accept_cb
av->accept_cb(fd, event, av->arg);
void (*accept_cb)(int, short, void *);
static void accept_cb(int, short, void *);
av->accept_cb = cb;
event_set(&av->ev, av->fd, EV_READ, accept_cb, av);
av->accept_cb(fd, event, av->arg);
void (*accept_cb)(int, short, void *);
void accept_cb(int, short, void *);
av->accept_cb = cb;
event_set(&av->ev, av->fd, EV_READ, accept_cb, av);