poly.hpp

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/*
    Copyright 2013 Adobe
    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)
*/
/**************************************************************************************************/
 
#ifndef ADOBE_POLY_HPP
#define ADOBE_POLY_HPP
 
#include <adobe/config.hpp>
 
#include <boost/mpl/bool.hpp>
#include <boost/mpl/if.hpp>
#include <boost/mpl/or.hpp>
#include <boost/utility/enable_if.hpp>
 
#include <adobe/implementation/swap.hpp>
#include <adobe/typeinfo.hpp>
 
#include <type_traits>
 
/**************************************************************************************************/
 
namespace adobe {
 


 
 
#if !defined(ADOBE_NO_DOCUMENTATION)
 
template <typename T, typename U>
struct is_base_derived_or_same
    : boost::mpl::or_<std::is_base_of<T, U>, std::is_base_of<U, T>, std::is_same<T, U>> {};
#endif
// !defined(ADOBE_NO_DOCUMENTATION)
 
/**************************************************************************************************/

 
struct poly_copyable_interface {
    virtual poly_copyable_interface* clone(void*) const = 0;
    virtual poly_copyable_interface* move_clone(void*) = 0;
    virtual void* cast() = 0;
    virtual const void* cast() const = 0;
    virtual const std::type_info& type_info() const = 0;
 
    // Precondition of assignment: this->type_info() == x.type_info()
    virtual void assign(const poly_copyable_interface& x) = 0;
 
    // Precondition of exchange: this->type_info() == x.type_info()
    virtual void exchange(poly_copyable_interface& x) = 0;
 
    virtual ~poly_copyable_interface() {}
};
 
/**************************************************************************************************/
 
#if !defined(ADOBE_NO_DOCUMENTATION)
 
/**************************************************************************************************/
 
namespace implementation {
 
/**************************************************************************************************/
 
template <typename ConcreteType, typename Interface>
struct poly_state_remote : Interface {
    typedef ConcreteType value_type;
    typedef Interface interface_type;
 
    const value_type& get() const { return *value_ptr_m; }
    value_type& get() { return *value_ptr_m; }
 
    poly_state_remote(poly_state_remote&& x) : value_ptr_m(x.value_ptr_m) {
        x.value_ptr_m = nullptr;
    }
 
    explicit poly_state_remote(value_type x) : value_ptr_m(::new value_type(std::move(x))) {}
 
    ~poly_state_remote() { delete value_ptr_m; }
 
    // Precondition : this->type_info() == x.type_info()
    void assign(const poly_copyable_interface& x) {
        *value_ptr_m = *static_cast<const poly_state_remote&>(x).value_ptr_m;
    }
 
    const std::type_info& type_info() const { return typeid(value_type); }
    const void* cast() const { return value_ptr_m; }
    void* cast() { return value_ptr_m; }
 
    // Precondition : this->type_info() == x.type_info()
    void exchange(poly_copyable_interface& x) {
        return std::swap(value_ptr_m, static_cast<poly_state_remote&>(x).value_ptr_m);
    }
 
    // Precondition : x.type_info() == y.type_info()
    friend bool operator==(const poly_state_remote& x, const poly_state_remote& y) {
        return *x.value_ptr_m == *y.value_ptr_m;
    }
 
    value_type* value_ptr_m;
};
 
/**************************************************************************************************/
 
template <typename ConcreteType, typename Interface>
struct poly_state_local : Interface {
    typedef ConcreteType value_type;
    typedef Interface interface_type;
 
    const value_type& get() const { return value_m; }
    value_type& get() { return value_m; }
 
    poly_state_local(poly_state_local&& x) noexcept : value_m(std::move(x.value_m)) {}
 
    explicit poly_state_local(value_type x) : value_m(std::move(x)) {}
 
    // Precondition : this->type_info() == x.type_info()
    void assign(const poly_copyable_interface& x) {
        value_m = static_cast<const poly_state_local&>(x).value_m;
    }
 
    const std::type_info& type_info() const { return typeid(value_type); }
    const void* cast() const { return &value_m; }
    void* cast() { return &value_m; }
 
    // Precondition : this->type_info() == x.type_info()
    void exchange(poly_copyable_interface& x) {
        return std::swap(value_m, static_cast<poly_state_local&>(x).value_m);
    }
 
