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cdllvb6

VB6 - Declaring and calling C DLL with pointers

I have an old C DLL I use to call from Ruby, but now I need to call it from VB6 and I can't figure out the correct way to do so.

Here is the header for the function I need:

int Decrunch(const BYTE *src, BYTE *dest, DWORD src_length)

*src is a sequence of bytes which will be decrypted by the function

*dest is a buffer which will recieve the decrypted data. I can call the function with dest=NULL and it will return the size of the decrypted data, so I can use it to create the buffer with the correct size.

I tried to declare it with both src and dest as Strings (like I do in Ruby) but it won't work. I've also tried to declare them as Byte and pass the first element of a byte array as I was pointed by some tutorials, but I think I didn't do it correctly.

Can someone help me with this?

Thank you!

Solution

  • Air code 

    Private Declare DecrunchGetLength Alias "Decrunch" Lib "somedll.DLL" (ByRef src As Byte, ByVal nullptr As Long, ByVal SrcLength As Long) As Long 

Private Declare Decrunch Alias "Decrunch" Lib "somedll.DLL" (ByRef src As Byte, ByRef dest As Byte, ByVal SrcLength As Long) As Long 

Dim destLen As Long
 Dim src(0 To 9) As Byte 
Dim dest() As Byte 

' get bytes into src somehow 

' get dest length 
destLen = DecrunchGetLen( src(0), 0, 10) 

ReDim dest(0 To destLen - 1) 
destLen = Decrunch( src(0), dest(0), 10)

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