Behold Vilya, Ring of Air and repository for our game and virtual worldly

extensions to the distributed environment provided by Narya. git-svn-id: svn+ssh://src.earth.threerings.net/vilya/trunk@1 c613c5cb-e716-0410-b11b-feb51c14d237
2006-06-23 17:58:11 +00:00
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+//
+// $Id: SceneUpdate.java 4191 2006-06-13 22:42:20Z ray $
+//
+// Narya library - tools for developing networked games
+// Copyright (C) 2002-2004 Three Rings Design, Inc., All Rights Reserved
+// http://www.threerings.net/code/narya/
+//
+// This library is free software; you can redistribute it and/or modify it
+// under the terms of the GNU Lesser General Public License as published
+// by the Free Software Foundation; either version 2.1 of the License, or
+// (at your option) any later version.
+//
+// This library 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
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+
+package com.threerings.whirled.data;
+
+import java.io.IOException;
+
+import com.samskivert.util.StringUtil;
+
+import com.threerings.io.ObjectInputStream;
+import com.threerings.io.ObjectOutputStream;
+import com.threerings.io.Streamable;
+
+import com.threerings.whirled.Log;
+
+/**
+ * Used to encapsulate updates to scenes in such a manner that updates can
+ * be stored persistently and sent to clients to update their own local
+ * copies of scenes.
+ */
+public class SceneUpdate
+    implements Streamable, Cloneable
+{
+    /**
+     * Initializes this scene update such that it will operate on a scene
+     * with the specified target scene and version number.
+     *
+     * @param targetId the id of the scene on which we are to operate.
+     * @param targetVersion the version of the scene on which we are to
+     * operate.
+     */
+    public void init (int targetId, int targetVersion)
+    {
+        _targetId = targetId;
+        _targetVersion = targetVersion;
+    }
+
+    /**
+     * Returns the scene id for which this update is appropriate.
+     */
+    public int getSceneId ()
+    {
+        return _targetId;
+    }
+
+    /**
+     * Returns the scene version for which this update is appropriate.
+     */
+    public int getSceneVersion ()
+    {
+        return _targetVersion;
+    }
+
+    /**
+     * Called to ensure that the scene is in the appropriate state prior
+     * to applying the update.
+     *
+     * @exception IllegalStateException thrown if the update cannot be
+     * applied to the scene because it is not in a valid state
+     * (appropriate previous updates were not applied, it's the wrong kind
+     * of scene, etc.).
+     */
+    public void validate (SceneModel model)
+        throws IllegalStateException
+    {
+        if (model.sceneId != _targetId) {
+            String errmsg = "Wrong target scene, expected id " +
+                _targetId + " got id " + model.sceneId;
+            throw new IllegalStateException(errmsg);
+        }
+        if (model.version != _targetVersion) {
+            String errmsg = "Target scene not proper version, expected " +
+                _targetVersion + " got " + model.version;
+            throw new IllegalStateException(errmsg);
+        }
+    }
+
+    /**
+     * Applies this update to the specified scene model. Derived classes
+     * will want to override this method and apply updates of their own,
+     * being sure to call <code>super.apply</code>.
+     */
+    public void apply (SceneModel model)
+    {
+        // increment the version; disallowing integer overflow
+        model.version = Math.max(_targetVersion + 1, model.version);
+
+        // sanity check for the amazing two billion updates
+        if (model.version == _targetVersion) {
+            Log.warning("Egads! This scene has been updated two billion " +
+                        "times [model=" + model + ", update=" + this + "].");
+        }
+    }
+
+    /**
+     * Writes our custom streamable fields.
+     */
+    public void writeObject (ObjectOutputStream out)
+        throws IOException
+    {
+        if (null == _dbSer.get()) {
+            out.writeInt(_targetId);
+            out.writeInt(_targetVersion);
+        }
+        out.defaultWriteObject();
+    }
+
+    /**
+     * Reads our custom streamable fields.
+     */
+    public void readObject (ObjectInputStream in)
+        throws IOException, ClassNotFoundException
+    {
+        if (null == _dbSer.get()) {
+            _targetId = in.readInt();
+            _targetVersion = in.readInt();
+        }
+        in.defaultReadObject();
+    }
+
+    /**
+     * Serializes the bare representation of this instance without the scene id
+     * and version fields.  Useful when storing updates in a database where the
+     * scene id and version fields are stored in separate columns and the rest
+     * if the representation is contained in an opaque blob.
+     */
+    public void persistTo (ObjectOutputStream out)
+        throws IOException
+    {
+        _dbSer.set(Boolean.TRUE);
+        try {
+            out.writeBareObject(this);
+        } finally {
+            _dbSer.set(null);
+        }
+    }
+
+    /**
+     * Unserializes this instance from the bare representation created by
+     * {@link #persistTo}.
+     */
+    public void unpersistFrom (ObjectInputStream in)
+        throws IOException, ClassNotFoundException
+    {
+        _dbSer.set(Boolean.TRUE);
+        try {
+            in.readBareObject(this);
+        } finally {
+            _dbSer.set(null);
+        }
+    }
+    
+    /**
+     * Generates a string representation of this instance.
+     */
+    public String toString ()
+    {
+        StringBuilder buf = new StringBuilder("[");
+        toString(buf);
+        return buf.append("]").toString();
+    }
+
+    /**
+     * An extensible mechanism for generating a string representation of
+     * this instance.
+     */
+    protected void toString (StringBuilder buf)
+    {
+        buf.append("sceneId=").append(_targetId);
+        buf.append(", version=").append(_targetVersion);
+        buf.append(", ");
+        StringUtil.fieldsToString(buf, this);
+    }
+
+    /** The version number of the scene on which we operate. */
+    protected transient int _targetId;
+
+    /** The version number of the scene on which we operate. */
+    protected transient int _targetVersion;
+    
+    /** Used when serializing this update for storage in the database. */
+    protected static ThreadLocal _dbSer = new ThreadLocal();
+}