presto-orc/src/main/java/io/prestosql/orc/OrcReader.java/OrcReader/isValidHeaderMagic
class OrcReader:    private static boolean isValidHeaderMagic(OrcDataSource source)
            throws IOException
    {
        Slice headerMagic = source.readFully(0, MAGIC.length());
        return MAGIC.equals(headerMagic);
    }