Method CreateSuccessors

Libraries/unrar/model.cpp:171–243

inline RARPPM_CONTEXT* ModelPPM::CreateSuccessors(bool Skip,RARPPM_STATE* p1)
{
  RARPPM_STATE UpState;
  RARPPM_CONTEXT* pc=MinContext, * UpBranch=FoundState->Successor;
  RARPPM_STATE * p, * ps[MAX_O], ** pps=ps;
  if ( !Skip ) 
  {
    *pps++ = FoundState;
    if ( !pc->Suffix )
      goto NO_LOOP;
  }
  if ( p1 ) 
  {
    p=p1;
    pc=pc->Suffix;
    goto LOOP_ENTRY;
  }
  do 
  {
    pc=pc->Suffix;
    if (pc->NumStats != 1) 
    {
      if ((p=pc->U.Stats)->Symbol != FoundState->Symbol)
        do 
        {
          p++; 
        } while (p->Symbol != FoundState->Symbol);
    } 
    else
      p=&(pc->OneState);
LOOP_ENTRY:
    if (p->Successor != UpBranch) 
    {
      pc=p->Successor;
      break;

    }
    // We ensure that PPM order input parameter does not exceed MAX_O (64),
    // so we do not really need this check and added it for extra safety.
    // See CVE-2017-17969 for details.
    if (pps>=ps+ASIZE(ps))
      return NULL;

    *pps++ = p;
  } while ( pc->Suffix );
NO_LOOP:
  if (pps == ps)
    return pc;
  UpState.Symbol=*(byte*) UpBranch;
  UpState.Successor=(RARPPM_CONTEXT*) (((byte*) UpBranch)+1);
  if (pc->NumStats != 1) 
  {
    if ((byte*) pc <= SubAlloc.pText)
      return(NULL);
    if ((p=pc->U.Stats)->Symbol != UpState.Symbol)
    do 
    { 
      p++;