/*! \file memory.hpp
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\brief Support for types found in \<memory\>
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\ingroup STLSupport */
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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 the copyright holder 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 THE COPYRIGHT HOLDER OR CONTRIBUTORS 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_TYPES_SHARED_PTR_HPP_
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#define CEREAL_TYPES_SHARED_PTR_HPP_
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#include "../cereal.hpp"
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#include <memory>
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#include <cstring>
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namespace cereal
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{
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namespace memory_detail
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{
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//! A wrapper class to notify cereal that it is ok to serialize the contained pointer
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/*! This mechanism allows us to intercept and properly handle polymorphic pointers
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@internal */
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template<class T>
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struct PtrWrapper
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{
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PtrWrapper(T && p) : ptr(std::forward<T>(p)) {}
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T & ptr;
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PtrWrapper( PtrWrapper const & ) = default;
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PtrWrapper & operator=( PtrWrapper const & ) = delete;
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};
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//! Make a PtrWrapper
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/*! @internal */
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template<class T> inline
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PtrWrapper<T> make_ptr_wrapper(T && t)
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{
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return {std::forward<T>(t)};
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}
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//! A struct that acts as a wrapper around calling load_andor_construct
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/*! The purpose of this is to allow a load_and_construct call to properly enter into the
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'data' NVP of the ptr_wrapper
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@internal */
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template <class Archive, class T>
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struct LoadAndConstructLoadWrapper
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{
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LoadAndConstructLoadWrapper( T * ptr ) :
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construct( ptr )
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{ }
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//! Constructor for embedding an early call for restoring shared_from_this
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template <class F>
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LoadAndConstructLoadWrapper( T * ptr, F && sharedFromThisFunc ) :
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construct( ptr, sharedFromThisFunc )
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{ }
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inline void CEREAL_SERIALIZE_FUNCTION_NAME( Archive & ar )
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{
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::cereal::detail::Construct<T, Archive>::load_andor_construct( ar, construct );
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}
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::cereal::construct<T> construct;
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};
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//! A helper struct for saving and restoring the state of types that derive from
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//! std::enable_shared_from_this
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/*! This special struct is necessary because when a user uses load_and_construct,
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the weak_ptr (or whatever implementation defined variant) that allows
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enable_shared_from_this to function correctly will not be initialized properly.
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This internal weak_ptr can also be modified by the shared_ptr that is created
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during the serialization of a polymorphic pointer, where cereal creates a
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wrapper shared_ptr out of a void pointer to the real data.
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In the case of load_and_construct, this happens because it is the allocation
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of shared_ptr that perform this initialization, which we let happen on a buffer
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of memory (aligned_storage). This buffer is then used for placement new
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later on, effectively overwriting any initialized weak_ptr with a default
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initialized one, eventually leading to issues when the user calls shared_from_this.
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To get around these issues, we will store the memory for the enable_shared_from_this
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portion of the class and replace it after whatever happens to modify it (e.g. the
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user performing construction or the wrapper shared_ptr in saving).
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Note that this goes into undefined behavior territory, but as of the initial writing
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of this, all standard library implementations of std::enable_shared_from_this are
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compatible with this memory manipulation. It is entirely possible that this may someday
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break or may not work with convoluted use cases.
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Example usage:
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@code{.cpp}
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T * myActualPointer;
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{
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EnableSharedStateHelper<T> helper( myActualPointer ); // save the state
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std::shared_ptr<T> myPtr( myActualPointer ); // modifies the internal weak_ptr
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// helper restores state when it goes out of scope
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}
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@endcode
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When possible, this is designed to be used in an RAII fashion - it will save state on
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construction and restore it on destruction. The restore can be done at an earlier time
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(e.g. after construct() is called in load_and_construct) in which case the destructor will
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do nothing. Performing the restore immediately following construct() allows a user to call
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shared_from_this within their load_and_construct function.
