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converting c++ API struct to c#

I am trying to convert c++ api example to c#. but I can not find the way of struct pointer in struct by the way struct has string types. Here is c++ structs and functions
struct AuthParam { char server_ip[32]; char username[50]; char password[50]; };
struct CameraInfo { int index; char devicename[100]; char smallrtsp[1000]; char bigrtsp[1000]; };
struct SingleDevice { char deviceid[50]; char devicename[100]; int flag_onuse; int cameralist_size; CameraInfo* cameralist; };
struct DeviceList { int listsize; SingleDevice* singledevicelist; };
typedef int (WINAPI capi_init)(void);
typedef int (WINAPI capi_disabled)(void);
typedef int (WINAPI capi_GetServerTimeCode)(char* server_ip, unsigned int* timecode);
typedef int (WINAPI GetDevicelist)(AuthParam auth_para, DeviceList* devicelist);
and this is my c# code but I can not find the way of defining struct pointer in struct I got "
Error CS0208 Cannot take the address of, get the size of, or declare a pointer to a managed type ('Form1.CameraInfo')" error.
public struct AuthParam
{
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
public string server_ip;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 50)]
public string username;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 50)]
public string password;
};
[StructLayout(LayoutKind.Sequential)]
public struct CameraInfo
{
public int index;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 100)]
public string devicename;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 1000)]
public string smallrtsp;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 1000)]
public string bigrtsp;
};
[StructLayout(LayoutKind.Sequential)]
public struct SingleDevice
{
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 50)]
public string deviceid;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 100)]
public string devicename;
public int flag_onuse;
public int cameralist_size;
public CameraInfo *cameralist;
};
[StructLayout(LayoutKind.Sequential)]
public unsafe struct DeviceList
{
public int listsize;
public SingleDevice *singledevicelist;
};
[DllImport("c:\\lib\\api_client.dll")] public static extern int capi_init();
[DllImport("c:\\lib\\api_client.dll")] public static extern int capi_disabled();
[DllImport("c:\\lib\\api_client.dll")] public static extern int capi_GetServerTimeCode(string ip, ref uint timecode);
[DllImport("c:\\lib\\api_client.dll")] public static extern int GetDevicelist (AuthParam auth_para,ref DeviceList devicelist);
is there any way to achieve this convertion?

i think this error because of the different nature of c++ (un-managed code) and c# (managed code), so maybe using System.IntPtr as a pointer to your camera struct.
please consider this question here, and you can find about P/Invoke Interop Assistant which is an open source tool to convert your code from the un-managed code to a managed C# code. with a small blog article about C++/C# interoperability

How to correctly parse IntPtr to Object in C# when marshaling from C++

I'm invoking a C++ function from within C#.
The function I am trying to invoke returns following C++ struct type result:
LPWFSCIMNOTETYPELIST lpNoteTypeList;
typedef struct _wfs_cim_note_type_list
{
USHORT usNumOfNoteTypes;
LPWFSCIMNOTETYPE *lppNoteTypes;
} WFSCIMNOTETYPELIST, *LPWFSCIMNOTETYPELIST;
typedef struct _wfs_cim_note_type
{
USHORT usNoteID;
CHAR cCurrencyID[3];
ULONG ulValues;
USHORT usRelease;
BOOL bConfigured;
} WFSCIMNOTETYPE, *LPWFSCIMNOTETYPE;
I found the suitable struct in C#:
[StructLayout(LayoutKind.Sequential, Pack = XFSConstants.STRUCTPACKSIZE, CharSet = CharSet.Ansi)]
public unsafe struct WfsCimNoteType
{
public ushort usNoteID;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 3)]
public char[] cCurrencyID;
public uint ulValues;
public ushort usRelease;
public byte bConfigured;
}
[StructLayout(LayoutKind.Sequential, Pack = XFSConstants.STRUCTPACKSIZE, CharSet = CharSet.Ansi)]
public unsafe struct WfsCimNoteTypeList
{
public ushort usNumOfNoteTypes;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 20)]
public WfsCimNoteType[] lppNoteTypes;
}
I used the following code to parse the result from invoked function:
WfsCimNoteTypeList data = new WfsCimNoteTypeList();
XFSUtil.PtrToStructure<WfsCimNoteTypeList>(lpBuffer, ref data);
(here lbBuffer is IntPtr)
XFSUtil.PtrToStructure is defined like this:
public static void PtrToStructure<T>(IntPtr ptr, ref T p) where T : struct
{
p = (T)Marshal.PtrToStructure(ptr, typeof(T));
}
But after parsing from IntPtr to WfsCimNoteType object array, I am getting different values???

