strform.pas

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unit StrForm;

interface

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

type
  TForm1 = class(TForm)
    ListBox1: TListBox;
    Button2: TButton;
    Button3: TButton;
    Button4: TButton;
    Button5: TButton;
    Button6: TButton;
    Button7: TButton;
    Label1: TLabel;
    Button1: TButton;
    Button8: TButton;
    procedure FormCreate(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
    procedure Button4Click(Sender: TObject);
    procedure Button5Click(Sender: TObject);
    procedure Button6Click(Sender: TObject);
    procedure Button7Click(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Button8Click(Sender: TObject);
  private
    Test, S2, S3: String;
  public
    procedure UpdateInfo;
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

function GetRefCount (const s: string) : Integer;
var
  RefCountPointer: Pointer;
begin
  if Pointer(s) <> nil then
  begin
    RefCountPointer :=
      Pointer (Integer (Pointer (s)) - 8);
    Result := Integer (RefCountPointer^);
  end
  else
    Result := 0;
end;

function GetSize (const s: String) : Integer;
var
 SizePointer: Pointer;
begin
  if Pointer(s) <> nil then
  begin
    SizePointer := Pointer (
      Integer (Pointer (s)) - 4);
    Result := Integer (SizePointer^);
  end
  else
    Result := 0;
end;

procedure TForm1.UpdateInfo;
begin
  with Listbox1.Items do
  begin
    Clear;
    Add ('Text: ' + Test);
    Add ('Pascal Size: ' + IntToStr (Length (Test)));
    Add ('PChar Size: ' + IntToStr (StrLen (PChar (Test))));
    Add (Format ('Address: %p', [Pointer (Test)]));
    Add ('Size Info: ' + IntToStr ( GetSize (Test)));
    Add ('RefCount Info: ' + IntToStr (GetRefCount (Test)));
  end;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Test := 'Test String';
  UpdateInfo;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  S2 := Test;
  UpdateInfo;
end;

procedure TForm1.Button3Click(Sender: TObject);
begin
  S2 := S2 + '*';
  UpdateInfo;
end;

procedure TForm1.Button4Click(Sender: TObject);
begin
  Test := Test + '*';
  UpdateInfo;  
end;

procedure TForm1.Button5Click(Sender: TObject);
begin
  S3 := Test;
  UpdateInfo;
end;

procedure TForm1.Button6Click(Sender: TObject);
begin
  SetLength (Test, 100);
  GetWindowText (Handle, PChar (Test), 100);
  UpdateInfo;
end;

procedure TForm1.Button7Click(Sender: TObject);
begin
  Test := PChar (Test);
  UpdateInfo;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  SetLength (Test, StrLen (PChar (Test)));
  UpdateInfo;
end;

procedure TForm1.Button8Click(Sender: TObject);
begin
  Test := '';
  UpdateInfo;
end;

end.