znakeeye wrote:
> Hi!
>
> I have made a DLL in C++/MFC. I have to implement a function that can
> fill a LabView 2D-array with some data. How can that be done?
>
> I suppose the function should look something like this:
> int MyDllFunction(unsigned char **matrix, int width, int height)
> {
> for (int r = 0; r < height; r++)
> {
> for (int c = 0; c < width; c++)
> matrix[r][c] = SomeData(r, c);
> }
>
> return 1;
> }
int MyDllFunction(unsigned char *matrix, int width, int height)
In fact this is what LabVIEW will generate to be passed to the DLL for a
two dimensional uInt8 array and your function will have to look like this:
int MyDllFunction(unsigned char *matrix, int width, int height)
{
for (int r = 0; r < height; r++)
{
for (int c = 0; c < width; c++)
matrix[r * width + c] = SomeData(r, c);
}
return 1;
}
Two dimensional arrays in C are a little underspecified. Some see it as
a single pointer with column * row elements, others as a pointer to an
array of pointers. LabVIEW chooses for the first!
> Where should the memory of the array be declared? Maybe LabView can
> allocate the memory itself and pass the function a char-array
> (together with the width and height) to my function? How does it work?
The memory should always be allocated by the caller, e.g. LabVIEW in
this case. Just use an Initialize Array function to allocate the 2
dimensional array before passing it to the Call Library Function.
Rolf K