Translating C++ DLL into C# - How to translate a struct included in a struct

I have to translate a C++ DLL into C# to use it in a project. Here is the part that causes me trouble. This is the C++ code of the header of the DLL :
struct initiate_rb
{
unsigned char Rem_Add;
unsigned char Features_Supported_1_m;
struct add_addr_param Add_Addr_Param;
};
struct add_addr_param
{
unsigned char D_Type;
unsigned char D_Len;
struct
{
unsigned char Network_Address[6];
unsigned short MAC_Address_Len;
unsigned char * MAC_Address;
} S_Addr;
};
I am not sure how to handle this in C#. Here is what I have achieved so far :
[StructLayout(LayoutKind.Sequential, Pack = 1)]
unsafe struct initiate_rb
{
public byte Rem_Add;
public byte Features_Supported_1_m;
public add_addr_param Add_Addr_Param;
}
[StructLayout(LayoutKind.Sequential, Pack = 1)]
unsafe struct add_addr_param
{
public byte D_Type;
public byte D_Len;
[StructLayout(LayoutKind.Sequential)]
public struct S_Addr
{
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 6)]
public byte[] Network_Address;
public ushort MAC_Address_Len;
public byte* MAC_Address;
};
}
I used Pack = 1 because in my DLL header file there is the line #pragma pack (1)
The problem is, this doesn't work when I have to use this struct. It returns me an error code.
So first, concerning this struct translation, am I doing it right ?
Thanks for helping.

I'm not sure about the attributes but I believe the second struct shoudn't be nested in C# because the one in C++ defines a variable of the struct's type just after the closing parentheses.
[StructLayout(LayoutKind.Sequential, Pack = 1)]
unsafe struct dpc2_add_addr_param
{
public byte D_Type;
public byte D_Len;
public S_Addr S_Addr;
}
[StructLayout(LayoutKind.Sequential)]
public struct S_Addr
{
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 6)]
public byte[] Network_Address;
public ushort MAC_Address_Len;
public byte* MAC_Address;
};

In fact I resolved this problem. The problem was that I was using a constructor for my initiate_rb struct
unsafe struct initiate_rb
{
public byte Rem_Add;
public byte Features_Supported_1_m;
public add_addr_param Add_Addr_Param;
public initiate_rb(int networkAddressLength) : this()
{
Rem_Add = (byte)0;
Features_Supported_1_m = (byte)0;
add_addr_param = new Add_Add_Param(networkAddressLength);
}
}
and this constructor for add_addr_param :
[StructLayout(LayoutKind.Sequential, Pack = 1)]
unsafe struct add_addr_param
{
public byte D_Type;
public byte D_Len;
[StructLayout(LayoutKind.Sequential)]
public struct S_Addr
{
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 6)]
public byte[] Network_Address;
public ushort MAC_Address_Len;
public byte* MAC_Address;
};
public add_addr_param(int networkAddressLength) : this()
{
D_Type = (byte)0;
D_Len = (byte)0;
S_Addr.Network_Address = new byte[6]; //problem with this line
}
}
This was the problem. Since I remove this line, the code was operating correctly. In fact I didn't need constructors since all parameters have to be set to 0.
Thanks for helping!

implement c function and parameter pointer struct to c#?

