统一的链表结构的详细介绍

这是在Linux下面最常用的一个统一的链表结构，Linux就是用这个结构将所有的Driver、Device什么的都分别串在一起。我觉得写得非常好，大家来看一看。

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#ifndef _LINUX_LIST_H
#define _LINUX_LIST_H

#ifdef __KERNEL__

struct list_head {
struct list_head *next, *prev;
};

#define LIST_HEAD_INIT(name) { &(name), &(name) }

#define LIST_HEAD(name) /
struct list_head name = LIST_HEAD_INIT(name)

#define INIT_LIST_HEAD(ptr) do { /
(ptr)->next = (ptr); (ptr)->prev = (ptr); /
} while (0)

/*
* Insert a new entry between two known consecutive entries.
* This is only for internal list manipulation where we know the prev/next entries already!
*/
static __inline__ void __list_add(struct list_head * new,struct list_head * prev,struct list_head * next)
{
next->prev = new;
new->next = next;
new->prev = prev;
prev->next = new;
}

/*
* list_add - add a new entry
* Insert a new entry after the specified head.
* This is good for implementing stacks.
*/
static __inline__ void list_add(struct list_head *new, struct list_head *head)
{
__list_add(new, head, head->next);
}

/*
* list_add_tail - add a new entry
* Insert a new entry before the specified head.
* This is useful for implementing queues.
*/
static __inline__ void list_add_tail(struct list_head *new, struct list_head *head)
{
__list_add(new, head->prev, head);
}

/*
* Delete a list entry by making the prev/next entries point to each other.
* This is only for internal list manipulation where we know the prev/next entries already!
*/
static __inline__ void __list_del(struct list_head * prev, struct list_head * next)
{
next->prev = prev;
prev->next = next;
}

/*
* list_del - deletes entry from list.
* Note: list_empty on entry does not return true after this, the entry is in an undefined state.
*/
static __inline__ void list_del(struct list_head *entry)
{
__list_del(entry->prev, entry->next);
}

/**
* list_del_init - deletes entry from list and reinitialize it.
*/
static __inline__ void list_del_init(struct list_head *entry)
{
__list_del(entry->prev, entry->next);
INIT_LIST_HEAD(entry);
}

/*
* list_empty - tests whether a list is empty
*/
static __inline__ int list_empty(struct list_head *head)
{
return head->next == head;
}

/**
* list_splice - join two lists
* @list: the new list to add.
* @head: the place to add it in the first list.
*/
static __inline__ void list_splice(struct list_head *list, struct list_head *head)
{
struct list_head *first = list->next;

if (first != list) {
struct list_head *last = list->prev;
struct list_head *at = head->next;
first->prev = head;
head->next = first;
last->next = at;
at->prev = last;
}
}

/**
* list_entry - get the struct for this entry
* @ptr:the &struct list_head pointer.
* @type:the type of the struct this is embedded in.
* @member:the name of the list_struct within the struct.
*/
#define list_entry(ptr, type, member) /
((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))

/**
* list_for_each-iterate over a list
* @pos:the &struct list_head to use as a loop counter.
* @head:the head for your list.
*/
#define list_for_each(pos, head) /
for (pos = (head)->next; pos != (head); pos = pos->next)

#endif /* __KERNEL__ */

#endif

补充一下——给看不懂的同志。

它是个双向的循环链表，这个链表可以用到任何结构里，比如：

struct kk {
type1 data1;
type2 data2;
......
struct list_head list;
typen datan;
}

再有一个链表头：LIST_HEAD(kk_list)

然后调用链表函数的时候是这样的，比如要把一个新结点kk_node加到链表尾

list_add_tail ( &(kk_node.list), &kk_list );

只是把结点中的list成员加进去，要获得某个包含list_head节点的结构指针

struct kk *p = list_entry( p, kk, list );

当调用delete操作时，仅仅是把结点从链表中去掉，并不真正释放结点所占用的空间，因为这是个通用结构嘛，分配释放由用户自己管理。