73 lines
2.5 KiB
Python
73 lines
2.5 KiB
Python
# Copyright (C) 2011 Jeff Forcier <jeff@bitprophet.org>
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#
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# This file is part of ssh.
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#
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# 'ssh' is free software; you can redistribute it and/or modify it under the
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# terms of the GNU Lesser General Public License as published by the Free
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# Software Foundation; either version 2.1 of the License, or (at your option)
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# any later version.
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#
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# 'ssh' is distrubuted in the hope that it will be useful, but WITHOUT ANY
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# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
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# A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
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# details.
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#
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# You should have received a copy of the GNU Lesser General Public License
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# along with 'ssh'; if not, write to the Free Software Foundation, Inc.,
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# 51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA.
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"""
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Resource manager.
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"""
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import weakref
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class ResourceManager (object):
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"""
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A registry of objects and resources that should be closed when those
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objects are deleted.
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This is meant to be a safer alternative to python's C{__del__} method,
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which can cause reference cycles to never be collected. Objects registered
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with the ResourceManager can be collected but still free resources when
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they die.
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Resources are registered using L{register}, and when an object is garbage
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collected, each registered resource is closed by having its C{close()}
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method called. Multiple resources may be registered per object, but a
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resource will only be closed once, even if multiple objects register it.
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(The last object to register it wins.)
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"""
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def __init__(self):
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self._table = {}
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def register(self, obj, resource):
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"""
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Register a resource to be closed with an object is collected.
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When the given C{obj} is garbage-collected by the python interpreter,
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the C{resource} will be closed by having its C{close()} method called.
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Any exceptions are ignored.
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@param obj: the object to track
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@type obj: object
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@param resource: the resource to close when the object is collected
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@type resource: object
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"""
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def callback(ref):
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try:
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resource.close()
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except:
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pass
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del self._table[id(resource)]
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# keep the weakref in a table so it sticks around long enough to get
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# its callback called. :)
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self._table[id(resource)] = weakref.ref(obj, callback)
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# singleton
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ResourceManager = ResourceManager()
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