any.hpp

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// any.hpp
/*
 *  Copyright (c) 2007 Leigh Johnston.
 *
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions are
 *  met:
 *
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *
 *     * Neither the name of Leigh Johnston nor the names of any
 *       other contributors to this software may be used to endorse or
 *       promote products derived from this software without specific prior
 *       written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 *  IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 *  THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 *  PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 *  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 *  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 *  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 *  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 *  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 *  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
 
#pragma once
 
#include <neolib/neolib.hpp>
#include <any>
#include <stdexcept>
#include <typeinfo>
 
#include <neolib/core/i_any.hpp>
#include <neolib/core/variant.hpp>
 
namespace neolib
{
    // todo: casts in this implementation of a polymorphic any mean this is not yet a solved problem (for passing across plugin boundaries)
 
    template <typename T>
    struct is_variant { static constexpr bool value = false; };
    template <typename... Types>
    struct is_variant<variant<Types...>> { static constexpr bool value = true; };
    template <typename T>
    constexpr bool is_variant_v = is_variant<T>::value;
 
    class any : public i_any, private std::any
    {
    private:
        template<class T>
        friend T any_cast(const any& operand);
        template<class T>
        friend T any_cast(any& operand);
        template<class T>
        friend T any_cast(any&& operand);
        template<class T>
        friend const T* any_cast(const any* operand) noexcept;
        template<class T>
        friend T* any_cast(any* operand) noexcept;
        template<class T>
        friend T unsafe_any_cast(const any& operand) noexcept;
        template<class T>
        friend T unsafe_any_cast(any& operand) noexcept;
    public:
        any() : 
            cptr{ nullptr }, 
            ptr{ nullptr }
        {
        }
        any(const i_any& aOther) :
            any{ static_cast<const any&>(aOther) } // todo - is it doable?
        {
        }
        any(i_any&& aOther) :
            any{ static_cast<any&>(aOther) } // todo - is it doable?
        {
        }
        any(const any& aOther) :
            std::any{ aOther.as_std_any() }, 
            cptr{ aOther.cptr }, 
            ptr{ aOther.ptr }
        {
        }
        any(any&& aOther) :
            std::any{ std::move(aOther.as_std_any()) }, 
            cptr{ aOther.cptr },
            ptr{ aOther.ptr }
        {
            aOther.cptr = nullptr;
            aOther.ptr = nullptr;
        }
        template <typename ValueType>
        any(ValueType&& aValue, std::enable_if_t<!is_variant_v<std::decay_t<ValueType>>, sfinae> = {}) :
            std::any{ std::decay_t<ValueType>{aValue} },
            cptr{ &any::do_cptr<std::decay_t<ValueType>> },
            ptr{ &any::do_ptr<std::decay_t<ValueType>> }
        {
        }
        template <typename ValueType>
        explicit any(ValueType&& aVariant, std::enable_if_t<is_variant_v<std::decay_t<ValueType>>, sfinae> = {}) :
            std::any{ std::decay_t<decltype(aVariant)>{aVariant} },
            cptr{ &any::do_cptr<std::decay_t<decltype(aVariant)>> },
            ptr{ &any::do_ptr<std::decay_t<decltype(aVariant)>> }
        {
        }
    public:
        any& operator=(const i_any& aRhs)
        {
            // todo - is it doable?
            return *this = static_cast<const any&>(aRhs);
        }
        any& operator=(i_any&& aRhs)
        {
            // todo - is it doable?
            return *this = static_cast<any&>(aRhs);
        }
        any& operator=(const any& aRhs)
        {
            std::any::operator=(aRhs.as_std_any());
            cptr = aRhs.cptr;
            ptr = aRhs.ptr;
            return *this;
        }
        any& operator=(any&& aRhs)
        {
            std::any::operator=(std::move(aRhs.as_std_any()));
            cptr = aRhs.cptr;
            ptr = aRhs.ptr;
            aRhs.cptr = nullptr;
            aRhs.ptr = nullptr;
            return *this;
        }
        template<typename ValueType>
        any& operator=(ValueType&& aRhs)
        {
            std::any::operator=(std::decay_t<ValueType>{aRhs});
