/*

  * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.

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

  *

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

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

  * published by the Free Software Foundation.  Oracle designates this

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

  * by Oracle in the LICENSE file that accompanied this code.

  *

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

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

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

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

  * accompanied this code).

  *

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

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

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

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

  */

 package java.util;

 import java.util.Map.Entry;

 import sun.misc.SharedSecrets;

 /**

  * A specialized {@link Map} implementation for use with enum type keys.  All

  * of the keys in an enum map must come from a single enum type that is

  * specified, explicitly or implicitly, when the map is created.  Enum maps

  * are represented internally as arrays.  This representation is extremely

  * compact and efficient.

  *

  * <p>Enum maps are maintained in the <i>natural order</i> of their keys

  * (the order in which the enum constants are declared).  This is reflected

  * in the iterators returned by the collections views ({@link #keySet()},

  * {@link #entrySet()}, and {@link #values()}).

  *

  * <p>Iterators returned by the collection views are <i>weakly consistent</i>:

  * they will never throw {@link ConcurrentModificationException} and they may

  * or may not show the effects of any modifications to the map that occur while

  * the iteration is in progress.

  *

  * <p>Null keys are not permitted.  Attempts to insert a null key will

  * throw {@link NullPointerException}.  Attempts to test for the

  * presence of a null key or to remove one will, however, function properly.

  * Null values are permitted.

  * <P>Like most collection implementations <tt>EnumMap</tt> is not

  * synchronized. If multiple threads access an enum map concurrently, and at

  * least one of the threads modifies the map, it should be synchronized

  * externally.  This is typically accomplished by synchronizing on some

  * object that naturally encapsulates the enum map.  If no such object exists,

  * the map should be "wrapped" using the {@link Collections#synchronizedMap}

  * method.  This is best done at creation time, to prevent accidental

  * unsynchronized access:

  *

  * <pre>

  *     Map<EnumKey, V> m

  *         = Collections.synchronizedMap(new EnumMap<EnumKey, V>(...));

  * </pre>

  *

  * <p>Implementation note: All basic operations execute in constant time.

  * They are likely (though not guaranteed) to be faster than their

  * {@link HashMap} counterparts.

  *

  * <p>This class is a member of the

  * <a href="{@docRoot}/../technotes/guides/collections/index.html">

  * Java Collections Framework</a>.

  *

  * @author Josh Bloch

  * @see EnumSet

  * @since 1.5

  */

 public class EnumMap<K extends Enum<K>, V> extends AbstractMap<K, V>

     implements java.io.Serializable, Cloneable

 {

     /**

      * The <tt>Class</tt> object for the enum type of all the keys of this map.

      *

      * @serial

      */

     private final Class<K> keyType;

     /**

      * All of the values comprising K.  (Cached for performance.)

      */

     private transient K[] keyUniverse;

     /**

      * Array representation of this map.  The ith element is the value

      * to which universe[i] is currently mapped, or null if it isn't

      * mapped to anything, or NULL if it's mapped to null.

      */

     private transient Object[] vals;

     /**

      * The number of mappings in this map.

      */

     private transient int size = 0;

     /**

      * Distinguished non-null value for representing null values.

      */

     private static final Object NULL = new Integer(0);

     private Object maskNull(Object value) {

         return (value == null ? NULL : value);

     }

     private V unmaskNull(Object value) {

         return (V) (value == NULL ? null : value);

     }

     private static final Enum[] ZERO_LENGTH_ENUM_ARRAY = new Enum[0];

     /**

      * Creates an empty enum map with the specified key type.

      *

      * @param keyType the class object of the key type for this enum map

      * @throws NullPointerException if <tt>keyType</tt> is null

      */

     public EnumMap(Class<K> keyType) {

         this.keyType = keyType;

         keyUniverse = getKeyUniverse(keyType);

         vals = new Object[keyUniverse.length];

     }

     /**

      * Creates an enum map with the same key type as the specified enum

      * map, initially containing the same mappings (if any).

      *

      * @param m the enum map from which to initialize this enum map

      * @throws NullPointerException if <tt>m</tt> is null

      */

     public EnumMap(EnumMap<K, ? extends V> m) {

         keyType = m.keyType;

         keyUniverse = m.keyUniverse;

         vals = m.vals.clone();

         size = m.size;

     }

     /**

      * Creates an enum map initialized from the specified map.  If the

      * specified map is an <tt>EnumMap</tt> instance, this constructor behaves

      * identically to {@link #EnumMap(EnumMap)}.  Otherwise, the specified map

      * must contain at least one mapping (in order to determine the new

      * enum map's key type).

