1*0957b409SSimon J. Gerraty /*
2*0957b409SSimon J. Gerraty * Copyright (c) 2017 Thomas Pornin <pornin@bolet.org>
3*0957b409SSimon J. Gerraty *
4*0957b409SSimon J. Gerraty * Permission is hereby granted, free of charge, to any person obtaining
5*0957b409SSimon J. Gerraty * a copy of this software and associated documentation files (the
6*0957b409SSimon J. Gerraty * "Software"), to deal in the Software without restriction, including
7*0957b409SSimon J. Gerraty * without limitation the rights to use, copy, modify, merge, publish,
8*0957b409SSimon J. Gerraty * distribute, sublicense, and/or sell copies of the Software, and to
9*0957b409SSimon J. Gerraty * permit persons to whom the Software is furnished to do so, subject to
10*0957b409SSimon J. Gerraty * the following conditions:
11*0957b409SSimon J. Gerraty *
12*0957b409SSimon J. Gerraty * The above copyright notice and this permission notice shall be
13*0957b409SSimon J. Gerraty * included in all copies or substantial portions of the Software.
14*0957b409SSimon J. Gerraty *
15*0957b409SSimon J. Gerraty * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16*0957b409SSimon J. Gerraty * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17*0957b409SSimon J. Gerraty * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
18*0957b409SSimon J. Gerraty * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
19*0957b409SSimon J. Gerraty * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
20*0957b409SSimon J. Gerraty * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
21*0957b409SSimon J. Gerraty * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
22*0957b409SSimon J. Gerraty * SOFTWARE.
23*0957b409SSimon J. Gerraty */
24*0957b409SSimon J. Gerraty
25*0957b409SSimon J. Gerraty #include "inner.h"
26*0957b409SSimon J. Gerraty
27*0957b409SSimon J. Gerraty /* see inner.h */
28*0957b409SSimon J. Gerraty void
br_i15_reduce(uint16_t * x,const uint16_t * a,const uint16_t * m)29*0957b409SSimon J. Gerraty br_i15_reduce(uint16_t *x, const uint16_t *a, const uint16_t *m)
30*0957b409SSimon J. Gerraty {
31*0957b409SSimon J. Gerraty uint32_t m_bitlen, a_bitlen;
32*0957b409SSimon J. Gerraty size_t mlen, alen, u;
33*0957b409SSimon J. Gerraty
34*0957b409SSimon J. Gerraty m_bitlen = m[0];
35*0957b409SSimon J. Gerraty mlen = (m_bitlen + 15) >> 4;
36*0957b409SSimon J. Gerraty
37*0957b409SSimon J. Gerraty x[0] = m_bitlen;
38*0957b409SSimon J. Gerraty if (m_bitlen == 0) {
39*0957b409SSimon J. Gerraty return;
40*0957b409SSimon J. Gerraty }
41*0957b409SSimon J. Gerraty
42*0957b409SSimon J. Gerraty /*
43*0957b409SSimon J. Gerraty * If the source is shorter, then simply copy all words from a[]
44*0957b409SSimon J. Gerraty * and zero out the upper words.
45*0957b409SSimon J. Gerraty */
46*0957b409SSimon J. Gerraty a_bitlen = a[0];
47*0957b409SSimon J. Gerraty alen = (a_bitlen + 15) >> 4;
48*0957b409SSimon J. Gerraty if (a_bitlen < m_bitlen) {
49*0957b409SSimon J. Gerraty memcpy(x + 1, a + 1, alen * sizeof *a);
50*0957b409SSimon J. Gerraty for (u = alen; u < mlen; u ++) {
51*0957b409SSimon J. Gerraty x[u + 1] = 0;
52*0957b409SSimon J. Gerraty }
53*0957b409SSimon J. Gerraty return;
54*0957b409SSimon J. Gerraty }
55*0957b409SSimon J. Gerraty
56*0957b409SSimon J. Gerraty /*
57*0957b409SSimon J. Gerraty * The source length is at least equal to that of the modulus.
58*0957b409SSimon J. Gerraty * We must thus copy N-1 words, and input the remaining words
59*0957b409SSimon J. Gerraty * one by one.
60*0957b409SSimon J. Gerraty */
61*0957b409SSimon J. Gerraty memcpy(x + 1, a + 2 + (alen - mlen), (mlen - 1) * sizeof *a);
62*0957b409SSimon J. Gerraty x[mlen] = 0;
63*0957b409SSimon J. Gerraty for (u = 1 + alen - mlen; u > 0; u --) {
64*0957b409SSimon J. Gerraty br_i15_muladd_small(x, a[u], m);
65*0957b409SSimon J. Gerraty }
66*0957b409SSimon J. Gerraty }
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