52 lines
1.6 KiB
Python
52 lines
1.6 KiB
Python
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)
|