pqc/external/flint-2.4.3/fmpz/gcdinv.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 "ulong_extras.h"
#include "fmpz.h"
void fmpz_gcdinv(fmpz_t d, fmpz_t a, const fmpz_t f, const fmpz_t g)
{
if (fmpz_is_zero(f))
{
fmpz_set(d, g);
return;
}
if (!COEFF_IS_MPZ(*g)) /* g is small, hence f is small */
{
if (COEFF_IS_MPZ(*d))
_fmpz_demote_val(d);
if (COEFF_IS_MPZ(*a))
_fmpz_demote_val(a);
*d = n_gcdinv((mp_limb_t *) a, *f, *g);
}
else /* g is large */
{
_fmpz_promote_val(d);
_fmpz_promote_val(a);
if (!COEFF_IS_MPZ(*f)) /* f is small */
{
mpz_t fptr;
fptr->_mp_alloc = 1;
fptr->_mp_size = 1;
fptr->_mp_d = (mp_limb_t *) f;
mpz_gcdext(COEFF_TO_PTR(*d), COEFF_TO_PTR(*a), NULL,
fptr, COEFF_TO_PTR(*g));
}
else /* f is large */
{
mpz_gcdext(COEFF_TO_PTR(*d), COEFF_TO_PTR(*a), NULL,
COEFF_TO_PTR(*f), COEFF_TO_PTR(*g));
}
_fmpz_demote_val(d);
_fmpz_demote_val(a);
}
}