return func() []byte {
		if !fetched {
			data = input()
			fetched = true
		}
		return metadataEncrypter(key)("compression-index", data)
	}
}

// compressionIndexDecrypt reverses compressionIndexEncrypter.
func (o *ObjectInfo) compressionIndexDecrypt(input []byte, h http.Header) ([]byte, error) {
	return o.metadataDecrypter(h)("compression-index", input)
}