Click here to Skip to main content
Rate this: bad
Please Sign up or sign in to vote.
See more: C++ C#
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
Rate this: bad
Please Sign up or sign in to vote.

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.
Rate this: bad
Please Sign up or sign in to vote.

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);
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)
        return 0; 

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

  Print Answers RSS
0 OriginalGriff 240
1 Kamal Rocks 184
2 PIEBALDconsult 150
3 BillWoodruff 148
4 Jochen Arndt 135
0 OriginalGriff 5,695
1 DamithSL 4,506
2 Maciej Los 4,007
3 Kornfeld Eliyahu Peter 3,480
4 Sergey Alexandrovich Kryukov 3,180

Advertise | Privacy | Mobile
Web01 | 2.8.141216.1 | Last Updated 18 Jun 2010
Copyright © CodeProject, 1999-2014
All Rights Reserved. Terms of Service
Layout: fixed | fluid

CodeProject, 503-250 Ferrand Drive Toronto Ontario, M3C 3G8 Canada +1 416-849-8900 x 100