blob: 11ed1370d581852a5722747437574c2843e5deec [file] [log] [blame]
# copyright 2003-2011 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
# contact --
# This file is part of logilab-common.
# logilab-common is free software: you can redistribute it and/or modify it under
# the terms of the GNU Lesser General Public License as published by the Free
# Software Foundation, either version 2.1 of the License, or (at your option) any
# later version.
# logilab-common is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
# details.
# You should have received a copy of the GNU Lesser General Public License along
# with logilab-common. If not, see <>.
"""Cache module, with a least recently used algorithm for the management of the
deletion of entries.
__docformat__ = "restructuredtext en"
from threading import Lock
from logilab.common.decorators import locked
_marker = object()
class Cache(dict):
"""A dictionary like cache.
len(self._usage) <= self.size
len( <= self.size
def __init__(self, size=100):
""" Warning : Cache.__init__() != dict.__init__().
Constructor does not take any arguments beside size.
assert size >= 0, 'cache size must be >= 0 (0 meaning no caching)'
self.size = size
self._usage = []
self._lock = Lock()
super(Cache, self).__init__()
def _acquire(self):
def _release(self):
def _update_usage(self, key):
if not self._usage:
elif self._usage[-1] != key:
except ValueError:
# we are inserting a new key
# check the size of the dictionary
# and remove the oldest item in the cache
if self.size and len(self._usage) >= self.size:
super(Cache, self).__delitem__(self._usage[0])
del self._usage[0]
pass # key is already the most recently used key
def __getitem__(self, key):
value = super(Cache, self).__getitem__(key)
return value
__getitem__ = locked(_acquire, _release)(__getitem__)
def __setitem__(self, key, item):
# Just make sure that size > 0 before inserting a new item in the cache
if self.size > 0:
super(Cache, self).__setitem__(key, item)
__setitem__ = locked(_acquire, _release)(__setitem__)
def __delitem__(self, key):
super(Cache, self).__delitem__(key)
__delitem__ = locked(_acquire, _release)(__delitem__)
def clear(self):
super(Cache, self).clear()
self._usage = []
clear = locked(_acquire, _release)(clear)
def pop(self, key, default=_marker):
if key in self:
#if default is _marker:
# return super(Cache, self).pop(key)
return super(Cache, self).pop(key, default)
pop = locked(_acquire, _release)(pop)
def popitem(self):
raise NotImplementedError()
def setdefault(self, key, default=None):
raise NotImplementedError()
def update(self, other):
raise NotImplementedError()