Add package "broadcast" for transmitting message to goroutines at the same time

utils/broadcast/broadcast.go

@@ -0,0 +1,73 @@
+package broadcast
+
+type Broadcast struct {
+	listeners  []chan interface{}
+	reg        chan (chan interface{})
+	unreg      chan (chan interface{})
+	in         chan interface{}
+	stop       chan int64
+	stopStatus bool
+}
+
+func NewBroadcast() *Broadcast {
+	b := &Broadcast{
+		listeners:  make([]chan interface{}, 0),
+		reg:        make(chan (chan interface{})),
+		unreg:      make(chan (chan interface{})),
+		in:         make(chan interface{}),
+		stop:       make(chan int64),
+		stopStatus: false,
+	}
+
+	go func() {
+		for {
+			select {
+			case l := <-b.unreg:
+				// remove L from b.listeners
+				// this operation is slow: O(n) but not used frequently
+				// unlike iterating over listeners
+				oldListeners := b.listeners
+				b.listeners = make([]chan interface{}, 0, len(oldListeners))
+				for _, oldL := range oldListeners {
+					if l != oldL {
+						b.listeners = append(b.listeners, oldL)
+					}
+				}
+
+			case l := <-b.reg:
+				b.listeners = append(b.listeners, l)
+
+			case item := <-b.in:
+				for _, l := range b.listeners {
+					l <- item
+				}
+
+			case _ = <-b.stop:
+				b.stopStatus = true
+				break
+			}
+		}
+	}()
+
+	return b
+}
+
+func (b *Broadcast) In() chan interface{} {
+	return b.in
+}
+
+func (b *Broadcast) Reg() chan interface{} {
+	listener := make(chan interface{})
+	b.reg <- listener
+	return listener
+}
+
+func (b *Broadcast) UnReg(listener chan interface{}) {
+	b.unreg <- listener
+}
+
+func (b *Broadcast) Close() {
+	if b.stopStatus == false {
+		b.stop <- 1
+	}
+}