Пример #1
0
        /// <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="SharpZipBaseException">
        /// 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 SharpZipBaseException("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 SharpZipBaseException("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 SharpZipBaseException("Inflater unknown mode");
                }
            }
            return true;
        }
Пример #2
0
 /// <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();
 }
Пример #3
0
        /// <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");
            }
        }
Пример #4
0
        static InflaterHuffmanTree()
        {
            try {
                byte[] codeLengths = new byte[288];
                int i = 0;
                while (i < 144) {
                    codeLengths[i++] = 8;
                }
                while (i < 256) {
                    codeLengths[i++] = 9;
                }
                while (i < 280) {
                    codeLengths[i++] = 7;
                }
                while (i < 288) {
                    codeLengths[i++] = 8;
                }
                defLitLenTree = new InflaterHuffmanTree(codeLengths);

                codeLengths = new byte[32];
                i = 0;
                while (i < 32) {
                    codeLengths[i++] = 5;
                }
                defDistTree = new InflaterHuffmanTree(codeLengths);
            } catch (Exception) {
                throw new SharpZipBaseException("InflaterHuffmanTree: static tree length illegal");
            }
        }