lib/base64.c

   1 /* base64.c
   2
   3    Copyright (c) 2010 Matthias Kramm <kramm@quiss.org>
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 2 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, write to the Free Software
  17    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  18 */
  19
  20 #include <stdio.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23 #include "base64.h"
  24
  25 static const char base64[65]=
  26 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  27
  28 void write_base64(FILE*fi, const char* s)
  29 {
  30     const unsigned char*b = (const unsigned char*)s;
  31     const unsigned char*end = b + strlen(b);
  32     const unsigned char*end_minus_3 = end - 3;
  33
  34     while(b <= end_minus_3) {
  35         char data[4];
  36         data[0] = base64[(b[0]>>2)&63        ];
  37         data[1] = base64[(b[0]<<4|b[1]>>4)&63];
  38         data[2] = base64[(b[1]<<2|b[2]>>6)&63];
  39         data[3] = base64[(b[2])&63           ];
  40         fwrite(data, 4, 1, fi);
  41         b += 3;
  42     }
  43
  44     unsigned char data[4];
  45     switch(end - b) {
  46         case 0:
  47             return; //done
  48         case 1:
  49             data[0] = base64[(b[0]>>2)&63];
  50             data[1] = base64[(b[0]<<4)&63];
  51             data[2] = '=';
  52             data[3] = '=';
  53         break;
  54         case 2:
  55             data[0] = base64[(b[0]>>2)&63];
  56             data[1] = base64[(b[0]<<4|b[1]>>4)&63];
  57             data[2] = base64[(b[1]<<2)&63];
  58             data[3] = '=';
  59         break;
  60         default:
  61             fprintf(stderr, "internal error in base64 implementation (%d)\n", end-b);
  62         break;
  63     }
  64     fwrite(data, 4, 1, fi);
  65 }