On Wed, 11 Jun 2003, Juan Rivera wrote:
> I don't understand well how the ring data structure works.
Have you read apr_ring.h? I tried to heavily document that file. If you
have and it's still unclear, I'd like to know how to make it more clear.
> How would the code look like? I tried unsplicing from the first bucket to
> the bucket previous to e and then splicing it at the tail of b. But
> didn't work.
A splice basically takes one chain of ring elements (buckets in this case)
that are already tied together [you pass in pointers to the first and last
elements in this chain] and inserts it either before or after some other
element (APR_RING_SPLICE_BEFORE() and APR_RING_SPLICE_AFTER()).
--Cliff
>From apr_ring.h:
/**
* Splice the sequence ep1..epN into the ring before element lep
* (..lep.. becomes ..ep1..epN..lep..)
* @warning This doesn't work for splicing before the first element or on
* empty rings... see APR_RING_SPLICE_HEAD for one that does
* @param lep Element in the ring to splice before
* @param ep1 First element in the sequence to splice in
* @param epN Last element in the sequence to splice in
* @param link The name of the APR_RING_ENTRY in the element struct
*/
#define APR_RING_SPLICE_BEFORE(lep, ep1, epN, link) do { \
APR_RING_NEXT((epN), link) = (lep); \
APR_RING_PREV((ep1), link) = APR_RING_PREV((lep), link); \
APR_RING_NEXT(APR_RING_PREV((lep), link), link) = (ep1); \
APR_RING_PREV((lep), link) = (epN); \
} while (0)
/**
* Splice the sequence ep1..epN into the ring after element lep
* (..lep.. becomes ..lep..ep1..epN..)
* @warning This doesn't work for splicing after the last element or on
* empty rings... see APR_RING_SPLICE_TAIL for one that does
* @param lep Element in the ring to splice after
* @param ep1 First element in the sequence to splice in
* @param epN Last element in the sequence to splice in
* @param link The name of the APR_RING_ENTRY in the element struct
*/
#define APR_RING_SPLICE_AFTER(lep, ep1, epN, link) do { \
APR_RING_PREV((ep1), link) = (lep); \
APR_RING_NEXT((epN), link) = APR_RING_NEXT((lep), link); \
APR_RING_PREV(APR_RING_NEXT((lep), link), link) = (epN); \
APR_RING_NEXT((lep), link) = (ep1); \
} while (0)
