1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
|
// InflaterHuffmanTree.cs
// Copyright (C) 2001 Mike Krueger
//
// This file was translated from java, it was part of the GNU Classpath
// Copyright (C) 2001 Free Software Foundation, Inc.
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library. Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.
//
// As a special exception, the copyright holders of this library give you
// permission to link this library with independent modules to produce an
// executable, regardless of the license terms of these independent
// modules, and to copy and distribute the resulting executable under
// terms of your choice, provided that you also meet, for each linked
// independent module, the terms and conditions of the license of that
// module. An independent module is a module which is not derived from
// or based on this library. If you modify this library, you may extend
// this exception to your version of the library, but you are not
// obligated to do so. If you do not wish to do so, delete this
// exception statement from your version.
using System;
using ICSharpCode.SharpZipLib.Zip.Compression.Streams;
namespace ICSharpCode.SharpZipLib.Zip.Compression
{
public class InflaterHuffmanTree
{
private static int MAX_BITLEN = 15;
private short[] tree;
public static InflaterHuffmanTree defLitLenTree, defDistTree;
static InflaterHuffmanTree()
{
try {
byte[] codeLengths = new byte[288];
int i = 0;
while (i < 144) {
codeLengths[i++] = 8;
}
while (i < 256) {
codeLengths[i++] = 9;
}
while (i < 280) {
codeLengths[i++] = 7;
}
while (i < 288) {
codeLengths[i++] = 8;
}
defLitLenTree = new InflaterHuffmanTree(codeLengths);
codeLengths = new byte[32];
i = 0;
while (i < 32) {
codeLengths[i++] = 5;
}
defDistTree = new InflaterHuffmanTree(codeLengths);
} catch (Exception) {
throw new ApplicationException("InflaterHuffmanTree: static tree length illegal");
}
}
/// <summary>
/// Constructs a Huffman tree from the array of code lengths.
/// </summary>
/// <param name = "codeLengths">
/// the array of code lengths
/// </param>
public InflaterHuffmanTree(byte[] codeLengths)
{
BuildTree(codeLengths);
}
private void BuildTree(byte[] codeLengths)
{
int[] blCount = new int[MAX_BITLEN + 1];
int[] nextCode = new int[MAX_BITLEN + 1];
for (int i = 0; i < codeLengths.Length; i++) {
int bits = codeLengths[i];
if (bits > 0) {
blCount[bits]++;
}
}
int code = 0;
int treeSize = 512;
for (int bits = 1; bits <= MAX_BITLEN; bits++) {
nextCode[bits] = code;
code += blCount[bits] << (16 - bits);
if (bits >= 10) {
/* We need an extra table for bit lengths >= 10. */
int start = nextCode[bits] & 0x1ff80;
int end = code & 0x1ff80;
treeSize += (end - start) >> (16 - bits);
}
}
/* -jr comment this out! doesnt work for dynamic trees and pkzip 2.04g
if (code != 65536)
{
throw new Exception("Code lengths don't add up properly.");
}
*/
/* Now create and fill the extra tables from longest to shortest
* bit len. This way the sub trees will be aligned.
*/
tree = new short[treeSize];
int treePtr = 512;
for (int bits = MAX_BITLEN; bits >= 10; bits--) {
int end = code & 0x1ff80;
code -= blCount[bits] << (16 - bits);
int start = code & 0x1ff80;
for (int i = start; i < end; i += 1 << 7) {
tree[DeflaterHuffman.BitReverse(i)] = (short) ((-treePtr << 4) | bits);
treePtr += 1 << (bits-9);
}
}
for (int i = 0; i < codeLengths.Length; i++) {
int bits = codeLengths[i];
if (bits == 0) {
continue;
}
code = nextCode[bits];
int revcode = DeflaterHuffman.BitReverse(code);
if (bits <= 9) {
do {
tree[revcode] = (short) ((i << 4) | bits);
revcode += 1 << bits;
} while (revcode < 512);
} else {
int subTree = tree[revcode & 511];
int treeLen = 1 << (subTree & 15);
subTree = -(subTree >> 4);
do {
tree[subTree | (revcode >> 9)] = (short) ((i << 4) | bits);
revcode += 1 << bits;
} while (revcode < treeLen);
}
nextCode[bits] = code + (1 << (16 - bits));
}
}
/// <summary>
/// Reads the next symbol from input. The symbol is encoded using the
/// huffman tree.
/// </summary>
/// <param name="input">
/// input the input source.
/// </param>
/// <returns>
/// the next symbol, or -1 if not enough input is available.
/// </returns>
public int GetSymbol(StreamManipulator input)
{
int lookahead, symbol;
if ((lookahead = input.PeekBits(9)) >= 0) {
if ((symbol = tree[lookahead]) >= 0) {
input.DropBits(symbol & 15);
return symbol >> 4;
}
int subtree = -(symbol >> 4);
int bitlen = symbol & 15;
if ((lookahead = input.PeekBits(bitlen)) >= 0) {
symbol = tree[subtree | (lookahead >> 9)];
input.DropBits(symbol & 15);
return symbol >> 4;
} else {
int bits = input.AvailableBits;
lookahead = input.PeekBits(bits);
symbol = tree[subtree | (lookahead >> 9)];
if ((symbol & 15) <= bits) {
input.DropBits(symbol & 15);
return symbol >> 4;
} else {
return -1;
}
}
} else {
int bits = input.AvailableBits;
lookahead = input.PeekBits(bits);
symbol = tree[lookahead];
if (symbol >= 0 && (symbol & 15) <= bits) {
input.DropBits(symbol & 15);
return symbol >> 4;
} else {
return -1;
}
}
}
}
}
|
