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Viewing changes to bzrlib/lock.py

  • Committer: John Arbash Meinel
  • Date: 2007-03-16 19:13:40 UTC
  • mto: This revision was merged to the branch mainline in revision 2363.
  • Revision ID: john@arbash-meinel.com-20070316191340-pddd21esqtzr35zp
Change utf8_decode_with_None to return what we care about.
Re-use utf8_decode_with_None in the outer loop to avoid decoding in the inner
process_entry
Change the name of the local variable, to make it clear what we are doing.

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bzrlib/lock.py
1
 
# Copyright (C) 2005-2010 Canonical Ltd
 
1
# Copyright (C) 2005, 2006, 2007 Canonical Ltd
2
2
#
3
3
# This program is free software; you can redistribute it and/or modify
4
4
# it under the terms of the GNU General Public License as published by
12
12
#
13
13
# You should have received a copy of the GNU General Public License
14
14
# along with this program; if not, write to the Free Software
15
 
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 
15
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
16
16
 
17
17
 
18
18
"""Locking using OS file locks or file existence.
35
35
"""
36
36
 
37
37
import errno
38
 
import os
39
38
import sys
40
 
import warnings
41
39
 
42
40
from bzrlib import (
43
 
    debug,
44
41
    errors,
45
42
    osutils,
46
43
    trace,
47
44
    )
48
 
from bzrlib.hooks import HookPoint, Hooks
49
 
 
50
 
 
51
 
class LockHooks(Hooks):
52
 
 
53
 
    def __init__(self):
54
 
        Hooks.__init__(self)
55
 
        self.create_hook(HookPoint('lock_acquired',
56
 
            "Called with a bzrlib.lock.LockResult when a physical lock is "
57
 
            "acquired.", (1, 8), None))
58
 
        self.create_hook(HookPoint('lock_released',
59
 
            "Called with a bzrlib.lock.LockResult when a physical lock is "
60
 
            "released.", (1, 8), None))
61
 
        self.create_hook(HookPoint('lock_broken',
62
 
            "Called with a bzrlib.lock.LockResult when a physical lock is "
63
 
            "broken.", (1, 15), None))
64
 
 
65
 
 
66
 
class Lock(object):
67
 
    """Base class for locks.
68
 
 
69
 
    :cvar hooks: Hook dictionary for operations on locks.
70
 
    """
71
 
 
72
 
    hooks = LockHooks()
73
 
 
74
 
 
75
 
class LockResult(object):
76
 
    """Result of an operation on a lock; passed to a hook"""
77
 
 
78
 
    def __init__(self, lock_url, details=None):
79
 
        """Create a lock result for lock with optional details about the lock."""
80
 
        self.lock_url = lock_url
81
 
        self.details = details
82
 
 
83
 
    def __eq__(self, other):
84
 
        return self.lock_url == other.lock_url and self.details == other.details
85
 
 
86
 
    def __repr__(self):
87
 
        return '%s(%s, %s)' % (self.__class__.__name__,
88
 
                             self.lock_url, self.details)
89
 
 
90
 
 
91
 
def cant_unlock_not_held(locked_object):
92
 
    """An attempt to unlock failed because the object was not locked.
93
 
 
94
 
    This provides a policy point from which we can generate either a warning 
95
 
    or an exception.
96
 
    """
97
 
    # This is typically masking some other error and called from a finally
98
 
    # block, so it's useful to have the option not to generate a new error
99
 
    # here.  You can use -Werror to make it fatal.  It should possibly also
100
 
    # raise LockNotHeld.
101
 
    if 'unlock' in debug.debug_flags:
102
 
        warnings.warn("%r is already unlocked" % (locked_object,),
103
 
            stacklevel=3)
104
 
    else:
105
 
        raise errors.LockNotHeld(locked_object)
106
 
 
107
 
 
108
 
try:
109
 
    import fcntl
110
 
    have_fcntl = True
111
 
except ImportError:
112
 
    have_fcntl = False
113
 
 
114
 
have_pywin32 = False
115
 
have_ctypes_win32 = False
116
 
if sys.platform == 'win32':
117
 
    import msvcrt
118
 
    try:
119
 
        import win32file, pywintypes, winerror
120
 
        have_pywin32 = True
121
 
    except ImportError:
122
 
        pass
123
 
 
124
 
    try:
125
 
        import ctypes
126
 
        have_ctypes_win32 = True
127
 
    except ImportError:
128
 
        pass
129
 
 
130
 
 
131
 
class _OSLock(object):
 
