presto-rcfile/src/main/java/io/prestosql/rcfile/text/StringEncoding.java/StringEncoding/encodeColumn
class StringEncoding:    @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 {
                Slice slice = type.getSlice(block, position);
                if (escapeByte != null && slice.indexOfByte(escapeByte) < 0) {
                    throw new IllegalArgumentException("escape not implemented");
                }
                output.writeBytes(slice);
            }
            encodeOutput.closeEntry();
        }
    }