event_priority_set
if (event_priority_set(&bufev->ev_read, priority) == -1)
if (event_priority_set(&bufev->ev_write, priority) == -1)
int event_priority_set(struct event *, int);
if (event_priority_set(&one.ev, 0) == -1) {
if (event_priority_set(&two.ev, npriorities - 1) == -1) {