/*
* Copyright 2014 Attila Szegedi, Daniel Dekany, Jonathan Revusky
*
* 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 freemarker.ext.util;
import java.util.AbstractCollection;
import java.util.AbstractMap;
import java.util.AbstractSet;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;
/**
* A variant of {@link java.util.HashMap} that uses
* {@link System#identityHashCode(Object)} for hashing, and reference comparison
* instead of {@link Object#equals(Object)}. Note that this applies only to keys,
* and not to values, i.e. {@link #containsValue(Object)} still uses {@link Object#equals(Object)}.
*/
public class IdentityHashMap
extends AbstractMap
implements Map, Cloneable, java.io.Serializable {
public static final long serialVersionUID = 362498820763181265L;
/**
* The hash table data.
*/
private transient Entry table[];
/**
* The total number of mappings in the hash table.
*/
private transient int count;
/**
* The table is rehashed when its size exceeds this threshold. (The
* value of this field is (int)(capacity * loadFactor).)
*/
private int threshold;
/**
* The load factor for the hashtable.
*/
private float loadFactor;
/**
* The number of times this IdentityHashMap has been structurally modified
* Structural modifications are those that change the number of mappings in
* the IdentityHashMap or otherwise modify its internal structure (e.g.,
* rehash). This field is used to make iterators on Collection-views of
* the IdentityHashMap fail-fast. (See ConcurrentModificationException).
*/
private transient int modCount = 0;
/**
* Constructs a new, empty map with the specified initial
* capacity and the specified load factor.
*
* @param initialCapacity the initial capacity of the IdentityHashMap.
* @param loadFactor the load factor of the IdentityHashMap
* @throws IllegalArgumentException if the initial capacity is less
* than zero, or if the load factor is nonpositive.
*/
public IdentityHashMap(int initialCapacity, float loadFactor) {
if (initialCapacity < 0)
throw new IllegalArgumentException(
"Illegal Initial Capacity: " + initialCapacity);
if (loadFactor <= 0 || Float.isNaN(loadFactor))
throw new IllegalArgumentException(
"Illegal Load factor: " + loadFactor);
if (initialCapacity == 0)
initialCapacity = 1;
this.loadFactor = loadFactor;
table = new Entry[initialCapacity];
threshold = (int) (initialCapacity * loadFactor);
}
/**
* Constructs a new, empty map with the specified initial capacity
* and default load factor, which is <tt>0.75</tt>.
*
* @param initialCapacity the initial capacity of the IdentityHashMap.
* @throws IllegalArgumentException if the initial capacity is less
* than zero.
*/
public IdentityHashMap(int initialCapacity) {
this(initialCapacity, 0.75f);
}
/**
* Constructs a new, empty map with a default capacity and load
* factor, which is <tt>0.75</tt>.
*/
public IdentityHashMap() {
this(11, 0.75f);
}
/**
* Constructs a new map with the same mappings as the given map. The
* map is created with a capacity of twice the number of mappings in
* the given map or 11 (whichever is greater), and a default load factor,
* which is <tt>0.75</tt>.
*
* @param t the map whose mappings are to be placed in this map.
*/
public IdentityHashMap(Map t) {
this(Math.max(2 * t.size(), 11), 0.75f);
putAll(t);
}
/**
* Returns the number of key-value mappings in this map.
*
* @return the number of key-value mappings in this map.
*/
@Override
public int size() {
return count;
}
/**
* Returns <tt>true</tt> if this map contains no key-value mappings.
*
* @return <tt>true</tt> if this map contains no key-value mappings.
*/
@Override
public boolean isEmpty() {
return count == 0;
}
/**
* Returns <tt>true</tt> 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 <tt>true</tt> if this map maps one or more keys to the
* specified value.
*/
@Override
public boolean containsValue(Object value) {
Entry tab[] = table;
if (value == null) {
for (int i = tab.length; i-- > 0; )
for (Entry e = tab[i]; e != null; e = e.next)
if (e.value == null)
return true;
} else {
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;
}
/**
* Returns <tt>true</tt> if this map contains a mapping for the specified
* key.
*
* @return <tt>true</tt> if this map contains a mapping for the specified
* key.
* @param key key whose presence in this Map is to be tested.
