bencode3/bencode.py at master · karamanolev/bencode3 · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
# The contents of this file are subject to the BitTorrent Open Source License
# Version 1.1 (the License).  You may not copy or use this file, in either
# source code or executable form, except in compliance with the License.  You
# may obtain a copy of the License at http://www.bittorrent.com/license/.
#
# Software distributed under the License is distributed on an AS IS basis,
# WITHOUT WARRANTY OF ANY KIND, either express or implied.  See the License
# for the specific language governing rights and limitations under the
# License.

# Written by Petru Paler, modified to run under Python 3 by Ivailo Karamanolev

class BTFailure(Exception):
    pass


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


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


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


def decode_dict(x, f):
    r, f = {}, f + 1
    while x[f] != ord('e'):
        k, f = decode_string(x, f)
        r[k], f = decode_func[x[f]](x, f)
    return r, f + 1


decode_func = {
    ord('l'): decode_list,
    ord('d'): decode_dict,
    ord('i'): decode_int,
    ord('1'): decode_string,
    ord('2'): decode_string,
    ord('0'): decode_string,
    ord('3'): decode_string,
    ord('4'): decode_string,
    ord('5'): decode_string,
    ord('6'): decode_string,
    ord('7'): decode_string,
    ord('8'): decode_string,
    ord('9'): decode_string,
}


def bdecode(x):
    try:
        r, l = decode_func[x[0]](x, 0)
    except (IndexError, KeyError, ValueError):
        raise BTFailure("not a valid bencoded string")
    if l != len(x):
        raise BTFailure("invalid bencoded value (data after valid prefix)")
    return r


def encode_int(x, r):
    r.extend((b'i', str(x).encode(), b'e'))


def encode_bool(x, r):
    if x:
        encode_int(1, r)
    else:
        encode_int(0, r)


def encode_string(x, r):
    r.extend((str(len(x)).encode(), b':', x))


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


def encode_dict(x, r):
    r.append(b'd')
    item_list = list(x.items())
    item_list.sort()
    for k, v in item_list:
        r.extend((str(len(k)).encode(), b':', k))
        encode_func[type(v)](v, r)
    r.append(b'e')


encode_func = {
    int: encode_int,
    bytes: encode_string,
    list: encode_list,
    tuple: encode_list,
    dict: encode_dict,
    bool: encode_bool,
}


def bencode(x):
    r = []
    encode_func[type(x)](x, r)
    return b''.join(r)