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|
"""
Copyright 2008 Benjamin M. Schwartz
DOBject is LGPLv2+
DObject 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 of the License, or
(at your option) any later version.
DObject 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 General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with DObject. If not, see <http://www.gnu.org/licenses/>.
"""
import dbus
import dbus.service
import dbus.gobject_service
import time
import logging
import threading
import thread
import random
from listset import ListSet
import stringtree
import cPickle
import dbus_tools
"""
DObject is a library of components useful for constructing distributed
applications that need to maintain coherent state while communicating over
Telepathy. The DObject tools are design to handle unexpected joins, leaves,
splits, and merges automatically, and always to leave each connected component
of users in a coherent state at quiescence.
"""
def PassFunction(*args,**kargs):
logging.debug("args=%s, kargs=%s" % (str(args),str(kargs)))
pass
def ReturnFunction(x):
return x
class Group:
"""A Group is a simple tool for organizing DObjects. Once it is set up
with a tubebox, the user may simply add objects to it, e.g.
self.group = Group(tb)
...
self.group['mydict1'] = HighScore('No one', 0)
and the group will take care of assigning a handler to the object with
the specified name.
For a Group g, g['a'] is equivalent in almost all ways to g.a, for
programmer convenience.
"""
tubebox = None
_locked = False
_d = None
def __init__(self, tubebox):
self._logger = logging.getLogger('groupthink.Group')
self._logger.debug('new Group')
self.tubebox = tubebox
self._d = dict()
self._history = dict()
self._handlers = dict()
self._locked = True
def __setitem__(self, name, dobj):
self._logger.debug("setitem(%s,%s)" % (name, str(dobj)))
if name in self.__dict__ or name in self._d:
raise #Cannot replace an existing attribute or object
h = dobj.HANDLER_TYPE(name, self.tubebox)
dobj.set_handler(h)
self.add_handler(h, dobj)
def add_handler(self, h, o=None):
"""This function is used to add a handler to the Group _after_ that
handler has already been registered to completion with its object."""
name = h.get_name()
self._handlers[name] = h
if name in self._history:
h.object.add_history(self._history[name])
del self._history[name]
if o is not None:
self._d[name] = o
else:
self._d[name] = h.object
for hc in h.get_copies(): #Recurse through a potential tree of handlers
self.add_handler(hc)
def __setattr__(self, name, val):
if self._locked:
self.__setitem__(name, val)
else:
self.__dict__[name] = val
def __getitem__(self, name):
if name in self._d:
return self._d[name]
else:
return self.__dict__[name]
__getattr__ = __getitem__
def __delattr__(self, name):
raise #Deletion is not supported
def dumps(self):
d = {}
for (name, handler) in self._handlers.iteritems():
d[name] = dbus_tools.undbox(handler.object.get_history())
d.update(self._history) #Include any "unclaimed history" thus far.
return cPickle.dumps(d)
def loads(self, s):
if s:
d = cPickle.loads(s)
for (name,hist) in d.iteritems():
if name in self._d:
handler = self._handlers[name]
handler.object.add_history(hist)
else:
self._history[name] = hist
class TubeBox:
""" A TubeBox is a box that either contains a Tube or does not.
The purpose of a TubeBox is to solve this problem: Activities are not
provided with the sharing Tube until they are shared, but DObjects should
not have to care whether or not they have been shared. That means that the
DObject handler must know whether or not a Tube has been provided. This
could be implemented within the handlers, but then the Activity's sharing
code would have to know a list of all DObject handlers.
Instead, the sharing code just needs to create a TubeBox and pass it to the
code that creates handlers. Once the tube arrives, it can be added to the
TubeBox with insert_tube. The handlers will then be notified automatically.
"""
def __init__(self):
self.tube = None
self.is_initiator = None
self._logger = logging.getLogger()
self._listeners = []
def register_listener(self, L):
"""This method is used by the DObject handlers to add a callback
function that will be called after insert_tube"""
self._listeners.append(L)
if self.tube is not None:
L(self.tube, self.is_initiator)
def insert_tube(self, tube, is_initiator=False):
"""This method is used by the sharing code to provide the tube, once it
is ready, along with a boolean indicating whether or not this computer
is the initiator (who may have special duties, as the first
participant)."""
self._logger.debug("insert_tube, notifying %s" % str(self._listeners))
self.tube = tube
self.is_initiator = is_initiator
for L in self._listeners:
L(tube, is_initiator)
class TimeHandler(dbus.gobject_service.ExportedGObject):
"""A TimeHandler provides a universal clock for a sharing instance. It is a
sort of cheap, decentralized synchronization system. The TimeHandler
determines the offset between local time and group time by sending a
broadcast and accepting the first response, and assuming that both transfer
displays were equal. The initiator's offset is 0.0, but once another group
member has synchronized, the initiator can leave and new members will still
be synchronized correctly. Errors at each synchronization are typically
between 0.1s and 2s.
TimeHandler is not perfectly resilient to disappearances. If the group
splits, and one of the daughter groups does not contain any members that
have had a chance to synchronize, then they will not sync to each other. I
am not yet aware of any sensible synchronization system that avoids this
problem.
"""
IFACE = "org.dobject.TimeHandler"
BASEPATH = "/org/dobject/TimeHandler/"
def __init__(self, name, tube_box, offset=0.0):
self.PATH = TimeHandler.BASEPATH + name
dbus.gobject_service.ExportedGObject.__init__(self)
self._logger = logging.getLogger(self.PATH)
self._tube_box = tube_box
self.tube = None
self.is_initiator = None
self.offset = offset
self._know_offset = False
self._offset_lock = threading.Lock()
self._tube_box.register_listener(self.get_tube)
def get_tube(self, tube, is_initiator):
"""Callback for the TubeBox"""
self._logger.debug("get_tube")
self._logger.debug(str(is_initiator))
self.tube = tube
self.add_to_connection(self.tube, self.PATH)
self.is_initiator = is_initiator
self._know_offset = is_initiator
self.tube.add_signal_receiver(self.tell_time, signal_name='What_time_is_it', dbus_interface=TimeHandler.IFACE, sender_keyword='sender', path=self.PATH)
if not self._know_offset:
self.ask_time()
def time(self):
"""Get the group time"""
return time.time() + self.offset
def get_offset(self):
"""Get the difference between local time and group time"""
self._logger.debug("get_offset " + str(self.offset))
return self.offset
def set_offset(self, offset):
"""Set the difference between local time and group time, and assert that
this is correct"""
self._logger.debug("set_offset " + str(offset))
self._offset_lock.acquire()
self.offset = offset
self._know_offset = True
self._offset_lock.release()
@dbus.service.signal(dbus_interface=IFACE, signature='d')
def What_time_is_it(self, asktime):
return
def ask_time(self):
self._logger.debug("ask_time")
self.What_time_is_it(time.time())
def tell_time(self, asktime, sender=None):
self._logger.debug("tell_time")
start_time = time.time()
try:
my_name = self.tube.get_unique_name()
if sender == my_name:
return
if self._know_offset:
self._logger.debug("telling offset")
remote = self.tube.get_object(sender, self.PATH)
start_time += self.offset
remote.receive_time(asktime, start_time, time.time() + self.offset, reply_handler=PassFunction, error_handler=PassFunction)
finally:
return
@dbus.service.method(dbus_interface=IFACE, in_signature='ddd', out_signature='')
def receive_time(self, asktime, start_time, finish_time):
self._logger.debug("receive_time")
rtime = time.time()
thread.start_new_thread(self._handle_incoming_time, (asktime, start_time, finish_time, rtime))
def _handle_incoming_time(self, ask, start, finish, receive):
self._offset_lock.acquire()
if not self._know_offset:
self.offset = ((start + finish)/2) - ((ask + receive)/2)
self._know_offset = True
self._offset_lock.release()
class UnorderedHandler(dbus.gobject_service.ExportedGObject):
"""The UnorderedHandler serves as the interface between a local UnorderedObject
(a pure python entity) and the d-bus/network system. Each UnorderedObject
is associated with a single Handler, and vice-versa. It is the Handler that
is actually exposed over D-Bus. The purpose of this system is to minimize
the amount of networking code required for each additional UnorderedObject.
