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# -*- test-case-name: twisted.test.test_persisted -*-
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.
"""
Utility classes for dealing with circular references.
"""
from __future__ import division, absolute_import
from twisted.python import log, reflect
from twisted.python.compat import range, _constructMethod
class NotKnown:
def __init__(self):
self.dependants = []
self.resolved = 0
def addDependant(self, mutableObject, key):
assert not self.resolved
self.dependants.append( (mutableObject, key) )
resolvedObject = None
def resolveDependants(self, newObject):
self.resolved = 1
self.resolvedObject = newObject
for mut, key in self.dependants:
mut[key] = newObject
def __hash__(self):
assert 0, "I am not to be used as a dictionary key."
class _Container(NotKnown):
"""
Helper class to resolve circular references on container objects.
"""
def __init__(self, l, containerType):
"""
@param l: The list of object which may contain some not yet referenced
objects.
@param containerType: A type of container objects (e.g., C{tuple} or
C{set}).
"""
NotKnown.__init__(self)
self.containerType = containerType
self.l = l
self.locs = list(range(len(l)))
for idx in range(len(l)):
if not isinstance(l[idx], NotKnown):
self.locs.remove(idx)
else:
l[idx].addDependant(self, idx)
if not self.locs:
self.resolveDependants(self.containerType(self.l))
def __setitem__(self, n, obj):
"""
Change the value of one contained objects, and resolve references if
all objects have been referenced.
"""
self.l[n] = obj
if not isinstance(obj, NotKnown):
self.locs.remove(n)
if not self.locs:
self.resolveDependants(self.containerType(self.l))
class _Tuple(_Container):
"""
Manage tuple containing circular references. Deprecated: use C{_Container}
instead.
"""
def __init__(self, l):
"""
@param l: The list of object which may contain some not yet referenced
objects.
"""
_Container.__init__(self, l, tuple)
class _InstanceMethod(NotKnown):
def __init__(self, im_name, im_self, im_class):
NotKnown.__init__(self)
self.my_class = im_class
self.name = im_name
# im_self _must_ be a NotKnown
im_self.addDependant(self, 0)
def __call__(self, *args, **kw):
import traceback
log.msg('instance method %s.%s' % (reflect.qual(self.my_class), self.name))
log.msg('being called with %r %r' % (args, kw))
traceback.print_stack(file=log.logfile)
assert 0
def __setitem__(self, n, obj):
assert n == 0, "only zero index allowed"
if not isinstance(obj, NotKnown):
method = _constructMethod(self.my_class, self.name, obj)
self.resolveDependants(method)
class _DictKeyAndValue:
def __init__(self, dict):
self.dict = dict
def __setitem__(self, n, obj):
if n not in (1, 0):
raise RuntimeError("DictKeyAndValue should only ever be called with 0 or 1")
if n: # value
self.value = obj
else:
self.key = obj
if hasattr(self, "key") and hasattr(self, "value"):
self.dict[self.key] = self.value
class _Dereference(NotKnown):
def __init__(self, id):
NotKnown.__init__(self)
self.id = id
from twisted.internet.defer import Deferred
class _Defer(Deferred, NotKnown):
def __init__(self):
Deferred.__init__(self)
NotKnown.__init__(self)
self.pause()
wasset = 0
def __setitem__(self, n, obj):
if self.wasset:
raise RuntimeError('setitem should only be called once, setting %r to %r' % (n, obj))
else:
self.wasset = 1
self.callback(obj)
def addDependant(self, dep, key):
# by the time I'm adding a dependant, I'm *not* adding any more
# callbacks
NotKnown.addDependant(self, dep, key)
self.unpause()
resovd = self.result
self.resolveDependants(resovd)
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