82 lines
2.2 KiB
C
82 lines
2.2 KiB
C
/* mpn_redc_n. Set rp[] <- up[]/R^n mod mp[]. Clobber up[].
|
|
mp[] is n limbs; up[] is 2n limbs, the inverse ip[] is n limbs.
|
|
|
|
THIS IS AN INTERNAL FUNCTION WITH A MUTABLE INTERFACE. IT IS ONLY
|
|
SAFE TO REACH THIS FUNCTION THROUGH DOCUMENTED INTERFACES.
|
|
|
|
Copyright 2009, 2012 Free Software Foundation, Inc.
|
|
|
|
This file is part of the GNU MP Library.
|
|
|
|
The GNU MP Library is free software; you can redistribute it and/or modify
|
|
it under the terms of either:
|
|
|
|
* the GNU Lesser General Public License as published by the Free
|
|
Software Foundation; either version 3 of the License, or (at your
|
|
option) any later version.
|
|
|
|
or
|
|
|
|
* 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.
|
|
|
|
or both in parallel, as here.
|
|
|
|
The GNU MP Library 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 copies of the GNU General Public License and the
|
|
GNU Lesser General Public License along with the GNU MP Library. If not,
|
|
see https://www.gnu.org/licenses/. */
|
|
|
|
#include "mpir.h"
|
|
#include "gmp-impl.h"
|
|
|
|
/*
|
|
TODO
|
|
|
|
* We assume mpn_mulmod_bnm1 is always faster than plain mpn_mul_n (or a
|
|
future mpn_mulhi) for the range we will be called. Follow up that
|
|
assumption.
|
|
|
|
* Decrease scratch usage.
|
|
|
|
* Consider removing the residue canonicalisation.
|
|
*/
|
|
|
|
void
|
|
mpn_redc_n (mp_ptr rp, mp_ptr up, mp_srcptr mp, mp_size_t n, mp_srcptr ip)
|
|
{
|
|
mp_ptr xp, yp, scratch;
|
|
mp_limb_t cy;
|
|
mp_size_t rn;
|
|
TMP_DECL;
|
|
TMP_MARK;
|
|
|
|
ASSERT (n > 8);
|
|
|
|
rn = mpn_mulmod_bnm1_next_size (n);
|
|
|
|
scratch = TMP_ALLOC_LIMBS (n + rn + mpn_mulmod_bnm1_itch (rn, n, n));
|
|
|
|
xp = scratch;
|
|
mpn_mullow_n (xp, up, ip, n); /* JPF: assuming now it does not overfolw */
|
|
|
|
yp = scratch + n;
|
|
mpn_mulmod_bnm1 (yp, rn, xp, n, mp, n, scratch + n + rn);
|
|
|
|
ASSERT_ALWAYS (2 * n > rn); /* could handle this */
|
|
|
|
cy = mpn_sub_n (yp + rn, yp, up, 2*n - rn); /* undo wrap around */
|
|
MPN_DECR_U (yp + 2*n - rn, rn, cy);
|
|
|
|
cy = mpn_sub_n (rp, up + n, yp + n, n);
|
|
if (cy != 0)
|
|
mpn_add_n (rp, rp, mp, n);
|
|
|
|
TMP_FREE;
|
|
}
|