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event: move type fixation logic into Feed.init (#27249) 

This is a minor optimization/refactoring of Feed.

---------

Co-authored-by: Felix Lange <fjl@twurst.com>
This commit is contained in:
Seungbae Yu 2023-05-30 23:34:32 +09:00 committed by GitHub
parent 560dceb58e
commit 8013a494fe
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 12 additions and 22 deletions
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34
event/feed.go
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@ -57,7 +57,8 @@ func (e feedTypeError) Error() string {
return "event: wrong type in " + e.op + " got " + e.got.String() + ", want " + e.want.String()
}
func (f *Feed) init() {
func (f *Feed) init(etype reflect.Type) {
f.etype = etype
f.removeSub = make(chan interface{})
f.sendLock = make(chan struct{}, 1)
f.sendLock <- struct{}{}
@ -70,8 +71,6 @@ func (f *Feed) init() {
// The channel should have ample buffer space to avoid blocking other subscribers.
// Slow subscribers are not dropped.
func (f *Feed) Subscribe(channel interface{}) Subscription {
f.once.Do(f.init)
chanval := reflect.ValueOf(channel)
chantyp := chanval.Type()
if chantyp.Kind() != reflect.Chan || chantyp.ChanDir()&reflect.SendDir == 0 {
@ -79,11 +78,13 @@ func (f *Feed) Subscribe(channel interface{}) Subscription {
}
sub := &feedSub{feed: f, channel: chanval, err: make(chan error, 1)}
f.mu.Lock()
defer f.mu.Unlock()
if !f.typecheck(chantyp.Elem()) {
f.once.Do(func() { f.init(chantyp.Elem()) })
if f.etype != chantyp.Elem() {
panic(feedTypeError{op: "Subscribe", got: chantyp, want: reflect.ChanOf(reflect.SendDir, f.etype)})
}
f.mu.Lock()
defer f.mu.Unlock()
// Add the select case to the inbox.
// The next Send will add it to f.sendCases.
cas := reflect.SelectCase{Dir: reflect.SelectSend, Chan: chanval}
@ -91,15 +92,6 @@ func (f *Feed) Subscribe(channel interface{}) Subscription {
return sub
}
// note: callers must hold f.mu
func (f *Feed) typecheck(typ reflect.Type) bool {
if f.etype == nil {
f.etype = typ
return true
}
return f.etype == typ
}
func (f *Feed) remove(sub *feedSub) {
// Delete from inbox first, which covers channels
// that have not been added to f.sendCases yet.
@ -128,19 +120,17 @@ func (f *Feed) remove(sub *feedSub) {
func (f *Feed) Send(value interface{}) (nsent int) {
rvalue := reflect.ValueOf(value)
f.once.Do(f.init)
f.once.Do(func() { f.init(rvalue.Type()) })
if f.etype != rvalue.Type() {
panic(feedTypeError{op: "Send", got: rvalue.Type(), want: f.etype})
}
<-f.sendLock
// Add new cases from the inbox after taking the send lock.
f.mu.Lock()
f.sendCases = append(f.sendCases, f.inbox...)
f.inbox = nil
if !f.typecheck(rvalue.Type()) {
f.sendLock <- struct{}{}
f.mu.Unlock()
panic(feedTypeError{op: "Send", got: rvalue.Type(), want: f.etype})
}
f.mu.Unlock()
// Set the sent value on all channels.