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Groups > comp.lang.c++ > #82747
| From | Juha Nieminen <nospam@thanks.invalid> |
|---|---|
| Newsgroups | comp.lang.c++ |
| Subject | Re: Can anyone improve this ? |
| Date | 2022-01-11 09:50 +0000 |
| Organization | Aioe.org NNTP Server |
| Message-ID | <srjjt8$khb$1@gioia.aioe.org> (permalink) |
| References | <srjdtm$d9c$1@dont-email.me> |
Bonita Montero <Bonita.Montero@gmail.com> wrote:
> I had an idea how to write a fast UTF-8 strlen, here it is:
>
> size_t utf8Strlen( char const *str )
> {
> struct encode_t { size_t lenIncr, strIncr; };
> static encode_t const encodes[] =
> {
> { 1, 1 },
> { 0, 0 },
> { 1, 2 },
> { 1, 3 },
> { 1, 4 },
> { 0, 0 },
> { 0, 0 },
> { 0, 0 },
> { 0, 0 }
> };
> size_t len = 0;
> for( unsigned char c; (c = *str); )
> {
> encode_t const &enc = encodes[(size_t)countl_zero<unsigned
> char>( ~c )];
> if( !enc.lenIncr ) [[unlikely]]
> return -1;
> len += enc.lenIncr;
> for( char const *cpEnd = str + enc.strIncr; ++str != cpEnd; )
> if( ((unsigned char)*str & 0x0C0) != 0x080 ) [[unlikely]]
> return -1;
> }
> return len;
> }
>
> Has anyone further ideas to improve this ?
How does it compare to the more straightforward:
std::size_t utf8Strlen(const char *str)
{
std::size_t length = 0;
for(std::size_t index = 0; str[index]; ++index, ++length)
if((str[index] & 0xC0) == 0xC0)
while((str[index+1] & 0xC0) == 0x80)
++index;
return length;
}
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Can anyone improve this ? Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-11 09:08 +0100
Re: Can anyone improve this ? Juha Nieminen <nospam@thanks.invalid> - 2022-01-11 09:50 +0000
Re: Can anyone improve this ? Juha Nieminen <nospam@thanks.invalid> - 2022-01-11 11:07 +0000
Re: Can anyone improve this ? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-01-11 11:08 +0000
Re: Can anyone improve this ? Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-11 18:28 +0100
Re: Can anyone improve this ? Christian Gollwitzer <auriocus@gmx.de> - 2022-01-11 18:41 +0100
Re: Can anyone improve this ? Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-11 19:36 +0100
Re: Can anyone improve this ? Öö Tiib <ootiib@hot.ee> - 2022-01-11 21:54 -0800
Re: Can anyone improve this ? Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-11 21:51 +0100
Re: Can anyone improve this ? Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-12 14:19 +0100
Re: Can anyone improve this ? Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-12 14:20 +0100
Re: Can anyone improve this ? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-01-12 14:14 +0000
Re: Can anyone improve this ? Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-12 17:20 +0100
Re: Can anyone improve this ? "james...@alumni.caltech.edu" <jameskuyper@alumni.caltech.edu> - 2022-01-12 08:38 -0800
Re: Can anyone improve this ? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-01-12 16:55 +0000
Re: Can anyone improve this ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-16 12:09 -0800
Re: Can anyone improve this ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-16 12:12 -0800
Re: Can anyone improve this ? Öö Tiib <ootiib@hot.ee> - 2022-01-16 13:00 -0800
Re: Can anyone improve this ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-17 10:13 -0800
Re: Can anyone improve this ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-17 10:28 -0800
Re: Can anyone improve this ? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-01-17 21:51 +0100
Re: Can anyone improve this ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-17 16:16 -0800
Re: Can anyone improve this ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-17 22:43 -0800
Re: Can anyone improve this ? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-01-18 12:09 +0100
Re: Can anyone improve this ? Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-18 09:18 +0100
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