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      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 
     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