1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
|
# Copyright (C) 2005, 2006 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
"""Locking using OS file locks or file existence.
Note: This method of locking is generally deprecated in favour of LockDir, but
is used to lock local WorkingTrees, and by some old formats. It's accessed
through Transport.lock_read(), etc.
This module causes two methods, lock() and unlock() to be defined in
any way that works on the current platform.
It is not specified whether these locks are reentrant (i.e. can be
taken repeatedly by a single process) or whether they exclude
different threads in a single process. That reentrancy is provided by
LockableFiles.
This defines two classes: ReadLock and WriteLock, which can be
implemented in different ways on different platforms. Both have an
unlock() method.
"""
import errno
import os
import sys
from bzrlib.errors import LockError
from bzrlib.osutils import realpath
from bzrlib.trace import mutter
class _base_Lock(object):
def _open(self, filename, filemode):
try:
self.f = open(filename, filemode)
return self.f
except IOError, e:
if e.errno != errno.ENOENT:
raise
# maybe this is an old branch (before may 2005)
mutter("trying to create missing branch lock %r", filename)
self.f = open(filename, 'wb+')
return self.f
def __del__(self):
if self.f:
from warnings import warn
warn("lock on %r not released" % self.f)
self.unlock()
def unlock(self):
raise NotImplementedError()
############################################################
# msvcrt locks
try:
import fcntl
class _fcntl_FileLock(_base_Lock):
f = None
def _unlock(self):
fcntl.lockf(self.f, fcntl.LOCK_UN)
self._clear_f()
def _clear_f(self):
"""Clear the self.f attribute cleanly."""
self.f.close()
del self.f
class _fcntl_WriteLock(_fcntl_FileLock):
open_locks = {}
def __init__(self, filename):
# standard IO errors get exposed directly.
self._open(filename, 'wb')
try:
self.filename = realpath(filename)
if self.filename in self.open_locks:
self._clear_f()
raise LockError("Lock already held.")
# reserve a slot for this lock - even if the lockf call fails,
# at thisi point unlock() will be called, because self.f is set.
# TODO: make this fully threadsafe, if we decide we care.
self.open_locks[self.filename] = self.filename
fcntl.lockf(self.f, fcntl.LOCK_EX)
except IOError, e:
# we should be more precise about whats a locking
# error and whats a random-other error
raise LockError(e)
def unlock(self):
del self.open_locks[self.filename]
self._unlock()
class _fcntl_ReadLock(_fcntl_FileLock):
def __init__(self, filename):
# standard IO errors get exposed directly.
self._open(filename, 'rb')
try:
fcntl.lockf(self.f, fcntl.LOCK_SH)
except IOError, e:
# we should be more precise about whats a locking
# error and whats a random-other error
raise LockError(e)
def unlock(self):
self._unlock()
WriteLock = _fcntl_WriteLock
ReadLock = _fcntl_ReadLock
except ImportError:
try:
import win32con, win32file, pywintypes
LOCK_SH = 0 # the default
LOCK_EX = win32con.LOCKFILE_EXCLUSIVE_LOCK
LOCK_NB = win32con.LOCKFILE_FAIL_IMMEDIATELY
class _w32c_FileLock(_base_Lock):
def _lock(self, filename, openmode, lockmode):
try:
self._open(filename, openmode)
self.hfile = win32file._get_osfhandle(self.f.fileno())
overlapped = pywintypes.OVERLAPPED()
win32file.LockFileEx(self.hfile, lockmode, 0, 0x7fff0000, overlapped)
except Exception, e:
if self.f:
self.f.close()
self.f = None
raise LockError(e)
def unlock(self):
try:
overlapped = pywintypes.OVERLAPPED()
win32file.UnlockFileEx(self.hfile, 0, 0x7fff0000, overlapped)
self.f.close()
self.f = None
except Exception, e:
raise LockError(e)
class _w32c_ReadLock(_w32c_FileLock):
def __init__(self, filename):
_w32c_FileLock._lock(self, filename, 'rb',
LOCK_NB)
class _w32c_WriteLock(_w32c_FileLock):
def __init__(self, filename):
_w32c_FileLock._lock(self, filename, 'wb',
LOCK_EX + LOCK_NB)
WriteLock = _w32c_WriteLock
ReadLock = _w32c_ReadLock
except ImportError:
try:
import msvcrt
# Unfortunately, msvcrt.locking() doesn't distinguish between
# read locks and write locks. Also, the way the combinations
# work to get non-blocking is not the same, so we
# have to write extra special functions here.
class _msvc_FileLock(_base_Lock):
LOCK_SH = 1
LOCK_EX = 2
LOCK_NB = 4
def unlock(self):
_msvc_unlock(self.f)
self.f.close()
self.f = None
class _msvc_ReadLock(_msvc_FileLock):
def __init__(self, filename):
_msvc_lock(self._open(filename, 'rb'), self.LOCK_SH)
class _msvc_WriteLock(_msvc_FileLock):
def __init__(self, filename):
_msvc_lock(self._open(filename, 'wb'), self.LOCK_EX)
def _msvc_lock(f, flags):
try:
# Unfortunately, msvcrt.LK_RLCK is equivalent to msvcrt.LK_LOCK
# according to the comments, LK_RLCK is open the lock for writing.
# Unfortunately, msvcrt.locking() also has the side effect that it
# will only block for 10 seconds at most, and then it will throw an
# exception, this isn't terrible, though.
if type(f) == file:
fpos = f.tell()
fn = f.fileno()
f.seek(0)
else:
fn = f
fpos = os.lseek(fn, 0,0)
os.lseek(fn, 0,0)
if flags & _msvc_FileLock.LOCK_SH:
if flags & _msvc_FileLock.LOCK_NB:
lock_mode = msvcrt.LK_NBLCK
else:
lock_mode = msvcrt.LK_LOCK
elif flags & _msvc_FileLock.LOCK_EX:
if flags & _msvc_FileLock.LOCK_NB:
lock_mode = msvcrt.LK_NBRLCK
else:
lock_mode = msvcrt.LK_RLCK
else:
raise ValueError('Invalid lock mode: %r' % flags)
try:
msvcrt.locking(fn, lock_mode, -1)
finally:
os.lseek(fn, fpos, 0)
except Exception, e:
raise LockError(e)
def _msvc_unlock(f):
try:
if type(f) == file:
fpos = f.tell()
fn = f.fileno()
f.seek(0)
else:
fn = f
fpos = os.lseek(fn, 0,0)
os.lseek(fn, 0,0)
try:
msvcrt.locking(fn, msvcrt.LK_UNLCK, -1)
finally:
os.lseek(fn, fpos, 0)
except Exception, e:
raise LockError(e)
WriteLock = _msvc_WriteLock
ReadLock = _msvc_ReadLock
except ImportError:
raise NotImplementedError("please write a locking method "
"for platform %r" % sys.platform)
|