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lib/queue.h

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/*    $OpenBSD: queue.h,v 1.22 2001/06/23 04:39:35 angelos Exp $    */
/*    $NetBSD: queue.h,v 1.11 1996/05/16 05:17:14 mycroft Exp $    */

/*
 * Copyright (c) 1991, 1993
 *    The Regents of the University of California.  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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    This product includes software developed by the University of
 *    California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR 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 USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *    @(#)queue.h    8.5 (Berkeley) 8/20/94
 */

#ifndef    _SYS_QUEUE_H_
#define    _SYS_QUEUE_H_

/*
 * This file defines five types of data structures: singly-linked lists, 
 * lists, simple queues, tail queues, and circular queues.
 *
 *
 * A singly-linked list is headed by a single forward pointer. The elements
 * are singly linked for minimum space and pointer manipulation overhead at
 * the expense of O(n) removal for arbitrary elements. New elements can be
 * added to the list after an existing element or at the head of the list.
 * Elements being removed from the head of the list should use the explicit
 * macro for this purpose for optimum efficiency. A singly-linked list may
 * only be traversed in the forward direction.  Singly-linked lists are ideal
 * for applications with large datasets and few or no removals or for
 * implementing a LIFO queue.
 *
 * A list is headed by a single forward pointer (or an array of forward
 * pointers for a hash table header). The elements are doubly linked
 * so that an arbitrary element can be removed without a need to
 * traverse the list. New elements can be added to the list before
 * or after an existing element or at the head of the list. A list
 * may only be traversed in the forward direction.
 *
 * A simple queue is headed by a pair of pointers, one the head of the
 * list and the other to the tail of the list. The elements are singly
 * linked to save space, so elements can only be removed from the
 * head of the list. New elements can be added to the list before or after
 * an existing element, at the head of the list, or at the end of the
 * list. A simple queue may only be traversed in the forward direction.
 *
 * A tail queue is headed by a pair of pointers, one to the head of the
 * list and the other to the tail of the list. The elements are doubly
 * linked so that an arbitrary element can be removed without a need to
 * traverse the list. New elements can be added to the list before or
 * after an existing element, at the head of the list, or at the end of
 * the list. A tail queue may be traversed in either direction.
 *
 * A circle queue is headed by a pair of pointers, one to the head of the
 * list and the other to the tail of the list. The elements are doubly
 * linked so that an arbitrary element can be removed without a need to
 * traverse the list. New elements can be added to the list before or after
 * an existing element, at the head of the list, or at the end of the list.
 * A circle queue may be traversed in either direction, but has a more
 * complex end of list detection.
 *
 * For details on the use of these macros, see the queue(3) manual page.
 */

/*
 * Singly-linked List definitions.
 */
#define SLIST_HEAD(name, type)                        \
struct name {                                \
    struct type *slh_first;    /* first element */            \
}

#define    SLIST_HEAD_INITIALIZER(head)                    \
    { NULL }

#define SLIST_ENTRY(type)                        \
struct {                                \
    struct type *sle_next;    /* next element */            \
}

/*
 * Singly-linked List access methods.
 */
#define    SLIST_FIRST(head)    ((head)->slh_first)
#define    SLIST_END(head)        NULL
#define    SLIST_EMPTY(head)    (SLIST_FIRST(head) == SLIST_END(head))
#define    SLIST_NEXT(elm, field)    ((elm)->field.sle_next)

#define    SLIST_FOREACH(var, head, field)                    \
    for((var) = SLIST_FIRST(head);                    \
        (var) != SLIST_END(head);                    \
        (var) = SLIST_NEXT(var, field))

/*
 * Singly-linked List functions.
 */
#define    SLIST_INIT(head) {                        \
    SLIST_FIRST(head) = SLIST_END(head);                \
}

#define    SLIST_INSERT_AFTER(slistelm, elm, field) do {            \
    (elm)->field.sle_next = (slistelm)->field.sle_next;        \
    (slistelm)->field.sle_next = (elm);                \
} while (0)

