http://labs.carrotsearch.com/hppc.html/hppc: High Performance Primitive Collections. Fundamental data structures (maps, sets, lists, stacks, queues) generated for combinations of object and primitive types to conserve JVM memory and speed up execution. (Carrot Search s.c.)
  • Dawid Weiss
  • Stanisław Osiński 
  
package com.carrotsearch.hppc;

import java.util.*;

import com.carrotsearch.hppc.cursors.*;
import com.carrotsearch.hppc.predicates.*;
import com.carrotsearch.hppc.procedures.*;

import static com.carrotsearch.hppc.HashContainers.*;
import static com.carrotsearch.hppc.Containers.*;


A hash map of short to Object, implemented using open
addressing with linear probing for collision resolution.

Note: read about important differences 
between hash and scatter sets.


See Also:
/**
 * A hash map of <code>short</code> to <code>Object</code>, implemented using open
 * addressing with linear probing for collision resolution.
 * 
 * <p><strong>Note:</strong> read about <a href="{@docRoot}/overview-summary.html#scattervshash">important differences 
 * between hash and scatter sets</a>.</p>
 * 
 * @see ShortObjectScatterMap
 * @see <a href="{@docRoot}/overview-summary.html#interfaces">HPPC interfaces diagram</a> 
 */
  @SuppressWarnings("unchecked")  
 @com.carrotsearch.hppc.Generated(
    date = "2018-05-21T12:24:06+0200",
    value = "KTypeVTypeHashMap.java") 
public class ShortObjectHashMap<VType>
  implements   
               
             ShortObjectMap<VType>,
             Preallocable,
             Cloneable
{
  
The array holding keys.

/** 
   * The array holding keys.
   */
  public   short []   
         keys;

  
The array holding values. 

/**
   * The array holding values. 
   */
  public    
         Object [] 
            
         values;

  
We perturb hash values with a container-unique
seed to avoid problems with nearly-sorted-by-hash 
values on iterations.

See Also:
  • hashKey
  • http://issues.carrot2.org/browse/HPPC-80
  • http://issues.carrot2.org/browse/HPPC-103
/**
   * We perturb hash values with a container-unique
   * seed to avoid problems with nearly-sorted-by-hash 
   * values on iterations.
   * 
   * @see #hashKey
   * @see "http://issues.carrot2.org/browse/HPPC-80"
   * @see "http://issues.carrot2.org/browse/HPPC-103"
   */
  protected int keyMixer;

  
The number of stored keys (assigned key slots), excluding the special "empty" key, if any (use size() instead). 
See Also:
/**
   * The number of stored keys (assigned key slots), excluding the special 
   * "empty" key, if any (use {@link #size()} instead).
   * 
   * @see #size()
   */
  protected int assigned;

  
Mask for slot scans in ShortObjectHashMap<VType>.keys. 
/**
   * Mask for slot scans in {@link #keys}.
   */
  protected int mask;

  /**
   * Expand (rehash) {@link #keys} when {@link #assigned} hits this value. 
   */
  protected int resizeAt;

  
Special treatment for the "empty slot" key marker.

/**
   * Special treatment for the "empty slot" key marker.
   */
  protected boolean hasEmptyKey;
  
  
The load factor for ShortObjectHashMap<VType>.keys. 
/**
   * The load factor for {@link #keys}.
   */
  protected double loadFactor;

  
Per-instance hash order mixing strategy.

See Also:
  • keyMixer
/**
   * Per-instance hash order mixing strategy.
   * @see #keyMixer
   */
  protected HashOrderMixingStrategy orderMixer;

  
New instance with sane defaults.

/**
   * New instance with sane defaults.
   */
  public ShortObjectHashMap() {
    this(DEFAULT_EXPECTED_ELEMENTS);
  }

  
New instance with sane defaults.

Params:
  • expectedElements – 
         The expected number of elements guaranteed not to cause buffer
         expansion (inclusive).
/**
   * New instance with sane defaults.
   * 
   * @param expectedElements
   *          The expected number of elements guaranteed not to cause buffer
   *          expansion (inclusive).
   */
  public ShortObjectHashMap(int expectedElements) {
    this(expectedElements, DEFAULT_LOAD_FACTOR);
  }

  
New instance with sane defaults.

