com.justai.jaicf.helpers.java.WeakIdentityHashMap Maven / Gradle / Ivy
/*
* JBoss, Home of Professional Open Source
* Copyright 2015, Red Hat, Inc., and individual contributors as indicated
* by the @authors tag.
*
* 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 com.justai.jaicf.helpers.java;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.util.*;
/**
* A hashtable-based Map implementation with weak keys and
* using reference-equality in place of object-equality when comparing keys
* (and values). In an WeakIdentityHashMap, two keys k1 and
* k2 are considered equal if and only if (k1==k2).
* An entry in a WeakIdentityHashMap will automatically be removed when
* its key is no longer in ordinary use. More precisely, the presence of a
* mapping for a given key will not prevent the key from being discarded by the
* garbage collector, that is, made finalizable, finalized, and then reclaimed.
* When a key has been discarded its entry is effectively removed from the map.
*
* Based on java.util.WeakHashMap
* Based on org.jboss.common.collection.WeakIdentityHashMap
*
* @author Dawid Kurzyniec
* @author Kabir Khan
* @author Emmanuel Bernard
* @see java.util.IdentityHashMap
* @see java.util.WeakHashMap
*/
public class WeakIdentityHashMap implements Map {
/**
* The default initial capacity -- MUST be a power of two.
*/
private static final int DEFAULT_INITIAL_CAPACITY = 16;
/**
* The maximum capacity, used if a higher value is implicitly specified
* by either of the constructors with arguments.
* MUST be a power of two <= 1<<30.
*/
private static final int MAXIMUM_CAPACITY = 1 << 30;
/**
* The load fast used when none specified in constructor.
*/
private static final float DEFAULT_LOAD_FACTOR = 0.75f;
/**
* The table, resized as necessary. Length MUST Always be a power of two.
*/
private Entry[] table;
/**
* The number of key-value mappings contained in this weak hash map.
*/
private int size;
/**
* The next size value at which to resize (capacity * load factor).
*/
private int threshold;
/**
* The load factor for the hash table.
*/
private final float loadFactor;
/**
* Reference queue for cleared WeakEntries
*/
private final ReferenceQueue queue = new ReferenceQueue();
/**
* The number of times this HashMap has been structurally modified
* Structural modifications are those that change the number of mappings in
* the HashMap or otherwise modify its internal structure (e.g.,
* rehash). This field is used to make iterators on Collection-views of
* the HashMap fail-fast. (See ConcurrentModificationException).
*/
private volatile int modCount;
/**
* Each of these fields are initialized to contain an instance of the
* appropriate view the first time this view is requested. The views are
* stateless, so there's no reason to create more than one of each.
*/
transient volatile Set keySet = null;
transient volatile Collection values = null;
/**
* Constructs a new, empty WeakIdentityHashMap with the given
* initial capacity and the given load factor.
*
* @param initialCapacity The initial capacity of the
* WeakIdentityHashMap
* @param loadFactor The load factor of the
* WeakIdentityHashMap
* @throws IllegalArgumentException If the initial capacity is negative,
* or if the load factor is nonpositive.
*/
public WeakIdentityHashMap(int initialCapacity, float loadFactor) {
if ( initialCapacity < 0 )
throw new IllegalArgumentException( "Illegal Initial Capacity: " +
initialCapacity );
if ( initialCapacity > MAXIMUM_CAPACITY )
initialCapacity = MAXIMUM_CAPACITY;
if ( loadFactor <= 0 || Float.isNaN( loadFactor ) )
throw new IllegalArgumentException( "Illegal Load factor: " +
loadFactor );
int capacity = 1;
while ( capacity < initialCapacity )
capacity <<= 1;
table = new Entry[capacity];
this.loadFactor = loadFactor;
threshold = (int) ( capacity * loadFactor );
}
/**
* Constructs a new, empty WeakIdentityHashMap with the given
* initial capacity and the default load factor, which is 0.75.