"""
IFACE = "org.dobject.Unordered"
BASEPATH = "/org/dobject/Unordered/"
def __init__(self, name, tube_box):
"""To construct a UO, the program must provide a name and a TubeBox.
The name is used to identify the UO; all UO with the same name on the
same Tube should be considered views into the same abstract distributed
object."""
self._myname = name
self.PATH = UnorderedHandler.BASEPATH + name
dbus.gobject_service.ExportedGObject.__init__(self)
self._logger = logging.getLogger(self.PATH)
self._tube_box = tube_box
self.tube = None
self._copies = []
self.object = None
self._tube_box.register_listener(self.set_tube)
def set_tube(self, tube, is_initiator):
self._logger.debug("set_tube(), is_initiator=%s" % str(is_initiator))
"""Callback for the TubeBox"""
self.tube = tube
self.add_to_connection(self.tube, self.PATH)
self.tube.add_signal_receiver(self.receive_message, signal_name='send', dbus_interface=UnorderedHandler.IFACE, sender_keyword='sender', path=self.PATH)
self.tube.add_signal_receiver(self.tell_history, signal_name='ask_history', dbus_interface=UnorderedHandler.IFACE, sender_keyword='sender', path=self.PATH)
# We need watch_participants because of the case in which several groups
# all having made changes, come together and need to update each other.
# There is no easy way to make this process more efficient without
# changing the Unordered interface dramatically to include per-message
# labels of some kind.
self.tube.watch_participants(self.members_changed)
#Alternative implementation of members_changed (not yet working)
#self.tube.add_signal_receiver(self.members_changed, signal_name="MembersChanged", dbus_interface="org.freedesktop.Telepathy.Channel.Interface.Group")
if self.object is not None:
self.ask_history()
def register(self, obj):
self._logger.debug("register(%s)" % str(obj))
"""This method registers obj as the UnorderedObject being managed by
this Handler. It is called by obj after obj has initialized itself."""
self.object = obj
if self.tube is not None:
self.ask_history()
def get_path(self):
"""Returns the DBus path of this handler. The path is the closest thing
to a unique identifier for each abstract DObject."""
return self.PATH
def get_tube(self):
"""Returns the TubeBox used to create this handler. This method is
necessary if one DObject wishes to create another."""
return self._tube_box
@dbus.service.signal(dbus_interface=IFACE, signature='v')
def send(self, message):
self._logger.debug("send(%s)" % str(message))
"""This method broadcasts message to all other handlers for this UO"""
return
def receive_message(self, message, sender=None):
self._logger.debug("receive_message(%s)" % str(message))
if self.object is None:
self._logger.error("got message before registration")
elif sender == self.tube.get_unique_name():
self._logger.debug("Ignoring message, because I am the sender.")
else:
self.object.receive_message(message)
@dbus.service.signal(dbus_interface=IFACE, signature='')
def ask_history(self):
self._logger.debug("ask_history()")
return
def tell_history(self, sender=None):
self._logger.debug("tell_history to " + str(sender))
try:
if sender == self.tube.get_unique_name():
self._logger.debug("tell_history aborted because I am" + str(sender))
return
if self.object is None:
self._logger.error("object not registered before tell_history")
return
self._logger.debug("getting proxy object")
remote = self.tube.get_object(sender, self.PATH)
self._logger.debug("got proxy object, getting history")
h = self.object.get_history()
self._logger.debug("got history, initiating transfer")
remote.receive_history(h, reply_handler=PassFunction, error_handler=PassFunction)
self._logger.debug("history transfer initiated")
except Exception, E:
self._logger.debug("tell_history failed: " % repr(E))
finally:
return
@dbus.service.method(dbus_interface=IFACE, in_signature = 'v', out_signature='')
def receive_history(self, hist):
self._logger.debug("receive_history(%s)" % str(hist))
if self.object is None:
self._logger.error("object not registered before receive_history")
return
self.object.add_history(hist)
#Alternative implementation of a members_changed (not yet working)
"""
def members_changed(self, message, added, removed, local_pending, remote_pending, actor, reason):
added_names = self.tube.InspectHandles(telepathy.CONNECTION_HANDLE_TYPE_LIST, added)
for name in added_names:
self.tell_history(name)
"""
def members_changed(self, added, removed):
self._logger.debug("members_changed")
for (handle, name) in added:
self.tell_history(sender=name)
def __repr__(self):
return 'UnorderedHandler(' + self._myname + ', ' + repr(self._tube_box) + ')'
def copy(self, name):
"""A convenience function for returning a new UnorderedHandler derived
from this one, with a new name. This is safe as long as copy() is called
with a different name every time."""
h = UnorderedHandler(self._myname + "/" + name, self._tube_box)
self._copies.append(h)
return h
def get_copies(self):
return self._copies
def get_name(self):
return self._myname
class HandlerAcceptor:
HANDLER_TYPE = NotImplementedError
def set_handler(self, handler):
raise NotImplementedError
class UnorderedHandlerAcceptor(HandlerAcceptor):
HANDLER_TYPE = UnorderedHandler
class UnorderedObject(UnorderedHandlerAcceptor):
""" The most basic DObject is the Unordered Object (UO). A UO has the
property that any changes to its state can be encapsulated as messages, and
these messages have no intrinsic ordering. Different instances of the same
UO, after receiving the same messages in different orders, should reach the
same state.
