--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/com/go/trove/util/IdentityMap.java	Sat Mar 21 11:00:06 2009 +0000
@@ -0,0 +1,1031 @@
+/* ====================================================================
+ * Trove - Copyright (c) 1997-2000 Walt Disney Internet Group
+ * ====================================================================
+ * The Tea Software License, Version 1.1
+ *
+ * Copyright (c) 2000 Walt Disney Internet Group. 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 following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. The end-user documentation included with the redistribution,
+ *    if any, must include the following acknowledgment:
+ *       "This product includes software developed by the
+ *        Walt Disney Internet Group (http://opensource.go.com/)."
+ *    Alternately, this acknowledgment may appear in the software itself,
+ *    if and wherever such third-party acknowledgments normally appear.
+ *
+ * 4. The names "Tea", "TeaServlet", "Kettle", "Trove" and "BeanDoc" must
+ *    not be used to endorse or promote products derived from this
+ *    software without prior written permission. For written
+ *    permission, please contact opensource@dig.com.
+ *
+ * 5. Products derived from this software may not be called "Tea",
+ *    "TeaServlet", "Kettle" or "Trove", nor may "Tea", "TeaServlet",
+ *    "Kettle", "Trove" or "BeanDoc" appear in their name, without prior
+ *    written permission of the Walt Disney Internet Group.
+ *
+ * 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 WALT DISNEY INTERNET GROUP OR ITS
+ * 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.
+ * ====================================================================
+ *
+ * For more information about Tea, please see http://opensource.go.com/.
+ */
+
+package com.go.trove.util;
+
+import java.lang.ref.*;
+import java.util.*;
+
+/******************************************************************************
+ * An IdentityMap is like WeakHashMap, except it uses a key's identity
+ * hashcode and equals methods. IdentityMap is not thread-safe and must be
+ * wrapped with Collections.synchronizedMap to be made thread-safe. Most of the
+ * implementation for this class is ripped off from java.util.HashMap, but not
+ * java.util.WeakHashMap, in order to acheive greater efficiency.
+ * <p>
+ * The documentation for WeakHashMap states that it is intended primarily
+ * for use with key objects whose equals methods test for object identity
+ * using the == operator. Because WeakHashMap uses a key's own equals and
+ * hashcode methods, it is better suited for implementing methods that behave
+ * like {@link String#intern}. However, because WeakHashMap stongly references
+ * values, {@link Utils#intern Utils.intern} provides a safer intern mechanism.
+ * <p>
+ * In this implementation, all key objects are tested for equality using the
+ * == operator, and null keys are not permitted. IdentityMap is therefore
+ * better suited for "canonicalized" mappings.
+ * <p>
+ * Note: Weakly referenced entries may be automatically removed during
+ * either accessor or mutator operations, possibly causing a concurrent
+ * modification to be detected. Therefore, even if multiple threads are only
+ * accessing this map, be sure to synchronize this map first. Also, do not
+ * rely on the value returned by size() when using an iterator from this map.
+ * The iterators may return less entries than the amount reported by size().
+ *
+ * @author Brian S O'Neill
+ * @version
+ * <!--$$Revision: 1.1 $-->, <!--$$JustDate:--> 00/12/18 <!-- $-->
+ * @see java.util.WeakHashMap
+ * @see java.util.HashMap
+ */
+public class IdentityMap extends AbstractMap implements Map, Cloneable {
+    // Types of Iterators
+    static final int KEYS = 0;
+    static final int VALUES = 1;
+    static final int ENTRIES = 2;
+
+    static final Iterator cEmptyHashIterator = new Iterator() {
+        public boolean hasNext() {
+            return false;
+        }
+        
+        public Object next() {
+            throw new NoSuchElementException();
+        }
+        
+        public void remove() {
+            throw new IllegalStateException();
+        }
+    };
+
+    /**
+     * Test program.
