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.

{
        uint32_t 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);
}

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

Referenced by ST_AddMeasure().

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