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Java > Open Source Codes > org > archive > util > Base32


1 /* Base32
2 *
3 * $Id: Base32.java,v 1.4 2004/04/15 19:04:01 stack-sf Exp $
4 *
5 * Created on Jan 21, 2004
6 *
7 * Copyright (C) 2004 Internet Archive.
8 *
9 * This file is part of the Heritrix web crawler (crawler.archive.org).
10 *
11 * Heritrix is free software; you can redistribute it and/or modify
12 * it under the terms of the GNU Lesser Public License as published by
13 * the Free Software Foundation; either version 2.1 of the License, or
14 * any later version.
15 *
16 * Heritrix is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU Lesser Public License for more details.
20 *
21 * You should have received a copy of the GNU Lesser Public License
22 * along with Heritrix; if not, write to the Free Software
23 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
24 */
25 package org.archive.util;
26
27 /**
28  * Base32 - encodes and decodes RFC3548 Base32
29  * (see http://www.faqs.org/rfcs/rfc3548.html )
30  *
31  * Imported public-domain code of Bitzi.
32  *
33  * @author Robert Kaye
34  * @author Gordon Mohr
35  */
36 public class Base32 {
37     private static final String JavaDoc base32Chars =
38         "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
39     private static final int[] base32Lookup =
40     { 0xFF,0xFF,0x1A,0x1B,0x1C,0x1D,0x1E,0x1F, // '0', '1', '2', '3', '4', '5', '6', '7'
41 0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF, // '8', '9', ':', ';', '<', '=', '>', '?'
42 0xFF,0x00,0x01,0x02,0x03,0x04,0x05,0x06, // '@', 'A', 'B', 'C', 'D', 'E', 'F', 'G'
43 0x07,0x08,0x09,0x0A,0x0B,0x0C,0x0D,0x0E, // 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O'
44 0x0F,0x10,0x11,0x12,0x13,0x14,0x15,0x16, // 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W'
45 0x17,0x18,0x19,0xFF,0xFF,0xFF,0xFF,0xFF, // 'X', 'Y', 'Z', '[', '\', ']', '^', '_'
46 0xFF,0x00,0x01,0x02,0x03,0x04,0x05,0x06, // '`', 'a', 'b', 'c', 'd', 'e', 'f', 'g'
47 0x07,0x08,0x09,0x0A,0x0B,0x0C,0x0D,0x0E, // 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o'
48 0x0F,0x10,0x11,0x12,0x13,0x14,0x15,0x16, // 'p', 'q', 'r', 's', 't', 'u', 'v', 'w'
49 0x17,0x18,0x19,0xFF,0xFF,0xFF,0xFF,0xFF // 'x', 'y', 'z', '{', '|', '}', '~', 'DEL'
50 };
51
52     /**
53      * Encodes byte array to Base32 String.
54      *
55      * @param bytes Bytes to encode.
56      * @return Encoded byte array <code>bytes</code> as a String.
57      *
58      */
59     static public String JavaDoc encode(final byte[] bytes) {
60         int i = 0, index = 0, digit = 0;
61         int currByte, nextByte;
62         StringBuffer JavaDoc base32 = new StringBuffer JavaDoc((bytes.length + 7) * 8 / 5);
63
64         while (i < bytes.length) {
65             currByte = (bytes[i] >= 0) ? bytes[i] : (bytes[i] + 256); // unsign
66
67             /* Is the current digit going to span a byte boundary? */
68             if (index > 3) {
69                 if ((i + 1) < bytes.length) {
70                     nextByte =
71                         (bytes[i + 1] >= 0) ? bytes[i + 1] : (bytes[i + 1] + 256);
72                 } else {
73                     nextByte = 0;
74                 }
75
76                 digit = currByte & (0xFF >> index);
77                 index = (index + 5) % 8;
78                 digit <<= index;
79                 digit |= nextByte >> (8 - index);
80                 i++;
81             } else {
82                 digit = (currByte >> (8 - (index + 5))) & 0x1F;
83                 index = (index + 5) % 8;
84                 if (index == 0)
85                     i++;
86             }
87             base32.append(base32Chars.charAt(digit));
88         }
89
90         return base32.toString();
91     }
92
93     /**
94      * Decodes the given Base32 String to a raw byte array.
95      *
96      * @param base32
97      * @return Decoded <code>base32</code> String as a raw byte array.
98      */
99     static public byte[] decode(final String JavaDoc base32) {
100         int i, index, lookup, offset, digit;
101         byte[] bytes = new byte[base32.length() * 5 / 8];
102
103         for (i = 0, index = 0, offset = 0; i < base32.length(); i++) {
104             lookup = base32.charAt(i) - '0';
105
106             /* Skip chars outside the lookup table */
107             if (lookup < 0 || lookup >= base32Lookup.length) {
108                 continue;
109             }
110
111             digit = base32Lookup[lookup];
112
113             /* If this digit is not in the table, ignore it */
114             if (digit == 0xFF) {
115                 continue;
116             }
117
118             if (index <= 3) {
119                 index = (index + 5) % 8;
120                 if (index == 0) {
121                     bytes[offset] |= digit;
122                     offset++;
123                     if (offset >= bytes.length)
124                         break;
125                 } else {
126                     bytes[offset] |= digit << (8 - index);
127                 }
128             } else {
129                 index = (index + 5) % 8;
130                 bytes[offset] |= (digit >>> index);
131                 offset++;
132
133                 if (offset >= bytes.length) {
134                     break;
135                 }
136                 bytes[offset] |= digit << (8 - index);
137             }
138         }
139         return bytes;
140     }
141
142     /** For testing, take a command-line argument in Base32, decode, print in hex,
143      * encode, print
144      *
145      * @param args
146      */
147     static public void main(String JavaDoc[] args) {
148         if (args.length == 0) {
149             System.out.println("Supply a Base32-encoded argument.");
150             return;
151         }
152         System.out.println(" Original: " + args[0]);
153         byte[] decoded = Base32.decode(args[0]);
154         System.out.print(" Hex: ");
155         for (int i = 0; i < decoded.length; i++) {
156             int b = decoded[i];
157             if (b < 0) {
158                 b += 256;
159             }
160             System.out.print((Integer.toHexString(b + 256)).substring(1));
161         }
162         System.out.println();
163         System.out.println("Reencoded: " + Base32.encode(decoded));
164     }
165 }
166
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