Marshall字符**从字符串问题从托管代码调用非托管代码 [英] Marshall char** to string problem calling unmanaged code from managed code

问题描述

我有这个C ++函式，

  bool MyClass :: my_function（int num，TCHAR ** filepath）
  

我已将函数公开为

  externC
 {
 __declspec（dllexport）bool MyFunction（int num，char * filepath []）
 {
 OutputDebugStringA（ -MyFunction--）; 
 TCHAR ** w_filepath =（TCHAR **）calloc（num，2 * sizeof（TCHAR **））; 
 for（int i = 0; i  {
 OutputDebugStringA（filepath [i]）; 
 int len = strlen（filepath [i]）+ 1; 
 w_filepath [i] =（TCHAR *）calloc（1，len）; 
 ctow（w_filepath [i]，filepath [i]）; // converted char to WCHAR 
} 
 
 bool ret = MyClass.my_function（num，w_filepath）; 
 OutputDebugStringA（End  -  MyFunction  - ）; 
 free（w_filepath）; 
 return ret; 
} 
} 
  

我有C＃封装为

  [DllImport（MyDll.dll）] 
 public static extern bool MyFunction（int num，[MarshalAs（UnmanagedType.LPArray，ArraySubType = UnmanagedType.LPTStr）] string [] filepath）; 
  

在C＃中，我调用Myfunction作为

  string [] filepath = {D：\\samplefile\\abc.txt，D：\\samplefile\\def.txt} 
 MyFunction（2，filepath）
  

在C ++函数中，它只获取文件路径的第一个字符。
例如，从上面调用如果我使用

打印C ++代码

  OutputDebugStringA 
  
 
 
 
只会为第一个和第二个打印D. 
 
 
 
 / p> 
 
 
  [MarshalAs（UnmanagedType.LPArray，ArraySubType = UnmanagedType.LPTStr）] 
  pre> 
 
 
来自c＃wrapper 
我将在
中获取Access违规错误。
 
 
 code> w_filepath [i] =（TCHAR *）calloc（1，len）
  
第二个档案。
 
 
 
请帮助我。
解决方案
 1） code> w_filepath [i] =（TCHAR *）calloc（1，len）;   -  calloc需要大小（以字节为单位），因此应为 w_filepath [i] = （wchar_t *）calloc（1，len * sizeof（wchar_t））;  
 
 
 
 2）c＃中的数据来自wchar_t *不需要转换例程，应该将函数声明更改为
  __ declspec（dllexport）bool MyFunction（int num，wchar_t * filepath []）
  
 
I've this C++ function,
    bool MyClass::my_function(int num, TCHAR** filepath)
I've expose the function as 
    extern "C"
    {
      __declspec(dllexport) bool MyFunction(int num, char* filepath[])
      {
          OutputDebugStringA("--MyFunction--");
          TCHAR **w_filepath = (TCHAR **)calloc(num, 2* sizeof(TCHAR **));
          for(int i = 0; i < num; i++) 
          {
            OutputDebugStringA(filepath[i]);
            int len = strlen(filepath[i]) + 1;
            w_filepath[i] = (TCHAR *)calloc (1, len);
            ctow(w_filepath[i], filepath[i]); // converts char to WCHAR
          }

          bool ret = MyClass.my_function(num, w_filepath);
          OutputDebugStringA("End -- MyFunction --");
          free(w_filepath);
          return ret;
      }
    }
I've C# wrapper as
    [DllImport("MyDll.dll")]
    public static extern bool MyFunction(int num, [MarshalAs(UnmanagedType.LPArray, ArraySubType = UnmanagedType.LPTStr)] string[] filepath);
In C#, i call Myfunction as
    string [] filepath = { "D:\\samplefile\\abc.txt", "D:\\samplefile\\def.txt"}
    MyFunction(2, filepath)
In C++ function, it gets only first character of filepath.
For example, from above call if i print in C++ code using 
    OutputDebugStringA
it prints only D for both first and second.

If i remove 
    [MarshalAs(UnmanagedType.LPArray, ArraySubType = UnmanagedType.LPTStr)]
from c# wrapper
I'll get Access violation error in 
    w_filepath[i] = (TCHAR *)calloc (1, len) 
for second file.

Please help me.
解决方案
1) w_filepath[i] = (TCHAR *)calloc (1, len); - calloc requires size in bytes, so it should be w_filepath[i] = (wchar_t *)calloc (1, len*sizeof(wchar_t));

2) data from c# comes as wchar_t*, so you don't need converting routines at all , and should change function declaration to
__declspec(dllexport) bool MyFunction(int num, wchar_t* filepath[])


                        
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