| # Copyright 2015, Tresys Technology, LLC |
| # |
| # This file is part of SETools. |
| # |
| # SETools is free software: you can redistribute it and/or modify |
| # it under the terms of the GNU Lesser General Public License as |
| # published by the Free Software Foundation, either version 2.1 of |
| # the License, or (at your option) any later version. |
| # |
| # SETools is distributed in the hope that it will be useful, |
| # but WITHOUT ANY WARRANTY; without even the implied warranty of |
| # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| # GNU Lesser General Public License for more details. |
| # |
| # You should have received a copy of the GNU Lesser General Public |
| # License along with SETools. If not, see |
| # <http://www.gnu.org/licenses/>. |
| # |
| from weakref import WeakKeyDictionary |
| |
| |
| class DiffResultDescriptor(object): |
| |
| """Descriptor for managing diff results.""" |
| |
| # @properties could be used instead, but there are so |
| # many result attributes, this will keep the code cleaner. |
| |
| def __init__(self, diff_function): |
| self.diff_function = diff_function |
| |
| # use weak references so instances can be |
| # garbage collected, rather than unnecessarily |
| # kept around due to this descriptor. |
| self.instances = WeakKeyDictionary() |
| |
| def __get__(self, obj, objtype=None): |
| if obj is None: |
| return self |
| |
| if self.instances.setdefault(obj, None) is None: |
| diff = getattr(obj, self.diff_function) |
| diff() |
| |
| return self.instances[obj] |
| |
| def __set__(self, obj, value): |
| self.instances[obj] = value |
