回调从C ++回到C＃

本文介绍了回调从C ++回到C＃的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

说我有一个用于计算PI的C ++库函数：

  // pi.h：
 #ifdef BUILDING_DLL 
 #define DLL_MACRO __declspec（dllexport）
 #else 
 #define DLL_MACRO __declspec（dllimport）
 #endif 
 
命名空间Cpp {
 class PI {
 public：
 static double DLL_MACRO compute（）; 
}; 
}; 
 
 // pi.cpp：
 #includepi.h
 #include< cmath> 
 
 double 
 Cpp :: PI :: compute（）{
 // Leibnitz求和公式：
 double sum = 0.0; 
 for（long n = 0; n  sum + = 4.0 * pow（-1.0，n）/（2 * n + 1.0） 
 return sum; 
}

我需要从C＃调用此函数，我想使用C ++ / CLI作为桥。但是这个C ++函数有点慢。因此，调用此函数的C＃代码需要获取回调函数告诉它函数在％中有多远。
C＃代码可能需要一些状态，例如。一个进度条，处理这个信息。
因此，C ++的回调函数必须在C＃方面输入成员函数。

所以我介绍：

  // piCLI.h：C＃和C ++之间的C ++ / CLI桥
 #includepi.h
 #pragma once 
 namespace CLI {
 public ref class PI abstract {
 public：
 double compute（）{
 return Cpp :: PI :: compute（）; 
} 
 virtual void progress（int percentCompleted）= 0; 
}; 
};

和

 命名空间CSharp 
 {
 public class PI：CLI.PI 
 {
 public override void progress（int percentCompleted）
 {
 System。 Console.WriteLine（percentCompleted +％completed。）; 
} 
} 
}

现在调用CSharp.PI。 compute（）工作正常:-)。它会将调用转发给Cpp :: PI :: compute（）。

但是如何让C ++库将进度更新转发到CSharp.PI.progress （）而Cpp :: PI :: compute（）正在运行？

先感谢任何答案！

 
 code> // pi.h：
 #pragma once 
 
 #ifndef DLL_MACRO 
 #ifdef BUILDING_DLL 
 #define DLL_MACRO __declspec（dllexport）
 #else 
 #define DLL_MACRO __declspec（dllimport）
 #endif 
 #endif 
 
 namespace Cpp {
 typedef void（__stdcall * ComputeProgressCallback） ）; 
 
 class PI {
 public：
 static double DLL_MACRO compute（ComputeProgressCallback callback）; 
}; 
} 
 
 // pi.cpp：
 #includepi.h
 #include< cmath> 
 
 double Cpp :: PI :: compute（Cpp :: ComputeProgressCallback callback）{
 double sum = 0 .; 
 for（long n = 0L; n！= 100000000L; ++ n）{
 sum + = 4. * std :: pow（-1。，n）/（2L * n + 1。 ）; 
 callback（/ * impl * /）; 
} 
 return sum; 
}

  // piCLI.h：C＃和C ++之间的C ++ / CLI桥
 #pragma once 
 #includepi.h
 
命名空间CLI {
 public delegate void ComputeProgressDelegate（int percentCompleted）; 
 
 public ref class PI abstract sealed {
 public：
 static double compute（ComputeProgressDelegate ^ callback）{
 using System :: IntPtr; 
 using System :: Runtime :: InteropServices :: Marshal; 
 
 IntPtr cbPtr = Marshal :: GetFunctionPointerForDelegate（callback）; 
 return Cpp :: PI :: compute（
 static_cast< Cpp :: ComputeProgressCallback>（cbPtr.ToPointer（））
）; 
} 
}; 
}

  namespace CSharp {
 public static class PI {
 public static double compute（）{
 CLI.PI.compute（
 percentCompleted => System.Console.WriteLine（
 percentCompleted.ToString（）+％completed。
）
）; 
} 
} 
}

progress 方法，而不是在C＃端创建一个委托：

  // piCLI.h：C＃和C ++之间的C ++ / CLI桥梁
 #pragma once 
 #includepi.h
 
命名空间CLI {
 public ref class PI abstract {
 delegate void ComputeProgressDelegate（int percentCompleted）; 
 
 public：
 double compute（）{
使用System :: IntPtr; 
 using System :: Runtime :: InteropServices :: Marshal; 
 
 ComputeProgressDelegate ^ callback = gcnew ComputeProgressDelegate（
 this，
& PI :: progress 
）; 
 IntPtr cbPtr = Marshal :: GetFunctionPointerForDelegate（callback）; 
 return Cpp :: PI :: compute（
 static_cast< Cpp :: ComputeProgressCallback>（cbPtr.ToPointer（））
）; 
} 
 
 protected：
 virtual void progress（int percentCompleted）abstract; 
}; 
}

 命名空间Csharp {
 public sealed class PI：CLI.PI {
 protected override void progress（int percentCompleted）{
 System.Console.WriteLine（
 percentCompleted.ToString（） ％已完成。
）; 
} 
} 
}

say I have a C++ library function for computing PI:

