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      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.
     42     public MediaCache(final int id, final String name) {
     43         this(DEFAULT_MEDIA_RESOURCE_CACHE_SIZE_IN_KILOBYTES, id, name);
     44     }
     45 
     46     public MediaCache(final int maxSize, final int id, final String name) {
     47         super(maxSize);
     48         mId = id;
     49         mName = name;
     50     }
     51 
     52     public void destroy() {
     53         evictAll();
     54     }
     55 
     56     public String getName() {
     57         return mName;
     58     }
     59 
     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      */
     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      */
     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
     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
    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 }