trunk/activemq-jmdns_1.0/src/main/java/org/apache/activemq/jmdns/DNSIncoming.java - activemq - Git at Google

 /**
  * Copyright 2003-2005 Arthur van Hoff, Rick Blair
  *
  * Licensed to the Apache Software Foundation (ASF) under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
  * The ASF licenses this file to You under the Apache License, Version 2.0
  * (the "License"); you may not use this file except in compliance with
  * the License.  You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 package org.apache.activemq.jmdns;

 import java.io.IOException;
 import java.net.DatagramPacket;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 import java.util.logging.Level;
 import java.util.logging.Logger;

 /**
  * Parse an incoming DNS message into its components.
  *
  * @version %I%, %G%
  * @author	Arthur van Hoff, Werner Randelshofer, Pierre Frisch
  */
 final class DNSIncoming
 {
     private static Logger logger = Logger.getLogger(DNSIncoming.class.toString());
     // Implementation note: This vector should be immutable.
     // If a client of DNSIncoming changes the contents of this vector,
     // we get undesired results. To fix this, we have to migrate to
     // the Collections API of Java 1.2. i.e we replace Vector by List.
     // final static Vector EMPTY = new Vector();

     private DatagramPacket packet;
     private int off;
     private int len;
     private byte data[];

     int id;
     private int flags;
     private int numQuestions;
     int numAnswers;
     private int numAuthorities;
     private int numAdditionals;
     private long receivedTime;

     List questions;
     List answers;

     /**
      * Parse a message from a datagram packet.
      */
     DNSIncoming(DatagramPacket packet) throws IOException
     {
         this.packet = packet;
         this.data = packet.getData();
         this.len = packet.getLength();
         this.off = packet.getOffset();
         this.questions = Collections.EMPTY_LIST;
         this.answers = Collections.EMPTY_LIST;
         this.receivedTime = System.currentTimeMillis();

         try
         {
             id = readUnsignedShort();
             flags = readUnsignedShort();
             numQuestions = readUnsignedShort();
             numAnswers = readUnsignedShort();
             numAuthorities = readUnsignedShort();
             numAdditionals = readUnsignedShort();

             // parse questions
             if (numQuestions > 0)
             {
                 questions = Collections.synchronizedList(new ArrayList(numQuestions));
                 for (int i = 0; i < numQuestions; i++)
                 {
                     DNSQuestion question = new DNSQuestion(readName(), readUnsignedShort(), readUnsignedShort());
                     questions.add(question);
                 }
             }

             // parse answers
             int n = numAnswers + numAuthorities + numAdditionals;
             if (n > 0)
             {
                 answers = Collections.synchronizedList(new ArrayList(n));
                 for (int i = 0; i < n; i++)
                 {
                     String domain = readName();
                     int type = readUnsignedShort();
                     int clazz = readUnsignedShort();
                     int ttl = readInt();
                     int len = readUnsignedShort();
                     int end = off + len;
                     DNSRecord rec = null;

                     switch (type)
                     {
                         case DNSConstants.TYPE_A:		// IPv4
                         case DNSConstants.TYPE_AAAA:	// IPv6 FIXME [PJYF Oct 14 2004] This has not been tested
                             rec = new DNSRecord.Address(domain, type, clazz, ttl, readBytes(off, len));
                             break;
                         case DNSConstants.TYPE_CNAME:
                         case DNSConstants.TYPE_PTR:
                             rec = new DNSRecord.Pointer(domain, type, clazz, ttl, readName());
                             break;
                         case DNSConstants.TYPE_TXT:
                             rec = new DNSRecord.Text(domain, type, clazz, ttl, readBytes(off, len));
                             break;
                         case DNSConstants.TYPE_SRV:
                             rec = new DNSRecord.Service(domain, type, clazz, ttl,
                                 readUnsignedShort(), readUnsignedShort(), readUnsignedShort(), readName());
                             break;
                         case DNSConstants.TYPE_HINFO:
                             // Maybe we should do something with those
                             break;
                         default :
                             logger.finer("DNSIncoming() unknown type:" + type);
                             break;
                     }

