fallbackdir: Update list generated on November 10, 2022

[tor.git] / src / ext / tor_queue.h

/*      $OpenBSD: queue.h,v 1.36 2012/04/11 13:29:14 naddy Exp $        */
/*      $NetBSD: queue.h,v 1.11 1996/05/16 05:17:14 mycroft Exp $       */

/*
 * Copyright (c) 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. 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 TOR_QUEUE_H_
#define TOR_QUEUE_H_

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

#if defined(QUEUE_MACRO_DEBUG) || (defined(_KERNEL) && defined(DIAGNOSTIC))
#define TOR_Q_INVALIDATE_(a) (a) = ((void *)-1)
#else
#define TOR_Q_INVALIDATE_(a)
#endif

/*
 * Singly-linked List definitions.
 */
#define TOR_SLIST_HEAD(name, type)                                              \
struct name {                                                           \
        struct type *slh_first; /* first element */                     \
}
 
#define TOR_SLIST_HEAD_INITIALIZER(head)                                        \
        { NULL }
 
#define TOR_SLIST_ENTRY(type)                                           \
struct {                                                                \
        struct type *sle_next;  /* next element */                      \
}
 
/*
 * Singly-linked List access methods.
 */
#define TOR_SLIST_FIRST(head)   ((head)->slh_first)
#define TOR_SLIST_END(head)             NULL
/* || 0 is for -Wparentheses-equality (-Wall?) appeasement under clang */
#define TOR_SLIST_EMPTY(head)   ((SLIST_FIRST(head) == TOR_SLIST_END(head)) || 0)
#define TOR_SLIST_NEXT(elm, field)      ((elm)->field.sle_next)

#define TOR_SLIST_FOREACH(var, head, field)                                     \
        for((var) = TOR_SLIST_FIRST(head);                                      \
            (var) != TOR_SLIST_END(head);                                       \
            (var) = TOR_SLIST_NEXT(var, field))

#define TOR_SLIST_FOREACH_SAFE(var, head, field, tvar)                  \
        for ((var) = TOR_SLIST_FIRST(head);                             \
            (var) && ((tvar) = TOR_SLIST_NEXT(var, field), 1);          \
            (var) = (tvar))

/*
 * Singly-linked List functions.
 */
#define TOR_SLIST_INIT(head) {                                          \
        TOR_SLIST_FIRST(head) = TOR_SLIST_END(head);                            \
}

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

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

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

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

#define TOR_SLIST_REMOVE(head, elm, type, field) do {                   \
        if ((head)->slh_first == (elm)) {                               \
                TOR_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;             \
                TOR_Q_INVALIDATE_((elm)->field.sle_next);                       \
        }                                                               \
} while (0)

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

#define TOR_LIST_HEAD_INITIALIZER(head)                                 \
        { NULL }

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

/*
 * List access methods
 */
#define TOR_LIST_FIRST(head)    ((head)->lh_first)
#define TOR_LIST_END(head)                NULL
/* || 0 is for -Wparentheses-equality (-Wall?) appeasement under clang */
#define TOR_LIST_EMPTY(head)      \
          ((TOR_LIST_FIRST(head) == TOR_LIST_END(head)) || 0)
#define TOR_LIST_NEXT(elm, field)               ((elm)->field.le_next)

#define TOR_LIST_FOREACH(var, head, field)                                      \
        for((var) = TOR_LIST_FIRST(head);                                       \
            (var)!= TOR_LIST_END(head);                                 \
            (var) = TOR_LIST_NEXT(var, field))

#define TOR_LIST_FOREACH_SAFE(var, head, field, tvar)                   \
        for ((var) = TOR_LIST_FIRST(head);                              \
            (var) && ((tvar) = TOR_LIST_NEXT(var, field), 1);           \
            (var) = (tvar))

/*
 * List functions.
 */
#define TOR_LIST_INIT(head) do {                                                \
        TOR_LIST_FIRST(head) = TOR_LIST_END(head);                              \
} while (0)

#define TOR_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 TOR_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 TOR_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 TOR_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;                   \
        TOR_Q_INVALIDATE_((elm)->field.le_prev);                                \
        TOR_Q_INVALIDATE_((elm)->field.le_next);                                \
} while (0)

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

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

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

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

/*
 * Simple queue access methods.
 */
#define TOR_SIMPLEQ_FIRST(head)     ((head)->sqh_first)
#define TOR_SIMPLEQ_END(head)         NULL
/* || 0 is for -Wparentheses-equality (-Wall?) appeasement under clang */
#define TOR_SIMPLEQ_EMPTY(head)     \
          ((TOR_SIMPLEQ_FIRST(head) == TOR_SIMPLEQ_END(head)) || 0)
#define TOR_SIMPLEQ_NEXT(elm, field)    ((elm)->field.sqe_next)

#define TOR_SIMPLEQ_FOREACH(var, head, field)                           \
        for((var) = TOR_SIMPLEQ_FIRST(head);                            \
            (var) != TOR_SIMPLEQ_END(head);                                     \
            (var) = TOR_SIMPLEQ_NEXT(var, field))

#define TOR_SIMPLEQ_FOREACH_SAFE(var, head, field, tvar)                        \
        for ((var) = TOR_SIMPLEQ_FIRST(head);                           \
            (var) && ((tvar) = TOR_SIMPLEQ_NEXT(var, field), 1);                \
            (var) = (tvar))

