread_create(&th[i], cftrec2_th, &ag[i]);
        }
    }
    for (i = 0; i < nthread; i++) {
        cdft_thread_wait(th[i]);
    }
}


void *cftrec1_th(void *p)
{
    int cfttree(int n, int j, int k, FFTFLT *a, int nw, FFTFLT *w);
    void cftleaf(int n, int isplt, FFTFLT *a, int nw, FFTFLT *w);
    void cftmdl1(int n, FFTFLT *a, FFTFLT *w);
    int isplt, j, k, m, n, n0, nw;
    FFTFLT *a, *w;

    n0 = ((cdft_arg_t *) p)->n0;
    n = ((cdft_arg_t *) p)->n;
    a = ((cdft_arg_t *) p)->a;
    nw = ((cdft_arg_t *) p)->nw;
    w = ((cdft_arg_t *) p)->w;
    m = n0;
    while (m > 512) {
        m >>= 2;
        cftmdl1(m, &a[n - m], &w[nw - (m >> 1)]);
    }
    cftleaf(m, 1, &a[n - m], nw, w);
    k = 0;
    for (j = n - m; j > 0; j -= m) {
        k++;
        isplt = cfttree(m, j, k, a, nw, w);
        cftleaf(m, isplt, &a[j - m], nw, w);
    }
    return (void *) 0;
}


void *cftrec2_th(void *p)
{
    int cfttree(int n, int j, int k, FFTFLT *a, int nw, FFTFLT *w);
    void cftleaf(int n, int isplt, FFTFLT *a, int nw, FFTFLT *w);
    void cftmdl2(int n, FFTFLT *a, FFTFLT *w);
    int isplt, j, k, m, n, n0, nw;
    FFTFLT *a, *w;

    n0 = ((cdft_arg_t *) p)->n0;
    n = ((cdft_arg_t *) p)->n;
    a = ((cdft_arg_t *) p)->a;
    nw = ((cdft_arg_t *) p)->nw;
    w = ((cdft_arg_t *) p)->w;
    k = 1;
    m = n0;
    while (m > 512) {
        m >>= 2;
        k <<= 2;
        cftmdl2(m, &a[n - m], &w[nw - m]);
    }
    cftleaf(m, 0, &a[n - m], nw, w);
    k >>= 1;
    for (j = n - m; j > 0; j -= m) {
        k++;
        isplt = cfttree(m, j, k, a, nw, w);
        cftleaf(m, isplt, &a[j - m], nw, w);
    }
    return (void *) 0;
}
#endif /* USE_CDFT_THREADS */


void cftrec4(int n, FFTFLT *a, int nw, FFTFLT *w)
{
    int cfttree(int n, int j, int k, FFTFLT *a, int nw, FFTFLT *w);
    void cftleaf(int n, int isplt, FFTFLT *a, int nw, FFTFLT *w);
    void cftmdl1(int n, FFTFLT *a, FFTFLT *w);
    int isplt, j, k, m;

    m = n;
    while (m > 512) {
        m >>= 2;
        cftmdl1(m, &a[n - m], &w[nw - (m >> 1)]);
    }
    cftleaf(m, 1, &a[n - m], nw, w);
    k = 0;
    for (j = n - m; j > 0; j -= m) {
        k++;
        isplt = cfttree(m, j, k, a, nw, w);
        cftleaf(m, isplt, &a[j - m], nw, w);
    }
}


int cfttree(int n, int j, int k, FFTFLT *a, int nw, FFTFLT *w)
{
    void cftmdl1(int n, FFTFLT *a, FFTFLT *w);
    void cftmdl2(int n, FFTFLT *a, FFTFLT *w);
    int i, isplt, m;

    if ((k & 3) != 0) {
        isplt = k & 1;
        if (isplt != 0) {
            cftmdl1(n, &a[j - n], &w[nw - (n >> 1)]);
        } else {
            cftmdl2(n, &a[j - n], &w[nw - n]);
        }
    } else {
        m = n;
        for (i = k; (i & 3) == 0; i >>= 2) {
            m <<= 2;
        }
        isplt = i & 1;
        if (isplt != 0) {
            while (m > 128) {
                cftmdl1(m, &a[j - m], &w[nw - (m >> 1)]);
                m >>= 2;
            }
        } else {
            while (m > 128) {
                cftmdl2(m, &a[j - m], &w[nw - m]);
                m >>= 2;
            }
        }
    }
    return isplt;
}


void cftleaf(int n, int isplt, FFTFLT *a, int nw, FFTFLT *w)
{
    void cftmdl1(int n, FFTFLT *a, FFTFLT *w);
    void cftmdl2(int n, FFTFLT *a, FFTFLT *w);
    void cftf161(FFTFLT *a, FFTFLT *w);
    void cftf162(FFTFLT *a, FFTFLT *w);
    void cftf081(FFTFLT *a, FFTFLT *w);
    void cftf082(FFTFLT *a, FFTFLT *w);

