编组float数组到C＃ [英] Marshalling float Array to c#

问题描述

我试图封送包含一个C浮子阵列++ DLL到C＃中的结构

I'm trying to marshal a struct that contains a float-Array from a C++ DLL to C#.

我创建从下面的代码的C ++ DLL：

I created the C++ DLL from the following code:

//MarshalTest.h
namespace mTest{

    typedef struct {

        float data[3];
        int otherStuff;

    } dataStruct;

    extern "C" __declspec(dllexport) dataStruct getData();
}

//MarshalTest.cpp
#include "MarshallTest.h"

using namespace std;

namespace mTest{
    dataStruct getData(){
        dataStruct d = {{ 16, 2, 77 }, 5};
        return d;
    }
}

我用下面的代码，以使的getData - 功能在C＃中可用：

I use the following code to make the getData-Function available in C#:

public unsafe struct dataStruct{
    public fixed byte data[3];
    public int otherStuff;

    public unsafe float[] Data{
        get{
            fixed (byte* ptr = data){
                IntPtr ptr2 = (IntPtr)ptr;
                float[] array = new float[3];

                Marshal.Copy(ptr2, array, 0, 3);
                return array;
            }
        }

        set{
            fixed (byte* ptr = data){
                //not needed
            }
        }
    }
}

[DllImport("MarshallTest", CallingConvention = CallingConvention.Cdecl)]
private static extern dataStruct getData ();

在打印数据[]在C＃中我得到以下的输出：
1.175494E-38
1.610935E-32
8.255635E-20

When printing data[] in C# I get the following output: 1.175494E-38 1.610935E-32 8.255635E-20

我在做什么错了？

推荐答案

您必须使用正确的类型：

You must use the right type:

public unsafe struct dataStruct2
{
    public fixed float data[3];
    public int otherStuff;

    public unsafe float[] Data
    {
        get
        {
            fixed (float* ptr = data)
            {
                float[] array = new float[3];

                Marshal.Copy((IntPtr)ptr, array, 0, 3);
                return array;
            }
        }
    }
}

请注意对于一小阵，你甚至可以用：

Note that for a small array, you can even use:

public struct dataStruct
{
    public float data1;
    public float data2;
    public float data3;
    public int otherStuff;

    public float[] Data
    {
        get
        {
            return new[] { data1, data2, data3 };
        }
    }
}

不使用不安全的代码。

without using unsafe code.

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