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 package com.android.messaging.datamodel.media;
17 
18 import android.util.LruCache;
19 
20 import com.android.messaging.util.LogUtil;
21 
22 /**
23  * A modified LruCache that is able to hold RefCountedMediaResource instances. It releases
24  * ref on the entries as they are evicted from the cache, and it uses the media resource
25  * size in kilobytes, instead of the entry count, as the size of the cache.
26  *
27  * This class is used by the MediaResourceManager class to maintain a number of caches for
28  * holding different types of {@link RefCountedMediaResource}
29  */
30 public class MediaCache<T extends RefCountedMediaResource> extends LruCache<String, T> {
31     private static final String TAG = LogUtil.BUGLE_IMAGE_TAG;
32 
33     // Default memory cache size in kilobytes
34     protected static final int DEFAULT_MEDIA_RESOURCE_CACHE_SIZE_IN_KILOBYTES = 1024 * 5;  // 5MB
35 
36     // Unique identifier for the cache.
37     private final int mId;
38     // Descriptive name given to the cache for debugging purposes.
39     private final String mName;
40 
41     // Convenience constructor that uses the default cache size.
MediaCache(final int id, final String name)42     public MediaCache(final int id, final String name) {
43         this(DEFAULT_MEDIA_RESOURCE_CACHE_SIZE_IN_KILOBYTES, id, name);
44     }
45 
MediaCache(final int maxSize, final int id, final String name)46     public MediaCache(final int maxSize, final int id, final String name) {
47         super(maxSize);
48         mId = id;
49         mName = name;
50     }
51 
destroy()52     public void destroy() {
53         evictAll();
54     }
55 
getName()56     public String getName() {
57         return mName;
58     }
59 
getId()60     public int getId() {
61         return mId;
62     }
63 
64     /**
65      * Gets a media resource from this cache. Must use this method to get resource instead of get()
66      * to ensure addRef() on the resource.
67      */
fetchResourceFromCache(final String key)68     public synchronized T fetchResourceFromCache(final String key) {
69         final T ret = get(key);
70         if (ret != null) {
71             if (LogUtil.isLoggable(TAG, LogUtil.VERBOSE)) {
72                 LogUtil.v(TAG, "cache hit in mediaCache @ " + getName() +
73                         ", total cache hit = " + hitCount() +
74                         ", total cache miss = " + missCount());
75             }
76             ret.addRef();
77         } else if (LogUtil.isLoggable(TAG, LogUtil.VERBOSE)) {
78             LogUtil.v(TAG, "cache miss in mediaCache @ " + getName() +
79                     ", total cache hit = " + hitCount() +
80                     ", total cache miss = " + missCount());
81         }
82         return ret;
83     }
84 
85     /**
86      * Add a media resource to this cache. Must use this method to add resource instead of put()
87      * to ensure addRef() on the resource.
88      */
addResourceToCache(final String key, final T mediaResource)89     public synchronized T addResourceToCache(final String key, final T mediaResource) {
90         mediaResource.addRef();
91         return put(key, mediaResource);
92     }
93 
94     /**
95      * Notify the removed entry that is no longer being cached
96      */
97     @Override
entryRemoved(final boolean evicted, final String key, final T oldValue, final T newValue)98     protected synchronized void entryRemoved(final boolean evicted, final String key,
99             final T oldValue, final T newValue) {
100         oldValue.release();
101     }
102 
103     /**
104      * Measure item size in kilobytes rather than units which is more practical
105      * for a media resource cache
106      */
107     @Override
sizeOf(final String key, final T value)108     protected int sizeOf(final String key, final T value) {
109         final int mediaSizeInKilobytes = value.getMediaSize() / 1024;
110         // Never zero-count any resource, count as at least 1KB.
111         return mediaSizeInKilobytes == 0 ? 1 : mediaSizeInKilobytes;
112     }
113 }