Passing an array of strings from VB to C++

This is a discussion on Passing an array of strings from VB to C++ within the Windows Programming forums, part of the Platform Specific Boards category; Hi, I have my C++ compiled as a DLL, and I need to call a function that expects an array ...

  1. #1
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    Passing an array of strings from VB to C++

    Hi, I have my C++ compiled as a DLL, and I need to call a function that expects an array of character arrays (that is, an array of strings, but not the STL string). How can I do this in VB?

    The function template is as follows:
    Code:
    int __stdcall startFunction(int numScenes, char** scenes, char* dest);
    The problem is I don't know how to pass the "scenes" variable. Please help!

  2. #2
    and the hat of wrongness Salem's Avatar
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    Whatever the answer, it's going to be windows specific.

    How about
    http://www.google.co.uk/search?q=vb+calling+c%2B%2B
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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  3. #3
    train spotter
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    not sure but have you looked at the VARIANT data type...
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  4. #4
    &TH of undefined behavior Fordy's Avatar
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    It's doable, but not that nice.

    C++ Dll Header
    Code:
    #include "stdafx.h"
    #include <oleauto.h>
    
    #define DLLEXPORT extern "C" __declspec(dllexport)
    
    DLLEXPORT void ReadOutArrayOfStrings(LPSAFEARRAY* StringArray);
    C++ Main File
    Code:
    #include "stdafx.h"
    #include "MyC++Dll.h"
    
    BOOL APIENTRY DllMain( HANDLE hModule, 
                           DWORD  ul_reason_for_call, 
                           LPVOID lpReserved
    					 )
    {
    	switch (ul_reason_for_call)
    	{
    	case DLL_PROCESS_ATTACH:
    	case DLL_THREAD_ATTACH:
    	case DLL_THREAD_DETACH:
    	case DLL_PROCESS_DETACH:
    		break;
    	}
        return TRUE;
    }
    
    
    DLLEXPORT void ReadOutArrayOfStrings(LPSAFEARRAY* StringArray)
    {
    	char** StrPtr = 0;
    	long LowerBound = 0;
    	long UpperBound = 0;
    
    	SafeArrayGetLBound(*StringArray,1,&LowerBound);
    	SafeArrayGetUBound(*StringArray,1,&UpperBound);
    
    	SafeArrayAccessData(*StringArray, reinterpret_cast<void**>(&StrPtr));
    
    	for(int i = LowerBound; i <= UpperBound;++i)
    		MessageBox(HWND_DESKTOP,StrPtr[i],"From VB",MB_OK);
    
    	SafeArrayUnaccessData(*StringArray);
    
    }
    VB Form Code
    Code:
    Private Declare Sub ReadOutArrayOfStrings _
        Lib "MyC++Dll.dll" (theArray() As String)
    
    
    Private Sub Command1_Click()
        Dim StringArray(9) As String
        StringArray(0) = "All"
        StringArray(1) = "Work"
        StringArray(2) = "And"
        StringArray(3) = "No"
        StringArray(4) = "Play"
        StringArray(5) = "Makes"
        StringArray(6) = "Jack"
        StringArray(7) = "A"
        StringArray(8) = "Dull"
        StringArray(9) = "Boy"
        
        ReadOutArrayOfStrings StringArray
        
    End Sub

  5. #5
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    OK Thanks!

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