Re: [boost] [serialization]A question about the implementation of XML_name in basic_xml_oarchive.ipp

From: David Abrahams (dave_at_[hidden])
Date: 2005-09-28 10:37:17

"Sean Huang" <huangsean_at_[hidden]> writes:

> I ran across the implementation of XML_name. It is a functor used to 
> validate each single character in an XML name. The initialization of a 
> stack-based look-up table everytime the functor is called puzzles me (see 
> excerpt below).
>
> void operator()(CharType t) const{
>         unsigned char lookup_table[] = {
>             0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
>             0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
>             0,0,0,0,0,0,0,0,0,0,1,1,0,0,0,0, // -.
>             1,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0, // 0-9
>             0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, // A-
>             1,1,1,1,1,1,1,1,1,1,1,0,0,0,0,1, // -Z _
>             0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, // a-
>             1,1,1,1,1,1,1,1,1,1,1,0,0,0,0,0, // -z
>             0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
>             0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
>         };
>         if((unsigned)t > 127)
>             return;
>         if(0 == lookup_table[(unsigned)t])
>             boost::throw_exception(
>                 xml_archive_exception(
>                     xml_archive_exception::xml_archive_tag_name_error
>                 )
>             );
>     }
>
> Is there any reason why it was done this way? For threading issues?

Hmm...
Also, is the apparent dependency on ASCII encoding truly portable?

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com