PacketParser.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 PacketParser internal header */

#ifndef IH_SENF_Packets_PacketParser_
#define IH_SENF_Packets_PacketParser_ 1

// Custom includes
#include <senf/Utils/mpl.hh>

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

namespace senf {
namespace detail {

    // PLEASE don't add this to doxygen ... it just looks to weird and does not help ...

#   ifndef DOXYGEN

    // Use SFINAE to check, if Parser has an integer-valued init_bytes member. If not,
    // 'Parser_TakeNum<Parser::init_bytes>' fails and the overload is removed from the overload
    // set.
    template <class Parser>
    PacketParserBase::size_type packetParserSize(
        Parser const & p, int, senf::mpl::take_uint<Parser::init_bytes> * = 0);

    // An ellipsis is always the worst match. A call 'packetParserSize(p,0) will prefer above
    // overload if that is not disabled by SFINAE.
    template <class Parser>
    PacketParserBase::size_type packetParserSize(Parser const & p, ...);

    // Same as above: This overload is only enabled, if Parser has an integer values 'init_bytes'
    // member.
    template <class Parser>
    senf::mpl::rv<0> ParserInitBytes_Choose_(senf::mpl::take_uint<Parser::init_bytes> *);

    template <class Parser>
    senf::mpl::rv<1> ParserInitBytes_Choose_(...);

    // This version of ParserInitBytes_Choose uses 'Parser::init_bytes' to provide 'value' (via
    // 'boost::integral_constant')
    template <class Parser, unsigned _>
    struct ParserInitBytes_Choose
        : public boost::integral_constant<PacketParserBase::size_type, Parser::init_bytes> {};
    // ^^-- g++ error signaled here:
    //    error: 'fixed_bytes' is not a member of 'some-class-name'
    //
    // The 'some-class-name' class (as given in the error message) does not seem to be a parser at
    // all (it has neither a 'fixed_bytes' nor an 'init_bytes' member).
    //
    // Either 'some-class-name' is not the class you wanted to use (it really is no parser) or you
    // left out either 'init_bytes' or 'fixed_bytes' when defining the parser. This will also
    // happen, if you forget to call 'SENF_PARSER_FINALIZE()' when defining a composite parser.
    //-/////////////////////////////////////////////////////////////////////////////////////////////

    // If Parser::init_bytes is not defined, this specialization is chosen which instead uses
    // 'Parser::fixed_bytes'
    template <class Parser>
    struct ParserInitBytes_Choose<Parser, 1>
        : public boost::integral_constant<PacketParserBase::size_type, Parser::fixed_bytes> {};

    template <class Parser>
    struct ParserInitBytes
        : public ParserInitBytes_Choose<Parser,SENF_MPL_RV(ParserInitBytes_Choose_<Parser>(0))> {};

    template <class Parser, unsigned _>
    struct ParserIsFixed_Choose
        : public boost::false_type {};

    template <class Parser>
    struct ParserIsFixed_Choose<Parser, 1>
        : public boost::true_type {};

    template <class Parser>
    struct ParserIsFixed
        : public ParserIsFixed_Choose<Parser,SENF_MPL_RV(ParserInitBytes_Choose_<Parser>(0))> {};

#   endif

}}

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


// Local Variables:
// mode: c++
// fill-column: 100
// c-file-style: "senf"
// indent-tabs-mode: nil
// ispell-local-dictionary: "american"
// compile-command: "scons -u test"
// comment-column: 40
// End: