~bzr-pqm/bzr/bzr.dev

# bencode structured encoding

#

# Written by Petru Paler

#

# 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.

#

# Modifications copyright (C) 2008 Canonical Ltd

class BDecoder(object):

    def __init__(self, yield_tuples=False):

        """Constructor.

        :param yield_tuples: if true, decode "l" elements as tuples rather than

            lists.

        """

        self.yield_tuples = yield_tuples

        decode_func = {}

        decode_func['l'] = self.decode_list

        decode_func['d'] = self.decode_dict

        decode_func['i'] = self.decode_int

        decode_func['0'] = self.decode_string

        decode_func['1'] = self.decode_string

        decode_func['2'] = self.decode_string

        decode_func['3'] = self.decode_string

        decode_func['4'] = self.decode_string

        decode_func['5'] = self.decode_string

        decode_func['6'] = self.decode_string

        decode_func['7'] = self.decode_string

        decode_func['8'] = self.decode_string

        decode_func['9'] = self.decode_string

        self.decode_func = decode_func

    def decode_int(self, x, f):

        f += 1

        newf = x.index('e', f)

        try:

            n = int(x[f:newf])

        except (OverflowError, ValueError):

            n = long(x[f:newf])

        if x[f] == '-':

            if x[f + 1] == '0':

                raise ValueError

        elif x[f] == '0' and newf != f+1:

            raise ValueError

        return (n, newf+1)

    def decode_string(self, x, f):

        colon = x.index(':', f)

        try:

            n = int(x[f:colon])

        except (OverflowError, ValueError):

            n = long(x[f:colon])

        if x[f] == '0' and colon != f+1:

            raise ValueError

        colon += 1

        return (x[colon:colon+n], colon+n)

    def decode_list(self, x, f):

        r, f = [], f+1

        while x[f] != 'e':

            v, f = self.decode_func[x[f]](x, f)

            r.append(v)

        if self.yield_tuples:

            r = tuple(r)

        return (r, f + 1)

    def decode_dict(self, x, f):

        r, f = {}, f+1

        lastkey = None

        while x[f] != 'e':

            k, f = self.decode_string(x, f)

            if lastkey >= k:

                raise ValueError

            lastkey = k

            r[k], f = self.decode_func[x[f]](x, f)

        return (r, f + 1)

    def bdecode(self, x):

        if type(x) != str:

            raise TypeError

        try:

            r, l = self.decode_func[x[0]](x, 0)

        except (IndexError, KeyError):

            raise ValueError

        if l != len(x):

            raise ValueError

        return r

_decoder = BDecoder()

bdecode = _decoder.bdecode

_tuple_decoder = BDecoder(True)

bdecode_as_tuple = _tuple_decoder.bdecode

from types import StringType, IntType, LongType, DictType, ListType, TupleType

class Bencached(object):

    __slots__ = ['bencoded']

    def __init__(self, s):

        self.bencoded = s

def encode_bencached(x,r):

    r.append(x.bencoded)

def encode_int(x, r):

    r.extend(('i', str(x), 'e'))

def encode_string(x, r):

    r.extend((str(len(x)), ':', x))

def encode_list(x, r):

    r.append('l')

    for i in x:

        encode_func[type(i)](i, r)

    r.append('e')

def encode_dict(x,r):

    r.append('d')

    ilist = x.items()

    ilist.sort()

    for k, v in ilist:

        r.extend((str(len(k)), ':', k))

        encode_func[type(v)](v, r)

    r.append('e')

encode_func = {}

encode_func[type(Bencached(0))] = encode_bencached

encode_func[IntType] = encode_int

encode_func[LongType] = encode_int

encode_func[StringType] = encode_string

encode_func[ListType] = encode_list

encode_func[TupleType] = encode_list

encode_func[DictType] = encode_dict

try:

    from types import BooleanType

except ImportError:

    pass

else:

    def encode_bool(x,r):

        encode_int(int(x), r)

    encode_func[BooleanType] = encode_bool

def bencode(x):

    r = []

    encode_func[type(x)](x, r)

    return ''.join(r)