Params:
  • expectedElements – 
         The expected number of elements guaranteed not to cause buffer
         expansion (inclusive).
  • loadFactor –  The load factor for internal buffers. Insane load factors (zero, full capacity) are rejected by verifyLoadFactor(double).
/**
   * New instance with sane defaults.
   * 
   * @param expectedElements
   *          The expected number of elements guaranteed not to cause buffer
   *          expansion (inclusive).
   * @param loadFactor
   *          The load factor for internal buffers. Insane load factors (zero, full capacity)
   *          are rejected by {@link #verifyLoadFactor(double)}.
   */
  public ShortObjectHashMap(int expectedElements, double loadFactor) {
    this(expectedElements, loadFactor, HashOrderMixing.defaultStrategy());
  }

  
New instance with the provided defaults.

Params:
  • expectedElements – 
         The expected number of elements guaranteed not to cause a rehash (inclusive).
  • loadFactor –  The load factor for internal buffers. Insane load factors (zero, full capacity) are rejected by verifyLoadFactor(double).
  • orderMixer –  Hash key order mixing strategy. See HashOrderMixing for predefined implementations. Use constant mixers only if you understand the potential consequences.
/**
   * New instance with the provided defaults.
   * 
   * @param expectedElements
   *          The expected number of elements guaranteed not to cause a rehash (inclusive).
   * @param loadFactor
   *          The load factor for internal buffers. Insane load factors (zero, full capacity)
   *          are rejected by {@link #verifyLoadFactor(double)}.
   * @param orderMixer
   *          Hash key order mixing strategy. See {@link HashOrderMixing} for predefined
   *          implementations. Use constant mixers only if you understand the potential
   *          consequences.
   */
  public ShortObjectHashMap(int expectedElements, double loadFactor, HashOrderMixingStrategy orderMixer) {
    this.orderMixer = orderMixer;
    this.loadFactor = verifyLoadFactor(loadFactor);
    ensureCapacity(expectedElements);
  }

  
Create a hash map from all key-value pairs of another container.

/**
   * Create a hash map from all key-value pairs of another container.
   */
  public ShortObjectHashMap(ShortObjectAssociativeContainer<? extends VType> container) {
    this(container.size());
    putAll(container);
  }

  
{@inheritDoc}

/**
   * {@inheritDoc}
   */
  @Override
  public VType put(short key, VType value) {
    assert assigned < mask + 1;

    final int mask = this.mask;
    if (((key) == 0)) {
      hasEmptyKey = true;
      VType previousValue = (VType) values[mask + 1];
      values[mask + 1] = value;
      return previousValue;
    } else {
      final short[] keys =  this.keys;
      int slot = hashKey(key) & mask;

      short existing;
      while (!((existing = keys[slot]) == 0)) {
        if (((existing) == ( key))) {
          final VType previousValue = (VType) values[slot];
          values[slot] = value;
          return previousValue;
        }
        slot = (slot + 1) & mask;
      }

      if (assigned == resizeAt) {
        allocateThenInsertThenRehash(slot, key, value);
      } else {
        keys[slot] = key;
        values[slot] = value;
      }

      assigned++;
      return null;
    }
  }

  
{@inheritDoc}

/**
   * {@inheritDoc}
   */
  @Override
  public int putAll(ShortObjectAssociativeContainer<? extends VType> container) {
    final int count = size();
    for (ShortObjectCursor<? extends VType> c : container) {
      put(c.key, c.value);
    }
    return size() - count;
  }

  
Puts all key/value pairs from a given iterable into this map.

/**
   * Puts all key/value pairs from a given iterable into this map.
   */
  @Override
  public int putAll(Iterable<? extends ShortObjectCursor<? extends VType>> iterable){
    final int count = size();
    for (ShortObjectCursor<? extends VType> c : iterable) {
      put(c.key, c.value);
    }
    return size() - count;
  }

  
Trove-inspired API method. An equivalent
of the following code:

if (!map.containsKey(key)) map.put(value);



Params:
  • key – The key of the value to check.
  • value – The value to put if key does not exist.
Returns:true if key did not exist and value
was placed in the map.
/**
   * <a href="http://trove4j.sourceforge.net">Trove</a>-inspired API method. An equivalent
   * of the following code:
   * <pre>
   * if (!map.containsKey(key)) map.put(value);
   * </pre>
   * 
   * @param key The key of the value to check.
   * @param value The value to put if <code>key</code> does not exist.
   * @return <code>true</code> if <code>key</code> did not exist and <code>value</code>
   * was placed in the map.
   */
  public boolean putIfAbsent(short key, VType value) {
    int keyIndex = indexOf(key);
    if (!indexExists(keyIndex)) {
      indexInsert(keyIndex, key, value);
      return true;
    } else {
      return false;
    }
  }

