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Hi all, I want to use P/Invoke method to call a C++ DLL, the C++ DLL has a callback function which defined as:
 

typedef long (CALLBACK * readFileData)(unsigned char * data, int length);

 
My question is how to define the "unsigned char *" parameter in C# ? Does this is correctly?
 
public delegate Int32 readFileData(byte[] data, Int32 length);
 
Thanks in advance.
Posted 18-Jun-10 7:09am
vnetoo132
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Solution 1

Given the the callback is called readFileData, then either byte[] or StringBuilder should work.
If it wasn't being changed, then byte[] or String should do.
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Solution 2

I just got this following test scenario working correctly:
 
C++ code
------------
 
typedef long (CALLBACK * READDATA)(unsigned char * data, int length);
 
extern "C" __declspec(dllexport)  void __stdcall SomeFunc(READDATA rd)
{
 unsigned char data[5] = {'a', 'b', 'c', 'd', 'e'};
 rd(data, 5);
}
 
C# code
-------------
 
delegate int ReadDataDelegate(IntPtr data, int len);
 
[DllImport("SimpleLib.dll")]
static extern void SomeFunc(ReadDataDelegate d);
 
private static void CallNativeWithCallback()
{
    ReadDataDelegate newCB = new ReadDataDelegate((data, len) => 
    {
        byte[] array = new byte[len];
        Marshal.Copy(data, array, 0, len);
        foreach (byte b in array)
        {
            Console.WriteLine((char)b);
        }
        Console.WriteLine(); 
        return 0; 
    });
    SomeFunc(newCB);
}
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