Merge branch 'develop' into connectErrors

Source/MQTTnet/Implementations/PlatformAbstractionLayer.cs

@@ -88,5 +88,17 @@ namespace MQTTnet.Implementations
 #endif
         }
 
+        public static Task CompletedTask
+        {
+            get 
+            {
+#if NET452 
+                return Task.FromResult(0);
+#else
+                return Task.CompletedTask;
+#endif
+            }
+        }
+
     }
 }

Source/MQTTnet/Internal/AsyncAutoResetEvent.cs

@@ -1,131 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Threading;
-using System.Threading.Tasks;
-
-namespace MQTTnet.Internal
-{
-    // Inspired from Stephen Toub (https://blogs.msdn.microsoft.com/pfxteam/2012/02/11/building-async-coordination-primitives-part-2-asyncautoresetevent/) and Chris Gillum (https://stackoverflow.com/a/43012490)
-    public class AsyncAutoResetEvent
-    {
-        private readonly LinkedList<TaskCompletionSource<bool>> _waiters = new LinkedList<TaskCompletionSource<bool>>();
-
-        private bool _isSignaled;
-
-        public AsyncAutoResetEvent()
-            : this(false)
-        {
-        }
-
-        public AsyncAutoResetEvent(bool signaled)
-        {
-            _isSignaled = signaled;
-        }
-
-        public int WaitersCount
-        {
-            get
-            {
-                lock (_waiters)
-                {
-                    return _waiters.Count;
-                }
-            }
-        }
-
-        public Task<bool> WaitOneAsync()
-        {
-            return WaitOneAsync(CancellationToken.None);
-        }
-
-        public Task<bool> WaitOneAsync(TimeSpan timeout)
-        {
-            return WaitOneAsync(timeout, CancellationToken.None);
-        }
-
-        public Task<bool> WaitOneAsync(CancellationToken cancellationToken)
-        {
-            return WaitOneAsync(Timeout.InfiniteTimeSpan, cancellationToken);
-        }
-
-        public async Task<bool> WaitOneAsync(TimeSpan timeout, CancellationToken cancellationToken)
-        {
-            cancellationToken.ThrowIfCancellationRequested();
-
-            TaskCompletionSource<bool> tcs;
-
-            lock (_waiters)
-            {
-                if (_isSignaled)
-                {
-                    _isSignaled = false;
-                    return true;
-                }
-
-                if (timeout == TimeSpan.Zero)
-                {
-                    return _isSignaled;
-                }
-
-                tcs = new TaskCompletionSource<bool>();
-                _waiters.AddLast(tcs);
-            }
-
-            Task winner;
-            if (timeout == Timeout.InfiniteTimeSpan)
-            {
-                using (cancellationToken.Register(() => { tcs.TrySetCanceled(); }))
-                {
-                    await tcs.Task.ConfigureAwait(false);
-                    winner = tcs.Task;
-                }               
-            }
-            else
-            {
-                winner = await Task.WhenAny(tcs.Task, Task.Delay(timeout, cancellationToken)).ConfigureAwait(false);
-            }
-            
-            var taskWasSignaled = winner == tcs.Task;
-            if (taskWasSignaled)
-            {
-                return true;
-            }
-
-            // We timed-out; remove our reference to the task.
-            // This is an O(n) operation since waiters is a LinkedList<T>.
-            lock (_waiters)
-            {
-                _waiters.Remove(tcs);
-
-                if (winner.Status == TaskStatus.Canceled)
-                {
-                    throw new OperationCanceledException(cancellationToken);
-                }
-
-                throw new TimeoutException();
-            }
-        }
-
-        public void Set()
-        {
-            TaskCompletionSource<bool> toRelease = null;
-
-            lock (_waiters)
-            {
-                if (_waiters.Count > 0)
-                {
-                    // Signal the first task in the waiters list.
-                    toRelease = _waiters.First.Value;
-                    _waiters.RemoveFirst();
-                }
-                else if (!_isSignaled)
-                {
-                    // No tasks are pending
-                    _isSignaled = true;
-                }
-            }
-
-            toRelease?.TrySetResult(true);
-        }
-    }
-}

Source/MQTTnet/Internal/Disposable.cs

@@ -44,12 +44,13 @@ namespace MQTTnet.Internal
             {
                 return;
             }
+
+            _isDisposed = true;
+
             // Do not change this code. Put cleanup code in Dispose(bool disposing) above.
             Dispose(true);
             // TODO: uncomment the following line if the finalizer is overridden above.
             // GC.SuppressFinalize(this);
-
-            _isDisposed = true;
         }
         #endregion
     }

