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
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25package jdk.internal.jimage.decompressor;
26
27import java.nio.ByteBuffer;
28import java.nio.ByteOrder;
29import java.util.Objects;
30import jdk.internal.jimage.decompressor.ResourceDecompressor.StringsProvider;
31
32/**
33 *
34 * A resource header for compressed resource. This class is handled internally,
35 * you don't have to add header to the resource, headers are added automatically
36 * for compressed resources.
37 *
38 * @implNote This class needs to maintain JDK 8 source compatibility.
39 *
40 * It is used internally in the JDK to implement jimage/jrtfs access,
41 * but also compiled and delivered as part of the jrtfs.jar to support access
42 * to the jimage file provided by the shipped JDK by tools running on JDK 8.
43 */
44public final class CompressedResourceHeader {
45
46    private static final int SIZE = 29;
47    public static final int MAGIC = 0xCAFEFAFA;
48    private final long uncompressedSize;
49    private final long compressedSize;
50    private final int decompressorNameOffset;
51    private final int contentOffset;
52    private final boolean isTerminal;
53
54    public CompressedResourceHeader(long compressedSize,
55            long uncompressedSize, int decompressorNameOffset, int contentOffset,
56            boolean isTerminal) {
57        this.compressedSize = compressedSize;
58        this.uncompressedSize = uncompressedSize;
59        this.decompressorNameOffset = decompressorNameOffset;
60        this.contentOffset = contentOffset;
61        this.isTerminal = isTerminal;
62    }
63
64    public boolean isTerminal() {
65        return isTerminal;
66    }
67
68    public int getDecompressorNameOffset() {
69        return decompressorNameOffset;
70    }
71
72    public int getContentOffset() {
73        return contentOffset;
74    }
75
76    public String getStoredContent(StringsProvider provider) {
77        Objects.requireNonNull(provider);
78        if(contentOffset == -1) {
79            return null;
80        }
81        return provider.getString(contentOffset);
82    }
83
84    public long getUncompressedSize() {
85        return uncompressedSize;
86    }
87
88    public long getResourceSize() {
89        return compressedSize;
90    }
91
92    public byte[] getBytes(ByteOrder order) {
93        Objects.requireNonNull(order);
94        ByteBuffer buffer = ByteBuffer.allocate(SIZE);
95        buffer.order(order);
96        buffer.putInt(MAGIC);
97        buffer.putLong(compressedSize);
98        buffer.putLong(uncompressedSize);
99        buffer.putInt(decompressorNameOffset);
100        buffer.putInt(contentOffset);
101        buffer.put(isTerminal ? (byte)1 : (byte)0);
102        return buffer.array();
103    }
104
105    public static int getSize() {
106        return SIZE;
107    }
108
109    public static CompressedResourceHeader readFromResource(ByteOrder order,
110            byte[] resource) {
111        Objects.requireNonNull(order);
112        Objects.requireNonNull(resource);
113        if (resource.length < getSize()) {
114            return null;
115        }
116        ByteBuffer buffer = ByteBuffer.wrap(resource, 0, SIZE);
117        buffer.order(order);
118        int magic = buffer.getInt();
119        if(magic != MAGIC) {
120            return null;
121        }
122        long size = buffer.getLong();
123        long uncompressedSize = buffer.getLong();
124        int decompressorNameOffset = buffer.getInt();
125        int contentIndex = buffer.getInt();
126        byte isTerminal = buffer.get();
127        return new CompressedResourceHeader(size, uncompressedSize,
128                decompressorNameOffset, contentIndex, isTerminal == 1);
129    }
130}
131