1 小顶堆计时器概要

 小根堆定时器的优点如下：

a.添加时间复杂度为O(1);

b.删除时间复杂度为O(1);

c.执行一个定时器的时间复杂度为O(1);

2 代码设计

        之前写的服务器定时器是全部轮询更新，这种计时器性能太差，每一帧都要全部迭代一次，客户端层应该把CPU性能压榨到极致，能少循环的尽量少循环尽可能的减少CPU循环次数，所以优化了算法，使用了小堆顶定时器。小顶堆是基于二叉树的排序算法，将剩余时间最小的节点交换到树的根节点。每次更新的时候只取树的根节点，判断是否超时，如果超时会对树重新进行排序，排序完成后继续轮询，查询到根节点无超时为止。

Timer.cs代码实现

using UnityEngine;
using System;
using Object = UnityEngine.Object;namespace UnityTimer
{public class Timer{public enum SCOPE{eLocal,eGlobal,}#region Public Properties/Fields/// 
/// 计时器回调时间持续时间/// 
public float duration { get; private set; }/// 
/// 执行完成后是否循环执行./// 
public bool isLooped { get; set; }/// 
/// 本帧是否完成/// 
public bool isCompletedThisFrame { get; private set; }/// 
/// 是否完成/// 
public bool isCompleted { get; private set; }/// 
/// 计时器使用的是实时时间还是游戏时间/// 
public bool usesRealTime { get; private set; }/// 
/// 计时器是否暂停/// 
public bool isPaused{get { return this._timeElapsedBeforePause.HasValue; }}/// 
/// 是否取消了/// 
public bool isCancelled{get { return this._timeElapsedBeforeCancel.HasValue; }}/// 
/// 是否完成/// 
public bool isDone{get { return this.isCompleted || this.isCancelled || this.isOwnerDestroyed; }}#endregion#region Public Static Methods/// 
/// 注册一个新的计时器，在一定时间后触发一个事件/// 在切换场景的时候，注册的计时器会被销毁/// 
/// 在一定秒后执行事件/// 计时器执行完回调事件./// 每次执行计时器执行的回调/// 计时器在执行后是否重复执行/// 是否使用实时时间/// 此计时器附加到的对象，物体被摧毁后,定时器将不执行/// 一个计时器对象public static Timer Regist(float duration, Action onComplete, Action onUpdate = null,bool isLooped = false, bool useRealTime = false, MonoBehaviour autoDestroyOwner = null){if (Timer._manager == null){TimerManager managerInScene = Object.FindObjectOfType();if (managerInScene != null){Timer._manager = managerInScene;}else{GameObject managerObject = new GameObject { name = "TimerManager" };Timer._manager = managerObject.AddComponent();}}Timer timer = new Timer(duration, onComplete, onUpdate, isLooped, useRealTime, autoDestroyOwner);Timer._manager.RegisterTimer(timer);return timer;}/// 
/// 作用同上，不同的是此API创建的计时器在程序的生命周期内都有效，不会随着场景的销毁而销毁/// 
public static Timer RegistGlobal(float duration, Action onComplete, Action onUpdate = null,bool isLooped = false, bool useRealTime = false, MonoBehaviour autoDestroyOwner = null){if (Timer._globalManager == null){GlobalTimerManager globalManager = Object.FindObjectOfType();if (globalManager != null){Timer._globalManager = globalManager;}else{GameObject globalManagerObject = new GameObject { name = "GlobalTimerManager" };Timer._globalManager = globalManagerObject.AddComponent();GameObject.DontDestroyOnLoad(Timer._globalManager);}}Timer timer = new Timer(duration, onComplete, onUpdate, isLooped, useRealTime, autoDestroyOwner);Timer._globalManager.RegisterTimer(timer);return timer;}public static void Cancel(Timer timer){if (timer != null){timer.Cancel();}}public static void Pause(Timer timer){if (timer != null){timer.Pause();}}public static void Resume(Timer timer){if (timer != null){timer.Resume();}}public static void CancelAllRegisteredTimers(SCOPE eScope = SCOPE.eLocal){//如果计时器不存在，不需要做任何事情if (eScope == SCOPE.eLocal){if (Timer._manager != null){Timer._manager.CancelAllTimers();}}else if (eScope == SCOPE.eGlobal){if (Timer._globalManager != null){Timer._globalManager.CancelAllTimers();}}}public static void PauseAllRegisteredTimers(SCOPE eScope = SCOPE.eLocal){//如果计时器不存在，不需要做任何事情if (eScope == SCOPE.eLocal){if (Timer._manager != null){Timer._manager.PauseAllTimers();}}else if (eScope == SCOPE.eGlobal){if (Timer._globalManager != null){Timer._globalManager.PauseAllTimers();}}}public static void ResumeAllRegisteredTimers(SCOPE eScope = SCOPE.eLocal){//如果计时器不存在，不需要做任何事情if (eScope == SCOPE.eLocal){if (Timer._manager != null){Timer._manager.ResumeAllTimers();}}else if (eScope == SCOPE.eGlobal){if (Timer._globalManager != null){Timer._globalManager.ResumeAllTimers();}}}#endregion#region Public Methodspublic void Cancel(){if (this.isDone){return;}this._timeElapsedBeforeCancel = this.GetTimeElapsed();this._timeElapsedBeforePause = null;}public void Pause(){if (this.isPaused || this.isDone){return;}this._timeElapsedBeforePause = this.GetTimeElapsed();}public void Resume(){if (!this.isPaused || this.isDone){return;}this._timeElapsedBeforePause = null;}public float GetTimeElapsed(){if (this.isCompleted || this.GetWorldTime() >= this.GetFireTime()){return this.duration;}return this._timeElapsedBeforeCancel ??this._timeElapsedBeforePause ??this.GetWorldTime() - this._startTime;}public float GetTimeRemaining(){return this.duration - this.GetTimeElapsed();}public float GetRatioComplete(){return this.GetTimeElapsed() / this.duration;}public float GetRatioRemaining(){return this.GetTimeRemaining() / this.duration;}#endregion#region Private Static Properties/Fieldsprivate static TimerManager _manager;private static GlobalTimerManager _globalManager;#endregion#region Private Properties/Fieldsprivate bool isOwnerDestroyed{get { return this._hasAutoDestroyOwner && this._autoDestroyOwner == null; }}private readonly Action _onComplete;private readonly Action _onUpdate;private float _startTime;private float _endTime;private float _lastUpdateTime;private float? _timeElapsedBeforeCancel;private float? _timeElapsedBeforePause;private readonly MonoBehaviour _autoDestroyOwner;private readonly bool _hasAutoDestroyOwner;#endregion#region 属性区public float EndTime { get { return _endTime; } }#endregion#region Private Constructor (use static Register method to create new timer)private Timer(float duration, Action onComplete, Action onUpdate,bool isLooped, bool usesRealTime, MonoBehaviour autoDestroyOwner){this.duration = duration;this._onComplete = onComplete;this._onUpdate = onUpdate;this.isLooped = isLooped;this.usesRealTime = usesRealTime;this._autoDestroyOwner = autoDestroyOwner;this._hasAutoDestroyOwner = autoDestroyOwner != null;this._startTime = this.GetWorldTime();this._lastUpdateTime = this._startTime;_endTime = _startTime + duration;}#endregion#region  Methodspublic float GetWorldTime(){return this.usesRealTime ? Time.realtimeSinceStartup : Time.time;}private float GetFireTime(){return this._startTime + this.duration;}private float GetTimeDelta(){return this.GetWorldTime() - this._lastUpdateTime;}public void Update(){isCompletedThisFrame = false;if (this.isDone){return;}if (this.isPaused){this._startTime += this.GetTimeDelta();this._lastUpdateTime = this.GetWorldTime();return;}this._lastUpdateTime = this.GetWorldTime();if (this._onUpdate != null){this._onUpdate(this.GetTimeElapsed());}if (this.GetWorldTime() >= this.GetFireTime()){isCompletedThisFrame = true;if (this._onComplete != null){this._onComplete();}if (this.isLooped){this._startTime = this.GetWorldTime();_endTime = _startTime + duration;}else{this.isCompleted = true;}}}#endregion }
}

