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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

C struct and use C dll in C#

everyone, I'm newbie in C#, and I have a problem with using "C" dll in C#, below is the C side code which work fine.
// myCode.h
typedef struct _SubABC
{
unsigned short WordCount;
unsigned char *WordData;
unsigned char SpeedUp;
} SubABC;
typedef struct _ABC
{
unsigned char SubFontNum;
SubABC subABC[5];
} ABC
extern __declspec(dllimport) int __stdcall MY_SetSth(unsigned char SerialNum, ABC *pABC);
//myCode.c
ABC myFun = { '\0' };
unsigned char text_c[] =
{
0x00,0x27,0xff,0xA5,0xC3, 0x00,0x27,0xff,0xA6,0x26, 0x00,0x23,0xff,0xA7,0xAE, 0x00,0x27,0xff,0xBA,0x7E,
0x00,0x27,0xff,0xC1,0x52, 0x00,0x27,0xff,0xAC,0xF9, 0x00,0x27,0xff,0x20,0x00,0x27,0xff,0x31, 0x00,0x27,0xff,0x20, 0x00,0x27,0xff,0xA4,0xC0, 0x00,0x27,0xff,0xC4,0xC1,
};
myFun.SubFontNum = 1;
myFun.subMABC[0].WordCount = sizeof(text_c);
myFun.subMABC[0].WordData = text_c;
myFun.subMABC[0].SpeedUp = 0;
int retvalue = MY_SetSth(1, &myFun);
and my C# code is below
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct SubABC
{
public ushort WordCount;
[MarshalAs(UnmanagedType.LPArray)]
public byte[] WordData;
public byte SpeedUp;
}
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct ABC
{
public byte SubFontNum;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 5)]
public SubABC[] subABC;
}
[DllImport("myDLL.dll", CharSet = CharSet.Ansi)]
public extern static int MY_SetSth(byte SerialNum, ref ABC pABC);
ABC myFun = new ABC();
ABC.subABC = new SubABC[5];
unsigned char text_c[] =
{
0x00,0x27,0xff,0xA5,0xC3, 0x00,0x27,0xff,0xA6,0x26, 0x00,0x23,0xff,0xA7,0xAE, 0x00,0x27,0xff,0xBA,0x7E,
0x00,0x27,0xff,0xC1,0x52, 0x00,0x27,0xff,0xAC,0xF9, 0x00,0x27,0xff,0x20,0x00,0x27,0xff,0x31, 0x00,0x27,0xff,0x20, 0x00,0x27,0xff,0xA4,0xC0, 0x00,0x27,0xff,0xC4,0xC1,
};
myFun.SubFontNum = 1;
myFun.subMABC[0].WordCount = (ushort)text_c.Length;
myFun.subMABC[0].WordData = text_c;
myFun.subMABC[0].SpeedUp = 0;
int retvalue = MY_SetSth(1, ref myFun);
I always get TypeLoadException: Cannot marshal field 'WordData' of type 'subABC': Invalid managed/unmanaged type combination (Array fields must be paired with ByValArray or SafeArray), because WordData is unknown size, I can't use ByValArray, and SafeArray get AccessViolationException: Attempted to read or write protected memory
I try to use IntPtr like below
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct SubABC
{
public ushort WordCount;
public IntPtr WordData;
public byte SpeedUp;
}
ABC.subABC[0].WordData = Marshal.AllocHGlobal(text_c.Length); ;
Marshal.Copy(text_c, 0, ABC.subABC[0].WordData, text_c.Length);
int retvalue = MY_SetSth(1, ref myFun);
I get error message AccessViolationException: Attempted to read or write protected memory
Can anyone help me? thank a lot.

