scope_exit.hpp

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// Range v3 library
//
//  Copyright Eric Niebler 2017-present
//
//  Use, modification and distribution is subject to 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)
//
// Project home: https://github.com/ericniebler/range-v3
//
#ifndef RANGES_V3_UTILITY_SCOPE_EXIT_HPP
#define RANGES_V3_UTILITY_SCOPE_EXIT_HPP
 
#include <functional>
#include <type_traits>
#include <utility>
 
#include <meta/meta.hpp>
 
#include <range/v3/detail/prologue.hpp>
 
namespace ranges
{
    template<typename Fun>
    struct scope_exit
    {
    private:
        using nothrow_move_t = std::is_nothrow_move_constructible<Fun>;
        using nothrow_copy_t = std::is_nothrow_copy_constructible<Fun>;
 
        Fun fun_;
        bool dismissed_{false};
 
        using ref_t = decltype(std::ref(std::declval<Fun const &>()));
        using guard = scope_exit<ref_t>;
 
        scope_exit(Fun const & fun, guard && g)
          : fun_(fun)
        {
            g.dismiss();
        }
 
        scope_exit(Fun const & fun, std::false_type)
          : scope_exit(fun, guard{std::ref(fun)})
        {}
 
        scope_exit(Fun const & fun, std::true_type) noexcept
          : fun_(fun)
        {}
 
        scope_exit(Fun && fun, std::true_type) noexcept
          : fun_(std::move(fun))
        {}
 
    public:
        explicit scope_exit(Fun const & fun) noexcept(
            noexcept(scope_exit(fun, nothrow_copy_t{})))
          : scope_exit(fun, nothrow_copy_t{})
        {}
 
        explicit scope_exit(Fun && fun) noexcept(noexcept(scope_exit(std::move(fun),
                                                                     nothrow_move_t{})))
          : scope_exit(std::move(fun), nothrow_move_t{})
        {}
 
        scope_exit(scope_exit const &) = delete;
 
        scope_exit(scope_exit && that) noexcept(
            std::is_nothrow_move_constructible<Fun>::value)
          : scope_exit(std::move((that.dismiss(), that)).fun_)
        {}
 
        ~scope_exit()
        {
            if(!dismissed_)
                fun_();
        }
 
        void dismiss() noexcept
        {
            dismissed_ = true;
        }
    };
 
    template<typename Fun, typename ScopeExit = scope_exit<meta::_t<std::decay<Fun>>>>
    ScopeExit make_scope_exit(Fun && fun) noexcept(
        noexcept(ScopeExit(ScopeExit((Fun &&) fun))))
    {
        return ScopeExit((Fun &&) fun);
    }
} // namespace ranges
 
#include <range/v3/detail/epilogue.hpp>
 
#endif