cpython/Modules/_decimal/libmpdec/fnt.c

/*
 * Copyright (c) 2008-2020 Stefan Krah. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */


#include "mpdecimal.h"

#include <assert.h>
#include <stdio.h>

#include "bits.h"
#include "difradix2.h"
#include "fnt.h"
#include "numbertheory.h"


/* Bignum: Fast transform for medium-sized coefficients. */


/* forward transform, sign = -1 */
int
std_fnt(mpd_uint_t *a, mpd_size_t n, int modnum)
{
    struct fnt_params *tparams;

    assert(ispower2(n));
    assert(n >= 4);
    assert(n <= 3*MPD_MAXTRANSFORM_2N);

    if ((tparams = _mpd_init_fnt_params(n, -1, modnum)) == NULL) {
        return 0;
    }
    fnt_dif2(a, n, tparams);

    mpd_free(tparams);
    return 1;
}

/* reverse transform, sign = 1 */
int
std_inv_fnt(mpd_uint_t *a, mpd_size_t n, int modnum)
{
    struct fnt_params *tparams;

    assert(ispower2(n));
    assert(n >= 4);
    assert(n <= 3*MPD_MAXTRANSFORM_2N);

    if ((tparams = _mpd_init_fnt_params(n, 1, modnum)) == NULL) {
        return 0;
    }
    fnt_dif2(a, n, tparams);

    mpd_free(tparams);
    return 1;
}