/
memoize_store.py
136 lines (106 loc) · 3.61 KB
/
memoize_store.py
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# -*- coding: utf-8 -*-
# Copyright (C) 2008-2011, Luis Pedro Coelho <luis@luispedro.org>
# vim: set ts=4 sts=4 sw=4 expandtab smartindent:
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
'''
memoize_store: a wrapper that never repeats a lookup.
'''
class memoize_store(object):
def __init__(self, base, list_base=False):
'''
'''
self.base = base
self.cache = {}
self.keys = None
self.locks = None
if list_base and hasattr(base, 'list'):
self.keys = set(base.list())
if list_base and hasattr(base, 'listlocks'):
self.locks = set(base.listlocks())
def dump(self, object, outname):
'''
dump(outname, object)
'''
raise NotImplementedError
def can_load(self, name):
'''
can = can_load(name)
'''
if self.keys is not None:
return name in self.keys
if ('can-load', name) not in self.cache:
self.cache['can-load', name] = self.base.can_load(name)
return self.cache['can-load',name]
def load(self, name):
'''
obj = load(name)
Loads the objects. Equivalent to pickle.load(), but a bit smarter at times.
'''
raise NotImplementedError
def remove(self, name):
'''
was_removed = remove(name)
Remove the entry associated with name.
Returns whether any entry was actually removed.
'''
raise NotImplementedError
def cleanup(self, active):
'''
cleanup()
Implement 'cleanup' command
'''
raise NotImplementedError
def getlock(self, name):
return cache_lock(self.base, name, self.locks)
def close(self):
pass
_UNKNOWN, _NOT_LOCKED, _LOCKED = -1,False,True
class cache_lock(object):
'''
cache_lock
Functions:
----------
get(): acquire the lock
release(): release the lock
is_locked(): check lock state
'''
def __init__(self, base, name, locks):
self.base = base.getlock(name)
self.status = _UNKNOWN
if locks is not None:
self.status = (_LOCKED if (name in locks) else _NOT_LOCKED)
def get(self):
'''
lock.get()
'''
raise NotImplementedError
def release(self):
'''
lock.release()
Removes lock
'''
raise NotImplementedError
def is_locked(self):
'''
locked = lock.is_locked()
'''
if self.status == _UNKNOWN:
self.status = (_LOCKED if self.base.is_locked() else _NOT_LOCKED)
return self.status