ngbrown · May 21, 2024 15:48 · May 21, 2024
diff --git a/SemaphoreSlimExtensions.cs b/SemaphoreSlimExtensions.cs
@@ -0,0 +1,51 @@
+public static class SemaphoreSlimExtensions
+{
+    /// <summary>
+    /// Blocks the current thread until it can enter the <see cref="SemaphoreSlim"/>. Returns an <see cref="IDisposable"/> to be used in <c>using</c>.
+    /// </summary>
+    /// <param name="semaphore">A <see cref="SemaphoreSlim"/> to lock.</param>
+    /// <returns>An <see cref="IDisposable"/> that will release the <see cref="SemaphoreSlim"/> when disposed.</returns>
+    public static IDisposable Lock(this SemaphoreSlim semaphore)
+    {
+        semaphore.Wait();
+        return new SemaphoreReleaser(semaphore);
+    }
+
+    /// <summary>
+    /// Asynchronously waits to enter the <see cref="SemaphoreSlim"/>, while observing a
+    /// <see cref="CancellationToken"/>. Returned task resolves an <see cref="IDisposable"/> to be used in <c>using</c>.
+    /// </summary>
+    /// <returns>
+    /// A task that will complete when the semaphore has been entered.
+    /// Task contains An <see cref="IDisposable"/> that will release the <see cref="SemaphoreSlim"/> when disposed.
+    /// </returns>
+    /// <param name="semaphore">A <see cref="SemaphoreSlim"/> to lock.</param>
+    /// <param name="cancellationToken">
+    /// The <see cref="CancellationToken"/> token to observe.
+    /// </param>
+    public static async Task<IDisposable> LockAsync(this SemaphoreSlim semaphore, CancellationToken cancellationToken = default)
+    {
+        var task = semaphore.WaitAsync(cancellationToken);
+        await task.ConfigureAwait(false);
+        return task.Status == TaskStatus.RanToCompletion ? new SemaphoreReleaser(semaphore) : new DisposableNoOp();
+    }
+
+    private sealed class SemaphoreReleaser(SemaphoreSlim semaphore) : IDisposable
+    {
+        private bool released;
+
+        public void Dispose()
+        {
+            if (released) return;
+            semaphore.Release();
+            this.released = true;
+        }
+    }
+
+    private sealed class DisposableNoOp : IDisposable
+    {
+        public void Dispose()
+        {
+        }
+    }
+}