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# sharedobject.py, classes to aid activities in sharing a state
# Reinier Heeres, reinier@heeres.eu
# Miguel Alvarez, miguel@laptop.org
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program 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 General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
#
# Change log:
# 2007-07-14: rwh, the big merge. Old function are kept with _nc
# (non-contiguous) appended
# 2007-07-07: miguel, conflict resolution added
# 2007-06-21: rwh, first version
import copy
import pickle
import base64
import difflib
import time
import logging
_logger = logging.getLogger('sharinghelper')
class DiffRec:
def __init__(self, versionid, sender, incremental, objstr):
self.version_id = versionid
self.sender = sender
self.incremental = incremental
self.obj = objstr
def is_newer(self, v2):
if self.version_id > v2.version_id or \
(self.version_id == v2.version_id and self.sender > v2.sender):
return True
else:
return False
def __str__(self):
return "[%d]%s" % (self.version_id, str(self.obj))
def __repr__(self):
return self.__str__()
class SharedObject:
"""Base class for shared objects, able to share python objects the
dumb way"""
def __init__(self, name, helper, opt = {}):
self._name = name
self._options = opt
self._helper = helper
self._value = None
self._version_id = 0
self._received_diffs = []
self._inverse_diffs = []
self._pending_diffs = {}
self._cached_versions = 8
self._locked = False
self._locked_by = None
self._locked_time = 0
def encode(self, obj):
return base64.b64encode(pickle.dumps(obj))
def decode(self, obj):
return pickle.loads(base64.b64decode(obj))
def _should_encode_incremental(self, incremental):
"""Decide whether to encode an object incrementally. If nothing is
specified (incremental=None) determine from self._options, else
return what is specified."""
if incremental is None:
if 'incremental' in self._options and self._options['incremental'] is True:
return True
else:
return False
return incremental
def changed_nc(self, diffobj, incremental):
"""This function should be called when the object has changed."""
self._version_id += 1
try:
diff = DiffRec(self._version_id, self._helper._own_bus_name, incremental, diffobj)
self.insert_diff(diff)
enc = self.encode(diff.obj)
if self._helper.tube_connected():
self._helper.SendObject(self._name, self._version_id, incremental, enc)
except Exception, inst:
_logger.error('changed(): %s', inst)
self.do_changed_callback()
def changed(self, diffobj, incremental=False):
"""This function should be called when the object has change
If diffobj is None the whole object will be sent
If defined, only this difference will be sent
A diff entry is also added to our received_diffs so that
we can properly sequence and undo/redo this change.
"""
try:
self.insert_diff(DiffRec(self._version_id+1,
self._helper._own_bus_name, incremental, diffobj))
if not incremental:
enc = self.encode(self._value)
else:
enc = self.encode(diffobj)
self._helper.SendObject(self._name, self._version_id, incremental, enc)
_logger.debug("Modification sent")
except Exception, inst:
_logger.error('changed(): %s, currval: %s', inst, self._value)
self.do_changed_callback()
def set_value_nc(self, v, incremental=None):
"""Function to set value of this object. Specifying incremental
(a boolean) allows forcing of either incremental/full encoding.
If not specified, the default will be used from self._options"""
incremental = self._should_encode_incremental(incremental)
_logger.debug('Setting value of %s to %s, incremental=%s', self._name, v, incremental)
if incremental:
old = copy.deepcopy(self._value)
self._value = v
d = self.diff(v, old)
_logger.debug('set_value(): generated diff:\n%r', d)
del old
if d is not None:
self.changed(d, True)
else:
self._value = v
self.changed_nc(v, False)
def set_value(self, v, incremental=False):
incremental = self._should_encode_incremental(incremental)
_logger.debug('Setting value of %s to %s, incremental=%s', self._name, v, incremental)
old = copy.deepcopy(self._value)
d = self.diff(v, old)
_logger.debug("Diff= %s", d)
self.changed(d, incremental)
def get_value(self):
return self._value
def do_changed_callback(self):
if 'changed' in self._options:
self._options['changed'](self._value)
def output_diff_stack(self):
_logger.debug('Diff stack:')
for versionid, incremental, objstr, sender in self._received_diffs:
_logger.debug('\tv:%d, inc:%d, sender:%d', versionid,
incremental, sender)
def get_version(self, versionid):
if versionid == self._version_id:
return self._value
if versionid > self._version_id or versionid < 0:
return None
target_index = self._get_diff_index(versionid + 1) #versionid of a diff== the version it leads _up_ to
if 0 > target_index or index > len(self._received_diffs):
return None
object = self._value
for i in range(len(self._received_diffs)-1, target_index -1, -1):
d = self._received_diffs[i]
object = self._apply_diff_to(object, self.inverse_diff(diff))
return object
def get_version(self, versionid):
if versionid == self._version_id:
return self._value
if versionid > self._version_id or versionid < 0:
return None
if versionid < self._received_diffs[0].version_id:
return None
i = len(self._received_diffs) - 1
while self._version_id > versionid:
obj = self._apply_diff_to(obj, self.inverse_diff(diff))
i -= 1
return obj
def inverse_diff(self, diff):
"""Invert a diff object, so that if was the result of an o -> n comparison, the
result is associated to a n -> o comparison."""
