diff options
Diffstat (limited to 'gallerycommon/src/com/android/gallery3d/common/LruCache.java')
-rw-r--r-- | gallerycommon/src/com/android/gallery3d/common/LruCache.java | 90 |
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>(); + } +} |