日期字符转化成时间戳
时间戳转化成日期

           /*                   @param       date                   @param       formart  of date                   @return      time_t                   @author      yangqijun@outlook.com                 */                time_t strtotime(char* const date,char* const format="%Y%m%d%H%M%S")                {                        struct tm tm;                        strptime(date,format, &tm) ;                        time_t ft=mktime(&tm);                        return ft;                }           string   timetodate(time_t const timer)                {                        struct tm *l=localtime(&timer);                           char buf[128];                        snprintf(buf,sizeof(buf),"%04d-%02d-%02d %02d:%02d:%02d",l->tm_year+1900,l->tm_mon+1,l->tm_mday,l->tm_hour,l->tm_min,l->tm_sec);                        string s(buf);                        return s;                      }