update sys-queue.h

index 5b6e2a0..3d0773e 100644
@@ -1,241 +1,338 @@
-/*
- * 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.
- * 4. 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	8.3 (Berkeley) 12/13/93
- */
-
-#ifndef	_SYS_QUEUE_H
-#define	_SYS_QUEUE_H 1
-
-/*
- * This file defines three types of data structures: lists, tail queues,
- * and circular queues.
- *
- * 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 after
- * an existing element or at the head of the list. A list may only be
- * traversed in the forward direction.
- *
- * A tail queue is headed by a pair of pointers, one to the head of the
- * list and the other to the tail of the list. The elements are doubly
- * linked so that an arbitrary element can be removed without a need to
- * traverse the list. New elements can be added to the list after
- * an existing element, at the head of the list, or at the end of the
- * list. A tail queue may only be traversed in the forward 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.
- */
-
-/*
- * List definitions.
- */
-#define LIST_HEAD(name, type)						\
-struct name {								\
-	struct type *lh_first;	/* first element */			\
-}
-
-#define LIST_ENTRY(type)						\
-struct {								\
-	struct type *le_next;	/* next element */			\
-	struct type **le_prev;	/* address of previous next element */	\
-}
-
-/*
- * List functions.
- */
-#define	LIST_INIT(head) {						\
-	(head)->lh_first = NULL;					\
-}
-
-#define LIST_INSERT_AFTER(listelm, elm, field) {			\
-	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;		\
-}
-
-#define LIST_INSERT_HEAD(head, elm, field) {				\
-	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;			\
-}
-
-#define LIST_REMOVE(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;			\
-}
-
-/*
- * 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_ENTRY(type)						\
-struct {								\
-	struct type *tqe_next;	/* next element */			\
-	struct type **tqe_prev;	/* address of previous next element */	\
-}
-
-/*
- * Tail queue functions.
- */
-#define	TAILQ_INIT(head) {						\
-	(head)->tqh_first = NULL;					\
-	(head)->tqh_last = &(head)->tqh_first;				\
-}
-
-#define TAILQ_INSERT_HEAD(head, elm, field) {				\
-	if (((elm)->field.tqe_next = (head)->tqh_first) != NULL)	\
-		(elm)->field.tqe_next->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;			\
-}
-
-#define TAILQ_INSERT_TAIL(head, elm, field) {				\
-	(elm)->field.tqe_next = NULL;					\
-	(elm)->field.tqe_prev = (head)->tqh_last;			\
-	*(head)->tqh_last = (elm);					\
-	(head)->tqh_last = &(elm)->field.tqe_next;			\
-}
-
-#define TAILQ_INSERT_AFTER(head, listelm, elm, field) {			\
-	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;		\
-}
-
-#define TAILQ_REMOVE(head, elm, field) {				\
-	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;			\
-}
-
-/*
- * Circular queue definitions.
- */
-#define CIRCLEQ_HEAD(name, type)					\
-struct name {								\
-	struct type *cqh_first;		/* first element */		\
-	struct type *cqh_last;		/* last element */		\
-}
-
-#define CIRCLEQ_ENTRY(type)						\
-struct {								\
-	struct type *cqe_next;		/* next element */		\
-	struct type *cqe_prev;		/* previous element */		\
-}
-
-/*
- * Circular queue functions.
- */
-#define	CIRCLEQ_INIT(head) {						\
-	(head)->cqh_first = (void *)(head);				\
-	(head)->cqh_last = (void *)(head);				\
-}
-
-#define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) {		\
-	(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);				\
-}
-
-#define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) {		\
-	(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);				\
-}
-
-#define CIRCLEQ_INSERT_HEAD(head, elm, field) {				\
-	(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);					\
-}
-
-#define CIRCLEQ_INSERT_TAIL(head, elm, field) {				\
-	(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);					\
-}
-
-#define	CIRCLEQ_REMOVE(head, elm, field) {				\
-	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;				\
-}
-#endif	/* sys/queue.h */
+/*      $NetBSD: queue.h,v 1.45.14.1 2007/07/18 20:13:24 liamjfoy Exp $ */
+
+/*
+ * Qemu version: Copy from netbsd, removed debug code, removed some of
+ * the implementations.  Left in lists, tail queues and circular queues.
