# Twisted, the Framework of Your Internet
# Copyright (C) 2001-2002 Matthew W. Lefkowitz
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of version 2.1 of the GNU Lesser General Public
# License as published by the Free Software Foundation.
#
# This library 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 this library; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
#
"""
This is code and support for
"""
# System Imports
import os
# Twisted Imports
from twisted.internet import defer
# Sibling Imports
from twisted.popsicle.repos import DirectoryRepository
from twisted.popsicle.freezer import PersistentReference,ref
class Picklesicle(DirectoryRepository):
"""I am a Repository that uses a directory full of Pickles to save
everything. This is the most naive implementation possible of a popsicle
backend, and useful for reference implementors.
"""
def __init__(self, dirname, persistentClasses):
DirectoryRepository.__init__(self, dirname)
self.persistentClasses = persistentClasses
def persistentLoad(self, pid):
sa, oid = pid.split(":")
if sa == "S": # synchronous reference
return self.loadOID(oid)
else:
return PersistentReference(oid, self, None)
def loadOID(self, oid):
# maintenance note: when implementing future, truly async loadOID
# methods, it may be useful to keep a dictionary around of
# previously-loaded OIDs during recursive loads to make sure that we
# don't send multiple requests to the DB for the same OID in the same
# actual request.
import cPickle
f = open(os.path.join(self.dirname, str(oid)))
up = cPickle.Unpickler(f)
up.persistent_load = self.persistentLoad
obj = up.load()
# cheating...
from twisted.persisted.styles import doUpgrade
doUpgrade()
return defer.succeed(obj)
def persistentID(self, obj):
if isinstance(obj, PersistentReference):
# It's a persistent reference. Does it belong to me?
oid = obj.acquireOID(self)
if oid is None:
# it doesn't belong to me, so just give it back as a pickled
# ref so we can have inter-db links (this really only works for
# flexible DBs... SQL is going to require all refs point to it)
# *possibly* we really want a warning here?
return None
else:
# It either belongs to me now (I acquired it during acquireOID)
# or it belonged to me before.
return "A:"+str(oid)
for pclas in self.persistentClasses:
if isinstance(obj, pclas):
# it's a persistent class
oid = ref(obj).acquireOID(self)
assert oid is not None, "Synchronous foreign database reference!"
if oid != self._savingOID:
return "S:"+str(oid)
def saveOID(self, oid, obj):
import cPickle
f = open(os.path.join(self.dirname, str(oid)), 'wb')
pl = cPickle.Pickler(f)
self._savingOID = oid
pl.persistent_id = self.persistentID
pl.dump(obj)
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