/*
 * 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
 */
/*
 * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#ifndef _SYS_QUEUE_H
#define _SYS_QUEUE_H

#include <sys/note.h>
#include <sys/containerof.h>

#ifdef __cplusplus
extern "C" {
#endif

/*
 * 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 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.h(3HEAD) manual page.
 */

#ifdef QUEUE_MACRO_DEBUG
#warn Use QUEUE_MACRO_DEBUG_TRACE and/or QUEUE_MACRO_DEBUG_TRASH
#define QUEUE_MACRO_DEBUG_TRACE
#define QUEUE_MACRO_DEBUG_TRASH
#endif

#ifdef QUEUE_MACRO_DEBUG_TRACE
/* Store the last 2 places the queue element or head was altered */
struct qm_trace {
        unsigned long   lastline;
        unsigned long   prevline;
        const char      *lastfile;
        const char      *prevfile;
};

#define TRACEBUF        struct qm_trace trace;
#define TRACEBUF_INITIALIZER    { __LINE__, 0, __FILE__, NULL },

#define QMD_TRACE_HEAD(head) do {                                       \
        (head)->trace.prevline = (head)->trace.lastline;                \
        (head)->trace.prevfile = (head)->trace.lastfile;                \
        (head)->trace.lastline = __LINE__;                              \
        (head)->trace.lastfile = __FILE__;                              \
        _NOTE(CONSTCOND)                                                \
} while (0)

#define QMD_TRACE_ELEM(elem) do {                                       \
        (elem)->trace.prevline = (elem)->trace.lastline;                \
        (elem)->trace.prevfile = (elem)->trace.lastfile;                \
        (elem)->trace.lastline = __LINE__;                              \
        (elem)->trace.lastfile = __FILE__;                              \
        _NOTE(CONSTCOND)                                                \
} while (0)

#else   /* !QUEUE_MACRO_DEBUG_TRACE */
#define QMD_TRACE_ELEM(elem)
#define QMD_TRACE_HEAD(head)
#define TRACEBUF
#define TRACEBUF_INITIALIZER
#endif  /* QUEUE_MACRO_DEBUG_TRACE */

#ifdef QUEUE_MACRO_DEBUG_TRASH
#define TRASHIT(x)              do {(x) = (void *)-1; } while (0)
#define QMD_IS_TRASHED(x)       ((x) == (void *)(intptr_t)-1)
#else   /* !QUEUE_MACRO_DEBUG_TRASH */
#define TRASHIT(x)
#define QMD_IS_TRASHED(x)       0
#endif  /* QUEUE_MACRO_DEBUG_TRASH */

#if defined(QUEUE_MACRO_DEBUG_TRACE) || defined(QUEUE_MACRO_DEBUG_TRASH)
#define QMD_SAVELINK(name, link)        void **name = (void *)&(link)
#else   /* !QUEUE_MACRO_DEBUG_TRACE && !QUEUE_MACRO_DEBUG_TRASH */
#define QMD_SAVELINK(name, link)
#endif  /* QUEUE_MACRO_DEBUG_TRACE || QUEUE_MACRO_DEBUG_TRASH */

#ifdef __cplusplus
/*
 * In C++ there can be structure lists and class lists:
 */
#define QUEUE_TYPEOF(type) type
#else
#define QUEUE_TYPEOF(type) struct type
#endif

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

#define SLIST_CLASS_HEAD(name, type)                                    \
struct name {                                                           \
        class type *slh_first;  /* first element */                     \
}

#define SLIST_HEAD_INITIALIZER(head)                                    \
        { NULL }

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

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

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

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

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

#define SLIST_FOREACH_SAFE(var, head, field, tvar)                      \
        for ((var) = SLIST_FIRST((head));                               \
                (var) != SLIST_END(head) &&                             \
                ((tvar) = SLIST_NEXT((var), field), 1);                 \
                (var) = (tvar))