*/
@Override
public boolean containsKey(Object key) {
Entry tab[] = table;
if (key != null) {
int hash = System.identityHashCode(key);
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index]; e != null; e = e.next)
if (e.hash == hash && key == e.key)
return true;
} else {
for (Entry e = tab[0]; e != null; e = e.next)
if (e.key == null)
return true;
}
return false;
}
/**
* Returns the value to which this map maps the specified key. Returns
* <tt>null</tt> if the map contains no mapping for this key. A return
* value of <tt>null</tt> does not <i>necessarily</i> indicate that the
* map contains no mapping for the key; it's also possible that the map
* explicitly maps the key to <tt>null</tt>. The <tt>containsKey</tt>
* operation may be used to distinguish these two cases.
*
* @return the value to which this map maps the specified key.
* @param key key whose associated value is to be returned.
*/
@Override
public Object get(Object key) {
Entry tab[] = table;
if (key != null) {
int hash = System.identityHashCode(key);
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index]; e != null; e = e.next)
if ((e.hash == hash) && key == e.key)
return e.value;
} else {
for (Entry e = tab[0]; e != null; e = e.next)
if (e.key == null)
return e.value;
}
return null;
}
/**
* Rehashes the contents of this map into a new <tt>IdentityHashMap</tt> instance
* with a larger capacity. This method is called automatically when the
* number of keys in this map exceeds its capacity and load factor.
*/
private void rehash() {
int oldCapacity = table.length;
Entry oldMap[] = table;
int newCapacity = oldCapacity * 2 + 1;
Entry newMap[] = new Entry[newCapacity];
modCount++;
threshold = (int) (newCapacity * loadFactor);
table = newMap;
for (int i = oldCapacity; i-- > 0; ) {
for (Entry old = oldMap[i]; old != null; ) {
Entry e = old;
old = old.next;
int index = (e.hash & 0x7FFFFFFF) % newCapacity;
e.next = newMap[index];
newMap[index] = 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 <tt>null</tt>
* if there was no mapping for key. A <tt>null</tt> return can
* also indicate that the IdentityHashMap previously associated
* <tt>null</tt> with the specified key.
*/
@Override
public Object put(Object key, Object value) {
// Makes sure the key is not already in the IdentityHashMap.
Entry tab[] = table;
int hash = 0;
int index = 0;
if (key != null) {
hash = System.identityHashCode(key);
index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index]; e != null; e = e.next) {
if ((e.hash == hash) && key == e.key) {
Object old = e.value;
e.value = value;
return old;
}
}
} else {
for (Entry e = tab[0]; e != null; e = e.next) {
if (e.key == null) {
Object old = e.value;
e.value = value;
return old;
}
}
}
modCount++;
if (count >= threshold) {
// Rehash the table if the threshold is exceeded
rehash();
tab = table;
index = (hash & 0x7FFFFFFF) % tab.length;
}
// Creates the new entry.
Entry e = new Entry(hash, key, value, tab[index]);
tab[index] = e;
count++;
return null;
}
/**
* 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 <tt>null</tt>
* if there was no mapping for key. A <tt>null</tt> return can
* also indicate that the map previously associated <tt>null</tt>
* with the specified key.
*/
@Override
public Object remove(Object key) {
Entry tab[] = table;
if (key != null) {
int hash = System.identityHashCode(key);
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index], prev = null;
e != null;
prev = e, e = e.next) {
if ((e.hash == hash) && key == e.key) {
modCount++;
if (prev != null)
prev.next = e.next;
else
tab[index] = e.next;
count--;
Object oldValue = e.value;
e.value = null;
return oldValue;
}
}
} else {
for (Entry e = tab[0], prev = null;
e != null;
prev = e, e = e.next) {
if (e.key == null) {
modCount++;
if (prev != null)
prev.next = e.next;
else
tab[0] = e.next;
count--;
Object oldValue = e.value;
e.value = null;
return oldValue;
}
}
}
return null;
}
/**
* Copies all of the mappings from the specified map to this one.
*
* These mappings 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.
*/
@Override
public void putAll(Map t) {
Iterator i = t.entrySet().iterator();
while (i.hasNext()) {
Map.Entry e = (Map.Entry) i.next();
put(e.getKey(), e.getValue());
}
}
/**
* Removes all mappings from this map.