Any UO could be implemented as a set of all messages received so far, and
coherency could be maintained by sending all messages ever transmitted to
each new joining member. However, many UOs will have the property that most
messages are obsolete, and need not be transmitted. Therefore, as an
optimization, UOs manage their own state structures for synchronizing state
with joining/merging users.
The following code is an abstract class for UnorderedObject, serving
primarily as documentation for the concept.
"""
handler = None
def set_handler(self, handler):
"""Each UO must accept an UnorderedHandler via set_handler
Whenever an action is taken on the local UO (e.g. a method call that changes
the object's state), the UO must call handler.send() with an appropriately
encoded message.
Subclasses may override this method if they wish to perform more actions
when a handler is set."""
if self.handler:
raise
else:
self.handler = handler
self.handler.register(self)
def receive_message(self,msg):
"""This method accepts and processes a message sent via handler.send().
Because objects are sent over DBus, it is advisable to DBus-ify the message
before calling send, and de-DBus-ify it inside receive_message."""
raise NotImplementedError
def get_history(self):
"""This method returns an encoded copy of all non-obsolete state, ready to be
sent over DBus."""
raise NotImplementedError
def add_history(self, state):
"""This method accepts and processes the state object returned by get_history()"""
raise NotImplementedError
def empty_translator(x, pack):
return x
class HighScore(UnorderedObject):
""" A HighScore is the simplest nontrivial DObject. A HighScore's state consists
of a value and a score. The user may suggest a new value and score. If the new
score is higher than the current score, then the value and score are updated.
Otherwise, they are not.
The value can be any object, and the score can be any comparable object.
To ensure that serialization works correctly, the user may specify a
translator function that converts values or scores to and from a format that
can be serialized reliably by dbus-python.
In the event of a tie, coherence cannot be guaranteed. If ties are likely
with the score of choice, the user may set break_ties=True, which appends a
random number to each message, and thereby reduces the probability of a tie
by a factor of 2**52.
"""
def __init__(self, initval, initscore, value_translator=empty_translator, score_translator=empty_translator, break_ties=False):
self._logger = logging.getLogger('stopwatch.HighScore')
self._lock = threading.Lock()
self._value = initval
self._score = initscore
self._break_ties = break_ties
if self._break_ties:
self._tiebreaker = random.random()
else:
self._tiebreaker = None
self._val_trans = value_translator
self._score_trans = score_translator
self._listeners = []
def _set_value_from_net(self, val, score, tiebreaker):
self._logger.debug("set_value_from_net " + str(val) + " " + str(score))
if self._actually_set_value(val, score, tiebreaker):
self._trigger()
def receive_message(self, message):
self._logger.debug("receive_message " + str(message))
if len(message) == 2: #Remote has break_ties=False
self._set_value_from_net(self._val_trans(message[0], False), self._score_trans(message[1], False), None)
elif len(message) == 3:
self._set_value_from_net(self._val_trans(message[0], False), self._score_trans(message[1], False), float_translator(message[2], False))
add_history = receive_message
def set_value(self, val, score):
"""This method suggests a value and score for this HighScore. If the
suggested score is higher than the current score, then both value and
score will be broadcast to all other participants.
"""
self._logger.debug("set_value " + str(val) + " " + str(score))
if self._actually_set_value(val, score, None) and self.handler:
self.handler.send(self.get_history())
def _actually_set_value(self, value, score, tiebreaker):
self._logger.debug("_actually_set_value " + str(value)+ " " + str(score))
if self._break_ties and (tiebreaker is None):
tiebreaker = random.random()
self._lock.acquire()
if self._break_ties:
if (self._score < score) or ((self._score == score) and (self._tiebreaker < tiebreaker)):
self._value = value
self._score = score
self._tiebreaker = tiebreaker
self._lock.release()
return True
else:
self._lock.release()
return False
elif self._score < score:
self._value = value
self._score = score
self._lock.release()
return True
else:
self._logger.debug("not changing value")
self._lock.release()
return False
def get_value(self):
""" Get the current winning value."""
return self._value
def get_score(self):
""" Get the current winning score."""
return self._score
def get_pair(self):
""" Get the current value and score, returned as a tuple (value, score)"""
self._lock.acquire()
pair = (self._value, self._score)
self._lock.release()
return pair
def _get_all(self):
if self._break_ties:
self._lock.acquire()
q = (self._value, self._score, self._tiebreaker)
self._lock.release()
return q
else:
return self.get_pair()
def get_history(self):
p = self._get_all()
if self._break_ties:
return (self._val_trans(p[0], True), self._score_trans(p[1], True), float_translator(p[2], True))
else:
return (self._val_trans(p[0], True), self._score_trans(p[1], True))
def register_listener(self, L):
"""Register a function L that will be called whenever another user sets
a new record. L must have the form L(value, score)."""
self._lock.acquire()
self._listeners.append(L)
self._lock.release()
(v,s) = self.get_pair()
L(v,s)
def _trigger(self):
(v,s) = self.get_pair()
for L in self._listeners:
L(v,s)
def float_translator(f, pack):
"""This translator packs and unpacks floats for dbus serialization"""
if pack:
return dbus.Double(f)
else:
return float(f)
def uint_translator(f, pack):
"""This translator packs and unpacks 64-bit uints for dbus serialization"""
if pack:
return dbus.UInt64(f)
else:
return int(f)
def int_translator(f, pack):
"""This translator packs and unpacks 32-bit ints for dbus serialization"""
if pack:
return dbus.Int32(f)
else:
return int(f)
def string_translator(s, pack):
"""This translator packs and unpacks unicode strings for dbus serialization"""
if pack:
return dbus.String(s)
else:
return str(s)
class Latest(HandlerAcceptor):
""" Latest is a variation on HighScore, in which the score is the current
timestamp. Latest uses TimeHandler to provide a groupwide coherent clock.
Because TimeHandler's guarantees about synchronization and resilience are
weak, Latest is not as resilient to failures as a true DObject.
The creator must provide the initial value. One may
optionally indicate the initial time (as a float in epoch-time), a
TimeHandler (otherwise a new one will be created), and a translator for
serialization of the values.
Note that if time_handler is not provided, the object will not be functional
until set_handler is called.
