Sets of file descriptors for polling
Wait for events, and return the output events matching the event
mask. This is level-triggered polling, i.e. if a descriptor continues
to match an event mask, it is again reported the next time
There is no guarantee that the list is complete.
It is unspecified how the set reacts on descriptors that became invalid (i.e. are closed) while being member of the set. The set implementation is free to silently disregard such descriptors, or to report them as invalid. It is strongly recommended to remove descriptors before closing them.
Release any OS resources associated with the pollset. The pollset
remains usable, however, and by invoking any method except
cancel_wait the required OS resources are automatically allocated
again. Only for
cancel_wait it is ensured that the disposal
remains in effect.
There is a cancel bit in the pollset, and this method sets it to the argument value.
When the bit is
wait invocation will immediately
time out. It is allowed to set the cancel bit from another thread,
and when it becomes
true, a parallel running
see that and timeout. Note that there is no
protection against race conditions: It is possible that
returns events that are found at the same time the cancellation
is carried out, i.e. you cannot rely on that the list returned
wait is empty.
This is the only method of a pollset that is allowed to be called from a different thread. If not supported on a platform this method will fail.