Date: Wed, 06 Mar 2013 15:19:57 -0800 From: Colin Percival <cperciva@freebsd.org> To: David Malone <dwmalone@maths.tcd.ie> Cc: svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org, src-committers@FreeBSD.org, Peter Grehan <grehan@FreeBSD.org> Subject: Re: svn commit: r247871 - head/usr.sbin/bhyve Message-ID: <5137CF1D.3020506@freebsd.org> In-Reply-To: <20130306231613.GA5146@walton.maths.tcd.ie> References: <201303060728.r267SKP3018477@svn.freebsd.org> <20130306231613.GA5146@walton.maths.tcd.ie>
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On 03/06/13 15:16, David Malone wrote: >> + /* >> + * We're just computing (a-b) in GF(216). > >> + ndesc = (unsigned)*hq->hq_avail_idx - (unsigned)hq->hq_cur_aidx; > > I think the comment here is wrong? Subtraction (and addition) in > GF(2^16) is just xor of 16 bit numbers. You seem to actually be > working in Z(2^16), where subtraction is normal subtraction mod > 65536. Given that there's no such thing as GF(216) due to 216 = 2^3 * 3^3 not being a prime power, the comment is definitely wrong. ;-) -- Colin Percival Security Officer Emeritus, FreeBSD | The power to serve Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid
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