BZip2InputStream.cs

// BZip2InputStream.cs
//
// Copyright © 2000-2016 AlphaSierraPapa for the SharpZipLib Team
//
// 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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, 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 System.IO;

using ICSharpCode.SharpZipLib.Checksums;

namespace ICSharpCode.SharpZipLib.BZip2 
{
	
	/// <summary>
	/// An input stream that decompresses files in the BZip2 format 
	/// </summary>
	public class BZip2InputStream : Stream
	{
		#region Constants
		const int START_BLOCK_STATE = 1;
		const int RAND_PART_A_STATE = 2;
		const int RAND_PART_B_STATE = 3;
		const int RAND_PART_C_STATE = 4;
		const int NO_RAND_PART_A_STATE = 5;
		const int NO_RAND_PART_B_STATE = 6;
		const int NO_RAND_PART_C_STATE = 7;
		#endregion
		#region Constructors
		/// <summary>
		/// Construct instance for reading from stream
		/// </summary>
		/// <param name="stream">Data source</param>
		public BZip2InputStream(Stream stream) 
		{
			// init arrays
			for (int i = 0; i < BZip2Constants.GroupCount; ++i) 
			{
				limit[i] = new int[BZip2Constants.MaximumAlphaSize];
				baseArray[i]  = new int[BZip2Constants.MaximumAlphaSize];
				perm[i]  = new int[BZip2Constants.MaximumAlphaSize];
			}
			
			BsSetStream(stream);
			Initialize();
			InitBlock();
			SetupBlock();
		}
		
		#endregion

		/// <summary>
		/// Get/set flag indicating ownership of underlying stream.
		/// When the flag is true <see cref="Close"></see> will close the underlying stream also.
		/// </summary>
		public bool IsStreamOwner
		{
			get { return isStreamOwner; }
			set { isStreamOwner = value; }
		}
		

		#region Stream Overrides
		/// <summary>
		/// Gets a value indicating if the stream supports reading
		/// </summary>
		public override bool CanRead 
		{
			get {
				return baseStream.CanRead;
			}
		}
		
		/// <summary>
		/// Gets a value indicating whether the current stream supports seeking.
		/// </summary>
		public override bool CanSeek {
			get {
				return baseStream.CanSeek;
			}
		}
		
		/// <summary>
		/// Gets a value indicating whether the current stream supports writing.
		/// This property always returns false
		/// </summary>
		public override bool CanWrite {
			get {
				return false;
			}
		}
		
		/// <summary>
		/// Gets the length in bytes of the stream.
		/// </summary>
		public override long Length {
			get {
				return baseStream.Length;
			}
		}
		
		/// <summary>
		/// Gets or sets the streams position.
		/// Setting the position is not supported and will throw a NotSupportException
		/// </summary>
		/// <exception cref="NotSupportedException">Any attempt to set the position</exception>
		public override long Position {
			get {
				return baseStream.Position;
			}
			set {
				throw new NotSupportedException("BZip2InputStream position cannot be set");
			}
		}
		
		/// <summary>
		/// Flushes the stream.
		/// </summary>
		public override void Flush()
		{
			if (baseStream != null) {
				baseStream.Flush();
			}
		}
		
		/// <summary>
		/// Set the streams position.  This operation is not supported and will throw a NotSupportedException
		/// </summary>
		/// <param name="offset">A byte offset relative to the <paramref name="origin"/> parameter.</param>
		/// <param name="origin">A value of type <see cref="SeekOrigin"/> indicating the reference point used to obtain the new position.</param>
		/// <returns>The new position of the stream.</returns>
		/// <exception cref="NotSupportedException">Any access</exception>
		public override long Seek(long offset, SeekOrigin origin)
		{
			throw new NotSupportedException("BZip2InputStream Seek not supported");
		}
		
		/// <summary>
		/// Sets the length of this stream to the given value.
		/// This operation is not supported and will throw a NotSupportedExceptionortedException
		/// </summary>
		/// <param name="value">The new length for the stream.</param>
		/// <exception cref="NotSupportedException">Any access</exception>
		public override void SetLength(long value)
		{
			throw new NotSupportedException("BZip2InputStream SetLength not supported");
		}
		
