org.eclipse.persistence.internal.helper.IdentityHashSet Maven / Gradle / Ivy
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/*
* Copyright (c) 1998, 2022 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0,
* or the Eclipse Distribution License v. 1.0 which is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
*/
// Contributors:
// Oracle - initial API and implementation from Oracle TopLink
package org.eclipse.persistence.internal.helper;
/**
* INTERNAL:
*
* Purpose: Define a {@link Set} that tests equality by reference,
* not equals(). This is required to track objects throughout the lifecycle
* of a {@link org.eclipse.persistence.sessions.UnitOfWork}, regardless if the domain
* object redefines its equals() method. Additionally, this implementation does
* not allow null elements.
*
* This class does not inherit from {@link AbstractSet} because the
* method {@link AbstractSet#removeAll removeAll(Collection c)} does not work
* correctly with reference equality testing (NB the Javadocs for
* {@link AbstractCollection} indicates that removeAll is an optional method).
*
* @author Mike Norman (since TopLink 10.1.3)
*
*/
// J2SE imports
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.AbstractCollection;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Set;
public class IdentityHashSet extends AbstractCollection implements Set, Cloneable, Serializable {
static final long serialVersionUID = 1619330892277906704L;
// the default initial capacity
static final int DEFAULT_INITIAL_CAPACITY = 32;
// the maximum capacity.
static final int MAXIMUM_CAPACITY = 1 << 30;
// the loadFactor used when none specified in constructor.
static final float DEFAULT_LOAD_FACTOR = 0.75f;
private transient Entry[] entries;// internal array of Entry's
protected transient int count = 0;
protected int threshold = 0;
protected float loadFactor = 0;
/**
* Constructs a new IdentityHashSet with the given initial
* capacity and the given loadFactor.
*
* @param initialCapacity the initial capacity of the
* IdentityHashSet.
* @param loadFactor the loadFactor of the IdentityHashSet.
* @throws IllegalArgumentException if the initial capacity is less
* than zero, or if the loadFactor is nonpositive.
*/
public IdentityHashSet(int initialCapacity, float loadFactor) {
if (initialCapacity < 0) {
throw new IllegalArgumentException("Illegal initialCapacity: " + initialCapacity);
}
if (initialCapacity > MAXIMUM_CAPACITY) {
initialCapacity = MAXIMUM_CAPACITY;
}
if ((loadFactor <= 0) || Float.isNaN(loadFactor)) {
throw new IllegalArgumentException("Illegal loadFactor: " + loadFactor);
}
// Find a power of 2 >= initialCapacity
int capacity = 1;
while (capacity < initialCapacity) {
capacity <<= 1;
}
this.loadFactor = loadFactor;
threshold = (int)(capacity * loadFactor);
entries = new Entry[capacity];
}
/**
* Constructs a new IdentityHashSet with the given
* initial capacity and a default loadFactor of 0.75.
*
* @param initialCapacity the initial capacity of the IdentityHashSet.
* @throws IllegalArgumentException if the initial capacity is less
* than zero.
*/
public IdentityHashSet(int initialCapacity) {
this(initialCapacity, DEFAULT_LOAD_FACTOR);
}
/**
* Constructs a new IdentityHashSet with a default initial
* capacity of 32 and a loadfactor of 0.75.
*/
public IdentityHashSet() {
loadFactor = DEFAULT_LOAD_FACTOR;
threshold = (int)(DEFAULT_INITIAL_CAPACITY * DEFAULT_LOAD_FACTOR);
entries = new Entry[DEFAULT_INITIAL_CAPACITY];
}
/**
* Constructs a new IdentityHashSet with the same contents
* as the given Collection. The new IdentityHashSet
* is created with an initial capacity sufficient to hold the elements of
* the given Collection.
*
* @param c the Collection whose contents are to be placed in the
* new IdentityHashSet.
*/
public IdentityHashSet(Collection c) {
this(Math.max((int)(c.size() / DEFAULT_LOAD_FACTOR) + 1, DEFAULT_INITIAL_CAPACITY), DEFAULT_LOAD_FACTOR);
addAll(c);
}
/**
* @return the size of this IdentityHashSet.
