Notify Objects

Introduction

A thread uses a Notify object to wait for event notification. For each thread intended to wait for events from an object (or objects), your application must create a Notify object. The source of firmware events are Motion, Sequence, and Recorder objects.

When it is desired to wait for event notifications from a single source, that source (i.e., object handle) can be passed as the second argument to mpiNotifyCreate. After a Notify object is appended to the EventMgr list of Notify objects, make a call to mpiNotifyEventWait to instruct the Notify object to wait for event notification.

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Implementation

Notify objects maintain a FIFO ("First In, First Out") buffer of events that have occurred. Each call to mpiNotifyEventWait removes one event from the buffer. If the event buffer is empty, mpiNotifyEventWait(...) will wait for an event to be sent to the Notify object. This ensures that events will not be missed in cases where multiple events have occurred between calls to mpiNotifyEventWait(...). However, the danger is that an application may not call mpiNotifyEventWait(...) for a long time. In this case, the event buffer may grow rather quickly and use a large amount of system memory. In order to prevent this problem from occurring, one should use mpiNotifyEventMaskSet to enable and disable event notification at the proper times.

Methods

Create, Delete, Validate Methods
	mpiNotifyCreate	Create a Notify object
	mpiNotifyDelete	Delete a Notify object
	mpiNotifyValidate	Validate a Notify object

Event Methods
	mpiNotifyEvent	Check to see if events have occurred
	mpiNotifyEventFlush	Flush pending events from event queue
	mpiNotifyEventMaskGet	Get event mask
	mpiNotifyEventMaskSet	Set event mask
	mpiNotifyEventWait	Get next event from queue or wait timeout msec for it to arrive
	mpiNotifyEventWake	Wake up thread waiting for notify object

Relational Methods
	List Methods for Event Sources
	mpiNotifySource	Get the indexth event source in list
	mpiNotifySourceAppend	Append an event source to list
	mpiNotifySourceCount	Count number of event sources in list
	mpiNotifySourceFirst	Get first event source in list
	mpiNotifySourceIndex	Get index value for event source in list
	mpiNotifySourceInsert	Place event source after source in list
	mpiNotifySourceLast	Get last event source in list
	mpiNotifySourceListGet	Get list of event sources
	mpiNotifySourceListSet	Create a list of event sources
	mpiNotifySourceNext	Get next event source after source in list
	mpiNotifySourcePrevious	Get the event source before source in list
	mpiNotifySourceRemove	Remove event source from list

Data Types

	MPINotifyMessage
	MEINotifyTrace