1/* ----------------------------------------------------------------------- *
2 *
3 *   Copyright 2005-2008 H. Peter Anvin - All Rights Reserved
4 *
5 *   Permission is hereby granted, free of charge, to any person
6 *   obtaining a copy of this software and associated documentation
7 *   files (the "Software"), to deal in the Software without
8 *   restriction, including without limitation the rights to use,
9 *   copy, modify, merge, publish, distribute, sublicense, and/or
10 *   sell copies of the Software, and to permit persons to whom
11 *   the Software is furnished to do so, subject to the following
12 *   conditions:
13 *
14 *   The above copyright notice and this permission notice shall
15 *   be included in all copies or substantial portions of the Software.
16 *
17 *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
18 *   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
19 *   OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
20 *   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
21 *   HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
22 *   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
23 *   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
24 *   OTHER DEALINGS IN THE SOFTWARE.
25 *
26 * ----------------------------------------------------------------------- */
27
28/*
29 * unbase64.c
30 *
31 * Convert a string in base64 format to a byte array.
32 */
33
34#include <string.h>
35#include <base64.h>
36
37static const unsigned char _base64chars[] =
38    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
39
40size_t unbase64(unsigned char *buffer, size_t bufsiz, const char *txt)
41{
42    unsigned int bits = 0;
43    int nbits = 0;
44    char base64tbl[256];
45    int i;
46    char v;
47    size_t nbytes = 0;
48
49    memset(base64tbl, -1, sizeof base64tbl);
50
51    for (i = 0; _base64chars[i]; i++) {
52	base64tbl[_base64chars[i]] = i;
53    }
54
55    /* Also support filesystem safe alternate base64 encoding */
56    base64tbl['.'] = 62;
57    base64tbl['-'] = 62;
58    base64tbl['_'] = 63;
59
60    while (*txt) {
61	if ((v = base64tbl[(unsigned char)*txt]) >= 0) {
62	    bits <<= 6;
63	    bits += v;
64	    nbits += 6;
65	    if (nbits >= 8) {
66		if (nbytes < bufsiz)
67		    *buffer++ = (bits >> (nbits - 8));
68		nbytes++;
69		nbits -= 8;
70	    }
71	}
72	txt++;
73    }
74
75    return nbytes;
76}
77