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C to VB 5 porting

Help
I'm having trouble converting a 3rd party example program from C to VB (5 Pro), they don't support VB :+(

C code
unsigned char *GlobalBlock = (unsigned char *)new unsigned char[5000];

Where GlobalBlock is used in the initialisation function
SAFEInitGlobal(GlobalBlock);

and the function prototype is
extern "C" short __declspec(dllexport) WINAPI SAFEInitGlobal(unsigned char*);

My C is very rusty so any help will be much appreciated.

Well Have a good winter holiday one and all.

MATT
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mbaker123
Asked:
mbaker123
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1 Solution
 
prozakCommented:
Try this:

'Declare the DLL function
Declare Function SAFEInitGlobal lib "dllname.dll" (ByVal strTheString As String)

Dim GlobalBlock as String

'Initialize your string (otherwise you'll get a protection fault when you call the DLL)
GlobalBlock = Space(5000)

'Call the DLL function
Call SAFEInitGlobal(GlobalBlock)

That should allow you to do it. Although the SAFEInitGlobal must be compiled stdcall (this refers to how arguments are passed to the function). Otherwise you'll get the error "Bad DLL calling convention" when you try to call SAFEInitGlobal.

Hope this helps...
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muffinthedogCommented:
mbaker123,
    should be able to call it like the following but by the name of the function, it seems it's just allocating global memory. Do you have the body of the function?

Declare Function SAFEInitGlobal Lib "Whatever" (lpChar As Any) As Integer


   Dim bte(5000) As Byte
   Dim ret As Long
   ret = SAFEInitGlobal(bte(0))

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prozakCommented:
Actually I pretty sure that muffinthedog's comment will not work. VB uses OLE SAFEARRAYs to store data in an array. Unlike C the memory is managed by windows and when you pass an array to a C function, you're not passing the block of elements. Your passing a pointer to a SAFEARRAY structure. I can pretty much guarantee that it will crash if you do it that way (passing an array of bytes).
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muffinthedogCommented:
Worked for me... passed a pointer to an array of bytes, kinda like a pointer to an array of characters...
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prozakCommented:
I stand corrected :)
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mbaker123Author Commented:
Cheers I'll give that a try
Festive stuff
Matt
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muffinthedogCommented:
mbaker123...
    just noticed I wrote Dim ret as long.....
    should be Integer... sorry, just playing...
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