vcs.maemo.org Git - physicsfs/blob - lzma/CS/7zip/Compress/RangeCoder/RangeCoder.cs

   1 using System;
   2
   3 namespace SevenZip.Compression.RangeCoder
   4 {
   5         class Encoder
   6         {
   7                 public const uint kTopValue = (1 << 24);
   8
   9                 System.IO.Stream Stream;
  10
  11                 public UInt64 Low;
  12                 public uint Range;
  13                 uint _cacheSize;
  14                 byte _cache;
  15
  16                 long StartPosition;
  17
  18                 public void SetStream(System.IO.Stream stream)
  19                 {
  20                         Stream = stream;
  21                 }
  22
  23                 public void ReleaseStream()
  24                 {
  25                         Stream = null;
  26                 }
  27
  28                 public void Init()
  29                 {
  30                         StartPosition = Stream.Position;
  31
  32                         Low = 0;
  33                         Range = 0xFFFFFFFF;
  34                         _cacheSize = 1;
  35                         _cache = 0;
  36                 }
  37
  38                 public void FlushData()
  39                 {
  40                         for (int i = 0; i < 5; i++)
  41                                 ShiftLow();
  42                 }
  43
  44                 public void FlushStream()
  45                 {
  46                         Stream.Flush();
  47                 }
  48
  49                 public void CloseStream()
  50                 {
  51                         Stream.Close();
  52                 }
  53
  54                 public void Encode(uint start, uint size, uint total)
  55                 {
  56                         Low += start * (Range /= total);
  57                         Range *= size;
  58                         while (Range < kTopValue)
  59                         {
  60                                 Range <<= 8;
  61                                 ShiftLow();
  62                         }
  63                 }
  64
  65                 public void ShiftLow()
  66                 {
  67                         if ((uint)Low < (uint)0xFF000000 || (uint)(Low >> 32) == 1)
  68                         {
  69                                 byte temp = _cache;
  70                                 do
  71                                 {
  72                                         Stream.WriteByte((byte)(temp + (Low >> 32)));
  73                                         temp = 0xFF;
  74                                 }
  75                                 while (--_cacheSize != 0);
  76                                 _cache = (byte)(((uint)Low) >> 24);
  77                         }
  78                         _cacheSize++;
  79                         Low = ((uint)Low) << 8;
  80                 }
  81
  82                 public void EncodeDirectBits(uint v, int numTotalBits)
  83                 {
  84                         for (int i = numTotalBits - 1; i >= 0; i--)
  85                         {
  86                                 Range >>= 1;
  87                                 if (((v >> i) & 1) == 1)
  88                                         Low += Range;
  89                                 if (Range < kTopValue)
  90                                 {
  91                                         Range <<= 8;
  92                                         ShiftLow();
  93                                 }
  94                         }
  95                 }
  96
  97                 public void EncodeBit(uint size0, int numTotalBits, uint symbol)
  98                 {
  99                         uint newBound = (Range >> numTotalBits) * size0;
 100                         if (symbol == 0)
 101                                 Range = newBound;
 102                         else
 103                         {
 104                                 Low += newBound;
 105                                 Range -= newBound;
 106                         }
 107                         while (Range < kTopValue)
 108                         {
 109                                 Range <<= 8;
 110                                 ShiftLow();
 111                         }
 112                 }
 113
 114                 public long GetProcessedSizeAdd()
 115                 {
 116                         return _cacheSize +
 117                                 Stream.Position - StartPosition + 4;
 118                         // (long)Stream.GetProcessedSize();
 119                 }
 120         }
 121
 122         class Decoder
 123         {
 124                 public const uint kTopValue = (1 << 24);
 125                 public uint Range;
 126                 public uint Code;
 127                 // public Buffer.InBuffer Stream = new Buffer.InBuffer(1 << 16);
 128                 public System.IO.Stream Stream;
 129
 130                 public void Init(System.IO.Stream stream)
 131                 {
 132                         // Stream.Init(stream);
 133                         Stream = stream;
 134
 135                         Code = 0;
 136                         Range = 0xFFFFFFFF;
 137                         for (int i = 0; i < 5; i++)
 138                                 Code = (Code << 8) | (byte)Stream.ReadByte();
 139                 }
 140
 141                 public void ReleaseStream()
 142                 {
 143                         // Stream.ReleaseStream();
 144                         Stream = null;
 145                 }
 146
 147                 public void CloseStream()
 148                 {
 149                         Stream.Close();
 150                 }
 151
 152                 public void Normalize()
 153                 {
 154                         while (Range < kTopValue)
 155                         {
 156                                 Code = (Code << 8) | (byte)Stream.ReadByte();
 157                                 Range <<= 8;
 158                         }
 159                 }
 160
 161                 public void Normalize2()
 162                 {
 163                         if (Range < kTopValue)
 164                         {
 165                                 Code = (Code << 8) | (byte)Stream.ReadByte();
 166                                 Range <<= 8;
 167                         }
 168                 }
 169
 170                 public uint GetThreshold(uint total)
 171                 {
 172                         return Code / (Range /= total);
 173                 }
 174
 175                 public void Decode(uint start, uint size, uint total)
 176                 {
 177                         Code -= start * Range;
 178                         Range *= size;
 179                         Normalize();
 180                 }
 181
 182                 public uint DecodeDirectBits(int numTotalBits)
 183                 {
 184                         uint range = Range;
 185                         uint code = Code;
 186                         uint result = 0;
 187                         for (int i = numTotalBits; i > 0; i--)
 188                         {
 189                                 range >>= 1;
 190                                 /*
 191                                 result <<= 1;
 192                                 if (code >= range)
 193                                 {
 194                                         code -= range;
 195                                         result |= 1;
 196                                 }
 197                                 */
 198                                 uint t = (code - range) >> 31;
 199                                 code -= range & (t - 1);
 200                                 result = (result << 1) | (1 - t);
 201
 202                                 if (range < kTopValue)
 203                                 {
 204                                         code = (code << 8) | (byte)Stream.ReadByte();
 205                                         range <<= 8;
 206                                 }
 207                         }
 208                         Range = range;
 209                         Code = code;
 210                         return result;
 211                 }
 212
 213                 public uint DecodeBit(uint size0, int numTotalBits)
 214                 {
 215                         uint newBound = (Range >> numTotalBits) * size0;
 216                         uint symbol;
 217                         if (Code < newBound)
 218                         {
 219                                 symbol = 0;
 220                                 Range = newBound;
 221                         }
 222                         else
 223                         {
 224                                 symbol = 1;
 225                                 Code -= newBound;
 226                                 Range -= newBound;
 227                         }
 228                         Normalize();
 229                         return symbol;
 230                 }
 231
 232                 // ulong GetProcessedSize() {return Stream.GetProcessedSize(); }
 233         }
 234 }