    // Precondition : x.type_info() == y.type_info()
    friend bool operator==(const poly_state_local& x, const poly_state_local& y) {
        return x.value_m == y.value_m;
    }
 
    value_type value_m;
};
 
 
/**************************************************************************************************/
 
typedef double storage_t[2];
 
template <typename T, int N = sizeof(storage_t)>
struct is_small {
    enum {
        value = sizeof(T) <= N && (std::is_nothrow_constructible<typename T::value_type>::value ||
                                   std::is_same<std::string, typename T::value_type>::value)
    };
};
 
/**************************************************************************************************/
 
template <typename F>
struct poly_instance : F {
    typedef typename F::value_type value_type;
    typedef typename F::interface_type interface_type;
 
    poly_instance(const value_type& x) : F(x) {}
    poly_instance(poly_instance&& x) : F(std::move(x)) {}
 
    poly_copyable_interface* clone(void* storage) const {
        return ::new (storage) poly_instance(this->get());
    }
 
    poly_copyable_interface* move_clone(void* storage) {
        return ::new (storage) poly_instance(std::move(*this));
    }
};
 
/**************************************************************************************************/
 
template <typename T>
class has_equals {
    typedef bool (T::*E)(const T&) const;
    typedef char (&no_type)[1];
    typedef char (&yes_type)[2];
    template <E e>
    struct sfinae {
        typedef yes_type type;
    };
    template <class U>
    static typename sfinae<&U::equals>::type test(int);
    template <class U>
    static no_type test(...);
 
public:
    enum { value = sizeof(test<T>(1)) == sizeof(yes_type) };
};
 
/**************************************************************************************************/
 
} // namespace implementation
 
/**************************************************************************************************/
 
#endif
//  !defined(ADOBE_NO_DOCUMENTATION)
 
/**************************************************************************************************/

 
template <typename ConcreteType, typename Interface>
struct optimized_storage_type
    : boost::mpl::if_<
          implementation::is_small<implementation::poly_state_local<ConcreteType, Interface>>,
          implementation::poly_state_local<ConcreteType, Interface>,
          implementation::poly_state_remote<ConcreteType, Interface>> {};
 
 
/**************************************************************************************************/

 
template <typename I, template <typename> class Instance>
struct poly_base {
 
    template <typename T, template <typename> class U>
    friend struct poly_base;
 
    typedef I interface_type;
 
    // Construct from value type
 
    template <typename T>
    explicit poly_base(T x, typename boost::disable_if<std::is_base_of<poly_base, T>>::type* = 0) {
        ::new (storage()) implementation::poly_instance<Instance<T>>(std::move(x));
    }
 
    // Construct from related interface (might throw on downcast)
    template <typename J, template <typename> class K>
    explicit poly_base(const poly_base<J, K>& x,
                       typename boost::enable_if<is_base_derived_or_same<I, J>>::type* = 0) {
        if (std::is_base_of<J, I>::value)
            dynamic_cast<const I&>(static_cast<const poly_copyable_interface&>(x.interface_ref()));
        x.interface_ref().clone(storage());
    }
 
    poly_base(const poly_base& x) { x.interface_ref().clone(storage()); }
 
    poly_base(poly_base&& x) { x.interface_ref().move_clone(storage()); }
 
    friend inline void swap(poly_base& x, poly_base& y) {
        interface_type& a(x.interface_ref());
        interface_type& b(y.interface_ref());
 
        if (a.type_info() == b.type_info()) {
            a.exchange(b);
            return;
        }
 
        // x->tmp
        poly_base tmp(std::move(x));
        a.~interface_type();
 
        // y->x
        b.move_clone(x.storage());
        b.~interface_type();
 
        // tmp->y
        tmp.interface_ref().move_clone(y.storage());
    }
 
    poly_base& operator=(poly_base x) {
        interface_ref().~interface_type();
        x.interface_ref().move_clone(storage());
        return *this;
    }
    ~poly_base() { interface_ref().~interface_type(); }
 
    template <typename J, template <typename> class K>
    static bool is_dynamic_convertible_from(const poly_base<J, K>& x) {
        return dynamic_cast<const I*>(
            static_cast<const poly_copyable_interface*>(&x.interface_ref()));
    }
 
    template <typename J>
    bool is_dynamic_convertible_to() const {
        return dynamic_cast<const J*>(
                   static_cast<const poly_copyable_interface*>(&interface_ref())) != NULL;
    }
 
