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.commons.codec.binary;
018
019/**
020 * <p>
021 * Operations on {@link CharSequence} that are <code>null</code> safe.
022 * </p>
023 * <p>
024 * Copied from Apache Commons Lang r1586295 on April 10, 2014 (day of 3.3.2 release).
025 * </p>
026 *
027 * @see CharSequence
028 * @since 1.10
029 */
030public class CharSequenceUtils {
031
032    /**
033     * Green implementation of regionMatches.
034     *
035     * @param cs
036     *            the <code>CharSequence</code> to be processed
037     * @param ignoreCase
038     *            whether or not to be case insensitive
039     * @param thisStart
040     *            the index to start on the <code>cs</code> CharSequence
041     * @param substring
042     *            the <code>CharSequence</code> to be looked for
043     * @param start
044     *            the index to start on the <code>substring</code> CharSequence
045     * @param length
046     *            character length of the region
047     * @return whether the region matched
048     */
049    static boolean regionMatches(final CharSequence cs, final boolean ignoreCase, final int thisStart,
050            final CharSequence substring, final int start, final int length) {
051        if (cs instanceof String && substring instanceof String) {
052            return ((String) cs).regionMatches(ignoreCase, thisStart, (String) substring, start, length);
053        }
054        int index1 = thisStart;
055        int index2 = start;
056        int tmpLen = length;
057
058        while (tmpLen-- > 0) {
059            final char c1 = cs.charAt(index1++);
060            final char c2 = substring.charAt(index2++);
061
062            if (c1 == c2) {
063                continue;
064            }
065
066            if (!ignoreCase) {
067                return false;
068            }
069
070            // The same check as in String.regionMatches():
071            if (Character.toUpperCase(c1) != Character.toUpperCase(c2) &&
072                    Character.toLowerCase(c1) != Character.toLowerCase(c2)) {
073                return false;
074            }
075        }
076
077        return true;
078    }
079}