libcxx/include/__memory/out_ptr.h

   1 // -*- C++ -*-
   2 //===----------------------------------------------------------------------===//
   3 //
   4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   5 // See https://llvm.org/LICENSE.txt for license information.
   6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #ifndef _LIBCPP___OUT_PTR_H
  11 #define _LIBCPP___OUT_PTR_H
  12
  13 #include <__config>
  14 #include <__memory/addressof.h>
  15 #include <__memory/pointer_traits.h>
  16 #include <__memory/shared_ptr.h>
  17 #include <__memory/unique_ptr.h>
  18 #include <__type_traits/is_pointer.h>
  19 #include <__type_traits/is_specialization.h>
  20 #include <__type_traits/is_void.h>
  21 #include <__utility/forward.h>
  22 #include <__utility/move.h>
  23 #include <tuple>
  24
  25 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  26 #  pragma GCC system_header
  27 #endif
  28
  29 _LIBCPP_PUSH_MACROS
  30 #include <__undef_macros>
  31
  32 _LIBCPP_BEGIN_NAMESPACE_STD
  33
  34 #if _LIBCPP_STD_VER >= 23
  35
  36 template <class _Smart, class _Pointer, class... _Args>
  37 class _LIBCPP_TEMPLATE_VIS out_ptr_t {
  38   static_assert(!__is_specialization_v<_Smart, shared_ptr> || sizeof...(_Args) > 0,
  39                 "Using std::shared_ptr<> without a deleter in std::out_ptr is not supported.");
  40
  41 public:
  42   _LIBCPP_HIDE_FROM_ABI explicit out_ptr_t(_Smart& __smart, _Args... __args)
  43       : __s_(__smart), __a_(std::forward<_Args>(__args)...), __p_() {
  44     using _Ptr = decltype(__smart);
  45     if constexpr (__resettable_smart_pointer<_Ptr>) {
  46       __s_.reset();
  47     } else if constexpr (is_constructible_v<_Smart>) {
  48       __s_ = _Smart();
  49     } else {
  50       static_assert(__resettable_smart_pointer<_Ptr> || is_constructible_v<_Smart>,
  51                     "The adapted pointer type must have a reset() member function or be default constructible.");
  52     }
  53   }
  54
  55   _LIBCPP_HIDE_FROM_ABI out_ptr_t(const out_ptr_t&) = delete;
  56
  57   _LIBCPP_HIDE_FROM_ABI ~out_ptr_t() {
  58     if (!__p_) {
  59       return;
  60     }
  61
  62     using _SmartPtr = __pointer_of_or_t<_Smart, _Pointer>;
  63     if constexpr (__resettable_smart_pointer_with_args<_Smart, _Pointer, _Args...>) {
  64       std::apply([&](auto&&... __args) { __s_.reset(static_cast<_SmartPtr>(__p_), std::forward<_Args>(__args)...); },
  65                  std::move(__a_));
  66     } else {
  67       static_assert(is_constructible_v<_Smart, _SmartPtr, _Args...>,
  68                     "The smart pointer must be constructible from arguments of types _Smart, _Pointer, _Args...");
  69       std::apply([&](auto&&... __args) { __s_ = _Smart(static_cast<_SmartPtr>(__p_), std::forward<_Args>(__args)...); },
  70                  std::move(__a_));
  71     }
  72   }
  73
  74   _LIBCPP_HIDE_FROM_ABI operator _Pointer*() const noexcept { return std::addressof(const_cast<_Pointer&>(__p_)); }
  75
  76   _LIBCPP_HIDE_FROM_ABI operator void**() const noexcept
  77     requires(!is_same_v<_Pointer, void*>)
  78   {
  79     static_assert(is_pointer_v<_Pointer>, "The conversion to void** requires _Pointer to be a raw pointer.");
  80
  81     return reinterpret_cast<void**>(static_cast<_Pointer*>(*this));
  82   }
  83
  84 private:
  85   _Smart& __s_;
  86   tuple<_Args...> __a_;
  87   _Pointer __p_ = _Pointer();
  88 };
  89
  90 template <class _Pointer = void, class _Smart, class... _Args>
  91 _LIBCPP_HIDE_FROM_ABI auto out_ptr(_Smart& __s, _Args&&... __args) {
  92   using _Ptr = conditional_t<is_void_v<_Pointer>, __pointer_of_t<_Smart>, _Pointer>;
  93   return std::out_ptr_t<_Smart, _Ptr, _Args&&...>(__s, std::forward<_Args>(__args)...);
  94 }
  95
  96 #endif // _LIBCPP_STD_VER >= 23
  97
  98 _LIBCPP_END_NAMESPACE_STD
  99
 100 _LIBCPP_POP_MACROS
 101
 102 #endif // _LIBCPP___OUT_PTR_H