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from ctypes import c_void_p
from django.contrib.gis.geos.error import GEOSException
# Trying to import GDAL libraries, if available. Have to place in
# try/except since this package may be used outside GeoDjango.
try:
from django.contrib.gis import gdal
except ImportError:
# A 'dummy' gdal module.
class GDALInfo(object):
HAS_GDAL = False
gdal = GDALInfo()
# NumPy supported?
try:
import numpy
except ImportError:
numpy = False
class GEOSBase(object):
"""
Base object for GEOS objects that has a pointer access property
that controls access to the underlying C pointer.
"""
# Initially the pointer is NULL.
_ptr = None
# Default allowed pointer type.
ptr_type = c_void_p
# Pointer access property.
def _get_ptr(self):
# Raise an exception if the pointer isn't valid don't
# want to be passing NULL pointers to routines --
# that's very bad.
if self._ptr:
return self._ptr
else:
raise GEOSException('NULL GEOS %s pointer encountered.' % self.__class__.__name__)
def _set_ptr(self, ptr):
# Only allow the pointer to be set with pointers of the
# compatible type or None (NULL).
if ptr is None or isinstance(ptr, self.ptr_type):
self._ptr = ptr
else:
raise TypeError('Incompatible pointer type')
# Property for controlling access to the GEOS object pointers. Using
# this raises an exception when the pointer is NULL, thus preventing
# the C library from attempting to access an invalid memory location.
ptr = property(_get_ptr, _set_ptr)
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