    if (n == 512) {
        cftmdl1(128, a, &w[nw - 64]);
        cftf161(a, &w[nw - 8]);
        cftf162(&a[32], &w[nw - 32]);
        cftf161(&a[64], &w[nw - 8]);
        cftf161(&a[96], &w[nw - 8]);
        cftmdl2(128, &a[128], &w[nw - 128]);
        cftf161(&a[128], &w[nw - 8]);
        cftf162(&a[160], &w[nw - 32]);
        cftf161(&a[192], &w[nw - 8]);
        cftf162(&a[224], &w[nw - 32]);
        cftmdl1(128, &a[256], &w[nw - 64]);
        cftf161(&a[256], &w[nw - 8]);
        cftf162(&a[288], &w[nw - 32]);
        cftf161(&a[320], &w[nw - 8]);
        cftf161(&a[352], &w[nw - 8]);
        if (isplt != 0) {
            cftmdl1(128, &a[384], &w[nw - 64]);
            cftf161(&a[480], &w[nw - 8]);
        } else {
            cftmdl2(128, &a[384], &w[nw - 128]);
            cftf162(&a[480], &w[nw - 32]);
        }
        cftf161(&a[384], &w[nw - 8]);
        cftf162(&a[416], &w[nw - 32]);
        cftf161(&a[448], &w[nw - 8]);
    } else {
        cftmdl1(64, a, &w[nw - 32]);
        cftf081(a, &w[nw - 8]);
        cftf082(&a[16], &w[nw - 8]);
        cftf081(&a[32], &w[nw - 8]);
        cftf081(&a[48], &w[nw - 8]);
        cftmdl2(64, &a[64], &w[nw - 64]);
        cftf081(&a[64], &w[nw - 8]);
        cftf082(&a[80], &w[nw - 8]);
        cftf081(&a[96], &w[nw - 8]);
        cftf082(&a[112], &w[nw - 8]);
        cftmdl1(64, &a[128], &w[nw - 32]);
        cftf081(&a[128], &w[nw - 8]);
        cftf082(&a[144], &w[nw - 8]);
        cftf081(&a[160], &w[nw - 8]);
        cftf081(&a[176], &w[nw - 8]);
        if (isplt != 0) {
            cftmdl1(64, &a[192], &w[nw - 32]);
            cftf081(&a[240], &w[nw - 8]);
        } else {
            cftmdl2(64, &a[192], &w[nw - 64]);
            cftf082(&a[240], &w[nw - 8]);
        }
        cftf081(&a[192], &w[nw - 8]);
        cftf082(&a[208], &w[nw - 8]);
        cftf081(&a[224], &w[nw - 8]);
    }
}


void cftmdl1(int n, FFTFLT *a, FFTFLT *w)
{
    int j, j0, j1, j2, j3, k, m, mh;
    FFTFLT wn4r, wk1r, wk1i, wk3r, wk3i;
    FFTFLT x0r, x0i, x1r, x1i, x2r, x2i, x3r, x3i;

    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];
    k = 0;
    for (j = 2; j < mh; j += 2) {
        k += 4;
        wk1r = w[k];
        wk1i = w[k + 1];
        wk3r = w[k + 2];
        wk3i = 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];
        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[j] = x0r + x2r;
        a[j + 1] = x0i + x2i;
        a[j1] = x0r - x2r;
        a[j1 + 1] = x0i - x2i;
        x0r = x1r - x3i;
        x0i = x1i + x3r;
        a[j2] = wk1r * x0r - wk1i * x0i;
        a[j2 + 1] = wk1r * x0i + wk1i * x0r;
        x0r = x1r + x3i;
        x0i = x1i - x3r;
        a[j3] = wk3r * x0r + wk3i * x0i;
        a[j3 + 1] = wk3r * x0i - wk3i * 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];
        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] = wk1i * x0r - wk1r * x0i;
        a[j2 + 1] = wk1i * x0i + wk1r * x0r;
        x0r = x1r + x3i;
        x0i = x1i - x3r;
        a[j3] = wk3i * x0r + wk3r * x0i;
        a[j3 + 1] = wk3i * x0i - wk3r * x0r;
    }
    j0 = mh;
    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];
    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);
}


void cftmdl2(int n, FFTFLT *a, FFTFLT *w)
{
    int j, j0, j1, j2, j3, k, kr, m, mh;
    FFTFLT wn4r, wk1r, wk1i, wk3r, wk3i, wd1r, wd1i, wd3r, wd3i;
    FFTFLT x0r, x0i, x1r, x1i, x2r, x2i, x3r, x3i, y0r, y0i, y2r, y2i;

