evmcallback.5 (2010 09)

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EvmCallback(5) EvmCallback(5)
NAME
EvmCallback() - event management (EVM) callback function
SYNOPSIS
void EventCB(
EvmConnection_t
connection ,
EvmCallbackArg_t
callbackArg ,
EvmCallbackData_t *
callbackData
);
DESCRIPTION
An EVM callback function is a function that you provide to allow your program to handle messages arriv-
ing on an EVM connection. Most messages are incoming events or responses to requests you have made
to the EVM daemon, but you may also get a callback for other reasons.
Specify the name (EventCB ) of the callback function in the callback parameter when you create an EVM
connection with a response mode of callback.
Your callback function is invoked by
EvmConnDispatch()
, which you must call whenever you detect
activity pending on the connection.
An EVM callback function must conform to the prototype shown.
Callback Function Parameters
• The connection parameter contains the connection context pertaining to this callback. This value
was returned by
EvmConnCreate()
when the connection was created. If you have one callback
function servicing multiple connections, you might test this to determine which connection a particu-
lar invocation is handling.
• The callbackArg parameter contains the value you specified as the callbackArg parameter to
EvmConnCreate() when you created the connection. For example, you might use it to hold a
pointer to your own context data for the connection.
• The callbackData parameter points to a structure containing the details of the callback. The struc-
ture includes a callback reason code, an event, and a union containing data specific to each possible
reason. The event member may contain NULL if it is not applicable to the reason. You may get
these reasons:
EvmREASON_EVENTS_MISSED
This callback reason indicates that the daemon was unable to deliver one or more events,
probably because the client process had not finished processing earlier events, causing the
connection buffer to overflow.
If necessary, you can use
EvmConnControl()
to increase the size of the receive buffer.
See the EvmConnControl(3) reference page.
EvmREASON_EVENT_DELIVERED
This callback reason indicates that an EVM event has been received from the daemon. The
event is available in the callbackData structure. You must use EvmEventDestroy()
to free the event when you have finished with it. See the EvmEventDestroy(3) reference
page.
EvmREASON_POST_COMPLETE
This callback reason indicates that a prior EvmEventPost() call has completed, usually
with a response from the daemon if the responseMode was specified as
EvmRESPONSE_CALLBACK when the connection was created. The posting status is avail-
able in the callbackData structure.
EvmREASON_REGISTRATION_DELIVERED
This callback reason indicates that a requested template has been delivered in response to
an EvmConnRegistrationGet() request. You must use EvmEventDestroy() to free
the template when you have finished with it.
EvmREASON_SUBSCRIBE_COMPLETE
This callback reason indicates that a prior EvmEventSubscribe() call has completed,
usually with a response from the daemon.
EvmREASON_TEMPLATE_INFO_DELIVERED
This callback reason indicates that event template information has been delivered in
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