package estimator import ( "sync" "sync/atomic" "time" ) type Estimator struct { interval time.Duration count uint32 mu sync.Mutex rate uint32 time time.Time } func New(interval time.Duration) *Estimator { return &Estimator{ interval: interval, time: time.Now(), } } func (e *Estimator) swap(now time.Time) { interval := now.Sub(e.time) count := atomic.SwapUint32(&e.count, 0) if interval < time.Millisecond { e.rate = 0 } else { e.rate = uint32(uint64(count*1000) / uint64(interval/time.Millisecond)) } e.time = now } func (e *Estimator) Add(count uint32) { atomic.AddUint32(&e.count, count) } func (e *Estimator) estimate(now time.Time) uint32 { if now.Sub(e.time) > e.interval { e.swap(now) } return e.rate } func (e *Estimator) Estimate() uint32 { now := time.Now() e.mu.Lock() defer e.mu.Unlock() return e.estimate(now) }