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      1 /*
      2  * Copyright (C) 2017 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 
     17 package com.android.car.internal;
     18 
     19 import java.util.Collection;
     20 import java.util.Collections;
     21 import java.util.HashMap;
     22 import java.util.Map;
     23 
     24 /**
     25  * Represent listeners for a sensor grouped by their rate.
     26  * @hide
     27  */
     28 public class CarRatedListeners<EventListenerType> {
     29     private final Map<EventListenerType, Integer> mListenersToRate = new HashMap<>(4);
     30 
     31     private int mUpdateRate;
     32 
     33     protected long mLastUpdateTime = -1;
     34 
     35     protected CarRatedListeners(int rate) {
     36         mUpdateRate = rate;
     37     }
     38 
     39     public boolean contains(EventListenerType listener) {
     40         return mListenersToRate.containsKey(listener);
     41     }
     42 
     43     public int getRate() {
     44         return mUpdateRate;
     45     }
     46 
     47     /**
     48      * Remove given listener from the list and update rate if necessary.
     49      *
     50      * @param listener
     51      * @return true if rate was updated. Otherwise, returns false.
     52      */
     53     public boolean remove(EventListenerType listener) {
     54         mListenersToRate.remove(listener);
     55         if (mListenersToRate.isEmpty()) {
     56             return false;
     57         }
     58         Integer updateRate = Collections.min(mListenersToRate.values());
     59         if (updateRate != mUpdateRate) {
     60             mUpdateRate = updateRate;
     61             return true;
     62         }
     63         return false;
     64     }
     65 
     66     public boolean isEmpty() {
     67         return mListenersToRate.isEmpty();
     68     }
     69 
     70     /**
     71      * Add given listener to the list and update rate if necessary.
     72      *
     73      * @param listener if null, add part is skipped.
     74      * @param updateRate
     75      * @return true if rate was updated. Otherwise, returns false.
     76      */
     77     public boolean addAndUpdateRate(EventListenerType listener, int updateRate) {
     78         Integer oldUpdateRate = mListenersToRate.put(listener, updateRate);
     79         if (mUpdateRate > updateRate) {
     80             mUpdateRate = updateRate;
     81             return true;
     82         } else if (oldUpdateRate != null && oldUpdateRate == mUpdateRate) {
     83             mUpdateRate = Collections.min(mListenersToRate.values());
     84         }
     85         return false;
     86     }
     87 
     88     public Collection<EventListenerType> getListeners() {
     89         return mListenersToRate.keySet();
     90     }
     91 }
     92