ctypes wrapper example

test_ctypes.py

import ctypes

"""
The Coord struct in C-land
typedef struct
{
  double lon,lat;
  double area;   
} Coord;
The Config struct in C-land
typedef struct
{
  char *pftpar_filename;
  char *soilpar_filename;
  char *coord_filename;
  char *soil_filename;
  char *temp_filename;
  char *prec_filename;
  char *cloud_filename;
  char *wet_filename;
  char *co2_filename;
  char *restart_filename;
  char *write_restart_filename;
  char **out_filename;
  int ngridcell,startgrid,nspinup,lastyear,totalgridcell,firstyear;
  int n_out;
  int seed;
  Coord resolution;
} Config;"""

class COORD ( ctypes.Structure ):
	_fields = [ ("lon",ctypes.c_double),\
		    ("lat", ctypes.c_double),\
		    ("area", ctypes.c_double)]
coords = COORD()
class CONFIG( ctypes.Structure ):
	_fields = [ ("pftpar_filename", ctypes.c_char_p),\
		    ("soilpar_filename", ctypes.c_char_p),\
       		    ("coord_filename", ctypes.c_char_p),\
		    ("soil_filename", ctypes.c_char_p),\
		    ("temp_filename", ctypes.c_char_p),\
		    ("prec_filename", ctypes.c_char_p),\
		    ("cloud_filename", ctypes.c_char_p),\
		    ("wet_filename", ctypes.c_char_p),\
		    ("co2_filename", ctypes.c_char_p),\
		    ("restart_filename", ctypes.c_char_p),\
		    ("write_restart_filename", ctypes.c_char_p),\
		    ("out_filename", ctypes.POINTER(ctypes.c_char_p)),\
		    ("ngridcell", ctypes.c_int),\
		    ("startgrid", ctypes.c_int),\
		    ("nspinup", ctypes.c_int),\
		    ("lastyear", ctypes.c_int),\
		    ("totalgridcell", ctypes.c_int),\
		    ("firstyear", ctypes.c_int),\
		    ("n_out", ctypes.c_int),\
		    ("seed", ctypes.c_int),\
		    ("resolution", COORD )   ]

lpj = ctypes.CDLL("./liblpj.so.1")
fscanconfig = lpj['fscanconfig']

fscanconfig.argtypes = [ctypes.POINTER( CONFIG), ctypes.POINTER(ctypes.c_int),\
			ctypes.POINTER(ctypes.c_char_p)]
fscanconfig.restype = ctypes.c_int


config = CONFIG()
argc = ctypes.c_int(4)
myargv = ctypes.c_char_p *4
argv = myargv("One","Two","Three","Four") # the 1st argv is the program name
Argv = ctypes.pointer ( argv )
urg = fscanconfig ( ctypes.byref(config), ctypes.byref(argc), ctypes.byref(Argv) )