		/// <summary>
		/// Writes a block of bytes to this stream using data from a buffer.
		/// This operation is not supported and will throw a NotSupportedException
		/// </summary>
		/// <param name="buffer">The buffer to source data from.</param>
		/// <param name="offset">The offset to start obtaining data from.</param>
		/// <param name="count">The number of bytes of data to write.</param>
		/// <exception cref="NotSupportedException">Any access</exception>
		public override void Write(byte[] buffer, int offset, int count)
		{
			throw new NotSupportedException("BZip2InputStream Write not supported");
		}
		
		/// <summary>
		/// Writes a byte to the current position in the file stream.
		/// This operation is not supported and will throw a NotSupportedException
		/// </summary>
		/// <param name="value">The value to write.</param>
		/// <exception cref="NotSupportedException">Any access</exception>
		public override void WriteByte(byte value)
		{
			throw new NotSupportedException("BZip2InputStream WriteByte not supported");
		}
		
		/// <summary>
		/// Read a sequence of bytes and advances the read position by one byte.
		/// </summary>
		/// <param name="buffer">Array of bytes to store values in</param>
		/// <param name="offset">Offset in array to begin storing data</param>
		/// <param name="count">The maximum number of bytes to read</param>
		/// <returns>The total number of bytes read into the buffer. This might be less
		/// than the number of bytes requested if that number of bytes are not 
		/// currently available or zero if the end of the stream is reached.
		/// </returns>
		public override int Read(byte[] buffer, int offset, int count)
		{
			if ( buffer == null )
			{
				throw new ArgumentNullException("buffer");
			}

			for (int i = 0; i < count; ++i) {
				int rb = ReadByte();
				if (rb == -1) {
					return i;
				}
				buffer[offset + i] = (byte)rb;
			}
			return count;
		}
		
		/// <summary>
		/// Closes the stream, releasing any associated resources.
		/// </summary>
		public override void Close()
		{
			if ( IsStreamOwner && (baseStream != null) ) {
				baseStream.Close();
			}
		}
		/// <summary>
		/// Read a byte from stream advancing position
		/// </summary>
		/// <returns>byte read or -1 on end of stream</returns>
		public override int ReadByte()
		{
			if (streamEnd) 
			{
				return -1; // ok
			}
			
			int retChar = currentChar;
			switch (currentState) 
			{
				case RAND_PART_B_STATE:
					SetupRandPartB();
					break;
				case RAND_PART_C_STATE:
					SetupRandPartC();
					break;
				case NO_RAND_PART_B_STATE:
					SetupNoRandPartB();
					break;
				case NO_RAND_PART_C_STATE:
					SetupNoRandPartC();
					break;
				case START_BLOCK_STATE:
				case NO_RAND_PART_A_STATE:
				case RAND_PART_A_STATE:
					break;
				default:
					break;
			}
			return retChar;
		}
		
		#endregion

		void MakeMaps() 
		{
			nInUse = 0;
			for (int i = 0; i < 256; ++i) {
				if (inUse[i]) {
					seqToUnseq[nInUse] = (byte)i;
					unseqToSeq[i] = (byte)nInUse;
					nInUse++;
				}
			}
		}
				
		void Initialize() 
		{
			char magic1 = BsGetUChar();
			char magic2 = BsGetUChar();
			
			char magic3 = BsGetUChar();
			char magic4 = BsGetUChar();
			
			if (magic1 != 'B' || magic2 != 'Z' || magic3 != 'h' || magic4 < '1' || magic4 > '9') {
				streamEnd = true;
				return;
			}
			
			SetDecompressStructureSizes(magic4 - '0');
			computedCombinedCRC = 0;
		}
		
		void InitBlock() 
		{
			char magic1 = BsGetUChar();
			char magic2 = BsGetUChar();
			char magic3 = BsGetUChar();
			char magic4 = BsGetUChar();
			char magic5 = BsGetUChar();
			char magic6 = BsGetUChar();
			
			if (magic1 == 0x17 && magic2 == 0x72 && magic3 == 0x45 && magic4 == 0x38 && magic5 == 0x50 && magic6 == 0x90) {
				Complete();
				return;
			}
			
			if (magic1 != 0x31 || magic2 != 0x41 || magic3 != 0x59 || magic4 != 0x26 || magic5 != 0x53 || magic6 != 0x59) {
				BadBlockHeader();
				streamEnd = true;
				return;
			}
			
			storedBlockCRC  = BsGetInt32();
			
			blockRandomised = (BsR(1) == 1);
			
