lwline_extend()

LWLINE* lwline_extend	(	const LWLINE *	line,
		double	distance_forward,
		double	distance_backward
	)

Extend the ends of a line.

Definition at line 682 of file lwline.c.

{
        POINTARRAY *pa, *opa;
        POINT4D p00, p01, p10, p11;
        POINT4D p_start, p_end;
        uint32_t i;
        bool forward = false, backward = false;
 
        if (distance_forward < 0 || distance_backward < 0)
                lwerror("%s: distances must be non-negative", __func__);
 
        if (!line || lwline_is_empty(line) || lwline_count_vertices(line) < 2)
        {
                lwerror("%s: line must have at least two points", __func__);
        }
 
        pa = line->points;
        if (distance_backward > 0.0)
        {
                i = 0;
                /* Get two distinct points at start of pointarray */
                getPoint4d_p(pa, i++, &p00);
                getPoint4d_p(pa, i, &p01);
                while(p4d_same(&p00, &p01))
                {
                        if (i == pa->npoints - 1)
                        {
                                lwerror("%s: line must have at least two distinct points", __func__);
                        }
                        i++;
                        getPoint4d_p(pa, i, &p01);
                }
                project_pt_pt(&p01, &p00, distance_backward, &p_start);
                backward = true;
        }
 
        if (distance_forward > 0.0)
        {
                i = pa->npoints - 1;
                /* Get two distinct points at end of pointarray */
                getPoint4d_p(pa, i--, &p10);
                getPoint4d_p(pa, i, &p11);
                while(p4d_same(&p10, &p11))
                {
                        if (i == 0)
                        {
                                lwerror("%s: line must have at least two distinct points", __func__);
                        }
                        i--;
                        getPoint4d_p(pa, i, &p11);
                }
                project_pt_pt(&p11, &p10, distance_forward, &p_end);
                forward = true;
        }
 
        opa = ptarray_construct_empty(ptarray_has_z(pa), ptarray_has_m(pa), pa->npoints + 2);
 
        if (backward)
        {
                ptarray_append_point(opa, &p_start, true);
        }
        ptarray_append_ptarray(opa, pa, -1.0);
        if (forward)
        {
                ptarray_append_point(opa, &p_end, true);
        }
        return lwline_construct(line->srid, NULL, opa);
}

References getPoint4d_p(), lwerror(), lwline_construct(), lwline_count_vertices(), lwline_is_empty(), POINTARRAY::npoints, p4d_same(), LWLINE::points, project_pt_pt(), ptarray_append_point(), ptarray_append_ptarray(), ptarray_construct_empty(), ptarray_has_m(), ptarray_has_z(), and LWLINE::srid.

Referenced by geometry_line_extend().

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