TLA  Line data    Source code

       1                 : //
       2                 : // Copyright (c) 2026 Steve Gerbino
       3                 : //
       4                 : // Distributed under the Boost Software License, Version 1.0. (See accompanying
       5                 : // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
       6                 : //
       7                 : // Official repository: https://github.com/cppalliance/capy
       8                 : //
       9                 : 
      10                 : #ifndef BOOST_CAPY_DETAIL_IO_RESULT_COMBINATORS_HPP
      11                 : #define BOOST_CAPY_DETAIL_IO_RESULT_COMBINATORS_HPP
      12                 : 
      13                 : #include <boost/capy/concept/io_awaitable.hpp>
      14                 : #include <boost/capy/io_result.hpp>
      15                 : 
      16                 : #include <system_error>
      17                 : #include <tuple>
      18                 : #include <type_traits>
      19                 : #include <utility>
      20                 : 
      21                 : namespace boost {
      22                 : namespace capy {
      23                 : namespace detail {
      24                 : 
      25                 : template<typename T>
      26                 : struct is_io_result : std::false_type {};
      27                 : 
      28                 : template<typename... Args>
      29                 : struct is_io_result<io_result<Args...>> : std::true_type {};
      30                 : 
      31                 : template<typename T>
      32                 : inline constexpr bool is_io_result_v = is_io_result<T>::value;
      33                 : 
      34                 : /// True when every awaitable in the pack returns an io_result.
      35                 : template<typename... As>
      36                 : concept all_io_result_awaitables =
      37                 :     (is_io_result_v<awaitable_result_t<As>> && ...);
      38                 : 
      39                 : /// True when the io_result-aware when_all overload should be used.
      40                 : template<typename... As>
      41                 : concept when_all_io_eligible =
      42                 :     (sizeof...(As) > 0)
      43                 :     && all_io_result_awaitables<As...>;
      44                 : 
      45                 : /// True when the io_result-aware when_any overload should be used.
      46                 : template<typename... As>
      47                 : concept when_any_io_eligible =
      48                 :     (sizeof...(As) > 0)
      49                 :     && all_io_result_awaitables<As...>;
      50                 : 
      51                 : /// Map an io_result specialization to its contributed payload type.
      52                 : ///
      53                 : ///   io_result<T>       -> T            (unwrap single)
      54                 : ///   io_result<Ts...>   -> tuple<Ts...> (zero, two, or more)
      55                 : template<typename IoResult>
      56                 : struct io_result_payload;
      57                 : 
      58                 : template<typename T>
      59                 : struct io_result_payload<io_result<T>>
      60                 : {
      61                 :     using type = T;
      62                 : };
      63                 : 
      64                 : template<typename... Ts>
      65                 : struct io_result_payload<io_result<Ts...>>
      66                 : {
      67                 :     using type = std::tuple<Ts...>;
      68                 : };
      69                 : 
      70                 : template<typename IoResult>
      71                 : using io_result_payload_t =
      72                 :     typename io_result_payload<IoResult>::type;
      73                 : 
      74                 : /// Extract the payload value(s) from an io_result,
      75                 : /// matching the type produced by io_result_payload_t.
      76                 : template<typename T>
      77                 : T
      78 HIT          66 : extract_io_payload(io_result<T>&& r)
      79                 : {
      80              66 :     return std::get<0>(std::move(r.values));
      81                 : }
      82                 : 
      83                 : template<typename... Ts>
      84                 : std::tuple<Ts...>
      85              38 : extract_io_payload(io_result<Ts...>&& r)
      86                 : {
      87              38 :     return std::move(r.values);
      88                 : }
      89                 : 
      90                 : /// Reconstruct a success io_result from a payload extracted by when_any.
      91                 : template<typename IoResult>
      92                 : struct io_result_from_payload;
      93                 : 
      94                 : template<typename T>
      95                 : struct io_result_from_payload<io_result<T>>
      96                 : {
      97                 :     static io_result<T> apply(T t)
      98                 :     {
      99                 :         return io_result<T>{{}, std::move(t)};
     100                 :     }
     101                 : };
     102                 : 
     103                 : template<typename... Ts>
     104                 : struct io_result_from_payload<io_result<Ts...>>
     105                 : {
     106                 :     static io_result<Ts...> apply(std::tuple<Ts...> t)
     107                 :     {
     108                 :         return std::apply([](auto&&... args) {
     109                 :             return io_result<Ts...>{{}, std::move(args)...};
     110                 :         }, std::move(t));
     111                 :     }
     112                 : };
     113                 : 
     114                 : /// Build the outer io_result for when_all from a tuple of child io_results.
     115                 : template<typename ResultType, typename Tuple, std::size_t... Is>
     116                 : ResultType
     117              36 : build_when_all_io_result_impl(Tuple&& results, std::index_sequence<Is...>)
     118                 : {
     119              36 :     std::error_code ec;
     120              71 :     (void)((std::get<Is>(results).ec && !ec
     121              20 :         ? (ec = std::get<Is>(results).ec, true)
     122              15 :         : false) || ...);
     123                 : 
     124              37 :     return ResultType{ec, extract_io_payload(
     125             106 :         std::move(std::get<Is>(results)))...};
     126              17 : }
     127                 : 
     128                 : template<typename ResultType, typename... IoResults>
     129                 : ResultType
     130              36 : build_when_all_io_result(std::tuple<IoResults...>&& results)
     131                 : {
     132                 :     return build_when_all_io_result_impl<ResultType>(
     133              36 :         std::move(results),
     134              36 :         std::index_sequence_for<IoResults...>{});
     135                 : }
     136                 : 
     137                 : } // namespace detail
     138                 : } // namespace capy
     139                 : } // namespace boost
     140                 : 
     141                 : #endif