예제 #1
0
파일: Inflater.cs 프로젝트: avs009/gsf
		/// <summary>
		/// Decodes the deflated stream.
		/// </summary>
		/// <returns>
		/// false if more input is needed, or if finished.
		/// </returns>
		/// <exception cref="CompressionExceptionBase">
		/// 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 CompressionExceptionBase("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 CompressionExceptionBase("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 CompressionExceptionBase("Inflater.Decode unknown mode");
			}
		}
예제 #2
0
파일: Inflater.cs 프로젝트: avs009/gsf
		/// <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 = noHeader ? DECODE_BLOCKS : DECODE_HEADER;
			totalIn = 0;
			totalOut = 0;
			input.Reset();
			outputWindow.Reset();
			dynHeader = null;
			litlenTree = null;
			distTree = null;
			isLastBlock = false;
			adler.Reset();
		}