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