链表与文件间的导入导出

一.将链表里面的内容导入到文件中

判断链表里面的内容是否为空

void judge_Linklist(List *ls, int fd)
{
	if(NULL == ls)
		return ;
	
	if(ls->head->next == NULL)
	{
		return ;
	}
	
	write_file(ls, fd);	
	
	//return TRUE;
}

将链表里面的内容写入文件

void write_file(List *ls, int fd)
{
	if(NULL == ls)
		return;
	
	Student *tmp = ls->head;
	
	while(tmp->next != NULL)	//找到链表末尾
	{
		ssize_t  ret_id      = write(fd,&tmp->next->data.id,sizeof(int));
		ssize_t  ret_name    = write(fd,tmp->next->data.name,sizeof(char));
		ssize_t  ret_tel     = write(fd,&tmp->next->data.tel,sizeof(long));
		ssize_t  ret_address = write(fd,tmp->next->data.address,sizeof(char));
		
		tmp = tmp->next;
	}
	
	return;	
}

二.将文件里面的内容导入到链表

将文件里面的内容导入链表

void file_read(List *ls,int fd)
{
	if(NULL == ls)
		return ;
	
	int ret_tmp = 0;
	int id;
	
	off_t ret = lseek(fd, 0, SEEK_SET);
	
	while ((ret_tmp = read(fd,&id, sizeof(int))) != 0)
	{
		Student *node = (Student *)malloc(sizeof(Student)/sizeof(char));//为新创建的链表分配空间
		
		if (NULL == node)
			return ;
		
		node->data.id = id;
		ssize_t  ret_name    = read(fd,node->data.name,sizeof(char));
		ssize_t  ret_tel     = read(fd,&node->data.tel,sizeof(long));
		ssize_t  ret_address = read(fd,node->data.address,sizeof(char));
		
		// 尾插
		node->next = NULL;
		
		Student *tmp = ls->head;
		
		while (tmp->next)
		{
			tmp = tmp->next;
		}
		
		tmp->next = node;
	}

	ftruncate(fd, 0);//清空文件
	
	return;	
}

检查文件是否为空

void Empty_File(List *ls,int fd)
{
	//获取文件大小
	off_t ret = lseek(fd, 0, SEEK_END);
	
	if(-1 == ret)
	{
		return;
	}

	if (ret > 0)
	{
		file_read(ls, fd);
	}
	
	return;
}