code: protected void reset(int linksSize, int varArraySize) {
      _frameTop = 0;
      _linksTop = 0;
  
      // Don't bother reallocating _links array if it exists already
      if (_links == null) {
        _links = new int[linksSize];
      }
  
      // Adding one here to the stack of frame positions will allow us always 
      // to look one under without having to check if we're at zero.
      // (As long as the caller doesn't screw up link/unlink.)
      _links[_linksTop++] = 0;
  
      // Get a clean _stackFrames array and discard the old one.
      _stackFrames = new XObject[varArraySize]; 
    }
docs: Reset the stack to a start position.
  @param linksSize Initial stack size to use
  @param varArraySize Initial variable array size to use