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     */
017    
018    package org.apache.commons.codec.binary;
019    
020    import java.io.UnsupportedEncodingException;
021    
022    import org.apache.commons.codec.BinaryDecoder;
023    import org.apache.commons.codec.BinaryEncoder;
024    import org.apache.commons.codec.CharEncoding;
025    import org.apache.commons.codec.DecoderException;
026    import org.apache.commons.codec.EncoderException;
027    
028    /**
029     * Converts hexadecimal Strings. The charset used for certain operation can be set, the default is set in
030     * {@link #DEFAULT_CHARSET_NAME}
031     * 
032     * @since 1.1
033     * @author Apache Software Foundation
034     * @version $Id: Hex.java 1080701 2011-03-11 17:52:27Z ggregory $
035     */
036    public class Hex implements BinaryEncoder, BinaryDecoder {
037    
038        /**
039         * Default charset name is {@link CharEncoding#UTF_8}
040         * 
041         * @since 1.4
042         */
043        public static final String DEFAULT_CHARSET_NAME = CharEncoding.UTF_8;
044    
045        /**
046         * Used to build output as Hex
047         */
048        private static final char[] DIGITS_LOWER = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
049    
050        /**
051         * Used to build output as Hex
052         */
053        private static final char[] DIGITS_UPPER = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
054    
055        /**
056         * Converts an array of characters representing hexadecimal values into an array of bytes of those same values. The
057         * returned array will be half the length of the passed array, as it takes two characters to represent any given
058         * byte. An exception is thrown if the passed char array has an odd number of elements.
059         * 
060         * @param data
061         *            An array of characters containing hexadecimal digits
062         * @return A byte array containing binary data decoded from the supplied char array.
063         * @throws DecoderException
064         *             Thrown if an odd number or illegal of characters is supplied
065         */
066        public static byte[] decodeHex(char[] data) throws DecoderException {
067    
068            int len = data.length;
069    
070            if ((len & 0x01) != 0) {
071                throw new DecoderException("Odd number of characters.");
072            }
073    
074            byte[] out = new byte[len >> 1];
075    
076            // two characters form the hex value.
077            for (int i = 0, j = 0; j < len; i++) {
078                int f = toDigit(data[j], j) << 4;
079                j++;
080                f = f | toDigit(data[j], j);
081                j++;
082                out[i] = (byte) (f & 0xFF);
083            }
084    
085            return out;
086        }
087    
088        /**
089         * Converts an array of bytes into an array of characters representing the hexadecimal values of each byte in order.
090         * The returned array will be double the length of the passed array, as it takes two characters to represent any
091         * given byte.
092         * 
093         * @param data
094         *            a byte[] to convert to Hex characters
095         * @return A char[] containing hexadecimal characters
096         */
097        public static char[] encodeHex(byte[] data) {
098            return encodeHex(data, true);
099        }
100    
101        /**
102         * Converts an array of bytes into an array of characters representing the hexadecimal values of each byte in order.
103         * The returned array will be double the length of the passed array, as it takes two characters to represent any
104         * given byte.
105         * 
106         * @param data
107         *            a byte[] to convert to Hex characters
108         * @param toLowerCase
109         *            <code>true</code> converts to lowercase, <code>false</code> to uppercase
110         * @return A char[] containing hexadecimal characters
111         * @since 1.4
112         */
113        public static char[] encodeHex(byte[] data, boolean toLowerCase) {
114            return encodeHex(data, toLowerCase ? DIGITS_LOWER : DIGITS_UPPER);
115        }
116    
117        /**
118         * Converts an array of bytes into an array of characters representing the hexadecimal values of each byte in order.
119         * The returned array will be double the length of the passed array, as it takes two characters to represent any
120         * given byte.
121         * 
122         * @param data
123         *            a byte[] to convert to Hex characters
124         * @param toDigits
125         *            the output alphabet
126         * @return A char[] containing hexadecimal characters
127         * @since 1.4
128         */
129        protected static char[] encodeHex(byte[] data, char[] toDigits) {
130            int l = data.length;
131            char[] out = new char[l << 1];
132            // two characters form the hex value.
133            for (int i = 0, j = 0; i < l; i++) {
134                out[j++] = toDigits[(0xF0 & data[i]) >>> 4];
135                out[j++] = toDigits[0x0F & data[i]];
136            }
137            return out;
138        }
139    
140        /**
141         * Converts an array of bytes into a String representing the hexadecimal values of each byte in order. The returned
142         * String will be double the length of the passed array, as it takes two characters to represent any given byte.
143         * 
144         * @param data
145         *            a byte[] to convert to Hex characters
146         * @return A String containing hexadecimal characters
147         * @since 1.4
148         */
149        public static String encodeHexString(byte[] data) {
150            return new String(encodeHex(data));
151        }
152    
153        /**
154         * Converts a hexadecimal character to an integer.
