# SyncMessage.java

    /*
    ** Module   : SyncMessage.java
    ** Abstract : state synchronization extensions to a standard message
    **
    ** Copyright (c) 2006-2023, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- --JPRM-- ----------------------------------Description------------------------------------
    ** 001 GES 20060726   @28197 Created initial version with state synchronization extensions to a standard
    **                           message.
    ** 002 GES 20060731   @28257 Removed extraneous call to the parent's readObject/writeObject methods since the
    **                           Java infrastructure does this for us.
    ** 003 GES 20060801   @28290 Converted to Externalizable to improve efficiency because Serializable has
    **                           unneeded processing (for versioning...) that is executed on "inflation".
    ** 004 CA  20200923          Changed StateSynchronizer to return Externalizable instances.
    **     CA  20200930          Used PayloadSerializer to write the state instance.
    ** 005 GBB 20230512          Logging methods replaced by CentralLogger/ConversionStatus.
    */
    /*
    ** This program is free software: you can redistribute it and/or modify
    ** it under the terms of the GNU Affero General Public License as
    ** published by the Free Software Foundation, either version 3 of the
    ** License, or (at your option) any later version.
    **
    ** This program is distributed in the hope that it will be useful,
    ** but WITHOUT ANY WARRANTY; without even the implied warranty of
    ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    ** GNU Affero General Public License for more details.
    **
    ** You may find a copy of the GNU Affero GPL version 3 at the following
    ** location: https://www.gnu.org/licenses/agpl-3.0.en.html
    **
    ** Additional terms under GNU Affero GPL version 3 section 7:
    **
    **   Under Section 7 of the GNU Affero GPL version 3, the following additional
    **   terms apply to the works covered under the License.  These additional terms
    **   are non-permissive additional terms allowed under Section 7 of the GNU
    **   Affero GPL version 3 and may not be removed by you.
    **
    **   0. Attribution Requirement.
    **
    **     You must preserve all legal notices or author attributions in the covered
    **     work or Appropriate Legal Notices displayed by works containing the covered
    **     work.  You may not remove from the covered work any author or developer
    **     credit already included within the covered work.
    **
    **   1. No License To Use Trademarks.
    **
    **     This license does not grant any license or rights to use the trademarks
    **     Golden Code, FWD, any Golden Code or FWD logo, or any other trademarks
    **     of Golden Code Development Corporation. You are not authorized to use the
    **     name Golden Code, FWD, or the names of any author or contributor, for
    **     publicity purposes without written authorization.
    **
    **   2. No Misrepresentation of Affiliation.
    **
    **     You may not represent yourself as Golden Code Development Corporation or FWD.
    **
    **     You may not represent yourself for publicity purposes as associated with
    **     Golden Code Development Corporation, FWD, or any author or contributor to
    **     the covered work, without written authorization.
    **
    **   3. No Misrepresentation of Source or Origin.
    **
    **     You may not represent the covered work as solely your work.  All modified
    **     versions of the covered work must be marked in a reasonable way to make it
    **     clear that the modified work is not originating from Golden Code Development
    **     Corporation or FWD.  All modified versions must contain the notices of
    **     attribution required in this license.
    */

    package com.goldencode.p2j.net;

    import java.io.*;

    import com.goldencode.util.*;

    /**
     * This class provides state synchronization extensions to a standard
     * message.  In particular, there is an additional "payload" that is
     * provided to allow any state changes that need to be synchronized to be
     * "piggybacked" into any existing message.
     *
     * @author GES
     */
    public class SyncMessage
    extends Message
    {
       /** State to be synchronized. */
       private Externalizable state = null;

       /**
        * Default constructor, used during de-serialization.
        */
       public SyncMessage()
       {
       }

       /**
        * Constructs an instance using an already existing message.
        *
        * @param    msg
        *           A valid message.  Must not be <code>null</code>.
        * @param    state
        *           The state to be piggybacked into the given message.
        */
       public SyncMessage(Message msg, Externalizable state)
       {
          super(msg);
          this.state = state;
       }

       /**
        * Get the state from the message.
        *
        * @return   The state carried in this message.
        */
       public Externalizable getState()
       {
          return state;
       }

       /**
        * Set the state in the message.
        *
        * @param    state
        *           The state to be carried in this message.
        */
       public void setState(Externalizable state)
       {
          this.state = state;
       }

       /**
        * Replacement for the default object reading method. The piggybacked
        * state is read from the input source. Note that the parent's version of
        * this method is called first because as an <code>Externalizable</code>
        * it won't be called by the serialization infrastructure.
        *
        * @param    in
        *           Input source from which fields will be restored.
        *
        * @throws   IOException
        *           In case of I/O errors.
        * @throws   ClassNotFoundException
        *           If payload can't be instantiated.
        */
       public void readExternal(ObjectInput in)
       throws IOException,
              ClassNotFoundException
       {
          super.readExternal(in);
          state = (Externalizable) PayloadSerializer.readPayload(in);
    //      LOG.finer("Deserialized: %s\n", state == null ? "null" : state.getClass().getName());
       }

       /**
        * Replacement for the default object writing method. The piggybacked
        * state is written to the output source. Note that the parent's version of
        * this method is called first because as an <code>Externalizable</code>
        * it won't be called by the serialization infrastructure.
        *
        * @param    out
        *           The output destination to which fields will be saved.
        *
        * @throws   IOException
        *           In case of I/O errors.
        */
       public void writeExternal(ObjectOutput out)
       throws IOException
       {
          super.writeExternal(out);
    //      LOG.finer("Serializing: %s\n", state == null ? "null" : state.getClass().getName());
          PayloadSerializer.writePayload(out, state);
       }
    }