xref: /freebsd/contrib/bearssl/src/int/i15_encode.c (revision 62cfcf62f627e5093fb37026a6d8c98e4d2ef04c)
1 /*
2  * Copyright (c) 2017 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 void
29 br_i15_encode(void *dst, size_t len, const uint16_t *x)
30 {
31 	unsigned char *buf;
32 	size_t u, xlen;
33 	uint32_t acc;
34 	int acc_len;
35 
36 	xlen = (x[0] + 15) >> 4;
37 	if (xlen == 0) {
38 		memset(dst, 0, len);
39 		return;
40 	}
41 	u = 1;
42 	acc = 0;
43 	acc_len = 0;
44 	buf = dst;
45 	while (len -- > 0) {
46 		if (acc_len < 8) {
47 			if (u <= xlen) {
48 				acc += (uint32_t)x[u ++] << acc_len;
49 			}
50 			acc_len += 15;
51 		}
52 		buf[len] = (unsigned char)acc;
53 		acc >>= 8;
54 		acc_len -= 8;
55 	}
56 }
57