C# P/Invoke 2 dimensional array

I am trying to call a C function from C# code:
typedef char IPTriggerNameType[256];
typedef unsigned long COMM_HANDLE;
typedef BYTE GUID_TYPE[16];
typedef long LONGINT;
typedef struct {
GUID_TYPE Guid;
IPTriggerNameType Name;
}IPCAM_GENERIC_EVENT_ID;
typedef struct {
IPCAM_GENERIC_EVENT_ID EventId;
LONGINT RelatedTriggerId;
LONGINT ObsoleteEvent;
}IPCAM_GENERIC_EVENT_INFO;
typedef struct
{
LONGINT NumOfEvents;
IPCAM_GENERIC_EVENT_INFO *GenericEventsList;
}VID_CHANNEL_GENERIC_EVENTS_STRUCT;
int __stdcall GetGenericEvents(
/* Inputs: */
COMM_HANDLE Handle,
LONGINT MaxNumOfChannelsInTable,
LONGINT MaxNumOfEventsPerChannel,
/* Outputs: */
LONGINT *NumOfChannels,
VID_CHANNEL_GENERIC_EVENTS_STRUCT *ChannelsEventsTable);
and the C# equivalent is as follows:
[StructLayout(LayoutKind.Sequential)]
public struct IPCAM_GENERIC_EVENT_ID
{
[MarshalAs(UnmanagedType.LPArray, SizeConst = 16)]
public byte[] Guid;
[MarshalAs(UnmanagedType.LPArray, SizeConst = 256)]
public char[] Name;
};
[StructLayout(LayoutKind.Sequential)]
public struct IPCAM_GENERIC_EVENT_INFO
{
public IPCAM_GENERIC_EVENT_ID EventId;
public int RelatedTriggerId;
public int ObsoleteEvent;
}
[StructLayout(LayoutKind.Sequential)]
public struct VID_CHANNEL_GENERIC_EVENTS_STRUCT
{
public int NumOfEvents;
[MarshalAs(UnmanagedType.LPArray, SizeConst = 100)]
public IPCAM_GENERIC_EVENT_INFO[] GenericEventsList;
}
[DllImport(dllName)]
public static extern int GetGenericEvents(
/* Inputs: */
int Handle,
int MaxNumOfChannelsInTable,
int MaxNumOfEventsPerChannel,
/* Outputs: */
out int NumOfChannels,
out VID_CHANNEL_GENERIC_EVENTS_STRUCT[] ChannelsEventsTable);
int numOfChannels = 16, actualNumOfChannels = 0;
int maxNumOfEvents = 100;
VID_CHANNEL_GENERIC_EVENTS_STRUCT[] genericEventsList = new VID_CHANNEL_GENERIC_EVENTS_STRUCT[numOfChannels];
for (int i = 0; i < numOfChannels; i++)
{
genericEventsList[i].GenericEventsList = new IPCAM_GENERIC_EVENT_INFO[maxNumOfEvents];
}
GetGenericEvents(conn, numOfChannels, maxNumOfEvents, out actualNumOfChannels, out genericEventsList);
when calling the C# method I get exception which crashes the application:
Managed Debugging Assistant 'FatalExecutionEngineError' has detected a
problem in 'My.exe'.
Additional information: The runtime has encountered a fatal error. The
address of the error was at 0x72a6cf41, on thread 0x5a98. The error
code is 0xc0000005. This error may be a bug in the CLR or in the
unsafe or non-verifiable portions of user code. Common sources of this
bug include user marshaling errors for COM-interop or PInvoke, which
may corrupt the stack.
What am I doing wrong ?

The field:
VID_CHANNEL_GENERIC_EVENTS_STRUCT.GenericEventsList
is a pointer, declared as:
IPCAM_GENERIC_EVENT_INFO *GenericEventsList
But you are declaring it as an array, included in the struct:
[MarshalAs(UnmanagedType.LPArray, SizeConst = 100)]
public IPCAM_GENERIC_EVENT_INFO[] GenericEventsList;
You may try to use an IntPtr and Marshal.AllocHGlobal. Check this out: How use pinvoke for C struct array pointer to C#

