Question

I want to (quickly) put a program/script together to read the fileset from a .torrent file. I want to then use that set to delete any files from a specific directory that do not belong to the torrent.

Any recommendations on a handy library for reading this index from the .torrent file? Whilst I don’t object to it, I don’t want to be digging deep into the bittorrent spec and rolling a load of code from scratch for this simple purpose.

I have no preference on language.

Answer 1

Effbot has your question answered. Here is the complete code to read the list of files from .torrent file (Python 2.4+):

import re  def tokenize(text, match=re.compile('([idel])|(\d+):|(-?\d+)').match):     i = 0     while i < len(text):         m = match(text, i)         s = m.group(m.lastindex)         i = m.end()         if m.lastindex == 2:             yield 's'             yield text[i:i+int(s)]             i = i + int(s)         else:             yield s  def decode_item(next, token):     if token == 'i':         # integer: 'i' value 'e'         data = int(next())         if next() != 'e':             raise ValueError     elif token == 's':         # string: 's' value (virtual tokens)         data = next()     elif token == 'l' or token == 'd':         # container: 'l' (or 'd') values 'e'         data = []         tok = next()         while tok != 'e':             data.append(decode_item(next, tok))             tok = next()         if token == 'd':             data = dict(zip(data[0::2], data[1::2]))     else:         raise ValueError     return data  def decode(text):     try:         src = tokenize(text)         data = decode_item(src.next, src.next())         for token in src: # look for more tokens             raise SyntaxError('trailing junk')     except (AttributeError, ValueError, StopIteration):         raise SyntaxError('syntax error')     return data  if __name__ == '__main__':     data = open('test.torrent', 'rb').read()     torrent = decode(data)     for file in torrent['info']['files']:         print '%r - %d bytes' % ('/'.join(file['path']), file['length'])