      *

      * @param m the map from which to initialize this enum map

      * @throws IllegalArgumentException if <tt>m</tt> is not an

      *     <tt>EnumMap</tt> instance and contains no mappings

      * @throws NullPointerException if <tt>m</tt> is null

      */

     public EnumMap(Map<K, ? extends V> m) {

         if (m instanceof EnumMap) {

             EnumMap<K, ? extends V> em = (EnumMap<K, ? extends V>) m;

             keyType = em.keyType;

             keyUniverse = em.keyUniverse;

             vals = em.vals.clone();

             size = em.size;

         } else {

             if (m.isEmpty())

                 throw new IllegalArgumentException("Specified map is empty");

             keyType = m.keySet().iterator().next().getDeclaringClass();

             keyUniverse = getKeyUniverse(keyType);

             vals = new Object[keyUniverse.length];

             putAll(m);

         }

     }

     // Query Operations

     /**

      * Returns the number of key-value mappings in this map.

      *

      * @return the number of key-value mappings in this map

      */

     public int size() {

         return size;

     }

     /**

      * Returns <tt>true</tt> if this map maps one or more keys to the

      * specified value.

      *

      * @param value the value whose presence in this map is to be tested

      * @return <tt>true</tt> if this map maps one or more keys to this value

      */

     public boolean containsValue(Object value) {

         value = maskNull(value);

         for (Object val : vals)

             if (value.equals(val))

                 return true;

         return false;

     }

     /**

      * Returns <tt>true</tt> if this map contains a mapping for the specified

      * key.

      *

      * @param key the key whose presence in this map is to be tested

      * @return <tt>true</tt> if this map contains a mapping for the specified

      *            key

      */

     public boolean containsKey(Object key) {

         return isValidKey(key) && vals[((Enum)key).ordinal()] != null;

     }

     private boolean containsMapping(Object key, Object value) {

         return isValidKey(key) &&

             maskNull(value).equals(vals[((Enum)key).ordinal()]);

     }

     /**

      * Returns the value to which the specified key is mapped,

      * or {@code null} if this map contains no mapping for the key.

      *

      * <p>More formally, if this map contains a mapping from a key

      * {@code k} to a value {@code v} such that {@code (key == k)},

      * then this method returns {@code v}; otherwise it returns

      * {@code null}.  (There can be at most one such mapping.)

      *

      * <p>A return value of {@code null} does not <i>necessarily</i>

      * indicate that the map contains no mapping for the key; it's also

      * possible that the map explicitly maps the key to {@code null}.

      * The {@link #containsKey containsKey} operation may be used to

      * distinguish these two cases.

      */

     public V get(Object key) {

         return (isValidKey(key) ?

                 unmaskNull(vals[((Enum)key).ordinal()]) : null);

     }

     // Modification Operations

     /**

      * Associates the specified value with the specified key in this map.

      * If the map previously contained a mapping for this key, the old

      * value is replaced.

      *

      * @param key the key with which the specified value is to be associated

      * @param value the value to be associated with the specified key

      *

      * @return the previous value associated with specified key, or

      *     <tt>null</tt> if there was no mapping for key.  (A <tt>null</tt>

      *     return can also indicate that the map previously associated

      *     <tt>null</tt> with the specified key.)

      * @throws NullPointerException if the specified key is null

      */

     public V put(K key, V value) {

         typeCheck(key);

         int index = key.ordinal();

         Object oldValue = vals[index];

         vals[index] = maskNull(value);

         if (oldValue == null)

             size++;

         return unmaskNull(oldValue);

     }

     /**

      * Removes the mapping for this key from this map if present.

      *

      * @param key the key whose mapping is to be removed from the map

      * @return the previous value associated with specified key, or

      *     <tt>null</tt> if there was no entry for key.  (A <tt>null</tt>

      *     return can also indicate that the map previously associated

      *     <tt>null</tt> with the specified key.)

      */

     public V remove(Object key) {

         if (!isValidKey(key))

             return null;

         int index = ((Enum)key).ordinal();

         Object oldValue = vals[index];

         vals[index] = null;

         if (oldValue != null)

             size--;

         return unmaskNull(oldValue);

     }

     private boolean removeMapping(Object key, Object value) {

         if (!isValidKey(key))

             return false;

         int index = ((Enum)key).ordinal();

         if (maskNull(value).equals(vals[index])) {

             vals[index] = null;

             size--;

             return true;

         }

         return false;

     }

     /**

      * Returns true if key is of the proper type to be a key in this

      * enum map.

