medashare/bencode.py

# Written by Petru Paler, Uoti Urpala, Ross Cohen and John Hoffman
# see LICENSE.txt for license information

# LICENSE.txt:
# Unless otherwise noted, all files are released under the MIT
# license, exceptions contain licensing information in them.
# 
# Copyright (C) 2001-2002 Bram Cohen
# 
# Permission is hereby granted, free of charge, to any person
# obtaining a copy of this software and associated documentation files
# (the "Software"), to deal in the Software without restriction,
# including without limitation the rights to use, copy, modify, merge,
# publish, distribute, sublicense, and/or sell copies of the Software,
# and to permit persons to whom the Software is furnished to do so,
# subject to the following conditions:
# 
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
# 
# The Software is provided "AS IS", without warranty of any kind,
# express or implied, including but not limited to the warranties of
# merchantability,  fitness for a particular purpose and
# noninfringement. In no event shall the  authors or copyright holders
# be liable for any claim, damages or other liability, whether in an
# action of contract, tort or otherwise, arising from, out of or in
# connection with the Software or the use or other dealings in the
# Software.


try:
    from types import BooleanType
except ImportError:
    BooleanType = None
try:
    from types import UnicodeType
except ImportError:
    UnicodeType = None
from io import StringIO

def decode_int(x, f):
    f += 1
    newf = x.index(b'e', f)
    n = int(x[f:newf])
    if x[f] == b'-'[0]:
        if x[f + 1] == b'0'[0]:
            raise ValueError
    elif x[f] == b'0'[0] and newf != f+1:
        raise ValueError
    return (n, newf+1)

def decode_string(x, f):
    colon = x.index(b':', f)
    n = int(x[f:colon])
    if x[f] == b'0'[0] and colon != f+1:
        raise ValueError
    colon += 1
    return (x[colon:colon+n], colon+n)

def decode_unicode(x, f):
    s, f = decode_string(x, f+1)
    return (s.decode('UTF-8'),f)

def decode_list(x, f):
    r, f = [], f+1
    while x[f] != b'e'[0]:
        v, f = decode_func[x[f]](x, f)
        r.append(v)
    return (r, f + 1)

def decode_dict(x, f):
    r, f = {}, f+1
    lastkey = b''
    while x[f] != b'e'[0]:
        k, f = decode_string(x, f)
        if lastkey >= k:
            raise ValueError
        lastkey = k
        r[k], f = decode_func[x[f]](x, f)
    return (r, f + 1)

decode_func = {}
decode_func[b'l'[0]] = decode_list
decode_func[b'd'[0]] = decode_dict
decode_func[b'i'[0]] = decode_int
decode_func[b'0'[0]] = decode_string
decode_func[b'1'[0]] = decode_string
decode_func[b'2'[0]] = decode_string
decode_func[b'3'[0]] = decode_string
decode_func[b'4'[0]] = decode_string
decode_func[b'5'[0]] = decode_string
decode_func[b'6'[0]] = decode_string
decode_func[b'7'[0]] = decode_string
decode_func[b'8'[0]] = decode_string
decode_func[b'9'[0]] = decode_string
#decode_func['u'[0]] = decode_unicode

def bdecode(x, sloppy = 0):
    try:
        r, l = decode_func[x[0]](x, 0)
#    except (IndexError, KeyError):
    except (IndexError, KeyError, ValueError):
        raise ValueError("bad bencoded data")
    if not sloppy and l != len(x):
        raise ValueError("bad bencoded data")
    return r

