fix: race condition when addUniverse called parallel

deno.json

@@ -1,6 +1,6 @@
 {
     "tasks": {
-        "test": "deno fmt && deno lint && deno check mod.ts && deno test"
+        "test": "deno fmt && deno lint && deno check mod.ts && deno test --allow-net --unstable"
     },
     "fmt": {
         "indentWidth": 4

src/receiver.test.ts

@@ -0,0 +1,27 @@
+/*
+* LMGU-Technik sACN-Deno
+
+* Copyright (C) 2023 Hans Schallmoser
+
+* This program is free software: you can redistribute it and/or modify
+* it under the terms of the GNU 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 General Public License for more details.
+
+* You should have received a copy of the GNU General Public License
+* along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+import { Receiver } from "../mod.ts";
+
+Deno.test("Add Universe", () => {
+    using recv = new Receiver();
+    recv.addUniverse(1);
+    recv.addUniverse(1);
+    recv.addUniverse(2);
+});

src/receiver.ts

@@ -73,14 +73,20 @@ export class Receiver {
     }
 
     // universe => MulticastMembership
-    private readonly multicast = new Map<number, MulticastV4Membership>();
+    private readonly multicast = new Map<
+        number,
+        MulticastV4Membership | null
+    >();
 
     // returns true if successful, false if already listening to universe
     public async addUniverse(universe: number): Promise<boolean> {
         if (this.multicast.has(universe)) {
             return false;
         }
 
+        // prevent race condition when calling multiple times parallel
+        this.multicast.set(universe, null);
+
         const membership: MulticastV4Membership = await this.socket
             .joinMulticastV4(
                 multicastGroup(universe),
@@ -92,11 +98,16 @@ export class Receiver {
 
     // returns true if successful, false if not listening to universe
     public async removeUniverse(universe: number) {
-        if (!this.multicast.has(universe)) {
+        const membership = this.multicast.get(universe);
+
+        if (!membership) {
             return false;
         }
 
-        await this.multicast.get(universe)!.leave();
+        this.multicast.set(universe, null);
+
+        await membership!.leave();
+
         this.multicast.delete(universe);
         return true;
     }