SysUtils.StrCopy、SysUtils.StrECopy

StrCopy 和 StrECopy 都是复制源 PChar 串到目标 PChar 串, 只是返回值不同;
StrCopy 返回结果的首地址, StrECopy 返回结果的尾(#0)地址.

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unit Unit1;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, StdCtrls;



type

  TForm1 = class(TForm)

    Button1: TButton;

    Button2: TButton;

    Button3: TButton;

    Button4: TButton;

    procedure Button1Click(Sender: TObject);

    procedure Button2Click(Sender: TObject);

    procedure Button3Click(Sender: TObject);

    procedure Button4Click(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



//一般用法, 看不出 StrCopy 与 StrECopy 的区别

procedure TForm1.Button1Click(Sender: TObject);

var

  arr: array[0..3] of Char; {假如 PChar 长度是 3, 这里数组要大出一个, PChar 最后还有一个 #0}

begin

  StrCopy(arr, 'ABC');

  ShowMessage(arr);    {ABC}

  

  StrCopy(arr, '123');

  ShowMessage(arr);    {123}



  StrECopy(arr, 'ABC');

  ShowMessage(arr);    {ABC}

  

  StrECopy(arr, '123');

  ShowMessage(arr);    {123}

end;



//测试 StrCopy 及其返回值:

procedure TForm1.Button2Click(Sender: TObject);

var

  p1,p2,p3,p: PChar;

begin

  p1 := '123456789';

  p2 := 'ABC';



  p3 := PChar(StringOfChar(#0, 9)); {这里用 StringOfChar 代替了 GetMem}

  

  p := StrCopy(p3, p1);

  ShowMessageFmt('%s, %s', [p3, p]); {123456789, 123456789}



  p := StrCopy(p3, p2);

  ShowMessageFmt('%s, %s', [p3, p]); {ABC, ABC}



  ShowMessageFmt('%s, %s', [p3+4, p+4]); {56789, 56789}

end;



//测试 StrECopy 及其返回值:

procedure TForm1.Button3Click(Sender: TObject);

var

  p1,p2,p3,p: PChar;

begin

  p1 := '123456789';

  p2 := 'ABC';



  p3 := PChar(StringOfChar(#0, 9)); {这里用 StringOfChar 代替了 GetMem}

  

  p := StrECopy(p3, p1);

  ShowMessageFmt('%s, %s', [p3, p]); {123456789, }



  p := StrECopy(p3, p2);

  ShowMessageFmt('%s, %s', [p3, p+1]); {ABC, 56789}

end;





//可以巧妙利用 StrECopy 的返回值:

procedure TForm1.Button4Click(Sender: TObject);

var

  p: PChar;

begin

  GetMem(p, 10);



  StrECopy(StrECopy(p,'12345'), '67890');

  ShowMessage(p); {1234567890}

  

  FreeMem(p);

end;



end.


 
   

SysUtils 单元下的公用函数目录

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