source-engine/utils/lzma/C/Bcj2.c

/* Bcj2.c -- Converter for x86 code (BCJ2)
2008-10-04 : Igor Pavlov : Public domain */

#include "Precomp.h"

#include "Bcj2.h"

#ifdef _LZMA_PROB32
#define CProb UInt32
#else
#define CProb UInt16
#endif

#define IsJcc(b0, b1) ((b0) == 0x0F && ((b1) & 0xF0) == 0x80)
#define IsJ(b0, b1) ((b1 & 0xFE) == 0xE8 || IsJcc(b0, b1))

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

#define kNumBitModelTotalBits 11
#define kBitModelTotal (1 << kNumBitModelTotalBits)
#define kNumMoveBits 5

#define RC_READ_BYTE (*buffer++)
#define RC_TEST { if (buffer == bufferLim) return SZ_ERROR_DATA; }
#define RC_INIT2 code = 0; range = 0xFFFFFFFF; \
  { int i; for (i = 0; i < 5; i++) { RC_TEST; code = (code << 8) | RC_READ_BYTE; }}

#define NORMALIZE if (range < kTopValue) { RC_TEST; range <<= 8; code = (code << 8) | RC_READ_BYTE; }

#define IF_BIT_0(p) ttt = *(p); bound = (range >> kNumBitModelTotalBits) * ttt; if (code < bound)
#define UPDATE_0(p) range = bound; *(p) = (CProb)(ttt + ((kBitModelTotal - ttt) >> kNumMoveBits)); NORMALIZE;
#define UPDATE_1(p) range -= bound; code -= bound; *(p) = (CProb)(ttt - (ttt >> kNumMoveBits)); NORMALIZE;

int Bcj2_Decode(
    const Byte *buf0, SizeT size0,
    const Byte *buf1, SizeT size1,
    const Byte *buf2, SizeT size2,
    const Byte *buf3, SizeT size3,
    Byte *outBuf, SizeT outSize)
{
  CProb p[256 + 2];
  SizeT inPos = 0, outPos = 0;

  const Byte *buffer, *bufferLim;
  UInt32 range, code;
  Byte prevByte = 0;

  unsigned int i;
  for (i = 0; i < sizeof(p) / sizeof(p[0]); i++)
    p[i] = kBitModelTotal >> 1;

  buffer = buf3;
  bufferLim = buffer + size3;
  RC_INIT2

  if (outSize == 0)
    return SZ_OK;

  for (;;)
  {
    Byte b;
    CProb *prob;
    UInt32 bound;
    UInt32 ttt;

    SizeT limit = size0 - inPos;
    if (outSize - outPos < limit)
      limit = outSize - outPos;
    while (limit != 0)
    {
      Byte b = buf0[inPos];
      outBuf[outPos++] = b;
      if (IsJ(prevByte, b))
        break;
      inPos++;
      prevByte = b;
      limit--;
    }

    if (limit == 0 || outPos == outSize)
      break;

    b = buf0[inPos++];

    if (b == 0xE8)
      prob = p + prevByte;
    else if (b == 0xE9)
      prob = p + 256;
    else
      prob = p + 257;

    IF_BIT_0(prob)
    {
      UPDATE_0(prob)
      prevByte = b;
    }
    else
    {
      UInt32 dest;
      const Byte *v;
      UPDATE_1(prob)
      if (b == 0xE8)
      {
        v = buf1;
        if (size1 < 4)
          return SZ_ERROR_DATA;
        buf1 += 4;
        size1 -= 4;
      }
      else
      {
        v = buf2;
        if (size2 < 4)
          return SZ_ERROR_DATA;
        buf2 += 4;
        size2 -= 4;
      }
      dest = (((UInt32)v[0] << 24) | ((UInt32)v[1] << 16) |
          ((UInt32)v[2] << 8) | ((UInt32)v[3])) - ((UInt32)outPos + 4);
      outBuf[outPos++] = (Byte)dest;
      if (outPos == outSize)
        break;
      outBuf[outPos++] = (Byte)(dest >> 8);
      if (outPos == outSize)
        break;
      outBuf[outPos++] = (Byte)(dest >> 16);
      if (outPos == outSize)
        break;
      outBuf[outPos++] = prevByte = (Byte)(dest >> 24);
    }
  }
  return (outPos == outSize) ? SZ_OK : SZ_ERROR_DATA;
}