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

From: Sean Huang (huangsean_at_[hidden])
Date: 2005-09-28 09:36:53

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?

Thanks,

Sean