repo sync | baa3858 | 2013-07-26 17:53:31 -0700 | [diff] [blame] | 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));
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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));
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| 71 | p[3] = (Byte)(dest >> 16);
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| 72 | p[2] = (Byte)(dest >> 8);
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| 73 | p[1] = (Byte)dest;
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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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