9c8389e7a87bfd37231d0d99ba62117a5c68ad97
1 # portalocker.py - Cross-platform (posix/nt) API for flock-style file locking.
2 # Requires python 1.5.2 or better.
4 # ID line added by richard for Roundup file tracking
5 # $Id: portalocker.py,v 1.7 2003-08-26 00:29:20 richard Exp $
7 """ Cross-platform (posix/nt) API for flock-style file locking.
9 Synopsis:
11 import portalocker
12 file = open("somefile", "r+")
13 portalocker.lock(file, portalocker.LOCK_EX)
14 file.seek(12)
15 file.write("foo")
16 file.close()
18 If you know what you're doing, you may choose to
20 portalocker.unlock(file)
22 before closing the file, but why?
24 Methods:
26 lock( file, flags )
27 unlock( file )
29 Constants:
31 LOCK_EX
32 LOCK_SH
33 LOCK_NB
35 I learned the win32 technique for locking files from sample code
36 provided by John Nielsen <nielsenjf@my-deja.com> in the documentation
37 that accompanies the win32 modules.
39 Author: Jonathan Feinberg <jdf@pobox.com>
40 Version: Id: portalocker.py,v 1.3 2001/05/29 18:47:55 Administrator Exp
41 **un-cvsified by richard so the version doesn't change**
42 """
43 import os
45 if os.name == 'nt':
46 import win32con
47 import win32file
48 import pywintypes
49 LOCK_EX = win32con.LOCKFILE_EXCLUSIVE_LOCK
50 LOCK_SH = 0 # the default
51 LOCK_NB = win32con.LOCKFILE_FAIL_IMMEDIATELY
52 # is there any reason not to reuse the following structure?
53 __overlapped = pywintypes.OVERLAPPED()
54 elif os.name == 'posix':
55 import fcntl
56 LOCK_EX = fcntl.LOCK_EX
57 LOCK_SH = fcntl.LOCK_SH
58 LOCK_NB = fcntl.LOCK_NB
59 else:
60 raise RuntimeError("PortaLocker only defined for nt and posix platforms")
62 if os.name == 'nt':
63 # eugh, we want 0xffff0000 here, but python 2.3 won't let us :(
64 FFFF0000 = -65536
65 def lock(file, flags):
66 hfile = win32file._get_osfhandle(file.fileno())
67 # LockFileEx is not supported on all Win32 platforms (Win95, Win98, WinME).
68 # If it's not supported, win32file will raise an exception.
69 # Try LockFileEx first, as it has more functionality and handles
70 # blocking locks more efficiently.
71 try:
72 win32file.LockFileEx(hfile, flags, 0, FFFF0000, __overlapped)
73 except win32file.error, e:
74 import winerror
75 # Propagate upwards all exceptions other than not-implemented.
76 if e[0] != winerror.ERROR_CALL_NOT_IMPLEMENTED:
77 raise e
79 # LockFileEx is not supported. Use LockFile.
80 # LockFile does not support shared locking -- always exclusive.
81 # Care: the low/high length params are reversed compared to LockFileEx.
82 if not flags & LOCK_EX:
83 import warnings
84 warnings.warn("PortaLocker does not support shared locking on Win9x", RuntimeWarning)
85 # LockFile only supports immediate-fail locking.
86 if flags & LOCK_NB:
87 win32file.LockFile(hfile, 0, 0, FFFF0000, 0)
88 else:
89 # Emulate a blocking lock with a polling loop.
90 import time
91 while 1:
92 # Attempt a lock.
93 try:
94 win32file.LockFile(hfile, 0, 0, FFFF0000, 0)
95 break
96 except win32file.error, e:
97 # Propagate upwards all exceptions other than lock violation.
98 if e[0] != winerror.ERROR_LOCK_VIOLATION:
99 raise e
100 # Sleep and poll again.
101 time.sleep(0.1)
102 # TODO: should this return the result of the lock?
104 def unlock(file):
105 hfile = win32file._get_osfhandle(file.fileno())
106 # UnlockFileEx is not supported on all Win32 platforms (Win95, Win98, WinME).
107 # If it's not supported, win32file will raise an api_error exception.
108 try:
109 win32file.UnlockFileEx(hfile, 0, FFFF0000, __overlapped)
110 except win32file.error, e:
111 import winerror
112 # Propagate upwards all exceptions other than not-implemented.
113 if e[0] != winerror.ERROR_CALL_NOT_IMPLEMENTED:
114 raise e
116 # UnlockFileEx is not supported. Use UnlockFile.
117 # Care: the low/high length params are reversed compared to UnLockFileEx.
118 win32file.UnlockFile(hfile, 0, 0, FFFF0000, 0)
120 elif os.name =='posix':
121 def lock(file, flags):
122 fcntl.flock(file.fileno(), flags)
123 # TODO: should this return the result of the lock?
125 def unlock(file):
126 fcntl.flock(file.fileno(), fcntl.LOCK_UN)
128 if __name__ == '__main__':
129 from time import time, strftime, localtime
130 import sys
131 import portalocker
133 log = open('log.txt', "a+")
134 portalocker.lock(log, portalocker.LOCK_EX)
136 timestamp = strftime("%m/%d/%Y %H:%M:%S\n", localtime(time()))
137 log.write( timestamp )
139 print "Wrote lines. Hit enter to release lock."
140 dummy = sys.stdin.readline()
142 log.close()