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
37 static const unsigned char _base64chars[] =
38 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
39
unbase64(unsigned char * buffer,size_t bufsiz,const char * txt)40 size_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