#define SLIST_FOREACH_FROM_SAFE(var, head, field, tvar)                 \
        for ((var) = ((var) != SLIST_END(head) ? (var) : SLIST_FIRST((head))); \
                (var) != SLIST_END(head) &&                             \
                ((tvar) = SLIST_NEXT((var), field), 1);                 \
                (var) = (tvar))

/*
 * Singly-linked List functions.
 */
#define SLIST_INIT(head) do {                                           \
        (head)->slh_first = SLIST_END(head);                            \
        _NOTE(CONSTCOND)                                                \
} while (0)

#define SLIST_CONCAT(head1, head2, type, field) do {                    \
        QUEUE_TYPEOF(type) *curelm = SLIST_FIRST(head1);                \
        if (curelm == SLIST_END(head1)) {                               \
                if ((SLIST_FIRST(head1) = SLIST_FIRST(head2)) !=        \
                    SLIST_END(head1))                                   \
                        SLIST_INIT(head2);                              \
        } else if (SLIST_FIRST(head2) != SLIST_END(head2)) {            \
                while (SLIST_NEXT(curelm, field) != SLIST_END(head1))   \
                        curelm = SLIST_NEXT(curelm, field);             \
                SLIST_NEXT(curelm, field) = SLIST_FIRST(head2);         \
                SLIST_INIT(head2);                                      \
        }                                                               \
        _NOTE(CONSTCOND)                                                \
} while (0)

#define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
        SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
        SLIST_NEXT((slistelm), field) = (elm);                          \
        _NOTE(CONSTCOND)                                                \
} while (0)

#define SLIST_INSERT_HEAD(head, elm, field) do {                        \
        SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
        SLIST_FIRST((head)) = (elm);                                    \
        _NOTE(CONSTCOND)                                                \
} while (0)

#define SLIST_REMOVE_HEAD(head, field) do {                             \
        SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
        _NOTE(CONSTCOND)                                                \
} while (0)

#define SLIST_REMOVE_AFTER(slistelm, field) do {                        \
        SLIST_NEXT((slistelm), field) =                                 \
            SLIST_NEXT(SLIST_NEXT((slistelm), field), field);           \
        _NOTE(CONSTCOND)                                                \
} while (0)

#define SLIST_REMOVE(head, elm, type, field) do {                       \
        QMD_SAVELINK(oldnext, SLIST_NEXT((elm), field));                \
        if (SLIST_FIRST((head)) == (elm)) {                             \
                SLIST_REMOVE_HEAD((head), field);                       \
        }                                                               \
        else {                                                          \
                QUEUE_TYPEOF(type) *curelm = SLIST_FIRST((head));       \
                while (SLIST_NEXT(curelm, field) != (elm))              \
                        curelm = SLIST_NEXT(curelm, field);             \
                SLIST_REMOVE_AFTER(curelm, field);                      \
        }                                                               \
        TRASHIT(*oldnext);                                              \
        _NOTE(CONSTCOND)                                                \
} while (0)

#define SLIST_SWAP(head1, head2, type) do {                             \
        QUEUE_TYPEOF(type) *swap_first = SLIST_FIRST(head1);            \
        SLIST_FIRST(head1) = SLIST_FIRST(head2);                        \
        SLIST_FIRST(head2) = swap_first;                                \
} while (0)

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

#define STAILQ_CLASS_HEAD(name, type)                                   \
struct name {                                                           \
        class type *stqh_first; /* first element */                     \
        class 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 */                      \
}

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

/*
 * Singly-linked Tail queue access methods.
 */
#define STAILQ_FIRST(head)      ((head)->stqh_first)
#define STAILQ_END(head)        NULL
#define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
#define STAILQ_EMPTY(head)      ((head)->stqh_first == STAILQ_END(head))

#define STAILQ_FOREACH(var, head, field)                                \
        for ((var) = STAILQ_FIRST(head);                                \
            (var) != STAILQ_END(head);                                  \
            (var) = STAILQ_NEXT((var), field))

#define STAILQ_FOREACH_FROM(var, head, field)                           \
        for ((var) =                                                    \
            ((var) != STAILQ_END(head) ? (var) : STAILQ_FIRST((head))); \
            (var) != STAILQ_END(head);                                  \
            (var) = STAILQ_NEXT((var), field))

