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      1 /*
      2  * Copyright (C) 2018 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.internal.textservice;
     18 
     19 import android.annotation.NonNull;
     20 import android.util.SparseIntArray;
     21 
     22 import com.android.internal.annotations.VisibleForTesting;
     23 
     24 import java.util.function.IntUnaryOperator;
     25 
     26 /**
     27  * Simple int-to-int key-value-store that is to be lazily initialized with the given
     28  * {@link IntUnaryOperator}.
     29  */
     30 @VisibleForTesting
     31 public final class LazyIntToIntMap {
     32 
     33     private final SparseIntArray mMap = new SparseIntArray();
     34 
     35     @NonNull
     36     private final IntUnaryOperator mMappingFunction;
     37 
     38     /**
     39      * @param mappingFunction int to int mapping rules to be (lazily) evaluated
     40      */
     41     public LazyIntToIntMap(@NonNull IntUnaryOperator mappingFunction) {
     42         mMappingFunction = mappingFunction;
     43     }
     44 
     45     /**
     46      * Deletes {@code key} and associated value.
     47      * @param key key to be deleted
     48      */
     49     public void delete(int key) {
     50         mMap.delete(key);
     51     }
     52 
     53     /**
     54      * @param key key associated with the value
     55      * @return value associated with the {@code key}. If this is the first time to access
     56      * {@code key}, then {@code mappingFunction} passed to the constructor will be evaluated
     57      */
     58     public int get(int key) {
     59         final int index = mMap.indexOfKey(key);
     60         if (index >= 0) {
     61             return mMap.valueAt(index);
     62         }
     63         final int value = mMappingFunction.applyAsInt(key);
     64         mMap.append(key, value);
     65         return value;
     66     }
     67 }
     68