ContainerHelpers.java revision 3ac77bf186f87ecad4bf0063b2f6c4384efbd56a 
1/*
2 * Copyright (C) 2013 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 android.support.v4.util;
18
19class 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