#define STAILQ_FOREACH_SAFE(var, head, field, tvar)                     \
        for ((var) = STAILQ_FIRST(head);                                \
            (var) != STAILQ_END(head) &&                                \
            ((tvar) = STAILQ_NEXT((var), field), 1);                    \
            (var) = (tvar))

#define STAILQ_FOREACH_FROM_SAFE(var, head, field, tvar)                \
        for ((var) =                                                    \
            ((var) != STAILQ_END(head) ? (var) : STAILQ_FIRST((head))); \
            (var) != STAILQ_END(head) &&                                \
            ((tvar) = STAILQ_NEXT((var), field), 1);                    \
            (var) = (tvar))

/*
 * Singly-linked Tail queue functions.
 */
#define STAILQ_INIT(head) do {                                          \
        STAILQ_FIRST(head) = STAILQ_END(head);                          \
        (head)->stqh_last = &STAILQ_FIRST((head));                      \
        _NOTE(CONSTCOND)                                                \
} while (0)

#define STAILQ_CONCAT(head1, head2) do {                                \
        if (!STAILQ_EMPTY((head2))) {                                   \
                *(head1)->stqh_last = STAILQ_FIRST((head2));            \
                (head1)->stqh_last = (head2)->stqh_last;                \
                STAILQ_INIT((head2));                                   \
        }                                                               \
        _NOTE(CONSTCOND)                                                \
} while (0)

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

#define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
        if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
                (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
        STAILQ_FIRST((head)) = (elm);                                   \
        _NOTE(CONSTCOND)                                                \
} while (0)

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

#define STAILQ_LAST(head, type, field)                                  \
        (STAILQ_EMPTY((head)) ? NULL :                                  \
            __containerof((head)->stqh_last,                            \
            QUEUE_TYPEOF(type), field.stqe_next))

#define STAILQ_REMOVE_HEAD(head, field) do {                            \
        if ((STAILQ_FIRST((head)) =                                     \
            STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)          \
                (head)->stqh_last = &STAILQ_FIRST((head));              \
        _NOTE(CONSTCOND)                                                \
} while (0)

#define STAILQ_REMOVE_AFTER(head, elm, field) do {                      \
        if ((STAILQ_NEXT(elm, field) =                                  \
            STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL)       \
                (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
        _NOTE(CONSTCOND)                                                \
} while (0)

#define STAILQ_REMOVE(head, elm, type, field) do {                      \
        QMD_SAVELINK(oldnext, (elm)->field.stqe_next);                  \
        if (STAILQ_FIRST((head)) == (elm)) {                            \
                STAILQ_REMOVE_HEAD((head), field);                      \
        } else {                                                        \
                QUEUE_TYPEOF(type) *curelm = STAILQ_FIRST(head);        \
                while (STAILQ_NEXT(curelm, field) != (elm))             \
                        curelm = STAILQ_NEXT(curelm, field);            \
                STAILQ_REMOVE_AFTER(head, curelm, field);               \
        }                                                               \
        TRASHIT(*oldnext);                                              \
        _NOTE(CONSTCOND)                                                \
} while (0)

#define STAILQ_SWAP(head1, head2, type) do {                            \
        QUEUE_TYPEOF(type) *swap_first = STAILQ_FIRST(head1);           \
        QUEUE_TYPEOF(type) **swap_last = (head1)->stqh_last;            \
        STAILQ_FIRST(head1) = STAILQ_FIRST(head2);                      \
        (head1)->stqh_last = (head2)->stqh_last;                        \
        STAILQ_FIRST(head2) = swap_first;                               \
        (head2)->stqh_last = swap_last;                                 \
        if (STAILQ_EMPTY(head1))                                        \
                (head1)->stqh_last = &STAILQ_FIRST(head1);              \
        if (STAILQ_EMPTY(head2))                                        \
                (head2)->stqh_last = &STAILQ_FIRST(head2);              \
        _NOTE(CONSTCOND)                                                \
} while (0)

