~bzr-pqm/bzr/bzr.dev

2353.3.8 by John Arbash Meinel
Fix Copyright in lock.py
1
# Copyright (C) 2005, 2006, 2007 Canonical Ltd
1887.1.1 by Adeodato Simó
Do not separate paragraphs in the copyright statement with blank lines,
2
#
577 by Martin Pool
- merge portable lock module from John
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.
1887.1.1 by Adeodato Simó
Do not separate paragraphs in the copyright statement with blank lines,
7
#
577 by Martin Pool
- merge portable lock module from John
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.
1887.1.1 by Adeodato Simó
Do not separate paragraphs in the copyright statement with blank lines,
12
#
577 by Martin Pool
- merge portable lock module from John
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
16
17
1553.5.39 by Martin Pool
More lock docs
18
"""Locking using OS file locks or file existence.
577 by Martin Pool
- merge portable lock module from John
19
1553.5.46 by Martin Pool
doc
20
Note: This method of locking is generally deprecated in favour of LockDir, but
21
is used to lock local WorkingTrees, and by some old formats.  It's accessed
22
through Transport.lock_read(), etc.
577 by Martin Pool
- merge portable lock module from John
23
24
This module causes two methods, lock() and unlock() to be defined in
25
any way that works on the current platform.
26
27
It is not specified whether these locks are reentrant (i.e. can be
28
taken repeatedly by a single process) or whether they exclude
2353.3.9 by John Arbash Meinel
Update the lock code and test code so that if more than one
29
different threads in a single process.  That reentrancy is provided by
1553.5.39 by Martin Pool
More lock docs
30
LockableFiles.
615 by Martin Pool
Major rework of locking code:
31
32
This defines two classes: ReadLock and WriteLock, which can be
33
implemented in different ways on different platforms.  Both have an
34
unlock() method.
614 by Martin Pool
- unify two defintions of LockError
35
"""
577 by Martin Pool
- merge portable lock module from John
36
1185.65.29 by Robert Collins
Implement final review suggestions.
37
import errno
2353.3.12 by John Arbash Meinel
Don't create the alternative lock types unless we are on windows.
38
import sys
577 by Martin Pool
- merge portable lock module from John
39
2353.3.11 by John Arbash Meinel
Code cleanup
40
from bzrlib import (
41
    errors,
42
    osutils,
43
    trace,
44
    )
1711.8.1 by John Arbash Meinel
Branch.lock_read/lock_write/unlock should handle failures
45
577 by Martin Pool
- merge portable lock module from John
46
2555.3.2 by Martin Pool
rename _base_Lock to _OSLock
47
class _OSLock(object):
1852.4.3 by Robert Collins
Alter working tree lock and unlock tests to test via the interface rather than via unpublished internals.
48
2353.3.4 by John Arbash Meinel
Clean up the lock.py code to use less indenting, and conform to better coding practise.
49
    def __init__(self):
50
        self.f = None
2353.3.10 by John Arbash Meinel
Cleanup errors, and change ReadOnlyLockError to pass around more details.
51
        self.filename = None
2353.3.4 by John Arbash Meinel
Clean up the lock.py code to use less indenting, and conform to better coding practise.
52
615 by Martin Pool
Major rework of locking code:
53
    def _open(self, filename, filemode):
2353.3.11 by John Arbash Meinel
Code cleanup
54
        self.filename = osutils.realpath(filename)
656 by Martin Pool
- create branch lock files if they don't exist
55
        try:
2353.3.10 by John Arbash Meinel
Cleanup errors, and change ReadOnlyLockError to pass around more details.
56
            self.f = open(self.filename, filemode)
656 by Martin Pool
- create branch lock files if they don't exist
57
            return self.f
58
        except IOError, e:
2353.3.5 by John Arbash Meinel
Fall back on ctypes to get LockFileEx, because msvcrt.locking()
59
            if e.errno in (errno.EACCES, errno.EPERM):
2872.5.1 by Martin Pool
Avoid internal error tracebacks on failure to lock on readonly transport (#129701).
