org.jboss.modules.IdentityHashSet Maven / Gradle / Ivy
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* JBoss, Home of Professional Open Source.
* Copyright 2014 Red Hat, Inc., and individual contributors
* as indicated by the @author tags.
*
* 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 org.jboss.modules;
import java.io.IOException;
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;
import java.util.Set;
/**
* An identity based hash set. A number of properties apply to this set. It
* compares only using object identity, it supports null entries, it allocates
* little more than a single object array, and it can be copied quickly. If the
* copy-ctor is passed another IdentityHashSet, or clone is called on this set,
* the shallow copy can be performed using little more than a single array copy.
*
* Note: It is very important to use a smaller load factor than you normally
* would for HashSet, since the implementation is open-addressed with linear
* probing. With a 50% load-factor a get is expected to return in only 2 probes.
* However, a 90% load-factor is expected to return in around 50 probes.
*
* @author Jason T. Greene
*/
class IdentityHashSet extends AbstractSet implements Set, Cloneable, Serializable {
/**
* Serialization ID
*/
private static final long serialVersionUID = 10929568968762L;
/**
* Same default as HashMap, must be a power of 2
*/
private static final int DEFAULT_CAPACITY = 8;
/**
* MAX_INT - 1
*/
private static final int MAXIMUM_CAPACITY = 1 << 30;
/**
* 67%, just like IdentityHashMap
*/
private static final float DEFAULT_LOAD_FACTOR = 0.67f;
/**
* The open-addressed table
*/
private transient Object[] table;
/**
* The current number of key-value pairs
*/
private transient int size;
/**
* The next resize
*/
private transient int threshold;
/**
* The user defined load factor which defines when to resize
*/
private final float loadFactor;
/**
* Counter used to detect changes made outside of an iterator
*/
private transient int modCount;
public IdentityHashSet(int initialCapacity, float loadFactor) {
if (initialCapacity < 0)
throw new IllegalArgumentException("Can not have a negative size table!");
if (initialCapacity > MAXIMUM_CAPACITY)
initialCapacity = MAXIMUM_CAPACITY;
if (!(loadFactor > 0F && loadFactor <= 1F))
throw new IllegalArgumentException("Load factor must be greater than 0 and less than or equal to 1");
this.loadFactor = loadFactor;
init(initialCapacity, loadFactor);
}
@SuppressWarnings("unchecked")
public IdentityHashSet(Set set) {
if (set instanceof IdentityHashSet) {
IdentityHashSet fast = (IdentityHashSet) set;
table = fast.table.clone();
loadFactor = fast.loadFactor;
size = fast.size;
threshold = fast.threshold;
} else {
loadFactor = DEFAULT_LOAD_FACTOR;
init(set.size(), loadFactor);
addAll(set);
}
}
private void init(int initialCapacity, float loadFactor) {
int c = 1;
for (; c < initialCapacity; c <<= 1);
threshold = (int) (c * loadFactor);
// Include the load factor when sizing the table for the first time
if (initialCapacity > threshold && c < MAXIMUM_CAPACITY) {
c <<= 1;
threshold = (int) (c * loadFactor);
}
table = new Object[c];
}
public IdentityHashSet(int initialCapacity) {
this(initialCapacity, DEFAULT_LOAD_FACTOR);
}
public IdentityHashSet() {
this(DEFAULT_CAPACITY);
}
// The normal bit spreader...
