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package oracle.toplink.essentials.internal.helper;
/**
* INTERNAL:
* <p>
* <b>Purpose</b>: Define a {@link Hashtable} that manages key equality by
* reference, not equals(). This is required to track objects throughout the
* lifecycle of a {@link oracle.toplink.essentials.sessions.UnitOfWork}, regardless if the
* domain object redefines its equals() method. Additionally, this implementation
* does <b>not</b> permit nulls.
*/
// J2SE imports
import java.io.*;
import java.util.*;
public class IdentityHashtable extends Dictionary implements Cloneable, Serializable {
static final long serialVersionUID = 1421746759512286392L;
// 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;
/** An "enum" of Enumeration types. */
static final int KEYS = 0;
/** An "enum" of Enumeration types. */
static final int ELEMENTS = 1;
private static EmptyEnumerator emptyEnumerator = new EmptyEnumerator();
protected transient Entry[] entries;// internal array of Entry's
protected transient int count = 0;
protected int threshold = 0;
protected float loadFactor = 0;
/**
* Constructs a new <tt>IdentityHashtable</tt> with the given
* initial capacity and the given loadFactor.
*
* @param initialCapacity the initial capacity of this
* <tt>IdentityHashtable</tt>.
* @param loadFactor the loadFactor of the <tt>IdentityHashtable</tt>.
* @throws IllegalArgumentException if the initial capacity is less
* than zero, or if the loadFactor is nonpositive.
*/
public IdentityHashtable(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 <tt>IdentityHashtable</tt> with the given
* initial capacity and a default loadFactor of <tt>0.75</tt>.
*
* @param initialCapacity the initial capacity of the
* <tt>IdentityHashtable</tt>.
* @throws <tt>IllegalArgumentException</tt> if the initial capacity is less
* than zero.
*/
public IdentityHashtable(int initialCapacity) {
this(initialCapacity, DEFAULT_LOAD_FACTOR);
}
/**
* Constructs a new <tt>IdentityHashtable</tt> with a default initial
* capacity of <tt>32</tt> and a loadfactor of <tt>0.75</tt>.
*/
public IdentityHashtable() {
loadFactor = DEFAULT_LOAD_FACTOR;
threshold = (int)(DEFAULT_INITIAL_CAPACITY * DEFAULT_LOAD_FACTOR);
entries = new Entry[DEFAULT_INITIAL_CAPACITY];
}
/**
* Removes all of the mappings from this <tt>IdentityHashtable</tt>.
*/
public synchronized 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 <tt>IdentityHashtable</tt> (the
* elements are not cloned).
*
* @return a shallow copy of this <tt>IdentityHashtable</tt>.
*/
public synchronized Object clone() {
try {
Entry[] copyOfEntries = entries;
IdentityHashtable clone = (IdentityHashtable)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();
}
}
/**
* Returns <tt>true</tt> if this <tt>IdentityHashtable</tt> contains
* the given object. Equality is tested by the equals() method.
*
* @param obj the object to find.
* @return <tt>true</tt> if this <tt>IdentityHashtable</tt> contains
* obj.
* @throws <tt>NullPointerException</tt> if obj is null</tt>.
*/
public synchronized boolean contains(Object obj) {
if (obj == null) {
throw new NullPointerException();
}
Entry[] copyOfEntries = entries;
for (int i = copyOfEntries.length; i-- > 0;) {
for (Entry e = copyOfEntries[i]; e != null; e = e.next) {
if (e.value.equals(obj)) {
return true;
}
}
}
return false;
}
/**
* Returns <tt>true</tt> if this <tt>IdentityHashtable</tt> contains a
* mapping for the given key. Equality is tested by reference.
*
* @param key object to be used as a key into this
* <tt>IdentityHashtable</tt>.
* @return <tt>true</tt> if this <tt>IdentityHashtable</tt> contains a
* mapping for key.
*/
public synchronized boolean containsKey(Object key) {
Entry[] copyOfEntries = entries;
int hash = System.identityHashCode(key);
int index = (hash & 0x7FFFFFFF) % copyOfEntries.length;
for (Entry e = copyOfEntries[index]; e != null; e = e.next) {
if (e.key == key) {
return true;
}
}
return false;
}
public synchronized Enumeration elements() {
if (count == 0) {
return emptyEnumerator;
} else {
return new Enumerator(ELEMENTS);
}
}
/**
* Returns the value to which the given key is mapped in this
* <tt>IdentityHashtable</tt>. Returns <tt>null</tt> if this
* <tt>IdentityHashtable</tt> contains no mapping for this key.
*
* @return the value to which this <tt>IdentityHashtable</tt> maps the
* given key.
* @param key key whose associated value is to be returned.
*/
public synchronized Object get(Object key) {
Entry[] copyOfEntries = entries;
int hash = System.identityHashCode(key);
int index = (hash & 0x7FFFFFFF) % copyOfEntries.length;
for (Entry e = copyOfEntries[index]; e != null; e = e.next) {
if (e.key == key) {
return e.value;
}
}
return null;
}
/**
* @return <tt>true</tt> if this <tt>IdentityHashtable</tt> is empty.
*/
public boolean isEmpty() {
return (count == 0);
}
public synchronized Enumeration keys() {
if (count == 0) {
return emptyEnumerator;
} else {
return new Enumerator(KEYS);
}
}
/**
* Associate the given object with the given key in this
* <tt>IdentityHashtable</tt>, replacing any existing mapping.
