/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.drill.common.collections;
import java.util.AbstractMap;
import java.util.Collection;
import java.util.Map;
import java.util.Set;
import com.google.common.base.Function;
import com.google.common.base.Preconditions;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.collect.Sets;
import io.netty.util.collection.IntObjectHashMap;
import io.netty.util.collection.IntObjectMap;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* An implementation of map that supports constant time look-up by a generic key or an ordinal.
*
* This class extends the functionality a regular {@link Map} with ordinal lookup support.
* Upon insertion an unused ordinal is assigned to the inserted (key, value) tuple.
* Upon update the same ordinal id is re-used while value is replaced.
* Upon deletion of an existing item, its corresponding ordinal is recycled and could be used by another item.
*
* For any instance with N items, this implementation guarantees that ordinals are in the range of [0, N). However,
* the ordinal assignment is dynamic and may change after an insertion or deletion. Consumers of this class are
* responsible for explicitly checking the ordinal corresponding to a key via
* {@link org.apache.drill.common.collections.MapWithOrdinal#getOrdinal(Object)} before attempting to execute a lookup
* with an ordinal.
*
* @param <K> key type
* @param <V> value type
*/
public class MapWithOrdinal<K, V> implements Map<K, V> {
private final static Logger logger = LoggerFactory.getLogger(MapWithOrdinal.class);
private final Map<K, Entry<Integer, V>> primary = Maps.newLinkedHashMap();
private final IntObjectHashMap<V> secondary = new IntObjectHashMap<>();
private final Map<K, V> delegate = new Map<K, V>() {
@Override
public boolean isEmpty() {
return size() == 0;
}
@Override
public int size() {
return primary.size();
}
@Override
public boolean containsKey(Object key) {
return primary.containsKey(key);
}
@Override
public boolean containsValue(Object value) {
return primary.containsValue(value);
}
@Override
public V get(Object key) {
Entry<Integer, V> pair = primary.get(key);
if (pair != null) {
return pair.getValue();
}
return null;
}
@Override
public V put(K key, V value) {
final Entry<Integer, V> oldPair = primary.get(key);
// if key exists try replacing otherwise, assign a new ordinal identifier
final int ordinal = oldPair == null ? primary.size():oldPair.getKey();
primary.put(key, new AbstractMap.SimpleImmutableEntry<>(ordinal, value));
secondary.put(ordinal, value);
return oldPair==null ? null:oldPair.getValue();
}
@Override
public V remove(Object key) {
final Entry<Integer, V> oldPair = primary.remove(key);
if (oldPair!=null) {
final int lastOrdinal = secondary.size();
final V last = secondary.get(lastOrdinal);
// normalize mappings so that all numbers until primary.size() is assigned
// swap the last element with the deleted one
secondary.put(oldPair.getKey(), last);
primary.put((K) key, new AbstractMap.SimpleImmutableEntry<>(oldPair.getKey(), last));
}
return oldPair==null ? null:oldPair.getValue();
}
@Override
public void putAll(Map<? extends K, ? extends V> m) {
throw new UnsupportedOperationException();
}
@Override
public void clear() {
primary.clear();
secondary.clear();
}
@Override
public Set<K> keySet() {
return primary.keySet();
}
@Override
public Collection<V> values() {
return Lists.newArrayList(Iterables.transform(secondary.entries(), new Function<IntObjectMap.Entry<V>, V>() {
@Override
public V apply(IntObjectMap.Entry<V> entry) {
return Preconditions.checkNotNull(entry).value();
}
}));
}
@Override
public Set<Entry<K, V>> entrySet() {
return Sets.newHashSet(Iterables.transform(primary.entrySet(), new Function<Entry<K, Entry<Integer, V>>, Entry<K, V>>() {
@Override
public Entry<K, V> apply(Entry<K, Entry<Integer, V>> entry) {
return new AbstractMap.SimpleImmutableEntry<>(entry.getKey(), entry.getValue().getValue());
}
}));
}
};
/**
* Returns the value corresponding to the given ordinal
*
* @param id ordinal value for lookup
* @return an instance of V
*/
public V getByOrdinal(int id) {
return secondary.get(id);
}
/**
* Returns the ordinal corresponding to the given key.
*
* @param key key for ordinal lookup
* @return ordinal value corresponding to key if it exists or -1
*/
public int getOrdinal(K key) {
Entry<Integer, V> pair = primary.get(key);
if (pair != null) {
return pair.getKey();
}
return -1;
}
@Override
public int size() {
return delegate.size();
}
@Override
public boolean isEmpty() {
return delegate.isEmpty();
}
@Override
public V get(Object key) {
return delegate.get(key);
}
/**
* Inserts the tuple (key, value) into the map extending the semantics of {@link Map#put} with automatic ordinal
* assignment. A new ordinal is assigned if key does not exists. Otherwise the same ordinal is re-used but the value
* is replaced.
*
* {@see java.util.Map#put}
*/
@Override
public V put(K key, V value) {
return delegate.put(key, value);
}
@Override
public Collection<V> values() {
return delegate.values();
}
@Override
public boolean containsKey(Object key) {
return delegate.containsKey(key);
}
@Override
public boolean containsValue(Object value) {
return delegate.containsValue(value);
}
/**
* Removes the element corresponding to the key if exists extending the semantics of {@link Map#remove} with ordinal
* re-cycling. The ordinal corresponding to the given key may be re-assigned to another tuple. It is important that
* consumer checks the ordinal value via {@link #getOrdinal(Object)} before attempting to look-up by ordinal.
*
* {@see java.util.Map#remove}
*/
@Override
public V remove(Object key) {
return delegate.remove(key);
}
@Override
public void putAll(Map<? extends K, ? extends V> m) {
delegate.putAll(m);
}
@Override
public void clear() {
delegate.clear();
}
@Override
public Set<K> keySet() {
return delegate.keySet();
}
@Override
public Set<Entry<K, V>> entrySet() {
return delegate.entrySet();
}
}