45
 
 
46
 
 
47
class _base_Lock(object):
132
48
 
133
49
    def __init__(self):
134
50
        self.f = None
141
57
            return self.f
142
58
        except IOError, e:
143
59
            if e.errno in (errno.EACCES, errno.EPERM):
144
 
                raise errors.LockFailed(self.filename, str(e))
 
60
                raise errors.ReadOnlyLockError(self.filename, str(e))
145
61
            if e.errno != errno.ENOENT:
146
62
                raise
147
63
 
167
83
        raise NotImplementedError()
168
84
 
169
85
 
 
86
try:
 
87
    import fcntl
 
88
    have_fcntl = True
 
89
except ImportError:
 
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
 
170
103
_lock_classes = []
171
104
 
172
105
 
173
106
if have_fcntl:
174
 
 
175
 
    class _fcntl_FileLock(_OSLock):
 
107
    LOCK_SH = fcntl.LOCK_SH
 
108
    LOCK_NB = fcntl.LOCK_NB
 
109
    lock_EX = fcntl.LOCK_EX
 
110
 
 
111
 
 
112
    class _fcntl_FileLock(_base_Lock):
176
113
 
177
114
        def _unlock(self):
178
115
            fcntl.lockf(self.f, fcntl.LOCK_UN)
181
118
 
182
119
    class _fcntl_WriteLock(_fcntl_FileLock):
183
120
 
184
 
        _open_locks = set()
 
121
        open_locks = {}
185
122
 
186
123
        def __init__(self, filename):
 
124
            # standard IO errors get exposed directly.
187
125
            super(_fcntl_WriteLock, self).__init__()
188
 
            # Check we can grab a lock before we actually open the file.
189
 
            self.filename = osutils.realpath(filename)
190
 
            if self.filename in _fcntl_WriteLock._open_locks:
 
126
            self._open(filename, 'rb+')
 
127
            if self.filename in self.open_locks:
191
128
                self._clear_f()
192
129
                raise errors.LockContention(self.filename)
193
 
            if self.filename in _fcntl_ReadLock._open_locks:
194
 
                if 'strict_locks' in debug.debug_flags:
195
 
                    self._clear_f()
196
 
                    raise errors.LockContention(self.filename)
197
 
                else:
198
 
                    trace.mutter('Write lock taken w/ an open read lock on: %s'
199
 
                                 % (self.filename,))
200
 
 
201
 
            self._open(self.filename, 'rb+')
202
130
            # reserve a slot for this lock - even if the lockf call fails,
203
 
            # at this point unlock() will be called, because self.f is set.
 
131
            # at thisi point unlock() will be called, because self.f is set.
204
132
            # TODO: make this fully threadsafe, if we decide we care.
205
 
            _fcntl_WriteLock._open_locks.add(self.filename)
 
133
            self.open_locks[self.filename] = self.filename
206
134
            try:
207
135
                # LOCK_NB will cause IOError to be raised if we can't grab a
208
136
                # lock right away.
213
141
                    self.unlock()
214
142
                # we should be more precise about whats a locking
215
143
                # error and whats a random-other error
216
 
                raise errors.LockContention(self.filename, e)
 
144
                raise errors.LockError(e)
217
145
 
218
146
        def unlock(self):
219
 
            _fcntl_WriteLock._open_locks.remove(self.filename)
 
147
            del self.open_locks[self.filename]
220
148
            self._unlock()
221
149
 
