// The last block will be sent along with an io.EOF.
func (r *Reader) nextSplit(skip int, dst []byte) ([]byte, error) {
	if cap(dst) < skip {
		dst = make([]byte, 0, skip+1024)
	}
	dst = dst[:skip]
	if skip > 0 {
		n, err := io.ReadFull(r.buf, dst)
		if err != nil && err != io.ErrUnexpectedEOF {
			// If an EOF happens after reading some but not all the bytes,

	if r.Tagger == nil {
		return nil
	}
	return r.Tagger.ETag()
}

// Wrap returns an io.Reader that reads from the wrapped
// io.Reader and implements the Tagger interaface.
//
// If content implements Tagger then the returned Reader
// 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.