关于正则表达式匹配无异常资源耗尽的解决方案

4/25/2007来源:C#应用人气:9080

        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www.eahan.com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);
                }
            }
        }
    }
}