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- /* Essentially an internal optional implementation :)
- (C) 2017-2019 Niall Douglas <http://www.nedproductions.biz/> (24 commits)
- File Created: June 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_VALUE_STORAGE_HPP
- #define BOOST_OUTCOME_VALUE_STORAGE_HPP
- #include "../config.hpp"
- BOOST_OUTCOME_V2_NAMESPACE_BEGIN
- namespace detail
- {
- template <class T, bool nothrow> struct strong_swap_impl
- {
- constexpr strong_swap_impl(bool &allgood, T &a, T &b)
- {
- allgood = true;
- using std::swap;
- swap(a, b);
- }
- };
- #ifndef BOOST_NO_EXCEPTIONS
- template <class T> struct strong_swap_impl<T, false>
- {
- strong_swap_impl(bool &allgood, T &a, T &b)
- {
- allgood = true;
- T v(static_cast<T &&>(a));
- try
- {
- a = static_cast<T &&>(b);
- }
- catch(...)
- {
- // Try to put back a
- try
- {
- a = static_cast<T &&>(v);
- // fall through as all good
- }
- catch(...)
- {
- // failed to completely restore
- allgood = false;
- // throw away second exception
- }
- throw; // rethrow original exception
- }
- // b has been moved to a, try to move v to b
- try
- {
- b = static_cast<T &&>(v);
- }
- catch(...)
- {
- // Try to restore a to b, and v to a
- try
- {
- b = static_cast<T &&>(a);
- a = static_cast<T &&>(v);
- // fall through as all good
- }
- catch(...)
- {
- // failed to completely restore
- allgood = false;
- // throw away second exception
- }
- throw; // rethrow original exception
- }
- }
- };
- #endif
- } // namespace detail
- /*!
- */
- BOOST_OUTCOME_TEMPLATE(class T)
- BOOST_OUTCOME_TREQUIRES(BOOST_OUTCOME_TPRED(std::is_move_constructible<T>::value &&std::is_move_assignable<T>::value))
- constexpr inline void strong_swap(bool &allgood, T &a, T &b) noexcept(detail::is_nothrow_swappable<T>::value)
- {
- detail::strong_swap_impl<T, detail::is_nothrow_swappable<T>::value>(allgood, a, b);
- }
- namespace detail
- {
- using status_bitfield_type = uint32_t;
- // WARNING: These bits are not tracked by abi-dumper, but changing them will break ABI!
- static constexpr status_bitfield_type status_have_value = (1U << 0U);
- static constexpr status_bitfield_type status_have_error = (1U << 1U);
- static constexpr status_bitfield_type status_have_exception = (1U << 2U);
- static constexpr status_bitfield_type status_lost_consistency = (1U << 3U); // failed to complete a strong swap
- static constexpr status_bitfield_type status_error_is_errno = (1U << 4U); // can errno be set from this error?
- // bit 7 unused
- // bits 8-15 unused
- // bits 16-31 used for user supplied 16 bit value
- static constexpr status_bitfield_type status_2byte_shift = 16;
- static constexpr status_bitfield_type status_2byte_mask = (0xffffU << status_2byte_shift);
- // Used if T is trivial
- template <class T> struct value_storage_trivial
- {
- using value_type = T;
- union {
- empty_type _empty;
- devoid<T> _value;
- };
- status_bitfield_type _status{0};
- constexpr value_storage_trivial() noexcept
- : _empty{}
- {
- }
- // Special from-void catchall constructor, always constructs default T irrespective of whether void is valued or not (can do no better if T cannot be copied)
- struct disable_void_catchall
- {
- };
- using void_value_storage_trivial = std::conditional_t<std::is_void<T>::value, disable_void_catchall, value_storage_trivial<void>>;
- explicit constexpr value_storage_trivial(const void_value_storage_trivial &o) noexcept(std::is_nothrow_default_constructible<value_type>::value)
- : _value()
- , _status(o._status)
- {
- }
- value_storage_trivial(const value_storage_trivial &) = default; // NOLINT
- value_storage_trivial(value_storage_trivial &&) = default; // NOLINT
- value_storage_trivial &operator=(const value_storage_trivial &) = default; // NOLINT
- value_storage_trivial &operator=(value_storage_trivial &&) = default; // NOLINT
- ~value_storage_trivial() = default;
- constexpr explicit value_storage_trivial(status_bitfield_type status)
- : _empty()
- , _status(status)
- {
- }
- template <class... Args>
- constexpr explicit value_storage_trivial(in_place_type_t<value_type> /*unused*/, Args &&... args) noexcept(std::is_nothrow_constructible<value_type, Args...>::value)
- : _value(static_cast<Args &&>(args)...)
