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