queue.h

/*  $NetBSD: queue.h,v 1.68 2014/11/19 08:10:01 uebayasi 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 _BMK_CORE_QUEUE_H_
#define _BMK_CORE_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 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.
 */

//#include <bmk-core/null.h>
/*  $NetBSD: null.h,v 1.9 2010/07/06 11:56:20 kleink Exp $  */

/*
 * Written by Klaus Klein <kleink@NetBSD.org>, December 22, 1999.
 * Public domain.
 */

#ifndef _BMK_CORE_NULL_H_
#define _BMK_CORE_NULL_H_
#ifndef NULL
#if !defined(__GNUG__) || __GNUG__ < 2 || (__GNUG__ == 2 && __GNUC_MINOR__ < 90)
#if !defined(__cplusplus)
#define NULL  ((void *)0)
#else
#define NULL  0
#endif /* !__cplusplus */
#else
#define NULL  __null
#endif
#endif
#endif /* _BMK_CORE_NULL_H_ */


#if defined(QUEUEDEBUG)
# if defined(_KERNEL)
#  define QUEUEDEBUG_ABORT(...) panic(__VA_ARGS__)
# else
#  include <err.h>
#  define QUEUEDEBUG_ABORT(...) err(1, __VA_ARGS__)
# endif
#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) ((head)->slh_first == NULL)
#define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)

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

#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))

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

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

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

#define SLIST_REMOVE_AFTER(slistelm, field) do {      \
  (slistelm)->field.sle_next =          \
      SLIST_NEXT(SLIST_NEXT((slistelm), field), field);   \
} while (/*CONSTCOND*/0)

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

#define SLIST_REMOVE(head, elm, type, field) do {     \
  if ((head)->slh_first == (elm)) {       \
    SLIST_REMOVE_HEAD((head), field);     \
  }               \
  else {                \
    struct type *curelm = (head)->slh_first;    \
    while(curelm->field.sle_next != (elm))      \
      curelm = curelm->field.sle_next;    \
    curelm->field.sle_next =        \
        curelm->field.sle_next->field.sle_next;   \
  }               \
} while (/*CONSTCOND*/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)    ((head)->lh_first == LIST_END(head))
#define LIST_NEXT(elm, field)   ((elm)->field.le_next)

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

#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_MOVE(head1, head2) do {          \
  LIST_INIT((head2));           \
  if (!LIST_EMPTY((head1))) {         \
    (head2)->lh_first = (head1)->lh_first;      \
    LIST_INIT((head1));         \
  }               \
} while (/*CONSTCOND*/0)

/*
 * List functions.
 */
#if defined(QUEUEDEBUG)
#define QUEUEDEBUG_LIST_INSERT_HEAD(head, elm, field)     \
  if ((head)->lh_first &&           \
      (head)->lh_first->field.le_prev != &(head)->lh_first) \
    QUEUEDEBUG_ABORT("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)          \
    QUEUEDEBUG_ABORT("LIST_* forw %p %s:%d", (elm),   \
        __FILE__, __LINE__);        \
  if (*(elm)->field.le_prev != (elm))       \
    QUEUEDEBUG_ABORT("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 {            \
  (head)->lh_first = LIST_END(head);        \
} while (/*CONSTCOND*/0)

#define LIST_INSERT_AFTER(listelm, elm, field) do {     \
  QUEUEDEBUG_LIST_OP((listelm), field)        \
  if (((elm)->field.le_next = (listelm)->field.le_next) !=  \
      LIST_END(head))           \
    (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 (/*CONSTCOND*/0)

#define LIST_INSERT_BEFORE(listelm, elm, field) do {      \
  QUEUEDEBUG_LIST_OP((listelm), field)        \
  (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 (/*CONSTCOND*/0)

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

#define LIST_REMOVE(elm, field) do {          \
  QUEUEDEBUG_LIST_OP((elm), field)        \
  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;     \
  QUEUEDEBUG_LIST_POSTREMOVE((elm), field)      \
} while (/*CONSTCOND*/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);        \
  QUEUEDEBUG_LIST_POSTREMOVE((elm), field)      \
} while (/*CONSTCOND*/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)   ((head)->sqh_first == SIMPLEQ_END(head))
#define SIMPLEQ_NEXT(elm, field)  ((elm)->field.sqe_next)

#define SIMPLEQ_FOREACH(var, head, field)       \
  for ((var) = ((head)->sqh_first);       \
      (var) != SIMPLEQ_END(head);         \
      (var) = ((var)->field.sqe_next))

#define SIMPLEQ_FOREACH_SAFE(var, head, field, next)      \
  for ((var) = ((head)->sqh_first);       \
      (var) != SIMPLEQ_END(head) &&       \
      ((next = ((var)->field.sqe_next)), 1);      \
      (var) = (next))

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

#define 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 (/*CONSTCOND*/0)

#define SIMPLEQ_REMOVE(head, elm, type, field) do {     \
  if ((head)->sqh_first == (elm)) {       \
    SIMPLEQ_REMOVE_HEAD((head), field);     \
  } else {              \
    struct type *curelm = (head)->sqh_first;    \
    while (curelm->field.sqe_next != (elm))     \
      curelm = curelm->field.sqe_next;    \
    if ((curelm->field.sqe_next =       \
      curelm->field.sqe_next->field.sqe_next) == NULL) \
          (head)->sqh_last = &(curelm)->field.sqe_next; \
  }               \
} while (/*CONSTCOND*/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));          \
  }               \
} while (/*CONSTCOND*/0)

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

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

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

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

/*
 * 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)   (TAILQ_FIRST(head) == TAILQ_END(head))


