bzip2inputstream.cs

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// BZip2InputStream.cs
//
// Copyright (C) 2001 Mike Krueger
//
// 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 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
	{
		/// <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>
		/// <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>
		/// <exception cref="NotSupportedException">Any access</exception>
		public override void SetLength(long val)
		{
			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>
		/// <exception cref="NotSupportedException">Any access</exception>
		public override void Write(byte[] array, 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>
		/// <exception cref="NotSupportedException">Any access</exception>
		public override void WriteByte(byte val)
		{
			throw new NotSupportedException("BZip2InputStream WriteByte not supported");
		}
		
		/// <summary>
		/// Read a sequence of bytes and advances the read position by one byte.
		/// </summary>
		/// <param name="b">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[] b, int offset, int count)
		{
			for (int i = 0; i < count; ++i) {
				int rb = ReadByte();
				if (rb == -1) {
					return i;
				}
				b[offset + i] = (byte)rb;
			}
			return count;
		}
		
		/// <summary>
		/// Closes the stream, releasing any associated resources.
		/// </summary>
		public override void Close()
		{
			if (baseStream != null) {
				baseStream.Close();
			}
		}
		
		void MakeMaps() 
		{
			nInUse = 0;
			for (int i = 0; i < 256; ++i) {
				if (inUse[i]) {
					seqToUnseq[nInUse] = (byte)i;
					unseqToSeq[i] = (byte)nInUse;
					nInUse++;
				}
			}
		}
		
		/*--
		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.MAX_SELECTORS];
		byte[] selectorMtf = new byte[BZip2Constants.MAX_SELECTORS];
		
		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.N_GROUPS][];
		int[][] baseArray = new int[BZip2Constants.N_GROUPS][];
		int[][] perm      = new int[BZip2Constants.N_GROUPS][];
		int[] minLens     = new int[BZip2Constants.N_GROUPS];
		
		Stream baseStream;
		bool   streamEnd = false;
		
		int currentChar = -1;
		
		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;
		
		int currentState = START_BLOCK_STATE;
		
		int storedBlockCRC, storedCombinedCRC;
		int computedBlockCRC;
		uint computedCombinedCRC;
		
		int count, chPrev, ch2;
		int tPos;
		int rNToGo = 0;
		int rTPos  = 0;
		int i2, j2;
		byte z;
		
		/// <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.N_GROUPS; ++i) {
				limit[i] = new int[BZip2Constants.MAX_ALPHA_SIZE];
				baseArray[i]  = new int[BZip2Constants.MAX_ALPHA_SIZE];
				perm[i]  = new int[BZip2Constants.MAX_ALPHA_SIZE];
			}
			
			ll8 = null;
			tt  = null;
			BsSetStream(stream);
			Initialize();
			InitBlock();
			SetupBlock();
		}
		
		/// <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;
		}
		
		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;
		}
		
		static void CompressedStreamEOF() 
		{
			throw new BZip2Exception("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");
		}
		
		
		void BsSetStream(Stream f) 
		{
			baseStream = f;
			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 BsGetint() 
		{
			int u = 0;
			u = (u << 8) | BsR(8);
			u = (u << 8) | BsR(8);
			u = (u << 8) | BsR(8);
			u = (u << 8) | BsR(8);
			return u;
		}
		
		int BsGetIntVS(int numBits) 
		{
			return (int)BsR(numBits);
		}
		
		int BsGetInt32() 
		{
			return (int)BsGetint();
		}
		
		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;
					}
				}
			}