social_media_platform/thesisenv/lib/python3.6/site-packages/BTrees/Length.py

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# Copyright (c) 2001, 2002 Zope Foundation and Contributors.
# All Rights Reserved.
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# This software is subject to the provisions of the Zope Public License,
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import persistent

class Length(persistent.Persistent):
    """BTree lengths are often 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.

    It is tempting to to assign length objects to __len__ attributes
    to provide instance-specific __len__ methods.  However, this no
    longer works as expected, because new-style classes cache
    class-defined slot methods (like __len__) in C type slots.  Thus,
    instance-defined slot fillers are ignored.
    """
    # class-level default required to keep copy.deepcopy happy -- see
    # https://bugs.launchpad.net/zodb/+bug/516653
    value = 0

    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):
        "Set the length value to v."
        self.value = v

    def _p_resolveConflict(self, old, s1, s2):
        return s1 + s2 - old

    def change(self, delta):
        "Add delta to the length value."
        self.value += delta

    def __call__(self, *args):
        "Return the current length value."
        return self.value