调用C++

提示

参考资料与非托管代码进行交互操作

数据类型对照

Windows API中的非托管类型	非托管C语言类型	托管类型	描述
VOID	void	System.Void	应用于不返回值的函数
HANDLE	void*	System.IntPtr或System.UIntPtr	在32位Windows操作系统上为32位、在64位Windows操作系统上为64位
BYTE	usigned char	System.Byte	8位
SHORT	short	System.Int16	16位
WORD	usigned short	System.UInt16	16位
INT	int	System.Int16	32位
UINT	unsigned int	System.UInt32	32位
LONG	long	System.Int32	32位
BOOL	long	System.Boolean或System.Int32	32位
DWORD	unsigned long	System.UInt32	32位
ULONG	unsigned long	System.UInt32	32位
CHAR	char	System.Char	用ANSI修饰
WCHAR	wchar_t	System.Char	用Unicode修饰
LPSTR	char *	System.String或System.Text.StringBuilder	用ANSI修饰
LPCSTR	const char *	System.String或System.Text.StringBuilder	用ANSI修饰
LPWSTR	wchar_t *	System.String或System.Text.StringBuilder	用Unicode修饰
LPCWSTR	const wchar_t *	System.String	用Unicode修饰
FLOAT	float	System.Single	32位
DOUBLE	double	System.Double	64位

C++动态连接库

声明头文件

创建头文件HelloCplusPlus.h

通过__declspec(dllexport)导出DLL文件

分为函数导出、类导出、静态类导出以及extern "C"导出

#pragma once

#ifndef  HelloCPlusPlusDll

#define  HelloCPlusPlusDll

//宏定义导出
#ifdef  HelloCPlusPlusDll
#define HelloCPlusPlusDll __declspec(dllexport)//导出
#else
#define HelloCPlusPlusDll __declspec(dllimport)//导入
#endif

HelloCPlusPlusDll int __stdcall Add(int, int);

extern "C" {
    HelloCPlusPlusDll  int __stdcall Sub(int, int);

    HelloCPlusPlusDll const wchar_t* __stdcall ReadString();

    HelloCPlusPlusDll void __stdcall Reset();

    HelloCPlusPlusDll const wchar_t* __stdcall WriteString(const wchar_t* input);

    HelloCPlusPlusDll const char* __stdcall WriteString2(const char* input);
}

class HelloCPlusPlusDll C
{
public:
    static int Mul(int, int);
};

class HelloCPlusPlusDll S
{
public:
    int Div(int, int);
};

#endif

实现头文件

创建源文件HelloCplusPlus.cpp

#include "HelloCPlusPlus.h"
#include <iostream>
#include <wchar.h>

using namespace std;

int Add(int a, int b) {
    return a + b;
}

int Sub(int a, int b) {
    return a - b;
}

wchar_t Hello[16]=L"Hello";
char Hello2[16] = "Hello";

const wchar_t* ReadString()
{
    return Hello;
}

void  Reset()
{
    fill(begin(Hello)+5,end(Hello),0);
    fill(begin(Hello2) + 5, end(Hello2), 0);
}

const wchar_t* WriteString(const wchar_t* input)
{
    wcscat_s(Hello,16,input);
    return Hello;
}

const char* WriteString2(const char* input)
{
    strcat_s(Hello2,16, input);
    return Hello2;
}

int C::Mul(int a, int b) {
    return a * b;
}

int S::Div(int a, int b) {
    return a / b;
}

编译

在配置属性\常规\配置类型改为动态库(.dll)

查看导出类型

安装VS后，打开Developer Command Prompt for VS2022，利用dumpbin查看定义

输入dumpbin /exports project1.dll

导出定义

发现通过extern "C"导出的名称与定义一致，这也是C#调用C++提升找不到入口点的原因之一

调用

注意

C++字符串以\0结尾，多占一位

CPlusPlus调用

1. 新建控制台项目
2. 新建include文件夹，拷贝HelloCPlusPlus.h头文件
3. 新建libs文件夹，拷贝生成的lib、dll文件
4. 打开配置属性\VC++目录\在包含目录添加include文件夹
5. 打开配置属性\链接器\常规下的附加库目录添加libs文件夹
6. 打开配置属性\链接器\输入下的附加依赖项添加project.lib文件

提示

可以不配置链接器，直接引用项目即可

#include <iostream>
#include<HelloCPlusPlus.h>
using namespace std;
int main()
{
    int a= Add(1, 2);
    cout << "1+2="<< a << endl;

    int a1 = Sub(2, 1);
    cout << "2-1="<<a1 << endl;

    C helloC;
    int a2 = helloC.Mul(2, 3);
    cout << "2*3=" << a2 << endl;

    S helloS;
    int a3 = helloS.Div(4, 2);
    cout << "4/2=" <<a3 << endl;

    const wchar_t* str= ReadString();
    wcout << "ReadString:" << str << endl;

    const wchar_t* input1 = L" World";
    const wchar_t* str1 = WriteString(input1);
    wcout << "WriteString:" << str1 <<" Length:" << wcslen(str1) << endl;

    const char input2[] = " World1234";
    const char* str2 = WriteString2(input2);
    cout << "WriteString2:" << str2 << " Length:" << strnlen_s(str2,16) << endl;
}

