source: mainline/uspace/lib/cpp/include/__bits/thread/future_common.hpp

/*
 * Copyright (c) 2019 Jaroslav Jindrak
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef LIBCPP_BITS_THREAD_FUTURE_COMMON
#define LIBCPP_BITS_THREAD_FUTURE_COMMON

#include <__bits/aux.hpp>
#include <system_error>
#include <stdexcept>

namespace std
{
    /**
     * 30.6, futures:
     */

    enum class future_errc
    { // The 5001 start is to not collide with system_error's codes.
        broken_promise = 5001,
        future_already_retrieved,
        promise_already_satisfied,
        no_state
    };

    enum class future_status
    {
        ready,
        timeout,
        deferred
    };

    /**
     * 30.6.2, error handling:
     */

    template<>
    struct is_error_code_enum<future_errc>: true_type
    { /* DUMMY BODY */ };

    error_code make_error_code(future_errc) noexcept;
    error_condition make_error_condition(future_errc) noexcept;

    const error_category& future_category() noexcept;

    /**
     * 30.6.3, class future_error:
     */

    class future_error: public logic_error
    {
        public:
            future_error(error_code ec);

            const error_code& code() const noexcept;
            const char* what() const noexcept;

        private:
            error_code code_;
    };

    namespace aux
    {
        /**
         * Auxilliary metafunctions that let us avoid
         * specializations in some cases. They represent
         * the inner stored type and the return type of
         * the get() member function, respectively.
         */

        template<class T>
        struct future_inner: aux::type_is<T>
        { /* DUMMY BODY */ };

        template<class T>
        struct future_inner<T&>: aux::type_is<T*>
        { /* DUMMY BODY */ };

        template<class T>
        using future_inner_t = typename future_inner<T>::type;

        template<class T>
        struct future_return_shared: aux::type_is<const T&>
        { /* DUMMY BODY */ };

        template<class T>
        struct future_return_shared<T&>: aux::type_is<T&>
        { /* DUMMY BODY */ };

        template<>
        struct future_return_shared<void>: aux::type_is<void>
        { /* DUMMY BODY */ };

        template<class T>
        using future_return_shared_t = typename future_return_shared<T>::type;
    }
}

#endif