xref: /freebsd/contrib/bearssl/src/int/i15_decode.c (revision 0957b409a90fd597c1e9124cbaf3edd2b488f4ac)
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
29*0957b409SSimon J. Gerraty br_i15_decode(uint16_t *x, const void *src, size_t len)
30*0957b409SSimon J. Gerraty {
31*0957b409SSimon J. Gerraty 	const unsigned char *buf;
32*0957b409SSimon J. Gerraty 	size_t v;
33*0957b409SSimon J. Gerraty 	uint32_t acc;
34*0957b409SSimon J. Gerraty 	int acc_len;
35*0957b409SSimon J. Gerraty 
36*0957b409SSimon J. Gerraty 	buf = src;
37*0957b409SSimon J. Gerraty 	v = 1;
38*0957b409SSimon J. Gerraty 	acc = 0;
39*0957b409SSimon J. Gerraty 	acc_len = 0;
40*0957b409SSimon J. Gerraty 	while (len -- > 0) {
41*0957b409SSimon J. Gerraty 		uint32_t b;
42*0957b409SSimon J. Gerraty 
43*0957b409SSimon J. Gerraty 		b = buf[len];
44*0957b409SSimon J. Gerraty 		acc |= (b << acc_len);
45*0957b409SSimon J. Gerraty 		acc_len += 8;
46*0957b409SSimon J. Gerraty 		if (acc_len >= 15) {
47*0957b409SSimon J. Gerraty 			x[v ++] = acc & 0x7FFF;
48*0957b409SSimon J. Gerraty 			acc_len -= 15;
49*0957b409SSimon J. Gerraty 			acc >>= 15;
50*0957b409SSimon J. Gerraty 		}
51*0957b409SSimon J. Gerraty 	}
52*0957b409SSimon J. Gerraty 	if (acc_len != 0) {
53*0957b409SSimon J. Gerraty 		x[v ++] = acc;
54*0957b409SSimon J. Gerraty 	}
55*0957b409SSimon J. Gerraty 	x[0] = br_i15_bit_length(x + 1, v - 1);
56*0957b409SSimon J. Gerraty }
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