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  void
29  br_i31_decode(uint32_t *x, const void *src, size_t len)
30  {
31  	const unsigned char *buf;
32  	size_t u, v;
33  	uint32_t acc;
34  	int acc_len;
35  
36  	buf = src;
37  	u = len;
38  	v = 1;
39  	acc = 0;
40  	acc_len = 0;
41  	while (u -- > 0) {
42  		uint32_t b;
43  
44  		b = buf[u];
45  		acc |= (b << acc_len);
46  		acc_len += 8;
47  		if (acc_len >= 31) {
48  			x[v ++] = acc & (uint32_t)0x7FFFFFFF;
49  			acc_len -= 31;
50  			acc = b >> (8 - acc_len);
51  		}
52  	}
53  	if (acc_len != 0) {
54  		x[v ++] = acc;
55  	}
56  	x[0] = br_i31_bit_length(x + 1, v - 1);
57  }