// Inflater.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.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 rfc1950.
	///
	/// 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>
		private 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>
		private 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>
		private 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>
		private 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>
		/// This are the state in which the inflater can be.
		/// </summary>
		private const int DECODE_HEADER           = 0;
		private const int DECODE_DICT             = 1;
		private const int DECODE_BLOCKS           = 2;
		private const int DECODE_STORED_LEN1      = 3;
		private const int DECODE_STORED_LEN2      = 4;
		private const int DECODE_STORED           = 5;
		private const int DECODE_DYN_HEADER       = 6;
		private const int DECODE_HUFFMAN          = 7;
		private const int DECODE_HUFFMAN_LENBITS  = 8;
		private const int DECODE_HUFFMAN_DIST     = 9;
		private const int DECODE_HUFFMAN_DISTBITS = 10;
		private const int DECODE_CHKSUM           = 11;
		private const int FINISHED                = 12;
		
		/// <summary>
		/// This variable contains the current state.
		/// </summary>
		private 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>
		private 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>
		private int neededBits;
		private int repLength, repDist;
		private 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>
		private bool isLastBlock;
		
		/// <summary>
		/// The total number of inflated bytes.
		/// </summary>
		private int totalOut;
		
		/// <summary>
		/// The total number of bytes set with setInput().  This is not the
		/// value returned by getTotalIn(), since this also includes the
		/// unprocessed input.
		/// </summary>
		private int totalIn;
		
		/// <summary>
		/// This variable stores the nowrap flag that was given to the constructor.
		/// True means, that the inflated stream doesn't contain a header nor the
		/// checksum in the footer.
		/// </summary>
		private bool nowrap;
		
		private StreamManipulator input;
		private OutputWindow outputWindow;
		private InflaterDynHeader dynHeader;
		private InflaterHuffmanTree litlenTree, distTree;
		private Adler32 adler;
		
		/// <summary>
		/// Creates a new inflater.
		/// </summary>
		public Inflater() : this(false)
		{
		}
		
		/// <summary>
		/// Creates a new inflater.
		/// </summary>
		/// <param name="nowrap">
		/// true if no header and checksum field appears in the
		/// stream.  This is used for GZIPed input.  For compatibility with
		/// Sun JDK you should provide one byte of input more than needed in
		/// this case.
		/// </param>
		public Inflater(bool nowrap)
		{
			this.nowrap = nowrap;
			this.adler = new Adler32();
			input = new StreamManipulator();
			outputWindow = new OutputWindow();
			mode = nowrap ? 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 = nowrap ? DECODE_BLOCKS : DECODE_HEADER;
			totalIn = totalOut = 0;
			input.Reset();
			outputWindow.Reset();
			dynHeader = null;
			litlenTree = null;
			distTree = null;
			isLastBlock = false;
			adler.Reset();
		}
		
		/// <summary>
		/// Decodes the deflate header.
		/// </summary>
		/// <returns>
		/// false if more input is needed.
		/// </returns>
		/// <exception cref="System.FormatException">
		/// if 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 FormatException("Header checksum illegal");
			}
			
			if ((header & 0x0f00) != (Deflater.DEFLATED << 8)) {
				throw new FormatException("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="System.FormatException">
		/// 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 FormatException("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 FormatException("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 FormatException();
				}
			}
			return true;
		}
		
		/// <summary>
		/// Decodes the adler checksum after the deflate stream.
		/// </summary>
		/// <returns>
		/// false if more input is needed.
		/// </returns>
		/// <exception cref="System.FormatException">
		/// DataFormatException, 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 FormatException("Adler chksum doesn't match: "
				                          + (int)adler.Value
				                          + " vs. " + readAdler);
			}
			mode = FINISHED;
			return false;
		}
		
		/// <summary>
		/// Decodes the deflated stream.
		/// </summary>
		/// <returns>
		/// false if more input is needed, or if finished.
		/// </returns>
		/// <exception cref="System.FormatException">
		/// DataFormatException, if deflated stream is invalid.
		/// </exception>
		private bool Decode()
		{
			switch (mode) {
				case DECODE_HEADER:
					return DecodeHeader();
				case DECODE_DICT:
					return DecodeDict();
				case DECODE_CHKSUM:
					return DecodeChksum();
				
				case DECODE_BLOCKS:
					if (isLastBlock) {
						if (nowrap) {
							mode = FINISHED;
							return false;
						} else {
							input.SkipToByteBoundary();
							neededBits = 32;
							mode = DECODE_CHKSUM;
							return true;
						}
					}
					
					int type = input.PeekBits(3);
					if (type < 0) {
						return false;
					}
					input.DropBits(3);
					
