com32/libutil/base64.c

   1 /*
   2  * Output a base64 string.
   3  *
   4  * Options include:
   5  * - Character 62 and 63;
   6  * - To pad or not to pad.
   7  */
   8
   9 #include <inttypes.h>
  10 #include <base64.h>
  11
  12 size_t genbase64(char *output, const void *input, size_t size, int flags)
  13 {
  14     static char charz[] =
  15         "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+_";
  16     uint8_t buf[3];
  17     int j;
  18     const uint8_t *p;
  19     char *q;
  20     uint32_t bv;
  21     int left = size;
  22
  23     charz[62] = (char)flags;
  24     charz[63] = (char)(flags >> 8);
  25
  26     p = input;
  27     q = output;
  28
  29     while (left > 0) {
  30         if (left < 3) {
  31             buf[0] = p[0];
  32             buf[1] = (left > 1) ? p[1] : 0;
  33             buf[2] = 0;
  34             p = buf;
  35         }
  36
  37         bv = (p[0] << 16) | (p[1] << 8) | p[2];
  38         p += 3;
  39         left -= 3;
  40
  41         for (j = 0; j < 4; j++) {
  42             *q++ = charz[(bv >> 18) & 0x3f];
  43             bv <<= 6;
  44         }
  45     }
  46
  47     switch (left) {
  48     case -1:
  49         if (flags & BASE64_PAD)
  50             q[-1] = '=';
  51         else
  52             q--;
  53         break;
  54
  55     case -2:
  56         if (flags & BASE64_PAD)
  57             q[-2] = q[-1] = '=';
  58         else
  59             q -= 2;
  60         break;
  61
  62     default:
  63         break;
  64     }
  65
  66     *q = '\0';
  67
  68     return q - output;
  69 }
  70
  71 #ifdef TEST
  72
  73 #include <stdio.h>
  74 #include <string.h>
  75
  76 int main(int argc, char *argv[])
  77 {
  78     int i;
  79     char buf[4096];
  80     int len, bytes;
  81
  82     for (i = 1; i < argc; i++) {
  83         printf("Original: \"%s\"\n", argv[i]);
  84
  85         len = strlen(argv[i]);
  86         bytes = genbase64(buf, argv[i], len, BASE64_MIME | BASE64_PAD);
  87         printf("    MIME: \"%s\" (%d)\n", buf, bytes);
  88         bytes = genbase64(buf, argv[i], len, BASE64_SAFE);
  89         printf("    Safe: \"%s\" (%d)\n", buf, bytes);
  90     }
  91
  92     return 0;
  93 }
  94
  95 #endif