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- #ifndef ENTT_ENTITY_ENTITY_HPP
- #define ENTT_ENTITY_ENTITY_HPP
-
- #include <cstddef>
- #include <cstdint>
- #include <type_traits>
- #include "../config/config.h"
- #include "fwd.hpp"
-
- namespace entt {
-
- /**
- * @cond TURN_OFF_DOXYGEN
- * Internal details not to be documented.
- */
-
- namespace internal {
-
- template<typename, typename = void>
- struct entt_traits;
-
- template<typename Type>
- struct entt_traits<Type, std::enable_if_t<std::is_enum_v<Type>>>
- : entt_traits<std::underlying_type_t<Type>> {};
-
- template<typename Type>
- struct entt_traits<Type, std::enable_if_t<std::is_class_v<Type>>>
- : entt_traits<typename Type::entity_type> {};
-
- template<>
- struct entt_traits<std::uint32_t> {
- using entity_type = std::uint32_t;
- using version_type = std::uint16_t;
-
- static constexpr entity_type entity_mask = 0xFFFFF;
- static constexpr entity_type version_mask = 0xFFF;
- static constexpr std::size_t entity_shift = 20u;
- };
-
- template<>
- struct entt_traits<std::uint64_t> {
- using entity_type = std::uint64_t;
- using version_type = std::uint32_t;
-
- static constexpr entity_type entity_mask = 0xFFFFFFFF;
- static constexpr entity_type version_mask = 0xFFFFFFFF;
- static constexpr std::size_t entity_shift = 32u;
- };
-
- } // namespace internal
-
- /**
- * Internal details not to be documented.
- * @endcond
- */
-
- /**
- * @brief Entity traits.
- * @tparam Type Type of identifier.
- */
- template<typename Type>
- class entt_traits: internal::entt_traits<Type> {
- using base_type = internal::entt_traits<Type>;
-
- public:
- /*! @brief Value type. */
- using value_type = Type;
- /*! @brief Underlying entity type. */
- using entity_type = typename base_type::entity_type;
- /*! @brief Underlying version type. */
- using version_type = typename base_type::version_type;
- /*! @brief Reserved identifier. */
- static constexpr entity_type reserved = base_type::entity_mask | (base_type::version_mask << base_type::entity_shift);
- /*! @brief Page size, default is `ENTT_SPARSE_PAGE`. */
- static constexpr auto page_size = ENTT_SPARSE_PAGE;
-
- /**
- * @brief Converts an entity to its underlying type.
- * @param value The value to convert.
- * @return The integral representation of the given value.
- */
- [[nodiscard]] static constexpr entity_type to_integral(const value_type value) ENTT_NOEXCEPT {
- return static_cast<entity_type>(value);
- }
-
- /**
- * @brief Returns the entity part once converted to the underlying type.
- * @param value The value to convert.
- * @return The integral representation of the entity part.
- */
- [[nodiscard]] static constexpr entity_type to_entity(const value_type value) ENTT_NOEXCEPT {
- return (to_integral(value) & base_type::entity_mask);
- }
-
- /**
- * @brief Returns the version part once converted to the underlying type.
- * @param value The value to convert.
- * @return The integral representation of the version part.
- */
- [[nodiscard]] static constexpr version_type to_version(const value_type value) ENTT_NOEXCEPT {
- return (to_integral(value) >> base_type::entity_shift);
- }
-
- /**
- * @brief Constructs an identifier from its parts.
- *
- * If the version part is not provided, a tombstone is returned.<br/>
- * If the entity part is not provided, a null identifier is returned.
- *
- * @param entity The entity part of the identifier.
- * @param version The version part of the identifier.
- * @return A properly constructed identifier.
- */
- [[nodiscard]] static constexpr value_type construct(const entity_type entity, const version_type version) ENTT_NOEXCEPT {
- return value_type{(entity & base_type::entity_mask) | (static_cast<entity_type>(version) << base_type::entity_shift)};
- }
-
- /**
- * @brief Combines two identifiers in a single one.
