예제 #1
0
        public bool Decode(StreamManipulator input)
        {
            decode_loop:
                for (;;) {
                    switch (mode) {
                        case LNUM:
                            lnum = input.PeekBits(5);
                            if (lnum < 0) {
                                return false;
                            }
                            lnum += 257;
                            input.DropBits(5);
                            //  	    System.err.println("LNUM: "+lnum);
                            mode = DNUM;
                            goto case DNUM; // fall through
                        case DNUM:
                            dnum = input.PeekBits(5);
                            if (dnum < 0) {
                                return false;
                            }
                            dnum++;
                            input.DropBits(5);
                            //  	    System.err.println("DNUM: "+dnum);
                            num = lnum+dnum;
                            litdistLens = new byte[num];
                            mode = BLNUM;
                            goto case BLNUM; // fall through
                        case BLNUM:
                            blnum = input.PeekBits(4);
                            if (blnum < 0) {
                                return false;
                            }
                            blnum += 4;
                            input.DropBits(4);
                            blLens = new byte[19];
                            ptr = 0;
                            //  	    System.err.println("BLNUM: "+blnum);
                            mode = BLLENS;
                            goto case BLLENS; // fall through
                        case BLLENS:
                            while (ptr < blnum) {
                                int len = input.PeekBits(3);
                                if (len < 0) {
                                    return false;
                                }
                                input.DropBits(3);
                                //  		System.err.println("blLens["+BL_ORDER[ptr]+"]: "+len);
                                blLens[BL_ORDER[ptr]] = (byte) len;
                                ptr++;
                            }
                            blTree = new InflaterHuffmanTree(blLens);
                            blLens = null;
                            ptr = 0;
                            mode = LENS;
                            goto case LENS; // fall through
                        case LENS:
                        {
                            int symbol;
                            while (((symbol = blTree.GetSymbol(input)) & ~15) == 0) {
                                /* Normal case: symbol in [0..15] */

                                //  		  System.err.println("litdistLens["+ptr+"]: "+symbol);
                                litdistLens[ptr++] = lastLen = (byte)symbol;

                                if (ptr == num) {
                                    /* Finished */
                                    return true;
                                }
                            }

                            /* need more input ? */
                            if (symbol < 0) {
                                return false;
                            }

                            /* otherwise repeat code */
                            if (symbol >= 17) {
                                /* repeat zero */
                                //  		  System.err.println("repeating zero");
                                lastLen = 0;
                            } else {
                                if (ptr == 0) {
                                    throw new SharpZipBaseException();
                                }
                            }
                            repSymbol = symbol-16;
                        }
                            mode = REPS;
                            goto case REPS; // fall through
                        case REPS:
                        {
                            int bits = repBits[repSymbol];
                            int count = input.PeekBits(bits);
                            if (count < 0) {
                                return false;
                            }
                            input.DropBits(bits);
                            count += repMin[repSymbol];
                            //  	      System.err.println("litdistLens repeated: "+count);

                            if (ptr + count > num) {
                                throw new SharpZipBaseException();
                            }
                            while (count-- > 0) {
                                litdistLens[ptr++] = lastLen;
                            }

                            if (ptr == num) {
                                /* Finished */
                                return true;
                            }
                        }
                            mode = LENS;
                            goto decode_loop;
                    }
                }
        }
예제 #2
0
 /// <summary>
 /// Reads the next symbol from input.  The symbol is encoded using the
 /// huffman tree.
 /// </summary>
 /// <param name="input">
 /// input the input source.
 /// </param>
 /// <returns>
 /// the next symbol, or -1 if not enough input is available.
 /// </returns>
 public int GetSymbol(StreamManipulator input)
 {
     int lookahead, symbol;
     if ((lookahead = input.PeekBits(9)) >= 0) {
         if ((symbol = tree[lookahead]) >= 0) {
             input.DropBits(symbol & 15);
             return symbol >> 4;
         }
         int subtree = -(symbol >> 4);
         int bitlen = symbol & 15;
         if ((lookahead = input.PeekBits(bitlen)) >= 0) {
             symbol = tree[subtree | (lookahead >> 9)];
             input.DropBits(symbol & 15);
             return symbol >> 4;
         } else {
             int bits = input.AvailableBits;
             lookahead = input.PeekBits(bits);
             symbol = tree[subtree | (lookahead >> 9)];
             if ((symbol & 15) <= bits) {
                 input.DropBits(symbol & 15);
                 return symbol >> 4;
             } else {
                 return -1;
             }
         }
     } else {
         int bits = input.AvailableBits;
         lookahead = input.PeekBits(bits);
         symbol = tree[lookahead];
         if (symbol >= 0 && (symbol & 15) <= bits) {
             input.DropBits(symbol & 15);
             return symbol >> 4;
         } else {
             return -1;
         }
     }
 }