has := int64(len(buf))
		if has >= n {
			return nil
		}
		if hasFull || n > size {
			return io.ErrUnexpectedEOF
		}
		extra := n - has
		if int64(cap(buf)) >= n {
			// Extend since we have enough space.
			buf = buf[:n]
		} else {
			buf = append(buf, make([]byte, extra)...)
		}
		_, err := io.ReadFull(r, buf[has:])
		if err != nil {
			if errors.Is(err, io.EOF) {