/*
* Copyright (C) 2007 Google Inc.
*
* 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.google.common.collect;
import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Objects;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkState;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import javax.annotation.Nullable;
/**
* A general-purpose bimap implementation using any two backing {@code Map}
* instances.
*
* <p>Note that this class contains {@code equals()} calls that keep it from
* supporting {@code IdentityHashMap} backing maps.
*
* @author Kevin Bourrillion
* @author Mike Bostock
*/
@GwtCompatible
abstract class AbstractBiMap<K, V> extends ForwardingMap<K, V>
implements BiMap<K, V>, Serializable {
private transient Map<K, V> delegate;
private transient AbstractBiMap<V, K> inverse;
/** Package-private constructor for creating a map-backed bimap. */
AbstractBiMap(Map<K, V> forward, Map<V, K> backward) {
setDelegates(forward, backward);
}
/** Private constructor for inverse bimap. */
private AbstractBiMap(Map<K, V> backward, AbstractBiMap<V, K> forward) {
delegate = backward;
inverse = forward;
}
@Override protected Map<K, V> delegate() {
return delegate;
}
/**
* Specifies the delegate maps going in each direction. Called by the
* constructor and by subclasses during deserialization.
*/
void setDelegates(Map<K, V> forward, Map<V, K> backward) {
checkState(delegate == null);
checkState(inverse == null);
checkArgument(forward.isEmpty());
checkArgument(backward.isEmpty());
checkArgument(forward != backward);
delegate = forward;
inverse = new Inverse<V, K>(backward, this);
}
void setInverse(AbstractBiMap<V, K> inverse) {
this.inverse = inverse;
}
// Query Operations (optimizations)
@Override public boolean containsValue(Object value) {
return inverse.containsKey(value);
}
// Modification Operations
@Override public V put(K key, V value) {
return putInBothMaps(key, value, false);
}
public V forcePut(K key, V value) {
return putInBothMaps(key, value, true);
}
private V putInBothMaps(@Nullable K key, @Nullable V value, boolean force) {
boolean containedKey = containsKey(key);
if (containedKey && Objects.equal(value, get(key))) {
return value;
}
if (force) {
inverse().remove(value);
} else {
checkArgument(!containsValue(value), "value already present: %s", value);
}
V oldValue = delegate.put(key, value);
updateInverseMap(key, containedKey, oldValue, value);
return oldValue;
}
private void updateInverseMap(
K key, boolean containedKey, V oldValue, V newValue) {
if (containedKey) {
removeFromInverseMap(oldValue);
}
inverse.delegate.put(newValue, key);
}
@Override public V remove(Object key) {
return containsKey(key) ? removeFromBothMaps(key) : null;
}
private V removeFromBothMaps(Object key) {
V oldValue = delegate.remove(key);
removeFromInverseMap(oldValue);
return oldValue;
}
private void removeFromInverseMap(V oldValue) {
inverse.delegate.remove(oldValue);
}
// Bulk Operations
@Override public void putAll(Map<? extends K, ? extends V> map) {
for (Entry<? extends K, ? extends V> entry : map.entrySet()) {
put(entry.getKey(), entry.getValue());
}
}
@Override public void clear() {
delegate.clear();
inverse.delegate.clear();
}
// Views
public BiMap<V, K> inverse() {
return inverse;
}
private transient Set<K> keySet;
@Override public Set<K> keySet() {
Set<K> result = keySet;
return (result == null) ? keySet = new KeySet() : result;
}
private class KeySet extends ForwardingSet<K> {
@Override protected Set<K> delegate() {
return delegate.keySet();
}
@Override public void clear() {
AbstractBiMap.this.clear();
}
@Override public boolean remove(Object key) {
if (!contains(key)) {
return false;
}
removeFromBothMaps(key);
return true;
}
@Override public boolean removeAll(Collection<?> keysToRemove) {
return Iterators.removeAll(iterator(), keysToRemove);
}
@Override public boolean retainAll(Collection<?> keysToRetain) {
return Iterators.retainAll(iterator(), keysToRetain);
}
@Override public Iterator<K> iterator() {
final Iterator<Entry<K, V>> iterator = delegate.entrySet().iterator();
return new Iterator<K>() {
Entry<K, V> entry;
public boolean hasNext() {
return iterator.hasNext();
}
public K next() {
entry = iterator.next();
return entry.getKey();
}
public void remove() {
checkState(entry != null);
V value = entry.getValue();
iterator.remove();
removeFromInverseMap(value);
}
};
}
}
private transient Set<V> valueSet;
@Override public Set<V> values() {
/*
* We can almost reuse the inverse's keySet, except we have to fix the
* iteration order so that it is consistent with the forward map.
