inflater.cs

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// Inflater.cs
//
// Copyright (C) 2001 Mike Krueger
// Copyright (C) 2004 John Reilly
//
// 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.Checksums;
using ICSharpCode.SharpZipLib.Zip.Compression.Streams;

namespace ICSharpCode.SharpZipLib.Zip.Compression 
{
	
	/// <summary>
	/// Inflater is used to decompress data that has been compressed according
	/// to the "deflate" standard described in rfc1951.
	/// 
	/// By default Zlib (rfc1950) headers and footers are expected in the input.
	/// You can use constructor <code> public Inflater(bool noHeader)</code> passing true
	/// if there is no Zlib header information
	///
	/// The usage is as following.  First you have to set some input with
	/// <code>setInput()</code>, then inflate() it.  If inflate doesn't
	/// inflate any bytes there may be three reasons:
	/// <ul>
	/// <li>needsInput() returns true because the input buffer is empty.
	/// You have to provide more input with <code>setInput()</code>.
	/// NOTE: needsInput() also returns true when, the stream is finished.
	/// </li>
	/// <li>needsDictionary() returns true, you have to provide a preset
	///    dictionary with <code>setDictionary()</code>.</li>
	/// <li>finished() returns true, the inflater has finished.</li>
	/// </ul>
	/// Once the first output byte is produced, a dictionary will not be
	/// needed at a later stage.
	///
	/// author of the original java version : John Leuner, Jochen Hoenicke
	/// </summary>
	public class Inflater
	{
		/// <summary>
		/// Copy lengths for literal codes 257..285
		/// </summary>
		static int[] CPLENS = {
								 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
								 35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258
							  };
		
		/// <summary>
		/// Extra bits for literal codes 257..285
		/// </summary>
		static int[] CPLEXT = {
								 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
								 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0
							  };
		
		/// <summary>
		/// Copy offsets for distance codes 0..29
		/// </summary>
		static int[] CPDIST = {
								1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
								257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
								8193, 12289, 16385, 24577
							  };
		
		/// <summary>
		/// Extra bits for distance codes
		/// </summary>
		static int[] CPDEXT = {
								0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6,
								7, 7, 8, 8, 9, 9, 10, 10, 11, 11,
								12, 12, 13, 13
							  };
		
		/// <summary>
		/// These are the possible states for an inflater
		/// </summary>
		const int DECODE_HEADER           = 0;
		const int DECODE_DICT             = 1;
		const int DECODE_BLOCKS           = 2;
		const int DECODE_STORED_LEN1      = 3;
		const int DECODE_STORED_LEN2      = 4;
		const int DECODE_STORED           = 5;
		const int DECODE_DYN_HEADER       = 6;
		const int DECODE_HUFFMAN          = 7;
		const int DECODE_HUFFMAN_LENBITS  = 8;
		const int DECODE_HUFFMAN_DIST     = 9;
		const int DECODE_HUFFMAN_DISTBITS = 10;
		const int DECODE_CHKSUM           = 11;
		const int FINISHED                = 12;
		
		/// <summary>
		/// This variable contains the current state.
		/// </summary>
		int mode;
		
		/// <summary>
		/// The adler checksum of the dictionary or of the decompressed
		/// stream, as it is written in the header resp. footer of the
		/// compressed stream. 
		/// Only valid if mode is DECODE_DICT or DECODE_CHKSUM.
		/// </summary>
		int readAdler;
		
		/// <summary>
		/// The number of bits needed to complete the current state.  This
		/// is valid, if mode is DECODE_DICT, DECODE_CHKSUM,
		/// DECODE_HUFFMAN_LENBITS or DECODE_HUFFMAN_DISTBITS.
		/// </summary>
		int neededBits;
		int repLength;
		int repDist;
		int uncomprLen;
		
		/// <summary>
		/// True, if the last block flag was set in the last block of the
		/// inflated stream.  This means that the stream ends after the
		/// current block.
		/// </summary>
		bool isLastBlock;
		
		/// <summary>
		/// The total number of inflated bytes.
		/// </summary>
		int totalOut;
		
		/// <summary>
		/// The total number of bytes set with setInput().  This is not the
		/// value returned by the TotalIn property, since this also includes the
		/// unprocessed input.
		/// </summary>
		int totalIn;
		
		/// <summary>
		/// This variable stores the noHeader flag that was given to the constructor.
		/// True means, that the inflated stream doesn't contain a Zlib header or 
		/// footer.
		/// </summary>
		bool noHeader;
		
		StreamManipulator input;
		OutputWindow outputWindow;
		InflaterDynHeader dynHeader;
		InflaterHuffmanTree litlenTree, distTree;
		Adler32 adler;
		
		/// <summary>
		/// Creates a new inflater or RFC1951 decompressor
		/// RFC1950/Zlib headers and footers will be expected in the input data
		/// </summary>
		public Inflater() : this(false)
		{
		}
		
		/// <summary>
		/// Creates a new inflater.
		/// </summary>
		/// <param name="noHeader">
		/// True if no RFC1950/Zlib header and footer fields are expected in the input data
		/// 
		/// This is used for GZIPed/Zipped input.
		/// 
		/// For compatibility with
		/// Sun JDK you should provide one byte of input more than needed in
		/// this case.
		/// </param>
		public Inflater(bool noHeader)
		{
			this.noHeader = noHeader;
			this.adler = new Adler32();
			input = new StreamManipulator();
			outputWindow = new OutputWindow();
			mode = noHeader ? DECODE_BLOCKS : DECODE_HEADER;
		}
		