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

#define LIST_CLASS_HEAD(name, type)                                     \
struct name {                                                           \
        class 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 */  \
}

#define LIST_CLASS_ENTRY(type)                                          \
struct {                                                                \
        class type *le_next;    /* next element */                      \
        class 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)                ((head)->lh_first == LIST_END(head))
#define LIST_NEXT(elm, field)           ((elm)->field.le_next)
#define LIST_PREV(elm, head, type, field)                               \
        ((elm)->field.le_prev == &LIST_FIRST((head)) ? NULL :           \
        __containerof((elm)->field.le_prev, type, field.le_next))

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

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

#define LIST_FOREACH_SAFE(var, head, field, tvar)                       \
        for ((var) = LIST_FIRST((head));                                \
            (var) != LIST_END(head) &&                          \
            ((tvar) = LIST_NEXT((var), field), 1);                      \
            (var) = (tvar))

#define LIST_FOREACH_FROM_SAFE(var, head, field, tvar)                  \
        for ((var) = ((var) != LIST_END(head) ? (var) : LIST_FIRST((head));\
            (var) != LIST_END(head) &&                          \
            ((tvar) = LIST_NEXT((var), field), 1);                      \
            (var) = (tvar))

/*
 * List functions.
 */
#if defined(_KERNEL) && defined(QUEUEDEBUG)
#define QUEUEDEBUG_LIST_INSERT_HEAD(head, elm, field)                   \
        if ((head)->lh_first &&                                         \
            (head)->lh_first->field.le_prev != &(head)->lh_first)       \
                panic("LIST_INSERT_HEAD %p %s:%d", (head), __FILE__, __LINE__);
#define QUEUEDEBUG_LIST_OP(elm, field)                                  \
        if ((elm)->field.le_next &&                                     \
            (elm)->field.le_next->field.le_prev !=                      \
            &(elm)->field.le_next)                                      \
                panic("LIST_* forw %p %s:%d", (elm), __FILE__, __LINE__);\
        if (*(elm)->field.le_prev != (elm))                             \
                panic("LIST_* back %p %s:%d", (elm), __FILE__, __LINE__);
#define QUEUEDEBUG_LIST_POSTREMOVE(elm, field)                          \
        (elm)->field.le_next = (void *)1L;                              \
        (elm)->field.le_prev = (void *)1L;
#else
#define QUEUEDEBUG_LIST_INSERT_HEAD(head, elm, field)
#define QUEUEDEBUG_LIST_OP(elm, field)
#define QUEUEDEBUG_LIST_POSTREMOVE(elm, field)
#endif

#define LIST_INIT(head) do {                                            \
        LIST_FIRST((head)) = LIST_END(head);                            \
        _NOTE(CONSTCOND)                                                \
} while (0)

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

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

#define LIST_INSERT_HEAD(head, elm, field) do {                         \
        QUEUEDEBUG_LIST_INSERT_HEAD((head), (elm), field)               \
        if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
                LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
        LIST_FIRST((head)) = (elm);                                     \
        (elm)->field.le_prev = &LIST_FIRST((head));                     \
        _NOTE(CONSTCOND)                                                \
} while (0)

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

#define LIST_SWAP(head1, head2, type, field) do {                       \
        QUEUE_TYPEOF(type) *swap_tmp = LIST_FIRST(head1);               \
        LIST_FIRST((head1)) = LIST_FIRST((head2));                      \
        LIST_FIRST((head2)) = swap_tmp;                                 \
        if ((swap_tmp = LIST_FIRST((head1))) != NULL)                   \
                swap_tmp->field.le_prev = &LIST_FIRST((head1));         \
        if ((swap_tmp = LIST_FIRST((head2))) != NULL)                   \
                swap_tmp->field.le_prev = &LIST_FIRST((head2));         \
        _NOTE(CONSTCOND)                                                \
} 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_CLASS_HEAD(name, type)                                  \
struct name {                                                           \
        class type *sqh_first;  /* first element */             \
        class 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 */                      \
}