222
150
 
223
151
    class _fcntl_ReadLock(_fcntl_FileLock):
224
152
 
225
 
        _open_locks = {}
 
153
        open_locks = {}
226
154
 
227
155
        def __init__(self, filename):
228
156
            super(_fcntl_ReadLock, self).__init__()
229
 
            self.filename = osutils.realpath(filename)
230
 
            if self.filename in _fcntl_WriteLock._open_locks:
231
 
                if 'strict_locks' in debug.debug_flags:
232
 
                    # We raise before calling _open so we don't need to
233
 
                    # _clear_f
234
 
                    raise errors.LockContention(self.filename)
235
 
                else:
236
 
                    trace.mutter('Read lock taken w/ an open write lock on: %s'
237
 
                                 % (self.filename,))
238
 
            _fcntl_ReadLock._open_locks.setdefault(self.filename, 0)
239
 
            _fcntl_ReadLock._open_locks[self.filename] += 1
240
157
            self._open(filename, 'rb')
241
158
            try:
242
159
                # LOCK_NB will cause IOError to be raised if we can't grab a
245
162
            except IOError, e:
246
163
                # we should be more precise about whats a locking
247
164
                # error and whats a random-other error
248
 
                raise errors.LockContention(self.filename, e)
 
165
                raise errors.LockError(e)
249
166
 
250
167
        def unlock(self):
251
 
            count = _fcntl_ReadLock._open_locks[self.filename]
252
 
            if count == 1:
253
 
                del _fcntl_ReadLock._open_locks[self.filename]
254
 
            else:
255
 
                _fcntl_ReadLock._open_locks[self.filename] = count - 1
256
168
            self._unlock()
257
169
 
