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

/*

 * Copyright (c) 2007 Emmanuelle Laprise

 * All rights reserved.

 *

 * 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: Emmanuelle Laprise <emmanuelle.laprise@bluekazoo.ca>

 */

#ifndef ETHERNET_TRAILER_H

#define ETHERNET_TRAILER_H

#include "ns3/trailer.h"

#include <string>

namespace ns3 {

class Packet;

/**

 * \brief Packet trailer for Ethernet

 *

 * This class can be used to add and verify the FCS at the end of an

 * ethernet packet. The actual FCS functionality is not yet coded and

 * so this acts more as a placeholder.

 */

class EthernetTrailer : public Trailer 

{

public:

  /**

   * \brief Construct a null ethernet trailer

   */

  EthernetTrailer ();

  /**

   * \brief Enable or disabled FCS checking and calculations

   * \param enable If true, enables FCS calculations.

   */

  static void EnableFcs (bool enable);

  /**

   * \brief Updates the Fcs Field to the correct FCS

   * \param p Reference to a packet on which the FCS should be

   * calculated. The packet should not currently contain an FCS

   * trailer.

   */

  void CalcFcs (Ptr<Packet> p);

  /**

   * \brief Sets the FCS to a new value

   * \param fcs New FCS value

   */

  void SetFcs (uint32_t fcs);

  /**

   * \return the FCS contained in this trailer

   */

  uint32_t GetFcs ();

  /**

   * \param p Reference to the packet on which the FCS should be

   * calculated. The packet should not contain an FCS trailer.

   * \return Returns true if the packet fcs is correct, false otherwise.

   *

   * If FCS checking is disabled, this method will always

   * return true.

   */

  bool CheckFcs (Ptr<Packet> p) const;

  /**

   *\return Returns the size of the trailer

   */ 

  uint32_t GetTrailerSize() const;

private:

  /**

   * Initializes the trailer parameters during construction.

   */

  void Init (void);

  /**

   * Enabled FCS calculations. If false, fcs is set to 0 and checkFCS

   * returns true.

   */

  static bool m_calcFcs;

  uint32_t m_fcs; /// Value of the fcs contained in the trailer

};

} // namespace ns3

#endif /* ETHERNET_TRAILER_H */