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/* vim: set sw=4 sts=4 et foldmethod=syntax : */

/*
 * Copyright (c) 2005, 2006 Ciaran McCreesh <ciaran.mccreesh@blueyonder.co.uk>
 *
 * This file is part of the Paludis package manager. Paludis is free software;
 * you can redistribute it and/or modify it under the terms of the GNU General
 * Public License version 2, as published by the Free Software Foundation.
 *
 * Paludis is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
 * Place, Suite 330, Boston, MA  02111-1307  USA
 */

#ifndef PALUDIS_GUARD_PALUDIS_SAVE_HH
#define PALUDIS_GUARD_PALUDIS_SAVE_HH 1

#include <paludis/util/instantiation_policy.hh>

/** \file
 * Declarations for the Save class.
 *
 * \ingroup grpsave
 */

namespace paludis
{
    /**
     * Save the value of a particular variable and assign it a new value for the
     * duration of the Save instance's lifetime (RAII, see \ref EffCpp item 13 or
     * \ref TCppPL section 14.4).
     *
     * \ingroup grpsave
     */
    template <typename T_>
    class Save :
        private InstantiationPolicy<Save<T_>, instantiation_method::NonCopyableTag>
    {
        private:
            T_ * const _ptr;
            const T_ _value;

        public:
            /**
             * Constructor.
             */
            Save(T_ * const p) :
                _ptr(p),
                _value(*p)
            {
            }

            /**
             * Constructor, with convenience assignment to new_value.
             */
            Save(T_ * const p, const T_ & new_value) :
                _ptr(p),
                _value(*p)
            {
                *p = new_value;
            }

            /**
             * Destructor.
             */
            ~Save()
            {
                *_ptr = _value;
            }
    };
}

#endif