140 lines
6.4 KiB
C++
140 lines
6.4 KiB
C++
/*! \file specialize.hpp
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\brief 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_SPECIALIZE_HPP_
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#define CEREAL_SPECIALIZE_HPP_
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namespace cereal
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{
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// Forward declaration of access class that users can become friends with
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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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#endif
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