class fnv {

  // Compile-time FNV-1a string hashing
  // kWEZEE, 2017.07

  // Usage:
  //    Find hash             : fnv{ }( TEXT )
  //    Find hash and compare : fnv{ }( TEXT, HASH )

  template< class _Ty, size_t _Size >
  constexpr auto get_hash_of( const _Ty ( &element )[ _Size ] ) {
    #if defined(_WIN64) || defined(__x86_64__)
      constexpr auto fnv_offset_basis = 14695981039346656037ull;
      constexpr auto fnv_prime        = 1099511628211ull;
    #else
      constexpr auto fnv_offset_basis = 2166136261u;
      constexpr auto fnv_prime        = 16777619u;
    #endif

    auto hash = fnv_offset_basis;

    for( size_t i{ }; i < _Size * sizeof _Ty; ++i ) {
      hash ^= element[ i ];
      hash *= fnv_prime;
    }

    return hash;
  }

public:
  template< class _Ty, size_t _Size >
  constexpr auto operator()( const _Ty ( &element )[ _Size ] ) {
    return this->get_hash_of( element );
  }

  template< class _Ty, size_t _Size >
  constexpr auto operator()( const _Ty ( &element )[ _Size ], const size_t &hash ) {
    return this->get_hash_of( element ) == hash;
  }

};