reactos/irc/TechBot/Compression/InflaterHuffmanTree.cs

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// 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;
}
}
}
}
}