2 files changed, 130 insertions, 0 deletions

diff --git a/OpenSim/Framework/IClientAPI.cs b/OpenSim/Framework/IClientAPI.cs
index fb32397..985e085 100644
--- a/OpenSim/Framework/IClientAPI.cs
+++ b/OpenSim/Framework/IClientAPI.cs
@@ -570,6 +570,8 @@ namespace OpenSim.Framework
         event UUIDNameRequest OnTeleportHomeRequest;
         
         event ScriptAnswer OnScriptAnswer;
+
+        event AgentSit OnUndo;
          
         LLVector3 StartPos { get; set; }
 
diff --git a/OpenSim/Framework/UndoStack.cs b/OpenSim/Framework/UndoStack.cs
new file mode 100644
index 0000000..0b97644
--- /dev/null
+++ b/OpenSim/Framework/UndoStack.cs
@@ -0,0 +1,128 @@
+/*
+ * Copyright (c) Contributors, http://opensimulator.org/
+ * See CONTRIBUTORS.TXT for a full list of copyright holders.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * 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.
+ *     * Neither the name of the OpenSim Project nor the
+ *       names of its contributors may be used to endorse or promote products
+ *       derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``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 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.
+ */
+
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace OpenSim.Framework
+{
+    /// <summary>
+    /// Undo stack.  Deletes entries beyond a certain capacity
+    /// </summary>
+    /// <typeparam name="T"></typeparam>
+    [Serializable]
+    public class UndoStack<T>
+    {
+
+        private int m_new = 1;
+        private int m_old = 0;
+        private T[] m_Undos;
+
+        public bool IsFull
+        {
+            get
+            {
+                return m_new == m_old;
+            }
+        }
+
+
+        public int Capacity
+        {
+            get
+            {
+                return m_Undos.Length - 1;
+            }
+        }
+
+       
+        public UndoStack(int capacity)
+        {
+            m_Undos = new T[capacity + 1];
+        }
+
+       public void Push(T item)
+        {
+            if (IsFull)
+            {
+                m_old++;
+                if (m_old >= m_Undos.Length)
+                    m_old -= m_Undos.Length;
+            }
+            if (++m_new >= m_Undos.Length)
+                m_new -= m_Undos.Length;
+            m_Undos[m_new] = item;
+        }
+
+        public T Pop()
+        {
+            if (Count > 0)
+            {
+                T deleted = m_Undos[m_new];
+                m_Undos[m_new--] = default(T);
+                if (m_new < 0)
+                    m_new += m_Undos.Length;
+                return deleted;
+            }
+            else
+                throw new InvalidOperationException("Cannot pop from emtpy stack");
+        }
+
+        public int Count
+        {
+            get
+            {
+                int count = m_new - m_old - 1;
+                if (count < 0)
+                    count += m_Undos.Length;
+                return count;
+            }
+        }
+
+
+        public T Peek()
+        {
+            return m_Undos[m_new];
+        }
+
+       
+        public void Clear()
+        {
+            if (Count > 0)
+            {
+                for (int i = 0; i < m_Undos.Length; i++)
+                {
+                    m_Undos[i] = default(T);
+                }
+                m_new = 1;
+                m_old = 0;
+            }
+        }
+
+    }
+}
\ No newline at end of file