内核链表实现任意两个节点交换位置

#include <stdio.h>
#include "list.h" //list.h这个文件需要你自己打造，可以拷贝内核源码，也可以参考我的博文

struct data_info {
    int data;
    struct list_head list;
};

int  cmp_data(struct list_head *a, struct list_head *b)
{
    struct data_info *pa = list_entry(a, struct data_info, list);
    struct data_info *pb = list_entry(b, struct data_info, list);
    return pa->data - pb->data;
}

void  swap(struct list_head *a, struct list_head *b)//加入一个节点作为缓存作用，具有通用性，不管两个节点是相邻还是不相邻。
{
    struct  list_head flag = {NULL, NULL};
    __list_add(&flag, b->prev, b);
    list_del(b);
    __list_add(b, a->prev, a);
    list_del(a);
    __list_add(a, flag.prev, &flag);
    list_del(&flag);
}

void  bubble_sort(struct list_head *head, int  (*compar)(struct list_head *, struct list_head *))
{
    struct list_head *start = NULL; 
    struct list_head *end = NULL;   
     //采用冒泡排序算法。
    list_for_each_reverse(end, head) //从尾向头遍历。
    {   
        list_for_each(start, head) //从头向尾遍历。
        {           
            if (start == end)                       
                break;

            if (compar(start, start->next) > 0) 
            {
                swap(start, start->next);                           
                start = start->prev; //start归位
                if (start == end) 
                    end = end->next; //end归位            
            }
        }
    }
}

int main(void)
{
    struct data_info s[] =  {{6}, {4}, {7}, {9}, {2}, {8}, {5}, {1}, {3}};

    LIST_HEAD(head);
    int i;
    for (i = 0; i < sizeof s/ sizeof *s; ++i) 
    {
        list_add_tail(&s[i].list, &head);
    } //尾插，构成链表

    struct data_info *pdata = NULL;
    list_for_each_entry(pdata, &head, list) 
    {
        printf("%d ", pdata->data);
    }
    printf("\n"); //排序之前

    bubble_sort(&head, cmp_data); //进行排序

    list_for_each_entry(pdata, &head, list) 
    {
        printf("%d ", pdata->data);
    }
    printf("\n"); //排序之后
    return 0;
}