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428 lines
18 KiB
428 lines
18 KiB
/*! \file access.hpp
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\brief Access control, default construction, and serialization disambiguation */
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/*
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Copyright (c) 2014, Randolph Voorhies, Shane Grant
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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* Neither the name of cereal nor the
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names of its contributors may be used to endorse or promote products
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derived from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL RANDOLPH VOORHIES OR SHANE GRANT BE LIABLE FOR ANY
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DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef CEREAL_ACCESS_HPP_
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#define CEREAL_ACCESS_HPP_
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#include <type_traits>
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#include <iostream>
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#include <cstdint>
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#include <cereal/macros.hpp>
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#include <cereal/details/helpers.hpp>
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namespace cereal
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{
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// ######################################################################
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//! A class that allows cereal to load smart pointers to types that have no default constructor
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/*! If your class does not have a default constructor, cereal will not be able
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to load any smart pointers to it unless you overload LoadAndConstruct
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for your class, and provide an appropriate load_and_construct method. You can also
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choose to define a member static function instead of specializing this class.
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The specialization of LoadAndConstruct must be placed within the cereal namespace:
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@code{.cpp}
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struct MyType
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{
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MyType( int x ); // note: no default ctor
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int myX;
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// Define a serialize or load/save pair as you normally would
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template <class Archive>
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void serialize( Archive & ar )
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{
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ar( myX );
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}
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};
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// Provide a specialization for LoadAndConstruct for your type
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namespace cereal
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{
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template <> struct LoadAndConstruct<MyType>
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{
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// load_and_construct will be passed the archive that you will be loading
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// from as well as a construct object which you can use as if it were the
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// constructor for your type. cereal will handle all memory management for you.
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template <class Archive>
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static void load_and_construct( Archive & ar, cereal::construct<MyType> & construct )
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{
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int x;
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ar( x );
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construct( x );
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}
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};
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} // end namespace cereal
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@endcode
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Please note that just as in using external serialization functions, you cannot get
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access to non-public members of your class by befriending cereal::access. If you
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have the ability to modify the class you wish to serialize, it is recommended that you
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use member serialize functions and a static member load_and_construct function.
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@tparam T The type to specialize for
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@ingroup Access */
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template <class T>
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struct LoadAndConstruct
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{
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//! Called by cereal if no default constructor exists to load and construct data simultaneously
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/*! Overloads of this should return a pointer to T and expect an archive as a parameter */
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static std::false_type load_and_construct(...)
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{ return std::false_type(); }
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};
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// forward decl for construct
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//! @cond PRIVATE_NEVERDEFINED
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namespace memory_detail{ template <class Ar, class T> struct LoadAndConstructLoadWrapper; }
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//! @endcond
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//! Used to construct types with no default constructor
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/*! When serializing a type that has no default constructor, cereal
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will attempt to call either the class static function load_and_construct
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or the appropriate template specialization of LoadAndConstruct. cereal
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will pass that function a reference to the archive as well as a reference
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to a construct object which should be used to perform the allocation once
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data has been appropriately loaded.
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@code{.cpp}
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struct MyType
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{
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// note the lack of default constructor
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MyType( int xx, int yy );
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int x, y;
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double notInConstructor;
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template <class Archive>
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void serialize( Archive & ar )
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{
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ar( x, y );
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ar( notInConstructor );
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}
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template <class Archive>
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static void load_and_construct( Archive & ar, cereal::construct<MyType> & construct )
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{
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int x, y;
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ar( x, y );
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// use construct object to initialize with loaded data
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construct( x, y );
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// access to member variables and functions via -> operator
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ar( construct->notInConstructor );
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// could also do the above section by:
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double z;
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ar( z );
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construct->notInConstructor = z;
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}
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};
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@endcode
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@tparam T The class type being serialized
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*/
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template <class T>
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class construct
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{
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public:
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//! Construct and initialize the type T with the given arguments
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/*! This will forward all arguments to the underlying type T,
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calling an appropriate constructor.
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Calling this function more than once will result in an exception
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being thrown.
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@param args The arguments to the constructor for T
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@throw Exception If called more than once */
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template <class ... Args>
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void operator()( Args && ... args );
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// implementation deferred due to reliance on cereal::access
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//! Get a reference to the initialized underlying object
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/*! This must be called after the object has been initialized.
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@return A reference to the initialized object
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@throw Exception If called before initialization */
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T * operator->()
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{
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if( !itsValid )
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throw Exception("Object must be initialized prior to accessing members");
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return itsPtr;
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}
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//! Returns a raw pointer to the initialized underlying object
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/*! This is mainly intended for use with passing an instance of
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a constructed object to cereal::base_class.
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It is strongly recommended to avoid using this function in
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any other circumstance.
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@return A raw pointer to the initialized type */
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T * ptr()
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{
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return operator->();
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}
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private:
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template <class A, class B> friend struct ::cereal::memory_detail::LoadAndConstructLoadWrapper;
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construct( T * p ) : itsPtr( p ), itsValid( false ) {}
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construct( construct const & ) = delete;
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construct & operator=( construct const & ) = delete;
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T * itsPtr;
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bool itsValid;
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};
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// ######################################################################
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//! A class that can be made a friend to give cereal access to non public functions
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/*! If you desire non-public serialization functions within a class, cereal can only
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access these if you declare cereal::access a friend.
