用 union 将 单链表 模块化

代码如下：

#include<stdio.h>#include<string.h>#include<stdlib.h>typedef unsigned int uint32_t;typedef char         uint8_t;typedef unsigned short uint16_t;typedef struct _BOOK{char name[32];uint32_t price;}Book;typedef struct _Game{char name[32];uint32_t price;}Game;typedef union _messdata{Book* book;Game* game;}messdata;typedef enum _messtype{em_info_unable = 0,BOOK_TYPE = 1,GAME_TYPE}messtype;typedef struct __Msg{messdata node; //用联合将所有的变量都封装起来了uint8_t type;struct __Msg* next;struct __Msg* pre;}Msg;typedef struct List{Msg*  msg;uint32_t  list_len; Msg* head; Msg* cur; Msg* tail;}List;Msg *xmlmess_node_alloc(messtype type){    if (em_info_unable != type)    {        Msg *node = (Msg *)malloc(sizeof(Msg));               if (NULL != node)        {            node->type = type;            node->next     = NULL;                        switch (type)            {                case BOOK_TYPE:                    node->node.book = (Book *)malloc(sizeof(Book));                    break;                                   case GAME_TYPE:                    node->node.game = (Game *)malloc(sizeof(Game));                    break;                                          default: break;                }        }                return node;    }     return NULL;}//create a list for xmlmessint create_list(List **pplist){    if (NULL != pplist)    {        List *listtemp = (List *)malloc(sizeof(List));        if (NULL != listtemp)        {            listtemp->head = listtemp->cur = listtemp->tail = NULL;  listtemp->list_len = 0;            *pplist = listtemp;                        return 0;        }    }        return -1;}// add alist int append_list(List* list, Msg* node){if(NULL == list || NULL == node)return -1;if (NULL == list->tail){list->head= list->cur = list->tail = node;list->list_len = 1;}else{list->tail->next = node;list->tail = node;++list->list_len;}return 1;}int travel_list(List* list){if(list->list_len == 0)return ;else{Msg* tmp = list->head;while(tmp){//printf("111111111\n");tmp = tmp->next;}}}int main(){List* list = NULL;if( create_list(&list) < 0)printf("create list failed\n");Msg* msg = xmlmess_node_alloc(BOOK_TYPE);msg->type = BOOK_TYPE;memcpy(msg->node.book->name, "lcf", 4);msg->node.book->price = 32;append_list(list, msg);travel_list(list);}