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/*
* Copyright (C) 2014 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.systemui.recents.model;
import android.util.LruCache;
import java.util.HashMap;
/**
* An LRU cache that internally support querying the keys as well as values. We use this to keep
* track of the task metadata to determine when to invalidate the cache when tasks have been
* updated. Generally, this cache will return the last known cache value for the requested task
* key.
*/
public class KeyStoreLruCache<V> {
// We keep a set of keys that are associated with the LRU cache, so that we can find out
// information about the Task that was previously in the cache.
HashMap<Integer, Task.TaskKey> mTaskKeys = new HashMap<Integer, Task.TaskKey>();
// The cache implementation, mapping task id -> value
LruCache<Integer, V> mCache;
public KeyStoreLruCache(int cacheSize) {
mCache = new LruCache<Integer, V>(cacheSize) {
@Override
protected void entryRemoved(boolean evicted, Integer taskId, V oldV, V newV) {
mTaskKeys.remove(taskId);
}
};
}
/** Gets a specific entry in the cache. */
final V get(Task.TaskKey key) {
return mCache.get(key.id);
}
/**
* Returns the value only if the Task has not updated since the last time it was in the cache.
*/
final V getAndInvalidateIfModified(Task.TaskKey key) {
Task.TaskKey lastKey = mTaskKeys.get(key.id);
if (lastKey != null && (lastKey.lastActiveTime < key.lastActiveTime)) {
// The task has updated (been made active since the last time it was put into the
// LRU cache) so invalidate that item in the cache
remove(key);
return null;
}
// Either the task does not exist in the cache, or the last active time is the same as
// the key specified, so return what is in the cache
return mCache.get(key.id);
}
/** Puts an entry in the cache for a specific key. */
final void put(Task.TaskKey key, V value) {
mCache.put(key.id, value);
mTaskKeys.put(key.id, key);
}
/** Removes a cache entry for a specific key. */
final void remove(Task.TaskKey key) {
mCache.remove(key.id);
mTaskKeys.remove(key.id);
}
/** Removes all the entries in the cache. */
final void evictAll() {
mCache.evictAll();
mTaskKeys.clear();
}
/** Returns the size of the cache. */
final int size() {
return mCache.size();
}
/** Trims the cache to a specific size */
final void trimToSize(int cacheSize) {
mCache.resize(cacheSize);
}
}
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