default_executor.hpp

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/*
    Copyright 2015 Adobe
    Distributed under the Boost Software License, Version 1.0.
    (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
*/
 
/**************************************************************************************************/
 
#ifndef STLAB_CONCURRENCY_DEFAULT_EXECUTOR_HPP
#define STLAB_CONCURRENCY_DEFAULT_EXECUTOR_HPP

 
#include <stlab/concurrency/task.hpp>
#include <stlab/execution/config.hpp>
 
#include <cstdint>
#include <type_traits>
#include <utility>
 
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namespace stlab {
inline namespace v2 {


using stlab_v2_task_proc = void (*)(void*) noexcept;

extern "C" void stlab_v2_default_executor_submit(const unsigned char* task_abi_guard,
                                                 const stlab_v2_task_concept* vtable,
                                                 stlab_v2_task_proc invoke,
                                                 void* source) noexcept;

extern "C" void stlab_v2_high_executor_submit(const unsigned char* task_abi_guard,
                                              const stlab_v2_task_concept* vtable,
                                              stlab_v2_task_proc invoke,
                                              void* source) noexcept;

extern "C" void stlab_v2_low_executor_submit(const unsigned char* task_abi_guard,
                                             const stlab_v2_task_concept* vtable,
                                             stlab_v2_task_proc invoke,
                                             void* source) noexcept;

extern "C" void stlab_v2_notify_default_executor_before_waiting() noexcept;

extern "C" std::int32_t stlab_v2_default_executor_supports_blocking() noexcept;

 
} // namespace v2
 
STLAB_EXECUTION_VERSION_NAMESPACE_BEGIN()

 
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namespace execution_detail {
 
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enum class executor_priority : std::uint8_t { high, medium, low };

inline void submit_executor_proc(executor_priority priority, task<void() noexcept>& t) {
    const auto* task_abi_guard = &current_task_storage_abi_guard::value;
    const auto* vtable = t.relocation_concept();
    const auto invoke = t.relocation_invoke();
    auto* source = t.relocation_source();
    switch (priority) {
        case executor_priority::high:
            stlab_v2_high_executor_submit(task_abi_guard, vtable, invoke, source);
            break;
        case executor_priority::medium:
            stlab_v2_default_executor_submit(task_abi_guard, vtable, invoke, source);
            break;
        case executor_priority::low:
            stlab_v2_low_executor_submit(task_abi_guard, vtable, invoke, source);
            break;
    }
}
 
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template <executor_priority P = executor_priority::medium>
struct executor_type {
    using result_type = void;

    template <class F>
    auto operator()(F&& f) const -> std::enable_if_t<std::is_nothrow_invocable_v<std::decay_t<F>>> {
        task<void() noexcept> t{std::forward<F>(f)};
        submit_executor_proc(P, t);
    }
};
 
/**************************************************************************************************/
 
} // namespace execution_detail
 
/**************************************************************************************************/

inline constexpr auto low_executor =
    execution_detail::executor_type<execution_detail::executor_priority::low>{};

inline constexpr auto default_executor =
    execution_detail::executor_type<execution_detail::executor_priority::medium>{};

inline constexpr auto high_executor =
    execution_detail::executor_type<execution_detail::executor_priority::high>{};
 
/**************************************************************************************************/

 
STLAB_EXECUTION_VERSION_NAMESPACE_END()
} // namespace stlab
 
/**************************************************************************************************/
 
#endif
 
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