60
                raise errors.LockFailed(self.filename, str(e))
656 by Martin Pool
- create branch lock files if they don't exist
61
            if e.errno != errno.ENOENT:
62
                raise
63
64
            # maybe this is an old branch (before may 2005)
2353.3.11 by John Arbash Meinel
Code cleanup
65
            trace.mutter("trying to create missing lock %r", self.filename)
2353.3.9 by John Arbash Meinel
Update the lock code and test code so that if more than one
66
2353.3.10 by John Arbash Meinel
Cleanup errors, and change ReadOnlyLockError to pass around more details.
67
            self.f = open(self.filename, 'wb+')
656 by Martin Pool
- create branch lock files if they don't exist
68
            return self.f
69
2353.3.4 by John Arbash Meinel
Clean up the lock.py code to use less indenting, and conform to better coding practise.
70
    def _clear_f(self):
71
        """Clear the self.f attribute cleanly."""
72
        if self.f:
73
            self.f.close()
74
            self.f = None
75
615 by Martin Pool
Major rework of locking code:
76
    def __del__(self):
77
        if self.f:
78
            from warnings import warn
79
            warn("lock on %r not released" % self.f)
80
            self.unlock()
2353.3.9 by John Arbash Meinel
Update the lock code and test code so that if more than one
81
615 by Martin Pool
Major rework of locking code:
82
    def unlock(self):
83
        raise NotImplementedError()
84
85
577 by Martin Pool
- merge portable lock module from John
86
try:
87
    import fcntl
2353.3.4 by John Arbash Meinel
Clean up the lock.py code to use less indenting, and conform to better coding practise.
88
    have_fcntl = True
89
except ImportError:
2353.3.9 by John Arbash Meinel
Update the lock code and test code so that if more than one
90
    have_fcntl = False
91
try:
92
    import win32con, win32file, pywintypes, winerror, msvcrt
93
    have_pywin32 = True
94
except ImportError:
95
    have_pywin32 = False
96
try:
97
    import ctypes, msvcrt
98
    have_ctypes = True
99
except ImportError:
100
    have_ctypes = False
101
102
103
_lock_classes = []
2353.3.4 by John Arbash Meinel
Clean up the lock.py code to use less indenting, and conform to better coding practise.
104
105
106
if have_fcntl:
107
    LOCK_SH = fcntl.LOCK_SH
108
    LOCK_NB = fcntl.LOCK_NB
109
    lock_EX = fcntl.LOCK_EX
110
615 by Martin Pool
Major rework of locking code:
111
2555.3.2 by Martin Pool
rename _base_Lock to _OSLock
112
    class _fcntl_FileLock(_OSLock):
1852.4.3 by Robert Collins
Alter working tree lock and unlock tests to test via the interface rather than via unpublished internals.
113
114
        def _unlock(self):
1185.9.2 by Harald Meland
Use fcntl.lockf() rather than fcntl.flock() to support NFS file systems.
115
            fcntl.lockf(self.f, fcntl.LOCK_UN)
1852.4.3 by Robert Collins
Alter working tree lock and unlock tests to test via the interface rather than via unpublished internals.
116
            self._clear_f()
117
118
615 by Martin Pool
Major rework of locking code:
119
    class _fcntl_WriteLock(_fcntl_FileLock):
1852.4.3 by Robert Collins
Alter working tree lock and unlock tests to test via the interface rather than via unpublished internals.
120
2353.4.1 by John Arbash Meinel
(broken) Change fcntl locks to be properly exclusive within the same process.
121
        _open_locks = set()
1852.4.3 by Robert Collins
Alter working tree lock and unlock tests to test via the interface rather than via unpublished internals.
122
615 by Martin Pool
Major rework of locking code:
123
        def __init__(self, filename):
2353.3.4 by John Arbash Meinel
Clean up the lock.py code to use less indenting, and conform to better coding practise.
