├── README.md
├── bencode.py
└── example.py


/README.md:
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 1 | 
 2 | Python module / script to parse a torrent file to a python object.
 3 | I just wrote this for fun one evening, and to learn a bit more about the torrent file format.
 4 | 
 5 | See http://www.bittorrent.org/beps/bep_0003.html for more info.
 6 | 
 7 | The decode method accepts a bytes object and returns a list.
 8 | 
 9 | bencode.py is the module.
10 | example.py is an example script that loads a torrent file and prettyprints the python object to a file.
11 | 
12 | Example:
13 | 
14 | ```python
15 | >>> import bencode
16 | >>>
17 | >>> with open("archlinux-2013.04.01-dual.iso.torrent", 'rb') as fh:
18 | ...     torrent_data = fh.read()
19 | ... 
20 | >>> torrent = bencode.decode(torrent_data)
21 | >>> 
22 | >>> print("announce: ", torrent[0][b'announce'])
23 | announce:  b'http://tracker.archlinux.org:6969/announce'
24 | >>> print("name: ", torrent[0][b'info'][b'name'])
25 | name:  b'archlinux-2013.04.01-dual.iso'
26 | >>> 
27 | ```
28 | 


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/bencode.py:
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 1 | #!/usr/bin/env python3
 2 | """ Module to construct / parse bencoded data """
 3 | 
 4 | 
 5 | def parse_blist(bdata):
 6 |     """ Convert bencoded data to python list """
 7 |     
 8 |     blist = []
 9 | 
10 |     if bdata[0:1] == b'l':
11 |         bdata = bdata[1:]
12 |     
13 |     while bdata[0:1] != b'' and bdata[0:1] != b'e':
14 |         
15 |         parse_func = btype_dict.get(bdata[0:1], parse_bstring)
16 |         elem, bdata = parse_func(bdata) 
17 |     
18 |         blist.append(elem)
19 | 
20 |     return blist, bdata[1:]
21 | 
22 | 
23 | def parse_bdict(bdata):
24 |     """ Convert bencoded data to python dict """
25 | 
26 |     bdict = {}
27 | 
28 |     if bdata[0:1] == b'd':
29 |         bdata = bdata[1:]
30 | 
31 |     while bdata[0:1] != b'' and bdata[0:1] != b'e':
32 |         
33 |         parse_func = btype_dict.get(bdata[0:1], parse_bstring)
34 |         key, bdata = parse_func(bdata)
35 |         
36 |         if bdata[0:1] == '' or bdata[0:1] == 'e':
37 |             value = None
38 |         else:
39 |             parse_func = btype_dict.get(bdata[0:1], parse_bstring)
40 |             value, bdata = parse_func(bdata)
41 | 
42 |         if key in bdict:
43 |             raise KeyError("Multiple keys in bencoded dictionary")
44 |         
45 |         bdict[key] = value
46 | 
47 |     return bdict, bdata[1:]
48 | 
49 | 
50 | def parse_bint(bdata):
51 |     """ Convert bencoded data to int """
52 |     
53 |     end_pos = bdata.index(ord('e'))
54 |     num_str = bdata[1:end_pos]
55 |     bdata = bdata[end_pos + 1:]
56 | 
57 |     return int(num_str), bdata
58 | 
59 | 
60 | def parse_bstring(bdata):
61 |     """ Convert bencoded data to string """
62 |     
63 |     delim_pos = bdata.index(ord(':'))
64 |     length = bdata[0:delim_pos]
65 |     length = int(length) 
66 |     
67 |     delim_pos += 1
68 |     bstring = bdata[delim_pos:delim_pos + length]
69 |     bdata = bdata[delim_pos + length:]
70 | 
71 |     if len(bstring) != length:
72 |         raise ValueError("Incorrect bencoded string length")
73 | 
74 |     return bstring, bdata
75 | 
76 | 
77 | def decode(bdata):
78 |     """ Parse data and return a list of objects """
79 | 
80 |     return parse_blist(bdata)[0]
81 |     
82 | 
83 | btype_dict = {
84 |     b'd' : parse_bdict,
85 |     b'l' : parse_blist,
86 |     b'i' : parse_bint
87 | }
88 | 
89 | 


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/example.py:
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 1 | #!/usr/bin/env python3
 2 | 
 3 | import sys
 4 | import pprint
 5 | import os
 6 | import bencode
 7 | 
 8 | 
 9 | if len(sys.argv) != 2:
10 |     print("Usage: example.py torrentfile.torrent")
11 | 
12 | with open(sys.argv[1], 'rb') as fh:
13 |     torrent_bytes = fh.read()
14 | 
15 | torrent = bencode.decode(torrent_bytes)
16 | outfilename = os.path.splitext(sys.argv[1])[0] + ".txt"
17 | 
18 | with open(outfilename, 'w') as fh:
19 |     fh.write(pprint.pformat(torrent))
20 | 
21 | 
22 | 


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