presto-rcfile/src/main/java/io/prestosql/rcfile/text/BooleanEncoding.java/BooleanEncoding/encodeValue
class BooleanEncoding:    private void encodeValue(Block block, int position, SliceOutput output)
    {
        if (type.getBoolean(block, position)) {
            output.writeBytes(TRUE);
        }
        else {
            output.writeBytes(FALSE);
        }
    }