tailq

 

首先看一下这个TAILQ链表的结构，TAILQ链表包括两个部分，一个叫HEAD的头部，另外一个就是ENTRY实体部分；下面是两部分的定义和一些典型的操作宏，分析可得出tailq 各个字段的含义，如下图所示。

#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;/* addr of previous next element*/ \
}                                                                
 
#define	TAILQ_INIT(head) do {				\
	(head)->tqh_first = NULL;				\
	(head)->tqh_last = &(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)
 

 

 

其他常用宏如下。----在linux的/usr/include/sys/queue.h头文件下

#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))


#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_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)