exit_codes_impl.hpp

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/******************************************************************************
** Copyright © 2019 by J.M.McGuiness, coder@hussar.me.uk
**
** This library is free software; you can redistribute it and/or
** modify it under the terms of the GNU Lesser General Public
** License as published by the Free Software Foundation; either
** version 2.1 of the License, or (at your option) any later version.
**
** This library is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
** Lesser General Public License for more details.
**
** You should have received a copy of the GNU Lesser General Public
** License along with this library; if not, write to the Free Software
** Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
 
namespace jmmcg { namespace LIBJMMCG_VER_NAMESPACE {
 
   namespace private_ {
      template<std::size_t I>
      struct finder {
         template<class E, class T>
         static constexpr auto get(E e, T const &t) noexcept(true) {
            auto const &v=std::get<I>(t);
            return std::get<0>(v)==e ? std::get<1>(v) : finder<I-1>::get(e, t);
         }
      };
      template<>
      struct finder<0> {
         template<class E, class T>
         static constexpr auto get([[maybe_unused]] E e, T const &t) noexcept(true) {
            auto const &v=std::get<0>(t);
            assert(std::get<0>(v)==e);
            return std::get<1>(v);
         }
      };
      template<std::size_t I>
      struct loop {
         template<class T, class Fn>
         static constexpr void get(T const &t, Fn &&f) noexcept(false) {
            auto const &v=std::get<I>(t);
            f(v);
            loop<I-1>::get(t, std::move(f));
         }
      };
      template<>
      struct loop<0> {
         template<class T, class Fn>
         static constexpr void get(T const &t, Fn &&f) noexcept(false) {
            auto const &v=std::get<0>(t);
            f(v);
         }
      };
   }
 
   inline std::string
   exit_codes::to_string(codes e) noexcept(false) {
      return private_::finder<std::tuple_size<decltype(descriptions)>::value-1>::get(e, descriptions);
   }
 
   inline std::string
   exit_codes::to_string() noexcept(false) {
      std::ostringstream os;
      os<<"Exit-code descriptions (error-conditions are output to 'std::cerr'):\n";
      auto print_element=[&os](auto const &desc) {
         os<<'['<<std::get<0>(desc)<<"] "<<std::get<1>(desc)<<": "<<std::get<2>(desc)<<'\n';
      };
      private_::loop<std::tuple_size<decltype(descriptions)>::value-1>::get(descriptions, std::move(print_element));
      return os.str();
   }
 
} }