geography_perimeter()

Datum geography_perimeter

(

PG_FUNCTION_ARGS

)

Definition at line 563 of file geography_measurement.c.

{
        LWGEOM *lwgeom = NULL;
        GSERIALIZED *g = NULL;
        double length;
        bool use_spheroid = LW_TRUE;
        SPHEROID s;
        int type;
 
        /* Get our geometry object loaded into memory. */
        g = PG_GETARG_GSERIALIZED_P(0);
 
        /* Only return for area features. */
        type = gserialized_get_type(g);
        if ( ! (type == POLYGONTYPE || type == MULTIPOLYGONTYPE || type == COLLECTIONTYPE) )
        {
                PG_RETURN_FLOAT8(0.0);
        }
 
        lwgeom = lwgeom_from_gserialized(g);
 
        /* EMPTY things have no perimeter */
        if ( lwgeom_is_empty(lwgeom) )
        {
                lwgeom_free(lwgeom);
                PG_RETURN_FLOAT8(0.0);
        }
 
        /* Read our calculation type */
        use_spheroid = PG_GETARG_BOOL(1);
 
        /* Initialize spheroid */
        spheroid_init_from_srid(gserialized_get_srid(g), &s);
 
        /* User requests spherical calculation, turn our spheroid into a sphere */
        if ( ! use_spheroid )
                s.a = s.b = s.radius;
 
        /* Calculate the length */
        length = lwgeom_length_spheroid(lwgeom, &s);
 
        /* Something went wrong... */
        if ( length < 0.0 )
        {
                elog(ERROR, "lwgeom_length_spheroid returned length < 0.0");
                PG_RETURN_NULL();
        }
 
        /* Clean up, but not all the way to the point arrays */
        lwgeom_free(lwgeom);
 
        PG_FREE_IF_COPY(g, 0);
        PG_RETURN_FLOAT8(length);
}

References COLLECTIONTYPE, gserialized_get_srid(), gserialized_get_type(), LW_TRUE, lwgeom_free(), lwgeom_from_gserialized(), lwgeom_is_empty(), lwgeom_length_spheroid(), MULTIPOLYGONTYPE, POLYGONTYPE, and s.

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