func persist(r ring.Ring, b *ring.Builder, filename string) error {
dir, name := path.Split(filename)
if dir == "" {
dir = "."
}
f, err := ioutil.TempFile(dir, name+".")
if err != nil {
return err
}
tmp := f.Name()
if r != nil {
err = r.Persist(f)
} else {
err = b.Persist(f)
}
if err != nil {
f.Close()
return err
}
if err = f.Close(); err != nil {
return err
}
return os.Rename(path.Join(dir, tmp), filename)
}
