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The Apache Commons Codec package contains simple encoder and decoders for various formats such as Base64 and Hexadecimal. In addition to these widely used encoders and decoders, the codec package also maintains a collection of phonetic encoding utilities.

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.codec.binary;

/**
 * 
 * Operations on {@link CharSequence} that are {@code null} safe.
 * 
 * 
 * Copied from Apache Commons Lang r1586295 on April 10, 2014 (day of 3.3.2 release).
 * 
 *
 * @see CharSequence
 * @since 1.10
 */
public class CharSequenceUtils {

    /**
     * Green implementation of regionMatches.
     *
     * @param cs
     *            the {@code CharSequence} to be processed
     * @param ignoreCase
     *            whether or not to be case insensitive
     * @param thisStart
     *            the index to start on the {@code cs} CharSequence
     * @param substring
     *            the {@code CharSequence} to be looked for
     * @param start
     *            the index to start on the {@code substring} CharSequence
     * @param length
     *            character length of the region
     * @return whether the region matched
     */
    static boolean regionMatches(final CharSequence cs, final boolean ignoreCase, final int thisStart,
            final CharSequence substring, final int start, final int length) {
        if (cs instanceof String && substring instanceof String) {
            return ((String) cs).regionMatches(ignoreCase, thisStart, (String) substring, start, length);
        }
        int index1 = thisStart;
        int index2 = start;
        int tmpLen = length;

        while (tmpLen-- > 0) {
            final char c1 = cs.charAt(index1++);
            final char c2 = substring.charAt(index2++);

            if (c1 == c2) {
                continue;
            }

            if (!ignoreCase) {
                return false;
            }

            // The same check as in String.regionMatches():
            if (Character.toUpperCase(c1) != Character.toUpperCase(c2) &&
                    Character.toLowerCase(c1) != Character.toLowerCase(c2)) {
                return false;
            }
        }

        return true;
    }
}