nel/3rdparty/seven_zip/Bra86.c

   1 /* Bra86.c -- Converter for x86 code (BCJ)
   2 2017-04-03 : Igor Pavlov : Public domain */
   3
   4 #include "Precomp.h"
   5
   6 #include "Bra.h"
   7
   8 #define Test86MSByte(b) ((((b) + 1) & 0xFE) == 0)
   9
  10 SizeT x86_Convert(Byte *data, SizeT size, UInt32 ip, UInt32 *state, int encoding)
  11 {
  12   SizeT pos = 0;
  13   UInt32 mask = *state & 7;
  14   if (size < 5)
  15     return 0;
  16   size -= 4;
  17   ip += 5;
  18
  19   for (;;)
  20   {
  21     Byte *p = data + pos;
  22     const Byte *limit = data + size;
  23     for (; p < limit; p++)
  24       if ((*p & 0xFE) == 0xE8)
  25         break;
  26
  27     {
  28       SizeT d = (SizeT)(p - data - pos);
  29       pos = (SizeT)(p - data);
  30       if (p >= limit)
  31       {
  32         *state = (d > 2 ? 0 : mask >> (unsigned)d);
  33         return pos;
  34       }
  35       if (d > 2)
  36         mask = 0;
  37       else
  38       {
  39         mask >>= (unsigned)d;
  40         if (mask != 0 && (mask > 4 || mask == 3 || Test86MSByte(p[(size_t)(mask >> 1) + 1])))
  41         {
  42           mask = (mask >> 1) | 4;
  43           pos++;
  44           continue;
  45         }
  46       }
  47     }
  48
  49     if (Test86MSByte(p[4]))
  50     {
  51       UInt32 v = ((UInt32)p[4] << 24) | ((UInt32)p[3] << 16) | ((UInt32)p[2] << 8) | ((UInt32)p[1]);
  52       UInt32 cur = ip + (UInt32)pos;
  53       pos += 5;
  54       if (encoding)
  55         v += cur;
  56       else
  57         v -= cur;
  58       if (mask != 0)
  59       {
  60         unsigned sh = (mask & 6) << 2;
  61         if (Test86MSByte((Byte)(v >> sh)))
  62         {
  63           v ^= (((UInt32)0x100 << sh) - 1);
  64           if (encoding)
  65             v += cur;
  66           else
  67             v -= cur;
  68         }
  69         mask = 0;
  70       }
  71       p[1] = (Byte)v;
  72       p[2] = (Byte)(v >> 8);
  73       p[3] = (Byte)(v >> 16);
  74       p[4] = (Byte)(0 - ((v >> 24) & 1));
  75     }
  76     else
  77     {
  78       mask = (mask >> 1) | 4;
  79       pos++;
  80     }
  81   }
  82 }