--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/org.eclipse.core.databinding.observable/src/org/eclipse/core/databinding/observable/list/ListDiff.d	Tue Apr 21 10:55:51 2009 +0200
@@ -0,0 +1,117 @@
+/*******************************************************************************
+ * Copyright (c) 2006, 2008 IBM Corporation and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     IBM Corporation - initial API and implementation
+ *     Matthew Hall - bug 208858
+ *******************************************************************************/
+
+package org.eclipse.core.databinding.observable.list;
+
+import org.eclipse.core.internal.databinding.Util;
+
+/**
+ * Object describing a diff between two lists.
+ * 
+ * @since 1.0
+ */
+public abstract class ListDiff {
+
+    /**
+     * Returns a ListDiffEntry array representing the differences in the list,
+     * in the order they are to be processed.
+     * 
+     * @return a ListDiffEntry array representing the differences in the list,
+     *         in the order they are to be processed.
+     */
+    public abstract ListDiffEntry[] getDifferences();
+
+    /**
+     * Traverses the {@link #getDifferences()} array, calling the appropriate
+     * method in <code>visitor</code> for each difference.
+     * <ol>
+     * <li>{@link ListDiffVisitor#handleReplace(int, Object, Object)} is called
+     * whenever a remove entry is immediately followed by an add entry which
+     * shares the same list index.
+     * <li>{@link ListDiffVisitor#handleMove(int, int, Object)} is called
+     * whenever a remove entry is immediately followed by an add entry with an
+     * equivalent element.
+     * <li>{@link ListDiffVisitor#handleRemove(int, Object)} is called whenever
+     * a remove entry does not match conditions 1 or 2.
+     * <li>{@link ListDiffVisitor#handleAdd(int, Object)} is called whenever an
+     * add entry does not match conditions in 1 or 2.
+     * </ol>
+     * 
+     * @param visitor
+     *            the visitor to receive callbacks.
+     * @see ListDiffVisitor
+     * @since 1.1
+     */
+    public void accept(ListDiffVisitor visitor) {
+        ListDiffEntry[] differences = getDifferences();
+        for (int i = 0; i < differences.length; i++) {
+            ListDiffEntry entry = differences[i];
+            int position = entry.getPosition();
+            Object element = entry.getElement();
+            bool addition = entry.isAddition();
+
+            if (!addition && i + 1 < differences.length) {
+                ListDiffEntry entry2 = differences[i + 1];
+                if (entry2.isAddition()) {
+                    int position2 = entry2.getPosition();
+                    Object element2 = entry2.getElement();
+                    if (position is position2) {
+                        visitor.handleReplace(position, element, element2);
+                        i++;
+                        continue;
+                    }
+                    if (Util.equals(element, element2)) {
+                        visitor.handleMove(position, position2, element);
+                        i++;
+                        continue;
+                    }
+                }
+            }
+            if (addition)
+                visitor.handleAdd(position, element);
+            else
+                visitor.handleRemove(position, element);
+        }
+    }
+
+    /**
+     * @see java.lang.Object#toString()
+     */
+    public String toString() {
+        ListDiffEntry[] differences = getDifferences();
+        StringBuffer buffer = new StringBuffer();
+        buffer.append(getClass().getName());
+        
+        if (differences is null || differences.length is 0) {
+            buffer
+                .append("{}"); //$NON-NLS-1$
+        } else {
+            buffer
+                .append("{"); //$NON-NLS-1$
+            
+            for (int i = 0; i < differences.length; i++) {
+                if (i > 0)
+                    buffer.append(", "); //$NON-NLS-1$
+                
+                buffer
+                    .append("difference[") //$NON-NLS-1$
+                    .append(i)
+                    .append("] [") //$NON-NLS-1$
+                    .append(differences[i] !is null ? differences[i].toString() : "null") //$NON-NLS-1$
+                    .append("]"); //$NON-NLS-1$
+            }
+            buffer.append("}"); //$NON-NLS-1$
+        }
+        
+        return buffer.toString();
+    }
+}