base32_to.c

   1 #include <stddef.h>
   2 #include <stdint.h>
   3 #include "types.h"
   4 #include "base32.h"
   5
   6 static const char base32t[32] = {
   7         'a', 'b', 'c', 'd', // 0
   8         'e', 'f', 'g', 'h', // 1
   9         'i', 'j', 'k', 'l', // 2
  10         'm', 'n', 'o', 'p', // 3
  11         'q', 'r', 's', 't', // 4
  12         'u', 'v', 'w', 'x', // 5
  13         'y', 'z', '2', '3', // 6
  14         '4', '5', '6', '7', // 7
  15 };
  16 /*
  17 +--first octet--+-second octet--+--third octet--+--forth octet--+--fifth octet--+
  18 |7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|
  19 +---------+-----+---+---------+-+-------+-------+-+---------+---+-----+---------+
  20 |4 3 2 1 0|4 3 2 1 0|4 3 2 1 0|4 3 2 1 0|4 3 2 1 0|4 3 2 1 0|4 3 2 1 0|4 3 2 1 0|
  21 +-1.index-+-2.index-+-3.index-+-4.index-+-5.index-+-6.index-+-7.index-+-8.index-+
  22 */
  23 // masks:
  24 // 0xFF 0x7F 0x3F 0x1F 0x0F 0x07 0x03 0x01
  25 //  255  127  63    31   15   7     3    1
  26 char *base32_to(char *dst,const u8 *src,size_t slen)
  27 {
  28         //printf("slen = %d\n", slen);
  29         //printhex(base32t, 32);
  30         //printhex(base32f, 256);
  31         // base32 eats in 5bit pieces;
  32         // closest we can provide is 40, which is 5 bytes
  33         size_t i;
  34         for (i = 0; i + 4 < slen; i += 5) {
  35                 //printf("ei!\n");
  36                 //char *od = dst;
  37                 *dst++ = base32t[src[i+0] >> 3];
  38                 *dst++ = base32t[((src[i+0] & 7) << 2) | (src[i+1] >> 6)];
  39                 *dst++ = base32t[(src[i+1] >> 1) & 31];
  40                 *dst++ = base32t[((src[i+1] & 1) << 4) | (src[i+2] >> 4)];
  41                 *dst++ = base32t[((src[i+2] & 15) << 1) | (src[i+3] >> 7)];
  42                 *dst++ = base32t[((src[i+3]) >> 2) & 31];
  43                 *dst++ = base32t[((src[i+3] & 3) << 3) | (src[i+4] >> 5)];
  44                 *dst++ = base32t[src[i+4] & 31];
  45                 //printhex(od, 8);
  46         }
  47         //char *od = dst;
  48         if (i < slen) {
  49                 //printf("oi!0\n");
  50                 *dst++ = base32t[src[i+0] >> 3];
  51                 if (i + 1 < slen) {
  52                         //printf("oi!1\n");
  53                         *dst++ = base32t[((src[i+0] & 7) << 2) | (src[i+1] >> 6)];
  54                         *dst++ = base32t[(src[i+1] >> 1) & 31];
  55                         if (i + 2 < slen) {
  56                                 //printf("oi!2\n");
  57                                 *dst++ = base32t[((src[i+1] & 1) << 4) | (src[i+2] >> 4)];
  58                                 if (i + 3 < slen) {
  59                                         //printf("oi!3\n");
  60                                         *dst++ = base32t[((src[i+2] & 15) << 1) | (src[i+3] >> 7)];
  61                                         *dst++ = base32t[(src[i+3] >> 2) & 31];
  62                                         *dst++ = base32t[(src[i+3] & 3) << 3];
  63                                 }
  64                                 else {
  65                                         *dst++ = base32t[(src[i+2] & 15) << 1];
  66                                 }
  67                         }
  68                         else
  69                                 *dst++ = base32t[(src[i+1] & 1) << 4];
  70                 }
  71                 else
  72                         *dst++ = base32t[(src[i+0] & 7) << 2];
  73         }
  74         //printhex(od, dst-od);
  75         *dst = 0;
  76         return dst;
  77 }