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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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