      */

     private boolean isValidKey(Object key) {

         if (key == null)

             return false;

         // Cheaper than instanceof Enum followed by getDeclaringClass

         Class keyClass = key.getClass();

         return keyClass == keyType || keyClass.getSuperclass() == keyType;

     }

     // Bulk Operations

     /**

      * Copies all of the mappings from the specified map to this map.

      * These mappings will replace any mappings that this map had for

      * any of the keys currently in the specified map.

      *

      * @param m the mappings to be stored in this map

      * @throws NullPointerException the specified map is null, or if

      *     one or more keys in the specified map are null

      */

     public void putAll(Map<? extends K, ? extends V> m) {

         if (m instanceof EnumMap) {

             EnumMap<? extends K, ? extends V> em =

                 (EnumMap<? extends K, ? extends V>)m;

             if (em.keyType != keyType) {

                 if (em.isEmpty())

                     return;

                 throw new ClassCastException(em.keyType + " != " + keyType);

             }

             for (int i = 0; i < keyUniverse.length; i++) {

                 Object emValue = em.vals[i];

                 if (emValue != null) {

                     if (vals[i] == null)

                         size++;

                     vals[i] = emValue;

                 }

             }

         } else {

             super.putAll(m);

         }

     }

     /**

      * Removes all mappings from this map.

      */

     public void clear() {

         Arrays.fill(vals, null);

         size = 0;

     }

     // Views

     /**

      * This field is initialized to contain an instance of the entry set

      * view the first time this view is requested.  The view is stateless,

      * so there's no reason to create more than one.

      */

     private transient Set<Map.Entry<K,V>> entrySet = null;

     /**

      * Returns a {@link Set} view of the keys contained in this map.

      * The returned set obeys the general contract outlined in

      * {@link Map#keySet()}.  The set's iterator will return the keys

      * in their natural order (the order in which the enum constants

      * are declared).

      *

      * @return a set view of the keys contained in this enum map

      */

     public Set<K> keySet() {

         Set<K> ks = keySet;

         if (ks != null)

             return ks;

         else

             return keySet = new KeySet();

     }

     private class KeySet extends AbstractSet<K> {

         public Iterator<K> iterator() {

             return new KeyIterator();

         }

         public int size() {

             return size;

         }

         public boolean contains(Object o) {

             return containsKey(o);

         }

         public boolean remove(Object o) {

             int oldSize = size;

             EnumMap.this.remove(o);

             return size != oldSize;

         }

         public void clear() {

             EnumMap.this.clear();

         }

     }

     /**

      * Returns a {@link Collection} view of the values contained in this map.

      * The returned collection obeys the general contract outlined in

      * {@link Map#values()}.  The collection's iterator will return the

      * values in the order their corresponding keys appear in map,

      * which is their natural order (the order in which the enum constants

      * are declared).

      *

      * @return a collection view of the values contained in this map

      */

     public Collection<V> values() {

         Collection<V> vs = values;

         if (vs != null)

             return vs;

         else

             return values = new Values();

     }

     private class Values extends AbstractCollection<V> {

         public Iterator<V> iterator() {

             return new ValueIterator();

         }

         public int size() {

             return size;

         }

         public boolean contains(Object o) {

             return containsValue(o);

         }

         public boolean remove(Object o) {

             o = maskNull(o);

             for (int i = 0; i < vals.length; i++) {

                 if (o.equals(vals[i])) {

                     vals[i] = null;

                     size--;

                     return true;

                 }

             }

             return false;

         }

         public void clear() {

             EnumMap.this.clear();

         }

     }

     /**

      * Returns a {@link Set} view of the mappings contained in this map.

      * The returned set obeys the general contract outlined in

      * {@link Map#keySet()}.  The set's iterator will return the

      * mappings in the order their keys appear in map, which is their

      * natural order (the order in which the enum constants are declared).