#define TAILQ_FOREACH(var, head, field)         \
  for ((var) = ((head)->tqh_first);       \
      (var) != TAILQ_END(head);         \
      (var) = ((var)->field.tqe_next))

#define TAILQ_FOREACH_SAFE(var, head, field, next)      \
  for ((var) = ((head)->tqh_first);       \
      (var) != TAILQ_END(head) &&         \
      ((next) = TAILQ_NEXT(var, field), 1); (var) = (next))

#define TAILQ_FOREACH_REVERSE(var, head, headname, field)   \
  for ((var) = (*(((struct headname *)((head)->tqh_last))->tqh_last));\
      (var) != TAILQ_END(head);         \
      (var) = (*(((struct headname *)((var)->field.tqe_prev))->tqh_last)))

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

/*
 * Tail queue functions.
 */
#if defined(QUEUEDEBUG)
#define QUEUEDEBUG_TAILQ_INSERT_HEAD(head, elm, field)      \
  if ((head)->tqh_first &&          \
      (head)->tqh_first->field.tqe_prev != &(head)->tqh_first)  \
    QUEUEDEBUG_ABORT("TAILQ_INSERT_HEAD %p %s:%d", (head),  \
        __FILE__, __LINE__);
#define QUEUEDEBUG_TAILQ_INSERT_TAIL(head, elm, field)      \
  if (*(head)->tqh_last != NULL)          \
    QUEUEDEBUG_ABORT("TAILQ_INSERT_TAIL %p %s:%d", (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)         \
    QUEUEDEBUG_ABORT("TAILQ_* forw %p %s:%d", (elm),  \
        __FILE__, __LINE__);        \
  if (*(elm)->field.tqe_prev != (elm))        \
    QUEUEDEBUG_ABORT("TAILQ_* back %p %s:%d", (elm),  \
        __FILE__, __LINE__);
#define QUEUEDEBUG_TAILQ_PREREMOVE(head, elm, field)      \
  if ((elm)->field.tqe_next == NULL &&        \
      (head)->tqh_last != &(elm)->field.tqe_next)     \
    QUEUEDEBUG_ABORT("TAILQ_PREREMOVE head %p elm %p %s:%d",\
        (head), (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 {           \
  (head)->tqh_first = TAILQ_END(head);        \
  (head)->tqh_last = &(head)->tqh_first;        \
} while (/*CONSTCOND*/0)

#define TAILQ_INSERT_HEAD(head, elm, field) do {      \
  QUEUEDEBUG_TAILQ_INSERT_HEAD((head), (elm), field)    \
  if (((elm)->field.tqe_next = (head)->tqh_first) != TAILQ_END(head))\
    (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 (/*CONSTCOND*/0)

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

#define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {    \
  QUEUEDEBUG_TAILQ_OP((listelm), field)       \
  if (((elm)->field.tqe_next = (listelm)->field.tqe_next) !=  \
      TAILQ_END(head))            \
    (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 (/*CONSTCOND*/0)

#define TAILQ_INSERT_BEFORE(listelm, elm, field) do {     \
  QUEUEDEBUG_TAILQ_OP((listelm), field)       \
  (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 (/*CONSTCOND*/0)

#define TAILQ_REMOVE(head, elm, field) do {       \
  QUEUEDEBUG_TAILQ_PREREMOVE((head), (elm), field)    \
  QUEUEDEBUG_TAILQ_OP((elm), field)       \
  if (((elm)->field.tqe_next) != TAILQ_END(head))     \
    (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;     \
  QUEUEDEBUG_TAILQ_POSTREMOVE((elm), field);      \
} while (/*CONSTCOND*/0)

#define TAILQ_REPLACE(head, elm, elm2, field) do {      \
        if (((elm2)->field.tqe_next = (elm)->field.tqe_next) !=   \
      TAILQ_END(head))              \
                (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);       \
  QUEUEDEBUG_TAILQ_POSTREMOVE((elm), field);      \
} while (/*CONSTCOND*/0)

#define TAILQ_CONCAT(head1, head2, field) do {        \
  if (!TAILQ_EMPTY(head2)) {          \
    *(head1)->tqh_last = (head2)->tqh_first;    \
    (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
    (head1)->tqh_last = (head2)->tqh_last;      \
    TAILQ_INIT((head2));          \
  }               \
} while (/*CONSTCOND*/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_HEAD_INITIALIZER(head)         \
  { NULL, &(head).stqh_first }

#define STAILQ_ENTRY(type)            \
struct {                \
  struct 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)  (STAILQ_FIRST(head) == STAILQ_END(head))

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

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

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

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

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

#define STAILQ_REMOVE(head, elm, type, field) do {      \
  if ((head)->stqh_first == (elm)) {        \
    STAILQ_REMOVE_HEAD((head), field);      \
  } else {              \
    struct type *curelm = (head)->stqh_first;   \
    while (curelm->field.stqe_next != (elm))      \
      curelm = curelm->field.stqe_next;   \
    if ((curelm->field.stqe_next =        \
      curelm->field.stqe_next->field.stqe_next) == NULL) \
          (head)->stqh_last = &(curelm)->field.stqe_next; \
  }               \
} while (/*CONSTCOND*/0)

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

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

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

#define STAILQ_LAST(head, type, field)          \
  (STAILQ_EMPTY((head)) ?           \
    NULL :              \
          ((struct type *)(void *)        \
    ((char *)((head)->stqh_last) - offsetof(struct type, field))))

#endif  /* !_BMK_CORE_QUEUE_H_ */