Hi,

I am using JNA for accessing DLL functions directly from JAVA, but I am stuck in a situation when I have to access a method that takes structure as a parameter which includes Function Pointers in it.

My problem is that JNA does not call my callback functions when their function pointers are part of a structure which is then passed as an argument to a C++ function.

In order to get a clearer picture of my problem please have a look at the code.

===================C++ Header File=================== typedef int (__stdcall *StringRevFunction) (); typedef int (__stdcall *StringAscFunction) (int val);

typedef struct TUssdCallbacks { StringAscFunction stringAscFunction; StringRevFunction stringRevFunction; };

extern "C" __declspec(dllexport) void RegisterStringCallbackFunc(TUssdCallbacks tUssdCallbacks);

===================C++ Implementation File=================== #include "stdafx.h" #include "CCallbackFunction.h"

extern "C" __declspec(dllexport) void RegisterStringCallbackFunc(TUssdCallbacks tUssdCallbacks){

(*tUssdCallbacks.stringAscFunction)((int)8);

(*tUssdCallbacks.stringRevFunction)(); }

===================Java Interface definition file===================

import com.sun.jna.Callback; import com.sun.jna.Library; import com.sun.jna.Native; import com.sun.jna.Structure;

public interface CCallbackFunction extends Library{

CCallbackFunction INSTANCE = (CCallbackFunction) Native.loadLibrary("CCallbackFunction",CCallbackFunction.class);

public static class TUssdCallbacks extends Structure{

public TUssdCallbacks (StringRevFunction stringRevFunction,StringAscFunction stringAscFunction){ super(2,ALIGN_DEFAULT); this.stringAscFunction = stringAscFunction; this.stringRevFunction = stringRevFunction; }

public StringRevFunction stringRevFunction; public StringAscFunction stringAscFunction; }

public void RegisterStringCallbackFunc(TUssdCallbacks tUssdCallbacks);

}

===================Java Main File===================

import com.sun.jna.Function;

public class Test {

public static void main(String[] args) { System.setProperty("jna.library.path","C:\\lib\\"); String s = System.getProperty("jna.library.path"); System.out.println( "Jna.library.path = "+s );

CCallbackFunction.StringAscFunction stringAscFunction = new CCallbackFunction.StringAscFunction(){

public int invoke() { System.out.println("------**-------"); return 0; }

};

CCallbackFunction.StringRevFunction stringRevFunction = new CCallbackFunction.StringRevFunction(){

public int invoke(int val) { System.out.println("-------**------"+val); return 0; }

};

CCallbackFunction.TUssdCallbacks callbacks = new CCallbackFunction.TUssdCallbacks(stringRevFunction,stringAscFunction);

CCallbackFunction.INSTANCE.RegisterStringCallbackFunc(callbacks);

}

}

The last highlighted line results in following error.

# # An unexpected error has been detected by Java Runtime Environment: # # EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x02dc2610, pid=3380, tid=5456 # # Java VM: Java HotSpot(TM) Client VM (11.0-b15 mixed mode, sharing windows-x86) # Problematic frame: # C 0x02dc2610 # # An error report file with more information is saved as: # D:\workspace\JavaJNA\hs_err_pid3380.log # # If you would like to submit a bug report, please visit: # http://java.sun.com/webapps/bugreport/crash.jsp # The crash happened outside the Java Virtual Machine in native code. # See problematic frame for where to report the bug. #

NOTE:

I have accessed same DLL in C# and it successfully calls my call back function. Moreover I have exposed another function in DLL with all the Function pointers as method parameter and then within the function I have initialized the structure with Function Pointer values and called same method which results in successful call to my callback functions that I have defined in JAVA.

The new exposed function is as follows.

extern "C" __declspec(dllexport) void RegisterStrCallbackFunc(StringRevFunction stringRevFunction,StringAscFunction stringAscFunction){ struct TUssdCallbacks tUssdCallbacks = { stringAscFunction,stringRevFunction};

RegisterStringCallbackFunc(tUssdCallbacks); }

Kindly guied me is it possible to register my callback functions using structure. If it is then please tell where am I doing wrong.

Thanking you in anticipation.

Regards,

Muhammad Noor-ul-haque

You can call me just noor.

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