(define-external ws_utlen int len)
(define-external ws_uts scheme-pointer s)
(= 1
   ((foreign-lambda* int ()
      "
    if (ws_utlen > UINT_MAX) { return -1; }

    int i;
    for (i = ws_utlen; i != 0; --i)
    {
        if (*((unsigned char*)ws_uts++) > 127)
        {
            C_return(0);
        }
    }

    C_return(1);
")))