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broadcaster.go
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broadcaster.go
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package broadcaster
import (
"errors"
"sync"
"time"
)
var ErrBroadcasterClosed = errors.New("broadcaster is closed")
type CancelFunc func()
type Converter[In, Out any] func(In) (Out, bool)
type Broadcaster[T any] interface {
Listen(opts ...ListenerOption) (<-chan T, CancelFunc, error)
IsClosed() bool
Done() <-chan struct{}
}
type broadcaster[In, Out any] struct {
broadcasterOptions
input <-chan In
convert Converter[In, Out]
listeners map[chan<- Out]listenerOptions
reg chan listenerRequest[Out]
unreg chan listenerRequest[Out]
closed chan struct{}
}
type listenerRequest[T any] struct {
channel chan<- T
opts listenerOptions
done chan struct{}
}
func NewBroadcaster[T any](input <-chan T, opts ...BroadcasterOption) Broadcaster[T] {
return NewConverterBroadcaster(input, noConversion, opts...)
}
func NewConverterBroadcaster[In, Out any](input <-chan In, convert Converter[In, Out], opts ...BroadcasterOption) Broadcaster[Out] {
b := &broadcaster[In, Out]{
broadcasterOptions: defaultBroadcasterOptions,
input: input,
convert: convert,
listeners: make(map[chan<- Out]listenerOptions),
reg: make(chan listenerRequest[Out]),
unreg: make(chan listenerRequest[Out]),
closed: make(chan struct{}),
}
for _, opt := range opts {
opt(&b.broadcasterOptions)
}
go b.run()
return b
}
func (b *broadcaster[In, Out]) Listen(opts ...ListenerOption) (<-chan Out, CancelFunc, error) {
lisOpts := listenerOptions{
bufSize: b.lisBufSize,
}
for _, opt := range opts {
opt(&lisOpts)
}
listener := make(chan Out, lisOpts.bufSize)
if err := b.register(listener, lisOpts); err != nil {
return nil, nil, err
}
cancel := sync.OnceFunc(func() { b.unregister(listener) })
if lisOpts.ctx != nil {
go func() {
<-lisOpts.ctx.Done()
cancel()
}()
}
return listener, cancel, nil
}
func (b *broadcaster[In, Out]) IsClosed() bool {
select {
case <-b.closed:
return true
default:
return false
}
}
func (b *broadcaster[In, Out]) Done() <-chan struct{} {
return b.closed
}
func (b *broadcaster[In, Out]) register(listener chan<- Out, opts listenerOptions) error {
req := listenerRequest[Out]{
channel: listener,
opts: opts,
done: make(chan struct{}),
}
select {
case <-b.closed:
return ErrBroadcasterClosed
case b.reg <- req:
<-req.done
return nil
}
}
func (b *broadcaster[In, Out]) unregister(listener chan<- Out) {
req := listenerRequest[Out]{
channel: listener,
done: make(chan struct{}),
}
select {
case <-b.closed:
case b.unreg <- req:
<-req.done
}
}
func (b *broadcaster[In, Out]) run() {
defer b.close()
var idleTimer *time.Timer
var idle <-chan time.Time
if b.idleTimeout > 0 {
idleTimer = time.NewTimer(b.idleTimeout)
idle = idleTimer.C
}
for {
if idleTimer != nil {
if !idleTimer.Stop() {
<-idleTimer.C
}
idleTimer.Reset(b.idleTimeout)
}
if b.blocking && len(b.listeners) == 0 {
select {
case req := <-b.reg:
b.listeners[req.channel] = req.opts
close(req.done)
case <-idle:
return
}
}
select {
case m, ok := <-b.input:
if !ok {
return
}
b.broadcast(m)
case req := <-b.reg:
b.listeners[req.channel] = req.opts
close(req.done)
case req := <-b.unreg:
if _, ok := b.listeners[req.channel]; ok {
delete(b.listeners, req.channel)
close(req.channel)
}
close(req.done)
case <-idle:
return
}
}
}
func (b *broadcaster[In, Out]) broadcast(in In) {
if len(b.listeners) == 0 {
return
}
out, ok := b.convert(in)
if !ok {
return
}
var wg sync.WaitGroup
wg.Add(len(b.listeners))
if b.timeout < 0 {
for listener := range b.listeners {
listener := listener
go func() {
defer wg.Done()
listener <- out
}()
}
wg.Wait()
return
}
timeout := make(chan struct{})
if b.timeout == 0 {
close(timeout)
} else {
time.AfterFunc(b.timeout, func() { close(timeout) })
}
unreg := make(chan chan<- Out, len(b.listeners))
for listener, opts := range b.listeners {
listener := listener
onTimeout := opts.onTimeout
go func() {
defer wg.Done()
select { // try non-blocking first
case listener <- out:
return
default:
}
select {
case listener <- out:
case <-timeout:
unreg <- listener
if onTimeout != nil {
go onTimeout()
}
}
}()
}
wg.Wait()
close(unreg)
for listener := range unreg {
delete(b.listeners, listener)
close(listener)
}
}
func (b *broadcaster[In, Out]) close() {
close(b.closed)
for listener := range b.listeners {
close(listener)
}
clear(b.listeners)
}
func noConversion[T any](t T) (T, bool) {
return t, true
}