Migrated source code from Simantics SVN

[simantics/platform.git] / bundles / org.simantics.scl.compiler / src / org / cojen / util / SoftValuedHashMap.java

diff --git a/bundles/org.simantics.scl.compiler/src/org/cojen/util/SoftValuedHashMap.java b/bundles/org.simantics.scl.compiler/src/org/cojen/util/SoftValuedHashMap.java
new file mode 100644 (file)
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+++ b/bundles/org.simantics.scl.compiler/src/org/cojen/util/SoftValuedHashMap.java
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+/*
+ *  Copyright 2004-2010 Brian S O'Neill
+ *
+ *  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 org.cojen.util;
+
+import java.lang.ref.Reference;
+import java.lang.ref.SoftReference;
+import java.util.Map;
+
+/**
+ * A Map that softly references its values and can be used as a simple cache.
+ * SoftValuedHashMap is not thread-safe and must be wrapped with
+ * Collections.synchronizedMap to be made thread-safe.
+ * <p>
+ * Note: Softly referenced entries may be automatically removed during
+ * either accessor or mutator operations, possibly causing a concurrent
+ * modification to be detected. Therefore, even if multiple threads are only
+ * accessing this map, be sure to synchronize this map first. Also, do not
+ * rely on the value returned by size() when using an iterator from this map.
+ * The iterators may return less entries than the amount reported by size().
+ * 
+ * @author Brian S O'Neill
+ */
+public class SoftValuedHashMap<K, V> extends ReferencedValueHashMap<K, V> {
+
+    /**
+     * Constructs a new, empty map with the specified initial 
+     * capacity and the specified load factor. 
+     *
+     * @param      initialCapacity   the initial capacity of the HashMap.
+     * @param      loadFactor        the load factor of the HashMap
+     * @throws     IllegalArgumentException  if the initial capacity is less
+     *               than zero, or if the load factor is nonpositive.
+     */
+    public SoftValuedHashMap(int initialCapacity, float loadFactor) {
+        super(initialCapacity, loadFactor);
+    }
+
+    /**
+     * Constructs a new, empty map with the specified initial capacity
+     * and default load factor, which is <tt>0.75</tt>.
+     *
+     * @param   initialCapacity   the initial capacity of the HashMap.
+     * @throws    IllegalArgumentException if the initial capacity is less
+     *              than zero.
+     */
+    public SoftValuedHashMap(int initialCapacity) {
+        super(initialCapacity);
+    }
+
+    /**
+     * Constructs a new, empty map with a default capacity and load
+     * factor, which is <tt>0.75</tt>.
+     */
+    public SoftValuedHashMap() {
+        super();
+    }
+
+    /**
+     * Constructs a new map with the same mappings as the given map.  The
+     * map is created with a capacity of twice the number of mappings in
+     * the given map or 11 (whichever is greater), and a default load factor,
+     * which is <tt>0.75</tt>.
+     */
+    public SoftValuedHashMap(Map<? extends K, ? extends V> t) {
+        super(t);
+    }
+
+    Entry<K, V> newEntry(int hash, K key, V value, Entry<K, V> next) {
+        return new SoftEntry<K, V>(hash, key, value, next);
+    }
+
+    static class SoftEntry<K, V> extends ReferencedValueHashMap.Entry<K, V> {
+
+        SoftEntry(int hash, K key, V value, Entry<K, V> next) {
+            super(hash, key, value, next);
+        }
+
+        SoftEntry(int hash, K key, Reference<V> value, Entry<K, V> next) {
+            super(hash, key, value, next);
+        }
+
+        @SuppressWarnings("rawtypes")
+        Entry newEntry(int hash, K key, Reference<V> value, Entry<K, V> next) {
+            return new SoftEntry<K, V>(hash, key, value, next);
+        }
+
+        Reference<V> newReference(V value) {
+            return new SoftReference<V>(value);
+        }
+    }
+}