first commit

NitroxServer-Subnautica/AppMutex.cs

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+using System;
+using System.Threading;
+
+namespace NitroxServer_Subnautica;
+
+public static class AppMutex
+{
+    private static readonly SemaphoreSlim mutexReleaseGate = new(1);
+    private static readonly SemaphoreSlim callerGate = new(1);
+
+    public static void Hold(Action onWaitingForMutex = null, CancellationToken ct = default)
+    {
+        Thread thread = new(o =>
+        {
+            bool first = true;
+            Mutex mutex = new(false, typeof(AppMutex).Assembly.FullName, out bool _);
+            try
+            {
+                try
+                {
+                    while (!mutex.WaitOne(100, false))
+                    {
+                        ct.ThrowIfCancellationRequested();
+                        if (first)
+                        {
+                            first = false;
+                            onWaitingForMutex?.Invoke();
+                        }
+                    }
+                }
+                catch (AbandonedMutexException)
+                {
+                    // Mutex was abandoned in another process, it will still get acquired
+                }
+            }
+            finally
+            {
+                callerGate.Release();
+                mutexReleaseGate.Wait(-1);
+                mutex.ReleaseMutex();
+            }
+        });
+        mutexReleaseGate.Wait(-1, ct);
+        callerGate.Wait(0, ct);
+        thread.Start();
+
+        while (!callerGate.Wait(100, ct))
+        {
+        }
+    }
+
+    public static void Release()
+    {
+        mutexReleaseGate.Release();
+    }
+}