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
018package org.apache.commons.codec.binary;
019
020import java.nio.charset.Charset;
021
022import org.apache.commons.codec.BinaryDecoder;
023import org.apache.commons.codec.BinaryEncoder;
024import org.apache.commons.codec.CharEncoding;
025import org.apache.commons.codec.Charsets;
026import org.apache.commons.codec.DecoderException;
027import org.apache.commons.codec.EncoderException;
028
029/**
030 * Converts hexadecimal Strings. The charset used for certain operation can be set, the default is set in
031 * {@link #DEFAULT_CHARSET_NAME}
032 *
033 * This class is thread-safe.
034 *
035 * @since 1.1
036 * @version $Id: Hex.java 1619948 2014-08-22 22:53:55Z ggregory $
037 */
038public class Hex implements BinaryEncoder, BinaryDecoder {
039
040    /**
041     * Default charset name is {@link Charsets#UTF_8}
042     *
043     * @since 1.7
044     */
045    public static final Charset DEFAULT_CHARSET = Charsets.UTF_8;
046
047    /**
048     * Default charset name is {@link CharEncoding#UTF_8}
049     *
050     * @since 1.4
051     */
052    public static final String DEFAULT_CHARSET_NAME = CharEncoding.UTF_8;
053
054    /**
055     * Used to build output as Hex
056     */
057    private static final char[] DIGITS_LOWER =
058        {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
059
060    /**
061     * Used to build output as Hex
062     */
063    private static final char[] DIGITS_UPPER =
064        {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
065
066    /**
067     * Converts an array of characters representing hexadecimal values into an array of bytes of those same values. The
068     * returned array will be half the length of the passed array, as it takes two characters to represent any given
069     * byte. An exception is thrown if the passed char array has an odd number of elements.
070     *
071     * @param data
072     *            An array of characters containing hexadecimal digits
073     * @return A byte array containing binary data decoded from the supplied char array.
074     * @throws DecoderException
075     *             Thrown if an odd number or illegal of characters is supplied
076     */
077    public static byte[] decodeHex(final char[] data) throws DecoderException {
078
079        final int len = data.length;
080
081        if ((len & 0x01) != 0) {
082            throw new DecoderException("Odd number of characters.");
083        }
084
085        final byte[] out = new byte[len >> 1];
086
087        // two characters form the hex value.
088        for (int i = 0, j = 0; j < len; i++) {
089            int f = toDigit(data[j], j) << 4;
090            j++;
091            f = f | toDigit(data[j], j);
092            j++;
093            out[i] = (byte) (f & 0xFF);
094        }
095
096        return out;
097    }
098
099    /**
100     * Converts an array of bytes into an array of characters representing the hexadecimal values of each byte in order.
101     * The returned array will be double the length of the passed array, as it takes two characters to represent any
102     * given byte.
103     *
104     * @param data
105     *            a byte[] to convert to Hex characters
106     * @return A char[] containing hexadecimal characters
107     */
108    public static char[] encodeHex(final byte[] data) {
109        return encodeHex(data, true);
110    }
111
112    /**
113     * Converts an array of bytes into an array of characters representing the hexadecimal values of each byte in order.
114     * The returned array will be double the length of the passed array, as it takes two characters to represent any
115     * given byte.
116     *
117     * @param data
118     *            a byte[] to convert to Hex characters
119     * @param toLowerCase
120     *            <code>true</code> converts to lowercase, <code>false</code> to uppercase
121     * @return A char[] containing hexadecimal characters
122     * @since 1.4
123     */
124    public static char[] encodeHex(final byte[] data, final boolean toLowerCase) {
125        return encodeHex(data, toLowerCase ? DIGITS_LOWER : DIGITS_UPPER);
126    }
127
128    /**
129     * Converts an array of bytes into an array of characters representing the hexadecimal values of each byte in order.
130     * The returned array will be double the length of the passed array, as it takes two characters to represent any
131     * given byte.
132     *
133     * @param data
134     *            a byte[] to convert to Hex characters
135     * @param toDigits
136     *            the output alphabet
137     * @return A char[] containing hexadecimal characters
138     * @since 1.4
139     */
140    protected static char[] encodeHex(final byte[] data, final char[] toDigits) {
141        final int l = data.length;
142        final char[] out = new char[l << 1];
143        // two characters form the hex value.
144        for (int i = 0, j = 0; i < l; i++) {
145            out[j++] = toDigits[(0xF0 & data[i]) >>> 4];
146            out[j++] = toDigits[0x0F & data[i]];
147        }
148        return out;
149    }
150
151    /**
152     * Converts an array of bytes into a String representing the hexadecimal values of each byte in order. The returned
153     * String will be double the length of the passed array, as it takes two characters to represent any given byte.
154     *
155     * @param data
156     *            a byte[] to convert to Hex characters
157     * @return A String containing hexadecimal characters
158     * @since 1.4
159     */
160    public static String encodeHexString(final byte[] data) {
161        return new String(encodeHex(data));
162    }
163
164    /**
165     * Converts a hexadecimal character to an integer.