"""
def __init__(self, initval, inittime=float('-inf'), time_handler=None, translator=empty_translator):
self._time_handler = time_handler
self._listeners = []
self._lock = threading.Lock()
self._highscore = HighScore(initval, inittime, translator, float_translator)
self._highscore.register_listener(self._highscore_cb)
def set_handler(self, handler):
if self.handler:
raise
else:
if self._time_handler is None:
self._time_handler = TimeHandler(handler.get_path(), handler.get_tube())
self._highscore.set_handler(handler)
def get_value(self):
""" Returns the latest value """
return self._highscore.get_value()
def set_value(self, val):
""" Suggest a new value """
if self._time_handler:
self._highscore.set_value(val, self._time_handler.time())
else:
raise #missing _time_handler
def register_listener(self, L):
""" Register a listener L(value), to be called whenever another user
adds a new latest value."""
self._lock.acquire()
self._listeners.append(L)
self._lock.release()
L(self.get_value())
def _highscore_cb(self, val, score):
for L in self._listeners:
L(val)
class Recentest(HandlerAcceptor):
""" Recentest is like Latest, but without using a clock or TimeHandler.
As a result, it can only guarantee causality, not synchrony.
"""
def __init__(self, initval, translator=empty_translator):
self._listeners = []
self._lock = threading.Lock()
self._highscore = HighScore(initval, 0, translator, uint_translator, break_ties=True)
self._highscore.register_listener(self._highscore_cb)
def set_handler(self, handler):
self._highscore.set_handler(handler)
def get_value(self):
""" Returns the current value """
return self._highscore.get_value()
def set_value(self, val):
""" Set a new value """
self._highscore.set_value(val, self._highscore.get_score() + 1)
def register_listener(self, L):
""" Register a listener L(value), to be called whenever another user
adds a new latest value."""
self._lock.acquire()
self._listeners.append(L)
self._lock.release()
L(self.get_value())
def _highscore_cb(self, val, score):
for L in self._listeners:
L(val)
class AddOnlySet(UnorderedObject):
"""The AddOnlySet is the archetypal UnorderedObject. It consists of a set,
supporting all the normal Python set operations except those that cause an
item to be removed from the set. Thanks to this restriction, a AddOnlySet
is perfectly coherent, since the order in which elements are added is not
important.
"""
def __init__(self, initset = (), translator=empty_translator):
self._logger = logging.getLogger('dobject.AddOnlySet')
self._set = set(initset)
self._lock = threading.Lock()
self._trans = translator
self._listeners = []
self.__and__ = self._set.__and__
self.__cmp__ = self._set.__cmp__
self.__contains__ = self._set.__contains__
self.__eq__ = self._set.__eq__
self.__ge__ = self._set.__ge__
# Not implementing getattribute
self.__gt__ = self._set.__gt__
self.__hash__ = self._set.__hash__
# Not implementing iand (it can remove items)
# Special wrapper for ior to trigger events
# Not implementing isub (it can remove items)
self.__iter__ = self._set.__iter__
# Not implementing ixor (it can remove items)
self.__le__ = self._set.__le__
self.__len__ = self._set.__len__
self.__lt__ = self._set.__lt__
self.__ne__ = self._set.__ne__
self.__or__ = self._set.__or__
self.__rand__ = self._set.__rand__
# Special implementation of repr
self.__ror__ = self._set.__ror__
self.__rsub__ = self._set.__rsub__
self.__rxor__ = self._set.__rxor__
self.__sub__ = self._set.__sub__
self.__xor__ = self._set.__xor__
# Special implementation of add to trigger events
# Not implementing clear
self.copy = self._set.copy
self.difference = self._set.difference
# Not implementing difference_update (it removes items)
# Not implementing discard (it removes items)
self.intersection = self._set.intersection
# Not implementing intersection_update (it removes items)
self.issubset = self._set.issubset
self.issuperset = self._set.issuperset
# Not implementing pop
# Not implementing remove
self.symmetric_difference = self._set.symmetric_difference
# Not implementing symmetric_difference_update
self.union = self._set.union
# Special implementation of update to trigger events
def update(self, y):
"""Add all the elements of an iterable y to the current set. If any of
these elements were not already present, they will be broadcast to all
other users."""
s = set(y)
d = s - self._set
if len(d) > 0:
self._set.update(d)
self._send(d)
__ior__ = update
def add(self, y):
""" Add the single element y to the current set. If y is not already
present, it will be broadcast to all other users."""
if y not in self._set:
self._set.add(y)
self._send((y,))
def _send(self, els):
if len(els) > 0 and self.handler is not None:
self.handler.send(dbus.Array([self._trans(el, True) for el in els]))
def _net_update(self, y):
s = set(y)
d = s - self._set
if len(d) > 0:
self._set.update(d)
self._trigger(d)
def receive_message(self, msg):
self._net_update((self._trans(el, False) for el in msg))
def get_history(self):
if len(self._set) > 0:
return dbus.Array([self._trans(el, True) for el in self._set])
else:
return dbus.Array([], type=dbus.Boolean) #Prevent introspection of empty list, which fails
add_history = receive_message
def register_listener(self, L):
"""Register a listener L(diffset). Every time another user adds items
to the set, L will be called with the set of new items."""
self._listeners.append(L)
L(self._set.copy())
def _trigger(self, s):
for L in self._listeners:
L(s)
def __repr__(self):
return 'AddOnlySet(' + repr(self.handler) + ', ' + repr(self._set) + ', ' + repr(self._trans) + ')'
class AddOnlySortedSet(UnorderedObject):
""" AddOnlySortedSet is much like AddOnlySet, only backed by a ListSet, which
provides a set for objects that are ordered under cmp(). Items are maintained
in order. This approach is most useful in cases where each item is a message,
and the messages are subject to a time-like ordering. Messages may still
arrive out of order, but they will be stored in the same order on each
computer.
"""
def __init__(self, initset = (), translatohr=empty_translator):
self._logger = logging.getLogger('dobject.AddOnlySortedSet')
self._set = ListSet(initset)
self._lock = threading.Lock()
self._trans = translator
self._listeners = []
self.__and__ = self._set.__and__
self.__contains__ = self._set.__contains__
# No self.__delitem__
self.__eq__ = self._set.__eq__
self.__ge__ = self._set.__ge__
# Not implementing getattribute
self.__getitem__ = self._set.__getitem__
self.__gt__ = self._set.__gt__
# Not implementing iand (it can remove items)
# Special wrapper for ior to trigger events
# Not implementing isub (it can remove items)
self.__iter__ = self._set.__iter__
# Not implementing ixor (it can remove items)
self.__le__ = self._set.__le__
self.__len__ = self._set.__len__
self.__lt__ = self._set.__lt__
self.__ne__ = self._set.__ne__
self.__or__ = self._set.__or__
self.__rand__ = self._set.__rand__
# Special implementation of repr
self.__ror__ = self._set.__ror__
self.__rsub__ = self._set.__rsub__
self.__rxor__ = self._set.__rxor__
self.__sub__ = self._set.__sub__
self.__xor__ = self._set.__xor__
# Special implementation of add to trigger events
# Not implementing clear
self.copy = self._set.copy
self.difference = self._set.difference
# Not implementing difference_update (it removes items)
# Not implementing discard (it removes items)
self.first = self._set.first
self.headset = self._set.headset
self.index = self._set.index
self.intersection = self._set.intersection
# Not implementing intersection_update (it removes items)
self.issubset = self._set.issubset
self.issuperset = self._set.issuperset
self.last = self._set.last
# Not implementing pop
self.position = self._set.position
# Not implementing remove
self.subset = self._set.subset
self.symmetric_difference = self._set.symmetric_difference
# Not implementing symmetric_difference_update
self.tailset = self._set.tailset
self.union = self._set.union
# Special implementation of update to trigger events
def update(self, y):
"""Add all the elements of an iterable y to the current set. If any of
these elements were not already present, they will be broadcast to all
other users."""
