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# sharedpython.py, classes to aid activities in sharing a state
# @author: Miguel Angel Alvarez, miguel@laptop.org
# @author: Reinier Heeres
#
# 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:
#
import pickle
import difflib
import logging
from sharedobject import DiffRec
_logger = logging.getLogger('sharedpython')
from sharedobject import SharedObject
class SharedPython(SharedObject):
def __init__(self, name, helper, opt={}):
SharedObject.__init__(self, name, helper, opt=opt)
self._value = None
self._picklestr = ''
def _divide_change(self, c):
"""Separate the index and the string parts of the chage string"""
if ' ' in c:
i = c.index(' ')
return (c[:i], c[i+1:])
else:
print c
return None
def inverse_diff(self, diff):
"""Return the inverse diff object"""
d = SharedObject.inverse_diff(self, diff)
if d == None:
obj = self._generate_inverse_diffobj(diff.obj)
return DiffRec(diff.version_id, diff.sender, True, obj)
def _generate_inverse_diffobj(self, changes):
ret = []
delta = 0
last_num = -1
last_n_in = -1
for c in changes:
n, s = self._divide_change(c)
l = len(s)
num = abs(int(n))
if num == last_num:
n_in = last_n_in
else:
n_in = num + delta
last_num = num
last_n_in = n_in
if c[0] == '+':
ret.append('-'+str(n_in)+' '+s)
delta += l
elif c[0] == '-':
ret.append('+'+str(n_in)+' '+s)
delta -= l
else:
print "Unknown line type:", c
ret = self._format_changes(ret)
return ret
def _update_interval(self, i, cs):
"""Get an 'exclusion interval' (where no other different edits are accepted) for the change cs[i]"""
c = cs[i]
n, d = self._divide_change(c)
n = int(n)
if n >= 0:
return (n+1, n+1)
else:
return (abs(n), abs(n) + len(d))
def _intersect(self, ia, ib):
"""function that takes 2 intervals (2 element ordered int lists) and returns whether they
intersect and, if not, which one is bigger:
ret > 0 => ia bigger
ret < 0 => ib bigger
ret = 0 => intersection"""
assert ia[1] >= ia[0] and len(ia) == 2
assert ib[1] >= ib[0] and len(ib) == 2
if ia[0] > ib[1]:
return 1 #No _intersect, ia bigger
if ia[1] < ib[0]:
return -1 #No _intersect, ia smaller
return 0 #Intersect
def _compatible_diffs(self, diff_a, diff_b):
""" It returns whether two change arrays act upon the same positions, and
cannot therefore be automatically merged without risking conflict"""
_logger.debug("_compatible_diffs(): a=%s, b=%s", diff_a, diff_b)
index_a = index_b = 0
while index_a < len(diff_a) and index_b < len(diff_b):
interval_a = self._update_interval(index_a, diff_a)
interval_b = self._update_interval(index_b, diff_b)
d = self._intersect(interval_a, interval_b)
if d == 0 :
## if diff_a[index_a] not in diff_b and diff_b[index_b] not in diff_a:
## print "change a:'%s'\tchange_b:'%s'" % (diff_a[index_a], diff_b[index_b])
## return False
## elif interval_a[1] > interval_b[1]:
## index_b += 1
## else:
## index_a += 1
## ATT: More restrictive version of compatible_diffs used right now
return False
elif d == 1:
index_b += 1
elif d == -1:
index_a += 1
else:
index_a += 1
index_b += 1
return True
def _format_changes(self, changes):
last_sign = None
last_num = -1
foreseen_index = -1
res=[]
for c in changes:
sign = c[0]
n, s = self._divide_change(c)
number = abs(int(n))
if sign == "+" and last_sign == "-" and (number == foreseen_index or number == last_num) :
res = res[:-1]+[sign +str(last_num)+" "+s, res[-1]]
last_sign = sign
foreseen_index = number + len(s)
last_num = number
else:
res.append(c)
last_sign = sign
foreseen_index = number + len(s)
last_num = number
return res
def diff(self, new_object, old_object):
"""Generate a change array from two python objects"""
_logger.debug("Diffing old:%s (type: %s), new: %s (type: %s)", old_object, type(old_object),
new_object, type(new_object))
differ = difflib.Differ()
old = pickle.dumps(old_object)
new = pickle.dumps(new_object)
## _logger.debug('Old text: %s', old)
## _logger.debug(' New text:%s', new)
ret = []
raw_delta = list(differ.compare(old, new))
## _logger.debug('raw delta: %s', raw_delta)
pos = 0
continuous = False
for r in raw_delta:
if r[:2] == "+ ":
if len(ret) > 0 and ret[-1][0] == "+" and continuous:
ret[-1] += r[2:]
#if 2 continuous additions occur, append at the end
else:
string = "+"+str(pos)+" "+r[2:]
ret.append(string)
continuous = True
elif r[:2] == "- ":
if len(ret) > 0 and ret[-1][0] == "-" and continuous:
ret[-1] += r[2:] #append at the end
else:
string = "-"+str(pos)+" "+r[2:]
ret.append(string)
continuous = True
pos += 1 # TODO: important change; verify
elif r[:2] == "? ":
pass
else:
continuous = False
pos += len(r) - 2
## _logger.debug('Ret before format changes: %s', ret)
return self._format_changes(ret)
def _apply_diff_to(self, object, diffobj):
""" Apply a diff to a given object and return the new version
In this case, the provided object gets modified, too."""
old = pickle.dumps(object)
_logger.debug("_apply_diff_to(): old=%r, diffobj=%s", old, diffobj)
new = ""
pos = old_pos = 0
for c in diffobj:
id, st = self._divide_change(c)
pos = abs(int(id))
new += old[old_pos:pos]
if id[0] == "+":
## _logger.debug("_apply_diff_to(): adding %r", st)
new += st
elif id[0] == "-":
## _logger.debug("_apply_diff_to(): deleting %r", st)
if old[pos:pos+len(st)] != st:
exc = "Bad delete at %d, expected %s, got %r" % (pos,
st, old[pos:pos+len(st)])
raise Exception(exc)
pos += len(st)
old_pos = pos
if pos < len(old):
new += old[pos:]
res = pickle.loads(new)
_logger.debug("_apply_diff_to(): new=%r, res=%s", new, res)
idiff = self._generate_inverse_diffobj(diffobj)
return (res, idiff)
def get_version(self, versionid):
_logger.debug("get_version(): called with versionid = %d", versionid)
if versionid == self._version_id:
return self._value
ret = self._value
if versionid > self._version_id:
return None
for i in range(len(self._received_diffs)-1, self._get_diff_index(versionid), -1):
d = self._received_diffs[i]
idobj = self._generate_inverse_diffobj(d.obj)
ret = self._apply_diff_to(ret, idobj)[0]
_logger.debug("get_version(): return value: %s", ret)
return ret
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