/*
* Created on Nov 1, 2011
* Created by Paul Gardner
*
* Copyright 2011 Vuze, Inc. All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; version 2 of the License only.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
*/
package com.aelitis.azureus.core.util;
import java.util.*;
import java.util.regex.Pattern;
import org.gudy.azureus2.core3.util.Debug;
public class
RegExUtil
{
private static ThreadLocal<Map<String,Object[]>> tls =
new ThreadLocal<Map<String,Object[]>>()
{
public Map<String,Object[]>
initialValue()
{
return( new HashMap<String,Object[]>());
}
};
public static Pattern
getCachedPattern(
String namespace,
String pattern )
{
return( getCachedPattern( namespace, pattern, 0 ));
}
public static Pattern
getCachedPattern(
String namespace,
String pattern,
int flags )
{
Map<String,Object[]> map = tls.get();
Object[] entry = map.get( namespace );
if ( entry == null || !pattern.equals((String)entry[0])){
Pattern result = Pattern.compile( pattern, flags );
map.put( namespace, new Object[]{ pattern, result });
return( result );
}else{
return((Pattern)entry[1]);
}
}
public static boolean
mightBeEvil(
String str )
{
// http://en.wikipedia.org/wiki/ReDoS
if ( !str.contains( ")" )){
return( false );
}
char[] chars = str.toCharArray();
Stack<Integer> stack = new Stack<Integer>();
for (int i=0;i<chars.length;i++){
char c = chars[i];
if ( c == '(' ){
stack.push( i+1 );
}else if ( c == ')' ){
if ( stack.isEmpty()){
Debug.out( "bracket un-matched in " + str + " - treating as evil" );
return( true );
}else{
int start = stack.pop();
if ( i < chars.length-1){
char next = chars[i+1];
if ( next == '*' || next == '+' || next == '{' ){
for ( int j=start;j<i;j++){
c = chars[j];
if ( "+*{|".indexOf( c ) != -1 ){
Debug.out( "regular expression " + str + " might be evil due to '" + str.substring( start-1, i+2) + "'" );
return( true );
}
}
}
}
}
}
}
return( false );
}
}