stdboxtraits.hpp

Go to the documentation of this file.

//==================================================================================================
/// \file
/// This header-file is part of the \aliblong.
///
/// Copyright 2013-2026 A-Worx GmbH, Germany.
/// Published under #"mainpage_license".
//==================================================================================================
namespace alib::boxing {
 
#if DOXYGEN
/// This namespace contains sub-namespaces that provide compatibility of 3rd-party types and
/// module \alib_boxing_nl.<br>
/// The entities of those namespaces become available with the inclusion of specific headers
/// that import a certain C++20-Module or inject the functionality into a namespace in a
/// traditional fashion, for example, header #"F;ALib.Boxing.StdFunctors.H".
namespace compatibility {
 
/// This namespace documents compatibility features of \alib_boxing_nl and the
/// standard C++ class library found in namespace \c std.
namespace std {
#endif
 
/// Specialization of struct #"%BoxTraits" for template type <c>std::array<T, Size>></c>
/// Instead of boxing a pointer to the array object, a boxed array is stored, hence a pointer
/// to the first element contents and the array's length.
///
/// To enable this behavior, header-file #"F;ALib.Compatibility.StdBoxtraits.H" needs to be included in
/// the corresponding compilation unit.
///
/// Excluded from the specialization are character arrays.
/// Boxing of \c std::array instances of those types is customized by the specialization of
/// #"ArrayTraits", as described in manual chapter
/// #"alib_boxing_strings".
///
/// \note As mandatory, the specialization is defined in #"alib::boxing".
///       To keep the reference documentation of that namespace clean, it is documented here.
///
/// @tparam TElement The element type of the array.
/// @tparam N        The size of the array.
template<typename TElement, size_t N>
requires ( !characters::IsCharacter<TElement> )
struct BoxTraits<std::array<TElement, N> > {
    /// Mapped type is \p{TElement[]}.
    using                   Mapping=  TElement;
 
    /// Mapped as array-type
    static constexpr bool   IsArray=  true;
 
    /// Implementation of custom boxing for template class std::array
    /// @param box    The placeholder of the box box.
    /// @param value     The object to box.
    static void Write( Placeholder& box, const std::array<TElement, N>& value)
    {
        box.Write( value.data(), integer( N ) );
    }
 
    /// Forbid unboxing by declaring Read as void.
    /// @param box Ignored.
    static void Read( const Placeholder& box);
};
 
/// Specialization of struct #"%BoxTraits" for template type <c>std::vector<T, std::allocator<T>></c>
/// Instead of boxing a pointer to the vector object, a boxed array is stored, hence a pointer
/// to the first element contents and the array length.
///
/// To enable this behavior, the header-file #"F;ALib.Compatibility.StdBoxtraits.H" needs to be
/// included in the corresponding compilation unit.
///
/// Excluded from the specialization are character arrays.
/// Boxing of \c std::vector instances of those types is customized by the specialization of
/// #"ArrayTraits", as described in manual chapter
/// #"alib_boxing_strings".
///
/// \note As mandatory, the specialization is defined in #"alib::boxing".
///       To keep the reference documentation of that namespace clean, it is documented here.
///
/// @tparam TElement The element type of the vector.
DOX_MARKER([DOX_BOXING_CUSTOM_VECTOR])
template<typename TElement>
requires (!characters::IsCharacter<TElement>)
struct BoxTraits<std::vector<TElement>>
{
    /// Mapped type is \c TElement[].
    using                   Mapping=  TElement;
 
    /// Mapped as array-type
    static constexpr bool   IsArray=  true;
 
    /// Implementation of custom boxing for template <c>class std::vector</c>.
    /// @param box    The placeholder of the box box.
    /// @param value  The object to box.
    static void Write( Placeholder& box, const std::vector<TElement>& value)
    { box.Write( value.data(), integer( value.size() ) ); }
 
    /// Forbid unboxing by declaring Read as void.
    /// @param box Ignored.
    static void        Read( const Placeholder& box);
};
DOX_MARKER([DOX_BOXING_CUSTOM_VECTOR])
 
#if DOXYGEN
}} // namespace alib::boxing[::compatibility::std]
#endif
 
//##################################################################################################
//###################### Utility methods in namespace alib::compatibility::std #####################
//##################################################################################################
namespace compatibility { namespace std {
 
/// Creates a deep copy of a boxed C++ array type by appending its contents to a given
/// \c std::vector of corresponding element type.<br>
/// Note that no type checks are performed on the given box.
///
/// @tparam TElement  The element type.
/// @param  target    The target vector to fill.
/// @param  box       The source box of type \p{TElement[]}.
DOX_MARKER([DOX_BOXING_SAMPLE_ARR_UNBOX_VECTOR_IMPLEMENTATION])
template<typename TElement>
inline void CopyToVector( ::std::vector<TElement>& target, const Box& box ) {
    target.reserve( target.size() + size_t( box.UnboxLength() ) );
    for( integer i= 0 ; i < box.UnboxLength() ; ++i )
        target.emplace_back( box.UnboxElement<TElement>( i ) );
}
DOX_MARKER([DOX_BOXING_SAMPLE_ARR_UNBOX_VECTOR_IMPLEMENTATION])
 
