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- /* Storage for a very simple basic_result type
- (C) 2017-2019 Niall Douglas <http://www.nedproductions.biz/> (6 commits)
- File Created: Oct 2017
- Boost Software License - Version 1.0 - August 17th, 2003
- Permission is hereby granted, free of charge, to any person or organization
- obtaining a copy of the software and accompanying documentation covered by
- this license (the "Software") to use, reproduce, display, distribute,
- execute, and transmit the Software, and to prepare derivative works of the
- Software, and to permit third-parties to whom the Software is furnished to
- do so, all subject to the following:
- The copyright notices in the Software and this entire statement, including
- the above license grant, this restriction and the following disclaimer,
- must be included in all copies of the Software, in whole or in part, and
- all derivative works of the Software, unless such copies or derivative
- works are solely in the form of machine-executable object code generated by
- a source language processor.
- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
- SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
- FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
- ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
- DEALINGS IN THE SOFTWARE.
- */
- #ifndef BOOST_OUTCOME_BASIC_RESULT_STORAGE_HPP
- #define BOOST_OUTCOME_BASIC_RESULT_STORAGE_HPP
- #include "../success_failure.hpp"
- #include "../trait.hpp"
- #include "value_storage.hpp"
- BOOST_OUTCOME_V2_NAMESPACE_EXPORT_BEGIN
- namespace detail
- {
- template <class State, class E> constexpr inline void _set_error_is_errno(State & /*unused*/, const E & /*unused*/) {}
- template <class R, class S, class NoValuePolicy> class basic_result_final;
- } // namespace detail
- namespace hooks
- {
- template <class R, class S, class NoValuePolicy> constexpr inline uint16_t spare_storage(const detail::basic_result_final<R, S, NoValuePolicy> *r) noexcept;
- template <class R, class S, class NoValuePolicy> constexpr inline void set_spare_storage(detail::basic_result_final<R, S, NoValuePolicy> *r, uint16_t v) noexcept;
- } // namespace hooks
- namespace policy
- {
- struct base;
- } // namespace policy
- namespace detail
- {
- template <bool value_throws, bool error_throws> struct basic_result_storage_swap;
- template <class R, class EC, class NoValuePolicy> //
- BOOST_OUTCOME_REQUIRES(trait::type_can_be_used_in_basic_result<R> &&trait::type_can_be_used_in_basic_result<EC> && (std::is_void<EC>::value || std::is_default_constructible<EC>::value)) //
- class basic_result_storage;
- template <class R, class EC, class NoValuePolicy> //
- BOOST_OUTCOME_REQUIRES(trait::type_can_be_used_in_basic_result<R> &&trait::type_can_be_used_in_basic_result<EC> && (std::is_void<EC>::value || std::is_default_constructible<EC>::value)) //
- class basic_result_storage
- {
- static_assert(trait::type_can_be_used_in_basic_result<R>, "The type R cannot be used in a basic_result");
- static_assert(trait::type_can_be_used_in_basic_result<EC>, "The type S cannot be used in a basic_result");
- static_assert(std::is_void<EC>::value || std::is_default_constructible<EC>::value, "The type S must be void or default constructible");
- friend struct policy::base;
- template <class T, class U, class V> //
- BOOST_OUTCOME_REQUIRES(trait::type_can_be_used_in_basic_result<T> &&trait::type_can_be_used_in_basic_result<U> && (std::is_void<U>::value || std::is_default_constructible<U>::value)) //
- friend class basic_result_storage;
- template <class T, class U, class V> friend class basic_result_final;
- template <class T, class U, class V> friend constexpr inline uint16_t hooks::spare_storage(const detail::basic_result_final<T, U, V> *r) noexcept; // NOLINT
- template <class T, class U, class V> friend constexpr inline void hooks::set_spare_storage(detail::basic_result_final<T, U, V> *r, uint16_t v) noexcept; // NOLINT
- template <bool value_throws, bool error_throws> struct basic_result_storage_swap;
- struct disable_in_place_value_type
- {
- };
- struct disable_in_place_error_type
- {
- };
- protected:
- using _value_type = std::conditional_t<std::is_same<R, EC>::value, disable_in_place_value_type, R>;
- using _error_type = std::conditional_t<std::is_same<R, EC>::value, disable_in_place_error_type, EC>;
- #ifdef BOOST_OUTCOME_STANDARDESE_IS_IN_THE_HOUSE
- detail::value_storage_trivial<_value_type> _state;
- #else
- detail::value_storage_select_impl<_value_type> _state;
- #endif
- detail::devoid<_error_type> _error;
