/*
 * Copyright (C) 2002-2015 Sebastiano Vigna
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License. 
 */
package squidpony.squidmath;

import squidpony.annotation.Beta;
import squidpony.annotation.GwtIncompatible;

import java.io.Serializable;
import java.util.*;

/**
 * A generic linked hash map with with a fast implementation, originally from fastutil as Object2ObjectLinkedOpenHashMap but modified to support indexed access.
 * <br>
 * <p>Instances of this class use a hash table to represent a map. The table is filled up to a specified <em>load factor</em>, and then doubled in size to accommodate new entries. If the table is
 * emptied below <em>one fourth</em> of the load factor, it is halved in size. However, halving is not performed when deleting entries from an iterator, as it would interfere with the iteration
 * process.
 * </p>
 * <p>Note that {@link #clear()} does not modify the hash table size. Rather, a family of {@linkplain #trim() trimming methods} lets you control the size of the table; this is particularly useful if
 * you reuse instances of this class.
 * </p>
 * <p>Iterators generated by this map will enumerate pairs in the same order in which they have been added to the map (addition of pairs whose key is already present in the set does not change the
 * iteration order). Note that this order has nothing in common with the natural order of the keys. The order is kept by means of a int-specialized list, {@link IntVLA}, and is modifiable with this
 * class' {@link #reorder(int...)} and {@link #shuffle(RNG)} methods, among other tools.
 * </p>
 * <p>This class implements the interface of a sorted map, so to allow easy access of the iteration order: for instance, you can get the first key in iteration order with {@code firstKey()} without
 * having to create an iterator; however, this class partially violates the {@link SortedMap} contract because all submap methods throw an exception and {@link #comparator()} returns always
 * <code>null</code>.
 * </p>
 * <p>Additional methods, such as <code>getAndMoveToFirst()</code>, make it easy to use instances of this class as a cache (e.g., with LRU policy).
 * </p>
 * <p>The iterators provided by the views of this class using are type-specific {@linkplain ListIterator list iterators}, and can be started at any element <em>which is a key of the map</em>,
 * or a {@link NoSuchElementException} exception will be thrown. If, however, the provided element is not the first or last key in the set, the first access to the list index will require linear time,
 * as in the worst case the entire key set must be scanned in iteration order to retrieve the positional index of the starting key.
 * </p>
 * <br>
 * Thank you, Sebastiano Vigna, for making FastUtil available to the public with such high quality.
 * <br>
 * See https://github.com/vigna/fastutil for the original library.
 * @author Sebastiano Vigna (responsible for all the hard parts)
 * @author Tommy Ettinger (mostly responsible for squashing several layers of parent classes into one monster class)
 */
@Beta
public class OrderedMap<K, V> implements SortedMap<K, V>, java.io.Serializable, Cloneable {
    private static final long serialVersionUID = 0L;
    /**
     * The array of keys.
     */
    protected K[] key;
    /**
     * The array of values.
     */
    protected V[] value;
    /**
     * The mask for wrapping a position counter.
     */
    protected int mask;
    /**
     * Whether this set contains the key zero.
     */
    protected boolean containsNullKey;
    /**
     * The index of the first entry in iteration order. It is valid iff {@link #size} is nonzero; otherwise, it contains -1.
     */
    protected int first = -1;
    /**
     * The index of the last entry in iteration order. It is valid iff {@link #size} is nonzero; otherwise, it contains -1.
     */
    protected int last = -1;
    /*
     * For each entry, the next and the previous entry in iteration order, stored as <code>((prev & 0xFFFFFFFFL) << 32) | (next & 0xFFFFFFFFL)</code>. The first entry contains predecessor -1, and the
     * last entry contains successor -1.
     */
    //protected long[] link;
    protected IntVLA order;
    /**
     * The current table size.
     */
    protected int n;
    /**
     * Threshold after which we rehash. It must be the table size times {@link #f}.
     */
    protected int maxFill;
    /**
     * Number of entries in the set (including the key zero, if present).
     */
    protected int size;
    /**
     * The acceptable load factor.
     */
    public final float f;
    /**
     * Cached set of entries.
     */
    protected volatile MapEntrySet entries;
    /**
     * Cached set of keys.
     */
    protected volatile KeySet keys;
    /**
     * Cached collection of values.
     */
    protected volatile Collection<V> values;
    /**
     * Default return value.
     */
    protected V defRetValue = null;

    /**
     * The initial default size of a hash table.
     */
    public static final int DEFAULT_INITIAL_SIZE = 16;
    /**
     * The default load factor of a hash table.
     */
    public static final float DEFAULT_LOAD_FACTOR = .375f; // .1875f; // .75f;
    /**
     * The load factor for a (usually small) table that is meant to be particularly fast.
     */
    public static final float FAST_LOAD_FACTOR = .5f;
    /**
     * The load factor for a (usually very small) table that is meant to be extremely fast.
     */
    public static final float VERY_FAST_LOAD_FACTOR = .25f;

    protected CrossHash.IHasher hasher = null;

    public void defaultReturnValue(final V rv) {
        defRetValue = rv;
    }

    public V defaultReturnValue() {
        return defRetValue;
    }

    /**
     * Creates a new OrderedMap.
     * <p>
     * <p>The actual table size will be the least power of two greater than <code>expected</code>/<code>f</code>.
     *
     * @param expected the expected number of elements in the hash set.
     * @param f        the load factor.
     */

    @SuppressWarnings("unchecked")
    public OrderedMap(final int expected, final float f) {
        if (f <= 0 || f > 1)
            throw new IllegalArgumentException("Load factor must be greater than 0 and smaller than or equal to 1");
        if (expected < 0) throw new IllegalArgumentException("The expected number of elements must be nonnegative");
        this.f = f;
        n = arraySize(expected, f);
        mask = n - 1;
        maxFill = maxFill(n, f);
        key = (K[]) new Object[n + 1];
        value = (V[]) new Object[n + 1];
        //link = new long[n + 1];
        order = new IntVLA(expected);
        hasher = CrossHash.defaultHasher;
    }

    /**
     * Creates a new OrderedMap with 0.75f as load factor.
     *
     * @param expected the expected number of elements in the OrderedMap.
     */
    public OrderedMap(final int expected) {
        this(expected, DEFAULT_LOAD_FACTOR);
    }

    /**
     * Creates a new OrderedMap with initial expected 16 entries and 0.75f as load factor.
     */
    public OrderedMap() {
        this(DEFAULT_INITIAL_SIZE, DEFAULT_LOAD_FACTOR);
    }

    /**
     * Creates a new OrderedMap copying a given one.
     *
     * @param m a {@link Map} to be copied into the new OrderedMap.
     * @param f the load factor.
     */
    public OrderedMap(final Map<? extends K, ? extends V> m, final float f) {
        this(m.size(), f);
        putAll(m);
    }

    /**
     * Creates a new OrderedMap with 0.75f as load factor copying a given one.
     *
     * @param m a {@link Map} to be copied into the new OrderedMap.
     */
    public OrderedMap(final Map<? extends K, ? extends V> m) {
        this(m, DEFAULT_LOAD_FACTOR);
    }

    /**
     * Creates a new OrderedMap using the elements of two parallel arrays.
     *
     * @param keyArray the array of keys of the new OrderedMap.
     * @param valueArray the array of corresponding values in the new OrderedMap.
     * @param f the load factor.
     * @throws IllegalArgumentException if <code>k</code> and <code>v</code> have different lengths.
     */
    public OrderedMap(final K[] keyArray, final V[] valueArray, final float f) {
        this(keyArray.length, f);
        if (keyArray.length != valueArray.length)
            throw new IllegalArgumentException("The key array and the value array have different lengths (" + keyArray.length + " and " + valueArray.length + ")");
        for (int i = 0; i < keyArray.length; i++)
            put(keyArray[i], valueArray[i]);
    }
    /**
     * Creates a new OrderedMap using the elements of two parallel arrays.
     *
     * @param keyColl the collection of keys of the new OrderedMap.
     * @param valueColl the collection of corresponding values in the new OrderedMap.
     * @param f the load factor.
     * @throws IllegalArgumentException if <code>k</code> and <code>v</code> have different lengths.
     */
    public OrderedMap(final Collection<K> keyColl, final Collection<V> valueColl, final float f) {
        this(keyColl.size(), f);
        if (keyColl.size() != valueColl.size())
            throw new IllegalArgumentException("The key array and the value array have different lengths (" + keyColl.size() + " and " + valueColl.size() + ")");
        Iterator<K> ki = keyColl.iterator();
        Iterator<V> vi = valueColl.iterator();
        while (ki.hasNext() && vi.hasNext())
        {
            put(ki.next(), vi.next());
        }
    }

    /**
     * Creates a new OrderedMap with 0.75f as load factor using the elements of two parallel arrays.
     *
     * @param keyArray the array of keys of the new OrderedMap.
     * @param valueArray the array of corresponding values in the new OrderedMap.
     * @throws IllegalArgumentException if <code>k</code> and <code>v</code> have different lengths.
     */
    public OrderedMap(final K[] keyArray, final V[] valueArray) {
        this(keyArray, valueArray, DEFAULT_LOAD_FACTOR);
    }

    /**
     * Creates a new OrderedMap.
     * <p>
     * <p>The actual table size will be the least power of two greater than <code>expected</code>/<code>f</code>.
     *
     * @param expected the expected number of elements in the hash set.
     * @param f        the load factor.
     * @param hasher used to hash items; typically only needed when K is an array, where CrossHash has implementations
     */

    @SuppressWarnings("unchecked")
    public OrderedMap(final int expected, final float f, CrossHash.IHasher hasher) {
        if (f <= 0 || f > 1)
            throw new IllegalArgumentException("Load factor must be greater than 0 and smaller than or equal to 1");
        if (expected < 0) throw new IllegalArgumentException("The expected number of elements must be nonnegative");
        this.f = f;
        n = arraySize(expected, f);
        mask = n - 1;
        maxFill = maxFill(n, f);
        key = (K[]) new Object[n + 1];
        value = (V[]) new Object[n + 1];
        //link = new long[n + 1];
        order = new IntVLA(expected);
        this.hasher = (hasher == null) ? CrossHash.defaultHasher : hasher;
    }
    /**
     * Creates a new OrderedMap with 0.75f as load factor.
     *
     * @param expected the expected number of elements in the OrderedMap.
     * @param hasher used to hash items; typically only needed when K is an array, where CrossHash has implementations
     */
    public OrderedMap(final int expected, CrossHash.IHasher hasher) {
        this(expected, DEFAULT_LOAD_FACTOR, hasher);
    }

