##############################################################################
#
# Copyright (c) 2001, 2002 Zope Corporation and Contributors.
# All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.0 (ZPL). A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE
#
##############################################################################
import Persistence
class Length(Persistence.Persistent):
"""BTree lengths are too expensive to compute
Objects that use BTrees need to keep track of lengths themselves.
This class provides an object for doing this.
As a bonus, the object support application-level conflict resolution.
"""
def __init__(self, v=0): self.value=v
def __getstate__(self): return self.value
def __setstate__(self, v): self.value=v
def set(self, v): self.value=v
def _p_resolveConflict(self, old, s1, s2): return s1 + s2 - old
def _p_independent(self):
# My state doesn't depend on or materially effect the state of
# other objects.
return 1
def change(self, delta): self.value = self.value + delta
def __call__(self, *args): return self.value
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