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annotate roundup/backends/portalocker.py @ 1244:8dd4f736370b

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merge from maintenance branch
author Richard Jones <richard@users.sourceforge.net>
date Thu, 03 Oct 2002 06:56:30 +0000
parents 509a101305da
children e975db910d9f
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1 # portalocker.py - Cross-platform (posix/nt) API for flock-style file locking.
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2 # Requires python 1.5.2 or better.
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3
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4 # ID line added by richard for Roundup file tracking
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5 # $Id: portalocker.py,v 1.2 2002-10-03 06:56:29 richard Exp $
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6
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7 """ Cross-platform (posix/nt) API for flock-style file locking.
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8
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9 Synopsis:
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10
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11 import portalocker
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12 file = open("somefile", "r+")
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13 portalocker.lock(file, portalocker.LOCK_EX)
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14 file.seek(12)
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15 file.write("foo")
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16 file.close()
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17
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18 If you know what you're doing, you may choose to
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19
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20 portalocker.unlock(file)
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21
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22 before closing the file, but why?
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23
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24 Methods:
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25
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26 lock( file, flags )
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27 unlock( file )
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28
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29 Constants:
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30
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31 LOCK_EX
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32 LOCK_SH
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33 LOCK_NB
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34
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35 I learned the win32 technique for locking files from sample code
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36 provided by John Nielsen <nielsenjf@my-deja.com> in the documentation
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37 that accompanies the win32 modules.
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38
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39 Author: Jonathan Feinberg <jdf@pobox.com>
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40 Version: Id: portalocker.py,v 1.3 2001/05/29 18:47:55 Administrator Exp
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41 **un-cvsified by richard so the version doesn't change**
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42 """
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43 import os
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44
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45 if os.name == 'nt':
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46 import win32con
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47 import win32file
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48 import pywintypes
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49 LOCK_EX = win32con.LOCKFILE_EXCLUSIVE_LOCK
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50 LOCK_SH = 0 # the default
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51 LOCK_NB = win32con.LOCKFILE_FAIL_IMMEDIATELY
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52 # is there any reason not to reuse the following structure?
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53 __overlapped = pywintypes.OVERLAPPED()
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54 elif os.name == 'posix':
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55 import fcntl
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56 LOCK_EX = fcntl.LOCK_EX
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57 LOCK_SH = fcntl.LOCK_SH
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58 LOCK_NB = fcntl.LOCK_NB
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59 else:
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60 raise RuntimeError("PortaLocker only defined for nt and posix platforms")
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61
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62 if os.name == 'nt':
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63 def lock(file, flags):
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64 hfile = win32file._get_osfhandle(file.fileno())
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65 win32file.LockFileEx(hfile, flags, 0, 0xffff0000, __overlapped)
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66
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67 def unlock(file):
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68 hfile = win32file._get_osfhandle(file.fileno())
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69 win32file.UnlockFileEx(hfile, 0, 0xffff0000, __overlapped)
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70
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71 elif os.name =='posix':
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72 def lock(file, flags):
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73 fcntl.flock(file.fileno(), flags)
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74
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75 def unlock(file):
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76 fcntl.flock(file.fileno(), fcntl.LOCK_UN)
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77
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78 if __name__ == '__main__':
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79 from time import time, strftime, localtime
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80 import sys
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81 import portalocker
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82
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83 log = open('log.txt', "a+")
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84 portalocker.lock(log, portalocker.LOCK_EX)
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85
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86 timestamp = strftime("%m/%d/%Y %H:%M:%S\n", localtime(time()))
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87 log.write( timestamp )
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88
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89 print "Wrote lines. Hit enter to release lock."
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90 dummy = sys.stdin.readline()
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91
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92 log.close()
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93
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