- , _status(status_have_value)
- {
- }
- template <class U, class... Args>
- constexpr value_storage_trivial(in_place_type_t<value_type> /*unused*/, std::initializer_list<U> il, Args &&... args) noexcept(std::is_nothrow_constructible<value_type, std::initializer_list<U>, Args...>::value)
- : _value(il, static_cast<Args &&>(args)...)
- , _status(status_have_value)
- {
- }
- template <class U> static constexpr bool enable_converting_constructor = !std::is_same<std::decay_t<U>, value_type>::value && std::is_constructible<value_type, U>::value;
- BOOST_OUTCOME_TEMPLATE(class U)
- BOOST_OUTCOME_TREQUIRES(BOOST_OUTCOME_TPRED(enable_converting_constructor<U>))
- constexpr explicit value_storage_trivial(const value_storage_trivial<U> &o) noexcept(std::is_nothrow_constructible<value_type, U>::value)
- : value_storage_trivial(((o._status & status_have_value) != 0) ? value_storage_trivial(in_place_type<value_type>, o._value) : value_storage_trivial()) // NOLINT
- {
- _status = o._status;
- }
- BOOST_OUTCOME_TEMPLATE(class U)
- BOOST_OUTCOME_TREQUIRES(BOOST_OUTCOME_TPRED(enable_converting_constructor<U>))
- constexpr explicit value_storage_trivial(value_storage_trivial<U> &&o) noexcept(std::is_nothrow_constructible<value_type, U>::value)
- : value_storage_trivial(((o._status & status_have_value) != 0) ? value_storage_trivial(in_place_type<value_type>, static_cast<U &&>(o._value)) : value_storage_trivial()) // NOLINT
- {
- _status = o._status;
- }
- constexpr void swap(value_storage_trivial &o) noexcept
- {
- // storage is trivial, so just use assignment
- auto temp = static_cast<value_storage_trivial &&>(*this);
- *this = static_cast<value_storage_trivial &&>(o);
- o = static_cast<value_storage_trivial &&>(temp);
- }
- };
- // Used if T is non-trivial
- template <class T> struct value_storage_nontrivial
- {
- using value_type = T;
- union {
- empty_type _empty;
- value_type _value;
- };
- status_bitfield_type _status{0};
- value_storage_nontrivial() noexcept
- : _empty{}
- {
- }
- value_storage_nontrivial &operator=(const value_storage_nontrivial &) = default; // if reaches here, copy assignment is trivial
- value_storage_nontrivial &operator=(value_storage_nontrivial &&) = default; // NOLINT if reaches here, move assignment is trivial
- value_storage_nontrivial(value_storage_nontrivial &&o) noexcept(std::is_nothrow_move_constructible<value_type>::value) // NOLINT
- : _status(o._status)
- {
- if(this->_status & status_have_value)
- {
- this->_status &= ~status_have_value;
- new(&_value) value_type(static_cast<value_type &&>(o._value)); // NOLINT
- _status = o._status;
- }
- }
- value_storage_nontrivial(const value_storage_nontrivial &o) noexcept(std::is_nothrow_copy_constructible<value_type>::value)
- : _status(o._status)
- {
- if(this->_status & status_have_value)
- {
- this->_status &= ~status_have_value;
- new(&_value) value_type(o._value); // NOLINT
- _status = o._status;
- }
- }
- // Special from-void constructor, constructs default T if void valued
- explicit value_storage_nontrivial(const value_storage_trivial<void> &o) noexcept(std::is_nothrow_default_constructible<value_type>::value)
- : _status(o._status)
- {
- if(this->_status & status_have_value)
- {
- this->_status &= ~status_have_value;
- new(&_value) value_type; // NOLINT
- _status = o._status;
- }
- }
- explicit value_storage_nontrivial(status_bitfield_type status)
- : _empty()
- , _status(status)
- {
- }
- template <class... Args>
- explicit value_storage_nontrivial(in_place_type_t<value_type> /*unused*/, Args &&... args) noexcept(std::is_nothrow_constructible<value_type, Args...>::value)
- : _value(static_cast<Args &&>(args)...) // NOLINT
- , _status(status_have_value)
- {
- }
- template <class U, class... Args>
- value_storage_nontrivial(in_place_type_t<value_type> /*unused*/, std::initializer_list<U> il, Args &&... args) noexcept(std::is_nothrow_constructible<value_type, std::initializer_list<U>, Args...>::value)
- : _value(il, static_cast<Args &&>(args)...)
