## root/libdb/queue.h

/* [<][>][^][v][top][bottom][index][help] */

## INCLUDED FROM

## DEFINITIONS

This source file includes following definitions.

1. insque
2. remque

    /*
     * 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. 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
     * $FreeBSD: src/sys/sys/queue.h,v 1.32.2.4 2001/03/31 03:33:39 hsu Exp $
     */

    #ifndef _SYS_QUEUE_H_
    #define _SYS_QUEUE_H_

    /* #include <machine/ansi.h>*/  /* for __offsetof */

    /*
     * This file defines five types of data structures: singly-linked lists,
     * singly-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 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.
     *
     *
     *                      SLIST   LIST    STAILQ  TAILQ   CIRCLEQ
     * _HEAD                +       +       +       +       +
     * _ENTRY               +       +       +       +       +
     * _INIT                +       +       +       +       +
     * _EMPTY               +       +       +       +       +
     * _FIRST               +       +       +       +       +
     * _NEXT                +       +       +       +       +
     * _PREV                -       -       -       +       +
     * _LAST                -       -       +       +       +
     * _FOREACH             +       +       +       +       +
     * _FOREACH_REVERSE     -       -       -       +       +
     * _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_HEAD_INITIALIZER(head)                                    \
            { NULL }

    #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, type, field)                                  \
            (STAILQ_EMPTY(head) ?                                           \
                    NULL :                                                  \
                    ((struct type *)                                        \
                    ((char *)((head)->stqh_last) - __offsetof(struct type, field))))

    #define STAILQ_FOREACH(var, head, field)                                \
            for((var) = (head)->stqh_first; (var); (var) = (var)->field.stqe_next)

    #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, headname, field)               \
            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_FOREACH_REVERSE(var, head, field)                       \
            for((var) = (head)->cqh_last;                                   \
                (var) != (void *)(head);                                    \
                (var) = (var)->field.cqe_prev)

    #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)

    #ifdef _KERNEL

    /*
     * XXX insque() and remque() are an old way of handling certain queues.
     * They bogusly assumes that all queue heads look alike.
     */

    struct quehead {
            struct quehead *qh_link;
            struct quehead *qh_rlink;
    };

    #ifdef  __GNUC__

    static __inline void
    insque(void *a, void *b)
    {
            struct quehead *element = a, *head = b;

            element->qh_link = head->qh_link;
            element->qh_rlink = head;
            head->qh_link = element;
            element->qh_link->qh_rlink = element;
    }

    static __inline void
    remque(void *a)
    {
            struct quehead *element = a;

            element->qh_link->qh_rlink = element->qh_rlink;
            element->qh_rlink->qh_link = element->qh_link;
            element->qh_rlink = 0;
    }

    #else /* !__GNUC__ */

    void    insque __P((void *a, void *b));
    void    remque __P((void *a));

    #endif /* __GNUC__ */

    #endif /* _KERNEL */

    #endif /* !_SYS_QUEUE_H_ */

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