Date: Mon, 19 Nov 2012 09:01:49 -0800 From: mdf@FreeBSD.org To: Andre Oppermann <andre@freebsd.org> Cc: Gleb Smirnoff <glebius@freebsd.org>, src-committers@freebsd.org, svn-src-user@freebsd.org Subject: Re: svn commit: r243215 - user/andre/tcp_workqueue/sys/sys Message-ID: <CAMBSHm_eu-z6fuxTL2bdavQeBjOcE1zvS5h4itGa%2BP%2BiQhqrrA@mail.gmail.com> In-Reply-To: <50AA3529.2030300@freebsd.org> References: <201211181217.qAICH7aH021497@svn.freebsd.org> <20121119114510.GQ38060@FreeBSD.org> <50AA3529.2030300@freebsd.org>
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On Mon, Nov 19, 2012 at 5:33 AM, Andre Oppermann <andre@freebsd.org> wrote: > On 19.11.2012 12:45, Gleb Smirnoff wrote: >> >> On Sun, Nov 18, 2012 at 12:17:07PM +0000, Andre Oppermann wrote: >> A> Author: andre >> A> Date: Sun Nov 18 12:17:07 2012 >> A> New Revision: 243215 >> A> URL: http://svnweb.freebsd.org/changeset/base/243215 >> A> >> A> Log: >> A> Add mtodo(m, o, t) macro taking an additional offset into >> A> the mbuf data section before the casting to type 't'. >> >> IMHO, argument order of (m, t, o) is more intuitive, since >> matches order of mtod(). > > > Yes, but that looks rather horrible and counter-intuitive: > > th = mtodo(m, struct tcphdr *, 20); > > vs. > > th = mtodo(m, 20, struct tcphdr *); > > Reads m->m_data at offset 20 is struct tcphdr. > > Naming it mtood() wasn't convincing either. ;-) Why a cast at all? Perpetuating the mistake of mtod()'s casting isn't necessary. mtod() can't be fixed for source reasons, but the new one doesn't need to cast. Since C automatically casts from void * to any other pointer, the code gets shorter (usually) too: th = mtodo(m, 20); Not that I care much, it's just if we're having a bikeshed I have my favorite colors. :-) Cheers, matthew >> A> >> A> Modified: >> A> user/andre/tcp_workqueue/sys/sys/mbuf.h >> A> >> A> Modified: user/andre/tcp_workqueue/sys/sys/mbuf.h >> A> >> ============================================================================== >> A> --- user/andre/tcp_workqueue/sys/sys/mbuf.h Sun Nov 18 12:16:50 2012 >> (r243214) >> A> +++ user/andre/tcp_workqueue/sys/sys/mbuf.h Sun Nov 18 12:17:07 2012 >> (r243215) >> A> @@ -64,8 +64,10 @@ >> A> * type: >> A> * >> A> * mtod(m, t) -- Convert mbuf pointer to data pointer of correct >> type. >> A> + * mtodo(m, o, t) - Same as above but with offset 'o' into data. >> A> */ >> A> #define mtod(m, t) ((t)((m)->m_data)) >> A> +#define mtodo(m, o, t) ((t)(((m)->m_data) + (o))) >> A> >> A> /* >> A> * Argument structure passed to UMA routines during mbuf and packet >> >
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