*/
Set<V> result = valueSet;
return (result == null) ? valueSet = new ValueSet() : result;
}
private class ValueSet extends ForwardingSet<V> {
final Set<V> valuesDelegate = inverse.keySet();
@Override protected Set<V> delegate() {
return valuesDelegate;
}
@Override public Iterator<V> iterator() {
final Iterator<V> iterator = delegate.values().iterator();
return new Iterator<V>() {
V valueToRemove;
/*@Override*/ public boolean hasNext() {
return iterator.hasNext();
}
/*@Override*/ public V next() {
return valueToRemove = iterator.next();
}
/*@Override*/ public void remove() {
iterator.remove();
removeFromInverseMap(valueToRemove);
}
};
}
@Override public Object[] toArray() {
return ObjectArrays.toArrayImpl(this);
}
@Override public <T> T[] toArray(T[] array) {
return ObjectArrays.toArrayImpl(this, array);
}
@Override public String toString() {
return Iterators.toString(iterator());
}
}
private transient Set<Entry<K, V>> entrySet;
@Override public Set<Entry<K, V>> entrySet() {
Set<Entry<K, V>> result = entrySet;
return (result == null) ? entrySet = new EntrySet() : result;
}
private class EntrySet extends ForwardingSet<Entry<K, V>> {
final Set<Entry<K, V>> esDelegate = delegate.entrySet();
@Override protected Set<Entry<K, V>> delegate() {
return esDelegate;
}
@Override public void clear() {
AbstractBiMap.this.clear();
}
@Override public boolean remove(Object object) {
if (!esDelegate.remove(object)) {
return false;
}
Entry<?, ?> entry = (Entry<?, ?>) object;
inverse.delegate.remove(entry.getValue());
return true;
}
@Override public Iterator<Entry<K, V>> iterator() {
final Iterator<Entry<K, V>> iterator = esDelegate.iterator();
return new Iterator<Entry<K, V>>() {
Entry<K, V> entry;
/*@Override*/ public boolean hasNext() {
return iterator.hasNext();
}
/*@Override*/ public Entry<K, V> next() {
entry = iterator.next();
final Entry<K, V> finalEntry = entry;
return new ForwardingMapEntry<K, V>() {
@Override protected Entry<K, V> delegate() {
return finalEntry;
}
@Override public V setValue(V value) {
// Preconditions keep the map and inverse consistent.
checkState(contains(this), "entry no longer in map");
// similar to putInBothMaps, but set via entry
if (Objects.equal(value, getValue())) {
return value;
}
checkArgument(!containsValue(value),
"value already present: %s", value);
V oldValue = finalEntry.setValue(value);
checkState(Objects.equal(value, get(getKey())),
"entry no longer in map");
updateInverseMap(getKey(), true, oldValue, value);
return oldValue;
}
};
}
/*@Override*/ public void remove() {
checkState(entry != null);
V value = entry.getValue();
iterator.remove();
removeFromInverseMap(value);
}
};
}
// See java.util.Collections.CheckedEntrySet for details on attacks.
@Override public Object[] toArray() {
return ObjectArrays.toArrayImpl(this);
}
@Override public <T> T[] toArray(T[] array) {
return ObjectArrays.toArrayImpl(this, array);
}
@Override public boolean contains(Object o) {
return Maps.containsEntryImpl(delegate(), o);
}
@Override public boolean containsAll(Collection<?> c) {
return Collections2.containsAll(this, c);
}
@Override public boolean removeAll(Collection<?> c) {
return Iterators.removeAll(iterator(), c);
}
@Override public boolean retainAll(Collection<?> c) {
return Iterators.retainAll(iterator(), c);
}
}
/** The inverse of any other {@code AbstractBiMap} subclass. */
private static class Inverse<K, V> extends AbstractBiMap<K, V> {
private Inverse(Map<K, V> backward, AbstractBiMap<V, K> forward) {
super(backward, forward);
}
/*
* Serialization stores the forward bimap, the inverse of this inverse.
* Deserialization calls inverse() on the forward bimap and returns that
* inverse.
*
* If a bimap and its inverse are serialized together, the deserialized
* instances have inverse() methods that return the other.
*/
/**
* @serialData the forward bimap
*/
private void writeObject(ObjectOutputStream stream) throws IOException {
stream.defaultWriteObject();
stream.writeObject(inverse());
}
@SuppressWarnings("unchecked") // reading data stored by writeObject
private void readObject(ObjectInputStream stream)
throws IOException, ClassNotFoundException {
stream.defaultReadObject();
setInverse((AbstractBiMap<V, K>) stream.readObject());
}
Object readResolve() {
return inverse().inverse();
}
private static final long serialVersionUID = 0;
}
private static final long serialVersionUID = 0;
}