调用从C＃到C函数接受来电者分配一个结构数组 [英] Calling from C# to C function which accept a struct array allocated by caller

问题描述

我有以下的C结构

 结构XYZ 
 {
 void *的一个; 
焦炭FN [MAX_FN] 
无符号长升; 
无符号长O; 
}; 
  

和我想打电话从C＃以下功能：

 的externCINT FUNC（INT处理，为int * numEntries，XYZ * xyzTbl）; 
  

在哪里xyzTbl是由主叫方分配的大小numEntires的XYZ数组

我已经定义了下面的C＃结构：

  [StructLayoutAttribute（顺序，字符集=字符集.Ansi）] 
公共结构XYZ 
 {
公共System.IntPtr RVA; 
 [MarshalAsAttribute（UnmanagedType.ByValTStr，SizeConst = 128）] 
公共字符串FN; 
公共UINT升; 
公共UINT O; 
} 
  

和方法：

 函数[DllImport（@xyzdll.dll，CallingConvention = CallingConvention.Cdecl）] 
公共静态外部的Int32 FUNC（的Int32手柄，裁判的Int32 numntries，
 [的MarshalAs（UnmanagedType.LPArray）XYZ [] ARR）; 
  

然后我尝试调用该函数：

  XYZ XYZ =新的XYZ [numEntries] 
为（...）XYZ [I] =新XYZ（）; 
 FUNC（手柄，numEntries，XYZ）; 
  

当然，这是行不通的。有人可以揭示什么我做错了？

解决方案

  [StructLayoutAttribute（顺序，字符集= CharSet.Ansi）] 
公共结构XYZ 
 {
公共System.IntPtr RVA; 
 [MarshalAsAttribute（UnmanagedType.ByValTStr，SizeConst = 128）] 
公共字符串FN; 
公共UINT升; 
公共UINT O; 
} 
  

应该不是那些 UINT 是 ULONG ？ ？此外，MAX_FN为128权

  XYZ XYZ =新的XYZ [numEntries] 
为（...）XYZ [I] =新XYZ（）; 
  

XYZ是值类型（结构），所以在这里第二行是多余的（结构总是被初始化）

 函数[DllImport（@xyzdll.dll，CallingConvention = CallingConvention.Cdecl）] 
公共静态外部的Int32 FUNC（的Int32手柄，裁判的Int32 numntries，
 [的MarshalAs（UnmanagedType.LPArray）XYZ [] ARR）; 
  

[的MarshalAs（UnmanagedType.LPArray）] 是多余的，编译器会看到它是一个结构数组。

I have the following C struct

struct XYZ
{
void            *a;
char            fn[MAX_FN];     
unsigned long   l;          
unsigned long   o;  
};

And I want to call the following function from C#:

extern "C"  int     func(int handle, int *numEntries, XYZ *xyzTbl);

Where xyzTbl is an array of XYZ of size numEntires which is allocated by the caller

I have defined the following C# struct:

[StructLayoutAttribute(Sequential, CharSet = CharSet.Ansi)]
public struct XYZ
{
   public System.IntPtr rva;
   [MarshalAsAttribute(UnmanagedType.ByValTStr, SizeConst = 128)]
   public string fn;
   public uint l;
   public uint o;
}

and a method:

 [DllImport(@"xyzdll.dll", CallingConvention = CallingConvention.Cdecl)]
 public static extern Int32 func(Int32 handle, ref Int32 numntries,
     [MarshalAs(UnmanagedType.LPArray)] XYZ[] arr);

Then I try to call the function :

XYZ xyz = new XYZ[numEntries];
for (...) xyz[i] = new XYZ();
func(handle,numEntries,xyz);

Of course it does not work. Can someone shed light on what I am doing wrong ?

解决方案

[StructLayoutAttribute(Sequential, CharSet = CharSet.Ansi)]
public struct XYZ
{
   public System.IntPtr rva;
   [MarshalAsAttribute(UnmanagedType.ByValTStr, SizeConst = 128)]
   public string fn;
   public uint l;
   public uint o;
}

Shouldn't those uint be ulong ? Also, MAX_FN is 128 right ?

XYZ xyz = new XYZ[numEntries];
for (...) xyz[i] = new XYZ(); 

XYZ is a value type (struct), so the second line here is redundant (structs are always initialized)

 [DllImport(@"xyzdll.dll", CallingConvention = CallingConvention.Cdecl)]
 public static extern Int32 func(Int32 handle, ref Int32 numntries,
 [MarshalAs(UnmanagedType.LPArray)] XYZ[] arr);

[MarshalAs(UnmanagedType.LPArray)] is redundant, the compiler will see it's a struct array.

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