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XML Pull parser library developed by extreme lab
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/*
 * $Header: /l/extreme/cvs/codes/xpp5/xis5/infoset_xpath_jaxen/org/xmlpull/infoset/xpath/jaxen/util/IdentityHashMap.java,v 1.1 2005/05/16 23:59:27 aslom Exp $
 * $Revision: 1.1 $
 * $Date: 2005/05/16 23:59:27 $
 *
 * ====================================================================
 *
 * Copyright (C) 2000-2002 bob mcwhirter & James Strachan.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions, and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions, and the disclaimer that follows 
 *    these conditions in the documentation and/or other materials 
 *    provided with the distribution.
 *
 * 3. The name "Jaxen" must not be used to endorse or promote products
 *    derived from this software without prior written permission.  For
 *    written permission, please contact [email protected].
 * 
 * 4. Products derived from this software may not be called "Jaxen", nor
 *    may "Jaxen" appear in their name, without prior written permission
 *    from the Jaxen Project Management ([email protected]).
 * 
 * In addition, we request (but do not require) that you include in the 
 * end-user documentation provided with the redistribution and/or in the 
 * software itself an acknowledgement equivalent to the following:
 *     "This product includes software developed by the
 *      Jaxen Project (http://www.jaxen.org/)."
 * Alternatively, the acknowledgment may be graphical using the logos 
 * available at http://www.jaxen.org/
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE Jaxen AUTHORS OR THE PROJECT
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * ====================================================================
 * This software consists of voluntary contributions made by many 
 * individuals on behalf of the Jaxen Project and was originally 
 * created by bob mcwhirter  and 
 * James Strachan .  For more information on the 
 * Jaxen Project, please see .
 * 
 * $Id: IdentityHashMap.java,v 1.1 2005/05/16 23:59:27 aslom Exp $
 */

package org.xmlpull.infoset.xpath.jaxen.util;
import java.io.*;

import java.util.*;

public class IdentityHashMap extends AbstractMap implements Map, Cloneable,
                                         java.io.Serializable {
    /**
     * The hash table data.
     */
    private transient Entry table[];

    /**
     * The total number of mappings in the hash table.
     */
    private transient int count;

    /**
     * The table is rehashed when its size exceeds this threshold.  (The
     * value of this field is (int)(capacity * loadFactor).)
     *
     * @serial
     */
    private int threshold;

    /**
     * The load factor for the hashtable.
     *
     * @serial
     */
    private float loadFactor;

    /**
     * The number of times this HashMap has been structurally modified
     * Structural modifications are those that change the number of mappings in
     * the HashMap or otherwise modify its internal structure (e.g.,
     * rehash).  This field is used to make iterators on Collection-views of
     * the HashMap fail-fast.  (See ConcurrentModificationException).
     */
    private transient int modCount = 0;

    /**
     * Constructs a new, empty map with the specified initial 
     * capacity and the specified load factor. 
     *
     * @param      initialCapacity   the initial capacity of the HashMap.
     * @param      loadFactor        the load factor of the HashMap
     * @throws     IllegalArgumentException  if the initial capacity is less
     *               than zero, or if the load factor is nonpositive.
     */
    public IdentityHashMap(int initialCapacity, float loadFactor) {
        if (initialCapacity < 0)
            throw new IllegalArgumentException("Illegal Initial Capacity: "+
                                               initialCapacity);
        if (loadFactor <= 0 || Float.isNaN(loadFactor))
            throw new IllegalArgumentException("Illegal Load factor: "+
                                               loadFactor);
        if (initialCapacity==0)
            initialCapacity = 1;
        this.loadFactor = loadFactor;
        table = new Entry[initialCapacity];
        threshold = (int)(initialCapacity * loadFactor);
    }

    /**
     * Constructs a new, empty map with the specified initial capacity
     * and default load factor, which is 0.75.
     *
     * @param   initialCapacity   the initial capacity of the HashMap.
     * @throws    IllegalArgumentException if the initial capacity is less
     *              than zero.
     */
    public IdentityHashMap(int initialCapacity) {
        this(initialCapacity, 0.75f);
    }

    /**
     * Constructs a new, empty map with a default capacity and load
     * factor, which is 0.75.
     */
    public IdentityHashMap() {
        this(11, 0.75f);
    }

