from spin to C , how to translate this address ?

I'm trying to convert the code for the OLED 128 from spin to C.

the function Fxn takes only 3 parameters:
- nb of arg
- command
- first adress of argument

With that it can be called with higher function with several parameter. see code below with function Drawcircle

How can it be translated correctly to C ?
this line cause me some problem :

pri Fxn(argCount,Command,ArgAddress)|index
   SendData(Command)
   index := 0
   repeat argCount
        SendData(long[ArgAddress][index++])                  ''Main Function to communicate with various methods 
    result := ser.CharIn                                    ''associated with the uOLED display


pub DrawCircle(X,Y,R,Co)                             
{{
Description:
draws a circle with center at X,Y with radius R using the specified color
}}
_Ack := Fxn(4,Cmd_gfx_Circle,@X)

pri SendData(Data)                                      ''Send Word variable to the uOLED display 
   ser.char(Data.byte[1])                                           
   ser.char(Data.byte[0])