    mh = n >> 3;
    m = 2 * mh;
    wn4r = w[1];
    j1 = m;
    j2 = j1 + m;
    j3 = j2 + m;
    x0r = a[0] - a[j2 + 1];
    x0i = a[1] + a[j2];
    x1r = a[0] + a[j2 + 1];
    x1i = a[1] - a[j2];
    x2r = a[j1] - a[j3 + 1];
    x2i = a[j1 + 1] + a[j3];
    x3r = a[j1] + a[j3 + 1];
    x3i = a[j1 + 1] - a[j3];
    y0r = wn4r * (x2r - x2i);
    y0i = wn4r * (x2i + x2r);
    a[0] = x0r + y0r;
    a[1] = x0i + y0i;
    a[j1] = x0r - y0r;
    a[j1 + 1] = x0i - y0i;
    y0r = wn4r * (x3r - x3i);
    y0i = wn4r * (x3i + x3r);
    a[j2] = x1r - y0i;
    a[j2 + 1] = x1i + y0r;
    a[j3] = x1r + y0i;
    a[j3 + 1] = x1i - y0r;
    k = 0;
    kr = 2 * m;
    for (j = 2; j < mh; j += 2) {
        k += 4;
        wk1r = w[k];
        wk1i = w[k + 1];
        wk3r = w[k + 2];
        wk3i = w[k + 3];
        kr -= 4;
        wd1i = w[kr];
        wd1r = w[kr + 1];
        wd3i = w[kr + 2];
        wd3r = w[kr + 3];
        j1 = j + m;
        j2 = j1 + m;
        j3 = j2 + m;
        x0r = a[j] - a[j2 + 1];
        x0i = a[j + 1] + a[j2];
        x1r = a[j] + a[j2 + 1];
        x1i = a[j + 1] - a[j2];
        x2r = a[j1] - a[j3 + 1];
        x2i = a[j1 + 1] + a[j3];
        x3r = a[j1] + a[j3 + 1];
        x3i = a[j1 + 1] - a[j3];
        y0r = wk1r * x0r - wk1i * x0i;
        y0i = wk1r * x0i + wk1i * x0r;
        y2r = wd1r * x2r - wd1i * x2i;
        y2i = wd1r * x2i + wd1i * x2r;
        a[j] = y0r + y2r;
        a[j + 1] = y0i + y2i;
        a[j1] = y0r - y2r;
        a[j1 + 1] = y0i - y2i;
        y0r = wk3r * x1r + wk3i * x1i;
        y0i = wk3r * x1i - wk3i * x1r;
        y2r = wd3r * x3r + wd3i * x3i;
        y2i = wd3r * x3i - wd3i * x3r;
        a[j2] = y0r + y2r;
        a[j2 + 1] = y0i + y2i;
        a[j3] = y0r - y2r;
        a[j3 + 1] = y0i - y2i;
        j0 = m - j;
        j1 = j0 + m;
        j2 = j1 + m;
        j3 = j2 + m;
        x0r = a[j0] - a[j2 + 1];
        x0i = a[j0 + 1] + a[j2];
        x1r = a[j0] + a[j2 + 1];
        x1i = a[j0 + 1] - a[j2];
        x2r = a[j1] - a[j3 + 1];
        x2i = a[j1 + 1] + a[j3];
        x3r = a[j1] + a[j3 + 1];
        x3i = a[j1 + 1] - a[j3];
        y0r = wd1i * x0r - wd1r * x0i;
        y0i = wd1i * x0i + wd1r * x0r;
        y2r = wk1i * x2r - wk1r * x2i;
        y2i = wk1i * x2i + wk1r * x2r;
        a[j0] = y0r + y2r;
        a[j0 + 1] = y0i + y2i;
        a[j1] = y0r - y2r;
        a[j1 + 1] = y0i - y2i;
        y0r = wd3i * x1r + wd3r * x1i;
        y0i = wd3i * x1i - wd3r * x1r;
        y2r = wk3i * x3r + wk3r * x3i;
        y2i = wk3i * x3i - wk3r * x3r;
        a[j2] = y0r + y2r;
        a[j2 + 1] = y0i + y2i;
        a[j3] = y0r - y2r;
        a[j3 + 1] = y0i - y2i;
    }
    wk1r = w[m];
    wk1i = w[m + 1];
    j0 = mh;
    j1 = j0 + m;
    j2 = j1 + m;
    j3 = j2 + m;
    x0r = a[j0] - a[j2 + 1];
    x0i = a[j0 + 1] + a[j2];
    x1r = a[j0] + a[j2 + 1];
    x1i = a[j0 + 1] - a[j2];
    x2r = a[j1] - a[j3 + 1];
    x2i = a[j1 + 1] + a[j3];
    x3r = a[j1] + a[j3 + 1];
    x3i = a[j1 + 1] - a[j3];
    y0r = wk1r * x0r - wk1i * x0i;
    y0i = wk1r * x0i + wk1i * x0r;
    y2r = wk1i * x2r - wk1r * x2i;
    y2i = wk1i * x2i + wk1r * x2r;
    a[j0] = y0r + y2r;
    a[j0 + 1] = y0i + y2i;
    a[j1] = y0r - y2r;
    a[j1 + 1] = y0i - y2i;
    y0r = wk1i * x1r - wk1r * x1i;
    y0i = wk1i * x1i + wk1r * x1r;
    y2r = wk1r * x3r - wk1i * x3i;
    y2i = wk1r * x3i + wk1i * x3r;
    a[j2] = y0r - y2r;
    a[j2 + 1] = y0i - y2i;
    a[j3] = y0r + y2r;
    a[j3 + 1] = y0i + y2i;
}


