How to poke with response using DDE

Question

I am trying to communicate with a windows application using the antiquated DDE interface, I know this interface has been overtaken by ActiveX but the application i am talking to (ZEMAX – optical modelling software) doesn't implement it.
I have managed to post requests to the application and receive responses, all successfully. However one of the functions that I need to implement requires passing a pointer to a data structure to the application, I have the c code equivalent but no idea how to implement it. I have been using the supplied dde.llb but can find no documentation for it.
This is the 'c' equivalent of the code i need to implement, can anyone help me with this???:
int PostArrayTraceMessage(char *szBuffer, DDERAYDATA *RD)
ATOM aItem;
HGLOBAL hPokeData;
DDEPOKE * lpPokeData;
long numbytes;
int numrays;
if (RD[0].opd > 4)
/* NSC Rays */
numrays = (int)RD[0].opd - 5;
else
/* sequential rays */
numrays = RD[0].error;
/* point to where the data is */
rdpGRD = RD;
ngNumRays = numrays;
numbytes = (1+numrays)*sizeof(DDERAYDATA);
hPokeData = GlobalAlloc(GMEM_MOVEABLE | GMEM_DDESHARE, (LONG) sizeof(DDEPOKE) + numbytes);
lpPokeData = (DDEPOKE *) GlobalLock(hPokeData);
lpPokeData->fRelease = TRUE;
lpPokeData->cfFormat = CF_TEXT;
memcpy(lpPokeData->Value, RD, numbytes);
/* clear the buffers */
szGlobalBuffer[0] = '\0';
szBuffer[0] = '\0';
aItem = GlobalAddAtom("RayArrayData");
GlobalUnlock(hPokeData);
if (!PostMessage(hwndServer, WM_DDE_POKE, (WPARAM) hwndClient, PackDDElParam(WM_DDE_POKE, (UINT) hPokeData, aItem)))
MessageBox (hwndClient, "Cannot communicate with ZEMAX!", "Hello?", MB_ICONEXCLAMATION | MB_OK);
GlobalDeleteAtom(aItem);
GlobalFree(hPokeData);
return -1;
GlobalDeleteAtom(aItem);
WaitForData(hwndClient);
strcpy(szBuffer, szGlobalBuffer);
/* clear the pointer */
rdpGRD = NULL;
if (GotData) return 0;
else return -1;
Thanks for your help.
Regards,
Tom

Answer 1

I'm not sure exactly what your code snippet is attempting, but if you are dependent on LabVIEW determining the pointer you probably are out of luck. There has been an ongoing thread in the last week regrading passing pointers to ActiveX and .NET so I won't belabor it too much other than to say that LabVIEW is running in its own memory space and isn't "aware" of what is in other code space. For a much better discussion look over the last few days (last week in particular) for the .NET/ActiveX discussions.
There may be solutions, there were a number of posts to that thread that I haven't looked at, like writing dll's that encapsulate the "offending code" and provide sort of a translation medium.
Good luck
P.M.
Putnam
Certified LabVIEW Developer
Senior Test Engineer
Currently using LV 6.1-LabVIEW 2012, RT8.5
LabVIEW Champion