*
* @param initialCapacity The initial capacity of the
* WeakIdentityHashMap
* @throws IllegalArgumentException If the initial capacity is negative.
*/
public WeakIdentityHashMap(int initialCapacity) {
this( initialCapacity, DEFAULT_LOAD_FACTOR );
}
/**
* Constructs a new, empty WeakIdentityHashMap with the default
* initial capacity (16) and the default load factor (0.75).
*/
public WeakIdentityHashMap() {
this.loadFactor = DEFAULT_LOAD_FACTOR;
threshold = DEFAULT_INITIAL_CAPACITY;
table = new Entry[DEFAULT_INITIAL_CAPACITY];
}
/**
* Constructs a new WeakIdentityHashMap with the same mappings as
* the specified Map. The WeakIdentityHashMap is created
* with default load factor, which is 0.75 and an initial capacity
* sufficient to hold the mappings in the specified Map.
*
* @param t the map whose mappings are to be placed in this map.
* @throws NullPointerException if the specified map is null.
*/
public WeakIdentityHashMap(Map t) {
this( Math.max( (int) ( t.size() / DEFAULT_LOAD_FACTOR ) + 1, 16 ),
DEFAULT_LOAD_FACTOR );
putAll( t );
}
// internal utilities
/**
* Value representing null keys inside tables.
*/
private static final Object NULL_KEY = new Object();
/**
* Use NULL_KEY for key if it is null.
*/
private static T maskNull(T key) {
return ( key == null ?
(T) NULL_KEY : //i don't think there is a better way
key );
}
/**
* Return internal representation of null key back to caller as null
*/
private static T unmaskNull(T key) {
return ( key == NULL_KEY ?
null :
key );
}
/**
* Return a hash code for non-null Object x.
*/
int hash(Object x) {
int h = System.identityHashCode( x );
return h - ( h << 7 ); // that is,, -127 * h
}
/**
* Return index for hash code h.
*/
static int indexFor(int h, int length) {
return h & ( length - 1 );
}
/**
* Expunge stale entries from the table.
*/
private void expungeStaleEntries() {
Object r;
while ( ( r = queue.poll() ) != null ) {
Entry e = (Entry) r;
int h = e.hash;
int i = indexFor( h, table.length );
Entry prev = table[i];
Entry p = prev;
while ( p != null ) {
Entry next = p.next;
if ( p == e ) {
if ( prev == e )
table[i] = next;
else
prev.next = next;
e.next = null; // Help GC
e.value = null; // " "
size--;
break;
}
prev = p;
p = next;
}
}
}
/**
* Return the table after first expunging stale entries
*/
private Entry[] getTable() {
expungeStaleEntries();
return table;
}
/**
* Returns the number of key-value mappings in this map.
* This result is a snapshot, and may not reflect unprocessed
* entries that will be removed before next attempted access
* because they are no longer referenced.
*/
public int size() {
if ( size == 0 )
return 0;
expungeStaleEntries();
return size;
}
/**
* Returns true if this map contains no key-value mappings.
* This result is a snapshot, and may not reflect unprocessed
* entries that will be removed before next attempted access
* because they are no longer referenced.
*/
public boolean isEmpty() {
return size() == 0;
}
/**
* Returns the value to which the specified key is mapped in this weak
* hash map, or null if the map contains no mapping for
* this key. A return value of null does not necessarily
* indicate that the map contains no mapping for the key; it is also
* possible that the map explicitly maps the key to null. The
* containsKey method may be used to distinguish these two
* cases.
*
* @param key the key whose associated value is to be returned.
* @return the value to which this map maps the specified key, or
* null if the map contains no mapping for this key.
* @see #put(Object,Object)
*/
public V get(Object key) {
Object k = maskNull( key );
int h = hash( k );
Entry[] tab = getTable();
int index = indexFor( h, tab.length );
Entry e = tab[index];
while ( e != null ) {
if ( e.hash == h && k == e.get() )
return e.value;
e = e.next;
}
return null;
}
/**
* Returns true if this map contains a mapping for the
* specified key.
