377 lines
12 KiB
C++
377 lines
12 KiB
C++
// Implementation of std::reference_wrapper -*- C++ -*-
|
|
|
|
// Copyright (C) 2004-2019 Free Software Foundation, Inc.
|
|
//
|
|
// This file is part of the GNU ISO C++ Library. This library is free
|
|
// software; you can redistribute it and/or modify it under the
|
|
// terms of the GNU General Public License as published by the
|
|
// Free Software Foundation; either version 3, or (at your option)
|
|
// any later version.
|
|
|
|
// This library is distributed in the hope that it will be useful,
|
|
// but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
// GNU General Public License for more details.
|
|
|
|
// Under Section 7 of GPL version 3, you are granted additional
|
|
// permissions described in the GCC Runtime Library Exception, version
|
|
// 3.1, as published by the Free Software Foundation.
|
|
|
|
// You should have received a copy of the GNU General Public License and
|
|
// a copy of the GCC Runtime Library Exception along with this program;
|
|
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
|
|
// <http://www.gnu.org/licenses/>.
|
|
|
|
/** @file include/bits/refwrap.h
|
|
* This is an internal header file, included by other library headers.
|
|
* Do not attempt to use it directly. @headername{functional}
|
|
*/
|
|
|
|
#ifndef _GLIBCXX_REFWRAP_H
|
|
#define _GLIBCXX_REFWRAP_H 1
|
|
|
|
#pragma GCC system_header
|
|
|
|
#if __cplusplus < 201103L
|
|
# include <bits/c++0x_warning.h>
|
|
#else
|
|
|
|
#include <bits/move.h>
|
|
#include <bits/invoke.h>
|
|
#include <bits/stl_function.h> // for unary_function and binary_function
|
|
|
|
namespace std _GLIBCXX_VISIBILITY(default)
|
|
{
|
|
_GLIBCXX_BEGIN_NAMESPACE_VERSION
|
|
|
|
/**
|
|
* Derives from @c unary_function or @c binary_function, or perhaps
|
|
* nothing, depending on the number of arguments provided. The
|
|
* primary template is the basis case, which derives nothing.
|
|
*/
|
|
template<typename _Res, typename... _ArgTypes>
|
|
struct _Maybe_unary_or_binary_function { };
|
|
|
|
/// Derives from @c unary_function, as appropriate.
|
|
template<typename _Res, typename _T1>
|
|
struct _Maybe_unary_or_binary_function<_Res, _T1>
|
|
: std::unary_function<_T1, _Res> { };
|
|
|
|
/// Derives from @c binary_function, as appropriate.
|
|
template<typename _Res, typename _T1, typename _T2>
|
|
struct _Maybe_unary_or_binary_function<_Res, _T1, _T2>
|
|
: std::binary_function<_T1, _T2, _Res> { };
|
|
|
|
template<typename _Signature>
|
|
struct _Mem_fn_traits;
|
|
|
|
template<typename _Res, typename _Class, typename... _ArgTypes>
|
|
struct _Mem_fn_traits_base
|
|
{
|
|
using __result_type = _Res;
|
|
using __maybe_type
|
|
= _Maybe_unary_or_binary_function<_Res, _Class*, _ArgTypes...>;
|
|
using __arity = integral_constant<size_t, sizeof...(_ArgTypes)>;
|
|
};
|
|
|
|
#define _GLIBCXX_MEM_FN_TRAITS2(_CV, _REF, _LVAL, _RVAL) \
|
|
template<typename _Res, typename _Class, typename... _ArgTypes> \
|
|
struct _Mem_fn_traits<_Res (_Class::*)(_ArgTypes...) _CV _REF> \
|
|
: _Mem_fn_traits_base<_Res, _CV _Class, _ArgTypes...> \
|
|
{ \
|
|
using __vararg = false_type; \
|
|
}; \
|
|
template<typename _Res, typename _Class, typename... _ArgTypes> \
|
|
struct _Mem_fn_traits<_Res (_Class::*)(_ArgTypes... ...) _CV _REF> \
|
|
: _Mem_fn_traits_base<_Res, _CV _Class, _ArgTypes...> \
|
|
{ \
|
|
using __vararg = true_type; \
|
|
};
|
|
|
|
#define _GLIBCXX_MEM_FN_TRAITS(_REF, _LVAL, _RVAL) \
|
|
_GLIBCXX_MEM_FN_TRAITS2( , _REF, _LVAL, _RVAL) \
|
|
_GLIBCXX_MEM_FN_TRAITS2(const , _REF, _LVAL, _RVAL) \
|
|
_GLIBCXX_MEM_FN_TRAITS2(volatile , _REF, _LVAL, _RVAL) \
|
|
_GLIBCXX_MEM_FN_TRAITS2(const volatile, _REF, _LVAL, _RVAL)
|
|
|
|
_GLIBCXX_MEM_FN_TRAITS( , true_type, true_type)
|
|
_GLIBCXX_MEM_FN_TRAITS(&, true_type, false_type)
|
|
_GLIBCXX_MEM_FN_TRAITS(&&, false_type, true_type)
|
|
|
|
#if __cplusplus > 201402L
|
|
_GLIBCXX_MEM_FN_TRAITS(noexcept, true_type, true_type)
|
|
_GLIBCXX_MEM_FN_TRAITS(& noexcept, true_type, false_type)
|
|
_GLIBCXX_MEM_FN_TRAITS(&& noexcept, false_type, true_type)
|
|
#endif
|
|
|
|
#undef _GLIBCXX_MEM_FN_TRAITS
|
|
#undef _GLIBCXX_MEM_FN_TRAITS2
|
|
|
|
/// If we have found a result_type, extract it.
