lbry-sdk/lbrynet/dht/encoding.py

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2018-11-09 20:02:03 +01:00
from lbrynet.dht.error import DecodeError
2017-03-31 19:32:43 +02:00
2016-12-14 00:08:29 +01:00
def bencode(data):
""" Encoder implementation of the Bencode algorithm (Bittorrent). """
if isinstance(data, int):
return b'i%de' % data
elif isinstance(data, (bytes, bytearray)):
return b'%d:%s' % (len(data), data)
elif isinstance(data, str):
return b'%d:%s' % (len(data), data.encode())
elif isinstance(data, (list, tuple)):
encoded_list_items = b''
for item in data:
encoded_list_items += bencode(item)
return b'l%se' % encoded_list_items
elif isinstance(data, dict):
encoded_dict_items = b''
keys = data.keys()
for key in sorted(keys):
encoded_dict_items += bencode(key)
encoded_dict_items += bencode(data[key])
return b'd%se' % encoded_dict_items
else:
raise TypeError("Cannot bencode '%s' object" % type(data))
def bdecode(data):
""" Decoder implementation of the Bencode algorithm. """
assert type(data) == bytes # fixme: _maybe_ remove this after porting
if len(data) == 0:
raise DecodeError('Cannot decode empty string')
try:
return _decode_recursive(data)[0]
except ValueError as e:
raise DecodeError(str(e))
def _decode_recursive(data, start_index=0):
if data[start_index] == ord('i'):
end_pos = data[start_index:].find(b'e') + start_index
return int(data[start_index + 1:end_pos]), end_pos + 1
elif data[start_index] == ord('l'):
start_index += 1
decoded_list = []
while data[start_index] != ord('e'):
list_data, start_index = _decode_recursive(data, start_index)
decoded_list.append(list_data)
return decoded_list, start_index + 1
elif data[start_index] == ord('d'):
start_index += 1
decoded_dict = {}
while data[start_index] != ord('e'):
key, start_index = _decode_recursive(data, start_index)
value, start_index = _decode_recursive(data, start_index)
decoded_dict[key] = value
return decoded_dict, start_index
elif data[start_index] == ord('f'):
# This (float data type) is a non-standard extension to the original Bencode algorithm
end_pos = data[start_index:].find(b'e') + start_index
return float(data[start_index + 1:end_pos]), end_pos + 1
elif data[start_index] == ord('n'):
# This (None/NULL data type) is a non-standard extension
# to the original Bencode algorithm
return None, start_index + 1
else:
split_pos = data[start_index:].find(b':') + start_index
try:
length = int(data[start_index:split_pos])
except ValueError:
raise DecodeError()
start_index = split_pos + 1
end_pos = start_index + length
b = data[start_index:end_pos]
return b, end_pos