gistfile1.c

static const long hextable[] = {
   ['0'] = 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
   ['A'] = 10, 11, 12, 13, 14, 15,
   ['a'] = 10, 11, 12, 13, 14, 15
};
 
/* 
 * Convert a hex string to its decimal number.
 * Unlimited length.
 * Won't produce negative values.
 * Works with odd lengths. (0xfff)
 * Should return -1 on error.
 */
long hexdec(const char *hex) {
   long ret = 0; 
   while (*hex && ret >= 0) {
      ret = (ret << 4) | hextable[*hex++];
   }
   return ret; 
}