pqc/external/flint-2.4.3/mpn_extras/mulmod_preinvn.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) 2012 William Hart
******************************************************************************/
#include <stdlib.h>
#include <gmp.h>
#include "flint.h"
#include "longlong.h"
#include "mpn_extras.h"
/*
TODO: speedup mpir's mullow and mulhigh and use instead of mul/mul_n
*/
void flint_mpn_mulmod_preinvn(mp_ptr r,
mp_srcptr a, mp_srcptr b, mp_size_t n,
mp_srcptr d, mp_srcptr dinv, ulong norm)
{
mp_limb_t cy;
mp_ptr t;
TMP_INIT;
TMP_START;
t = TMP_ALLOC(5*n*sizeof(mp_limb_t));
mpn_mul_n(t, a, b, n);
if (norm)
mpn_rshift(t, t, 2*n, norm);
mpn_mul_n(t + 3*n, t + n, dinv, n);
mpn_add_n(t + 4*n, t + 4*n, t + n, n);
mpn_mul_n(t + 2*n, t + 4*n, d, n);
cy = t[n] - t[3*n] - mpn_sub_n(r, t, t + 2*n, n);
while (cy > 0)
cy -= mpn_sub_n(r, r, d, n);
if (mpn_cmp(r, d, n) >= 0)
mpn_sub_n(r, r, d, n);
TMP_END;
}