258
 
        def temporary_write_lock(self):
259
 
            """Try to grab a write lock on the file.
260
 
 
261
 
            On platforms that support it, this will upgrade to a write lock
262
 
            without unlocking the file.
263
 
            Otherwise, this will release the read lock, and try to acquire a
264
 
            write lock.
265
 
 
266
 
            :return: A token which can be used to switch back to a read lock.
267
 
            """
268
 
            if self.filename in _fcntl_WriteLock._open_locks:
269
 
                raise AssertionError('file already locked: %r'
270
 
                    % (self.filename,))
271
 
            try:
272
 
                wlock = _fcntl_TemporaryWriteLock(self)
273
 
            except errors.LockError:
274
 
                # We didn't unlock, so we can just return 'self'
275
 
                return False, self
276
 
            return True, wlock
277
 
 
278
 
 
279
 
    class _fcntl_TemporaryWriteLock(_OSLock):
280
 
        """A token used when grabbing a temporary_write_lock.
281
 
 
282
 
        Call restore_read_lock() when you are done with the write lock.
283
 
        """
284
 
 
285
 
        def __init__(self, read_lock):
286
 
            super(_fcntl_TemporaryWriteLock, self).__init__()
287
 
            self._read_lock = read_lock
288
 
            self.filename = read_lock.filename
289
 
 
290
 
            count = _fcntl_ReadLock._open_locks[self.filename]
291
 
            if count > 1:
292
 
                # Something else also has a read-lock, so we cannot grab a
293
 
                # write lock.
294
 
                raise errors.LockContention(self.filename)
295
 
 
296
 
            if self.filename in _fcntl_WriteLock._open_locks:
297
 
                raise AssertionError('file already locked: %r'
298
 
                    % (self.filename,))
299
 
 
300
 
            # See if we can open the file for writing. Another process might
301
 
            # have a read lock. We don't use self._open() because we don't want
302
 
            # to create the file if it exists. That would have already been
303
 
            # done by _fcntl_ReadLock
304
 
            try:
305
 
                new_f = open(self.filename, 'rb+')
306
 
            except IOError, e:
307
 
                if e.errno in (errno.EACCES, errno.EPERM):
308
 
                    raise errors.LockFailed(self.filename, str(e))
309
 
                raise
310
 
            try:
311
 
                # LOCK_NB will cause IOError to be raised if we can't grab a
312
 
                # lock right away.
313
 
                fcntl.lockf(new_f, fcntl.LOCK_EX | fcntl.LOCK_NB)
314
 
            except IOError, e:
315
 
                # TODO: Raise a more specific error based on the type of error
316
 
                raise errors.LockContention(self.filename, e)
317
 
            _fcntl_WriteLock._open_locks.add(self.filename)
318
 
 
319
 
            self.f = new_f
320
 
 
321
 
        def restore_read_lock(self):
322
 
            """Restore the original ReadLock."""
323
 
            # For fcntl, since we never released the read lock, just release the
324
 
            # write lock, and return the original lock.
325
 
            fcntl.lockf(self.f, fcntl.LOCK_UN)
326
 
            self._clear_f()
327
 
            _fcntl_WriteLock._open_locks.remove(self.filename)
328
 
            # Avoid reference cycles
329
 
            read_lock = self._read_lock
330
 
            self._read_lock = None
331
 
            return read_lock
332
 
 
333
170
 
334
171
    _lock_classes.append(('fcntl', _fcntl_WriteLock, _fcntl_ReadLock))
335
172
 
336
173
 
337
174
if have_pywin32 and sys.platform == 'win32':
338
 
    if os.path.supports_unicode_filenames:
339
 
        # for Windows NT/2K/XP/etc
340
 
        win32file_CreateFile = win32file.CreateFileW
341
 
    else:
342
 
        # for Windows 98
343
 
        win32file_CreateFile = win32file.CreateFile
344
 
 
345
 
    class _w32c_FileLock(_OSLock):
346
 
 
347
 
        def _open(self, filename, access, share, cflags, pymode):
348
 
            self.filename = osutils.realpath(filename)
 
175
    LOCK_SH = 0 # the default
 
176
    LOCK_EX = win32con.LOCKFILE_EXCLUSIVE_LOCK
 
177
    LOCK_NB = win32con.LOCKFILE_FAIL_IMMEDIATELY
 
178
 
 
179
 
 
180
    class _w32c_FileLock(_base_Lock):
 
181
 
 
182
        def _lock(self, filename, openmode, lockmode):
 
183
            self._open(filename, openmode)
 
184
 
 
185
            self.hfile = msvcrt.get_osfhandle(self.f.fileno())
 
186
            overlapped = pywintypes.OVERLAPPED()
349
187
            try:
350
 
                self._handle = win32file_CreateFile(filename, access, share,
351
 
                    None, win32file.OPEN_ALWAYS,
352
 
                    win32file.FILE_ATTRIBUTE_NORMAL, None)
 
188
                win32file.LockFileEx(self.hfile, lockmode, 0, 0x7fff0000,
 
189
                                     overlapped)
353
190
            except pywintypes.error, e:
354
 
                if e.args[0] == winerror.ERROR_ACCESS_DENIED:
355
 
                    raise errors.LockFailed(filename, e)
356
 
                if e.args[0] == winerror.ERROR_SHARING_VIOLATION:
357
 
                    raise errors.LockContention(filename, e)
 
191
                self._clear_f()
 
192
                if e.args[0] in (winerror.ERROR_LOCK_VIOLATION,):
 
193
                    raise errors.LockContention(filename)
 
194
                ## import pdb; pdb.set_trace()
358
195
                raise
359
 
            fd = win32file._open_osfhandle(self._handle, cflags)
360
 
            self.f = os.fdopen(fd, pymode)
361
 
            return self.f
 
196
            except Exception, e:
 
197
                self._clear_f()
 
198
                raise errors.LockError(e)
362
199
 
363
200
        def unlock(self):
364
 
            self._clear_f()
365
 
            self._handle = None
 
201
            overlapped = pywintypes.OVERLAPPED()
 
202
            try:
 
203
                win32file.UnlockFileEx(self.hfile, 0, 0x7fff0000, overlapped)
 
204
                self._clear_f()
 
205
            except Exception, e:
 
