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  }