2 * Copyright (c) 2016 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_i31_from_monty(uint32_t *x
, const uint32_t *m
, uint32_t m0i
)
33 len
= (m
[0] + 31) >> 5;
34 for (u
= 0; u
< len
; u
++) {
38 f
= MUL31_lo(x
[1], m0i
);
40 for (v
= 0; v
< len
; v
++) {
43 z
= (uint64_t)x
[v
+ 1] + MUL31(f
, m
[v
+ 1]) + cc
;
46 x
[v
] = (uint32_t)z
& 0x7FFFFFFF;
49 x
[len
] = (uint32_t)cc
;
53 * We may have to do an extra subtraction, but only if the
54 * value in x[] is indeed greater than or equal to that of m[],
55 * which is why we must do two calls (first call computes the
56 * carry, second call performs the subtraction only if the carry
59 br_i31_sub(x
, m
, NOT(br_i31_sub(x
, m
, 0)));