74 lines
2.2 KiB
C++
74 lines
2.2 KiB
C++
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#pragma once
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#include <array>
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#include <cstddef>
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#include <stdexcept>
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#include <type_traits>
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template <class E> struct enum_traits;
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template <class E>
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concept EnumLike = std::is_enum_v<E>;
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template <EnumLike E>
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constexpr std::size_t enum_count_v =
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static_cast<std::size_t>(enum_traits<E>::last) -
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static_cast<std::size_t>(enum_traits<E>::first) + 1;
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template <EnumLike E, class T> struct enum_array {
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using value_type = T;
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using enum_type = E;
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using underlying_index_type = std::size_t;
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static constexpr E first = enum_traits<E>::first;
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static constexpr E last = enum_traits<E>::last;
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static constexpr std::size_t size_value = enum_count_v<E>;
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std::array<T, size_value> _data{};
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static constexpr std::size_t size() noexcept { return size_value; }
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constexpr T *data() noexcept { return _data.data(); }
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constexpr const T *data() const noexcept { return _data.data(); }
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constexpr T *begin() noexcept { return _data.begin().operator->(); }
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constexpr const T *begin() const noexcept {
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return _data.begin().operator->();
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}
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constexpr T *end() noexcept { return _data.end().operator->(); }
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constexpr const T *end() const noexcept { return _data.end().operator->(); }
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constexpr T &operator[](E e) noexcept { return _data[to_index(e)]; }
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constexpr const T &operator[](E e) const noexcept {
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return _data[to_index(e)];
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}
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constexpr T &at(E e) {
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auto i = to_index(e);
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if (i >= size_value)
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throw std::out_of_range("enum_array::at");
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return _data[i];
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}
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constexpr const T &at(E e) const {
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auto i = to_index(e);
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if (i >= size_value)
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throw std::out_of_range("enum_array::at");
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return _data[i];
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}
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constexpr void fill(const T &v) { _data.fill(v); }
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private:
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static constexpr std::size_t to_index(E e) noexcept {
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return static_cast<std::size_t>(e) - static_cast<std::size_t>(first);
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}
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};
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template <class E, class T, class... U>
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requires EnumLike<E> && (std::is_same_v<T, U> && ...)
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constexpr auto make_enum_array(T &&first_val, U &&...rest) {
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enum_array<E, std::decay_t<T>> arr;
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static_assert(sizeof...(rest) + 1 == enum_count_v<E>,
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"initializer count must match enum range");
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arr._data = {std::forward<T>(first_val), std::forward<U>(rest)...};
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return arr;
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}
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