*
* @param key The key whose presence in this map is to be tested
* @return true if there is a mapping for key;
* false otherwise
*/
public boolean containsKey(Object key) {
return getEntry( key ) != null;
}
/**
* Returns the entry associated with the specified key in the HashMap.
* Returns null if the HashMap contains no mapping for this key.
*/
Entry getEntry(Object key) {
Object k = maskNull( key );
int h = hash( k );
Entry[] tab = getTable();
int index = indexFor( h, tab.length );
Entry e = tab[index];
while ( e != null && !( e.hash == h && k == e.get() ) )
e = e.next;
return e;
}
/**
* Associates the specified value with the specified key in this map.
* If the map previously contained a mapping for this key, the old
* value is replaced.
*
* @param key key with which the specified value is to be associated.
* @param value value to be associated with the specified key.
* @return previous value associated with specified key, or null
* if there was no mapping for key. A null return can
* also indicate that the HashMap previously associated
* null with the specified key.
*/
public V put(K key, V value) {
K k = maskNull( key );
int h = hash( k );
Entry[] tab = getTable();
int i = indexFor( h, tab.length );
for ( Entry e = tab[i]; e != null; e = e.next ) {
if ( h == e.hash && k == e.get() ) {
V oldValue = e.value;
if ( value != oldValue )
e.value = value;
return oldValue;
}
}
modCount++;
tab[i] = new Entry( k, value, queue, h, tab[i] );
if ( ++size >= threshold )
resize( tab.length * 2 );
return null;
}
/**
* Rehashes the contents of this map into a new HashMap instance
* with a larger capacity. This method is called automatically when the
* number of keys in this map exceeds its capacity and load factor.
*
* Note that this method is a no-op if it's called with newCapacity ==
* 2*MAXIMUM_CAPACITY (which is Integer.MIN_VALUE).
*
* @param newCapacity the new capacity, MUST be a power of two.
*/
void resize(int newCapacity) {
// assert (newCapacity & -newCapacity) == newCapacity; // power of 2
Entry[] oldTable = getTable();
int oldCapacity = oldTable.length;
// check if needed
if ( size < threshold || oldCapacity > newCapacity )
return;
Entry[] newTable = new Entry[newCapacity];
transfer( oldTable, newTable );
table = newTable;
/*
* If ignoring null elements and processing ref queue caused massive
* shrinkage, then restore old table. This should be rare, but avoids
* unbounded expansion of garbage-filled tables.
*/
if ( size >= threshold / 2 ) {
threshold = (int) ( newCapacity * loadFactor );
}
else {
expungeStaleEntries();
transfer( newTable, oldTable );
table = oldTable;
}
}
/**
* Transfer all entries from src to dest tables
*/
private void transfer(Entry[] src, Entry[] dest) {
for ( int j = 0; j < src.length; ++j ) {
Entry e = src[j];
src[j] = null;
while ( e != null ) {
Entry next = e.next;
K key = e.get();
if ( key == null ) {
e.next = null; // Help GC
e.value = null; // " "
size--;
}
else {
int i = indexFor( e.hash, dest.length );
e.next = dest[i];
dest[i] = e;
}
e = next;
}
}
}
/**
* Copies all of the mappings from the specified map to this map These
* mappings will replace any mappings that this map had for any of the
* keys currently in the specified map.
*
* @param t mappings to be stored in this map.
* @throws NullPointerException if the specified map is null.
*/
public void putAll(Map t) {
// Expand enough to hold t's elements without resizing.
int n = t.size();
if ( n == 0 )
return;
if ( n >= threshold ) {
n = (int) ( n / loadFactor + 1 );
if ( n > MAXIMUM_CAPACITY )
n = MAXIMUM_CAPACITY;
int capacity = table.length;
while ( capacity < n )
capacity <<= 1;
resize( capacity );
}
for ( Iterator i = t.entrySet().iterator(); i.hasNext(); ) {
Map.Entry e = (Map.Entry) i.next(); //FIXME should not have to cast
put( e.getKey(), e.getValue() );
}
}
/**
* Removes the mapping for this key from this map if present.
