From e6b2d1e0aa80baba32a4f114ebe84230d89e16f5 Mon Sep 17 00:00:00 2001
From: Joachim Bauch <bauch@struktur.de>
Date: Thu, 19 Jan 2023 15:00:46 +0100
Subject: [PATCH] Add helper class to handle close channels.

---
 closer.go      | 47 ++++++++++++++++++++++++++++++++++++++
 closer_test.go | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 109 insertions(+)
 create mode 100644 closer.go
 create mode 100644 closer_test.go

diff --git a/closer.go b/closer.go
new file mode 100644
index 0000000..a68c850
--- /dev/null
+++ b/closer.go
@@ -0,0 +1,47 @@
+/**
+ * Standalone signaling server for the Nextcloud Spreed app.
+ * Copyright (C) 2023 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 (
+	"sync/atomic"
+)
+
+type Closer struct {
+	closed uint32
+	C      chan struct{}
+}
+
+func NewCloser() *Closer {
+	return &Closer{
+		C: make(chan struct{}),
+	}
+}
+
+func (c *Closer) IsClosed() bool {
+	return atomic.LoadUint32(&c.closed) != 0
+}
+
+func (c *Closer) Close() {
+	if atomic.CompareAndSwapUint32(&c.closed, 0, 1) {
+		close(c.C)
+	}
+}
diff --git a/closer_test.go b/closer_test.go
new file mode 100644
index 0000000..1a14ea1
--- /dev/null
+++ b/closer_test.go
@@ -0,0 +1,62 @@
+/**
+ * Standalone signaling server for the Nextcloud Spreed app.
+ * Copyright (C) 2023 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 (
+	"sync"
+	"testing"
+)
+
+func TestCloserMulti(t *testing.T) {
+	closer := NewCloser()
+
+	var wg sync.WaitGroup
+	count := 10
+	for i := 0; i < count; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			<-closer.C
+		}()
+	}
+
+	if closer.IsClosed() {
+		t.Error("should not be closed")
+	}
+	closer.Close()
+	if !closer.IsClosed() {
+		t.Error("should be closed")
+	}
+	wg.Wait()
+}
+
+func TestCloserCloseBeforeWait(t *testing.T) {
+	closer := NewCloser()
+	closer.Close()
+	if !closer.IsClosed() {
+		t.Error("should be closed")
+	}
+	<-closer.C
+	if !closer.IsClosed() {
+		t.Error("should be closed")
+	}
+}