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
|
# Copyright 2016 Google Inc. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import errno
import time
import pywintypes
import win32con
import win32file
from oauth2client.contrib import locked_file
class _Win32Opener(locked_file._Opener):
"""Open, lock, and unlock a file using windows primitives."""
# Error #33:
# 'The process cannot access the file because another process'
FILE_IN_USE_ERROR = 33
# Error #158:
# 'The segment is already unlocked.'
FILE_ALREADY_UNLOCKED_ERROR = 158
def open_and_lock(self, timeout, delay):
"""Open the file and lock it.
Args:
timeout: float, How long to try to lock for.
delay: float, How long to wait between retries
Raises:
AlreadyLockedException: if the lock is already acquired.
IOError: if the open fails.
CredentialsFileSymbolicLinkError: if the file is a symbolic
link.
"""
if self._locked:
raise locked_file.AlreadyLockedException(
'File {0} is already locked'.format(self._filename))
start_time = time.time()
locked_file.validate_file(self._filename)
try:
self._fh = open(self._filename, self._mode)
except IOError as e:
# If we can't access with _mode, try _fallback_mode
# and don't lock.
if e.errno == errno.EACCES:
self._fh = open(self._filename, self._fallback_mode)
return
# We opened in _mode, try to lock the file.
while True:
try:
hfile = win32file._get_osfhandle(self._fh.fileno())
win32file.LockFileEx(
hfile,
(win32con.LOCKFILE_FAIL_IMMEDIATELY |
win32con.LOCKFILE_EXCLUSIVE_LOCK), 0, -0x10000,
pywintypes.OVERLAPPED())
self._locked = True
return
except pywintypes.error as e:
if timeout == 0:
raise
# If the error is not that the file is already
# in use, raise.
if e[0] != _Win32Opener.FILE_IN_USE_ERROR:
raise
# We could not acquire the lock. Try again.
if (time.time() - start_time) >= timeout:
locked_file.logger.warn('Could not lock %s in %s seconds',
self._filename, timeout)
if self._fh:
self._fh.close()
self._fh = open(self._filename, self._fallback_mode)
return
time.sleep(delay)
def unlock_and_close(self):
"""Close and unlock the file using the win32 primitive."""
if self._locked:
try:
hfile = win32file._get_osfhandle(self._fh.fileno())
win32file.UnlockFileEx(hfile, 0, -0x10000,
pywintypes.OVERLAPPED())
except pywintypes.error as e:
if e[0] != _Win32Opener.FILE_ALREADY_UNLOCKED_ERROR:
raise
self._locked = False
if self._fh:
self._fh.close()
|