    

    

  
{@inheritDoc}

/**
   * {@inheritDoc}
   */
  @Override
  public VType remove(short key) {
    final int mask = this.mask;
    if (((key) == 0)) {
      hasEmptyKey = false;
      VType previousValue = (VType) values[mask + 1];
      values[mask + 1] = null;
      return previousValue;
    } else {
      final short[] keys =  this.keys;
      int slot = hashKey(key) & mask;

      short existing;
      while (!((existing = keys[slot]) == 0)) {
        if (((existing) == ( key))) {
          final VType previousValue = (VType) values[slot];
          shiftConflictingKeys(slot);
          return previousValue;
        }
        slot = (slot + 1) & mask;
      }

      return null;
    }
  }

  
{@inheritDoc}

/**
   * {@inheritDoc}
   */
  @Override
  public int removeAll(ShortContainer other) {
    final int before = size();

    // Try to iterate over the smaller set of values or
    // over the container that isn't implementing 
    // efficient contains() lookup.

    if (other.size() >= size() &&
        other instanceof ShortLookupContainer) {
      if (hasEmptyKey) {
        if (other.contains(((short) 0))) {
          hasEmptyKey = false;
          values[mask + 1] = null;
        }
      }

      final short[] keys =  this.keys;
      for (int slot = 0, max = this.mask; slot <= max;) {
        short existing;
        if (!((existing = keys[slot]) == 0) && other.contains(existing)) {
          // Shift, do not increment slot.
          shiftConflictingKeys(slot);
        } else {
          slot++;
        }
      }
    } else {
      for (ShortCursor c : other) {
        this.remove( c.value);
      }
    }

    return before - size();
  }

  
{@inheritDoc}

/**
   * {@inheritDoc}
   */
  @Override
  public int removeAll(ShortObjectPredicate<? super VType> predicate) {
    final int before = size();

    final int mask = this.mask;

    if (hasEmptyKey) {
      if (predicate.apply(((short) 0), (VType) values[mask + 1])) {
        hasEmptyKey = false;
        values[mask + 1] = null;
      }
    }

    final short[] keys =  this.keys;
    final VType[] values = (VType[]) this.values;
    for (int slot = 0; slot <= mask;) {
      short existing;
      if (!((existing = keys[slot]) == 0) && 
          predicate.apply(existing, values[slot])) {
        // Shift, do not increment slot.
        shiftConflictingKeys(slot);
      } else {
        slot++;
      }
    }

    return before - size();    
  }

  
{@inheritDoc}

/**
   * {@inheritDoc}
   */
  @Override
  public int removeAll(ShortPredicate predicate) {
    final int before = size();

    if (hasEmptyKey) {
      if (predicate.apply(((short) 0))) {
        hasEmptyKey = false;
        values[mask + 1] = null;
      }
    }

    final short[] keys =  this.keys;
    for (int slot = 0, max = this.mask; slot <= max;) {
      short existing;
      if (!((existing = keys[slot]) == 0) &&
          predicate.apply(existing)) {
        // Shift, do not increment slot.
        shiftConflictingKeys(slot);
      } else {
        slot++;
      }
    }

    return before - size();
  }

  
{@inheritDoc}

/**
   * {@inheritDoc}
   */
  @Override
  public VType get(short key) {
    if (((key) == 0)) {
      return hasEmptyKey ? (VType) values[mask + 1] : null;
    } else {
      final short[] keys =  this.keys;
      final int mask = this.mask;
      int slot = hashKey(key) & mask;

      short existing;
      while (!((existing = keys[slot]) == 0)) {
        if (((existing) == ( key))) {
          return (VType) values[slot];
        }
        slot = (slot + 1) & mask;
      }

      return null;
    }
  }

  
{@inheritDoc}

/**
   * {@inheritDoc}
   */
  @Override
  public VType getOrDefault(short key, VType defaultValue) {
    if (((key) == 0)) {
      return hasEmptyKey ? (VType) values[mask + 1] : defaultValue;
    } else {
      final short[] keys =  this.keys;
      final int mask = this.mask;
      int slot = hashKey(key) & mask;

