pqc/external/flint-2.4.3/fmpz/preinvn_init.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) 2013 William Hart
******************************************************************************/
#include <gmp.h>
#include "flint.h"
#include "ulong_extras.h"
#include "mpn_extras.h"
#include "fmpz.h"
void fmpz_preinvn_init(fmpz_preinvn_t inv, fmpz_t f)
{
fmpz c = *f;
mp_bitcnt_t norm;
mp_ptr t;
if (c == 0)
{
flint_printf("Exception (fmpz_preinvn_init). Division by zero.\n");
abort();
} else if (!COEFF_IS_MPZ(c)) /* c is small */
{
inv->dinv = flint_malloc(sizeof(mp_limb_t));
if (c < 0) c = -c;
count_leading_zeros(norm, c);
if (norm) c <<= norm;
flint_mpn_preinvn(inv->dinv, (mp_ptr) &c, 1);
inv->n = 1;
} else /* c is big */
{
__mpz_struct * mpz_ptr = COEFF_TO_PTR(c);
slong size = FLINT_ABS(mpz_ptr->_mp_size);
inv->dinv = flint_malloc(size*sizeof(mp_limb_t));
count_leading_zeros(norm, mpz_ptr->_mp_d[size - 1]);
if (norm)
{
t = flint_malloc(size*sizeof(mp_limb_t));
mpn_lshift(t, mpz_ptr->_mp_d, size, norm);
} else
t = mpz_ptr->_mp_d;
flint_mpn_preinvn(inv->dinv, t, size);
inv->n = size;
if (norm) flint_free(t);
}
inv->norm = norm;
}