How to change the entry point of a Java program to a C-signature?

Question

I cheated on JNA while trying to execute C code in a Java program. This is a working example that I found online (JNA is required in the build path):

package core;

import com.sun.jna.Library;
import com.sun.jna.Native;
import com.sun.jna.Platform;

public class CoreController {
    public interface CLibrary extends Library {
        CLibrary INSTANCE = (CLibrary) Native.loadLibrary(
                (Platform.isWindows() ? "msvcrt" : "c"), CLibrary.class);

        void printf(String format, Object... args);
    }

    public static void main(String[] args) {
        CLibrary.INSTANCE.printf("Hello, World\n");
        for (int i = 0; i < args.length; i++) {
            CLibrary.INSTANCE.printf("Argument %d: %s\n", i, args[i]);
        }

        Native.main(args);
    }
}

In fact, I'm trying to do three (seemingly ugly) things.

1.) The entry point of the program should be changed to the following C-signature:

void __stdcall RVExtension(char *output, int outputSize, const char *function);

2.) The Java program should be able to set the given parameter output.
3.) The program must be compiled into a DLL.

In C ++, this problem will be solved as follows:

#include "stdafx.h"

extern "C" {
    __declspec (dllexport) void __stdcall RVExtension(char *output, int outputSize, const char *function);
}

void __stdcall RVExtension(char *output, int outputSize, const char *function) {
    strncpy_s(output, outputSize, "IT WORKS!", _TRUNCATE);
}

So the question is, what is possible with Java? If so, I would be glad to see an example of the code, since I am introducing a lot of new territory here. I don’t even know if JNA is suitable here. If anyone has another idea, please let me know!

Regards,
Jayson

Answer 1

C DLL Java Invocation API Java Java . , , . JNA .