Source/MQTTnet/PacketDispatcher/MqttPacketAwaiter.cs

@@ -9,7 +9,7 @@ namespace MQTTnet.PacketDispatcher
 {
     public sealed class MqttPacketAwaiter<TPacket> : Disposable, IMqttPacketAwaiter where TPacket : MqttBasePacket
     {
-        private readonly TaskCompletionSource<MqttBasePacket> _taskCompletionSource = new TaskCompletionSource<MqttBasePacket>();
+        private readonly TaskCompletionSource<MqttBasePacket> _taskCompletionSource;
         private readonly ushort? _packetIdentifier;
         private readonly MqttPacketDispatcher _owningPacketDispatcher;
         
@@ -17,13 +17,18 @@ namespace MQTTnet.PacketDispatcher
         {
             _packetIdentifier = packetIdentifier;
             _owningPacketDispatcher = owningPacketDispatcher ?? throw new ArgumentNullException(nameof(owningPacketDispatcher));
+#if NET452
+            _taskCompletionSource = new TaskCompletionSource<MqttBasePacket>();
+#else
+            _taskCompletionSource = new TaskCompletionSource<MqttBasePacket>(TaskCreationOptions.RunContinuationsAsynchronously);
+#endif
         }
 
         public async Task<TPacket> WaitOneAsync(TimeSpan timeout)
         {
             using (var timeoutToken = new CancellationTokenSource(timeout))
             {
-                timeoutToken.Token.Register(() => _taskCompletionSource.TrySetException(new MqttCommunicationTimedOutException()));
+                timeoutToken.Token.Register(() => Fail(new MqttCommunicationTimedOutException()));
 
                 var packet = await _taskCompletionSource.Task.ConfigureAwait(false);
                 return (TPacket)packet;
@@ -33,24 +38,47 @@ namespace MQTTnet.PacketDispatcher
         public void Complete(MqttBasePacket packet)
         {
             if (packet == null) throw new ArgumentNullException(nameof(packet));
-            
+
+
+#if NET452
             // To prevent deadlocks it is required to call the _TrySetResult_ method
             // from a new thread because the awaiting code will not(!) be executed in
             // a new thread automatically (due to await). Furthermore _this_ thread will
             // do it. But _this_ thread is also reading incoming packets -> deadlock.
+            // NET452 does not support RunContinuationsAsynchronously
             Task.Run(() => _taskCompletionSource.TrySetResult(packet));
+#else
+            _taskCompletionSource.TrySetResult(packet);
+#endif
         }
 
         public void Fail(Exception exception)
         {
             if (exception == null) throw new ArgumentNullException(nameof(exception));
-
+#if NET452
+            // To prevent deadlocks it is required to call the _TrySetResult_ method
+            // from a new thread because the awaiting code will not(!) be executed in
+            // a new thread automatically (due to await). Furthermore _this_ thread will
+            // do it. But _this_ thread is also reading incoming packets -> deadlock.
+            // NET452 does not support RunContinuationsAsynchronously
             Task.Run(() => _taskCompletionSource.TrySetException(exception));
+#else
+            _taskCompletionSource.TrySetException(exception);
+#endif
         }
 
         public void Cancel()
         {
+#if NET452
+            // To prevent deadlocks it is required to call the _TrySetResult_ method
+            // from a new thread because the awaiting code will not(!) be executed in
+            // a new thread automatically (due to await). Furthermore _this_ thread will
+            // do it. But _this_ thread is also reading incoming packets -> deadlock.
+            // NET452 does not support RunContinuationsAsynchronously
             Task.Run(() => _taskCompletionSource.TrySetCanceled());
+#else
+            _taskCompletionSource.TrySetCanceled();
+#endif
         }
 
         protected override void Dispose(bool disposing)

Source/MQTTnet/Server/MqttRetainedMessagesManager.cs

@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
 using MQTTnet.Diagnostics;
+using MQTTnet.Implementations;
 using MQTTnet.Internal;
 
 namespace MQTTnet.Server
@@ -21,7 +22,7 @@ namespace MQTTnet.Server
             if (logger == null) throw new ArgumentNullException(nameof(logger));
             _logger = logger.CreateChildLogger(nameof(MqttRetainedMessagesManager));
             _options = options ?? throw new ArgumentNullException(nameof(options));
-            return Task.CompletedTask;
+            return PlatformAbstractionLayer.CompletedTask;
         }
 
         public async Task LoadMessagesAsync()