presto-rcfile/src/main/java/io/prestosql/rcfile/text/BinaryEncoding.java/BinaryEncoding/encodeValueInto
class BinaryEncoding:    @Override
    public void encodeValueInto(int depth, Block block, int position, SliceOutput output)
    {
        Slice slice = type.getSlice(block, position);
        byte[] data = slice.getBytes();
        slice = Slices.wrappedBuffer(base64Encoder.encode(data));
        output.writeBytes(slice);
    }