t.Fatalf("got %d headers, want %d headers", len(hdrs), len(v.headers))
			}

			for i, sum := range chksums {
				if i >= len(v.chksums) {
					t.Fatalf("entry %d: unexpected sum: got %s", i, sum)
				}
				if sum != v.chksums[i] {
					t.Fatalf("entry %d: incorrect checksum: got %s, want %s", i, sum, v.chksums[i])
				}
			}

			if err != v.err {
				t.Fatalf("unexpected error: got %v, want %v", err, v.err)

		chkSums, _ := objInfo.decryptChecksums(0, r.Header)
		// AWS does not appear to append part number on this API call.
		if len(chkSums) > 0 {
			OA.Checksum = &objectAttributesChecksum{
				ChecksumCRC32:     strings.Split(chkSums["CRC32"], "-")[0],
				ChecksumCRC32C:    strings.Split(chkSums["CRC32C"], "-")[0],
				ChecksumSHA1:      strings.Split(chkSums["SHA1"], "-")[0],

// If the checksum fails, then FormatUnknown is returned.
func (b *block) getFormat() Format {
	// Verify checksum.
	var p parser
	value := p.parseOctal(b.toV7().chksum())
	chksum1, chksum2 := b.computeChecksum()
	if p.err != nil || (value != chksum1 && value != chksum2) {
		return FormatUnknown
	}

	// Guess the magic values.
	magic := string(b.toUSTAR().magic())
	version := string(b.toUSTAR().version())