static void dissect_GAP(tvbuff_t *tvb, packet_info *pinfo, gint offset,
                guint8 flags, const guint encoding, int octets_to_next_header,
                proto_tree *tree, endpoint_guid *guid) {
  /* RTPS 1.0/1.1:
   * 0...2...........7...............15.............23...............31
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   * |   GAP         |X|X|X|X|X|X|X|E|      octetsToNextHeader       |
   * +---------------+---------------+---------------+---------------+
   * | ObjectId readerObjectId                                       |
   * +---------------+---------------+---------------+---------------+
   * | ObjectId writerObjectId                                       |
   * +---------------+---------------+---------------+---------------+
   * |                                                               |
   * + SequenceNumber firstSeqNumber                                 +
   * |                                                               |
   * +---------------+---------------+---------------+---------------+
   * |                                                               |
   * + Bitmap bitmap                                                 +
   * |                                                               |
   * +---------------+---------------+---------------+---------------+
   *
   * RTPS 1.2/2.0
   * 0...2...........7...............15.............23...............31
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   * |   GAP         |X|X|X|X|X|X|F|E|      octetsToNextHeader       |
   * +---------------+---------------+---------------+---------------+
   * | EntityId readerEntityId                                       |
   * +---------------+---------------+---------------+---------------+
   * | EntityId writerEntityId                                       |
   * +---------------+---------------+---------------+---------------+
   * |                                                               |
   * + SequenceNumber gapStart                                       +
   * |                                                               |
   * +---------------+---------------+---------------+---------------+
   * |                                                               |
   * ~ SequenceNumberSet gapList                                     ~
   * |                                                               |
   * +---------------+---------------+---------------+---------------+
   */
  proto_item *octet_item;
  guint32 wid;
  proto_tree_add_bitmask_value(tree, tvb, offset + 1, hf_rtps_sm_flags, ett_rtps_flags, GAP_FLAGS, flags);

  octet_item = proto_tree_add_item(tree, hf_rtps_sm_octets_to_next_header, tvb,
                        offset + 2, 2, encoding);

  if (octets_to_next_header < 24) {
    expert_add_info_format(pinfo, octet_item, &ei_rtps_sm_octets_to_next_header_error, "(Error: should be >= 24)");
    return;
  }

  offset += 4;

  /* readerEntityId */
  rtps_util_add_entity_id(tree, tvb, offset,
                        hf_rtps_sm_rdentity_id, hf_rtps_sm_rdentity_id_key, hf_rtps_sm_rdentity_id_kind,
                        ett_rtps_rdentity, "readerEntityId", NULL);
  offset += 4;

  /* writerEntityId */
  rtps_util_add_entity_id(tree, tvb, offset,
                        hf_rtps_sm_wrentity_id, hf_rtps_sm_wrentity_id_key, hf_rtps_sm_wrentity_id_kind,
                        ett_rtps_wrentity, "writerEntityId", &wid);
  offset += 4;
  guid->entity_id = wid;
  guid->fields_present |= GUID_HAS_ENTITY_ID;
  rtps_util_topic_info_add_tree(tree, tvb, offset, guid);


 /* First Sequence Number */
  rtps_util_add_seq_number(tree, tvb, offset, encoding, "gapStart");
  offset += 8;

  /* Bitmap */
  rtps_util_add_bitmap(tree, tvb, offset, encoding, "gapList", FALSE);
}
static void dissect_GAP(tvbuff_t *tvb, packet_info *pinfo, gint offset,
                guint8 flags, const guint encoding, int octets_to_next_header,
                proto_tree *tree, endpoint_guid *guid) {
   
  proto_item *octet_item;
  guint32 wid;
  proto_tree_add_bitmask_value(tree, tvb, offset + 1, hf_rtps_sm_flags, ett_rtps_flags, GAP_FLAGS, flags);

  octet_item = proto_tree_add_item(tree, hf_rtps_sm_octets_to_next_header, tvb,
                        offset + 2, 2, encoding);

  if (octets_to_next_header < 24) {
    expert_add_info_format(pinfo, octet_item, &ei_rtps_sm_octets_to_next_header_error, "(Error: should be >= 24)");
    return;
  }

  offset += 4;

   
  rtps_util_add_entity_id(tree, tvb, offset,
                        hf_rtps_sm_rdentity_id, hf_rtps_sm_rdentity_id_key, hf_rtps_sm_rdentity_id_kind,
                        ett_rtps_rdentity, "readerEntityId", NULL);
  offset += 4;

   
  rtps_util_add_entity_id(tree, tvb, offset,
                        hf_rtps_sm_wrentity_id, hf_rtps_sm_wrentity_id_key, hf_rtps_sm_wrentity_id_kind,
                        ett_rtps_wrentity, "writerEntityId", &wid);
  offset += 4;
  guid->entity_id = wid;
  guid->fields_present |= GUID_HAS_ENTITY_ID;
  rtps_util_topic_info_add_tree(tree, tvb, offset, guid);


  
  rtps_util_add_seq_number(tree, tvb, offset, encoding, "gapStart");
  offset += 8;

   
  rtps_util_add_bitmap(tree, tvb, offset, encoding, "gapList", FALSE);
}