                     if (rec != null)
                     {
                         // Add a record, if we were able to create one.
                         answers.add(rec);
                     }
                     else
                     {
                         // Addjust the numbers for the skipped record
                         if (answers.size() < numAnswers)
                         {
                             numAnswers--;
                         }
                         else
                         {
                             if (answers.size() < numAnswers + numAuthorities)
                             {
                                 numAuthorities--;
                             }
                             else
                             {
                                 if (answers.size() < numAnswers + numAuthorities + numAdditionals)
                                 {
                                     numAdditionals--;
                                 }
                             }
                         }
                     }
                     off = end;
                 }
             }
         }
         catch (IOException e)
         {
             logger.log(Level.WARNING, "DNSIncoming() dump " + print(true) + "\n exception ", e);
             throw e;
         }
     }

     /**
      * Check if the message is a query.
      */
     boolean isQuery()
     {
         return (flags & DNSConstants.FLAGS_QR_MASK) == DNSConstants.FLAGS_QR_QUERY;
     }

     /**
      * Check if the message is truncated.
      */
     boolean isTruncated()
     {
         return (flags & DNSConstants.FLAGS_TC) != 0;
     }

     /**
      * Check if the message is a response.
      */
     boolean isResponse()
     {
         return (flags & DNSConstants.FLAGS_QR_MASK) == DNSConstants.FLAGS_QR_RESPONSE;
     }

     private int get(int off) throws IOException
     {
         if ((off < 0) || (off >= len))
         {
             throw new IOException("parser error: offset=" + off);
         }
         return data[off] & 0xFF;
     }

     private int readUnsignedShort() throws IOException
     {
         return (get(off++) << 8) + get(off++);
     }

     private int readInt() throws IOException
     {
         return (readUnsignedShort() << 16) + readUnsignedShort();
     }

     private byte[] readBytes(int off, int len) throws IOException
     {
         byte bytes[] = new byte[len];
         System.arraycopy(data, off, bytes, 0, len);
         return bytes;
     }

     private void readUTF(StringBuffer buf, int off, int len) throws IOException
     {
         for (int end = off + len; off < end;)
         {
             int ch = get(off++);
             switch (ch >> 4)
             {
                 case 0:
                 case 1:
                 case 2:
                 case 3:
                 case 4:
                 case 5:
                 case 6:
                 case 7:
                     // 0xxxxxxx
                     break;
                 case 12:
                 case 13:
                     // 110x xxxx   10xx xxxx
                     ch = ((ch & 0x1F) << 6) | (get(off++) & 0x3F);
                     break;
                 case 14:
                     // 1110 xxxx  10xx xxxx  10xx xxxx
                     ch = ((ch & 0x0f) << 12) | ((get(off++) & 0x3F) << 6) | (get(off++) & 0x3F);
                     break;
                 default:
                     // 10xx xxxx,  1111 xxxx
                     ch = ((ch & 0x3F) << 4) | (get(off++) & 0x0f);
                     break;
             }
             buf.append((char) ch);
         }
     }

     private String readName() throws IOException
     {
         StringBuffer buf = new StringBuffer();
         int off = this.off;
         int next = -1;
         int first = off;

         while (true)
         {
             int len = get(off++);
             if (len == 0)
             {
                 break;
             }
             switch (len & 0xC0)
             {
                 case 0x00:
                     //buf.append("[" + off + "]");
                     readUTF(buf, off, len);
                     off += len;
                     buf.append('.');
                     break;
                 case 0xC0:
                     //buf.append("<" + (off - 1) + ">");
                     if (next < 0)
                     {
                         next = off + 1;
                     }
                     off = ((len & 0x3F) << 8) | get(off++);
                     if (off >= first)
                     {
                         throw new IOException("bad domain name: possible circular name detected");
                     }
                     first = off;
                     break;
                 default:
                     throw new IOException("bad domain name: '" + buf + "' at " + off);
             }
         }
         this.off = (next >= 0) ? next : off;
         return buf.toString();
     }

