BranchX86.c
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/* BranchX86.c */
#include "BranchX86.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 *buffer, SizeT endPos, UInt32 nowPos, UInt32 *prevMaskMix, int encoding)
{
SizeT bufferPos = 0, prevPosT;
UInt32 prevMask = *prevMaskMix & 0x7;
if (endPos < 5)
return 0;
nowPos += 5;
prevPosT = (SizeT)0 - 1;
for(;;)
{
Byte *p = buffer + bufferPos;
Byte *limit = buffer + endPos - 4;
for (; p < limit; p++)
if ((*p & 0xFE) == 0xE8)
break;
bufferPos = (SizeT)(p - buffer);
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 = (nowPos + (UInt32)bufferPos) + src;
else
dest = src - (nowPos + (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;
*prevMaskMix = ((prevPosT > 3) ? 0 : ((prevMask << ((int)prevPosT - 1)) & 0x7));
return bufferPos;
}