Method DecodeAudio

Libraries/unrar/unpack20.cpp:288–379

byte Unpack::DecodeAudio(int Delta)
{
  struct AudioVariables *V=&AudV[UnpCurChannel];
  V->ByteCount++;
  V->D4=V->D3;
  V->D3=V->D2;
  V->D2=V->LastDelta-V->D1;
  V->D1=V->LastDelta;
  int PCh=8*V->LastChar+V->K1*V->D1+V->K2*V->D2+V->K3*V->D3+V->K4*V->D4+V->K5*UnpChannelDelta;
  PCh=(PCh>>3) & 0xFF;

  uint Ch=PCh-Delta;

  int D=(signed char)Delta;
  // Left shift of negative value is undefined behavior in C++,
  // so we cast it to unsigned to follow the standard.
  D=(uint)D<<3;

  V->Dif[0]+=abs(D);
  V->Dif[1]+=abs(D-V->D1);
  V->Dif[2]+=abs(D+V->D1);
  V->Dif[3]+=abs(D-V->D2);
  V->Dif[4]+=abs(D+V->D2);
  V->Dif[5]+=abs(D-V->D3);
  V->Dif[6]+=abs(D+V->D3);
  V->Dif[7]+=abs(D-V->D4);
  V->Dif[8]+=abs(D+V->D4);
  V->Dif[9]+=abs(D-UnpChannelDelta);
  V->Dif[10]+=abs(D+UnpChannelDelta);

  UnpChannelDelta=V->LastDelta=(signed char)(Ch-V->LastChar);
  V->LastChar=Ch;

  if ((V->ByteCount & 0x1F)==0)
  {
    uint MinDif=V->Dif[0],NumMinDif=0;
    V->Dif[0]=0;
    for (uint I=1;I<ASIZE(V->Dif);I++)
    {
      if (V->Dif[I]<MinDif)
      {
        MinDif=V->Dif[I];
        NumMinDif=I;
      }
      V->Dif[I]=0;
    }
    switch(NumMinDif)
    {
      case 1:
        if (V->K1>=-16)
          V->K1--;
        break;
      case 2:
        if (V->K1<16)
          V->K1++;
        break;
      case 3:
        if (V->K2>=-16)