001/*
002 *  This file is part of the Jikes RVM project (http://jikesrvm.org).
003 *
004 *  This file is licensed to You under the Eclipse Public License (EPL);
005 *  You may not use this file except in compliance with the License. You
006 *  may obtain a copy of the License at
007 *
008 *      http://www.opensource.org/licenses/eclipse-1.0.php
009 *
010 *  See the COPYRIGHT.txt file distributed with this work for information
011 *  regarding copyright ownership.
012 */
013package org.jikesrvm.util;
014
015import org.jikesrvm.util.ImmutableEntryHashMapRVM.Bucket;
016import org.jikesrvm.runtime.Magic;
017
018/**
019 * A hash map with entirely immutable buckets. It doesn't correctly support
020 * remove, and its values cannot be mutated by a put with the same key.
021 */
022public final class ImmutableEntryIdentityHashMapRVM<K, V> extends AbstractHashMapRVM<K,V> {
023
024  @Override
025  AbstractBucket<K,V> createNewBucket(K key, V value, AbstractBucket<K, V> next) {
026    return new Bucket<K,V>(key, value, next);
027  }
028
029  public ImmutableEntryIdentityHashMapRVM() {
030    super(DEFAULT_SIZE);
031  }
032
033  public ImmutableEntryIdentityHashMapRVM(int size) {
034    super(size);
035  }
036
037  @Override
038  public V remove(K key) {
039    throw new UnsupportedOperationException();
040  }
041
042  @Override
043  public void removeAll() {
044    throw new UnsupportedOperationException();
045  }
046
047  @Override
048  protected boolean same(K k1, K k2) {
049    return k1 == k2;
050  }
051
052  @Override
053  protected int hashTheKey(K key) {
054    if (!org.jikesrvm.VM.runningVM) {
055      return Magic.bootImageIdentityHashCode(key);
056    } else {
057      return System.identityHashCode(key);
058    }
059  }
060}