Source Code for Module web2py.gluon.portalocker

  1  #!/usr/bin/env python 
  2  # -*- coding: utf-8 -*- 
  3  # portalocker.py - Cross-platform (posix/nt) API for flock-style file locking. 
  4  #                  Requires python 1.5.2 or better. 
  5   
  6  """ 
  7  Cross-platform (posix/nt) API for flock-style file locking. 
  8   
  9  Synopsis: 
 10   
 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() 
 17   
 18  If you know what you're doing, you may choose to 
 19   
 20     portalocker.unlock(file) 
 21   
 22  before closing the file, but why? 
 23   
 24  Methods: 
 25   
 26     lock( file, flags ) 
 27     unlock( file ) 
 28   
 29  Constants: 
 30   
 31     LOCK_EX 
 32     LOCK_SH 
 33     LOCK_NB 
 34   
 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. 
 38   
 39  Author: Jonathan Feinberg <jdf@pobox.com> 
 40  Version: $Id: portalocker.py,v 1.3 2001/05/29 18:47:55 Administrator Exp $ 
 41  """ 
 42   
 43  import logging 
 44  import platform 
 45  logger = logging.getLogger("web2py") 
 46   
 47  os_locking = None 
 48  try: 
 49      import google.appengine 
 50      os_locking = 'gae' 
 51  except: 
 52      try: 
 53          import fcntl 
 54          os_locking = 'posix' 
 55      except: 
 56          try: 
 57              import win32con 
 58              import win32file 
 59              import pywintypes 
 60              os_locking = 'windows' 
 61          except: 
 62              pass 
 63   
 64  if os_locking == 'windows': 
 65      LOCK_EX = win32con.LOCKFILE_EXCLUSIVE_LOCK 
 66      LOCK_SH = 0  # the default 
 67      LOCK_NB = win32con.LOCKFILE_FAIL_IMMEDIATELY 
 68   
 69      # is there any reason not to reuse the following structure? 
 70   
 71      __overlapped = pywintypes.OVERLAPPED() 
 72   
 73 -    def lock(file, flags): 
 74          hfile = win32file._get_osfhandle(file.fileno()) 
 75          win32file.LockFileEx(hfile, flags, 0, 0x7fff0000, __overlapped) 
 76   
 77 -    def unlock(file): 
 78          hfile = win32file._get_osfhandle(file.fileno()) 
 79          win32file.UnlockFileEx(hfile, 0, 0x7fff0000, __overlapped) 
 80   
 81   
 82  elif os_locking == 'posix': 
 83      LOCK_EX = fcntl.LOCK_EX 
 84      LOCK_SH = fcntl.LOCK_SH 
 85      LOCK_NB = fcntl.LOCK_NB 
 86   
 87 -    def lock(file, flags): 
 88          fcntl.flock(file.fileno(), flags) 
 89   
 90 -    def unlock(file): 
 91          fcntl.flock(file.fileno(), fcntl.LOCK_UN) 
 92   
 93   
 94  else: 
 95      if platform.system() == 'Windows': 
 96          logger.error('no file locking, you must install the win32 extensions from: http://sourceforge.net/projects/pywin32/files/') 
 97      elif os_locking != 'gae': 
 98          logger.debug('no file locking, this will cause problems') 
 99   
100      LOCK_EX = None 
101      LOCK_SH = None 
102      LOCK_NB = None 
103   
104 -    def lock(file, flags): 
105          pass 
106   
107 -    def unlock(file): 
108          pass 
109   
110   
111  if __name__ == '__main__': 
112      from time import time, strftime, localtime 
113      import sys 
114   
115      log = open('log.txt', 'a+') 
116      lock(log, LOCK_EX) 
117   
118      timestamp = strftime('%m/%d/%Y %H:%M:%S\n', localtime(time())) 
119      log.write(timestamp) 
120   
121      print 'Wrote lines. Hit enter to release lock.' 
122      dummy = sys.stdin.readline() 
123   
124      log.close() 
125