/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */

/*

 * Copyright (c) 2005 INRIA

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation;

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 *

 * Author: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>

 */

#ifndef HEAP_SCHEDULER_H

#define HEAP_SCHEDULER_H

#include "scheduler.h"

#include <stdint.h>

#include <vector>

namespace ns3 {

/**

 * \ingroup scheduler

 * \brief a binary heap event scheduler

 * 

 * This code started as a c++ translation of a java-based code written in 2005

 * to implement a heap sort. So, this binary heap is really a pretty 

 * straightforward implementation of the classic data structure. Not much to say

 * about it.

 *

 * What is smart about this code ?

 *  - it does not use the index 0 in the array to avoid having to convert

 *    C-style array indexes (which start at zero) and heap-style indexes

 *    (which start at 1). This is why _all_ indexes start at 1, and that

 *    the index of the root is 1.

 *  - It uses a slightly non-standard while loop for top-down heapify

 *    to move one if statement out of the loop.

 */

class HeapScheduler : public Scheduler 

{

public:

  static TypeId GetTypeId (void);

  HeapScheduler ();

  virtual ~HeapScheduler ();

  virtual void Insert (const Event &ev);

  virtual bool IsEmpty (void) const;

  virtual Event PeekNext (void) const;

  virtual Event RemoveNext (void);

  virtual void Remove (const Event &ev);

private:

  typedef std::vector<Event> BinaryHeap;

  inline uint32_t Parent (uint32_t id) const;

  uint32_t Sibling (uint32_t id) const;

  inline uint32_t LeftChild (uint32_t id) const;

  inline uint32_t RightChild (uint32_t id) const;

  inline uint32_t Root (void) const;

  /* Return the position in the array of the last element included in it. */

  uint32_t Last (void) const;

  inline bool IsRoot (uint32_t id) const;

  inline bool IsBottom (uint32_t id) const;

  inline bool IsLessStrictly (uint32_t a, uint32_t b) const;

  inline uint32_t Smallest (uint32_t a, uint32_t b) const;

  inline void Exch (uint32_t a, uint32_t b);

  void BottomUp (void);

  void TopDown (uint32_t start);

  BinaryHeap m_heap;

};

} // namespace ns3

#endif /* HEAP_SCHEDULER_H */