TimerMgr.cs代码实现

using System.Collections.Generic;
using UnityEngine;
using System;
using Object = UnityEngine.Object;namespace UnityTimer
{public class TimerManager : MonoBehaviour{//protected List _timers = new List();//初始化默认new 1个空间出来protected Timer[] m_szTimers = new Timer[1];//已使用的空间protected uint m_iUsedSize = 0;//protected List _timersToAdd = new List();protected void Resize(){int iOldCapacity = m_szTimers.Length;int iNewCapacity = iOldCapacity * 2;Timer[] szTempTimer = new Timer[iNewCapacity];//尾部全部设置成nullfor (int i = iOldCapacity; i < iNewCapacity; ++i){szTempTimer[i] = null;}//copy oldData -> newDataArray.Copy(m_szTimers, szTempTimer, m_szTimers.Length);//指向新地址m_szTimers = szTempTimer;//解除引用szTempTimer = null;}/// 
/// 小顶堆排序   /// 
public void HeapAdjustSmall(int parent){if (parent >= m_szTimers.Length){return;}Timer tmp = m_szTimers[parent];//时间复杂度应该在O(LogN)附近for (int child = parent * 2 + 1; child < m_iUsedSize; child = child * 2 + 1){if (child + 1 < m_iUsedSize && m_szTimers[child].EndTime > m_szTimers[child + 1].EndTime){child++;}if (tmp.EndTime > m_szTimers[child].EndTime){m_szTimers[parent] = m_szTimers[child];parent = child;}else{break;}}m_szTimers[parent] = tmp;}public void AddTimer(Timer timer){if (null == timer){return;}if (m_iUsedSize >= m_szTimers.Length){Resize();}uint hole = m_iUsedSize;++m_iUsedSize;// 由于新结点在最后，因此将其进行上滤，以符合最小堆for (uint parent = (hole - 1) / 2; hole > 0; parent = (hole - 1) / 2){//把时间最短的计时器交换到树根节点if (m_szTimers[parent].EndTime > timer.EndTime){m_szTimers[hole] = m_szTimers[parent];hole = parent;}else{break;}}m_szTimers[hole] = timer;}public void PopTimer(){if (0 == m_iUsedSize){return;}if (null != m_szTimers[0]){m_szTimers[0] = m_szTimers[--m_iUsedSize];HeapAdjustSmall(0);}}public void RegisterTimer(Timer timer){AddTimer(timer);}public void CancelAllTimers(){Timer timer = null;for (int i = 0; i < m_szTimers.Length; ++i){timer = m_szTimers[i];if (null != timer){timer.Cancel();m_szTimers[i] = null;}}m_iUsedSize = 0;}public void PauseAllTimers(){Timer timer = null;for (int i = 0; i < m_szTimers.Length; ++i){timer = m_szTimers[i];if (null != timer)timer.Pause();}}public void ResumeAllTimers(){Timer timer = null;for (int i = 0; i < m_szTimers.Length; ++i){timer = m_szTimers[i];if (null != timer)timer.Resume();}}protected void Update(){UpdateAllTimers();}protected void UpdateAllTimers(){Timer tm = null;//for (int i = 0; i < m_szTimers.Length; ++i)//{//    tm = m_szTimers[i];//    if (null != tm)//        tm.Update();//}Timer tmp = null;tmp = m_szTimers[0];while (m_iUsedSize > 0){if (null == tmp)break;tmp.Update();//循环类型的计时器，如果到了时间，重新排序，而不清理if (tmp.isCompletedThisFrame && tmp.isLooped){HeapAdjustSmall(0);tmp = m_szTimers[0];continue;}if (!tmp.isDone)break;PopTimer();tmp = m_szTimers[0];}}}public class GlobalTimerManager : TimerManager{}}

3 测试数据对比

在更新所有timer的地方，开启10w定时器测试使用小顶堆和不使用小顶堆做了对比：

计时器不使用小堆顶：更新全部，cpu main 在 14.1左右浮动；

计时器使用小堆顶：计时器timeout时间取的是1-10w,cpu mian 平均 在1.6左右浮动，在雪崩(全部更新的情况)情况下 cpuMian会突然上升到9.6左右；

通过数据比对，使用了小顶堆比不使用小顶堆，在综合情况下效率要快将近8.8倍
 

引用

文章：基于STL的小根堆定时器实现（C++）_AlwaysSimple的博客-CSDN博客_小根堆定时器