GNU bug report logs - #18777
[PATCH] dfa: improvement for checking of multibyte character boundary

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From: Norihiro Tanaka <noritnk <at> kcn.ne.jp>
To: arnold <at> skeeve.com
Cc: eblake <at> redhat.com, 18777 <at> debbugs.gnu.org
Subject: bug#18777: [PATCH] dfa: improvement for checking of multibyte character boundary
Date: Thu, 23 Oct 2014 00:28:35 +0900

arnold <at> skeeve.com wrote:
> Gawk does not remove CR in advance, unless someone specifically
> set RS = "\r\n", in which case the full regex matcher is used
> to first find \r\n in the raw input buffer.

Thanks, I also confirmed it on source code of Gawk.

> So for gawk, adding a check for (c == eolbyte || c == '\r')
> should produce more speedup on Windows.
> 
> (Hmm, on Windows the default is probably text mode which causes
> the library/OS to hide the \r anway. Harumph.  But if binary mode
> wsa requested then it could still make a difference.)

I think It's better to build KWset rather than rely on checking for '\r'
in non-UTF8 multibyte mode of DFA.

Further more, even if we add checking for '\r' to DFA, I think that we
can't use to speed up on Windows, so that DFA can't correctly locate a matched
position except a pattern which is fixed string.

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