     /**
      * Debugging.
      */
     String print(boolean dump)
     {
         StringBuffer buf = new StringBuffer();
         buf.append(toString() + "\n");
         for (Iterator iterator = questions.iterator(); iterator.hasNext();)
         {
             buf.append("    ques:" + iterator.next() + "\n");
         }
         int count = 0;
         for (Iterator iterator = answers.iterator(); iterator.hasNext(); count++)
         {
             if (count < numAnswers)
             {
                 buf.append("    answ:");
             }
             else
             {
                 if (count < numAnswers + numAuthorities)
                 {
                     buf.append("    auth:");
                 }
                 else
                 {
                     buf.append("    addi:");
                 }
             }
             buf.append(iterator.next() + "\n");
         }
         if (dump)
         {
             for (int off = 0, len = packet.getLength(); off < len; off += 32)
             {
                 int n = Math.min(32, len - off);
                 if (off < 10)
                 {
                     buf.append(' ');
                 }
                 if (off < 100)
                 {
                     buf.append(' ');
                 }
                 buf.append(off);
                 buf.append(':');
                 for (int i = 0; i < n; i++)
                 {
                     if ((i % 8) == 0)
                     {
                         buf.append(' ');
                     }
                     buf.append(Integer.toHexString((data[off + i] & 0xF0) >> 4));
                     buf.append(Integer.toHexString((data[off + i] & 0x0F) >> 0));
                 }
                 buf.append("\n");
                 buf.append("    ");
                 for (int i = 0; i < n; i++)
                 {
                     if ((i % 8) == 0)
                     {
                         buf.append(' ');
                     }
                     buf.append(' ');
                     int ch = data[off + i] & 0xFF;
                     buf.append(((ch > ' ') && (ch < 127)) ? (char) ch : '.');
                 }
                 buf.append("\n");

                 // limit message size
                 if (off + 32 >= 256)
                 {
                     buf.append("....\n");
                     break;
                 }
             }
         }
         return buf.toString();
     }

     public String toString()
     {
         StringBuffer buf = new StringBuffer();
         buf.append(isQuery() ? "dns[query," : "dns[response,");
         if (packet.getAddress() != null)
         {
             buf.append(packet.getAddress().getHostAddress());
         }
         buf.append(':');
         buf.append(packet.getPort());
         buf.append(",len=");
         buf.append(packet.getLength());
         buf.append(",id=0x");
         buf.append(Integer.toHexString(id));
         if (flags != 0)
         {
             buf.append(",flags=0x");
             buf.append(Integer.toHexString(flags));
             if ((flags & DNSConstants.FLAGS_QR_RESPONSE) != 0)
             {
                 buf.append(":r");
             }
             if ((flags & DNSConstants.FLAGS_AA) != 0)
             {
                 buf.append(":aa");
             }
             if ((flags & DNSConstants.FLAGS_TC) != 0)
             {
                 buf.append(":tc");
             }
         }
         if (numQuestions > 0)
         {
             buf.append(",questions=");
             buf.append(numQuestions);
         }
         if (numAnswers > 0)
         {
             buf.append(",answers=");
             buf.append(numAnswers);
         }
         if (numAuthorities > 0)
         {
             buf.append(",authorities=");
             buf.append(numAuthorities);
         }
         if (numAdditionals > 0)
         {
             buf.append(",additionals=");
             buf.append(numAdditionals);
         }
         buf.append("]");
         return buf.toString();
     }

     /**
      * Appends answers to this Incoming.
      *
      * @throws IllegalArgumentException If not a query or if Truncated.
      */
     void append(DNSIncoming that)
     {
         if (this.isQuery() && this.isTruncated() && that.isQuery())
         {
             this.questions.addAll(that.questions);
             this.numQuestions += that.numQuestions;

             if (Collections.EMPTY_LIST.equals(answers))
             {
                 answers = Collections.synchronizedList(new ArrayList());
             }

             if (that.numAnswers > 0)
             {
                 this.answers.addAll(this.numAnswers, that.answers.subList(0, that.numAnswers));
                 this.numAnswers += that.numAnswers;
             }
             if (that.numAuthorities > 0)
             {
                 this.answers.addAll(this.numAnswers + this.numAuthorities, that.answers.subList(that.numAnswers, that.numAnswers + that.numAuthorities));
                 this.numAuthorities += that.numAuthorities;
             }
             if (that.numAdditionals > 0)
             {
                 this.answers.addAll(that.answers.subList(that.numAnswers + that.numAuthorities, that.numAnswers + that.numAuthorities + that.numAdditionals));
                 this.numAdditionals += that.numAdditionals;
             }
         }
         else
         {
             throw new IllegalArgumentException();
         }
     }