- *
- * The returned identifier is a copy of the first element except for its
- * version, which is taken from the second element.
- *
- * @param lhs The identifier from which to take the entity part.
- * @param rhs The identifier from which to take the version part.
- * @return A properly constructed identifier.
- */
- [[nodiscard]] static constexpr value_type combine(const entity_type lhs, const entity_type rhs) ENTT_NOEXCEPT {
- constexpr auto mask = (base_type::version_mask << base_type::entity_shift);
- return value_type{(lhs & base_type::entity_mask) | (rhs & mask)};
- }
- };
-
- /**
- * @copydoc entt_traits<Entity>::to_integral
- * @tparam Entity The value type.
- */
- template<typename Entity>
- [[nodiscard]] constexpr typename entt_traits<Entity>::entity_type to_integral(const Entity value) ENTT_NOEXCEPT {
- return entt_traits<Entity>::to_integral(value);
- }
-
- /**
- * @copydoc entt_traits<Entity>::to_entity
- * @tparam Entity The value type.
- */
- template<typename Entity>
- [[nodiscard]] constexpr typename entt_traits<Entity>::entity_type to_entity(const Entity value) ENTT_NOEXCEPT {
- return entt_traits<Entity>::to_entity(value);
- }
-
- /**
- * @copydoc entt_traits<Entity>::to_version
- * @tparam Entity The value type.
- */
- template<typename Entity>
- [[nodiscard]] constexpr typename entt_traits<Entity>::version_type to_version(const Entity value) ENTT_NOEXCEPT {
- return entt_traits<Entity>::to_version(value);
- }
-
- /*! @brief Null object for all identifiers. */
- struct null_t {
- /**
- * @brief Converts the null object to identifiers of any type.
- * @tparam Entity Type of identifier.
- * @return The null representation for the given type.
- */
- template<typename Entity>
- [[nodiscard]] constexpr operator Entity() const ENTT_NOEXCEPT {
- using entity_traits = entt_traits<Entity>;
- return entity_traits::combine(entity_traits::reserved, entity_traits::reserved);
- }
-
- /**
- * @brief Compares two null objects.
- * @param other A null object.
- * @return True in all cases.
- */
- [[nodiscard]] constexpr bool operator==([[maybe_unused]] const null_t other) const ENTT_NOEXCEPT {
- return true;
- }
-
- /**
- * @brief Compares two null objects.
- * @param other A null object.
- * @return False in all cases.
- */
- [[nodiscard]] constexpr bool operator!=([[maybe_unused]] const null_t other) const ENTT_NOEXCEPT {
- return false;
- }
-
- /**
- * @brief Compares a null object and an identifier of any type.
- * @tparam Entity Type of identifier.
- * @param entity Identifier with which to compare.
- * @return False if the two elements differ, true otherwise.
- */
- template<typename Entity>
- [[nodiscard]] constexpr bool operator==(const Entity entity) const ENTT_NOEXCEPT {
- using entity_traits = entt_traits<Entity>;
- return entity_traits::to_entity(entity) == entity_traits::to_entity(*this);
- }
-
- /**
- * @brief Compares a null object and an identifier of any type.
- * @tparam Entity Type of identifier.
- * @param entity Identifier with which to compare.
- * @return True if the two elements differ, false otherwise.
- */
- template<typename Entity>
- [[nodiscard]] constexpr bool operator!=(const Entity entity) const ENTT_NOEXCEPT {
- return !(entity == *this);
- }
- };
-
- /**
- * @brief Compares a null object and an identifier of any type.
- * @tparam Entity Type of identifier.
- * @param entity Identifier with which to compare.
- * @param other A null object yet to be converted.
- * @return False if the two elements differ, true otherwise.
- */
- template<typename Entity>
- [[nodiscard]] constexpr bool operator==(const Entity entity, const null_t other) ENTT_NOEXCEPT {
- return other.operator==(entity);
- }
-
- /**
- * @brief Compares a null object and an identifier of any type.