#define SIMPLEQ_CLASS_ENTRY(type)                                       \
struct {                                                                \
        class 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)             ((head)->sqh_first == 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))

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

#define SIMPLEQ_FOREACH_SAFE(var, head, field, tvar)                    \
        for ((var) = SIMPLEQ_FIRST((head));                             \
            (var) != SIMPLEQ_END(head) &&                               \
            ((tvar) = SIMPLEQ_NEXT((var), field), 1);                   \
            (var) = (tvar))

#define SIMPLEQ_FOREACH_FROM_SAFE(var, head, field, tvar)               \
        for ((var) =                                                    \
            ((var) != SIMPLEQ_END(head) ? (var) : SIMPLEQ_FIRST((head)));\
            (var) != SIMPLEQ_END(head) &&                               \
            ((tvar) = SIMPLEQ_NEXT((var), field), 1);                   \
            (var) = (tvar))

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

#define SIMPLEQ_INSERT_HEAD(head, elm, field) do {                      \
        if ((SIMPLEQ_NEXT((elm), field) = SIMPLEQ_FIRST((head))) == NULL)\
                (head)->sqh_last = &SIMPLEQ_NEXT((elm), field);         \
        SIMPLEQ_FIRST((head)) = (elm);                                  \
        _NOTE(CONSTCOND)                                                \
} while (0)

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

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

#define SIMPLEQ_REMOVE_HEAD(head, field) do {                           \
        if ((SIMPLEQ_FIRST((head)) =                                    \
            SIMPLEQ_NEXT(SIMPLEQ_FIRST((head)), field)) == NULL)        \
                (head)->sqh_last = &SIMPLEQ_FIRST((head));              \
        _NOTE(CONSTCOND)                                                \
} while (0)

#define SIMPLEQ_REMOVE_AFTER(head, elm, field) do {                     \
        if ((SIMPLEQ_NEXT((elm)) =                                      \
            SIMPLEQ_NEXT(SIMPLEQ_NEXT((elm), field), field)) == NULL)   \
                (head)->sqh_last = &SIMPLEQ_NEXT((elm), field);         \
        _NOTE(CONSTCOND)                                                \
} while (0)

#define SIMPLEQ_REMOVE(head, elm, type, field) do {                     \
        if (SIMPLEQ_FIRST((head)) == (elm)) {                           \
                SIMPLEQ_REMOVE_HEAD((head), field);                     \
        } else {                                                        \
                QUEUE_TYPEOF(type) *curelm = SIMPLEQ_FIRST((head));     \
                while (SIMPLEQ_NEXT(curelm, field) != (elm))            \
                        curelm = SIMPLEQ_NEXT(curelm, field);           \
                SIMPLEQ_REMOVE_AFTER((head), curelm, field);            \
        }                                                               \
        _NOTE(CONSTCOND)                                                \
} while (0)

#define SIMPLEQ_CONCAT(head1, head2) do {                               \
        if (!SIMPLEQ_EMPTY((head2))) {                                  \
                *(head1)->sqh_last = (head2)->sqh_first;                \
                (head1)->sqh_last = (head2)->sqh_last;                  \
                SIMPLEQ_INIT((head2));                                  \
        }                                                               \
        _NOTE(CONSTCOND)                                                \
} while (0)

#define SIMPLEQ_LAST(head, type, field)                                 \
        (SIMPLEQ_EMPTY((head)) ?                                        \
            NULL :                                                      \
            ((QUEUE_TYPEOF(type) *)(void *)                             \
            ((char *)((head)->sqh_last) - offsetof(QUEUE_TYPEOF(type), field))))

/*
 * 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 */         \
        TRACEBUF                                                        \
}

#define TAILQ_CLASS_HEAD(name, type)                                    \
struct name {                                                           \
        class type *tqh_first;          /* first element */             \
        class type **tqh_last;  /* addr of last next element */         \
        TRACEBUF                                                        \
}

#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 */  \
        TRACEBUF                                                        \
}

