if p.err != nil {
				return nil, p.err
			}
			spd = append(spd, sparseEntry{Offset: offset, Length: length})
		}

		if s.isExtended()[0] > 0 {
			// There are more entries. Read an extension header and parse its entries.
			if _, err := mustReadFull(tr.r, blk[:]); err != nil {
				return nil, err
			}
			s = blk.toSparse()
			continue
		}
		return spd, nil // Done
	}
}