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 2786 of file lwgeom_topo.c.

{
  int numfaceedges;
  LWT_ISO_EDGE *edges;
  LWT_ISO_FACE *face;
  LWPOLY *out;
  LWGEOM *outg;
  int i;
  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_FACE_LEFT |
           LWT_COL_EDGE_FACE_RIGHT
           ;
  edges = lwt_be_getEdgeByFace( topo, &faceid, &numfaceedges, fields, NULL );
  if ( numfaceedges == -1 ) {
    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 == -1 ) {
      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 */
    out = lwpoly_construct_empty(topo->srid, topo->hasZ, 0);
    return lwpoly_as_lwgeom(out);
  }
 
  outg = _lwt_FaceByEdges( topo, edges, numfaceedges );
  _lwt_release_edges(edges, numfaceedges);
 
  return outg;
}

References _lwt_FaceByEdges(), _lwt_release_edges(), LWT_TOPOLOGY_T::be_iface, LWT_TOPOLOGY_T::hasZ, lwerror(), lwfree(), lwpoly_as_lwgeom(), lwpoly_construct_empty(), lwt_be_getEdgeByFace(), lwt_be_getFaceById(), lwt_be_lastErrorMessage(), 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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