src/minwii/backwardsfilereader.py

   1 ## {{{ http://code.activestate.com/recipes/439045/ (r2)
   2 #!/usr/bin/env python
   3 # -*-mode: python; coding: iso-8859-1 -*-
   4 #
   5 # Copyright (c) Peter Astrand <astrand@cendio.se>
   6 # $Id$
   7 # $URL$
   8
   9 import string
  10
  11 class BackwardsReader:
  12     """Read a file line by line, backwards"""
  13
  14     def readline(self):
  15         while 1:
  16             newline_pos = string.rfind(self.buf, "\n")
  17             pos = self.file.tell()
  18             if newline_pos != -1:
  19                 # Found a newline
  20                 line = self.buf[newline_pos+1:]
  21                 self.buf = self.buf[:newline_pos]
  22                 if pos != 0 or newline_pos != 0 or self.trailing_newline:
  23                     line += "\n"
  24                 return line
  25             else:
  26                 if pos == 0:
  27                     # Start-of-file
  28                     return ""
  29                 else:
  30                     # Need to fill buffer
  31                     toread = min(self.BLKSIZE, pos)
  32                     self.file.seek(-toread, 1)
  33                     self.buf = self.file.read(toread) + self.buf
  34                     self.file.seek(-toread, 1)
  35                     if pos - toread == 0:
  36                         self.buf = "\n" + self.buf
  37
  38     def __init__(self, file, BLKSIZE=4096):
  39         self.file = file
  40         self.BLKSIZE = BLKSIZE
  41         self.buf = ""
  42         self.file.seek(-1, 2)
  43         self.trailing_newline = 0
  44         lastchar = self.file.read(1)
  45         if lastchar == "\n":
  46             self.trailing_newline = 1
  47             self.file.seek(-1, 2)