一個統一的連結串列結構 (轉)

一個統一的連結串列結構 (轉)[@more@]

這是在下面最常用的一個統一的連結串列結構，Linux就是用這個結構將所有的、Device什麼的都分別串在一起。我覺得寫得非常好，大家來看一看。

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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 l counter.
 * @head: the head for your list.
 */
#define list_for_each(pos, head)
　　for (p= (head)->next; pos != (head); pos = pos->next)

#endif /* __KERNEL__ */

#endif

補充一下——給看不懂的同志。

它是個雙向的迴圈連結串列，這個連結串列可以用到任何結構裡，比如：

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

再有一個連結串列頭：LIST_HEAD(kk_list)

然後連結串列的時候是這樣的，比如要把一個新結點kk_node加到連結串列尾

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

只是把結點中的list成員加進去，要獲得某個包含list_head節點的結構指標

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

當呼叫delete操作時，僅僅是把結點從連結串列中去掉，並不真正釋放結點所佔用的空間，因為這是個通用結構嘛，分配釋放由自己管理。