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490 lines
17 KiB
490 lines
17 KiB
#ifndef ENTT_CORE_ANY_HPP
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#define ENTT_CORE_ANY_HPP
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#include <cstddef>
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#include <memory>
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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 "../core/utility.hpp"
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#include "fwd.hpp"
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#include "type_info.hpp"
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#include "type_traits.hpp"
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namespace entt {
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/**
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* @brief A SBO friendly, type-safe container for single values of any type.
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* @tparam Len Size of the storage reserved for the small buffer optimization.
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* @tparam Align Optional alignment requirement.
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*/
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template<std::size_t Len, std::size_t Align>
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class basic_any {
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enum class operation : std::uint8_t {
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copy,
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move,
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transfer,
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assign,
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destroy,
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compare,
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get
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};
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enum class policy : std::uint8_t {
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owner,
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ref,
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cref
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};
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using storage_type = std::aligned_storage_t<Len + !Len, Align>;
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using vtable_type = const void *(const operation, const basic_any &, const void *);
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template<typename Type>
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static constexpr bool in_situ = Len && alignof(Type) <= alignof(storage_type) && sizeof(Type) <= sizeof(storage_type) && std::is_nothrow_move_constructible_v<Type>;
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template<typename Type>
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static const void *basic_vtable([[maybe_unused]] const operation op, [[maybe_unused]] const basic_any &value, [[maybe_unused]] const void *other) {
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static_assert(!std::is_same_v<Type, void> && std::is_same_v<std::remove_cv_t<std::remove_reference_t<Type>>, Type>, "Invalid type");
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const Type *element = nullptr;
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if constexpr(in_situ<Type>) {
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element = value.owner() ? reinterpret_cast<const Type *>(&value.storage) : static_cast<const Type *>(value.instance);
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} else {
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element = static_cast<const Type *>(value.instance);
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}
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switch(op) {
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case operation::copy:
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if constexpr(std::is_copy_constructible_v<Type>) {
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static_cast<basic_any *>(const_cast<void *>(other))->initialize<Type>(*element);
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}
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break;
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case operation::move:
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if constexpr(in_situ<Type>) {
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if(value.owner()) {
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return new(&static_cast<basic_any *>(const_cast<void *>(other))->storage) Type{std::move(*const_cast<Type *>(element))};
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}
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}
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return (static_cast<basic_any *>(const_cast<void *>(other))->instance = std::exchange(const_cast<basic_any &>(value).instance, nullptr));
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case operation::transfer:
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if constexpr(std::is_move_assignable_v<Type>) {
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*const_cast<Type *>(element) = std::move(*static_cast<Type *>(const_cast<void *>(other)));
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return other;
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}
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[[fallthrough]];
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case operation::assign:
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if constexpr(std::is_copy_assignable_v<Type>) {
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*const_cast<Type *>(element) = *static_cast<const Type *>(other);
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return other;
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}
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break;
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case operation::destroy:
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if constexpr(in_situ<Type>) {
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element->~Type();
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} else if constexpr(std::is_array_v<Type>) {
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delete[] element;
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} else {
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delete element;
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}
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break;
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case operation::compare:
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if constexpr(!std::is_function_v<Type> && !std::is_array_v<Type> && is_equality_comparable_v<Type>) {
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return *static_cast<const Type *>(element) == *static_cast<const Type *>(other) ? other : nullptr;
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} else {
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return (element == other) ? other : nullptr;
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}
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case operation::get:
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return element;
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}
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return nullptr;
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}
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template<typename Type, typename... Args>
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void initialize([[maybe_unused]] Args &&...args) {
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if constexpr(!std::is_void_v<Type>) {
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info = &type_id<std::remove_cv_t<std::remove_reference_t<Type>>>();
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vtable = basic_vtable<std::remove_cv_t<std::remove_reference_t<Type>>>;
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if constexpr(std::is_lvalue_reference_v<Type>) {
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static_assert(sizeof...(Args) == 1u && (std::is_lvalue_reference_v<Args> && ...), "Invalid arguments");
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mode = std::is_const_v<std::remove_reference_t<Type>> ? policy::cref : policy::ref;
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instance = (std::addressof(args), ...);
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} else if constexpr(in_situ<Type>) {
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if constexpr(sizeof...(Args) != 0u && std::is_aggregate_v<Type>) {
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new(&storage) Type{std::forward<Args>(args)...};
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} else {
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new(&storage) Type(std::forward<Args>(args)...);
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}
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} else {
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if constexpr(sizeof...(Args) != 0u && std::is_aggregate_v<Type>) {
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instance = new Type{std::forward<Args>(args)...};
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} else {
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instance = new Type(std::forward<Args>(args)...);
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}
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}
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}
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}
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basic_any(const basic_any &other, const policy pol) ENTT_NOEXCEPT
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: instance{other.data()},
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info{other.info},
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vtable{other.vtable},
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mode{pol} {}
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public:
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/*! @brief Size of the internal storage. */
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static constexpr auto length = Len;
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/*! @brief Alignment requirement. */
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static constexpr auto alignment = Align;
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/*! @brief Default constructor. */
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constexpr basic_any() ENTT_NOEXCEPT
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: instance{},
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info{&type_id<void>()},
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vtable{},
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mode{policy::owner} {}
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/**
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* @brief Constructs a wrapper by directly initializing the new object.