    /**
     * Creates a new OrderedMap with initial expected 16 entries and 0.75f as load factor.
     */
    public OrderedMap(CrossHash.IHasher hasher) {
        this(DEFAULT_INITIAL_SIZE, DEFAULT_LOAD_FACTOR, hasher);
    }

    /**
     * Creates a new OrderedMap copying a given one.
     *
     * @param m a {@link Map} to be copied into the new OrderedMap.
     * @param f the load factor.
     * @param hasher used to hash items; typically only needed when K is an array, where CrossHash has implementations
     */
    public OrderedMap(final Map<? extends K, ? extends V> m, final float f, CrossHash.IHasher hasher) {
        this(m.size(), f, hasher);
        putAll(m);
    }

    /**
     * Creates a new OrderedMap with 0.75f as load factor copying a given one.
     * @param m a {@link Map} to be copied into the new OrderedMap.
     * @param hasher used to hash items; typically only needed when K is an array, where CrossHash has implementations
     */
    public OrderedMap(final Map<? extends K, ? extends V> m, CrossHash.IHasher hasher) {
        this(m, DEFAULT_LOAD_FACTOR, hasher);
    }

    /**
     * Creates a new OrderedMap using the elements of two parallel arrays.
     *
     * @param keyArray the array of keys of the new OrderedMap.
     * @param valueArray the array of corresponding values in the new OrderedMap.
     * @param f the load factor.
     * @param hasher used to hash items; typically only needed when K is an array, where CrossHash has implementations
     * @throws IllegalArgumentException if <code>k</code> and <code>v</code> have different lengths.
     */
    public OrderedMap(final K[] keyArray, final V[] valueArray, final float f, CrossHash.IHasher hasher) {
        this(keyArray.length, f, hasher);
        if (keyArray.length != valueArray.length)
            throw new IllegalArgumentException("The key array and the value array have different lengths (" + keyArray.length + " and " + valueArray.length + ")");
        for (int i = 0; i < keyArray.length; i++)
            put(keyArray[i], valueArray[i]);
    }
    /**
     * Creates a new OrderedMap with 0.75f as load factor using the elements of two parallel arrays.
     *
     * @param keyArray the array of keys of the new OrderedMap.
     * @param valueArray the array of corresponding values in the new OrderedMap.
     * @param hasher used to hash items; typically only needed when K is an array, where CrossHash has implementations
     * @throws IllegalArgumentException if <code>k</code> and <code>v</code> have different lengths.
     */
    public OrderedMap(final K[] keyArray, final V[] valueArray, CrossHash.IHasher hasher) {
        this(keyArray, valueArray, DEFAULT_LOAD_FACTOR, hasher);
    }

    private int realSize() {
        return containsNullKey ? size - 1 : size;
    }
    private void ensureCapacity(final int capacity) {
        final int needed = arraySize(capacity, f);
        if (needed > n)
            rehash(needed);
    }
    private void tryCapacity(final long capacity) {
        final int needed = (int) Math.min(
                1 << 30,
                Math.max(2, HashCommon.nextPowerOfTwo((long) Math.ceil(capacity
                        / f))));
        if (needed > n)
            rehash(needed);
    }
    private V removeEntry(final int pos) {
        final V oldValue = value[pos];
        value[pos] = null;
        size--;
        fixOrder(pos);
        shiftKeys(pos);
        if (size < maxFill / 4 && n > DEFAULT_INITIAL_SIZE)
            rehash(n / 2);
        return oldValue;
    }
    private V removeNullEntry() {
        containsNullKey = false;
        key[n] = null;
        final V oldValue = value[n];
        value[n] = null;
        size--;
        fixOrder(n);
        if (size < maxFill / 4 && n > DEFAULT_INITIAL_SIZE)
            rehash(n / 2);
        return oldValue;
    }
    /** {@inheritDoc} */
    public void putAll(Map<? extends K, ? extends V> m) {
        if (f <= .5)
            ensureCapacity(m.size()); // The resulting map will be sized for
            // m.size() elements
        else
            tryCapacity(size() + m.size()); // The resulting map will be
        int n = m.size();
        final Iterator<? extends Map.Entry<? extends K, ? extends V>> i = m
                .entrySet().iterator();
        if (m instanceof OrderedMap) {
            Entry<? extends K, ? extends V> e;
            while (n-- != 0) {
                e = i.next();
                put(e.getKey(), e.getValue());
            }
        } else {
            Map.Entry<? extends K, ? extends V> e;
            while (n-- != 0) {
                e = i.next();
                put(e.getKey(), e.getValue());
            }
        }
    }
    private int insert(final K k, final V v) {
        int pos;
        if (k == null) {
            if (containsNullKey)
                return n;
            containsNullKey = true;
            pos = n;
        } else {
            K curr;
            final K[] key = this.key;
            // The starting point.
            if ((curr = key[pos = HashCommon.mix(hasher.hash(k)) & mask]) != null) {
                if (curr.equals(k))
                    return pos;
                while ((curr = key[pos = (pos + 1) & mask]) != null)
                    if (curr.equals(k))
                        return pos;
            }
        }
        key[pos] = k;
        value[pos] = v;
        if (size == 0) {
            first = last = pos;
        } else {
            last = pos;
        }
        order.add(pos);
        if (size++ >= maxFill)
            rehash(arraySize(size + 1, f));
        return -1;
    }
    public V put(final K k, final V v) {
        final int pos = insert(k, v);
        if (pos < 0)
            return defRetValue;
        final V oldValue = value[pos];
        value[pos] = v;
        return oldValue;
    }
    /**
     * Shifts left entries with the specified hash code, starting at the
     * specified position, and empties the resulting free entry.
     *
     * @param pos
     *            a starting position.
     */
    protected final void shiftKeys(int pos) {
        // Shift entries with the same hash.
        int last, slot;
        K curr;
        final K[] key = this.key;
        for (;;) {
            pos = ((last = pos) + 1) & mask;
            for (;;) {
                if ((curr = key[pos]) == null) {
                    key[last] = null;
                    value[last] = null;
                    return;
                }
                slot = HashCommon.mix(hasher.hash(curr))
                        & mask;
                if (last <= pos ? last >= slot || slot > pos : last >= slot
                        && slot > pos)
                    break;
                pos = (pos + 1) & mask;
            }
            key[last] = curr;
            value[last] = value[pos];
            fixOrder(pos, last);
        }
    }
    @SuppressWarnings("unchecked")
    public V remove(final Object k) {
        if ((K) k == null) {
            if (containsNullKey)
                return removeNullEntry();
            return defRetValue;
        }
        K curr;
        final K[] key = this.key;
        int pos;
        // The starting point.
        if ((curr = key[pos = HashCommon.mix(hasher.hash(k)) & mask]) == null)
            return defRetValue;
        if (k.equals(curr))
            return removeEntry(pos);
        while (true) {
            if ((curr = key[pos = (pos + 1) & mask]) == null)
                return defRetValue;
            if (k.equals(curr))
                return removeEntry(pos);
        }
    }
    private V setValue(final int pos, final V v) {
        final V oldValue = value[pos];
        value[pos] = v;
        return oldValue;
    }
    /**
     * Removes the mapping associated with the first key in iteration order.
     *
     * @return the value previously associated with the first key in iteration
     *         order.
     * @throws NoSuchElementException
     *             is this map is empty.
     */
    public V removeFirst() {
        if (size == 0)
            throw new NoSuchElementException();
        final int pos = first;
        order.removeIndex(0);
        if(order.size > 0)
            first = order.get(0);
        else
            first = -1;

