irc/TechBot/Compression/InflaterDynHeader.cs

   1 // InflaterDynHeader.cs
   2 // Copyright (C) 2001 Mike Krueger
   3 //
   4 // This file was translated from java, it was part of the GNU Classpath
   5 // Copyright (C) 2001 Free Software Foundation, Inc.
   6 //
   7 // This program is free software; you can redistribute it and/or
   8 // modify it under the terms of the GNU General Public License
   9 // as published by the Free Software Foundation; either version 2
  10 // of the License, or (at your option) any later version.
  11 //
  12 // This program is distributed in the hope that it will be useful,
  13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 // GNU General Public License for more details.
  16 //
  17 // You should have received a copy of the GNU General Public License
  18 // along with this program; if not, write to the Free Software
  19 // Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  20 //
  21 // Linking this library statically or dynamically with other modules is
  22 // making a combined work based on this library.  Thus, the terms and
  23 // conditions of the GNU General Public License cover the whole
  24 // combination.
  25 //
  26 // As a special exception, the copyright holders of this library give you
  27 // permission to link this library with independent modules to produce an
  28 // executable, regardless of the license terms of these independent
  29 // modules, and to copy and distribute the resulting executable under
  30 // terms of your choice, provided that you also meet, for each linked
  31 // independent module, the terms and conditions of the license of that
  32 // module.  An independent module is a module which is not derived from
  33 // or based on this library.  If you modify this library, you may extend
  34 // this exception to your version of the library, but you are not
  35 // obligated to do so.  If you do not wish to do so, delete this
  36 // exception statement from your version.
  37
  38 using System;
  39
  40 using ICSharpCode.SharpZipLib.Zip.Compression.Streams;
  41
  42 namespace ICSharpCode.SharpZipLib.Zip.Compression
  43 {
  44
  45         class InflaterDynHeader
  46         {
  47                 const int LNUM   = 0;
  48                 const int DNUM   = 1;
  49                 const int BLNUM  = 2;
  50                 const int BLLENS = 3;
  51                 const int LENS   = 4;
  52                 const int REPS   = 5;
  53
  54                 static readonly int[] repMin  = { 3, 3, 11 };
  55                 static readonly int[] repBits = { 2, 3,  7 };
  56
  57                 byte[] blLens;
  58                 byte[] litdistLens;
  59
  60                 InflaterHuffmanTree blTree;
  61
  62                 int mode;
  63                 int lnum, dnum, blnum, num;
  64                 int repSymbol;
  65                 byte lastLen;
  66                 int ptr;
  67
  68                 static readonly int[] BL_ORDER =
  69                 { 16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15 };
  70
  71                 public InflaterDynHeader()
  72                 {
  73                 }
  74
  75                 public bool Decode(StreamManipulator input)
  76                 {
  77                         decode_loop:
  78                                 for (;;) {
  79                                         switch (mode) {
  80                                                 case LNUM:
  81                                                         lnum = input.PeekBits(5);
  82                                                         if (lnum < 0) {
  83                                                                 return false;
  84                                                         }
  85                                                         lnum += 257;
  86                                                         input.DropBits(5);
  87                                                         //          System.err.println("LNUM: "+lnum);
  88                                                         mode = DNUM;
  89                                                         goto case DNUM; // fall through
  90                                                 case DNUM:
  91                                                         dnum = input.PeekBits(5);
  92                                                         if (dnum < 0) {
  93                                                                 return false;
  94                                                         }
  95                                                         dnum++;
  96                                                         input.DropBits(5);
  97                                                         //          System.err.println("DNUM: "+dnum);
  98                                                         num = lnum+dnum;
  99                                                         litdistLens = new byte[num];
 100                                                         mode = BLNUM;
 101                                                         goto case BLNUM; // fall through
 102                                                 case BLNUM:
 103                                                         blnum = input.PeekBits(4);
 104                                                         if (blnum < 0) {
 105                                                                 return false;
 106                                                         }
 107                                                         blnum += 4;
 108                                                         input.DropBits(4);
 109                                                         blLens = new byte[19];
 110                                                         ptr = 0;
 111                                                         //          System.err.println("BLNUM: "+blnum);
 112                                                         mode = BLLENS;
 113                                                         goto case BLLENS; // fall through
 114                                                 case BLLENS:
 115                                                         while (ptr < blnum) {
 116                                                                 int len = input.PeekBits(3);