|
|
template<typename _Functor, typename = __void_t<>>
|
|
struct _Maybe_get_result_type
|
|
{ };
|
|
|
|
template<typename _Functor>
|
|
struct _Maybe_get_result_type<_Functor,
|
|
__void_t<typename _Functor::result_type>>
|
|
{ typedef typename _Functor::result_type result_type; };
|
|
|
|
/**
|
|
* Base class for any function object that has a weak result type, as
|
|
* defined in 20.8.2 [func.require] of C++11.
|
|
*/
|
|
template<typename _Functor>
|
|
struct _Weak_result_type_impl
|
|
: _Maybe_get_result_type<_Functor>
|
|
{ };
|
|
|
|
/// Retrieve the result type for a function type.
|
|
template<typename _Res, typename... _ArgTypes _GLIBCXX_NOEXCEPT_PARM>
|
|
struct _Weak_result_type_impl<_Res(_ArgTypes...) _GLIBCXX_NOEXCEPT_QUAL>
|
|
{ typedef _Res result_type; };
|
|
|
|
/// Retrieve the result type for a varargs function type.
|
|
template<typename _Res, typename... _ArgTypes _GLIBCXX_NOEXCEPT_PARM>
|
|
struct _Weak_result_type_impl<_Res(_ArgTypes......) _GLIBCXX_NOEXCEPT_QUAL>
|
|
{ typedef _Res result_type; };
|
|
|
|
/// Retrieve the result type for a function pointer.
|
|
template<typename _Res, typename... _ArgTypes _GLIBCXX_NOEXCEPT_PARM>
|
|
struct _Weak_result_type_impl<_Res(*)(_ArgTypes...) _GLIBCXX_NOEXCEPT_QUAL>
|
|
{ typedef _Res result_type; };
|
|
|
|
/// Retrieve the result type for a varargs function pointer.
|
|
template<typename _Res, typename... _ArgTypes _GLIBCXX_NOEXCEPT_PARM>
|
|
struct
|
|
_Weak_result_type_impl<_Res(*)(_ArgTypes......) _GLIBCXX_NOEXCEPT_QUAL>
|
|
{ typedef _Res result_type; };
|
|
|
|
// Let _Weak_result_type_impl perform the real work.
|
|
template<typename _Functor,
|
|
bool = is_member_function_pointer<_Functor>::value>
|
|
struct _Weak_result_type_memfun
|
|
: _Weak_result_type_impl<_Functor>
|
|
{ };
|
|
|
|
// A pointer to member function has a weak result type.
|
|
template<typename _MemFunPtr>
|
|
struct _Weak_result_type_memfun<_MemFunPtr, true>
|
|
{
|
|
using result_type = typename _Mem_fn_traits<_MemFunPtr>::__result_type;
|
|
};
|
|
|
|
// A pointer to data member doesn't have a weak result type.
|
|
template<typename _Func, typename _Class>
|
|
struct _Weak_result_type_memfun<_Func _Class::*, false>
|
|
{ };
|
|
|
|
/**
|
|
* Strip top-level cv-qualifiers from the function object and let
|
|
* _Weak_result_type_memfun perform the real work.
|
|
*/
|
|
template<typename _Functor>
|
|
struct _Weak_result_type
|
|
: _Weak_result_type_memfun<typename remove_cv<_Functor>::type>
|
|
{ };
|
|
|
|
// Detect nested argument_type.
