c++/cli 将(托管)委托传递给非托管代码 [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) 传递给非托管方法?我读了几篇文章，例如 这篇来自 MSDN，但它描述了两个不同的程序集，而我只想要一个.

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.

这是我的代码:

1) 标头 (MyInterop.ManagedCppLib.h):

1) Header (MyInterop.ManagedCppLib.h):

#pragma once

using namespace System;

namespace MyInterop { namespace ManagedCppLib {

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

2) CPP 代码 (MyInterop.ManagedCppLib.cpp)

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??? */);
}

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

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

推荐答案

是的，你想要 Marshal::GetFunctionPointerForDelegate().您的代码片段缺少您要调用的托管函数，我只是编造了一个.您还必须声明托管委托类型并创建它的实例，然后才能获得函数指针.这很好用:

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);    // Important: ensure stub can't be collected while native code is running
        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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