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 
 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 
 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 
 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
 69     public int add(final String string) {
 70         int offset = find(string);
 71 
 72         return offset == NOT_FOUND ? addString(string) : offset;
 73     }
 74 
 75     int find(final String string) {
 76         Integer offset = stringToOffsetMap.get(string);
 77 
 78         return offset != null ? offset : NOT_FOUND;
 79     }
 80 
 81     @Override
 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 
108     ImageStream getStream() {
109         return stream;
110     }
111 
112     int getSize() {
113         return stream.getSize();
114     }
115 
116     int getCount() {
117         return stringToOffsetMap.size();
118     }
119 }