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diff --git a/cpp/src/qpid/SessionState.h b/cpp/src/qpid/SessionState.h
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+#ifndef QPID_SESSIONSTATE_H
+#define QPID_SESSIONSTATE_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 <qpid/framing/SequenceNumber.h>
+#include <qpid/framing/SequenceSet.h>
+#include <qpid/framing/AMQFrame.h>
+#include <boost/operators.hpp>
+#include <vector>
+#include <iosfwd>
+
+namespace qpid {
+using framing::SequenceNumber;
+using framing::SequenceSet;
+
+/** A point in the session. Points to command id + offset */
+struct SessionPoint : boost::totally_ordered1<SessionPoint> {
+    SessionPoint(SequenceNumber command_=0, uint64_t offset_ = 0) : command(command_), offset(offset_) {}
+
+    SequenceNumber command;
+    uint64_t offset;
+
+    /** Advance past frame f */
+    void advance(const framing::AMQFrame& f);
+
+    bool operator<(const SessionPoint&) const;
+    bool operator==(const SessionPoint&) const;
+};
+
+std::ostream& operator<<(std::ostream&, const SessionPoint&);
+
+/** The sending half of session state */
+class SendState {
+  public:
+    typedef std::vector<framing::AMQFrame> ReplayList;
+
+    /** Record frame f for replay. Should not be called during replay. */
+    void send(const framing::AMQFrame& f);
+
+    /** @return true if we should send flush for confirmed and completed commands. */
+    bool needFlush() const;
+
+    /** Called when flush for confirmed and completed commands is sent to peer. */
+    void sendFlush();
+
+    /** Called when the peer confirms up to commands. */
+    void peerConfirmed(const SessionPoint& confirmed);
+
+    /** Called when the peer indicates commands completed */
+    void peerCompleted(const SequenceSet& commands);
+
+    /** Get the replay list. @see getReplayPoint. */
+    const ReplayList& getReplayList() const { return replayList; }
+
+    /**
+     * The replay point is the point up to which all data has been
+     * confirmed.  Partial replay is not supported, it will always
+     * have offset==0.
+     */
+    const SessionPoint& getReplayPoint() const { return replayPoint; }
+
+    const SessionPoint& getSendPoint() const { return sendPoint; } 
+    const SequenceSet& getCompleted() const { return sentCompleted; }
+
+  protected:
+    SendState(size_t replaySyncSize, size_t replayKillSize);
+
+  private:
+    size_t replaySyncSize, replayKillSize; // @see SessionState::Configuration.
+    // invariant: replayPoint <= flushPoint <= sendPoint
+    SessionPoint replayPoint;   // Can replay from this point
+    SessionPoint sendPoint;     // Send from this point
+    SessionPoint flushPoint;    // Point of last flush
+    ReplayList replayList; // Starts from replayPoint.
+    size_t unflushedSize;       // Un-flushed bytes in replay list.
+    SequenceSet sentCompleted; // Commands sent and acknowledged as completed.
+};
+
+/** Receiving half of SessionState */
+class ReceiveState {
+  public:
+    bool hasState();
+
+    /** Set the command point. */
+    void setExpecting(const SessionPoint& point);
+
+    /** Returns true if frame should be be processed, false if it is a duplicate. */
+    bool receive(const framing::AMQFrame& f);
+
+    /** Command completed locally */
+    void localCompleted(SequenceNumber command);
+
+    /** Peer has indicated commands are known completed */
+    void peerKnownComplete(const SequenceSet& commands);
+
+    /** Recieved, completed and possibly not known by peer to be completed */
+    const SequenceSet& getReceivedCompleted() const { return receivedCompleted; }
+    const SessionPoint& getExpecting() const { return expecting; }
+    const SessionPoint& getReceived() const { return received; }
+
+  protected:
+    ReceiveState();
+
+  private:
+    bool stateful;              // True if session has state.
+    SessionPoint expecting;     // Expecting from here
+    SessionPoint received;      // Received to here. Invariant: expecting <= received.
+    SequenceSet receivedCompleted; // Received & completed, may not be not known-completed by peer
+};
+
+/** Identifier for a session */
+class SessionId : boost::totally_ordered1<SessionId> {
+    std::string userId;
+    std::string name;
+  public:
+    SessionId(const std::string& userId=std::string(), const std::string& name=std::string());
+    std::string getUserId() const { return userId; }
+    std::string getName() const { return name; }
+    bool operator<(const SessionId&) const ;
+    bool operator==(const SessionId& id) const;
+};
+
+
+/**
+ * Support for session idempotence barrier and resume as defined in
+ * AMQP 0-10.
+ *
+ * We only issue/use contiguous confirmations, out-of-order confirmation
+ * is ignored. Out of order completion is fully supported.
+ * 
+ * Raises NotImplemented if the command point is set greater than the
+ * max currently received command data, either explicitly via
+ * session.command-point or implicitly via session.gap.
+ *
+ * Partial replay is not supported, replay always begins on a command
+ * boundary, and we never confirm partial commands.
+ *
+ * The SessionPoint data structure does store offsets so this class
+ * could be extended to support partial replay without
+ * source-incompatbile API changes.
+ */
+class SessionState : public SendState, public ReceiveState {
+  public:
+    struct Configuration {
+        Configuration();
+        size_t replaySyncSize; // Issue a sync when the replay list holds >= N bytes
+        size_t replayKillSize; // Kill session if replay list grows beyond N bytes.
+    };
+    
+    SessionState(const SessionId& =SessionId(), const Configuration& =Configuration());
+
+    const SessionId& getId() const { return id; }
+    uint32_t getTimeout() const { return timeout; }
+    void setTimeout(uint32_t seconds) { timeout = seconds; }
+
+    /** Clear all state except Id. */
+    void clear();
+
+  private:
+    SessionId id;
+    uint32_t timeout;
+    Configuration config;
+};
+
+} // namespace qpid
+
+
+#endif  /*!QPID_SESSIONSTATE_H*/