zt:DupeString 与 StringOfChar 的区别

StringOfChar 是反复 “字符” 成 “字符串” 的函数;

DupeString 是反复 “字符串” 成 “新字符串” 的函数;

StringOfChar 来自 System 单元, 可以直接使用;

DupeString 来自 StrUtils 单元, 使用时需要 uses StrUtils;

如果仅仅是反复 “字符”, 当然应该用 StringOfChar , 它是用汇编代码实现的, 速度会稍好一些.

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 来自这个单元}

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;

{如果只是反复字符, StringOfChar 肯定会更快一些; 速度测试:}
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.