+     */
+    /*
+    public static void main(String[] args) throws Exception {
+        Map map = new IdentityMap();
+        map.put("Hello", "There");
+        for (int i=0; i<1000000; i++) {
+            if (i % 5 == 0) {
+                map.put(new String("Hello"), "Dude");
+            }
+            map.get("Hello");
+            map.get("Stuff");
+        }
+
+        System.out.println(map.containsValue("Dude"));
+        System.out.println(map.get("Hello"));
+
+        System.gc();
+
+        System.out.println(map);
+        System.out.println(map.size());
+
+        System.out.println(map.containsValue("Dude"));
+        System.out.println(map.get("Hello"));
+
+        map.remove("Hello");
+
+        System.out.println(map);
+        System.out.println(map.size());
+
+        System.out.println(map.containsValue("Dude"));
+        System.out.println(map.get("Hello"));
+    }
+    */
+
+    /**
+     * Converts a string to a collection without calling size(). Iterators from
+     * this map may return less entries than the amount reported by size().
+     */
+    static String toString(Collection c) {
+        StringBuffer buf = new StringBuffer();
+        Iterator it = c.iterator();
+        buf.append("[");
+        for (int i = 0; it.hasNext(); i++) {
+            if (i > 0) {
+                buf.append(", ");
+            }
+            buf.append(String.valueOf(it.next()));
+        }
+        buf.append("]");
+        return buf.toString();
+    }
+
+    /**
+     * The hash table data.
+     */
+    private transient Entry mTable[];
+
+    /**
+     * The total number of mappings in the hash table.
+     */
+    private transient int mCount;
+
+    /**
+     * The table is rehashed when its size exceeds this threshold.  (The
+     * value of this field is (int)(capacity * loadFactor).)
+     *
+     * @serial
+     */
+    private int mThreshold;
+
+    /**
+     * The load factor for the hashtable.
+     *
+     * @serial
+     */
+    private float mLoadFactor;
+
+    /**
+     * 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 mModCount = 0;
+
+    // Views
+    
+    private transient Set mKeySet = null;
+    private transient Set mEntrySet = null;
+    private transient Collection mValues = null;
+
+    /**
+     * 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 IdentityMap(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;
+        }
+
+        mLoadFactor = loadFactor;
+        mTable = new Entry[initialCapacity];
+        mThreshold = (int)(initialCapacity * loadFactor);
+    }
+    
+    /**
+     * Constructs a new, empty map with the specified initial capacity
+     * and default load factor, which is <tt>0.75</tt>.
+     *
+     * @param   initialCapacity   the initial capacity of the HashMap.
+     * @throws    IllegalArgumentException if the initial capacity is less
+     *              than zero.
+     */
+    public IdentityMap(int initialCapacity) {
+        this(initialCapacity, 0.75f);
+    }
+
+    /**
+     * Constructs a new, empty map with a default capacity and load
+     * factor, which is <tt>0.75</tt>.
+     */
+    public IdentityMap() {
+        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 <tt>0.75</tt>.
+     */
+    public IdentityMap(Map t) {
+        this(Math.max(2 * t.size(), 11), 0.75f);
+        putAll(t);
+    }
+
+    /**
+     * Returns the number of key-value mappings in this map, but this value
+     * may be larger than actual amount of entries produced by an iterator.
+     *
+     * @return the number of key-value mappings in this map.
+     */
+    public int size() {
+        return mCount;
+    }
+
+    /**
+     * Returns <tt>true</tt> if this map contains no key-value mappings.
+     *
+     * @return <tt>true</tt> if this map contains no key-value mappings.
+     */
+    public boolean isEmpty() {
+        return mCount == 0;
+    }
+
+    /**
+     * Returns <tt>true</tt> 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 <tt>true</tt> if this map maps one or more keys to the
+     *         specified value.
+     */
+    public boolean containsValue(Object value) {
+        Entry tab[] = mTable;
+        
+        if (value == null) {
+            for (int i = tab.length ; i-- > 0 ;) {
+                for (Entry e = tab[i], prev = null; e != null; e = e.mNext) {
+                    if (e.getKey() == null) {
+                        // Clean up after a cleared Reference.
+                        mModCount++;
+                        if (prev != null) {
+                            prev.mNext = e.mNext;
+                        }
+                        else {
+                            tab[i] = e.mNext;
+                        }
+                        mCount--;
+                    }
+                    else if (e.mValue == null) {
+                        return true;
+                    }
+                    else {
+                        prev = e;
+                    }
+                }
+            }
+        }
+        else {
+            for (int i = tab.length ; i-- > 0 ;) {
+                for (Entry e = tab[i], prev = null; e != null; e = e.mNext) {
+                    if (e.getKey() == null) {
+                        // Clean up after a cleared Reference.
