package lamport import ( "fmt" "io/ioutil" "os" "path/filepath" ) type Persisted struct { Clock filePath string } func NewPersisted(filePath string) (*Persisted, error) { clock := &Persisted{ Clock: NewClock(), filePath: filePath, } dir := filepath.Dir(filePath) err := os.MkdirAll(dir, 0777) if err != nil { return nil, err } return clock, nil } func LoadPersisted(filePath string) (*Persisted, error) { clock := &Persisted{ filePath: filePath, } err := clock.read() if err != nil { return nil, err } return clock, nil } func (c *Persisted) Increment() (Time, error) { time := c.Clock.Increment() return time, c.Write() } func (c *Persisted) Witness(time Time) error { // TODO: rework so that we write only when the clock was actually updated c.Clock.Witness(time) return c.Write() } func (c *Persisted) read() error { content, err := ioutil.ReadFile(c.filePath) if err != nil { return err } var value uint64 n, err := fmt.Sscanf(string(content), "%d", &value) if err != nil { return err } if n != 1 { return fmt.Errorf("could not read the clock") } c.Clock = NewClockWithTime(value) return nil } func (c *Persisted) Write() error { data := []byte(fmt.Sprintf("%d", c.counter)) return ioutil.WriteFile(c.filePath, data, 0644) }