124
            super(_fcntl_WriteLock, self).__init__()
2353.4.2 by John Arbash Meinel
[merge] LockCleanup changes.
125
            # Check we can grab a lock before we actually open the file.
126
            self.filename = osutils.realpath(filename)
2363.3.3 by John Arbash Meinel
make Write locks not block on Read locks, so that revert tests don't fail
127
            if self.filename in _fcntl_WriteLock._open_locks:
2353.4.1 by John Arbash Meinel
(broken) Change fcntl locks to be properly exclusive within the same process.
128
                self._clear_f()
129
                raise errors.LockContention(self.filename)
130
2353.4.2 by John Arbash Meinel
[merge] LockCleanup changes.
131
            self._open(self.filename, 'rb+')
2255.10.2 by John Arbash Meinel
Update to dirstate locking.
132
            # reserve a slot for this lock - even if the lockf call fails,
133
            # at thisi point unlock() will be called, because self.f is set.
134
            # TODO: make this fully threadsafe, if we decide we care.
2353.4.1 by John Arbash Meinel
(broken) Change fcntl locks to be properly exclusive within the same process.
135
            _fcntl_WriteLock._open_locks.add(self.filename)
615 by Martin Pool
Major rework of locking code:
136
            try:
2255.10.2 by John Arbash Meinel
Update to dirstate locking.
137
                # LOCK_NB will cause IOError to be raised if we can't grab a
138
                # lock right away.
139
                fcntl.lockf(self.f, fcntl.LOCK_EX | fcntl.LOCK_NB)
1185.65.29 by Robert Collins
Implement final review suggestions.
140
            except IOError, e:
2255.10.2 by John Arbash Meinel
Update to dirstate locking.
141
                if e.errno in (errno.EAGAIN, errno.EACCES):
142
                    # We couldn't grab the lock
143
                    self.unlock()
1185.65.29 by Robert Collins
Implement final review suggestions.
144
                # we should be more precise about whats a locking
145
                # error and whats a random-other error
2323.9.1 by John Arbash Meinel
Raise LockContetion rather than LockError
146
                raise errors.LockContention(e)
615 by Martin Pool
Major rework of locking code:
147
1852.4.3 by Robert Collins
Alter working tree lock and unlock tests to test via the interface rather than via unpublished internals.
148
        def unlock(self):
2353.4.1 by John Arbash Meinel
(broken) Change fcntl locks to be properly exclusive within the same process.
149
            _fcntl_WriteLock._open_locks.remove(self.filename)
1852.4.3 by Robert Collins
Alter working tree lock and unlock tests to test via the interface rather than via unpublished internals.
150
            self._unlock()
151
152
615 by Martin Pool
Major rework of locking code:
153
    class _fcntl_ReadLock(_fcntl_FileLock):
1185.65.29 by Robert Collins
Implement final review suggestions.
154
2353.4.1 by John Arbash Meinel
(broken) Change fcntl locks to be properly exclusive within the same process.
155
        _open_locks = {}
2353.3.3 by John Arbash Meinel
Define an explicit error when trying to grab a write lock on a readonly file.
156
2353.4.11 by John Arbash Meinel
Remove the unused _ignore_write_lock parameter.
157
        def __init__(self, filename):
2353.3.4 by John Arbash Meinel
Clean up the lock.py code to use less indenting, and conform to better coding practise.
158
            super(_fcntl_ReadLock, self).__init__()
2353.4.2 by John Arbash Meinel
[merge] LockCleanup changes.
159
            self.filename = osutils.realpath(filename)
2353.4.1 by John Arbash Meinel
(broken) Change fcntl locks to be properly exclusive within the same process.
160
            _fcntl_ReadLock._open_locks.setdefault(self.filename, 0)
161
            _fcntl_ReadLock._open_locks[self.filename] += 1
1185.65.29 by Robert Collins
Implement final review suggestions.
