ceph/src/boost/boost/spirit/home/classic/core/non_terminal/impl/static.hpp

   1 /*=============================================================================
   2     Copyright (c) 2006 Joao Abecasis
   3     http://spirit.sourceforge.net/
   4
   5   Distributed under the Boost Software License, Version 1.0. (See accompanying
   6   file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   7 =============================================================================*/
   8 #if !defined(BOOST_SPIRIT_STATIC_HPP)
   9 #define BOOST_SPIRIT_STATIC_HPP
  10
  11 #include <boost/noncopyable.hpp>
  12 #include <boost/call_traits.hpp>
  13 #include <boost/aligned_storage.hpp>
  14
  15 #include <boost/type_traits/add_pointer.hpp>
  16 #include <boost/type_traits/alignment_of.hpp>
  17
  18 #include <boost/thread/once.hpp>
  19
  20 #include <memory>   // for placement new
  21
  22 #include <boost/spirit/home/classic/namespace.hpp>
  23
  24 namespace boost { namespace spirit {
  25
  26 BOOST_SPIRIT_CLASSIC_NAMESPACE_BEGIN
  27
  28     //
  29     //  Provides thread-safe initialization of a single static instance of T.
  30     //
  31     //  This instance is guaranteed to be constructed on static storage in a
  32     //  thread-safe manner, on the first call to the constructor of static_.
  33     //
  34     //  Requirements:
  35     //      T is default constructible
  36     //          (There's an alternate implementation that relaxes this
  37     //              requirement -- Joao Abecasis)
  38     //      T::T() MUST not throw!
  39     //          this is a requirement of boost::call_once.
  40     //
  41     template <class T, class Tag>
  42     struct static_
  43         : boost::noncopyable
  44     {
  45     private:
  46
  47         struct destructor
  48         {
  49             ~destructor()
  50             {
  51                 static_::get_address()->~value_type();
  52             }
  53         };
  54
  55         struct default_ctor
  56         {
  57             static void construct()
  58             {
  59                 ::new (static_::get_address()) value_type();
  60                 static destructor d;
  61             }
  62         };
  63
  64     public:
  65
  66         typedef T value_type;
  67         typedef typename boost::call_traits<T>::reference reference;
  68         typedef typename boost::call_traits<T>::const_reference const_reference;
  69
  70         static_(Tag = Tag())
  71         {
  72             boost::call_once(&default_ctor::construct, constructed_);
  73         }
  74
  75         operator reference()
  76         {
  77             return this->get();
  78         }
  79
  80         operator const_reference() const
  81         {
  82             return this->get();
  83         }
  84
  85         reference get()
  86         {
  87             return *this->get_address();
  88         }
  89
  90         const_reference get() const
  91         {
  92             return *this->get_address();
  93         }
  94
  95     private:
  96         typedef typename boost::add_pointer<value_type>::type pointer;
  97
  98         static pointer get_address()
  99         {
 100             return static_cast<pointer>(data_.address());
 101         }
 102
 103         typedef boost::aligned_storage<sizeof(value_type),
 104             boost::alignment_of<value_type>::value> storage_type;
 105
 106         static storage_type data_;
 107         static once_flag constructed_;
 108     };
 109
 110     template <class T, class Tag>
 111     typename static_<T, Tag>::storage_type static_<T, Tag>::data_;
 112
 113     template <class T, class Tag>
 114 #ifndef BOOST_THREAD_PROVIDES_ONCE_CXX11
 115     once_flag static_<T, Tag>::constructed_ = BOOST_ONCE_INIT;
 116 #else
 117     once_flag static_<T, Tag>::constructed_;
 118 #endif
 119
 120 BOOST_SPIRIT_CLASSIC_NAMESPACE_END
 121
 122 }} // namespace BOOST_SPIRIT_CLASSIC_NS
 123
 124 #endif // include guard