148 lines
3.3 KiB
Python
148 lines
3.3 KiB
Python
'''
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A Python 3 translation of bcode.py
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https://pypi.python.org/pypi/bcode/0.5
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'''
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def bencode(data):
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'''
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Encode python types to bencode.
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'''
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if data is None:
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return None
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data_type = type(data)
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encoders = {
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bytes: encode_bytes,
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str: encode_string,
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float: encode_float,
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int: encode_int,
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dict: encode_dict,
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}
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encoder = encoders.get(data_type, None)
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if encoder is None:
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try:
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return encode_iterator(iter(data))
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except TypeError:
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raise ValueError('Invalid field type %s' % data_type)
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return encoder(data)
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def encode_bytes(data):
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return '%d:%s' % (len(data), data)
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def encode_dict(data):
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result = []
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keys = list(data.keys())
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keys.sort()
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for key in keys:
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result.append(bencode(key))
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result.append(bencode(data[key]))
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result = ''.join(result)
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return 'd%se' % result
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def encode_float(data):
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return encode_string(str(data))
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def encode_int(data):
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return 'i%de' % data
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def encode_iterator(data):
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result = []
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for item in data:
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result.append(bencode(item))
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result = ''.join(result)
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return 'l%se' % result
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def encode_string(data):
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return encode_bytes(data)
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# =============================================================================
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def bdecode(data):
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'''
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Decode bencode to python types.
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Returns a dictionary
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{
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'result': the decoded item
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'remainder': what's left of the input text
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}
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'''
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if data is None:
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return None
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data = data.strip()
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if isinstance(data, bytes):
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data = data.decode('utf-8')
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if data[0] == 'i':
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return decode_int(data)
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if data[0].isdigit():
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return decode_string(data)
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if data[0] == 'l':
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return decode_list(data)
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if data[0] == 'd':
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return decode_dict(data)
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raise ValueError('Invalid initial delimiter "%s"' % data[0])
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def decode_dict(data):
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result = {}
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# slice leading d
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remainder = data[1:]
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while remainder[0] != 'e':
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temp = bdecode(remainder)
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key = temp['result']
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remainder = temp['remainder']
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temp = bdecode(remainder)
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value = temp['result']
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remainder = temp['remainder']
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result[key] = value
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# slice ending 3
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remainder = remainder[1:]
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return {'result': result, 'remainder': remainder}
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def decode_int(data):
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end = data.find('e')
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if end == -1:
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raise ValueError('Missing end delimiter "e"')
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# slice leading i and closing e
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result = data[1:end]
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remainder = data[end+1:]
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return {'result': result, 'remainder': remainder}
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def decode_list(data):
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result = []
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# slice leading l
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remainder = data[1:]
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while remainder[0] != 'e':
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item = bdecode(data)
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result.append(item['result'])
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reaminder = item['remainder']
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# slice ending e
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remainder = remainder[1:]
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return {'result': result, 'remainder': remainder}
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def decode_string(data):
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start = data.find(':') + 1
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size = int(data[:start-1])
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end = start + size
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text = data[start:end]
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if len(text) < size:
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raise ValueError('Actual length %d is less than declared length %d' % len(text), size)
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remainder = data[end:]
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return {'result': text, 'remainder': remainder}
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