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1563.2.12
by Robert Collins
Checkpointing: created InterObject to factor out common inter object worker code, added InterVersionedFile and tests to allow making join work between any versionedfile. |
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# Copyright (C) 2006 Canonical Ltd
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#
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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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#
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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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#
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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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carried out between.
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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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"""
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# _optimisers = set()
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# Each concrete InterObject type should have its own optimisers set.
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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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InterFOO if possible.
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"""
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self.source = source |
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self.target = target |
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@classmethod
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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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"""
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for provider in 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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@classmethod
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def register_optimiser(klass, optimiser): |
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"""Register an InterObject optimiser."""
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klass._optimisers.add(optimiser) |
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@classmethod
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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) |