core/org.eclipse.cdt.core/index/org/eclipse/cdt/internal/core/index/impl/WordEntryHashedArray.java

/*******************************************************************************
 * Copyright (c) 2000, 2003 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.cdt.internal.core.index.impl;

import org.eclipse.cdt.internal.core.CharOperation;

public final class WordEntryHashedArray {
	
	// to avoid using Enumerations, walk the objects skipping nulls
	public WordEntry elements[];
	public int elementSize; // number of elements in the table
	public int threshold;
	
	public WordEntryHashedArray(int size) {
		if (size < 7) size = 7;
		this.elements = new WordEntry[2 * size + 1];
		this.elementSize = 0;
		this.threshold = size + 1; // size is the expected number of elements
	}
	
	public WordEntry add(WordEntry entry) {
		int length = elements.length;
		char[] word = entry.getWord();
		int index = CharOperation.hashCode(word) % length;
		WordEntry current;
		while ((current = elements[index]) != null) {
			if (CharOperation.equals(current.getWord(), word)) return elements[index] = entry;
			if (++index == length) index = 0;
		}
		elements[index] = entry;
	
		// assumes the threshold is never equal to the size of the table
		if (++elementSize > threshold) grow();
		return entry;
	}
	
	public WordEntry[] asArray() {
		WordEntry[] array = new WordEntry[elementSize];
		for (int i = 0, j = 0, length = elements.length; i < length; i++) {
			WordEntry current = elements[i];
			if (current != null) array[j++] = current;
		}
		return array;
	}
	
	public WordEntry get(char[] word) {
		int length = elements.length;
		int index = CharOperation.hashCode(word) % length;
		WordEntry current;
		while ((current = elements[index]) != null) {
			if (CharOperation.equals(current.getWord(), word)) return current;
			if (++index == length) index = 0;
		}
		return null;
	}
	
	private void grow() {
		WordEntryHashedArray newArray = new WordEntryHashedArray(elementSize * 2); // double the number of expected elements
		for (int i = 0, length = elements.length; i < length; i++)
			if (elements[i] != null)
				newArray.add(elements[i]);
	
		this.elements = newArray.elements;
		this.elementSize = newArray.elementSize;
		this.threshold = newArray.threshold;
	}
	
	public String toString() {
		String s = ""; //$NON-NLS-1$
		WordEntry[] entries = asArray();
		for (int i = 0, length = entries.length; i < length; i++)
			s += entries[i].toString() + "\n"; 	//$NON-NLS-1$
		return s;
	}
}