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# Copyright (C) 2005-2011 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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from bzrlib.lazy_import import lazy_import
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lazy_import(globals(), """
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from bzrlib.decorators import (
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# XXX: The tracking here of lock counts and whether the lock is held is
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# somewhat redundant with what's done in LockDir; the main difference is that
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# LockableFiles permits reentrancy.
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class _LockWarner(object):
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"""Hold a counter for a lock and warn if GCed while the count is >= 1.
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This is separate from LockableFiles because putting a __del__ on
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LockableFiles can result in uncollectable cycles.
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def __init__(self, repr):
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if self.lock_count >= 1:
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# There should have been a try/finally to unlock this.
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warnings.warn("%r was gc'd while locked" % self.repr)
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class LockableFiles(object):
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"""Object representing a set of related files locked within the same scope.
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This coordinates access to the lock along with providing a transaction.
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LockableFiles manage a lock count and can be locked repeatedly by
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a single caller. (The underlying lock implementation generally does not
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Instances of this class are often called control_files.
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This class is now deprecated; code should move to using the Transport
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directly for file operations and using the lock or CountedLock for
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:ivar _lock: The real underlying lock (e.g. a LockDir)
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:ivar _counted_lock: A lock decorated with a semaphore, so that it
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# _lock_mode: None, or 'r' or 'w'
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# _lock_count: If _lock_mode is true, a positive count of the number of
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# times the lock has been taken *by this process*.
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def __init__(self, transport, lock_name, lock_class):
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"""Create a LockableFiles group
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:param transport: Transport pointing to the directory holding the
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control files and lock.
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:param lock_name: Name of the lock guarding these files.
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:param lock_class: Class of lock strategy to use: typically
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either LockDir or TransportLock.
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self._transport = transport
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self.lock_name = lock_name
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self._transaction = None
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self._lock_mode = None
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self._lock_warner = _LockWarner(repr(self))
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esc_name = self._escape(lock_name)
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self._lock = lock_class(transport, esc_name,
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file_modebits=self._file_mode,
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dir_modebits=self._dir_mode)
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self._counted_lock = counted_lock.CountedLock(self._lock)
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def create_lock(self):
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This should normally be called only when the LockableFiles directory
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is first created on disk.
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self._lock.create(mode=self._dir_mode)
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return '%s(%r)' % (self.__class__.__name__,
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return 'LockableFiles(%s, %s)' % (self.lock_name, self._transport.base)
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def break_lock(self):
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"""Break the lock of this lockable files group if it is held.
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The current ui factory will be used to prompt for user conformation.
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self._lock.break_lock()
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def _escape(self, file_or_path):
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"""DEPRECATED: Do not use outside this class"""
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if not isinstance(file_or_path, basestring):
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file_or_path = '/'.join(file_or_path)
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if file_or_path == '':
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return urlutils.escape(osutils.safe_unicode(file_or_path))
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def _find_modes(self):
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"""Determine the appropriate modes for files and directories.
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:deprecated: Replaced by BzrDir._find_creation_modes.
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# XXX: The properties created by this can be removed or deprecated
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# once all the _get_text_store methods etc no longer use them.
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st = self._transport.stat('.')
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except errors.TransportNotPossible:
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self._dir_mode = 0755
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self._file_mode = 0644
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# Check the directory mode, but also make sure the created
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# directories and files are read-write for this user. This is
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# mostly a workaround for filesystems which lie about being able to
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# write to a directory (cygwin & win32)
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self._dir_mode = (st.st_mode & 07777) | 00700
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# Remove the sticky and execute bits for files
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self._file_mode = self._dir_mode & ~07111
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def leave_in_place(self):
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"""Set this LockableFiles to not clear the physical lock on unlock."""
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self._lock.leave_in_place()
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def dont_leave_in_place(self):
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"""Set this LockableFiles to clear the physical lock on unlock."""
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self._lock.dont_leave_in_place()
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def lock_write(self, token=None):
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"""Lock this group of files for writing.
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:param token: if this is already locked, then lock_write will fail
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unless the token matches the existing lock.
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:returns: a token if this instance supports tokens, otherwise None.
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:raises TokenLockingNotSupported: when a token is given but this
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instance doesn't support using token locks.