162
            self._open(filename, 'rb')
615 by Martin Pool
Major rework of locking code:
163
            try:
2255.10.2 by John Arbash Meinel
Update to dirstate locking.
164
                # LOCK_NB will cause IOError to be raised if we can't grab a
165
                # lock right away.
166
                fcntl.lockf(self.f, fcntl.LOCK_SH | fcntl.LOCK_NB)
1185.65.29 by Robert Collins
Implement final review suggestions.
167
            except IOError, e:
168
                # we should be more precise about whats a locking
169
                # error and whats a random-other error
2323.9.1 by John Arbash Meinel
Raise LockContetion rather than LockError
170
                raise errors.LockContention(e)
615 by Martin Pool
Major rework of locking code:
171
1852.4.3 by Robert Collins
Alter working tree lock and unlock tests to test via the interface rather than via unpublished internals.
172
        def unlock(self):
2353.4.1 by John Arbash Meinel
(broken) Change fcntl locks to be properly exclusive within the same process.
173
            count = _fcntl_ReadLock._open_locks[self.filename]
174
            if count == 1:
175
                del _fcntl_ReadLock._open_locks[self.filename]
176
            else:
177
                _fcntl_ReadLock._open_locks[self.filename] = count - 1
1852.4.3 by Robert Collins
Alter working tree lock and unlock tests to test via the interface rather than via unpublished internals.
178
            self._unlock()
179
2353.4.3 by John Arbash Meinel
Implement a 'ReadLock.temporary_write_lock()' to upgrade to a write-lock in-process.
180
        def temporary_write_lock(self):
181
            """Try to grab a write lock on the file.
182
183
            On platforms that support it, this will upgrade to a write lock
184
            without unlocking the file.
185
            Otherwise, this will release the read lock, and try to acquire a
186
            write lock.
187
188
            :return: A token which can be used to switch back to a read lock.
189
            """
190
            assert self.filename not in _fcntl_WriteLock._open_locks
2353.4.7 by John Arbash Meinel
Change the temporary_write_lock api, so that it always returns a lock object,
191
            try:
192
                wlock = _fcntl_TemporaryWriteLock(self)
193
            except errors.LockError:
194
                # We didn't unlock, so we can just return 'self'
195
                return False, self
196
            return True, wlock
2353.4.3 by John Arbash Meinel
Implement a 'ReadLock.temporary_write_lock()' to upgrade to a write-lock in-process.
197
198
2555.3.2 by Martin Pool
rename _base_Lock to _OSLock
199
    class _fcntl_TemporaryWriteLock(_OSLock):
2353.4.3 by John Arbash Meinel
Implement a 'ReadLock.temporary_write_lock()' to upgrade to a write-lock in-process.
200
        """A token used when grabbing a temporary_write_lock.
201
202
        Call restore_read_lock() when you are done with the write lock.
203
        """
204
205
        def __init__(self, read_lock):
206
            super(_fcntl_TemporaryWriteLock, self).__init__()
207
            self._read_lock = read_lock
208
            self.filename = read_lock.filename
209
210
            count = _fcntl_ReadLock._open_locks[self.filename]
211
            if count > 1:
212
                # Something else also has a read-lock, so we cannot grab a
213
                # write lock.
214
                raise errors.LockContention(self.filename)
215
216
            assert self.filename not in _fcntl_WriteLock._open_locks
217
218
            # See if we can open the file for writing. Another process might
219
            # have a read lock. We don't use self._open() because we don't want
220
            # to create the file if it exists. That would have already been
221
            # done by _fcntl_ReadLock
222
            try:
223
                new_f = open(self.filename, 'rb+')
224
            except IOError, e:
225
                if e.errno in (errno.EACCES, errno.EPERM):
2872.5.1 by Martin Pool
Avoid internal error tracebacks on failure to lock on readonly transport (#129701).
226
                    raise errors.LockFailed(self.filename, str(e))
2353.4.3 by John Arbash Meinel
Implement a 'ReadLock.temporary_write_lock()' to upgrade to a write-lock in-process.
