commit b555388dac71696c6a1028805094e16b5e5b2b82
Author: Nick Mathewson <[email protected]>
Date:   Fri Oct 12 17:05:06 2012 -0400

    Add a copy of OpenBSD's sys/queue.h as tor_queue.h
    
    There are as many divergent implementations of sys/queue.h as there
    are operating systems shipping it, it would seem.  They have some code
    in common, but have drifted apart, and have added other stuff named
    differently.  So I'm taking a relatively sane one, and hoping for the
    best.
    
    I'm taking OpenBSD's in particular because of the lack of external
    dependencies, the presence of a CIRCLEQ (we could use one of those in
    places), and the liberal licensing terms.
    
    I'm naming the file tor_queue.h, since historically we've run into
    trouble having headers with the same names as system headers (log.h,
    for example.)
---
 LICENSE             |   29 +++
 changes/bsd_queue   |    7 +
 src/ext/README      |    8 +
 src/ext/include.am  |    3 +-
 src/ext/tor_queue.h |  568 +++++++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 614 insertions(+), 1 deletions(-)

diff --git a/LICENSE b/LICENSE
index 47eaf97..3058377 100644
--- a/LICENSE
+++ b/LICENSE
@@ -70,6 +70,35 @@ under the following license:
  * 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.
+===============================================================================
+src/ext/tor_queue.h is licensed under the following license:
+
+ * 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.
 
 ===============================================================================
 src/config/geoip is licensed under the following license:
diff --git a/changes/bsd_queue b/changes/bsd_queue
new file mode 100644
index 0000000..024ca6f
--- /dev/null
+++ b/changes/bsd_queue
@@ -0,0 +1,7 @@
+  o Code simplification and refactoring:
+    - Start using OpenBSD's implementation of queue.h, so that we don't
+      need to hand-roll our own pointer and list structures whenever we
+      need them. (We can't rely on a sys/queue.h, since some operating
+      systems don't have them, and the ones that do have them don't all
+      present the same extensions.)
+
diff --git a/src/ext/README b/src/ext/README
index 2c303c1..7aeaba5 100644
--- a/src/ext/README
+++ b/src/ext/README
@@ -29,3 +29,11 @@ tinytest_macros.h
 
     A unit testing framework. https://github.com/nmathewson/tinytest
 
+tor_queue.h
+
+    A copy of sys/queue.h from OpenBSD.  We keep our own copy rather
+    than using sys/queue.h, since some platforms don't have a
+    sys/queue.h, and the ones that do have diverged in incompatible
+    ways.  (CIRCLEQ or no CIRCLEQ? SIMPLQ or STAILQ?)
+
+    
diff --git a/src/ext/include.am b/src/ext/include.am
index fa9ee94..ea7e58e 100644
--- a/src/ext/include.am
+++ b/src/ext/include.am
@@ -9,7 +9,8 @@ EXTHEADERS = \
   src/ext/tinytest.h   \
   src/ext/strlcat.c    \
   src/ext/strlcpy.c    \
-  src/ext/tinytest_macros.h
+  src/ext/tinytest_macros.h \
+  src/ext/tor_queue.h
 
 noinst_HEADERS+= $(EXTHEADERS)
 
diff --git a/src/ext/tor_queue.h b/src/ext/tor_queue.h
new file mode 100644
index 0000000..622301d
--- /dev/null
+++ b/src/ext/tor_queue.h
@@ -0,0 +1,568 @@
+/*     $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        _SYS_QUEUE_H_
+#define        _SYS_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 _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_SAFE(var, head, field, tvar)                      
\
+       for ((var) = SLIST_FIRST(head);                         \
+           (var) && ((tvar) = SLIST_NEXT(var, field), 1);              \
+           (var) = (tvar))
+
+/*
+ * 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_AFTER(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))
+
+#define        LIST_FOREACH_SAFE(var, head, field, tvar)                       
\
+       for ((var) = LIST_FIRST(head);                          \
+           (var) && ((tvar) = LIST_NEXT(var, field), 1);               \
+           (var) = (tvar))
+
+/*
+ * 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))
+
+#define        SIMPLEQ_FOREACH_SAFE(var, head, field, tvar)                    
\
+       for ((var) = SIMPLEQ_FIRST(head);                               \
+           (var) && ((tvar) = SIMPLEQ_NEXT(var, field), 1);            \
+           (var) = (tvar))
+
+/*
+ * 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)
+
+#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 (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_SAFE(var, head, field, tvar)                      
\
+       for ((var) = TAILQ_FIRST(head);                                 \
+           (var) != TAILQ_END(head) &&                                 \
+           ((tvar) = TAILQ_NEXT(var, field), 1);                       \
+           (var) = (tvar))
+
+
+#define TAILQ_FOREACH_REVERSE(var, head, headname, field)              \
+       for((var) = TAILQ_LAST(head, headname);                         \
+           (var) != TAILQ_END(head);                                   \
+           (var) = TAILQ_PREV(var, headname, field))
+
+#define        TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)    
\
+       for ((var) = TAILQ_LAST(head, headname);                        \
+           (var) != TAILQ_END(head) &&                                 \
+           ((tvar) = TAILQ_PREV(var, headname, field), 1);             \
+           (var) = (tvar))
+
+/*
+ * 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)
+
+/*
+ * 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_SAFE(var, head, field, tvar)                    
\
+       for ((var) = CIRCLEQ_FIRST(head);                               \
+           (var) != CIRCLEQ_END(head) &&                               \
+           ((tvar) = CIRCLEQ_NEXT(var, field), 1);                     \
+           (var) = (tvar))
+
+#define CIRCLEQ_FOREACH_REVERSE(var, head, field)                      \
+       for((var) = CIRCLEQ_LAST(head);                                 \
+           (var) != CIRCLEQ_END(head);                                 \
+           (var) = CIRCLEQ_PREV(var, field))
+
+#define        CIRCLEQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)  
\
+       for ((var) = CIRCLEQ_LAST(head, headname);                      \
+           (var) != CIRCLEQ_END(head) &&                               \
+           ((tvar) = CIRCLEQ_PREV(var, headname, field), 1);           \
+           (var) = (tvar))
+
+/*
+ * 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)
+
+#endif /* !_SYS_QUEUE_H_ */



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