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

/*
 * 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))
#define TAILQ_PREV(elm, headname, field) \
        (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
#define TAILQ_EMPTY(head)               ((head)->tqh_first == 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_FROM(var, head, field)                            \
        for ((var) = ((var) != TAILQ_END((head)) ?                      \
            (var) : TAILQ_FIRST((head)));                               \
            (var) != TAILQ_END(head);                                   \
            (var) = TAILQ_NEXT((var), field))

#define TAILQ_FOREACH_SAFE(var, head, field, tvar)                      \
        for ((var) = TAILQ_FIRST((head));                               \
            (var) != TAILQ_END(head) &&                                 \
            ((tvar) = TAILQ_NEXT((var), field), 1);                     \
            (var) = (tvar))

#define TAILQ_FOREACH_FROM_SAFE(var, head, field, tvar)                 \
        for ((var) = ((var) != TAILQ_END((head)) ?                      \
            (var) : TAILQ_FIRST((head)));                               \
            (var) != TAILQ_END(head) &&                                 \
            ((tvar) = TAILQ_NEXT((var), field), 1);                     \
            (var) = (tvar))

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

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

#define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)    \
        for ((var) = TAILQ_LAST((head), headname);                      \
            (var) != TAILQ_END(head) &&                                 \
            ((tvar) = TAILQ_PREV((var), headname, field), 1);           \
            (var) = (tvar))

#define TAILQ_FOREACH_REVERSE_FROM_SAFE(var, head, headname, field, tvar)\
        for ((var) = ((var) != TAILQ_END((head)) ?                      \
            (var) : TAILQ_LAST((head), headname));                      \
            (var) != TAILQ_END(head) &&                                 \
            ((tvar) = TAILQ_PREV((var), headname, field), 1);           \
            (var) = (tvar))

/*
 * Tail queue functions.
 */
#if defined(_KERNEL) && defined(QUEUEDEBUG)
#define QUEUEDEBUG_TAILQ_INSERT_HEAD(head, elm, field)                  \
        if ((head)->tqh_first &&                                        \
            (head)->tqh_first->field.tqe_prev != &(head)->tqh_first)    \
                panic("TAILQ_INSERT_HEAD %p %s:%d", (void *)(head),     \
                    __FILE__, __LINE__);
#define QUEUEDEBUG_TAILQ_INSERT_TAIL(head, elm, field)                  \
        if (*(head)->tqh_last != NULL)                                  \
                panic("TAILQ_INSERT_TAIL %p %s:%d", (void *)(head),     \
                    __FILE__, __LINE__);
#define QUEUEDEBUG_TAILQ_OP(elm, field)                                 \
        if ((elm)->field.tqe_next &&                                    \
            (elm)->field.tqe_next->field.tqe_prev !=                    \
            &(elm)->field.tqe_next)                                     \
                panic("TAILQ_* forw %p %s:%d", (void *)(elm),           \
                    __FILE__, __LINE__);\
        if (*(elm)->field.tqe_prev != (elm))                            \
                panic("TAILQ_* back %p %s:%d", (void *)(elm),           \
                    __FILE__, __LINE__);
#define QUEUEDEBUG_TAILQ_PREREMOVE(head, elm, field)                    \
        if ((elm)->field.tqe_next == NULL &&                            \
            (head)->tqh_last != &(elm)->field.tqe_next)                 \
                panic("TAILQ_PREREMOVE head %p elm %p %s:%d",           \
                    (void *)(head), (void *)(elm), __FILE__, __LINE__);
#define QUEUEDEBUG_TAILQ_POSTREMOVE(elm, field)                         \
        (elm)->field.tqe_next = (void *)1L;                             \
        (elm)->field.tqe_prev = (void *)1L;
#else
#define QUEUEDEBUG_TAILQ_INSERT_HEAD(head, elm, field)
#define QUEUEDEBUG_TAILQ_INSERT_TAIL(head, elm, field)
#define QUEUEDEBUG_TAILQ_OP(elm, field)
#define QUEUEDEBUG_TAILQ_PREREMOVE(head, elm, field)
#define QUEUEDEBUG_TAILQ_POSTREMOVE(elm, field)
#endif

