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From: gwyn@brl-tgr.ARPA (Doug Gwyn <gwyn>)
Newsgroups: net.lang.c
Subject: Re: reversing a mask
Message-ID: <6055@brl-tgr.ARPA>
Date: Sun, 25-Nov-84 14:46:11 EST
Article-I.D.: brl-tgr.6055
Posted: Sun Nov 25 14:46:11 1984
Date-Received: Tue, 27-Nov-84 03:56:15 EST
References: <1@imd.UUCP> <469@ncoast.UUCP> <691@gloria.UUCP> <4069@rochester.UUCP>
Organization: Ballistic Research Lab
Lines: 11

> >What's the fastest way to reverse a 16-bit mask in C?  In 68000 asl?
> 
> Actually the 65536 combination answer wasn't too far from a plausible
> method - split the word up into 2 8 bit bytes and then do two lookups.
> Then swap bytes.  This way you only need one 256 byte table.
> 
> You could do lookups on nybbles, etc, ad nauseum.

Hey!  Take this to the logical extreme:  split into 16 1-bit fields,
then you can dispense with the table altogether (since the reversal
of a 1-bit field is itself).  :-)