get_unit.hpp

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//
// (c) Copyright 2013 DESY, Eugen Wintersberger <eugen.wintersberger@desy.de>
//
// This file is part of libpniio.
//
// libpniio is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 2 of the License, or
// (at your option) any later version.
//
// libpniio 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 libpniio.  If not, see <http://www.gnu.org/licenses/>.
// ===========================================================================
// Created on: Jul 1, 2013
//     Author: Eugen Wintersberger <eugen.wintersberger@desy.de>
//
#pragma once

#include <pni/core/types.hpp>
#include <pni/core/error.hpp>
#include "../nxobject.hpp"
#include "../nxobject_traits.hpp"

namespace pni{
namespace io{
namespace nx{

    template<typename FTYPE> pni::core::string get_unit(const FTYPE &field)
    {
        typedef nximp_code_map<FTYPE> imp_map;
        typedef typename nxobject_trait<imp_map::icode>::field_type field_type;
        
        static_assert(std::is_same<FTYPE,field_type>::value,
                      "UNIT CAN ONLY BE RETRIEFVED FROM A FIELD TYPE!");

        pni::core::string buffer;

        if(field.attributes.exists("units"))
            field.attributes["units"].read(buffer);

        return buffer;
    }

    //------------------------------------------------------------------------
    template<
             typename GTYPE,
             typename FTYPE,
             typename ATYPE,
             typename LTYPE
            > 
    class get_unit_visitor : public boost::static_visitor<pni::core::string>
    {
        public:
            using result_type = pni::core::string;
            using group_type = GTYPE;
            using field_type = FTYPE;
            using attribute_type = ATYPE;
            using link_type = LTYPE;
    
            //-----------------------------------------------------------------
            result_type operator()(const group_type &) const
            {
                using namespace pni::core;
                throw type_error(EXCEPTION_RECORD,
                        "Cannot retreive a unit from a group!");

                return result_type();
            }

            //-----------------------------------------------------------------
            result_type operator()(const field_type &f) const
            {
                return get_unit(f);
            }

            //-----------------------------------------------------------------
            result_type operator()(const attribute_type &) const
            {
                using namespace pni::core;
                throw type_error(EXCEPTION_RECORD,
                        "Cannot retrieve a unit from an attribute type!");
                return result_type();
            }
            
            //-----------------------------------------------------------------
            result_type operator()(const link_type &) const
            {
                using namespace pni::core;
                throw type_error(EXCEPTION_RECORD,
                        "Cannot retrieve a unit from a link type!");
                return result_type();
            }
    };

    //------------------------------------------------------------------------
    template<
             typename GTYPE,
             typename FTYPE,
             typename ATYPE,
             typename LTYPE
            > 
    pni::core::string get_unit(const nxobject<GTYPE,FTYPE,ATYPE,LTYPE> &o)
    {
        using visitor_type = get_unit_visitor<GTYPE,FTYPE,ATYPE,LTYPE>;
        return boost::apply_visitor(visitor_type(),o);
    }

//end of namespace
}
}
}