//
// This function mutates src and returns a normalized map where:
//   - adjacent fragments are coalesced together
//   - only the last fragment may be empty
//   - the endOffset of the last fragment is the total size
func invertSparseEntries(src []sparseEntry, size int64) []sparseEntry {
	dst := src[:0]
	var pre sparseEntry
	for _, cur := range src {
		if cur.Length == 0 {