Added support for distributed sets: unordered collections of elements

where the elements are user defined objects that know how to read and
write themselves on a stream. Sets are required to contain elements all of
the same type to make network traffic more efficient (avoid sending the
classname every time an element is added or removed).


git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@264 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/java/com/threerings/presents/dobj/EntryAddedEvent.java

@@ -0,0 +1,199 @@
+//
+// $Id: EntryAddedEvent.java,v 1.1 2001/08/16 03:31:09 mdb Exp $
+
+package com.threerings.cocktail.cher.dobj;
+
+import java.io.*;
+
+import com.threerings.cocktail.cher.Log;
+
+/**
+ * An element added event is dispatched when an element is added to a
+ * <code>DSet</code> attribute of a distributed element. It can also be
+ * constructed to request the addition of an element to a
+ * <code>DSet</code> attribute of an element and posted to the dobjmgr.
+ *
+ * @see DObjectManager#postEvent
+ */
+public class ElementAddedEvent extends TypedEvent
+{
+    /** The typed object code for this event. */
+    public static final short TYPE = TYPE_BASE + 8;
+
+    /**
+     * Constructs a new element added event on the specified target object
+     * with the supplied set attribute name and element to add.
+     *
+     * @param targetOid the object id of the object to whose set we will
+     * add an element.
+     * @param name the name of the attribute to which to add the specified
+     * element.
+     * @param elem the element to add to the set attribute.
+     */
+    public ElementAddedEvent (int targetOid, String name, DSet.Element elem)
+    {
+        super(targetOid);
+        _name = name;
+        _elem = elem;
+    }
+
+    /**
+     * Constructs a blank instance of this event in preparation for
+     * unserialization from the network.
+     */
+    public ElementAddedEvent ()
+    {
+    }
+
+    /**
+     * Returns the name of the set attribute to which an element has been
+     * added.
+     */
+    public String getName ()
+    {
+        return _name;
+    }
+
+    /**
+     * Returns the element that has been added.
+     */
+    public DSet.Element getElement ()
+    {
+        return _elem;
+    }
+
+    /**
+     * Applies this event to the object.
+     */
+    public boolean applyToObject (DObject target)
+        throws ObjectAccessException
+    {
+        DSet set = (DSet)target.getAttribute(_name);
+
+        // now that we have access to our target set, we can unflatten our
+        // element (if need be)
+        if (_elem == null) {
+            try {
+                _elem = unflatten(set, _bytes);
+            } catch (Exception e) {
+                Log.warning("Error unflattening element " + this + ".");
+                Log.logStackTrace(e);
+                return false;
+            }
+        }
+
+        set.add(_elem);
+        return true;
+    }
+
+    public short getType ()
+    {
+        return TYPE;
+    }
+
+    public void writeTo (DataOutputStream out)
+        throws IOException
+    {
+        super.writeTo(out);
+        out.writeUTF(_name);
+        flatten(out, _elem);
+    }
+
+    public void readFrom (DataInputStream in)
+        throws IOException
+    {
+        super.readFrom(in);
+        _name = in.readUTF();
+
+        // we read in the raw element data now and decode it later when we
+        // have access to the object and the DSet instance that knows what
+        // type of element we need to decode
+        int bcount = in.readInt();
+        _bytes = new byte[bcount];
+        in.readFully(_bytes, 0, bcount);
+    }
+
+    protected void toString (StringBuffer buf)
+    {
+        buf.append("ELADD:");
+        super.toString(buf);
+        buf.append(", name=").append(_name);
+        buf.append(", elem=").append(_elem);
+    }
+
+    protected String _name;
+    protected byte[] _bytes;
+    protected DSet.Element _elem;
+
+    /**
+     * Because we don't know the type of the element at the time that the
+     * event is read from the network (we only know it once the event is
+     * being applied to the object and we can ask the target
+     * <code>DSet</code> instance what type it manages), we flatten the
+     * element before writing it to the wire so that we can prepend it by
+     * a byte count. The receiver will read in the raw bytes and decode
+     * them only later when it has access to the <code>DSet</code>
+     * instance that knows what element type to use. This method should
+     * really only be called by the conmgr thread, but we synchronize just
+     * in case someone decides to write an event out in some other
+     * peculiar context. Uncontested syncs are pretty fast.
+     */
+    protected static synchronized void flatten (
+        DataOutputStream out, DSet.Element elem)
+        throws IOException
+    {
+        elem.writeTo(_dout);
+        _dout.flush();
+        out.writeInt(_bout.size());
+        _bout.writeTo(out);
+    }
+
+    /**
+     * Unflattens an element given the serialized element data. We know
+     * this will always be called on the dobjmgr thread, so we need not
+     * synchronize.
+     */
+    protected static DSet.Element unflatten (DSet set, byte[] data)
+        throws IOException
+    {
+        _bin.setBytes(data);
+        DSet.Element elem = set.newElement();
+        elem.readFrom(_din);
+        return elem;
+    }
+
+    /**
+     * We extend byte array input stream to avoid having to create a new
+     * input stream every time we unserialize an element. Our extensions
+     * allow us to repurpose this input stream to read from a new byte
+     * array each time we unserialize.
+     */
+    protected static class ReByteArrayInputStream extends ByteArrayInputStream
+    {
+        public ReByteArrayInputStream ()
+        {
+            super(new byte[0]);
+        }
+
+        public void setBytes (byte[] bytes)
+        {
+            buf = bytes;
+            pos = 0;
+            count = buf.length;
+            mark = 0;
+        }
+    }
+
+    /** Used when serializing elements. */
+    protected static ByteArrayOutputStream _bout = new ByteArrayOutputStream();
+
+    /** Used when serializing elements. */
+    protected static DataOutputStream _dout = new DataOutputStream(_bout);
+
+    /** Used when unserializing elements. */
+    protected static ReByteArrayInputStream _bin =
+        new ReByteArrayInputStream();
+
+    /** Used when unserializing elements. */
+    protected static DataInputStream _din = new DataInputStream(_bin);
+}