    const std::type_info& type_info() const { return interface_ref().type_info(); }
 
    template <typename T>
    const T& cast() const {
        if (type_info() != typeid(T))
            throw bad_cast(type_info(), typeid(T));
        return *static_cast<const T*>(interface_ref().cast());
    }
 
    template <typename T>
    T& cast() {
        if (type_info() != typeid(T))
            throw bad_cast(type_info(), typeid(T));
        return *static_cast<T*>(interface_ref().cast());
    }
 
    template <typename T>
    bool cast(T& x) const {
        if (type_info() != typeid(T))
            return false;
        x = cast<T>();
        return true;
    }
 
    template <typename T>
    poly_base& assign(const T& x) {
        if (type_info() == typeid(T))
            cast<T>() = x;
        else {
            poly_base tmp(x);
            swap(*this, tmp);
        }
        return *this;
    }
 
    // Assign from related (may throw if downcastisng)
    template <typename J, template <typename> class K>
    typename boost::enable_if<is_base_derived_or_same<I, J>>::type
    assign(const poly_base<J, K>& x) {
        if (std::is_base_of<J, I>::value)
            dynamic_cast<I&>(static_cast<J&>(*x.interface_ptr())); // make sure type safe
        interface_ref().~interface_type();
        x.interface_ref().clone(storage());
    }
 
    const interface_type* operator->() const { return &interface_ref(); }
 
    interface_type* operator->() { return &interface_ref(); }
 
    interface_type& interface_ref() { return *static_cast<interface_type*>(storage()); }
 
    const interface_type& interface_ref() const {
        return *static_cast<const interface_type*>(storage());
    }
 
    void* storage() { return &data_m; }
    const void* storage() const { return &data_m; }
 
    implementation::storage_t data_m;
};
 
template <class J, template <typename> class K>
inline typename boost::enable_if<implementation::has_equals<J>, bool>::type
operator==(const poly_base<J, K>& x, const poly_base<J, K>& y) {
    return x.interface_ref().equals(y.interface_ref());
}
 
 
/**************************************************************************************************/

 
template <class F>
class poly : public F {
public:
    template <typename T>
    explicit poly(const T& x) : F(x) {}
 
    poly(poly&& x) : F(std::move(x)) {}
    poly(const poly&) = default;
 
    poly& operator=(poly x) {
        static_cast<F&>(*this) = std::move(static_cast<F&>(x));
        return *this;
    }
 
    poly() : F() {}
};
 
/**************************************************************************************************/

template <typename T, typename U>
T poly_cast(poly<U>& x) {
    typedef typename boost::remove_reference<T>::type target_type;
    typedef typename target_type::interface_type target_interface_type;
    if (!x.template is_dynamic_convertible_to<target_interface_type>())
        throw bad_cast(typeid(poly<U>), typeid(T));
    return reinterpret_cast<T>(x);
}
 
/**************************************************************************************************/

 
template <typename T, typename U>
T poly_cast(const poly<U>& x) {
    typedef typename boost::remove_reference<T>::type target_type;
    typedef typename target_type::interface_type target_interface_type;
    if (!x.template is_dynamic_convertible_to<target_interface_type>())
        throw bad_cast(typeid(poly<U>), typeid(T));
    return reinterpret_cast<T>(x);
}
 
/**************************************************************************************************/

 
template <typename T, typename U>
T poly_cast(poly<U>* x) {
    typedef typename std::remove_pointer<T>::type target_type;
    typedef typename target_type::interface_type target_interface_type;
    return x->template is_dynamic_convertible_to<target_interface_type>() ? reinterpret_cast<T>(x)
                                                                          : NULL;
}
 
/**************************************************************************************************/

 
 
template <typename T, typename U>
T poly_cast(const poly<U>* x) {
    typedef typename std::remove_pointer<T>::type target_type;
    typedef typename target_type::interface_type target_interface_type;
    return x->template is_dynamic_convertible_to<target_interface_type>() ? reinterpret_cast<T>(x)
                                                                          : NULL;
}
 
/**************************************************************************************************/

 
template <class T>
inline bool operator!=(const poly<T>& x, const poly<T>& y) {
    return !(x == y);
}
 

 
/**************************************************************************************************/
 
} // namespace adobe
 
/**************************************************************************************************/
 
#endif
 
/**************************************************************************************************/