How to pass String BYREF to C function?

Hi there,

 

I have the following example C function that basically take 2 arguments and
"halves the first string" and puts that result in the second argument.

 


int executeUserExit(char *buffer, char **userExitResultBuffer){

   int total_len;

 

   total_len = strlen(buffer) / 2;

   *userExitResultBuffer = (char*) malloc(total_len);

   strncpy(*userExitResultBuffer, buffer, total_len);

   return 0;

}

 

I have call this from C code happily, but am having trouble from Python.

 

I created a DLL from the code above

 


import ctypes as c

import os

 

if __name__ == "__main__":

      if os.name=='nt':            

            userExit = c.cdll.LoadLibrary("libUserExits.dll")

            executeUserExit = userExit.executeUserExit

            executeUserExit.argtypes = [c.c_char_p, c.c_char_p]

            executeUserExit.restype = c.c_int

            stream = c.c_char_p()

            stream.value = "hello world"            

            exitResult = c.c_char_p()

            result = executeUserExit(c.pointer(stream), c.byref(exitResult))

            print result

      

      print "Finished"      

            

 

I am not too sure how the BYREF and POINTER stuff should work in the above
code?

 

I keep getting the error:

 

"ctypes.ArgumentError: argument 1: <type 'exceptions.TypeError'>: wrong
type"

 

I have been reading online but cannot find any nice example to follow, can
someone please give me some advise on this?

 

Your help is greatly appreciated ;-)

 

Lynton

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