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17 package org.apache.asn1.codec.binary;
18
19 import org.apache.asn1.codec.BinaryDecoder;
20 import org.apache.asn1.codec.BinaryEncoder;
21 import org.apache.asn1.codec.DecoderException;
22 import org.apache.asn1.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 1.14 2004/07/28 19:27:45 ggregory Exp $
30 */
31 public class Hex implements BinaryEncoder, BinaryDecoder {
32
33 /***
34 * Used to build 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
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
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(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 decode(Object object) throws DecoderException {
149 try {
150 char[] charArray = object instanceof String ? ((String) object).toCharArray() : (char[]) object;
151 return decodeHex(charArray);
152 } catch (ClassCastException 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(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 encode(Object object) throws EncoderException {
183 try {
184 byte[] byteArray = object instanceof String ? ((String) object).getBytes() : (byte[]) object;
185 return encodeHex(byteArray);
186 } catch (ClassCastException e) {
187 throw new EncoderException(e.getMessage());
188 }
189 }
190
191 }
192