libcxx/include/__memory/inout_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___INOUT_PTR_H
  11 #define _LIBCPP___INOUT_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_same.h>
  20 #include <__type_traits/is_specialization.h>
  21 #include <__type_traits/is_void.h>
  22 #include <__utility/forward.h>
  23 #include <__utility/move.h>
  24 #include <tuple>
  25
  26 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  27 #  pragma GCC system_header
  28 #endif
  29
  30 _LIBCPP_PUSH_MACROS
  31 #include <__undef_macros>
  32
  33 _LIBCPP_BEGIN_NAMESPACE_STD
  34
  35 #if _LIBCPP_STD_VER >= 23
  36
  37 template <class _Smart, class _Pointer, class... _Args>
  38 class _LIBCPP_TEMPLATE_VIS inout_ptr_t {
  39   static_assert(!__is_specialization_v<_Smart, shared_ptr>, "std::shared_ptr<> is not supported with std::inout_ptr.");
  40
  41 public:
  42   _LIBCPP_HIDE_FROM_ABI explicit inout_ptr_t(_Smart& __smart, _Args... __args)
  43       : __s_(__smart), __a_(std::forward<_Args>(__args)...), __p_([&__smart] {
  44           if constexpr (is_pointer_v<_Smart>) {
  45             return __smart;
  46           } else {
  47             return __smart.get();
  48           }
  49         }()) {
  50     if constexpr (requires { __s_.release(); }) {
  51       __s_.release();
  52     } else {
  53       __s_ = _Smart();
  54     }
  55   }
  56
  57   _LIBCPP_HIDE_FROM_ABI inout_ptr_t(const inout_ptr_t&) = delete;
  58
  59   _LIBCPP_HIDE_FROM_ABI ~inout_ptr_t() {
  60     // LWG-3897 inout_ptr will not update raw pointer to null
  61     if constexpr (!is_pointer_v<_Smart>) {
  62       if (!__p_) {
  63         return;
  64       }
  65     }
  66
  67     using _SmartPtr = __pointer_of_or_t<_Smart, _Pointer>;
  68     if constexpr (is_pointer_v<_Smart>) {
  69       std::apply([&](auto&&... __args) { __s_ = _Smart(static_cast<_SmartPtr>(__p_), std::forward<_Args>(__args)...); },
  70                  std::move(__a_));
  71     } else if constexpr (__resettable_smart_pointer_with_args<_Smart, _Pointer, _Args...>) {
  72       std::apply([&](auto&&... __args) { __s_.reset(static_cast<_SmartPtr>(__p_), std::forward<_Args>(__args)...); },
  73                  std::move(__a_));
  74     } else {
  75       static_assert(is_constructible_v<_Smart, _SmartPtr, _Args...>,
  76                     "The smart pointer must be constructible from arguments of types _Smart, _Pointer, _Args...");
  77       std::apply([&](auto&&... __args) { __s_ = _Smart(static_cast<_SmartPtr>(__p_), std::forward<_Args>(__args)...); },
  78                  std::move(__a_));
  79     }
  80   }
  81
  82   _LIBCPP_HIDE_FROM_ABI operator _Pointer*() const noexcept { return std::addressof(const_cast<_Pointer&>(__p_)); }
  83
  84   _LIBCPP_HIDE_FROM_ABI operator void**() const noexcept
  85     requires(!is_same_v<_Pointer, void*>)
  86   {
  87     static_assert(is_pointer_v<_Pointer>, "The conversion to void** requires _Pointer to be a raw pointer.");
  88
  89     return reinterpret_cast<void**>(static_cast<_Pointer*>(*this));
  90   }
  91
  92 private:
  93   _Smart& __s_;
  94   tuple<_Args...> __a_;
  95   _Pointer __p_;
  96 };
  97
  98 template <class _Pointer = void, class _Smart, class... _Args>
  99 _LIBCPP_HIDE_FROM_ABI auto inout_ptr(_Smart& __s, _Args&&... __args) {
 100   using _Ptr = conditional_t<is_void_v<_Pointer>, __pointer_of_t<_Smart>, _Pointer>;
 101   return std::inout_ptr_t<_Smart, _Ptr, _Args&&...>(__s, std::forward<_Args>(__args)...);
 102 }
 103
 104 #endif // _LIBCPP_STD_VER >= 23
 105
 106 _LIBCPP_END_NAMESPACE_STD
 107
 108 _LIBCPP_POP_MACROS
 109
 110 #endif // _LIBCPP___INOUT_PTR_H