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Copy pathpubsub.go
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89 lines (75 loc) · 2.04 KB
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/*
* MinIO Cloud Storage, (C) 2019 MinIO, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package pubsub
import (
"sync"
)
// Sub - subscriber entity.
type Sub struct {
ch chan interface{}
filter func(entry interface{}) bool
}
// PubSub holds publishers and subscribers
type PubSub struct {
subs []*Sub
sync.RWMutex
}
// Publish message to the subscribers.
// Note that publish is always nob-blocking send so that we don't block on slow receivers.
// Hence receivers should use buffered channel so as not to miss the published events.
func (ps *PubSub) Publish(item interface{}) {
ps.RLock()
defer ps.RUnlock()
for _, sub := range ps.subs {
if sub.filter == nil || sub.filter(item) {
select {
case sub.ch <- item:
default:
}
}
}
}
// Subscribe - Adds a subscriber to pubsub system
func (ps *PubSub) Subscribe(subCh chan interface{}, doneCh <-chan struct{}, filter func(entry interface{}) bool) {
ps.Lock()
defer ps.Unlock()
sub := &Sub{subCh, filter}
ps.subs = append(ps.subs, sub)
go func() {
<-doneCh
ps.Lock()
defer ps.Unlock()
for i, s := range ps.subs {
if s == sub {
ps.subs = append(ps.subs[:i], ps.subs[i+1:]...)
}
}
}()
}
// HasSubscribers returns true if pubsub system has subscribers
func (ps *PubSub) HasSubscribers() bool {
return ps.NumSubscribers() > 0
}
// NumSubscribers returns the number of current subscribers
func (ps *PubSub) NumSubscribers() int {
ps.RLock()
defer ps.RUnlock()
return len(ps.subs)
}
// New inits a PubSub system
func New() *PubSub {
return &PubSub{}
}