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Filename : import_mangled_helpers.hpp
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// Copyright 2015-2018 Klemens D. Morgenstern
//
// 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 BOOST_DLL_DETAIL_IMPORT_MANGLED_HELPERS_HPP_
#define BOOST_DLL_DETAIL_IMPORT_MANGLED_HELPERS_HPP_


#include <boost/type_traits/conditional.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/type_traits/is_class.hpp>
#include <boost/type_traits/is_function.hpp>
#include <boost/type_traits/remove_cv.hpp>


#ifdef BOOST_HAS_PRAGMA_ONCE
# pragma once
#endif

namespace boost { namespace dll { namespace experimental { namespace detail {

//the following could be done by fusion, though it's simple enough to just declare it here.
template<class ...Args>
struct sequence {};

template<class Value, class Seq> struct push_front;
template<class Value, class ...Args>
struct push_front<Value, sequence<Args...>>
{
    typedef sequence<Value, Args...> type;
};

template<class Lhs, class Rhs>
struct unqalified_is_same :
        boost::is_same<
            typename boost::remove_cv<Lhs>::type,
            typename boost::remove_cv<Rhs>::type
        >
{
};

/* ********************************** function sequence type traits ******************************/

//determine if it's a sequence of functions.
template<class T> struct is_function_seq;

//type-trait for function overloads
template<class Class, class...Args> struct is_function_seq<sequence<Class, Args...>>
            : boost::conditional<
                boost::is_function<Class>::value,
                is_function_seq<sequence<Args...>>,
                boost::false_type>::type
{};

template<class Class>
struct is_function_seq<sequence<Class>> : boost::is_function<Class>
{
};

template<>
struct is_function_seq<sequence<>> : boost::false_type
{
};

/* ********************************* Function Tuple ***************************  */

//a tuple of plain functions.
template <class ...Ts>
struct function_tuple;

template <class Return, class...Args, class T2, class ...Ts>
struct function_tuple<Return(Args...), T2, Ts...>
    : function_tuple<T2, Ts...>
{
    Return(*f_)(Args...);

    constexpr function_tuple(Return(* t)(Args...), T2* t2, Ts* ... ts)
        : function_tuple<T2, Ts...>(t2, ts...)
        , f_(t)
    {}

    Return operator()(Args...args) const {
        return (*f_)(static_cast<Args>(args)...);
    }
    using function_tuple<T2, Ts...>::operator();
};

template <class Return, class...Args>
struct function_tuple<Return(Args...)> {
    Return(*f_)(Args...);

    constexpr function_tuple(Return(* t)(Args...))
        : f_(t)
    {}

    Return operator()(Args...args) const {
        return (*f_)(static_cast<Args>(args)...);
    }
};


/* ********************************** MemFn sequence type traits ******************************/

template<class Class, class Func>
struct mem_fn_def
{
    typedef Class class_type;
    typedef Func  func_type;
    typedef typename boost::dll::detail::get_mem_fn_type<Class, Func>::mem_fn mem_fn;
};

template<class ...Args>
struct make_mem_fn_seq;

// B: is T1 another version of T0?
template<bool, class T0, class T1, class T2>
struct make_mem_fn_seq_getter;

template<class T0, class T1, class T2>
struct make_mem_fn_seq_getter<true, T0, T1, T2>
{
    typedef mem_fn_def<T1, T2> type;
};

template<class T0, class T1, class T2>
struct make_mem_fn_seq_getter<false, T0, T1, T2>
{
    typedef mem_fn_def<T0, T1> type;
};

template<class Class, class Signature>
struct make_mem_fn_seq<Class, Signature>
{
    typedef mem_fn_def<Class, Signature> mem_fn;
    typedef sequence<mem_fn>   type;
};

template<class Class>
struct make_mem_fn_seq<Class>
{
    typedef sequence<>   type;
};

template<class T0, class T1, class T2, class ... Args>
struct make_mem_fn_seq<T0, T1, T2, Args...>
{
    /* Since we might have ovls, it might be :
     * Class, void(int), void(int, int) //--> just us class for both
     * Class, const Class, void(int)//--> ovl class.
     *
     */
    static_assert(boost::is_object<T0>::value, "");
    typedef typename make_mem_fn_seq_getter<
           unqalified_is_same<T0, T1>::value, T0, T1, T2>::type mem_fn_type;

    typedef typename boost::conditional<
        unqalified_is_same<T0, T1>::value,
        make_mem_fn_seq<T1, Args...>,
        make_mem_fn_seq<T0, T2, Args...>> ::type next;

    typedef typename push_front<mem_fn_type, typename next::type>::type type;
};




