ImageStringsWriter.java revision 13901:b2a69d66dc65 
1/*
2 * Copyright (c) 2014, 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 */
25
26package jdk.tools.jlink.internal;
27
28import java.nio.ByteBuffer;
29import java.util.HashMap;
30import jdk.internal.jimage.ImageStream;
31import jdk.internal.jimage.ImageStrings;
32import jdk.internal.jimage.ImageStringsReader;
33
34class ImageStringsWriter implements ImageStrings {
35    private static final int NOT_FOUND = -1;
36    static final int EMPTY_OFFSET = 0;
37
38    private final HashMap<String, Integer> stringToOffsetMap;
39    private final ImageStream stream;
40
41    ImageStringsWriter() {
42        this.stringToOffsetMap = new HashMap<>();
43        this.stream = new ImageStream();
44
45        // Reserve 0 offset for empty string.
46        int offset = addString("");
47        assert offset == 0 : "Empty string not zero offset";
48        // Reserve 1 offset for frequently used ".class".
49        addString("class");
50    }
51
52    private int addString(final String string) {
53        int offset = stream.getPosition();
54        byte[] bytes = ImageStringsReader.mutf8FromString(string);
55        stream.put(bytes, 0, bytes.length);
56        stream.put('\0');
57        stringToOffsetMap.put(string, offset);
58
59        return offset;
60    }
61
62    @Override
63    public int add(final String string) {
64        int offset = find(string);
65
66        return offset == NOT_FOUND ? addString(string) : offset;
67    }
68
69    int find(final String string) {
70        Integer offset = stringToOffsetMap.get(string);
71
72        return offset != null ? offset : NOT_FOUND;
73    }
74
75    @Override
76    public String get(int offset) {
77        ByteBuffer buffer = stream.getBuffer();
78        int capacity = buffer.capacity();
79        assert 0 <= offset && offset < capacity : "String buffer offset out of range";
80        int zero = NOT_FOUND;
81        for (int i = offset; i < capacity; i++) {
82            if (buffer.get(i) == '\0') {
83                zero = i;
84                break;
85            }
86        }
87        assert zero != NOT_FOUND;
88        int length = zero - offset;
89        byte[] bytes = new byte[length];
90        int mark = buffer.position();
91        buffer.position(offset);
92        buffer.get(bytes);
93        buffer.position(mark);
94
95        return ImageStringsReader.stringFromMUTF8(bytes);
96    }
97
98    ImageStream getStream() {
99        return stream;
100    }
101
102    int getSize() {
103        return stream.getSize();
104    }
105
106    int getCount() {
107        return stringToOffsetMap.size();
108    }
109}
110