| VBBR |
Posted - Jul 10 2004 : 08:35:16 AM
If I'm calling an external function from a DLL, where one of its arguments in C is defined as "const char *variable", how should I pass the string? ByVal or ByRef? Should I append a Chr(0) at the end of the string? |
| Eric Coleman |
Posted - Jul 11 2004 : 01:49:01 AM
You can also decalre the function as ByRef Data As Any instead of ByVal Data As Long.
To call the function when decalared as ByRef Data As Any, you use the following syntax for Single and Double byte systems.
For single byte characters
Dim S as string: s = "hello"
Dim bytArray() as Byte
bytArray = StrConv(S & Chr$(0), vbFromUnicode)
Call MyFunction ( bytArray(0) )
For Double byte characters.
Dim S as string: s = "hello"
Dim bytArray() as Byte
bytArray = S & Chr$(0)
Call MyFunction ( bytArray(0) ) |
| Eric Coleman |
Posted - Jul 11 2004 : 01:36:49 AM
Is it a double byte character function or a single byte?
For a single byte function, you would declare it as
(ByVal Data As Long)
and then to call the funtion..
Dim S as String: S = "hello"
Call MyFunction(StrPtr(StrConv(S, vbFromUnicode)))
For a double byte string, you would decalre the function the same way.
(ByVal Data As Long)
but when calling the function it would look like
Dim S as String: S = "hello"
Call MyFunction(StrPtr(S)) |
| Sr. Guapo |
Posted - Jul 10 2004 : 11:15:46 AM
I'm not sure if you can pass a constant, seems like that wouldn't work... Also, I don't *think* you can pass an actual "pointer" from VB, but you can pass a reference. They are similar, and I don't know what's different. If you can't tell, my C++ skills are severly lacking, sorry I couldn't be of more help. |
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