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
17package com.android.sdklib.util;
18
19import 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
35    private ArrayUtils() { /* cannot be instantiated */ }
36
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
45    public static int idealBooleanArraySize(int need) {
46        return idealByteArraySize(need);
47    }
48
49    public static int idealShortArraySize(int need) {
50        return idealByteArraySize(need * 2) / 2;
51    }
52
53    public static int idealCharArraySize(int need) {
54        return idealByteArraySize(need * 2) / 2;
55    }
56
57    public static int idealIntArraySize(int need) {
58        return idealByteArraySize(need * 4) / 4;
59    }
60
61    public static int idealFloatArraySize(int need) {
62        return idealByteArraySize(need * 4) / 4;
63    }
64
65    public static int idealObjectArraySize(int need) {
66        return idealByteArraySize(need * 4) / 4;
67    }
68
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     */
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")
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     */
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