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Async/Await Could Be Better

, 11 Apr 2012
This article will explain how the async/await pair really works and why it could be better if real cooperative threading was used instead.
using System;
using System.Threading;

namespace Pfz.Threading.Cooperative
{
	public sealed class CooperativeJob
	{
		[ThreadStatic]
		internal static CooperativeJob _current;
		public static CooperativeJob Current
		{
			get
			{
				return _current;
			}
		}

		internal CooperativeJobManager _thread;
		internal bool _waiting;
		internal StackSaver _stackSaver;
		internal CooperativeJob(CooperativeJobManager thread)
		{
			_thread = thread;
		}

		internal bool _Continue()
		{
			return _stackSaver.Execute();
		}

		public static void Yield()
		{
			StackSaver.StaticYieldReturn();
		}
		public static void Wait(CooperativeWaitEvent waitEvent)
		{
			if (waitEvent == null)
				throw new ArgumentNullException("waitEvent");

			lock(waitEvent._lock)
			{
				if (waitEvent._set)
					return;

				if (waitEvent._task != null)
					throw new InvalidOperationException("There is another task already waiting on this event.");

				var current = _current;
				if (current == null)
					throw new InvalidOperationException("This method is not running inside a cooperative task.");

				waitEvent._task = current;
				current._waiting = true;
			}
			StackSaver.StaticYieldReturn();
		}
		public static void Wait(int milliseconds)
		{
			var waitEvent = new CooperativeWaitEvent();
			
			var thread = new Thread
				(
				() => 
				{
					Thread.Sleep(milliseconds);
					waitEvent.Set();
				}
			);
			thread.Start();
			
			Wait(waitEvent);
		}
	}
}

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This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Paulo Zemek
Architect
Canada Canada
I started to program computers when I was 11 years old, as a hobbist, programming in AMOS Basic and Blitz Basic for Amiga.
At 12 I had my first try with assembler, but it was too difficult at the time. Then, in the same year, I learned C and, after learning C, I was finally able to learn assembler (for Motorola 680x0).
Not sure, but probably between 12 and 13, I started to learn C++. I always programmed "in an object oriented way", but using function pointers instead of virtual methods.
 
At 15 I started to learn Pascal at school and to use Delphi. At 16 I started my first internship (using Delphi). At 18 I started to work professionally using C++ and since then I've developed my programming skills as a professional developer in C++ and C#, generally creating libraries that help other developers do they work easier, faster and with less errors.
 
Want more info or simply want to contact me?
Take a look at: http://paulozemek.azurewebsites.net/
Or e-mail me at: paulozemek@outlook.com
 
Codeproject MVP 2012
Microsoft MVP 2013

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