geography_line_substring()

Datum geography_line_substring

(

PG_FUNCTION_ARGS

)

Definition at line 1211 of file geography_measurement.c.

{
        GSERIALIZED *gs = PG_GETARG_GSERIALIZED_P(0);
        double from_fraction = PG_GETARG_FLOAT8(1);
        double to_fraction = PG_GETARG_FLOAT8(2);
        LWLINE *lwline;
        LWGEOM *lwresult;
        SPHEROID s;
        GSERIALIZED *result;
        bool use_spheroid = true;
 
        if ( PG_NARGS() > 3 && ! PG_ARGISNULL(3) )
        use_spheroid = PG_GETARG_BOOL(3);
 
        /* Return NULL on empty argument. */
        if ( gserialized_is_empty(gs) )
        {
                PG_FREE_IF_COPY(gs, 0);
                PG_RETURN_NULL();
        }
 
        if ( from_fraction < 0 || from_fraction > 1 )
        {
                elog(ERROR,"%s: second argument is not within [0,1]", __func__);
                PG_FREE_IF_COPY(gs, 0);
                PG_RETURN_NULL();
        }
        if ( to_fraction < 0 || to_fraction > 1 )
        {
                elog(ERROR,"%s: argument arg is not within [0,1]", __func__);
                PG_FREE_IF_COPY(gs, 0);
                PG_RETURN_NULL();
        }
        if ( from_fraction > to_fraction )
        {
                elog(ERROR, "%s: second argument must be smaller than third argument", __func__);
                PG_RETURN_NULL();
        }
 
        lwline = lwgeom_as_lwline(lwgeom_from_gserialized(gs));
        if ( !lwline )
        {
                elog(ERROR,"%s: first argument is not a line", __func__);
                PG_FREE_IF_COPY(gs, 0);
                PG_RETURN_NULL();
        }
 
        /* Initialize spheroid */
        spheroid_init_from_srid(gserialized_get_srid(gs), &s);
        /* Set to sphere if requested */
        if ( ! use_spheroid )
                s.a = s.b = s.radius;
 
        lwresult = geography_substring(lwline, &s,
                from_fraction, to_fraction, FP_TOLERANCE);
 
        lwline_free(lwline);
        PG_FREE_IF_COPY(gs, 0);
        lwgeom_set_geodetic(lwresult, true);
        result = geography_serialize(lwresult);
        lwgeom_free(lwresult);
 
        PG_RETURN_POINTER(result);
}

References FP_TOLERANCE, geography_substring(), gserialized_get_srid(), gserialized_is_empty(), lwgeom_as_lwline(), lwgeom_free(), lwgeom_from_gserialized(), lwgeom_set_geodetic(), lwline_free(), result, and s.

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