        size--;
        final V v = value[pos];
        if (pos == n) {
            containsNullKey = false;
            key[n] = null;
            value[n] = null;
        } else
            shiftKeys(pos);
        if (size < maxFill / 4 && n > DEFAULT_INITIAL_SIZE)
            rehash(n / 2);
        return v;
    }
    /**
     * Removes the mapping associated with the last key in iteration order.
     *
     * @return the value previously associated with the last key in iteration
     *         order.
     * @throws NoSuchElementException
     *             is this map is empty.
     */
    public V removeLast() {
        if (size == 0)
            throw new NoSuchElementException();
        final int pos = last;
        order.pop();
        if(order.size > 0)
            last = order.get(order.size - 1);
        else
            last = -1;
        size--;
        final V v = value[pos];
        if (pos == n) {
            containsNullKey = false;
            key[n] = null;
            value[n] = null;
        } else
            shiftKeys(pos);
        if (size < maxFill / 4 && n > DEFAULT_INITIAL_SIZE)
            rehash(n / 2);
        return v;
    }
    private void moveIndexToFirst(final int i) {
        if(size <= 1 || first == i)
            return;
        order.moveToFirst(i);
        if (last == i) {
            last = order.peek();
            //last = (int) (link[i] >>> 32);
            // Special case of SET_NEXT( link[ last ], -1 );
            //link[last] |= -1 & 0xFFFFFFFFL;
        }/* else {
            final long linki = link[i];
            final int prev = (int) (linki >>> 32);
            final int next = (int) linki;
            link[prev] ^= ((link[prev] ^ (linki & 0xFFFFFFFFL)) & 0xFFFFFFFFL);
            link[next] ^= ((link[next] ^ (linki & 0xFFFFFFFF00000000L)) & 0xFFFFFFFF00000000L);
        }
        link[first] ^= ((link[first] ^ ((i & 0xFFFFFFFFL) << 32)) & 0xFFFFFFFF00000000L);
        link[i] = ((-1 & 0xFFFFFFFFL) << 32) | (first & 0xFFFFFFFFL);
        */
        first = i;
    }
    private void moveIndexToLast(final int i) {
        if(size <= 1 || last == i)
            return;
        order.moveToLast(i);
        if (first == i) {
            first = order.get(0);
            //first = (int) link[i];
            // Special case of SET_PREV( link[ first ], -1 );
            //link[first] |= (-1 & 0xFFFFFFFFL) << 32;
        } /*else {
            final long linki = link[i];
            final int prev = (int) (linki >>> 32);
            final int next = (int) linki;
            link[prev] ^= ((link[prev] ^ (linki & 0xFFFFFFFFL)) & 0xFFFFFFFFL);
            link[next] ^= ((link[next] ^ (linki & 0xFFFFFFFF00000000L)) & 0xFFFFFFFF00000000L);
        }
        link[last] ^= ((link[last] ^ (i & 0xFFFFFFFFL)) & 0xFFFFFFFFL);
        link[i] = ((last & 0xFFFFFFFFL) << 32) | (-1 & 0xFFFFFFFFL);
        */
        last = i;
    }
    /**
     * Returns the value to which the given key is mapped; if the key is
     * present, it is moved to the first position of the iteration order.
     *
     * @param k
     *            the key.
     * @return the corresponding value, or the
     *         {@linkplain #defaultReturnValue() default return value} if no
     *         value was present for the given key.
     */
    public V getAndMoveToFirst(final K k) {
        if (k == null) {
            if (containsNullKey) {
                moveIndexToFirst(n);
                return value[n];
            }
            return defRetValue;
        }
        K curr;
        final K[] key = this.key;
        int pos;
        // The starting point.
        if ((curr = key[pos = HashCommon.mix(hasher.hash(k)) & mask]) == null)
            return defRetValue;
        if (k.equals(curr)) {
            moveIndexToFirst(pos);
            return value[pos];
        }
        // There's always an unused entry.
        while (true) {
            if ((curr = key[pos = (pos + 1) & mask]) == null)
                return defRetValue;
            if (k.equals(curr)) {
                moveIndexToFirst(pos);
                return value[pos];
            }
        }
    }
    /**
     * Returns the value to which the given key is mapped; if the key is
     * present, it is moved to the last position of the iteration order.
     *
     * @param k the key.
     * @return the corresponding value, or the
     *         {@linkplain #defaultReturnValue() default return value} if no
     *         value was present for the given key.
     */
    public V getAndMoveToLast(final K k) {
        if (k == null) {
            if (containsNullKey) {
                moveIndexToLast(n);
                return value[n];
            }
            return defRetValue;
        }
        K curr;
        final K[] key = this.key;
        int pos;
        // The starting point.
        if ((curr = key[pos = HashCommon.mix(hasher.hash(k)) & mask]) == null)
            return defRetValue;
        if (k.equals(curr)) {
            moveIndexToLast(pos);
            return value[pos];
        }
        // There's always an unused entry.
        while (true) {
            if ((curr = key[pos = (pos + 1) & mask]) == null)
                return defRetValue;
            if (k.equals(curr)) {
                moveIndexToLast(pos);
                return value[pos];
            }
        }
    }
    /**
     * Adds a pair to the map; if the key is already present, it is moved to the
     * first position of the iteration order.
     *
     * @param k
     *            the key.
     * @param v
     *            the value.
     * @return the old value, or the {@linkplain #defaultReturnValue() default
     *         return value} if no value was present for the given key.
     */
    public V putAndMoveToFirst(final K k, final V v) {
        int pos;
        if (k == null) {
            if (containsNullKey) {
                moveIndexToFirst(n);
                return setValue(n, v);
            }
            containsNullKey = true;
            pos = n;
        } else {
            K curr;
            final K[] key = this.key;
            // The starting point.
            if (!((curr = key[pos = HashCommon.mix(hasher.hash(k)) & mask]) == null)) {
                if (curr.equals(k)) {
                    moveIndexToFirst(pos);
                    return setValue(pos, v);
                }
                while (!((curr = key[pos = (pos + 1) & mask]) == null))
                    if (curr.equals(k)) {
                        moveIndexToFirst(pos);
                        return setValue(pos, v);
                    }
            }
        }
        key[pos] = k;
        value[pos] = v;
        if (size == 0) {
            first = last = pos;
            // Special case of SET_UPPER_LOWER( link[ pos ], -1, -1 );
            //link[pos] = -1L;
        } else {
            //link[first] ^= ((link[first] ^ ((pos & 0xFFFFFFFFL) << 32)) & 0xFFFFFFFF00000000L);
            //link[pos] = ((-1 & 0xFFFFFFFFL) << 32) | (first & 0xFFFFFFFFL);
            first = pos;
        }
        order.insert(0, pos);
        if (size++ >= maxFill)
            rehash(arraySize(size, f));
        return defRetValue;
    }
    /**
     * Adds a pair to the map; if the key is already present, it is moved to the
     * last position of the iteration order.
     *
     * @param k
     *            the key.
     * @param v
     *            the value.
     * @return the old value, or the {@linkplain #defaultReturnValue() default
     *         return value} if no value was present for the given key.
     */
    public V putAndMoveToLast(final K k, final V v) {
        int pos;
        if (k == null) {
            if (containsNullKey) {
                moveIndexToLast(n);
                return setValue(n, v);
            }
            containsNullKey = true;
            pos = n;
        } else {
            K curr;
            final K[] key = this.key;
            // The starting point.
            if (!((curr = key[pos = HashCommon.mix(hasher.hash(k)) & mask]) == null)) {
                if (curr.equals(k)) {
                    moveIndexToLast(pos);
                    return setValue(pos, v);
                }
                while (!((curr = key[pos = (pos + 1) & mask]) == null))
                    if (curr.equals(k)) {
                        moveIndexToLast(pos);
                        return setValue(pos, v);
                    }
            }
        }
        key[pos] = k;
        value[pos] = v;
        if (size == 0) {
            first = last = pos;
            // Special case of SET_UPPER_LOWER( link[ pos ], -1, -1 );
            //link[pos] = -1L;
        } else {
            //link[last] ^= ((link[last] ^ (pos & 0xFFFFFFFFL)) & 0xFFFFFFFFL);
            //link[pos] = ((last & 0xFFFFFFFFL) << 32) | (-1 & 0xFFFFFFFFL);
            last = pos;
        }
        order.add(pos);
        if (size++ >= maxFill)
            rehash(arraySize(size, f));
        return defRetValue;
    }
    public V get(final Object k) {
        if (k == null)
            return containsNullKey ? value[n] : defRetValue;
        K curr;
        final K[] key = this.key;
        int pos;
        // The starting point.
        if ((curr = key[pos = HashCommon.mix(hasher.hash(k)) & mask]) == null)
            return defRetValue;
        if (k.equals(curr))
            return value[pos];
        // There's always an unused entry.
        while (true) {
            if ((curr = key[pos = (pos + 1) & mask]) == null)
                return defRetValue;
            if (k.equals(curr))
                return value[pos];
        }
    }

    public boolean containsKey(final Object k) {
        if (k == null)
            return containsNullKey;
        K curr;
        final K[] key = this.key;
        int pos;
        // The starting point.
        if ((curr = key[pos = HashCommon.mix(hasher.hash(k)) & mask]) == null)
            return false;
        if (k.equals(curr))
            return true;
        // There's always an unused entry.
        while (true) {
            if ((curr = key[pos = (pos + 1) & mask]) == null)
                return false;
            if (k.equals(curr))
                return true;
        }
    }
    public boolean containsValue(final Object v) {
        final V value[] = this.value;
        final K key[] = this.key;
        if (containsNullKey
                && (value[n] == null ? v == null : value[n].equals(v)))
            return true;
        for (int i = n; i-- != 0;)
            if (key[i] != null
                    && (value[i] == null ? v == null : value[i].equals(v)))
                return true;
        return false;
    }
    /*
     * Removes all elements from this map.
     *
     * <P>To increase object reuse, this method does not change the table size.
     * If you want to reduce the table size, you must use {@link #trim()}.
     */
    public void clear() {
        if (size == 0)
            return;
        size = 0;
        containsNullKey = false;
        Arrays.fill(key, null);
        Arrays.fill(value, null);
        first = last = -1;
        order.clear();
    }

    public int size() {
        return size;
    }

    public boolean isEmpty() {
        return size == 0;
    }

    /**
     * A no-op for backward compatibility.
     *
     * @param growthFactor unused.
     * @deprecated Since <code>fastutil</code> 6.1.0, hash tables are doubled when they are too full.
     */
    @Deprecated
    public void growthFactor(int growthFactor) {
    }

    /**
     * Gets the growth factor (2).
     *
     * @return the growth factor of this set, which is fixed (2).
     * @see #growthFactor(int)
     * @deprecated Since <code>fastutil</code> 6.1.0, hash tables are doubled when they are too full.
     */
    @Deprecated
    public int growthFactor() {
        return 16;
    }

    /**
     * The entry class for a OrderedMap does not record key and value, but rather the position in the hash table of the corresponding entry. This is necessary so that calls to
     * {@link Entry#setValue(Object)} are reflected in the map
     */
    final class MapEntry
            implements
            Entry<K, V> {
        // The table index this entry refers to, or -1 if this entry has been
        // deleted.
        int index;
        MapEntry(final int index) {
            this.index = index;
        }
        MapEntry() {
        }
        public K getKey() {
            return key[index];
        }
        public V getValue() {
            return value[index];
        }
        public V setValue(final V v) {
            final V oldValue = value[index];
            value[index] = v;
            return oldValue;
        }
        @SuppressWarnings("unchecked")
        public boolean equals(final Object o) {
            if (!(o instanceof Map.Entry))
                return false;
            Map.Entry<K, V> e = (Map.Entry<K, V>) o;
            return (key[index] == null
                    ? e.getKey() == null
                    : key[index].equals(e.getKey()))
                    && (value[index] == null
                    ? e.getValue() == null
                    : value[index].equals(e.getValue()));
        }
        public int hashCode() {
            return hasher.hash(key[index])
                    ^ (value[index] == null ? 0 : value[index].hashCode());
        }
        @Override
        public String toString() {
            return key[index] + "=>" + value[index];
        }
    }

