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https://github.com/tahoe-lafs/tahoe-lafs.git
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39 lines
1.6 KiB
Python
39 lines
1.6 KiB
Python
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def netstring(s):
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assert isinstance(s, str), s # no unicode here
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return "%d:%s," % (len(s), s,)
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def split_netstring(data, numstrings,
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position=0,
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required_trailer=None):
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"""like string.split(), but extracts netstrings. Ignore all bytes of data
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before the 'position' byte. Return a tuple of (list of elements (numstrings
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in length), new position index). The new position index points to the first
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byte which was not consumed (the 'required_trailer', if any, counts as
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consumed). If 'required_trailer' is not None, throw ValueError if leftover
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data does not exactly equal 'required_trailer'."""
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assert type(position) in (int, long), (repr(position), type(position))
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elements = []
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assert numstrings >= 0
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while position < len(data):
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colon = data.index(":", position)
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length = int(data[position:colon])
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string = data[colon+1:colon+1+length]
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assert len(string) == length, (len(string), length)
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elements.append(string)
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position = colon+1+length
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assert data[position] == ",", position
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position += 1
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if len(elements) == numstrings:
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break
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if len(elements) < numstrings:
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raise ValueError("ran out of netstrings")
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if required_trailer is not None:
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if ((len(data) - position) != len(required_trailer)) or (data[position:] != required_trailer):
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raise ValueError("leftover data in netstrings")
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return (elements, position + len(required_trailer))
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else:
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return (elements, position)
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