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 
17 package com.android.messaging.datamodel;
18 
19 import com.android.messaging.Factory;
20 
21 import 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  */
27 public class MemoryCacheManager {
28     private final HashSet<MemoryCache> mMemoryCaches = new HashSet<MemoryCache>();
29     private final Object mMemoryCacheLock = new Object();
30 
get()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 {
reclaim()39         void reclaim();
40     }
41 
42     /**
43      * Register the memory cache with the application.
44      */
registerMemoryCache(final MemoryCache cache)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      */
unregisterMemoryCache(final MemoryCache cache)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")
reclaimMemory()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