#define    SLIST_INSERT_HEAD(head, elm, field) do {            \
    (elm)->field.sle_next = (head)->slh_first;            \
    (head)->slh_first = (elm);                    \
} while (0)

#define    SLIST_REMOVE_HEAD(head, field) do {                \
    (head)->slh_first = (head)->slh_first->field.sle_next;        \
} while (0)

#define SLIST_REMOVE(head, elm, type, field) do {            \
    if ((head)->slh_first == (elm)) {                \
        SLIST_REMOVE_HEAD((head), field);            \
    }                                \
    else {                                \
        struct type *curelm = (head)->slh_first;        \
        while( curelm->field.sle_next != (elm) )        \
            curelm = curelm->field.sle_next;        \
        curelm->field.sle_next =                \
            curelm->field.sle_next->field.sle_next;        \
    }                                \
} while (0)

/*
 * List definitions.
 */
#define LIST_HEAD(name, type)                        \
struct name {                                \
    struct type *lh_first;    /* first element */            \
}

#define LIST_HEAD_INITIALIZER(head)                    \
    { NULL }

#define LIST_ENTRY(type)                        \
struct {                                \
    struct type *le_next;    /* next element */            \
    struct type **le_prev;    /* address of previous next element */    \
}

/*
 * List access methods
 */
#define    LIST_FIRST(head)        ((head)->lh_first)
#define    LIST_END(head)            NULL
#define    LIST_EMPTY(head)        (LIST_FIRST(head) == LIST_END(head))
#define    LIST_NEXT(elm, field)        ((elm)->field.le_next)

#define LIST_FOREACH(var, head, field)                    \
    for((var) = LIST_FIRST(head);                    \
        (var)!= LIST_END(head);                    \
        (var) = LIST_NEXT(var, field))

/*
 * List functions.
 */
#define    LIST_INIT(head) do {                        \
    LIST_FIRST(head) = LIST_END(head);                \
} while (0)

#define LIST_INSERT_AFTER(listelm, elm, field) do {            \
    if (((elm)->field.le_next = (listelm)->field.le_next) != NULL)    \
        (listelm)->field.le_next->field.le_prev =        \
            &(elm)->field.le_next;                \
    (listelm)->field.le_next = (elm);                \
    (elm)->field.le_prev = &(listelm)->field.le_next;        \
} while (0)

#define    LIST_INSERT_BEFORE(listelm, elm, field) do {            \
    (elm)->field.le_prev = (listelm)->field.le_prev;        \
    (elm)->field.le_next = (listelm);                \
    *(listelm)->field.le_prev = (elm);                \
    (listelm)->field.le_prev = &(elm)->field.le_next;        \
} while (0)

#define LIST_INSERT_HEAD(head, elm, field) do {                \
    if (((elm)->field.le_next = (head)->lh_first) != NULL)        \
        (head)->lh_first->field.le_prev = &(elm)->field.le_next;\
    (head)->lh_first = (elm);                    \
    (elm)->field.le_prev = &(head)->lh_first;            \
} while (0)

#define LIST_REMOVE(elm, field) do {                    \
    if ((elm)->field.le_next != NULL)                \
        (elm)->field.le_next->field.le_prev =            \
            (elm)->field.le_prev;                \
    *(elm)->field.le_prev = (elm)->field.le_next;            \
} while (0)

#define LIST_REPLACE(elm, elm2, field) do {                \
    if (((elm2)->field.le_next = (elm)->field.le_next) != NULL)    \
        (elm2)->field.le_next->field.le_prev =            \
            &(elm2)->field.le_next;                \
    (elm2)->field.le_prev = (elm)->field.le_prev;            \
    *(elm2)->field.le_prev = (elm2);                \
} while (0)

/*
 * Simple queue definitions.
 */
#define SIMPLEQ_HEAD(name, type)                    \
struct name {                                \
    struct type *sqh_first;    /* first element */            \
    struct type **sqh_last;    /* addr of last next element */        \
}

#define SIMPLEQ_HEAD_INITIALIZER(head)                    \
    { NULL, &(head).sqh_first }

