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      1 /* Bcj2.c -- Converter for x86 code (BCJ2)
      2 2008-10-04 : Igor Pavlov : Public domain */
      3 
      4 #include "Bcj2.h"
      5 
      6 #ifdef _LZMA_PROB32
      7 #define CProb UInt32
      8 #else
      9 #define CProb UInt16
     10 #endif
     11 
     12 #define IsJcc(b0, b1) ((b0) == 0x0F && ((b1) & 0xF0) == 0x80)
     13 #define IsJ(b0, b1) ((b1 & 0xFE) == 0xE8 || IsJcc(b0, b1))
     14 
     15 #define kNumTopBits 24
     16 #define kTopValue ((UInt32)1 << kNumTopBits)
     17 
     18 #define kNumBitModelTotalBits 11
     19 #define kBitModelTotal (1 << kNumBitModelTotalBits)
     20 #define kNumMoveBits 5
     21 
     22 #define RC_READ_BYTE (*buffer++)
     23 #define RC_TEST { if (buffer == bufferLim) return SZ_ERROR_DATA; }
     24 #define RC_INIT2 code = 0; range = 0xFFFFFFFF; \
     25   { int i; for (i = 0; i < 5; i++) { RC_TEST; code = (code << 8) | RC_READ_BYTE; }}
     26 
     27 #define NORMALIZE if (range < kTopValue) { RC_TEST; range <<= 8; code = (code << 8) | RC_READ_BYTE; }
     28 
     29 #define IF_BIT_0(p) ttt = *(p); bound = (range >> kNumBitModelTotalBits) * ttt; if (code < bound)
     30 #define UPDATE_0(p) range = bound; *(p) = (CProb)(ttt + ((kBitModelTotal - ttt) >> kNumMoveBits)); NORMALIZE;
     31 #define UPDATE_1(p) range -= bound; code -= bound; *(p) = (CProb)(ttt - (ttt >> kNumMoveBits)); NORMALIZE;
     32 
     33 int Bcj2_Decode(
     34     const Byte *buf0, SizeT size0,
     35     const Byte *buf1, SizeT size1,
     36     const Byte *buf2, SizeT size2,
     37     const Byte *buf3, SizeT size3,
     38     Byte *outBuf, SizeT outSize)
     39 {
     40   CProb p[256 + 2];
     41   SizeT inPos = 0, outPos = 0;
     42 
     43   const Byte *buffer, *bufferLim;
     44   UInt32 range, code;
     45   Byte prevByte = 0;
     46 
     47   unsigned int i;
     48   for (i = 0; i < sizeof(p) / sizeof(p[0]); i++)
     49     p[i] = kBitModelTotal >> 1;
     50 
     51   buffer = buf3;
     52   bufferLim = buffer + size3;
     53   RC_INIT2
     54 
     55   if (outSize == 0)
     56     return SZ_OK;
     57 
     58   for (;;)
     59   {
     60     Byte b;
     61     CProb *prob;
     62     UInt32 bound;
     63     UInt32 ttt;
     64 
     65     SizeT limit = size0 - inPos;
     66     if (outSize - outPos < limit)
     67       limit = outSize - outPos;
     68     while (limit != 0)
     69     {
     70       Byte b = buf0[inPos];
     71       outBuf[outPos++] = b;
     72       if (IsJ(prevByte, b))
     73         break;
     74       inPos++;
     75       prevByte = b;
     76       limit--;
     77     }
     78 
     79     if (limit == 0 || outPos == outSize)
     80       break;
     81 
     82     b = buf0[inPos++];
     83 
     84     if (b == 0xE8)
     85       prob = p + prevByte;
     86     else if (b == 0xE9)
     87       prob = p + 256;
     88     else
     89       prob = p + 257;
     90 
     91     IF_BIT_0(prob)
     92     {
     93       UPDATE_0(prob)
     94       prevByte = b;
     95     }
     96     else
     97     {
     98       UInt32 dest;
     99       const Byte *v;
    100       UPDATE_1(prob)
    101       if (b == 0xE8)
    102       {
    103         v = buf1;
    104         if (size1 < 4)
    105           return SZ_ERROR_DATA;
    106         buf1 += 4;
    107         size1 -= 4;
    108       }
    109       else
    110       {
    111         v = buf2;
    112         if (size2 < 4)
    113           return SZ_ERROR_DATA;
    114         buf2 += 4;
    115         size2 -= 4;
    116       }
    117       dest = (((UInt32)v[0] << 24) | ((UInt32)v[1] << 16) |
    118           ((UInt32)v[2] << 8) | ((UInt32)v[3])) - ((UInt32)outPos + 4);
    119       outBuf[outPos++] = (Byte)dest;
    120       if (outPos == outSize)
    121         break;
    122       outBuf[outPos++] = (Byte)(dest >> 8);
    123       if (outPos == outSize)
    124         break;
    125       outBuf[outPos++] = (Byte)(dest >> 16);
    126       if (outPos == outSize)
    127         break;
    128       outBuf[outPos++] = prevByte = (Byte)(dest >> 24);
    129     }
    130   }
    131   return (outPos == outSize) ? SZ_OK : SZ_ERROR_DATA;
    132 }
    133