mirror of
https://github.com/ZDoom/qzdoom-gpl.git
synced 2024-11-16 09:11:17 +00:00
85 lines
2.2 KiB
C
85 lines
2.2 KiB
C
/* 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;
|
|
}
|