      short existing;
      while (!((existing = keys[slot]) == 0)) {
        if (((existing) == ( key))) {
          return (VType) values[slot];
        }
        slot = (slot + 1) & mask;
      }

      return defaultValue;
    }
  }

  
{@inheritDoc}

/**
   * {@inheritDoc}
   */
  @Override
  public boolean containsKey(short key) {
    if (((key) == 0)) {
      return hasEmptyKey;
    } else {
      final short[] keys =  this.keys;
      final int mask = this.mask;
      int slot = hashKey(key) & mask;

      short existing;
      while (!((existing = keys[slot]) == 0)) {
        if (((existing) == ( key))) {
          return true;
        }
        slot = (slot + 1) & mask;
      }    

      return false;
    }
  }

  
{@inheritDoc}

/**
   * {@inheritDoc}
   */
  @Override
  public int indexOf(short key) {
    final int mask = this.mask;
    if (((key) == 0)) {
      return hasEmptyKey ? mask + 1 : ~(mask + 1);
    } else {
      final short[] keys =  this.keys;
      int slot = hashKey(key) & mask;

      short existing;
      while (!((existing = keys[slot]) == 0)) {
        if (((existing) == ( key))) {
          return slot;
        }
        slot = (slot + 1) & mask;
      }

      return ~slot;
    }
  }

  
{@inheritDoc}

/**
   * {@inheritDoc}
   */
  @Override
  public boolean indexExists(int index) {
    assert index < 0 || 
           (index >= 0 && index <= mask) ||
           (index == mask + 1 && hasEmptyKey);

    return index >= 0; 
  }

  
{@inheritDoc}

/**
   * {@inheritDoc}
   */
  @Override
  public VType indexGet(int index) {
    assert index >= 0 : "The index must point at an existing key.";
    assert index <= mask ||
           (index == mask + 1 && hasEmptyKey);

    return (VType) values[index];
  }

  
{@inheritDoc}

/**
   * {@inheritDoc}
   */
  @Override
  public VType indexReplace(int index, VType newValue) {
    assert index >= 0 : "The index must point at an existing key.";
    assert index <= mask ||
           (index == mask + 1 && hasEmptyKey);

    VType previousValue = (VType) values[index];
    values[index] = newValue;
    return previousValue;
  }

  
{@inheritDoc}

/**
   * {@inheritDoc}
   */
  @Override
  public void indexInsert(int index, short key, VType value) {
    assert index < 0 : "The index must not point at an existing key.";

    index = ~index;
    if (((key) == 0)) {
      assert index == mask + 1;
      values[index] = value;
      hasEmptyKey = true;
    } else {
      assert ((keys[index]) == 0);

      if (assigned == resizeAt) {
        allocateThenInsertThenRehash(index, key, value);
      } else {
        keys[index] = key;
        values[index] = value;
      }

      assigned++;
    }
  }

  
{@inheritDoc}

/**
   * {@inheritDoc}
   */
  @Override
  public void clear() {
    assigned = 0;
    hasEmptyKey = false;

    Arrays.fill(keys, ((short) 0));

    /*  */ 
    Arrays.fill(values, null);
    /*  */
  }

  
{@inheritDoc}

/**
   * {@inheritDoc}
   */
  @Override
  public void release() {
    assigned = 0;
    hasEmptyKey = false;

    keys = null;
    values = null;
    ensureCapacity(Containers.DEFAULT_EXPECTED_ELEMENTS);
  }

  
{@inheritDoc}

/**
   * {@inheritDoc}
   */
  @Override
  public int size() {
    return assigned + (hasEmptyKey ? 1 : 0);
  }

  
{@inheritDoc}

/**
   * {@inheritDoc}
   */
  public boolean isEmpty() {
    return size() == 0;
  }

  
{@inheritDoc}

/**
   * {@inheritDoc}
   */
  @Override
  public int hashCode() {
    int h = hasEmptyKey ? 0xDEADBEEF : 0;
    for (ShortObjectCursor<VType> c : this) {
      h += BitMixer.mix(c.key) +
           BitMixer.mix(c.value);
    }
    return h;
  }

  
{@inheritDoc} 

/**
   * {@inheritDoc} 
   */
  @Override
  public boolean equals(Object obj) {
    return obj != null &&
           getClass() == obj.getClass() &&
           equalElements(getClass().cast(obj));
  }

  
Return true if all keys of some other container exist in this container. Values are compared using Object.equals(Object) method. 
/**
   * Return true if all keys of some other container exist in this container.
   * Values are compared using {@link Objects#equals(Object)} method.
   */
  protected boolean equalElements(ShortObjectHashMap<?> other) {
    if (other.size() != size()) {
      return false;
    }

    for (ShortObjectCursor<?> c : other) {
      short key =  c.key;
      if (!containsKey(key) ||
          !java.util.Objects.equals(get(key), c.value)) {
        return false;
      }
    }

    return true;
  }

  
Ensure this container can hold at least the
given number of keys (entries) without resizing its buffers.

