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