1 files changed, 78 insertions, 0 deletions
diff --git a/src/com/android/gallery3d/util/IdentityCache.java b/src/com/android/gallery3d/util/IdentityCache.java
new file mode 100644
index 000000000..3edc424a3
--- /dev/null
+++ b/src/com/android/gallery3d/util/IdentityCache.java
@@ -0,0 +1,78 @@
+/*
+ * Copyright (C) 2010 The Android Open Source Project
+ *
+ * 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.android.gallery3d.util;
+
+import java.lang.ref.ReferenceQueue;
+import java.lang.ref.WeakReference;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.Set;
+
+public class IdentityCache<K, V> {
+
+    private final HashMap<K, Entry<K, V>> mWeakMap =
+            new HashMap<K, Entry<K, V>>();
+    private ReferenceQueue<V> mQueue = new ReferenceQueue<V>();
+
+    public IdentityCache() {
+    }
+
+    private static class Entry<K, V> extends WeakReference<V> {
+        K mKey;
+
+        public Entry(K key, V value, ReferenceQueue<V> queue) {
+            super(value, queue);
+            mKey = key;
+        }
+    }
+
+    private void cleanUpWeakMap() {
+        Entry<K, V> entry = (Entry<K, V>) mQueue.poll();
+        while (entry != null) {
+            mWeakMap.remove(entry.mKey);
+            entry = (Entry<K, V>) mQueue.poll();
+        }
+    }
+
+    public synchronized V put(K key, V value) {
+        cleanUpWeakMap();
+        Entry<K, V> entry = mWeakMap.put(
+                key, new Entry<K, V>(key, value, mQueue));
+        return entry == null ? null : entry.get();
+    }
+
+    public synchronized V get(K key) {
+        cleanUpWeakMap();
+        Entry<K, V> entry = mWeakMap.get(key);
+        return entry == null ? null : entry.get();
+    }
+
+    // This is currently unused.
+    /*
+    public synchronized void clear() {
+        mWeakMap.clear();
+        mQueue = new ReferenceQueue<V>();
+    }
+    */
+
+    // This is for debugging only
+    public synchronized ArrayList<K> keys() {
+        Set<K> set = mWeakMap.keySet();
+        ArrayList<K> result = new ArrayList<K>(set);
+        return result;
+    }
+}