From e8c1e69a0dbab1a7db894eeff6b052bbd350a8f5 Mon Sep 17 00:00:00 2001
From: John Hurliman
Date: Tue, 13 Oct 2009 18:56:54 -0700
Subject: * Copied LocklessQueue.cs into OpenSim.Framework and added the .Count
 property and .Clear() method * Changed the way the QueueEmpty callback is
 fired. It will be fired asynchronously as soon as an empty queue is detected
 (this can happen immediately following a dequeue), and will not be fired
 again until at least one packet is dequeued from that queue. This will give
 callbacks advanced notice of an empty queue and prevent callbacks from
 stacking up while the queue is empty * Added LLUDPClient.IsConnected checks
 in several places to prevent unwanted network activity after a client
 disconnects * Prevent LLClientView.Close() from being called twice every
 disconnect * Removed the packet resend limit and improved the client timeout
 check

---
 OpenSim/Framework/LocklessQueue.cs | 130 +++++++++++++++++++++++++++++++++++++
 1 file changed, 130 insertions(+)
 create mode 100644 OpenSim/Framework/LocklessQueue.cs

(limited to 'OpenSim/Framework/LocklessQueue.cs')

diff --git a/OpenSim/Framework/LocklessQueue.cs b/OpenSim/Framework/LocklessQueue.cs
new file mode 100644
index 0000000..dd3d201
--- /dev/null
+++ b/OpenSim/Framework/LocklessQueue.cs
@@ -0,0 +1,130 @@
+/*
+ * Copyright (c) 2009, openmetaverse.org
+ * All rights reserved.
+ *
+ * - 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.
+ * - Neither the name of the openmetaverse.org 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 COPYRIGHT HOLDERS AND CONTRIBUTORS "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 COPYRIGHT OWNER OR 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.Threading;
+
+namespace OpenSim.Framework
+{
+    public sealed class LocklessQueue<T>
+    {
+        private sealed class SingleLinkNode
+        {
+            public SingleLinkNode Next;
+            public T Item;
+        }
+
+        SingleLinkNode head;
+        SingleLinkNode tail;
+        int count;
+
+        public int Count { get { return count; } }
+
+        public LocklessQueue()
+        {
+            Init();
+        }
+
+        public void Enqueue(T item)
+        {
+            SingleLinkNode oldTail = null;
+            SingleLinkNode oldTailNext;
+
+            SingleLinkNode newNode = new SingleLinkNode();
+            newNode.Item = item;
+
+            bool newNodeWasAdded = false;
+
+            while (!newNodeWasAdded)
+            {
+                oldTail = tail;
+                oldTailNext = oldTail.Next;
+
+                if (tail == oldTail)
+                {
+                    if (oldTailNext == null)
+                        newNodeWasAdded = CAS(ref tail.Next, null, newNode);
+                    else
+                        CAS(ref tail, oldTail, oldTailNext);
+                }
+            }
+
+            CAS(ref tail, oldTail, newNode);
+            Interlocked.Increment(ref count);
+        }
+
+        public bool Dequeue(out T item)
+        {
+            item = default(T);
+            SingleLinkNode oldHead = null;
+            bool haveAdvancedHead = false;
+
+            while (!haveAdvancedHead)
+            {
+                oldHead = head;
+                SingleLinkNode oldTail = tail;
+                SingleLinkNode oldHeadNext = oldHead.Next;
+
+                if (oldHead == head)
+                {
+                    if (oldHead == oldTail)
+                    {
+                        if (oldHeadNext == null)
+                            return false;
+
+                        CAS(ref tail, oldTail, oldHeadNext);
+                    }
+                    else
+                    {
+                        item = oldHeadNext.Item;
+                        haveAdvancedHead = CAS(ref head, oldHead, oldHeadNext);
+                    }
+                }
+            }
+
+            Interlocked.Decrement(ref count);
+            return true;
+        }
+
+        public void Clear()
+        {
+            Init();
+        }
+
+        private void Init()
+        {
+            count = 0;
+            head = tail = new SingleLinkNode();
+        }
+
+        private static bool CAS(ref SingleLinkNode location, SingleLinkNode comparand, SingleLinkNode newValue)
+        {
+            return
+                (object)comparand ==
+                (object)Interlocked.CompareExchange<SingleLinkNode>(ref location, newValue, comparand);
+        }
+    }
+}
\ No newline at end of file
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