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