inflater.cs

SharpZipLib之前叫做NZipLib

			}

			mode = FINISHED;
			return false;
		}
		
		/// <summary>
		/// Decodes the deflated stream.
		/// </summary>
		/// <returns>
		/// false if more input is needed, or if finished.
		/// </returns>
		/// <exception cref="SharpZipBaseException">
		/// 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 (noHeader) {
							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 SharpZipBaseException("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 SharpZipBaseException("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 SharpZipBaseException("Inflater.Decode unknown mode");
			}
		}
			
		/// <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>
		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="index">
		/// The index into buffer where the dictionary starts.
		/// </param>
		/// <param name="count">
		/// The number of bytes in the dictionary.
		/// </param>
		/// <exception cref="System.InvalidOperationException">
		/// No dictionary is needed.
		/// </exception>
		/// <exception cref="SharpZipBaseException">
		/// The adler checksum for the buffer is invalid
		/// </exception>
		public void SetDictionary(byte[] buffer, int index, int count)
		{
			if ( buffer == null ) {
				throw new ArgumentNullException("buffer");
			}

			if ( index < 0 ) {
				throw new ArgumentOutOfRangeException("index");
			}

			if ( count < 0 ) {
				throw new ArgumentOutOfRangeException("count");
			}

			if (!IsNeedingDictionary) {
				throw new InvalidOperationException("Dictionary is not needed");
			}
			
			adler.Update(buffer, index, count);

			if ((int)adler.Value != readAdler) {
				throw new SharpZipBaseException("Wrong adler checksum");
			}
			adler.Reset();
			outputWindow.CopyDict(buffer, index, count);
			mode = DECODE_BLOCKS;
		}
		
		/// <summary>
		/// Sets the input.  This should only be called, if needsInput()
		/// returns true.
		/// </summary>
		/// <param name="buffer">
		/// the input.
		/// </param>
		public void SetInput(byte[] buffer)
		{
			SetInput(buffer, 0, buffer.Length);
		}
		
		/// <summary>
		/// Sets the input.  This should only be called, if needsInput()
		/// returns true.
		/// </summary>
		/// <param name="buffer">
		/// The source of input data
		/// </param>
		/// <param name="index">
		/// The index into buffer where the input starts.
		/// </param>
		/// <param name="count">
		/// The number of bytes of input to use.
		/// </param>
		/// <exception cref="System.InvalidOperationException">
		/// No input is needed.
		/// </exception>
		/// <exception cref="System.ArgumentOutOfRangeException">
		/// The index and/or count are wrong.
		/// </exception>
		public void SetInput(byte[] buffer, int index, int count)
		{
			input.SetInput(buffer, index, count);
			totalIn += (long)count;
		}
		
		/// <summary>
		/// Inflates the compressed stream to the output buffer.  If this
		/// returns 0, you should check, whether IsNeedingDictionary(),
		/// IsNeedingInput() or IsFinished() returns true, to determine why no
		/// further output is produced.
		/// </summary>
		/// <param name="buffer">
		/// 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 buffer has length 0.
		/// </exception>
		/// <exception cref="System.FormatException">
		/// if deflated stream is invalid.
		/// </exception>
		public int Inflate(byte[] buffer)
		{
			if ( buffer == null )
			{
				throw new ArgumentNullException("buffer");
			}

			return Inflate(buffer, 0, buffer.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="buffer">
		/// the output buffer.
		/// </param>
		/// <param name="offset">
		/// the offset in buffer where storing starts.
		/// </param>
		/// <param name="count">
		/// the maximum number of bytes to 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 count is less than 0.
		/// </exception>
		/// <exception cref="System.ArgumentOutOfRangeException">
		/// if the index and / or count are wrong.
		/// </exception>
		/// <exception cref="System.FormatException">
		/// if deflated stream is invalid.
		/// </exception>
		public int Inflate(byte[] buffer, int offset, int count)
		{
			if ( buffer == null )
			{
				throw new ArgumentNullException("buffer");
			}

			if ( count < 0 ) {
#if NETCF_1_0
				throw new ArgumentOutOfRangeException("count");
#else
				throw new ArgumentOutOfRangeException("count", "count cannot be negative");
#endif
			}

			if ( offset < 0 ) {
#if NETCF_1_0
				throw new ArgumentOutOfRangeException("offset");
#else
				throw new ArgumentOutOfRangeException("offset", "offset cannot be negative");
#endif
			}

			if ( offset + count > buffer.Length ) {
				throw new ArgumentException("count exceeds buffer bounds");
			}

			// Special case: count may be zero
			if (count == 0) 
			{
				if (!IsFinished) { // -jr- 08-Nov-2003 INFLATE_BUG fix..
					Decode();
				}
				return 0;
			}

			int bytesCopied = 0;

			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:
					*   IsNeedingInput() and not IsFinished()
					*   implies more output can be produced.
					*/
					int more = outputWindow.CopyOutput(buffer, offset, count);
					if ( more > 0 ) {
						adler.Update(buffer, offset, more);
						offset += more;
						bytesCopied += more;
						totalOut += (long)more;
						count -= more;
						if (count == 0) {
							return bytesCopied;
						}
					}
				}
			} while (Decode() || ((outputWindow.GetAvailable() > 0) && (mode != DECODE_CHKSUM)));
			return bytesCopied;
		}
		
		/// <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 long 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 long TotalIn {
			get {
				return totalIn - (long)RemainingInput;
			}
		}
		
		/// <summary>
		/// Gets the number of unprocessed input bytes.  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 have not been processed.
		/// </returns>
		public int RemainingInput {
			// TODO: This should be a long?
			get {
				return input.AvailableBytes;
			}
		}
	}
}