}

// UnreadRune unreads the last rune returned by [Buffer.ReadRune].
// If the most recent read or write operation on the buffer was
// not a successful [Buffer.ReadRune], UnreadRune returns an error.  (In this regard
// it is stricter than [Buffer.UnreadByte], which will unread the last byte
// from any read operation.)
func (b *Buffer) UnreadRune() error {
	if b.lastRead <= opInvalid {

	b.lastRuneSize = size
	return r, size, nil
}

// UnreadRune unreads the last rune. If the most recent method called on
// the [Reader] was not a [Reader.ReadRune], [Reader.UnreadRune] returns an error. (In this
// regard it is stricter than [Reader.UnreadByte], which will unread the last byte
// from any read operation.)
func (b *Reader) UnreadRune() error {
	if b.lastRuneSize < 0 || b.r < b.lastRuneSize {
		return ErrInvalidUnreadRune

			if opts.Kind != nil {
				encrd, objectEncryptionKey, err := newEncryptReader(ctx, hr, opts.Kind, opts.KeyID, opts.Key, bucket, req.Key, userDefined, opts.KmsCtx)
				if err != nil {
					errs[idx] = err
					return
				}

				// do not try to verify encrypted content/
				hr, err = hash.NewReader(ctx, encrd, -1, "", "", -1)
				if err != nil {
					errs[idx] = err
					return
				}