高效.NET脏字过滤算法与应用实例

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Collections;
using System.Data;
namespace WNF
{
 public class BadWordsFilter
 {
 private HashSet<string> hash = new HashSet<string>(); //关键字
 private byte[] fastCheck = new byte[char.MaxValue];
 private byte[] fastLength = new byte[char.MaxValue];
 private BitArray charCheck = new BitArray(char.MaxValue);
 private BitArray endCheck = new BitArray(char.MaxValue);
 private int maxWordLength = 0;
 private int minWordLength = int.MaxValue;
 public BadWordsFilter()
 {
 }
 //初始化关键字
 public void Init(DataTable badwords)
 {
 for (int j = 0; j < badwords.Rows.Count; j++)
 {
 string word = badwords.Rows[j][0].ToString();
 maxWordLength = Math.Max(maxWordLength, word.Length);
 minWordLength = Math.Min(minWordLength, word.Length);
 for (int i = 0; i < 7 && i < word.Length; i++)
 {
 fastCheck[word[i]] |= (byte)(1 << i);
 }
 for (int i = 7; i < word.Length; i++)
 {
 fastCheck[word[i]] |= 0x80;
 }
 if (word.Length == 1)
 {
 charCheck[word[0]] = true;
 }
 else
 {
 fastLength[word[0]] |= (byte)(1 << (Math.Min(7, word.Length - 2)));
 endCheck[word[word.Length - 1]] = true;
 hash.Add(word);
 }
 }
 }
 public string Filter(string text, string mask)
 {
 throw new NotImplementedException();
 }
 //检查是否有关键字
 public bool HasBadWord(string text)
 {
 int index = 0;
 while (index < text.Length)
 {
 int count = 1;
 if (index > 0 || (fastCheck[text[index]] & 1) == 0)
 {
 while (index < text.Length - 1 && (fastCheck[text[++index]] & 1) == 0) ;
 }
 char begin = text[index];
 if (minWordLength == 1 && charCheck[begin])
 {
 return true;
 }
 for (int j = 1; j <= Math.Min(maxWordLength, text.Length - index - 1); j++)
 {
 char current = text[index + j];
 if ((fastCheck[current] & 1) == 0)
 {
 ++count;
 }
 if ((fastCheck[current] & (1 << Math.Min(j, 7))) == 0)
 {
 break;
 }
 if (j + 1 >= minWordLength)
 {
 if ((fastLength[begin] & (1 << Math.Min(j - 1, 7))) > 0 && endCheck[current])
 {
 string sub = text.Substring(index, j + 1);
 if (hash.Contains(sub))
 {
 return true;
 }
 }
 }
 }
 index += count;
 }
 return false;
 }
 }
}

string sql = "select keywords from tb_keyword";
BadWordsFilter badwordfilter = new BadWordsFilter();
//初始化关键字
badwordfilter.Init(oEtb.GetDataSet(sql).Tables[0]);
//检查是否有存在关键字
bool a = badwordfilter.HasBadWord(TextBox1.Text);
if (a == true)
{
 Page.RegisterClientScriptBlock("a", "<script>alert('该评论含有不合法文字！')</script>");
}
else
{
 PingLun();//写入评论表
}