zt:DupeString 與 StringOfChar 的區別

StringOfChar 是反覆 “字元” 成 “字串” 的函數;

DupeString 是反覆 “字串” 成 “新字串” 的函數;

StringOfChar 來自 System 單元, 可以直接使用;

DupeString 來自 StrUtils 單元, 使用時需要 uses StrUtils;

如果僅僅是反覆 “字元”, 當然應該用 StringOfChar , 它是用彙編代碼實現的, 速度會稍好一些.

 

 

代碼

unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;

type
TForm1 = class(TForm)
Button1: TButton;
procedure FormCreate(Sender: TObject);
procedure Button1Click(Sender: TObject);
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

uses StrUtils; {DupeString 來自這個單元}

procedure TForm1.FormCreate(Sender: TObject);
var
str: string;
begin
str := System.StringOfChar(‘A’, 5);
ShowMessage(str); {AAAAA}

str := StrUtils.DupeString(‘A’, 5);
ShowMessage(str); {AAAAA}

str := StrUtils.DupeString(‘ABC’, 5);
ShowMessage(str); {ABCABCABCABCABC}
end;

{如果只是反覆字元, StringOfChar 肯定會更快一些; 速度測試:}
procedure TForm1.Button1Click(Sender: TObject);
var
t1,t2: Cardinal;
i: Integer;
begin
t1 := GetTickCount;
for i := 0 to 1000000 do DupeString(‘A’, 5);
t1 := GetTickCount – t1;

t2 := GetTickCount;
for i := 0 to 1000000 do StringOfChar(‘A’, 5);
t2 := GetTickCount – t2;

ShowMessageFmt(‘DupeString: %d; StringOfChar: %d’, [t1,t2]);
end;

end.