 117                                                                 if (len < 0) {
 118                                                                         return false;
 119                                                                 }
 120                                                                 input.DropBits(3);
 121                                                                 //              System.err.println("blLens["+BL_ORDER[ptr]+"]: "+len);
 122                                                                 blLens[BL_ORDER[ptr]] = (byte) len;
 123                                                                 ptr++;
 124                                                         }
 125                                                         blTree = new InflaterHuffmanTree(blLens);
 126                                                         blLens = null;
 127                                                         ptr = 0;
 128                                                         mode = LENS;
 129                                                         goto case LENS; // fall through
 130                                                 case LENS:
 131                                                 {
 132                                                         int symbol;
 133                                                         while (((symbol = blTree.GetSymbol(input)) & ~15) == 0) {
 134                                                                 /* Normal case: symbol in [0..15] */
 135
 136                                                                 //                System.err.println("litdistLens["+ptr+"]: "+symbol);
 137                                                                 litdistLens[ptr++] = lastLen = (byte)symbol;
 138
 139                                                                 if (ptr == num) {
 140                                                                         /* Finished */
 141                                                                         return true;
 142                                                                 }
 143                                                         }
 144
 145                                                         /* need more input ? */
 146                                                         if (symbol < 0) {
 147                                                                 return false;
 148                                                         }
 149
 150                                                         /* otherwise repeat code */
 151                                                         if (symbol >= 17) {
 152                                                                 /* repeat zero */
 153                                                                 //                System.err.println("repeating zero");
 154                                                                 lastLen = 0;
 155                                                         } else {
 156                                                                 if (ptr == 0) {
 157                                                                         throw new Exception();
 158                                                                 }
 159                                                         }
 160                                                         repSymbol = symbol-16;
 161                                                 }
 162                                                         mode = REPS;
 163                                                         goto case REPS; // fall through
 164                                                 case REPS:
 165                                                 {
 166                                                         int bits = repBits[repSymbol];
 167                                                         int count = input.PeekBits(bits);
 168                                                         if (count < 0) {
 169                                                                 return false;
 170                                                         }
 171                                                         input.DropBits(bits);
 172                                                         count += repMin[repSymbol];
 173                                                         //            System.err.println("litdistLens repeated: "+count);
 174
 175                                                         if (ptr + count > num) {
 176                                                                 throw new Exception();
 177                                                         }
 178                                                         while (count-- > 0) {
 179                                                                 litdistLens[ptr++] = lastLen;
 180                                                         }
 181
 182                                                         if (ptr == num) {
 183                                                                 /* Finished */
 184                                                                 return true;
 185                                                         }
 186                                                 }
 187                                                         mode = LENS;
 188                                                         goto decode_loop;
 189                                         }
 190                                 }
 191                 }
 192
 193                 public InflaterHuffmanTree BuildLitLenTree()
 194                 {
 195                         byte[] litlenLens = new byte[lnum];
 196                         Array.Copy(litdistLens, 0, litlenLens, 0, lnum);
 197                         return new InflaterHuffmanTree(litlenLens);
 198                 }
 199
 200                 public InflaterHuffmanTree BuildDistTree()
 201                 {
 202                         byte[] distLens = new byte[dnum];
 203                         Array.Copy(litdistLens, lnum, distLens, 0, dnum);
 204                         return new InflaterHuffmanTree(distLens);
 205                 }
 206         }
 207 }