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  • Committer: Marius Kruger
  • Date: 2010-07-10 21:28:56 UTC
  • mto: (5384.1.1 integration)
  • mto: This revision was merged to the branch mainline in revision 5385.
  • Revision ID: marius.kruger@enerweb.co.za-20100710212856-uq4ji3go0u5se7hx
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bzrlib/inter.py
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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"""Inter-object utility class."""
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from __future__ import absolute_import
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from .errors import BzrError
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from .lock import LogicalLockResult
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class NoCompatibleInter(BzrError):
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    _fmt = ('No compatible object available for operations from %(source)r '
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            'to %(target)r.')
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    def __init__(self, source, target):
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        self.source = source
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        self.target = target
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class InterObject(object):
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    """This class represents operations taking place between two objects.
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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.
 
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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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                       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 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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        raise NoCompatibleInter(source, target)
 
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        return klass(source, target)
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    def lock_read(self):
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        """Take out a logical read lock.
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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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        return LogicalLockResult(self.unlock)
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    def lock_write(self):
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        """Take out a logical write lock.
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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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        return LogicalLockResult(self.unlock)
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    @classmethod
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    def register_optimiser(klass, optimiser):