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      1 /*	$OpenBSD: queue.h,v 1.30 2005/10/25 06:37:47 otto Exp $	*/
      2 /*	$NetBSD: queue.h,v 1.11 1996/05/16 05:17:14 mycroft Exp $	*/
      3 
      4 /*
      5  * Copyright (c) 1991, 1993
      6  *	The Regents of the University of California.  All rights reserved.
      7  *
      8  * Redistribution and use in source and binary forms, with or without
      9  * modification, are permitted provided that the following conditions
     10  * are met:
     11  * 1. Redistributions of source code must retain the above copyright
     12  *    notice, this list of conditions and the following disclaimer.
     13  * 2. Redistributions in binary form must reproduce the above copyright
     14  *    notice, this list of conditions and the following disclaimer in the
     15  *    documentation and/or other materials provided with the distribution.
     16  * 3. Neither the name of the University nor the names of its contributors
     17  *    may be used to endorse or promote products derived from this software
     18  *    without specific prior written permission.
     19  *
     20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     30  * SUCH DAMAGE.
     31  *
     32  *	@(#)queue.h	8.5 (Berkeley) 8/20/94
     33  */
     34 
     35 #ifndef	SM_TAILQ_H_
     36 #define	SM_TAILQ_H_
     37 
     38 #pragma ident	"%Z%%M%	%I%	%E% SMI"
     39 
     40 /*
     41  * $Id: tailq.h,v 1.2 2007/06/29 23:09:57 ca Exp $
     42  *
     43  * This file is a modified copy of queue.h from a BSD system:
     44  * we only need tail queues here.
     45  * We do not use queue.h directly because there is a conflict with
     46  * some versions of that file on some OSs.
     47  *
     48  * A tail queue is headed by a pair of pointers, one to the head of the
     49  * list and the other to the tail of the list. The elements are doubly
     50  * linked so that an arbitrary element can be removed without a need to
     51  * traverse the list. New elements can be added to the list before or
     52  * after an existing element, at the head of the list, or at the end of
     53  * the list. A tail queue may be traversed in either direction.
     54  */
     55 
     56 /*
     57  * Tail queue definitions.
     58  */
     59 #define SM_TAILQ_HEAD(name, type)					\
     60 struct name {								\
     61 	struct type *tqh_first;	/* first element */			\
     62 	struct type **tqh_last;	/* addr of last next element */		\
     63 }
     64 
     65 #define SM_TAILQ_HEAD_INITIALIZER(head)					\
     66 	{ NULL, &(head).tqh_first }
     67 
     68 #define SM_TAILQ_ENTRY(type)						\
     69 struct {								\
     70 	struct type *tqe_next;	/* next element */			\
     71 	struct type **tqe_prev;	/* address of previous next element */	\
     72 }
     73 
     74 /*
     75  * tail queue access methods
     76  */
     77 #define	SM_TAILQ_FIRST(head)		((head)->tqh_first)
     78 #define	SM_TAILQ_END(head)		NULL
     79 #define	SM_TAILQ_NEXT(elm, field)	((elm)->field.tqe_next)
     80 #define SM_TAILQ_LAST(head, headname)					\
     81 	(*(((struct headname *)((head)->tqh_last))->tqh_last))
     82 /* XXX */
     83 #define SM_TAILQ_PREV(elm, headname, field)				\
     84 	(*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
     85 #define	SM_TAILQ_EMPTY(head)						\
     86 	(SM_TAILQ_FIRST(head) == SM_TAILQ_END(head))
     87 
     88 #define SM_TAILQ_FOREACH(var, head, field)				\
     89 	for((var) = SM_TAILQ_FIRST(head);				\
     90 	    (var) != SM_TAILQ_END(head);				\
     91 	    (var) = SM_TAILQ_NEXT(var, field))
     92 
     93 #define SM_TAILQ_FOREACH_REVERSE(var, head, headname, field)		\
     94 	for((var) = SM_TAILQ_LAST(head, headname);			\
     95 	    (var) != SM_TAILQ_END(head);				\
     96 	    (var) = SM_TAILQ_PREV(var, headname, field))
     97 
     98 /*
     99  * Tail queue functions.
    100  */
    101 #define	SM_TAILQ_INIT(head) do {					\
    102 	(head)->tqh_first = NULL;					\
    103 	(head)->tqh_last = &(head)->tqh_first;				\
    104 } while (0)
    105 
    106 #define SM_TAILQ_INSERT_HEAD(head, elm, field) do {			\
    107 	if (((elm)->field.tqe_next = (head)->tqh_first) != NULL)	\
    108 		(head)->tqh_first->field.tqe_prev =			\
    109 		    &(elm)->field.tqe_next;				\
    110 	else								\
    111 		(head)->tqh_last = &(elm)->field.tqe_next;		\
    112 	(head)->tqh_first = (elm);					\
    113 	(elm)->field.tqe_prev = &(head)->tqh_first;			\
    114 } while (0)
    115 
    116 #define SM_TAILQ_INSERT_TAIL(head, elm, field) do {			\
    117 	(elm)->field.tqe_next = NULL;					\
    118 	(elm)->field.tqe_prev = (head)->tqh_last;			\
    119 	*(head)->tqh_last = (elm);					\
    120 	(head)->tqh_last = &(elm)->field.tqe_next;			\
    121 } while (0)
    122 
    123 #define SM_TAILQ_INSERT_AFTER(head, listelm, elm, field) do {		\
    124 	if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\
    125 		(elm)->field.tqe_next->field.tqe_prev =			\
    126 		    &(elm)->field.tqe_next;				\
    127 	else								\
    128 		(head)->tqh_last = &(elm)->field.tqe_next;		\
    129 	(listelm)->field.tqe_next = (elm);				\
    130 	(elm)->field.tqe_prev = &(listelm)->field.tqe_next;		\
    131 } while (0)
    132 
    133 #define	SM_TAILQ_INSERT_BEFORE(listelm, elm, field) do {		\
    134 	(elm)->field.tqe_prev = (listelm)->field.tqe_prev;		\
    135 	(elm)->field.tqe_next = (listelm);				\
    136 	*(listelm)->field.tqe_prev = (elm);				\
    137 	(listelm)->field.tqe_prev = &(elm)->field.tqe_next;		\
    138 } while (0)
    139 
    140 #define SM_TAILQ_REMOVE(head, elm, field) do {				\
    141 	if (((elm)->field.tqe_next) != NULL)				\
    142 		(elm)->field.tqe_next->field.tqe_prev =			\
    143 		    (elm)->field.tqe_prev;				\
    144 	else								\
    145 		(head)->tqh_last = (elm)->field.tqe_prev;		\
    146 	*(elm)->field.tqe_prev = (elm)->field.tqe_next;			\
    147 } while (0)
    148 
    149 #define SM_TAILQ_REPLACE(head, elm, elm2, field) do {			\
    150 	if (((elm2)->field.tqe_next = (elm)->field.tqe_next) != NULL)	\
    151 		(elm2)->field.tqe_next->field.tqe_prev =		\
    152 		    &(elm2)->field.tqe_next;				\
    153 	else								\
    154 		(head)->tqh_last = &(elm2)->field.tqe_next;		\
    155 	(elm2)->field.tqe_prev = (elm)->field.tqe_prev;			\
    156 	*(elm2)->field.tqe_prev = (elm2);				\
    157 } while (0)
    158 
    159 #endif	/* !SM_TAILQ_H_ */
    160