viUninstallHandler
Purpose
Uninstalls handlers for events.
C Syntax
ViStatus viUninstallHandler(ViSession vi, ViEventType eventType, ViHndlr handler, ViAddr userHandle)
Visual Basic Syntax
N/A
Resource Classes
All I/O session types
Parameters
| Name | Direction | Description |
|---|---|---|
|
vi |
IN |
Unique logical identifier to a session. |
|
eventType |
IN |
Logical event identifier. |
|
handler |
IN |
Interpreted as a valid reference to a handler to be uninstalled by a client application. |
|
userHandle |
IN |
A value specified by an application that can be used for identifying handlers uniquely in a session for an event. |
Return Values
| Completion Codes | Description |
|---|---|
|
VI_SUCCESS |
Event handler successfully uninstalled. |
| Error Codes | Description |
|---|---|
|
VI_ERROR_INV_OBJECT |
The given session reference is invalid. |
|
VI_ERROR_INV_EVENT |
Specified event type is not supported by the resource. |
|
VI_ERROR_INV_HNDLR_REF |
Either the specified handler reference or the user context value (or both) does not match any installed handler. |
|
VI_ERROR_HNDLR_NINSTALLED |
A handler is not currently installed for the specified event. |
Description
The viUninstallHandler() operation allows applications to uninstall handlers for events on sessions. Applications should also specify the value in the userHandle parameter that was passed while installing the handler. VISA identifies handlers uniquely using the handler reference and this value. All the handlers, for which the handler reference and the value matches, are uninstalled. Specifying VI_ANY_HNDLR as the value for the handler parameter causes the operation to uninstall all the handlers with the matching value in the userHandle parameter.
 |
Note Calling viUninstallHandler() removes the specified handler from the list of active handlers on the given session. If no handlers remain for the specified event type, the VISA driver disables that event type on the given session. It is not valid for a user to call this operation from within a callback, because this may cause a deadlock condition within the VISA driver. |
Related Topics