*/
@Override
public void clear() {
Entry tab[] = table;
modCount++;
for (int index = tab.length; --index >= 0; )
tab[index] = null;
count = 0;
}
/**
* Returns a shallow copy of this <tt>IdentityHashMap</tt> instance: the keys and
* values themselves are not cloned.
*
* @return a shallow copy of this map.
*/
@Override
public Object clone() {
try {
IdentityHashMap t = (IdentityHashMap) super.clone();
t.table = new Entry[table.length];
for (int i = table.length; i-- > 0; ) {
t.table[i] =
(table[i] != null) ? (Entry) table[i].clone() : null;
}
t.keySet = null;
t.entrySet = null;
t.values = null;
t.modCount = 0;
return t;
} catch (CloneNotSupportedException e) {
// this shouldn't happen, since we are Cloneable
throw new InternalError();
}
}
// Views
private transient Set keySet = null;
private transient Set entrySet = null;
private transient Collection values = 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 <tt>Iterator.remove</tt>,
* <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt>, and
* <tt>clear</tt> operations. It does not support the <tt>add</tt> or
* <tt>addAll</tt> operations.
*
* @return a set view of the keys contained in this map.
*/
@Override
public Set keySet() {
if (keySet == null) {
keySet = new AbstractSet()
{
@Override
public Iterator iterator() {
return getHashIterator(KEYS);
}
@Override
public int size() {
return count;
}
@Override
public boolean contains(Object o) {
return containsKey(o);
}
@Override
public boolean remove(Object o) {
int oldSize = count;
IdentityHashMap.this.remove(o);
return count != oldSize;
}
@Override
public void clear() {
IdentityHashMap.this.clear();
}
};
}
return keySet;
}
/**
* 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
* <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> operations.
* It does not support the <tt>add</tt> or <tt>addAll</tt> operations.
*
* @return a collection view of the values contained in this map.
*/
@Override
public Collection values() {
if (values == null) {
values = new AbstractCollection()
{
@Override
public Iterator iterator() {
return getHashIterator(VALUES);
}
@Override
public int size() {
return count;
}
@Override
public boolean contains(Object o) {
return containsValue(o);
}
@Override
public void clear() {
IdentityHashMap.this.clear();
}
};
}
return values;
}
/**
* Returns a collection view of the mappings contained in this map. Each
* element in the returned collection is a <tt>Map.Entry</tt>. 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
* <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> operations.
* It does not support the <tt>add</tt> or <tt>addAll</tt> operations.
*
* @return a collection view of the mappings contained in this map.
* @see java.util.Map.Entry
*/
@Override
public Set entrySet() {
if (entrySet == null) {
entrySet = new AbstractSet()
{
@Override
public Iterator iterator() {
return getHashIterator(ENTRIES);
}
@Override
public boolean contains(Object o) {
if (!(o instanceof Map.Entry))
return false;
Map.Entry entry = (Map.Entry) o;
Object key = entry.getKey();
Entry tab[] = table;
int hash = (key == null ? 0 : System.identityHashCode(key));
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index]; e != null; e = e.next)
if (e.hash == hash && e.equals(entry))
return true;
return false;
}
@Override
public boolean remove(Object o) {
if (!(o instanceof Map.Entry))
return false;
Map.Entry entry = (Map.Entry) o;
Object key = entry.getKey();
Entry tab[] = table;
int hash = (key == null ? 0 : System.identityHashCode(key));
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index], prev = null;
e != null;
prev = e, e = e.next) {
if (e.hash == hash && e.equals(entry)) {
modCount++;
if (prev != null)
prev.next = e.next;
else
tab[index] = e.next;
count--;
e.value = null;
return true;
}
}
return false;
}
@Override
public int size() {
return count;
}
@Override
public void clear() {
IdentityHashMap.this.clear();
}
};
}
return entrySet;
}
private Iterator getHashIterator(int type) {
if (count == 0) {
return emptyHashIterator;
} else {
return new HashIterator(type);
}
}
/**
* IdentityHashMap collision list entry.