*
* @param key key whose mapping is to be removed from the map.
* @return previous value associated with specified key, or null
* if there was no mapping for key. A null return can
* also indicate that the map previously associated null
* with the specified key.
*/
public V remove(Object key) {
Object k = maskNull( key );
int h = hash( k );
Entry[] tab = getTable();
int i = indexFor( h, tab.length );
Entry prev = tab[i];
Entry e = prev;
while ( e != null ) {
Entry next = e.next;
if ( h == e.hash && k == e.get() ) {
modCount++;
size--;
if ( prev == e )
tab[i] = next;
else
prev.next = next;
return e.value;
}
prev = e;
e = next;
}
return null;
}
/**
* Special version of remove needed by Entry set
*/
Entry removeMapping(Object o) {
if ( !( o instanceof Map.Entry ) )
return null;
Entry[] tab = getTable();
Map.Entry entry = (Map.Entry) o;
Object k = maskNull( entry.getKey() );
int h = hash( k );
int i = indexFor( h, tab.length );
Entry prev = tab[i];
Entry e = prev;
while ( e != null ) {
Entry next = e.next;
if ( h == e.hash && e.equals( entry ) ) {
modCount++;
size--;
if ( prev == e )
tab[i] = next;
else
prev.next = next;
return e;
}
prev = e;
e = next;
}
return null;
}
/**
* Removes all mappings from this map.
*/
public void clear() {
// clear out ref queue. We don't need to expunge entries
// since table is getting cleared.
while ( queue.poll() != null )
;
modCount++;
Entry tab[] = table;
for ( int i = 0; i < tab.length; ++i )
tab[i] = null;
size = 0;
// Allocation of array may have caused GC, which may have caused
// additional entries to go stale. Removing these entries from the
// reference queue will make them eligible for reclamation.
while ( queue.poll() != null )
;
}
/**
* Returns true if this map maps one or more keys to the
* specified value.
*
* @param value value whose presence in this map is to be tested.
* @return true if this map maps one or more keys to the
* specified value.
*/
public boolean containsValue(Object value) {
if ( value == null )
return containsNullValue();
Entry tab[] = getTable();
for ( int i = tab.length; i-- > 0; )
for ( Entry e = tab[i]; e != null; e = e.next )
if ( value.equals( e.value ) )
return true;
return false;
}
/**
* Special-case code for containsValue with null argument
*/
private boolean containsNullValue() {
Entry tab[] = getTable();
for ( int i = tab.length; i-- > 0; )
for ( Entry e = tab[i]; e != null; e = e.next )
if ( e.value == null )
return true;
return false;
}
/**
* Remove elements having the according value.
* Intended to avoid concurrent access exceptions
* It is expected that nobody add a key being removed by value
*
* @param value value whose presence in this map is to be removed.
* @return true if this map maps one or more keys to the
* specified value.
*/
public boolean removeValue(Object value) {
if ( value == null )
return removeNullValue();
Entry tab[] = getTable();
Set keys = new HashSet();
for ( int i = tab.length; i-- > 0; )
for ( Entry e = tab[i]; e != null; e = e.next )
if ( value.equals( e.value ) )
keys.add( e.getKey() );
for ( Object key : keys ) remove( key );
return !keys.isEmpty();
}
/**
* Special-case code for removeValue with null argument
*/
private boolean removeNullValue() {
Entry tab[] = getTable();
Set keys = new HashSet();
for ( int i = tab.length; i-- > 0; )
for ( Entry e = tab[i]; e != null; e = e.next )
if ( e.value == null )
keys.add( e.getKey() );
for ( Object key : keys ) remove( key );
return !keys.isEmpty();
}
/**
* The entries in this hash table extend WeakReference, using its main ref
* field as the key.
*/
private static class Entry extends WeakReference implements Map.Entry {
private V value;
private final int hash;
private Entry next;
/**
* Create new entry.
