DLL调用和结构转换 [英] DLL call and structure conversion

问题描述

调用导入的DLL函数所需的帮助

Help needed in calling imported DLL function

[DllImport("ABC.DLL")
public static extern uint Func(IntPtr pOutput, IntPtr pNum);

[StructLayout(LayoutKind.Sequential, CharSet=CharSet.Ansi)]
public struct MyStruct
{
  [MarshalAs(UnmanagedType.ByValArray, SizeConst=16)]
  public byte[] ID;
  [MarshalAs(UnmanagedType.LPStr)]
  public string Path;
  public IntPtr AnotherStruct;
  ...
}
[StructLayout(LayoutKind.Sequential, CharSet=CharSet.Ansi)]
public struct AnotherStruct
{
  public ushort FormatType;
  public ushort FormatIndex;
}

// calling imported function...
MyStruct Arr=new MyStruct[16];
AnotherStruct FormatArr=new AnotherStruct[16];

IntPtr pArr=Marshal.AllocHGlobal(Marshal.SizeOf(typeof(MyStruct))*16);

for(int i=0; i<16; i++) // allocate memory for AnotherStruct
Arr[i].AnotherSruct=Marshal.AllocHGlobal(Marshal.Sizeof(AnotherStruct[i]));

int iCount=0; IntPtr pCount=new IntPtr(iCount);
if(Func(out pArr, out pCount)!=0) return false;

return true;
}

Func()返回true，但pArr内容保持不变.
我在结构转换或内存分配上做错了吗?

感谢您的任何建议.
C ++代码如下...

Func() return true, but the pArr contents remain intact.
Did I do wrong in the structure conversion or memory allocation?

Thanks for any suggestions.
The C++ codes is as follow...

Func(MyStruct** pStruct, unsigned int* pNum);

struct MyStruct
{
  unsigned char ID[16];
  unsigned int* pPath;
  AnotherStruct* pFormat;
}
struct AnotherStruct
{
  unsigned int FormatType;
  unsigned int FormatIndex;
}

推荐答案

您不能在C#中直接使用指针符号.如果要返回指针，则以 System.IntPtr 类型捕获地址.

遵循的步骤
1.首先，使用Marshal.AllocHGlobal()在非托管区域中分配一个内存，以从托管代码中复制结构.
2.使用Marshal.Copy()复制结构.

请参考MSDN上的一些示例，或者看看 .NET Interop Revisited. [ ^ ]

You can not directly use pointer notation in C#. If you are returning a pointer then catch the address in System.IntPtr type.

Steps to Follow
1. First allocate a memory in unmanaged area to copy the structure from managed code, using Marshal.AllocHGlobal().
2. Copy the structure using Marshal.Copy().

Refer some examples on MSDN or else have a look at .NET Interop Revisited.[^]

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