void cftfx41(int n, FFTFLT *a, int nw, FFTFLT *w)
{
    void cftf161(FFTFLT *a, FFTFLT *w);
    void cftf162(FFTFLT *a, FFTFLT *w);
    void cftf081(FFTFLT *a, FFTFLT *w);
    void cftf082(FFTFLT *a, FFTFLT *w);

    if (n == 128) {
        cftf161(a, &w[nw - 8]);
        cftf162(&a[32], &w[nw - 32]);
        cftf161(&a[64], &w[nw - 8]);
        cftf161(&a[96], &w[nw - 8]);
    } else {
        cftf081(a, &w[nw - 8]);
        cftf082(&a[16], &w[nw - 8]);
        cftf081(&a[32], &w[nw - 8]);
        cftf081(&a[48], &w[nw - 8]);
    }
}


void cftf161(FFTFLT *a, FFTFLT *w)
{
    FFTFLT wn4r, wk1r, wk1i,
        x0r, x0i, x1r, x1i, x2r, x2i, x3r, x3i,
        y0r, y0i, y1r, y1i, y2r, y2i, y3r, y3i,
        y4r, y4i, y5r, y5i, y6r, y6i, y7r, y7i,
        y8r, y8i, y9r, y9i, y10r, y10i, y11r, y11i,
        y12r, y12i, y13r, y13i, y14r, y14i, y15r, y15i;

