1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 */
19 package org.eclipse.aether.util;
20
21 import java.nio.charset.StandardCharsets;
22 import java.security.MessageDigest;
23 import java.security.NoSuchAlgorithmException;
24
25 /**
26 * A simple digester utility for Strings. Uses {@link MessageDigest} for requested algorithm. Supports one-pass or
27 * several rounds of updates, and as result emits hex encoded String.
28 *
29 * @since 1.9.0
30 */
31 public final class StringDigestUtil {
32 private final MessageDigest digest;
33
34 /**
35 * Constructs instance with given algorithm.
36 *
37 * @see #sha1()
38 * @see #sha1(String)
39 */
40 public StringDigestUtil(final String alg) {
41 try {
42 this.digest = MessageDigest.getInstance(alg);
43 } catch (NoSuchAlgorithmException e) {
44 throw new IllegalStateException("Not supported digest algorithm: " + alg);
45 }
46 }
47
48 /**
49 * Updates instance with passed in string.
50 */
51 public StringDigestUtil update(String data) {
52 if (data != null && !data.isEmpty()) {
53 digest.update(data.getBytes(StandardCharsets.UTF_8));
54 }
55 return this;
56 }
57
58 /**
59 * Returns the digest of all strings passed via {@link #update(String)} as hex string. There is no state preserved
60 * and due implementation of {@link MessageDigest#digest()}, same applies here: this instance "resets" itself.
61 * Hence, the digest hex encoded string is returned only once.
62 *
63 * @see MessageDigest#digest()
64 */
65 public String digest() {
66 return toHexString(digest.digest());
67 }
68
69 /**
70 * Helper method to create {@link StringDigestUtil} using SHA-1 digest algorithm.
71 */
72 public static StringDigestUtil sha1() {
73 return new StringDigestUtil("SHA-1");
74 }
75
76 /**
77 * Helper method to calculate SHA-1 digest and hex encode it.
78 */
79 public static String sha1(final String string) {
80 return sha1().update(string).digest();
81 }
82
83 /**
84 * Creates a hexadecimal representation of the specified bytes. Each byte is converted into a two-digit hex number
85 * and appended to the result with no separator between consecutive bytes.
86 *
87 * @param bytes The bytes to represent in hex notation, may be {@code null}.
88 * @return The hexadecimal representation of the input or {@code null} if the input was {@code null}.
89 * @since 2.0.0
90 */
91 @SuppressWarnings("checkstyle:magicnumber")
92 public static String toHexString(byte[] bytes) {
93 if (bytes == null) {
94 return null;
95 }
96
97 StringBuilder buffer = new StringBuilder(bytes.length * 2);
98
99 for (byte aByte : bytes) {
100 int b = aByte & 0xFF;
101 if (b < 0x10) {
102 buffer.append('0');
103 }
104 buffer.append(Integer.toHexString(b));
105 }
106
107 return buffer.toString();
108 }
109
110 /**
111 * Creates a byte array out of hexadecimal representation of the specified bytes. If input string is {@code null},
112 * {@code null} is returned. Input value must have even length (due hex encoding = 2 chars one byte).
113 *
114 * @param hexString The hexString to convert to byte array, may be {@code null}.
115 * @return The byte array of the input or {@code null} if the input was {@code null}.
116 * @since 2.0.0
117 */
118 @SuppressWarnings("checkstyle:magicnumber")
119 public static byte[] fromHexString(String hexString) {
120 if (hexString == null) {
121 return null;
122 }
123 if (hexString.isEmpty()) {
124 return new byte[] {};
125 }
126 int len = hexString.length();
127 if (len % 2 != 0) {
128 throw new IllegalArgumentException("hexString length not even");
129 }
130 byte[] data = new byte[len / 2];
131 for (int i = 0; i < len; i += 2) {
132 data[i / 2] = (byte)
133 ((Character.digit(hexString.charAt(i), 16) << 4) + Character.digit(hexString.charAt(i + 1), 16));
134 }
135 return data;
136 }
137 }