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ZooDB Java JDO Object Database.
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/*
* Copyright 2009-2013 Tilmann Zaeschke. All rights reserved.
*
* This file is part of ZooDB.
*
* ZooDB is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* ZooDB is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with ZooDB. If not, see
* @author Tilmann Zaeschke
*/
public final class ObjectIdentitySet implements Set
{
private ObjectIdentitySetEntry[] table;
private int count;
private int threshold;
private static final float LOAD_FACTOR = 0.75f;
private static final int INITIAL_CAPACITY = 127;
/**
* Create a new ObjectIdentitySet.
*/
public ObjectIdentitySet () {
this (INITIAL_CAPACITY);
}
@SuppressWarnings("unchecked")
public ObjectIdentitySet (int initial_capacity) {
if (initial_capacity > INITIAL_CAPACITY) {
//First get a good number: (2^n)-1 > initial_capacity
//Ideally, n would be a prime, but that's getting too
//difficult here.
int p = 1;
while (initial_capacity > 1) {
initial_capacity = initial_capacity >> 2;
p++;
}
if (p%2 == 0) {
p++;
}
initial_capacity = (int) Math.pow(2, p) - 1;
} else {
//Go for minimal feasible size (expecting resizing)
initial_capacity = INITIAL_CAPACITY;
}
int initial_size = (int) (initial_capacity / LOAD_FACTOR);
table = new ObjectIdentitySetEntry [initial_size];
count = 0;
threshold = initial_capacity;
}
/**
* @param object
* @return Returns true if the object was added, otherwise
* false.
* @see java.util.Set#add(java.lang.Object)
*/
public final boolean add (E object) {
int hash = System.identityHashCode (object);
int index = (hash & 0x7FFFFFFF) % table.length;
ObjectIdentitySetEntry head = table [index];
for (ObjectIdentitySetEntry e = head; e != null; e = e.next) {
if (object == e.object)
return false;
}
table [index] = new ObjectIdentitySetEntry (object, head);
count++;
if (count >= threshold)
rehash (count * 2 + 1);
return true;
}
final void add (E[] objects) {
for (E obj: objects) {
add (obj);
}
}
/**
* @see java.util.Set#contains(java.lang.Object)
*/
public final boolean contains (Object object) {
int hash = System.identityHashCode (object);
int index = (hash & 0x7FFFFFFF) % table.length;
ObjectIdentitySetEntry e;
for (e = table [index]; e != null; e = e.next) {
if (object == e.object)
return true;
}
return false;
}
@SuppressWarnings("unchecked")
final void rehash (int new_length) {
ObjectIdentitySetEntry[] old_table = table;
int old_length = old_table.length;
//int new_length = old_length * 2 + 1;
ObjectIdentitySetEntry[] new_table =
new ObjectIdentitySetEntry [new_length];
for (int i = 0; i < old_length; i++) {
ObjectIdentitySetEntry next;
ObjectIdentitySetEntry e;
for (e = old_table [i]; e != null; e = next) {
int hash = System.identityHashCode (e.object);
int new_index = ((hash & 0x7FFFFFFF) % new_length);
next = e.next;
e.next = new_table [new_index];
new_table [new_index] = e;
}
}
table = new_table;
threshold = (int) (new_length * LOAD_FACTOR);
}
/**
* @see java.util.Set#size()
*/
public final int size() {
return count;
}
/**
* @see java.util.Set#clear()
*/
@SuppressWarnings("unchecked")
public final void clear() {
threshold = INITIAL_CAPACITY;
count = 0;
table = new ObjectIdentitySetEntry [(int) (threshold / LOAD_FACTOR)];
}
/**
* @see java.util.Set#isEmpty()
*/
public final boolean isEmpty() {
return count == 0;
}
/**
* @see java.util.Set#toArray()
*/
public final Object[] toArray() {
Object[] a = new Object[count];
int j = 0;
for (Iterator i = this.iterator(); i.hasNext(); ) {
a[j++] = i.next();
}
return a;
}
/**
* @see java.util.Set#remove(java.lang.Object)
*/
public final boolean remove(Object obj) {
int hash = System.identityHashCode (obj);
int index = (hash & 0x7FFFFFFF) % table.length;
ObjectIdentitySetEntry e;
ObjectIdentitySetEntry prev = null;
for (e = table [index]; e != null; e = e.next) {
if (obj == e.object) {
//delete it
if (prev == null) {
//first element
table [index] = e.next;
} else {
prev.next = e.next;
}
count--;
// rehash if < 25% filled and size > 127
if (count < threshold*(1-LOAD_FACTOR)
&& count > INITIAL_CAPACITY)
rehash (count / 2 + 1);
return true;
}
prev = e;
}
return false;
}
/**
* @see java.util.Set#addAll(java.util.Collection)
*/
public final boolean addAll(Collection c) {
boolean ret = false;
for (E o: c) {
ret |= add(o);
}
return ret;
}
/**
* Add all elements of in the enumeration
* @param en
*/
public final void addAll(Enumeration en) {
while (en.hasMoreElements()) {
add(en.nextElement());
}
}
/**
* @see java.util.Set#containsAll(java.util.Collection)
*/
public final boolean containsAll(Collection c) {
if (c == null) {
throw new NullPointerException();
}
throw new UnsupportedOperationException();
}
/**
* @see java.util.Set#removeAll(java.util.Collection)
*/
public final boolean removeAll(Collection c) {
if (c == null) {
throw new NullPointerException();
}
boolean hasChanged = false;
for (Object o: c) {
if (remove(o)) hasChanged = true;
}
return hasChanged;
}
/**
* @see java.util.Set#retainAll(java.util.Collection)
*/
public final boolean retainAll(Collection c) {
if (c == null) {
throw new NullPointerException();
}
throw new UnsupportedOperationException();
}
/**
* @see java.util.Set#iterator()
*/
public final Iterator iterator() {
return new ObjectIdentitySetIterator();
}
/**
* @param a
* @param
* @return Array representation of this container
* @see java.util.Set#toArray(Object[])
*/
public final T[] toArray(T[] a) {
if (a == null) {
throw new NullPointerException();
}
throw new UnsupportedOperationException();
}
/**
* @see java.lang.Object#toString()
*/
public final String toString() {
StringBuffer buf = new StringBuffer();
buf.append("ObjectIdentitySet(" + count + "): ");
for (Iterator i = this.iterator(); i.hasNext(); ) {
buf.append(i.next() + "; ");
}
return buf.toString();
}
private final static class ObjectIdentitySetEntry {
private final T object;
private ObjectIdentitySetEntry next;
ObjectIdentitySetEntry (T object1, ObjectIdentitySetEntry next1) {
object = object1;
next = next1;
}
}
private final class ObjectIdentitySetIterator implements Iterator {
private int pos = 0;
private ObjectIdentitySetEntry next = null;
/**
* @see java.util.Iterator#remove()
*/
public final void remove() {
throw new UnsupportedOperationException();
}
/**
* @see java.util.Iterator#hasNext()
*/
public final boolean hasNext() {
if (next == null) {
for( ; pos < table.length; pos++) {
if (table[pos] != null) {
next = table[pos];
pos++;
return true;
}
}
return false;
}
return true;
}
/**
* @see java.util.Iterator#next()
*/
public final E next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
ObjectIdentitySetEntry n = next;
next = next.next;
return n.object;
}
}
}
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