1 /* 2 * Copyright (C) 2006 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.util; 18 19 import java.lang.reflect.Array; 20 import java.util.Collection; 21 22 // XXX these should be changed to reflect the actual memory allocator we use. 23 // it looks like right now objects want to be powers of 2 minus 8 24 // and the array size eats another 4 bytes 25 26 /** 27 * ArrayUtils contains some methods that you can call to find out 28 * the most efficient increments by which to grow arrays. 29 */ 30 public class ArrayUtils 31 { 32 private static Object[] EMPTY = new Object[0]; 33 private static final int CACHE_SIZE = 73; 34 private static Object[] sCache = new Object[CACHE_SIZE]; 35 ArrayUtils()36 private ArrayUtils() { /* cannot be instantiated */ } 37 idealByteArraySize(int need)38 public static int idealByteArraySize(int need) { 39 for (int i = 4; i < 32; i++) 40 if (need <= (1 << i) - 12) 41 return (1 << i) - 12; 42 43 return need; 44 } 45 idealBooleanArraySize(int need)46 public static int idealBooleanArraySize(int need) { 47 return idealByteArraySize(need); 48 } 49 idealShortArraySize(int need)50 public static int idealShortArraySize(int need) { 51 return idealByteArraySize(need * 2) / 2; 52 } 53 idealCharArraySize(int need)54 public static int idealCharArraySize(int need) { 55 return idealByteArraySize(need * 2) / 2; 56 } 57 idealIntArraySize(int need)58 public static int idealIntArraySize(int need) { 59 return idealByteArraySize(need * 4) / 4; 60 } 61 idealFloatArraySize(int need)62 public static int idealFloatArraySize(int need) { 63 return idealByteArraySize(need * 4) / 4; 64 } 65 idealObjectArraySize(int need)66 public static int idealObjectArraySize(int need) { 67 return idealByteArraySize(need * 4) / 4; 68 } 69 idealLongArraySize(int need)70 public static int idealLongArraySize(int need) { 71 return idealByteArraySize(need * 8) / 8; 72 } 73 74 /** 75 * Checks if the beginnings of two byte arrays are equal. 76 * 77 * @param array1 the first byte array 78 * @param array2 the second byte array 79 * @param length the number of bytes to check 80 * @return true if they're equal, false otherwise 81 */ equals(byte[] array1, byte[] array2, int length)82 public static boolean equals(byte[] array1, byte[] array2, int length) { 83 if (array1 == array2) { 84 return true; 85 } 86 if (array1 == null || array2 == null || array1.length < length || array2.length < length) { 87 return false; 88 } 89 for (int i = 0; i < length; i++) { 90 if (array1[i] != array2[i]) { 91 return false; 92 } 93 } 94 return true; 95 } 96 97 /** 98 * Returns an empty array of the specified type. The intent is that 99 * it will return the same empty array every time to avoid reallocation, 100 * although this is not guaranteed. 101 */ emptyArray(Class<T> kind)102 public static <T> T[] emptyArray(Class<T> kind) { 103 if (kind == Object.class) { 104 return (T[]) EMPTY; 105 } 106 107 int bucket = ((System.identityHashCode(kind) / 8) & 0x7FFFFFFF) % CACHE_SIZE; 108 Object cache = sCache[bucket]; 109 110 if (cache == null || cache.getClass().getComponentType() != kind) { 111 cache = Array.newInstance(kind, 0); 112 sCache[bucket] = cache; 113 114 // Log.e("cache", "new empty " + kind.getName() + " at " + bucket); 115 } 116 117 return (T[]) cache; 118 } 119 120 /** 121 * Checks that value is present as at least one of the elements of the array. 122 * @param array the array to check in 123 * @param value the value to check for 124 * @return true if the value is present in the array 125 */ contains(T[] array, T value)126 public static <T> boolean contains(T[] array, T value) { 127 for (T element : array) { 128 if (element == null) { 129 if (value == null) return true; 130 } else { 131 if (value != null && element.equals(value)) return true; 132 } 133 } 134 return false; 135 } 136 contains(int[] array, int value)137 public static boolean contains(int[] array, int value) { 138 for (int element : array) { 139 if (element == value) { 140 return true; 141 } 142 } 143 return false; 144 } 145 } 146