#define SIMPLEQ_ENTRY(type)                        \
struct {                                \
    struct type *sqe_next;    /* next element */            \
}

/*
 * Simple queue access methods.
 */
#define    SIMPLEQ_FIRST(head)        ((head)->sqh_first)
#define    SIMPLEQ_END(head)        NULL
#define    SIMPLEQ_EMPTY(head)        (SIMPLEQ_FIRST(head) == SIMPLEQ_END(head))
#define    SIMPLEQ_NEXT(elm, field)    ((elm)->field.sqe_next)

#define SIMPLEQ_FOREACH(var, head, field)                \
    for((var) = SIMPLEQ_FIRST(head);                \
        (var) != SIMPLEQ_END(head);                    \
        (var) = SIMPLEQ_NEXT(var, field))

/*
 * Simple queue functions.
 */
#define    SIMPLEQ_INIT(head) do {                        \
    (head)->sqh_first = NULL;                    \
    (head)->sqh_last = &(head)->sqh_first;                \
} while (0)

#define SIMPLEQ_INSERT_HEAD(head, elm, field) do {            \
    if (((elm)->field.sqe_next = (head)->sqh_first) == NULL)    \
        (head)->sqh_last = &(elm)->field.sqe_next;        \
    (head)->sqh_first = (elm);                    \
} while (0)

#define SIMPLEQ_INSERT_TAIL(head, elm, field) do {            \
    (elm)->field.sqe_next = NULL;                    \
    *(head)->sqh_last = (elm);                    \
    (head)->sqh_last = &(elm)->field.sqe_next;            \
} while (0)

#define SIMPLEQ_INSERT_AFTER(head, listelm, elm, field) do {        \
    if (((elm)->field.sqe_next = (listelm)->field.sqe_next) == NULL)\
        (head)->sqh_last = &(elm)->field.sqe_next;        \
    (listelm)->field.sqe_next = (elm);                \
} while (0)

#define SIMPLEQ_REMOVE_HEAD(head, elm, field) do {            \
    if (((head)->sqh_first = (elm)->field.sqe_next) == NULL)    \
        (head)->sqh_last = &(head)->sqh_first;            \
} while (0)

/*
 * Tail queue definitions.
 */
#define TAILQ_HEAD(name, type)                        \
struct name {                                \
    struct type *tqh_first;    /* first element */            \
    struct type **tqh_last;    /* addr of last next element */        \
}

#define TAILQ_HEAD_INITIALIZER(head)                    \
    { NULL, &(head).tqh_first }

#define TAILQ_ENTRY(type)                        \
struct {                                \
    struct type *tqe_next;    /* next element */            \
    struct type **tqe_prev;    /* address of previous next element */    \
}

/* 
 * tail queue access methods 
 */
#define    TAILQ_FIRST(head)        ((head)->tqh_first)
#define    TAILQ_END(head)            NULL
#define    TAILQ_NEXT(elm, field)        ((elm)->field.tqe_next)
#define TAILQ_LAST(head, headname)                    \
    (*(((struct headname *)((head)->tqh_last))->tqh_last))
/* XXX */
#define TAILQ_PREV(elm, headname, field)                \
    (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
#define    TAILQ_EMPTY(head)                        \
    (TAILQ_FIRST(head) == TAILQ_END(head))

#define TAILQ_FOREACH(var, head, field)                    \
    for((var) = TAILQ_FIRST(head);                    \
        (var) != TAILQ_END(head);                    \
        (var) = TAILQ_NEXT(var, field))

#define TAILQ_FOREACH_REVERSE(var, head, field, headname)        \
    for((var) = TAILQ_LAST(head, headname);                \
        (var) != TAILQ_END(head);                    \
        (var) = TAILQ_PREV(var, headname, field))

/*
 * Tail queue functions.
 */
#define    TAILQ_INIT(head) do {                        \
    (head)->tqh_first = NULL;                    \
    (head)->tqh_last = &(head)->tqh_first;                \
} while (0)

