include/sdbusplus/async/stdexec/__detail/__cpo.hpp

/*
 * Copyright (c) 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 "__config.hpp"
#include "__execution_fwd.hpp"

#define STDEXEC_EAT_THIS_this
#define STDEXEC_EAT_AUTO_auto
#define STDEXEC_EAT_VOID_void

///////////////////////////////////////////////////////////////////////////////
/// To hook a customization point like stdexec::get_env, first bring the names
/// in stdexec::tags into scope:
///
/// @code
/// using namespace stdexec::tags;
/// @endcode
///
/// Then define a member function like this:
///
/// @code
/// STDEXEC_MEMFN_DECL(auto get_env)(this const MySender& self) {
///   return ...;
/// }
/// @endcode
#define STDEXEC_MEMFN_DECL(...)                                                \
    friend STDEXEC_TAG_INVOKE(STDEXEC_IS_AUTO(__VA_ARGS__), __VA_ARGS__)       \
        STDEXEC_TAG_INVOKE_ARGS

#define STDEXEC_TAG_INVOKE(_ISAUTO, ...)                                        \
    STDEXEC_IIF(_ISAUTO, STDEXEC_RETURN_AUTO, STDEXEC_RETURN_TYPE)(__VA_ARGS__) \
    tag_invoke( \
    STDEXEC_IIF(_ISAUTO, STDEXEC_TAG_AUTO, STDEXEC_TAG_WHAT)(__VA_ARGS__)

#define STDEXEC_PROBE_AUTO_auto STDEXEC_PROBE(~)
#define STDEXEC_IS_AUTO(_TY, ...)                                              \
    STDEXEC_CHECK(STDEXEC_CAT(STDEXEC_PROBE_AUTO_, _TY))

#define STDEXEC_PROBE_VOID_void STDEXEC_PROBE(~)
#define STDEXEC_IS_VOID(_TY, ...)                                              \
    STDEXEC_CHECK(STDEXEC_CAT(STDEXEC_PROBE_VOID_, _TY))

#define STDEXEC_RETURN_AUTO(...) auto
#define STDEXEC_RETURN_TYPE(...) ::stdexec::__arg_type_t<void(__VA_ARGS__())>

#define STDEXEC_TAG_AUTO(...)                                                  \
    STDEXEC_CAT(STDEXEC_CAT(STDEXEC_EAT_AUTO_, __VA_ARGS__), _t)
#define STDEXEC_TAG_WHAT(...)                                                  \
    STDEXEC_IIF(STDEXEC_IS_VOID(__VA_ARGS__), STDEXEC_TAG_VOID,                \
                STDEXEC_TAG_TYPE)                                              \
    (__VA_ARGS__)

#define STDEXEC_TAG_VOID(...)                                                  \
    STDEXEC_CAT(STDEXEC_CAT(STDEXEC_EAT_VOID_, __VA_ARGS__), _t)
#define STDEXEC_TAG_TYPE(...)                                                  \
    ::stdexec::__tag_type_t<STDEXEC_CAT(__VA_ARGS__, _t::*)>

#define STDEXEC_TAG_INVOKE_ARGS(...)                                           \
    __VA_OPT__(,) STDEXEC_CAT(STDEXEC_EAT_THIS_, __VA_ARGS__))

#if STDEXEC_MSVC()
#pragma deprecated(STDEXEC_CUSTOM)
#endif

#if STDEXEC_GCC() || (STDEXEC_CLANG() && __clang_major__ < 14)
#define STDEXEC_CUSTOM                                                                   \
    _Pragma(                                                                             \
        "GCC warning \"STDEXEC_CUSTOM is deprecated; use STDEXEC_MEMFN_DECL instead.\"") \
        STDEXEC_MEMFN_DECL
#else
#define STDEXEC_CUSTOM STDEXEC_MEMFN_DECL
#endif

#if STDEXEC_CLANG() && __clang_major__ >= 14
#pragma clang deprecated(STDEXEC_CUSTOM, "use STDEXEC_MEMFN_DECL instead.")
#endif

namespace stdexec
{
template <class>
struct __arg_type;

template <class _Arg>
struct __arg_type<void(_Arg (*)())>
{
    using type = _Arg;
};

template <class _Fn>
using __arg_type_t = typename __arg_type<_Fn>::type;

template <class>
struct __tag_type;

template <class _Ret, class _Tag>
struct __tag_type<_Ret _Tag::*>
{
    using type = _Tag;
};

template <class _Fn>
using __tag_type_t = typename __tag_type<_Fn>::type;

namespace tags
{
using stdexec::connect_t;
using stdexec::get_completion_signatures_t;
using stdexec::get_env_t;
using stdexec::set_error_t;
using stdexec::set_stopped_t;
using stdexec::set_value_t;
using stdexec::start_t;
} // namespace tags
} // namespace stdexec