/* * Copyright (C) 2006 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * *      http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package com.android.internal.util;import java.lang.reflect.Array;import java.util.Collection;// XXX these should be changed to reflect the actual memory allocator we use.// it looks like right now objects want to be powers of 2 minus 8// and the array size eats another 4 bytes/** * ArrayUtils contains some methods that you can call to find out * the most efficient increments by which to grow arrays. */public class ArrayUtils{    private static Object[] EMPTY = new Object[0];    private static final int CACHE_SIZE = 73;    private static Object[] sCache = new Object[CACHE_SIZE];    private ArrayUtils() { /* cannot be instantiated */ }    public static int idealByteArraySize(int need) {        for (int i = 4; i < 32; i++)            if (need <= (1 << i) - 12)                return (1 << i) - 12;        return need;    }    public static int idealBooleanArraySize(int need) {        return idealByteArraySize(need);    }    public static int idealShortArraySize(int need) {        return idealByteArraySize(need * 2) / 2;    }    public static int idealCharArraySize(int need) {        return idealByteArraySize(need * 2) / 2;    }    public static int idealIntArraySize(int need) {        return idealByteArraySize(need * 4) / 4;    }    public static int idealFloatArraySize(int need) {        return idealByteArraySize(need * 4) / 4;    }    public static int idealObjectArraySize(int need) {        return idealByteArraySize(need * 4) / 4;    }    public static int idealLongArraySize(int need) {        return idealByteArraySize(need * 8) / 8;    }    /**     * Checks if the beginnings of two byte arrays are equal.     *     * @param array1 the first byte array     * @param array2 the second byte array     * @param length the number of bytes to check     * @return true if they're equal, false otherwise     */    public static boolean equals(byte[] array1, byte[] array2, int length) {        if (array1 == array2) {            return true;        }        if (array1 == null || array2 == null || array1.length < length || array2.length < length) {            return false;        }        for (int i = 0; i < length; i++) {            if (array1[i] != array2[i]) {                return false;            }        }        return true;    }    /**     * Returns an empty array of the specified type.  The intent is that     * it will return the same empty array every time to avoid reallocation,     * although this is not guaranteed.     */    public static <T> T[] emptyArray(Class<T> kind) {        if (kind == Object.class) {            return (T[]) EMPTY;        }        int bucket = ((System.identityHashCode(kind) / 8) & 0x7FFFFFFF) % CACHE_SIZE;        Object cache = sCache[bucket];        if (cache == null || cache.getClass().getComponentType() != kind) {            cache = Array.newInstance(kind, 0);            sCache[bucket] = cache;            // Log.e("cache", "new empty " + kind.getName() + " at " + bucket);        }        return (T[]) cache;    }    /**     * Checks that value is present as at least one of the elements of the array.     * @param array the array to check in     * @param value the value to check for     * @return true if the value is present in the array     */    public static <T> boolean contains(T[] array, T value) {        for (T element : array) {            if (element == null) {                if (value == null) return true;            } else {                if (value != null && element.equals(value)) return true;            }        }        return false;    }}