从C＃调用C ++函数 - 奇怪的参数 [英] Call C++ function in C# from DLL - strange parameters

问题描述

我有一个函数writen在C ++与下一个标题：

I have a function writen in C++ with the next header:

void EncodeFromBufferIN(void* bufferIN,int bufferINSize, unsigned char*  &bufferOUT, int &bufferOUTSize);

我已经编辑了.h和.cpp文件，在C＃中导入DLL：

I've edited the .h and .cpp files like this, to be able calling the function by importing the DLL in C#:

**EncodeFromBufferIN.h**
extern "C" {
     __declspec(dllexport) void EncodeFromBufferIN(void* bufferIN, int bufferINSize, unsigned char*  &bufferOUT, int &bufferOUTSize);
}
**EncodeFromBufferIN.cpp**
extern void EncodeFromBufferIN(void* bufferIN, int bufferINSize, unsigned char*  &bufferOUT, int &bufferOUTSize){
    // stuff to be done
}

但现在我的问题是，我不知道调用C＃中的函数。我已经添加了下面的代码在C＃，但不知道如何传递参数的函数。

But now my problem is that I don't know how to call the function in C#. I've added the next code in C# but not sure how to pass the parameters to the function.

[DllImport("QASEncoder.dll")]
        unsafe public static extern void EncodeFromBufferIN(void* bufferIN, int bufferINSize, out char[] bufferOUT, out int bufferOUTSize);

bufferIN和bufferOUT应该是字符串，但是如果我像这样调用函数：

The bufferIN and bufferOUT should be strings but if I'm calling the function like this:

public string prepareJointsForQAS()
{
   string bufferIN = "0 0 0 0 0";
   char[] bufferOUT;
   int bufferOUTSize;
   EncodeFromBufferIN(bufferIN, bufferIN.Length, bufferOUT, bufferOUTSize);
}

我得到这个错误：最好的重载方法matrch for ...一些无效参数。那么如何传递参数呢？

I get this error: "The best overloaded method matrch for ... has some invalid arguments". So how should the parameters be passed?

推荐答案

Marshalling最适合使用C Style调用。所以最好在你的公共接口上使用
pure C。
如果将本机代码更改为

Marshalling works best with C Style calls. So it is best to use pure C on your public interface. If it is at all feasible to change the native code to

void EncodeFromBufferIN(
    unsigned char* bufferIN, 
    int bufferINSize, 
    unsigned char* bufferOUT,     
    int* bufferOUTSize);

$ b

Then the call in C# can be thus

[DllImport("QASEncoder.dll")]
public static extern void EncodeFromBufferIN(
    String bufferIN, 
    int bufferINSize, 
    StringBuilder bufferOUT, 
    ref int bufferOUTSize);

String inStr = new String(255);
int inSize = 255;
// make an educated estimate for the output size 
// and preallocate in C# (I am guessing 255)
StringBuilder outStr = new StringBuilder(255);
int outSize = 255;

EncodeFromBufferIN(inStr, inSize, outStr, outSize);

<乱。

This way you can avoid memory allocations in unmanaged code which (although feasible) can get messy.

希望这会让你走。

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