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@code{.cpp}
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class MyClass
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{
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private:
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friend class cereal::access; // gives access to the private serialize
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template <class Archive>
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void serialize( Archive & ar )
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{
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// some code
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}
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};
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@endcode
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@ingroup Access */
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class access
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{
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public:
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// ####### Standard Serialization ########################################
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template<class Archive, class T> inline
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static auto member_serialize(Archive & ar, T & t) -> decltype(t.CEREAL_SERIALIZE_FUNCTION_NAME(ar))
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{ return t.CEREAL_SERIALIZE_FUNCTION_NAME(ar); }
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template<class Archive, class T> inline
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static auto member_save(Archive & ar, T const & t) -> decltype(t.CEREAL_SAVE_FUNCTION_NAME(ar))
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{ return t.CEREAL_SAVE_FUNCTION_NAME(ar); }
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template<class Archive, class T> inline
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static auto member_save_non_const(Archive & ar, T & t) -> decltype(t.CEREAL_SAVE_FUNCTION_NAME(ar))
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{ return t.CEREAL_SAVE_FUNCTION_NAME(ar); }
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template<class Archive, class T> inline
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static auto member_load(Archive & ar, T & t) -> decltype(t.CEREAL_LOAD_FUNCTION_NAME(ar))
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{ return t.CEREAL_LOAD_FUNCTION_NAME(ar); }
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template<class Archive, class T> inline
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static auto member_save_minimal(Archive const & ar, T const & t) -> decltype(t.CEREAL_SAVE_MINIMAL_FUNCTION_NAME(ar))
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{ return t.CEREAL_SAVE_MINIMAL_FUNCTION_NAME(ar); }
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template<class Archive, class T> inline
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static auto member_save_minimal_non_const(Archive const & ar, T & t) -> decltype(t.CEREAL_SAVE_MINIMAL_FUNCTION_NAME(ar))
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{ return t.CEREAL_SAVE_MINIMAL_FUNCTION_NAME(ar); }
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template<class Archive, class T, class U> inline
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static auto member_load_minimal(Archive const & ar, T & t, U && u) -> decltype(t.CEREAL_LOAD_MINIMAL_FUNCTION_NAME(ar, std::forward<U>(u)))
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{ return t.CEREAL_LOAD_MINIMAL_FUNCTION_NAME(ar, std::forward<U>(u)); }
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// ####### Versioned Serialization #######################################
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template<class Archive, class T> inline
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static auto member_serialize(Archive & ar, T & t, const std::uint32_t version ) -> decltype(t.CEREAL_SERIALIZE_FUNCTION_NAME(ar, version))
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{ return t.CEREAL_SERIALIZE_FUNCTION_NAME(ar, version); }
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template<class Archive, class T> inline
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static auto member_save(Archive & ar, T const & t, const std::uint32_t version ) -> decltype(t.CEREAL_SAVE_FUNCTION_NAME(ar, version))
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{ return t.CEREAL_SAVE_FUNCTION_NAME(ar, version); }
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template<class Archive, class T> inline
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static auto member_save_non_const(Archive & ar, T & t, const std::uint32_t version ) -> decltype(t.CEREAL_SAVE_FUNCTION_NAME(ar, version))
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{ return t.CEREAL_SAVE_FUNCTION_NAME(ar, version); }
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template<class Archive, class T> inline
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static auto member_load(Archive & ar, T & t, const std::uint32_t version ) -> decltype(t.CEREAL_LOAD_FUNCTION_NAME(ar, version))
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{ return t.CEREAL_LOAD_FUNCTION_NAME(ar, version); }
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template<class Archive, class T> inline
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static auto member_save_minimal(Archive const & ar, T const & t, const std::uint32_t version) -> decltype(t.CEREAL_SAVE_MINIMAL_FUNCTION_NAME(ar, version))
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{ return t.CEREAL_SAVE_MINIMAL_FUNCTION_NAME(ar, version); }
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template<class Archive, class T> inline
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static auto member_save_minimal_non_const(Archive const & ar, T & t, const std::uint32_t version) -> decltype(t.CEREAL_SAVE_MINIMAL_FUNCTION_NAME(ar, version))
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{ return t.CEREAL_SAVE_MINIMAL_FUNCTION_NAME(ar, version); }
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template<class Archive, class T, class U> inline
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static auto member_load_minimal(Archive const & ar, T & t, U && u, const std::uint32_t version) -> decltype(t.CEREAL_LOAD_MINIMAL_FUNCTION_NAME(ar, std::forward<U>(u), version))
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{ return t.CEREAL_LOAD_MINIMAL_FUNCTION_NAME(ar, std::forward<U>(u), version); }
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// ####### Other Functionality ##########################################
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// for detecting inheritance from enable_shared_from_this
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template <class T> inline
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static auto shared_from_this(T & t) -> decltype(t.shared_from_this());
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// for placement new
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template <class T, class ... Args> inline
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static void construct( T *& ptr, Args && ... args )
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{
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new (ptr) T( std::forward<Args>( args )... );
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}
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// for non-placement new with a default constructor
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template <class T> inline
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static T * construct()
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{
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return new T();
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}
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template <class T> inline
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static std::false_type load_and_construct(...)