d = ListSet(y)
d -= self._set
if len(d) > 0:
self._set.update(d)
self._send(d)
__ior__ = update
def add(self, y):
""" Add the single element y to the current set. If y is not already
present, it will be broadcast to all other users."""
if y not in self._set:
self._set.add(y)
self._send((y,))
def _send(self, els):
if len(els) > 0 and self.handler is not None:
self.handler.send(dbus.Array([self._trans(el, True) for el in els]))
def _net_update(self, y):
d = ListSet()
d._list = y
d -= self._set
if len(d) > 0:
self._set |= d
self._trigger(d)
def receive_message(self, msg):
self._net_update([self._trans(el, False) for el in msg])
def get_history(self):
if len(self._set._list) > 0:
return dbus.Array([self._trans(el, True) for el in self._set._list])
else:
return dbus.Array([], type=dbus.Boolean) #prevent introspection of empty list, which fails
add_history = receive_message
def register_listener(self, L):
"""Register a listener L(diffset). Every time another user adds items
to the set, L will be called with the set of new items as a SortedSet."""
self._listeners.append(L)
L(self._set.copy())
def _trigger(self, s):
for L in self._listeners:
L(s)
def __repr__(self):
return 'AddOnlySortedSet(' + repr(self.handler) + ', ' + repr(self._set) + ', ' + repr(self._trans) + ')'
class CausalHandler:
"""The CausalHandler is analogous to the UnorderedHandler, in that it
presents an interface with which to build a wide variety of objects with
distributed state. The CausalHandler is different from the Unordered in two
ways:
1. The send() method of an CausalHandler returns an index, which must be
stored by the CausalObject in connection with the information that was sent.
This index is a universal, fully-ordered, strictly causal identifier
for each message.
2. A CausalObject's receive_message method takes two arguments: the message
and its index.
As a convenience, there is also
3. A get_index() method, which provides a new index on each call, always
higher than all previous indexes.
CausalObjects are responsible for including index information in the
return value of get_history, and processing index information in add_history.
It is noteworthy that CausalHandler is in fact implemented on _top_ of
UnorderedHandler. The imposition of ordering does not require lower-level
access to the network. This fact of implementation may change in the
future, but CausalObjects will not be able to tell the difference.
"""
ZERO_INDEX = (0,0)
def __init__(self, name, tube_box):
self._myname = name
self._tube_box = tube_box
self._unordered = UnorderedHandler(name, tube_box)
self._counter = 0
self._copies = []
self.object = None
def register(self, obj):
self.object = obj
self._unordered.register(self)
def get_index(self):
"""get_index returns a new index, higher than all previous indexes.
The primary reason to use get_index is if you wish two know the index
of an item _before_ calling send()"""
self._counter += 1
return (self._counter, random.getrandbits(64))
def index_trans(self, index, pack):
"""index_trans is a standard serialization translator for the index
format. Thanks to this translator, a CausalObject can and should treat
each index as an opaque, comparable object."""
if pack:
return dbus.Struct((dbus.UInt64(index[0]), dbus.UInt64(index[1])), signature='tt')
else:
return (int(index[0]), int(index[1]))
def send(self, msg, index=None):
"""send() broadcasts a message to all other participants. If called
with one argument, send() broadcasts that message, along with a new
index, and returns the index. If called with two arguments, the second
may be an index, which will be used for this message. The index must
have been acquired using get_index(). In this case, the index must be
acquired immediately prior to calling send(). Otherwise, another
message may arrive in the interim, causing a violation of causality."""
if index is None:
index = self.get_index()
self._unordered.send(dbus.Struct((msg, self.index_trans(index, True))))
return index
def receive_message(self, msg):
m = msg[0]
index = self.index_trans(msg[1], False)
self._counter = max(self._counter, index[0])
self.object.receive_message(m, index)
def add_history(self, hist):
h = hist[0]
index = self.index_trans(hist[1], False)
self._counter = max(self._counter, index[0])
self.object.add_history(h)
def get_history(self):
h = self.object.get_history()
hist = dbus.Struct((h, self.index_trans(self.get_index(), True)))
return
def copy(self, name):
"""A convenience function for returning a new CausalHandler derived
from this one, with a new name. This is safe as long as copy() is called
with a different name every time."""
h = CausalHandler(self._myname + "/" + name, self._tube_box)
self._copies.append(h)
return h
def get_copies(self):
return self._copies
def get_name(self):
return self._myname
class CausalHandlerAcceptor(HandlerAcceptor):
HANDLER_TYPE = CausalHandler
def set_handler(self, handler):
raise NotImplementedError
class CausalObject(CausalHandlerAcceptor):
"""A CausalObject is almost precisely like an UnorderedObject, except
that whereas an UnorderedObject is completely specified by a set of messages,
a CausalObject is completely specified by an ordered list of messages,
sorted according to an opaque index associated with each message.
This index must be monotonically increasing in time for new messages as they
are created, but old messages may arrive long after they were created, and
are then inserted into the middle of the timestream.
The following code is an abstract class for CausalObject, serving
primarily as documentation for the concept.
"""
handler = None
def set_handler(self, handler):
"""Each CO must accept a CausalHandler via set_handler.
Subclasses may override this method if they wish to perform more actions
when a handler is set."""
if self.handler:
raise
else:
self.handler = handler
self.handler.register(self)
def receive_message(self, msg, index):
"""This method accepts and processes a message sent via handler.send().
Because objects are sent over DBus, it is advisable to DBus-ify the message
before calling send, and de-DBus-ify it inside receive_message.
The index argument is an opaque index used for determining the ordering."""
raise NotImplementedError
def get_history(self):
"""This method returns an encoded copy of all non-obsolete state, ready to be
sent over DBus."""
raise NotImplementedError
def add_history(self, state):
"""This method accepts and processes the state object returned by get_history()"""
raise NotImplementedError
class CausalDict(CausalObject):
"""NOTE: CausalDict is UNTESTED. Other things may be buggy, but CausalDict
PROBABLY DOES NOT WORK. A CausalDict WILL NOT WORK UNTIL set_handler IS CALLED.