    /**
     * Constructs a new map with the same mappings as the given map.  The
     * map is created with a capacity of twice the number of mappings in
     * the given map or 11 (whichever is greater), and a default load factor,
     * which is 0.75.
     *
     * @param t the map whose mappings are to be placed in this map.
     */
    public IdentityHashMap(Map t) {
        this(Math.max(2*t.size(), 11), 0.75f);
        putAll(t);
    }

    /**
     * Returns the number of key-value mappings in this map.
     *
     * @return the number of key-value mappings in this map.
     */
    public int size() {
        return count;
    }

    /**
     * Returns true if this map contains no key-value mappings.
     *
     * @return true if this map contains no key-value mappings.
     */
    public boolean isEmpty() {
        return count == 0;
    }

    /**
     * Returns true if this map maps one or more keys to the
     * specified value.
     *
     * @param value value whose presence in this map is to be tested.
     * @return true if this map maps one or more keys to the
     *         specified value.
     */
    public boolean containsValue(Object value) {
        Entry tab[] = table;

        if (value==null) {
            for (int i = tab.length ; i-- > 0 ;)
                for (Entry e = tab[i] ; e != null ; e = e.next)
                    if (e.value==null)
                        return true;
        } else {
            for (int i = tab.length ; i-- > 0 ;)
                for (Entry e = tab[i] ; e != null ; e = e.next)
                    if (value.equals(e.value))
                        return true;
        }

        return false;
    }

    /**
     * Returns true if this map contains a mapping for the specified
     * key.
     * 
     * @return true if this map contains a mapping for the specified
     * key.
     * @param key key whose presence in this Map is to be tested.
     */
    public boolean containsKey(Object key) {
        Entry tab[] = table;
        if (key != null) {
            //int hash = key.hashCode();
            int hash = System.identityHashCode( key );
            int index = (hash & 0x7FFFFFFF) % tab.length;
            for (Entry e = tab[index]; e != null; e = e.next)
                // if (e.hash==hash && key.equals(e.key))
                if (e.hash==hash && ( key == e.key ) )
                    return true;
        } else {
            for (Entry e = tab[0]; e != null; e = e.next)
                if (e.key==null)
                    return true;
        }

        return false;
    }

    /**
     * Returns the value to which this map maps the specified key.  Returns
     * null if the map contains no mapping for this key.  A return
     * value of null does not necessarily indicate that the
     * map contains no mapping for the key; it's also possible that the map
     * explicitly maps the key to null.  The containsKey
     * operation may be used to distinguish these two cases.
     *
     * @return the value to which this map maps the specified key.
     * @param key key whose associated value is to be returned.
     */
    public Object get(Object key) {
        Entry tab[] = table;

        if (key != null) {
            // int hash = key.hashCode();
            int hash = System.identityHashCode( key );
            int index = (hash & 0x7FFFFFFF) % tab.length;
            for (Entry e = tab[index]; e != null; e = e.next)
                // if ((e.hash == hash) && key.equals(e.key))
                if ((e.hash == hash) && ( key == e.key ) )
                    return e.value;
        } else {
            for (Entry e = tab[0]; e != null; e = e.next)
                if (e.key==null)
                    return e.value;
        }

        return null;
    }

    /**
     * Rehashes the contents of this map into a new IdentityHashMap instance
     * with a larger capacity. This method is called automatically when the
     * number of keys in this map exceeds its capacity and load factor.
     */
    private void rehash() {
        int oldCapacity = table.length;
        Entry oldMap[] = table;

        int newCapacity = oldCapacity * 2 + 1;
        Entry newMap[] = new Entry[newCapacity];

        modCount++;
        threshold = (int)(newCapacity * loadFactor);
        table = newMap;

        for (int i = oldCapacity ; i-- > 0 ;) {
            for (Entry old = oldMap[i] ; old != null ; ) {
                Entry e = old;
                old = old.next;

                int index = (e.hash & 0x7FFFFFFF) % newCapacity;
                e.next = newMap[index];
                newMap[index] = e;
            }
        }
    }

