/* Bcj2.c -- BCJ2 Decoder (Converter for x86 code)

2018-04-28 : Igor Pavlov : Public domain */

#include "Precomp.h"

#include "Bcj2.h"

#include "CpuArch.h"

#define CProb UInt16

#define kTopValue ((UInt32)1 << 24)

#define kNumModelBits 11

#define kBitModelTotal (1 << kNumModelBits)

#define kNumMoveBits 5

#define _IF_BIT_0 ttt = *prob; bound = (p->range >> kNumModelBits) * ttt; if (p->code < bound)

#define _UPDATE_0 p->range = bound; *prob = (CProb)(ttt + ((kBitModelTotal - ttt) >> kNumMoveBits));

#define _UPDATE_1 p->range -= bound; p->code -= bound; *prob = (CProb)(ttt - (ttt >> kNumMoveBits));

void Bcj2Dec_Init(CBcj2Dec *p)

{

  unsigned i;

  p->state = BCJ2_DEC_STATE_OK;

  p->ip = 0;

  p->temp[3] = 0;

  p->range = 0;

  p->code = 0;

  for (i = 0; i < sizeof(p->probs) / sizeof(p->probs[0]); i++)

    p->probs[i] = kBitModelTotal >> 1;

}

SRes Bcj2Dec_Decode(CBcj2Dec *p)

{

  if (p->range <= 5)

  {

    p->state = BCJ2_DEC_STATE_OK;

    for (; p->range != 5; p->range++)

    {

      if (p->range == 1 && p->code != 0)

        return SZ_ERROR_DATA;

      if (p->bufs[BCJ2_STREAM_RC] == p->lims[BCJ2_STREAM_RC])

      {

        p->state = BCJ2_STREAM_RC;

        return SZ_OK;

      }

      p->code = (p->code << 8) | *(p->bufs[BCJ2_STREAM_RC])++;

    }

    if (p->code == 0xFFFFFFFF)

      return SZ_ERROR_DATA;

    p->range = 0xFFFFFFFF;

  }

  else if (p->state >= BCJ2_DEC_STATE_ORIG_0)

  {

    while (p->state <= BCJ2_DEC_STATE_ORIG_3)

    {

      Byte *dest = p->dest;

      if (dest == p->destLim)

        return SZ_OK;

      *dest = p->temp[(size_t)p->state - BCJ2_DEC_STATE_ORIG_0];

      p->state++;

      p->dest = dest + 1;

    }

  }

  /*

  if (BCJ2_IS_32BIT_STREAM(p->state))

  {

    const Byte *cur = p->bufs[p->state];

    if (cur == p->lims[p->state])

      return SZ_OK;

    p->bufs[p->state] = cur + 4;

    {

      UInt32 val;

      Byte *dest;

      SizeT rem;

      p->ip += 4;

      val = GetBe32(cur) - p->ip;

      dest = p->dest;

      rem = p->destLim - dest;

      if (rem < 4)

      {

        SizeT i;

        SetUi32(p->temp, val);

        for (i = 0; i < rem; i++)

          dest[i] = p->temp[i];

        p->dest = dest + rem;

        p->state = BCJ2_DEC_STATE_ORIG_0 + (unsigned)rem;

        return SZ_OK;

      }

      SetUi32(dest, val);

      p->temp[3] = (Byte)(val >> 24);

      p->dest = dest + 4;

      p->state = BCJ2_DEC_STATE_OK;

    }

  }

  */

  for (;;)

  {

    if (BCJ2_IS_32BIT_STREAM(p->state))

      p->state = BCJ2_DEC_STATE_OK;

    else

    {

      if (p->range < kTopValue)

      {

        if (p->bufs[BCJ2_STREAM_RC] == p->lims[BCJ2_STREAM_RC])

        {

          p->state = BCJ2_STREAM_RC;

          return SZ_OK;

        }

        p->range <<= 8;

        p->code = (p->code << 8) | *(p->bufs[BCJ2_STREAM_RC])++;