*/
private static class Entry implements Map.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;
}
@Override
protected Object clone() {
return new Entry(
hash,
key,
value,
(next == null ? null : (Entry) next.clone()));
}
// Map.Entry Ops
public Object getKey() {
return key;
}
public Object getValue() {
return value;
}
public Object setValue(Object value) {
Object oldValue = this.value;
this.value = value;
return oldValue;
}
@Override
public boolean equals(Object o) {
if (!(o instanceof Map.Entry))
return false;
Map.Entry e = (Map.Entry) o;
return (key == e.getKey())
&& (value == null
? e.getValue() == null
: value.equals(e.getValue()));
}
@Override
public int hashCode() {
return hash ^ (value == null ? 0 : value.hashCode());
}
@Override
public String toString() {
return key + "=" + value;
}
}
// Types of Iterators
private static final int KEYS = 0;
private static final int VALUES = 1;
private static final int ENTRIES = 2;
private static EmptyHashIterator emptyHashIterator =
new EmptyHashIterator();
private static class EmptyHashIterator implements Iterator {
EmptyHashIterator() {
}
public boolean hasNext() {
return false;
}
public Object next() {
throw new NoSuchElementException();
}
public void remove() {
throw new IllegalStateException();
}
}
private class HashIterator implements Iterator {
Entry[] table = IdentityHashMap.this.table;
int index = table.length;
Entry entry = null;
Entry lastReturned = null;
int type;
/**
* The modCount value that the iterator believes that the backing
* List should have. If this expectation is violated, the iterator
* has detected concurrent modification.
*/
private int expectedModCount = modCount;
HashIterator(int type) {
this.type = type;
}
public boolean hasNext() {
Entry e = entry;
int i = index;
Entry t[] = table;
/* Use locals for faster loop iteration */
while (e == null && i > 0)
e = t[--i];
entry = e;
index = i;
return e != null;
}
public Object next() {
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
Entry et = entry;
int i = index;
Entry t[] = table;
/* Use locals for faster loop iteration */
while (et == null && i > 0)
et = t[--i];
entry = et;
index = i;
if (et != null) {
Entry e = lastReturned = entry;
entry = e.next;
return type == KEYS ? e.key : (type == VALUES ? e.value : e);
}
throw new NoSuchElementException();
}
public void remove() {
if (lastReturned == null)
throw new IllegalStateException();
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
Entry[] tab = IdentityHashMap.this.table;
int index = (lastReturned.hash & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index], prev = null;
e != null;
prev = e, e = e.next) {
if (e == lastReturned) {
modCount++;
expectedModCount++;
if (prev == null)
tab[index] = e.next;
else
prev.next = e.next;
count--;
lastReturned = null;
return;
}
}
throw new ConcurrentModificationException();
}
}
/**
* Save the state of the <tt>IdentityHashMap</tt> instance to a stream (i.e.,
* serialize it).
*
* @serialData The <i>capacity</i> of the IdentityHashMap (the length of the
* bucket array) is emitted (int), followed by the
* <i>size</i> of the IdentityHashMap (the number of key-value
* mappings), followed by the key (Object) and value (Object)
* for each key-value mapping represented by the IdentityHashMap
* The key-value mappings are emitted in no particular order.
*/
private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException {
// Write out the threshold, loadfactor, and any hidden stuff
s.defaultWriteObject();
// Write out number of buckets
s.writeInt(table.length);
// Write out size (number of Mappings)
s.writeInt(count);
// Write out keys and values (alternating)
for (int index = table.length - 1; index >= 0; index--) {
Entry entry = table[index];
while (entry != null) {
s.writeObject(entry.key);
s.writeObject(entry.value);
entry = entry.next;
}
}
}
/**
* Reconstitute the <tt>IdentityHashMap</tt> instance from a stream (i.e.,
* deserialize it).
*/
private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
// Read in the threshold, loadfactor, and any hidden stuff
s.defaultReadObject();
// Read in number of buckets and allocate the bucket array;
int numBuckets = s.readInt();
table = new Entry[numBuckets];
// Read in size (number of Mappings)
int size = s.readInt();
// Read the keys and values, and put the mappings in the IdentityHashMap
for (int i = 0; i < size; i++) {
Object key = s.readObject();
Object value = s.readObject();
put(key, value);
}
}
int capacity() {
return table.length;
}
float loadFactor() {
return loadFactor;
}
}