Events

As a data object, an event has two roles:

• Programs create event objects to register interest in the set of matching event occurrences. Each event object represents the program’s interest in a set of events, and the event’s parameters specify that set.
• Rendezvous presents the event object to the appropriate callback function whenever an event occurs. In this context, the event object signifies the actual event that occurred.

Event Parameters

These parameters are common to all event creation calls. Additional parameters are specific to each type of event.

Parameter

Description

queue

For each occurrence of the event, place the event object on this event queue.

See Event Queues.

callback

Upon dispatch, process the event with this callback function.

See Callback Functions.

closure

Store this closure data in the event object.

See Closure Data.

Event Classes

Rendezvous software recognizes three classes of events.

Event Classes

Message

An inbound message has arrived. Additional creation parameters specify the subject name and transport. See also, Listener Event Semantics.

Timer

A timer interval has elapsed. An additional creation parameter specifies the interval. See also, Timer Event Semantics.

The Rendezvous .NET API does not support this kind of event.

I/O

An I/O socket is ready. Additional creation parameters specify the socket, and the I/O condition. See also, I/O Event Semantics.

The Rendezvous Java and .NET APIs do not support this kind of event.

Signals

 

Earlier releases supported UNIX operating system signals as Rendezvous events. This feature is obsolete starting in release 6.

 

Warning 

Programmers may use signal() calls, if the operating system supports them. Use caution and test extensively, as the semantics of signal() in a multi-threaded environment can vary.