PWideChar in dll call from LabVIEW

[Anthony_L]

Here is a simple function:

GetPDFPageCount
function:

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GetPDFPageCount(const FileName: PWideChar): LongInt; stdcall;

I have tried defining the Argument:

FileName as string input but the dll was not able to read the filename.

Question: how does LabVIEW DEFINE PWideChar input datatype?

Anthony

[rolfk · Accepted solution]

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@Anthony_L wrote:

Question: how does LabVIEW DEFINE PWideChar input datatype?

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Simple answer: Not!

Complicated answer: You have to do some C compiler work of your own on the LabVIEW diagram. Basically a PWideChar is the Pascal variant of LPWCHAR Windows datatype. So you have to call the Windows API MultiByteToWideChar() to turn the LabVIEW string, which is an 8-bit ASCII string, into a Unicode Widechar array.

You can find in this post a library to do the conversion.  I would use the variant that creates an U16 array. It has the advantage that you do not need to deallocate any pointers after use, since the data is a LabVIEW array and managed by LabVIEW directly.

Your function parameter then has to be configured to be an Array of UInt16, Passed as C string pointer.

[Anthony_L]

Rolfk:

That worked perfectly!!! Thanks!!

Here is a picture of the code base

Anthony