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