release: 0.41.0

src/SquidStd.Core/Interfaces/Threading/IEventLoopService.cs

@@ -15,4 +15,7 @@ public interface IEventLoopService
 
     /// <summary>Worst observed tick elapsed time in milliseconds.</summary>
     double MaxTickMs { get; }
+
+    /// <summary>True when the calling thread is the dedicated event-loop thread.</summary>
+    bool IsOnLoopThread { get; }
 }

src/SquidStd.Services.Core/Services/EventLoop/EventLoopService.cs

@@ -28,6 +28,7 @@ public sealed class EventLoopService : IEventLoopService, ISquidStdService, IMet
     private double _maxTickMs;
     private Thread? _thread;
     private long _tickCount;
+    private volatile int _loopThreadId = -1;
 
     /// <inheritdoc />
     public long TickCount => Interlocked.Read(ref _tickCount);
@@ -56,6 +57,9 @@ public double MaxTickMs
         }
     }
 
+    /// <inheritdoc />
+    public bool IsOnLoopThread => _loopThreadId == Environment.CurrentManagedThreadId;
+
     /// <inheritdoc />
     public string ProviderName => "eventloop";
 
@@ -85,6 +89,9 @@ public ValueTask StopAsync(CancellationToken cancellationToken = default)
         _cts.Cancel();
         _thread?.Join(TimeSpan.FromSeconds(5));
 
+        // Reset so a recycled managed thread id can't later report as the loop thread.
+        _loopThreadId = -1;
+
         return ValueTask.CompletedTask;
     }
 
@@ -136,6 +143,8 @@ internal int Tick()
 
     private void RunLoop()
     {
+        _loopThreadId = Environment.CurrentManagedThreadId;
+
         while (!_cts.IsCancellationRequested)
         {
             var work = Tick();

tests/SquidStd.Tests/EventLoop/EventLoopServiceTests.cs

@@ -80,4 +80,30 @@ public async Task StartStop_ExecutesPostedWork()
 
         Assert.True(fired);
     }
+
+    [Fact]
+    public async Task IsOnLoopThread_TrueInsidePostedWork_FalseOutside()
+    {
+        var dispatcher = new MainThreadDispatcherService();
+        var timer = new FakeTimerService();
+        using var loop = new EventLoopService(dispatcher, timer, new EventLoopConfig());
+
+        Assert.False(loop.IsOnLoopThread);
+
+        bool onLoopInside = false;
+        var signal = new ManualResetEventSlim(false);
+        dispatcher.Post(() =>
+            {
+                onLoopInside = loop.IsOnLoopThread;
+                signal.Set();
+            }
+        );
+
+        await loop.StartAsync();
+        signal.Wait(TimeSpan.FromSeconds(2));
+        await loop.StopAsync();
+
+        Assert.True(onLoopInside);
+        Assert.False(loop.IsOnLoopThread);
+    }
 }