r> 最近在瞅libevent源码...发现其和内核一样， 都是用宏实现了各种常用的链表， 刚开始觉得挺好玩的，看着看着就稀里糊涂的，为了消灭这种稀里糊涂， 那就好好看一下其实现。 其实我挺讨厌宏的， 虽然在写C代码的时候经常会用到宏， 但是仍然接受不了这种反人类的代码.
libevent 在compat/sys中有一个文件queue.h， 分别实现了单链表、双链表以及一些常用的的数据结构
/* $OpenBSD: queue.h,v 1.16 2000/09/07 19:47:59 art 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.
*/
/*
* Singly-linked List definitions.
*/
#define SLIST_HEAD(name, type) \
struct name { \
struct type *slh_first; /* first element */ \
}
#define SLIST_HEAD_INITIALIZER(head) \
{ NULL }
#ifndef _WIN32
#define SLIST_ENTRY(type) \
struct { \
struct type *sle_next; /* next element */ \
}
#endif
/*
* 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))
/*
* 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_HEAD(head, field) do { \
(head)->slh_first = (head)->slh_first->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; \
} 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); \
} 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, elm, field) do { \
if (((head)->sqh_first = (elm)->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; \
} 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); \
} 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; \
} 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); \
} while (0)
#endif /* !SYS_QUEUE_H__ */