- , _status(status_have_value)
- {
- }
- template <class U> static constexpr bool enable_converting_constructor = !std::is_same<std::decay_t<U>, value_type>::value && std::is_constructible<value_type, U>::value;
- BOOST_OUTCOME_TEMPLATE(class U)
- BOOST_OUTCOME_TREQUIRES(BOOST_OUTCOME_TPRED(enable_converting_constructor<U>))
- constexpr explicit value_storage_nontrivial(const value_storage_nontrivial<U> &o) noexcept(std::is_nothrow_constructible<value_type, U>::value)
- : value_storage_nontrivial((o._status & status_have_value) != 0 ? value_storage_nontrivial(in_place_type<value_type>, o._value) : value_storage_nontrivial())
- {
- _status = o._status;
- }
- BOOST_OUTCOME_TEMPLATE(class U)
- BOOST_OUTCOME_TREQUIRES(BOOST_OUTCOME_TPRED(enable_converting_constructor<U>))
- constexpr explicit value_storage_nontrivial(const value_storage_trivial<U> &o) noexcept(std::is_nothrow_constructible<value_type, U>::value)
- : value_storage_nontrivial((o._status & status_have_value) != 0 ? value_storage_nontrivial(in_place_type<value_type>, o._value) : value_storage_nontrivial())
- {
- _status = o._status;
- }
- BOOST_OUTCOME_TEMPLATE(class U)
- BOOST_OUTCOME_TREQUIRES(BOOST_OUTCOME_TPRED(enable_converting_constructor<U>))
- constexpr explicit value_storage_nontrivial(value_storage_nontrivial<U> &&o) noexcept(std::is_nothrow_constructible<value_type, U>::value)
- : value_storage_nontrivial((o._status & status_have_value) != 0 ? value_storage_nontrivial(in_place_type<value_type>, static_cast<U &&>(o._value)) : value_storage_nontrivial())
- {
- _status = o._status;
- }
- BOOST_OUTCOME_TEMPLATE(class U)
- BOOST_OUTCOME_TREQUIRES(BOOST_OUTCOME_TPRED(enable_converting_constructor<U>))
- constexpr explicit value_storage_nontrivial(value_storage_trivial<U> &&o) noexcept(std::is_nothrow_constructible<value_type, U>::value)
- : value_storage_nontrivial((o._status & status_have_value) != 0 ? value_storage_nontrivial(in_place_type<value_type>, static_cast<U &&>(o._value)) : value_storage_nontrivial())
- {
- _status = o._status;
- }
- ~value_storage_nontrivial() noexcept(std::is_nothrow_destructible<T>::value)
- {
- if(this->_status & status_have_value)
- {
- this->_value.~value_type(); // NOLINT
- this->_status &= ~status_have_value;
- }
- }
- constexpr void swap(value_storage_nontrivial &o) noexcept(detail::is_nothrow_swappable<value_type>::value)
- {
- using std::swap;
- if((_status & status_have_value) == 0 && (o._status & status_have_value) == 0)
- {
- swap(_status, o._status);
- return;
- }
- if((_status & status_have_value) != 0 && (o._status & status_have_value) != 0)
- {
- 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;
- }
- }
- } _{_status, o._status};
- strong_swap(_.all_good, _value, o._value);
- swap(_status, o._status);
- return;
- }
- // One must be empty and the other non-empty, so use move construction
- if((_status & status_have_value) != 0)
- {
- // Move construct me into other
- new(&o._value) value_type(static_cast<value_type &&>(_value)); // NOLINT
- this->_value.~value_type(); // NOLINT
- swap(_status, o._status);
- }
- else
- {
- // Move construct other into me
- new(&_value) value_type(static_cast<value_type &&>(o._value)); // NOLINT
- o._value.~value_type(); // NOLINT
- swap(_status, o._status);
- }
- }
- };
- template <class Base> struct value_storage_delete_copy_constructor : Base // NOLINT
- {
- using Base::Base;
- using value_type = typename Base::value_type;
- value_storage_delete_copy_constructor() = default;
- value_storage_delete_copy_constructor(const value_storage_delete_copy_constructor &) = delete;
- value_storage_delete_copy_constructor(value_storage_delete_copy_constructor &&) = default; // NOLINT
- };
- template <class Base> struct value_storage_delete_copy_assignment : Base // NOLINT