+                        mModCount++;
+                        if (prev != null) {
+                            prev.mNext = e.mNext;
+                        }
+                        else {
+                            tab[i] = e.mNext;
+                        }
+                        mCount--;
+                    }
+                    else if (value.equals(e.mValue)) {
+                        return true;
+                    }
+                    else {
+                        prev = e;
+                    }
+                }
+            }
+        }
+
+        return false;
+    }
+
+    /**
+     * Returns <tt>true</tt> if this map contains a mapping for the specified
+     * key.
+     * 
+     * @return <tt>true</tt> 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) {
+        if (key == null) {
+            return false;
+        }
+
+        Entry tab[] = mTable;
+        int hash = System.identityHashCode(key);
+        int index = (hash & 0x7FFFFFFF) % tab.length;
+
+        for (Entry e = tab[index], prev = null; e != null; e = e.mNext) {
+            Object entryKey = e.getKey();
+
+            if (entryKey == null) {
+                // Clean up after a cleared Reference.
+                mModCount++;
+                if (prev != null) {
+                    prev.mNext = e.mNext;
+                }
+                else {
+                    tab[index] = e.mNext;
+                }
+                mCount--;
+            }
+            else if (e.mHash == hash && key == entryKey) {
+                return true;
+            }
+            else {
+                prev = e;
+            }
+        }
+
+        return false;
+    }
+
+    /**
+     * Returns the value to which this map maps the specified key.  Returns
+     * <tt>null</tt> if the map contains no mapping for this key.  A return
+     * value of <tt>null</tt> does not <i>necessarily</i> indicate that the
+     * map contains no mapping for the key; it's also possible that the map
+     * explicitly maps the key to <tt>null</tt>.  The <tt>containsKey</tt>
+     * 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) {
+        if (key == null) {
+            return null;
+        }
+
+        Entry tab[] = mTable;
+        int hash = System.identityHashCode(key);
+        int index = (hash & 0x7FFFFFFF) % tab.length;
+
+        for (Entry e = tab[index], prev = null; e != null; e = e.mNext) {
+            Object entryKey = e.getKey();
+
+            if (entryKey == null) {
+                // Clean up after a cleared Reference.
+                mModCount++;
+                if (prev != null) {
+                    prev.mNext = e.mNext;
+                }
+                else {
+                    tab[index] = e.mNext;
+                }
+                mCount--;
+            }
+            else if (e.mHash == hash && key == entryKey) {
+                return e.mValue;
+            }
+            else {
+                prev = e;
+            }
+        }
+
+        return null;
+    }
+
+    /**
+     * Scans the contents of this map, removing all entries that have a
+     * cleared weak key.
+     */
+    private void cleanup() {
+        Entry tab[] = mTable;
+        
+        for (int i = tab.length ; i-- > 0 ;) {
+            for (Entry e = tab[i], prev = null; e != null; e = e.mNext) {
+                if (e.getKey() == null) {
+                    // Clean up after a cleared Reference.
+                    mModCount++;
+                    if (prev != null) {
+                        prev.mNext = e.mNext;
+                    }
+                    else {
+                        tab[i] = e.mNext;
+                    }
+                    mCount--;
+                }
+                else {
+                    prev = e;
+                }
+            }
+        }
+    }
+
+    /**
+     * Rehashes the contents of this map into a new <tt>HashMap</tt> 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 = mTable.length;
+        Entry oldMap[] = mTable;
+        
+        int newCapacity = oldCapacity * 2 + 1;
+        Entry newMap[] = new Entry[newCapacity];
+        
+        mModCount++;
+        mThreshold = (int)(newCapacity * mLoadFactor);
+        mTable = newMap;
+        
+        for (int i = oldCapacity ; i-- > 0 ;) {
+            for (Entry old = oldMap[i] ; old != null ; ) {
+                Entry e = old;
+                old = old.mNext;
+
+                // Only copy entry if its key hasn't been cleared.
+                if (e.getKey() == null) {
+                    mCount--;
+                }
+                else {
+                    int index = (e.mHash & 0x7FFFFFFF) % newCapacity;
+                    e.mNext = 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 <tt>null</tt>
+     *         if there was no mapping for key.  A <tt>null</tt> return can
+     *         also indicate that the HashMap previously associated
+     *         <tt>null</tt> with the specified key.