    wn4r = w[1];
    wk1r = w[2];
    wk1i = w[3];
    x0r = a[0] + a[16];
    x0i = a[1] + a[17];
    x1r = a[0] - a[16];
    x1i = a[1] - a[17];
    x2r = a[8] + a[24];
    x2i = a[9] + a[25];
    x3r = a[8] - a[24];
    x3i = a[9] - a[25];
    y0r = x0r + x2r;
    y0i = x0i + x2i;
    y4r = x0r - x2r;
    y4i = x0i - x2i;
    y8r = x1r - x3i;
    y8i = x1i + x3r;
    y12r = x1r + x3i;
    y12i = x1i - x3r;
    x0r = a[2] + a[18];
    x0i = a[3] + a[19];
    x1r = a[2] - a[18];
    x1i = a[3] - a[19];
    x2r = a[10] + a[26];
    x2i = a[11] + a[27];
    x3r = a[10] - a[26];
    x3i = a[11] - a[27];
    y1r = x0r + x2r;
    y1i = x0i + x2i;
    y5r = x0r - x2r;
    y5i = x0i - x2i;
    x0r = x1r - x3i;
    x0i = x1i + x3r;
    y9r = wk1r * x0r - wk1i * x0i;
    y9i = wk1r * x0i + wk1i * x0r;
    x0r = x1r + x3i;
    x0i = x1i - x3r;
    y13r = wk1i * x0r - wk1r * x0i;
    y13i = wk1i * x0i + wk1r * x0r;
    x0r = a[4] + a[20];
    x0i = a[5] + a[21];
    x1r = a[4] - a[20];
    x1i = a[5] - a[21];
    x2r = a[12] + a[28];
    x2i = a[13] + a[29];
    x3r = a[12] - a[28];
    x3i = a[13] - a[29];
    y2r = x0r + x2r;
    y2i = x0i + x2i;
    y6r = x0r - x2r;
    y6i = x0i - x2i;
    x0r = x1r - x3i;
    x0i = x1i + x3r;
    y10r = wn4r * (x0r - x0i);
    y10i = wn4r * (x0i + x0r);
    x0r = x1r + x3i;
    x0i = x1i - x3r;
    y14r = wn4r * (x0r + x0i);
    y14i = wn4r * (x0i - x0r);
    x0r = a[6] + a[22];
    x0i = a[7] + a[23];
    x1r = a[6] - a[22];
    x1i = a[7] - a[23];
    x2r = a[14] + a[30];
    x2i = a[15] + a[31];
    x3r = a[14] - a[30];
    x3i = a[15] - a[31];
    y3r = x0r + x2r;
    y3i = x0i + x2i;
    y7r = x0r - x2r;
    y7i = x0i - x2i;
    x0r = x1r - x3i;
    x0i = x1i + x3r;
    y11r = wk1i * x0r - wk1r * x0i;
    y11i = wk1i * x0i + wk1r * x0r;
    x0r = x1r + x3i;
    x0i = x1i - x3r;
    y15r = wk1r * x0r - wk1i * x0i;
    y15i = wk1r * x0i + wk1i * x0r;
    x0r = y12r - y14r;
    x0i = y12i - y14i;
    x1r = y12r + y14r;
    x1i = y12i + y14i;
    x2r = y13r - y15r;
    x2i = y13i - y15i;
    x3r = y13r + y15r;
    x3i = y13i + y15i;
    a[24] = x0r + x2r;
    a[25] = x0i + x2i;
    a[26] = x0r - x2r;
    a[27] = x0i - x2i;
    a[28] = x1r - x3i;
    a[29] = x1i + x3r;
    a[30] = x1r + x3i;
    a[31] = x1i - x3r;
    x0r = y8r + y10r;
    x0i = y8i + y10i;
    x1r = y8r - y10r;
    x1i = y8i - y10i;
    x2r = y9r + y11r;
    x2i = y9i + y11i;
    x3r = y9r - y11r;
    x3i = y9i - y11i;
    a[16] = x0r + x2r;
    a[17] = x0i + x2i;
    a[18] = x0r - x2r;
    a[19] = x0i - x2i;
    a[20] = x1r - x3i;
    a[21] = x1i + x3r;
    a[22] = x1r + x3i;
    a[23] = x1i - x3r;
    x0r = y5r - y7i;
    x0i = y5i + y7r;
    x2r = wn4r * (x0r - x0i);
    x2i = wn4r * (x0i + x0r);
    x0r = y5r + y7i;
    x0i = y5i - y7r;
    x3r = wn4r * (x0r - x0i);
    x3i = wn4r * (x0i + x0r);
    x0r = y4r - y6i;
    x0i = y4i + y6r;
    x1r = y4r + y6i;
    x1i = y4i - y6r;
    a[8] = x0r + x2r;
    a[9] = x0i + x2i;
    a[10] = x0r - x2r;
    a[11] = x0i - x2i;
    a[12] = x1r - x3i;
    a[13] = x1i + x3r;
    a[14] = x1r + x3i;
    a[15] = x1i - x3r;
    x0r = y0r + y2r;
    x0i = y0i + y2i;
    x1r = y0r - y2r;
    x1i = y0i - y2i;
    x2r = y1r + y3r;
    x2i = y1i + y3i;
    x3r = y1r - y3r;
    x3i = y1i - y3i;
    a[0] = x0r + x2r;
    a[1] = x0i + x2i;
    a[2] = x0r - x2r;
    a[3] = x0i - x2i;
    a[4] = x1r - x3i;
    a[5] = x1i + x3r;
    a[6] = x1r + x3i;
    a[7] = x1i - x3r;
}


void cftf162(FFTFLT *a, FFTFLT *w)
{
    FFTFLT wn4r, wk1r, wk1i, wk2r, wk2i, wk3r, wk3i,
        x0r, x0i, x1r, x1i, x2r, x2i,
        y0r, y0i, y1r, y1i, y2r, y2i, y3r, y3i,
        y4r, y4i, y5r, y5i, y6r, y6i, y7r, y7i,
        y8r, y8i, y9r, y9i, y10r, y10i, y11r, y11i,
        y12r, y12i, y13r, y13i, y14r, y14i, y15r, y15i;

