lib/base64.c

   1 #include "config.h"
   2
   3 #if HAVE_STDIO_H
   4 #include <stdio.h>
   5 #endif
   6 #if HAVE_STDLIB_H
   7 #include <stdlib.h>
   8 #endif
   9
  10 #include "ansiproto.h"
  11
  12 static void base64_init _PARAMS((void));
  13
  14 static int base64_initialized = 0;
  15 int base64_value[256];
  16 char base64_code[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  17
  18 static void
  19 base64_init(void)
  20 {
  21     int i;
  22
  23     for (i = 0; i < 256; i++)
  24         base64_value[i] = -1;
  25
  26     for (i = 0; i < 64; i++)
  27         base64_value[(int) base64_code[i]] = i;
  28     base64_value['='] = 0;
  29
  30     base64_initialized = 1;
  31 }
  32
  33 char *
  34 base64_decode(const char *p)
  35 {
  36     static char result[8192];
  37     int c;
  38     long val;
  39     int i;
  40     char *d;
  41
  42     if (!p)
  43         return NULL;
  44
  45     if (!base64_initialized)
  46         base64_init();
  47
  48     val = c = 0;
  49     d = result;
  50     while (*p) {
  51         i = base64_value[(int) *p++];
  52         if (i >= 0) {
  53             val = val * 64 + i;
  54             c++;
  55         }
  56         if (c == 4) {           /* One quantum of four encoding characters/24 bit */
  57             *d++ = val >> 16;   /* High 8 bits */
  58             *d++ = (val >> 8) & 0xff;   /* Mid 8 bits */
  59             *d++ = val & 0xff;  /* Low 8 bits */
  60             val = c = 0;
  61         }
  62     }
  63     *d = 0;
  64     return *result ? result : NULL;
  65 }