h := sha256.New()
	for i, meta := range metaArr {
		if !meta.IsValid() {
			continue
		}
		etagOnly := modTime.Equal(timeSentinel) && (etag != "" && etag == meta.Metadata["etag"])
		mtimeValid := meta.ModTime.Equal(modTime)
		if mtimeValid || etagOnly {
			fmt.Fprintf(h, "%v", meta.XLV1)
			for _, part := range meta.Parts {
				fmt.Fprintf(h, "part.%d", part.Number)
				fmt.Fprintf(h, "part.%d", part.Size)

			continue
		}
		newMeta[k] = v
	}
	return newMeta
}

// Extracts etag value from the metadata.
func extractETag(metadata map[string]string) string {
	etag, ok := metadata["etag"]
	if !ok {
		// md5Sum tag is kept for backward compatibility.
		etag = metadata["md5Sum"]
	}
	// Success.
	return etag
}

// HasPrefix - Prefix matcher string matches prefix in a platform specific way.

}

var isETagSealedTests = []struct {
	ETag     string
	IsSealed bool
}{
	{ETag: "", IsSealed: false},                                  // 0
	{ETag: "90682b8e8cc7609c4671e1d64c73fc30", IsSealed: false},  // 1
	{ETag: "f201040c9dc593e39ea004dc1323699bcd", IsSealed: true}, // 2 not valid ciphertext but looks like sealed ETag

    /**
     * Extension header set by OkHttp specifying the timestamp when the cached HTTP response was
     * first received.
     */
    private var receivedResponseMillis = 0L

    /** Etag of the cached response. */
    private var etag: String? = null

    /** Age of the cached response. */
    private var ageSeconds = -1

    /**
     * Returns true if computeFreshnessLifetime used a heuristic. If we used a heuristic to serve a

}

// Object represents object metadata of the event.
type Object struct {
	Key          string            `json:"key"`
	Size         int64             `json:"size,omitempty"`
	ETag         string            `json:"eTag,omitempty"`
	ContentType  string            `json:"contentType,omitempty"`
	UserMetadata map[string]string `json:"userMetadata,omitempty"`
	VersionID    string            `json:"versionId,omitempty"`

// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package http

// Standard S3 HTTP response constants
const (
	LastModified       = "Last-Modified"
	Date               = "Date"
	ETag               = "ETag"
	ContentType        = "Content-Type"
	ContentMD5         = "Content-Md5"
	ContentEncoding    = "Content-Encoding"
	Expires            = "Expires"
	ContentLength      = "Content-Length"

		// as well as common modtime, if modtime is not possible
		// verify if it has common "etag" at least.
		if onlineMeta[i].IsValid() && onlineMeta[i].Erasure.Equal(fi.Erasure) {
			ok := onlineMeta[i].ModTime.Equal(modTime)
			if modTime.IsZero() || modTime.Equal(timeSentinel) {
				ok = etag != "" && etag == fi.Metadata["etag"]
			}
			if ok {
				continue
			}

    // Special case some of the weird HTTP Header names...
    ImmutableBiMap<String, String> specialCases =
        ImmutableBiMap.<String, String>builder()
            .put("CDN_LOOP", "CDN-Loop")
            .put("ETAG", "ETag")
            .put("SOURCE_MAP", "SourceMap")
            .put("SEC_CH_UA_WOW64", "Sec-CH-UA-WoW64")
            .put("SEC_WEBSOCKET_ACCEPT", "Sec-WebSocket-Accept")

}

// GenETag - generate UUID based ETag
func GenETag() string {
	return ToS3ETag(getMD5Hash([]byte(mustGetUUID())))
}

// ToS3ETag - return checksum to ETag
func ToS3ETag(etag string) string {
	etag = canonicalizeETag(etag)

	if !strings.HasSuffix(etag, "-1") {
		// Tools like s3cmd uses ETag as checksum of data to validate.
		// Append "-1" to indicate ETag is not a checksum.
		etag += "-1"
	}

func GetObject(ctx context.Context, api ObjectLayer, bucket, object string, startOffset int64, length int64, writer io.Writer, etag string, opts ObjectOptions) (err error) {
	var header http.Header
	if etag != "" {
		header.Set("ETag", etag)
	}
	Range := &HTTPRangeSpec{Start: startOffset, End: startOffset + length}

	reader, err := api.GetObjectNInfo(ctx, bucket, object, Range, header, opts)