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From: Hans Petter Selasky <hselasky@c2i.net>
To: freebsd-arch@freebsd.org
Date: Sat, 5 May 2007 16:17:34 +0200
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Subject: Missing LIST_PREV() ?
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Hi,

Why should LISTs only be forward traversable? The following piece of code make 
lists backward traversable:

/sys/sys/queue.h:

+#define LIST_PREV(head,elm,field) \
+  (((elm) == LIST_FIRST(head)) ? ((__typeof(elm))0) : \
+   ((__typeof(elm))(((uint8_t *)((elm)->field.le_prev)) - \
+                   ((uint8_t *)&LIST_NEXT((__typeof(elm))0,field)))))


Any comments?

--HPS