*/
@Override
public int size() {
return count;
}
/**
* @return true if this IdentityHashSet is empty.
*/
@Override
public boolean isEmpty() {
return (count == 0);
}
/**
* Returns true if this IdentityHashSet contains
* the given object.
*
* @param obj the object to find.
* @return true if this IdentityHashSet contains
* obj by reference.
*/
@Override
public boolean contains(Object obj) {
if (obj == null) {
return false;
}
Entry[] copyOfEntries = entries;
int hash = System.identityHashCode(obj);
int index = (hash & 0x7FFFFFFF) % copyOfEntries.length;
for (Entry e = copyOfEntries[index]; e != null; e = e.next) {
if ((e.hash == hash) && (obj == e.value)) {
return true;
}
}
return false;
}
/**
* INTERNAL:
* Re-builds the internal array of Entry's with a larger capacity.
* This method is called automatically when the number of objects in this
* IdentityHashSet exceeds its current threshold.
*/
private void rehash() {
int oldCapacity = entries.length;
Entry[] oldEntries = entries;
int newCapacity = (oldCapacity * 2) + 1;
Entry[] newEntries = new Entry[newCapacity];
threshold = (int)(newCapacity * loadFactor);
entries = newEntries;
for (int i = oldCapacity; i-- > 0;) {
for (Entry old = oldEntries[i]; old != null;) {
Entry e = old;
old = old.next;
int index = (e.hash & 0x7FFFFFFF) % newCapacity;
e.next = newEntries[index];
newEntries[index] = e;
}
}
}
/**
* Adds the given object to this IdentityHashSet.
*
* @param obj object to add.
* @return true if this IdentityHashSet did not
* already contain obj.
* @throws NullPointerException if obj is null.
*/
@Override
public boolean add(Object obj) {
if (obj == null) {
throw new NullPointerException();
}
// Makes sure the object is not already in the IdentityHashSet.
Entry[] copyOfEntries = entries;
int hash = System.identityHashCode(obj);
int index = (hash & 0x7FFFFFFF) % copyOfEntries.length;
for (Entry e = copyOfEntries[index]; e != null; e = e.next) {
if ((e.hash == hash) && (obj == e.value)) {
return false;
}
}
if (count >= threshold) {
// Rehash the table if the threshold is exceeded
rehash();
copyOfEntries = entries;
index = (hash & 0x7FFFFFFF) % copyOfEntries.length;
}
// Creates the new entry.
Entry e = new Entry(hash, obj, copyOfEntries[index]);
copyOfEntries[index] = e;
count++;
return true;
}
/**
* Removes the given object from this IdentityHashSet, if
* present.
*
* @param obj the object to be removed from this IdentityHashSet.
* @return true if this IdentityHashSet contained
* obj.
*/
@Override
public boolean remove(Object obj) {
if (obj == null) {
return false;
}
Entry[] copyOfEntries = entries;
int hash = System.identityHashCode(obj);
int index = (hash & 0x7FFFFFFF) % copyOfEntries.length;
for (Entry e = copyOfEntries[index], prev = null; e != null; prev = e, e = e.next) {
if ((e.hash == hash) && (obj == e.value)) {
if (prev != null) {
prev.next = e.next;
} else {
copyOfEntries[index] = e.next;
}
count--;
return true;
}
}
return false;
}
/**
* This implementation throws an UnsupportedOperationException
* because removeAll does not work correctly with reference
* equality testing.
*/
@Override
public boolean removeAll(Collection c) {
throw new UnsupportedOperationException("IdentityHashSet removeAll");
}
/**
* This implementation throws an UnsupportedOperationException.
* The Javadocs for {@link AbstractCollection} indicates that retainAll
* is an optional method.
*/
@Override
public boolean retainAll(Collection c) {
throw new UnsupportedOperationException("IdentityHashSet retainAll");
}
/**
* Removes all of the objects from this IdentityHashSet.
*/
@Override
public void clear() {
if (count > 0) {
Entry[] copyOfEntries = entries;
for (int i = copyOfEntries.length; --i >= 0;) {
copyOfEntries[i] = null;
}
count = 0;
}
}
/**
* Returns a shallow copy of this IdentityHashSet (the
* elements are not cloned).
