SimpleWordSet.java

/*******************************************************************************
 * Copyright (c) 2000, 2009 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jdt.internal.core.util;

import org.eclipse.jdt.core.compiler.CharOperation;

public final class SimpleWordSet {

// to avoid using Enumerations, walk the individual values skipping nulls
	public char[][] words;

	public int elementSize; // number of elements in the table

	public int threshold;

	public SimpleWordSet(int size) {
		this.elementSize= 0;
		this.threshold= size; // size represents the expected number of elements
		int extraRoom= (int)(size * 1.5f);
		if (this.threshold == extraRoom)
			extraRoom++;
		this.words= new char[extraRoom][];
	}

	public char[] add(char[] word) {
		int length= this.words.length;
		int index= CharOperation.hashCode(word) % length;
		char[] current;
		while ((current= this.words[index]) != null) {
			if (CharOperation.equals(current, word))
				return current;
			if (++index == length)
				index= 0;
		}
		this.words[index]= word;

		// assumes the threshold is never equal to the size of the table
		if (++this.elementSize > this.threshold)
			rehash();
		return word;
	}

	public boolean includes(char[] word) {
		int length= this.words.length;
		int index= CharOperation.hashCode(word) % length;
		char[] current;
		while ((current= this.words[index]) != null) {
			if (CharOperation.equals(current, word))
				return true;
			if (++index == length)
				index= 0;
		}
		return false;
	}

	private void rehash() {
		SimpleWordSet newSet= new SimpleWordSet(this.elementSize * 2); // double the number of expected elements
		char[] current;
		for (int i= this.words.length; --i >= 0;)
			if ((current= this.words[i]) != null)
				newSet.add(current);

		this.words= newSet.words;
		this.elementSize= newSet.elementSize;
		this.threshold= newSet.threshold;
	}
}