lwt_GetFaceGeometry()

LWGEOM* lwt_GetFaceGeometry	(	LWT_TOPOLOGY *	topo,
		LWT_ELEMID	face
	)

Return the geometry of a face.

For ST_GetFaceGeometry

Parameters

topo	the topology to operate on
face	identifier of the face

Returns

a polygon geometry representing the face, ownership to caller, to be released with lwgeom_release, or NULL on error (liblwgeom error handler will be invoked with error message)

Definition at line 2841 of file lwgeom_topo.c.

{
        uint64_t numfaceedges;
        LWT_ISO_EDGE *edges;
        LWT_ISO_FACE *face;
        LWPOLY *out;
        LWGEOM *outg;
        uint64_t i, edgeid;
        int fields;
 
        if (faceid == 0)
        {
                lwerror("SQL/MM Spatial exception - universal face has no geometry");
                return NULL;
        }
 
  /* Construct the face geometry */
  numfaceedges = 1;
  fields = LWT_COL_EDGE_GEOM |
           LWT_COL_EDGE_EDGE_ID |
           LWT_COL_EDGE_FACE_LEFT |
           LWT_COL_EDGE_FACE_RIGHT
           ;
  edges = lwt_be_getEdgeByFace( topo, &faceid, &numfaceedges, fields, NULL );
  if (numfaceedges == UINT64_MAX)
  {
          lwerror("Backend error: %s", lwt_be_lastErrorMessage(topo->be_iface));
          return NULL;
  }
 
  if ( numfaceedges == 0 )
  {
    i = 1;
    face = lwt_be_getFaceById(topo, &faceid, &i, LWT_COL_FACE_FACE_ID);
    if (i == UINT64_MAX)
    {
            lwerror("Backend error: %s", lwt_be_lastErrorMessage(topo->be_iface));
            return NULL;
    }
    if ( i == 0 ) {
      lwerror("SQL/MM Spatial exception - non-existent face.");
      return NULL;
    }
    lwfree( face );
    if ( i > 1 ) {
      lwerror("Corrupted topology: multiple face records have face_id=%"
              LWTFMT_ELEMID, faceid);
      return NULL;
    }
    /* Face has no boundary edges, we'll return EMPTY, see
     * https://trac.osgeo.org/postgis/ticket/3221 */
    lwnotice("Corrupted topology: face %"
        LWTFMT_ELEMID " has no associated edges.", faceid);
    out = lwpoly_construct_empty(topo->srid, topo->hasZ, 0);
    return lwpoly_as_lwgeom(out);
  }
  edgeid = edges[0].edge_id;
 
  outg = _lwt_FaceByEdges( topo, edges, numfaceedges );
  _lwt_release_edges(edges, numfaceedges);
 
  if ( ! outg )
  {
    /* Face did have edges but no polygon could be constructed
     * with that material, sounds like a corrupted topology..
     *
     * We'll return EMPTY, see
     * https://trac.osgeo.org/postgis/ticket/3221 */
      lwnotice("Corrupted topology: face %"
        LWTFMT_ELEMID " could not be constructed only from edges "
        "knowing about it (like edge %" LWTFMT_ELEMID ").",
        faceid, edgeid);
      out = lwpoly_construct_empty(topo->srid, topo->hasZ, 0);
      return lwpoly_as_lwgeom(out);
  }
 
  return outg;
}

References _lwt_FaceByEdges(), _lwt_release_edges(), LWT_TOPOLOGY_T::be_iface, LWT_ISO_EDGE::edge_id, LWT_TOPOLOGY_T::hasZ, lwerror(), lwfree(), lwnotice(), lwpoly_as_lwgeom(), lwpoly_construct_empty(), lwt_be_getEdgeByFace(), lwt_be_getFaceById(), lwt_be_lastErrorMessage(), LWT_COL_EDGE_EDGE_ID, LWT_COL_EDGE_FACE_LEFT, LWT_COL_EDGE_FACE_RIGHT, LWT_COL_EDGE_GEOM, LWT_COL_FACE_FACE_ID, LWTFMT_ELEMID, and LWT_TOPOLOGY_T::srid.

Referenced by lwt_AddPolygon(), and lwt_ChangeEdgeGeom().

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