~bzr-pqm/bzr/bzr.dev : contents of bzrlib/counted

~bzr-pqm/bzr/bzr.dev : (revision 6591.1.1)

3474.1.2 by Martin Pool CountedLock.unlock should raise LockNotHeld if appropriate	1	# Copyright (C) 2007, 2008 Canonical Ltd
2475.4.1 by Martin Pool Start adding CountedLock class to partially replace LockableFiles	2	#
	3	# This program is free software; you can redistribute it and/or modify
	4	# it under the terms of the GNU General Public License as published by
	5	# the Free Software Foundation; either version 2 of the License, or
	6	# (at your option) any later version.
	7	#
	8	# This program is distributed in the hope that it will be useful,
	9	# but WITHOUT ANY WARRANTY; without even the implied warranty of
	10	# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	11	# GNU General Public License for more details.
	12	#
	13	# You should have received a copy of the GNU General Public License
	14	# along with this program; if not, write to the Free Software
4183.7.1 by Sabin Iacob update FSF mailing address	15	# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
2475.4.1 by Martin Pool Start adding CountedLock class to partially replace LockableFiles	16
6379.6.7 by Jelmer Vernooij Move importing from future until after doc string, otherwise the doc string will disappear.	17	"""Counted lock class"""
	18
6379.6.1 by Jelmer Vernooij Import absolute_import in a few places.	19	from __future__ import absolute_import
	20
3474.1.2 by Martin Pool CountedLock.unlock should raise LockNotHeld if appropriate	21	from bzrlib import (
	22	errors,
2475.4.1 by Martin Pool Start adding CountedLock class to partially replace LockableFiles	23	)
	24
	25
	26	class CountedLock(object):
	27	"""Decorator around a lock that makes it reentrant.
	28
	29	This can be used with any object that provides a basic Lock interface,
	30	including LockDirs and OS file locks.
3407.2.19 by Martin Pool CountedLock should manage lock tokens	31
	32	:ivar _token: While a write lock is held, this is the token
	33	for it.
2475.4.1 by Martin Pool Start adding CountedLock class to partially replace LockableFiles	34	"""
	35
	36	def __init__(self, real_lock):
	37	self._real_lock = real_lock
	38	self._lock_mode = None
	39	self._lock_count = 0
	40
3474.1.2 by Martin Pool CountedLock.unlock should raise LockNotHeld if appropriate	41	def __repr__(self):
	42	return "%s(%r)" % (self.__class__.__name__,
	43	self._real_lock)
	44
2475.4.1 by Martin Pool Start adding CountedLock class to partially replace LockableFiles	45	def break_lock(self):
	46	self._real_lock.break_lock()
	47	self._lock_mode = None
	48	self._lock_count = 0
	49
4570.3.5 by Martin Pool Add CountedLock.get_physical_lock_status	50	def get_physical_lock_status(self):
	51	"""Return physical lock status.
	52
	53	Returns true if a lock is held on the transport. If no lock is held, or
	54	the underlying locking mechanism does not support querying lock
	55	status, false is returned.
	56	"""
	57	try:
	58	return self._real_lock.peek() is not None
	59	except NotImplementedError:
	60	return False
	61
2475.4.1 by Martin Pool Start adding CountedLock class to partially replace LockableFiles	62	def is_locked(self):
	63	return self._lock_mode is not None
	64
	65	def lock_read(self):
	66	"""Acquire the lock in read mode.
	67
	68	If the lock is already held in either read or write mode this
	69	increments the count and succeeds. If the lock is not already held,
	70	it is taken in read mode.
	71	"""
	72	if self._lock_mode:
	73	self._lock_count += 1
	74	else:
	75	self._real_lock.lock_read()
	76	self._lock_count = 1
	77	self._lock_mode = 'r'
	78
3407.2.20 by Martin Pool Add lock token support to CountedLock	79	def lock_write(self, token=None):
2475.4.1 by Martin Pool Start adding CountedLock class to partially replace LockableFiles	80	"""Acquire the lock in write mode.
	81
	82	If the lock was originally acquired in read mode this will fail.
3407.2.19 by Martin Pool CountedLock should manage lock tokens	83
3407.2.20 by Martin Pool Add lock token support to CountedLock	84	:param token: If given and the lock is already held,
	85	then validate that we already hold the real
	86	lock with this token.
	87
3407.2.19 by Martin Pool CountedLock should manage lock tokens	88	:returns: The token from the underlying lock.
2475.4.1 by Martin Pool Start adding CountedLock class to partially replace LockableFiles	89	"""
	90	if self._lock_count == 0:
3407.2.20 by Martin Pool Add lock token support to CountedLock	91	self._token = self._real_lock.lock_write(token=token)
2475.4.1 by Martin Pool Start adding CountedLock class to partially replace LockableFiles	92	self._lock_mode = 'w'
3474.1.3 by Martin Pool CountedLock now handles and tests lock tokens	93	self._lock_count += 1
3468.3.2 by Martin Pool merge trunk	94	return self._token
2475.4.1 by Martin Pool Start adding CountedLock class to partially replace LockableFiles	95	elif self._lock_mode != 'w':
3474.1.2 by Martin Pool CountedLock.unlock should raise LockNotHeld if appropriate	96	raise errors.ReadOnlyError(self)
3474.1.3 by Martin Pool CountedLock now handles and tests lock tokens	97	else:
	98	self._real_lock.validate_token(token)
	99	self._lock_count += 1
3468.3.4 by Martin Pool CountedLock.lock_write should return existing known token	100	return self._token
2475.4.1 by Martin Pool Start adding CountedLock class to partially replace LockableFiles	101
	102	def unlock(self):
	103	if self._lock_count == 0:
3474.1.3 by Martin Pool CountedLock now handles and tests lock tokens	104	raise errors.LockNotHeld(self)
2475.4.1 by Martin Pool Start adding CountedLock class to partially replace LockableFiles	105	elif self._lock_count == 1:
3474.1.3 by Martin Pool CountedLock now handles and tests lock tokens	106	# these are decremented first; if we fail to unlock the most
	107	# reasonable assumption is that we still don't have the lock
	108	# anymore
	109	self._lock_mode = None
	110	self._lock_count -= 1
2475.4.1 by Martin Pool Start adding CountedLock class to partially replace LockableFiles	111	self._real_lock.unlock()
3474.1.3 by Martin Pool CountedLock now handles and tests lock tokens	112	else:
	113	self._lock_count -= 1