155         * 
156         * @param ch
157         *            A character to convert to an integer digit
158         * @param index
159         *            The index of the character in the source
160         * @return An integer
161         * @throws DecoderException
162         *             Thrown if ch is an illegal hex character
163         */
164        protected static int toDigit(char ch, int index) throws DecoderException {
165            int digit = Character.digit(ch, 16);
166            if (digit == -1) {
167                throw new DecoderException("Illegal hexadecimal character " + ch + " at index " + index);
168            }
169            return digit;
170        }
171    
172        private final String charsetName;
173    
174        /**
175         * Creates a new codec with the default charset name {@link #DEFAULT_CHARSET_NAME}
176         */
177        public Hex() {
178            // use default encoding
179            this.charsetName = DEFAULT_CHARSET_NAME;
180        }
181    
182        /**
183         * Creates a new codec with the given charset name.
184         * 
185         * @param csName
186         *            the charset name.
187         * @since 1.4
188         */
189        public Hex(String csName) {
190            this.charsetName = csName;
191        }
192    
193        /**
194         * Converts an array of character bytes representing hexadecimal values into an array of bytes of those same values.
195         * The returned array will be half the length of the passed array, as it takes two characters to represent any given
196         * byte. An exception is thrown if the passed char array has an odd number of elements.
197         * 
198         * @param array
199         *            An array of character bytes containing hexadecimal digits
200         * @return A byte array containing binary data decoded from the supplied byte array (representing characters).
201         * @throws DecoderException
202         *             Thrown if an odd number of characters is supplied to this function
203         * @see #decodeHex(char[])
204         */
205        public byte[] decode(byte[] array) throws DecoderException {
206            try {
207                return decodeHex(new String(array, getCharsetName()).toCharArray());
208            } catch (UnsupportedEncodingException e) {
209                throw new DecoderException(e.getMessage(), e);
210            }
211        }
212    
213        /**
214         * Converts a String or an array of character bytes representing hexadecimal values into an array of bytes of those
215         * same values. The returned array will be half the length of the passed String or array, as it takes two characters
216         * to represent any given byte. An exception is thrown if the passed char array has an odd number of elements.
217         * 
218         * @param object
219         *            A String or, an array of character bytes containing hexadecimal digits
220         * @return A byte array containing binary data decoded from the supplied byte array (representing characters).
221         * @throws DecoderException
222         *             Thrown if an odd number of characters is supplied to this function or the object is not a String or
223         *             char[]
224         * @see #decodeHex(char[])
225         */
226        public Object decode(Object object) throws DecoderException {
227            try {
228                char[] charArray = object instanceof String ? ((String) object).toCharArray() : (char[]) object;
229                return decodeHex(charArray);
230            } catch (ClassCastException e) {
231                throw new DecoderException(e.getMessage(), e);
232            }
233        }
234    
235        /**
236         * Converts an array of bytes into an array of bytes for the characters representing the hexadecimal values of each
237         * byte in order. The returned array will be double the length of the passed array, as it takes two characters to
238         * represent any given byte.
239         * <p>
240         * The conversion from hexadecimal characters to the returned bytes is performed with the charset named by
241         * {@link #getCharsetName()}.
242         * </p>
243         * 
244         * @param array
245         *            a byte[] to convert to Hex characters
246         * @return A byte[] containing the bytes of the hexadecimal characters
247         * @throws IllegalStateException
248         *             if the charsetName is invalid. This API throws {@link IllegalStateException} instead of
249         *             {@link UnsupportedEncodingException} for backward compatibility.
250         * @see #encodeHex(byte[])
251         */
252        public byte[] encode(byte[] array) {
253            return StringUtils.getBytesUnchecked(encodeHexString(array), getCharsetName());
254        }
255    
256        /**
257         * Converts a String or an array of bytes into an array of characters representing the hexadecimal values of each
258         * byte in order. The returned array will be double the length of the passed String or array, as it takes two
259         * characters to represent any given byte.
260         * <p>
261         * The conversion from hexadecimal characters to bytes to be encoded to performed with the charset named by
262         * {@link #getCharsetName()}.
263         * </p>
264         * 
265         * @param object
266         *            a String, or byte[] to convert to Hex characters
267         * @return A char[] containing hexadecimal characters
268         * @throws EncoderException
269         *             Thrown if the given object is not a String or byte[]
270         * @see #encodeHex(byte[])
271         */
272        public Object encode(Object object) throws EncoderException {
273            try {
274                byte[] byteArray = object instanceof String ? ((String) object).getBytes(getCharsetName()) : (byte[]) object;
275                return encodeHex(byteArray);
276            } catch (ClassCastException e) {
277                throw new EncoderException(e.getMessage(), e);
278            } catch (UnsupportedEncodingException e) {
279                throw new EncoderException(e.getMessage(), e);
280            }
281        }
282    
283        /**
284         * Gets the charset name.
285         * 
286         * @return the charset name.
287         * @since 1.4
288         */
289        public String getCharsetName() {
290            return this.charsetName;
291        }
292    
293        /**
294         * Returns a string representation of the object, which includes the charset name.
295         * 
296         * @return a string representation of the object.
297         */
298        public String toString() {
299            return super.toString() + "[charsetName=" + this.charsetName + "]";
300        }
301    }