227
                raise
228
            try:
229
                # LOCK_NB will cause IOError to be raised if we can't grab a
230
                # lock right away.
2379.3.1 by John Arbash Meinel
Cherry-pick the 2 locking fixes from the 0.15 branch.
231
                fcntl.lockf(new_f, fcntl.LOCK_EX | fcntl.LOCK_NB)
2353.4.3 by John Arbash Meinel
Implement a 'ReadLock.temporary_write_lock()' to upgrade to a write-lock in-process.
232
            except IOError, e:
233
                # TODO: Raise a more specific error based on the type of error
2323.9.1 by John Arbash Meinel
Raise LockContetion rather than LockError
234
                raise errors.LockContention(e)
2353.4.3 by John Arbash Meinel
Implement a 'ReadLock.temporary_write_lock()' to upgrade to a write-lock in-process.
235
            _fcntl_WriteLock._open_locks.add(self.filename)
236
237
            self.f = new_f
238
239
        def restore_read_lock(self):
2353.4.4 by John Arbash Meinel
Implement temporary_write_lock, and restore_read_lock for win32 locks.
240
            """Restore the original ReadLock."""
241
            # For fcntl, since we never released the read lock, just release the
242
            # write lock, and return the original lock.
2353.4.3 by John Arbash Meinel
Implement a 'ReadLock.temporary_write_lock()' to upgrade to a write-lock in-process.
243
            fcntl.lockf(self.f, fcntl.LOCK_UN)
244
            self._clear_f()
245
            _fcntl_WriteLock._open_locks.remove(self.filename)
246
            # Avoid reference cycles
247
            read_lock = self._read_lock
248
            self._read_lock = None
249
            return read_lock
250
1852.4.3 by Robert Collins
Alter working tree lock and unlock tests to test via the interface rather than via unpublished internals.
251
2353.3.9 by John Arbash Meinel
Update the lock code and test code so that if more than one
252
    _lock_classes.append(('fcntl', _fcntl_WriteLock, _fcntl_ReadLock))
577 by Martin Pool
- merge portable lock module from John
253
2353.3.11 by John Arbash Meinel
Code cleanup
254
2353.3.12 by John Arbash Meinel
Don't create the alternative lock types unless we are on windows.
255
if have_pywin32 and sys.platform == 'win32':
2353.3.4 by John Arbash Meinel
Clean up the lock.py code to use less indenting, and conform to better coding practise.
256
    LOCK_SH = 0 # the default
257
    LOCK_EX = win32con.LOCKFILE_EXCLUSIVE_LOCK
258
    LOCK_NB = win32con.LOCKFILE_FAIL_IMMEDIATELY
259
260
2555.3.2 by Martin Pool
rename _base_Lock to _OSLock
261
    class _w32c_FileLock(_OSLock):
2353.3.4 by John Arbash Meinel
Clean up the lock.py code to use less indenting, and conform to better coding practise.
262
263
        def _lock(self, filename, openmode, lockmode):
2353.3.5 by John Arbash Meinel
Fall back on ctypes to get LockFileEx, because msvcrt.locking()
264
            self._open(filename, openmode)
2353.3.4 by John Arbash Meinel
Clean up the lock.py code to use less indenting, and conform to better coding practise.
265
2353.3.5 by John Arbash Meinel
Fall back on ctypes to get LockFileEx, because msvcrt.locking()
266
            self.hfile = msvcrt.get_osfhandle(self.f.fileno())
2353.3.4 by John Arbash Meinel
Clean up the lock.py code to use less indenting, and conform to better coding practise.
267
            overlapped = pywintypes.OVERLAPPED()
268
            try:
2353.3.5 by John Arbash Meinel
Fall back on ctypes to get LockFileEx, because msvcrt.locking()
269
                win32file.LockFileEx(self.hfile, lockmode, 0, 0x7fff0000,
270
                                     overlapped)
2353.3.4 by John Arbash Meinel
Clean up the lock.py code to use less indenting, and conform to better coding practise.
