lwgeom_symdifference()

LWGEOM* lwgeom_symdifference	(	const LWGEOM *	geom1,
		const LWGEOM *	geom2
	)

Definition at line 870 of file liblwgeom/lwgeom_geos.c.

References error_if_srid_mismatch(), LWGEOM::flags, FLAGS_GET_Z, GEOS2LWGEOM(), LWDEBUGF, lwerror(), LWGEOM2GEOS(), lwgeom_clone_deep(), lwgeom_geos_errmsg, lwgeom_geos_error(), lwgeom_is_empty(), lwnotice(), and LWGEOM::srid.

Referenced by symdifference().

{
        GEOSGeometry *g1, *g2, *g3;
        LWGEOM *result;
        int is3d;
        int srid;

        /* A.SymDifference(Empty) == A */
        if ( lwgeom_is_empty(geom2) )
                return lwgeom_clone_deep(geom1);

        /* Empty.DymDifference(B) == B */
        if ( lwgeom_is_empty(geom1) )
                return lwgeom_clone_deep(geom2);

        /* ensure srids are identical */
        srid = (int)(geom1->srid);
        error_if_srid_mismatch(srid, (int)(geom2->srid));

        is3d = (FLAGS_GET_Z(geom1->flags) || FLAGS_GET_Z(geom2->flags)) ;

        initGEOS(lwnotice, lwgeom_geos_error);

        g1 = LWGEOM2GEOS(geom1, 0);

        if ( 0 == g1 )   /* exception thrown at construction */
        {
                lwerror("First argument geometry could not be converted to GEOS: %s", lwgeom_geos_errmsg);
                return NULL;
        }

        g2 = LWGEOM2GEOS(geom2, 0);

        if ( 0 == g2 )   /* exception thrown at construction */
        {
                lwerror("Second argument geometry could not be converted to GEOS: %s", lwgeom_geos_errmsg);
                GEOSGeom_destroy(g1);
                return NULL;
        }

        g3 = GEOSSymDifference(g1,g2);

        if (g3 == NULL)
        {
                GEOSGeom_destroy(g1);
                GEOSGeom_destroy(g2);
                lwerror("GEOSSymDifference: %s", lwgeom_geos_errmsg);
                return NULL; /*never get here */
        }

        LWDEBUGF(3, "result: %s", GEOSGeomToWKT(g3));

        GEOSSetSRID(g3, srid);

        result = GEOS2LWGEOM(g3, is3d);

        if (result == NULL)
        {
                GEOSGeom_destroy(g1);
                GEOSGeom_destroy(g2);
                GEOSGeom_destroy(g3);
                lwerror("GEOS symdifference() threw an error (result postgis geometry formation)!");
                return NULL ; /*never get here */
        }

        GEOSGeom_destroy(g1);
        GEOSGeom_destroy(g2);
        GEOSGeom_destroy(g3);

        return result;
}

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