    /**
     * Modifies the ordering so that the given entry is removed. This method will complete in logarithmic time.
     *
     * @param i the index of an entry.
     */
    protected void fixOrder(final int i) {
        if (size == 0) {
            first = last = -1;
            return;
        }
        order.removeValue(i);
        if (first == i) {
            first = order.get(0);
            //first = (int) link[i];
            /*
            if (0 <= first) {
                // Special case of SET_PREV( link[ first ], -1 )
                link[first] |= (-1 & 0xFFFFFFFFL) << 32;
            }
            return;
            */
        }
        if (last == i) {
            last = order.peek();
            //last = (int) (link[i] >>> 32);
            /*if (0 <= last) {
                // Special case of SET_NEXT( link[ last ], -1 )
                link[last] |= -1 & 0xFFFFFFFFL;
            }
            return;
            */
        }
        /*
        final long linki = link[i];
        final int prev = (int) (linki >>> 32);
        final int next = (int) linki;
        link[prev] ^= ((link[prev] ^ (linki & 0xFFFFFFFFL)) & 0xFFFFFFFFL);
        link[next] ^= ((link[next] ^ (linki & 0xFFFFFFFF00000000L)) & 0xFFFFFFFF00000000L);
        */
    }

    /**
     * Modifies the ordering for a shift from s to d.
     * <br>
     * This method will complete in logarithmic time or better.
     *
     * @param s the source position.
     * @param d the destination position.
     */
    protected void fixOrder(int s, int d) {
        if (size == 1) {
            first = last = d;
            // Special case of SET_UPPER_LOWER( link[ d ], -1, -1 )
            //link[d] = -1L;
            order.set(0, d);
        }
        else if (first == s) {
            first = d;
            order.set(0, d);
            //link[(int) link[s]] ^= ((link[(int) link[s]] ^ ((d & 0xFFFFFFFFL) << 32)) & 0xFFFFFFFF00000000L);
            //link[d] = link[s];
        }
        else if (last == s) {
            last = d;
            order.set(order.size - 1, d);
            //link[(int) (link[s] >>> 32)] ^= ((link[(int) (link[s] >>> 32)] ^ (d & 0xFFFFFFFFL)) & 0xFFFFFFFFL);
            //link[d] = link[s];
        }
        else
        {
            order.set(order.indexOf(s), d);
        }
        /*
        final long links = link[s];
        final int prev = (int) (links >>> 32);
        final int next = (int) links;
        link[prev] ^= ((link[prev] ^ (d & 0xFFFFFFFFL)) & 0xFFFFFFFFL);
        link[next] ^= ((link[next] ^ ((d & 0xFFFFFFFFL) << 32)) & 0xFFFFFFFF00000000L);
        link[d] = links;
        */
    }

    /**
     * Returns the first key of this map in iteration order.
     *
     * @return the first key in iteration order.
     */
    public K firstKey() {
        if (size == 0)
            throw new NoSuchElementException();
        return key[first];
    }
    /**
     * Returns the last key of this map in iteration order.
     *
     * @return the last key in iteration order.
     */
    public K lastKey() {
        if (size == 0)
            throw new NoSuchElementException();
        return key[last];
    }
    public Comparator<? super K> comparator() {
        return null;
    }
    public SortedMap<K, V> tailMap(K from) {
        throw new UnsupportedOperationException();
    }
    public SortedMap<K, V> headMap(K to) {
        throw new UnsupportedOperationException();
    }
    public SortedMap<K, V> subMap(K from, K to) {
        throw new UnsupportedOperationException();
    }
    /**
     * A list iterator over a OrderedMap.
     *
     * <P>
     * This class provides a list iterator over a OrderedMap. The
     * constructor runs in constant time.
     */
    private class MapIterator {
        /**
         * The entry that will be returned by the next call to
         * {@link java.util.ListIterator#previous()} (or <code>null</code> if no
         * previous entry exists).
         */
        int prev = -1;
        /**
         * The entry that will be returned by the next call to
         * {@link java.util.ListIterator#next()} (or <code>null</code> if no
         * next entry exists).
         */
        int next = -1;
        /**
         * The last entry that was returned (or -1 if we did not iterate or used
         * {@link java.util.Iterator#remove()}).
         */
        int curr = -1;
        /**
         * The current index (in the sense of a {@link java.util.ListIterator}).
         * Note that this value is not meaningful when this iterator has been
         * created using the nonempty constructor.
         */
        int index = 0;
        private MapIterator() {
            next = first;
            index = 0;
        }
        /*
        private MapIterator(final K from) {
            if (((from) == null)) {
                if (containsNullKey) {
                    next = (int) link[n];
                    prev = n;
                    return;
                } else
                    throw new NoSuchElementException("The key null"
                            + " does not belong to this map.");
            }
            if (((key[last]) != null && (key[last]).equals(from))) {
                prev = last;
                index = size;
                return;
            }
            // The starting point.
            int pos = (HashCommon.mix((from).hashCode()))
                    & mask;
            // There's always an unused entry.
            while (!((key[pos]) == null)) {
                if (((key[pos]).equals(from))) {
                    // Note: no valid index known.
                    next = (int) link[pos];
                    prev = pos;
                    return;
                }
                pos = (pos + 1) & mask;
            }
            throw new NoSuchElementException("The key " + from
                    + " does not belong to this map.");
        }*/
        public boolean hasNext() {
            return next != -1;
        }
        public boolean hasPrevious() {
            return prev != -1;
        }
        private void ensureIndexKnown() {
            if (index >= 0)
                return;
            if (prev == -1) {
                index = 0;
                return;
            }
            if (next == -1) {
                index = size;
                return;
            }
            index = 0;
            /*while (pos != prev) {
                pos = (int) link[pos];
                index++;
            }*/
        }
        public int nextIndex() {
            ensureIndexKnown();
            return index + 1;
        }
        public int previousIndex() {
            ensureIndexKnown();
            return index - 1;
        }
        public int nextEntry() {
            if (!hasNext())
                throw new NoSuchElementException();
            curr = next;
            if(++index >= order.size)
                next = -1;
            else
                next = order.get(index);//(int) link[curr];
            prev = curr;
            return curr;
        }
        public int previousEntry() {
            if (!hasPrevious())
                throw new NoSuchElementException();
            curr = prev;
            if(--index < 1)
                prev = -1;
            else
                prev = order.get(index - 1);
            //prev = (int) (link[curr] >>> 32);
            next = curr;
            return curr;
        }
        public void remove() {
            ensureIndexKnown();
            if (curr == -1)
                throw new IllegalStateException();
            if (curr == prev) {
				/*
				 * If the last operation was a next(), we are removing an entry
				 * that precedes the current index, and thus we must decrement
				 * it.
				 */
                if(--index >= 1)
                    prev = order.get(index - 1); //(int) (link[curr] >>> 32);
                else
                    prev = -1;
            } else {
                if(index < order.size - 1)
                    next = order.get(index + 1);
                else
                    next = -1;
            }
            /*
			 * Now we manually fix the pointers. Because of our knowledge of
			 * next and prev, this is going to be faster than calling
			 * fixOrder().
			 */
            if (prev == -1)
                first = next;
            if (next == -1)
                last = prev;
            order.removeIndex(index);
            size--;
            int last, slot, pos = curr;
            curr = -1;
            if (pos == n) {
                containsNullKey = false;
                key[n] = null;
                value[n] = null;
            } else {
                K curr;
                final K[] key = OrderedMap.this.key;
                // We have to horribly duplicate the shiftKeys() code because we
                // need to update next/prev.
                for (;;) {
                    pos = ((last = pos) + 1) & mask;
                    for (;;) {
                        if ((curr = key[pos]) == null) {
                            key[last] = null;
                            value[last] = null;
                            return;
                        }
                        slot = HashCommon.mix(hasher.hash(curr)) & mask;
                        if (last <= pos
                                ? last >= slot || slot > pos
                                : last >= slot && slot > pos)
                            break;
                        pos = (pos + 1) & mask;
                    }
                    key[last] = curr;
                    value[last] = value[pos];
                    if (next == pos)
                        next = last;
                    if (prev == pos)
                        prev = last;
                    fixOrder(pos, last);
                }
            }
        }
        public int skip(final int n) {
            int i = n;
            while (i-- != 0 && hasNext())
                nextEntry();
            return n - i - 1;
        }
        public int back(final int n) {
            int i = n;
            while (i-- != 0 && hasPrevious())
                previousEntry();
            return n - i - 1;
        }
    }
    private class EntryIterator extends MapIterator
            implements
            Iterator<Entry<K, V>>, Serializable {
        private static final long serialVersionUID = 0L;

        private MapEntry entry;
        public EntryIterator() {
        }
        public MapEntry next() {
            return entry = new MapEntry(nextEntry());
        }
        public MapEntry previous() {
            return entry = new MapEntry(previousEntry());
        }
        @Override
        public void remove() {
            super.remove();
            entry.index = -1; // You cannot use a deleted entry.
        }
        public void set(Entry<K, V> ok) {
            throw new UnsupportedOperationException();
        }
        public void add(Entry<K, V> ok) {
            throw new UnsupportedOperationException();
        }
    }

    public class FastEntryIterator extends MapIterator implements ListIterator<MapEntry>, Serializable {
        private static final long serialVersionUID = 0L;

        final MapEntry entry = new MapEntry();