- public:
- // Used by iostream support to access state
- detail::value_storage_select_impl<_value_type> &_iostreams_state() { return _state; }
- const detail::value_storage_select_impl<_value_type> &_iostreams_state() const { return _state; }
- // Hack to work around MSVC bug in /permissive-
- detail::value_storage_select_impl<_value_type> &_msvc_nonpermissive_state() { return _state; }
- detail::devoid<_error_type> &_msvc_nonpermissive_error() { return _error; }
- protected:
- basic_result_storage() = default;
- basic_result_storage(const basic_result_storage &) = default; // NOLINT
- basic_result_storage(basic_result_storage &&) = default; // NOLINT
- basic_result_storage &operator=(const basic_result_storage &) = default; // NOLINT
- basic_result_storage &operator=(basic_result_storage &&) = default; // NOLINT
- ~basic_result_storage() = default;
- template <class... Args>
- constexpr explicit basic_result_storage(in_place_type_t<_value_type> _, Args &&... args) noexcept(std::is_nothrow_constructible<_value_type, Args...>::value)
- : _state{_, static_cast<Args &&>(args)...}
- , _error()
- {
- }
- template <class U, class... Args>
- constexpr basic_result_storage(in_place_type_t<_value_type> _, std::initializer_list<U> il, Args &&... args) noexcept(std::is_nothrow_constructible<_value_type, std::initializer_list<U>, Args...>::value)
- : _state{_, il, static_cast<Args &&>(args)...}
- , _error()
- {
- }
- template <class... Args>
- constexpr explicit basic_result_storage(in_place_type_t<_error_type> /*unused*/, Args &&... args) noexcept(std::is_nothrow_constructible<_error_type, Args...>::value)
- : _state{detail::status_have_error}
- , _error(static_cast<Args &&>(args)...)
- {
- _set_error_is_errno(_state, _error);
- }
- template <class U, class... Args>
- constexpr basic_result_storage(in_place_type_t<_error_type> /*unused*/, std::initializer_list<U> il, Args &&... args) noexcept(std::is_nothrow_constructible<_error_type, std::initializer_list<U>, Args...>::value)
- : _state{detail::status_have_error}
- , _error{il, static_cast<Args &&>(args)...}
- {
- _set_error_is_errno(_state, _error);
- }
- struct compatible_conversion_tag
- {
- };
- template <class T, class U, class V>
- constexpr basic_result_storage(compatible_conversion_tag /*unused*/, const basic_result_storage<T, U, V> &o) noexcept(std::is_nothrow_constructible<_value_type, T>::value &&std::is_nothrow_constructible<_error_type, U>::value)
- : _state(o._state)
- , _error(o._error)
- {
- }
- template <class T, class V>
- constexpr basic_result_storage(compatible_conversion_tag /*unused*/, const basic_result_storage<T, void, V> &o) noexcept(std::is_nothrow_constructible<_value_type, T>::value)
- : _state(o._state)
- , _error(_error_type{})
- {
- }
- template <class T, class U, class V>
- constexpr basic_result_storage(compatible_conversion_tag /*unused*/, basic_result_storage<T, U, V> &&o) noexcept(std::is_nothrow_constructible<_value_type, T>::value &&std::is_nothrow_constructible<_error_type, U>::value)
- : _state(static_cast<decltype(o._state) &&>(o._state))
- , _error(static_cast<U &&>(o._error))
- {
- }
- template <class T, class V>
- constexpr basic_result_storage(compatible_conversion_tag /*unused*/, basic_result_storage<T, void, V> &&o) noexcept(std::is_nothrow_constructible<_value_type, T>::value)
- : _state(static_cast<decltype(o._state) &&>(o._state))
- , _error(_error_type{})
- {
- }
- struct make_error_code_compatible_conversion_tag
- {
- };
- template <class T, class U, class V>
- constexpr basic_result_storage(make_error_code_compatible_conversion_tag /*unused*/, const basic_result_storage<T, U, V> &o) noexcept(std::is_nothrow_constructible<_value_type, T>::value &&noexcept(make_error_code(std::declval<U>())))
- : _state(o._state)
- , _error(make_error_code(o._error))
- {
- }
- template <class T, class U, class V>
- constexpr basic_result_storage(make_error_code_compatible_conversion_tag /*unused*/, basic_result_storage<T, U, V> &&o) noexcept(std::is_nothrow_constructible<_value_type, T>::value &&noexcept(make_error_code(std::declval<U>())))
- : _state(static_cast<decltype(o._state) &&>(o._state))
- , _error(make_error_code(static_cast<U &&>(o._error)))
- {
- }
- struct make_exception_ptr_compatible_conversion_tag
- {
- };
- template <class T, class U, class V>
- constexpr basic_result_storage(make_exception_ptr_compatible_conversion_tag /*unused*/, const basic_result_storage<T, U, V> &o) noexcept(std::is_nothrow_constructible<_value_type, T>::value &&noexcept(make_exception_ptr(std::declval<U>())))
