如何将浮点数组指针从C ++ / CLI传递给IntPtr到C＃

问题描述：

大家好，

我已经将mfc vs6应用程序转换为vs2010。

我的愿望是将托管代码用于非托管c ++应用程序。我在属性页面上激活了CLI扩展功能。

现在来询问我想询问你的输入：

在非托管代码中，我有一个：

Hello Everybody,

I have converted a mfc vs6 application to vs2010.

My wish is to use managed code into a unmanaged c++ application. I have activated on the property page, the CLI extension feature.

Now come the query I would like to ask your inputs about:

In the unmanaged code, I have a:

void UnmanagedFunction()
{
   float* pfValues = (float*) malloc(20 * sizeof(float));

   pfValues[0..19] = random value.

   CNetHelper^ Helper = gcnew CNetHelper();

   int iSize = Marshal.SizeOf(typeof(float)) * 20;

   IntPtr ptrValues = = Marshal.AllocHGlobal(iSize);

   Marshal.Copy(pfValues, 0, ptrValues , 20);

   Helper->HelpMethod(ptrValues);

   Marshal.FreeHGlobal(ptrValues); 

}

in c＃

in c#

public class CNetHelper
{
  public void HelpMethod(IntPtr ptrValues)
  {
   // retrieve the samples
   // I will mange it via Block.Copy
  }
}

The problem:
pfValues cannot be converted from float* to float[]
How should I proceed to copy the float array via pfValues into IntPtr to pass it then to csharp method ?

非常感谢您提前。

祝你好运。

MiQi 。

Thank you very much in advance.
Best regards.
MiQi.

答

没有理由做这样的代码。在C＃端使用float []，在C ++ / CLI中可以直接调用该方法。类似于：

C＃side：

There are no reason to do such code as that. On C# side use float[] and in C++/CLI you can call directly that method. Something like:

C# side:

public class CNetHelper
{
  public void HelpMethod(float[] values)
  {
   // You work there as you always do in C#
  }
}

C ++ / CLI方面：

C++/CLI side:

void CppCliFunction()
{
   cli::array<float> ^values = gcnew cli::array<float>(20);

   // Fill array with random values...
   for (int i = 0; i != values->Length; ++i)
   {
      values[i] = random value.
   }

   CNetHelper^ Helper = gcnew CNetHelper();
 
   Helper->HelpMethod(values);
}

有一个不太明显的解决方案...

在C＃程序中，将其添加为另一个帮助方法：

Well there is one not-so-obvious solution...

In the C# program, add this as another "help method":

public unsafe float[] GetFloatArray(float* floats, int count)
{
    float[] retVal = new float[count];

    for (int i = 0; i < count; i++)
    {
        retVal[i++] = *floats;
        floats++;
    }

    return retVal;
}

它不明显，因为大多数人都没有意识到.NET很适合使用指针类型就像C ++一样。您必须使用unsafe标志设置编译程序（Properties-> Build->允许不安全的代码，或/或命令行中的/ unsafe）。

现在我还没有尝试过上面的代码所以你可能需要做一些调整，但是概念就在那里，你可以从一个浮点指针和浮点数组的长度。

Its not obvious because most people don't realize that .NET happily works with pointer types just like C++. You will have to compile the program with the "unsafe" flag set (Properties->Build->Allow unsafe code, or /unsafe from the command line).

Now I haven't tried the above code so there may be tweaks you have to do, but the concept is there, you can convert from a floating point pointer and a length to a float array.

如何将浮点数组指针从C ++ / CLI传递给IntPtr到C＃

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