C#呼叫C++類庫的幾種方式
阿新 • • 發佈:2019-01-13
1、 直接呼叫C++類庫中的公共方法
使用DllImport特性對方法進行呼叫,比如一個C++類庫SampleCppWrapper.dll中的公共方法:
extern "C" __declspec(dllexport) int __stdcall Add(int n1, int n2);
__stdcall表示呼叫約定:引數都是從右向左通過堆疊傳遞, 函式呼叫在返回前要由被呼叫者清理堆疊。
在C#中,呼叫如下:
[DllImport("SampleCppWrapper.dll")] private static extern int Add(intn1, int n2);
注意引數的型別,之後,可直接在C#程式設計中使用這個方法。
2、 呼叫C++類庫中的類的方法
C#不能直接呼叫C++類庫中的類,需要一種變通的解決方式,通過再做一個C++類庫把要呼叫的類成員方法暴露出來,比如下面這個C++類:
SampleCppClass.h
#pragma once class __declspec(dllexport) SampleCppClass { public: SampleCppClass(void); ~SampleCppClass(void);int Add(int n1, int n2); int Sub(int n1, int n2); };
SampleCppClass.cpp
#include "SampleCppClass.h" SampleCppClass::SampleCppClass(void) { } SampleCppClass::~SampleCppClass(void) { } int SampleCppClass::Add(int n1, int n2) { return n1 + n2; } int SampleCppClass::Sub(intn1, int n2) { return n1 - n2; }
我們要呼叫SampleCppClass中的Add和Sub兩個方法,所以我們再寫一個C++類庫,通過公共方法間接呼叫類成員方法:
SampleCppWrapper.h
#pragma once #include "..\SampleCppClass\SampleCppClass.h" namespace SampleCppWrapper { extern "C" __declspec(dllexport) int __stdcall Add(int n1, int n2); extern "C" __declspec(dllexport) int __stdcall Sub(int n1, int n2); }
SampleCppWrapper.cpp
#include "SampleCppWrapper.h" namespace SampleCppWrapper { SampleCppClass* g_pObj = new SampleCppClass(); int __stdcall Add(int n1, int n2) { return g_pObj->Add(n1, n2); } int __stdcall Sub(int n1, int n2) { return g_pObj->Sub(n1, n2); } }
在C#中,再呼叫SampleCppWrapper.dll中的公共方法:
[DllImport("SampleCppWrapper.dll")] private static extern int Add(int n1, int n2); [DllImport("SampleCppWrapper.dll")] private static extern int Sub(int n1, int n2);
3、 使用C++類庫中的回撥函式
C++的回撥函式是一種事件響應機制,和C#的委託相似,比如一個C++類中的回撥函式:
SampleCppClass.h
#pragma once typedef void (*LoopCallback)(void* pContext); class __declspec(dllexport) SampleCppClass { public: SampleCppClass(void); ~SampleCppClass(void); void SetCallbackFunc(LoopCallback callback); void SetCallbackContext(void* pContext); void Loop(); private: LoopCallback m_callback; void* m_pContext; };
SampleCppClass.cpp
#include "SampleCppClass.h" SampleCppClass::SampleCppClass(void) { } SampleCppClass::~SampleCppClass(void) { } void SampleCppClass::SetCallbackFunc(LoopCallback callback) { m_callback = callback; } void SampleCppClass::SetCallbackContext(void* pContext) { m_pContext = pContext; } void SampleCppClass::Loop() { for (int i=0; i<10; i++) { if (m_callback != NULL) { m_callback(m_pContext); } } }
我們通過C++再寫一個類庫進行封裝,把類中的方法暴露出來:
SampleCppWrapper.h
#pragma once #include "..\SampleCppClass\SampleCppClass.h" namespace SampleCppWrapper { typedef void (__stdcall *LoopCallbackWrapper)(void* pContext); extern "C" __declspec(dllexport) void __stdcall SetCallbackFunc(LoopCallbackWrapper callback); extern "C" __declspec(dllexport) void __stdcall SetCallbackContext(void* pContext); extern "C" __declspec(dllexport) void __stdcall Loop(); }
SampleCppWrapper.cpp
#include "SampleCppWrapper.h" namespace SampleCppWrapper { LoopCallbackWrapper g_callbackWrapper; SampleCppClass* g_pObj = new SampleCppClass(); void LoopCallbackFunc(void* pContext); void __stdcall SetCallbackFunc(LoopCallbackWrapper callback) { g_callbackWrapper = callback; g_pObj->SetCallbackFunc(LoopCallbackFunc); } void __stdcall SetCallbackContext(void* pContext) { g_pObj->SetCallbackContext(pContext); } void __stdcall Loop() { g_pObj->Loop(); } void LoopCallbackFunc(void* pContext) { if (g_callbackWrapper != NULL) { g_callbackWrapper(pContext); } } }
然後,在C#中進行呼叫:
using System; using System.Runtime.InteropServices; using System.Windows.Forms; namespace SampleCsTest { public partial class Form1 : Form { [StructLayout(LayoutKind.Sequential)] private class Context { public Form1 Form { get; set; } } private delegate void LoopCallbackHandler(IntPtr pContext); private static LoopCallbackHandler callback = LoopCallback; [DllImport("SampleCppWrapper.dll")] private static extern void SetCallbackFunc(LoopCallbackHandler callback); [DllImport("SampleCppWrapper.dll")] private static extern void SetCallbackContext(IntPtr pContext); [DllImport("SampleCppWrapper.dll")] private static extern void Loop(); private Context ctx = new Context(); public Form1() { InitializeComponent(); } private void Form1_Load(object sender, EventArgs e) { SetCallbackFunc(callback); ctx.Form = this; IntPtr ptr = Marshal.AllocHGlobal(Marshal.SizeOf(ctx)); Marshal.StructureToPtr(ctx, ptr, false); SetCallbackContext(ptr); } private void button1_Click(object sender, EventArgs e) { Loop(); } private static void LoopCallback(IntPtr pContext) { Context ctx = (Context)Marshal.PtrToStructure(pContext, typeof(Context)); ctx.Form.textBox1.Text += "callback" + Environment.NewLine; } } }