        public FastEntryIterator() {
        }
        public MapEntry next() {
            entry.index = nextEntry();
            return entry;
        }
        public MapEntry previous() {
            entry.index = previousEntry();
            return entry;
        }
        public void set(MapEntry ok) {
            throw new UnsupportedOperationException();
        }
        public void add(MapEntry ok) {
            throw new UnsupportedOperationException();
        }
    }
    private final class MapEntrySet
            implements Cloneable, SortedSet<Entry<K, V>>, Set<Entry<K, V>>, Collection<Entry<K, V>>, Serializable {
        private static final long serialVersionUID = 0L;
        public EntryIterator iterator() {
            return new EntryIterator();
        }
        public Comparator<? super Entry<K, V>> comparator() {
            return null;
        }
        public SortedSet<Entry<K, V>> subSet(
                Entry<K, V> fromElement,
                Entry<K, V> toElement) {
            throw new UnsupportedOperationException();
        }
        public SortedSet<Entry<K, V>> headSet(
                Entry<K, V> toElement) {
            throw new UnsupportedOperationException();
        }
        public SortedSet<Entry<K, V>> tailSet(
                Entry<K, V> fromElement) {
            throw new UnsupportedOperationException();
        }
        public Entry<K, V> first() {
            if (size == 0)
                throw new NoSuchElementException();
            return new MapEntry(OrderedMap.this.first);
        }
        public Entry<K, V> last() {
            if (size == 0)
                throw new NoSuchElementException();
            return new MapEntry(OrderedMap.this.last);
        }
        @SuppressWarnings("unchecked")
        public boolean contains(final Object o) {
            if (!(o instanceof Map.Entry))
                return false;
            final Map.Entry<?, ?> e = (Map.Entry<?, ?>) o;
            final K k = (K) e.getKey();
            final V v = (V) e.getValue();
            if (k == null)
                return containsNullKey
                        && (value[n] == null ? v == null : value[n]
                        .equals(v));
            K curr;
            final K[] key = OrderedMap.this.key;
            int pos;
            // The starting point.
            if ((curr = key[pos = HashCommon.mix(hasher.hash(k)) & mask]) == null)
                return false;
            if (k.equals(curr))
                return value[pos] == null ? v == null : value[pos]
                        .equals(v);
            // There's always an unused entry.
            while (true) {
                if ((curr = key[pos = (pos + 1) & mask]) == null)
                    return false;
                if (k.equals(curr))
                    return value[pos] == null ? v == null : value[pos]
                            .equals(v);
            }
        }
        @SuppressWarnings("unchecked")
        public boolean remove(final Object o) {
            if (!(o instanceof Map.Entry))
                return false;
            final Map.Entry<?, ?> e = (Map.Entry<?, ?>) o;
            final K k = (K) e.getKey();
            final V v = (V) e.getValue();
            if (k == null) {
                if (containsNullKey
                        && (value[n] == null ? v == null : value[n]
                        .equals(v))) {
                    removeNullEntry();
                    return true;
                }
                return false;
            }
            K curr;
            final K[] key = OrderedMap.this.key;
            int pos;
            // The starting point.
            if ((curr = key[pos = HashCommon.mix(hasher.hash(k)) & mask]) == null)
                return false;
            if (curr.equals(k)) {
                if (value[pos] == null ? v == null : value[pos]
                        .equals(v)) {
                    removeEntry(pos);
                    return true;
                }
                return false;
            }
            while (true) {
                if ((curr = key[pos = (pos + 1) & mask]) == null)
                    return false;
                if (curr.equals(k)) {
                    if (value[pos] == null ? v == null : value[pos]
                            .equals(v)) {
                        removeEntry(pos);
                        return true;
                    }
                }
            }
        }
        public int size() {
            return size;
        }
        public void clear() {
            OrderedMap.this.clear();
        }

        public FastEntryIterator fastIterator() {
            return new FastEntryIterator();
        }

        @Override
        public boolean equals(final Object o) {
            if (o == this)
                return true;
            if (!(o instanceof Set))
                return false;
            Set<?> s = (Set<?>) o;
            return s.size() == size() && containsAll(s);
        }

        public Object[] toArray() {
            final Object[] a = new Object[size()];
            objectUnwrap(iterator(), a);
            return a;
        }

        @SuppressWarnings("unchecked")
        public <T> T[] toArray(T[] a) {
            if (a == null || a.length < size()) a = (T[]) new Object[size()];
            objectUnwrap(iterator(), a);
            return a;
        }

        /**
         * Unsupported.
         *
         * @param c ignored
         * @return nothing, throws UnsupportedOperationException
         * @throws UnsupportedOperationException always
         */
        public boolean addAll(Collection<? extends Entry<K, V>> c) {
            throw new UnsupportedOperationException("addAll not supported");
        }

        /**
         * Unsupported.
         *
         * @param k ignored
         * @return nothing, throws UnsupportedOperationException
         * @throws UnsupportedOperationException always
         */
        public boolean add(Entry<K, V> k) {
            throw new UnsupportedOperationException("add not supported");
        }

        /**
         * Checks whether this collection contains all elements from the given
         * collection.
         *
         * @param c a collection.
         * @return <code>true</code> if this collection contains all elements of the
         * argument.
         */
        public boolean containsAll(Collection<?> c) {
            int n = c.size();
            final Iterator<?> i = c.iterator();
            while (n-- != 0)
                if (!contains(i.next()))
                    return false;
            return true;
        }

        /**
         * Retains in this collection only elements from the given collection.
         *
         * @param c a collection.
         * @return <code>true</code> if this collection changed as a result of the
         * call.
         */
        public boolean retainAll(Collection<?> c) {
            boolean retVal = false;
            int n = size();
            final Iterator<?> i = iterator();
            while (n-- != 0) {
                if (!c.contains(i.next())) {
                    i.remove();
                    retVal = true;
                }
            }
            return retVal;
        }

        /**
         * Remove from this collection all elements in the given collection. If the
         * collection is an instance of this class, it uses faster iterators.
         *
         * @param c a collection.
         * @return <code>true</code> if this collection changed as a result of the
         * call.
         */
        public boolean removeAll(Collection<?> c) {
            boolean retVal = false;
            int n = c.size();
            final Iterator<?> i = c.iterator();
            while (n-- != 0)
                if (remove(i.next()))
                    retVal = true;
            return retVal;
        }

        public boolean isEmpty() {
            return size() == 0;
        }

        @Override
        public String toString() {
            final StringBuilder s = new StringBuilder();
            final EntryIterator i = iterator();
            int n = size();
            Object k;
            boolean first = true;
            s.append("{");
            while (n-- != 0) {
                if (first)
                    first = false;
                else
                    s.append(", ");
                k = i.next();
                if (this == k)
                    s.append("(this collection)");
                else
                    s.append(String.valueOf(k));
            }
            s.append("}");
            return s.toString();
        }

    }

    @Override
    public SortedSet<Entry<K, V>> entrySet() {
        if (entries == null) entries = new MapEntrySet();
        return entries;
    }
    public MapEntrySet mapEntrySet() {
        if (entries == null) entries = new MapEntrySet();
        return entries;
    }

    /**
     * An iterator on keys.
     * <p>
     * <P>We simply override the {@link ListIterator#next()}/{@link ListIterator#previous()} methods (and possibly their type-specific counterparts) so that they return keys
     * instead of entries.
     */
    public final class KeyIterator extends MapIterator implements Iterator<K>, Serializable {
        private static final long serialVersionUID = 0L;
        public K previous() {
            return key[previousEntry()];
        }
        public void set(K k) {
            throw new UnsupportedOperationException();
        }
        public void add(K k) {
            throw new UnsupportedOperationException();
        }
        public KeyIterator() {}
        public K next() {
            return key[nextEntry()];
        }
        public void remove() { super.remove(); }
    }

    public final class KeySet implements SortedSet<K>, Serializable {
        private static final long serialVersionUID = 0L;

        public KeyIterator iterator() {
            return new KeyIterator();
        }

        public int size() {
            return size;
        }

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

        public K first() {
            if (size == 0) throw new NoSuchElementException();
            return key[first];
        }

        public K last() {
            if (size == 0) throw new NoSuchElementException();
            return key[last];
        }

        public Comparator<K> comparator() {
            return null;
        }

        public final SortedSet<K> tailSet(K from) {
            throw new UnsupportedOperationException();
        }

        public final SortedSet<K> headSet(K to) {
            throw new UnsupportedOperationException();
        }

        public final SortedSet<K> subSet(K from, K to) {
            throw new UnsupportedOperationException();
        }

        @SuppressWarnings("unchecked")
        @Override
        public <T> T[] toArray(T[] a) {
            if (a == null || a.length < size()) a = (T[]) new Object[size()];
            unwrap(iterator(), a);
            return a;
        }

        /**
         * Always throws an UnsupportedOperationException
         */
        public boolean remove(Object ok) {
            throw new UnsupportedOperationException("Cannot remove from the key set directly");
        }

        /**
         * Always throws an UnsupportedOperationException
         */
        public boolean add(final K o) {
            throw new UnsupportedOperationException("Cannot add to the key set directly");
        }

        /**
         * Delegates to the corresponding type-specific method.
         */
        public boolean contains(final Object o) {
            return containsKey(o);
        }

        /**
         * Checks whether this collection contains all elements from the given type-specific collection.
         *
         * @param c a type-specific collection.
         * @return <code>true</code> if this collection contains all elements of the argument.
         */
        public boolean containsAll(Collection<?> c) {
            final Iterator<?> i = c.iterator();
            int n = c.size();
            while (n-- != 0)
                if (!contains(i.next())) return false;
            return true;
        }

        /**
         * Retains in this collection only elements from the given type-specific collection.
         *
         * @param c a type-specific collection.
         * @return <code>true</code> if this collection changed as a result of the call.
         */
        public boolean retainAll(Collection<?> c) {
            boolean retVal = false;
            int n = size();
            final Iterator<?> i = iterator();
            while (n-- != 0) {
                if (!c.contains(i.next())) {
                    i.remove();
                    retVal = true;
                }
            }
            return retVal;
        }

        /**
         * Remove from this collection all elements in the given type-specific collection.
         *
         * @param c a type-specific collection.
         * @return <code>true</code> if this collection changed as a result of the call.
         */
        public boolean removeAll(Collection<?> c) {
            boolean retVal = false;
            int n = c.size();
            final Iterator<?> i = c.iterator();
            while (n-- != 0)
                if (remove(i.next())) retVal = true;
            return retVal;
        }

        public Object[] toArray() {
            final Object[] a = new Object[size()];
            objectUnwrap(iterator(), a);
            return a;
        }

        /**
         * Adds all elements of the given collection to this collection.
         *
         * @param c a collection.
         * @return <code>true</code> if this collection changed as a result of the call.
         */
        public boolean addAll(Collection<? extends K> c) {
            boolean retVal = false;
            final Iterator<? extends K> i = c.iterator();
            int n = c.size();
            while (n-- != 0)
                if (add(i.next())) retVal = true;
            return retVal;
        }

