ModuleHashes.java revision 16177:89ef4b822745 
1/*
2 * Copyright (c) 2015, 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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24 */
25
26package jdk.internal.module;
27
28import java.io.IOException;
29import java.io.UncheckedIOException;
30import java.nio.ByteBuffer;
31import java.nio.channels.FileChannel;
32import java.nio.file.Path;
33import java.security.MessageDigest;
34import java.security.NoSuchAlgorithmException;
35import java.util.Collections;
36import java.util.HashMap;
37import java.util.Map;
38import java.util.Set;
39
40/**
41 * The result of hashing the contents of a number of module artifacts.
42 */
43
44public final class ModuleHashes {
45
46    /**
47     * A supplier of a message digest.
48     */
49    public static interface HashSupplier {
50        byte[] generate(String algorithm);
51    }
52
53
54    private final String algorithm;
55    private final Map<String, byte[]> nameToHash;
56
57    /**
58     * Creates a {@code ModuleHashes}.
59     *
60     * @param algorithm   the algorithm used to create the hashes
61     * @param nameToHash  the map of module name to hash value
62     */
63    public ModuleHashes(String algorithm, Map<String, byte[]> nameToHash) {
64        this.algorithm = algorithm;
65        this.nameToHash = Collections.unmodifiableMap(nameToHash);
66    }
67
68    /**
69     * Returns the algorithm used to hash the modules ("SHA-256" for example).
70     */
71    public String algorithm() {
72        return algorithm;
73    }
74
75    /**
76     * Returns the set of module names for which hashes are recorded.
77     */
78    public Set<String> names() {
79        return nameToHash.keySet();
80    }
81
82    /**
83     * Returns the hash for the given module name, {@code null}
84     * if there is no hash recorded for the module.
85     */
86    public byte[] hashFor(String mn) {
87        return nameToHash.get(mn);
88    }
89
90    /**
91     * Returns unmodifiable map of module name to hash
92     */
93    public Map<String, byte[]> hashes() {
94        return nameToHash;
95    }
96
97    /**
98     * Computes the hash for the given file with the given message digest
99     * algorithm.
100     *
101     * @throws UncheckedIOException if an I/O error occurs
102     * @throws RuntimeException if the algorithm is not available
103     */
104    public static byte[] computeHash(Path file, String algorithm) {
105        try {
106            MessageDigest md = MessageDigest.getInstance(algorithm);
107
108            // Ideally we would just mmap the file but this consumes too much
109            // memory when jlink is running concurrently on very large jmods
110            try (FileChannel fc = FileChannel.open(file)) {
111                ByteBuffer bb = ByteBuffer.allocate(32*1024);
112                while (fc.read(bb) > 0) {
113                    bb.flip();
114                    md.update(bb);
115                    assert bb.remaining() == 0;
116                    bb.clear();
117                }
118            }
119
120            return md.digest();
121        } catch (NoSuchAlgorithmException e) {
122            throw new RuntimeException(e);
123        } catch (IOException ioe) {
124            throw new UncheckedIOException(ioe);
125        }
126    }
127
128    /**
129     * Computes the hash for every entry in the given map, returning a
130     * {@code ModuleHashes} to encapsulate the result. The map key is
131     * the entry name, typically the module name. The map value is the file
132     * path to the entry (module artifact).
133     *
134     * @return ModuleHashes that encapsulates the hashes
135     */
136    public static ModuleHashes generate(Map<String, Path> map, String algorithm) {
137        Map<String, byte[]> nameToHash = new HashMap<>();
138        for (Map.Entry<String, Path> entry: map.entrySet()) {
139            String name = entry.getKey();
140            Path path = entry.getValue();
141            nameToHash.put(name, computeHash(path, algorithm));
142        }
143        return new ModuleHashes(algorithm, nameToHash);
144    }
145}
146