private static int hash(Object o) {
int h = System.identityHashCode(o);
h ^= (h >>> 20) ^ (h >>> 12);
return h ^ (h >>> 7) ^ (h >>> 4);
}
private int nextIndex(int index, int length) {
index = (index >= length - 1) ? 0 : index + 1;
return index;
}
private static int index(int hashCode, int length) {
return hashCode & (length - 1);
}
public int size() {
return size;
}
public boolean isEmpty() {
return size == 0;
}
public boolean contains(Object entry) {
if (entry == null) return false;
int hash = hash(entry);
int length = table.length;
int index = index(hash, length);
for (int start = index;;) {
Object e = table[index];
if (e == null)
return false;
if (entry == e)
return true;
index = nextIndex(index, length);
if (index == start) // Full table
return false;
}
}
public boolean add(E entry) {
if (entry == null) {
throw new NullPointerException("entry is null");
}
Object[] table = this.table;
int hash = hash(entry);
int length = table.length;
int index = index(hash, length);
for (int start = index;;) {
Object e = table[index];
if (e == null)
break;
if (e == entry)
return false;
index = nextIndex(index, length);
if (index == start)
throw new IllegalStateException("Table is full!");
}
modCount++;
table[index] = entry;
if (++size >= threshold)
resize(length);
return true;
}
private void resize(int from) {
int newLength = from << 1;
// Can't get any bigger
if (newLength > MAXIMUM_CAPACITY || newLength <= from)
return;
Object[] newTable = new Object[newLength];
Object[] old = table;
for (Object e : old) {
if (e == null)
continue;
int index = index(hash(e), newLength);
while (newTable[index] != null)
index = nextIndex(index, newLength);
newTable[index] = e;
}
threshold = (int) (loadFactor * newLength);
table = newTable;
}
@SuppressWarnings({ "unchecked" })
public boolean addAll(Collection collection) {
int size = collection.size();
if (size == 0)
return false;
if (size > threshold) {
if (size > MAXIMUM_CAPACITY)
size = MAXIMUM_CAPACITY;
int length = table.length;
for (; length < size; length <<= 1);
resize(length);
}
boolean state = false;
if (collection instanceof IdentityHashSet) {
for (E e : ((E[]) (((IdentityHashSet) collection).table)))
if (e != null) state |= add(e);
} else {
for (E e : collection)
state |= add(e);
}
return state;
}
public boolean remove(Object o) {
if (o == null) return false;
Object[] table = this.table;
int length = table.length;
int hash = hash(o);
int start = index(hash, length);
for (int index = start;;) {
Object e = table[index];
if (e == null)
return false;
if (e == o) {
table[index] = null;
relocate(index);
modCount++;
size--;
return true;
}
index = nextIndex(index, length);
if (index == start)
return false;
}
}
private void relocate(int start) {
Object[] table = this.table;
int length = table.length;
int current = nextIndex(start, length);
for (;;) {
Object e = table[current];
if (e == null)
return;
// A Doug Lea variant of Knuth's Section 6.4 Algorithm R.
// This provides a non-recursive method of relocating
// entries to their optimal positions once a gap is created.
int prefer = index(hash(e), length);
if ((current < prefer && (prefer <= start || start <= current)) || (prefer <= start && start <= current)) {
table[start] = e;
table[current] = null;
start = current;
}
current = nextIndex(current, length);
}
}
public void clear() {
modCount++;
Object[] table = this.table;
for (int i = 0; i < table.length; i++)
table[i] = null;
size = 0;
}
@SuppressWarnings("unchecked")
public IdentityHashSet clone() {
try {
IdentityHashSet clone = (IdentityHashSet) super.clone();
clone.table = table.clone();
return clone;
} catch (CloneNotSupportedException e) {
// should never happen
throw new IllegalStateException(e);
}
}
/**
* Advanced method that returns a copy of the internal table. The resulting
* array will contain nulls at random places that must be skipped. In
* addition, it will not operate correctly if a null was inserted into the
* set. Use at your own risk....
*
* @return an array containing elements in this set along with randomly
* placed nulls,
*/
@SuppressWarnings({ "unchecked" })
public E[] toScatteredArray(E[] dummy) {
final E[] ret = (E[]) Array.newInstance(dummy.getClass().getComponentType(), table.length);
System.arraycopy((E[])table, 0, ret, 0, ret.length);
return ret;
}
/**
* Warning: this will crap out if the set contains a {@code null}.
