ChannelMicroThreadAwaiter.cs

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// Copyright (c) 2014 Silicon Studio Corp. (http://siliconstudio.co.jp)
// This file is distributed under GPL v3. See LICENSE.md for details.
using System;
using System.Collections.Generic;
using System.Runtime.CompilerServices;

namespace SiliconStudio.Core.MicroThreading
{
    public class ChannelMicroThreadAwaiter<T> : ICriticalNotifyCompletion
    {
        private static List<ChannelMicroThreadAwaiter<T>> pool = new List<ChannelMicroThreadAwaiter<T>>();

        private bool isCompleted = false;

        internal MicroThread MicroThread;
        internal Action Continuation;
        internal T Result;

        public static ChannelMicroThreadAwaiter<T> New(MicroThread microThread)
        {
            lock (pool)
            {
                if (pool.Count > 0)
                {
                    var index = pool.Count - 1;
                    var lastItem = pool[index];
                    pool.RemoveAt(index);

                    lastItem.MicroThread = microThread;

                    return lastItem;
                }

                return new ChannelMicroThreadAwaiter<T>(microThread);
            }
        }

        public ChannelMicroThreadAwaiter(MicroThread microThread)
        {
            MicroThread = microThread;
        }

        public ChannelMicroThreadAwaiter<T> GetAwaiter()
        {
            return this;
        }

        public void OnCompleted(Action continuation)
        {
            Continuation = continuation;
        }

        public void UnsafeOnCompleted(Action continuation)
        {
            Continuation = continuation;
        }

        public T GetResult()
        {
            // Check Task Result (exception, etc...)
            var result = Result;

            // After result has been taken, we can reuse this item, so put it in the pool
            // We mitigate pool size, but another approach than hard limit might be interesting
            lock (pool)
            {
                if (pool.Count < 4096)
                {
                    isCompleted = false;
                    MicroThread = null;
                    Continuation = null;
                    Result = default(T);
                }

                pool.Add(this);
            }

            return result;
        }

        public bool IsCompleted
        {
            get { return isCompleted; }
            set { isCompleted = value; }
        }
    }
}