1 files changed, 73 insertions, 0 deletions

diff --git a/OpenSim/Region/ClientStack/LindenUDP/IncomingPacketHistoryCollection.cs b/OpenSim/Region/ClientStack/LindenUDP/IncomingPacketHistoryCollection.cs
new file mode 100644
index 0000000..1f73a1d
--- /dev/null
+++ b/OpenSim/Region/ClientStack/LindenUDP/IncomingPacketHistoryCollection.cs
@@ -0,0 +1,73 @@
+/*
+ * 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 OpenSimulator 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;
+
+namespace OpenSim.Region.ClientStack.LindenUDP
+{
+    /// <summary>
+    /// A circular buffer and hashset for tracking incoming packet sequence
+    /// numbers
+    /// </summary>
+    public sealed class IncomingPacketHistoryCollection
+    {
+        private readonly uint[] m_items;
+        private HashSet<uint> m_hashSet;
+        private int m_first;
+        private int m_next;
+        private int m_capacity;
+
+        public IncomingPacketHistoryCollection(int capacity)
+        {
+            this.m_capacity = capacity;
+            m_items = new uint[capacity];
+            m_hashSet = new HashSet<uint>();
+        }
+
+        public bool TryEnqueue(uint ack)
+        {
+            lock (m_hashSet)
+            {
+                if (m_hashSet.Add(ack))
+                {
+                    m_items[m_next] = ack;
+                    m_next = (m_next + 1) % m_capacity;
+                    if (m_next == m_first)
+                    {
+                        m_hashSet.Remove(m_items[m_first]);
+                        m_first = (m_first + 1) % m_capacity;
+                    }
+
+                    return true;
+                }
+            }
+
+            return false;
+        }
+    }
+}