From owner-cvs-all Tue Feb 6 10:55:37 2001
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To: Peter Wemm <peter@netplex.com.au>
Cc: Garrett Wollman <wollman@khavrinen.lcs.mit.edu>,
cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject: Re: cvs commit: src/sys/dev/awi awi.c src/sys/dev/ed if_ed.c src/sys/dev/fe if_fe.c src/sys/dev/ie if_ie.c src/sys/dev/lnc if_lnc.c src/sys/dev/pdq pdq_ifsubr.c src/sys/dev/ray if_ray.c src/sys/dev/sn if_sn.c src/sys/dev/snc dp83932.c src/sys/dev/usb ...
In-Reply-To: Your message of "Tue, 06 Feb 2001 10:27:52 PST."
<200102061827.f16IRqt49819@mobile.wemm.org>
Date: Tue, 06 Feb 2001 19:55:10 +0100
Message-ID: <36763.981485710@critter>
From: Poul-Henning Kamp <phk@critter.freebsd.dk>
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In message <200102061827.f16IRqt49819@mobile.wemm.org>, Peter Wemm writes:
>TAILQ_PREV is only nasty because of a HORRIBLE hack. There is no structure
>for the tailq entry nodes, so it abuses the head structure definition.
>TAILQ_PREV can be quite easily be fixed to not need to do this abuse if
>we put a differient hack in another place. LIST_PREV can do the same thing
>without needing a head structure.. But it will need to know what the head
>of the list is so that it can detect when it hits it.
I already said that.
That would make the LIST_PREV rather inconvenient, and in all but
a few cases, would mean that the size of the pointer your saved in
the _HEAD structure will be spent several times over compensating
for it's absense, in the process making LIST_PREV unusable for the
case where you don't know what head a particular element is hung
from.
As I see it now:
If I have many _HEAD's (as in a hash table), LIST can save me a
little space.
All other cases: use TAILQ.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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