*
* @return a shallow copy of this IdentityHashSet.
*/
@Override
public Object clone() {
try {
Entry[] copyOfEntries = entries;
IdentityHashSet clone = (IdentityHashSet)super.clone();
clone.entries = new Entry[copyOfEntries.length];
for (int i = copyOfEntries.length; i-- > 0;) {
clone.entries[i] = (copyOfEntries[i] != null) ? (Entry)copyOfEntries[i].clone() : null;
}
return clone;
} catch (CloneNotSupportedException e) {
// this shouldn't happen, since we are Cloneable
throw new InternalError();
}
}
/**
* Get an iterator for this IdentityHashSet
*/
@Override
public Iterator iterator() {
return new IdentityHashSetIterator();
}
/**
* IdentityHashSet entry.
*/
private static class Entry {
int hash;
Object value;
Entry next;
Entry(int hash, Object value, Entry next) {
this.hash = hash;
this.value = value;
this.next = next;
}
@Override
protected Object clone() {
Entry currentNode = this;
Entry rootNode = new Entry(hash, value, null);
Entry currentNodeClone = rootNode;
while (currentNode.next != null) {
currentNodeClone.next = new Entry(currentNode.next.hash, currentNode.next.value, null);
currentNode = currentNode.next;
currentNodeClone = currentNodeClone.next;
}
return rootNode;
}
}
class IdentityHashSetIterator implements Iterator {
Entry[] copyOfEntries = IdentityHashSet.this.entries;
int index = copyOfEntries.length;
Entry entry = null;
Entry lastReturned = null;
IdentityHashSetIterator() {
}
@Override
public boolean hasNext() {
Entry e = entry;
int i = index;
Entry[] tmp = copyOfEntries;
while ((e == null) && (i > 0)) {
e = tmp[--i];
}
entry = e;
index = i;
return e != null;
}
@Override
public Object next() {
Entry et = entry;
int i = index;
Entry[] tmp = copyOfEntries;
while ((et == null) && (i > 0)) {
et = tmp[--i];
}
entry = et;
index = i;
if (et != null) {
Entry e = lastReturned = entry;
entry = e.next;
return e.value;
}
throw new NoSuchElementException();
}
@Override
public void remove() {
if (lastReturned == null) {
throw new IllegalStateException();
}
Entry[] copyOfEntries = IdentityHashSet.this.entries;
int index = (lastReturned.hash & 0x7FFFFFFF) % copyOfEntries.length;
for (Entry e = copyOfEntries[index], prev = null; e != null; prev = e, e = e.next) {
if (e == lastReturned) {
if (prev == null) {
copyOfEntries[index] = e.next;
} else {
prev.next = e.next;
}
count--;
lastReturned = null;
return;
}
}
throw new ConcurrentModificationException();
}
}
/**
* Serialize the state of this IdentityHashSet to a stream.
*
* @serialData The capacity of the IdentityHashSet
* (the length of the bucket array) is emitted (int), followed by the
* size of the IdentityHashSet, followed by the
* contents (in no particular order).
*/
private void writeObject(ObjectOutputStream s) throws IOException, ClassNotFoundException {
// Write out the threshold, loadfactor (and any hidden 'magic' stuff).
s.defaultWriteObject();
// Write out number of buckets
s.writeInt(entries.length);
// Write out count
s.writeInt(count);
// Write out contents
for (Iterator i = iterator(); i.hasNext();) {
s.writeObject(i.next());
}
}
/**
* Deserialize the IdentityHashSet from a stream.
*/
private void readObject(ObjectInputStream s) throws IOException, ClassNotFoundException {
// Read in the threshold, loadfactor (and any hidden 'magic' stuff).
s.defaultReadObject();
// Read in number of buckets and allocate the bucket array;
int numBuckets = s.readInt();
entries = new Entry[numBuckets];
// Read in size (count)
int size = s.readInt();
// Read the objects and add to the IdentityHashSet
for (int i = 0; i < size; i++) {
add(s.readObject());
}
}
}