711301abb3
To make the further integration into IaaS OSS (OpenStack and CloudStack) easier, we switch to Apache 2.0 license. ryu/app/wsapi.py is still under GPL3 or later. We replace it later. Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
49 lines
1.8 KiB
Python
49 lines
1.8 KiB
Python
# Copyright (C) 2012 Isaku Yamahata <yamahata at valinux co jp>
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain 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,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
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# implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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# This is mixin class to track instances of a given class
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#
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# http://docs.python.org/faq/programming.html#how-do-i-get-a-list-of-all-instances-of-a-given-class
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# How do I get a list of all instances of a given class?
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# Python does not keep track of all instances of a class (or of a
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# built-in type). You can program the class's constructor to keep
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# track of all instances by keeping a list of weak references to each
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# instance.
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from collections import defaultdict
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# Although WeakSet can be used directory, WeakValueDictionary is used instead
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# for python 2.6 which is used by REHL6 because WeakSet is supported by
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# python 2.7+.
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# Correspondence:
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# wvd = WeakValueDictionary() ws = WeakSet()
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# wvd[id(value)] = value ws = value
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# wvd.values() ws: iterator
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from weakref import WeakValueDictionary
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class TrackInstances(object):
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# weak reference is needed in order to make instances freeable by avoiding
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# refrence count. Otherwise, instances will never be freed.
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__refs__ = defaultdict(WeakValueDictionary)
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def __init__(self):
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self.__refs__[self.__class__][id(self)] = self
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@classmethod
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def all_instances(cls):
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return cls.__refs__[cls].values()
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