How to use preprocess​or directives (#define) in C++ header file with LabVIEW 8.2

Question

I have a C++ header file that contains around 2000 preprocessor directives:
#define MEM_1   0xC
#define MEM_2   0xD
#define MEM_3   0x18
I want to be able to "access" these memory offsets by identifier name (MEM_1) in my LabVIEW program like I would in a C++ program.  I do not want the overhead of parsing through the header file and storing all the offsets into an array or similar structure. 
I've written a simple Win32 console program to return the memory offset given the identifier (see code below), and created a DLL to use with my LabVIEW program.  In the console program, you notice that I can call a function and pass in the identifer name, and get the offset back correctly:
getOffset(MEM_1);
In LabVIEW, I was hoping to be able to pass in the identifier (MEM_1) but was unsure what datatype to use.  In my C++ code, I defined the parameter as an int.  But in LabVIEW, I can't enter in MEM_1 as an int.   Can someone advise on how to do this?  Or if there is an alternate way to use #define's from external code inside LabVIEW?
#include "stdafx.h"
#include "scrmem.h"
#include "stdio.h"
void getOffset (int var);
int _tmain(int argc, _TCHAR* argv[])
 getOffset(MEM_1);
canf("%d");
 return 0;
void getOffset (int var)
 printf("The address of MEM_1 is %x", var); 

Answer 1

kaycea114 wrote:
Hi,
Where do you think I should use the string? 
The way that getOffset is currently defined in the DLL, I have to connect an integer input into the LabVIEW function.  This prevents me from entering in: MEM_1 as the input to the LabVIEW function.
Are you suggesting that I change getOffset to receive a String parameter ("MEM_1")?  Does that mean I need to do a string compare (line by line) through the header file to get the offset?  It seems like doing this search through the header file would degrade performance, but if that's the only work around, then I'll do it.
Please advise.
Well, what you want to do is indeed entering a string and getting back the assigned integer. That is what the C preprocessor is doing too although there it is done only once at the preprocessor stage of course and not at runtime anymore. But LabVIEW is not a C preprocessor.
What you did so far seems to be to define getOffset() that accepts an enum that needs to be created from the C source code to then return the assigned constant. That's of course not very helpful.
And writing a VI that could parse the C header file and create a name/constant array is really a lot easier than doing the same in C. You don't even need to parse the file each time again, but can instead cache them in an uninitialized shift register (LV2 style global).
Even more easy would be to create from that data a ring control using property nodes and save it as custom control and voila you have the most direct lookup you can get in LabVIEW and it works just as comfortable as using the define in C code. It would mean that you need to seperate your header file possibly into several different files to only get related constants into the same ring control, but that is easily done.
Rolf Kalbermatter
Rolf Kalbermatter
CIT Engineering Netherlands
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