206
                raise errors.LockError(e)
366
207
 
367
208
 
368
209
    class _w32c_ReadLock(_w32c_FileLock):
369
210
        def __init__(self, filename):
370
211
            super(_w32c_ReadLock, self).__init__()
371
 
            self._open(filename, win32file.GENERIC_READ,
372
 
                win32file.FILE_SHARE_READ, os.O_RDONLY, "rb")
373
 
 
374
 
        def temporary_write_lock(self):
375
 
            """Try to grab a write lock on the file.
376
 
 
377
 
            On platforms that support it, this will upgrade to a write lock
378
 
            without unlocking the file.
379
 
            Otherwise, this will release the read lock, and try to acquire a
380
 
            write lock.
381
 
 
382
 
            :return: A token which can be used to switch back to a read lock.
383
 
            """
384
 
            # I can't find a way to upgrade a read lock to a write lock without
385
 
            # unlocking first. So here, we do just that.
386
 
            self.unlock()
387
 
            try:
388
 
                wlock = _w32c_WriteLock(self.filename)
389
 
            except errors.LockError:
390
 
                return False, _w32c_ReadLock(self.filename)
391
 
            return True, wlock
 
212
            self._lock(filename, 'rb', LOCK_SH + LOCK_NB)
392
213
 
393
214
 
394
215
    class _w32c_WriteLock(_w32c_FileLock):
395
216
        def __init__(self, filename):
396
217
            super(_w32c_WriteLock, self).__init__()
397
 
            self._open(filename,
398
 
                win32file.GENERIC_READ | win32file.GENERIC_WRITE, 0,
399
 
                os.O_RDWR, "rb+")
400
 
 
401
 
        def restore_read_lock(self):
402
 
            """Restore the original ReadLock."""
403
 
            # For win32 we had to completely let go of the original lock, so we
404
 
            # just unlock and create a new read lock.
405
 
            self.unlock()
406
 
            return _w32c_ReadLock(self.filename)
 
218
            self._lock(filename, 'rb+', LOCK_EX + LOCK_NB)
407
219
 
408
220
 
409
221
    _lock_classes.append(('pywin32', _w32c_WriteLock, _w32c_ReadLock))
410
222
 
