"fmt"
	"hash"
	"io"
)

// Tagger is the interface that wraps the basic ETag method.
type Tagger interface {
	ETag() ETag
}

type wrapReader struct {
	io.Reader
	Tagger
}

var _ Tagger = wrapReader{} // compiler check

// ETag returns the ETag of the underlying Tagger.
func (r wrapReader) ETag() ETag {
	if r.Tagger == nil {
		return nil
	}
	return r.Tagger.ETag()
}