/
events.go
231 lines (182 loc) · 4.6 KB
/
events.go
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package events
import (
"container/list"
"context"
"fmt"
"sync"
"github.com/libp2p/go-libp2p/core/event"
"github.com/libp2p/go-libp2p/p2p/host/eventbus"
)
type Event interface{}
// EmitterInterface Root interface for events dispatch
type EmitterInterface interface {
// Deprecated: Emit Sends an event to the subscribed listeners
Emit(context.Context, Event)
// Deprecated: GlobalChannel returns a glocal channel that receives emitted events
GlobalChannel(ctx context.Context) <-chan Event
// Deprecated: Subscribe Returns a channel that receives emitted events
Subscribe(ctx context.Context) <-chan Event
// Deprecated: UnsubscribeAll close all listeners channels
UnsubscribeAll()
}
// Deprecated: use event bus directly
// EventEmitter Registers listeners and dispatches events to them
type EventEmitter struct {
bus event.Bus
muEmitters sync.Mutex
cglobal <-chan Event
emitter event.Emitter
cancels []context.CancelFunc
}
type eventBox struct {
evt interface{}
}
// Deprecated: use event bus directly
// Emit Sends an event to the subscribed listeners
func (e *EventEmitter) Emit(_ context.Context, evt Event) {
e.muEmitters.Lock()
bus := e.getBus()
if e.emitter == nil {
var err error
e.emitter, err = bus.Emitter(new(eventBox))
if err != nil {
serr := fmt.Sprintf("unable to init eventBox emitter: %s", err.Error())
panic(serr)
}
}
e.muEmitters.Unlock()
box := eventBox{evt}
_ = e.emitter.Emit(box)
}
// Deprecated: use event Bus directly
// Subscribe Returns a channel that receives emitted events
func (e *EventEmitter) Subscribe(ctx context.Context) <-chan Event {
e.muEmitters.Lock()
bus := e.getBus()
sub, err := bus.Subscribe(event.WildcardSubscription)
if err != nil {
serr := fmt.Sprintf("unable to subscribe: %s", err.Error())
panic(serr)
}
ctx, cancel := context.WithCancel(ctx)
if e.cancels == nil {
e.cancels = []context.CancelFunc{}
}
e.cancels = append(e.cancels, cancel)
e.muEmitters.Unlock()
return e.handleSubscriber(ctx, sub)
}
// Deprecated: use event bus directly
// UnsubscribeAll close all listeners channels
func (e *EventEmitter) UnsubscribeAll() {
e.muEmitters.Lock()
for _, cancel := range e.cancels {
cancel()
}
e.muEmitters.Unlock()
}
func (e *EventEmitter) handleSubscriber(ctx context.Context, sub event.Subscription) <-chan Event {
cevent := make(chan Event, 16)
condProcess := sync.NewCond(&sync.Mutex{})
queue := list.New()
wg := sync.WaitGroup{}
wg.Add(1)
go func() {
defer wg.Done()
defer sub.Close()
for {
var e interface{}
select {
case e = <-sub.Out():
case <-ctx.Done():
condProcess.Signal()
return
}
if box, ok := e.(eventBox); ok {
e = box.evt
}
condProcess.L.Lock()
if queue.Len() == 0 {
// try to push event to the queue
select {
case cevent <- e:
condProcess.L.Unlock()
continue
default:
}
}
// push elem to the queue if the channel is blocking or
// we already have some events to process
queue.PushBack(e)
// signal that we have element to process
condProcess.Signal()
condProcess.L.Unlock()
}
}()
go func() {
condProcess.L.Lock()
for ctx.Err() == nil {
if queue.Len() == 0 {
condProcess.Wait()
continue
}
e := queue.Remove(queue.Front())
// Unlock cond mutex while sending the event
condProcess.L.Unlock()
select {
case <-ctx.Done():
case cevent <- e:
}
condProcess.L.Lock()
}
condProcess.L.Unlock()
wg.Wait()
close(cevent)
}()
return cevent
}
// Deprecated: use event bus directly
// GlobalChannel returns a glocal channel that receives emitted events
func (e *EventEmitter) GlobalChannel(ctx context.Context) (cc <-chan Event) {
e.muEmitters.Lock()
if e.cglobal == nil {
bus := e.getBus()
sub, err := bus.Subscribe(event.WildcardSubscription)
if err != nil {
serr := fmt.Sprintf("unable to subscribe: %s", err.Error())
panic(serr)
}
ctx, cancel := context.WithCancel(ctx)
if e.cancels == nil {
e.cancels = []context.CancelFunc{}
}
e.cancels = append(e.cancels, cancel)
e.cglobal = e.handleSubscriber(ctx, sub)
}
cc = e.cglobal
e.muEmitters.Unlock()
return
}
func (e *EventEmitter) GetBus() (bus event.Bus) {
e.muEmitters.Lock()
bus = e.getBus()
e.muEmitters.Unlock()
return
}
// set event bus, return an error if the bus is already set
func (e *EventEmitter) SetBus(bus event.Bus) (err error) {
e.muEmitters.Lock()
if e.bus == nil {
e.bus = bus
} else {
err = fmt.Errorf("bus is already init")
}
e.muEmitters.Unlock()
return
}
func (e *EventEmitter) getBus() (bus event.Bus) {
if e.bus == nil {
e.bus = eventbus.NewBus()
}
return e.bus
}