class poll_engine :This engine waits until one of the passed operations can be carried out, or until one of the operations times out. In these cases, the state of the engine changes to
?extra_match:exn -> bool -> (Unixqueue.operation * float) list -> Unixqueue.event_system ->
`Done ev, where
evis the corresponding event.
The argument list enumerates the operations to watch for. For every operation there may be a positive timeout value, or a negative number to indicate that no timeout is specified.
After one event has been caught, the engine terminates operation.
restart can be called to activate it again (with the
same event condition, and the same notification list). See the
restart for possible problems.
extra_match: This function is called when an
Extraevent is found. If the function returns
truefor the argument exception of
Extra, the event is caught; otherwise it is rejected.
The notification lists are kept, but note that observers often
detach when final states are reached. This may cause problems.
method group :