Apache Commons Codec library provides implementations of common encoders and decoders such as Base64, Hex, Phonetic and URLs.

Apache Commons Codec Source Code files are provided in both binary packge (commons-codec-3.15-bin.zip) and source package (commons-codec-3.15-src.zip). You can download them at Apache Commons Codec Website.

Apache Commons Codec Source Code has no dependencies. You can compile it to generate your own version of Apache Commons Codec JAR file.

The source code of Apache Commons Codec 1.15 is provided below:

⏎ org/apache/commons/codec/net/Utils.java

/*
 * 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.net;

import org.apache.commons.codec.DecoderException;

/**
 * Utility methods for this package.
 *
 * <p>This class is immutable and thread-safe.</p>
 *
 * @since 1.4
 */
class Utils {

    /**
     * Radix used in encoding and decoding.
     */
    private static final int RADIX = 16;

    /**
     * Returns the numeric value of the character {@code b} in radix 16.
     *
     * @param b
     *            The byte to be converted.
     * @return The numeric value represented by the character in radix 16.
     *
     * @throws DecoderException
     *             Thrown when the byte is not valid per {@link Character#digit(char,int)}
     */
    static int digit16(final byte b) throws DecoderException {
        final int i = Character.digit((char) b, RADIX);
        if (i == -1) {
            throw new DecoderException("Invalid URL encoding: not a valid digit (radix " + RADIX + "): " + b);
        }
        return i;
    }

    /**
     * Returns the upper case hex digit of the lower 4 bits of the int.
     *
     * @param b the input int
     * @return the upper case hex digit of the lower 4 bits of the int.
     */
    static char hexDigit(final int b) {
        return Character.toUpperCase(Character.forDigit(b & 0xF, RADIX));
    }

}

⏎ org/apache/commons/codec/net/Utils.java

Or download all of them as a single archive file:

File name: commons-codec-1.15-sources.jar
File size: 364441 bytes
Release date: 2020-09-01
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