unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Memo1: TMemo;
    Memo2: TMemo;
    Button1: TButton;
    Button2: TButton;

    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

var
  mStream: TStream; {声明一个流对象}

procedure TForm1.FormCreate(Sender: TObject);
begin
  mStream := TMemoryStream.Create;
  {TStream 是抽象类, 只能通过其子类实例化; 这里我们用了内存流来生成实例}

  Memo1.Lines.Text := 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
  {给 Memo1 个初始值}
end;


procedure TForm1.Button1Click(Sender: TObject);
begin
  Memo1.Lines.SaveToStream(mStream);       {把 Memo1 中的内容写入到流}

  ShowMessage(IntToStr(mStream.Size));     {26, 当前流的大小}
  ShowMessage(IntToStr(mStream.Position)); {26, 当前流的指针}
end;


procedure TForm1.Button2Click(Sender: TObject);
begin
  mStream.Position := 4;               {调整流的当前指针位置}
  Memo2.Lines.LoadFromStream(mStream); {读出流中的内容到 Memo2}

  {
    现在 Memo2 中的内容应该是: EFGHIJKLMNOPQRSTUVWXYZ
    如果 Position 是 0, Memo2 读出的内容会是: ABCDEFGHIJKLMNOPQRSTUVWXYZ
    如果 Position 等于 Size, 在这里如果是 26, Memo2 就读不出什么了.
  }

end;


procedure TForm1.FormDestroy(Sender: TObject);
begin
  mStream.Free; {流释放时, 所用内存当然也会同时释放}
end;

end.