4.18.10 kqueue
usage
(require bsd) (import :std/os/kqueue)
4.18.10.1 kevent-udata
(kevent-udata events index) => (Maybe :foreign)
Returns the event’s user-data pointer, or #f for a null pointer. The accessor
does not take ownership of the pointed-to memory. set-kevent-udata! and the
user-data: argument of kevent-set! accept a foreign pointer or #f.