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# Copyright 2011 OpenStack Foundation.
# All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
"""Local storage of variables using weak references"""
import threading
import weakref
class WeakLocal(threading.local):
def __getattribute__(self, attr):
rval = super(WeakLocal, self).__getattribute__(attr)
if rval:
# NOTE(mikal): this bit is confusing. What is stored is a weak
# reference, not the value itself. We therefore need to lookup
# the weak reference and return the inner value here.
rval = rval()
return rval
def __setattr__(self, attr, value):
value = weakref.ref(value)
return super(WeakLocal, self).__setattr__(attr, value)
# NOTE(mikal): the name "store" should be deprecated in the future
store = WeakLocal()
# A "weak" store uses weak references and allows an object to fall out of scope
# when it falls out of scope in the code that uses the thread local storage. A
# "strong" store will hold a reference to the object so that it never falls out
# of scope.
weak_store = WeakLocal()
strong_store = threading.local()
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