/*
 * 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,
 * slingly-linked tail queues, lists, 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 singly-linked 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
 * 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, at the head of the list, or at the
 * end of the list. Elements being removed from the head of the tail queue
 * should use the explicit macro for this purpose for optimum efficiency.
 * A singly-linked tail queue may only be traversed in the forward direction.
 * Singly-linked tail queues are ideal for applications with large datasets
 * and few or no removals or for implementing a FIFO 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 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 only be traversed in the forward 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.
 *
 *                  SLIST   LIST    STAILQ  TAILQ   CIRCLEQ
 * _HEAD            +       +       +       +       +
 * _ENTRY           +       +       +       +       +
 * _INIT            +       +       +       +       +
 * _EMPTY           +       +       +       +       +
 * _FIRST           +       +       +       +       +
 * _NEXT            +       +       +       +       +
 * _PREV            -       -       -       +       +
 * _LAST            -       -       +       +       +
 * _FOREACH         +       +       -       +       +
 * _INSERT_HEAD     +       +       +       +       +
 * _INSERT_BEFORE   -       +       -       +       +
 * _INSERT_AFTER    +       +       +       +       +
 * _INSERT_TAIL     -       -       +       +       +
 * _REMOVE_HEAD     +       -       +       -       -
 * _REMOVE          +       +       +       +       +
 *
 */

/*
 * Singly-linked List definitions.
 */
#define SLIST_HEAD(name, type)                                              \
struct name {                                                               \
    struct type *slh_first; /* first element */                             \
}
 
#define SLIST_ENTRY(type)                                                   \
struct {                                                                    \
    struct type *sle_next;  /* next element */                              \
}
 
/*
 * Singly-linked List functions.
 */
#define SLIST_EMPTY(head)   ((head)->slh_first == NULL)

#define SLIST_FIRST(head)   ((head)->slh_first)

#define SLIST_FOREACH(var, head, field)                                     \
    for((var) = (head)->slh_first; (var); (var) = (var)->field.sle_next)

#define SLIST_INIT(head) {                                                  \
    (head)->slh_first = NULL;                                               \
}

#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_NEXT(elm, field)  ((elm)->field.sle_next)

#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)

/*
 * Singly-linked Tail queue definitions.
 */
#define STAILQ_HEAD(name, type)                                             \
struct name {                                                               \
    struct type *stqh_first;    /* first element */                         \
    struct type **stqh_last;    /* addr of last next element */             \
}

#define STAILQ_HEAD_INITIALIZER(head)                                       \
    { NULL, &(head).stqh_first }

#define STAILQ_ENTRY(type)                                                  \
struct {                                                                    \
    struct type *stqe_next; /* next element */                              \
}

/*
 * Singly-linked Tail queue functions.
 */
#define STAILQ_EMPTY(head)  ((head)->stqh_first == NULL)

#define STAILQ_INIT(head) do {                                              \
    (head)->stqh_first = NULL;                                              \
    (head)->stqh_last = &(head)->stqh_first;                                \
} while (0)

#define STAILQ_FIRST(head)  ((head)->stqh_first)
#define STAILQ_LAST(head)   (*(head)->stqh_last)

#define STAILQ_INSERT_HEAD(head, elm, field) do {                           \
    if (((elm)->field.stqe_next = (head)->stqh_first) == NULL)              \
        (head)->stqh_last = &(elm)->field.stqe_next;                        \
    (head)->stqh_first = (elm);                                             \
} while (0)

#define STAILQ_INSERT_TAIL(head, elm, field) do {                           \
    (elm)->field.stqe_next = NULL;                                          \
    *(head)->stqh_last = (elm);                                             \
    (head)->stqh_last = &(elm)->field.stqe_next;                            \
} while (0)

#define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {                   \
    if (((elm)->field.stqe_next = (tqelm)->field.stqe_next) == NULL)        \
        (head)->stqh_last = &(elm)->field.stqe_next;                        \
    (tqelm)->field.stqe_next = (elm);                                       \
} while (0)

#define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)

#define STAILQ_REMOVE_HEAD(head, field) do {                                \
    if (((head)->stqh_first =                                               \
        (head)->stqh_first->field.stqe_next) == NULL)                       \
        (head)->stqh_last = &(head)->stqh_first;                            \
} while (0)

#define STAILQ_REMOVE_HEAD_UNTIL(head, elm, field) do {                     \
    if (((head)->stqh_first = (elm)->field.stqe_next) == NULL)              \
        (head)->stqh_last = &(head)->stqh_first;                            \
} while (0)

#define STAILQ_REMOVE(head, elm, type, field) do {                          \
    if ((head)->stqh_first == (elm)) {                                      \
        STAILQ_REMOVE_HEAD(head, field);                                    \
    }                                                                       \
    else {                                                                  \
        struct type *curelm = (head)->stqh_first;                           \
        while( curelm->field.stqe_next != (elm) )                           \
            curelm = curelm->field.stqe_next;                               \
        if((curelm->field.stqe_next =                                       \
            curelm->field.stqe_next->field.stqe_next) == NULL)              \
            (head)->stqh_last = &(curelm)->field.stqe_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 functions.
 */

#define LIST_EMPTY(head)    ((head)->lh_first == NULL)

#define LIST_FIRST(head)    ((head)->lh_first)

#define LIST_FOREACH(var, head, field)                                      \
    for((var) = (head)->lh_first; (var); (var) = (var)->field.le_next)

#define LIST_INIT(head) do {                                                \
    (head)->lh_first = NULL;                                                \
} 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_NEXT(elm, field)   ((elm)->field.le_next)

#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)

/*
 * 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 functions.
 */
#define TAILQ_EMPTY(head)   ((head)->tqh_first == NULL)

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

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

#define TAILQ_FIRST(head)   ((head)->tqh_first)

#define TAILQ_LAST(head, headname)                                          \
    (*(((struct headname *)((head)->tqh_last))->tqh_last))

#define TAILQ_NEXT(elm, field)  ((elm)->field.tqe_next)

#define TAILQ_PREV(elm, headname, field)                                    \
    (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))

#define TAILQ_INIT(head) do {                                               \
    (head)->tqh_first = NULL;                                               \
    (head)->tqh_last = &(head)->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)

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

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

/*
 * Circular queue functions.
 */
#define CIRCLEQ_EMPTY(head) ((head)->cqh_first == (void *)(head))

#define CIRCLEQ_FIRST(head) ((head)->cqh_first)

#define CIRCLEQ_FOREACH(var, head, field)                                   \
    for((var) = (head)->cqh_first;                                          \
        (var) != (void *)(head);                                            \
        (var) = (var)->field.cqe_next)

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

#define CIRCLEQ_LAST(head)  ((head)->cqh_last)

#define CIRCLEQ_NEXT(elm,field) ((elm)->field.cqe_next)

#define CIRCLEQ_PREV(elm,field) ((elm)->field.cqe_prev)

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

#endif  /* !_SYS_QUEUE_H_ */

/*
 * EOF
 *
 * vim:ts=4:expandtab
 */
