/* Bra86.c -- Converter for x86 code (BCJ)

2017-04-03 : Igor Pavlov : Public domain */

#include "Precomp.h"

#include "Bra.h"

#define Test86MSByte(b) ((((b) + 1) & 0xFE) == 0)

SizeT x86_Convert(Byte *data, SizeT size, UInt32 ip, UInt32 *state, int encoding)

{

  SizeT pos = 0;

  UInt32 mask = *state & 7;

  if (size < 5)

    return 0;

  size -= 4;

  ip += 5;

  for (;;)

  {

    Byte *p = data + pos;

    const Byte *limit = data + size;

    for (; p < limit; p++)

      if ((*p & 0xFE) == 0xE8)

        break;

    {

      SizeT d = (SizeT)(p - data - pos);

      pos = (SizeT)(p - data);

      if (p >= limit)

      {

        *state = (d > 2 ? 0 : mask >> (unsigned)d);

        return pos;

      }

      if (d > 2)

        mask = 0;

      else

      {

        mask >>= (unsigned)d;

        if (mask != 0 && (mask > 4 || mask == 3 || Test86MSByte(p[(size_t)(mask >> 1) + 1])))

        {

          mask = (mask >> 1) | 4;

          pos++;

          continue;

        }

      }

    }

    if (Test86MSByte(p[4]))

    {

      UInt32 v = ((UInt32)p[4] << 24) | ((UInt32)p[3] << 16) | ((UInt32)p[2] << 8) | ((UInt32)p[1]);

      UInt32 cur = ip + (UInt32)pos;

      pos += 5;

      if (encoding)

        v += cur;

      else

        v -= cur;

      if (mask != 0)

      {

        unsigned sh = (mask & 6) << 2;

        if (Test86MSByte((Byte)(v >> sh)))

        {

          v ^= (((UInt32)0x100 << sh) - 1);

          if (encoding)

            v += cur;

          else

            v -= cur;

        }

        mask = 0;

      }

      p[1] = (Byte)v;

      p[2] = (Byte)(v >> 8);

      p[3] = (Byte)(v >> 16);

      p[4] = (Byte)(0 - ((v >> 24) & 1));

    }

    else

    {

      mask = (mask >> 1) | 4;

      pos++;

    }

  }

}