			GetAndMoveToFrontDecode();
			
			mCrc.Reset();
			currentState = START_BLOCK_STATE;
		}
		
		void EndBlock() 
		{
			computedBlockCRC = (int)mCrc.Value;
			
			// -- A bad CRC is considered a fatal error. --
			if (storedBlockCRC != computedBlockCRC) {
				CrcError();
			}
			
			// 1528150659
			computedCombinedCRC = ((computedCombinedCRC << 1) & 0xFFFFFFFF) | (computedCombinedCRC >> 31);
			computedCombinedCRC = computedCombinedCRC ^ (uint)computedBlockCRC;
		}
		
		void Complete() 
		{
			storedCombinedCRC = BsGetInt32();
			if (storedCombinedCRC != (int)computedCombinedCRC) {
				CrcError();
			}
			
			streamEnd = true;
		}
		
		void BsSetStream(Stream stream) 
		{
			baseStream = stream;
			bsLive = 0;
			bsBuff = 0;
		}
		
		void FillBuffer()
		{
			int thech = 0;
			
			try {
				thech = baseStream.ReadByte();
			} catch (Exception) {
				CompressedStreamEOF();
			}
			
			if (thech == -1) {
				CompressedStreamEOF();
			}
			
			bsBuff = (bsBuff << 8) | (thech & 0xFF);
			bsLive += 8;
		}
		
		int BsR(int n) 
		{
			while (bsLive < n) {
				FillBuffer();
			}
			
			int v = (bsBuff >> (bsLive - n)) & ((1 << n) - 1);
			bsLive -= n;
			return v;
		}
		
		char BsGetUChar() 
		{
			return (char)BsR(8);
		}
		
		int BsGetIntVS(int numBits) 
		{
			return BsR(numBits);
		}
		
		int BsGetInt32()
		{
			int result = BsR(8);
			result = (result << 8) | BsR(8);
			result = (result << 8) | BsR(8);
			result = (result << 8) | BsR(8);
			return result;
		}
		
		void RecvDecodingTables() 
		{
			char[][] len = new char[BZip2Constants.GroupCount][];
			for (int i = 0; i < BZip2Constants.GroupCount; ++i) {
				len[i] = new char[BZip2Constants.MaximumAlphaSize];
			}
			
			bool[] inUse16 = new bool[16];
			
			//--- Receive the mapping table ---
			for (int i = 0; i < 16; i++) {
				inUse16[i] = (BsR(1) == 1);
			} 
			
			for (int i = 0; i < 16; i++) {
				if (inUse16[i]) {
					for (int j = 0; j < 16; j++) {
						inUse[i * 16 + j] = (BsR(1) == 1);
					}
				} else {
					for (int j = 0; j < 16; j++) {
						inUse[i * 16 + j] = false;
					}
				}
			}
			
			MakeMaps();
			int alphaSize = nInUse + 2;
			
			//--- Now the selectors ---
			int nGroups    = BsR(3);
			int nSelectors = BsR(15);
			
			for (int i = 0; i < nSelectors; i++) {
				int j = 0;
				while (BsR(1) == 1) {
					j++;
				}
				selectorMtf[i] = (byte)j;
			}
			
			//--- Undo the MTF values for the selectors. ---
			byte[] pos = new byte[BZip2Constants.GroupCount];
			for (int v = 0; v < nGroups; v++) {
				pos[v] = (byte)v;
			}
			
			for (int i = 0; i < nSelectors; i++) {
				int  v   = selectorMtf[i];
				byte tmp = pos[v];
				while (v > 0) {
					pos[v] = pos[v - 1];
					v--;
				}
				pos[0]      = tmp;
				selector[i] = tmp;
			}
			
			//--- Now the coding tables ---
			for (int t = 0; t < nGroups; t++) {
				int curr = BsR(5);
				for (int i = 0; i < alphaSize; i++) {
					while (BsR(1) == 1) {
						if (BsR(1) == 0) {
							curr++;
						} else {
							curr--;
						}
					}
					len[t][i] = (char)curr;
				}
			}
			
