1/* 2 * Copyright (C) 2014 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.systemui.recents.model; 18 19import android.util.LruCache; 20 21import java.util.HashMap; 22 23/** 24 * An LRU cache that internally support querying the keys as well as values. We use this to keep 25 * track of the task metadata to determine when to invalidate the cache when tasks have been 26 * updated. Generally, this cache will return the last known cache value for the requested task 27 * key. 28 */ 29public class KeyStoreLruCache<V> { 30 // We keep a set of keys that are associated with the LRU cache, so that we can find out 31 // information about the Task that was previously in the cache. 32 HashMap<Integer, Task.TaskKey> mTaskKeys = new HashMap<Integer, Task.TaskKey>(); 33 // The cache implementation, mapping task id -> value 34 LruCache<Integer, V> mCache; 35 36 public KeyStoreLruCache(int cacheSize) { 37 mCache = new LruCache<Integer, V>(cacheSize) { 38 39 @Override 40 protected void entryRemoved(boolean evicted, Integer taskId, V oldV, V newV) { 41 mTaskKeys.remove(taskId); 42 } 43 }; 44 } 45 46 /** Gets a specific entry in the cache. */ 47 final V get(Task.TaskKey key) { 48 return mCache.get(key.id); 49 } 50 51 /** 52 * Returns the value only if the Task has not updated since the last time it was in the cache. 53 */ 54 final V getAndInvalidateIfModified(Task.TaskKey key) { 55 Task.TaskKey lastKey = mTaskKeys.get(key.id); 56 if (lastKey != null && (lastKey.lastActiveTime < key.lastActiveTime)) { 57 // The task has updated (been made active since the last time it was put into the 58 // LRU cache) so invalidate that item in the cache 59 remove(key); 60 return null; 61 } 62 // Either the task does not exist in the cache, or the last active time is the same as 63 // the key specified, so return what is in the cache 64 return mCache.get(key.id); 65 } 66 67 /** Puts an entry in the cache for a specific key. */ 68 final void put(Task.TaskKey key, V value) { 69 mCache.put(key.id, value); 70 mTaskKeys.put(key.id, key); 71 } 72 73 /** Removes a cache entry for a specific key. */ 74 final void remove(Task.TaskKey key) { 75 mCache.remove(key.id); 76 mTaskKeys.remove(key.id); 77 } 78 79 /** Removes all the entries in the cache. */ 80 final void evictAll() { 81 mCache.evictAll(); 82 mTaskKeys.clear(); 83 } 84 85 /** Returns the size of the cache. */ 86 final int size() { 87 return mCache.size(); 88 } 89 90 /** Trims the cache to a specific size */ 91 final void trimToSize(int cacheSize) { 92 mCache.resize(cacheSize); 93 } 94} 95