optional.hpp
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#ifndef BOOST_LEAF_DETAIL_OPTIONAL_HPP_INCLUDED
#define BOOST_LEAF_DETAIL_OPTIONAL_HPP_INCLUDED
// Copyright 2018-2022 Emil Dotchevski and Reverge Studios, Inc.
// Distributed under 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)
#include <boost/leaf/config.hpp>
#include <utility>
#include <new>
namespace boost { namespace leaf {
namespace leaf_detail
{
template <class T>
class optional
{
int key_;
union { T value_; };
public:
typedef T value_type;
BOOST_LEAF_CONSTEXPR optional() noexcept:
key_(0)
{
}
BOOST_LEAF_CONSTEXPR optional( optional const & x ):
key_(x.key_)
{
if( x.key_ )
(void) new (&value_) T( x.value_ );
}
BOOST_LEAF_CONSTEXPR optional( optional && x ) noexcept:
key_(x.key_)
{
if( x.key_ )
{
(void) new (&value_) T( std::move(x.value_) );
x.reset();
}
}
BOOST_LEAF_CONSTEXPR optional( int key, T const & v ):
key_(key),
value_(v)
{
BOOST_LEAF_ASSERT(!empty());
}
BOOST_LEAF_CONSTEXPR optional( int key, T && v ) noexcept:
key_(key),
value_(std::move(v))
{
BOOST_LEAF_ASSERT(!empty());
}
BOOST_LEAF_CONSTEXPR optional & operator=( optional const & x )
{
reset();
if( int key = x.key() )
{
put(key, x.value_);
key_ = key;
}
return *this;
}
BOOST_LEAF_CONSTEXPR optional & operator=( optional && x ) noexcept
{
reset();
if( int key = x.key() )
{
put(key, std::move(x.value_));
x.reset();
}
return *this;
}
~optional() noexcept
{
reset();
}
BOOST_LEAF_CONSTEXPR bool empty() const noexcept
{
return key_==0;
}
BOOST_LEAF_CONSTEXPR int key() const noexcept
{
return key_;
}
BOOST_LEAF_CONSTEXPR void reset() noexcept
{
if( key_ )
{
value_.~T();
key_=0;
}
}
BOOST_LEAF_CONSTEXPR T & put( int key, T const & v )
{
BOOST_LEAF_ASSERT(key);
reset();
(void) new(&value_) T(v);
key_=key;
return value_;
}
BOOST_LEAF_CONSTEXPR T & put( int key, T && v ) noexcept
{
BOOST_LEAF_ASSERT(key);
reset();
(void) new(&value_) T(std::move(v));
key_=key;
return value_;
}
BOOST_LEAF_CONSTEXPR T const * has_value(int key) const noexcept
{
BOOST_LEAF_ASSERT(key);
return key_==key ? &value_ : nullptr;
}
BOOST_LEAF_CONSTEXPR T * has_value(int key) noexcept
{
BOOST_LEAF_ASSERT(key);
return key_==key ? &value_ : nullptr;
}
BOOST_LEAF_CONSTEXPR T const & value(int key) const & noexcept
{
BOOST_LEAF_ASSERT(has_value(key) != 0);
(void) key;
return value_;
}
BOOST_LEAF_CONSTEXPR T & value(int key) & noexcept
{
BOOST_LEAF_ASSERT(has_value(key) != 0);
(void) key;
return value_;
}
BOOST_LEAF_CONSTEXPR T const && value(int key) const && noexcept
{
BOOST_LEAF_ASSERT(has_value(key) != 0);
(void) key;
return value_;
}
BOOST_LEAF_CONSTEXPR T value(int key) && noexcept
{
BOOST_LEAF_ASSERT(has_value(key) != 0);
(void) key;
T tmp(std::move(value_));
reset();
return tmp;
}
};
}
} }
#endif