*
* @param key key to map to given object.
* @param obj object to be associated with key.
* @return the previous object for key or <tt>null</tt> if this
* <tt>IdentityHashtable</tt> did not have one.
* @throws <tt>NullPointerException</tt> if obj is null</tt>.
*/
public synchronized Object put(Object key, Object obj) {
if (obj == null) {
throw new NullPointerException();
}
Entry[] copyOfEntries = entries;
int hash = System.identityHashCode(key);
int index = (hash & 0x7FFFFFFF) % copyOfEntries.length;
for (Entry e = copyOfEntries[index]; e != null; e = e.next) {
if (e.key == key) {
Object old = e.value;
e.value = obj;
return old;
}
}
if (count >= threshold) {
rehash();
copyOfEntries = entries;
index = (hash & 0x7FFFFFFF) % copyOfEntries.length;
}
Entry e = new Entry(hash, key, obj, copyOfEntries[index]);
copyOfEntries[index] = e;
count++;
return null;
}
/**
* 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
* IdentityHashtable 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;
}
}
}
/**
* Removes the mapping (key and its corresponding value) from this
* <tt>IdentityHashtable</tt>, if present.
*
* @param key key whose mapping is to be removed from the map.
* @return the previous object for key or <tt>null</tt> if this
* <tt>IdentityHashtable</tt> did not have one.
*/
public synchronized Object remove(Object key) {
Entry[] copyOfEntries = entries;
int hash = System.identityHashCode(key);
int index = (hash & 0x7FFFFFFF) % copyOfEntries.length;
for (Entry e = copyOfEntries[index], prev = null; e != null; prev = e, e = e.next) {
if (e.key == key) {
if (prev != null) {
prev.next = e.next;
} else {
copyOfEntries[index] = e.next;
}
count--;
return e.value;
}
}
return null;
}
/**
* @return the size of this <tt>IdentityHashtable</tt>.
*/
public int size() {
return count;
}
/**
* Return the string representation of this <tt>IdentityHashtable</tt>.
*
* @return the string representation of this <tt>IdentityHashtable</tt>.
*/
public synchronized String toString() {
int max = size() - 1;
StringBuffer buf = new StringBuffer();
Enumeration k = keys();
Enumeration e = elements();
buf.append("{");
for (int i = 0; i <= max; i++) {
String s1 = k.nextElement().toString();
String s2 = e.nextElement().toString();
buf.append(s1 + "=" + s2);
if (i < max) {
buf.append(", ");
}
}
buf.append("}");
return buf.toString();
}
/**
* Serialize the state of this <tt>IdentityHashtable</tt> to a stream.
*
* @serialData The <i>capacity</i> of the <tt>IdentityHashtable</tt>
* (the length of the bucket array) is emitted (int), followed by the
* <i>size</i> of the <tt>IdentityHashtable</tt>, followed by the
* key-value mappings (in no particular order).
*/
private void writeObject(ObjectOutputStream s) throws IOException {
// 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 (int i = entries.length - 1; i >= 0; i--) {
Entry entry = entries[i];
while (entry != null) {
s.writeObject(entry.key);
s.writeObject(entry.value);
entry = entry.next;
}
}
}
/**
* Deserialize the <tt>IdentityHashtable</tt> 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 mappings and add to the TopLinkIdentityHashMap
for (int i = 0; i < size; i++) {
Object key = s.readObject();
Object value = s.readObject();
put(key, value);
}
}
private static class EmptyEnumerator implements Enumeration {
EmptyEnumerator() {
}
public boolean hasMoreElements() {
return false;
}
public Object nextElement() {
throw new NoSuchElementException();
}
}
class Enumerator implements Enumeration {
int enumeratorType;
int index;
Entry entry;
Enumerator(int enumeratorType) {
this.enumeratorType = enumeratorType;
index = IdentityHashtable.this.entries.length;
}
public boolean hasMoreElements() {
if (entry != null) {
return true;
}
while (index-- > 0) {
if ((entry = IdentityHashtable.this.entries[index]) != null) {
return true;
}
}
return false;
}
public Object nextElement() {
if (entry == null) {
while ((index-- > 0) && ((entry = IdentityHashtable.this.entries[index]) == null)) {
;
}
}
if (entry != null) {
Entry e = entry;
entry = e.next;
if (enumeratorType == KEYS) {
return e.key;
} else {
return e.value;
}
}
throw new NoSuchElementException("IdentityHashtable.Enumerator");
}
}
/**
* IdentityHashtable entry.
*/
private static class Entry {
int hash;
Object key;
Object value;
Entry next;
Entry(int hash, Object key, Object value, Entry next) {
this.hash = hash;
this.key = key;
this.value = value;
this.next = next;
}
protected Object clone() {
return new Entry(hash, key, value, ((next == null) ? null : (Entry)next.clone()));
}
public Object getKey() {
return key;
}
public Object getValue() {
return value;
}
public Object setValue(Object value) {
Object oldValue = this.value;
this.value = value;
return oldValue;
}
public boolean equals(Object o) {
if (!(o instanceof Entry)) {
return false;
}
Entry e = (Entry)o;
return (key == e.getKey()) && ((value == null) ? (e.getValue() == null) : value.equals(e.getValue()));
}
public int hashCode() {
return hash ^ ((value == null) ? 0 : value.hashCode());
}
public String toString() {
return key + "=" + value;
}
}
}
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