     int elapseSinceArrival()
     {
         return (int) (System.currentTimeMillis() - receivedTime);
     }
 }
	/**
	* Copyright 2003-2005 Arthur van Hoff, Rick Blair
	*
	* Licensed to the Apache Software Foundation (ASF) under one or more
	* contributor license agreements. See the NOTICE file distributed with
	* this work for additional information regarding copyright ownership.
	* The ASF licenses this file to You under the Apache License, Version 2.0
	* (the "License"); you may not use this file except in compliance with
	* the License. You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/
	package org.apache.activemq.jmdns;

	import java.io.IOException;
	import java.net.DatagramPacket;
	import java.util.ArrayList;
	import java.util.Collections;
	import java.util.Iterator;
	import java.util.List;
	import java.util.logging.Level;
	import java.util.logging.Logger;

	/**
	* Parse an incoming DNS message into its components.
	*
	* @version %I%, %G%
	* @author Arthur van Hoff, Werner Randelshofer, Pierre Frisch
	*/
	final class DNSIncoming
	{
	private static Logger logger = Logger.getLogger(DNSIncoming.class.toString());
	// Implementation note: This vector should be immutable.
	// If a client of DNSIncoming changes the contents of this vector,
	// we get undesired results. To fix this, we have to migrate to
	// the Collections API of Java 1.2. i.e we replace Vector by List.
	// final static Vector EMPTY = new Vector();

	private DatagramPacket packet;
	private int off;
	private int len;
	private byte data[];

	int id;
	private int flags;
	private int numQuestions;
	int numAnswers;
	private int numAuthorities;
	private int numAdditionals;
	private long receivedTime;

	List questions;
	List answers;

	/**
	* Parse a message from a datagram packet.
	*/
	DNSIncoming(DatagramPacket packet) throws IOException
	{
	this.packet = packet;
	this.data = packet.getData();
	this.len = packet.getLength();
	this.off = packet.getOffset();
	this.questions = Collections.EMPTY_LIST;
	this.answers = Collections.EMPTY_LIST;
	this.receivedTime = System.currentTimeMillis();

	try
	{
	id = readUnsignedShort();
	flags = readUnsignedShort();
	numQuestions = readUnsignedShort();
	numAnswers = readUnsignedShort();
	numAuthorities = readUnsignedShort();
	numAdditionals = readUnsignedShort();

	// parse questions
	if (numQuestions > 0)
	{
	questions = Collections.synchronizedList(new ArrayList(numQuestions));
	for (int i = 0; i < numQuestions; i++)
	{
	DNSQuestion question = new DNSQuestion(readName(), readUnsignedShort(), readUnsignedShort());
	questions.add(question);
	}
	}

	// parse answers
	int n = numAnswers + numAuthorities + numAdditionals;
	if (n > 0)
	{
	answers = Collections.synchronizedList(new ArrayList(n));
	for (int i = 0; i < n; i++)
	{
	String domain = readName();
	int type = readUnsignedShort();
	int clazz = readUnsignedShort();
	int ttl = readInt();
	int len = readUnsignedShort();
	int end = off + len;
	DNSRecord rec = null;

	switch (type)
	{
	case DNSConstants.TYPE_A: // IPv4
	case DNSConstants.TYPE_AAAA: // IPv6 FIXME [PJYF Oct 14 2004] This has not been tested
	rec = new DNSRecord.Address(domain, type, clazz, ttl, readBytes(off, len));
	break;
	case DNSConstants.TYPE_CNAME:
	case DNSConstants.TYPE_PTR:
	rec = new DNSRecord.Pointer(domain, type, clazz, ttl, readName());
	break;
	case DNSConstants.TYPE_TXT:
	rec = new DNSRecord.Text(domain, type, clazz, ttl, readBytes(off, len));
	break;
	case DNSConstants.TYPE_SRV:
	rec = new DNSRecord.Service(domain, type, clazz, ttl,
	readUnsignedShort(), readUnsignedShort(), readUnsignedShort(), readName());
	break;
	case DNSConstants.TYPE_HINFO:
	// Maybe we should do something with those
	break;
	default :
	logger.finer("DNSIncoming() unknown type:" + type);
	break;
	}