*/
Entry(K key, V value, ReferenceQueue queue,
int hash, Entry next) {
super( key, queue );
this.value = value;
this.hash = hash;
this.next = next;
}
public K getKey() {
return WeakIdentityHashMap.unmaskNull( this.get() );
}
public V getValue() {
return value;
}
public V setValue(V newValue) {
V oldValue = value;
value = newValue;
return oldValue;
}
public boolean equals(Object o) {
if ( !( o instanceof Map.Entry ) )
return false;
Map.Entry e = (Map.Entry) o;
Object k1 = getKey();
Object k2 = e.getKey();
if ( k1 == k2 ) {
Object v1 = getValue();
Object v2 = e.getValue();
if ( v1 == v2 || ( v1 != null && v1.equals( v2 ) ) )
return true;
}
return false;
}
public int hashCode() {
Object k = getKey();
Object v = getValue();
return ( ( k == null ?
0 :
System.identityHashCode( k ) ) ^
( v == null ?
0 :
v.hashCode() ) );
}
public String toString() {
return getKey() + "=" + getValue();
}
}
private abstract class HashIterator implements Iterator {
int index;
Entry entry = null;
Entry lastReturned = null;
int expectedModCount = modCount;
/**
* Strong reference needed to avoid disappearance of key
* between hasNext and next
*/
Object nextKey = null;
/**
* Strong reference needed to avoid disappearance of key
* between nextEntry() and any use of the entry
*/
Object currentKey = null;
HashIterator() {
index = ( size() != 0 ?
table.length :
0 );
}
public boolean hasNext() {
Entry[] t = table;
while ( nextKey == null ) {
Entry e = entry;
int i = index;
while ( e == null && i > 0 )
e = t[--i];
entry = e;
index = i;
if ( e == null ) {
currentKey = null;
return false;
}
nextKey = e.get(); // hold on to key in strong ref
if ( nextKey == null )
entry = entry.next;
}
return true;
}
/**
* The common parts of next() across different types of iterators
*/
protected Entry nextEntry() {
if ( modCount != expectedModCount )
throw new ConcurrentModificationException();
if ( nextKey == null && !hasNext() )
throw new NoSuchElementException();
lastReturned = entry;
entry = entry.next;
currentKey = nextKey;
nextKey = null;
return lastReturned;
}
public void remove() {
if ( lastReturned == null )
throw new IllegalStateException();
if ( modCount != expectedModCount )
throw new ConcurrentModificationException();
WeakIdentityHashMap.this.remove( currentKey );
expectedModCount = modCount;
lastReturned = null;
currentKey = null;
}
}
private class ValueIterator extends HashIterator {
public Object next() {
return nextEntry().value;
}
}
private class KeyIterator extends HashIterator {
public Object next() {
return nextEntry().getKey();
}
}
private class EntryIterator extends HashIterator> {
public Map.Entry next() {
return nextEntry();
}
}
// Views
private transient Set> entrySet = null;
/**
* Returns a set view of the keys contained in this map. The set is
* backed by the map, so changes to the map are reflected in the set, and
* vice-versa. The set supports element removal, which removes the
* corresponding mapping from this map, via the Iterator.remove,
* Set.remove, removeAll, retainAll, and
* clear operations. It does not support the add or
* addAll operations.
*
* @return a set view of the keys contained in this map.
*/
public Set keySet() {
Set ks = keySet;
return ( ks != null ?
