if int64(len(p)) < unreadPartLen {
		n1, err = d.decrypter.Read(p)
		if err != nil {
			return 0, err
		}
		d.partDecRelOffset += int64(n1)
	} else {
		n1, err = io.ReadFull(d.decrypter, p[:unreadPartLen])
		if err != nil {
			return 0, err
		}

		// We should now proceed to next part, reset all
		// values appropriately.
		d.partEncRelOffset = 0
		d.partDecRelOffset = 0