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1 /* Bra86.c -- Converter for x86 code (BCJ)
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2 2008-10-04 : Igor Pavlov : Public domain */
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3
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4 #include "Bra.h"
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5
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6 #define Test86MSByte(b) ((b) == 0 || (b) == 0xFF)
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7
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8 const Byte kMaskToAllowedStatus[8] = {1, 1, 1, 0, 1, 0, 0, 0};
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9 const Byte kMaskToBitNumber[8] = {0, 1, 2, 2, 3, 3, 3, 3};
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10
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11 SizeT x86_Convert(Byte *data, SizeT size, UInt32 ip, UInt32 *state, int encoding)
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12 {
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13 SizeT bufferPos = 0, prevPosT;
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14 UInt32 prevMask = *state & 0x7;
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15 if (size < 5)
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16 return 0;
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17 ip += 5;
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18 prevPosT = (SizeT)0 - 1;
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19
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20 for (;;)
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21 {
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22 Byte *p = data + bufferPos;
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23 Byte *limit = data + size - 4;
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24 for (; p < limit; p++)
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25 if ((*p & 0xFE) == 0xE8)
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26 break;
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27 bufferPos = (SizeT)(p - data);
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28 if (p >= limit)
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29 break;
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30 prevPosT = bufferPos - prevPosT;
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31 if (prevPosT > 3)
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32 prevMask = 0;
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33 else
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34 {
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35 prevMask = (prevMask << ((int)prevPosT - 1)) & 0x7;
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36 if (prevMask != 0)
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37 {
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38 Byte b = p[4 - kMaskToBitNumber[prevMask]];
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39 if (!kMaskToAllowedStatus[prevMask] || Test86MSByte(b))
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40 {
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41 prevPosT = bufferPos;
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42 prevMask = ((prevMask << 1) & 0x7) | 1;
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43 bufferPos++;
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44 continue;
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45 }
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46 }
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47 }
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48 prevPosT = bufferPos;
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49
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50 if (Test86MSByte(p[4]))
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51 {
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52 UInt32 src = ((UInt32)p[4] << 24) | ((UInt32)p[3] << 16) | ((UInt32)p[2] << 8) | ((UInt32)p[1]);
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53 UInt32 dest;
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54 for (;;)
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55 {
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56 Byte b;
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57 int index;
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58 if (encoding)
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59 dest = (ip + (UInt32)bufferPos) + src;
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60 else
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61 dest = src - (ip + (UInt32)bufferPos);
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62 if (prevMask == 0)
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63 break;
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64 index = kMaskToBitNumber[prevMask] * 8;
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65 b = (Byte)((dest >> (24 - index)) & 0xFF);
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66 if (!Test86MSByte(b))
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67 break;
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68 src = dest ^ ((1 << (32 - index)) - 1);
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69 }
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70 p[4] = (Byte)((~(((dest >> 24) & 1) - 1)) & 0xFF);
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71 p[3] = (Byte)((dest >> 16) & 0xFF);
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72 p[2] = (Byte)((dest >> 8) & 0xFF);
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73 p[1] = (Byte)(dest & 0xFF);
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74 bufferPos += 5;
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75 }
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76 else
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77 {
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78 prevMask = ((prevMask << 1) & 0x7) | 1;
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79 bufferPos++;
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80 }
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81 }
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82 prevPosT = bufferPos - prevPosT;
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83 *state = ((prevPosT > 3) ? 0 : ((prevMask << ((int)prevPosT - 1)) & 0x7));
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84 return bufferPos;
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85 }
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