PassThru driver on C# , Help

[pekovbg]

Hello. I try to Make PassThru driver on C# . for example i have exported function :

[DllExport(CallingConvention.StdCall,ExportName = "PassThruReadVersion")]
 public static J2534Err test_version(int deviceId,  ref IntPtr firmwareVersion,  ref IntPtr dllVersion,  ref IntPtr apiVersion)
 {
     firmwareVersion = Marshal.AllocHGlobal(80);
     firmwareVersion = Marshal.StringToHGlobalAnsi(dll_string);

   Marshal.FreeHGlobal(firmwareVersion);
   return J2534Err.STATUS_NOERROR;
 }   

but i have the problem , the application cannot read string from dll . I test with c# Wrapper , but i don't receive random string. Can you help me with this case ?

The Wrapper read code

        [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
        public delegate int PassThruReadVersion(int deviceId, IntPtr firmwareVersion, IntPtr dllVersion, IntPtr apiVersion);
        public PassThruReadVersion ReadVersion;

        public J2534Err ReadVersion(int deviceId, ref string firmwareVersion, ref string dllVersion, ref string apiVersion)
        {
            J2534Err returnValue = J2534Err.ERR_FAILED;
            try
            {
                IntPtr pFirmwareVersion = Marshal.AllocHGlobal(120);
                IntPtr pDllVersion = Marshal.AllocHGlobal(120);
                IntPtr pApiVersion = Marshal.AllocHGlobal(120);

                 returnValue = (J2534Err)m_wrapper.ReadVersion(deviceId, pFirmwareVersion, pDllVersion, pApiVersion);
                if (returnValue == J2534Err.STATUS_NOERROR)
                {
                    firmwareVersion = Marshal.PtrToStringAnsi(pFirmwareVersion);
                    dllVersion = Marshal.PtrToStringAnsi(pDllVersion);
                    apiVersion = Marshal.PtrToStringAnsi(pApiVersion);
                }
               
                Marshal.FreeHGlobal(pFirmwareVersion);
                Marshal.FreeHGlobal(pDllVersion);
                Marshal.FreeHGlobal(pApiVersion);
            }
            catch(Exception er) { Console.WriteLine(er.Message); Console.WriteLine(er.StackTrace); Debug.WriteLine(er.Message); Debug.WriteLine(er.StackTrace); }
            return returnValue;
        }

On c++ work , for example :

PANDAJ2534DLL_API long PTAPI PassThruReadVersion(unsigned long DeviceID, char *pFirmwareVersion, char *pDllVersion, char *pApiVersion) {
	#pragma EXPORT
	//if (!loadedFine) return ERR_DEVICE_NOT_CONNECTED;
	//auto res = LocalReadVersion(DeviceID, pFirmwareVersion, pDllVersion, pApiVersion);

	auto res = STATUS_NOERROR;

	strcpy(pFirmwareVersion,"1.0.0");
	strcpy(pDllVersion, "1.0.0");
	strcpy(pApiVersion, "1.0.0");
        return res;
}

. .

The question is related to:

• DllExport -version:
• Copy-paste from Data tab:

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[3F]

Hello,

remove ref from ref IntPtr that's like over through over here and ... in general your wrapper is too complicated and not safe in case of possible memory leaks; use try/finally for FreeHGlobal etc.

Okay, tl;dr, let's try to look at something related:

play with tests:

• https://github.com/3F/DllExport/blob/master/src/DllExport/assets/NetfxAsset/Basic.cs
• https://github.com/3F/DllExport/blob/master/src/DllExport/UnitedTest/NetfxAssetBasicTest.cs

play with docs (+video):

https://github.com/3F/DllExport/wiki/Examples-Part-2

Let me know if this doesn't help

[pekovbg]

Thanks for the quick reply, I tried it without ref, then I don't get any data at all, with ref I get a random string. Thanks for the additional materials, before writing to you I read them and tried them.