#define TAILQ_INIT(head) do {                                           \
        TAILQ_FIRST((head)) = TAILQ_END((head));                        \
        (head)->tqh_last = &TAILQ_FIRST((head));                        \
        _NOTE(CONSTCOND)                                                \
} while (0)

#define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
        QUEUEDEBUG_TAILQ_INSERT_HEAD((head), (elm), field)              \
        if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
                TAILQ_FIRST((head))->field.tqe_prev =                   \
                    &TAILQ_NEXT((elm), field);                          \
        else                                                            \
                (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
        TAILQ_FIRST((head)) = (elm);                                    \
        (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
        _NOTE(CONSTCOND)                                                \
} while (0)

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

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

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

#define TAILQ_REMOVE(head, elm, field) do {                             \
        QUEUEDEBUG_TAILQ_PREREMOVE((head), (elm), field)                \
        QUEUEDEBUG_TAILQ_OP((elm), field)                               \
        if ((TAILQ_NEXT((elm), field)) != NULL)                         \
                TAILQ_NEXT((elm), field)->field.tqe_prev =              \
                    (elm)->field.tqe_prev;                              \
        else                                                            \
                (head)->tqh_last = (elm)->field.tqe_prev;               \
        *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
        QUEUEDEBUG_TAILQ_POSTREMOVE((elm), field);                      \
        _NOTE(CONSTCOND)                                                \
} while (0)

#define TAILQ_SWAP(head1, head2, type, field) do {                      \
        QUEUE_TYPEOF(type) *swap_first = TAILQ_FIRST((head1));          \
        QUEUE_TYPEOF(type) **swap_last = (head1)->tqh_last;             \
        TAILQ_FIRST((head1)) = TAILQ_FIRST((head2));                    \
        (head1)->tqh_last = (head2)->tqh_last;                          \
        TAILQ_FIRST((head2)) = swap_first;                              \
        (head2)->tqh_last = swap_last;                                  \
        if ((swap_first = TAILQ_FIRST((head1))) != NULL)                \
                swap_first->field.tqe_prev = &TAILQ_FIRST((head1));     \
        else                                                            \
                (head1)->tqh_last = &TAILQ_FIRST((head1));              \
        if ((swap_first = TAILQ_FIRST((head2))) != NULL)                \
                swap_first->field.tqe_prev = &TAILQ_FIRST((head2));     \
        else                                                            \
                (head2)->tqh_last = &TAILQ_FIRST((head2));              \
        _NOTE(CONSTCOND)                                                \
} while (0)

/*
 * Circular queue definitions. Do not use. We still keep the macros
 * for compatibility but because of pointer aliasing issues their use
 * is discouraged!
 */
#define CIRCLEQ_HEAD(name, type)                                        \
struct name {                                                           \
        struct type *cqh_first;         /* first element */     \
        struct type *cqh_last;          /* last element */              \
}

#define CIRCLEQ_HEAD_INITIALIZER(head)                                  \
        { (void *)&head, (void *)&head }

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

/*
 * Circular queue access methods.
 */
#define CIRCLEQ_EMPTY(head)             ((head)->cqh_first == (void *)(head))
#define CIRCLEQ_FIRST(head)             ((head)->cqh_first)
#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_LOOP_NEXT(head, elm, field)                             \
        (((elm)->field.cqe_next == (void *)(head))                      \
            ? ((head)->cqh_first)                                       \
            : (elm->field.cqe_next))
#define CIRCLEQ_LOOP_PREV(head, elm, field)                             \
        (((elm)->field.cqe_prev == (void *)(head))                      \
            ? ((head)->cqh_last)                                        \
            : (elm->field.cqe_prev))

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

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

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

#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;                              \
        _NOTE(CONSTCOND)                                                \
} while (0)

#ifdef __cplusplus
}
#endif

#endif  /* !_SYS_QUEUE_H */