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Re: in which we present an ugly hack to make sys/queue.h CIRCLEQ work
>This functionally works, but the TAILQ data structure is not the same as
>the CIRCLEQ data structure (i.e. no ABI compatibility, if that matters;
>I'm not quite sure why it does) and unnecessarily penalizes applications
>which need to traverse the list in the tail->head direction.
I know the data structures aren't the same, but if you're using the macros
you don't ever notice this. As for the penalty ... you're talking
#define CIRCLEQ_PREV(elm,field) ((elm)->field.cqe_prev)
#define TAILQ_PREV(elm, headname, field) \
(*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
One extra pointer dereference is what we're talking about; I have to
believe that for 99% of applications it wouldn't matter.
Also, I see that CIRCLEQ has more complicated logic if you want to
insert elements at the end of it. So obviously there are tradeoffs (but
again, I don't really think it matters to nearly everybody).
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