presto-rcfile/src/main/java/io/prestosql/rcfile/text/BooleanEncoding.java/BooleanEncoding/encodeColumn
class BooleanEncoding:    @Override
    public void encodeColumn(Block block, SliceOutput output, EncodeOutput encodeOutput)
    {
        for (int position = 0; position < block.getPositionCount(); position++) {
            if (block.isNull(position)) {
                output.writeBytes(nullSequence);
            }
            else {
                encodeValue(block, position, output);
            }
            encodeOutput.closeEntry();
        }
    }