/// Initializes \alib_boxing_nl in respect to <c>std::string</c>-types.
///
/// This method is \b not automatically invoked with function #"Bootstrap", because support
/// for boxing <c>std::string</c>-types is optional and provided with the inclusion of header
/// #"F;ALib.Compatibility.StdBoxtraits.H".
///
/// In general, boxing of <c>std::string</c>-types works well without the one-time invocation of
/// this function at the bootstrap of a process.
/// This method registers box-function #"FAppend" for <c>std::string</c>-types
/// types when #"alib_boxing_customizing_identity;custom boxing is bypassed" by wrapping the
/// types in \c std::reference_wrapper<T>.
/// The function is implemented with the help of #"FAppend::WrappedAppendable"
/// for wrapped <c>std::string</c>-types, each for character types #"characters::nchar" and
/// #"characters::wchar".
///
/// \note
///   If invoked \b after bootstrap and modules \alib_threads_nl and \alib_monomem_nl are included in
///   the \alibbuild,  mutex #"GLOBAL_ALLOCATOR_LOCK" has to be locked before an
///   invocation.
///   Bootstrapping may look as follows:
///     \snippet "gtest_main.cpp"     DOX_COMPATIBILITY_BOOTSTRAP
///
/// \note
///   (Note, that the curly brackets create a compound that releases the automatic owner instance
///   after the call.) <br>
///   Alternatively, bootstrapping can be performed until #"BootstrapPhases::PrepareConfig;2"
///   and then this function can be invoked. In this case, no locking is necessary.
///
inline void BootstrapStdStringBoxing() {
    #if ALIB_STRINGS && ALIB_BOXING
 
        alib::boxing::BootstrapRegister<FAppend<nchar, lang::HeapAllocator>, ::std::reference_wrapper<::std::string   >>( boxing::FAppend<nchar, lang::HeapAllocator>::WrappedAppendable<::std::string   >);
        alib::boxing::BootstrapRegister<FAppend<wchar, lang::HeapAllocator>, ::std::reference_wrapper<::std::string   >>( boxing::FAppend<wchar, lang::HeapAllocator>::WrappedAppendable<::std::string   >);
        alib::boxing::BootstrapRegister<FAppend<nchar, lang::HeapAllocator>, ::std::reference_wrapper<::std::wstring  >>( boxing::FAppend<nchar, lang::HeapAllocator>::WrappedAppendable<::std::wstring  >);
        alib::boxing::BootstrapRegister<FAppend<wchar, lang::HeapAllocator>, ::std::reference_wrapper<::std::wstring  >>( boxing::FAppend<wchar, lang::HeapAllocator>::WrappedAppendable<::std::wstring  >);
        alib::boxing::BootstrapRegister<FAppend<nchar, lang::HeapAllocator>, ::std::reference_wrapper<::std::u8string >>( boxing::FAppend<nchar, lang::HeapAllocator>::WrappedAppendable<::std::u8string >);
        alib::boxing::BootstrapRegister<FAppend<wchar, lang::HeapAllocator>, ::std::reference_wrapper<::std::u8string >>( boxing::FAppend<wchar, lang::HeapAllocator>::WrappedAppendable<::std::u8string >);
        #if ALIB_SIZEOF_WCHAR_T == 4
        alib::boxing::BootstrapRegister<FAppend<nchar, lang::HeapAllocator>, ::std::reference_wrapper<::std::u16string>>( boxing::FAppend<nchar, lang::HeapAllocator>::WrappedAppendable<::std::u16string>);
        alib::boxing::BootstrapRegister<FAppend<wchar, lang::HeapAllocator>, ::std::reference_wrapper<::std::u16string>>( boxing::FAppend<wchar, lang::HeapAllocator>::WrappedAppendable<::std::u16string>);
        #else
        alib::boxing::BootstrapRegister<FAppend<nchar, lang::HeapAllocator>, ::std::reference_wrapper<::std::u32string>>( boxing::FAppend<nchar, lang::HeapAllocator>::WrappedAppendable<::std::u32string>);
        alib::boxing::BootstrapRegister<FAppend<wchar, lang::HeapAllocator>, ::std::reference_wrapper<::std::u32string>>( boxing::FAppend<wchar, lang::HeapAllocator>::WrappedAppendable<::std::u32string>);
        #endif
 
    #endif
}
 
}}} // namespace [alib::boxing::custom::std]