combine_geometries()

static int combine_geometries ( UNIONFIND *  uf, void **  geoms, uint32_t  num_geoms, void ***  clusterGeoms, uint32_t *  num_clusters, char  is_lwgeom  )

static

Uses a UNIONFIND to identify the set with which each input geometry is associated, and groups the geometries into GeometryCollections.

Supplied geometry array may be of either LWGEOM* or GEOSGeometry*; is_lwgeom is used to identify which. Caller is responsible for freeing input geometry array but not the items contained within it.

Definition at line 546 of file lwgeom_geos_cluster.c.

{
        size_t i, j, k;
 
        /* Combine components of each cluster into their own GeometryCollection */
        *num_clusters = uf->num_clusters;
        *clusterGeoms = lwalloc(*num_clusters * sizeof(void*));
 
        void** geoms_in_cluster = lwalloc(num_geoms * sizeof(void*));
        uint32_t* ordered_components = UF_ordered_by_cluster(uf);
        for (i = 0, j = 0, k = 0; i < num_geoms; i++)
        {
                geoms_in_cluster[j++] = geoms[ordered_components[i]];
 
                /* Is this the last geometry in the component? */
                if ((i == num_geoms - 1) ||
                        (UF_find(uf, ordered_components[i]) != UF_find(uf, ordered_components[i+1])))
                {
                        if (k >= uf->num_clusters) {
                                /* Should not get here - it means that we have more clusters than uf->num_clusters thinks we should. */
                                return LW_FAILURE;
                        }
 
                        if (is_lwgeom)
                        {
                                LWGEOM** components = lwalloc(j * sizeof(LWGEOM*));
                                memcpy(components, geoms_in_cluster, j * sizeof(LWGEOM*));
                                (*clusterGeoms)[k++] = lwcollection_construct(COLLECTIONTYPE, components[0]->srid, NULL, j, (LWGEOM**) components);
                        }
                        else
                        {
                                int srid = GEOSGetSRID(((GEOSGeometry**) geoms_in_cluster)[0]);
                                GEOSGeometry* combined = GEOSGeom_createCollection(GEOS_GEOMETRYCOLLECTION, (GEOSGeometry**) geoms_in_cluster, j);
                                GEOSSetSRID(combined, srid);
                                (*clusterGeoms)[k++] = combined;
                        }
                        j = 0;
                }
        }
 
        lwfree(geoms_in_cluster);
        lwfree(ordered_components);
 
        return LW_SUCCESS;
}

References COLLECTIONTYPE, LW_FAILURE, LW_SUCCESS, lwalloc(), lwcollection_construct(), lwfree(), UNIONFIND::num_clusters, UF_find(), and UF_ordered_by_cluster().

Referenced by cluster_intersecting(), and cluster_within_distance().

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