pfr/detail/size_array.hpp

0001 // Copyright (c) 2016-2025 Antony Polukhin
0002 //
0003 // Distributed under the Boost Software License, Version 1.0. (See accompanying
0004 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0005
0006 #ifndef BOOST_PFR_DETAIL_SIZE_ARRAY_HPP
0007 #define BOOST_PFR_DETAIL_SIZE_ARRAY_HPP
0008 #pragma once
0009
0010 #include <boost/pfr/detail/config.hpp>
0011
0012 #ifdef BOOST_PFR_HAS_STD_MODULE
0013 import std;
0014 #else
0015 #include <cstddef>
0016 #endif
0017
0018 namespace boost { namespace pfr { namespace detail {
0019
0020 ///////////////////// Array that has the constexpr
0021 template <std::size_t N>
0022 struct size_array {                         // libc++ misses constexpr on operator[]
0023     typedef std::size_t type;
0024     std::size_t data[N];
0025
0026     static constexpr std::size_t size() noexcept { return N; }
0027
0028     constexpr std::size_t count_nonzeros() const noexcept {
0029         std::size_t count = 0;
0030         for (std::size_t i = 0; i < size(); ++i) {
0031             if (data[i]) {
0032                 ++ count;
0033             }
0034         }
0035         return count;
0036     }
0037
0038     constexpr std::size_t count_from_opening_till_matching_parenthis_seq(std::size_t from, std::size_t opening_parenthis, std::size_t closing_parenthis) const noexcept {
0039         if (data[from] != opening_parenthis) {
0040             return 0;
0041         }
0042         std::size_t unclosed_parnthesis = 0;
0043         std::size_t count = 0;
0044         for (; ; ++from) {
0045             if (data[from] == opening_parenthis) {
0046                 ++ unclosed_parnthesis;
0047             } else if (data[from] == closing_parenthis) {
0048                 -- unclosed_parnthesis;
0049             }
0050             ++ count;
0051
0052             if (unclosed_parnthesis == 0) {
0053                 return count;
0054             }
0055         }
0056
0057         return count;
0058     }
0059 };
0060
0061 template <>
0062 struct size_array<0> {                         // libc++ misses constexpr on operator[]
0063     typedef std::size_t type;
0064     std::size_t data[1];
0065
0066     static constexpr std::size_t size() noexcept { return 0; }
0067
0068     constexpr std::size_t count_nonzeros() const noexcept {
0069         return 0;
0070     }
0071 };
0072
0073 template <std::size_t I, std::size_t N>
0074 constexpr std::size_t get(const size_array<N>& a) noexcept {
0075     static_assert(I < N, "====================> Boost.PFR: Array index out of bounds");
0076     return a.data[I];
0077 }
0078
0079
0080
0081 }}} // namespace boost::pfr::detail
0082
0083 #endif // BOOST_PFR_DETAIL_SIZE_ARRAY_HPP