def test_bdecode():
    try:
        bdecode(b'0:0:')
        assert 0
    except ValueError:
        pass
    try:
        bdecode(b'ie')
        assert 0
    except ValueError:
        pass
    try:
        bdecode(b'i341foo382e')
        assert 0
    except ValueError:
        pass
    assert bdecode(b'i4e') == 4
    assert bdecode(b'i0e') == 0
    assert bdecode(b'i123456789e') == 123456789
    assert bdecode(b'i-10e') == -10
    try:
        bdecode(b'i-0e')
        assert 0
    except ValueError:
        pass
    try:
        bdecode(b'i123')
        assert 0
    except ValueError:
        pass
    try:
        bdecode(b'')
        assert 0
    except ValueError:
        pass
    try:
        bdecode('')
        assert 0
    except ValueError:
        pass
    try:
        bdecode(b'i6easd')
        assert 0
    except ValueError:
        pass
    try:
        bdecode(b'35208734823ljdahflajhdf')
        assert 0
    except ValueError:
        pass
    try:
        bdecode(b'2:abfdjslhfld')
        assert 0
    except ValueError:
        pass
    assert bdecode(b'0:') == b''
    assert bdecode(b'3:abc') == b'abc'
    assert bdecode(b'10:1234567890') == b'1234567890'
    try:
        bdecode(b'02:xy')
        assert 0
    except ValueError:
        pass
    try:
        bdecode(b'l')
        assert 0
    except ValueError:
        pass
    assert bdecode(b'le') == []
    try:
        bdecode(b'leanfdldjfh')
        assert 0
    except ValueError:
        pass
    assert bdecode(b'l0:0:0:e') == [b'', b'', b'']
    try:
        bdecode(b'relwjhrlewjh')
        assert 0
    except ValueError:
        pass
    assert bdecode(b'li1ei2ei3ee') == [1, 2, 3]
    assert bdecode(b'l3:asd2:xye') == [b'asd', b'xy']
    assert bdecode(b'll5:Alice3:Bobeli2ei3eee') == [[b'Alice', b'Bob'], [2, 3]]
    try:
        bdecode(b'd')
        assert 0
    except ValueError:
        pass
    try:
        bdecode(b'defoobar')
        assert 0
    except ValueError:
        pass
    assert bdecode(b'de') == {}
    assert bdecode(b'd3:agei25e4:eyes4:bluee') == {b'age': 25, b'eyes': b'blue'}
    assert bdecode(b'd8:spam.mp3d6:author5:Alice6:lengthi100000eee') == {b'spam.mp3': {b'author': b'Alice', b'length': 100000}}
    try:
        bdecode(b'd3:fooe')
        assert 0
    except ValueError:
        pass
    try:
        bdecode(b'di1e0:e')
        assert 0
    except ValueError:
        pass
    try:
        bdecode(b'd1:b0:1:a0:e')
        assert 0
    except ValueError:
        pass
    try:
        bdecode(b'd1:a0:1:a0:e')
        assert 0
    except ValueError:
        pass
    try:
        bdecode(b'i03e')
        assert 0
    except ValueError:
        pass
    try:
        bdecode(b'l01:ae')
        assert 0
    except ValueError:
        pass
    try:
        bdecode(b'9999:x')
        assert 0
    except ValueError:
        pass
    try:
        bdecode(b'l0:')
        assert 0
    except ValueError:
        pass
    try:
        bdecode(b'd0:0:')
        assert 0
    except ValueError:
        pass
    try:
        bdecode(b'd0:')
        assert 0
    except ValueError:
        pass

bencached_marker = []

class Bencached:
    def __init__(self, s):
        self.marker = bencached_marker
        self.bencoded = s

BencachedType = type(Bencached(b'')) # insufficient, but good as a filter

def encode_bencached(x,r):
    assert x.marker == bencached_marker
    r.append(x.bencoded)

def encode_int(x,r):
    r.append(b'i%de' % x)

def encode_bool(x,r):
    encode_int(int(x),r)

def encode_bytes(x,r):
    r.extend((b'%d:' % len(x),x))

def encode_string(x,r):
    #r.append('u')
    encode_bytes(x.encode('UTF-8'),r)

def encode_list(x,r):
        r.append(b'l')
        for e in x:
            encode_func[type(e)](e, r)
        r.append(b'e')

def encode_dict(x,r):
    r.append(b'd')
    for k,v in sorted(x.items()):
        r.extend((b'%d:' % len(k),k.encode('UTF-8')))
        encode_func[type(v)](v, r)
    r.append(b'e')

encode_func = {}
encode_func[BencachedType] = encode_bencached
encode_func[int] = encode_int
encode_func[str] = encode_string
encode_func[list] = encode_list
encode_func[tuple] = encode_list
encode_func[type({})] = encode_dict
if BooleanType:
    encode_func[BooleanType] = encode_bool
if UnicodeType:
    encode_func[UnicodeType] = encode_unicode

def bencode(x):
    r = []
    try:
        encode_func[type(x)](x, r)
    except:
        raise ValueError("could not encode type %s (value: %s)" % (type(x), x))
    return b''.join(r)

def test_bencode():
    assert bencode(4) == b'i4e'
    assert bencode(0) == b'i0e'
    assert bencode(-10) == b'i-10e'
    assert bencode(12345678901234567890) == b'i12345678901234567890e'
    assert bencode('') == b'0:'
    assert bencode('abc') == b'3:abc'
    assert bencode('1234567890') == b'10:1234567890'
    assert bencode([]) == b'le'
    assert bencode([1, 2, 3]) == b'li1ei2ei3ee'
    assert bencode([['Alice', 'Bob'], [2, 3]]) == b'll5:Alice3:Bobeli2ei3eee'
    assert bencode({}) == b'de'
    assert bencode({'age': 25, 'eyes': 'blue'}) == b'd3:agei25e4:eyes4:bluee'
    assert bencode({'spam.mp3': {'author': 'Alice', 'length': 100000}}) == b'd8:spam.mp3d6:author5:Alice6:lengthi100000eee'
    try:
        bencode({1: 'foo'})
        assert 0
    except (ValueError, AssertionError):
        pass


try:
    import psyco
    psyco.bind(bdecode)
    psyco.bind(bencode)
except ImportError:
    pass