+ */
+
+/*
+ * 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 _SYS_QUEUE_H_
+#define _SYS_QUEUE_H_
+
+/*
+ * This file defines three types of data structures:
+ * lists, tail queues, and circular queues.
+ *
+ * A list is headed by a single forward pointer (or an array of forward
+ * pointers for a hash table header). The elements are doubly linked
+ * so that an arbitrary element can be removed without a need to
+ * traverse the list. New elements can be added to the list before
+ * or after an existing element or at the head of the list. A list
+ * may only be traversed in the forward direction.
+ *
+ * A tail queue is headed by a pair of pointers, one to the head of the
+ * list and the other to the tail of the list. The elements are doubly
+ * linked so that an arbitrary element can be removed without a need to
+ * traverse the list. New elements can be added to the list before or
+ * after an existing element, at the head of the list, or at the end of
+ * the list. A tail queue may be traversed in either direction.
+ *
+ * A circle queue is headed by a pair of pointers, one to the head of the
+ * list and the other to the tail of the list. The elements are doubly
+ * linked so that an arbitrary element can be removed without a need to
+ * traverse the list. New elements can be added to the list before or after
+ * an existing element, at the head of the list, or at the end of the list.
+ * A circle queue may be traversed in either direction, but has a more
+ * complex end of list detection.
+ *
+ * For details on the use of these macros, see the queue(3) manual page.
+ */
+
+/*
+ * List definitions.
+ */
+#define LIST_HEAD(name, type)                                           \
+struct name {                                                           \
+        struct type *lh_first;  /* first element */                     \
+}
+
+#define LIST_HEAD_INITIALIZER(head)                                     \
+        { NULL }
+
+#define LIST_ENTRY(type)                                                \
+struct {                                                                \
+        struct type *le_next;   /* next element */                      \
+        struct type **le_prev;  /* address of previous next element */  \
+}
+
+/*
+ * List functions.
+ */
+#define LIST_INIT(head) do {                                            \
+        (head)->lh_first = NULL;                                        \
+} while (/*CONSTCOND*/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 (/*CONSTCOND*/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 (/*CONSTCOND*/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 (/*CONSTCOND*/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;                   \
+} while (/*CONSTCOND*/0)
+
+#define LIST_FOREACH(var, head, field)                                  \
+        for ((var) = ((head)->lh_first);                                \
+                (var);                                                  \
+                (var) = ((var)->field.le_next))
+
+/*
+ * List access methods.
+ */
+#define LIST_EMPTY(head)                ((head)->lh_first == NULL)
+#define LIST_FIRST(head)                ((head)->lh_first)
+#define LIST_NEXT(elm, field)           ((elm)->field.le_next)
+
+
+/*
+ * 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)                                    \
+        { NULL, &(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 functions.
+ */
+#define TAILQ_INIT(head) do {                                           \
+        (head)->tqh_first = NULL;                                       \
+        (head)->tqh_last = &(head)->tqh_first;                          \
+} while (/*CONSTCOND*/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 (/*CONSTCOND*/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 (/*CONSTCOND*/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 (/*CONSTCOND*/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 (/*CONSTCOND*/0)
+
+#define TAILQ_REMOVE(head, elm, field) do {                             \
+        if (((elm)->field.tqe_next) != NULL)                            \
+                (elm)->field.tqe_next->field.tqe_prev =                 \
+                    (elm)->field.tqe_prev;                              \
+        else                                                            \
+                (head)->tqh_last = (elm)->field.tqe_prev;               \
+        *(elm)->field.tqe_prev = (elm)->field.tqe_next;                 \
+} while (/*CONSTCOND*/0)
+
+#define TAILQ_FOREACH(var, head, field)                                 \
+        for ((var) = ((head)->tqh_first);                               \
+                (var);                                                  \
+                (var) = ((var)->field.tqe_next))
+
+#define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
+        for ((var) = (*(((struct headname *)((head)->tqh_last))->tqh_last));    \
+                (var);                                                  \
+                (var) = (*(((struct headname *)((var)->field.tqe_prev))->tqh_last)))
+
+/*
+ * Tail queue access methods.
