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clock.go
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clock.go
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package mtg
import (
"encoding/binary"
"sync"
"time"
)
const clockStorePropertyKey = "MTG:GROUP:CLOCK:MONOTONIC"
type Clock struct {
sync.RWMutex
store Store
now time.Time
}
func NewClock(store Store) (*Clock, error) {
ts, err := readPropertyAsTime(store)
if err != nil {
return nil, err
}
if now := time.Now(); ts.Before(now) {
ts = now
}
clock := new(Clock)
clock.store = store
clock.now = ts
return clock, nil
}
func (c *Clock) Now() time.Time {
c.Lock()
defer c.Unlock()
for {
now := time.Now()
if now.After(c.now) {
c.now = now
break
}
time.Sleep(100 * time.Millisecond)
}
val := binary.BigEndian.AppendUint64(nil, uint64(c.now.UnixNano()))
for {
err := c.store.WriteProperty([]byte(clockStorePropertyKey), val)
if err == nil {
break
}
time.Sleep(100 * time.Millisecond)
}
return c.now
}
func readPropertyAsTime(store Store) (time.Time, error) {
bs, err := store.ReadProperty([]byte(clockStorePropertyKey))
if err != nil || bs == nil {
return time.Now(), err
}
return time.Unix(0, int64(binary.BigEndian.Uint64(bs))), nil
}