static void
     itoa (char *buf, int base, int d)
     {
       char *p = buf;
       char *p1, *p2;
       unsigned long ud = d;
       int divisor = 10;

       /* If %d is specified and D is minus, put `-' in the head. */
       if (base == 'd' && d < 0)
         {
           *p++ = '-';
           buf++;
           ud = -d;
         }
       else if (base == 'x')
         divisor = 16;

       /* Divide UD by DIVISOR until UD == 0. */
       do
         {
           int remainder = ud % divisor;

           *p++ = (remainder < 10) ? remainder + '0' : remainder + 'a' - 10;
         }
       while (ud /= divisor);

       /* Terminate BUF. */
       *p = 0;

       /* Reverse BUF. */
       p1 = buf;
       p2 = p - 1;
       while (p1 < p2)
         {
           char tmp = *p1;
           *p1 = *p2;
           *p2 = tmp;
           p1++;
           p2--;
         }
     }