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@tparam T Type pointed to by shared_ptr
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@internal */
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template <class T>
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class EnableSharedStateHelper
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{
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// typedefs for parent type and storage type
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using BaseType = typename ::cereal::traits::get_shared_from_this_base<T>::type;
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using ParentType = std::enable_shared_from_this<BaseType>;
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using StorageType = typename std::aligned_storage<sizeof(ParentType), CEREAL_ALIGNOF(ParentType)>::type;
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public:
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//! Saves the state of some type inheriting from enable_shared_from_this
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/*! @param ptr The raw pointer held by the shared_ptr */
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inline EnableSharedStateHelper( T * ptr ) :
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itsPtr( static_cast<ParentType *>( ptr ) ),
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itsState(),
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itsRestored( false )
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{
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std::memcpy( &itsState, itsPtr, sizeof(ParentType) );
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}
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//! Restores the state of the held pointer (can only be done once)
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inline void restore()
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{
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if( !itsRestored )
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{
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// void * cast needed when type has no trivial copy-assignment
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std::memcpy( static_cast<void *>(itsPtr), &itsState, sizeof(ParentType) );
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itsRestored = true;
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}
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}
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//! Restores the state of the held pointer if not done previously
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inline ~EnableSharedStateHelper()
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{
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restore();
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}
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private:
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ParentType * itsPtr;
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StorageType itsState;
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bool itsRestored;
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}; // end EnableSharedStateHelper
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//! Performs loading and construction for a shared pointer that is derived from
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//! std::enable_shared_from_this
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/*! @param ar The archive
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@param ptr Raw pointer held by the shared_ptr
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@internal */
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template <class Archive, class T> inline
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void loadAndConstructSharedPtr( Archive & ar, T * ptr, std::true_type /* has_shared_from_this */ )
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{
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memory_detail::EnableSharedStateHelper<T> state( ptr );
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memory_detail::LoadAndConstructLoadWrapper<Archive, T> loadWrapper( ptr, [&](){ state.restore(); } );
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// let the user perform their initialization, shared state will be restored as soon as construct()
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// is called
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ar( CEREAL_NVP_("data", loadWrapper) );
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}
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//! Performs loading and construction for a shared pointer that is NOT derived from
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//! std::enable_shared_from_this
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/*! This is the typical case, where we simply pass the load wrapper to the
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archive.
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@param ar The archive
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@param ptr Raw pointer held by the shared_ptr
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@internal */
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template <class Archive, class T> inline
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void loadAndConstructSharedPtr( Archive & ar, T * ptr, std::false_type /* has_shared_from_this */ )
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{
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memory_detail::LoadAndConstructLoadWrapper<Archive, T> loadWrapper( ptr );
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ar( CEREAL_NVP_("data", loadWrapper) );
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}
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} // end namespace memory_detail
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//! Saving std::shared_ptr for non polymorphic types
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template <class Archive, class T> inline
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typename std::enable_if<!std::is_polymorphic<T>::value, void>::type
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CEREAL_SAVE_FUNCTION_NAME( Archive & ar, std::shared_ptr<T> const & ptr )
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{
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ar( CEREAL_NVP_("ptr_wrapper", memory_detail::make_ptr_wrapper( ptr )) );
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}
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//! Loading std::shared_ptr, case when no user load and construct for non polymorphic types
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template <class Archive, class T> inline
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typename std::enable_if<!std::is_polymorphic<T>::value, void>::type
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CEREAL_LOAD_FUNCTION_NAME( Archive & ar, std::shared_ptr<T> & ptr )
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{
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ar( CEREAL_NVP_("ptr_wrapper", memory_detail::make_ptr_wrapper( ptr )) );
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}
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//! Saving std::weak_ptr for non polymorphic types
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template <class Archive, class T> inline
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typename std::enable_if<!std::is_polymorphic<T>::value, void>::type
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CEREAL_SAVE_FUNCTION_NAME( Archive & ar, std::weak_ptr<T> const & ptr )
