any.h

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#ifndef ANY_H
#define ANY_H
 
#include <algorithm>
#include <memory>
#include <stdexcept>
#include <typeinfo>
#include <type_traits>
 
 
namespace bfl
{
namespace any
{
 
class any
{
public:
    any() noexcept :
        content(nullptr)
    { }
 
 
    any(const any& other) :
        content(other.content ? other.content->clone() : nullptr)
    { }
 
 
    any(any&& other) noexcept :
        content(other.content)
    {
        other.content = nullptr;
    }
 
 
    template<typename ValueType>
    any(const ValueType& value) :
        content(new holder<typename std::remove_cv<typename std::decay<const ValueType>::type>::type>(value))
    { }
 
 
    template<typename ValueType>
    any(ValueType&& value, typename std::enable_if<!std::is_same<any&, ValueType>::value>::type* = nullptr, typename std::enable_if<!std::is_const<ValueType>::value>::type* = nullptr) :
        content(new holder<typename std::decay<ValueType>::type>(static_cast<ValueType&&>(value)))
    { }
 
 
    any& operator=(const any& rhs)
    {
        any(rhs).swap(*this);
        return *this;
    }
 
 
    any& operator=(any&& rhs) noexcept
    {
        if (this == &rhs)
            return *this;
 
        rhs.swap(*this);
        any().swap(rhs);
 
        return *this;
    }
 
 
    template <class ValueType>
    any& operator=(ValueType&& rhs)
    {
        any(static_cast<ValueType&&>(rhs)).swap(*this);
 
        return *this;
    }
 
 
    ~any() noexcept
    {
        delete content;
    }
 
 
    void reset() noexcept
    {
        any().swap(*this);
    }
 
 
    any& swap(any& rhs) noexcept
    {
        std::swap(content, rhs.content);
 
        return *this;
    }
 
    bool has_value() const noexcept
    {
        return content;
    }
 
 
    const std::type_info& type() const noexcept
    {
        return content ? content->type() : typeid(void);
    }
 
 
private:
    class placeholder
    {
    public:
        virtual ~placeholder()
        { }
 
 
        virtual const std::type_info& type() const noexcept = 0;
 
 
        virtual placeholder* clone() const = 0;
 
    };
 
 
    template<typename ValueType>
    class holder : public placeholder
    {
    public:
        holder(const ValueType& value) :
          held(value)
        { }
 
 
        holder(ValueType&& value) :
          held(static_cast<ValueType&&>(value))
        { }
 
 
        virtual const std::type_info& type() const noexcept
        {
            return typeid(ValueType);
        }
 
 
        virtual placeholder* clone() const
        {
            return new holder(held);
        }
 
 
        ValueType held;
 
 
    private:
        /* Intentionally left unimplemented. */
        holder& operator=(const holder&);
    };
 
 
    template<typename ValueType>
    friend ValueType* any_cast(any* operand) noexcept;
 
 
    placeholder* content;
};
 
 
inline void swap(any& lhs, any& rhs) noexcept
{
    lhs.swap(rhs);
}
 
 
class bad_any_cast : public std::bad_cast
{
public:
    virtual const char* what() const noexcept override
    {
        return "bad any_cast";
    }
};
 
 
template<typename ValueType>
ValueType* any_cast(any* operand) noexcept
{
    return operand && operand->type() == typeid(ValueType) ? std::addressof(static_cast<any::holder<typename std::remove_cv<ValueType>::type>*>(operand->content)->held) : nullptr;
}
 
 
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>(std::addressof(operand));
    if(!result)
        throw bad_any_cast();
 
    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 || std::is_const<typename std::remove_reference<ValueType>::type>::value, "any_cast shall not be used for getting nonconst references to temporary objects");
 
    return any_cast<ValueType>(operand);
}
 
}
}
 
#endif /* ANY_H */