Re: struct.el -- a package to encode/decode binary data

["Stefan Monnier" <monnier+gnu/emacs@RUM.cs.yale.edu>]

> "Stefan Monnier" <monnier+gnu/emacs@RUM.cs.yale.edu> writes:
> > But now that I think about it, if 160-255 can be an eight-bit-graphic
> > character, how does the code does with "backward-char" ?
> > Looking at DEC_POS in charset.h I see that we do
> 
> > 	while (p > p_min && !CHAR_HEAD_P (*p)) p--;
> 
> Please don't skip the following four lines:
> 
> 	len = pend + 1 - p;						\
> 	PARSE_MULTIBYTE_SEQ (p, len, bytes);				\
> 	if (bytes == len)						\
> 	  pos_byte -= len - 1;						\
> 
> which handles the above case.  When we at last reach a
> char-head, PARSE_MULTIBYTE_SEQ checks how long the byte
> sequence should be.  We update pos_byte only if the length
> is the same as what we decreased.

Yes, I saw that, so indeed the code is correct.  But it seems
that going back over the whole buffer (potentially) only
to discover that a single byte was needed is kind of silly.
Hence my suggestion to set p_min to max (p_min, p - MAX_MULTIBYTE_LENGTH)


	Stefan


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