// is nil.
func (sses3) CreateMetadata(metadata map[string]string, keyID string, kmsKey []byte, sealedKey SealedKey) map[string]string {
	if sealedKey.Algorithm != SealAlgorithm {
		logger.CriticalIf(context.Background(), Errorf("The seal algorithm '%s' is invalid for SSE-S3", sealedKey.Algorithm))
	}

	// There are two possibilities:
	// - We use a KMS -> There must be non-empty key ID and a KMS data key.

			z.PartNumber, err = dc.ReadInt()
			if err != nil {
				err = msgp.WrapError(err, "PartNumber")
				return
			}
		case "Algorithm":
			{
				var zb0002 uint
				zb0002, err = dc.ReadUint()
				if err != nil {
					err = msgp.WrapError(err, "Algorithm")
					return
				}
				z.Algorithm = BitrotAlgorithm(zb0002)
			}
		case "Hash":
			z.Hash, err = dc.ReadBytes(z.Hash)
			if err != nil {

	region := globalSite.Region
	date := UTCNow()
	scope := getScope(date, region)
	credential := fmt.Sprintf("%s/%s", accessKeyID, scope)

	// Set URL query.
	query := req.URL.Query()
	query.Set("X-Amz-Algorithm", signV4Algorithm)
	query.Set("X-Amz-Date", date.Format(iso8601Format))
	query.Set("X-Amz-Expires", strconv.FormatInt(expires, 10))
	query.Set("X-Amz-SignedHeaders", "host")
	query.Set("X-Amz-Credential", credential)

		}
		// Will get index or nil if closed.
		gotIdx = <-indexCh
		return gotIdx
	}
}

// compressSelfTest performs a self-test to ensure that compression
// algorithms completes a roundtrip. If any algorithm
// produces an incorrect checksum it fails with a hard error.
//
// compressSelfTest tries to catch any issue in the compression implementation
// early instead of silently corrupting data.

	// undefined.
	if !st.Mode().IsRegular() {
		return 0, errIsNotRegular
	}

	if verifier == nil {
		n, err = file.ReadAt(buffer, offset)
		return int64(n), err
	}

	h := verifier.algorithm.New()
	if _, err = io.Copy(h, io.LimitReader(file, offset)); err != nil {
		return 0, err
	}

	if n, err = io.ReadFull(file, buffer); err != nil {
		return int64(n), err
	}

	if err != nil {
		t.Fatal(err)
	}

		Mode:             0,
		Metadata:         nil,
		Parts:            nil,
		Erasure: ErasureInfo{
			Algorithm:    ReedSolomon.String(),
			DataBlocks:   4,
			ParityBlocks: 2,
			BlockSize:    10000,
			Index:        1,
			Distribution: []int{1, 2, 3, 4, 5, 6, 7, 8},
			Checksums: []ChecksumInfo{{
				PartNumber: 1,
				Algorithm:  HighwayHash256S,
				Hash:       nil,
			}},
		},
		MarkDeleted:      false,

	{file: "myobject", offset: 1, length: 120, algorithm: SHA256, expError: errFileCorrupt},     // 4
	{file: "myobject", offset: 3, length: 1100, algorithm: SHA256, expError: nil},               // 5
	{file: "myobject", offset: 2, length: 100, algorithm: SHA256, expError: errFileCorrupt},     // 6
	{file: "myobject", offset: 1000, length: 1001, algorithm: SHA256, expError: nil},            // 7

	sealedKey := key.Seal(extKey[:], iv, "SSE-S3", "bucket", "object")
	sealedKey.Algorithm = InsecureSealAlgorithm
	if err := key.Unseal(extKey[:], sealedKey, "SSE-S3", "bucket", "object"); err == nil {
		t.Errorf("'%s' test succeeded but it should fail because the legacy algorithm was used", sealedKey.Algorithm)
	}
}

var derivePartKeyTest = []struct {
	PartID  uint32
	PartKey string
}{

- *If total drives has many common divisors the algorithm chooses the minimum amounts of erasure sets possible for a erasure set size of any N*.  In the example with 1024 drives - 4, 8, 16 are GCD factors. With 16 drives we get a total of 64 possible sets, with 8 drives we get a total of 128 possible sets, with 4 drives we get a total of 256 possible sets. So algorithm automatically chooses 64 sets, which is *16* 64 = 1024* drives in total.