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* @tparam Type Type of object to use to initialize the wrapper.
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* @tparam Args Types of arguments to use to construct the new instance.
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* @param args Parameters to use to construct the instance.
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*/
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template<typename Type, typename... Args>
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explicit basic_any(std::in_place_type_t<Type>, Args &&...args)
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: basic_any{} {
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initialize<Type>(std::forward<Args>(args)...);
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}
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/**
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* @brief Constructs a wrapper from a given value.
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* @tparam Type Type of object to use to initialize the wrapper.
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* @param value An instance of an object to use to initialize the wrapper.
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*/
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template<typename Type, typename = std::enable_if_t<!std::is_same_v<std::decay_t<Type>, basic_any>>>
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basic_any(Type &&value)
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: basic_any{} {
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initialize<std::decay_t<Type>>(std::forward<Type>(value));
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}
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/**
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* @brief Copy constructor.
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* @param other The instance to copy from.
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*/
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basic_any(const basic_any &other)
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: basic_any{} {
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if(other.vtable) {
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other.vtable(operation::copy, other, this);
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}
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}
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/**
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* @brief Move constructor.
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* @param other The instance to move from.
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*/
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basic_any(basic_any &&other) ENTT_NOEXCEPT
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: instance{},
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info{other.info},
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vtable{other.vtable},
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mode{other.mode} {
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if(other.vtable) {
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other.vtable(operation::move, other, this);
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}
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}
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/*! @brief Frees the internal storage, whatever it means. */
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~basic_any() {
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if(vtable && owner()) {
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vtable(operation::destroy, *this, nullptr);
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}
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}
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/**
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* @brief Copy assignment operator.
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* @param other The instance to copy from.
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* @return This any object.
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*/
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basic_any &operator=(const basic_any &other) {
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reset();
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if(other.vtable) {
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other.vtable(operation::copy, other, this);
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}
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return *this;
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}
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/**
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* @brief Move assignment operator.
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* @param other The instance to move from.
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* @return This any object.
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*/
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basic_any &operator=(basic_any &&other) ENTT_NOEXCEPT {
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reset();
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if(other.vtable) {
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other.vtable(operation::move, other, this);
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info = other.info;
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vtable = other.vtable;
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mode = other.mode;
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}
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return *this;
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}
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/**
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* @brief Value assignment operator.
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* @tparam Type Type of object to use to initialize the wrapper.
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* @param value An instance of an object to use to initialize the wrapper.
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* @return This any object.
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*/
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template<typename Type>
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std::enable_if_t<!std::is_same_v<std::decay_t<Type>, basic_any>, basic_any &>
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operator=(Type &&value) {
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emplace<std::decay_t<Type>>(std::forward<Type>(value));
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return *this;
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}
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/**
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* @brief Returns the object type if any, `type_id<void>()` otherwise.
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* @return The object type if any, `type_id<void>()` otherwise.
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*/
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[[nodiscard]] const type_info &type() const ENTT_NOEXCEPT {
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return *info;
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}
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/**
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* @brief Returns an opaque pointer to the contained instance.
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* @return An opaque pointer the contained instance, if any.
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*/
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[[nodiscard]] const void *data() const ENTT_NOEXCEPT {
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return vtable ? vtable(operation::get, *this, nullptr) : nullptr;
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}
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/**
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* @brief Returns an opaque pointer to the contained instance.