CausalDict is a distributed version of a Dict (hash table). All users keep
a copy of the entire table, so this is not a "Distributed Hash Table"
according to the terminology of the field.
CausalDict permits all Dict operations, including removing keys and
modifying the value of existing keys. This would not be possible using an
Unordered approach, because two value assignments to the same key could
arrive in different orders for different users, leaving them in different
states at quiescence.
To solve this problem, every assignment and removal is given a monotonically
increasing unique index, and whenever there is a conflict, the higher-index
operation wins.
One side effect of this design is that deleted keys cannot be forgotten. If
an assignment operation is received whose index is lower than
the deletion's, then that assignment is considered obsolete and must not be
executed.
To provide a mechanism for reducing memory usage, the clear() method has
been interpreted to remove not only all entries received so far, but also
all entries that will ever be received with index less than the current
index.
"""
ADD = 0
DELETE = 1
CLEAR = 2
def __init__(self, initdict=(), key_translator=empty_translator, value_translator=empty_translator):
self._dict = dict(initdict)
self._listeners = []
self._key_trans = key_translator
self._val_trans = value_translator
self.__contains__ = self._dict.__contains__
#Special __delitem__
self.__eq__ = self._dict.__eq__
self.__ge__ = self._dict.__ge__
self.__getitem__ = self._dict.__getitem__
self.__gt__ = self._dict.__gt__
self.__le__ = self._dict.__le__
self.__len__ = self._dict.__len__
self.__lt__ = self._dict.__lt__
self.__ne__ = self._dict.__ne__
# special __setitem__
#Special clear
self.copy = self._dict.copy
self.get = self._dict.get
self.has_key = self._dict.has_key
self.items = self._dict.items
self.iteritems = self._dict.iteritems
self.iterkeys = self._dict.iterkeys
self.itervalues = self._dict.itervalues
self.keys = self._dict.keys
#Special pop
#Special popitem
#special setdefault
#special update
self.values = self._dict.values
def set_handler(self, handler):
if self.handler is not None:
raise
else:
self.handler = handler
self._clear = self.handler.get_index() #this must happen before index_dict initialization, so that self._clear is less than any index in index_dict
self._index_dict = dict(((k, self.handler.get_index()) for k in self._dict))
self.handler.register(self)
def __delitem__(self, key):
"""Same as for dict"""
del self._dict[key]
n = self.handler.send(((dbus.Int32(CausalDict.DELETE), self._key_trans(key, True))))
self._index_dict[key] = n
def __setitem__(self, key, value):
"""Same as for dict"""
self._dict[key] = value
n = self.handler.send(dbus.Array([(dbus.Int32(CausalDict.ADD), self._key_trans(key, True), self._val_trans(value, True))]))
self._index_dict[key] = n
def clear(self):
"""Same as for dict"""
self._dict.clear()
self._index_dict.clear()
n = self.handler.send(dbus.Array([(dbus.Int32(CausalDict.CLEAR))]))
self._clear = n
def pop(self, key, x=None):
"""Same as for dict"""
t = (key in self._dict)
if x is None:
r = self._dict.pop(key)
else:
r = self._dict.pop(key, x)
if t:
n = self.handler.send(dbus.Array([(dbus.Int32(CausalDict.DELETE), self._key_trans(key, True))]))
self._index_dict[key] = n
return r
def popitem(self):
"""Same as for dict"""
p = self._dict.popitem()
key = p[0]
n = self.handler.send(dbus.Array([(dbus.Int32(CausalDict.DELETE), self._key_trans(key, True))]))
self._index_dict[key] = n
return p
def setdefault(self, key, x):
"""Same as for dict"""
if key not in self._dict:
self._dict[key] = x
n = self.handler.send(dbus.Array([(dbus.Int32(CausalDict.ADD), self._key_trans(key, True), self._val_trans(value, True))]))
self._index_dict[key] = n
def update(*args,**kargs):
"""Same as for dict"""
d = dict()
d.update(*args,**kargs)
newpairs = []
for p in d.items():
if (p[0] not in self._dict) or (self._dict[p[0]] != p[1]):
newpairs.append(p)
self._dict[p[0]] = p[1]
n = self.handler.send(dbus.Array([(dbus.Int32(CausalDict.ADD), self._key_trans(p[0], True), self._val_trans(p[1], True)) for p in newpairs]))
for p in newpairs:
self._index_dict[p[0]] = n
def receive_message(self, msg, n):
if n > self._clear:
a = dict()
r = dict()
for m in msg:
flag = int(m[0]) #don't know length of m without checking flag
if flag == CausalDict.ADD:
key = self._key_trans(m[1], False)
if (key not in self._index_dict) or (self._index_dict[key] < n):
val = self._val_trans(m[2], False)
if key in self._dict:
r[key] = self._dict[key]
self._dict[key] = val
a[key] = val
self._index_dict[key] = n
elif flag == CausalDict.DELETE:
key = self._key_trans(m[1], False)
if key not in self._index_dict:
self._index_dict[key] = n
elif (self._index_dict[key] < n):
self._index_dict[key] = n
if key in self._dict:
r[key] = self._dict[key]
del self._dict[key]
elif flag == CausalDict.CLEAR:
self._clear = n
for (k, ind) in self._index_dict.items():
if ind < self._clear:
del self._index_dict[k]
if k in self._dict:
r[k] = self._dict[k]
del self._dict[k]
if (len(a) > 0) or (len(r) > 0):
self._trigger(a,r)
def get_history(self):
c = self.handler.index_trans(self._clear, True)
d = dbus.Array([(self._key_trans(p[0], True), self._val_trans(p[1], True)) for p in self._dict.items()])
i = dbus.Array([(self._key_trans(p[0], True), self.handler.index_trans(p[1], True)) for p in self._index_dict.items()])
return dbus.Struct((c,d,i),signature='itt')
def add_history(self, hist):
c = self.handler.index_trans(hist[0], False)
d = dict(((self._key_trans(p[0], False), self._val_trans(p[1], False)) for p in hist[1]))
i = [(self._key_trans(p[0], False), self.handler.index_trans(p[1], False)) for p in hist[2]]
a = dict()
r = dict()
if c > self._clear:
self._clear = c
for (k, n) in self._index_dict.items():
if n < self._clear:
del self._index_dict[k]
if k in self._dict:
r[k] = self._dict[k]
del self._dict[k]
k_changed = []
for (k, n) in i:
if (((k not in self._index_dict) and (n > self._clear)) or
((k in self._index_dict) and (n > self._index_dict[k]))):
k_changed.append(k)
self._index_dict[k] = n
for k in k_changed:
if k in d:
if (k in self._dict) and (self._dict[k] != d[k]):
r[k] = self._dict[k]
a[k] = d[k]
elif k not in self._dict:
a[k] = d[k]
self._dict[k] = d[k]
else:
if k in self._dict:
r[k] = self._dict[k]
del self._dict[k]
if (len(a) > 0) or (len(r) > 0):
self._trigger(a,r)
def register_listener(self, L):
"""Register a change-listener L. Whenever another user makes a change
to this dict, L will be called with L(dict_added, dict_removed). The
two arguments are the dict of new entries, and the dict of entries that
have been deleted or overwritten."""
