| from ctypes import c_void_p |
| from types import NoneType |
| from django.contrib.gis.gdal.error import GDALException |
| |
| class GDALBase(object): |
| """ |
| Base object for GDAL 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| else: raise GDALException('GDAL %s pointer no longer valid.' % 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 isinstance(ptr, (int, long)): |
| self._ptr = self.ptr_type(ptr) |
| elif isinstance(ptr, (self.ptr_type, NoneType)): |
| self._ptr = ptr |
| else: |
| raise TypeError('Incompatible pointer type') |
| |
| ptr = property(_get_ptr, _set_ptr) |
| |
