/*

 * 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;

    }

}