self._listeners.append(L)
L(self._dict.copy(), dict())
def _trigger(self, added, removed):
for L in self._listeners:
L(added, removed)
class UserDict(dbus.gobject_service.ExportedGObject):
IFACE = "org.dobject.UserDict"
BASEPATH = "/org/dobject/UserDict/"
def __init__(self, name, tubebox, myval, translator = empty_translator):
self._myname = name
self.PATH = UserDict.BASEPATH + name
dbus.gobject_service.ExportedGObject.__init__(self)
self._logger = logging.getLogger(self.PATH)
self._tube_box = tube_box
self.tube = None
self._dict = dict()
self._myval = myval
self._trans = translator
self._tube_box.register_listener(self.set_tube)
self.__contains__ = self._dict.__contains__
#No __delitem__
self.__eq__ = self._dict.__eq__
self.__ge__ = self._dict.__ge__
self.__getitem__ = self._dict.__getitem__
self.__gt__ = self._dict.__gt__
self.__le__ = self._dict.__le__
self.__len__ = self._dict.__len__
self.__lt__ = self._dict.__lt__
self.__ne__ = self._dict.__ne__
#No __setitem__
#No clear
self.copy = self._dict.copy
self.get = self._dict.get
self.has_key = self._dict.has_key
self.items = self._dict.items
self.iteritems = self._dict.iteritems
self.iterkeys = self._dict.iterkeys
self.itervalues = self._dict.itervalues
self.keys = self._dict.keys
#No pop
#No popitem
#No setdefault
#No update
self.values = self._dict.values
def set_tube(self, tube, is_initiator):
"""Callback for the TubeBox"""
self.tube = tube
self.add_to_connection(self.tube, self.PATH)
self.tube.add_signal_receiver(self.receive_value, signal_name='send_value', dbus_interface=UserDict.IFACE, sender_keyword='sender', path=self.PATH)
self.tube.add_signal_receiver(self.tell_value, signal_name='ask_values', dbus_interface=UserDict.IFACE, sender_keyword='sender', path=self.PATH)
self.tube.watch_participants(self.members_changed)
#Alternative implementation of members_changed (not yet working)
#self.tube.add_signal_receiver(self.members_changed, signal_name="MembersChanged", dbus_interface="org.freedesktop.Telepathy.Channel.Interface.Group")
self.ask_values()
def get_path(self):
"""Returns the DBus path of this handler. The path is the closest thing
to a unique identifier for each abstract DObject."""
return self.PATH
def get_tube(self):
"""Returns the TubeBox used to create this handler. This method is
necessary if one DObject wishes to create another."""
return self._tube_box
@dbus.service.signal(dbus_interface=IFACE, signature='v')
def send_value(self, value):
"""This method broadcasts message to all other handlers for this UO"""
return
@dbus.service.signal(dbus_interface=IFACE, signature='')
def ask_values(self):
return
def tell_value(self, sender=None):
self._logger.debug("tell_history to " + str(sender))
try:
if sender == self.tube.get_unique_name():
return
remote = self.tube.get_object(sender, self.PATH)
remote.receive_value(self._myval, sender_keyword='sender', reply_handler=PassFunction, error_handler=PassFunction)
finally:
return
@dbus.service.method(dbus_interface=IFACE, in_signature = 'v', out_signature='', sender_keyword = 'sender')
def receive_value(self, value, sender=None):
self._dict[sender] = self._trans(value, False)
#Alternative implementation of a members_changed (not yet working)
"""
def members_changed(self, message, added, removed, local_pending, remote_pending, actor, reason):
added_names = self.tube.InspectHandles(telepathy.CONNECTION_HANDLE_TYPE_LIST, added)
for name in added_names:
self.tell_history(name)
"""
def members_changed(self, added, removed):
self._logger.debug("members_changed")
for (handle, name) in removed:
if name in self._dict:
del self._dict[name]
for (handle, name) in added:
self.tell_value(sender=name)
class UnorderedString(UnorderedObject):
def __init__(self,initstring=''):
self._tree = stringtree.SimpleStringTree()
self._listeners = []
self._newbuffer = []
if initstring:
self.insert(initstring, 0)
def insert(self, text, pos):
x = self._tree.insert(text,pos)
if self.handler is not None:
self.handler.send(dbus.Array(stringtree.translator(i,True) for i in x))
def delete(self, k, n):
x = self._tree.delete(k,n)
if self.handler is not None:
self.handler.send(dbus.Array(stringtree.translator(i,True) for i in x))
def _net_update(self, L):
transformed_list = []
self._newbuffer.append(L)
for li in self._newbuffer[::-1]:
if self._tree.is_ready(li[0]): #each update from the net is required to
#obey the rule that if the tree is ready for the first Change,
#then it is ready for all the changes. This may be a sort of
#violation of the Unordered abstraction...
for c in li:
transformed_list.extend(self._tree.add_change(c))
self._newbuffer.pop() #Having handled the contents of li, we
#should make sure it doesn't come up for consideration again
self._trigger(transformed_list)
def get_history(self):
return dbus.Array((stringtree.translator(c, True)
for c in self._tree.get_changes()),
signature = 'v')
def add_history(self, msg):
L = []
for el in msg:
change = stringtree.translator(el, False)
if change.unique_id not in self._tree._id2rec:
L.append(change)
if L:
self._net_update(L)
receive_message = add_history
def register_listener(self, L):
"""Register a listener L(editlist). Every time another user modifies
the string, L will be called with a set of edits that represent those
changes on the local version of the string. Note that the edits must
be performed in order."""
self._listeners.append(L)
def _trigger(self, editlist):
for L in self._listeners:
L(editlist)
class CausalTree(CausalObject):
#SET_PARENT and DELETE_NODE are opcodes to be sent over the wire, and also
#to the trigger. MAJOR_CHANGE is sent only to the trigger, and it is not
#an opcode. It represents a significant but undefined changed in the tree.
