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# Copyright (C) 2005-2011 Canonical Ltd
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
from bzrlib.lazy_import import lazy_import
lazy_import(globals(), """
import warnings
from bzrlib import (
counted_lock,
errors,
lock,
osutils,
transactions,
urlutils,
)
""")
from bzrlib.decorators import (
only_raises,
)
# XXX: The tracking here of lock counts and whether the lock is held is
# somewhat redundant with what's done in LockDir; the main difference is that
# LockableFiles permits reentrancy.
class _LockWarner(object):
"""Hold a counter for a lock and warn if GCed while the count is >= 1.
This is separate from LockableFiles because putting a __del__ on
LockableFiles can result in uncollectable cycles.
"""
def __init__(self, repr):
self.lock_count = 0
self.repr = repr
def __del__(self):
if self.lock_count >= 1:
# There should have been a try/finally to unlock this.
warnings.warn("%r was gc'd while locked" % self.repr)
class LockableFiles(object):
"""Object representing a set of related files locked within the same scope.
This coordinates access to the lock along with providing a transaction.
LockableFiles manage a lock count and can be locked repeatedly by
a single caller. (The underlying lock implementation generally does not
support this.)
Instances of this class are often called control_files.
This class is now deprecated; code should move to using the Transport
directly for file operations and using the lock or CountedLock for
locking.
:ivar _lock: The real underlying lock (e.g. a LockDir)
:ivar _counted_lock: A lock decorated with a semaphore, so that it
can be re-entered.
"""
# _lock_mode: None, or 'r' or 'w'
# _lock_count: If _lock_mode is true, a positive count of the number of
# times the lock has been taken *by this process*.
def __init__(self, transport, lock_name, lock_class):
"""Create a LockableFiles group
:param transport: Transport pointing to the directory holding the
control files and lock.
:param lock_name: Name of the lock guarding these files.
:param lock_class: Class of lock strategy to use: typically
either LockDir or TransportLock.
"""
self._transport = transport
self.lock_name = lock_name
self._transaction = None
self._lock_mode = None
self._lock_warner = _LockWarner(repr(self))
self._find_modes()
esc_name = self._escape(lock_name)
self._lock = lock_class(transport, esc_name,
file_modebits=self._file_mode,
dir_modebits=self._dir_mode)
self._counted_lock = counted_lock.CountedLock(self._lock)
def create_lock(self):
"""Create the lock.
This should normally be called only when the LockableFiles directory
is first created on disk.
"""
self._lock.create(mode=self._dir_mode)
def __repr__(self):
return '%s(%r)' % (self.__class__.__name__,
self._transport)
def __str__(self):
return 'LockableFiles(%s, %s)' % (self.lock_name, self._transport.base)
def break_lock(self):
"""Break the lock of this lockable files group if it is held.
The current ui factory will be used to prompt for user conformation.
"""
self._lock.break_lock()
def _escape(self, file_or_path):
"""DEPRECATED: Do not use outside this class"""
if not isinstance(file_or_path, basestring):
file_or_path = '/'.join(file_or_path)
if file_or_path == '':
return u''
return urlutils.escape(osutils.safe_unicode(file_or_path))
def _find_modes(self):
"""Determine the appropriate modes for files and directories.
:deprecated: Replaced by BzrDir._find_creation_modes.
"""
# XXX: The properties created by this can be removed or deprecated
# once all the _get_text_store methods etc no longer use them.
# -- mbp 20080512
try:
st = self._transport.stat('.')
except errors.TransportNotPossible:
self._dir_mode = 0755
self._file_mode = 0644
else:
# Check the directory mode, but also make sure the created
# directories and files are read-write for this user. This is
# mostly a workaround for filesystems which lie about being able to
# write to a directory (cygwin & win32)
self._dir_mode = (st.st_mode & 07777) | 00700
# Remove the sticky and execute bits for files
self._file_mode = self._dir_mode & ~07111
def leave_in_place(self):
"""Set this LockableFiles to not clear the physical lock on unlock."""
self._lock.leave_in_place()
def dont_leave_in_place(self):
"""Set this LockableFiles to clear the physical lock on unlock."""
self._lock.dont_leave_in_place()
def lock_write(self, token=None):
"""Lock this group of files for writing.
:param token: if this is already locked, then lock_write will fail
unless the token matches the existing lock.
:returns: a token if this instance supports tokens, otherwise None.
