Oracle函数值取字符串真实长度

create or replace function f_getstrlen(pv_String in varchar2) return integer is
  Result integer;
  i number;
begin
  Result:=0;
  if length(pv_String)=0 then
    return(Result);
  end if;
  for i in 1 .. length(pv_String) loop
    if ascii(substr(pv_String,i,1))<256 then
      Result:=Result+1;
    else
      Result:=Result+2;
    end if;
  end loop;
  return(Result);
end f_getstrlen;