    wn4r = w[1];
    wk1r = w[4];
    wk1i = w[5];
    wk3r = w[6];
    wk3i = -w[7];
    wk2r = w[8];
    wk2i = w[9];
    x1r = a[0] - a[17];
    x1i = a[1] + a[16];
    x0r = a[8] - a[25];
    x0i = a[9] + a[24];
    x2r = wn4r * (x0r - x0i);
    x2i = wn4r * (x0i + x0r);
    y0r = x1r + x2r;
    y0i = x1i + x2i;
    y4r = x1r - x2r;
    y4i = x1i - x2i;
    x1r = a[0] + a[17];
    x1i = a[1] - a[16];
    x0r = a[8] + a[25];
    x0i = a[9] - a[24];
    x2r = wn4r * (x0r - x0i);
    x2i = wn4r * (x0i + x0r);
    y8r = x1r - x2i;
    y8i = x1i + x2r;
    y12r = x1r + x2i;
    y12i = x1i - x2r;
    x0r = a[2] - a[19];
    x0i = a[3] + a[18];
    x1r = wk1r * x0r - wk1i * x0i;
    x1i = wk1r * x0i + wk1i * x0r;
    x0r = a[10] - a[27];
    x0i = a[11] + a[26];
    x2r = wk3i * x0r - wk3r * x0i;
    x2i = wk3i * x0i + wk3r * x0r;
    y1r = x1r + x2r;
    y1i = x1i + x2i;
    y5r = x1r - x2r;
    y5i = x1i - x2i;
    x0r = a[2] + a[19];
    x0i = a[3] - a[18];
    x1r = wk3r * x0r - wk3i * x0i;
    x1i = wk3r * x0i + wk3i * x0r;
    x0r = a[10] + a[27];
    x0i = a[11] - a[26];
    x2r = wk1r * x0r + wk1i * x0i;
    x2i = wk1r * x0i - wk1i * x0r;
    y9r = x1r - x2r;
    y9i = x1i - x2i;
    y13r = x1r + x2r;
    y13i = x1i + x2i;
    x0r = a[4] - a[21];
    x0i = a[5] + a[20];
    x1r = wk2r * x0r - wk2i * x0i;
    x1i = wk2r * x0i + wk2i * x0r;
    x0r = a[12] - a[29];
    x0i = a[13] + a[28];
    x2r = wk2i * x0r - wk2r * x0i;
    x2i = wk2i * x0i + wk2r * x0r;
    y2r = x1r + x2r;
    y2i = x1i + x2i;
    y6r = x1r - x2r;
    y6i = x1i - x2i;
    x0r = a[4] + a[21];
    x0i = a[5] - a[20];
    x1r = wk2i * x0r - wk2r * x0i;
    x1i = wk2i * x0i + wk2r * x0r;
    x0r = a[12] + a[29];
    x0i = a[13] - a[28];
    x2r = wk2r * x0r - wk2i * x0i;
    x2i = wk2r * x0i + wk2i * x0r;
    y10r = x1r - x2r;
    y10i = x1i - x2i;
    y14r = x1r + x2r;
    y14i = x1i + x2i;
    x0r = a[6] - a[23];
    x0i = a[7] + a[22];
    x1r = wk3r * x0r - wk3i * x0i;
    x1i = wk3r * x0i + wk3i * x0r;
    x0r = a[14] - a[31];
    x0i = a[15] + a[30];
    x2r = wk1i * x0r - wk1r * x0i;
    x2i = wk1i * x0i + wk1r * x0r;
    y3r = x1r + x2r;
    y3i = x1i + x2i;
    y7r = x1r - x2r;
    y7i = x1i - x2i;
    x0r = a[6] + a[23];
    x0i = a[7] - a[22];
    x1r = wk1i * x0r + wk1r * x0i;
    x1i = wk1i * x0i - wk1r * x0r;
    x0r = a[14] + a[31];
    x0i = a[15] - a[30];
    x2r = wk3i * x0r - wk3r * x0i;
    x2i = wk3i * x0i + wk3r * x0r;
    y11r = x1r + x2r;
    y11i = x1i + x2i;
    y15r = x1r - x2r;
    y15i = x1i - x2i;
    x1r = y0r + y2r;
    x1i = y0i + y2i;
    x2r = y1r + y3r;
    x2i = y1i + y3i;
    a[0] = x1r + x2r;
    a[1] = x1i + x2i;
    a[2] = x1r - x2r;
    a[3] = x1i - x2i;
    x1r = y0r - y2r;
    x1i = y0i - y2i;
    x2r = y1r - y3r;
    x2i = y1i - y3i;
    a[4] = x1r - x2i;
    a[5] = x1i + x2r;
    a[6] = x1r + x2i;
    a[7] = x1i - x2r;
    x1r = y4r - y6i;
    x1i = y4i + y6r;
    x0r = y5r - y7i;
    x0i = y5i + y7r;
    x2r = wn4r * (x0r - x0i);
    x2i = wn4r * (x0i + x0r);
    a[8] = x1r + x2r;
    a[9] = x1i + x2i;
    a[10] = x1r - x2r;
    a[11] = x1i - x2i;
    x1r = y4r + y6i;
    x1i = y4i - y6r;
    x0r = y5r + y7i;
    x0i = y5i - y7r;
    x2r = wn4r * (x0r - x0i);
    x2i = wn4r * (x0i + x0r);
    a[12] = x1r - x2i;
    a[13] = x1i + x2r;
    a[14] = x1r + x2i;
    a[15] = x1i - x2r;
    x1r = y8r + y10r;
    x1i = y8i + y10i;
    x2r = y9r - y11r;
    x2i = y9i - y11i;
    a[16] = x1r + x2r;
    a[17] = x1i + x2i;
    a[18] = x1r - x2r;
    a[19] = x1i - x2i;
    x1r = y8r - y10r;
    x1i = y8i - y10i;
    x2r = y9r + y11r;
    x2i = y9i + y11i;
    a[20] = x1r - x2i;
    a[21] = x1i + x2r;
    a[22] = x1r + x2i;
    a[23] = x1i - x2r;
    x1r = y12r - y14i;
    x1i = y12i + y14r;
    x0r = y13r + y15i;
    x0i = y13i - y15r;
    x2r = wn4r * (x0r - x0i);
    x2i = wn4r * (x0i + x0r);
    a[24] = x1r + x2r;
    a[25] = x1i + x2i;
    a[26] = x1r - x2r;
    a[27] = x1i - x2i;
    x1r = y12r + y14i;
    x1i = y12i - y14r;
    x0r = y13r - y15i;
    x0i = y13i + y15r;
    x2r = wn4r * (x0r - x0i);
    x2i = wn4r * (x0i + x0r);
    a[28] = x1r - x2i;
    a[29] = x1i + x2r;
    a[30] = x1r + x2i;
    a[31] = x1i - x2r;
}


