Creating a New Queue
New queues can be created on a Windows CE device by calling the MQCreateQueue (Table 15.2) function and initializing a MQQUEUEPROPS structure with the following properties:
The data for both these properties is VT_LPWSTR. The pwszVal member for PROPID_Q_PATHNAME is a pointer to a string containing the pathname. In the following code example, the "." refers to the local Windows CE device, "PRIVATE$" specifies this is a private queue (remember, public queues are not supported), and "WinCEInQueue" is the name of the new queue.
LPWSTR wszPathName = _T(".\PRIVATE$\WinCEInQueue");
aQueuePropId[0] = PROPID_Q_PATHNAME;
aQueuePropVar[0].vt = VT_LPWSTR;
aQueuePropVar[0].pwszVal = wszPathName;
| MQCreateQueue | |
|---|---|
| PSECURITY_DESCRIPTOR pSecurityDescriptor | Not supported, pass as NULL. |
| MQQUEUEPROPS *pQueueProps | Pointer to a MQQUEUEPROPS structure describing the queue to create. |
| LPWSTR lpwcsFormatName | Pointer to a buffer to receive the format name of the new queue. This can be NULL. |
| LPDWORD lpdwFormatNameLength | Length of the new buffer receiving the format name. |
| HRESULT Return Value | MQ_OK for success, otherwise error code. |
The PROPID_Q_LABEL can be used to provide a more descriptive name for the queue:
LPWSTR wszQueueLabel =
_T("Message to be received by Windows CE Device");
aQueuePropId[1] = PROPID_Q_LABEL;
aQueuePropVar[1].vt = VT_LPWSTR;
aQueuePropVar[1].pwszVal = wszQueueLabel;
The queue to be created is specified by a pathname, and the MQCreateQueue function will return the format name if required. The code in Listing 15.2 shows how to initialize properties and call MQCreateQueue to create a new queue on a Windows CE Device.
Listing 15.2. Creating a new queue
void Listing15_2()
{
DWORD cPropId = 0;
MQQUEUEPROPS QueueProps;
MQPROPVARIANT aQueuePropVar[2];
QUEUEPROPID aQueuePropId[2];
HRESULT aQueueStatus[2];
HRESULT hr
PSECURITY_DESCRIPTOR pSecurityDescriptor=NULL
// Queue pathname
LPWSTR wszPathName = _T(".\PRIVATE$\WinCEInQueue");
// Queue label
LPWSTR wszQueueLabel =
_T("Message to be received by Windows CE Device");
// Format name buffer for queue
DWORD dwFormatNameLength = 256
WCHAR wszFormatName[256];
aQueuePropId[cPropId] = PROPID_Q_PATHNAME;
aQueuePropVar[cPropId].vt = VT_LPWSTR;
aQueuePropVar[cPropId].pwszVal = wszPathName;
cPropId++;
aQueuePropId[cPropId] = PROPID_Q_LABEL;
aQueuePropVar[cPropId].vt = VT_LPWSTR;
aQueuePropVar[cPropId].pwszVal = wszQueueLabel;
cPropId++;
QueueProps.cProp = cPropId;
QueueProps.aPropID = aQueuePropId;
QueueProps.aPropVar = aQueuePropVar;
QueueProps.aStatus = aQueueStatus;
hr = MQCreateQueue(pSecurityDescriptor,
&QueueProps,
wszFormatName,
&dwFormatNameLength);
if(hr == MQ_OK)
cout ≪ wszFormatName ≪ _T(" created") ≪ endl;
else if(hr == MQ_ERROR_ACCESS_DENIED )
cout ≪ _T("Access Denied") ≪ endl;
else if(hr == MQ_ERROR_ILLEGAL_PROPERTY_VALUE )
cout ≪ _T("Illegal Property Value") ≪ endl;
else if(hr == MQ_ERROR_ILLEGAL_QUEUE_PATHNAME )
cout ≪ _T("Illegal pathname") ≪ endl;
else if(hr == MQ_ERROR_ILLEGAL_SECURITY_DESCRIPTOR )
cout ≪ _T("Illegal security descriptor")
≪ endl;
else if(hr == MQ_ERROR_INSUFFICIENT_PROPERTIES )
cout ≪ _T("Path name not specified") ≪ endl;
else if(hr == MQ_ERROR_INVALID_OWNER )
cout ≪ _T("Invalid owner") ≪ endl;
else if(hr == MQ_ERROR_PROPERTY )
cout ≪ _T("Error in property specification")
≪ endl;
else if(hr == MQ_ERROR_PROPERTY_NOTALLOWED )
cout ≪ _T("Property not allowed when creating queue")
≪ endl;
else if(hr == MQ_ERROR_QUEUE_EXISTS )
cout ≪ _T("Queue already exists") ≪ endl;
else if(hr == MQ_ERROR_SERVICE_NOT_AVAILABLE )
cout ≪ _T("Service not available") ≪ endl;
else if(hr ==
MQ_INFORMATION_FORMATNAME_BUFFER_TOO_SMALL )
cout ≪ _T("Format name buffer too small")
≪ endl;
else if(hr == MQ_INFORMATION_PROPERTY )
cout ≪
_T("Succeeded, but property returned warning")
≪ endl;
}
|
Once the queue has been created, you will need to open the queue before messages can be sent or received from it. Queues can be deleted by calling the MQDeleteQueue function, and this is passed the format name of the queue to be deleted.