基于jdk21 ffm api的jni封装。
以下示例C++文件,定义打印菲波那切函数和输出最大Point函数
// MathLibrary.h - Contains declarations of math functions
#pragma once
#ifdef MATHLIBRARY_EXPORTS
#define MATHLIBRARY_API __declspec(dllexport)
#else
#define MATHLIBRARY_API __declspec(dllimport)
#endif
// The Fibonacci recurrence relation describes a sequence F
// where F(n) is { n = 0, a
// { n = 1, b
// { n > 1, F(n-2) + F(n-1)
// for some initial integral values a and b.
// If the sequence is initialized F(0) = 1, F(1) = 1,
// then this relation produces the well-known Fibonacci
// sequence: 1, 1, 2, 3, 5, 8, 13, 21, 34, ...
// Initialize a Fibonacci relation sequence
// such that F(0) = a, F(1) = b.
// This function must be called before any other function.
extern "C" MATHLIBRARY_API void fibonacci_init(
const unsigned long long a, const unsigned long long b);
// Produce the next value in the sequence.
// Returns true on success and updates current value and index;
// false on overflow, leaves current value and index unchanged.
extern "C" MATHLIBRARY_API bool fibonacci_next();
// Get the current value in the sequence.
extern "C" MATHLIBRARY_API unsigned long long fibonacci_current();
// Get the position of the current value in the sequence.
extern "C" MATHLIBRARY_API unsigned fibonacci_index();
struct Point {
int x;
int y;
};
extern "C" MATHLIBRARY_API Point test_point(Point points[], long count);
// MathLibrary.cpp : Defines the exported functions for the DLL.
#include "pch.h" // use stdafx.h in Visual Studio 2017 and earlier
#include <utility>
#include <limits.h>
#include "MathLibrary.h"
#include <iostream> // Include for using std::cout
// DLL internal state variables:
static unsigned long long previous_; // Previous value, if any
static unsigned long long current_; // Current sequence value
static unsigned index_; // Current seq. position
// Initialize a Fibonacci relation sequence
// such that F(0) = a, F(1) = b.
// This function must be called before any other function.
void fibonacci_init(
const unsigned long long a,
const unsigned long long b)
{
index_ = 0;
current_ = a;
previous_ = b; // see special case when initialized
}
// Produce the next value in the sequence.
// Returns true on success, false on overflow.
bool fibonacci_next()
{
// check to see if we'd overflow result or position
if ((ULLONG_MAX - previous_ < current_) ||
(UINT_MAX == index_))
{
return false;
}
// Special case when index == 0, just return b value
if (index_ > 0)
{
// otherwise, calculate next sequence value
previous_ += current_;
}
std::swap(current_, previous_);
++index_;
return true;
}
// Get the current value in the sequence.
unsigned long long fibonacci_current()
{
return current_;
}
// Get the current index position in the sequence.
unsigned fibonacci_index()
{
return index_;
}
Point test_point(Point points[],long count)
{
if (count <= 0) {
// Return a default Point with x and y set to 0
Point defaultPoint = { 0, 0 };
return defaultPoint;
}
Point maxPoint = points[0];
int maxSum = maxPoint.x + maxPoint.y;
for (int i = 1; i < count; ++i) {
int currentSum = points[i].x + points[i].y;
if (currentSum > maxSum) {
maxSum = currentSum;
maxPoint = points[i];
}
}
int x = maxPoint.x;
int y = maxPoint.y;
std::cout << "x = " << x << ", y = " << y << std::endl;
return maxPoint;
}
与jna使用相似,继承Library定义接口,使用Native.load加载dll
public record Point(int x,int y) {
}
import org.example.jna.Library;
import org.example.jna.Native;
import java.util.List;
public interface MathLibrary extends Library {
MathLibrary DLL = Native.load("src\\main\\resources\\MathLibrary.dll", MathLibrary.class);
Long fibonacci_init(Long a, Long b);
Boolean fibonacci_next();
Long fibonacci_current();
Long fibonacci_index();
Point test_point(Point[] point, long count);
}
public class TestNative {
public static void main(String[] args) {
// 菲波那切打印
Long l = MathLibrary.DLL.fibonacci_init(1L, 1L);
do {
System.out.println(MathLibrary.DLL.fibonacci_index() + ": " + MathLibrary.DLL.fibonacci_current());
} while (MathLibrary.DLL.fibonacci_next());
// 筛选x+y最大值Point
Point[] pointArray = new Point[10];
for (int j = 0; j < pointArray.length; j++) {
pointArray[j] = new Point(j, j);
}
Point point = MathLibrary.DLL.test_point(pointArray, pointArray.length);
System.out.println(point);
}
}