lwmline_measured_from_lwmline()

LWMLINE* lwmline_measured_from_lwmline	(	const LWMLINE *	lwmline,
		double	m_start,
		double	m_end
	)

Re-write the measure ordinate (or add one, if it isn't already there) interpolating the measure between the supplied start and end values.

Definition at line 56 of file lwmline.c.

References LWMLINE::flags, FLAGS_GET_Z, LWMLINE::geoms, if(), lwalloc(), lwcollection_construct(), lwcollection_construct_empty(), lwerror(), lwgeom_is_empty(), lwline_measured_from_lwline(), MULTILINETYPE, LWMLINE::ngeoms, POINTARRAY::npoints, LWLINE::points, ptarray_length_2d(), LWGEOM::srid, LWGEOM::type, and LWMLINE::type.

Referenced by ST_AddMeasure().

{
        int i = 0;
        int hasm = 0, hasz = 0;
        double length = 0.0, length_so_far = 0.0;
        double m_range = m_end - m_start;
        LWGEOM **geoms = NULL;

        if ( lwmline->type != MULTILINETYPE )
        {
                lwerror("lwmline_measured_from_lmwline: only multiline types supported");
                return NULL;
        }

        hasz = FLAGS_GET_Z(lwmline->flags);
        hasm = 1;

        /* Calculate the total length of the mline */
        for ( i = 0; i < lwmline->ngeoms; i++ )
        {
                LWLINE *lwline = (LWLINE*)lwmline->geoms[i];
                if ( lwline->points && lwline->points->npoints > 1 )
                {
                        length += ptarray_length_2d(lwline->points);
                }
        }

        if ( lwgeom_is_empty((LWGEOM*)lwmline) )
        {
                return (LWMLINE*)lwcollection_construct_empty(MULTILINETYPE, lwmline->srid, hasz, hasm);
        }

        geoms = lwalloc(sizeof(LWGEOM*) * lwmline->ngeoms);

        for ( i = 0; i < lwmline->ngeoms; i++ )
        {
                double sub_m_start, sub_m_end;
                double sub_length = 0.0;
                LWLINE *lwline = (LWLINE*)lwmline->geoms[i];

                if ( lwline->points && lwline->points->npoints > 1 )
                {
                        sub_length = ptarray_length_2d(lwline->points);
                }

                sub_m_start = (m_start + m_range * length_so_far / length);
                sub_m_end = (m_start + m_range * (length_so_far + sub_length) / length);

                geoms[i] = (LWGEOM*)lwline_measured_from_lwline(lwline, sub_m_start, sub_m_end);

                length_so_far += sub_length;
        }

        return (LWMLINE*)lwcollection_construct(lwmline->type, lwmline->srid, NULL, lwmline->ngeoms, geoms);
}

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