2.4/dev/core/src/com/google/gwt/dev/util/collect/HashSet.java - gwt - Git at Google

 /*
  * Copyright 2009 Google Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not
  * use this file except in compliance with the License. You may obtain a copy of
  * the License at
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  * License for the specific language governing permissions and limitations under
  * the License.
  */
 package com.google.gwt.dev.util.collect;

 import java.io.IOException;
 import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
 import java.io.Serializable;
 import java.lang.reflect.Array;
 import java.util.AbstractSet;
 import java.util.Collection;
 import java.util.ConcurrentModificationException;
 import java.util.Iterator;
 import java.util.NoSuchElementException;

 /**
  * A memory-efficient hash set.
  *
  * @param <E> the element type
  */
 public class HashSet<E> extends AbstractSet<E> implements Serializable {

   private class SetIterator implements Iterator<E> {
     private Object[] coModCheckTable = table;
     private int index = 0;
     private int last = -1;

     public boolean hasNext() {
       if (coModCheckTable != table) {
         throw new ConcurrentModificationException();
       }
       advanceToItem();
       return index < table.length;
     }

     @SuppressWarnings("unchecked")
     public E next() {
       if (!hasNext()) {
         throw new NoSuchElementException();
       }
       last = index;
       return (E) unmaskNull(table[index++]);
     }

     public void remove() {
       if (last < 0) {
         throw new IllegalStateException();
       }
       if (coModCheckTable != table) {
         throw new ConcurrentModificationException();
       }
       internalRemove(last);
       if (table[last] != null) {
         // Hole was plugged.
         index = last;
       }
       last = -1;
     }

     private void advanceToItem() {
       for (; index < table.length; ++index) {
         if (table[index] != null) {
           return;
         }
       }
     }
   }

   /**
    * In the interest of memory-savings, we start with the smallest feasible
    * power-of-two table size that can hold three items without rehashing. If we
    * started with a size of 2, we'd have to expand as soon as the second item
    * was added.
    */
   private static final int INITIAL_TABLE_SIZE = 4;

   private static final Object NULL_ITEM = new Serializable() {
     Object readResolve() {
       return NULL_ITEM;
     }
   };

   static Object maskNull(Object o) {
     return (o == null) ? NULL_ITEM : o;
   }

   static Object unmaskNull(Object o) {
     return (o == NULL_ITEM) ? null : o;
   }

   /**
    * Number of objects in this set; transient due to custom serialization.
    * Default access to avoid synthetic accessors from inner classes.
    */
   transient int size = 0;

   /**
    * Backing store for all the objects; transient due to custom serialization.
    * Default access to avoid synthetic accessors from inner classes.
    */
   transient Object[] table;

   public HashSet() {
     table = new Object[INITIAL_TABLE_SIZE];
   }

   public HashSet(Collection<? extends E> c) {
     int newCapacity = INITIAL_TABLE_SIZE;
     int expectedSize = c.size();
     while (newCapacity * 3 < expectedSize * 4) {
       newCapacity <<= 1;
     }

     table = new Object[newCapacity];
     super.addAll(c);
   }

   /**
    * Works just like {@link #HashSet(Collection)}, but for arrays. Used to avoid
    * having to synthesize a collection in {@link Sets}.
    */
   HashSet(E[] c) {
     int newCapacity = INITIAL_TABLE_SIZE;
     int expectedSize = c.length;
     while (newCapacity * 3 < expectedSize * 4) {
       newCapacity <<= 1;
     }

     table = new Object[newCapacity];
     for (E e : c) {
       add(e);
     }
   }

   @Override
   public boolean add(E e) {
     int index = findOrEmpty(e);
     if (table[index] == null) {
       // Not in the map, may need to grow.
       if (ensureSizeFor(++size)) {
         // If we had to grow the table, must recompute the index.
         index = findOrEmpty(e);
       }
       table[index] = maskNull(e);
       return true;
     }
     return false;
   }

   @Override
   public boolean addAll(Collection<? extends E> c) {
     resizeForJoin(c.size());
     return super.addAll(c);
   }

   @Override
   public void clear() {
     table = new Object[INITIAL_TABLE_SIZE];
     size = 0;
   }

   @Override
   public boolean contains(Object o) {
     return find(o) >= 0;
   }

   @Override
   public Iterator<E> iterator() {
     return new SetIterator();
   }

   @Override
   public boolean remove(Object o) {
     int index = find(o);
     if (index < 0) {
       return false;
     }
     internalRemove(index);
     return true;
   }