    /**
     * Associates the specified value with the specified key in this map.
     * If the map previously contained a mapping for this key, the old
     * value is replaced.
     *
     * @param key key with which the specified value is to be associated.
     * @param value value to be associated with the specified key.
     * @return previous value associated with specified key, or null
     *         if there was no mapping for key.  A null return can
     *         also indicate that the IdentityHashMap previously associated
     *         null with the specified key.
     */
    public Object put(Object key, Object value) {
        // Makes sure the key is not already in the IdentityHashMap.
        Entry tab[] = table;
        int hash = 0;
        int index = 0;

        if (key != null) {
            // hash = key.hashCode();
            hash = System.identityHashCode( key );
            index = (hash & 0x7FFFFFFF) % tab.length;
            for (Entry e = tab[index] ; e != null ; e = e.next) {
                // if ((e.hash == hash) && key.equals(e.key)) {
                if ((e.hash == hash) && ( key == e.key ) ) {
                    Object old = e.value;
                    e.value = value;
                    return old;
                }
            }
        } else {
            for (Entry e = tab[0] ; e != null ; e = e.next) {
                if (e.key == null) {
                    Object old = e.value;
                    e.value = value;
                    return old;
                }
            }
        }

        modCount++;
        if (count >= threshold) {
            // Rehash the table if the threshold is exceeded
            rehash();

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

        // Creates the new entry.
        Entry e = new Entry(hash, key, value, tab[index]);
        tab[index] = e;
        count++;
        return null;
    }

    /**
     * Removes the mapping for this key from this map if present.
     *
     * @param key key whose mapping is to be removed from the map.
     * @return previous value associated with specified key, or null
     *         if there was no mapping for key.  A null return can
     *         also indicate that the map previously associated null
     *         with the specified key.
     */
    public Object remove(Object key) {
        Entry tab[] = table;

        if (key != null) {
            // int hash = key.hashCode();
            int hash = System.identityHashCode( key );
            int index = (hash & 0x7FFFFFFF) % tab.length;

            for (Entry e = tab[index], prev = null; e != null;
                 prev = e, e = e.next) {
                // if ((e.hash == hash) && key.equals(e.key)) {
                if ((e.hash == hash) && ( key == e.key ) ) {
                    modCount++;
                    if (prev != null)
                        prev.next = e.next;
                    else
                        tab[index] = e.next;

                    count--;
                    Object oldValue = e.value;
                    e.value = null;
                    return oldValue;
                }
            }
        } else {
            for (Entry e = tab[0], prev = null; e != null;
                 prev = e, e = e.next) {
                if (e.key == null) {
                    modCount++;
                    if (prev != null)
                        prev.next = e.next;
                    else
                        tab[0] = e.next;

                    count--;
                    Object oldValue = e.value;
                    e.value = null;
                    return oldValue;
                }
            }
        }

        return null;
    }

    /**
     * Copies all of the mappings from the specified map to this one.
     * 
     * These mappings replace any mappings that this map had for any of the
     * keys currently in the specified Map.
     *
     * @param t Mappings to be stored in this map.
     */
    public void putAll(Map t) {
        Iterator i = t.entrySet().iterator();
        while (i.hasNext()) {
            Map.Entry e = (Map.Entry) i.next();
            put(e.getKey(), e.getValue());
        }
    }

    /**
     * Removes all mappings from this map.
     */
    public void clear() {
        Entry tab[] = table;
        modCount++;
        for (int index = tab.length; --index >= 0; )
            tab[index] = null;
        count = 0;
    }

    /**
     * Returns a shallow copy of this IdentityHashMap instance: the keys and
     * values themselves are not cloned.
     *
     * @return a shallow copy of this map.
     */
    public Object clone() {
        try { 
            IdentityHashMap t = (IdentityHashMap)super.clone();
            t.table = new Entry[table.length];
            for (int i = table.length ; i-- > 0 ; ) {
                t.table[i] = (table[i] != null) 
                    ? (Entry)table[i].clone() : null;
            }
            t.keySet = null;
            t.entrySet = null;
            t.values = null;
            t.modCount = 0;
            return t;
        } catch (CloneNotSupportedException e) { 
            // this shouldn't happen, since we are Cloneable
            throw new InternalError();
        }
    }

    // Views

    private transient Set keySet = null;
    private transient Set entrySet = null;
    private transient Collection values = null;

    /**
     * Returns a set view of the keys contained in this map.  The set is
     * backed by the map, so changes to the map are reflected in the set, and
     * vice-versa.  The set supports element removal, which removes the
     * corresponding mapping from this map, via the Iterator.remove,
     * Set.remove, removeAll, retainAll, and
     * clear operations.  It does not support the add or
     * addAll operations.
     *
     * @return a set view of the keys contained in this map.
     */
    public Set keySet() {
        if (keySet == null) {
            keySet = new AbstractSet() {
                public Iterator iterator() {
                    return getHashIterator(KEYS);
                }
                public int size() {
                    return count;
                }
                public boolean contains(Object o) {
                    return containsKey(o);
                }
                public boolean remove(Object o) {
                    int oldSize = count;
                    IdentityHashMap.this.remove(o);
                    return count != oldSize;
                }
                public void clear() {
                    IdentityHashMap.this.clear();
                }
            };
        }
        return keySet;
    }

