pqc/external/flint-2.4.3/ulong_extras/mod_precomp.c

40 lines
1.4 KiB
C
Raw Normal View History

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) 2009 William Hart
******************************************************************************/
#include <gmp.h>
#include "flint.h"
#include "ulong_extras.h"
mp_limb_t n_mod_precomp(mp_limb_t a, mp_limb_t n, double npre)
{
mp_limb_t quot, rem;
quot = (mp_limb_t) ((double) a * npre);
rem = a - quot*n;
if ((slong) rem < 0) /* unlikely */
rem += n;
return rem - (n & (((mp_limb_signed_t) (n - rem - 1)) >> (FLINT_BITS-1)));
}