[Python-Dev] Decoding incomplete unicode (original) (raw)

Hye-Shik Chang hyeshik at gmail.com
Wed Jul 28 05:51:30 CEST 2004

On Tue, 27 Jul 2004 22:39:45 +0200, Walter Dörwald <walter at livinglogic.de> wrote:

Pythons unicode machinery currently has problems when decoding incomplete input.

When codecs.StreamReader.read() encounters a decoding error it reads more bytes from the input stream and retries decoding. This is broken for two reasons: 1) The error might be due to a malformed byte sequence in the input, a problem that can't be fixed by reading more bytes. 2) There may be no more bytes available at this time. Once more data is available decoding can't continue because bytes from the input stream have already been read and thrown away. (sio.DecodingInputFilter has the same problems)

StreamReaders and -Writers from CJK codecs are not suffering from this problems because they have internal buffer for keeping states and incomplete bytes of a sequence. In fact, CJK codecs has its own implementation for UTF-8 and UTF-16 on base of its multibytecodec system. It provides a "working" StreamReader/Writer already. :)

I've uploaded a patch that fixes these problems to SF: http://www.python.org/sf/998993

The patch implements a few additional features: - read() has an additional argument chars that can be used to specify the number of characters that should be returned. - readline() is supported on all readers derived from codecs.StreamReader().

I have no comment for these, yet.

- readline() and readlines() have an additional option for dropping the u"\n".

+1

I wonder whether we need to add optional argument for writelines() to add newline characters for each lines, then.

Hye-Shik

More information about the Python-Dev mailing list