孙广东   2014.7.19

无意之间看到了，Unity维基上的一篇文章，  是关于自己写协程的介绍。

   认为非常好，这样能更好的了解到协程的执行机制等特性。还是不错的。

原文链接地址例如以下：

http://wiki.unity3d.com/index.php?title=CoroutineScheduler

项目地址:  http://download.csdn.net/detail/u010019717/8912069

详细的内容例如以下：
        一个简单的协同调度程序。

这个协同调度程序同意全然控制一套协同程序的执行机制。 阅读代码也将帮助您了解  协同怎样在幕后工作。了解协同程序怎样构建.Net 发电机的基础上构建，将同意您将协同支持加入到非Unity的项目。

         协同能够yield等待 直到下次更新"yield;",   直到给定的数量的更新已通过 "yield anInt;",   直到给定的秒已通过 "yield aFloat;", 或者直到还有一个协程已完毕"yield scheduler.StartCoroutine(Coroutine());".StartCoroutine(Coroutine());"。 

    多个 调度 程序实例支持，而且能够非常实用。协同执行能够执行在一个全然不同的 调度程序实例下 (等待)。

       不使用Unity的 YieldInstruction 类。由于我门不能訪问这个类所需的调度的内部数据。  语义学Semantics 是和Unity的调度程序略有不同。  比如，在 Unity 中假设你開始协同   它将对其第一次的 yield 马上执行，然而 在自己写的调度程序中，它将不会执行，直到下一次调用 UpdateAllCoroutines。 此功能同意在不论什么时候的不论什么代码開始启动一个协程。

同一时候确保启动协同程序仅仅能执行在特定的时间。

        在同样的update协同程序执行之间不应该依赖 更新order。

为更深入地了解和学会很多其它关于 协同程序 怎样实现。

使用：

using UnityEngine;
using System.Collections;


/// <summary>
/// CoroutineSchedulerTest.cs
/// 
/// Port of the Javascript version from 
/// http://www.unifycommunity.com/wiki/index.php?title=CoroutineScheduler
/// 
/// Linked list node type used by coroutine scheduler to track scheduling of coroutines.
///  
/// BMBF Researchproject http://playfm.htw-berlin.de
/// PlayFM - Serious Games für den IT-gestützten Wissenstransfer im Facility Management 
///	Gef?rdert durch das bmb+f - Programm Forschung an Fachhochschulen profUntFH
///	
///	<author>Frank.Otto@htw-berlin.de</author>
///
/// </summary>

public class testAPI : MonoBehaviour {
	CoroutineScheduler scheduler;
	CoroutineScheduler m_scheduler2;
	string requestURL = "http://www.my-server.com/cgi-bin/screenshot.pl";

	void Start () {
		scheduler = new CoroutineScheduler ();
		scheduler.StartCoroutine (MyCoroutine ());

		m_scheduler2 = new CoroutineScheduler();
		m_scheduler2.StartCoroutine(test());
	}

	IEnumerator MyCoroutine ()
	{
		Debug.Log ("MyCoroutine: Begin");
		yield return 0;
		// wait for next update
		Debug.Log ("MyCoroutine: next update;" + Time.time);
		yield return 2;
		// wait for 2 updates, same as yield; yield;
		Debug.Log ("MyCoroutine: After yield 2;" + Time.time);
		yield return 3.5f;
		// wait for 3.5 seconds
		Debug.Log ("MyCoroutine: After 3.5 seconds;" + Time.time);
		// you can also yield for a coroutine running on a completely different scheduler instance
		yield return scheduler.StartCoroutine (WaitForMe ());
		Debug.Log ("MyCoroutine: After WaitForMe() finished;" + Time.time);
	}
	
	IEnumerator WaitForMe ()
	{
		yield return 7.8f;
		// wait for 7.8 seconds before finishing
	}
	
	// Update is called once per 	
	void Update ()
	{
		
		scheduler.UpdateAllCoroutines (Time.frameCount, Time.time);
	}

	
	IEnumerator test()
	{
		// ...set up request
		
		var www = new UnityEngine.WWW(requestURL);
		yield return new UnityWWWYieldWrapper(www);
		
		// ...loading complete do some stuff
	}
}

CoroutineScheduler.cs

using System.Collections;
using UnityEngine;

