inflater.cs

C#开发的QQ,希望大家喜欢.献给大家作参考

			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="offset">
		/// The offset into buffer where the dictionary starts.
		/// </param>
		/// <param name="len">
		/// The length of 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 offset, int len)
		{
			if (!IsNeedingDictionary) {
				throw new InvalidOperationException();
			}
			
			adler.Update(buffer, offset, len);
			if ((int)adler.Value != readAdler) {
				throw new SharpZipBaseException("Wrong adler checksum");
			}
			adler.Reset();
			outputWindow.CopyDict(buffer, offset, len);
			mode = DECODE_BLOCKS;
		}
		
		/// <summary>
		/// Sets the input.  This should only be called, if needsInput()
		/// returns true.
		/// </summary>
		/// <param name="buf">
		/// the input.
		/// </param>
		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="buffer">
		/// The source of input data
		/// </param>
		/// <param name="offset">
		/// The offset into buffer where the input starts.
		/// </param>
		/// <param name="length">
		/// The number of bytes of input to use.
		/// </param>
		/// <exception cref="System.InvalidOperationException">
		/// No input is needed.
		/// </exception>
		/// <exception cref="System.ArgumentOutOfRangeException">
		/// The off and/or len are wrong.
		/// </exception>
		public void SetInput(byte[] buffer, int offset, int length)
		{
			input.SetInput(buffer, offset, length);
			totalIn += 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>
		/// <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 = "offset">
		/// 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 offset and/or len are wrong.
		/// </exception>
		/// <exception cref="System.FormatException">
		/// if deflated stream is invalid.
		/// </exception>
		public int Inflate(byte[] buf, int offset, int len)
		{
			if (len < 0) {
				throw new ArgumentOutOfRangeException("len < 0");
			}
			
			// Special case: len may be zero
			if (len == 0) {
				if (IsFinished == false) { // -jr- 08-Nov-2003 INFLATE_BUG fix..
					Decode();
				}
				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, offset, len);
					adler.Update(buf, offset, more);
					offset += 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;
			}
		}
		
#if TEST_HAK		
		/// <summary>
		/// -jr test hak trying to figure out a bug
		///</summary>
		public int UnseenInput {
			get {
				return totalIn - ((input.AvailableBits + 7) >> 3);
			}
		}
		
		/// <summary>
		/// -jr test hak trying to figure out a bug
		///</summary>
		public int PlainTotalIn {
			get {
				return totalIn;
			}
		}
#endif
		
		/// <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 {
			get {
				return input.AvailableBytes;
			}
		}
	}
}