ceph/src/boost/libs/type_traits/include/boost/type_traits/integral_constant.hpp

   1 //  (C) Copyright John Maddock 2015.
   2 //  Use, modification and distribution are subject to the
   3 //  Boost Software License, Version 1.0. (See accompanying file
   4 //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   5
   6 #ifndef BOOST_TYPE_TRAITS_INTEGRAL_CONSTANT_HPP
   7 #define BOOST_TYPE_TRAITS_INTEGRAL_CONSTANT_HPP
   8
   9 #include <boost/config.hpp>
  10 #include <boost/detail/workaround.hpp>
  11
  12 #if (BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1400)) \
  13    || BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x610)) \
  14    || BOOST_WORKAROUND(__DMC__, BOOST_TESTED_AT(0x840)) \
  15    || BOOST_WORKAROUND(__MWERKS__, BOOST_TESTED_AT(0x3202)) \
  16    || BOOST_WORKAROUND(BOOST_INTEL_CXX_VERSION, BOOST_TESTED_AT(810)) )
  17
  18
  19 namespace boost{
  20    namespace mpl
  21    {
  22       template <bool B> struct bool_;
  23       template <class I, I val> struct integral_c;
  24       struct integral_c_tag;
  25    }
  26 }
  27
  28 #else
  29
  30 namespace mpl_{
  31
  32    template <bool B> struct bool_;
  33    template <class I, I val> struct integral_c;
  34    struct integral_c_tag;
  35 }
  36
  37 namespace boost
  38 {
  39    namespace mpl
  40    {
  41       using ::mpl_::bool_;
  42       using ::mpl_::integral_c;
  43       using ::mpl_::integral_c_tag;
  44    }
  45 }
  46
  47 #endif
  48
  49 namespace boost{
  50
  51    template <class T, T val>
  52    struct integral_constant
  53    {
  54       typedef mpl::integral_c_tag tag;
  55       typedef T value_type;
  56       typedef integral_constant<T, val> type;
  57       static const T value = val;
  58       //
  59       // This helper function is just to disable type-punning
  60       // warnings from GCC:
  61       //
  62       template <class U>
  63       static U& dereference(U* p) { return *p; }
  64
  65       operator const mpl::integral_c<T, val>& ()const
  66       {
  67          static const char data[sizeof(long)] = { 0 };
  68          return dereference(reinterpret_cast<const mpl::integral_c<T, val>*>(&data));
  69       }
  70       BOOST_CONSTEXPR operator T()const { return val; }
  71    };
  72
  73    template <class T, T val>
  74    T const integral_constant<T, val>::value;
  75
  76    template <bool val>
  77    struct integral_constant<bool, val>
  78    {
  79       typedef mpl::integral_c_tag tag;
  80       typedef bool value_type;
  81       typedef integral_constant<bool, val> type;
  82       static const bool value = val;
  83       //
  84       // This helper function is just to disable type-punning
  85       // warnings from GCC:
  86       //
  87       template <class T>
  88       static T& dereference(T* p) { return *p; }
  89
  90       operator const mpl::bool_<val>& ()const
  91       {
  92          static const char data = 0;
  93          return dereference(reinterpret_cast<const mpl::bool_<val>*>(&data));
  94       }
  95       BOOST_CONSTEXPR operator bool()const { return val; }
  96    };
  97
  98    template <bool val>
  99    bool const integral_constant<bool, val>::value;
 100
 101    typedef integral_constant<bool, true> true_type;
 102    typedef integral_constant<bool, false> false_type;
 103
 104 }
 105
 106 #endif