code: protected int addKey(String k) {
      Integer rv = rkeys.get(k);
      if (rv == null) {
        rv = generateOpaque();
        keys.put(rv, k);
        bkeys.put(rv, KeyUtil.getKeyBytes(k));
        rkeys.put(k, rv);
        synchronized (vbmap) {
          vbmap.put(k, new Short((short) 0));
        }
      }
      return rv;
    }
docs: Add a key (and return its new opaque value).