1 /* mpn_redc_n. Set cp[] <- up[]/R^n mod mp[]. Clobber up[].
2 mp[] is n limbs; up[] is 2n limbs, the inverse ip[] is n limbs.
4 THIS IS AN INTERNAL FUNCTION WITH A MUTABLE INTERFACE. IT IS ONLY
5 SAFE TO REACH THIS FUNCTION THROUGH DOCUMENTED INTERFACES.
7 Copyright (C) 2009 Free Software Foundation, Inc.
9 This file is part of the GNU MP Library.
11 The GNU MP Library is free software; you can redistribute it and/or modify
12 it under the terms of the GNU Lesser General Public License as published by
13 the Free Software Foundation; either version 3 of the License, or (at your
14 option) any later version.
16 The GNU MP Library is distributed in the hope that it will be useful, but
17 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
18 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
19 License for more details.
21 You should have received a copy of the GNU Lesser General Public License
22 along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */
30 * We assume mpn_mulmod_bnm1 is always faster than plain mpn_mul_n (or a
31 future mpn_mulhi) for the range we will be called. Follow up that
34 * Decrease scratch usage.
38 mpn_redc_n (mp_ptr rp, mp_ptr up, mp_srcptr mp, mp_size_t n, mp_srcptr ip)
40 mp_ptr xp, yp, scratch;
46 rn = mpn_mulmod_bnm1_next_size (n);
48 scratch = TMP_ALLOC_LIMBS (n + rn + mpn_mulmod_bnm1_itch (rn, n, n));
51 mpn_mullo_n (xp, up, ip, n);
54 mpn_mulmod_bnm1 (yp, rn, xp, n, mp, n, scratch + n + rn);
56 ASSERT_ALWAYS (2 * n > rn); /* could handle this */
58 cy = mpn_sub_n (yp + rn, yp, up, 2*n - rn); /* undo wrap around */
59 MPN_DECR_U (yp + 2*n - rn, rn, cy);
61 cy = mpn_sub_n (rp, up + n, yp + n, n);
63 mpn_add_n (rp, rp, mp, n);