+ */
+#define TAILQ_EMPTY(head)               ((head)->tqh_first == NULL)
+#define TAILQ_FIRST(head)               ((head)->tqh_first)
+#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))
+
+
+/*
+ * 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)                                  \
+        { (void *)&head, (void *)&head }
+
+#define CIRCLEQ_ENTRY(type)                                             \
+struct {                                                                \
+        struct type *cqe_next;          /* next element */              \
+        struct type *cqe_prev;          /* previous element */          \
+}
+
+/*
+ * Circular queue functions.
+ */
+#define CIRCLEQ_INIT(head) do {                                         \
+        (head)->cqh_first = (void *)(head);                             \
+        (head)->cqh_last = (void *)(head);                              \
+} while (/*CONSTCOND*/0)
+
+#define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do {            \
+        (elm)->field.cqe_next = (listelm)->field.cqe_next;              \
+        (elm)->field.cqe_prev = (listelm);                              \
+        if ((listelm)->field.cqe_next == (void *)(head))                \
+                (head)->cqh_last = (elm);                               \
+        else                                                            \
+                (listelm)->field.cqe_next->field.cqe_prev = (elm);      \
+        (listelm)->field.cqe_next = (elm);                              \
+} while (/*CONSTCOND*/0)
+
+#define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do {           \
+        (elm)->field.cqe_next = (listelm);                              \
+        (elm)->field.cqe_prev = (listelm)->field.cqe_prev;              \
+        if ((listelm)->field.cqe_prev == (void *)(head))                \
+                (head)->cqh_first = (elm);                              \
+        else                                                            \
+                (listelm)->field.cqe_prev->field.cqe_next = (elm);      \
+        (listelm)->field.cqe_prev = (elm);                              \
+} while (/*CONSTCOND*/0)
+
+#define CIRCLEQ_INSERT_HEAD(head, elm, field) do {                      \
+        (elm)->field.cqe_next = (head)->cqh_first;                      \
+        (elm)->field.cqe_prev = (void *)(head);                         \
+        if ((head)->cqh_last == (void *)(head))                         \
+                (head)->cqh_last = (elm);                               \
+        else                                                            \
+                (head)->cqh_first->field.cqe_prev = (elm);              \
+        (head)->cqh_first = (elm);                                      \
+} while (/*CONSTCOND*/0)
+
+#define CIRCLEQ_INSERT_TAIL(head, elm, field) do {                      \
+        (elm)->field.cqe_next = (void *)(head);                         \
+        (elm)->field.cqe_prev = (head)->cqh_last;                       \
+        if ((head)->cqh_first == (void *)(head))                        \
+                (head)->cqh_first = (elm);                              \
+        else                                                            \
+                (head)->cqh_last->field.cqe_next = (elm);               \
+        (head)->cqh_last = (elm);                                       \
+} while (/*CONSTCOND*/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;                              \
+} while (/*CONSTCOND*/0)
+
+#define CIRCLEQ_FOREACH(var, head, field)                               \
+        for ((var) = ((head)->cqh_first);                               \
+                (var) != (const void *)(head);                          \
+                (var) = ((var)->field.cqe_next))
+
+#define CIRCLEQ_FOREACH_REVERSE(var, head, field)                       \
+        for ((var) = ((head)->cqh_last);                                \
+                (var) != (const void *)(head);                          \
+                (var) = ((var)->field.cqe_prev))
+
+/*
+ * 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))
+
+#endif  /* !_SYS_QUEUE_H_ */