      *

      * @return a set view of the mappings contained in this enum map

      */

     public Set<Map.Entry<K,V>> entrySet() {

         Set<Map.Entry<K,V>> es = entrySet;

         if (es != null)

             return es;

         else

             return entrySet = new EntrySet();

     }

     private class EntrySet extends AbstractSet<Map.Entry<K,V>> {

         public Iterator<Map.Entry<K,V>> iterator() {

             return new EntryIterator();

         }

         public boolean contains(Object o) {

             if (!(o instanceof Map.Entry))

                 return false;

             Map.Entry entry = (Map.Entry)o;

             return containsMapping(entry.getKey(), entry.getValue());

         }

         public boolean remove(Object o) {

             if (!(o instanceof Map.Entry))

                 return false;

             Map.Entry entry = (Map.Entry)o;

             return removeMapping(entry.getKey(), entry.getValue());

         }

         public int size() {

             return size;

         }

         public void clear() {

             EnumMap.this.clear();

         }

         public Object[] toArray() {

             return fillEntryArray(new Object[size]);

         }

         @SuppressWarnings("unchecked")

         public <T> T[] toArray(T[] a) {

             int size = size();

             if (a.length < size)

                 a = (T[])java.lang.reflect.Array

                     .newInstance(a.getClass().getComponentType(), size);

             if (a.length > size)

                 a[size] = null;

             return (T[]) fillEntryArray(a);

         }

         private Object[] fillEntryArray(Object[] a) {

             int j = 0;

             for (int i = 0; i < vals.length; i++)

                 if (vals[i] != null)

                     a[j++] = new AbstractMap.SimpleEntry<>(

                         keyUniverse[i], unmaskNull(vals[i]));

             return a;

         }

     }

     private abstract class EnumMapIterator<T> implements Iterator<T> {

         // Lower bound on index of next element to return

         int index = 0;

         // Index of last returned element, or -1 if none

         int lastReturnedIndex = -1;

         public boolean hasNext() {

             while (index < vals.length && vals[index] == null)

                 index++;

             return index != vals.length;

         }

         public void remove() {

             checkLastReturnedIndex();

             if (vals[lastReturnedIndex] != null) {

                 vals[lastReturnedIndex] = null;

                 size--;

             }

             lastReturnedIndex = -1;

         }

         private void checkLastReturnedIndex() {

             if (lastReturnedIndex < 0)

                 throw new IllegalStateException();

         }

     }

     private class KeyIterator extends EnumMapIterator<K> {

         public K next() {

             if (!hasNext())

                 throw new NoSuchElementException();

             lastReturnedIndex = index++;

             return keyUniverse[lastReturnedIndex];

         }

     }

     private class ValueIterator extends EnumMapIterator<V> {

         public V next() {

             if (!hasNext())

                 throw new NoSuchElementException();

             lastReturnedIndex = index++;

             return unmaskNull(vals[lastReturnedIndex]);

         }

     }

     private class EntryIterator extends EnumMapIterator<Map.Entry<K,V>> {

         private Entry lastReturnedEntry = null;

         public Map.Entry<K,V> next() {

             if (!hasNext())

                 throw new NoSuchElementException();

             lastReturnedEntry = new Entry(index++);

             return lastReturnedEntry;

         }

         public void remove() {

             lastReturnedIndex =

                 ((null == lastReturnedEntry) ? -1 : lastReturnedEntry.index);

             super.remove();

             lastReturnedEntry.index = lastReturnedIndex;

             lastReturnedEntry = null;

         }

         private class Entry implements Map.Entry<K,V> {

             private int index;

             private Entry(int index) {

                 this.index = index;

             }

             public K getKey() {

                 checkIndexForEntryUse();

                 return keyUniverse[index];

             }

             public V getValue() {

                 checkIndexForEntryUse();

                 return unmaskNull(vals[index]);

             }

             public V setValue(V value) {

                 checkIndexForEntryUse();

                 V oldValue = unmaskNull(vals[index]);

                 vals[index] = maskNull(value);

                 return oldValue;

             }

             public boolean equals(Object o) {

                 if (index < 0)

                     return o == this;

                 if (!(o instanceof Map.Entry))

                     return false;

                 Map.Entry e = (Map.Entry)o;

                 V ourValue = unmaskNull(vals[index]);

                 Object hisValue = e.getValue();

                 return (e.getKey() == keyUniverse[index] &&

                         (ourValue == hisValue ||

                          (ourValue != null && ourValue.equals(hisValue))));

             }

             public int hashCode() {

                 if (index < 0)

                     return super.hashCode();

                 return entryHashCode(index);

             }

             public String toString() {

                 if (index < 0)

                     return super.toString();

                 return keyUniverse[index] + "="

                     + unmaskNull(vals[index]);

             }

             private void checkIndexForEntryUse() {

                 if (index < 0)

                     throw new IllegalStateException("Entry was removed");

             }

         }

     }

     // Comparison and hashing

     /**

      * Compares the specified object with this map for equality.  Returns

      * <tt>true</tt> if the given object is also a map and the two maps

      * represent the same mappings, as specified in the {@link

      * Map#equals(Object)} contract.

