need help custom marshaling..??

Question

Hi,

i need help about custom marshaling..i have a native DLL..the parameters of the some DLL functions is defined with unsigned char*

for example;

typedef short apiStatus;
    apiStatus __declspec(dllexport) __stdcall DrfGetFirmwareVersion (HANDLE hCom, unsigned char *major,unsigned char *minor, unsigned char ReaderAddr = 0xff); 

the documentation that i have describing the arguments of the function as follows;

Input parameter：

• hCom－Serial port handle
• major－main version No. of firmware program
• minor－subversion No. of firmware program
• ReaderAddr－ reader address, for fixed reader RS485 net application, default value “0XFF”(not applicable for handheld and module)

how can i declare this function into C#..??

Any help at all would be really appreciated

Answer 1

If this DLL is really, really old (back when char was still unsigned) then it could be returning strings. That's pretty unlikely though, just declare them as out byte:

[DllImport("blah.dll")]
private static extern noidea DrfGetFirmwareVersion(IntPtr handle, 
   out byte major, out byte minor, byte address);

Where "noidea" presumably is void or some kind of int error code. Another thing to fret about is the DllImport.CallingConvention property, it could be Cdecl. Use that when you get a MDA warning about a stack imbalance. And don't forget to set your project's Platform Target to x86 or it will bomb on 64-bit operating systems.

Answer 2

i have used overloed for the default parameter(VS2005).i have imported the function as follows;

public class sDrfGetFirmwareVersion
        {
            //apiStatus __declspec(dllexport) __stdcall DrfGetFirmwareVersion (HANDLE hCom, unsigned char *major,unsigned char *minor, unsigned char ReaderAddr = 0xff);

            [DllImport("DrfApiV10.dll", CallingConvention = CallingConvention.StdCall,CharSet=CharSet.Ansi,EntryPoint="DrfGetFirmwareVersion", ExactSpelling=false)]
            public static extern short DrfGetFirmwareVersion(IntPtr hCom, out byte major, out byte minor,byte ReaderAddr);
            public static short DrfGetFirmwareVersion(IntPtr hCom, out byte major,out byte minor)
              {
                  return DrfGetFirmwareVersion(hCom, out major,out minor, 0xff);
              }
        }

can you verify me please ??