1 /* BranchX86.c */

     2 

     3 #include "BranchX86.h"

     4 

     5 #define Test86MSByte(b) ((b) == 0 || (b) == 0xFF)

     6 

     7 const Byte kMaskToAllowedStatus[8] = {1, 1, 1, 0, 1, 0, 0, 0};

     8 const Byte kMaskToBitNumber[8] = {0, 1, 2, 2, 3, 3, 3, 3};

     9 

    10 SizeT x86_Convert(Byte *buffer, SizeT endPos, UInt32 nowPos, UInt32 *prevMaskMix, int encoding)

    11 {

    12   SizeT bufferPos = 0, prevPosT;

    13   UInt32 prevMask = *prevMaskMix & 0x7;

    14   if (endPos < 5)

    15     return 0;

    16   nowPos += 5;

    17   prevPosT = (SizeT)0 - 1;

    18 

    19   for(;;)

    20   {

    21     Byte *p = buffer + bufferPos;

    22     Byte *limit = buffer + endPos - 4;

    23     for (; p < limit; p++)

    24       if ((*p & 0xFE) == 0xE8)

    25         break;

    26     bufferPos = (SizeT)(p - buffer);

    27     if (p >= limit)

    28       break;

    29     prevPosT = bufferPos - prevPosT;

    30     if (prevPosT > 3)

    31       prevMask = 0;

    32     else

    33     {

    34       prevMask = (prevMask << ((int)prevPosT - 1)) & 0x7;

    35       if (prevMask != 0)

    36       {

    37         Byte b = p[4 - kMaskToBitNumber[prevMask]];

    38         if (!kMaskToAllowedStatus[prevMask] || Test86MSByte(b))

    39         {

    40           prevPosT = bufferPos;

    41           prevMask = ((prevMask << 1) & 0x7) | 1;

    42           bufferPos++;

    43           continue;

    44         }

    45       }

    46     }

    47     prevPosT = bufferPos;

    48 

    49     if (Test86MSByte(p[4]))

    50     {

    51       UInt32 src = ((UInt32)p[4] << 24) | ((UInt32)p[3] << 16) | ((UInt32)p[2] << 8) | ((UInt32)p[1]);

    52       UInt32 dest;

    53       for (;;)

    54       {

    55         Byte b;

    56         int index;

    57         if (encoding)

    58           dest = (nowPos + (UInt32)bufferPos) + src;

    59         else

    60           dest = src - (nowPos + (UInt32)bufferPos);

    61         if (prevMask == 0)

    62           break;

    63         index = kMaskToBitNumber[prevMask] * 8;

    64         b = (Byte)(dest >> (24 - index));

    65         if (!Test86MSByte(b))

    66           break;

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

    68       }

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

    70       p[3] = (Byte)(dest >> 16);

    71       p[2] = (Byte)(dest >> 8);

    72       p[1] = (Byte)dest;

    73       bufferPos += 5;

    74     }

    75     else

    76     {

    77       prevMask = ((prevMask << 1) & 0x7) | 1;

    78       bufferPos++;

    79     }

    80   }

    81   prevPosT = bufferPos - prevPosT;

    82   *prevMaskMix = ((prevPosT > 3) ? 0 : ((prevMask << ((int)prevPosT - 1)) & 0x7));

    83   return bufferPos;

    84 }