xref: /openbmc/sdbusplus/include/sdbusplus/async/stdexec/__detail/__receivers.hpp (revision 06f265f6)

/*
 * Copyright (c) 2022-2024 NVIDIA Corporation
 *
 * Licensed under the Apache License Version 2.0 with LLVM Exceptions
 * (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 *
 *   https://llvm.org/LICENSE.txt
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#pragma once

#include "../functional.hpp"
#include "__concepts.hpp"
#include "__diagnostics.hpp"
#include "__env.hpp"
#include "__execution_fwd.hpp"
#include "__tag_invoke.hpp"

#include <exception>

namespace stdexec
{
/////////////////////////////////////////////////////////////////////////////
// [execution.receivers]
namespace __rcvrs
{
struct set_value_t
{
    template <class _Fn, class... _Args>
    using __f = __minvoke<_Fn, _Args...>;

    template <__same_as<set_value_t> _Self, class _Receiver, class... _As>
    STDEXEC_ATTRIBUTE((host, device, always_inline))
    friend auto tag_invoke(_Self, _Receiver&& __rcvr, _As&&... __as) noexcept
        -> decltype(static_cast<_Receiver&&>(__rcvr).set_value(
            static_cast<_As&&>(__as)...))
    {
        static_assert(noexcept(static_cast<_Receiver&&>(__rcvr).set_value(
                          static_cast<_As&&>(__as)...)),
                      "set_value member functions must be noexcept");
        static_assert(
            __same_as<decltype(static_cast<_Receiver&&>(__rcvr).set_value(
                          static_cast<_As&&>(__as)...)),
                      void>,
            "set_value member functions must return void");
        static_cast<_Receiver&&>(__rcvr).set_value(static_cast<_As&&>(__as)...);
    }

    template <class _Receiver, class... _As>
        requires tag_invocable<set_value_t, _Receiver, _As...>
    STDEXEC_ATTRIBUTE((host, device, always_inline))
    void operator()(_Receiver&& __rcvr, _As&&... __as) const noexcept
    {
        static_assert(nothrow_tag_invocable<set_value_t, _Receiver, _As...>);
        (void)tag_invoke(stdexec::set_value_t{},
                         static_cast<_Receiver&&>(__rcvr),
                         static_cast<_As&&>(__as)...);
    }
};

struct set_error_t
{
    template <class _Fn, class... _Args>
        requires(sizeof...(_Args) == 1)
    using __f = __minvoke<_Fn, _Args...>;

    template <__same_as<set_error_t> _Self, class _Receiver, class _Error>
    STDEXEC_ATTRIBUTE((host, device, always_inline))
    friend auto tag_invoke(_Self, _Receiver&& __rcvr, _Error&& __err) noexcept
        -> decltype(static_cast<_Receiver&&>(__rcvr).set_error(
            static_cast<_Error&&>(__err)))
    {
        static_assert(noexcept(static_cast<_Receiver&&>(__rcvr).set_error(
                          static_cast<_Error&&>(__err))),
                      "set_error member functions must be noexcept");
        static_assert(
            __same_as<decltype(static_cast<_Receiver&&>(__rcvr).set_error(
                          static_cast<_Error&&>(__err))),
                      void>,
            "set_error member functions must return void");
        static_cast<_Receiver&&>(__rcvr).set_error(
            static_cast<_Error&&>(__err));
    }

    template <class _Receiver, class _Error>
        requires tag_invocable<set_error_t, _Receiver, _Error>
    STDEXEC_ATTRIBUTE((host, device, always_inline))
    void operator()(_Receiver&& __rcvr, _Error&& __err) const noexcept
    {
        static_assert(nothrow_tag_invocable<set_error_t, _Receiver, _Error>);
        (void)tag_invoke(stdexec::set_error_t{},
                         static_cast<_Receiver&&>(__rcvr),
                         static_cast<_Error&&>(__err));
    }
};

struct set_stopped_t
{
    template <class _Fn, class... _Args>
        requires(sizeof...(_Args) == 0)
    using __f = __minvoke<_Fn, _Args...>;

    template <__same_as<set_stopped_t> _Self, class _Receiver>
    STDEXEC_ATTRIBUTE((host, device, always_inline))
    friend auto tag_invoke(_Self, _Receiver&& __rcvr) noexcept
        -> decltype(static_cast<_Receiver&&>(__rcvr).set_stopped())
    {
        static_assert(noexcept(static_cast<_Receiver&&>(__rcvr).set_stopped()),
                      "set_stopped member functions must be noexcept");
        static_assert(
            __same_as<decltype(static_cast<_Receiver&&>(__rcvr).set_stopped()),
                      void>,
            "set_stopped member functions must return void");
        static_cast<_Receiver&&>(__rcvr).set_stopped();
    }