/* Ok, this needs to be documented, so here's some pseudo-code:
 *
 * @code
 *
 * bool unqalified_is_same(lhs, rhs)
 * {
 *    return remove_cv(lhs) == remove_cv(rhs);
 * }
 *
 * mem_fn make_mem_fn_seq_getter(b, cl, T2, T3)
 * {
 *    if (b) //b means, that T2 is another version of cl, i.e. qualified
 *       return get_mem_fn_type(T2, T3);
 *    else //means that T2 is a function.
 *       return get_mem_fn_type(cl, T2);
 * }
 *
 * sequence make_mem_fn_seq(type cl, type T2, type T3, types...)
 * {
 *     mem_fn = make_mem_fn_seq_getter(
 *               unqalified_is_same(cl, T2), cl, T2, T3);
 *
 *     next = unqalified_is_same(cl, T2) ?
 *              make_mem_fn_seq(T2, types...) //because: T2 is another version of cl, hence i use this. T3 was already consumed.
 *              :
 *              make_mem_fn_seq(Class, T3, types...) //because: T2 was a function, hence it is consumed and class remains unchanged.
 *              ;
 *     return push_front(mem_fn, next) ;
 * };
 * @endcode
 */



template<class T, class U, class ...Args>
struct is_mem_fn_seq_impl
{
    typedef typename boost::conditional<
                 boost::is_function<U>::value || boost::dll::experimental::detail::unqalified_is_same<T, U>::value,
                 typename is_mem_fn_seq_impl<T, Args...>::type,
                 boost::false_type>::type type;
};

template<class T, class U>
struct is_mem_fn_seq_impl<T, U>
{
    typedef typename boost::conditional<
                 boost::is_function<U>::value && boost::is_object<T>::value,
                 boost::true_type, boost::false_type>::type type;
};

template<class T, class U, class Last>
struct is_mem_fn_seq_impl<T, U, Last>
{
    typedef typename boost::conditional<
                 (boost::is_function<U>::value || boost::dll::experimental::detail::unqalified_is_same<T, U>::value)
                 && boost::is_function<Last>::value,
                 boost::true_type, boost::false_type>::type type;
};

template<class T> struct is_mem_fn_seq : boost::false_type {};

//If only two arguments are provided at all.
template<class T, class U>
struct is_mem_fn_seq<sequence<T, U>> : boost::conditional<
                 boost::is_object<T>::value && boost::is_function<U>::value,
                 boost::true_type, boost::false_type>::type
{
};


template<class T, class Func, class ...Args>
struct is_mem_fn_seq<sequence<T, Func, Args...>> :
        boost::conditional<
            boost::is_class<T>::value && boost::is_function<Func>::value,
            typename is_mem_fn_seq_impl<T, Args...>::type,
            boost::false_type>::type {};


/* ********************************** mem fn sequence tuple ******************************/

/* A tuple of member functions
 * Unlike for plain functions a sequence here might contain classes as well as functions.
 */
template <class ...Ts>
struct mem_fn_tuple;

template <class Class, class Return, class...Args, class T2, class ...Ts>
struct mem_fn_tuple<mem_fn_def<Class, Return(Args...)>, T2, Ts...>
    : mem_fn_tuple<T2, Ts...>
{
    typedef typename boost::dll::detail::get_mem_fn_type<Class, Return(Args...)>::mem_fn mem_fn;
    mem_fn f_;

    constexpr mem_fn_tuple(mem_fn f, typename T2::mem_fn t2, typename Ts::mem_fn ... ts)
        : mem_fn_tuple<T2, Ts...>(t2, ts...)
        , f_(f)
    {}

    Return operator()(Class* const cl, Args...args) const {
        return (cl->*f_)(static_cast<Args>(args)...);
    }
    using mem_fn_tuple<T2, Ts...>::operator();

};

template <class Class, class Return, class...Args>
struct mem_fn_tuple<mem_fn_def<Class, Return(Args...)>> {
    typedef typename boost::dll::detail::get_mem_fn_type<Class, Return(Args...)>::mem_fn mem_fn;
    mem_fn f_;

    constexpr mem_fn_tuple(mem_fn f)
        : f_(f)
    {}

    Return operator()(Class * const cl, Args...args) const {
        return (cl->*f_)(static_cast<Args>(args)...);
    }
};

}}}}
#endif /* BOOST_DLL_DETAIL_IMPORT_MANGLED_HELPERS_HPP_ */