83 lines
1.8 KiB
Go
83 lines
1.8 KiB
Go
// Package hub provides a simple event dispatcher for publish/subscribe pattern.
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package hub
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import "sync"
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type Kind int
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// Event is an interface for published events.
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type Event interface {
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Kind() Kind
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}
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// Hub is an event dispatcher, publishes events to the subscribers
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// which are subscribed for a specific event type.
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// Optimized for publish calls.
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// The handlers may be called in order different than they are registered.
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type Hub struct {
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subscribers map[Kind][]handler
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m sync.RWMutex
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seq uint64
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}
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type handler struct {
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f func(Event)
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id uint64
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}
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// Subscribe registers f for the event of a specific kind.
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func (h *Hub) Subscribe(kind Kind, f func(Event)) (cancel func()) {
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var cancelled bool
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h.m.Lock()
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h.seq++
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id := h.seq
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if h.subscribers == nil {
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h.subscribers = make(map[Kind][]handler)
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}
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h.subscribers[kind] = append(h.subscribers[kind], handler{id: id, f: f})
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h.m.Unlock()
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return func() {
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h.m.Lock()
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if cancelled {
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h.m.Unlock()
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return
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}
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cancelled = true
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a := h.subscribers[kind]
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for i, f := range a {
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if f.id == id {
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a[i], h.subscribers[kind] = a[len(a)-1], a[:len(a)-1]
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break
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}
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}
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if len(a) == 0 {
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delete(h.subscribers, kind)
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}
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h.m.Unlock()
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}
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}
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// Publish an event to the subscribers.
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func (h *Hub) Publish(e Event) {
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h.m.RLock()
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if handlers, ok := h.subscribers[e.Kind()]; ok {
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for _, h := range handlers {
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h.f(e)
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}
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}
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h.m.RUnlock()
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}
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// DefaultHub is the default Hub used by Publish and Subscribe.
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var DefaultHub Hub
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// Subscribe registers f for the event of a specific kind in the DefaultHub.
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func Subscribe(kind Kind, f func(Event)) (cancel func()) {
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return DefaultHub.Subscribe(kind, f)
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}
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// Publish an event to the subscribers in DefaultHub.
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func Publish(e Event) {
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DefaultHub.Publish(e)
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}
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