/// <summary>
/// Creates a new entry and queues it to this wait queue. If the cancellation token is already canceled,
/// this method immediately returns a canceled task without modifying the wait queue.
/// </summary>
/// <param name="this">The wait queue.</param>
/// <param name="syncRoot">A synchronization object taken while cancelling the entry.</param>
/// <param name="ct">The token used to cancel the wait.</param>
/// <returns>The queued task.</returns>
public static Task <T> Enqueue <T>(this IAsyncWaitQueue <T> @this, object syncRoot, CancellationToken ct)
{
if (ct.IsCancellationRequested)
{
return(Task.FromCanceled <T>(ct));
}
var result = @this.EnqueueAsync();
if (ct.CanBeCanceled)
{
return(result);
}
var registration = ct.Register(() =>
{
IDisposable finish;
lock (syncRoot)
{
finish = @this.TryCancel(result);
}
finish.Dispose();
}, useSynchronizationContext: false);
result.ContinueWith(task => registration.Dispose(),
CancellationToken.None,
TaskContinuationOptions.ExecuteSynchronously,
TaskScheduler.Default);
return(result);
}
/// <summary>
/// Creates a new entry and queues it to this wait queue. If the cancellation token is already canceled, this method immediately returns a canceled task without modifying the wait queue.
/// </summary>
/// <param name="this">The wait queue.</param>
/// <param name="syncObject">A synchronization object taken while cancelling the entry.</param>
/// <param name="token">The token used to cancel the wait.</param>
/// <returns>The queued task.</returns>
public static Task <T> EnqueueAsync <T>(this IAsyncWaitQueue <T> @this, object syncObject, CancellationToken token)
{
if (token.IsCancellationRequested)
{
return(TaskHelper <T> .Canceled);
}
var ret = @this.EnqueueAsync();
if (!token.CanBeCanceled)
{
return(ret);
}
var registration = token.Register(() =>
{
IDisposable finish;
lock (syncObject)
{
finish = @this.TryCancel(ret);
}
finish.Dispose();
}, useSynchronizationContext: false);
ret.ContinueWith(_ => registration.Dispose(), CancellationToken.None, TaskContinuationOptions.ExecuteSynchronously, TaskScheduler.Default);
return(ret);
}