namespace RealitySimulation.Utils.Threading
{
#region Using directives
using System;
using System.Collections.Generic;
using System.Text;
using System.Threading;
#endregion
/// <summary>
/// 同步屏障.
/// </summary>
public interface ISyncBarrier
{
/// <summary>
/// 获取正在有屏障处理的线程总数.
/// </summary>
/// <remarks>
/// 改变线程总数,是一个同步操作.
/// 请在确保没有任何线程使用当前
/// 屏障(或初始化)时改动总数.如果已经有线
/// 程使用屏障,请使用ExchangingThreads
/// 异步更改线程的数量.
/// </remarks>
int TotalThreads { get;set;}
/// <summary>
/// 获取或者设置等待交换的线程数.
/// </summary>
/// <remarks>
/// 可以通过交换向线程总数中
/// 添加或者删除线程.
/// 使用这种方法主要是因为
/// 线程同步过程中,只能在
/// 重建屏障的时候改变线程
/// 总数.而其他时候将造成
/// 同步的失败.
/// 此值为正,意味着添加
/// 线程,相反意味着删除
/// 线程.
/// 当交换完成,此值自动
/// 置零.
/// 此外,如果线程的减少
/// 量大于当前线程总量,
/// 直接将总量置零,而不
/// 考虑余量.
/// 注意,这是一个异步操作,
/// 屏障可能不会立即实现
/// 这个操作.请观察此值,
/// 以确定是否进行添加.
/// </remarks>
int ExchangingThreads { get;set;}
/// <summary>
/// 获取当前被阻碍的线程数.
/// </summary>
int BarricadedThreads { get;}
/// <summary>
/// 穿越屏障.
/// </summary>
/// <remarks>
/// 线程通过调用穿越屏障,
/// 将对控制的安排交给屏障.
/// 当逃离条件满足,也就是
/// 到达线程数量已经达到
/// 要求的数量,屏障将自动
/// 开放,而线程在此时可以
/// 穿越.当逃离条件尚未满
/// 足,线程将在穿越屏障的
/// 时候被屏障阻塞.
/// </remarks>
void Stride();
}
public class SyncBarrier:ISyncBarrier
{
protected int unbarricadedThreads = 0;
protected int exchangingThreads = 0;
protected int totalThreads = 0;
public virtual int BarricadedThreads
{
get { return this.totalThreads - this.unbarricadedThreads; }
}
public virtual int TotalThreads
{
get { return this.totalThreads; }
set { this.Rebuild(value); }
}
public virtual int ExchangingThreads
{
get { return this.exchangingThreads; }
set { this.exchangingThreads = value; }
}
public SyncBarrier():this(1){}
public SyncBarrier(int totalThreads)
{
this.Rebuild(totalThreads);
}
public virtual void Stride()
{
//Barrier is designed for threads, no thread takes no effect.
//And single thread will not be barricaded.
if (this.totalThreads > 0)
{
lock (this)
{
if (this.unbarricadedThreads > 0)
{
this.unbarricadedThreads--;
//All threads arrived
if (this.unbarricadedThreads == 0)
{
//Rebuild first, then pulse the signal!
this.Rebuild(this.totalThreads+this.exchangingThreads);
Monitor.PulseAll(this);
}
else//Not all threads arrived.
{
Monitor.Wait(this);
}
//Threads escapes here.
}
}
}
}
protected virtual void Rebuild(int totalThreads)
{
this.unbarricadedThreads = this.totalThreads = totalThreads;
this.exchangingThreads = 0;
}
}
}