get coefficients and odd # occurrence after N steps

//in : sieveNum, steps
//out : return value, a, b
uint32_t getCoefficientsAndOddOccurrence(const mp::cpp_int& sieveNum, const uint32_t steps, mp::cpp_int& a, mp::cpp_int& b)
{
  uint32_t odds = 0;
  a = mp::cpp_int(1u) << steps;
  b = sieveNum;
  for (uint32_t i = 0; i < steps; ++i)
  {
    if (static_cast<uint32_t>(b)& 1u)
    {
      a += a >> 1;
      b += (b + 1) >> 1;
      ++odds;
    }
    else
    {
      a >>= 1;
      b >>= 1;
    }
  } //for()
  return odds;
}//getCoefficientsAndOddOccurrence()