inflaterdynheader.cs

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// InflaterDynHeader.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 
{
	
	class InflaterDynHeader
	{
		const int LNUM   = 0;
		const int DNUM   = 1;
		const int BLNUM  = 2;
		const int BLLENS = 3;
		const int LENS   = 4;
		const int REPS   = 5;
		
		static readonly int[] repMin  = { 3, 3, 11 };
		static readonly int[] repBits = { 2, 3,  7 };
		
		byte[] blLens;
		byte[] litdistLens;
		
		InflaterHuffmanTree blTree;
		
		int mode;
		int lnum, dnum, blnum, num;
		int repSymbol;
		byte lastLen;
		int ptr;
		
		static readonly int[] BL_ORDER = { 16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15 };
		
		public InflaterDynHeader()
		{
		}
		
		public bool Decode(StreamManipulator input)
		{
			decode_loop:
				for (;;) 
				{
					switch (mode) 
					{
						case LNUM:
							lnum = input.PeekBits(5);
							if (lnum < 0) 
							{
								return false;
							}
							lnum += 257;
							input.DropBits(5);
							//  	    System.err.println("LNUM: "+lnum);
							mode = DNUM;
							goto case DNUM; // fall through
						case DNUM:
							dnum = input.PeekBits(5);
							if (dnum < 0) 
							{
								return false;
							}
							dnum++;
							input.DropBits(5);
							//  	    System.err.println("DNUM: "+dnum);
							num = lnum+dnum;
							litdistLens = new byte[num];
							mode = BLNUM;
							goto case BLNUM; // fall through
						case BLNUM:
							blnum = input.PeekBits(4);
							if (blnum < 0) 
							{
								return false;
							}
							blnum += 4;
							input.DropBits(4);
							blLens = new byte[19];
							ptr = 0;
							//  	    System.err.println("BLNUM: "+blnum);
							mode = BLLENS;
							goto case BLLENS; // fall through
						case BLLENS:
							while (ptr < blnum) 
							{
								int len = input.PeekBits(3);
								if (len < 0) 
								{
									return false;
								}
								input.DropBits(3);
								//  		System.err.println("blLens["+BL_ORDER[ptr]+"]: "+len);
								blLens[BL_ORDER[ptr]] = (byte) len;
								ptr++;
							}
							blTree = new InflaterHuffmanTree(blLens);
							blLens = null;
							ptr = 0;
							mode = LENS;
							goto case LENS; // fall through
						case LENS: 
						{
							int symbol;
							while (((symbol = blTree.GetSymbol(input)) & ~15) == 0) 
							{
								/* Normal case: symbol in [0..15] */
							
								//  		  System.err.println("litdistLens["+ptr+"]: "+symbol);
								litdistLens[ptr++] = lastLen = (byte)symbol;
							
								if (ptr == num) 
								{
									/* Finished */
									return true;
								}
							}
						
							/* need more input ? */
							if (symbol < 0)
								return false;
						
							/* otherwise repeat code */
							if (symbol >= 17) 
							{
								/* repeat zero */
								//  		  System.err.println("repeating zero");
								lastLen = 0;
							} 
							else 
							{
								if (ptr == 0) 
								{
									throw new Exception();
								}
							}
							repSymbol = symbol-16;
						}
							mode = REPS;
							goto case REPS; // fall through
						case REPS:
						{
							int bits = repBits[repSymbol];
							int count = input.PeekBits(bits);
							if (count < 0) 
							{
								return false;
							}
							input.DropBits(bits);
							count += repMin[repSymbol];
							//  	      System.err.println("litdistLens repeated: "+count);
							
							if (ptr + count > num) 
							{
								throw new Exception();
							}
							while (count-- > 0) 
							{
								litdistLens[ptr++] = lastLen;
							}
							
							if (ptr == num) 
							{
								/* Finished */
								return true;
							}
						}
							mode = LENS;
							goto decode_loop;
					}
				}
		}
		
		public InflaterHuffmanTree BuildLitLenTree()
		{
			byte[] litlenLens = new byte[lnum];
			Array.Copy(litdistLens, 0, litlenLens, 0, lnum);
			return new InflaterHuffmanTree(litlenLens);
		}
		
		public InflaterHuffmanTree BuildDistTree()
		{
			byte[] distLens = new byte[dnum];
			Array.Copy(litdistLens, lnum, distLens, 0, dnum);
			return new InflaterHuffmanTree(distLens);
		}
	}
}