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