78 lines
2.5 KiB
C
78 lines
2.5 KiB
C
/* Bra86.c -- Converter for x86 code (BCJ)
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2008-10-04 : Igor Pavlov : Public domain */
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#include "Bra.h"
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#define Test86MSByte(b) ((b) == 0 || (b) == 0xFF)
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const Byte kMaskToAllowedStatus[8] = { 1, 1, 1, 0, 1, 0, 0, 0 };
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const Byte kMaskToBitNumber[8] = { 0, 1, 2, 2, 3, 3, 3, 3 };
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SizeT x86_Convert(Byte* data, SizeT size, UInt32 ip, UInt32* state, int encoding)
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{
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SizeT bufferPos = 0, prevPosT;
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UInt32 prevMask = *state & 0x7;
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if (size < 5)
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return 0;
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ip += 5;
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prevPosT = (SizeT)0 - 1;
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for (;;) {
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Byte* p = data + bufferPos;
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Byte* limit = data + size - 4;
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for (; p < limit; p++)
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if ((*p & 0xFE) == 0xE8)
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break;
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bufferPos = (SizeT)(p - data);
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if (p >= limit)
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break;
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prevPosT = bufferPos - prevPosT;
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if (prevPosT > 3)
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prevMask = 0;
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else {
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prevMask = (prevMask << ((int)prevPosT - 1)) & 0x7;
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if (prevMask != 0) {
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Byte b = p[4 - kMaskToBitNumber[prevMask]];
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if (!kMaskToAllowedStatus[prevMask] || Test86MSByte(b)) {
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prevPosT = bufferPos;
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prevMask = ((prevMask << 1) & 0x7) | 1;
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bufferPos++;
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continue;
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}
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}
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}
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prevPosT = bufferPos;
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if (Test86MSByte(p[4])) {
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UInt32 src = ((UInt32)p[4] << 24) | ((UInt32)p[3] << 16) | ((UInt32)p[2] << 8) | ((UInt32)p[1]);
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UInt32 dest;
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for (;;) {
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Byte b;
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int index;
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if (encoding)
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dest = (ip + (UInt32)bufferPos) + src;
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else
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dest = src - (ip + (UInt32)bufferPos);
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if (prevMask == 0)
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break;
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index = kMaskToBitNumber[prevMask] * 8;
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b = (Byte)(dest >> (24 - index));
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if (!Test86MSByte(b))
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break;
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src = dest ^ ((1 << (32 - index)) - 1);
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}
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p[4] = (Byte)(~(((dest >> 24) & 1) - 1));
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p[3] = (Byte)(dest >> 16);
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p[2] = (Byte)(dest >> 8);
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p[1] = (Byte)dest;
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bufferPos += 5;
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} else {
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prevMask = ((prevMask << 1) & 0x7) | 1;
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bufferPos++;
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}
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}
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prevPosT = bufferPos - prevPosT;
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*state = ((prevPosT > 3) ? 0 : ((prevMask << ((int)prevPosT - 1)) & 0x7));
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return bufferPos;
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}
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