lwgeom_difference()

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

Definition at line 772 of file liblwgeom/lwgeom_geos.c.

{
        LWGEOM* result;
        int32_t srid = RESULT_SRID(geom1, geom2);
        uint8_t is3d = (FLAGS_GET_Z(geom1->flags) || FLAGS_GET_Z(geom2->flags));
        GEOSGeometry *g1, *g2, *g3;
 
        if (srid == SRID_INVALID) return NULL;
 
        /* A.Intersection(Empty) == Empty */
        if (lwgeom_is_empty(geom2)) return lwgeom_clone_deep(geom1); /* match empty type? */
 
        /* Empty.Intersection(A) == Empty */
        if (lwgeom_is_empty(geom1)) return lwgeom_clone_deep(geom1); /* match empty type? */
 
        initGEOS(lwnotice, lwgeom_geos_error);
 
        if (!(g1 = LWGEOM2GEOS(geom1, AUTOFIX))) GEOS_FAIL();
        if (!(g2 = LWGEOM2GEOS(geom2, AUTOFIX))) GEOS_FREE_AND_FAIL(g1);
 
        g3 = GEOSDifference(g1, g2);
 
        if (!g3) GEOS_FREE_AND_FAIL(g1, g2);
        GEOSSetSRID(g3, srid);
 
        if (!(result = GEOS2LWGEOM(g3, is3d)))
                GEOS_FREE_AND_FAIL(g1, g2, g3);
 
        GEOS_FREE(g1, g2, g3);
        return result;
}

References AUTOFIX, LWGEOM::flags, FLAGS_GET_Z, GEOS2LWGEOM(), GEOS_FAIL, GEOS_FREE, GEOS_FREE_AND_FAIL, LWGEOM2GEOS(), lwgeom_clone_deep(), lwgeom_geos_error(), lwgeom_is_empty(), lwnotice(), RESULT_SRID, and SRID_INVALID.

Referenced by _lwt_AddLine(), and ST_Difference().

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