/*
* 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.util.AbstractSet;
import java.util.Arrays;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Set;
/**
* A HashSet that is optimized for fast shallow copies. If the copy-ctor is
* passed another FastCopyHashSet, or clone is called on this set, the shallow
* copy can be performed using little more than a single array copy. In order to
* accomplish this, immutable objects must be used internally, so update
* operations result in slightly more object churn than <code>HashSet</code>.
* <p/>
* 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
* @author <a href="mailto:david.lloyd@redhat.com">David M. Lloyd</a>
*/
class FastCopyHashSet<E> extends AbstractSet<E> implements Set<E>, 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 = 64;
/**
* MAX_INT - 1
*/
private static final int MAXIMUM_CAPACITY = 1 << 30;
/**
* 50%
*/
private static final float DEFAULT_LOAD_FACTOR = 0x0.5p0f;
/**
* The open-addressed table
*/
private transient E[] 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;
/**
* Accumulated hash code
*/
private transient int hashCode;
FastCopyHashSet(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);
}
FastCopyHashSet(Set<? extends E> set) {
if (set instanceof FastCopyHashSet) {
FastCopyHashSet<? extends E> fast = (FastCopyHashSet<? extends E>) set;
table = fast.table.clone();
loadFactor = fast.loadFactor;
size = fast.size;
threshold = fast.threshold;
hashCode = fast.hashCode;
} else {
loadFactor = DEFAULT_LOAD_FACTOR;
init(set.size(), loadFactor);
addAll(set);
}
}
@SuppressWarnings("unchecked")
private void init(int initialCapacity, float loadFactor) {
int c = 1;
while (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 = (E[]) new Object[c];
}
FastCopyHashSet(int initialCapacity) {
this(initialCapacity, DEFAULT_LOAD_FACTOR);
}
FastCopyHashSet() {
this(DEFAULT_CAPACITY);
}
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 key) {
if (key == null) {
return false;
}
int hash = key.hashCode();
int length = table.length;
int index = index(hash, length);
for (int start = index; ;) {
E e = table[index];
if (e == null)
return false;
if (key.equals(e))
return true;
index = nextIndex(index, length);
if (index == start) // Full table
return false;
}
}
public boolean add(E key) {
if (key == null) {
throw new IllegalArgumentException("key is null");
}
E[] table = this.table;
int hash = key.hashCode();
int length = table.length;
int index = index(hash, length);
boolean f = false;
for (int start = index; ;) {
E e = table[index];
if (e == null)
break;
if (! f) {
f= true;
}
if (key.equals(e)) {
return false;
}
index = nextIndex(index, length);
if (index == start)
throw new IllegalStateException("Table is full!");
}
modCount++;
table[index] = key;
hashCode += key.hashCode();
if (++size >= threshold)
resize(length);
return true;
}
@SuppressWarnings("unchecked")
private void resize(int from) {
int newLength = from << 1;
// Can't get any bigger
if (newLength > MAXIMUM_CAPACITY || newLength <= from)
return;
E[] newTable = (E[]) new Object[newLength];
E[] old = table;
for (E e : old) {
if (e == null)
continue;
int index = index(e.hashCode(), newLength);
while (newTable[index] != null)
index = nextIndex(index, newLength);
newTable[index] = e;
}
threshold = (int) (loadFactor * newLength);
table = newTable;
}
public boolean addAll(Collection<? extends E> set) {
int size = set.size();
if (size == 0)
return false;
boolean changed = false;
for (E e : set) {
if (add(e)) {
changed = true;
}
}
return changed;
}
public boolean remove(Object key) {
E[] table = this.table;
int length = table.length;
int hash = key.hashCode();
int start = index(hash, length);
for (int index = start; ;) {
E e = table[index];
if (e == null)
return false;
if (key.equals(e)) {
table[index] = null;
hashCode -= hash;
relocate(index);
modCount++;
size--;
return true;
}
index = nextIndex(index, length);
if (index == start)
return false;
}
}
private void relocate(int start) {
E[] table = this.table;
int length = table.length;
int current = nextIndex(start, length);
for (; ;) {
E 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(e.hashCode(), 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++;
E[] table = this.table;
for (int i = 0; i < table.length; i++)
table[i] = null;
size = hashCode = 0;
}
@SuppressWarnings("unchecked")
public FastCopyHashSet<E> clone() {
try {
FastCopyHashSet<E> clone = (FastCopyHashSet<E>) super.clone();
clone.table = table.clone();
return clone;
}
catch (CloneNotSupportedException e) {
// should never happen
throw new IllegalStateException(e);
}
}
public Iterator<E> iterator() {
return new KeyIterator();
}
public void printDebugStats() {
int optimal = 0;
int total = 0;
int totalSkew = 0;
int maxSkew = 0;
for (int i = 0; i < table.length; i++) {
E e = table[i];
if (e != null) {
total++;
int target = index(e.hashCode(), 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++) {
E key = (E) s.readObject();
putForCreate(key);
}
this.size = size;
}
@SuppressWarnings("unchecked")
private void putForCreate(E key) {
E[] table = this.table;
int hash = key.hashCode();
int length = table.length;
int index = index(hash, length);
E e = table[index];
while (e != null) {
index = nextIndex(index, length);
e = table[index];
}
table[index] = key;
}
private void writeObject(java.io.ObjectOutputStream s) throws IOException {
s.defaultWriteObject();
s.writeInt(size);
for (E e : table) {
if (e != null) {
s.writeObject(e);
}
}
}
public boolean containsAll(final Collection<?> c) {
final E[] table = this.table;
for (E e : table) {
if (e != null) {
if (! c.contains(e)) {
return false;
}
}
}
return true;
}
@SuppressWarnings("NonFinalFieldReferenceInEquals")
public boolean equals(final Object o) {
if (o == this)
return true;
if (! (o instanceof Set))
return false;
if (o instanceof FastCopyHashSet) {
final FastCopyHashSet<?> set = (FastCopyHashSet<?>) o;
if (hashCode != set.hashCode) {
return false;
}
if (table.length == set.table.length) {
return Arrays.equals(table, set.table);
}
}
Set<?> set = (Set<?>) o;
if (set.size() != size())
return false;
try {
return containsAll(set);
} catch (ClassCastException unused) {
return false;
} catch (NullPointerException unused) {
return false;
}
}
@SuppressWarnings("NonFinalFieldReferencedInHashCode")
public int hashCode() {
return hashCode;
}
public Object[] getRawArray() {
return table;
}
private class KeyIterator implements Iterator<E> {
private int next = 0;
private int expectedCount = modCount;
private int current = -1;
private boolean hasNext;
private E[] table = FastCopyHashSet.this.table;
public E next() {
if (modCount != expectedCount)
throw new ConcurrentModificationException();
if (!hasNext && !hasNext())
throw new NoSuchElementException();
current = next++;
hasNext = false;
return table[current];
}
public boolean hasNext() {
if (hasNext == true)
return true;
E[] 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 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;
E[] table = this.table;
if (table != FastCopyHashSet.this.table) {
FastCopyHashSet.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);
E e = table[i];
if (e == null)
break;
int prefer = index(e.hashCode(), 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 == FastCopyHashSet.this.table) {
int remaining = length - current;
E[] newTable = (E[]) 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;
}
}
}
}
}