utility.hpp

Go to the documentation of this file.

// Copyright (C) 2015-2023 Jonathan Müller and foonathan/memory contributors
// SPDX-License-Identifier: Zlib
 
#ifndef WPI_MEMORY_DETAIL_UTILITY_HPP
#define WPI_MEMORY_DETAIL_UTILITY_HPP
 
// implementation of some functions from <utility> to prevent dependencies on it
 
#include <type_traits>
 
#include "../config.hpp"
 
#if WPI_HOSTED_IMPLEMENTATION
#include <utility>
#endif
 
namespace wpi
{
    namespace memory
    {
        namespace detail
        {
            // move - taken from http://stackoverflow.com/a/7518365
            template <typename T>
            typename std::remove_reference<T>::type&& move(T&& arg) noexcept
            {
                return static_cast<typename std::remove_reference<T>::type&&>(arg);
            }
            // forward - taken from http://stackoverflow.com/a/27501759
            template <class T>
            T&& forward(typename std::remove_reference<T>::type& t) noexcept
            {
                return static_cast<T&&>(t);
            }
            template <class T>
            T&& forward(typename std::remove_reference<T>::type&& t) noexcept
            {
                static_assert(!std::is_lvalue_reference<T>::value,
                              "Can not forward an rvalue as an lvalue.");
                return static_cast<T&&>(t);
            }
 
            namespace swap_
            {
#if WPI_HOSTED_IMPLEMENTATION
                using std::swap;
#else
                template <typename T>
                void swap(T& a, T& b)
                {
                    T tmp = move(a);
                    a     = move(b);
                    b     = move(tmp);
                }
#endif
            } // namespace swap_
 
            // ADL aware swap
            template <typename T>
            void adl_swap(T& a, T& b) noexcept
            {
                using swap_::swap;
                swap(a, b);
            }
 
// fancier syntax for enable_if
// used as (template) parameter
// also useful for doxygen
// define PREDEFINED: WPI_REQUIRES(x):=
#define WPI_REQUIRES(Expr) typename std::enable_if<(Expr), int>::type = 0
 
// same as above, but as return type
// also useful for doxygen:
// defined PREDEFINED: WPI_REQUIRES_RET(x,r):=r
#define WPI_REQUIRES_RET(Expr, ...) typename std::enable_if<(Expr), __VA_ARGS__>::type
 
// fancier syntax for enable_if on non-templated member function
#define WPI_ENABLE_IF(Expr)                                                                  \
    template <typename Dummy = std::true_type, WPI_REQUIRES(Dummy::value && (Expr))>
 
// fancier syntax for general expression SFINAE
// used as (template) parameter
// also useful for doxygen:
// define PREDEFINED: WPI_SFINAE(x):=
#define WPI_SFINAE(Expr) decltype((Expr), int()) = 0
 
// avoids code repetition for one-line forwarding functions
#define WPI_AUTO_RETURN(Expr)                                                                \
    decltype(Expr)                                                                                 \
    {                                                                                              \
        return Expr;                                                                               \
    }
 
// same as above, but requires certain type
#define WPI_AUTO_RETURN_TYPE(Expr, T)                                                        \
    decltype(Expr)                                                                                 \
    {                                                                                              \
        static_assert(std::is_same<decltype(Expr), T>::value,                                      \
                      #Expr " does not have the return type " #T);                                 \
        return Expr;                                                                               \
    }
 
            // whether or not a type is an instantiation of a template
            template <template <typename...> class Template, typename T>
            struct is_instantiation_of : std::false_type
            {
            };
 
            template <template <typename...> class Template, typename... Args>
            struct is_instantiation_of<Template, Template<Args...>> : std::true_type
            {
            };
        } // namespace detail
    }     // namespace memory
} // namespace wpi
 
#endif //WPI_MEMORY_DETAIL_UTILITY_HPP