+     */
+    public Object put(Object key, Object value) {
+        if (key == null) {
+            throw new NullPointerException("Null key is not permitted");
+        }
+
+        // Makes sure the key is not already in the HashMap.
+        Entry tab[] = mTable;
+        int hash = System.identityHashCode(key);
+        int index = (hash & 0x7FFFFFFF) % tab.length;
+
+        for (Entry e = tab[index], prev = null; e != null; e = e.mNext) {
+            Object entryKey = e.getKey();
+
+            if (entryKey == null) {
+                // Clean up after a cleared Reference.
+                mModCount++;
+                if (prev != null) {
+                    prev.mNext = e.mNext;
+                }
+                else {
+                    tab[index] = e.mNext;
+                }
+                mCount--;
+            }
+            else if (e.mHash == hash && key == entryKey) {
+                Object old = e.mValue;
+                e.mValue = value;
+                return old;
+            }
+            else {
+                prev = e;
+            }
+        }
+
+        mModCount++;
+
+        if (mCount >= mThreshold) {
+            // Cleanup the table if the threshold is exceeded.
+            cleanup();
+        }
+
+        if (mCount >= mThreshold) {
+            // Rehash the table if the threshold is still exceeded.
+            rehash();
+            tab = mTable;
+            index = (hash & 0x7FFFFFFF) % tab.length;
+        }
+        
+        // Creates the new entry.
+        Entry e = new Entry(hash, key, value, tab[index]);
+        tab[index] = e;
+        mCount++;
+        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 <tt>null</tt>
+     *         if there was no mapping for key.  A <tt>null</tt> return can
+     *         also indicate that the map previously associated <tt>null</tt>
+     *         with the specified key.
+     */
+    public Object remove(Object key) {
+        Entry tab[] = mTable;
+        int hash = System.identityHashCode(key);
+        int index = (hash & 0x7FFFFFFF) % tab.length;
+            
+        for (Entry e = tab[index], prev = null; e != null; e = e.mNext) {
+            Object entryKey = e.getKey();
+
+            if (entryKey == null) {
+                // Clean up after a cleared Reference.
+                mModCount++;
+                if (prev != null) {
+                    prev.mNext = e.mNext;
+                }
+                else {
+                    tab[index] = e.mNext;
+                }
+                mCount--;
+            }
+            else if (e.mHash == hash && key == entryKey) {
+                mModCount++;
+                if (prev != null) {
+                    prev.mNext = e.mNext;
+                }
+                else {
+                    tab[index] = e.mNext;
+                }
+                mCount--;
+
+                Object oldValue = e.mValue;
+                e.mValue = null;
+                return oldValue;
+            }
+            else {
+                prev = e;
+            }
+        }
+
+        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[] = mTable;
+        mModCount++;
+        for (int index = tab.length; --index >= 0; ) {
+            tab[index] = null;
+        }
+        mCount = 0;
+    }
+
+    /**
+     * Returns a shallow copy of this <tt>HashMap</tt> instance: the keys and
+     * values themselves are not cloned.
+     *
+     * @return a shallow copy of this map.
+     */
+    public Object clone() {
+        try { 
+            IdentityMap t = (IdentityMap)super.clone();
+            t.mTable = new Entry[mTable.length];
+            for (int i = mTable.length ; i-- > 0 ; ) {
+                t.mTable[i] = (mTable[i] != null) 
+                    ? (Entry)mTable[i].clone() : null;
+            }
+            t.mKeySet = null;
+            t.mEntrySet = null;
+            t.mValues = null;
+            t.mModCount = 0;
+            return t;
+        }
+        catch (CloneNotSupportedException e) { 
+            // this shouldn't happen, since we are Cloneable
+            throw new InternalError();
+        }
+    }
+    
+    /**
+     * 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 <tt>Iterator.remove</tt>,
+     * <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt>, and
+     * <tt>clear</tt> operations.  It does not support the <tt>add</tt> or
+     * <tt>addAll</tt> operations.
+     *
+     * @return a set view of the keys contained in this map.