411
223
 
412
 
if have_ctypes_win32:
413
 
    from ctypes.wintypes import DWORD, LPCSTR, LPCWSTR
414
 
    LPSECURITY_ATTRIBUTES = ctypes.c_void_p # used as NULL no need to declare
415
 
    HANDLE = ctypes.c_int # rather than unsigned as in ctypes.wintypes
416
 
    if os.path.supports_unicode_filenames:
417
 
        _function_name = "CreateFileW"
418
 
        LPTSTR = LPCWSTR
419
 
    else:
420
 
        _function_name = "CreateFileA"
421
 
        class LPTSTR(LPCSTR):
422
 
            def __new__(cls, obj):
423
 
                return LPCSTR.__new__(cls, obj.encode("mbcs"))
424
 
 
425
 
    # CreateFile <http://msdn.microsoft.com/en-us/library/aa363858.aspx>
426
 
    _CreateFile = ctypes.WINFUNCTYPE(
427
 
            HANDLE,                # return value
428
 
            LPTSTR,                # lpFileName
429
 
            DWORD,                 # dwDesiredAccess
430
 
            DWORD,                 # dwShareMode
431
 
            LPSECURITY_ATTRIBUTES, # lpSecurityAttributes
432
 
            DWORD,                 # dwCreationDisposition
433
 
            DWORD,                 # dwFlagsAndAttributes
434
 
            HANDLE                 # hTemplateFile
435
 
        )((_function_name, ctypes.windll.kernel32))
436
 
 
437
 
    INVALID_HANDLE_VALUE = -1
438
 
 
439
 
    GENERIC_READ = 0x80000000
440
 
    GENERIC_WRITE = 0x40000000
441
 
    FILE_SHARE_READ = 1
442
 
    OPEN_ALWAYS = 4
443
 
    FILE_ATTRIBUTE_NORMAL = 128
444
 
 
445
 
    ERROR_ACCESS_DENIED = 5
446
 
    ERROR_SHARING_VIOLATION = 32
447
 
 
448
 
    class _ctypes_FileLock(_OSLock):
449
 
 
450
 
        def _open(self, filename, access, share, cflags, pymode):
451
 
            self.filename = osutils.realpath(filename)
452
 
            handle = _CreateFile(filename, access, share, None, OPEN_ALWAYS,
453
 
                FILE_ATTRIBUTE_NORMAL, 0)
454
 
            if handle in (INVALID_HANDLE_VALUE, 0):
455
 
                e = ctypes.WinError()
456
 
                if e.args[0] == ERROR_ACCESS_DENIED:
457
 
                    raise errors.LockFailed(filename, e)
458
 
                if e.args[0] == ERROR_SHARING_VIOLATION:
459
 
                    raise errors.LockContention(filename, e)
460
 
                raise e
461
 
            fd = msvcrt.open_osfhandle(handle, cflags)
462
 
            self.f = os.fdopen(fd, pymode)
463
 
            return self.f
 
224
if have_ctypes and sys.platform == 'win32':
 
225
    # These constants were copied from the win32con.py module.
 
226
    LOCKFILE_FAIL_IMMEDIATELY = 1
 
227
    LOCKFILE_EXCLUSIVE_LOCK = 2
 
228
    # Constant taken from winerror.py module
 
229
    ERROR_LOCK_VIOLATION = 33
 
230
 
 
231
    LOCK_SH = 0
 
232
    LOCK_EX = LOCKFILE_EXCLUSIVE_LOCK
 
233
    LOCK_NB = LOCKFILE_FAIL_IMMEDIATELY
 
234
    _LockFileEx = ctypes.windll.kernel32.LockFileEx
 
235
    _UnlockFileEx = ctypes.windll.kernel32.UnlockFileEx
 
236
    _GetLastError = ctypes.windll.kernel32.GetLastError
 
237
 
 
238
    ### Define the OVERLAPPED structure.
 
239
    #   http://msdn2.microsoft.com/en-us/library/ms684342.aspx
 
240
    # typedef struct _OVERLAPPED {
 
241
    #   ULONG_PTR Internal;
 
242
    #   ULONG_PTR InternalHigh;
 
243
    #   union {
 
244
    #     struct {
 
245
    #       DWORD Offset;
 
246
    #       DWORD OffsetHigh;
 
247
    #     };
 
248
    #     PVOID Pointer;
 
249
    #   };
 
250
    #   HANDLE hEvent;
 
251
    # } OVERLAPPED,
 
252
 
 
253
    class _inner_struct(ctypes.Structure):
 
254
        _fields_ = [('Offset', ctypes.c_uint), # DWORD
 
255
                    ('OffsetHigh', ctypes.c_uint), # DWORD
 
256
                   ]
 
257
 
 
258
    class _inner_union(ctypes.Union):
 
259
        _fields_  = [('anon_struct', _inner_struct), # struct
 
260
                     ('Pointer', ctypes.c_void_p), # PVOID
 
261
                    ]
 
262
 
 
263
    class OVERLAPPED(ctypes.Structure):
 
264
        _fields_ = [('Internal', ctypes.c_void_p), # ULONG_PTR
 
265
                    ('InternalHigh', ctypes.c_void_p), # ULONG_PTR
 
266
                    ('_inner_union', _inner_union),
 
267
                    ('hEvent', ctypes.c_void_p), # HANDLE
 
268
                   ]
 
269
 
 
270
    class _ctypes_FileLock(_base_Lock):
 
271
 
 
272
        def _lock(self, filename, openmode, lockmode):
 
273
            self._open(filename, openmode)
 
274
 
 
275
            self.hfile = msvcrt.get_osfhandle(self.f.fileno())
 
276
            overlapped = OVERLAPPED()
 
277
            p_overlapped = ctypes.pointer(overlapped)
 
278
            result = _LockFileEx(self.hfile, # HANDLE hFile
 
279
                                 lockmode,   # DWORD dwFlags
 
280
                                 0,          # DWORD dwReserved
 
281
                                 0x7fffffff, # DWORD nNumberOfBytesToLockLow
 
282
                                 0x00000000, # DWORD nNumberOfBytesToLockHigh
 
283
                                 p_overlapped, # lpOverlapped
 
284
                                )
 
285
            if result == 0:
 
286
                self._clear_f()
 
287
                last_err = _GetLastError()
 
288
                if last_err in (ERROR_LOCK_VIOLATION,):
 
