presto-orc/src/main/java/io/prestosql/orc/writer/ListColumnWriter.java/ListColumnWriter/writeColumnarArray
class ListColumnWriter:    private void writeColumnarArray(ColumnarArray columnarArray)
    {
        // write nulls and lengths
        for (int position = 0; position < columnarArray.getPositionCount(); position++) {
            boolean present = !columnarArray.isNull(position);
            presentStream.writeBoolean(present);
            if (present) {
                nonNullValueCount++;
                lengthStream.writeLong(columnarArray.getLength(position));
            }
        }

        // write element values
        Block elementsBlock = columnarArray.getElementsBlock();
        if (elementsBlock.getPositionCount() > 0) {
            elementWriter.writeBlock(elementsBlock);
        }
    }