lwcollection_extract()

LWCOLLECTION* lwcollection_extract	(	LWCOLLECTION *	col,
		int	type
	)

Takes a potentially heterogeneous collection and returns a homogeneous collection consisting only of the specified type.

WARNING: the output will contain references to geometries in the input, so the result must be carefully released, not freed.

Definition at line 369 of file lwcollection.c.

References LWGEOM::bbox, LWCOLLECTION::bbox, LWCOLLECTION::flags, FLAGS_GET_M, FLAGS_GET_Z, gbox_copy(), LWCOLLECTION::geoms, LINETYPE, lwalloc(), lwcollection_construct(), lwcollection_construct_empty(), lwerror(), lwfree(), lwgeom_calculate_gbox(), lwgeom_clone(), lwgeom_is_empty(), lwrealloc(), lwtype_is_collection(), lwtype_name(), MULTILINETYPE, MULTIPOINTTYPE, MULTIPOLYGONTYPE, LWCOLLECTION::ngeoms, POINTTYPE, POLYGONTYPE, LWCOLLECTION::srid, and LWGEOM::type.

Referenced by _lwt_AddLineEdge(), lwgeom_to_basic_type(), ST_CollectionExtract(), and test_lwcollection_extract().

{
        int i = 0;
        LWGEOM **geomlist;
        LWCOLLECTION *outcol;
        int geomlistsize = 16;
        int geomlistlen = 0;
        uint8_t outtype;

        if ( ! col ) return NULL;

        switch (type)
        {
        case POINTTYPE:
                outtype = MULTIPOINTTYPE;
                break;
        case LINETYPE:
                outtype = MULTILINETYPE;
                break;
        case POLYGONTYPE:
                outtype = MULTIPOLYGONTYPE;
                break;
        default:
                lwerror("Only POLYGON, LINESTRING and POINT are supported by lwcollection_extract. %s requested.", lwtype_name(type));
                return NULL;
        }

        geomlist = lwalloc(sizeof(LWGEOM*) * geomlistsize);

        /* Process each sub-geometry */
        for ( i = 0; i < col->ngeoms; i++ )
        {
                int subtype = col->geoms[i]->type;
                /* Don't bother adding empty sub-geometries */
                if ( lwgeom_is_empty(col->geoms[i]) )
                {
                        continue;
                }
                /* Copy our sub-types into the output list */
                if ( subtype == type )
                {
                        /* We've over-run our buffer, double the memory segment */
                        if ( geomlistlen == geomlistsize )
                        {
                                geomlistsize *= 2;
                                geomlist = lwrealloc(geomlist, sizeof(LWGEOM*) * geomlistsize);
                        }
                        geomlist[geomlistlen] = lwgeom_clone(col->geoms[i]);
                        geomlistlen++;
                }
                /* Recurse into sub-collections */
                if ( lwtype_is_collection( subtype ) )
                {
                        int j = 0;
                        LWCOLLECTION *tmpcol = lwcollection_extract((LWCOLLECTION*)col->geoms[i], type);
                        for ( j = 0; j < tmpcol->ngeoms; j++ )
                        {
                                /* We've over-run our buffer, double the memory segment */
                                if ( geomlistlen == geomlistsize )
                                {
                                        geomlistsize *= 2;
                                        geomlist = lwrealloc(geomlist, sizeof(LWGEOM*) * geomlistsize);
                                }
                                geomlist[geomlistlen] = tmpcol->geoms[j];
                                geomlistlen++;
                        }
                        if (tmpcol->geoms)
                                lwfree(tmpcol->geoms);
                        if (tmpcol->bbox)
                                lwfree(tmpcol->bbox);
                        lwfree(tmpcol);
                }
        }

        if ( geomlistlen > 0 )
        {
                GBOX gbox;
                outcol = lwcollection_construct(outtype, col->srid, NULL, geomlistlen, geomlist);
                lwgeom_calculate_gbox((LWGEOM *) outcol, &gbox);
                outcol->bbox = gbox_copy(&gbox);
        }
        else
        {
                lwfree(geomlist);
                outcol = lwcollection_construct_empty(outtype, col->srid, FLAGS_GET_Z(col->flags), FLAGS_GET_M(col->flags));
        }

        return outcol;
}

Here is the call graph for this function:

Here is the caller graph for this function: