in   []sparseEntry
		size int64

		wantValid    bool          // Result of validateSparseEntries
		wantAligned  []sparseEntry // Result of alignSparseEntries
		wantInverted []sparseEntry // Result of invertSparseEntries
	}{{
		in: []sparseEntry{}, size: 0,
		wantValid:    true,
		wantInverted: []sparseEntry{{0, 0}},
	}, {
		in: []sparseEntry{}, size: 5000,
		wantValid:    true,

		var spd sparseDatas
		var spb []byte
		if len(hdr.SparseHoles) > 0 {
			sph := append([]sparseEntry{}, hdr.SparseHoles...) // Copy sparse map
			sph = alignSparseEntries(sph, hdr.Size)
			spd = invertSparseEntries(sph, hdr.Size)

			// Format the sparse map.
			hdr.Size = 0 // Replace with encoded size
			spb = append(strconv.AppendInt(spb, int64(len(spd)), 10), '\n')
			for _, s := range spd {
				hdr.Size += s.Length

			end -= blockPadding(-end) // Round-down to nearest blockSize
		}
		if pos < end {
			dst = append(dst, sparseEntry{Offset: pos, Length: end - pos})
		}
	}
	return dst
}

// invertSparseEntries converts a sparse map from one form to the other.
// If the input is sparseHoles, then it will output sparseDatas and vice-versa.
// The input must have been already validated.
//

			fw = &regFileWriter{w, maker.size}
			wantStr = maker.wantStr
		case makeSparse:
			if !validateSparseEntries(maker.sph, maker.size) {
				t.Fatalf("invalid sparse map: %v", maker.sph)
			}
			spd := invertSparseEntries(maker.sph, maker.size)
			fw = &regFileWriter{w, maker.makeReg.size}
			fw = &sparseFileWriter{fw, spd, 0}
			wantStr = maker.makeReg.wantStr
		default:

	// Note that it is possible for len(sp) == 0.
	if err == nil && spd != nil {
		if isHeaderOnlyType(hdr.Typeflag) || !validateSparseEntries(spd, hdr.Size) {
			return ErrHeader
		}
		sph := invertSparseEntries(spd, hdr.Size)
		tr.curr = &sparseFileReader{tr.curr, sph, 0}
	}
	return err
}

// readGNUSparsePAXHeaders checks the PAX headers for GNU sparse headers.

			fr = &regFileReader{r, maker.size}
		case makeSparse:
			if !validateSparseEntries(maker.spd, maker.size) {
				t.Fatalf("invalid sparse map: %v", maker.spd)
			}
			sph := invertSparseEntries(maker.spd, maker.size)
			r := testNonEmptyReader{strings.NewReader(maker.makeReg.str)}
			fr = &regFileReader{r, maker.makeReg.size}
			fr = &sparseFileReader{fr, sph, 0}
		default: