__cxx03/__memory/out_ptr.h

0001 // -*- C++ -*-
0002 //===----------------------------------------------------------------------===//
0003 //
0004 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0005 // See https://llvm.org/LICENSE.txt for license information.
0006 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0007 //
0008 //===----------------------------------------------------------------------===//
0009
0010 #ifndef _LIBCPP___CXX03___OUT_PTR_H
0011 #define _LIBCPP___CXX03___OUT_PTR_H
0012
0013 #include <__cxx03/__config>
0014 #include <__cxx03/__memory/addressof.h>
0015 #include <__cxx03/__memory/pointer_traits.h>
0016 #include <__cxx03/__memory/shared_ptr.h>
0017 #include <__cxx03/__memory/unique_ptr.h>
0018 #include <__cxx03/__type_traits/is_specialization.h>
0019 #include <__cxx03/__type_traits/is_void.h>
0020 #include <__cxx03/__utility/forward.h>
0021 #include <__cxx03/__utility/move.h>
0022 #include <__cxx03/tuple>
0023
0024 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0025 #  pragma GCC system_header
0026 #endif
0027
0028 _LIBCPP_PUSH_MACROS
0029 #include <__cxx03/__undef_macros>
0030
0031 _LIBCPP_BEGIN_NAMESPACE_STD
0032
0033 #if _LIBCPP_STD_VER >= 23
0034
0035 template <class _Smart, class _Pointer, class... _Args>
0036 class _LIBCPP_TEMPLATE_VIS out_ptr_t {
0037   static_assert(!__is_specialization_v<_Smart, shared_ptr> || sizeof...(_Args) > 0,
0038                 "Using std::shared_ptr<> without a deleter in std::out_ptr is not supported.");
0039
0040 public:
0041   _LIBCPP_HIDE_FROM_ABI explicit out_ptr_t(_Smart& __smart, _Args... __args)
0042       : __s_(__smart), __a_(std::forward<_Args>(__args)...), __p_() {
0043     using _Ptr = decltype(__smart);
0044     if constexpr (__resettable_smart_pointer<_Ptr>) {
0045       __s_.reset();
0046     } else if constexpr (is_constructible_v<_Smart>) {
0047       __s_ = _Smart();
0048     } else {
0049       static_assert(__resettable_smart_pointer<_Ptr> || is_constructible_v<_Smart>,
0050                     "The adapted pointer type must have a reset() member function or be default constructible.");
0051     }
0052   }
0053
0054   _LIBCPP_HIDE_FROM_ABI out_ptr_t(const out_ptr_t&) = delete;
0055
0056   _LIBCPP_HIDE_FROM_ABI ~out_ptr_t() {
0057     if (!__p_) {
0058       return;
0059     }
0060
0061     using _SmartPtr = __pointer_of_or_t<_Smart, _Pointer>;
0062     if constexpr (__resettable_smart_pointer_with_args<_Smart, _Pointer, _Args...>) {
0063       std::apply([&](auto&&... __args) { __s_.reset(static_cast<_SmartPtr>(__p_), std::forward<_Args>(__args)...); },
0064                  std::move(__a_));
0065     } else {
0066       static_assert(is_constructible_v<_Smart, _SmartPtr, _Args...>,
0067                     "The smart pointer must be constructible from arguments of types _Smart, _Pointer, _Args...");
0068       std::apply([&](auto&&... __args) { __s_ = _Smart(static_cast<_SmartPtr>(__p_), std::forward<_Args>(__args)...); },
0069                  std::move(__a_));
0070     }
0071   }
0072
0073   _LIBCPP_HIDE_FROM_ABI operator _Pointer*() const noexcept { return std::addressof(const_cast<_Pointer&>(__p_)); }
0074
0075   _LIBCPP_HIDE_FROM_ABI operator void**() const noexcept
0076     requires(!is_same_v<_Pointer, void*>)
0077   {
0078     static_assert(is_pointer_v<_Pointer>, "The conversion to void** requires _Pointer to be a raw pointer.");
0079
0080     return reinterpret_cast<void**>(static_cast<_Pointer*>(*this));
0081   }
0082
0083 private:
0084   _Smart& __s_;
0085   tuple<_Args...> __a_;
0086   _Pointer __p_ = _Pointer();
0087 };
0088
0089 template <class _Pointer = void, class _Smart, class... _Args>
0090 _LIBCPP_HIDE_FROM_ABI auto out_ptr(_Smart& __s, _Args&&... __args) {
0091   using _Ptr = conditional_t<is_void_v<_Pointer>, __pointer_of_t<_Smart>, _Pointer>;
0092   return std::out_ptr_t<_Smart, _Ptr, _Args&&...>(__s, std::forward<_Args>(__args)...);
0093 }
0094
0095 #endif // _LIBCPP_STD_VER >= 23
0096
0097 _LIBCPP_END_NAMESPACE_STD
0098
0099 _LIBCPP_POP_MACROS
0100
0101 #endif // _LIBCPP___CXX03___OUT_PTR_H