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# Copyright (C) 2006 Canonical Ltd
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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"""Inter-object utility class."""
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class InterObject(object):
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"""This class represents operations taking place between two objects.
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Its instances have methods like join or copy_content or fetch, and contain
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references to the source and target objects these operations can be
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Often we will provide convenience methods on the objects which carry out
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operations with another of similar type - they will always forward to
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a subclass of InterObject - i.e.
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InterVersionedFile.get(other).method_name(parameters).
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If the source and target objects implement the locking protocol -
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lock_read, lock_write, unlock, then the InterObject's lock_read,
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lock_write and unlock methods may be used (optionally in conjunction with
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the needs_read_lock and needs_write_lock decorators.)
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When looking for an inter, the most recently registered types are tested
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first. So typically the most generic and slowest InterObjects should be
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# _optimisers = list()
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# Each concrete InterObject type should have its own optimisers list.
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def __init__(self, source, target):
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"""Construct a default InterObject instance. Please use 'get'.
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Only subclasses of InterObject should call
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InterObject.__init__ - clients should call InterFOO.get where FOO
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is the base type of the objects they are interacting between. I.e.
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InterVersionedFile or InterRepository.
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get() is a convenience class method which will create an optimised
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def _double_lock(self, lock_source, lock_target):
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"""Take out two locks, rolling back the first if the second throws."""
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# we want to ensure that we don't leave source locked by mistake.
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# and any error on target should not confuse source.
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def get(klass, source, target):
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"""Retrieve a Inter worker object for these objects.
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:param source: the object to be the 'source' member of
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the InterObject instance.
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:param target: the object to be the 'target' member of
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the InterObject instance.
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If an optimised worker exists it will be used otherwise
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a default Inter worker instance will be created.
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for provider in reversed(klass._optimisers):
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if provider.is_compatible(source, target):
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return provider(source, target)
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return klass(source, target)
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"""Take out a logical read lock.
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This will lock the source branch and the target branch. The source gets
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a read lock and the target a read lock.
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self._double_lock(self.source.lock_read, self.target.lock_read)
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"""Take out a logical write lock.
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This will lock the source branch and the target branch. The source gets
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a read lock and the target a write lock.
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self._double_lock(self.source.lock_read, self.target.lock_write)
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def register_optimiser(klass, optimiser):
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"""Register an InterObject optimiser."""
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klass._optimisers.append(optimiser)
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"""Release the locks on source and target."""
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def unregister_optimiser(klass, optimiser):
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"""Unregister an InterObject optimiser."""
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klass._optimisers.remove(optimiser)
added
removed
bzrlib/inter.py
