/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * particular file as subject to the "Classpath" exception as provided

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 */

/*

 * Licensed Materials - Property of IBM

 * RMI-IIOP v1.0

 * Copyright IBM Corp. 1998 1999  All Rights Reserved

 *

 */

package com.sun.corba.se.impl.util;

import java.util.Dictionary;

import java.util.Enumeration;

import java.util.NoSuchElementException;

/**

 * IdentityHashtable is a modified copy of the 1.1.6 Hashtable class which

 * does not rely on the hashCode() and equals() methods of the key or value;

 * instead, it uses the System.identityHashcode() method and pointer comparison.

 * In addition, all synchronization has been removed.

 */

/**

 * IdentityHashtable collision list.

 */

class IdentityHashtableEntry {

        int hash;

        Object key;

        Object value;

        IdentityHashtableEntry next;

}

public final class IdentityHashtable extends Dictionary {

    /**

     * The hash table data.

     */

    private transient IdentityHashtableEntry table[];

    /**

     * The total number of entries in the hash table.

     */

    private transient int count;

    /**

     * Rehashes the table when count exceeds this threshold.

     */

    private int threshold;

    /**

     * The load factor for the hashtable.

     */

    private float loadFactor;

    /**

     * Constructs a new, empty hashtable with the specified initial

     * capacity and the specified load factor.

     *

     * @param      initialCapacity   the initial capacity of the hashtable.

     * @param      loadFactor        a number between 0.0 and 1.0.

     * @exception  IllegalArgumentException  if the initial capacity is less

     *               than or equal to zero, or if the load factor is less than

     *               or equal to zero.

     * @since      JDK1.0

     */

    public IdentityHashtable(int initialCapacity, float loadFactor) {

        if ((initialCapacity <= 0) || (loadFactor <= 0.0)) {

            throw new IllegalArgumentException();

        }

        this.loadFactor = loadFactor;

        table = new IdentityHashtableEntry[initialCapacity];

        threshold = (int)(initialCapacity * loadFactor);

    }

    /**

     * Constructs a new, empty hashtable with the specified initial capacity

     * and default load factor.

     *

     * @param   initialCapacity   the initial capacity of the hashtable.

     * @since   JDK1.0

     */

    public IdentityHashtable(int initialCapacity) {

        this(initialCapacity, 0.75f);

    }

    /**

     * Constructs a new, empty hashtable with a default capacity and load

     * factor.

     *

     * @since   JDK1.0

     */

    public IdentityHashtable() {

        this(101, 0.75f);

    }

    /**

     * Returns the number of keys in this hashtable.

     *

     * @return  the number of keys in this hashtable.

     * @since   JDK1.0

     */

    public int size() {

        return count;

    }

    /**

     * Tests if this hashtable maps no keys to values.

     *

     * @return  <code>true</code> if this hashtable maps no keys to values;

     *          <code>false</code> otherwise.

     * @since   JDK1.0

     */

    public boolean isEmpty() {

        return count == 0;

    }

    /**

     * Returns an enumeration of the keys in this hashtable.

     *

     * @return  an enumeration of the keys in this hashtable.

     * @see     java.util.Enumeration

     * @see     java.util.Hashtable#elements()

     * @since   JDK1.0

     */

    public Enumeration keys() {

        return new IdentityHashtableEnumerator(table, true);

    }

    /**

     * Returns an enumeration of the values in this hashtable.

     * Use the Enumeration methods on the returned object to fetch the elements

     * sequentially.

     *

     * @return  an enumeration of the values in this hashtable.

     * @see     java.util.Enumeration

     * @see     java.util.Hashtable#keys()

     * @since   JDK1.0

     */

    public Enumeration elements() {

        return new IdentityHashtableEnumerator(table, false);

    }

    /**

     * Tests if some key maps into the specified value in this hashtable.

     * This operation is more expensive than the <code>containsKey</code>

     * method.

     *

     * @param      value   a value to search for.

     * @return     <code>true</code> if some key maps to the

     *             <code>value</code> argument in this hashtable;

     *             <code>false</code> otherwise.

     * @exception  NullPointerException  if the value is <code>null</code>.

     * @see        java.util.Hashtable#containsKey(java.lang.Object)

     * @since      JDK1.0

     */

    public boolean contains(Object value) {

        if (value == null) {

            throw new NullPointerException();

        }

        IdentityHashtableEntry tab[] = table;

        for (int i = tab.length ; i-- > 0 ;) {

            for (IdentityHashtableEntry e = tab[i] ; e != null ; e = e.next) {

                if (e.value == value) {

                    return true;

                }

            }

        }

        return false;

    }

    /**

     * Tests if the specified object is a key in this hashtable.

     *

     * @param   key   possible key.

     * @return  <code>true</code> if the specified object is a key in this

     *          hashtable; <code>false</code> otherwise.

     * @see     java.util.Hashtable#contains(java.lang.Object)

     * @since   JDK1.0

     */

    public boolean containsKey(Object key) {

        IdentityHashtableEntry tab[] = table;

        int hash = System.identityHashCode(key);

        int index = (hash & 0x7FFFFFFF) % tab.length;

        for (IdentityHashtableEntry e = tab[index] ; e != null ; e = e.next) {

            if ((e.hash == hash) && e.key == key) {

                return true;

            }

        }

        return false;

    }

    /**

     * Returns the value to which the specified key is mapped in this hashtable.