			//--- Create the Huffman decoding tables ---
			for (int t = 0; t < nGroups; t++) {
				int minLen = 32;
				int maxLen = 0;
				for (int i = 0; i < alphaSize; i++) {
					maxLen = Math.Max(maxLen, len[t][i]);
					minLen = Math.Min(minLen, len[t][i]);
				}
				HbCreateDecodeTables(limit[t], baseArray[t], perm[t], len[t], minLen, maxLen, alphaSize);
				minLens[t] = minLen;
			}
		}
		
		void GetAndMoveToFrontDecode() 
		{
			byte[] yy = new byte[256];
			int nextSym;
			
			int limitLast = BZip2Constants.BaseBlockSize * blockSize100k;
			origPtr = BsGetIntVS(24);
			
			RecvDecodingTables();
			int EOB = nInUse+1;
			int groupNo = -1;
			int groupPos = 0;
			
			/*--
			Setting up the unzftab entries here is not strictly
			necessary, but it does save having to do it later
			in a separate pass, and so saves a block's worth of
			cache misses.
			--*/
			for (int i = 0; i <= 255; i++) {
				unzftab[i] = 0;
			}
			
			for (int i = 0; i <= 255; i++) {
				yy[i] = (byte)i;
			}
			
			last = -1;
			
			if (groupPos == 0) {
				groupNo++;
				groupPos = BZip2Constants.GroupSize;
			}
			
			groupPos--;
			int zt = selector[groupNo];
			int zn = minLens[zt];
			int zvec = BsR(zn);
			int zj;
			
			while (zvec > limit[zt][zn]) {
				if (zn > 20) { // the longest code
					throw new BZip2Exception("Bzip data error");
				}
				zn++;
				while (bsLive < 1) {
					FillBuffer();
				}
				zj = (bsBuff >> (bsLive-1)) & 1;
				bsLive--;
				zvec = (zvec << 1) | zj;
			}
			if (zvec - baseArray[zt][zn] < 0 || zvec - baseArray[zt][zn] >= BZip2Constants.MaximumAlphaSize) {
				throw new BZip2Exception("Bzip data error");
			}
			nextSym = perm[zt][zvec - baseArray[zt][zn]];
			
			while (true) {
				if (nextSym == EOB) {
					break;
				}
				
				if (nextSym == BZip2Constants.RunA || nextSym == BZip2Constants.RunB) {
					int s = -1;
					int n = 1;
					do {
						if (nextSym == BZip2Constants.RunA) {
							s += (0 + 1) * n;
						} else if (nextSym == BZip2Constants.RunB) {
							s += (1 + 1) * n;
						}

						n <<= 1;
						
						if (groupPos == 0) {
							groupNo++;
							groupPos = BZip2Constants.GroupSize;
						}
						
						groupPos--;
						
						zt = selector[groupNo];
						zn = minLens[zt];
						zvec = BsR(zn);
						
						while (zvec > limit[zt][zn]) {
							zn++;
							while (bsLive < 1) {
								FillBuffer();
							}
							zj = (bsBuff >> (bsLive - 1)) & 1;
							bsLive--;
							zvec = (zvec << 1) | zj;
						}
						nextSym = perm[zt][zvec - baseArray[zt][zn]];
					} while (nextSym == BZip2Constants.RunA || nextSym == BZip2Constants.RunB);
					
					s++;
					byte ch = seqToUnseq[yy[0]];
					unzftab[ch] += s;
					
					while (s > 0) {
						last++;
						ll8[last] = ch;
						s--;
					}
					
					if (last >= limitLast) {
						BlockOverrun();
					}
					continue;
				} else {
					last++;
					if (last >= limitLast) {
						BlockOverrun();
					}
					
					byte tmp = yy[nextSym - 1];
					unzftab[seqToUnseq[tmp]]++;
					ll8[last] = seqToUnseq[tmp];
					
					for (int j = nextSym-1; j > 0; --j) {
						yy[j] = yy[j - 1];
					}
					yy[0] = tmp;
					
					if (groupPos == 0) {
						groupNo++;
						groupPos = BZip2Constants.GroupSize;
					}
					
					groupPos--;
					zt = selector[groupNo];
					zn = minLens[zt];
					zvec = BsR(zn);
					while (zvec > limit[zt][zn]) {
						zn++;
						while (bsLive < 1) {
							FillBuffer();
						}
						zj = (bsBuff >> (bsLive-1)) & 1;
						bsLive--;
						zvec = (zvec << 1) | zj;
					}
					nextSym = perm[zt][zvec - baseArray[zt][zn]];
					continue;
				}
			}
		}
		
		void SetupBlock() 
		{
			int[] cftab = new int[257];
			