    template <class _Receiver>
        requires tag_invocable<set_stopped_t, _Receiver>
    STDEXEC_ATTRIBUTE((host, device, always_inline))
    void operator()(_Receiver&& __rcvr) const noexcept
    {
        static_assert(nothrow_tag_invocable<set_stopped_t, _Receiver>);
        (void)tag_invoke(stdexec::set_stopped_t{},
                         static_cast<_Receiver&&>(__rcvr));
    }
};
} // namespace __rcvrs

using __rcvrs::set_error_t;
using __rcvrs::set_stopped_t;
using __rcvrs::set_value_t;
inline constexpr set_value_t set_value{};
inline constexpr set_error_t set_error{};
inline constexpr set_stopped_t set_stopped{};

struct receiver_t
{
    using receiver_concept = receiver_t; // NOT TO SPEC
};

namespace __detail
{
template <class _Receiver>
concept __enable_receiver =                                              //
    (STDEXEC_NVHPC(requires { typename _Receiver::receiver_concept; }&&) //
     derived_from<typename _Receiver::receiver_concept, receiver_t>) ||
    requires { typename _Receiver::is_receiver; } // back-compat, NOT TO SPEC
    || STDEXEC_IS_BASE_OF(receiver_t,
                          _Receiver); // NOT TO SPEC, for receiver_adaptor
} // namespace __detail

template <class _Receiver>
inline constexpr bool enable_receiver =
    __detail::__enable_receiver<_Receiver>; // NOT TO SPEC

template <class _Receiver>
concept receiver =                               //
    enable_receiver<__decay_t<_Receiver>>        //
    && environment_provider<__cref_t<_Receiver>> //
    && move_constructible<__decay_t<_Receiver>>  //
    && constructible_from<__decay_t<_Receiver>, _Receiver>;

namespace __detail
{
template <class _Receiver, class _Tag, class... _Args>
auto __try_completion(_Tag (*)(_Args...))
    -> __mexception<_MISSING_COMPLETION_SIGNAL_<_Tag(_Args...)>,
                    _WITH_RECEIVER_<_Receiver>>;

template <class _Receiver, class _Tag, class... _Args>
    requires nothrow_tag_invocable<_Tag, _Receiver, _Args...>
auto __try_completion(_Tag (*)(_Args...)) -> __msuccess;

template <class _Receiver, class... _Sigs>
auto __try_completions(completion_signatures<_Sigs...>*) //
    -> decltype((
        __msuccess(), ...,
        __detail::__try_completion<_Receiver>(static_cast<_Sigs*>(nullptr))));
} // namespace __detail

template <class _Receiver, class _Completions>
concept receiver_of =      //
    receiver<_Receiver> && //
    requires(_Completions* __completions) {
        {
            __detail::__try_completions<__decay_t<_Receiver>>(__completions)
        } -> __ok;
    };

template <class _Receiver, class _Sender>
concept __receiver_from =
    receiver_of<_Receiver,
                __completion_signatures_of_t<_Sender, env_of_t<_Receiver>>>;

/// A utility for calling set_value with the result of a function invocation:
template <bool _CanThrow = false, class _Receiver, class _Fun, class... _As>
void __set_value_invoke(_Receiver&& __rcvr, _Fun&& __fun,
                        _As&&... __as) noexcept(!_CanThrow)
{
    if constexpr (_CanThrow || __nothrow_invocable<_Fun, _As...>)
    {
        if constexpr (same_as<void, __invoke_result_t<_Fun, _As...>>)
        {
            __invoke(static_cast<_Fun&&>(__fun), static_cast<_As&&>(__as)...);
            stdexec::set_value(static_cast<_Receiver&&>(__rcvr));
        }
        else
        {
            set_value(static_cast<_Receiver&&>(__rcvr),
                      __invoke(static_cast<_Fun&&>(__fun),
                               static_cast<_As&&>(__as)...));
        }
    }
    else
    {
        try
        {
            stdexec::__set_value_invoke<true>(static_cast<_Receiver&&>(__rcvr),
                                              static_cast<_Fun&&>(__fun),
                                              static_cast<_As&&>(__as)...);
        }
        catch (...)
        {
            stdexec::set_error(static_cast<_Receiver&&>(__rcvr),
                               std::current_exception());
        }
    }
}
} // namespace stdexec