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

   @Override
   public Object[] toArray() {
     return toArray(new Object[size]);
   }

   @SuppressWarnings("unchecked")
   @Override
   public <T> T[] toArray(T[] a) {
     if (a.length < size) {
       a = (T[]) Array.newInstance(a.getClass().getComponentType(), size);
     }
     int index = 0;
     for (int i = 0; i < table.length; ++i) {
       Object e = table[i];
       if (e != null) {
         a[index++] = (T) unmaskNull(e);
       }
     }
     while (index < a.length) {
       a[index++] = null;
     }
     return a;
   }

   /**
    * Adapted from {@link org.apache.commons.collections.map.AbstractHashedMap}.
    */
   @SuppressWarnings("unchecked")
   protected void doReadObject(ObjectInputStream in) throws IOException,
       ClassNotFoundException {
     table = new Object[in.readInt()];
     int items = in.readInt();
     for (int i = 0; i < items; i++) {
       add((E) in.readObject());
     }
   }

   /**
    * Adapted from {@link org.apache.commons.collections.map.AbstractHashedMap}.
    */
   protected void doWriteObject(ObjectOutputStream out) throws IOException {
     out.writeInt(table.length);
     out.writeInt(size);
     for (int i = 0; i < table.length; ++i) {
       Object e = table[i];
       if (e != null) {
         out.writeObject(unmaskNull(e));
       }
     }
   }

   /**
    * Returns whether two items are equal for the purposes of this set.
    */
   protected boolean itemEquals(Object a, Object b) {
     return (a == null) ? (b == null) : a.equals(b);
   }

   /**
    * Return the hashCode for an item.
    */
   protected int itemHashCode(Object o) {
     return (o == null) ? 0 : o.hashCode();
   }

   /**
    * Removes the item at the specified index, and performs internal management
    * to make sure we don't wind up with a hole in the table. Default access to
    * avoid synthetic accessors from inner classes.
    */
   void internalRemove(int index) {
     table[index] = null;
     --size;
     plugHole(index);
   }

   /**
    * Ensures the set is large enough to contain the specified number of entries.
    */
   private boolean ensureSizeFor(int expectedSize) {
     if (table.length * 3 >= expectedSize * 4) {
       return false;
     }

     int newCapacity = table.length << 1;
     while (newCapacity * 3 < expectedSize * 4) {
       newCapacity <<= 1;
     }

     Object[] oldTable = table;
     table = new Object[newCapacity];
     for (Object o : oldTable) {
       if (o != null) {
         int newIndex = getIndex(unmaskNull(o));
         while (table[newIndex] != null) {
           if (++newIndex == table.length) {
             newIndex = 0;
           }
         }
         table[newIndex] = o;
       }
     }
     return true;
   }

   /**
    * Returns the index in the table at which a particular item resides, or -1 if
    * the item is not in the table.
    */
   private int find(Object o) {
     int index = getIndex(o);
     while (true) {
       Object existing = table[index];
       if (existing == null) {
         return -1;
       }
       if (itemEquals(o, unmaskNull(existing))) {
         return index;
       }
       if (++index == table.length) {
         index = 0;
       }
     }
   }

   /**
    * Returns the index in the table at which a particular item resides, or the
    * index of an empty slot in the table where this item should be inserted if
    * it is not already in the table.
    */
   private int findOrEmpty(Object o) {
     int index = getIndex(o);
     while (true) {
       Object existing = table[index];
       if (existing == null) {
         return index;
       }
       if (itemEquals(o, unmaskNull(existing))) {
         return index;
       }
       if (++index == table.length) {
         index = 0;
       }
     }
   }

   private int getIndex(Object o) {
     int h = itemHashCode(o);
     // Copied from Apache's AbstractHashedMap; prevents power-of-two collisions.
     h += ~(h << 9);
     h ^= (h >>> 14);
     h += (h << 4);
     h ^= (h >>> 10);
     // Power of two trick.
     return h & (table.length - 1);
   }

   /**
    * Tricky, we left a hole in the map, which we have to fill. The only way to
    * do this is to search forwards through the map shuffling back values that
    * match this index until we hit a null.
    */
   private void plugHole(int hole) {
     int index = hole + 1;
     if (index == table.length) {
       index = 0;
     }
     while (table[index] != null) {
       int targetIndex = getIndex(unmaskNull(table[index]));
       if (hole < index) {
         /*
          * "Normal" case, the index is past the hole and the "bad range" is from
          * hole (exclusive) to index (inclusive).
          */
         if (!(hole < targetIndex && targetIndex <= index)) {
           // Plug it!
           table[hole] = table[index];
           table[index] = null;
           hole = index;
         }
       } else {
         /*
          * "Wrapped" case, the index is before the hole (we've wrapped) and the
          * "good range" is from index (exclusive) to hole (inclusive).
          */
         if (index < targetIndex && targetIndex <= hole) {
           // Plug it!
           table[hole] = table[index];
           table[index] = null;
           hole = index;
         }
       }
       if (++index == table.length) {
         index = 0;
       }
     }
   }

   private void readObject(ObjectInputStream in) throws IOException,
       ClassNotFoundException {
     in.defaultReadObject();
     doReadObject(in);
   }

   /**
    * Resizes this set to accommodate the minimum size required to join this set
    * with another set. This is an optimization to prevent multiple resizes
    * during the join operation. Naively, it would seem like we should resize to
    * hold {@code (size + otherSize)}. However, the incoming set might have
    * duplicates with this set; it might even be all duplicates. The correct
    * behavior when the incoming set is all duplicates is NOT to resize, and
    * therefore not to invalidate any iterators.
    * <p>
    * In practice, this strategy results in a worst-case of two resizes. In the
    * worst case, where {@code size} and {@code otherSize} are roughly equal and
    * the sets are completely disjoint, we might do 1 initial rehash and then 1
    * additional rehash down the road. But this is an edge case that requires
    * getting unlucky on both boundaries. Most of the time, we do either 1
    * initial rehash or 1 down the road, because doubling the capacity generally
    * allows this set to absorb an equally-sized disjoint set.
    */
   private void resizeForJoin(int sizeOther) {
     ensureSizeFor(Math.max(size, sizeOther));
   }

   private void writeObject(ObjectOutputStream out) throws IOException {
     out.defaultWriteObject();
     doWriteObject(out);
   }
 }
	/*
	* Copyright 2009 Google Inc.
	*
	* Licensed under the Apache License, Version 2.0 (the "License"); you may not
	* use this file except in compliance with the License. You may obtain a copy of
	* the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
	* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
	* License for the specific language governing permissions and limitations under
	* the License.
	*/
	package com.google.gwt.dev.util.collect;

	import java.io.IOException;
	import java.io.ObjectInputStream;
	import java.io.ObjectOutputStream;
	import java.io.Serializable;
	import java.lang.reflect.Array;
	import java.util.AbstractSet;
	import java.util.Collection;
	import java.util.ConcurrentModificationException;
	import java.util.Iterator;
	import java.util.NoSuchElementException;

	/**
	* A memory-efficient hash set.
	*
	* @param <E> the element type
	*/
	public class HashSet<E> extends AbstractSet<E> implements Serializable {

	private class SetIterator implements Iterator<E> {
	private Object[] coModCheckTable = table;
	private int index = 0;
	private int last = -1;

	public boolean hasNext() {
	if (coModCheckTable != table) {
	throw new ConcurrentModificationException();
	}
	advanceToItem();
	return index < table.length;
	}

	@SuppressWarnings("unchecked")
	public E next() {
	if (!hasNext()) {
	throw new NoSuchElementException();
	}
	last = index;
	return (E) unmaskNull(table[index++]);
	}

	public void remove() {
	if (last < 0) {
	throw new IllegalStateException();
	}
	if (coModCheckTable != table) {
	throw new ConcurrentModificationException();
	}
	internalRemove(last);
	if (table[last] != null) {
	// Hole was plugged.
	index = last;
	}
	last = -1;
	}

	private void advanceToItem() {
	for (; index < table.length; ++index) {
	if (table[index] != null) {
	return;
	}
	}
	}
	}

	/**
	* In the interest of memory-savings, we start with the smallest feasible
	* power-of-two table size that can hold three items without rehashing. If we
	* started with a size of 2, we'd have to expand as soon as the second item
	* was added.
	*/
	private static final int INITIAL_TABLE_SIZE = 4;

	private static final Object NULL_ITEM = new Serializable() {
	Object readResolve() {
	return NULL_ITEM;
	}
	};

	static Object maskNull(Object o) {
	return (o == null) ? NULL_ITEM : o;
	}

	static Object unmaskNull(Object o) {
	return (o == NULL_ITEM) ? null : o;
	}

	/**
	* Number of objects in this set; transient due to custom serialization.
	* Default access to avoid synthetic accessors from inner classes.
	*/
	transient int size = 0;

	/**
	* Backing store for all the objects; transient due to custom serialization.
	* Default access to avoid synthetic accessors from inner classes.
	*/
	transient Object[] table;

	public HashSet() {
	table = new Object[INITIAL_TABLE_SIZE];
	}

	public HashSet(Collection<? extends E> c) {
	int newCapacity = INITIAL_TABLE_SIZE;
	int expectedSize = c.size();
	while (newCapacity * 3 < expectedSize * 4) {
	newCapacity <<= 1;
	}

	table = new Object[newCapacity];
	super.addAll(c);
	}

	/**
	* Works just like {@link #HashSet(Collection)}, but for arrays. Used to avoid
	* having to synthesize a collection in {@link Sets}.
	*/
	HashSet(E[] c) {
	int newCapacity = INITIAL_TABLE_SIZE;
	int expectedSize = c.length;
	while (newCapacity * 3 < expectedSize * 4) {
	newCapacity <<= 1;
	}

	table = new Object[newCapacity];
	for (E e : c) {
	add(e);
	}
	}

	@Override
	public boolean add(E e) {
	int index = findOrEmpty(e);
	if (table[index] == null) {
	// Not in the map, may need to grow.
	if (ensureSizeFor(++size)) {
	// If we had to grow the table, must recompute the index.
	index = findOrEmpty(e);
	}
	table[index] = maskNull(e);
	return true;
	}
	return false;
	}

	@Override
	public boolean addAll(Collection<? extends E> c) {
	resizeForJoin(c.size());
	return super.addAll(c);
	}

	@Override
	public void clear() {
	table = new Object[INITIAL_TABLE_SIZE];
	size = 0;
	}

	@Override
	public boolean contains(Object o) {
	return find(o) >= 0;
	}

	@Override
	public Iterator<E> iterator() {
	return new SetIterator();
	}

	@Override
	public boolean remove(Object o) {
	int index = find(o);
	if (index < 0) {
	return false;
	}
	internalRemove(index);
	return true;
	}

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

	@Override
	public Object[] toArray() {
	return toArray(new Object[size]);
	}

	@SuppressWarnings("unchecked")
	@Override
	public <T> T[] toArray(T[] a) {
	if (a.length < size) {
	a = (T[]) Array.newInstance(a.getClass().getComponentType(), size);
	}
	int index = 0;
	for (int i = 0; i < table.length; ++i) {
	Object e = table[i];
	if (e != null) {
	a[index++] = (T) unmaskNull(e);
	}
	}
	while (index < a.length) {
	a[index++] = null;
	}
	return a;
	}

	/**
	* Adapted from {@link org.apache.commons.collections.map.AbstractHashedMap}.
	*/
	@SuppressWarnings("unchecked")
	protected void doReadObject(ObjectInputStream in) throws IOException,
	ClassNotFoundException {
	table = new Object[in.readInt()];
	int items = in.readInt();
	for (int i = 0; i < items; i++) {
	add((E) in.readObject());
	}
	}

	/**
	* Adapted from {@link org.apache.commons.collections.map.AbstractHashedMap}.
	*/
	protected void doWriteObject(ObjectOutputStream out) throws IOException {
	out.writeInt(table.length);
	out.writeInt(size);
	for (int i = 0; i < table.length; ++i) {
	Object e = table[i];
	if (e != null) {
	out.writeObject(unmaskNull(e));
	}
	}
	}

	/**
	* Returns whether two items are equal for the purposes of this set.
	*/
	protected boolean itemEquals(Object a, Object b) {
	return (a == null) ? (b == null) : a.equals(b);
	}

	/**
	* Return the hashCode for an item.
	*/
	protected int itemHashCode(Object o) {
	return (o == null) ? 0 : o.hashCode();
	}

	/**
	* Removes the item at the specified index, and performs internal management
	* to make sure we don't wind up with a hole in the table. Default access to
	* avoid synthetic accessors from inner classes.
	*/
	void internalRemove(int index) {
	table[index] = null;
	--size;
	plugHole(index);
	}

