spb = append(strconv.AppendInt(spb, s.Offset, 10), '\n')
				spb = append(strconv.AppendInt(spb, s.Length, 10), '\n')
			}
			pad := blockPadding(int64(len(spb)))
			spb = append(spb, zeroBlock[:pad]...)
			hdr.Size += int64(len(spb)) // Accounts for encoded sparse map

			// Add and modify appropriate PAX records.
			dir, file := path.Split(realName)
			hdr.Name = path.Join(dir, "GNUSparseFile.0", file)