index = self._get_diff_index(diff)
if 0 < index < len(self._inverse_diffs): #found (?)
return self._inverse_diffs[index]
return None
def _get_diff_index(self, vi):
for i in xrange(len(self._received_diffs)-1, -1 , -1):
if self._received_diffs[i].version_id == vi:
return i
return -1
def insert_diff_nc(self, d):
if len(self._received_diffs) > 0 and self._received_diffs[0].is_newer(d):
return -1
if len(self._received_diffs) >= self._cached_versions:
del(self._received_diffs[0])
i = len(self._received_diffs) - 1
while i > -1:
if d.is_newer(self._received_diffs[i]):
break
i -= 1
self._received_diffs.insert(i + 1, d)
self._inverse_diffs.insert(i + 1, DiffRec(d.version_id, d.sender, d.incremental, None))
return i + 1
def insert_diff(self, recv_diff, old=None):
""" Places a new and compatible change of incremental type in its correct place, and
actualizes thevalue of the shared object accordingly."""
_logger.debug("insert_diff(): Current versionid:%s, recv_diff:%s", self._version_id, recv_diff)
if not recv_diff.incremental:
_logger.debug("insert_diff(): Applying non-incremental diff")
if recv_diff in self._received_diffs:
_logger.debug("Dupe")
return True
recvi = recv_diff.version_id
index = self._get_diff_index(recvi)
if old == None:
old = self.get_version(recvi - 1)
#if old == None: #can't find the father, doesn't use
# self._discarded_diff = recv_diff
# #TODO: signal that we have a discarded diff --> return False
# return False
_logger.debug("insert_diff(): old=%s", old)
if index < 0:
diffs = []
else:
diffs = self._received_diffs[index:]
i = 0
while len(diffs) > 0 and recv_diff.is_newer(diffs[0]):
diffs = diffs[1:]
index += 1
i += 1
recv_diff.version_id += i
for d in diffs:
d.version_id += 1
res = [recv_diff] + diffs
ret = old
invdiffs = []
for d in res:
_logger.debug("[insert_diff] Applying %s to %s", d.obj, ret)
ret, id = self._apply_diff_to(ret, d.obj)
invdiffs.append(id)
self._value = ret
if index >= 0:
self._received_diffs = self._received_diffs[:index] + res
self._inverse_diffs = self._inverse_diffs[:index] + invdiffs
_logger.info("insert_diff(): recv_diff inserted at %d", index)
else:
self._received_diffs = self._received_diffs + res
self._inverse_diffs = self._inverse_diffs + invdiffs
_logger.debug("insert_diff(): recv_diff inserted at %d", len(self._received_diffs))
self._version_id += 1
if not self._version_id == self._received_diffs[-1].version_id:
_logger.debug("Version inconsistency: expected %s, got %s", self._received_diffs[-1], self._version_id)
self._version_id = self._received_diffs[-1].version_id
_logger.debug("new version_id: %s, actualized received_diffs: %s", self._version_id, self._received_diffs)
return True
def process_update_nc(self, versionid, incremental, objstr, sender, force=False):
"""Process an update:
-Undo all newer diffs
-Apply the just added one
-Redo all newer diffs
"""
obj = self.decode(objstr)
d = DiffRec(versionid, sender, incremental, obj)
i = self.insert_diff(d)
_logger.debug('Inserted diff at position %d', i)
if i == -1:
return False
j = len(self._received_diffs) - 1 # Don't include ourselve
while j > i:
if not self._received_diffs[j].incremental:
break # not necessary to continue beyond replacement object
self.apply_diff(self._inverse_diffs[j].obj)
j -= 1
while j < len(self._received_diffs):
if not self._received_diffs[j].incremental:
self._value = self._received_diffs[j].obj
else:
self._inverse_diffs[j].obj = self.apply_diff(self._received_diffs[j].obj)
self._version_id = self._received_diffs[j].version_id
j += 1
self.do_changed_callback()
return True
def process_update(self, versionid, incremental, objstr, sender, force=False):
"""Process an update:
-Undo all newer diffs to get to the common version
