sub apply_encoding
{
    my ($self, $meta, $fn) = @_;
    defined $fn or $fn = "file handle " . fileno ($meta->{fh});
    if (my $enc = $meta->{f_encoding}) {
	binmode $meta->{fh}, ":encoding($enc)" or
	    croak "Failed to set encoding layer '$enc' on $fn: $!";
	}
    else {
	binmode $meta->{fh} or croak "Failed to set binary mode on $fn: $!";
	}
    } # apply_encoding