third_party/lzma_sdk/Bra86.c

   1 /* Bra86.c -- Converter for x86 code (BCJ)
   2 2008-10-04 : Igor Pavlov : Public domain */
   3
   4 #include "Bra.h"
   5
   6 #define Test86MSByte(b) ((b) == 0 || (b) == 0xFF)
   7
   8 const Byte kMaskToAllowedStatus[8] = {1, 1, 1, 0, 1, 0, 0, 0};
   9 const Byte kMaskToBitNumber[8] = {0, 1, 2, 2, 3, 3, 3, 3};
  10
  11 SizeT x86_Convert(Byte *data, SizeT size, UInt32 ip, UInt32 *state, int encoding)
  12 {
  13   SizeT bufferPos = 0, prevPosT;
  14   UInt32 prevMask = *state & 0x7;
  15   if (size < 5)
  16     return 0;
  17   ip += 5;
  18   prevPosT = (SizeT)0 - 1;
  19
  20   for (;;)
  21   {
  22     Byte *p = data + bufferPos;
  23     Byte *limit = data + size - 4;
  24     for (; p < limit; p++)
  25       if ((*p & 0xFE) == 0xE8)
  26         break;
  27     bufferPos = (SizeT)(p - data);
  28     if (p >= limit)
  29       break;
  30     prevPosT = bufferPos - prevPosT;
  31     if (prevPosT > 3)
  32       prevMask = 0;
  33     else
  34     {
  35       prevMask = (prevMask << ((int)prevPosT - 1)) & 0x7;
  36       if (prevMask != 0)
  37       {
  38         Byte b = p[4 - kMaskToBitNumber[prevMask]];
  39         if (!kMaskToAllowedStatus[prevMask] || Test86MSByte(b))
  40         {
  41           prevPosT = bufferPos;
  42           prevMask = ((prevMask << 1) & 0x7) | 1;
  43           bufferPos++;
  44           continue;
  45         }
  46       }
  47     }
  48     prevPosT = bufferPos;
  49
  50     if (Test86MSByte(p[4]))
  51     {
  52       UInt32 src = ((UInt32)p[4] << 24) | ((UInt32)p[3] << 16) | ((UInt32)p[2] << 8) | ((UInt32)p[1]);
  53       UInt32 dest;
  54       for (;;)
  55       {
  56         Byte b;
  57         int index;
  58         if (encoding)
  59           dest = (ip + (UInt32)bufferPos) + src;
  60         else
  61           dest = src - (ip + (UInt32)bufferPos);
  62         if (prevMask == 0)
  63           break;
  64         index = kMaskToBitNumber[prevMask] * 8;
  65         b = (Byte)(dest >> (24 - index));
  66         if (!Test86MSByte(b))
  67           break;
  68         src = dest ^ ((1 << (32 - index)) - 1);
  69       }
  70       p[4] = (Byte)(~(((dest >> 24) & 1) - 1));
  71       p[3] = (Byte)(dest >> 16);
  72       p[2] = (Byte)(dest >> 8);
  73       p[1] = (Byte)dest;
  74       bufferPos += 5;
  75     }
  76     else
  77     {
  78       prevMask = ((prevMask << 1) & 0x7) | 1;
  79       bufferPos++;
  80     }
  81   }
  82   prevPosT = bufferPos - prevPosT;
  83   *state = ((prevPosT > 3) ? 0 : ((prevMask << ((int)prevPosT - 1)) & 0x7));
  84   return bufferPos;
  85 }