void cftf081(FFTFLT *a, FFTFLT *w)
{
    FFTFLT wn4r, x0r, x0i, x1r, x1i, x2r, x2i, x3r, x3i,
        y0r, y0i, y1r, y1i, y2r, y2i, y3r, y3i,
        y4r, y4i, y5r, y5i, y6r, y6i, y7r, y7i;

    wn4r = w[1];
    x0r = a[0] + a[8];
    x0i = a[1] + a[9];
    x1r = a[0] - a[8];
    x1i = a[1] - a[9];
    x2r = a[4] + a[12];
    x2i = a[5] + a[13];
    x3r = a[4] - a[12];
    x3i = a[5] - a[13];
    y0r = x0r + x2r;
    y0i = x0i + x2i;
    y2r = x0r - x2r;
    y2i = x0i - x2i;
    y1r = x1r - x3i;
    y1i = x1i + x3r;
    y3r = x1r + x3i;
    y3i = x1i - x3r;
    x0r = a[2] + a[10];
    x0i = a[3] + a[11];
    x1r = a[2] - a[10];
    x1i = a[3] - a[11];
    x2r = a[6] + a[14];
    x2i = a[7] + a[15];
    x3r = a[6] - a[14];
    x3i = a[7] - a[15];
    y4r = x0r + x2r;
    y4i = x0i + x2i;
    y6r = x0r - x2r;
    y6i = x0i - x2i;
    x0r = x1r - x3i;
    x0i = x1i + x3r;
    x2r = x1r + x3i;
    x2i = x1i - x3r;
    y5r = wn4r * (x0r - x0i);
    y5i = wn4r * (x0r + x0i);
    y7r = wn4r * (x2r - x2i);
    y7i = wn4r * (x2r + x2i);
    a[8] = y1r + y5r;
    a[9] = y1i + y5i;
    a[10] = y1r - y5r;
    a[11] = y1i - y5i;
    a[12] = y3r - y7i;
    a[13] = y3i + y7r;
    a[14] = y3r + y7i;
    a[15] = y3i - y7r;
    a[0] = y0r + y4r;
    a[1] = y0i + y4i;
    a[2] = y0r - y4r;
    a[3] = y0i - y4i;
    a[4] = y2r - y6i;
    a[5] = y2i + y6r;
    a[6] = y2r + y6i;
    a[7] = y2i - y6r;
}


void cftf082(FFTFLT *a, FFTFLT *w)
{
    FFTFLT wn4r, wk1r, wk1i, x0r, x0i, x1r, x1i,
        y0r, y0i, y1r, y1i, y2r, y2i, y3r, y3i,
        y4r, y4i, y5r, y5i, y6r, y6i, y7r, y7i;

