any.h

// Boost Software License - Version 1.0 - August 17th, 2003
// 
// Permission is hereby granted, free of charge, to any person or organization
// obtaining a copy of the software and accompanying documentation covered by
// this license (the "Software") to use, reproduce, display, distribute,
// execute, and transmit the Software, and to prepare derivative works of the
// Software, and to permit third-parties to whom the Software is furnished to
// do so, all subject to the following:
// 
// The copyright notices in the Software and this entire statement, including
// the above license grant, this restriction and the following disclaimer,
// must be included in all copies of the Software, in whole or in part, and
// all derivative works of the Software, unless such copies or derivative
// works are solely in the form of machine-executable object code generated by
// a source language processor.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

// See http://www.boost.org/libs/any for Documentation.

#ifndef MOMEMTA_ANY_INCLUDED
#define MOMEMTA_ANY_INCLUDED

#if defined(_MSC_VER)
# pragma once
#endif

// what:  variant type momemta::any
// who:   contributed by Kevlin Henney,
//        with features contributed and bugs found by
//        Antony Polukhin, Ed Brey, Mark Rodgers,
//        Peter Dimov, and James Curran
// when:  July 2001, April 2013 - May 2013

// extracted from boost for MoMEMta

#include <algorithm>
#include <type_traits>
#include <typeinfo>

namespace momemta
{
    class any
    {
    public: // structors

        any() noexcept
          : content(0)
        {
        }

        template<typename ValueType>
        any(const ValueType & value)
          : content(new holder<
                typename std::remove_cv<typename std::decay<const ValueType>::type>::type
            >(value))
        {
        }

        any(const any & other)
          : content(other.content ? other.content->clone() : 0)
        {
        }

        // Move constructor
        any(any&& other) noexcept
          : content(other.content)
        {
            other.content = 0;
        }

        // Perfect forwarding of ValueType
        template<typename ValueType>
        any(ValueType&& value
            , typename std::enable_if<!std::is_same<any&, ValueType>::value>::type* = 0 // disable if value has type `any&`
            , typename std::enable_if<!std::is_const<ValueType>::value>::type* = 0) // disable if value has type `const ValueType&&`
          : content(new holder< typename std::decay<ValueType>::type >(static_cast<ValueType&&>(value)))
        {
        }

        ~any() noexcept
        {
            delete content;
        }

    public: // modifiers

        any & swap(any & rhs) noexcept
        {
            std::swap(content, rhs.content);
            return *this;
        }


        any & operator=(const any& rhs)
        {
            any(rhs).swap(*this);
            return *this;
        }

        // move assignement
        any & operator=(any&& rhs) noexcept
        {
            rhs.swap(*this);
            any().swap(rhs);
            return *this;
        }

        // Perfect forwarding of ValueType
        template <class ValueType>
        any & operator=(ValueType&& rhs)
        {
            any(static_cast<ValueType&&>(rhs)).swap(*this);
            return *this;
        }

    public: // queries

        bool empty() const noexcept
        {
            return !content;
        }

        void clear() noexcept
        {
            any().swap(*this);
        }

        const std::type_info& type() const noexcept
        {
            return content ? content->type() : typeid(void);
        }

    private: // types

        class placeholder
        {
        public: // structors

            virtual ~placeholder()
            {
            }

        public: // queries

            virtual const std::type_info& type() const noexcept = 0;

            virtual placeholder * clone() const = 0;

        };

        template<typename ValueType>
        class holder : public placeholder
        {
        public: // structors

            holder(const ValueType & value)
              : held(value)
            {
            }

            holder(ValueType&& value)
              : held(static_cast< ValueType&& >(value))
            {
            }
        public: // queries

            virtual const std::type_info& type() const noexcept
            {
                return typeid(ValueType);
            }

            virtual placeholder * clone() const
            {
                return new holder(held);
            }

        public: // representation

            ValueType held;

        private: // intentionally left unimplemented
            holder & operator=(const holder &);
        };

    private: // representation

        template<typename ValueType>
        friend ValueType * any_cast(any *) noexcept;

        template<typename ValueType>
        friend ValueType * unsafe_any_cast(any *) noexcept;

        placeholder * content;

    };

    inline void swap(any & lhs, any & rhs) noexcept
    {
        lhs.swap(rhs);
    }

    class __attribute__((__visibility__("default"))) bad_any_cast :
        public std::bad_cast
    {
    public:
        virtual const char * what() const noexcept
        {
            return "momemta::bad_any_cast: "
                   "failed conversion using momemta::any_cast";
        }
    };

    template<typename ValueType>
    ValueType * any_cast(any * operand) noexcept
    {
        return operand && operand->type() == typeid(ValueType)
            ? &static_cast<any::holder<typename std::remove_cv<ValueType>::type> *>(operand->content)->held
            : 0;
    }

    template<typename ValueType>
    inline const ValueType * any_cast(const any * operand) noexcept
    {
        return any_cast<ValueType>(const_cast<any *>(operand));
    }

    template<typename ValueType>
    ValueType any_cast(any & operand)
    {
        typedef typename std::remove_reference<ValueType>::type nonref;


        nonref * result = any_cast<nonref>(&operand);
        if(!result)
            throw bad_any_cast();

        // Attempt to avoid construction of a temporary object in cases when
        // `ValueType` is not a reference. Example:
        // `static_cast<std::string>(*result);`
        // which is equal to `std::string(*result);`
        typedef typename std::conditional<
            std::is_reference<ValueType>::value,
            ValueType,
            typename std::add_lvalue_reference<ValueType>::type
        >::type ref_type;

        return static_cast<ref_type>(*result);
    }

    template<typename ValueType>
    inline ValueType any_cast(const any & operand)
    {
        typedef typename std::remove_reference<ValueType>::type nonref;
        return any_cast<const nonref &>(const_cast<any &>(operand));
    }

    template<typename ValueType>
    inline ValueType any_cast(any&& operand)
    {
        static_assert(
            std::is_rvalue_reference<ValueType&&>::value /*true if ValueType is rvalue or just a value*/
            || std::is_const< typename std::remove_reference<ValueType>::type >::value,
            "momemta::any_cast shall not be used for getting nonconst references to temporary objects"
        );
        return any_cast<ValueType>(operand);
    }


    // Note: The "unsafe" versions of any_cast are not part of the
    // public interface and may be removed at any time. They are
    // required where we know what type is stored in the any and can't
    // use typeid() comparison, e.g., when our types may travel across
    // different shared libraries.
    template<typename ValueType>
    inline ValueType * unsafe_any_cast(any * operand) noexcept
    {
        return &static_cast<any::holder<ValueType> *>(operand->content)->held;
    }

    template<typename ValueType>
    inline const ValueType * unsafe_any_cast(const any * operand) noexcept
    {
        return unsafe_any_cast<ValueType>(const_cast<any *>(operand));
    }
}

// Copyright Kevlin Henney, 2000, 2001, 2002. All rights reserved.
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)

#endif