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Java > Open Source Codes > org > apache > commons > codec > binary > Hex


1 /*
2  * Copyright 2001-2004 The Apache Software Foundation.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16
17 package org.apache.commons.codec.binary;
18
19 import org.apache.commons.codec.BinaryDecoder;
20 import org.apache.commons.codec.BinaryEncoder;
21 import org.apache.commons.codec.DecoderException;
22 import org.apache.commons.codec.EncoderException;
23
24 /**
25  * Hex encoder and decoder.
26  *
27  * @since 1.1
28  * @author Apache Software Foundation
29  * @version $Id: Hex.java,v 1.13 2004/04/18 18:22:33 ggregory Exp $
30  */
31 public class Hex implements BinaryEncoder, BinaryDecoder {
32
33     /**
34      * Used building output as Hex
35      */
36     private static final char[] DIGITS = {
37         '0', '1', '2', '3', '4', '5', '6', '7',
38            '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
39     };
40
41     /**
42      * Converts an array of characters representing hexidecimal values into an
43      * array of bytes of those same values. The returned array will be half the
44      * length of the passed array, as it takes two characters to represent any
45      * given byte. An exception is thrown if the passed char array has an odd
46      * number of elements.
47      *
48      * @param data An array of characters containing hexidecimal digits
49      * @return A byte array containing binary data decoded from
50      * the supplied char array.
51      * @throws DecoderException Thrown if an odd number or illegal of characters
52      * is supplied
53      */
54     public static byte[] decodeHex(char[] data) throws DecoderException {
55
56         int len = data.length;
57
58         if ((len & 0x01) != 0) {
59             throw new DecoderException("Odd number of characters.");
60         }
61
62         byte[] out = new byte[len >> 1];
63
64         // two characters form the hex value.
65 for (int i = 0, j = 0; j < len; i++) {
66             int f = toDigit(data[j], j) << 4;
67             j++;
68             f = f | toDigit(data[j], j);
69             j++;
70             out[i] = (byte) (f & 0xFF);
71         }
72
73         return out;
74     }
75
76     /**
77      * Converts a hexadecimal character to an integer.
78      *
79      * @param ch A character to convert to an integer digit
80      * @param index The index of the character in the source
81      * @return An integer
82      * @throws DecoderException Thrown if ch is an illegal hex character
83      */
84     protected static int toDigit(char ch, int index) throws DecoderException {
85         int digit = Character.digit(ch, 16);
86         if (digit == -1) {
87             throw new DecoderException("Illegal hexadecimal charcter " + ch + " at index " + index);
88         }
89         return digit;
90     }
91
92     /**
93      * Converts an array of bytes into an array of characters representing the hexidecimal values of each byte in order.
94      * The returned array will be double the length of the passed array, as it takes two characters to represent any
95      * given byte.
96      *
97      * @param data
98      * a byte[] to convert to Hex characters
99      * @return A char[] containing hexidecimal characters
100      */
101     public static char[] encodeHex(byte[] data) {
102
103         int l = data.length;
104
105            char[] out = new char[l << 1];
106
107            // two characters form the hex value.
108 for (int i = 0, j = 0; i < l; i++) {
109                out[j++] = DIGITS[(0xF0 & data[i]) >>> 4 ];
110                out[j++] = DIGITS[ 0x0F & data[i] ];
111            }
112
113            return out;
114     }
115     
116     /**
117      * Converts an array of character bytes representing hexidecimal 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 array An array of character bytes containing hexidecimal digits
124      * @return A byte array containing binary data decoded from
125      * the supplied byte array (representing characters).
126      * @throws DecoderException Thrown if an odd number of characters is supplied
127      * to this function
128      * @see #decodeHex(char[])
129      */
130     public byte[] decode(byte[] array) throws DecoderException {
131         return decodeHex(new String JavaDoc(array).toCharArray());
132     }
133     
134     /**
135      * Converts a String or an array of character bytes representing hexidecimal values into an
136      * array of bytes of those same values. The returned array will be half the
137      * length of the passed String or array, as it takes two characters to represent any
138      * given byte. An exception is thrown if the passed char array has an odd
139      * number of elements.
140      *
141      * @param object A String or, an array of character bytes containing hexidecimal digits
142      * @return A byte array containing binary data decoded from
143      * the supplied byte array (representing characters).
144      * @throws DecoderException Thrown if an odd number of characters is supplied
145      * to this function or the object is not a String or char[]
146      * @see #decodeHex(char[])
147      */
148     public Object JavaDoc decode(Object JavaDoc object) throws DecoderException {
149         try {
150             char[] charArray = object instanceof String JavaDoc ? ((String JavaDoc) object).toCharArray() : (char[]) object;
151             return decodeHex(charArray);
152         } catch (ClassCastException JavaDoc e) {
153             throw new DecoderException(e.getMessage());
154         }
155     }
156     
157     /**
158      * Converts an array of bytes into an array of bytes for the characters representing the
159      * hexidecimal values of each byte in order. The returned array will be
160      * double the length of the passed array, as it takes two characters to
161      * represent any given byte.
162      *
163      * @param array a byte[] to convert to Hex characters
164      * @return A byte[] containing the bytes of the hexidecimal characters
165      * @see #encodeHex(byte[])
166      */
167     public byte[] encode(byte[] array) {
168         return new String JavaDoc(encodeHex(array)).getBytes();
169     }
170
171     /**
172      * Converts a String or an array of bytes into an array of characters representing the
173      * hexidecimal values of each byte in order. The returned array will be
174      * double the length of the passed String or array, as it takes two characters to
175      * represent any given byte.
176      *
177      * @param object a String, or byte[] to convert to Hex characters
178      * @return A char[] containing hexidecimal characters
179      * @throws EncoderException Thrown if the given object is not a String or byte[]
180      * @see #encodeHex(byte[])
181      */
182     public Object JavaDoc encode(Object JavaDoc object) throws EncoderException {
183         try {
184             byte[] byteArray = object instanceof String JavaDoc ? ((String JavaDoc) object).getBytes() : (byte[]) object;
185             return encodeHex(byteArray);
186         } catch (ClassCastException JavaDoc e) {
187             throw new EncoderException(e.getMessage());
188         }
189     }
190
191 }
192
193
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