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event: use sync.Once for init for faster/cleaner locking

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This commit is contained in:
Péter Szilágyi 2017-02-03 14:04:57 +02:00
parent d52b0c32a0
commit 9b5c7153c9
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1 changed files with 5 additions and 11 deletions
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16
event/feed.go
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@ -33,9 +33,8 @@ var errBadChannel = errors.New("event: Subscribe argument does not have sendable
// //
// The zero value is ready to use. // The zero value is ready to use.
type Feed struct { type Feed struct {
// sendLock has a one-element buffer and is empty when held. once sync.Once // ensures that init only runs once
// It protects sendCases. sendLock chan struct{} // sendLock has a one-element buffer and is empty when held.It protects sendCases.
sendLock chan struct{}
removeSub chan interface{} // interrupts Send removeSub chan interface{} // interrupts Send
sendCases caseList // the active set of select cases used by Send sendCases caseList // the active set of select cases used by Send
@ -60,9 +59,6 @@ func (e feedTypeError) Error() string {
} }
func (f *Feed) init() { func (f *Feed) init() {
if f.sendLock != nil {
return
}
f.removeSub = make(chan interface{}) f.removeSub = make(chan interface{})
f.sendLock = make(chan struct{}, 1) f.sendLock = make(chan struct{}, 1)
f.sendLock <- struct{}{} f.sendLock <- struct{}{}
@ -75,6 +71,8 @@ func (f *Feed) init() {
// The channel should have ample buffer space to avoid blocking other subscribers. // The channel should have ample buffer space to avoid blocking other subscribers.
// Slow subscribers are not dropped. // Slow subscribers are not dropped.
func (f *Feed) Subscribe(channel interface{}) Subscription { func (f *Feed) Subscribe(channel interface{}) Subscription {
f.once.Do(f.init)
chanval := reflect.ValueOf(channel) chanval := reflect.ValueOf(channel)
chantyp := chanval.Type() chantyp := chanval.Type()
if chantyp.Kind() != reflect.Chan || chantyp.ChanDir()&reflect.SendDir == 0 { if chantyp.Kind() != reflect.Chan || chantyp.ChanDir()&reflect.SendDir == 0 {
@ -84,7 +82,6 @@ func (f *Feed) Subscribe(channel interface{}) Subscription {
f.mu.Lock() f.mu.Lock()
defer f.mu.Unlock() defer f.mu.Unlock()
f.init()
if !f.typecheck(chantyp.Elem()) { if !f.typecheck(chantyp.Elem()) {
panic(feedTypeError{op: "Subscribe", got: chantyp, want: reflect.ChanOf(reflect.SendDir, f.etype)}) panic(feedTypeError{op: "Subscribe", got: chantyp, want: reflect.ChanOf(reflect.SendDir, f.etype)})
} }
@ -130,10 +127,7 @@ func (f *Feed) remove(sub *feedSub) {
// Send delivers to all subscribed channels simultaneously. // Send delivers to all subscribed channels simultaneously.
// It returns the number of subscribers that the value was sent to. // It returns the number of subscribers that the value was sent to.
func (f *Feed) Send(value interface{}) (nsent int) { func (f *Feed) Send(value interface{}) (nsent int) {
f.mu.Lock() f.once.Do(f.init)
f.init()
f.mu.Unlock()
<-f.sendLock <-f.sendLock
// Add new cases from the inbox after taking the send lock. // Add new cases from the inbox after taking the send lock.