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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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