# Class type Netsys_pollset.pollset

    class type pollset = object .. end

    method find : Unix.file_descr -> Netsys_posix.poll_req_events

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.

    method add : Unix.file_descr -> Netsys_posix.poll_req_events -> unit

Add a descriptor or modify an existing descriptor

    method remove : Unix.file_descr -> unit

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

    method wait : float ->
           (Unix.file_descr * Netsys_posix.poll_req_events *
            Netsys_posix.poll_act_events)
           list

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.

    method dispose : unit -> unit

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.

    method cancel_wait : bool -> unit

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.