Adding a concurrent variant for SimpleSubject<T>.

AsyncRx.NET/System.Reactive.Async/System/Reactive/Subjects/ConcurrentSimpleAsyncSubject.cs

@@ -0,0 +1,127 @@
+// 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.Linq;
+using System.Reactive.Disposables;
+using System.Threading.Tasks;
+
+namespace System.Reactive.Subjects
+{
+    public class ConcurrentSimpleAsyncSubject<T> : IAsyncSubject<T>
+    {
+        private readonly object _gate = new object();
+        private readonly List<IAsyncObserver<T>> _observers = new List<IAsyncObserver<T>>();
+        private bool _done;
+        private Exception _error;
+
+        public async Task OnCompletedAsync()
+        {
+            IAsyncObserver<T>[] observers;
+
+            lock (_gate)
+            {
+                if (_done || _error != null)
+                {
+                    return;
+                }
+
+                _done = true;
+
+                observers = _observers.ToArray();
+            }
+
+            await Task.WhenAll(observers.Select(observer => observer.OnCompletedAsync())).ConfigureAwait(false);
+        }
+
+        public async Task OnErrorAsync(Exception error)
+        {
+            if (error == null)
+                throw new ArgumentNullException(nameof(error));
+
+            IAsyncObserver<T>[] observers;
+
+            lock (_gate)
+            {
+                if (_done || _error != null)
+                {
+                    return;
+                }
+
+                _error = error;
+
+                observers = _observers.ToArray();
+            }
+
+            await Task.WhenAll(observers.Select(observer => observer.OnErrorAsync(error))).ConfigureAwait(false);
+        }
+
+        public async Task OnNextAsync(T value)
+        {
+            IAsyncObserver<T>[] observers;
+
+            lock (_gate)
+            {
+                if (_done || _error != null)
+                {
+                    return;
+                }
+
+                observers = _observers.ToArray();
+            }
+
+            await Task.WhenAll(observers.Select(observer => observer.OnNextAsync(value))).ConfigureAwait(false);
+        }
+
+        public async Task<IAsyncDisposable> SubscribeAsync(IAsyncObserver<T> observer)
+        {
+            if (observer == null)
+                throw new ArgumentNullException(nameof(observer));
+
+            bool done;
+            Exception error;
+
+            lock (_gate)
+            {
+                done = _done;
+                error = _error;
+
+                if (!done && error == null)
+                {
+                    _observers.Add(observer);
+                }
+            }
+
+            if (done)
+            {
+                await observer.OnCompletedAsync().ConfigureAwait(false);
+
+                return AsyncDisposable.Nop;
+            }
+            else if (error != null)
+            {
+                await observer.OnErrorAsync(error).ConfigureAwait(false);
+
+                return AsyncDisposable.Nop;
+            }
+            else
+            {
+                return AsyncDisposable.Create(() =>
+                {
+                    lock (_gate)
+                    {
+                        var i = _observers.LastIndexOf(observer);
+
+                        if (i >= 0)
+                        {
+                            _observers.RemoveAt(i);
+                        }
+                    }
+
+                    return Task.CompletedTask;
+                });
+            }
+        }
+    }
+}

AsyncRx.NET/System.Reactive.Async/System/Reactive/Subjects/SimpleAsyncSubject.cs → AsyncRx.NET/System.Reactive.Async/System/Reactive/Subjects/SequentialSimpleAsyncSubject.cs

@@ -8,7 +8,7 @@ using System.Threading.Tasks;
 
 namespace System.Reactive.Subjects
 {
-    public class SimpleAsyncSubject<T> : IAsyncSubject<T>
+    public class SequentialSimpleAsyncSubject<T> : IAsyncSubject<T>
     {
         private readonly object _gate = new object();
         private readonly List<IAsyncObserver<T>> _observers = new List<IAsyncObserver<T>>();