遍历索引时，无法获取文件的正确时间

string get_date_time(long t)
{
	char	    	datetime[32];
	struct tm	    *newtime;
	string	    	ret;

    if(t == 0)
    {
        return "";
    }

	newtime = localtime(&t);
	sprintf(datetime,"%04d-%02d-%02d %02d:%02d:%02d",
    	newtime->tm_year+1900,
    	newtime->tm_mon+1,
    	newtime->tm_mday,
    	newtime->tm_hour,
    	newtime->tm_min,
    	newtime->tm_sec);
	ret = datetime;
	return ret;
}


int search_folder(string path)
{
	DIR	            *pdir;
	struct dirent	*pentry;
	struct stat		m_stat;

	pdir = opendir(path.c_str());
	if(pdir == NULL)
    {
    	return ret_invalid_handle;
    }

	while((pentry = readdir(pdir)) != NULL)
    {
    	if(strcmp(pentry->d_name,".")==0 || strcmp(pentry->d_name,"..")==0)
        {
        	continue;
        }

    	if(pentry->d_type == DT_DIR)
        {
        	search_folder(path+"/"+pentry->d_name);
        }
    	else if(pentry->d_type == DT_REG || pentry->d_type == DT_UNKNOWN) //cygwin下，有系统属性的文件会被识别为DT_UNKNOWN类型
        {
        	lstat(pentry->d_name,&m_stat);
        	printf("%s  %s\n",get_date_time(m_stat.st_mtime).c_str(),pentry->d_name);
        }
    }

	closedir(pdir);
	return ret_ok;
}