      *

      * @param o the object to be compared for equality with this map

      * @return <tt>true</tt> if the specified object is equal to this map

      */

     public boolean equals(Object o) {

         if (this == o)

             return true;

         if (o instanceof EnumMap)

             return equals((EnumMap)o);

         if (!(o instanceof Map))

             return false;

         Map<K,V> m = (Map<K,V>)o;

         if (size != m.size())

             return false;

         for (int i = 0; i < keyUniverse.length; i++) {

             if (null != vals[i]) {

                 K key = keyUniverse[i];

                 V value = unmaskNull(vals[i]);

                 if (null == value) {

                     if (!((null == m.get(key)) && m.containsKey(key)))

                        return false;

                 } else {

                    if (!value.equals(m.get(key)))

                       return false;

                 }

             }

         }

         return true;

     }

     private boolean equals(EnumMap em) {

         if (em.keyType != keyType)

             return size == 0 && em.size == 0;

         // Key types match, compare each value

         for (int i = 0; i < keyUniverse.length; i++) {

             Object ourValue =    vals[i];

             Object hisValue = em.vals[i];

             if (hisValue != ourValue &&

                 (hisValue == null || !hisValue.equals(ourValue)))

                 return false;

         }

         return true;

     }

     /**

      * Returns the hash code value for this map.  The hash code of a map is

      * defined to be the sum of the hash codes of each entry in the map.

      */

     public int hashCode() {

         int h = 0;

         for (int i = 0; i < keyUniverse.length; i++) {

             if (null != vals[i]) {

                 h += entryHashCode(i);

             }

         }

         return h;

     }

     private int entryHashCode(int index) {

         return (keyUniverse[index].hashCode() ^ vals[index].hashCode());

     }

     /**

      * Returns a shallow copy of this enum map.  (The values themselves

      * are not cloned.

      *

      * @return a shallow copy of this enum map

      */

     public EnumMap<K, V> clone() {

         EnumMap<K, V> result = null;

         try {

             result = (EnumMap<K, V>) super.clone();

         } catch(CloneNotSupportedException e) {

             throw new AssertionError();

         }

         result.vals = result.vals.clone();

         return result;

     }

     /**

      * Throws an exception if e is not of the correct type for this enum set.

      */

     private void typeCheck(K key) {

         Class keyClass = key.getClass();

         if (keyClass != keyType && keyClass.getSuperclass() != keyType)

             throw new ClassCastException(keyClass + " != " + keyType);

     }

     /**

      * Returns all of the values comprising K.

      * The result is uncloned, cached, and shared by all callers.

      */

     private static <K extends Enum<K>> K[] getKeyUniverse(Class<K> keyType) {

         return SharedSecrets.getJavaLangAccess()

                                         .getEnumConstantsShared(keyType);

     }

     private static final long serialVersionUID = 458661240069192865L;

     /**

      * Save the state of the <tt>EnumMap</tt> instance to a stream (i.e.,

      * serialize it).

      *

      * @serialData The <i>size</i> of the enum map (the number of key-value

      *             mappings) is emitted (int), followed by the key (Object)

      *             and value (Object) for each key-value mapping represented

      *             by the enum map.

      */

     private void writeObject(java.io.ObjectOutputStream s)

         throws java.io.IOException

     {

         // Write out the key type and any hidden stuff

         s.defaultWriteObject();

         // Write out size (number of Mappings)

         s.writeInt(size);

         // Write out keys and values (alternating)

         int entriesToBeWritten = size;

         for (int i = 0; entriesToBeWritten > 0; i++) {

             if (null != vals[i]) {

                 s.writeObject(keyUniverse[i]);

                 s.writeObject(unmaskNull(vals[i]));

                 entriesToBeWritten--;

             }

         }

     }

     /**

      * Reconstitute the <tt>EnumMap</tt> instance from a stream (i.e.,

      * deserialize it).

      */

     private void readObject(java.io.ObjectInputStream s)

         throws java.io.IOException, ClassNotFoundException

     {

         // Read in the key type and any hidden stuff

         s.defaultReadObject();

         keyUniverse = getKeyUniverse(keyType);

         vals = new Object[keyUniverse.length];

         // Read in size (number of Mappings)

         int size = s.readInt();

         // Read the keys and values, and put the mappings in the HashMap

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

             K key = (K) s.readObject();

             V value = (V) s.readObject();

             put(key, value);

         }

     }

 }