1 // InflaterHuffmanTree.cs
2 // Copyright (C) 2001 Mike Krueger
4 // This file was translated from java, it was part of the GNU Classpath
5 // Copyright (C) 2001 Free Software Foundation, Inc.
7 // This program is free software; you can redistribute it and/or
8 // modify it under the terms of the GNU General Public License
9 // as published by the Free Software Foundation; either version 2
10 // of the License, or (at your option) any later version.
12 // This program is distributed in the hope that it will be useful,
13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 // GNU General Public License for more details.
17 // You should have received a copy of the GNU General Public License
18 // along with this program; if not, write to the Free Software
19 // Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
21 // Linking this library statically or dynamically with other modules is
22 // making a combined work based on this library. Thus, the terms and
23 // conditions of the GNU General Public License cover the whole
26 // As a special exception, the copyright holders of this library give you
27 // permission to link this library with independent modules to produce an
28 // executable, regardless of the license terms of these independent
29 // modules, and to copy and distribute the resulting executable under
30 // terms of your choice, provided that you also meet, for each linked
31 // independent module, the terms and conditions of the license of that
32 // module. An independent module is a module which is not derived from
33 // or based on this library. If you modify this library, you may extend
34 // this exception to your version of the library, but you are not
35 // obligated to do so. If you do not wish to do so, delete this
36 // exception statement from your version.
40 using ICSharpCode
.SharpZipLib
.Zip
.Compression
.Streams
;
42 namespace ICSharpCode
.SharpZipLib
.Zip
.Compression
45 public class InflaterHuffmanTree
47 private static int MAX_BITLEN
= 15;
50 public static InflaterHuffmanTree defLitLenTree
, defDistTree
;
52 static InflaterHuffmanTree()
55 byte[] codeLengths
= new byte[288];
69 defLitLenTree
= new InflaterHuffmanTree(codeLengths
);
71 codeLengths
= new byte[32];
76 defDistTree
= new InflaterHuffmanTree(codeLengths
);
78 throw new ApplicationException("InflaterHuffmanTree: static tree length illegal");
83 /// Constructs a Huffman tree from the array of code lengths.
85 /// <param name = "codeLengths">
86 /// the array of code lengths
88 public InflaterHuffmanTree(byte[] codeLengths
)
90 BuildTree(codeLengths
);
93 private void BuildTree(byte[] codeLengths
)
95 int[] blCount
= new int[MAX_BITLEN
+ 1];
96 int[] nextCode
= new int[MAX_BITLEN
+ 1];
98 for (int i
= 0; i
< codeLengths
.Length
; i
++) {
99 int bits
= codeLengths
[i
];
107 for (int bits
= 1; bits
<= MAX_BITLEN
; bits
++) {
108 nextCode
[bits
] = code
;
109 code
+= blCount
[bits
] << (16 - bits
);
111 /* We need an extra table for bit lengths >= 10. */
112 int start
= nextCode
[bits
] & 0x1ff80;
113 int end
= code
& 0x1ff80;
114 treeSize
+= (end
- start
) >> (16 - bits
);
117 /* -jr comment this out! doesnt work for dynamic trees and pkzip 2.04g
120 throw new Exception("Code lengths don't add up properly.");
123 /* Now create and fill the extra tables from longest to shortest
124 * bit len. This way the sub trees will be aligned.
126 tree
= new short[treeSize
];
128 for (int bits
= MAX_BITLEN
; bits
>= 10; bits
--) {
129 int end
= code
& 0x1ff80;
130 code
-= blCount
[bits
] << (16 - bits
);
131 int start
= code
& 0x1ff80;
132 for (int i
= start
; i
< end
; i
+= 1 << 7) {
133 tree
[DeflaterHuffman
.BitReverse(i
)] = (short) ((-treePtr
<< 4) | bits
);
134 treePtr
+= 1 << (bits
-9);
138 for (int i
= 0; i
< codeLengths
.Length
; i
++) {
139 int bits
= codeLengths
[i
];
143 code
= nextCode
[bits
];
144 int revcode
= DeflaterHuffman
.BitReverse(code
);
147 tree
[revcode
] = (short) ((i
<< 4) | bits
);
148 revcode
+= 1 << bits
;
149 } while (revcode
< 512);
151 int subTree
= tree
[revcode
& 511];
152 int treeLen
= 1 << (subTree
& 15);
153 subTree
= -(subTree
>> 4);
155 tree
[subTree
| (revcode
>> 9)] = (short) ((i
<< 4) | bits
);
156 revcode
+= 1 << bits
;
157 } while (revcode
< treeLen
);
159 nextCode
[bits
] = code
+ (1 << (16 - bits
));
165 /// Reads the next symbol from input. The symbol is encoded using the
168 /// <param name="input">
169 /// input the input source.
172 /// the next symbol, or -1 if not enough input is available.
174 public int GetSymbol(StreamManipulator input
)
176 int lookahead
, symbol
;
177 if ((lookahead
= input
.PeekBits(9)) >= 0) {
178 if ((symbol
= tree
[lookahead
]) >= 0) {
179 input
.DropBits(symbol
& 15);
182 int subtree
= -(symbol
>> 4);
183 int bitlen
= symbol
& 15;
184 if ((lookahead
= input
.PeekBits(bitlen
)) >= 0) {
185 symbol
= tree
[subtree
| (lookahead
>> 9)];
186 input
.DropBits(symbol
& 15);
189 int bits
= input
.AvailableBits
;
190 lookahead
= input
.PeekBits(bits
);
191 symbol
= tree
[subtree
| (lookahead
>> 9)];
192 if ((symbol
& 15) <= bits
) {
193 input
.DropBits(symbol
& 15);
200 int bits
= input
.AvailableBits
;
201 lookahead
= input
.PeekBits(bits
);
202 symbol
= tree
[lookahead
];
203 if (symbol
>= 0 && (symbol
& 15) <= bits
) {
204 input
.DropBits(symbol
& 15);