pqc/external/flint-2.4.3/fmpz_mod_poly/evaluate_fmpz.c

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2014-05-18 22:03:37 +00:00
/*=============================================================================
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 Sebastian Pancratz
******************************************************************************/
#include <gmp.h>
#include "flint.h"
#include "fmpz_mod_poly.h"
void _fmpz_mod_poly_evaluate_fmpz(fmpz_t res, const fmpz *poly, slong len,
const fmpz_t a, const fmpz_t p)
{
if (len == 0)
{
fmpz_zero(res);
}
else if (len == 1 || fmpz_is_zero(a))
{
fmpz_set(res, poly);
}
else
{
slong i = len - 1;
fmpz_t t;
fmpz_init(t);
fmpz_set(res, poly + i);
for (i = len - 2; i >= 0; i--)
{
fmpz_mul(t, res, a);
fmpz_mod(t, t, p);
fmpz_add(res, poly + i, t);
}
fmpz_clear(t);
if (fmpz_cmpabs(res, p) >= 0)
fmpz_sub(res, res, p);
}
}
void fmpz_mod_poly_evaluate_fmpz(fmpz_t res,
const fmpz_mod_poly_t poly, const fmpz_t a)
{
if (res == a)
{
fmpz_t t;
fmpz_init(t);
_fmpz_mod_poly_evaluate_fmpz(t, poly->coeffs, poly->length,
a, &(poly->p));
fmpz_swap(res, t);
fmpz_clear(t);
}
else
{
_fmpz_mod_poly_evaluate_fmpz(res, poly->coeffs, poly->length,
a, &(poly->p));
}
}