RefValueHashMap.java

/*
 * Copyright 2000-2013 JetBrains s.r.o.
 *
 * 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.intellij.util.containers;

import gnu.trove.THashMap;
import gnu.trove.TObjectHashingStrategy;
import org.jetbrains.annotations.NotNull;

import java.lang.ref.ReferenceQueue;
import java.util.*;

abstract class RefValueHashMap<K,V> implements Map<K,V>{
  private final Map<K,MyReference<K,V>> myMap;
  private final ReferenceQueue<V> myQueue = new ReferenceQueue<V>();

  protected interface MyReference<K,T> {
    K getKey();
    T get();
  }

  public RefValueHashMap() {
    myMap = new THashMap<K, MyReference<K,V>>();
  }

  public RefValueHashMap(@NotNull TObjectHashingStrategy<K> strategy) {
    myMap = new THashMap<K, MyReference<K,V>>(strategy);
  }

  protected abstract MyReference<K,V> createReference(@NotNull K key, V value, @NotNull ReferenceQueue<V> queue);

  private void processQueue() {
    while (true) {
      @SuppressWarnings("unchecked")
      MyReference<K,V> ref = (MyReference<K,V>)myQueue.poll();
      if (ref == null) {
        return;
      }
      K key = ref.getKey();
      if (myMap.get(key) == ref) {
        myMap.remove(key);
      }
    }
  }

  @Override
  public V get(Object key) {
    MyReference<K,V> ref = myMap.get(key);
    if (ref == null) return null;
    return ref.get();
  }

  @Override
  public V put(@NotNull K key, V value) {
    processQueue();
    MyReference<K, V> reference = createReference(key, value, myQueue);
    MyReference<K,V> oldRef = myMap.put(key, reference);
    return oldRef != null ? oldRef.get() : null;
  }

  @Override
  public V remove(Object key) {
    processQueue();
    MyReference<K,V> ref = myMap.remove(key);
    return ref != null ? ref.get() : null;
  }

  @Override
  public void putAll(@NotNull Map<? extends K, ? extends V> t) {
    throw new RuntimeException("method not implemented");
  }

  @Override
  public void clear() {
    myMap.clear();
  }

  @Override
  public int size() {
    return myMap.size(); //?
  }

  @Override
  public boolean isEmpty() {
    return myMap.isEmpty(); //?
  }

  @Override
  public boolean containsKey(Object key) {
    return get(key) != null;
  }

  @Override
  public boolean containsValue(Object value) {
    throw new RuntimeException("method not implemented");
  }

  @NotNull
  @Override
  public Set<K> keySet() {
    return myMap.keySet();
  }

  @NotNull
  @Override
  public Collection<V> values() {
    List<V> result = new ArrayList<V>();
    final Collection<MyReference<K, V>> refs = myMap.values();
    for (MyReference<K, V> ref : refs) {
      final V value = ref.get();
      if (value != null) {
        result.add(value);
      }
    }
    return result;
  }

  @NotNull
  @Override
  public Set<Entry<K, V>> entrySet() {
    throw new RuntimeException("method not implemented");
  }
}