ceph/src/boost/boost/multi_index/detail/auto_space.hpp

   1 /* Copyright 2003-2018 Joaquin M Lopez Munoz.
   2  * Distributed under the Boost Software License, Version 1.0.
   3  * (See accompanying file LICENSE_1_0.txt or copy at
   4  * http://www.boost.org/LICENSE_1_0.txt)
   5  *
   6  * See http://www.boost.org/libs/multi_index for library home page.
   7  */
   8
   9 #ifndef BOOST_MULTI_INDEX_DETAIL_AUTO_SPACE_HPP
  10 #define BOOST_MULTI_INDEX_DETAIL_AUTO_SPACE_HPP
  11
  12 #if defined(_MSC_VER)
  13 #pragma once
  14 #endif
  15
  16 #include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */
  17 #include <algorithm>
  18 #include <boost/multi_index/detail/adl_swap.hpp>
  19 #include <boost/multi_index/detail/allocator_traits.hpp>
  20 #include <boost/noncopyable.hpp>
  21 #include <memory>
  22
  23 namespace boost{
  24
  25 namespace multi_index{
  26
  27 namespace detail{
  28
  29 /* auto_space provides uninitialized space suitably to store
  30  * a given number of elements of a given type.
  31  */
  32
  33 /* NB: it is not clear whether using an allocator to handle
  34  * zero-sized arrays of elements is conformant or not. GCC 3.3.1
  35  * and prior fail here, other stdlibs handle the issue gracefully.
  36  * To be on the safe side, the case n==0 is given special treatment.
  37  * References:
  38  *   GCC Bugzilla, "standard allocator crashes when deallocating segment
  39  *    "of zero length", http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14176
  40  *   C++ Standard Library Defect Report List (Revision 28), issue 199
  41  *     "What does allocate(0) return?",
  42  *     http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#199
  43  */
  44
  45 template<typename T,typename Allocator=std::allocator<T> >
  46 struct auto_space:private noncopyable
  47 {
  48   typedef typename rebind_alloc_for<
  49     Allocator,T>
  50   ::type                                   allocator;
  51   typedef allocator_traits<allocator>      alloc_traits;
  52   typedef typename alloc_traits::pointer   pointer;
  53   typedef typename alloc_traits::size_type size_type;
  54
  55   explicit auto_space(const Allocator& al=Allocator(),size_type n=1):
  56   al_(al),n_(n),data_(n_?alloc_traits::allocate(al_,n_):pointer(0))
  57   {}
  58
  59   ~auto_space(){if(n_)alloc_traits::deallocate(al_,data_,n_);}
  60
  61   Allocator get_allocator()const{return al_;}
  62
  63   pointer data()const{return data_;}
  64
  65   void swap(auto_space& x)
  66   {
  67     if(al_!=x.al_)adl_swap(al_,x.al_);
  68     std::swap(n_,x.n_);
  69     std::swap(data_,x.data_);
  70   }
  71
  72 private:
  73   allocator al_;
  74   size_type n_;
  75   pointer   data_;
  76 };
  77
  78 template<typename T,typename Allocator>
  79 void swap(auto_space<T,Allocator>& x,auto_space<T,Allocator>& y)
  80 {
  81   x.swap(y);
  82 }
  83
  84 } /* namespace multi_index::detail */
  85
  86 } /* namespace multi_index */
  87
  88 } /* namespace boost */
  89
  90 #endif