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* @param req Expected type.
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* @return An opaque pointer the contained instance, if any.
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*/
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[[nodiscard]] const void *data(const type_info &req) const ENTT_NOEXCEPT {
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return *info == req ? data() : nullptr;
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}
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/**
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* @brief Returns an opaque pointer to the contained instance.
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* @return An opaque pointer the contained instance, if any.
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*/
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[[nodiscard]] void *data() ENTT_NOEXCEPT {
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return (!vtable || mode == policy::cref) ? nullptr : const_cast<void *>(vtable(operation::get, *this, nullptr));
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}
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/**
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* @brief Returns an opaque pointer to the contained instance.
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* @param req Expected type.
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* @return An opaque pointer the contained instance, if any.
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*/
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[[nodiscard]] void *data(const type_info &req) ENTT_NOEXCEPT {
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return *info == req ? data() : nullptr;
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}
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/**
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* @brief Replaces the contained object by creating a new instance directly.
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* @tparam Type Type of object to use to initialize the wrapper.
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* @tparam Args Types of arguments to use to construct the new instance.
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* @param args Parameters to use to construct the instance.
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*/
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template<typename Type, typename... Args>
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void emplace(Args &&...args) {
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reset();
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initialize<Type>(std::forward<Args>(args)...);
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}
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/**
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* @brief Assigns a value to the contained object without replacing it.
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* @param other The value to assign to the contained object.
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* @return True in case of success, false otherwise.
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*/
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bool assign(const any &other) {
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if(vtable && mode != policy::cref && *info == *other.info) {
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return (vtable(operation::assign, *this, other.data()) != nullptr);
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}
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return false;
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}
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/*! @copydoc assign */
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bool assign(any &&other) {
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if(vtable && mode != policy::cref && *info == *other.info) {
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if(auto *val = other.data(); val) {
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return (vtable(operation::transfer, *this, val) != nullptr);
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} else {
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return (vtable(operation::assign, *this, std::as_const(other).data()) != nullptr);
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}
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}
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return false;
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}
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/*! @brief Destroys contained object */
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void reset() {
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if(vtable && owner()) {
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vtable(operation::destroy, *this, nullptr);
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}
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info = &type_id<void>();
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vtable = nullptr;
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mode = policy::owner;
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}
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/**
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* @brief Returns false if a wrapper is empty, true otherwise.
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* @return False if the wrapper is empty, true otherwise.
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*/
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[[nodiscard]] explicit operator bool() const ENTT_NOEXCEPT {
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return vtable != nullptr;
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}
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/**
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* @brief Checks if two wrappers differ in their content.
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* @param other Wrapper with which to compare.
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* @return False if the two objects differ in their content, true otherwise.
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*/
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bool operator==(const basic_any &other) const ENTT_NOEXCEPT {
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if(vtable && *info == *other.info) {
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return (vtable(operation::compare, *this, other.data()) != nullptr);
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}
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return (!vtable && !other.vtable);
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}
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/**
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* @brief Aliasing constructor.
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* @return A wrapper that shares a reference to an unmanaged object.
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*/
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[[nodiscard]] basic_any as_ref() ENTT_NOEXCEPT {
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return basic_any{*this, (mode == policy::cref ? policy::cref : policy::ref)};
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}
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/*! @copydoc as_ref */
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[[nodiscard]] basic_any as_ref() const ENTT_NOEXCEPT {
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return basic_any{*this, policy::cref};
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}
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/**
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* @brief Returns true if a wrapper owns its object, false otherwise.
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* @return True if the wrapper owns its object, false otherwise.
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*/
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[[nodiscard]] bool owner() const ENTT_NOEXCEPT {
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return (mode == policy::owner);
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}
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private:
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union {
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const void *instance;
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storage_type storage;
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};
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const type_info *info;
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vtable_type *vtable;
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policy mode;
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};
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/**
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* @brief Checks if two wrappers differ in their content.
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* @tparam Len Size of the storage reserved for the small buffer optimization.
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* @tparam Align Alignment requirement.
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* @param lhs A wrapper, either empty or not.
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* @param rhs A wrapper, either empty or not.
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* @return True if the two wrappers differ in their content, false otherwise.
