实验2:内核链表

操作

定义

内核中定义的双向循环链表 /include/linux/types.h

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

声明和初始化

声明：

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

声明并初始化：

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

static inline void INIT_LIST_HEAD(struct list_head *list)
{
	list->next = list;
	list->prev = list;
}

插入

从头部插入

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
 * @new: new entry to be added
 * @head: list head to add it after
 *
 * 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);
}

从尾部插入

/**
 * list_add_tail - add a new entry
 * @new: new entry to be added
 * @head: list head to add it before
 *
 * 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);
}

删除

/*
 * 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;
}

遍历

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

/**
 * list_for_each_safe - iterate over a list safe against removal of list entry
 * @pos:	the &struct list_head to use as a loop cursor.
 * @n:		another &struct list_head to use as temporary storage
 * @head:	the head for your list.
 */
#define list_for_each_safe(pos, n, head) \
	for (pos = (head)->next, n = pos->next; pos != (head); \
		pos = n, n = pos->next)

/**
 * list_for_each_entry	-	iterate over list of given type
 * @pos:	the type * to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 */
#define list_for_each_entry(pos, head, member)				\
	for (pos = list_first_entry(head, typeof(*pos), member);	\
	     &pos->member != (head);					\
	     pos = list_next_entry(pos, member))
/**
 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
 * @pos:	the type * to use as a loop cursor.
 * @n:		another type * to use as temporary storage
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 */
#define list_for_each_entry_safe(pos, n, head, member)			\
	for (pos = list_first_entry(head, typeof(*pos), member),	\
		n = list_next_entry(pos, member);			\
	     &pos->member != (head); 					\
	     pos = n, n = list_next_entry(n, member))

实验

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#include "list.h"

struct num {
	int i;
	struct list_head list;
};

int main(int argc, char **argv) {
	LIST_HEAD(test_list);
	int i;
	struct num *num;
	struct num *num1;

	srand((unsigned)time(NULL));

	/* Add */	
	printf("add 100 element into list\n");
	for (i = 0; i < 100; i++) {
		num = (struct num*)malloc(sizeof(struct num));
		num->i = i;
		list_add_tail(&num->list, &test_list);
	}

	i = 0;
	/* print list */
	printf("printf the list\n");
	list_for_each_entry(num, &test_list, list) {
		printf("%2d ", num->i);
		if ((i+1)%10 == 0)
			printf("\n");
		i++;
	}
	printf("\n");

	/* Delete */
	list_for_each_entry_safe(num, num1, &test_list, list) {
		list_del(&num->list);
		free(num);
	}

	if (list_empty(&test_list))
		printf("Free test_list successfully\n");

	return 0;
}