#define TAILQ_COPY(dst, src, field) do {                        \
    *(dst) = *(src);                                            \
    if (((dst)->tqh_first) != NULL)                                \
        (dst)->tqh_first->field.tqe_prev = &(dst)->tqh_first;    \
    else                                                        \
        (dst)->tqh_last = &(dst)->tqh_first;                    \
} while (0)

#define TAILQ_INSERT_HEAD(head, elm, field) do {            \
    if (((elm)->field.tqe_next = (head)->tqh_first) != NULL)    \
        (head)->tqh_first->field.tqe_prev =            \
            &(elm)->field.tqe_next;                \
    else                                \
        (head)->tqh_last = &(elm)->field.tqe_next;        \
    (head)->tqh_first = (elm);                    \
    (elm)->field.tqe_prev = &(head)->tqh_first;            \
} while (0)

#define TAILQ_INSERT_TAIL(head, elm, field) do {            \
    (elm)->field.tqe_next = NULL;                    \
    (elm)->field.tqe_prev = (head)->tqh_last;            \
    *(head)->tqh_last = (elm);                    \
    (head)->tqh_last = &(elm)->field.tqe_next;            \
} while (0)

#define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {        \
    if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\
        (elm)->field.tqe_next->field.tqe_prev =            \
            &(elm)->field.tqe_next;                \
    else                                \
        (head)->tqh_last = &(elm)->field.tqe_next;        \
    (listelm)->field.tqe_next = (elm);                \
    (elm)->field.tqe_prev = &(listelm)->field.tqe_next;        \
} while (0)

#define    TAILQ_INSERT_BEFORE(listelm, elm, field) do {            \
    (elm)->field.tqe_prev = (listelm)->field.tqe_prev;        \
    (elm)->field.tqe_next = (listelm);                \
    *(listelm)->field.tqe_prev = (elm);                \
    (listelm)->field.tqe_prev = &(elm)->field.tqe_next;        \
} while (0)

#define TAILQ_REMOVE(head, elm, field) do {                \
    if (((elm)->field.tqe_next) != NULL)                \
        (elm)->field.tqe_next->field.tqe_prev =            \
            (elm)->field.tqe_prev;                \
    else                                \
        (head)->tqh_last = (elm)->field.tqe_prev;        \
    *(elm)->field.tqe_prev = (elm)->field.tqe_next;            \
} while (0)

#define TAILQ_REPLACE(head, elm, elm2, field) do {            \
    if (((elm2)->field.tqe_next = (elm)->field.tqe_next) != NULL)    \
        (elm2)->field.tqe_next->field.tqe_prev =        \
            &(elm2)->field.tqe_next;                \
    else                                \
        (head)->tqh_last = &(elm2)->field.tqe_next;        \
    (elm2)->field.tqe_prev = (elm)->field.tqe_prev;            \
    *(elm2)->field.tqe_prev = (elm2);                \
} while (0)

/*
 * Circular queue definitions.
 */
#define CIRCLEQ_HEAD(name, type)                    \
struct name {                                \
    struct type *cqh_first;        /* first element */        \
    struct type *cqh_last;        /* last element */        \
}

#define CIRCLEQ_HEAD_INITIALIZER(head)                    \
    { CIRCLEQ_END(&head), CIRCLEQ_END(&head) }

#define CIRCLEQ_ENTRY(type)                        \
struct {                                \
    struct type *cqe_next;        /* next element */        \
    struct type *cqe_prev;        /* previous element */        \
}

/*
 * Circular queue access methods 
 */
#define    CIRCLEQ_FIRST(head)        ((head)->cqh_first)
#define    CIRCLEQ_LAST(head)        ((head)->cqh_last)
#define    CIRCLEQ_END(head)        ((void *)(head))
#define    CIRCLEQ_NEXT(elm, field)    ((elm)->field.cqe_next)
#define    CIRCLEQ_PREV(elm, field)    ((elm)->field.cqe_prev)
#define    CIRCLEQ_EMPTY(head)                        \
    (CIRCLEQ_FIRST(head) == CIRCLEQ_END(head))

