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110 lines
1.7 KiB
110 lines
1.7 KiB
#pragma once
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#include "gp_config.hpp"
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#include "gp/functional/bind_front.hpp"
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#include "gp/algorithms/move.hpp"
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#include "gp/exception.hpp"
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#include <type_traits>
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#include <new>
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namespace gp{
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struct nullopt_t final{};
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constexpr nullopt_t nullopt;
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template<typename T>
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class optional final{
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bool ready = false;
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alignas(T) char buffer[sizeof(T)];
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public:
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constexpr optional()
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: ready{false}
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{}
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constexpr optional(nullopt_t)
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: ready{false}
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{}
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constexpr optional(T& value)
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: ready{true}
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{
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new(buffer) T(value);
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}
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constexpr optional(T&& value)
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: ready{true}
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{
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new(buffer) T(gp::forward<T>(value));
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}
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~optional() {
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if(ready) {
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((T*)buffer)->~T();
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}
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}
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optional& operator=(nullopt_t) {
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if(ready) {
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((T*)buffer)->~T();
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ready = false;
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}
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return *this;
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}
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optional& operator=(T& value) {
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if(ready) {
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*(T*)buffer = value;
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} else {
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ready = true;
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new(buffer) T(value);
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}
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return *this;
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}
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optional& operator=(T&& value) {
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if(ready) {
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*(T*)buffer = gp::forward<T>(value);
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} else {
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ready = true;
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new(buffer) T(gp::forward<T>(value));
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}
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return *this;
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}
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constexpr bool has_value() const
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{
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return ready;
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}
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constexpr T& value()
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{
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if constexpr (gp_config::has_exceptions)
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{
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if(!ready)
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{
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throw bad_optional{};
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}
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} else {
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gp_config::assertion(ready, "bad optional access");
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}
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return *reinterpret_cast<T*>(buffer);
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}
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constexpr const T& value() const
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{
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if constexpr (gp_config::has_exceptions)
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{
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if(!ready)
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{
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throw bad_optional{};
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}
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} else {
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gp_config::assertion(ready, "bad optional access");
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}
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return *reinterpret_cast<const T*>(buffer);
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}
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};
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}
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