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      1 /*
      2  * Copyright 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 androidx.collection;
     18 
     19 class ContainerHelpers {
     20     static final int[] EMPTY_INTS = new int[0];
     21     static final long[] EMPTY_LONGS = new long[0];
     22     static final Object[] EMPTY_OBJECTS = new Object[0];
     23 
     24     public static int idealIntArraySize(int need) {
     25         return idealByteArraySize(need * 4) / 4;
     26     }
     27 
     28     public static int idealLongArraySize(int need) {
     29         return idealByteArraySize(need * 8) / 8;
     30     }
     31 
     32     public static int idealByteArraySize(int need) {
     33         for (int i = 4; i < 32; i++)
     34             if (need <= (1 << i) - 12)
     35                 return (1 << i) - 12;
     36 
     37         return need;
     38     }
     39 
     40     public static boolean equal(Object a, Object b) {
     41         return a == b || (a != null && a.equals(b));
     42     }
     43 
     44     // This is Arrays.binarySearch(), but doesn't do any argument validation.
     45     static int binarySearch(int[] array, int size, int value) {
     46         int lo = 0;
     47         int hi = size - 1;
     48 
     49         while (lo <= hi) {
     50             int mid = (lo + hi) >>> 1;
     51             int midVal = array[mid];
     52 
     53             if (midVal < value) {
     54                 lo = mid + 1;
     55             } else if (midVal > value) {
     56                 hi = mid - 1;
     57             } else {
     58                 return mid;  // value found
     59             }
     60         }
     61         return ~lo;  // value not present
     62     }
     63 
     64     static int binarySearch(long[] array, int size, long value) {
     65         int lo = 0;
     66         int hi = size - 1;
     67 
     68         while (lo <= hi) {
     69             final int mid = (lo + hi) >>> 1;
     70             final long midVal = array[mid];
     71 
     72             if (midVal < value) {
     73                 lo = mid + 1;
     74             } else if (midVal > value) {
     75                 hi = mid - 1;
     76             } else {
     77                 return mid;  // value found
     78             }
     79         }
     80         return ~lo;  // value not present
     81     }
     82 
     83     private ContainerHelpers() {
     84     }
     85 }
     86