[htdig-dev] Re: bitfields

[Lachlan A. <lh...@ee...>]

On Sat, 9 Nov 2002 02:55, Geoff Hutchison wrote:
> I do think it makes sense to have a bit field.
> I can imagine that some XML documents might want
> combined bits
> Yes, some of the current flags could be in a lookup, but
> some (i.e. FLAG_CAPITAL) are clearly a bitfield.

I wasn't meaning to suggest a lookup table in the sense of 
"coding  n  flags in  log(n)  bits".  I meant a table of 
*combinations* of flags which are compatible.  This can 
still result in a moderate saving in bits, without losing 
much flexibility at all.  Even FLAG_CAPITAL may not make 
sense in some contexts, such as for an email address or a 
META date.

Of course, the "lookup table" approach can (in principle) 
degenerate to a collection of pure bit fields if *all* 
combinations are considered meaningful.  That way it 
provides the most generality for a given number of bits 
(albeit at the expense of a huge table if the number of 
bits is large).

Cheers,
Lachlan

-- 
Lachlan Andrew  Phone: +613 8344-3816 Fax: +613 8344-6678
Dept of Electrical and Electronic Engg		CRICOS Provider Code
University of Melbourne, Victoria, 3010  AUSTRALIA	00116K