// pi.h:
#ifdef BUILDING_DLL
#define DLL_MACRO __declspec(dllexport)
#else
#define DLL_MACRO __declspec(dllimport)
#endif

namespace Cpp {
  class PI {
  public:
    static double DLL_MACRO compute();
  };
};

// pi.cpp:
#include "pi.h"
#include <cmath>

double
Cpp::PI::compute() {
   // Leibnitz summation formulae:
   double sum = 0.0;
   for(long n = 0; n < 100*1000*1000; n++)
     sum += 4.0*pow(-1.0, n)/(2*n + 1.0);
   return sum;
}

I need to call this function from C#, and I want to use C++/CLI as a "bridge". However this C++ function is somewhat slow. Therefore the C# code calling this function need to get callbacks telling it how far the function has come in %.The C# code might need some state, e.g. a progress bar, to deal with this info.So the callbacks from C++ must enter into a member function on the C# side.

So I introduce:

// piCLI.h: The C++/CLI "bridge" between C# and C++
#include "pi.h"
#pragma once
namespace CLI {
   public ref class PI abstract {
   public:
      double compute() {
        return Cpp::PI::compute();
      }
      virtual void progress(int percentCompleted) = 0;
   };
 };

and

 namespace CSharp
 {
    public class PI : CLI.PI
    {
       public override void progress(int percentCompleted)
       {
          System.Console.WriteLine(percentCompleted + "% completed.");
       }
     }
  }

Now invoking CSharp.PI.compute() works fine :-). It forwards the call to Cpp::PI::compute() as intended.

But how do I get the C++ library to forward progress updates to CSharp.PI.progress() whilst Cpp::PI::compute() is running?

Thanks in advance for any answers!

解决方案

I would take a function pointer/delegate approach as well:

// pi.h:
#pragma once

#ifndef DLL_MACRO
#ifdef BUILDING_DLL
#define DLL_MACRO __declspec(dllexport)
#else
#define DLL_MACRO __declspec(dllimport)
#endif
#endif

namespace Cpp {
    typedef void (__stdcall *ComputeProgressCallback)(int);

    class PI {
    public:
        static double DLL_MACRO compute(ComputeProgressCallback callback);
    };
}

// pi.cpp:
#include "pi.h"
#include <cmath>

double Cpp::PI::compute(Cpp::ComputeProgressCallback callback) {
    double sum = 0.;
    for (long n = 0L; n != 100000000L; ++n) {
        sum += 4. * std::pow(-1., n) / (2L * n + 1.);
        callback(/*impl*/);
    }
    return sum;
}

// piCLI.h: The C++/CLI "bridge" between C# and C++
#pragma once
#include "pi.h"

namespace CLI {
    public delegate void ComputeProgressDelegate(int percentCompleted);

    public ref class PI abstract sealed {
    public:
        static double compute(ComputeProgressDelegate^ callback) {
            using System::IntPtr;
            using System::Runtime::InteropServices::Marshal;

            IntPtr cbPtr = Marshal::GetFunctionPointerForDelegate(callback);
            return Cpp::PI::compute(
                static_cast<Cpp::ComputeProgressCallback>(cbPtr.ToPointer())
            );
        }
    };
}

namespace CSharp {
    public static class PI {
        public static double compute() {
            CLI.PI.compute(
                percentCompleted => System.Console.WriteLine(
                    percentCompleted.ToString() + "% completed."
                )
            );
        }
    }
}

Or, to override an abstract progress method rather than creating a delegate on the C# side:

// piCLI.h: The C++/CLI "bridge" between C# and C++
#pragma once
#include "pi.h"

namespace CLI {
    public ref class PI abstract {
        delegate void ComputeProgressDelegate(int percentCompleted);

    public:
        double compute() {
            using System::IntPtr;
            using System::Runtime::InteropServices::Marshal;

            ComputeProgressDelegate^ callback = gcnew ComputeProgressDelegate(
                this,
                &PI::progress
            );
            IntPtr cbPtr = Marshal::GetFunctionPointerForDelegate(callback);
            return Cpp::PI::compute(
                static_cast<Cpp::ComputeProgressCallback>(cbPtr.ToPointer())
            );
        }

    protected:
        virtual void progress(int percentCompleted) abstract;
    };
}

namespace CSharp {
    public sealed class PI : CLI.PI {
        protected override void progress(int percentCompleted) {
            System.Console.WriteLine(
                percentCompleted.ToString() + "% completed."
            );
        }
    }
}

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