        @Override
        public boolean equals(final Object o) {
            if (o == this)
                return true;
            if (!(o instanceof Set))
                return false;
            Set<?> s = (Set<?>) o;
            if (s.size() != size())
                return false;
            return containsAll(s);
        }
        /**
         * Unwraps an iterator into an array starting at a given offset for a given number of elements.
         * <p>
         * <P>This method iterates over the given type-specific iterator and stores the elements returned, up to a maximum of <code>length</code>, in the given array starting at <code>offset</code>. The
         * number of actually unwrapped elements is returned (it may be less than <code>max</code> if the iterator emits less than <code>max</code> elements).
         *
         * @param i      a type-specific iterator.
         * @param array  an array to contain the output of the iterator.
         * @param offset the first element of the array to be returned.
         * @param max    the maximum number of elements to unwrap.
         * @return the number of elements unwrapped.
         */
        public int unwrap(final KeyIterator i, final Object[] array, int offset, final int max) {
            if (max < 0) throw new IllegalArgumentException("The maximum number of elements (" + max + ") is negative");
            if (offset < 0 || offset + max > array.length) throw new IllegalArgumentException();
            int j = max;
            while (j-- != 0 && i.hasNext())
                array[offset++] = i.next();
            return max - j - 1;
        }

        /**
         * Unwraps an iterator into an array.
         * <p>
         * <P>This method iterates over the given type-specific iterator and stores the elements returned in the given array. The iteration will stop when the iterator has no more elements or when the end
         * of the array has been reached.
         *
         * @param i     a type-specific iterator.
         * @param array an array to contain the output of the iterator.
         * @return the number of elements unwrapped.
         */
        public int unwrap(final KeyIterator i, final Object[] array) {
            return unwrap(i, array, 0, array.length);
        }

        public boolean isEmpty() {
            return size() == 0;
        }

        @Override
        public String toString() {
            final StringBuilder s = new StringBuilder();
            final KeyIterator i = iterator();
            int n = size();
            boolean first = true;
            s.append("{");
            while (n-- != 0) {
                if (first) first = false;
                else s.append(", ");
                s.append(i.next());
            }
            s.append("}");
            return s.toString();
        }
    }

    public KeySet keySet() {
        if (keys == null) keys = new KeySet();
        return keys;
    }

    public OrderedSet<K> keysAsOrderedSet()
    {
        OrderedSet<K> os = new OrderedSet<K>(size, f, hasher);
        for (int i = 0; i < size; i++) {
            os.add(keyAt(i));
        }
        return os;
    }

    /**
     * An iterator on values.
     * <p>
     * <P>We simply override the {@link ListIterator#next()}/{@link ListIterator#previous()} methods (and possibly their type-specific counterparts) so that they return values
     * instead of entries.
     */
    public final class ValueIterator extends MapIterator implements ListIterator<V>, Serializable {
        private static final long serialVersionUID = 0L;

        public V previous() {
            return value[previousEntry()];
        }
        public void set(V v) {
            throw new UnsupportedOperationException();
        }
        public void add(V v) {
            throw new UnsupportedOperationException();
        }
        public ValueIterator() {}
        public V next() {
            return value[nextEntry()];
        }
        public void remove() { super.remove(); }
    }
    public final class ValueCollection extends AbstractCollection<V> implements Serializable
    {
        private static final long serialVersionUID = 0L;
        public ValueIterator iterator() {
            return new ValueIterator();
        }
        public int size() {
            return size;
        }
        public boolean contains(Object v) {
            return containsValue(v);
        }
        public void clear() {
            OrderedMap.this.clear();
        }
    }
    public Collection<V> values() {
        if (values == null) values = new ValueCollection();
        return values;
    }

    public ArrayList<V> valuesAsList()
    {
        ArrayList<V> ls = new ArrayList<>(size);
        for (int i = 0; i < size; i++) {
            ls.add(getAt(i));
        }
        return ls;
    }

    /**
     * A no-op for backward compatibility. The kind of tables implemented by this class never need rehashing.
     * <p>
     * <P>If you need to reduce the table size to fit exactly this set, use {@link #trim()}.
     *
     * @return true.
     * @see #trim()
     * @deprecated A no-op.
     */
    @Deprecated
    public boolean rehash() {
        return true;
    }

    /**
     * Rehashes the map, making the table as small as possible.
     * <p>
     * <P>This method rehashes the table to the smallest size satisfying the load factor. It can be used when the set will not be changed anymore, so to optimize access speed and size.
     * <p>
     * <P>If the table size is already the minimum possible, this method does nothing.
     *
     * @return true if there was enough memory to trim the map.
     * @see #trim(int)
     */
    public boolean trim() {
        final int l = arraySize(size, f);
        if (l >= n || size > maxFill(l, f)) return true;
        try {
            rehash(l);
        } catch (Exception cantDoIt) {
            return false;
        }
        return true;
    }

    /**
     * Rehashes this map if the table is too large.
     * <p>
     * <P>Let <var>N</var> be the smallest table size that can hold <code>max(n,{@link #size()})</code> entries, still satisfying the load factor. If the current table size is smaller than or equal to
     * <var>N</var>, this method does nothing. Otherwise, it rehashes this map in a table of size <var>N</var>.
     * <p>
     * <P>This method is useful when reusing maps. {@linkplain #clear() Clearing a map} leaves the table size untouched. If you are reusing a map many times, you can call this method with a typical
     * size to avoid keeping around a very large table just because of a few large transient maps.
     *
     * @param n the threshold for the trimming.
     * @return true if there was enough memory to trim the map.
     * @see #trim()
     */
    public boolean trim(final int n) {
        final int l = HashCommon.nextPowerOfTwo((int) Math.ceil(n / f));
        if (l >= n || size > maxFill(l, f)) return true;
        try {
            rehash(l);
        } catch (Exception cantDoIt) {
            return false;
        }
        return true;
    }

    /**
     * Rehashes the map.
     *
     * <P>
     * This method implements the basic rehashing strategy, and may be overriden
     * by subclasses implementing different rehashing strategies (e.g.,
     * disk-based rehashing). However, you should not override this method
     * unless you understand the internal workings of this class.
     *
     * @param newN
     *            the new size
     */

    @SuppressWarnings("unchecked")
    protected void rehash(final int newN) {
        final K key[] = this.key;
        final V value[] = this.value;
        final int mask = newN - 1; // Note that this is used by the hashing
        // macro
        final K newKey[] = (K[]) new Object[newN + 1];
        final V newValue[] = (V[]) new Object[newN + 1];
        int i, pos, sz = order.size, originalFirst = first, originalLast = last;
        for (int q = 0; q < sz; q++) {
            i = order.get(q);
            if (key[i] == null)
                pos = newN;
            else {
                pos = HashCommon.mix(hasher.hash(key[i])) & mask;
                while (!(newKey[pos] == null))
                    pos = (pos + 1) & mask;
            }
            newKey[pos] = key[i];
            newValue[pos] = value[i];
            order.set(q, pos);
            if(i == originalFirst)
                first = pos;
            if(i == originalLast)
                last = pos;
        }
        n = newN;
        this.mask = mask;
        maxFill = maxFill(n, f);
        this.key = newKey;
        this.value = newValue;
    }
    /*
    @SuppressWarnings("unchecked")
    protected void rehash(final int newN) {
        final K key[] = this.key;
        final V value[] = this.value;
        final int mask = newN - 1; // Note that this is used by the hashing
        // macro
        final K newKey[] = (K[]) new Object[newN + 1];
        final V newValue[] = (V[]) new Object[newN + 1];
        int i = first, prev = -1, newPrev = -1, t, pos;
        final long link[] = this.link;
        final long newLink[] = new long[newN + 1];
        first = -1;
        for (int j = size; j-- != 0;) {
            if (((key[i]) == null))
                pos = newN;
            else {
                pos = (HashCommon.mix((key[i]).hashCode())) & mask;
                while (!((newKey[pos]) == null))
                    pos = (pos + 1) & mask;
            }
            newKey[pos] = key[i];
            newValue[pos] = value[i];
            if (prev != -1) {
                newLink[newPrev] ^= ((newLink[newPrev] ^ (pos & 0xFFFFFFFFL)) & 0xFFFFFFFFL);
                newLink[pos] ^= ((newLink[pos] ^ ((newPrev & 0xFFFFFFFFL) << 32)) & 0xFFFFFFFF00000000L);
                newPrev = pos;
            } else {
                newPrev = first = pos;
                // Special case of SET(newLink[ pos ], -1, -1);
                newLink[pos] = -1L;
            }
            t = i;
            i = (int) link[i];
            prev = t;
        }
        this.link = newLink;
        this.last = newPrev;
        if (newPrev != -1)
            // Special case of SET_NEXT( newLink[ newPrev ], -1 );
            newLink[newPrev] |= -1 & 0xFFFFFFFFL;
        n = newN;
        this.mask = mask;
        maxFill = maxFill(n, f);
        this.key = newKey;
        this.value = newValue;
    }
    */
    /**
     * Returns a deep copy of this map.
     *
     * <P>
     * This method performs a deep copy of this OrderedMap; the data stored in the
     * map, however, is not cloned. Note that this makes a difference only for
     * object keys.
     *
     * @return a deep copy of this map.
     */
    @SuppressWarnings("unchecked")
    @GwtIncompatible
    public OrderedMap<K, V> clone() {
        OrderedMap<K, V> c;
        try {
            c = (OrderedMap<K, V>) super.clone();
            c.key = (K[]) new Object[n + 1];
            System.arraycopy(key, 0, c.key, 0, n + 1);
            c.value = (V[]) new Object[n + 1];
            System.arraycopy(value, 0, c.value, 0, n + 1);
            c.order = (IntVLA) order.clone();
            c.hasher = hasher;
            return c;
        } catch (Exception cantHappen) {
            throw new UnsupportedOperationException(cantHappen + (cantHappen.getMessage() != null ?
                    "; " + cantHappen.getMessage() : ""));
        }
    }
    /**
     * Returns a hash code for this map.
     *
     * This method overrides the generic method provided by the superclass.
     * Since <code>equals()</code> is not overriden, it is important that the
     * value returned by this method is the same value as the one returned by
     * the overriden method.
     *
     * @return a hash code for this map.
     */
    public int hashCode() {
        int h = 0;
        for (int j = realSize(), i = 0, t = 0; j-- != 0;) {
            while (key[i] == null)
                i++;
            if (this != key[i])
                t = hasher.hash(key[i]);
            if (this != value[i])
                t ^= value[i] == null ? 0 : value[i].hashCode();
            h += t;
            i++;
        }
        // Zero / null keys have hash zero.
        if (containsNullKey)
            h += value[n] == null ? 0 : value[n].hashCode();
        return h;
    }
    /**
     * Returns the maximum number of entries that can be filled before rehashing.
     *
     * @param n the size of the backing array.
     * @param f the load factor.
     * @return the maximum number of entries before rehashing.
     */
    public static int maxFill(final int n, final float f) {
        /* We must guarantee that there is always at least
		 * one free entry (even with pathological load factors). */
        return Math.min((int) Math.ceil(n * f), n - 1);
    }