SET_PARENT = 0
DELETE_NODE = 1
CLEAR = 2
MAJOR_CHANGE = -1
ROOT = 0
def __init__(self):
self._timeline = ListSet()
self._reverse = {}
self._listeners = []
self._reset()
def _reset(self):
self._parent = {}
self._children = {self.ROOT:set()}
def __contains__(self, node):
return node in self._children
def get_parent(self,node):
if node == self.ROOT:
return self.ROOT
else:
return self._parent[node]
def get_children(self, node):
return frozenset(self._children[node])
def _process_local_cmd(self,cmd):
i = self.handler.get_index()
self._timeline.add((i,cmd))
rev = self._step(cmd)
self._reverse[(i,cmd)] = rev
self.handler.send(self._cmd_trans(cmd,True),i)
def change_parent(self,node,newparent):
if (node in self._parent) and (newparent in self._children):
if self._parent[node] != newparent:
cmd = (self.SET_PARENT, node, newparent)
self._process_local_cmd(cmd)
else:
raise KeyError("One or both nodes is not present")
def new_child(self,parent):
node = random.getrandbits(64)
cmd = (self.SET_PARENT, node, parent)
self._process_local_cmd(cmd)
return node
def delete(self,node):
if node == self.ROOT:
raise KeyError("You cannot delete the root node.")
if node not in self._children:
raise KeyError("No such node.")
cmd = (self.DELETE_NODE, node)
self._process_local_cmd(cmd)
def clear(self):
cmd = (self.CLEAR,)
self._process_local_cmd(cmd)
def _step(self, cmd):
# Returns () if the command failed or had no effect
# If the command succeeded, returns an iterable of the commands necessary
# to undo this command
if cmd[0] == self.SET_PARENT:
if cmd[2] in self._children: #if newparent is known
if cmd[1] in self._parent: #if node is known
if self._parent[cmd[1]] == cmd[2]:
return () #No change necessary. This SET_PARENT is redundant
if cmd[1] in self._allparents(cmd[2]): #if node is above newparent
#This command would create a loop. It is therefore illegal
#and should be ignored
return ()
else:
#remove node from under its current parent
oldp = self._parent[cmd[1]]
self._children[oldp].remove(cmd[1])
self._children[cmd[2]].add(cmd[1])
self._parent[cmd[1]] = cmd[2]
return ((self.SET_PARENT, cmd[1], oldp),)
else:
#Node is unknown, so it must be added
self._children[cmd[1]] = set()
self._children[cmd[2]].add(cmd[1])
self._parent[cmd[1]] = cmd[2]
return ((self.DELETE_NODE, cmd[1]),) #the command executed successfully
else:
#The new parent is unknown, so the command is illegal and should
#be ignored.
return ()
elif cmd[0] == self.DELETE_NODE:
if cmd[1] == self.ROOT:
#Deleting the root node is not allowed, so this command is illegal and should be ignored
return ()
if cmd[1] in self._children:
p = self._parent[cmd[1]]
self._children[p].remove(cmd[1])
cmds = [(self.SET_PARENT, cmd[1], p)]
for c in self._children[cmd[1]]:
self._children[p].add(c)
self._parent[c] = p
cmds.append((self.SET_PARENT,c,cmd[1]))
del self._children[cmd[1]]
del self._parent[cmd[1]]
return cmds #The command completed successfully
else:
#cmd[1] is an unknown node, so this command should be ignored
return ()
elif cmd[0] == self.CLEAR:
deleted = self._parent.keys() #relies on self.ROOT not being in _parent
cmds = []
stack = [self.ROOT]
while len(stack) > 0:
n = stack.pop()
for c in self._children[n]:
cmds.append((self.SET_PARENT, c, n))
stack.append(c)
self._reset()
return cmds
def _allparents(self, node):
s = set()
while node != self.ROOT:
s.add(node)
node = self._parent[node]
s.add(self.ROOT)
return s
def _cmd_trans(self,cmd,pack):
#This code does not completely specify the dbus typing because it avoids
#calling dbus.Struct. The tuple will be introspected.
if len(cmd) == 1: #CLEAR
return (self._instruction_trans(cmd[0],pack),)
if len(cmd) == 2: #DELETE_NODE
return (self._instruction_trans(cmd[0],pack), self.node_trans(cmd[1],pack))
elif len(cmd) == 3: #SET_PARENT
return (self._instruction_trans(cmd[0],pack),
self.node_trans(cmd[1],pack),
self.node_trans(cmd[2],pack))
def _instruction_trans(self,ins,pack):
return int_translator(ins,pack)
def node_trans(self,node,pack):
return uint_translator(node,pack)
def register_listener(self, L):
self._listeners.append(L)
def receive_message(self, cmd, i):
cmd = self._cmd_trans(cmd,False)
elt = (i, cmd)
if elt > self._timeline.last():
self._timeline.add(elt)
s = self._step(cmd)
self._reverse[elt] = s
if s:
self._trigger((cmd,),s)
else:
(forward, reverse) = self._antestep((elt,))
if forward:
self._trigger(forward, reverse)
def _antestep(self, elts):
#_antestep accepts an iterable of (i, cmd)s that may have
# occurred at previous times. It incorporates these changes into the
# timeline and state. It also returns a two-element tuple:
# a list of cmds that would have the same effect as the inclusion of elts, and a
# list of cmds that would reverse this effect.
newelts = [e for e in elts if e not in self._timeline]
if len(newelts) == 0:
return (False, False)
affected = [e for e in self._timeline.tailset(newelts[0]) if self._reverse[e]]
rollback = []
for l in affected[::-1]:
rollback.extend(self._reverse[l])
for cmd in rollback:
self._step(cmd)
# We have now rolled back to the point where newelts[0] is inserted
self._timeline.update(newelts)
new_effective = []
reversers = []
for (i,cmd) in self._timeline.tailset(newelts[0]):
rev = self._step(cmd)
self._reverse[(i,cmd)] = rev
if rev: #If the command had any effect
reversers.append(rev)
new_effective.append(cmd)
reversers.reverse()
reversenew = []
for l in reversers:
reversenew.extend(l)
forward = rollback
forward.extend(new_effective)
reverse = reversenew
reverse.extend(affected)
return (forward, reverse)
#This implementation is extremely suboptimal. An ideal implementation
#would use some knowledge about the commutativity of different commands
#to shorten forward and reverse substantially. As is, they will likely
#contain mostly redundant undo-and-then-redo.
def get_history(self):
return dbus.Array(
(self.handler.index_trans(i,True), self._cmd_trans(cmd,True))
for (i,cmd) in self._timeline)
def add_history(self,h):
elts = ((self.handler.index_trans(i,False), self._cmd_trans(cmd,False))
for (i,cmd) in h)
(forward, reverse) = self._antestep(elts)
if forward:
self._trigger(forward, reverse)
def _trigger(self, info):
# info is either (added, removed, affected) if that info is available,
# or False if there has been a change but no info is available
for L in self._listeners:
L(info)
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