实现c函数和参数指针结构到c#

本文关键字：结构 指针 参数 函数 实现 | 更新日期: 2023-09-27 18:06:24

我有一个关于实现c++ DLL到c#的问题

我的头文件代码如下:

typedef struct{    
 uchar  Command[4];     
 ushort Lc;    
 uchar  DataIn[512];    
 ushort Le;    
}CON_SEND;

typedef struct{    
 ushort LenOut;     
 uchar  DataOut[512];    
 uchar  outA;    
 uchar  outB;    
}CON_RESP;
SDK_C_DLL_API int   Csdk_Cmd(uchar port, CON_SEND * ConSend,CON_RESP * ConResp);
SDK_C_DLL_API int   Csdk_Open(uchar port);

和c#类

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public struct CON_SEND
{
    public byte[] Command;
    public System.UInt16 Lc;
    public byte[] DataIn;
    public System.UInt16 Le;
}

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public struct CON_RESP
{
    public System.UInt16 LenOut;
    public byte[] DataOut;
    public byte outA;
    public byte outB;
}

[DllImport("SDK_C.dll")]
public static extern System.Int16 Csdk_Cmd(System.Byte port, ref CON_SEND ConSend, ref CON_RESP ConResp);
[DllImport("SDK_C.dll")]
public static extern System.Int16 Csdk_Open(System.Byte port);

现在我使用Csdk_Cmd;

if(SDK_C.Csdk_Open(0x00)== 0)
    lblStatus.Text = "Gate 0 is busy";
else
    lblStatus.Text = "You can use Gate 0";

但是当我尝试使用此代码Csdk_Cmd给定的"NotSupportedException"

CON_SEND SendCon = new CON_SEND(); 
 SendCon.Command = new byte[] { 0xE0, 0xA0, 0xC4, 0x72 };
 SendCon.DataIn = new byte[]{0xAA, 0xAB, 0xAC, 0xAD, 0xAE, 0xAF, 0xA0};
 SendCon.Lc = 0x0007;
 SendCon.Le = 0x0000;
CON_RESP RespCon = new CON_RESP();
 RespCon.DataOut = new byte[512];
SDK_C.Csdk_Cmd(0, ref SendCon, ref RespCon); // THIS LINE

实现c函数和参数指针结构到c#

您的结构声明不正确。C代码具有内联字节数组，简单地说，它们与byte[]的默认封送不匹配。修复它的最简单方法是使用MarshalAs(UnmanagedType.ByValArray)。这样的:

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct CON_SEND
{
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 4)]
    public byte[] Command;
    public ushort Lc;
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 512)]
    public byte[] DataIn;
    public ushort Le;
}

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct CON_RESP
{
    public ushort LenOut;
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 512)]
    public byte[] DataOut;
    public byte outA;
    public byte outB;
}

你的函数也有错误的返回值。c# int映射到c# int。所以它们的声明应该是:

[DllImport("SDK_C.dll")]
public static extern int Csdk_Cmd(byte port, ref CON_SEND ConSend, 
    ref CON_RESP ConResp);
[DllImport("SDK_C.dll")]
public static extern int Csdk_Open(byte port);

另一件需要仔细检查的事情是调用约定。上面的c#函数使用默认的Stdcall。你确定C代码也可以吗?由于返回值和函数名之间没有指定任何内容，因此我怀疑函数实际上是Cdecl。在这种情况下，您需要:

[DllImport("SDK_C.dll", CallingConvention = CallingConvention.Cdecl)]
public static extern int Csdk_Cmd(byte port, ref CON_SEND ConSend, 
    ref CON_RESP ConResp);
[DllImport("SDK_C.dll", CallingConvention = CallingConvention.Cdecl)]
public static extern int Csdk_Open(byte port);

这实际上更像是一种猜测，但是您在c++中使用内联(固定)数组声明结构体，因此您也需要告诉c#这样做。你可以设置固定大小的缓冲区:

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public struct CON_SEND
{
   public fixed byte Command[4];
   public System.UInt16 Lc;
   public fixed byte DataIn[512];
   public System.UInt16 Le;
}

警告:此代码需要使用不安全编译，并出现在不安全块中。

或者，您可以考虑更好地为您的结构定义封送属性:

http://www.codeproject.com/Articles/66244/Marshaling-with-C-Chapter-2-Marshaling-Simple-Type

(见@DavidHeffernan，答案如下)

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