isbadstringptru.pas

DelphiWin32核心API参考光盘内容.是学习书籍中的源码,便于学习.

unit IsBadStringPtru;

interface

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

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.Button1Click(Sender: TObject);
var
  Stringptr : PChar;
begin
  Stringptr := StrAlloc(20);
  Stringptr := 'Delphi Rocks';

  {Try for valid string access}
  If IsBadStringPtr(Stringptr, 20)
    then ShowMessage('no read access to string')
    else ShowMessage('Valid read access to string');
end;

procedure TForm1.Button2Click(Sender: TObject);
var
  Stringptr: PChar;
begin
  {try for invalid access}
  Stringptr := nil;
  if IsBadStringPtr(Stringptr,10000)
    then ShowMessage('no read access to string')
    else ShowMessage('Valid read access to string');
end;

end.