View Javadoc
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   
7   package org.htmlunit.util.brotli;
8   
9   /**
10   * Common context lookup table for all context modes.
11   */
12  final class Context {
13  
14    static final int[] LOOKUP = new int[2048];
15  
16    private static final String UTF_MAP = "         !!  !                  \"#$##%#$&'##(#)#+++++++++"
17        + "+((&*'##,---,---,-----,-----,-----&#'###.///.///./////./////./////&#'# ";
18    private static final String UTF_RLE = "A/*  ':  & : $  \u0081 @";
19  
20    private static void unpackLookupTable(int[] lookup, String utfMap, String utfRle) {
21      // LSB6, MSB6, SIGNED
22      for (int i = 0; i < 256; ++i) {
23        lookup[i] = i & 0x3F;
24        lookup[512 + i] = i >> 2;
25        lookup[1792 + i] = 2 + (i >> 6);
26      }
27      // UTF8
28      for (int i = 0; i < 128; ++i) {
29        lookup[1024 + i] = 4 * (utfMap.charAt(i) - 32);
30      }
31      for (int i = 0; i < 64; ++i) {
32        lookup[1152 + i] = i & 1;
33        lookup[1216 + i] = 2 + (i & 1);
34      }
35      int offset = 1280;
36      for (int k = 0; k < 19; ++k) {
37        final int value = k & 3;
38        final int rep = utfRle.charAt(k) - 32;
39        for (int i = 0; i < rep; ++i) {
40          lookup[offset++] = value;
41        }
42      }
43      // SIGNED
44      for (int i = 0; i < 16; ++i) {
45        lookup[1792 + i] = 1;
46        lookup[2032 + i] = 6;
47      }
48      lookup[1792] = 0;
49      lookup[2047] = 7;
50      for (int i = 0; i < 256; ++i) {
51        lookup[1536 + i] = lookup[1792 + i] << 3;
52      }
53    }
54  
55    static {
56      unpackLookupTable(LOOKUP, UTF_MAP, UTF_RLE);
57    }
58  }