|
|
template<typename _Tp, typename = __void_t<>>
|
|
struct _Refwrap_base_arg1
|
|
{ };
|
|
|
|
// Nested argument_type.
|
|
template<typename _Tp>
|
|
struct _Refwrap_base_arg1<_Tp,
|
|
__void_t<typename _Tp::argument_type>>
|
|
{
|
|
typedef typename _Tp::argument_type argument_type;
|
|
};
|
|
|
|
// Detect nested first_argument_type and second_argument_type.
|
|
template<typename _Tp, typename = __void_t<>>
|
|
struct _Refwrap_base_arg2
|
|
{ };
|
|
|
|
// Nested first_argument_type and second_argument_type.
|
|
template<typename _Tp>
|
|
struct _Refwrap_base_arg2<_Tp,
|
|
__void_t<typename _Tp::first_argument_type,
|
|
typename _Tp::second_argument_type>>
|
|
{
|
|
typedef typename _Tp::first_argument_type first_argument_type;
|
|
typedef typename _Tp::second_argument_type second_argument_type;
|
|
};
|
|
|
|
/**
|
|
* Derives from unary_function or binary_function when it
|
|
* can. Specializations handle all of the easy cases. The primary
|
|
* template determines what to do with a class type, which may
|
|
* derive from both unary_function and binary_function.
|
|
*/
|
|
template<typename _Tp>
|
|
struct _Reference_wrapper_base
|
|
: _Weak_result_type<_Tp>, _Refwrap_base_arg1<_Tp>, _Refwrap_base_arg2<_Tp>
|
|
{ };
|
|
|
|
// - a function type (unary)
|
|
template<typename _Res, typename _T1 _GLIBCXX_NOEXCEPT_PARM>
|
|
struct _Reference_wrapper_base<_Res(_T1) _GLIBCXX_NOEXCEPT_QUAL>
|
|
: unary_function<_T1, _Res>
|
|
{ };
|
|
|
|
template<typename _Res, typename _T1>
|
|
struct _Reference_wrapper_base<_Res(_T1) const>
|
|
: unary_function<_T1, _Res>
|
|
{ };
|
|
|
|
template<typename _Res, typename _T1>
|
|
struct _Reference_wrapper_base<_Res(_T1) volatile>
|
|
: unary_function<_T1, _Res>
|
|
{ };
|
|
|
|
template<typename _Res, typename _T1>
|
|
struct _Reference_wrapper_base<_Res(_T1) const volatile>
|
|
: unary_function<_T1, _Res>
|
|
{ };
|
|
|
|
// - a function type (binary)
|
|
template<typename _Res, typename _T1, typename _T2 _GLIBCXX_NOEXCEPT_PARM>
|
|
struct _Reference_wrapper_base<_Res(_T1, _T2) _GLIBCXX_NOEXCEPT_QUAL>
|
|
: binary_function<_T1, _T2, _Res>
|
|
{ };
|
|
|
|
template<typename _Res, typename _T1, typename _T2>
|
|
struct _Reference_wrapper_base<_Res(_T1, _T2) const>
|
|
: binary_function<_T1, _T2, _Res>
|
|
{ };
|
|
|
|
template<typename _Res, typename _T1, typename _T2>
|
|
struct _Reference_wrapper_base<_Res(_T1, _T2) volatile>
|
|
: binary_function<_T1, _T2, _Res>
|
|
{ };
|
|
|
|
template<typename _Res, typename _T1, typename _T2>
|
|
struct _Reference_wrapper_base<_Res(_T1, _T2) const volatile>
|
|
: binary_function<_T1, _T2, _Res>
|
|
{ };
|
|
|
|
// - a function pointer type (unary)
|
|
template<typename _Res, typename _T1 _GLIBCXX_NOEXCEPT_PARM>
|
|
struct _Reference_wrapper_base<_Res(*)(_T1) _GLIBCXX_NOEXCEPT_QUAL>
|
|
: unary_function<_T1, _Res>
|
|
{ };
|
|
|
|
// - a function pointer type (binary)
|
|
template<typename _Res, typename _T1, typename _T2 _GLIBCXX_NOEXCEPT_PARM>
|
|
struct _Reference_wrapper_base<_Res(*)(_T1, _T2) _GLIBCXX_NOEXCEPT_QUAL>
|
|
: binary_function<_T1, _T2, _Res>
|
|
{ };
|
|
|
|
template<typename _Tp, bool = is_member_function_pointer<_Tp>::value>
|
|
struct _Reference_wrapper_base_memfun
|
|
: _Reference_wrapper_base<_Tp>
|
|
{ };
|
|
|
|
template<typename _MemFunPtr>
|
|
struct _Reference_wrapper_base_memfun<_MemFunPtr, true>
|
|
: _Mem_fn_traits<_MemFunPtr>::__maybe_type
|
|
{
|
|
using result_type = typename _Mem_fn_traits<_MemFunPtr>::__result_type;
|
|
};
|
|
|
|
/**
|
|
* @brief Primary class template for reference_wrapper.
