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59 lines
1.6 KiB
59 lines
1.6 KiB
#ifndef ENTT_CORE_IDENT_HPP
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#define ENTT_CORE_IDENT_HPP
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#include <cstddef>
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#include <type_traits>
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#include <utility>
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#include "../config/config.h"
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#include "fwd.hpp"
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#include "type_traits.hpp"
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namespace entt {
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/**
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* @brief Types identifiers.
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*
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* Variable template used to generate identifiers at compile-time for the given
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* types. Use the `get` member function to know what's the identifier associated
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* to the specific type.
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*
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* @note
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* Identifiers are constant expression and can be used in any context where such
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* an expression is required. As an example:
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* @code{.cpp}
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* using id = entt::identifier<a_type, another_type>;
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*
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* switch(a_type_identifier) {
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* case id::type<a_type>:
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* // ...
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* break;
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* case id::type<another_type>:
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* // ...
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* break;
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* default:
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* // ...
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* }
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* @endcode
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*
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* @tparam Types List of types for which to generate identifiers.
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*/
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template<typename... Types>
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class identifier {
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template<typename Type, std::size_t... Index>
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[[nodiscard]] static constexpr id_type get(std::index_sequence<Index...>) ENTT_NOEXCEPT {
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static_assert((std::is_same_v<Type, Types> || ...), "Invalid type");
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return (0 + ... + (std::is_same_v<Type, type_list_element_t<Index, type_list<std::decay_t<Types>...>>> ? id_type{Index} : id_type{}));
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}
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public:
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/*! @brief Unsigned integer type. */
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using identifier_type = id_type;
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/*! @brief Statically generated unique identifier for the given type. */
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template<typename Type>
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static constexpr identifier_type type = get<std::decay_t<Type>>(std::index_sequence_for<Types...>{});
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};
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} // namespace entt
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#endif
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