Source Code for Module gluon.portalocker

  1  #!/usr/bin/env python 
  2  # -*- coding: utf-8 -*- 
  3   
  4  """ 
  5  Cross-platform (posix/nt) API for flock-style file locking. 
  6   
  7  Synopsis:: 
  8   
  9     import portalocker 
 10     file = open(\"somefile\", \"r+\") 
 11     portalocker.lock(file, portalocker.LOCK_EX) 
 12     file.seek(12) 
 13     file.write(\"foo\") 
 14     file.close() 
 15   
 16  If you know what you're doing, you may choose to:: 
 17   
 18     portalocker.unlock(file) 
 19   
 20  before closing the file, but why? 
 21   
 22  Methods:: 
 23   
 24     lock( file, flags ) 
 25     unlock( file ) 
 26   
 27  Constants:: 
 28   
 29     LOCK_EX 
 30     LOCK_SH 
 31     LOCK_NB 
 32   
 33  I learned the win32 technique for locking files from sample code 
 34  provided by John Nielsen <nielsenjf@my-deja.com> in the documentation 
 35  that accompanies the win32 modules. 
 36   
 37  Author: Jonathan Feinberg <jdf@pobox.com> 
 38  Version: $Id: portalocker.py,v 1.3 2001/05/29 18:47:55 Administrator Exp $ 
 39  """ 
 40   
 41  import logging 
 42  import platform 
 43  logger = logging.getLogger("web2py") 
 44   
 45  os_locking = None 
 46  try: 
 47      import google.appengine 
 48      os_locking = 'gae' 
 49  except: 
 50      try: 
 51          import fcntl 
 52          os_locking = 'posix' 
 53      except: 
 54          try: 
 55              import win32con 
 56              import win32file 
 57              import pywintypes 
 58              os_locking = 'windows' 
 59          except: 
 60              pass 
 61   
 62  if os_locking == 'windows': 
 63      LOCK_EX = win32con.LOCKFILE_EXCLUSIVE_LOCK 
 64      LOCK_SH = 0  # the default 
 65      LOCK_NB = win32con.LOCKFILE_FAIL_IMMEDIATELY 
 66   
 67      # is there any reason not to reuse the following structure? 
 68   
 69      __overlapped = pywintypes.OVERLAPPED() 
 70   
 71 -    def lock(file, flags): 
 72          hfile = win32file._get_osfhandle(file.fileno()) 
 73          win32file.LockFileEx(hfile, flags, 0, 0x7fff0000, __overlapped) 
 74   
 75 -    def unlock(file): 
 76          hfile = win32file._get_osfhandle(file.fileno()) 
 77          win32file.UnlockFileEx(hfile, 0, 0x7fff0000, __overlapped) 
 78   
 79   
 80  elif os_locking == 'posix': 
 81      LOCK_EX = fcntl.LOCK_EX 
 82      LOCK_SH = fcntl.LOCK_SH 
 83      LOCK_NB = fcntl.LOCK_NB 
 84   
 85 -    def lock(file, flags): 
 86          fcntl.flock(file.fileno(), flags) 
 87   
 88 -    def unlock(file): 
 89          fcntl.flock(file.fileno(), fcntl.LOCK_UN) 
 90   
 91   
 92  else: 
 93      if platform.system() == 'Windows': 
 94          logger.error('no file locking, you must install the win32 extensions from: http://sourceforge.net/projects/pywin32/files/') 
 95      elif os_locking != 'gae': 
 96          logger.debug('no file locking, this will cause problems') 
 97   
 98      LOCK_EX = None 
 99      LOCK_SH = None 
100      LOCK_NB = None 
101   
102 -    def lock(file, flags): 
103          pass 
104   
105 -    def unlock(file): 
106          pass 
107   
108   
109 -class LockedFile(object): 
110 -    def __init__(self, filename, mode='rb'): 
111          self.filename = filename 
112          self.mode = mode 
113          self.file = None 
114          if 'r' in mode: 
115              self.file = open(filename, mode) 
116              lock(self.file, LOCK_SH) 
117          elif 'w' in mode or 'a' in mode: 
118              self.file = open(filename, mode.replace('w', 'a')) 
119              lock(self.file, LOCK_EX) 
120              if not 'a' in mode: 
121                  self.file.seek(0) 
122                  self.file.truncate() 
123          else: 
124              raise RuntimeError("invalid LockedFile(...,mode)") 
125   
126 -    def read(self, size=None): 
127          return self.file.read() if size is None else self.file.read(size) 
128   
129 -    def readline(self): 
130          return self.file.readline() 
131   
132 -    def readlines(self): 
133          return self.file.readlines() 
134   
135 -    def write(self, data): 
136          self.file.write(data) 
137          self.file.flush() 
138   
139 -    def close(self): 
140          if not self.file is None: 
141              unlock(self.file) 
142              self.file.close() 
143              self.file = None 
144   
145 -    def __del__(self): 
146          if not self.file is None: 
147              self.close() 
148   
149   
150 -def read_locked(filename): 
151      fp = LockedFile(filename, 'r') 
152      data = fp.read() 
153      fp.close() 
154      return data 
155   
156   
157 -def write_locked(filename, data): 
158      fp = LockedFile(filename, 'w') 
159      data = fp.write(data) 
160      fp.close() 
161   
162  if __name__ == '__main__': 
163      import sys 
164      f = LockedFile('test.txt', mode='wb') 
165      f.write('test ok') 
166      f.close() 
167      f = LockedFile('test.txt', mode='rb') 
168      sys.stdout.write(f.read()+'\n') 
169      f.close() 
170