_lwt_MakeRingShell()

static LWPOLY* _lwt_MakeRingShell ( LWT_TOPOLOGY *  topo, LWT_ELEMID *  signed_edge_ids, int  num_signed_edge_ids  )

static

Definition at line 1743 of file lwgeom_topo.c.

{
  LWT_ELEMID *edge_ids;
  int numedges, i, j;
  LWT_ISO_EDGE *ring_edges;
 
  /* Construct a polygon using edges of the ring */
  numedges = 0;
  edge_ids = lwalloc(sizeof(LWT_ELEMID)*num_signed_edge_ids);
  for (i=0; i<num_signed_edge_ids; ++i) {
    int absid = llabs(signed_edge_ids[i]);
    int found = 0;
    /* Do not add the same edge twice */
    for (j=0; j<numedges; ++j) {
      if ( edge_ids[j] == absid ) {
        found = 1;
        break;
      }
    }
    if ( ! found ) edge_ids[numedges++] = absid;
  }
  i = numedges;
  ring_edges = lwt_be_getEdgeById(topo, edge_ids, &i,
                                  LWT_COL_EDGE_EDGE_ID|LWT_COL_EDGE_GEOM);
  lwfree( edge_ids );
  if ( i == -1 )
  {
    lwerror("Backend error: %s", lwt_be_lastErrorMessage(topo->be_iface));
    return NULL;
  }
  else if ( i != numedges )
  {
    lwfree( signed_edge_ids );
    _lwt_release_edges(ring_edges, i);
    lwerror("Unexpected error: %d edges found when expecting %d", i, numedges);
    return NULL;
  }
 
  /* Should now build a polygon with those edges, in the order
   * given by GetRingEdges.
   */
  POINTARRAY *pa = NULL;
  for ( i=0; i<num_signed_edge_ids; ++i )
  {
    LWT_ELEMID eid = signed_edge_ids[i];
    LWDEBUGF(2, "Edge %d in ring is edge %" LWTFMT_ELEMID, i, eid);
    LWT_ISO_EDGE *edge = NULL;
    POINTARRAY *epa;
    for ( j=0; j<numedges; ++j )
    {
      if ( ring_edges[j].edge_id == llabs(eid) )
      {
        edge = &(ring_edges[j]);
        break;
      }
    }
    if ( edge == NULL )
    {
      _lwt_release_edges(ring_edges, numedges);
      lwerror("missing edge that was found in ring edges loop");
      return NULL;
    }
 
    if ( pa == NULL )
    {
      pa = ptarray_clone_deep(edge->geom->points);
      if ( eid < 0 ) ptarray_reverse_in_place(pa);
    }
    else
    {
      if ( eid < 0 )
      {
        epa = ptarray_clone_deep(edge->geom->points);
        ptarray_reverse_in_place(epa);
        ptarray_append_ptarray(pa, epa, 0);
        ptarray_free(epa);
      }
      else
      {
        /* avoid a clone here */
        ptarray_append_ptarray(pa, edge->geom->points, 0);
      }
    }
  }
  _lwt_release_edges(ring_edges, numedges);
  POINTARRAY **points = lwalloc(sizeof(POINTARRAY*));
  points[0] = pa;
 
  /* NOTE: the ring may very well have collapsed components,
   *       which would make it topologically invalid
   */
  LWPOLY* shell = lwpoly_construct(0, 0, 1, points);
  return shell;
}

References _lwt_release_edges(), LWT_TOPOLOGY_T::be_iface, LWT_ISO_EDGE::geom, lwalloc(), LWDEBUGF, lwerror(), lwfree(), lwpoly_construct(), lwt_be_getEdgeById(), lwt_be_lastErrorMessage(), LWT_COL_EDGE_EDGE_ID, LWT_COL_EDGE_GEOM, LWTFMT_ELEMID, LWLINE::points, ptarray_append_ptarray(), ptarray_clone_deep(), ptarray_free(), and ptarray_reverse_in_place().

Referenced by _lwt_AddFaceSplit().

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