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package util
import (
"fmt"
"io/ioutil"
"os"
"path/filepath"
)
type PersistedLamport struct {
LamportClock
filePath string
}
func NewPersistedLamport(filePath string) *PersistedLamport {
clock := &PersistedLamport{
filePath: filePath,
}
return clock
}
func LoadPersistedLamport(filePath string) (*PersistedLamport, error) {
clock := &PersistedLamport{
filePath: filePath,
}
err := clock.read()
if err != nil {
return nil, err
}
return clock, nil
}
func (c *PersistedLamport) Witness(time LamportTime) error {
c.LamportClock.Witness(time)
return c.Write()
}
func (c *PersistedLamport) Time() LamportTime {
// Equivalent to:
//
// res = c.LamportClock.Time()
// bugClock.Increment()
//
// ... but thread safe
return c.Increment() - 1
}
func (c *PersistedLamport) 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.LamportClock = NewLamportClockWithTime(value)
return nil
}
func (c *PersistedLamport) Write() error {
dir := filepath.Dir(c.filePath)
err := os.MkdirAll(dir, 0777)
if err != nil {
return err
}
data := []byte(fmt.Sprintf("%d", c.LamportClock.Time()))
return ioutil.WriteFile(c.filePath, data, 0644)
}
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