1 files changed, 85 insertions, 0 deletions
diff --git a/cpp/src/qpid/ha/QueueRange.h b/cpp/src/qpid/ha/QueueRange.h
new file mode 100644
index 0000000000..d734326910
--- /dev/null
+++ b/cpp/src/qpid/ha/QueueRange.h
@@ -0,0 +1,85 @@
+#ifndef QPID_HA_QUEUERANGE_H
+#define QPID_HA_QUEUERANGE_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 "ReplicatingSubscription.h"
+#include "qpid/broker/Queue.h"
+#include "qpid/framing/FieldTable.h"
+#include "qpid/framing/SequenceNumber.h"
+#include <iostream>
+
+namespace qpid {
+namespace ha {
+
+/**
+ * Get the front/back range of a queue or from a ReplicatingSubscription arguments table.
+ *
+ * The *back* of the queue is the position of the latest (most recently pushed)
+ * message on the queue or, if the queue is empty, the back is n-1 where n is
+ * the position that will be assigned to the next message pushed onto the queue.
+ *
+ * The *front* of the queue is the position of the oldest (next to be consumed) message
+ * on the queue or, if the queue is empty, it is the position that will be occupied
+ * by the next message pushed onto the queue.
+ *
+ * This leads to the slightly surprising conclusion that for an empty queue
+ * front = back+1
+ */
+struct QueueRange {
+  public:
+    framing::SequenceNumber front, back;
+
+    QueueRange() : front(1), back(0) { } // Empty range.
+
+    QueueRange(broker::Queue& q) {
+        if (ReplicatingSubscription::getFront(q, front))
+            back = q.getPosition();
+        else {
+            back = q.getPosition();
+            front = back+1;     // empty
+        }
+        assert(front <= back + 1);
+    }
+
+    QueueRange(const framing::FieldTable& args) {
+        back = args.getAsInt(ReplicatingSubscription::QPID_BACK);
+        front = back+1;
+        if (args.isSet(ReplicatingSubscription::QPID_FRONT))
+            front = args.getAsInt(ReplicatingSubscription::QPID_FRONT);
+        if (back+1 < front)
+            throw Exception(QPID_MSG("Invalid range [" << front << "," << back <<"]"));
+    }
+
+    bool empty() const { return front == back+1; }
+};
+
+
+inline std::ostream& operator<<(std::ostream& o, const QueueRange& qr) {
+    if (qr.front > qr.back) return o << "[-," << qr.back << "]";
+    else return o << "[" << qr.front << "," << qr.back << "]";
+}
+
+
+}} // namespace qpid::ha
+
+#endif  /*!QPID_HA_QUEUERANGE_H*/