- : _state(o._state)
- , _error(make_exception_ptr(o._error))
- {
- }
- template <class T, class U, class V>
- constexpr basic_result_storage(make_exception_ptr_compatible_conversion_tag /*unused*/, basic_result_storage<T, U, V> &&o) noexcept(std::is_nothrow_constructible<_value_type, T>::value &&noexcept(make_exception_ptr(std::declval<U>())))
- : _state(static_cast<decltype(o._state) &&>(o._state))
- , _error(make_exception_ptr(static_cast<U &&>(o._error)))
- {
- }
- };
- // Neither value nor error type can throw during swap
- #ifndef BOOST_NO_EXCEPTIONS
- template <> struct basic_result_storage_swap<false, false>
- #else
- template <bool value_throws, bool error_throws> struct basic_result_storage_swap
- #endif
- {
- template <class R, class EC, class NoValuePolicy> constexpr basic_result_storage_swap(basic_result_storage<R, EC, NoValuePolicy> &a, basic_result_storage<R, EC, NoValuePolicy> &b)
- {
- using std::swap;
- a._msvc_nonpermissive_state().swap(b._msvc_nonpermissive_state());
- swap(a._msvc_nonpermissive_error(), b._msvc_nonpermissive_error());
- }
- };
- #ifndef BOOST_NO_EXCEPTIONS
- // Swap potentially throwing value first
- template <> struct basic_result_storage_swap<true, false>
- {
- template <class R, class EC, class NoValuePolicy> constexpr basic_result_storage_swap(basic_result_storage<R, EC, NoValuePolicy> &a, basic_result_storage<R, EC, NoValuePolicy> &b)
- {
- using std::swap;
- a._msvc_nonpermissive_state().swap(b._msvc_nonpermissive_state());
- swap(a._msvc_nonpermissive_error(), b._msvc_nonpermissive_error());
- }
- };
- // Swap potentially throwing error first
- template <> struct basic_result_storage_swap<false, true>
- {
- template <class R, class EC, class NoValuePolicy> constexpr basic_result_storage_swap(basic_result_storage<R, EC, NoValuePolicy> &a, basic_result_storage<R, EC, NoValuePolicy> &b)
- {
- struct _
- {
- unsigned &a, &b;
- bool all_good{false};
- ~_()
- {
- if(!all_good)
- {
- // We lost one of the values
- a |= status_lost_consistency;
- b |= status_lost_consistency;
- }
- }
- } _{a._msvc_nonpermissive_state()._status, b._msvc_nonpermissive_state()._status};
- strong_swap(_.all_good, a._msvc_nonpermissive_error(), b._msvc_nonpermissive_error());
- a._msvc_nonpermissive_state().swap(b._msvc_nonpermissive_state());
- }
- };
- // Both could throw
- template <> struct basic_result_storage_swap<true, true>
- {
- template <class R, class EC, class NoValuePolicy> basic_result_storage_swap(basic_result_storage<R, EC, NoValuePolicy> &a, basic_result_storage<R, EC, NoValuePolicy> &b)
- {
- using std::swap;
- // Swap value and status first, if it throws, status will remain unchanged
- a._msvc_nonpermissive_state().swap(b._msvc_nonpermissive_state());
- bool all_good = false;
- try
- {
- strong_swap(all_good, a._msvc_nonpermissive_error(), b._msvc_nonpermissive_error());
- }
- catch(...)
- {
- if(!all_good)
- {
- a._msvc_nonpermissive_state()._status |= detail::status_lost_consistency;
- b._msvc_nonpermissive_state()._status |= detail::status_lost_consistency;
- }
- else
- {
- // We may still be able to rescue tis
- // First try to put the value and status back
- try
- {
- a._msvc_nonpermissive_state().swap(b._msvc_nonpermissive_state());
- // If that succeeded, continue by rethrowing the exception
- }
- catch(...)
- {
- all_good = false;
- }
- }
- if(!all_good)
- {
- // We are now trapped. The value swapped, the error did not,
- // trying to restore the value failed. We now have
- // inconsistent result objects. Best we can do is fix up the
- // status bits to prevent has_value() == has_error().
- auto check = [](basic_result_storage<R, EC, NoValuePolicy> &x) {
- bool has_value = (x._state._status & detail::status_have_value) != 0;
- bool has_error = (x._state._status & detail::status_have_error) != 0;
- bool has_exception = (x._state._status & detail::status_have_exception) != 0;
- x._state._status |= detail::status_lost_consistency;
- if(has_value == (has_error || has_exception))
- {
- if(has_value)
- {
- // We know the value swapped and is now set, so clear error and exception
- x._state._status &= ~(detail::status_have_error | detail::status_have_exception);
- }
- else
- {
- // We know the value swapped and is now unset, so set error
- x._state._status |= detail::status_have_error;
- // TODO: Should I default construct reset _error? It's guaranteed default constructible.
- }
- }
- };
- check(a);
- check(b);
- }
- throw;
- }
- }
- };
- #endif
- } // namespace detail
- BOOST_OUTCOME_V2_NAMESPACE_END
- #endif
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