diff options
author | Kali Kaneko <kali@leap.se> | 2016-04-28 15:52:30 -0400 |
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committer | Kali Kaneko <kali@leap.se> | 2016-07-12 03:09:17 +0200 |
commit | 7abf86737562b5c79e902921df722f01e71178e6 (patch) | |
tree | e3aa3a1b6c444a0bcf9abd2a2eaef948559f6e63 /common/src/leap/soledad/common/l2db/vectorclock.py | |
parent | 9b3737a66b4df0a6e0fd4d91da097f36e94bd8e2 (diff) |
[refactor] fork u1db
Diffstat (limited to 'common/src/leap/soledad/common/l2db/vectorclock.py')
-rw-r--r-- | common/src/leap/soledad/common/l2db/vectorclock.py | 89 |
1 files changed, 89 insertions, 0 deletions
diff --git a/common/src/leap/soledad/common/l2db/vectorclock.py b/common/src/leap/soledad/common/l2db/vectorclock.py new file mode 100644 index 00000000..42bceaa8 --- /dev/null +++ b/common/src/leap/soledad/common/l2db/vectorclock.py @@ -0,0 +1,89 @@ +# Copyright 2011 Canonical Ltd. +# +# This file is part of u1db. +# +# u1db is free software: you can redistribute it and/or modify +# it under the terms of the GNU Lesser General Public License version 3 +# as published by the Free Software Foundation. +# +# u1db 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 u1db. If not, see <http://www.gnu.org/licenses/>. + +"""VectorClockRev helper class.""" + + +class VectorClockRev(object): + """Track vector clocks for multiple replica ids. + + This allows simple comparison to determine if one VectorClockRev is + newer/older/in-conflict-with another VectorClockRev without having to + examine history. Every replica has a strictly increasing revision. When + creating a new revision, they include all revisions for all other replicas + which the new revision dominates, and increment their own revision to + something greater than the current value. + """ + + def __init__(self, value): + self._values = self._expand(value) + + def __repr__(self): + s = self.as_str() + return '%s(%s)' % (self.__class__.__name__, s) + + def as_str(self): + s = '|'.join(['%s:%d' % (m, r) for m, r + in sorted(self._values.items())]) + return s + + def _expand(self, value): + result = {} + if value is None: + return result + for replica_info in value.split('|'): + replica_uid, counter = replica_info.split(':') + counter = int(counter) + result[replica_uid] = counter + return result + + def is_newer(self, other): + """Is this VectorClockRev strictly newer than other. + """ + if not self._values: + return False + if not other._values: + return True + this_is_newer = False + other_expand = dict(other._values) + for key, value in self._values.iteritems(): + if key in other_expand: + other_value = other_expand.pop(key) + if other_value > value: + return False + elif other_value < value: + this_is_newer = True + else: + this_is_newer = True + if other_expand: + return False + return this_is_newer + + def increment(self, replica_uid): + """Increase the 'replica_uid' section of this vector clock. + + :return: A string representing the new vector clock value + """ + self._values[replica_uid] = self._values.get(replica_uid, 0) + 1 + + def maximize(self, other_vcr): + for replica_uid, counter in other_vcr._values.iteritems(): + if replica_uid not in self._values: + self._values[replica_uid] = counter + else: + this_counter = self._values[replica_uid] + if this_counter < counter: + self._values[replica_uid] = counter |