delphi 利用TFileStream和TcxProgressBar拷贝文件

procedure TForm11.Button5Click(Sender: TObject);
var
  getPath: string;
  setPath: string;
  getstream, setstream: TFileStream;
  num, n: Integer;
  buf: PByte;
  bufsize, block: Integer;
begin
  getPath := ExtractFilePath(Application.ExeName) + '1234.zip';
  setPath := ExtractFilePath(Application.ExeName) + '1234_bak.zip';

  getstream := TFileStream.Create(getPath, fmOpenRead or fmShareExclusive);
  setstream := TFileStream.Create(setPath, fmCreate);

  num := getstream.Size;
  setstream.Size := num;
  getstream.Position := 0;
  setstream.Position := 0;

  bufsize := num;  //bufsize记录流的总大小
  block := bufsize div 100;  //block记录每块的大小
  GetMem(buf, bufsize);

  cxProgressBar1.Properties.Max := 100;
  cxProgressBar1.Properties.Min := 0;
  cxProgressBar1.Position := 0;

  while num <> 0 do
  begin
    Application.ProcessMessages;
    n := block;
    if n > num then
    begin
      n := num; //判断最后一个时, 有多少算多少
      cxProgressBar1.Position := 100;
      Break;
    end;

    getstream.Read(buf^, n);
    setstream.Write(buf^, n);
    cxProgressBar1.Position := Trunc((1 - num / bufsize) * 100);
    Dec(num, n);  //剩余大小
  end;

  FreeMem(buf, bufsize);
  getstream.Free;
  setstream.Free;

  ShowMessage('拷贝完毕!');
  cxProgressBar1.Position := 0;
end;