5.2 Packet interface

The public member functions of a Packet object are as follows:

5.2.1 Constructors

    /**
     * Create an empty packet with a new uid (as returned
     * by getUid).
     */
    Packet ();
    /**
     * Create a packet with a zero-filled payload.
     * The memory necessary for the payload is not allocated:
     * it will be allocated at any later point if you attempt
     * to fragment this packet or to access the zero-filled
     * bytes. The packet is allocated with a new uid (as
     * returned by getUid).
     *
     * \param size the size of the zero-filled payload
     */
    Packet (uint32_t size);

5.2.2 Adding and removing Buffer data

The below code is reproduced for Header class only; similar functions exist for Trailers.

    /**
     * Add header to this packet. This method invokes the
     * ns3::Header::serializeTo method to request the header to serialize
     * itself in the packet buffer.
     *
     * \param header a reference to the header to add to this packet.
     */
    void Add (Header const &header);
    /**
     * Deserialize header from this packet. This method invokes the
     * ns3::Header::deserializeFrom method to request the header to deserialize
     * itself from the packet buffer. This method does not remove
     * the data from the buffer. It merely reads it.
     *
     * \param header a reference to the header to deserialize from the buffer
     */
    void Peek (Header &header);
    /**
     * Remove a deserialized header from the internal buffer.
     * This method removes the bytes read by Packet::peek from
     * the packet buffer.
     *
     * \param header a reference to the header to remove from the internal buffer.
     */
    void Remove (Header const &header);
    /**
     * Add trailer to this packet. This method invokes the
     * ns3::Trailer::serializeTo method to request the trailer to serialize
     * itself in the packet buffer.
     *
     * \param trailer a reference to the trailer to add to this packet.
     */

5.2.3 Adding and removing Tags

    /**
     * Attach a tag to this packet. The tag is fully copied
     * in a packet-specific internal buffer. This operation
     * is expected to be really fast.
     *
     * \param tag a pointer to the tag to attach to this packet.
     */
    template <typename T>
    void AddTag (T const &tag);
    /**
     * Remove a tag from this packet. The data stored internally
     * for this tag is copied in the input tag if an instance
     * of this tag type is present in the internal buffer. If this
     * tag type is not present, the input tag is not modified.
     *
     * This operation can be potentially slow and might trigger
     * unexpectedly large memory allocations. It is thus
     * usually a better idea to create a copy of this packet,
     * and invoke removeAllTags on the copy to remove all
     * tags rather than remove the tags one by one from a packet.
     *
     * \param tag a pointer to the tag to remove from this packet
     * \returns true if an instance of this tag type is stored
     *          in this packet, false otherwise.
     */
    template <typename T>
    bool RemoveTag (T &tag);
    /**
     * Copy a tag stored internally to the input tag. If no instance
     * of this tag is present internally, the input tag is not modified.
     *
     * \param tag a pointer to the tag to read from this packet
     * \returns true if an instance of this tag type is stored
     *          in this packet, false otherwise.
     */
    template <typename T>
    bool PeekTag (T &tag) const;
    /**
     * Remove all the tags stored in this packet. This operation is
     * much much faster than invoking removeTag n times.
     */
    void RemoveAllTags (void);

5.2.4 Fragmentation

    /**
     * Create a new packet which contains a fragment of the original
     * packet. The returned packet shares the same uid as this packet.
     *
     * \param start offset from start of packet to start of fragment to create
     * \param length length of fragment to create
     * \returns a fragment of the original packet
     */
    Packet CreateFragment (uint32_t start, uint32_t length) const;

        /**
         * Concatenate the input packet at the end of the current
         * packet. This does not alter the uid of either packet.
         * 
         * \param packet packet to concatenate
         */
    void addAtEnd (Packet packet);

        /oncatenate the input packet at the end of the current
     * packet. This does not alter the uid of either packet.
     *
     * \param packet packet to concatenate
     */
    void AddAtEnd (Packet packet);
    /**
     * Concatenate the fragment of the input packet identified
     * by the offset and size parameters at the end of the current
     * packet. This does not alter the uid of either packet.
     *
     * \param packet to concatenate
     * \param offset offset of fragment to copy from the start of the input packet
     * \param size size of fragment of input packet to copy.
     */
    void AddAtEnd (Packet packet, uint32_t offset, uint32_t size);
    /**
     * Remove size bytes from the end of the current packet
     * It is safe to remove more bytes that what is present in
     * the packet.
     *
     * \param size number of bytes from remove
     */
    void RemoveAtEnd (uint32_t size);
    /**
     * Remove size bytes from the start of the current packet.
     * It is safe to remove more bytes that what is present in
     * the packet.
     *
     * \param size number of bytes from remove
     */
    void RemoveAtStart (uint32_t size);

5.2.5 Miscellaneous

    /**
     * \returns the size in bytes of the packet (including the zero-filled
     *          initial payload)
     */
    uint32_t GetSize (void) const;
    /**
     * If you try to change the content of the buffer
     * returned by this method, you will die.
     *
     * \returns a pointer to the internal buffer of the packet.
     */
    uint8_t const *PeekData (void) const;
    /**
     * A packet is allocated a new uid when it is created
     * empty or with zero-filled payload.
     *
     * \returns an integer identifier which uniquely
     *          identifies this packet.
     */
    uint32_t GetUid (void) const;

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