95 lines
2.8 KiB
Python
95 lines
2.8 KiB
Python
# urllib3/_collections.py
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# Copyright 2008-2013 Andrey Petrov and contributors (see CONTRIBUTORS.txt)
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#
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# This module is part of urllib3 and is released under
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# the MIT License: http://www.opensource.org/licenses/mit-license.php
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from collections import MutableMapping
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from threading import Lock
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try: # Python 2.7+
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from collections import OrderedDict
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except ImportError:
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from .packages.ordered_dict import OrderedDict
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__all__ = ['RecentlyUsedContainer']
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_Null = object()
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class RecentlyUsedContainer(MutableMapping):
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"""
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Provides a thread-safe dict-like container which maintains up to
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``maxsize`` keys while throwing away the least-recently-used keys beyond
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``maxsize``.
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:param maxsize:
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Maximum number of recent elements to retain.
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:param dispose_func:
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Every time an item is evicted from the container,
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``dispose_func(value)`` is called. Callback which will get called
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"""
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ContainerCls = OrderedDict
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def __init__(self, maxsize=10, dispose_func=None):
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self._maxsize = maxsize
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self.dispose_func = dispose_func
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self._container = self.ContainerCls()
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self._lock = Lock()
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def __getitem__(self, key):
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# Re-insert the item, moving it to the end of the eviction line.
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with self._lock:
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item = self._container.pop(key)
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self._container[key] = item
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return item
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def __setitem__(self, key, value):
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evicted_value = _Null
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with self._lock:
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# Possibly evict the existing value of 'key'
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evicted_value = self._container.get(key, _Null)
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self._container[key] = value
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# If we didn't evict an existing value, we might have to evict the
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# least recently used item from the beginning of the container.
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if len(self._container) > self._maxsize:
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_key, evicted_value = self._container.popitem(last=False)
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if self.dispose_func and evicted_value is not _Null:
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self.dispose_func(evicted_value)
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def __delitem__(self, key):
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with self._lock:
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value = self._container.pop(key)
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if self.dispose_func:
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self.dispose_func(value)
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def __len__(self):
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with self._lock:
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return len(self._container)
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def __iter__(self):
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raise NotImplementedError('Iteration over this class is unlikely to be threadsafe.')
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def clear(self):
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with self._lock:
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# Copy pointers to all values, then wipe the mapping
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# under Python 2, this copies the list of values twice :-|
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values = list(self._container.values())
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self._container.clear()
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if self.dispose_func:
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for value in values:
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self.dispose_func(value)
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def keys(self):
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with self._lock:
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return self._container.keys()
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