JSON.hpp

/* Copyright 2020-2021 Franz Poeschel
 *
 * This file is part of openPMD-api.
 *
 * openPMD-api is free software: you can redistribute it and/or modify
 * it under the terms of of either the GNU General Public License or
 * the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * openPMD-api 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 and the GNU Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU General Public License
 * and the GNU Lesser General Public License along with openPMD-api.
 * If not, see <http://www.gnu.org/licenses/>.
 */
 
#pragma once
 
#include "openPMD/config.hpp"
 
#include <nlohmann/json.hpp>
 
#if openPMD_HAVE_MPI
#   include <mpi.h>
#endif
 
#include <memory>  // std::shared_ptr
#include <utility> // std::forward
 
namespace openPMD
{
namespace auxiliary
{
    class TracingJSON
    {
    public:
        TracingJSON();
        TracingJSON( nlohmann::json );
 
        inline nlohmann::json &
        json()
        {
            return *m_positionInOriginal;
        }
 
        template< typename Key >
        TracingJSON operator[]( Key && key );
 
        nlohmann::json const &
        getShadow();
 
        nlohmann::json
        invertShadow();
 
        void
        declareFullyRead();
 
    private:
        std::shared_ptr< nlohmann::json > m_originalJSON;
        std::shared_ptr< nlohmann::json > m_shadow;
        nlohmann::json * m_positionInOriginal;
        nlohmann::json * m_positionInShadow;
        bool m_trace = true;
 
        void
        invertShadow( nlohmann::json & result, nlohmann::json const & shadow );
 
        TracingJSON(
            std::shared_ptr< nlohmann::json > originalJSON,
            std::shared_ptr< nlohmann::json > shadow,
            nlohmann::json * positionInOriginal,
            nlohmann::json * positionInShadow,
            bool trace );
    };
 
    template< typename Key >
    TracingJSON TracingJSON::operator[]( Key && key )
    {
        nlohmann::json * newPositionInOriginal =
            &m_positionInOriginal->operator[]( key );
        // If accessing a leaf in the JSON tree from an object (not an array!)
        // erase the corresponding key
        static nlohmann::json nullvalue;
        nlohmann::json * newPositionInShadow = &nullvalue;
        if( m_trace && m_positionInOriginal->is_object() )
        {
            newPositionInShadow = &m_positionInShadow->operator[]( key );
        }
        bool traceFurther = newPositionInOriginal->is_object();
        return TracingJSON(
            m_originalJSON,
            m_shadow,
            newPositionInOriginal,
            newPositionInShadow,
            traceFurther );
    }
 
    nlohmann::json parseOptions( std::string const & options );
 
#if openPMD_HAVE_MPI
 
    nlohmann::json parseOptions( std::string const & options, MPI_Comm comm );
 
#endif
 
} // namespace auxiliary
} // namespace openPMD