解决|正则
在c#中使用正则表达式进行匹配,有时候我们会遇到这种情况,cpu使用率100%,但是正则表达式并没有异常抛出,正则一直处于匹配过程中,这将导致系统资源被耗尽,应用程序被卡住,这是由于正则不完全匹配,而且Regex中没有Timeout属性,使正则处理器陷入了死循环。
这种情况尤其可能发生在对非可靠的被匹配对象的匹配过程中,例如在我的个人网站项目中,对多个网站页面的自动采集匹配,就经常发生该问题。为了避免资源耗尽的情况发生,我写了一个AsynchronousRegex类,顾名思义,异步的Regex。给该类一个设置一个Timeout属性,将Regex匹配的动作置于单独的线程中,AsynchronousRegex监控Regex匹配超过Timeout限定时销毁线程。
using System;
using System.Text.RegularExpressions;
using System.Threading;
namespace LZT.Eahan.Common
{
public class AsynchronousRegex
{
private MatchCollection mc;
private int _timeout; // 最长休眠时间(超时),毫秒
private int sleepCounter;
private int sleepInterval; // 休眠间隔,毫秒
private bool _isTimeout;
public bool IsTimeout
{
get {return this._isTimeout;}
}
public AsynchronousRegex(int timeout)
{
this._timeout = timeout;
this.sleepCounter = 0;
this.sleepInterval = 100;
this._isTimeout = false;
this.mc = null;
}
public MatchCollection Matchs(Regex regex, string input)
{
Reg r = new Reg(regex, input);
r.OnMatchComplete += new Reg.MatchCompleteHandler(this.MatchCompleteHandler);
Thread t = new Thread(new ThreadStart(r.Matchs));
t.Start();
this.Sleep(t);
t = null;
return mc;
}
private void Sleep(Thread t)
{
if (t != null && t.IsAlive)
{
Thread.Sleep(TimeSpan.FromMilliseconds(this.sleepInterval));
this.sleepCounter ++;
if (this.sleepCounter * this.sleepInterval >= this._timeout)
{
t.Abort();
this._isTimeout = true;
}
else
{
this.Sleep(t);
}
}
}
private void MatchCompleteHandler(MatchCollection mc)
{
this.mc = mc;
}
class Reg
{
internal delegate void MatchCompleteHandler(MatchCollection mc);
internal event MatchCompleteHandler OnMatchComplete;
public Reg(Regex regex, string input)
{
this._regex = regex;
this._input = input;
}
private string _input;
public string Input
{
get {return this._input;}
set {this._input = value;}
}
private Regex _regex;
public Regex Regex
{
get {return this._regex;}
set {this._regex = value;}
}
internal void Matchs()
{
MatchCollection mc = this._regex.Matches(this._input);
if (mc != null && mc.Count > 0) // 这里有可能造成cpu资源耗尽
{
this.OnMatchComplete(mc);
}
}
}
}
}