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diff --git a/cpp/src/qpid/cluster/Numbering.h b/cpp/src/qpid/cluster/Numbering.h
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+++ b/cpp/src/qpid/cluster/Numbering.h
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+#ifndef QPID_CLUSTER_NUMBERING_H
+#define QPID_CLUSTER_NUMBERING_H
+
+/*
+ *
+ * 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.
+ *
+ */
+
+#include <map>
+#include <vector>
+
+namespace qpid {
+namespace cluster {
+
+/**
+ * A set of numbered T, with two way mapping number->T T->number
+ * Used to construct numberings of objects by code sending and receiving updates.
+ */
+template <class T> class Numbering
+{
+  public:
+    size_t size() const { return byNumber.size(); }
+
+    size_t add(const T& t) {
+        size_t n = (*this)[t];  // Already in the set?
+        if (n == size()) {
+            byObject[t] = n;
+            byNumber.push_back(t);
+        }
+        return n;
+    }
+
+    void clear() { byObject.clear(); byNumber.clear(); }
+
+    /**@return object at index n or T() if n > size() */
+    T operator[](size_t n) const { return(n < size()) ? byNumber[n] : T(); }
+
+    /**@return index of t or size() if t is not in the map */
+    size_t operator[](const T& t) const {
+        typename Map::const_iterator i = byObject.find(t);
+        return (i != byObject.end()) ? i->second : size();
+    }
+
+    bool contains(const T& t) const { return (*this)[t] == size(); }
+
+  private:
+    typedef std::map<T, size_t> Map;
+    Map byObject;
+    std::vector<T> byNumber;
+};
+
+}} // namespace qpid::cluster
+
+#endif  /*!QPID_CLUSTER_NUMBERING_H*/