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# Copyright 2016, Tresys Technology, LLC
# Copyright 2018, Chris PeBenito <pebenito@ieee.org>
#
# SPDX-License-Identifier: LGPL-2.1-only
#
from collections import defaultdict
from typing import NamedTuple, Set
from ..policyrep import Type, TypeAttribute
from .descriptors import DiffResultDescriptor
from .difference import Difference, SymbolWrapper
from .typing import SymbolCache
_typeattr_cache: SymbolCache[TypeAttribute] = defaultdict(dict)
class ModifiedTypeAttribute(NamedTuple):
"""Difference details for a modified type attribute."""
added_types: Set[Type]
removed_types: Set[Type]
matched_types: Set[Type]
def typeattr_wrapper_factory(attr: TypeAttribute) -> SymbolWrapper[TypeAttribute]:
"""
Wrap type attributes from the specified policy.
This caches results to prevent duplicate wrapper
objects in memory.
"""
try:
return _typeattr_cache[attr.policy][attr]
except KeyError:
a = SymbolWrapper(attr)
_typeattr_cache[attr.policy][attr] = a
return a
class TypeAttributesDifference(Difference):
"""Determine the difference in type attributes between two policies."""
added_type_attributes = DiffResultDescriptor("diff_type_attributes")
removed_type_attributes = DiffResultDescriptor("diff_type_attributes")
modified_type_attributes = DiffResultDescriptor("diff_type_attributes")
def diff_type_attributes(self) -> None:
"""Generate the difference in type attributes between the policies."""
self.log.info(
"Generating type attribute differences from {0.left_policy} to {0.right_policy}".
format(self))
self.added_type_attributes, self.removed_type_attributes, matched_attributes = \
self._set_diff(
(SymbolWrapper(r) for r in self.left_policy.typeattributes()),
(SymbolWrapper(r) for r in self.right_policy.typeattributes()))
self.modified_type_attributes = dict()
for left_attribute, right_attribute in matched_attributes:
# Criteria for modified attributes
# 1. change to type set
added_types, removed_types, matched_types = self._set_diff(
(SymbolWrapper(t) for t in left_attribute.expand()),
(SymbolWrapper(t) for t in right_attribute.expand()))
if added_types or removed_types:
self.modified_type_attributes[left_attribute] = ModifiedTypeAttribute(
added_types, removed_types, matched_types)
#
# Internal functions
#
def _reset_diff(self) -> None:
"""Reset diff results on policy changes."""
self.log.debug("Resetting type attribute differences")
self.added_type_attributes = None
self.removed_type_attributes = None
self.modified_type_attributes = None