core/plugins/org.eclipse.dltk.core/model/org/eclipse/dltk/internal/core/util/SimpleWordSet.java

/*******************************************************************************
 * Copyright (c) 2000, 2007 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
 *
 
 *******************************************************************************/
package org.eclipse.dltk.internal.core.util;

import org.eclipse.dltk.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 = words[index]) != null) {
			if (CharOperation.equals(current, word))
				return current;
			if (++index == length)
				index = 0;
		}
		words[index] = word;

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

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

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

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