GNU bug report logs - #16232
[PATCH] grep: make --ignore-case (-i) faster (sometimes 10x) in multibyte locales

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From: Pádraig Brady <P <at> draigBrady.com>
To: Jim Meyering <jim <at> meyering.net>
Cc: 16232 <16232 <at> debbugs.gnu.org>
Subject: bug#16232: [PATCH] grep: make --ignore-case (-i) faster (sometimes 10x) in multibyte locales
Date: Sat, 11 Jan 2014 11:33:47 +0000

On 01/11/2014 05:40 AM, Jim Meyering wrote:
> On Fri, Jan 10, 2014 at 8:52 PM, Jim Meyering <jim <at> meyering.net> wrote:
>>> I wonder might this faster path be restricted to a safer but very common input subset of:
>>>
>>> (MB_CUR_MAX == 1 || (in_utf8 && *c < 0x80))
>>
>> That sounds like a good approach.
>> Now I need another test case, to demonstrate that the current code can
>> cause trouble.
> 
> Hmm... after thinking about this for a while and actually trying to
> break the current code (did not find a way to demonstrate a regression),
> I have concluded that the current approach is no worse than the prior
> one of matching a case-mapped regexp vs. each case-mapped input line.
> 
> That's not to say that it's perfect, of course.
> The "LATIN SMALL LETTER J WITH CARON, COMBINING DOT BELOW" example
> from gnulib's test-ulc-casecmp.c is a great example: this matches:
> 
>     printf '\x6A\xCC\x8C\xCC\xA3\n'|src/grep -i "$(printf
> '\x6A\xCC\x8C\xCC\xA3')"
> 
> but this does not, yet probably should:
> 
>     printf '\xC7\xB0\xCC\xA3\n'|src/grep -i "$(printf '\x6A\xCC\x8C\xCC\xA3')"
> 
> Can you see a way to demonstrate a regression?

Oh right, it doesn't handle these cases already.
Fair enough I don't see a regression then.

+1

Pádraig.

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