python调用C/C++动态库的实践案例

// example.c
#include <stdio.h>

// 简单加法函数
int add(int a, int b) {
    return a + b;
}

// 字符串处理函数
void reverse_string(char* str) {
    int len = 0;
    while (str[len] != '\0') len++;
    
    for (int i = 0; i < len/2; i++) {
        char temp = str[i];
        str[i] = str[len - i - 1];
        str[len - i - 1] = temp;
    }
}

# Linux/macOS
gcc -shared -o example.so -fPIC example.c

# Windows (MinGW)
gcc -shared -o example.dll example.c

import ctypes

# 加载动态库
lib = ctypes.CDLL('./example.so')  # Linux/macOS
# lib = ctypes.CDLL('./example.dll')  # Windows

# 调用add函数
add_result = lib.add(3, 4)
print(f"3 + 4 = {add_result}")  # 输出: 7

# 调用reverse_string函数
# 注意：需要传递可变的字节数组
s = ctypes.create_string_buffer(b"hello")
lib.reverse_string(s)
print(f"Reversed: {s.value.decode()}")  # 输出: olleh

#include <stdio.h>

// 定义结构体
typedef struct {
    int x;
    int y;
} Point;

// 结构体加法函数
Point add_points(Point a, Point b) {
    Point result;
    result.x = a.x + b.x;
    result.y = a.y + b.y;
    return result;
}

// 修改结构体内容
void scale_point(Point* p, int factor) {
    p->x *= factor;
    p->y *= factor;
}

gcc -shared -o struct_example.so -fPIC struct_example.c

import ctypes

# 加载动态库
lib = ctypes.CDLL('./struct_example.so')

# 定义Point结构体
class Point(ctypes.Structure):
    _fields_ = [
        ("x", ctypes.c_int),
        ("y", ctypes.c_int)
    ]

# 设置函数参数和返回值类型
lib.add_points.argtypes = [Point, Point]
lib.add_points.restype = Point

lib.scale_point.argtypes = [ctypes.POINTER(Point), ctypes.c_int]
lib.scale_point.restype = None

# 调用add_points函数
p1 = Point(1, 2)
p2 = Point(3, 4)
result = lib.add_points(p1, p2)
print(f"({p1.x}, {p1.y}) + ({p2.x}, {p2.y}) = ({result.x}, {result.y})")
# 输出: (1, 2) + (3, 4) = (4, 6)

# 调用scale_point函数
p = Point(5, 6)
lib.scale_point(ctypes.byref(p), 2)
print(f"缩放后的点: ({p.x}, {p.y})")
# 输出: 缩放后的点: (10, 12)

#include <stdio.h>

// 计算数组元素之和
int sum_array(int* arr, int size) {
    int sum = 0;
    for (int i = 0; i < size; i++) {
        sum += arr[i];
    }
    return sum;
}

// 修改数组内容
void multiply_array(int* arr, int size, int factor) {
    for (int i = 0; i < size; i++) {
        arr[i] *= factor;
    }
}

gcc -shared -o array_example.so -fPIC array_example.c

import ctypes

# 加载动态库
lib = ctypes.CDLL('./array_example.so')

# 创建C整数数组类型
IntArray5 = ctypes.c_int * 5  # 定义长度为5的整数数组

# 设置函数参数类型
lib.sum_array.argtypes = [ctypes.POINTER(ctypes.c_int), ctypes.c_int]
lib.sum_array.restype = ctypes.c_int

lib.multiply_array.argtypes = [ctypes.POINTER(ctypes.c_int), ctypes.c_int, ctypes.c_int]
lib.multiply_array.restype = None

# 调用sum_array函数
arr = IntArray5(1, 2, 3, 4, 5)
sum_result = lib.sum_array(arr, 5)
print(f"数组和: {sum_result}")  # 输出: 15

# 调用multiply_array函数
lib.multiply_array(arr, 5, 10)
print(f"修改后的数组: {[arr[i] for i in range(5)]}")
# 输出: [10, 20, 30, 40, 50]

#include <iostream>
using namespace std;

// C++类
class Calculator {
public:
    int add(int a, int b) { return a + b; }
    int subtract(int a, int b) { return a - b; }
};

// 封装C++类的C接口
extern "C" {
    // 创建对象
    Calculator* Calculator_new() { return new Calculator(); }
    // 释放对象
    void Calculator_delete(Calculator* calc) { delete calc; }
    // 调用成员函数
    int Calculator_add(Calculator* calc, int a, int b) { return calc->add(a, b); }
    int Calculator_subtract(Calculator* calc, int a, int b) { return calc->subtract(a, b); }
}

g++ -shared -o cpp_example.so -fPIC cpp_example.cpp

import ctypes

# 加载动态库
lib = ctypes.CDLL('./cpp_example.so')

# 定义函数参数和返回值类型
lib.Calculator_new.restype = ctypes.c_void_p
lib.Calculator_delete.argtypes = [ctypes.c_void_p]
lib.Calculator_add.argtypes = [ctypes.c_void_p, ctypes.c_int, ctypes.c_int]
lib.Calculator_add.restype = ctypes.c_int
lib.Calculator_subtract.argtypes = [ctypes.c_void_p, ctypes.c_int, ctypes.c_int]
lib.Calculator_subtract.restype = ctypes.c_int

# 创建Calculator对象
calc_ptr = lib.Calculator_new()

# 调用成员函数
result_add = lib.Calculator_add(calc_ptr, 10, 5)
result_sub = lib.Calculator_subtract(calc_ptr, 10, 5)

print(f"10 + 5 = {result_add}")  # 输出: 15
print(f"10 - 5 = {result_sub}")  # 输出: 5

# 释放对象
lib.Calculator_delete(calc_ptr)