271
            except pywintypes.error, e:
272
                self._clear_f()
273
                if e.args[0] in (winerror.ERROR_LOCK_VIOLATION,):
274
                    raise errors.LockContention(filename)
275
                ## import pdb; pdb.set_trace()
276
                raise
277
            except Exception, e:
278
                self._clear_f()
2323.9.1 by John Arbash Meinel
Raise LockContetion rather than LockError
279
                raise errors.LockContention(e)
2353.3.4 by John Arbash Meinel
Clean up the lock.py code to use less indenting, and conform to better coding practise.
280
281
        def unlock(self):
2353.3.5 by John Arbash Meinel
Fall back on ctypes to get LockFileEx, because msvcrt.locking()
282
            overlapped = pywintypes.OVERLAPPED()
2353.3.4 by John Arbash Meinel
Clean up the lock.py code to use less indenting, and conform to better coding practise.
283
            try:
284
                win32file.UnlockFileEx(self.hfile, 0, 0x7fff0000, overlapped)
285
                self._clear_f()
286
            except Exception, e:
2323.9.1 by John Arbash Meinel
Raise LockContetion rather than LockError
287
                raise errors.LockContention(e)
2353.3.4 by John Arbash Meinel
Clean up the lock.py code to use less indenting, and conform to better coding practise.
288
289
290
    class _w32c_ReadLock(_w32c_FileLock):
291
        def __init__(self, filename):
292
            super(_w32c_ReadLock, self).__init__()
293
            self._lock(filename, 'rb', LOCK_SH + LOCK_NB)
294
2353.4.4 by John Arbash Meinel
Implement temporary_write_lock, and restore_read_lock for win32 locks.
295
        def temporary_write_lock(self):
296
            """Try to grab a write lock on the file.
297
298
            On platforms that support it, this will upgrade to a write lock
299
            without unlocking the file.
300
            Otherwise, this will release the read lock, and try to acquire a
301
            write lock.
302
303
            :return: A token which can be used to switch back to a read lock.
304
            """
305
            # I can't find a way to upgrade a read lock to a write lock without
306
            # unlocking first. So here, we do just that.
307
            self.unlock()
2353.4.7 by John Arbash Meinel
Change the temporary_write_lock api, so that it always returns a lock object,
308
            try:
309
                wlock = _w32c_WriteLock(self.filename)
310
            except errors.LockError:
311
                return False, _w32c_ReadLock(self.filename)
312
            return True, wlock
2353.4.4 by John Arbash Meinel
Implement temporary_write_lock, and restore_read_lock for win32 locks.
313
2353.3.11 by John Arbash Meinel
Code cleanup
314
2353.3.4 by John Arbash Meinel
Clean up the lock.py code to use less indenting, and conform to better coding practise.
315
    class _w32c_WriteLock(_w32c_FileLock):
316
        def __init__(self, filename):
317
            super(_w32c_WriteLock, self).__init__()
318
            self._lock(filename, 'rb+', LOCK_EX + LOCK_NB)
319
2353.4.4 by John Arbash Meinel
Implement temporary_write_lock, and restore_read_lock for win32 locks.
320
        def restore_read_lock(self):
321
            """Restore the original ReadLock."""
322
            # For win32 we had to completely let go of the original lock, so we
323
            # just unlock and create a new read lock.
324
            self.unlock()
325
            return _w32c_ReadLock(self.filename)
326
2353.3.11 by John Arbash Meinel
Code cleanup
327
2353.3.9 by John Arbash Meinel
Update the lock code and test code so that if more than one
328
    _lock_classes.append(('pywin32', _w32c_WriteLock, _w32c_ReadLock))
329
2353.3.11 by John Arbash Meinel
Code cleanup
330
2353.3.12 by John Arbash Meinel
Don't create the alternative lock types unless we are on windows.