      }

      {

        const Byte *src = p->bufs[BCJ2_STREAM_MAIN];

        const Byte *srcLim;

        Byte *dest;

        SizeT num = p->lims[BCJ2_STREAM_MAIN] - src;

        if (num == 0)

        {

          p->state = BCJ2_STREAM_MAIN;

          return SZ_OK;

        }

        dest = p->dest;

        if (num > (SizeT)(p->destLim - dest))

        {

          num = p->destLim - dest;

          if (num == 0)

          {

            p->state = BCJ2_DEC_STATE_ORIG;

            return SZ_OK;

          }

        }

        srcLim = src + num;

        if (p->temp[3] == 0x0F && (src[0] & 0xF0) == 0x80)

          *dest = src[0];

        else for (;;)

        {

          Byte b = *src;

          *dest = b;

          if (b != 0x0F)

          {

            if ((b & 0xFE) == 0xE8)

              break;

            dest++;

            if (++src != srcLim)

              continue;

            break;

          }

          dest++;

          if (++src == srcLim)

            break;

          if ((*src & 0xF0) != 0x80)

            continue;

          *dest = *src;

          break;

        }

        num = src - p->bufs[BCJ2_STREAM_MAIN];

        if (src == srcLim)

        {

          p->temp[3] = src[-1];

          p->bufs[BCJ2_STREAM_MAIN] = src;

          p->ip += (UInt32)num;

          p->dest += num;

          p->state =

            p->bufs[BCJ2_STREAM_MAIN] ==

            p->lims[BCJ2_STREAM_MAIN] ?

              (unsigned)BCJ2_STREAM_MAIN :

              (unsigned)BCJ2_DEC_STATE_ORIG;

          return SZ_OK;

        }

        {

          UInt32 bound, ttt;

          CProb *prob;

          Byte b = src[0];

          Byte prev = (Byte)(num == 0 ? p->temp[3] : src[-1]);

          p->temp[3] = b;

          p->bufs[BCJ2_STREAM_MAIN] = src + 1;

          num++;

          p->ip += (UInt32)num;

          p->dest += num;

          prob = p->probs + (unsigned)(b == 0xE8 ? 2 + (unsigned)prev : (b == 0xE9 ? 1 : 0));

          _IF_BIT_0

          {

            _UPDATE_0

            continue;

          }

          _UPDATE_1

        }

      }

    }

    {

      UInt32 val;

      unsigned cj = (p->temp[3] == 0xE8) ? BCJ2_STREAM_CALL : BCJ2_STREAM_JUMP;

      const Byte *cur = p->bufs[cj];

      Byte *dest;

      SizeT rem;

      if (cur == p->lims[cj])

      {

        p->state = cj;

        break;

      }

      val = GetBe32(cur);

      p->bufs[cj] = cur + 4;

      p->ip += 4;

      val -= p->ip;

      dest = p->dest;

      rem = p->destLim - dest;

      if (rem < 4)

      {

        p->temp[0] = (Byte)val; if (rem > 0) dest[0] = (Byte)val; val >>= 8;

        p->temp[1] = (Byte)val; if (rem > 1) dest[1] = (Byte)val; val >>= 8;

        p->temp[2] = (Byte)val; if (rem > 2) dest[2] = (Byte)val; val >>= 8;

        p->temp[3] = (Byte)val;

        p->dest = dest + rem;

        p->state = BCJ2_DEC_STATE_ORIG_0 + (unsigned)rem;

        break;

      }

      SetUi32(dest, val);

      p->temp[3] = (Byte)(val >> 24);

      p->dest = dest + 4;

    }

  }

  if (p->range < kTopValue && p->bufs[BCJ2_STREAM_RC] != p->lims[BCJ2_STREAM_RC])

  {

    p->range <<= 8;

    p->code = (p->code << 8) | *(p->bufs[BCJ2_STREAM_RC])++;

  }

  return SZ_OK;

}