1/*
2 * Copyright (C) 2015 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.messaging.datamodel;
18
19import com.android.messaging.Factory;
20
21import java.util.HashSet;
22
23/**
24 * Utility abstraction which allows MemoryCaches in an application to register and then when there
25 * is memory pressure provide a callback to reclaim the memory in the caches.
26 */
27public class MemoryCacheManager {
28    private final HashSet<MemoryCache> mMemoryCaches = new HashSet<MemoryCache>();
29    private final Object mMemoryCacheLock = new Object();
30
31    public static MemoryCacheManager get() {
32        return Factory.get().getMemoryCacheManager();
33    }
34
35    /**
36     * Extend this interface to provide a reclaim method on a memory cache.
37     */
38    public interface MemoryCache {
39        void reclaim();
40    }
41
42    /**
43     * Register the memory cache with the application.
44     */
45    public void registerMemoryCache(final MemoryCache cache) {
46        synchronized (mMemoryCacheLock) {
47            mMemoryCaches.add(cache);
48        }
49    }
50
51    /**
52     * Unregister the memory cache with the application.
53     */
54    public void unregisterMemoryCache(final MemoryCache cache) {
55        synchronized (mMemoryCacheLock) {
56            mMemoryCaches.remove(cache);
57        }
58    }
59
60    /**
61     * Reclaim memory in all the memory caches in the application.
62     */
63    @SuppressWarnings("unchecked")
64    public void reclaimMemory() {
65        // We're creating a cache copy in the lock to ensure we're not working on a concurrently
66        // modified set, then reclaim outside of the lock to minimize the time within the lock.
67        final HashSet<MemoryCache> shallowCopy;
68        synchronized (mMemoryCacheLock) {
69            shallowCopy = (HashSet<MemoryCache>) mMemoryCaches.clone();
70        }
71        for (final MemoryCache cache : shallowCopy) {
72            cache.reclaim();
73        }
74    }
75}
76