populateSparseMap := func(sa sparseArray, sps []string) []string {
		for i := 0; len(sps) > 0 && i < sa.maxEntries(); i++ {
			copy(sa.entry(i), sps[0])
			sps = sps[1:]
		}
		if len(sps) > 0 {
			copy(sa.isExtended(), "\x80")
		}
		return sps
	}

	makeInput := func(format Format, size string, sps ...string) (out []byte) {
		// Write the initial GNU header.