mysql二元分词法函数

DELIMITER $$;
DROP FUNCTION IF EXISTS `radius`.`fun_split`$$
CREATE DEFINER=`root`@`%` FUNCTION `fun_split`(nm varchar(100)) RETURNS varchar(500) CHARSET latin1    READS SQL DATABEGIN      declare i int;      declare rtn int;      declare rtn1 int;      declare sec varchar(10);      declare rtnstr varchar(500);          set i=1;      set rtnstr='';          WHILE i <length(nm) DO      set rtn= ascii(substring(nm,i,1));      IF rtn>127 THEN          set rtn1= ascii(right(substring(nm,i,2),1));         IF rtn1> 127 THEN            IF i<length(nm)-1 THEN          IF (ascii(right(substring(nm,i,3),1))>127 and ascii(right(substring(nm,i,4),1))>127) THEN             set sec=concat(right(concat('00',rtn-160),2),right(concat('00',rtn1-160),2),right(concat('00',ascii(right(substring(nm,i,3),1))-160),2),right(concat('00',ascii(right(substring(nm,i,4),1))-160),2),' ');          ELSE             set sec='';          END IF;            ELSE          set sec='';            END IF ;         ELSE            set sec=concat(char(rtn),char(rtn1));         END IF;         SET i = i + 1;      ELSE          IF i<length(nm)-1 THEN          IF (ascii(right(substring(nm,i,2),1))>127 and ascii(right(substring(nm,i,3),1))>127) THEN              set sec=concat(char(rtn),' ');          ELSE              set sec=char(rtn);          END IF;         ELSE          IF (ascii(right(substring(nm,i,2),1))>127 and ascii(right(substring(nm,i,3),1))>127) THEN              set sec=char(rtn);          ELSE              set sec=char(rtn,ascii(right(substring(nm,i,2),1)));          END IF;         END IF;               END IF;      set rtnstr=concat(rtnstr,sec);      SET i = i + 1;            END WHILE;       RETURN rtnstr;      END$$
DELIMITER ;$$