1 /*
2 * Copyright 2015 The Netty Project
3 *
4 * The Netty Project licenses this file to you under the Apache License, version 2.0 (the
5 * "License"); you may not use this file except in compliance with the License. You may obtain a
6 * 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 distributed under the License
11 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
12 * or implied. See the License for the specific language governing permissions and limitations under
13 * the License.
14 */
15 package io.netty.util.internal;
16
17 /**
18 * Math utility methods.
19 */
20 public final class MathUtil {
21
22 private MathUtil() {
23 }
24
25 /**
26 * Fast method of finding the next power of 2 greater than or equal to the supplied value.
27 * <p>If the value is {@code <= 0} then 1 will be returned.
28 * This method is not suitable for {@link Integer#MIN_VALUE} or numbers greater than 2^30.
29 *
30 * @param value from which to search for next power of 2
31 * @return The next power of 2 or the value itself if it is a power of 2
32 */
33 public static int findNextPositivePowerOfTwo(final int value) {
34 assert value > Integer.MIN_VALUE && value < 0x40000000;
35 return 1 << (32 - Integer.numberOfLeadingZeros(value - 1));
36 }
37
38 /**
39 * Fast method of finding the next power of 2 greater than or equal to the supplied value.
40 * <p>This method will do runtime bounds checking and call {@link #findNextPositivePowerOfTwo(int)} if within a
41 * valid range.
42 * @param value from which to search for next power of 2
43 * @return The next power of 2 or the value itself if it is a power of 2.
44 * <p>Special cases for return values are as follows:
45 * <ul>
46 * <li>{@code <= 0} -> 1</li>
47 * <li>{@code >= 2^30} -> 2^30</li>
48 * </ul>
49 */
50 public static int safeFindNextPositivePowerOfTwo(final int value) {
51 return value <= 0 ? 1 : value >= 0x40000000 ? 0x40000000 : findNextPositivePowerOfTwo(value);
52 }
53
54 /**
55 * Determine if the requested {@code index} and {@code length} will fit within {@code capacity}.
56 * @param index The starting index.
57 * @param length The length which will be utilized (starting from {@code index}).
58 * @param capacity The capacity that {@code index + length} is allowed to be within.
59 * @return {@code true} if the requested {@code index} and {@code length} will fit within {@code capacity}.
60 * {@code false} if this would result in an index out of bounds exception.
61 */
62 public static boolean isOutOfBounds(int index, int length, int capacity) {
63 return (index | length | (index + length) | (capacity - (index + length))) < 0;
64 }
65
66 /**
67 * Compare to {@code long} values.
68 * @param x the first {@code long} to compare.
69 * @param y the second {@code long} to compare.
70 * @return
71 * <ul>
72 * <li>0 if {@code x == y}</li>
73 * <li>{@code > 0} if {@code x > y}</li>
74 * <li>{@code < 0} if {@code x < y}</li>
75 * </ul>
76 */
77 public static int compare(long x, long y) {
78 return (x < y) ? -1 : (x > y) ? 1 : 0;
79 }
80 }