331
if have_ctypes and sys.platform == 'win32':
2353.3.5 by John Arbash Meinel
Fall back on ctypes to get LockFileEx, because msvcrt.locking()
332
    # These constants were copied from the win32con.py module.
333
    LOCKFILE_FAIL_IMMEDIATELY = 1
334
    LOCKFILE_EXCLUSIVE_LOCK = 2
335
    # Constant taken from winerror.py module
336
    ERROR_LOCK_VIOLATION = 33
337
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    LOCK_SH = 0
339
    LOCK_EX = LOCKFILE_EXCLUSIVE_LOCK
340
    LOCK_NB = LOCKFILE_FAIL_IMMEDIATELY
341
    _LockFileEx = ctypes.windll.kernel32.LockFileEx
342
    _UnlockFileEx = ctypes.windll.kernel32.UnlockFileEx
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    _GetLastError = ctypes.windll.kernel32.GetLastError
344
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    ### Define the OVERLAPPED structure.
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    #   http://msdn2.microsoft.com/en-us/library/ms684342.aspx
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    # typedef struct _OVERLAPPED {
348
    #   ULONG_PTR Internal;
349
    #   ULONG_PTR InternalHigh;
350
    #   union {
351
    #     struct {
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    #       DWORD Offset;
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    #       DWORD OffsetHigh;
354
    #     };
355
    #     PVOID Pointer;
356
    #   };
357
    #   HANDLE hEvent;
2353.3.9 by John Arbash Meinel
Update the lock code and test code so that if more than one
358
    # } OVERLAPPED,
2353.3.5 by John Arbash Meinel
Fall back on ctypes to get LockFileEx, because msvcrt.locking()
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    class _inner_struct(ctypes.Structure):
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        _fields_ = [('Offset', ctypes.c_uint), # DWORD
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                    ('OffsetHigh', ctypes.c_uint), # DWORD
363
                   ]
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    class _inner_union(ctypes.Union):
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        _fields_  = [('anon_struct', _inner_struct), # struct
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                     ('Pointer', ctypes.c_void_p), # PVOID
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                    ]
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    class OVERLAPPED(ctypes.Structure):
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        _fields_ = [('Internal', ctypes.c_void_p), # ULONG_PTR
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                    ('InternalHigh', ctypes.c_void_p), # ULONG_PTR
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                    ('_inner_union', _inner_union),
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                    ('hEvent', ctypes.c_void_p), # HANDLE
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                   ]
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2555.3.2 by Martin Pool
rename _base_Lock to _OSLock
377
    class _ctypes_FileLock(_OSLock):
2353.3.5 by John Arbash Meinel
Fall back on ctypes to get LockFileEx, because msvcrt.locking()
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        def _lock(self, filename, openmode, lockmode):
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            self._open(filename, openmode)
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            self.hfile = msvcrt.get_osfhandle(self.f.fileno())
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            overlapped = OVERLAPPED()
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            result = _LockFileEx(self.hfile, # HANDLE hFile
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                                 lockmode,   # DWORD dwFlags
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                                 0,          # DWORD dwReserved
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                                 0x7fffffff, # DWORD nNumberOfBytesToLockLow
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                                 0x00000000, # DWORD nNumberOfBytesToLockHigh
2353.4.9 by John Arbash Meinel
[merge] bzr.dev 2359
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                                 ctypes.byref(overlapped), # lpOverlapped
2353.3.5 by John Arbash Meinel
Fall back on ctypes to get LockFileEx, because msvcrt.locking()
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                                )
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            if result == 0:
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                self._clear_f()
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                last_err = _GetLastError()
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                if last_err in (ERROR_LOCK_VIOLATION,):
