get_attribute.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 2, 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<
             template<nximp_code> class PTYPE,
             nximp_code IMPID
           >
    typename nxobject_trait<IMPID>::object_type
    get_attribute(const PTYPE<IMPID> &parent,const pni::core::string &name)
    {
        using field_type = typename nxobject_trait<IMPID>::field_type;
        using group_type = typename nxobject_trait<IMPID>::group_type;

        static_assert(std::is_same<field_type,PTYPE<IMPID>>::value || 
                      std::is_same<group_type,PTYPE<IMPID>>::value,
                      "Parent must be a field or a group!");

        return parent.attributes[name];
    }


    //------------------------------------------------------------------------
    template<
             typename GTYPE,
             typename FTYPE,
             typename ATYPE,
             typename LTYPE
            > 
    class get_attribute_visitor : public boost::static_visitor<
                                  nxobject<GTYPE,FTYPE,ATYPE,LTYPE>
                                  >
    {
        private:
            pni::core::string _attribute; 
        public:
            using result_type = ATYPE;
            using group_type = GTYPE;
            using field_type = FTYPE;
            using attribute_type =  ATYPE;
            using link_type = LTYPE;
      
            //-----------------------------------------------------------------
            get_attribute_visitor(const pni::core::string &attr):
                _attribute(attr) 
            {}
          
            //---------------------------------------------------------------------
            result_type operator()(const group_type &g) const
            {
                return get_attribute(g,_attribute);
            }

            //---------------------------------------------------------------------
            result_type operator()(const field_type &f) const
            {
                return get_attribute(f,_attribute);
            }

            //---------------------------------------------------------------------
            result_type operator()(const attribute_type &) const
            {
                using namespace pni::core;
                throw type_error(EXCEPTION_RECORD,
                        "Attributes cannot have attributes by themself!");
                return result_type();
            }

            //-----------------------------------------------------------------
            result_type operator()(const link_type &) const
            {
                using namespace pni::core;
                throw type_error(EXCEPTION_RECORD,
                        "Instances of link do not have attribtues!");
                return result_type();
            }
    };

    template<
             typename GTYPE,
             typename FTYPE,
             typename ATYPE,
             typename LTYPE
            > 
    nxobject<GTYPE,FTYPE,ATYPE,LTYPE>
    get_attribute(const nxobject<GTYPE,FTYPE,ATYPE,LTYPE> &parent,
                  const pni::core::string &name)
    {
        using visitor_type = get_attribute_visitor<GTYPE,FTYPE,ATYPE,LTYPE>;
        return boost::apply_visitor(visitor_type(name),parent);
    }

//end of namespace 
}
}
}