1 """

     2  This module is for the miscellaneous GEOS routines, particularly the

     3  ones that return the area, distance, and length.

     4 """

     5 from ctypes import c_int, c_double, POINTER

     6 from django.contrib.gis.geos.libgeos import lgeos, GEOM_PTR

     7 from django.contrib.gis.geos.prototypes.errcheck import check_dbl

     8 

     9 ### ctypes generator function ###

    10 def dbl_from_geom(func, num_geom=1):

    11     """

    12     Argument is a Geometry, return type is double that is passed

    13     in by reference as the last argument.

    14     """

    15     argtypes = [GEOM_PTR for i in xrange(num_geom)]

    16     argtypes += [POINTER(c_double)]

    17     func.argtypes = argtypes

    18     func.restype = c_int # Status code returned

    19     func.errcheck = check_dbl

    20     return func

    21 

    22 ### ctypes prototypes ###

    23 

    24 # Area, distance, and length prototypes.

    25 geos_area = dbl_from_geom(lgeos.GEOSArea)

    26 geos_distance = dbl_from_geom(lgeos.GEOSDistance, num_geom=2)

    27 geos_length = dbl_from_geom(lgeos.GEOSLength)