- Check for compatability between the received update and the 'combined' newer diffs
- If compatible, insert the received one
- If not, apply the 'winning' one, and pass the other to the 'rejected' folder
We return 'True' if there is no conflict, and 'False' if there was one
"""
if (versionid == self._version_id):
_logger.debug("Maybe dupe? our versionid:%d, received:%d", self._version_id, versionid)
a = len(self._received_diffs) > 0
b = (sender == self._received_diffs[-1].sender)
_logger.debug("Two tests: %s, %s", a, b)
if a and b:
return True #Dupe
obj = self.decode(objstr)
_logger.debug( "process_update: version: %s, obj: %s" % (versionid, obj))
if versionid > self._version_id + 1 and incremental and not force:
#Disordered diffs. Store for later use
self._pending_diffs[versionid] = DiffRec(versionid, sender, incremental, obj)
for i in range(self._version_id+1, versionid):
#TODO : Call for missing diffs:
pass
_logger.debug("Disordered diffs. returning")
return True
old = self.get_version(versionid - 1) #supposed common ancestor
if not incremental: #we get the incremental version maually
obj2 = self.diff(obj, old)
else:
obj2 = obj
db = DiffRec(versionid, sender, True, obj2)
if versionid > self._version_id or force: #expected version number
if not incremental:
_logger.debug("Update in expected range, non incremental")
self._value = obj
self._received_diffs.append(db)
self._version_id = versionid
else:
_logger.debug("Update in expected range, incremental")
self.insert_diff(db, old)
while self._version_id + 1 in self._pending_diffs:
#We get the pending diff and apply it
pd = self._pending_diffs[self._version_id + 1]
if not pd.incremental:
self._value = pd.obj
pd.obj = self.diff(pd.obj, self._value)
pd.incremental = True
else:
self.insert_diff(pd, self._value)
self._received_diffs.append(pd)
self._version_id += 1
del self._pending_diffs[self._version_id +1]
_logger.debug("Updated value: %s", self._value)
self.do_changed_callback()
return True
else:
_logger.debug("Conflicting versionids: mine:%d, his:%d" %(self._version_id, versionid))
obj_da = self.diff(self._value, old)
if len(self._received_diffs)>0:
sender_a = self._received_diffs[-1].sender
else:
sender_a = None
da = DiffRec(self._version_id, sender_a, True, obj_da)
_logger.debug("Verifying compatibility")
if self._compatible_diffs(da.obj, db.obj):
_logger.debug("compatible diff")
if self.insert_diff(db, old):
#insert does take care of version actualization and updates self._version_id
_logger.debug("changed without error")
self.do_changed_callback()
return True
else:
_logger.debug("Error with insertion")
return False
def _compatible_diffs(self, da, db):
return True
def diff(self, new, old):
return None
def apply_diff_to(self, obj, diffobj):
return (obj, diffobj)
def apply_diff(self, diffobj):
(newobj, idiff) = self.apply_diff_to(self._value, diffobj)
self._value = newobj
return idiff
def is_locked(self):
return self._locked
def lock(self):
if not self._locked:
self._locked = True
self._locked_by = "me"
self._locked_time = time.time()
self._helper.LockObject(self._name, self._locked_time)
def receive_lock(self, sender, when):
if not self._locked or \
(self._locked and self._locked_time > when):
if self._locked and 'locklost' in self._options:
self._options['locklost']()
self._locked = True
self._locked_by = sender
self._locked_time = when
if 'locked' in self._options:
self._options['locked'](sender)
def unlock(self):
if self._locked and self._locked_by is 'me':
self._helper.UnlockObject(self._name)
def receive_unlock(self, sender):
if self._locked:
self._locked = False
self._locked_by = None
self._locked_time = 0
if 'unlocked' in self._options:
self._options['unlocked'](sender)
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