src/qpid/broker/PriorityQueue.h

#ifndef QPID_BROKER_PRIORITYQUEUE_H
#define QPID_BROKER_PRIORITYQUEUE_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/broker/MessageDeque.h"
#include "qpid/broker/IndexedDeque.h"
#include "qpid/sys/IntegerTypes.h"
#include <deque>
#include <vector>

namespace qpid {
namespace broker {

/**
 * Basic priority queue with a configurable number of recognised
 * priority levels. This is implemented as a separate deque per
 * priority level.
 *
 * Browsing is FIFO not priority order. There is a MessageDeque
 * for fast browsing.
 */
class PriorityQueue : public Messages
{
  public:
    PriorityQueue(int levels);
    virtual ~PriorityQueue() {}
    size_t size();

    bool deleted(const QueueCursor&);
    void publish(const Message& added);
    Message* next(QueueCursor&);
    Message* release(const QueueCursor& cursor);
    Message* find(const QueueCursor&);
    Message* find(const framing::SequenceNumber&, QueueCursor*);

    void foreach(Functor);
    static uint getPriority(const Message&);
  protected:
    const int levels;
    struct Priority
    {
        const int start;
        int current;
        Priority(int s) : start(s), current(start) {}
    };
    virtual Priority firstLevel();
    virtual bool nextLevel(Priority& );

  private:
    struct MessageHolder
    {
        Message message;
        int priority;
        framing::SequenceNumber id;
        framing::SequenceNumber getSequence() const;
        void setState(MessageState);
        MessageState getState() const;
        operator Message&();
    };
    struct MessagePointer
    {
        MessageHolder* holder;
        framing::SequenceNumber id;//used only for padding
        framing::SequenceNumber getSequence() const;
        void setState(MessageState);
        MessageState getState() const;
        operator Message&();
    };
    typedef IndexedDeque<MessageHolder> Deque;
    typedef std::vector<Deque> PriorityLevels;
    typedef std::vector<framing::SequenceNumber> Counters;

    /** Holds pointers to messages (stored in the fifo index) separated by priority.
     */
    PriorityLevels messages;
    Counters counters;
    /** FIFO index of messages for fast browsing and indexing */
    IndexedDeque<MessagePointer> fifo;
    uint frontLevel;
    bool haveFront;
    bool cached;

    uint getPriorityLevel(const Message&) const;
    MessageHolder priorityPadding(qpid::framing::SequenceNumber);
    MessagePointer fifoPadding(qpid::framing::SequenceNumber);
};

}} // namespace qpid::broker

#endif  /*!QPID_BROKER_PRIORITYQUEUE_H*/