UnityFiberScheduler.cs

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/*

Author: Aaron Oneal, http://aarononeal.info

Copyright (c) 2012 Spicy Pixel, http://spicypixel.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.Collections;
using System.Collections.Generic;
using System.Collections.Concurrent;
using System.Threading;
using UnityEngine;

namespace SpicyPixel.Threading
{
    public sealed class UnityFiberScheduler : FiberScheduler
    {   
        internal const string UnityCoroutineKey = "spicypixel.threading.unity.coroutine";

        private static readonly UnityFiberScheduler instance = new UnityFiberScheduler(ConcurrentBehaviour.SharedInstance);

        public static UnityFiberScheduler Default {
            get {
                return instance;
            }
        }

        private MonoBehaviour behaviour;

        private ConcurrentQueue<Fiber> fiberQueue = new ConcurrentQueue<Fiber>();
        
        private CancellationTokenSource fiberQueueCancelSource = new CancellationTokenSource();

        public UnityFiberScheduler(MonoBehaviour behaviour)
        {
            this.behaviour = behaviour;
            behaviour.StartCoroutine(ProcessFiberQueue());
        }

        protected override void QueueFiber(Fiber fiber)
        {
            if(isDisposed)
                throw new ObjectDisposedException(GetType().FullName);
            
            // Coroutines are always inlined up to their
            // first yield, so enqueuing here likely doesn't do
            // anything other than delay a frame. But, it does
            // ensure the correct thread.
            if(AllowInlining && SchedulerThread == Thread.CurrentThread)
                StartUnityFiber(fiber);
            else
                fiberQueue.Enqueue(fiber);
        }

        private IEnumerator ProcessFiberQueue()
        {
            Fiber fiber;
            while(!fiberQueueCancelSource.IsCancellationRequested)
            {
                while(!fiberQueueCancelSource.IsCancellationRequested && fiberQueue.TryDequeue(out fiber))
                    StartUnityFiber(fiber);

                yield return null;
            }
        }

        private void StartUnityFiber(Fiber fiber)
        {   
            Coroutine coroutine = behaviour.StartCoroutine(ExecuteFiberInternal(fiber));
            fiber.Properties[UnityCoroutineKey] = coroutine;
        }

        private IEnumerator ExecuteFiberInternal(Fiber fiber, bool singleStep = false, int fiberSwitchCount = 0)
        {
            FiberInstruction fiberInstruction = null;
            bool ranOnce = false;

            while(!fiber.IsCompleted)
            {
                // If we are set to only advance one instruction then
                // abort if we have already done that
                if(singleStep && ranOnce)
                    yield break;
                ranOnce = true;

                // Execute the fiber
                fiberInstruction = ExecuteFiber(fiber);
    
                // Nothing more to do if stopped
                if(fiberInstruction is StopInstruction)
                    yield break;

                // Not supported in Unity
                if(fiberInstruction is YieldToFiber)
                    throw new InvalidOperationException("YieldToFiber is not supported by the Unity scheduler.");
    
                // Yield to any fiber means send null to the Unity scheduler
                if(fiberInstruction is YieldToAnyFiber)
                {
                    yield return null;
                    continue;
                }
    
                // Pass back any objects directly to the Unity scheduler since
                // these could be Unity scheduler commands
                if(fiberInstruction is ObjectInstruction)
                {
                    yield return ((ObjectInstruction)fiberInstruction).Value;
                    continue;
                }
    
                // Convert framework wait instruction to Unity instruction
                if(fiberInstruction is YieldForSeconds)
                {
                    yield return new WaitForSeconds(((YieldForSeconds)fiberInstruction).Seconds);
                    continue;
                }

                // Convert framework wait instruction to Unity instruction
                if(fiberInstruction is YieldUntilComplete)
                {
                    // Yield the coroutine that was stored when the instruction was started.
                    yield return ((YieldUntilComplete)fiberInstruction).Fiber.Properties[UnityCoroutineKey];
                    continue;
                }               
            }
        }

        public override string ToString()
        {
            if(SchedulerThread == Thread.CurrentThread)
                return string.Format("[UnityFiberScheduler][{0}]", behaviour.ToString());
            else
                return base.ToString();
        }
        
        private bool isDisposed = false;
        
        protected override void Dispose (bool disposing)
        {
            if(isDisposed)
                return;
            
            if(disposing)
            {
                fiberQueueCancelSource.Cancel();
                Fiber fiber;
                while(fiberQueue.TryDequeue(out fiber));
            }
            
            isDisposed = true;
            
            base.Dispose (disposing);
        }
    }
}