RuleSet.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package edu.uci.ics.crawler4j.robotstxt;

import java.util.SortedSet;
import java.util.TreeSet;

public class RuleSet extends TreeSet<String> {

	private static final long serialVersionUID = 1L;

	@Override
	public boolean add(String str) {
		SortedSet<String> sub = headSet(str);
		if (!sub.isEmpty() && str.startsWith(sub.last())) {
			// no need to add; prefix is already present
			return false;
		}
		boolean retVal = super.add(str);
		sub = tailSet(str + "\0");
		while (!sub.isEmpty() && sub.first().startsWith(str)) {
			// remove redundant entries
			sub.remove(sub.first());
		}
		return retVal;
	}
	
	public boolean containsPrefixOf(String s) {
		SortedSet<String> sub = headSet(s);
		// because redundant prefixes have been eliminated,
		// only a test against last item in headSet is necessary
		if (!sub.isEmpty() && s.startsWith(sub.last())) {
			return true; // prefix substring exists
		} 
		// might still exist exactly (headSet does not contain boundary)
		return contains(s); 
	}
}