freeze/bkfile.py

   1 _orig_open = open
   2
   3 class _BkFile:
   4     def __init__(self, file, mode, bufsize):
   5         import os
   6         self.__filename = file
   7         self.__backup = file + '~'
   8         try:
   9             os.unlink(self.__backup)
  10         except os.error:
  11             pass
  12         try:
  13             os.rename(file, self.__backup)
  14         except os.error:
  15             self.__backup = None
  16         self.__file = _orig_open(file, mode, bufsize)
  17         self.closed = self.__file.closed
  18         self.fileno = self.__file.fileno
  19         self.flush = self.__file.flush
  20         self.isatty = self.__file.isatty
  21         self.mode = self.__file.mode
  22         self.name = self.__file.name
  23         self.read = self.__file.read
  24         self.readinto = self.__file.readinto
  25         self.readline = self.__file.readline
  26         self.readlines = self.__file.readlines
  27         self.seek = self.__file.seek
  28         self.softspace = self.__file.softspace
  29         self.tell = self.__file.tell
  30         self.truncate = self.__file.truncate
  31         self.write = self.__file.write
  32         self.writelines = self.__file.writelines
  33
  34     def close(self):
  35         self.__file.close()
  36         if self.__backup is None:
  37             return
  38         import filecmp
  39         if filecmp.cmp(self.__backup, self.__filename, shallow = 0):
  40             import os
  41             os.unlink(self.__filename)
  42             os.rename(self.__backup, self.__filename)
  43
  44 def open(file, mode = 'r', bufsize = -1):
  45     if 'w' not in mode:
  46         return _orig_open(file, mode, bufsize)
  47     return _BkFile(file, mode, bufsize)