libstdc++
new_allocator.h
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00001 // Allocator that wraps operator new -*- C++ -*-
00002 
00003 // Copyright (C) 2001-2019 Free Software Foundation, Inc.
00004 //
00005 // This file is part of the GNU ISO C++ Library.  This library is free
00006 // software; you can redistribute it and/or modify it under the
00007 // terms of the GNU General Public License as published by the
00008 // Free Software Foundation; either version 3, or (at your option)
00009 // any later version.
00010 
00011 // This library is distributed in the hope that it will be useful,
00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00014 // GNU General Public License for more details.
00015 
00016 // Under Section 7 of GPL version 3, you are granted additional
00017 // permissions described in the GCC Runtime Library Exception, version
00018 // 3.1, as published by the Free Software Foundation.
00019 
00020 // You should have received a copy of the GNU General Public License and
00021 // a copy of the GCC Runtime Library Exception along with this program;
00022 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
00023 // <http://www.gnu.org/licenses/>.
00024 
00025 /** @file ext/new_allocator.h
00026  *  This file is a GNU extension to the Standard C++ Library.
00027  */
00028 
00029 #ifndef _NEW_ALLOCATOR_H
00030 #define _NEW_ALLOCATOR_H 1
00031 
00032 #include <bits/c++config.h>
00033 #include <new>
00034 #include <bits/functexcept.h>
00035 #include <bits/move.h>
00036 #if __cplusplus >= 201103L
00037 #include <type_traits>
00038 #endif
00039 
00040 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
00041 {
00042 _GLIBCXX_BEGIN_NAMESPACE_VERSION
00043 
00044   using std::size_t;
00045   using std::ptrdiff_t;
00046 
00047   /**
00048    *  @brief  An allocator that uses global new, as per [20.4].
00049    *  @ingroup allocators
00050    *
00051    *  This is precisely the allocator defined in the C++ Standard.
00052    *    - all allocation calls operator new
00053    *    - all deallocation calls operator delete
00054    *
00055    *  @tparam  _Tp  Type of allocated object.
00056    */
00057   template<typename _Tp>
00058     class new_allocator
00059     {
00060     public:
00061       typedef size_t     size_type;
00062       typedef ptrdiff_t  difference_type;
00063       typedef _Tp*       pointer;
00064       typedef const _Tp* const_pointer;
00065       typedef _Tp&       reference;
00066       typedef const _Tp& const_reference;
00067       typedef _Tp        value_type;
00068 
00069       template<typename _Tp1>
00070         struct rebind
00071         { typedef new_allocator<_Tp1> other; };
00072 
00073 #if __cplusplus >= 201103L
00074       // _GLIBCXX_RESOLVE_LIB_DEFECTS
00075       // 2103. propagate_on_container_move_assignment
00076       typedef std::true_type propagate_on_container_move_assignment;
00077 #endif
00078 
00079       _GLIBCXX20_CONSTEXPR
00080       new_allocator() _GLIBCXX_USE_NOEXCEPT { }
00081 
00082       _GLIBCXX20_CONSTEXPR
00083       new_allocator(const new_allocator&) _GLIBCXX_USE_NOEXCEPT { }
00084 
00085       template<typename _Tp1>
00086         _GLIBCXX20_CONSTEXPR
00087         new_allocator(const new_allocator<_Tp1>&) _GLIBCXX_USE_NOEXCEPT { }
00088 
00089       ~new_allocator() _GLIBCXX_USE_NOEXCEPT { }
00090 
00091       pointer
00092       address(reference __x) const _GLIBCXX_NOEXCEPT
00093       { return std::__addressof(__x); }
00094 
00095       const_pointer
00096       address(const_reference __x) const _GLIBCXX_NOEXCEPT
00097       { return std::__addressof(__x); }
00098 
00099       // NB: __n is permitted to be 0.  The C++ standard says nothing
00100       // about what the return value is when __n == 0.
00101       _GLIBCXX_NODISCARD pointer
00102       allocate(size_type __n, const void* = static_cast<const void*>(0))
00103       {
00104         if (__n > this->max_size())
00105           std::__throw_bad_alloc();
00106 
00107 #if __cpp_aligned_new
00108         if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
00109           {
00110             std::align_val_t __al = std::align_val_t(alignof(_Tp));
00111             return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp), __al));
00112           }
00113 #endif
00114         return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp)));
00115       }
00116 
00117       // __p is not permitted to be a null pointer.
00118       void
00119       deallocate(pointer __p, size_type)
00120       {
00121 #if __cpp_aligned_new
00122         if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
00123           {
00124             ::operator delete(__p, std::align_val_t(alignof(_Tp)));
00125             return;
00126           }
00127 #endif
00128         ::operator delete(__p);
00129       }
00130 
00131       size_type
00132       max_size() const _GLIBCXX_USE_NOEXCEPT
00133       {
00134 #if __PTRDIFF_MAX__ < __SIZE_MAX__
00135         return size_t(__PTRDIFF_MAX__) / sizeof(_Tp);
00136 #else
00137         return size_t(-1) / sizeof(_Tp);
00138 #endif
00139       }
00140 
00141 #if __cplusplus >= 201103L
00142       template<typename _Up, typename... _Args>
00143         void
00144         construct(_Up* __p, _Args&&... __args)
00145         noexcept(noexcept(::new((void *)__p)
00146                             _Up(std::forward<_Args>(__args)...)))
00147         { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
00148 
00149       template<typename _Up>
00150         void
00151         destroy(_Up* __p)
00152         noexcept(noexcept( __p->~_Up()))
00153         { __p->~_Up(); }
00154 #else
00155       // _GLIBCXX_RESOLVE_LIB_DEFECTS
00156       // 402. wrong new expression in [some_] allocator::construct
00157       void
00158       construct(pointer __p, const _Tp& __val)
00159       { ::new((void *)__p) _Tp(__val); }
00160 
00161       void
00162       destroy(pointer __p) { __p->~_Tp(); }
00163 #endif
00164 
00165       template<typename _Up>
00166         friend bool
00167         operator==(const new_allocator&, const new_allocator<_Up>&)
00168         _GLIBCXX_NOTHROW
00169         { return true; }
00170 
00171       template<typename _Up>
00172         friend bool
00173         operator!=(const new_allocator&, const new_allocator<_Up>&)
00174         _GLIBCXX_NOTHROW
00175         { return false; }
00176     };
00177 
00178 _GLIBCXX_END_NAMESPACE_VERSION
00179 } // namespace
00180 
00181 #endif