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{
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auto const sptr = ptr.lock();
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ar( CEREAL_NVP_("ptr_wrapper", memory_detail::make_ptr_wrapper( sptr )) );
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}
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//! Loading std::weak_ptr for non polymorphic types
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template <class Archive, class T> inline
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typename std::enable_if<!std::is_polymorphic<T>::value, void>::type
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CEREAL_LOAD_FUNCTION_NAME( Archive & ar, std::weak_ptr<T> & ptr )
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{
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std::shared_ptr<T> sptr;
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ar( CEREAL_NVP_("ptr_wrapper", memory_detail::make_ptr_wrapper( sptr )) );
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ptr = sptr;
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}
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//! Saving std::unique_ptr for non polymorphic types
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template <class Archive, class T, class D> inline
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typename std::enable_if<!std::is_polymorphic<T>::value, void>::type
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CEREAL_SAVE_FUNCTION_NAME( Archive & ar, std::unique_ptr<T, D> const & ptr )
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{
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ar( CEREAL_NVP_("ptr_wrapper", memory_detail::make_ptr_wrapper( ptr )) );
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}
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//! Loading std::unique_ptr, case when user provides load_and_construct for non polymorphic types
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template <class Archive, class T, class D> inline
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typename std::enable_if<!std::is_polymorphic<T>::value, void>::type
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CEREAL_LOAD_FUNCTION_NAME( Archive & ar, std::unique_ptr<T, D> & ptr )
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{
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ar( CEREAL_NVP_("ptr_wrapper", memory_detail::make_ptr_wrapper( ptr )) );
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}
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// ######################################################################
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// Pointer wrapper implementations follow below
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//! Saving std::shared_ptr (wrapper implementation)
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/*! @internal */
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template <class Archive, class T> inline
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void CEREAL_SAVE_FUNCTION_NAME( Archive & ar, memory_detail::PtrWrapper<std::shared_ptr<T> const &> const & wrapper )
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{
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auto & ptr = wrapper.ptr;
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uint32_t id = ar.registerSharedPointer( ptr );
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ar( CEREAL_NVP_("id", id) );
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if( id & detail::msb_32bit )
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{
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ar( CEREAL_NVP_("data", *ptr) );
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}
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}
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//! Loading std::shared_ptr, case when user load and construct (wrapper implementation)
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/*! @internal */
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template <class Archive, class T> inline
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typename std::enable_if<traits::has_load_and_construct<T, Archive>::value, void>::type
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CEREAL_LOAD_FUNCTION_NAME( Archive & ar, memory_detail::PtrWrapper<std::shared_ptr<T> &> & wrapper )
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{
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uint32_t id;
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ar( CEREAL_NVP_("id", id) );
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if( id & detail::msb_32bit )
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{
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// Storage type for the pointer - since we can't default construct this type,
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// we'll allocate it using std::aligned_storage and use a custom deleter
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using ST = typename std::aligned_storage<sizeof(T), CEREAL_ALIGNOF(T)>::type;
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// Valid flag - set to true once construction finishes
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// This prevents us from calling the destructor on
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// uninitialized data.
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auto valid = std::make_shared<bool>( false );
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// Allocate our storage, which we will treat as
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// uninitialized until initialized with placement new
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using NonConstT = typename std::remove_const<T>::type;
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std::shared_ptr<NonConstT> ptr(reinterpret_cast<NonConstT *>(new ST()),
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[=]( NonConstT * t )
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{
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if( *valid )
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t->~T();
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delete reinterpret_cast<ST *>( t );
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} );
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// Register the pointer
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ar.registerSharedPointer( id, ptr );
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// Perform the actual loading and allocation
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memory_detail::loadAndConstructSharedPtr( ar, ptr.get(), typename ::cereal::traits::has_shared_from_this<NonConstT>::type() );
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// Mark pointer as valid (initialized)
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*valid = true;
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wrapper.ptr = std::move(ptr);
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}
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else
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wrapper.ptr = std::static_pointer_cast<T>(ar.getSharedPointer(id));
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}
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//! Loading std::shared_ptr, case when no user load and construct (wrapper implementation)
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/*! @internal */
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template <class Archive, class T> inline
