Question

我有一个CLR C ++ dll，用于编写静态C ++库。我有以下课程：

#pragma once

#include <windows.h>
#include <sddl.h>

#include <LibEx.h>
using namespace System;
#using <mscorlib.dll>

namespace LIB_WrapperNamespace {

    public ref class LIB_WrapperClass
    {
    public:
        BOOL WINAPI T_LibEx_ConsoleConnect(IN DWORD num1, IN LPWSTR Name)
        {
            return LibEx_ConsoleConnect(num1,Name);
        }
        };
}

在C＃中，我添加了对库的引用

LIB_WrapperNamespace.LIB_WrapperClass myLib = new LIB_WrapperNamespace.LIB_WrapperClass();

现在如何调用此函数，如何将字符串发送到char *？来自C＃：

string myName = "NAME";
myLib.T_LibEx_ConsoleConnect(1,**myName**);

Answer 1

API应该将该参数公开为wchar_t*，因此您需要在C＃中提供指针值。请尝试以下

IntPtr ptr = IntPtr.Zero;
try { 
  ptr = Marshal.StringToCoTaskMemUni("NAME");
  unsafe { 
    myLib.T_LibEx_Consoleconnect(1, (char*)(ptr.ToPointer()));
  }
} finally { 
  if (ptr != IntPtr.Zero) { 
    Marshal.FreeCoTaskMem(ptr);
  }
}

不幸的是，虽然您已经使用原始指针值公开了该方法，但是如果没有unsafe代码，就无法在C＃中使用它。另一种方法是暴露一个过载，它需要string^。这可以在C＃中使用，C ++ / CLI代码可以处理从string^到LPWSTR的编组

BOOL WINAPI T_LibEx_ConsoleConnect(DWORD num1, String^ Name) { 
   IntPtr ip = Marshal::StringToHGlobalUni(Name);
   BOOL ret = T_LibEx_ConsoleConnect(num1, static_cast<LPWSTR>(ip.ToPointer()));
   Marshal::FreeHGlobal(ip);
   return ret;
}

// From C#
myLib.T_LibEx_ConsoleConnect(1, "NAME");

Answer 2

为什么在将封送问题“暴露”给封装器的用户时，构建C ++ \ CLI项目来包装？ C ++ \ CLI的想法是隐藏包装器内的编组故障。您应该为.NET本机声明该函数：

#pragma once

#include <Windows.h>
#include <stdlib.h>
#include <string.h>
#include <msclr\marshal_cppstd.h> 
#include <vector>

namespace ClassLibrary2 {
public ref class Class1
{
public:
    //Expose .NET types to .NET users.
    System::Boolean T_LibEx_ConsoleConnect(System::UInt64 num1, System::String^ Name);
};

}

实现这个包装函数，你在感觉正确时编组，它看起来像这样：

#include "ClassLibrary2.h"

namespace ClassLibrary2 {
System::Boolean Class1::T_LibEx_ConsoleConnect(
    System::UInt64 num1, 
    System::String^ Name)
{
    //Initialize marshaling infrastructure. You can use its instance many times 
    //through out life span of your application.
    msclr::interop::marshal_context^ marshalContext = gcnew msclr::interop::marshal_context();

    //Turn System::String into LPWSTR. Keep in mind that you are now the owner of 
    //memory buffer allocated for unmanagedName. You need to release it somewhere.
    const wchar_t* clsConstChars = marshalContext->marshal_as<const wchar_t*>(Name);
    LPWSTR unmanagedName = const_cast<LPWSTR>(clsConstChars);

    //System::UInt64 num1 will be marshalled to DWORD natively by compiler.
    return LibEx_ConsoleConnect(num1, unmanagedName);
}}

使用来自C＃的char *调用c ++函数

2 个答案: