to_fixed_string.hpp

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//   ___ __  __ ___ 
//  / __|  \/  | _ \ GMP(Generative Metaprogramming)
// | (_ | |\/| |  _/ version 0.3.0
//  \___|_|  |_|_|   https://github.com/lkimuk/gmp
//
// SPDX-FileCopyrightText: 2026 Miles Li <https://www.cppmore.com/>
// SPDX-License-Identifier: MIT
//
// This file is part of the GMP (Generative Metaprogramming) library.
// Full project source: https://github.com/lkimuk/gmp
 
#ifndef GMP_META_TO_FIXED_STRING_HPP_
#define GMP_META_TO_FIXED_STRING_HPP_
 
#include <cstdint>
#include <gmp/meta/fixed_string.hpp>
 
namespace gmp {
 
namespace detail {
 
template<std::intmax_t N>
struct to_fixed_string_impl {
    static constexpr auto value = []() {
        constexpr auto buflen = []() {
            unsigned int len = (N == 0) ? 1 : (N > 0 ? 1 : 2);
            for (auto n = N; n; len++, n /= 10);
            return len;
        }();
        
        char buf[buflen] = {};
        auto ptr = buf + buflen;
        *--ptr = '\0';
        
        if constexpr (N != 0) {
            auto n = N < 0 ? -N : N;
            for (; n; n /= 10)
                *--ptr = "0123456789"[n % 10];
            if constexpr (N < 0)
                *--ptr = '-';
        } else {
            buf[0] = '0';
        }
        
        return fixed_string<buflen - 1>(buf);
    }();
};
 
} // namespace detail
 
template<std::intmax_t N>
static constexpr auto to_fixed_string_v = detail::to_fixed_string_impl<N>::value;
 
} // namespace gmp
 
#endif // GMP_META_TO_FIXED_STRING_HPP_