Creating Dynamic Libraries

Windows DLL Development

To create a Windows dynamic link library, start by establishing a DLL project. The core functionality is implemented in the source file:

#include "framework.h"

extern "C" __declspec(dllexport) int addValues(int x, int y) {
    return x + y;
}

BOOL APIENTRY DllMain(HMODULE module, DWORD callReason, LPVOID reserved) {
    switch (callReason) {
        case DLL_PROCESS_ATTACH:
        case DLL_THREAD_ATTACH:
        case DLL_THREAD_DETACH:
        case DLL_PROCESS_DETACH:
            break;
    }
    return TRUE;
}

The corresponding header defines the exported function:

#ifndef FRAMEWORK_H
#define FRAMEWORK_H

#include <windows.h>

#endif

extern "C" __declspec(dllexport) int addValues(int x, int y);

Build the project in Release configuration to genertae the DLL file.

Linux Shared Object Creation

For Linux platforms, create a shared object file using:

extern "C" {
    int calculateSum(int first, int second) {
        return first + second;
    }
}

Compile this source to produce a .so file.

Consuming Libraries

C++ Application Integration

Create a new executable project and implement library loading:

#include <iostream>
#include <windows.h>

typedef int (*sumFunction)(int, int);

int main() {
    HMODULE libraryHandle = LoadLibrary(L"mathlibrary.dll");
    
    if (libraryHandle) {
        std::cout << "Library loaded successfully\n";
        sumFunction addFunc = (sumFunction)GetProcAddress(libraryHandle, "addValues");
        
        if (addFunc) {
            std::cout << "Function call result: " << addFunc(150, 250) << std::endl;
        } else {
            std::cout << "Function not found\n";
        }
        
        FreeLibrary(libraryHandle);
    } else {
        std::cout << "Failed to load library\n";
    }
    
    return 0;
}

Place the compiled DLL in the executable directory before running.

C# Integration

Define P/Invoke signatures for native library access:

using System.Runtime.InteropServices;

internal static class MathBridge
{
    private const string WindowsLibrary = "mathlibrary.dll";
    private const string LinuxLibrary = "libmathlibrary.so";
    
    [DllImport(WindowsLibrary, CallingConvention = CallingConvention.Cdecl)]
    public static extern int addValues(int operand1, int operand2);
    
    [DllImport(LinuxLibrary, CallingConvention = CallingConvention.Cdecl)]
    public static extern int calculateSum(int operand1, int operand2);
}

Consume the native functions in application code:

using System;

class Program
{
    static void Main()
    {
        int result = MathBridge.addValues(12, 1000);
        Console.WriteLine($"Computed sum: {result}");
        Console.ReadKey();
    }
}

Java Integration Using JNA

Implement Java interfaces to map native library functions:

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

public interface WindowsMathLibrary extends Library {
    WindowsMathLibrary INSTANCE = 
        (WindowsMathLibrary) Native.loadLibrary("mathlibrary.dll", WindowsMathLibrary.class);
    
    int addValues(int first, int second);
}

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

public interface LinuxMathLibrary extends Library {
    LinuxMathLibrary INSTANCE = 
        (LinuxMathLibrary) Native.loadLibrary("libmathlibrary.so", LinuxMathLibrary.class);
    
    int calculateSum(int first, int second);
}

Main application logic for cross-platform execution:

public class Application {
    public static void main(String[] args) {
        String platform = System.getProperty("os.name").toLowerCase();
        int computationResult = 0;
        
        if (platform.contains("windows")) {
            computationResult = WindowsMathLibrary.INSTANCE.addValues(5, 6);
        } else if (platform.contains("linux")) {
            computationResult = LinuxMathLibrary.INSTANCE.calculateSum(5, 6);
        } else {
            System.out.println("Unsupported platform: " + platform);
        }
        
        System.out.println("Native function output: " + computationResult);
    }
}

Include JNA dependency in project configuraton:

<dependencies>
    <dependency>
        <groupId>com.sun.jna</groupId>
        <artifactId>jna</artifactId>
        <version>5.12.1</version>
    </dependency>
</dependencies>