#define CIRCLEQ_FOREACH(var, head, field)                \
    for((var) = CIRCLEQ_FIRST(head);                \
        (var) != CIRCLEQ_END(head);                    \
        (var) = CIRCLEQ_NEXT(var, field))

#define CIRCLEQ_FOREACH_REVERSE(var, head, field)            \
    for((var) = CIRCLEQ_LAST(head);                    \
        (var) != CIRCLEQ_END(head);                    \
        (var) = CIRCLEQ_PREV(var, field))

/*
 * Circular queue functions.
 */
#define    CIRCLEQ_INIT(head) do {                        \
    (head)->cqh_first = CIRCLEQ_END(head);                \
    (head)->cqh_last = CIRCLEQ_END(head);                \
} while (0)

#define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do {        \
    (elm)->field.cqe_next = (listelm)->field.cqe_next;        \
    (elm)->field.cqe_prev = (listelm);                \
    if ((listelm)->field.cqe_next == CIRCLEQ_END(head))        \
        (head)->cqh_last = (elm);                \
    else                                \
        (listelm)->field.cqe_next->field.cqe_prev = (elm);    \
    (listelm)->field.cqe_next = (elm);                \
} while (0)

#define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do {        \
    (elm)->field.cqe_next = (listelm);                \
    (elm)->field.cqe_prev = (listelm)->field.cqe_prev;        \
    if ((listelm)->field.cqe_prev == CIRCLEQ_END(head))        \
        (head)->cqh_first = (elm);                \
    else                                \
        (listelm)->field.cqe_prev->field.cqe_next = (elm);    \
    (listelm)->field.cqe_prev = (elm);                \
} while (0)

#define CIRCLEQ_INSERT_HEAD(head, elm, field) do {            \
    (elm)->field.cqe_next = (head)->cqh_first;            \
    (elm)->field.cqe_prev = CIRCLEQ_END(head);            \
    if ((head)->cqh_last == CIRCLEQ_END(head))            \
        (head)->cqh_last = (elm);                \
    else                                \
        (head)->cqh_first->field.cqe_prev = (elm);        \
    (head)->cqh_first = (elm);                    \
} while (0)

#define CIRCLEQ_INSERT_TAIL(head, elm, field) do {            \
    (elm)->field.cqe_next = CIRCLEQ_END(head);            \
    (elm)->field.cqe_prev = (head)->cqh_last;            \
    if ((head)->cqh_first == CIRCLEQ_END(head))            \
        (head)->cqh_first = (elm);                \
    else                                \
        (head)->cqh_last->field.cqe_next = (elm);        \
    (head)->cqh_last = (elm);                    \
} while (0)

#define    CIRCLEQ_REMOVE(head, elm, field) do {                \
    if ((elm)->field.cqe_next == CIRCLEQ_END(head))            \
        (head)->cqh_last = (elm)->field.cqe_prev;        \
    else                                \
        (elm)->field.cqe_next->field.cqe_prev =            \
            (elm)->field.cqe_prev;                \
    if ((elm)->field.cqe_prev == CIRCLEQ_END(head))            \
        (head)->cqh_first = (elm)->field.cqe_next;        \
    else                                \
        (elm)->field.cqe_prev->field.cqe_next =            \
            (elm)->field.cqe_next;                \
} while (0)

#define CIRCLEQ_REPLACE(head, elm, elm2, field) do {            \
    if (((elm2)->field.cqe_next = (elm)->field.cqe_next) ==        \
        CIRCLEQ_END(head))                        \
        (head).cqh_last = (elm2);                \
    else                                \
        (elm2)->field.cqe_next->field.cqe_prev = (elm2);    \
    if (((elm2)->field.cqe_prev = (elm)->field.cqe_prev) ==        \
        CIRCLEQ_END(head))                        \
        (head).cqh_first = (elm2);                \
    else                                \
        (elm2)->field.cqe_prev->field.cqe_next = (elm2);    \
} while (0)

#endif /* !_SYS_QUEUE_H_ */