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# Copyright 2015-2016, Tresys Technology, LLC
# Copyright 2018, Chris PeBenito <pebenito@ieee.org>
#
# 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 collections import defaultdict
from .difference import Wrapper
_cond_cache = defaultdict(dict)
def conditional_wrapper_factory(cond):
"""
Wrap type attributes from the specified policy.
This caches results to prevent duplicate wrapper
objects in memory.
"""
try:
return _cond_cache[cond.policy][cond]
except KeyError:
a = ConditionalWrapper(cond)
_cond_cache[cond.policy][cond] = a
return a
class ConditionalWrapper(Wrapper):
"""Wrap conditional policy expressions to allow comparisons by truth table."""
__slots__ = ("truth_table")
def __init__(self, cond):
self.origin = cond
self.truth_table = cond.truth_table()
def __hash__(self):
return hash(self.origin)
def __eq__(self, other):
return self.truth_table == other.truth_table
def __lt__(self, other):
return str(self.origin) < str(other)