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comparison org.eclipse.swt.win32.win32.x86/src/org/eclipse/swt/internal/image/PngHuffmanTable.d @ 0:6dd524f61e62

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add dwt win and basic java stuff
author Frank Benoit <benoit@tionex.de>
date Mon, 02 Mar 2009 14:44:16 +0100
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children 536e43f63c81
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-1:000000000000 0:6dd524f61e62
1 /*******************************************************************************
2 * Copyright (c) 2000, 2008 IBM Corporation and others.
3 * All rights reserved. This program and the accompanying materials
4 * are made available under the terms of the Eclipse Public License v1.0
5 * which accompanies this distribution, and is available at
6 * http://www.eclipse.org/legal/epl-v10.html
7 *
8 * Contributors:
9 * IBM Corporation - initial API and implementation
10 * Port to the D programming language:
11 * Frank Benoit <benoit@tionex.de>
12 *******************************************************************************/
13 module org.eclipse.swt.internal.image.PngHuffmanTable;
14
15 import org.eclipse.swt.internal.image.PngDecodingDataStream;
16
17 public class PngHuffmanTable {
18 CodeLengthInfo[] codeLengthInfo;
19 int[] codeValues;
20
21 static const int MAX_CODE_LENGTH = 15;
22 static const int BAD_CODE = 0xFFFFFFF;
23 static const int incs[] = [1391376, 463792, 198768, 86961, 33936, 13776, 4592, 1968, 861, 336, 112, 48, 21, 7, 3, 1];
24
25 this (int[] lengths) {
26 initialize(lengths);
27 generateTable(lengths);
28 }
29
30 private void initialize(int[] lengths) {
31 codeValues = new int[lengths.length];
32 for (int i = 0; i < codeValues.length; i++) {
33 codeValues[i] = i;
34 }
35
36 // minCodesByLength[n] : The smallest Huffman code of length n + 1.
37 // maxCodesByLength[n] : The largest Huffman code of length n + 1.
38 // indexesByLength[n] : Index into the values array. First value with a code of length n + 1.
39 codeLengthInfo = new CodeLengthInfo[MAX_CODE_LENGTH];
40 for (int i = 0; i < MAX_CODE_LENGTH; i++) {
41 codeLengthInfo[i] = new CodeLengthInfo();
42 codeLengthInfo[i].length = i;
43 codeLengthInfo[i].baseIndex = 0;
44 codeLengthInfo[i].min = BAD_CODE;
45 codeLengthInfo[i].max = -1;
46 }
47 }
48
49 private void generateTable(int[] lengths) {
50 // Sort the values using shellsort. Primary key is code size. Secondary key is value.
51 int codeValuesTemp;
52 for (int k = 0; k < 16; k++) {
53 for (int h = incs[k], i = h; i < lengths.length; i++) {
54 int v = lengths[i];
55 codeValuesTemp = codeValues[i];
56 int j = i;
57 while (j >= h && (lengths[j - h] > v || (lengths[j - h] is v && codeValues[j - h] > codeValuesTemp))) {
58 lengths[j] = lengths[j - h];
59 codeValues[j] = codeValues[j - h];
60 j -= h;
61 }
62 lengths[j] = v;
63 codeValues[j] = codeValuesTemp;
64 }
65 }
66
67 // These values in these arrays correspond to the elements of the
68 // "values" array. The Huffman code for codeValues[N] is codes[N]
69 // and the length of the code is lengths[N].
70 int[] codes = new int[lengths.length];
71 int lastLength = 0;
72 int code = 0;
73 for (int i = 0; i < lengths.length; i++) {
74 while (lastLength !is lengths[i]) {
75 lastLength++;
76 code <<= 1;
77 }
78 if (lastLength !is 0) {
79 codes[i] = code;
80 code++;
81 }
82 }
83
84 int last = 0;
85 for (int i = 0; i < lengths.length; i++) {
86 if (last !is lengths[i]) {
87 last = lengths[i];
88 codeLengthInfo[last - 1].baseIndex = i;
89 codeLengthInfo[last - 1].min = codes[i];
90 }
91 if (last !is 0) codeLengthInfo[last - 1].max = codes[i];
92 }
93 }
94
95 int getNextValue(PngDecodingDataStream stream) {
96 int code = stream.getNextIdatBit();
97 int codelength = 0;
98
99 // Here we are taking advantage of the fact that 1 bits are used as
100 // a prefix to the longer codeValues.
101 while (codelength < MAX_CODE_LENGTH && code > codeLengthInfo[codelength].max) {
102 code = ((code << 1) | stream.getNextIdatBit());
103 codelength++;
104 }
105 if (codelength >= MAX_CODE_LENGTH) stream.error();
106
107 // Now we have a Huffman code of length (codelength + 1) that
108 // is somewhere in the range
109 // minCodesByLength[codelength]..maxCodesByLength[codelength].
110 // This code is the (offset + 1)'th code of (codelength + 1);
111 int offset = code - codeLengthInfo[codelength].min;
112
113 // indexesByLength[codelength] is the first code of length (codelength + 1)
114 // so now we can look up the value for the Huffman code in the table.
115 int index = codeLengthInfo[codelength].baseIndex + offset;
116 return codeValues[index];
117 }
118
119 static class CodeLengthInfo {
120 int length;
121 int max;
122 int min;
123 int baseIndex;
124 }
125
126 }