    /**
     * Returns a collection view of the values contained in this map.  The
     * collection is backed by the map, so changes to the map are reflected in
     * the collection, and vice-versa.  The collection supports element
     * removal, which removes the corresponding mapping from this map, via the
     * Iterator.remove, Collection.remove,
     * removeAll, retainAll, and clear operations.
     * It does not support the add or addAll operations.
     *
     * @return a collection view of the values contained in this map.
     */
    public Collection values() {
        if (values==null) {
            values = new AbstractCollection() {
                public Iterator iterator() {
                    return getHashIterator(VALUES);
                }
                public int size() {
                    return count;
                }
                public boolean contains(Object o) {
                    return containsValue(o);
                }
                public void clear() {
                    IdentityHashMap.this.clear();
                }
            };
        }
        return values;
    }

    /**
     * Returns a collection view of the mappings contained in this map.  Each
     * element in the returned collection is a Map.Entry.  The
     * collection is backed by the map, so changes to the map are reflected in
     * the collection, and vice-versa.  The collection supports element
     * removal, which removes the corresponding mapping from the map, via the
     * Iterator.remove, Collection.remove,
     * removeAll, retainAll, and clear operations.
     * It does not support the add or addAll operations.
     *
     * @return a collection view of the mappings contained in this map.
     * @see Map.Entry
     */
    public Set entrySet() {
        if (entrySet==null) {
            entrySet = new AbstractSet() {
                public Iterator iterator() {
                    return getHashIterator(ENTRIES);
                }

                public boolean contains(Object o) {
                    if (!(o instanceof Map.Entry))
                        return false;
                    Map.Entry entry = (Map.Entry)o;
                    Object key = entry.getKey();
                    Entry tab[] = table;
                    // int hash = (key==null ? 0 : key.hashCode());
                    int hash = (key==null ? 0 : System.identityHashCode( key ) );
                    int index = (hash & 0x7FFFFFFF) % tab.length;

                    for (Entry e = tab[index]; e != null; e = e.next)
                        if (e.hash==hash && e.equals(entry))
                            return true;
                    return false;
                }

                public boolean remove(Object o) {
                    if (!(o instanceof Map.Entry))
                        return false;
                    Map.Entry entry = (Map.Entry)o;
                    Object key = entry.getKey();
                    Entry tab[] = table;
                    // int hash = (key==null ? 0 : key.hashCode());
                    int hash = (key==null ? 0 : System.identityHashCode( key ) );
                    int index = (hash & 0x7FFFFFFF) % tab.length;

                    for (Entry e = tab[index], prev = null; e != null;
                         prev = e, e = e.next) {
                        if (e.hash==hash && e.equals(entry)) {
                            modCount++;
                            if (prev != null)
                                prev.next = e.next;
                            else
                                tab[index] = e.next;

                            count--;
                            e.value = null;
                            return true;
                        }
                    }
                    return false;
                }

                public int size() {
                    return count;
                }

                public void clear() {
                    IdentityHashMap.this.clear();
                }
            };
        }

        return entrySet;
    }

    private Iterator getHashIterator(int type) {
        if (count == 0) {
            return emptyHashIterator;
        } else {
            return new HashIterator(type);
        }
    }

    /**
     * IdentityHashMap collision list entry.
     */
    private static class Entry implements Map.Entry {
        int hash;
        Object key;
        Object value;
        Entry next;

        Entry(int hash, Object key, Object value, Entry next) {
            this.hash = hash;
            this.key = key;
            this.value = value;
            this.next = next;
        }

        protected Object clone() {
            return new Entry(hash, key, value,
                             (next==null ? null : (Entry)next.clone()));
        }

