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      1 // Guarded Allocation -*- C++ -*-
      2 
      3 // Copyright (C) 2014-2024 Free Software Foundation, Inc.
      4 //
      5 // This file is part of the GNU ISO C++ Library.  This library is free
      6 // software; you can redistribute it and/or modify it under the
      7 // terms of the GNU General Public License as published by the
      8 // Free Software Foundation; either version 3, or (at your option)
      9 // any later version.
     10 
     11 // This library is distributed in the hope that it will be useful,
     12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
     13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     14 // GNU General Public License for more details.
     15 
     16 // Under Section 7 of GPL version 3, you are granted additional
     17 // permissions described in the GCC Runtime Library Exception, version
     18 // 3.1, as published by the Free Software Foundation.
     19 
     20 // You should have received a copy of the GNU General Public License and
     21 // a copy of the GCC Runtime Library Exception along with this program;
     22 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
     23 // <http://www.gnu.org/licenses/>.
     24 
     25 /** @file bits/allocated_ptr.h
     26  *  This is an internal header file, included by other library headers.
     27  *  Do not attempt to use it directly. @headername{memory}
     28  */
     29 
     30 #ifndef _ALLOCATED_PTR_H
     31 #define _ALLOCATED_PTR_H 1
     32 
     33 #if __cplusplus < 201103L
     34 # include <bits/c++0xwarning.h>
     35 #else
     36 # include <type_traits>
     37 # include <bits/ptr_traits.h>
     38 # include <bits/alloc_traits.h>
     39 
     40 namespace std _GLIBCXX_VISIBILITY(default)
     41 {
     42 _GLIBCXX_BEGIN_NAMESPACE_VERSION
     43 /// @cond undocumented
     44 
     45   /// Non-standard RAII type for managing pointers obtained from allocators.
     46   template<typename _Alloc>
     47     struct __allocated_ptr
     48     {
     49       using pointer = typename allocator_traits<_Alloc>::pointer;
     50       using value_type = typename allocator_traits<_Alloc>::value_type;
     51 
     52       /// Take ownership of __ptr
     53       __allocated_ptr(_Alloc& __a, pointer __ptr) noexcept
     54       : _M_alloc(std::__addressof(__a)), _M_ptr(__ptr)
     55       { }
     56 
     57       /// Convert __ptr to allocator's pointer type and take ownership of it
     58       template<typename _Ptr,
     59 	       typename _Req = _Require<is_same<_Ptr, value_type*>>>
     60       __allocated_ptr(_Alloc& __a, _Ptr __ptr)
     61       : _M_alloc(std::__addressof(__a)),
     62 	_M_ptr(pointer_traits<pointer>::pointer_to(*__ptr))
     63       { }
     64 
     65       /// Transfer ownership of the owned pointer
     66       __allocated_ptr(__allocated_ptr&& __gd) noexcept
     67       : _M_alloc(__gd._M_alloc), _M_ptr(__gd._M_ptr)
     68       { __gd._M_ptr = nullptr; }
     69 
     70       /// Deallocate the owned pointer
     71       ~__allocated_ptr()
     72       {
     73 	if (_M_ptr != nullptr)
     74 	  std::allocator_traits<_Alloc>::deallocate(*_M_alloc, _M_ptr, 1);
     75       }
     76 
     77       /// Release ownership of the owned pointer
     78       __allocated_ptr&
     79       operator=(std::nullptr_t) noexcept
     80       {
     81 	_M_ptr = nullptr;
     82 	return *this;
     83       }
     84 
     85       /// Get the address that the owned pointer refers to.
     86       value_type* get() { return std::__to_address(_M_ptr); }
     87 
     88     private:
     89       _Alloc* _M_alloc;
     90       pointer _M_ptr;
     91     };
     92 
     93   /// Allocate space for a single object using __a
     94   template<typename _Alloc>
     95     __allocated_ptr<_Alloc>
     96     __allocate_guarded(_Alloc& __a)
     97     {
     98       return { __a, std::allocator_traits<_Alloc>::allocate(__a, 1) };
     99     }
    100 
    101 /// @endcond
    102 _GLIBCXX_END_NAMESPACE_VERSION
    103 } // namespace std
    104 
    105 #endif
    106 #endif
    107