1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.codec.digest;
18
19 import java.util.Random;
20
21 /**
22 * Base64 like method to convert binary bytes into ASCII chars.
23 *
24 * TODO: Can Base64 be reused?
25 *
26 * <p>
27 * This class is immutable and thread-safe.
28 * </p>
29 *
30 * @version $Id: B64.java 1435550 2013-01-19 14:09:52Z tn $
31 * @since 1.7
32 */
33 class B64 {
34
35 /**
36 * Table with characters for Base64 transformation.
37 */
38 static final String B64T = "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
39
40 /**
41 * Base64 like conversion of bytes to ASCII chars.
42 *
43 * @param b2
44 * A byte from the result.
45 * @param b1
46 * A byte from the result.
47 * @param b0
48 * A byte from the result.
49 * @param outLen
50 * The number of expected output chars.
51 * @param buffer
52 * Where the output chars is appended to.
53 */
54 static void b64from24bit(final byte b2, final byte b1, final byte b0, final int outLen,
55 final StringBuilder buffer) {
56 // The bit masking is necessary because the JVM byte type is signed!
57 int w = ((b2 << 16) & 0x00ffffff) | ((b1 << 8) & 0x00ffff) | (b0 & 0xff);
58 // It's effectively a "for" loop but kept to resemble the original C code.
59 int n = outLen;
60 while (n-- > 0) {
61 buffer.append(B64T.charAt(w & 0x3f));
62 w >>= 6;
63 }
64 }
65
66 /**
67 * Generates a string of random chars from the B64T set.
68 *
69 * @param num
70 * Number of chars to generate.
71 */
72 static String getRandomSalt(final int num) {
73 final StringBuilder saltString = new StringBuilder();
74 for (int i = 1; i <= num; i++) {
75 saltString.append(B64T.charAt(new Random().nextInt(B64T.length())));
76 }
77 return saltString.toString();
78 }
79 }