001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.shiro.lang.codec;
020
021
022/**
023 * <a href="http://en.wikipedia.org/wiki/Hexadecimal">Hexadecimal</a> encoder and decoder.
024 * <p/>
025 * This class was borrowed from Apache Commons Codec SVN repository (rev. {@code 560660}) with modifications
026 * to enable Hex conversion without a full dependency on Commons Codec.  We didn't want to reinvent the wheel of
027 * great work they've done, but also didn't want to force every Shiro user to depend on the commons-codec.jar
028 * <p/>
029 * As per the Apache 2.0 license, the original copyright notice and all author and copyright information have
030 * remained in tact.
031 *
032 * @see <a href="http://en.wikipedia.org/wiki/Hexadecimal">Wikipedia: Hexadecimal</a>
033 * @since 0.9
034 */
035@SuppressWarnings("checkstyle:MagicNumber")
036public final class Hex {
037
038    /**
039     * Used to build output as Hex
040     */
041    private static final char[] DIGITS = {
042            '0', '1', '2', '3', '4', '5', '6', '7',
043            '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
044    };
045
046    private Hex() {
047
048    }
049
050    /**
051     * Encodes the specified byte array to a character array and then returns that character array
052     * as a String.
053     *
054     * @param bytes the byte array to Hex-encode.
055     * @return A String representation of the resultant hex-encoded char array.
056     */
057    public static String encodeToString(byte[] bytes) {
058        char[] encodedChars = encode(bytes);
059        return new String(encodedChars);
060    }
061
062    /**
063     * Converts an array of bytes into an array of characters representing the hexadecimal values of each byte in order.
064     * The returned array will be double the length of the passed array, as it takes two characters to represent any
065     * given byte.
066     *
067     * @param data byte[] to convert to Hex characters
068     * @return A char[] containing hexadecimal characters
069     */
070    public static char[] encode(byte[] data) {
071
072        int l = data.length;
073
074        char[] out = new char[l << 1];
075
076        // two characters form the hex value.
077        for (int i = 0, j = 0; i < l; i++) {
078            out[j++] = DIGITS[(0xF0 & data[i]) >>> 4];
079            out[j++] = DIGITS[0x0F & data[i]];
080        }
081
082        return out;
083    }
084
085    /**
086     * Converts an array of character bytes representing hexadecimal values into an
087     * array of bytes of those same values. The returned array will be half the
088     * length of the passed array, as it takes two characters to represent any
089     * given byte. An exception is thrown if the passed char array has an odd
090     * number of elements.
091     *
092     * @param array An array of character bytes containing hexadecimal digits
093     * @return A byte array containing binary data decoded from
094     * the supplied byte array (representing characters).
095     * @throws IllegalArgumentException Thrown if an odd number of characters is supplied
096     *                                  to this function
097     * @see #decode(char[])
098     */
099    public static byte[] decode(byte[] array) throws IllegalArgumentException {
100        String s = CodecSupport.toString(array);
101        return decode(s);
102    }
103
104    /**
105     * Converts the specified Hex-encoded String into a raw byte array.  This is a
106     * convenience method that merely delegates to {@link #decode(char[])} using the
107     * argument's hex.toCharArray() value.
108     *
109     * @param hex a Hex-encoded String.
110     * @return A byte array containing binary data decoded from the supplied String's char array.
111     */
112    public static byte[] decode(String hex) {
113        return decode(hex.toCharArray());
114    }
115
116    /**
117     * Converts an array of characters representing hexadecimal values into an
118     * array of bytes of those same values. The returned array will be half the
119     * length of the passed array, as it takes two characters to represent any
120     * given byte. An exception is thrown if the passed char array has an odd
121     * number of elements.
122     *
123     * @param data An array of characters containing hexadecimal digits
124     * @return A byte array containing binary data decoded from
125     * the supplied char array.
126     * @throws IllegalArgumentException if an odd number or illegal of characters
127     *                                  is supplied
128     */
129    @SuppressWarnings("magicNumber")
130    public static byte[] decode(char[] data) throws IllegalArgumentException {
131
132        int len = data.length;
133
134        if ((len & 0x01) != 0) {
135            throw new IllegalArgumentException("Odd number of characters.");
136        }
137
138        byte[] out = new byte[len >> 1];
139
140        // two characters form the hex value.
141        for (int i = 0, j = 0; j < len; i++) {
142            int f = toDigit(data[j], j) << 4;
143            j++;
144            f = f | toDigit(data[j], j);
145            j++;
146            out[i] = (byte) (f & 0xFF);
147        }
148
149        return out;
150    }
151
152    /**
153     * Converts a hexadecimal character to an integer.
154     *
155     * @param ch    A character to convert to an integer digit
156     * @param index The index of the character in the source
157     * @return An integer
158     * @throws IllegalArgumentException if ch is an illegal hex character
159     */
160    protected static int toDigit(char ch, int index) throws IllegalArgumentException {
161        int digit = Character.digit(ch, 2 << 3);
162        if (digit == -1) {
163            throw new IllegalArgumentException("Illegal hexadecimal character " + ch + " at index " + index);
164        }
165        return digit;
166    }
167
168
169}