input        chan *queueItem  // input for workers
	queue        chan *queueItem  // output from workers in order
	err          error            // global error state, only touched by Reader.Read
	bufferPool   sync.Pool        // pool of []byte objects for input
	csvDstPool   sync.Pool        // pool of [][]string used for output

		}
	}

	n = len(b0) - len(b)
	switch {
	case err == io.EOF:
		return n, errMissData // Less data in dense file than sparse file
	case err != nil:
		return n, err
	case sr.logicalRemaining() == 0 && sr.physicalRemaining() > 0:
		return n, errUnrefData // More data in dense file than sparse file
	case finished:
		return n, io.EOF
	default:
		return n, nil
	}
}