*
* @param target the target to write to
* @param offs the offset into the target
* @param len the length to write
* @return the target array
*/
@SuppressWarnings({ "unchecked" })
public E[] toArray(final E[] target, final int offs, final int len) {
assert len <= size;
final E[] table = (E[]) this.table;
E e;
final int last = offs + len;
for (int i = offs, j = 0; i < last; j ++) {
e = table[j];
if (e != null) {
target[i++] = e;
}
}
return target;
}
public void printDebugStats() {
int optimal = 0;
int total = 0;
int totalSkew = 0;
int maxSkew = 0;
for (int i = 0; i < table.length; i++) {
Object e = table[i];
if (e != null) {
total++;
int target = index(hash(e), table.length);
if (i == target)
optimal++;
else {
int skew = Math.abs(i - target);
if (skew > maxSkew)
maxSkew = skew;
totalSkew += skew;
}
}
}
System.out.println(" Size: " + size);
System.out.println(" Real Size: " + total);
System.out.println(" Optimal: " + optimal + " (" + (float) optimal * 100 / total + "%)");
System.out.println(" Average Distance: " + ((float) totalSkew / (total - optimal)));
System.out.println(" Max Distance: " + maxSkew);
}
@SuppressWarnings("unchecked")
private void readObject(java.io.ObjectInputStream s) throws IOException, ClassNotFoundException {
s.defaultReadObject();
int size = s.readInt();
init(size, loadFactor);
for (int i = 0; i < size; i++) {
putForCreate((E) s.readObject());
}
this.size = size;
}
private void putForCreate(E entry) {
Object[] table = this.table;
int hash = hash(entry);
int length = table.length;
int index = index(hash, length);
Object e = table[index];
while (e != null) {
index = nextIndex(index, length);
e = table[index];
}
table[index] = entry;
}
private void writeObject(java.io.ObjectOutputStream s) throws IOException {
s.defaultWriteObject();
s.writeInt(size);
for (Object e : table) {
if (e != null) {
s.writeObject(e);
}
}
}
@Override
public Iterator iterator() {
return new IdentityHashSetIterator();
}
private class IdentityHashSetIterator implements Iterator {
private int next = 0;
private int expectedCount = modCount;
private int current = -1;
private boolean hasNext;
Object table[] = IdentityHashSet.this.table;
public boolean hasNext() {
if (hasNext == true)
return true;
Object table[] = this.table;
for (int i = next; i < table.length; i++) {
if (table[i] != null) {
next = i;
return hasNext = true;
}
}
next = table.length;
return false;
}
@SuppressWarnings("unchecked")
public E next() {
if (modCount != expectedCount)
throw new ConcurrentModificationException();
if (!hasNext && !hasNext())
throw new NoSuchElementException();
current = next++;
hasNext = false;
return (E) table[current];
}
public void remove() {
if (modCount != expectedCount)
throw new ConcurrentModificationException();
int current = this.current;
int delete = current;
if (current == -1)
throw new IllegalStateException();
// Invalidate current (prevents multiple remove)
this.current = -1;
// Start were we relocate
next = delete;
Object[] table = this.table;
if (table != IdentityHashSet.this.table) {
IdentityHashSet.this.remove(table[delete]);
table[delete] = null;
expectedCount = modCount;
return;
}
int length = table.length;
int i = delete;
table[delete] = null;
size--;
for (;;) {
i = nextIndex(i, length);
Object e = table[i];
if (e == null)
break;
int prefer = index(hash(e), length);
if ((i < prefer && (prefer <= delete || delete <= i)) || (prefer <= delete && delete <= i)) {
// Snapshot the unseen portion of the table if we have
// to relocate an entry that was already seen by this
// iterator
if (i < current && current <= delete && table == IdentityHashSet.this.table) {
int remaining = length - current;
Object[] newTable = new Object[remaining];
System.arraycopy(table, current, newTable, 0, remaining);
// Replace iterator's table.
// Leave table local var pointing to the real table
this.table = newTable;
next = 0;
}
// Do the swap on the real table
table[delete] = e;
table[i] = null;
delete = i;
}
}
}
}
}
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