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single_notifier.go
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single_notifier.go
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/**
* Standalone signaling server for the Nextcloud Spreed app.
* Copyright (C) 2022 struktur AG
*
* @author Joachim Bauch <bauch@struktur.de>
*
* @license GNU AGPL version 3 or any later version
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package signaling
import (
"context"
"sync"
)
type SingleWaiter struct {
root bool
ch chan struct{}
once sync.Once
}
func newSingleWaiter() *SingleWaiter {
return &SingleWaiter{
root: true,
ch: make(chan struct{}),
}
}
func (w *SingleWaiter) subWaiter() *SingleWaiter {
return &SingleWaiter{
ch: w.ch,
}
}
func (w *SingleWaiter) Wait(ctx context.Context) error {
select {
case <-w.ch:
return nil
case <-ctx.Done():
return ctx.Err()
}
}
func (w *SingleWaiter) cancel() {
if !w.root {
return
}
w.once.Do(func() {
close(w.ch)
})
}
type SingleNotifier struct {
sync.Mutex
waiter *SingleWaiter
waiters map[*SingleWaiter]bool
}
func (n *SingleNotifier) NewWaiter() *SingleWaiter {
n.Lock()
defer n.Unlock()
if n.waiter == nil {
n.waiter = newSingleWaiter()
}
if n.waiters == nil {
n.waiters = make(map[*SingleWaiter]bool)
}
w := n.waiter.subWaiter()
n.waiters[w] = true
return w
}
func (n *SingleNotifier) Reset() {
n.Lock()
defer n.Unlock()
if n.waiter != nil {
n.waiter.cancel()
n.waiter = nil
}
n.waiters = nil
}
func (n *SingleNotifier) Release(w *SingleWaiter) {
n.Lock()
defer n.Unlock()
if _, found := n.waiters[w]; found {
delete(n.waiters, w)
if len(n.waiters) == 0 {
n.waiters = nil
if n.waiter != nil {
n.waiter.cancel()
n.waiter = nil
}
}
}
}
func (n *SingleNotifier) Notify() {
n.Lock()
defer n.Unlock()
if n.waiter != nil {
n.waiter.cancel()
}
n.waiters = nil
}