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# Copyright (C) 2003-2007 Robey Pointer <robeypointer@gmail.com>
#
# This file is part of paramiko.
#
# Paramiko is free software; you can redistribute it and/or modify it under the
# terms of the GNU Lesser General Public License as published by the Free
# Software Foundation; either version 2.1 of the License, or (at your option)
# any later version.
#
# Paramiko 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 Paramiko; if not, write to the Free Software Foundation, Inc.,
# 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
"""
Resource manager.
"""
import weakref
class ResourceManager (object):
"""
A registry of objects and resources that should be closed when those
objects are deleted.
This is meant to be a safer alternative to Python's ``__del__`` method,
which can cause reference cycles to never be collected. Objects registered
with the ResourceManager can be collected but still free resources when
they die.
Resources are registered using `register`, and when an object is garbage
collected, each registered resource is closed by having its ``close()``
method called. Multiple resources may be registered per object, but a
resource will only be closed once, even if multiple objects register it.
(The last object to register it wins.)
"""
def __init__(self):
self._table = {}
def register(self, obj, resource):
"""
Register a resource to be closed with an object is collected.
When the given ``obj`` is garbage-collected by the Python interpreter,
the ``resource`` will be closed by having its ``close()`` method called.
Any exceptions are ignored.
:param object obj: the object to track
:param object resource:
the resource to close when the object is collected
"""
def callback(ref):
try:
resource.close()
except:
pass
del self._table[id(resource)]
# keep the weakref in a table so it sticks around long enough to get
# its callback called. :)
self._table[id(resource)] = weakref.ref(obj, callback)
# singleton
ResourceManager = ResourceManager()
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