	if (rec != null)
	{
	// Add a record, if we were able to create one.
	answers.add(rec);
	}
	else
	{
	// Addjust the numbers for the skipped record
	if (answers.size() < numAnswers)
	{
	numAnswers--;
	}
	else
	{
	if (answers.size() < numAnswers + numAuthorities)
	{
	numAuthorities--;
	}
	else
	{
	if (answers.size() < numAnswers + numAuthorities + numAdditionals)
	{
	numAdditionals--;
	}
	}
	}
	}
	off = end;
	}
	}
	}
	catch (IOException e)
	{
	logger.log(Level.WARNING, "DNSIncoming() dump " + print(true) + "\n exception ", e);
	throw e;
	}
	}

	/**
	* Check if the message is a query.
	*/
	boolean isQuery()
	{
	return (flags & DNSConstants.FLAGS_QR_MASK) == DNSConstants.FLAGS_QR_QUERY;
	}

	/**
	* Check if the message is truncated.
	*/
	boolean isTruncated()
	{
	return (flags & DNSConstants.FLAGS_TC) != 0;
	}

	/**
	* Check if the message is a response.
	*/
	boolean isResponse()
	{
	return (flags & DNSConstants.FLAGS_QR_MASK) == DNSConstants.FLAGS_QR_RESPONSE;
	}

	private int get(int off) throws IOException
	{
	if ((off < 0) \|\| (off >= len))
	{
	throw new IOException("parser error: offset=" + off);
	}
	return data[off] & 0xFF;
	}

	private int readUnsignedShort() throws IOException
	{
	return (get(off++) << 8) + get(off++);
	}

	private int readInt() throws IOException
	{
	return (readUnsignedShort() << 16) + readUnsignedShort();
	}

	private byte[] readBytes(int off, int len) throws IOException
	{
	byte bytes[] = new byte[len];
	System.arraycopy(data, off, bytes, 0, len);
	return bytes;
	}

	private void readUTF(StringBuffer buf, int off, int len) throws IOException
	{
	for (int end = off + len; off < end;)
	{
	int ch = get(off++);
	switch (ch >> 4)
	{
	case 0:
	case 1:
	case 2:
	case 3:
	case 4:
	case 5:
	case 6:
	case 7:
	// 0xxxxxxx
	break;
	case 12:
	case 13:
	// 110x xxxx 10xx xxxx
	ch = ((ch & 0x1F) << 6) \| (get(off++) & 0x3F);
	break;
	case 14:
	// 1110 xxxx 10xx xxxx 10xx xxxx
	ch = ((ch & 0x0f) << 12) \| ((get(off++) & 0x3F) << 6) \| (get(off++) & 0x3F);
	break;
	default:
	// 10xx xxxx, 1111 xxxx
	ch = ((ch & 0x3F) << 4) \| (get(off++) & 0x0f);
	break;
	}
	buf.append((char) ch);
	}
	}

	private String readName() throws IOException
	{
	StringBuffer buf = new StringBuffer();
	int off = this.off;
	int next = -1;
	int first = off;

	while (true)
	{
	int len = get(off++);
	if (len == 0)
	{
	break;
	}
	switch (len & 0xC0)
	{
	case 0x00:
	//buf.append("[" + off + "]");
	readUTF(buf, off, len);
	off += len;
	buf.append('.');
	break;
	case 0xC0:
	//buf.append("<" + (off - 1) + ">");
	if (next < 0)
	{
	next = off + 1;
	}
	off = ((len & 0x3F) << 8) \| get(off++);
	if (off >= first)
	{
	throw new IOException("bad domain name: possible circular name detected");
	}
	first = off;
	break;
	default:
	throw new IOException("bad domain name: '" + buf + "' at " + off);
	}
	}
	this.off = (next >= 0) ? next : off;
	return buf.toString();
	}

