| /* |
| * Copyright (C) 2022 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.server; |
| |
| import android.annotation.Nullable; |
| import android.util.ArrayMap; |
| |
| import java.util.Collection; |
| import java.util.LinkedList; |
| |
| /** |
| * CircularQueue of length limit which puts keys in a circular LinkedList and values in an ArrayMap. |
| * @param <K> key |
| * @param <V> value |
| */ |
| public class CircularQueue<K, V> extends LinkedList<K> { |
| private final int mLimit; |
| private final ArrayMap<K, V> mArrayMap = new ArrayMap<>(); |
| |
| public CircularQueue(int limit) { |
| this.mLimit = limit; |
| } |
| |
| @Override |
| public boolean add(K k) throws IllegalArgumentException { |
| throw new IllegalArgumentException("Call of add(key) prohibited. Please call put(key, " |
| + "value) instead. "); |
| } |
| |
| /** |
| * Put a (key|value) pair in the CircularQueue. Only the key will be added to the queue. Value |
| * will be added to the ArrayMap. |
| * @return the most recently removed value if keys were removed, or {@code null} if no keys were |
| * removed. |
| */ |
| @Nullable |
| public V put(K key, V value) { |
| super.add(key); |
| mArrayMap.put(key, value); |
| V removedValue = null; |
| while (size() > mLimit) { |
| K removedKey = super.remove(); |
| removedValue = mArrayMap.remove(removedKey); |
| } |
| return removedValue; |
| } |
| |
| /** |
| * Removes the element for the provided key from the data structure. |
| * @param key which should be removed |
| * @return the value which was removed |
| */ |
| public V removeElement(K key) { |
| super.remove(key); |
| return mArrayMap.remove(key); |
| } |
| |
| /** |
| * Retrieve a value from the array. |
| * @param key The key of the value to retrieve. |
| * @return Returns the value associated with the given key, |
| * or null if there is no such key. |
| */ |
| public V getElement(K key) { |
| return mArrayMap.get(key); |
| } |
| |
| /** |
| * Check whether a key exists in the array. |
| * |
| * @param key The key to search for. |
| * @return Returns true if the key exists, else false. |
| */ |
| public boolean containsKey(K key) { |
| return mArrayMap.containsKey(key); |
| } |
| |
| /** |
| * Return a {@link java.util.Collection} for iterating over and interacting with all values |
| * in the array map. |
| * |
| * <p><b>Note:</b> this is a fairly inefficient way to access the array contents, it |
| * requires generating a number of temporary objects and allocates additional state |
| * information associated with the container that will remain for the life of the container.</p> |
| */ |
| public Collection<V> values() { |
| return mArrayMap.values(); |
| } |
| } |