Method version

example/cpp11/icmp/ipv4_header.hpp:56–56

  ipv4_header() { std::fill(rep_, rep_ + sizeof(rep_), 0); }

  unsigned char version() const { return (rep_[0] >> 4) & 0xF; }
  unsigned short header_length() const { return (rep_[0] & 0xF) * 4; }
  unsigned char type_of_service() const { return rep_[1]; }
  unsigned short total_length() const { return decode(2, 3); }