/// <summary>
/// CoroutineScheduler.cs
/// 
/// Port of the Javascript version from 
/// http://www.unifycommunity.com/wiki/index.php?
title=CoroutineScheduler
/// 
/// Linked list node type used by coroutine scheduler to track scheduling of coroutines.
/// 
/// 
/// BMBF Researchproject http://playfm.htw-berlin.de
/// PlayFM - Serious Games für den IT-gestützten Wissenstransfer im Facility Management 
///	Gef?rdert durch das bmb+f - Programm Forschung an Fachhochschulen profUntFH
///	
///	<author>Frank.Otto@htw-berlin.de</author>
///
/// 
/// A simple coroutine scheduler. Coroutines can yield until the next update
/// "yield;", until a given number of updates "yield anInt", until a given
/// amount of seconds "yield aFloat;", or until another coroutine has finished
/// "yield scheduler.StartCoroutine(Coroutine())".
/// 
/// Multiple scheduler instances are supported and can be very useful. A
/// coroutine running under one scheduler can yield (wait) for a coroutine
/// running under a completely different scheduler instance.
/// 
/// Unity‘s YieldInstruction classes are not used because I cannot
/// access their internal data needed for scheduling. Semantics are slightly
/// different from Unity‘s scheduler. For example, in Unity if you start a
/// coroutine it will run up to its first yield immediately, while in this
/// scheduler it will not run until the next time UpdateAllCoroutines is called.
/// This feature allows any code to start coroutines at any time, while
/// making sure the started coroutines only run at specific times.
/// 
/// You should not depend on update order between coroutines running on the same
/// update. For example, StartCoroutine(A), StartCoroutine(B), StartCoroutine(C)
/// where A, B, C => while(true) { print(A|B|C); yield; }, do not expect "ABC" or
/// "CBA" or any other specific ordering.
/// </summary>
public class CoroutineScheduler : MonoBehaviour
{
	
	CoroutineNode first = null;
	int currentFrame;
	float currentTime;
	
	/**
   * Starts a coroutine, the coroutine does not run immediately but on the
   * next call to UpdateAllCoroutines. The execution of a coroutine can
   * be paused at any point using the yield statement. The yield return value
   * specifies when the coroutine is resumed.
   */
	
	public CoroutineNode StartCoroutine (IEnumerator fiber)
	{
		// if function does not have a yield, fiber will be null and we no-op
		if (fiber == null) {
			return null;
		}
		// create coroutine node and run until we reach first yield
		CoroutineNode coroutine = new CoroutineNode (fiber);
		AddCoroutine (coroutine);
		return coroutine;
	}
	
	/**
   * Stops all coroutines running on this behaviour. Use of this method is
   * discouraged, think of a natural way for your coroutines to finish
   * on their own instead of being forcefully stopped before they finish.
   * If you need finer control over stopping coroutines you can use multiple
   * schedulers.
   */
	public void StopAllCoroutines ()
	{
		first = null;
	}
	
	/**
   * Returns true if this scheduler has any coroutines. You can use this to
   * check if all coroutines have finished or been stopped.
   */
	public bool HasCoroutines ()
	{
		return first != null;
	}
	
	/**
   * Runs all active coroutines until their next yield. Caller must provide
   * the current frame and time. This allows for schedulers to run under
   * frame and time regimes other than the Unity‘s main game loop.
   */
	public void UpdateAllCoroutines(int frame, float time)
	{
		currentFrame = frame;
		currentTime = time;
		CoroutineNode coroutine = this.first;
		while (coroutine != null)
		{
			// store listNext before coroutine finishes and is removed from the list
			CoroutineNode listNext = coroutine.listNext;
			
			if (coroutine.waitForFrame > 0 && frame >= coroutine.waitForFrame)
			{
				coroutine.waitForFrame = -1;
				UpdateCoroutine(coroutine);
			}
			else if (coroutine.waitForTime > 0.0f && time >= coroutine.waitForTime)
			{
				coroutine.waitForTime = -1.0f;
				UpdateCoroutine(coroutine);
			}
			else if (coroutine.waitForCoroutine != null && coroutine.waitForCoroutine.finished)
			{
				coroutine.waitForCoroutine = null;
				UpdateCoroutine(coroutine);
			}
			else if (coroutine.waitForUnityObject != null && coroutine.waitForUnityObject.finished)//lonewolfwilliams
			{
				coroutine.waitForUnityObject = null;
				UpdateCoroutine(coroutine);
			}
			else if (coroutine.waitForFrame == -1 && coroutine.waitForTime == -1.0f 
			         && coroutine.waitForCoroutine == null && coroutine.waitForUnityObject == null)
			{
				// initial update
				UpdateCoroutine(coroutine);
			}
			coroutine = listNext;
		}
	}
	
	/**
   * Executes coroutine until next yield. If coroutine has finished, flags
   * it as finished and removes it from scheduler list.
   */
	private void UpdateCoroutine(CoroutineNode coroutine)
	{
		IEnumerator fiber = coroutine.fiber;
		if (coroutine.fiber.MoveNext())
		{
			System.Object yieldCommand = fiber.Current == null ? (System.Object)1 : fiber.Current;
			
			if (yieldCommand.GetType() == typeof(int))
			{
				coroutine.waitForFrame = (int)yieldCommand;
				coroutine.waitForFrame += (int)currentFrame;
			}
			else if (yieldCommand.GetType() == typeof(float))
			{
				coroutine.waitForTime = (float)yieldCommand;
				coroutine.waitForTime += (float)currentTime;
			}
			else if (yieldCommand.GetType() == typeof(CoroutineNode))
			{
				coroutine.waitForCoroutine = (CoroutineNode)yieldCommand;
			}
			else if (yieldCommand is IYieldWrapper) //lonewolfwilliams
			{
				coroutine.waitForUnityObject = yieldCommand as IYieldWrapper;
			}
			else
			{
				throw new System.ArgumentException("CoroutineScheduler: Unexpected coroutine yield type: " + yieldCommand.GetType());
				