            cptr = &any::do_cptr<std::decay_t<ValueType>>;
            ptr = &any::do_ptr<std::decay_t<ValueType>>;
            return *this;
        }
    public:
        template<class ValueType, class... Args>
        std::decay_t<ValueType>& emplace(Args&&... args)
        {
            auto& result = std::any::emplace<ValueType>(std::forward<Args...>(args...));
            cptr = &any::do_cptr<std::decay_t<ValueType>>;
            ptr = &any::do_ptr<std::decay_t<ValueType>>;
            return result;
        }
        template<class ValueType, class U, class... Args>
        std::decay_t<ValueType>& emplace(std::initializer_list<U> il, Args&&... args)
        {
            auto& result = std::any::emplace<ValueType>(il, std::forward<Args...>(args...));
            cptr = &any::do_cptr<std::decay_t<ValueType>>;
            ptr = &any::do_ptr<std::decay_t<ValueType>>;
            return result;
        }
        void reset() override
        {
            std::any::reset();
            cptr = nullptr;
            ptr = nullptr;
        }
        void swap(any& aOther)
        {
            std::any::swap(aOther.as_std_any());
            std::swap(cptr, aOther.cptr);
            std::swap(ptr, aOther.ptr);
        }
    public:
        bool has_value() const override
        {
            return std::any::has_value();
        }
        std::type_info const& type() const override
        {
            return std::any::type();
        }
    public:
        bool operator==(const i_any& aOther) const override
        {
            return *this == static_cast<const any&>(aOther);
        }
        bool operator!=(const i_any& aOther) const override
        {
            return *this != static_cast<const any&>(aOther);
        }
        bool operator<(const i_any& aOther) const override
        {
            return *this < static_cast<const any&>(aOther);
        }
        bool operator==(const any& aOther) const
        {
            if (cptr != nullptr && aOther.cptr != nullptr)
                return cptr(*this) == aOther.cptr(aOther);
            else
                return cptr == aOther.cptr;
        }
        bool operator!=(const any& aOther) const
        {
            if (cptr != nullptr && aOther.cptr != nullptr)
                return cptr(*this) != aOther.cptr(aOther);
            else
                return cptr != aOther.cptr;
        }
        bool operator<(const any& aOther) const
        {
            if (cptr != nullptr && aOther.cptr != nullptr)
                return cptr(*this) < aOther.cptr(aOther);
            else
                return cptr < aOther.cptr;
        }
    private:
        const std::any& as_std_any() const override
        {
            return *this;
        }
        std::any& as_std_any() override
        {
            return *this;
        }
        const void* unsafe_ptr() const override
        {
            if (cptr != nullptr)
                return cptr(*this);
            else
                return nullptr;
        }
        void* unsafe_ptr() override
        {
            if (cptr != nullptr)
                return ptr(*this);
            else
                return nullptr;
        }
        template <typename T>
        static const void* do_cptr(const any& aArg)
        {
            return &std::any_cast<const T&>(aArg.as_std_any());
        }
        template <typename T>
        static void* do_ptr(any& aArg)
        {
            return &std::any_cast<T&>(aArg.as_std_any());
        }
    private:
        const void*(*cptr)(const any&);
        void*(*ptr)(any&);
    };
 
    inline void swap(any& aLhs, any& aRhs)
    {
        aLhs.swap(aRhs);
    }
 
    template<class T>
    inline T any_cast(const any& operand)
    {
        return std::any_cast<T>(operand.as_std_any());
    }
    template<class T>
    inline T any_cast(any& operand)
    {
        return std::any_cast<T>(operand.as_std_any());
    }
    template<class T>
    inline T any_cast(any&& operand)
    {
        return std::any_cast<T>(std::move(operand.as_std_any()));
    }
    template<class T>
    inline const T* any_cast(const any* operand) noexcept
    {
        return std::any_cast<const T*>(&operand->as_std_any());
    }
    template<class T>
    inline T* any_cast(any* operand) noexcept
    {
        return std::any_cast<T*>(&operand->as_std_any());
    }
    template<class T>
    inline T unsafe_any_cast(const any& operand) noexcept
    {
        return *static_cast<const std::decay_t<T>*>(operand.unsafe_ptr());
    }
    template<class T>
    inline T unsafe_any_cast(any& operand) noexcept
    {
        return *static_cast<std::decay_t<T>*>(operand.unsafe_ptr());
    }
}