					if ((type & 1) != 0) {
						isLastBlock = true;
					}
					switch (type >> 1) {
						case DeflaterConstants.STORED_BLOCK:
							input.SkipToByteBoundary();
							mode = DECODE_STORED_LEN1;
							break;
						case DeflaterConstants.STATIC_TREES:
							litlenTree = InflaterHuffmanTree.defLitLenTree;
							distTree = InflaterHuffmanTree.defDistTree;
							mode = DECODE_HUFFMAN;
							break;
						case DeflaterConstants.DYN_TREES:
							dynHeader = new InflaterDynHeader();
							mode = DECODE_DYN_HEADER;
							break;
						default:
							throw new FormatException("Unknown block type "+type);
					}
					return true;
				
				case DECODE_STORED_LEN1: {
					if ((uncomprLen = input.PeekBits(16)) < 0) {
						return false;
					}
					input.DropBits(16);
					mode = DECODE_STORED_LEN2;
				}
				goto case DECODE_STORED_LEN2; /* fall through */
				case DECODE_STORED_LEN2: {
					int nlen = input.PeekBits(16);
					if (nlen < 0) {
						return false;
					}
					input.DropBits(16);
					if (nlen != (uncomprLen ^ 0xffff)) {
						throw new FormatException("broken uncompressed block");
					}
					mode = DECODE_STORED;
				}
				goto case DECODE_STORED;/* fall through */
				case DECODE_STORED: {
					int more = outputWindow.CopyStored(input, uncomprLen);
					uncomprLen -= more;
					if (uncomprLen == 0) {
						mode = DECODE_BLOCKS;
						return true;
					}
					return !input.IsNeedingInput;
				}
				
				case DECODE_DYN_HEADER:
					if (!dynHeader.Decode(input)) {
						return false;
					}
					
					litlenTree = dynHeader.BuildLitLenTree();
					distTree = dynHeader.BuildDistTree();
					mode = DECODE_HUFFMAN;
					goto case DECODE_HUFFMAN; /* fall through */
				case DECODE_HUFFMAN:
				case DECODE_HUFFMAN_LENBITS:
				case DECODE_HUFFMAN_DIST:
				case DECODE_HUFFMAN_DISTBITS:
					return DecodeHuffman();
				case FINISHED:
					return false;
				default:
					throw new FormatException();
			}
		}
			
		/// <summary>
		/// Sets the preset dictionary.  This should only be called, if
		/// needsDictionary() returns true and it should set the same
		/// dictionary, that was used for deflating.  The getAdler()
		/// function returns the checksum of the dictionary needed.
		/// </summary>
		/// <param name="buffer">
		/// the dictionary.
		/// </param>
		/// <exception cref="System.InvalidOperationException">
		/// if no dictionary is needed.
		/// </exception>
		/// <exception cref="System.ArgumentException">
		/// if the dictionary checksum is wrong.
		/// </exception>
		public void SetDictionary(byte[] buffer)
		{
			SetDictionary(buffer, 0, buffer.Length);
		}
		
		/// <summary>
		/// Sets the preset dictionary.  This should only be called, if
		/// needsDictionary() returns true and it should set the same
		/// dictionary, that was used for deflating.  The getAdler()
		/// function returns the checksum of the dictionary needed.
		/// </summary>
		/// <param name="buffer">
		/// the dictionary.
		/// </param>
		/// <param name="off">
		/// the offset into buffer where the dictionary starts.
		/// </param>
		/// <param name="len">
		/// the length of the dictionary.
		/// </param>
		/// <exception cref="System.InvalidOperationException">
		/// if no dictionary is needed.
		/// </exception>
		/// <exception cref="System.ArgumentException">
		/// if the dictionary checksum is wrong.
		/// </exception>
		/// <exception cref="System.ArgumentOutOfRangeException">
		/// if the off and/or len are wrong.
		/// </exception>
		public void SetDictionary(byte[] buffer, int off, int len)
		{
			if (!IsNeedingDictionary) {
				throw new InvalidOperationException();
			}
			
			adler.Update(buffer, off, len);
			if ((int) adler.Value != readAdler) {
				throw new ArgumentException("Wrong adler checksum");
			}
			adler.Reset();
			outputWindow.CopyDict(buffer, off, len);
			mode = DECODE_BLOCKS;
		}
		
		/// <summary>
		/// Sets the input.  This should only be called, if needsInput()
		/// returns true.
		/// </summary>
		/// <param name="buf">
		/// the input.
		/// </param>
		/// <exception cref="System.InvalidOperationException">
		/// if no input is needed.
		/// </exception>
		public void SetInput(byte[] buf)
		{
			SetInput(buf, 0, buf.Length);
		}
		
		/// <summary>
		/// Sets the input.  This should only be called, if needsInput()
		/// returns true.
		/// </summary>
		/// <param name="buf">
		/// the input.
		/// </param>
		/// <param name="off">
		/// the offset into buffer where the input starts.
		/// </param>
		/// <param name="len">
		/// the length of the input.
		/// </param>
		/// <exception cref="System.InvalidOperationException">
		/// if no input is needed.
		/// </exception>
		/// <exception cref="System.ArgumentOutOfRangeException">
		/// if the off and/or len are wrong.
		/// </exception>
		public void SetInput(byte[] buf, int off, int len)
		{
			input.SetInput(buf, off, len);
			totalIn += len;
		}
		
