module Netsys_pollset

Checks whether a descriptor is member of the set, and returns its event mask. Raises Not_found if the descriptor is not in the set.

Add a descriptor or modify an existing descriptor

Remove a descriptor from the set (if it is member)

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 wait is invoked.

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 true, any 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 wait will see that and timeout. Note that there is no protection against race conditions: It is possible that wait returns events that are found at the same time the cancellation is carried out, i.e. you cannot rely on that the list returned by 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.