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                    raise errors.LockContention(filename)
2323.9.1 by John Arbash Meinel
Raise LockContetion rather than LockError
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                raise errors.LockContention('Unknown locking error: %s'
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                                            % (last_err,))
2353.3.5 by John Arbash Meinel
Fall back on ctypes to get LockFileEx, because msvcrt.locking()
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        def unlock(self):
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            overlapped = OVERLAPPED()
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            result = _UnlockFileEx(self.hfile, # HANDLE hFile
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                                   0,          # DWORD dwReserved
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                                   0x7fffffff, # DWORD nNumberOfBytesToLockLow
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                                   0x00000000, # DWORD nNumberOfBytesToLockHigh
2353.4.9 by John Arbash Meinel
[merge] bzr.dev 2359
405
                                   ctypes.byref(overlapped), # lpOverlapped
2353.3.5 by John Arbash Meinel
Fall back on ctypes to get LockFileEx, because msvcrt.locking()
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                                  )
407
            self._clear_f()
408
            if result == 0:
409
                self._clear_f()
410
                last_err = _GetLastError()
2323.9.1 by John Arbash Meinel
Raise LockContetion rather than LockError
411
                raise errors.LockContention('Unknown unlocking error: %s'
412
                                            % (last_err,))
2353.3.5 by John Arbash Meinel
Fall back on ctypes to get LockFileEx, because msvcrt.locking()
413
414
415
    class _ctypes_ReadLock(_ctypes_FileLock):
416
        def __init__(self, filename):
417
            super(_ctypes_ReadLock, self).__init__()
418
            self._lock(filename, 'rb', LOCK_SH + LOCK_NB)
419
2353.4.4 by John Arbash Meinel
Implement temporary_write_lock, and restore_read_lock for win32 locks.
420
        def temporary_write_lock(self):
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            """Try to grab a write lock on the file.
422
423
            On platforms that support it, this will upgrade to a write lock
424
            without unlocking the file.
425
            Otherwise, this will release the read lock, and try to acquire a
426
            write lock.
427
428
            :return: A token which can be used to switch back to a read lock.
429
            """
430
            # I can't find a way to upgrade a read lock to a write lock without
431
            # unlocking first. So here, we do just that.
432
            self.unlock()
2353.4.7 by John Arbash Meinel
Change the temporary_write_lock api, so that it always returns a lock object,
433
            try:
434
                wlock = _ctypes_WriteLock(self.filename)
435
            except errors.LockError:
436
                return False, _ctypes_ReadLock(self.filename)
437
            return True, wlock
2353.3.11 by John Arbash Meinel
Code cleanup
438
2353.3.5 by John Arbash Meinel
Fall back on ctypes to get LockFileEx, because msvcrt.locking()
439
    class _ctypes_WriteLock(_ctypes_FileLock):
440
        def __init__(self, filename):
441
            super(_ctypes_WriteLock, self).__init__()
442
            self._lock(filename, 'rb+', LOCK_EX + LOCK_NB)
443
2353.4.4 by John Arbash Meinel
Implement temporary_write_lock, and restore_read_lock for win32 locks.
444
        def restore_read_lock(self):
445
            """Restore the original ReadLock."""
446
            # For win32 we had to completely let go of the original lock, so we
447
            # just unlock and create a new read lock.
448
            self.unlock()
2353.4.6 by John Arbash Meinel
ctypes locks should return ctypes locks.
449
            return _ctypes_ReadLock(self.filename)
2353.4.4 by John Arbash Meinel
Implement temporary_write_lock, and restore_read_lock for win32 locks.
450
2353.3.11 by John Arbash Meinel
Code cleanup
451
2353.3.9 by John Arbash Meinel
Update the lock code and test code so that if more than one
452
    _lock_classes.append(('ctypes', _ctypes_WriteLock, _ctypes_ReadLock))
453
454
455
if len(_lock_classes) == 0:
2353.3.11 by John Arbash Meinel
Code cleanup
456
    raise NotImplementedError(
457
        "We must have one of fcntl, pywin32, or ctypes available"
458
        " to support OS locking."
459
        )
460
2353.3.9 by John Arbash Meinel
Update the lock code and test code so that if more than one
461
462
# We default to using the first available lock class.
463
_lock_type, WriteLock, ReadLock = _lock_classes[0]
464