package events import ( "sync" "sync/atomic" ) type EventSwitch struct { mtx sync.RWMutex eventCells map[string]*eventCell listeners map[string]*eventListener running uint32 quit chan struct{} } func (evsw *EventSwitch) Start() { if atomic.CompareAndSwapUint32(&evsw.running, 0, 1) { evsw.eventCells = make(map[string]*eventCell) evsw.listeners = make(map[string]*eventListener) evsw.quit = make(chan struct{}) } } func (evsw *EventSwitch) Stop() { if atomic.CompareAndSwapUint32(&evsw.running, 1, 0) { evsw.eventCells = nil evsw.listeners = nil close(evsw.quit) } } func (evsw *EventSwitch) AddListenerForEvent(listenerId, event string, cb eventCallback) { // Get/Create eventCell and listener evsw.mtx.Lock() eventCell := evsw.eventCells[event] if eventCell == nil { eventCell = newEventCell() evsw.eventCells[event] = eventCell } listener := evsw.listeners[listenerId] if listener == nil { listener = newEventListener(listenerId) evsw.listeners[listenerId] = listener } evsw.mtx.Unlock() // Add event and listener eventCell.AddListener(listenerId, cb) listener.AddEvent(event) } func (evsw *EventSwitch) RemoveListener(listenerId string) { // Get and remove listener evsw.mtx.RLock() listener := evsw.listeners[listenerId] delete(evsw.listeners, listenerId) evsw.mtx.RUnlock() if listener == nil { return } // Remove callback for each event. listener.SetRemoved() for _, event := range listener.GetEvents() { evsw.RemoveListenerForEvent(event, listenerId) } } func (evsw *EventSwitch) RemoveListenerForEvent(event string, listenerId string) { // Get eventCell evsw.mtx.Lock() eventCell := evsw.eventCells[event] evsw.mtx.Unlock() if eventCell == nil { return } // Remove listenerId from eventCell numListeners := eventCell.RemoveListener(listenerId) // Maybe garbage collect eventCell. if numListeners == 0 { // Lock again and double check. evsw.mtx.Lock() // OUTER LOCK eventCell.mtx.Lock() // INNER LOCK if len(eventCell.listeners) == 0 { delete(evsw.eventCells, event) } eventCell.mtx.Unlock() // INNER LOCK evsw.mtx.Unlock() // OUTER LOCK } } func (evsw *EventSwitch) FireEvent(event string, msg interface{}) { // Get the eventCell evsw.mtx.RLock() eventCell := evsw.eventCells[event] evsw.mtx.RUnlock() if eventCell == nil { return } // Fire event for all listeners in eventCell eventCell.FireEvent(msg) } //----------------------------------------------------------------------------- // eventCell handles keeping track of listener callbacks for a given event. type eventCell struct { mtx sync.RWMutex listeners map[string]eventCallback } func newEventCell() *eventCell { return &eventCell{ listeners: make(map[string]eventCallback), } } func (cell *eventCell) AddListener(listenerId string, cb eventCallback) { cell.mtx.Lock() cell.listeners[listenerId] = cb cell.mtx.Unlock() } func (cell *eventCell) RemoveListener(listenerId string) int { cell.mtx.Lock() delete(cell.listeners, listenerId) numListeners := len(cell.listeners) cell.mtx.Unlock() return numListeners } func (cell *eventCell) FireEvent(msg interface{}) { cell.mtx.RLock() for _, listener := range cell.listeners { listener(msg) } cell.mtx.RUnlock() } //----------------------------------------------------------------------------- type eventCallback func(msg interface{}) type eventListener struct { id string mtx sync.RWMutex removed bool events []string } func newEventListener(id string) *eventListener { return &eventListener{ id: id, removed: false, events: nil, } } func (evl *eventListener) AddEvent(event string) { evl.mtx.Lock() defer evl.mtx.Unlock() if evl.removed { return } evl.events = append(evl.events, event) } func (evl *eventListener) GetEvents() []string { evl.mtx.RLock() defer evl.mtx.RUnlock() events := make([]string, len(evl.events)) copy(events, evl.events) return events } func (evl *eventListener) SetRemoved() { evl.mtx.Lock() defer evl.mtx.Unlock() evl.removed = true }