queue.h

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/*      $OpenBSD: queue.h,v 1.1 2007/10/26 03:14:08 niallo 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
 */

#pragma once

/*
 * 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 _Q_INVALIDATE(a) (a) = ((void *)-1)
#else
#define _Q_INVALIDATE(a)
#endif

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

#define SLIST_HEAD_INITIALIZER(head) \
    { NULL }

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

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

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

#define SLIST_FOREACH_PREVPTR(var, varp, head, field) \
    for ((varp) = &SLIST_FIRST((head));               \
         ((var) = *(varp)) != SLIST_END(head);        \
         (varp) = &SLIST_NEXT((var), field))

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

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

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

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

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

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

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

#define LIST_HEAD_INITIALIZER(head) \
    { NULL }

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

/* Swaps two consecutive elements. 'second' *MUST* follow 'first' */
#define TAILQ_SWAP(first, second, head, field)                                     \
    do {                                                                           \
        *((first)->field.tqe_prev) = (second);                                     \
        (second)->field.tqe_prev = (first)->field.tqe_prev;                        \
        (first)->field.tqe_prev = &((second)->field.tqe_next);                     \
        (first)->field.tqe_next = (second)->field.tqe_next;                        \
        if ((second)->field.tqe_next)                                              \
            (second)->field.tqe_next->field.tqe_prev = &((first)->field.tqe_next); \
        (second)->field.tqe_next = first;                                          \
        if ((head)->tqh_last == &((second)->field.tqe_next))                       \
            (head)->tqh_last = &((first)->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_HEAD_INITIALIZER(head) \
    { CIRCLEQ_END(&head), CIRCLEQ_END(&head) }

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

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

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

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

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

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

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

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

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

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

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