How To Use Exported Function "CallInstrument" of LabView.exe ?

Question

Hello!
I want to use the function "CallInstrument" to dynamically call VIs with LabView. Did anyone has experiences with this function?
All I kow is following:
The function is used by LabView Internals and its Runtime Library. Its exported by LabView.Exe and lvrt.dll.
Its prototype is maybe:
int CallInstrument(CPStr* VIPath, int controlcount, int indicatorcount, int options, [ Variable List of Control/Indicator Parameters ]... );
( CPStr Type is a StringArray of PStr (Short PascalStrings) as it is used by LabView to store Path datatypes. )
I whould be glad, if anyone has information about this function.

Answer 1

Dear Rolf Kalbermatter,
Thirst, thanks a lot for your answer! -
You sure right, It whould be much much more comfortable to use the VI Server.
And you're also right... using a undocumented dll-function is absolutly no longtime solution.
Currently I am using VI Server for my problem, but it doesn't fit my interesst so much.
But I will explain, what I'm trying to do.
I want to call a VI dynamically from LabView, giving Parameters to its Controls and receive Results from its Indicators.
Realy no big job, but VI Server only let you do this that easy if you have a VI Typedef. otherwise... with untyped VIs, its not that simple. Ok.. its not impossible, you can use "GetAllControlValues" and "SetControlValue" (functions from VI server) and the call "RunVi". But this can get slow (>100ms per call :/ )
I'm looking for a alternative function, which let me call a VI dynamically with userdefined Parameters. Maybe you know the ActiveX Interface IVirtualInstrument and its Function "Call2" - it is a nice example, what kind of function i want.
But this function is not directly available by the VI Server--- i don't know for what reason.
Then i tried to make use of "Call2" from within LabView, and it took me some time to find out the right Parametersyntax but finnaly i got it and it worked fine ... but it was no long time until problems occur. I cannot tell what really went wrong, but sometimes labview simply crashed or hang into a loop reseting some VIs. And its also impossible to stop a running vi, with has made a call to "Call2", if the call doesn't return by itself.
Next step is/was trying to take advantage of CallInstrument. So, yesterday... after hours of analysing assemblercode, i finnally found out the correct use of LabView.exe->CallInstrument and i'm very impressed about its speed (0-15ms per call). The prototype seem to be the same as you explained in your reply int CallInstrument(Path path, Bool modal, int32 nInputs, int32 nOutputs, ...)
But It has the same problem as its ActiveX derivat "Call2".. if you call an endless looping VI, LabView cannot stop your caller-vi. The other bad thing is, that this function is using dynamic paramterlist, which are placed directly onto the stack!
That means that the paramter count on the stack is NOT FIXED (printf makes it the same). LabVIews DLL InvokeNode doesn't support this.
At my current position, it looks like i have three possiblities but no one fits into my interesst.
(continued with next answer)