KB_QSIZE
if (sc->gkb_q_length == KB_QSIZE)
p = (sc->gkb_q_start + sc->gkb_q_length) % KB_QSIZE;
if (len >= KB_QSIZE - sc->gkb_q_start)
len = KB_QSIZE - sc->gkb_q_start;
sc->gkb_q_start = (sc->gkb_q_start + len) % KB_QSIZE;
char gkb_q[KB_QSIZE]; /* input queue */