Subject: RE: nsec++

From: "Andrew Draper" <[email-masked]>
Date: Fri, 5 Dec 2003 10:45:39 -0000

> > 	If you want to start at 32 bit boundraries you stop the
> > 	current bitmap if you have a 32 bit subwindow that is all
> > 	zeros.
> > 	
> > 	It takes 4 octets to represent a empty 32 bit subwindow.
> > 	It takes 2 octets to start a new window.
> > 
> > 	The algorithm would be:
> > 
> 	Find the first/next active 32 bit window.  If the last three
> 	octets of this 32 bit window are zero the bitmap is complete,
> 	remove trailing zero octets.  If the next the next 32 bit
> 	window is active include in in the current bitmap otherwise
> 	the current bitmap is complete, remove trailing zero octets.
> 	If the last three octets of this 32 bit window are zero the
> 	current bitmap is complete, remove trailing zero octets.
> 	Repeat adding 32 bit windows until the bitmap is 256 bits
> 	long.
>  	
>  	Repeat until all types are accounted for.
> 
> 	In otherword start a new bitmap if you save more than the
> 	cost of introducing a new bitmap.
> 
> 	If the last two octets of the current map are zero it is
> 	a break even situation so you include the next 32 bit
> 	window in the current map.

This is exactly the algorithm I was intending to describe, both with my suggested set of MUSTs and with my pseudo-code.  Thanks for describing it in an easier to understand way.

    Andy

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