/* 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; | |
} |