from ctypes import c_void_p class CPointerBase: """ Base class for objects that have a pointer access property that controls access to the underlying C pointer. """ _ptr = None # Initially the pointer is NULL. ptr_type = c_void_p destructor = None null_ptr_exception_class = AttributeError @property def ptr(self): # Raise an exception if the pointer isn't valid so that NULL pointers # aren't passed to routines -- that's very bad. if self._ptr: return self._ptr raise self.null_ptr_exception_class( "NULL %s pointer encountered." % self.__class__.__name__ ) @ptr.setter def ptr(self, ptr): # Only allow the pointer to be set with pointers of the compatible # type or None (NULL). if not (ptr is None or isinstance(ptr, self.ptr_type)): raise TypeError("Incompatible pointer type: %s." % type(ptr)) self._ptr = ptr def __del__(self): """ Free the memory used by the C++ object. """ if self.destructor and self._ptr: try: self.destructor(self.ptr) except (AttributeError, ImportError, TypeError): pass # Some part might already have been garbage collected