93 lines
2.7 KiB
C++
93 lines
2.7 KiB
C++
#ifndef ENTT_COMMON_THROWING_ALLOCATOR_HPP
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#define ENTT_COMMON_THROWING_ALLOCATOR_HPP
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#include <cstddef>
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#include <limits>
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#include <memory>
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#include <type_traits>
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#include <entt/container/dense_map.hpp>
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#include <entt/core/fwd.hpp>
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#include <entt/core/type_info.hpp>
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namespace test {
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struct throwing_allocator_exception {};
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template<typename Type>
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class throwing_allocator {
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template<typename Other>
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friend class throwing_allocator;
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template<typename Other, typename = std::enable_if_t<!std::is_void_v<Type> || std::is_constructible_v<std::allocator<Type>, std::allocator<Other>>>>
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throwing_allocator(int, const throwing_allocator<Other> &other)
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: allocator{other.allocator},
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config{other.config} {}
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template<typename Other, typename = std::enable_if_t<std::is_void_v<Type> && !std::is_constructible_v<std::allocator<Type>, std::allocator<Other>>>>
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throwing_allocator(char, const throwing_allocator<Other> &other)
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: allocator{},
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config{other.config} {}
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public:
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using value_type = Type;
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using pointer = value_type *;
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using const_pointer = const value_type *;
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using void_pointer = void *;
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using const_void_pointer = const void *;
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using propagate_on_container_move_assignment = std::true_type;
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using propagate_on_container_swap = std::true_type;
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using container_type = entt::dense_map<entt::id_type, std::size_t>;
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template<typename Other>
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struct rebind {
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using other = throwing_allocator<Other>;
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};
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throwing_allocator()
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: allocator{},
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config{std::allocate_shared<container_type>(allocator)} {}
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template<typename Other>
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throwing_allocator(const throwing_allocator<Other> &other)
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// std::allocator<void> has no cross constructors (waiting for C++20)
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: throwing_allocator{0, other} {}
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pointer allocate(std::size_t length) {
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if(const auto hash = entt::type_id<Type>().hash(); config->contains(hash)) {
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if(auto &elem = (*config)[hash]; elem == 0u) {
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config->erase(hash);
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throw throwing_allocator_exception{};
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} else {
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--elem;
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}
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}
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return allocator.allocate(length);
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}
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void deallocate(pointer mem, std::size_t length) {
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allocator.deallocate(mem, length);
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}
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template<typename Other>
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void throw_counter(const std::size_t len) {
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(*config)[entt::type_id<Other>().hash()] = len;
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}
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bool operator==(const throwing_allocator<Type> &) const {
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return true;
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}
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bool operator!=(const throwing_allocator<Type> &other) const {
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return !(*this == other);
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}
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private:
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std::allocator<Type> allocator;
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std::shared_ptr<container_type> config;
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};
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} // namespace test
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#endif
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