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{ return std::false_type(); }
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template<class T, class Archive> inline
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static auto load_and_construct(Archive & ar, ::cereal::construct<T> & construct) -> decltype(T::load_and_construct(ar, construct))
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{
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T::load_and_construct( ar, construct );
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}
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}; // end class access
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// ######################################################################
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//! A specifier used in conjunction with cereal::specialize to disambiguate
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//! serialization in special cases
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/*! @relates specialize
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@ingroup Access */
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enum class specialization
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{
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member_serialize, //!< Force the use of a member serialize function
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member_load_save, //!< Force the use of a member load/save pair
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member_load_save_minimal, //!< Force the use of a member minimal load/save pair
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non_member_serialize, //!< Force the use of a non-member serialize function
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non_member_load_save, //!< Force the use of a non-member load/save pair
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non_member_load_save_minimal //!< Force the use of a non-member minimal load/save pair
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};
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//! A class used to disambiguate cases where cereal cannot detect a unique way of serializing a class
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/*! cereal attempts to figure out which method of serialization (member vs. non-member serialize
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or load/save pair) at compile time. If for some reason cereal cannot find a non-ambiguous way
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of serializing a type, it will produce a static assertion complaining about this.
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This can happen because you have both a serialize and load/save pair, or even because a base
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class has a serialize (public or private with friend access) and a derived class does not
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overwrite this due to choosing some other serialization type.
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Specializing this class will tell cereal to explicitly use the serialization type you specify
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and it will not complain about ambiguity in its compile time selection. However, if cereal detects
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an ambiguity in specializations, it will continue to issue a static assertion.
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@code{.cpp}
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class MyParent
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{
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friend class cereal::access;
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template <class Archive>
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void serialize( Archive & ar ) {}
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};
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// Although serialize is private in MyParent, to cereal::access it will look public,
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// even through MyDerived
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class MyDerived : public MyParent
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{
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public:
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template <class Archive>
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void load( Archive & ar ) {}
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template <class Archive>
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void save( Archive & ar ) {}
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};
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// The load/save pair in MyDerived is ambiguous because serialize in MyParent can
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// be accessed from cereal::access. This looks the same as making serialize public
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// in MyParent, making it seem as though MyDerived has both a serialize and a load/save pair.
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// cereal will complain about this at compile time unless we disambiguate:
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namespace cereal
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{
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// This struct specialization will tell cereal which is the right way to serialize the ambiguity
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template <class Archive> struct specialize<Archive, MyDerived, cereal::specialization::member_load_save> {};
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// If we only had a disambiguation for a specific archive type, it would look something like this
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template <> struct specialize<cereal::BinaryOutputArchive, MyDerived, cereal::specialization::member_load_save> {};
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}
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@endcode
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You can also choose to use the macros CEREAL_SPECIALIZE_FOR_ALL_ARCHIVES or
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CEREAL_SPECIALIZE_FOR_ARCHIVE if you want to type a little bit less.
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@tparam T The type to specialize the serialization for
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@tparam S The specialization type to use for T
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@ingroup Access */
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template <class Archive, class T, specialization S>
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struct specialize : public std::false_type {};
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//! Convenient macro for performing specialization for all archive types
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/*! This performs specialization for the specific type for all types of archives.
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This macro should be placed at the global namespace.
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@code{cpp}
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struct MyType {};
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CEREAL_SPECIALIZE_FOR_ALL_ARCHIVES( MyType, cereal::specialization::member_load_save );
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@endcode
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@relates specialize
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@ingroup Access */
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#define CEREAL_SPECIALIZE_FOR_ALL_ARCHIVES( Type, Specialization ) \
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namespace cereal { template <class Archive> struct specialize<Archive, Type, Specialization> {}; }
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//! Convenient macro for performing specialization for a single archive type
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/*! This performs specialization for the specific type for a single type of archive.
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This macro should be placed at the global namespace.
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@code{cpp}
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struct MyType {};
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CEREAL_SPECIALIZE_FOR_ARCHIVE( cereal::XMLInputArchive, MyType, cereal::specialization::member_load_save );
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@endcode
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@relates specialize
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@ingroup Access */
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#define CEREAL_SPECIALIZE_FOR_ARCHIVE( Archive, Type, Specialization ) \
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namespace cereal { template <> struct specialize<Archive, Type, Specialization> {}; }
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// ######################################################################
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// Deferred Implementation, see construct for more information
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template <class T> template <class ... Args> inline
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void construct<T>::operator()( Args && ... args )
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{
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if( itsValid )
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throw Exception("Attempting to construct an already initialized object");
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::cereal::access::construct( itsPtr, std::forward<Args>( args )... );
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itsValid = true;
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}
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} // namespace cereal
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#endif // CEREAL_ACCESS_HPP_
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