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*/
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template<std::size_t Len, std::size_t Align>
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[[nodiscard]] inline bool operator!=(const basic_any<Len, Align> &lhs, const basic_any<Len, Align> &rhs) ENTT_NOEXCEPT {
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return !(lhs == rhs);
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}
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/**
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* @brief Performs type-safe access to the contained object.
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* @tparam Type Type to which conversion is required.
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* @tparam Len Size of the storage reserved for the small buffer optimization.
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* @tparam Align Alignment requirement.
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* @param data Target any object.
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* @return The element converted to the requested type.
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*/
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template<typename Type, std::size_t Len, std::size_t Align>
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Type any_cast(const basic_any<Len, Align> &data) ENTT_NOEXCEPT {
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const auto *const instance = any_cast<std::remove_reference_t<Type>>(&data);
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ENTT_ASSERT(instance, "Invalid instance");
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return static_cast<Type>(*instance);
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}
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/*! @copydoc any_cast */
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template<typename Type, std::size_t Len, std::size_t Align>
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Type any_cast(basic_any<Len, Align> &data) ENTT_NOEXCEPT {
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// forces const on non-reference types to make them work also with wrappers for const references
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auto *const instance = any_cast<std::remove_reference_t<const Type>>(&data);
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ENTT_ASSERT(instance, "Invalid instance");
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return static_cast<Type>(*instance);
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}
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/*! @copydoc any_cast */
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template<typename Type, std::size_t Len, std::size_t Align>
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Type any_cast(basic_any<Len, Align> &&data) ENTT_NOEXCEPT {
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if constexpr(std::is_copy_constructible_v<std::remove_cv_t<std::remove_reference_t<Type>>>) {
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if(auto *const instance = any_cast<std::remove_reference_t<Type>>(&data); instance) {
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return static_cast<Type>(std::move(*instance));
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} else {
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return any_cast<Type>(data);
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}
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} else {
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auto *const instance = any_cast<std::remove_reference_t<Type>>(&data);
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ENTT_ASSERT(instance, "Invalid instance");
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return static_cast<Type>(std::move(*instance));
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}
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}
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/*! @copydoc any_cast */
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template<typename Type, std::size_t Len, std::size_t Align>
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const Type *any_cast(const basic_any<Len, Align> *data) ENTT_NOEXCEPT {
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const auto &info = type_id<std::remove_cv_t<std::remove_reference_t<Type>>>();
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return static_cast<const Type *>(data->data(info));
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}
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/*! @copydoc any_cast */
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template<typename Type, std::size_t Len, std::size_t Align>
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Type *any_cast(basic_any<Len, Align> *data) ENTT_NOEXCEPT {
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const auto &info = type_id<std::remove_cv_t<std::remove_reference_t<Type>>>();
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// last attempt to make wrappers for const references return their values
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return static_cast<Type *>(static_cast<constness_as_t<basic_any<Len, Align>, Type> *>(data)->data(info));
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}
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/**
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* @brief Constructs a wrapper from a given type, passing it all arguments.
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* @tparam Type Type of object to use to initialize the wrapper.
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* @tparam Len Size of the storage reserved for the small buffer optimization.
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* @tparam Align Optional alignment requirement.
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* @tparam Args Types of arguments to use to construct the new instance.
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* @param args Parameters to use to construct the instance.
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* @return A properly initialized wrapper for an object of the given type.
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*/
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template<typename Type, std::size_t Len = basic_any<>::length, std::size_t Align = basic_any<Len>::alignment, typename... Args>
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basic_any<Len, Align> make_any(Args &&...args) {
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return basic_any<Len, Align>{std::in_place_type<Type>, std::forward<Args>(args)...};
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}
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/**
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* @brief Forwards its argument and avoids copies for lvalue references.
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* @tparam Len Size of the storage reserved for the small buffer optimization.
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* @tparam Align Optional alignment requirement.
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* @tparam Type Type of argument to use to construct the new instance.
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* @param value Parameter to use to construct the instance.
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* @return A properly initialized and not necessarily owning wrapper.
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*/
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template<std::size_t Len = basic_any<>::length, std::size_t Align = basic_any<Len>::alignment, typename Type>
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basic_any<Len, Align> forward_as_any(Type &&value) {
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return basic_any<Len, Align>{std::in_place_type<std::conditional_t<std::is_rvalue_reference_v<Type>, std::decay_t<Type>, Type>>, std::forward<Type>(value)};
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}
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} // namespace entt
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#endif
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