	/**
	* Debugging.
	*/
	String print(boolean dump)
	{
	StringBuffer buf = new StringBuffer();
	buf.append(toString() + "\n");
	for (Iterator iterator = questions.iterator(); iterator.hasNext();)
	{
	buf.append(" ques:" + iterator.next() + "\n");
	}
	int count = 0;
	for (Iterator iterator = answers.iterator(); iterator.hasNext(); count++)
	{
	if (count < numAnswers)
	{
	buf.append(" answ:");
	}
	else
	{
	if (count < numAnswers + numAuthorities)
	{
	buf.append(" auth:");
	}
	else
	{
	buf.append(" addi:");
	}
	}
	buf.append(iterator.next() + "\n");
	}
	if (dump)
	{
	for (int off = 0, len = packet.getLength(); off < len; off += 32)
	{
	int n = Math.min(32, len - off);
	if (off < 10)
	{
	buf.append(' ');
	}
	if (off < 100)
	{
	buf.append(' ');
	}
	buf.append(off);
	buf.append(':');
	for (int i = 0; i < n; i++)
	{
	if ((i % 8) == 0)
	{
	buf.append(' ');
	}
	buf.append(Integer.toHexString((data[off + i] & 0xF0) >> 4));
	buf.append(Integer.toHexString((data[off + i] & 0x0F) >> 0));
	}
	buf.append("\n");
	buf.append(" ");
	for (int i = 0; i < n; i++)
	{
	if ((i % 8) == 0)
	{
	buf.append(' ');
	}
	buf.append(' ');
	int ch = data[off + i] & 0xFF;
	buf.append(((ch > ' ') && (ch < 127)) ? (char) ch : '.');
	}
	buf.append("\n");

	// limit message size
	if (off + 32 >= 256)
	{
	buf.append("....\n");
	break;
	}
	}
	}
	return buf.toString();
	}

	public String toString()
	{
	StringBuffer buf = new StringBuffer();
	buf.append(isQuery() ? "dns[query," : "dns[response,");
	if (packet.getAddress() != null)
	{
	buf.append(packet.getAddress().getHostAddress());
	}
	buf.append(':');
	buf.append(packet.getPort());
	buf.append(",len=");
	buf.append(packet.getLength());
	buf.append(",id=0x");
	buf.append(Integer.toHexString(id));
	if (flags != 0)
	{
	buf.append(",flags=0x");
	buf.append(Integer.toHexString(flags));
	if ((flags & DNSConstants.FLAGS_QR_RESPONSE) != 0)
	{
	buf.append(":r");
	}
	if ((flags & DNSConstants.FLAGS_AA) != 0)
	{
	buf.append(":aa");
	}
	if ((flags & DNSConstants.FLAGS_TC) != 0)
	{
	buf.append(":tc");
	}
	}
	if (numQuestions > 0)
	{
	buf.append(",questions=");
	buf.append(numQuestions);
	}
	if (numAnswers > 0)
	{
	buf.append(",answers=");
	buf.append(numAnswers);
	}
	if (numAuthorities > 0)
	{
	buf.append(",authorities=");
	buf.append(numAuthorities);
	}
	if (numAdditionals > 0)
	{
	buf.append(",additionals=");
	buf.append(numAdditionals);
	}
	buf.append("]");
	return buf.toString();
	}

	/**
	* Appends answers to this Incoming.
	*
	* @throws IllegalArgumentException If not a query or if Truncated.
	*/
	void append(DNSIncoming that)
	{
	if (this.isQuery() && this.isTruncated() && that.isQuery())
	{
	this.questions.addAll(that.questions);
	this.numQuestions += that.numQuestions;

	if (Collections.EMPTY_LIST.equals(answers))
	{
	answers = Collections.synchronizedList(new ArrayList());
	}

	if (that.numAnswers > 0)
	{
	this.answers.addAll(this.numAnswers, that.answers.subList(0, that.numAnswers));
	this.numAnswers += that.numAnswers;
	}
	if (that.numAuthorities > 0)
	{
	this.answers.addAll(this.numAnswers + this.numAuthorities, that.answers.subList(that.numAnswers, that.numAnswers + that.numAuthorities));
	this.numAuthorities += that.numAuthorities;
	}
	if (that.numAdditionals > 0)
	{
	this.answers.addAll(that.answers.subList(that.numAnswers + that.numAuthorities, that.numAnswers + that.numAuthorities + that.numAdditionals));
	this.numAdditionals += that.numAdditionals;
	}
	}
	else
	{
	throw new IllegalArgumentException();
	}
	}

	int elapseSinceArrival()
	{
	return (int) (System.currentTimeMillis() - receivedTime);
	}
	}