1/* Copyright 2015 Google Inc. All Rights Reserved.
2
3   Distributed under MIT license.
4   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
5*/
6
7package org.brotli.dec;
8
9import java.nio.ByteBuffer;
10
11/**
12 * Collection of static dictionary words.
13 *
14 * <p>Dictionary content is loaded from binary resource when {@link #getData()} is executed for the
15 * first time. Consequently, it saves memory and CPU in case dictionary is not required.
16 *
17 * <p>One possible drawback is that multiple threads that need dictionary data may be blocked (only
18 * once in each classworld). To avoid this, it is enough to call {@link #getData()} proactively.
19 */
20public final class Dictionary {
21  private static volatile ByteBuffer data;
22
23  private static class DataLoader {
24    static final boolean OK;
25
26    static {
27      boolean ok = true;
28      try {
29        Class.forName(Dictionary.class.getPackage().getName() + ".DictionaryData");
30      } catch (Throwable ex) {
31        ok = false;
32      }
33      OK = ok;
34    }
35  }
36
37  public static void setData(ByteBuffer data) {
38    if (!data.isDirect() || !data.isReadOnly()) {
39      throw new BrotliRuntimeException("data must be a direct read-only byte buffer");
40    }
41    Dictionary.data = data;
42  }
43
44  public static ByteBuffer getData() {
45    if (data != null) {
46      return data;
47    }
48    if (!DataLoader.OK) {
49      throw new BrotliRuntimeException("brotli dictionary is not set");
50    }
51    /* Might have been set when {@link DictionaryData} was loaded.*/
52    return data;
53  }
54}
55