/*
 * Copyright (c) 2003, 2012, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

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;
 }

 @SuppressWarnings("unchecked")
 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 o 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;
 }
}