				//this is an alternative if you don‘t have access to the function passed to the couroutineScheduler - maybe it‘s                      
				//precompiled in a dll for example - remember you will have to add a case every time you add a wrapper :/
				/*
         var commandType = yieldCommand.GetType();
	 if(commandType == typeof(UnityEngine.WWW))
         {
	    coroutine.waitForUnityObject = 
               new UnityWWWWrapper(yieldCommand as UnityEngine.WWW);
	 }
	 else if(commandType == typeof(UnityEngine.AsyncOperation))
	 {
	    coroutine.waitForUnityObject = 
	       new UnityASyncOpWrapper(yieldCommand as UnityEngine.AsyncOperation);
	 }
	 else if(commandType == typeof(UnityEngine.AssetBundleRequest))
	 {
	    coroutine.waitForUnityObject = 
	       new UnityAssetBundleRequestWrapper(yieldCommand as UnityEngine.AssetBundleRequest);
	 }
	 else
	 {
            throw new System.ArgumentException("CoroutineScheduler: Unexpected coroutine yield type: " + yieldCommand.GetType());
	 }
         */
			}
		}
		else
		{
			// coroutine finished
			coroutine.finished = true;
			RemoveCoroutine(coroutine);
		}
	}
	
	private void AddCoroutine (CoroutineNode coroutine)
	{
		
		if (this.first != null) {
			coroutine.listNext = this.first;
			first.listPrevious = coroutine;
		}
		first = coroutine;
	}
	
	private void RemoveCoroutine (CoroutineNode coroutine)
	{
		if (this.first == coroutine) {
			// remove first
			this.first = coroutine.listNext;
		} else {
			// not head of list
			if (coroutine.listNext != null) {
				// remove between
				coroutine.listPrevious.listNext = coroutine.listNext;
				coroutine.listNext.listPrevious = coroutine.listPrevious;
			} else if (coroutine.listPrevious != null) {
				// and listNext is null
				coroutine.listPrevious.listNext = null;
				// remove last
			}
		}
		coroutine.listPrevious = null;
		coroutine.listNext = null;
	}
	
}//class

CoroutineNode.cs

using System.Collections;
using UnityEngine;


/// <summary>
/// CoroutineNode.cs
/// 
/// Port of the Javascript version from 
/// http://www.unifycommunity.com/wiki/index.php?title=CoroutineScheduler
/// 
/// Linked list node type used by coroutine scheduler to track scheduling of coroutines.
///  
/// BMBF Researchproject http://playfm.htw-berlin.de
/// PlayFM - Serious Games für den IT-gestützten Wissenstransfer im Facility Management 
///	Gef?rdert durch das bmb+f - Programm Forschung an Fachhochschulen profUntFH
///	
///	<author>Frank.Otto@htw-berlin.de</author>
///
/// </summary>

public class CoroutineNode
{
	public CoroutineNode listPrevious = null;
	public CoroutineNode listNext = null;
	public IEnumerator fiber;
	public bool finished = false;
	public int waitForFrame = -1;
	public float waitForTime = -1.0f;
	public CoroutineNode waitForCoroutine;
	public IYieldWrapper waitForUnityObject; //lonewolfwilliams
	
	public CoroutineNode(IEnumerator _fiber)
	{
		this.fiber = _fiber;
	}
}

IYieldWrapper.cs

/*
 * gareth williams 
 * http://www.lonewolfwilliams.com
 */

public interface IYieldWrapper
{
	bool finished { get; }
}

Example Wrappers

Below are some examples of wrappers I have used, in fact they have almost identical signatures so a more generic implementation could probably be written ^_^

UnityASyncOpWrapper

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

/*
*   Gareth Williams
*   http://www.lonewolfwilliams.com
*/

class UnityASyncOpWrapper : IYieldWrapper
{
	private UnityEngine.AsyncOperation m_UnityObject;
	public bool finished
	{
		get
		{
			return m_UnityObject.isDone;
		}
	}
	
	public UnityASyncOpWrapper(UnityEngine.AsyncOperation wraps)
	{
		m_UnityObject = wraps;
	}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
 
/*
 * Gareth Williams
 * http://www.lonewolfwilliams.com
 */
 
public class UnityWWWYieldWrapper : IYieldWrapper
{
   private UnityEngine.WWW m_UnityObject;
   public bool finished
   {
      get
      {
         return m_UnityObject.isDone;
      }
   }
 
   public UnityWWWYieldWrapper(UnityEngine.WWW wraps)
   {
      m_UnityObject = wraps;
   }
}