Imported Upstream version 5.12.0.220

Former-commit-id: c477e03582759447177c6d4bf412cd2355aad476

mcs/class/System/System.Net/WebCompletionSource.cs

@@ -0,0 +1,155 @@
+//
+// WebCompletionSource.cs
+//
+// Author:
+//       Martin Baulig <mabaul@microsoft.com>
+//
+// Copyright (c) 2018 Xamarin Inc. (http://www.xamarin.com)
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using System.Runtime.ExceptionServices;
+
+namespace System.Net
+{
+	class WebCompletionSource<T>
+	{
+		TaskCompletionSource<Result> completion;
+		Result currentResult;
+
+		public WebCompletionSource (bool runAsync = true)
+		{
+			completion = new TaskCompletionSource<Result> (
+				runAsync ?
+				TaskCreationOptions.RunContinuationsAsynchronously :
+				TaskCreationOptions.None);
+		}
+
+		/*
+		 * Provide a non-blocking way of getting the current status.
+		 * 
+		 * We are using `TaskCreationOptions.RunContinuationsAsynchronously`
+		 * to prevent any user continuations from being run during the
+		 * `TrySet*()` methods - to make these safe to be called while holding
+		 * internal locks.
+		 * 
+		 */
+		internal Result CurrentResult => currentResult;
+
+		internal Status CurrentStatus => currentResult?.Status ?? Status.Running;
+
+		internal Task Task => completion.Task;
+
+		public bool TrySetCompleted (T argument)
+		{
+			var result = new Result (argument);
+			if (Interlocked.CompareExchange (ref currentResult, result, null) != null)
+				return false;
+			return completion.TrySetResult (result);
+		}
+
+		public bool TrySetCompleted ()
+		{
+			var result = new Result (Status.Completed, null);
+			if (Interlocked.CompareExchange (ref currentResult, result, null) != null)
+				return false;
+			return completion.TrySetResult (result);
+		}
+
+		public bool TrySetCanceled ()
+		{
+			return TrySetCanceled (new OperationCanceledException ());
+		}
+
+		public bool TrySetCanceled (OperationCanceledException error)
+		{
+			var result = new Result (Status.Canceled, ExceptionDispatchInfo.Capture (error));
+			if (Interlocked.CompareExchange (ref currentResult, result, null) != null)
+				return false;
+			return completion.TrySetResult (result);
+		}
+
+		public bool TrySetException (Exception error)
+		{
+			var result = new Result (Status.Faulted, ExceptionDispatchInfo.Capture (error));
+			if (Interlocked.CompareExchange (ref currentResult, result, null) != null)
+				return false;
+			return completion.TrySetResult (result);
+		}
+
+		public void ThrowOnError ()
+		{
+			if (!completion.Task.IsCompleted)
+				return;
+			completion.Task.Result.Error?.Throw ();
+		}
+
+		public async Task<T> WaitForCompletion ()
+		{
+			var result = await completion.Task.ConfigureAwait (false);
+			if (result.Status == Status.Completed)
+				return (T)result.Argument;
+			// This will always throw once we get here.
+			result.Error.Throw ();
+			throw new InvalidOperationException ("Should never happen.");
+		}
+
+		internal enum Status : int {
+			Running,
+			Completed,
+			Canceled,
+			Faulted
+		}
+
+		internal class Result
+		{
+			public Status Status {
+				get;
+			}
+
+			public bool Success => Status == Status.Completed;
+
+			public ExceptionDispatchInfo Error {
+				get;
+			}
+
+			public T Argument {
+				get;
+			}
+
+			public Result (T argument)
+			{
+				Status = Status.Completed;
+				Argument = argument;
+			}
+
+			public Result (Status state, ExceptionDispatchInfo error)
+			{
+				Status = state;
+				Error = error;
+			}
+		}
+	}
+
+	class WebCompletionSource : WebCompletionSource<object>
+	{
+	}
+}