sub add {
  my $self = shift;
  my $data = join '', @_;
  $self->{'size'} += length $data;
  if (defined $self->{'fh'}) {
    my $fh = $self->{'fh'};
    print $fh $data;
  }
  else {
    $self->{'data'} .= $data;
  }
}