LWGEOM_line_substring()

Datum LWGEOM_line_substring

(

PG_FUNCTION_ARGS

)

Definition at line 509 of file lwgeom_functions_analytic.c.

{
        GSERIALIZED *geom = PG_GETARG_GSERIALIZED_P(0);
        double from = PG_GETARG_FLOAT8(1);
        double to = PG_GETARG_FLOAT8(2);
        LWGEOM *olwgeom;
        POINTARRAY *ipa, *opa;
        GSERIALIZED *ret;
        int type = gserialized_get_type(geom);
 
        if ( from < 0 || from > 1 )
        {
                elog(ERROR,"line_interpolate_point: 2nd arg isn't within [0,1]");
                PG_RETURN_NULL();
        }
 
        if ( to < 0 || to > 1 )
        {
                elog(ERROR,"line_interpolate_point: 3rd arg isn't within [0,1]");
                PG_RETURN_NULL();
        }
 
        if ( from > to )
        {
                elog(ERROR, "2nd arg must be smaller then 3rd arg");
                PG_RETURN_NULL();
        }
 
        if ( type == LINETYPE )
        {
                LWLINE *iline = lwgeom_as_lwline(lwgeom_from_gserialized(geom));
 
                if ( lwgeom_is_empty((LWGEOM*)iline) )
                {
                        /* TODO return empty line */
                        lwline_release(iline);
                        PG_FREE_IF_COPY(geom, 0);
                        PG_RETURN_NULL();
                }
 
                ipa = iline->points;
 
                opa = ptarray_substring(ipa, from, to, 0);
 
                if ( opa->npoints == 1 ) /* Point returned */
                        olwgeom = (LWGEOM *)lwpoint_construct(iline->srid, NULL, opa);
                else
                        olwgeom = (LWGEOM *)lwline_construct(iline->srid, NULL, opa);
 
        }
        else if ( type == MULTILINETYPE )
        {
                LWMLINE *iline;
                uint32_t i = 0, g = 0;
                int homogeneous = LW_TRUE;
                LWGEOM **geoms = NULL;
                double length = 0.0, sublength = 0.0, minprop = 0.0, maxprop = 0.0;
 
                iline = lwgeom_as_lwmline(lwgeom_from_gserialized(geom));
 
                if ( lwgeom_is_empty((LWGEOM*)iline) )
                {
                        /* TODO return empty collection */
                        lwmline_release(iline);
                        PG_FREE_IF_COPY(geom, 0);
                        PG_RETURN_NULL();
                }
 
                /* Calculate the total length of the mline */
                for ( i = 0; i < iline->ngeoms; i++ )
                {
                        LWLINE *subline = (LWLINE*)iline->geoms[i];
                        if ( subline->points && subline->points->npoints > 1 )
                                length += ptarray_length_2d(subline->points);
                }
 
                geoms = lwalloc(sizeof(LWGEOM*) * iline->ngeoms);
 
                /* Slice each sub-geometry of the multiline */
                for ( i = 0; i < iline->ngeoms; i++ )
                {
                        LWLINE *subline = (LWLINE*)iline->geoms[i];
                        double subfrom = 0.0, subto = 0.0;
 
                        if ( subline->points && subline->points->npoints > 1 )
                                sublength += ptarray_length_2d(subline->points);
 
                        /* Calculate proportions for this subline */
                        minprop = maxprop;
                        maxprop = sublength / length;
 
                        /* This subline doesn't reach the lowest proportion requested
                           or is beyond the highest proporton */
                        if ( from > maxprop || to < minprop )
                                continue;
 
                        if ( from <= minprop )
                                subfrom = 0.0;
                        if ( to >= maxprop )
                                subto = 1.0;
 
                        if ( from > minprop && from <= maxprop )
                                subfrom = (from - minprop) / (maxprop - minprop);
 
                        if ( to < maxprop && to >= minprop )
                                subto = (to - minprop) / (maxprop - minprop);
 
 
                        opa = ptarray_substring(subline->points, subfrom, subto, 0);
                        if ( opa && opa->npoints > 0 )
                        {
                                if ( opa->npoints == 1 ) /* Point returned */
                                {
                                        geoms[g] = (LWGEOM *)lwpoint_construct(SRID_UNKNOWN, NULL, opa);
                                        homogeneous = LW_FALSE;
                                }
                                else
                                {
                                        geoms[g] = (LWGEOM *)lwline_construct(SRID_UNKNOWN, NULL, opa);
                                }
                                g++;
                        }
 
 
 
                }
                /* If we got any points, we need to return a GEOMETRYCOLLECTION */
                if ( ! homogeneous )
                        type = COLLECTIONTYPE;
 
                olwgeom = (LWGEOM*)lwcollection_construct(type, iline->srid, NULL, g, geoms);
        }
        else
        {
                elog(ERROR,"line_substring: 1st arg isn't a line");
                PG_RETURN_NULL();
        }
 
        ret = geometry_serialize(olwgeom);
        lwgeom_free(olwgeom);
        PG_FREE_IF_COPY(geom, 0);
        PG_RETURN_POINTER(ret);
 
}

References COLLECTIONTYPE, LWMLINE::geoms, gserialized_get_type(), LINETYPE, LW_FALSE, LW_TRUE, lwalloc(), lwcollection_construct(), lwgeom_as_lwline(), lwgeom_as_lwmline(), lwgeom_free(), lwgeom_from_gserialized(), lwgeom_is_empty(), lwline_construct(), lwline_release(), lwmline_release(), lwpoint_construct(), MULTILINETYPE, LWMLINE::ngeoms, POINTARRAY::npoints, LWLINE::points, ptarray_length_2d(), ptarray_substring(), LWLINE::srid, LWMLINE::srid, and SRID_UNKNOWN.

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