    /**
     * Returns the maximum number of entries that can be filled before rehashing.
     *
     * @param n the size of the backing array.
     * @param f the load factor.
     * @return the maximum number of entries before rehashing.
     */
    public static long maxFill(final long n, final float f) {
		/* We must guarantee that there is always at least
		 * one free entry (even with pathological load factors). */
        return Math.min((long) Math.ceil(n * f), n - 1);
    }

    /**
     * Returns the least power of two smaller than or equal to 2<sup>30</sup> and larger than or equal to <code>Math.ceil( expected / f )</code>.
     *
     * @param expected the expected number of elements in a hash table.
     * @param f        the load factor.
     * @return the minimum possible size for a backing array.
     * @throws IllegalArgumentException if the necessary size is larger than 2<sup>30</sup>.
     */
    public static int arraySize(final int expected, final float f) {
        final long s = Math.max(2, HashCommon.nextPowerOfTwo((long) Math.ceil(expected / f)));
        if (s > (1 << 30))
            throw new IllegalArgumentException("Too large (" + expected + " expected elements with load factor " + f + ")");
        return (int) s;
    }

    private static class HashCommon {

        private HashCommon() {
        }

        ;

        /**
         * This reference is used to fill keys and values of removed entries (if
         * they are objects). <code>null</code> cannot be used as it would confuse the
         * search algorithm in the presence of an actual <code>null</code> key.
         */
        public static final Object REMOVED = new Object();

        /**
         * 2<sup>32</sup> &middot; &phi;, &phi; = (&#x221A;5 &minus; 1)/2.
         */
        private static final int INT_PHI = 0x9E3779B9;
        /**
         * The reciprocal of {@link #INT_PHI} modulo 2<sup>32</sup>.
         */
        private static final int INV_INT_PHI = 0x144cbc89;
        /**
         * 2<sup>64</sup> &middot; &phi;, &phi; = (&#x221A;5 &minus; 1)/2.
         */
        private static final long LONG_PHI = 0x9E3779B97F4A7C15L;
        /**
         * The reciprocal of {@link #LONG_PHI} modulo 2<sup>64</sup>.
         */
        private static final long INV_LONG_PHI = 0xF1DE83E19937733DL;

        /**
         * Avalanches the bits of an integer by applying the finalisation step of MurmurHash3.
         * <br>
         * <br>This method implements the finalisation step of Austin Appleby's <a href="http://code.google.com/p/smhasher/">MurmurHash3</a>.
         * Its purpose is to avalanche the bits of the argument to within 0.25% bias.
         *
         * @param x an integer.
         * @return a hash value with good avalanching properties.
         */
        static int murmurHash3(int x) {
            x ^= x >>> 16;
            x *= 0x85ebca6b;
            x ^= x >>> 13;
            x *= 0xc2b2ae35;
            x ^= x >>> 16;
            return x;
        }


        /**
         * Avalanches the bits of a long integer by applying the finalisation step of MurmurHash3.
         * <br>
         * <br>This method implements the finalisation step of Austin Appleby's <a href="http://code.google.com/p/smhasher/">MurmurHash3</a>.
         * Its purpose is to avalanche the bits of the argument to within 0.25% bias.
         *
         * @param x a long integer.
         * @return a hash value with good avalanching properties.
         */
        static long murmurHash3(long x) {
            x ^= x >>> 33;
            x *= 0xff51afd7ed558ccdL;
            x ^= x >>> 33;
            x *= 0xc4ceb9fe1a85ec53L;
            x ^= x >>> 33;
            return x;
        }

        /**
         * Quickly mixes the bits of an integer.
         * <br>This method mixes the bits of the argument by multiplying by the golden ratio and
         * xorshifting the result. It is borrowed from <a href="https://github.com/OpenHFT/Koloboke">Koloboke</a>, and
         * it has slightly worse behaviour than {@link #murmurHash3(int)} (in open-addressing hash tables the average number of probes
         * is slightly larger), but it's much faster.
         *
         * @param x an integer.
         * @return a hash value obtained by mixing the bits of {@code x}.
         * @see #invMix(int)
         */
        static int mix(final int x) {
            final int h = x * INT_PHI;
            return h ^ (h >>> 16);
        }

        /**
         * The inverse of {@link #mix(int)}. This method is mainly useful to create unit tests.
         *
         * @param x an integer.
         * @return a value that passed through {@link #mix(int)} would give {@code x}.
         */
        static int invMix(final int x) {
            return (x ^ x >>> 16) * INV_INT_PHI;
        }

        /**
         * Quickly mixes the bits of a long integer.
         * <br>This method mixes the bits of the argument by multiplying by the golden ratio and
         * xorshifting twice the result. It is borrowed from <a href="https://github.com/OpenHFT/Koloboke">Koloboke</a>, and
         * it has slightly worse behaviour than {@link #murmurHash3(long)} (in open-addressing hash tables the average number of probes
         * is slightly larger), but it's much faster.
         *
         * @param x a long integer.
         * @return a hash value obtained by mixing the bits of {@code x}.
         */
        static long mix(final long x) {
            long h = x * LONG_PHI;
            h ^= h >>> 32;
            return h ^ (h >>> 16);
        }

        /**
         * The inverse of {@link #mix(long)}. This method is mainly useful to create unit tests.
         *
         * @param x a long integer.
         * @return a value that passed through {@link #mix(long)} would give {@code x}.
         */
        static long invMix(long x) {
            x ^= x >>> 32;
            x ^= x >>> 16;
            return (x ^ x >>> 32) * INV_LONG_PHI;
        }

        /**
         * Return the least power of two greater than or equal to the specified value.
         * <br>Note that this function will return 1 when the argument is 0.
         *
         * @param x an integer smaller than or equal to 2<sup>30</sup>.
         * @return the least power of two greater than or equal to the specified value.
         */
        static int nextPowerOfTwo(int x) {
            if (x == 0) return 1;
            x--;
            x |= x >> 1;
            x |= x >> 2;
            x |= x >> 4;
            x |= x >> 8;
            return (x | x >> 16) + 1;
        }

        /**
         * Return the least power of two greater than or equal to the specified value.
         * <br>Note that this function will return 1 when the argument is 0.
         *
         * @param x a long integer smaller than or equal to 2<sup>62</sup>.
         * @return the least power of two greater than or equal to the specified value.
         */
        static long nextPowerOfTwo(long x) {
            if (x == 0) return 1;
            x--;
            x |= x >> 1;
            x |= x >> 2;
            x |= x >> 4;
            x |= x >> 8;
            x |= x >> 16;
            return (x | x >> 32) + 1;
        }

        /**
         * Returns the least power of two larger than or equal to <code>Math.ceil( expected / f )</code>.
         *
         * @param expected the expected number of elements in a hash table.
         * @param f        the load factor.
         * @return the minimum possible size for a backing big array.
         */
        static long bigArraySize(final long expected, final float f) {
            return nextPowerOfTwo((long) Math.ceil(expected / f));
        }
    }

    /**
     * Unwraps an iterator into an array starting at a given offset for a given number of elements.
     * <p>
     * <P>This method iterates over the given type-specific iterator and stores the elements returned, up to a maximum of <code>length</code>, in the given array starting at <code>offset</code>. The
     * number of actually unwrapped elements is returned (it may be less than <code>max</code> if the iterator emits less than <code>max</code> elements).
     *
     * @param i      a type-specific iterator.
     * @param array  an array to contain the output of the iterator.
     * @param offset the first element of the array to be returned.
     * @param max    the maximum number of elements to unwrap.
     * @return the number of elements unwrapped.
     */
    private int unwrap(final ValueIterator i, final Object[] array, int offset, final int max) {
        if (max < 0) throw new IllegalArgumentException("The maximum number of elements (" + max + ") is negative");
        if (offset < 0 || offset + max > array.length) throw new IllegalArgumentException();
        int j = max;
        while (j-- != 0 && i.hasNext())
            array[offset++] = i.next();
        return max - j - 1;
    }

    /**
     * Unwraps an iterator into an array.
     * <p>
     * <P>This method iterates over the given type-specific iterator and stores the elements returned in the given array. The iteration will stop when the iterator has no more elements or when the end
     * of the array has been reached.
     *
     * @param i     a type-specific iterator.
     * @param array an array to contain the output of the iterator.
     * @return the number of elements unwrapped.
     */
    private int unwrap(final ValueIterator i, final Object[] array) {
        return unwrap(i, array, 0, array.length);
    }


    /** Unwraps an iterator into an array starting at a given offset for a given number of elements.
     *
     * <P>This method iterates over the given type-specific iterator and stores the elements returned, up to a maximum of <code>length</code>, in the given array starting at <code>offset</code>. The
     * number of actually unwrapped elements is returned (it may be less than <code>max</code> if the iterator emits less than <code>max</code> elements).
     *
     * @param i a type-specific iterator.
     * @param array an array to contain the output of the iterator.
     * @param offset the first element of the array to be returned.
     * @param max the maximum number of elements to unwrap.
     * @return the number of elements unwrapped. */
    private static <K> int objectUnwrap(final Iterator<? extends K> i, final K array[], int offset, final int max ) {
        if ( max < 0 ) throw new IllegalArgumentException( "The maximum number of elements (" + max + ") is negative" );
        if ( offset < 0 || offset + max > array.length ) throw new IllegalArgumentException();
        int j = max;
        while ( j-- != 0 && i.hasNext() )
            array[ offset++ ] = i.next();
        return max - j - 1;
    }

