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Posted to cvs@httpd.apache.org by fa...@locus.apache.org on 2000/09/08 04:00:06 UTC
cvs commit: apache-2.0/src/include ap_ring.h
fanf 00/09/07 19:00:06
Added: src/include ap_ring.h
Log:
Macros for implementing doubly-linked lists that bite their own tails like
Friedrich August Kekul�'s benzene rings.
Revision Changes Path
1.1 apache-2.0/src/include/ap_ring.h
Index: ap_ring.h
===================================================================
/* ====================================================================
* The Apache Software License, Version 1.1
*
* Copyright (c) 2000 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution,
* if any, must include the following acknowledgment:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowledgment may appear in the software itself,
* if and wherever such third-party acknowledgments normally appear.
*
* 4. The names "Apache" and "Apache Software Foundation" must
* not be used to endorse or promote products derived from this
* software without prior written permission. For written
* permission, please contact apache@apache.org.
*
* 5. Products derived from this software may not be called "Apache",
* nor may "Apache" appear in their name, without prior written
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*
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* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
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*/
/*
* This code draws heavily from the 4.4BSD <sys/queue.h> macros
* and Dean Gaudet's "splim/ring.h".
* <http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/sys/queue.h>
* <http://www.arctic.org/~dean/splim/>
*
* We'd use Dean's code directly if we could guarantee the
* availability of inline functions.
*/
#ifndef AP_RING_H
#define AP_RING_H
/*
* for offsetof()
*/
#include <stddef.h>
/*
* A ring is a kind of doubly-linked list.
*/
/*
* A struct on a ring contains a field linking it to the other
* elements in the ring, e.g.
*
* struct my_item_t {
* AP_RING_ENTRY(my_item_t) link;
* int foo;
* char *bar;
* };
*
* A struct may be put on more than one ring if it has more than one
* AP_RING_ENTRY field.
*/
#define AP_RING_ENTRY(elem) \
struct { \
struct elem *next; \
struct elem *prev; \
}
/*
* Each ring is managed via its head, which is a struct declared like this:
*
* AP_RING_HEAD(my_ring_t, my_item_t);
* struct my_ring_t ring, *ringp;
*
* This struct looks just like the element link struct so that we can
* be sure that the typecasting games will work as expected.
*
* The first element in the ring is next after the head, and the last
* element is just before the head.
*/
#define AP_RING_HEAD(head, elem) \
struct head { \
struct elem *next; \
struct elem *prev; \
}
/*
* The head itself isn't an element, but in order to get rid of all
* the special cases when dealing with the ends of the ring, we play
* typecasting games to make it look like one. The sentinel is the
* magic pointer value that occurs before the first and after the last
* elements in the ring, computed from the address of the ring's head.
*
* Note that for strict C standards compliance you should put the
* AP_RING_ENTRY first in struct elem_tag unless the head is always
* part of a larger object with enough earlier fields to accommodate
* the offsetof() computed below. You can usually ignore this caveat.
*/
#define AP_RING_SENTINAL(hp, elem, link) \
(struct elem *)((char *)(hp) - offsetof(struct elem, link))
/*
* Accessor macros. Use these rather than footling inside the
* structures directly so that you can more easily change to a
* different flavour of list from BSD's <sys/queue.h>.
*/
#define AP_RING_FIRST(hp) (hp)->next
#define AP_RING_LAST(hp) (hp)->prev
#define AP_RING_NEXT(ep, link) (ep)->link.next
#define AP_RING_PREV(ep, link) (ep)->link.prev
/*
* Empty rings and singleton elements.
*/
#define AP_RING_INIT(hp, elem, link) do { \
AP_RING_FIRST((hp)) = AP_RING_SENTINEL((hp), elem, link); \
AP_RING_LAST((hp)) = AP_RING_SENTINEL((hp), elem, link); \
} while (0)
#define AP_RING_EMPTY(hp, elem, link) \
(AP_RING_FIRST((hp)) == AP_RING_SENTINEL((hp), elem, link))
#define AP_RING_ELEM_INIT(ep, link) do { \
AP_RING_NEXT((ep), link) = (ep); \
AP_RING_PREV((ep), link) = (ep); \
} while (0)
/*
* Adding elements.
