Re: [RFC] Add fast path for strcoll and strcasecmp

[OndÅej BÃlka <neleai at seznam dot cz>]

On Wed, Nov 26, 2014 at 10:07:21AM +0100, Leonhard Holz wrote:
> 
> 
> Am 25.11.2014 21:36, schrieb OndÅej BÃlka:
> >On Tue, Nov 25, 2014 at 09:04:04PM +0100, Leonhard Holz wrote:
> >>Am 24.11.2014 00:47, schrieb OndÅej BÃlka:
> >>>On Sun, Nov 23, 2014 at 11:52:06PM +0100, Leonhard Holz wrote:
> >>>>Hi OndÅej,
> >>>>
> >>>>as far as I understood, the current strcoll implementation scans
> >>>>both strings for collation sequences and compares the weights of
> >>>>them, whereby a collation sequence can be multiple bytes long. So
> >>>>whatever strcmp_l returns as index, you would need a general way of
> >>>>finding the start of the collation sequence this index is in.
> >>>>Unfortunately I cannot tell if or how this can be done.
> >>>>
> >>>As I wrote below you do not have to do that. Just precompute a table that
> >>>is zero for characters that are part of some collation sequence and use
> >>>old method when one of compared characters is in that table.
> >>>
> >>
> >>Ok, I understand the idea and it would be great if it worked. BTW do
> >>you know how UTF-8 chars above 7F are handled?
> >>
> >A UTF-8 char consist of starting byte larger than 0xbf followed by
> >characters in 0x80-0xbf range, see
> >
> >http://en.wikipedia.org/wiki/UTF-8
> >
> 
> Sorry for confusion. The question was ought to ask how the algorithm
> handles them. E.g. what to do when strcmp stops at a char with value
> 0x81.

check which of three characters before is starting one.