1/*
2 * Copyright (C) 2009 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.android.camera.gallery;
18
19import java.lang.ref.ReferenceQueue;
20import java.lang.ref.WeakReference;
21import java.util.HashMap;
22import java.util.LinkedHashMap;
23import java.util.Map;
24
25public class LruCache<K, V> {
26
27    private final HashMap<K, V> mLruMap;
28    private final HashMap<K, Entry<K, V>> mWeakMap =
29            new HashMap<K, Entry<K, V>>();
30    private ReferenceQueue<V> mQueue = new ReferenceQueue<V>();
31
32    @SuppressWarnings("serial")
33    public LruCache(final int capacity) {
34        mLruMap = new LinkedHashMap<K, V>(16, 0.75f, true) {
35            @Override
36            protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
37                return size() > capacity;
38            }
39        };
40    }
41
42    private static class Entry<K, V> extends WeakReference<V> {
43        K mKey;
44
45        public Entry(K key, V value, ReferenceQueue<V> queue) {
46            super(value, queue);
47            mKey = key;
48        }
49    }
50
51    @SuppressWarnings("unchecked")
52    private void cleanUpWeakMap() {
53        Entry<K, V> entry = (Entry<K, V>) mQueue.poll();
54        while (entry != null) {
55            mWeakMap.remove(entry.mKey);
56            entry = (Entry<K, V>) mQueue.poll();
57        }
58    }
59
60    public synchronized V put(K key, V value) {
61        cleanUpWeakMap();
62        mLruMap.put(key, value);
63        Entry<K, V> entry = mWeakMap.put(
64                key, new Entry<K, V>(key, value, mQueue));
65        return entry == null ? null : entry.get();
66    }
67
68    public synchronized V get(K key) {
69        cleanUpWeakMap();
70        V value = mLruMap.get(key);
71        if (value != null) return value;
72        Entry<K, V> entry = mWeakMap.get(key);
73        return entry == null ? null : entry.get();
74    }
75
76    public synchronized void clear() {
77        mLruMap.clear();
78        mWeakMap.clear();
79        mQueue = new ReferenceQueue<V>();
80    }
81}
82