+     */
+    public Set keySet() {
+        if (mKeySet == null) {
+            mKeySet = new AbstractSet() {
+                public Iterator iterator() {
+                    return getHashIterator(KEYS);
+                }
+                public int size() {
+                    return mCount;
+                }
+                public boolean contains(Object o) {
+                    return containsKey(o);
+                }
+                public boolean remove(Object o) {
+                    return o == null ? false : IdentityMap.this.remove(o) == o;
+                }
+                public void clear() {
+                    IdentityMap.this.clear();
+                }
+                public String toString() {
+                    return IdentityMap.this.toString(this);
+                }
+            };
+        }
+        return mKeySet;
+    }
+    
+    /**
+     * 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
+     * <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
+     * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> operations.
+     * It does not support the <tt>add</tt> or <tt>addAll</tt> operations.
+     *
+     * @return a collection view of the values contained in this map.
+     */
+    public Collection values() {
+        if (mValues==null) {
+            mValues = new AbstractCollection() {
+                public Iterator iterator() {
+                    return getHashIterator(VALUES);
+                }
+                public int size() {
+                    return mCount;
+                }
+                public boolean contains(Object o) {
+                    return containsValue(o);
+                }
+                public void clear() {
+                    IdentityMap.this.clear();
+                }
+                public String toString() {
+                    return IdentityMap.this.toString(this);
+                }
+            };
+        }
+        return mValues;
+    }
+
+    /**
+     * Returns a collection view of the mappings contained in this map.  Each
+     * element in the returned collection is a <tt>Map.Entry</tt>.  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
+     * <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
+     * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> operations.
+     * It does not support the <tt>add</tt> or <tt>addAll</tt> operations.
+     *
+     * @return a collection view of the mappings contained in this map.
+     * @see Map.Entry
+     */
+    public Set entrySet() {
+        if (mEntrySet==null) {
+            mEntrySet = 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[] = mTable;
+                    int hash = System.identityHashCode(key);
+                    int index = (hash & 0x7FFFFFFF) % tab.length;
+
+                    for (Entry e = tab[index], prev = null; e != null; e = e.mNext) {
+                        Object entryKey = e.getKey();
+                        
+                        if (entryKey == null) {
+                            // Clean up after a cleared Reference.
+                            mModCount++;
+                            if (prev != null) {
+                                prev.mNext = e.mNext;
+                            }
+                            else {
+                                tab[index] = e.mNext;
+                            }
+                            mCount--;
+                        }
+                        else if (e.mHash == hash && e.identityEquals(entry)) {
+                            return true;
+                        }
+                        else {
+                            prev = e;
+                        }
+                    }
+
+                    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[] = mTable;
+                    int hash = System.identityHashCode(key);
+                    int index = (hash & 0x7FFFFFFF) % tab.length;
+
+                    for (Entry e = tab[index], prev = null; e != null; e = e.mNext) {
+                        Object entryKey = e.getKey();
+                        
+                        if (entryKey == null) {
+                            // Clean up after a cleared Reference.
+                            mModCount++;
+                            if (prev != null) {
+                                prev.mNext = e.mNext;
+                            }
+                            else {
+                                tab[index] = e.mNext;
+                            }
+                            mCount--;
+                        }
+                        else if (e.mHash == hash && e.identityEquals(entry)) {
+                            mModCount++;
+                            if (prev != null) {
+                                prev.mNext = e.mNext;
+                            }
+                            else {
+                                tab[index] = e.mNext;
+                            }
+                            mCount--;
+
+                            e.mValue = null;
+                            return true;
+                        }
+                        else {
+                            prev = e;
+                        }
+                    }
+                    return false;
+                }
+
+                public int size() {
+                    return mCount;
+                }
+                
+                public void clear() {
+                    IdentityMap.this.clear();
+                }
+
+                public String toString() {
+                    return IdentityMap.this.toString(this);
+                }
+            };
+        }
+        
+        return mEntrySet;
+    }
+    
+    public String toString() {
+        StringBuffer buf = new StringBuffer();
+        Iterator it = entrySet().iterator();
+        
+        buf.append("{");
+        for (int i = 0; it.hasNext(); i++) {
+            if (i > 0) {
+                buf.append(", ");
+            }
+            Map.Entry e = (Map.Entry)it.next();
+            buf.append(e.getKey() + "=" + e.getValue());
+        }
+        buf.append("}");
+        return buf.toString();
+    }
+
+    private Iterator getHashIterator(int type) {
+        if (mCount == 0) {
+            return cEmptyHashIterator;
+        }
+        else {
+            return new HashIterator(type);
+        }
+    }
+
+    /**
+     * HashMap collision list entry.
