CODEWITHSUNDEEP
pythoncdllctypes
Dogdripnet
Dogdripnet

Reputation: 23

Handler Issues Applying cdll in Python

I'm trying to porting some C dll(FANUC FOCAS Library - for CNC) code via Python using ctypes, so I wrote porting code. (as belows), but get a very strange result when loading the DLL and calling the function. In my case, I don't understand using handler in python.

I would like to apply the following c code in python.

Declaration(for c)

#include "fwlib64.h"
FWLIBAPI short WINAPI cnc_allclibhndl3(const char *ipaddr,unsigned short port,
long timeout, unsigned short *FlibHndl);

Example Code(in focas library manual for c)

#include "fwlib64.h"
void example( void )
{
unsigned short h;               
short ret;                           
ODBST buf;                        
ret = cnc_allclibhndl3( "192.168.0.100", 8193, 1, &h ) ; 
//
if ( !ret ) {
        cnc_statinfo( h, &buf ) ;    
        cnc_freelibhndl( h ) ;       
} else {
        printf( "ERROR!(%d)\n", ret ) ;   
}
}

Testfocas.py

from ctypes import *
mylib = cdll.LoadLibrary('./Fwlib64.dll')
class ODBSYS(Structure):
    pass
_fields_ =[
    ("dummy", c_ushort),
    ("max_axis", c_char*2),
    ("cnc_type", c_char*2),
    ("mt_type",c_char*2),
    ("series",c_char*4),
    ("version",c_char*4),
    ("axes",c_char*2),]

h=c_ushort()
pt=pointer(h)
ret=c_short()
buf=ODBSYS()

ret=mylib.cnc_allclibhndl3('192.168.0.100',8193,1,pt)
mylib.cnc_statinfo(h,buf)
mylib.cnc_freelibhndl(h)

I want the function to return 0 or -16 but, in my case the function return is

cnc_allclibhndl3 = 65520 (i guess open port)

cnc_statinfo = -8

cnc_freelibhndl -8

Return Status of Data Window Functions

EW_OK(0)  Normal termination  
EW_SOCKET(-16)  Socket communication error Check the power supply of CNC, Ethernet I/F board, Ethernet connection cable. 
EW_HANDLE(-8)  Allocation of handle number is failed.

I do not know what I was wrong with.

Upvotes: 2

Views: 2089

Answers (1)

Mark Tolonen
Mark Tolonen

Reputation: 177471

CDLL is for __cdecl calling convention. cdll is not recommended for use because it is a shared instance across modules.

WINAPI is defined as __stdcall, so use WinDLL:

mylib = WinDLL.LoadLibrary('./Fwlib64.dll')

Next, define argtypes and restype for your argument and result types for your function:

mylib.cnc_allclibhndl3.argtypes = c_char_p,c_ushort,c_long,POINTER(c_ushort)
mylib.cnc_allclibhndl3.restype = c_short

Finally, pass the output parameter by reference. It is more efficient than creating a pointer:

h = c_ushort()
ret = mylib.cnc_allclibhndl3('192.168.0.100',8193,1,byref(h))

Prototypes for cnc_statinfo and cnc_freelibhndl were not provided. Define argtypes and restype for them as well.

Upvotes: 3

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