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

/*

 * Copyright (c) 2008 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>

 */

#include <stdint.h>

#include "ns3/type-id.h"

#include "tag-buffer.h"

namespace ns3 {

/**

 * \ingroup packet

 *

 * \brief keep track of the tags stored in a packet.

 *

 * This class is mostly private to the Packet implementation and users

 * should never have to access it directly.

 *

 * \internal

 * The implementation of this class is a bit tricky so, there are a couple

 * of things to keep in mind here:

 *

 *   - it stores all tags in a single byte buffer: each tag is stored

 *     as 4 32bit integers (TypeId, tag data size, start, end) followed 

 *     by the tag data as generated by Tag::Serialize.

 *

 *     is shared and, thus, reference-counted. This data structure is unshared

 *     as-needed to emulate COW semantics.

 *

 *   - each tag tags a unique set of bytes identified by the pair of offsets 

 *     (start,end). These offsets are provided by Buffer::GetCurrentStartOffset

 *     and Buffer::GetCurrentEndOffset which means that they are relative to 

 *     the start of the 'virtual byte buffer' as explained in the documentation

 *     for the ns3::Buffer class. Whenever the origin of the offset of the Buffer

 *     reports this to its container Packet class as a bool return value

 *     in Buffer::AddAtStart and Buffer::AddAtEnd. In both cases, when this happens

 *

 *     are never updated because we rely on the fact that they will be updated in

 *     either the next call to Packet::AddHeader or Packet::AddTrailer or when

 *     the user iterates the tag list with Packet::GetTagIterator and 

 *     TagIterator::Next.

 */

{

public:

  class Iterator

  {

  public:

    struct Item 

    {

      TypeId tid;

      uint32_t size;

      int32_t start;

      int32_t end;

      TagBuffer buf;

      Item (TagBuffer buf);

    private:

    };

    bool HasNext (void) const;

    uint32_t GetOffsetStart (void) const;

  private:

    Iterator (uint8_t *start, uint8_t *end, int32_t offsetStart, int32_t offsetEnd);

    void PrepareForNext (void);

    uint8_t *m_current;

    uint8_t *m_end;

    int32_t m_offsetStart;

    int32_t m_offsetEnd;

    uint32_t m_nextTid;

    uint32_t m_nextSize;

    int32_t m_nextStart;

    int32_t m_nextEnd;

  };

  /**

   * \param tid the typeid of the tag added

   * \param bufferSize the size of the tag when its serialization will 

   *        be completed. Typically, the return value of Tag::GetSerializedSize

   * \param start offset which uniquely identifies the first byte tagged by this tag.

   * \param end offset which uniquely identifies the last byte tagged by this tag.

   * \returns a buffer which can be used to write the tag data.     

   *

   * 

   */

  TagBuffer Add (TypeId tid, uint32_t bufferSize, int32_t start, int32_t end);

  /**

   * \param o the other list of tags to aggregate.

   *

   * Aggregate the two lists of tags.

   */

  void RemoveAll (void);

  /**

   * \param offsetStart the offset which uniquely identifies the first data byte 

   * \param offsetEnd the offset which uniquely identifies the last data byte 

   * \returns an iterator

   *

   * The returned iterator will allow you to loop through the set of tags present

   * in this list: the boundaries of each tag as reported by their start and

   * end offsets will be included within the input offsetStart and offsetEnd.

   */

  /**

   * Adjust the offsets stored internally by the adjustment delta and

   * make sure that all offsets are smaller than appendOffset which represents

   * the location where new bytes have been added to the byte buffer.

   */

  void AddAtEnd (int32_t adjustment, int32_t appendOffset);

  /**

   * Adjust the offsets stored internally by the adjustment delta and

   * make sure that all offsets are bigger than prependOffset which represents

   * the location where new bytes have been added to the byte buffer.

   */

  void AddAtStart (int32_t adjustment, int32_t prependOffset);

private:

  bool IsDirtyAtEnd (int32_t appendOffset);

  bool IsDirtyAtStart (int32_t prependOffset);

  uint16_t m_used;

};

} // namespace ns3