Mercurial > vba-linux

     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)) & 0xFF);

    66         if (!Test86MSByte(b))

    67           break;

    68         src = dest ^ ((1 << (32 - index)) - 1);

    69       }

    70       p[4] = (Byte)((~(((dest >> 24) & 1) - 1)) & 0xFF);

    71       p[3] = (Byte)((dest >> 16) & 0xFF);

    72       p[2] = (Byte)((dest >> 8) & 0xFF);

    73       p[1] = (Byte)(dest & 0xFF);

    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 }
author	Robert McIntyre <rlm@mit.edu>
date	Sat, 03 Mar 2012 10:31:47 -0600
parents	f9f4f1b99eed
children