class CeosFileReader {

    public double readGn(final int n) throws IOException, IllegalCeosFormatException {
        final long streamPosition = stream.getStreamPosition();
        try {
            return readFn(n);
        } catch (IllegalCeosFormatException e) {
            final String message = String.format(CeosFileReader.EM_READING_X_TYPE, "Gn");
            throw new IllegalCeosFormatException(message, streamPosition, e);
        }
    }

    public  CeosFileReader(final ImageInputStream stream);

}