Task.Delay backport

TaskExtensions.cs

using System;
using System.Threading.Tasks;
using System.Threading;

namespace Couchbase.Lite.Shared
{
    public static class TaskExtensions
    {
        static int CheckTimeout (TimeSpan timeout)
        {
            try {
                return checked ((int)timeout.TotalMilliseconds);
            } catch (System.OverflowException) {
                throw new ArgumentOutOfRangeException ("timeout");
            }
        }

        public static Task Delay (int millisecondsDelay)
        {
            return Delay (millisecondsDelay, CancellationToken.None);
        }

        public static Task Delay (TimeSpan delay)
        {
            return Delay (CheckTimeout (delay), CancellationToken.None);
        }

        public static Task Delay (TimeSpan delay, CancellationToken cancellationToken)
        {
            return Delay (CheckTimeout (delay), cancellationToken);
        }

        public static Task Delay (int millisecondsDelay, CancellationToken cancellationToken)
        {
            if (millisecondsDelay < -1)
                throw new ArgumentOutOfRangeException ("millisecondsDelay");

            var tcs = new TaskCompletionSource<bool>();

            if (cancellationToken.IsCancellationRequested)
            {
                tcs.SetCanceled();
                return tcs.Task;
            }

            //            var task = new Task (TaskActionInvoker.Empty, null, cancellationToken, TaskCreationOptions.None, null, null);
            //            task.SetupScheduler (TaskScheduler.Default);

            var task = tcs.Task;

            if (millisecondsDelay != Timeout.Infinite) {
                var timer = new Timer (delegate (object state) {
                    var t = (Task) state;
                    //                    if (t.Status == TaskStatus.WaitingForActivation) {
                    //                        t.Status = TaskStatus.Running;
                    //                    }
                    tcs.SetResult(true);
                }, task, millisecondsDelay, -1);
                //
                task.ContinueWith ((t) => timer.Dispose());
            }

            return task;
        }
    }
}