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BenDcode

A python module for decoding bencoded data

Bencoding

Bencoding is a meta data representation format fot the BitTorrent Protocol (BTP). The Augmented BNF syntax for Bencoding is given below

dictionary = "d" 1*(string anytype) "e"
  list       = "l" 1*anytype "e"
  integer    = "i" signumber "e"
  string     = number ":" <number long sequence of any CHAR>
  anytype    = dictionary / list / integer / string
  signumber  = "-" number / number
  number     = 1*DIGIT
  CHAR       = %x00-FF
  DIGIT      = "0" / "1" / "2" / "3" / "4" /
               "5" / "6" / "7" / "8" / "9"

Source: BTP RFC

Usage

Decoding bencoded data is simple.

>>> import bendcode
>>> bendcode.decode('i123e')
123
>>> bendcode.decode('4:John')
'John'
>>> bendcode.decode('li234ei123ee')
[234, 123]
>>> bendcode.decode('d1:ai123e1:bi234ee')
{'a': 123, 'b': 234}

You can decode invidual types too !

>>> import bendcode
>>> bendcode.match_string('3:abc')
('abc', '')
>>> bendcode.match_int('i-123e')
(-123, '')
>>> bendcode.match_list('li123ee')
([123], '')
>>> bendcode.match_dict('d1:a1:bei123e')
({'a': 'b'}, 'i123e')

Note: The match_* series of functions return a tuple (first_possbile_match, remaining_unmatched_string)

Bendcode can encode too

>>> import bendcode
>>> bendcode.encode(123)
'i123e'
>>> bendcode.encode('John')
'4:John'
>>> bendcode.encode([123, 'bro'])
'li123e3:broe'
>>> bendcode.encode({'hello': 123})
'd5:helloi123ee'
>>> bendcode.encode(None)
''

You decide whether to raise an exception or not for any functions mentioned above by setting the fail_silently parameter to True or False

>>> import bendcode
>>> bendcode.match_string('abc')
(None, 'abc')
>>> bendcode.match_string('abc', fail_silently=False)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "bendcode\bendcode.py", line 39, in match_string
    raise MalformedBencodeError('Failed to match string in ' + str(raw))
bendcode.exceptions.MalformedBencodeError: Failed to match string in abc

Tests

Run tests using the following code

>>> from bendcode import tests
>>> tests.run_tests()
..................................
----------------------------------------
Ran 34 tests in 0.015s

OK

Issues

If you find any bug, feel free to create an issue here.

License

BenDcode uses GNU v2 License. Read the terms of the license here.