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.sdklib.util; 18 19 import java.lang.reflect.Array; 20 21 // XXX these should be changed to reflect the actual memory allocator we use. 22 // it looks like right now objects want to be powers of 2 minus 8 23 // and the array size eats another 4 bytes 24 25 /** 26 * ArrayUtils contains some methods that you can call to find out 27 * the most efficient increments by which to grow arrays. 28 */ 29 /* package */ class ArrayUtils 30 { 31 private static Object[] EMPTY = new Object[0]; 32 private static final int CACHE_SIZE = 73; 33 private static Object[] sCache = new Object[CACHE_SIZE]; 34 ArrayUtils()35 private ArrayUtils() { /* cannot be instantiated */ } 36 idealByteArraySize(int need)37 public static int idealByteArraySize(int need) { 38 for (int i = 4; i < 32; i++) 39 if (need <= (1 << i) - 12) 40 return (1 << i) - 12; 41 42 return need; 43 } 44 idealBooleanArraySize(int need)45 public static int idealBooleanArraySize(int need) { 46 return idealByteArraySize(need); 47 } 48 idealShortArraySize(int need)49 public static int idealShortArraySize(int need) { 50 return idealByteArraySize(need * 2) / 2; 51 } 52 idealCharArraySize(int need)53 public static int idealCharArraySize(int need) { 54 return idealByteArraySize(need * 2) / 2; 55 } 56 idealIntArraySize(int need)57 public static int idealIntArraySize(int need) { 58 return idealByteArraySize(need * 4) / 4; 59 } 60 idealFloatArraySize(int need)61 public static int idealFloatArraySize(int need) { 62 return idealByteArraySize(need * 4) / 4; 63 } 64 idealObjectArraySize(int need)65 public static int idealObjectArraySize(int need) { 66 return idealByteArraySize(need * 4) / 4; 67 } 68 idealLongArraySize(int need)69 public static int idealLongArraySize(int need) { 70 return idealByteArraySize(need * 8) / 8; 71 } 72 73 /** 74 * Checks if the beginnings of two byte arrays are equal. 75 * 76 * @param array1 the first byte array 77 * @param array2 the second byte array 78 * @param length the number of bytes to check 79 * @return true if they're equal, false otherwise 80 */ equals(byte[] array1, byte[] array2, int length)81 public static boolean equals(byte[] array1, byte[] array2, int length) { 82 if (array1 == array2) { 83 return true; 84 } 85 if (array1 == null || array2 == null || array1.length < length || array2.length < length) { 86 return false; 87 } 88 for (int i = 0; i < length; i++) { 89 if (array1[i] != array2[i]) { 90 return false; 91 } 92 } 93 return true; 94 } 95 96 /** 97 * Returns an empty array of the specified type. The intent is that 98 * it will return the same empty array every time to avoid reallocation, 99 * although this is not guaranteed. 100 */ 101 @SuppressWarnings("unchecked") 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 } 137