presto-spi/src/main/java/io/prestosql/spi/block/ByteArrayBlock.java/ByteArrayBlock/getRegion
class ByteArrayBlock:    @Override
    public Block getRegion(int positionOffset, int length)
    {
        checkValidRegion(getPositionCount(), positionOffset, length);

        return new ByteArrayBlock(positionOffset + arrayOffset, length, valueIsNull, values);
    }