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_RESULTS_COMBINATORS_HPP
      11                 : #define BOOST_CAPY_DETAIL_RESULTS_COMBINATORS_HPP
      12                 : 
      13                 : #include <boost/capy/concept/context_awaitable.hpp>
      14                 : #include <boost/capy/results.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                 : /// True when every awaitable in the pack returns a `results`.
      26                 : template<typename... As>
      27                 : concept all_results_awaitables =
      28                 :     (is_results_v<awaitable_result_t<As>> && ...);
      29                 : 
      30                 : /// True when the `results`-aware when_all overload should be used.
      31                 : template<typename... As>
      32                 : concept when_all_results_eligible =
      33                 :     (sizeof...(As) > 0)
      34                 :     && all_results_awaitables<As...>;
      35                 : 
      36                 : /// True when the `results`-aware when_any overload should be used.
      37                 : template<typename... As>
      38                 : concept when_any_results_eligible =
      39                 :     (sizeof...(As) > 0)
      40                 :     && all_results_awaitables<As...>;
      41                 : 
      42                 : /// Map a `results` specialization to its contributed payload type.
      43                 : ///
      44                 : ///   results<T>       -> T            (unwrap single)
      45                 : ///   results<Ts...>   -> tuple<Ts...> (zero, two, or more)
      46                 : template<typename Result>
      47                 : struct results_payload;
      48                 : 
      49                 : template<typename T>
      50                 : struct results_payload<results<T>>
      51                 : {
      52                 :     using type = T;
      53                 : };
      54                 : 
      55                 : template<typename... Ts>
      56                 : struct results_payload<results<Ts...>>
      57                 : {
      58                 :     using type = std::tuple<Ts...>;
      59                 : };
      60                 : 
      61                 : template<typename Result>
      62                 : using results_payload_t =
      63                 :     typename results_payload<Result>::type;
      64                 : 
      65                 : /// Extract the payload value(s) from a `results`,
      66                 : /// matching the type produced by results_payload_t.
      67                 : template<typename T>
      68                 : T
      69 HIT         107 : extract_results_payload(results<T>&& r)
      70                 : {
      71             107 :     return std::get<1>(std::move(r));
      72                 : }
      73                 : 
      74                 : template<typename... Ts>
      75                 : std::tuple<Ts...>
      76              55 : extract_results_payload(results<Ts...>&& r)
      77                 : {
      78              61 :     return [&]<std::size_t... Is>(std::index_sequence<Is...>) {
      79              55 :         return std::tuple<Ts...>(std::get<Is + 1>(std::move(r))...);
      80              56 :     }(std::index_sequence_for<Ts...>{});
      81                 : }
      82                 : 
      83                 : /// Reconstruct a success `results` from a payload extracted by when_any.
      84                 : template<typename Result>
      85                 : struct results_from_payload;
      86                 : 
      87                 : template<typename T>
      88                 : struct results_from_payload<results<T>>
      89                 : {
      90                 :     static results<T> apply(T t)
      91                 :     {
      92                 :         return results<T>{std::error_code(), std::move(t)};
      93                 :     }
      94                 : };
      95                 : 
      96                 : template<typename... Ts>
      97                 : struct results_from_payload<results<Ts...>>
      98                 : {
      99                 :     static results<Ts...> apply(std::tuple<Ts...> t)
     100                 :     {
     101                 :         return std::tuple_cat(
     102                 :             std::tuple<std::error_code>(), std::move(t));
     103                 :     }
     104                 : };
     105                 : 
     106                 : /// Build the outer `results` for when_all from a tuple of child `results`.
     107                 : template<typename ResultType, typename Tuple, std::size_t... Is>
     108                 : ResultType
     109              50 : build_when_all_results_impl(Tuple&& results, std::index_sequence<Is...>)
     110                 : {
     111              50 :     std::error_code ec;
     112             109 :     (void)((std::get<0>(std::get<Is>(results)) && !ec
     113              23 :         ? (ec = std::get<0>(std::get<Is>(results)), true)
     114              36 :         : false) || ...);
     115                 : 
     116             141 :     return ResultType{ec, extract_results_payload(
     117             147 :         std::move(std::get<Is>(results)))...};
     118              20 : }
     119                 : 
     120                 : template<typename ResultType, typename... Results>
     121                 : ResultType
     122              50 : build_when_all_results(std::tuple<Results...>&& results)
     123                 : {
     124                 :     return build_when_all_results_impl<ResultType>(
     125              50 :         std::move(results),
     126              50 :         std::index_sequence_for<Results...>{});
     127                 : }
     128                 : 
     129                 : } // namespace detail
     130                 : } // namespace capy
     131                 : } // namespace boost
     132                 : 
     133                 : #endif