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