Date: Tue, 06 Feb 2001 18:08:03 +0100 From: Poul-Henning Kamp <phk@critter.freebsd.dk> 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 ... Message-ID: <35662.981479283@critter> In-Reply-To: Your message of "Tue, 06 Feb 2001 09:04:38 PST." <200102061704.f16H4ct48889@mobile.wemm.org>
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In message <200102061704.f16H4ct48889@mobile.wemm.org>, Peter Wemm writes: >Garrett Wollman wrote: >> <<On Tue, 06 Feb 2001 08:41:00 -0800, Peter Wemm <peter@netplex.com.au> said: >> >> > I thought LIST was doubly linked, which means we should be able to have a >> > LIST_PREV(), right? SLIST is singly linked as is STAILQ. >> >> There is a LIST_PREV macro, but in order to traverse the entire list >> backwards, one must first get to the very end, which requires a loop >> in LIST and a single dereference in TAILQ. > >Do you know where we can get one? For completeness we should have it and it >is missing from our queue.h. It could probably be a simple enough variant >of the recently added TAILQ_PREV() macro - which still gives me a headache >trying to understand. :-) If you want to implement it, you have to put a second pointer in the LIST_HEAD, and then you might as well make that pointer point to the last element at which point a global s/LIST/TAILQ/g makes more sense. The TAILQ_PREV is nasty, but as far as I can tell safe. -- 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. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message
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