void quantiles_sketch::check_header_validity()

in quantiles/include/quantiles_sketch_impl.hpp [831:863]

• 30 lines of code
• 16 McCabe index (conditional complexity)

void quantiles_sketch<T, C, A>::check_header_validity(uint8_t preamble_longs, uint8_t flags_byte, uint8_t serial_version) {
  const bool empty = (flags_byte & (1 << flags::IS_EMPTY)) > 0;
  const bool compact = (flags_byte & (1 << flags::IS_COMPACT)) > 0;

  const uint8_t sw = (compact ? 1 : 0) + (2 * (empty ? 1 : 0))
                     + (4 * (serial_version & 0xF)) + (32 * (preamble_longs & 0x3F));
  bool valid = true;
  
  switch (sw) { // exhaustive list and description of all valid cases
      case 38  : break; //!compact,  empty, serVer = 1, preLongs = 1; always stored as not compact
      case 164 : break; //!compact, !empty, serVer = 1, preLongs = 5; always stored as not compact
      case 42  : break; //!compact,  empty, serVer = 2, preLongs = 1; always stored as compact
      case 72  : break; //!compact, !empty, serVer = 2, preLongs = 2; always stored as compact
      case 47  : break; // compact,  empty, serVer = 3, preLongs = 1;
      case 46  : break; //!compact,  empty, serVer = 3, preLongs = 1;
      case 79  : break; // compact,  empty, serVer = 3, preLongs = 2;
      case 78  : break; //!compact,  empty, serVer = 3, preLongs = 2;
      case 77  : break; // compact, !empty, serVer = 3, preLongs = 2;
      case 76  : break; //!compact, !empty, serVer = 3, preLongs = 2;
      default : //all other case values are invalid
        valid = false;
  }

  if (!valid) {
    std::ostringstream os;
    os << "Possible sketch corruption. Inconsistent state: "
       << "preamble_longs = " << preamble_longs
       << ", empty = " << (empty ? "true" : "false")
       << ", serialization_version = " << serial_version
       << ", compact = " << (compact ? "true" : "false");
    throw std::invalid_argument(os.str());
  }
}