~bzr-pqm/bzr/bzr.dev

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).
1852.11.1 by Robert Collins
Deprecate compare_trees and move its body to InterTree.changes_from.
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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.)
2241.1.4 by Martin Pool
Moved old weave-based repository formats into bzrlib.repofmt.weaverepo.
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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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    registered first.
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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    """
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1910.2.15 by Aaron Bentley
Back out inter.get changes, make optimizers an ordered list
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    # _optimisers = list()
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    # Each concrete InterObject type should have its own optimisers list.
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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    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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1852.11.1 by Robert Collins
Deprecate compare_trees and move its body to InterTree.changes_from.
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    def _double_lock(self, lock_source, lock_target):
1852.11.3 by Robert Collins
Fix typo in inter.py.
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        """Take out two locks, rolling back the first if the second throws."""
1852.11.1 by Robert Collins
Deprecate compare_trees and move its body to InterTree.changes_from.
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        lock_source()
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        try:
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            lock_target()
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        except Exception:
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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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            self.source.unlock()
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            raise
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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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    @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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        """
1910.2.15 by Aaron Bentley
Back out inter.get changes, make optimizers an ordered list
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        for provider in reversed(klass._optimisers):
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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            if provider.is_compatible(source, target):
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                return provider(source, target)
1910.2.15 by Aaron Bentley
Back out inter.get changes, make optimizers an ordered list
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        return klass(source, target)
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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1852.11.1 by Robert Collins
Deprecate compare_trees and move its body to InterTree.changes_from.
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    def lock_read(self):
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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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        """
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        self._double_lock(self.source.lock_read, self.target.lock_read)
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    def lock_write(self):
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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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        """
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        self._double_lock(self.source.lock_read, self.target.lock_write)
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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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    @classmethod
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    def register_optimiser(klass, optimiser):
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        """Register an InterObject optimiser."""
1910.2.15 by Aaron Bentley
Back out inter.get changes, make optimizers an ordered list
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        klass._optimisers.append(optimiser)
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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1852.11.1 by Robert Collins
Deprecate compare_trees and move its body to InterTree.changes_from.
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    def unlock(self):
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        """Release the locks on source and target."""
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        try:
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            self.target.unlock()
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        finally:
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            self.source.unlock()
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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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    @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)