Scaffolding for Amb.

AsyncRx.NET/System.Reactive.Async/System/Reactive/Linq/Operators/Amb.cs

@@ -0,0 +1,98 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the Apache 2.0 License.
+// See the LICENSE file in the project root for more information. 
+
+using System.Collections.Generic;
+using System.Reactive.Disposables;
+using System.Threading;
+
+namespace System.Reactive.Linq
+{
+    partial class AsyncObservable
+    {
+        public static IAsyncObservable<TSource> Amb<TSource>(this IAsyncObservable<TSource> first, IAsyncObservable<TSource> second)
+        {
+            if (first == null)
+                throw new ArgumentNullException(nameof(first));
+            if (second == null)
+                throw new ArgumentNullException(nameof(second));
+
+            return Create<TSource>(async observer =>
+            {
+                IAsyncDisposable firstSubscription = null;
+                IAsyncDisposable secondSubscription = null;
+
+                var (firstObserver, secondObserver) = AsyncObserver.Amb(observer, firstSubscription, secondSubscription);
+
+                var firstTask = first.SubscribeAsync(firstObserver);
+                var secondTask = second.SubscribeAsync(secondObserver);
+
+                var d1 = await firstTask.ConfigureAwait(false);
+                var d2 = await secondTask.ConfigureAwait(false);
+
+                return StableCompositeAsyncDisposable.Create(d1, d2);
+            });
+        }
+    }
+
+    partial class AsyncObserver
+    {
+        public static (IAsyncObserver<TSource>, IAsyncObserver<TSource>) Amb<TSource>(IAsyncObserver<TSource> observer, IAsyncDisposable first, IAsyncDisposable second)
+        {
+            if (observer == null)
+                throw new ArgumentNullException(nameof(observer));
+            if (first == null)
+                throw new ArgumentNullException(nameof(first));
+            if (second == null)
+                throw new ArgumentNullException(nameof(second));
+
+            var gate = new AsyncLock();
+
+            return
+                (
+                    Create<TSource>(
+                        async x =>
+                        {
+                            using (await gate.LockAsync().ConfigureAwait(false))
+                            {
+                            }
+                        },
+                        async ex =>
+                        {
+                            using (await gate.LockAsync().ConfigureAwait(false))
+                            {
+                                await observer.OnErrorAsync(ex).ConfigureAwait(false);
+                            }
+                        },
+                        async () =>
+                        {
+                            using (await gate.LockAsync().ConfigureAwait(false))
+                            {
+                            }
+                        }
+                    ),
+                    Create<TSource>(
+                        async x =>
+                        {
+                            using (await gate.LockAsync().ConfigureAwait(false))
+                            {
+                            }
+                        },
+                        async ex =>
+                        {
+                            using (await gate.LockAsync().ConfigureAwait(false))
+                            {
+                                await observer.OnErrorAsync(ex).ConfigureAwait(false);
+                            }
+                        },
+                        async () =>
+                        {
+                            using (await gate.LockAsync().ConfigureAwait(false))
+                            {
+                            }
+                        }
+                    )
+                );
+        }
+    }
+}