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.internal.jimage;
  27 
  28 import java.nio.ByteBuffer;
  29 import java.util.HashMap;
  30 
  31 class ImageStringsWriter implements ImageStrings {
  32     private static final int NOT_FOUND = -1;
  33     static final int EMPTY_OFFSET = 0;
  34     static final UTF8String CLASS_STRING = new UTF8String("class");
  35 
  36     private final HashMap<UTF8String, Integer> stringToOffsetMap;
  37     private final ImageStream stream;
  38 
  39     ImageStringsWriter() {
  40         this.stringToOffsetMap = new HashMap<>();
  41         this.stream = new ImageStream();
  42 
  43         // Reserve 0 offset for empty string.
  44         int offset = addString(UTF8String.EMPTY_STRING);
  45         assert offset == 0 : "Empty string not zero offset";
  46         // Reserve 1 offset for frequently used ".class".
  47         addString(CLASS_STRING);
  48     }
  49 
  50     private int addString(final UTF8String string) {
  51         int offset = stream.getPosition();
  52         string.writeTo(stream);
  53         stream.put('\0');
  54         stringToOffsetMap.put(string, offset);
  55 
  56         return offset;
  57     }
  58 
  59     @Override
  60     public int add(final UTF8String string) {
  61         int offset = find(string);
  62 
  63         return offset == NOT_FOUND ? addString(string) : offset;
  64     }
  65 
  66     int find(final UTF8String string) {
  67         Integer offset = stringToOffsetMap.get(string);
  68 
  69         return offset != null ? offset : NOT_FOUND;
  70     }
  71 
  72     @Override
  73     public UTF8String get(int offset) {
  74         ByteBuffer buffer = stream.getBuffer();
  75         assert 0 <= offset && offset < buffer.capacity() : "String buffer offset out of range";
  76         int zero = NOT_FOUND;
  77         for (int i = offset; i < buffer.capacity(); i++) {
  78             if (buffer.get(i) == '\0') {
  79                 zero = i;
  80                 break;
  81             }
  82         }
  83         assert zero != UTF8String.NOT_FOUND;
  84         int length = zero - offset;
  85         byte[] bytes = new byte[length];
  86         int mark = buffer.position();
  87         buffer.position(offset);
  88         buffer.get(bytes);
  89         buffer.position(mark);
  90 
  91         return new UTF8String(bytes, 0, length);
  92     }
  93 
  94     ImageStream getStream() {
  95         return stream;
  96     }
  97 
  98     int getSize() {
  99         return stream.getSize();
 100     }
 101 
 102     int getCount() {
 103         return stringToOffsetMap.size();
 104     }
 105 }