		/// <summary>
		/// Resets the inflater so that a new stream can be decompressed.  All
		/// pending input and output will be discarded.
		/// </summary>
		public void Reset()
		{
			mode = noHeader ? DECODE_BLOCKS : DECODE_HEADER;
			totalIn = totalOut = 0;
			input.Reset();
			outputWindow.Reset();
			dynHeader = null;
			litlenTree = null;
			distTree = null;
			isLastBlock = false;
			adler.Reset();
		}
		
		/// <summary>
		/// Decodes a zlib/RFC1950 header.
		/// </summary>
		/// <returns>
		/// False if more input is needed.
		/// </returns>
		/// <exception cref="SharpZipBaseException">
		/// The header is invalid.
		/// </exception>
		private bool DecodeHeader()
		{
			int header = input.PeekBits(16);
			if (header < 0) {
				return false;
			}
			input.DropBits(16);
			
			/* The header is written in "wrong" byte order */
			header = ((header << 8) | (header >> 8)) & 0xffff;
			if (header % 31 != 0) {
				throw new SharpZipBaseException("Header checksum illegal");
			}
			
			if ((header & 0x0f00) != (Deflater.DEFLATED << 8)) {
				throw new SharpZipBaseException("Compression Method unknown");
			}
			
			/* Maximum size of the backwards window in bits.
			* We currently ignore this, but we could use it to make the
			* inflater window more space efficient. On the other hand the
			* full window (15 bits) is needed most times, anyway.
			int max_wbits = ((header & 0x7000) >> 12) + 8;
			*/
			
			if ((header & 0x0020) == 0) { // Dictionary flag?
				mode = DECODE_BLOCKS;
			} else {
				mode = DECODE_DICT;
				neededBits = 32;
			}
			return true;
		}
		
		/// <summary>
		/// Decodes the dictionary checksum after the deflate header.
		/// </summary>
		/// <returns>
		/// False if more input is needed.
		/// </returns>
		private bool DecodeDict()
		{
			while (neededBits > 0) {
				int dictByte = input.PeekBits(8);
				if (dictByte < 0) {
					return false;
				}
				input.DropBits(8);
				readAdler = (readAdler << 8) | dictByte;
				neededBits -= 8;
			}
			return false;
		}
		
		/// <summary>
		/// Decodes the huffman encoded symbols in the input stream.
		/// </summary>
		/// <returns>
		/// false if more input is needed, true if output window is
		/// full or the current block ends.
		/// </returns>
		/// <exception cref="SharpZipBaseException">
		/// if deflated stream is invalid.
		/// </exception>
		private bool DecodeHuffman()
		{
			int free = outputWindow.GetFreeSpace();
			while (free >= 258) {
				int symbol;
				switch (mode) {
					case DECODE_HUFFMAN:
						/* This is the inner loop so it is optimized a bit */
						while (((symbol = litlenTree.GetSymbol(input)) & ~0xff) == 0) {
							outputWindow.Write(symbol);
							if (--free < 258) {
								return true;
							}
						}
						
						if (symbol < 257) {
							if (symbol < 0) {
								return false;
							} else {
								/* symbol == 256: end of block */
								distTree = null;
								litlenTree = null;
								mode = DECODE_BLOCKS;
								return true;
							}
						}
						
						try {
							repLength = CPLENS[symbol - 257];
							neededBits = CPLEXT[symbol - 257];
						} catch (Exception) {
							throw new SharpZipBaseException("Illegal rep length code");
						}
						goto case DECODE_HUFFMAN_LENBITS; /* fall through */
						
					case DECODE_HUFFMAN_LENBITS:
						if (neededBits > 0) {
							mode = DECODE_HUFFMAN_LENBITS;
							int i = input.PeekBits(neededBits);
							if (i < 0) {
								return false;
							}
							input.DropBits(neededBits);
							repLength += i;
						}
						mode = DECODE_HUFFMAN_DIST;
						goto case DECODE_HUFFMAN_DIST;/* fall through */
						
					case DECODE_HUFFMAN_DIST:
						symbol = distTree.GetSymbol(input);
						if (symbol < 0) {
							return false;
						}
						
						try {
							repDist = CPDIST[symbol];
							neededBits = CPDEXT[symbol];
						} catch (Exception) {
							throw new SharpZipBaseException("Illegal rep dist code");
						}
						
						goto case DECODE_HUFFMAN_DISTBITS;/* fall through */
						
					case DECODE_HUFFMAN_DISTBITS:
						if (neededBits > 0) {
							mode = DECODE_HUFFMAN_DISTBITS;
							int i = input.PeekBits(neededBits);
							if (i < 0) {
								return false;
							}
							input.DropBits(neededBits);
							repDist += i;
						}
						
						outputWindow.Repeat(repLength, repDist);
						free -= repLength;
						mode = DECODE_HUFFMAN;
						break;
					
					default:
						throw new SharpZipBaseException("Inflater unknown mode");
				}
			}
			return true;
		}
		
		/// <summary>
		/// Decodes the adler checksum after the deflate stream.
		/// </summary>
		/// <returns>
		/// false if more input is needed.
		/// </returns>
		/// <exception cref="SharpZipBaseException">
		/// If checksum doesn't match.
		/// </exception>
		private bool DecodeChksum()
		{
			while (neededBits > 0) {
				int chkByte = input.PeekBits(8);
				if (chkByte < 0) {
					return false;
				}
				input.DropBits(8);
				readAdler = (readAdler << 8) | chkByte;
				neededBits -= 8;
			}
			if ((int) adler.Value != readAdler) {
				throw new SharpZipBaseException("Adler chksum doesn't match: " + (int)adler.Value + " vs. " + readAdler);
			}
			mode = FINISHED;