#include stdio.h
/*
** xtoi -- convert hex string to integer nbr
** Returns field size if successful, else ERR.
*/
xtoi(hexstr, nbr) char *hexstr; int *nbr; {
  int d, t; d=0;  
  *nbr = 0;
  while(1) {
    if((*hexstr>='0')&(*hexstr<='9')) t=48;
    else if((*hexstr>='A')&(*hexstr<='F')) t=55;
    else if((*hexstr>='a')&(*hexstr<='f')) t=55;
    else break;
    if(d<4) ++d; else return ERR;
    *nbr=*nbr<<4;
    *nbr=*nbr+(*hexstr++)-t;
    }
  return d;
  }