    /** Unwraps an iterator into an array.
     *
     * <P>This method iterates over the given type-specific iterator and stores the elements returned in the given array. The iteration will stop when the iterator has no more elements or when the end
     * of the array has been reached.
     *
     * @param i a type-specific iterator.
     * @param array an array to contain the output of the iterator.
     * @return the number of elements unwrapped. */
    private static <K> int objectUnwrap(final Iterator<? extends K> i, final K array[] ) {
        return objectUnwrap(i, array, 0, array.length );
    }

    @Override
    public String toString() {
        final StringBuilder s = new StringBuilder();
        int n = size(), i = 0;
        boolean first = true;
        s.append("OrderedMap{");
        while (i < n) {
            if (first) first = false;
            else s.append(", ");
            s.append(entryAt(i++));
        }
        s.append("}");
        return s.toString();
    }
    @Override
    public boolean equals(Object o) {
        if (o == this)
            return true;
        if (!(o instanceof Map))
            return false;
        Map<?, ?> m = (Map<?, ?>) o;
        if (m.size() != size())
            return false;
        return entrySet().containsAll(m.entrySet());
    }

    @GwtIncompatible
    private void writeObject(java.io.ObjectOutputStream s)
            throws java.io.IOException {
        final K key[] = this.key;
        final V value[] = this.value;
        final MapIterator i = new MapIterator();
        s.defaultWriteObject();
        s.writeObject(hasher);
        for (int j = size, e; j-- != 0;) {
            e = i.nextEntry();
            s.writeObject(key[e]);
            s.writeObject(value[e]);
        }
    }
    @GwtIncompatible
    @SuppressWarnings("unchecked")
    private void readObject(java.io.ObjectInputStream s)
            throws java.io.IOException, ClassNotFoundException {
        s.defaultReadObject();
        hasher = (CrossHash.IHasher) s.readObject();
        n = arraySize(size, f);
        maxFill = maxFill(n, f);
        mask = n - 1;
        final K key[] = this.key = (K[]) new Object[n + 1];
        final V value[] = this.value = (V[]) new Object[n + 1];
        final IntVLA order = this.order = new IntVLA(n + 1);
        int prev = -1;
        first = last = -1;
        K k;
        V v;
        for (int i = size, pos; i-- != 0;) {
            k = (K) s.readObject();
            v = (V) s.readObject();
            if (k == null) {
                pos = n;
                containsNullKey = true;
            } else {
                pos = HashCommon.mix(hasher.hash(k))
                        & mask;
                while (!(key[pos] == null))
                    pos = (pos + 1) & mask;
            }

            key[pos] = k;
            value[pos] = v;
            if (first != -1) {
                prev = pos;
            } else {
                prev = first = pos;
            }
            order.add(pos);
        }
        last = prev;
    }

    /**
     * Gets the value at the given index in the iteration order in constant time (random-access).
     * @param idx the index in the iteration order of the value to fetch
     * @return the value at the index, if the index is valid, otherwise the default return value
     */
    public V getAt(final int idx) {
        int pos;
        if (idx < 0 || idx >= order.size)
            return defRetValue;
        // The starting point.
        if (key[pos = order.get(idx)] == null)
            return containsNullKey ? value[n] : defRetValue;
        return value[pos];
    }
    /**
     * Gets the key at the given index in the iteration order in constant time (random-access).
     * @param idx the index in the iteration order of the key to fetch
     * @return the key at the index, if the index is valid, otherwise null
     */
    public K keyAt(final int idx) {
        if (idx < 0 || idx >= order.size)
            return null;
        // The starting point.
        return key[order.get(idx)];
    }

    /**
     * Gets the key-value Map.Entry at the given index in the iteration order in constant time (random-access).
     * @param idx the index in the iteration order of the entry to fetch
     * @return the key-value entry at the index, if the index is valid, otherwise null
     */
    public Entry<K, V> entryAt(final int idx)
    {
        if (idx < 0 || idx >= order.size)
            return null;
        return new MapEntry(order.get(idx));
    }

    /**
     * Removes the key and value at the given index in the iteration order in not-exactly constant time (though it still
     * should be efficient).
     * @param idx the index in the iteration order of the key and value to remove
     * @return the value removed, if there was anything removed, or the default return value otherwise (often null)
     */
    public V removeAt(final int idx) {

        if (idx < 0 || idx >= order.size)
            return defRetValue;
        int pos = order.get(idx);
        if (key[pos] == null) {
            if (containsNullKey)
                return removeNullEntry();
            return defRetValue;
        }
        return removeEntry(pos);
    }
    /**
     * Gets a random value from this OrderedMap in constant time, using the given RNG to generate a random number.
     * @param rng used to generate a random index for a value
     * @return a random value from this OrderedMap
     */
    public V randomValue(RNG rng)
    {
        return getAt(rng.nextInt(order.size));
    }

    /**
     * Gets a random key from this OrderedMap in constant time, using the given RNG to generate a random number.
     * @param rng used to generate a random index for a key
     * @return a random key from this OrderedMap
     */
    public K randomKey(RNG rng)
    {
        return keyAt(rng.nextInt(order.size));
    }

    /**
     * Gets a random entry from this OrderedMap in constant time, using the given RNG to generate a random number.
     * @param rng used to generate a random index for a entry
     * @return a random key-value entry from this OrderedMap
     */
    public Entry<K, V> randomEntry(RNG rng)
    {
        return new MapEntry(order.getRandomElement(rng));
    }

    /**
     * Randomly alters the iteration order for this OrderedMap using the given RNG to shuffle.
     * @param rng used to generate a random ordering
     * @return this for chaining
     */
    public OrderedMap<K, V> shuffle(RNG rng)
    {
        if(size < 2)
            return this;
        order.shuffle(rng);
        first = order.get(0);
        last = order.peek();
        return this;
    }

    /**
     * Given an array or varargs of replacement indices for this OrderedMap's iteration order, reorders this so the
     * first item in the returned version is the same as {@code getAt(ordering[0])} (with some care taken for negative
     * or too-large indices), the second item in the returned version is the same as {@code getAt(ordering[1])}, etc.
     * <br>
     * Negative indices are considered reversed distances from the end of ordering, so -1 refers to the same index as
     * {@code ordering[ordering.length - 1]}. If ordering is smaller than {@code size()}, only the indices up to the
     * length of ordering will be modified. If ordering is larger than {@code size()}, only as many indices will be
     * affected as {@code size()}, and reversed distances are measured from the end of this Map's entries instead of
     * the end of ordering. Duplicate values in ordering will produce duplicate values in the returned Map.
     * <br>
     * This method modifies this OrderedMap in-place and also returns it for chaining.
     * @param ordering an array or varargs of int indices, where the nth item in ordering changes the nth item in this
     *                 Map to have the value currently in this Map at the index specified by the value in ordering
     * @return this for chaining, after modifying it in-place
     */
    public OrderedMap<K, V> reorder(int... ordering)
    {
        order.reorder(ordering);
        first = order.get(0);
        last = order.peek();
        return this;
    }
    private V alterEntry(final int pos, final K replacement) {
        key[pos] = null;

        final V[] value = this.value;
        V v = value[pos];
        value[pos] = null;

        int rep;
        if (replacement == null) {
            if (containsNullKey)
                return v;
            rep = n;
            containsNullKey = true;
        } else {
            K curr;
            final K[] key = this.key;

            // The starting point.
            if (!((curr = key[rep = HashCommon.mix(hasher.hash(replacement)) & mask]) == null)) {
                if (curr.equals(replacement))
                    return v;
                while (!((curr = key[rep = (rep + 1) & mask]) == null))
                    if (curr.equals(replacement))
                        return v;
            }
            key[rep] = replacement;
            value[rep] = v;
        }
        fixOrder(pos, rep);
        return v;
    }
    private V alterNullEntry(final K replacement) {
        containsNullKey = false;
        key[n] = null;
        final V[] value = this.value;
        V v = value[n];
        value[n] = null;

        int rep;
        if (replacement == null) {
            rep = n;
            containsNullKey = true;
        } else {
            K curr;
            final K[] key = this.key;
            // The starting point.
            if ((curr = key[rep = HashCommon.mix(hasher.hash(replacement)) & mask]) != null) {
                if (curr.equals(replacement))
                    return v;
                while ((curr = key[rep = (rep + 1) & mask]) != null)
                    if (curr.equals(replacement))
                        return v;
            }
            key[rep] = replacement;
            value[rep] = v;

        }
        fixOrder(n, rep);
        return v;
    }

    /**
     * Swaps a key, original, for another key, replacement, while keeping replacement at the same point in the iteration
     * order as original and keeping it associated with the same value (which also keeps its iteration index).
     * @param original the key to find and swap out
     * @param replacement the key to replace original with
     * @return the value associated with original before, and replacement now
     */
    public V alter(final K original, final K replacement) {
        if (original == null) {
            if (containsNullKey) {
                return alterNullEntry(replacement);
            }
            else
                return put(replacement, null);
        }
        else if(original.equals(replacement))
            return get(original);
        K curr;
        final K[] key = this.key;
        int pos;
        // The starting point.
        if ((curr = key[pos = HashCommon.mix(hasher.hash(original)) & mask]) == null)
            return put(replacement, null);
        if (original.equals(curr))
            return alterEntry(pos, replacement);
        while (true) {
            if ((curr = key[pos = (pos + 1) & mask]) == null)
                return put(replacement, null);
            if (original.equals(curr))
                return alterEntry(pos, replacement);
        }
    }

    public List<V> getMany(Collection<K> keys)
    {
        if(keys == null)
            return new ArrayList<>(1);
        ArrayList<V> vals = new ArrayList<>(keys.size());
        for(K k : keys)
        {
            vals.add(get(k));
        }
        return vals;
    }
}
