124 lines
3.7 KiB
Python
124 lines
3.7 KiB
Python
"""
|
|
The MIT License
|
|
|
|
Copyright (c) 2015 Fred Stober
|
|
|
|
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.
|
|
"""
|
|
|
|
class BTFailure(Exception):
|
|
pass
|
|
|
|
# Encoding functions ##############################################
|
|
|
|
import sys
|
|
if sys.version_info[0] >= 3:
|
|
str_to_bytes = lambda x: x.encode('ascii')
|
|
else:
|
|
str_to_bytes = lambda x: x
|
|
|
|
def bencode_proc(result, x):
|
|
t = type(x)
|
|
if t == str:
|
|
result.extend((str_to_bytes(str(len(x))), b':', str_to_bytes(x)))
|
|
elif t == bytes:
|
|
result.extend((str_to_bytes(str(len(x))), b':', x))
|
|
elif t == int:
|
|
result.extend((b'i', str_to_bytes(str(x)), b'e'))
|
|
elif t == dict:
|
|
result.append(b'd')
|
|
for k, v in sorted(x.items()):
|
|
bencode_proc(result, k)
|
|
bencode_proc(result, v)
|
|
result.append(b'e')
|
|
elif t == list:
|
|
result.append(b'l')
|
|
for item in x:
|
|
bencode_proc(result, item)
|
|
result.append(b'e')
|
|
|
|
def bencode(x):
|
|
result = []
|
|
bencode_proc(result, x)
|
|
return b''.join(result)
|
|
|
|
# Decoding functions ##############################################
|
|
|
|
bdecode_marker_int = ord('i')
|
|
bdecode_marker_str_min = ord('0')
|
|
bdecode_marker_str_max = ord('9')
|
|
bdecode_marker_list = ord('l')
|
|
bdecode_marker_dict = ord('d')
|
|
bdecode_marker_end = ord('e')
|
|
|
|
def bdecode_proc(msg, pos):
|
|
t = msg[pos]
|
|
if t == bdecode_marker_int:
|
|
pos += 1
|
|
pos_end = msg.index(b'e', pos)
|
|
return (int(msg[pos:pos_end]), pos_end + 1)
|
|
elif t >= bdecode_marker_str_min and t <= bdecode_marker_str_max:
|
|
sep = msg.index(b':', pos)
|
|
n = int(msg[pos:sep])
|
|
sep += 1
|
|
return (bytes(msg[sep:sep + n]), sep + n)
|
|
elif t == bdecode_marker_dict:
|
|
result = {}
|
|
pos += 1
|
|
while msg[pos] != bdecode_marker_end:
|
|
k, pos = bdecode_proc(msg, pos)
|
|
result[k], pos = bdecode_proc(msg, pos)
|
|
return (result, pos + 1)
|
|
elif t == bdecode_marker_list:
|
|
result = []
|
|
pos += 1
|
|
while msg[pos] != bdecode_marker_end:
|
|
v, pos = bdecode_proc(msg, pos)
|
|
result.append(v)
|
|
return (result, pos + 1)
|
|
raise BTFailure("invalid bencoded data (invalid token)! %r" % msg)
|
|
|
|
def bdecode_extra(msg):
|
|
try:
|
|
result, pos = bdecode_proc(bytearray(msg), 0)
|
|
except (IndexError, KeyError, ValueError):
|
|
raise BTFailure("invalid bencoded data! %r" % msg)
|
|
return (result, pos)
|
|
|
|
def bdecode(msg):
|
|
try:
|
|
result, pos = bdecode_extra(msg)
|
|
except (IndexError, KeyError, ValueError):
|
|
raise BTFailure("invalid bencoded data: %r" % msg)
|
|
if pos != len(msg):
|
|
raise BTFailure("invalid bencoded value (data after valid prefix)")
|
|
return result
|
|
|
|
if __name__ == '__main__':
|
|
import logging
|
|
logging.basicConfig()
|
|
test = {b'k1': 145, b'k2': {b'sk1': list(range(10)), b'sk2': b'0'*60}}
|
|
for x in range(100):
|
|
assert(bdecode(bencode(test)) == test)
|
|
for test_bytes in [b'd5:keyi0ee', b'x3:keyi0ee', b'd3:keyi0ee...']:
|
|
try:
|
|
bdecode(test_bytes)
|
|
except BTFailure as ex:
|
|
logging.exception('expected bdecode exception')
|