presto-rcfile/src/main/java/io/prestosql/rcfile/binary/BlockEncoding.java/BlockEncoding/encodeValueInto
class BlockEncoding:    @Override
    public final void encodeValueInto(Block block, int position, SliceOutput output)
    {
        buffer.reset();
        encodeValue(block, position, buffer);

        // structural types nested in structural types are length prefixed
        Slice slice = buffer.slice();
        output.writeInt(Integer.reverseBytes(slice.length()));
        output.writeBytes(slice);
    }