// WriteHeaders writes the response headers for conditional requests
func (oi ObjectInfo) WriteHeaders(w http.ResponseWriter, preamble, statusCode func()) {
	preamble()

	if !oi.ModTime.IsZero() {
		w.Header().Set(xhttp.LastModified, oi.ModTime.UTC().Format(http.TimeFormat))
	}

	if oi.ETag != "" {
		w.Header()[xhttp.ETag] = []string{"\"" + oi.ETag + "\""}
	}

	if oi.Expires != "" {
		w.Header().Set(xhttp.Expires, oi.Expires)
	}

		oi1.ModTime.Unix() > oi2.LastModified.Unix() && oi1.VersionID == nullVersionID {
		return replicateNone
	}
	sz, _ := oi1.GetActualSize()

	// needs full replication
	if oi1.ETag != oi2.ETag ||
		oi1.VersionID != oi2.VersionID ||
		sz != oi2.Size ||
		oi1.DeleteMarker != oi2.IsDeleteMarker ||
		oi1.ModTime.Unix() != oi2.LastModified.Unix() {
		return replicateAll
	}

		xhttp.ServerInfo,
		xhttp.Connection,
		xhttp.AcceptRanges,
		xhttp.ContentRange,
		xhttp.ContentEncoding,
		xhttp.ContentLength,
		xhttp.ContentType,
		xhttp.ContentDisposition,
		xhttp.LastModified,
		xhttp.ContentLanguage,
		xhttp.CacheControl,
		xhttp.RetryAfter,
		xhttp.AmzBucketRegion,
		xhttp.Expires,
		"X-Amz*",
		"x-amz*",
		"*",
	}
	opts := cors.Options{

type PartInfo struct {
	// Part number that identifies the part. This is a positive integer between
	// 1 and 10,000.
	PartNumber int

	// Date and time at which the part was uploaded.
	LastModified time.Time

	// Entity tag returned when the part was initially uploaded.
	ETag string

	// Size in bytes of the part.
	Size int64

	// Real size of the object uploaded by client.
	ActualSize int64

// generates CopyObjectResponse from etag and lastModified time.
func generateCopyObjectResponse(etag string, lastModified time.Time) CopyObjectResponse {
	return CopyObjectResponse{
		ETag:         "\"" + etag + "\"",
		LastModified: amztime.ISO8601Format(lastModified.UTC()),
	}
}

// generates CopyObjectPartResponse from etag and lastModified time.

	for obj := range objCh {
		if obj.Err != nil {
			log.Fatalf("Listing error: %v", obj.Err)
		}
		fmt.Printf("Key: %s\nSize: %d\nLast Modified: %s\n===\n", obj.Key, obj.Size, obj.LastModified)
	}

		for object := range s3Client.ListObjects(context.Background(), bucket, opts) {
			if object.Err != nil {
				log.Println("FAILED: LIST with error:", object.Err)
				continue
			}
			if !minModTime.IsZero() && object.LastModified.Before(minModTime) {
				continue
			}
			if object.IsDeleteMarker {
				log.Println("SKIPPED: DELETE marker object:", objFullPath(object))
				continue
			}

		if err != nil {
			writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL)
			return
		}

		response := generateCopyObjectPartResponse(partInfo.ETag, partInfo.LastModified)
		encodedSuccessResponse := encodeResponse(response)

		// Write success response.
		writeSuccessResponseXML(w, encodedSuccessResponse)
		return
	}

	actualPartSize = length

		return
	}

	OA := new(getObjectAttributesResponse)

	if opts.Versioned {
		w.Header().Set(xhttp.AmzVersionID, objInfo.VersionID)
	}

	lastModified := objInfo.ModTime.UTC().Format(http.TimeFormat)
	w.Header().Set(xhttp.LastModified, lastModified)
	w.Header().Del(xhttp.ContentType)

	if _, ok := opts.ObjectAttributes[xhttp.Checksum]; ok {
		chkSums := objInfo.decryptChecksums(0)

	c.Assert(response.StatusCode, http.StatusOK)

	// retrieve the info of last modification time of the object from the response header.
	lastModified := response.Header.Get("Last-Modified")
	// Parse it into time.Time structure.
	t, err := time.Parse(http.TimeFormat, lastModified)
	c.Assert(err, nil)

	// make HTTP request to obtain object info.