rlm@1: /* Bra86.c -- Converter for x86 code (BCJ)
rlm@1: 2008-10-04 : Igor Pavlov : Public domain */
rlm@1: 
rlm@1: #include "Bra.h"
rlm@1: 
rlm@1: #define Test86MSByte(b) ((b) == 0 || (b) == 0xFF)
rlm@1: 
rlm@1: const Byte kMaskToAllowedStatus[8] = {1, 1, 1, 0, 1, 0, 0, 0};
rlm@1: const Byte kMaskToBitNumber[8] = {0, 1, 2, 2, 3, 3, 3, 3};
rlm@1: 
rlm@1: SizeT x86_Convert(Byte *data, SizeT size, UInt32 ip, UInt32 *state, int encoding)
rlm@1: {
rlm@1:   SizeT bufferPos = 0, prevPosT;
rlm@1:   UInt32 prevMask = *state & 0x7;
rlm@1:   if (size < 5)
rlm@1:     return 0;
rlm@1:   ip += 5;
rlm@1:   prevPosT = (SizeT)0 - 1;
rlm@1: 
rlm@1:   for (;;)
rlm@1:   {
rlm@1:     Byte *p = data + bufferPos;
rlm@1:     Byte *limit = data + size - 4;
rlm@1:     for (; p < limit; p++)
rlm@1:       if ((*p & 0xFE) == 0xE8)
rlm@1:         break;
rlm@1:     bufferPos = (SizeT)(p - data);
rlm@1:     if (p >= limit)
rlm@1:       break;
rlm@1:     prevPosT = bufferPos - prevPosT;
rlm@1:     if (prevPosT > 3)
rlm@1:       prevMask = 0;
rlm@1:     else
rlm@1:     {
rlm@1:       prevMask = (prevMask << ((int)prevPosT - 1)) & 0x7;
rlm@1:       if (prevMask != 0)
rlm@1:       {
rlm@1:         Byte b = p[4 - kMaskToBitNumber[prevMask]];
rlm@1:         if (!kMaskToAllowedStatus[prevMask] || Test86MSByte(b))
rlm@1:         {
rlm@1:           prevPosT = bufferPos;
rlm@1:           prevMask = ((prevMask << 1) & 0x7) | 1;
rlm@1:           bufferPos++;
rlm@1:           continue;
rlm@1:         }
rlm@1:       }
rlm@1:     }
rlm@1:     prevPosT = bufferPos;
rlm@1: 
rlm@1:     if (Test86MSByte(p[4]))
rlm@1:     {
rlm@1:       UInt32 src = ((UInt32)p[4] << 24) | ((UInt32)p[3] << 16) | ((UInt32)p[2] << 8) | ((UInt32)p[1]);
rlm@1:       UInt32 dest;
rlm@1:       for (;;)
rlm@1:       {
rlm@1:         Byte b;
rlm@1:         int index;
rlm@1:         if (encoding)
rlm@1:           dest = (ip + (UInt32)bufferPos) + src;
rlm@1:         else
rlm@1:           dest = src - (ip + (UInt32)bufferPos);
rlm@1:         if (prevMask == 0)
rlm@1:           break;
rlm@1:         index = kMaskToBitNumber[prevMask] * 8;
rlm@1:         b = (Byte)((dest >> (24 - index)) & 0xFF);
rlm@1:         if (!Test86MSByte(b))
rlm@1:           break;
rlm@1:         src = dest ^ ((1 << (32 - index)) - 1);
rlm@1:       }
rlm@1:       p[4] = (Byte)((~(((dest >> 24) & 1) - 1)) & 0xFF);
rlm@1:       p[3] = (Byte)((dest >> 16) & 0xFF);
rlm@1:       p[2] = (Byte)((dest >> 8) & 0xFF);
rlm@1:       p[1] = (Byte)(dest & 0xFF);
rlm@1:       bufferPos += 5;
rlm@1:     }
rlm@1:     else
rlm@1:     {
rlm@1:       prevMask = ((prevMask << 1) & 0x7) | 1;
rlm@1:       bufferPos++;
rlm@1:     }
rlm@1:   }
rlm@1:   prevPosT = bufferPos - prevPosT;
rlm@1:   *state = ((prevPosT > 3) ? 0 : ((prevMask << ((int)prevPosT - 1)) & 0x7));
rlm@1:   return bufferPos;
rlm@1: }