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  • Committer: Bazaar Package Importer
  • Author(s): Jeff Bailey
  • Date: 2005-11-07 13:17:53 UTC
  • Revision ID: james.westby@ubuntu.com-20051107131753-qsy145z1rfug5i27
Tags: upstream-0.6.2
Import upstream version 0.6.2

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bzrlib/lock.py
 
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# Copyright (C) 2005 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.
 
12
 
 
13
# 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 
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17
 
 
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"""Locking wrappers.
 
19
 
 
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This only does local locking using OS locks for now.
 
21
 
 
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This module causes two methods, lock() and unlock() to be defined in
 
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any way that works on the current platform.
 
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It is not specified whether these locks are reentrant (i.e. can be
 
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taken repeatedly by a single process) or whether they exclude
 
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different threads in a single process.  
 
28
 
 
29
Eventually we may need to use some kind of lock representation that
 
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will work on a dumb filesystem without actual locking primitives.
 
31
 
 
32
This defines two classes: ReadLock and WriteLock, which can be
 
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implemented in different ways on different platforms.  Both have an
 
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unlock() method.
 
35
"""
 
36
 
 
37
 
 
38
import sys
 
39
import os
 
40
 
 
41
from bzrlib.trace import mutter, note, warning
 
42
from bzrlib.errors import LockError
 
43
 
 
44
class _base_Lock(object):
 
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    def _open(self, filename, filemode):
 
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        import errno
 
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        try:
 
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            self.f = open(filename, filemode)
 
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            return self.f
 
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        except IOError, e:
 
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            if e.errno != errno.ENOENT:
 
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                raise
 
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            # maybe this is an old branch (before may 2005)
 
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            mutter("trying to create missing branch lock %r" % filename)
 
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            self.f = open(filename, 'wb')
 
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            return self.f
 
59
 
 
60
 
 
61
    def __del__(self):
 
62
        if self.f:
 
63
            from warnings import warn
 
64
            warn("lock on %r not released" % self.f)
 
65
            self.unlock()
 
66
            
 
67
 
 
68
    def unlock(self):
 
69
        raise NotImplementedError()
 
70
 
 
71
        
 
72
 
 
73
 
 
74
 
 
75
 
 
76
############################################################
 
77
# msvcrt locks
 
78
 
 
79
 
 
80
try:
 
81
    import fcntl
 
82
 
 
83
    class _fcntl_FileLock(_base_Lock):
 
84
        f = None
 
85
 
 
86
        def unlock(self):
 
87
            fcntl.lockf(self.f, fcntl.LOCK_UN)
 
88
            self.f.close()
 
89
            del self.f 
 
90
 
 
91
 
 
92
    class _fcntl_WriteLock(_fcntl_FileLock):
 
93
        def __init__(self, filename):
 
94
            try:
 
95
                fcntl.lockf(self._open(filename, 'wb'), fcntl.LOCK_EX)
 
96
            except Exception, e:
 
97
                raise LockError(e)
 
98
 
 
99
 
 
100
    class _fcntl_ReadLock(_fcntl_FileLock):
 
101
        def __init__(self, filename):
 
102
            try:
 
103
                fcntl.lockf(self._open(filename, 'rb'), fcntl.LOCK_SH)
 
104
            except Exception, e:
 
105
                raise LockError(e)
 
106
 
 
107
    WriteLock = _fcntl_WriteLock
 
108
    ReadLock = _fcntl_ReadLock
 
109
 
 
110
except ImportError:
 
111
    try:
 
112
        import win32con, win32file, pywintypes
 
113
 
 
114
 
 
115
        LOCK_SH = 0 # the default
 
116
        LOCK_EX = win32con.LOCKFILE_EXCLUSIVE_LOCK
 
117
        LOCK_NB = win32con.LOCKFILE_FAIL_IMMEDIATELY
 
118
 
 
119
        class _w32c_FileLock(_base_Lock):
 
120
            def _lock(self, filename, openmode, lockmode):
 
121
                try:
 
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)
 
126
                except Exception, e:
 
127
                    raise LockError(e)
 
128
 
 
129
            def unlock(self):
 
130
                try:
 
131
                    overlapped = pywintypes.OVERLAPPED()
 
132
                    win32file.UnlockFileEx(self.hfile, 0, 0x7fff0000, overlapped)
 
133
                    self.f.close()
 
134
                    self.f = None
 
135
                except Exception, e:
 
136
                    raise LockError(e)
 
137
 
 
138
 
 
139
 
 
140
        class _w32c_ReadLock(_w32c_FileLock):
 
141
            def __init__(self, filename):
 
