lwt_GetNodeByPoint()

LWT_ELEMID lwt_GetNodeByPoint	(	LWT_TOPOLOGY *	topo,
		LWPOINT *	pt,
		double	tol
	)

Retrieve the id of a node at a point location.

Parameters

topo	the topology to operate on
point	the point to use for query
tol	max distance around the given point to look for a node

Returns

a node identifier if one is found, 0 if none is found, -1 on error (multiple nodes within distance). The liblwgeom error handler will be invoked in case of error.

Definition at line 4647 of file lwgeom_topo.c.

{
  LWT_ISO_NODE *elem;
  int num;
  int flds = LWT_COL_NODE_NODE_ID|LWT_COL_NODE_GEOM; /* geom not needed */
  LWT_ELEMID id = 0;
  POINT2D qp; /* query point */
 
  if ( ! getPoint2d_p(pt->point, 0, &qp) )
  {
    lwerror("Empty query point");
    return -1;
  }
  elem = lwt_be_getNodeWithinDistance2D(topo, pt, tol, &num, flds, 0);
  if ( num == -1 )
  {
    lwerror("Backend error: %s", lwt_be_lastErrorMessage(topo->be_iface));
    return -1;
  }
  else if ( num )
  {
    if ( num > 1 )
    {
      _lwt_release_nodes(elem, num);
      lwerror("Two or more nodes found");
      return -1;
    }
    id = elem[0].node_id;
    _lwt_release_nodes(elem, num);
  }
 
  return id;
}

References _lwt_release_nodes(), LWT_TOPOLOGY_T::be_iface, getPoint2d_p(), lwerror(), lwt_be_getNodeWithinDistance2D(), lwt_be_lastErrorMessage(), LWT_COL_NODE_GEOM, LWT_COL_NODE_NODE_ID, LWT_ISO_NODE::node_id, and LWPOINT::point.

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