Tools/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 cmp
  39                 # don't use cmp.cmp because of NFS bugs :-( and
  40                 # anyway, the stat mtime values differ so do_cmp will
  41                 # most likely be called anyway
  42                 if cmp.do_cmp(self.__backup, self.__filename):
  43                         import os
  44                         os.unlink(self.__filename)
  45                         os.rename(self.__backup, self.__filename)
  46
  47 def open(file, mode = 'r', bufsize = -1):
  48         if 'w' not in mode:
  49                 return _orig_open(file, mode, bufsize)
  50         return _BkFile(file, mode, bufsize)