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

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

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

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

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

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

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

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

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

/* 
 * tail queue access methods 
 */
#define TOR_TAILQ_FIRST(head)           ((head)->tqh_first)
#define TOR_TAILQ_END(head)                     NULL
#define TOR_TAILQ_NEXT(elm, field)              ((elm)->field.tqe_next)
#define TOR_TAILQ_LAST(head, headname)                                  \
        (*(((struct headname *)((head)->tqh_last))->tqh_last))
/* XXX */
#define TOR_TAILQ_PREV(elm, headname, field)                            \
        (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
/* || 0 is for -Wparentheses-equality (-Wall?) appeasement under clang */
#define TOR_TAILQ_EMPTY(head)                                           \
        ((TOR_TAILQ_FIRST(head) == TOR_TAILQ_END(head)) || 0)

#define TOR_TAILQ_FOREACH(var, head, field)                                     \
        for((var) = TOR_TAILQ_FIRST(head);                                      \
            (var) != TOR_TAILQ_END(head);                                       \
            (var) = TOR_TAILQ_NEXT(var, field))

#define TOR_TAILQ_FOREACH_SAFE(var, head, field, tvar)                  \
        for ((var) = TOR_TAILQ_FIRST(head);                                     \
            (var) != TOR_TAILQ_END(head) &&                                     \
            ((tvar) = TOR_TAILQ_NEXT(var, field), 1);                   \
            (var) = (tvar))


#define TOR_TAILQ_FOREACH_REVERSE(var, head, headname, field)           \
        for((var) = TOR_TAILQ_LAST(head, headname);                             \
            (var) != TOR_TAILQ_END(head);                                       \
            (var) = TOR_TAILQ_PREV(var, headname, field))

#define TOR_TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)        \
        for ((var) = TOR_TAILQ_LAST(head, headname);                    \
            (var) != TOR_TAILQ_END(head) &&                                     \
            ((tvar) = TOR_TAILQ_PREV(var, headname, field), 1);         \
            (var) = (tvar))

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

#define TOR_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 TOR_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 TOR_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 TOR_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 TOR_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;                 \
        TOR_Q_INVALIDATE_((elm)->field.tqe_prev);                               \
        TOR_Q_INVALIDATE_((elm)->field.tqe_next);                               \
} while (0)

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

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

#define TOR_CIRCLEQ_HEAD_INITIALIZER(head)                                      \
        { TOR_CIRCLEQ_END(&head), TOR_CIRCLEQ_END(&head) }

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

/*
 * Circular queue access methods 
 */
#define TOR_CIRCLEQ_FIRST(head)         ((head)->cqh_first)
#define TOR_CIRCLEQ_LAST(head)          ((head)->cqh_last)
#define TOR_CIRCLEQ_END(head)           ((void *)(head))
#define TOR_CIRCLEQ_NEXT(elm, field)    ((elm)->field.cqe_next)
#define TOR_CIRCLEQ_PREV(elm, field)    ((elm)->field.cqe_prev)
/* || 0 is for -Wparentheses-equality (-Wall?) appeasement under clang */
#define TOR_CIRCLEQ_EMPTY(head)                                         \
        ((TOR_CIRCLEQ_FIRST(head) == TOR_CIRCLEQ_END(head)) || 0)

#define TOR_CIRCLEQ_FOREACH(var, head, field)                           \
        for((var) = TOR_CIRCLEQ_FIRST(head);                            \
            (var) != TOR_CIRCLEQ_END(head);                                     \
            (var) = TOR_CIRCLEQ_NEXT(var, field))

#define TOR_CIRCLEQ_FOREACH_SAFE(var, head, field, tvar)                        \
        for ((var) = TOR_CIRCLEQ_FIRST(head);                           \
            (var) != TOR_CIRCLEQ_END(head) &&                           \
            ((tvar) = TOR_CIRCLEQ_NEXT(var, field), 1);                 \
            (var) = (tvar))

#define TOR_CIRCLEQ_FOREACH_REVERSE(var, head, field)                   \
        for((var) = TOR_CIRCLEQ_LAST(head);                                     \
            (var) != TOR_CIRCLEQ_END(head);                                     \
            (var) = TOR_CIRCLEQ_PREV(var, field))

#define TOR_CIRCLEQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)      \
        for ((var) = TOR_CIRCLEQ_LAST(head, headname);                  \
            (var) != TOR_CIRCLEQ_END(head) &&                           \
            ((tvar) = TOR_CIRCLEQ_PREV(var, headname, field), 1);               \
            (var) = (tvar))

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

#define TOR_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 == TOR_CIRCLEQ_END(head))         \
                (head)->cqh_last = (elm);                               \
        else                                                            \
                (listelm)->field.cqe_next->field.cqe_prev = (elm);      \
        (listelm)->field.cqe_next = (elm);                              \
} while (0)

#define TOR_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 == TOR_CIRCLEQ_END(head))         \
                (head)->cqh_first = (elm);                              \
        else                                                            \
                (listelm)->field.cqe_prev->field.cqe_next = (elm);      \
        (listelm)->field.cqe_prev = (elm);                              \
} while (0)

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

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

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

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

#endif  /* !_SYS_QUEUE_H_ */