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_ecdsa_i15_bits2int(uint16_t *x,
30 	const void *src, size_t len, uint32_t ebitlen)
31 {
32 	uint32_t bitlen, hbitlen;
33 	int sc;
34 
35 	bitlen = ebitlen - (ebitlen >> 4);
36 	hbitlen = (uint32_t)len << 3;
37 	if (hbitlen > bitlen) {
38 		len = (bitlen + 7) >> 3;
39 		sc = (int)((hbitlen - bitlen) & 7);
40 	} else {
41 		sc = 0;
42 	}
43 	br_i15_zero(x, ebitlen);
44 	br_i15_decode(x, src, len);
45 	br_i15_rshift(x, sc);
46 	x[0] = ebitlen;
47 }
48