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typename std::enable_if<!traits::has_load_and_construct<T, Archive>::value, void>::type
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CEREAL_LOAD_FUNCTION_NAME( Archive & ar, memory_detail::PtrWrapper<std::shared_ptr<T> &> & wrapper )
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{
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uint32_t id;
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ar( CEREAL_NVP_("id", id) );
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if( id & detail::msb_32bit )
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{
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using NonConstT = typename std::remove_const<T>::type;
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std::shared_ptr<NonConstT> ptr( detail::Construct<NonConstT, Archive>::load_andor_construct() );
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ar.registerSharedPointer( id, ptr );
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ar( CEREAL_NVP_("data", *ptr) );
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wrapper.ptr = std::move(ptr);
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}
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else
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wrapper.ptr = std::static_pointer_cast<T>(ar.getSharedPointer(id));
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}
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//! Saving std::unique_ptr (wrapper implementation)
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/*! @internal */
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template <class Archive, class T, class D> inline
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void CEREAL_SAVE_FUNCTION_NAME( Archive & ar, memory_detail::PtrWrapper<std::unique_ptr<T, D> const &> const & wrapper )
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{
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auto & ptr = wrapper.ptr;
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// unique_ptr get one byte of metadata which signifies whether they were a nullptr
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// 0 == nullptr
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// 1 == not null
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if( !ptr )
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ar( CEREAL_NVP_("valid", uint8_t(0)) );
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else
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{
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ar( CEREAL_NVP_("valid", uint8_t(1)) );
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ar( CEREAL_NVP_("data", *ptr) );
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}
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}
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//! Loading std::unique_ptr, case when user provides load_and_construct (wrapper implementation)
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/*! @internal */
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template <class Archive, class T, class D> inline
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typename std::enable_if<traits::has_load_and_construct<T, Archive>::value, void>::type
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CEREAL_LOAD_FUNCTION_NAME( Archive & ar, memory_detail::PtrWrapper<std::unique_ptr<T, D> &> & wrapper )
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{
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uint8_t isValid;
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ar( CEREAL_NVP_("valid", isValid) );
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auto & ptr = wrapper.ptr;
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if( isValid )
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{
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using NonConstT = typename std::remove_const<T>::type;
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// Storage type for the pointer - since we can't default construct this type,
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// we'll allocate it using std::aligned_storage
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using ST = typename std::aligned_storage<sizeof(NonConstT), CEREAL_ALIGNOF(NonConstT)>::type;
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// Allocate storage - note the ST type so that deleter is correct if
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// an exception is thrown before we are initialized
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std::unique_ptr<ST> stPtr( new ST() );
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// Use wrapper to enter into "data" nvp of ptr_wrapper
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memory_detail::LoadAndConstructLoadWrapper<Archive, NonConstT> loadWrapper( reinterpret_cast<NonConstT *>( stPtr.get() ) );
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// Initialize storage
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ar( CEREAL_NVP_("data", loadWrapper) );
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// Transfer ownership to correct unique_ptr type
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ptr.reset( reinterpret_cast<T *>( stPtr.release() ) );
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}
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else
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ptr.reset( nullptr );
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}
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//! Loading std::unique_ptr, case when no load_and_construct (wrapper implementation)
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/*! @internal */
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template <class Archive, class T, class D> inline
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typename std::enable_if<!traits::has_load_and_construct<T, Archive>::value, void>::type
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CEREAL_LOAD_FUNCTION_NAME( Archive & ar, memory_detail::PtrWrapper<std::unique_ptr<T, D> &> & wrapper )
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{
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uint8_t isValid;
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ar( CEREAL_NVP_("valid", isValid) );
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if( isValid )
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{
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using NonConstT = typename std::remove_const<T>::type;
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std::unique_ptr<NonConstT, D> ptr( detail::Construct<NonConstT, Archive>::load_andor_construct() );
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ar( CEREAL_NVP_( "data", *ptr ) );
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wrapper.ptr = std::move(ptr);
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}
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else
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{
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wrapper.ptr.reset( nullptr );
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}
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}
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} // namespace cereal
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// automatically include polymorphic support
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#include "../types/polymorphic.hpp"
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#endif // CEREAL_TYPES_SHARED_PTR_HPP_
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