1// Copyright (c) 1999-2004 Brian Wellington (bwelling@xbill.org)
2
3package org.xbill.DNS.utils;
4
5import java.io.*;
6
7/**
8 * Routines for converting between Strings of base32-encoded data and arrays
9 * of binary data.  This currently supports the base32 and base32hex alphabets
10 * specified in RFC 4648, sections 6 and 7.
11 *
12 * @author Brian Wellington
13 */
14
15public class base32 {
16
17public static class Alphabet {
18	private Alphabet() {}
19
20	public static final String BASE32 =
21		"ABCDEFGHIJKLMNOPQRSTUVWXYZ234567=";
22	public static final String BASE32HEX =
23		"0123456789ABCDEFGHIJKLMNOPQRSTUV=";
24};
25
26private String alphabet;
27private boolean padding, lowercase;
28
29/**
30 * Creates an object that can be used to do base32 conversions.
31 * @param alphabet Which alphabet should be used
32 * @param padding Whether padding should be used
33 * @param lowercase Whether lowercase characters should be used.
34 * default parameters (The standard base32 alphabet, no padding, uppercase)
35 */
36public
37base32(String alphabet, boolean padding, boolean lowercase) {
38	this.alphabet = alphabet;
39	this.padding = padding;
40	this.lowercase = lowercase;
41}
42
43static private int
44blockLenToPadding(int blocklen) {
45	switch (blocklen) {
46	case 1:
47		return 6;
48	case 2:
49		return 4;
50	case 3:
51		return 3;
52	case 4:
53		return 1;
54	case 5:
55		return 0;
56	default:
57		return -1;
58	}
59}
60
61static private int
62paddingToBlockLen(int padlen) {
63	switch (padlen) {
64	case 6:
65		return 1;
66	case 4:
67		return 2;
68	case 3:
69		return 3;
70	case 1:
71		return 4;
72	case 0:
73		return 5;
74	default :
75		return -1;
76	}
77}
78
79/**
80 * Convert binary data to a base32-encoded String
81 *
82 * @param b An array containing binary data
83 * @return A String containing the encoded data
84 */
85public String
86toString(byte [] b) {
87	ByteArrayOutputStream os = new ByteArrayOutputStream();
88
89	for (int i = 0; i < (b.length + 4) / 5; i++) {
90		short s[] = new short[5];
91		int t[] = new int[8];
92
93		int blocklen = 5;
94		for (int j = 0; j < 5; j++) {
95			if ((i * 5 + j) < b.length)
96				s[j] = (short) (b[i * 5 + j] & 0xFF);
97			else {
98				s[j] = 0;
99				blocklen--;
100			}
101		}
102		int padlen = blockLenToPadding(blocklen);
103
104		// convert the 5 byte block into 8 characters (values 0-31).
105
106		// upper 5 bits from first byte
107		t[0] = (byte) ((s[0] >> 3) & 0x1F);
108		// lower 3 bits from 1st byte, upper 2 bits from 2nd.
109		t[1] = (byte) (((s[0] & 0x07) << 2) | ((s[1] >> 6) & 0x03));
110		// bits 5-1 from 2nd.
111		t[2] = (byte) ((s[1] >> 1) & 0x1F);
112		// lower 1 bit from 2nd, upper 4 from 3rd
113		t[3] = (byte) (((s[1] & 0x01) << 4) | ((s[2] >> 4) & 0x0F));
114		// lower 4 from 3rd, upper 1 from 4th.
115		t[4] = (byte) (((s[2] & 0x0F) << 1) | ((s[3] >> 7) & 0x01));
116		// bits 6-2 from 4th
117		t[5] = (byte) ((s[3] >> 2) & 0x1F);
118		// lower 2 from 4th, upper 3 from 5th;
119		t[6] = (byte) (((s[3] & 0x03) << 3) | ((s[4] >> 5) & 0x07));
120		// lower 5 from 5th;
121		t[7] = (byte) (s[4] & 0x1F);
122
123		// write out the actual characters.
124		for (int j = 0; j < t.length - padlen; j++) {
125			char c = alphabet.charAt(t[j]);
126			if (lowercase)
127				c = Character.toLowerCase(c);
128			os.write(c);
129		}
130
131		// write out the padding (if any)
132		if (padding) {
133			for (int j = t.length - padlen; j < t.length; j++)
134				os.write('=');
135		}
136	}
137
138    return new String(os.toByteArray());
139}
140
141/**
142 * Convert a base32-encoded String to binary data
143 *
144 * @param str A String containing the encoded data
145 * @return An array containing the binary data, or null if the string is invalid
146 */
147public byte[]
148fromString(String str) {
149	ByteArrayOutputStream bs = new ByteArrayOutputStream();
150	byte [] raw = str.getBytes();
151	for (int i = 0; i < raw.length; i++)
152	{
153		char c = (char) raw[i];
154		if (!Character.isWhitespace(c)) {
155			c = Character.toUpperCase(c);
156			bs.write((byte) c);
157		}
158	}
159
160	if (padding) {
161		if (bs.size() % 8 != 0)
162			return null;
163	} else {
164		while (bs.size() % 8 != 0)
165			bs.write('=');
166	}
167
168	byte [] in = bs.toByteArray();
169
170	bs.reset();
171	DataOutputStream ds = new DataOutputStream(bs);
172
173	for (int i = 0; i < in.length / 8; i++) {
174		short[] s = new short[8];
175		int[] t = new int[5];
176
177		int padlen = 8;
178		for (int j = 0; j < 8; j++) {
179			char c = (char) in[i * 8 + j];
180			if (c == '=')
181				break;
182			s[j] = (short) alphabet.indexOf(in[i * 8 + j]);
183			if (s[j] < 0)
184				return null;
185			padlen--;
186		}
187		int blocklen = paddingToBlockLen(padlen);
188		if (blocklen < 0)
189			return null;
190
191		// all 5 bits of 1st, high 3 (of 5) of 2nd
192		t[0] = (s[0] << 3) | s[1] >> 2;
193		// lower 2 of 2nd, all 5 of 3rd, high 1 of 4th
194		t[1] = ((s[1] & 0x03) << 6) | (s[2] << 1) | (s[3] >> 4);
195		// lower 4 of 4th, high 4 of 5th
196		t[2] = ((s[3] & 0x0F) << 4) | ((s[4] >> 1) & 0x0F);
197		// lower 1 of 5th, all 5 of 6th, high 2 of 7th
198		t[3] = (s[4] << 7) | (s[5] << 2) | (s[6] >> 3);
199		// lower 3 of 7th, all of 8th
200		t[4] = ((s[6] & 0x07) << 5) | s[7];
201
202		try {
203			for (int j = 0; j < blocklen; j++)
204				ds.writeByte((byte) (t[j] & 0xFF));
205		}
206		catch (IOException e) {
207		}
208	}
209
210    return bs.toByteArray();
211}
212
213}
214