			cftab[0] = 0;
			Array.Copy(unzftab, 0, cftab, 1, 256);
			
			for (int i = 1; i <= 256; i++) {
				cftab[i] += cftab[i - 1];
			}
			
			for (int i = 0; i <= last; i++) {
				byte ch = ll8[i];
				tt[cftab[ch]] = i;
				cftab[ch]++;
			}
			
			cftab = null;
			
			tPos = tt[origPtr];
			
			count = 0;
			i2    = 0;
			ch2   = 256;   /*-- not a char and not EOF --*/
			
			if (blockRandomised) {
				rNToGo = 0;
				rTPos = 0;
				SetupRandPartA();
			} else {
				SetupNoRandPartA();
			}
		}
		
		void SetupRandPartA() 
		{
			if (i2 <= last) {
				chPrev = ch2;
				ch2  = ll8[tPos];
				tPos = tt[tPos];
				if (rNToGo == 0) {
					rNToGo = BZip2Constants.RandomNumbers[rTPos];
					rTPos++;
					if (rTPos == 512) {
						rTPos = 0;
					}
				}
				rNToGo--;
				ch2 ^= (int)((rNToGo == 1) ? 1 : 0);
				i2++;
				
				currentChar  = ch2;
				currentState = RAND_PART_B_STATE;
				mCrc.Update(ch2);
			} else {
				EndBlock();
				InitBlock();
				SetupBlock();
			}
		}
		
		void SetupNoRandPartA() 
		{
			if (i2 <= last) {
				chPrev = ch2;
				ch2  = ll8[tPos];
				tPos = tt[tPos];
				i2++;
				
				currentChar = ch2;
				currentState = NO_RAND_PART_B_STATE;
				mCrc.Update(ch2);
			} else {
				EndBlock();
				InitBlock();
				SetupBlock();
			}
		}
		
		void SetupRandPartB() 
		{
			if (ch2 != chPrev) {
				currentState = RAND_PART_A_STATE;
				count = 1;
				SetupRandPartA();
			} else {
				count++;
				if (count >= 4) {
					z = ll8[tPos];
					tPos = tt[tPos];
					if (rNToGo == 0) {
						rNToGo = BZip2Constants.RandomNumbers[rTPos];
						rTPos++;
						if (rTPos == 512) {
							rTPos = 0;
						}
					}
					rNToGo--;
					z ^= (byte)((rNToGo == 1) ? 1 : 0);
					j2 = 0;
					currentState = RAND_PART_C_STATE;
					SetupRandPartC();
				} else {
					currentState = RAND_PART_A_STATE;
					SetupRandPartA();
				}
			}
		}
		
		void SetupRandPartC() 
		{
			if (j2 < (int)z) {
				currentChar = ch2;
				mCrc.Update(ch2);
				j2++;
			} else {
				currentState = RAND_PART_A_STATE;
				i2++;
				count = 0;
				SetupRandPartA();
			}
		}
		
		void SetupNoRandPartB() 
		{
			if (ch2 != chPrev) {
				currentState = NO_RAND_PART_A_STATE;
				count = 1;
				SetupNoRandPartA();
			} else {
				count++;
				if (count >= 4) {
					z = ll8[tPos];
					tPos = tt[tPos];
					currentState = NO_RAND_PART_C_STATE;
					j2 = 0;
					SetupNoRandPartC();
				} else {
					currentState = NO_RAND_PART_A_STATE;
					SetupNoRandPartA();
				}
			}
		}
		
		void SetupNoRandPartC() 
		{
			if (j2 < (int)z) {
				currentChar = ch2;
				mCrc.Update(ch2);
				j2++;
			} else {
				currentState = NO_RAND_PART_A_STATE;
				i2++;
				count = 0;
				SetupNoRandPartA();
			}
		}
		
		void SetDecompressStructureSizes(int newSize100k) 
		{
			if (!(0 <= newSize100k && newSize100k <= 9 && 0 <= blockSize100k && blockSize100k <= 9)) {
				throw new BZip2Exception("Invalid block size");
			}
			
			blockSize100k = newSize100k;
			
			if (newSize100k == 0) {
				return;
			}
			
			int n = BZip2Constants.BaseBlockSize * newSize100k;
			ll8 = new byte[n];
			tt  = new int[n];
		}

		static void CompressedStreamEOF() 
		{
			throw new EndOfStreamException("BZip2 input stream end of compressed stream");
		}
		
