misc/libphysfs/lzma/C/Compress/Branch/BranchX86.c
changeset 12213 bb5522e88ab2
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12212:ea891871f481 12213:bb5522e88ab2
       
     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 }