		/// <summary>
		/// Inflates the compressed stream to the output buffer.  If this
		/// returns 0, you should check, whether needsDictionary(),
		/// needsInput() or finished() returns true, to determine why no
		/// further output is produced.
		/// </summary>
		/// <param name = "buf">
		/// the output buffer.
		/// </param>
		/// <returns>
		/// the number of bytes written to the buffer, 0 if no further
		/// output can be produced.
		/// </returns>
		/// <exception cref="System.ArgumentOutOfRangeException">
		/// if buf has length 0.
		/// </exception>
		/// <exception cref="System.FormatException">
		/// if deflated stream is invalid.
		/// </exception>
		public int Inflate(byte[] buf)
		{
			return Inflate(buf, 0, buf.Length);
		}
		
		/// <summary>
		/// Inflates the compressed stream to the output buffer.  If this
		/// returns 0, you should check, whether needsDictionary(),
		/// needsInput() or finished() returns true, to determine why no
		/// further output is produced.
		/// </summary>
		/// <param name = "buf">
		/// the output buffer.
		/// </param>
		/// <param name = "off">
		/// the offset into buffer where the output should start.
		/// </param>
		/// <param name = "len">
		/// the maximum length of the output.
		/// </param>
		/// <returns>
		/// the number of bytes written to the buffer, 0 if no further output can be produced.
		/// </returns>
		/// <exception cref="System.ArgumentOutOfRangeException">
		/// if len is &lt;= 0.
		/// </exception>
		/// <exception cref="System.ArgumentOutOfRangeException">
		/// if the off and/or len are wrong.
		/// </exception>
		/// <exception cref="System.FormatException">
		/// if deflated stream is invalid.
		/// </exception>
		public int Inflate(byte[] buf, int off, int len)
		{
			if (len < 0) {
				throw new ArgumentOutOfRangeException("len < 0");
			}
			// Special case: len may be zero
			if (len == 0) {
				return 0;
			}
/*			// Check for correct buff, off, len triple
			if (off < 0 || off + len >= buf.Length) {
				throw new ArgumentException("off/len outside buf bounds");
			}*/
			int count = 0;
			int more;
			do {
				if (mode != DECODE_CHKSUM) {
					/* Don't give away any output, if we are waiting for the
					* checksum in the input stream.
					*
					* With this trick we have always:
					*   needsInput() and not finished()
					*   implies more output can be produced.
					*/
					more = outputWindow.CopyOutput(buf, off, len);
					adler.Update(buf, off, more);
					off += more;
					count += more;
					totalOut += more;
					len -= more;
					if (len == 0) {
						return count;
					}
				}
			} while (Decode() || (outputWindow.GetAvailable() > 0 &&
			                      mode != DECODE_CHKSUM));
			return count;
		}
		
		/// <summary>
		/// Returns true, if the input buffer is empty.
		/// You should then call setInput(). 
		/// NOTE: This method also returns true when the stream is finished.
		/// </summary>
		public bool IsNeedingInput {
			get {
				return input.IsNeedingInput;
			}
		}
		
		/// <summary>
		/// Returns true, if a preset dictionary is needed to inflate the input.
		/// </summary>
		public bool IsNeedingDictionary {
			get {
				return mode == DECODE_DICT && neededBits == 0;
			}
		}
		
		/// <summary>
		/// Returns true, if the inflater has finished.  This means, that no
		/// input is needed and no output can be produced.
		/// </summary>
		public bool IsFinished {
			get {
				return mode == FINISHED && outputWindow.GetAvailable() == 0;
			}
		}
		
		/// <summary>
		/// Gets the adler checksum.  This is either the checksum of all
		/// uncompressed bytes returned by inflate(), or if needsDictionary()
		/// returns true (and thus no output was yet produced) this is the
		/// adler checksum of the expected dictionary.
		/// </summary>
		/// <returns>
		/// the adler checksum.
		/// </returns>
		public int Adler {
			get {
				return IsNeedingDictionary ? readAdler : (int) adler.Value;
			}
		}
		
		/// <summary>
		/// Gets the total number of output bytes returned by inflate().
		/// </summary>
		/// <returns>
		/// the total number of output bytes.
		/// </returns>
		public int TotalOut {
			get {
				return totalOut;
			}
		}
		
		/// <summary>
		/// Gets the total number of processed compressed input bytes.
		/// </summary>
		/// <returns>
		/// the total number of bytes of processed input bytes.
		/// </returns>
		public int TotalIn {
			get {
				return totalIn - RemainingInput;
			}
		}
		
		/// <summary>
		/// Gets the number of unprocessed input.  Useful, if the end of the
		/// stream is reached and you want to further process the bytes after
		/// the deflate stream.
		/// </summary>
		/// <returns>
		/// the number of bytes of the input which were not processed.
		/// </returns>
		public int RemainingInput {
			get {
				return input.AvailableBytes;
			}
		}
	}
}
