text: #ifndef ENTT_CORE_HASHED_STRING_HPP
  #define ENTT_CORE_HASHED_STRING_HPP
  
  
  #include <cstddef>
  #include <cstdint>
  #include "../config/config.h"
  
  
  namespace entt {
  
  
  /**
   * @cond TURN_OFF_DOXYGEN
   * Internal details not to be documented.
   */
  
  
  namespace internal {
  
  
  template<typename>
  struct fnv1a_traits;
  
  
  template<>
  struct fnv1a_traits<std::uint32_t> {
      static constexpr std::uint32_t offset = 2166136261;
      static constexpr std::uint32_t prime = 16777619;
  };
  
  
  template<>
  struct fnv1a_traits<std::uint64_t> {
      static constexpr std::uint64_t offset = 14695981039346656037ull;
      static constexpr std::uint64_t prime = 1099511628211ull;
  };
  
  
  }
  
  
  /**
   * Internal details not to be documented.
   * @endcond TURN_OFF_DOXYGEN
   */
  
  
  /**
   * @brief Zero overhead unique identifier.
   *
   * A hashed string is a compile-time tool that allows users to use
   * human-readable identifers in the codebase while using their numeric
   * counterparts at runtime.<br/>
   * Because of that, a hashed string can also be used in constant expressions if
   * required.
   */
  class hashed_string {
      using traits_type = internal::fnv1a_traits<ENTT_HASH_TYPE>;
  
      struct const_wrapper {
          // non-explicit constructor on purpose
          constexpr const_wrapper(const char *str) ENTT_NOEXCEPT: str{str} {}
          const char *str;
      };
  
      // Fowler–Noll–Vo hash function v. 1a - the good
      inline static constexpr ENTT_HASH_TYPE helper(ENTT_HASH_TYPE partial, const char *str) ENTT_NOEXCEPT {
          return str[0] == 0 ? partial : helper((partial^str[0])*traits_type::prime, str+1);
      }
  
  public:
      /*! @brief Unsigned integer type. */
      using hash_type = ENTT_HASH_TYPE;
  
      /**
       * @brief Returns directly the numeric representation of a string.
       *
       * Forcing template resolution avoids implicit conversions. An
       * human-readable identifier can be anything but a plain, old bunch of
       * characters.<br/>
       * Example of use:
       * @code{.cpp}
       * const auto value = hashed_string::to_value("my.png");
       * @endcode
       *
       * @tparam N Number of characters of the identifier.
       * @param str Human-readable identifer.
       * @return The numeric representation of the string.
       */
      template<std::size_t N>
      inline static constexpr hash_type to_value(const char (&str)[N]) ENTT_NOEXCEPT {
          return helper(traits_type::offset, str);
      }
  
      /**
       * @brief Returns directly the numeric representation of a string.
       * @param wrapper Helps achieving the purpose by relying on overloading.
       * @return The numeric representation of the string.
       */
      inline static hash_type to_value(const_wrapper wrapper) ENTT_NOEXCEPT {
          return helper(traits_type::offset, wrapper.str);
      }
  
      /*! @brief Constructs an empty hashed string. */
      constexpr hashed_string() ENTT_NOEXCEPT
          : hash{}, str{nullptr}
      {}
  
      /**
       * @brief Constructs a hashed string from an array of const chars.
       *
       * Forcing template resolution avoids implicit conversions. An
       * human-readable identifier can be anything but a plain, old bunch of
       * characters.<br/>
       * Example of use:
       * @code{.cpp}
       * hashed_string hs{"my.png"};
       * @endcode
       *
       * @tparam N Number of characters of the identifier.
       * @param str Human-readable identifer.
       */
      template<std::size_t N>
      constexpr hashed_string(const char (&str)[N]) ENTT_NOEXCEPT
          : hash{helper(traits_type::offset, str)}, str{str}
      {}
  
      /**
       * @brief Explicit constructor on purpose to avoid constructing a hashed
       * string directly from a `const char *`.
       *
       * @param wrapper Helps achieving the purpose by relying on overloading.
       */
      explicit constexpr hashed_string(const_wrapper wrapper) ENTT_NOEXCEPT
          : hash{helper(traits_type::offset, wrapper.str)}, str{wrapper.str}
      {}
  
      /**
       * @brief Returns the human-readable representation of a hashed string.
       * @return The string used to initialize the instance.
       */
      constexpr const char * data() const ENTT_NOEXCEPT {
          return str;
      }
  
      /**
       * @brief Returns the numeric representation of a hashed string.
       * @return The numeric representation of the instance.
       */
      constexpr hash_type value() const ENTT_NOEXCEPT {
          return hash;
      }
  
      /**
       * @brief Returns the human-readable representation of a hashed string.
       * @return The string used to initialize the instance.
       */
      constexpr operator const char *() const ENTT_NOEXCEPT { return str; }
  
      /*! @copydoc value */
      constexpr operator hash_type() const ENTT_NOEXCEPT { return hash; }
  
      /**
       * @brief Compares two hashed strings.
       * @param other Hashed string with which to compare.
       * @return True if the two hashed strings are identical, false otherwise.
       */
      constexpr bool operator==(const hashed_string &other) const ENTT_NOEXCEPT {
          return hash == other.hash;
      }
  
  private:
      const hash_type hash;
      const char *str;
  };
  
  
  /**
   * @brief Compares two hashed strings.
   * @param lhs A valid hashed string.
   * @param rhs A valid hashed string.
   * @return True if the two hashed strings are identical, false otherwise.
   */
  constexpr bool operator!=(const hashed_string &lhs, const hashed_string &rhs) ENTT_NOEXCEPT {
      return !(lhs == rhs);
  }
  
  
  }
  
  
  /**
   * @brief User defined literal for hashed strings.
   * @param str The literal without its suffix.
   * @return A properly initialized hashed string.
   */
  constexpr entt::hashed_string operator"" ENTT_HS_SUFFIX(const char *str, std::size_t) ENTT_NOEXCEPT {
      return entt::hashed_string{str};
  }
  
  
  #endif // ENTT_CORE_HASHED_STRING_HPP
  