trailer http.Header

	sha256 hash.Hash
}

// Options are optional arguments to NewReaderWithOpts, Options
// simply converts positional arguments to NewReader() into a
// more flexible way to provide optional inputs. This is currently
// used by the FanOut API call mostly to disable expensive md5sum
// calculation repeatedly under hash.Reader.
type Options struct {
	MD5Hex     string
	SHA256Hex  string

// returns ETag of the content. Otherwise, it returns
// nil as ETag.
//
// Wrap provides an adapter for io.Reader implementations
// that don't implement the Tagger interface.
// It is mainly used to provide a high-level io.Reader
// access to the ETag computed by a low-level io.Reader:
//
//	content := etag.NewReader(r.Body, nil)
//
//	compressedContent := Compress(content)
//	encryptedContent := Encrypt(compressedContent)