pqc/external/flint-2.4.3/nmod_poly/mulmod.c
2014-05-24 23:16:06 +02:00

103 lines
2.9 KiB
C

/*=============================================================================
This file is part of FLINT.
FLINT is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
FLINT is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with FLINT; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
=============================================================================*/
/******************************************************************************
Copyright (C) 2011 Fredrik Johansson
******************************************************************************/
#include <stdlib.h>
#include <gmp.h>
#include "flint.h"
#include "nmod_vec.h"
#include "nmod_poly.h"
void _nmod_poly_mulmod(mp_ptr res, mp_srcptr poly1, slong len1,
mp_srcptr poly2, slong len2, mp_srcptr f,
slong lenf, nmod_t mod)
{
mp_ptr T, Q;
slong lenT, lenQ;
lenT = len1 + len2 - 1;
lenQ = lenT - lenf + 1;
T = _nmod_vec_init(lenT + lenQ);
Q = T + lenT;
if (len1 >= len2)
_nmod_poly_mul(T, poly1, len1, poly2, len2, mod);
else
_nmod_poly_mul(T, poly2, len2, poly1, len1, mod);
_nmod_poly_divrem(Q, res, T, lenT, f, lenf, mod);
_nmod_vec_clear(T);
}
void
nmod_poly_mulmod(nmod_poly_t res,
const nmod_poly_t poly1, const nmod_poly_t poly2, const nmod_poly_t f)
{
slong len1, len2, lenf;
mp_ptr fcoeffs;
lenf = f->length;
len1 = poly1->length;
len2 = poly2->length;
if (lenf == 0)
{
flint_printf("Exception (nmod_poly_mulmod). Divide by zero.\n");
abort();
}
if (lenf == 1 || len1 == 0 || len2 == 0)
{
nmod_poly_zero(res);
return;
}
if (len1 + len2 - lenf > 0)
{
if (f == res)
{
fcoeffs = flint_malloc(sizeof(mp_limb_t) * lenf);
_nmod_vec_set(fcoeffs, f->coeffs, lenf);
}
else
fcoeffs = f->coeffs;
nmod_poly_fit_length(res, lenf - 1);
_nmod_poly_mulmod(res->coeffs, poly1->coeffs, len1,
poly2->coeffs, len2,
fcoeffs, lenf,
res->mod);
if (f == res)
flint_free(fcoeffs);
res->length = lenf - 1;
_nmod_poly_normalise(res);
}
else
{
nmod_poly_mul(res, poly1, poly2);
}
}