CA_ServerReleaseObjData
HRESULT CA_ServerReleaseObjData (CAServerObjHandle serverObjectHandle);
Purpose
Call this function when you finish using the data returned by CA_ServerGetObjData. CA_ServerGetObjData acquires a lock to protect your data from multithread access. This function releases that lock.
 |
Note Use the CA_ServerSetObjData, CA_ServerGetObjData, and CA_ServerReleaseObjData functions to manage any data associated with the object. These functions protect the object data from multithread access based on the server's threading model. If you do not use these functions, you must protect any object data from multithread access. |
Example Code
The following code demonstrates the use of object data functions:
// Structure to represent the object data
typedef struct __MyObjData {
double dVal;
int iVal;
} MyObjData;
// Object callback function
HRESULT CVIFUNC SrvrObjCb (CAServerObjHandle objHandle, const CLSID *pClsid, int event, void *callbackData)
{
HRESULT hr = S_OK;
MyObjData *pData = NULL;
if (event == CA_SERVER_EVENT_OBJECT_CREATE) {
// Allocating per-object data on the heap
// Memory will be valid for the lifetime of the object
pData = CA_AllocMemory (sizeof (MyObjData));
if (pData) {
pData->dVal = 3.1415;
pData->iVal = 4;
hr = CA_ServerSetObjData (objHandle, pData);
pData = NULL;
}
else {
hr = E_OUTOFMEMORY;
}
}
else if (event == CA_SERVER_EVENT_OBJECT_DESTROY) {
hr = CA_ServerGetObjData (objHandle, &pData);
if (SUCCEEDED (hr)) {
if (pData) {
CA_FreeMemory (pData);
pData = NULL;
}
hr = CA_ServerReleaseObjData (objHandle);
}
}
return hr;
}
// Simple function that uses the object data
HRESULT UseObjectData (CAServerObjHandle objHandle, double dV, int iV)
{
HRESULT hr;
void *pvObjData = NULL;
// Get ptr to object data
hr = CA_ServerGetObjData (objHandle, &pvObjData);
if (FAILED (hr))
return hr;
if (pvObjData) {
// Use object data
MyObjData pData = (MyObjData*) pvObjData;
printf ("Double Data: %f, Int Data: %d");
pData.dVal = dV;
pData.iVal = iV;
// Prevent further use of ptr to object data
pvObjData = NULL;
}
// Release ptr to object data
// MUST be called because CA_ServerGetObjData succeeded
hr = CA_ServerReleaseObjData (objHandle);
return hr;
}
Parameters
| Input | ||
| Name | Type | Description |
| serverObjectHandle | CAServerObjHandle | The handle to an ActiveX object in your ActiveX server. |
Return Value
| Name | Type | Description | ||
| status | HRESULT | A value indicating whether an error occurred. Function failure is indicated by a negative error code. Error codes are defined in CVIversion\include\cviauto.h and <Program Files>\National Instruments\Shared\MSDTRedistributables\SDKHeaderFiles\8.1\winerror.h. The LabWindows/CVI ActiveX Library explicitly returns error codes. Other error codes in winerror.h are generated by the COM runtime and passed on to you by the ActiveX Library. You can use CA_GetAutomationErrorString to get the description of an error code or CA_DisplayErrorInfo to display the description of the error code.
The error codes defined in <Program Files>\National Instruments\Shared\MSDTRedistributables\SDKHeaderFiles\8.1\winerror.h are too numerous to display here. These error codes can be returned to your ActiveX clients. |
Additional Information
Library: ActiveX Library
Include file: cviauto.h
LabWindows/CVI compatibility: LabWindows/CVI 6.0 and later