func Polygon(g *geos.Geos, nodes []element.Node) (*geos.Geom, error) {
nodes = unduplicateNodes(nodes)
if len(nodes) < 4 {
return nil, ErrorNoRing
}
coordSeq, err := g.CreateCoordSeq(uint32(len(nodes)), 2)
if err != nil {
return nil, err
}
// coordSeq inherited by LinearRing, no destroy
for i, nd := range nodes {
err := coordSeq.SetXY(g, uint32(i), nd.Long, nd.Lat)
if err != nil {
return nil, err
}
}
ring, err := coordSeq.AsLinearRing(g)
if err != nil {
// coordSeq gets Destroy by GEOS
return nil, err
}
// ring inherited by Polygon, no destroy
geom := g.CreatePolygon(ring, nil)
if geom == nil {
g.Destroy(ring)
return nil, errors.New("unable to create polygon")
}
g.DestroyLater(geom)
return geom, nil
}