consume c# array of structs using c++ unmanaged Dll

as i am new to the unmanaged world, and after a success test of interacting with c++ DLL on a simple task,
i am now trying to consume in c#, data manipulated by c++ via an array of struct
i have also tried to wrap the struct[] within another struct to simplify the marshal but i did not succeed in any way.
what is the correct (and most efficient performance wise) way to handle the data returned from c++ given the code below.
C#
[StructLayout(LayoutKind.Sequential)]
public struct chars
{
public int V;
//[MarshalAsAttribute(UnmanagedType.ByValTStr, SizeConst = 10)]
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 32)]
public char[] testStr;
}
[DllImport("ExportStructArr.dll", CallingConvention = CallingConvention.Cdecl), SuppressUnmanagedCodeSecurity]
public static extern void dodata(int requestedMasterArrLength, int requestedStringSize,[MarshalAs(UnmanagedType.LPArray), Out()] chars[] Cars);
//tried also this signature
public static extern void dodata(
int requestedMasterArrLength,
int requestedStringSize,
out IntPtr chars);
c++
#ifdef EXPORTSTRUCTARR_EXPORTS
#define EXPORTSTRUCTARR_API extern "C" __declspec(dllexport)
typedef struct {
int Id;
char *StrVal;
}Unit;
EXPORTSTRUCTARR_API void dodata(int requestedMasterArrLength,int requestedStringSize, Unit **UntArr)
{
int ccountr,count;
count=0;
*UntArr = (Unit*)LocalAlloc(0, requestedMasterArrLength * sizeof(Unit));
Unit *CurU = *UntArr;
while(count!= requestedMasterArrLength)
{
char dummyStringDataObject[]= "abcdefgHi";
CurU[count].StrVal = NULL;
dummyStringDataObject[0] = count+'0';
CurU[count].Id = count;
CurU[count].StrVal= (char*) LocalAlloc(0,(sizeof(char)* requestedStringSize));
ccountr=0;
while(ccountr!= requestedStringSize){
CurU[count].StrVal[ccountr] = dummyStringDataObject[ccountr];
++ccountr;
}
++count;
}
}

DllImport signature error

I have an DLL file named WD_SDK.dll (it go with an SDK.h file).
I open the SDK.h and I see:
typedef void (CALLBACK * VideoCaptureCB_Ptr)(PVOID pContext, BYTE * apData[3],
VideoSampleInfo_T * pVSI);
typedef struct _VideoSampleInfo_T
{
ULONG idFormat; //
ULONG lSignalState;
int nLen; // not used for raw video data(e.g. YUV420)
int nWidth;
int nHeight;
int anPitchs[3]; // only used for raw video data(e.g. YUV420)
ULONG dwMicrosecsPerFrame; // 1000*1000/FPS
ULONG field;
int iSerial;
} VideoSampleInfo_T;
WD_RegisterVideoPreviewCB(HANDLE hChannel, PVOID pContext, VideoCaptureCB_Ptr pCB);
I want to call the WD_RegisterVideoPreviewCB in C#. So I use the DllImport to declare it in C#. It look like this:
[DllImport("WD_SDK.dll", EntryPoint = "_WD_RegisterVideoPreviewCB#12", ExactSpelling = true)]
static extern int WD_RegisterVideoPreviewCB(IntPtr hChannel, object pContext, VideoCaptureCB_Ptr pCB);
Then I re-declare the C++ struct and CALLBACK in C# like this:
public delegate void VideoCaptureCB_Ptr(IntPtr pContext, byte[] apData, VideoSampleInfo_T pVSI);
[StructLayout(LayoutKind.Sequential)]
public struct VideoSampleInfo_T
{
public uint idFormat;
public uint lSignalState;
public int nLen; // not used for raw video data(e.g. YUV420)
public int nWidth;
public int nHeight;
public int[] anPitchs; // only used for raw video data(e.g. YUV420)
public uint dwMicrosecsPerFrame; // 1000*1000/FPS
public uint field;
public int iSerial;
}
And one delegate implement
public static void HandleVideoStatic(IntPtr pContext, byte[] apData, VideoSampleInfo_T pVSI)
{
}
When i run my code :
WD_RegisterVideoPreviewCB(m_ahChannels[i], m_aMediaHandler[i], HandleVideoStatic);
THe program show me an error does not match the unmanaged target signature.
I thinks encountered problem with the PVOID pContext, I changed it to object pContext. But I have to pass the m_aMediaHandler[i] (It's an instance of a class not a pointer) to it, the error raised " .."invalid agruments"
P/S: The WD_RegisterVideoPreviewCB call in C++
WD_RegisterVideoPreviewCB(m_ahChannels[i], &m_aMediaHandler[i], HandleVideoStatic);