166     *
167     * @param ch
168     *            A character to convert to an integer digit
169     * @param index
170     *            The index of the character in the source
171     * @return An integer
172     * @throws DecoderException
173     *             Thrown if ch is an illegal hex character
174     */
175    protected static int toDigit(final char ch, final int index) throws DecoderException {
176        final int digit = Character.digit(ch, 16);
177        if (digit == -1) {
178            throw new DecoderException("Illegal hexadecimal character " + ch + " at index " + index);
179        }
180        return digit;
181    }
182
183    private final Charset charset;
184
185    /**
186     * Creates a new codec with the default charset name {@link #DEFAULT_CHARSET}
187     */
188    public Hex() {
189        // use default encoding
190        this.charset = DEFAULT_CHARSET;
191    }
192
193    /**
194     * Creates a new codec with the given Charset.
195     *
196     * @param charset
197     *            the charset.
198     * @since 1.7
199     */
200    public Hex(final Charset charset) {
201        this.charset = charset;
202    }
203
204    /**
205     * Creates a new codec with the given charset name.
206     *
207     * @param charsetName
208     *            the charset name.
209     * @throws java.nio.charset.UnsupportedCharsetException
210     *             If the named charset is unavailable
211     * @since 1.4
212     * @since 1.7 throws UnsupportedCharsetException if the named charset is unavailable
213     */
214    public Hex(final String charsetName) {
215        this(Charset.forName(charsetName));
216    }
217
218    /**
219     * Converts an array of character bytes representing hexadecimal values into an array of bytes of those same values.
220     * The returned array will be half the length of the passed array, as it takes two characters to represent any given
221     * byte. An exception is thrown if the passed char array has an odd number of elements.
222     *
223     * @param array
224     *            An array of character bytes containing hexadecimal digits
225     * @return A byte array containing binary data decoded from the supplied byte array (representing characters).
226     * @throws DecoderException
227     *             Thrown if an odd number of characters is supplied to this function
228     * @see #decodeHex(char[])
229     */
230    @Override
231    public byte[] decode(final byte[] array) throws DecoderException {
232        return decodeHex(new String(array, getCharset()).toCharArray());
233    }
234
235    /**
236     * Converts a String or an array of character bytes representing hexadecimal values into an array of bytes of those
237     * same values. The returned array will be half the length of the passed String or array, as it takes two characters
238     * to represent any given byte. An exception is thrown if the passed char array has an odd number of elements.
239     *
240     * @param object
241     *            A String or, an array of character bytes containing hexadecimal digits
242     * @return A byte array containing binary data decoded from the supplied byte array (representing characters).
243     * @throws DecoderException
244     *             Thrown if an odd number of characters is supplied to this function or the object is not a String or
245     *             char[]
246     * @see #decodeHex(char[])
247     */
248    @Override
249    public Object decode(final Object object) throws DecoderException {
250        try {
251            final char[] charArray = object instanceof String ? ((String) object).toCharArray() : (char[]) object;
252            return decodeHex(charArray);
253        } catch (final ClassCastException e) {
254            throw new DecoderException(e.getMessage(), e);
255        }
256    }
257
258    /**
259     * Converts an array of bytes into an array of bytes for the characters representing the hexadecimal values of each
260     * byte in order. The returned array will be double the length of the passed array, as it takes two characters to
261     * represent any given byte.
262     * <p>
263     * The conversion from hexadecimal characters to the returned bytes is performed with the charset named by
264     * {@link #getCharset()}.
265     * </p>
266     *
267     * @param array
268     *            a byte[] to convert to Hex characters
269     * @return A byte[] containing the bytes of the hexadecimal characters
270     * @since 1.7 No longer throws IllegalStateException if the charsetName is invalid.
271     * @see #encodeHex(byte[])
272     */
273    @Override
274    public byte[] encode(final byte[] array) {
275        return encodeHexString(array).getBytes(this.getCharset());
276    }
277
278    /**
279     * Converts a String or an array of bytes into an array of characters representing the hexadecimal values of each
280     * byte in order. The returned array will be double the length of the passed String or array, as it takes two
281     * characters to represent any given byte.
282     * <p>
283     * The conversion from hexadecimal characters to bytes to be encoded to performed with the charset named by
284     * {@link #getCharset()}.
285     * </p>
286     *
287     * @param object
288     *            a String, or byte[] to convert to Hex characters
289     * @return A char[] containing hexadecimal characters
290     * @throws EncoderException
291     *             Thrown if the given object is not a String or byte[]
292     * @see #encodeHex(byte[])
293     */
294    @Override
295    public Object encode(final Object object) throws EncoderException {
296        try {
297            final byte[] byteArray = object instanceof String ?
298                                   ((String) object).getBytes(this.getCharset()) : (byte[]) object;
299            return encodeHex(byteArray);
300        } catch (final ClassCastException e) {
301            throw new EncoderException(e.getMessage(), e);
302        }
303    }
304
305    /**
306     * Gets the charset.
307     *
308     * @return the charset.
309     * @since 1.7
310     */
311    public Charset getCharset() {
312        return this.charset;
313    }
314
315    /**
316     * Gets the charset name.
317     *
318     * @return the charset name.
319     * @since 1.4
320     */
321    public String getCharsetName() {
322        return this.charset.name();
323    }
324
325    /**
326     * Returns a string representation of the object, which includes the charset name.
327     *
328     * @return a string representation of the object.
329     */
330    @Override
331    public String toString() {
332        return super.toString() + "[charsetName=" + this.charset + "]";
333    }
334}