I Have a problem about implementint of C++ DLL to C#
My Header File code is this :
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);
and my C# class
[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);
now i use Csdk_Cmd; is working no problem this code :
if(SDK_C.Csdk_Open(0x00)== 0)
lblStatus.Text = "Gate 0 is busy";
else
lblStatus.Text = "You can use Gate 0";
but when i try to use this code Csdk_Cmd given "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

Your struct declarations are not correct. The C code has inline byte arrays and simply put, they do not match the default marshalling for byte[]. The easiest way to fix it is to use MarshalAs(UnmanagedType.ByValArray). Like this:
[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;
}
Your functions also have incorrect return value. A C int maps to C# int. So they declarations should be:
[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);
The other thing to double check is the calling convention. The C# function above use the default of Stdcall. Are you sure that the C code also does? Since there is nothing specified between the return value and the function name, I suspect that the functions are actually Cdecl. In which case you need:
[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);

This is more of a guess really, but you are declaring your structs with inline (fixed) arrays in C++, so you'll need to tell c# to to do that too. You can do this with Fixed Size Buffers:
[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;
}
Warning: this code needs to be compiled with unsafe and appear in unsafe block.
Alternatively, you could look into better defining the marshaling attributes for your struct:
http://www.codeproject.com/Articles/66244/Marshaling-with-C-Chapter-2-Marshaling-Simple-Type
(See #DavidHeffernan, answer below)

How use struct with union in c#

Hi I writing a wrapper in c# and i have some problem. I have this struct in c++.
typedef struct pjmedia_format
{
pj_uint32_t id;
pjmedia_type type;
pjmedia_format_detail_type detail_type;
union
{
pjmedia_audio_format_detail aud;
pjmedia_video_format_detail vid;
char user[PJMEDIA_FORMAT_DETAIL_USER_SIZE];
} det;
} pjmedia_format;
This is link to this struct pjmedia_format
in c# I have this:
[StructLayout(LayoutKind.Sequential)]
public struct pjmedia_format
{
public uint id;
public pjmedia_type type;
public pjmedia_format_detail_type detail_type;
public det_t det;
}
[StructLayout(LayoutKind.Explicit)]
public struct det_t
{
[FieldOffset(0)]
[MarshalAs(UnmanagedType.Struct)]
public pjmedia_audio_format_detail aud;
[FieldOffset(36)]
[MarshalAs(UnmanagedType.Struct)]
public pjmedia_video_format_detail vid;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 1)]
[FieldOffset(60)]
public char[] user;
}
[StructLayout(LayoutKind.Sequential)]
public struct pjmedia_audio_format_detail
{
public uint clock_rate;
public uint channel_count;
public uint frame_time_usec;
public uint bits_per_sample;
public int avg_bps;
public int max_bps;
}
[StructLayout(LayoutKind.Sequential)]
public struct pjmedia_video_format_detail
{
public pjmedia_rect_size size;
public pjmedia_ratio fps;
public int avg_bps;
public int max_bps;
}
and when i want to use this struct i get this error
System.Runtime.InteropServices.MarshalDirectiveException was unhandled.
Message="A method signature is not PInvoke compatible with the element."
I try to use some attributes like size or pack but it doesn't help (probably i use it wrong). I tested singly other struct e.g. pjmedia_video_format_detail and they works well. Any advice?
Best regards
Andrzej

As this is a union, shouldn't that be:
[StructLayout(LayoutKind.Explicit)]
public struct det_t
{
[FieldOffset(0)]
[MarshalAs(UnmanagedType.Struct)]
public pjmedia_audio_format_detail aud;
[FieldOffset(0)]
[MarshalAs(UnmanagedType.Struct)]
public pjmedia_video_format_detail vid;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 1)]
[FieldOffset(0)]
public char[] user;
}
i.e. overlapping? Also, you might need user to be a fixed buffer rather than an array.

In the C++ code, det is a union. That means that all the fields have zero offset, they are overlayed. Simply change your C# declaration to match by using [FieldOffset(0)] for all fields in det_t.