fixed_string.hpp

// Copyright Take Vos 2021-2022.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)
 
#pragma once
 
#include "utility.hpp"
#include <string>
#include <string_view>
#include <format>
#include <array>
 
namespace hi::inline v1 {
 
template<int N>
struct fixed_string {
    using value_type = char;
 
    std::array<char, N> _str = {};
 
    constexpr fixed_string() noexcept = default;
    constexpr fixed_string(fixed_string const&) noexcept = default;
    constexpr fixed_string(fixed_string&&) noexcept = default;
    constexpr fixed_string& operator=(fixed_string const&) noexcept = default;
    constexpr fixed_string& operator=(fixed_string&&) noexcept = default;
 
    template<std::size_t O>
    constexpr fixed_string(char const (&str)[O]) noexcept requires((O - 1) == N)
    {
        for (auto i = 0_uz; i != (O - 1); ++i) {
            _str[i] = str[i];
        }
    }
 
    constexpr operator std::string_view() const noexcept
    {
        return std::string_view{_str.data(), size()};
    }
 
    constexpr operator std::string() const noexcept
    {
        return std::string{_str.data(), size()};
    }
 
    [[nodiscard]] constexpr std::size_t size() const noexcept
    {
        return N;
    }
 
    [[nodiscard]] constexpr char& operator[](size_t index) noexcept
    {
#ifndef NDEBUG
        if (not(index < N)) {
            std::terminate();
        }
#endif
        return _str[index];
    }
 
    [[nodiscard]] constexpr char const& operator[](size_t index) const noexcept
    {
#ifndef NDEBUG
        if (not(index < N)) {
            std::terminate();
        }
#endif
        return _str[index];
    }
 
    [[nodiscard]] constexpr auto begin() noexcept
    {
        return _str.begin();
    }
 
    [[nodiscard]] constexpr auto end() noexcept
    {
        return _str.begin() + size();
    }
 
    [[nodiscard]] constexpr bool operator==(fixed_string const& rhs) const noexcept = default;
    [[nodiscard]] constexpr auto operator<=>(fixed_string const& rhs) const noexcept = default;
 
    template<size_t O>
    [[nodiscard]] constexpr bool operator==(fixed_string<O> const& rhs) const noexcept requires(O != N)
    {
        return false;
    }
 
    template<size_t O>
    [[nodiscard]] constexpr auto operator<=>(fixed_string<O> const& rhs) const noexcept requires(O != N)
    {
        return static_cast<std::string_view>(*this) <=> static_cast<std::string_view>(rhs);
    }
 
    [[nodiscard]] constexpr bool operator==(std::string_view rhs) const noexcept
    {
        return static_cast<std::string_view>(*this) == rhs;
    }
    
    [[nodiscard]] constexpr auto operator<=>(std::string_view rhs) const noexcept
    {
        return static_cast<std::string_view>(*this) <=> rhs;
    }
 
    [[nodiscard]] constexpr bool operator==(std::string const &rhs) const noexcept
    {
        return static_cast<std::string_view>(*this) == rhs;
    }
 
    [[nodiscard]] constexpr auto operator<=>(std::string const &rhs) const noexcept
    {
        return static_cast<std::string_view>(*this) <=> rhs;
    }
 
    [[nodiscard]] constexpr bool operator==(char const *rhs) const noexcept
    {
        return static_cast<std::string_view>(*this) == rhs;
    }
 
    [[nodiscard]] constexpr auto operator<=>(char const *rhs) const noexcept
    {
        return static_cast<std::string_view>(*this) <=> rhs;
    }
 
    template<size_t O>
    [[nodiscard]] constexpr bool operator==(char const (&rhs)[O]) const noexcept
    {
        return *this == fixed_string<O - 1>(rhs);
    }
 
    template<size_t O>
    [[nodiscard]] constexpr auto operator<=>(char const (&rhs)[O]) const noexcept
    {
        return *this <=> fixed_string<O - 1>(rhs);
    }
 
    template<size_t O>
    [[nodiscard]] constexpr auto operator+(fixed_string<O> const& rhs) const noexcept
    {
        auto r = fixed_string<N + O>{};
        auto dst_i = 0_uz;
        for (auto src_i = 0_uz; src_i != N; ++src_i, ++dst_i) {
            r[dst_i] = (*this)[src_i];
        }
        for (auto src_i = 0_uz; src_i != O; ++src_i, ++dst_i) {
            r[dst_i] = rhs[src_i];
        }
 
        return r;
    }
};
 
// template<typename CharT>
//[[nodiscard]] constexpr std::size_t fixed_string_length_(CharT const *str) noexcept
//{
//     std::size_t i = 0;
//     while (str[i++] != CharT{}) {}
//     return i;
// }
 
template<std::size_t N>
fixed_string(char const (&str)[N]) -> fixed_string<N - 1>;
 
} // namespace hi::inline v1
 
template<std::size_t N, typename CharT>
struct std::formatter<hi::fixed_string<N>, CharT> : std::formatter<std::string_view, CharT> {
    constexpr auto format(hi::fixed_string<N> const& t, auto& fc)
    {
        return std::formatter<std::string_view, CharT>::format(static_cast<std::string_view>(t), fc);
    }
};