:raises TokenLockingNotSupported: when a token is given but this
instance doesn't support using token locks.
:raises MismatchedToken: if the specified token doesn't match the token
of the existing lock.
A token should be passed in if you know that you have locked the object
some other way, and need to synchronise this object's state with that
fact.
"""
# TODO: Upgrade locking to support using a Transport,
# and potentially a remote locking protocol
if self._lock_mode:
if self._lock_mode != 'w' or not self.get_transaction().writeable():
raise errors.ReadOnlyError(self)
self._lock.validate_token(token)
self._lock_warner.lock_count += 1
return self._token_from_lock
else:
token_from_lock = self._lock.lock_write(token=token)
#traceback.print_stack()
self._lock_mode = 'w'
self._lock_warner.lock_count = 1
self._set_write_transaction()
self._token_from_lock = token_from_lock
return token_from_lock
def lock_read(self):
if self._lock_mode:
if self._lock_mode not in ('r', 'w'):
raise ValueError("invalid lock mode %r" % (self._lock_mode,))
self._lock_warner.lock_count += 1
else:
self._lock.lock_read()
#traceback.print_stack()
self._lock_mode = 'r'
self._lock_warner.lock_count = 1
self._set_read_transaction()
def _set_read_transaction(self):
"""Setup a read transaction."""
self._set_transaction(transactions.ReadOnlyTransaction())
# 5K may be excessive, but hey, its a knob.
self.get_transaction().set_cache_size(5000)
def _set_write_transaction(self):
"""Setup a write transaction."""
self._set_transaction(transactions.WriteTransaction())
@only_raises(errors.LockNotHeld, errors.LockBroken)
def unlock(self):
if not self._lock_mode:
return lock.cant_unlock_not_held(self)
if self._lock_warner.lock_count > 1:
self._lock_warner.lock_count -= 1
else:
#traceback.print_stack()
self._finish_transaction()
try:
self._lock.unlock()
finally:
self._lock_mode = self._lock_warner.lock_count = None
@property
def _lock_count(self):
return self._lock_warner.lock_count
def is_locked(self):
"""Return true if this LockableFiles group is locked"""
return self._lock_warner.lock_count >= 1
def get_physical_lock_status(self):
"""Return physical lock status.
Returns true if a lock is held on the transport. If no lock is held, or
the underlying locking mechanism does not support querying lock
status, false is returned.
"""
try:
return self._lock.peek() is not None
except NotImplementedError:
return False
def get_transaction(self):
"""Return the current active transaction.
If no transaction is active, this returns a passthrough object
for which all data is immediately flushed and no caching happens.
"""
if self._transaction is None:
return transactions.PassThroughTransaction()
else:
return self._transaction
def _set_transaction(self, new_transaction):
"""Set a new active transaction."""
if self._transaction is not None:
raise errors.LockError('Branch %s is in a transaction already.' %
self)
self._transaction = new_transaction
def _finish_transaction(self):
"""Exit the current transaction."""
if self._transaction is None:
raise errors.LockError('Branch %s is not in a transaction' %
self)
transaction = self._transaction
self._transaction = None
transaction.finish()
class TransportLock(object):
"""Locking method which uses transport-dependent locks.
On the local filesystem these transform into OS-managed locks.
These do not guard against concurrent access via different
transports.
This is suitable for use only in WorkingTrees (which are at present
always local).
"""
def __init__(self, transport, escaped_name, file_modebits, dir_modebits):
self._transport = transport
self._escaped_name = escaped_name
self._file_modebits = file_modebits
self._dir_modebits = dir_modebits
def break_lock(self):
raise NotImplementedError(self.break_lock)
def leave_in_place(self):
raise NotImplementedError(self.leave_in_place)
def dont_leave_in_place(self):
raise NotImplementedError(self.dont_leave_in_place)
def lock_write(self, token=None):
if token is not None:
raise errors.TokenLockingNotSupported(self)
self._lock = self._transport.lock_write(self._escaped_name)
def lock_read(self):
self._lock = self._transport.lock_read(self._escaped_name)
def unlock(self):
self._lock.unlock()
self._lock = None
def peek(self):
raise NotImplementedError()
def create(self, mode=None):
"""Create lock mechanism"""
# for old-style locks, create the file now
self._transport.put_bytes(self._escaped_name, '',
mode=self._file_modebits)
def validate_token(self, token):
if token is not None:
raise errors.TokenLockingNotSupported(self)
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