minio/pkg/pubsub/pubsub.go

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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"
)
// PubSub holds publishers and subscribers
type PubSub struct {
subs []chan interface{}
pub chan interface{}
mutex sync.Mutex
}
// process item to subscribers.
func (ps *PubSub) process() {
for item := range ps.pub {
ps.mutex.Lock()
for _, sub := range ps.subs {
go func(s chan interface{}) {
s <- item
}(sub)
}
ps.mutex.Unlock()
}
}
// Publish message to pubsub system
func (ps *PubSub) Publish(item interface{}) {
ps.pub <- item
}
// Subscribe - Adds a subscriber to pubsub system
func (ps *PubSub) Subscribe() chan interface{} {
ps.mutex.Lock()
defer ps.mutex.Unlock()
ch := make(chan interface{})
ps.subs = append(ps.subs, ch)
return ch
}
// Unsubscribe removes current subscriber
func (ps *PubSub) Unsubscribe(ch chan interface{}) {
ps.mutex.Lock()
defer ps.mutex.Unlock()
for i, sub := range ps.subs {
if sub == ch {
close(ch)
ps.subs = append(ps.subs[:i], ps.subs[i+1:]...)
}
}
}
// HasSubscribers returns true if pubsub system has subscribers
func (ps *PubSub) HasSubscribers() bool {
ps.mutex.Lock()
defer ps.mutex.Unlock()
return len(ps.subs) > 0
}
// New inits a PubSub system
func New() *PubSub {
ps := &PubSub{}
ps.pub = make(chan interface{})
go ps.process()
return ps
}