1 files changed, 198 insertions, 0 deletions
diff --git a/qpid/java/broker/src/main/java/org/apache/qpid/server/queue/SimpleQueueEntryList.java b/qpid/java/broker/src/main/java/org/apache/qpid/server/queue/SimpleQueueEntryList.java
new file mode 100644
index 0000000000..b97c2c55c5
--- /dev/null
+++ b/qpid/java/broker/src/main/java/org/apache/qpid/server/queue/SimpleQueueEntryList.java
@@ -0,0 +1,198 @@
+package org.apache.qpid.server.queue;
+
+import org.apache.qpid.server.message.InboundMessage;
+import org.apache.qpid.server.message.ServerMessage;
+
+import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
+import java.util.concurrent.atomic.AtomicLong;
+
+/*
+*
+* Licensed to the Apache Software Foundation (ASF) under one
+* or more contributor license agreements.  See the NOTICE file
+* distributed with this work for additional information
+* regarding copyright ownership.  The ASF licenses this file
+* to you under the Apache License, Version 2.0 (the
+* "License"); you may not use this file except in compliance
+* with the License.  You may obtain a copy of the License at
+*
+*   http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing,
+* software distributed under the License is distributed on an
+* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+* KIND, either express or implied.  See the License for the
+* specific language governing permissions and limitations
+* under the License.
+*
+*/
+public class SimpleQueueEntryList implements QueueEntryList
+{
+
+    private final QueueEntryImpl _head;
+
+    private volatile QueueEntryImpl _tail;
+
+    static final AtomicReferenceFieldUpdater<SimpleQueueEntryList, QueueEntryImpl>
+            _tailUpdater =
+        AtomicReferenceFieldUpdater.newUpdater
+        (SimpleQueueEntryList.class, QueueEntryImpl.class, "_tail");
+
+
+    private final AMQQueue _queue;
+
+    static final AtomicReferenceFieldUpdater<QueueEntryImpl, QueueEntryImpl>
+                _nextUpdater =
+            AtomicReferenceFieldUpdater.newUpdater
+            (QueueEntryImpl.class, QueueEntryImpl.class, "_next");
+
+    private AtomicLong _scavenges = new AtomicLong(0L);
+    private final long _scavengeCount = Integer.getInteger("qpid.queue.scavenge_count", 50);
+
+
+    public SimpleQueueEntryList(AMQQueue queue)
+    {
+        _queue = queue;
+        _head = new QueueEntryImpl(this);
+        _tail = _head;
+    }
+
+    void advanceHead()
+    {
+        QueueEntryImpl next = _head.nextNode();
+        QueueEntryImpl newNext = _head.getNext();
+
+        if (next == newNext)
+        {
+            if (_scavenges.incrementAndGet() > _scavengeCount)
+            {
+                _scavenges.set(0L);
+                scavenge();
+            }
+        }
+    }
+
+    void scavenge()
+    {
+        QueueEntryImpl next = _head.getNext();
+
+        while (next != null)
+        {
+            next = next.getNext();
+        }
+    }
+
+
+    public AMQQueue getQueue()
+    {
+        return _queue;
+    }
+
+
+    public QueueEntry add(ServerMessage message)
+    {
+        QueueEntryImpl node = createQueueEntry(message);
+        for (;;)
+        {
+            QueueEntryImpl tail = _tail;
+            QueueEntryImpl next = tail.nextNode();
+            if (tail == _tail)
+            {
+                if (next == null)
+                {
+                    node.setEntryId(tail.getEntryId()+1);
+                    if (_nextUpdater.compareAndSet(tail, null, node))
+                    {
+                        _tailUpdater.compareAndSet(this, tail, node);
+
+                        return node;
+                    }
+                }
+                else
+                {
+                    _tailUpdater.compareAndSet(this,tail, next);
+                }
+            }
+        }
+    }
+
+    protected QueueEntryImpl createQueueEntry(ServerMessage message)
+    {
+        return new QueueEntryImpl(this, message);
+    }
+
+    public QueueEntry next(QueueEntry node)
+    {
+        return ((QueueEntryImpl)node).getNext();
+    }
+
+
+    public static class QueueEntryIteratorImpl implements QueueEntryIterator
+    {
+
+        private QueueEntryImpl _lastNode;
+
+        QueueEntryIteratorImpl(QueueEntryImpl startNode)
+        {
+            _lastNode = startNode;
+        }
+
+
+        public boolean atTail()
+        {
+            return _lastNode.nextNode() == null;
+        }
+
+        public QueueEntry getNode()
+        {
+
+            return _lastNode;
+
+        }
+
+        public boolean advance()
+        {
+
+            if(!atTail())
+            {
+                QueueEntryImpl nextNode = _lastNode.nextNode();
+                while(nextNode.isDeleted() && nextNode.nextNode() != null)
+                {
+                    nextNode = nextNode.nextNode();
+                }
+                _lastNode = nextNode;
+                return true;
+
+            }
+            else
+            {
+                return false;
+            }
+
+        }
+
+    }
+
+
+    public QueueEntryIterator iterator()
+    {
+        return new QueueEntryIteratorImpl(_head);
+    }
+
+
+    public QueueEntry getHead()
+    {
+        return _head;
+    }
+
+    static class Factory implements QueueEntryListFactory
+    {
+
+        public QueueEntryList createQueueEntryList(AMQQueue queue)
+        {
+            return new SimpleQueueEntryList(queue);
+        }
+    }
+    
+
+}