142
                _w32c_FileLock._lock(self, filename, 'rb',
 
143
                                     LOCK_NB)
 
144
 
 
145
        class _w32c_WriteLock(_w32c_FileLock):
 
146
            def __init__(self, filename):
 
147
                _w32c_FileLock._lock(self, filename, 'wb',
 
148
                                     LOCK_EX + LOCK_NB)
 
149
 
 
150
 
 
151
 
 
152
        WriteLock = _w32c_WriteLock
 
153
        ReadLock = _w32c_ReadLock
 
154
 
 
155
    except ImportError:
 
156
        try:
 
157
            import msvcrt
 
158
 
 
159
 
 
160
            # Unfortunately, msvcrt.locking() doesn't distinguish between
 
161
            # read locks and write locks. Also, the way the combinations
 
162
            # work to get non-blocking is not the same, so we
 
163
            # have to write extra special functions here.
 
164
 
 
165
 
 
166
            class _msvc_FileLock(_base_Lock):
 
167
                LOCK_SH = 1
 
168
                LOCK_EX = 2
 
169
                LOCK_NB = 4
 
170
                def unlock(self):
 
171
                    _msvc_unlock(self.f)
 
172
                    self.f.close()
 
173
                    self.f = None
 
174
 
 
175
 
 
176
            class _msvc_ReadLock(_msvc_FileLock):
 
177
                def __init__(self, filename):
 
178
                    _msvc_lock(self._open(filename, 'rb'), self.LOCK_SH)
 
179
 
 
180
 
 
181
            class _msvc_WriteLock(_msvc_FileLock):
 
182
                def __init__(self, filename):
 
183
                    _msvc_lock(self._open(filename, 'wb'), self.LOCK_EX)
 
184
 
 
185
 
 
186
 
 
187
            def _msvc_lock(f, flags):
 
188
                try:
 
189
                    # Unfortunately, msvcrt.LK_RLCK is equivalent to msvcrt.LK_LOCK
 
190
                    # according to the comments, LK_RLCK is open the lock for writing.
 
191
 
 
192
                    # Unfortunately, msvcrt.locking() also has the side effect that it
 
193
                    # will only block for 10 seconds at most, and then it will throw an
 
194
                    # exception, this isn't terrible, though.
 
195
                    if type(f) == file:
 
196
                        fpos = f.tell()
 
197
                        fn = f.fileno()
 
198
                        f.seek(0)
 
199
                    else:
 
200
                        fn = f
 
201
                        fpos = os.lseek(fn, 0,0)
 
202
                        os.lseek(fn, 0,0)
 
203
 
 
204
                    if flags & _msvc_FileLock.LOCK_SH:
 
205
                        if flags & _msvc_FileLock.LOCK_NB:
 
206
                            lock_mode = msvcrt.LK_NBLCK
 
207
                        else:
 
208
                            lock_mode = msvcrt.LK_LOCK
 
209
                    elif flags & _msvc_FileLock.LOCK_EX:
 
210
                        if flags & _msvc_FileLock.LOCK_NB:
 
211
                            lock_mode = msvcrt.LK_NBRLCK
 
212
                        else:
 
213
                            lock_mode = msvcrt.LK_RLCK
 
214
                    else:
 
215
                        raise ValueError('Invalid lock mode: %r' % flags)
 
216
                    try:
 
217
                        msvcrt.locking(fn, lock_mode, -1)
 
218
                    finally:
 
219
                        os.lseek(fn, fpos, 0)
 
220
                except Exception, e:
 
221
                    raise LockError(e)
 
222
 
 
223
            def _msvc_unlock(f):
 
224
                try:
 
225
                    if type(f) == file:
 
226
                        fpos = f.tell()
 
227
                        fn = f.fileno()
 
228
                        f.seek(0)
 
229
                    else:
 
230
                        fn = f
 
231
                        fpos = os.lseek(fn, 0,0)
 
232
                        os.lseek(fn, 0,0)
 
233
 
 
234
                    try:
 
235
                        msvcrt.locking(fn, msvcrt.LK_UNLCK, -1)
 
236
                    finally:
 
237
                        os.lseek(fn, fpos, 0)
 
238
                except Exception, e:
 
239
                    raise LockError(e)
 
240
 
 
241
 
 
242
 
 
243
            WriteLock = _msvc_WriteLock
 
244
            ReadLock = _msvc_ReadLock
 
245
        except ImportError:
 
246
            raise NotImplementedError("please write a locking method "
 
247
                                      "for platform %r" % sys.platform)
 
248
 
 
249
 
 
250
 
 
251
 
 
252
 
 
253
 
 
254