presto-rcfile/src/main/java/io/prestosql/rcfile/binary/ByteEncoding.java/ByteEncoding/encodeColumn
class ByteEncoding:    @Override
    public void encodeColumn(Block block, SliceOutput output, EncodeOutput encodeOutput)
    {
        for (int position = 0; position < block.getPositionCount(); position++) {
            if (!block.isNull(position)) {
                output.writeByte((byte) type.getLong(block, position));
            }
            encodeOutput.closeEntry();
        }
    }