ListBParser.ih

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//
// Copyright (c) 2020 Fraunhofer Institute for Applied Information Technology (FIT)
//                    Network Research Group (NET)
//                    Schloss Birlinghoven, 53754 Sankt Augustin, GERMANY
//                    Contact: support@wiback.org
//
// This file is part of the SENF code tree.
// It is licensed under the 3-clause BSD License (aka New BSD License).
// See LICENSE.txt in the top level directory for details or visit
// https://opensource.org/licenses/BSD-3-Clause
//


/** \file
    \brief ListBParser internal header */

#ifndef IH_SENF_Packets_ListBParser_
#define IH_SENF_Packets_ListBParser_ 1

// Custom includes
#include "ListParser.ih"

//-/////////////////////////////////////////////////////////////////////////////////////////////////

namespace senf {
namespace detail {

    /** \brief Internal: ListPolicy defing the ListBParser parser
        \internal
        \see \ref ListParser
     */
    template <class ElementParser, class AuxPolicy>
    struct ListBParser_Policy
        : public AuxPolicy
    {
        // This policy needs to work around a serious problem with this type of list: When we change
        // the size of any (direct or indirect) sub-element of the list, this will change will
        // render the list completely invalid and un-parseable since the 'byte' field will now be
        // invalid.
        //
        // The solution we apply is to store the *size* (i.e. the number of elements) of the list
        // when creating the container wrapper. We also maintain this value across insert/erase
        // statements. Additionally we also safe the complete size of the data container (the vector
        // holding the bytes). Since we only allow packet changes through this container while it
        // exists, any change in the container size must be a change within this list and therefore
        // mandates an update of the 'bytes' field.
        //
        // The list container wrapper will call 'update' policy member before every access to the
        // container and also in the destructor. This gives us a chance to fix the bytes header
        // before the invalid header is seen by anyone (This is so, since we only allow access to
        // the list through the container wrapper ...). Since we know the number of list elements,
        // we can always find the correct 'bytes' value by traversing the list for that number of
        // elements.
        //
        // By caching the container size, all this can be made reasonably efficient and usable: The
        // updates are done automatically by only if needed. It would of course be more efficient to
        // just apply the size change directly to the bytes header (no need to traverse the
        // list). However, the implementation of this approach would be much more complex and even
        // more invasive and would probably suffer from the same restrictions to the user.

        struct container_policy;

        typedef PacketParserBase::data_iterator data_iterator;
        typedef PacketParserBase::state_type state_type;
        typedef PacketParserBase::size_type size_type;

        typedef ElementParser element_type;
        typedef ListParser<ListBParser_Policy> parser_type;
        typedef ListParser_Container<container_policy> container_type;

        static const size_type init_bytes = AuxPolicy::aux_bytes;

        ListBParser_Policy();
        template <class Arg> ListBParser_Policy(Arg const & arg);

        size_type bytes  (data_iterator i, state_type s) const;
        size_type size   (data_iterator i, state_type s) const;
        void      init   (data_iterator i, state_type s) const;

        /** \brief Internal: ListBParser container/wrapper policy */
        struct container_policy
            : public AuxPolicy::WrapperPolicy
        {
            typedef PacketParserBase::data_iterator data_iterator;
            typedef PacketParserBase::state_type state_type;
            typedef PacketParserBase::size_type size_type;

            typedef ListBParser_Policy<ElementParser, AuxPolicy> parser_policy;
            typedef typename parser_policy::element_type element_type;
            typedef typename parser_policy::parser_type parser_type;
            typedef typename parser_policy::container_type container_type;

            static const size_type init_bytes = parser_policy::init_bytes;

            container_policy(parser_policy const & p);

            size_type bytes  (data_iterator i, state_type s) const;
            size_type size   (data_iterator i, state_type s) const;
            void      init   (data_iterator i, state_type s);

            void      construct (container_type & c) const;
            void      destruct  (container_type & c) const;
            void      erase     (container_type & c, data_iterator p);
            void      insert    (container_type & c, data_iterator p);
            void      update    (container_type const & c) const;

            /** \brief Internal: ListBParser specific iterator data */
            struct iterator_data {};

            data_iterator setBegin        (container_type const & c, iterator_data & d) const;
            data_iterator setEnd          (container_type const & c, iterator_data & d) const;
            void          setFromPosition (container_type const & c, iterator_data & d,
                                           data_iterator p) const;

            data_iterator next            (container_type const & c, iterator_data & d) const;
            data_iterator raw             (container_type const & c, iterator_data const & d) const;

            size_type n_;
            mutable size_type container_size_;
        };
    };

#ifndef DOXYGEN

    template <class ElementParser, class AuxPolicy>
    struct ListParserPolicy<ElementParser, AuxPolicy, senf::detail::auxtag::bytes>
    {
        typedef ListBParser_Policy<ElementParser, AuxPolicy> type;
    };

    template <class ElementParser, class AuxPolicy, class Transform>
    struct ListParserPolicy<ElementParser, AuxPolicy,
                            senf::detail::auxtag::transform<Transform,
                                                            senf::detail::auxtag::bytes> >
    {
        typedef ListBParser_Policy< ElementParser,
                                    TransformAuxParserPolicy<AuxPolicy, Transform> > type;
    };

#endif

}}

//-/////////////////////////////////////////////////////////////////////////////////////////////////
#endif


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