/*

  * Copyright (c) 2003, 2011, 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;

 /**

  * Private implementation class for EnumSet, for "regular sized" enum types

  * (i.e., those with 64 or fewer enum constants).

  *

  * @author Josh Bloch

  * @since 1.5

  * @serial exclude

  */

 class RegularEnumSet<E extends Enum<E>> extends EnumSet<E> {

     private static final long serialVersionUID = 3411599620347842686L;

     /**

      * Bit vector representation of this set.  The 2^k bit indicates the

      * presence of universe[k] in this set.

      */

     private long elements = 0L;

     RegularEnumSet(Class<E>elementType, Enum[] universe) {

         super(elementType, universe);

     }

     void addRange(E from, E to) {

         elements = (-1L >>>  (from.ordinal() - to.ordinal() - 1)) << from.ordinal();

     }

     void addAll() {

         if (universe.length != 0)

             elements = -1L >>> -universe.length;

     }

     void complement() {

         if (universe.length != 0) {

             elements = ~elements;

             elements &= -1L >>> -universe.length;  // Mask unused bits

         }

     }

     /**

      * Returns an iterator over the elements contained in this set.  The

      * iterator traverses the elements in their <i>natural order</i> (which is

      * the order in which the enum constants are declared). The returned

      * Iterator is a "snapshot" iterator that will never throw {@link

      * ConcurrentModificationException}; the elements are traversed as they

      * existed when this call was invoked.

      *

      * @return an iterator over the elements contained in this set

      */

     public Iterator<E> iterator() {

         return new EnumSetIterator<>();

     }

     private class EnumSetIterator<E extends Enum<E>> implements Iterator<E> {

         /**

          * A bit vector representing the elements in the set not yet

          * returned by this iterator.

          */

         long unseen;

         /**

          * The bit representing the last element returned by this iterator

          * but not removed, or zero if no such element exists.

          */

         long lastReturned = 0;

         EnumSetIterator() {

             unseen = elements;

         }

         public boolean hasNext() {

             return unseen != 0;

         }

         public E next() {

             if (unseen == 0)

                 throw new NoSuchElementException();

             lastReturned = unseen & -unseen;

             unseen -= lastReturned;

             return (E) universe[Long.numberOfTrailingZeros(lastReturned)];

         }

         public void remove() {

             if (lastReturned == 0)

                 throw new IllegalStateException();

             elements &= ~lastReturned;

             lastReturned = 0;

         }

     }

     /**

      * Returns the number of elements in this set.

      *

      * @return the number of elements in this set

      */

     public int size() {

         return Long.bitCount(elements);

     }

     /**

      * Returns <tt>true</tt> if this set contains no elements.

      *

      * @return <tt>true</tt> if this set contains no elements

      */

     public boolean isEmpty() {

         return elements == 0;

     }

     /**

      * Returns <tt>true</tt> if this set contains the specified element.

      *

      * @param e element to be checked for containment in this collection

      * @return <tt>true</tt> if this set contains the specified element

      */

     public boolean contains(Object e) {

         if (e == null)

             return false;

         Class eClass = e.getClass();

         if (eClass != elementType && eClass.getSuperclass() != elementType)

             return false;

         return (elements & (1L << ((Enum)e).ordinal())) != 0;

     }

     // Modification Operations

     /**

      * Adds the specified element to this set if it is not already present.

      *

      * @param e element to be added to this set

      * @return <tt>true</tt> if the set changed as a result of the call

      *

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

      */

     public boolean add(E e) {

         typeCheck(e);

         long oldElements = elements;

         elements |= (1L << ((Enum)e).ordinal());

         return elements != oldElements;

     }

     /**

      * Removes the specified element from this set if it is present.

      *

      * @param e element to be removed from this set, if present

      * @return <tt>true</tt> if the set contained the specified element

      */

     public boolean remove(Object e) {

         if (e == null)

             return false;

         Class eClass = e.getClass();

         if (eClass != elementType && eClass.getSuperclass() != elementType)

             return false;

         long oldElements = elements;

         elements &= ~(1L << ((Enum)e).ordinal());

         return elements != oldElements;

     }

     // Bulk Operations

     /**

      * Returns <tt>true</tt> if this set contains all of the elements

      * in the specified collection.

      *

      * @param c collection to be checked for containment in this set

      * @return <tt>true</tt> if this set contains all of the elements

      *        in the specified collection

      * @throws NullPointerException if the specified collection is null

      */

     public boolean containsAll(Collection<?> c) {

         if (!(c instanceof RegularEnumSet))

             return super.containsAll(c);

         RegularEnumSet es = (RegularEnumSet)c;

         if (es.elementType != elementType)

             return es.isEmpty();

         return (es.elements & ~elements) == 0;

     }

     /**

      * Adds all of the elements in the specified collection to this set.

      *

      * @param c collection whose elements are to be added to this set

      * @return <tt>true</tt> if this set changed as a result of the call

      * @throws NullPointerException if the specified collection or any

      *     of its elements are null

      */

     public boolean addAll(Collection<? extends E> c) {

         if (!(c instanceof RegularEnumSet))

             return super.addAll(c);

         RegularEnumSet es = (RegularEnumSet)c;

         if (es.elementType != elementType) {

             if (es.isEmpty())

                 return false;

             else

                 throw new ClassCastException(

                     es.elementType + " != " + elementType);

         }

         long oldElements = elements;

         elements |= es.elements;

         return elements != oldElements;

     }

     /**

      * Removes from this set all of its elements that are contained in

      * the specified collection.

      *

      * @param c elements to be removed from this set

      * @return <tt>true</tt> if this set changed as a result of the call

      * @throws NullPointerException if the specified collection is null

      */

     public boolean removeAll(Collection<?> c) {

         if (!(c instanceof RegularEnumSet))

             return super.removeAll(c);

         RegularEnumSet es = (RegularEnumSet)c;

         if (es.elementType != elementType)

             return false;

         long oldElements = elements;

         elements &= ~es.elements;

         return elements != oldElements;

     }

     /**

      * Retains only the elements in this set that are contained in the

      * specified collection.

      *

      * @param c elements to be retained in this set

      * @return <tt>true</tt> if this set changed as a result of the call

      * @throws NullPointerException if the specified collection is null

      */

     public boolean retainAll(Collection<?> c) {

         if (!(c instanceof RegularEnumSet))

             return super.retainAll(c);

         RegularEnumSet<?> es = (RegularEnumSet<?>)c;

         if (es.elementType != elementType) {

             boolean changed = (elements != 0);

             elements = 0;

             return changed;

         }

         long oldElements = elements;

         elements &= es.elements;

         return elements != oldElements;

     }

     /**

      * Removes all of the elements from this set.

      */

     public void clear() {

         elements = 0;

     }

     /**

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

      * <tt>true</tt> if the given object is also a set, the two sets have

      * the same size, and every member of the given set is contained in

      * this set.

      *

      * @param e object to be compared for equality with this set

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

      */

     public boolean equals(Object o) {

         if (!(o instanceof RegularEnumSet))

             return super.equals(o);

         RegularEnumSet es = (RegularEnumSet)o;

         if (es.elementType != elementType)

             return elements == 0 && es.elements == 0;

         return es.elements == elements;

     }

 }