The Tor Browser: other-licenses/7zstub/src/7zip/Compress/Branch/BranchX86.c@925c144e1f1f

     1 /* BranchX86.c */

     3 #include "BranchX86.h"

     5 /*

     6 static int inline Test86MSByte(Byte b)

7 {

     8   return (b == 0 || b == 0xFF);

9 }

    10 */

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

    13 const int kMaskToAllowedStatus[8] = {1, 1, 1, 0, 1, 0, 0, 0};

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

    16 /*

    17 void x86_Convert_Init(UInt32 *prevMask, UInt32 *prevPos)

    18 {

    19   *prevMask = 0;

    20   *prevPos = (UInt32)(-5);

    21 }

    22 */

    24 UInt32 x86_Convert(Byte *buffer, UInt32 endPos, UInt32 nowPos,

    25     UInt32 *prevMask, UInt32 *prevPos, int encoding)

    26 {

    27   UInt32 bufferPos = 0;

    28   UInt32 limit;

    30   if (endPos < 5)

    31     return 0;

    33   if (nowPos - *prevPos > 5)

    34     *prevPos = nowPos - 5;

    36   limit = endPos - 5;

    37   while(bufferPos <= limit)

    38   {

    39     Byte b = buffer[bufferPos];

    40     UInt32 offset;

    41     if (b != 0xE8 && b != 0xE9)

    42     {

    43       bufferPos++;

    44       continue;

    45     }

    46     offset = (nowPos + bufferPos - *prevPos);

    47     *prevPos = (nowPos + bufferPos);

    48     if (offset > 5)

    49       *prevMask = 0;

    50     else

    51     {

    52       UInt32 i;

    53       for (i = 0; i < offset; i++)

    54       {

    55         *prevMask &= 0x77;

    56         *prevMask <<= 1;

    57       }

    58     }

    59     b = buffer[bufferPos + 4];

    60     if (Test86MSByte(b) && kMaskToAllowedStatus[(*prevMask >> 1) & 0x7] &&

    61       (*prevMask >> 1) < 0x10)

    62     {

    63       UInt32 src =

    64         ((UInt32)(b) << 24) |

    65         ((UInt32)(buffer[bufferPos + 3]) << 16) |

    66         ((UInt32)(buffer[bufferPos + 2]) << 8) |

    67         (buffer[bufferPos + 1]);

    69       UInt32 dest;

    70       while(1)

    71       {

    72         UInt32 index;

    73         if (encoding)

    74           dest = (nowPos + bufferPos + 5) + src;

    75         else

    76           dest = src - (nowPos + bufferPos + 5);

    77         if (*prevMask == 0)

    78           break;

    79         index = kMaskToBitNumber[*prevMask >> 1];

    80         b = (Byte)(dest >> (24 - index * 8));

    81         if (!Test86MSByte(b))

    82           break;

    83         src = dest ^ ((1 << (32 - index * 8)) - 1);

    84       }

    85       buffer[bufferPos + 4] = (Byte)(~(((dest >> 24) & 1) - 1));

    86       buffer[bufferPos + 3] = (Byte)(dest >> 16);

    87       buffer[bufferPos + 2] = (Byte)(dest >> 8);

    88       buffer[bufferPos + 1] = (Byte)dest;

    89       bufferPos += 5;

    90       *prevMask = 0;

    91     }

    92     else

    93     {

    94       bufferPos++;

    95       *prevMask |= 1;

    96       if (Test86MSByte(b))

    97         *prevMask |= 0x10;

    98     }

    99   }

   100   return bufferPos;

   101 }

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