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25 
26 package jdk.tools.jlink.internal;
27 
28 import java.nio.ByteBuffer;
29 import java.util.HashMap;
30 import jdk.internal.jimage.ImageStream;
31 import jdk.internal.jimage.ImageStrings;
32 import jdk.internal.jimage.ImageStringsReader;
33 
34 class 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 
ImageStringsWriter()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         if (offset != 0) {
48             throw new InternalError("Empty string not offset zero");
49         }
50 
51         // Reserve 1 offset for frequently used ".class".
52         offset = addString("class");
53         if (offset != 1) {
54             throw new InternalError("'class' string not offset one");
55         }
56     }
57 
addString(final String string)58     private int addString(final String string) {
59         int offset = stream.getPosition();
60         byte[] bytes = ImageStringsReader.mutf8FromString(string);
61         stream.put(bytes, 0, bytes.length);
62         stream.put('\0');
63         stringToOffsetMap.put(string, offset);
64 
65         return offset;
66     }
67 
68     @Override
add(final String string)69     public int add(final String string) {
70         int offset = find(string);
71 
72         return offset == NOT_FOUND ? addString(string) : offset;
73     }
74 
find(final String string)75     int find(final String string) {
76         Integer offset = stringToOffsetMap.get(string);
77 
78         return offset != null ? offset : NOT_FOUND;
79     }
80 
81     @Override
get(int offset)82     public String get(int offset) {
83         ByteBuffer buffer = stream.getBuffer();
84         int capacity = buffer.capacity();
85         if (offset < 0 || offset >= capacity) {
86             throw new InternalError("String buffer offset out of range");
87         }
88         int zero = NOT_FOUND;
89         for (int i = offset; i < capacity; i++) {
90             if (buffer.get(i) == '\0') {
91                 zero = i;
92                 break;
93             }
94         }
95         if (zero == NOT_FOUND) {
96             throw new InternalError("String zero terminator not found");
97         }
98         int length = zero - offset;
99         byte[] bytes = new byte[length];
100         int mark = buffer.position();
101         buffer.position(offset);
102         buffer.get(bytes);
103         buffer.position(mark);
104 
105         return ImageStringsReader.stringFromMUTF8(bytes);
106     }
107 
getStream()108     ImageStream getStream() {
109         return stream;
110     }
111 
getSize()112     int getSize() {
113         return stream.getSize();
114     }
115 
getCount()116     int getCount() {
117         return stringToOffsetMap.size();
118     }
119 }
120