     *

     * @param   key   a key in the hashtable.

     * @return  the value to which the key is mapped in this hashtable;

     *          <code>null</code> if the key is not mapped to any value in

     *          this hashtable.

     * @see     java.util.Hashtable#put(java.lang.Object, java.lang.Object)

     * @since   JDK1.0

     */

    public Object get(Object key) {

        IdentityHashtableEntry tab[] = table;

        int hash = System.identityHashCode(key);

        int index = (hash & 0x7FFFFFFF) % tab.length;

        for (IdentityHashtableEntry e = tab[index] ; e != null ; e = e.next) {

            if ((e.hash == hash) && e.key == key) {

                return e.value;

            }

        }

        return null;

    }

    /**

     * Rehashes the contents of the hashtable into a hashtable with a

     * larger capacity. This method is called automatically when the

     * number of keys in the hashtable exceeds this hashtable's capacity

     * and load factor.

     *

     * @since   JDK1.0

     */

    protected void rehash() {

        int oldCapacity = table.length;

        IdentityHashtableEntry oldTable[] = table;

        int newCapacity = oldCapacity * 2 + 1;

        IdentityHashtableEntry newTable[] = new IdentityHashtableEntry[newCapacity];

        threshold = (int)(newCapacity * loadFactor);

        table = newTable;

        //System.out.println("rehash old=" + oldCapacity + ", new=" + newCapacity + ", thresh=" + threshold + ", count=" + count);

        for (int i = oldCapacity ; i-- > 0 ;) {

            for (IdentityHashtableEntry old = oldTable[i] ; old != null ; ) {

                IdentityHashtableEntry e = old;

                old = old.next;

                int index = (e.hash & 0x7FFFFFFF) % newCapacity;

                e.next = newTable[index];

                newTable[index] = e;

            }

        }

    }

    /**

     * Maps the specified <code>key</code> to the specified

     * <code>value</code> in this hashtable. Neither the key nor the

     * value can be <code>null</code>.

     * <p>

     * The value can be retrieved by calling the <code>get</code> method

     * with a key that is equal to the original key.

     *

     * @param      key     the hashtable key.

     * @param      value   the value.

     * @return     the previous value of the specified key in this hashtable,

     *             or <code>null</code> if it did not have one.

     * @exception  NullPointerException  if the key or value is

     *               <code>null</code>.

     * @see     java.util.Hashtable#get(java.lang.Object)

     * @since   JDK1.0

     */

    public Object put(Object key, Object value) {

        // Make sure the value is not null

        if (value == null) {

            throw new NullPointerException();

        }

        // Makes sure the key is not already in the hashtable.

        IdentityHashtableEntry tab[] = table;

        int hash = System.identityHashCode(key);

        int index = (hash & 0x7FFFFFFF) % tab.length;

        for (IdentityHashtableEntry e = tab[index] ; e != null ; e = e.next) {

            if ((e.hash == hash) && e.key == key) {

                Object old = e.value;

                e.value = value;

                return old;

            }

        }

        if (count >= threshold) {

            // Rehash the table if the threshold is exceeded

            rehash();

            return put(key, value);

        }

        // Creates the new entry.

        IdentityHashtableEntry e = new IdentityHashtableEntry();

        e.hash = hash;

        e.key = key;

        e.value = value;

        e.next = tab[index];

        tab[index] = e;

        count++;

        return null;

    }

        /**

     * Removes the key (and its corresponding value) from this

     * hashtable. This method does nothing if the key is not in the hashtable.

     *

     * @param   key   the key that needs to be removed.

     * @return  the value to which the key had been mapped in this hashtable,

     *          or <code>null</code> if the key did not have a mapping.

     * @since   JDK1.0

     */

    public Object remove(Object key) {

        IdentityHashtableEntry tab[] = table;

        int hash = System.identityHashCode(key);

        int index = (hash & 0x7FFFFFFF) % tab.length;

        for (IdentityHashtableEntry e = tab[index], prev = null ; e != null ; prev = e, e = e.next) {

            if ((e.hash == hash) && e.key == key) {

                if (prev != null) {

                    prev.next = e.next;

                } else {

                    tab[index] = e.next;

                }

                count--;

                return e.value;

            }

        }

        return null;

    }

    /**

     * Clears this hashtable so that it contains no keys.

     *

     * @since   JDK1.0

     */

    public void clear() {

        IdentityHashtableEntry tab[] = table;

        for (int index = tab.length; --index >= 0; )

            tab[index] = null;

        count = 0;

    }

    /**

     * Returns a rather long string representation of this hashtable.

     *

     * @return  a string representation of this hashtable.

     * @since   JDK1.0

     */

    public String toString() {

        int max = size() - 1;

        StringBuffer buf = new StringBuffer();

        Enumeration k = keys();

        Enumeration e = elements();

        buf.append("{");

        for (int i = 0; i <= max; i++) {

            String s1 = k.nextElement().toString();

            String s2 = e.nextElement().toString();

            buf.append(s1 + "=" + s2);

            if (i < max) {

                buf.append(", ");

            }

        }

        buf.append("}");

        return buf.toString();

    }

}