// Serializable - interface for serializable objects
//
// Copyright (C) 1996 by Jef Poskanzer <jef@mail.acme.com>.  All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
// OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
// OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
// SUCH DAMAGE.
//
// Visit the ACME Labs Java page for up-to-date versions of this and other
// fine Java utilities: http://www.acme.com/java/

package Acme;

import java.io.*;

/// Interface for serializable objects.
// <P>
// This implementation of serialization is much simpler and less convenient
// to use than the official one that will be in JDK1.1; but it has the
// significant albeit temporary advantage that it works in current browsers.
// <P>
// One thing this version does not do is handle cyclic graphs of objects.
// It only handles tree-shaped graphs.  If you need to serialize more
// complicated structures, consider using an ID-based scheme - instead of
// having your objects contain actual references to other objects, have
// them contain IDs which can be translated into real references by an
// ID-manager class.  This scheme also has the advantage that you don't
// have to deserialize the entire graph all at once, you can do it piece
// by piece as needed, and you can even set up a least-recently-used
// flush policy in the ID-manager.
// <P>
// There are five simple steps to making your class serializable.
// <OL>
// <LI> Add "implements Acme.Serializable" to the class declaration.
// <LI> Make sure you have a no-arguments constructor that doesn't
// do anything permanent.
// <LI> Add a getVersion() method.
// <LI> Add a serialize() method that serializes all your class's variables.
// <LI> Add a deserialize() method that deserializes all your class's variables.
// </OL>
// <P>
// Here's an example of a class that uses this interface:
// <PRE><CODE>
// import java.io.*;
// 
// public class Tree implements Acme.Serializable
//     {
// 
//     long hash;
//     Tree left, right;
// 
//     /// Real constructor.
//     public Tree( long hash, Tree left, Tree right )
//         {
//         this.hash = hash;
//         this.left = left;
//         this.right = right;
//         }
// 
//     /// No-args constructor, makes a blank instance to be filled in by the
//     // deserializer.
//     public Tree()
//         {
//         }
// 
//     /// Version routine.
//     public String getVersion()
//         {
//         return "1";
//         }
// 
//     /// Serialize routine.
//     public void serialize( DataOutputStream dout ) throws IOException
//         {
//         Acme.SerialUtils.serializeLong( hash, dout );
//         Acme.SerialUtils.serializeObject( left, dout );
//         Acme.SerialUtils.serializeObject( right, dout );
//         }
// 
//     /// Deserialize routine.
//     public void deserialize( DataInputStream din ) throws IOException
//         {
//         hash = Acme.SerialUtils.deserializeLong( din );
//         left = (Tree) Acme.SerialUtils.deserializeObject(
//             this.getClass(), din );
//         right = (Tree) Acme.SerialUtils.deserializeObject(
//             this.getClass(), din );
//         }
// 
//     }
// </CODE></PRE>
// <P>
// Once you've got your class all set up, you'll need some code to
// start the serialization / deserialization process going.
// Here are examples of that:
// <PRE><CODE>
//     // Serialize.
//     Tree t = [...];
//     DataOutputStream dout = new DataOutputStream( System.out );
//     try
//         {
//         SerialUtils.serializeObject( t, dout );
//         dout.flush();
//         }
//     catch ( IOException e )
//         {
//         System.err.println( e.toString() );
//         }
//
//     // Deserialize.
//     Tree t = new Tree();
//     DataInputStream din = new DataInputStream( System.in );
//     try
//         {
//         t = (Tree) SerialUtils.deserializeObject( t.getClass(), din );
//         }
//     catch ( IOException e )
//         {
//         System.err.println( e.toString() );
//         }
// </CODE></PRE>
// <P>
// <A HREF="/resources/classes/Acme/Serializable.java">Fetch the software.</A><BR>
// <A HREF="/resources/classes/Acme.tar.gz">Fetch the entire Acme package.</A>
// <P>
// @see SerialUtils

public interface Serializable extends Versioned
    {

    /// Write a serial representation of the object to the stream.
    public void serialize( DataOutputStream dout ) throws IOException;

    /// Read a serial representation of the object from the stream.
    // The object must have already been constructed, presumably by
    // an empty no-arguments constructor.  This routine just fills
    // in the fields.
    public void deserialize( DataInputStream din ) throws IOException;

    }