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
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
|
import ssl
COLON = b':'
COMMA = b','
ZERO = b'0'
ZERO_ORD = ord(ZERO)
class NetstringException(Exception):
pass
class WantRead(NetstringException):
pass
class InappropriateParserState(NetstringException):
pass
class ParseError(NetstringException):
pass
class IncompleteNetstring(ParseError):
pass
class TooLong(ParseError):
pass
class BadLength(ParseError):
pass
class BadTerminator(ParseError):
pass
class SingleNetstringFetcher:
def __init__(self, incoming, maxlen=-1):
self._incoming = incoming
self._maxlen = maxlen
self._len_known = False
self._len = None
self._done = False
self._length_bytes = b''
def done(self):
return self._done
def pending(self):
return self._len is not None
def read(self, nbytes=65536):
# pylint: disable=too-many-branches
if not self._len_known:
# reading length
while True:
symbol = self._incoming.read(1)
if not symbol:
raise WantRead()
if symbol == COLON:
if self._len is None:
raise BadLength("No netstring length digits seen.")
self._len_known = True
break
if not symbol.isdigit():
raise BadLength("Non-digit symbol in netstring length.")
val = ord(symbol) - ZERO_ORD
self._len = val if self._len is None else self._len * 10 + val
if self._maxlen != -1 and self._len > self._maxlen:
raise TooLong("Netstring length is over limit.")
# reading data
if self._len:
buf = self._incoming.read(min(nbytes, self._len))
if not buf:
raise WantRead()
self._len -= len(buf)
return buf
else:
if not self._done:
symbol = self._incoming.read(1)
if not symbol:
raise WantRead()
if symbol == COMMA:
self._done = True
else:
raise BadTerminator("Bad netstring terminator.")
return b''
class StreamReader:
""" Async Netstring protocol decoder with interface
alike to ssl.SSLObject BIO interface.
next_string() method returns SingleNetstringFetcher class which
fetches parts of netstring.
SingleNestringFetcher.read() returns b'' in case of string end or raises
WantRead exception when StreamReader needs to be filled with additional
data. Parsing errors signalized with exceptions subclassing ParseError"""
def __init__(self, maxlen=-1):
""" Creates StreamReader instance.
Params:
maxlen - maximal allowed netstring length.
"""
self._maxlen = maxlen
self._incoming = ssl.MemoryBIO()
self._fetcher = None
def pending(self):
return self._fetcher is not None and self._fetcher.pending()
def feed(self, data):
self._incoming.write(data)
def next_string(self):
if self._fetcher is not None and not self._fetcher.done():
raise InappropriateParserState("next_string() invoked while "
"previous fetcher is not exhausted")
self._fetcher = SingleNetstringFetcher(self._incoming, self._maxlen)
return self._fetcher
def encode(data):
return b'%d:%s,' % (len(data), data)
def decode(data):
reader = StreamReader()
reader.feed(data)
try:
while True:
res = []
string_reader = reader.next_string()
while True:
buf = string_reader.read()
if not buf:
break
res.append(buf)
yield b''.join(res)
except WantRead:
if reader.pending():
# pylint: disable=raise-missing-from
raise IncompleteNetstring("Input ends on unfinished string.")
|
