1 files changed, 131 insertions, 0 deletions
diff --git a/qpid/java/broker/src/main/java/org/apache/qpid/server/util/CircularBuffer.java b/qpid/java/broker/src/main/java/org/apache/qpid/server/util/CircularBuffer.java
new file mode 100644
index 0000000000..e730e2f3c3
--- /dev/null
+++ b/qpid/java/broker/src/main/java/org/apache/qpid/server/util/CircularBuffer.java
@@ -0,0 +1,131 @@
+/*
+ *
+ * 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.
+ *
+ */
+package org.apache.qpid.server.util;
+
+import java.util.Iterator;
+
+import org.apache.log4j.Logger;
+
+public class CircularBuffer implements Iterable
+{
+
+    private static final Logger _logger = Logger.getLogger(CircularBuffer.class);
+
+    private final Object[] _log;
+    private int _size;
+    private int _index;
+
+    public CircularBuffer(int size)
+    {
+        _log = new Object[size];
+    }
+
+    public void add(Object o)
+    {
+        _log[_index++] = o;
+        _size = Math.min(_size+1, _log.length);
+        if(_index >= _log.length)
+        {
+            _index = 0;
+        }
+    }
+
+    public Object get(int i)
+    {
+        if(i >= _log.length)
+        {
+            throw new ArrayIndexOutOfBoundsException(i);
+        }
+        return _log[index(i)];
+    }
+
+    public int size() {
+        return _size;
+    }
+
+    public Iterator iterator()
+    {
+        return new Iterator()
+        {
+            private int i = 0;
+
+            public boolean hasNext()
+            {
+                return i < _size;
+            }
+
+            public Object next()
+            {
+                return get(i++);
+            }
+
+            public void remove()
+            {
+                throw new UnsupportedOperationException();
+            }
+        };
+    }
+
+    public String toString()
+    {
+        StringBuilder s = new StringBuilder();
+        boolean first = true;
+        for(Object o : this)
+        {
+            if(!first)
+            {
+                s.append(", ");
+            }
+            else
+            {
+                first = false;
+            }
+            s.append(o);
+        }
+        return s.toString();
+    }
+
+    public void dump()
+    {
+        for(Object o : this)
+        {
+         _logger.info(o);
+        }
+    }
+
+    int index(int i)
+    {
+        return _size == _log.length ? (_index + i) % _log.length : i;
+    }
+
+    public static void main(String[] artgv)
+    {
+        String[] items = new String[]{
+                "A","B","C","D","E","F","G","H","I","J","K"
+        };
+        CircularBuffer buffer = new CircularBuffer(5);
+        for(String s : items)
+        {
+            buffer.add(s);
+            _logger.info(buffer);
+        }
+    }
+}