function RightStr(Const Str: String; Size: Word): String;
begin
  if Size > Length(Str) then Size := Length(Str) ;
    RightStr := Copy(Str, Length(Str)-Size+1, Size)
end;

function MidStr(Const Str: String; From, Size: Word): String;
begin
  MidStr := Copy(Str, From, Size)
end;

function LeftStr(Const Str: String; Size: Word): String;
begin
   LeftStr := Copy(Str, 1, Size)
end;

function LeftStrEx(const AText: string; ACount: Integer): string;
var
  I,ChrLen,
  BreakLen:Integer;
  IsMBCS:Boolean;
begin
   I := 1;
   BreakLen := 0;
   IsMBCS := False;
   if Length(AText)>ACount then
   begin
      while I<=ACount do
      begin
         if AText[I] in LeadBytes then
         begin
            ChrLen := CharLength(AText,I)-1;
            I:= I + ChrLen;
            //说明AText[ACount]不是一个中文字符的末尾
            if I>ACount then
            begin
               IsMBCS := True;
               BreakLen := I - ChrLen - 1;
               Break;
            end;
         end;
         //..
         Inc(I);
      end;
   end;
   //AText[ACount]不是半个中文字符
   if not IsMBCS then
      Result := LeftStr(AText,ACount)
   else
      Result := LeftStr(AText,BreakLen);
end;