Params:
  • expectedElements – The total number of keys, inclusive.
/**
   * Ensure this container can hold at least the
   * given number of keys (entries) without resizing its buffers.
   * 
   * @param expectedElements The total number of keys, inclusive.
   */
  @Override
  public void ensureCapacity(int expectedElements) {
    if (expectedElements > resizeAt || keys == null) {
      final short[] prevKeys =  this.keys;
      final VType[] prevValues = (VType[]) this.values;
      allocateBuffers(minBufferSize(expectedElements, loadFactor));
      if (prevKeys != null && !isEmpty()) {
        rehash(prevKeys, prevValues);
      }
    }
  }

  
An iterator implementation for ShortObjectHashMap<VType>.iterator. 
/**
   * An iterator implementation for {@link #iterator}.
   */
  private final class EntryIterator extends AbstractIterator<ShortObjectCursor<VType>> {
    private final ShortObjectCursor<VType> cursor;
    private final int max = mask + 1;
    private int slot = -1;

    public EntryIterator() {
      cursor = new ShortObjectCursor<VType>();
    }

    @Override
    protected ShortObjectCursor<VType> fetch() {
      if (slot < max) {
        short existing;
        for (slot++; slot < max; slot++) {
          if (!((existing =  keys[slot]) == 0)) {
            cursor.index = slot;
            cursor.key = existing;
            cursor.value = (VType) values[slot];
            return cursor;
          }
        }
      }

      if (slot == max && hasEmptyKey) {
        cursor.index = slot;
        cursor.key = ((short) 0);
        cursor.value = (VType) values[max];
        slot++;
        return cursor;
      }

      return done();
    }
  }

  
{@inheritDoc}

/**
   * {@inheritDoc}
   */
  @Override
  public Iterator<ShortObjectCursor<VType>> iterator() {
      return new EntryIterator();
  }

  
{@inheritDoc}

/**
   * {@inheritDoc}
   */
  @Override
  public <T extends ShortObjectProcedure<? super VType>> T forEach(T procedure) {
    final short[] keys =  this.keys;
    final VType[] values = (VType[]) this.values;

    if (hasEmptyKey) {
      procedure.apply(((short) 0), (VType) values[mask + 1]);
    }

    for (int slot = 0, max = this.mask; slot <= max; slot++) {
      if (!((keys[slot]) == 0)) {
        procedure.apply(keys[slot], values[slot]);
      }
    }

    return procedure;
  }

  
{@inheritDoc}

/**
   * {@inheritDoc}
   */
  @Override
  public <T extends ShortObjectPredicate<? super VType>> T forEach(T predicate) {
    final short[] keys =  this.keys;
    final VType[] values = (VType[]) this.values;

    if (hasEmptyKey) {
      if (!predicate.apply(((short) 0), (VType) values[mask + 1])) {
        return predicate;
      }
    }

    for (int slot = 0, max = this.mask; slot <= max; slot++) {
      if (!((keys[slot]) == 0)) {
        if (!predicate.apply(keys[slot], values[slot])) {
          break;
        }
      }
    }

    return predicate;
  }

  
Returns a specialized view of the keys of this associated container. The view additionally implements ObjectLookupContainer. 
/**
   * Returns a specialized view of the keys of this associated container. The
   * view additionally implements {@link ObjectLookupContainer}.
   */
  public KeysContainer keys() {
    return new KeysContainer();
  }

  
A view of the keys inside this hash map.