//输出
//1+2=3
//2-1=1
//2*3=6
//4/2=2
//ReadString:Hello
//WriteString:Hello World Length:11
//WriteString2:Hello World1234 Length:15

CSharp调用

使用DllImport访问非托管函数

引用using System.Runtime.InteropServices;

using System.Runtime.InteropServices;
using System.Text;

short a = Add(1, 2);
Console.WriteLine($"1+2={a}");

short a1 = Sub(2, 1);
Console.WriteLine($"2-1={a1}");

short a2 = Mul(2, 3);
Console.WriteLine($"2*3={a2}");

short a3 = Div(4, 2);
Console.WriteLine($"4/2={a3}");

IntPtr readPtr1 = ReadString();
//方式一：指针转换字符串
var readValue1 = Marshal.PtrToStringUni(readPtr1); 
//方式二：通过字节数组转换
//byte[] bytes1 = new byte[16];
//Marshal.Copy(readPtr1, bytes1, 0, 16);
//var readValue1 = Encoding.Unicode.GetString(bytes1);
Console.WriteLine("ReadString:"+readValue1);

//方式一:通过指针转换
//var writeValue2 = " World";
//var writePtr2=Marshal.StringToHGlobalUni(writeValue2);
//方式二:通过字节转换，末尾需要`\0`
var writeValue2 = " World\0";
var byteStr2 = Encoding.Unicode.GetBytes(writeValue2);
IntPtr writePtr2 = Marshal.AllocHGlobal(byteStr2.Length);
Marshal.Copy(byteStr2, 0, writePtr2, byteStr2.Length);
IntPtr readPtr2 = WriteString(writePtr2);
var readValue2 = Marshal.PtrToStringUni(readPtr2);
Console.WriteLine("WriteString:" + readValue2 + " Length:"+readValue2.Length);

//WriteStringAs和WriteString使用同一个操作进行拼接，超出上限需要重置
Reset();

string writeValue3 = " World12";
var readValuePtr3 = WriteStringAs(writeValue3);
var readValue3 = Marshal.PtrToStringUni(readValuePtr3);
Console.WriteLine("WriteString:" + readValue3 + " Length:"+readValue2.Length);

var writeValue4 = " World1234";
var writeValuePtr4 = Marshal.StringToHGlobalAnsi(writeValue4);
IntPtr readValuePtr4 = WriteString2(writeValuePtr4);
var readValue4 = Marshal.PtrToStringAnsi(readValuePtr4);
Console.WriteLine("WriteString2:" + readValue4 + " Length:"+readValue2.Length);

Marshal.FreeHGlobal(readPtr1);
Marshal.FreeHGlobal(readPtr2);
Marshal.FreeHGlobal(readValuePtr3);
Marshal.FreeHGlobal(readValuePtr4);

[DllImport(@".\lib\Project1.dll",CharSet =CharSet.Unicode, EntryPoint = "?Add@@YAHHH@Z")]
static extern short Add(short a, short b);
[DllImport(@".\lib\Project1.dll", CharSet = CharSet.Unicode)]
static extern short Sub(short a, short b);
[DllImport(@".\lib\Project1.dll", CharSet = CharSet.Unicode, EntryPoint = "?Mul@C@@SAHHH@Z")]
static extern short Mul(short a, short b);
[DllImport(@".\lib\Project1.dll", CharSet = CharSet.Unicode, EntryPoint = "?Div@S@@QEAAHHH@Z")]
static extern short Div(short a, short b);
[DllImport(@".\lib\Project1.dll", CharSet = CharSet.Unicode)]
static extern IntPtr ReadString();
[DllImport(@".\lib\Project1.dll", CharSet = CharSet.Unicode)]
static extern IntPtr WriteString(IntPtr input);
[DllImport(@".\lib\Project1.dll", CharSet = CharSet.Unicode,EntryPoint = "WriteString")]
static extern IntPtr WriteStringAs(string input);
[DllImport(@".\lib\Project1.dll", CharSet = CharSet.Unicode)]
static extern IntPtr WriteString2(IntPtr input);
[DllImport(@".\lib\Project1.dll", CharSet = CharSet.Unicode)]
static extern void Reset();

//输出
//1+2=3
//2-1=1
//2*3=6
//4/2=0
//ReadString:Hello
//WriteString:Hello World Length:11
//WriteString:Hello World12 Length:13
//WriteString2:Hello World1234 Length:15

C#的WriteString和WriteStringAs方法都是调用C++的WriteString，通过EntryPoint更改入口点名称。它们唯一的区别在于形参参数传递，一个通过IntPtr，一个通过string，返回结果string无效。

发现Div函数输出结果不正确，调试C#与C++代码发现传递两个参数，结果C++代码接收的参数多一个，调整代码

var a3 = Div(0,4, 2);
Console.WriteLine($"4/2={a3}");

[DllImport(@".\lib\Project1.dll", CharSet = CharSet.Unicode, EntryPoint = "?Div@S@@QEAAHHH@Z")]
static extern short Div(short i,short a, short b);

//输出
//4/2=2

结果按预期输出，C#是无法直接调用C++类，需要进行包装处理，但是为什么多加一个参数可以? 。