const (
	IfModifiedSince   = "If-Modified-Since"
	IfUnmodifiedSince = "If-Unmodified-Since"
	IfMatch           = "If-Match"
	IfNoneMatch       = "If-None-Match"

	// Request tags used in GetObjectAttributes
	Checksum     = "Checksum"
	StorageClass = "StorageClass"
	ObjectSize   = "ObjectSize"
	ObjectParts  = "ObjectParts"

	// S3 storage class
	AmzStorageClass = "x-amz-storage-class"

	ObjectAttributes    map[string]struct{} // Attribute tags defined by the users for the GetObjectAttributes request
	MaxParts            int                 // used in GetObjectAttributes. Signals how many parts we should return
	PartNumberMarker    int                 // used in GetObjectAttributes. Signals the part number after which results should be returned

			t.Path(r.path)
		}

		// Object operations
		// HeadObject
		router.Methods(http.MethodHead).Path("/{object:.+}").
			HandlerFunc(s3APIMiddleware(api.HeadObjectHandler))

		// GetObjectAttributes
		router.Methods(http.MethodGet).Path("/{object:.+}").
			HandlerFunc(s3APIMiddleware(api.GetObjectAttributesHandler, traceHdrsS3HFlag)).
			Queries("attributes", "")

		// CopyObjectPart

		Object:       objInfo,
		ReqParams:    extractReqParams(r),
		RespElements: extractRespElements(w),
		UserAgent:    r.UserAgent(),
		Host:         handlers.GetSourceIP(r),
	})
}

// GetObjectAttributes ...
func (api objectAPIHandlers) getObjectAttributesHandler(ctx context.Context, objectAPI ObjectLayer, bucket, object string, w http.ResponseWriter, r *http.Request) {