/**
   * A view of the keys inside this hash map.
   */
  public final class KeysContainer extends AbstractShortCollection 
                                   implements ShortLookupContainer {
    private final ShortObjectHashMap<VType> owner = ShortObjectHashMap.this;

    @Override
    public boolean contains(short e) {
      return owner.containsKey(e);
    }

    @Override
    public <T extends ShortProcedure> T forEach(final T procedure) {
      owner.forEach(new ShortObjectProcedure<VType>() {
        @Override
        public void apply(short key, VType value) {
          procedure.apply(key);
        }
      });

      return procedure;
    }

    @Override
    public <T extends ShortPredicate> T forEach(final T predicate) {
      owner.forEach(new ShortObjectPredicate<VType>() {
        @Override
        public boolean apply(short key, VType value) {
          return predicate.apply(key);
        }
      });

      return predicate;
    }

    @Override
    public boolean isEmpty() {
      return owner.isEmpty();
    }

    @Override
    public Iterator<ShortCursor> iterator() {
      return new KeysIterator();
    }

    @Override
    public int size() {
      return owner.size();
    }

    @Override
    public void clear() {
      owner.clear();
    }
    
    @Override
    public void release() {
      owner.release();
    }

    @Override
    public int removeAll(ShortPredicate predicate) {
      return owner.removeAll(predicate);
    }

    @Override
    public int removeAll(final short e) {
      final boolean hasKey = owner.containsKey(e);
      if (hasKey) {
        owner.remove(e);
        return 1;
      } else {
        return 0;
      }
    }
  };

  
An iterator over the set of assigned keys.

/**
   * An iterator over the set of assigned keys.
   */
  private final class KeysIterator extends AbstractIterator<ShortCursor> {
    private final ShortCursor cursor;
    private final int max = mask + 1;
    private int slot = -1;

    public KeysIterator() {
      cursor = new ShortCursor();
    }

    @Override
    protected ShortCursor fetch() {
      if (slot < max) {
        short existing;
        for (slot++; slot < max; slot++) {
          if (!((existing =  keys[slot]) == 0)) {
            cursor.index = slot;
            cursor.value = existing;
            return cursor;
          }
        }
      }

      if (slot == max && hasEmptyKey) {
        cursor.index = slot;
        cursor.value = ((short) 0);
        slot++;
        return cursor;
      }

      return done();
    }
  }

  
Returns:Returns a container with all values stored in this map.
/**
   * @return Returns a container with all values stored in this map.
   */
  @Override
  public ObjectCollection<VType> values() {
    return new ValuesContainer();
  }

  
A view over the set of values of this map.

/**
   * A view over the set of values of this map.
   */
  private final class ValuesContainer extends AbstractObjectCollection<VType> {
    private final ShortObjectHashMap<VType> owner = ShortObjectHashMap.this;

    @Override
    public int size() {
      return owner.size();
    }

    @Override
    public boolean isEmpty() {
      return owner.isEmpty();
    }

    @Override
    public boolean contains(VType value) {
      for (ShortObjectCursor<VType> c : owner) {
        if (java.util.Objects.equals(c.value, value)) {
          return true;
        }
      }
      return false;
    }

    @Override
    public <T extends ObjectProcedure<? super VType>> T forEach(T procedure) {
      for (ShortObjectCursor<VType> c : owner) {
        procedure.apply(c.value);
      }
      return procedure;
    }

    @Override
    public <T extends ObjectPredicate<? super VType>> T forEach(T predicate) {
      for (ShortObjectCursor<VType> c : owner) {
        if (!predicate.apply(c.value)) {
          break;
        }
      }
      return predicate;
    }

    @Override
    public Iterator<ObjectCursor<VType>> iterator() {
      return new ValuesIterator();
    }

    @Override
    public int removeAll(final VType e) {
      return owner.removeAll(new ShortObjectPredicate<VType>() {
        @Override
        public boolean apply(short key, VType value) {
          return java.util.Objects.equals(value, e);
        }
      });
    }

    @Override
    public int removeAll(final ObjectPredicate<? super VType> predicate) {
      return owner.removeAll(new ShortObjectPredicate<VType>() {
        @Override
        public boolean apply(short key, VType value) {
          return predicate.apply(value);
        }
      });
    }

    @Override
    public void clear() {
      owner.clear();
    }
    
    @Override
    public void release() {
      owner.release();
    }
  }
  
  
An iterator over the set of assigned values.