ks :
( keySet = new KeySet() ) );
}
private class KeySet extends AbstractSet {
public Iterator iterator() {
return new KeyIterator();
}
public int size() {
return WeakIdentityHashMap.this.size();
}
public boolean contains(Object o) {
return containsKey( o );
}
public boolean remove(Object o) {
if ( containsKey( o ) ) {
WeakIdentityHashMap.this.remove( o );
return true;
}
else
return false;
}
public void clear() {
WeakIdentityHashMap.this.clear();
}
public Object[] toArray() {
Collection c = new ArrayList( size() );
for ( Iterator i = iterator(); i.hasNext(); )
c.add( i.next() );
return c.toArray();
}
public Object[] toArray(Object a[]) {
Collection c = new ArrayList( size() );
for ( Iterator i = iterator(); i.hasNext(); )
c.add( i.next() );
return c.toArray( a );
}
}
/**
* Returns a collection view of the values contained in this map. The
* collection is backed by the map, so changes to the map are reflected in
* the collection, and vice-versa. The collection supports element
* removal, which removes the corresponding mapping from this map, via the
* Iterator.remove, Collection.remove,
* removeAll, retainAll, and clear operations.
* It does not support the add or addAll operations.
*
* @return a collection view of the values contained in this map.
*/
public Collection values() {
Collection vs = values;
return ( vs != null ?
vs :
( values = new Values() ) );
}
private class Values extends AbstractCollection {
public Iterator iterator() {
return new ValueIterator();
}
public int size() {
return WeakIdentityHashMap.this.size();
}
public boolean contains(Object o) {
return containsValue( o );
}
public void clear() {
WeakIdentityHashMap.this.clear();
}
public Object[] toArray() {
Collection c = new ArrayList( size() );
for ( Iterator i = iterator(); i.hasNext(); )
c.add( i.next() );
return c.toArray();
}
public Object[] toArray(Object a[]) {
Collection c = new ArrayList( size() );
for ( Iterator i = iterator(); i.hasNext(); )
c.add( i.next() );
return c.toArray( a );
}
}
/**
* Returns a collection view of the mappings contained in this map. Each
* element in the returned collection is a Map.Entry. The
* collection is backed by the map, so changes to the map are reflected in
* the collection, and vice-versa. The collection supports element
* removal, which removes the corresponding mapping from the map, via the
* Iterator.remove, Collection.remove,
* removeAll, retainAll, and clear operations.
* It does not support the add or addAll operations.
*
* @return a collection view of the mappings contained in this map.
* @see java.util.Map.Entry
*/
public Set> entrySet() {
Set> es = entrySet;
return ( es != null ?
es :
( entrySet = new EntrySet() ) );
}
private class EntrySet extends AbstractSet> {
public Iterator> iterator() {
return new EntryIterator();
}
public boolean contains(Object o) {
if ( !( o instanceof Map.Entry ) )
return false;
Map.Entry e = (Map.Entry) o;
Object k = e.getKey();
Entry candidate = getEntry( e.getKey() );
return candidate != null && candidate.equals( e );
}
public boolean remove(Object o) {
return removeMapping( o ) != null;
}
public int size() {
return WeakIdentityHashMap.this.size();
}
public void clear() {
WeakIdentityHashMap.this.clear();
}
public Object[] toArray() {
Collection c = new ArrayList( size() );
for ( Iterator i = iterator(); i.hasNext(); )
c.add( new SimpleEntry( (Map.Entry) i.next() ) );
return c.toArray();
}
public Object[] toArray(Object a[]) {
Collection c = new ArrayList( size() );
for ( Iterator i = iterator(); i.hasNext(); )
c.add( new SimpleEntry( (Map.Entry) i.next() ) );
return c.toArray( a );
}
}
static class SimpleEntry implements Map.Entry {
Object key;
Object value;
public SimpleEntry(Object key, Object value) {
this.key = key;
this.value = value;
}
public SimpleEntry(Map.Entry e) {
this.key = e.getKey();
this.value = e.getValue();
}
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 Map.Entry ) )
return false;
Map.Entry e = (Map.Entry) o;
return eq( key, e.getKey() ) && eq( value, e.getValue() );
}
public int hashCode() {
Object v;
return ( ( key == null ) ?
0 :
key.hashCode() ) ^
( ( value == null ) ?
0 :
value.hashCode() );
}
public String toString() {
return key + "=" + value;
}
private static boolean eq(Object o1, Object o2) {
return ( o1 == null ?
o2 == null :
o1.equals( o2 ) );
}
}
}