1
# Copyright (C) 2005 Canonical Ltd
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.
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.
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
15
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20
This only does local locking using OS locks for now.
22
This module causes two methods, lock() and unlock() to be defined in
23
any way that works on the current platform.
25
It is not specified whether these locks are reentrant (i.e. can be
26
taken repeatedly by a single process) or whether they exclude
27
different threads in a single process.
29
Eventually we may need to use some kind of lock representation that
30
will work on a dumb filesystem without actual locking primitives.
32
This defines two classes: ReadLock and WriteLock, which can be
33
implemented in different ways on different platforms. Both have an
41
from bzrlib.trace import mutter, note, warning
42
from bzrlib.errors import LockError
44
class _base_Lock(object):
45
def _open(self, filename, filemode):
48
self.f = open(filename, filemode)
51
if e.errno != errno.ENOENT:
54
# maybe this is an old branch (before may 2005)
55
mutter("trying to create missing branch lock %r" % filename)
57
self.f = open(filename, 'wb')
63
from warnings import warn
64
warn("lock on %r not released" % self.f)
69
raise NotImplementedError()
76
############################################################
83
class _fcntl_FileLock(_base_Lock):
87
fcntl.flock(self.f, fcntl.LOCK_UN)
92
class _fcntl_WriteLock(_fcntl_FileLock):
93
def __init__(self, filename):
95
fcntl.flock(self._open(filename, 'wb'), fcntl.LOCK_EX)
100
class _fcntl_ReadLock(_fcntl_FileLock):
101
def __init__(self, filename):
103
fcntl.flock(self._open(filename, 'rb'), fcntl.LOCK_SH)
107
WriteLock = _fcntl_WriteLock
108
ReadLock = _fcntl_ReadLock
112
import win32con, win32file, pywintypes
115
#LOCK_SH = 0 # the default
116
#LOCK_EX = win32con.LOCKFILE_EXCLUSIVE_LOCK
117
#LOCK_NB = win32con.LOCKFILE_FAIL_IMMEDIATELY
119
class _w32c_FileLock(_base_Lock):
120
def _lock(self, filename, openmode, lockmode):
122
self._open(filename, openmode)
123
self.hfile = win32file._get_osfhandle(self.f.fileno())
124
overlapped = pywintypes.OVERLAPPED()
125
win32file.LockFileEx(self.hfile, lockmode, 0, 0x7fff0000, overlapped)
131
overlapped = pywintypes.OVERLAPPED()
132
win32file.UnlockFileEx(self.hfile, 0, 0x7fff0000, overlapped)
140
class _w32c_ReadLock(_w32c_FileLock):
141
def __init__(self, filename):
142
_w32c_FileLock._lock(self, filename, 'rb', 0)
144
class _w32c_WriteLock(_w32c_FileLock):
145
def __init__(self, filename):
146
_w32c_FileLock._lock(self, filename, 'wb',
147
win32con.LOCKFILE_EXCLUSIVE_LOCK)
151
WriteLock = _w32c_WriteLock
152
ReadLock = _w32c_ReadLock
159
# Unfortunately, msvcrt.locking() doesn't distinguish between
160
# read locks and write locks. Also, the way the combinations
161
# work to get non-blocking is not the same, so we
162
# have to write extra special functions here.
165
class _msvc_FileLock(_base_Lock):
173
class _msvc_ReadLock(_msvc_FileLock):
174
def __init__(self, filename):
175
_msvc_lock(self._open(filename, 'rb'), self.LOCK_SH)
178
class _msvc_WriteLock(_msvc_FileLock):
179
def __init__(self, filename):
180
_msvc_lock(self._open(filename, 'wb'), self.LOCK_EX)
184
def _msvc_lock(f, flags):
186
# Unfortunately, msvcrt.LK_RLCK is equivalent to msvcrt.LK_LOCK
187
# according to the comments, LK_RLCK is open the lock for writing.
189
# Unfortunately, msvcrt.locking() also has the side effect that it
190
# will only block for 10 seconds at most, and then it will throw an
191
# exception, this isn't terrible, though.
198
fpos = os.lseek(fn, 0,0)
201
if flags & self.LOCK_SH:
202
if flags & self.LOCK_NB:
203
lock_mode = msvcrt.LK_NBLCK
205
lock_mode = msvcrt.LK_LOCK
206
elif flags & self.LOCK_EX:
207
if flags & self.LOCK_NB:
208
lock_mode = msvcrt.LK_NBRLCK
210
lock_mode = msvcrt.LK_RLCK
212
raise ValueError('Invalid lock mode: %r' % flags)
214
msvcrt.locking(fn, lock_mode, -1)
216
os.lseek(fn, fpos, 0)
228
fpos = os.lseek(fn, 0,0)
232
msvcrt.locking(fn, msvcrt.LK_UNLCK, -1)
234
os.lseek(fn, fpos, 0)
240
WriteLock = _msvc_WriteLock
241
ReadLock = _msvc_ReadLock
243
raise NotImplementedError("please write a locking method "
244
"for platform %r" % sys.platform)
added
removed
bzrlib/lock.py