/**
   * An iterator over the set of assigned values.
   */
  private final class ValuesIterator extends AbstractIterator<ObjectCursor<VType>> {
    private final ObjectCursor<VType> cursor;
    private final int max = mask + 1;
    private int slot = -1;

    public ValuesIterator() {
      cursor = new ObjectCursor<VType>();
    }

    @Override
    protected ObjectCursor<VType> fetch() {
      if (slot < max) {
        for (slot++; slot < max; slot++) {
          if (!(( keys[slot]) == 0)) {
            cursor.index = slot;
            cursor.value = (VType) values[slot];
            return cursor;
          }
        }
      }

      if (slot == max && hasEmptyKey) {
        cursor.index = slot;
        cursor.value = (VType) values[max];
        slot++;
        return cursor;
      }

      return done();
    }
  }

  
{@inheritDoc}

/**
   * {@inheritDoc}
   */
  @Override
  public ShortObjectHashMap<VType> clone() {
    try {
      /*  */
      ShortObjectHashMap<VType> cloned = (ShortObjectHashMap<VType>) super.clone();
      cloned.keys = keys.clone();
      cloned.values = values.clone();
      cloned.hasEmptyKey = cloned.hasEmptyKey;
      cloned.orderMixer = orderMixer.clone();
      return cloned;
    } catch (CloneNotSupportedException e) {
      throw new RuntimeException(e);
    }
  }

  
Convert the contents of this map to a human-friendly string.

/**
   * Convert the contents of this map to a human-friendly string.
   */
  @Override
  public String toString() {
    final StringBuilder buffer = new StringBuilder();
    buffer.append("[");

    boolean first = true;
    for (ShortObjectCursor<VType> cursor : this) {
      if (!first) {
        buffer.append(", ");
      }
      buffer.append(cursor.key);
      buffer.append("=>");
      buffer.append(cursor.value);
      first = false;
    }
    buffer.append("]");
    return buffer.toString();
  }

  @Override
  public String visualizeKeyDistribution(int characters) {
    return ShortBufferVisualizer.visualizeKeyDistribution(keys, mask, characters);
  }

  
Creates a hash map from two index-aligned arrays of key-value pairs.

/**
   * Creates a hash map from two index-aligned arrays of key-value pairs.
   */
  public static <VType> ShortObjectHashMap<VType> from(short[] keys, VType[] values) {
    if (keys.length != values.length) {
      throw new IllegalArgumentException("Arrays of keys and values must have an identical length.");
    }

    ShortObjectHashMap<VType> map = new ShortObjectHashMap<>(keys.length);
    for (int i = 0; i < keys.length; i++) {
      map.put(keys[i], values[i]);
    }

    return map;
  }
    
  
Returns a hash code for the given key.

The default implementation mixes the hash of the key with ShortObjectHashMap<VType>.keyMixer to differentiate hash order of keys between hash containers. Helps alleviate problems resulting from linear conflict resolution in open addressing.


The output from this function should evenly distribute keys across the
entire integer range.


/**
   * Returns a hash code for the given key.
   * 
   * <p>The default implementation mixes the hash of the key with {@link #keyMixer}
   * to differentiate hash order of keys between hash containers. Helps
   * alleviate problems resulting from linear conflict resolution in open
   * addressing.</p>
   * 
   * <p>The output from this function should evenly distribute keys across the
   * entire integer range.</p>
   */
    protected  
  int hashKey(short key) {
    assert !((key) == 0); // Handled as a special case (empty slot marker).
    return BitMixer.mix(key, this.keyMixer);
  }

  
Validate load factor range and return it. Override and suppress if you need
insane load factors.

/**
   * Validate load factor range and return it. Override and suppress if you need
   * insane load factors.
   */
  protected double verifyLoadFactor(double loadFactor) {
    checkLoadFactor(loadFactor, MIN_LOAD_FACTOR, MAX_LOAD_FACTOR);
    return loadFactor;
  }

  
Rehash from old buffers to new buffers. 

/**
   * Rehash from old buffers to new buffers. 
   */
  protected void rehash(short[] fromKeys, VType[] fromValues) {
    assert fromKeys.length == fromValues.length &&
           HashContainers.checkPowerOfTwo(fromKeys.length - 1);
    
    // Rehash all stored key/value pairs into the new buffers.
    final short[] keys =  this.keys;
    final VType[] values = (VType[]) this.values;
    final int mask = this.mask;
    short existing;

    // Copy the zero element's slot, then rehash everything else.
    int from = fromKeys.length - 1;
    keys[keys.length - 1] = fromKeys[from];
    values[values.length - 1] = fromValues[from];
    while (--from >= 0) {
      if (!((existing = fromKeys[from]) == 0)) {
        int slot = hashKey(existing) & mask;
        while (!((keys[slot]) == 0)) {
          slot = (slot + 1) & mask;
        }
        keys[slot] = existing;
        values[slot] = fromValues[from];
      }
    }
  }

  
Allocate new internal buffers. This method attempts to allocate
and assign internal buffers atomically (either allocations succeed or not).

