c ++ / cli传递（托管）委托给非托管代码 [英] c++/cli pass (managed) delegate to unmanaged code

问题描述

如何将函数指针从托管C ++（C ++ / CLI）传递到非托管方法？我阅读了几篇文章，例如 MSDN中的此，但它描述了两个不同的程序集，而

1）头文件（MyInterop.ManagedCppLib.h）

  #pragma once 
 
使用命名空间System; 
 
命名空间MyInterop {namespace ManagedCppLib {
 
 public ref class MyManagedClass 
 {
 public：
 void DoSomething（）; 
}; 
}} 
  

2）CPP代码（MyInterop.ManagedCppLib.cpp）

  #includestdafx.h
 #includeMyInterop.ManagedCppLib.h
 
 #pragma unmanaged 
 void UnmanagedMethod（int a，int b，void（* sum）（const int））
 {
 int result = a + b; 
 sum（result）; 
} 
 
 #pragma managed 
 void MyInterop :: ManagedCppLib :: MyManagedClass :: DoSomething（）
 {
 System :: Console :: WriteLine hello from managed C ++）; 
 UnmanagedMethod（3，7，/ * ANY IDEA ??? * /）; 
} 
  

我尝试创建托管委托，然后尝试使用 Marshal :: GetFunctionPointerForDelegate 方法，但我无法编译。

解决方案

想要Marshal :: GetFunctionPointerForDelegate（）。您的代码段缺少您想要调用的托管函数，我刚刚创建了一个。您还必须声明托管委托类型并创建它的实例，然后才能获取函数指针。这很好：

  #includestdafx.h
 
使用命名空间System; 
 using namespace System :: Runtime :: InteropServices; 
 
 #pragma managed（push，off）
 typedef void（* UnmanagedSummer）（int arg）; 
 
 void UnmanagedMethod（int a，int b，UnmanagedSummer sum）
 {
 int result = a + b; 
 sum（result）; 
} 
 #pragma managed（pop）
 
 ref class Test {
 delegate void ManagedSummer（int arg）; 
 public：
 static void Run（）{
 Test ^ t = gcnew Test（）; 
 ManagedSummer ^ managed = gcnew ManagedSummer（t，& Sum）; 
 IntPtr stubPointer = Marshal :: GetFunctionPointerForDelegate（managed）; 
 UnmanagedSummer functionPointer = static_cast< UnmanagedSummer>（stubPointer.ToPointer（））; 
 UnmanagedMethod（1，2，functionPointer）; 
 GC :: KeepAlive（managed）; 
 System :: Diagnostics :: Debug :: Assert（t-> summed == 3）; 
} 
 void Sum（int arg）{
 summed + = arg; 
} 
 int summed; 
}; 
 
 int main（array< System :: String ^> ^ args）
 {
 Test :: Run（）; 
 return 0; 
} 
  

How do I pass a function pointer from managed C++ (C++/CLI) to an unmanaged method? I read a few articles, like this one from MSDN, but it describes two different assemblies, while I want only one.

Here is my code:

1) Header (MyInterop.ManagedCppLib.h):

#pragma once

using namespace System;

namespace MyInterop { namespace ManagedCppLib {

    public ref class MyManagedClass
    {
    public:
        void DoSomething();
    };
}}

2) CPP Code (MyInterop.ManagedCppLib.cpp)

#include "stdafx.h"
#include "MyInterop.ManagedCppLib.h"

#pragma unmanaged
void UnmanagedMethod(int a, int b, void (*sum)(const int))
{
    int result = a + b;
    sum(result);
}

#pragma managed
void MyInterop::ManagedCppLib::MyManagedClass::DoSomething()
{
    System::Console::WriteLine("hello from managed C++");
    UnmanagedMethod(3, 7, /* ANY IDEA??? */);
}

I tried creating my managed delegate and then I tried to use Marshal::GetFunctionPointerForDelegate method, but I couldn't compile.

解决方案

Yes, you want Marshal::GetFunctionPointerForDelegate(). Your code snippet is missing the managed function you'd want to call, I just made one up. You will also have to declare the managed delegate type and create an instance of it before you can get a function pointer. This worked well:

#include "stdafx.h"

using namespace System;
using namespace System::Runtime::InteropServices;

#pragma managed(push, off)
typedef void (* UnmanagedSummer)(int arg);

void UnmanagedMethod(int a, int b, UnmanagedSummer sum)
{
    int result = a + b;
    sum(result);
}
#pragma managed(pop)

ref class Test {
    delegate void ManagedSummer(int arg);
public:
    static void Run() {
        Test^ t = gcnew Test();
        ManagedSummer^ managed = gcnew ManagedSummer(t, &Sum);
        IntPtr stubPointer = Marshal::GetFunctionPointerForDelegate(managed);
        UnmanagedSummer functionPointer = static_cast<UnmanagedSummer>(stubPointer.ToPointer());
        UnmanagedMethod(1, 2, functionPointer);
        GC::KeepAlive(managed);
        System::Diagnostics::Debug::Assert(t->summed == 3);
    }
    void Sum(int arg) {
        summed += arg;
    }
    int summed;
};

int main(array<System::String ^> ^args)
{
    Test::Run();
    return 0;
}

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