Added generic API for date range validation (with callbacks).
[BearSSL] / int / i32_decmod.c
1 /*
2 * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
3 *
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:
11 *
12 * The above copyright notice and this permission notice shall be
13 * included in all copies or substantial portions of the Software.
14 *
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
22 * SOFTWARE.
23 */
24
25 #include "inner.h"
26
27 /* see inner.h */
28 uint32_t
29 br_i32_decode_mod(uint32_t *x, const void *src, size_t len, const uint32_t *m)
30 {
31 const unsigned char *buf;
32 uint32_t r;
33 size_t u, v, mlen;
34
35 buf = src;
36
37 /*
38 * First pass: determine whether the value fits. The 'r' value
39 * will contain the comparison result, as 0x00000000 (value is
40 * equal to the modulus), 0x00000001 (value is greater than the
41 * modulus), or 0xFFFFFFFF (value is lower than the modulus).
42 */
43 mlen = (m[0] + 7) >> 3;
44 r = 0;
45 for (u = (mlen > len) ? mlen : len; u > 0; u --) {
46 uint32_t mb, xb;
47
48 v = u - 1;
49 if (v >= mlen) {
50 mb = 0;
51 } else {
52 mb = (m[1 + (v >> 2)] >> ((v & 3) << 3)) & 0xFF;
53 }
54 if (v >= len) {
55 xb = 0;
56 } else {
57 xb = buf[len - u];
58 }
59 r = MUX(EQ(r, 0), (uint32_t)CMP(xb, mb), r);
60 }
61
62 /*
63 * Only r == 0xFFFFFFFF is acceptable. We want to set r to 0xFF if
64 * the value fits, 0x00 otherwise.
65 */
66 r >>= 24;
67 br_i32_zero(x, m[0]);
68 u = (mlen > len) ? len : mlen;
69 while (u > 0) {
70 uint32_t xb;
71
72 xb = buf[len - u] & r;
73 u --;
74 x[1 + (u >> 2)] |= xb << ((u & 3) << 3);
75 }
76 return r >> 7;
77 }