        // Map.Entry Ops 

        public Object getKey() {
            return key;
        }

        public Object getValue() {
            return value;
        }

        public Object setValue(Object value) {
            Object oldValue = this.value;
            this.value = value;
            return oldValue;
        }

        public boolean equals(Object o) {
            if (!(o instanceof Map.Entry))
                return false;
            Map.Entry e = (Map.Entry)o;

            return (key==null ? e.getKey()==null : key.equals(e.getKey())) &&
               (value==null ? e.getValue()==null : value.equals(e.getValue()));
        }

        public int hashCode() {
            return hash ^ (value==null ? 0 : value.hashCode());
        }

        public String toString() {
            return key+"="+value;
        }
    }

    // Types of Iterators
    private static final int KEYS = 0;
    private static final int VALUES = 1;
    private static final int ENTRIES = 2;

    private static EmptyHashIterator emptyHashIterator 
        = new EmptyHashIterator();
                                             
    private static class EmptyHashIterator implements Iterator {
        
        EmptyHashIterator() {
            
        }

        public boolean hasNext() {
            return false;
        }

        public Object next() {
            throw new NoSuchElementException();
        }
        
        public void remove() {
            throw new IllegalStateException();
        }

    }                   
                    
    private class HashIterator implements Iterator {
        Entry[] table = IdentityHashMap.this.table;
        int index = table.length;
        Entry entry = null;
        Entry lastReturned = null;
        int type;

        /**
         * The modCount value that the iterator believes that the backing
         * List should have.  If this expectation is violated, the iterator
         * has detected concurrent modification.
         */
        private int expectedModCount = modCount;

        HashIterator(int type) {
            this.type = type;
        }

        public boolean hasNext() {
            Entry e = entry;
            int i = index;
            Entry t[] = table;
            /* Use locals for faster loop iteration */
            while (e == null && i > 0)
                e = t[--i];
            entry = e;
            index = i;
            return e != null;
        }

        public Object next() {
            if (modCount != expectedModCount)
                throw new ConcurrentModificationException();

            Entry et = entry;
            int i = index;
            Entry t[] = table;

            /* Use locals for faster loop iteration */
            while (et == null && i > 0) 
                et = t[--i];

            entry = et;
            index = i;
            if (et != null) {
                Entry e = lastReturned = entry;
                entry = e.next;
                return type == KEYS ? e.key : (type == VALUES ? e.value : e);
            }
            throw new NoSuchElementException();
        }

        public void remove() {
            if (lastReturned == null)
                throw new IllegalStateException();
            if (modCount != expectedModCount)
                throw new ConcurrentModificationException();

            Entry[] tab = IdentityHashMap.this.table;
            int index = (lastReturned.hash & 0x7FFFFFFF) % tab.length;

            for (Entry e = tab[index], prev = null; e != null;
                 prev = e, e = e.next) {
                if (e == lastReturned) {
                    modCount++;
                    expectedModCount++;
                    if (prev == null)
                        tab[index] = e.next;
                    else
                        prev.next = e.next;
                    count--;
                    lastReturned = null;
                    return;
                }
            }
            throw new ConcurrentModificationException();
        }
    }

    /**
     * Save the state of the IdentityHashMap instance to a stream (i.e.,
     * serialize it).
     *
     * @serialData The capacity of the IdentityHashMap (the length of the
     *             bucket array) is emitted (int), followed  by the
     *             size of the IdentityHashMap (the number of key-value
     *             mappings), followed by the key (Object) and value (Object)
     *             for each key-value mapping represented by the IdentityHashMap
     * The key-value mappings are emitted in no particular order.
     */
    private void writeObject(java.io.ObjectOutputStream s)
        throws IOException
    {
        // Write out the threshold, loadfactor, and any hidden stuff
        s.defaultWriteObject();

        // Write out number of buckets
        s.writeInt(table.length);

        // Write out size (number of Mappings)
        s.writeInt(count);

        // Write out keys and values (alternating)
        for (int index = table.length-1; index >= 0; index--) {
            Entry entry = table[index];

            while (entry != null) {
                s.writeObject(entry.key);
                s.writeObject(entry.value);
                entry = entry.next;
            }
        }
    }

    private static final long serialVersionUID = 362498820763181265L;

    /**
     * Reconstitute the IdentityHashMap instance from a stream (i.e.,
     * deserialize it).
     */
    private void readObject(java.io.ObjectInputStream s)
         throws IOException, ClassNotFoundException
    {
        // Read in the threshold, loadfactor, and any hidden stuff
        s.defaultReadObject();

        // Read in number of buckets and allocate the bucket array;
        int numBuckets = s.readInt();
        table = new Entry[numBuckets];

        // Read in size (number of Mappings)
        int size = s.readInt();

        // Read the keys and values, and put the mappings in the IdentityHashMap
        for (int i=0; i