/**
   * Append a timestamp component and a random value component to interest's name. This ensures that
   * the timestamp is greater than the timestamp used in the previous call. Then use keyChain to
   * sign the interest which appends a SignatureInfo component and a component with the signature
   * bits. If the interest lifetime is not set, this sets it.
   *
   * @param interest The interest whose name is append with components.
   * @param keyChain The KeyChain for calling sign.
   * @param certificateName The certificate name of the key to use for signing.
   * @param wireFormat A WireFormat object used to encode the SignatureInfo and to encode interest
   *     name for signing.
   */
  public void generate(
      Interest interest, KeyChain keyChain, Name certificateName, WireFormat wireFormat)
      throws SecurityException {
    double timestamp;
    synchronized (lastTimestampLock_) {
      timestamp = Math.round(Common.getNowMilliseconds());
      while (timestamp <= lastTimestamp_) timestamp += 1.0;
      // Update the timestamp now while it is locked. In the small chance that
      //   signing fails, it just means that we have bumped the timestamp.
      lastTimestamp_ = timestamp;
    }

    // The timestamp is encoded as a TLV nonNegativeInteger.
    TlvEncoder encoder = new TlvEncoder(8);
    encoder.writeNonNegativeInteger((long) timestamp);
    interest.getName().append(new Blob(encoder.getOutput(), false));

    // The random value is a TLV nonNegativeInteger too, but we know it is 8 bytes,
    //   so we don't need to call the nonNegativeInteger encoder.
    ByteBuffer randomBuffer = ByteBuffer.allocate(8);
    // Note: SecureRandom is thread safe.
    Common.getRandom().nextBytes(randomBuffer.array());
    interest.getName().append(new Blob(randomBuffer, false));

    keyChain.sign(interest, certificateName, wireFormat);

    if (interest.getInterestLifetimeMilliseconds() < 0)
      // The caller has not set the interest lifetime, so set it here.
      interest.setInterestLifetimeMilliseconds(1000.0);
  }
 /** Create a new CommandInterestGenerator and initialize the timestamp to now. */
 public CommandInterestGenerator() {
   lastTimestamp_ = Math.round(Common.getNowMilliseconds());
 }