- {
- using Base::Base;
- using value_type = typename Base::value_type;
- value_storage_delete_copy_assignment() = default;
- value_storage_delete_copy_assignment(const value_storage_delete_copy_assignment &) = default;
- value_storage_delete_copy_assignment(value_storage_delete_copy_assignment &&) = default; // NOLINT
- value_storage_delete_copy_assignment &operator=(const value_storage_delete_copy_assignment &o) = delete;
- value_storage_delete_copy_assignment &operator=(value_storage_delete_copy_assignment &&o) = default; // NOLINT
- };
- template <class Base> struct value_storage_delete_move_assignment : Base // NOLINT
- {
- using Base::Base;
- using value_type = typename Base::value_type;
- value_storage_delete_move_assignment() = default;
- value_storage_delete_move_assignment(const value_storage_delete_move_assignment &) = default;
- value_storage_delete_move_assignment(value_storage_delete_move_assignment &&) = default; // NOLINT
- value_storage_delete_move_assignment &operator=(const value_storage_delete_move_assignment &o) = default;
- value_storage_delete_move_assignment &operator=(value_storage_delete_move_assignment &&o) = delete;
- };
- template <class Base> struct value_storage_delete_move_constructor : Base // NOLINT
- {
- using Base::Base;
- using value_type = typename Base::value_type;
- value_storage_delete_move_constructor() = default;
- value_storage_delete_move_constructor(const value_storage_delete_move_constructor &) = default;
- value_storage_delete_move_constructor(value_storage_delete_move_constructor &&) = delete;
- };
- template <class Base> struct value_storage_nontrivial_move_assignment : Base // NOLINT
- {
- using Base::Base;
- using value_type = typename Base::value_type;
- value_storage_nontrivial_move_assignment() = default;
- value_storage_nontrivial_move_assignment(const value_storage_nontrivial_move_assignment &) = default;
- value_storage_nontrivial_move_assignment(value_storage_nontrivial_move_assignment &&) = default; // NOLINT
- value_storage_nontrivial_move_assignment &operator=(const value_storage_nontrivial_move_assignment &o) = default;
- value_storage_nontrivial_move_assignment &operator=(value_storage_nontrivial_move_assignment &&o) noexcept(std::is_nothrow_move_assignable<value_type>::value) // NOLINT
- {
- if((this->_status & status_have_value) != 0 && (o._status & status_have_value) != 0)
- {
- this->_value = static_cast<value_type &&>(o._value); // NOLINT
- }
- else if((this->_status & status_have_value) != 0 && (o._status & status_have_value) == 0)
- {
- this->_value.~value_type(); // NOLINT
- }
- else if((this->_status & status_have_value) == 0 && (o._status & status_have_value) != 0)
- {
- new(&this->_value) value_type(static_cast<value_type &&>(o._value)); // NOLINT
- }
- this->_status = o._status;
- return *this;
- }
- };
- template <class Base> struct value_storage_nontrivial_copy_assignment : Base // NOLINT
- {
- using Base::Base;
- using value_type = typename Base::value_type;
- value_storage_nontrivial_copy_assignment() = default;
- value_storage_nontrivial_copy_assignment(const value_storage_nontrivial_copy_assignment &) = default;
- value_storage_nontrivial_copy_assignment(value_storage_nontrivial_copy_assignment &&) = default; // NOLINT
- value_storage_nontrivial_copy_assignment &operator=(value_storage_nontrivial_copy_assignment &&o) = default; // NOLINT
- value_storage_nontrivial_copy_assignment &operator=(const value_storage_nontrivial_copy_assignment &o) noexcept(std::is_nothrow_copy_assignable<value_type>::value)
- {
- if((this->_status & status_have_value) != 0 && (o._status & status_have_value) != 0)
- {
- this->_value = o._value; // NOLINT
- }
- else if((this->_status & status_have_value) != 0 && (o._status & status_have_value) == 0)
