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timerwheel.go
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timerwheel.go
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package internal
import (
"math/bits"
"time"
)
func next2Power(x uint) uint {
x--
x |= x >> 1
x |= x >> 2
x |= x >> 4
x |= x >> 8
x |= x >> 16
x |= x >> 32
x++
return x
}
type Clock struct {
start time.Time
}
func (c *Clock) nowNano() int64 {
return time.Since(c.start).Nanoseconds()
}
func (c *Clock) expireNano(ttl time.Duration) int64 {
return c.nowNano() + ttl.Nanoseconds()
}
type TimerWheel[K comparable, V any] struct {
clock *Clock
buckets []uint
spans []uint
shift []uint
wheel [][]*List[K, V]
nanos int64
}
func NewTimerWheel[K comparable, V any](size uint) *TimerWheel[K, V] {
clock := &Clock{start: time.Now()}
buckets := []uint{64, 64, 32, 4, 1}
spans := []uint{
next2Power(uint((1 * time.Second).Nanoseconds())),
next2Power(uint((1 * time.Minute).Nanoseconds())),
next2Power(uint((1 * time.Hour).Nanoseconds())),
next2Power(uint((24 * time.Hour).Nanoseconds())),
next2Power(uint((24 * time.Hour).Nanoseconds())) * 4,
next2Power(uint((24 * time.Hour).Nanoseconds())) * 4,
}
shift := []uint{
uint(bits.TrailingZeros(spans[0])),
uint(bits.TrailingZeros(spans[1])),
uint(bits.TrailingZeros(spans[2])),
uint(bits.TrailingZeros(spans[3])),
uint(bits.TrailingZeros(spans[4])),
}
wheel := [][]*List[K, V]{}
for i := 0; i < 5; i++ {
tmp := []*List[K, V]{}
for j := 0; j < int(buckets[i]); j++ {
tmp = append(tmp, NewList[K, V](0, WHEEL_LIST))
}
wheel = append(wheel, tmp)
}
return &TimerWheel[K, V]{
buckets: buckets,
spans: spans,
shift: shift,
wheel: wheel,
nanos: clock.nowNano(),
clock: clock,
}
}
func (tw *TimerWheel[K, V]) findIndex(expire int64) (int, int) {
duration := expire - tw.nanos
for i := 0; i < 5; i++ {
if duration < int64(tw.spans[i+1]) {
ticks := expire >> int(tw.shift[i])
slot := int(ticks) & (int(tw.buckets[i]) - 1)
return i, slot
}
}
return 4, 0
}
func (tw *TimerWheel[K, V]) deschedule(entry *Entry[K, V]) {
entry.prev(WHEEL_LIST).setNext(entry.next(WHEEL_LIST), WHEEL_LIST)
entry.next(WHEEL_LIST).setPrev(entry.prev(WHEEL_LIST), WHEEL_LIST)
entry.setNext(nil, WHEEL_LIST)
entry.setPrev(nil, WHEEL_LIST)
}
func (tw *TimerWheel[K, V]) schedule(entry *Entry[K, V]) {
if entry.meta.wheelPrev != nil {
tw.deschedule(entry)
}
x, y := tw.findIndex(entry.expire.Load())
tw.wheel[x][y].PushFront(entry)
}
func (tw *TimerWheel[K, V]) advance(now int64, remove func(entry *Entry[K, V], reason RemoveReason)) {
if now == 0 {
now = tw.clock.nowNano()
}
previous := tw.nanos
tw.nanos = now
for i := 0; i < 5; i++ {
prevTicks := previous >> int64(tw.shift[i])
currentTicks := tw.nanos >> int64(tw.shift[i])
if currentTicks <= prevTicks {
break
}
tw.expire(i, prevTicks, currentTicks-prevTicks, remove)
}
}
func (tw *TimerWheel[K, V]) expire(index int, prevTicks int64, delta int64, remove func(entry *Entry[K, V], reason RemoveReason)) {
mask := tw.buckets[index] - 1
steps := tw.buckets[index]
if delta < int64(steps) {
steps = uint(delta)
}
start := prevTicks & int64(mask)
end := start + int64(steps)
for i := start; i < end; i++ {
list := tw.wheel[index][i&int64(mask)]
entry := list.Front()
for entry != nil {
next := entry.Next(WHEEL_LIST)
if entry.expire.Load() <= tw.nanos {
tw.deschedule(entry)
remove(entry, EXPIRED)
} else {
tw.schedule(entry)
}
entry = next
}
list.Reset()
}
}