lwt_AddIsoEdge()

LWT_ELEMID lwt_AddIsoEdge	(	LWT_TOPOLOGY *	topo,
		LWT_ELEMID	startNode,
		LWT_ELEMID	endNode,
		const LWLINE *	geom
	)

Add an isolated edge connecting two existing isolated nodes.

For ST_AddIsoEdge

Parameters

topo	the topology to operate on
start_node	identifier of the starting node
end_node	identifier of the ending node
geom	the edge geometry

Returns

ID of the newly added edge, or -1 on error (liblwgeom error handler will be invoked with error message)

Definition at line 770 of file lwgeom_topo.c.

{
  int num_nodes;
  int i;
  LWT_ISO_EDGE newedge;
  LWT_ISO_NODE *endpoints;
  LWT_ELEMID containing_face = -1;
  LWT_ELEMID node_ids[2];
  LWT_ISO_NODE updated_nodes[2];
  int skipISOChecks = 0;
  POINT2D p1, p2;
 
  /* NOT IN THE SPECS:
   * A closed edge is never isolated (as it forms a face)
   */
  if ( startNode == endNode )
  {
    lwerror("Closed edges would not be isolated, try lwt_AddEdgeNewFaces");
    return -1;
  }
 
  if ( ! skipISOChecks )
  {
    /* Acurve must be simple */
    if ( ! lwgeom_is_simple(lwline_as_lwgeom(geom)) )
    {
      lwerror("SQL/MM Spatial exception - curve not simple");
      return -1;
    }
  }
 
  /*
   * Check for:
   *    existence of nodes
   *    nodes faces match
   * Extract:
   *    nodes face id
   *    nodes geoms
   */
  num_nodes = 2;
  node_ids[0] = startNode;
  node_ids[1] = endNode;
  endpoints = lwt_be_getNodeById( topo, node_ids, &num_nodes,
                                             LWT_COL_NODE_ALL );
  if ( num_nodes < 0 )
  {
    lwerror("Backend error: %s", lwt_be_lastErrorMessage(topo->be_iface));
    return -1;
  }
  else if ( num_nodes < 2 )
  {
    if ( num_nodes ) _lwt_release_nodes(endpoints, num_nodes);
    lwerror("SQL/MM Spatial exception - non-existent node");
    return -1;
  }
  for ( i=0; i<num_nodes; ++i )
  {
    const LWT_ISO_NODE *n = &(endpoints[i]);
    if ( n->containing_face == -1 )
    {
      _lwt_release_nodes(endpoints, num_nodes);
      lwerror("SQL/MM Spatial exception - not isolated node");
      return -1;
    }
    if ( containing_face == -1 ) containing_face = n->containing_face;
    else if ( containing_face != n->containing_face )
    {
      _lwt_release_nodes(endpoints, num_nodes);
      lwerror("SQL/MM Spatial exception - nodes in different faces");
      return -1;
    }
 
    if ( ! skipISOChecks )
    {
      if ( n->node_id == startNode )
      {
        /* l) Check that start point of acurve match start node geoms. */
        getPoint2d_p(geom->points, 0, &p1);
        getPoint2d_p(n->geom->point, 0, &p2);
        if ( ! p2d_same(&p1, &p2) )
        {
          _lwt_release_nodes(endpoints, num_nodes);
          lwerror("SQL/MM Spatial exception - "
                  "start node not geometry start point.");
          return -1;
        }
      }
      else
      {
        /* m) Check that end point of acurve match end node geoms. */
        getPoint2d_p(geom->points, geom->points->npoints-1, &p1);
        getPoint2d_p(n->geom->point, 0, &p2);
        if ( ! p2d_same(&p1, &p2) )
        {
          _lwt_release_nodes(endpoints, num_nodes);
          lwerror("SQL/MM Spatial exception - "
                  "end node not geometry end point.");
          return -1;
        }
      }
    }
  }
 
  if ( num_nodes ) _lwt_release_nodes(endpoints, num_nodes);
 
  if ( ! skipISOChecks )
  {
    if ( _lwt_CheckEdgeCrossing( topo, startNode, endNode, geom, 0 ) )
    {
      /* would have called lwerror already, leaking :( */
      return -1;
    }
  }
 
  /*
   * All checks passed, time to prepare the new edge
   */
 
  newedge.edge_id = lwt_be_getNextEdgeId( topo );
  if ( newedge.edge_id == -1 ) {
    lwerror("Backend error: %s", lwt_be_lastErrorMessage(topo->be_iface));
    return -1;
  }
 
  /* TODO: this should likely be an exception instead ! */
  if ( containing_face == -1 ) containing_face = 0;
 
  newedge.start_node = startNode;
  newedge.end_node = endNode;
  newedge.face_left = newedge.face_right = containing_face;
  newedge.next_left = -newedge.edge_id;
  newedge.next_right = newedge.edge_id;
  newedge.geom = (LWLINE *)geom; /* const cast.. */
 
  int ret = lwt_be_insertEdges(topo, &newedge, 1);
  if ( ret == -1 ) {
    lwerror("Backend error: %s", lwt_be_lastErrorMessage(topo->be_iface));
    return -1;
  } else if ( ret == 0 ) {
    lwerror("Insertion of split edge failed (no reason)");
    return -1;
  }
 
  /*
   * Update Node containing_face values
   *
   * the nodes anode and anothernode are no more isolated
   * because now there is an edge connecting them
   */
  updated_nodes[0].node_id = startNode;
  updated_nodes[0].containing_face = -1;
  updated_nodes[1].node_id = endNode;
  updated_nodes[1].containing_face = -1;
  ret = lwt_be_updateNodesById(topo, updated_nodes, 2,
                               LWT_COL_NODE_CONTAINING_FACE);
  if ( ret == -1 ) {
    lwerror("Backend error: %s", lwt_be_lastErrorMessage(topo->be_iface));
    return -1;
  }
 
  return newedge.edge_id;
}

References _lwt_CheckEdgeCrossing(), _lwt_release_nodes(), LWT_TOPOLOGY_T::be_iface, LWT_ISO_NODE::containing_face, LWT_ISO_EDGE::edge_id, LWT_ISO_EDGE::end_node, LWT_ISO_EDGE::face_left, LWT_ISO_EDGE::face_right, LWT_ISO_NODE::geom, LWT_ISO_EDGE::geom, getPoint2d_p(), lwerror(), lwgeom_is_simple(), lwline_as_lwgeom(), lwt_be_getNextEdgeId(), lwt_be_getNodeById(), lwt_be_insertEdges(), lwt_be_lastErrorMessage(), lwt_be_updateNodesById(), LWT_COL_NODE_ALL, LWT_COL_NODE_CONTAINING_FACE, LWT_ISO_EDGE::next_left, LWT_ISO_EDGE::next_right, LWT_ISO_NODE::node_id, POINTARRAY::npoints, p2d_same(), LWPOINT::point, LWLINE::points, and LWT_ISO_EDGE::start_node.

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