--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/com.oracle.max.base/src/com/sun/max/collect/HashMapping.java	Sat Dec 17 19:59:18 2011 +0100
@@ -0,0 +1,138 @@
+/*
+ * Copyright (c) 2007, 2011, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package com.sun.max.collect;
+
+import java.util.*;
+
+/**
+ * This class provides a skeletal implementation of the {@link Mapping} interface, to minimize the effort required to
+ * implement this interface.
+ * <p>
+ * This class also includes a number of factory methods for creating {@code Mapping} instances with various properties.
+ */
+public abstract class HashMapping<K, V> implements Mapping<K, V> {
+
+    private final HashEquivalence<K> equivalence;
+
+    /**
+     * Determines if two given keys are equal.
+     * <p>
+     * Subclasses override this method to define equivalence without delegating to a {@link HashEquivalence} object.
+     */
+    protected boolean equivalent(K key1, K key2) {
+        return equivalence.equivalent(key1, key2);
+    }
+
+    /**
+     * Computes a hash code for a given key.
+     * <p>
+     * Subclasses override this method to compute a hash code without delegating to a {@link HashEquivalence} object.
+     */
+    protected int hashCode(K key) {
+        // Don't guard against a negative number here as the caller needs to convert the hash code into a valid index
+        // which will involve range checking anyway
+        return equivalence.hashCode(key);
+    }
+
+    /**
+     * Creates a hash table.
+     *
+     * @param equivalence
+     *            the semantics to be used for comparing keys. If {@code null} is provided, then {@link HashEquality} is
+     *            used.
+     */
+    protected HashMapping(HashEquivalence<K> equivalence) {
+        if (equivalence == null) {
+            final Class<HashEquality<K>> type = null;
+            this.equivalence = HashEquality.instance(type);
+        } else {
+            this.equivalence = equivalence;
+        }
+    }
+
+    public boolean containsKey(K key) {
+        return get(key) != null;
+    }
+
+    protected abstract class HashMappingIterable<Type> implements IterableWithLength<Type> {
+        public int size() {
+            return HashMapping.this.length();
+        }
+    }
+
+    /**
+     * Gets an iterator over the values in this mapping by looking up each {@linkplain #keys() key}.
+     * <p>
+     * Subclasses will most likely override this method with a more efficient implementation.
+     */
+    public IterableWithLength<V> values() {
+        return new HashMappingIterable<V>() {
+            private final IterableWithLength<K> keys = keys();
+            public Iterator<V> iterator() {
+                return new Iterator<V>() {
+                    private final Iterator<K> keyIterator = keys.iterator();
+
+                    public boolean hasNext() {
+                        return keyIterator.hasNext();
+                    }
+
+                    public V next() {
+                        return get(keyIterator.next());
+                    }
+
+                    public void remove() {
+                        throw new UnsupportedOperationException();
+                    }
+                };
+            }
+        };
+    }
+
+    public static <K, V> Mapping<K, V> createMapping(HashEquivalence<K> equivalence) {
+        return new OpenAddressingHashMapping<K, V>(equivalence);
+    }
+
+    public static <K, V> Mapping<K, V> createIdentityMapping() {
+        final Class<HashIdentity<K>> type = null;
+        return createMapping(HashIdentity.instance(type));
+    }
+
+    public static <K, V> Mapping<K, V> createEqualityMapping() {
+        final Class<HashEquality<K>> type = null;
+        return createMapping(HashEquality.instance(type));
+    }
+
+    public static <K, V> Mapping<K, V> createVariableMapping(HashEquivalence<K> equivalence) {
+        return new ChainedHashMapping<K, V>(equivalence);
+    }
+
+    public static <K, V> Mapping<K, V> createVariableIdentityMapping() {
+        final Class<HashIdentity<K>> type = null;
+        return createVariableMapping(HashIdentity.instance(type));
+    }
+
+    public static <K, V> Mapping<K, V> createVariableEqualityMapping() {
+        final Class<HashEquality<K>> type = null;
+        return createVariableMapping(HashEquality.instance(type));
+    }
+}