		static void BlockOverrun() 
		{
			throw new BZip2Exception("BZip2 input stream block overrun");
		}
		
		static void BadBlockHeader() 
		{
			throw new BZip2Exception("BZip2 input stream bad block header");
		}
		
		static void CrcError() 
		{
			throw new BZip2Exception("BZip2 input stream crc error");
		}
		
		static void HbCreateDecodeTables(int[] limit, int[] baseArray, int[] perm, char[] length, int minLen, int maxLen, int alphaSize) 
		{
			int pp = 0;
			
			for (int i = minLen; i <= maxLen; ++i) 
			{
				for (int j = 0; j < alphaSize; ++j) 
				{
					if (length[j] == i) 
					{
						perm[pp] = j;
						++pp;
					}
				}
			}
			
			for (int i = 0; i < BZip2Constants.MaximumCodeLength; i++) 
			{
				baseArray[i] = 0;
			}
			
			for (int i = 0; i < alphaSize; i++) 
			{
				++baseArray[length[i] + 1];
			}
			
			for (int i = 1; i < BZip2Constants.MaximumCodeLength; i++) 
			{
				baseArray[i] += baseArray[i - 1];
			}
			
			for (int i = 0; i < BZip2Constants.MaximumCodeLength; i++) 
			{
				limit[i] = 0;
			}
			
			int vec = 0;
			
			for (int i = minLen; i <= maxLen; i++) 
			{
				vec += (baseArray[i + 1] - baseArray[i]);
				limit[i] = vec - 1;
				vec <<= 1;
			}
			
			for (int i = minLen + 1; i <= maxLen; i++) 
			{
				baseArray[i] = ((limit[i - 1] + 1) << 1) - baseArray[i];
			}
		}
		
		#region Instance Fields
		/*--
		index of the last char in the block, so
		the block size == last + 1.
		--*/
		int last;
		
		/*--
		index in zptr[] of original string after sorting.
		--*/
		int origPtr;
		
		/*--
		always: in the range 0 .. 9.
		The current block size is 100000 * this number.
		--*/
		int blockSize100k;
		
		bool blockRandomised;
		
		int bsBuff;
		int bsLive;
		IChecksum mCrc = new StrangeCRC();
		
		bool[] inUse = new bool[256];
		int    nInUse;
		
		byte[] seqToUnseq = new byte[256];
		byte[] unseqToSeq = new byte[256];
		
		byte[] selector    = new byte[BZip2Constants.MaximumSelectors];
		byte[] selectorMtf = new byte[BZip2Constants.MaximumSelectors];
		
		int[] tt;
		byte[] ll8;
		
		/*--
		freq table collected to save a pass over the data
		during decompression.
		--*/
		int[] unzftab = new int[256];
		
		int[][] limit     = new int[BZip2Constants.GroupCount][];
		int[][] baseArray = new int[BZip2Constants.GroupCount][];
		int[][] perm      = new int[BZip2Constants.GroupCount][];
		int[] minLens     = new int[BZip2Constants.GroupCount];
		
		Stream baseStream;
		bool   streamEnd;
		
		int currentChar = -1;
	
		int currentState = START_BLOCK_STATE;
		
		int storedBlockCRC, storedCombinedCRC;
		int computedBlockCRC;
		uint computedCombinedCRC;
		
		int count, chPrev, ch2;
		int tPos;
		int rNToGo;
		int rTPos;
		int i2, j2;
		byte z;
		bool isStreamOwner = true;
		#endregion
	}
}
/* This file was derived from a file containing this license:
 * 
 * This file is a part of bzip2 and/or libbzip2, a program and
 * library for lossless, block-sorting data compression.
 * 
 * Copyright (C) 1996-1998 Julian R Seward.  All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * 1. Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 * 
 * 2. The origin of this software must not be misrepresented; you must 
 * not claim that you wrote the original software.  If you use this 
 * software in a product, an acknowledgment in the product 
 * documentation would be appreciated but is not required.
 * 
 * 3. Altered source versions must be plainly marked as such, and must
 * not be misrepresented as being the original software.
 * 
 * 4. The name of the author may not be used to endorse or promote 
 * products derived from this software without specific prior written 
 * permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * 
 * Java version ported by Keiron Liddle, Aftex Software <keiron@aftexsw.com> 1999-2001
 */