|
|
* @ingroup functors
|
|
* @{
|
|
*/
|
|
template<typename _Tp>
|
|
class reference_wrapper
|
|
: public _Reference_wrapper_base_memfun<typename remove_cv<_Tp>::type>
|
|
{
|
|
_Tp* _M_data;
|
|
|
|
static _Tp* _S_fun(_Tp& __r) noexcept { return std::__addressof(__r); }
|
|
static void _S_fun(_Tp&&) = delete;
|
|
|
|
template<typename _Up, typename _Up2 = __remove_cvref_t<_Up>>
|
|
using __not_same
|
|
= typename enable_if<!is_same<reference_wrapper, _Up2>::value>::type;
|
|
|
|
public:
|
|
typedef _Tp type;
|
|
|
|
// _GLIBCXX_RESOLVE_LIB_DEFECTS
|
|
// 2993. reference_wrapper<T> conversion from T&&
|
|
// 3041. Unnecessary decay in reference_wrapper
|
|
template<typename _Up, typename = __not_same<_Up>, typename
|
|
= decltype(reference_wrapper::_S_fun(std::declval<_Up>()))>
|
|
reference_wrapper(_Up&& __uref)
|
|
noexcept(noexcept(reference_wrapper::_S_fun(std::declval<_Up>())))
|
|
: _M_data(reference_wrapper::_S_fun(std::forward<_Up>(__uref)))
|
|
{ }
|
|
|
|
reference_wrapper(const reference_wrapper&) = default;
|
|
|
|
reference_wrapper&
|
|
operator=(const reference_wrapper&) = default;
|
|
|
|
operator _Tp&() const noexcept
|
|
{ return this->get(); }
|
|
|
|
_Tp&
|
|
get() const noexcept
|
|
{ return *_M_data; }
|
|
|
|
template<typename... _Args>
|
|
typename result_of<_Tp&(_Args&&...)>::type
|
|
operator()(_Args&&... __args) const
|
|
{
|
|
return std::__invoke(get(), std::forward<_Args>(__args)...);
|
|
}
|
|
};
|
|
|
|
#if __cpp_deduction_guides
|
|
template<typename _Tp>
|
|
reference_wrapper(_Tp&) -> reference_wrapper<_Tp>;
|
|
#endif
|
|
|
|
/// Denotes a reference should be taken to a variable.
|
|
template<typename _Tp>
|
|
inline reference_wrapper<_Tp>
|
|
ref(_Tp& __t) noexcept
|
|
{ return reference_wrapper<_Tp>(__t); }
|
|
|
|
/// Denotes a const reference should be taken to a variable.
|
|
template<typename _Tp>
|
|
inline reference_wrapper<const _Tp>
|
|
cref(const _Tp& __t) noexcept
|
|
{ return reference_wrapper<const _Tp>(__t); }
|
|
|
|
template<typename _Tp>
|
|
void ref(const _Tp&&) = delete;
|
|
|
|
template<typename _Tp>
|
|
void cref(const _Tp&&) = delete;
|
|
|
|
/// std::ref overload to prevent wrapping a reference_wrapper
|
|
template<typename _Tp>
|
|
inline reference_wrapper<_Tp>
|
|
ref(reference_wrapper<_Tp> __t) noexcept
|
|
{ return __t; }
|
|
|
|
/// std::cref overload to prevent wrapping a reference_wrapper
|
|
template<typename _Tp>
|
|
inline reference_wrapper<const _Tp>
|
|
cref(reference_wrapper<_Tp> __t) noexcept
|
|
{ return { __t.get() }; }
|
|
|
|
// @} group functors
|
|
|
|
_GLIBCXX_END_NAMESPACE_VERSION
|
|
} // namespace std
|
|
|
|
#endif // C++11
|
|
|
|
#endif // _GLIBCXX_REFWRAP_H
|