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_i32_encode(void *dst, size_t len, const uint32_t *x)
30  {
31  	unsigned char *buf;
32  	size_t k;
33  
34  	buf = dst;
35  
36  	/*
37  	 * Compute the announced size of x in bytes; extra bytes are
38  	 * filled with zeros.
39  	 */
40  	k = (x[0] + 7) >> 3;
41  	while (len > k) {
42  		*buf ++ = 0;
43  		len --;
44  	}
45  
46  	/*
47  	 * Now we use k as index within x[]. That index starts at 1;
48  	 * we initialize it to the topmost complete word, and process
49  	 * any remaining incomplete word.
50  	 */
51  	k = (len + 3) >> 2;
52  	switch (len & 3) {
53  	case 3:
54  		*buf ++ = x[k] >> 16;
55  		/* fall through */
56  	case 2:
57  		*buf ++ = x[k] >> 8;
58  		/* fall through */
59  	case 1:
60  		*buf ++ = x[k];
61  		k --;
62  	}
63  
64  	/*
65  	 * Encode all complete words.
66  	 */
67  	while (k > 0) {
68  		br_enc32be(buf, x[k]);
69  		k --;
70  		buf += 4;
71  	}
72  }