- * @tparam Entity Type of identifier.
- * @param entity Identifier with which to compare.
- * @param other A null object yet to be converted.
- * @return True if the two elements differ, false otherwise.
- */
- template<typename Entity>
- [[nodiscard]] constexpr bool operator!=(const Entity entity, const null_t other) ENTT_NOEXCEPT {
- return !(other == entity);
- }
-
- /*! @brief Tombstone object for all identifiers. */
- struct tombstone_t {
- /**
- * @brief Converts the tombstone object to identifiers of any type.
- * @tparam Entity Type of identifier.
- * @return The tombstone representation for the given type.
- */
- template<typename Entity>
- [[nodiscard]] constexpr operator Entity() const ENTT_NOEXCEPT {
- using entity_traits = entt_traits<Entity>;
- return entity_traits::combine(entity_traits::reserved, entity_traits::reserved);
- }
-
- /**
- * @brief Compares two tombstone objects.
- * @param other A tombstone object.
- * @return True in all cases.
- */
- [[nodiscard]] constexpr bool operator==([[maybe_unused]] const tombstone_t other) const ENTT_NOEXCEPT {
- return true;
- }
-
- /**
- * @brief Compares two tombstone objects.
- * @param other A tombstone object.
- * @return False in all cases.
- */
- [[nodiscard]] constexpr bool operator!=([[maybe_unused]] const tombstone_t other) const ENTT_NOEXCEPT {
- return false;
- }
-
- /**
- * @brief Compares a tombstone object and an identifier of any type.
- * @tparam Entity Type of identifier.
- * @param entity Identifier with which to compare.
- * @return False if the two elements differ, true otherwise.
- */
- template<typename Entity>
- [[nodiscard]] constexpr bool operator==(const Entity entity) const ENTT_NOEXCEPT {
- using entity_traits = entt_traits<Entity>;
- return entity_traits::to_version(entity) == entity_traits::to_version(*this);
- }
-
- /**
- * @brief Compares a tombstone object and an identifier of any type.
- * @tparam Entity Type of identifier.
- * @param entity Identifier with which to compare.
- * @return True if the two elements differ, false otherwise.
- */
- template<typename Entity>
- [[nodiscard]] constexpr bool operator!=(const Entity entity) const ENTT_NOEXCEPT {
- return !(entity == *this);
- }
- };
-
- /**
- * @brief Compares a tombstone object and an identifier of any type.
- * @tparam Entity Type of identifier.
- * @param entity Identifier with which to compare.
- * @param other A tombstone object yet to be converted.
- * @return False if the two elements differ, true otherwise.
- */
- template<typename Entity>
- [[nodiscard]] constexpr bool operator==(const Entity entity, const tombstone_t other) ENTT_NOEXCEPT {
- return other.operator==(entity);
- }
-
- /**
- * @brief Compares a tombstone object and an identifier of any type.
- * @tparam Entity Type of identifier.
- * @param entity Identifier with which to compare.
- * @param other A tombstone object yet to be converted.
- * @return True if the two elements differ, false otherwise.
- */
- template<typename Entity>
- [[nodiscard]] constexpr bool operator!=(const Entity entity, const tombstone_t other) ENTT_NOEXCEPT {
- return !(other == entity);
- }
-
- /**
- * @brief Compile-time constant for null entities.
- *
- * There exist implicit conversions from this variable to identifiers of any
- * allowed type. Similarly, there exist comparison operators between the null
- * entity and any other identifier.
- */
- inline constexpr null_t null{};
-
- /**
- * @brief Compile-time constant for tombstone entities.
- *
- * There exist implicit conversions from this variable to identifiers of any
- * allowed type. Similarly, there exist comparison operators between the
- * tombstone entity and any other identifier.
- */
- inline constexpr tombstone_t tombstone{};
-
- } // namespace entt
-
- #endif
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