optional.hh

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#ifndef DUMUX_COMMON_OPTIONAL_HH
#define DUMUX_COMMON_OPTIONAL_HH
 
#include <utility>
 
#include <dune/common/typeutilities.hh>
 
namespace Dumux {
 
template<class T>
class Optional
{
public:
 
    Optional() :
        p_(nullptr)
    {}
 
    template<class TT, Dune::disableCopyMove<Optional, TT> = 0>
    Optional(TT&& t) :
        p_(nullptr)
    {
        emplace(std::forward<TT>(t));
    }
 
    Optional(Optional&& other)
    {
        if (other)
            p_ = new (buffer_) T(std::move(other.value()));
        else
            p_ = nullptr;
    }
 
    Optional(const Optional& other)
    {
        if (other)
            p_ = new (buffer_) T(other.value());
        else
            p_ = nullptr;
    }
 
    ~Optional()
    {
        if (operator bool())
            p_->~T();
    }
 
    template<class TT, Dune::disableCopyMove<Optional, TT> = 0 >
    Optional& operator=(TT&& t)
    {
        if (operator bool())
            *p_ = std::forward<T>(t);
        else
            p_ = new (buffer_) T(std::forward<T>(t));
        return *this;
    }
 
    Optional& operator=(const Optional& other)
    {
        if (other)
            *this = other.value();
        else if (operator bool())
        {
            p_->~T();
            p_ = nullptr;
        }
        return *this;
    }
 
    Optional& operator=(Optional&& other)
    {
        if (other)
            *this = std::move(other.value());
        else if (operator bool())
        {
            p_->~T();
            p_ = nullptr;
        }
        return *this;
    }
 
    explicit operator bool() const
    {
        return p_;
    }
 
    const T& value() const
    {
        return *p_;
    }
 
    T& value()
    {
        return *p_;
    }
 
    template< class... Args >
    void emplace(Args&&... args)
    {
        if (operator bool())
            p_->~T();
        p_ = new (buffer_) T(std::forward<Args>(args)...);
    }
 
    void release()
    {
        if (operator bool())
        {
            p_->~T();
            p_ = nullptr;
        }
    }
 
private:
 
    alignas(T) char buffer_[sizeof(T)];
    T* p_;
};
 
 
} // namespace Dumux
 
#endif // DUMUX_COMMON_OPTIONAL_HH