81 lines
2.5 KiB
Python
81 lines
2.5 KiB
Python
from datetime import timedelta
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import weakref
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from collections import OrderedDict
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from six.moves import _thread
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class _TzSingleton(type):
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def __init__(cls, *args, **kwargs):
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cls.__instance = None
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super(_TzSingleton, cls).__init__(*args, **kwargs)
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def __call__(cls):
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if cls.__instance is None:
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cls.__instance = super(_TzSingleton, cls).__call__()
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return cls.__instance
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class _TzFactory(type):
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def instance(cls, *args, **kwargs):
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"""Alternate constructor that returns a fresh instance"""
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return type.__call__(cls, *args, **kwargs)
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class _TzOffsetFactory(_TzFactory):
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def __init__(cls, *args, **kwargs):
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cls.__instances = weakref.WeakValueDictionary()
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cls.__strong_cache = OrderedDict()
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cls.__strong_cache_size = 8
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cls._cache_lock = _thread.allocate_lock()
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def __call__(cls, name, offset):
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if isinstance(offset, timedelta):
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key = (name, offset.total_seconds())
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else:
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key = (name, offset)
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instance = cls.__instances.get(key, None)
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if instance is None:
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instance = cls.__instances.setdefault(key,
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cls.instance(name, offset))
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# This lock may not be necessary in Python 3. See GH issue #901
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with cls._cache_lock:
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cls.__strong_cache[key] = cls.__strong_cache.pop(key, instance)
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# Remove an item if the strong cache is overpopulated
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if len(cls.__strong_cache) > cls.__strong_cache_size:
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cls.__strong_cache.popitem(last=False)
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return instance
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class _TzStrFactory(_TzFactory):
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def __init__(cls, *args, **kwargs):
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cls.__instances = weakref.WeakValueDictionary()
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cls.__strong_cache = OrderedDict()
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cls.__strong_cache_size = 8
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cls.__cache_lock = _thread.allocate_lock()
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def __call__(cls, s, posix_offset=False):
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key = (s, posix_offset)
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instance = cls.__instances.get(key, None)
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if instance is None:
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instance = cls.__instances.setdefault(key,
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cls.instance(s, posix_offset))
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# This lock may not be necessary in Python 3. See GH issue #901
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with cls.__cache_lock:
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cls.__strong_cache[key] = cls.__strong_cache.pop(key, instance)
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# Remove an item if the strong cache is overpopulated
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if len(cls.__strong_cache) > cls.__strong_cache_size:
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cls.__strong_cache.popitem(last=False)
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return instance
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