+     */
+    private static class Entry extends WeakReference implements Map.Entry {
+        int mHash;
+        Object mValue;
+        Entry mNext;
+        
+        Entry(int hash, Object key, Object value, Entry next) {
+            super(key);
+            mHash = hash;
+            mValue = value;
+            mNext = next;
+        }
+        
+        protected Object clone() {
+            return new Entry(mHash, getKey(), mValue,
+                             (mNext == null ? null : (Entry)mNext.clone()));
+        }
+        
+        // Map.Entry Ops 
+        
+        public Object getKey() {
+            return Entry.this.get();
+        }
+        
+        public Object getValue() {
+            return mValue;
+        }
+        
+        public Object setValue(Object value) {
+            Object oldValue = mValue;
+            mValue = value;
+            return oldValue;
+        }
+        
+        public boolean equals(Object o) {
+            if (!(o instanceof Map.Entry)) {
+                return false;
+            }
+            Map.Entry e = (Map.Entry)o;
+
+            Object key = getKey();
+            
+            return (key==null ? e.getKey()==null : key.equals(e.getKey())) &&
+                (mValue==null ? e.getValue()==null : mValue.equals(e.getValue()));
+        }
+
+        public boolean identityEquals(Map.Entry e) {
+            return (getKey() == e.getKey()) &&
+                (mValue==null ? e.getValue()==null : mValue.equals(e.getValue()));
+        }
+        
+        public int hashCode() {
+            return mHash ^ (mValue==null ? 0 : mValue.hashCode());
+        }
+        
+        public String toString() {
+            return getKey() + "=" + mValue;
+        }
+    }
+
+    private class HashIterator implements Iterator {
+        private Entry[] mTable = IdentityMap.this.mTable;
+        private int mIndex = mTable.length;
+        private Entry mEntry;
+        // To ensure that the iterator doesn't return cleared entries, keep a
+        // hard reference to the key. Its existence will prevent the weak
+        // key from being cleared.
+        private Object mEntryKey;
+        private Entry mLastReturned;
+        private int mType;
+        
+        /**
+         * 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 = mModCount;
+        
+        HashIterator(int type) {
+            mType = type;
+        }
+        
+        public boolean hasNext() {
+            while (mEntry == null ||
+                   (mEntryKey = mEntry.getKey()) == null) {
+                if (mEntry != null) {
+                    // Clean up after a cleared Reference.
+                    remove(mEntry);
+                    mEntry = mEntry.mNext;
+                }
+                else {
+                    if (mIndex <= 0) {
+                        return false;
+                    }
+                    else {
+                        mEntry = mTable[--mIndex];
+                    }
+                }
+            }
+
+            return true;
+        }
+        
+        public Object next() {
+            if (mModCount != expectedModCount) {
+                throw new ConcurrentModificationException();
+            }
+            
+            if (!hasNext()) {
+                throw new NoSuchElementException();
+            }
+
+            mLastReturned = mEntry;
+            mEntry = mEntry.mNext;
+
+            return mType == KEYS ? mLastReturned.getKey() :
+                (mType == VALUES ? mLastReturned.getValue() : mLastReturned);
+        }
+        
+        public void remove() {
+            if (mLastReturned == null) {
+                throw new IllegalStateException();
+            }
+            if (mModCount != expectedModCount) {
+                throw new ConcurrentModificationException();
+            }
+            remove(mLastReturned);
+            mLastReturned = null;
+        }
+
+        private void remove(Entry toRemove) {
+            Entry[] tab = mTable;
+            int index = (toRemove.mHash & 0x7FFFFFFF) % tab.length;
+            
+            for (Entry e = tab[index], prev = null; e != null; e = e.mNext) {
+                if (e == toRemove) {
+                    mModCount++;
+                    expectedModCount++;
+                    if (prev == null) {
+                        tab[index] = e.mNext;
+                    }
+                    else {
+                        prev.mNext = e.mNext;
+                    }
+                    mCount--;
+                    return;
+                }
+                else {
+                    prev = e;
+                }
+            }
+            throw new ConcurrentModificationException();
+        }
+    }
+}