    wn4r = w[1];
    wk1r = w[2];
    wk1i = w[3];
    y0r = a[0] - a[9];
    y0i = a[1] + a[8];
    y1r = a[0] + a[9];
    y1i = a[1] - a[8];
    x0r = a[4] - a[13];
    x0i = a[5] + a[12];
    y2r = wn4r * (x0r - x0i);
    y2i = wn4r * (x0i + x0r);
    x0r = a[4] + a[13];
    x0i = a[5] - a[12];
    y3r = wn4r * (x0r - x0i);
    y3i = wn4r * (x0i + x0r);
    x0r = a[2] - a[11];
    x0i = a[3] + a[10];
    y4r = wk1r * x0r - wk1i * x0i;
    y4i = wk1r * x0i + wk1i * x0r;
    x0r = a[2] + a[11];
    x0i = a[3] - a[10];
    y5r = wk1i * x0r - wk1r * x0i;
    y5i = wk1i * x0i + wk1r * x0r;
    x0r = a[6] - a[15];
    x0i = a[7] + a[14];
    y6r = wk1i * x0r - wk1r * x0i;
    y6i = wk1i * x0i + wk1r * x0r;
    x0r = a[6] + a[15];
    x0i = a[7] - a[14];
    y7r = wk1r * x0r - wk1i * x0i;
    y7i = wk1r * x0i + wk1i * x0r;
    x0r = y0r + y2r;
    x0i = y0i + y2i;
    x1r = y4r + y6r;
    x1i = y4i + y6i;
    a[0] = x0r + x1r;
    a[1] = x0i + x1i;
    a[2] = x0r - x1r;
    a[3] = x0i - x1i;
    x0r = y0r - y2r;
    x0i = y0i - y2i;
    x1r = y4r - y6r;
    x1i = y4i - y6i;
    a[4] = x0r - x1i;
    a[5] = x0i + x1r;
    a[6] = x0r + x1i;
    a[7] = x0i - x1r;
    x0r = y1r - y3i;
    x0i = y1i + y3r;
    x1r = y5r - y7r;
    x1i = y5i - y7i;
    a[8] = x0r + x1r;
    a[9] = x0i + x1i;
    a[10] = x0r - x1r;
    a[11] = x0i - x1i;
    x0r = y1r + y3i;
    x0i = y1i - y3r;
    x1r = y5r + y7r;
    x1i = y5i + y7i;
    a[12] = x0r - x1i;
    a[13] = x0i + x1r;
    a[14] = x0r + x1i;
    a[15] = x0i - x1r;
}


void cftf040(FFTFLT *a)
{
    FFTFLT x0r, x0i, x1r, x1i, x2r, x2i, x3r, x3i;

    x0r = a[0] + a[4];
    x0i = a[1] + a[5];
    x1r = a[0] - a[4];
    x1i = a[1] - a[5];
    x2r = a[2] + a[6];
    x2i = a[3] + a[7];
    x3r = a[2] - a[6];
    x3i = a[3] - a[7];
    a[0] = x0r + x2r;
    a[1] = x0i + x2i;
    a[2] = x1r - x3i;
    a[3] = x1i + x3r;
    a[4] = x0r - x2r;
    a[5] = x0i - x2i;
    a[6] = x1r + x3i;
    a[7] = x1i - x3r;
}


void cftb040(FFTFLT *a)
{
    FFTFLT x0r, x0i, x1r, x1i, x2r, x2i, x3r, x3i;

    x0r = a[0] + a[4];
    x0i = a[1] + a[5];
    x1r = a[0] - a[4];
    x1i = a[1] - a[5];
    x2r = a[2] + a[6];
    x2i = a[3] + a[7];
    x3r = a[2] - a[6];
    x3i = a[3] - a[7];
    a[0] = x0r + x2r;
    a[1] = x0i + x2i;
    a[2] = x1r + x3i;
    a[3] = x1i - x3r;
    a[4] = x0r - x2r;
    a[5] = x0i - x2i;
    a[6] = x1r - x3i;
    a[7] = x1i + x3r;
}


void cftx020(FFTFLT *a)
{
    FFTFLT x0r, x0i;

    x0r = a[0] - a[2];
    x0i = a[1] - a[3];
    a[0] += a[2];
    a[1] += a[3];
    a[2] = x0r;
    a[3] = x0i;
}


void rftfsub(int n, FFTFLT *a, int nc, FFTFLT *c)
{
    int j, k, kk, ks, m;
    FFTFLT 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;
    }
}


void rftbsub(int n, FFTFLT *a, int nc, FFTFLT *c)
{
    int j, k, kk, ks, m;
    FFTFLT 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;
    }
}


void dctsub(int n, FFTFLT *a, int nc, FFTFLT *c)
{
    int j, k, kk, ks, m;
    FFTFLT 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[j] - wkr * a[k];
        a[j] = wkr * a[j] + wki * a[k];
        a[k] = xr;
    }
    a[m] *= c[0];
}


void dstsub(int n, FFTFLT *a, int nc, FFTFLT *c)
{
    int j, k, kk, ks, m;
    FFTFLT 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];
}

