1 files changed, 90 insertions, 0 deletions
diff --git a/gallerycommon/src/com/android/gallery3d/common/LruCache.java b/gallerycommon/src/com/android/gallery3d/common/LruCache.java
new file mode 100644
index 000000000..81dabf773
--- /dev/null
+++ b/gallerycommon/src/com/android/gallery3d/common/LruCache.java
@@ -0,0 +1,90 @@
+/*
+ * Copyright (C) 2009 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.common;
+
+import java.lang.ref.ReferenceQueue;
+import java.lang.ref.WeakReference;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+/**
+ * An LRU cache which stores recently inserted entries and all entries ever
+ * inserted which still has a strong reference elsewhere.
+ */
+public class LruCache<K, V> {
+
+    private final HashMap<K, V> mLruMap;
+    private final HashMap<K, Entry<K, V>> mWeakMap =
+            new HashMap<K, Entry<K, V>>();
+    private ReferenceQueue<V> mQueue = new ReferenceQueue<V>();
+
+    @SuppressWarnings("serial")
+    public LruCache(final int capacity) {
+        mLruMap = new LinkedHashMap<K, V>(16, 0.75f, true) {
+            @Override
+            protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
+                return size() > capacity;
+            }
+        };
+    }
+
+    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;
+        }
+    }
+
+    @SuppressWarnings("unchecked")
+    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 boolean containsKey(K key) {
+        cleanUpWeakMap();
+        return mWeakMap.containsKey(key);
+    }
+
+    public synchronized V put(K key, V value) {
+        cleanUpWeakMap();
+        mLruMap.put(key, value);
+        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();
+        V value = mLruMap.get(key);
+        if (value != null) return value;
+        Entry<K, V> entry = mWeakMap.get(key);
+        return entry == null ? null : entry.get();
+    }
+
+    public synchronized void clear() {
+        mLruMap.clear();
+        mWeakMap.clear();
+        mQueue = new ReferenceQueue<V>();
+    }
+}