*/
#define AP_RING_SPLICE_BEFORE(lep, ep1, epN, link) do { \
AP_RING_NEXT((epN), link) = (lep); \
AP_RING_PREV((ep1), link) = AP_RING_PREV((lep), link); \
AP_RING_NEXT(AP_RING_PREV((lep), link), link) = (ep1); \
AP_RING_PREV((lep), link) = (epN); \
} while (0)
#define AP_RING_SPLICE_AFTER(lep, ep1, epN, link) do { \
AP_RING_PREV((ep1), link) = (lep); \
AP_RING_NEXT((epN), link) = AP_RING_NEXT((lep), link); \
AP_RING_PREV(AP_RING_NEXT((lep), link), link) = (epN); \
AP_RING_NEXT((lep), link) = (ep1); \
} while (0)
#define AP_RING_INSERT_BEFORE(lep, nep, link) \
AP_RING_SPLICE_BEFORE((lep), (nep), (nep), link)
#define AP_RING_INSERT_AFTER(lep, nep, link) \
AP_RING_SPLICE_AFTER((lep), (nep), (nep), link)
/*
* We could implement these by splicing after and before the sentinel
* instead of before the first and after the last respectively, but
* then the caller would have to pass in the element type.
*/
#define AP_RING_SPLICE_HEAD(hp, ep1, epN, link) \
AP_RING_SPLICE_BEFORE(AP_RING_FIRST((hp)), (ep1), (epN), link)
#define AP_RING_SPLICE_TAIL(hp, ep1, epN, link) \
AP_RING_SPLICE_AFTER(AP_RING_LAST((hp)), (ep1), (epN), link)
#define AP_RING_INSERT_HEAD(lep, nep, link) \
AP_RING_SPLICE_HEAD((lep), (nep), (nep), link)
#define AP_RING_INSERT_TAIL(lep, nep, link) \
AP_RING_SPLICE_TAIL((lep), (nep), (nep), link)
/*
* Concatenating ring h2 onto the end of ring h1 leaves h2 empty.
*
* Doing this without asking for the element type is ugly.
*/
#define AP_RING_CONCAT(h1, h2, elem, link) do { \
if (!AP_RING_EMPTY((h2), elem, link)) { \
AP_RING_SPLICE_BEFORE(AP_RING_SENTINEL((h1), elem, link), \
AP_RING_FIRST((h2)), \
AP_RING_LAST((h2)), link); \
AP_RING_INIT((h2), elem, link); \
} \
} while (0)
/*
* Removing elements. Be warned that the unspliced elements are left
* with dangling pointers at either end!
*/
#define AP_RING_UNSPLICE(ep1, epN, link) do { \
AP_RING_NEXT(AP_RING_PREV((ep1), link), link) = \
AP_RING_NEXT((epN), link); \
AP_RING_PREV(AP_RING_NEXT((epN), link), link) = \
AP_RING_PREV((ep1), link); \
} while (0)
#define AP_RING_REMOVE(ep, link) \
AP_RING_UNSPLICE((ep), (ep), link)
/*
* Iteration.
*/
#define AP_RING_FOREACH(ep, hp, elem, link) \
for ((ep) = AP_RING_FIRST((hp)); \
(ep) != AP_RING_SENTINEL((hp), elem, link); \
(ep) = AP_RING_NEXT((ep), link))
#define AP_RING_FOREACH_REVERSE(ep, hp, elem, link) \
for ((ep) = AP_RING_LAST((hp)); \
(ep) != AP_RING_SENTINEL((hp), elem, link); \
(ep) = AP_RING_PREV((ep), link))
#endif /* !AP_RING_H */
RE: cvs commit: apache-2.0/src/include ap_ring.h
Posted by Allan Edwards <ak...@raleigh.ibm.com>.
> Added: src/include ap_ring.h
> Log:
> Macros for implementing doubly-linked lists that bite their own
> tails like Friedrich August Kekulé's benzene rings.
>
What platform was this tesed on? It doesn't seem to work on either
Windows or Linux for us and debugging these macros is a PITA.