Golang Geos.Clone方法代碼示例

func flattenLineStrings(g *geos.Geos, geoms []*geos.Geom) []*geos.Geom {
	var result []*geos.Geom
	for _, geom := range geoms {
		if g.Type(geom) == "MultiLineString" {
			for _, part := range g.Geoms(geom) {
				result = append(result, g.Clone(part))
			}
			g.Destroy(geom)
		} else if g.Type(geom) == "LineString" {
			result = append(result, geom)
		} else {
			log.Printf("unexpected geometry type in flattenLineStrings: %s", g.Type(geom))
			g.Destroy(geom)
		}
	}
	return result
}

func filterGeometryByType(g *geos.Geos, geom *geos.Geom, targetType string) []*geos.Geom {
	// Filter (multi)geometry for compatible `geom_type`,
	// because we can't insert points into linestring tables for example

	geomType := g.Type(geom)

	if geomType == targetType {
		// same type is fine
		return []*geos.Geom{geom}
	}
	if geomType == "Polygon" && targetType == "MultiPolygon" {
		// multipolygon mappings also support polygons
		return []*geos.Geom{geom}
	}
	if geomType == "MultiPolygon" && targetType == "Polygon" {
		// polygon mappings should also support multipolygons
		return []*geos.Geom{geom}
	}

	if g.NumGeoms(geom) >= 1 {
		// GeometryCollection or MultiLineString? return list of geometries
		var geoms []*geos.Geom
		for _, part := range g.Geoms(geom) {
			// only parts with same type
			if g.Type(part) == targetType {
				geoms = append(geoms, g.Clone(part))
			}
		}
		g.Destroy(geom)
		if len(geoms) != 0 {
			return geoms
		}
		return []*geos.Geom{}
	}
	g.Destroy(geom)
	return []*geos.Geom{}
}

// buildRelGeometry builds the geometry of rel by creating a multipolygon of all rings.
// rings need to be sorted by area (large to small).
func buildRelGeometry(g *geos.Geos, rel *element.Relation, rings []*ring) (*geos.Geom, error) {
	totalRings := len(rings)
	shells := map[*ring]bool{rings[0]: true}
	for i := 0; i < totalRings; i++ {
		testGeom := g.Prepare(rings[i].geom)
		if testGeom == nil {
			return nil, errors.New("Error while preparing geometry")
		}
		for j := i + 1; j < totalRings; j++ {
			if g.PreparedContains(testGeom, rings[j].geom) {
				if rings[j].containedBy != -1 {
					// j is inside a larger ring, remove that relationship
					// e.g. j is hole inside a hole (i)
					delete(rings[rings[j].containedBy].holes, rings[j])
					delete(shells, rings[j])
				}
				// remember parent
				rings[j].containedBy = i
				// add ring as hole or shell
				if ringIsHole(rings, j) {
					rings[i].holes[rings[j]] = true
					rings[i].outer = false
				} else {
					shells[rings[j]] = true
					rings[i].outer = true
				}
			}
		}
		if rings[i].containedBy == -1 {
			// add as shell if it is not a hole
			shells[rings[i]] = true
			rings[i].outer = true
		}
		g.PreparedDestroy(testGeom)
	}

	var polygons []*geos.Geom
	for shell, _ := range shells {
		var interiors []*geos.Geom
		for hole, _ := range shell.holes {
			ring := g.Clone(g.ExteriorRing(hole.geom))
			g.Destroy(hole.geom)
			if ring == nil {
				return nil, errors.New("Error while getting exterior ring.")
			}
			interiors = append(interiors, ring)
		}
		exterior := g.Clone(g.ExteriorRing(shell.geom))
		g.Destroy(shell.geom)
		if exterior == nil {
			return nil, errors.New("Error while getting exterior ring.")
		}
		polygon := g.Polygon(exterior, interiors)
		if polygon == nil {
			return nil, errors.New("Error while building polygon.")
		}
		polygons = append(polygons, polygon)
	}
	var result *geos.Geom

	if len(polygons) == 1 {
		result = polygons[0]
	} else {
		result = g.MultiPolygon(polygons)
		if result == nil {
			return nil, errors.New("Error while building multi-polygon.")
		}
	}
	var err error
	result, err = g.MakeValid(result)
	if err != nil {
		return nil, err
	}

	g.DestroyLater(result)

	outer := make(map[int64]struct{})
	for i := range rings {
		if rings[i].outer {
			for _, w := range rings[i].ways {
				outer[w.Id] = struct{}{}
			}
		}
	}
	for i := range rel.Members {
		mid := rel.Members[i].Id
		if _, ok := outer[mid]; ok {
			rel.Members[i].Role = "outer"
		} else {
			rel.Members[i].Role = "inner"
		}
	}

	return result, nil
}