Delphi X秒生成大量垃圾字符

function RandomStr(Digit:Integer):string;
var
i: integer;
s: string;
begin
s := 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
setLength(Result,Digit);
Randomize;
for i := 1 to Digit do //循环次数也就是字节数

begin
Result[I] := s[Random(Length(s)-1)+1];
end;
end;