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:raises MismatchedToken: if the specified token doesn't match the token
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of the existing lock.
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A token should be passed in if you know that you have locked the object
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some other way, and need to synchronise this object's state with that
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# TODO: Upgrade locking to support using a Transport,
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# and potentially a remote locking protocol
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if self._lock_mode != 'w' or not self.get_transaction().writeable():
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raise errors.ReadOnlyError(self)
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self._lock.validate_token(token)
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self._lock_warner.lock_count += 1
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return self._token_from_lock
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token_from_lock = self._lock.lock_write(token=token)
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#traceback.print_stack()
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self._lock_mode = 'w'
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self._lock_warner.lock_count = 1
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self._set_write_transaction()
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self._token_from_lock = token_from_lock
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return token_from_lock
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if self._lock_mode not in ('r', 'w'):
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raise ValueError("invalid lock mode %r" % (self._lock_mode,))
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self._lock_warner.lock_count += 1
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self._lock.lock_read()
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#traceback.print_stack()
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self._lock_mode = 'r'
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self._lock_warner.lock_count = 1
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self._set_read_transaction()
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def _set_read_transaction(self):
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"""Setup a read transaction."""
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self._set_transaction(transactions.ReadOnlyTransaction())
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# 5K may be excessive, but hey, its a knob.
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self.get_transaction().set_cache_size(5000)
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def _set_write_transaction(self):
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"""Setup a write transaction."""
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self._set_transaction(transactions.WriteTransaction())
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@only_raises(errors.LockNotHeld, errors.LockBroken)
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if not self._lock_mode:
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return lock.cant_unlock_not_held(self)
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if self._lock_warner.lock_count > 1:
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self._lock_warner.lock_count -= 1
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#traceback.print_stack()
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self._finish_transaction()
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self._lock_mode = self._lock_warner.lock_count = None
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def _lock_count(self):
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return self._lock_warner.lock_count
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"""Return true if this LockableFiles group is locked"""
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return self._lock_warner.lock_count >= 1
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def get_physical_lock_status(self):
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"""Return physical lock status.
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Returns true if a lock is held on the transport. If no lock is held, or
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the underlying locking mechanism does not support querying lock
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status, false is returned.
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return self._lock.peek() is not None
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except NotImplementedError:
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def get_transaction(self):
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"""Return the current active transaction.
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If no transaction is active, this returns a passthrough object
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for which all data is immediately flushed and no caching happens.
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if self._transaction is None:
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return transactions.PassThroughTransaction()
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return self._transaction
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def _set_transaction(self, new_transaction):
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"""Set a new active transaction."""
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if self._transaction is not None:
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raise errors.LockError('Branch %s is in a transaction already.' %
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self._transaction = new_transaction
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def _finish_transaction(self):
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"""Exit the current transaction."""
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if self._transaction is None:
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raise errors.LockError('Branch %s is not in a transaction' %
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transaction = self._transaction
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self._transaction = None
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class TransportLock(object):
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"""Locking method which uses transport-dependent locks.
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On the local filesystem these transform into OS-managed locks.
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These do not guard against concurrent access via different
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This is suitable for use only in WorkingTrees (which are at present
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def __init__(self, transport, escaped_name, file_modebits, dir_modebits):
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self._transport = transport
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self._escaped_name = escaped_name
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self._file_modebits = file_modebits
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self._dir_modebits = dir_modebits
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def break_lock(self):
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raise NotImplementedError(self.break_lock)
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def leave_in_place(self):
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raise NotImplementedError(self.leave_in_place)
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def dont_leave_in_place(self):
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raise NotImplementedError(self.dont_leave_in_place)
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def lock_write(self, token=None):
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if token is not None:
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raise errors.TokenLockingNotSupported(self)
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self._lock = self._transport.lock_write(self._escaped_name)
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self._lock = self._transport.lock_read(self._escaped_name)
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raise NotImplementedError()
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def create(self, mode=None):
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"""Create lock mechanism"""
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# for old-style locks, create the file now
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self._transport.put_bytes(self._escaped_name, '',
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mode=self._file_modebits)
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def validate_token(self, token):
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if token is not None:
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raise errors.TokenLockingNotSupported(self)
added
removed
bzrlib/lockable_files.py
