001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache license, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the license for the specific language governing permissions and
015 * limitations under the license.
016 */
017package org.apache.logging.log4j.core.util;
018
019import org.apache.logging.log4j.util.Strings;
020
021/**
022 * Helps deal with integers.
023 */
024public final class Integers {
025
026    private static final int BITS_PER_INT = 32;
027
028    private Integers() {
029    }
030
031    /**
032     * Parses the string argument as a signed decimal integer.
033     *
034     * @param s a {@code String} containing the {@code int} representation to parse, may be {@code null} or {@code ""}
035     * @param defaultValue the return value, use {@code defaultValue} if {@code s} is {@code null} or {@code ""}
036     * @return the integer value represented by the argument in decimal.
037     * @throws NumberFormatException if the string does not contain a parsable integer.
038     */
039    public static int parseInt(final String s, final int defaultValue) {
040        return Strings.isEmpty(s) ? defaultValue : Integer.parseInt(s);
041    }
042
043    /**
044     * Parses the string argument as a signed decimal integer.
045     *
046     * @param s a {@code String} containing the {@code int} representation to parse, may be {@code null} or {@code ""}
047     * @return the integer value represented by the argument in decimal.
048     * @throws NumberFormatException if the string does not contain a parsable integer.
049     */
050    public static int parseInt(final String s) {
051        return parseInt(s, 0);
052    }
053
054    /**
055     * Calculate the next power of 2, greater than or equal to x.
056     * <p>
057     * From Hacker's Delight, Chapter 3, Harry S. Warren Jr.
058     *
059     * @param x Value to round up
060     * @return The next power of 2 from x inclusive
061     */
062    public static int ceilingNextPowerOfTwo(final int x) {
063        return 1 << (BITS_PER_INT - Integer.numberOfLeadingZeros(x - 1));
064    }
065}