/*******************************************************************************
 * 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 net.sourceforge.phpdt.internal.compiler.codegen;

public class ObjectCache {
	public Object keyTable[];

	public int valueTable[];

	int elementSize;

	int threshold;

	/**
	 * Constructs a new, empty hashtable. A default capacity is used. Note that
	 * the hashtable will automatically grow when it gets full.
	 */
	public ObjectCache() {
		this(13);
	}

	/**
	 * Constructs a new, empty hashtable with the specified initial capacity.
	 * 
	 * @param initialCapacity
	 *            int the initial number of buckets
	 */
	public ObjectCache(int initialCapacity) {
		this.elementSize = 0;
		this.threshold = (int) (initialCapacity * 0.66f);
		this.keyTable = new Object[initialCapacity];
		this.valueTable = new int[initialCapacity];
	}

	/**
	 * Clears the hash table so that it has no more elements in it.
	 */
	public void clear() {
		for (int i = keyTable.length; --i >= 0;) {
			keyTable[i] = null;
			valueTable[i] = 0;
		}
		elementSize = 0;
	}

	/**
	 * Returns true if the collection contains an element for the key.
	 * 
	 * @param char[]
	 *            key the key that we are looking for
	 * @return boolean
	 */
	public boolean containsKey(Object key) {
		int index = hashCode(key);
		while (keyTable[index] != null) {
			if (keyTable[index] == key)
				return true;
			index = (index + 1) % keyTable.length;
		}
		return false;
	}

	/**
	 * Gets the object associated with the specified key in the hashtable.
	 * 
	 * @param key
	 *            <CODE>char[]</CODE> the specified key
	 * @return int the element for the key or -1 if the key is not defined in
	 *         the hash table.
	 */
	public int get(Object key) {
		int index = hashCode(key);
		while (keyTable[index] != null) {
			if (keyTable[index] == key)
				return valueTable[index];
			index = (index + 1) % keyTable.length;
		}
		return -1;
	}

	/**
	 * Return the hashcode for the key parameter
	 * 
	 * @param key
	 *            net.sourceforge.phpdt.internal.compiler.lookup.MethodBinding
	 * @return int
	 */
	public int hashCode(Object key) {
		return (key.hashCode() & 0x7FFFFFFF) % keyTable.length;
	}

	/**
	 * Puts the specified element into the hashtable, using the specified key.
	 * The element may be retrieved by doing a get() with the same key. The key
	 * and the element cannot be null.
	 * 
	 * @param key
	 *            <CODE>Object</CODE> the specified key in the hashtable
	 * @param value
	 *            <CODE>int</CODE> the specified element
	 * @return int the old value of the key, or -1 if it did not have one.
	 */
	public int put(Object key, int value) {
		int index = hashCode(key);
		while (keyTable[index] != null) {
			if (keyTable[index] == key)
				return valueTable[index] = value;
			index = (index + 1) % keyTable.length;
		}
		keyTable[index] = key;
		valueTable[index] = value;

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

	/**
	 * Rehashes the content of the table into a bigger table. This method is
	 * called automatically when the hashtable's size exceeds the threshold.
	 */
	private void rehash() {
		ObjectCache newHashtable = new ObjectCache(keyTable.length * 2);
		for (int i = keyTable.length; --i >= 0;)
			if (keyTable[i] != null)
				newHashtable.put(keyTable[i], valueTable[i]);

		this.keyTable = newHashtable.keyTable;
		this.valueTable = newHashtable.valueTable;
		this.threshold = newHashtable.threshold;
	}

	/**
	 * Returns the number of elements contained in the hashtable.
	 * 
	 * @return <CODE>int</CODE> The size of the table
	 */
	public int size() {
		return elementSize;
	}

	/**
	 * Converts to a rather lengthy String.
	 * 
	 * @return String the ascii representation of the receiver
	 */
	public String toString() {
		int max = size();
		StringBuffer buf = new StringBuffer();
		buf.append("{"); //$NON-NLS-1$
		for (int i = 0; i < max; ++i) {
			if (keyTable[i] != null) {
				buf.append(keyTable[i]).append("->").append(valueTable[i]); //$NON-NLS-1$
			}
			if (i < max) {
				buf.append(", "); //$NON-NLS-1$
			}
		}
		buf.append("}"); //$NON-NLS-1$
		return buf.toString();
	}
}