	/**
	* Ensures the set is large enough to contain the specified number of entries.
	*/
	private boolean ensureSizeFor(int expectedSize) {
	if (table.length * 3 >= expectedSize * 4) {
	return false;
	}

	int newCapacity = table.length << 1;
	while (newCapacity * 3 < expectedSize * 4) {
	newCapacity <<= 1;
	}

	Object[] oldTable = table;
	table = new Object[newCapacity];
	for (Object o : oldTable) {
	if (o != null) {
	int newIndex = getIndex(unmaskNull(o));
	while (table[newIndex] != null) {
	if (++newIndex == table.length) {
	newIndex = 0;
	}
	}
	table[newIndex] = o;
	}
	}
	return true;
	}

	/**
	* Returns the index in the table at which a particular item resides, or -1 if
	* the item is not in the table.
	*/
	private int find(Object o) {
	int index = getIndex(o);
	while (true) {
	Object existing = table[index];
	if (existing == null) {
	return -1;
	}
	if (itemEquals(o, unmaskNull(existing))) {
	return index;
	}
	if (++index == table.length) {
	index = 0;
	}
	}
	}

	/**
	* Returns the index in the table at which a particular item resides, or the
	* index of an empty slot in the table where this item should be inserted if
	* it is not already in the table.
	*/
	private int findOrEmpty(Object o) {
	int index = getIndex(o);
	while (true) {
	Object existing = table[index];
	if (existing == null) {
	return index;
	}
	if (itemEquals(o, unmaskNull(existing))) {
	return index;
	}
	if (++index == table.length) {
	index = 0;
	}
	}
	}

	private int getIndex(Object o) {
	int h = itemHashCode(o);
	// Copied from Apache's AbstractHashedMap; prevents power-of-two collisions.
	h += ~(h << 9);
	h ^= (h >>> 14);
	h += (h << 4);
	h ^= (h >>> 10);
	// Power of two trick.
	return h & (table.length - 1);
	}

	/**
	* Tricky, we left a hole in the map, which we have to fill. The only way to
	* do this is to search forwards through the map shuffling back values that
	* match this index until we hit a null.
	*/
	private void plugHole(int hole) {
	int index = hole + 1;
	if (index == table.length) {
	index = 0;
	}
	while (table[index] != null) {
	int targetIndex = getIndex(unmaskNull(table[index]));
	if (hole < index) {
	/*
	* "Normal" case, the index is past the hole and the "bad range" is from
	* hole (exclusive) to index (inclusive).
	*/
	if (!(hole < targetIndex && targetIndex <= index)) {
	// Plug it!
	table[hole] = table[index];
	table[index] = null;
	hole = index;
	}
	} else {
	/*
	* "Wrapped" case, the index is before the hole (we've wrapped) and the
	* "good range" is from index (exclusive) to hole (inclusive).
	*/
	if (index < targetIndex && targetIndex <= hole) {
	// Plug it!
	table[hole] = table[index];
	table[index] = null;
	hole = index;
	}
	}
	if (++index == table.length) {
	index = 0;
	}
	}
	}

	private void readObject(ObjectInputStream in) throws IOException,
	ClassNotFoundException {
	in.defaultReadObject();
	doReadObject(in);
	}

	/**
	* Resizes this set to accommodate the minimum size required to join this set
	* with another set. This is an optimization to prevent multiple resizes
	* during the join operation. Naively, it would seem like we should resize to
	* hold {@code (size + otherSize)}. However, the incoming set might have
	* duplicates with this set; it might even be all duplicates. The correct
	* behavior when the incoming set is all duplicates is NOT to resize, and
	* therefore not to invalidate any iterators.
	* <p>
	* In practice, this strategy results in a worst-case of two resizes. In the
	* worst case, where {@code size} and {@code otherSize} are roughly equal and
	* the sets are completely disjoint, we might do 1 initial rehash and then 1
	* additional rehash down the road. But this is an edge case that requires
	* getting unlucky on both boundaries. Most of the time, we do either 1
	* initial rehash or 1 down the road, because doubling the capacity generally
	* allows this set to absorb an equally-sized disjoint set.
	*/
	private void resizeForJoin(int sizeOther) {
	ensureSizeFor(Math.max(size, sizeOther));
	}

	private void writeObject(ObjectOutputStream out) throws IOException {
	out.defaultWriteObject();
	doWriteObject(out);
	}
	}