boost/variant/detail/backup_holder.hpp

//-----------------------------------------------------------------------------
// boost variant/detail/backup_holder.hpp header file
// See http://www.boost.org for updates, documentation, and revision history.
//-----------------------------------------------------------------------------
//
// Copyright (c) 2003
// Eric Friedman
//
// 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)
#ifndef BOOST_VARIANT_DETAIL_BACKUP_HOLDER_HPP
#define BOOST_VARIANT_DETAIL_BACKUP_HOLDER_HPP
#include <boost/config.hpp>
#include <boost/assert.hpp>
namespace boost {
namespace detail { namespace variant {
template <typename T>
class backup_holder
{
private: // representation
    T* backup_;
public: // structors
    ~backup_holder() BOOST_NOEXCEPT
    {
        delete backup_;
    }
    explicit backup_holder(T* backup) BOOST_NOEXCEPT
        : backup_(backup)
    {
    }
    backup_holder(const backup_holder&);
public: // modifiers
    backup_holder& operator=(const backup_holder& rhs)
    {
        *backup_ = rhs.get();
        return *this;
    }
    backup_holder& operator=(const T& rhs)
    {
        *backup_ = rhs;
        return *this;
    }
    void swap(backup_holder& rhs) BOOST_NOEXCEPT
    {
        T* tmp = rhs.backup_;
        rhs.backup_ = this->backup_;
        this->backup_ = tmp;
    }
public: // queries
    T& get() BOOST_NOEXCEPT
    {
        return *backup_;
    }
    const T& get() const BOOST_NOEXCEPT
    {
        return *backup_;
    }
};
template <typename T>
backup_holder<T>::backup_holder(const backup_holder&)
    : backup_(0)
{
    // not intended for copy, but do not want to prohibit syntactically
    BOOST_ASSERT(false);
}
template <typename T>
void swap(backup_holder<T>& lhs, backup_holder<T>& rhs) BOOST_NOEXCEPT
{
    lhs.swap(rhs);
}
}} // namespace detail::variant
} // namespace boost
#endif // BOOST_VARIANT_DETAIL_BACKUP_HOLDER_HPP