- {
- this->_value.~value_type(); // NOLINT
- }
- else if((this->_status & status_have_value) == 0 && (o._status & status_have_value) != 0)
- {
- new(&this->_value) value_type(o._value); // NOLINT
- }
- this->_status = o._status;
- return *this;
- }
- };
- // We don't actually need all of std::is_trivial<>, std::is_trivially_copyable<> is sufficient
- template <class T> using value_storage_select_trivality = std::conditional_t<std::is_trivially_copyable<devoid<T>>::value, value_storage_trivial<T>, value_storage_nontrivial<T>>;
- template <class T> using value_storage_select_move_constructor = std::conditional_t<std::is_move_constructible<devoid<T>>::value, value_storage_select_trivality<T>, value_storage_delete_move_constructor<value_storage_select_trivality<T>>>;
- template <class T> using value_storage_select_copy_constructor = std::conditional_t<std::is_copy_constructible<devoid<T>>::value, value_storage_select_move_constructor<T>, value_storage_delete_copy_constructor<value_storage_select_move_constructor<T>>>;
- template <class T>
- using value_storage_select_move_assignment = std::conditional_t<std::is_trivially_move_assignable<devoid<T>>::value, value_storage_select_copy_constructor<T>,
- std::conditional_t<std::is_move_assignable<devoid<T>>::value, value_storage_nontrivial_move_assignment<value_storage_select_copy_constructor<T>>, value_storage_delete_copy_assignment<value_storage_select_copy_constructor<T>>>>;
- template <class T>
- using value_storage_select_copy_assignment = std::conditional_t<std::is_trivially_copy_assignable<devoid<T>>::value, value_storage_select_move_assignment<T>,
- std::conditional_t<std::is_copy_assignable<devoid<T>>::value, value_storage_nontrivial_copy_assignment<value_storage_select_move_assignment<T>>, value_storage_delete_copy_assignment<value_storage_select_move_assignment<T>>>>;
- template <class T> using value_storage_select_impl = value_storage_select_copy_assignment<T>;
- #ifndef NDEBUG
- // Check is trivial in all ways except default constructibility
- // static_assert(std::is_trivial<value_storage_select_impl<int>>::value, "value_storage_select_impl<int> is not trivial!");
- // static_assert(std::is_trivially_default_constructible<value_storage_select_impl<int>>::value, "value_storage_select_impl<int> is not trivially default constructible!");
- static_assert(std::is_trivially_copyable<value_storage_select_impl<int>>::value, "value_storage_select_impl<int> is not trivially copyable!");
- static_assert(std::is_trivially_assignable<value_storage_select_impl<int>, value_storage_select_impl<int>>::value, "value_storage_select_impl<int> is not trivially assignable!");
- static_assert(std::is_trivially_destructible<value_storage_select_impl<int>>::value, "value_storage_select_impl<int> is not trivially destructible!");
- static_assert(std::is_trivially_copy_constructible<value_storage_select_impl<int>>::value, "value_storage_select_impl<int> is not trivially copy constructible!");
- static_assert(std::is_trivially_move_constructible<value_storage_select_impl<int>>::value, "value_storage_select_impl<int> is not trivially move constructible!");
- static_assert(std::is_trivially_copy_assignable<value_storage_select_impl<int>>::value, "value_storage_select_impl<int> is not trivially copy assignable!");
- static_assert(std::is_trivially_move_assignable<value_storage_select_impl<int>>::value, "value_storage_select_impl<int> is not trivially move assignable!");
- // Also check is standard layout
- static_assert(std::is_standard_layout<value_storage_select_impl<int>>::value, "value_storage_select_impl<int> is not a standard layout type!");
- #endif
- } // namespace detail
- BOOST_OUTCOME_V2_NAMESPACE_END
- #endif
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