1 from ctypes import c_void_p

     2 from types import NoneType

     3 from django.contrib.gis.gdal.error import GDALException

     4 

     5 class GDALBase(object):

     6     """

     7     Base object for GDAL objects that has a pointer access property

     8     that controls access to the underlying C pointer.

     9     """

    10     # Initially the pointer is NULL.

    11     _ptr = None

    12 

    13     # Default allowed pointer type.

    14     ptr_type = c_void_p

    15 

    16     # Pointer access property.

    17     def _get_ptr(self):

    18         # Raise an exception if the pointer isn't valid don't

    19         # want to be passing NULL pointers to routines --

    20         # that's very bad.

    21         if self._ptr: return self._ptr

    22         else: raise GDALException('GDAL %s pointer no longer valid.' % self.__class__.__name__)

    23 

    24     def _set_ptr(self, ptr):

    25         # Only allow the pointer to be set with pointers of the

    26         # compatible type or None (NULL).

    27         if isinstance(ptr, int):

    28             self._ptr = self.ptr_type(ptr)

    29         elif isinstance(ptr, (self.ptr_type, NoneType)):

    30             self._ptr = ptr

    31         else:

    32             raise TypeError('Incompatible pointer type')

    33 

    34     ptr = property(_get_ptr, _set_ptr)

    35