内核链表例题 C语言实现

问题：

将下面的数据节点信息转换为链表结构，并遍历输出。要求根据type的值来决定val的类型。

type为1代表bool类型，2代表整形，3代表浮点型。无需解析文本，直接赋值形成节点即可。

代码：

list.c

#include <stdio.h>
#include <string.h>
#include <stdbool.h>
#include <stdlib.h>
#include "list.h"/*定义Value共用体*/
typedef union{bool bool_val;int int_val;float float_val;
} Value;/*定义Data结构体*/
typedef struct Data{int key;int type;Value val;struct list_head list;
}Data;
/*初始化结点*/
Data create_node(int key,int type,char* val_str){Data node;node.key = key;node.type = type;/*根据类型存数据*/switch(type){case 1:node.val.bool_val = atoi(val_str) != 0;break;case 2:node.val.int_val = atoi(val_str);break;case 3:node.val.float_val = atof(val_str);break;default:printf("error\n");exit(1);}node.list.next = NULL;node.list.prev = NULL;return node;
}
/*输出结点*/
void print_node(Data *tmp){switch(tmp->type){case 1:printf("key = %d,val = %s\n",tmp->key,(tmp->val.bool_val == 0 ? "false":"true"));;break;case 2:printf("key = %d,val = %d\n",tmp->key,tmp->val.int_val);break;case 3:printf("key = %d,val = %.2f\n",tmp->key,tmp->val.float_val);break;default:printf("print error\n");exit(1);}
}int main(){struct list_head head;INIT_LIST_HEAD(&head);Data data1,data2,data3;/*初始化结点*/data1 = create_node(1,2,"10");data2 = create_node(2,1,"0");data3 = create_node(3,3,"22.5");/*把结点加入链表*/list_add(&data1.list, &head);list_add(&data2.list, &head);list_add(&data3.list, &head);struct list_head *pos;Data *tmp;printf("init list\n");/*遍历链表*/list_for_each(pos, &head){tmp = list_entry(pos, Data, list); // 获取当前结点print_node(tmp); // 输出结点}printf("\n");puts("del last\n");pos = get_last(&head);list_del(pos); // 删除末尾结点printf("after del:\n");/*遍历链表*/list_for_each(pos, &head){tmp = list_entry(pos, Data, list); // 获取当前结点print_node(tmp); // 输出结点}printf("\n");
}

list.h

/***********************************************************************************
Copy right:	Coffee Tech.
Author:			wanghan
Version:		V1.0
Date:			2025-1
Description:	从linux内核抽出来链表，可以做通用链表使用，可保留
***********************************************************************************/#ifndef _LIST_H
#define _LIST_H//定义核心链表结构
struct list_head
{struct list_head *next, *prev;
};//链表初始化
static inline void INIT_LIST_HEAD(struct list_head *list)
{list->next = list;list->prev = list;
}//插入结点
static inline void __list_add(struct list_head *new_list,struct list_head *prev, struct list_head *next)
{next->prev = new_list;new_list->next = next;new_list->prev = prev;prev->next = new_list;
}//在链表头部插入
static inline void list_add(struct list_head *new_list, struct list_head *head)
{__list_add(new_list, head, head->next);
}//尾部插入结点
static inline void list_add_tail(struct list_head *new_list, struct list_head *head)
{__list_add(new_list, head->prev, head);
}static inline void __list_del(struct list_head *prev, struct list_head *next)
{next->prev = prev;prev->next = next;
}//删除任意结点
static inline void list_del(struct list_head *entry)
{__list_del(entry->prev, entry->next);
}//是否为空
static inline int list_empty(const struct list_head *head)
{return head->next == head;
}//得到第一个结点
static inline struct list_head *get_first(const struct list_head *head)
{return head->next;
}//得到最后一个结点
static inline struct list_head *get_last(const struct list_head *head)
{return head->prev;
}static inline void __list_splice(const struct list_head *list,struct list_head *prev,struct list_head *next)
{struct list_head *first = list->next;struct list_head *last = list->prev;first->prev = prev;prev->next = first;last->next = next;next->prev = last;
}/*** list_splice - join two lists, this is designed for stacks* @list: the new list to add.* @head: the place to add it in the first list.*/
static inline void list_splice(const struct list_head *list,struct list_head *head)
{if (!list_empty(list))__list_splice(list, head, head->next);
}/*** list_splice_tail - join two lists, each list being a queue* @list: the new list to add.* @head: the place to add it in the first list.*/
static inline void list_splice_tail(struct list_head *list,struct list_head *head)
{if (!list_empty(list))__list_splice(list, head->prev, head);
}//后序（指针向后走）遍历链表
#define list_for_each(pos, head) \for (pos = (head)->next; pos != (head); pos = pos->next)#define list_for_each_safe(pos, n, head) \for (pos = (head)->next, n = pos->next; pos != (head); pos = n, n = pos->next)//前序（指针向前走）遍历链表
#define list_for_each_prev(pos, head) \for (pos = (head)->prev; pos != (head); pos = pos->prev)#define offsetof_list(TYPE, MEMBER) ((size_t) & ((TYPE *)0)->MEMBER)#define list_entry(ptr, type, member) ({			\const typeof( ((type *)0)->member ) *__mptr = (ptr);	\(type *)( (char *)__mptr - offsetof_list(type,member) ); })#endif