release/src-rt-6.x/linux/linux-2.6/scripts/squashfs/lzma/C/7zip/Compress/RangeCoder/RangeCoderBit.cpp

   1 // Compress/RangeCoder/RangeCoderBit.cpp
   2
   3 #include "StdAfx.h"
   4
   5 #include "RangeCoderBit.h"
   6
   7 namespace NCompress {
   8 namespace NRangeCoder {
   9
  10 UInt32 CPriceTables::ProbPrices[kBitModelTotal >> kNumMoveReducingBits];
  11 static CPriceTables g_PriceTables;
  12
  13 CPriceTables::CPriceTables() { Init(); }
  14
  15 void CPriceTables::Init()
  16 {
  17   const int kNumBits = (kNumBitModelTotalBits - kNumMoveReducingBits);
  18   for(int i = kNumBits - 1; i >= 0; i--)
  19   {
  20     UInt32 start = 1 << (kNumBits - i - 1);
  21     UInt32 end = 1 << (kNumBits - i);
  22     for (UInt32 j = start; j < end; j++)
  23       ProbPrices[j] = (i << kNumBitPriceShiftBits) +
  24           (((end - j) << kNumBitPriceShiftBits) >> (kNumBits - i - 1));
  25   }
  26
  27   /*
  28   // simplest: bad solution
  29   for(UInt32 i = 1; i < (kBitModelTotal >> kNumMoveReducingBits) - 1; i++)
  30     ProbPrices[i] = kBitPrice;
  31   */
  32
  33   /*
  34   const double kDummyMultMid = (1.0 / kBitPrice) / 2;
  35   const double kDummyMultMid = 0;
  36   // float solution
  37   double ln2 = log(double(2));
  38   double lnAll = log(double(kBitModelTotal >> kNumMoveReducingBits));
  39   for(UInt32 i = 1; i < (kBitModelTotal >> kNumMoveReducingBits) - 1; i++)
  40     ProbPrices[i] = UInt32((fabs(lnAll - log(double(i))) / ln2 + kDummyMultMid) * kBitPrice);
  41   */
  42
  43   /*
  44   // experimental, slow, solution:
  45   for(UInt32 i = 1; i < (kBitModelTotal >> kNumMoveReducingBits) - 1; i++)
  46   {
  47     const int kCyclesBits = 5;
  48     const UInt32 kCycles = (1 << kCyclesBits);
  49
  50     UInt32 range = UInt32(-1);
  51     UInt32 bitCount = 0;
  52     for (UInt32 j = 0; j < kCycles; j++)
  53     {
  54       range >>= (kNumBitModelTotalBits - kNumMoveReducingBits);
  55       range *= i;
  56       while(range < (1 << 31))
  57       {
  58         range <<= 1;
  59         bitCount++;
  60       }
  61     }
  62     bitCount <<= kNumBitPriceShiftBits;
  63     range -= (1 << 31);
  64     for (int k = kNumBitPriceShiftBits - 1; k >= 0; k--)
  65     {
  66       range <<= 1;
  67       if (range > (1 << 31))
  68       {
  69         bitCount += (1 << k);
  70         range -= (1 << 31);
  71       }
  72     }
  73     ProbPrices[i] = (bitCount
  74       // + (1 << (kCyclesBits - 1))
  75       ) >> kCyclesBits;
  76   }
  77   */
  78 }
  79
  80 }}