/**
   * Allocate new internal buffers. This method attempts to allocate
   * and assign internal buffers atomically (either allocations succeed or not).
   */
  protected void allocateBuffers(int arraySize) {
    assert Integer.bitCount(arraySize) == 1;

    // Compute new hash mixer candidate before expanding.
    final int newKeyMixer = this.orderMixer.newKeyMixer(arraySize);

    // Ensure no change is done if we hit an OOM.
    short[] prevKeys =  this.keys;
    VType[] prevValues = (VType[]) this.values;
    try {
      int emptyElementSlot = 1;
      this.keys = (new short [arraySize + emptyElementSlot]);
      this.values = ((VType[]) new Object [arraySize + emptyElementSlot]);
    } catch (OutOfMemoryError e) {
      this.keys = prevKeys;
      this.values = prevValues;
      throw new BufferAllocationException(
          "Not enough memory to allocate buffers for rehashing: %,d -> %,d", 
          e,
          this.mask + 1, 
          arraySize);
    }

    this.resizeAt = expandAtCount(arraySize, loadFactor);
    this.keyMixer = newKeyMixer;
    this.mask = arraySize - 1;
  }

  
This method is invoked when there is a new key/ value pair to be inserted into
the buffers but there is not enough empty slots to do so.
New buffers are allocated. If this succeeds, we know we can proceed
with rehashing so we assign the pending element to the previous buffer
(possibly violating the invariant of having at least one empty slot)
and rehash all keys, substituting new buffers at the end.  

/**
   * This method is invoked when there is a new key/ value pair to be inserted into
   * the buffers but there is not enough empty slots to do so.
   * 
   * New buffers are allocated. If this succeeds, we know we can proceed
   * with rehashing so we assign the pending element to the previous buffer
   * (possibly violating the invariant of having at least one empty slot)
   * and rehash all keys, substituting new buffers at the end.  
   */
  protected void allocateThenInsertThenRehash(int slot, short pendingKey, VType pendingValue) {
    assert assigned == resizeAt
           && (( keys[slot]) == 0)
           && !((pendingKey) == 0);

    // Try to allocate new buffers first. If we OOM, we leave in a consistent state.
    final short[] prevKeys =  this.keys;
    final VType[] prevValues = (VType[]) this.values;
    allocateBuffers(nextBufferSize(mask + 1, size(), loadFactor));
    assert this.keys.length > prevKeys.length;

    // We have succeeded at allocating new data so insert the pending key/value at
    // the free slot in the old arrays before rehashing.
    prevKeys[slot] = pendingKey;
    prevValues[slot] = pendingValue;

    // Rehash old keys, including the pending key.
    rehash(prevKeys, prevValues);
  }
  
  
Shift all the slot-conflicting keys and values allocated to 
(and including) slot.

/**
   * Shift all the slot-conflicting keys and values allocated to 
   * (and including) <code>slot</code>.
   */
  protected void shiftConflictingKeys(int gapSlot) {
    final short[] keys =  this.keys;
    final VType[] values = (VType[]) this.values;
    final int mask = this.mask;

    // Perform shifts of conflicting keys to fill in the gap.
    int distance = 0;
    while (true) {
      final int slot = (gapSlot + (++distance)) & mask;
      final short existing = keys[slot];
      if (((existing) == 0)) {
        break;
      }

      final int idealSlot = hashKey(existing);
      final int shift = (slot - idealSlot) & mask;
      if (shift >= distance) {
        // Entry at this position was originally at or before the gap slot.
        // Move the conflict-shifted entry to the gap's position and repeat the procedure
        // for any entries to the right of the current position, treating it
        // as the new gap.
        keys[gapSlot] = existing;
        values[gapSlot] = values[slot]; 
        gapSlot = slot;
        distance = 0;
      }
    }

    // Mark the last found gap slot without a conflict as empty.
    keys[gapSlot] = ((short) 0);
    values[gapSlot] = null;
    assigned--;
  }

        
}