289
                    raise errors.LockContention(filename)
 
290
                raise errors.LockError('Unknown locking error: %s'
 
291
                                       % (last_err,))
464
292
 
465
293
        def unlock(self):
 
294
            overlapped = OVERLAPPED()
 
295
            p_overlapped = ctypes.pointer(overlapped)
 
296
            result = _UnlockFileEx(self.hfile, # HANDLE hFile
 
297
                                   0,          # DWORD dwReserved
 
298
                                   0x7fffffff, # DWORD nNumberOfBytesToLockLow
 
299
                                   0x00000000, # DWORD nNumberOfBytesToLockHigh
 
300
                                   p_overlapped, # lpOverlapped
 
301
                                  )
466
302
            self._clear_f()
 
303
            if result == 0:
 
304
                self._clear_f()
 
305
                last_err = _GetLastError()
 
306
                raise errors.LockError('Unknown unlocking error: %s'
 
307
                                       % (last_err,))
467
308
 
468
309
 
469
310
    class _ctypes_ReadLock(_ctypes_FileLock):
470
311
        def __init__(self, filename):
471
312
            super(_ctypes_ReadLock, self).__init__()
472
 
            self._open(filename, GENERIC_READ, FILE_SHARE_READ, os.O_RDONLY,
473
 
                "rb")
474
 
 
475
 
        def temporary_write_lock(self):
476
 
            """Try to grab a write lock on the file.
477
 
 
478
 
            On platforms that support it, this will upgrade to a write lock
479
 
            without unlocking the file.
480
 
            Otherwise, this will release the read lock, and try to acquire a
481
 
            write lock.
482
 
 
483
 
            :return: A token which can be used to switch back to a read lock.
484
 
            """
485
 
            # I can't find a way to upgrade a read lock to a write lock without
486
 
            # unlocking first. So here, we do just that.
487
 
            self.unlock()
488
 
            try:
489
 
                wlock = _ctypes_WriteLock(self.filename)
490
 
            except errors.LockError:
491
 
                return False, _ctypes_ReadLock(self.filename)
492
 
            return True, wlock
 
313
            self._lock(filename, 'rb', LOCK_SH + LOCK_NB)
 
314
 
493
315
 
494
316
    class _ctypes_WriteLock(_ctypes_FileLock):
495
317
        def __init__(self, filename):
496
318
            super(_ctypes_WriteLock, self).__init__()
497
 
            self._open(filename, GENERIC_READ | GENERIC_WRITE, 0, os.O_RDWR,
498
 
                "rb+")
499
 
 
500
 
        def restore_read_lock(self):
501
 
            """Restore the original ReadLock."""
502
 
            # For win32 we had to completely let go of the original lock, so we
503
 
            # just unlock and create a new read lock.
504
 
            self.unlock()
505
 
            return _ctypes_ReadLock(self.filename)
 
319
            self._lock(filename, 'rb+', LOCK_EX + LOCK_NB)
506
320
 
507
321
 
508
322
    _lock_classes.append(('ctypes', _ctypes_WriteLock, _ctypes_ReadLock))
518
332
# We default to using the first available lock class.
519
333
_lock_type, WriteLock, ReadLock = _lock_classes[0]
520
334
 
521
 
 
522
 
class _RelockDebugMixin(object):
523
 
    """Mixin support for -Drelock flag.
524
 
 
525
 
    Add this as a base class then call self._note_lock with 'r' or 'w' when
526
 
    acquiring a read- or write-lock.  If this object was previously locked (and
527
 
    locked the same way), and -Drelock is set, then this will trace.note a
528
 
    message about it.
529
 
    """
530
 
    
531
 
    _prev_lock = None
532
 
 
533
 
    def _note_lock(self, lock_type):
534
 
        if 'relock' in debug.debug_flags and self._prev_lock == lock_type:
535
 
            if lock_type == 'r':
536
 
                type_name = 'read'
537
 
            else:
538
 
                type_name = 'write'
539
 
            trace.note('%r was %s locked again', self, type_name)
540
 
        self._prev_lock = lock_type
541